Note: This page contains sample records for the topic conditional lethal mutants from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Conditional lethality involving a cytoplasmic mutant and chlorophyll-deficient malate dehydrogenase mutants in soybean  

Microsoft Academic Search

Conditional lethality in soybean, Glycine max (L.) Merr., occurred in F2 plants when cytoplasmicchlorophyll mutant Genetic Type T275 was the female parent and when either nuclear mutants T253 or T323 plants were the male parents. Mutant T253 [Mdh1-n (Urbana) y20 (Urbana) k2] is missing two of three mitochondrial malate dehydrogenase isozymes [Mdh1-n (Urbana)] and has yellowish-green leaves [y20 (Urbana)] and

R. G. Palmer

1992-01-01

2

A Nutritional Conditional Lethal Mutant Due to Pyridoxine 5?-Phosphate Oxidase Deficiency in Drosophila melanogaster  

PubMed Central

The concept of auxotrophic complementation has been proposed as an approach to identify genes in essential metabolic pathways in Drosophila melanogaster. However, it has achieved limited success to date, possibly due to the low probability of finding mutations fit with the chemically defined profile. Instead of using the chemically defined culture media lacking specific nutrients, we used bare minimum culture medium, i.e., 4% sucrose, for adult Drosophila. We identified a nutritional conditional lethal mutant and localized a c.95C > A mutation in the Drosophila pyridoxine 5?-phosphate oxidase gene [dPNPO or sugarlethal (sgll)] using meiotic recombination mapping, deficiency mapping, and whole genome sequencing. PNPO converts dietary vitamin B6 such as pyridoxine to its active form pyridoxal 5?-phosphate (PLP). The missense mutation (sgll95) results in the substitution of alanine to aspartate (p.Ala32Asp). The sgll95 flies survive well on complete medium but all die within 6 d on 4% sucrose only diet, which can be rescued by pyridoxine or PLP supplement, suggesting that the mutation does not cause the complete loss of PNPO activity. The sgll knockdown further confirms its function as the Drosophila PNPO. Because better tools for positional cloning and cheaper whole genome sequencing have made the identification of point mutations much easier than before, alleviating the necessity to pinpoint specific metabolic pathways before gene identification, we propose that nutritional conditional screens based on bare minimum growth media like ours represent promising approaches for discovering important genes and mutations in metabolic pathways, thereby accelerating the establishment of in vivo models that recapitulate human metabolic diseases.

Chi, Wanhao; Zhang, Li; Du, Wei; Zhuang, Xiaoxi

2014-01-01

3

Identification and sequence analysis of the gene mutated in the conditionally lethal outer membrane permeability mutant SS-C of Salmonella typhimurium.  

PubMed Central

The biosynthesis and structure-function relationships of the enterobacterial outer membrane are subjects of current intensive research. We have previously described the antibiotic supersensitive SS-C mutant (SH7622) of Salmonella typhimurium and shown that its outer membrane permeability barrier against hydrophobic antibiotics is severely defective. In this study, we show that this mutant is heat-sensitive, conditionally lethal, and carries a missense base-pair substitution in a novel gene which we have recently reported and now named the ssc gene. ssc encodes an earlier uncharacterized 36 kd protein (the Ssc protein) and the mutant expresses Ssc which has valine 291 changed to methionine in a methionine-rich region of Ssc. A plasmid containing the wild-type ssc allele completely reverts the antibiotic- and heat-sensitive phenotype of the SS-C mutant. Corresponding plasmids carrying the mutant allele, or an identical mutant allele prepared by localized mutagenesis, are inactive. The ssc gene is probably analogous to the firA locus of Escherichia coli which has earlier been implicated in a totally different function, mRNA synthesis. Furthermore, ssc apparently lies very close to the lpx genes involved in the thus far known steps of lipid A biosynthesis (the distance, approximately 560 bp). To conclude, our findings define a new essential gene involved in the generation of the outer membrane. Images

Hirvas, L; Koski, P; Vaara, M

1991-01-01

4

Characterization of conditionally expressed mutants affecting age-specific survival in inbred lines of Drosophila melanogaster: lethal conditions and temperature-sensitive periods.  

PubMed Central

The specific genetic basis of inbreeding depression is poorly understood. To address this question, two conditionally expressed lethal effects that were found to cause line-specific life span reductions in two separate inbred lines of Drosophila melanogaster were characterized phenotypically and genetically in terms of whether the accelerated mortality effects are dominant or recessive. The mortality effect in one line (I4) is potentially a temperature-sensitive semilethal that expresses in adult males only and is partially dominant. The other line (I10) responds as one would expect for a recessive lethal. It requires a cold shock for expression and is cold sensitive. Flies exhibiting this lethal condition responded as pupae and freshly eclosed imagoes. The effect is recessive in both males and females. The expression of the lethal effects in both lines is highly dependent upon environmental conditions. These results will serve as a basis for more detailed and mechanistic genetic research on inbreeding depression and are relevant to sex- and environment-specific effects on life span observed in quantitative trait loci studies using inbred lines.

Vermeulen, C J; Bijlsma, R

2004-01-01

5

Defective kernel mutants of maize. I. Genetic and lethality studies.  

PubMed

A planting of 3,919 M(1) kernels from normal ears crossed by EMS-treated pollen produced 3,461 M(1) plants and 3,172 selfed ears. These plants yielded 2,477 (72%) total heritable changes; the selfed ears yielded 2,457 (78%) recessive mutants, including 855 (27%) recessive kernel mutants and 8 (0.23%) viable dominant mutants. The ratio of recessive to dominant mutants was 201:1. The average mutation frequency for four known loci was three per 3,172 genomes analyzed. The estimated total number of loci mutated was 535 and the estimated number of kernel mutant loci mutated was 285. Among the 855 kernel mutants, 432 had a nonviable embryo, and 59 germinated but had a lethal seedling. A sample of 194 of the latter two types was tested for heritability, lethality, chromosome arm location and endosperm-embryo interaction between mutant and nonmutant tissues in special hyper-hypoploid combinations produced by manipulation of B-A translocations. The selected 194 mutants were characterized and catalogued according to endosperm phenotype and investigated to determine their effects on the morphology and development of the associated embryo. The possibility of rescuing some of the lethal mutants by covering the mutant embryo with a normal endosperm was investigated. Ninety of these 194 mutants were located on 17 of the 18 chromosome arms tested. Nineteen of the located mutants were examined to determine the effect of having a normal embryo in the same kernel with a mutant endosperm, and vice versa, as compared to the expression observed in kernels with both embryo and endosperm in a mutant condition. In the first situation, for three of the 19 mutants, the mutant endosperm was less extreme (the embryo helped); for seven cases, the mutant endosperm was more extreme (the embryo hindered); and for nine cases, there was no change. In the reverse situation, for four cases the normal endosperm helped the mutant embryo; for 14 cases there was no change and one case was inconclusive. PMID:17249053

Neuffer, M G; Sheridan, W F

1980-08-01

6

The Saccharomyces cerevisiae Hyperrecombination Mutant hpr1? Is Synthetically Lethal with Two Conditional Alleles of the Acetyl Coenzyme A Carboxylase Gene and Causes a Defect in Nuclear Export of Polyadenylated RNA  

PubMed Central

In a screen for mutants that display synthetic lethal interaction with hpr1?, a hyperrecombination mutant of Saccharomyces cerevisiae, we have isolated a novel cold-sensitive allele of the acetyl coenzyme A (CoA) carboxylase gene, acc1cs, encoding the rate-limiting enzyme of fatty acid synthesis. The synthetic lethal phenotype of the acc1cs hpr1? double mutant was only partially complemented by exogenous fatty acids. hpr1? was also synthetically lethal with a previously isolated, temperature-sensitive allele of ACC1, mtr7 (mRNA transport), indicating that the lethality of the acc1cs hpr1? double mutant was not allele specific. The basis for the interaction between conditional acc1 alleles and hpr1? was investigated in more detail. In the hpr1? mutant background, acetyl-CoA carboxylase enzyme activity was reduced about 15-fold and steady-state levels of biotinylated Acc1p and ACC1 mRNA were reduced 2-fold. The reduced Acc1p activity in hpr1? cells, however, did not result in an altered lipid or fatty acid composition of the mutant membranes but rendered cells hypersensitive to soraphen A, an inhibitor of Acc1p. Similar to mtr7, hpr1? and acc1cs mutant cells displayed a defect in nuclear export of polyadenylated RNA. Oversized transcripts were detected in hpr1?, and rRNA processing was disturbed, but pre-mRNA splicing appeared wild type. Surprisingly, the transport defect of hpr1? and acc1cs mutant cells was accompanied by an altered ring-shaped structure of the nucleolus. These observations suggest that the basis for the synthetic lethal interaction between hpr1? and acc1 may lie in a functional overlap of the two mutations in nuclear poly(A)+ RNA production and export that results in an altered structure of the nucleolus.

Schneiter, Roger; Guerra, Cesar E.; Lampl, Manfred; Gogg, Gabriela; Kohlwein, Sepp D.; Klein, Hannah L.

1999-01-01

7

Novel lethal mouse mutants produced in balancer chromosome screens.  

PubMed

Mutagenesis screens are a valuable method to identify genes that are required for normal development. Previous mouse mutagenesis screens for lethal mutations were targeted at specific time points or for developmental processes. Here we present the results of lethal mutant isolation from two mutagenesis screens that use balancer chromosomes. One screen was localized to mouse chromosome 4, between the STS markers D4Mit281 and D4Mit51. The second screen covered the region between Trp53 and Wnt3 on mouse chromosome 11. These screens identified all lethal mutations in the balancer regions, without bias towards any phenotype or stage of death. We have isolated 19 lethal lines on mouse chromosome 4, and 59 lethal lines on chromosome 11, many of which are distinct from previous mutants that map to these regions of the genome. We have characterized the mutant lines to determine the time of death, and performed a pair-wise complementation cross to determine if the mutations are allelic. Our data suggest that the majority of mouse lethal mutations die during mid-gestation, after uterine implantation, with a variety of defects in gastrulation, heart, neural tube, vascular, or placental development. This initial group of mutants provides a functional annotation of mouse chromosomes 4 and 11, and indicates that many novel developmental phenotypes can be quickly isolated in defined genomic intervals through balancer chromosome mutagenesis screens. PMID:16466971

Hentges, Kathryn E; Nakamura, Hisashi; Furuta, Yasuhide; Yu, Yuejin; Thompson, Debrah M; O'Brien, William; Bradley, Allan; Justice, Monica J

2006-08-01

8

Complementation Analysis of Late Lethal Mutants of DROSOPHILA MELANOGASTER  

PubMed Central

Late larval and pupal lethal mutants of Drosophila define those gene functions which are essential for the development of pupae (metamorphosis) but not for embryonic or larval development. In a previous report the isolation of a large number of such mutants was outlined, and a description of the imaginal disc defects in those mutants was described. This report concerns genetic analysis of those mutants. 3746 different pairwise combinations of mutants have been tested for complementation. Only 10 pairs fail to complement. In all of the cases tested, the lethal mutation in each member of a non-complementing pair has a similar map location. In addition to the non-complementing pairs one group of seven partially-complementing mutants has been identified.Comparisons of the imaginal disc defects within the non-complementing pairs and the lethal hybrids formed by the respective pairs were made to test for uniformity of phenotype. No significant qualitative differences were detected between any non-complementing pairs or their respective hybrids.

Shearn, Allen

1974-01-01

9

Medical Conditions and Nearly Lethal Suicide Attempts.  

ERIC Educational Resources Information Center

This population-based, case-control study examined physical illness as a risk factor for suicidal behavior. Case patients were more likely than controls to report having any serious medical conditions. Results suggest that young men with medical conditions are at increased risk for nearly lethal suicide attempts. (Contains 33 references and 3…

Ikeda, Robin M.; Kresnow, Marcie-jo; Mercy, James A.; Powell, Kenneth E.; Simon, Thomas R.; Potter, Lloyd B.; Durant, Tonji M.; Swahn, Monica H.

2002-01-01

10

Extragenic Suppression and Synthetic Lethality among Chlamydomonas Reinhardtii Mutants Resistant to anti-Microtubule Drugs  

PubMed Central

The antimicrotubule agents oryzalin (ORY), colchicine (COL) and taxol (TAX) were used to select three recessive, conditional lethal (ts(-)) mutants which defined two new essential loci, ory1 and cor1. The two ory1 mutants conferred resistance to ORY, TAX, and COL; the cor1 mutant conferred resistance only to COL. Each of the mutants displayed wild-type sensitivity to a number of unrelated inhibitors. Assembly and disassembly of flagellar microtubules in the ory1 mutants displayed wild-type sensitivity to ORY and COL, suggesting that the ory1 gene product either does not participate in these processes or the ory1 gene product alone is not sufficient to confer resistance. The ory1 locus mapped to linkage group X; cor1 was mapped to the left arm of linkage group XII. A synthetic lethal interaction was observed between ory1 and cor1 mutations, i.e., inferred ory1 cor1 double mutants were inviable at the permissive temperature. The conditional lethal phenotype of ory1-1 was used to select many spontaneous TS(+) revertants, which arose at high frequencies. Genetic and phenotypic characterization of the revertants demonstrated that (1) the revertants fell into four phenotypic classes, including some which conferred supersensitivity to ORY and others which conferred cold-sensitive lethality, (2) reversion was caused in most or all cases by extragenic suppressors, (3) suppressor mutations displayed complex behavior in heterozygous (sup/+) diploids, (4) many different loci may be capable of suppressing ory1 mutants, and (5) suppressors of ory1-1 efficiently suppressed an independently isolated allele, ory1-2. Taken together the ory1, cor1, and suppressor mutations identify a number of interacting loci involved in essential cellular processes which are specifically susceptible to antimicrotubule agents.

James, S. W.; Silflow, C. D.; Thompson, M. D.; Ranum, LPW.; Lefebvre, P. A.

1989-01-01

11

Growth in vitro of arrested embryos from lethal mutants of Arabidopsis thaliana  

Microsoft Academic Search

Seventeen embryo-lethal mutants ofArabidopsis thaliana with lethal phases ranging from the globular to mature cotyledon stages of development were analyzed by culturing arrested embryos on nutrient media designed to promote either callus formation or the completion of embryo development and the recovery of homozygous mutant plants. Enriched media supplemented with vitamins, amino acids, and nucleosides were used to identify potential

A. D. Baus; L. Franzmann; D. W. Meinke

1986-01-01

12

Lethal tuberculosis in interleukin-6-deficient mutant mice.  

PubMed Central

Tuberculosis is a chronic infectious disease which causes major health problems globally. Acquired resistance is mediated by T lymphocytes and executed by activated macrophages. In vitro studies have emphasized the importance of macrophage activation for mycobacterial growth inhibition. In vivo, the protective host response is focused on granulomatous lesions in which Mycobacterium tuberculosis is contained. A cellular immune response of the T helper 1 (Th1) type is considered central for control of tuberculosis. Using interleukin-6 (IL-6)-deficient mice, we here demonstrate a crucial role of this pluripotent cytokine in protection against M. tuberculosis but not against Mycobacterium bovis BCG. Infection with M. tuberculosis was lethal for the IL-6-deficient mice at inocula that were still controlled by IL-6-competent mice. Spleen cells from M. tuberculosis-infected IL-6-/- mouse mutants produced elevated levels of IL-4 and reduced levels of gamma interferon compared to the control levels. Cytofluorometric analyses of spleen cells from M. tuberculosis-infected mice revealed more-profound alterations in T-cell ratios in IL-6-/- mice than in control mice. We assume that IL-6 contributes to host resistance by its proinflammatory activity and by its influence on cytokine secretion.

Ladel, C H; Blum, C; Dreher, A; Reifenberg, K; Kopf, M; Kaufmann, S H

1997-01-01

13

Generation of Osr1 conditional mutant mice  

PubMed Central

Summary The Odd-skipped related 1 (Osr1) gene encodes a zinc finger protein homologous to the Drosophila Odd-skipped transcription factor. During mouse embryogenesis, Osr1 is expressed in multiple tissues, including the developing heart, kidney, limb, lung, and craniofacial structures. While characterization of targeted mutant mice has revealed essential roles for Osr1 in heart and kidney development, the embryonic lethality of the Osr1 null mice has hindered investigation of its role in many other developmental processes. We report here the generation of conditional mutant mice containing two loxP sites flanking Exon 2 of the Osr1 gene. Mice homozygous for this targeted Osr1fneo allele are normal and fertile. Crossing the Osr1fneo/fneo mice with the EIIa-Cre transgenic mice resulted in Cre-mediated deletion of the loxP-flanked Exon2 in the germ line and mice homozygous for this deletion recapitulated the Osr1 null mutant phenotypes. The Osr1fneo conditional mice will be valuable for tissue-specific analysis of the roles of Osr1 in embryonic and postnatal developmental processes.

Lan, Yu; Liu, Han; Ovitt, Catherine E.; Jiang, Rulang

2011-01-01

14

DEFECTIVE KERNEL MUTANTS OF MAIZE. I. GENETIC AND LETHALITY STUDIES  

Microsoft Academic Search

A planting of 3,919 MI kernels from normal ears crossed by EMS-treated pollen produced 3,461 MI plants and 3,172 selfed ears. These plants yielded 2,477 (72%) total heritable changes; the selfed ears yielded 2,457 (78%) recessive mutants, including 855 (27%) recessive kernel mutants and 8 (0.23%) viable dominant mutants. The ratio of recessive to dominant mutants was 201:l. The average

M. G. NEUFFER; WILLIAM F. SHERIDAN

15

Toxin-Deficient Mutants of Bacillus anthracis Are Lethal in a Murine Model for Pulmonary Anthrax?  

PubMed Central

Bacillus anthracis, the etiologic agent of anthrax, produces at least three primary virulence factors: lethal toxin, edema toxin, and a capsule. The capsule is absolutely required for dissemination and lethality in a murine model of inhalation anthrax, yet the roles for the toxins during infection are ill-defined. We show in a murine model that when spores of specific toxin-null mutants are introduced into the lung, dissemination and lethality are comparable to those of the parent strain. Mutants lacking one or more of the structural genes for the toxin proteins, i.e., protective antigen, lethal factor, and edema factor, disseminated from the lung to the spleen at rates similar to that of the virulent parental strain. The 50% lethal dose (LD50) and mean time to death (MTD) of the mutants did not differ significantly from those of the parent. The LD50s or MTDs were also unaffected relative to those of the parent strain when mice were inoculated intravenously with vegetative cells. Nonetheless, histopathological examination of tissues revealed subtle but distinct differences in infections by the parent compared to some toxin mutants, suggesting that the host response is affected by toxin proteins synthesized during infection.

Heninger, Sara; Drysdale, Melissa; Lovchik, Julie; Hutt, Julie; Lipscomb, Mary F.; Koehler, Theresa M.; Lyons, C. Rick

2006-01-01

16

Brain lipid composition in grey-lethal mutant mouse characterized by severe malignant osteopetrosis  

Microsoft Academic Search

The grey-lethal mouse (gl\\/gl) mutant most closely resembles the severe human malignant autosomal recessive OSTM1-dependent form of osteopetrosis that\\u000a it has been described to be associated with neurological abnormalities. For this reason, we have analyzed the brain lipid\\u000a composition (gangliosides, neutral glycosphingolipids, phospholipids and cholesterol), from gl\\/gl mice at different ages of development and compared with wild type mice. Both

Alessandro Prinetti; Federica Rocchetta; Elvira Costantino; Annalisa Frattini; Elena Caldana; Francesca Rucci; Arianna Bettiga; Pietro L. Poliani; Vanna Chigorno; Sandro Sonnino

2009-01-01

17

Regulators of the Actin Cytoskeleton Mediate Lethality in a Caenorhabditis elegans dhc-1 Mutant  

PubMed Central

Functional analysis of cytoplasmic dynein in Caenorhabditis elegans has revealed a wide range of cellular functions for this minus-end–directed motor protein. Dynein transports a variety of cargos to diverse cellular locations, and thus cargo selection and destination are likely regulated by accessory proteins. The microtubule-associated proteins LIS-1 and dynein interact, but the nature of this interaction remains poorly understood. Here we show that both LIS-1 and the dynein heavy-chain DHC-1 are required for integrity of the actin cytoskeleton in C. elegans. Although both dhc-1(or195ts) and lis-1 loss-of-function disrupt the actin cytoskeleton and produce embryonic lethality, a double mutant suppresses these defects. A targeted RNA interference screen revealed that knockdown of other actin regulators, including actin-capping protein genes and prefoldin subunit genes, suppresses dhc-1(or195ts)–induced lethality. We propose that release or relocation of the mutant dynein complex mediates this suppression of dhc-1(or195ts)--induced phenotypes. These results reveal an unexpected direct or indirect interaction between the actin cytoskeleton and dynein activity.

Gil-Krzewska, Aleksandra J.; Farber, Erica; Buttner, Edgar A.

2010-01-01

18

Correlation between In Vitro Cytotoxicity and In Vivo Lethal Activity in Mice of Epsilon Toxin Mutants from Clostridium perfringens  

PubMed Central

Epsilon toxin (Etx) from Clostridium perfringens is a pore-forming protein with a lethal effect on livestock, producing severe enterotoxemia characterized by general edema and neurological alterations. Site-specific mutations of the toxin are valuable tools to study the cellular and molecular mechanism of the toxin activity. In particular, mutants with paired cysteine substitutions that affect the membrane insertion domain behaved as dominant-negative inhibitors of toxin activity in MDCK cells. We produced similar mutants, together with a well-known non-toxic mutant (Etx-H106P), as green fluorescent protein (GFP) fusion proteins to perform in vivo studies in an acutely intoxicated mouse model. The mutant (GFP-Etx-I51C/A114C) had a lethal effect with generalized edema, and accumulated in the brain parenchyma due to its ability to cross the blood-brain barrier (BBB). In the renal system, this mutant had a cytotoxic effect on distal tubule epithelial cells. The other mutants studied (GFP-Etx-V56C/F118C and GFP-Etx-H106P) did not have a lethal effect or cross the BBB, and failed to induce a cytotoxic effect on renal epithelial cells. These data suggest a direct correlation between the lethal effect of the toxin, with its cytotoxic effect on the kidney distal tubule cells, and the ability to cross the BBB.

Dorca-Arevalo, Jonatan; Pauillac, Serge; Diaz-Hidalgo, Laura; Martin-Satue, Mireia; Popoff, Michel R.; Blasi, Juan

2014-01-01

19

Protease-Deficient DegP Suppresses Lethal Effects of a Mutant OmpC Protein by Its Capture  

PubMed Central

The expression of assembly-defective outer membrane proteins can confer lethality if they are not degraded by envelope proteases. We report here that the expression of a mutant OmpC protein, OmpC2Cys, which forms disulfide bonds in the periplasm due to the presence of two non-native cysteine residues, is lethal in cells lacking the major periplasmic protease, DegP. This lethality is not observed in dsbA strains that have diminished ability to form periplasmic disulfide bonds. Our data show that this OmpC2Cys-mediated lethality in a degP::Kmr dsbA+ background can be reversed by a DegP variant, DegPS210A, that is devoid of its proteolytic activity but retains its reported chaperone activity. However, DegPS210A does not reverse the lethal effect of OmpC2Cys by correcting its assembly but rather by capturing misfolded mutant OmpC polypeptides and thus removing them from the assembly pathway. Displacement of OmpC2Cys by DegPS210A also alleviates the negative effect that the mutant OmpC protein has on wild-type OmpF.

CastilloKeller, Maria; Misra, Rajeev

2003-01-01

20

Dominant-Lethal ?-Tubulin Mutants Defective in Microtubule Depolymerization in YeastV?  

PubMed Central

The dynamic instability of microtubules has long been understood to depend on the hydrolysis of GTP bound to ?-tubulin, an event stimulated by polymerization and necessary for depolymerization. Crystallographic studies of tubulin show that GTP is bound by ?-tubulin at the longitudinal dimer-dimer interface and contacts particular ?-tubulin residues in the next dimer along the protofilament. This structural arrangement suggests that these contacts could account for assembly-stimulated GTP hydrolysis. As a test of this hypothesis, we examined, in yeast cells, the effect of mutating the ?-tubulin residues predicted, on structural grounds, to be involved in GTPase activation. Mutation of these residues to alanine (i.e., D252A and E255A) created poisonous ?-tubulins that caused lethality even as minor components of the ?-tubulin pool. When the mutant ?-tubulins were expressed from the galactose-inducible promoter of GAL1, cells rapidly acquired aberrant microtubule structures. Cytoplasmic microtubules were largely bundled, spindle assembly was inhibited, preexisting spindles failed to completely elongate, and occasional, stable microtubules were observed unattached to spindle pole bodies. Time-lapse microscopy showed that microtubule dynamics had ceased. Microtubules containing the mutant proteins did not depolymerize, even in the presence of nocodazole. These data support the view that ?-tubulin is a GTPase-activating protein that acts, during microtubule polymerization, to stimulate GTP hydrolysis in ?-tubulin and thereby account for the dynamic instability of microtubules.

Anders, Kirk R.; Botstein, David

2001-01-01

21

Inactivated pep27 mutant as an effective mucosal vaccine against a secondary lethal pneumococcal challenge in mice  

PubMed Central

Purpose A pep27 mutant may be able to elicit mucosal immunity against pneumococcal diseases, and could be employed as an inexpensive attenuated vaccine. However, this particular mutant contains an erythromycin-resistance marker. The purpose of the current study is to develop a markerless pep27 mutant and assess whether this inactivated mutant is able to induce mucosal immunity. Materials and Methods Mice were vaccinated intranasally with the inactivated markerless pep27 mutant every 2 weeks for a total of three times, after which time serum samples were analyzed for antibody titers. The mice were then challenged with a lethal D39 strain and their survival time was measured. The cross-reactivity of the antisera against pep27 was also compared to other mutant serotypes. Results Intranasal immunization of mice with the inactivated markerless pep27 mutant provides effective protection and rapidly cleared bacterial colonization in vivo. Moreover, antisera raised against the pep27 mutant may cross-react with several other serotype strains. Conclusion Intranasal immunization with the inactivated pep27 mutant may be able to provide mucosal immunity, and could represent an efficient mucosal vaccine.

Choi, Sang-Yoon; Tran, Thao Dang-Hien; Briles, David E.

2013-01-01

22

cdc9 Ligase-defective mutants of Saccharomyces cerevisiae exhibit lowered resistance to lethal effects of bleomycin  

SciTech Connect

Conditional ligase-deficient mutants of Saccharomyces cerevisiae were more sensitive than their parental (CDC9) strain to dose-dependent killing by bleomycin, even when mutant cells were pregrown and exposed to the antibiotic at permissive temperatures. Pretreatment incubation at the restrictive temperature (37/sup 0/C) under growing or nongrowing conditions enhanced bleomycin killing of both cdc9-1 and cdc9-9 mutants. This sensitization could be relieved by incubation at the permissive temperature before treatment.

Moore, C.W.

1982-09-01

23

TATA-binding protein mutants that are lethal in the absence of the Nhp6 high-mobility-group protein.  

PubMed

The Saccharomyces cerevisiae Nhp6 protein is related to the high-mobility-group B family of architectural DNA-binding proteins that bind DNA nonspecifically but bend DNA sharply. Nhp6 is involved in transcriptional activation by both RNA polymerase II (Pol II) and Pol III. Our previous genetic studies have implicated Nhp6 in facilitating TATA-binding protein (TBP) binding to some Pol II promoters in vivo, and we have used a novel genetic screen to isolate 32 new mutations in TBP that are viable in wild-type cells but lethal in the absence of Nhp6. The TBP mutations that are lethal in the absence of Nhp6 cluster in three regions: on the upper surface of TBP that may have a regulatory role, near residues that contact Spt3, or near residues known to contact either TFIIA or Brf1 (in TFIIIB). The latter set of mutations suggests that Nhp6 becomes essential when a TBP mutant compromises its ability to interact with either TFIIA or Brf1. Importantly, the synthetic lethality for some of the TBP mutations is suppressed by a multicopy plasmid with SNR6 or by an spt3 mutation. It has been previously shown that nhp6ab mutants are defective in expressing SNR6, a Pol III-transcribed gene encoding the U6 splicing RNA. Chromatin immunoprecipitation experiments show that TBP binding to SNR6 is reduced in an nhp6ab mutant. Nhp6 interacts with Spt16/Pob3, the yeast equivalent of the FACT elongation complex, consistent with nhp6ab cells being extremely sensitive to 6-azauracil (6-AU). However, this 6-AU sensitivity can be suppressed by multicopy SNR6 or BRF1. Additionally, strains with SNR6 promoter mutations are sensitive to 6-AU, suggesting that decreased SNR6 RNA levels contribute to 6-AU sensitivity. These results challenge the widely held belief that 6-AU sensitivity results from a defect in transcriptional elongation. PMID:15226442

Eriksson, Peter; Biswas, Debabrata; Yu, Yaxin; Stewart, James M; Stillman, David J

2004-07-01

24

Potentially lethal damage repair is due to the difference of DNA double-strand break repair under immediate and delayed plating conditions  

SciTech Connect

Cells plated immediately after irradiation on nutrient agar (immediate plating) exhibit a lower survival than cells which are kept under nongrowth conditions before plating (delayed plating). The difference between the survival curves obtained after immediate plating and delayed plating is considered to exhibit the cell's capacity to repair potentially lethal damage. In yeast evidence has been presented previously for the DNA double-strand break (DSB) as the molecular lesion involved in the repair of potentially lethal damage observed at the cellular level. Radiation-induced DSB are repaired in cells plated on nutrient agar, i.e., under growth conditions, as well as in cells kept under nongrowth conditions. In this paper DSB repair under growth and nongrowth conditions is studied with the help of the yeast mutant rad54-3 which is temperature conditional for DSB repair. It is shown that the extent of repair of potentially lethal damage can be varied by shifting the relative fractions of repair of DSB under growth conditions versus nongrowth conditions. Repair of DSB in cells plated on nutrient agar is promoted when glucose is substituted by Na-succinate as an energy source. As a result the immediate plating survival curve approaches the delayed plating survival curve, thus reducing the operationally defined repair of potentially lethal damage. We show that this reduced potentially lethal damage repair is caused, however, by a higher amount of DSB repair in cells immediately plated on succinate agar as compared to glucose agar.

Frankenberg-Schwager, M.; Frankenberg, D.; Harbich, R.

1987-08-01

25

Enterobacterial Common Antigen Mutants of Salmonella enterica Serovar Typhimurium Establish a Persistent Infection and Provide Protection against Subsequent Lethal Challenge  

PubMed Central

Infection with Salmonella spp. is a significant source of disease globally. A substantial proportion of these infections are caused by Salmonella enterica serovar Typhimurium. Here, we characterize the role of the enterobacterial common antigen (ECA), a surface glycolipid ubiquitous among enteric bacteria, in S. Typhimurium pathogenesis. Construction of a defined mutation in the UDP-N-acetylglucosamine-1-phosphate transferase gene, wecA, in two clinically relevant strains of S. Typhimurium, TML and SL1344, resulted in strains that were unable to produce ECA. Loss of ECA did not affect the gross cell surface ultrastructure, production of lipopolysaccharide (LPS), flagella, or motility. However, the wecA mutant strains were attenuated in both oral and intraperitoneal mouse models of infection (P < 0.001 for both routes of infection; log rank test), and virulence could be restored by complementation of the wecA gene in trans. Despite the avirulence of the ECA-deficient strains, the wecA mutant strains were able to persistently colonize systemic sites (spleen and liver) at moderate levels for up to 70 days postinfection. Moreover, immunization with the wecA mutant strains provided protection against a subsequent lethal oral or intraperitoneal challenge with wild-type S. Typhimurium. Thus, wecA mutant (ECA-negative) strains of Salmonella may be useful as live attenuated vaccine strains or as vehicles for heterologous antigen expression.

Gilbreath, Jeremy J.; Colvocoresses Dodds, Jennifer; Rick, Paul D.; Soloski, Mark J.

2012-01-01

26

Enterobacterial common antigen mutants of Salmonella enterica serovar Typhimurium establish a persistent infection and provide protection against subsequent lethal challenge.  

PubMed

Infection with Salmonella spp. is a significant source of disease globally. A substantial proportion of these infections are caused by Salmonella enterica serovar Typhimurium. Here, we characterize the role of the enterobacterial common antigen (ECA), a surface glycolipid ubiquitous among enteric bacteria, in S. Typhimurium pathogenesis. Construction of a defined mutation in the UDP-N-acetylglucosamine-1-phosphate transferase gene, wecA, in two clinically relevant strains of S. Typhimurium, TML and SL1344, resulted in strains that were unable to produce ECA. Loss of ECA did not affect the gross cell surface ultrastructure, production of lipopolysaccharide (LPS), flagella, or motility. However, the wecA mutant strains were attenuated in both oral and intraperitoneal mouse models of infection (P<0.001 for both routes of infection; log rank test), and virulence could be restored by complementation of the wecA gene in trans. Despite the avirulence of the ECA-deficient strains, the wecA mutant strains were able to persistently colonize systemic sites (spleen and liver) at moderate levels for up to 70 days postinfection. Moreover, immunization with the wecA mutant strains provided protection against a subsequent lethal oral or intraperitoneal challenge with wild-type S. Typhimurium. Thus, wecA mutant (ECA-negative) strains of Salmonella may be useful as live attenuated vaccine strains or as vehicles for heterologous antigen expression. PMID:22025511

Gilbreath, Jeremy J; Colvocoresses Dodds, Jennifer; Rick, Paul D; Soloski, Mark J; Merrell, D Scott; Metcalf, Eleanor S

2012-01-01

27

Perinatal synthetic lethality and hematopoietic defects in compound mafG::mafK mutant mice.  

PubMed

Prior studies exploring the mechanisms controlling erythroid gene regulation implicated MARE (Maf recognition element) cis-elements as crucial to the transcriptional activity of many erythroid genes. Numerous transcription factors can elicit responses through MAREs, including not only the AP-1 family proteins, but also a growing list of factors composed of Cap-N-Collar (CNC)-small Maf heterodimers. While these factors can activate transcription from MAREs in co-transfection assays, mouse germline mutations in cnc genes tested to date have failed to reveal primary erythroid phenotypes. Here we report that after combining the mafK and mafG targeted null alleles, mutant animals display several synthetic phenotypes, including erythroid deficiencies. First, compound homozygous small maf gene mutants survive embryogenesis, but die postnatally. Secondly, compound mutant animals develop severe neurological disorders. Thirdly, they exhibit an exacerbated mafG deficiency in megakaryopoiesis, specifically in proplatelet formation, resulting in profound thrombocytopenia. Finally, the compound mutant animals develop severe anemia accompanied by abnormal erythrocyte morphology and membrane protein composition. These data provide direct evidence that the small Maf transcription factors play an important regulatory role in erythropoiesis. PMID:10716933

Onodera, K; Shavit, J A; Motohashi, H; Yamamoto, M; Engel, J D

2000-03-15

28

A pH-conditional mutant of Escherichia coli.  

PubMed Central

Mutants of Escherichia coli have been isolated that are able to grow on lactose at pH 7.0 but not at pH 8.1. One of these mutants was analyzed and shown to map in the Z region of the lactose operon. beta-Galactosidase (beta-D-galactoside galactohydrolase; EC 3.2.1.23) activity in toluenized mutant cells at pH 8.0 was one-tenth that at pH 7.0. Enzyme purified to near homogeneity from the pH-conditional mutant similarly exhibited pH-conditional activity under conditions where wild-type enzyme was unaffected over a pH range of 6.0-8.0. The pH-conditional beta-galactosidase was used in vivo as a probe for intracellular pH. We show that an internal pH of approximately 7.8-8.0 is maintained through an external pH range of 5.9-7.8. The phenotype of pH-conditional mutants was defined on medium with lactose as the sole carbon source. Under such conditions the gene product itself, beta-galactosidase, is required to maintain intracellular pH, since such maintenance is clearly energy-dependent. Therefore, we were able to recover a pH-conditional mutant in a cytoplasmic gene product. We predict that with any phenotype independent of energy production, however, pH-sensitive mutants will be recovered only in surface elements.

Colb, M; Shapiro, L

1977-01-01

29

When a Fly Has to Fly to Reproduce: Selection against Conditional Recessive Lethals in "Drosophila"  

ERIC Educational Resources Information Center

We propose an experimental model suitable for demonstrating allele frequency change in Drosophila melanogaster populations caused by selection against an easily scorable conditional lethal, namely recessive flightless alleles such as apterous and vestigial. Homozygotes for these alleles are excluded from reproduction because the food source used…

Plunkett, Andrea D.; Yampolsky, Lev Y.

2010-01-01

30

Dictyostelium discoideum mutants with conditional defects in phagocytosis  

Microsoft Academic Search

We have isolated and characterized Dic- tyostelium discoideum mutants with conditional defects in phagocytosis. Under suspension conditions, the mu- tants exhibited dramatic reductions in the uptake of bacteria and polystyrene latex beads. The initial bind- ing of these ligands was unaffected, however, indicat- ing that the defect was not in a plasma membrane receptor. Because of the phagocytosis defect, the

Christopher J. Cohen; Rebecca Bacon; Margaret Clarke; Keith Joiner; Ira Mellman

1994-01-01

31

Lethality in PARP-1/Ku80 double mutant mice reveals physiologicalsynergy during early embryogenesis  

SciTech Connect

Ku is an abundant heterodimeric nuclear protein, consisting of 70-kDa and 86-kDa tightly associated subunits that comprise the DNA binding component of DNA-dependent protein kinase. Poly(ADP)ribose polymerase-1 (PARP-1) is a 113-kDa protein that catalyzes the synthesis of poly(ADP-ribose) on target proteins. Both Ku and PARP-1 recognize and bind to DNA ends. Ku functions in the non-homologous end joining (NHEJ) repair pathway whereas PARP-1 functions in the single strand break repair and base excision repair (BER) pathways. Recent studies have revealed that PARP-1 and Ku80 interact in vitro. To determine whether the association of PARP-1 and Ku80 has any physiological significance or synergistic function in vivo, mice lacking both PARP-1 and Ku80 were generated. The resulting offspring died during embryonic development displaying abnormalities around the gastrulation stage. In addition, PARP-1-/-Ku80-/- cultured blastocysts had an increased level of apoptosis. These data suggest that the functions of both Ku80 and PARP-1 are essential for normal embryogenesis and that a loss of genomic integrity leading to cell death through apoptosis is likely the cause of the embryonic lethality observed in these mice.

Henrie, Melinda S.; Kurimasa, Akihiro; Burma, Sandeep; Menissier-de Murcia, Josiane; de Murcia, Gilbert; Li, Gloria C.; Chen,David J.

2002-09-24

32

Lethal Accumulation of Guanylic Nucleotides in Saccharomyces cerevisiae HPT1-Deregulated Mutants  

PubMed Central

Guanylic nucleotide biosynthesis is a conserved and highly regulated process. Drugs reducing GMP synthesis affect the immunological response and mutations enabling guanylic-derivative recycling lead to severe mental retardation. While the effects of decreased GMP synthesis have been well documented, the consequences of GMP overproduction in eukaryotes are poorly understood. In this work, we selected and characterized several mutations making yeast hypoxanthine–guanine phosphoribosyltransferase insensitive to feedback inhibition by GMP. In these mutants, accumulation of guanylic nucleotides can be triggered by addition of extracellular guanine. We show that such an accumulation is highly toxic for yeast cells and results in arrest of proliferation and massive cell death. This growth defect could be partially suppressed by overexpression of Rfx1p, a transcriptional repressor of the DNA damage response pathway. Importantly, neither guanylic nucleotide toxicity nor its suppression by Rfx1p was associated with an alteration of forward mutation frequency.

Breton, Annick; Pinson, Benoit; Coulpier, Fanny; Giraud, Marie-France; Dautant, Alain; Daignan-Fornier, Bertrand

2008-01-01

33

Pathogenesis of Lethal Cardiac Arrhythmias in Mecp2 Mutant Mice: Implication for Therapy in Rett Syndrome  

PubMed Central

Rett Syndrome is a neurodevelopmental disorder typically caused by mutations in Methyl-CpG-Binding Protein 2 (MECP2) in which 26% of deaths are sudden and of unknown cause. To explore the hypothesis that these deaths may be due to cardiac dysfunction, we characterized the electrocardiograms (ECGs) in 379 people with Rett syndrome and found that 18.5% show prolongation of the corrected QT interval (QTc), indicating a repolarization abnormality that can predispose to the development of an unstable fatal cardiac rhythm. Male mice lacking MeCP2 function, Mecp2Null/Y, also have prolonged QTc and show increased susceptibility to induced ventricular tachycardia. Female heterozygous null mice, Mecp2Null/+, show an age-dependent prolongation of QTc associated with ventricular tachycardia and cardiac-related death. Genetic deletion of MeCP2 function in only the nervous system was sufficient to cause long QTc and ventricular tachycardia, implicating neuronally-mediated changes to cardiac electrical conduction as a potential cause of ventricular tachycardia in Rett syndrome. The standard therapy for prolonged QTc in Rett syndrome, ?-adrenergic receptor blockers, did not prevent ventricular tachycardia in Mecp2Null/Y mice. To determine whether an alternative therapy would be more appropriate, we characterized cardiomyocytes from Mecp2Null/Y mice and found increased persistent sodium current, which was normalized when cells were treated with the sodium channel-blocking anti-seizure drug phenytoin. Treatment with phenytoin reduced both QTc and sustained ventricular tachycardia in Mecp2Null/Y mice. These results demonstrate that cardiac abnormalities in Rett syndrome are secondary to abnormal nervous system control, which leads to increased persistent sodium current. Our findings suggest that treatment in people with Rett syndrome would be more effective if it targeted the increased persistent sodium current in order to prevent lethal cardiac arrhythmias.

McCauley, Mark D.; Wang, Tiannan; Mike, Elise; Herrera, Jose; Beavers, David L.; Huang, Teng-Wei; Ward, Christopher S.; Skinner, Steven; Percy, Alan K.; Glaze, Daniel G.; Wehrens, Xander H. T.; Neul, Jeffrey L.

2013-01-01

34

Zinc supplement greatly improves the condition of parkin mutant Drosophila.  

PubMed

Parkinson's disease (PD) is a progressive neurodegenerative disorder in which oxidative stress is implicated as a major causative factor. Mutations in the gene encoding Parkin, a ubiquitin ligase, are responsible for a familial form of PD. In a Drosophila disease model lacking Parkin (park(25) null mutant), we tested the effect of zinc supplementation. Zinc is an essential trace metal and a component of many enzymes and transcriptional regulators. Unlike copper and iron, zinc is not redox-active and under most conditions serves as an antioxidant. We find that the condition of parkin mutants raised on zinc-supplemented food is greatly improved. At zinc concentrations where controls begin to show adverse effects as a result of the metal supplement, parkin mutants perform best, as manifested in a higher frequency of reaching adulthood, extended lifespan and improved motoric abilities. PMID:20302514

Saini, Nidhi; Schaffner, Walter

2010-05-01

35

Cancer susceptibility and embryonic lethality in Mob1a/1b double-mutant mice  

PubMed Central

Mps one binder 1a (MOB1A) and MOB1B are key components of the Hippo signaling pathway and are mutated or inactivated in many human cancers. Here we show that intact Mob1a or Mob1b is essential for murine embryogenesis and that loss of the remaining WT Mob1 allele in Mob1a?/?1btr/+ or Mob1a?/+1btr/tr mice results in tumor development. Because most of these cancers resembled trichilemmal carcinomas, we generated double-mutant mice bearing tamoxifen-inducible, keratinocyte-specific homozygous-null mutations of Mob1a and Mob1b (kDKO mice). kDKO mice showed hyperplastic keratinocyte progenitors and defective keratinocyte terminal differentiation and soon died of malnutrition. kDKO keratinocytes exhibited hyperproliferation, apoptotic resistance, impaired contact inhibition, enhanced progenitor self renewal, and increased centrosomes. Examination of Hippo pathway signaling in kDKO keratinocytes revealed that loss of Mob1a/b altered the activities of the downstream Hippo mediators LATS and YAP1. Similarly, YAP1 was activated in some human trichilemmal carcinomas, and some of these also exhibited MOB1A/1B inactivation. Our results clearly demonstrate that MOB1A and MOB1B have overlapping functions in skin homeostasis, and exert their roles as tumor suppressors by regulating downstream elements of the Hippo pathway.

Nishio, Miki; Hamada, Koichi; Kawahara, Kohichi; Sasaki, Masato; Noguchi, Fumihito; Chiba, Shuhei; Mizuno, Kensaku; Suzuki, Satoshi O.; Dong, Youyi; Tokuda, Masaaki; Morikawa, Takumi; Hikasa, Hiroki; Eggenschwiler, Jonathan; Yabuta, Norikazu; Nojima, Hiroshi; Nakagawa, Kentaro; Hata, Yutaka; Nishina, Hiroshi; Mimori, Koshi; Mori, Masaki; Sasaki, Takehiko; Mak, Tak W.; Nakano, Toru; Itami, Satoshi; Suzuki, Akira

2012-01-01

36

The Triplo-Lethal Locus of Drosophila: Reexamination of Mutants and Discovery of a Second-Site Suppressor  

PubMed Central

In the genome of Drosophila melanogaster there is a single locus, Triplo-lethal (Tpl), that causes lethality when present in either one or three copies in an otherwise diploid animal. Previous attempts to mutagenize Tpl produced alleles that were viable over a chromosome bearing a duplication of Tpl, but were not lethal in combination with a wild-type chromosome, as deficiencies for Tpl are. These mutations were interpreted as hypomorphic alleles of Tpl. In this work, we show that these alleles are not mutations at Tpl; rather, they are dominant mutations in a tightly linked, but cytologically distant, locus that we have named Suppressor-of-Tpl (Su(Tpl)). Su(Tpl) mutations suppress the lethality associated with three copies of the Triplo-lethal locus and are recessive lethal. We have mapped Su(Tpl) to the approximate map position 3-46.5, within the cytological region 76B-76D.

Dorer, D. R.; Ezekiel, D. H.; Christensen, A. C.

1995-01-01

37

A conditional mutant allele for analysis of Mixl1 function in the mouse.  

PubMed

Mixl1 is the only member of the Mix/Bix homeobox gene family identified in mammals. During mouse embryogenesis, Mixl1 is first expressed at embryonic day (E)5.5 in cells of the visceral endoderm (VE). At the time of gastrulation, Mixl1 expression is detected in the vicinity of the primitive streak. Mixl1 is expressed in cells located within the primitive streak, in nascent mesoderm cells exiting the primitive streak, and in posterior VE overlying the primitive streak. Genetic ablation of Mixl1 in mice has revealed its crucial role in mesoderm and endoderm cell specification and tissue morphogenesis during early embryonic development. However, the early lethality of the constitutive Mixl1(-) (/-) mutant precludes the study of its role at later stages of embryogenesis and in adult mice. To circumvent this limitation, we have generated a conditional Mixl1 allele (Mixl1(c) (KO) ) that permits temporal as well as spatial control of gene ablation. Animals homozygous for the Mixl1(c) (KO) conditional allele were viable and fertile. Mixl1(KO) (/) (KO) embryos generated by crossing of Mixl1(c) (KO) (/c) (KO) mice with Sox2-Cre or EIIa-Cre transgenic mice were embryonic lethal at early somite stages. By contrast to wild-type embryos, Mixl1(KO) (/) (KO) embryos contained no detectable Mixl1, validating the Mixl1(c) (KO) as a protein null after Cre-mediated excision. Mixl1(KO) (/) (KO) embryos resembled the previously reported Mixl1(-) (/) (-) mutant phenotype. Therefore, the Mixl1 cKO allele provides a tool for investigating the temporal and tissue-specific requirements for Mixl1 in the mouse. genesis 52:417-423, 2014. © 2014 Wiley Periodicals, Inc. PMID:24596343

Pulina, Maria V; Sahr, Kenneth E; Nowotschin, Sonja; Baron, Margaret H; Hadjantonakis, Anna-Katerina

2014-05-01

38

Lethal, potentially lethal lesion model  

SciTech Connect

A theoretical framework to describe the formation of lethal mutations by radiation is presented. Lesions that are repaired (and misrepaired) in each type of experiment described (delayed plating and split dose) are assumed to be the same. In this model the same (potentially lethal) lesions cause both sublethal and potentially lethal damage. Potentially lethal damage is defined as damage which may be modified by alterations in postirradiation conditions. Sublethal damage is cellular damage whose accumulation may lead to lethality. A crucial consideration in the expression of the damage is the kind of medium in which the cells are placed during the repair period. Fresh or growth medium (F-medium) is assumed to cause fixation of damage after about 3 hours, while no fixation (only misrepair) occurs in conditioned medium (C-medium).

Curtis, S.B.

1983-07-01

39

An Arabidopsis Mutant Tolerant to Lethal Ultraviolet-B Levels Shows Constitutively Elevated Accumulation of Flavonoids and Other Phenolics1  

PubMed Central

The isolation and characterization of mutants hypersensitive to ultraviolet (UV) radiation has been a powerful tool to learn about the mechanisms that protect plants against UV-induced damage. To increase our understanding of the various mechanisms of defense against UVB radiation, we searched for mutations that would increase the level of tolerance of Arabidopsis plants to UV radiation. We describe a single gene dominant mutation (uvt1) that leads to a remarkable tolerance to UVB radiation conditions that would kill wild-type plants. Pigment analyses show a constitutive increase in accumulation of UV-absorbing compounds in uvt1 that increases the capacity of the leaves to block UVB radiation and therefore is likely to be responsible for the elevated resistance of this mutant to UVB radiation. These increases in absorption in the UV region are due, at least in part, to increases in flavonoid and sinapate accumulation. Expression of chalcone synthase (CHS) mRNA was shown to be constitutively elevated in uvt1 plants, suggesting that the increases in absorption may be a consequence of changes in gene expression. Expression of CHS in uvt1 was shown to be still inducible by UV, indicating that the uvt1 lesion may not affect the UV-mediated regulation of CHS gene expression. Our data support an important role for UV screens in the overall protection of plants to UVB radiation. The uvt1 mutant could prove to be an important tool to elucidate further the exact role of UV-absorbing pigments in UV protection as well as the relative contribution of other mechanisms to the overall tolerance of plants to UV radiation.

Bieza, Kim; Lois, Rodrigo

2001-01-01

40

Production of viable seeds from the seedling lethal mutant ppi2-2 lacking the atToc159 chloroplast protein import receptor using plastic containers, and characterization of the homozygous mutant progeny.  

