[Lactose malabsorption and -intolerance - who will benefit from a lactose-reduced diet?

PubMed

Malham, Mikkel; Olin, Anne Bille; Pærregaard, Anders

2017-02-06

During the last decade, lactose-free diets have become increasingly popular in the general population, either isolated or as a part of a cow's milk-free diet. However, health-related benefits from a lactose-free diet are only documented for individuals with clinical lactose intolerance due to decreased intestinal lactase activity and subsequent lactose malabsorption. In this paper we summarize the current knowledge of lactose intolerance regarding diagnostic procedures and treatment.

Detecting uber-operons in prokaryotic genomes

PubMed Central

Che, Dongsheng; Li, Guojun; Mao, Fenglou; Wu, Hongwei; Xu, Ying

2006-01-01

We present a study on computational identification of uber-operons in a prokaryotic genome, each of which represents a group of operons that are evolutionarily or functionally associated through operons in other (reference) genomes. Uber-operons represent a rich set of footprints of operon evolution, whose full utilization could lead to new and more powerful tools for elucidation of biological pathways and networks than what operons have provided, and a better understanding of prokaryotic genome structures and evolution. Our prediction algorithm predicts uber-operons through identifying groups of functionally or transcriptionally related operons, whose gene sets are conserved across the target and multiple reference genomes. Using this algorithm, we have predicted uber-operons for each of a group of 91 genomes, using the other 90 genomes as references. In particular, we predicted 158 uber-operons in Escherichia coli K12 covering 1830 genes, and found that many of the uber-operons correspond to parts of known regulons or biological pathways or are involved in highly related biological processes based on their Gene Ontology (GO) assignments. For some of the predicted uber-operons that are not parts of known regulons or pathways, our analyses indicate that their genes are highly likely to work together in the same biological processes, suggesting the possibility of new regulons and pathways. We believe that our uber-operon prediction provides a highly useful capability and a rich information source for elucidation of complex biological processes, such as pathways in microbes. All the prediction results are available at our Uber-Operon Database: , the first of its kind. PMID:16682449

Detecting uber-operons in prokaryotic genomes.

PubMed

Che, Dongsheng; Li, Guojun; Mao, Fenglou; Wu, Hongwei; Xu, Ying

2006-01-01

We present a study on computational identification of uber-operons in a prokaryotic genome, each of which represents a group of operons that are evolutionarily or functionally associated through operons in other (reference) genomes. Uber-operons represent a rich set of footprints of operon evolution, whose full utilization could lead to new and more powerful tools for elucidation of biological pathways and networks than what operons have provided, and a better understanding of prokaryotic genome structures and evolution. Our prediction algorithm predicts uber-operons through identifying groups of functionally or transcriptionally related operons, whose gene sets are conserved across the target and multiple reference genomes. Using this algorithm, we have predicted uber-operons for each of a group of 91 genomes, using the other 90 genomes as references. In particular, we predicted 158 uber-operons in Escherichia coli K12 covering 1830 genes, and found that many of the uber-operons correspond to parts of known regulons or biological pathways or are involved in highly related biological processes based on their Gene Ontology (GO) assignments. For some of the predicted uber-operons that are not parts of known regulons or pathways, our analyses indicate that their genes are highly likely to work together in the same biological processes, suggesting the possibility of new regulons and pathways. We believe that our uber-operon prediction provides a highly useful capability and a rich information source for elucidation of complex biological processes, such as pathways in microbes. All the prediction results are available at our Uber-Operon Database: http://csbl.bmb.uga.edu/uber, the first of its kind.

Transport by the lactose permease of Escherichia coli as the basis of lactose killing.

PubMed Central

Dykhuizen, D; Hartl, D

1978-01-01

Lactose killing is a peculiar phenomenon in which 80 to 98% of the Escherichia coli cells taken from a lactose-limited chemostat die when plated on standard lactose minimal media. This unique form of suicide is caused by the action of the lactose permease. Since uptake of either lactose or galactose by the lactose permease caused death, the action of rapid transport across the membrane must be the cause of the phenomenon. Alternative causes of lactose killing, such as accumulation of toxic metabolic intermediates or action of the beta-galactosidase, have been eliminated. It is proposed that rapid uptake of sugars by the lactose permease disrupts membrane function, perhaps causing collapse of the membrane potential. PMID:99437

Lactose (mal)digestion evaluated by the 13C-lactose digestion test.

PubMed

Vonk, R J; Lin, Y; Koetse, H A; Huang, C; Zeng, G; Elzinga, H; Antoine, J; Stellaard, F

2000-02-01

The prevalence of genetically determined lactase nonpersistence is based on the results of the lactose H2 breath test. This test, however, is an indirect test, which might lead to misinterpretation. We determined lactase activity in healthy Chinese and Dutch students using a novel 13C-lactose digestion test. The cut-off value of this test was established in a Chinese population with a homogenous genetic background of lactase nonpersistence and was compared with the results obtained in a Caucasian population. Twenty-five grams of a 13C-lactose solution was consumed by 12 known H2-positive and 5 H2-negative Chinese students and 48 Dutch students and, subsequently, 13C-glucose concentration in plasma and H2 excretion in breath were measured. A similar 13C-glucose response curve was found in all Chinese students. The mean response curve in the Dutch students was more pronounced (P < 0.01). The 1 h (peak) plasma 13C-glucose concentration was the best discriminator between lactose digesting and maldigesting subjects. The cut-off level of 2 mmol L-1 13C-glucose in plasma was defined in the H2-positive Chinese students group. Based on the 13C-glucose response the prevalence of lactose maldigestion in the Dutch subjects was 25%; based on the lactose H2 breath test 17%. Using the 13C-lactose digestion test the results demonstrate a higher prevalence of lactose maldigestion in a Caucasian population than indicated by the results of the H2 breath test. A moderate increase in the plasma 13C-glucose concentration after consumption of 13C-lactose in the young adult Chinese subjects indicates a residual lactase activity in that age group, even when a positive H2 breath test result is obtained. These results indicate that the 13C-glucose concentration in plasma more accurately reflects the small intestinal lactose digestion capacity than the lactose H2 breath test.

Lactose Intolerance

MedlinePlus

... tract from stool and changes it from a liquid to a solid form. In the colon, bacteria break down undigested lactose and create fluid and gas. Not all people with lactase deficiency and lactose ...

Structural Explanation for Allolactose (lac Operon Inducer) Synthesis by lacZ β-Galactosidase and the Evolutionary Relationship between Allolactose Synthesis and the lac Repressor

PubMed Central

Wheatley, Robert W.; Lo, Summie; Jancewicz, Larisa J.; Dugdale, Megan L.; Huber, Reuben E.

2013-01-01

β-Galactosidase (lacZ) has bifunctional activity. It hydrolyzes lactose to galactose and glucose and catalyzes the intramolecular isomerization of lactose to allolactose, the lac operon inducer. β-Galactosidase promotes the isomerization by means of an acceptor site that binds glucose after its cleavage from lactose and thus delays its exit from the site. However, because of its relatively low affinity for glucose, details of this site have remained elusive. We present structural data mapping the glucose site based on a substituted enzyme (G794A-β-galactosidase) that traps allolactose. Various lines of evidence indicate that the glucose of the trapped allolactose is in the acceptor position. The evidence includes structures with Bis-Tris (2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol) and l-ribose in the site and kinetic binding studies with substituted β-galactosidases. The site is composed of Asn-102, His-418, Lys-517, Ser-796, Glu-797, and Trp-999. Ser-796 and Glu-797 are part of a loop (residues 795–803) that closes over the active site. This loop appears essential for the bifunctional nature of the enzyme because it helps form the glucose binding site. In addition, because the loop is mobile, glucose binding is transient, allowing the release of some glucose. Bioinformatics studies showed that the residues important for interacting with glucose are only conserved in a subset of related enzymes. Thus, intramolecular isomerization is not a universal feature of β-galactosidases. Genomic analyses indicated that lac repressors were co-selected only within the conserved subset. This shows that the glucose binding site of β-galactosidase played an important role in lac operon evolution. PMID:23486479

Identification of lactose phosphotransferase systems in Lactobacillus gasseri ATCC 33323 required for lactose utilization.

PubMed

Francl, Alyssa L; Hoeflinger, Jennifer L; Miller, Michael J

2012-04-01

Improving the annotation of sugar catabolism-related genes requires functional characterization. Our objective was to identify the genes necessary for lactose utilization by Lactobacillus gasseri ATCC 33323 (NCK334). The mechanism of lactose transport in many lactobacilli is a lactose/galactose-specific permease, yet no orthologue was found in NCK334. Characterization of an EI knockout strain [EI (enzyme I) is required for phosphotransferase system transporter (PTS) function] demonstrated that L. gasseri requires PTS(s) to utilize lactose. In order to determine which PTS(s) were necessary for lactose utilization, we compared transcript expression profiles in response to lactose for the 15 complete PTSs identified in the NCK334 genome. PTS 6CB (LGAS_343) and PTS 8C (LGAS_497) were induced in the presence of lactose 107- and 53-fold, respectively. However, L. gasseri ATCC 33323 PTS 6CB, PTS 8C had a growth rate similar to that of the wild-type on semisynthetic deMan, Rogosa, Sharpe (MRS) medium with lactose. Expression profiles of L. gasseri ATCC 33323 PTS 6CB, PTS 8C in response to lactose identified PTS 9BC (LGAS_501) as 373-fold induced, whereas PTS 9BC was not induced in NCK334. Elimination of growth on lactose required the inactivation of both PTS 6CB and PTS 9BC. Among the six candidate phospho-β-galactosidase genes present in the NCK334 genome, LGAS_344 was found to be induced 156-fold in the presence of lactose. In conclusion, we have determined that: (1) NCK334 uses a PTS to import lactose; (2) PTS 6CB and PTS 8C gene expression is strongly induced by lactose; and (3) elimination of PTS 6CB and PTS 9BC is required to prevent growth on lactose.

Evidence against the selfish operon theory.

PubMed

Pál, Csaba; Hurst, Laurence D

2004-06-01

According to the selfish operon hypothesis, the clustering of genes and their subsequent organization into operons is beneficial for the constituent genes because it enables the horizontal gene transfer of weakly selected, functionally coupled genes. The majority of these are expected to be non-essential genes. From our analysis of the Escherichia coli genome, we conclude that the selfish operon hypothesis is unlikely to provide a general explanation for clustering nor can it account for the gene composition of operons. Contrary to expectations, essential genes with related functions have an especially strong tendency to cluster, even if they are not in operons. Moreover, essential genes are particularly abundant in operons.

A study of lactose metabolism in Lactococcus garvieae reveals a genetic marker for distinguishing between dairy and fish biotypes.

PubMed

Fortina, Maria Grazia; Ricci, Giovanni; Borgo, Francesca

2009-06-01

Dairy and fish isolates of Lactococcus garvieae were tested for their ability to utilize lactose and to grow in milk. Fish isolates were unable to assimilate lactose, but unexpectedly, they possessed the ability to grow in milk. Genetic studies, carried out constructing different vectorette libraries, provided evidence that in fish isolates, no genes involved in lactose utilization were present. For L. garvieae dairy isolates, a single system for the catabolism of lactose was found. It consists of a lactose transport and hydrolysis depending on a phosphoenolpyruvate-dependent phosphotransferase system combined with a phospho-beta-galactosidase. The genes involved were highly similar at the nucleotide sequence level to their counterparts in Lactococcus lactis; however, while in many L. lactis strains these genes are plasmid encoded, in L. garvieae they are chromosomally located. Thus, in the species L. garvieae, the phospho-beta-galactosidase gene, detectable in all strains of dairy origin but lacking in fish isolates, can be considered a reliable genetic marker for distinguishing biotypes in the two diverse ecological niches. Moreover, we obtained information regarding the complete nucleotide sequence of the gal operon in L. garvieae, consisting of a galactose permease and the Leloir pathway enzymes. This is one of the first reports concerning the determination of the nucleotide sequences of genes (other than the 16S rDNA gene) in L. garvieae and should be considered a step in a continuous effort to explore the genome of this species, with the aim of determining the real relationship between the presence of L. garvieae in dairy products and food safety.

Bistable Mechanisms for Space Applications

PubMed Central

Zirbel, Shannon A.; Tolman, Kyler A.; Trease, Brian P.

2016-01-01

Compliant bistable mechanisms are monolithic devices with two stable equilibrium positions separated by an unstable equilibrium position. They show promise in space applications as nonexplosive release mechanisms in deployment systems, thereby eliminating friction and improving the reliability and precision of those mechanical devices. This paper presents both analytical and numerical models that are used to predict bistable behavior and can be used to create bistable mechanisms in materials not previously feasible for compliant mechanisms. Materials compatible with space applications are evaluated for use as bistable mechanisms and prototypes are fabricated in three different materials. Pin-puller and cutter release mechanisms are proposed as potential space applications. PMID:28030588

Improved clinical tolerance to chronic lactose ingestion in subjects with lactose intolerance: a placebo effect?

PubMed Central

Briet, F; Pochart, P; Marteau, P; Flourie, B; Arrigoni, E; Rambaud, J

1997-01-01

Background—Uncontrolled studies of lactose intolerant subjects have shown that symptom severity decreases after chronic lactose consumption. Adaptation of the colonic flora might explain this improvement. 
Aims—To compare the effects of regular administration of either lactose or sucrose on clinical tolerance and bacterial adaptation to lactose. 
Methods—Forty six lactose intolerant subjects underwent two 50 g lactose challenges on days 1 and 15. Between these days they were given 34 g of lactose or sucrose per day, in a double blind protocol. Stool samples were obtained on days 0 and 14, to measure faecal β-galactosidase and pH. Symptoms, breath H2 excretion, faecal weight and electrolytes, and orofaecal transit time were assessed. 
Results—Except for faecal weight, symptoms were significantly milder during the second challenge in both groups, and covariance analysis showed no statistical difference between them. In the lactose group, but not in the sucrose group, faecal β-galactosidase activity increased, pH dropped, and breath H2 excretion decreased. 
Conclusion—Bacterial adaptation occurred when lactose intolerant subjects ingested lactose for 13 days, and all symptoms except diarrhoea regressed. Clinical improvement was also observed in the control group which displayed no signs of metabolic adaptation. This suggests that improved clinical tolerance may be just a placebo effect. 

 Keywords: lactose; lactose intolerance; colonic adaptation; lactase deficiency PMID:9414969

Lactose intolerance in Thai adults.

PubMed

Densupsoontorn, Narumon; Jirapinyo, Pipop; Thamonsiri, Nuchnoi; Chantaratin, Sasitorn; Wongarn, Renu

2004-12-01

Lactose intolerance is common in Thai adults who ingest cow's milk but its incidence has not been clearly defined The authors evaluated 45 volunteers (15 males, 35 females), aged 21-31 yrs old, who drank one 240-ml box of milk daily. A Lactose tolerance test was performed using a breath-hydrogen test (BHT) after oral intake of 25 g of lactose dissolved in 250 ml of water The presence of gastrointestinal symptoms of lactose intolerance, flatulence, abdominal pain and diarrhea, were recorded Twenty-one subjects (47%) were categorized as lactose malabsorbers and intolerant, two subjects (4%) were malabsorbers but tolerant, and 22 of 45 (49%) were absorbers and tolerant. The incidence of lactose malabsorption was, thus, 51%; symptoms of intolerance were found in 21 of the 23 malabsorbers, making the incidence of lactose intolerance 47%. In the lactose malabsorbant and intolerant group, the more breath-hydrogen (H) the more symptoms observed All subjects who had a negative breath-H2 test had no symptoms. The breath-H2 test should be used as a standard method to evaluate lactose absorption and lactose tolerance. The incidence of lactose intolerance has decreased from the past and the symptoms are not so severe that the people limit the consumption of milk since it is a major source of food containing good quality of protein and calcium.

Regulation and Adaptive Evolution of Lactose Operon Expression in Lactobacillus delbrueckii

PubMed Central

Lapierre, Luciane; Mollet, Beat; Germond, Jacques-Edouard

2002-01-01

Lactobacillus delbrueckii subsp. bulgaricus and L. delbrueckii subsp. lactis are both used in the dairy industry as homofermentative lactic acid bacteria in the production of fermented milk products. After selective pressure for the fast fermentation of milk in the manufacture of yogurts, L. delbrueckii subsp. bulgaricus loses its ability to regulate lac operon expression. A series of mutations led to the constitutive expression of the lac genes. A complex of insertion sequence (IS) elements (ISL4 inside ISL5), inserted at the border of the lac promoter, induced the loss of the palindromic structure of one of the operators likely involved in the binding of regulatory factors. A lac repressor gene was discovered downstream of the β-galactosidase gene of L. delbrueckii subsp. lactis and was shown to be inactivated by several mutations in L. delbrueckii subsp. bulgaricus. Regulatory mechanisms of the lac gene expression of L. delbrueckii subsp. bulgaricus and L. delbrueckii subsp. lactis were compared by heterologous expression in Lactococcus lactis of the two lac promoters in front of a reporter gene (β-glucuronidase) in the presence or absence of the lac repressor gene. Insertion of the complex of IS elements in the lac promoter of L. delbrueckii subsp. bulgaricus increased the promoter's activity but did not prevent repressor binding; rather, it increased the affinity of the repressor for the promoter. Inactivation of the lac repressor by mutations was then necessary to induce the constitutive expression of the lac genes in L. delbrueckii subsp. bulgaricus. PMID:11807052

Undernourished Children and Milk Lactose.

PubMed

Grenov, Benedikte; Briend, André; Sangild, Per T; Thymann, Thomas; Rytter, Maren H; Hother, Anne-Louise; Mølgaard, Christian; Michaelsen, Kim F

2016-03-01

Lactose is an important energy source in young mammals, and in fully breast-fed human infants, it constitutes around 40% of the total daily energy intake. The role of lactose in feeding of undernourished infants and young children is not well described. A narrative review of the potential positive and negative effects of lactose in the treatment of undernourished children. Searches were conducted using PUBMED and Web of Science up to July 2015. Relevant references in the retrieved articles were included. Lactose may exhibit several health benefits in young children, including a prebiotic effect on the gut microbiota and a positive effect on mineral absorption. Studies in piglets suggest there might also be a stimulating effect on growth, relative to other carbohydrates. Lactose intolerance is a potential concern for undernourished children. Most undernourished children seem to tolerate the currently recommended (low lactose level) therapeutic foods well. However, a subgroup of severely undernourished children with secondary lactase deficiency due to severe diarrhea or severe enteropathy may benefit from products with even more restricted lactose content. At limited extra costs, lactose or lactose-containing milk ingredients may have beneficial effects if added to food products for undernourished children. Lactose may be an overlooked beneficial nutrient for young and undernourished children. Research is needed to define the balance between beneficial and detrimental effects of lactose in undernourished children at different ages and with different degrees of diarrhea and intestinal integrity. © The Author(s) 2016.

lac operon induction in Escherichia coli: Systematic comparison of IPTG and TMG induction and influence of the transacetylase LacA.

PubMed

Marbach, Anja; Bettenbrock, Katja

2012-01-01

Most commonly used expression systems in bacteria are based on the Escherichia coli lac promoter. Furthermore, lac operon elements are used today in systems and synthetic biology. In the majority of the cases the gratuitous inducers IPTG or TMG are used. Here we report a systematic comparison of lac promoter induction by TMG and IPTG which focuses on the aspects inducer uptake, population heterogeneity and a potential influence of the transacetylase, LacA. We provide induction curves in E. coli LJ110 and in isogenic lacY and lacA mutant strains and we show that both inducers are substrates of the lactose permease at low inducer concentrations but can also enter cells independently of lactose permease if present at higher concentrations. Using a gfp reporter strain we compared TMG and IPTG induction at single cell level and showed that bimodal induction with IPTG occurred at approximately ten-fold lower concentrations than with TMG. Furthermore, we observed that lac operon induction is influenced by the transacetylase, LacA. By comparing two Plac-gfp reporter strains with and without a lacA deletion we could show that in the lacA(+) strain the fluorescence level decreased after few hours while the fluorescence further increased in the lacA(-) strain. The results indicate that through the activity of LacA the IPTG concentration can be reduced below an inducing threshold concentration-an influence that should be considered if low inducer amounts are used. Copyright © 2011 Elsevier B.V. All rights reserved.

Lactose intolerance and other disaccharidase deficiency.

PubMed

Tomar, Balvir S

2014-09-01

Intolerance to foods which contain lactose can cause a range of intestinal and systemic symptoms. These symptoms are caused by Lactase deficiency which is encoded by a single gene (LCT) of ≈ 50 kb located on chromosome 2q21. In some food items, lactose has been missed because of "hidden" lactose due to inadequately labeled, confusing diagnosis of lactose intolerance based on dietary restriction of dairy foods. Two polymorphisms, C/T13910 and G/A22018, linked to hypolactasia, correlate with breath hydrogen and symptoms after lactose. The key in the management of lactose intolerance is the dietary removal of lactose. Patients diagnosed as lactose intolerant must be advised of "risk" foods, inadequately labeled, including processed meats, bread, cake mixes, soft drinks, and lagers. This review highlights the types, symptoms and management of lactose intolerance and also highlights differences from milk allergy which closely mimics the symptoms of lactose intolerance.

[Pharmaceutical drugs containing lactose can as a rule be used by persons with lactose intolerance].

PubMed

Vinther, Siri; Rumessen, Jöri Johannes; Christensen, Mikkel

2015-03-09

Lactose is often used as an excipient in pharmaceutical drugs. Current evidence indicates that the amount of lactose in most drugs is not sufficient to cause symptoms in persons with lactose intolerance, although interindividual differences in sensitivity probably exist. Patient preferences and/or suboptimal treatment adherence could be reasons for considering lactose-free drug alternatives.

Construction of lactose-consuming Saccharomyces cerevisiae for lactose fermentation into ethanol fuel.

PubMed

Zou, Jing; Guo, Xuewu; Shen, Tong; Dong, Jian; Zhang, Cuiying; Xiao, Dongguang

2013-04-01

Two lactose-consuming diploid Saccharomyces cerevisiae strains, AY-51024A and AY-51024M, were constructed by expressing the LAC4 and LAC12 genes of Kluyveromyces marxianus in the host strain AY-5. In AY-51024A, both genes were targeted to the ATH1 and NTH1 gene-encoding regions to abolish the activity of acid/neutral trehalase. In AY-51024M, both genes were respectively integrated into the MIG1 and NTH1 gene-encoding regions to relieve glucose repression. Physiologic studies of the two transformants under anaerobic cultivations in glucose and galactose media indicated that the expression of both LAC genes did not physiologically burden the cells, except for AY-51024A in glucose medium. Galactose consumption was initiated at higher glucose concentrations in the MIG1 deletion strain AY-51024M than in the corresponding wild-type strain and AY-51024A, wherein galactose was consumed until glucose was completely depleted in the mixture. In lactose medium, the Sp. growth rates of AY-51024A and AY-51024M under anaerobic shake-flasks were 0.025 and 0.067 h(-1), respectively. The specific lactose uptake rate and ethanol production of AY-51024M were 2.50 g lactose g CDW(-1) h(-1) and 23.4 g l(-1), respectively, whereas those of AY-51024A were 0.98 g lactose g CDW(-1) h(-1) and 24.3 g lactose g CDW(-1) h(-1), respectively. In concentrated cheese whey powder solutions, AY-51024M produced 63.3 g l(-1) ethanol from approximately 150 g l(-1) initial lactose in 120 h, conversely, AY-51024A consumed 63.7 % of the initial lactose and produced 35.9 g l(-1) ethanol. Therefore, relieving glucose repression is an effective strategy for constructing lactose-consuming S. cerevisiae.

Radiative bistability and thermal memory.

PubMed

Kubytskyi, Viacheslav; Biehs, Svend-Age; Ben-Abdallah, Philippe

2014-08-15

We predict the existence of a thermal bistability in many-body systems out of thermal equilibrium which exchange heat by thermal radiation using insulator-metal transition materials. We propose a writing-reading procedure and demonstrate the possibility to exploit the thermal bistability to make a volatile thermal memory. We show that this thermal memory can be used to store heat and thermal information (via an encoding temperature) for arbitrary long times. The radiative thermal bistability could find broad applications in the domains of thermal management, information processing, and energy storage.

Evolutionary dynamics of nematode operons: easy come, slow go.

PubMed

Qian, Wenfeng; Zhang, Jianzhi

2008-03-01

Operons are widespread in prokaryotes, but are uncommon in eukaryotes, except nematode worms, where approximately 15% of genes reside in over 1100 operons in the model organism Caenorhabditis elegans. It is unclear how operons have become abundant in nematode genomes. The "one-way street" hypothesis asserts that once formed by chance, operons are very difficult to break, because the breakage would leave downstream genes in an operon without a promoter, and hence, unexpressed. To test this hypothesis, we analyzed the presence and absence of C. elegans operons in Caenorhabditis briggsae, Caenorhabditis remanei, and Caenorhabditis brenneri, using Pristionchus pacificus and Brugia malayi as outgroups, and identified numerous operon gains and losses. Coupled with experimental examination of trans-splicing patterns, our comparative genomic analysis revealed diverse molecular mechanisms of operon losses, including inversion, insertion, and relocation, but the presence of internal promoters was not found to facilitate operon losses. In several cases, the data allowed inference of mechanisms by which downstream genes are expressed after operon breakage. We found that the rate of operon gain is approximately 3.3 times that of operon loss. Thus, the evolutionary dynamics of nematode operons is better described as "easy come, slow go," rather than a "one-way street." Based on a mathematic model of operon gains and losses and additional assumptions, we projected that the number of operons in C. elegans will continue to rise by 6%-18% in future evolution before reaching equilibrium between operon gains and losses.

Problem-Solving Test: Tryptophan Operon Mutants

ERIC Educational Resources Information Center

Szeberenyi, Jozsef

2010-01-01

This paper presents a problem-solving test that deals with the regulation of the "trp" operon of "Escherichia coli." Two mutants of this operon are described: in mutant A, the operator region of the operon carries a point mutation so that it is unable to carry out its function; mutant B expresses a "trp" repressor protein unable to bind…

Decrease in TSH levels after lactose restriction in Hashimoto's thyroiditis patients with lactose intolerance.

PubMed

Asik, Mehmet; Gunes, Fahri; Binnetoglu, Emine; Eroglu, Mustafa; Bozkurt, Neslihan; Sen, Hacer; Akbal, Erdem; Bakar, Coskum; Beyazit, Yavuz; Ukinc, Kubilay

2014-06-01

We aimed to evaluate the prevalence of lactose intolerance (LI) in patients with Hashimoto's thyroiditis(HT) and the effects of lactose restriction on thyroid function in these patients. Eighty-three HT patients taking L-thyroxine (LT4) were enrolled, and lactose tolerance tests were performed on all patients. Lactose intolerance was diagnosed in 75.9 % of the patients with HT. Thirty-eight patients with LI were started on a lactose-restricted diet for 8 weeks. Thirty-eight patients with LI (30 euthyroid and 8 with subclinical hypothyroidism), and 12 patients without LI were included in the final analysis. The level of TSH significantly decreased in the euthyroid and subclinical hypothyroid patients with LI [from 2.06 ± 1.02 to 1.51 ±1.1 IU/mL and from 5.45 ± 0.74 to 2.25 ± 1.88 IU/mL,respectively (both P<0.05)]. However, the level of TSH in patients without LI did not change significantly over the 8 weeks (P>0.05). Lactose intolerance occurs at a high frequency in HT patients. Lactose restriction leads to decreased levels of TSH, and LI should be considered in hypothyroid patients who require increasing LT4 doses,have irregular TSH levels and are resistant to LT4 treatment.

Prevalence of Lactose Malabsorption and Lactose Intolerance in Pediatric Patients with Selected Gastrointestinal Diseases.

PubMed

Pawłowska, Katarzyna; Umławska, Wioleta; Iwańczak, Barbara

2015-01-01

Lactase is an enzyme involved in the hydrolysis of lactose. Deficiency of the enzyme (hypolactasia) may be determined genetically or arise secondarily to disease of small intestine. Under this condition, lactose enters the colon where it is fermented by intestinal microflora and turns to gases and short-chain fatty acids, causing gastrointestinal symptoms known as lactose intolerance (LI). To investigate the incidence of lactose malabsorption (LM), LI and the coexistence of these two conditions in children with upper gastrointestinal tract diseases (UGTD), malabsorption syndrome, inflammatory bowel disease (IBD) and functional gastrointestinal disorders (FGID). Hydrogen breath test (HBT) was conducted in 387 pediatric patients in years 2010-2013. Two hundred thirty two children with gastrointestinal tract diseases were selected and assigned to groups - UGTD, malabsorption syndrome, IBD or FGID. For each group the frequency of LM, frequency and severity of LI and the frequency of their co-occurrence were calculated. Lactose malabsorption was observed in 37.08% of patients with gastrointestinal diseases. Positive HBT result was the most common in children with malabsorption syndrome (52.50%) and less common in UGTD (30.85%), especially in ulcer disease (23.53%). Symptoms after lactose ingestion affected 36.64% of the subjects, and were more specific to lactose malabsorbers than to lactose absorbers (72.10% vs. 15.75%). The higher frequency of LI was noted in children with FGID, especially in irritable bowel syndrome (IBS) (65.22%). The lowest incidence of symptoms was obtained in children with UGTD, especially in those with ulcer disease (27.44%). The incidence of LM with LI was noted in 27.16% of all patients and was the highest in IBS (47.83%) and the lowest in ulcer disease (15.78%). Lactose malabsorption is a common problem in children with gastrointestinal diseases, especially in children with bowel diseases. Lactose intolerance is related to LM, but does not

Bistability of Cavity Magnon Polaritons

NASA Astrophysics Data System (ADS)

Wang, Yi-Pu; Zhang, Guo-Qiang; Zhang, Dengke; Li, Tie-Fu; Hu, C.-M.; You, J. Q.

2018-01-01

We report the first observation of the magnon-polariton bistability in a cavity magnonics system consisting of cavity photons strongly interacting with the magnons in a small yttrium iron garnet (YIG) sphere. The bistable behaviors emerged as sharp frequency switchings of the cavity magnon polaritons (CMPs) and related to the transition between states with large and small numbers of polaritons. In our experiment, we align, respectively, the [100] and [110] crystallographic axes of the YIG sphere parallel to the static magnetic field and find very different bistable behaviors (e.g., clockwise and counter-clockwise hysteresis loops) in these two cases. The experimental results are well fitted and explained as being due to the Kerr nonlinearity with either a positive or negative coefficient. Moreover, when the magnetic field is tuned away from the anticrossing point of CMPs, we observe simultaneous bistability of both magnons and cavity photons by applying a drive field on the lower branch.

Bistability of Cavity Magnon Polaritons.

PubMed

Wang, Yi-Pu; Zhang, Guo-Qiang; Zhang, Dengke; Li, Tie-Fu; Hu, C-M; You, J Q

2018-02-02

We report the first observation of the magnon-polariton bistability in a cavity magnonics system consisting of cavity photons strongly interacting with the magnons in a small yttrium iron garnet (YIG) sphere. The bistable behaviors emerged as sharp frequency switchings of the cavity magnon polaritons (CMPs) and related to the transition between states with large and small numbers of polaritons. In our experiment, we align, respectively, the [100] and [110] crystallographic axes of the YIG sphere parallel to the static magnetic field and find very different bistable behaviors (e.g., clockwise and counter-clockwise hysteresis loops) in these two cases. The experimental results are well fitted and explained as being due to the Kerr nonlinearity with either a positive or negative coefficient. Moreover, when the magnetic field is tuned away from the anticrossing point of CMPs, we observe simultaneous bistability of both magnons and cavity photons by applying a drive field on the lower branch.

The molecular basis of lactose intolerance.

PubMed

Campbell, Anthony K; Waud, Jonathan P; Matthews, Stephanie B

2009-01-01

A staggering 4000 million people cannot digest lactose, the sugar in milk, properly. All mammals, apart from white Northern Europeans and few tribes in Africa and Asia, lose most of their lactase, the enzyme that cleaves lactose into galactose and glucose, after weaning. Lactose intolerance causes gut and a range of systemic symptoms, though the threshold to lactose varies considerably between ethnic groups and individuals within a group. The molecular basis of inherited hypolactasia has yet to be identified, though two polymorphisms in the introns of a helicase upstream from the lactase gene correlate closely with hypolactasia, and thus lactose intolerance. The symptoms of lactose intolerance are caused by gases and toxins produced by anaerobic bacteria in the large intestine. Bacterial toxins may play a key role in several other diseases, such as diabetes, rheumatoid arthritis, multiple sclerosis and some cancers. The problem of lactose intolerance has been exacerbated because of the addition of products containing lactose to various foods and drinks without being on the label. Lactose intolerance fits exactly the illness that Charles Darwin suffered from for over 40 years, and yet was never diagnosed. Darwin missed something else--the key to our own evolution--the Rubicon some 300 million years ago that produced lactose and lactase in sufficient amounts to be susceptible to natural selection.

Lactose-free frozen yogurt: production and characteristics.

PubMed

Skryplonek, Katarzyna; Gomes, David; Viegas, Jorge; Pereira, Carlos; Henriques, Marta

2017-01-01

Nowadays, consumer demand is driving better and more nutritious dairy products. Changing from traditional to new lactose-free products poses technological challenges for the food industry in order to maintain or improve their food characteristics and consumer preferences. This study investigates the production of lactose-free frozen yogurt by enzymati- cally hydrolysis of lactose, and its influence on the final product characteristics. In the case of lactose-free products, commercial Ha-lactase® was used for hydrolysis, and the reaction occurred simultaneously with fermentation. The effect of lactose hydrolysis on the physicochemical properties, texture, viscosity, overrun and sensory attributes in the final product was investigated. After yogurt maturation, the acidity of the lactose-free product was significantly higher than in the control, suggesting that breaking down lactose enhances the fermentation process. Lactose-free frozen yogurt had significantly lower hardness and stickiness and higher viscosity than control frozen yogurt. Moreover, lactose hydrolysis promoted a smooth and creamy consistency, whereas in the case of conventional prod- ucts a coarse structure, due to the presence of large ice crystals, was identified. Hydrolysis of lactose also improved the sweetness and brightness of frozen yogurt. The improved textural properties of lactose-free product results from the fact that monosaccharides produced during lactose hydrolysis depress the freezing point of the mix, which enables product with softer structure and bigger resistance to ice recrystallization to be obtained. The study showed that lactose-free frozen yogurt may be used successfully for production of novel lactose-free frozen desserts. Lactose hydrolysis improves the texture and viscosity of the product,     as well as enhancing its sensory quality.

Systematic review: effective management strategies for lactose intolerance.

PubMed

Shaukat, Aasma; Levitt, Michael D; Taylor, Brent C; MacDonald, Roderick; Shamliyan, Tatyana A; Kane, Robert L; Wilt, Timothy J

2010-06-15

Lactose intolerance resulting in gastrointestinal symptoms is a common health concern. Diagnosis and management of this condition remain unclear. To assess the maximum tolerable dose of lactose and interventions for reducing symptoms of lactose intolerance among persons with lactose intolerance and malabsorption. Multiple electronic databases, including MEDLINE and the Cochrane Library, for trials published in English from 1967 through November 2009. Randomized, controlled trials of individuals with lactose intolerance or malabsorption. Three investigators independently reviewed articles, extracted data, and assessed study quality. 36 unique randomized studies (26 on lactase- or lactose-hydrolyzed milk supplements, lactose-reduced milk, or tolerable doses of lactose; 7 on probiotics; 2 on incremental lactose administration for colonic adaptation; and 1 on another agent) met inclusion criteria. Moderate-quality evidence indicated that 12 to 15 g of lactose (approximately 1 cup of milk) is well tolerated by most adults. Evidence was insufficient that lactose-reduced solution or milk with a lactose content of 0 to 2 g, compared with greater than 12 g, is effective in reducing symptoms of lactose intolerance. Evidence for probiotics, colonic adaptation, and other agents was also insufficient. Most studies evaluated persons with lactose malabsorption rather than lactose intolerance. Variation in enrollment criteria, outcome reporting, and the composition and dosing of studied agents precluded pooling of results and limited interpretation. Most individuals with presumed lactose intolerance or malabsorption can tolerate 12 to 15 g of lactose. Additional studies are needed to determine the effectiveness of lactose intolerance treatment.

[Calcium supplementation uncovering lactose intolerance - a case report].

PubMed

Trifina, Eva; Geissler, Dietmar; Zwettler, Elisabeth; Klaushofer, Klaus; Mikosch, Peter

2012-03-01

A 44 yr-old female with osteoporosis had no relevant gastrointestinal symptoms and did not avoid any specific food. However, after prescription of a lactose-rich calcium supplementation, clinical symptoms suspicious for lactose intolerance occurred, which were thereafter confirmed by a lactose tolerance test. Lactose intolerance may present with only slight or subtle symptoms. Drugs containing lactose may induce or increase gastrointestinal symptoms in patients with lactose intolerance. In case of gastrointestinal symptoms occurring after the initiation of drugs containing lactose, the possibility of lactose intolerance should be considered and tested by lactose tolerance test or genetic testing for the LCT (-13910) polymorphism. Due to the prevalence of about 15-25% lactose intolerance in the Austrian population, lactose free drugs should be prescribed as widely as possible.

Bistable microelectromechanical actuator

DOEpatents

Fleming, James G.

1999-01-01

A bistable microelectromechanical (MEM) actuator is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can be formed for applications including nonvolatile memories, optical displays and optical computing.

Bistable microelectromechanical actuator

DOEpatents

Fleming, J.G.

1999-02-02

A bistable microelectromechanical (MEM) actuator is formed on a substrate and includes a stressed membrane of generally rectangular shape that upon release assumes a curvilinear cross-sectional shape due to attachment at a midpoint to a resilient member and at opposing edges to a pair of elongate supports. The stressed membrane can be electrostatically switched between a pair of mechanical states having mirror-image symmetry, with the MEM actuator remaining in a quiescent state after a programming voltage is removed. The bistable MEM actuator according to various embodiments of the present invention can be used to form a nonvolatile memory element, an optical modulator (with a pair of mirrors supported above the membrane and moving in synchronism as the membrane is switched), a switchable mirror (with a single mirror supported above the membrane at the midpoint thereof) and a latching relay (with a pair of contacts that open and close as the membrane is switched). Arrays of bistable MEM actuators can be formed for applications including nonvolatile memories, optical displays and optical computing. 49 figs.

Nonlinear Geometric Effects in Mechanical Bistable Morphing Structures

NASA Astrophysics Data System (ADS)

Chen, Zi; Guo, Qiaohang; Majidi, Carmel; Chen, Wenzhe; Srolovitz, David J.; Haataja, Mikko P.

2012-09-01

Bistable structures associated with nonlinear deformation behavior, exemplified by the Venus flytrap and slap bracelet, can switch between different functional shapes upon actuation. Despite numerous efforts in modeling such large deformation behavior of shells, the roles of mechanical and nonlinear geometric effects on bistability remain elusive. We demonstrate, through both theoretical analysis and tabletop experiments, that two dimensionless parameters control bistability. Our work classifies the conditions for bistability, and extends the large deformation theory of plates and shells.

Is it just lactose intolerance?

PubMed

Olivier, Celso Eduardo; Lorena, Sônia Letícia Silva; Pavan, Célia Regina; dos Santos, Raquel Acácia Pereira Gonçalves; dos Santos Lima, Regiane Patussi; Pinto, Daiana Guedes; da Silva, Mariana Dias; de Lima Zollner, Ricardo

2012-01-01

Acquired delayed-onset hypolactasia is a common autosomal recessive condition. Cow's milk allergies, conversely, are less common conditions that may manifest with equivalent symptoms and are able to simulate and/or aggravate lactose intolerance. This study was designed to evaluate the contribution of IgE-mediated cow's milk sensitization to the symptomatology of adult patients with lactose-free diet refractory lactose intolerance. Forty-six adult patients with lactose intolerance and persistent symptoms despite a lactose-free diet underwent skin-prick test to investigate cow's milk, goat's milk, and soy protein-specific-IgE. SDS-PAGE immunoblotting was used to investigate the presence of cow's milk protein-specific IgE. The percentage of patients who had skin reactions to whole cow's milk, alpha-lactalbumin, beta-lactoglobulin, caseins, goat's milk, and soy was 69.5, 36.9, 56.5, 56.5%, 54.3, and 50%, respectively. The percentage of patients with immunoblot-detected IgE specific for alpha-lactalbumin, beta-lactoglobulin, caseins, and bovine serum albumin was 21.7, 63, 67.3, and 2.1%, respectively. IgE-mediated sensitization to cow's milk is a frequent comorbidity in subjects with lactose-free diet refractory lactose intolerance and is worth consideration in patients with this condition.

Valley-Selective Exciton Bistability in a Suspended Monolayer Semiconductor

NASA Astrophysics Data System (ADS)

Xie, Hongchao; Jiang, Shengwei; Shan, Jie; Mak, Kin Fai

2018-05-01

We demonstrate robust power- and wavelength-dependent optical bistability in fully suspended monolayers of WSe2 near the exciton resonance. Bistability has been achieved under continuous-wave optical excitation at an intensity level of 10^3 W/cm^2. The observed bistability is originated from a photo-thermal mechanism, which provides both optical nonlinearity and passive feedback, two essential elements for optical bistability. Under a finite magnetic field, the exciton bistability becomes helicity dependent, which enables repeatable switching of light purely by its polarization.

Lactose intolerance: from diagnosis to correct management.

PubMed

Di Rienzo, T; D'Angelo, G; D'Aversa, F; Campanale, M C; Cesario, V; Montalto, M; Gasbarrini, A; Ojetti, V

2013-01-01

This review discusses one of the most relevant problems in gastrointestinal clinical practice: lactose intolerance. The role of lactase-persistence alleles the diagnosis of lactose malabsorption the development of lactose intolerance symptoms and its management. Most people are born with the ability to digest lactose, the major carbohydrate in milk and the main source of nutrition until weaning. Approximately, 75% of the world's population loses this ability at some point, while others can digest lactose into adulthood. Symptoms of lactose intolerance include abdominal pain, bloating, flatulence and diarrhea with a considerable intraindividual and interindividual variability in the severity. Diagnosis is most commonly performed by the non invasive lactose hydrogen breath test. Management of lactose intolerance consists of two possible clinical choice not mutually exclusive: alimentary restriction and drug therapy.

Lactose Intolerance (For Teens)

MedlinePlus

... gut and gets broken down by bacteria, causing gas, bloating, stomach cramps, and diarrhea. Lactose intolerance is ... lactose intolerance will experience nausea, stomach cramps, bloating, gas, and diarrhea. This can be unpleasant, not to ...

Regulation of the Salmonella enterica std fimbrial operon by DNA adenine methylation, SeqA, and HdfR.

PubMed

Jakomin, Marcello; Chessa, Daniela; Bäumler, Andreas J; Casadesús, Josep

2008-11-01

DNA adenine methylase (dam) mutants of Salmonella enterica serovar Typhimurium grown under laboratory conditions express the std fimbrial operon, which is tightly repressed in the wild type. Here, we show that uncontrolled production of Std fimbriae in S. enterica serovar Typhimurium dam mutants contributes to attenuation in mice, as indicated by the observation that an stdA dam strain is more competitive than a dam strain upon oral infection. Dam methylation appears to regulate std transcription, rather than std mRNA stability or turnover. A genetic screen for std regulators showed that the GATC-binding protein SeqA directly or indirectly represses std expression, while the poorly characterized yifA gene product serves as an std activator. YifA encodes a putative LysR-like protein and has been renamed HdfR, like its Escherichia coli homolog. Activation of std expression by HdfR is observed only in dam and seqA backgrounds. These data suggest that HdfR directly or indirectly activates std transcription. Since SeqA is unable to bind nonmethylated DNA, it is possible that std operon derepression in dam and seqA mutants may result from unconstrained HdfR-mediated activation of std transcription. Derepression of std in dam and seqA mutants of S. enterica occurs in only a fraction of the bacterial population, suggesting the occurrence of either bistable expression or phase variation.

Compaction behaviour and mechanical strength of lactose-sodium starch glycolate and lactose-croscarmellose sodium binary tablets

NASA Astrophysics Data System (ADS)

Ashikin Yaakub, Nur; Shamsul Anuar, Mohd; Tahir, Suraya Mohd

2018-04-01

The focus of this study is to elucidate the effects of adding super disintegrants (SSG and Acdisol) to a filler (lactose) in terms of the compaction behaviour and mechanical strength of the formed binary tablets. The tablets were formed in a uniaxial die compaction process with compaction pressures ranging from 37.7MPa to 150.7 MPa. Consequently, the findings indicated that the increasing of the compaction pressure and the percentage mass composition of the super disintegrants would led to the increased in the strength of the tablets as well as their plastic energies, where this was more apparent for the case of the binary lactose/Acdisol tablets. In addition, as the compaction pressure increased, the maximum ejection pressure required to eject the tablet from the die cavity also increased. In contrast, a decreased in the maximum ejection pressure was observed as the composition of both super disintegrants increased in the lactose-super disintegrant binary tablets. In conclusion, the addition of super disintegrant; SSG with lactose and Acdisol with lactose; would enhanced the mechanical strength of lactose based tablets especially for the case of acdisol-lactose binary tablets in the experimental conditions adopted in this current work.

Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment.

PubMed

Misselwitz, Benjamin; Pohl, Daniel; Frühauf, Heiko; Fried, Michael; Vavricka, Stephan R; Fox, Mark

2013-06-01

Lactose malabsorption is a common condition caused by reduced expression or activity of lactase in the small intestine. In such patients, lactose intolerance is characterized by abdominal symptoms (e.g. nausea, bloating, and pain) after ingestion of dairy products. The genetic basis of lactose malabsorption is established and several tests for this condition are available, including genetic, endoscopic, and H2-breath tests. In contrast, lactose intolerance is less well understood. Recent studies show that the risk of symptoms after lactose ingestion depends on the dose of lactose, lactase expression, intestinal flora, and sensitivity of the gastrointestinal tract. Lactose intolerance has recently been defined as symptoms developing after ingestion of lactose which do not develop after placebo challenge in a person with lactose maldigestion. Such blinded testing might be especially important in those with functional gastrointestinal diseases in whom self-reported lactose intolerance is common. However, placebo-controlled testing is not part of current clinical practice. Updated protocols and high-quality outcome studies are needed. Treatment options of lactose intolerance include lactose-reduced diet and enzyme replacement. Documenting the response to multiple doses can guide rational dietary management; however, the clinical utility of this strategy has not been tested. This review summarizes the genetic basis, diagnosis, and treatment of lactose malabsorption and intolerance.

Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment

PubMed Central

Pohl, Daniel; Frühauf, Heiko; Fried, Michael; Vavricka, Stephan R; Fox, Mark

2013-01-01

Lactose malabsorption is a common condition caused by reduced expression or activity of lactase in the small intestine. In such patients, lactose intolerance is characterized by abdominal symptoms (e.g. nausea, bloating, and pain) after ingestion of dairy products. The genetic basis of lactose malabsorption is established and several tests for this condition are available, including genetic, endoscopic, and H2-breath tests. In contrast, lactose intolerance is less well understood. Recent studies show that the risk of symptoms after lactose ingestion depends on the dose of lactose, lactase expression, intestinal flora, and sensitivity of the gastrointestinal tract. Lactose intolerance has recently been defined as symptoms developing after ingestion of lactose which do not develop after placebo challenge in a person with lactose maldigestion. Such blinded testing might be especially important in those with functional gastrointestinal diseases in whom self-reported lactose intolerance is common. However, placebo-controlled testing is not part of current clinical practice. Updated protocols and high-quality outcome studies are needed. Treatment options of lactose intolerance include lactose-reduced diet and enzyme replacement. Documenting the response to multiple doses can guide rational dietary management; however, the clinical utility of this strategy has not been tested. This review summarizes the genetic basis, diagnosis, and treatment of lactose malabsorption and intolerance. PMID:24917953

Lactose Intolerance (For Kids)

MedlinePlus

... First Aid & Safety Doctors & Hospitals Videos Recipes for Kids Kids site Sitio para niños How the Body Works ... Educators Search English Español Lactose Intolerance KidsHealth / For Kids / Lactose Intolerance What's in this article? What Is ...

Multistability in the lactose utilization network of Escherichia coli

NASA Astrophysics Data System (ADS)

Ozbudak, Ertugrul M.; Thattai, Mukund; Lim, Han N.; Shraiman, Boris I.; van Oudenaarden, Alexander

2004-02-01

Multistability, the capacity to achieve multiple internal states in response to a single set of external inputs, is the defining characteristic of a switch. Biological switches are essential for the determination of cell fate in multicellular organisms, the regulation of cell-cycle oscillations during mitosis and the maintenance of epigenetic traits in microbes. The multistability of several natural and synthetic systems has been attributed to positive feedback loops in their regulatory networks. However, feedback alone does not guarantee multistability. The phase diagram of a multistable system, a concise description of internal states as key parameters are varied, reveals the conditions required to produce a functional switch. Here we present the phase diagram of the bistable lactose utilization network of Escherichia coli. We use this phase diagram, coupled with a mathematical model of the network, to quantitatively investigate processes such as sugar uptake and transcriptional regulation in vivo. We then show how the hysteretic response of the wild-type system can be converted to an ultrasensitive graded response. The phase diagram thus serves as a sensitive probe of molecular interactions and as a powerful tool for rational network design.

Steady state statistical correlations predict bistability in reaction motifs.

PubMed

Chakravarty, Suchana; Barik, Debashis

2017-03-28

Various cellular decision making processes are regulated by bistable switches that take graded input signals and convert them to binary all-or-none responses. Traditionally, a bistable switch generated by a positive feedback loop is characterized either by a hysteretic signal response curve with two distinct signaling thresholds or by characterizing the bimodality of the response distribution in the bistable region. To identify the intrinsic bistability of a feedback regulated network, here we propose that bistability can be determined by correlating higher order moments and cumulants (≥2) of the joint steady state distributions of two components connected in a positive feedback loop. We performed stochastic simulations of four feedback regulated models with intrinsic bistability and we show that for a bistable switch with variation of the signal dose, the steady state variance vs. covariance adopts a signatory cusp-shaped curve. Further, we find that the (n + 1)th order cross-cumulant vs. nth order cross-cumulant adopts a closed loop structure for at least n = 3. We also propose that our method is capable of identifying systems without intrinsic bistability even though the system may show bimodality in the marginal response distribution. The proposed method can be used to analyze single cell protein data measured at steady state from experiments such as flow cytometry.

A global analysis of adaptive evolution of operons in cyanobacteria.

PubMed

Memon, Danish; Singh, Abhay K; Pakrasi, Himadri B; Wangikar, Pramod P

2013-02-01

Operons are an important feature of prokaryotic genomes. Evolution of operons is hypothesized to be adaptive and has contributed significantly towards coordinated optimization of functions. Two conflicting theories, based on (i) in situ formation to achieve co-regulation and (ii) horizontal gene transfer of functionally linked gene clusters, are generally considered to explain why and how operons have evolved. Furthermore, effects of operon evolution on genomic traits such as intergenic spacing, operon size and co-regulation are relatively less explored. Based on the conservation level in a set of diverse prokaryotes, we categorize the operonic gene pair associations and in turn the operons as ancient and recently formed. This allowed us to perform a detailed analysis of operonic structure in cyanobacteria, a morphologically and physiologically diverse group of photoautotrophs. Clustering based on operon conservation showed significant similarity with the 16S rRNA-based phylogeny, which groups the cyanobacterial strains into three clades. Clade C, dominated by strains that are believed to have undergone genome reduction, shows a larger fraction of operonic genes that are tightly packed in larger sized operons. Ancient operons are in general larger, more tightly packed, better optimized for co-regulation and part of key cellular processes. A sub-clade within Clade B, which includes Synechocystis sp. PCC 6803, shows a reverse trend in intergenic spacing. Our results suggest that while in situ formation and vertical descent may be a dominant mechanism of operon evolution in cyanobacteria, optimization of intergenic spacing and co-regulation are part of an ongoing process in the life-cycle of operons.

Rheological properties of lactose-free dairy desserts.

PubMed

Sahin, Serpil; Hamamci, Haluk; Garayev, Sultan

2016-10-01

People suffering from lactose intolerance cannot digest milk or lactose-containing foods. Lactose-free diet is essential for them since they do not have the ability to produce lactase to breakdown milk sugar. Physical properties of lactose-free dairy desserts will most probably be different than that of lactose containing ones because of lactose hydrolysis. In this study, it was aimed to analyze the rheological and textural behaviors of different lactose-free dessert formulations containing different gum types and different waxy maize starch and sucrose concentrations. Waxy maize starch was used at concentrations of 0.032 g·mL -1 , 0.040 g·mL -1 , and 0.048 g·mL -1 In addition to waxy maize starch, guar gum, gum arabic, or κ-carrageenan at two different concentrations (1.0% w/w and 0.5% w/w) was added. Sucrose was added at concentrations of 0.14 g·mL -1 and 0.10 g·mL -1 in lactose-free desserts. Power law model was found to be suitable to explain the flow behavior of desserts. The storage and loss modulus of lactose-free desserts were higher than that of lactose-containing desserts. The κ-Carrageenan was found to be the most effective gum for structure build-up. © The Author(s) 2016.

Adult lactose digestion status and effects on disease.

PubMed

Szilagyi, Andrew

2015-04-01

Adult assimilation of lactose divides humans into dominant lactase-persistent and recessive nonpersistent phenotypes. To review three medical parameters of lactose digestion, namely: the changing concept of lactose intolerance; the possible impact on diseases of microbial adaptation in lactase-nonpersistent populations; and the possibility that the evolution of lactase has influenced some disease pattern distributions. A PubMed, Google Scholar and manual review of articles were used to provide a narrative review of the topic. The concept of lactose intolerance is changing and merging with food intolerances. Microbial adaptation to regular lactose consumption in lactase-nonpersistent individuals is supported by limited evidence. There is evidence suggestive of a relationship among geographical distributions of latitude, sunhine exposure and lactase proportional distributions worldwide. The definition of lactose intolerance has shifted away from association with lactose maldigestion. Lactose sensitivity is described equally in lactose digesters and maldigesters. The important medical consequence of withholding dairy foods could have a detrimental impact on several diseases; in addition, microbial adaptation in lactase-nonpersistent populations may alter risk for some diseases. There is suggestive evidence that the emergence of lactase persistence, together with human migrations before and after the emergence of lactase persistence, have impacted modern-day diseases. Lactose maldigestion and lactose intolerance are not synonymous. Withholding dairy foods is a poor method to treat lactose intolerance. Further epidemiological work could shed light on the possible effects of microbial adaptation in lactose maldigesters. The evolutionary impact of lactase may be still ongoing.

21 CFR 184.1979a - Reduced lactose whey.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Reduced lactose whey. 184.1979a Section 184.1979a... Listing of Specific Substances Affirmed as GRAS § 184.1979a Reduced lactose whey. (a) Reduced lactose whey is the substance obtained by the removal of lactose from whey. The lactose content of the finished...

21 CFR 184.1979a - Reduced lactose whey.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Reduced lactose whey. 184.1979a Section 184.1979a... Listing of Specific Substances Affirmed as GRAS § 184.1979a Reduced lactose whey. (a) Reduced lactose whey is the substance obtained by the removal of lactose from whey. The lactose content of the finished...

Does visual attention drive the dynamics of bistable perception?

PubMed

Dieter, Kevin C; Brascamp, Jan; Tadin, Duje; Blake, Randolph

2016-10-01

How does attention interact with incoming sensory information to determine what we perceive? One domain in which this question has received serious consideration is that of bistable perception: a captivating class of phenomena that involves fluctuating visual experience in the face of physically unchanging sensory input. Here, some investigations have yielded support for the idea that attention alone determines what is seen, while others have implicated entirely attention-independent processes in driving alternations during bistable perception. We review the body of literature addressing this divide and conclude that in fact both sides are correct-depending on the form of bistable perception being considered. Converging evidence suggests that visual attention is required for alternations in the type of bistable perception called binocular rivalry, while alternations during other types of bistable perception appear to continue without requiring attention. We discuss some implications of this differential effect of attention for our understanding of the mechanisms underlying bistable perception, and examine how these mechanisms operate during our everyday visual experiences.

Valley-Selective Exciton Bistability in a Suspended Monolayer Semiconductor.

PubMed

Xie, Hongchao; Jiang, Shengwei; Shan, Jie; Mak, Kin Fai

2018-05-09

We demonstrate robust optical bistability, the phenomenon of two well-discriminated stable states depending upon the history of the optical input, in fully suspended monolayers of WSe 2 at low temperatures near the exciton resonance. Optical bistability has been achieved under continuous-wave optical excitation that is red-detuned from the exciton resonance at an intensity level of 10 3 W/cm 2 . The observed bistability is originated from a photothermal mechanism, which provides both optical nonlinearity and passive feedback, two essential elements for optical bistability. The low thermal conductance of suspended samples is primarily responsible for the low excitation intensities required for optical bistability. Under a finite out-of-plane magnetic field, the exciton bistability becomes helicity dependent due to the exciton valley Zeeman effect, which enables repeatable switching of the sample reflectance by light polarization. Our study has opened up exciting opportunities in controlling light with light, including its wavelength, power, and polarization, using monolayer semiconductors.

A phylogenomic analysis of the Actinomycetales mce operons.

PubMed

Casali, Nicola; Riley, Lee W

2007-02-26

The genome of Mycobacterium tuberculosis harbors four copies of a cluster of genes termed mce operons. Despite extensive research that has demonstrated the importance of these operons on infection outcome, their physiological function remains obscure. Expanding databases of complete microbial genome sequences facilitate a comparative genomic approach that can provide valuable insight into the role of uncharacterized proteins. The M. tuberculosis mce loci each include two yrbE and six mce genes, which have homology to ABC transporter permeases and substrate-binding proteins, respectively. Operons with an identical structure were identified in all Mycobacterium species examined, as well as in five other Actinomycetales genera. Some of the Actinomycetales mce operons include an mkl gene, which encodes an ATPase resembling those of ABC uptake transporters. The phylogenetic profile of Mkl orthologs exactly matched that of the Mce and YrbE proteins. Through topology and motif analyses of YrbE homologs, we identified a region within the penultimate cytoplasmic loop that may serve as the site of interaction with the putative cognate Mkl ATPase. Homologs of the exported proteins encoded adjacent to the M. tuberculosis mce operons were detected in a conserved chromosomal location downstream of the majority of Actinomycetales operons. Operons containing linked mkl, yrbE and mce genes, resembling the classic organization of an ABC importer, were found to be common in Gram-negative bacteria and appear to be associated with changes in properties of the cell surface. Evidence presented suggests that the mce operons of Actinomycetales species and related operons in Gram-negative bacteria encode a subfamily of ABC uptake transporters with a possible role in remodeling the cell envelope.

A phylogenomic analysis of the Actinomycetales mce operons

PubMed Central

Casali, Nicola; Riley, Lee W

2007-01-01

Background The genome of Mycobacterium tuberculosis harbors four copies of a cluster of genes termed mce operons. Despite extensive research that has demonstrated the importance of these operons on infection outcome, their physiological function remains obscure. Expanding databases of complete microbial genome sequences facilitate a comparative genomic approach that can provide valuable insight into the role of uncharacterized proteins. Results The M. tuberculosis mce loci each include two yrbE and six mce genes, which have homology to ABC transporter permeases and substrate-binding proteins, respectively. Operons with an identical structure were identified in all Mycobacterium species examined, as well as in five other Actinomycetales genera. Some of the Actinomycetales mce operons include an mkl gene, which encodes an ATPase resembling those of ABC uptake transporters. The phylogenetic profile of Mkl orthologs exactly matched that of the Mce and YrbE proteins. Through topology and motif analyses of YrbE homologs, we identified a region within the penultimate cytoplasmic loop that may serve as the site of interaction with the putative cognate Mkl ATPase. Homologs of the exported proteins encoded adjacent to the M. tuberculosis mce operons were detected in a conserved chromosomal location downstream of the majority of Actinomycetales operons. Operons containing linked mkl, yrbE and mce genes, resembling the classic organization of an ABC importer, were found to be common in Gram-negative bacteria and appear to be associated with changes in properties of the cell surface. Conclusion Evidence presented suggests that the mce operons of Actinomycetales species and related operons in Gram-negative bacteria encode a subfamily of ABC uptake transporters with a possible role in remodeling the cell envelope. PMID:17324287

Adult lactose digestion status and effects on disease

PubMed Central

Szilagyi, Andrew

2015-01-01

BACKGROUND: Adult assimilation of lactose divides humans into dominant lactase-persistent and recessive nonpersistent phenotypes. OBJECTIVES: To review three medical parameters of lactose digestion, namely: the changing concept of lactose intolerance; the possible impact on diseases of microbial adaptation in lactase-nonpersistent populations; and the possibility that the evolution of lactase has influenced some disease pattern distributions. METHODS: A PubMed, Google Scholar and manual review of articles were used to provide a narrative review of the topic. RESULTS: The concept of lactose intolerance is changing and merging with food intolerances. Microbial adaptation to regular lactose consumption in lactase-nonpersistent individuals is supported by limited evidence. There is evidence suggestive of a relationship among geographical distributions of latitude, sunhine exposure and lactase proportional distributions worldwide. DISCUSSION: The definition of lactose intolerance has shifted away from association with lactose maldigestion. Lactose sensitivity is described equally in lactose digesters and maldigesters. The important medical consequence of withholding dairy foods could have a detrimental impact on several diseases; in addition, microbial adaptation in lactase-nonpersistent populations may alter risk for some diseases. There is suggestive evidence that the emergence of lactase persistence, together with human migrations before and after the emergence of lactase persistence, have impacted modern-day diseases. CONCLUSIONS: Lactose maldigestion and lactose intolerance are not synonymous. Withholding dairy foods is a poor method to treat lactose intolerance. Further epidemiological work could shed light on the possible effects of microbial adaptation in lactose maldigesters. The evolutionary impact of lactase may be still ongoing. PMID:25855879

Lactose carrier mutants of Escherichia coli with changes in sugar recognition (lactose versus melibiose).

PubMed

Varela, M F; Brooker, R J; Wilson, T H

1997-09-01

The purpose of this research was to identify amino acid residues that mediate substrate recognition in the lactose carrier of Escherichia coli. The lactose carrier transports the alpha-galactoside sugar melibiose as well as the beta-galactoside sugar lactose. Mutants from cells containing the lac genes on an F factor were selected by the ability to grow on succinate in the presence of the toxic galactoside beta-thio-o-nitrophenylgalactoside. Mutants that grew on melibiose minimal plates but failed to grow on lactose minimal plates were picked. In sugar transport assays, mutant cells showed the striking result of having low levels of lactose downhill transport but high levels of melibiose downhill transport. Accumulation (uphill) of melibiose was completely defective in all of the mutants. Kinetic analysis of melibiose transport in the mutants showed either no change or a greater than normal apparent affinity for melibiose. PCR was used to amplify the lacY DNA of each mutant, which was then sequenced by the Sanger method. The following six mutations were found in the lacY structural genes of individual mutants: Tyr-26-->Asp, Phe-27-->Tyr, Phe-29-->Leu, Asp-240-->Val, Leu-321-->Gln, and His-322-->Tyr. We conclude from these experiments that Tyr-26, Phe-27, Phe-29 (helix 1), Asp-240 (helix 7), Leu-321, and His-322 (helix 10) either directly or indirectly mediate sugar recognition in the lactose carrier of E. coli.

[Efficacy of Lactose-free Milk in Korean Adults with Lactose Intolerance].

PubMed

Park, Sun Hee; Chang, Young Woon; Kim, Soo Jung; Lee, Min Hye; Nam, Ji Hyeok; Oh, Chi Hyuk; Kim, Jung-Wook; Jang, Jae-Young; Yang, Jin Oh; Yoo, Jin Ah; Chung, Jin Young

2016-01-25

Lactose-free milk (LFM) is available for nutrient supply for those with lactose intolerance (LI). However, there are no consistent results of the efficacy of LFM in LI subjects. We aimed to examine the changes of gastrointestinal (GI) symptoms and hydrogen breath test (HBT) values after ingestion of lactose contained milk (LCM) vs. LFM. From May 2015 to September 2015, thirty-five healthy adults with history of LCM-induced GI symptoms were recruited at a tertiary hospital. For the diagnosis of LI, HBT with LCM 550 mL (lactose 25 g) was performed every 20 minutes for 3 hours. The test was defined as "positive" when H2 peak exceeded 20 ppm above baseline values (ΔH2>20 ppm). When the subjects are diagnosed as LI, the second HBT using LFM 550 mL (lactose 0 g) was performed 7 days later. Subjects were asked to complete a questionnaire about the occurrence and severity of GI symptoms. Among a total of 35 subjects, 31 were diagnosed with LI at first visit, and their LCM-related symptoms were abdominal pain (98.6%), borborygmus (96.8%), diarrhea (90.3%), and flatus (87.1%). The ΔH2 value in subjects taking LCM (103.7±66.3ppm) significantly decreased to 6.3±4.9 ppm after ingesting LFM (p<0.0001). There were also significant reduction in total symptom scores and the severity of each symptom when LCM was changed to LFM (p<0.0001). This is the first report that LFM reduce LCM-related GI symptoms and H2 production in Korean adults. LFM can be an effective alternative for LCM in adults with LI.

Temporal nonlocality in bistable perception

NASA Astrophysics Data System (ADS)

Atmanspacher, Harald; Filk, Thomas

2012-12-01

A novel conceptual framework for theoretical psychology is presented and illustrated for the example of bistable perception. A basic formal feature of this framework is the non-commutativity of operations acting on mental states. A corresponding model for the bistable perception of ambiguous stimuli, the Necker-Zeno model, is sketched and some empirical evidence for it so far is described. It is discussed how a temporal nonlocality of mental states, predicted by the model, can be understood and tested.

Does visual attention drive the dynamics of bistable perception?

PubMed Central

Dieter, Kevin C.; Brascamp, Jan; Tadin, Duje; Blake, Randolph

2016-01-01

How does attention interact with incoming sensory information to determine what we perceive? One domain in which this question has received serious consideration is that of bistable perception: a captivating class of phenomena that involves fluctuating visual experience in the face of physically unchanging sensory input. Here, some investigations have yielded support for the idea that attention alone determines what is seen, while others have implicated entirely attention-independent processes in driving alternations during bistable perception. We review the body of literature addressing this divide and conclude that in fact both sides are correct – depending on the form of bistable perception being considered. Converging evidence suggests that visual attention is required for alternations in the type of bistable perception called binocular rivalry, while alternations during other types of bistable perception appear to continue without requiring attention. We discuss some implications of this differential effect of attention for our understanding of the mechanisms underlying bistable perception, and examine how these mechanisms operate during our everyday visual experiences. PMID:27230785

Technological aspects of lactose-hydrolyzed milk powder.

PubMed

Torres, Jansen Kelis Ferreira; Stephani, Rodrigo; Tavares, Guilherme M; de Carvalho, Antônio Fernandes; Costa, Renata Golin Bueno; de Almeida, Carlos Eduardo Rocha; Almeida, Mariana Ramos; de Oliveira, Luiz Fernando Cappa; Schuck, Pierre; Perrone, Ítalo Tuler

2017-11-01

Few reports describe the effect of lactose hydrolysis on the properties of milk powder during production and storage. Hence, the aim of this study was to evaluate the effects of five different levels of enzymatic lactose hydrolysis during the production and storage of milk powder. As the lactose hydrolysis rate increased, adhesion to the drying chamber also increased, due to higher levels of particle agglomeration. Additionally, more brown powder was obtained when the lactose hydrolysis rate was increased, which in turn negatively affected rehydration ability. Using Raman spectroscopy, crystallization of the lactose residues in various samples was assessed over 6weeks of accelerated aging at a room temperature environment with 75.5% of air moisture. Products with 25% or greater lactose hydrolysis showed no signs of crystallization, in contrast to the non-hydrolyzed sample. Copyright © 2017. Published by Elsevier Ltd.

A Radiochemical Biotechnological Approach: Preliminary Study of Lactose Uptake Rate by Kefir Cells, Using 14C-labeled Lactose, in Anaerobic Fermentation

NASA Astrophysics Data System (ADS)

Golfinopoulos, A.; Soupioni, M.; Kanellaki, M.; Koutinas, A. A.

2008-08-01

The effect of initial lactose concentration on lactose uptake rate by kefir free cells, during the lactose fermentation, was studied in this work. For the investigation 14C-labelled lactose was used due to the fact that labeled and unlabeled molecules are fermented in the same way. The results illustrated lactose uptake rates are about up to two fold higher at lower initial ∘Bé densities as compared with higher initial ∘Bé densities.

Bistability: Requirements on Cell-Volume, Protein Diffusion, and Thermodynamics

PubMed Central

Endres, Robert G.

2015-01-01

Bistability is considered wide-spread among bacteria and eukaryotic cells, useful e.g. for enzyme induction, bet hedging, and epigenetic switching. However, this phenomenon has mostly been described with deterministic dynamic or well-mixed stochastic models. Here, we map known biological bistable systems onto the well-characterized biochemical Schlögl model, using analytical calculations and stochastic spatiotemporal simulations. In addition to network architecture and strong thermodynamic driving away from equilibrium, we show that bistability requires fine-tuning towards small cell volumes (or compartments) and fast protein diffusion (well mixing). Bistability is thus fragile and hence may be restricted to small bacteria and eukaryotic nuclei, with switching triggered by volume changes during the cell cycle. For large volumes, single cells generally loose their ability for bistable switching and instead undergo a first-order phase transition. PMID:25874711

Fundamental role of bistability in optimal homeostatic control

NASA Astrophysics Data System (ADS)

Wang, Guanyu

2013-03-01

Bistability is a fundamental phenomenon in nature and has a number of fine properties. However, these properties are consequences of bistability at the physiological level, which do not explain why it had to emerge during evolution. Using optimal homeostasis as the first principle and Pontryagin's Maximum Principle as the optimization approach, I find that bistability emerges as an indispensable control mechanism. Because the mathematical model is general and the result is independent of parameters, it is likely that most biological systems use bistability to control homeostasis. Glucose homeostasis represents a good example. It turns out that bistability is the only solution to a dilemma in glucose homeostasis: high insulin efficiency is required for rapid plasma glucose clearance, whereas an insulin sparing state is required to guarantee the brain's safety during fasting. This new perspective can illuminate studies on the twin epidemics of obesity and diabetes and the corresponding intervening strategies. For example, overnutrition and sedentary lifestyle may represent sudden environmental changes that cause the lose of optimality, which may contribute to the marked rise of obesity and diabetes in our generation.

Lactose uptake driven by galactose efflux in Streptococcus thermophilus: Evidence for a galactose-lactose antiporter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hutkins, R.W.; Ponne, C.

1991-04-01

Galactose-nonfermenting (Gal{sup {minus}}) Streptococcus thermophilus TS2 releases galactose into the extracellular medium when grown in medium containing excess lactose. Starved and de-energized Gal{sup {minus}} cells, however, could be loaded with galactose to levels approximately equal to the extracellular concentration (0 to 50 mM). When loaded cells were separated from the medium and resuspended in fresh broth containing 5 mM lactose, galactose efflux occurred. De-energized, galactose-loaded cells, resuspended in buffer or medium, accumulated ({sup 14}C)lactose at a greater rate and to significantly higher intracellular concentrations than unloaded cells. Uptake of lactose by loaded cells was inhibited more than that by unloadedmore » cells in the presence of extracellular galactose, indicating that a galactose gradient was involved in the exchange system. When de-energized, galactose-loaded cells were resuspended in carbohydrate-free medium at pH 6.7, a proton motive force ({Delta}p) of 86 to 90 mV was formed, whereas de-energized, nonloaded cells maintained a {Delta}p of about 56 mV. However, uptake of lactose by loaded cells occurred when the proton motive force was abolished by the addition of an uncoupler or in the presence of a proton-translocating ATPase inhibitor. These results support the hypothesis that galactose efflux in Gal{sup {minus}} S. thermophilus is electrogenic and that the exchange reaction (lactose uptake and galactose efflux) probably occurs via an antiporter system.« less

Hypermutation in derepressed operons of Escherichia coli K12

PubMed Central

Wright, Barbara E.; Longacre, Angelika; Reimers, Jacqueline M.

1999-01-01

This article presents evidence that starvation for leucine in an Escherichia coli auxotroph triggers metabolic activities that specifically target the leu operon for derepression, increased rates of transcription, and mutation. Derepression of the leu operon was a prerequisite for its activation by the signal nucleotide, guanosine tetraphosphate, which accumulates in response to nutritional stress (the stringent response). A quantitative correlation was established between leuB mRNA abundance and leuB− reversion rates. To further demonstrate that derepression increased mutation rates, the chromosomal leu operon was placed under the control of the inducible tac promoter. When the leu operon was induced by isopropyl-d-thiogalactoside, both leuB mRNA abundance and leuB− reversion rates increased. These investigations suggest that guanosine tetraphosphate may contribute as much as attenuation in regulating leu operon expression and that higher rates of mutation are specifically associated with the derepressed leu operon. PMID:10220423

Lactose digestion from yogurt: mechanism and relevance.

PubMed

Savaiano, Dennis A

2014-05-01

Yogurt is traditionally consumed throughout the world among populations who are seemingly unable to digest lactose. This review provides a historical overview of the studies that show lactose digestion and tolerance from yogurt by lactose-intolerant people. The lactose in yogurt is digested more efficiently than other dairy sources of lactose because the bacteria inherent in yogurt assist with its digestion. The bacterial lactase survives the acidic conditions of the stomach, apparently being physically protected within the bacterial cells and facilitated by the buffering capacity of yogurt. The increasing pH as the yogurt enters the small intestine and a slower gastrointestinal transit time allow the bacterial lactase to be active, digesting lactose from yogurt sufficiently to prevent symptoms in lactose-intolerant people. There is little difference in the lactase capability of different commercial yogurts, because they apparently contain Lactobacillus bulgaricus and Streptococcus thermophilus in sufficient quantities (10(8) bacteria/mL). However, Lactobacillus acidophilus appears to require cell membrane disruption to physically release the lactase. Compared with unflavored yogurts, flavored yogurts appear to exhibit somewhat reduced lactase activity but are still well tolerated.

Triggered Snap-Through of Bistable Shells

NASA Astrophysics Data System (ADS)

Cai, Yijie; Huang, Shicheng; Trase, Ian; Hu, Nan; Chen, Zi

Elastic bistable shells are common structures in nature and engineering, such as the lobes of the Venus flytrap or the surface of a toy jumping poppers. Despite their ubiquity, the parameters that control the bistability of such structures are not well understood. In this study, we explore how the geometrical features of radially symmetric elastic shells affect the shape and potential energy of a shell's stable states, and how to tune certain parameters in order to generate a snap-through transition from a convex semi-stable state to concave stable state. We fabricated a series of elastic shells with varying geometric parameters out of silicone rubber and measured the resulting potential energy in the semi-stable state. Finite element simulations were also conducted in order to determine the deformation and stress in the shells during snap-through. It was found that the energy of the semi-stable state is controlled by only two geometric parameters and a dimensionless ratio. We also noted two distinct transitions during snap-through, one between monostability and semi-bistability (the state a popper toy is in before it snaps-through and jumps), and a second transition between semi-bistability and true bistability. This work shows that it is possible to use a set of simple parameters to tailor the energy landscape of an elastic shell in order to generate complex trigger motions for their potential use in smart applications. Z.C. acknowledge support from Society in Science-Branco Weiss Fellowship, administered by ETH Zurich.

Crystallization in lactose refining-a review.

PubMed

Wong, Shin Yee; Hartel, Richard W

2014-03-01

In the dairy industry, crystallization is an important separation process used in the refining of lactose from whey solutions. In the refining operation, lactose crystals are separated from the whey solution through nucleation, growth, and/or aggregation. The rate of crystallization is determined by the combined effect of crystallizer design, processing parameters, and impurities on the kinetics of the process. This review summarizes studies on lactose crystallization, including the mechanism, theory of crystallization, and the impact of various factors affecting the crystallization kinetics. In addition, an overview of the industrial crystallization operation highlights the problems faced by the lactose manufacturer. The approaches that are beneficial to the lactose manufacturer for process optimization or improvement are summarized in this review. Over the years, much knowledge has been acquired through extensive research. However, the industrial crystallization process is still far from optimized. Therefore, future effort should focus on transferring the new knowledge and technology to the dairy industry. © 2014 Institute of Food Technologists®

The role of colonic metabolism in lactose intolerance.

PubMed

He, T; Venema, K; Priebe, M G; Welling, G W; Brummer, R-J M; Vonk, R J

2008-08-01

Lactose maldigestion and intolerance affect a large part of the world population. The underlying factors of lactose intolerance are not fully understood. In this review, the role of colonic metabolism is discussed, i.e. fermentation of lactose by the colonic microbiota, colonic processing of the fermentation metabolites and how these processes would play a role in the pathophysiology of lactose intolerance. We suggest that the balance between the removal and production rate of osmotic-active components (lactose, and intermediate metabolites, e.g. lactate, succinate, etc.) in the colon is a key factor in the development of symptoms. The involvement of the colon may provide the basis for designing new targeted strategies for dietary and clinical management of lactose intolerance.

Automated design of genetic toggle switches with predetermined bistability.

PubMed

Chen, Shuobing; Zhang, Haoqian; Shi, Handuo; Ji, Weiyue; Feng, Jingchen; Gong, Yan; Yang, Zhenglin; Ouyang, Qi

2012-07-20

Synthetic biology aims to rationally construct biological devices with required functionalities. Methods that automate the design of genetic devices without post-hoc adjustment are therefore highly desired. Here we provide a method to predictably design genetic toggle switches with predetermined bistability. To accomplish this task, a biophysical model that links ribosome binding site (RBS) DNA sequence to toggle switch bistability was first developed by integrating a stochastic model with RBS design method. Then, to parametrize the model, a library of genetic toggle switch mutants was experimentally built, followed by establishing the equivalence between RBS DNA sequences and switch bistability. To test this equivalence, RBS nucleotide sequences for different specified bistabilities were in silico designed and experimentally verified. Results show that the deciphered equivalence is highly predictive for the toggle switch design with predetermined bistability. This method can be generalized to quantitative design of other probabilistic genetic devices in synthetic biology.

Exploiting bistable oscillator subharmonics for magnified broadband vibration energy harvesting

NASA Astrophysics Data System (ADS)

Huguet, Thomas; Badel, Adrien; Lallart, Mickaël

2017-10-01

Recent research on primary battery alternatives for supplying autonomous wireless devices has recently highlighted the advantages of nonlinear oscillators' dynamics and more particularly bistable oscillators' behavior for ambient vibration harvesting. The key property of bistable oscillators compared to linear ones is their enhanced operational frequency bandwidth under harmonic excitation, potentially leading to a better adaptation to the environment. However, the classical frequency response characterization of such devices does not reveal all the possible dynamic behaviors offered by bistable oscillators. Thus, subharmonic motions are experimentally investigated in this letter, and their energy harvesting potential as well as their ability to enhance the bistable generator bandwidth is evaluated. The results obtained with a generator integrating buckled beams for the bistability feature show that, in addition to the commonly considered harmonic behavior, subharmonics allow widening of the useful operating frequency band of the bistable microgenerator by 180% compared to the sole exploitation of the first harmonic motion.

Perception of lactose intolerance in irritable bowel syndrome patients.

PubMed

Dainese, Raffaella; Casellas, Francesc; Mariné-Barjoan, Eugènia; Vivinus-Nébot, Mylène; Schneider, Stéphane M; Hébuterne, Xavier; Piche, Thierry

2014-10-01

The importance of lactose malabsorption in irritable bowel syndrome (IBS) is not well defined and these patients often complain of lactose intolerance. To objectively measure lactose malabsorption, a hydrogen breath test (HBT) can be performed, but a discrepancy emerges between the results of the HBT and the symptomatic response during the HBT. To determine in a group of IBS patients whether self-perceived lactose intolerance and the symptomatic response to lactose HBT were conditioned by other factors besides the presence of lactose malabsorption. Oral challenge to lactose (50 g) was tested in 51 IBS patients to assess HBT malabsorption and the symptomatic response to lactose intolerance was scored on a validated questionnaire. Allergological screening for common inhalants and food allergens (including cow's milk) was performed. The presence of psychological factors (e.g. anxiety, depression, fatigue) was evaluated using validated questionnaires. A total of 21 out of 51 patients (41.1%) were self-perceived to be lactose intolerant, 24/51 (47%) had a positive HBT, and 14/51 (27.4%) presented with symptoms of lactose intolerance during HBT. The serological screening for inhalant and food allergens was positive in 6/21 (28.6%) and 4/21 (19%) of patients who self-perceived lactose intolerance and in 5/14 (37.5%) and 3/14 (21.4%) in intolerant patients symptomatic during HBT. Only 1/51 (1.9%) presented evidence of IgE-mediated hypersensitivity to cow's milk. Patients who experienced symptoms of lactose intolerance during HBT presented more severe IBS symptoms [326 (296-398) vs. 215 (126-295) P=0.05] and a higher score of anxiety, depression, and fatigue. Factors influencing the symptoms of lactose intolerance during HBT resulted in an increase in hydrogen produced and in the severity of IBS. In a cohort of 51 IBS patients, the symptoms of lactose intolerance during HBT were influenced by the capacity to absorb lactose and the severity of IBS. Other factors, such as

Lactose Intolerance in Adults: Biological Mechanism and Dietary Management

PubMed Central

Deng, Yanyong; Misselwitz, Benjamin; Dai, Ning; Fox, Mark

2015-01-01

Lactose intolerance related to primary or secondary lactase deficiency is characterized by abdominal pain and distension, borborygmi, flatus, and diarrhea induced by lactose in dairy products. The biological mechanism and lactose malabsorption is established and several investigations are available, including genetic, endoscopic and physiological tests. Lactose intolerance depends not only on the expression of lactase but also on the dose of lactose, intestinal flora, gastrointestinal motility, small intestinal bacterial overgrowth and sensitivity of the gastrointestinal tract to the generation of gas and other fermentation products of lactose digestion. Treatment of lactose intolerance can include lactose-reduced diet and enzyme replacement. This is effective if symptoms are only related to dairy products; however, lactose intolerance can be part of a wider intolerance to variably absorbed, fermentable oligo-, di-, monosaccharides and polyols (FODMAPs). This is present in at least half of patients with irritable bowel syndrome (IBS) and this group requires not only restriction of lactose intake but also a low FODMAP diet to improve gastrointestinal complaints. The long-term effects of a dairy-free, low FODMAPs diet on nutritional health and the fecal microbiome are not well defined. This review summarizes recent advances in our understanding of the genetic basis, biological mechanism, diagnosis and dietary management of lactose intolerance. PMID:26393648

Lactose Intolerance in Adults: Biological Mechanism and Dietary Management.

PubMed

Deng, Yanyong; Misselwitz, Benjamin; Dai, Ning; Fox, Mark

2015-09-18

Lactose intolerance related to primary or secondary lactase deficiency is characterized by abdominal pain and distension, borborygmi, flatus, and diarrhea induced by lactose in dairy products. The biological mechanism and lactose malabsorption is established and several investigations are available, including genetic, endoscopic and physiological tests. Lactose intolerance depends not only on the expression of lactase but also on the dose of lactose, intestinal flora, gastrointestinal motility, small intestinal bacterial overgrowth and sensitivity of the gastrointestinal tract to the generation of gas and other fermentation products of lactose digestion. Treatment of lactose intolerance can include lactose-reduced diet and enzyme replacement. This is effective if symptoms are only related to dairy products; however, lactose intolerance can be part of a wider intolerance to variably absorbed, fermentable oligo-, di-, monosaccharides and polyols (FODMAPs). This is present in at least half of patients with irritable bowel syndrome (IBS) and this group requires not only restriction of lactose intake but also a low FODMAP diet to improve gastrointestinal complaints. The long-term effects of a dairy-free, low FODMAPs diet on nutritional health and the fecal microbiome are not well defined. This review summarizes recent advances in our understanding of the genetic basis, biological mechanism, diagnosis and dietary management of lactose intolerance.

Differential impact of lactose/lactase phenotype on colonic microflora

PubMed Central

Szilagyi, Andrew; Shrier, Ian; Heilpern, Debra; Je, Jung Sung; Park, Sunghoon; Chong, George; Lalonde, Catherine; Cote, Louis-Francois; Lee, Byong

2010-01-01

BACKGROUND: The ability to digest lactose divides the world’s population into two phenotypes that may be risk variability markers for several diseases. Prebiotic effects likely favour lactose maldigesters who experience lactose spilling into their colon. OBJECTIVE: To evaluate the effects of fixed-dose lactose solutions on fecal bifidobacteria and lactobacilli in digesters and maldigesters, and to determine whether the concept of a difference in ability to digest lactose is supported. METHODS: A four-week study was performed in 23 lactose mal-digesters and 18 digesters. Following two weeks of dairy food withdrawal, subjects ingested 25 g of lactose twice a day for two weeks. Stool bifidobacteria and lactobacilli counts pre- and postintervention were measured as the primary outcome. For secondary outcomes, total anaerobes, Enterobacteriaceae, beta-galactosidase and N-acetyl-beta-D-glucosaminidase activity in stool, as well as breath hydrogen and symptoms following lactose challenge tests, were measured. RESULTS: Lactose maldigesters had a mean change difference (0.72 log10 colony forming units/g stool; P=0.04) in bifidobacteria counts compared with lactose digesters. Lactobacilli counts were increased, but not significantly. Nevertheless, reduced breath hydrogen after lactose ingestion correlated with lactobacilli (r=−0.5; P<0.001). Reduced total breath hydrogen and symptom scores together, with a rise in fecal enzymes after intervention, were appropriate, but not significant. CONCLUSIONS: Despite failure to achieve full colonic adaptation, the present study provided evidence for a differential impact of lactose on microflora depending on genetic lactase status. A prebiotic effect was evident in lactose maldigesters but not in lactose digesters. This may play a role in modifying the mechanisms of certain disease risks related to dairy food consumption between the two phenotypes. PMID:20559580

Teaching the Big Ideas of Biology with Operon Models

ERIC Educational Resources Information Center

Cooper, Robert A.

2015-01-01

This paper presents an activity that engages students in model-based reasoning, requiring them to predict the behavior of the trp and lac operons under different environmental conditions. Students are presented six scenarios for the "trp" operon and five for the "lac" operon. In most of the scenarios, specific mutations have…

Gene context conservation of a higher order than operons.

PubMed

Lathe, W C; Snel, B; Bork, P

2000-10-01

Operons, co-transcribed and co-regulated contiguous sets of genes, are poorly conserved over short periods of evolutionary time. The gene order, gene content and regulatory mechanisms of operons can be very different, even in closely related species. Here, we present several lines of evidence which suggest that, although an operon and its individual genes and regulatory structures are rearranged when comparing the genomes of different species, this rearrangement is a conservative process. Genomic rearrangements invariably maintain individual genes in very specific functional and regulatory contexts. We call this conserved context an uber-operon.

Bistable microvalve and microcatheter system

DOEpatents

Seward, Kirk Patrick

2003-05-20

A bistable microvalve of shape memory material is operatively connected to a microcatheter. The bistable microvalve includes a tip that can be closed off until it is in the desired position. Once it is in position it can opened and closed. The system uses heat and pressure to open and close the microvalve. The shape memory material will change stiffness and shape when heated above a transition temperature. The shape memory material is adapted to move from a first shape to a second shape, either open or closed, where it can perform a desired function.

Lactose intolerance in Indonesian children.

PubMed

Hegar, Badriul; Widodo, Ariani

2015-01-01

"Lactose intolerance (LI)" is considered a common problem in Asians, and in many parts of the world. Its prevalence and age of manifestation varies between by Asian country, for possible genetic or cultural reasons. Studies in Indonesian children 3-15 years old (y) are available within the past two decades, using a pure lactose tolerance test. The prevalences of lactose malabsorption (LM) in pre-elementary (3-5 y), elementary (6-11 y), and junior high (12-14 y) school-children were 21.3%, 57.8%, and 73%, respectively. An increasing trend for LM prevalence was seen within the pre-elementary group, from 9.1% at 3 y to 28.6% at 5 y. The most frequent symptoms of LI in junior high school (JHS) group were abdominal pain (64.1%), abdominal distention (22.6%), nausea (15.1%), flatulence (5.7%), and diarrhea (1.9%), mostly within one hour of lactose ingestion. In children with regular and irregular milk drinking, LM occurred in 81.2% and 69.6%; LI was found in 56.2% and 52.1%, respectively. Most JHS children with dairy-associated recurrent abdominal pain (RAP) symptoms proved to be malabsorbers. Dairy products most related to RAP were milk and yogurt. LI was found in 81% of RAP children with abdominal pain most frequently, followed by nausea, bloating, diarrhea, borborygmi, and flatulence. Symp-tom onset occurred 30 minutes after lactose ingestion, especially nausea, bloating, and abdominal pain. In RAP children LI symptoms mostly found in breath hydrogen concentration>20 ppm. More LI symptoms were found in lactose malabsorbers, but symptoms were mild and generally disappeared in 7 hours, and in most by 15 hours.

Lactase Non-persistence and Lactose Intolerance.

PubMed

Bayless, Theodore M; Brown, Elizabeth; Paige, David M

2017-05-01

To evaluate the clinical and nutritional significance of genetically determined lactase non-persistence and potential lactose and milk intolerance in 65-70% of the world's adult population. Milk consumption is decreasing in the USA and is the lowest in countries with a high prevalence of lactase non-persistence. The dairy industry and Minnesota investigators have made efforts to minimize the influence of lactose intolerance on milk consumption. Some lactose intolerant individuals, without co-existent irritable bowel syndrome, are able to consume a glass of milk with a meal with no or minor symptoms. The high frequency of lactase persistence in offspring of Northern European countries and in some nomadic African tribes is due to mutations in the promoter of the lactase gene in association with survival advantage of milk drinking. Educational and commercial efforts to improve calcium and Vitamin D intake have focused on urging consumption of tolerable amounts of milk with a meal, use of lowered lactose-content foods including hard cheeses, yogurt, and lactose-hydrolyzed milk products.

Non-volatile, solid state bistable electrical switch

NASA Technical Reports Server (NTRS)

Williams, Roger M. (Inventor)

1994-01-01

A bistable switching element is made of a material whose electrical resistance reversibly decreases in response to intercalation by positive ions. Flow of positive ions between the bistable switching element and a positive ion source is controlled by means of an electrical potential applied across a thermal switching element. The material of the thermal switching element generates heat in response to electrical current flow therethrough, which in turn causes the material to undergo a thermal phase transition from a high electrical resistance state to a low electrical resistance state as the temperature increases above a predetermined value. Application of the electrical potential in one direction renders the thermal switching element conductive to pass electron current out of the ion source. This causes positive ions to flow from the source into the bistable switching element and intercalate the same to produce a non-volatile, low resistance logic state. Application of the electrical potential in the opposite direction causes reverse current flow which de-intercalates the bistable logic switching element and produces a high resistance logic state.

Bistable energy harvesting enhancement with an auxiliary linear oscillator

NASA Astrophysics Data System (ADS)

Harne, R. L.; Thota, M.; Wang, K. W.

2013-12-01

Recent work has indicated that linear vibrational energy harvesters with an appended degree-of-freedom (DOF) may be advantageous for introducing new dynamic forms to extend the operational bandwidth. Given the additional interest in bistable harvester designs, which exhibit a propitious snap through effect from one stable state to the other, it is a logical extension to explore the influence of an added DOF to a bistable system. However, bistable snap through is not a resonant phenomenon, which tempers the presumption that the dynamics induced by an additional DOF on bistable designs would inherently be beneficial as for linear systems. This paper presents two analytical formulations to assess the fundamental and superharmonic steady-state dynamics of an excited bistable energy harvester to which is attached an auxiliary linear oscillator. From an energy harvesting perspective, the model predicts that the additional linear DOF uniformly amplifies the bistable harvester response magnitude and generated power for excitation frequencies less than the attachment’s resonance while improved power density spans a bandwidth below this frequency. Analyses predict bandwidths having co-existent responses composed of a unique proportion of fundamental and superharmonic dynamics. Experiments validate key analytical predictions and observe the ability for the coupled system to develop an advantageous multi-harmonic interwell response when the initial conditions are insufficient for continuous high-energy orbit at the excitation frequency. Overall, the addition of an auxiliary linear oscillator to a bistable harvester is found to be an effective means of enhancing the energy harvesting performance and robustness.

[Lactose intolerance: past and present. Part 1].

PubMed

Buzás, György Miklós

2015-09-20

Lactose intolerance is the most prevalent intestinal malabsorption disorder. After presentation of its history, the author describes the emergence of lactose intolerance during the evolution of species, and the biochemistry of lactose as well as features of human and bacterial lactase enzymes are then described. The unequal distribution of lactose intolerance in different continents and population is discussed, followed by presentation of past and present prevalence data in Hungary. Adult-type hypolactasia is caused by a polymorphism of the MCM6 gene located upstream from the lactase gene on the long arm of the chromosome 2. It can be determined with the polymerase chain reaction. The intestinal symptoms of lactose intolerance are well known, but its extra-intestinal manifestations are less recognised. Invasive diagnostic methods (determination of lactase activity from small intestinal biopsies, lactose tolerance test), are accurate, but have been replaced by the non-invasive methods; their gold standard is the H2 breath test. Genetic testing is being used more and more frequently in Hungary too, and, presumably, the methane breath test will be also available in the near future. Lactose intolerance can be accompanied by inflammatory bowel diseases, coeliac disease and irritable bowel syndrome; it could be established whether this association is causal or not in order to start a correct diet and therapy.

Refreshable tactile displays based on bistable electroactive polymer

NASA Astrophysics Data System (ADS)

Niu, Xiaofan; Brochu, Paul; Salazar, Brandon; Pei, Qibing

2011-04-01

Refreshable tactile displays can significantly improve the education of blind children and the quality of life of people with severe vision impairment. A number of actuator technologies have been investigated. Bistable Electroactive Polymer (BSEP) appears to be well suited for this application. The BSEP exhibits a bistable electrically actuated strain as large as 335%. We present improved refreshable tactile display devices fabricated on thin plastic sheets. Stacked BSEP films were employed to meet the requirements in raised dot height and supporting force. The bistable nature of the actuation reduces the power consumption and simplifies the device operation.

Lactose Intolerance: Exploring Reaction Kinetics Governing Lactose Conversion of Dairy Products within the Undergraduate Laboratory

ERIC Educational Resources Information Center

Smart, Jimmy L.

2008-01-01

Lactose intolerance is a condition suffered by an estimated 50 million Americans. Certain ethnic and racial populations are more widely affected than others. As many as 75 percent of all African-American, Jewish, Native American, and Mexican-American adults, and 90 percent of Asian-American adults are lactose intolerant. Some populations in Africa…

High accuracy operon prediction method based on STRING database scores.

PubMed

Taboada, Blanca; Verde, Cristina; Merino, Enrique

2010-07-01

We present a simple and highly accurate computational method for operon prediction, based on intergenic distances and functional relationships between the protein products of contiguous genes, as defined by STRING database (Jensen,L.J., Kuhn,M., Stark,M., Chaffron,S., Creevey,C., Muller,J., Doerks,T., Julien,P., Roth,A., Simonovic,M. et al. (2009) STRING 8-a global view on proteins and their functional interactions in 630 organisms. Nucleic Acids Res., 37, D412-D416). These two parameters were used to train a neural network on a subset of experimentally characterized Escherichia coli and Bacillus subtilis operons. Our predictive model was successfully tested on the set of experimentally defined operons in E. coli and B. subtilis, with accuracies of 94.6 and 93.3%, respectively. As far as we know, these are the highest accuracies ever obtained for predicting bacterial operons. Furthermore, in order to evaluate the predictable accuracy of our model when using an organism's data set for the training procedure, and a different organism's data set for testing, we repeated the E. coli operon prediction analysis using a neural network trained with B. subtilis data, and a B. subtilis analysis using a neural network trained with E. coli data. Even for these cases, the accuracies reached with our method were outstandingly high, 91.5 and 93%, respectively. These results show the potential use of our method for accurately predicting the operons of any other organism. Our operon predictions for fully-sequenced genomes are available at http://operons.ibt.unam.mx/OperonPredictor/.

Crystallization of spray-dried lactose/protein mixtures in humid air

NASA Astrophysics Data System (ADS)

Shawqi Barham, A.; Kamrul Haque, Md.; Roos, Yrjö H.; Kieran Hodnett, B.

2006-10-01

An in situ crystallization technique with X-ray diffraction analysis complemented by ex situ scanning electron microscopy and chromatographic analysis of the α/( α+ β) solid-state anomeric ratios has been developed to study the crystallization of lactose/protein mixtures in humid air. This technique was used to determine changes in phase composition and morphology during crystallization. Following an induction period during which water is sorbed, crystallization is rapid and the predominant phase observed using the in situ method in spray-dried lactose/sodium-caseinate, albumin and gelatin is α-lactose monohydrate. However, in the case of spray-dried lactose/whey protein isolate (WPI) the predominant phase that appears is the α/ β mixed phase with smaller amounts of α-lactose monohydrate. With pure lactose the α/ β mixed phase appears as a transient shortly after the onset of crystallization and α-lactose monohydrate and β-lactose both appear as stable crystalline phases at longer times. Another transient phase with 2 θ=12.2°, 20.7° and 21.8° was observed in spray-dried lactose/albumin. This phase decomposed as α-lactose monohydrate developed. Three phases seem to persist in the case of spray-dried lactose/gelatin, namely the phase with peaks at 2 θ=12.2°, 20.7° and 21.8°, α-lactose monohydrate and β-lactose for the duration of the in situ experiment.

[Lactose intolerance in neonates with non-infectious diarrhea].

PubMed

Su, Hui-Min; Jiang, Yi; Hu, Yu-Lian; Yang, Hui; Dong, Tian-Jin

2016-04-01

To investigate the development of lactose intolerance in neonates with non-infectious diarrhea and its association with diarrhea, and to evaluate the diagnostic values of fecal pH value and urine galactose determination for neonatal lactase deficiency. Seventy hospitalized neonates who developed non-infectious diarrhea between October 2012 and June 2015 were enrolled as the diarrhea group, and 162 hospitalized neonates without non-infectious diarrhea were enrolled as the non-diarrhea group. Test paper was used to determine fecal pH value. The galactose oxidase method was used to detect urine galactose. The neonates with positive galactose oxidase were diagnosed with lactase deficiency, and those with lactase deficiency and diarrhea were diagnosed with lactose intolerance. According to the results of urine galactose detection, 69 neonates in the diarrhea group who underwent urine galactose detection were classified into lactose intolerance group (45 neonates) and lactose tolerance group (24 neonates), and their conditions after treatment were compared between the two groups. The follow-up visits were performed for neonates with diarrhea at 3 months after discharge. Fecal pH value and positive rate of urine galactose (65% vs 54%) showed no significant differences between the diarrhea and non-diarrhea groups (P>0.05). Fecal pH value showed no significant difference between the lactose intolerance and lactose tolerance groups (P>0.05), while the neonates in the lactose intolerance group had a significantly longer time to recovery of defecation than those in the lactose tolerance group (P<0.05). The incidence of lactase deficiency is high in neonates, and diarrhea due to lactose intolerance tends to occur. Determination of fecal pH value has no significance in the diagnosis of lactose intolerance in neonates with diarrhea.

Operon Formation is Driven by Co-Regulation and Not by Horizontal Gene Transfer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, Morgan N.; Huang, Katherine H.; Arkin, Adam P.

Although operons are often subject to horizontal gene transfer (HGT), non-HGT genes are particularly likely to be in operons. To resolve this apparent discrepancy and to determine whether HGT is involved in operon formation, we examined the evolutionary history of the genes and operons in Escherichia coli K12. We show that genes that have homologs in distantly related bacteria but not in close relatives of E. coli (indicating HGTi) form new operons at about the same rates as native genes. Furthermore, genes in new operons are no more likely than other genes to have phylogenetic trees that are inconsistent withmore » the species tree. In contrast, essential genes and ubiquitous genes without paralogs (genes believed to undergo HGT rarely) often form new operons. We conclude that HGT is not associated with operon formation, but instead promotes the prevalence of pre-existing operons. To explain operon formation, we propose that new operons reduce the amount of regulatory information required to specify optimal expression patterns. Consistent with this hypothesis, operons have greater amounts of conserved regulatory sequences than do individually transcribed genes.« less

Lactose, galactose and glucose determination in naturally "lactose free" hard cheese: HPAEC-PAD method validation.

PubMed

Monti, Lucia; Negri, Stefano; Meucci, Aurora; Stroppa, Angelo; Galli, Andrea; Contarini, Giovanna

2017-04-01

A chromatographic method by HPAEC-PAD was developed and in-house validated for the quantification of low sugar levels in hard cheese, specifically Grana Padano PDO cheese. Particular attention was paid to the extraction procedure, due to residual microbial and enzymatic activities. Specificity in detection and linearity were verified. Recoveries ranged from 93% for lactose to 98% for glucose and galactose. The obtained LOD and LOQ values were, respectively, 0.25 and 0.41mg/100g for lactose, 0.14 and 0.27mg/100g for galactose, and 0.16 and 0.26mg/100g for glucose. The method was applied to 59 samples of Grana Padano PDO cheese: galactose showed the highest concentration and variability among the samples (1.36±0.89), compared to both lactose (0.45±0.12) and glucose (0.46±0.13). Considering the very low levels of sugars detected, authentic PDO Grana Padano could be safely included in the diet of people suffering from lactose intolerance. Copyright © 2016 Elsevier Ltd. All rights reserved.

Milling induced amorphisation and recrystallization of α-lactose monohydrate.

PubMed

Badal Tejedor, Maria; Pazesh, Samaneh; Nordgren, Niklas; Schuleit, Michael; Rutland, Mark W; Alderborn, Göran; Millqvist-Fureby, Anna

2018-02-15

Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the α-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed α-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between unprocessed α-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spray-dried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during

Influence of lactose hydrolysis on galacto-oligosaccharides, lactose, volatile profile and physicochemical parameters of different yogurt varieties.

PubMed

Vénica, Claudia I; Wolf, Irma V; Bergamini, Carina V; Perotti, María C

2016-12-01

Different types of reduced-lactose yogurt, obtained by lactose hydrolysis using β-galactosidase enzyme, are commercially available. The breakdown of lactose modifies the carbohydrate profile, including the production of prebiotic galacto-oligosaccharides (GOS), which could affect the survival and activity of starter and probiotic cultures and the parameters of yogurt quality. The extension of these changes is dependent on the yogurt matrix composition. This study aimed to evaluate the influence of lactose hydrolysis on GOS, lactose, volatile profile and physicochemical parameters of different yogurt varieties during storage. The presence of β-galactosidase enzyme did not affect either the global composition or the survival of cultures. Overall, the hydrolyzed products had lower acidity than traditional ones. GOS were found at similar levels in fresh hydrolyzed yogurts, whereas in traditional yogurts they were not detected. The proportion of ketones, acids and aldehydes seems to be more dependent on yogurt variety than on addition of the enzyme. Likewise, the storage period affected the volatile fraction to different degree; the increase in acid compounds was more pronounced in hydrolyzed than in traditional yogurts. This work shows that it is possible to obtain different varieties of reduced-lactose yogurt, some of them with additional benefits to health such as reduced fat, reduced calories, added with probiotic/inulin and enriched in GOS, with similar characteristics to traditional products. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

Lactose intolerance: diagnosis, genetic, and clinical factors

PubMed Central

Mattar, Rejane; de Campos Mazo, Daniel Ferraz; Carrilho, Flair José

2012-01-01

Most people are born with the ability to digest lactose, the major carbohydrate in milk and the main source of nutrition until weaning. Approximately 75% of the world’s population loses this ability at some point, while others can digest lactose into adulthood. This review discusses the lactase-persistence alleles that have arisen in different populations around the world, diagnosis of lactose intolerance, and its symptomatology and management. PMID:22826639

Glycopeptide Resistance vanA Operons in Paenibacillus Strains Isolated from Soil

PubMed Central

Guardabassi, Luca; Perichon, Bruno; van Heijenoort, Jean; Blanot, Didier; Courvalin, Patrice

2005-01-01

The sequence and gene organization of the van operons in vancomycin (MIC of >256 μg/ml)- and teicoplanin (MIC of ≥32 μg/ml)-resistant Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B isolated from soil were determined. Both operons had regulatory (vanR and vanS), resistance (vanH, vanA, and vanX), and accessory (vanY, vanZ, and vanW) genes homologous to the corresponding genes in enterococcal vanA and vanB operons. The vanAPT operon in P. thiaminolyticus PT-2B1 had the same gene organization as that of vanA operons whereas vanAPA in P. apiarius PA-B2B resembled vanB operons due to the presence of vanW upstream from the vanHAX cluster but was closer to vanA operons in sequence. Reference P. apiarius strains NRRL B-4299 and NRRL B-4188 were found to harbor operons indistinguishable from vanAPA by PCR mapping, restriction fragment length polymorphism, and partial sequencing, suggesting that this operon was species specific. As in enterococci, resistance was inducible by glycopeptides and associated with the synthesis of pentadepsipeptide peptidoglycan precursors ending in d-Ala-d-Lac, as demonstrated by d,d-dipeptidase activities, high-pressure liquid chromatography, and mass spectrometry. The precursors differed from those in enterococci by the presence of diaminopimelic acid instead of lysine in the peptide chain. Altogether, the results are compatible with the notion that van operons in soil Paenibacillus strains and in enterococci have evolved from a common ancestor. PMID:16189102

Glycopeptide resistance vanA operons in Paenibacillus strains isolated from soil.

PubMed

Guardabassi, Luca; Perichon, Bruno; van Heijenoort, Jean; Blanot, Didier; Courvalin, Patrice

2005-10-01

The sequence and gene organization of the van operons in vancomycin (MIC of >256 microg/ml)- and teicoplanin (MIC of > or =32 microg/ml)-resistant Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B isolated from soil were determined. Both operons had regulatory (vanR and vanS), resistance (vanH, vanA, and vanX), and accessory (vanY, vanZ, and vanW) genes homologous to the corresponding genes in enterococcal vanA and vanB operons. The vanA(PT) operon in P. thiaminolyticus PT-2B1 had the same gene organization as that of vanA operons whereas vanA(PA) in P. apiarius PA-B2B resembled vanB operons due to the presence of vanW upstream from the vanHAX cluster but was closer to vanA operons in sequence. Reference P. apiarius strains NRRL B-4299 and NRRL B-4188 were found to harbor operons indistinguishable from vanA(PA) by PCR mapping, restriction fragment length polymorphism, and partial sequencing, suggesting that this operon was species specific. As in enterococci, resistance was inducible by glycopeptides and associated with the synthesis of pentadepsipeptide peptidoglycan precursors ending in D-Ala-D-Lac, as demonstrated by D,D-dipeptidase activities, high-pressure liquid chromatography, and mass spectrometry. The precursors differed from those in enterococci by the presence of diaminopimelic acid instead of lysine in the peptide chain. Altogether, the results are compatible with the notion that van operons in soil Paenibacillus strains and in enterococci have evolved from a common ancestor.

Perception of lactose intolerance impairs health-related quality of life.

PubMed

Casellas, F; Aparici, A; Pérez, M J; Rodríguez, P

2016-09-01

Chronic conditions impair perception of well-being. Malabsorption of lactose is the most frequent form of malabsorption and manifests as lactose intolerance. There is a lack of information regarding their impact on self-perception of health. The objective of this study is to determine the subjective impact of self-reported lactose intolerance or objective lactose malabsorption on patient health by using a patient-reported outcome to measure health-related quality of life (HRQOL) and modification of lactose-containing food diet. A 3-year prospective, cross-sectional study was performed in patients referred for a lactose hydrogen breath test. Patients were asked about their subjective opinion relative to their lactose tolerance and completed a validated, specific questionnaire to determine symptoms of intolerance during habitual consumption of dairy. A 50-g lactose breath test was then performed. Patients were grouped as absorbers vs malabsorbers and tolerant vs intolerants. A total of 580 patients were included (median age 30 years, 419 female). Overall, 324 patients (56%) considered themselves lactose intolerant and that perception was associated with avoidance of dairy consumption (55% vs only 9% of self-defined tolerants). Self-perception of intolerance was associated with lower HRQOL scores (median, 60 vs 70, P<0.01). In contrast, lactose objective malabsorption was not clearly associated with dairy avoidance (41% of malabsorbers avoided dairy vs 31% of absorbers). However, HRQOL scores were also significantly lower in malabsorbers than in absorbers (60 vs 70 respectively, P<0.001). Subjective perception of lactose intolerance affects the decision to avoid dairy even more than objective malabsorption. However, both self-perception of lactose intolerance and objective lactose malabsorption are associated with poorer perceived quality of life.

Lactose metabolism by Staphylococcus aureus: characterization of lacABCD, the structural genes of the tagatose 6-phosphate pathway.

PubMed Central

Rosey, E L; Oskouian, B; Stewart, G C

1991-01-01

The nucleotide and deduced amino acid sequences of the lacA and lacB genes of the Staphylococcus aureus lactose operon (lacABCDFEG) are presented. The primary translation products are polypeptides of 142 (Mr = 15,425) and 171 (Mr = 18,953) amino acids, respectively. The lacABCD loci were shown to encode enzymes of the tagatose 6-phosphate pathway through both in vitro studies and complementation analysis in Escherichia coli. A serum aldolase assay, modified to allow detection of the tagatose 6-phosphate pathway enzymes utilizing galactose 6-phosphate or fructose phosphate analogs as substrate, is described. Expression of both lacA and lacB was required for galactose 6-phosphate isomerase activity. LacC (34 kDa) demonstrated tagatose 6-phosphate kinase activity and was found to share significant homology with LacC from Lactococcus lactis and with both the minor 6-phosphofructokinase (PfkB) and 1-phosphofructokinase (FruK) from E. coli. Detection of tagatose 1,6-bisphosphate aldolase activity was dependent on expression of the 36-kDa protein specified by lacD. The LacD protein is highly homologous with LacD of L. lactis. Thus, the lacABCD genes comprise the tagatose 6-phosphate pathway and are cotranscribed with genes lacFEG, which specify proteins for transport and cleavage of lactose in S. aureus. PMID:1655695

Lactose Intolerance

MedlinePlus

... a necessity for infants, who get all their nutrition from milk. As children replace milk with other foods, their lactase production normally decreases, but remains high enough to digest the amount of dairy in a typical adult diet. In primary lactose ...

Bistable dynamics of a levitated nanoparticle (Presentation Recording)

NASA Astrophysics Data System (ADS)

Ricci, Francesco; Spasenovic, M.; Rica, Raúl A.; Novotny, Lukas; Quidant, Romain

2015-08-01

Bistable systems are ubiquitous in nature. Classical examples in chemistry and biology include relaxation kinetics in chemical reactions [1] and stochastic resonance processes such as neuron firing [2,3]. Likewise, bistable systems play a key role in signal processing and information handling at the nanoscale, giving rise to intriguing applications such as optical switches [4], coherent signal amplification [5,6] and weak forces detection [5]. The interest and applicability of bistable systems are intimately connected with the complexity of their dynamics, typically due to the presence of a large number of parameters and nonlinearities. Appropriate modeling is therefore challenging. Alternatively, the possibility to experimentally recreate bistable systems in a clean and controlled way has recently become very appealing, but elusive and complicated. With this aim, we combined optical tweezers with a novel active feedback-cooling scheme to develop a well-defined opto-mechanical platform reaching unprecedented performances in terms of Q-factor, frequency stability and force sensitivity [7,8]. Our experimental system consists of a single nanoparticle levitated in high vacuum with optical tweezers, which behaves as a non-linear (Duffing) oscillator under appropriate conditions. Here, we prove it to be an ideal tool for a deep study of bistability. We demonstrate bistability of the nanoparticle by noise activated switching between two oscillation states, discussing our results in terms of a double-well potential model. We also show the flexibility of our system in shaping the potential at will, in order to meet the conditions prescribed by any bistable system that could therefore then be simulated with our setup. References [1] T. Amemiya, T. Ohmori, M. Nakaiwa, T. Yamamoto, and T. Yamaguchi, "Modeling of Nonlinear Chemical Reaction Systems and Two-Parameter Stochastic Resonance," J. Biol. Phys. 25 (1999) 73 [2] F. Moss, L. M. Ward, and W. G. Sannita, "Stochastic

Sequence and features of the tryptophan operon of Vibrio parahemolyticus.

PubMed

Crawford, I P; Han, C Y; Silverman, M

1991-01-01

The nucleotide sequence of the trp operon of the marine enteric bacterium Vibrio parahemolyticus is presented. The gene order E, G, D, C(F), B, A is identical to that of other enterics. The structural genes of the operon are preceded by a long leader region encoding a 41-residue peptide containing five tryptophan residues. The organization of the leader region suggests that transcription of the operon is subject to attenuation control. The promoter-operator region of the V. parahemolyticus trp operon is almost identical to the corresponding promoter-operator of E. coli. The similarities suggest that promoter strength and operator function are identical in the two species, and that transcription initiation is regulated by repression. The operon appears to lack the internal promoter within trpD that is common in terrestrial enteric species.

Bending stresses and bistable behavior in Fe-rich amorphous wire

NASA Astrophysics Data System (ADS)

Vázquez, M.; Gómez Polo, C.; Velázquez, J.; Hernando, A.

1994-05-01

The aim of this work is to analyze for the first time the changes in magnetic properties of an Fe-rich amorphous wire (Fe77.5Si7.5B15) when it is submitted to bending stresses. Upon a reduction of the radius of curvature, Rc, of the wire (i.e., increasing bending stresses), the main changes in the magnetic properties are summarized as follows: (a) Bistable behavior disappears when reducing Rc below about 11 cm but it is again observed for Rc less than about 2.5 cm. This latter effect is also obtained for short wires (less than around 7 cm) which do not show spontaneous bistability. (b) For the case when bending stresses make bistability disappear, the susceptibility increases more than one order of magnitude with regards to the case of bistable wire, and parallel to the increase of susceptibility, a reduction of remanent magnetization is observed. The disappearance and later occurrence of the bistable behavior with increasing bending stresses are discussed in terms of the tensile and compressive stresses induced when the sample is bent. The possibility of having bistable wires with toroidal symmetry is also discussed owing to its interest for particular applications as pulse generators with reduced size and magnetic switches.

Lactose-induced cell death of beta-galactosidase mutants in Kluyveromyces lactis.

PubMed

Lodi, Tiziana; Donnini, Claudia

2005-05-01

The Kluyveromyces lactis lac4 mutants, lacking the beta-galactosidase gene, cannot assimilate lactose, but grow normally on many other carbon sources. However, when these carbon sources and lactose were simultaneously present in the growth media, the mutants were unable to grow. The effect of lactose was cytotoxic since the addition of lactose to an exponentially-growing culture resulted in 90% loss of viability of the lac4 cells. An osmotic stabilizing agent prevented cells killing, supporting the hypothesis that the lactose toxicity could be mainly due to intracellular osmotic pressure. Deletion of the lactose permease gene, LAC12, abolished the inhibitory effect of lactose and allowed the cell to assimilate other carbon substrates. The lac4 strains gave rise, with unusually high frequency, to spontaneous mutants tolerant to lactose (lar1 mutation: lactose resistant). These mutants were unable to take up lactose. Indeed, lar1 mutation turned out to be allelic to LAC12. The high mutability of the LAC12 locus may be an advantage for survival of K. lactis whose main habitat is lactose-containing niches.

Characterization of Physical and Mechanical Properties of Miscible Lactose-Sugars Systems.

PubMed

Li, Runjing; Roos, Yrjö H; Miao, Song

2017-09-01

Lactose-sugars systems were produced by spray drying. They were lactose, lactose-glucose (4:1) mixtures, lactose-maltose (4:1) mixtures, lactose-sucrose (4:1) mixtures, lactose-trehalose (4:1) mixtures, and lactose-corn syrup solids (CSS) (4:1) mixtures. The physical characteristics, water sorption behavior, glass transition, and mechanical properties of miscible lactose-sugars systems were investigated. Lactose-glucose mixtures had larger particle size than other lactose-sugars systems after spray drying. The presence of glucose or sucrose in lactose-sugars mixtures decreased the glass transition temperatures of amorphous systems, while the presence of maltose and trehalose had only minor impact on the glass transition temperatures. Moreover, glucose accelerated the crystallization of amorphous system at 0.44 a w , but its presence delayed the loss of sorbed water at higher water activities (≥0.54 a w ). Mechanical property study indicated that glucose and sucrose in amorphous system could result in an increase of molecular mobility, while the presence of CSS could decrease the free volume and maintain the stiffness of the miscible systems. © 2017 Institute of Food Technologists®.

Selfish operons: the evolutionary impact of gene clustering in prokaryotes and eukaryotes.

PubMed

Lawrence, J

1999-12-01

The Selfish Operon Model postulates that the organization of bacterial genes into operons is beneficial to the constituent genes in that proximity allows horizontal cotransfer of all genes required for a selectable phenotype; eukaryotic operons formed for very different reasons. Horizontal transfer of selfish operons most probably promotes bacterial diversification.

Lactose behaviour in the presence of lactic acid and calcium.

PubMed

Wijayasinghe, Rangani; Vasiljevic, Todor; Chandrapala, Jayani

2016-08-01

Physical properties of lactose appeared influenced by presence of lactic acid in the system. Some other components such as Ca may further attenuate lactose behaviour and impact its phase transition. A model-based study was thus implemented with varying concentrations of Ca (0·12, 0·072 or 0·035% w/w) and lactic acid (0·05, 0·2, 0·4 or 1% w/w) in establishing the effects of these two main acid whey constituents on lactose phase behaviour. Concentrated solutions (50% w/w) containing lactose, lactic acid and Ca were analysed for thermal behaviour and structural changes by Differential Scanning Colorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR), respectively. Presence of 1% (w/w) lactic acid and 0·12% (w/w) Ca in lactose solution significantly increased the evaporation enthalpy of water, delayed and increased the energy required for lactose crystallisation as compared to pure lactose. FTIR analysis indicated a strong hydration layer surrounding lactose molecules, restricting water mobility and/or inducing structural changes of lactose, hindering its crystallisation. The formation of calcium lactate, which restricts the diffusion of lactose molecules, is also partly responsible. It appears that Ca removal from acid whey may be a necessary step in improving the processability of acid whey.

Improving lactose digestion and symptoms of lactose intolerance with a novel galacto-oligosaccharide (RP-G28): a randomized, double-blind clinical trial.

PubMed

Savaiano, Dennis A; Ritter, Andrew J; Klaenhammer, Todd R; James, Gareth M; Longcore, Amy T; Chandler, Justin R; Walker, W Allan; Foyt, Howard L

2013-12-13

Lactose intolerance (LI) is a common medical problem with limited treatment options. The primary symptoms are abdominal pain, diarrhea, bloating, flatulence, and cramping. Limiting dairy foods to reduce symptoms contributes to low calcium intake and the risk for chronic disease. Adaptation of the colon bacteria to effectively metabolize lactose is a novel and potentially useful approach to improve lactose digestion and tolerance. RP-G28 is novel galacto-oligosaccharide (GOS) being investigated to improve lactose digestion and the symptoms of lactose intolerance in affected patients. A randomized, double-blind, parallel group, placebo-controlled study was conducted at 2 sites in the United States. RP-G28 or placebo was administered to 85 patients with LI for 35 days. Post-treatment, subjects reintroduced dairy into their daily diets and were followed for 30 additional days to evaluate lactose digestion as measured by hydrogen production and symptom improvements via a patient-reported symptom assessment instrument. Lactose digestion and symptoms of LI trended toward improvement on RP-G28 at the end of treatment and 30 days post-treatment. A reduction in abdominal pain was also demonstrated in the study results. Fifty percent of RP-G28 subjects with abdominal pain at baseline reported no abdominal pain at the end of treatment and 30 days post treatment (p = 0.0190). RP-G28 subjects were also six times more likely to claim lactose tolerance post-treatment once dairy foods had been re-introduced into their diets (p = 0.0389). Efficacy trends and favorable safety/tolerability findings suggest that RP-G28 appears to be a potentially useful approach for improving lactose digestion and LI symptoms. The concurrent reduction in abdominal pain and improved overall tolerance could be a meaningful benefit to lactose intolerant individuals.

Improving lactose digestion and symptoms of lactose intolerance with a novel galacto-oligosaccharide (RP-G28): a randomized, double-blind clinical trial

PubMed Central

2013-01-01

Background Lactose intolerance (LI) is a common medical problem with limited treatment options. The primary symptoms are abdominal pain, diarrhea, bloating, flatulence, and cramping. Limiting dairy foods to reduce symptoms contributes to low calcium intake and the risk for chronic disease. Adaptation of the colon bacteria to effectively metabolize lactose is a novel and potentially useful approach to improve lactose digestion and tolerance. RP-G28 is novel galacto-oligosaccharide (GOS) being investigated to improve lactose digestion and the symptoms of lactose intolerance in affected patients. Methods A randomized, double-blind, parallel group, placebo-controlled study was conducted at 2 sites in the United States. RP-G28 or placebo was administered to 85 patients with LI for 35 days. Post-treatment, subjects reintroduced dairy into their daily diets and were followed for 30 additional days to evaluate lactose digestion as measured by hydrogen production and symptom improvements via a patient-reported symptom assessment instrument. Results Lactose digestion and symptoms of LI trended toward improvement on RP-G28 at the end of treatment and 30 days post-treatment. A reduction in abdominal pain was also demonstrated in the study results. Fifty percent of RP-G28 subjects with abdominal pain at baseline reported no abdominal pain at the end of treatment and 30 days post treatment (p = 0.0190). RP-G28 subjects were also six times more likely to claim lactose tolerance post-treatment once dairy foods had been re-introduced into their diets (p = 0.0389). Conclusions Efficacy trends and favorable safety/tolerability findings suggest that RP-G28 appears to be a potentially useful approach for improving lactose digestion and LI symptoms. The concurrent reduction in abdominal pain and improved overall tolerance could be a meaningful benefit to lactose intolerant individuals. Study registration ClinicalTrials.gov NCT01113619. PMID:24330605

Evolutionary Dynamics on Protein Bi-stability Landscapes can Potentially Resolve Adaptive Conflicts

PubMed Central

Sikosek, Tobias; Bornberg-Bauer, Erich; Chan, Hue Sun

2012-01-01

Experimental studies have shown that some proteins exist in two alternative native-state conformations. It has been proposed that such bi-stable proteins can potentially function as evolutionary bridges at the interface between two neutral networks of protein sequences that fold uniquely into the two different native conformations. Under adaptive conflict scenarios, bi-stable proteins may be of particular advantage if they simultaneously provide two beneficial biological functions. However, computational models that simulate protein structure evolution do not yet recognize the importance of bi-stability. Here we use a biophysical model to analyze sequence space to identify bi-stable or multi-stable proteins with two or more equally stable native-state structures. The inclusion of such proteins enhances phenotype connectivity between neutral networks in sequence space. Consideration of the sequence space neighborhood of bridge proteins revealed that bi-stability decreases gradually with each mutation that takes the sequence further away from an exactly bi-stable protein. With relaxed selection pressures, we found that bi-stable proteins in our model are highly successful under simulated adaptive conflict. Inspired by these model predictions, we developed a method to identify real proteins in the PDB with bridge-like properties, and have verified a clear bi-stability gradient for a series of mutants studied by Alexander et al. (Proc Nat Acad Sci USA 2009, 106:21149–21154) that connect two sequences that fold uniquely into two different native structures via a bridge-like intermediate mutant sequence. Based on these findings, new testable predictions for future studies on protein bi-stability and evolution are discussed. PMID:23028272

Mini review on role of β-galactosidase in lactose intolerance

NASA Astrophysics Data System (ADS)

A, Nivetha; V, Mohanasrinivasan

2017-11-01

This review mainly focuses on the role and properties of β-galactosidase in lactose intolerance and its industrial application. β-Galactosidase, hydrolyses the lactose into glucose and galactose and it is most commonly used in food based technology, particularly in the dairy manufacturing industry. This catalyst mainly focus for the improvement of new and novel products with hydrolyzed lactose, which can be appropriate for the lactose-intolerant persons, to improve the technological, texture and scientific properties of non-fermented dairy products. β-Galactosidase derived from the group of saccharides which is a converting enzymes in the family of hydrolases. They are broadly distributed in the several biological living systems. The enzymatic hydrolysis of lactose is also preferred in food based technology due to the low soluble range of lactose. The concentration lactose was found to be high in fermented dairy products such as ice cream, butter, cheese curd, yogurt, etc., can prompt extreme lactose crystallization bringing about items through a coarse, abrasive surface. Lactose hydrolysis in dairy products enhances adaptability also, richness altogether. These products are extra edible. Also for this purpose, the utilization of β-galactosidase enzyme prior to the condensing operation can reduce the lactose content to a point where lactose was no longer a problem industrial application of β-galactosidase. In Industries, due to the positive and constructive effect on intestinal bacterial microflora, different types of applications are possible in β-galactosidase enzyme.

[Lactose intolerance: past and present. Part II].

PubMed

Buzás, György Miklós

2015-10-25

The author summarises the interrelations between lactose intolerance, calcium and vitamin D metabolism and osteoporosis. Lactose intolerance enhances the risk of forearm and hip fractures in some patients. Lactase gene genotype and fracture risk are related in some populations. Calcium and vitamin D supplementation increase bone mineral content and they are justified in children, during pregnancy and lactation, and in postmenopausal women. The intake of milk and milk products could increase the risk of ovarian carcinoma. CC genotype of the lactase gene increased the risk of colorectal carcinoma in Finns; no such effect was observed in British, Spanish and Italian patients. Even small quantities of lactose in drugs (10-750 mg) could elicit intolerance symptoms due to individual susceptibility. In spite of public knowledge and advertising, controlled studies did not prove the beneficial effect of either a lactose-free diet, enzyme supplementation or probiotics in an evidence-based manner. While accepted guidelines are lacking, a personalised therapy is mandatory. In spite of increasing public interest in lactose intolerance, many unknown factors must still be studied.

[Breath tests in children with suspected lactose intolerance].

PubMed

Parra, P Ángela; Furió, C Simone; Arancibia, A Gabriel

2015-01-01

Up to 70% of the world population is lactose intolerance. However, there are no epidemiological studies among Chilean pediatric population affected by this condition. Clinical characterization of a series of children who underwent the lactose intolerance breath test for lactose intolerance study, establishing intolerance and malabsorption frequencies, the most frequent symptoms, and test performance depending on the origin. Patients under 18 years old who took the lactose intolerance breath test in the Gastroenterology Laboratory of the Catholic University of Chile, and who were admitted due to clinically suspected lactose intolerance. Malabsorption was considered when there was as an increase of ≥20ppm above the baseline (H2) or ≥34ppm of H2 and methane (CH4) combined. Intolerance was considered when the above was associated with a symptom intensity score ≥7 during registration. The analysis included194 patients aged 1 to17 years of age. Of these, 102 (53%) presented with malabsorption, and 53 (27%) were intolerant. The frequency of lactose intolerance varied from 7.1 to 45.4%, and it occurred more frequently at older ages. The most common reported symptoms were abdominal pain, bloating and rumbling. Lactose malabsorption and intolerance can be investigated from the first years of life using the lactose breath test plus a symptom questionnaire. An increase in the frequency of intolerance with age, and a greater number of positive tests, if they were requested by a gastroenterologist, were observed. Copyright © 2015 Sociedad Chilena de Pediatría. Publicado por Elsevier España, S.L.U. All rights reserved.

Piezoresistive sensing of bistable micro mechanism state

NASA Astrophysics Data System (ADS)

Anderson, Jeffrey K.; Howell, Larry L.; Wittwer, Jonathan W.; McLain, Timothy W.

2006-05-01

The objective of this work is to demonstrate the feasibility of on-chip sensing of bistable mechanism state using the piezoresistive properties of polysilicon, thus eliminating the need for electrical contacts. Changes in position are detected by observing changes in resistance across the mechanism. Sensing the state of bistable mechanisms is critical for various applications, including high-acceleration sensing arrays and alternative forms of nonvolatile memory. A fully compliant bistable micro mechanism was designed, fabricated and tested to demonstrate the feasibility of this sensing technique. Testing results from two fabrication processes, SUMMiT IV and MUMPs, are presented. The SUMMiT mechanism was then integrated into various Wheatstone bridge configurations to investigate their potential advantages and to demonstrate various design layouts. Repeatable and detectable results were found with independent mechanisms and with those integrated into Wheatstone bridges.

Four-sample lactose hydrogen breath test for diagnosis of lactose malabsorption in irritable bowel syndrome patients with diarrhea

PubMed Central

Yang, Jian-Feng; Fox, Mark; Chu, Hua; Zheng, Xia; Long, Yan-Qin; Pohl, Daniel; Fried, Michael; Dai, Ning

2015-01-01

AIM: To validate 4-sample lactose hydrogen breath testing (4SLHBT) compared to standard 13-sample LHBT in the clinical setting. METHODS: Irritable bowel syndrome patients with diarrhea (IBS-D) and healthy volunteers (HVs) were enrolled and received a 10 g, 20 g, or 40 g dose lactose hydrogen breath test (LHBT) in a randomized, double-blinded, controlled trial. The lactase gene promoter region was sequenced. Breath samples and symptoms were acquired at baseline and every 15 min for 3 h (13 measurements). The detection rates of lactose malabsorption (LM) and lactose intolerance (LI) for a 4SLHBT that acquired four measurements at 0, 90, 120, and 180 min from the same data set were compared with the results of standard LHBT. RESULTS: Sixty IBS-D patients and 60 HVs were studied. The genotype in all participants was C/C-13910. LM and LI detection rates increased with lactose dose from 10 g, 20 g to 40 g in both groups (P < 0.001). 4SLHBT showed excellent diagnostic concordance with standard LHBT (97%-100%, Kappa​​ 0.815-0.942) with high sensitivity (90%-100%) and specificity (100%) at all three lactose doses in both groups. CONCLUSION: Reducing the number of measurements from 13 to 4 samples did not significantly impact on the accuracy of LHBT in health and IBS-D. 4SLHBT is a valid test for assessment of LM and LI in clinical practice. PMID:26140004

Four-sample lactose hydrogen breath test for diagnosis of lactose malabsorption in irritable bowel syndrome patients with diarrhea.