PubMed

Biogenesis of chloroplasts is essential for plant growth and development. A number of homozygous mutants lacking a chloroplast protein exhibit an albino phenotype. In general, it is challenging to grow albino Arabidopsis plants on soil until they set seeds. Homozygous albino mutants are usually obtained as progenies of heterozygous parents. Here, we describe a method of recovering seeds from the seedling lethal Arabidopsis mutant ppi2-2, which lacks the atToc159 protein import receptor at the outer envelope membrane of chloroplast. Using plastic containers, we were able to grow homozygous ppi2-2 plants until these set seed. Although the germination rate of the harvested seeds was relatively low, it was still sufficient to allow us to further analyze the ppi2-2 progeny. Using ppi2-2 homozygous seeds, we were able to analyze the role of plastid protein import in the light-regulated induction of nuclear genes. We propose that this method be applied to other seedling lethal Arabidopsis mutants to obtain homozygous seeds, helping us further investigate the roles of plastid proteins in plant growth and development. PMID:24926298

Tada, Akari; Adachi, Fumi; Kakizaki, Tomohiro; Inaba, Takehito

2014-01-01

41

Production of viable seeds from the seedling lethal mutant ppi2-2 lacking the atToc159 chloroplast protein import receptor using plastic containers, and characterization of the homozygous mutant progeny  

PubMed Central

Biogenesis of chloroplasts is essential for plant growth and development. A number of homozygous mutants lacking a chloroplast protein exhibit an albino phenotype. In general, it is challenging to grow albino Arabidopsis plants on soil until they set seeds. Homozygous albino mutants are usually obtained as progenies of heterozygous parents. Here, we describe a method of recovering seeds from the seedling lethal Arabidopsis mutant ppi2-2, which lacks the atToc159 protein import receptor at the outer envelope membrane of chloroplast. Using plastic containers, we were able to grow homozygous ppi2-2 plants until these set seed. Although the germination rate of the harvested seeds was relatively low, it was still sufficient to allow us to further analyze the ppi2-2 progeny. Using ppi2-2 homozygous seeds, we were able to analyze the role of plastid protein import in the light-regulated induction of nuclear genes. We propose that this method be applied to other seedling lethal Arabidopsis mutants to obtain homozygous seeds, helping us further investigate the roles of plastid proteins in plant growth and development.

Tada, Akari; Adachi, Fumi; Kakizaki, Tomohiro; Inaba, Takehito

2014-01-01

42

Use of a conditionally lethal gene in Anabaena sp. strain PCC 7120 to select for double recombinants and to entrap insertion sequences  

SciTech Connect

Use of the sacB gene provides a simple, effective, positive selection for double recombinants in Anabaena sp. strain PCC 7120, a filamentous cyanobacterium. This gene, which encodes the secretory levansucrase of Bacillus subtilis, was inserted into the vector portion of a suicide plasmid bearing a mutant version of a chromosomal gene. Cells of colonies in which such a plasmid had integrated into the Anabaena chromosome through single recombination were plated on solid medium containing 5% sucrose. Under this condition, the presence of the sacB gene is lethal. A small fraction of the cells from initially sucrose-sensitive colonies became sucrose resistant; the majority of these sucrose-resistant derivatives had undergone a second recombinational event in which the sacB-containing vector had been lost and the wild-type form of the chromosomal gene had been replaced by the mutant form. By the use of this technique, they mutated two selected genes in the chromosome of Anabaena sp. strain PCC 7120. The conditionally lethal nature of the sacB gene was also used to detect insertion sequences from this Anabaena strain. Sucrose-resistant colonies derived from cells bearing a sacB-containing autonomously replicating plasmid were analyzed. Five different, presumed insertion sequences were found to have inserted into the sacB gene of the plasmids in these colonies. One of them, denoted IS892, was characterized by physical mapping. It is 1.7 kilobases in size and is present in at least five copies in the genome of Anabaena sp. strain PCC 7120.

Cai, Yuping; Wolk, C.P. (Michigan State Univ., East Lansing (USA))

1990-06-01

43

An Arabidopsis Mutant Tolerant to Lethal Ultraviolet-B Levels Shows Constitutively Elevated Accumulation of Flavonoids and Other Phenolics  

Microsoft Academic Search

The isolation and characterization of mutants hypersensitive to ultraviolet (UV) radiation has been a powerful tool to learn about the mechanisms that protect plants against UV-induced damage. To increase our understanding of the various mechanisms of defense against UVB radiation, we searched for mutations that would increase the level of tolerance of Arabidopsis plants to UV radiation. We describe a

Kim Bieza; Rodrigo Lois

2001-01-01

44

C. elegans ten-1 is synthetic lethal with mutations in cytoskeleton regulators, and enhances many axon guidance defective mutants  

Microsoft Academic Search

BACKGROUND: Teneurins are transmembrane proteins that assist morphogenetic processes in many organisms. ten-1 is the C. elegans teneurin homolog with two transcripts, ten-1a and ten-1b, that respectively encode a long (TEN-1L) and short (TEN-1S) form of the protein. We previously isolated a C. elegans mutant where one pharyngeal neuron was frequently misplaced, and now show that it corresponds to a

Catarina Mörck; Vivekanand Vivekanand; Gholamali Jafari; Marc Pilon

2010-01-01

45

Identification of two DNA helicases UvrD and DinG as suppressors for lethality caused by mutant cspA mRNAs.  

PubMed

CspA is a major cold shock-inducible protein (70 aa), and its major role in the cold shock response was shown to be as an RNA chaperone destabilizing secondary structure of mRNAs at low temperature. Previously, we showed that the overexpression of mutant cspA containing premature non-sense codons at various positions led to stalled ribosomes on mutant cspA transcripts, ultimately leading to cell death. This lethality is primarily due to the highly translatable cspA 5'-UTR that recruits most of the ribosomes from other mRNAs, which are then stalled at the abnormal stop codon. This was called the 'LACE' effect. We show here that non-sense mutation even at the 67th position as well as substitutions of aromatic amino acid residues present on the RNA-binding surface of CspA protein to alanine caused the LACE effect by trapping a substantial amount of ribosomes on cspA mRNAs. In an attempt to identify a suppressor(s), which may help the cells to recover from the inhibitory LACE effect, genetic screening of an Escherichia coli genomic library was performed. We isolated suppressors that contained the genomic fragments encoding uvrD and dinG, respectively, whose gene products are ATP-dependent DNA helicases. The nucleic acid-binding and ATPase activities of these two helicases were found to be essential for their suppression activity. This genomic screening offers an approach to shed light on the mechanistic of 5'-UTR of cspA mRNA and novel roles of E. coli helicases that function in DNA repair. PMID:22832783

Hwang, Jihwan; Lee, Kangseok; Phadtare, Sangita; Inouye, Masayori

2012-01-01

46

Conditional DNA repair mutants enable highly precise genome engineering  

PubMed Central

Oligonucleotide-mediated multiplex genome engineering is an important tool for bacterial genome editing. The efficient application of this technique requires the inactivation of the endogenous methyl-directed mismatch repair system that in turn leads to a drastically elevated genomic mutation rate and the consequent accumulation of undesired off-target mutations. Here, we present a novel strategy for mismatch repair evasion using temperature-sensitive DNA repair mutants and temporal inactivation of the mismatch repair protein complex in Escherichia coli. Our method relies on the transient suppression of DNA repair during mismatch carrying oligonucleotide integration. Using temperature-sensitive control of methyl-directed mismatch repair protein activity during multiplex genome engineering, we reduced the number of off-target mutations by 85%, concurrently maintaining highly efficient and unbiased allelic replacement.

Nyerges, Akos; Csorgo, Balint; Nagy, Istvan; Latinovics, Dora; Szamecz, Bela; Posfai, Gyorgy; Pal, Csaba

2014-01-01

47

The zebrafish early arrest mutants.  

PubMed

This report describes mutants of the zebrafish having phenotypes causing a general arrest in early morphogenesis. These mutants identify a group of loci making up about 20% of the loci identified by mutants with visible morphological phenotypes within the first day of development. There are 12 Class I mutants, which fall into 5 complementation groups and have cells that lyse before morphological defects are observed. Mutants at three loci, speed bump, ogre and zombie, display abnormal nuclei. The 8 Class II mutants, which fall into 6 complementation groups, arrest development before cell lysis is observed. These mutants seemingly stop development in the late segmentation stages, and maintain a body shape similar to a 20 hour embryo. Mutations in speed bump, ogre, zombie, specter, poltergeist and troll were tested for cell lethality by transplanting mutant cells into wild-type hosts. With poltergeist, transplanted mutant cells all survive. The remainder of the mutants tested were autonomously but conditionally lethal: mutant cells, most of which lyse, sometimes survive to become notochord, muscles, or, in rare cases, large neurons, all cell types which become postmitotic in the gastrula. Some of the genes of the early arrest group may be necessary for progression though the cell cycle; if so, the survival of early differentiating cells may be based on having their terminal mitosis before the zygotic requirement for these genes. PMID:9007229

Kane, D A; Maischein, H M; Brand, M; van Eeden, F J; Furutani-Seiki, M; Granato, M; Haffter, P; Hammerschmidt, M; Heisenberg, C P; Jiang, Y J; Kelsh, R N; Mullins, M C; Odenthal, J; Warga, R M; Nüsslein-Volhard, C

1996-12-01

48

Classical conditioning and retention in normal and mutant Drosophila melanogaster  

Microsoft Academic Search

Summary By changing the conditioned discrimination paradigm of Quinn et al. (1974) from an instrumental procedure to a classical (Pavlovian) one, we have demonstrated strong learning in type flies. About 150 flies were sequestered in a closed chamber and trained by explosing them sequentially to two odors in air currents. Flies received twelve electric shock pulses in the presence of

Tim Tully; William G. Quinn

1985-01-01

49

Growth Properties of Rhodospirillum rubrum Mutants and Fermentation of Pyruvate in Anaerobic, Dark Conditions1  

PubMed Central

Mutant C and G1 were obtained earlier from Rhodospirillum rubrum S1 during growth in the dark under strict anaerobic conditions in medium containing sodium pyruvate. Mutant C and mutant G1 grew in the dark with generation times of 5.8 h and 4.6 h, respectively. Mutant C cells grew equally well when switched between anaerobic (dark or light) or aerobic, dark conditions. Mutant G1 cells grew only in the dark (anaerobic or aerobic conditions), but a fraction of cells in anaerobic, dark cultures grew when placed in light. This number increased about 3,000-fold when G1 cells were incubated aerobically in the dark. During anaerobic, dark growth, C and G1 organisms incorporated similar amounts of [2-14C]sodium pyruvate. About 34% of the incorporated radioactivity was found in lipid fractions from C cells that developed chromatophores during dark growth. Similar results were obtained using G1 cells, which formed only trace amounts of photosynthetic structures. Both mutants fermented sodium pyruvate and produced acetate, formate, carbon dioxide, and hydrogen gas. Molar growth yield coefficients indicated that the cells obtained about 1 mol of adenosine triphosphate per mol of sodium pyruvate fermented. Results suggested that pyruvate fermentation during dark growth occurred via a pyruvate formate-lyase or the pyruvate ferredoxin-oxidoreductase pathway, or both.

Uffen, R. L.

1973-01-01

50

The uses of genome-wide yeast mutant collections  

Microsoft Academic Search

We assess five years of usage of the major genome-wide collections of mutants from Saccharomyces cerevisiae: single deletion mutants, double mutants conferring 'synthetic' lethality and the 'TRIPLES' collection of mutants obtained\\u000a by random transposon insertion. Over 100 experimental conditions have been tested and more than 5,000 novel phenotypic traits\\u000a have been assigned to yeast genes using these collections.

Bart Scherens; Andre Goffeau

2004-01-01

51

Swimming Behaviour and Otolith Characteristics of wildtype and mutant Zebrafish (AIE) under diminished Gravity Conditions  

NASA Astrophysics Data System (ADS)

During microgravity humans often suffer from sensorimotor disorders e g motion sickness a kinetosis Using fish as vertebrate model systems we could previously provide ample evidence that the individually different susceptibility to such disorders is based on an individually differently pronounced asymmetric mineralisation calcification of inner ear stones otoliths In the course of a preliminary study we subjected mutant zebrafish Danio rerio due to malformation of the inner ear - see below - this mutant was termed Asymmetric Inner Ear AIE to diminished gravity conditions during parabolic aircraft flight PF As compared to wildtype WT animals the mutants showed a pronounced kinetotic behaviour The gross-morphology of the inner ears of AIE and WT animals strikingly differed In WT specimens the saccular otoliths were located at the periphery of the inner ear whereas the utricular stones were positioned mediad as it is usually the case in teleosts in most AIE animals dissected however the respective otoliths were positioned in an opposite arrangement Moreover the mutants sported transparent otoliths whereas the otoliths of WT specimens had an opaque appearance This finding clearly indicates that mutant otoliths differed from wildtype ones in their lattice structure i e the calcium carbonate polymorph and thus the compostion of the proteinacious matrix which is a template for calcium carbonate deposition In the course of the present study the PF experiment is scheduled to be carried out in March 2006 we intend to statistically verify

Weigele, J.; Anken, R.; Hilbig, R.

52

Characterization of the Two Maize Embryo-Lethal Defective Kernel Mutants Rgh*-1210 and Fl*-1253b: Effects on Embryo and Gametophyte Development  

PubMed Central

We have examined the effects on embryonic and gametophytic development of two nonallelic defective-kernel mutants of maize. Earlier studies indicated that both mutants are abnormal in embryonic morphogenesis as well as in the formation of their endosperm. Mutant rgh*-1210 embryos depart from the normal embryogenic pathway at the proembryo and transition stage, by developing meristematic lobes and losing bilateral symmetry. They continue growth as irregular cell masses that enlarge and become necrotic. Somatic embryos arising in rgh*-1210 callus cultures display the rgh*-1210 mutant phenotype. Mutant fl*-1253B embryos are variably blocked from the coleoptilar stage through stage 2. Following formation of the shoot apex in the mutant embryos the leaf primordia and tissues surrounding the embryonic axis continue growth and cell division, while the scutellum ceases development and becomes hypertrophied. Mutant fl*-1253B embryos are unable to germinate, either in mutant kernels or as immature embryos in culture, and the mutant scutellar tissue does not produce regenerable callus. Expression of the fl*-1253B locus during male gametophytic development is revealed by a marked reduction in pollen transmission as a result of mutant expression during the interval between meiosis and the initiation of pollen tube growth. In both mutants, there is considerable proliferation of the aleurone cells of the endosperm. Mutant expression of rgh*-1210 in the female gametophyte is revealed by the abnormal antipodal cells of the embryo sac. These results show that these two gene loci play unique and crucial roles in normal morphogenesis of the embryo. In addition, it is evident that both mutants are pleiotropic in affecting the development of the endosperm and gametophyte as well as the embryo. These pleiotropisms suggest some commonality in the gene regulation of development in these three tissues.

Clark, J. K.; Sheridan, W. F.

1988-01-01

53

Rhodobacter sphaeroides mutants which accumulate 5-aminolevulinic acid under aerobic and dark conditions.  

PubMed

The photosynthetic bacterium Rhodobacter sphaeroides accumulates 5-aminolevulinic acid (ALA), which is a precursor in tetrapyrrole biosynthesis, under light illumination and upon addition of levulinic acid as an inhibitor of ALA dehydratase. To generate an industrial strain which produces ALA in the absence of light, we sequentially mutated R. sphaeroides CR-286 using N-methyl-N'-nitro-N-nitrosoguanidine (NTG). The mutant strains were screened by cultivating in the absence of light and assayed for ALA by the Ehrlich reaction in a 96-well microtiter plate. The mutant strain CR-386, derived from R. sphaeroides CR-286, was selected as a mutant that exhibited significant ALA accumulation. While CR-286 required light illumination for ALA production, CR-386 was able to accumulate 1.5 mM ALA in the presence of 50 mM glucose, 60 mM glycine, 15 mM levulinic acid and 1.0% (w/v) yeast extract under conditions of agitation in the absence of light. The mutant strain CR-450, derived from strain CR-386, was selected further as a mutant that exhibited significant ALA accumulation but no accumulation of aminoacetone, analogue of ALA. CR-450 accumulated 3.8 mM ALA under the same conditions. In the presence of 50 mM glucose, 60 mM glycine, 5 mM levulinic acid and 1.0% (w/v) yeast extract, the mutant strain CR-520, derived from strain CR-450, and strain CR-606, derived from strain CR-520, accumulated 8.1 mM and 11.2 mM ALA, respectively. In batch fermentation, the strain CR-606 accumulated 20 mM ALA over 18 h after the addition of glycine, levulinic acid, glucose and yeast extract. PMID:16232557

Nishikawa, S; Watanabe, K; Tanaka, T; Miyachi, N; Hotta, Y; Murooka, Y

1999-01-01

54

Enhanced extinction of contextual fear conditioning in Clock?19 mutant mice.  

PubMed

Clock genes have been implicated in several disorders, such as schizophrenia, bipolar disorder, autism spectrum disorders, and drug dependence. However, few studies to date have examined the role of clock genes in fear-related behaviors. The authors used mice with the Clock?19 mutation to assess the involvement of this gene in contextual fear conditioning. Male wild-type (WT) and Clock?19 mutant mice underwent a single session of contextual fear conditioning (12 min, 4 unsignaled shocks), followed by daily 12-min retention trials. There were no differences between mutant and WT mice in the acquisition of contextual fear, and WT and mutant mice demonstrated similar freezing during the first retention session. However, extinction of contextual fear was accelerated in mutant mice across the remaining retention sessions, as compared to WT mice, suggesting a role for Clock in extinction following aversive learning. Because the Clock?19 mutation has previously been demonstrated to result in an increase in dopamine signaling, the authors confirmed the role of dopamine in extinction learning using preretention session administration of a low dose of the dopamine transport reuptake inhibitor modafinil (0.75 mg/kg), which resulted in decreased freezing across retention sessions. These findings are consistent with an emerging portrayal of the importance of Clock genes in noncircadian functions, as well as the important role of dopamine in extinction learning. (PsycINFO Database Record (c) 2014 APA, all rights reserved). PMID:24865659

Bernardi, Rick E; Spanagel, Rainer

2014-08-01

55

The Live Attenuated Actinobacillus pleuropneumoniae Triple-Deletion Mutant ?apxIC ?apxIIC ?apxIV-ORF1 Strain, SLW05, Immunizes Pigs against Lethal Challenge with Haemophilus parasuis  

PubMed Central

Haemophilus parasuis and Actinobacillus pleuropneumoniae both belong to the family Pasteurellaceae and are major respiratory pathogens that cause large economic losses in the pig industry worldwide. We previously constructed an attenuated A. pleuropneumoniae serovar 1 live vaccine prototype, SLW05 (?apxIC ?apxIIC ?apxIV-ORF1), which is able to produce nontoxic but immunogenic ApxIA, ApxIIA, and ApxIVA. This triple-deletion mutant strain was shown to elicit protective immunity against virulent A. pleuropneumoniae. In the present study, we investigated whether immunization with SLW05 could also protect against lethal challenge with virulent H. parasuis SH0165 (serovar 5) or MD0322 (serovar 4). The SLW05 strain was found to elicit a strong humoral antibody response in pigs and to confer significant protection against challenge with a lethal dose of H. parasuis SH0165 or MD0322. IgG subtype analysis revealed that SLW05 induces a bias toward a Th1-type immune response and stimulates interleukin 2 (IL-2) and gamma interferon (IFN-?) production. Moreover, antisera from SLW05-vaccinated pigs efficiently inhibited both A. pleuropneumoniae and H. parasuis growth in a whole-blood assay. This is the first report that a live attenuated A. pleuropneumoniae vaccine with SLW05 can protect against lethal H. parasuis infection, which provides a novel approach for developing an attenuated H. parasuis vaccine.

Fu, Shulin; Ou, Jiwen; Zhang, Minmin; Xu, Juan; Liu, Huazhen; Liu, Jinlin; Yuan, Fangyan; Chen, Huanchun

2013-01-01

56

Optimized Condition for Enhanced Soluble-Expression of Recombinant Mutant Anabaena Variabilis Phenylalanine Ammonia Lyase  

PubMed Central

Purpose: Recently discovered Anabaena variabilis phenylalanine ammonia lyase (AvPAL) proved to be a good candidate for enzyme replacement therapy of phenylketonuria. Outstanding stability properties of a mutant version of this enzyme, produced already in our laboratory, have led us to the idea of culture conditions optimization for soluble expression of this therapeutically valuable enzyme in E. coli. Methods: In the present study, the gene encoding mutant version of AvPAL was cloned into the pET28a expression vector. Different concentrations of IPTG, induction period, growth temperature, shaking speed, as well as different types of culture media were examined with respect to the amount of recombinant protein produced and specific activity of the enzyme. Results: Based upon our findings, maximum amount of active mutant enzyme was attained by addition of 0.5 mM IPTG at 150 rpm to the TB culture media. The yield of active enzyme at cluture tempreature of 25 °C and induction period of 18 hour was the highest. Conclusion: The results of this study indicated that the yield of mutant AvPAL production in E. coli can be affected mainly by culture temperature and inducer concentration.

Zarei Jaliani, Hossein; Farajnia, Safar; Safdari, Yaghoub; Mohammadi, Seyyed Abolghasem; Barzegar, Abolfazl; Talebi, Saeed

2014-01-01

57

Optimized condition for enhanced soluble-expression of recombinant mutant anabaena variabilis phenylalanine ammonia lyase.  

PubMed

Purpose: Recently discovered Anabaena variabilis phenylalanine ammonia lyase (AvPAL) proved to be a good candidate for enzyme replacement therapy of phenylketonuria. Outstanding stability properties of a mutant version of this enzyme, produced already in our laboratory, have led us to the idea of culture conditions optimization for soluble expression of this therapeutically valuable enzyme in E. coli. Methods: In the present study, the gene encoding mutant version of AvPAL was cloned into the pET28a expression vector. Different concentrations of IPTG, induction period, growth temperature, shaking speed, as well as different types of culture media were examined with respect to the amount of recombinant protein produced and specific activity of the enzyme. Results: Based upon our findings, maximum amount of active mutant enzyme was attained by addition of 0.5 mM IPTG at 150 rpm to the TB culture media. The yield of active enzyme at cluture tempreature of 25 °C and induction period of 18 hour was the highest. Conclusion: The results of this study indicated that the yield of mutant AvPAL production in E. coli can be affected mainly by culture temperature and inducer concentration. PMID:24754010

Zarei Jaliani, Hossein; Farajnia, Safar; Safdari, Yaghoub; Mohammadi, Seyyed Abolghasem; Barzegar, Abolfazl; Talebi, Saeed

2014-01-01

58

Conditional Deletion of Insulin-Like Growth Factor-I in Collagen Type 1?2-Expressing Cells Results in Postnatal Lethality and a Dramatic Reduction in Bone Accretion  

PubMed Central

IGF-I acts through endocrine and local, autocrine/paracrine routes. Disruption of both endocrine and local IGF-I action leads to neonatal lethality and impaired growth in various tissues including bone; however, the severity of growth and skeletal phenotype caused by disruption of endocrine IGF-I action is far less than with total IGF-I disruption. Based on these data and the fact that bone cells express IGF-I in high abundance, we and others predicted that locally produced IGF-I is also critical in regulating growth and bone accretion. To determine the role of local IGF-I, type 1?2 collagen-Cre mice were crossed with IGF-I loxP mice to generate Cre+ (conditional mutant) and Cre? (control) loxP homozygous mice. Surprisingly, approximately 40–50% of the conditional mutants died at birth, which is similar to total IGF-I disruption, but not observed in mice lacking circulating IGF-I. Expression of IGF-I in bone and muscle but not liver and brain was significantly decreased in the conditional mutant. Accordingly, circulating levels of serum IGF-I were also not affected. Disruption of local IGF-I dramatically reduced body weight 28–37%, femur areal bone mineral density 10–25%, and femur bone size 18–24% in growing mice. In addition, mineralization was reduced as early as during embryonic development. Consistently, histomorphometric analysis determined impaired osteoblast function as demonstrated by reduced mineral apposition rate (14–30%) and bone formation rate (35–57%). In conclusion, both local and endocrine IGF-I actions are involved in regulating growth of various tissues including bone, but they act via different mechanisms.

Govoni, Kristen E.; Wergedal, Jon E.; Florin, Lore; Angel, Peter; Baylink, David J.; Mohan, Subburaman

2010-01-01

59

Growth stimulation in inflorescences of an Arabidopsis tubulin mutant under microgravity conditions in space.  

PubMed

Cortical microtubules are involved in plant resistance to hypergravity, but their roles in resistance to 1 g gravity are still uncertain. To clarify this point, we cultivated an Arabidopsis ?-tubulin 6 mutant (tua6) in the Cell Biology Experiment Facility on the Kibo Module of the International Space Station, and analyzed growth and cell wall mechanical properties of inflorescences. Growth of inflorescence stems was stimulated under microgravity conditions, as compared with ground and on-orbit 1 g conditions. The stems were 10-45% longer and their growth rate 15-55% higher under microgravity conditions than those under both 1 g conditions. The degree of growth stimulation tended to be higher in the tua6 mutant than the wild-type Columbia. Under microgravity conditions, the cell wall extensibility in elongating regions of inflorescences was significantly higher than the controls, suggesting that growth stimulation was caused by cell wall modifications. No clear differences were detected in any growth or cell wall property between ground and on-orbit 1 g controls. These results support the hypothesis that cortical microtubules generally play an important role in plant resistance to the gravitational force. PMID:24148142

Hoson, T; Soga, K; Wakabayashi, K; Hashimoto, T; Karahara, I; Yano, S; Tanigaki, F; Shimazu, T; Kasahara, H; Masuda, D; Kamisaka, S

2014-01-01

60

Optimisation of biotransformation conditions for production of 2-phenylethanol by a Saccharomyces cerevisiae CWY132 mutant  

Microsoft Academic Search

A mutant Saccharomyces cerevisiae CWY132 was isolated, producing 1.393?g?L 2-phenylethanol (2-PE) in a batch process containing 5?g?L L-phenylalanine (L-Phe), which is equivalent to an increase of 38.3% compared to the initial strain. In this study, biotransformation conditions of this strain were studied. We found glucose, KH2PO4, (NH4)2SO4, and amounts of inoculum cells had significant effects on the biotransformation process; in

Zhifeng Cui; Xiao Yang; Qingjia Shen; Kun Wang; Tingheng Zhu

2011-01-01

61

Retinal isomer composition in some bacteriorhodopsin mutants under light and dark adaptation conditions  

SciTech Connect

The isomeric composition of retinal was measured in a number of bacteriorhodopsin (bR) mutants (D85N, D212N, R82A, Y185F, and D115N) under various conditions, using a rapid retinal extraction technique followed by HPLC analysis. Besides the 13-cis and the all-trans retinal isomers observed in wild type (wt) bR under physiological conditions, the 11-cis and 9-cis retinal isomers were observed in variable but minor amounts in the bR mutants. In addition, the values of the equilibrium constant at two temperatures and the enthalpy change for the all-trans to 13-cis isomerization process in the dark-adapted state of D212N, D85N, deionized blue bR, and wt bR were determined. We find that perturbation of the retinal cavity (pocket) by residue replacement changes the relative thermal stability of the different retinal isomers, allowing for thermal-and/or photoisomerization of the retinal chromophore along C{sub 9}-C{sub 10} and C{sub 11}-C{sub 12} bonds to moderately compete with the isomerization around the C{sub 13}-C{sub 14} bond. The bR mutants expressed in Halobacterium salinarium studied in the present work showed normal 13-cis to all-trans light adaptation, in contrast with abnormal all-trans to 13-cis light adaptation observed for D212E, D212A, and D212N expressed in Escherichia coli, suggesting an influence of the purple membrane lattice and/or the lipids on the stability of the different retinal isomers within the protein. 38 refs., 2 tabs.

Song, L.; Yang, D.; El-Sayed, M.A. [Georgia Inst. of Technology, Atlanta, GA (United States); Lanyi, J.K. [Univ. of California, Irvine, CA (United States)

1995-06-15

62

Mutant DISC1 affects methamphetamine-induced sensitization and conditioned place preference: a comorbidity model.  

PubMed

Genetic factors involved in neuroplasticity have been implicated in major psychiatric illnesses such as schizophrenia, depression, and substance abuse. Given its extended interactome, variants in the Disrupted-In-Schizophrenia-1 (DISC1) gene could contribute to drug addiction and psychiatric diseases. Thus, we evaluated how dominant-negative mutant DISC1 influenced the neurobehavioral and molecular effects of methamphetamine (METH). Control and mutant DISC1 mice were studied before or after treatment with non-toxic escalating dose (ED) of METH. In naïve mice, we assessed METH-induced conditioned place preference (CPP), dopamine (DA) D2 receptor density and the basal and METH-induced activity of DISC1 partners, AKT and GSK-3? in the ventral striatum. In ED-treated mice, 4 weeks after METH treatment, we evaluated fear conditioning, depression-like responses in forced swim test, and the basal and METH-induced activity of AKT and GSK-3? in the ventral striatum. We found impairment in METH-induced CPP, decreased DA D2 receptor density and altered METH-induced phosphorylation of AKT and GSK-3? in naïve DISC1 female mice. The ED regimen was not neurotoxic as evidenced by unaltered brain regional monoamine tissue content. Mutant DISC1 significantly delayed METH ED-produced sensitization and affected drug-induced phosphorylation of AKT and GSK-3? in female mice. Our results suggest that perturbations in DISC1 functions in the ventral striatum may impact the molecular mechanisms of reward and sensitization, contributing to comorbidity between drug abuse and major mental diseases. PMID:21315744

Pogorelov, Vladimir M; Nomura, Jun; Kim, Jongho; Kannan, Geetha; Ayhan, Yavuz; Yang, Chunxia; Taniguchi, Yu; Abazyan, Bagrat; Valentine, Heather; Krasnova, Irina N; Kamiya, Atsushi; Cadet, Jean Lud; Wong, Dean F; Pletnikov, Mikhail V

2012-03-01

63

Generation of a conditional mutant allele for Tab1 in mouse  

PubMed Central

TAK1 binding protein1 (TAB1) binds and induces autophosphrylation of TGF-? activating kinase (TAK1). TAK1, a mitogen activated kinase kinase kinase, is involving in several distinct signaling pathways including non-Smad pathways for TGF-? superfamily members and inflammatory responses caused by cytokines. Conventional disruption of the murine Tab1 gene results in late gestation lethality showing intraventricular septum defects and under developed lung alveoli. To gain a better understanding of the roles of TAB1 in different tissues at different stages of development and in pathological conditions, we generated Tab1 floxed mice in which loxP sites flank exons 9 and 10 to remove the C-terminal region of TAB1 protein necessary for activation of TAK1. We demonstrate that Cre-mediated recombination using Sox2-Cre, a Cre line expressed in the epiblast during early embryogenesis, results in deletion of the gene and protein. These homozygous Cre-recombined null embryos display an identical phenotype to conventional null embryos. This animal model will be useful to reveal distinct roles of TAB1 in different tissues at different stages.

Inagaki, Maiko; Komatsu, Yoshihiro; Scott, Greg; Yamada, Gen; Ray, Manas; Ninomiya-Tsuji, Jun; Mishina, Yuji

2009-01-01

64

Contribution of Oxidative Damage to Antimicrobial Lethality?  

PubMed Central

A potential pathway linking hydroxyl radicals to antimicrobial lethality was examined by using mutational and chemical perturbations of Escherichia coli. Deficiencies of sodA or sodB had no effect on norfloxacin lethality; however, the absence of both genes together reduced lethal activity, consistent with rapid conversion of excessive superoxide to hydrogen peroxide contributing to quinolone lethality. Norfloxacin was more lethal with a mutant deficient in katG than with its isogenic parent, suggesting that detoxification of peroxide to water normally reduces quinolone lethality. An iron chelator (bipyridyl) and a hydroxyl radical scavenger (thiourea) reduced the lethal activity of norfloxacin, indicating that norfloxacin-stimulated accumulation of peroxide affects lethal activity via hydroxyl radicals generated through the Fenton reaction. Ampicillin and kanamycin, antibacterials unrelated to fluoroquinolones, displayed behavior similar to that of norfloxacin except that these two agents showed hyperlethality with an ahpC (alkyl hydroperoxide reductase) mutant rather than with a katG mutant. Collectively, these data are consistent with antimicrobial stress increasing the production of superoxide, which then undergoes dismutation to peroxide, from which a highly toxic hydroxyl radical is generated. Hydroxyl radicals then enhance antimicrobial lethality, as suggested by earlier work. Such findings indicate that oxidative stress networks may provide targets for antimicrobial potentiation.

Wang, Xiuhong; Zhao, Xilin

2009-01-01

65

Enhanced inactivation of Escherichia coli and Listeria monocytogenes by exposure to 405 nm light under sub-lethal temperature, salt and acid stress conditions.  

PubMed

The antimicrobial effects of 405 nm light have generated interest in its use as an emerging disinfection technology with potential food-related applications. The aim of this study was to assess the bactericidal efficacy of 405 nm light for inactivation of Escherichia coli and Listeria monocytogenes under sub-lethally stressed environmental conditions. Bacteria were exposed to 405 nm light from a light emitting diode (LED) array under various temperature, salt (NaCl) and acid conditions to determine if bacterial susceptibility to 405 nm light inactivation is affected when exposed under these conditions. Non-stressed bacterial populations (10(5) CFU/mL) were exposed to increasing doses of 405 nm light (~70 mW/cm(2)) and the inactivation results were compared with those generated under stress conditions. Bacteria were held at various temperatures (4°C, 22°C and 45°C), acid concentrations (pH3, 3.5 and 7) and salt concentrations (0%, 0.8%, 10% and 15% NaCl), and simultaneously exposed to 405 nm light. Enhanced inactivation of both E. coli and L. monocytogenes was achieved when light exposure was combined with each of the sub-lethal stresses, with significantly increased inactivation rates compared to non-stressed populations (P?0.05). One exception was with L. monocytogenes when light-exposed in the presence of 15% salt, as this combination reduced bacterial inactivation. The greatest enhancement of 405 nm light inactivation for both bacterial species was achieved when light exposure was combined with sub-lethal acid stress conditions at pH3. This was demonstrated by a 5-log10 reduction of E. coli following a 405 nm light dose of 84 J/cm(2) compared to 378 J/cm(2) for non-stressed populations (77% reduction in dose) and by a 5-log10 reduction of L. monocytogenes achieved with a dose of 42 J/cm(2) which corresponded to 50% of the dose required for the equivalent reduction of non-stressed populations. This acid-enhanced 405 nm light inactivation effect was demonstrated with E. coli and L. monocytogenes when dispersed in liquid suspension and when deposited on a test surface. Overall, results from this study have shown that sub-lethally stressed bacteria have increased susceptibility to 405 nm light inactivation, thereby providing a synergistic inactivation effect, findings which increase the potential of this new light-based decontamination technology for food related applications. PMID:24291187

McKenzie, Karen; Maclean, Michelle; Timoshkin, Igor V; MacGregor, Scott J; Anderson, John G

2014-01-17

66

Bactericidal activity of PA-824 against Mycobacterium tuberculosis under anaerobic conditions and computational analysis of its novel analogues against mutant Ddn receptor  

PubMed Central

Background The resurgence of multi-drug resistant tuberculosis (MDR-TB) and HIV associated tuberculosis (TB) are of serious global concern. To contain this situation, new anti-tuberculosis drugs and reduced treatment regimens are imperative. Recently, a nitroimidazole, PA-824, has been shown to be active against both replicating and non-replicating bacteria. It is activated by the enzyme Deazaflavin-dependent nitroreductase (Ddn) present in Mycobacterium tuberculosis which catalyzes the reduction of PA-824, resulting in the release of lethal reactive nitrogen species (RNS) within the bacteria. In this context, PA-824 was analyzed for its activity against latent tuberculosis under anaerobic conditions and compared with rifampicin (RIF) and pyrazinamide (PZA). Recent mutagenesis studies have identified A76E mutation which affects the above mentioned catalysis and leads to PA-824 resistance. Hence, novel analogues which could cope up with their binding to mutant Ddn receptor were also identified through this study. Results PA-824 at an optimum concentration of 12.5 ?g/ml showed enhanced bactericidal activity, resulting in 0 CFU/ml growth when compared to RIF and PZA at normal pH and anaerobic condition. Further docking studies revealed that a combinatorial structure of PA-824 conjugated with moxifloxacin (ligand 8) has the highest binding affinity with the wild type and mutant Ddn receptor. Conclusions PA-824 has been demonstrated to have better activity under anaerobic condition at 12.5 ?g/ml, indicating an optimized dose that is required for overcoming the detoxifying mechanisms of M. tuberculosis and inducing its death. Further, the development of resistance through A76E mutation could be overcome through the in silico evolved ligand 8.

2013-01-01

67

Tn5-induced mutants of Azotobacter vinelandii affected in nitrogen fixation under Mo-deficient and Mo-sufficient conditions  

SciTech Connect

Mutants of Azotobacter vinelandii affected in N/sub 2/ fixation in the presence of 1 ..mu..M Na/sub 2/MoO/sub 4/ (conventional system), 50 nM V/sub 2/O/sub 5/, or under Mo deficiency (alternative system) have been isolated after Tn5 mutagenesis with the suicide plasmid pSUP1011. These mutants are grouped into four broad phenotypic classes. Mutants in the first class are Nif/sup -/ under Mo sufficiency but Nif/sup +/ under Mo deficiency or in the presence of V/sub 2/O/sub 5/. Mutants in the second class are Nif/sup -/ under all conditions. An FeMo-cofactor-negative mutant (NifB/sup -/) belongs to this class. The third mutant class consists of mutants incapable of N/sub 2/-dependent growth under Mo deficiency. Most of the mutants of this class are also affected in N/sub 2/ fixation in the presence of 1 ..mu..M Na/sub 2/MoO/sub 4/, with acetylene reduction rates ranging from 28 to 51% of the rates of the wild type. Strains constructed by genetic transfer of the Kan/sup r/ marker of mutants from this class into nifHDK or nifK deletion mutants showed N/sub 2/-dependent growth only in the presence of V/sup 2/O/sub 5/. The only mutant in the fourth class shows wild-type nitrogenase activity under Mo sufficiency, but only 10% of the acetylene reduction activity of the wild type in the presence of 50 nM V/sub 2/O/sub 5/. The acetylene reduction rates of whole cells of this mutant are identical in Mo-deficient medium and in medium containing V/sub 2/O/sub 5/. The conventional nitrogenase subunits are expressed in this mutant even under Mo deficiency or in the presence of V/sub 2/O/sub 5/; however, the NH/sub 4//sup +/-and Mo-repressible proteins normally seen under these conditions could not be detected on two-dimensional gels.

Joerger, R.D.; Premakumar, R.; Bishop, P.E.

1986-11-01

68

Conditionally lethal mutations in chinese hamster cells. Characterization of a cell line with a possible defect in the Krebs cycle.  

PubMed

A variant Chinese hamster cell line has been isolated from a mutagenized population that has a markedly reduced ability to oxidize a variety of substrates via the Krebs cycle. The production of 14CO2 from 14C-labeled compounds was measured using pyruvate, acetate, beta-hydroxybutyrate, palmitate and glutamate, and in all cases it was neglibible in the mutant. In contrast to this, significant amounts of 14CO2 were produced from 14C-aspartate and 14C-succinate which suggest that some reactions of the Krebs cycle can take place and this conclusion is supported by tracer experiments with labeled compounds. The rate of respiration measured with a Clark oxygen electrode in the mutant was compared to several normal Chinese hamster cell lines and was found to be only 8%. Mitochondria appear to be present in normal numbers and with only minor differences in morphology. The measurement of difference spectra between oxidized and reduced states permits us to conclude that the cytochromes are all present and functional. These results lead us to believe that there may be a defect in the Krebs cycle between alpha-ketoglutarate and succinate. Alternatively a defect in a structural component of the mitochondria or in the electron-transport chain itself may be causing pleiotropic effects in the Krebs cycle and respiration. PMID:1123408

DeFrancesco, L; Werntz, D; Scheffler, I E

1975-04-01

69

Manipulating Individual Decisions and Environmental Conditions Reveal Individual Quality in Decision-Making and Non-Lethal Costs of Predation Risk  

PubMed Central

Habitat selection is a crucial decision for any organism. Selecting a high quality site will positively impact survival and reproductive output. Predation risk is an important component of habitat quality that is known to impact reproductive success and individual condition. However, separating the breeding consequences of decision-making of wild animals from individual quality is difficult. Individuals face reproductive decisions that often vary with quality such that low quality individuals invest less. This reduced reproductive performance could appear a cost of increased risk but may simply reflect lower quality. Thus, teasing apart the effects of individual quality and the effect of predation risk is vital to understand the physiological and reproductive costs of predation risk alone on breeding animals. In this study we alter the actual territory location decisions of pied flycatchers by moving active nests relative to breeding sparrowhawks, the main predators of adult flycatchers. We experimentally measure the non-lethal effects of predation on adults and offspring while controlling for effects of parental quality, individual territory choice and initiation of breeding. We found that chicks from high predation risk nests (<50 m of hawk) were significantly smaller than chicks from low risk nests (>200 m from hawk). However, in contrast to correlative results, females in manipulated high risk nests did not suffer decreased body condition or increased stress response (HSP60 and HSP70). Our results suggest that territory location decisions relative to breeding avian predators cause spatial gradients in individual quality. Small adjustments in territory location decisions have crucial consequences and our results confirm non-lethal costs of predation risk that were expressed in terms of smaller offspring produced. However, females did not show costs in physiological condition which suggests that part of the costs incurred by adults exposed to predation risk are quality determined.

Thomson, Robert L.; Tomas, Gustavo; Forsman, Jukka T.; Monkkonen, Mikko

2012-01-01

70

Analysis of the Role of Vaccinia Virus H7 in Virion Membrane Biogenesis with an H7-Deletion Mutant  

PubMed Central

Essential vaccinia virus genes are often studied with conditional-lethal inducible mutants. Here, we constructed a deletion mutant lacking the essential H7R gene (the ?H7 mutant) with an H7-expressing cell line. Compared to an inducible H7 mutant, the ?H7 mutant showed a defect at an earlier step of virion membrane biogenesis, before the development of short crescent-shaped precursors of the viral envelope. Our studies refine the role of H7 in virion membrane biogenesis and highlight the values of analyzing deletion mutants.

Meng, Xiangzhi; Wu, Xiang; Yan, Bo; Deng, Junpeng

2013-01-01

71

Assessment of fruit quality attributes of tomato hybrids involving ripening mutants under high temperature conditions  

Microsoft Academic Search

Tomato (Solanum lycopersicum L.) is the most important horticultural crop worldwide. High temperature causes significant losses in tomato production due to reduced fruit set and lower quality fruits. A few pleiotropic, single gene ripening mutants such as slow-ripening alcobaca (alc), ripening inhibitor (rin), and non-ripening (nor) have been reported in tomato. The F1 hybrids involving these mutants have in the

Naveen Garg; Devinder Singh Cheema

2011-01-01

72

Optimization of culture conditions for 1,3-propanediol production from glycerol using a mutant strain of Klebsiella pneumoniae.  

PubMed

In the present work, mutant strains of Klebsiella pneumoniae with deletions of the als gene encoding acetolactate synthase involved in synthesis of 2,3-butanediol, the ldhA gene encoding lactate dehydrogenase required for lactate synthesis, or both genes, were prepared. Production of 1,3-propanediol (1,3-PD) from glycerol was enhanced in the ldhA mutant strain (?ldhA), but lower in ?als or ?als ?ldhA mutant strains compared to the parent strain, concomitant with a reduction in the glycerol consumption rate, indicating that deletion of ldhA alone was useful to improve 1,3-PD production. Fed-batch fermentation analysis revealed that, in the ?ldhA mutant strain, 1,3-PD production was higher at low pH than at neutral pH; the reverse was true for the parent strain. Further optimization of culture conditions, by variation of aeration and glycerol feed rates, dramatically improved the production of 1,3-PD by the mutant strain. The maximum level attained was 102.7 g?l(-1) of 1,3-PD from glycerol. PMID:22072138

Oh, Baek-Rock; Seo, Jeong-Woo; Heo, Sun-Yeon; Hong, Won-Kyung; Luo, Lian Hua; Kim, Seonghun; Park, Don-Hee; Kim, Chul Ho

2012-01-01

73

The Activity of Nodules of the Supernodulating Mutant Mtsunn Is not Limited by Photosynthesis under Optimal Growth Conditions  

PubMed Central

Legumes match the nodule number to the N demand of the plant. When a mutation in the regulatory mechanism deprives the plant of that ability, an excessive number of nodules are formed. These mutants show low productivity in the fields, mainly due to the high carbon burden caused through the necessity to supply numerous nodules. The objective of this study was to clarify whether through optimal conditions for growth and CO2 assimilation a higher nodule activity of a supernodulating mutant of Medicago truncatula (M. truncatula) can be induced. Several experimental approaches reveal that under the conditions of our experiments, the nitrogen fixation of the supernodulating mutant, designated as sunn (super numeric nodules), was not limited by photosynthesis. Higher specific nitrogen fixation activity could not be induced through short- or long-term increases in CO2 assimilation around shoots. Furthermore, a whole plant P depletion induced a decline in nitrogen fixation, however this decline did not occur significantly earlier in sunn plants, nor was it more intense compared to the wild-type. However, a distinctly different pattern of nitrogen fixation during the day/night cycles of the experiment indicates that the control of N2 fixing activity of the large number of nodules is an additional problem for the productivity of supernodulating mutants.

Cabeza, Ricardo A.; Lingner, Annika; Liese, Rebecca; Sulieman, Saad; Senbayram, Mehmet; Trankner, Merle; Dittert, Klaus; Schulze, Joachim

2014-01-01

74

Autophagy in yeast demonstrated with proteinase-deficient mutants and conditions for its induction  

Microsoft Academic Search

For determination of the physiological role and mechanism of vacuolar proteolysis in the yeast Saccharomyces cerevisiae, mutant cells lacking pro- teinase A, B, and carboxypeptidase Y were transferred from a nutrient medium to a synthetic medium devoid of various nutrients and morphological changes of their vacuoles were investigated. After incubation for 1 h in nutrient-deficient media, a few spherical bodies

Kazuhiko Takeshige; Misuzu Baba; Shigeru Tsuboi; Takeshi Noda; Yoshinori Ohsumi

1992-01-01

75

Effect of culture conditions on astaxanthin production by a mutant of Phaffia rhodozyma in batch and chemostat culture  

Microsoft Academic Search

Temperature and pH had only a slight effect on the astaxanthin content of a Phaffia rhodozyma mutant, but influenced the maximum specific growth rate and cell yield profoundly. The optimum conditions for astaxanthin production were 22°C at pH 5.0 with a low concentration of carbon source. Astaxanthin production was growth-associated, and the volumetric astaxanthin concentration gradually decreased after depletion of

Petrus S. Meyer; James C. Du Preez

1994-01-01

76

Rhodobacter sphaeroides mutants which accumulate 5-aminolevulinic acid under aerobic and dark conditions  

Microsoft Academic Search

The photosynthetic bacterium Rhodobacter sphaeroides accumulates 5-aminolevulinic acid (ALA), which is a precursor in tetrapyrrole biosynthesis, under light illumination and upon addition of levulinic acid as an inhibitor of ALA dehydratase. To generate an industrial strain which produces ALA in the absence of light, we sequentially mutated R. sphaeroides CR-286 using N-methyl-N?-nitro-N-nitrosoguanidine (NTG). The mutant strains were screened by cultivating

Seiji Nishikawa; Keitaro Watanabe; Tohru Tanaka; Nobuya Miyachi; Yasushi Hotta; Yoshikatsu Murooka

1999-01-01

77

Conditional Derepression of Ferritin Synthesis in Cells Expressing a Constitutive IRP1 Mutant  

Microsoft Academic Search

Iron regulatory protein 1 (IRP1), a major posttranscriptional regulator of cellular iron and energy metab- olism, is controlled by an iron-sulfur cluster switch. Cysteine-437 is critical for coordinating the cluster, and its replacement yields mutants that do not respond to iron perturbations and constitutively bind to cognate mRNA iron-responsive elements (IREs). The expression of IRP1C437S in cells has been associated

Jian Wang; Kostas Pantopoulos

2002-01-01

78

A unique class of conditional sir2 mutants displays distinct silencing defects in Saccharomyces cerevisiae.  

PubMed Central

Silencing provides a critical means of repressing transcription through the assembly and modification of chromatin proteins. The NAD(+)-dependent deacetylation of histones by the Sir2p family of proteins lends mechanistic insight into how SIR2 contributes to silencing. Here we describe three locus-specific sir2 mutants that have a spectrum of silencing phenotypes in yeast. These mutants are dependent on SIR1 for silencing function at the HM silent mating-type loci, display distinct phenotypes at the rDNA, and have dominant silencing defects at the telomeres. Telomeric silencing is restored if the mutant proteins are directly tethered to subtelomeric regions, via a Gal4p DNA-binding domain (GBD), or are recruited by tethered GBD-Sir1p. These sir2 mutations are found within conserved residues of the SIR2 family and lead to defects in catalytic activity. Since one of the mutations lies outside the previously defined minimal catalytic core, our results show that additional regions of Sir2p can be important for enzymatic activity and that differences in levels of activity may have distinct effects at the silenced loci.

Garcia, Sandra N; Pillus, Lorraine

2002-01-01

79

Synaptic E3 Ligase SCRAPPER in Contextual Fear Conditioning: Extensive Behavioral Phenotyping of Scrapper Heterozygote and Overexpressing Mutant Mice  

PubMed Central

SCRAPPER, an F-box protein coded by FBXL20, is a subunit of SCF type E3 ubiquitin ligase. SCRAPPER localizes synapses and directly binds to Rab3-interacting molecule 1 (RIM1), an essential factor for synaptic vesicle release, thus it regulates neural transmission via RIM1 degradation. A defect in SCRAPPER leads to neurotransmission abnormalities, which could subsequently result in neurodegenerative phenotypes. Because it is likely that the alteration of neural transmission in Scrapper mutant mice affect their systemic condition, we have analyzed the behavioral phenotypes of mice with decreased or increased the amount of SCRAPPER. We carried out a series of behavioral test batteries for Scrapper mutant mice. Scrapper transgenic mice overexpressing SCRAPPER in the hippocampus did not show any significant difference in every test argued in this manuscript by comparison with wild-type mice. On the other hand, heterozygotes of Scrapper knockout [SCR (+/?)] mice showed significant difference in the contextual but not cued fear conditioning test. In addition, SCR (+/?) mice altered in some tests reflecting anxiety, which implies the loss of functions of SCRAPPER in the hippocampus. The behavioral phenotypes of Scrapper mutant mice suggest that molecular degradation conferred by SCRAPPER play important roles in hippocampal-dependent fear memory formation.

Yao, Ikuko; Takao, Keizo; Miyakawa, Tsuyoshi; Ito, Seiji; Setou, Mitsutoshi

2011-01-01

80

Bright Mutants of Vibrio fischeri ES114 Reveal Conditions and Regulators That Control Bioluminescence and Expression of the lux Operon?  

PubMed Central

Vibrio fischeri ES114, an isolate from the Euprymna scolopes light organ, produces little bioluminescence in culture but is ?1,000-fold brighter when colonizing the host. Cell-density-dependent regulation alone cannot explain this phenomenon, because cells within colonies on solid medium are much dimmer than symbiotic cells despite their similar cell densities. To better understand this low luminescence in culture, we screened ?20,000 mini-Tn5 mutants of ES114 for increased luminescence and identified 28 independent “luminescence-up” mutants with insertions in 14 loci. Mutations affecting the Pst phosphate uptake system led to the discovery that luminescence is upregulated under low-phosphate conditions by PhoB, and we also found that ainS, which encodes an autoinducer synthase, mediates repression of luminescence during growth on plates. Other novel luminescence-up mutants had insertions in acnB, topA, tfoY, phoQ, guaB, and two specific tRNA genes. Two loci, hns and lonA, were previously described as repressors of bioluminescence in transgenic Escherichia coli carrying the light-generating lux genes, and mutations in arcA and arcB were consistent with our report that Arc represses lux. Our results reveal a complex regulatory web governing luminescence and show how certain environmental conditions are integrated into regulation of the pheromone-dependent lux system.

Lyell, Noreen L.; Dunn, Anne K.; Bose, Jeffrey L.; Stabb, Eric V.