PubMed

Yang, Jian-Feng; Fox, Mark; Chu, Hua; Zheng, Xia; Long, Yan-Qin; Pohl, Daniel; Fried, Michael; Dai, Ning

2015-06-28

To validate 4-sample lactose hydrogen breath testing (4SLHBT) compared to standard 13-sample LHBT in the clinical setting. Irritable bowel syndrome patients with diarrhea (IBS-D) and healthy volunteers (HVs) were enrolled and received a 10 g, 20 g, or 40 g dose lactose hydrogen breath test (LHBT) in a randomized, double-blinded, controlled trial. The lactase gene promoter region was sequenced. Breath samples and symptoms were acquired at baseline and every 15 min for 3 h (13 measurements). The detection rates of lactose malabsorption (LM) and lactose intolerance (LI) for a 4SLHBT that acquired four measurements at 0, 90, 120, and 180 min from the same data set were compared with the results of standard LHBT. Sixty IBS-D patients and 60 HVs were studied. The genotype in all participants was C/C-13910. LM and LI detection rates increased with lactose dose from 10 g, 20 g to 40 g in both groups (P < 0.001). 4SLHBT showed excellent diagnostic concordance with standard LHBT (97%-100%, Kappa​​ 0.815-0.942) with high sensitivity (90%-100%) and specificity (100%) at all three lactose doses in both groups. Reducing the number of measurements from 13 to 4 samples did not significantly impact on the accuracy of LHBT in health and IBS-D. 4SLHBT is a valid test for assessment of LM and LI in clinical practice.

Experimental investigation of broadband energy harvesting of a bi-stable composite piezoelectric plate

NASA Astrophysics Data System (ADS)

Pan, Diankun; Ma, Benbiao; Dai, Fuhong

2017-03-01

In this work, a bi-stable vibration energy harvester is presented to scavenge energy from ambient vibrations over a wide frequency range. This bi-stable harvester consists of a bi-stable hybrid composite plate as host structure and several pieces of piezoelectric ceramics. Three linear harvesters with the same geometry were employed as the control samples to illustrate the advantages of this bi-stable harvester. The voltage-frequency responses were measured with different g-level excitations, and the output powers across various resistances were measured at different frequencies and accelerations. Unlike the linear harvesters which are effective only near their natural frequencies, the obvious nonlinearities of this bi-stable harvester broaden its working bandwidth. Additionally, the characteristics of this bi-stable host structure contribute to the output power. Under the same condition, when this bi-stable harvester is under cross-well oscillation pattern the maximum output powers are several times higher than those of the linear harvesters. The measured highest output power of this bi-stable harvester is 36.2 mW with 38 Hz frequency and 5g acceleration (g = 9.8 m s-2).

Unprecedented high-resolution view of bacterial operon architecture revealed by RNA sequencing.

PubMed

Conway, Tyrrell; Creecy, James P; Maddox, Scott M; Grissom, Joe E; Conkle, Trevor L; Shadid, Tyler M; Teramoto, Jun; San Miguel, Phillip; Shimada, Tomohiro; Ishihama, Akira; Mori, Hirotada; Wanner, Barry L

2014-07-08

We analyzed the transcriptome of Escherichia coli K-12 by strand-specific RNA sequencing at single-nucleotide resolution during steady-state (logarithmic-phase) growth and upon entry into stationary phase in glucose minimal medium. To generate high-resolution transcriptome maps, we developed an organizational schema which showed that in practice only three features are required to define operon architecture: the promoter, terminator, and deep RNA sequence read coverage. We precisely annotated 2,122 promoters and 1,774 terminators, defining 1,510 operons with an average of 1.98 genes per operon. Our analyses revealed an unprecedented view of E. coli operon architecture. A large proportion (36%) of operons are complex with internal promoters or terminators that generate multiple transcription units. For 43% of operons, we observed differential expression of polycistronic genes, despite being in the same operons, indicating that E. coli operon architecture allows fine-tuning of gene expression. We found that 276 of 370 convergent operons terminate inefficiently, generating complementary 3' transcript ends which overlap on average by 286 nucleotides, and 136 of 388 divergent operons have promoters arranged such that their 5' ends overlap on average by 168 nucleotides. We found 89 antisense transcripts of 397-nucleotide average length, 7 unannotated transcripts within intergenic regions, and 18 sense transcripts that completely overlap operons on the opposite strand. Of 519 overlapping transcripts, 75% correspond to sequences that are highly conserved in E. coli (>50 genomes). Our data extend recent studies showing unexpected transcriptome complexity in several bacteria and suggest that antisense RNA regulation is widespread. Importance: We precisely mapped the 5' and 3' ends of RNA transcripts across the E. coli K-12 genome by using a single-nucleotide analytical approach. Our resulting high-resolution transcriptome maps show that ca. one-third of E. coli operons are

Optical Bistability under Nonresonant Excitation in Spinor Polariton Condensates

NASA Astrophysics Data System (ADS)

Pickup, L.; Kalinin, K.; Askitopoulos, A.; Hatzopoulos, Z.; Savvidis, P. G.; Berloff, N. G.; Lagoudakis, P. G.

2018-06-01

We realize bistability in the spinor of polariton condensates under nonresonant optical excitation and in the absence of biasing external fields. Numerical modeling of the system using the Ginzburg-Landau equation with an internal Josephson coupling between the two spin components of the condensate qualitatively describes the experimental observations. We demonstrate that polariton spin bistability strongly depends on the condensate's overlap with the exciton reservoir by tuning the excitation geometry and sample temperature. We obtain noncollapsing bistability hysteresis loops for a record range of sweep times, [10 μ s , 1 s], offering a promising route to spin switches and spin memory elements.

Lactose malabsorption and intolerance: What should be the best clinical management?

PubMed

Usai-Satta, Paolo; Scarpa, Mariella; Oppia, Francesco; Cabras, Francesco

2012-06-06

Lactose malabsorption (LM) is the incomplete hydrolysis of lactose due to lactase deficiency, which may occur as a primary disorder or secondary to other intestinal diseases. Primary adult-type hypolactasia is an autosomal recessive condition resulting from the physiological decline of lactase activity. Different methods have been used to diagnose LM. Lactose breath test represents the most reliable technique. A recent consensus conference has proposed the more physiological dosage of 25 g of lactose and a standardized procedure for breath testing. Recently a new genetic test, based on C/T13910 polymorphism, has been proposed for the diagnosis of adult-type hypolactasia, complementing the role of breath testing. LM represents a well-known cause of abdominal symptoms although only some lactose malabsorbers are also intolerants. Diagnosing lactose intolerance is not straightforward. Many non-malabsorber subjects diagnose themselves as being lactose intolerant. Blind lactose challenge studies should be recommended to obtain objective results. Besides several studies indicate that subjects with lactose intolerance can ingest up to 15 g of lactose with no or minor symptoms. Therefore a therapeutic strategy consists of a lactose restricted diet avoiding the nutritional disadvantages of reduced calcium and vitamin intake.Various pharmacological options are also available. Unfortunately there is insufficient evidence that these therapies are effective. Further double-blind studies are needed to demonstrate treatment effectiveness in lactose intolerance.

Lactose malabsorption and intolerance: What should be the best clinical management?

PubMed Central

Usai-Satta, Paolo; Scarpa, Mariella; Oppia, Francesco; Cabras, Francesco

2012-01-01

Lactose malabsorption (LM) is the incomplete hydrolysis of lactose due to lactase deficiency, which may occur as a primary disorder or secondary to other intestinal diseases. Primary adult-type hypolactasia is an autosomal recessive condition resulting from the physiological decline of lactase activity. Different methods have been used to diagnose LM. Lactose breath test represents the most reliable technique. A recent consensus conference has proposed the more physiological dosage of 25 g of lactose and a standardized procedure for breath testing. Recently a new genetic test, based on C/T13910 polymorphism, has been proposed for the diagnosis of adult-type hypolactasia, complementing the role of breath testing. LM represents a well-known cause of abdominal symptoms although only some lactose malabsorbers are also intolerants. Diagnosing lactose intolerance is not straightforward. Many non-malabsorber subjects diagnose themselves as being lactose intolerant. Blind lactose challenge studies should be recommended to obtain objective results. Besides several studies indicate that subjects with lactose intolerance can ingest up to 15 g of lactose with no or minor symptoms. Therefore a therapeutic strategy consists of a lactose restricted diet avoiding the nutritional disadvantages of reduced calcium and vitamin intake.Various pharmacological options are also available. Unfortunately there is insufficient evidence that these therapies are effective. Further double-blind studies are needed to demonstrate treatment effectiveness in lactose intolerance. PMID:22966480

Controllable optical bistability in a three-mode optomechanical system with atom-cavity-mirror couplings

NASA Astrophysics Data System (ADS)

Chen, Bin; Wang, Xiao-Fang; Yan, Jia-Kai; Zhu, Xiao-Fei; Jiang, Cheng

2018-01-01

We theoretically investigate the optical bistable behavior in a three-mode optomechanical system with atom-cavity-mirror couplings. The effects of the cavity-pump detuning and the pump power on the bistable behavior are discussed detailedly, the impacts of the atom-pump detuning and the atom-cavity coupling strength on the bistability of the system are also explored, and the influences of the cavity-resonator coupling strength and the cavity decay rate are also taken into consideration. The numerical results demonstrate that by tuning these parameters the bistable behavior of the system can be freely switched on or off, and the threshold of the pump power for the bistability as well as the bistable region width can also be effectively controlled. These results can find potential applications in optical bistable switch in the quantum information processing.

Comment on 'Observation of intrinsic bistability in resonant-tunneling structures'

NASA Technical Reports Server (NTRS)

Sollner, T. C. L. G.

1987-01-01

It is suggested that the intrinsic bistability observed by Goldman et al. (1987) occurred not because of charging of the well, as is claimed, but because of oscillations in the negative-resistance region. A typical I-V curve for a double-barrier resonant-tunneling (DBRT) diode which is known to be oscillating is presented. In a reply to this comment, Goldman et al. show that the series resistance (of about 100 ohms) in Sollner's sample leads to extrinsic, rather than intrinsic, bistability. It is furthermore suggested that the mere presence of an oscillation does not in itself exclude intrinsic bistability in a DBRT structure. It is also noted that the intrinsic bistability and buildup of negative charge-space in a DBRT structure well has been demonstrated experimentally by Payling et al. (1987).

Amazonian forest-savanna bistability and human impact

NASA Astrophysics Data System (ADS)

Wuyts, Bert; Champneys, Alan R.; House, Joanna I.

2017-05-01

A bimodal distribution of tropical tree cover at intermediate precipitation levels has been presented as evidence of fire-induced bistability. Here we subdivide satellite vegetation data into those from human-unaffected areas and those from regions close to human-cultivated zones. Bimodality is found to be almost absent in the unaffected regions, whereas it is significantly enhanced close to cultivated zones. Assuming higher logging rates closer to cultivated zones and spatial diffusion of fire, our spatiotemporal mathematical model reproduces these patterns. Given a gradient of climatic and edaphic factors, rather than bistability there is a predictable spatial boundary, a Maxwell point, that separates regions where forest and savanna states are naturally selected. While bimodality can hence be explained by anthropogenic edge effects and natural spatial heterogeneity, a narrow range of bimodality remaining in the human-unaffected data indicates that there is still bistability, although on smaller scales than claimed previously.

Operon Conservation and the Evolution of trans-Splicing in the Phylum Nematoda

PubMed Central

Guiliano, David B; Blaxter, Mark L

2006-01-01

The nematode Caenorhabditis elegans is unique among model animals in that many of its genes are cotranscribed as polycistronic pre-mRNAs from operons. The mechanism by which these operonic transcripts are resolved into mature mRNAs includes trans-splicing to a family of SL2-like spliced leader exons. SL2-like spliced leaders are distinct from SL1, the major spliced leader in C. elegans and other nematode species. We surveyed five additional nematode species, representing three of the five major clades of the phylum Nematoda, for the presence of operons and the use of trans-spliced leaders in resolution of polycistronic pre-mRNAs. Conserved operons were found in Pristionchus pacificus, Nippostrongylus brasiliensis, Strongyloides ratti, Brugia malayi, and Ascaris suum. In nematodes closely related to the rhabditine C. elegans, a related family of SL2-like spliced leaders is used for operonic transcript resolution. However, in the tylenchine S. ratti operonic transcripts are resolved using a family of spliced leaders related to SL1. Non-operonic genes in S. ratti may also receive these SL1 variants. In the spirurine nematodes B. malayi and A. suum operonic transcripts are resolved using SL1. Mapping these phenotypes onto the robust molecular phylogeny for the Nematoda suggests that operons evolved before SL2-like spliced leaders, which are an evolutionary invention of the rhabditine lineage. PMID:17121468

Recent advances on lactose intolerance: Tolerance thresholds and currently available answers.

PubMed

Corgneau, M; Scher, J; Ritie-Pertusa, L; Le, D T L; Petit, J; Nikolova, Y; Banon, S; Gaiani, C

2017-10-13

The genetically programmed reduction in lactase activity during adulthood affects 70% of the world adult population and can cause severe digestive disorders, which are the sign of lactose intolerance. Lactose intolerance symptoms vary depending on the residual lactase activity, the small bowel transit time, and especially the amount of ingested lactose. To formulate dairy products suitable for the vast majority of lactose intolerants, it is essential to define lactose intolerance threshold. A recent meta-analysis permitted to show that almost all lactose intolerants tolerate 12 g of lactose in one intake and approximately 18 g of lactose spread over the day. The prevalence and severity of lactose intolerance are probably overestimated by the general public. This misconception usually leads to an unnecessary reduction of dairy foodstuff consumption. Nevertheless, dairy products are essential for health mainly due to their calcium content and the positive influence of probiotic bacteria. The formulation of dairy products suitable for most intolerant and suspicious subjects seems necessary. The use of exogenous enzyme preparations, as well as the consumption of lactose-free products or products rich in probiotic bacteria are proposed as symptom-reducing strategies.

Unidirectional Transition Waves in Bistable Lattices

NASA Astrophysics Data System (ADS)

Nadkarni, Neel; Arrieta, Andres F.; Chong, Christopher; Kochmann, Dennis M.; Daraio, Chiara

2016-06-01

We present a model system for strongly nonlinear transition waves generated in a periodic lattice of bistable members connected by magnetic links. The asymmetry of the on-site energy wells created by the bistable members produces a mechanical diode that supports only unidirectional transition wave propagation with constant wave velocity. We theoretically justify the cause of the unidirectionality of the transition wave and confirm these predictions by experiments and simulations. We further identify how the wave velocity and profile are uniquely linked to the double-well energy landscape, which serves as a blueprint for transition wave control.

Origin of bistability underlying mammalian cell cycle entry

PubMed Central

Yao, Guang; Tan, Cheemeng; West, Mike; Nevins, Joseph R; You, Lingchong

2011-01-01

Precise control of cell proliferation is fundamental to tissue homeostasis and differentiation. Mammalian cells commit to proliferation at the restriction point (R-point). It has long been recognized that the R-point is tightly regulated by the Rb–E2F signaling pathway. Our recent work has further demonstrated that this regulation is mediated by a bistable switch mechanism. Nevertheless, the essential regulatory features in the Rb–E2F pathway that create this switching property have not been defined. Here we analyzed a library of gene circuits comprising all possible link combinations in a simplified Rb–E2F network. We identified a minimal circuit that is able to generate robust, resettable bistability. This minimal circuit contains a feed-forward loop coupled with a mutual-inhibition feedback loop, which forms an AND-gate control of the E2F activation. Underscoring its importance, experimental disruption of this circuit abolishes maintenance of the activated E2F state, supporting its importance for the bistability of the Rb–E2F system. Our findings suggested basic design principles for the robust control of the bistable cell cycle entry at the R-point. PMID:21525871

Optical Bistability under Nonresonant Excitation in Spinor Polariton Condensates.

PubMed

Pickup, L; Kalinin, K; Askitopoulos, A; Hatzopoulos, Z; Savvidis, P G; Berloff, N G; Lagoudakis, P G

2018-06-01

We realize bistability in the spinor of polariton condensates under nonresonant optical excitation and in the absence of biasing external fields. Numerical modeling of the system using the Ginzburg-Landau equation with an internal Josephson coupling between the two spin components of the condensate qualitatively describes the experimental observations. We demonstrate that polariton spin bistability strongly depends on the condensate's overlap with the exciton reservoir by tuning the excitation geometry and sample temperature. We obtain noncollapsing bistability hysteresis loops for a record range of sweep times, [10  μs, 1 s], offering a promising route to spin switches and spin memory elements.

Geometric and potential dynamics interpretation of the optic ring resonator bistability

NASA Astrophysics Data System (ADS)

Chiangga, S.; Chittha, T.; Frank, T. D.

2015-07-01

The optical bistability is a fundamental nonlinear feature of the ring resonator. A geometric and potential dynamics interpretation of the bistability is given. Accordingly, the bistability of the nonlinear system is shown to be a consequence of geometric laws of vector calculus describing the resonator ring. In contrast, the so-called transcendental relations that have been obtained in the literature in order to describe the optical wave are interpreted in terms of potential dynamical systems. The proposed novel interpretation provides new insights into the nature of the ring resonator optical bistability. The fundamental work by Rukhlenko, Premaratne and Agrawal (2010) as well as a more recent study by Chiangga, Pitakwongsaporn, Frank and Yupapin (2013) are considered.

Numerical and experimental study of bistable plates for morphing structures

NASA Astrophysics Data System (ADS)

Nicassio, F.; Scarselli, G.; Avanzini, G.; Del Core, G.

2017-04-01

This study is concerned with the activation energy threshold of bistable composite plates in order to tailor a bistable system for specific aeronautical applications. The aim is to explore potential configurations of the bistable plates and their dynamic behavior for designing novel morphing structure suitable for aerodynamic surfaces and, as a possible further application, for power harvesters. Bistable laminates have two stable mechanical shapes that can withstand aerodynamic loads without additional constraint forces or locking mechanisms. This kind of structures, when properly loaded, snap-through from one stable configuration to another, causing large strains that can also be used for power harvesting scopes. The transition between the stable states of the composite laminate can be triggered, in principle, simply by aerodynamic loads (pilot, disturbance or passive inputs) without the need of servo-activated control systems. Both numerical simulations based on Finite Element models and experimental testing based on different activating forcing spectra are used to validate this concept. The results show that dynamic activation of bistable plates depend on different parameters that need to be carefully managed for their use as aircraft passive wing flaps.

A comparison between lactose breath test and quick test on duodenal biopsies for diagnosing lactase deficiency in patients with self-reported lactose intolerance.

PubMed

Furnari, Manuele; Bonfanti, Daria; Parodi, Andrea; Franzè, Jolanda; Savarino, Edoardo; Bruzzone, Luca; Moscatelli, Alessandro; Di Mario, Francesco; Dulbecco, Pietro; Savarino, Vincenzo

2013-02-01

A lactose breath test (LBT) is usually used to diagnose lactase deficiency, and a lactose quick test (LQT) has been proposed as a new test on duodenal biopsies to detect this disorder. We aimed to assess the diagnostic accuracy of LBT and LQT and their ability to predict the clinical response to a lactose-free diet in patients with self-reported lactose intolerance. Fifty-five patients (age 47 ± 14 y; M/F 15/36) underwent upper gastrointestinal endoscopy and 25g-LBT. Two duodenal biopsies were taken to determine lactase deficiency (normal, mild, or severe) by LQT and to rule out other causes of secondary lactose malabsorption. Patients with a positive LBT and normal LQT also underwent a glucose breath test to exclude small intestinal bacterial overgrowth as a cause of the former result. The severity of gastrointestinal symptoms was measured with a GSS questionnaire, under basal condition and 1 month after a lactose-free diet. Lactose malabsorption was detected in 31/51 patients with LBT and in 37/51 patients with LQT (P = NS). Celiac disease was found in 2 patients. Two LBT+ patients showed a positive glucose breath test for small intestinal bacterial overgrowth. Eight patients had a mild hypolactasia by LQT and a negative LBT, but they had a significant improvement of symptoms after diet. LQT and LBT were concordant in 83% of cases and predicted the response to a lactose-free diet in 98% and 81% of the cases, respectively (P = 0.03). LQT is as sensitive as LBT in detecting lactase deficiency; however, it seems to be more accurate than LBT in predicting the clinical response to a lactose-free diet.

Proposed model for bistability in nanowire nonvolatile memory

NASA Astrophysics Data System (ADS)

Pokalyakin, V.; Tereshin, S.; Varfolomeev, A.; Zaretsky, D.; Baranov, A.; Banerjee, A.; Wang, Y.; Ramanathan, S.; Bandyopadhyay, S.

2005-06-01

Cadmium sulfide nanowires of 10-nm diameter, electrodeposited in porous anodic alumina films, exhibit an electronic bistability that can be harnessed for nonvolatile memory. The current-voltage characteristics of the wires show two stable conductance states that are well separated (conductances differ by more than four orders of magnitude) and long lived (longevity>1yr at room temperature). These two states can encode binary bits 0 and 1. It is possible to switch between them by varying the voltage across the wires, thus "writing" data. Transport behavior of this system has been investigated at different temperatures in an effort to understand the origin of bistability, and a model is presented to explain the observed features. Based on this model, we estimate that about 40 trapped electrons per nanowire are responsible for the bistability.

Lack of effect of lactose digestion status on baseline fecal microflora

PubMed Central

Szilagyi, Andrew; Shrier, Ian; Chong, George; Je, Jung Sung; Park, Sunghoon; Heilpern, Debra; Lalonde, Catherine; Cote, Louis-Francois; Lee, Byong

2009-01-01

BACKGROUND: The genetics of intestinal lactase divide the world’s population into two phenotypes: the ability (a dominant trait) or inability (a recessive trait) to digest lactose. A prebiotic effect of lactose may impact the colonic flora of these phenotypes differently. OBJECTIVE: To detect and evaluate the effects of lactose on subjects divided according to their ability to digest lactose. METHODS: A total of 57 healthy maldigesters (n=30) and digesters (n=27) completed diet questionnaires, genetic and breath hydrogen testing, and quantitative stool analysis for species of bacteria. Log10 transformation of bacterial counts was compared with lactose intake in both groups using multiple regression analysis. RESULTS: There was a significant relationship between genetic and breath hydrogen tests. Daily lactose intake was marginally lower in lactose maldigesters (median [interquartile range] 12.2 g [31 g] versus 15 g [29.6 g], respectively). There was no relationship between lactose intake and breath hydrogen tests in either group. There were no differences in bacterial counts between the two groups, nor was there a relationship between bacterial counts and lactose intake in either group. CONCLUSION: The differential bacterial effects of lactose were not quantitatively detected in stool samples taken in the present study. PMID:19893771

Influence of amorphous content on compaction behaviour of anhydrous alpha-lactose.

PubMed

Ziffels, S; Steckel, H

2010-03-15

Modified lactoses are widely used as filler-binders in direct compression of tablets. Until today, little about the compaction behaviour of anhydrous alpha-lactose is known. In this study, a new method to prepare anhydrous alpha-lactose from alpha-lactose monohydrate by desiccation with heated ethanol was evaluated and the influence of amorphous content in the lactose powder prior to modification on powder properties, compaction behaviour and storage stability was determined. The modification process led to anhydrous alpha-lactose with decreased bulk and tapped density, increased flow rate and significantly higher specific surface area. Due to the higher specific surface area, the compaction behaviour of the anhydrous alpha-lactose was found to be significantly better than the compaction behaviour of powder blends consisting of alpha-lactose monohydrate and amorphous lactose. An influence of the amorphous content prior to modification could be observed only at higher compaction forces. In general, tablets of modified powders needed longer time to disintegrate directly after compression. However, the storage stability of modified tablets was found to be better compared to the amorphous-crystalline tablets which were influenced by storage conditions, initial crushing strength as well as amorphous content due to the re-crystallization of amorphous lactose during storage. 2009 Elsevier B.V. All rights reserved.

Solving a discrete model of the lac operon using Z3

NASA Astrophysics Data System (ADS)

Gutierrez, Natalia A.

2014-05-01

A discrete model for the Lcac Operon is solved using the SMT-solver Z3. Traditionally the Lac Operon is formulated in a continuous math model. This model is a system of ordinary differential equations. Here, it was considerated as a discrete model, based on a Boolean red. The biological problem of Lac Operon is enunciated as a problem of Boolean satisfiability, and it is solved using an STM-solver named Z3. Z3 is a powerful solver that allows understanding the basic dynamic of the Lac Operon in an easier and more efficient way. The multi-stability of the Lac Operon can be easily computed with Z3. The code that solves the Boolean red can be written in Python language or SMT-Lib language. Both languages were used in local version of the program as online version of Z3. For future investigations it is proposed to solve the Boolean red of Lac Operon using others SMT-solvers as cvc4, alt-ergo, mathsat and yices.

Is the subjective perception of lactose intolerance influenced by the psychological profile?

PubMed

Tomba, C; Baldassarri, A; Coletta, M; Cesana, B M; Basilisco, G

2012-10-01

Symptoms of lactose intolerance are often attributed to lactose malabsorption but, as this relationship has not been demonstrated when a small dose of lactose similar to that contained in one cup of milk is ingested by intolerant patients, psychological factors may play a role in altered symptom perception. To assess the hypothesis that the psychological profile influences the symptoms of lactose intolerance. One hundred and two consecutive patients underwent a 15 g lactose hydrogen breath test to assess lactose malabsorption. The patients recorded the presence and severity of symptoms of lactose intolerance during the breath test using visual analogue scales. The psychological profile was assessed using a psychological symptom checklist, and health-related quality of life by means of the short-form health survey. Lactose malabsorption and intolerance were diagnosed in, respectively, 18% and 29% of the patients. The two conditions were not associated, and the severity of intolerance was even less in the patients with malabsorption. Multivariate logistic analysis showed that a high somatisation t-score was significantly associated with lactose intolerance (odds ratio 4.184; 1.704-10.309); the effects of the other psychological variables and of lactose malabsorption were not statistically significant. Health-related quality of life was significantly reduced in the patients with somatisation, but not in those with lactose malabsorption. The symptoms of lactose intolerance during hydrogen breath testing at a low physiological lactose load, are unrelated to lactose malabsorption, but may reveal a tendency towards somatisation that could impair the quality of life. © 2012 Blackwell Publishing Ltd.

Ancient Origin of the Tryptophan Operon and the Dynamics of Evolutionary Change†

PubMed Central

Xie, Gary; Keyhani, Nemat O.; Bonner; Jensen, Roy A.

2003-01-01

The seven conserved enzymatic domains required for tryptophan (Trp) biosynthesis are encoded in seven genetic regions that are organized differently (whole-pathway operons, multiple partial-pathway operons, and dispersed genes) in prokaryotes. A comparative bioinformatics evaluation of the conservation and organization of the genes of Trp biosynthesis in prokaryotic operons should serve as an excellent model for assessing the feasibility of predicting the evolutionary histories of genes and operons associated with other biochemical pathways. These comparisons should provide a better understanding of possible explanations for differences in operon organization in different organisms at a genomics level. These analyses may also permit identification of some of the prevailing forces that dictated specific gene rearrangements during the course of evolution. Operons concerned with Trp biosynthesis in prokaryotes have been in a dynamic state of flux. Analysis of closely related organisms among the Bacteria at various phylogenetic nodes reveals many examples of operon scission, gene dispersal, gene fusion, gene scrambling, and gene loss from which the direction of evolutionary events can be deduced. Two milestone evolutionary events have been mapped to the 16S rRNA tree of Bacteria, one splitting the operon in two, and the other rejoining it by gene fusion. The Archaea, though less resolved due to a lesser genome representation, appear to exhibit more gene scrambling than the Bacteria. The trp operon appears to have been an ancient innovation; it was already present in the common ancestor of Bacteria and Archaea. Although the operon has been subjected, even in recent times, to dynamic changes in gene rearrangement, the ancestral gene order can be deduced with confidence. The evolutionary history of the genes of the pathway is discernible in rough outline as a vertical line of descent, with events of lateral gene transfer or paralogy enriching the analysis as interesting

[Determination of lactose intolerance frequency in children with food allergy].

PubMed

Hutyra, Tomasz; Iwańczak, Barbara

2008-10-01

Lactose malabsorption and lactose intolerance symptoms are the most common alimentary tract disorders in children. Lactose intolerance is a result of lactase deficiency or lack of lactase and lactose malabsorption. Hypersensitivity in food allergy is connected with the presence of specific IgE (specific antibodies against some allergens) or lymphocytes. Lactose intolerance and food allergy may coexist in the same patient. The aim of this study was determination of lactose intolerance frequency in children with food allergy who were below and above 5 years of age. The number of 87 children with food allergy aged from 0.7 to 18 years were included in the study (48 boys and 39 girls). 51 patients above 5 years of age and 36 patients below 5 years of age were studied. Lactose intolerance symptoms, hydrogen breath test, activity of lactase and villous atrophy were investigated. Decreased absorption of lactose in hydrogen breath test was observed in 28% of children above 5 years of age and in 5% in younger children. Positive result of biological trial in hydrogen breath test was observed in 10% of patients who were below 5 years of age and in 26% patients above 5 years. There was no statistically significant difference in lactose intolerance frequency and in decreased activity of lactase in intestinal mucosa between these two groups. Frequent partial villous atrophy was observed in younger patients (41,38%) than in children above 5 years of age (17.86%). Lactose intolerance was observed in 10% patients who were below 5 years of age and in 26% patients above 5 years of age with food allergy. There was no statistically significant difference between these two groups.

Bistable Topological Insulator with Exciton-Polaritons

NASA Astrophysics Data System (ADS)

Kartashov, Yaroslav V.; Skryabin, Dmitry V.

2017-12-01

The functionality of many nonlinear and quantum optical devices relies on the effect of optical bistability. Using microcavity exciton-polaritons in a honeycomb arrangement of microcavity pillars, we report the resonance response and bistability of topological edge states. A balance between the pump, loss, and nonlinearity ensures a broad range of dynamical stability and controls the distribution of power between counterpropagating states on the opposite edges of the honeycomb lattice stripe. Tuning energy and polarization of the pump photons, while keeping their momentum constant, we demonstrate control of the propagation direction of the dominant edge state. Our results facilitate the development of practical applications of topological photonics.

Dynamics of a bistable Miura-origami structure

NASA Astrophysics Data System (ADS)

Fang, Hongbin; Li, Suyi; Ji, Huimin; Wang, K. W.

2017-05-01

Origami-inspired structures and materials have shown extraordinary properties and performances originating from the intricate geometries of folding. However, current state of the art studies have mostly focused on static and quasistatic characteristics. This research performs a comprehensive experimental and analytical study on the dynamics of origami folding through investigating a stacked Miura-Ori (SMO) structure with intrinsic bistability. We fabricate and experimentally investigated a bistable SMO prototype with rigid facets and flexible crease lines. Under harmonic base excitation, the SMO exhibits both intrawell and interwell oscillations. Spectrum analyses reveal that the dominant nonlinearities of SMO are quadratic and cubic, which generate rich dynamics including subharmonic and chaotic oscillations. The identified nonlinearities indicate that a third-order polynomial can be employed to approximate the measured force-displacement relationship. Such an approximation is validated via numerical study by qualitatively reproducing the phenomena observed in the experiments. The dynamic characteristics of the bistable SMO resemble those of a Helmholtz-Duffing oscillator (HDO); this suggests the possibility of applying the established tools and insights of HDO to predict origami dynamics. We also show that the bistability of SMO can be programmed within a large design space via tailoring the crease stiffness and initial stress-free configurations. The results of this research offer a wealth of fundamental insights into the dynamics of origami folding, and provide a solid foundation for developing foldable and deployable structures and materials with embedded dynamic functionalities.

Bistability of mangrove forests and competition with freshwater plants

USGS Publications Warehouse

Jiang, Jiang; Fuller, Douglas O; Teh, Su Yean; Zhai, Lu; Koh, Hock Lye; DeAngelis, Donald L.; Sternberg, L.D.S.L.

2015-01-01

Halophytic communities such as mangrove forests and buttonwood hammocks tend to border freshwater plant communities as sharp ecotones. Most studies attribute this purely to underlying physical templates, such as groundwater salinity gradients caused by tidal flux and topography. However, a few recent studies hypothesize that self-reinforcing feedback between vegetation and vadose zone salinity are also involved and create a bistable situation in which either halophytic dominated habitat or freshwater plant communities may dominate as alternative stable states. Here, we revisit the bistability hypothesis and demonstrate the mechanisms that result in bistability. We demonstrate with remote sensing imagery the sharp boundaries between freshwater hardwood hammock communities in southern Florida and halophytic communities such as buttonwood hammocks and mangroves. We further document from the literature how transpiration of mangroves and freshwater plants respond differently to vadose zone salinity, thus altering the salinity through feedback. Using mathematical models, we show how the self-reinforcing feedback, together with physical template, controls the ecotones between halophytic and freshwater communities. Regions of bistability along environmental gradients of salinity have the potential for large-scale vegetation shifts following pulse disturbances such as hurricane tidal surges in Florida, or tsunamis in other regions. The size of the region of bistability can be large for low-lying coastal habitat due to the saline water table, which extends inland due to salinity intrusion. We suggest coupling ecological and hydrologic processes as a framework for future studies.

Interplay of Noisy Gene Expression and Dynamics Explains Patterns of Bacterial Operon Organization

NASA Astrophysics Data System (ADS)

Igoshin, Oleg

2011-03-01

Bacterial chromosomes are organized into operons -- sets of genes co-transcribed into polycistronic messenger RNA. Hypotheses explaining the emergence and maintenance of operons include proportional co-regulation, horizontal transfer of intact ``selfish'' operons, emergence via gene duplication, and co-production of physically interacting proteins to speed their association. We hypothesized an alternative: operons can reduce or increase intrinsic gene expression noise in a manner dependent on the post-translational interactions, thereby resulting in selection for or against operons in depending on the network architecture. We devised five classes of two-gene network modules and show that the effects of operons on intrinsic noise depend on class membership. Two classes exhibit decreased noise with co-transcription, two others reveal increased noise, and the remaining one does not show a significant difference. To test our modeling predictions we employed bioinformatic analysis to determine the relationship gene expression noise and operon organization. The results confirm the overrepresentation of noise-minimizing operon architectures and provide evidence against other hypotheses. Our results thereby suggest a central role for gene expression noise in selecting for or maintaining operons in bacterial chromosomes. This demonstrates how post-translational network dynamics may provide selective pressure for organizing bacterial chromosomes, and has practical consequences for designing synthetic gene networks. This work is supported by National Institutes of Health grant 1R01GM096189-01.

Bi-stable optical actuator

DOEpatents

Holdener, Fred R.; Boyd, Robert D.

2000-01-01

The present invention is a bi-stable optical actuator device that is depowered in both stable positions. A bearing is used to transfer motion and smoothly transition from one state to another. The optical actuator device may be maintained in a stable position either by gravity or a restraining device.

Bistability in Josephson Junction array resonator

NASA Astrophysics Data System (ADS)

Muppalla, Phani Raja; Alexandre Blais Collaboration; Christian Kraglund Andersen Collaboration; Ioan Pop, Lukas Gruenhaupt Collaboration; Michel Devoret Collaboration; Oscar Garguilo, Gerhard Kirchmair Team

``We present an experimental analysis of the Kerr effect of extended plasma resonances in a 1000 Josephson junction (JJ) chain resonator inside a rectangular waveguide. The Kerr effect manifests itself as a frequency shift that depends linearly on the number of photons in a resonant mode. We study the bistable behavior, using a pump probe scheme on two modes of the JJ array, exploiting the Cross-Kerr effect in our system. In order to understand the behavior of the bi-stability we perform continuous time measurements to observe the switching between the two metastable states. We observe a strong dependence of the switching rates on the photon number and the drive frequency.''

Prevalence of lactose intolerance in Chile: a double-blind placebo study.

PubMed

Latorre, Gonzalo; Besa, Pablo; Parodi, Carmen G; Ferrer, Verónica; Azocar, Lorena; Quirola, Marife; Villarroel, Luis; Miquel, Juan F; Agosin, Eduardo; Chianale, José

2014-01-01

Lactase non-persistence (LNP), or primary hypolactasia, is a genetic condition that mediates lactose malabsorption and can cause lactose intolerance. Here we report the prevalence of lactose intolerance in a double-blind placebo study. The LCT C>T-13910 variant was genotyped by RT-PCR in 121 volunteers and lactose malabsorption was assessed using the hydrogen breath test (HBT) after consuming 25 g of lactose. Lactose intolerance was assessed by scoring symptoms (SS) using a standardized questionnaire following challenge with a lactose solution or saccharose placebo. The LNP genotype was observed in 57% of the volunteers, among whom 87% were HBT⁺. In the HBT⁺ group the median SS was 9 and in the HBT⁻ group the median SS was 3 (p < 0.001). No difference was observed in the SS when both groups were challenged with the placebo. The most common symptoms included audible bowel sounds, abdominal pain and meteorism. In the ROC curve analysis, an SS ≥ 6 demonstrated 72% sensitivity and 81% specificity for predicting a positive HBT. To estimate prevalence, lactose intolerance was defined as the presence of an SS ≥ 6 points after subtracting the placebo effect and 34% of the study population met this definition. The LNP genotype was present in more than half of subjects evaluated and the observed prevalence of lactose intolerance was 34%. © 2014 S. Karger AG, Basel.

75 FR 2551 - NIH Consensus Development Conference: Lactose Intolerance and Health; Notice

Federal Register 2010, 2011, 2012, 2013, 2014

2010-01-15

... Conference: Lactose Intolerance and Health; Notice Notice is hereby given by the National Institutes of Health (NIH) of the ``NIH Consensus Development Conference: Lactose Intolerance and Health'' to be held... the public. Lactose intolerance is the inability to digest significant amounts of lactose, a sugar...

Two Bistable Switches Govern M Phase Entry.

PubMed

Mochida, Satoru; Rata, Scott; Hino, Hirotsugu; Nagai, Takeharu; Novák, Béla

2016-12-19

The abrupt and irreversible transition from interphase to M phase is essential to separate DNA replication from chromosome segregation. This transition requires the switch-like phosphorylation of hundreds of proteins by the cyclin-dependent kinase 1 (Cdk1):cyclin B (CycB) complex. Previous studies have ascribed these switch-like phosphorylations to the auto-activation of Cdk1:CycB through the removal of inhibitory phosphorylations on Cdk1-Tyr15 [1, 2]. The positive feedback in Cdk1 activation creates a bistable switch that makes mitotic commitment irreversible [2-4]. Here, we surprisingly find that Cdk1 auto-activation is dispensable for irreversible, switch-like mitotic entry due to a second mechanism, whereby Cdk1:CycB inhibits its counteracting phosphatase (PP2A:B55). We show that the PP2A:B55-inhibiting Greatwall (Gwl)-endosulfine (ENSA) pathway is both necessary and sufficient for switch-like phosphorylations of mitotic substrates. Using purified components of the Gwl-ENSA pathway in a reconstituted system, we found a sharp Cdk1 threshold for phosphorylation of a luminescent mitotic substrate. The Cdk1 threshold to induce mitotic phosphorylation is distinctly higher than the Cdk1 threshold required to maintain these phosphorylations-evidence for bistability. A combination of mathematical modeling and biochemical reconstitution show that the bistable behavior of the Gwl-ENSA pathway emerges from its mutual antagonism with PP2A:B55. Our results demonstrate that two interlinked bistable mechanisms provide a robust solution for irreversible and switch-like mitotic entry. Copyright © 2016 Elsevier Ltd. All rights reserved.

A Novel Method for Accurate Operon Predictions in All SequencedProkaryotes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Price, Morgan N.; Huang, Katherine H.; Alm, Eric J.

2004-12-01

We combine comparative genomic measures and the distance separating adjacent genes to predict operons in 124 completely sequenced prokaryotic genomes. Our method automatically tailors itself to each genome using sequence information alone, and thus can be applied to any prokaryote. For Escherichia coli K12 and Bacillus subtilis, our method is 85 and 83% accurate, respectively, which is similar to the accuracy of methods that use the same features but are trained on experimentally characterized transcripts. In Halobacterium NRC-1 and in Helicobacterpylori, our method correctly infers that genes in operons are separated by shorter distances than they are in E.coli, andmore » its predictions using distance alone are more accurate than distance-only predictions trained on a database of E.coli transcripts. We use microarray data from sixphylogenetically diverse prokaryotes to show that combining intergenic distance with comparative genomic measures further improves accuracy and that our method is broadly effective. Finally, we survey operon structure across 124 genomes, and find several surprises: H.pylori has many operons, contrary to previous reports; Bacillus anthracis has an unusual number of pseudogenes within conserved operons; and Synechocystis PCC6803 has many operons even though it has unusually wide spacings between conserved adjacent genes.« less

Perceived lactose intolerance in adult Canadians: a national survey.

PubMed

Barr, Susan I

2013-08-01

Although double-blind studies show that lactose-intolerant individuals can consume moderate quantities of milk products without perceptible symptoms, many who perceive that they are lactose intolerant limit or avoid milk products, potentially compromising calcium and vitamin D intakes. Adult Canadians are at risk of inadequate intakes of these nutrients, but no data exist on the prevalence, correlates, and potential impact of perceived lactose intolerance among Canadians. To address this, a Web-based survey of a population-representative sample of 2251 Canadians aged ≥19 years was conducted. Overall, 16% self-reported lactose intolerance. This was more common in women (odds ratio (OR), 1.84; 95% CI, 1.46-2.33) and in nonwhites (OR, 1.79; 95% CI, 1.24-2.58) and less common in those >50 years of age (OR, 0.71; 95% CI, 0.56-0.90) and in those completing the survey in French (OR, 0.74; 95% CI, 0.56-0.99). Those with self-reported lactose intolerance had lower covariate-adjusted milk product and alternative intakes (mean ± SE; 1.40 ± 0.08 servings·day(-1) vs. 2.33 ± 0.03 servings·day(-1), p < 0.001). A greater proportion used supplements containing calcium (52% vs. 37%, p < 0.001) and vitamin D (58% vs. 46%, p < 0.001), but calcium intakes from the combination of milk products, alternatives, and supplements were lower (739 ± 30 mg·day(-1) vs. 893 ± 13 mg·day(-1), p < 0.0001). Variation in self-reported lactose intolerance by sex, age, and language preference was unexpected and suggests that some groups may be more vulnerable to the perception that they are lactose intolerant. Regardless of whether lactose intolerance is physiologically based or perceptual, education is required to ensure that calcium intakes are not compromised.

Analytic descriptions of stochastic bistable systems under force ramp

DOE PAGES

Friddle, Raymond W.

2016-05-13

Solving the two-state master equation with time-dependent rates, the ubiquitous driven bistable system, is a long-standing problem that does not permit a complete solution for all driving rates. We show an accurate approximation to this problem by considering the system in the control parameter regime. Moreover, the results are immediately applicable to a diverse range of bistable systems including single-molecule mechanics.

Effects of pacing magnitudes and forms on bistability width in a modeled ventricular tissue

NASA Astrophysics Data System (ADS)

Huang, Xiaodong; Liu, Xuemei; Zheng, Lixian; Mi, Yuanyuan; Qian, Yu

2013-07-01

Bistability in periodically paced cardiac tissue is relevant to cardiac arrhythmias and its control. In the present paper, one-dimensional tissue of the phase I Luo-Rudy model is numerically investigated. The effects of various parameters of pacing signals on bistability width are studied. The following conclusions are obtained: (i) Pacing can be classified into two types: pulsatile and sinusoidal types. Pulsatile pacing reduces bistability width as its magnitude is increased. Sinusoidal pacing increases the width as its amplitude is increased. (ii) In a pacing period the hyperpolarizing part plays a more important role than the depolarizing part. Variations of the hyperpolarizing ratio in a period evidently change the width of bistability and its variation tendency. (iii) A dynamical mechanism is proposed to qualitatively explain the phenomena, which reveals the reason for the different effects of pulsatile and sinusoidal pacing on bistability. The methods for changing bistability width by external pacing may help control arrhythmias in cardiology.

Bistable Microvalve For Use With Microcatheter System

DOEpatents

Seward, Kirk Patrick

2003-12-16

A bistable microvalve of shape memory material is operatively connected to a microcatheter. The bistable microvalve includes a tip that can be closed off until it is in the desired position. Once it is in position it can be opened and closed. The system uses heat and pressure to open and close the microvalve. The shape memory material will change stiffness and shape when heated above a transition temperature. The shape memory material is adapted to move from a first shape to a second shape, either open or closed, where it can perform a desired function.

The groESL Chaperone Operon of Lactobacillus johnsonii†

PubMed Central

Walker, D. Carey; Girgis, Hany S.; Klaenhammer, Todd R.

1999-01-01

The Lactobacillus johnsonii VPI 11088 groESL operon was localized on the chromosome near the insertion element IS1223. The operon was initially cloned as a series of three overlapping PCR fragments, which were sequenced and used to design primers to amplify the entire operon. The amplified fragment was used as a probe to recover the chromosomal copy of the groESL operon from a partial library of L. johnsonii VPI 11088 (NCK88) DNA, cloned in the shuttle vector pTRKH2. The 2,253-bp groESL fragment contained three putative open reading frames, two of which encoded the ubiquitous GroES and GroEL chaperone proteins. Analysis of the groESL promoter region revealed three transcription initiation sites, as well as three sets of inverted repeats (IR) positioned between the transcription and translation start sites. Two of the three IR sets bore significant homology to the CIRCE elements, implicated in negative regulation of the heat shock response in many bacteria. Northern analysis and primer extension revealed that multiple temperature-sensitive promoters preceded the groESL chaperone operon, suggesting that stress protein production in L. johnsonii is strongly regulated. Maximum groESL transcription activity was observed following a shift to 55°C, and a 15 to 30-min exposure of log-phase cells to this temperature increased the recovery of freeze-thawed L. johnsonii VPI 11088. These results suggest that a brief, preconditioning heat shock can be used to trigger increased chaperone production and provide significant cross-protection from the stresses imposed during the production of frozen culture concentrates. PMID:10388700

Hypolactasia & lactose intolerance among three ethnic groups in Malaysia.

PubMed

Asmawi, M Z; Seppo, L; Vapaatalo, H; Korpela, R

2006-12-01

Prevalence of adult-type hypolactasia is known to vary among different countries and in different ethnic populations in the same country. The present study was undertaken to evaluate the prevalence of hypolactasia and lactose intolerance in three different ethnic populations living in similar environmental conditions in Malaysia. The correlation between different symptoms and lactose intolerance test was also studied. A total of 300 Malaysian subjects from three different ethnic populations: Malays, Chinese and Indians (100 volunteers in each group, 18-49 yr old working or studying in a University) were included. Urine galactose excretion and gastrointestinal symptoms were measured after lactose intake (50 g). Based on galactose excretion, 88 per cent of the Malays, 91 per cent of the Chinese and 83 per cent of the Indians were hypolactasic. The differences were statistically not significant. When the symptoms were also considered, prevalence of lactose intolerance appeared to be significantly lowest among the Indians. When the subjects were divided into low, middle and high galactose excretion groups some correlation was found between the symptoms and galactose excretion. There was no clear association between hypolactasia and gastrointestinal symptoms in all the study groups. However, the lactose intolerance was high in all the study groups indicating the increasing demand for low lactose dairy products in the Asian countries.

A combination of acid lactase from Aspergillus oryzae and yogurt bacteria improves lactose digestion in lactose maldigesters synergistically: A randomized, controlled, double-blind cross-over trial.

PubMed

de Vrese, Michael; Laue, Christiane; Offick, Birte; Soeth, Edlyn; Repenning, Frauke; Thoß, Angelika; Schrezenmeir, Jürgen

2015-06-01

Lactose digestion can be improved in subjects with impaired or completely absent intestinal lactase activity by administration of lactase preparations and particularly of acid lactase, which is active in the stomach, or by yogurt containing live lactic acid bacteria. It is the question, if lactose digestion can be further enhanced by combining these two approaches. We investigated in a randomised, placebo-controlled, double-blind, 5-arm crossover study on 24 lactose malabsorbers with variable degrees of lactase deficiency if different lactase preparations and freeze-dried yogurt culture affect gastrointestinal lactose digestion after consuming moderate amounts of lactose (12.5 g) by assessing hydrogen exhalation over 6 h. Furthermore, symptoms of lactose intolerance (excess gas production, abdominal pain, diarrhoea or nausea) were assessed using validated questionnaires. All preparations increased lactose digestion and reduced peak hydrogen exhalation by -27% (yogurt), -29/-33% (3300/9000 FCC(1) ((1) One FCC hydrolyses about 5 or 1.7-2.5 mg lactose in aquous solution or in (artificial) chyme, respectively, according to the FCC-III method of the Committee on Codex Specifications, Food and Nutrition Board, National Research Council. Food Chemicals Codex, 3rd edition. Washington, DC, National Academy Press, 1981 It cannot precisely be defined how much lactose can be hydrolysed in vivo by the consumption of a certain number of FCC units.) units acid lactase from Aspergillus oryzae) or -46%, respectively (3300 FCC units lactase plus yogurt culture combined), as compared with placebo (p < 0.001, Friedman test). The combination preparation had not only the strongest effect, but also showed the lowest variance in H(2)-exhalation values (less malabsorbers with no reduction of H(2)-exhalation) Apart from this, both the higher dose lactase and the combination preparation significantly reduced the symptoms most closely associated with H(2)-exhalation, namely flatulences and

Optical bistability for optical signal processing and computing

NASA Astrophysics Data System (ADS)

Peyghambarian, N.; Gibbs, H. M.

1985-02-01

Optical bistability (OB) is a phenomenon in which a nonlinear medium responds to an optical input beam by changing its transmission abruptly from one value to another. A 'nonlinear medium' is a medium in which the index of refraction depends on the incident light intensity. A device is said to be optically bistable if two stable output states exist for the same value of the input. Optically bistable devices can perform a number of logic functions related to optical memory, optical transistor, optical discriminator, optical limiter, optical oscillator, and optical gate. They also have the potential for subpicosecond switching, greatly exceeding the capability of electronics. This potential is one of several advantages of optical data processing over electronic processing. Other advantages are greater immunity to electromagnetic interference and crosstalk, and highly parallel processing capability. The present investigation is mainly concerned with all-optical etalon devices. The considered materials, include GaAs, ZnS and ZnSe, CuCl, InSb, InAs, and CdS.

Evidence for distinct mechanisms underlying attentional priming and sensory memory for bistable perception.

PubMed

Brinkhuis, M A B; Kristjánsson, Á; Brascamp, J W

2015-08-01

Attentional selection in visual search paradigms and perceptual selection in bistable perception paradigms show functional similarities. For example, both are sensitive to trial history: They are biased toward previously selected targets or interpretations. We investigated whether priming by target selection in visual search and sensory memory for bistable perception are related. We did this by presenting two trial types to observers. We presented either ambiguous spheres that rotated over a central axis and could be perceived as rotating in one of two directions, or search displays in which the unambiguously rotating target and distractor spheres closely resembled the two possible interpretations of the ambiguous stimulus. We interleaved both trial types within experiments, to see whether priming by target selection during search trials would affect the perceptual outcome of bistable perception and, conversely, whether sensory memory during bistable perception would affect target selection times during search. Whereas we found intertrial repetition effects among consecutive search trials and among consecutive bistable trials, we did not find cross-paradigm effects. Thus, even though we could ascertain that our experiments robustly elicited processes of both search priming and sensory memory for bistable perception, these same experiments revealed no interaction between the two.

Dynamo efficiency controlled by hydrodynamic bistability.

PubMed

Miralles, Sophie; Herault, Johann; Herault, Johann; Fauve, Stephan; Gissinger, Christophe; Pétrélis, François; Daviaud, François; Dubrulle, Bérengère; Boisson, Jean; Bourgoin, Mickaël; Verhille, Gautier; Odier, Philippe; Pinton, Jean-François; Plihon, Nicolas

2014-06-01

Hydrodynamic and magnetic behaviors in a modified experimental setup of the von Kármán sodium flow-where one disk has been replaced by a propeller-are investigated. When the rotation frequencies of the disk and the propeller are different, we show that the fully turbulent hydrodynamic flow undergoes a global bifurcation between two configurations. The bistability of these flow configurations is associated with the dynamics of the central shear layer. The bistable flows are shown to have different dynamo efficiencies; thus for a given rotation rate of the soft-iron disk, two distinct magnetic behaviors are observed depending on the flow configuration. The hydrodynamic transition controls the magnetic field behavior, and bifurcations between high and low magnetic field branches are investigated.

NIH consensus development conference statement: Lactose intolerance and health.

PubMed

Suchy, Frederick J; Brannon, Patsy M; Carpenter, Thomas O; Fernandez, Jose R; Gilsanz, Vicente; Gould, Jeffrey B; Hall, Karen; Hui, Siu L; Lupton, Joanne; Mennella, Julie; Miller, Natalie J; Osganian, Stavroula Kalis; Sellmeyer, Deborah E; Wolf, Marshall A

2010-02-24

To provide health care providers, patients, and the general public with a responsible assessment of currently available data on lactose intolerance and health. A non-DHHS, nonadvocate 14-member panel representing the fields of internal medicine, pediatrics, pediatric and adult endocrinology, gastroenterology, hepatology, neonatology and perinatology, geriatrics, racial/ethnic disparities, radiology, maternal and fetal nutrition, vitamin and mineral metabolism, nutritional sciences, bone health, preventive medicine, biopsychology, biostatistics, statistical genetics, epidemiology, and a public representative. In addition, 22 experts from pertinent fields presented data to the panel and conference audience. Presentations by experts and a systematic review of the literature prepared by the University of Minnesota Evidence-based Practice Center, through the Agency for Healthcare Research and Quality. Scientific evidence was given precedence over anecdotal experience. The panel drafted its statement based on scientific evidence presented in open forum and on published scientific literature. The draft statement was presented on the final day of the conference and circulated to the audience for comment. The panel released a revised statement later that day at http://consensus.nih.gov. This statement is an independent report of the panel and is not a policy statement of the NIH or the Federal Government. • Lactose intolerance is a real and important clinical syndrome, but its true prevalence is not known. • The majority of people with lactose malabsorption do not have clinical lactose intolerance. Many individuals who think they are lactose intolerant are not lactose malabsorbers. • Many individuals with real or perceived lactose intolerance avoid dairy and ingest inadequate amounts of calcium and vitamin D, which may predispose them to decreased bone accrual, osteoporosis, and other adverse health outcomes. In most cases, individuals do not need to eliminate dairy

Insights into arsenic multi-operons expression and resistance mechanisms in Rhodopseudomonas palustris CGA009

PubMed Central

Zhao, Chungui; Zhang, Yi; Chan, Zhuhua; Chen, Shicheng; Yang, Suping

2015-01-01

Arsenic (As) is widespread in the environment and causes numerous health problems. Rhodopseudomonas palustris has been regarded as a good model organism for studying arsenic detoxification since it was first demonstrated to methylate environmental arsenic by conversion to soluble or gaseous methylated species. However, the detailed arsenic resistance mechanisms remain unknown though there are at least three arsenic-resistance operons (ars1, ars2, and ars3) in R. palustris. In this study, we investigated how arsenic multi-operons contributed to arsenic detoxification in R. palustris. The expression of ars2 or ars3 operons increased with increasing environmental arsenite (As(III)) concentrations (up to 1.0 mM) while transcript of ars1 operon was not detected in the middle log-phase (55 h). ars2 operon was actively expressed even at the low concentration of As(III) (0.01 μM), whereas the ars3 operon was expressed at 1.0 μM of As(III), indicating that there was a differential regulation mechanism for the three arsenic operons. Furthermore, ars2 and ars3 operons were maximally transcribed in the early log-phase where ars2 operon was 5.4-fold higher than that of ars3 operon. A low level of ars1 transcript was only detected at 43 h (early log-phase). Arsenic speciation analysis demonstrated that R. palustris could reduce As(V) to As(III). Collectively, strain CGA009 detoxified arsenic by using arsenic reduction and methylating arsenic mechanism, while the latter might occur with the presence of higher concentrations of arsenic. PMID:26441915

Impact of orocecal transit time on patient´s perception of lactose intolerance.

PubMed

Casellas, Francesc; Aparici, Anna; Casaus, Maite; Rodríguez, Purificación; Malagelada, Juan R

2013-01-01

symptoms attributed to the lactose intolerance are an important public health issue because of their prevalence and social relevance. Also because they may cause undue rejection of dairy products consume with potential health consequences. Transit time is a putative factor implied in the severity of symptoms associated with lactose. to elucidate the relation between orocecal transit time (OCTT) and lactose intolerance symptoms. observational study in patients referred to a lactose hydrogen breath test who showed an increase in breath H2 excretion higher than 25 ppm. OCTT was measured with the breath test and symptoms of lactose tolerance with a validated scale. Symptoms were measured twice: before receiving the lactose, inquiring about self perceived symptoms when patients consumed dairy products at home ("home symptoms"), and again after completing the lactose breath test ("test symptoms"). 161 patients were included. There was no correlation between OCTT and home symptoms (r = -0.1). When OCTT was faster than 60 minutes, intensity of "test symptoms" was similar to "home symptoms". However, in patients with normal or slow OCTT, the "home symptoms" were more intense than the "test symptoms" (p < 0.05). At home, symptoms were independent of OCTT but with the lactose test load the symptoms were proportionately more intense with faster OCTT. in lactose maldigesters, selfreported symptoms of lactose intolerance are more pronounced at home than after a high lactose challenge. Intolerance symptoms that patients attributed to lactose consume at home are due to factors other than fast OCTT.

Analytical study of optical bistability in silicon-waveguide resonators.

PubMed

Rukhlenko, Ivan D; Premaratne, Malin; Agrawal, Govind P

2009-11-23

We present a theoretical model that describes accurately the nonlinear phenomenon of optical bistability in silicon-waveguide resonators but remains amenable to analytical results. Using this model, we derive a transcendental equation governing the intensity of a continuous wave transmitted through a Fabry-Perot resonator formed using a silicon-on-insulator waveguide. This equation reveals a dual role of free carriers in the formation of optical bistability in silicon. First, it shows that free-carrier absorption results in a saturation of the transmitted intensity. Second, the free-carrier dispersion and the thermo-optic effect may introduce phase shifts far exceeding those resulting from the Kerr effect alone, thus enabling one to achieve optical bistability in ultrashort resonators that are only a few micrometers long. Bistability can occur even when waveguide facets are not coated because natural reflectivity of the silicon- r interface can provide sufficient feedback. We find that it is possible to control the input-output characteristics of silicon-based resonators by changing the free-carrier lifetime using a reverse-biased p-n junction. We show theoretically that such a technique is suitable for realization of electronically assisted optical switching at a fixed input power and it may lead to silicon-based, nanometer-size, optical memories.

mar Operon Involved in Multidrug Resistance of Enterobacter aerogenes

PubMed Central

Chollet, Renaud; Bollet, Claude; Chevalier, Jacqueline; Malléa, Monique; Pagès, Jean-Marie; Davin-Regli, Anne

2002-01-01

We determined the sequence of the entire marRAB operon in Enterobacter aerogenes. It is functionally and structurally analogous to the Escherichia coli operon. The overexpression of E. aerogenes MarA induces a multidrug resistance phenotype in a susceptible strain, demonstrated by a noticeable resistance to various antibiotics, a decrease in immunodetected porins, and active efflux of norfloxacin. PMID:11897595

Lactose Intolerance (For Parents)

MedlinePlus

... Doctors usually diagnose lactose intolerance through a simple hydrogen breath test. A person blows into a tube ... there is a higher than average level of hydrogen and methane in the breath. That's because undigested ...

Novel products and new technologies for use of a familiar carbohydrate, milk lactose.

PubMed

Yang, S T; Silva, E M

1995-11-01

The cheese industry produces large amounts of lactose in the form of cheese whey and whey permeate, generating approximately 27 million tonnes/yr in the US alone. Many uses have been found for whey and lactose, including uses in infant formula; bakery, dairy, and confectionery products; animal feed; and feedstocks for lactose derivatives and several industrial fermentations. Lactose use in food products, however, is somewhat limited because of its low solubility and indigestibility in many individuals. For this reason, lactose is often hydrolyzed before use. Still, demand is insufficient to use all available whey lactose. The result is a low market value for lactose; almost half of the whey produced each year remains unused and is a significant waste disposal problem. Several approaches are possible for transforming lactose into value-added products. For example, galactooligosaccharides can be produce through enzymatic treatments of lactose and may be used as a probiotic food ingredient. Organic acids or xanthan gum may be produced via whey fermentation, and the fermented whey product can be used as a food ingredient with special functionality. This paper reviews the physical characteristics, production techniques, and current uses of lactose, whey, and lactose derivatives. Also examined are novel fermentation and separation technologies developed in our laboratory for the production of lactate, propionate, acetate, and xanthan gum from whey.

Harnessing the bistable composite shells to design a tunable phononic band gap structure

NASA Astrophysics Data System (ADS)

Li, Yi; Xu, Yanlong

2018-02-01

By proposing a system composed of an array of bistable composite shells immersed in air, we develop a new class of periodic structure to control the propagation of sound. Through numerical investigation, we find that the acoustic band gap of this system can be switched on and off by triggering the snap through deformation of the bistable composite shells. The shape of cross section and filling fraction of unit cell can be altered by different number of bistable composite shells, and they have strong impact on the position and width of the band gap. The proposed concept paves the way of using the bistable structures to design a new class of metamaterials that can be enable to manipulate sound.

Roller compaction: Effect of relative humidity of lactose powder.

PubMed

Omar, Chalak S; Dhenge, Ranjit M; Palzer, Stefan; Hounslow, Michael J; Salman, Agba D

2016-09-01

The effect of storage at different relative humidity conditions, for various types of lactose, on roller compaction behaviour was investigated. Three types of lactose were used in this study: anhydrous lactose (SuperTab21AN), spray dried lactose (SuperTab11SD) and α-lactose monohydrate 200M. These powders differ in their amorphous contents, due to different manufacturing processes. The powders were stored in a climatic chamber at different relative humidity values ranging from 10% to 80% RH. It was found that the roller compaction behaviour and ribbon properties were different for powders conditioned to different relative humidities. The amount of fines produced, which is undesirable in roller compaction, was found to be different at different relative humidity. The minimum amount of fines produced was found to be for powders conditioned at 20-40% RH. The maximum amount of fines was produced for powders conditioned at 80% RH. This was attributed to the decrease in powder flowability, as indicated by the flow function coefficient ffc and the angle of repose. Particle Image Velocimetry (PIV) was also applied to determine the velocity of primary particles during ribbon production, and it was found that the velocity of the powder during the roller compaction decreased with powders stored at high RH. This resulted in less powder being present in the compaction zone at the edges of the rollers, which resulted in ribbons with a smaller overall width. The relative humidity for the storage of powders has shown to have minimal effect on the ribbon tensile strength at low RH conditions (10-20%). The lowest tensile strength of ribbons produced from lactose 200M and SD was for powders conditioned at 80% RH, whereas, ribbons produced from lactose 21AN at the same condition of 80% RH showed the highest tensile strength. The storage RH range 20-40% was found to be an optimum condition for roll compacting three lactose powders, as it resulted in a minimum amount of fines in the

Design of a fully compliant bistable micromechanism for switching devices

NASA Astrophysics Data System (ADS)

Chang, Hsin-An; Tsay, Jinni; Sung, Cheng-Kuo

2001-11-01

This paper proposes a design of a bistable micromechanism for the application of switching devices. The topology of a fully compliant four-bar mechanism is adopted herein. The central mass of the mechanism is employed as a carriage to carry switching components, such as mirror, electrical contact, etc. The equations that predict the existence of bistable states, the extreme positions of the motion range and the maximum stress states of members were derived. MUMPs provided by Cronos Integrated Microsystems fabricated the proposed micromechanisms for the purpose of verifying the theoretical predictions. Finally, an experimental rig was established. The bistable mechanisms were switched either by the probe or actuators to push the central mass. The experimental results demonstrated that the motions observed approximately met the predicted values.

Effects of glucose on lactose synthesis in mammary epithelial cells from dairy cow.

PubMed

Lin, Ye; Sun, Xiaoxu; Hou, Xiaoming; Qu, Bo; Gao, Xuejun; Li, Qingzhang

2016-05-26

Lactose, as the primary osmotic component in milk, is the major determinant of milk volume. Glucose is the primary precursor of lactose. However, the effect of glucose on lactose synthesis in dairy cow mammary glands and the mechanism governing this process are poorly understood. Here we showed that glucose has the ability to induce lactose synthesis in dairy cow mammary epithelial cells, as well as increase cell viability and proliferation. A concentration of 12 mM glucose was the optimum concentration to induce cell growth and lactose synthesis in cultured dairy cow mammary epithelial cells. In vitro, 12 mM glucose enhanced lactose content, along with the expression of genes involved in glucose transportation and the lactose biosynthesis pathway, including GLUT1, SLC35A2, SLC35B1, HK2, β4GalT-I, and AKT1. In addition, we found that AKT1 knockdown inhibited cell growth and lactose synthesis as well as expression of GLUT1, SLC35A2, SLC35B1, HK2, and β4GalT-I. Glucose induces cell growth and lactose synthesis in dairy cow mammary epithelial cells. Protein kinase B alpha acts as a regulator of metabolism in dairy cow mammary gland to mediate the effects of glucose on lactose synthesis.