2010-01-01

81

RecA-Dependent Replication in the nrdA101(Ts) Mutant of Escherichia coli under Restrictive Conditions?  

PubMed Central

Cells carrying the thermosensitive nrdA101 allele are able to replicate entire chromosomes at 42°C when new DNA initiation events are inhibited. We investigated the role of the recombination enzymes on the progression of the DNA replication forks in the nrdA101 mutant at 42°C in the presence of rifampin. Using pulsed-field gel electrophoresis (PFGE), we demonstrated that the replication forks stalled and reversed during the replication progression under this restrictive condition. DNA labeling and flow cytometry experiments supported this finding as the deleterious effects found in the RecB-deficient background were suppressed specifically by the absence of RuvABC; however, this did not occur in a RecG-deficient background. Furthermore, we show that the RecA protein is absolutely required for DNA replication in the nrdA101 mutant at restrictive temperature when the replication forks are reversed. The detrimental effect of the recA deletion is not related to the chromosomal degradation caused by the absence of RecA. The inhibition of DNA replication observed in the nrdA101 recA mutant at 42°C in the presence of rifampin was reverted by the presence of the wild-type RecA protein expressed ectopically but only partially suppressed by the RecA protein with an S25P mutation [RecA(S25P)], deficient in the rescue of the stalled replication forks. We propose that RecA is required to maintain the integrity of the reversed forks in the nrdA101 mutant under certain restrictive conditions, supporting the relationship between DNA replication and recombination enzymes through the stabilization and repair of the stalled replication forks.

Salguero, Israel; Guarino, Estrella; Guzman, Elena C.

2011-01-01

82

Conditional poliovirus mutants made by random deletion mutagenesis of infectious cDNA.  

PubMed Central

Small deletions were introduced into DNA plasmids bearing cDNA copies of Mahoney type 1 poliovirus RNA. The procedure used was similar to that of P. Hearing and T. Shenk (J. Mol. Biol. 167:809-822, 1983), with modifications designed to introduce only one lesion randomly into each DNA molecule. Methods to map small deletions in either large DNA or RNA molecules were employed. Two poliovirus mutants, VP1-101 and VP1-102, were selected from mutagenized populations on the basis of their host range phenotype, showing a large reduction in the relative numbers of plaques on CV1 and HeLa cells compared with wild-type virus. The deletions borne by the mutant genomes were mapped to the region encoding the amino terminus of VP1. That these lesions were responsible for the mutant phenotypes was substantiated by reintroduction of the sequenced lesions into a wild-type poliovirus cDNA by deoxyoligonucleotide-directed mutagenesis. The deletion of nucleotides encoding amino acids 8 and 9 of VP1 was responsible for the VP1-101 phenotype; the VP1-102 defect was caused by the deletion of the sequences encoding the first four amino acids of VP1. The peptide sequence at the VP1-VP3 proteolytic cleavage site was altered from glutamine-glycine to glutamine-methionine in VP1-102; this apparently did not alter the proteolytic cleavage pattern. The biochemical defects resulting from these mutations are discussed in the accompanying report. Images

Kirkegaard, K; Nelsen, B

1990-01-01

83

Canonical Notch signaling is not necessary for prosensory induction in the mouse cochlea: Insights from a conditional mutant of RBPj?  

PubMed Central

The mammalian organ of Corti consists of a highly organized array of hair cells and supporting cells that originate from a common population of prosensory progenitors. Proper differentiation of this complex cellular mosaic requires lateral inhibition mediated by Notch signaling. Several studies also have implicated Notch signaling in the earlier induction of the prosensory domain that lies along the length of the cochlear duct, and which forms prior to the onset of hair cell and supporting cell differentiation. To investigate the role of Notch signaling in prosensory domain formation, we conditionally inactivated the transcriptional mediator of canonical Notch signaling, RBPj?, throughout the inner ear. While RBPj? mutants have severe vestibular defects and a shortened cochlear duct, markers of the prosensory domain appear at the normal time and location in the cochlea of RBPj? mutants. Despite the lack of RBPj?, hair cell and supporting cell markers also appear at appropriate times in the cochlea, suggesting that RBPj? is dispensable for differentiation of the cochlear sensory epithelium. However, we also observed that differentiating hair cells and supporting cells rapidly die in RBPj? mutants, suggesting a requirement of RBPj? for cell survival in this tissue. Finally, in contrast to the chick basilar papilla, ectopic activation of Notch signaling did not induce ectopic sensory patches in non-sensory regions of the cochlea. Our results indicate that canonical Notch signaling is not necessary for prosensory specification in the mouse cochlea, suggesting that other signaling pathways may specify this highly derived sensory organ.

Basch, Martin L.; Ohyama, Takahiro; Segil, Neil; Groves, Andrew K.

2011-01-01

84

Dilute down lethal: a new lethal mutation in Japanese quail.  

PubMed

"Dilute down lethal (DDL)" is a new mutation of Japanese quail (Coturnix japonica). Neonatal plumage of the DDL mutant is the same as the wild type in pattern, but its coloration is slightly lighter than that of the wild type. In addition to the down color abnormality, some DDL chicks have bent digits. All DDL chicks die within three days of age. Genetic analysis revealed that the DDL mutation is controlled by an autosomal recessive gene. The proposed gene symbol is ddl. PMID:9027479

Tsudzuki, M; Nakane, Y; Wada, A

1997-01-01

85

Elemental Concentrations in the Seed of Mutants and Natural Variants of Arabidopsis thaliana Grown under Varying Soil Conditions  

PubMed Central

The concentrations of mineral nutrients in seeds are critical to both the life cycle of plants as well as human nutrition. These concentrations are strongly influenced by soil conditions, as shown here by quantifying the concentration of 14 elements in seeds from Arabidopsis thaliana plants grown under four different soil conditions: standard, or modified with NaCl, heavy metals, or alkali. Each of the modified soils resulted in a unique change to the seed ionome (the mineral nutrient content of the seeds). To help identify the genetic networks regulating the seed ionome, changes in elemental concentrations were evaluated using mutants corresponding to 760 genes as well as 10 naturally occurring accessions. The frequency of ionomic phenotypes supports an estimate that as much as 11% of the A. thaliana genome encodes proteins of functional relevance to ion homeostasis in seeds. A subset of mutants were analyzed with two independent alleles, providing five examples of genes important for regulation of the seed ionome: SOS2, ABH1, CCC, At3g14280 and CNGC2. In a comparison of nine different accessions to a Col-0 reference, eight accessions were observed to have reproducible differences in elemental concentrations, seven of which were dependent on specific soil conditions. These results indicate that the A. thaliana seed ionome is distinct from the vegetative ionome, and that elemental analysis is a sensitive approach to identify genes controlling ion homeostasis, including those that regulate gene expression, phospho-regulation, and ion transport.

McDowell, Stephen C.; Akmakjian, Garo; Sladek, Chris; Mendoza-Cozatl, David; Morrissey, Joe B.; Saini, Nick; Mittler, Ron; Baxter, Ivan; Salt, David E.; Ward, John M.; Schroeder, Julian I.; Guerinot, Mary Lou; Harper, Jeffrey F.

2013-01-01

86

Peptidoglycan Synthesis in Cocci and Rods of a pH-Dependent, Morphologically Conditional Mutant of Klebsiella pneumoniae  

PubMed Central

Mir M7 is a spontaneous morphologically conditional mutant of Klebsiella pneumoniae which grows as round cells (cocci) at pH 7 and as normal rods at pH 5.8. We studied the rates of peptidoglycan synthesis of cocci and rods growing at pH values of 7 and 5.8, respectively. It was found that exponentially growing cocci produced a reduced amount of peptidoglycan per cell, compared with rods. Moreover, a shift of cocci to the permissive pH (5.8) caused an increase in the rate of peptidoglycan synthesis, whereas the reverse shift of rods to pH 7 determined a twofold reduction in the rate of [3H]diaminopimelic acid incorporation. During synchronous growth at pH 7, the rate of peptidoglycan synthesis after cell division decreased with time and rose before and during the first division. The susceptibilities of rods and cocci to ?-lactam antibiotics were also studied. It was found that cocci were more sensitive both to penicillin G and to cephalexin than were rods, but they showed a high level of resistance to mecillinam. The peculiar behavior of this mutant was interpreted as supporting the existence in bacterial rods of two different sites for peptidoglycan synthesis: one responsible for lateral wall elongation and one responsible for septum formation. In Mir M7, shape damage is described as dependent on the specific inhibition, at the nonpermissive pH, of the site for lateral wall extension. Images

Satta, G.; Fontana, R.; Canepari, P.; Botta, G.

1979-01-01

87

Theory of lethality  

SciTech Connect

Today the basic concepts and definitions essential to the development of a theory of lethality have not been established. For the most part, lethality is not considered an engineering problem. Rather, lethality studies are conducted on an intuitive basis with the emphasis placed on discovering an emotional appeal to help secure a favorable political climate for the continued existence of weapon system programs. As a consequence, the lethality of advanced weapon concepts is difficult to establish and lethality considerations are secondary, and perhaps even optional, to the thrust of a technology program. It is the author's contention that lethality is, at best, a poorly understood concept, but that a general theory of lethality can be developed which will permit lethality studies to be performed systematically and to produce credible results. A definition of lethality is presented that requires accurate and efficient evaluation of the survivability of the target systems. Methods for evaluating the survivability of a target system are discussed. A life cycle concept of lethality is introduced which may assist management of 6.1 through 6.4 programs. The author's observations are based upon experiences while participating in the Air Force Neutral Particle Beam Program.

Browning, J.S.

1984-01-01

88

Transposon Tn5 as an identifiable marker in rhizobia: Survival and genetic stability of Tn5 mutant bean rhizobia under temperature stressed conditions in desert soils.  

PubMed

Five transposon Tn5 insertion mutants of a beanRhizobium strain (Rhizobium leguminosarum b. v.phaseoli) were used in an ecological study to evaluate the extent to which transposon Tn5 was stable to serve as an identifiable marker in rhizobia under a high temperature stress condition in two Sonoran Desert soils. All the mutants possessed single chromosomal insertions of the transposon. In both soils, under the temperature stress conditions that were employed (40°C), both wild type and mutant populations possessing functional transposable elements declined rapidly. After 12 days, mutant cells, when screened using the Tn5 coded antibiotic resistance markers, were significantly less in number than when they were screened using only their intrinsic antibiotic resistance markers. There were no significant differences in numbers between the mutant cell population and the wild type when the mutant cells were screened using only the intrinsic antibiotic resistance markers. DNA-DNA hybridizations using a probe indicated neither deletion nor transposition of the transposable element. The results indicate that transposon DNA sequences are present within cells under high temperature stress conditions, but kanamycin/neomycin resistance is not expressed by some of these cells, suggesting that Tn5 undergoes a possible functional inactivation under these conditions. The possible implications of these findings are discussed. PMID:24194199

Pillai, S D; Pepper, I L

1991-12-01

89

Conditional identification of phosphate-starvation-response mutants in Arabidopsis thaliana  

Microsoft Academic Search

.   Plants have evolved elaborate metabolic and developmental adaptations to low phosphorus availability. Biochemical responses\\u000a to phosphate limitation include increased production and secretion of phosphate-acquisition proteins such as nucleases, acid\\u000a phosphatases, and high-affinity phosphate transporters. However, the signal transduction pathways that sense phosphate availability\\u000a and integrate the phosphate-starvation response in plants are unknown. We have devised a screen for conditional

Donna L. Chen; Carla A. Delatorre; Aleida Bakker; Steffen Abel

2000-01-01

90

Failure of chimerism formation and tolerance induction from Fas ligand mutant bone marrow donors after nonmyeloablative conditioning.  

PubMed

Formation of donor-recipient mixed chimerism after nonmyeloablative conditioning allows co-existence of donor and recipient hematopoietic stem cells, with solid organ allograft tolerance and less likeliness of graft versus host development. Using a post-transplant bronchiolitis obliterans murine model, we aimed to test the hypothesis that allograft preservation after mixed chimerism formation is dependent on the presence of a functional Fas ligand (FasL) on donor hematopoietic cells. To form mixed chimerism, two aliquots of 30 × 10(6) whole bone marrow cells (BMC) from either wild-type C57BL/6 in one group, or transgenic gld mice with mutant FasL (d = 0 and 2+) in the other were used, with both groups receiving intravenous busulfan (10mg/kg) on d-1 and intraperitoneal cyclophosphamide (200mg/kg) on d+1. Tracheal allografts obtained from C57BL/6 mice were implanted into recipient BALB/c mice subcutaneously on d = 0. Tracheal allografts were harvested at d+28 post-transplant and were evaluated by histopathology. Mixed chimerism formation was detected in wild type C57BL/6 whole BMC recipients, which was accompanied by tracheal allograft acceptance with near normal structure at d+28 post implantation. However, in recipients of FasL mutant whole BMC, neither mixed chimerism formation nor tracheal allograft acceptance was obtained. We thus conclude that bone marrow cells lacking functional FasL molecules could not be engrafted in allogeneic recipients to form stable mixed chimerism after nonmyeloablative conditioning, thus not allowing tracheal allograft acceptance. PMID:22801052

Nusair, Samir; Gincberg, Galit; Almogi-Hazan, Osnat; Breuer, Raphael; Or, Reuven; Wallach-Dayan, Shulamit B

2012-12-01

91

LETHALS, STERILES AND DEFICIENCIES IN A REGION OF THE X CHROMOSOME OF CAENORHABDZTZS ELEGANS  

Microsoft Academic Search

Twenty-one X-linked recessive lethal and sterile mutations balanced by an unlinked X-chromosome duplication have been identified following EMS treat- ment of the small nematode, Caenorhabditis elegans. The mutations have been assigned by complementation analysis to 14 genes, four of which have more than one mutant allele. Four mutants, all alleles, are temperature-sensitive embryonic lethals. Twelve mutants, in ten genes, are

PHILIP M. MENEELY; ROBERT K. HERMAN

1979-01-01

92

Lethals in subdivided populations.  

PubMed

The fate of lethal alleles in populations is of interest in evolutionary and conservation biology for several reasons. For instance, lethals may contribute substantially to inbreeding depression. The frequency of lethal alleles depends on population size, but it is not clear how it is affected by population structure. By analysing the case of the infinite island model by numerical approaches and analytical approximations it is shown that, like population size, population structure affects the fate of lethal alleles if dominance levels are low. Inbreeding depression caused by such alleles is also affected by the population structure, whereas the mutation load is only weakly affected. Heterosis also depends on population structure, but it always remains low, of the order of the mutation rate or less. These patterns are compared with those caused by mildly deleterious mutations to give a general picture of the effect of population structure on inbreeding depression, heterosis, and the mutation load. PMID:16181522

Glémin, Sylvain

2005-08-01

93

pH-Conditional, Ammonia Assimilation-Deficient Mutants of Hydrogenomonas eutropha: Evidence for the Nature of the Mutation1  

PubMed Central

Two amination-deficient mutants of Hydrogenomonas eutropha, characterized by pH-dependent linear growth on non-amino acid substrates, were investigated to determine the exact nature of the mutation. Glutamate dehydrogenase, the only aminating enzyme found in wild-type cells, was present at similar levels in mutant cells. Phenylalanine and aspartate, which allowed normal growth of the mutants, could transaminate 2-oxoglutarate to glutamate, whereas alanine, which does not support normal growth, could not transfer its amino nitrogen to form glutamate. In H. eutropha, l-alanine is apparently synthesized by ?-decarboxylation of aspartate. Studies with NH4+ ions as the sole nitrogen source demonstrated that growth rates of the mutant strains were dependent on both extracellular pH and NH4+ ion concentration. Comparison of these results revealed that the growth rate of mutant cultures was proportional to the concentration of extracellular NH3. Wild-type cultures were not dependent on extracellular NH3 since exponential growth rates did not vary with pH or NH4+ ion concentration. The results suggest that the mutant strains lack an NH4+ ion transport system and consequently are dependent on NH3 diffusion which does not support optimal amination rates. The significance of the findings for the amino acid metabolism of H. eutropha is discussed.

Strenkoski, Leon F.; DeCicco, B. T.

1971-01-01

94

Cold-sensitive mutants of bacteriophage phi x174. II. Comparison of two cold-sensitive mutants.  

PubMed

Cold-sensitive bacteriophage phiX174 mutants, another class of conditional lethals, were examined with regard to growth parameters, DNA synthesis, and particle properties. Two mutants, cs70 and cs82, were examined. Mutant cs70 was eclipse defective, showing altered eclipse kinetics at permissive temperature (40 C) and failing entirely to eclipse at restrictive temperature (25 C). Mutant cs70 replicated well at 25 C if allowed prior eclipse at 40 C. Mutant cs82 had wild-type eclipse at both temperatures but was defective in single-strand synthesis at 25 C, which led to delayed progeny phage appearance, decreased progeny phage synthesis rate, and greatly reduced burst size. The cs82 block could not be bypassed by temperature shift. Since complementation analysis of cs70 and cs82 was not feasible due to the unique properties of these mutants, those phiX174 properties affected by the virus coat were examined as an index of a mutation in a coat protein gene. Mutant cs70 had aberrant attachment kinetics at both 25 C and 40 C, evidence of a coat protein alteration. Mutant cs70 also exhibited significantly decreased thermal stability, further evidence of an altered virus structure. Mutant cs82 had increased thermal stability, but the difference was not sufficient to allow unequivocal assignment of this mutant to a coat protein gene. Both mutants had wild-type antiserum inactivation and host range, although cs70 was subject to less of (low-level) plating restriction by endogenous F(+) factors. PMID:4610177

Segal, D J; Dowell, C E

1974-11-01

95

[Temperature-sensitive autosomal dominant lethal mutations in Drosophila melanogaster induced by ethylmethane sulfonate].  

PubMed

Cold- and heat-sensitive dominant autosome and recessive sex-linked lethals were scored using C(1)RM, y; vg bw; e ss tester stock. The frequencies of heat-sensitive mutations were 1.43, 0.30, 0.07% and of cold-sensitive ones were 0.39, 0.16 and 0.09% in the 1-st, 2-nd and 3-rd chromosomes, respectively. For the first time, dominant cold-sensitive lethals were obtained in chromosome 3. The data from genetic analysis point to the fact that penetrance of such mutations strongly depends on the genetic background. That may be the reason, why they were not obtained using some of the balancer-3 chromosomes. Also, "cryptic" dominant autosome mutants were found which were not conditional but only revealed in the F2 generation. Their possible origin as gonado-somatic mosaics is discussed. PMID:6407896

Miasniankina, E N; Generalova, M V; Mitrofanov, V G

1983-04-01

96

Lethal effect of a bait for Rhodnius prolixus (Hemiptera: Reduviidae), the vector of Chagas' disease, containing hexachlorocyclohexane (HCH), under laboratory conditions.  

PubMed

The lethal effect of a bait containing an aqueous hexachlorocyclohexane (HCH) suspension at the concentration of 1g/l and maintained at room temperature was studied in the laboratory over a period of 12 weeks. The suspension was placed in a latex bag hanging inside a 1000-ml beaker tightly covered with nylon netting, and left there with no changes for 85 days. Sixteen groups of R. prolixus bugs, consisting on average of 30 specimens each, were successively exposed to the bait and observed at different intervals for one week each. The mortality rate was 100% for all groups, except for the 16th, whose mortality rate was 96.7%. As the groups succeeded one another, mortality started to occur more rapidly and was more marked at the 6- and 24-h intervals. Later tests respectively started at 6:00 a.m. and 6:00 p.m. showed that diurnal and nocturnal periodicity in the offer of food had no effect on mortality. First- and 2nd- instar nymphs and adults male were more sensitive and 5th- instar nymphs were more resistant to the active principle of the bait. PMID:1285256

Lima, M M; Rey, L; de Mello, R P

1992-01-01

97

A Mutant of Listeria monocytogenes LO28 Unable To Induce an Acid Tolerance Response Displays Diminished Virulence in a Murine Model  

Microsoft Academic Search

Exposing Listeria monocytogenes LO28 to sublethal pH induces protection against normally lethal pH conditions, a phenomenon known as the acid tolerance response. We identified a mutant, L. monocytogenes ATR1, which is incapable of inducing such tolerance, either against low pH or against any other stress tested. The virulence of this mutant was considerably decreased, suggesting that the acid tolerance response

LYNDA MARRON; NATHAN EMERSON; CORMAC G. M. GAHAN; COLIN HILL

1997-01-01

98

Molecular Foundations of Reproductive Lethality in Arabidopsis thaliana  

PubMed Central

The SeedGenes database (www.seedgenes.org) contains information on more than 400 genes required for embryo development in Arabidopsis. Many of these EMBRYO-DEFECTIVE (EMB) genes encode proteins with an essential function required throughout the life cycle. This raises a fundamental question. Why does elimination of an essential gene in Arabidopsis often result in embryo lethality rather than gametophyte lethality? In other words, how do mutant (emb) gametophytes survive and participate in fertilization when an essential cellular function is disrupted? Furthermore, why do some mutant embryos proceed further in development than others? To address these questions, we first established a curated dataset of genes required for gametophyte development in Arabidopsis based on information extracted from the literature. This provided a basis for comparison with EMB genes obtained from the SeedGenes dataset. We also identified genes that exhibited both embryo and gametophyte defects when disrupted by a loss-of-function mutation. We then evaluated the relationship between mutant phenotype, gene redundancy, mutant allele strength, gene expression pattern, protein function, and intracellular protein localization to determine what factors influence the phenotypes of lethal mutants in Arabidopsis. After removing cases where continued development potentially resulted from gene redundancy or residual function of a weak mutant allele, we identified numerous examples of viable mutant (emb) gametophytes that required further explanation. We propose that the presence of gene products derived from transcription in diploid (heterozygous) sporocytes often enables mutant gametophytes to survive the loss of an essential gene in Arabidopsis. Whether gene disruption results in embryo or gametophyte lethality therefore depends in part on the ability of residual, parental gene products to support gametophyte development. We also highlight here 70 preglobular embryo mutants with a zygotic pattern of inheritance, which provide valuable insights into the maternal-to-zygotic transition in Arabidopsis and the timing of paternal gene activation during embryo development.

Muralla, Rosanna; Lloyd, Johnny; Meinke, David

2011-01-01

99

Acetyl-CoA Carboxylase 2?/? Mutant Mice are Protected against Fatty Liver under High-fat, High-carbohydrate Dietary and de Novo Lipogenic Conditions*  

PubMed Central

Hepatic fat accumulation resulting from increased de novo fatty acid synthesis leads to hepatic steatosis and hepatic insulin resistance. We have shown previously that acetyl-CoA carboxylase 2 (Acc2?/?) mutant mice, when fed a high-fat (HF) or high-fat, high-carbohydrate (HFHC) diet, are protected against diet-induced obesity and maintained whole body and hepatic insulin sensitivity. To determine the effect of an ACC2 deletion on hepatic fat metabolism, we studied the regulation of the enzymes involved in the lipogenic pathway under Western HFHC dietary and de novo lipogenic conditions. After completing the HFHC regimen, Acc2?/? mutant mice were found to have lower body weight, smaller epididymal fat pads, lower blood levels of nonesterified fatty acids and triglycerides, and higher hepatic cholesterol than wild-type mice. Significant up-regulation of lipogenic enzymes and an elevation in hepatic peroxisome proliferator-activated receptor-? (PPAR-?) protein were found in Acc2?/? mutant mice under de novo lipogenic conditions. The increase in lipogenic enzyme levels was accompanied by up-regulation of the transcription factors, sterol regulatory element-binding proteins 1 and 2, and carbohydrate response element-binding protein. In contrast, hepatic levels of the PPAR-? and PPAR-? proteins were significantly lower in the Acc2?/? mutant mice fed an HFHC diet. When compared with wild-type mice fed the same diet, Acc2?/? mutant mice exhibited a similar level of AKT but with a significant increase in pAKT. Hence, deleting ACC2 ameliorates the metabolic syndrome and protects against fatty liver despite increased de novo lipogenesis and dietary conditions known to induce obesity and diabetes.

Abu-Elheiga, Lutfi; Wu, Hongmei; Gu, Ziwei; Bressler, Rubin; Wakil, Salih J.

2012-01-01

100

Production of infectious RNA transcripts from Sindbis virus cDNA clones: mapping of lethal mutations, rescue of a temperature-sensitive marker, and in vitro mutagenesis to generate defined mutants.  

PubMed Central

We constructed full-length cDNA clones of Sindbis virus that can be transcribed in vitro by SP6 RNA polymerase to produce infectious genome-length transcripts. Viruses produced from in vitro transcripts are identical to Sindbis virus and show strain-specific phenotypes reflecting the source of RNA used for cDNA synthesis. The cDNA clones were used to confirm the mapping of the causal mutation of ts2 to the capsid protein. A general strategy for mapping Sindbis virus mutations is described and was used to identify two lethal mutations in an original full-length construct which did not produce infectious transcripts. An XbaI linker was inserted in the cDNA clone near the transcriptional start of the subgenomic mRNA; the resulting virus retains the XbaI recognition sequence, thus providing formal evidence that viruses are derived from in vitro transcripts of cDNA clones. The potential applications of the cDNA clones are discussed. Images

Rice, C M; Levis, R; Strauss, J H; Huang, H V

1987-01-01

101

Therapeutic Efficacy of G207, a Conditionally Replicating Herpes Simplex Virus Type 1 Mutant, for Gallbladder Carcinoma in Immunocompetent Hamsters  

Microsoft Academic Search

Gallbladder cancer is an extremely difficult disease to cure once metastases occur. In this paper, we explored the potential of G207, an oncolytic, replication-competent herpes simplex virus type 1 mutant, as a new therapeutic means for gallbladder cancer. Gallbladder carcinoma cell lines (four human and one hamster) showed nearly total cell killing within 72 h of G207 infection at a

Kenji Nakano; Tomoki Todo; Kazuo Chijiiwa; Masao Tanaka

2001-01-01

102

Theory of lethal mutagenesis for viruses.  

PubMed

Mutation is the basis of adaptation. Yet, most mutations are detrimental, and elevating mutation rates will impair a population's fitness in the short term. The latter realization has led to the concept of lethal mutagenesis for curing viral infections, and work with drugs such as ribavirin has supported this perspective. As yet, there is no formal theory of lethal mutagenesis, although reference is commonly made to Eigen's error catastrophe theory. Here, we propose a theory of lethal mutagenesis. With an obvious parallel to the epidemiological threshold for eradication of a disease, a sufficient condition for lethal mutagenesis is that each viral genotype produces, on average, less than one progeny virus that goes on to infect a new cell. The extinction threshold involves an evolutionary component based on the mutation rate, but it also includes an ecological component, so the threshold cannot be calculated from the mutation rate alone. The genetic evolution of a large population undergoing mutagenesis is independent of whether the population is declining or stable, so there is no runaway accumulation of mutations or genetic signature for lethal mutagenesis that distinguishes it from a level of mutagenesis under which the population is maintained. To detect lethal mutagenesis, accurate measurements of the genome-wide mutation rate and the number of progeny per infected cell that go on to infect new cells are needed. We discuss three methods for estimating the former. Estimating the latter is more challenging, but broad limits to this estimate may be feasible. PMID:17202214

Bull, J J; Sanjuán, R; Wilke, C O

2007-03-01

103

Analysis of Influenza Virus Hemagglutinin Receptor Binding Mutants with Limited Receptor Recognition Properties and Conditional Replication Characteristics?  

PubMed Central

To examine the range of selective processes that potentially operate when poorly binding influenza viruses adapt to replicate more efficiently in alternative environments, we passaged a virus containing an attenuating mutation in the hemagglutinin (HA) receptor binding site in mice and characterized the resulting mutants with respect to the structural locations of mutations selected, the replication phenotypes of the viruses, and their binding properties on glycan microarrays. The initial attenuated virus had a tyrosine-to-phenylalanine mutation at HA1 position 98 (Y98F), located in the receptor binding pocket, but viruses that were selected contained second-site pseudoreversion mutations in various structural locations that revealed a range of molecular mechanisms for modulating receptor binding that go beyond the scope that is generally mapped using receptor specificity mutants. A comparison of virus titers in the mouse respiratory tract versus MDCK cells in culture showed that the mutants displayed distinctive replication properties depending on the system, but all were less attenuated in mice than the Y98F virus. An analysis of receptor binding properties confirmed that the initial Y98F virus bound poorly to several different species of erythrocytes, while all mutants reacquired various degrees of hemagglutination activity. Interestingly, both the Y98F virus and pseudoreversion mutants were shown to bind very inefficiently to standard glycan microarrays containing an abundance of binding substrates for most influenza viruses that have been characterized to date, provided by the Consortium for Functional Glycomics. The viruses were also examined on a recently developed microarray containing glycans terminating in sialic acid derivatives, and limited binding to a potentially interesting subset of glycans was revealed. The results are discussed with respect to mechanisms for HA-mediated receptor binding, as well as regarding the species of molecules that may act as receptors for influenza virus on host cell surfaces.

Bradley, Konrad C.; Galloway, Summer E.; Lasanajak, Yi; Song, Xuezheng; Heimburg-Molinaro, Jamie; Yu, Hai; Chen, Xi; Talekar, Ganesh R.; Smith, David F.; Cummings, Richard D.; Steinhauer, David A.

2011-01-01

104

Euglena gracilis as source of the antioxidant vitamin E. Effects of culture conditions in the wild strain and in the natural mutant WZSL  

Microsoft Academic Search

The photosynthetic wild type and the spontaneous non-photosynthetic WZSL mutant of the unicellular flagellate Euglena gracilis\\u000a were grown to investigate the influence of photoheterotrophic and heterotrophic conditions on ?-tocopherol (vitamin E) content.\\u000a HPLC analysis demonstrated a marked enhancement (almost 100%) of tocopherol content in the light in both strains, independent\\u000a of the presence of chloroplasts. These findings indicate that the

C. Kusmic; R. Barsacchi; L. Barsanti; P. Gualtieri; V. Passarelli

1998-01-01

105

Metabolic Flux Analysis of Escherichia coli creB and arcA Mutants Reveals Shared Control of Carbon Catabolism under Microaerobic Growth Conditions?  

PubMed Central

Escherichia coli has several elaborate sensing mechanisms for response to availability of oxygen and other electron acceptors, as well as the carbon source in the surrounding environment. Among them, the CreBC and ArcAB two-component signal transduction systems are responsible for regulation of carbon source utilization and redox control in response to oxygen availability, respectively. We assessed the role of CreBC and ArcAB in regulating the central carbon metabolism of E. coli under microaerobic conditions by means of 13C-labeling experiments in chemostat cultures of a wild-type strain, ?creB and ?arcA single mutants, and a ?creB ?arcA double mutant. Continuous cultures were conducted at D = 0.1 h?1 under carbon-limited conditions with restricted oxygen supply. Although all experimental strains metabolized glucose mainly through the Embden-Meyerhof-Parnas pathway, mutant strains had significantly lower fluxes in both the oxidative and the nonoxidative pentose phosphate pathways. Significant differences were also found at the pyruvate branching point. Both pyruvate-formate lyase and the pyruvate dehydrogenase complex contributed to acetyl-coenzyme A synthesis from pyruvate, and their activity seemed to be modulated by both ArcAB and CreBC. Strains carrying the creB deletion showed a higher biomass yield on glucose compared to the wild-type strain and its ?arcA derivative, which also correlated with higher fluxes from building blocks to biomass. Glyoxylate shunt and lactate dehydrogenase were active mainly in the ?arcA strain. Finally, it was observed that the tricarboxylic acid cycle reactions operated in a rather cyclic fashion under our experimental conditions, with reduced activity in the mutant strains.

Nikel, Pablo I.; Zhu, Jiangfeng; San, Ka-Yiu; Mendez, Beatriz S.; Bennett, George N.

2009-01-01

106

Metabolic flux analysis of Escherichia coli creB and arcA mutants reveals shared control of carbon catabolism under microaerobic growth conditions.  

PubMed

Escherichia coli has several elaborate sensing mechanisms for response to availability of oxygen and other electron acceptors, as well as the carbon source in the surrounding environment. Among them, the CreBC and ArcAB two-component signal transduction systems are responsible for regulation of carbon source utilization and redox control in response to oxygen availability, respectively. We assessed the role of CreBC and ArcAB in regulating the central carbon metabolism of E. coli under microaerobic conditions by means of (13)C-labeling experiments in chemostat cultures of a wild-type strain, DeltacreB and DeltaarcA single mutants, and a DeltacreB DeltaarcA double mutant. Continuous cultures were conducted at D = 0.1 h(-1) under carbon-limited conditions with restricted oxygen supply. Although all experimental strains metabolized glucose mainly through the Embden-Meyerhof-Parnas pathway, mutant strains had significantly lower fluxes in both the oxidative and the nonoxidative pentose phosphate pathways. Significant differences were also found at the pyruvate branching point. Both pyruvate-formate lyase and the pyruvate dehydrogenase complex contributed to acetyl-coenzyme A synthesis from pyruvate, and their activity seemed to be modulated by both ArcAB and CreBC. Strains carrying the creB deletion showed a higher biomass yield on glucose compared to the wild-type strain and its DeltaarcA derivative, which also correlated with higher fluxes from building blocks to biomass. Glyoxylate shunt and lactate dehydrogenase were active mainly in the DeltaarcA strain. Finally, it was observed that the tricarboxylic acid cycle reactions operated in a rather cyclic fashion under our experimental conditions, with reduced activity in the mutant strains. PMID:19561129

Nikel, Pablo I; Zhu, Jiangfeng; San, Ka-Yiu; Méndez, Beatriz S; Bennett, George N

2009-09-01

107

Growth-dependent DNA breakage and cell death in a gyrase mutant of Salmonella.  

PubMed Central

A class of gyrase mutants of Salmonella enterica mimics the properties of bacteria exposed to quinolones. These mutants suffer spontaneous DNA breakage during normal growth and depend on recombinational repair for viability. Unlike quinolone-treated bacteria, however, they do not show accumulation of cleavable gyrase-DNA complexes. In recA or recB mutant backgrounds, the temperature-sensitive (ts) allele gyrA208 causes rapid cell death at 43 degrees. Here, we isolated "suppressor-of-death" mutations, that is, secondary changes that allow a gyrA208 recB double mutant to survive a prolonged exposure to 43 degrees and subsequently to form colonies at 28 degrees. In most isolates, the secondary change was itself a ts mutation. Three ts alleles were mapped in genes coding for amino acyl tRNA synthetases (alaS, glnS, and lysS). Allele alaS216 completely abolished DNA breakage in a gyrA208 recA double mutant. Likewise, treating this mutant with chloramphenicol prevented death and DNA damage at 43 degrees. Additional suppressors of gyrA208 lethality include rpoB mutations and, surprisingly, icd mutations inactivating isocitrate dehydrogenase. We postulate that the primary effect of the gyrase alteration is to hamper replication fork movement. Inhibiting DNA replication under conditions of continuing macromolecular synthesis ("unbalanced growth") activates a mechanism that causes DNA breakage and cell death, reminiscent of "thymineless" lethality.

Gari, E; Bossi, L; Figueroa-Bossi, N

2001-01-01

108

Lethal midline granuloma.  

PubMed

Lethal midline granuloma is a relatively rare disease characterized by destruction and mutilation of the nose and other structures of respiratory passages. The nonspecificity of symptoms obscures the correct diagnosis and is responsible for the delay in treatment which can be detrimental as this grave disease calls for urgent intervention. We present a case report of this disease in a 35 year old male who gave a short two month history of the clinical symptoms. PMID:23440011

Mallya, Varuna; Singh, Avninder; Pahwa, Manish

2013-01-01

109

Deficits in Adult Neurogenesis, Contextual Fear Conditioning, and Spatial Learning in a Gfap Mutant Mouse Model of Alexander Disease  

PubMed Central

Glial fibrillary acidic protein (GFAP) is the major intermediate filament of mature astrocytes in the mammalian CNS. Dominant gain of function mutations in GFAP lead to the fatal neurodegenerative disorder, Alexander disease (AxD), which is characterized by cytoplasmic protein aggregates known as Rosenthal fibers along with variable degrees of leukodystrophy and intellectual disability. The mechanisms by which mutant GFAP leads to these pleiotropic effects are unknown. In addition to astrocytes, GFAP is also expressed in other cell types, particularly neural stem cells that form the reservoir supporting adult neurogenesis in the hippocampal dentate gyrus and subventricular zone of the lateral ventricles. Here, we show that mouse models of AxD exhibit significant pathology in GFAP-positive radial glia-like cells in the dentate gyrus, and suffer from deficits in adult neurogenesis. In addition, they display impairments in contextual learning and spatial memory. This is the first demonstration of cognitive phenotypes in a model of primary astrocyte disease.

Paylor, Richard; Messing, Albee

2013-01-01

110

Isolation of a wheat (Triticum aestivum L.) mutant in ABA 8?-hydroxylase gene: effect of reduced ABA catabolism on germination inhibition under field condition  

PubMed Central

Pre-harvest sprouting, the germination of mature seeds on the mother plant under moist condition, is a serious problem in cereals. To investigate the effect of reduced abscisic acid (ABA) catabolism on germination in hexaploid wheat (Triticum aestivum L.), we cloned the wheat ABA 8?-hydroxyase gene which was highly expressed during seed development (TaABA8?OH1) and screened for mutations that lead to reduced ABA catabolism. In a screen for natural variation, one insertion mutation in exon 5 of TaABA8?OH1 on the D genome (TaABA8?OH1-D) was identified in Japanese cultivars including ‘Tamaizumi’. However, a single mutation in TaABA8?OH1-D had no clear effect on germination inhibition in double haploid lines. In a screen for a mutation, one deletion mutant lacking the entire TaABA8?OH1 on the A genome (TaABA8?OH1-A), TM1833, was identified from gamma-ray irradiation lines of ‘Tamaizumi’. TM1833 (a double mutant in TaABA8?OH1-A and TaABA8?OH1-D) showed lower TaABA8?OH1 expression, higher ABA content in embryos during seed development under field condition and lower germination than those in ‘Tamaizumi’ (a single mutant in TaABA8?OH1-D). These results indicate that reduced ABA catabolism through mutations in TaABA8?OH1 may be effective in germination inhibition in field-grown wheat.

Chono, Makiko; Matsunaka, Hitoshi; Seki, Masako; Fujita, Masaya; Kiribuchi-Otobe, Chikako; Oda, Shunsuke; Kojima, Hisayo; Kobayashi, Daisuke; Kawakami, Naoto

2013-01-01

111

Mice Lacking Ras-GRF1 Show Contextual Fear Conditioning but not Spatial Memory Impairments: Convergent Evidence from Two Independently Generated Mouse Mutant Lines.  

PubMed

Ras-GRF1 is a neuronal specific guanine exchange factor that, once activated by both ionotropic and metabotropic neurotransmitter receptors, can stimulate Ras proteins, leading to long-term phosphorylation of downstream signaling. The two available reports on the behavior of two independently generated Ras-GRF1 deficient mouse lines provide contrasting evidence on the role of Ras-GRF1 in spatial memory and contextual fear conditioning. These discrepancies may be due to the distinct alterations introduced in the mouse genome by gene targeting in the two lines that could differentially affect expression of nearby genes located in the imprinted region containing the Ras-grf1 locus. In order to determine the real contribution of Ras-GRF1 to spatial memory we compared in Morris Water Maze learning Brambilla's mice with a third mouse line (GENA53) in which a non-sense mutation was introduced in the Ras-GRF1 coding region without additional changes in the genome and we found that memory in this task is normal. Also, we measured both contextual and cued fear conditioning, which were previously reported to be affected in Brambilla's mice, and we confirmed that contextual learning but not cued conditioning is impaired in both mouse lines. In addition, we also tested both lines for the first time in conditioned place aversion in the Intellicage, an ecological and remotely controlled behavioral test, and we observed normal learning. Finally, based on previous reports of other mutant lines suggesting that Ras-GRF1 may control body weight, we also measured this non-cognitive phenotype and we confirmed that both Ras-GRF1 deficient mutants are smaller than their control littermates. In conclusion, we demonstrate that Ras-GRF1 has no unique role in spatial memory while its function in contextual fear conditioning is likely to be due not only to its involvement in amygdala functions but possibly to some distinct hippocampal connections specific to contextual learning. PMID:22164138

d'Isa, Raffaele; Clapcote, Steven J; Voikar, Vootele; Wolfer, David P; Giese, Karl Peter; Brambilla, Riccardo; Fasano, Stefania

2011-01-01

112

Light down lethal: a new autosomal recessive down color mutation in Japanese quail.  

PubMed

A new plumage color mutation of Japanese quail (Coturnix japonica) was named "light down lethal" based on its light coloration of neonatal plumage and almost total mortality by 3 weeks of age. Prehatch mortality of the light down lethal was also higher (36.8%) than the wild type (8.2%). The majority of the light down lethal chicks that hatched died within 1 week of age. Among the 103 light down lethal chicks that hatched, only two males survived to adulthood and reproduced normally. Their adult mutant plumage was very similar to that of the wild type. The mutant down showed the same striped pattern on the dorsal surface as the wild-type chick, but the color of the stripes was lighter than the wild type. Genetic analysis revealed that the mutant phenotype is controlled by an autosomal recessive gene. The proposed gene symbol is ldl. PMID:7657997

Tsudzuki, M

1995-01-01

113

Therapeutic efficacy of G207, a conditionally replicating herpes simplex virus type 1 mutant, for gallbladder carcinoma in immunocompetent hamsters.  

PubMed

Gallbladder cancer is an extremely difficult disease to cure once metastases occur. In this paper, we explored the potential of G207, an oncolytic, replication-competent herpes simplex virus type 1 mutant, as a new therapeutic means for gallbladder cancer. Gallbladder carcinoma cell lines (four human and one hamster) showed nearly total cell killing within 72 h of G207 infection at a m.o.i. of 0.25 to 2.5 in vitro. The susceptibility to G207 cytopathic activity correlated with the infection efficiency demonstrated by lacZ expression. Intraneoplastic inoculation of G207 (1 x 10(7) pfu) in immunocompetent hamsters bearing established subcutaneous KIGB-5 tumors caused a significant inhibition of tumor growth and prolongation of survival. Repeated inoculations (three times with 4-day intervals) were significantly more efficacious than a single inoculation. In hamsters with bilateral subcutaneous KIGB-5 tumors, inoculation of one tumor alone with G207 caused regression or growth reduction of uninoculated tumors as well as inoculated tumors. In athymic mice, however, the anti-tumor effect was largely reduced in inoculated tumors and completely abolished in remote tumors, suggesting large contribution of T-cell-mediated immune responses to both local and systemic anti-tumor effect of G207. These results indicate that G207 may be useful as a new strategy for gallbladder cancer treatment. PMID:11319903

Nakano, K; Todo, T; Chijiiwa, K; Tanaka, M

2001-04-01

114

Deficits in adult neurogenesis, contextual fear conditioning, and spatial learning in a Gfap mutant mouse model of Alexander disease.  

PubMed

Glial fibrillary acidic protein (GFAP) is the major intermediate filament of mature astrocytes in the mammalian CNS. Dominant gain of function mutations in GFAP lead to the fatal neurodegenerative disorder, Alexander disease (AxD), which is characterized by cytoplasmic protein aggregates known as Rosenthal fibers along with variable degrees of leukodystrophy and intellectual disability. The mechanisms by which mutant GFAP leads to these pleiotropic effects are unknown. In addition to astrocytes, GFAP is also expressed in other cell types, particularly neural stem cells that form the reservoir supporting adult neurogenesis in the hippocampal dentate gyrus and subventricular zone of the lateral ventricles. Here, we show that mouse models of AxD exhibit significant pathology in GFAP-positive radial glia-like cells in the dentate gyrus, and suffer from deficits in adult neurogenesis. In addition, they display impairments in contextual learning and spatial memory. This is the first demonstration of cognitive phenotypes in a model of primary astrocyte disease. PMID:24259590

Hagemann, Tracy L; Paylor, Richard; Messing, Albee

2013-11-20

115

Repair of potentially lethal damage following irradiation with x rays or cyclotron neutrons: response of the EMT-6/UW tumor system treated under various growth conditions in vitro and in vivo  

SciTech Connect

Postirradiation potentially lethal damage (PLD) repair was examined in the EMT-6/UW tumor system under a variety of in vitro and in vivo growth conditions. Following x irradiation, surviving fraction increased in fed and unfed plateau cultures if subculture and plating were delayed; in exponentially growing cultures if they were covered with depleted medium for the first 6 h postirradiation; and in tumors in vivo if excision for preparation of a cell suspension was delayed. Following irradiation with 21.5 meV (d/sup +/ ..-->.. Be) neutrons, PLD repair was measurable only in unfed plateau cultures when subculture was delayed and in exponentially growing cells exposed to depleted culture medium immediately after irradiation. In x-irradiated EMT-6/UW cells, the greatest repair capacity and the highest surviving fraction ratios were measured in unfed plateau cultures; the least repair was observed in exponentially growing cells exposed to depleted medium. Thus post-neutron repair was not limited to situations where the amount of repair of photon PLD is large. The demonstration of PLD repair in tumors irradiated in vivo with X rays and the absence of such repair after neutrons could have important implications in radiotherapy if this is a general phenomenon.

Rasey, J.S.; Nelson, N.J.

1981-01-01

116

Physiological and biochemical responses of fruit exocarp of tomato (Lycopersicon esculentum Mill.) mutants to natural photo-oxidative conditions.  

PubMed

Photo-oxidative stress was imposed under natural solar radiation on exposed and shaded sections of detached fruit of immature green tomato (Lycopersicon esculentum Miller = Solanum lycopersicum L.) mutants (anthocyanin absent, beta-carotene, Delta, and high pigment-1) and their nearly isogenic parents ('Ailsa Craig' and 'Rutgers'). After 5 h exposure to high solar irradiance, either with or without ultraviolet (UV) radiation, surface colour changes, pigment composition, photosynthetic efficiency, antioxidant metabolites and enzyme activities, and selected flavonoids and antioxidant proteins in exocarp tissue were evaluated. The imposed photo-oxidative stress reproduced the symptoms observed on attached fruit. Both high temperature and solar irradiance caused fruit surface discoloration with faster degradation of chlorophyll (Chl) than carotenoids (Car), leading to an increase in the Car/Chl ratio. Surface bleaching was mostly caused by visible light, whereas elevated temperatures were mostly responsible for the inactivation of photosynthesis, measured as decreased F(v)/F(m). Ascorbate, glutathione, and total soluble protein concentrations decreased in the exocarp as the duration of exposure increased. Specific activities of superoxide dismutase, ascorbate peroxidase, dehydroascorbate reductase, monodehydroascorbate reductase (MDHAR), glutathione reductase (GR), and catalase increased with exposure, suggesting that these proteins were conserved during the imposed stress. GR protein expression remained stable during the imposed stress, whereas, MDHAR protein expression increased. Quercetin and kaempferol concentrations increased rapidly upon exposure, but not to UV radiation, suggesting rapid photo-protection in response to visible light; however, naringenin synthesis was not induced. The apparent increased tolerance of hp-1 fruit is discussed. PMID:16698820

Torres, Carolina A; Andrews, Preston K; Davies, Neal M

2006-01-01

117

Escherichia coli genes that reduce the lethal effects of stress  

PubMed Central

Background The continuing emergence of antimicrobial resistance requires the development of new compounds and/or enhancers of existing compounds. Genes that protect against the lethal effects of antibiotic stress are potential targets of enhancers. To distinguish such genes from those involved in drug uptake and efflux, a new susceptibility screen is required. Results Transposon (Tn5)-mediated mutagenesis was used to create a library of Escherichia coli mutants that was screened for hypersensitivity to the lethal action of quinolones and counter-screened to have wild-type bacteriostatic susceptibility. Mutants with this novel "hyperlethal" phenotype were found. The phenotype was transferable to other E. coli strains by P1-mediated transduction, and for a subset of the mutants the phenotype was complemented by the corresponding wild-type gene cloned into a plasmid. Thus, the inactivation of these genes was responsible for hyperlethality. Nucleotide sequence analysis identified 14 genes, mostly of unknown function, as potential factors protecting from lethal effects of stress. The 14 mutants were killed more readily than wild-type cells by mitomycin C and hydrogen peroxide; nine were also more readily killed by UV irradiation, and several exhibited increased susceptibility to killing by sodium dodecyl sulfate. No mutant was more readily killed by high temperature. Conclusions A new screening strategy identified a diverse set of E. coli genes involved in the response to lethal antimicrobial and environmental stress, with some genes being involved in the response to multiple stressors. The gene set, which differed from sets previously identified with bacteriostatic assays, provides an entry point for obtaining small-molecule enhancers that will affect multiple antimicrobial agents.

2010-01-01

118

Lethality test system  

SciTech Connect

The Lethality Test System (LTS), presently under construction at Los Alamos, is an electromagnetic launcher facility designed to perform impact experiments at velocities up to 15 km/s. The launcher is a 25 mm round bore, plasma armature railgun extending 22 m in length. Preinjection is accomplished with a two-stage gas gun capable of 7 km/s. The railgun power supply utilizes traction motors, vacuum interrupters, and pulse transformers. An assembly of 28 traction motors, equipped with flywheels, stores approximately 80 MJ at 92% of full speed and energizes the primary windings of three pulse transformers at a current of 50 kA. At peak current an array of vacuum interrupters disconnects the transformer primary windings and forces the current to flow in the secondary windings. The secondary windings are connected to the railgun, and by staging the vacuum interrupter openings, a 1 MA to 1.3 MA ramped current waveform will be delivered to the railgun.

Parsons, W.M.; Sims, J.R.; Parker, J.V.

1986-01-01

119

The Lethality Test System  

NASA Astrophysics Data System (ADS)

The Lethality Test System (LTS) under construction at Los Alamos is an electromagnetic launcher facility designed to perform impact experiments at velocities up to 15 km/sec. The launcher is a 25 mm round bore, plasma armature railgun 22 m in length. Preinjection is accomplished with a two-stage light gas gun capable of 7 km/sec. The railgun power supply utilizes traction motors, vacuum interrupters, and pulse transformers. An assembly of 28 traction motors, equipped with flywheels, stores approximately 80 MJ at 92 percent of full speed and energizes the primary windings of three pulse transformers at a current of 50 kA. At peak current an array of vacuum interrupters disconnects the transformer primary windings and forces the current to flow in the secondary windings. The secondary windings are connected to the railgun, and by staging the vacuum interrupter openings, a 1-1.3 MA ramped current waveform will be delivered to the railgun.

Parsons, W. M.; Sims, J. R.; Parker, J. V.

1986-11-01

120

Conditional loss of ErbB3 delays mammary gland hyperplasia induced by mutant PIK3CA without affecting mammary tumor latency, gene expression, or signaling.  

PubMed

Mutations in PIK3CA, the gene encoding the p110? catalytic subunit of phosphoinositide 3-kinase (PI3K), have been shown to transform mammary epithelial cells (MEC). Studies suggest this transforming activity requires binding of mutant p110? via p85 to phosphorylated YXXM motifs in activated receptor tyrosine kinases (RTK) or adaptors. Using transgenic mice, we examined if ErbB3, a potent activator of PI3K, is required for mutant PIK3CA-mediated transformation of MECs. Conditional loss of ErbB3 in mammary epithelium resulted in a delay of PIK3CA(H1047R)-dependent mammary gland hyperplasia, but tumor latency, gene expression, and PI3K signaling were unaffected. In ErbB3-deficient tumors, mutant PI3K remained associated with several tyrosyl phosphoproteins, potentially explaining the dispensability of ErbB3 for tumorigenicity and PI3K activity. Similarly, inhibition of ErbB RTKs with lapatinib did not affect PI3K signaling in PIK3CA(H1047R)-expressing tumors. However, the p110?-specific inhibitor BYL719 in combination with lapatinib impaired mammary tumor growth and PI3K signaling more potently than BYL719 alone. Furthermore, coinhibition of p110? and ErbB3 potently suppressed proliferation and PI3K signaling in human breast cancer cells harboring PIK3CA(H1047R). These data suggest that PIK3CA(H1047R)-driven tumor growth and PI3K signaling can occur independently of ErbB RTKs. However, simultaneous blockade of p110? and ErbB RTKs results in superior inhibition of PI3K and mammary tumor growth, suggesting a rational therapeutic combination against breast cancers harboring PIK3CA activating mutations. PMID:23633485

Young, Christian D; Pfefferle, Adam D; Owens, Philip; Kuba, María G; Rexer, Brent N; Balko, Justin M; Sánchez, Violeta; Cheng, Hailing; Perou, Charles M; Zhao, Jean J; Cook, Rebecca S; Arteaga, Carlos L

2013-07-01

121

Stem cell expansion during carcinogenesis in stem cell-depleted conditional telomeric repeat factor 2 null mutant mice.  

PubMed

To examine the role of telomeric repeat-binding factor 2 (TRF2) in epithelial tumorigenesis, we characterized conditional loss of TRF2 expression in the basal layer of mouse epidermis. These mice exhibit some characteristics of dyskeratosis congenita, a human stem cell depletion syndrome caused by telomere dysfunction. The epidermis in conditional TRF2 null mice exhibited DNA damage response and apoptosis, which correlated with stem cell depletion. The stem cell population in conditional TRF2 null epidermis exhibited shorter telomeres than those in control mice. Squamous cell carcinomas induced in conditional TRF2 null mice developed with increased latency and slower growth due to reduced numbers of proliferating cells as the result of increased apoptosis. TRF2 null epidermal stem cells were found in both primary and metastatic tumors. Despite the low-grade phenotype of the conditional TRF2 null primary tumors, the number of metastatic lesions was similar to control cancers. Basal cells from TRF2 null tumors demonstrated extreme telomere shortening and dramatically increased numbers of telomeric signals by fluorescence in situ hybridization due to increased genomic instability and aneuploidy in these cancers. DNA damage response signals were detected at telomeres in TRF2 null tumor cells from these mice. The increased genomic instability in these tumors correlated with eightfold expansion of the transformed stem cell population compared with that in control cancers. We concluded that genomic instability resulting from loss of TRF2 expression provides biological advantages to the cancer stem cell population. PMID:23178498

Bojovic, B; Ho, H-Y; Wu, J; Crowe, D L

2013-10-24

122

Serum Amyloid A Protects Murine Macrophages from Lethal Toxin-Mediated Death1  

PubMed Central

Lethal toxin, a key virulence factor produced by Bacillus anthracis, induces cell death, in part by disrupting numerous signaling pathways, in mouse macrophages. However, exposure to sublethal doses of lethal toxin allows some cells to survive. Because these pro-survival signaling events occur within a few hours after exposure to sublethal doses, we hypothesized that acute phase proteins might influence macrophage survival. Our data show that serum amyloid A (SAA) is produced in response to lethal toxin treatment. Moreover, pre-treatment of macrophages with exogenous SAA protected macrophages from lethal toxin-mediated death. Exogenous SAA activated the p38 mitogen activated protein kinase (MAP) kinase pathway, while lethal toxin mutants incapable of p38 activation were incapable of causing cell death. Chemical inhibition of the p38 activation pathway abrogated the protective effects of SAA. These data show that SAA affords protection against lethal toxin in mouse macrophages and link this response to the p38 pathway.

Rose, Kira; Long, Paul; Shankar, Malini; Ballard, Jimmy D.; Webb, Carol F.

2011-01-01

123

Swollen down plumules, an autosomal recessive lethal in turkeys.  

PubMed

Swollen down plumules, an embryonic lethal condition characterized by an enlargement of the dermal pulp cavity of down feathers, has been observed in a subline of turkeys. The lethality of the condition is expressed between 20 days of incubation and the time of pipping. Phenotypic variation of the disorder is expressed in the number of pterylae that contain the abnormal down plumules. The disorder is inherited as an autosomal recessive trait, and the gene symbol, sdp, is proposed. PMID:3725721

Savage, T F; Wallner-Pendelton, E; Harper, J A

1986-05-01

124

Biogenesis of thylakoid membranes is controlled by light intensity in the conditional chlorophyll b-deficient CD3 mutant of wheat  

PubMed Central

Biogenesis of thylakoid membranes in the conditional chlorophyll b- deficient CD3 mutant of wheat is dramatically altered by relatively small differences in the light intensity under which seedlings are grown. When the CD3 mutant is grown at 400 microE/m2 S (high light, about one-fifth full sunlight) plants are deficient in chlorophyll b (chlorophyll a/b ratio greater than 6.0) and lack or contain greatly reduced amounts of the chlorophyll a/b-binding complexes CPII/CPII (mobile or peripheral LHCII), CP29, CP24 and LHCI, as shown by mildly denaturing 'green gel' electrophoresis, by fully denaturing SDS-PAGE, and by Western blot analysis. High light CD3 chloroplasts display an unusual morphology characterized by large, sheet-like stromal thylakoids formed into parallel unstacked arrays and a limited number of small grana stacks displaced toward the edges of the arrays. Changes in the supramolecular organization of CD3 thylakoids, seen with freeze- fracture electron microscopy, include a reduction in the size of EFs particles, which correspond to photosystem II centers with variable amounts of attached LHCII, and a redistribution of EF particles from the stacked to the unstacked regions. When CD3 seedlings are grown at 150 microE/m2 S (low light) there is a substantial reversal of all of these effects. Thus, chlorophyll b and the chlorophyll a/b-binding proteins accumulate to near wild-type levels (chlorophyll a/b ratio = 3.5-4.5) and thylakoid morphology is more nearly wild type in appearance. Growth of the CD3 mutant in the presence of chloramphenicol stimulates the accumulation of chlorophyll b and its binding proteins (Duysen, M. E., T. P. Freeman, N. D. Williams, and L. L. Huckle. 1985. Plant Physiol. 78:531-536). We show that this partial rescue of the CD3 high light phenotype is accompanied by large changes in thylakoid structure. The CD3 mutant, which defines a new class of chlorophyll b- deficient phenotype, is discussed in the more general context of chlorophyll b deficiency.

1988-01-01

125

Identification of adult mineralized tissue zebrafish mutants  

PubMed Central

Zebrafish craniofacial, skeletal, and tooth development closely resembles that of higher vertebrates. Our goal is to identify viable adult zebrafish mutants that can be used as models for human mineralized craniofacial, dental, and skeletal system disorders. We utilized a large-scale forward-genetic chemical N-ethyl-nitroso-urea (ENU) mutagenesis screen to identify 17 early lethal homozygous recessive mutants with defects in craniofacial cartilage elements, and 7 adult homozygous recessive mutants with mineralized tissue phenotypes including craniofacial shape defects, fused sutures, dysmorphic or missing skeletal elements, scoliosis, and neural arch defects. One mutant displayed both an early lethal homozygous phenotype and an adult heterozygous phenotype. These results extend the utility of the zebrafish model beyond the embryo, to study human bone and cartilage disorders.

Andreeva, Viktoria; Connolly, Michelle H.; Stewart-Swift, Caitlin; Fraher, Daniel; Burt, Jeffrey; Cardarelli, Justin; Yelick, Pamela C.

2012-01-01

126

[The "lethality" of attempted suicide].  

PubMed

It is possible to quantify medical severity of a suicide attempt ("lethality") and its relationships with other components of the suicidal gesture have to be analysed. Our study about 758 suicide attempts aims to define psychiatric and psychological factors which are linked to "lethality" as measured by Weisman and Worden scale. Results of factorial analysis show a strong relation between "lethality" and some variables proving the intensity of psychological difficulties. Those results suggest the existence of relationship between "high lethality" on one hand, and diagnosis of psychosis, depressive symptomatology, high suicidal intent, some conceptions of death, on the other hand. A "low lethality" is associated with hedonistic conception of death, lack of positive signs of depression, existence of impulsiveness, psychopathic behaviors or lack of established mental disorder. These results reinforce the hypothesis of a relation between severity of patients psychological difficulties and medical severity of suicide attempt. PMID:2817656

Pedinielli, J L; Delahousse, J; Chabaud, B

1989-01-01

127

Severity of mutant phenotype in a series of chlorophyll-deficient wheat mutants depends on light intensity and the severity of the block in chlorophyll synthesis.  

PubMed Central

Analyses of a series of allelic chlorina mutants of wheat (Triticum aestivum L.), which have partial blocks in chlorophyll (Chl) synthesis and, therefore, a limited Chl supply, reinforce the principle that Chl is required for the stable accumulation of Chl-binding proteins and that only reaction centers accumulate when the supply of Chl is severely limited. Depending on the rate of Chl accumulation (determined by the severity of the mutation) and on the rate of turnover of Chl and its precursors (determined by the environment in which the plant is grown), the mutants each reach an equilibrium of Chl synthesis and degradation. Together these mutants generate a spectrum of phenotypes. Under the harshest conditions (high illumination), plants with moderate blocks in Chl synthesis have membranes with very little Chl and Chl-proteins and membrane stacks resembling the thylakoids of the lethal xantha mutants of barely grown at low to medium light intensities (which have more severe blocks). In contrast, when grown under low-light conditions the same plants with moderate blocks have thylakoids resembling those of the wild type. The wide range of phenotypes of Chl b-deficient mutants has historically produced more confusion than enlightenment, but incomparable growth conditions can now explain the discrepancies reported in the literature.

Falbel, T G; Meehl, J B; Staehelin, L A

1996-01-01

128

Dominant lethal mutations in the plasma membrane H(+)-ATPase gene of Saccharomyces cerevisiae.  

PubMed

The plasma membrane H(+)-ATPase of Saccharomyces cerevisiae is an essential protein that is required to establish cellular membrane potential and maintain a normal internal pH. An Asp-378 to Asn substitution at the residue phosphorylated during catalysis is dominant lethal when the pma1-D378N mutation is expressed along with a wild-type plasma membrane H(+)-ATPase (PMA1) gene. Several mutations in the first two putative transmembrane domains are also dominant lethal. However, these dominant lethal mutants often appear to be innocuous, because they are frequently lost by gene conversion to the wild-type sequence during the process of introducing the mutant sequence and subsequently removing the wild-type gene. Loss of the mutation by gene conversion does not occur while introducing recessive lethal mutations. Cells carrying the wild-type PMA1 gene on the chromosome and a dominant lethal mutation under the control of a GAL1 promoter on a centromere-containing plasmid exhibit a galactose-dependent lethality. Indirect immunofluorescence staining using anti-Pma1 antibodies shows that induction of dominant lethal PMA1 mutations leads to the accumulation of a number of intensely staining cytoplasmic structures that are not coincident with the nucleus and its immediately surrounding endoplasmic reticulum. These structures also accumulate the endoplasmic reticulum protein Kar2. Expression of the dominant lethal protein also prevents transport of the wild-type ATPase to the plasma membrane. PMID:7937988

Harris, S L; Na, S; Zhu, X; Seto-Young, D; Perlin, D S; Teem, J H; Haber, J E

1994-10-25

129

Conditionally replicating herpes simplex virus mutant, G207 for the treatment of malignant glioma: results of a phase I trial.  

PubMed

G207 is a conditionally replicating derivative of herpes simplex virus (HSV) type-1 strain F engineered with deletions of both gamma(1)34.5 loci and a lacZ insertion disabling the UL39 gene. We have demonstrated the efficacy of G207 in treating malignant glial tumors in athymic mice, as well as the safety of intracerebral G207 inoculation in mice and in Aotus nancymai. We sought to determine the safety of G207 inoculation into cerebral malignant glial tumors in humans. Criteria for inclusion into this dose-escalation study were the diagnosis of histologically proven malignant glioma, Karnofsky score > or = 70, recurrence despite surgery and radiation therapy, and an enhancing lesion greater than 1 cm in diameter. Serial magnetic resonance images were obtained for volumetric analysis. The trial commenced at a dose of 10(6) plaque forming units (p.f.u.) inoculated at a single enhancing site and was completed when the 21st patient was inoculated with 3x10(9) p.f.u. at five sites. While adverse events were noted in some patients, no toxicity or serious adverse events could unequivocally be ascribed to G207. No patient developed HSV encephalitis. We found radiographic and neuropathologic evidence suggestive of anti-tumor activity and long-term presence of viral DNA in some cases. PMID:10845725

Markert, J M; Medlock, M D; Rabkin, S D; Gillespie, G Y; Todo, T; Hunter, W D; Palmer, C A; Feigenbaum, F; Tornatore, C; Tufaro, F; Martuza, R L

2000-05-01

130

HETEROGENEITY OF LETHALS IN A \\  

Microsoft Academic Search

Of 24 ethyl methanesulphonate-induced, recessive-lethal mutations in the re- gion 9E1-9F13 of the X chromosome of Drosophila melanogaster, eight fall into a typically homogeneous lethal complementation group associated with the rasp- berry (ras) locus. Mutations in this group have previously been shown to be pleiotropic, affecting not only ras but also two other genetic entities, gual and purl, which yield

FRANK C. JANCA; EFFIE P. WOLOSHYN; DAVID NASH

1986-01-01

131

A glutathione reductase mutant of yeast accumulates high levels of oxidized glutathione and requires thioredoxin for growth.  

PubMed Central

A glutathione reductase null mutant of Saccharomyces cerevisiae was isolated in a synthetic lethal genetic screen for mutations which confer a requirement for thioredoxin. Yeast mutants that lack glutathione reductase (glr1 delta) accumulate high levels of oxidized glutathione and have a twofold increase in total glutathione. The disulfide form of glutathione increases 200-fold and represents 63% of the total glutathione in a glr1 delta mutant compared with only 6% in wild type. High levels of oxidized glutathione are also observed in a trx1 delta, trx2 delta double mutant (22% of total), in a glr1 delta, trx1 delta double mutant (71% of total), and in a glr1 delta, trx2 delta double mutant (69% of total). Despite the exceptionally high ratio of oxidized/reduced glutathione, the glr1 delta mutant grows with a normal cell cycle. However, either one of the two thioredoxins is essential for growth. Cells lacking both thioredoxins and glutathione reductase are not viable under aerobic conditions and grow poorly anaerobically. In addition, the glr1 delta mutant shows increased sensitivity to the thiol oxidant diamide. The sensitivity to diamide was suppressed by deletion of the TRX2 gene. The genetic analysis of thioredoxin and glutathione reductase in yeast runs counter to previous studies in Escherichia coli and for the first time links thioredoxin with the redox state of glutathione in vivo. Images

Muller, E G

1996-01-01

132

Lethal and Mutagenic Action of Black Light (325 to 400 nm) on Haemophilus influenzae in the Presence of Air  

PubMed Central

Near-ultraviolet (UV) light (325 to 400 nm), in the presence of air and the absence of exogenous photosensitizing compounds, is lethal and mutagenic for Haemophilus influenzae. The lethal effect is the same for both wild type and streptomycin-resistant mutants, indicating that the mutants are not selected by the irradiation. The inactivation and mutagenicity show a large shoulder, suggesting the existence of repair systems. Filters were used to eliminate the possibility of short-UV irradiation. The effective radiation is between 325 to 400 nm. The lethal and mutagenic effects are higher during mid and late log phase than during early log or stationary phase.

Cabrera-Juarez, Emiliano; Espinosa-Lara, Mercedes

1974-01-01

133

Ethanol-hypersensitive and ethanol-dependent cdc- mutants in Schizosaccharomyces pombe.  

PubMed

Ethanol-hypersensitive strains (ets mutants), unable to grow on media containing 6% ethanol, were isolated from a sample of mutagenized Schizosaccharomyces pombe wild-type cells. Genetic analysis of these ets strains demonstrated that the ets phenotype is associated with mutations in a large set of genes, including cell division cycle (cdc) genes, largely non-overlapping with the set represented by the temperature conditional method; accordingly, we isolated some ets non-ts cdc- mutants, which may identify novel essential genes required for regulation of the S. pombe cell cycle. Conversely, seven well characterized ts cdc- mutants were tested for their ethanol sensitivity; among them, cdc1-7 and cdc13-117 exhibited a tight ets phenotype. Ethanol sensitivity was also tested in strains bearing different alleles of the cdc2 gene, and we found that some of them were ets, but others were non-ets; thus, ethanol hypersensitivity is an allele-specific phenotype. Based on the single base changes found in each particular allele of the cdc2 gene, it is shown that a single amino acid substitution in the p34cdc2 gene product can produce this ets phenotype, and that ethanol hypersensitivity is probably due to the influence of this alcohol on the secondary and/or tertiary structure of the target protein. Ethanol-dependent (etd) mutants were also identified as mutants that can only be propagated on ethanol-containing media. This novel type of conditional phenotype also covers many unrelated genes. One of these etd mutants, etd1-1, was further characterized because of the lethal cdc- phenotype of the mutant cells under restrictive conditions (absence of ethanol). The isolation of extragenic suppressors of etd1-1, and the complementation cloning of a DNA fragment encompassing the etd1+ wild-type gene (or an extragenic multicopy suppressor) demonstrate that current genetic techniques may be applied to mutants isolated by using ethanol as a selective agent. PMID:7845361

Jimenez, J; Oballe, J

1994-10-17

134

A novel tankyrase inhibitor decreases canonical Wnt signaling in colon carcinoma cells and reduces tumor growth in conditional APC mutant mice.  

PubMed

Increased nuclear accumulation of ?-catenin, a mediator of canonical Wnt signaling, is found in numerous tumors and is frequently associated with tumor progression and metastasis. Inhibition of Wnt/?-catenin signaling therefore is an attractive strategy for anticancer drugs. In this study, we have identified a novel small molecule inhibitor of the ?-catenin signaling pathway, JW55, that functions via inhibition of the PARP domain of tankyrase 1 and tankyrase 2 (TNKS1/2), regulators of the ?-catenin destruction complex. Inhibition of TNKS1/2 poly(ADP-ribosyl)ation activity by JW55 led to stabilization of AXIN2, a member of the ?-catenin destruction complex, followed by increased degradation of ?-catenin. In a dose-dependent manner, JW55 inhibited canonical Wnt signaling in colon carcinoma cells that contained mutations in either the APC (adenomatous polyposis coli) locus or in an allele of ?-catenin. In addition, JW55 reduced XWnt8-induced axis duplication in Xenopus embryos and tamoxifen-induced polyposis formation in conditional APC mutant mice. Together, our findings provide a novel chemotype for targeting canonical Wnt/?-catenin signaling through inhibiting the PARP domain of TNKS1/2. PMID:22440753

Waaler, Jo; Machon, Ondrej; Tumova, Lucie; Dinh, Huyen; Korinek, Vladimir; Wilson, Steven Ray; Paulsen, Jan Erik; Pedersen, Nina Marie; Eide, Tor J; Machonova, Olga; Gradl, Dietmar; Voronkov, Andrey; von Kries, Jens Peter; Krauss, Stefan

2012-06-01

135

Genetic Characterization and High Efficiency Photosynthesis of an Aurea Mutant of Tobacco  

PubMed Central

A new tobacco (Nicotiana tabacum) aurea mutant was isolated from the progeny of a selfed variegated tobacco plant. The new mutant is termed Su/su var. Aurea. If the mutant is selfed, the seeds obtained give rise to four types of plants: green seedlings which correspond to the wild type; yellow-green seedlings which correspond to the earlier described Su/su; yellow seedlings which correspond to the new tobacco aurea mutant Su/su var. Aurea; and white lethal seedlings. The frequency ratio of the four phenotypes is 1:1:1:1. It appears that the mutation is due to two independent nuclear factors, su and aur, both of which have to be present in a heterozygous conditions, Su/su Aur/aur, to give rise to the new aurea phenotype. The aurea mutant Su/su var. Aurea has a reduced photosynthetic unit size which is approximately one-eighth of the wild type. Despite its chlorophyll deficiency, the plant grows well and exhibits maximal photosynthetic rates on a chlorophyll basis which are at least seven times higher than those of the green wild type provided the temperature and the light intensities are high enough. In contrast to the earlier described Su/su, the new mutant does not exhibit more photorespiration than the wild type. It appears that the factor aur causes either repression of photorespiration or an increase in the number of functioning photosynthetic units. Images

Okabe, Keiichiro; Schmid, Georg H.; Straub, Joseph

1977-01-01

136

Structural Basis for a Lethal Mutation in U6 RNA†,‡  

PubMed Central

U6 RNA is essential for nuclear pre-mRNA splicing and has been implicated directly in catalysis of intron removal. The U80G mutation at the essential magnesium binding site of the U6 3? intramolecular stem–loop region (ISL) is lethal in yeast. To further understand the structure and function of the U6 ISL, we have investigated the structural basis for the lethal U80G mutation by NMR and optical spectroscopy. The NMR structure reveals that the U80G mutation causes a structural rearrangement within the ISL resulting in the formation of a new Watson–Crick base pair (C67·G80), and disrupts a protonated C67·A79 wobble pair that forms in the wild-type structure. Despite the structural change, the accessibility of the metal binding site is unperturbed, and cadmium titration produces similar phosphorus chemical shift changes for both the U80G mutant and wild-type RNAs. The thermodynamic stability of the U80G mutant is significantly increased (??Gfold = ?3.6 ± 1.9 kcal/mol), consistent with formation of the Watson–Crick pair. Our structural and thermodynamic data, in combination with previous genetic data, suggest that the lethal basis for the U80G mutation is stem–loop hyperstabilization. This hyperstabilization may prevent the U6 ISL melting and rearrangement necessary for association with U4.

Sashital, Dipali G.; Allmann, Anne M.; Van Doren, Steven R.; Butcher, Samuel E.

2011-01-01

137

Lethal electric currents  

Microsoft Academic Search

Commercial-frequency currents of a few milliamperes flowing through the body will cause muscular contractions, resulting in the inability of the victim to release his grasp on a live conductor. Values of ``let-go'' current are very important criteria in the establishment of safe-current requirements. Since ventricular fibrillation, a condition in which circulation is arrested, is probably the most common cause of

Charles F. Dalziel; W. R. Lee

1969-01-01

138

Isolation and Characterization of Mutants Which Show an Oversecretion Phenotype in Saccharomyces Cerevisiae  

PubMed Central

We have isolated mutants responsible for an oversecretion phenotype in Saccharomyces cerevisiae, using a promoter of SUC2 and the gene coding for ?-amylase from mouse as a marker of secretion. These mutations defined two complementation groups, designated as ose1 (over secretion) and rgr1 (resistant to glucose repression). The ose1 mutant produced an oversecretion of amylase by 12- to 15-fold under derepressing conditions; however, the amylase mRNA was present at nearly the same amount as it was in the parent cells. No expression of the amylase gene was detected under repressing conditions. The rgr1 mutant oversecreted amylase by 11- to 13-fold under repressing conditions and by 15- to 18-fold under derepressing conditions. The rgr1 mutant showed pleiotropic effects on the following cellular functions: (1) resistance to glucose repression, (2) temperature-sensitive lethality, (3) sporulation deficiency in homozygous diploid cells, and (4) abnormal cell morphology. The rgr1 mutation was not allelic with ssn6 and cyc9, and failed to suppress snf1.

Sakai, A.; Shimizu, Y.; Hishinuma, F.

1988-01-01

139

Chemically induced conditional rescue of the reduced epidermal fluorescence8 mutant of Arabidopsis reveals rapid restoration of growth and selective turnover of secondary metabolite pools.  

PubMed

The phenylpropanoid pathway is responsible for the biosynthesis of diverse and important secondary metabolites including lignin and flavonoids. The reduced epidermal fluorescence8 (ref8) mutant of Arabidopsis (Arabidopsis thaliana), which is defective in a lignin biosynthetic enzyme p-coumaroyl shikimate 3'-hydroxylase (C3'H), exhibits severe dwarfism and sterility. To better understand the impact of perturbation of phenylpropanoid metabolism on plant growth, we generated a chemically inducible C3'H expression construct and transformed it into the ref8 mutant. Application of dexamethasone to these plants greatly alleviates the dwarfism and sterility and substantially reverses the biochemical phenotypes of ref8 plants, including the reduction of lignin content and hyperaccumulation of flavonoids and p-coumarate esters. Induction of C3'H expression at different developmental stages has distinct impacts on plant growth. Although early induction effectively restored the elongation of primary inflorescence stem, application to 7-week-old plants enabled them to produce new rosette inflorescence stems. Examination of hypocotyls of these plants revealed normal vasculature in the newly formed secondary xylem, presumably restoring water transport in the mutant. The ref8 mutant accumulates higher levels of salicylic acid than the wild type, but depletion of this compound in ref8 did not relieve the mutant's growth defects, suggesting that the hyperaccumulation of salicylic acid is unlikely to be responsible for dwarfism in this mutant. PMID:24381065

Kim, Jeong Im; Ciesielski, Peter N; Donohoe, Bryon S; Chapple, Clint; Li, Xu

2014-02-01

140

Drosophila Embryonic Cell-Cycle Mutants  

PubMed Central

Nearly all cell division mutants in Drosophila were recovered in late larval/pupal lethal screens, with less than 10 embryonic lethal mutants identified, because larval development occurs without a requirement for cell division. Only cells in the nervous system and the imaginal cells that generate the adult body divide during larval stages, with larval tissues growing by increasing ploidy rather than cell number. Thus, most mutants perturbing mitosis or the cell cycle do not manifest a phenotype until the adult body differentiates in late larval and pupal stages. To identify cell-cycle components whose maternal pools are depleted in embryogenesis or that have specific functions in embryogenesis, we screened for mutants defective in cell division during embryogenesis. Five new alleles of Cyclin E were recovered, ranging from a missense mutation that is viable to stop codons causing embryonic lethality. These permitted us to investigate the requirements for Cyclin E function in neuroblast cell fate determination, a role previously shown for a null Cyclin E allele. The mutations causing truncation of the protein affect cell fate of the NB6-4 neuroblast, whereas the weak missense mutation has no effect. We identified mutations in the pavarotti (pav) and tumbleweed (tum) genes needed for cytokinesis by a phenotype of large and multinucleate cells in the embryonic epidermis and nervous system. Other mutations affecting the centromere protein CAL1 and the kinetochore protein Spc105R caused mitotic defects in the nervous system.

Unhavaithaya, Yingdee; Park, Eugenia A.; Royzman, Irena; Orr-Weaver, Terry L.

2013-01-01

141

Construction and Characterization of a Mycobacterium tuberculosis Mutant Lacking the Alternate Sigma Factor Gene, sigF  

PubMed Central

The alternate RNA polymerase sigma factor gene, sigF, which is expressed in stationary phase and under stress conditions in vitro, has been deleted in the virulent CDC1551 strain of Mycobacterium tuberculosis. The growth rate of the ?sigF mutant was identical to that of the isogenic wild-type strain in exponential phase, although in stationary phase the mutant achieved a higher density than the wild type. The mutant showed increased susceptibility to rifampin and rifapentine. Additionally, the ?sigF mutant displayed diminished uptake of chenodeoxycholate, and this effect was reversed by complementation with a wild-type sigF gene. No differences in short-term intracellular growth between mutant and wild-type organisms within human monocytes were observed. Similarly, the organisms did not differ in their susceptibilities to lymphocyte-mediated inhibition of intracellular growth. However, mice infected with the ?sigF mutant showed a median time to death of 246 days compared with 161 days for wild-type strain-infected animals (P < 0.001). These data indicate that M. tuberculosis sigF is a nonessential alternate sigma factor both in axenic culture and for survival in macrophages in vitro. While the ?sigF mutant produces a lethal infection of mice, it is less virulent than its wild-type counterpart by time-to-death analysis.

Chen, Ping; Ruiz, Rafael E.; Li, Qing; Silver, Richard F.; Bishai, William R.

2000-01-01

142

Histidinol Dehydrogenase (hisD) Mutants of Salmonella typhimurium1  

PubMed Central

A multidisciplinary analysis has been applied to over 150 hisD mutants of Salmonella typhimurium in a study of gene-enzyme relationship. The mutants were examined for production of immunologically cross-reacting material by using antibody to purified histidinol dehydrogenase, and for genetic complementation by using a set of F? factors bearing Escherichia coli hisD complementing mutants. Classifications as to missense, nonsense, frameshift, or deletion mutant are proposed on the basis of mutagenesis and suppression tests. For the suppression tests the mutants were examined both by a simultaneous suppression technique and by testing for response to E. coli F? factors bearing a recessive lethal amber and a recessive lethal ochre suppressor. The data are interpreted in relation to the position of the mutations in the recombination and complementation maps and in relation to the known composition of histidinol dehydrogenase. The gene hisD appears to be single cistron for the production of a single biosynthetic polypeptide. Images

Greeb, J.; Atkins, J. F.; Loper, J. C.

1971-01-01

143

Arenavirus extinction through lethal mutagenesis  

Microsoft Academic Search

Viral hemorrhagic fevers represent serious human public health problems causing devastating and often lethal disease. Several hemorrhagic fevers are caused by arenaviruses including Lassa fever virus (LFV) and the South American viral hemorrhagic fevers (SAHF). In recent years, increased air travel between Africa and other areas has led to the importation of LFV into the US, Europe, Japan, and Canada.

Juan Carlos de la Torre

2005-01-01

144

Synthetic Lethality of Cohesins with PARPs and Replication Fork Mediators  

PubMed Central

Synthetic lethality has been proposed as a way to leverage the genetic differences found in tumor cells to affect their selective killing. Cohesins, which tether sister chromatids together until anaphase onset, are mutated in a variety of tumor types. The elucidation of synthetic lethal interactions with cohesin mutants therefore identifies potential therapeutic targets. We used a cross-species approach to identify robust negative genetic interactions with cohesin mutants. Utilizing essential and non-essential mutant synthetic genetic arrays in Saccharomyces cerevisiae, we screened genome-wide for genetic interactions with hypomorphic mutations in cohesin genes. A somatic cell proliferation assay in Caenorhabditis elegans demonstrated that the majority of interactions were conserved. Analysis of the interactions found that cohesin mutants require the function of genes that mediate replication fork progression. Conservation of these interactions between replication fork mediators and cohesin in both yeast and C. elegans prompted us to test whether other replication fork mediators not found in the yeast were required for viability in cohesin mutants. PARP1 has roles in the DNA damage response but also in the restart of stalled replication forks. We found that a hypomorphic allele of the C. elegans SMC1 orthologue, him-1(e879), genetically interacted with mutations in the orthologues of PAR metabolism genes resulting in a reduced brood size and somatic cell defects. We then demonstrated that this interaction is conserved in human cells by showing that PARP inhibitors reduce the viability of cultured human cells depleted for cohesin components. This work demonstrates that large-scale genetic interaction screening in yeast can identify clinically relevant genetic interactions and suggests that PARP inhibitors, which are currently undergoing clinical trials as a treatment of homologous recombination-deficient cancers, may be effective in treating cancers that harbor cohesin mutations.

Barrett, Irene; Ferree, Elizabeth; van Pel, Derek M.; Ushey, Kevin; Sipahimalani, Payal; Bryan, Jennifer; Rose, Ann M.; Hieter, Philip

2012-01-01

145

A Genome-wide RNAi Screen Identifies Multiple Synthetic Lethal Interactions with the Ras Oncogene  

Microsoft Academic Search

SUMMARY Oncogenic mutations in the small GTPase Ras are highly prevalent in cancer, but an understanding of the vulnerabilities of these cancers is lacking. We undertook a genome-wide RNAi screen to identify synthetic lethal interactions with the KRAS onco- gene. We discovered a diverse set of proteins whose depletion selectively impaired the viability of Ras mutant cells. Among these we

Ji Luo; Michael J. Emanuele; Danan Li; Chad J. Creighton; Michael R. Schlabach; Thomas F. Westbrook; Kwok-Kin Wong; Stephen J. Elledge

2009-01-01

146

The VirS/VirR Two-Component System Regulates the Anaerobic Cytotoxicity, Intestinal Pathogenicity, and Enterotoxemic Lethality of Clostridium perfringens Type C Isolate CN3685  

PubMed Central

Clostridium perfringens vegetative cells cause both histotoxic infections (e.g., gas gangrene) and diseases originating in the intestines (e.g., hemorrhagic necrotizing enteritis or lethal enterotoxemia). Despite their medical and veterinary importance, the molecular pathogenicity of C. perfringens vegetative cells causing diseases of intestinal origin remains poorly understood. However, C. perfringens beta toxin (CPB) was recently shown to be important when vegetative cells of C. perfringens type C strain CN3685 induce hemorrhagic necrotizing enteritis and lethal enterotoxemia. Additionally, the VirS/VirR two-component regulatory system was found to control CPB production by CN3685 vegetative cells during aerobic infection of cultured enterocyte-like Caco-2 cells. Using an isogenic virR null mutant, the current study now reports that the VirS/VirR system also regulates CN3685 cytotoxicity during infection of Caco-2 cells under anaerobic conditions, as found in the intestines. More importantly, the virR mutant lost the ability to cause hemorrhagic necrotic enteritis in rabbit small intestinal loops. Western blot analyses demonstrated that the VirS/VirR system mediates necrotizing enteritis, at least in part, by controlling in vivo CPB production. In addition, vegetative cells of the isogenic virR null mutant were, relative to wild-type vegetative cells, strongly attenuated in their lethality in a mouse enterotoxemia model. Collectively, these results identify the first regulator of in vivo pathogenicity for C. perfringens vegetative cells causing disease originating in the complex intestinal environment. Since VirS/VirR also mediates histotoxic infections, this two-component regulatory system now assumes a global role in regulating a spectrum of infections caused by C. perfringens vegetative cells.

Ma, Menglin; Vidal, Jorge; Saputo, Juliann; McClane, Bruce A.; Uzal, Francisco

2011-01-01

147

Lethal Effects of Low and "Null" Activity Alleles of 6-Phosphogluconate Dehydrogenase in DROSOPHILA MELANOGASTER  

PubMed Central

EMS-induced "null" and low activity alleles for 6-phosphogluconate dehydrogenase were characterized with respect to enzymatic activity, relative viability, fertility, and the effective lethal phase. It was determined that flies hemizygous and homozygous for the low activity allele, Pgd-, possessed a depressed developmental rate, diminished viability, and loss of female fertility. Heterozygotes for Pgd- and a deficiency for Pgd+ were lethal. The "null" activity allele demonstrated a lethal phenotype in both the hemizygous and homozygous condition. The effective lethal phase for the "null" allele occurs during late embryonic development (20–22 hr).

Bewley, Glenn C.; Lucchesi, John C.

1975-01-01

148

Arabidopsis genes essential for seedling viability: isolation of insertional mutants and molecular cloning.  

PubMed Central

We have undertaken a large-scale genetic screen to identify genes with a seedling-lethal mutant phenotype. From screening approximately 38,000 insertional mutant lines, we identified >500 seedling-lethal mutants, completed cosegregation analysis of the insertion and the lethal phenotype for >200 mutants, molecularly characterized 54 mutants, and provided a detailed description for 22 of them. Most of the seedling-lethal mutants seem to affect chloroplast function because they display altered pigmentation and affect genes encoding proteins predicted to have chloroplast localization. Although a high level of functional redundancy in Arabidopsis might be expected because 65% of genes are members of gene families, we found that 41% of the essential genes found in this study are members of Arabidopsis gene families. In addition, we isolated several interesting classes of mutants and genes. We found three mutants in the recently discovered nonmevalonate isoprenoid biosynthetic pathway and mutants disrupting genes similar to Tic40 and tatC, which are likely to be involved in chloroplast protein translocation. Finally, we directly compared T-DNA and Ac/Ds transposon mutagenesis methods in Arabidopsis on a genome scale. In each population, we found only about one-third of the insertion mutations cosegregated with a mutant phenotype.

Budziszewski, G J; Lewis, S P; Glover, L W; Reineke, J; Jones, G; Ziemnik, L S; Lonowski, J; Nyfeler, B; Aux, G; Zhou, Q; McElver, J; Patton, D A; Martienssen, R; Grossniklaus, U; Ma, H; Law, M; Levin, J Z

2001-01-01

149

Proton gradient regulation 5-mediated cyclic electron flow under ATP- or redox-limited conditions: a study of ?ATpase pgr5 and ?rbcL pgr5 mutants in the green alga Chlamydomonas reinhardtii.  

PubMed

The Chlamydomonas reinhardtii proton gradient regulation5 (Crpgr5) mutant shows phenotypic and functional traits similar to mutants in the Arabidopsis (Arabidopsis thaliana) ortholog, Atpgr5, providing strong evidence for conservation of PGR5-mediated cyclic electron flow (CEF). Comparing the Crpgr5 mutant with the wild type, we discriminate two pathways for CEF and determine their maximum electron flow rates. The PGR5/proton gradient regulation-like1 (PGRL1) ferredoxin (Fd) pathway, involved in recycling excess reductant to increase ATP synthesis, may be controlled by extreme photosystem I acceptor side limitation or ATP depletion. Here, we show that PGR5/PGRL1-Fd CEF functions in accordance with an ATP/redox control model. In the absence of Rubisco and PGR5, a sustained electron flow is maintained with molecular oxygen instead of carbon dioxide serving as the terminal electron acceptor. When photosynthetic control is decreased, compensatory alternative pathways can take the full load of linear electron flow. In the case of the ATP synthase pgr5 double mutant, a decrease in photosensitivity is observed compared with the single ATPase-less mutant that we assign to a decreased proton motive force. Altogether, our results suggest that PGR5/PGRL1-Fd CEF is most required under conditions when Fd becomes overreduced and photosystem I is subjected to photoinhibition. CEF is not a valve; it only recycles electrons, but in doing so, it generates a proton motive force that controls the rate of photosynthesis. The conditions where the PGR5 pathway is most required may vary in photosynthetic organisms like C. reinhardtii from anoxia to high light to limitations imposed at the level of carbon dioxide fixation. PMID:24623849

Johnson, Xenie; Steinbeck, Janina; Dent, Rachel M; Takahashi, Hiroko; Richaud, Pierre; Ozawa, Shin-Ichiro; Houille-Vernes, Laura; Petroutsos, Dimitris; Rappaport, Fabrice; Grossman, Arthur R; Niyogi, Krishna K; Hippler, Michael; Alric, Jean

2014-05-01

150

A Novel Histone H4 Mutant Defective in Nuclear Division and Mitotic Chromosome Transmission  

Microsoft Academic Search

The histone proteins are essential for the assembly and function of the eukaryotic chromosome. Here we report thefirst isolation of a temperature-sensitive lethal histone H4 mutant defective in mitotic chromosome transmission inSaccharomyces cerevisiae. The mutant requires two amino acid substitutions in histone H4: a lethal Thr-to-Ile change at position 82, which lies within one of the DNA-binding surfaces of the

M. MITCHELL SMITH; PEIRONG YANG; MARIA SOLEDAD SANTISTEBAN; PAUL W. BOONE; ANDREW T. GOLDSTEIN; ANDPAUL C. MEGEE

151

The "Lethal Chamber": Further Evidence of the Euthanasia Option.  

ERIC Educational Resources Information Center

Historical discussions of the euthanasia or "lethal chamber" option in relation to people with mental retardation are presented. The paper concludes that eugenic beliefs in the primacy of heredity over environment and the positive role of natural selection may have condoned the poor conditions characteristic of large, segregated institutions and…

Elks, Martin A.

1993-01-01

152

Protein sorting in Saccharomyces cerevisiae: isolation of mutants defective in the delivery and processing of multiple vacuolar hydrolases.  

PubMed Central

Using a selection for spontaneous mutants that mislocalize a vacuolar carboxypeptidase Y (CPY)-invertase fusion protein to the cell surface, we identified vacuolar protein targeting (vpt) mutants in 25 new vpt complementation groups. Additional alleles in each of the eight previously identified vpt complementation groups (vpt1 through vpt8) were also obtained. Representative alleles from each of the 33 vpt complementation groups (vpt1 through vpt33) were shown to exhibit defects in the sorting and processing of several native vacuolar proteins, including the soluble hydrolases CPY, proteinase A, and proteinase B. Of the 33 complementation groups, 19 were found to contain mutant alleles that led to extreme defects. In these mutants, CPY accumulated in its Golgi complex-modified precursor form which was secreted by the mutant cells. Normal protein secretion appeared to be unaffected in the vpt mutants. The lack of significant leakage of cytosolic markers from the vpt mutant cells indicated that the vacuolar protein-sorting defects associated with these mutants do not result from cell lysis. In addition, the observation that the precursor rather than the mature forms of CPY, proteinase A, proteinase B were secreted from the vpt mutants was consistent with the fact that mislocalization occurred at a stage after Golgi complex-specific modification, but before final vacuolar sorting of these enzymes. Vacuolar membrane protein sorting appeared to be unaffected in the majority of the vpt mutants. However, a subset of the vpt mutants (vpt11, vpt16, vpt18, and vpt33) was found to exhibit defects in the sorting of a vacuolar membrane marker enzyme, alpha-mannosidase. Up to 50% of the alpha-mannosidase enzyme activity was found to be mislocalized to the cell surface in these vpt mutants. Seven of the vpt complementation groups (vpt3, vpt11, vpt15, vpt16, vpt18, vpt29, and vpt33) contained alleles that led to a conditional lethal phenotype; the mutants were temperature sensitive for vegetative cell growth. This temperature-sensitive phenotype has been shown to be recessive and to cosegregate with the vacuolar protein-sorting defect in each case. Tetrad analysis showed that vpt3 mapped to the right arm of chromosome XV and that vpt15 mapped to the right arm of chromosome II. Intercrosses with other mutants that exhibited defects in vacuolar protein sorting or function (vpl, sec, pep, and end mutants) revealed several overlaps among these different sets of genes. Together, these data indicate that more than 50 gene products are involved, directly or indirectly, in the process of vacuolar protein sorting. Images

Robinson, J S; Klionsky, D J; Banta, L M; Emr, S D

1988-01-01

153

Effects of oxygen and nitrogen conditions on the transformation kinetics of 1,2-dichloroethenes by Methylosinus trichosporium OB3b and its sMMO C mutant  

Microsoft Academic Search

Transformation kinetics of trans- andcis-dichloroethylenes (DCE) by Methylosinus trichosporium OB3b wild type (WT)and PP319, a mutant that expresses soluble methane monooxygenase at copper levels upto ~12 µM Cu (sMMOC), were determined to assess theeffects of O2level and N2-fixation on degradationcapabilities. Two issues were examined: (1) the influence of O2level and nitrogen-limitation on DCE degradationkinetics and toxicity in both organisms, and

Hyung J. Kim; David W. Graham

2003-01-01

154

The Effect of the Plant Growth Stimulant Bactozole on Rhizobium leguminosarum bv. viciae 250a and Its Nitrogen-Tolerant Mutant M-71 under Different Nitrogen Supply Conditions  

Microsoft Academic Search

The effect of the plant growth stimulant bactozole on the growth of Rhizobium leguminosarum bv. viciae 250a and its nitrogen-tolerant mutant M-71 and the synthesis of extracellular carbohydrates was studied. At a low content of nitrate (6 mM) in the medium, all three bactozole concentrations tested (0.001, 0.01, and 0.1%) exerted similar stimulating effects on the growth of the parent

L. V. Kosenko; N. M. Mandrovskaya; E. D. Krugova; L. D. Varbanets

2003-01-01

155

Virulence of a Salmonella typhimurium OmpD Mutant  

Microsoft Academic Search

An ompD mutation caused by a Tn10 insertion was transduced into Salmonella typhimurium SL1344 and UK-1. The adherence and invasion capabilities of the resultant ompD mutants were examined by tissue culture analysis. The virulence of the S. typhimurium ompD mutants was ascertained by a 50% lethal dose (LD50) study and by determining colonization ability with BALB\\/c mice. We found no

PAUL N. MEYER; MARY R. WILMES-RIESENBERG; CHRISTOS STATHOPOULOS; ROY CURTISS III

156

Mutations Synthetically Lethal with Tpm1? Lie in Genes Involved in Morphogenesis  

PubMed Central

Yeast contains two genes, TPM1 and TPM2, encoding tropomyosins, either of which can provide an essential function in the yeast cytoskeleton. To elucidate more clearly the function of the major tropomyosin, encoded by TPM1, we have isolated mutations that confer synthetic lethality with the null mutant of TPM1. Here we describe a phenotypic and genetic analysis of mutations in TSL1/BEM2, TSL2, TSL3, TSL5, and TSL6 (tropomyosin synthetic lethal). All the mutants exhibit clear morphological and some actin cytoskeletal defects, but are not noticeably defective in secretion, endocytosis, or organelle segregation. The lethality conferred by tsl tpm1? mutations could be specifically suppressed by either TPM1 or an additional copy of TPM2. This implies that the essential function compromised in the tsl tpm1? constructs is the same essential function for which Tpm1p or Tpm2p is necessary. Synthetic interactions and unlinked noncomplementation were observed between the tsl mutants, suggesting that they participate in related functions involving morphogenesis. In support of this, tsl6-1 was identified as an allele of the nonessential gene SLT2 or MPK1 whose product is a MAP kinase regulating cell wall synthesis. These results indicate that this synthetic lethality approach provides a sensitive screen for the isolation of mutations affecting morphogenesis, many of which are likely to be in nonessential genes, like BEM2 and SLT2.

Wang, T.; Bretscher, A.

1997-01-01

157

Starch mutants of Chlamydomonas  

SciTech Connect

Wild type Chlamydomonas accumulates starch and triglycerides when grown under nitrogen limiting conditions. Toward elucidation of the mechanisms for control of starch biosynthesis, we isolated mutants impaired int he accumulation of storage carbohydrates. Chlamydomonas reinhardtii (strain ya-12) was mutagenized by UV irradiation and colonies were screened by iodine staining after growth in darkness. Mutants, denoted ais for altered in iodine staining, have been characterized by electron microscopy and assays for starch synthease, ADPG-pyrophosphorylase, phosphoglucose isomerase (PGI), phosphoglucomutase and fructose 1,6-bisphosphatase, and amylase activities. Transcript analysis of wild type and mutant RNAs with PGI, ADPG-pyrophosphorylase, and waxy probes have also been carried out. No deficiencies of any of these components have been detected. Furthermore, long-term cultures of ya-12 and ais-1d in nitrogen-limited chemostats have been studied; starch also does not accumulate in ais-1d under these conditions. Thus, the lesion affects an essential factor of unknown identity that is required for starch synthesis.

Berry-Lowe, S.L.; Schmidt, G.W. (Univ. of Georgia, Athens (USA))

1990-05-01

158

Conditional expression of the mutant Ki-rasG12C allele results in formation of benign lung adenomas: development of a novel mouse lung tumor model  

PubMed Central

To determine the effects of expression of mutant Ki-ras on lung tumorigenesis, we developed a bitransgenic mouse model that expresses the human Ki-rasG12C allele in alveolar type II and/or Clara cells in a tetracycline-inducible, lung-specific manner. Expression of Ki-rasG12C caused multiple, small lung tumors over a 12-month time period. Although tumor multiplicity increased upon continued Ki-ras expression, most lung lesions were hyperplasias or well-differentiated adenomas. This is in contrast to the more severe phenotypes observed in other transgenic mouse models in which different mutant Ki-ras alleles were expressed in the lung. Expression of Ki-rasG12C was associated with a 2-fold increase in the activation of the Ras and Ral signaling pathways and increased phosphorylation of Ras downstream effectors, including Erk, p90 ribosomal S6 kinase, ribosomal S6 protein, p38 and MAPKAPK-2. In contrast, expression of the transgene had no effect on the activation of the JNK and Akt signaling pathways. Withdrawal of doxycycline for 1 month resulted in almost a complete absence of proliferative pulmonary lesions, suggesting tumor regression in the absence of Ki-ras expression. Mutant Ki-rasG12C expression was sufficient for initial lung tumor transformation, required for maintenance of tumor phenotype, and induced transformation of lung epithelial cells by the activation of multiple effector pathways. These results describe a novel mouse lung tumor model demonstrating benign tumor development in the absence of tumor progression, which will provide a new tool for understanding the early stages of lung tumor pathogenesis.

S.Floyd, Heather; L.Farnsworth, Charles; D.Kock, Nancy; C.Mizesko, Melissa; L.Little, Joy; T.Dance, Stephanie; Everitt, Jeff; Tichelaar, Jay; A.Whitsett, Jeffrey; Miller, Mark Steven

2005-01-01

159

Early events of lethal action by tobramycin in Pseudomonas aeruginosa  

SciTech Connect

The immediate activities of the aminoglycoside antibiotic, tobramycin, were investigated in Pseudomonas aeruginosa PAO1. The influence of carbon growth substate and the antibiotic exposure environment in the magnitude of activity were examined. Lethality by 8 {mu}g/ml tobramycin occurred rapidly (1 to 3 minutes). The release of specific cellular components into the supernatant was associated with lethality. This material was initially detected as an increase in UV-absorbance. Magnesium in the reaction mixture provided protection against lethality and leakage, but did not reverse lethal damage after a 3 minute tobramycin treatment. Also, uptake of {sup 3}H-tobramycin was reduced in the presence of magnesium. Cells grown with glucose as a carbon source were more susceptible than organic acid grown cells as was the rapidity and amount of cell damage. Analyses of the leakage material revealed a 2-fold increase of protein in the supernatant after a 1-3 minute treatment which paralleled lethality. A prominent 29 kDa protein was observed by SDS-PAGE in the released material, which has been identified as the periplasmic enzyme, {beta}-lactamase. The immediate activities of tobramycin did not involve (i) release of overall cell protein, (ii) massive loss of total pool amino acids, (iii) cell lysis, (iv) inhibition of proline uptake, (v) release of lipopolysaccharide, or (vi) leakage of ATP. Electron microscopy showed no apparent damage after a 3 minute exposure. 40% inhibition of protein synthesis had occurred by 3 minutes of exposure, while release of UV-absorbing material and lethality were detectable after only 1 minute. Resistant cystic fibrosis isolates of P. aeruginosa did not leak under the same experimental conditions, but one of two susceptible strains examined did show increased UV-absorbance following treatment.

Raulston, J.E.

1988-01-01

160

Characteristics of a Virescent Cotton Mutant 1  

PubMed Central

The virescent cotton (Gossypium hirsutum) mutant described here differs from normal cultivated cotton by a single mutation in the nucleus. The mutant exhibits nuclear control of chlorophyll and carotenoid development. Young leaves are distinctly yellow and become green with age. There is no unusual photometabolism of 14CO2 or 14C-acetate in this mutant. It is probable that the nuclear virescent mutation is in a locus concerned with making structural units. The yellow leaves do show a high photosynthetic capacity on a chlorophyll basis. At saturating light intensity the rate of CO2 fixation is 8 fold higher than the green control leaves. Thus, impaired pigment synthesis which could be lethal is offset by a high photosynthetic capacity in the virescent leaves.

Benedict, C. R.; Kohel, R. J.