Responses of bistable piezoelectric-composite energy harvester by means of recurrences

NASA Astrophysics Data System (ADS)

Syta, Arkadiusz; Bowen, Christopher R.; Kim, H. Alicia; Rysak, Andrzej; Litak, Grzegorz

2016-08-01

In this paper we examine the modal response of a bistable electro-mechanical energy harvesting device based on characterization of the experimental time-series. A piezoelectric element attached to a vibrating bistable carbon-fibre reinforced polymer laminate plate was used for the conversion of mechanical vibrations to electrical energy under harmonic excitations at a variety of frequencies and amplitudes. The inherent bistability of the mechanical resonator and snap-through phenomenon between stable states were exploited for energy harvesting. To identify the dynamics of the response of the studied harvesting structure and the associated output power generation we used the Fourier spectrum and Recurrence Quantification Analysis (RQA).

Lactose carrier protein of Escherichia coli. Transport and binding of 2'-(N-dansyl)aminoethyl beta-D-thiogalactopyranoside and p-nitrophenyl alpha-d-galactopyranoside.

PubMed

Overath, P; Teather, R M; Simoni, R D; Aichele, G; Wilhelm, U

1979-01-09

The elevated level of lactose carrier protein present in cytoplasmic membranes derived from Escherichia coli strain T31RT, which carries the Y gene of the lac operon on a plasmid vector (Teather, R. M., et al. (1978) Mol. Gen. Genet. 159, 239--248), has allowed the detection of a complex between the carrier and the fluorescent substrate 2'-(N-dansyl)-aminoethyl beta-D-thiogalactopyranoside (Dns2-S-Gal). Binding is accompanied by a 50-nm blue shift in the emission maximum of the dansyl residue. The complex (dissociation constant, KD = 30 micron) rapidly dissociates upon addition of competing substrates such as beta-D-galactopyranosyl 1-thio-beta-D-galactopyranoside or upon reaction with the thiol reagent p-chloromercuribenzenesulfonate. Binding of both Dns2-S-Gal and p-nitrophenyl alpha-D-galactopyranoside (alpha-NPG) occurs spontaneously in the absence of an electrochemical potential gradient across the membrane. Comparison of equilibrium binding experiments using Dns2-S-Gal or alpha-NPG and differential labeling of the carrier with radioactive amino acids shows that the carrier binds 1 mol of substrate per mol of polypeptide (molecular weight 30 000). In addition to specific binding to the lactose carrier, Dns2-S-gal binds unspecifically to lipid vesicles or membranes, as described by a partition coefficient, K = 60, resulting in a 25-nm blue shift in the emission maximum of the dansyl group. Both Dns2-S-Gal and alpha-NPG are not only bound by the lactose carrier but also transported across the membrane by this transport protein in cells and membrane vesicles. The fluorescence changes observed with dansylated galactosides in membrane vesicles in the presence of an electrochemical gradient (Schuldiner et al. (1975) J. Biol. Chem. 250, 1361--1370)) are interpreted as an increase in unspecific binding after translocation.

Mechanism analysis and numerical investigation of optical bistability in 2μm Tm,Ho:YLF solid laser

NASA Astrophysics Data System (ADS)

Zhang, Xin-Lu; Jiang, Bo; Dong, Guang-Zong; Li, Li; Peng, Yu-Feng

2010-11-01

A self-saturated absorption regime is proposed to theoretically investigate the optical bistability of Tm,Ho:YLF laser. Based on this bistability regime, the rate equation model of the optical bistability is established. The optical bistability behaviors of Tm,Ho:YLF laser are obtained by numerical simulating. The relation between laser gain and loss are also analyzed to confirm the rationality of the bistability mechanism. Furthermore, the time characters of the optical bistability are investigated. It is found that the high pulse power and the duration of the pre-pump are two major factors that affect the laser turn-on delay time and their influences on the turn-on delay are analyzed.

Nutritional support of malnourished lactose intolerant African patients.

PubMed

O'Keefe, S J; Adam, J K; Cakata, E; Epstein, S

1984-09-01

The effectiveness of two commonly available liquid diets was assessed in 40 severely malnourished black African patients. All patients were shown to have normal xylose absorption. The diets were given according to the manufacturer's recommendations. One diet was lactose containing (LC diet) (150 g/d) and high protein (112 g/d), the other normal protein and lactose free (LF diet) (protein 67 g/d), total energy content being similar. Patients were randomly divided into two equal groups and allocated (blind) to one of the diets. Tolerance and nitrogen balance were assessed over two three day periods on half and then full strength formulations. Severe intolerant symptoms were observed in 50% of patients on half strength and 94% of patients on full strength lactose containing diet with evidence of malabsorption of fluid, nitrogen, and fat. Despite high stool nitrogen losses (3.75 +/- 1.04 g/d), however, positive nitrogen balance was achieved in most patients receiving the full strength LC formulation. On the other hand, the full strength LF diet was generally well tolerated and was associated with significantly lower faecal losses and positive nitrogen balance. The results indicate that high density lactose containing liquid formulae are poorly tolerated by severely malnourished black African patients, while lactose free formulae containing approximately 10 g nitrogen/d are well tolerated and result in positive nitrogen balance.

Working cycles of devices based on bistable carbon nanotubes

NASA Astrophysics Data System (ADS)

Shklyaev, Oleg; Mockensturm, Eric; Crespi, Vincent; Carbon Nanotubes Collaboration

2013-03-01

Shape-changing nanotubes are an example of variable-shape sp2 carbon-based systems where the competition between strain and surface energies can be moderated by an externally controllable stimuli such as applied voltage, temperature, or pressure of gas encapsulated inside the tube. Using any of these stimuli one can transition a bistable carbon nanotube between the collapsed and inflated states and thus perform mechanical work. During the working cycle of such a device, energy from an electric or heat source is transferred to mechanical energy. Combinations of these stimuli allow the system to convert energy between different sources using the bistable shape-changing tube as a mediator. For example, coupling a bistable carbon nanotube to the heat and charge reservoirs can enable energy transfer between heat and electric forms. The developed theory can be extended to other nano-systems which change configurations in response to external stimuli.

Performance metric comparison study for non-magnetic bi-stable energy harvesters

NASA Astrophysics Data System (ADS)

Udani, Janav P.; Wrigley, Cailin; Arrieta, Andres F.

2017-04-01

Energy harvesting employing non-linear systems offers considerable advantages over linear systems given the broadband resonant response which is favorable for applications involving diverse input vibrations. In this respect, the rich dynamics of bi-stable systems present a promising means for harvesting vibrational energy from ambient sources. Harvesters deriving their bi-stability from thermally induced stresses as opposed to magnetic forces are receiving significant attention as it reduces the need for ancillary components and allows for bio- compatible constructions. However, the design of these bi-stable harvesters still requires further optimization to completely exploit the dynamic behavior of these systems. This study presents a comparison of the harvesting capabilities of non-magnetic, bi-stable composite laminates under variations in the design parameters as evaluated utilizing established power metrics. Energy output characteristics of two bi-stable composite laminate plates with a piezoelectric patch bonded on the top surface are experimentally investigated for variations in the thickness ratio and inertial mass positions for multiple load conditions. A particular design configuration is found to perform better over the entire range of testing conditions which include single and multiple frequency excitation, thus indicating that design optimization over the geometry of the harvester yields robust performance. The experimental analysis further highlights the need for appropriate design guidelines for optimization and holistic performance metrics to account for the range of operational conditions.

Lactose intolerance and intestinal villi morphology in Thai people.

PubMed

Thong-Ngam, D; Suwangool, P; Prempracha, J; Tangkijvanich, P; Vivatvekin, B; Sriratanabun, A

2001-08-01

To study the relationship of lactose intolerance and intestinal villi morphology in Thai people. Subjects for this study were patients with functional dyspepsia who had no history of milk allergy and underwent gastroduodenoscopy. Two mucosal biopsy specimens were taken from beyond the distal end of the second part of the duodenum. The specimens were carefully orientated and were graded according to the following scheme: group I: finger shaped villi; group II: mixed finger and leaf shaped villi; group III: clubbing or blunting shaped villi. All subjects were tested for lactose malabsorption by breath hydrogen analysis after consuming 50 gram lactose. Breath hydrogen concentration was analyzed in samples collected intermittently by end-expiratory technique. A rise in breath hydrogen concentration of 20 PPM over baseline was considered evidence of lactose malabsorption. The twenty-five subjects were twenty females (80.0%) and five males (20.0%) who ranged in age from 18 to 53 years (mean 31 +/- 8.29). Sixteen subjects belonged to the finger shaped villi group (64.0%), five to the mixed finger and leaf shaped villi, group (20.0%) and four to the clubbing or blunting shaped villi group (16.0%). Results of breath hydrogen excretion test identified the prevalence of lactose intolerance in 68 per cent of the subjects: 15/16 (93.75%) of group I; 1/5 (20.0%) of group II and 1/4 (25%) of group III respectively (P<0.001). The symptom of diarrhea after lactose loading was correlated well in patients who had positive breath hydrogen analysis. As shown in this study, the lactose intolerance is not related to intestinal villi morphology. It is implied that primary lactase deficiency is more common in Thai people than secondary lactase deficiency.

Lactose and Fructose Intolerance in Turkish Children with Chronic Abdominal Pain.

PubMed

Yuce, Ozlem; Kalayci, Ayhan Gazi; Comba, Atakan; Eren, Esra; Caltepe, Gonul

2016-05-08

To investigate the prevalence of lactose and fructose intolerance in children with chronic abdominal pain. Hydrogen breath tests were done to detect lactose and fructose malabsorption in 86 children with chronic abdominal pain (44 irritable bowel syndrome, 24 functional abdominal pain and 17 functional abdominal pain syndrome as per Rome III criteria) presenting to a Pediatric Gastroentreology department. 14 (16.3%) of patients were diagnosed with lactose intolerance and 11 (12.8%) with fructose intolerance. Lactose and fructose intolerance in children can lead to chronic abdominal pain and symptoms improve with dietary modifications.

Lactose absorption and mucosal disaccharidases in convalescent pellagra and kwashiorkor children

PubMed Central

Prinsloo, J. G.; Wittmann, W.; Kruger, H.; Freier, E.

1971-01-01

Oral lactose and glucose/galactose loading tests were done in Bantu children convalescing from kwashiorkor and pellagra. Small bowel biopsies and disaccharidase estimations were performed in all except 2 patients. Lactose absorption was more impaired and intestinal lactase levels were lower in the pellagra than in the kwashiorkor group. The fact that diarrhoea after admission to hospital was less common in pellagra than kwashiorkor was ascribed to a lesser lactose load due to the early introduction of a mixed diet in the former group, in comparison with milk feeds only in the latter group. The absence of troublesome diarrhoea while on moderate quantities of lactose in the diet, in the presence of low intestinal lactase levels, but evidence of lactose malabsorption after loading, has a bearing on preventive and therapeutic nutrition programmes in non-Caucasian children. Lactase deficiency is not necessarily synonymous with symptomatic lactose intolerance if the threshold is not exceeded. Concern is expressed that excessive caution against the use of milk may lead to a worsening of infantile malnutrition in developing countries. PMID:5109409

Conductance bistability of gold nanowires at room temperature

NASA Astrophysics Data System (ADS)

Kiguchi, Manabu; Konishi, Tatsuya; Murakoshi, Kei

2006-03-01

Quantized conductance behavior of gold nanowires was studied under electrochemical potential control. We fabricated 1-nm -long monoatomic wires in solution at room temperature. Electrochemical potential significantly affected the stability of the monoatomic wire and fractional conductance peak occurrence in the conductance histogram. We revealed that the hydrogen adsorption on gold monoatomic wires was a decisive factor of the fractional peak, which was originated from the dynamic structural transition between two bistable states of the monoatomic wire showing the unit and the fractional values of the conductance. We could tune the stability of these bistable states to make the fractional conductance state preferable.

Bistable resistive memory behavior in gelatin-CdTe quantum dot composite film

NASA Astrophysics Data System (ADS)

Vallabhapurapu, Sreedevi; Rohom, Ashwini; Chaure, N. B.; Du, Shengzhi; Srinivasan, Ananthakrishnan

2018-05-01

Bistable memory behavior has been observed for the first time in gelatin type A thin film dispersed with functionalized CdTe quantum dots. The two terminal device with the polymer nanocomposite layer sandwiched between an indium tin oxide coated glass plate and an aluminium top electrode performs as a bistable resistive random access memory module. Butterfly shaped (O-shaped with a hysteresis in forward and reverse sweeps) current-voltage response is observed in this device. The conduction mechanism leading to the bistable electrical switching has been deduced to be a combination of ohmic and electron hopping.

Delay induced stability switch, multitype bistability and chaos in an intraguild predation model.

PubMed

Shu, Hongying; Hu, Xi; Wang, Lin; Watmough, James

2015-12-01

In many predator-prey models, delay has a destabilizing effect and induces oscillations; while in many competition models, delay does not induce oscillations. By analyzing a rather simple delayed intraguild predation model, which combines both the predator-prey relation and competition, we show that delay in intraguild predation models promotes very complex dynamics. The delay can induce stability switches exhibiting a destabilizing role as well as a stabilizing role. It is shown that three types of bistability are possible: one stable equilibrium coexists with another stable equilibrium (node-node bistability); one stable equilibrium coexists with a stable periodic solution (node-cycle bistability); one stable periodic solution coexists with another stable periodic solution (cycle-cycle bistability). Numerical simulations suggest that delay can also induce chaos in intraguild predation models.

A novel optic bistable device with very low threshold intensity using photorefractive films

NASA Astrophysics Data System (ADS)

Wang, Sean X.; Sun, Yuankun; Trivedi, Sudhir B.; Li, Guifang

1994-08-01

Brimrose Corporation of America reports the successful completion of the SBIR Phase I research in low-threshold intensity optical bistable devices using photorefractive nonlinearity. A thin photorefractive film optical bistable device was proposed in the Phase I proposal. The feasibility of this device was theoretically investigated. The theoretical feasibility study formulates the materials requirements in such a kind of configuration for Phase II research. In addition, we have proposed and investigated another configuration of optical bistable devices that do not require advanced photorefractive materials, namely, the self-pumped phase conjugator. We have successfully demonstrated a low-threshold optical bistable operation in a KNSBN:CU crystal. To the best of our knowledge, the threshold of 650 mW/sq. cm is the lowest of its kind to be achieved so far.

Continuous ethanol fermentation of lactose by a recombinant flocculating Saccharomyces cerevisiae strain

DOE Office of Scientific and Technical Information (OSTI.GOV)

Domingues, L.; Dantas, M.M.; Lima, N.

1999-09-20

Alcohol fermentation of lactose was investigated using a recombinant flocculating Saccharomyces cetevisiae, expressing the LAC4 (coding the {beta}-galactosidase) and LAC12 (coding for lactose permease) genes of Kluyveromyces marxianus. Data on yeast fermentation and growth on a medium containing lactose as the sole carbon source are presented. In the range of studied lactose concentrations, total lactose consumption was observed with a conversion yield of ethanol close to the expected theoretical value. For the continuously operating bioreactor, an ethanol productivity of 11 g L{sup {minus}1} h{sup {minus}1} (corresponding to a feed lactose concentration of 50 g L{sup {minus}1} and a dilution ratemore » of 0.55 h{sup {minus}1}) was obtained, which is 7 times larger than the continuous conventional systems. The system stability was confirmed by keeping it in operation for 6 months.« less

Low threshold optical bistability in one-dimensional gratings based on graphene plasmonics.

PubMed

Guo, Jun; Jiang, Leyong; Jia, Yue; Dai, Xiaoyu; Xiang, Yuanjiang; Fan, Dianyuan

2017-03-20

Optical bistability of graphene surface plasmon is investigated numerically, using grating coupling method at normal light incidence. The linear surface plasmon resonance is strongly dependent on Femi-level of graphene, hence it can be tuned in a large wavelength range. Due to the field enhancement of graphene surface plasmon resonance and large third-order nonlinear response of graphene, a low-threshold optical hysteresis has been observed. The threshold value with 20MW/cm² and response time with 1.7ps have been verified. Especially, it is found that this optical bistability phenomenon is angular insensitivity for near 15° incident angle. The threshold of optical bistability can be further lowered to 0.5MW/cm² by using graphene nanoribbons, and the response time is also shorten to 800fs. We believe that our results will find potential applications in bistable devices and all-optical switching from mid-IR to THz range.

Inhibition of Recrystallization of Amorphous Lactose in Nanocomposites Formed by Spray-Drying.

PubMed

Hellrup, Joel; Alderborn, Göran; Mahlin, Denny

2015-11-01

This study aims at investigating the recrystallization of amorphous lactose in nanocomposites. In particular, the focus is on the influence of the nano- to micrometer length scale nanofiller arrangement on the amorphous to crystalline transition. Further, the relative significance of formulation composition and manufacturing process parameters for the properties of the nanocomposite was investigated. Nanocomposites of amorphous lactose and fumed silica were produced by co-spray-drying. Solid-state transformation of the lactose was studied at 43%, 84%, and 94% relative humidity using X-ray powder diffraction and microcalorimetry. Design of experiments was used to analyze spray-drying process parameters and nanocomposite composition as factors influencing the time to 50% recrystallization. The spray-drying process parameters showed no significant influence. However, the recrystallization of the lactose in the nanocomposites was affected by the composition (fraction silica). The recrystallization rate constant decreased as a function of silica content. The lowered recrystallization rate of the lactose in the nanocomposites could be explained by three mechanisms: (1) separation of the amorphous lactose into discrete compartments on a micrometer length scale (compartmentalization), (2) lowered molecular mobility caused by molecular interactions between the lactose molecules and the surface of the silica (rigidification), and/or (3) intraparticle confinement of the amorphous lactose. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Short communication: Lactose enhances bile tolerance of yogurt culture bacteria.

PubMed

Mena, Behannis; Aryana, Kayanush

2018-03-01

Lactose is an energy source for culture bacteria. Bile tolerance is an important probiotic property. Our aim was to elucidate the effect of lactose on bile tolerance of yogurt starter culture Lactobacillus bulgaricus LB-12 and Streptococcus thermophilus ST-M5. Bile tolerance of pure cultures was determined using 0.3% oxgall in MRS THIO broth (Difco, Becton Dickinson, Sparks, MD) for L. bulgaricus and 0.3% oxgall in M17 broth (Oxoid, Basingstoke, UK) for Strep. thermophilus. Lactose was added to both broths at 0 (control), 1, 3, and 5% (wt/vol) broth. Dilutions were plated hourly for 12 h. Experiments were replicated 3 times. At 2, 4, and 12 h of incubation, lactose incorporated at all amounts, 1, 3, and 5% (wt/vol), showed higher counts of Strep. thermophilus ST-M5 compared with the control. Lactose use at 5% (wt/vol) significantly enhanced bile tolerance of both L. bulgaricus and Strep. thermophilus compared with control. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Bistable electroactive polymers (BSEP): large-strain actuation of rigid polymers

NASA Astrophysics Data System (ADS)

Yu, Zhibin; Niu, Xiaofan; Brochu, Paul; Yuan, Wei; Li, Huafeng; Chen, Bin; Pei, Qibing

2010-04-01

Reversible, large-strain, bistable actuation has been a lasting puzzle in the pursuit of smart materials and structures. Conducting polymers are bistable, but the achievable strain is small. Large deformations have been achieved in dielectric elastomers at the expense of mechanical strength. The gel or gel-like soft polymers generally have elastic moduli around or less than 10 MPa. The deformed polymer relaxes to its original shape once the applied electric field is removed. We report new, bistable electroactive polymers (BSEP) that are capable of electrically actuated strains as high as 335% area strain. The BSEP could be useful for constructing rigid structures. The structures can support high mechanical loads, and be actuated to large-strain deformations. We will present one unique application of the BSEP for Braille displays that can be quickly refreshed and maintain the displayed contents without a bias voltage.

Lactose maldigestion, calcium intake and osteoporosis in African-, Asian-, and Hispanic-Americans.

PubMed

Jackson, K A; Savaiano, D A

2001-04-01

Dietary calcium is critical for the development of the human skeleton and likely plays an important role in the prevention of osteoporosis. Dairy products provide approximately three-fourths of calcium consumed in the diet and are the most concentrated sources of this essential nutrient. One obstacle that likely interferes with calcium consumption among many ethnic groups is lactose maldigestion. The real or perceived occurrence of intolerance symptoms after dairy food consumption may cause maldigesters to avoid dairy products. Several investigators have observed a relationship between lactose maldigestion, dietary calcium and osteoporosis in Caucasian populations. Research on ethnically diverse populations is necessary to better understand how lactose maldigestion influences the risk for osteoporosis. Low calcium intakes, a greater than previously thought potential for low bone density and extensive lactose maldigestion among Hispanic-American and Asian-American populations may create an elevated risk for osteoporosis. Dietary management strategies for lactose maldigesters to increase calcium consumption include consuming (1) dairy foods with meals, (2) yogurts, (3) calcium-fortified foods, (4) using lactose digestive aids and (5) including dairy foods daily in the diet to enhance colonic metabolism of lactose.

rrndb: the Ribosomal RNA Operon Copy Number Database

PubMed Central

Klappenbach, Joel A.; Saxman, Paul R.; Cole, James R.; Schmidt, Thomas M.

2001-01-01

The Ribosomal RNA Operon Copy Number Database (rrndb) is an Internet-accessible database containing annotated information on rRNA operon copy number among prokaryotes. Gene redundancy is uncommon in prokaryotic genomes, yet the rRNA genes can vary from one to as many as 15 copies. Despite the widespread use of 16S rRNA gene sequences for identification of prokaryotes, information on the number and sequence of individual rRNA genes in a genome is not readily accessible. In an attempt to understand the evolutionary implications of rRNA operon redundancy, we have created a phylogenetically arranged report on rRNA gene copy number for a diverse collection of prokaryotic microorganisms. Each entry (organism) in the rrndb contains detailed information linked directly to external websites including the Ribosomal Database Project, GenBank, PubMed and several culture collections. Data contained in the rrndb will be valuable to researchers investigating microbial ecology and evolution using 16S rRNA gene sequences. The rrndb web site is directly accessible on the WWW at http://rrndb.cme.msu.edu. PMID:11125085

Bistable traveling waves for a competitive-cooperative system with nonlocal delays

NASA Astrophysics Data System (ADS)

Tian, Yanling; Zhao, Xiao-Qiang

2018-04-01

This paper is devoted to the study of bistable traveling waves for a competitive-cooperative reaction and diffusion system with nonlocal time delays. The existence of bistable waves is established by appealing to the theory of monotone semiflows and the finite-delay approximations. Then the global stability of such traveling waves is obtained via a squeezing technique and a dynamical systems approach.

Lactose-Inducible System for Metabolic Engineering of Clostridium ljungdahlii

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, A; Leang, C; Ueki, T

2014-03-25

The development of tools for genetic manipulation of Clostridium ljungdahlii has increased its attractiveness as a chassis for autotrophic production of organic commodities and biofuels from syngas and microbial electrosynthesis and established it as a model organism for the study of the basic physiology of acetogenesis. In an attempt to expand the genetic toolbox for C. ljungdahlii, the possibility of adapting a lactose-inducible system for gene expression, previously reported for Clostridium perfringens, was investigated. The plasmid pAH2, originally developed for C. perfringens with a gusA reporter gene, functioned as an effective lactose-inducible system in C. ljungdahlii. Lactose induction of C.more » ljungdahlii containing pB1, in which the gene for the aldehyde/alcohol dehydrogenase AdhE1 was downstream of the lactose-inducible promoter, increased expression of adhE1 30-fold over the wild-type level, increasing ethanol production 1.5-fold, with a corresponding decrease in acetate production. Lactose-inducible expression of adhE1 in a strain in which adhE1 and the adhE1 homolog adhE2 had been deleted from the chromosome restored ethanol production to levels comparable to those in the wild-type strain. Inducing expression of adhE2 similarly failed to restore ethanol production, suggesting that adhE1 is the homolog responsible for ethanol production. Lactose-inducible expression of the four heterologous genes necessary to convert acetyl coenzyme A (acetyl-CoA) to acetone diverted ca. 60% of carbon flow to acetone production during growth on fructose, and 25% of carbon flow went to acetone when carbon monoxide was the electron donor. These studies demonstrate that the lactose-inducible system described here will be useful for redirecting carbon and electron flow for the biosynthesis of products more valuable than acetate. Furthermore, this tool should aid in optimizing microbial electrosynthesis and for basic studies on the physiology of acetogenesis.« less

Bistability induces episodic spike communication by inhibitory neurons in neuronal networks.

PubMed

Kazantsev, V B; Asatryan, S Yu

2011-09-01

Bistability is one of the important features of nonlinear dynamical systems. In neurodynamics, bistability has been found in basic Hodgkin-Huxley equations describing the cell membrane dynamics. When the neuron is clamped near its threshold, the stable rest potential may coexist with the stable limit cycle describing periodic spiking. However, this effect is often neglected in network computations where the neurons are typically reduced to threshold firing units (e.g., integrate-and-fire models). We found that the bistability may induce spike communication by inhibitory coupled neurons in the spiking network. The communication is realized in the form of episodic discharges with synchronous (correlated) spikes during the episodes. A spiking phase map is constructed to describe the synchronization and to estimate basic spike phase locking modes.

Synthesis and characterization of lactose-based homopolymers, hydrophilic/hydrophobic copolymers, and hydrogels

NASA Astrophysics Data System (ADS)

Zhou, Wenjing

The focus of this dissertation is the synthesis and characterization of lactose-based functional polymers. Currently 60% of lactose, a by-product from the cheese industry, is being utilized and the remaining fraction represents a serious disposal problem because of the high biological oxygen demand. Therefore, further development of utilization of lactose is an important issue both for industry and environment. Herein, the syntheses of lactose-based polymers such glycopolymers, hydrophilic/hydrophobic copolymers, and hydrogels are reported. A brief review of lactose formation, physical properties, and production is presented in Chapter 1. Syntheses and applications of lactose derivatives such as lactitol, lactulose, lactaime, lactosylurea, lactosylamine, lactone, and barbituric derivative are documented. Previous work in lactose-based polymers include: (1) hydrogels from cross linking of LPEP, borate complexation of lactose-containing polymer, and copolymerization of lactose monomer with crosslinkers; (2) lactose-based polyurethane rigid foams and adhesives; and (3) lactose-containing glycopolymers are also included. Chapter 2 documents the synthesis of acrylamidolactamine and the free radical copolymerization of this monomer with N-isopropylacrylamide in the presence of BisA to make hydrogels. Swelling behavior of the hydrogels at different temperatures as well as DSC study of these hydrogels are also carried out to characterize the swelling transition and the organization of water in the copolymer hydrogels. In Chapter 3, novel monomer syntheses of N-lactosyl- N'-(4-vinylbenzyl)urea or N '-lactosyl-N,N-methyl(4-vinylbenzyl)urea are described. Polymerization of these new urea monomers using a redox initiator gave water-soluble homopolymers with molecular weights in the range of 1.9 x 103 to 5.3 x 106. Synthesis and polymerization of lactose-O-(p-vinylbenzyl)hydroxime are documented in Chapter 4. The resulting polymers had high molecular weight (106) and narrow

Temporal dynamics of different cases of bi-stable figure-ground perception.

PubMed

Kogo, Naoki; Hermans, Lore; Stuer, David; van Ee, Raymond; Wagemans, Johan

2015-01-01

Segmentation of a visual scene in "figure" and "ground" is essential for perception of the three-dimensional layout of a scene. In cases of bi-stable perception, two distinct figure-ground interpretations alternate over time. We were interested in the temporal dynamics of these alternations, in particular when the same image is presented repeatedly, with short blank periods in-between. Surprisingly, we found that the intermittent presentation of Rubin's classical "face-or-vase" figure, which is frequently taken as a standard case of bi-stable figure-ground perception, often evoked perceptual switches during the short presentations and stabilization was not prominent. Interestingly, bi-stable perception of Kanizsa's anomalous transparency figure did strongly stabilize across blanks. We also found stabilization for the Necker cube, which we used for comparison. The degree of stabilization (and the lack of it) varied across stimuli and across individuals. Our results indicate, against common expectation, that the stabilization phenomenon cannot be generally evoked by intermittent presentation. We argue that top-down feedback factors such as familiarity, semantics, expectation, and perceptual bias contribute to the complex processes underlying the temporal dynamics of bi-stable figure-ground perception. Copyright © 2014 Elsevier Ltd. All rights reserved.

The incidence of infants with rotavirus enteritis combined with lactose intolerance.

PubMed

Hu, Yulian; Gui, Linyan; Chang, Jing; Liu, Jingyan; Xu, Shuling; Deng, Caiyan; Yu, Fengqin; Ma, Zhanmin; Wang, Guangzhou; Zhang, Changjun

2016-01-01

This study was to research the incidence of infants with rotavirus enteritis combined with lactose intolerance and the clinical effect of low lactose milk powder for infantile rotavirus enteritis with lactose intolerance. The control groups were 126 cases of infants with diarrhea randomly collected from our hospital at the same period, which their rotavirus detection was negative. The observation group was 185 cases of infants with rotavirus, which was tested to be positive. Through the urine galactose determination, 62 cases of the control group were positive and 124 cases of the observation group were positive. Then 124 cases of infants with rotavirus combined with lactose intolerance were randomly divided into two groups. 60 cases in the control group were given rehydration, correction of acidosis, oral smecta, Intestinal probiotics and other conventional treatment, then continued to the original feeding method. While, 64 cases in the treatment group, on the basis of routine treatment, applied the low lactose milk feeding. To observe the total effective rate for the two groups. The incidence of lactose intolerance in children with rotavirus enteritis (67.03%) was significantly higher than that of children with diarrhea (49.2%), which was tested to be negative. And the difference was statistically significant (p<0.5). In the aspect of reducing the frequency of diarrhea, and diarrhea stool forming time, the treatment group has the obvious superiority. The total effective rate was 95.4% for treatment group, which was higher than that in the control group (76.7%), the difference was statistically significant (P<0.05). Infants with rotavirus enteritis was easier to merge with lactose intolerance. The low lactose milk powder could improve the therapeutic effectively and could reduce the duration of disease, and restored to normal diet for 2 weeks feeding time.

Short communication: Conversion of lactose and whey into lactic acid by engineered yeast.

PubMed

Turner, Timothy L; Kim, Eunbee; Hwang, ChangHoon; Zhang, Guo-Chang; Liu, Jing-Jing; Jin, Yong-Su

2017-01-01

Lactose is often considered an unwanted and wasted byproduct, particularly lactose trapped in acid whey from yogurt production. But using specialized microbial fermentation, the surplus wasted acid whey could be converted into value-added chemicals. The baker's yeast Saccharomyces cerevisiae, which is commonly used for industrial fermentation, cannot natively ferment lactose. The present study describes how an engineered S. cerevisiae yeast was constructed to produce lactic acid from purified lactose, whey, or dairy milk. Lactic acid is an excellent proof-of-concept chemical to produce from lactose, because lactic acid has many food, pharmaceutical, and industrial uses, and over 250,000 t are produced for industrial use annually. To ferment the milk sugar lactose, a cellodextrin transporter (CDT-1, which also transports lactose) and a β-glucosidase (GH1-1, which also acts as a β-galactosidase) from Neurospora crassa were expressed in a S. cerevisiae strain. A heterologous lactate dehydrogenase (encoded by ldhA) from the fungus Rhizopus oryzae was integrated into the CDT-1/GH1-1-expressing strain of S. cerevisiae. As a result, the engineered strain was able to produce lactic acid from purified lactose, whey, and store-bought milk. A lactic acid yield of 0.358g/g of lactose was achieved from whey fermentation, providing an initial proof of concept for the production of value-added chemicals from excess industrial whey using engineered yeast. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Impact of short-chain galactooligosaccharides on the gut microbiome of lactose-intolerant individuals.

PubMed

Azcarate-Peril, M Andrea; Ritter, Andrew J; Savaiano, Dennis; Monteagudo-Mera, Andrea; Anderson, Carlton; Magness, Scott T; Klaenhammer, Todd R

2017-01-17

Directed modulation of the colonic bacteria to metabolize lactose effectively is a potentially useful approach to improve lactose digestion and tolerance. A randomized, double-blind, multisite placebo-controlled trial conducted in human subjects demonstrated that administration of a highly purified (>95%) short-chain galactooligosaccharide (GOS), designated "RP-G28," significantly improved clinical outcomes for lactose digestion and tolerance. In these individuals, stool samples were collected pretreatment (day 0), after GOS treatment (day 36), and 30 d after GOS feeding stopped and consumption of dairy products was encouraged (day 66). In this study, changes in the fecal microbiome were investigated using 16S rRNA amplicon pyrosequencing and high-throughput quantitative PCR. At day 36, bifidobacterial populations were increased in 27 of 30 of GOS subjects (90%), demonstrating a bifidogenic response in vivo. Relative abundance of lactose-fermenting Bifidobacterium, Faecalibacterium, and Lactobacillus were significantly increased in response to GOS. When dairy was introduced into the diet, lactose-fermenting Roseburia species increased from day 36 to day 66. The results indicated a definitive change in the fecal microbiome of lactose-intolerant individuals, increasing the abundance of lactose-metabolizing bacteria that were responsive to dietary adaptation to GOS. This change correlated with clinical outcomes of improved lactose tolerance.

Impact of short-chain galactooligosaccharides on the gut microbiome of lactose-intolerant individuals

PubMed Central

Azcarate-Peril, M. Andrea; Ritter, Andrew J.; Savaiano, Dennis; Monteagudo-Mera, Andrea; Anderson, Carlton; Magness, Scott T.; Klaenhammer, Todd R.

2017-01-01

Directed modulation of the colonic bacteria to metabolize lactose effectively is a potentially useful approach to improve lactose digestion and tolerance. A randomized, double-blind, multisite placebo-controlled trial conducted in human subjects demonstrated that administration of a highly purified (>95%) short-chain galactooligosaccharide (GOS), designated “RP-G28,” significantly improved clinical outcomes for lactose digestion and tolerance. In these individuals, stool samples were collected pretreatment (day 0), after GOS treatment (day 36), and 30 d after GOS feeding stopped and consumption of dairy products was encouraged (day 66). In this study, changes in the fecal microbiome were investigated using 16S rRNA amplicon pyrosequencing and high-throughput quantitative PCR. At day 36, bifidobacterial populations were increased in 27 of 30 of GOS subjects (90%), demonstrating a bifidogenic response in vivo. Relative abundance of lactose-fermenting Bifidobacterium, Faecalibacterium, and Lactobacillus were significantly increased in response to GOS. When dairy was introduced into the diet, lactose-fermenting Roseburia species increased from day 36 to day 66. The results indicated a definitive change in the fecal microbiome of lactose-intolerant individuals, increasing the abundance of lactose-metabolizing bacteria that were responsive to dietary adaptation to GOS. This change correlated with clinical outcomes of improved lactose tolerance. PMID:28049818

Prevalence of abnormal lactose breath hydrogen tests in children with functional abdominal pain.

PubMed

Garg, Neha; Basu, Srikanta; Singh, Preeti; Kumar, Ruchika; Sharma, Lokesh; Kumar, Praveen

2017-05-01

The study was undertaken to determine the prevalence of abnormal lactose breath hydrogen test in children with non-organic chronic abdominal pain. Children with chronic abdominal pain were examined and investigated for organic causes. All children without a known organic cause underwent lactose and glucose breath hydrogen test. After a standard dose of 2 g/kg of lactose to a maximum of 50 g, hydrogen in breath was measured at 15 min intervals for 3 h. A rise of 20 ppm above baseline was considered suggestive of lactose malabsorption. Of 108 children screened, organic causes were found in 46 children. Sixty-two patients without any organic cause underwent hydrogen breath test. Lactose hydrogen breath test (HBT) was positive in 36 of 62 (58%), while 11 (17%) had positive HBT with glucose suggestive of small intestinal bacterial overgrowth (SIBO). Twenty out of 34 (59%) improved on lactose free diet while 8 out of 11 (72%) children of SIBO improved on antibiotics. Lactose malabsorption was seen in 58% of children with non-organic chronic abdominal pain.

Lactose intolerance: a non-allergic disorder often managed by allergologists.

PubMed

Perino, A; Cabras, S; Obinu, D; Cavalli Sforza, L

2009-02-01

Lactose malabsorption is a very common condition characterized by intestinal lactase deficiency. Primary lactose malabsorption is an inherited deficit present in the majority of the world's population, while secondary bypolactasia can be the consequence of an intestinal disease. The presence of malabsorbed lactose in the colonic lumen may cause gastrointestinal symptoms. This condition is known as lactose intolerance. Lactase non-persistence is the ancestral state, whilst two single nucleotide polymorphisms in the lactase gene have been associated with lactase persistence. These are C/T 13910 and G/A 22018 substitutions. Lactase persistence, this Mendelian dominant trait, only became advantageous after the invention of agriculture, when milk from domesticated animals became available for adults to drink. Lactase persistence is then strongly correlated with the diary history of the population. Diagnosis is assessed clinically by elimination of dietary lactose or, better, by non-invasive tests including hydrogen breath test and genetic test. In patients with lactase non-persistence, treatment should be considered exclusively if intolerance symptoms are present. In the absence of guidelines, the common therapeutic approach tends to exclude milk and dairy products from the diet. However, this strategy may have serious nutritional disadvantages. Several studies have been carried out to find alternative approaches, such as exogenous beta-galactosidase, yogurt and probiotics for their bacterial lactase activity, strategies that can prolong contact time between enzyme and substrate delaying gastrointestinal transit time, and chronic lactose ingestion to enhance colonic adaptation.

Conditional bistability, a generic cellular mnemonic mechanism for robust and flexible working memory computations.

PubMed

Rodriguez, Guillaume; Sarazin, Matthieu; Clemente, Alexandra; Holden, Stephanie; Paz, Jeanne T; Delord, Bruno

2018-04-30

Persistent neural activity, the substrate of working memory, is thought to emerge from synaptic reverberation within recurrent networks. However, reverberation models do not robustly explain fundamental dynamics of persistent activity, including high-spiking irregularity, large intertrial variability, and state transitions. While cellular bistability may contribute to persistent activity, its rigidity appears incompatible with persistent activity labile characteristics. Here, we unravel in a cellular model a form of spike-mediated conditional bistability that is robust, generic and provides a rich repertoire of mnemonic computations. Under asynchronous synaptic inputs of the awakened state, conditional bistability generates spiking/bursting episodes, accounting for the irregularity, variability and state transitions characterizing persistent activity. This mechanism has likely been overlooked because of the sub-threshold input it requires and we predict how to assess it experimentally. Our results suggest a reexamination of the role of intrinsic properties in the collective network dynamics responsible for flexible working memory. SIGNIFICANCE STATEMENT This study unravels a novel form of intrinsic neuronal property, i.e. conditional bistability. We show that, thanks of its conditional character, conditional bistability favors the emergence of flexible and robust forms of persistent activity in PFC neural networks, in opposition to previously studied classical forms of absolute bistability. Specifically, we demonstrate for the first time that conditional bistability 1) is a generic biophysical spike-dependent mechanism of layer V pyramidal neurons in the PFC and that 2) it accounts for essential neurodynamical features for the organisation and flexibility of PFC persistent activity (the large irregularity and intertrial variability of the discharge and its organization under discrete stable states), which remain unexplained in a robust fashion by current models

Crystallization and X-ray diffraction of crystals formed in water-plasticized amorphous lactose.

PubMed

Jouppila, K; Kansikas, J; Roos, Y H

1998-01-01

Effects of storage time and relative humidity on crystallization and crystal forms produced from amorphous lactose were investigated. Crystallization was observed from time-dependent loss of sorbed water and increasing intensities of peaks in X-ray diffraction patterns. The rate of crystallization increased with increasing storage relative humidity. Lactose crystallized mainly as alpha-lactose monohydrate and anhydrous crystals with alpha- and beta-lactose in a molar ratio of 5:3. The results suggested that the crystal form was defined by the early nucleation process. The crystallization data are important in modeling of crystallization phenomena and prediction of stability of lactose-containing food and pharmaceutical materials.

Bistability, epigenetics, and bet-hedging in bacteria.

PubMed

Veening, Jan-Willem; Smits, Wiep Klaas; Kuipers, Oscar P

2008-01-01

Clonal populations of microbial cells often show a high degree of phenotypic variability under homogeneous conditions. Stochastic fluctuations in the cellular components that determine cellular states can cause two distinct subpopulations, a property called bistability. Phenotypic heterogeneity can be readily obtained by interlinking multiple gene regulatory pathways, effectively resulting in a genetic logic-AND gate. Although switching between states can occur within the cells' lifetime, cells can also pass their cellular state over to the next generation by a mechanism known as epigenetic inheritance and thus perpetuate the phenotypic state. Importantly, heterogeneous populations can demonstrate increased fitness compared with homogeneous populations. This suggests that microbial cells employ bet-hedging strategies to maximize survival. Here, we discuss the possible roles of interlinked bistable networks, epigenetic inheritance, and bet-hedging in bacteria.

Lactose Hydrolysis in Milk and Dairy Whey Using Microbial β-Galactosidases

PubMed Central

Dutra Rosolen, Michele; Gennari, Adriano; Volpato, Giandra; Volken de Souza, Claucia Fernanda

2015-01-01

This work aimed at evaluating the influence of enzyme concentration, temperature, and reaction time in the lactose hydrolysis process in milk, cheese whey, and whey permeate, using two commercial β-galactosidases of microbial origins. We used Aspergillus oryzae (at temperatures of 10 and 55°C) and Kluyveromyces lactis (at temperatures of 10 and 37°C) β-galactosidases, both in 3, 6, and 9 U/mL concentrations. In the temperature of 10°C, the K. lactis β-galactosidase enzyme is more efficient in the milk, cheese whey, and whey permeate lactose hydrolysis when compared to A. oryzae. However, in the enzyme reaction time and concentration conditions evaluated, 100% lactose hydrolysis was not reached using the K. lactis β-galactosidase. The total lactose hydrolysis in whey and permeate was obtained with the A. oryzae enzyme, when using its optimum temperature (55°C), at the end of a 12 h reaction, regardless of the enzyme concentration used. For the lactose present in milk, this result occurred in the concentrations of 6 and 9 U/mL, with the same time and temperature conditions. The studied parameters in the lactose enzymatic hydrolysis are critical for enabling the application of β-galactosidases in the food industry. PMID:26587283

Lactose Hydrolysis in Milk and Dairy Whey Using Microbial β-Galactosidases.

PubMed

Dutra Rosolen, Michele; Gennari, Adriano; Volpato, Giandra; Volken de Souza, Claucia Fernanda

2015-01-01

This work aimed at evaluating the influence of enzyme concentration, temperature, and reaction time in the lactose hydrolysis process in milk, cheese whey, and whey permeate, using two commercial β-galactosidases of microbial origins. We used Aspergillus oryzae (at temperatures of 10 and 55°C) and Kluyveromyces lactis (at temperatures of 10 and 37°C) β-galactosidases, both in 3, 6, and 9 U/mL concentrations. In the temperature of 10°C, the K. lactis β-galactosidase enzyme is more efficient in the milk, cheese whey, and whey permeate lactose hydrolysis when compared to A. oryzae. However, in the enzyme reaction time and concentration conditions evaluated, 100% lactose hydrolysis was not reached using the K. lactis β-galactosidase. The total lactose hydrolysis in whey and permeate was obtained with the A. oryzae enzyme, when using its optimum temperature (55°C), at the end of a 12 h reaction, regardless of the enzyme concentration used. For the lactose present in milk, this result occurred in the concentrations of 6 and 9 U/mL, with the same time and temperature conditions. The studied parameters in the lactose enzymatic hydrolysis are critical for enabling the application of β-galactosidases in the food industry.

Incorporation of a horizontally transferred gene into an operon during cnidarian evolution.

PubMed

Dana, Catherine E; Glauber, Kristine M; Chan, Titus A; Bridge, Diane M; Steele, Robert E

2012-01-01

Genome sequencing has revealed examples of horizontally transferred genes, but we still know little about how such genes are incorporated into their host genomes. We have previously reported the identification of a gene (flp) that appears to have entered the Hydra genome through horizontal transfer. Here we provide additional evidence in support of our original hypothesis that the transfer was from a unicellular organism, and we show that the transfer occurred in an ancestor of two medusozoan cnidarian species. In addition we show that the gene is part of a bicistronic operon in the Hydra genome. These findings identify a new animal phylum in which trans-spliced leader addition has led to the formation of operons, and define the requirements for evolution of an operon in Hydra. The identification of operons in Hydra also provides a tool that can be exploited in the construction of transgenic Hydra strains.

Prevalence and Symptom Correlation of Lactose Intolerance in the North East Part of Bangladesh.

PubMed

Saha, M; Shil, B C; Saha, S K; Chowdhury, M; Perveen, I; Banik, R; Rahman, M H

2016-01-01

This study was designed to see the prevalence of lactose intolerance and symptom correlation following oral lactose challenge in healthy volunteers in the north east part of Bangladesh. Symptoms of abdominal pain, nausea, borborygmi, flatulence, diarrhea and others were noted for 24 hours and blood glucose was estimated at 0 hour and 30 minutes after 50 gm oral lactose load to healthy volunteers. Failure to rise blood glucose level ≥1.1 mmol/l at 30 minutes after lactose intake from fasting level was taken as lactose malabsorption (LM) i.e., lactose intolerance. Sensitivity and specificity of different symptoms were then found out. A total of 171 volunteers (male 123, female 48) with a mean age 34.08 years participated in this study. Lactose intolerance was found among 82.5% (n=141, M=100, F=41) subjects. Symptoms mostly experience by the lactose malabsorbers were diarrhea 93(66.0%), borborygmi 80(56.7%), abdominal pain 31(22.0%) and flatulence 32(22.7%). LM prevalence was found to increase with increasing number of symptoms up to 3 symptoms. A week positive correlation (r=0.205, P=0.007) was found between the number of symptoms and proportion of subjects having positive lactose tolerance test. Lactose intolerance among healthy adults of North East part of our country is as common as in other Asian countries including China and Malaysia. But LM is higher than that of Europeans and south Indians. Diarrhea and borborygmi were mostly associated with LM.

Escherichia coli mutant with altered respiratory control of the frd operon.

PubMed Central

Iuchi, S; Kuritzkes, D R; Lin, E C

1985-01-01

In wild-type Escherichia coli, fumarate reductase encoded by the frd operon is inducible by its substrate in the absence of molecular oxygen and nitrate. Synthesis of this enzyme under permissive conditions requires the fnr+ gene product, which is believed to be a pleiotropic regulatory protein that activates transcription. A spontaneous mutant was isolated in which the expression of the frd operon no longer depended on the presence of fumarate or the fnr+ gene product. Aerobic repression of the operon was abolished, but nitrate repression remained intact. Transductional analysis showed that the mutation was closely linked to the frd locus. The mutant phenotype strongly suggests that repression by molecular oxygen and nitrate is mediated by different mechanisms. PMID:3882660

Lactose digestion by human jejunal biopsies: the relationship between hydrolysis and absorption.

PubMed Central

Dawson, D J; Lobley, R W; Burrows, P C; Miller, V; Holmes, R

1986-01-01

The relationship between lactose hydrolysis and absorption of released glucose was investigated by determining the kinetics of lactose digestion by jejunal biopsies incubated in vitro. Lactase activity in intact biopsies correlated with conventional assay of tissue homogenates (r = 0.85, p less than 0.001), and glucose uptake from 28 mM lactose was directly proportional to lactase activity (r = 0.95, p less than 0.001) in 21 subjects with normal lactase levels, six with hypolactasia (primary or secondary to coeliac disease) and two with lactose intolerance but normal lactase activity. Kinetic analysis at 0.56-56 mM lactose in five normal subjects showed saturable kinetics for hydrolysis (app Km = 33.9 +/- 2.2 mM; app Vmax = 26.5 +/- 1.1 nmol/min/mg dry weight) but glucose uptake could be fitted to a model either of saturable uptake (app Kt = 47.2 +/- 0.3 mM; app Jmax = 14.1 +/- 0.2 nmol/min/mg) or saturable uptake plus a linear component (app Kt = 21.3 +/- 1.15; app Jmax = 4.59 +/- 0.12; app Kd = 0.093 +/- 0.010 nmol/min/mg/mM). The proportion of glucose taken into the tissue did not significantly exceed 50% of the total released at any lactose concentration suggesting the lack of an efficient capture mechanism for the released glucose. The results suggest that lactose hydrolysis is the rate limiting step in the overall absorption of glucose from lactose in vitro, and that the relationship between hydrolysis and absorption is the same in normal subjects and in hypolactasic subjects. PMID:3084346

A predictive biophysical model of translational coupling to coordinate and control protein expression in bacterial operons

PubMed Central

Tian, Tian; Salis, Howard M.

2015-01-01

Natural and engineered genetic systems require the coordinated expression of proteins. In bacteria, translational coupling provides a genetically encoded mechanism to control expression level ratios within multi-cistronic operons. We have developed a sequence-to-function biophysical model of translational coupling to predict expression level ratios in natural operons and to design synthetic operons with desired expression level ratios. To quantitatively measure ribosome re-initiation rates, we designed and characterized 22 bi-cistronic operon variants with systematically modified intergenic distances and upstream translation rates. We then derived a thermodynamic free energy model to calculate de novo initiation rates as a result of ribosome-assisted unfolding of intergenic RNA structures. The complete biophysical model has only five free parameters, but was able to accurately predict downstream translation rates for 120 synthetic bi-cistronic and tri-cistronic operons with rationally designed intergenic regions and systematically increased upstream translation rates. The biophysical model also accurately predicted the translation rates of the nine protein atp operon, compared to ribosome profiling measurements. Altogether, the biophysical model quantitatively predicts how translational coupling controls protein expression levels in synthetic and natural bacterial operons, providing a deeper understanding of an important post-transcriptional regulatory mechanism and offering the ability to rationally engineer operons with desired behaviors. PMID:26117546

Roller compaction: Effect of morphology and amorphous content of lactose powder on product quality.

PubMed

Omar, Chalak S; Dhenge, Ranjit M; Osborne, James D; Althaus, Tim O; Palzer, Stefan; Hounslow, Michael J; Salman, Agba D

2015-12-30

The effect of morphology and amorphous content, of three types of lactose, on the properties of ribbon produced using roller compaction was investigated. The three types of lactose powders were; anhydrous SuperTab21AN, α-lactose monohydrate 200 M, and spray dried lactose SuperTab11SD. The morphology of the primary particles was identified using scanning electron microscopy (SEM) and the powder amorphous content was quantified using NIR technique. SEM images showed that 21AN and SD are agglomerated type of lactose whereas the 200 M is a non-agglomerated type. During ribbon production, an online thermal imaging technique was used to monitor the surface temperature of the ribbon. It was found that the morphology and the amorphous content of lactose powders have significant effects on the roller compaction behaviour and on ribbon properties. The agglomerated types of lactose produced ribbon with higher surface temperature and tensile strength, larger fragment size, lower porosity and lesser fines percentages than the non-agglomerated type of lactose. The lactose powder with the highest amorphous content showed to result in a better binding ability between the primary particles. This type of lactose produced ribbons with the highest temperature and tensile strength, and the lowest porosity and amount of fines in the product. It also produced ribbon with more smooth surfaces in comparison to the other two types of lactose. It was noticed that there is a relationship between the surface temperature of the ribbon during production and the tensile strength of the ribbon; the higher the temperature of the ribbon during production the higher the tensile strength of the ribbon. Copyright © 2015 Elsevier B.V. All rights reserved.

Limited Resources Induce Bistability in Microtubule Length Regulation

NASA Astrophysics Data System (ADS)

Rank, Matthias; Mitra, Aniruddha; Reese, Louis; Diez, Stefan; Frey, Erwin

2018-04-01

The availability of protein is an important factor for the determination of the size of the mitotic spindle. Involved in spindle-size regulation is kinesin-8, a molecular motor and microtubule (MT) depolymerase, which is known to tightly control MT length. Here, we propose and analyze a theoretical model in which kinesin-induced MT depolymerization competes with spontaneous polymerization while supplies of both tubulin and kinesin are limited. In contrast to previous studies where resources were unconstrained, we find that, for a wide range of concentrations, MT length regulation is bistable. We test our predictions by conducting in vitro experiments and find that the bistable behavior manifests in a bimodal MT length distribution.

Surface modification of lactose inhalation blends by moisture.

PubMed

Watling, C P; Elliott, J A; Scruton, C; Cameron, R E

2010-05-31

We present an investigation of the effects of relative humidity (RH) on lactose powders during storage, with the aims of determining the humidity conditions under which lactose inhalation blends are stable, and characterising the surface changes that occur as a result of water condensation. Lactose inhalation powders manufactured by milling and sieving were stored in environments of RH from 32% to 100% (at room temperature) and changes in surface properties were observed using BET nitrogen adsorption, environmental scanning electron microscopy and laser diffraction particle size analysis. We found that the specific surface area of all lactose powders decreased during storage, with the rate of decrease and final drop being larger at higher RH (ranging from a 62% decrease at 100% RH to a 34% decrease at 32% RH, at room temperature). The specific surface area decrease corresponded to a reduction in the volume of fine particles (<5 microm) in the blend. Two effects were found to contribute to the decrease in specific surface area: the smoothing of coarse particles, attributed to the surface fine particles undergoing deliquescence due to their enhanced solubility by the Kelvin effect (i.e. due to their greater curvature and consequently greater surface energy), and solid bridging between fine particles in agglomerates, such that loose fine particles disappeared from the powder blend, having bonded with coarser particles. These changes in particle properties resulting from moisture exposure are expected to influence the fine particle fraction of drug released from the powder blends, and the observation that lactose inhalation blends were unstable even at 32% RH could potentially be a concern for the pharmaceutical industry. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Novel epoxy activated hydrogels for solving lactose intolerance.

PubMed

Elnashar, Magdy M M; Hassan, Mohamed E

2014-01-01

"Lactose intolerance" is a medical problem for almost 70% of the world population. Milk and dairy products contain 5-10% w/v lactose. Hydrolysis of lactose by immobilized lactase is an industrial solution. In this work, we succeeded to increase the lactase loading capacity to more than 3-fold to 36.3 U/g gel using epoxy activated hydrogels compared to 11 U/g gel using aldehyde activated carrageenan. The hydrogel's mode of interaction was proven by FTIR, DSC, and TGA. The high activity of the epoxy group was regarded to its ability to attach to the enzyme's -SH, -NH, and -OH groups, whereas the aldehyde group could only bind to the enzyme's -NH2 group. The optimum conditions for immobilization such as epoxy chain length and enzyme concentration have been studied. Furthermore, the optimum enzyme conditions were also deliberated and showed better stability for the immobilized enzyme and the Michaelis constants, K m and V max, were doubled. Results revealed also that both free and immobilized enzymes reached their maximum rate of lactose conversion after 2 h, albeit, the aldehyde activated hydrogel could only reach 63% of the free enzyme. In brief, the epoxy activated hydrogels are more efficient in immobilizing more enzymes than the aldehyde activated hydrogel.

Large-Scale Analysis of Network Bistability for Human Cancers

PubMed Central

Shiraishi, Tetsuya; Matsuyama, Shinako; Kitano, Hiroaki

2010-01-01

Protein–protein interaction and gene regulatory networks are likely to be locked in a state corresponding to a disease by the behavior of one or more bistable circuits exhibiting switch-like behavior. Sets of genes could be over-expressed or repressed when anomalies due to disease appear, and the circuits responsible for this over- or under-expression might persist for as long as the disease state continues. This paper shows how a large-scale analysis of network bistability for various human cancers can identify genes that can potentially serve as drug targets or diagnosis biomarkers. PMID:20628618

Lowering the milk lactose content in vivo: potential interests, strategies and physiological consequences.

PubMed

Vilotte, Jean-Luc

2002-01-01

Lactose is the major sugar present in milk and an important osmotic regulator of lactation. It is digested by intestinal lactase, an enzyme expressed in new-borns. Its activity declines following weaning. As a result, adult mammals are normally lactose-intolerant and more than 75% of the human adult population suffers from lactase deficiency. A reduction in milk lactose content could be beneficial for nutritional but also agricultural and industrial purposes (less volume to transport, better milk coagulation, less effluent production). Several attempts to create transgenic mice producing milk with modified carbohydrate compositions have recently been described. Depending on whether these modifications resulted from an alteration of lactose synthesis or from lactose hydrolysis, striking physiological differences are observed.

Oxygen Impurities Link Bistability and Magnetoresistance in Organic Spin Valves.

PubMed

Bergenti, Ilaria; Borgatti, Francesco; Calbucci, Marco; Riminucci, Alberto; Cecchini, Raimondo; Graziosi, Patrizio; MacLaren, Donald A; Giglia, Angelo; Rueff, Jean Pascal; Céolin, Denis; Pasquali, Luca; Dediu, Valentin

2018-03-07

Vertical crossbar devices based on manganite and cobalt injecting electrodes and a metal-quinoline molecular transport layer are known to manifest both magnetoresistance (MR) and electrical bistability. The two effects are strongly interwoven, inspiring new device applications such as electrical control of the MR and magnetic modulation of bistability. To explain the device functionality, we identify the mechanism responsible for electrical switching by associating the electrical conductivity and the impedance behavior with the chemical states of buried layers obtained by in operando photoelectron spectroscopy. These measurements revealed that a significant fraction of oxygen ions migrate under voltage application, resulting in a modification of the electronic properties of the organic material and of the oxidation state of the interfacial layer with the ferromagnetic contacts. Variable oxygen doping of the organic molecules represents the key element for correlating bistability and MR, and our measurements provide the first experimental evidence in favor of the impurity-driven model describing the spin transport in organic semiconductors in similar devices.

Parallel replica dynamics method for bistable stochastic reaction networks: Simulation and sensitivity analysis

NASA Astrophysics Data System (ADS)

Wang, Ting; Plecháč, Petr

2017-12-01

Stochastic reaction networks that exhibit bistable behavior are common in systems biology, materials science, and catalysis. Sampling of stationary distributions is crucial for understanding and characterizing the long-time dynamics of bistable stochastic dynamical systems. However, simulations are often hindered by the insufficient sampling of rare transitions between the two metastable regions. In this paper, we apply the parallel replica method for a continuous time Markov chain in order to improve sampling of the stationary distribution in bistable stochastic reaction networks. The proposed method uses parallel computing to accelerate the sampling of rare transitions. Furthermore, it can be combined with the path-space information bounds for parametric sensitivity analysis. With the proposed methodology, we study three bistable biological networks: the Schlögl model, the genetic switch network, and the enzymatic futile cycle network. We demonstrate the algorithmic speedup achieved in these numerical benchmarks. More significant acceleration is expected when multi-core or graphics processing unit computer architectures and programming tools such as CUDA are employed.

Bistable flapping of flexible flyers in oscillatory flow

NASA Astrophysics Data System (ADS)

Huang, Yangyang; Kanso, Eva

2016-11-01

Biological and bio-inspired flyers move by shape actuation. The direct control of shape variables for locomotory purposes is well studied. Less is known about indirect shape actuation via the fluid medium. Here, we consider a flexible Λ-flyer in oscillatory flow that is free to flap and rotate around its fixed apex. We study its motion in the context of the inviscid vortex sheet model. We first analyze symmetric flapping about the vertical axis of gravity. We find that there is a finite value of the flexibility that maximizes both the flapping amplitude and elastic energy storage. Our results show that rather than resonance, the flyer relies on fluidic effects to optimize these two quantities. We then perturb the flyer away from the vertical and analyze its stability. Four distinct types of rolling behavior are identified: mono-stable, bistable, bistable oscillatory rotations and chaotic dynamics. We categorize these types of behavior in terms of the flyer's and flow parameters. In particular, the transition from mono-stable to bistable behavior occurs at a constant value of the product of the flow amplitude and acceleration. This product can be interpreted as the ratio of fluidic drag to gravity, confirming the fluid role in this transition.

Tunable Bistability in Hybrid Bose-Einstein Condensate Optomechanics

PubMed Central

Yasir, Kashif Ammar; Liu, Wu-Ming

2015-01-01

Cavity-optomechanics, a rapidly developing area of research, has made a remarkable progress. A stunning manifestation of optomechanical phenomena is in exploiting the mechanical effects of light to couple the optical degree of freedom with mechanical degree of freedom. In this report, we investigate the controlled bistable dynamics of such hybrid optomechanical system composed of cigar-shaped Bose-Einstein condensate (BEC) trapped inside high-finesse optical cavity with one moving-end mirror and is driven by a single mode optical field. The numerical results provide evidence for controlled optical bistability in optomechanics using transverse optical field which directly interacts with atoms causing the coupling of transverse field with momentum side modes, exited by intra-cavity field. This technique of transverse field coupling is also used to control bistable dynamics of both moving-end mirror and BEC. The report provides an understanding of temporal dynamics of moving-end mirror and BEC with respect to transverse field. Moreover, dependence of effective potential of the system on transverse field has also been discussed. To observe this phenomena in laboratory, we have suggested a certain set of experimental parameters. These findings provide a platform to investigate the tunable behavior of novel phenomenon like electromagnetically induced transparency and entanglement in hybrid systems. PMID:26035206

The pressure-induced, lactose-dependent changes in the composition and size of casein micelles.

PubMed

Wang, Pengjie; Jin, Shaoming; Guo, Huiyuan; Zhao, Liang; Ren, Fazheng

2015-04-15

The effects of lactose on the changes in the composition and size of casein micelles induced by high-pressure treatment and the related mechanism of action were investigated. Dispersions of ultracentrifuged casein micelle pellets with 0-10% (w/v) lactose were subjected to high pressure (400 MPa) at 20 °C for 40 min. The results indicated that the level of non-sedimentable caseins was positively related to the amount of lactose added prior to pressure treatment, and negatively correlated to the size. A mechanism for the pressure-induced, lactose-dependent changes in the casein micelles is proposed. Lactose inhibits the hydrophobic interactions between the micellar fragments during or after pressure release, through the hydrophilic layer formed by their hydrogen bonds around the micellar fragments. In addition, lactose does not favour the association between calcium and the casein aggregates after pressure release. Due to these two functions, lactose inhibited the formation of larger micelles after pressure treatment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Multiple regulatory elements for the glpA operon encoding anaerobic glycerol-3-phosphate dehydrogenase and the glpD operon encoding aerobic glycerol-3-phosphate dehydrogenase in Escherichia coli: further characterization of respiratory control.

PubMed

Iuchi, S; Cole, S T; Lin, E C

1990-01-01

In Escherichia coli, sn-glycerol-3-phosphate can be oxidized by two different flavo-dehydrogenases, an anaerobic enzyme encoded by the glpACB operon and an aerobic enzyme encoded by the glpD operon. These two operons belong to the glp regulon specifying the utilization of glycerol, sn-glycerol-3-phosphate, and glycerophosphodiesters. In glpR mutant cells grown under conditions of low catabolite repression, the glpA operon is best expressed anaerobically with fumarate as the exogenous electron acceptor, whereas the glpD operon is best expressed aerobically. Increased anaerobic expression of glpA is dependent on the fnr product, a pleiotropic activator of genes involved in anaerobic respiration. In this study we found that the expression of a glpA1(Oxr) (oxygen-resistant) mutant operon, selected for increased aerobic expression, became less dependent on the FNR protein but more dependent on the cyclic AMP-catabolite gene activator protein complex mediating catabolite repression. Despite the increased aerobic expression of glpA1(Oxr), a twofold aerobic repressibility persisted. Moreover, anaerobic repression by nitrate respiration remained normal. Thus, there seems to exist a redox control apart from the FNR-mediated one. We also showed that the anaerobic repression of the glpD operon was fully relieved by mutations in either arcA (encoding a presumptive DNA recognition protein) or arcB (encoding a presumptive redox sensor protein). The arc system is known to mediate pleiotropic control of genes of aerobic function.

Lactose oleate as new biocompatible surfactant for pharmaceutical applications.

PubMed

Perinelli, D R; Lucarini, S; Fagioli, L; Campana, R; Vllasaliu, D; Duranti, A; Casettari, L

2018-03-01

Sugar fatty acid esters are an interesting class of non-ionic, biocompatible and biodegradable sugar-based surfactants, recently emerged as a valid alternative to the traditional commonly employed (e.g. polysorbates and polyethylene glycol derivatives). By varying the polar head (carbohydrate moiety) and the hydrophobic tail (fatty acid), surfactants with different physico-chemical characteristics can be easily prepared. While many research papers have focused on sucrose derivatives, relatively few studies have been carried out on lactose-based surfactants. In this work, we present the synthesis and the physico-chemical characterization of lactose oleate. The new derivative was obtained by enzymatic mono-esterification of lactose with oleic acid. Thermal, surface, and aggregation properties of the surfactant were studied in detail and the cytotoxicity profile was investigated by MTS and LDH assays on intestinal Caco-2 monolayers. Transepithelial electrical resistance (TEER) measurements on Caco-2 cells showed a transient and reversible effect on the tight junctions opening, which correlates with the increased permeability of 4 kDa fluorescein-labelled dextran (as model for macromolecular drugs) in a concentration dependent manner. Moreover, lactose oleate displayed a satisfactory antimicrobial activity over a range of Gram-positive and Gram-negative bacteria. Overall, the obtained results are promising for a further development of lactose oleate as an intestinal absorption enhancer and/or an alternative biodegradable preservative for pharmaceutical and food applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Optimization and shelf life of a low-lactose yogurt with Lactobacillus rhamnosus HN001.