1968-01-01

161

Extinction of Hepatitis C Virus by Ribavirin in Hepatoma Cells Involves Lethal Mutagenesis  

PubMed Central

Lethal mutagenesis, or virus extinction produced by enhanced mutation rates, is under investigation as an antiviral strategy that aims at counteracting the adaptive capacity of viral quasispecies, and avoiding selection of antiviral-escape mutants. To explore lethal mutagenesis of hepatitis C virus (HCV), it is important to establish whether ribavirin, the purine nucleoside analogue used in anti-HCV therapy, acts as a mutagenic agent during virus replication in cell culture. Here we report the effect of ribavirin during serial passages of HCV in human hepatoma Huh-7.5 cells, regarding viral progeny production and complexity of mutant spectra. Ribavirin produced an increase of mutant spectrum complexity and of the transition types associated with ribavirin mutagenesis, resulting in HCV extinction. Ribavirin-mediated depletion of intracellular GTP was not the major contributory factor to mutagenesis since mycophenolic acid evoked a similar decrease in GTP without an increase in mutant spectrum complexity. The intracellular concentration of the other nucleoside-triphosphates was elevated as a result of ribavirin treatment. Mycophenolic acid extinguished HCV without an intervening mutagenic activity. Ribavirin-mediated, but not mycophenolic acid-mediated, extinction of HCV occurred via a decrease of specific infectivity, a feature typical of lethal mutagenesis. We discuss some possibilities to explain disparate results on ribavirin mutagenesis of HCV.

Ortega-Prieto, Ana M.; Sheldon, Julie; Grande-Perez, Ana; Tejero, Hector; Gregori, Josep; Quer, Josep; Esteban, Juan I.; Domingo, Esteban; Perales, Celia

2013-01-01

162

D-2-hydroxyglutarate produced by mutant IDH1 perturbs collagen maturation and basement membrane function.  

PubMed

Isocitrate dehydrogenase-1 (IDH1) R132 mutations occur in glioma, but their physiological significance is unknown. Here we describe the generation and characterization of brain-specific Idh1 R132H conditional knock-in (KI) mice. Idh1 mutation results in hemorrhage and perinatal lethality. Surprisingly, intracellular reactive oxygen species (ROS) are attenuated in Idh1-KI brain cells despite an apparent increase in the NADP(+)/NADPH ratio. Idh1-KI cells also show high levels of D-2-hydroxyglutarate (D2HG) that are associated with inhibited prolyl-hydroxylation of hypoxia-inducible transcription factor-1? (Hif1?) and up-regulated Hif1? target gene transcription. Intriguingly, D2HG also blocks prolyl-hydroxylation of collagen, causing a defect in collagen protein maturation. An endoplasmic reticulum (ER) stress response induced by the accumulation of immature collagens may account for the embryonic lethality of these mutants. Importantly, D2HG-mediated impairment of collagen maturation also led to basement membrane (BM) aberrations that could play a part in glioma progression. Our study presents strong in vivo evidence that the D2HG produced by the mutant Idh1 enzyme is responsible for the above effects. PMID:22925884

Sasaki, Masato; Knobbe, Christiane B; Itsumi, Momoe; Elia, Andrew J; Harris, Isaac S; Chio, Iok In Christine; Cairns, Rob A; McCracken, Susan; Wakeham, Andrew; Haight, Jillian; Ten, Annick You; Snow, Bryan; Ueda, Takeshi; Inoue, Satoshi; Yamamoto, Kazuo; Ko, Myunggon; Rao, Anjana; Yen, Katharine E; Su, Shinsan M; Mak, Tak Wah

2012-09-15

163

D-2-hydroxyglutarate produced by mutant IDH1 perturbs collagen maturation and basement membrane function  

PubMed Central

Isocitrate dehydrogenase-1 (IDH1) R132 mutations occur in glioma, but their physiological significance is unknown. Here we describe the generation and characterization of brain-specific Idh1 R132H conditional knock-in (KI) mice. Idh1 mutation results in hemorrhage and perinatal lethality. Surprisingly, intracellular reactive oxygen species (ROS) are attenuated in Idh1-KI brain cells despite an apparent increase in the NADP+/NADPH ratio. Idh1-KI cells also show high levels of D-2-hydroxyglutarate (D2HG) that are associated with inhibited prolyl-hydroxylation of hypoxia-inducible transcription factor-1? (Hif1?) and up-regulated Hif1? target gene transcription. Intriguingly, D2HG also blocks prolyl-hydroxylation of collagen, causing a defect in collagen protein maturation. An endoplasmic reticulum (ER) stress response induced by the accumulation of immature collagens may account for the embryonic lethality of these mutants. Importantly, D2HG-mediated impairment of collagen maturation also led to basement membrane (BM) aberrations that could play a part in glioma progression. Our study presents strong in vivo evidence that the D2HG produced by the mutant Idh1 enzyme is responsible for the above effects.

Sasaki, Masato; Knobbe, Christiane B.; Itsumi, Momoe; Elia, Andrew J.; Harris, Isaac S.; Chio, Iok In Christine; Cairns, Rob A.; McCracken, Susan; Wakeham, Andrew; Haight, Jillian; Ten, Annick You; Snow, Bryan; Ueda, Takeshi; Inoue, Satoshi; Yamamoto, Kazuo; Ko, Myunggon; Rao, Anjana; Yen, Katharine E.; Su, Shinsan M.; Mak, Tak Wah

2012-01-01

164

Influence on DNA Repair Inhibitors on Dominant Lethal Factors after gamma Irradiation.  

National Technical Information Service (NTIS)

Experiments were performed in order to test the hypothesis of a correlation between ionizing radiation and DNA repair inhibition under in vivo conditions. In a biometrically planned dominant lethal test on mice, the repair inhibition on the male gametes b...

D. Engl

1978-01-01

165

Alcohol Consumption and Nearly Lethal Suicide Attempts.  

ERIC Educational Resources Information Center

Presents a case-control study of the association between nearly lethal suicide attempts and facets of alcohol consumption; namely, drinking frequency, drinking quantity, binge drinking, alcoholism, drinking within 3 hours of suicide attempt, and age began drinking. In bivariate analyses, all measures were associated with nearly lethal suicide…

Powell, Kenneth E.; Kresnow, Marcie-jo; Mercy, James A.; Potter, Lloyd B.; Swann, Alan C.; Frankowski, Ralph F.; Lee, Roberta K.; Bayer, Timothy L.

2002-01-01

166

Recovery of plants from “Near-Lethal” stress  

Microsoft Academic Search

This study reports on the dieback and recovery of red-osier dogwood, Cornus sericea L. plants from “near-lethal” (NL, sublethal) stress after varying lengths of post-stress environment (PSE). Intact dormant stems were subjected to 47° C for one hour during either October, November or December, and then placed into either constant 0° C or 23° C (dark condition) or kept under

A. M. Shirazi; L. H. Fuchigami

1993-01-01

167

Hypopigmentation and maternal-zygotic embryonic lethality caused by a hypomorphic mbtps1 mutation in mice.  

PubMed

The site 1 protease, encoded by Mbtps1, mediates the initial cleavage of site 2 protease substrates, including sterol regulatory element binding proteins and CREB/ATF transcription factors. We demonstrate that a hypomorphic mutation of Mbtps1 called woodrat (wrt) caused hypocholesterolemia, as well as progressive hypopigmentation of the coat, that appears to be mechanistically unrelated. Hypopigmentation was rescued by transgenic expression of wild-type Mbtps1, and reciprocal grafting studies showed that normal pigmentation depended upon both cell-intrinsic or paracrine factors, as well as factors that act systemically, both of which are lacking in wrt homozygotes. Mbtps1 exhibited a maternal-zygotic effect characterized by fully penetrant embryonic lethality of maternal-zygotic wrt mutant offspring and partial embryonic lethality (~40%) of zygotic wrt mutant offspring. Mbtps1 is one of two maternal-zygotic effect genes identified in mammals to date. It functions nonredundantly in pigmentation and embryogenesis. PMID:22540041

Rutschmann, Sophie; Crozat, Karine; Li, Xiaohong; Du, Xin; Hanselman, Jeffrey C; Shigeoka, Alana A; Brandl, Katharina; Popkin, Daniel L; McKay, Dianne B; Xia, Yu; Moresco, Eva Marie Y; Beutler, Bruce

2012-04-01

168

Hypopigmentation and Maternal-Zygotic Embryonic Lethality Caused by a Hypomorphic Mbtps1 Mutation in Mice  

PubMed Central

The site 1 protease, encoded by Mbtps1, mediates the initial cleavage of site 2 protease substrates, including sterol regulatory element binding proteins and CREB/ATF transcription factors. We demonstrate that a hypomorphic mutation of Mbtps1 called woodrat (wrt) caused hypocholesterolemia, as well as progressive hypopigmentation of the coat, that appears to be mechanistically unrelated. Hypopigmentation was rescued by transgenic expression of wild-type Mbtps1, and reciprocal grafting studies showed that normal pigmentation depended upon both cell-intrinsic or paracrine factors, as well as factors that act systemically, both of which are lacking in wrt homozygotes. Mbtps1 exhibited a maternal-zygotic effect characterized by fully penetrant embryonic lethality of maternal-zygotic wrt mutant offspring and partial embryonic lethality (~40%) of zygotic wrt mutant offspring. Mbtps1 is one of two maternal-zygotic effect genes identified in mammals to date. It functions nonredundantly in pigmentation and embryogenesis.

Rutschmann, Sophie; Crozat, Karine; Li, Xiaohong; Du, Xin; Hanselman, Jeffrey C.; Shigeoka, Alana A.; Brandl, Katharina; Popkin, Daniel L.; McKay, Dianne B.; Xia, Yu; Moresco, Eva Marie Y.; Beutler, Bruce

2012-01-01

169

Lethal and Amanitin-Resistance Mutations in the Caenorhabditis Elegans Ama-1 and Ama-2 Genes  

PubMed Central

Mutants of Caenorhabditis elegans resistant to ?-amanitin have been isolated at a frequency of about 1.6 X 10(-6) after EMS mutagenesis of the wild-type strain, N2. Four new dominant resistance mutations have been studied genetically. Three are alleles of a previously identified gene, ama-1 IV, encoding the largest subunit of RNA polymerase II. The fourth mutation defines a new gene, ama-2 V. Unlike the ama-1 alleles, the ama-2 mutation exhibits a recessive-lethal phenotype. Growth and reproduction of N2 was inhibited at a concentration of 10 ?g/ml amanitin, whereas ama-2/+ animals were inhibited at 100 ?g/ml, and 800 ?g/ml was required to inhibit growth of ama-1/+ larvae. We have also determined that two reference strains used for genetic mapping, dpy-11(e224)V and sma-1(e30)V, are at least four-fold more sensitive to amanitin that the wild-type strain. Using an amanitin-resistant ama-1(m118) or ama-1(m322) strain as a parent, we have isolated amanitin-sensitive mutants that carry recessive-lethal ama-1 alleles. The frequency of EMS-induced lethal ama-1 mutations is approximately 1.7 X 10(-3), 1000-fold higher than the frequency of amanitin-resistance alleles. Nine of the lethal alleles are apparent null mutations, and they exhibit L1-lethal phenotypes at both 20° and 25°. Six alleles result in partial loss of RNA polymerase II function as determined by their sterile phenotypes at 20°. All but one of these latter mutations exhibit a more severe phenotype at 25°C. We have also selected seven EMS-induced revertants of three different ama-1 lethals. These revertants restore dominant resistance to amanitin. The selection for revertants also produced eight new dominant amanitin resistance alleles on the balancer chromosome, nT1.

Rogalski, T. M.; Bullerjahn, AME.; Riddle, D. L.

1988-01-01

170

Properties of r Mutants of Bacteriophage T4 Photodynamically Induced in the Presence of Thiopyronin and Psoralen  

PubMed Central

About 4 × 10?4r mutants were induced per lethal hit, a frequency characteristic of weak mutagens. Collections of mutants produced in the presence of either dye were indistinguishable in most of their properties. The rII mutants differed sharply from spontaneous mutants in their mutational spectra (fine scale map distribution) and their reversion responses to specific mutagens. Few or none of the induced mutants were induced to revert with proflavine (sign mutants; reading frame shift mutants). A majority were induced to revert with base analogues (base pair substitution mutants), and about half of these also responded to the hydroxymethylcytosine-specific agent hydroxylamine. A large minority of the mutants reverted spontaneously but failed to respond either to proflavine or to base analogues. We believe these mutants, as well as some of the mutants which did respond to base analogues, to be transversions (base pair substitutions which reverse the purine-pyrimidine orientation).

Drake, John W.; McGuire, Janice

1967-01-01

171

Lethal photosensitization of Helicobacter species  

NASA Astrophysics Data System (ADS)

Helicobacter pylori (H. pylori) is associated with a large number of gastroduodenal disorders. Clearance of the bacteria has been shown to benefit patients with duodenal ulcers, gastric ulcers, and certain rare types of gastric tumors. Broad-spectrum antibiotics are the mainstay of current treatment strategies but side-effects, poor compliance, and drug resistance limit their usefulness. We sensitized H. pylori with toluidine blue, haematoporphyrin derivative, aluminum disulphonated phthalocyanine, methylene blue or protoporphyrin IX prior to exposure to low-power laser light from either a gallium aluminum arsenide laser or a helium neon gas laser. All 5 sensitizers caused reductions of greater than 1000-fold in the number of viable bacteria. Light alone had no effect and only HpD caused a significant decrease in bacterial numbers without laser light. Next, we sensitized H. mustelae on explanted ferret gastric mucosa (ex vivo) with the same sensitizers and exposed them to light from a copper vapor pumped dye laser tuned appropriately. MB caused significant reductions in bacterial counts. Successful lethal photosensitization of Helicobacter pylori both in vitro and ex vivo raises the possibility of a local method for eradicating the bacteria, especially as the bacteria are only found in those parts of the upper gastrointestinal tract that are accessible to the endoscope.

Millson, Charles E.; Wilson, Michael; MacRobert, Alexander J.; Thurrell, Wendy; Mlkvy, Peter; Davies, Claire; Bown, S. G.

1995-01-01

172

Reaming experiments for the lethality test system  

SciTech Connect

Various reaming techniques were tried for use on the barrel of the Lethality Test System railgun. This report covers the successes and failures of the reamers and the techniques that were tried. 5 figs.

Hooten, D.; Stanley, P.

1988-01-01

173

Calcineurin, the Ca2+/calmodulin-dependent protein phosphatase, is essential in yeast mutants with cell integrity defects and in mutants that lack a functional vacuolar H(+)-ATPase.  

PubMed Central

Calcineurin is a conserved Ca2+/calmodulin-dependent protein phosphatase that plays a critical role in Ca(2+)-mediated signaling in many cells. Yeast cells lacking functional calcineurin (cna1 cna2 or cnb1 mutants) display growth defects under specific environmental conditions, for example, in the presence of high concentrations of Na+, Li+, Mn2+, or OH- but are indistinguishable from wild-type cells under standard culture conditions. To characterize regulatory pathways that may overlap with calcineurin, we performed a synthetic lethal screen to identify mutants that require calcineurin on standard growth media. The characterization of one such mutant, cnd1-8, is presented. The CND1 gene was cloned, and sequence analysis predicts that it encodes a novel protein 1,876 amino acids in length with multiple membrane-spanning domains. CND1 is identical to the gene identified previously as FKS1, ETG1, and CWH53, cnd1 mutants are sensitive to FK506 and cyclosporin A and exhibit slow growth that is improved by the addition of osmotic stabilizing agents. This osmotic agent-remedial growth defect and microscopic evidence of spontaneous cell lysis in cnd1 cultures suggest that cell integrity is compromised in these mutants. Mutations in the genes for yeast protein kinase C (pkc1) and a MAP kinase (mpk1/slt2) disrupt a Ca(2+)-dependent signaling pathway required to maintain a normal cell wall and cell integrity. We show that pkc1 and mpk1/slt2 growth defects are more severe in the absence of calcineurin function and less severe in the presence of a constitutively active form of calcineurin. These observations suggest that calcineurin and protein kinase C perform independent but physiologically related functions in yeast cells. We show that several mutants that lack a functional vacuolar H(+)-ATPase (vma) require calcineurin for vegetative growth. We discuss possible roles for calcineurin in regulating intracellular ion homeostasis and in maintaining cell integrity.

Garrett-Engele, P; Moilanen, B; Cyert, M S

1995-01-01

174

Mutant E. coli strain with increased succinic acid production  

US Patent & Trademark Office Database

The invention relates to a mutant strain of bacteria, which either lacks or contains mutant genes for several key metabolic enzymes, and which produces high amounts of succinic acid under anaerobic conditions.

2010-09-07

175

Tn5tac1, a derivative of transposon Tn5 that generates conditional mutations.  

PubMed

Conditional lethal mutations are valuable for analyzing essential genes. We describe here a derivative of the bacterial transposon Tn5 called Tn5tac1 and its use in an innovative strategy for making mutations with conditional phenotypes. The 4.6-kilobase Tn5tac1 element contains a strong, regulatable, outward-facing promoter (Ptac) near one end and is polar on the expression of distal genes when the inducer of Ptac [isopropyl beta-D-thiogalactoside (IPTG)] is absent. Our results show that two unusual conditional mutant phenotypes can result from Tn5tac1 insertion in Escherichia coli: one is corrected by IPTG while the other is induced by IPTG. The broad host range of Tn5 and the conditional nature of these mutant phenotypes makes Tn5tac1 well suited for identifying essential genes in diverse bacterial species. PMID:2842773

Chow, W Y; Berg, D E

1988-09-01

176

COMPLEMENTATION ANALYSIS OF METHYL METHANE SULFONATE-INDUCED RECESSIVE LETHAL MUTATIONS IN THE ZESTE-WHITE REGION OF THE X CHROMOSOME OF DROSOPHILA MELANOGASTERI  

Microsoft Academic Search

Recessive lethal mutations in the 3A1 to 3C2 region of the X chromosome of Drosophila melanogaster were detected in 113 of 33,544 sperm treated by feeding 5 mM methyl metllanesulfonate in 1% sucrose for 22 hours. Seven of the 113 lethals were sterile, leaving 106 for analysis by complementation tests. With only one exception, these mutants were found to have

J. K. LIM

177

Clearance of mutant huntingtin.  

PubMed

Mutant huntingtin (htt) carries an expanded polyglutamine (polyQ) repeat (> 36 glutamines) in its N-terminal region, which leads htt to become misfolded and kill neuronal cells in Huntington disease (HD). The cytotoxicity of N-terminal mutant htt fragments is evident by severe neurological phenotypes of transgenic mice that express these htt fragments. Clearance of mutant htt is primarily mediated by the ubiquitin-proteasomal sysmtem (UPS) and autophagy. However, the relative efficiency of these two systems to remove toxic forms of mutant htt has not been rigorously compared. Using cellular and mouse models of HD, we found that inhibiting the UPS leads to a greater accumulation of mutant htt than inhibiting autophagy. Moreover, N-terminal mutant htt fragments, but not full-length mutant htt, accumulate in the HD mouse brains after inhibiting the UPS. These findings suggest that the UPS is more efficient than autophagy to remove N-terminal mutant htt. PMID:20519964

Li, Xiao-Jiang; Li, He; Li, Shihua

2010-07-01

178

Environmentally sensitive, SA-dependent defense responses in the cpr22 mutant of Arabidopsis.  

PubMed

To investigate the signaling pathways through which defense responses are activated following pathogen infection, we have isolated and characterized the cpr22 mutant. This plant carries a semidominant, conditional lethal mutation that confers constitutive expression of the pathogenesis-related (PR) genes PR-1, PR-2, PR-5 and the defensin gene PDF1.2. cpr22 plants also display spontaneous lesion formation, elevated levels of salicylic acid (SA) and heightened resistance to Peronospora parasitica Emco5. The cpr22 locus was mapped to chromosome 2, approximately 2 cM telomeric to the AthB102 marker. By analyzing the progeny of crosses between cpr22 plants and either NahG transgenic plants or npr1 mutants, all of the cpr22-associated phenotypes except PDF1.2 expression were found to be SA dependent. However, the SA signal transducer NPR1 was required only for constitutive PR-1 expression. A cross between cpr22 and ndr1-1 mutants revealed that enhanced resistance to P. parasitica is mediated by an NDR1-dependent pathway, while the other cpr22-induced defenses are not. Crosses between either coi1-1 or etr1-1 mutants further demonstrated that constitutive PDF1.2 expression is mediated by a JA- and ethylene-dependent pathway. Based on these results, the cpr22 mutation appears to induce its associated phenotypes by activating NPR1-dependent and NPR1-independent branches of the SA pathway, as well as an ethylene/JA signaling pathway. Interestingly, the SA-dependent phenotypes, but not the SA-independent phenotypes, are suppressed when cpr22 mutants are grown under high humidity. PMID:11439131

Yoshioka, K; Kachroo, P; Tsui, F; Sharma, S B; Shah, J; Klessig, D F

2001-05-01

179

A rapid procedure for selective enrichment of photosynthetic electron transport mutants.  

PubMed Central

Metronidazole (2-methyl-5-nitroimidazole-l-ethanol) is shown to be effective for the selective enrichment of mutants of Chlamydomonas reinhardtii that posses impaired photosynthetic electron transport. More than 99.9% of wild-type cells are killed when incubated in the presence of 6-10 mM metronidazole for 24 hr under illumination of 7500 lux. Survival of wild-type cells in darkness and of mutants that are blocked at different steps in photosynthetic electron transport is nearly 100% when incubated in the presence of the drug under identical conditions. The toxicity of metronidazole is demonstrated to depend upon its reduction by photosynthetic electron transport. Light-dependent oxygen uptake mediated by metronidazole is shown to require active photosystem l in vitro and in vivo. Ferredoxin is necessary for metronidazole reduction by thylakoid membrane fractions enriched in photosystem l activity. We propose that the toxicity of metronidazole is due to the formation of lethal derivatives of the drug or to the accumulation of hydrogen peroxide, which could occur upon autooxidation of metronidazole reduced by one electron. The results indicate that mutants of C. reinhardtii, and probably other photosynthetic organisms, with any lesion in photosynthetic electron transport from the oxidizing side of photosystem ll to ferredoxin can be isolated by metronidazole treatment of mutagenized cultures.

Schmidt, G W; Matlin, K S; Chua, N H

1977-01-01

180

Drosophila switch gene Sex-lethal can bypass its switch-gene target transformer to regulate aspects of female behavior  

PubMed Central

The switch gene Sex-lethal (Sxl) was thought to elicit all aspects of Drosophila female somatic differentiation other than size dimorphism by controlling only the switch gene transformer (tra). Here we show instead that Sxl controls an aspect of female sexual behavior by acting on a target other than or in addition to tra. We inferred the existence of this unknown Sxl target from the observation that a constitutively feminizing tra transgene that restores fertility to tra? females failed to restore fertility to Sxl-mutant females that were adult viable but functionally tra?. The sterility of these mutant females was caused by an ovulation failure. Because tra expression is not sufficient to render these Sxl-mutant females fertile, we refer to this pathway as the tra-insufficient feminization (TIF) branch of the sex-determination regulatory pathway. Using a transgene that conditionally expresses two Sxl feminizing isoforms, we find that the TIF branch is required developmentally for neurons that also sex-specifically express fruitless, a tra gene target controlling sexual behavior. Thus, in a subset of fruitless neurons, targets of the TIF and tra pathways appear to collaborate to control ovulation. In most insects, Sxl has no sex-specific functions, and tra, rather than Sxl, is both the target of the primary sex signal and the gene that maintains the female developmental commitment via positive autoregulation. The TIF pathway may represent an ancestral female-specific function acquired by Sxl in an early evolutionary step toward its becoming the regulator of tra in Drosophila.

Evans, Daniel S.; Cline, Thomas W.

2013-01-01

181

Crystallographic studies of the Anthrax lethal toxin. Annual report  

SciTech Connect

The lethal form of Anthrax results from the inhalation of anthrax spores. Death is primarily due to the effects of the lethal toxin (Protective Antigen (PA) + Lethal Factor) from the causative agent, Bacillus anthracis. All the Anthrax vaccines currently in use or under development contain or produce PA, the major antigenic component of anthrax toxin, and there is a clear need for an improved vaccine for human use. In the previous report we described the first atomic resolution structure of PA, revealing that the molecule is composed largely of beta-sheets organized into four domains. This information can be used in the design. of recombinant PA vaccines. In this report we describe additional features of the full-length PA molecule derived from further crystallographic refinement and careful examination of the structure. We compare two crystal forms of PA grown at different pH values and discuss the functional implications. A complete definition of the function of each domain must await the crystal structure of the PA63 heptamer. We have grown crystals of the heptamer under both detergent and detergent-free conditions, and made substantial progress towards the crystal structure. The mechanism of anthrax intoxication in the light of our results is reviewed.

Frederick, C.A.

1996-07-01

182

Isolation and Characterization of ?-Ketoacyl-Acyl Carrier Protein Reductase (fabG) Mutants of Escherichia coli and Salmonella enterica Serovar Typhimurium  

PubMed Central

FabG, ?-ketoacyl-acyl carrier protein (ACP) reductase, performs the NADPH-dependent reduction of ?-ketoacyl-ACP substrates to ?-hydroxyacyl-ACP products, the first reductive step in the elongation cycle of fatty acid biosynthesis. We report the first documented fabG mutants and their characterization. By chemical mutagenesis followed by a tritium suicide procedure, we obtained three conditionally lethal temperature-sensitive fabG mutants. The Escherichia coli [fabG (Ts)] mutant contains two point mutations: A154T and E233K. The ?-ketoacyl-ACP reductase activity of this mutant was extremely thermolabile, and the rate of fatty acid synthesis measured in vivo was inhibited upon shift to the nonpermissive temperature. Moreover, synthesis of the acyl-ACP intermediates of the pathway was inhibited upon shift of mutant cultures to the nonpermissive temperature, indicating blockage of the synthetic cycle. Similar results were observed for in vitro fatty acid synthesis. Complementation analysis revealed that only the E233K mutation was required to give the temperature-sensitive growth phenotype. In the two Salmonella enterica serovar Typhimurium fabG(Ts) mutants one strain had a single point mutation, S224F, whereas the second strain contained two mutations (M125I and A223T). All of the altered residues of the FabG mutant proteins are located on or near the twofold axes of symmetry at the dimer interfaces in this homotetrameric protein, suggesting that the quaternary structures of the mutant FabG proteins may be disrupted at the nonpermissive temperature.

Lai, Chiou-Yan; Cronan, John E.

2004-01-01

183

Taste aversion learning in fyn mutant mice.  

PubMed

Conditioned taste aversion (CTA) learning is a robust form of classical conditioning in which animals rapidly associate a flavor with aversive internal symptoms. The present study assessed CTA learning in transgenic mice deficient in a specific nonreceptor tyrosine kinase (the fyn mutant). Fyn mutants show impaired long-term potentiation and marked deficits in acquisition of spatial learning tasks. To assess whether they are also impaired in CTA learning, fyn mutant and wild-type mice received 2 conditioning trials consisting of access to a flavored solution followed by administration of LiCl. Fyn mutant mice acquired significant CTAs following a single conditioning trial and these aversions were comparable to those seen in wild-type mice. These results indicate that the fyn mutation does not interfere with the acquisition of CTAs and hence that this mutation is not associated with a global learning deficit. PMID:8864276

Schafe, G E; Stein, P L; Park, C R; Bernstein, I L

1996-08-01

184

Development of ELISA based detection system for lethal toxin of Clostridium sordellii  

PubMed Central

Background & objectives: Clostridium sordellii and its toxins are associated with diseases in animals as well as human. C. sordellii produces two protein toxins (lethal toxin and haemorrhagic toxin). Lethal toxin has gained more importance due its high toxicity. The present study was carried out to develop a sandwich ELISA for detection of lethal toxin of C. sordellii. Methods: The catalytic domain (1.6kb) of lethal toxin of C. sordellii was PCR amplified, cloned into pQE30 UA vector and transformed into Escherichia coli SG 13009. Expression conditions were optimized and the recombinant protein was purified under native condition using Ni-NTA affinity chromatography, confirmed by SDS-PAGE and Western blot. Antibody was generated against the purified recombinant protein using Freund's complete and incomplete adjuvants (FCA and FIA) in BALB/c mice and rabbit. A sandwich ELISA was optimized for the detection of lethal toxin. Results: The maximum recombinant protein expression was achieved at 0.5 mM IPTG (isopropylthiogalactoside) induction 4.0 h of post-induction. The polyclonal antibody raised in mice and rabbit showed a titre up to 1:512000. The produced antibody was highly sensitive with the detection limit of 0.3 ng/ml of lethal toxin at 1:4000 dilutions of mice (capturing) and rabbit (revealing) antibody. Interpretation & conclusions: An ELISA based detection system was developed for the detection of lethal toxin of C. sordellii. The developed detection system was found to be specific as there was no cross-reactivity with any other clostridial toxins. It will be useful for the detection of lethal toxin of C. sordellii in clinical and environmental samples.

Arya, Preetika; Ponmariappan, S.; Singh, Lokendra; Kumar, Om

2013-01-01

185

Synthetic Lethal Interaction of the Mitochondrial Phosphatidylethanolamine Biosynthetic Machinery with the Prohibitin Complex of Saccharomyces cerevisiae  

PubMed Central

The majority of mitochondrial phosphatidylethanolamine (PtdEtn), a phospholipid essential for aerobic growth of yeast cells, is synthesized by phosphatidylserine decarboxylase 1 (Psd1p) in the inner mitochondrial membrane (IMM). To identify components that become essential when the level of mitochondrial PtdEtn is decreased, we screened for mutants that are synthetically lethal with a temperature-sensitive (ts) allele of PSD1. This screen unveiled mutations in PHB1 and PHB2 encoding the two subunits of the prohibitin complex, which is located to the IMM and required for the stability of mitochondrially encoded proteins. Deletion of PHB1 and PHB2 resulted in an increase of mitochondrial PtdEtn at 30°C. On glucose media, phb1? psd1? and phb2? psd1? double mutants were rescued only for a limited number of generations by exogenous ethanolamine, indicating that a decrease of the PtdEtn level is detrimental for prohibitin mutants. Similar to phb mutants, deletion of PSD1 destabilizes polypeptides encoded by the mitochondrial genome. In a phb1? phb2? psd1ts strain the destabilizing effect is dramatically enhanced. In addition, the mitochondrial genome is lost in this triple mutant, and nuclear-encoded proteins of the IMM are assembled at a very low rate. At the nonpermissive temperature mitochondria of phb1? phb2? psd1ts were fragmented and aggregated. In conclusion, destabilizing effects triggered by low levels of mitochondrial PtdEtn seem to account for synthetic lethality of psd1? with phb mutants.

Birner, Ruth; Nebauer, Ruth; Schneiter, Roger; Daum, Gunther

2003-01-01

186

Appearance of recessive lethal mutations in derivatives of an unstable X{sup Z} chromosome of Drosophila melanogaster  

SciTech Connect

An X{sup Z} chromosome isolated from a natural population of Drosophila melanogaster is characterized by spontaneous mutability of the genes yellow, white, and singed and the appearance of chromosomal rearrangements. In mutant lines derived from the line carrying the X{sup Z} chromosome that had one, two, or three unstable vision mutations (markers), the rate of appearance of sex-linked lethal mutations was analyzed. This rate was shown to increase with an increase in the number of markers in a line. This phenomenon, termed {open_quotes}marker induction,{close_quotes} might explain the phenotypic homogeneity of natural Drosophila populations. Spontaneous lethal mutations were mapped, and their nonrandom distribution along the X{sup Z} chromosome was shown. Along with common {open_quotes}hot spot{close_quotes} sites of lethal mutations, the derivatives of the X{sup Z} chromosomes had their own specific sites for lethal mutations. In some cases, the appearance of lethal mutations was accompanied by the formation of inversions in the X{sup Z} chromosome. The lethal destabilization of the X{sup Z} derivatives, caused by selection for accumulation of visible mutations, is associated with an increase in the number of hot spots for nuclear mutations. Presumably, these hot spots are hot sites for the transposition of mobile genetic elements. 18 refs., 4 figs., 3 tabs.

Yurchenko, N.N.; Koryakov, D.E.; Zakharov, I.K. [Institute of Cytology and Genetics, Novosibirsk (Russian Federation)

1995-09-01

187

Live deaths online: internet suicide and lethality.  

PubMed

The Internet provides an infinite platform for the portrayal of lethal events. Beyond mere display, however, it dispenses information, allows for participation and sharing of content, and constitutes a virtual interactive forum. The Internet may ultimately shape society's approach to perceiving and dealing with death. Thus, psychiatrists may wish to be aware of these matters so that they may be considered in assessments and clinical care. In this article, the author attempts to identify key online locations where lethality is portrayed and how it may affect the individual patient and practitioner and the population at large. PMID:23233475

Klein, Carolina A

2012-01-01

188

A new lethal syndrome of exomphalos, short limbs, and macrogonadism  

PubMed Central

We report a new lethal multiple congenital abnormality (MCA) syndrome of exomphalos, short limbs, nuchal web, macrogonadism, and facial dysmorphism in seven fetuses (six males and one female) belonging to three unrelated families. X rays showed enlarged and irregular metaphyses with a heterogeneous pattern of mineralisation of the long bones. Pathological examination showed adrenal cytomegaly, hyperplasia of Leydig cells, ovarian stroma cells, and Langherans cells, and renal microcysts. We suggest that this condition is a new autosomal recessive MCA syndrome different from Beckwith-Wiedemann syndrome, especially as no infracytogenetic deletion or uniparental disomy of chromosome 11 was found.???Keywords: MCA syndrome; exomphalos; short limbs; abnormal metaphyses

Faivre, L.; Delezoide, A.; Narcy, F.; Razavi, F.; Bouvier, R.; Cormier-Daire, V.; Briard, M.; Lyonnet, S.; Vekemans, M.; Munnich, A.; Le Merrer, M.

1999-01-01

189

Random mutagenesis of proximal mouse chromosome 5 uncovers predominantly embryonic lethal mutations  

PubMed Central

A region-specific ENU mutagenesis screen was conducted to elucidate the functional content of proximal mouse Chr 5. We used the visibly marked, recessive, lethal inversion Rump White (Rw) as a balancer in a three-generation breeding scheme to identify recessive mutations within the ?50 megabases spanned by Rw. A total of 1003 pedigrees were produced, representing the largest inversion screen performed in mice. Test-class animals, homozygous for the ENU-mutagenized proximal Chr 5 and visibly distinguishable from nonhomozygous littermates, were screened for fertility, hearing, vestibular function, DNA repair, behavior, and dysmorphology. Lethals were identifiable by failure to derive test-class animals within a pedigree. Embryonic lethal mutations (total of 34) were overwhelmingly the largest class of mutants recovered. We characterized them with respect to the time of embryonic death, revealing that most act at midgestation (8.5–10.5) or sooner. To position the mutations within the Rw region and to guide allelism tests, we performed complementation analyses with a set of new and existing chromosomal deletions, as well as standard recombinational mapping on a subset of the mutations. By pooling the data from this and other region-specific mutagenesis projects, we calculate that the mouse genome contains ?3479–4825 embryonic lethal genes, or about 13.7%–19% of all genes.

Wilson, Lawriston; Ching, Yung-Hao; Farias, Michael; Hartford, Suzanne A.; Howell, Gareth; Shao, Hongguang; Bucan, Maja; Schimenti, John C.

2005-01-01

190

Random mutagenesis of proximal mouse chromosome 5 uncovers predominantly embryonic lethal mutations.  

PubMed

A region-specific ENU mutagenesis screen was conducted to elucidate the functional content of proximal mouse Chr 5. We used the visibly marked, recessive, lethal inversion Rump White (Rw) as a balancer in a three-generation breeding scheme to identify recessive mutations within the approximately 50 megabases spanned by Rw. A total of 1003 pedigrees were produced, representing the largest inversion screen performed in mice. Test-class animals, homozygous for the ENU-mutagenized proximal Chr 5 and visibly distinguishable from nonhomozygous littermates, were screened for fertility, hearing, vestibular function, DNA repair, behavior, and dysmorphology. Lethals were identifiable by failure to derive test-class animals within a pedigree. Embryonic lethal mutations (total of 34) were overwhelmingly the largest class of mutants recovered. We characterized them with respect to the time of embryonic death, revealing that most act at midgestation (8.5-10.5) or sooner. To position the mutations within the Rw region and to guide allelism tests, we performed complementation analyses with a set of new and existing chromosomal deletions, as well as standard recombinational mapping on a subset of the mutations. By pooling the data from this and other region-specific mutagenesis projects, we calculate that the mouse genome contains approximately 3479-4825 embryonic lethal genes, or about 13.7%-19% of all genes. PMID:16024820

Wilson, Lawriston; Ching, Yung-Hao; Farias, Michael; Hartford, Suzanne A; Howell, Gareth; Shao, Hongguang; Bucan, Maja; Schimenti, John C

2005-08-01

191

?-Lactalbumin unfolding is not sufficient to cause apoptosis, but is required for the conversion to HAMLET (human ?-lactalbumin made lethal to tumor cells)  

PubMed Central

HAMLET (human ?-lactalbumin made lethal to tumor cells) is a complex of human ?-lactalbumin and oleic acid (C18:1:9 cis) that kills tumor cells by an apoptosis-like mechanism. Previous studies have shown that a conformational change is required to form HAMLET from ?-lactalbumin, and that a partially unfolded conformation is maintained in the HAMLET complex. This study examined if unfolding of ?-lactalbumin is sufficient to induce cell death. We used the bovine ?-lactalbumin Ca2+ site mutant D87A, which is unable to bind Ca2+, and thus remains partially unfolded regardless of solvent conditions. The D87A mutant protein was found to be inactive in the apoptosis assay, but could readily be converted to a HAMLET-like complex in the presence of oleic acid. BAMLET (bovine ?-lactalbumin made lethal to tumor cells) and D87A-BAMLET complexes were both able to kill tumor cells. This activity was independent of the Ca2+site, as HAMLET maintained a high affinity for Ca2+ but D87A-BAMLET was active with no Ca2+ bound. We conclude that partial unfolding of ?-lactalbumin is necessary but not sufficient to trigger cell death, and that the activity of HAMLET is defined both by the protein and the lipid cofactor. Furthermore, a functional Ca2+-binding site is not required for conversion of ?-lactalbumin to the active complex or to cause cell death. This suggests that the lipid cofactor stabilizes the altered fold without interfering with the Ca2+site.

Svensson, Malin; Fast, Jonas; Mossberg, Ann-Kristin; Duringer, Caroline; Gustafsson, Lotta; Hallgren, Oskar; Brooks, Charles L.; Berliner, Lawrence; Linse, Sara; Svanborg, Catharina

2003-01-01

192

Innovation in Non-Lethal Weapon Technology.  

National Technical Information Service (NTIS)

ZARC is the founder of Oleoresin Capsicum (0C Pepper Agent) non- lethal weapon technology. This proprietary OC technology is currently packaged in an aerosol form under the recognized brandname CAP-STUN, the very first pepper spray on the market developed...

C. Logman

1998-01-01

193

Lethal Malaria: Marchiafava and Bignami Were Right  

PubMed Central

One hundred and twenty years ago, the Italian malariologists Marchiafava and Bignami proposed that the fundamental pathological process underlying lethal falciparum malaria was microvascular obstruction. Since then, several alternative hypotheses have been proposed. These formed the basis for adjunctive interventions, which have either been ineffective or harmful. Recent evidence strongly suggests that Marchiafava and Bignami were right.

White, Nicholas J.; Turner, Gareth D. H.; Day, Nicholas P. J.; Dondorp, Arjen M.

2013-01-01

194

Unexpected double lethal oleander poisoning.  

PubMed

Nerium oleander is a very popular urban ornamental plant in Europe, but it is also extremely dangerous because it contains several types of glycosides, accidental ingestion of which can cause cardiac arrhythmias and even deaths. The rarity of such cases makes it difficult to think of oleander poisoning without evidences that suggest this possibility as the cause of the unexpected death. This report concerns the discovery of the bodies of 2 young people, a man and a woman, in a forest in conditions of extreme malnutrition. Medicolegal investigations showed neither pathologic nor traumatic causes of death, but the presence of vegetal remains in the stomach was noticed. A common toxicological analysis resulted negative, but the implementation of more detailed investigations showed the presence of digoxin in the blood of both cadavers, excluding the possibility of a pharmaceutical provenience of digoxin, this laboratory result was interpreted as evidence of ingestion of oleander, which contains oleandrine, the cross reaction of which with digoxin is widely described in the literature. Identification of the 2 subjects, which occurred after 4 years, strengthened the hypothesis of accidental poisoning by oleander because it was ascertained that the 2 young people were vegans--extreme vegetarians who reject the ingestion of foods of animal origin and live by eating only what they find in nature. PMID:21926903

Papi, Luigi; Luciani, Alessandro Bassi; Forni, David; Giusiani, Mario

2012-03-01

195

Phenotypes of lexA Mutations in Salmonella enterica: Evidence for a Lethal lexA Null Phenotype Due to the Fels-2 Prophage  

PubMed Central

The LexA protein of Escherichia coli represses the damage-inducible SOS regulon, which includes genes for repair of DNA. Surprisingly, lexA null mutations in Salmonella enterica are lethal even with a sulA mutation, which corrects lexA lethality in E. coli. Nine suppressors of lethality isolated in a sulA mutant of S. enterica had lost the Fels-2 prophage, and seven of these (which grew better) had also lost the Gifsy-1 and Gifsy-2 prophages. All three phage genomes included a homologue of the tum gene of coliphage 186, which encodes a LexA-repressed cI antirepressor. The tum homologue of Fels-2 was responsible for lexA lethality and had a LexA-repressed promoter. This basis of lexA lethality was unexpected because the four prophages of S. enterica LT2 are not strongly UV inducible and do not sensitize strains to UV killing. In S. enterica, lexA(Ind?) mutants have the same phenotypes as their E. coli counterparts. Although lexA null mutants express their error-prone DinB polymerase constitutively, they are not mutators in either S. enterica or E. coli.

Bunny, Kim; Liu, Jing; Roth, John

2002-01-01

196

Disruption of the Rice Plastid Ribosomal Protein S20 Leads to Chloroplast Developmental Defects and Seedling Lethality  

PubMed Central

Plastid ribosomal proteins (PRPs) are essential for ribosome biogenesis, plastid protein biosynthesis, chloroplast differentiation, and early chloroplast development. This study identifies the first rice PRP mutant, asl1 (albino seedling lethality1), which exhibits an albino lethal phenotype at the seedling stage. This albino phenotype was associated with altered chlorophyll (Chl) content and chloroplast development. Map-based cloning revealed that ASL1 encodes PRP S20 (PRPS20), which localizes to the chloroplast. ASL1 showed tissue-specific expression, as it was highly expressed in plumule and young seedlings but expressed at much lower levels in other tissues. In addition, ASL1 expression was regulated by light. The transcript levels of nuclear genes for Chl biosynthesis and chloroplast development were strongly affected in asl1 mutants; transcripts of some plastid genes for photosynthesis were undetectable. Our findings indicate that nuclear-encoded PRPS20 plays an important role in chloroplast development in rice.

Gong, Xiaodi; Jiang, Quan; Xu, Jianlong; Zhang, Jianhui; Teng, Sheng; Lin, Dongzhi; Dong, Yanjun

2013-01-01

197

A Toxin-Antitoxin Module in Bacillus subtilis Can Both Mitigate and Amplify Effects of Lethal Stress  

PubMed Central

Background Bacterial type-2 (protein-protein) toxin-antitoxin (TA) modules are two-gene operons that are thought to participate in the response to stress. Previous work with Escherichia coli has led to a debate in which some investigators conclude that the modules protect from stress, while others argue that they amplify lethal stress and lead to programmed cell death. To avoid ambiguity arising from the presence of multiple TA modules in E. coli, the effect of the sole type-2 toxin-antitoxin module of Bacillus subtilis was examined for several types of lethal stress. Methodology/Principal Findings Genetic knockout of the toxin gene, ndoA (ydcE), conferred protection to lethal stressors that included kanamycin, moxifloxacin, hydrogen peroxide, and UV irradiation. However, at low doses of UV irradiation the ndoA deficiency increased lethality. Indeed, gradually increasing UV dose with the ndoA mutant revealed a crossover response – from the mutant being more sensitive than wild-type cells to being less sensitive. For high temperature and nutrient starvation, the toxin deficiency rendered cells hypersensitive. The ndoA deficiency also reduced sporulation frequency, indicating a role for toxin-antitoxin modules in this developmental process. In the case of lethal antimicrobial treatment, deletion of the toxin eliminated a surge in hydrogen peroxide accumulation observed in wild-type cells. Conclusions A single toxin-antitoxin module can mediate two opposing effects of stress, one that lowers lethality and another that raises it. Protective effects are thought to arise from toxin-mediated inhibition of translation based on published work. The enhanced, stress-mediated killing probably involves toxin-dependent accumulation of reactive oxygen species, since a deficiency in the NdoA toxin suppressed peroxide accumulation following antimicrobial treatment. The type and perhaps the level of stress appear to be important for determining whether this toxin will have a protective or detrimental effect.

Wu, Xiangli; Wang, Xiuhong; Drlica, Karl; Zhao, Xilin

2011-01-01

198

Lethal Time of Centruroides Sculpturatus Venom in Rats.  

National Technical Information Service (NTIS)

The effects of sex, weight, and dosage on the lethal time of scorpion Centruroides sculpturatus venom was studied. Sex and weight of the rats did not significantly alter lethal time whereas increased dosages of venom did.

H. L. Stahnke

1967-01-01

199

The effects of Fragment Ricochet on Munition Lethality.  

National Technical Information Service (NTIS)

This report presents the results of a contractual effort to determine the effects of fragment ricochet on munition lethality in tactical environments and to develop modifications to the lethal area programs to account for fragment ricochet effects. The De...

C. Hayes W. Reeves J. Collins

1975-01-01

200

Lethal and amanitin-resistance mutations in the Caenorhabditis elegans ama-1 and ama-2 genes.  

PubMed

Mutants of Caenorhabditis elegans resistant to alpha-amanitin have been isolated at a frequency of about 1.6 x 10(-6) after EMS mutagenesis of the wild-type strain, N2. Four new dominant resistance mutations have been studied genetically. Three are alleles of a previously identified gene, ama-1 IV, encoding the largest subunit of RNA polymerase II. The fourth mutation defines a new gene, ama-2 V. Unlike the ama-1 alleles, the ama-2 mutation exhibits a recessive-lethal phenotype. Growth and reproduction of N2 was inhibited at a concentration of 10 micrograms/ml amanitin, whereas ama-2/+ animals were inhibited at 100 micrograms/ml, and 800 micrograms/ml was required to inhibit growth of ama-1/+ larvae. We have also determined that two reference strains used for genetic mapping, dpy-11(e224)V and sma-1(e30)V, are at least four-fold more sensitive to amanitin that the wild-type strain. Using an amanitin-resistant ama-1(m118) or ama-1(m322) strain as a parent, we have isolated amanitin-sensitive mutants that carry recessive-lethal ama-1 alleles. The frequency of EMS-induced lethal ama-1 mutations is approximately 1.7 x 10(-3), 1000-fold higher than the frequency of amanitin-resistance alleles. Nine of the lethal alleles are apparent null mutations, and they exhibit L1-lethal phenotypes at both 20 degrees and 25 degrees. Six alleles result in partial loss of RNA polymerase II function as determined by their sterile phenotypes at 20 degrees. All but one of these latter mutations exhibit a more severe phenotype at 25 degrees C. We have also selected seven EMS-induced revertants of three different ama-1 lethals. These revertants restore dominant resistance to amanitin. The selection for revertants also produced eight new dominant amanitin resistance alleles on the balancer chromosome, nT1. PMID:3197954

Rogalski, T M; Bullerjahn, A M; Riddle, D L

1988-10-01

201

The Streptococcus pyogenes Capsule Is Required for Adhesion of Bacteria to Virus-Infected Alveolar Epithelial Cells and Lethal Bacterial-Viral Superinfection  

Microsoft Academic Search

An apparent worldwide resurgence of invasive group A Streptococcus (GAS) infections remains unexplained. However, we recently demonstrated in mice that when an otherwise nonlethal intranasal GAS infection is preceded by a nonlethal influenza A virus (IAV) infection, induction of lethal invasive GAS infections is often the result. In the present study, we established several isogenic mutants from a GAS isolate

Shigefumi Okamoto; Shigetada Kawabata; Yutaka Terao; Hideaki Fujitaka; Yoshinobu Okuno; Shigeyuki Hamada

2004-01-01

202

SspA Is Required for Lethal Salmonella enterica Serovar Typhimurium Infections in Calves but Is Not Essential for Diarrhea  

Microsoft Academic Search

Salmonella pathogenicity island 1 (SPI-1) encodes virulence determinants, which are important for entero- pathogenicity in calves. To determine whether the Salmonella enterica serovar Typhimurium SPI-1 effector proteins SspA and SptP are important for enteropathogenicity, strains lacking these proteins were tested during oral infection of calves. Calves infected with a sptP mutant or its isogenic parent developed diarrhea and lethal morbidity.

RENEE M. TSOLIS; L. GARRY ADAMS; MICHAEL J. HANTMAN; CHRISTINA A. SCHERER; TYLER KIMBROUGH; ROBERT A. KINGSLEY; THOMAS A. FICHT; SAMUEL I. MILLER; ANDREAS J. BAUMLER

2000-01-01

203

FUNCTIONAL CENTRALITY: DETECTING LETHALITY OF PROTEINS IN PROTEIN INTERACTION NETWORKS  

Microsoft Academic Search

Identifying lethal proteins is important for understanding the intricate mechanism gov- erning life. Researchers have shown that the lethality of a protein can be computed based on its topological position in the protein-protein interaction (PPI) network. Performance of current approaches has been less than satisfactory as the lethality of a protein is a functional characteristic that cannot be determined solely

Kar Leong Tewl; Xiao-Li Lil; Soon-Heng Tan

204

A novel histone H4 mutant defective in nuclear division and mitotic chromosome transmission.  

PubMed Central

The histone proteins are essential for the assembly and function of th e eukaryotic chromosome. Here we report the first isolation of a temperature-sensitive lethal histone H4 mutant defective in mitotic chromosome transmission Saccharomyces cerevisiae. The mutant requires two amino acid substitutions in histone H4: a lethal Thr-to-Ile change at position 82, which lies within one of the DNA-binding surfaces of the protein, and a substitution of Ala to Val at position 89 that is an intragenic suppressor. Genetic and biochemical evidence shows that the mutant histone H4 is temperature sensitive for function but not for synthesis, deposition, or stability. The chromatin structure of 2 micrometer circle minichromosomes is temperature sensitive in vivo, consistent with a defect in H4-DNA interactions. The mutant also has defects in transcription, displaying weak Spt- phenotypes. At the restrictive temperature, mutant cells arrest in the cell cycle at nuclear division, with a large bud, a single nucleus with 2C DNA content, and a short bipolar spindle. At semipermissive temperatures, the frequency of chromosome loss is elevated 60-fold in the mutant while DNA recombination frequencies are unaffected. High-copy CSE4, encoding an H3 variant related to the mammalian CENP-A kinetochore antigen, was found to suppress the temperature sensitivity of the mutant without suppressing the Spt- transcription defect. These genetic, biochemical, and phenotypic results indicate that this novel histone H4 mutant defines one or more chromatin-dependent steps in chromosome segregation.