PubMed

Ibarra, A; Acha, R; Calleja, M-T; Chiralt-Boix, A; Wittig, E

2012-07-01

Lactose intolerance results in gastrointestinal discomfort and the malabsorption of certain nutrients, such as calcium. The replacement of milk with low-lactose and probiotic-enriched dairy products is an effective strategy of mitigating the symptoms of lactose intolerance. Lactobacillus rhamnosus HN001 (HN001) is a safe, immunity-stimulating probiotic. We have developed a process to increase the hydrolysis of lactose and HN001 growth in yogurt versus β-galactosidase (βG) concentration and enzymatic hydrolysis time (EHT) before bacterial fermentation. The objective of this study was to optimize the conditions by which yogurt is processed as a function of βG and EHT using a multifactorial design, with lactose content, HN001 growth, process time, and sensory quality as dependent variables. Further, the shelf life of the optimized yogurt was evaluated. In the optimization study, polynomials explained the dependent variables. Based on Pearson correlation coefficients, HN001 growth correlated positively with the hydrolysis of lactose. However, low lactose content and high HN001 count increased the fermentation time and lowered the sensory quality. The optimized conditions-using polynomials to obtain yogurt with >1 × 10(7) cfu of HN001/mL, <10 g of lactose/L, and a minimum overall sensory quality of 7 on the Karlsruhe scale-yielded a theoretical value of 910 neutral lactose units/kg for βG and 2.3h for EHT, which were validated in an industrial-scale assay. Based on a shelf-life study at 3 temperatures, the hydrolysis of lactose and the growth of HN001 continue during storage. Arrhenius equations were developed for the variables in the shelf-life study. Our results demonstrate that it is feasible to develop a low-lactose yogurt to which HN001 has been added for lactose-intolerant persons who wish to strengthen their immune system. Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Effect of raw milk on lactose intolerance: a randomized controlled pilot study.

PubMed

Mummah, Sarah; Oelrich, Beibei; Hope, Jessica; Vu, Quyen; Gardner, Christopher D

2014-01-01

This pilot study aimed to determine whether raw milk reduces lactose malabsorption and/or lactose intolerance symptoms relative to pasteurized milk. We performed a crossover trial involving 16 adults with self-reported lactose intolerance and lactose malabsorption confirmed by hydrogen (H2) breath testing. Participants underwent 3, 8-day milk phases (raw vs 2 controls: pasteurized, soy) in randomized order separated by 1-week washout periods. On days 1 and 8 of each phase, milk consumption was 473 mL (16 oz); on days 2 to 7, milk dosage increased daily by 118 mL (4 oz), beginning with 118 mL (4 oz) on day 2 and reaching 710 mL (24 oz) on day 7. Outcomes were area under the breath H2 curve (AUC H2) and self-reported symptom severity (visual analog scales: flatulence/gas, audible bowel sounds, abdominal cramping, diarrhea). AUC H2 (mean ± standard error of the mean) was higher for raw vs pasteurized on day 1 (113 ± 21 vs 71 ± 12 ppm·min·10(-2), respectively, P = .01) but not day 8 (72 ± 14 vs 74 ± 15 ppm·min·10(-2), respectively, P = .9). Symptom severities were not different for raw vs pasteurized on day 7 with the highest dosage (P >.7). AUC H2 and symptom severities were higher for both dairy milks compared with soy milk. Raw milk failed to reduce lactose malabsorption or lactose intolerance symptoms compared with pasteurized milk among adults positive for lactose malabsorption. These results do not support widespread anecdotal claims that raw milk reduces the symptoms of lactose intolerance.

Use of lactose against the deadly biological toxin ricin.

PubMed

Nagatsuka, Takehiro; Uzawa, Hirotaka; Ohsawa, Isaac; Seto, Yasuo; Nishida, Yoshihiro

2010-04-01

Developing a technology for detecting and decontaminating biological toxins is needed. Ricin from Ricinus communis is a highly poisonous toxin; it was formerly used for an assassination in London and in postal attacks in the United States. Ricin is readily available from castor beans and could be used as a biological agent. We propose using glycotechnology against the illegal use of ricin. Lactose (a natural ligand of this toxin) was incorporated into polyacrylamide-based glycopolymers at variable sugar densities (18-100%) and evaluated with surface plasmon resonance (SPR) spectroscopy and the real agent, ricin. Glycopolymers (18-65% lactose densities) effectively interfered with the toxin-lactoside adhesion event (>99% efficiency within 20 min). This supported the notion of using the mammary sugar lactose against a deadly biological toxin.

Managing acute pain in patients who report lactose intolerance: the safety of an old excipient re-examined.

PubMed

Mill, Deanna; Dawson, Jessica; Johnson, Jacinta Lee

2018-05-01

Lactose intolerance is exceedingly common, reportedly affecting up to 70% of the world's population, leading to both abdominal and systemic symptoms. Current treatment focuses predominantly on restricting dietary consumption of lactose. Given lactose is one of the most commonly used excipients in the pharmaceutical industry, consideration must be given to the lactose content and therefore safety of pharmaceutical preparations prescribed for patients with lactose intolerance. This article summarizes the current literature examining the likelihood of inducing adverse effects through the administration of lactose-containing pharmaceutical preparations in patients reporting lactose intolerance, describes how to assess this risk on an individual patient basis and reviews suitable analgesic options for this population. A case study is presented detailing a patient reporting lactose intolerance who insists on treatment with the lactose-free product codeine/ibuprofen (Nurofen Plus) rather than other codeine-free analgesics. It is important to assess the likelihood of lactose as an excipient inducing symptoms in this scenario, as reluctance to cease codeine could suggest codeine dependence, an issue that is becoming increasingly common in countries such as Australia and Canada. Given codeine dependence is associated with serious sequelae including hospitalization and death, the patient must either be reassured the lactose component in their prescribed analgesics will not induce symptoms or an alternative treatment strategy must be confirmed. General recommendations applying theory from the literature to the management of acute pain in lactose-intolerant patients are discussed and specific treatment options are outlined. Although large inter-individual variability is reported, most lactose-intolerant patients can tolerate the small quantities of lactose found in pharmaceutical preparations. Cumulative lactose exposure can be assessed in patients taking multiple medications

Managing acute pain in patients who report lactose intolerance: the safety of an old excipient re-examined

PubMed Central

Mill, Deanna; Dawson, Jessica; Johnson, Jacinta Lee

2018-01-01

Lactose intolerance is exceedingly common, reportedly affecting up to 70% of the world’s population, leading to both abdominal and systemic symptoms. Current treatment focuses predominantly on restricting dietary consumption of lactose. Given lactose is one of the most commonly used excipients in the pharmaceutical industry, consideration must be given to the lactose content and therefore safety of pharmaceutical preparations prescribed for patients with lactose intolerance. This article summarizes the current literature examining the likelihood of inducing adverse effects through the administration of lactose-containing pharmaceutical preparations in patients reporting lactose intolerance, describes how to assess this risk on an individual patient basis and reviews suitable analgesic options for this population. A case study is presented detailing a patient reporting lactose intolerance who insists on treatment with the lactose-free product codeine/ibuprofen (Nurofen Plus) rather than other codeine-free analgesics. It is important to assess the likelihood of lactose as an excipient inducing symptoms in this scenario, as reluctance to cease codeine could suggest codeine dependence, an issue that is becoming increasingly common in countries such as Australia and Canada. Given codeine dependence is associated with serious sequelae including hospitalization and death, the patient must either be reassured the lactose component in their prescribed analgesics will not induce symptoms or an alternative treatment strategy must be confirmed. General recommendations applying theory from the literature to the management of acute pain in lactose-intolerant patients are discussed and specific treatment options are outlined. Although large inter-individual variability is reported, most lactose-intolerant patients can tolerate the small quantities of lactose found in pharmaceutical preparations. Cumulative lactose exposure can be assessed in patients taking multiple medications

Experimental chaotic quantification in bistable vortex induced vibration systems

NASA Astrophysics Data System (ADS)

Huynh, B. H.; Tjahjowidodo, T.

2017-02-01

The study of energy harvesting by means of vortex induced vibration systems has been initiated a few years ago and it is considered to be potential as a low water current energy source. The energy harvester is realized by exposing an elastically supported blunt structure under water flow. However, it is realized that the system will only perform at a limited operating range (water flow) that is attributed to the resonance phenomenon that occurs only at a frequency that corresponds to the fluid flow. An introduction of nonlinear elements seems to be a prominent solution to overcome the problem. Among many nonlinear elements, a bistable spring is known to be able to improve the harvested power by a vortex induced vibrations (VIV) based energy converter at the low velocity water flows. However, it is also observed that chaotic vibrations will occur at different operating ranges that will erratically diminish the harvested power and cause a difficulty in controlling the system that is due to the unpredictability in motions of the VIV structure. In order to design a bistable VIV energy converter with improved harvested power and minimum negative effect of chaotic vibrations, the bifurcation map of the system for varying governing parameters is highly on demand. In this study, chaotic vibrations of a VIV energy converter enhanced by a bistable stiffness element are quantified in a wide range of the governing parameters, i.e. damping and bistable gap. Chaotic vibrations of the bistable VIV energy converter are simulated by utilization of a wake oscillator model and quantified based on the calculation of the Lyapunov exponent. Ultimately, a series of experiments of the system in a water tunnel, facilitated by a computer-based force-feedback testing platform, is carried out to validate the existence of chaotic responses. The main challenge in dealing with experimental data is in distinguishing chaotic response from noise-contaminated periodic responses as noise will smear

Autocatalytic, bistable, oscillatory networks of biologically relevant organic reactions.

PubMed

Semenov, Sergey N; Kraft, Lewis J; Ainla, Alar; Zhao, Mengxia; Baghbanzadeh, Mostafa; Campbell, Victoria E; Kang, Kyungtae; Fox, Jerome M; Whitesides, George M

2016-09-29

Networks of organic chemical reactions are important in life and probably played a central part in its origin. Network dynamics regulate cell division, circadian rhythms, nerve impulses and chemotaxis, and guide the development of organisms. Although out-of-equilibrium networks of chemical reactions have the potential to display emergent network dynamics such as spontaneous pattern formation, bistability and periodic oscillations, the principles that enable networks of organic reactions to develop complex behaviours are incompletely understood. Here we describe a network of biologically relevant organic reactions (amide formation, thiolate-thioester exchange, thiolate-disulfide interchange and conjugate addition) that displays bistability and oscillations in the concentrations of organic thiols and amides. Oscillations arise from the interaction between three subcomponents of the network: an autocatalytic cycle that generates thiols and amides from thioesters and dialkyl disulfides; a trigger that controls autocatalytic growth; and inhibitory processes that remove activating thiol species that are produced during the autocatalytic cycle. In contrast to previous studies that have demonstrated oscillations and bistability using highly evolved biomolecules (enzymes and DNA) or inorganic molecules of questionable biochemical relevance (for example, those used in Belousov-Zhabotinskii-type reactions), the organic molecules we use are relevant to metabolism and similar to those that might have existed on the early Earth. By using small organic molecules to build a network of organic reactions with autocatalytic, bistable and oscillatory behaviour, we identify principles that explain the ways in which dynamic networks relevant to life could have developed. Modifications of this network will clarify the influence of molecular structure on the dynamics of reaction networks, and may enable the design of biomimetic networks and of synthetic self-regulating and evolving

Autocatalytic, bistable, oscillatory networks of biologically relevant organic reactions

NASA Astrophysics Data System (ADS)

Semenov, Sergey N.; Kraft, Lewis J.; Ainla, Alar; Zhao, Mengxia; Baghbanzadeh, Mostafa; Campbell, Victoria E.; Kang, Kyungtae; Fox, Jerome M.; Whitesides, George M.

2016-09-01

Networks of organic chemical reactions are important in life and probably played a central part in its origin. Network dynamics regulate cell division, circadian rhythms, nerve impulses and chemotaxis, and guide the development of organisms. Although out-of-equilibrium networks of chemical reactions have the potential to display emergent network dynamics such as spontaneous pattern formation, bistability and periodic oscillations, the principles that enable networks of organic reactions to develop complex behaviours are incompletely understood. Here we describe a network of biologically relevant organic reactions (amide formation, thiolate-thioester exchange, thiolate-disulfide interchange and conjugate addition) that displays bistability and oscillations in the concentrations of organic thiols and amides. Oscillations arise from the interaction between three subcomponents of the network: an autocatalytic cycle that generates thiols and amides from thioesters and dialkyl disulfides; a trigger that controls autocatalytic growth; and inhibitory processes that remove activating thiol species that are produced during the autocatalytic cycle. In contrast to previous studies that have demonstrated oscillations and bistability using highly evolved biomolecules (enzymes and DNA) or inorganic molecules of questionable biochemical relevance (for example, those used in Belousov-Zhabotinskii-type reactions), the organic molecules we use are relevant to metabolism and similar to those that might have existed on the early Earth. By using small organic molecules to build a network of organic reactions with autocatalytic, bistable and oscillatory behaviour, we identify principles that explain the ways in which dynamic networks relevant to life could have developed. Modifications of this network will clarify the influence of molecular structure on the dynamics of reaction networks, and may enable the design of biomimetic networks and of synthetic self-regulating and evolving

Effect of compression pressure on inhalation grade lactose as carrier for dry powder inhalations

PubMed Central

Raut, Neha Sureshrao; Jamaiwar, Swapnil; Umekar, Milind Janrao; Kotagale, Nandkishor Ramdas

2016-01-01

Introduction: This study focused on the potential effects of compression forces experienced during lactose (InhaLac 70, 120, and 230) storage and transport on the flowability and aerosol performance in dry powder inhaler formulation. Materials and Methods: Lactose was subjected to typical compression forces 4, 10, and 20 N/cm2. Powder flowability and particle size distribution analysis of un-compressed and compressed lactose was evaluated by Carr's index, Hausner's ratio, the angle of repose and by laser diffraction method. Aerosol performance of un-compressed and compressed lactose was assessed in dispersion studies using glass twin-stage-liquid-impenger at flow rate 40-80 L/min. Results: At compression forces, the flowability of compressed lactose was observed same or slightly improved. Furthermore, compression of lactose caused a decrease in in vitro aerosol dispersion performance. Conclusion: The present study illustrates that, as carrier size increases, a concurrent decrease in drug aerosolization performance was observed. Thus, the compression of the lactose fines onto the surfaces of the larger lactose particles due to compression pressures was hypothesized to be the cause of these observed performance variations. The simulations of storage and transport in an industrial scale can induce significant variations in formulation performance, and it could be a source of batch-to-batch variations. PMID:27014618

Plasmon-modulated bistable four-wave mixing signals from a metal nanoparticle-monolayer MoS2 nanoresonator hybrid system

NASA Astrophysics Data System (ADS)

Li, Jian-Bo; Tan, Xiao-Long; Ma, Jin-Hong; Xu, Si-Qin; Kuang, Zhi-Wei; Liang, Shan; Xiao, Si; He, Meng-Dong; Kim, Nam-Chol; Luo, Jian-Hua; Chen, Li-Qun

2018-06-01

We present a study for the impact of exciton-phonon and exciton-plasmon interactions on bistable four-wave mixing (FWM) signals in a metal nanoparticle (MNP)-monolayer MoS2 nanoresonator hybrid system. Via tracing the FWM response we predict that, depending on the excitation conditions and the system parameters, such a system exhibits ‘U-shaped’ bistable FWM signals. We also map out bistability phase diagrams within the system’s parameter space. Especially, we show that compared with the exciton-phonon interaction, a strong exciton-plasmon interaction plays a dominant role in the generation of optical bistability, and the bistable region will be greatly broadened by shortening the distance between the MNP and the monolayer MoS2 nanoresonator. In the weak exciton-plasmon coupling regime, the impact of exciton-phonon interaction on optical bistability will become obvious. The scheme proposed may be used for building optical switches and logic-gate devices for optical computing and quantum information processing.

Plasmon-modulated bistable four-wave mixing signals from a metal nanoparticle-monolayer MoS2 nanoresonator hybrid system.

PubMed

Li, Jian-Bo; Tan, Xiao-Long; Ma, Jin-Hong; Xu, Si-Qin; Kuang, Zhi-Wei; Liang, Shan; Xiao, Si; He, Meng-Dong; Kim, Nam-Chol; Luo, Jian-Hua; Chen, Li-Qun

2018-06-22

We present a study for the impact of exciton-phonon and exciton-plasmon interactions on bistable four-wave mixing (FWM) signals in a metal nanoparticle (MNP)-monolayer MoS 2 nanoresonator hybrid system. Via tracing the FWM response we predict that, depending on the excitation conditions and the system parameters, such a system exhibits 'U-shaped' bistable FWM signals. We also map out bistability phase diagrams within the system's parameter space. Especially, we show that compared with the exciton-phonon interaction, a strong exciton-plasmon interaction plays a dominant role in the generation of optical bistability, and the bistable region will be greatly broadened by shortening the distance between the MNP and the monolayer MoS 2 nanoresonator. In the weak exciton-plasmon coupling regime, the impact of exciton-phonon interaction on optical bistability will become obvious. The scheme proposed may be used for building optical switches and logic-gate devices for optical computing and quantum information processing.

Influence of Fano interference and incoherent processes on optical bistability in a four-level quantum dot nanostructure

NASA Astrophysics Data System (ADS)

Seyyed, Hossein Asadpour; G, Solookinejad; M, Panahi; E Ahmadi, Sangachin

2016-03-01

Role of Fano interference and incoherent pumping field on optical bistability in a four-level designed InGaN/GaN quantum dot nanostructure embedded in a unidirectional ring cavity are analyzed. It is found that intensity threshold of optical bistability can be manipulated by Fano interference. It is shown that incoherent pumping fields make the threshold of optical bistability behave differently by Fano interference. Moreover, in the presence of Fano interference the medium becomes phase-dependent. Therefore, the relative phase of applied fields can affect the behaviors of optical bistability and intensity threshold can be controlled easily.

Effect of Raw Milk on Lactose Intolerance: A Randomized Controlled Pilot Study

PubMed Central

Mummah, Sarah; Oelrich, Beibei; Hope, Jessica; Vu, Quyen; Gardner, Christopher D.

2014-01-01

PURPOSE This pilot study aimed to determine whether raw milk reduces lactose malabsorption and/or lactose intolerance symptoms relative to pasteurized milk. METHODS We performed a crossover trial involving 16 adults with self-reported lactose intolerance and lactose malabsorption confirmed by hydrogen (H2) breath testing. Participants underwent 3, 8-day milk phases (raw vs 2 controls: pasteurized, soy) in randomized order separated by 1-week washout periods. On days 1 and 8 of each phase, milk consumption was 473 mL (16 oz); on days 2 to 7, milk dosage increased daily by 118 mL (4 oz), beginning with 118 mL (4 oz) on day 2 and reaching 710 mL (24 oz) on day 7. Outcomes were area under the breath H2 curve (AUC ∆H2) and self-reported symptom severity (visual analog scales: flatulence/gas, audible bowel sounds, abdominal cramping, diarrhea). RESULTS AUC ∆H2 (mean ± standard error of the mean) was higher for raw vs pasteurized on day 1 (113 ± 21 vs 71 ± 12 ppm·min·10−2, respectively, P = .01) but not day 8 (72 ± 14 vs 74 ± 15 ppm·min·10−2, respectively, P = .9). Symptom severities were not different for raw vs pasteurized on day 7 with the highest dosage (P >.7). AUC ∆H2 and symptom severities were higher for both dairy milks compared with soy milk. CONCLUSIONS Raw milk failed to reduce lactose malabsorption or lactose intolerance symptoms compared with pasteurized milk among adults positive for lactose malabsorption. These results do not support widespread anecdotal claims that raw milk reduces the symptoms of lactose intolerance. PMID:24615309

Effect of age and lactose on sup 67 Cu utilization in rats

DOE Office of Scientific and Technical Information (OSTI.GOV)

Link, J.; Dowdy, R.; Michelmann, E.

1991-03-15

Young and old male Fischer 344 rats were fed a control diet or a lactose diet. After four weeks rats were gavaged with approximately 6.24 uCl {sup 67}Cu, placed in metabolism cages, and fed their respective diets for an additional two weeks. Daily whole body, urine and fecal radioactivity measurements were made. Rats were killed on day 42 and livers removed for radioactivity determination. Diet had no effect on whole body retention of {sup 67}Cu in the old rats; approximately 20% of the initial dose was retained by the end of the study. In the young rats, however, lactose appearedmore » to enhance initial {sup 67}Cu retention; by day three young control rats retained only 30% of the initial dose, while the young lactose rats retained about 50%. Retention of {sup 67}Cu at the end of the study was approximately 15% and 20% for young control and young lactose rats, respectively. During the first four days post dosing, cumulative fecal {sup 67}Cu excretion was approximately 83% for young control rats and 69% for young lactose rats indicating enhancement of {sup 67}Cu absorption by lactose in the young rats. For old rats cumulative {sup 67}Cu excretion in feces was about 50% regardless of diet. Cumulative urinary {sup 67}Cu excretion was approximately 6% and 8% for young control and lactose rats, respectively vs about 11% for old rats. {sup 67}Cu retention in liver was greater in old rats regardless of diet. The early increase in {sup 67}Cu absorption after a bolus dose may have therapeutic implications. In light of current concern regarding Cu-carbohydrate interactions, the apparent enhancement Cu retention by lactose in young rats deserves further attention.« less

On the functional relevance of frontal cortex for passive and voluntarily controlled bistable vision.

PubMed

de Graaf, Tom A; de Jong, Maartje C; Goebel, Rainer; van Ee, Raymond; Sack, Alexander T

2011-10-01

In bistable vision, one constant ambiguous stimulus leads to 2 alternating conscious percepts. This perceptual switching occurs spontaneously but can also be influenced through voluntary control. Neuroimaging studies have reported that frontal regions are activated during spontaneous perceptual switches, leading some researchers to suggest that frontal regions causally induce perceptual switches. But the opposite also seems possible: frontal activations may themselves be caused by spontaneous switches. Classically implicated in attentional processes, these same regions are also candidates for the origins of voluntary control over bistable vision. Here too, it remains unknown whether frontal cortex is actually functionally relevant. It is even possible that spontaneous perceptual switches and voluntarily induced switches are mediated by the same top-down mechanisms. To directly address these issues, we here induced "virtual lesions," with transcranial magnetic stimulation, in frontal, parietal, and 2 lower level visual cortices using an established ambiguous structure-from-motion stimulus. We found that dorsolateral prefrontal cortex was causally relevant for voluntary control over perceptual switches. In contrast, we failed to find any evidence for an active role of frontal cortex in passive bistable vision. Thus, it seems the same pathway used for willed top-down modulation of bistable vision is not used during passive bistable viewing.

Bistability in cell signaling: How to make continuous processes discontinuous, and reversible processes irreversible

NASA Astrophysics Data System (ADS)

Ferrell, James E.; Xiong, Wen

2001-03-01

Xenopus oocyte maturation is an example of an all-or-none, irreversible cell fate induction process. In response to a submaximal concentration of the steroid hormone progesterone, a given oocyte may either mature or not mature, but it can exist in intermediate states only transiently. Moreover, once an oocyte has matured, it will remain arrested in the mature state even after the progesterone is removed. It has been hypothesized that the all-or-none character of oocyte maturation, and some aspects of the irreversibility of maturation, arise out of the bistability of the signal transduction system that triggers maturation. The bistability, in turn, is hypothesized to arise from the way the signal transducers are organized into a signaling circuit that includes positive feedback (which makes it so that the system cannot rest in intermediate states) and ultrasensitivity (which filters small stimuli out of the feedback loop, allowing the system to have a stable off-state). Here we review two simple graphical methods that are commonly used to analyze bistable systems, discuss the experimental evidence for bistability in oocyte maturation, and suggest that bistability may be a common means of producing all-or-none responses and a type of biochemical memory.

Ontogeny of intestinal safety factors: lactase capacities and lactose loads.

PubMed

O'Connor, T P; Diamond, J

1999-03-01

We measured intestinal safety factors (ratio of a physiological capacity to the load on it) for lactose digestion in developing rat pups. Specifically, we assessed the quantitative relationships between lactose load and the series capacities of lactase and the Na+-glucose cotransporter (SGLT-1). Both capacities increased significantly with age in suckling pups as a result of increasing intestinal mass and maintenance of mass-specific activities. The youngest pups examined (5 days) had surprisingly high safety factors of 8-13 for both lactase and SGLT-1, possibly because milk contains lactase substrates other than lactose; it also, however, suggests that their intestinal capacities were being prepared to meet future demands rather than just current ones. By day 10 (and also at day 15), increased lactose loads resulted in lower safety factors of 4-6, values more typical of adult intestines. The safety factor of SGLT-1 in day 30 (weanling) and day 100 (adult) rats was only approximately 1.0. This was initially unexpected, because most adult intestines maintain a modest reserve capacity beyond nutrient load values, but postweaning rats appear to use hindgut fermentation, assessed by gut morphology and hydrogen production assays, as a built-in reserve capacity. The series capacities of lactase and SGLT-1 varied in concert with each other over ontogeny and as lactose load was manipulated by experimental variation in litter size.

Identification and characterization of transcripts from the biotin biosynthetic operon of Bacillus subtilis.

PubMed

Perkins, J B; Bower, S; Howitt, C L; Yocum, R R; Pero, J

1996-11-01

Northern (RNA) blot analysis of the Bacillus subtilis biotin operon, bioWAFDBIorf2, detected at least two steady-state polycistronic transcripts initiated from a putative vegetative (Pbio) promoter that precedes the operon, i.e., a full-length 7.2-kb transcript covering the entire operon and a more abundant 5.1-kb transcript covering just the first five genes of the operon. Biotin and the B. subtilis birA gene product regulated synthesis of the transcripts. Moreover, replacing the putative Pbio promoter and regulatory sequence with a constitutive SP01 phage promoter resulted in higher-level constitutive synthesis. Removal of a rho-independent terminator-like sequence located between the fifth (bioB) and sixth (bioI) genes prevented accumulation of the 5.1-kb transcript, suggesting that the putative terminator functions to limit expression of bioI, which is thought to be involved in an early step in biotin synthesis.

Single coil bistable, bidirectional micromechanical actuator

DOEpatents

Tabat, Ned; Guckel, Henry

1998-09-15

Micromechanical actuators capable of bidirectional and bistable operation can be formed on substrates using lithographic processing techniques. Bistable operation of the microactuator is obtained using a single coil and a magnetic core with a gap. A plunger having two magnetic heads is supported for back and forth linear movement with respect to the gap in the magnetic core, and is spring biased to a neutral position in which the two heads are on each side of the gap in the core. The single electrical coil is coupled to the core and is provided with electrical current to attract one of the heads toward the core by reluctance action to drive the plunger to a limit of travel in one direction. The current is then cut off and the plunger returns by spring action toward the gap, whereafter the current is reapplied to the coil to attract the other head of the plunger by reluctance action to drive the plunger to its other limit of travel. This process can be repeated at a time when switching of the actuator is required.

Contribution of Colonic Fermentation and Fecal Water Toxicity to the Pathophysiology of Lactose-Intolerance.

PubMed

Windey, Karen; Houben, Els; Deroover, Lise; Verbeke, Kristin

2015-09-08

Whether or not abdominal symptoms occur in subjects with small intestinal lactose malabsorption might depend on differences in colonic fermentation. To evaluate this hypothesis, we collected fecal samples from subjects with lactose malabsorption with abdominal complaints (LM-IT, n = 11) and without abdominal complaints (LM-T, n = 8) and subjects with normal lactose digestion (NLD, n = 15). Lactose malabsorption was diagnosed using a (13)C-lactose breath test. Colonic fermentation was characterized in fecal samples at baseline and after incubation with lactose for 3 h, 6 h and 24 h through a metabolomics approach using gas chromatography-mass spectrometry (GC-MS). Fecal water cytotoxicity was analyzed using a colorimetric assay. Fecal water cytotoxicity was not different between the three groups (Kruskall-Wallis p = 0.164). Cluster analysis of the metabolite patterns revealed separate clusters for NLD, LM-T and LM-IT samples at baseline and after 24 h incubation with lactose. Levels of 5-methyl-2-furancarboxaldehyde were significantly higher in LM-IT and LM-T compared to NLD whereas those of an unidentified aldehyde were significantly higher in LM-IT compared to LM-T and NLD. Incubation with lactose increased short chain fatty acid (SCFA) concentrations more in LM-IT and LM-T compared to NLD. In conclusion, fermentation patterns were clearly different in NLD, LM-IT and LM-T, but not related to differences in fecal water cytotoxicity.

Quantification of lactose content in human and cow's milk using UPLC-tandem mass spectrometry.

PubMed

Fusch, Gerhard; Choi, Arum; Rochow, Niels; Fusch, Christoph

2011-12-01

A sensitive, accurate, and specific quantitative UPLC-MS/MS method was developed for lactose measurement of cow's and human milk and validated with cow's milk samples certified by an external laboratory. The new method employs only a dilution of raw cow's and human milk for simple preparation with no need to remove protein and fat prior to analysis with UPLC-MS/MS. It was operated in negative mode to detect lactose molecules and labeled (13)C(12)-lactose with the highest sensitivity. The principle advantages of the new LC-MS/MS method were: completed lactose determination in 5 min, absolute recovery of 97-107%, lower limit of detection <5 ng/L, and 99% linearity over the concentration range of 0.7-4.4 mg/L for both cow's and human milk. The mean lactose concentration of 51 human milk samples was measured as 56.8 ± 5.5 g/L ranging from 43 to 65 g/L. The described method represents validated lactose analysis with high accuracy and precision for a routine lactose determination in raw human milk. Crown Copyright © 2011. Published by Elsevier B.V. All rights reserved.

Identification of an operon, Pil-Chp, that controls twitching motility and virulence in Xylella fastidiosa.

PubMed

Cursino, Luciana; Galvani, Cheryl D; Athinuwat, Dusit; Zaini, Paulo A; Li, Yaxin; De La Fuente, Leonardo; Hoch, Harvey C; Burr, Thomas J; Mowery, Patricia

2011-10-01

Xylella fastidiosa is an important phytopathogenic bacterium that causes many serious plant diseases, including Pierce's disease of grapevines. Disease manifestation by X. fastidiosa is associated with the expression of several factors, including the type IV pili that are required for twitching motility. We provide evidence that an operon, named Pil-Chp, with genes homologous to those found in chemotaxis systems, regulates twitching motility. Transposon insertion into the pilL gene of the operon resulted in loss of twitching motility (pilL is homologous to cheA genes encoding kinases). The X. fastidiosa mutant maintained the type IV pili, indicating that the disrupted pilL or downstream operon genes are involved in pili function, and not biogenesis. The mutated X. fastidiosa produced less biofilm than wild-type cells, indicating that the operon contributes to biofilm formation. Finally, in planta the mutant produced delayed and less severe disease, indicating that the Pil-Chp operon contributes to the virulence of X. fastidiosa, presumably through its role in twitching motility.

Digital optical signal processing with polarization-bistable semiconductor lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jai-Ming Liu,; Ying-Chin Chen,

1985-04-01

The operations of a complete set of optical AND, NAND, OR, and NOR gates and clocked optical S-R, D, J-K, and T flip-flops are demonstrated, based on direct polarization switching and polarization bistability, which we have recently observed in InGaAsP/InP semiconductor lasers. By operating the laser in the direct-polarizationswitchable mode, the output of the laser can be directly switched between the TM00 and TE00 modes with high extinction ratios by changing the injection-current level, and optical logic gates are constructed with two optoelectronic switches or photodetectors. In the polarization-bistable mode, the laser exhibits controllable hysteresis loops in the polarization-resolved powermore » versus current characteristics. When the laser is biased in the middle of the hysteresis loop, the light output can be switched between the two polarization states by injection of short electrical or optical pulses, and clocked optical flip-flops are constructed with a few optoelectronic switches and/or photodetectors. The 1 and 0 states of these devices are defined through polarization changes of the laser and direct complement functions are obtainable from the TE and TM output signals from the same laser. Switching of the polarization-bistable lasers with fast-rising current pulses has an instrument-limited mode-switching time on the order of 1 ns. With fast optoelectronic switches and/or fast photodetectors, the overall switching speed of the logic gates and flip-flops is limited by the polarizationbistable laser to <1 ns. We have demonstrated the operations of these devices using optical signals generated by semiconductor lasers. The proposed schemes of our devices are compatible with monolithic integration based on current fabrication technology and are applicable to other types of bistable semiconductor lasers.« less

Effect of humidity on solid-state isomerization of various kinds of lactose during grinding.

PubMed

Otsuka, M; Ohtani, H; Otsuka, K; Kaneniwa, N

1993-01-01

The effect of humidity on isomerization during grinding of alpha-monohydrate, alpha-anhydrate and beta-anhydrate of lactose was investigated. Samples were ground in an agate centrifugal ball mill at 270 rev min-1 at room temperature (21 degrees C) and at 5 and 60% relative humidity. Crystallinity of the ground lactose was measured by Hermans' method from the powder X-ray diffraction profiles. The alpha- and beta-lactose content of the ground lactose was measured by using angular rotation spectrophotometry. The crystalline lactose samples were transformed into noncrystalline solids by mechanical stress during grinding. After grinding, the adsorbed water content of all ground lactose samples increased, and the isomerized amount increased with increase of the water content during grinding at 5 and 60% relative humidity. The results suggest that the isomerization rate of alpha-monohydrate during grinding may depend on the crystallinity, but those of alpha- and beta-anhydrate depend on the content of adsorbed water.

Large-strain, rigid-to-rigid deformation of bistable electroactive polymers

NASA Astrophysics Data System (ADS)

Yu, Zhibin; Yuan, Wei; Brochu, Paul; Chen, Bin; Liu, Zhitian; Pei, Qibing

2009-11-01

Thermoplastic poly(tert-butyl acrylate) (PTBA) is reported as an electroactive polymer that is rigid at ambient conditions and turns into a dielectric elastomer above a transition temperature. In the rubbery state, a PTBA thin film can be electrically actuated to strains up to 335% in area expansion. The calculated actuation pressure is 3.2 MPa. The actuation is made bistable by cooling to below glass transition temperature. The PTBA represents the bistable electroactive polymer (BSEP) that can be actuated to various largely strained, rigid shapes. The application of the BSEP for refreshable Braille display, an active tactile display, is also demonstrated.

Identification and characterization of transcripts from the biotin biosynthetic operon of Bacillus subtilis.

PubMed Central

Perkins, J B; Bower, S; Howitt, C L; Yocum, R R; Pero, J

1996-01-01

Northern (RNA) blot analysis of the Bacillus subtilis biotin operon, bioWAFDBIorf2, detected at least two steady-state polycistronic transcripts initiated from a putative vegetative (Pbio) promoter that precedes the operon, i.e., a full-length 7.2-kb transcript covering the entire operon and a more abundant 5.1-kb transcript covering just the first five genes of the operon. Biotin and the B. subtilis birA gene product regulated synthesis of the transcripts. Moreover, replacing the putative Pbio promoter and regulatory sequence with a constitutive SP01 phage promoter resulted in higher-level constitutive synthesis. Removal of a rho-independent terminator-like sequence located between the fifth (bioB) and sixth (bioI) genes prevented accumulation of the 5.1-kb transcript, suggesting that the putative terminator functions to limit expression of bioI, which is thought to be involved in an early step in biotin synthesis. PMID:8892842

Internal optical bistability of quasi-two-dimensional semiconductor nanoheterostructures

NASA Astrophysics Data System (ADS)

Derevyanchuk, Oleksandr V.; Kramar, Natalia K.; Kramar, Valeriy M.

2018-01-01

We represent the results of numerical computations of the frequency and temperature domains of possible realization of internal optical bistability in flat quasi-two-dimensional semiconductor nanoheterostructures with a single quantum well (i.e., nanofilms). Particular computations have been made for a nanofilm of layered semiconductor PbI2 embedded in dielectric medium, i.e. ethylene-methacrylic acid (E-MAA) copolymer. It is shown that an increase in the nanofilm's thickness leads to a long-wave shift of the frequency range of the manifestation the phenomenon of bistability, to increase the size of the hysteresis loop, as well as to the expansion of the temperature interval at which the realization of this phenomenon is possible.

Powder compression mechanics of spray-dried lactose nanocomposites.

PubMed

Hellrup, Joel; Nordström, Josefina; Mahlin, Denny

2017-02-25

The aim of this study was to investigate the structural impact of the nanofiller incorporation on the powder compression mechanics of spray-dried lactose. The lactose was co-spray-dried with three different nanofillers, that is, cellulose nanocrystals, sodium montmorillonite and fumed silica, which led to lower micron-sized nanocomposite particles with varying structure and morphology. The powder compression mechanics of the nanocomposites and physical mixtures of the neat spray-dried components were evaluated by a rational evaluation method with compression analysis as a tool, using the Kawakita equation and the Shapiro-Konopicky-Heckel equation. Particle rearrangement dominated the initial compression profiles due to the small particle size of the materials. The strong contribution of particle rearrangement in the materials with fumed silica continued throughout the whole compression profile, which prohibited an in-depth material characterization. However, the lactose/cellulose nanocrystals and the lactose/sodium montmorillonite nanocomposites demonstrated high yield pressure compared with the physical mixtures indicating increased particle hardness upon composite formation. This increase has likely to do with a reinforcement of the nanocomposite particles by skeleton formation of the nanoparticles. In summary, the rational evaluation of mechanical properties done by applying powder compression analysis proved to be a valuable tool for mechanical evaluation for this type of spray-dried composite materials, unless they demonstrate particle rearrangement throughout the whole compression profile. Copyright © 2016 Elsevier B.V. All rights reserved.

Confinement of Amorphous Lactose in Pores Formed Upon Co-Spray Drying With Nanoparticles.

PubMed

Hellrup, Joel; Mahlin, Denny

2017-01-01

This study aims at investigating factors influencing humidity-induced recrystallization of amorphous lactose, produced by co-spray drying with particles of cellulose nanocrystals or sodium montmorillonite. In particular, the focus is on how the nanoparticle shape and surface properties influence the nanometer to micrometer length scale nanofiller arrangement in the nanocomposites and how the arrangements influence the mechanisms involved in the inhibition of the amorphous to crystalline transition. The nanocomposites were produced by co-spray drying. Solid-state transformations were analyzed at 60%-94% relative humidity using X-ray powder diffraction, microcalorimetry, and light microscopy. The recrystallization rate constant for the lactose/cellulose nanocrystals and lactose/sodium montmorillonite nanocomposites was lowered at nanofiller contents higher than 60% and was stable for months at 80% nanofiller. The most likely explanation to these results is spontaneous formations of mesoporous particle networks that the lactose is confined upon co-spray drying at high filler content. Compartmentalization and rigidification of the amorphous lactose proved to be less important mechanisms involved in the stabilization of lactose in the nanocomposites. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Coarse-grained Simulations of Sugar Transport and Conformational Changes of Lactose Permease

NASA Astrophysics Data System (ADS)

Liu, Jin; Jewel, S. M. Yead; Dutta, Prashanta

2016-11-01

Escherichia coli lactose permease (LacY) actively transports lactose and other galactosides across cell membranes through lactose/H+ symport process. Lactose/H+ symport is a highly complex process that involves sugar translocation, H+ transfer, as well as large-scale protein conformational changes. The complete picture of lactose/H+ symport is largely unclear due to the complexity and multiscale nature of the process. In this work, we develop the force field for sugar molecules compatible with PACE, a hybrid and coarse-grained force field that couples the united-atom protein models with the coarse-grained MARTINI water/lipid. After validation, we implement the new force field to investigate the transport of a β-D-galactopyranosyl-1-thio- β-D-galactopyranoside (TDG) molecule across a wild-type LacY during lactose/H+ symport process. Results show that the local interactions between TDG and LacY at the binding pocket are consistent with the X-ray experiment. Protonation of Glu325 stabilizes the TDG and inward-facing conformation of LacY. Protonation of Glu269 induces a dramatic protein structural reorganization and causes the expulsion of TDG from LacY to both sides of the membrane. The structural changes occur primarily in the N-terminal domain of LacY. This work is supported by NSF Grants: CBET-1250107 and CBET -1604211.

The effect of particle size on the dehydration/rehydration behaviour of lactose.

PubMed

Crisp, J L; Dann, S E; Edgar, M; Blatchford, C G

2010-05-31

Ethanolic suspensions of spray dried and micronized alpha lactose monohydrate (L(alpha)xH(2)O) with average particle size between 3 and 200 microm, have been prepared and their dehydration behaviour was investigated by (13)C CP-MASNMR spectroscopy. Sub-micron lactose suspension prepared by a novel high pressure homogenisation method has been compared with the standard ethanolic suspensions of (L(alpha).H(2)O prepared by reflux or static room temperature methods. In all cases, suspensions were shown to contain the stable anhydrous form of lactose ((L(alpha)(S)). Several approaches were employed to remove ethanol from these suspensions and the resulting dry lactose powders were then analysed by FT-IR, PXRD and SEM to evaluate the effect of drying procedure on type and distribution of lactose polymorphs and particle size. For samples with mean particle size greater than 1 microm, the stable anhydrous polymorphic form of lactose was retained on removal of the ethanol, although differences in the morphology and particle size of the crystals were apparent depending on method of suspension formation. Sub-micron (L(alpha)(S), while stable in dry conditions, has been shown to be less stable to atmospheric water vapour than (L(alpha)(S) with particle size between 3 and 200 microm. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Prevalence of self-reported lactose intolerance in multiethnic sample of adults

USDA-ARS?s Scientific Manuscript database

According to the National Institute of Diabetes and Digestive and Kidney Diseases, between 30 and 50 million Americans have the potential for lactose-intolerance symptoms. However, lactose-intolerance prevalence rates in practical life settings may be lower than originally suggested. The goal of thi...

Design of the lac gene circuit revisited

PubMed Central

Savageau, Michael A.

2011-01-01

The lactose (lac) operon of Escherichia coli serves as the paradigm for gene regulation, not only for bacteria, but also for all biological systems from simple phage to humans. The details of the systems may differ, but the key conceptual framework remains, and the original system continues to reveal deeper insights with continued experimental and theoretical study. Nearly as long lasting in impact as the pivotal work of Jacob and Monod is the classic experiment of Novick and Weiner in which they demonstrated all-or-none gene expression in response to an artificial inducer. These results are often cited in claims that normal gene expression is in fact a discontinuous bistable phenomenon. In this paper, I review several levels of analysis of the lac system and introduce another perspective based on the construction of the system design space. These represent variations on a theme, based on a simply stated design principle, that captures the key qualitative features of the system in a largely mechanism-independent fashion. Moreover, this principle can be readily interpreted in terms of specific mechanisms to make predictions regarding monostable vs. bistable behavior. The regions of design space representing bifurcations are compared with the corresponding regions identified through bifurcation analysis. I present evidence based on biological considerations as well as modeling and analysis to suggest that induction of the lac system in its natural setting is a monostable continuously graded phenomenon. Nevertheless, it must be acknowledged that the lac stability question remains unsettled, and it undoubtedly will remain so until there are definitive experimental results. PMID:21414326

Preferred hexoses influence long-term memory and induction of lactose catabolism by Streptococcus mutans.

PubMed

Zeng, Lin; Chen, Lulu; Burne, Robert A

2018-05-11

Bacteria prioritize sugar metabolism via carbohydrate catabolite repression, which regulates global gene expression to optimize the catabolism of preferred substrates. Here, we report an unusual long-term memory effect in certain Streptococcus mutans strains that alters adaptation to growth on lactose after prior exposure to glucose or fructose. In strain GS-5, cells that were first cultured on fructose then transferred to lactose displayed an exceptionally long lag (>11 h) and slower growth, compared to cells first cultured on glucose or cellobiose, which displayed a reduction in lag phase by as much as 10 h. Mutants lacking the cellobiose-PTS or phospho-β-glucosidase lost the accelerated growth on lactose associated with prior culturing on glucose. The memory effects of glucose or fructose on lactose catabolism were not as profound in strain UA159, but the lag phase was considerably shorter in mutants lacking the glucose-PTS EII Man Interestingly, when S. mutans was cultivated on lactose, significant quantities of free glucose accumulated in the medium, with higher levels found in the cultures of strains lacking EII Man , glucokinase, or both. Free glucose was also detected in cultures that were utilizing cellobiose or trehalose, albeit at lower levels. Such release of hexoses by S. mutans is likely of biological significance as it was found that cells required small amounts of glucose or other preferred carbohydrates to initiate efficient growth on lactose. These findings suggest that S. mutans modulates the induction of lactose utilization based on its prior exposure to glucose or fructose, which can be liberated from common disaccharides. IMPORTANCE. Understanding the molecular mechanisms employed by oral bacteria to control sugar metabolism is key to developing novel therapies for management of dental caries and other oral diseases. Lactose is a naturally occurring disaccharide that is abundant in dairy products and commonly ingested by humans. However, for

Dairy Intake, Dietary Adequacy, and Lactose Intolerance12

PubMed Central

Heaney, Robert P.

2013-01-01

Despite repeated emphasis in the Dietary Guidelines for Americans on the importance of calcium in the adult American diet and the recommendation to consume 3 dairy servings a day, dairy intake remains well below recommendations. Insufficient health professional awareness of the benefits of calcium and concern for lactose intolerance are among several possible reasons, This mini-review highlights both the role of calcium (and of dairy, its principal source in modern diets) in health maintenance and reviews the means for overcoming lactose intolerance (real or perceived). PMID:23493531

Bidirectional optical bistability in a dual-pumped erbium doped fiber ring laser.

PubMed

Lai, W J; Shum, P; Binh, L

2004-11-15

We investigate bidirectional optical wave propagations in a dual-pumped erbium doped fiber ring laser without isolator, and observe optical bistability behaviors. Consequently, we propose and construct a NOLM-NALM fiber ring laser to demonstrate and exploit this bidirectional optical bistability phenomenon in optical switching by introducing two tunable variable ratio couplers in the system. Numerical analyses based on the proposed laser structure have also been demonstrated corroborated with the experimental results.

Contribution of Colonic Fermentation and Fecal Water Toxicity to the Pathophysiology of Lactose-Intolerance

PubMed Central

Windey, Karen; Houben, Els; Deroover, Lise; Verbeke, Kristin

2015-01-01

Whether or not abdominal symptoms occur in subjects with small intestinal lactose malabsorption might depend on differences in colonic fermentation. To evaluate this hypothesis, we collected fecal samples from subjects with lactose malabsorption with abdominal complaints (LM-IT, n = 11) and without abdominal complaints (LM-T, n = 8) and subjects with normal lactose digestion (NLD, n = 15). Lactose malabsorption was diagnosed using a 13C-lactose breath test. Colonic fermentation was characterized in fecal samples at baseline and after incubation with lactose for 3 h, 6 h and 24 h through a metabolomics approach using gas chromatography-mass spectrometry (GC-MS). Fecal water cytotoxicity was analyzed using a colorimetric assay. Fecal water cytotoxicity was not different between the three groups (Kruskall-Wallis p = 0.164). Cluster analysis of the metabolite patterns revealed separate clusters for NLD, LM-T and LM-IT samples at baseline and after 24 h incubation with lactose. Levels of 5-methyl-2-furancarboxaldehyde were significantly higher in LM-IT and LM-T compared to NLD whereas those of an unidentified aldehyde were significantly higher in LM-IT compared to LM-T and NLD. Incubation with lactose increased short chain fatty acid (SCFA) concentrations more in LM-IT and LM-T compared to NLD. In conclusion, fermentation patterns were clearly different in NLD, LM-IT and LM-T, but not related to differences in fecal water cytotoxicity. PMID:26371036

Induction of lactose transport in Escherichia coli during the absence of phospholipid synthesis.

PubMed Central

Weisberg, L J; Cronan, J E; Nunn, W D

1975-01-01

Induction of lactose transport and of beta-galactosidase synthesis was examined in two Escherichia coli strains that require exogenous glycerol for phospholipid synthesis and growth. No preferential inhibition of lactose transport induction was observed when phospholipid synthesis was restricted to 5 to 10% of the normal rate. We conclude that the lactose transport system does not require concurrent phospholipid synthesis for its functional assembly. PMID:1097412

Salmonellosis in calves due to lactose fermenting Salmonella typhimurium.

PubMed

Johnston, K G; Jones, R T

1976-04-03

A lactose fermenting strain of Salmonella typhimurium was isolated from two calves which died during an outbreak of acute enteritis. The organism was biochemically typical in all other respects. In one calf, uncomplicated by treatment before death, the autopsy findings were those of a severe fibrinous enteritis which was reproduced in another calf dosed orally with culture. Attention is drawn to scattered reports of lactose fermenting salmonelle causing morbidity and mortality in calves and man.

Effect of pH and lactose concentration on solvent production from whey permeate using Clostridium acetobutylicum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ennis, B.M.; Maddox, I.S.

1987-02-20

A study was performed to optimize the production of solvents from whey permeate in batch fermentation using Clostridium acetobutylicum P262. Fermentations performed at relatively low pH values resulted in high solvent yields and productivities, but lactose utilization was incomplete. At higher pH values, lactose-utilization was improved but acid production dominated over solvent production. When operating at the higher pH values, an increase in the initial lactose concentration of the whey permeate resulted in lower rates of lactose utilization, and this was accompanied by increased solvent production and decreased acid production. Analysis of data from several experiments revealed a strong inversemore » relationship between solvent yield and lactose utilization rate. Thus, conditions which minimize the lactose utilization rate such as low culture pH values or high initial lactose concentrations, favor solventogenesis at the expense of acid production. 12 references.« less

The Interrelationships between Lactose Intolerance and the Modern Dairy Industry: Global Perspectives in Evolutional and Historical Backgrounds.

PubMed

Silanikove, Nissim; Leitner, Gabriel; Merin, Uzi

2015-08-31

Humans learned to exploit ruminants as a source of milk about 10,000 years ago. Since then, the use of domesticated ruminants as a source of milk and dairy products has expanded until today when the dairy industry has become one of the largest sectors in the modern food industry, including the spread at the present time to countries such as China and Japan. This review analyzes the reasons for this expansion and flourishing. As reviewed in detail, milk has numerous nutritional advantages, most important being almost an irreplaceable source of dietary calcium, hence justifying the effort required to increase its consumption. On the other hand, widespread lactose intolerance among the adult population is a considerable drawback to dairy-based foods consumption. Over the centuries, three factors allowed humans to overcome limitations imposed by lactose intolerance: (i) mutations, which occurred in particular populations, most notably in the north European Celtic societies and African nomads, in which carriers of the lactose intolerance gene converted from being lactose intolerant to lactose tolerant; (ii) the ability to develop low-lactose products such as cheese and yogurt; and (iii) colon microbiome adaptation, which allow lactose intolerant individuals to overcome its intolerance. However, in a few examples in the last decade, modern dairy products, such as the popular and widespread bio-cultured yogurts, were suspected to be unsuitable for lactose intolerant peoples. In addition, the use of lactose and milk-derived products containing lactose in non-dairy products has become widespread. For these reasons, it is concluded that it might be important and helpful to label food that may contain lactose because such information will allow lactose intolerant groups to control lactose intake within the physiological limitations of ~12 g per a single meal.

The Interrelationships between Lactose Intolerance and the Modern Dairy Industry: Global Perspectives in Evolutional and Historical Backgrounds

PubMed Central

Silanikove, Nissim; Leitner, Gabriel; Merin, Uzi

2015-01-01

Humans learned to exploit ruminants as a source of milk about 10,000 years ago. Since then, the use of domesticated ruminants as a source of milk and dairy products has expanded until today when the dairy industry has become one of the largest sectors in the modern food industry, including the spread at the present time to countries such as China and Japan. This review analyzes the reasons for this expansion and flourishing. As reviewed in detail, milk has numerous nutritional advantages, most important being almost an irreplaceable source of dietary calcium, hence justifying the effort required to increase its consumption. On the other hand, widespread lactose intolerance among the adult population is a considerable drawback to dairy-based foods consumption. Over the centuries, three factors allowed humans to overcome limitations imposed by lactose intolerance: (i) mutations, which occurred in particular populations, most notably in the north European Celtic societies and African nomads, in which carriers of the lactose intolerance gene converted from being lactose intolerant to lactose tolerant; (ii) the ability to develop low-lactose products such as cheese and yogurt; and (iii) colon microbiome adaptation, which allow lactose intolerant individuals to overcome its intolerance. However, in a few examples in the last decade, modern dairy products, such as the popular and widespread bio-cultured yogurts, were suspected to be unsuitable for lactose intolerant peoples. In addition, the use of lactose and milk-derived products containing lactose in non-dairy products has become widespread. For these reasons, it is concluded that it might be important and helpful to label food that may contain lactose because such information will allow lactose intolerant groups to control lactose intake within the physiological limitations of ~12 g per a single meal. PMID:26404364

Regulation of the glv Operon in Bacillus subtilis: YfiA (GlvR) Is a Positive Regulator of the Operon That Is Repressed through CcpA and cre

PubMed Central

Yamamoto, Hiroki; Serizawa, Masakuni; Thompson, John; Sekiguchi, Junichi

2001-01-01

Maltose metabolism and the regulation of the glv operon of Bacillus subtilis, comprising three genes, glvA (6-phospho-α-glucosidase), yfiA (now designated glvR), and glvC (EIICB transport protein), were investigated. Maltose dissimilation was dependent primarily upon the glv operon, and insertional inactivation of either glvA, glvR, or glvC markedly inhibited growth on the disaccharide. A second system (MalL) contributed to a minor extent to maltose metabolism. Northern blotting revealed two transcripts corresponding to a monocistronic mRNA of glvA and a polycistronic mRNA of glvA-glvR-glvC. Primer extension analysis showed that both transcripts started at the same base (G) located 26 bp upstream of the 5′ end of glvA. When glvR was placed under control of the spac promoter, expression of the glv operon was dependent upon the presence of isopropyl-β-d-thiogalactopyranoside (IPTG). In regulatory studies, the promoter sequence of the glv operon was fused to lacZ and inserted into the amyE locus, and the resultant strain (AMGLV) was then transformed with a citrate-controlled glvR plasmid, pHYCM2VR. When cultured in Difco sporulation medium containing citrate, this transformant [AMGLV(pHYCM2VR)] expressed LacZ activity, but synthesis of LacZ was repressed by glucose. In an isogenic strain, [AMGLVCR(pHYCM2VR)], except for a mutation in the sequence of a catabolite-responsive element (cre), LacZ activity was expressed in the presence of citrate and glucose. Insertion of a citrate-controlled glvR plasmid at the amyE locus of ccpA+ and ccpA mutant organisms yielded strains AMCMVR and AMCMVRCC, respectively. In the presence of both glucose and citrate, AMCMVR failed to express the glv operon, whereas under the same conditions high-level expression of both mRNA transcripts was found in strain AMCMVRCC. Collectively, our findings suggest that GlvR (the product of the glvR gene) is a positive regulator of the glv operon and that glucose exerts its effect via catabolite

Bi-stable dendrite in constant electric field: a model analysis.

PubMed

Baginskas, A; Gutman, A; Svirskis, G

1993-03-01

Some neurons possess dendritic persistent inward current, which is activated during depolarization. Dendrites can be stably depolarized, i.e. they are bi-stable if the net current is inward. A proper method to show the existence of dendritic bi-stability is putting the neuron into the electric field to induce transmembrane potential changes along the dendrites. Here we present analytical and computer simulation of the bi-stable dendrite in the d.c. field. A prominent jump to a depolarization plateau can be seen in the soma upon initial hyperpolarization of its membrane. If a considerable portion of dendrites are parallel to the field it is impossible to switch off the depolarization plateau by changing the direction and the strength of the electric field. There is nothing similar in neurons with ohmic dendrites. The results of the simulation conform to the experimental observations in turtle motoneurons [Hounsgaard J. and Kiehn O. (1993) J. Physiol., Lond. (in press)]; comparison of the theoretical and the experimental results makes semi-quantitative estimation of some electrical parameters of dendrites possible. We propose modifications of the experiment which enable one to measure dendritic length constants and other parameters of stained neurons.

Evolution of the bi-stable wake of a square-back automotive shape

NASA Astrophysics Data System (ADS)

Pavia, Giancarlo; Passmore, Martin; Sardu, Costantino

2018-01-01

Square-back shapes are popular in the automotive market for their high level of practicality. These geometries, however, are usually characterised by high drag and their wake dynamics present aspects, such as the coexistence of a long-time bi-stable behaviour and short-time global fluctuating modes that are not fully understood. In the present paper, the unsteady behaviour of the wake of a generic square-back car geometry is characterised with an emphasis on identifying the causal relationship between the different dynamic modes in the wake. The study is experimental, consisting of balance, pressure, and stereoscopic PIV measurements. Applying wavelet and cross-wavelet transforms to the balance data, a quasi-steady correlation is demonstrated between the forces and bi-stable modes. This is investigated by applying proper orthogonal decomposition to the pressure and velocity data sets and a new structure is proposed for each bi-stable state, consisting of a hairpin vortex that originates from one of the two model's vertical trailing edges and bends towards the opposite side as it merges into a single streamwise vortex downstream. The wake pumping motion is also identified and for the first time linked with the motion of the bi-stable vortical structure in the streamwise direction, resulting in out-of-phase pressure variations between the two vertical halves of the model base. A phase-averaged low-order model is also proposed that provides a comprehensive description of the mechanisms of the switch between the bi-stable states. It is demonstrated that, during the switch, the wake becomes laterally symmetric and, at this point, the level of interaction between the recirculating structures and the base reaches a minimum, yielding, for this geometry, a 7% reduction of the base drag compared to the time-averaged result.

Prevalence of transcription promoters within archaeal operons and coding sequences

PubMed Central

Koide, Tie; Reiss, David J; Bare, J Christopher; Pang, Wyming Lee; Facciotti, Marc T; Schmid, Amy K; Pan, Min; Marzolf, Bruz; Van, Phu T; Lo, Fang-Yin; Pratap, Abhishek; Deutsch, Eric W; Peterson, Amelia; Martin, Dan; Baliga, Nitin S

2009-01-01

Despite the knowledge of complex prokaryotic-transcription mechanisms, generalized rules, such as the simplified organization of genes into operons with well-defined promoters and terminators, have had a significant role in systems analysis of regulatory logic in both bacteria and archaea. Here, we have investigated the prevalence of alternate regulatory mechanisms through genome-wide characterization of transcript structures of ∼64% of all genes, including putative non-coding RNAs in Halobacterium salinarum NRC-1. Our integrative analysis of transcriptome dynamics and protein–DNA interaction data sets showed widespread environment-dependent modulation of operon architectures, transcription initiation and termination inside coding sequences, and extensive overlap in 3′ ends of transcripts for many convergently transcribed genes. A significant fraction of these alternate transcriptional events correlate to binding locations of 11 transcription factors and regulators (TFs) inside operons and annotated genes—events usually considered spurious or non-functional. Using experimental validation, we illustrate the prevalence of overlapping genomic signals in archaeal transcription, casting doubt on the general perception of rigid boundaries between coding sequences and regulatory elements. PMID:19536208

Prevalence of transcription promoters within archaeal operons and coding sequences.

PubMed

Koide, Tie; Reiss, David J; Bare, J Christopher; Pang, Wyming Lee; Facciotti, Marc T; Schmid, Amy K; Pan, Min; Marzolf, Bruz; Van, Phu T; Lo, Fang-Yin; Pratap, Abhishek; Deutsch, Eric W; Peterson, Amelia; Martin, Dan; Baliga, Nitin S

2009-01-01

Despite the knowledge of complex prokaryotic-transcription mechanisms, generalized rules, such as the simplified organization of genes into operons with well-defined promoters and terminators, have had a significant role in systems analysis of regulatory logic in both bacteria and archaea. Here, we have investigated the prevalence of alternate regulatory mechanisms through genome-wide characterization of transcript structures of approximately 64% of all genes, including putative non-coding RNAs in Halobacterium salinarum NRC-1. Our integrative analysis of transcriptome dynamics and protein-DNA interaction data sets showed widespread environment-dependent modulation of operon architectures, transcription initiation and termination inside coding sequences, and extensive overlap in 3' ends of transcripts for many convergently transcribed genes. A significant fraction of these alternate transcriptional events correlate to binding locations of 11 transcription factors and regulators (TFs) inside operons and annotated genes-events usually considered spurious or non-functional. Using experimental validation, we illustrate the prevalence of overlapping genomic signals in archaeal transcription, casting doubt on the general perception of rigid boundaries between coding sequences and regulatory elements.

Synergic role of the two ars operons in arsenic tolerance in Pseudomonas putida KT2440.

PubMed

Fernández, Matilde; Udaondo, Zulema; Niqui, José-Luis; Duque, Estrella; Ramos, Juan-Luis

2014-10-01

The chromosome of Pseudomonas putida KT2440 carries two clusters of genes, denoted ars1 and ars2, that are annotated as putative arsenic resistance operons. In this work, we present evidence that both operons encode functional arsenic-response regulatory genes as well as arsenic extrusion systems that confer resistance to both arsenite [As(III)] and arsenate [As(V)]. Transcriptional fusions of P(ars1) and P(ars2) to lacZ revealed that expression of both operons was induced by arsenite and arsenate. We generated single mutants in ars1 and ars2, which showed lower resistance to arsenic than the wild-type strain. A double ars1/ars2 was found to be highly sensitive to arsenic. Minimum inhibitory concentrations (MICs) for single mutants decreased two- to fourfold with respect to the parental strain, while in the double mutant the MIC decreased 128-fold for arsenite and 32-fold for arsenate. Bioinformatic analysis revealed that the ars2 resistance operon is part of the core genome of P. putida, while the ars1 operon appears to only occur in the KT2440 strain, suggesting that ars1 was acquired by horizontal gene transfer. The presence of ars1 in KT2440 may explain why it exhibits higher resistance to arsenic than other P. putida strains, which bear only the ars2 operon.

Hydroxyurea-Lactose Interaction Study: In Silico and In Vitro Evaluation.

PubMed

Bachchhao, Kunal B; Patil, R R; Patil, C R; Patil, Dipak D

2017-11-01

The Maillard reaction between hydroxyurea (a primary amine-containing drug) and lactose (used as an excipient) was explored. The adduct of these compounds was synthesized by heating hydroxyurea with lactose monohydrate at 60 °C in borate buffer (pH 9.2) for 12 h. Synthesis of the adduct was confirmed using UV-visible spectroscopy and Fourier transform infrared, differential scanning calorimetry, high-pressure liquid chromatography, and liquid chromatography-mass spectrometry studies. An in silico investigation of how the adduct formation affected the interactions of hydroxyurea with its biological target oxyhemoglobin, to which it binds to generate nitric oxide and regulates fetal hemoglobin synthesis, was carried out. The in silico evaluations were complemented by an in vitro assay of the anti-sickling activity. Co-incubation of hydroxyurea with deoxygenated blood samples reduced the percentage of sickled cells from 38% to 12 ± 1.6%, whereas the percentage of sickled cells in samples treated with the adduct was 17 ± 1.2%. This indicated loss of anti-sickling activity in the case of the adduct. This study confirmed that hydroxyurea can participate in a Maillard reaction if lactose is used as a diluent. Although an extended study at environmentally feasible temperatures was not carried out in the present investigation, the partial loss of the anti-sickling activity of hydroxyurea was investigated along with the in silico drug-target interactions. The results indicated that the use of lactose in hydroxyurea formulations needs urgent reconsideration and that lactose must be replaced by other diluents that do not form Maillard adducts.

Radiation-induced oxidative damage to the DNA-binding domain of the lactose repressor

PubMed Central

Gillard, Nathalie; Goffinont, Stephane; Buré, Corinne; Davidkova, Marie; Maurizot, Jean-Claude; Cadene, Martine; Spotheim-Maurizot, Melanie

2007-01-01

Understanding the cellular effects of radiation-induced oxidation requires the unravelling of key molecular events, particularly damage to proteins with important cellular functions. The Escherichia coli lactose operon is a classical model of gene regulation systems. Its functional mechanism involves the specific binding of a protein, the repressor, to a specific DNA sequence, the operator. We have shown previously that upon irradiation with γ-rays in solution, the repressor loses its ability to bind the operator. Water radiolysis generates hydroxyl radicals (OH· radicals) which attack the protein. Damage of the repressor DNA-binding domain, called the headpiece, is most likely to be responsible of this loss of function. Using CD, fluorescence spectroscopy and a combination of proteolytic cleavage with MS, we have examined the state of the irradiated headpiece. CD measurements revealed a dose-dependent conformational change involving metastable intermediate states. Fluorescence measurements showed a gradual degradation of tyrosine residues. MS was used to count the number of oxidations in different regions of the headpiece and to narrow down the parts of the sequence bearing oxidized residues. By calculating the relative probabilities of reaction of each amino acid with OH· radicals, we can predict the most probable oxidation targets. By comparing the experimental results with the predictions we conclude that Tyr7, Tyr12, Tyr17, Met42 and Tyr47 are the most likely hotspots of oxidation. The loss of repressor function is thus correlated with chemical modifications and conformational changes of the headpiece. PMID:17263689

Development and Characterization of Lactose-Positive Pediococcus Species for Milk Fermentation

PubMed Central

Caldwell, S. L.; McMahon, D. J.; Oberg, C. J.; Broadbent, J. R.