Smith, M M; Yang, P; Santisteban, M S; Boone, P W; Goldstein, A T; Megee, P C

1996-01-01

205

A Saccharomyces cerevisiae Genome-Wide Mutant Screen for Altered Sensitivity to K1 Killer Toxin  

Microsoft Academic Search

Using the set of Saccharomyces cerevisiae mutants individually deleted for 5718 yeast genes, we screened for altered sensitivity to the antifungal protein, K1 killer toxin, that binds to a cell wall -glucan receptor and subsequently forms lethal pores in the plasma membrane. Mutations in 268 genes, including 42 in genes of unknown function, had a phenotype, often mild, with 186

Nicolas Page ´; Manon Gerard-Vincent; Patrice Menard; Maude Beaulieu; Masayuki Azuma; Gerrit J. P. Dijkgraaf; Thuy Nguyen; Tim Dowse; Anne-Marie Sdicu; Howard Bussey

206

Efficient synthetic inhibitors of anthrax lethal factor  

PubMed Central

Inhalation anthrax is a deadly disease for which there is currently no effective treatment. Bacillus anthracis lethal factor (LF) metalloproteinase is an integral component of the tripartite anthrax lethal toxin that is essential for the onset and progression of anthrax. We report here on a fragment-based approach that allowed us to develop inhibitors of LF. The small-molecule inhibitors we have designed, synthesized, and tested are highly potent and selective against LF in both in vitro tests and cell-based assays. These inhibitors do not affect the prototype human metalloproteinases that are structurally similar to LF. Initial in vivo evaluation of postexposure efficacy of our inhibitors combined with antibiotic ciprofloxican against B. anthracis resulted in significant protection. Our data strongly indicate that the scaffold of inhibitors we have identified is the foundation for the development of novel, safe, and effective emergency therapy of postexposure inhalation anthrax.

Forino, Martino; Johnson, Sherida; Wong, Thiang Y.; Rozanov, Dmitri V.; Savinov, Alexei Y.; Li, Wei; Fattorusso, Roberto; Becattini, Barbara; Orry, Andrew J.; Jung, Dawoon; Abagyan, Ruben A.; Smith, Jeffrey W.; Alibek, Ken; Liddington, Robert C.; Strongin, Alex Y.; Pellecchia, Maurizio

2005-01-01

207

Synthetic lethality to overcome cancer drug resistance.  

PubMed

A large body of evidence point out that the onset of synthetic lethality may provide a useful tool for amplifying the efficacy of drugs in anticancer regimens, to uncover interdependence between genes and to identify predictive factors that would be extremely useful to guide in the selection of more effective targeted drugs and drug combinations for each patient. Here, we provide an overview on the exploitation of synthetic lethality to overcome drug resistance to conventional chemotherapy in several types of solid tumors. We report recent findings on cellular markers and gene mutations which are specifically essential for the viability of cancer cells and for resistance to chemotherapeutics. In addition, new molecularly targeted strategies to overcome drug resistance are suggested. PMID:22788762

Porcelli, L; Quatrale, A E; Mantuano, P; Silvestris, N; Brunetti, A E; Calvert, H; Paradiso, A; Azzariti, A

2012-01-01

208

Bullying and Lethal Acts of School Violence  

Microsoft Academic Search

\\u000a In Chap. 3, we address a topic that has received considerable research attention over the past decade and has been implicated as a causal\\u000a factor in LSV. It has been reported that many lethal school shootings were in part in retaliation for being bullied. Within\\u000a this chapter, we address prevalence of bullying in the USA and then discuss different forms

Jeffrey A. Daniels; Mary C. Bradley

209

Fighting back: Lethal responses to predatory attacks  

Microsoft Academic Search

Each year millions of Americans become victims of predatory crimes. The way victims respond to these attacks varies from complicance\\u000a with offenders' requests to physically challenging offenders. In some cases, the physical defense of self and property has\\u000a lethal consequences for the initial offender. While much is known about felony murder victims and typical homicide offenders,\\u000a little is known about

Kent R. Kerley; Heith Copes; Andrew L. Hochstetler; Anne Carroll

2002-01-01

210

Rescue of Progeria in Trichothiodystrophy by Homozygous Lethal Xpd Alleles  

PubMed Central

Although compound heterozygosity, or the presence of two different mutant alleles of the same gene, is common in human recessive disease, its potential to impact disease outcome has not been well documented. This is most likely because of the inherent difficulty in distinguishing specific biallelic effects from differences in environment or genetic background. We addressed the potential of different recessive alleles to contribute to the enigmatic pleiotropy associated with XPD recessive disorders in compound heterozygous mouse models. Alterations in this essential helicase, with functions in both DNA repair and basal transcription, result in diverse pathologies ranging from elevated UV sensitivity and cancer predisposition to accelerated segmental progeria. We report a variety of biallelic effects on organismal phenotype attributable to combinations of recessive Xpd alleles, including the following: (i) the ability of homozygous lethal Xpd alleles to ameliorate a variety of disease symptoms when their essential basal transcription function is supplied by a different disease-causing allele, (ii) differential developmental and tissue-specific functions of distinct Xpd allele products, and (iii) interallelic complementation, a phenomenon rarely reported at clinically relevant loci in mammals. Our data suggest a re-evaluation of the contribution of “null” alleles to XPD disorders and highlight the potential of combinations of recessive alleles to affect both normal and pathological phenotypic plasticity in mammals.

Andressoo, Jaan-Olle; Jans, Judith; de Wit, Jan; Coin, Frederic; Hoogstraten, Deborah; van de Ven, Marieke; Toussaint, Wendy; Huijmans, Jan; Thio, H. Bing; van Leeuwen, Wibeke J; de Boer, Jan; Egly, Jean-Marc; Hoeijmakers, Jan H. J; van der Horst, Gijsbertus T. J; Mitchell, James R

2006-01-01

211

Effect of vanillic acid on COQ6 mutants identified in patients with coenzyme Q10 deficiency.  

PubMed

Human COQ6 encodes a monooxygenase which is responsible for the C5-hydroxylation of the quinone ring of coenzyme Q (CoQ). Mutations in COQ6 cause primary CoQ deficiency, a condition responsive to oral CoQ10 supplementation. Treatment is however still problematic given the poor bioavailability of CoQ10. We employed S. cerevisiae lacking the orthologous gene to characterize the two different human COQ6 isoforms and the mutations found in patients. COQ6 isoform a can partially complement the defective yeast, while isoform b, which lacks part of the FAD-binding domain, is inactive but partially stable, and could have a regulatory/inhibitory function in CoQ10 biosynthesis. Most mutations identified in patients, including the frameshift Q461fs478X mutation, retain residual enzymatic activity, and all patients carry at least one hypomorphic allele, confirming that the complete block of CoQ biosynthesis is lethal. These mutants are also partially stable and allow the assembly of the CoQ biosynthetic complex. In fact treatment with two hydroxylated analogues of 4-hydroxybenzoic acid, namely, vanillic acid or 3-4-hydroxybenzoic acid, restored the respiratory growth of yeast ?coq6 cells expressing the mutant huCOQ6-isoa proteins. These compounds, and particularly vanillic acid, could therefore represent an interesting therapeutic option for COQ6 patients. PMID:24140869

Doimo, Mara; Trevisson, Eva; Airik, Rannar; Bergdoll, Marc; Santos-Ocaña, Carlos; Hildebrandt, Friedhelm; Navas, Placido; Pierrel, Fabien; Salviati, Leonardo

2014-01-01

212

Production of cholera toxin-like toxin by Vibrio mimicus and non-O1 Vibrio cholerae: batch culture conditions for optimum yields and isolation of hypertoxigenic lincomycin-resistant mutants.  

PubMed Central

Vibrio mimicus 61892, isolated in 1977 from a case of watery diarrhea in Bangladesh, produces an enterotoxin which possesses activity in Y-1 mouse adrenal cells and in rabbit ileal loops which is identical to the prototype cholera toxin (CT) produced by Vibrio cholerae 569B. The neutralization of the adrenal cell activity of 61892 toxin and 569B CT by homologous and heterologous antisera generates parallel titration curves which show complete neutralization in all cases. Paired titrations in the ganglioside GM1 enzyme-linked immunosorbent assay (using either CT or Escherichia coli heat-labile toxin antitoxin) of both toxins indicates that 61892 toxin is antigenically indistinguishable from 569B CT. The specific activity of the two toxins in the rabbit ileal loop is virtually identical. Batch culture production of CT-like toxin and CT by isolates of V. mimicus and different biotypes of V. cholerae was found to be highest in shake flask cultures of Casamino Acids-yeast extract broth grown at 27 degrees C with vigorous aeration. Incorporation of lincomycin into the growth medium at a concentration of 50 micrograms/ml increased yields from wild-type strains. Dramatically higher yields were obtained when a spontaneous resistance mutant of strain 61892 was grown in the presence of 200 to 300 micrograms of lincomycin per ml. Under these conditions, yields of CT-like toxin were increased by 300- to 500-fold, and the highest yields reached more than 100 micrograms/ml after 44 h of culture. This is substantially higher than that reported in the literature for CT production by any strain of V. cholerae, including hypertoxigenic strain 569B.

Spira, W M; Fedorka-Cray, P J

1983-01-01

213

Protection by alpha 1-acid glycoprotein against tumor necrosis factor- induced lethality  

PubMed Central

We here report that alpha 1-acid glycoprotein, a typical acute phase protein, protects mice from lethal shock induced by tumor necrosis factor (TNF) or endotoxin. The protection is observed both in normal and in galactosamine-sensitized mice. Optimal desensitization requires at least 3 mg alpha 1-acid glycoprotein administered 2 h before the lethal challenge. Under these conditions, complete inhibition of all TNF-induced metabolic changes was observed: fall in body temperature, release of liver transaminases, enhanced clotting time, and mortality. The known platelet aggregation-inhibitory activity of alpha 1-acid glycoprotein provides a possible explanation for this protective capacity.

1994-01-01

214

Autophagy in endosomal mutants  

PubMed Central

The endosomal and autophagic pathways are essential for the degradation and renewal of cellular components. After a complex maturation process, both pathways converge to their final destination, the lysosome. A close link between these two pathways was described along the last decade, notably through the analysis of ESCRT mutants. Although in mammals ESCRT mutants are unable to complete autophagic maturation due to the lack of fusion with the endolysosomal system, the role of ESCRT in the autophagic process still remains an open issue. Using C. elegans, we recently showed that blockage of the endosomal maturation triggers the induction of autophagic activity in ESCRT mutant.1 This increase of autophagic flux is an attempt to correct cellular defects and promote the survival of mutant animals.

Michelet, Xavier; Legouis, Renaud

2012-01-01

215

Lethal and Sub-lethal Effects of UVB on Juvenile Biomphalaria glabrata (Mollusca: Pulmonata)  

PubMed Central

Although Schistosoma mansoni occurs mainly in the tropics, where intense levels of solar radiation are present, the impact of ultraviolet (UV) light on schistosome transmission is not known. The purpose of this study was to investigate potential effects of UVB (290–320 nm) on juvenile Biomphalaria glabrata, the snail intermediate host of S. mansoni. Albino and wild type snails were exposed to doses of UVB from UV-fluorescent lamps, and the following were measured: survival, photoreactivation (light-mediated DNA repair), effects on feeding behavior, and morphological tissue abnormalities. Irradiation with UVB is lethal to B. glabrata in a dose-dependent manner. Exposure to white light subsequent to UVB irradiation enhances survival, probably by photoreactivation. The shell offers some, but not complete, protection. Experiments in which UVB transmittance through the shell was blocked with black nail polish suggest that injury to both exposed (headfoot) and shell-enclosed (mantle and visceral mass) tissues contributes to mortality in lethally-irradiated snails. Wild-type (pigmented) snails are less susceptible to lethal effects of UVB than albino snails, and they may be more capable of photoreactivation. UVB exposure inhibits snail feeding behavior, and causes tentacle forks and growths on the headfoot. Thus, UVB may influence the life cycle of S. mansoni by both lethal and sub-lethal damage to the snail intermediate host. However, the ability of snails to photoreactivate may mitigate these effects.

Ruelas, Debbie S.; Karentz, Deneb; Sullivan, John T.

2007-01-01

216

Importance of repair of potentially lethal damage in assays of cytotoxic agents  

SciTech Connect

Most in vitro assays expose growing cells to cytotoxic agents for a fixed period of time. However, these assays fail to account for repair of potentially lethal damage, the enhancement in survival that occurs when cells are maintained under nongrowth conditions after treatment with cytotoxic agents. This study extends previous observations of the repair of potentially lethal damage in human melanoma cells to parallel in vitro and in vivo experiments with the F10 subline of B16 melanoma. An in vivo (in C57BL/6 mice) and in vitro (in plastic plates) radiation dose-response relationship for the F10 subline of B16 melanoma was determined (200 to 1100 rads). Time delay until explant, allowing repair of potentially lethal damage, resulted in a significant and progressive enhancement of survival, five- to sixfold, both in vivo and in vitro. Survival with 700 rads and 24-hour delay was equivalent to that after treatment with 300 rads and no delay. Repair of potentially lethal damage, demonstrated in human cells in vitro and in animal preparations in vitro and in vivo, may account for the lack of clinical efficacy of some cytotoxic agents. Our results suggest that repair of potentially lethal damage should be taken into consideration in the design of in vitro chemotherapy and radiation therapy assays.

Richie, J.P.; Weichselbaum, R.R.; Little, J.B.

1982-08-01

217

Essential plasticity and redundancy of metabolism unveiled by synthetic lethality analysis.  

PubMed

We unravel how functional plasticity and redundancy are essential mechanisms underlying the ability to survive of metabolic networks. We perform an exhaustive computational screening of synthetic lethal reaction pairs in Escherichia coli in a minimal medium and we find that synthetic lethal pairs divide in two different groups depending on whether the synthetic lethal interaction works as a backup or as a parallel use mechanism, the first corresponding to essential plasticity and the second to essential redundancy. In E. coli, the analysis of pathways entanglement through essential redundancy supports the view that synthetic lethality affects preferentially a single function or pathway. In contrast, essential plasticity, the dominant class, tends to be inter-pathway but strongly localized and unveils Cell Envelope Biosynthesis as an essential backup for Membrane Lipid Metabolism. When comparing E. coli and Mycoplasma pneumoniae, we find that the metabolic networks of the two organisms exhibit a large difference in the relative importance of plasticity and redundancy which is consistent with the conjecture that plasticity is a sophisticated mechanism that requires a complex organization. Finally, coessential reaction pairs are explored in different environmental conditions to uncover the interplay between the two mechanisms. We find that synthetic lethal interactions and their classification in plasticity and redundancy are basically insensitive to medium composition, and are highly conserved even when the environment is enriched with nonessential compounds or overconstrained to decrease maximum biomass formation. PMID:24854166

Güell, Oriol; Sagués, Francesc; Serrano, M Ángeles

2014-05-01

218

Essential Plasticity and Redundancy of Metabolism Unveiled by Synthetic Lethality Analysis  

PubMed Central

We unravel how functional plasticity and redundancy are essential mechanisms underlying the ability to survive of metabolic networks. We perform an exhaustive computational screening of synthetic lethal reaction pairs in Escherichia coli in a minimal medium and we find that synthetic lethal pairs divide in two different groups depending on whether the synthetic lethal interaction works as a backup or as a parallel use mechanism, the first corresponding to essential plasticity and the second to essential redundancy. In E. coli, the analysis of pathways entanglement through essential redundancy supports the view that synthetic lethality affects preferentially a single function or pathway. In contrast, essential plasticity, the dominant class, tends to be inter-pathway but strongly localized and unveils Cell Envelope Biosynthesis as an essential backup for Membrane Lipid Metabolism. When comparing E. coli and Mycoplasma pneumoniae, we find that the metabolic networks of the two organisms exhibit a large difference in the relative importance of plasticity and redundancy which is consistent with the conjecture that plasticity is a sophisticated mechanism that requires a complex organization. Finally, coessential reaction pairs are explored in different environmental conditions to uncover the interplay between the two mechanisms. We find that synthetic lethal interactions and their classification in plasticity and redundancy are basically insensitive to medium composition, and are highly conserved even when the environment is enriched with nonessential compounds or overconstrained to decrease maximum biomass formation.

2014-01-01

219

Genetic and molecular characterization of embryonic mutants identified following seed transformation in Arabidopsis.  

PubMed

Over 5000 transgenic families of Arabidopsis thaliana produced following seed transformation with Agrobacterium tumefaciens were screened for embryonic lethals, defectives, and pattern mutants. One hundred and seventy-eight mutants with a wide range of developmental abnormalities were identified. Forty-one mutants appear from genetic studies to be tagged (36% of the 115 mutants examined in detail). Mapping with visible markers demonstrated that mutant genes were randomly distributed throughout the genome. Seven mutant families appeared to contain chromosomal translocations because the mutant genes exhibited linkage to visible markers on two different chromosomes. Chromosomal rearrangements may therefore be widespread following seed transformation. DNA gel blot hybridizations with 34 tagged mutants and three T-DNA probes revealed a wide range of insertion patterns. Models of T-DNA structure at each mutant locus were constructed to facilitate gene isolation. The value of such models was demonstrated by using plasmid rescue to clone flanking plant DNA from four tagged mutants. Further analysis of genes isolated from these insertional mutants should help to elucidate the relationship between gene function and plant embryogenesis. PMID:8264525

Castle, L A; Errampalli, D; Atherton, T L; Franzmann, L H; Yoon, E S; Meinke, D W

1993-12-01

220

Lethal infection thresholds of Paenibacillus larvae for honeybee drone and worker larvae (Apis mellifera).  

PubMed

We compared the mortality of honeybee (Apis mellifera) drone and worker larvae from a single queen under controlled in vitro conditions following infection with Paenibacillus larvae, a bacterium causing the brood disease American Foulbrood (AFB). We also determined absolute P. larvae cell numbers and lethal titres in deceased individuals of both sexes up to 8 days post infection using quantitative real-time PCR (qPCR). Our results show that in drones the onset of infection induced mortality is delayed by 1 day, the cumulative mortality is reduced by 10% and P. larvae cell numbers are higher than in worker larvae. Since differences in bacterial cell titres between sexes can be explained by differences in body size, larval size appears to be a key parameter for a lethal threshold in AFB tolerance. Both means and variances for lethal thresholds are similar for drone and worker larvae suggesting that drone resistance phenotypes resemble those of related workers. PMID:20545737

Behrens, Dieter; Forsgren, Eva; Fries, Ingemar; Moritz, Robin F A

2010-10-01

221

Evaluation of the database on mutant frequencies and DNA sequence alterations of vermilion mutations induced in germ cells of Drosophila shows the importance of a neutral mutation detection system.  

PubMed

The vermilion gene in Drosophila has extensively been used for the molecular analysis of mutations induced by chemicals in germ cells in vivo. The gene is located on the X-chromosome and is a useful target for the study of mutagenesis since all types of mutations are generated. We have critically evaluated this system with respect to sensitivity for mutation induction and selectivity for different types of mutations, using a database of more than 600 vermilion mutants induced in postmeiotic male germ cells by 18 mutagens. From most of these mutants the mutation has been analysed. These data showed 336 base substitutions, 96 intra-locus DNA rearrangements and 78 multi-locus deletions (MLD). Mutants containing a MLD were either heterozygous sterile or homozygous and hemizygous lethal. The distribution of both basepair (bp) changes and intra-locus rearrangements over the coding region of the vermilion gene was uniform with no preferences concerning 5' or 3' regions, certain exons, splice sites, specific amino acid changes or nonsense mutations. Possible hotspots for base substitutions seem to be related to the type of DNA damage rather than to the vermilion system. Gene mutations other than bp changes were examined on sequence characteristics flanking the deletion breakpoints. Induction frequencies of vermilion mosaic mutants were, in general, higher than those of vermilion complete mutants, suggesting that persistent lesions are the main contributors to the molecular spectra. Comparison of induction frequencies of vermilion mutants and sex-linked recessive lethal (SLRL) mutants for the 18 mutagens showed that the sensitivity of the vermilion gene against a mutagenic insult is representative for genes located on the X-chromosome. The effect of nucleotide excision repair (NER) on the formation of SLRL mutants correlated with an increase of transversions in the vermilion spectra under NER deficient conditions. Furthermore, the clastogenic potency of the mutagens, i.e., the efficiency to induce chromosomal-losses vs. SLRL forward mutations, shows a positive correlation with the percentage of DNA deletions in the molecular spectra of vermilion mutants. PMID:10656485

Nivard, M J; Aguirrezabalaga, I; Ballering, L A; Pastink, A; Sierra, L M; Vogel, E W

1999-12-16

222

Erythroid-specific expression of the erythropoietin receptor rescued its null mutant mice from lethality  

Microsoft Academic Search

Erythropoietin (Epo) and its receptor (EpoR) are indispensable to erythropoi- esis. Although roles besides angiogen- esis, such as neuroprotection and heart development, have been reported for the Epo-EpoR system, the precise contribu- tion of Epo-EpoR to these nonhematopoi- etic tissues requires clarification. Exploit- ing a GATA-1 minigene cassette with hematopoietic regulatory domains, we es- tablished 2 lines of transgene-rescued EpoR-null

Norio Suzuki; Osamu Ohneda; Satoru Takahashi; Masato Higuchi; Harumi Y. Mukai; Tatsutoshi Nakahata; Shigehiko Imagawa; Masayuki Yamamoto

2002-01-01

223

Extensive brain hemorrhage and embryonic lethality in a mouse null mutant of CREB-binding protein  

Microsoft Academic Search

CREB-binding protein (CBP) is a transcriptional co-activator which is required by many transcription factors. Rubinstein–Taybi syndrome (RTS), which is an autosomal dominant syndrome characterized by abnormal pattern formation, is associated with mutations in the human CBP gene. Various abnormalities occur at high frequency in the skeletal system of heterozygous Cbp-deficient mice, but some features of RTS such as cardiac anomalies

Yasunori Tanaka; Ichiro Naruse; Takuya Hongo; Ming-Jiang Xu; Tatsutoshi Nakahata; Toshio Maekawa; Shunsuke Ishii

2000-01-01

224

Characterization of poliovirus clones containing lethal and nonlethal mutations in the genome-linked protein VPg.  

PubMed Central

Viral RNA synthesis was assayed in HeLa cells transfected with nonviable poliovirus RNA mutated in the genome-linked protein VPg-coding region. The transfecting RNA was transcribed in vitro from full-length poliovirus type 1 (Mahoney) cDNA containing a VPg mutagenesis cartridge. Hybridization experiments using ribonucleotide probes specific for the 3' end of positive- and negative-sense poliovirus RNA indicated that all mutant RNAs encoding a linking tyrosine in position 3 or 4 of VPg were replicated even though no virus was produced. VPg, but no VPg precursor, was found to be linked to the 5' end of the newly synthesized RNA. Encapsidated mutant RNAs were not found in transfected-cell lysates. After extended maintenance of transfected HeLa cells, a viable revertant of one of the nonviable RNAs was recovered; the revertant lost the lethal lesion in VPg by restoring the wild-type amino acid, but it retained all other nucleotide changes introduced during construction of the mutagenesis cartridge. Mutant RNA encoding phenylalanine or serine rather than tyrosine, the linking amino acid in VPg, was not replicated in transfected cells. A chimeric mutant containing the VPg-coding region of coxsackievirus within the poliovirus genome was viable but displayed impaired multiplication. A poliovirus-coxsackievirus chimera lacking a linking tyrosine in VPg was nonviable and replication-negative. The results indicate that a linkage-competent VPg is necessary for poliovirus RNA synthesis to occur but that a step in poliovirus replication other than initiation of RNA synthesis can be interrupted by lethal mutations in VPg. Images

Reuer, Q; Kuhn, R J; Wimmer, E

1990-01-01

225

Programmed Cell Death in the Leaves of the Arabidopsis Spontaneous Necrotic Spots (sns-D) Mutant Correlates with Increased Expression of the Eukaryotic Translation Initiation Factor eIF4B2  

PubMed Central

From a pool of transgenic Arabidopsis (Arabidopsis thaliana) plants harboring an activator T-DNA construct, one mutant was identified that developed spontaneous necrotic spots (sns-D) on the rosette leaves under aseptic conditions. The sns-D mutation is dominant and homozygous plants are embryo lethal. The mutant produced smaller rosettes with a different number of stomata than the wild-type. DNA fragmentation in the nuclei of cells in the necrotic spots and a significant increase of caspase-3 and caspase-6 like activities in sns-D leaf extracts indicated that the sns-D mutation caused programmed cell death (PCD). The integration of the activator T-DNA caused an increase of the expression level of At1g13020, which encodes the eukaryotic translation initiation factor eIF4B2. The expression level of eIF4B2 was positively correlated with the severity of sns-D mutant phenotype. Overexpression of the eIF4B2 cDNA mimicked phenotypic traits of the sns-D mutant indicating that the sns-D mutant phenotype is indeed caused by activation tagging of eIF4B2. Thus, incorrect regulation of translation initiation may result in PCD.

Gaussand, Gwenael M. D. J.-M.; Jia, Qi; van der Graaff, Eric; Lamers, Gerda E. M.; Fransz, Paul F.; Hooykaas, Paul J. J.; de Pater, Sylvia

2011-01-01

226

Lethal and non-lethal violence against women in Australia: measurement challenges, conceptual frameworks, and limitations in knowledge.  

PubMed

Understanding pathways from non-lethal violence to lethal violence between intimate partners is a notable challenge for both policy and practice in partner violence prevention. Of particular interest is whether lethal violence represents an "escalation" of violence from "low" to "high" risk over time, or is best predicted by specific behavioral "typologies" of perpetrators. Testing the "escalation" and "typology" theories is hampered in Australia by limitations in knowledge about non-lethal and lethal violence against women. This article discusses data limitations, measurement problems, and conceptual shortcomings, and suggests approaches to improving evidence quality in the field of violence prevention and risk assessment. PMID:23008430

McPhedran, Samara; Baker, Jeanine

2012-08-01

227

Mutation Induced Extinction in Finite Populations: Lethal Mutagenesis and Lethal Isolation  

PubMed Central

Reproduction is inherently risky, in part because genomic replication can introduce new mutations that are usually deleterious toward fitness. This risk is especially severe for organisms whose genomes replicate “semi-conservatively,” e.g. viruses and bacteria, where no master copy of the genome is preserved. Lethal mutagenesis refers to extinction of populations due to an unbearably high mutation rate (U), and is important both theoretically and clinically, where drugs can extinguish pathogens by increasing their mutation rate. Previous theoretical models of lethal mutagenesis assume infinite population size (N). However, in addition to high U, small N can accelerate extinction by strengthening genetic drift and relaxing selection. Here, we examine how the time until extinction depends jointly on N and U. We first analytically compute the mean time until extinction (?) in a simplistic model where all mutations are either lethal or neutral. The solution motivates the definition of two distinct regimes: a survival phase and an extinction phase, which differ dramatically in both how ? scales with N and in the coefficient of variation in time until extinction. Next, we perform stochastic population-genetics simulations on a realistic fitness landscape that both (i) features an epistatic distribution of fitness effects that agrees with experimental data on viruses and (ii) is based on the biophysics of protein folding. More specifically, we assume that mutations inflict fitness penalties proportional to the extent that they unfold proteins. We find that decreasing N can cause phase transition-like behavior from survival to extinction, which motivates the concept of “lethal isolation.” Furthermore, we find that lethal mutagenesis and lethal isolation interact synergistically, which may have clinical implications for treating infections. Broadly, we conclude that stably folded proteins are only possible in ecological settings that support sufficiently large populations.

Wylie, C. Scott; Shakhnovich, Eugene I.

2012-01-01

228

The heterozygous abp1/ABP1 insertional mutant has defects in functions requiring polar auxin transport and in regulation of early auxin-regulated genes.  

PubMed

AUXIN-BINDING PROTEIN 1 (ABP1) is not easily accessible for molecular studies because the homozygous T-DNA insertion mutant is embryo-lethal. We found that the heterozygous abp1/ABP1 insertion mutant has defects in auxin physiology-related responses: higher root slanting angles, longer hypocotyls, agravitropic roots and hypocotyls, aphototropic hypocotyls, and decreased apical dominance. Heterozygous plants flowered earlier than wild-type plants under short-day conditions. The length of the main root, the lateral root density and the hypocotyl length were little altered in the mutant in response to auxin. Compared to wild-type plants, transcription of early auxin-regulated genes (IAA2, IAA11, IAA13, IAA14, IAA19, IAA20, SAUR9, SAUR15, SAUR23, GH3.5 and ABP1) was less strongly up-regulated in the mutant by 0.1, 1 and 10 ?m IAA. Surprisingly, ABP1 was itself an early auxin-up-regulated gene. IAA uptake into the mutant seedlings during auxin treatments was indistinguishable from wild-type. Basipetal auxin transport in young roots was slower in the mutant, indicating a PIN2/EIR1 defect, while acropetal transport was indistinguishable from wild-type. In the eir1 background, three of the early auxin-regulated genes tested (IAA2, IAA13 and ABP1) were more strongly induced by 1 ?m IAA in comparison to wild-type, but eight of them were less up-regulated in comparison to wild-type. Similar but not identical disturbances in regulation of early auxin-regulated genes indicate tight functional linkage of ABP1 and auxin transport regulation. We hypothesize that ABP1 is involved in the regulation of polar auxin transport, and thus affects local auxin concentration and early auxin gene regulation. In turn, ABP1 itself is under the transcriptional control of auxin. PMID:21223392

Effendi, Yunus; Rietz, Steffen; Fischer, Urs; Scherer, Günther F E

2011-01-01

229

Deciphering the Mechanisms of Developmental Disorders (DMDD): a new programme for phenotyping embryonic lethal mice  

PubMed Central

Summary International efforts to test gene function in the mouse by the systematic knockout of each gene are creating many lines in which embryonic development is compromised. These homozygous lethal mutants represent a potential treasure trove for the biomedical community. Developmental biologists could exploit them in their studies of tissue differentiation and organogenesis; for clinical researchers they offer a powerful resource for investigating the origins of developmental diseases that affect newborns. Here, we outline a new programme of research in the UK aiming to kick-start research with embryonic lethal mouse lines. The ‘Deciphering the Mechanisms of Developmental Disorders’ (DMDD) programme has the ambitious goal of identifying all embryonic lethal knockout lines made in the UK over the next 5 years, and will use a combination of comprehensive imaging and transcriptomics to identify abnormalities in embryo structure and development. All data will be made freely available, enabling individual researchers to identify lines relevant to their research. The DMDD programme will coordinate its work with similar international efforts through the umbrella of the International Mouse Phenotyping Consortium [see accompanying Special Article (Adams et al., 2013)] and, together, these programmes will provide a novel database for embryonic development, linking gene identity with molecular profiles and morphology phenotypes.

Mohun, Timothy; Adams, David J.; Baldock, Richard; Bhattacharya, Shoumo; Copp, Andrew J.; Hemberger, Myriam; Houart, Corinne; Hurles, Matt E.; Robertson, Elizabeth; Smith, James C.; Weaver, Tom; Weninger, Wolfgang

2013-01-01

230

Dominant lethal mutagenicity study on hair dyes  

Microsoft Academic Search

A dominant lethal mutagenicity study was performed in rats with the following chemicals that may be used to dye hair: 2?nitro?p?phenylenediamine, 4?nitro?o?phenylenediamine, m?phenylenediamine, o?phenylenediamine, p?phenylenediamine, p?toluenediamine, 2,4?diaminoanisole, 2,5?diaminoanlsole, 2?amino?4?nitrophenol, 2?amino?5?nitrophenol, and 4?amino?2?nitrophenol. The compounds were administered intraperitoneally three times weekly for 8 weeks to groups of 20 sexually mature Charles River CD male rats at a dose of 20 mg\\/kg.

C. Burnett; R. Loehr; J. Corbett

1977-01-01

231

Analysis of the Albino-Locus Region of the Mouse. III. Time of Death of Prenatal Lethals  

PubMed Central

The stage at which homozygotes die was determined for 28 mutations (general symbol c*) at the albino (c) locus, of which 26 had earlier been found to be probably prenatally lethal. Within each of the mutant stocks, the uterine contents of c*/cch females, made pregnant either by c*/cch males ("Ex" series) or by cch/cch males ("Co" series), were examined between 13 and 17 days postconception. Altogether, 743 females were dissected and 7197 corpora lutea (representing ovulations) counted. In selected stocks, an additional 40 and 13 females were dissected on days seven or nine, respectively.—In each of the 26 presumed prenatally lethal mutants, there was a deficiency of living fetuses in the Ex, as compared with the Co, group. Overall, this deficiency was 23.6% (expectation, 25% c*/c*). All meaningful excesses were in numbers either of moles (death shortly before, during, or just after implantation), or of early preimplantation losses. Homozygotes in none of the mutant stocks die between days nine and 19 postconception. Of 24 c-locus mutants known to be deficiencies since they lack the closely linked Mod-2, 13 clearly kill before implantation, ten around implantation, and one neonatally. The c and Mod-2 loci and the region between them are not needed for intrauterine survival.—There are indications that the distinction between early-preimplantation death and implantation death may, in a general way, be related to length of the deficiency.

Russell, Liane B.; Raymer, G. D.

1979-01-01

232

Reduced LPS phosphorylation in Escherichia coli lowers the elevated ori/ter ratio in seqA mutants  

PubMed Central

Summary The seqA defect in E. coli increases the ori/ter ratio and causes chromosomal fragmentation, making seqA mutants dependent on recombinational repair (the seqA recA co-lethality). To understand the nature of this chromosomal fragmentation, we characterized ?seqA mutants and isolated suppressors of the ?seqA recA lethality. We demonstrate that our ?seqA alleles have normal function of the downstream pgm gene and normal ratios of the major phospholipids in the membranes, but increased surface lipopolysaccharide (LPS) phosphorylation. The predominant class of ?seqA recA suppressors disrupts the rfaQGP genes, reducing phosphorylation of the inner core region of LPS. The rfaQGP suppressors also reduce the elevated ori/ter ratio of the ?seqA mutants, but, unexpectedly, the suppressed mutants still exhibit the high levels of chromosomal fragmentation and SOS induction, characteristic of the ?seqA mutants. We also found that co-lethality of rfaP with defects in the production of acidic phospholipids is suppressed by alternative initiation of chromosomal replication, suggesting that LPS phosphorylation stimulates replication initiation. The rfaQGP suppression of the seqA recA lethality provides genetic support for the surprising physical evidence that the oriC DNA forms complexes with the outer membrane.

Rotman, Ella; Bratcher, Preston; Kuzminov, Andrei

2009-01-01

233

Synthetic lethality of Drosophila in the absence of the MUS81 endonuclease and the DmBlm helicase is associated with elevated apoptosis.  

PubMed

Mus81-Mms4 (Mus81-Eme1 in some species) is a heterodimeric DNA structure-specific endonuclease that has been implicated in meiotic recombination and processing of damaged replication forks in fungi. We generated and characterized mutations in Drosophila melanogaster mus81 and mms4. Unlike the case in fungi, we did not find any role for MUS81-MMS4 in meiotic crossing over. A possible role for this endonuclease in repairing double-strand breaks that arise during DNA replication is suggested by the finding that mus81 and mms4 mutants are hypersensitive to camptothecin; however, these mutants are not hypersensitive to other agents that generate lesions that slow or block DNA replication. In fungi, mus81, mms4, and eme1 mutations are synthetically lethal with mutations in genes encoding RecQ helicase homologs. Similarly, we found that mutations in Drosophila mus81 and mms4 are synthetically lethal with null mutations in mus309, which encodes the ortholog of the Bloom Syndrome helicase. Synthetic lethality is associated with high levels of apoptosis in proliferating tissues. Lethality and elevated apoptosis were partially suppressed by a mutation in spn-A, which encodes the ortholog of the strand invasion protein Rad51. These findings provide insights into the causes of synthetic lethality. PMID:17603121

Trowbridge, Kirsten; McKim, Kim; Brill, Steven J; Sekelsky, Jeff

2007-08-01

234

NonLethal Weapons, NonLethal Policy, and Complex Contingencies.  

National Technical Information Service (NTIS)

Advocates promote NonLethal Weapons (NLWs) use in a complex contingency as a way to enforce U.S. with an absolute minimum of violence and destruction. They believe that NLWs will offer the operational commander a rheostatic means of applying force that wi...

R. D. Sheldon

1999-01-01

235

Suicide Intent and Accurate Expectations of Lethality: Predictors of Medical Lethality of Suicide Attempts  

Microsoft Academic Search

The degree of intent to commit suicide and the severity of self-injury were examined in individuals (N = 180) who had recently attempted suicide. Although a minimal association was found between the degree of suicide intent and the degree of lethality of the attempt, the accuracy of expectations about the likelihood of dying was found to moderate the relationship between

Gregory K. Brown; Gregg R. Henriques; Daniella Sosdjan; Aaron T. Beck

2004-01-01

236

Enhancing CHK1 inhibitor lethality in glioblastoma  

PubMed Central

The present studies were initiated to determine whether inhibitors of MEK1/2 or SRC signaling, respectively, enhance CHK1 inhibitor lethality in primary human glioblastoma cells. Multiple MEK1/2 inhibitors (CI-1040 (PD184352); AZD6244 (ARRY-142886)) interacted with multiple CHK1 inhibitors (UCN-01, AZD7762) to kill multiple primary human glioma cell isolates that have a diverse set of genetic alterations typically found in the disease. Inhibition of SRC family proteins also enhanced CHK1 inhibitor lethality. Combined treatment of glioma cells with (MEK1/2 + CHK1) inhibitors enhanced radiosensitivity. Combined (MEK1/2 + CHK1) inhibitor treatment led to dephosphorylation of ERK1/2 and S6 ribosomal protein, whereas the phosphorylation of JNK and p38 was increased. MEK1/2 + CHK1 inhibitor-stimulated cell death was associated with the cleavage of pro-caspases 3 and 7 as well as the caspase substrate (PARP). We also observed activation of pro-apoptotic BCL-2 effector proteins BAK and BAX and reduced levels of pro-survival BCL-2 family protein BCL-XL. Overexpression of BCL-XL alleviated but did not completely abolish MEK1/2 + CHK1 inhibitor cytotoxicity in GBM cells. These findings argue that multiple inhibitors of the SRC-MEK pathway have the potential to interact with multiple CHK1 inhibitors to kill glioma cells.

Tang, Yong; Dai, Yun; Grant, Steven; Dent, Paul

2012-01-01

237

Lethal outcomes in Klippel-Trenaunay syndrome.  

PubMed

Klippel-Trenaunay syndrome (KTS) is an uncommon congenital angiodysplasia that manifests in infancy and is characterized by venous and lymphatic malformations of the skin, soft tissue, and bone causing limb hypertrophy. We report 2 patients with long-term KTS who developed lethal complications from uncommon and unusual manifestations. The 1st patient was a female with KTS who at 2 years of age underwent a below-the-knee amputation for a massively hypertrophied and malformed left foot. Two years later she required additional surgical removal of vascular malformations involving her left calf with extension to the groin, pubis, and ipsilateral abdomen. Fifteen years later she underwent splenectomy (400 g) revealing multifocal, cystically dilated vascular channels distorting the splenic architecture and died suddenly of massive intra-abdominal hemorrhage on the 2nd postoperative day. The 2nd patient was a 72-year-old male with long-standing KTS who presented with debilitating chronic penile and scrotal edema. Surgical excision of his lymphedematous scrotal and penile skin revealed a low-grade angiosarcoma arising in the setting of chronic lymphedema. The patient died shortly after surgery from massive hemorrhage due to traumatic rupture of malformed leg vessels. KTS may lead to significant morbidity and mortality, and pathologic consequences from long-term KTS have been rarely reported. These cases illustrate the risk of lethal hemorrhage, organomegaly from protracted vascular malformation, and development of vascular neoplasia associated with chronic lymphedema in KTS. PMID:23915076

Karunamurthy, Arivarasan; Pantanowitz, Liron; Lepe, Jorge Guzman; Reyes-Múgica, Miguel

2013-01-01

238

Role of macrophage oxidative burst in the action of anthrax lethal toxin.  

PubMed Central

BACKGROUND: Major symptoms and death from systemic Bacillus anthracis infections are mediated by the action of the pathogen's lethal toxin on host macrophages. High levels of the toxin are cytolytic to macrophages, whereas low levels stimulate these cells to produce cytokines (interleukin-1 beta and tumor necrosis factor-alpha), which induce systemic shock and death. MATERIALS AND METHODS: Experiments were performed to assess the possibility that the oxidative burst may be involved in one or both of lethal toxin's effects on macrophages. Toximediated cell lysis, superoxide anion and cytokine production were measured. Effects of antioxidants and macrophage mutations were examined. RESULTS: RAW264.7 murine macrophages treated with high levels of toxin released large amounts of superoxide anion, beginning at about 1 hr, which correlates with the onset of cytolysis. Cytolysis could be blocked with various exogenous antioxidants or with N-acetyl-L-cysteine and methionine, which promote production of the endogenous antioxidant, glutathione. Mutant murine macrophage lines deficient in production of reactive oxygen intermediates (ROIs) were relatively insensitive to the lytic effects of the toxin, whereas a line with increased oxidative burst potential showed elevated sensitivity. Also, cultured blood monocyte-derived macrophages from a patient with Chronic Granulomatous Disease, a disorder in which the phagocyte's oxidative burst is disabled, were totally resistant to toxin, in contrast to control monocytes. CONCLUSIONS: These results imply that the cytolytic effect of the toxin is mediated by ROIs. Additionally, cytokine production and consequent pathologies showed partial dependence on macrophage ROIs. Antioxidants moderately inhibited toxin-induced cytokine production in vitro, and BALB/c mice pretreated with N-acetyl-L-cysteine or mepacrine showed partial protection against lethal toxin. Thus ROIs are involved in both the cytolytic action of anthrax lethal toxin and the overall pathologic process in vivo.

Hanna, P. C.; Kruskal, B. A.; Ezekowitz, R. A.; Bloom, B. R.; Collier, R. J.

1994-01-01

239

A dominant negative mutant of PMA1 interferes with the folding of the wild type enzyme.  

PubMed

Misfolded proteins are usually arrested in the endoplasmic reticulum (ER) and degraded by the ER-associated degradation (ERAD) machinery. Several mutant alleles of PMA1, the gene coding for the plasma membrane H (+)-ATPase, render misfolded proteins that are subjected to ERAD. A subset of misfolded PMA1 mutants exhibits a dominant negative effect on yeast growth since, when co-expressed with the wild type allele, both proteins are retained in the ER and degraded. We have used a PMA1-D378T dominant lethal allele to analyse the mechanism underlying the retention of the wild type enzyme by the dominant negative mutant. A genetic screen was performed for isolation of intragenic suppressors of PMA1-D378T allele. This analysis pointed to transmembrane helix 10 (TM10) as an important element in the establishment of the dominant lethality. Deletion of the TM10 was able to suppress not only the PMA1-D378T but all the dominant lethal alleles tested. Biochemical analyses suggest that dominant lethal proteins obstruct, through TM10, the correct folding of the wild type enzyme leading to its retention and degradation by ERAD. PMID:19929866

Eraso, Pilar; Mazón, María J; Portillo, Francisco

2010-01-01

240

Non-lethal effects of predation in birds  

Microsoft Academic Search

Predators can affect individual fitness and population and community processes through lethal effects (direct consumption or 'density' effects), where prey is consumed, or through non-lethal effects (trait-mediated effects or interactions), where behavioural compensation to predation risk occurs, such as animals avoiding areas of high predation risk. Studies of invertebrates, fish and amphibians have shown that non-lethal effects may be larger

WILL CRESSWELL

2008-01-01

241

Apparent lethal concentrations of pyrolysis products of some polymeric materials  

NASA Technical Reports Server (NTRS)

Thirty-nine samples of polymeric materials were evaluated to determine the apparent lethal concentrations of their pyrolysis products. The materials were compared on the basis of the apparent lethal concentration for 50 percent of the test animals. Relative toxicity rankings based o apparent lethal concentration values can differ significantly depending on whether they are based on weight of sample charged or weight of sample pyrolyzed. The ranking of polyphenylene sulfide is particularly sensitive to this difference.

Hilado, C. J.; Marcussen, W. H.; Furst, A.; Kourtides, D. A.; Parker, J. A.

1976-01-01

242

The Deoxyhypusine Synthase Mutant dys1-1 Reveals the Association of eIF5A and Asc1 with Cell Wall Integrity  

PubMed Central

The putative eukaryotic translation initiation factor 5A (eIF5A) is a highly conserved protein among archaea and eukaryotes that has recently been implicated in the elongation step of translation. eIF5A undergoes an essential and conserved posttranslational modification at a specific lysine to generate the residue hypusine. The enzymes deoxyhypusine synthase (Dys1) and deoxyhypusine hydroxylase (Lia1) catalyze this two-step modification process. Although several Saccharomyces cerevisiae eIF5A mutants have importantly contributed to the study of eIF5A function, no conditional mutant of Dys1 has been described so far. In this study, we generated and characterized the dys1-1 mutant, which showed a strong depletion of mutated Dys1 protein, resulting in more than 2-fold decrease in hypusine levels relative to the wild type. The dys1-1 mutant demonstrated a defect in total protein synthesis, a defect in polysome profile indicative of a translation elongation defect and a reduced association of eIF5A with polysomes. The growth phenotype of dys1-1 mutant is severe, growing only in the presence of 1 M sorbitol, an osmotic stabilizer. Although this phenotype is characteristic of Pkc1 cell wall integrity mutants, the sorbitol requirement from dys1-1 is not associated with cell lysis. We observed that the dys1-1 genetically interacts with the sole yeast protein kinase C (Pkc1) and Asc1, a component of the 40S ribosomal subunit. The dys1-1 mutant was synthetically lethal in combination with asc1? and overexpression of TIF51A (eIF5A) or DYS1 is toxic for an asc1? strain. Moreover, eIF5A is more associated with translating ribosomes in the absence of Asc1 in the cell. Finally, analysis of the sensitivity to cell wall-perturbing compounds revealed a more similar behavior of the dys1-1 and asc1? mutants in comparison with the pkc1? mutant. These data suggest a correlated role for eIF5A and Asc1 in coordinating the translational control of a subset of mRNAs associated with cell integrity.

Silveira, Wagner da Silva; Valentini, Sandro Roberto; Zanelli, Cleslei Fernando

2013-01-01

243

MICROBIOLOGY: Enhanced: Fighting Anthrax with a Mutant Toxin  

NSDL National Science Digital Library

Access to the article is free, however registration and sign-in are required: There is an urgent need to develop new therapeutics against the microbe causing anthrax, which has the potential to be used in biological warfare. In their Perspective, Olsnes and Wesche discuss a new therapeutic approach designed by Sellman and colleagues. In this approach, a mutant subunit of the toxin prevents correct assembly of wild-type subunits into a pore in the host cell membrane. In this way, lethal bacterial enzymes are prevented from translocating into the host cell.

Sjur Olsnes (Institute for Cancer Research;Department of Biochemistry); Jørgen Wesche (Institute for Cancer Research;Department of Biochemistry)

2008-10-05

244

Rapid Antibiotic Resistance Evolution of GASP Mutants  

NASA Astrophysics Data System (ADS)

The GASP phenotype in bacteria is due to a mutation which enables the bacteria to grow under high stress conditions where other bacteria stop growing. We probe using our Death Galaxy microenvironment how rapidly the GASP mutant can evolve resistance to mutagenic antibiotics compared to wild-type bacteria, and explore the genomic landscape changes due to the evolution of resistance.

Zhang, Qiucen; Kim, Hyunsung; Pourmand, Nader; Austin, Robert

2012-02-01

245

Superior triacylglycerol (TAG) accumulation in starchless mutants of Scenedesmus obliquus: (I) mutant generation and characterization  

PubMed Central

Background Microalgae are a promising platform for producing neutral lipids, to be used in the application for biofuels or commodities in the feed and food industry. A very promising candidate is the oleaginous green microalga Scenedesmus obliquus, because it accumulates up to 45% w/w triacylglycerol (TAG) under nitrogen starvation. Under these conditions, starch is accumulated as well. Starch can amount up to 38% w/w under nitrogen starvation, which is a substantial part of the total carbon captured. When aiming for optimized TAG production, blocking the formation of starch could potentially increase carbon allocation towards TAG. In an attempt to increase TAG content, productivity and yield, starchless mutants of this high potential strain were generated using UV mutagenesis. Previous studies in Chlamydomonas reinhardtii have shown that blocking the starch synthesis yields higher TAG contents, although these TAG contents do not surpass those of oleaginous microalgae yet. So far no starchless mutants in oleaginous green microalgae have been isolated that result in higher TAG productivities. Results Five starchless mutants have been isolated successfully from over 3,500 mutants. The effect of the mutation on biomass and total fatty acid (TFA) and TAG productivity under nitrogen-replete and nitrogen-depleted conditions was studied. All five starchless mutants showed a decreased or completely absent starch content. In parallel, an increased TAG accumulation rate was observed for the starchless mutants and no substantial decrease in biomass productivity was perceived. The most promising mutant showed an increase in TFA productivity of 41% at 4 days after nitrogen depletion, reached a TAG content of 49.4% (% of dry weight) and had no substantial change in biomass productivity compared to the wild type. Conclusions The improved S. obliquus TAG production strains are the first starchless mutants in an oleaginous green microalga that show enhanced TAG content under photoautotrophic conditions. These results can pave the way towards a more feasible microalgae-driven TAG production platform.

2014-01-01

246

Architectural phenotypes in the transparent testa mutants of Arabidopsis thaliana  

PubMed Central

Flavonoids are low molecular weight secondary plant metabolites with a myriad of functions. As flavonoids affect auxin transport (an important growth-controlling hormone) and are biologically active in eukaryotes, flavonoid mutants were expected to have undescribed architectural phenotypes. The Arabidopsis thaliana transparent testa (tt) mutants are compromised in the enzymatic steps or transcriptional regulators affecting flavonoid synthesis. tt mutant seedlings were grown on hard-slanted agar (a stress condition), under varying light conditions, and in soil to examine the resulting growth patterns. These tt mutants revealed a wide variety of architectural phenotypes in root and aerial tissues. Mutants with increased inflorescences, siliques, and lateral root density or reduced stature are traits that could affect plant yield or performance under certain environmental conditions. The regulatory genes affected in architectural traits may provide useful molecular targets for examination in other plants.

Buer, Charles S.; Djordjevic, Michael A.

2009-01-01

247

Alleged lethal sorcery in East Timor.  

PubMed

A wide range of cultural and social perspectives exists on the concept of sudden and unexpected death. In countries, without a formal system of death investigation, sudden death is shrouded in mysticism often based on traditional belief systems. This cultural perspective on sudden death is often at variance with medical and forensic concepts and may include explanations such as sorcery, magic, and voodoo. In this case report, the postmortem findings in an alleged victim of lethal 'black magic', known as ema halo by the indigenous people of East Timor, is described. The alleged victim died suddenly in front of witnesses. At autopsy, marked dilation of a bicuspid aortic valve with annuloaortic ectasia and a sinus of Valsalva aneurysm was found after exhumation of the body. The findings mitigated the local belief in witchcraft and established a natural manner of death. PMID:14687768

Pollanen, Michael S

2004-01-01

248

Electronic combat and lethal defense suppression  

NASA Astrophysics Data System (ADS)

Air forces across the world strive to protect their valuable resources from both the air and ground threats. Over the past few years, the surface-to-air missile threat has become more sophisticated and more deadly. It is far cheaper and less technical for a country to own and operate a ground missile system than to maintain a credible air force. It is for this reason that the attention to the ground threat has grown over the past few years. This paper discusses the approach the U.S. Air Force has taken in protecting its aircraft from these ground threats and how the mission of Lethal Defense Suppression has evolved into the complimentary tasks of Reactive Suppression and Pre-emptive Destruction.

Rose, Leo. J.

1995-01-01

249

Sub-lethal glyphosate exposure alters flowering phenology and causes transient male-sterility in Brassica spp  

PubMed Central

Background Herbicide resistance in weedy plant populations can develop through different mechanisms such as gene flow of herbicide resistance transgenes from crop species into compatible weedy species or by natural evolution of herbicide resistance or tolerance following selection pressure. Results from our previous studies suggest that sub-lethal levels of the herbicide glyphosate can alter the pattern of gene flow between glyphosate resistant Canola®, Brassica napus, and glyphosate sensitive varieties of B. napus and B. rapa. The objectives of this study were to examine the phenological and developmental changes that occur in Brassica crop and weed species following sub-lethal doses of the herbicides glyphosate and glufosinate. We examined several vegetative and reproductive traits of potted plants under greenhouse conditions, treated with sub-lethal herbicide sprays. Results Our results indicate that exposure of Brassica spp. to a sub-lethal dose of glyphosate results in altering flowering phenology and reproductive function. Flowering of all sensitive species was significantly delayed and reproductive function, specifically male fertility, was suppressed. Higher dosage levels typically contributed to an increase in the magnitude of phenotypic changes. Conclusions These results demonstrate that Brassica spp. plants that are exposed to sub-lethal doses of glyphosate could be subject to very different pollination patterns and an altered pattern of gene flow that would result from changes in the overlap of flowering phenology between species. Implications include the potential for increased glyphosate resistance evolution and spread in weedy communities exposed to sub-lethal glyphosate.

2014-01-01

250

Mutant maize variety containing the glt1-1 allele  

DOEpatents

A maize plant has in its genome a non-mutable form of a mutant allele designated vitX-8132. The allele is located at a locus designated as glt which conditions kernels having an altered starch characteristic. Maize plants including such a mutant allele produce a starch that does not increase in viscosity on cooling, after heating.

Nelson, Oliver E. (Cross Plains, WI); Pan, David (Madison, WI)

1994-01-01

251

Mutant maize variety containing the glt1-1 allele  

DOEpatents

A maize plant has in its genome a non-mutable form of a mutant allele designated vitX-8132. The allele is located at a locus designated as glt which conditions kernels having an altered starch characteristic. Maize plants including such a mutant allele produce a starch that does not increase in viscosity on cooling, after heating. 2 figs.

Nelson, O.E.; Pan, D.

1994-07-19

252

Growth and development of maize that contains mutant tubulin genes  

SciTech Connect

Mutant maize plants containing a Mu transposon disrupting one of the five beta tubulin genes of interest were followed for several generations and hybridized with each other to produce plants containing disruptions in both copies of a single gene or disruption of more than one tubulin gene. Seedlings of some of these plants were grown under chilling conditions for a few weeks. After DOE funding ended, plants have been assessed to see whether mutant are more or less tolerant to chilling. Other mutant plants will be assessed for their male and female fertility relative to non-mutant siblings or other close relatives.

Susan M. Wick

2004-07-23

253

Differentiation of lethal and non lethal prostate cancer: PSA and PSA isoforms and kinetics  

PubMed Central

Prostate-specific antigen (PSA) testing for the early diagnosis of prostate cancer has led to a decrease in cancer mortality. However, the high prevalence of low-grade prostate cancer and its long natural history, competing causes of death in older men and treatment patterns of prostate cancer, have led to dramatic overtreatment of the disease. Improved markers of prostate cancer lethality are needed to reduce the overtreatment of prostate cancer that leads to a reduced quality of life without extending life for a high proportion of men. The PSA level prior to treatment is routinely used in multivariable models to predict prostate cancer aggressiveness. PSA isoforms and PSA kinetics have been associated with more aggressive phenotypes, but are not routinely employed as part of prediction tools prior to treatment. PSA kinetics is a valuable marker of lethality post treatment and routinely used in determining the need for salvage therapy.

Ballentine Carter, H

2012-01-01

254

Isolation of protein glycosylation mutants in the fission yeast Schizosaccharomyces pombe.  

PubMed Central

We have isolated mutants in the fission yeast Schizosaccharomyces pombe that are defective in protein glycosylation. A collection of osmotically sensitive mutants was prepared and screened for glycosylation defects using lectin staining as an assay. Mutants singly defective in four glycoprotein synthesis genes (gps1-4) were isolated, all of which bind less galactose-specific lectin. Acid phosphatase and other glycoproteins from the gps mutants have increased electrophoretic mobility, suggesting that these mutants make glycans of reduced size. N-linked glycan analysis revealed that terminal oligosaccharide modification is defective in the gps1 and gps2 mutants. Both mutants synthesize the Man9GlcNAc2 core glycan but have reduced amounts of larger structures. Modified core glycans from gps1 cells have normal amounts of galactose (Gal) residues, but reduced amounts of Man, consistent with a defect in a Golgi mannosyltransferase in this mutant. In contrast, N-linked oligosaccharides from gps2 mutants have much less Gal than wild type, because of reduced levels of the Gal donor, UDP-Gal. This reduction is caused by decreased activity of UDP-glucose 4-epimerase, which synthesizes UDP-Gal. Neither the gps1 or gps2 mutations are lethal, although the cells grow at reduced rates. These findings suggest that S. pombe cells can survive with incompletely glycosylated cell wall glycoproteins. In particular, these results suggest that Gal, which comprises approximately 30% by weight of cell wall glycoprotein glycans, is not crucial for cell growth or survival. Images

Huang, K M; Snider, M D

1995-01-01

255

Replacement of Lipopolysaccharide with Free Lipid A Molecules in Escherichia coli Mutants Lacking All Core Sugars  

PubMed Central

Escherichia coli mutants deficient in 2-keto-3-deoxy-d-manno-octulosonic acid (Kdo) biosynthesis are conditionally lethal, but their phenotypes are bypassed by certain suppressor mutations or by over-expression of MsbA, the inner membrane flippase for core-lipid A. These strains grow on broth with the tetra-acylated precursor lipid IVA replacing lipopolysaccharide (Meredith, T. C. et al. ACS Chem. Biol. 1, 33–42, 2006). Deletion of kdtA, which encodes the Kdo transferase, is possible under these conditions. We now show that lipid IVA reaches the outer surface of the outer membrane in these strains, as judged by its accessibility to the lipase PagL. On the assumption that MsbA is optimized to transport penta- or hexa-acylated lipid A, we over-expressed the lauroyl or the myristoyl transferase of lipid A biosynthesis, encoded by lpxL and lpxM respectively, and demonstrated that kdtA deletion mutants were also viable in this setting. Although E. coli LpxL is stimulated by the presence of the Kdo-disaccharide in its acceptor substrate, LpxL does slowly acylate lipid IVA. Over-expression of LpxL from a plasmid suppressed the lethality of kdtA deletions on nutrient broth at 30 or 37 °C without the need for MsbA over-production. These strains accumulated penta- and hexa-acylated free lipid A containing a secondary laurate chain, or a laurate and a myristate chain, respectively. Deletion of kdtA in strains over-expressing LpxM accumulated penta-acylated lipid A with a secondary myristate moiety. None of the strains lacking kdtA grew in the presence of bile salts at any temperature or on nutrient broth at 42 °C. Our findings show that the main function of Kdo is to provide the right substrates for the acyltransferases LpxL and LpxM, resulting in the synthesis of penta- and hexa-acylated lipid A, which is optimal for the MsbA flippase.

Reynolds, C. Michael; Raetz, Christian R. H.

2009-01-01

256

Pseudomonas aeruginosa potentiates the lethal effect of intestinal ischemia-reperfusion injury: The role of in vivo virulence activation  

PubMed Central

Introduction Experimental models of intestinal ischemia reperfusion (IR) injury are invariably performed in mice harboring their normal commensal flora, even though multiple intestinal IR events occur in humans during prolonged intensive care confinement when they are colonized by a highly pathogenic hospital flora. The aims of this study were to determine if the presence of the human pathogen P. aeruginosa in the distal intestine potentiates the lethality of mice exposed to intestinal IR and to determine what role if any in vivo virulence activation plays in the observed mortality. Methods 7-9 week old C57/BL6 mice were exposed to 15 minutes of superior mesenteric artery occlusion (SMAO) followed by direct intestinal inoculation of 1.0 × 106 CFU of P. aeruginosa PAO1 into the ileum and observed for mortality. Reiterative studies were performed in separate groups of mice to evaluate both the migration/dissemination pattern and in vivo virulence activation of intestinally inoculated strains using live photon camera imaging of both a constitutive bioluminescent P. aeruginosa PAO1 derivative XEN41 and an inducible reporter derivative of PAO1, the PAO1/lecA?luxCDABE that conditionally expresses the quorum sensing dependent epithelial disrupting virulence protein PA-IL. Results Mice exposed to 15 minutes of SMAO and reperfusion with intestinal inoculation of P. aeruginosa had a significantly increased mortality rate (p<0.001) of 100% compared to <10% for sham operated mice intestinally inoculated with P. aeruginosa without SMAO and intestinal IR alone (<50%). Migration/dissemination patterns of P. aeruginosa in mice subjected to intestinal IR demonstrated proximal migration of distally injected strains and translocation to mesenteric lymph nodes, liver, spleen, lung, and kidney. A key role for in vivo virulence expression of the barrier disrupting adhesin PA-IL during intestinal IR was established since its expression was enhanced during IR and mutant strains lacking PA-IL displayed attenuated mortality. Conclusions The presence of intestinal P. aeruginosa potentiates the lethal effect of intestinal IR in mice in part due to in vivo virulence activation of its epithelial barrier disrupting protein PA-IL.

Fink, David; Romanowski, Kathleen; Valuckaite, Vesta; Babrowski, Trissa; Kim, Moses; Matthews, Jeffrey B.; Liu, Donald; Zaborina, Olga; Alverdy, John C.

2011-01-01

257

Syn-Lethality: An Integrative Knowledge Base of Synthetic Lethality towards Discovery of Selective Anticancer Therapies  

PubMed Central

Synthetic lethality (SL) is a novel strategy for anticancer therapies, whereby mutations of two genes will kill a cell but mutation of a single gene will not. Therefore, a cancer-specific mutation combined with a drug-induced mutation, if they have SL interactions, will selectively kill cancer cells. While numerous SL interactions have been identified in yeast, only a few have been known in human. There is a pressing need to systematically discover and understand SL interactions specific to human cancer. In this paper, we present Syn-Lethality, the first integrative knowledge base of SL that is dedicated to human cancer. It integrates experimentally discovered and verified human SL gene pairs into a network, associated with annotations of gene function, pathway, and molecular mechanisms. It also includes yeast SL genes from high-throughput screenings which are mapped to orthologous human genes. Such an integrative knowledge base, organized as a relational database with user interface for searching and network visualization, will greatly expedite the discovery of novel anticancer drug targets based on synthetic lethality interactions. The database can be downloaded as a stand-alone Java application.

Li, Xue-juan; Mishra, Shital K.; Wu, Min; Zhang, Fan

2014-01-01

258

High-lethality status in patients with borderline personality disorder.  

PubMed

Recurrent suicidal behaviors in patients with Borderline Personality Disorder (BPD) are often considered communicative gestures; however, 10% complete suicide. This study seeks to identify risk factors for suicide within a BPD sample by comparing patients with High- and Low-Lethality attempts. BPD attempters (n = 113) were assessed on demographic, diagnostic, and personality variables: clinical symptoms, suicidal behaviors; childhood, family, and treatment histories; social adjustment; and recent life events. Forty-four High-Lethality attempters, defined by a score of 4 or more on Beck's Medical Lethality Scale, were compared to 69 Low-Lethality attempters. Discriminating variables were entered in a multivariate logistic regression model to define predictors of High-Lethality status. High-Lethality attempters were older, with children, less education, and lower socioeconomic class (SES) than Low-Lethality attempters. They were more likely to have Major Depressive Disorder (MDD), co-morbid Antisocial Personality Disorder (ASPD), and family histories of substance abuse. They reported greater intent to die, more lifetime attempts, hospitalizations, and time in the hospital. High-Lethality status was best predicted by low SES, co-morbid ASPD, extensive treatment histories, and greater intent to die. These characteristics resemble profiles of patients who complete suicide, are not specific for BPD, and do not include impulsivity, aggression, or severity of BPD criteria. PMID:16178681

Soloff, Paul H; Fabio, Anthony; Kelly, Thomas M; Malone, Kevin M; Mann, J John

2005-08-01

259

Mapping Genetically Compensatory Pathways from Synthetic Lethal Interactions in Yeast  

PubMed Central

Background Synthetic lethal genetic interaction analysis has been successfully applied to predicting the functions of genes and their pathway identities. In the context of synthetic lethal interaction data alone, the global similarity of synthetic lethal interaction patterns between two genes is used to predict gene function. With physical interaction data, such as protein-protein interactions, the enrichment of physical interactions within subsets of genes and the enrichment of synthetic lethal interactions between those subsets of genes are used as an indication of compensatory pathways. Result In this paper, we propose a method of mapping genetically compensatory pathways from synthetic lethal interactions. Our method is designed to discover pairs of gene-sets in which synthetic lethal interactions are depleted among the genes in an individual set and where such gene-set pairs are connected by many synthetic lethal interactions. By its nature, our method could select compensatory pathway pairs that buffer the deleterious effect of the failure of either one, without the need of physical interaction data. By focusing on compensatory pathway pairs where genes in each individual pathway have a highly homogenous cellular function, we show that many cellular functions have genetically compensatory properties. Conclusion We conclude that synthetic lethal interaction data are a powerful source to map genetically compensatory pathways, especially in systems lacking physical interaction information, and that the cellular function network contains abundant compensatory properties.

Ma, Xiaotu; Tarone, Aaron M.; Li, Wenyuan

2008-01-01

260

Antagonistic effects against single lethal doses of Amanita phalloides  

Microsoft Academic Search

Agents with antagonistic effects against phalloidin or a-amanitin were tested in mice against lethal doses of an extract from the whole mushroom amanita phalloides. The following categories of agents reduced lethality after the extract. First, agents protecting only against phalloidin such as rifampicin, phenylbutazone and antamanide. Second, silymarin and prednisolone which display both antiamatoxic and marked (silymarin) or moderate (prednisolone)

G. L. Floersheim

1976-01-01

261

The Influence of Geographic Mobility on Nearly Lethal Suicide Attempts.  

ERIC Educational Resources Information Center

Presents a population-based, case-control study of nearly lethal suicide attempts with 153 cases and 513 controls. Results indicate that moving in the past year is positively associated with a nearly lethal suicide attempt, as are specific characteristics of the move. Findings confirm and extend prior research by demonstrating a relationship…

Potter, Lloyd B.; Kresnow, Marcie-jo; Powell, Kenneth E.; Simon, Thomas R.; Mercy, James A.; Lee, Roberta K.; Frankowski, Ralph F.; Swann, Alan C.; Bayer, Timothy; O'Carroll, Patrick W.

2002-01-01

262

Connexin Mutants and Cataracts  

PubMed Central

The lens is a multicellular, but avascular tissue that must stay transparent to allow normal transmission of light and focusing of it on the retina. Damage to lens cells and/or proteins can cause cataracts, opacities that disrupt these processes. The normal survival of the lens is facilitated by an extensive network of gap junctions formed predominantly of connexin46 and connexin50. Mutations of the genes that encode these connexins (GJA3 and GJA8) have been identified and linked to inheritance of cataracts in human families and mouse lines. In vitro expression studies of several of these mutants have shown that they exhibit abnormalities that may lead to disease. Many of the mutants reduce or modify intercellular communication due to channel alterations (including loss of function or altered gating) or due to impaired cellular trafficking which reduces the number of gap junction channels within the plasma membrane. However, the abnormalities detected in studies of other mutants suggest that they cause cataracts through other mechanisms including gain of hemichannel function (leading to cell injury and death) and formation of cytoplasmic accumulations (that may act as light scattering particles). These observations and the anticipated results of ongoing studies should elucidate the mechanisms of cataract development due to mutations of lens connexins and abnormalities of other lens proteins. They may also contribute to our understanding of the mechanisms of disease due to connexin mutations in other tissues.

Beyer, Eric C.; Ebihara, Lisa; Berthoud, Viviana M.

2013-01-01

263

A genetic screen for zygotic embryonic lethal mutations affecting cuticular morphology in the wasp Nasonia vitripennis.  

PubMed Central

We have screened for zygotic embryonic lethal mutations affecting cuticular morphology in Nasonia vitripennis (Hymenoptera; Chalcidoidea). Our broad goal was to investigate the use of Nasonia for genetically surveying conservation and change in regulatory gene systems, as a means to understand the diversity of developmental strategies that have arisen during the course of evolution. Specifically, we aim to compare anteroposterior patterning gene functions in two long germ band insects, Nasonia and Drosophila. In Nasonia, unfertilized eggs develop as haploid males while fertilized eggs develop as diploid females, so the entire genome can be screened for recessive zygotic mutations by examining the progeny of F1 females. We describe 74 of >100 lines with embryonic cuticular mutant phenotypes, including representatives of coordinate, gap, pair-rule, segment polarity, homeotic, and Polycomb group functions, as well as mutants with novel phenotypes not directly comparable to those of known Drosophila genes. We conclude that Nasonia is a tractable experimental organism for comparative developmental genetic study. The mutants isolated here have begun to outline the extent of conservation and change in the genetic programs controlling embryonic patterning in Nasonia and Drosophila.

Pultz, M A; Zimmerman, K K; Alto, N M; Kaeberlein, M; Lange, S K; Pitt, J N; Reeves, N L; Zehrung, D L

2000-01-01

264

A mutation in the nuclear-encoded plastid ribosomal protein S9 leads to early embryo lethality in maize.  

PubMed

Seeds of the lethal embryo 1 (lem1) mutant in maize (Zea mays) display a non-concordant lethal phenotype: whereas the embryo aborts very early, before the transition stage, the endosperm develops almost normally. The mutant was identified in a collection of maize lines that carried the transposon Activation (Ac) at different locations in the genome. Co-segregation and reversion analysis showed that lem1 was tagged by Ac. The lem1 gene encodes a protein that is highly similar to the rice plastid 30S ribosomal protein S9 (PRPS9). lem1 maps to chromosome 1L and appears to be the only copy of prps9 in the maize genome. Green fluorescent protein (GFP) fusion constructs containing only the putative transit peptide (TP) of LEM1 localize exclusively to the plastids, confirming that the LEM1 protein is a PRP. In contrast, GFP fusion constructs containing the entire LEM1 protein co-localize to the plastids and to the nucleus, suggesting a possible dual function for this protein. Two alternative, although not mutually exclusive, explanations are considered for the lem phenotype of the lem1 mutant: (i) functional plastids are required for normal embryo development; and (ii) the PRPS9 has an extra-ribosomal function required for embryogenesis. PMID:14675435

Ma, Zhengrong; Dooner, Hugo K

2004-01-01

265

Transient hematopoietic stem cell rescue using umbilical cord blood for a lethally irradiated nuclear accident victim  

Microsoft Academic Search

We performed stem cell rescue and allogeneic skin transplantation on a lethally neutron-irradiated nuclear accident victim. HLA-DRB1 mismatched unrelated umbilical cord blood cells (2.08 × 107\\/kg recipient body weight) were transplanted to an 8–10 Gy equivalent neutron-irradiated patient because of a lack of a suitable bone marrow or peripheral blood donor. Pre-transplant conditioning consisted of anti-thymocyte ?-globulin alone, and GVHD

H Nagayama; K Misawa; H Tanaka; J Ooi; T Iseki; A Tojo; K Tani; Y Yamada; H Kodo; TA Takahashi; N Yamashita; S Shimazaki; S Asano

2002-01-01

266

Temperature-Sensitive Osmotically Fragile Mutants of Staphylococcus aureus  

PubMed Central

Temperature-sensitive fragile mutants of Staphylococcus aureus which grow at the restrictive temperature only in the presence of osmotic stabilizers and appear to have conditionally defective cell wall integrity were isolated and partially characterized.

Good, C. M.; Pattee, P. A.

1970-01-01

267

The Aspartate-Semialdehyde Dehydrogenase of Edwardsiella ictaluri and Its Use as Balanced-Lethal System in Fish Vaccinology  

PubMed Central

asdA mutants of Gram-negative bacteria have an obligate requirement for diaminopimelic acid (DAP), which is an essential constituent of the peptidoglycan layer of the cell wall of these organisms. In environments deprived of DAP, i.e., animal tissues, they will undergo lysis. Deletion of the asdA gene has previously been exploited to develop antibiotic-sensitive strains of live attenuated recombinant bacterial vaccines. Introduction of an Asd+ plasmid into a ?asdA mutant makes the bacterial strain plasmid-dependent. This dependence on the Asd+ plasmid vector creates a balanced-lethal complementation between the bacterial strain and the recombinant plasmid. E. ictaluri is an enteric Gram-negative fish pathogen that causes enteric septicemia in catfish. Because E. ictaluri is a nasal/oral invasive intracellular pathogen, this bacterium is a candidate to develop a bath/oral live recombinant attenuated Edwardsiella vaccine (RAEV) for the catfish aquaculture industry. As a first step to develop an antibiotic-sensitive RAEV strain, we characterized and deleted the E. ictaluri asdA gene. E. ictaluri ?asdA01 mutants exhibit an absolute requirement for DAP to grow. The asdA gene of E. ictaluri was complemented by the asdA gene from Salmonella. Several Asd+ expression vectors with different origins of replication were transformed into E. ictaluri ?asdA01. Asd+ vectors were compatible with the pEI1 and pEI2 E. ictaluri native plasmids. The balanced-lethal system was satisfactorily evaluated in vivo. Recombinant GFP, PspA, and LcrV proteins were synthesized by E. ictaluri ?asdA01 harboring Asd+ plasmids. Here we constructed a balanced-lethal system, which is the first step to develop an antibiotic-sensitive RAEV for the aquaculture industry.

Santander, Javier; Xin, Wei; Yang, Zhao; Curtiss, Roy

2010-01-01

268

Human cooperation by lethal group competition.  

PubMed

Why humans are prone to cooperate puzzles biologists, psychologists and economists alike. Between-group conflict has been hypothesized to drive within-group cooperation. However, such conflicts did not have lasting effects in laboratory experiments, because they were about luxury goods, not needed for survival ("looting"). Here, we find within-group cooperation to last when between-group conflict is implemented as "all-out war" (eliminating the weakest groups). Human subjects invested in helping group members to avoid having the lowest collective pay-off, whereas they failed to cooperate in control treatments with random group elimination or with no subdivision in groups. When the game was repeated, experience was found to promote helping. Thus, not within-group interactions alone, not random group elimination, but pay-off-dependent group elimination was found to drive within-group cooperation in our experiment. We suggest that some forms of human cooperation are maintained by multi-level selection: reciprocity within groups and lethal competition among groups acting together. PMID:23459158

Egas, Martijn; Kats, Ralph; van der Sar, Xander; Reuben, Ernesto; Sabelis, Maurice W

2013-01-01

269

Human cooperation by lethal group competition  

PubMed Central

Why humans are prone to cooperate puzzles biologists, psychologists and economists alike. Between-group conflict has been hypothesized to drive within-group cooperation. However, such conflicts did not have lasting effects in laboratory experiments, because they were about luxury goods, not needed for survival (“looting”). Here, we find within-group cooperation to last when between-group conflict is implemented as “all-out war” (eliminating the weakest groups). Human subjects invested in helping group members to avoid having the lowest collective pay-off, whereas they failed to cooperate in control treatments with random group elimination or with no subdivision in groups. When the game was repeated, experience was found to promote helping. Thus, not within-group interactions alone, not random group elimination, but pay-off-dependent group elimination was found to drive within-group cooperation in our experiment. We suggest that some forms of human cooperation are maintained by multi-level selection: reciprocity within groups and lethal competition among groups acting together.

Egas, Martijn; Kats, Ralph; van der Sar, Xander; Reuben, Ernesto; Sabelis, Maurice W.

2013-01-01

270

Lethal methemoglobinemia and automobile exhaust inhalation.  

PubMed

Inhalation of automobile exhaust gas often leads to death by CO intoxication. In some cases the measured carbon monoxide hemoglobin saturation level (COHb) is considerably below what is considered to be lethal. The death in such cases has been attributed to a combination of a high CO2 and a low O2 tension. In a recent case the deceased was found dead in a car equipped with a catalytic converter, with a hose leading exhaust from the engine to the interior of the car. Analysis revealed a moderately elevated COHb and a high methemoglobin saturation level (MetHb) in peripheral blood. No ethanol, narcotics or drugs were detected. Reports mentioning MetHb or methemoglobinemia in post-mortem cases are surprisingly scarce, and very few have related exhaust gas deaths to methemoglobinemia. High-degree methemoglobinemia causes serious tissue hypoxia leading to unconsciousness, arrhythmia and death. The existing literature in this field and the knowledge that exhaust fumes contain nitrogen oxide gases (NOx) that by inhalation and absorption can result in severe methemoglobinemia, led us to postulate that this death could possibly be attributed to a combination of methemoglobinemia and a moderately high COHb concentration. PMID:19261402

Vevelstad, Merete; Morild, Inge

2009-05-30

271

28 CFR 552.25 - Use of less-than-lethal weapons, including chemical agents.  

Code of Federal Regulations, 2013 CFR

... false Use of less-than-lethal weapons, including chemical agents. 552...552.25 Use of less-than-lethal weapons, including chemical agents. (a...authorize the use of less-than-lethal weapons, including those containing...

2013-07-01

272

Mutagen sensitivities and mutator effects of MMS-sensitive mutants in Neurospora.  

PubMed

7 mus (mutagen-sensitive) mutants of Neurospora crassa, which are more sensitive to the toxic effects of MMS (methyl methanesulfonate) than wild-type, were investigated for cross-sensitivities to other mutagens and inhibitors. These mutants have recently been mapped in 5 new genes, mus-7 to mus-11, and mutant alleles from each gene were checked for their effects on mutation frequencies. It was found that mutants in 3 of these 5 genes showed radiation-induced mutation frequencies similar to wild-type. These included 2 alleles of the gene mus-10, which were cross-sensitive only to UV and were the only mutants that produced some viable ascospores in homozygous crosses. The mutant of the second gene, mus-8, was especially sensitive to UV and mitomycin C and produced slightly reduced frequencies of spontaneous mutation. In contrast, the mutant of the third gene, mus-7, was not UV-sensitive but showed some cross-sensitivity to X-rays; mus-7 was highly sensitive to MMS and also to histidine, which inhibits various repair-defective mutants at concentrations well below those that reduce wild-type growth. None of these mus resemble mutants previously found in Neurospora, nor do they conform clearly to mutant types identified in E. coli or yeast. On the other hand mutants in 2 further genes, mus-11, and especially 2 alleles of mus-9, are very similar to uvs-3 of Neurospora and generally resemble mutants that are considered to be defective in "error-prone" repair. They were UV- as well as X-ray-sensitive, and showed strong spontaneous mutator effects but almost no increase in recessive lethal frequencies in heterokaryons after UV-treatments. PMID:6451802

Käfer, E

1981-01-01

273

Systematic Triple Mutant Analysis Uncovers Functional Connectivity Between Pathways Involved in Chromosome Regulation  

PubMed Central

Genetic interactions reveal the functional relationships between pairs of genes. In this study, we describe a method for the systematic generation and quantitation of triple mutants, termed Triple Mutant Analysis (TMA). We have used this approach to interrogate partially redundant pairs of genes in S. cerevisiae, including ASF1 and CAC1, two histone chaperones. After subjecting asf1? cac1? to TMA, we found that the Swi/Snf Rdh54 protein, compensates for the absence of Asf1 and Cac1. Rdh54 more strongly associates with the chromatin apparatus and the pericentromeric region in the double mutant. Moreover, Asf1 is responsible for the synthetic lethality observed in cac1? strains lacking the HIRA-like proteins. A similar TMA was carried out after deleting both CLB5 and CLB6, cyclins that regulate DNA replication, revealing a strong functional connection to chromosome segregation. This approach can reveal functional redundancies that cannot be uncovered using traditional double mutant analyses.

Haber, James E.; Braberg, Hannes; Wu, Qiuqin; Alexander, Richard; Haase, Julian; Ryan, Colm; Lipkin-Moore, Zach; Franks-Skiba, Kathleen E.; Johnson, Tasha; Shales, Michael; Lenstra, Tineke L.; Holstege, Frank C. P.; Johnson, Jeffrey R.; Bloom, Kerry; Krogan, Nevan J.

2013-01-01

274

Key tissue targets responsible for anthrax-toxin-induced lethality.  

PubMed

Bacillus anthracis, the causative agent of anthrax disease, is lethal owing to the actions of two exotoxins: anthrax lethal toxin (LT) and oedema toxin (ET). The key tissue targets responsible for the lethal effects of these toxins are unknown. Here we generated cell-type-specific anthrax toxin receptor capillary morphogenesis protein-2 (CMG2)-null mice and cell-type-specific CMG2-expressing mice and challenged them with the toxins. Our results show that lethality induced by LT and ET occurs through damage to distinct cell types; whereas targeting cardiomyocytes and vascular smooth muscle cells is required for LT-induced mortality, ET-induced lethality occurs mainly through its action in hepatocytes. Notably, and in contradiction to what has been previously postulated, targeting of endothelial cells by either toxin does not seem to contribute significantly to lethality. Our findings demonstrate that B. anthracis has evolved to use LT and ET to induce host lethality by coordinately damaging two distinct vital systems. PMID:23995686

Liu, Shihui; Zhang, Yi; Moayeri, Mahtab; Liu, Jie; Crown, Devorah; Fattah, Rasem J; Wein, Alexander N; Yu, Zu-Xi; Finkel, Toren; Leppla, Stephen H

2013-09-01

275

Expression of either Lethal Toxin or Edema Toxin by Bacillus anthracis Is Sufficient for Virulence in a Rabbit Model of Inhalational Anthrax  

PubMed Central

The development of therapeutics against biothreats requires that we understand the pathogenesis of the disease in relevant animal models. The rabbit model of inhalational anthrax is an important tool in the assessment of potential therapeutics against Bacillus anthracis. We investigated the roles of B. anthracis capsule and toxins in the pathogenesis of inhalational anthrax in rabbits by comparing infection with the Ames strain versus isogenic mutants with deletions of the genes for the capsule operon (capBCADE), lethal factor (lef), edema factor (cya), or protective antigen (pagA). The absence of capsule or protective antigen (PA) resulted in complete avirulence, while the presence of either edema toxin or lethal toxin plus capsule resulted in lethality. The absence of toxin did not influence the ability of B. anthracis to traffic to draining lymph nodes, but systemic dissemination required the presence of at least one of the toxins. Histopathology studies demonstrated minimal differences among lethal wild-type and single toxin mutant strains. When rabbits were coinfected with the Ames strain and the PA? mutant strain, the toxin produced by the Ames strain was not able to promote dissemination of the PA? mutant, suggesting that toxigenic action occurs in close proximity to secreting bacteria. Taken together, these findings suggest that a major role for toxins in the pathogenesis of anthrax is to enable the organism to overcome innate host effector mechanisms locally and that much of the damage during the later stages of infection is due to the interactions of the host with the massive bacterial burden.

Drysdale, Melissa; Koehler, Theresa M.; Hutt, Julie A.; Lyons, C. Rick

2012-01-01

276

Synthetic lethal interactions for the development of cancer therapeutics: biological and methodological advancements  

Microsoft Academic Search

Synthetic lethal interaction is defined as a combination of two mutations that is lethal when present in the same cell; each\\u000a individual mutation is non-lethal. Synthetic lethal interactions attract attention in cancer research fields since the discovery\\u000a of synthetic lethal genes with either oncogenes or tumor suppressor genes (TSGs) provides novel cancer therapeutic targets.\\u000a Due to the selective lethal effect

Shinji Mizuarai; Hidehito Kotani

2010-01-01

277

Dissecting the pathways that destabilize mutant p53  

PubMed Central

One fundamental feature of mutant forms of p53 consists in their accumulation at high levels in tumors. At least in the case of neomorphic p53 mutations, which acquire oncogenic activity, stabilization is a driving force for tumor progression. It is well documented that p53 mutants are resistant to proteasome-dependent degradation compared with wild-type p53, but the exact identity of the pathways that affect mutant p53 stability is still debated. We have recently shown that macroautophagy (autophagy) provides a route for p53 mutant degradation during restriction of glucose. Here we further show that in basal conditions of growth, inhibition of autophagy with chemical inhibitors or by downregulation of the essential autophagic genes ATG1/Ulk1, Beclin-1 or ATG5, results in p53 mutant stabilization. Conversely, overexpression of Beclin-1 or ATG1/Ulk1 leads to p53 mutant depletion. Furthermore, we found that in many cell lines, prolonged inhibition of the proteasome does not stabilize mutant p53 but leads to its autophagic-mediated degradation. Therefore, we conclude that autophagy is a key mechanism for regulating the stability of several p53 mutants. We discuss plausible mechanisms involved in this newly identified degradation pathway as well as the possible role played by autophagy during tumor evolution driven by mutant p53.

Choudhury, Sujata; Kolukula, Vamsi K.; Preet, Anju; Albanese, Chris; Avantaggiati, Maria Laura

2013-01-01

278

Neonatal lethality of LGR5 null mice is associated with ankyloglossia and gastrointestinal distension.  

PubMed

The physiological role of an orphan G protein-coupled receptor, LGR5, was investigated by targeted deletion of this seven-transmembrane protein containing a large N-terminal extracellular domain with leucine-rich repeats. LGR5 null mice exhibited 100% neonatal lethality characterized by gastrointestinal tract dilation with air and an absence of milk in the stomach. Gross and histological examination revealed fusion of the tongue to the floor of oral cavity in the mutant newborns and immunostaining of LGR5 expression in the epithelium of the tongue and in the mandible of the wild-type embryos. The observed ankyloglossia phenotype provides a model for understanding the genetic basis of this craniofacial defect in humans and an opportunity to elucidate the physiological role of the LGR5 signaling system during embryonic development. PMID:15509778

Morita, Hiroki; Mazerbourg, Sabine; Bouley, Donna M; Luo, Ching-Wei; Kawamura, Kazuhiro; Kuwabara, Yoshimitsu; Baribault, Helene; Tian, Hui; Hsueh, Aaron J W

2004-11-01

279

Bloomsbury report on mouse embryo phenotyping: recommendations from the IMPC workshop on embryonic lethal screening  

PubMed Central

Identifying genes that are important for embryo development is a crucial first step towards understanding their many functions in driving the ordered growth, differentiation and organogenesis of embryos. It can also shed light on the origins of developmental disease and congenital abnormalities. Current international efforts to examine gene function in the mouse provide a unique opportunity to pinpoint genes that are involved in embryogenesis, owing to the emergence of embryonic lethal knockout mutants. Through internationally coordinated efforts, the International Knockout Mouse Consortium (IKMC) has generated a public resource of mouse knockout strains and, in April 2012, the International Mouse Phenotyping Consortium (IMPC), supported by the EU InfraCoMP programme, convened a workshop to discuss developing a phenotyping pipeline for the investigation of embryonic lethal knockout lines. This workshop brought together over 100 scientists, from 13 countries, who are working in the academic and commercial research sectors, including experts and opinion leaders in the fields of embryology, animal imaging, data capture, quality control and annotation, high-throughput mouse production, phenotyping, and reporter gene analysis. This article summarises the outcome of the workshop, including (1) the vital scientific importance of phenotyping embryonic lethal mouse strains for basic and translational research; (2) a common framework to harmonise international efforts within this context; (3) the types of phenotyping that are likely to be most appropriate for systematic use, with a focus on 3D embryo imaging; (4) the importance of centralising data in a standardised form to facilitate data mining; and (5) the development of online tools to allow open access to and dissemination of the phenotyping data.

Adams, David; Baldock, Richard; Bhattacharya, Shoumo; Copp, Andrew J.; Dickinson, Mary; Greene, Nicholas D. E.; Henkelman, Mark; Justice, Monica; Mohun, Timothy; Murray, Stephen A.; Pauws, Erwin; Raess, Michael; Rossant, Janet; Weaver, Tom; West, David

2013-01-01

280

A strong loss-of-function mutation in RAN1 results in constitutive activation of the ethylene response pathway as well as a rosette-lethal phenotype  

NASA Technical Reports Server (NTRS)

A recessive mutation was identified that constitutively activated the ethylene response pathway in Arabidopsis and resulted in a rosette-lethal phenotype. Positional cloning of the gene corresponding to this mutation revealed that it was allelic to responsive to antagonist1 (ran1), a mutation that causes seedlings to respond in a positive manner to what is normally a competitive inhibitor of ethylene binding. In contrast to the previously identified ran1-1 and ran1-2 alleles that are morphologically indistinguishable from wild-type plants, this ran1-3 allele results in a rosette-lethal phenotype. The predicted protein encoded by the RAN1 gene is similar to the Wilson and Menkes disease proteins and yeast Ccc2 protein, which are integral membrane cation-transporting P-type ATPases involved in copper trafficking. Genetic epistasis analysis indicated that RAN1 acts upstream of mutations in the ethylene receptor gene family. However, the rosette-lethal phenotype of ran1-3 was not suppressed by ethylene-insensitive mutants, suggesting that this mutation also affects a non-ethylene-dependent pathway regulating cell expansion. The phenotype of ran1-3 mutants is similar to loss-of-function ethylene receptor mutants, suggesting that RAN1 may be required to form functional ethylene receptors. Furthermore, these results suggest that copper is required not only for ethylene binding but also for the signaling function of the ethylene receptors.

Woeste, K. E.; Kieber, J. J.; Evans, M. L. (Principal Investigator)

2000-01-01

281

Human cathepsin L rescues the neurodegeneration and lethality incathepsin B/L double deficient mice  

SciTech Connect

Cathepsin B (CTSB) and cathepsin L (CTSL) are two widelyexpressed cysteine proteases thought to predominantly reside withinlysosomes. Functional analysis of CTSL in humans is complicated by theexistence of two CTSL-like homologues (CTSL and CTSL2), in contrast tomice which contain only one CTSL enzyme. Thus transgenic expression ofhuman CTSL in CTSL deficient mice provides an opportunity to study the invivo functions of this human protease without interference by its highlyrelated homologue. While mice with single gene deficiencies for murineCTSB or CTSL survive without apparent neuromuscular impairment, murineCTSB/CTSL double deficient mice display degeneration of cerebellarPurkinje cells and neurons of the cerebral cortex, resulting in severehypotrophy, motility defects, and lethality during their third to fourthweek of life. Here we show that expression of human CTSL through agenomic transgene results in widespread expression of human CTSL in themouse which is capable of rescuing the lethality found in CTSB/CTSLdouble-deficient animals. Human CTSL is expressed in the brain of thesecompound mutants predominantly in neurons of the cerebral cortex and inPurkinje cells of the cerebellum, where it appears to prevent neuronalcell death.

Sevenich, Lisa; Pennacchio, Len A.; Peters, Christoph; Reinheckel, Thomas

2006-01-09

282

A requirement for recombinational repair in Saccharomyces cerevisiae is caused by DNA replication defects of mec1 mutants.  

PubMed

To examine the role of the RAD52 recombinational repair pathway in compensating for DNA replication defects in Saccharomyces cerevisiae, we performed a genetic screen to identify mutants that require Rad52p for viability. We isolated 10 mec1 mutations that display synthetic lethality with rad52. These mutations (designated mec1-srf for synthetic lethality with rad-fifty-two) simultaneously cause two types of phenotypes: defects in the checkpoint function of Mec1p and defects in the essential function of Mec1p. Velocity sedimentation in alkaline sucrose gradients revealed that mec1-srf mutants accumulate small single-stranded DNA synthesis intermediates, suggesting that Mec1p is required for the normal progression of DNA synthesis. sml1 suppressor mutations suppress both the accumulation of DNA synthesis intermediates and the requirement for Rad52p in mec1-srf mutants, but they do not suppress the checkpoint defect in mec1-srf mutants. Thus, it appears to be the DNA replication defects in mec1-srf mutants that cause the requirement for Rad52p. By using hydroxyurea to introduce similar DNA replication defects, we found that single-stranded DNA breaks frequently lead to double-stranded DNA breaks that are not rapidly repaired in rad52 mutants. Taken together, these data suggest that the RAD52 recombinational repair pathway is required to prevent or repair double-stranded DNA breaks caused by defective DNA replication in mec1-srf mutants. PMID:10511542

Merrill, B J; Holm, C

1999-10-01

283

Scaffolding proteins altered in the ability to perform a conformational switch confer dominant lethal assembly defects.  

PubMed

In the phiX174 procapsid crystal structure, 240 external scaffolding protein D subunits form 60 pairs of asymmetric dimers, D(1)D(2) and D(3)D(4), in a non-quasi-equivalent structure. To achieve this arrangement, alpha-helix 3 assumes two different conformations: (i) kinked 30 degrees at glycine residue 61 in subunits D(1) and D(3) and (ii) straight in subunits D(2) and D(4). Substitutions for G61 may inhibit viral assembly by preventing the protein from achieving its fully kinked conformation while still allowing it to interact with other scaffolding and structural proteins. Mutations designed to inhibit conformational switching in alpha-helix 3 were introduced into a cloned gene, and expression was demonstrated to inhibit wild-type morphogenesis. The severity of inhibition appears to be related to the size of the substituted amino acid. For infections in which only the mutant protein is present, morphogenesis does not proceed past the first step that requires the wild-type external scaffolding protein. Thus, mutant subunits alone appear to have little or no morphogenetic function. In contrast, assembly in the presence of wild-type and mutant subunits is blocked prematurely, before D protein is required in a wild-type infection, or channeled into an off-pathway reaction. These data suggest that the wild-type protein transports the inhibitory protein to the pathway. Viruses resistant to the lethal dominant proteins were isolated, and mutations were mapped to the coat and internal scaffolding proteins. The affected amino acids cluster in the atomic structure and may act to exclude mutant subunits from occupying particular positions atop pentamers of the viral coat protein. PMID:18400861

Cherwa, James E; Uchiyama, Asako; Fane, Bentley A

2008-06-01

284

Dominant lethal mutations near the 5' substrate binding site affect RNA polymerase propagation.  

PubMed

The segment Asp1064-Lys1073 in the beta subunit of Escherichia coli RNA polymerase is evolutionarily conserved and is located near the "5' face" of the nucleotide binding pocket as was shown by affinity labeling with priming substrates (Grachev, M. A., Lukhtamov, E. A., Mustaev, A. A., Zaychikov, E. F., Abdukayumov, M. N., Rabinov, I. V., Richter, V. I., Skoblov, Y. S., and Chistyakov, P. G. (1989) Eur. J. Biochem. 180, 577-585). We engineered single Xaa-->Ala or Ala-->Ser substitutions of eight evolutionarily conserved amino acids in this segment as well as a multiple alanine (KRNK) substitution of four of these residues. The KRNK mutation as well as four of the single substitutions were dominant lethal, two of the single mutations were recessive lethal, and two were viable. RNA polymerase bearing the dominant mutations was prepared for biochemical study by in vitro reconstitution from subunits. All of the mutant enzymes formed stable, specific promoter complexes, capable of initiating RNA synthesis. However, the KRNK polymerase was totally blocked in initiation-to-elongation transition, whereas the four point mutants displayed allele-specific changes in promoter clearance rate. Each of the four mutations changed, in a specific way, both the pattern of short oligomers generated in abortive initiation and the pattern of RNA polymerase pausing during elongation. Thus, the mutations appear to distort but not destroy the active center and to alter, in allele-specific manner, the coupling between the catalytic reaction and RNA polymerase propagation along the template. PMID:8420987

Sagitov, V; Nikiforov, V; Goldfarb, A

1993-01-25

285

Engineered Repressible Lethality for Controlling the Pink Bollworm, a Lepidopteran Pest of Cotton  

PubMed Central

The sterile insect technique (SIT) is an environmentally friendly method of pest control in which insects are mass-produced, irradiated and released to mate with wild counterparts. SIT has been used to control major pest insects including the pink bollworm (Pectinophora gossypiella Saunders), a global pest of cotton. Transgenic technology has the potential to overcome disadvantages associated with the SIT, such as the damaging effects of radiation on released insects. A method called RIDL (Release of Insects carrying a Dominant Lethal) is designed to circumvent the need to irradiate insects before release. Premature death of insects’ progeny can be engineered to provide an equivalent to sterilisation. Moreover, this trait can be suppressed by the provision of a dietary antidote. In the pink bollworm, we generated transformed strains using different DNA constructs, which showed moderate-to-100% engineered mortality. In permissive conditions, this effect was largely suppressed. Survival data on cotton in field cages indicated that field conditions increase the lethal effect. One strain, called OX3402C, showed highly penetrant and highly repressible lethality, and was tested on host plants where its larvae caused minimal damage before death. These results highlight a potentially valuable insecticide-free tool against pink bollworm, and indicate its potential for development in other lepidopteran pests.

Morrison, Neil I.; Simmons, Gregory S.; Fu, Guoliang; O'Connell, Sinead; Walker, Adam S.; Dafa'alla, Tarig; Walters, Michelle; Claus, John; Tang, Guolei; Jin, Li; Marubbi, Thea; Epton, Matthew J.; Harris, Claire L.; Staten, Robert T.; Miller, Ernest; Miller, Thomas A.; Alphey, Luke

2012-01-01

286

Mice With an Anterior Cleft of the Palate Survive Neonatal Lethality  

PubMed Central

Many genes are known to function in a region-specific manner in the developing secondary palate. We have previously shown that Shox2-deficient embryos die at mid-gestation stage and develop an anterior clefting phenotype. Here, we show that mice carrying a conditional inactivation of Shox2 in the palatal mesenchyme survive the embryonic and neonatal lethality, but develop a wasting syndrome. Phenotypic analyses indicate a delayed closure of the secondary palate at the anterior end, leading to a failed fusion of the primary and secondary palates. Consistent with a role proposed for Shox2 in skeletogenesis, Shox2 inactivation causes a significantly reduced bone formation in the hard palate, probably due to a down-regulation of Runx2 and Osterix. We conclude that the secondary palatal shelves are capable of fusion with each other, but fail to fuse with the primary palate in a developmentally delayed manner. Mice carrying an anterior cleft can survive neonatal lethality.

Gu, Shuping; Wei, Na; Yu, Xueyan; Jiang, Yiping; Fei, Jian; Chen, YiPing

2009-01-01

287

Protection by recombinant human superoxide dismutase in lethal rat endotoxemia.  

PubMed

In summary as mechanism of the overall protective effect of r-HSOD in lethal rat endotoxemia, inhibition of hemoconcentration, a tendency of a decreased leukocyte activation and attenuation of consumption coagulopathy could be established. PMID:2675076

Schneider, J; Friderichs, E; Giertz, H

1989-01-01

288

Biochemical Changes in Blood Components after Lethal Doses of Radiation.  

National Technical Information Service (NTIS)

Nonpeptide, peptide, and protein blood components were measured postirradiation in Wistar rats to investigate biochemical changes that might be related to or form the basis of radiation-induced emesis. The rats were irradiated with lethal doses of radiati...

A. M. Magro

1982-01-01

289

Field Evaluation of Lethal Ovitrap against Dengue Vectors.  

National Technical Information Service (NTIS)

Ovitraps have been used to effectively sample dengue mosquito vector populations, particularly Aedes aegypti, for over a decade. Modifying a standard ovitrap by incorporating an insecticide would result in a lethal ovitrap (LO) that could be used as an in...

L. Foil

2005-01-01

290

Fractional Cell Lethality Approach to Space Radiation Hazards.  

National Technical Information Service (NTIS)

A method of radiation hazard evaluation has been introduced in which the fractional number of inactivated cells of an organ is calculated. This fractional cell lethality (FCL) depends only on the particle energy spectrum and the probability of cell inacti...

S. B. Curtis D. L. Dye W. R. Sheldon

1964-01-01

291

Antagonistic effects against single lethal doses of Amanita phalloides.  

PubMed

Agents with antagonistic effects against phalloidin or alpha-amanitin were tested in mice against lethal doses of an extract from the whole mushroom Amanita phalloides. The following categories of agents reduced lethality after the extract. First, agents protecting only against phalloidin such as rifampicin, phenylbutazone and antamanide. Second, silymarin and prednisolone which display both antiamatoxic and marked (silymarin) or moderate (prednisolone) anti-phallotoxic acitivty. Thioctic acid displayed some activity when tested against mid-lethal doses of the extract. Cytochrome c, a chemical with curative potencies against alpha-amanitin did not reduce the lethality of the exact. All of the effective agents acted only when applied prior to the poisoning. The pattern or protective activity would indicate that in mice death after single doses of Amanita phalloides may follow a qualitatively particular couse which is difficult to ascribe to phallo- or amatoxic effects alone. PMID:183152

Floersheim, G L

1976-05-01

292

Lethal Concentrations of Heavy Metals in Tissue of Earthworms.  

National Technical Information Service (NTIS)

This toxicological research report addresses lethal concentrations of heavy metals in tissue of earthworms. We have presented the work in progress in the first interim report to improve 1) ecotoxicological test, 2) field procedures and 3) standardization ...

A. Rida J. Y. Gal M. B. Bouche P. Brun

1987-01-01

293

Lipopolysaccharide-Induced Lethality and Cytokine Production in Aged Mice  

Microsoft Academic Search

This study was designed to define the lipopolysaccharide (LPS) sensitivity of aged mice in terms of lethality and cytokine production and to determine down-regulating responses of corticosterone and interleukin 10 (IL-10). The 50% lethal doses of LPS in young (6- to 7-week-old) and aged (98- to 102-week-old) mice were 601 and 93 mg per mouse (25.6 and 1.6 mg per

KAZUHIRO TATEDA; TETSUYA MATSUMOTO; SHUICHI MIYAZAKI; ANDKEIZO YAMAGUCHI

1996-01-01

294

GPS targeting methods for non-lethal systems  

Microsoft Academic Search

Non-lethal systems consist of devices and methods which can be used to incapacitate an adversary's capability, while minimizing casualties and collateral property or environmental damages. Examples of military non-lethal concepts include wire mesh entanglements to snag tank treads, highly expansive sticky foams to immobilize personnel and material, anti-material agents to degrade supplies, and information warfare tactics such as the use

Gerald Frost; Calvin Shipbaugh

1994-01-01

295

ECB deacylase mutants  

DOEpatents

A method for in vitro mutagenesis and recombination of polynucleotide sequences based on polymerase-catalyzed extension of primer oligonucleotides is disclosed. The method involves priming template polynucleotide(s) with random-sequences or defined-sequence primers to generate a pool of short DNA fragments with a low level of point mutations. The DNA fragments are subjected to denaturization followed by annealing and further enzyme-catalyzed DNA polymerization. This procedure is repeated a sufficient number of times to produce full-length genes which comprise mutants of the original template polynucleotides. These genes can be further amplified by the polymerase chain reaction and cloned into a vector for expression of the encoded proteins.