1996-01-01

Bacteriophages against Streptococcus thermophilus are a growing problem in the Italian cheese industry. One possible control method involves replacing S. thermophilus in mozzarella starter blends with lactic acid bacteria from a different genus or species. In this study, we evaluated lactose-positive pediococci for this application. Because we could not identify any commercially available pediococci with fast acid-producing ability in milk, we transformed Pediococcus pentosaceus ATCC 25744, P. pentosaceus ATCC 25745, and Pediococcus acidilactici ATCC 12697 by electroporation with pPN-1, a 35-kb Lactococcus lactis lactose plasmid. Transformants of P. pentosaceus ATCC 25745 and P. acidilactici ATCC 12697 were then used to examine lactose-positive pediococci for properties related to milk fermentation. Both transformants rapidly produced acid and efficiently retained pPN-1 in lactose broth, and neither bacterium was attacked by bacteriophages in whey collected from commercial cheese facilities. Paired starter combinations of Pediococcus spp. and Lactobacillus helveticus LH100 exhibited synergistic pH reduction in milk, and small-scale cheese trials showed that these cultures could be used to manufacture part-skim mozzarella cheese. Results demonstrate that lactose-positive pediococci have potential as replacement cocci for S. thermophilus in Italian cheese starter blends and may facilitate development of new strain rotation schemes to combat S. thermophilus bacteriophage problems in mozzarella cheese plants. PMID:16535280

Structure and regulation of the Yersinia pestis yscBCDEF operon.

PubMed Central

Haddix, P L; Straley, S C

1992-01-01

We have investigated the physical and genetic structure and regulation of the Yersinia pestis yscBCDEF region, previously called lcrC. DNA sequence analysis showed that this region is homologous to the corresponding part of the ysc locus of Yersinia enterocolitica and suggested that the yscBCDEF cistrons belong to a single operon on the low-calcium response virulence plasmid pCD1. Promoter activity measurements of ysc subclones indicated that yscBCDEF constitutes a suboperon of the larger ysc region by revealing promoter activity in a clone containing the 3' end of yscD, intact yscE and yscF, and part of yscG. These experiments also revealed an additional weak promoter upstream of yscD. Northern (RNA) analysis with a yscD probe showed that operon transcription is thermally induced and downregulated in the presence of Ca2+. Primer extension of operon transcripts suggested that two promoters, a moderate-level constitutive one and a stronger, calcium-downregulated one, control full-length operon transcription at 37 degrees C. Primer extension provided additional support for the proposed designation of a yscBCDEF suboperon by identifying a 5' end within yscF, for which relative abundances in the presence and absence of Ca2+ revealed regulation that is distinct from that for transcripts initiating farther upstream. YscB and YscC were expressed in Escherichia coli by using a high-level transcription system. Attempts to express YscD were only partially successful, but they revealed interesting regulation at the translational level. Images PMID:1624469

Lactose intolerance in prostate cancer patients: incidence and associated factors.

PubMed

Agarwal, Mayank Mohan; Rana, Satyavati V; Mandal, Arup Kumar; Malhotra, Sunita; Khandelwal, Niranjan; Kumar, Santosh; Acharya, Naveen Chandra; Singh, Shrawan Kumar

2008-03-01

Osteoporosis is common in prostate cancer (CaP) patients both before and after institution of androgen deprivation therapy and is associated with significant morbidity. Lactose intolerance (LI) can affect bone mass but has not been studied in this group of patients. The objective of this study was to compare the incidence of LI in CaP patients with that in the general population and to identify factors affecting lactose intolerance in CaP patients. Fifty-five men with CaP planned for bilateral orchidectomy were enrolled in the study and their baseline characteristics including age, weight, height, body mass index (BMI), prostate-specific antigen, serum calcium profile, lactose tolerance status, physical activity, alcohol intake and smoking, bone mineral density and calcium intake were registered. The data on lactose tolerance in these patients were compared with those of 81 age-matched controls (data taken from the available database). The incidence of LI in CaP patients was significantly less than that in the control group (36.2% and 58.3%, respectively, p = 0.027). A significantly greater number of CaP patients in the lactose-tolerant group had a calcium intake of >1500 mg/day (p = 0.03) and that of milk >500 ml/day (p = 0.05) than those in the intolerant group. Age >70 years, BMI <25 kg/m2, height >163 cm, lower physical activity and co-abuse of alcohol and smoking significantly correlated with the presence of LI (p < or = 0.05). Patients with serum calcium <9 mg/dl had higher fasting breath H2 levels and a higher proportion had a BMI >25 kg/m2 and weight >65 kg. The incidence of LI in CaP patients is less than that in the general population despite a higher incidence of osteoporosis, indicating a complex etiology of CaP-related osteoporosis. Certain physical characteristics and personal habits are important in determining lactose-tolerant status.

Bistability in a hybrid optomechanical system: effect of a gain medium

NASA Astrophysics Data System (ADS)

Asghari Nejad, A.; Baghshahi, H. R.; Askari, H. R.

2017-11-01

In this paper, we investigate the optical bistability of a hybrid optomechanical system consisting of two coupled cavities: a bare optomechanical cavity (with an oscillating mirror at one end) and a traditional one. The traditional cavity is filled with an optical parametric amplifier (OPA), and an input pump laser is applied to it. The Hamiltonian of the system is written in a rotating frame. The dynamics of the system is driven by the quantum Langevin equations of motion. We demonstrate that the presence of an OPA can dramatically affect the type of stability of the optomechanical cavity. We show that it is possible to create a proper optical bistability for the optomechanical cavity by changing the gain coefficient of the OPA. Also, it is shown that changing the phase of the field driving the OPA has two different effects on the bistability region of the optomechanical cavity. Moreover, we show that by choosing a proper value for the detuning of the traditional cavity it is possible to observe a tristable behavior in the optomechanical cavity.

Optical bistability in a single-sided cavity coupled to a quantum channel

NASA Astrophysics Data System (ADS)

Payravi, M.; Solookinejad, Gh; Jabbari, M.; Nafar, M.; Ahmadi Sangachin, E.

2018-06-01

In this paper, we discuss the long wavelength optical reflection and bistable behavior of an InGaN/GaN quantum dot nanostructure coupled to a single-sided cavity. It is found that due to the presence of a strong coupling field, the reflection coefficient can be controlled at long wavelength, which is essential for adjusting the threshold of reflected optical bistability. Moreover, the phase shift features of the reflection pulse inside an electromagnetically induced transparency window are also discussed.

The effects of probiotics in lactose intolerance: A systematic review.

PubMed

Oak, Sophia J; Jha, Rajesh

2018-02-09

Over 60 percent of the human population has a reduced ability to digest lactose due to low levels of lactase enzyme activity. Probiotics are live bacteria or yeast that supplements the gastrointestinal flora. Studies have shown that probiotics exhibit various health beneficial properties such as improvement of intestinal health, enhancement of the immune responses, and reduction of serum cholesterol. Accumulating evidence has shown that probiotic bacteria in fermented and unfermented milk products can be used to alleviate the clinical symptoms of lactose intolerance (LI). In this systematic review, the effectiveness of probiotics in the treatment of LI was evaluated using 15 randomized double-blind studies. Eight probiotic strains with the greatest number of proven benefits were studied. Results showed varying degrees of efficacy but an overall positive relationship between probiotics and lactose intolerance.

Positions of Trp Codons in the Leader Peptide-Coding Region of the at Operon Influence Anti-Trap Synthesis and trp Operon Expression in Bacillus licheniformis▿

PubMed Central

Levitin, Anastasia; Yanofsky, Charles

2010-01-01

Tryptophan, phenylalanine, tyrosine, and several other metabolites are all synthesized from a common precursor, chorismic acid. Since tryptophan is a product of an energetically expensive biosynthetic pathway, bacteria have developed sensing mechanisms to downregulate synthesis of the enzymes of tryptophan formation when synthesis of the amino acid is not needed. In Bacillus subtilis and some other Gram-positive bacteria, trp operon expression is regulated by two proteins, TRAP (the tryptophan-activated RNA binding protein) and AT (the anti-TRAP protein). TRAP is activated by bound tryptophan, and AT synthesis is increased upon accumulation of uncharged tRNATrp. Tryptophan-activated TRAP binds to trp operon leader RNA, generating a terminator structure that promotes transcription termination. AT binds to tryptophan-activated TRAP, inhibiting its RNA binding ability. In B. subtilis, AT synthesis is upregulated both transcriptionally and translationally in response to the accumulation of uncharged tRNATrp. In this paper, we focus on explaining the differences in organization and regulatory functions of the at operon's leader peptide-coding region, rtpLP, of B. subtilis and Bacillus licheniformis. Our objective was to correlate the greater growth sensitivity of B. licheniformis to tryptophan starvation with the spacing of the three Trp codons in its at operon leader peptide-coding region. Our findings suggest that the Trp codon location in rtpLP of B. licheniformis is designed to allow a mild charged-tRNATrp deficiency to expose the Shine-Dalgarno sequence and start codon for the AT protein, leading to increased AT synthesis. PMID:20061467

The rpoE operon regulates heat stress response in Burkholderia pseudomallei.

PubMed

Vanaporn, Muthita; Vattanaviboon, Paiboon; Thongboonkerd, Visith; Korbsrisate, Sunee

2008-07-01

Burkholderia pseudomallei is a gram-negative bacterium and the causative agent of melioidosis, one of the important lethal diseases in tropical regions. In this article, we demonstrate the crucial role of the B. pseudomallei rpoE locus in the response to heat stress. The rpoE operon knockout mutant exhibited growth retardation and reduced survival when exposed to a high temperature. Expression analysis using rpoH promoter-lacZ fusion revealed that heat stress induction of rpoH, which encodes heat shock sigma factor (sigma(H)), was abolished in the B. pseudomallei rpoE mutant. Analysis of the rpoH promoter region revealed sequences sharing high homology to the consensus sequence of sigma(E)-dependent promoters. Moreover, the putative heat-induced sigma(H)-regulated heat shock proteins (i.e. GroEL and HtpG) were also absent in the rpoE operon mutant. Altogether, our data suggest that the rpoE operon regulates B. pseudomallei heat stress response through the function of rpoH.

Characterization and selection of suitable grades of lactose as functional fillers for capsule filling: part 1.

PubMed

Moolchandani, Vikas; Augsburger, Larry L; Gupta, Abhay; Khan, Mansoor; Langridge, John; Hoag, Stephen W

2015-01-01

The purpose of this work is to characterize thermal, physical and mechanical properties of different grades of lactose and better understand the relationships between these properties and capsule filling performance. Eight grades of commercially available lactose were evaluated: Pharmatose 110 M, 125 M, 150 M, 200 M, 350 M (α-lactose monohydrate), AL (anhydrous lactose containing ∼80% β-AL), DCL11 (spray dried α-lactose monohydrate containing ∼15% amorphous lactose) and DCL15 (granulated α-lactose monohydrate containing ∼12% β-AL). In this study, different lactose grades were characterized by thermal, solid state, physical and mechanical properties and later evaluated using principal component analysis (PCA) to assess the inter-relationships among some of these properties. The lactose grades were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), moisture sorption/desorption isotherms, particle size distribution; the flow was characterized by Carr Index (CI), critical orifice diameter (COD) and angle of friction. Plug mechanical strength was estimated from its diametric crushing strength. The first and second principal components (PC) captured 47.6% and 27.4% of variation in the physical and mechanical property data, respectively. The PCA plot grouped together 110 M, AL, DCL11 and DCL15 on the one side of plot which possessed superior properties for capsule formulation and these grades were selected for future formulation development studies (part II of this work).

Electrical bistabilities and memory mechanisms of nonvolatile organic bistable devices based on exfoliated muscovite-type mica nanoparticle/poly(methylmethacrylate) nanocomposites

NASA Astrophysics Data System (ADS)

Lim, Won Gyu; Lee, Dea Uk; Na, Han Gil; Kim, Hyoun Woo; Kim, Tae Whan

2018-02-01

Organic bistable devices (OBDs) with exfoliated mica nanoparticles (NPs) embedded into an insulating poly(methylmethacrylate) (PMMA) layer were fabricated by using a spin-coating method. Current-voltage (I-V) curves for the Al/PMMA/exfoliated mica NP/PMMA/indium-tin-oxide/glass devices at 300 K showed a clockwise current hysteresis behavior due to the existence of the exfoliated muscovite-type mica NPs, which is an essential feature for bistable devices. Write-read-erase-read data showed that the OBDs had rewritable nonvolatile memories and an endurance number of ON/OFF switching for the OBDs of 102 cycles. An ON/OFF ratio of 1 × 103 was maintained for retention times larger than 1 × 104 s. The memory mechanisms of the fabricated OBDs were described by using the trapping and the tunneling processes within a PMMA active layer containing exfoliated muscovite-type mica NPs on the basis of the energy band diagram and the I-V curves.

The Lactose and Galactose Content of Cheese Suitable for Galactosaemia: New Analysis.

PubMed

Portnoi, P A; MacDonald, A

2016-01-01

The UK Medical Advisory Panel of the Galactosaemia Support Group report the lactose and galactose content of 5 brands of mature Cheddar cheese, Comte and Emmi Emmental fondue mix from 32 cheese samples. The Medical Advisory Panel define suitable cheese in galactosaemia to have a lactose and galactose content consistently below 10 mg/100 g. A total of 32 samples (5 types of mature Cheddar cheese, Comte and "Emmi Swiss Fondue", an emmental fondue mix) were analysed by high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) technology used to perform lactose and galactose analysis. Cheddar cheese types: Valley Spire West Country, Parkham, Lye Cross Vintage, Lye Cross Mature, Tesco West Country Farmhouse Extra Mature and Sainsbury's TTD West Country Farmhouse Extra Mature had a lactose and galactose content consistently below 10 mg/100 g (range <0.05 to 12.65 mg). All Comte samples had a lactose content below the lower limit of detection (<0.05 mg) with galactose content from <0.05 to 1.86 mg/100 g; all samples of Emmi Swiss Fondue had lactose below the lower limit of detection (<0.05 mg) and galactose between 2.19 and 3.04 mg/100 g. All of these cheese types were suitable for inclusion in a low galactose diet for galactosaemia. It is possible that the galactose content of cheese may change over time depending on its processing, fermentation time and packaging techniques.

A silicon-nanowire memory driven by optical gradient force induced bistability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, B.; Institute of Microelectronics, A*STAR; Cai, H., E-mail: caih@ime.a-star.edu.sg

2015-12-28

In this paper, a bistable optical-driven silicon-nanowire memory is demonstrated, which employs ring resonator to generate optical gradient force over a doubly clamped silicon-nanowire. Two stable deformation positions of a doubly clamped silicon-nanowire represent two memory states (“0” and “1”) and can be set/reset by modulating the light intensity (<3 mW) based on the optical force induced bistability. The time response of the optical-driven memory is less than 250 ns. It has applications in the fields of all optical communication, quantum computing, and optomechanical circuits.

Front propagation in one-dimensional spatially periodic bistable media

NASA Astrophysics Data System (ADS)

Löber, Jakob; Bär, Markus; Engel, Harald

2012-12-01

Front propagation in heterogeneous bistable media is studied using the Schlögl model as a representative example. Spatially periodic modulations in the parameters of the bistable kinetics are taken into account perturbatively. Depending on the ratio L/l (L is the spatial period of the heterogeneity, l is the front width), appropriate singular perturbation techniques are applied to derive an ordinary differential equation for the position of the front in the presence of the heterogeneities. From this equation, the dependence of the average propagation speed on L/l as well as on the modulation amplitude is calculated. The analytical results obtained predict velocity overshoot, different cases of propagation failure, and the propagation speed for very large spatial periods in quantitative agreement with the results of direct numerical simulations of the underlying reaction-diffusion equation.

Compatibility studies of acyclovir and lactose in physical mixtures and commercial tablets.

PubMed

Monajjemzadeh, Farnaz; Hassanzadeh, Davoud; Valizadeh, Hadi; Siahi-Shadbad, Mohammad R; Mojarrad, Javid Shahbazi; Robertson, Thomas A; Roberts, Michael S

2009-11-01

This study documents drug-excipient incompatibility studies of acyclovir in physical mixtures with lactose and in different tablet brands. Differential scanning calorimetry (DSC) was initially used to assess compatibility of mixtures. The Fourier-transform infrared (FTIR) spectrum was also compared with the spectra of pure drug and excipient. Although DSC results indicated incompatibility with lactose, FTIR spectra were mostly unmodified due to overlapping peaks. Samples of isothermally stressed physical mixture were stored at 95 degrees C for 24 h. The residual drug was monitored using a validated high-performance liquid chromatography (HPLC) assay and data fitting to solid-state kinetic models was performed. The drug loss kinetics followed a diffusion model. The aqueous mixture of drug and excipient was heated in order to prepare an adduct mixture. HPLC analysis revealed one extra peak that was fractionated and subsequently injected into the liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) system. The MRM (Multiple Reaction Monitoring) chromatograms characterized the peak with molecular mass corresponding to an acyclovir-lactose Maillard reaction product. The presence of lactose in commercial tablets was checked using a new TLC method. Overall, the incompatibility of acyclovir with lactose was successfully evaluated using a combination of thermal methods and LC-MS/MS.

Investigation of electrostatic behavior of a lactose carrier for dry powder inhalers.

PubMed

Chow, Keat Theng; Zhu, Kewu; Tan, Reginald B H; Heng, Paul W S

2008-12-01

This study aims to elucidate the electrostatic behavior of a model lactose carrier used in dry powder inhaler formulations by examining the effects of ambient relative humidity (RH), aerosolization air flow rate, repeated inhaler use, gelatin capsule and tapping on the specific charge (nC/g) of bulk and aerosolized lactose. Static and dynamic electrostatic charge measurements were performed using a Faraday cage connected to an electrometer. Experiments were conducted inside a walk-in environmental chamber at 25 degrees C and RHs of 20% to 80%. Aerosolization was achieved using air flow rates of 30, 45, 60 and 75 L/min. The initial charges of the bulk and capsulated lactose were a magnitude lower than the charges of tapped or aerosolized lactose. Dynamic charge increased linearly with aerosolization air flow rate and RH. Greater frictional forces at higher air flow rate induced higher electrostatic charges. Increased RH enhanced charge generation. Repeated inhaler use significantly influenced electrostatic charge due to repeated usage. This study demonstrated the significance of interacting influences by variables commonly encountered in the use DPI such as variation in patient's inspiratory flow rate, ambient RH and repeated inhaler use on the electrostatic behavior of a lactose DPI carrier.

Modeling bistable behaviors in morphing structures through finite element simulations.

PubMed

Guo, Qiaohang; Zheng, Huang; Chen, Wenzhe; Chen, Zi

2014-01-01

Bistable structures, exemplified by the Venus flytrap and slap bracelets, can transit between different configurations upon certain external stimulation. Here we study, through three-dimensional finite element simulations, the bistable behaviors in elastic plates in the absence of terminate loads, but with pre-strains in one (or both) of the two composite layers. Both the scenarios with and without a given geometric mis-orientation angle are investigated, the results of which are consistent with recent theoretical and experimental studies. This work can open ample venues for programmable designs of plant/shell structures with large deformations, with applications in designing bio-inspired robotics for biomedical research and morphing/deployable structures in aerospace engineering.

Bistable aggregate of all-trans-astaxanthin in an aqueous solution

NASA Astrophysics Data System (ADS)

Mori, Yuso; Yamano, Kuniko; Hashimoto, Hideki

1996-05-01

The temperature dependence of the optical absorption spectra for astaxanthin aggregate has been studied between 2 and 32°C. Red-shifted absorption bands as compared to the monomer absorption band are found above 21°C in addition to the blue-shifted band of the aggregate. The spectra suggest that the molecular arrangement in the aggregate is a bistable one consisting of head-to-tail and card-packed arrangements. A diagram describing the bistability together with the monomer state is proposed in the space defined by the free energy and the quantity of Σi = 1 N< θ12 + < σθ12 for the ith molecule in the N-molecule aggregate.

Effect of lactose concentration on batch production of ethanol from cheese whey using Candida pseudotropicalis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghaly, A.E.; El-Taweel, A.A.

1995-07-01

The effect of lactose concentration on growth of Candida pseudotropicalis and ethanol production from cheese whey under batch conditions was investigated. Four initial lactose concentrations ranging from 50 to 200 g/L (5 to 20% wt/vol) were used. High concentration of lactose had an inhibitory effect on the specific growth rate, lactose utilization rate, and ethanol production rate. The maximum cell concentration was influenced by the initial substrate concentration as well as ethanol concentration. Inhibition of ethanol production was more pronounced at higher initial lactose concentrations. The maximum ethanol yield (96.6% of the theoretical yield) was achieved with the 100 g/Lmore » initial substrate concentration. The results indicated that pH control during alcohol fermentation of cheese whey is not necessary. 41 refs., 12 figs., 1 tab.« less

Design of a bistable electromagnetic coupling mechanism for underactuated manipulators

NASA Astrophysics Data System (ADS)

Miyuranga Kaluarachchi, Malaka; Ho, Jee-Hou; Yahya, Samer; Teh, Sze-Hong

2018-07-01

Electromagnetic clutches have been widely used in underactuated lightweight manipulator designs as a coupling mechanism due to their advantages of fast activation and electrical controllability. However, an electromagnetic clutch consumes electrical energy continuously during its operation. Furthermore, conventional electromagnetic clutches are not fail-safe in unexpected power failure conditions. These factors have a significant impact on the energy efficiency and the safety of the design, and these are vital aspects for underactuated lightweight manipulators. This paper introduces a bistable electromagnetic coupling mechanism design, with reduced energy consumption and with a fail-safe mechanism. The concept of a bistable electromagnetic mechanism consists of an electromagnet with two permanent magnets. The design has the capability to maintain stable mechanism states, either engaged or disengaged, without a continuous electrical power supply, thus enhancing fail-safety and efficiency. Moreover, the design incorporates the advantages of conventional electromagnetic clutches such as rapid activation and electrical controllability. The experimental results highlight the effectiveness of the proposed mechanism in reducing electric energy consumption. Besides this, a theoretical model is developed and a good correlation is achieved between the theoretical and experimental results. The reduced electric energy consumption and fail-safe design make the bistable electromagnetic mechanism a promising concept for underactuated lightweight manipulators.

Interplay of bistable kinetics of gene expression during cellular growth

NASA Astrophysics Data System (ADS)

Zhdanov, Vladimir P.

2009-02-01

In cells, the bistable kinetics of gene expression can be observed on the level of (i) one gene with positive feedback between protein and mRNA production, (ii) two genes with negative mutual feedback between protein and mRNA production, or (iii) in more complex cases. We analyse the interplay of two genes of type (ii) governed by a gene of type (i) during cellular growth. In particular, using kinetic Monte Carlo simulations, we show that in the case where gene 1, operating in the bistable regime, regulates mutually inhibiting genes 2 and 3, also operating in the bistable regime, the latter genes may eventually be trapped either to the state with high transcriptional activity of gene 2 and low activity of gene 3 or to the state with high transcriptional activity of gene 3 and low activity of gene 2. The probability to get to one of these states depends on the values of the model parameters. If genes 2 and 3 are kinetically equivalent, the probability is equal to 0.5. Thus, our model illustrates how different intracellular states can be chosen at random with predetermined probabilities. This type of kinetics of gene expression may be behind complex processes occurring in cells, e.g., behind the choice of the fate by stem cells.

Manually Operatable On-Chip Bistable Pneumatic Microstructures for Microfluidic Manipulations

PubMed Central

Chen, A.; Pan, T.

2014-01-01

Bistable microvalves are of particular interest because of their distinct nature requiring energy consumption only during the transition between the open and closed states. This characteristic can be highly advantageous in reducing the number of external inputs and the complexity of control circuitries for microfluidic devices as contemporary lab-on-a-chip platforms are transferring from research settings to low-resource environments with high integratability and small form factor. In this paper, we first present manually operatable, on-chip bistable pneumatic microstructures (BPM) for microfluidic manipulation. The structural design and operation of the BPM devices can be readily integrated into any pneumatically powered microfluidic network consisting of pneumatic and fluidic channels. It is mainly comprised of a vacuum activation chamber (VAC) and a pressure release chamber (PRC), which users have direct control through finger pressing to switch between bistable vacuum state (VS) or atmospheric state (AS). We have integrated multiple BPM devices into a 4-to-1 microfluidic multiplexor to demonstrate on-chip digital flow switching from different sources. Furthermore, we have shown its clinical relevance in a point-of-care diagnostic chip that process blood samples to identify the distinct blood types (A/B/O) on chip. PMID:25007840

Manually operatable on-chip bistable pneumatic microstructures for microfluidic manipulations.

PubMed

Chen, Arnold; Pan, Tingrui

2014-09-07

Bistable microvalves are of particular interest because of their distinct nature of requiring energy consumption only during the transition between the open and closed states. This characteristic can be highly advantageous in reducing the number of external inputs and the complexity of control circuitries since microfluidic devices as contemporary lab-on-a-chip platforms are transferring from research settings to low-resource environments with high integrability and a small form factor. In this paper, we first present manually operatable, on-chip bistable pneumatic microstructures (BPMs) for microfluidic manipulation. The structural design and operation of the BPM devices can be readily integrated into any pneumatically powered microfluidic network consisting of pneumatic and fluidic channels. It is mainly composed of a vacuum activation chamber (VAC) and a pressure release chamber (PRC), of which users have direct control through finger pressing to switch either to the bistable vacuum state (VS) or the atmospheric state (AS). We have integrated multiple BPM devices into a 4-to-1 microfluidic multiplexor to demonstrate on-chip digital flow switching from different sources. Furthermore, we have shown its clinical relevance in a point-of-care diagnostic chip that processes blood samples to identify the distinct blood types (A/B/O) on-chip.

Optical bistability and second-harmonic generation in thin film coupled cavity photonic crystal structures

NASA Astrophysics Data System (ADS)

Diao, Liyong

This thesis deals with design, fabrication and modeling of bistable and multi-stable switching dynamics and second-harmonic generation in two groups of thin film coupled cavity photonic crystal structures. The first component studies optical bistability and multistability in such structures. Optical bistability and multistability are modelled by a nonlinear transfer matrix method. The second component is focused on the modelling and experimental measurement of second-harmonic generation in such structures. It is found that coupled cavity structures can reduce the threshold and index change for bistable operation, but single cavity structures can do the same. However, there is a clear advantage in using coupled cavity structures for multistability in that the threshold for multistability can be reduced. Second-harmonic generation is enhanced by field localization due to the resonant effect at the fundamental wavelength in single and coupled cavity structures by simulated and measured results. The work in this thesis makes three significant contributions. First, in the successful fabrication of thin film coupled cavity structures, the simulated linear transmissions of such structures match those of the fabricated structures almost exactly. Second, the newly defined figure of merit at the maximum transmission point on the bistable curve can be used to compare the material damage tolerance to any other Kerr effect nonlinear gate. Third, the simulated second-harmonic generation agrees excellently with experimental results. More generally optical thin film fabrication has commercial applications in many industry sections, such as electronics, opto-electronics, optical coating, solar cell and MEMS.

Implications of the spatial dynamics of fire spread for the bistability of savanna and forest.

PubMed

Schertzer, E; Staver, A C; Levin, S A

2015-01-01

The role of fire in expanding the global distribution of savanna is well recognized. Empirical observations and modeling suggest that fire spread has a threshold response to fuel-layer continuity, which sets up a positive feedback that maintains savanna-forest bistability. However, modeling has so far failed to examine fire spread as a spatial process that interacts with vegetation. Here, we use simple, well-supported assumptions about fire spread as an infection process and its effects on trees to ask whether spatial dynamics qualitatively change the potential for savanna-forest bistability. We show that the spatial effects of fire spread are the fundamental reason that bistability is possible: because fire spread is an infection process, it exhibits a threshold response to fuel continuity followed by a rapid increase in fire size. Other ecological processes affecting fire spread may also contribute including temporal variability in demography or fire spread. Finally, including the potential for spatial aggregation increases the potential both for savanna-forest bistability and for savanna and forest to coexist in a landscape mosaic.

Bistability in mushroom-type metamaterials

NASA Astrophysics Data System (ADS)

Fernandes, David E.; Silveirinha, Mário G.

2017-07-01

Here, we study the electromagnetic response of asymmetric mushroom-type metamaterials loaded with nonlinear elements. It is shown that near a Fano resonance, these structures may have a strong tunable, bistable, and switchable response and enable giant nonlinear effects. By using an effective medium theory and full wave simulations, it is proven that the nonlinear elements may allow the reflection and transmission coefficients to follow hysteresis loops, and to switch the metamaterial between "go" and "no-go" states similar to an ideal electromagnetic switch.

Population Dynamics of a Lac(-) Strain of Escherichia Coli during Selection for Lactose Utilization

PubMed Central

Foster, P. L.

1994-01-01

During selection for lactose utilization, Lac(+) revertants of FC40, a Lac(-) strain of Escherichia coli, appear at a high rate. Yet, no Lac(+) revertants appear in the absence of lactose, or in its presence if the cells have another, unfulfilled requirement for growth. This study investigates more fully the population dynamics of FC40 when incubated in the absence of a carbon source or when undergoing selection for lactose utilization. In the absence of a carbon source, the viable cell numbers do not change over 6 days. When incubated in liquid lactose medium, Lac(-) cells do not undergo any measurable increase in numbers or in turbidity for at least 2 days. When FC40 is plated on lactose minimum medium in the presence of scavenger cells, the upper limit to the amount of growth of Lac(-) cells during 5 days is one doubling, and there is no evidence for turnover (i.e., a balance between growth and death). The presence of a minority population that could form microcolonies was not detected. The implications of these results, plus the fact that the appearance of Lac(+) revertants during lactose selection is nearly constant with time, are discussed in reference to several models that have been postulated to account for adaptive mutations. PMID:7828809

Acute and Chronic Effects of Dietary Lactose in Adult Rats Are not Explained by Residual Intestinal Lactase Activity

PubMed Central

van de Heijning, Bert J. M.; Kegler, Diane; Schipper, Lidewij; Voogd, Eline; Oosting, Annemarie; van der Beek, Eline M.

2015-01-01

Neonatal rats have a high intestinal lactase activity, which declines around weaning. Yet, the effects of lactose-containing products are often studied in adult animals. This report is on the residual, post-weaning lactase activity and on the short- and long-term effects of lactose exposure in adult rats. Acutely, the postprandial plasma response to increasing doses of lactose was studied, and chronically, the effects of a 30% lactose diet fed from postnatal (PN) Day 15 onwards were evaluated. Intestinal lactase activity, as assessed both in vivo and in vitro, was compared between both test methods and diet groups (lactose vs. control). A 50%–75% decreased digestive capability towards lactose was observed from weaning into adulthood. Instillation of lactose in adult rats showed disproportionally low increases in plasma glucose levels and did not elicit an insulin response. However, gavages comprising maltodextrin gave rise to significant plasma glucose and insulin responses, indicative of a bias of the adult GI tract to digest glucose polymers. Despite the residual intestinal lactase activity shown, a 30% lactose diet was poorly digested by adult rats: the lactose diet rendered the animals less heavy and virtually devoid of body fat, whereas their cecum tripled in size, suggesting an increased bacterial fermentation. The observed acute and chronic effects of lactose exposure in adult rats cannot be explained by the residual intestinal lactase activity assessed. PMID:26184291

Unsaturated fatty acids lactose esters: cytotoxicity, permeability enhancement and antimicrobial activity.

PubMed

Lucarini, Simone; Fagioli, Laura; Campana, Raffaella; Cole, Hannah; Duranti, Andrea; Baffone, Wally; Vllasaliu, Driton; Casettari, Luca

2016-10-01

Sugar based surfactants conjugated with fatty acid chains are an emerging broad group of highly biocompatible and biodegradable compounds with established and potential future applications in the pharmaceutical, cosmetic and food industries. In this work, we investigated absorption enhancing and antimicrobial properties of disaccharide lactose, monoesterified with unsaturated fatty acids through an enzymatic synthetic approach. After chemical and cytotoxicity characterizations, their permeability enhancing activity was demonstrated using intestinal Caco-2 monolayers through transepithelial electrical resistance (TEER) and permeability studies. The synthesized compounds, namely lactose palmitoleate (URB1076) and lactose nervonate (URB1077), were shown to exhibit antimicrobial activity versus eight pathogenic species belonging to Gram-positive, Gram-negative microorganisms and fungi. Copyright © 2016 Elsevier B.V. All rights reserved.

Synthesis of novel bioactive lactose-derived oligosaccharides by microbial glycoside hydrolases

PubMed Central

Díez-Municio, Marina; Herrero, Miguel; Olano, Agustín; Moreno, F Javier

2014-01-01

Prebiotic oligosaccharides are increasingly demanded within the Food Science domain because of the interesting healthy properties that these compounds may induce to the organism, thanks to their beneficial intestinal microbiota growth promotion ability. In this regard, the development of new efficient, convenient and affordable methods to obtain this class of compounds might expand even further their use as functional ingredients. This review presents an overview on the most recent interesting approaches to synthesize lactose-derived oligosaccharides with potential prebiotic activity paying special focus on the microbial glycoside hydrolases that can be effectively employed to obtain these prebiotic compounds. The most notable advantages of using lactose-derived carbohydrates such as lactosucrose, galactooligosaccharides from lactulose, lactulosucrose and 2-α-glucosyl-lactose are also described and commented. PMID:24690139

A mutation in a new gene bglJ, activates the bgl operon in Escherichia coli K-12

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giel, M.; Desnoyer, M.; Lopilato, J.

1996-06-01

A new mutation , bglJ4, has been characterized that results in the expression of the silent bgl operon. The bgl operon encodes proteins necessary for the transport and utilization of the aromatic {beta}-glucosides arbutin and salicin. A variety of mutations activate the operon and result in a Bgl{sup +} phenotype. Activating mutations are located upstream of the bgl promoter and in genes located elsewhere on the chromosome. Mutations outside of the bgl operon occur in the genes encoding DNA gyrase and in the gene encoding the nucleoid associated protein H-NS. The mutation described here, bglJ4, has been mapped to amore » new locus at min 99 on the Escherichia coli K-12 genetic map. The putative protein encoded by the bglJ gene has homology to a family of transcriptional activators. Evidence is presented that increased expression of the bglJ product is needed for activation of the bgl operon. 56 refs., 3 figs., 3 tabs.« less

Systematic appraisal of lactose intolerance as cause of increased need for oral thyroxine.

PubMed

Cellini, Miriam; Santaguida, Maria Giulia; Gatto, Ilenia; Virili, Camilla; Del Duca, Susanna Carlotta; Brusca, Nunzia; Capriello, Silvia; Gargano, Lucilla; Centanni, Marco

2014-08-01

An increased need for T4 has been described in patients with different gastrointestinal disorders. However, there is a lack of systematic studies assessing the need for T4 in hypothyroid patients with lactose intolerance, a widespread and often occult disorder. The objective of the study was to assess the replacement T4 dose required in hypothyroid patients with lactose intolerance. This was a cohort study. The study was conducted at an outpatient endocrinology unit in a University Hospital. The replacement T4 dose has been analyzed, from 2009 to 2012, in 34 hypothyroid patients due to Hashimoto's thyroiditis and lactose intolerance and being noncompliant with a lactose-free diet. An individually tailored T4 dose was measured. In all patients with isolated Hashimoto's thyroiditis, target TSH (median TSH 1.02 mU/L) was obtained at a median T4 dose of 1.31 μg/kg/d. In patients with lactose intolerance, only five of 34 patients reached the desired TSH (median TSH 0.83 mU/L) with a similar T4 dose (1.29 μg/kg/d). In the remaining 29 patients, the T4 dose was progressively increased and the target TSH (median TSH 1.21 mU/L) was attained at a median T4 dose of 1.81 μg/kg/d (+38%, P < .0001). In six of these patients, other gastrointestinal disorders were diagnosed, and their median T4 requirement was higher (2.04 μg/kg/d; +55%; P = .0032). In the remaining 23 patients with isolated lactose intolerance, a median T4 dose of 1.72 μg/kg/d (+31% P < .0001) has been required to attain pharmacological thyroid homeostasis. These findings show that lactose intolerance significantly increased the need for oral T4 in hypothyroid patients.

Deployable structures using bistable reeled composites

NASA Astrophysics Data System (ADS)

Daton-Lovett, Andrew J.; Compton-Bishop, Quentin M.; Curry, Richard G.

2000-06-01

This paper describes an innovative, patented use of composite materials developed by RolaTube Technology Ltd. to make smart deployable structures. Bi-stable reeled composites (BRCs) can alternate between two stable forms; that of a strong, rigid structure and that of a compact coil of flat-wound material. Bi-stability arises as a result of the manipulation of Poisson's ratio and isotropy in the various layers of the material. BRCs are made of fiber- reinforced composite materials, most often with a thermoplastic matrix. A range of fibers and polymer matrices can be used according to the requirements of the operating environment. Samples of a BRC structure were constructed using layers of unidirectional, fiber-reinforced thermoplastic sheet with the layers at different angles. The whole assembly was then consolidated under conditions of elevated temperature and pressure. The properties of the BRC are described and the result of a series of experiments performed on the sample to determine the tensile strength of the BRC structure are reported. A full analysis using finite element methods is being undertaken in collaboration with the University of Cambridge, England. The first commercial use has been to fabricate boom and drive mechanisms for the remote inspection of industrial plant.

Butanol production from concentrated lactose/whey permeate: Use of pervaporation membrane to recover and concentrate product

USDA-ARS?s Scientific Manuscript database

In these studies butanol (acetone butanol ethanol, or ABE) was produced from concentrated lactose/whey permeate containing 211 gL-1 lactose. Fermentation of such a highly concentrated lactose solution was possible due to simultaneous product removal using a pervaporation membrane. In this system a p...

Optimization of an innovative hollow-fiber process to produce lactose-reduced skim milk.

PubMed

Neuhaus, Winfried; Novalin, Senad; Klimacek, Mario; Splechtna, Barbara; Petzelbauer, Inge; Szivak, Alexander; Kulbe, Klaus D

2006-07-01

The research field for applications of lactose hydrolysis has been investigated for several decades. Lactose intolerance, improvement for technical processing of solutions containing lactose, and utilization of lactose in whey are the main topics for development of biotechnological processes. We report here the optimization of a hollow-fiber membrane reactor process for enzymatic lactose hydrolysis. Lactase was circulated abluminally during luminal flow of skim milk. The main problem, the growth of microorganisms in the enzyme solution, was minimized by sterile filtration, ultraviolet irradiation, and temperature adjustment. Based on previous experiments at 23 +/- 2 degrees C, further characterization was carried out at 8 +/- 2 degrees C, 15 +/- 2 degrees C (beta-galactosidase), and 58 +/- 2 degrees C (thermostable beta-glycosidase) varying enzyme activity and flow rates. For a cost-effective process, the parameters 15 +/- 2 degrees C, 240 U/mL of beta-galactosidase, an enzyme solution flow rate of 25 L/h, and a skim milk flow rate of about 9 L/h should be used in order to achieve an aimed productivity of 360 g/(L x h) and to run at conditions for the highest process long-term stability.

Bistable dark solitons of a cubic-quintic Helmholtz equation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Christian, J. M.; McDonald, G. S.; Chamorro-Posada, P.

2010-05-15

We provide a report on exact analytical bistable dark spatial solitons of a nonlinear Helmholtz equation with a cubic-quintic refractive-index model. Our analysis begins with an investigation of the modulational instability characteristics of Helmholtz plane waves. We then derive a dark soliton by mapping the desired asymptotic form onto a uniform background field and obtain a more general solution by deploying rotational invariance laws in the laboratory frame. The geometry of the new soliton is explored in detail, and a range of new physical predictions is uncovered. Particular attention is paid to the unified phenomena of arbitrary-angle off-axis propagation andmore » nondegenerate bistability. Crucially, the corresponding solution of paraxial theory emerges in a simultaneous multiple limit. We conclude with a set of computer simulations that examine the role of Helmholtz dark solitons as robust attractors.« less

Construction of a lactose-assimilating strain of baker's yeast.

PubMed

Adam, A C; Prieto, J A; Rubio-Texeira, M; Polaina, J

1999-09-30

A recombinant strain of baker's yeast has been constructed which can assimilate lactose efficiently. This strain has been designed to allow its propagation in whey, the byproduct resulting from cheese-making. The ability to metabolize lactose is conferred by the functional expression of two genes from Kluyveromyces lactis, LAC12 and LAC4, which encode a lactose permease and a beta-galactosidase, respectively. To make the recombinant strain more acceptable for its use in bread-making, the genetic transformation of the host baker's yeast was carried out with linear fragments of DNA of defined sequence, carrying as the only heterologous material the coding regions of the two K. lactis genes. Growth of the new strain on cheese whey affected neither the quality of bread nor the yeast gassing power. The significance of the newly developed strain is two-fold: it affords a cheap alternative to the procedure generally used for the propagation of baker's yeast, and it offers a profitable use for cheese whey. Copyright 1999 John Wiley & Sons, Ltd.

Simultaneous determination of dextrose, sucrose, maltose, and lactose in sausage products by liquid chromatography.

PubMed

Ali, M S

1988-01-01

A liquid chromatographic (LC) method for the simultaneous determination of dextrose, sucrose, maltose, and lactose in sausage products has been developed. Dextrose, sucrose, maltose, and lactose are extracted from comminuted meat products with 52% ethanol. After filtration, the extracts are purified by passing them through a C18 Sep-Pak cartridge and 2 ion exchange resin Econo-columns in series. After concentration and filtration, extracts are analyzed by LC using a normal phase amino column and a differential refractometer detector. Homogeneously ground samples of cooked and fresh sausages are fortified with dextrose, sucrose, maltose, and lactose at 4 different concentrations. Average recovery for dextrose, sucrose, maltose, and lactose at all 4 levels of fortification was greater than 80% with a coefficient of variation less than 10%.

Parallel Evolution and Horizontal Gene Transfer of the pst Operon in Firmicutes from Oligotrophic Environments

PubMed Central

Moreno-Letelier, Alejandra; Olmedo, Gabriela; Eguiarte, Luis E.; Martinez-Castilla, Leon; Souza, Valeria

2011-01-01

The high affinity phosphate transport system (pst) is crucial for phosphate uptake in oligotrophic environments. Cuatro Cienegas Basin (CCB) has extremely low P levels and its endemic Bacillus are closely related to oligotrophic marine Firmicutes. Thus, we expected the pst operon of CCB to share the same evolutionary history and protein similarity to marine Firmicutes. Orthologs of the pst operon were searched in 55 genomes of Firmicutes and 13 outgroups. Phylogenetic reconstructions were performed for the pst operon and 14 concatenated housekeeping genes using maximum likelihood methods. Conserved domains and 3D structures of the phosphate-binding protein (PstS) were also analyzed. The pst operon of Firmicutes shows two highly divergent clades with no correlation to the type of habitat nor a phylogenetic congruence, suggesting horizontal gene transfer. Despite sequence divergence, the PstS protein had a similar 3D structure, which could be due to parallel evolution after horizontal gene transfer events. PMID:21461370

Lactase persistence versus lactose intolerance: Is there an intermediate phenotype?

PubMed

Dzialanski, Zbigniew; Barany, Michael; Engfeldt, Peter; Magnuson, Anders; Olsson, Lovisa A; Nilsson, Torbjörn K

2016-02-01

According to the prevailing theory about the genetic background to lactose intolerance, there are three genotypes but only two adult physiological phenotypes: lactase persistence in individuals with the CT and TT genotypes and lactase non-persistence in individuals with the CC genotype. However, analysis of lactase activity from intestinal biopsies has revealed three distinct levels of activity, suggesting that an intermediate physiological phenotype may exist. To assess possible disparities between different genotypes with regard to biomarkers of lactase activity and physical symptoms during an oral lactose load test. A retrospective study using an oral lactose load test (n=487). Concentrations of hydrogen in exhaled air and blood glucose were measured. Afterwards, subjects were asked to provide oral mucosa samples for genotyping and answer a questionnaire (participation rate 56%, n=274). Mean hydrogen levels in exhaled air at 120min were significantly higher in the CT genotype than in the TT genotype. There was no significant difference in blood glucose levels between the two groups. Reported symptoms, with the possible exception of abdominal pain, were equally prevalent in both groups. Subjects with the CT and TT genotypes, hitherto classified as lactase-persistent, differ in their physiological response to lactose intake, indicating differences in phenotype which could have clinical significance. Copyright © 2015 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.

Biohydrogen production from lactose: influence of substrate and nitrogen concentration.

PubMed

Moreno, R; Fierro, J; Fernández, C; Cuetos, M J; Gómez, X

2015-01-01

Hydrogen produced from renewable sources may be considered the energy vector of the future. However, reducing process costs is imperative in order to achieve this goal. In the present research, the effect of nitrogen (N), initial pH and substrate content for starting up the dark fermentative process was studied using the response surface methodology. Anaerobic digested dried sludge (biosolid pellets) was used as the inoculum. Synthetic wastewater was used as the substrate in batch reactors. A decrease in H2 production was observed with the increase in N and lactose concentrations. This drop was considerably greater when the concentration of lactose was at its lower level. Although the increase in lactose concentration results in a lower H2 production, the effect of N on the response is attenuated at higher levels of lactose. On the other hand, the effect of initial pH on the fermentation system was not significant. The evaluation on the process under semi-continuous conditions was performed using anaerobic sequencing batch reactors (ASBRs). The process was evaluated at different C/N ratios using synthetic wastewater. Results showed higher hydrogen yields with the gradual decrease in nitrogen content. The addition of cheese whey to the ASBR resulted in a H2 production rate of 0.18 L H2 L(-1) d(-1).

Quantifying translational coupling in E. coli synthetic operons using RBS modulation and fluorescent reporters.

PubMed

Levin-Karp, Ayelet; Barenholz, Uri; Bareia, Tasneem; Dayagi, Michal; Zelcbuch, Lior; Antonovsky, Niv; Noor, Elad; Milo, Ron

2013-06-21

Translational coupling is the interdependence of translation efficiency of neighboring genes encoded within an operon. The degree of coupling may be quantified by measuring how the translation rate of a gene is modulated by the translation rate of its upstream gene. Translational coupling was observed in prokaryotic operons several decades ago, but the quantitative range of modulation translational coupling leads to and the factors governing this modulation were only partially characterized. In this study, we systematically quantify and characterize translational coupling in E. coli synthetic operons using a library of plasmids carrying fluorescent reporter genes that are controlled by a set of different ribosome binding site (RBS) sequences. The downstream gene expression level is found to be enhanced by the upstream gene expression via translational coupling with the enhancement level varying from almost no coupling to over 10-fold depending on the upstream gene's sequence. Additionally, we find that the level of translational coupling in our system is similar between the second and third locations in the operon. The coupling depends on the distance between the stop codon of the upstream gene and the start codon of the downstream gene. This study is the first to systematically and quantitatively characterize translational coupling in a synthetic E. coli operon. Our analysis will be useful in accurate manipulation of gene expression in synthetic biology and serves as a step toward understanding the mechanisms involved in translational expression modulation.

Lactose metabolism by Streptococcus mutans: evidence for induction of the tagatose 6-phosphate pathway.

PubMed Central

Hamilton, I R; Lebtag, H

1979-01-01

Growth on lactose by strains of Streptococcus mutans resulted in the induction of the lactose-phosphoenolpyruvate-phosphotransferase system, phospho-beta-galactosidase, and the enzymes of the tagatose 6-phosphate pathway. PMID:230175

Lactose-modified DNA tile nanostructures as drug carriers.

PubMed

Akkus Sut, Pinar; Tunc, Cansu Umran; Culha, Mustafa

2016-09-01

DNA hybridization allows the preparation of nanoscale DNA structures with desired shape and size. DNA structures using simple base pairing can be used for the delivery of drug molecules into the cells. Since DNA carries multiple negative charges, their cellular uptake efficiency is low. Thus, the modification of the DNA structures with molecules that may enhance the cellular internalization may be an option. The objective of this study is to construct DNA-based nanocarrier system and to investigate the cellular uptake of DNA tile with/without lactose modification. Doxorubicin was intercalated to DNA tile and cellular uptake of drug-loaded DNA-based carrier with/without lactose modification was investigated in vitro. HeLa, BT-474, and MDA-MB-231 cancer cells were used for cellular uptake studies and cytotoxicity assays. Using fluorescence spectroscopy, flow cytometry, and confocal microscopy, cellular uptake behavior of DNA tile was investigated. The cytotoxicity of DNA tile structures was determined with WST-1 assay. The results show that modification with lactose effectively increases the intracellular uptake of doxorubicin loaded DNA tile structure by cancer cells compared with the unmodified DNA tile. The findings of this study suggest that DNA-based nanostructures modified with carbohydrates can be used as suitable multifunctional nanocarriers with simple chemical modifications.

Chromosomal Organization of Rrna Operons in Bacillus Subtilis

PubMed Central

Jarvis, E. D.; Widom, R. L.; LaFauci, G.; Setoguchi, Y.; Richter, I. R.; Rudner, R.

1988-01-01

Integrative mapping with vectors containing ribosomal DNA sequences were used to complete the mapping of the 10 rRNA gene sets in the endospore forming bacterium Bacillus subtilis. Southern hybridizations allowed the assignment of nine operons to distinct BclI restriction fragments and their genetic locus identified by transductional crosses. Nine of the ten rRNA gene sets are located between 0 and 70° on the genomic map. In the region surrounding cysA14, two sets of closely spaced tandem clusters are present. The first (rrnJ and rrnW) is located between purA16 and cysA14 closely linked to the latter; the second (rrnI, rrnH and rrnG) previously mapped within this area is located between attSPO2 and glpT6. The operons at or near the origin of replication (rrnO,rrnA and rrnJ,rrnW) represent ``hot spots'' of plasmid insertion. PMID:2465199

A quantitative study of the benefits of co-regulation using the spoIIA operon as an example

PubMed Central

Iber, Dagmar

2006-01-01

The distribution of most genes is not random, and functionally linked genes are often found in clusters. Several theories have been put forward to explain the emergence and persistence of operons in bacteria. Careful analysis of genomic data favours the co-regulation model, where gene organization into operons is driven by the benefits of coordinated gene expression and regulation. Direct evidence that coexpression increases the individual's fitness enough to ensure operon formation and maintenance is, however, still lacking. Here, a previously described quantitative model of the network that controls the transcription factor σF during sporulation in Bacillus subtilis is employed to quantify the benefits arising from both organization of the sporulation genes into the spoIIA operon and from translational coupling. The analysis shows that operon organization, together with translational coupling, is important because of the inherent stochastic nature of gene expression, which skews the ratios between protein concentrations in the absence of co-regulation. The predicted impact of different forms of gene regulation on fitness and survival agrees quantitatively with published sporulation efficiencies. PMID:16924264

A quantitative study of the benefits of co-regulation using the spoIIA operon as an example.

PubMed

Iber, Dagmar

2006-01-01

The distribution of most genes is not random, and functionally linked genes are often found in clusters. Several theories have been put forward to explain the emergence and persistence of operons in bacteria. Careful analysis of genomic data favours the co-regulation model, where gene organization into operons is driven by the benefits of coordinated gene expression and regulation. Direct evidence that coexpression increases the individual's fitness enough to ensure operon formation and maintenance is, however, still lacking. Here, a previously described quantitative model of the network that controls the transcription factor sigma(F) during sporulation in Bacillus subtilis is employed to quantify the benefits arising from both organization of the sporulation genes into the spoIIA operon and from translational coupling. The analysis shows that operon organization, together with translational coupling, is important because of the inherent stochastic nature of gene expression, which skews the ratios between protein concentrations in the absence of co-regulation. The predicted impact of different forms of gene regulation on fitness and survival agrees quantitatively with published sporulation efficiencies.

Lactose-fermenting, multiple drug-resistant Salmonella typhi strains isolated from a patient with postoperative typhoid fever.

PubMed Central

Kohbata, S; Takahashi, M; Yabuuchi, E

1983-01-01

Two lactose-fermenting Salmonella typhi strains were isolated from bile and blood specimens of a typhoid fever patient who underwent a cholecystectomy due to cholelithiasis. One lactose-fermenting S. typhi strain was also isolated from a pus specimen which was obtained at the tip of the T-shaped tube withdrawn from the operative wound of the common bile duct of the patient. These three lactose-fermenting isolates: GIFU 11924 from bile, GIFU 11926 from pus, and GIFU 11927 from blood, were phenotypically identical to the type strain (GIFU 11801 = ATCC 19430 = NCTC 8385) of S. typhi, except that the three strains fermented lactose and failed to blacken the butt of Kligler iron agar or triple sugar iron agar medium. All three lactose-fermenting strains were resistant to chloramphenicol, ampicillin, sulfomethoxazole, trimethoprim, gentamicin, cephaloridine, and four other antimicrobial agents. The type strain was uniformly susceptible to these 10 drugs. The strain GIFU 11925, a lactose-negative dissociant from strain GIFU 11926, was also susceptible to these drugs, with the sole exception of chloramphenicol (minimal inhibitory concentration, 100 micrograms/ml). PMID:6630471

Comparison of the overlapping frd and ampC operons of Escherichia coli with the corresponding DNA sequences in other gram-negative bacteria.

PubMed

Bergström, S; Lindberg, F P; Olsson, O; Normark, S

1983-09-01

Specific DNA probes from Escherichia coli K-12 were used to analyze the sequence divergence of the frd and ampC operons in various species of gram-negative bacteria. These operons code for the fumarate reductase complex and the chromosomal beta-lactamase, respectively. We demonstrate that the two operons show the same general pattern of divergence, although the frd operon is considerably more conserved than is the ampC operon. The major exception is Salmonella typhimurium LT2, which shows a strong homology to the E. coli frd probe but none to the E. coli ampC probe. The operons from Citrobacter freundii and Shigella sonnei were cloned and characterized by physical mapping, Southern hybridization, and protein synthesis in minicells. In S. sonnei, as in E. coli K-12, the frd and ampC operons overlap (T. Grundström and B. Jaurin, Proc. Natl. Acad. Sci. U.S.A. 79:1111-1115, 1982). Only minor discrepancies between the two operons were found over the entire frd-ampC region. In C. freundii, the ampC and frd operons do not overlap, being separated by about 1,100 base pairs. Presumably the inducible property of the C. freundii chromosomal beta-lactamase is encoded by this 1,100-base-pair DNA segment.

Review of inductively coupled plasmas: Nano-applications and bistable hysteresis physics

NASA Astrophysics Data System (ADS)

Lee, Hyo-Chang

2018-03-01

Many different gas discharges and plasmas exhibit bistable states under a given set of conditions, and the history-dependent hysteresis that is manifested by intensive quantities of the system upon variation of an external parameter has been observed in inductively coupled plasmas (ICPs). When the external parameters (such as discharge powers) increase, the plasma density increases suddenly from a low- to high-density mode, whereas decreasing the power maintains the plasma in a relatively high-density mode, resulting in significant hysteresis. To date, a comprehensive description of plasma hysteresis and a physical understanding of the main mechanism underlying their bistability remain elusive, despite many experimental observations of plasma bistability conducted under radio-frequency ICP excitation. This fundamental understanding of mode transitions and hysteresis is essential and highly important in various applied fields owing to the widespread use of ICPs, such as semiconductor/display/solar-cell processing (etching, deposition, and ashing), wireless light lamp, nanostructure fabrication, nuclear-fusion operation, spacecraft propulsion, gas reformation, and the removal of hazardous gases and materials. If, in such applications, plasma undergoes a mode transition and hysteresis occurs in response to external perturbations, the process result will be strongly affected. Due to these reasons, this paper comprehensively reviews both the current knowledge in the context of the various applied fields and the global understanding of the bistability and hysteresis physics in the ICPs. At first, the basic understanding of the ICP is given. After that, applications of ICPs to various applied fields of nano/environmental/energy-science are introduced. Finally, the mode transition and hysteresis in ICPs are studied in detail. This study will show the fundamental understanding of hysteresis physics in plasmas and give open possibilities for applications to various applied

Genetic parameters for lactose and its correlation with other milk production traits and fitness traits in pasture-based production systems.

PubMed

Haile-Mariam, M; Pryce, J E

2017-05-01

Lactose is a major component of milk (typically around 5% of composition) that is not usually directly considered in national genetic improvement programs of dairy cattle. Daily test-day lactose yields and percentage data from pasture-based seasonal calving herds in Australia were analyzed to assess if lactose content can be used for predicting fitness traits and if an additional benefit is achieved by including lactose yield in selecting for milk yield traits. Data on lactose percentage collected from 2007 to 2014, from about 600 herds, were used to estimated genetic parameters for lactose percentage and lactose yield and correlations with other milk yield traits, somatic cell count (SCC), calving interval (CIV), and survival. Daily test-day data were analyzed using bivariate random regression models. In addition, multi-trait models were also performed mainly to assess the value of lactose to predict fitness traits. The heritability of lactose percentage (0.25 to 0.37) was higher than lactose yield (0.11 to 0.20) in the first parity. Genetically, the correlation of lactose percentage with protein percentage varied from 0.3 at the beginning of lactation to -0.24 at the end of the lactation in the first parity. Similar patterns in genetic correlations were also observed in the second and third parity. At all levels (i.e., genetic, permanent environmental, and residual), the correlation between milk yield and lactose yield was close to 1. The genetic and permanent environmental correlations between lactose percentage and SCC were stronger in the second and third parity and toward the end of the lactation (-0.35 to -0.50) when SCC levels are at their maximum. The genetic correlation between lactose percentage in the first 120 d and CIV (-0.23) was similar to correlation of CIV with protein percentage (-0.28), another component trait with the potential to predict fertility. Furthermore, the correlations of estimated breeding values of lactose percentage and estimated

Random-order fractional bistable system and its stochastic resonance

NASA Astrophysics Data System (ADS)

Gao, Shilong; Zhang, Li; Liu, Hui; Kan, Bixia

2017-01-01

In this paper, the diffusion motion of Brownian particles in a viscous liquid suffering from stochastic fluctuations of the external environment is modeled as a random-order fractional bistable equation, and as a typical nonlinear dynamic behavior, the stochastic resonance phenomena in this system are investigated. At first, the derivation process of the random-order fractional bistable system is given. In particular, the random-power-law memory is deeply discussed to obtain the physical interpretation of the random-order fractional derivative. Secondly, the stochastic resonance evoked by random-order and external periodic force is mainly studied by numerical simulation. In particular, the frequency shifting phenomena of the periodical output are observed in SR induced by the excitation of the random order. Finally, the stochastic resonance of the system under the double stochastic excitations of the random order and the internal color noise is also investigated.

Harnessing bistability for directional propulsion of soft, untethered robots.

PubMed

Chen, Tian; Bilal, Osama R; Shea, Kristina; Daraio, Chiara

2018-05-29

In most macroscale robotic systems, propulsion and controls are enabled through a physical tether or complex onboard electronics and batteries. A tether simplifies the design process but limits the range of motion of the robot, while onboard controls and power supplies are heavy and complicate the design process. Here, we present a simple design principle for an untethered, soft swimming robot with preprogrammed, directional propulsion without a battery or onboard electronics. Locomotion is achieved by using actuators that harness the large displacements of bistable elements triggered by surrounding temperature changes. Powered by shape memory polymer (SMP) muscles, the bistable elements in turn actuate the robot's fins. Our robots are fabricated using a commercially available 3D printer in a single print. As a proof of concept, we show the ability to program a vessel, which can autonomously deliver a cargo and navigate back to the deployment point.

Shape memory alloy-actuated bistable composites for morphing structures

NASA Astrophysics Data System (ADS)

Chillara, Venkata Siva C.; Dapino, Marcelo J.

2018-03-01

Laminated composites with orthogonally-applied mechanical prestress have been shown to exhibit two stable shapes where each shape is influenced by only one prestrained lamina. The application of mechanical prestress is associated with an irreversible non-zero stress state; when combined with smart materials with controllable stress-states, this results in multifunctionality in morphing composites. This study presents an experimental characterization of the shape transition or snap-through in mechanically-prestressed bistable laminates. Measurements, conducted using tensile testing and 3D motion capture, show that snap-through in these laminates is a multi-stage phenomenon. An active bistable morphing composite is demonstrated using NiTi shape memory wire actuators in push-pull configuration; activation of one wire resets the second wire as the composite morphs. The set of shape memory actuators not only actuate the composite in both directions, but also act as dampers that enable vibration-free shape transition.

Dispersive bi-stability in a vertical microcavity-based saturable absorber due to photo-thermal effect and initial phase-detuning

NASA Astrophysics Data System (ADS)

Pradhan, R.; Saha, S.; Datta, P. K.

2013-01-01

Round-trip phase-shifts with intensity of an input signal due to saturable index change and optically induced thermal effects in a vertical cavity semiconductor (quantum wells) saturable absorber (VCSSA) are investigated analytically to observe counter-clockwise bi-stability in transmission mode and clockwise bi-stability in reflection mode. Simultaneous effects of Kerr nonlinearity and cavity heating on resonance wavelength-shift of the VCSSA micro-cavity are investigated. It is found that these bi-stable characteristics are possible to the absorption edge of nonlinear material for long wavelength side operations of low intensity resonance wavelength of the micro-cavity, where dispersion of absorption and refraction are neglected over a small range of optical wavelength tuning (δλ˜10 nm). Simulations are carried out to find out optimized parameters of the device for bi-stable characteristics. Operations are demonstrated for InGaAs/InP quantum wells based VCSSA with low intensity resonance wavelength of 1570 nm. For counter-clockwise bi-stable switching at working wavelength of 1581 nm, an input intensity variation of 0.79IS is required with top (Rt) and back DBR reflectivity (Rb) of 91% and 93%, respectively, where IS represents the absorption saturation intensity of nonlinear medium. Whereas, the clockwise bi-stability occurs at 0.22IS for working wavelength of 1578 nm with Rt of 90% and Rb of 98%, respectively.

Additional Value of CH4 Measurement in a Combined 13C/H2 Lactose Malabsorption Breath Test: A Retrospective Analysis

PubMed Central

Houben, Els; De Preter, Vicky; Billen, Jaak; Van Ranst, Marc; Verbeke, Kristin

2015-01-01

The lactose hydrogen breath test is a commonly used, non-invasive method for the detection of lactose malabsorption and is based on an abnormal increase in breath hydrogen (H2) excretion after an oral dose of lactose. We use a combined 13C/H2 lactose breath test that measures breath 13CO2 as a measure of lactose digestion in addition to H2 and that has a better sensitivity and specificity than the standard test. The present retrospective study evaluated the results of 1051 13C/H2 lactose breath tests to assess the impact on the diagnostic accuracy of measuring breath CH4 in addition to H2 and 13CO2. Based on the 13C/H2 breath test, 314 patients were diagnosed with lactase deficiency, 138 with lactose malabsorption or small bowel bacterial overgrowth (SIBO), and 599 with normal lactose digestion. Additional measurement of CH4 further improved the accuracy of the test as 16% subjects with normal lactose digestion and no H2-excretion were found to excrete CH4. These subjects should have been classified as subjects with lactose malabsorption or SIBO. In conclusion, measuring CH4-concentrations has an added value to the 13C/H2 breath test to identify methanogenic subjects with lactose malabsorption or SIBO. PMID:26371034

Transcriptional and posttranscriptional regulation of Bacillus sp. CDB3 arsenic-resistance operon ars1

PubMed Central

Yu, Xuefei; Zheng, Wei; Bhat, Somanath; Aquilina, J. Andrew

2015-01-01

Bacillus sp. CDB3 possesses a novel eight-gene ars cluster (ars1, arsRYCDATorf7orf8) with some unusual features in regard to expression regulation. This study demonstrated that the cluster is a single operon but can also produce a short three-gene arsRYC transcript. A hairpin structure formed by internal inverted repeats between arsC and arsD was shown to diminish the expression of the full operon, thereby probably acting as a transcription attenuator. A degradation product of the arsRYC transcript was also identified. Electrophoretic mobility shift analysis demonstrated that ArsR interacts with the ars1 promoter forming a protein-DNA complex that could be impaired by arsenite. However, no interaction was detected between ArsD and the ars1 promoter, suggesting that the CDB3 ArsD protein may not play a regulatory role. Compared to other ars gene clusters, regulation of the Bacillus sp. CDB3 ars1 operon is more complex. It represents another example of specific mRNA degradation in the transporter gene region and possibly the first case of attenuator-mediated regulation of ars operons. PMID:26355338

Stochastic sensitivity of a bistable energy model for visual perception

NASA Astrophysics Data System (ADS)

Pisarchik, Alexander N.; Bashkirtseva, Irina; Ryashko, Lev

2017-01-01

Modern trends in physiology, psychology and cognitive neuroscience suggest that noise is an essential component of brain functionality and self-organization. With adequate noise the brain as a complex dynamical system can easily access different ordered states and improve signal detection for decision-making by preventing deadlocks. Using a stochastic sensitivity function approach, we analyze how sensitive equilibrium points are to Gaussian noise in a bistable energy model often used for qualitative description of visual perception. The probability distribution of noise-induced transitions between two coexisting percepts is calculated at different noise intensity and system stability. Stochastic squeezing of the hysteresis range and its transition from positive (bistable regime) to negative (intermittency regime) are demonstrated as the noise intensity increases. The hysteresis is more sensitive to noise in the system with higher stability.

Phase-locking and bistability in neuronal networks with synaptic depression

NASA Astrophysics Data System (ADS)

Akcay, Zeynep; Huang, Xinxian; Nadim, Farzan; Bose, Amitabha

2018-02-01

We consider a recurrent network of two oscillatory neurons that are coupled with inhibitory synapses. We use the phase response curves of the neurons and the properties of short-term synaptic depression to define Poincaré maps for the activity of the network. The fixed points of these maps correspond to phase-locked modes of the network. Using these maps, we analyze the conditions that allow short-term synaptic depression to lead to the existence of bistable phase-locked, periodic solutions. We show that bistability arises when either the phase response curve of the neuron or the short-term depression profile changes steeply enough. The results apply to any Type I oscillator and we illustrate our findings using the Quadratic Integrate-and-Fire and Morris-Lecar neuron models.

Novel high-performance metagenome β-galactosidases for lactose hydrolysis in the dairy industry.

PubMed

Erich, Sarah; Kuschel, Beatrice; Schwarz, Thilo; Ewert, Jacob; Böhmer, Nico; Niehaus, Frank; Eck, Jürgen; Lutz-Wahl, Sabine; Stressler, Timo; Fischer, Lutz

2015-09-20

The industrially utilised β-galactosidases from Kluyveromyces spp. and Aspergillus spp. feature undesirable kinetic properties in praxis, such as an unsatisfactory lactose affinity (KM) and product inhibition (KI) by galactose. In this study, a metagenome library of about 1.3 million clones was investigated with a three-step activity-based screening strategy in order to find new β-galactosidases with more favourable kinetic properties. Six novel metagenome β-galactosidases (M1-M6) were found with an improved lactose hydrolysis performance in original milk when directly compared to the commercial β-galactosidase from Kluyveromyces lactis (GODO-YNL2). The best metagenome candidate, called "M1", was recombinantly produced in Escherichia coli BL21(DE3) in a bioreactor (volume 35 L), resulting in a total β-galactosidase M1 activity of about 1100 μkatoNPGal,37 °C L(-1). Since milk is a sensitive and complex medium, it has to be processed at 5-10 °C in the dairy industry. Therefore, the β-galactosidase M1 was tested at 8 °C in milk and possessed a good stability (t1/2=21.8 d), a desirably low apparent KM,lactose,8 °C value of 3.8±0.7 mM and a high apparent KI,galactose,8 °C value of 196.6±55.5 mM. A lactose hydrolysis process (milk, 40 nkatlactose mLmilk,8 °C(-1)) was conducted at a scale of 0.5L to compare the performance of M1 with the commercial β-galactosidase from K. lactis (GODO-YNL2). Lactose was completely (>99.99%) hydrolysed by M1 and to 99.6% (w/v) by K. lactis β-galactosidase after 25 h process time. Thus, M1 was able to achieve the limit of <100 mg lactose per litre milk, which is recommended for dairy products labelled as "lactose-free". Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Lactose/whey utilization and ethanol production by transformed Saccharomyces cerevisiae cells.

PubMed

Porro, D; Martegani, E; Ranzi, B M; Alberghina, L

1992-04-05

Strains of Saccharomyces cerevisiae transformed with a multicopy expression vector bearing both the Escherichia coli beta-galactosidase gene under the control of the upstream activating sequence of the GAL1-10 genes and the GAL4 activator gene release part of beta-galactosidase in the growth medium. This release is due to cell lysis of the older mother cells; the enzyme maintains its activity in buffered growth media. Fermentation studies with transformed yeast strains showed that the release of beta-galactosidase allowed an efficient growth on buffered media containing lactose as carbon source as well as on whey-based media. The transformed strains utilized up to 95% of the lactose and a high growth yield was obtained in rich media. High productions of ethanol were also observed in stationary phase after growth in lactose minimal media.

Room temperature operation of electro-optical bistability in the edge-emitting tunneling-collector transistor laser

NASA Astrophysics Data System (ADS)

Feng, M.; Holonyak, N.; Wang, C. Y.

2017-09-01

Optical bistable devices are fundamental to digital photonics as building blocks of switches, logic gates, and memories in future computer systems. Here, we demonstrate both optical and electrical bistability and capability for switching in a single transistor operated at room temperature. The electro-optical hysteresis is explained by the interaction of electron-hole (e-h) generation and recombination dynamics with the cavity photon modulation in different switching paths. The switch-UP and switch-DOWN threshold voltages are determined by the rate difference of photon generation at the base quantum-well and the photon absorption via intra-cavity photon-assisted tunneling controlled by the collector voltage. Thus, the transistor laser electro-optical bistable switching is programmable with base current and collector voltage, and the basis for high speed optical logic processors.

Maximizing direct current power delivery from bistable vibration energy harvesting beams subjected to realistic base excitations

NASA Astrophysics Data System (ADS)

Dai, Quanqi; Harne, Ryan L.

2017-04-01

Effective development of vibration energy harvesters is required to convert ambient kinetic energy into useful electrical energy as power supply for sensors, for example in structural health monitoring applications. Energy harvesting structures exhibiting bistable nonlinearities have previously been shown to generate large alternating current (AC) power when excited so as to undergo snap-through responses between stable equilibria. Yet, most microelectronics in sensors require rectified voltages and hence direct current (DC) power. While researchers have studied DC power generation from bistable energy harvesters subjected to harmonic excitations, there remain important questions as to the promise of such harvester platforms when the excitations are more realistic and include both harmonic and random components. To close this knowledge gap, this research computationally and experimentally studies the DC power delivery from bistable energy harvesters subjected to such realistic excitation combinations as those found in practice. Based on the results, it is found that the ability for bistable energy harvesters to generate peak DC power is significantly reduced by introducing sufficient amount of stochastic excitations into an otherwise harmonic input. On the other hand, the elimination of a low amplitude, coexistent response regime by way of the additive noise promotes power delivery if the device was not originally excited to snap-through. The outcomes of this research indicate the necessity for comprehensive studies about the sensitivities of DC power generation from bistable energy harvester to practical excitation scenarios prior to their optimal deployment in applications.

Discrete dynamical laser equation for the critical onset of bistability, entanglement and disappearance

NASA Astrophysics Data System (ADS)

Abdul, M.; Farooq, U.; Akbar, Jehan; Saif, F.

2018-06-01

We transform the semi-classical laser equation for single mode homogeneously broadened lasers to a one-dimensional nonlinear map by using the discrete dynamical approach. The obtained mapping, referred to as laser logistic mapping (LLM), characteristically exhibits convergent, cyclic and chaotic behavior depending on the control parameter. Thus, the so obtained LLM explains stable, bistable, multi-stable, and chaotic solutions for output field intensity. The onset of bistability takes place at a critical value of the effective gain coefficient. The obtained analytical results are confirmed through numerical calculations.

The complete nucleotide sequence of the glnALG operon of Escherichia coli K12.

PubMed Central

Miranda-Ríos, J; Sánchez-Pescador, R; Urdea, M; Covarrubias, A A

1987-01-01

The nucleotide sequence of the E. coli glnALG operon has been determined. The glnL (ntrB) and glnG (ntrC) genes present a high homology, at the nucleotide and aminoacid levels, with the corresponding genes of Klebsiella pneumoniae. The predicted aminoacid sequence for glutamine synthetase allowed us to locate some of the enzyme domains. The structure of this operon is discussed. PMID:2882477

Identification of a Dehydrogenase Required for Lactose Metabolism in Caulobacter crescentus▿ †‡

PubMed Central

Arellano, Benjamin H.; Ortiz, Janett D.; Manzano, Janet; Chen, Joseph C.

2010-01-01

Caulobacter crescentus, which thrives in freshwater environments with low nutrient levels, serves as a model system for studying bacterial cell cycle regulation and organelle development. We examined its ability to utilize lactose (i) to gain insight into the metabolic capacities of oligotrophic bacteria and (ii) to obtain an additional genetic tool for studying this model organism, aiming to eliminate the basal enzymatic activity that hydrolyzes the chromogenic substrate 5-bromo-4-chloro-3-indolyl-β-d-galactopyranoside (X-gal). Using a previously isolated transposon mutant, we identified a gene, lacA, that is required for growth on lactose as the sole carbon source and for turning colonies blue in the presence of X-gal. LacA, which contains a glucose-methanol-choline (GMC) oxidoreductase domain, has homology to the flavin subunit of Pectobacterium cypripedii's gluconate dehydrogenase. Sequence comparisons indicated that two genes near lacA, lacB and lacC, encode the other subunits of the membrane-bound dehydrogenase. In addition to lactose, all three lac genes are involved in the catabolism of three other β-galactosides (lactulose, lactitol, and methyl-β-d-galactoside) and two glucosides (salicin and trehalose). Dehydrogenase assays confirmed that the lac gene products oxidize lactose, salicin, and trehalose. This enzymatic activity is inducible, and increased lac expression in the presence of lactose and salicin likely contributes to the induction. Expression of lacA also depends on the presence of the lac genes, implying that the dehydrogenase participates in induction. The involvement of a dehydrogenase suggests that degradation of lactose and other sugars in C. crescentus may resemble a proposed pathway in Agrobacterium tumefaciens. PMID:20190087

Lactococcus lactis expressing food-grade β-galactosidase alleviates lactose intolerance symptoms in post-weaning Balb/c mice.

PubMed

Li, Jingjie; Zhang, Wen; Wang, Chuan; Yu, Qian; Dai, Ruirui; Pei, Xiaofang

2012-12-01

The endogenous β-galactosidase expressed in intestinal microbes is demonstrated to help humans in lactose usage, and treatment associated with the promotion of beneficial microorganism in the gut is correlated with lactose tolerance. From this point, a kind of recombinant live β-galactosidase delivery system using food-grade protein expression techniques and selected probiotics as vehicle was promoted by us for the purpose of application in lactose intolerance subjects. Previously, a recombinant Lactococcus lactis MG1363 strain expressing food-grade β-galactosidase, the L. lactis MG1363/FGZW, was successfully constructed and evaluated in vitro. This study was conducted to in vivo evaluate its efficacy on alleviating lactose intolerance symptoms in post-weaning Balb/c mice, which were orally administered with 1 × 10⁶ CFU or 1 × 10⁸ CFU of L. lactis MG1363/FGZW daily for 4 weeks before lactose challenge. In comparison with naïve mice, the mice administered with L. lactis MG1363/FGZW showed significant alleviation of diarrhea symptoms in less total feces weight within 6 h post-challenge and suppressed intestinal motility after lactose challenge, although there was no significant increase of β-galactosidase activity in small intestine. The alleviation also correlated with higher species abundance, more Bifidobacterium colonization, and stronger colonization resistance in mice intestinal microflora. Therefore, this recombinant L. lactis strain effectively alleviated diarrhea symptom induced by lactose uptake in lactose intolerance model mice with the probable mechanism of promotion of lactic acid bacteria to differentiate and predominantly colonize in gut microbial community, thus making it a promising probiotic for lactose intolerance subjects.

Insertional Mutations in the Hydrogenase vhc and frc Operons Encoding Selenium-Free Hydrogenases in Methanococcus voltae

PubMed Central

Berghofer, Y.; Klein, A.

1995-01-01

Methanococcus voltae, which contains four different gene groups that encode [NiFe]-hydrogenases, was transformed with integration vectors to achieve polar inactivation of two of the four hydrogenase operons that encode the selenium-free enzymes Vhc and Frc. Transformants which were selected by their acquired puromycin resistance showed site-specific insertions in either the vhc or frc operon by single crossover events. Southern hybridization revealed tandem integrations of whole vectors in the vhc operon, whereas only one vector copy was found in the frc operon. Northern (RNA) hybridizations showed a pac transcript of defined size, indicating strong termination in front of the hydrogenase genes downstream. In spite of the apparent abolition of expression of selenium-free hydrogenases through these polar insertions, they were not lethal to cells upon growth in selenium-deprived minimal medium, which we had previously shown to strongly induce transcription of the respective operons in M. voltae. Instead, like wild-type control cultures, transformants responded to selenium deprivation only with a reduction in growth rate. We conclude that loss of the potential to express a selenium-free hydrogenase can nevertheless be balanced by very small amounts of selenium hydrogenases under laboratory conditions in which the hydrogen supply is not likely to be a limiting growth factor. PMID:16535019

Basins of attraction of the bistable region of time-delayed cutting dynamics

NASA Astrophysics Data System (ADS)

Yan, Yao; Xu, Jian; Wiercigroch, Marian

2017-09-01

This paper investigates the effects of bistability in a nonsmooth time-delayed dynamical system, which is often manifested in science and engineering. Previous studies on cutting dynamics have demonstrated persistent coexistence of chatter and chatter-free responses in a bistable region located in the linearly stable zone. As there is no widely accepted definition of basins of attraction for time-delayed systems, bistable regions are coined as unsafe zones (UZs). Hence, we have attempted to define the basins of attraction and stability basins for a typical delayed system to get insight into the bistability in systems with time delays. Special attention was paid to the influences of delayed initial conditions, starting points, and states at time zero on the long-term dynamics of time-delayed systems. By using this concept, it has been confirmed that the chatter is prone to occur when the waviness frequency in the workpiece surface coincides with the effective natural frequency of the cutting process. Further investigations unveil a thin "boundary layer" inside the UZ in the immediate vicinity of the stability boundary, in which we observe an extremely fast growth of the chatter basin stability. The results reveal that the system is more stable when the initial cutting depth is smaller. The physics of the tool deflection at the instant of the tool-workpiece engagement is used to evaluate the cutting safety, and the safe level could be zero when the geometry of tool engagement is unfavorable. Finally, the basins of attraction are used to quench the chatter by a single strike, where the resultant "islands" offer an opportunity to suppress the chatter even when the cutting is very close to the stability boundary.

Stability of sugar solutions: a novel study of the epimerization kinetics of lactose in water.

PubMed

Jawad, Rim; Drake, Alex F; Elleman, Carole; Martin, Gary P; Warren, Frederick J; Perston, Benjamin B; Ellis, Peter R; Hassoun, Mireille A; Royall, Paul G

2014-07-07

This article reports on the stereochemical aspects of the chemical stability of lactose solutions stored between 25 and 60 °C. The lactose used for the preparation of the aqueous solutions was α-lactose monohydrate with an anomer purity of 96% α and 4% β based on the supplied certificate of analysis (using a GC analytical protocol), which was further confirmed here by nuclear magnetic resonance (NMR) analysis. Aliquots of lactose solutions were collected at different time points after the solutions were prepared and freeze-dried to remove water and halt epimerization for subsequent analysis by NMR. Epimerization was also monitored by polarimetry and infrared spectroscopy using a specially adapted Fourier transform infrared attenuated total reflectance (FTIR-ATR) method. Hydrolysis was analyzed by ion chromatography. The three different analytical approaches unambiguously showed that the epimerization of lactose in aqueous solution follows first order reversible kinetics between 25 to 60 °C. The overall rate constant was 4.4 × 10(-4) s(-1) ± 0.9 (± standard deviation (SD)) at 25 °C. The forward rate constant was 1.6 times greater than the reverse rate constant, leading to an equilibrium constant of 1.6 ± 0.1 (±SD) at 25 °C. The rate of epimerization for lactose increased with temperature and an Arrhenius plot yielded an activation energy of +52.3 kJ/mol supporting the hypothesis that the mechanism of lactose epimerization involves the formation of extremely short-lived intermediate structures. The main mechanism affecting lactose stability is epimerization, as no permanent hydrolysis or chemical degradation was observed. When preparing aqueous solutions of lactose, immediate storage in an ice bath at 0 °C will allow approximately 3 min (180 s) of analysis time before the anomeric ratio alters significantly (greater than 1%) from the solid state composition of the starting material. In contrast a controlled anomeric composition (~38% α and ~62% β) will

Cloning and Molecular Analysis of a Mannitol Operon of Phosphoenolpyruvate-dependent Phosphotransferase (PTS) type From Vibrio cholerae O395

PubMed Central

Kumar, Sanath; Smith, Kenneth P.; Floyd, Jody L.; Varela, Manuel F.

2010-01-01

A putative mannitol operon of the phosphoenolpyruvate phosphotransferase (PTS) type was cloned from Vibrio cholerae O395 and its activity studied in Escherichia coli. The 3.9 kb operon comprising of three genes is organized as mtlADR. Based on the sequence analysis, these were identified as genes encoding a putative mannitol-specific enzyme IICBA (EIIMtl) component (MtlA), a mannitol-1-phosphate dehydrogenase (MtlD) and a mannitol operon repressor (MtlR). The transport of [3H]mannitol by the cloned mannitol operon in E. coli was 13.8±1.4 nmol/min/mg protein. The insertional inactivation of EIIMtl abolished mannitol and sorbitol transport in V. cholerae O395. Comparison of the mannitol utilization apparatus of V. cholerae with those of Gram-negative and Gram positive bacteria suggests highly conserved nature of the system. MtlA and MtlD exhibit 75% similarity with corresponding sequences of E. coli mannitol operon genes, while MtlR has 63% similarity with MtlR of E. coli. The cloning of V. cholerae mannitol utilization system in an E. coli background will help in elucidating the functional properties of this operon. PMID:21184218

Klebsiella pneumoniae yfiRNB operon affects biofilm formation, polysaccharide production and drug susceptibility.

PubMed

Huertas, Mónica G; Zárate, Lina; Acosta, Iván C; Posada, Leonardo; Cruz, Diana P; Lozano, Marcela; Zambrano, María M

2014-12-01

Klebsiella pneumoniae is an opportunistic pathogen important in hospital-acquired infections, which are complicated by the rise of drug-resistant strains and the capacity of cells to adhere to surfaces and form biofilms. In this work, we carried out an analysis of the genes in the K. pneumoniae yfiRNB operon, previously implicated in biofilm formation. The results indicated that in addition to the previously reported effect on type 3 fimbriae expression, this operon also affected biofilm formation due to changes in cellulose as part of the extracellular matrix. Deletion of yfiR resulted in enhanced biofilm formation and an altered colony phenotype indicative of cellulose overproduction when grown on solid indicator media. Extraction of polysaccharides and treatment with cellulase were consistent with the presence of cellulose in biofilms. The enhanced cellulose production did not, however, correlate with virulence as assessed using a Caenorhabditis elegans assay. In addition, cells bearing mutations in genes of the yfiRNB operon varied with respect to the WT control in terms of susceptibility to the antibiotics amikacin, ciprofloxacin, imipenem and meropenem. These results indicated that the yfiRNB operon is implicated in the production of exopolysaccharides that alter cell surface characteristics and the capacity to form biofilms--a phenotype that does not necessarily correlate with properties related with survival, such as resistance to antibiotics. © 2014 The Authors.

Extrachromosomal Nucleolus-Like Compartmentalization by a Plasmid-Borne Ribosomal RNA Operon and Its Role in Nucleoid Compaction.

PubMed

Mata Martin, Carmen; Sun, Zhe; Zhou, Yan Ning; Jin, Ding Jun

2018-01-01

In the fast-growing Escherichia coli cells, RNA polymerase (RNAP) molecules are concentrated and form foci at clusters of ribosomal RNA (rRNA) operons resembling eukaryotic nucleolus. The bacterial nucleolus-like organization, spatially compartmentalized at the surface of the compact bacterial chromosome (nucleoid), serves as transcription factories for rRNA synthesis and ribosome biogenesis, which influences the organization of the nucleoid. Unlike wild type that has seven rRNA operons in the genome in a mutant that has six (Δ6 rrn ) rRNA operons deleted in the genome, there are no apparent transcription foci and the nucleoid becomes uncompacted, indicating that formation of RNAP foci requires multiple copies of rRNA operons clustered in space and is critical for nucleoid compaction. It has not been determined, however, whether a multicopy plasmid-borne rRNA operon (p rrnB ) could substitute the multiple chromosomal rRNA operons for the organization of the bacterial nucleolus-like structure in the mutants of Δ6 rrn and Δ7 rrn that has all seven rRNA operons deleted in the genome. We hypothesized that extrachromosomal nucleolus-like structures are similarly organized and functional in trans from p rrnB in these mutants. In this report, using multicolor images of three-dimensional superresolution Structured Illumination Microscopy (3D-SIM), we determined the distributions of both RNAP and NusB that are a transcription factor involved in rRNA synthesis and ribosome biogenesis, p rrnB clustering, and nucleoid structure in these two mutants in response to environmental cues. Our results found that the extrachromosomal nucleolus-like organization tends to be spatially located at the poles of the mutant cells. In addition, formation of RNAP foci at the extrachromosomal nucleolus-like structure condenses the nucleoid, supporting the idea that active transcription at the nucleolus-like organization is a driving force in nucleoid compaction.

Dispersibility of lactose fines as compared to API in dry powders for inhalation.

PubMed

Thalberg, Kyrre; Åslund, Simon; Skogevall, Marcus; Andersson, Patrik

2016-05-17

This work investigates the dispersion performance of fine lactose particles as function of processing time, and compares it to the API, using Beclomethasone Dipropionate (BDP) as model API. The total load of fine particles is kept constant in the formulations while the proportions of API and lactose fines are varied. Fine particle assessment demonstrates that the lactose fines have higher dispersibility than the API. For standard formulations, processing time has a limited effect on the Fine Particle Fraction (FPF). For formulations containing magnesium stearate (MgSt), FPF of BDP is heavily influenced by processing time, with an initial increase, followed by a decrease at longer mixing times. An equation modeling the observed behavior is presented. Surprisingly, the dispersibility of the lactose fines present in the same formulation remains unaffected by mixing time. Magnesium analysis demonstrates that MgSt is transferred to the fine particles during the mixing process, thus lubrication both BDP and lactose fines, which leads to an increased FPF. Dry particle sizing of the formulations reveals a loss of fine particles at longer mixing times. Incorporation of fine particles into the carrier surfaces is believed to be behind this, and is hence a mechanism of importance as regards the dispersion performance of dry powders for inhalation. Copyright © 2016 Elsevier B.V. All rights reserved.

Mechanisms for the target patterns formation in a stochastic bistable excitable medium

NASA Astrophysics Data System (ADS)

Verisokin, Andrey Yu.; Verveyko, Darya V.; Postnov, Dmitry E.

2018-04-01

We study the features of formation and evolution of spatiotemporal chaotic regime generated by autonomous pacemakers in excitable deterministic and stochastic bistable active media using the example of the FitzHugh - Nagumo biological neuron model under discrete medium conditions. The following possible mechanisms for the formation of autonomous pacemakers have been studied: 1) a temporal external force applied to a small region of the medium, 2) geometry of the solution region (the medium contains regions with Dirichlet or Neumann boundaries). In our work we explore the conditions for the emergence of pacemakers inducing target patterns in a stochastic bistable excitable system and propose the algorithm for their analysis.

Remnants of semiclassical bistability in the few-photon regime of cavity QED.

PubMed

Kerckhoff, Joseph; Armen, Michael A; Mabuchi, Hideo

2011-11-21

Broadband homodyne detection of the light transmitted by a Fabry-Perot cavity containing a strongly-coupled (133)Cs atom is used to probe the dynamic optical response in a regime where semiclassical theory predicts bistability but strong quantum corrections should apply. While quantum fluctuations destabilize true equilibrium bistability, our observations confirm the existence of metastable states with finite lifetimes and a hysteretic response is apparent when the optical drive is modulated on comparable timescales. Our experiment elucidates remnant semiclassical behavior in the attojoule (~10 photon) regime of single-atom cavity QED, of potential significance for ultra-low power photonic signal processing. © 2011 Optical Society of America

Bistability and displacement fluctuations in a quantum nanomechanical oscillator

NASA Astrophysics Data System (ADS)

Avriller, R.; Murr, B.; Pistolesi, F.

2018-04-01

Remarkable features have been predicted for the mechanical fluctuations at the bistability transition of a classical oscillator coupled capacitively to a quantum dot [Micchi et al., Phys. Rev. Lett. 115, 206802 (2015), 10.1103/PhysRevLett.115.206802]. These results have been obtained in the regime ℏ ω0≪kBT ≪ℏ Γ , where ω0, T , and Γ are the mechanical resonating frequency, the temperature, and the tunneling rate, respectively. A similar behavior could be expected in the quantum regime of ℏ Γ ≪kBT ≪ℏ ω0 . We thus calculate the energy- and displacement-fluctuation spectra and study their behavior as a function of the electromechanical coupling constant when the system enters the Frank-Condon regime. We find that in analogy with the classical case, the energy-fluctuation spectrum and the displacement spectrum widths show a maximum for values of the coupling constant at which a mechanical bistability is established.

Photo-switchable bistable twisted nematic liquid crystal optical switch.

PubMed

Wang, Chun-Ta; Wu, Yueh-Chi; Lin, Tsung-Hsien

2013-02-25

This work demonstrates a photo-switchable bistable optical switch that is based on an azo-chiral doped liquid crystal (ACDLC). The photo-induced isomerization of the azo-chiral dopant can change the chirality of twisted nematic liquid crystal and the gap/pitch ratio of an ACDLC device, enabling switching between 0° and 180° twist states in a homogeneous aligned cell. The bistable 180° and 0° twist states of the azo-chiral doped liquid crystal between crossed polarizers correspond to the ON and OFF states of a light shutter, respectively, and they can be maintained stably for tens of hours. Rapid switching between 180° and 0° twist states can be carried out using 408 and 532 nm addressing light. Such a photo-controllable optical switch requires no specific asymmetric alignment layer or precise control of the cell gap/pitch ratio, so it is easily fabricated and has the potential for use in optical systems.

Severe lactose intolerance with lactosuria and vomiting.

PubMed Central

Hosková, A; Sabacký, J; Mrskos, A; Pospísil, R

1980-01-01

An infant with lactose intolerance is described. A breast-fed infant developed vomiting at 3 weeks, and became dehydrated. Lactosuria, aminoaciduria, and liver damage were preesent. A milk-free diet led to rapid recovery. At 6 months a normal diet was well tolerated. PMID:7416780

Assessment of the inhibition of ricin toxicity by lactose in milk.

PubMed

Lumor, Stephen E; Deen, Bronwyn D; Ronningen, Ian; Smith, Kenneth; Fredrickson, Neal R; Diez-Gonzalez, Francisco; Labuza, Theodore P

2013-12-01

The effect of lactose at the concentration typically found in milk (134 mM) on the ability of ricin to inhibit protein synthesis in HeLa cells was studied. Ricin (0.001 to 300 μg/ml) that was either not treated or treated with 134 mM lactose was added to test tubes containing 1 ml of HeLa cells (approximately 3 × 10(5) cells in a low-leucine medium). After 2 h of incubation at 37°C, 0.5 μCi of L-[U-(14)C]-leucine was added to each tube and incubated for another 60 min. The cells were harvested by centrifugation and lysed, and cellular proteins were separated. The amount of radioactivity incorporated into the proteins was determined by liquid scintillation. The biological activity of ricin, i. e., the amount of radioactivity in a sample relative to that of the control (cells not treated with ricin), was calculated for each treatment. The inhibitory effect of 134 mM lactose on the biological activity of ricin was only significant at concentrations of ricin below 1 μg/ml. At higher ricin concentrations, the effect of 134 mM lactose decreased as the concentration of ricin increased, resulting in an increase in the inhibition of proteins synthesis. Our results also indicated that bovine milk, when used in place of 134 mM lactose, was more effective for reducing the activity of ricin at concentrations below 1 μg/ml but was ineffective against ricin concentrations greater than 1 μg/ml. These results suggest that milk may not protect against ricin intoxication at the concentration (0.89 μg/ml) equivalent to the lowest limit of its 50 % lethal dose for a 20-kg child consuming 225 ml (8 oz) of milk.

Dynamics of a discrete chain of bi-stable elements: A biomimetic shock absorbing mechanism

NASA Astrophysics Data System (ADS)

Cohen, T.; Givli, S.

2014-03-01

A biomimetic shock absorbing mechanism, inspired by the bi-stable elongation behavior of the giant protein titin, is examined. A bi-stable element, composed of three mass particles with monotonous interaction forces, is suggested to facilitate an internal degree of freedom of finite mass which contributes significantly to dissipation upon unlocking of an internal link. An essential feature of the suggested element is that it undergoes reversible rapture and therefore retrieves its initial configuration once unloaded. The quasistatic and dynamic behaviors are investigated showing similarity to the common tri-linear bi-stable response, with two steady phases separated by a spinodal region. The dynamic behavior of a chain of elements is also examined, for several loading scenarios, showing that the suggested mechanism serves as an efficient shock absorber in a sub-critical dampening environment, as compared with a simple mass on spring system. Propagation of shock waves and refraction waves in an element chain is observed and the effect of natural imperfections is considered.

Lactose binding to galectin-1 modulates structural dynamics, increases conformational entropy, and occurs with apparent negative cooperativity.

PubMed

Nesmelova, Irina V; Ermakova, Elena; Daragan, Vladimir A; Pang, Mabel; Menéndez, Margarita; Lagartera, Laura; Solís, Dolores; Baum, Linda G; Mayo, Kevin H

2010-04-16

Galectins are a family of lectins with a conserved carbohydrate recognition domain that interacts with beta-galactosides. By binding cell surface glycoconjugates, galectin-1 (gal-1) is involved in cell adhesion and migration processes and is an important regulator of tumor angiogenesis. Here, we used heteronuclear NMR spectroscopy and molecular modeling to investigate lactose binding to gal-1 and to derive solution NMR structures of gal-1 in the lactose-bound and unbound states. Structure analysis shows that the beta-strands and loops around the lactose binding site, which are more open and dynamic in the unbound state, fold in around the bound lactose molecule, dampening internal motions at that site and increasing motions elsewhere throughout the protein to contribute entropically to the binding free energy. CD data support the view of an overall more open structure in the lactose-bound state. Analysis of heteronuclear single quantum coherence titration binding data indicates that lactose binds the two carbohydrate recognition domains of the gal-1 dimer with negative cooperativity, in that the first lactose molecule binds more strongly (K(1)=21+/-6 x 10(3) M(-1)) than the second (K(2)=4+/-2 x 10(3) M(-1)). Isothermal calorimetry data fit using a sequential binding model present a similar picture, yielding K(1)=20+/-10 x 10(3) M(-1) and K(2)=1.67+/-0.07 x 10(3) M(-1). Molecular dynamics simulations provide insight into structural dynamics of the half-loaded lactose state and, together with NMR data, suggest that lactose binding at one site transmits a signal through the beta-sandwich and loops to the second binding site. Overall, our results provide new insight into gal-1 structure-function relationships and to protein-carbohydrate interactions in general. Copyright (c) 2010. Published by Elsevier Ltd.

Clinical evaluation, biochemistry and genetic polymorphism analysis for the diagnosis of lactose intolerance in a population from northeastern Brazil.

PubMed

Ponte, Paulo Roberto Lins; de Medeiros, Pedro Henrique Quintela Soares; Havt, Alexandre; Caetano, Joselany Afio; Cid, David A C; Prata, Mara de Moura Gondim; Soares, Alberto Melo; Guerrant, Richard L; Mychaleckyj, Josyf; Lima, Aldo Ângelo Moreira

2016-02-01

This work aimed to evaluate and correlate symptoms, biochemical blood test results and single nucleotide polymorphisms for lactose intolerance diagnosis. A cross-sectional study was conducted in Fortaleza, Ceará, Brazil, with a total of 119 patients, 54 of whom were lactose intolerant. Clinical evaluation and biochemical blood tests were conducted after lactose ingestion and blood samples were collected for genotyping evaluation. In particular, the single nucleotide polymorphisms C>T-13910 and G>A-22018 were analyzed by restriction fragment length polymorphism/polymerase chain reaction and validated by DNA sequencing. Lactose-intolerant patients presented with more symptoms of flatulence (81.4%), bloating (68.5%), borborygmus (59.3%) and diarrhea (46.3%) compared with non-lactose-intolerant patients (p<0.05). We observed a significant association between the presence of the alleles T-13910 and A-22018 and the lactose-tolerant phenotype (p<0.05). After evaluation of the biochemical blood test results for lactose, we found that the most effective cutoff for glucose levels obtained for lactose malabsorbers was <15 mg/dL, presenting an area under the receiver operating characteristic curve greater than 80.3%, with satisfactory values for sensitivity and specificity. These data corroborate the association of these single nucleotide polymorphisms (C>T-13910 and G>A-22018) with lactose tolerance in this population and suggest clinical management for patients with lactose intolerance that considers single nucleotide polymorphism detection and a change in the biochemical blood test cutoff from <25 mg/dL to <15 mg/dL.

Clinical evaluation, biochemistry and genetic polymorphism analysis for the diagnosis of lactose intolerance in a population from northeastern Brazil

PubMed Central

Ponte, Paulo Roberto Lins; de Medeiros, Pedro Henrique Quintela Soares; Havt, Alexandre; Caetano, Joselany Afio; Cid, David A C; de Moura Gondim Prata, Mara; Soares, Alberto Melo; Guerrant, Richard L; Mychaleckyj, Josyf; Lima, Aldo Ângelo Moreira

2016-01-01

OBJECTIVE: This work aimed to evaluate and correlate symptoms, biochemical blood test results and single nucleotide polymorphisms for lactose intolerance diagnosis. METHOD: A cross-sectional study was conducted in Fortaleza, Ceará, Brazil, with a total of 119 patients, 54 of whom were lactose intolerant. Clinical evaluation and biochemical blood tests were conducted after lactose ingestion and blood samples were collected for genotyping evaluation. In particular, the single nucleotide polymorphisms C>T-13910 and G>A-22018 were analyzed by restriction fragment length polymorphism/polymerase chain reaction and validated by DNA sequencing. RESULTS: Lactose-intolerant patients presented with more symptoms of flatulence (81.4%), bloating (68.5%), borborygmus (59.3%) and diarrhea (46.3%) compared with non-lactose-intolerant patients (p<0.05). We observed a significant association between the presence of the alleles T-13910 and A-22018 and the lactose-tolerant phenotype (p<0.05). After evaluation of the biochemical blood test results for lactose, we found that the most effective cutoff for glucose levels obtained for lactose malabsorbers was <15 mg/dL, presenting an area under the receiver operating characteristic curve greater than 80.3%, with satisfactory values for sensitivity and specificity. CONCLUSIONS: These data corroborate the association of these single nucleotide polymorphisms (C>T-13910 and G>A-22018) with lactose tolerance in this population and suggest clinical management for patients with lactose intolerance that considers single nucleotide polymorphism detection and a change in the biochemical blood test cutoff from <25 mg/dL to <15 mg/dL. PMID:26934237

Is it possible to find presence of lactose in pharmaceuticals? - Preliminary studies by ATR-FTIR spectroscopy and chemometrics

NASA Astrophysics Data System (ADS)

Banas, A.; Banas, K.; Kalaiselvi, S. M. P.; Pawlicki, B.; Kwiatek, W. M.; Breese, M. B. H.

2017-01-01

Lactose and saccharose have the same molecular formula; however, the arrangement of their atoms is different. A major difference between lactose and saccharose with regard to digestion and processing is that it is not uncommon for individuals to be lactose intolerant (around two thirds of the population has a limited ability to digest lactose after infancy), but it is rather unlikely to be saccharose intolerant. The pharmaceutical industry uses lactose and saccharose as inactive ingredients of drugs to help form tablets because of their excellent compressibility properties. Some patients with severe lactose intolerance may experience symptoms of many allergic reactions after taking medicine that contains this substance. People who are specifically "allergic" to lactose (not just lactose intolerant) should not use tablets containing this ingredient. Fourier Transform Infrared (FTIR) spectroscopy has a unique chemical fingerprinting capability and plays a significant important role in the identification and characterization of analyzed samples and hence has been widely used in pharmaceutical science. However, a typical FTIR spectrum collected from tablets contains a myriad of valuable information hidden in a family of tiny peaks. Powerful multivariate spectral data processing can transform FTIR spectroscopy into an ideal tool for high volume, rapid screening and characterization of even minor tablet components. In this paper a method for distinction between FTIR spectra collected for tablets with or without lactose is presented. The results seem to indicate that the success of identifying one component in FTIR spectra collected for pharmaceutical composition (that is tablet) is largely dependent on the choice of the chemometric technique applied.

Input-Independent Energy Harvesting in Bistable Lattices from Transition Waves.

PubMed

Hwang, Myungwon; Arrieta, Andres F

2018-02-26

We demonstrate the utilisation of transition waves for realising input-invariant, frequency-independent energy harvesting in 1D lattices of bistable elements. We propose a metamaterial-inspired design with an integrated electromechanical transduction mechanism to the unit cell, rendering the power conversion capability an intrinsic property of the lattice. Moreover, focusing of transmitted energy to desired locations is demonstrated numerically and experimentally by introducing engineered defects in the form of perturbation in mass or inter-element forcing. We achieve further localisation of energy and numerically observe a breather-like mode for the first time in this type of lattice, improving the harvesting performance by an order of magnitude. Our approach considers generic bistable unit cells and thus provides a universal mechanism to harvest energy and realise metamaterials effectively behaving as a capacitor and power delivery system.

Bi-stable optical element actuator device

DOEpatents

Holdener, Fred R.; Boyd, Robert D.

2002-01-01

The present invention is a bistable optical element actuator device utilizing a powered means to move an actuation arm, to which an optical element is attached, between two stable positions. A non-powered means holds the actuation arm in either of the two stable positions. The optical element may be a electromagnetic (EM) radiation or particle source, an instrument, or EM radiation or particle transmissive reflective or absorptive elements. A bearing is used to transfer motion and smoothly transition the actuation arm between the two stable positions.

Discovery of an operon that participates in agmatine metabolism and regulates biofilm formation in Pseudomonas aeruginosa

PubMed Central

Williams, Bryan J.; Du, Rui-Hong; Calcutt, M. Wade; Abdolrasulnia, Rasul; Christman, Brian W.; Blackwell, Timothy S.

2013-01-01

Summary Agmatine is the decarboxylation product of arginine and a number of bacteria have devoted enzymatic pathways for its metabolism. Pseudomonas aeruginosa harbours the aguBA operon that metabolizes agmatine to putrescine, which can be subsequently converted into other polyamines or shunted into the TCA cycle for energy production. We discovered an alternate agmatine operon in the P. aeruginosa strain PA14 named agu2ABCA′ that contains two genes for agmatine deiminases (agu2A and agu2A′). This operon was found to be present in 25% of clinical P. aeruginosa isolates. Agu2A′ contains a twin-arginine translocation signal at its N-terminus and site-directed mutagenesis and cell fractionation experiments confirmed this protein is secreted to the periplasm. Analysis of the agu2ABCA′ promoter demonstrates that agmatine induces expression of the operon during the stationary phase of growth and during biofilm growth and agu2ABCA′ provides only weak complementation of aguBA, which is induced during log phase. Biofilm assays of mutants of all three agmatine deiminase genes in PA14 revealed that deletion of agu2ABCA′, specifically its secreted product Agu2A′, reduces biofilm production of PA14 following addition of exogenous agmatine. Together, these findings reveal a novel role for the agu2ABCA′ operon in the biofilm development of P. aeruginosa. PMID:20149107

Design and experiment of controlled bistable vortex induced vibration energy harvesting systems operating in chaotic regions

NASA Astrophysics Data System (ADS)

Huynh, B. H.; Tjahjowidodo, T.; Zhong, Z.-W.; Wang, Y.; Srikanth, N.

2018-01-01

Vortex induced vibration based energy harvesting systems have gained interests in these recent years due to its potential as a low water current energy source. However, the effectiveness of the system is limited only at a certain water current due to the resonance principle that governs the concept. In order to extend the working range, a bistable spring to support the structure is introduced on the system. The improvement on the performance is essentially dependent on the bistable gap as one of the main parameters of the nonlinear spring. A sufficiently large bistable gap will result in a significant performance improvement. Unfortunately, a large bistable gap might also increase a chance of chaotic responses, which in turn will result in diminutive harvested power. To mitigate the problem, an appropriate control structure is required to stabilize the chaotic vibrations of a VIV energy converter with the bistable supporting structure. Based on the nature of the double-well potential energy in a bistable spring, the ideal control structure will attempt to drive the responses to inter-well periodic vibrations in order to maximize the harvested power. In this paper, the OGY control algorithm is designed and implemented to the system. The control strategy is selected since it requires only a small perturbation in a structural parameter to execute the control effort, thus, minimum power is needed to drive the control input. Facilitated by a wake oscillator model, the bistable VIV system is modelled as a 4-dimensional autonomous continuous-time dynamical system. To implement the controller strategy, the system is discretized at a period estimated from the subspace hyperplane intersecting to the chaotic trajectory, whereas the fixed points that correspond to the desired periodic orbits are estimated by the recurrence method. Simultaneously, the Jacobian and sensitivity matrices are estimated by the least square regression method. Based on the defined fixed point and the

Bistable four-wave mixing response in a semiconductor quantum dot coupled to a photonic crystal nanocavity.

PubMed

Li, Jian-Bo; Xiao, Si; Liang, Shan; He, Meng-Dong; Luo, Jian-Hua; Kim, Nam-Chol; Chen, Li-Qun

2017-10-16

We perform a theoretical study of the bistable four-wave mixing (FWM) response in a coupled system comprised of a semiconductor quantum dot (SQD) and a photonic crystal (PC) nanocavity in which the SQD is embedded. It is shown that the shape of the FWM spectrum can switch among single-peaked, double-peaked, triple-peaked, and four-peaked arising from the vacuum Rabi splitting and the exciton-nanocavity coupling. Especially, we map out bistability phase diagrams within a parameter subspace of the system, and find that it is easy to turn on or off the bistable FWM response by only adjusting the excitation frequency or the pumping intensity. Our results offer a feasible means for measuring the SQD-PC nanocavity coupling strength and open a new avenue to design optical switches and memories.

Bistable (latching) solenoid actuated propellant isolation valve

NASA Technical Reports Server (NTRS)

Wichmann, H.; Deboi, H. H.

1979-01-01

The design, fabrication, assembly and test of a development configuration bistable (latching) solenoid actuated propellant isolation valve suitable for the control hydrazine and liquid fluorine to an 800 pound thrust rocket engine is described. The valve features a balanced poppet, utilizing metal bellows, a hard poppet/seat interface and a flexure support system for the internal moving components. This support system eliminates sliding surfaces, thereby rendering the valve free of self generated particles.

Bistability in dual-frequency nematic liquid crystals

NASA Astrophysics Data System (ADS)

Palto, S. P.; Barnik, M. I.

2007-03-01

Different modes of bistable switching in liquid crystals with frequency inversion of the dielectric anisotropy sign are discussed. The study is performed by numerical simulation and experimentally. It is shown that dual frequency driving can be effectively used to control switching between topologically equivalent and non-equivalent director field distributions. The experimental results on temperature performance of the dual-frequency switching and possible driving methods for energy consumption and expanding the temperature range are presented.

Release of indomethacin from ultrasound dry granules containing lactose-based excipients.

PubMed

Cavallari, Cristina; Albertini, Beatrice; Rodriguez, Lorenzo; Rabasco, Antonio M; Fini, Adamo

2005-01-20

Physical mixtures were prepared containing indomethacin and beta-lactose and alpha-lactose-based excipients (Ludipress and Cellactose). The mixtures were compacted with the aid of ultrasound, obtaining tablets, which were milled and sieved. Granules thus obtained were examined by optical microscopy and differential scanning calorimetry. The intense yellow color of the granules and the absence of indomethacin peak in thermograms suggest important modifications of indomethacin physical state; the drug thus modified appears to be spread on the excipient particle surface as a thin film, giving a lustrous appearance. No influence of ultrasound was observed on phase transition concerning lactose; only loss of water was important under high energy ultrasound. Dissolution profiles suggest an increased release of the drug from the systems treated with ultrasound at high energy, with respect to a traditional compaction; while no difference could be evidenced among the three excipients that, however, appear all suitable for this ultrasound-aided direct compression process.

Genome-wide analysis of trans-splicing in the nematode Pristionchus pacificus unravels conserved gene functions for germline and dauer development in divergent operons.

PubMed

Sinha, Amit; Langnick, Claudia; Sommer, Ralf J; Dieterich, Christoph

2014-09-01

Discovery of trans-splicing in multiple metazoan lineages led to the identification of operon-like gene organization in diverse organisms, including trypanosomes, tunicates, and nematodes, but the functional significance of such operons is not completely understood. To see whether the content or organization of operons serves similar roles across species, we experimentally defined operons in the nematode model Pristionchus pacificus. We performed affinity capture experiments on mRNA pools to specifically enrich for transcripts that are trans-spliced to either the SL1- or SL2-spliced leader, using spliced leader-specific probes. We obtained distinct trans-splicing patterns from the analysis of three mRNA pools (total mRNA, SL1 and SL2 fraction) by RNA-seq. This information was combined with a genome-wide analysis of gene orientation and spacing. We could confirm 2219 operons by RNA-seq data out of 6709 candidate operons, which were predicted by sequence information alone. Our gene order comparison of the Caenorhabditis elegans and P. pacificus genomes shows major changes in operon organization in the two species. Notably, only 128 out of 1288 operons in C. elegans are conserved in P. pacificus. However, analysis of gene-expression profiles identified conserved functions such as an enrichment of germline-expressed genes and higher expression levels of operonic genes during recovery from dauer arrest in both species. These results provide support for the model that a necessity for increased transcriptional efficiency in the context of certain developmental processes could be a selective constraint for operon evolution in metazoans. Our method is generally applicable to other metazoans to see if similar functional constraints regulate gene organization into operons. © 2014 Sinha et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

Stochastic dynamics and non-equilibrium thermodynamics of a bistable chemical system: the Schlögl model revisited.

PubMed

Vellela, Melissa; Qian, Hong

2009-10-06

Schlögl's model is the canonical example of a chemical reaction system that exhibits bistability. Because the biological examples of bistability and switching behaviour are increasingly numerous, this paper presents an integrated deterministic, stochastic and thermodynamic analysis of the model. After a brief review of the deterministic and stochastic modelling frameworks, the concepts of chemical and mathematical detailed balances are discussed and non-equilibrium conditions are shown to be necessary for bistability. Thermodynamic quantities such as the flux, chemical potential and entropy production rate are defined and compared across the two models. In the bistable region, the stochastic model exhibits an exchange of the global stability between the two stable states under changes in the pump parameters and volume size. The stochastic entropy production rate shows a sharp transition that mirrors this exchange. A new hybrid model that includes continuous diffusion and discrete jumps is suggested to deal with the multiscale dynamics of the bistable system. Accurate approximations of the exponentially small eigenvalue associated with the time scale of this switching and the full time-dependent solution are calculated using Matlab. A breakdown of previously known asymptotic approximations on small volume scales is observed through comparison with these and Monte Carlo results. Finally, in the appendix section is an illustration of how the diffusion approximation of the chemical master equation can fail to represent correctly the mesoscopically interesting steady-state behaviour of the system.

Lactose digestion by yogurt beta-galactosidase: influence of pH and microbial cell integrity.

PubMed

Martini, M C; Bollweg, G L; Levitt, M D; Savaiano, D A

1987-02-01

Lactase-deficient subjects more effectively digest lactose in yogurt than lactose in other dairy products, apparently due to yogurt microbial beta-galactosidase (beta-gal) which is active in the GI tract. We evaluated the effects of buffering capacity of yogurt, gastric pH, and microbial cell disruption on beta-gal activity and lactose digestion. Three times more acid was required to acidify yogurt than to acidify milk. Yogurt beta-gal was stable at pH 4.0 but inactivated at lower pH. When yogurt was sonicated to disrupt microbial cell structure, only 20% activity remained after incubation at pH 4.0 for 60 min. In vivo gastric pH remained greater than 2.7 for 3 h after ingestion of yogurt. Acidified milk alone or with disrupted yogurt microorganisms caused twice as much lactose malabsorption as did acidified milk containing intact yogurt microorganisms. The results provide a possible explanation for the survival of beta-gal activity from yogurt in the GI tract.

Behavioral Intervention in Adolescents Improves Bone Mass, Yet Lactose Maldigestion Is a Barrier

PubMed Central

Lee, Yujin; Savaiano, Dennis A.; McCabe, George P.; Pottenger, Francis M.; Welshimer, Kathleen; Weaver, Connie M.; McCabe, Linda D.; Novotny, Rachel; Read, Marsha; Going, Scott; Mason, April; Van Loan, Marta

2018-01-01

Calcium intake during adolescence is important for attainment of peak bone mass. Lactose maldigestion is an autosomal recessive trait, leading to lower calcium intake. The Adequate Calcium Today study aimed to determine if a school-based targeted behavioral intervention over one year could improve calcium intake and bone mass in early adolescent girls. The school-randomized intervention was conducted at middle schools in six states over one school year. A total of 473 girls aged 10–13 years were recruited for outcome assessments. Bone mineral content (BMC) was determined by dual energy X-ray absorptiometry. Dietary calcium intake was assessed with a semi-quantitative food frequency questionnaire. Baseline calcium intake and BMC were not significantly different between groups. After the intervention period, there were no differences in changes in calcium intake and BMC at any site between groups. An unanticipated outcome was a greater increase in spinal BMC among lactose digesters than lactose maldigesters in the intervention schools only (12 months) (6.9 ± 0.3 g vs. 6.0 ± 0.4 g, p = 0.03) and considering the entire study period (18 months) (9.9 ± 0.4 vs. 8.7 ± 0.5 g, p < 0.01). Overall, no significant differences between the intervention and control schools were observed. However, lactose digesters who received the intervention program increased bone mass to a greater extent than lactose maldigesters. PMID:29597337

Thermal bistability-based method for real-time optimization of ultralow-threshold whispering gallery mode microlasers.

PubMed

Lin, Guoping; Candela, Y; Tillement, O; Cai, Zhiping; Lefèvre-Seguin, V; Hare, J

2012-12-15

A method based on thermal bistability for ultralow-threshold microlaser optimization is demonstrated. When sweeping the pump laser frequency across a pump resonance, the dynamic thermal bistability slows down the power variation. The resulting line shape modification enables a real-time monitoring of the laser characteristic. We demonstrate this method for a functionalized microsphere exhibiting a submicrowatt laser threshold. This approach is confirmed by comparing the results with a step-by-step recording in quasi-static thermal conditions.

Cross-Regulation between the phz1 and phz2 Operons Maintain a Balanced Level of Phenazine Biosynthesis in Pseudomonas aeruginosa PAO1

PubMed Central

Jiang, Bei; Xiao, Bo; Liu, Linde; Ge, Yihe; Hu, Xiaomei

2016-01-01

Gene duplication often provides selective advantages for the survival of microorganisms in adapting to varying environmental conditions. P. aeruginosa PAO1 possesses two seven-gene operons [phz1 (phzA1B1C1D1E1F1G1) and phz2 (phzA2B2C2D2E2F2G2)] that are involved in the biosynthesis of phenazine-1-carboxylic acid and its derivatives. Although the two operons are highly homologous and their functions are well known, it is unclear how the two phz operons coordinate their expressions to maintain the phenazine biosynthesis. By constructing single and double deletion mutants of the two phz operons, we found that the phz1-deletion mutant produced the same or less amount of phenazine-1-carboxylic acid and pyocyanin in GA medium than the phz2-knockout mutant while the phz1-phz2 double knockout mutant did not produce any phenazines. By generating phzA1 and phzA2 translational and transcriptional fusions with a truncated lacZ reporter, we found that the expression of the phz1 operon increased significantly at the post-transcriptional level and did not alter at the transcriptional level in the absence of the phz2 operon. Surprisingly, the expression the phz2 operon increased significantly at the post-transcriptional level and only moderately at the transcriptional level in the absence of the phz1 operon. Our findings suggested that a complex cross-regulation existed between the phz1 and phz2 operons. By mediating the upregulation of one phz operon expression while the other was deleted, this crosstalk would maintain the homeostatic balance of phenazine biosynthesis in P. aeruginosa PAO1. PMID:26735915

Optical bistability and optical response of an infrared quantum dot hybridized to VO2 nanoparticle

NASA Astrophysics Data System (ADS)

Zamani, Naser; Hatef, Ali; Nadgaran, Hamid; Keshavarz, Alireza

2017-08-01

In this work, we theoretically investigate optical bistability and optical response of a hybrid system consisting of semiconductor quantum dot (SQD) coupled with a vanadium dioxide nanoparticle (VO2NP) in the infrared (IR) regime. The VO2 material exists in semiconductor and metallic phases below and above the critical temperature, respectively where the particle optical properties dramatically change during this phase transition. In our calculations a filling fraction factor controls the VO2NP phase transition when the hybrid system interacts with a laser field. We demonstrate that the switch-up threshold for optical bistability is strongly controlled by filling fraction without changing the structure of the hybrid system. Also, it is shown that, the threshold of optical bistability increases when the VO2NP phases changes from semiconductor to metallic phase. The presented results have the potential to be applied in designing optical switching and optical storage.

Production of galacto-oligosaccharides from lactose by Aspergillus oryzae beta-galactosidase immobilized on cotton cloth.

PubMed

Albayrak, Nedim; Yang, Shang-Tian

2002-01-05

The production of galacto-oligosaccharides (GOS) from lactose by A. oryzae beta-galactosidase immobilized on cotton cloth was studied. The total amounts and types of GOS produced were mainly affected by the initial lactose concentration in the reaction media. In general, more and larger GOS can be produced with higher initial lactose concentrations. A maximum GOS production of 27% (w/w) of initial lactose was achieved at 50% lactose conversion with 500 g/L of initial lactose concentration. Tri-saccharides were the major types of GOS formed, accounting for more than 70% of the total GOS produced in the reactions. Temperature and pH affected the reaction rate, but did not result in any changes in GOS formation. The presence of galactose and glucose at the concentrations encountered near maximum GOS greatly inhibited the reactions and reduced GOS yield by as much as 15%. The cotton cloth as the support matrix for enzyme immobilization did not affect the GOS formation characteristics of the enzyme, suggesting no diffusion limitation in the enzyme carrier. The thermal stability of the enzyme increased approximately 25-fold upon immobilization on cotton cloth. The half-life for the immobilized enzyme on cotton cloth was more than 1 year at 40 degrees C and 48 days at 50 degrees C. Stable, continuous operation in a plugflow reactor was demonstrated for 2 weeks without any apparent problem. A maximum GOS production of 21 and 26% (w/w) of total sugars was attained with a feed solution containing 200 and 400 g/L of lactose, respectively, at pH 4.5 and 40 degrees C. The corresponding reactor productivities were 80 and 106 g/L/h, respectively, which are at least several-fold higher than those previously reported. Copyright 2002 John Wiley & Sons, Inc.

Lactose intolerance and health disparities among African Americans and Hispanic Americans: an updated consensus statement.

PubMed

Bailey, Rahn K; Fileti, Cecelia Pozo; Keith, Jeanette; Tropez-Sims, Susanne; Price, Winston; Allison-Ottey, Sharon Denise

2013-01-01

Dairy foods contribute nine essential nutrients to the diet including calcium, potassium and vitamin D; nutrients identified by the 2010 Dietary Guidelines for Americans as being "of public health concern" within the U.S. population. Milk and milk product intake is associated with better diet quality and has been associated with a reduced risk of chronic diseases or conditions including hypertension, cardiovascular disease, metabolic syndrome, Type 2 Diabetes and osteoporosis. Some research also indicates dairy food intake may be linked to reduced body fat, when accompanied by energy-restriction. On average, both African Americans and Hispanic Americans consume less than the recommended levels of dairy foods, and perceived or actual lactose intolerance can be a primary reason for limiting or avoiding dairy intake. True lactose intolerance prevalence is not known because healthcare providers do not routinely measure for it, and no standardized assessment method exists. Avoiding dairy may lead to shortfalls of essential nutrients and increased susceptibility to chronic disease. This updated Consensus Statement aims to provide the most current information about lactose intolerance and health, with specific relevance to the African American and Hispanic American communities. Topics covered include diagnostic considerations, actual and recommended dairy food intake and levels of consumption of key dairy nutrients among African Americans and Hispanic Americans; prevalence of self-reported lactose intolerance among various racial/ethnic groups; the association between dairy food intake, lactose intolerance and chronic disease; and research-based management recommendations for those with lactose intolerance.

Lactose intolerance and gastrointestinal cow's milk allergy in infants and children - common misconceptions revisited.

PubMed

Heine, Ralf G; AlRefaee, Fawaz; Bachina, Prashant; De Leon, Julie C; Geng, Lanlan; Gong, Sitang; Madrazo, José Armando; Ngamphaiboon, Jarungchit; Ong, Christina; Rogacion, Jossie M

2017-01-01

Lactose is the main carbohydrate in human and mammalian milk. Lactose requires enzymatic hydrolysis by lactase into D-glucose and D-galactose before it can be absorbed. Term infants express sufficient lactase to digest about one liter of breast milk daily. Physiological lactose malabsorption in infancy confers beneficial prebiotic effects, including the establishment of Bifidobacterium-rich fecal microbiota. In many populations, lactase levels decline after weaning (lactase non-persistence; LNP). LNP affects about 70% of the world's population and is the physiological basis for primary lactose intolerance (LI). Persistence of lactase beyond infancy is linked to several single nucleotide polymorphisms in the lactase gene promoter region on chromosome 2. Primary LI generally does not manifest clinically before 5 years of age. LI in young children is typically caused by underlying gut conditions, such as viral gastroenteritis, giardiasis, cow's milk enteropathy, celiac disease or Crohn's disease. Therefore, LI in childhood is mostly transient and improves with resolution of the underlying pathology. There is ongoing confusion between LI and cow's milk allergy (CMA) which still leads to misdiagnosis and inappropriate dietary management. In addition, perceived LI may cause unnecessary milk restriction and adverse nutritional outcomes. The treatment of LI involves the reduction, but not complete elimination, of lactose-containing foods. By contrast, breastfed infants with suspected CMA should undergo a trial of a strict cow's milk protein-free maternal elimination diet. If the infant is not breastfed, an extensively hydrolyzed or amino acid-based formula and strict cow's milk avoidance are the standard treatment for CMA. The majority of infants with CMA can tolerate lactose, except when an enteropathy with secondary lactase deficiency is present.

Functional Analysis of the Magnetosome Island in Magnetospirillum gryphiswaldense: The mamAB Operon Is Sufficient for Magnetite Biomineralization

PubMed Central

Lohße, Anna; Ullrich, Susanne; Katzmann, Emanuel; Borg, Sarah; Wanner, Gerd; Richter, Michael; Voigt, Birgit; Schweder, Thomas; Schüler, Dirk

2011-01-01

Bacterial magnetosomes are membrane-enveloped, nanometer-sized crystals of magnetite, which serve for magnetotactic navigation. All genes implicated in the synthesis of these organelles are located in a conserved genomic magnetosome island (MAI). We performed a comprehensive bioinformatic, proteomic and genetic analysis of the MAI in Magnetospirillum gryphiswaldense. By the construction of large deletion mutants we demonstrate that the entire region is dispensable for growth, and the majority of MAI genes have no detectable function in magnetosome formation and could be eliminated without any effect. Only <25% of the region comprising four major operons could be associated with magnetite biomineralization, which correlated with high expression of these genes and their conservation among magnetotactic bacteria. Whereas only deletion of the mamAB operon resulted in the complete loss of magnetic particles, deletion of the conserved mms6, mamGFDC, and mamXY operons led to severe defects in morphology, size and organization of magnetite crystals. However, strains in which these operons were eliminated together retained the ability to synthesize small irregular crystallites, and weakly aligned in magnetic fields. This demonstrates that whereas the mamGFDC, mms6 and mamXY operons have crucial and partially overlapping functions for the formation of functional magnetosomes, the mamAB operon is the only region of the MAI, which is necessary and sufficient for magnetite biomineralization. Our data further reduce the known minimal gene set required for magnetosome formation and will be useful for future genome engineering approaches. PMID:22043287

Variability of rRNA Operon Copy Number and Growth Rate Dynamics of Bacillus Isolated from an Extremely Oligotrophic Aquatic Ecosystem

PubMed Central

Valdivia-Anistro, Jorge A.; Eguiarte-Fruns, Luis E.; Delgado-Sapién, Gabriela; Márquez-Zacarías, Pedro; Gasca-Pineda, Jaime; Learned, Jennifer; Elser, James J.; Olmedo-Alvarez, Gabriela; Souza, Valeria

2016-01-01

The ribosomal RNA (rrn) operon is a key suite of genes related to the production of protein synthesis machinery and thus to bacterial growth physiology. Experimental evidence has suggested an intrinsic relationship between the number of copies of this operon and environmental resource availability, especially the availability of phosphorus (P), because bacteria that live in oligotrophic ecosystems usually have few rrn operons and a slow growth rate. The Cuatro Ciénegas Basin (CCB) is a complex aquatic ecosystem that contains an unusually high microbial diversity that is able to persist under highly oligotrophic conditions. These environmental conditions impose a variety of strong selective pressures that shape the genome dynamics of their inhabitants. The genus Bacillus is one of the most abundant cultivable bacterial groups in the CCB and usually possesses a relatively large number of rrn operon copies (6–15 copies). The main goal of this study was to analyze the variation in the number of rrn operon copies of Bacillus in the CCB and to assess their growth-related properties as well as their stoichiometric balance (N and P content). We defined 18 phylogenetic groups within the Bacilli clade and documented a range of from six to 14 copies of the rrn operon. The growth dynamic of these Bacilli was heterogeneous and did not show a direct relation to the number of operon copies. Physiologically, our results were not consistent with the Growth Rate Hypothesis, since the copies of the rrn operon were decoupled from growth rate. However, we speculate that the diversity of the growth properties of these Bacilli as well as the low P content of their cells in an ample range of rrn copy number is an adaptive response to oligotrophy of the CCB and could represent an ecological mechanism that allows these taxa to coexist. These findings increase the knowledge of the variability in the number of copies of the rrn operon in the genus Bacillus and give insights about the

Carrier transport in flexible organic bistable devices of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) polymer layer.

PubMed

Son, Dong-Ick; Park, Dong-Hee; Choi, Won Kook; Cho, Sung-Hwan; Kim, Won-Tae; Kim, Tae Whan

2009-05-13

The bistable effects of ZnO nanoparticles embedded in an insulating poly(methyl methacrylate) (PMMA) polymer single layer by using flexible polyethylene terephthalate (PET) substrates were investigated. Transmission electron microscopy (TEM) images revealed that ZnO nanoparticles were formed inside the PMMA polymer layer. Current-voltage (I-V) measurement on the Al/ZnO nanoparticles embedded in an insulating PMMA polymer layer/ITO/PET structures at 300 K showed a nonvolatile electrical bistability behavior with a flat-band voltage shift due to the existence of the ZnO nanoparticles, indicative of trapping, storing, and emission of charges in the electronic states of the ZnO nanoparticles. The carrier transport mechanism of the bistable behavior for the fabricated organic bistable device (OBD) structures is described on the basis of the I-V results by analyzing the effect of space charge.

Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on Cheddar cheese quality: manufacture and composition.

PubMed

Upreti, P; Metzger, L E

2006-02-01

Eight Cheddar cheeses with 2 levels of calcium (Ca) and phosphorus (P), residual lactose, and salt-to-moisture ratio (S/M) were manufactured. All cheeses were made using a stirred-curd procedure and were replicated 3 times. Treatments with a high level of Ca and P were produced by setting the milk and drawing the whey at a higher pH (6.6 and 6.3, respectively) compared with the treatments with a low level of Ca and P (pH of 6.2 and 5.7, respectively). The lactose content in the cheeses was varied by adding lactose (2.5% by weight of milk) to the milk for high lactose cheeses, and washing the curd for low lactose cheeses. The difference in S/M was obtained by dividing the curds into halves, weighing each half, and salting at 3.5 and 2.25% of the weight of the curd for high and low S/M, respectively. All cheeses were salted at a pH of 5.4. Modifications in cheese-making protocols produced cheeses with desired differences in Ca and P, residual lactose, and S/M. Average Ca and P in the high Ca and P cheeses was 0.68 and 0.48%, respectively, vs. 0.53 and 0.41% for the low Ca and P cheeses. Average lactose content of the high lactose treatments at d 1 was 1.48% compared with 0.30% for the low lactose treatments. The S/M for the high and low S/M cheeses was 6.68 and 4.77%, respectively. Mean moisture, fat, and protein content of the cheeses ranged from 32.07 to 37.57%, 33.32 to 35.93%, and 24.46 to 26.40%, respectively. The moisture content differed among the treatments, whereas fat and protein content on dry basis was similar.

Maillard reaction of lactose and fluoxetine hydrochloride, a secondary amine.

PubMed

Wirth, D D; Baertschi, S W; Johnson, R A; Maple, S R; Miller, M S; Hallenbeck, D K; Gregg, S M

1998-01-01

Analysis of commercially available generic formulations of fluoxetine HCl revealed the presence of lactose as the most common excipient. We show that such formulations are inherently less stable than formulations with starch as the diluent due to the Maillard reaction between the drug, a secondary amine hydrochloride, and lactose. The Amadori rearrangement product was isolated and characterized; the characterization was aided by reduction with sodium borohydride and subsequent characterization of this reduced adduct. The lactose-fluoxetine HCl reaction was examined in aqueous ethanol and in the solid state, in which factors such as water content, lubricant concentration, and temperature were found to influence the degradation. N-Formylfluoxetine was identified as a major product of this Maillard reaction and it is proposed that N-formyl compounds be used as markers for this drug-excipient interaction since they are easy to prepare synthetically. Many characteristic volatile products of the Maillard reaction have been identified by GC/MS, including furaldehyde, maltol, and 2,3-dihydro-3,5-dihydroxy-6-methyl-4 H-pyran-4-one. Close similarity between the degradation products of simple mixtures and formulated generic products was found; however, at least one product decomposed at a rate nearly 10 times that predicted from the simple models. Maillard products have also been identified in unstressed capsules. The main conclusion is that drugs which are secondary amines (not just primary amines as sometimes reported) undergo the Maillard reaction with lactose under pharmaceutically relevant conditions. This finding should be considered during the selection of excipients and stability protocols for drugs which are secondary amines or their salts, just as it currently is for primary amines.

On square-wave-driven stochastic resonance for energy harvesting in a bistable system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Dongxu, E-mail: sudx@iis.u-tokyo.ac.jp; Zheng, Rencheng; Nakano, Kimihiko

Stochastic resonance is a physical phenomenon through which the throughput of energy within an oscillator excited by a stochastic source can be boosted by adding a small modulating excitation. This study investigates the feasibility of implementing square-wave-driven stochastic resonance to enhance energy harvesting. The motivating hypothesis was that such stochastic resonance can be efficiently realized in a bistable mechanism. However, the condition for the occurrence of stochastic resonance is conventionally defined by the Kramers rate. This definition is inadequate because of the necessity and difficulty in estimating white noise density. A bistable mechanism has been designed using an explicit analyticalmore » model which implies a new approach for achieving stochastic resonance in the paper. Experimental tests confirm that the addition of a small-scale force to the bistable system excited by a random signal apparently leads to a corresponding amplification of the response that we now term square-wave-driven stochastic resonance. The study therefore indicates that this approach may be a promising way to improve the performance of an energy harvester under certain forms of random excitation.« less

[Abdominal spasms, meteorism, diarrhea: fructose intolerance, lactose intolerance or IBS?].

PubMed

Litschauer-Poursadrollah, Margaritha; El-Sayad, Sabine; Wantke, Felix; Fellinger, Christina; Jarisch, Reinhart

2012-12-01

Meteorism, abdominal spasms, diarrhea, casually obstipation, flatulence and nausea are symptoms of fructose malabsorption (FIT) and/or lactose intolerance (LIT), but are also symptoms of irritable bowel syndrome (IBS). Therefore these diseases should be considered primarily in patients with digestive complaints. For diagnosis an H(2)-breath test is used.In 1,935 patients (526 m, 1,409 f) a fructose intolerance test and in 1,739 patients (518 m,1,221 f) a lactose intolerance test was done.FIT is found more frequently than LIT (57 versus 52 % in adults (p < 0,02) and in children 90 versus 62 % (p < 0,001)) and is in polyintolerances most frequently correlated to histamine intolerance (HIT). Headache (ca. 10 %), fatigue (ca. 5 %) and dizziness (ca. 3 %) may occur after the test, irrespective whether the test was positive or negative.In more than 2/3 of patients a diet reduced in fructose or lactose may lead to improvement or remission of these metabolic disorders. IBS, which is often correlated with FIT (183/221 patients = 83 %), can be improved by relevant but also not relevant diets indicating that irritable bowel disease seems to be caused primarily by psychological disorders.

Dynamic and energetic characteristics of a bistable piezoelectric vibration energy harvester with an elastic magnifier

NASA Astrophysics Data System (ADS)

Wang, Guangqing; Liao, Wei-Hsin; Yang, Binqiang; Wang, Xuebao; Xu, Wentan; Li, Xiuling

2018-05-01

Bistable piezoelectric energy harvesters are being increasingly seen as an alternative to batteries in low-power devices. However, their energy harvesting characteristics are limited. To enhance these, we use a configuration including an elastic magnifier to amplify base excitation and provide sufficient kinetic energy to overcome potential well barriers, thus leading to large-amplitude bistable motion. We derive the distributed parameter mathematical model of this configuration by using Hamilton's principle. We then investigate the nonlinear dynamic behaviors and energetic characteristics and analyze the bifurcation for the equilibrium solution of the model. The simulations and experiments show high electromechanical responses and energy generation characteristics of the proposed system over a broad frequency band. The results suggest that, compared with a typical bistable piezoelectric energy harvester, the proposed energy harvester system with an elastic magnifier can provide higher output over a broader frequency band at lower excitation levels by adjusting the system's mass and stiffness ratios.

Control of optical bistability and third-order nonlinearity via tunneling induced quantum interference in triangular quantum dot molecules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tian, Si-Cong, E-mail: tiansicong@ciomp.ac.cn; Tong, Cun-Zhu, E-mail: tongcz@ciomp.ac.cn; Zhang, Jin-Long

The optical bistability of a triangular quantum dot molecules embedded inside a unidirectional ring cavity is studied. The type, the threshold and the hysteresis loop of the optical bistability curves can be modified by the tunneling parameters, as well as the probe laser field. The linear and nonlinear susceptibilities of the medium are also studied to interpret the corresponding results. The physical interpretation is that the tunneling can induce the quantum interference, which modifies the linear and the nonlinear response of the medium. As a consequence, the characteristics of the optical bistability are changed. The scheme proposed here can bemore » utilized for optimizing and controlling the optical switching process.« less

Tunable bistable devices for harvesting energy from spinning wheels

NASA Astrophysics Data System (ADS)

Elhadidi, Mohamed; Helal, Mohammed; Nassar, Omar; Arafa, Mustafa; Zeyada, Yasser

2015-04-01

Bistable systems have recently been employed for vibration energy harvesting owing to their favorable dynamic characteristics and desirable response for wideband excitation. In this paper, we investigate the use of bistable harvesters to extract energy from spinning wheels. The proposed harvester consists of a piezoelectric cantilever beam that is mounted on a rigid spinning hub and carries a tip mass in the form of a permanent magnet. Magnetic repulsion forces from an opposite magnet cause the beam to possess two stable equilibrium positions. Inter-well lead-lag oscillations caused by rotation in a vertical plane provide a good source for energy extraction. The design offers frequency tuning, as the centrifugal forces strain the harvester, thereby increasing its natural frequency to cope with a variable rotational speed. This has applications in self-powered sensors mounted on spinning wheels, such as tire pressure monitoring sensors. An effort is made to select the design parameters to enable the harvester to exhibit favorable inter-well oscillations across a range of rotational speeds for enhanced energy harvesting. Findings of the present work are verified both numerically and experimentally.

Preparation of lactose-free pasteurized milk with a recombinant thermostable β-glucosidase from Pyrococcus furiosus

PubMed Central

2013-01-01

Background Lactose intolerance is a common health concern causing gastrointestinal symptoms and avoidance of dairy products by afflicted individuals. Since milk is a primary source of calcium and vitamin D, lactose intolerant individuals often obtain insufficient amounts of these nutrients which may lead to adverse health outcomes. Production of lactose-free milk can provide a solution to this problem, although it requires use of lactase from microbial sources and increases potential for contamination. Use of thermostable lactase enzymes can overcome this issue by functioning under pasteurization conditions. Results A thermostable β-glucosidase gene from Pyrococcus furiosus was cloned in frame with the Saccharomyces cerecisiae a-factor secretory signal and expressed in Pichia pastoris strain X-33. The recombinant enzyme was purified by a one-step method of weak anion exchange chromatography. The optimum temperature and pH for this β-glucosidase activity was 100°C and pH 6.0, respectively. The enzyme activity was not significantly inhibited by Ca2+. We tested the additive amount, hydrolysis time, and the influence of glucose on the enzyme during pasteurization and found that the enzyme possessed a high level of lactose hydrolysis in milk that was not obviously influenced by glucose. Conclusions The thermostablity of this recombinant β-glucosidase, combined with its neutral pH activity and favorable temperature activity optima, suggest that this enzyme is an ideal candidate for the hydrolysis of lactose in milk, and it would be suitable for application in low-lactose milk production during pasteurization. PMID:24053641

A novel combined thermometric and amperometric biosensor for lactose determination based on immobilised cellobiose dehydrogenase.

PubMed

Yakovleva, Maria; Buzas, Orsolya; Matsumura, Hirotoshi; Samejima, Masahiro; Igarashi, Kiyohiko; Larsson, Per-Olof; Gorton, Lo; Danielsson, Bengt

2012-01-15

A novel method for lactose determination in milk is proposed. It is based on oxidation of lactose by cellobiose dehydrogenase (CDH) from the basidiomycete Phanerochaete chrysosporium, immobilised in an enzyme reactor. The reactor was prepared by cross-linking CDH onto aminopropyl-silanised controlled pore glass (CPG) beads using glutaraldehyde. The combined biosensor worked in flow injection analysis (FIA) mode and was developed for simultaneous monitoring of the thermometric signal associated with the enzymatic oxidation of lactose using p-benzoquinone as electron acceptor and the electrochemically generated current associated with the oxidation of the hydroquinone formed. A highly reproducible linear response for lactose was obtained between 0.05 mM and 30 mM. For a set of more than 500 samples an R.S.D. of less than 10% was achieved. The assay time was ca. 2 min per sample. The sensor was applied for the determination of lactose in dairy milk samples (milk with a fat content of 1.5% or 3% and also "lactose free" milk). No sample preparation except dilution with buffer was needed. The proposed method is rapid, suitable for repeated use and allows the possibility to compare results from two different detection methods, thus providing a built-in quality assurance. Some differences in the response observed between the methods indicate that the dual approach can be useful in mechanistic studies of redox enzymes. In addition, a dual system opens up interesting possibilities for studies of enzyme properties and mechanisms. Copyright © 2011 Elsevier B.V. All rights reserved.

Lysines 72, 80 and 213 and aspartic acid 210 of the Lactococcus lactis LacR repressor are involved in the response to the inducer tagatose-6-phosphate leading to induction of lac operon expression.

PubMed

van Rooijen, R J; Dechering, K J; Niek, C; Wilmink, J; de Vos, W M

1993-02-01

Site-directed mutagenesis of the Lactococcus lactis lacR gene was performed to identify residues in the LacR repressor that are involved in the induction of lacABCDFEGX operon expression by tagatose-6-phosphate. A putative inducer binding domain located near the C-terminus was previously postulated based on homology studies with the Escherichia coli DeoR family of repressors, which all have a phosphorylated sugar as inducer. Residues within this domain and lysine residues that are charge conserved in the DeoR family were changed into alanine or arginine. The production of the LacR mutants K72A, K80A, K80R, D210A, K213A and K213R in the LacR-deficient L.lactis strain NZ3015 resulted in repressed phospho-beta-galactosidase (LacG) activities and decreased growth rates on lactose. Gel mobility shift assays showed that the complex between a DNA fragment carrying the lac operators and LacR mutants K72A, K80A, K213A and D210A did not dissociate in the presence of tagatose-6-phosphate, in contrast to wild type LacR. Other mutations (K62A/K63A, K72R, K73A, K73R, T212A, F214R, R216R and R216K) exhibited no gross effects on inducer response. The results strongly suggest that the lysines at positions 72, 80 and 213 and aspartic acid at position 210 are involved in the induction of lac operon expression by tagatose-6-phosphate.

A relationship between vitamin D, parathyroid hormone, calcium levels and lactose intolerance in type 2 diabetic patients and healthy subjects.

PubMed

Rana, SatyaVati; Morya, Rajesh Kumar; Malik, Aastha; Bhadada, Sanjay Kumar; Sachdeva, Naresh; Sharma, Gaurav

2016-11-01

Type 2 diabetes mellitus is chronic metabolic disorder. Common gastrointestinal symptoms in type 2 diabetic patients are flatulence, constipation and/or diarrhea. Reason for these may be lactose intolerance leading to change in vitamin D, Calcium and parathyroid hormone which further regulate bone mineralization. To measure lactose intolerance, vitamin D, calcium and parathyroid hormone in type 2 diabetic patients. 150 type 2 diabetic patients attending Endocrinology Clinic in PGI, Chandigarh and 150 age and sex matched healthy controls were enrolled. Lactose intolerance was measured using non-invasive lactose breath test. 25-hydroxyvitamin D (total) and Parathyroid hormone were measured in plasma using immunoassay. Serum calcium was measured using auto analyzer. T score was recorded from DXA scan for bone mineral density measurement. Lactose intolerance was observed significantly higher (p<0.001) diabetic patients (59.3%) as compared to controls (42%). Levels of plasma 25-OH vitamin D (total), parathyroid hormone and serum calcium were significantly lower in patients as compared to controls. Furthermore, levels of plasma 25-OH vitamin D (total), parathyroid hormone and serum calcium were more decreased in lactose intolerant diabetic patients than lactose tolerant patients. Sixty seven percent (67%) of diabetic patients suffered from osteoporosis and 20% of controls. Eighty percent (80%) diabetic patients and 16% controls with osteoporosis suffered from lactose intolerance. From this study we can conclude that measurement of lactose intolerance using non-invasive lactose breath test is suggested for type 2 diabetic patients along with timely measurement of 25-OH vitamin D (total), calcium and parathyroid hormone levels. Copyright © 2016 Elsevier B.V. All rights reserved.

Two Paralogous Families of a Two-Gene Subtilisin Operon Are Widely Distributed in Oral Treponemes

PubMed Central

Correia, Frederick F.; Plummer, Alvin R.; Ellen, Richard P.; Wyss, Chris; Boches, Susan K.; Galvin, Jamie L.; Paster, Bruce J.; Dewhirst, Floyd E.

2003-01-01

Certain oral treponemes express a highly proteolytic phenotype and have been associated with periodontal diseases. The periodontal pathogen Treponema denticola produces dentilisin, a serine protease of the subtilisin family. The two-gene operon prcA-prtP is required for expression of active dentilisin (PrtP), a putative lipoprotein attached to the treponeme's outer membrane or sheath. The purpose of this study was to examine the diversity and structure of treponemal subtilisin-like proteases in order to better understand their distribution and function. The complete sequences of five prcA-prtP operons were determined for Treponema lecithinolyticum, “Treponema vincentii,” and two canine species. Partial operon sequences were obtained for T. socranskii subsp. 04 as well as 450- to 1,000-base fragments of prtP genes from four additional treponeme strains. Phylogenetic analysis demonstrated that the sequences fall into two paralogous families. The first family includes the sequence from T. denticola. Treponemes possessing this operon family express chymotrypsin-like protease activity and can cleave the substrate N-succinyl-alanyl-alanyl-prolyl-phenylalanine-p-nitroanilide (SAAPFNA). Treponemes possessing the second paralog family do not possess chymotrypsin-like activity or cleave SAAPFNA. Despite examination of a range of protein and peptide substrates, the specificity of the second protease family remains unknown. Each of the fully sequenced prcA and prtP genes contains a 5′ hydrophobic leader sequence with a treponeme lipobox. The two paralogous families of treponeme subtilisins represent a new subgroup within the subtilisin family of proteases and are the only subtilisin lipoprotein family. The present study demonstrated that the subtilisin paralogs comprising a two-gene operon are widely distributed among treponemes. PMID:14617650

On the bistable zone of milling processes

PubMed Central

Dombovari, Zoltan; Stepan, Gabor

2015-01-01

A modal-based model of milling machine tools subjected to time-periodic nonlinear cutting forces is introduced. The model describes the phenomenon of bistability for certain cutting parameters. In engineering, these parameter domains are referred to as unsafe zones, where steady-state milling may switch to chatter for certain perturbations. In mathematical terms, these are the parameter domains where the periodic solution of the corresponding nonlinear, time-periodic delay differential equation is linearly stable, but its domain of attraction is limited due to the existence of an unstable quasi-periodic solution emerging from a secondary Hopf bifurcation. A semi-numerical method is presented to identify the borders of these bistable zones by tracking the motion of the milling tool edges as they might leave the surface of the workpiece during the cutting operation. This requires the tracking of unstable quasi-periodic solutions and the checking of their grazing to a time-periodic switching surface in the infinite-dimensional phase space. As the parameters of the linear structural behaviour of the tool/machine tool system can be obtained by means of standard modal testing, the developed numerical algorithm provides efficient support for the design of milling processes with quick estimates of those parameter domains where chatter can still appear in spite of setting the parameters into linearly stable domains. PMID:26303918

Substantial replacement of lactose with fat in a high-lactose milk replacer diet increases liver fat accumulation but does not affect insulin sensitivity in veal calves.

PubMed

Pantophlet, A J; Gerrits, W J J; Vonk, R J; van den Borne, J J G C

2016-12-01

In veal calves, the major portion of digestible energy intake originates from milk replacer (MR), with lactose and fat contributing approximately 45 and 35%, respectively. In veal calves older than 4 mo, prolonged high intakes of MR may lead to problems with glucose homeostasis and insulin sensitivity, ultimately resulting in sustained insulin resistance, hepatic steatosis, and impaired animal performance. The contribution of each of the dietary energy sources (lactose and fat) to deteriorated glucose homeostasis and insulin resistance is currently unknown. Therefore, an experiment was designed to compare the effects of a high-lactose and a high-fat MR on glucose homeostasis and insulin sensitivity in veal calves. Sixteen male Holstein-Friesian calves (120±2.8kg of BW) were assigned to either a high-lactose (HL) or a high-fat (HF) MR for 13 consecutive weeks. After at least 7 wk of adaptation, whole-body insulin sensitivity and insulin secretion were assessed by euglycemic-hyperinsulinemic and hyperglycemic clamps, respectively. Postprandial blood samples were collected to assess glucose, insulin, and triglyceride responses to feeding, and 24-h urine was collected to quantify urinary glucose excretion. At the end of the trial, liver and muscle biopsies were taken to assess triglyceride contents in these tissues. Long-term exposure of calves to HF or HL MR did not affect whole-body insulin sensitivity (averaging 4.2±0.5×10 -2 [(mg/kg∙min)/(μU/mL)]) and insulin secretion. Responses to feeding were greater for plasma glucose and tended to be greater for plasma insulin in HL calves than in HF calves. Urinary glucose excretion was substantially higher in HL calves (75±13g/d) than in HF calves (21±6g/d). Muscle triglyceride content was not affected by treatment and averaged 4.5±0.6g/kg, but liver triglyceride content was higher in HF calves (16.4±0.9g/kg) than in HL calves (11.2±0.7g/kg), indicating increased hepatic fat accumulation. We conclude that

Experimental analysis of the dynamical response of energy harvesting devices based on bistable laminated plates.

PubMed

Syta, A; Bowen, C R; Kim, H A; Rysak, A; Litak, G

The use of bistable laminates is a potential approach to realize broadband piezoelectric based energy harvesting systems. In this paper the dynamic response of a piezoelectric material attached to a bistable laminate plate is examined based on the experimental generated voltage time series. The system was subjected to harmonic excitations and exhibited single-well and snap-through vibrations of both periodic and chaotic character. To identify the dynamics of the system response we examined the frequency spectrum, bifurcation diagrams, phase portraits, and the 0-1 test.

Structural characterization of glucosylated lactose derivatives synthesized by the Lactobacillus reuteri GtfA and Gtf180 glucansucrase enzymes.

PubMed

Pham, Hien T T; Dijkhuizen, Lubbert; van Leeuwen, Sander S

2017-09-08

Glucansucrase enzymes from lactic acid bacteria are receiving strong interest because of their wide range of gluco-oligosaccharide and polysaccharide products from sucrose, some of which have prebiotic potential. Glucansucrases GtfA and Gtf180 from Lactobacillus reuteri strains are known to convert sucrose into α-glucans with different types of linkages, but also to use other molecules as acceptor substrates. Here we report that incubation of (N-terminally truncated versions of) these enzymes with lactose plus sucrose resulted in synthesis of at least 5 glucosylated lactose products of a degree of polymerization (DP) of 3-4. Only glucansucrase Gtf180-ΔN also produced larger lactose-based oligosaccharides (up to DP9). Structural characterization of the glucosylated lactose products DP3-4 revealed glycosidic bonds other than (α1→4)/(α1→6) typical for GtfA-ΔN and (α1→3)/(α1→6) typical for Gtf180-ΔN: Both GtfA-ΔN and Gtf180-ΔN now introduced a glucosyl residue (α1→3)- or (α1→4)-linked to the non-reducing galactose unit of lactose. Both enzymes also were able to introduce a glucosyl residue (α1→2)-linked to the reducing glucose unit of lactose. These lactose derived oligosaccharides potentially are interesting prebiotic compounds. Copyright © 2017 Elsevier Ltd. All rights reserved.

Cloning, sequencing, and characterization of the Bacillus subtilis biotin biosynthetic operon.

PubMed

Bower, S; Perkins, J B; Yocum, R R; Howitt, C L; Rahaim, P; Pero, J

1996-07-01

A 10-kb region of the Bacillus subtilis genome that contains genes involved in biotin-biosynthesis was cloned and sequenced. DNA sequence analysis indicated that B. subtilis contains homologs of the Escherichia coli and Bacillus sphaericus bioA, bioB, bioD, and bioF genes. These four genes and a homolog of the B. sphaericus bioW gene are arranged in a single operon in the order bioWAFDR and are followed by two additional genes, bioI and orf2. bioI and orf2 show no similarity to any other known biotin biosynthetic genes. The bioI gene encodes a protein with similarity to cytochrome P-450s and was able to complement mutations in either bioC or bioH of E. coli. Mutations in bioI caused B. subtilis to grow poorly in the absence of biotin. The bradytroph phenotype of bioI mutants was overcome by pimelic acid, suggesting that the product of bioI functions at a step prior to pimelic acid synthesis. The B. subtilis bio operon is preceded by a putative vegetative promoter sequence and contains just downstream a region of dyad symmetry with homology to the bio regulatory region of B. sphaericus. Analysis of a bioW-lacZ translational fusion indicated that expression of the biotin operon is regulated by biotin and the B. subtilis birA gene.

Cloning, sequencing, and characterization of the Bacillus subtilis biotin biosynthetic operon.

PubMed Central

Bower, S; Perkins, J B; Yocum, R R; Howitt, C L; Rahaim, P; Pero, J

1996-01-01

A 10-kb region of the Bacillus subtilis genome that contains genes involved in biotin-biosynthesis was cloned and sequenced. DNA sequence analysis indicated that B. subtilis contains homologs of the Escherichia coli and Bacillus sphaericus bioA, bioB, bioD, and bioF genes. These four genes and a homolog of the B. sphaericus bioW gene are arranged in a single operon in the order bioWAFDR and are followed by two additional genes, bioI and orf2. bioI and orf2 show no similarity to any other known biotin biosynthetic genes. The bioI gene encodes a protein with similarity to cytochrome P-450s and was able to complement mutations in either bioC or bioH of E. coli. Mutations in bioI caused B. subtilis to grow poorly in the absence of biotin. The bradytroph phenotype of bioI mutants was overcome by pimelic acid, suggesting that the product of bioI functions at a step prior to pimelic acid synthesis. The B. subtilis bio operon is preceded by a putative vegetative promoter sequence and contains just downstream a region of dyad symmetry with homology to the bio regulatory region of B. sphaericus. Analysis of a bioW-lacZ translational fusion indicated that expression of the biotin operon is regulated by biotin and the B. subtilis birA gene. PMID:8763940

Double-well chimeras in 2D lattice of chaotic bistable elements

NASA Astrophysics Data System (ADS)

Shepelev, I. A.; Bukh, A. V.; Vadivasova, T. E.; Anishchenko, V. S.; Zakharova, A.

2018-01-01

We investigate spatio-temporal dynamics of a 2D ensemble of nonlocally coupled chaotic cubic maps in a bistability regime. In particular, we perform a detailed study on the transition ;coherence - incoherence; for varying coupling strength for a fixed interaction radius. For the 2D ensemble we show the appearance of amplitude and phase chimera states previously reported for 1D ensembles of nonlocally coupled chaotic systems. Moreover, we uncover a novel type of chimera state, double-well chimera, which occurs due to the interplay of the bistability of the local dynamics and the 2D ensemble structure. Additionally, we find double-well chimera behavior for steady states which we call double-well chimera death. A distinguishing feature of chimera patterns observed in the lattice is that they mainly combine clusters of different chimera types: phase, amplitude and double-well chimeras.

Thiol-modified MoS2 nanosheets as a functional layer for electrical bistable devices

NASA Astrophysics Data System (ADS)

Li, Guan; Tan, Fenxue; Lv, Bokun; Wu, Mengying; Wang, Ruiqi; Lu, Yue; Li, Xu; Li, Zhiqiang; Teng, Feng

2018-01-01

Molybdenum disulfide nanosheets have been synthesized by one-pot method using 1-ODT as sulfur source and surfactant. The structure, morphology and optical properties of samples were investigated by XRD, FTIR, Abs spectrum and TEM patterns. The XRD pattern indicated that the as-obtained MoS2 belong to hexagonal system. The as-obtained MoS2 nanosheets blending with PVK could be used to fabricate an electrically bistable devices through a simple spin-coating method and the device exhibited an obvious electrical bistability properties. The charge transport mechanism of the device was discussed based on the filamentary switching models.

Optical bi-stable shutter development/improvement

NASA Astrophysics Data System (ADS)

Lizon, J. L.; Haddad, N.; Castillo, R.

2012-09-01

Two of the VLT instruments (Giraffe and VIMOS) are using the large magnetic E/150 from Prontor (with an aperture diameter of 150 mm). As we were facing an unacceptable number of failures with this component some improvement plan was discussed already in 2004. The final decision for starting this program was conditioned by the decision from the constructor to stop the production. The opportunity was taken to improve the design building a fully bi-stable mechanism in order to reduce the thermal dissipation. The project was developed in collaboration between the two main ESO sites doing the best use of the manpower and of the technical capability available at the two centers. The project took advantage of the laser Mask Manufacturing Unit and the invar sheets used to prepare the VIMOS MOS mask to fabricate the shutter petals. Our paper describes the development including the intensive and long optimization period. To conclude this optimization we proceed with a long life test on two units. These units have demonstrate a very high level of reliability (up to 100 000 cycles without failure which can be estimated to an equivalent 6 years of operation of the instrument) A new bi-stable shutter driver and controller have also been developed. Some of the highlights of this unit are the fully configurable coil driving parameters, usage of braking strategy to dump mechanical vibration and reduce mechanical wearing, configurable usage of OPEN and CLOSE sensors, non volatile storage of parameters, user friendly front panel interface.

Silencing of Essential Genes within a Highly Coordinated Operon in Escherichia coli

PubMed Central

Hohmeier, Angela; Stone, Timothy C.; Offord, Victoria; Sarabia, Francisco; Garcia-Ruiz, Cristina; Good, Liam

2015-01-01

Essential bacterial genes located within operons are particularly challenging to study independently because of coordinated gene expression and the nonviability of knockout mutants. Essentiality scores for many operon genes remain uncertain. Antisense RNA (asRNA) silencing or in-frame gene disruption of genes may help establish essentiality but can lead to polar effects on genes downstream or upstream of the target gene. Here, the Escherichia coli ribF-ileS-lspA-fkpB-ispH operon was used to evaluate the possibility of independently studying an essential gene using expressed asRNA and target gene overexpression to deregulate coupled expression. The gene requirement for growth in conditional silencing strains was determined by the relationship of target mRNA reduction with growth inhibition as the minimum transcript level required for 50% growth (MTL50). Mupirocin and globomycin, the protein inhibitors of IleS and LspA, respectively, were used in sensitization assays of strains containing both asRNA-expressing and open reading frame-expressing plasmids to examine deregulation of the overlapping ileS-lspA genes. We found upstream and downstream polar silencing effects when either ileS or lspA was silenced, indicating coupled expression. Weighted MTL50 values (means and standard deviations) of ribF, ileS, and lspA were 0.65 ± 0.18, 0.64 ± 0.06, and 0.76 ± 0.10, respectively. However, they were not significantly different (P = 0.71 by weighted one-way analysis of variance). The gene requirement for ispH could not be determined due to insufficient growth reduction. Mupirocin and globomycin sensitization experiments indicated that ileS-lspA expression could not be decoupled. The results highlight the inherent challenges associated with genetic analyses of operons; however, coupling of essential genes may provide opportunities to improve RNA-silencing antimicrobials. PMID:26070674

Study of thermally-induced optical bistability and the role of surface treatments in Si-based mid-infrared photonic crystal cavities.

PubMed

Shankar, Raji; Bulu, Irfan; Leijssen, Rick; Lončar, Marko

2011-11-21

We report the observation of optical bistability in Si-based photonic crystal cavities operating around 4.5 µm. Time domain measurements indicate that the source of this optical bistability is thermal, with a time constant on the order of 5 µs. Quality (Q) factor improvement is shown by the use of surface treatments (wet processes and annealing), resulting in a significant increase in Q-factor, which in our best devices is on the order of ~45,000 at 4.48 µm. After annealing in a N(2) environment, optical bistability is no longer seen in our cavities. © 2011 Optical Society of America

Characterization of a lactose-responsive promoter of ATP-binding cassette (ABC) transporter gene from Lactobacillus acidophilus 05-172.

PubMed

Zeng, Zhu; Zuo, Fanglei; Yu, Rui; Zhang, Bo; Ma, Huiqin; Chen, Shangwu

2017-09-01

A novel lactose-responsive promoter of the ATP-binding cassette (ABC) transporter gene Lba1680 of Lactobacillus acidophilus strain 05-172 isolated from a traditionally fermented dairy product koumiss was characterized. In L. acidophilus 05-172, expression of Lba1680 was induced by lactose, with lactose-induced transcription of Lba1680 being 6.1-fold higher than that induced by glucose. This is in contrast to L. acidophilus NCFM, a strain isolated from human feces, in which expression of Lba1680 and Lba1679 is induced by glucose. Both gene expression and enzyme activity assays in L. paracasei transformed with a vector containing the inducible Lba1680 promoter (PLba1680) of strain 05-172 and a heme-dependent catalase gene as reporter confirmed that PLba1680 is specifically induced by lactose. Its regulatory expression could not be repressed by glucose, and was independent of cAMP receptor protein. This lactose-responsive promoter might be used in the expression of functional genes in L. paracasei incorporated into a lactose-rich environment, such as dairy products. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Mutants of the lactose carrier of Escherichia coli which show altered sugar recognition plus a severe defect in sugar accumulation.

PubMed

Varela, M F; Wilson, T H; Rodon-Rivera, V; Shepherd, S; Dehne, T A; Rector, A C

2000-04-01

Lactose and melibiose are actively accumulated by the wild-type Escherichia coli lactose carrier, which is an integral membrane protein energized by the proton motive force. Mutants of the E. coli lactose carrier were isolated by their ability to grow on minimal plates with succinate plus IPTG in the presence of the toxic lactose analog beta-thio-o-nitrophenylgalactoside (TONPG). TONPG-resistant mutants were streaked on melibiose MacConkey indicator plates, and red clones were picked. These melibiose positive mutants were then streaked on lactose MacConkey plates, and white clones were picked. Transport assays indicated that the mutants had altered sugar recognition and a defect in sugar accumulation. The mutants had a poor apparent K(m) for both lactose and melibiose in transport. One mutant had almost no ability to take up lactose, but melibiose downhill transport was 58% (V(max)) of normal. All of the mutants accumulated methyl-alpha-d-galactopyranoside (TMG) to only 8% or less of normal, and two failed to accumulate. Immunoblot analysis of the mutant lactose carrier proteins indicated that loss of sugar transport activity was not due to loss of expression in the membrane. Nucleotide sequencing of the lacY gene from the mutants revealed changes in the following amino acids of the lactose carrier: M23I, W151L, G257D, A295D and G377V. Two of the mutants (G257D and G377V) are novel in that they represent the first amino acids in periplasmic loops to be implicated with changes in sugar recognition. We conclude that the amino acids M23, W151, G257, A295 and G377 of the E. coli lactose carrier play either a direct or an indirect role in sugar recognition and accumulation.

A simple photometric factor in perceived depth order of bistable transparency patterns.

PubMed

Fukiage, Taiki; Oishi, Takeshi; Ikeuchi, Katsushi

2014-05-05

Previous studies on perceptual transparency defined the photometric condition in which perceived depth ordering between two surfaces becomes ambiguous. Even under this bistable transparency condition, it is known that depth-order perceptions are often biased toward one specific interpretation (Beck, Prazdny, & Ivry, 1984; Delogu, Fedorov, Belardinelli, & van Leeuwen, 2010; Kitaoka, 2005; Oyama & Nakahara, 1960). In this study, we examined what determines the perceived depth ordering for bistable transparency patterns using stimuli that simulated two partially overlapping disks resulting in four regions: a (background), b (portion of right disk), p (portion of left disk), and q (shared region). In contrast to the previous theory that proposed contributions of contrast against the background region (i.e., contrast at contour b/a and contrast at contour p/a) to perceived depth order in bistable transparency patterns, the present study demonstrated that contrast against the background region has little influence on perceived depth order compared with contrast against the shared region (i.e., contrast at contour b/q and contrast at contour p/q). In addition, we found that the perceived depth ordering is well predicted by a simpler model that takes into consideration only relative size of lightness difference against the shared region. Specifically, the probability that the left disk is perceived as being in front is proportional to (|b - q| - |p - q|) / (|b - q| + |p - q|) calculated based on lightness.

A novel extractive fermentation process for propionic acid production from whey lactose

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, V.P.; Yang, Shangtian

An extractive fermentation process was developed to produce propionate from lactose. The bacterium Propionibacterium acidipropionici was immobilized in a spiral wound, fibrous matrix packed in the reactor. Propionic acid is the major product from lactose fermentation, with acetic acid and carbon dioxide as byproducts. Propionic acid is a strong inhibitor to this fermentation. A tertiary amine was used to selectively extract propionic acid from the bioreactor, hence enhancing reactor productivity by over 100%. The authors also speculate that by selectively extracting propionic acid, lactose metabolism can be directed to yield more propionate and less byproducts. Other advantages of extractive fermentationmore » include better pH control and a purer product. The propionic acid present in the extractant can be easily stripped with small amounts of an alkaline solution, resulting in a concentrated propionate salt. The extractant was also regenerated in this stripping step. Thus, the process is energy-efficient and economically attractive.« less

Fructose and lactose intolerance and malabsorption testing: the relationship with symptoms in functional gastrointestinal disorders.

PubMed

Wilder-Smith, C H; Materna, A; Wermelinger, C; Schuler, J

2013-06-01

The association of fructose and lactose intolerance and malabsorption with the symptoms of different functional gastrointestinal disorders (FGID) remains unclear. To investigate the prevalence of fructose and lactose intolerance (symptom induction) and malabsorption and their association with clinical gastrointestinal (GI) as well as non-GI symptoms in FGID and the outcome of dietary intervention. Fructose and lactose intolerance (defined by positive symptom index) and malabsorption (defined by increased hydrogen/methane) were determined in 1372 FGID patients in a single centre using breath testing. Results were correlated with clinical symptoms in different FGID Rome III subgroups. The effectiveness of a targeted saccharide-reduced diet was assessed after 6-8 weeks. Intolerance prevalence across all FGIDs was 60% to fructose, 51% to lactose and 33% to both. Malabsorption occurred in 45%, 32% and 16% respectively. There were no differences in intolerance or malabsorption prevalence between FGID subgroups. FGID symptoms correlated with symptoms evoked during testing (r = 0.35-0.61. P < 0.0001), but not with malabsorption. Non-GI symptoms occurred more commonly in patients with intolerances. Methane breath levels were not associated with constipation using several cut-off thresholds. Adequate symptom relief was achieved in >80% of intolerant patients, irrespective of malabsorption. Fructose and lactose intolerances are common in FGID and associated with increased non-GI symptoms, but not with specific FGID subtypes. Symptoms experienced during breath testing, but not malabsorption, correlate with FGID symptoms. Effective symptom relief with dietary adaptation is not associated with malabsorption. Mechanisms relating to the generation of GI and non-GI symptoms due to lactose and fructose in FGID need to be explored further. © 2013 Blackwell Publishing Ltd.

Fructose and lactose intolerance and malabsorption testing: the relationship with symptoms in functional gastrointestinal disorders

PubMed Central

Wilder-Smith, C H; Materna, A; Wermelinger, C; Schuler, J

2013-01-01

Background The association of fructose and lactose intolerance and malabsorption with the symptoms of different functional gastrointestinal disorders (FGID) remains unclear. Aim To investigate the prevalence of fructose and lactose intolerance (symptom induction) and malabsorption and their association with clinical gastrointestinal (GI) as well as non-GI symptoms in FGID and the outcome of dietary intervention. Methods Fructose and lactose intolerance (defined by positive symptom index) and malabsorption (defined by increased hydrogen/methane) were determined in 1372 FGID patients in a single centre using breath testing. Results were correlated with clinical symptoms in different FGID Rome III subgroups. The effectiveness of a targeted saccharide-reduced diet was assessed after 6–8 weeks. Results Intolerance prevalence across all FGIDs was 60% to fructose, 51% to lactose and 33% to both. Malabsorption occurred in 45%, 32% and 16% respectively. There were no differences in intolerance or malabsorption prevalence between FGID subgroups. FGID symptoms correlated with symptoms evoked during testing (r = 0.35–0.61. P < 0.0001), but not with malabsorption. Non-GI symptoms occurred more commonly in patients with intolerances. Methane breath levels were not associated with constipation using several cut-off thresholds. Adequate symptom relief was achieved in >80% of intolerant patients, irrespective of malabsorption. Conclusions Fructose and lactose intolerances are common in FGID and associated with increased non-GI symptoms, but not with specific FGID subtypes. Symptoms experienced during breath testing, but not malabsorption, correlate with FGID symptoms. Effective symptom relief with dietary adaptation is not associated with malabsorption. Mechanisms relating to the generation of GI and non-GI symptoms due to lactose and fructose in FGID need to be explored further. PMID:23574302

Effect of pelvic irradiation of lactose absorption. [. gamma. rays or x rays were used in gynecologic malignancy therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stryker, J.A.; Mortel, R.; Hepner, G.W.

1978-01-01

Twenty-four patients undergoing pelvic irradiation for gynecologic malignancies had /sup 14/C-lactose breath tests performed in the first and fifth weeks of their treatment. The /sup 14/C-lactose breath test was performed by administering 2 ..mu..Ci of /sup 14/C-lactose by mouth along with 50 g of lactose. Breath samples were collected in ethanolic hyamine 1, 2, and 3 hr later; the radioactivity of the trapped /sup 14/CO/sub 2/ was determined by liquid scintillation spectroscopy. In the first week of treatment the percentage of administered /sup 14/C excreted as /sup 14/CO/sub 2/ at 1, 2, and 3 hr was 1.7 +- 0.8% (meanmore » +- SD), 4.5 +- 1.6%, and 5.8 +- 1.4%, respectively. In the fifth week of treatment the 1-hr, 2-hr, and 3-hr values were 1.2 +- 0.9%, 3.6 +- 2.0%, and 4.7 +- 1.9%, respectively. The difference between the first week and fifth week test results at 1, 2, and 3 hr was statistically significant (t = 2.64, p < 0.02), (t = 2.24, p < 0.05), (t = 2.95, p < 0.01). There was a negative correlation between the 1-hr /sup 14/C-lactose breath test results in the fifth week and the stool frequency at that time (r = -0.44, p < 0.05). Seven of 12 patients whose 1 hr /sup 14/C-lactose breath test results in the fifth week were below normal (<1.2%) had nausea at that time. The data suggest that in some patients, lactose malabsorption as a result of the effect of radiation on small intestinal function may be etiologically related to the symptoms of nausea and diarrhea which occur commonly in patients who are undergoing pelvic irradiation. In addition, the results suggest that lactose-containing foods should be restricted in some patients who are undergoing pelvic irradiation to prevent symptoms resulting from radiation-induced lactose intolerance.« less

A comparison of diagnostic tests for lactose malabsorption - which one is the best?

PubMed Central

2009-01-01

Background Perceived milk intolerance is a common complaint, and tests for lactose malabsorption (LM) are unreliable. This study assesses the agreement between diagnostic tests for LM and describes the diagnostic properties of the tests. Methods Patients above 18 years of age with suspected LM were included. After oral intake of 25 g lactose, a combined test with measurement of serum glucose (s-glucose) and hydrogen (H2) and methane (CH4) in expired air was performed and symptoms were recorded. In patients with discrepancies between the results, the combined test was repeated and a gene test for lactose non-persistence was added. The diagnosis of LM was based on an evaluation of all tests. The following tests were compared: Increase in H2, CH4, H2+CH4 and H2+CH4x2 in expired air, increase in s-glucose, and symptoms. The agreement was calculated and the diagnostic properties described. Results Sixty patients were included, seven (12%) had LM. The agreement (kappa-values) between the methods varied from 0.25 to 0.91. The best test was the lactose breath test with measurement of the increase in H2 + CH4x2 in expired air. With a cut-off level < 18 ppm, the area under the ROC-curve was 0.967 and sensitivity was 100%. This shows that measurement of CH4 in addition to H2 improves the diagnostic properties of the breath test. Conclusion The agreement between commonly used methods for the diagnosis of LM was unsatisfactory. A lactose breath test with measurement of H2 + CH4x2 in expired air had the best diagnostic properties. PMID:19878587

One-third of children with lactose intolerance managed to achieve a regular diet at the three-year follow-up point.

PubMed

Yerushalmy-Feler, Anat; Soback, Hagai; Lubetzky, Ronit; Ben-Tov, Amir; Dali-Levy, Margalit; Galai, Tut; Cohen, Shlomi

2018-03-05

This study described outcomes following treatment for lactose intolerance, which is common in children. The medical records of children aged 6-18 years who underwent lactose hydrogen breath testing at Dana-Dwek Children's Hospital, Tel Aviv, Israel, from August 2012 to August 2014 were analysed. We compared 154 children with gastrointestinal symptoms and positive lactose hydrogen breath tests to 49 children with negative test results. Of the 154 children in the study group, 89 (57.8%) were advised to follow a lactose-restricted diet, 32 (20.8%) were advised to avoid lactose completely, 18 (11.7%) were instructed to use substitute enzymes, and 15 (9.7%) did not receive specific recommendations. Only 11 patients (7.1%) received recommendations to add calcium-rich foods or calcium supplements to their diet. Lactose reintroduction was attempted in 119 of 154 patients (77.3%), and 65 of 154 (42.2%) experienced clinical relapses. At the final follow-up of 3.3 years, 62.3% of the study children were still observing a restricted diet. Older children and those who were symptomatic during lactose hydrogen breath testing were more likely to be on a prolonged restricted diet. Our long-term follow-up of lactose-intolerant children showed that only a third were able to achieve a regular diet. ©2018 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

[Food intolerances caused by enzyme defects and carbohydrate malassimiliations : Lactose intolerance and Co].

PubMed

Schäfer, Christiane

2016-06-01

Apart from allergic conditions, carbohydrate malassimiliations (sugar metabolism disorders) are classified within the group of food intolerances. These dose-dependent, yet non-immunological reactions require gastroenterological or internal diagnosis following nutritional therapy. Intolerances to carbohydrates such as lactose (milk sugar) and fructose (fruit sugar) in addition to sugar alcohols (sorbitol, mannitol, lactitol etc.) have been gaining increasing attention in recent decades as they are the cause of a wide range of gastrointestinal symptoms. There are currently various options for both diagnosis and therapy that differ notably in terms of effort, costs, and efficiency. Nutritional change and patient education are the bases of therapy. Non-observance of the trigger will result in increasing complaints and possibly even more infections, e.g., diverticula, rectal disorders, bacterial miscolonization, bile acid malabsorption). For an optimal therapy, the following sugar metabolism disorders have to be differentiated: hypolactasia versus lactose maldigestion, fructose malabsorption versus fructose overload, combined lactose and fructose intolerance, and isolated adverse reactions against sorbitol.For the medical conditions listed above, a three- or four-stage treatment regimen is recommended. Extensive dietary restrictions with regard to the relevant sugar, except for lactose, should not be maintained over a longer period of time.

Bioelectric memory: modeling resting potential bistability in amphibian embryos and mammalian cells.

PubMed

Law, Robert; Levin, Michael

2015-10-15

Bioelectric gradients among all cells, not just within excitable nerve and muscle, play instructive roles in developmental and regenerative pattern formation. Plasma membrane resting potential gradients regulate cell behaviors by regulating downstream transcriptional and epigenetic events. Unlike neurons, which fire rapidly and typically return to the same polarized state, developmental bioelectric signaling involves many cell types stably maintaining various levels of resting potential during morphogenetic events. It is important to begin to quantitatively model the stability of bioelectric states in cells, to understand computation and pattern maintenance during regeneration and remodeling. To facilitate the analysis of endogenous bioelectric signaling and the exploitation of voltage-based cellular controls in synthetic bioengineering applications, we sought to understand the conditions under which somatic cells can stably maintain distinct resting potential values (a type of state memory). Using the Channelpedia ion channel database, we generated an array of amphibian oocyte and mammalian membrane models for voltage evolution. These models were analyzed and searched, by simulation, for a simple dynamical property, multistability, which forms a type of voltage memory. We find that typical mammalian models and amphibian oocyte models exhibit bistability when expressing different ion channel subsets, with either persistent sodium or inward-rectifying potassium, respectively, playing a facilitative role in bistable memory formation. We illustrate this difference using fast sodium channel dynamics for which a comprehensive theory exists, where the same model exhibits bistability under mammalian conditions but not amphibian conditions. In amphibians, potassium channels from the Kv1.x and Kv2.x families tend to disrupt this bistable memory formation. We also identify some common principles under which physiological memory emerges, which suggest specific strategies for

Self-perceived lactose intolerance results in lower intakes of calcium and dairy foods and is associated with hypertension and diabetes in adults.

PubMed

Nicklas, Theresa A; Qu, Haiyan; Hughes, Sheryl O; He, Mengying; Wagner, Sara E; Foushee, Herman R; Shewchuk, Richard M

2011-07-01

Self-perceived lactose intolerance may result in adverse dietary modifications; thus, more studies are needed to understand the prevalence of self-perceived lactose intolerance and how it relates to calcium intake and selected health conditions. The objective was to examine the effects of self-perceived lactose intolerance as it relates to calcium intake and specific health problems that have been attributed to reduced intakes of calcium and dairy foods in a nationally representative multiethnic sample of adults. This was a cross-sectional study in a national sample of 3452 adults. The relation between self-perceived lactose intolerance, calcium intakes, and physician-diagnosed health conditions was analyzed by using linear regression analyses. Of the total sample, 12.3% of respondents perceived themselves to be lactose intolerant. The age-adjusted prevalence of self-perceived lactose intolerance was 7.8% for non-Hispanic whites, 20.1% for non-Hispanic blacks, and 8.8% for Hispanics. Respondents with self-perceived lactose intolerance had significantly lower (P < 0.05) average daily calcium intakes from dairy foods than did those without self-perceived lactose intolerance. A significantly higher (P < 0.05) percentage of respondents with self-perceived lactose intolerance than of respondents without self-perceived lactose intolerance reported having physician-diagnosed diabetes and hypertension. The odds of self-reported physician-diagnosed diabetes or hypertension decreased by factors of 0.70 and 0.60, respectively, for a 1000-mg increase in calcium intake from dairy foods per day. Self-perceived lactose-intolerant respondents had a significantly lower calcium intake from dairy foods and reported having a significantly higher rate of physician-diagnosed diabetes and hypertension.

The rec A operon: a novel stress response gene cluster in Bacteroides fragilis

PubMed Central

Nicholson, Samantha A; Smalley, Darren; Smith, C. Jeffrey; Abratt, Valerie R

2014-01-01

Bacteroides fragilis, an opportunistic pathogen of humans, is a leading cause of bacteraemias and anaerobic abscesses which are often treated with metronidazole, a drug which damages DNA. This study investigated the responses of the B. fragilis recA three gene operon to the stress experienced during metronidazole treatment and exposure to reactive oxygen species simulating those generated by the host immune system during infection. A transcriptionally regulated response was observed using quantitative RT-PCR after metronidazole and hydrogen peroxide treatment, with all three genes being upregulated under stress conditions. In vivo and in vitro analysis of the functional role of the second gene of the operon was done using heterologous complementation and protein expression (in Escherichia coli), with subsequent biochemical assay. This gene encoded a functional bacterioferritin co-migratory protein (BCP) which was thiol-specific and had antioxidant properties, including protection of the glutamine synthetase III enzyme. This in vitro data supports the hypothesis that the genes of the operon may be involved in protection of the bacteria from the oxidative burst during tissue invasion and may play a significant role in bacterial survival and metronidazole resistance during treatment of B. fragilis infections. PMID:24703997

Characterization of the regulation of a plant polysaccharide utilization operon and its role in biofilm formation in Bacillus subtilis

PubMed Central

Habib, Cameron; Yu, Yiyang; Gozzi, Kevin; Ching, Carly; Shemesh, Moshe

2017-01-01

The soil bacterium Bacillus subtilis is often found in association with plants in the rhizosphere. Previously, plant polysaccharides have been shown to stimulate formation of root-associated multicellular communities, or biofilms, in this bacterium, yet the underlying mechanism is not fully understood. A five-gene gan operon (ganSPQAB) in B. subtilis has recently been shown to be involved in utilization of the plant-derived polysaccharide galactan. Despite these findings, molecular details about the regulation of the operon and the role of the operon in biofilm formation remain elusive. In this study, we performed comprehensive genetic analyses on the regulation of the gan operon. We show that this operon is regulated both by a LacI-like transcription repressor (GanR), which directly binds to pairs of inverted DNA repeats in the promoter region of the operon, and by the catabolite control protein A (CcpA). Derepression can be triggered by the presence of the inducer β-1,4-galactobiose, a hydrolysis product of galactan, or in situ when B. subtilis cells are associated with plant roots. In addition to the transcriptional regulation, the encoded ß-galactosidase GanA (by ganA), which hydrolyzes ß-1,4-galactobiose into galactose, is inhibited at the enzymatic level by the catalytic product galactose. Thus, the galactan utilization pathway is under complex regulation involving both positive and negative feedback mechanisms in B. subtilis. We discuss about the biological significance of such complex regulation as well as a hypothesis of biofilm induction by galactan via multiple mechanisms. PMID:28617843

Electroencephalograph (EEG) study of brain bistable illusion

NASA Astrophysics Data System (ADS)

Meng, Qinglei; Hong, Elliot; Choa, Fow-Sen

2015-05-01

Bistable illusion reflects two different kinds of interpretations for a single image, which is currently known as a competition between two groups of antagonism of neurons. Recent research indicates that these two groups of antagonism of neurons express different comprehension, while one group is emitting a pulse, the other group will be restrained. On the other hand, when this inhibition mechanism becomes weaker, the other antagonism neurons group will take over the interpretation. Since attention plays key roles controlling cognition, is highly interesting to find the location and frequency band used by brain (with either top-down or bottom-up control) to reach deterministic visual perceptions. In our study, we used a 16-channel EEG system to record brain signals from subjects while conducting bistable illusion testing. An extra channel of the EEG system was used for temporal marking. The moment when subjects reach a perception switch, they click the channel and mark the time. The recorded data were presented in form of brain electrical activity map (BEAM) with different frequency bands for analysis. It was found that the visual cortex in the on the right side between parietal and occipital areas was controlling the switching of perception. In the periods with stable perception, we can constantly observe all the delta, theta, alpha and beta waves. While the period perception is switching, almost all theta, alpha, and beta waves were suppressed by delta waves. This result suggests that delta wave may control the processing of perception switching.

Exploration of Structural Changes in Lactose Permease on Sugar Binding and Proton Transport through Atomistic Simulations

NASA Astrophysics Data System (ADS)

Liu, Jin; Jewel, Yead; Dutta, Prashanta

2017-11-01

Escherichia coli lactose permease (LacY) actively transports lactose and other galactosides across cell membranes through lactose/H+ symport process. Lactose/H+ symport is a highly complex process that involves large-scale protein conformational changes. The complete picture of lactose/H+ symport is largely unclear. In this work, we develop the force field for sugar molecules compatible with PACE, a hybrid and coarse-grained force field that couples the united-atom protein models with the coarse-grained MARTINI water/lipid. After validation, we implement the new force field to investigate the binding of a β-D-galactopyranosyl-1-thio- β-D-galactopyranoside (TDG) molecule to a wild-type LacY. Transitions from inward-facing to outward-facing conformations upon TDG binding and protonation of Glu269 have been achieved from microsecond simulations. Both the opening of the periplasmic side and closure of the cytoplasmic side of LacY are consistent with experiments. Our analysis suggest that the conformational changes of LacY are a cumulative consequence of inter-domain H-bonds breaking at the periplasmic side, inter-domain salt-bridge formation at the cytoplasmic side, as well as the TDG orientational changes during the transition. This work is supported by US National Science Foundation under Grant No. CBET-1604211.

Simultaneous hydrolysis and co-fermentation of whey lactose with wheat for ethanol production.

PubMed

Jin, Yiqiong; Parashar, Archana; Mason, Beth; Bressler, David C

2016-12-01

Whey permeate was used as a co-substrate to replace part of the wheat for ethanol production by Saccharomyces cerevisiae. The simultaneous saccharification and fermentation was achieved with β-galactosidase added at the onset of the fermentation to promote whey lactose hydrolysis. Aspergillus oryzae and Kluyveromyces lactis β-galactosidases were two enzymes selected and used in the co-fermentation of wheat and whey permeate for the comparison of their effectiveness on lactose hydrolysis. The possibility of co-fermentations in both STARGEN and jet cooking systems was investigated in 5L bioreactors. Ethanol yields from the co-fermentations of wheat and whey permeate were evaluated. It was found that A. oryzae β-galactosidase was more efficient for lactose hydrolysis during the co-fermentation and that whey permeate supplementation can contribute to ethanol yield in co-fermentations with wheat. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermal Stability and Kinetic Study of Fluvoxamine Stability in Binary Samples with Lactose.

PubMed

Ghaderi, Faranak; Nemati, Mahboob; Siahi-Shadbad, Mohammad Reza; Valizadeh, Hadi; Monajjemzadeh, Farnaz

2017-04-01

Purpose: In the present study the incompatibility of FLM (fluvoxamine) with lactose in solid state mixtures was investigated. The compatibility was evaluated using different physicochemical methods such as differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and mass spectrometry. Methods: Non-Isothermally stressed physical mixtures were used to calculate the solid-state kinetic parameters. Different thermal models such as Friedman, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) were used for the characterization of the drug-excipient interaction. Results: Overall, the incompatibility of FLM with lactose as a reducing carbohydrate was successfully evaluated and the activation energy of this interaction was calculated. Conclusion: In this research the lactose and FLM Maillard interaction was proved using physicochemical techniques including DSC and FTIR. It was shown that DSC- based kinetic analysis provides fast and versatile kinetic comparison of Arrhenius activation energies for different pharmaceutical samples.

Thermal Stability and Kinetic Study of Fluvoxamine Stability in Binary Samples with Lactose

PubMed Central

Ghaderi, Faranak; Nemati, Mahboob; Siahi-Shadbad, Mohammad Reza; Valizadeh, Hadi; Monajjemzadeh, Farnaz

2017-01-01

Purpose: In the present study the incompatibility of FLM (fluvoxamine) with lactose in solid state mixtures was investigated. The compatibility was evaluated using different physicochemical methods such as differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy and mass spectrometry. Methods: Non-Isothermally stressed physical mixtures were used to calculate the solid–state kinetic parameters. Different thermal models such as Friedman, Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) were used for the characterization of the drug-excipient interaction. Results: Overall, the incompatibility of FLM with lactose as a reducing carbohydrate was successfully evaluated and the activation energy of this interaction was calculated. Conclusion: In this research the lactose and FLM Maillard interaction was proved using physicochemical techniques including DSC and FTIR. It was shown that DSC- based kinetic analysis provides fast and versatile kinetic comparison of Arrhenius activation energies for different pharmaceutical samples. PMID:28507936

Organization and post-transcriptional processing of the psb B operon from chloroplasts of Populus deltoides.

PubMed

Dixit, R; Trivedi, P K; Nath, P; Sane, P V

1999-09-01

Chloroplast genes are typically organized into polycistronic transcription units that give rise to complex sets of mono- and oligo-cistronic overlapping RNAs through a series of processing steps. The psbB operon contains genes for the PSII (psbB, psbT, psbH) and cytochrome b(6)f (petB and petD) complexes which are needed in different amounts during chloroplast biogenesis. The functional significance of gene organization in this polycistronic unit, containing information for two different complexes, is not known and is of interest. To determine the organization and expression of these complexes, studies have been carried out on crop plants by different groups, but not much information is known about trees. We present the nucleotide sequences of PSII genes and RNA profiles of the genes located in the psbB operon from Populus deltoides, a tree species. Although the gene organization of this operon in P. deltoides is similar to that in other species, a few variations have been observed in the processing scheme.

Mathematical model of rhamnolipid production using E.coli bacteria

NASA Astrophysics Data System (ADS)

Adham, Muhammad Fariduddin; Apri, Mochamad; Moeis, Maelita Ramdani

2018-03-01

Rhamnolipid is one of biosurfactants that is widely used in many industries. Despite its wide use, production of rhamnolipid usually involves a pathogen that may endanger our health. To tackle this issue, in iGEM (International Genetically Engineered Machine) competition 2015, our team engineered Escherichia coli (E.coli) to produce rhamnolipid. The bacteria were then put into medium containing glucose and lactose. It turned out that bacteria E. coli produced lower rhamnolipid than that by pseudomonas, therefore a good strategy is required to improve their productivity. We present a mathematical model to describe the production of rhamnolipid by the engineered E coli. Using bifurcation analysis, the equilibrium points of the model and their stabilities were analyzed as the amount of lactose was varied. We show that the system produces bistability behavior for some interval values of lactose. From this analysis we found that to guarantee a high production of rhamnolipid, a high level of lactose is required. To maintain the productivity, however, it is sufficient to maintain the lactose level above a certain threshold value.

Phase dependence of optical bistability and multistability in a four-level quantum system near a plasmonic nanostructure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asadpour, Seyyed Hossein; Rahimpour Soleimani, H., E-mail: Rahimpour@guilan.ac.ir

2016-01-14

The optical bistability and multistability properties of a four-level quantum system near a plasmonic nanostructure embedded in a unidirectional ring cavity are studied theoretically. Two orthogonal circularly polarized laser fields with the same frequency, different phases and electric fields amplitude are interacted by four-level quantum system. It is found that in the presence of the plasmonic nanostructure, the bistable behaviors related to one of the laser fields propagating through the unidirectional ring cavity can be modified by relative phase and amplitude control of another laser fields. Our obtained results show that the optical bistability can be converted into the opticalmore » multistability by varying the value of distance between the quantum system and the surface of the plasmonic nanostructure. Moreover, it is shown that under specific condition related to the distance, the lasing without population inversion can be obtained.« less

A bi-stable nanoelectromechanical non-volatile memory based on van der Waals force

NASA Astrophysics Data System (ADS)

Soon, Bo Woon; Jiaqiang Ng, Eldwin; Qian, You; Singh, Navab; Julius Tsai, Minglin; Lee, Chengkuo

2013-07-01

By using complementary-metal-oxide-semiconductor processes, a silicon based bi-stable nanoelectromechanical non-volatile memory is fabricated and characterized. The main feature of this device is an 80 nm wide and 3 μm high silicon nanofin (SiNF) of a high aspect ratio (1:35). The switching mechanism is realized by electrostatic actuation between two lateral electrodes, i.e., terminals. Bi-stable hysteresis behavior is demonstrated when the SiNF maintains its contact to one of the two terminals by leveraging on van der Waals force even after voltage bias is turned off. The compelling results indicate that this design is promising for realization of high density non-volatile memory application due to its nano-scale footprint and zero on-hold power consumption.

Bistability and hysteresis of the 'Secteur' differentiation are controlled by a two-gene locus in Nectria haematococca

PubMed Central

Graziani, Stéphane; Silar, Philippe; Daboussi, Marie-Josée

2004-01-01

Background Bistability and hysteresis are increasingly recognized as major properties of regulatory networks governing numerous biological phenomena, such as differentiation and cell cycle progression. The full scope of the underlying molecular mechanisms leading to bistability and hysteresis remains elusive. Nectria haemaotcocca, a saprophytic or pathogenic fungus with sexual reproduction, exhibits a bistable morphological modification characterized by a reduced growth rate and an intense pigmentation. Bistability is triggered by the presence or absence of σ, a cytoplasmic determinant. This determinant spreads in an infectious manner in the hyphae of the growing margin, insuring hysteresis of the differentiation. Results Seven mutants specifically affected in the generation of σ were selected through two different screening strategies. The s1 and s2 mutations completely abolish the generation of σ and of its morphological expression, the Secteur. The remaining five mutations promote its constitutive generation, which determines an intense pigmentation but not growth alteration. The seven mutations map at the same locus, Ses (for 'Secteur-specific'). The s2 mutant was obtained by an insertional mutagenesis strategy, which permitted the cloning of the Ses locus. Sequence and transcription analysis reveals that Ses is composed of two closely linked genes, SesA, mutated in the s1 and s2 mutant strains, and SesB, mutated in the s* mutant strains. SesB shares sequence similarity with animal and fungal putative proteins, with potential esterase/lipase/thioesterase activity, whereas SesA is similar to proteins of unknown function present only in the filamentous fungi Fusarium graminearum and Podospora anserina. Conclusions The cloning of Ses provides evidence that a system encoded by two linked genes directs a bistable and hysteretic switch in a eukaryote. Atypical regulatory relations between the two proteins may account for the hysteresis of Secteur differentiation

Study of whey fermentation by kefir immobilized on low cost supports using 14C-labelled lactose.

PubMed

Soupioni, Magdalini; Golfinopoulos, Aristidis; Kanellaki, Maria; Koutinas, Athanasios A

2013-10-01

Brewer's Spent Grains (BSG) and Malt Spent Rootlets (MSR) were used as supports for kefir cells immobilization and the role of lactose uptake rate by kefir in the positive activity of produced biocatalysts during whey fermentation was investigated. Lactose uptake rate by the immobilized cells was recorded using (14)C-labelled lactose and the effect of various conditions (pH, temperature and kind of support) on it and consequently on fermentation time and ethanol production was examined. The results showed that lactose uptake rate was correlated to fermentation rate and increased as temperature was increased up to 30°C at pH 5.5. The same results have been recently noticed by using biocatalysts with Delignified Cellulosic Materials (DCM) and Gluten Pellets (GP), but fermentation time of about 7h by kefir immobilized on DCM and BSG resulted to two fold lower than that on GP and MSR. The highest alcohol concentration was observed by MSR. Copyright © 2012 Elsevier Ltd. All rights reserved.

Hydrogen breath test for the diagnosis of lactose intolerance, is the routine sugar load the best one?

PubMed Central

Argnani, Fiorenza; Camillo, Mauro Di; Marinaro, Vanessa; Foglietta, Tiziana; Avallone, Veronica; Cannella, Carlo; Vernia, Piero

2008-01-01

AIM: To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25. METHODS: Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g. Peak hydrogen production, area under the curve of hydrogen excretion and occurrence of symptoms were recorded. RESULTS: Only 16 patients (17.77%) with positive HBT-25 proved positive at HBT-12.5. Hydrogen production was lower as compared to HBT-25 (peak value 21.55 parts per million (ppm) ± 29.54 SD vs 99.43 ppm ± 40.01 SD; P < 0.001). Symptoms were present in only 13 patients. The absence of symptoms during the high-dose test has a high negative predictive value (0.84) for a negative low-dose test. The presence of symptoms during the first test was not useful for predicting a positive low-dose test (positive predictive value 0.06-0.31). CONCLUSION: Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a “standard” HBT is, in most instances, unnecessary. Thus, the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI, and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance. PMID:18985811

Hydrogen breath test for the diagnosis of lactose intolerance, is the routine sugar load the best one?

PubMed

Argnani, Fiorenza; Di Camillo, Mauro; Marinaro, Vanessa; Foglietta, Tiziana; Avallone, Veronica; Cannella, Carlo; Vernia, Piero

2008-10-28

To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25. Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g. Peak hydrogen production, area under the curve of hydrogen excretion and occurrence of symptoms were recorded. Only 16 patients (17.77%) with positive HBT-25 proved positive at HBT-12.5. Hydrogen production was lower as compared to HBT-25 (peak value 21.55 parts per million (ppm) +/- 29.54 SD vs 99.43 ppm +/- 40.01 SD; P < 0.001). Symptoms were present in only 13 patients. The absence of symptoms during the high-dose test has a high negative predictive value (0.84) for a negative low-dose test. The presence of symptoms during the first test was not useful for predicting a positive low-dose test (positive predictive value 0.06-0.31). Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a "standard" HBT is, in most instances, unnecessary. Thus, the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI, and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance.

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