Arnold, Frances H. (Pasadena, CA); Shao, Zhixin (Penzberg, DE); Zhao, Huimin (San Diego, CA); Giver, Lorraine J. (Sunnyvale, CA)

2002-01-01

296

Zebrafish Mutants calamity and catastrophe Define Critical Pathways of Gene-Nutrient Interactions in Developmental Copper Metabolism  

PubMed Central

Nutrient availability is an important environmental variable during development that has significant effects on the metabolism, health, and viability of an organism. To understand these interactions for the nutrient copper, we used a chemical genetic screen for zebrafish mutants sensitive to developmental copper deficiency. In this screen, we isolated two mutants that define subtleties of copper metabolism. The first contains a viable hypomorphic allele of atp7a and results in a loss of pigmentation when exposed to mild nutritional copper deficiency. This mutant displays incompletely penetrant skeletal defects affected by developmental copper availability. The second carries an inactivating mutation in the vacuolar ATPase that causes punctate melanocytes and embryonic lethality. This mutant, catastrophe, is sensitive to copper deprivation revealing overlap between ion metabolic pathways. Together, the two mutants illustrate the utility of chemical genetic screens in zebrafish to elucidate the interaction of nutrient availability and genetic polymorphisms in cellular metabolism.

Madsen, Erik C.; Gitlin, Jonathan D.

2008-01-01

297

Behavioral mutants of Drosophila melanogaster. III. Isolation and mapping of mutations by direct visual observations of behavioral phenotypes.  

PubMed

Sex-linked behavioral mutants were induced in Drosophila melanogaster with ethyl methanesulfonate (EMS) and isolated by direct visual observation of abnormal phenotypes. The four behavioral phenotypes used were flight-reduction, hyperactivity, hypoactivity and stress-sensitivity, and are easily discernable in either single or small populations of mutant flies. In one screen, forty-two behavioral mutants were recovered from strains derived from 800 mutagen-treated X chromosomes In a second screen, 139 behavioral mutants were obtained from 2369 X chromosomes. The high rate at which behavioral mutants were recovered in the second screen, when compared to new visibles (28) and new temperature-sensitive lethals (124), suggests that the isolation of behavioral mutations on the autosomes of Drosophila and in the genomes of larger insects should be practical. PMID:6770227

Homyk, T; Szidonya, J; Suzuki, D T

1980-01-01

298

Functional centrality: detecting lethality of proteins in protein interaction networks.  

PubMed

Identifying lethal proteins is important for understanding the intricate mechanism governing life. Researchers have shown that the lethality of a protein can be computed based on its topological position in the protein-protein interaction (PPI) network. Performance of current approaches has been less than satisfactory as the lethality of a protein is a functional characteristic that cannot be determined solely by network topology. Furthermore, a significant number of lethal proteins have low connectivity in the interaction networks but are overlooked by most current methods. Our work reveals that a protein's lethality correlates more strongly with its "functional centrality" than pure topological centrality. We define functional centrality as the topological centrality within a subnetwork of proteins with similar functions. Evaluation experiments on four Saccharomyces cerevisiae PPI datasets showed that NFC performed significantly better than all the other existing computational techniques. Our method was able to detect low connectivity lethal proteins that were previously undetected by conventional methods. The results and an online version of NFC is available at http://lethalproteins.i2r.a-star.edu.sg. PMID:18546514

Tew, Kar Leong; Li, Xiao-Li; Tan, Soon-Heng

2007-01-01

299

Transferrin iron starvation therapy for lethal bacterial and fungal infections.  

PubMed

New strategies to treat antibiotic-resistant infections are urgently needed. We serendipitously discovered that stem cell conditioned media possessed broad antimicrobial properties. Biochemical, functional, and genetic assays confirmed that the antimicrobial effect was mediated by supra-physiological concentrations of transferrin. Human transferrin inhibited growth of gram-positive (Staphylococcus aureus), gram-negative (Acinetobacter baumannii), and fungal (Candida albicans) pathogens by sequestering iron and disrupting membrane potential. Serial passage in subtherapeutic transferrin concentrations resulted in no emergence of resistance. Infected mice treated with intravenous human transferrin had improved survival and reduced microbial burden. Finally, adjunctive transferrin reduced the emergence of rifampin-resistant mutants of S. aureus in infected mice treated with rifampin. Transferrin is a promising, novel antimicrobial agent that merits clinical investigation. These results provide proof of principle that bacterial infections can be treated in vivo by attacking host targets (ie, trace metal availability) rather than microbial targets. PMID:24446527

Lin, Lin; Pantapalangkoor, Paul; Tan, Brandon; Bruhn, Kevin W; Ho, Tiffany; Nielsen, Travis; Skaar, Eric P; Zhang, Yaofang; Bai, Ruipeng; Wang, Amy; Doherty, Terence M; Spellberg, Brad

2014-07-15

300

Generation of a conditional mouse model to target Acvr1b disruption in adult tissues.  

PubMed

Alk4 is a type I receptor that belongs to the transforming growth factor-beta (TGF-?) family. It takes part in the signaling of TGF-? ligands such as Activins, Gdfs, and Nodal that had been demonstrated to participate in numerous mechanisms ranging from early embryonic development to adult-tissue homeostasis. Evidences indicate that Alk4 is a key regulator of many embryonic processes, but little is known about its signaling in adult tissues and in pathological conditions where Alk4 mutations had been reported. Conventional deletion of Alk4 gene (Acvr1b) results in early embryonic lethality prior gastrulation, which has precluded study of Alk4 functions in postnatal and adult mice. To circumvent this problem, we have generated a conditional Acvr1b floxed-allele by flanking the fifth and sixth exons of the Acvr1b gene with loxP sites. Cre-mediated deletion of the floxed allele generates a deleted allele, which behaves as an Acvr1b null allele leading to embryonic lethality in homozygous mutant animals. A tamoxifen-inducible approach to target disruption of Acvr1b specifically in adult tissues was used and proved to be efficient for studying Alk4 functions in various organs. We report, therefore, a novel conditional model allowing investigation of biological role played by Alk4 in a variety of tissue-specific contexts. PMID:23109354

Ripoche, Doriane; Gout, Johann; Pommier, Roxane M; Jaafar, Rami; Zhang, Chang X; Bartholin, Laurent; Bertolino, Philippe

2013-02-01

301

Pas1, a G1 cyclin, regulates amino acid uptake and rescues a delay in G1 arrest in Tsc1 and Tsc2 mutants in Schizosaccharomyces pombe.  

PubMed

Tuberous sclerosis complex is a tumor suppressor syndrome caused by mutations in either the TSC1 or the TSC2 gene. Previous studies have shown that deletion of the TSC1 or TSC2 ortholog in Schizosaccharomyces pombe results in an amino acid uptake defect, with conditional lethality. We identified a G1 cyclin, pas1+, as a high-copy suppressor of this defect in Deltatsc1. Disruption of pas1+ causes defects in arginine and leucine uptake that are remarkably similar to Deltatsc1 and Deltatsc2, whereas Deltapas1Deltatsc1 and Deltapas1Deltatsc2 double mutants have more severe amino acid uptake defects. In a second screen, we identified a novel G63D/S165 N mutant of the small GTPase Rhb1, the target of the Tsc1/Tsc2 protein complex. The Rhb1 mutant suppresses amino acid uptake in Deltatsc1 yeast, but not in Deltapas1 yeast. Hence, Pas1 does not regulate amino acid uptake through Rhb1. To determine whether Pas1 links nutrient availability to cell cycle progression downstream of the Tsc1/Tsc2 complex, we examined the kinetics of G1 arrest in single and double mutant strains. After nitrogen starvation, Deltatsc1 and Deltatsc2 yeast had a delay in G1 arrest when compared with wild-type, which was rescued by deletion of pas1+. In summary, we identified the G1 cyclin, Pas1, as a novel regulator of amino acid uptake. Our data support a model in which Pas1 inhibits G1 arrest downstream of Tsc1 and Tsc2, linking nutrient uptake and cell cycle progression in yeast. PMID:16115814

van Slegtenhorst, Marjon; Mustafa, Aladdin; Henske, Elizabeth Petri

2005-10-01

302

Altered cellular infiltration and cytokine levels during early Mycobacterium tuberculosis sigC mutant infection are associated with late-stage disease attenuation and milder immunopathology in mice  

Microsoft Academic Search

Background  Mouse virulence assessments of certain Mycobacterium tuberculosis mutants have revealed an immunopathology defect in which high tissue CFU counts are observed but the tissue pathology and\\u000a lethality are reduced. M. tuberculosis mutants which grow and persist in the mouse lungs, but have attenuated disease progression, have the immunopathology (imp) phenotype. The antigenic properties of these strains may alter the progression

Khairul-Bariah Abdul-Majid; Lan H Ly; Paul J Converse; Deborah E Geiman; David N McMurray; William R Bishai

2008-01-01

303

Mutation rate and novel tt mutants of Arabidopsis thaliana induced by carbon ions.  

PubMed Central

Irradiation of Arabidopsis thaliana by carbon ions was carried out to investigate the mutational effect of ion particles in higher plants. Frequencies of embryonic lethals and chlorophyll-deficient mutants were found to be significantly higher after carbon-ion irradiation than after electron irradiation (11-fold and 7.8-fold per unit dose, respectively). To estimate the mutation rate of carbon ions, mutants with no pigments on leaves and stems (tt) and no trichomes on leaves (gl) were isolated at the M2 generation and subjected to analysis. Averaged segregation rate of the backcrossed mutants was 0.25, which suggested that large deletions reducing the viability of the gametophytes were not transmitted, if generated, in most cases. During the isolation of mutants, two new classes of flavonoid mutants (tt18, tt19) were isolated from carbon-ion-mutagenized M2 plants. From PCR and sequence analysis, two of the three tt18 mutant alleles were found to have a small deletion within the LDOX gene and the other was revealed to contain a rearrangement. Using the segregation rates, the mutation rate of carbon ions was estimated to be 17-fold higher than that of electrons. The isolation of novel mutants and the high mutation rate suggest that ion particles can be used as a valuable mutagen for plant genetics.

Shikazono, Naoya; Yokota, Yukihiko; Kitamura, Satoshi; Suzuki, Chihiro; Watanabe, Hiroshi; Tano, Shigemitsu; Tanaka, Atsushi

2003-01-01

304

Mapping the lethal factor and edema factor binding sites on oligomeric anthrax protective antigen  

PubMed Central

Assembly of anthrax toxin complexes at the mammalian cell surface involves competitive binding of the edema factor (EF) and lethal factor (LF) to heptameric oligomers and lower order intermediates of PA63, the activated carboxyl-terminal 63-kDa fragment of protective antigen (PA). We used sequence differences between PA63 and homologous PA-like proteins to delineate a region within domain 1? of PA that may represent the binding site for these ligands. Substitution of alanine for any of seven residues in or near this region (R178, K197, R200, P205, I207, I210, and K214) strongly inhibited ligand binding. Selected mutations from this set were introduced into two oligomerization-deficient PA mutants, and the mutants were used in various combinations to map the single ligand site within dimeric PA63. The site was found to span the interface between two adjacent subunits, explaining the dependence of ligand binding on PA oligomerization. The locations of residues comprising the site suggest that a single ligand molecule sterically occludes two adjacent sites, consistent with the finding that the PA63 heptamer binds a maximum of three ligand molecules. These results elucidate the process by which the components of anthrax toxin, and perhaps other binary bacterial toxins, assemble into toxic complexes.

Cunningham, Kristina; Lacy, D. Borden; Mogridge, Jeremy; Collier, R. John

2002-01-01

305

Loss of p53 Ser18 and Atm Results in Embryonic Lethality without Cooperation in Tumorigenesis  

PubMed Central

Phosphorylation at murine Serine 18 (human Serine 15) is a critical regulatory process for the tumor suppressor function of p53. p53Ser18 residue is a substrate for ataxia-telangiectasia mutated (ATM) and ATM-related (ATR) protein kinases. Studies of mice with a germ-line mutation that replaces Ser18 with Ala (p53S18A mice) have demonstrated that loss of phosphorylation of p53Ser18 leads to the development of tumors, including lymphomas, fibrosarcomas, leukemia and leiomyosarcomas. The predominant lymphoma is B-cell lymphoma, which is in contrast to the lymphomas observed in Atm?/? animals. This observation and the fact that multiple kinases phosphorylate p53Ser18 suggest Atm-independent tumor suppressive functions of p53Ser18. Therefore, in order to examine p53Ser18 function in relationship to ATM, we analyzed the lifespan and tumorigenesis of mice with combined mutations in p53Ser18 and Atm. Surprisingly, we observed no cooperation in survival and tumorigenesis in compound p53S18A and Atm?/? animals. However, we observed embryonic lethality in the compound mutant animals. In addition, the homozygous p53Ser18 mutant allele impacted the weight of Atm?/? animals. These studies examine the genetic interaction of p53Ser18 and Atm in vivo. Furthermore, these studies demonstrate a role of p53Ser18 in regulating embryonic survival and motor coordination.

Armata, Heather L.; Shroff, Punita; Garlick, David E.; Penta, Krista; Tapper, Andrew R.; Sluss, Hayla K.

2011-01-01

306

A functional cancer genomics screen identifies a druggable synthetic lethal interaction between MSH3 and PRKDC.  

PubMed

Here, we use a large-scale cell line-based approach to identify cancer cell-specific mutations that are associated with DNA-dependent protein kinase catalytic subunit (DNA-PKcs) dependence. For this purpose, we profiled the mutational landscape across 1,319 cancer-associated genes of 67 distinct cell lines and identified numerous genes involved in homologous recombination-mediated DNA repair, including BRCA1, BRCA2, ATM, PAXIP, and RAD50, as being associated with non-oncogene addiction to DNA-PKcs. Mutations in the mismatch repair gene MSH3, which have been reported to occur recurrently in numerous human cancer entities, emerged as the most significant predictors of DNA-PKcs addiction. Concordantly, DNA-PKcs inhibition robustly induced apoptosis in MSH3-mutant cell lines in vitro and displayed remarkable single-agent efficacy against MSH3-mutant tumors in vivo. Thus, we here identify a therapeutically actionable synthetic lethal interaction between MSH3 and the non-homologous end joining kinase DNA-PKcs. Our observations recommend DNA-PKcs inhibition as a therapeutic concept for the treatment of human cancers displaying homologous recombination defects. PMID:24556366

Dietlein, Felix; Thelen, Lisa; Jokic, Mladen; Jachimowicz, Ron D; Ivan, Laura; Knittel, Gero; Leeser, Uschi; van Oers, Johanna; Edelmann, Winfried; Heukamp, Lukas C; Reinhardt, H Christian

2014-05-01

307

Clock Mutants of Drosophila melanogaster  

Microsoft Academic Search

Three mutants have been isolated in which the normal 24-hour rhythm is drastically changed. One mutant is arrhythmic; another has a period of 19 hr; a third has a period of 28 hr. Both the eclosion rhythm of a population and the locomotor activity of individual flies are affected. All these mutations appear to involve the same functional gene on

Ronald J. Konopka; Seymour Benzer

1971-01-01

308

Determination of synthetic lethal interactions in KRAS oncogene-dependent cancer cells reveals novel therapeutic targeting strategies.  

PubMed

Oncogenic mutations in RAS genes are very common in human cancer, resulting in cells with well-characterized selective advantages, but also less well-understood vulnerabilities. We have carried out a large-scale loss-of-function screen to identify genes that are required by KRAS-transformed colon cancer cells, but not by derivatives lacking this oncogene. Top-scoring genes were then tested in a larger panel of KRAS mutant and wild-type cancer cells. Cancer cells expressing oncogenic KRAS were found to be highly dependent on the transcription factor GATA2 and the DNA replication initiation regulator CDC6. Extending this analysis using a collection of drugs with known targets, we found that cancer cells with mutant KRAS showed selective addiction to proteasome function, as well as synthetic lethality with topoisomerase inhibition. Combination targeting of these functions caused improved killing of KRAS mutant cells relative to wild-type cells. These observations suggest novel targets and new ways of combining existing therapies for optimal effect in RAS mutant cancers, which are traditionally seen as being highly refractory to therapy. PMID:22613949

Steckel, Michael; Molina-Arcas, Miriam; Weigelt, Britta; Marani, Michaela; Warne, Patricia H; Kuznetsov, Hanna; Kelly, Gavin; Saunders, Becky; Howell, Michael; Downward, Julian; Hancock, David C

2012-08-01

309

Morphogenesis Is Not Required for Candida albicans-Staphylococcus aureus Intra-Abdominal Infection-Mediated Dissemination and Lethal Sepsis.  

PubMed

Intra-abdominal polymicrobial infections cause significant morbidity and mortality. An established experimental mouse model of Staphylococcus aureus-Candida albicans intra-abdominal infection results in ?60% mortality within 48 h postinoculation, concomitant with amplified local inflammatory responses, while monomicrobial infections are avirulent. The purpose of this study was to characterize early local and systemic innate responses during coinfection and determine the role of C. albicans morphogenesis in lethality, a trait involved in virulence and physical interaction with S. aureus. Local and systemic proinflammatory cytokines were significantly elevated during coinfection at early time points (4 to 12 h) compared to those in monoinfection. In contrast, microbial burdens in the organs and peritoneal lavage fluid were similar between mono- and coinfected animals through 24 h, as was peritoneal neutrophil infiltration. After optimizing the model for 100% mortality within 48 h, using 3.5 × 10(7) C. albicans (5× increase), coinfection with C. albicans yeast-locked or hypha-locked mutants showed similar mortality, dissemination, and local and systemic inflammation to the isogenic control. However, coinfection with the yeast-locked C. albicans mutant given intravenously (i.v.) and S. aureus given intraperitoneally (i.p.) failed to induce mortality. These results suggest a unique intra-abdominal interaction between the host and C. albicans-S. aureus that results in strong inflammatory responses, dissemination, and lethal sepsis, independent of C. albicans morphogenesis. PMID:24891104

Nash, Evelyn E; Peters, Brian M; Palmer, Glen E; Fidel, Paul L; Noverr, Mairi C

2014-08-01

310

Lethal mutations in the major homology region and their suppressors act by modulating the dimerization of the rous sarcoma virus capsid protein C-terminal domain.  

PubMed

An infective retrovirus requires a mature capsid shell around the viral replication complex. This shell is formed by about 1500 capsid protein monomers, organized into hexamer and pentamer rings that are linked to each other by the dimerization of the C-terminal domain (CTD). The major homology region (MHR), the most highly conserved protein sequence across retroviral genomes, is part of the CTD. Several mutations in the MHR appear to block infectivity by preventing capsid formation. Suppressor mutations have been identified that are distant in sequence and structure from the MHR and restore capsid formation. The effects of two lethal and two suppressor mutations on the stability and function of the CTD were examined. No correlation with infectivity was found for the stability of the lethal mutations (D155Y-CTD, F167Y-CTD) and suppressor mutations (R185W-CTD, I190V-CTD). The stabilities of three double mutant proteins (D155Y/R185W-CTD, F167Y/R185W-CTD, and F167Y/I190V-CTD) were additive. However, the dimerization affinity of the mutant proteins correlated strongly with biological function. The CTD proteins with lethal mutations did not dimerize, while those with suppressor mutations had greater dimerization affinity than WT-CTD. The suppressor mutations were able to partially correct the dimerization defect caused by the lethal MHR mutations in double mutant proteins. Despite their dramatic effects on dimerization, none of these residues participate directly in the proposed dimerization interface in a mature capsid. These findings suggest that the conserved sequence of the MHR has critical roles in the conformation(s) of the CTD that are required for dimerization and correct capsid maturation. PMID:23011855

Dalessio, Paula M; Craven, Rebecca C; Lokhandwala, Parvez M; Ropson, Ira J

2013-02-01

311

Interpretation of the dose and LET dependence of RBE values for lethal lesions in yeast cells  

SciTech Connect

Survival data on yeast cells proficient or deficient in the repair of DNA double-strand breaks (dsb) and data on the induction of dsb are used to interpret the dose dependence of the RBE value for lethal lesions after irradiation at high dose rate followed by 72-hr liquid holding providing optimum conditions for repair of potentially lethal lesions (RBE/sub DP/, DP = delayed plating). The radiations applied are conventional (150 kV), soft (50 kV), and ultrasoft (4 kV) X rays, 30-MeV electrons (or /sup 60/Co ..gamma.. rays), and 3.5-MeV ..cap alpha.. particles. Analysis shows that the dose dependence of the RBE/sub DP/ value can be explained by the combination of two dose-independent RBE values, one for the single-particle traversal effect (RBE/sub spt/) and the other for the accumulation of dsb (RBE/sub dsb/) due to the traversal of more than one particle through the cell nucleus. Furthermore, it is shown that the LET dependence of RBE/sub spt/ values describing the linear component of the lethal lesions must be considered separately for ''electron'' and ''particle'' radiations.

Frankenberg, D.

1984-02-01

312

Interpretation of the dose and LET dependence of RBE values for lethal lesions in yeast cells  

SciTech Connect

Survival data on yeast cells proficient or deficient in the repair of DNA double-strand breaks (dsb) and data on the induction of dsb are used to interpret the dose dependence of the RBE value for lethal lesions after irradiation at high dose rate followed by 72-hr liquid holding providing optimum conditions for repair of potentially lethal lesions (RBE/sub DP/, DP = delayed plating). The radiations applied are conventional (150 kV), soft (50 kV), and ultrasoft (4 kV) X rays, 30-MeV electrons (or /sup 60/Co ..gamma.. rays), and 3.5-MeV ..cap alpha.. particles. Analysis shows that the dose dependence of the RBE/sub DP/ value can be explained by the combination of two dose-independent RBE values, one for the single-particle traversal effect (RBE/sub spt/) and the other for the accumulation of dsb (RBE/sub dsb/) due to the traversal of more than one particle though the cell nucleus. Furthermore, it is shown that the LET dependence of RBE/sub spt/ values describing the linear component of the lethal lesions must be considered separately for ''electron'' and ''particle'' radiations.

Frankenberg, D.

1984-02-01

313

The population genetics of X-autosome synthetic lethals and steriles.  

PubMed

Epistatic interactions are widespread, and many of these interactions involve combinations of alleles at different loci that are deleterious when present in the same individual. The average genetic environment of sex-linked genes differs from that of autosomal genes, suggesting that the population genetics of interacting X-linked and autosomal alleles may be complex. Using both analytical theory and computer simulations, we analyzed the evolutionary trajectories and mutation-selection balance conditions for X-autosome synthetic lethals and steriles. Allele frequencies follow a set of fundamental trajectories, and incompatible alleles are able to segregate at much higher frequencies than single-locus expectations. Equilibria exist, and they can involve fixation of either autosomal or X-linked alleles. The exact equilibrium depends on whether synthetic alleles are dominant or recessive and whether fitness effects are seen in males, females, or both sexes. When single-locus fitness effects and synthetic incompatibilities are both present, population dynamics depend on the dominance of alleles and historical contingency (i.e., whether X-linked or autosomal mutations occur first). Recessive synthetic lethality can result in high-frequency X-linked alleles, and dominant synthetic lethality can result in high-frequency autosomal alleles. Many X-autosome incompatibilities in natural populations may be cryptic, appearing to be single-locus effects because one locus is fixed. We also discuss the implications of these findings with respect to standing genetic variation and the origins of Haldane's rule. PMID:21900269

Lachance, Joseph; Johnson, Norman A; True, John R

2011-11-01

314

Lethal and sublethal effects of fenpropathrin on the biological performance of Scolothrips longicornis (Thysanoptera: Thripidae).  

PubMed

Determination of negative nontarget effects of pesticides on beneficial organisms by measuring only lethal effects is likely to underestimate effects of sublethal doses. In this study, the sublethal effects of fenpropathrin on the predatory thrips Scolothrips longicornis Priesner (Thysanoptera: Thripidae) fed on Tetranychus urticae Koch (Acari: Tetranychidae) were evaluated under laboratory conditions. The estimated values of LC50 for female and male predators were 6.53 and 5.47 microg a.i./ml, respectively. Exposure to low-lethal concentrations (LC10, LC20, and LC30) of fenpropathrin significantly affected the biological characteristics of treated females of S. longicornis, the most noticeable effects being a shortening of female life span by > 70% accompanied by large reductions in oviposition period and fecundity. The offspring of females treated with low-lethal concentrations of fenpropathrin likewise had significantly reduced longevity, oviposition period, and fecundity, although not to the same extent as experienced by their mothers. Their juvenile development time was, however, not affected. These effects on the offspring were reflected in reduced rates of population increase and increased doubling times. PMID:24498736

Pakyari, Hajar; Enkegaard, Annie

2013-12-01

315

Overexpression of dilp2 causes nutrient-dependent semi-lethality in Drosophila  

PubMed Central

Insulin/insulin-like growth factor (IGF) plays an important role as a systemic regulator of metabolism in multicellular organisms. Hyperinsulinemia, a high level of blood insulin, is often associated with impaired physiological conditions such as hypoglycemia, insulin resistance, and diabetes. However, due to the complex pathophysiology of hyperinsulinemia, the causative role of excess insulin/IGF signaling has remained elusive. To investigate the biological effects of a high level of insulin in metabolic homeostasis and physiology, we generated flies overexpressing Drosophila insulin-like peptide 2 (Dilp2), which has the highest potential of promoting tissue growth among the Ilp genes in Drosophila. In this model, a UAS-Dilp2 transgene was overexpressed under control of sd-Gal4 that drives expression predominantly in developing imaginal wing discs. Overexpression of Dilp2 caused semi-lethality, which was partially suppressed by mutations in the insulin receptor (InR) or Akt1, suggesting that dilp2-induced semi-lethality is mediated by the PI3K/Akt1 signaling. We found that dilp2-overexpressing flies exhibited intensive autophagy in fat body cells. Interestingly, the dilp2-induced autophagy as well as the semi-lethality was partially rescued by increasing the protein content relative to glucose in the media. Our results suggest that excess insulin/IGF signaling impairs the physiology of animals, which can be ameliorated by controlling the nutritional balance between proteins and carbohydrates, at least in flies.

Sato-Miyata, Yukiko; Muramatsu, Keigo; Funakoshi, Masabumi; Tsuda, Manabu; Aigaki, Toshiro

2014-01-01

316

Overexpression of dilp2 causes nutrient-dependent semi-lethality in Drosophila.  

PubMed

Insulin/insulin-like growth factor (IGF) plays an important role as a systemic regulator of metabolism in multicellular organisms. Hyperinsulinemia, a high level of blood insulin, is often associated with impaired physiological conditions such as hypoglycemia, insulin resistance, and diabetes. However, due to the complex pathophysiology of hyperinsulinemia, the causative role of excess insulin/IGF signaling has remained elusive. To investigate the biological effects of a high level of insulin in metabolic homeostasis and physiology, we generated flies overexpressing Drosophila insulin-like peptide 2 (Dilp2), which has the highest potential of promoting tissue growth among the Ilp genes in Drosophila. In this model, a UAS-Dilp2 transgene was overexpressed under control of sd-Gal4 that drives expression predominantly in developing imaginal wing discs. Overexpression of Dilp2 caused semi-lethality, which was partially suppressed by mutations in the insulin receptor (InR) or Akt1, suggesting that dilp2-induced semi-lethality is mediated by the PI3K/Akt1 signaling. We found that dilp2-overexpressing flies exhibited intensive autophagy in fat body cells. Interestingly, the dilp2-induced autophagy as well as the semi-lethality was partially rescued by increasing the protein content relative to glucose in the media. Our results suggest that excess insulin/IGF signaling impairs the physiology of animals, which can be ameliorated by controlling the nutritional balance between proteins and carbohydrates, at least in flies. PMID:24795642

Sato-Miyata, Yukiko; Muramatsu, Keigo; Funakoshi, Masabumi; Tsuda, Manabu; Aigaki, Toshiro

2014-01-01

317

The Population Genetics of X-Autosome Synthetic Lethals and Steriles  

PubMed Central

Epistatic interactions are widespread, and many of these interactions involve combinations of alleles at different loci that are deleterious when present in the same individual. The average genetic environment of sex-linked genes differs from that of autosomal genes, suggesting that the population genetics of interacting X-linked and autosomal alleles may be complex. Using both analytical theory and computer simulations, we analyzed the evolutionary trajectories and mutation–selection balance conditions for X–autosome synthetic lethals and steriles. Allele frequencies follow a set of fundamental trajectories, and incompatible alleles are able to segregate at much higher frequencies than single-locus expectations. Equilibria exist, and they can involve fixation of either autosomal or X-linked alleles. The exact equilibrium depends on whether synthetic alleles are dominant or recessive and whether fitness effects are seen in males, females, or both sexes. When single-locus fitness effects and synthetic incompatibilities are both present, population dynamics depend on the dominance of alleles and historical contingency (i.e., whether X-linked or autosomal mutations occur first). Recessive synthetic lethality can result in high-frequency X-linked alleles, and dominant synthetic lethality can result in high-frequency autosomal alleles. Many X–autosome incompatibilities in natural populations may be cryptic, appearing to be single-locus effects because one locus is fixed. We also discuss the implications of these findings with respect to standing genetic variation and the origins of Haldane’s rule.

Lachance, Joseph; Johnson, Norman A.; True, John R.

2011-01-01

318

Embryonic lethality in mice lacking mismatch-specific thymine DNA glycosylase is partially prevented by DOPS, a precursor of noradrenaline.  

PubMed

Thymine DNA glycosylase (TDG) is involved in the repair of G:T and G:U mismatches caused by hydrolytic deamination of 5-methylcytosine and cytosine, respectively. Recent studies have shown that TDG not only has G-T/U glycosylase activities but also acts in the maintaining proper epigenetic status. In order to investigate the function of TDG in vivo, mice lacking Tdg, Tdg (-/-), were generated. Tdg mutant mice died in utero by 11.5 days post coitum (dpc), although there were no significant differences in the spontaneous mutant frequencies between wild type and Tdg (-/-) embryos. On the other hand, the levels of noradrenaline in 10.5 dpc whole embryos, which is necessary for normal embryogenesis, were dramatically reduced in Tdg (-/-) embryos. Consequently, we tested the effect of D, L-threo-3, 4-dihydroxyphenylserine (DOPS), a synthetic precursor of noradrenaline, on the survival of the Tdg (-/-) embryos. DOPS was given to pregnant Tdg (+/-) mice from 6.5 dpc through drinking water. Most of the Tdg (-/-) embryos were alive at 11.5 dpc, and they were partially rescued up to 14.5 dpc by the administration of DOPS. In contrast, the administration of L-3, 4-dihydroxyphenylalanine (L-DOPA) had marginal effects on Tdg (-/-) embryonic lethality. No embryo was alive without DOPS beyond 11.5 dpc, suggesting that the lethality in (-/-) embryos is partially due to the reduction of noradrenaline. These results suggest that embryonic lethality in Tdg (-/-) embryos is due, in part, to the reduction of noradrenaline levels. PMID:22200605

Saito, Yusuke; Ono, Tetsuya; Takeda, Naoki; Nohmi, Takehiko; Seki, Masayuki; Enomoto, Takemi; Noda, Tetsuo; Uehara, Yoshihiko

2012-01-01

319

[Study of a Pseudomonas mutant altered in methanol metabolism].  

PubMed

A glycine-resistant mutant was isolated from a methylotrophic strain of Pseudomonas species possessing serine pathway. This mutant presents some improvements in regard to growth parameters, and is able to excrete a fluorescent pigment under certain culture conditions. This pigment is capable of accelerating the reduction rate of formaldehyde to formate coupled with NAD. The same cannot be said for the wild type. PMID:397685

Ratomahenina, R; Arthaud, J F; Cabane, B; Galzy, P

1979-01-01

320

Are High-Lethality Suicide Attempters With Bipolar Disorder a Distinct Phenotype?  

Microsoft Academic Search

Because Bipolar Disorder (BD) individuals making highly lethal suicide attempts have greater injury burden and risk for suicide, early identification is critical. BD patients were classified as high- or low-lethality attempters. High-lethality attempts required inpatient medical treatment. Mixed effects logistic regression models and permutation analyses examined correlations between lethality, number, and order of attempts. High-lethality attempters reported greater suicidal intent

Maria A. Oquendo; Juan Jose Carballo; Namita Rajouria; Dianne Currier; Adrienne Tin; Jessica Merville; Hanga C. Galfalvy; Leo Sher; Michael F. Grunebaum; Ainsley K. Burke; J. John Mann

2009-01-01

321

Empirical Complexities in the Genetic Foundations of Lethal Mutagenesis  

PubMed Central

From population genetics theory, elevating the mutation rate of a large population should progressively reduce average fitness. If the fitness decline is large enough, the population will go extinct in a process known as lethal mutagenesis. Lethal mutagenesis has been endorsed in the virology literature as a promising approach to viral treatment, and several in vitro studies have forced viral extinction with high doses of mutagenic drugs. Yet only one empirical study has tested the genetic models underlying lethal mutagenesis, and the theory failed on even a qualitative level. Here we provide a new level of analysis of lethal mutagenesis by developing and evaluating models specifically tailored to empirical systems that may be used to test the theory. We first quantify a bias in the estimation of a critical parameter and consider whether that bias underlies the previously observed lack of concordance between theory and experiment. We then consider a seemingly ideal protocol that avoids this bias—mutagenesis of virions—but find that it is hampered by other problems. Finally, results that reveal difficulties in the mere interpretation of mutations assayed from double-strand genomes are derived. Our analyses expose unanticipated complexities in testing the theory. Nevertheless, the previous failure of the theory to predict experimental outcomes appears to reside in evolutionary mechanisms neglected by the theory (e.g., beneficial mutations) rather than from a mismatch between the empirical setup and model assumptions. This interpretation raises the specter that naive attempts at lethal mutagenesis may augment adaptation rather than retard it.

Bull, James J.; Joyce, Paul; Gladstone, Eric; Molineux, Ian J.

2013-01-01

322

Mucidin-nonproducing mutants of oudemansiella mucida.  

PubMed

Mutants of Oudemansiella mucida, blocked in the biosynthesis of the antibiotic mucidin, were obtained at a 0.28% frequency after the application of N-methyl-N'-nitro-N-nitrosoguanidine (MNG) to basidiospores under conditions leading to 0.5--5.0% survival rates. Loss of antibiotic activity was in most isolates accompanied by a decrease in mycelium growth rate and a suppression of dikaryotizing and fructification ability. Recombination analysis of two stable mutants revealed that the block in mucidin synthesis is the result of mutation in the same chromosomal gene (muc). In contrast to the action of MNG, UV-irradiation leads neither to the loss of biosynthetic activity nor to any morphological change. PMID:7193624

Semerdzieva, M; Musílek, V

1981-01-01

323

Conformational properties of nine purified cystathionine beta-synthase mutants  

PubMed Central

Protein misfolding due to missense mutations is a common pathogenic mechanism in cystathionine beta-synthase (CBS) deficiency. In our previous studies, we have successfully expressed, purified and characterized nine CBS mutant enzymes containing the following patient mutations: P49L, P78R, A114V, R125Q, E176K, R266K, P422L, I435T and S466L. These purified mutants exhibited full heme saturation, normal tetrameric assembly and high catalytic activity. In this work, we used several spectroscopic and proteolytic techniques to provide a more thorough insight into the conformation of these mutant enzymes. Far-UV circular dichroism, fluorescence and second derivative-UV spectroscopy revealed that the spatial arrangement of these CBS mutants is similar to the wild-type although the microenvironment of the chromophores may be slightly altered. Using proteolysis with thermolysin under native conditions, we found that the majority of the studied mutants is more susceptible towards cleavage suggesting their increased local flexibility or propensity to local unfolding. Interestingly, the presence of the CBS allosteric activator, S-adenosylmethionine (AdoMet), increased the cleavage rate of wild-type and the AdoMet-responsive mutants, while the proteolytic rate of the AdoMet-unresponsive mutants was not significantly changed. Pulse proteolysis analysis suggested that the protein structure of the R125Q and E176K mutants is significantly less stable than that of wild-type and the other mutants. Taken together, the proteolytic data show that the conformation of pathogenic mutants is altered despite retained catalytic activity and normal tetrameric assembly. This study demonstrates that the proteolytic techniques are a useful tool for the assessment of the biochemical penalty of missense mutations in CBS.

Hnizda, Ales; Majtan, Tomas; Liu, Lu; Pey, Angel L.; Carpenter, John F.; Kodicek, Milan; Kozich, Viktor; Kraus, Jan P.

2012-01-01

324

Fitness Analyses of All Possible Point-Mutants for Regions of Genes in Yeast  

PubMed Central

Deep sequencing can accurately measure the relative abundance of hundreds of mutants in a single bulk competition experiment, which can give a direct readout of the fitness of each mutant. Here, we describe a protocol that we previously developed and optimized to measure the fitness effects of all possible individual codon substitutions for 10 amino acid regions of essential genes in yeast. Starting with a conditional strain (i.e., a temperature sensitive strain), we describe how to efficiently generate plasmid libraries of point mutants that can then be transformed to generate libraries of yeast. The yeast libraries are competed under conditions that select for mutant function. Deep sequencing analyses are used to determine the relative fitness of all mutants. This approach is faster and cheaper per mutant compared to analyzing individually isolated mutants. The protocol can be performed in ~4 weeks and many 10 amino acid regions can be analyzed in parallel.

Hietpas, Ryan; Roscoe, Benjamin; Jiang, Li; Bolon, Daniel N. A.

2012-01-01

325

Four mutants of Micrococcus radiodurans defective in the ability to repair DNA damaged by mitomycin-C, two of which have wild-type resistance to ultraviolet radiation  

Microsoft Academic Search

Four genes concerned with the resistance of wild-type Micrococcus radiodurans to the lethal action of mitomycin-C (MTC), mtcA, mtcB, uvsA and uvsB, have been identified by isolating mutants sensitive to MTC.

B. E. B. Moseley; H. J. R. Copland

1978-01-01

326

Novel memory mutants in Drosophila : Behavioral characteristics of the P-Insertional mutant Ent2 P124  

Microsoft Academic Search

The Drosophila mutant P124, carrying insertion of P (lacW) vector in the second chromosome on the background of the w mutation in the X chromosome, was previously isolated as showing memory deficiency after courtship conditioning. Here we\\u000a report additional features of the mutant phenotype: (1) abnormal adaptation to darklight transition; (2) impaired perception\\u000a by males of nuances of visual image

N. G. Molotova; N. N. Iliadi; Yu. V. Bragina; E. A. Kamysheva; S. A. Soboleva; K. G. Iliadi; N. G. Kamyshev

2009-01-01

327

Crossover suppressors and balanced recessive lethals in Caenorhabditis elegans.  

PubMed

Two dominant suppressors of crossing over have been identified following X-ray treatment of the small nematode C. elegans. They suppress crossing over in linkage group II (LGII) about 100-fold and 50-fold and are both tightly linked to LGII markers. One, called C1, segregates independently of all other linkage groups and is homozygous fertile. The other is a translocation involving LGII and X. The translocation also suppresses crossing over along the right half of X and is homozygous lethal. C1 has been used as a balancer of LGII recessive lethal and sterile mutations induced by EMS. The frequencies of occurrence of lethals and steriles were approximately equal. Fourteen mutations were assigned to complementation groups and mapped. They tended to map in the same region where LGII visibles are clustered. PMID:631558

Herman, R K

1978-01-01

328

Lethal toxicity of cadmium to Cyprinus carpio and Tilapia aurea  

SciTech Connect

There have been several studies of the lethal toxicity of cadmium to freshwater fishes, but further information is required on a number of points. For example, the shallow slope which is characteristic of the cadmium toxicity curve makes interspecific comparisons difficult. There also is a paucity of information on cadmium toxicity to non-Salmonid European species. As part of a study of the water quality requirements of cultured fish species in the Mediterranean, the authors report on the lethal toxicity of cadmium to two such species, the common carp Cyprinus carpio, and Tilapia aurea, for which little information has previously been reported.

Not Available

1986-09-01

329

Legionella pneumophila mutants that are defective for iron acquisition and assimilation and intracellular infection.  

PubMed Central

Legionella pneumophila, a parasite of macrophages and protozoa, requires iron for optimal extracellular and intracellular growth. However, its mechanisms of iron acquisition remain uncharacterized. Using mini-Tn10 mutagenesis, we isolated 17 unique L. pneumophila strains which appeared to be defective for iron acquisition and assimilation. Eleven of these mutants were both sensitive to the iron chelator ethylenediamine di(o-hydroxyphenylacetic acid) and resistant to streptonigrin, an antibiotic whose lethal effect requires high levels of intracellular iron. Six mutants were also defective for the infection of macrophage-like U937 cells. Although none were altered in entry, mutants generally exhibited prolonged lag phases and in some cases replicated at slower rates. Overall, the reduced recoveries of mutants, relative to that of the wild type, ranged from 3- to 1,000-fold. Strain NU216, the mutant displaying the most severe lag phase and the slowest rate of replication, was studied further. Importantly, within U937 cells, NU216 was approximately 100-fold more sensitive than the wild type was to treatment with the Fe3+ chelator deferoxamine, indicating that it is defective for intracellular iron acquisition and assimilation. Furthermore, this strain was unable to mediate any cytopathic effect and was impaired for infectivity of an amoebal host. Taken together, the isolation of these mutants offers genetic proof that iron acquisition and assimilation are critical for intracellular infection by L. pneumophila.

Pope, C D; O'Connell, W; Cianciotto, N P

1996-01-01

330

Receptor-selective mutants of tumour necrosis factor in the therapy of cancer: preclinical studies.  

PubMed

The use of TNF-mutants that are selective agonists of the TNF-R55 is one strategy that is being explored to broaden the therapeutic margin of TNF. Several problems still have to be overcome before they can be used in clinical trials. Regarding the sensitizing effect of some infections and some tumours, we identified IFN-gamma as a mediator in BCG- but not in tumour-induced sensitization. In both models, the vessel wall is most probably the key tissue as alpha-LFA-1 antibodies could protect against lethality. Studies in primates showed that an unexpected feature, namely, the longer half-life of such mutants, might interfere with this strategy. Recent observations also indicate that the mechanism of tolerance-induction, another way to separate antitumour and toxic effects of TNF, might reside in the functional ablation of the TNF-R75. Using IL-60/0 knockout mice, we could not find any causal role for IL-6 in TNF-mediated lethality, this in contrast to results obtained previously with neutralizing antibodies. Finally, we identified the acute phase protein alpha 1-acid glycoprotein as a protein with protective properties towards TNF-induced lethality and liver damage. PMID:7895324

Brouckaert, P; Ameloot, P; Cauwels, A; Everaerdt, B; Libert, C; Takahashi, N; Van Molle, W; Fiers, W

1994-08-01

331

Inviability of a DNA2 deletion mutant is due to the DNA damage checkpoint.  

PubMed

Dna2 is a dual polarity exo/endonuclease, and 5' to 3' DNA helicase involved in Okazaki Fragment Processing (OFP) and Double-Strand Break (DSB) Repair. In yeast, DNA2 is an essential gene, as expected for a DNA replication protein. Suppression of the lethality of dna2? mutants has been found to occur by two mechanisms: overexpression of RAD27 (scFEN1) , encoding a 5' to 3' exo/endo nuclease that processes Okazaki fragments (OFs) for ligation, or deletion of PIF1, a 5' to 3' helicase involved in mitochondrial recombination, telomerase inhibition and OFP. Mapping of a novel, spontaneously arising suppressor of dna2? now reveals that mutation of rad9 and double mutation of rad9 mrc1 can also suppress the lethality of dna2? mutants. Interaction of dna2? and DNA damage checkpoint mutations provides insight as to why dna2? is lethal but rad27? is not, even though evidence shows that Rad27 (ScFEN1) processes most of the Okazaki fragments, while Dna2 processes only a subset. PMID:21508669

Budd, Martin E; Antoshechkin, Igor A; Reis, Clara; Wold, Barbara J; Campbell, Judith L

2011-05-15

332

Effects of sub-lethal and lethal doses of lambda-cyhalothrin on oviposition experience and host-searching behaviour of a parasitic wasp, Aphidius ervi.  

PubMed

In many parasitoid species, the recognition of chemical signals is essential to find specific hosts. This function is often impaired by exposure to insecticides that are usually neurotoxic. The behaviour of the Hymenopterous parasitoid Aphidius ervi (Haliday) (Hymenoptera: Aphidiinae) after surviving low doses of the pyrethroid lambda-cyhalothrin was examined in laboratory conditions. The host aphid was Myzus persicae (Sulzer) (Homoptera: Aphididae) on oilseed rape. Parasitoid females were exposed by contact with dry residues of the active ingredient at a lethal dose, LD20, and a sub-lethal dose, LD0.1. In a four-armed olfactometer, untreated and inexperienced females were attracted by the odour of M. persicae-infested plants and previous oviposition experience increased the duration of the attraction response. The response of inexperienced females decreased after an exposure to LD0.1 but not to LD20. No effect was observed when females had an oviposition experience prior to the olfactometer test. The oviposition activity was significantly decreased in the LD20-treated group but not in the LD0.1-treated one. All effects disappeared within 24h. Our work shows that orientation and oviposition behaviours may be impaired by low doses of lambda-cyhalothrin, depending on the dose, the parasitoid experience and the type of behaviour. PMID:15119601

Desneux, Nicolas; Pham-Delègue, Minh-Hà; Kaiser, Laure

2004-04-01

333

Determination of Lethality Rate Constants and D-Values for Bacillus atrophaeus (ATCC 9372) Spores Exposed to Dry Heat from 115°C to 170°C  

NASA Astrophysics Data System (ADS)

Dry heat microbial reduction is the NASA-approved sterilization method to reduce the microbial bioburden on spaceflight hardware for missions with planetary protection requirements. The method involves heating the spaceflight hardware to temperatures between 104°C and 125°C for up to 50 hours, while controlling the humidity to very low values. Collection of lethality data at temperatures above 125°C and with ambient (uncontrolled) humidity conditions would establish whether any microbial reduction credit can be offered to the flight project for processes that occur at temperatures greater than 125°C. The goal of this research is to determine the survival rates of Bacillus atrophaeus (ATCC 9372) spores subjected to temperatures higher than 125°C under both dry (controlled) and room ambient humidity (36 66% relative humidity) conditions. Spores were deposited inside thin, stainless steel thermal spore exposure vessels (TSEVs) and heated under ambient or controlled humidity conditions from 115°C to 170°C. After the exposures, the TSEVs were cooled rapidly, and the spores were recovered and plated. Survivor ratios, lethality rate constants, and D-values were calculated at each temperature. At 115°C and 125°C, the controlled humidity lethality rate constant was faster than th:e ambient humidity lethality rate constant. At 135°C, the ambient and controlled humidity lethality rate constants were statistically identical. At 150°C and 170°C, the ambient humidity lethality rate constant was slightly faster than the controlled humidity lethality rate constant. These results provide evidence for possibly modifying the NASA dry heat microbial reduction specification.

Kempf, M. J.; Schubert, W. W.; Beaudet, R. A.

2008-12-01

334

Design, Preparation, and Characterization of High-Activity Mutants of Human Butyrylcholinesterase Specific for Detoxification of Cocaine  

PubMed Central

Cocaine is a widely abused drug without a U.S. Food and Drug Administration-approved medication. There is a recognized, promising anticocaine medication to accelerate cocaine metabolism, producing biologically inactive metabolites via a route similar to the primary cocaine-metabolizing pathway [i.e., cocaine hydrolysis catalyzed by butyrylcholinesterase (BChE) in plasma]. An ideal, therapeutically valuable mutant of human BChE should have not only a significantly improved catalytic activity against (?)-cocaine but also certain selectivity for (?)-cocaine over neurotransmitter acetylcholine (ACh), such that one would not expect systemic administration of the BChE mutant to interrupt cholinergic transmission. The present study accounting for the mutation-caused changes of the catalytic activities of BChE against both (?)-cocaine and ACh by means of molecular modeling and site-directed mutagenesis has led to identification of three BChE mutants that have not only a considerably improved catalytic efficiency against (?)-cocaine but also the desirable selectivity for (?)-cocaine over ACh. Two representative BChE mutants have been confirmed to be potent in actual protection of mice from acute toxicity (convulsion and lethality) of a lethal dose of cocaine (180 mg/kg). Pretreatment with the BChE mutant (i.e., 1 min before cocaine administration) dose-dependently protected mice against cocaine-induced convulsions and lethality. In particular, all mice pretreated with the mutant (e.g., 0.02 mg or more of A199S/F227A/S287G/A328W/E441D BChE) survived. The in vivo data reveal the primary factor (i.e., the relative catalytic efficiency), determining the efficacy in practical protection of mice from the acute cocaine toxicity and future direction for further improving the efficacy of the enzyme in the cocaine overdose treatment.

Xue, Liu; Ko, Mei-Chuan; Tong, Min; Yang, Wenchao; Hou, Shurong; Fang, Lei; Liu, Junjun; Zheng, Fang; Woods, James H.; Tai, Hsin-Hsiung

2011-01-01

335

Conditional control of gene function by an invertible gene trap in zebrafish  

PubMed Central

Conditional mutations are essential for determining the stage- and tissue-specific functions of genes. Here we achieve conditional mutagenesis in zebrafish using FT1, a gene-trap cassette that can be stably inverted by both Cre and Flp recombinases. We demonstrate that intronic insertions in the gene-trapping orientation severely disrupt the expression of the host gene, whereas intronic insertions in the neutral orientation do not significantly affect host gene expression. Cre- and Flp-mediated recombination switches the orientation of the gene-trap cassette, permitting conditional rescue in one orientation and conditional knockout in the other. To illustrate the utility of this system we analyzed the functional consequence of intronic FT1 insertion in supv3l1, a gene encoding a mitochondrial RNA helicase. Global supv311 mutants have impaired mitochondrial function, embryonic lethality, and agenesis of the liver. Conditional rescue of supv311 expression in hepatocytes specifically corrected the liver defects. To test whether the liver function of supv311 is required for viability we used Flp-mediated recombination in the germline to generate a neutral allele at the locus. Subsequently, tissue-specific expression of Cre conditionally inactivated the targeted locus. Hepatocyte-specific inactivation of supv311 caused liver degeneration, growth retardation, and juvenile lethality, a phenotype that was less severe than the global disruption of supv311. Thus, supv311 is required in multiple tissues for organismal viability. Our mutagenesis approach is very efficient and could be used to generate conditional alleles throughout the zebrafish genome. Furthermore, because FT1 is based on the promiscuous Tol2 transposon, it should be applicable to many organisms.

Ni, Terri T.; Lu, Jianjun; Zhu, Meiying; Maddison, Lisette A.; Boyd, Kelli L.; Huskey, Lindsey; Ju, Bensheng; Hesselson, Daniel; Zhong, Tao P.; Page-McCaw, Patrick S.; Stainier, Didier Y.; Chen, Wenbiao

2012-01-01

336

Anthrax Lethal Factor Activates K+ Channels To Induce IL-1? Secretion in Macrophages  

PubMed Central

Anthrax lethal toxin (LeTx) is a virulence factor of Bacilillus anthracis that is a bivalent toxin, containing lethal factor (LF) and protective Ag proteins, which causes cytotoxicity and altered macrophage function. LeTx exposure results in early K+ efflux from macrophages associated with caspase-1 activation and increased IL-1? release. The mechanism of this toxin-induced K+ efflux is unknown. The goals of the current study were to determine whether LeTx-induced K+ efflux from macrophages is mediated by toxin effects on specific K+ channels and whether altered K+-channel activity is involved in LeTx-induced IL-1? release. Exposure of macrophages to LeTx induced a significant increase in the activities of two types of K+ channels that have been identified in mouse macrophages: Ba2+-sensitive inwardly rectifying K+ (Kir) channels and 4-aminopyridine–sensitive outwardly rectifying voltage-gated K+ (Kv) channels. LeTx enhancement of both Kir and Kv required the proteolytic activity of LF, because exposure of macrophages to a mutant LF-protein (LFE687C) combined with protective Ag protein had no effect on the currents. Furthermore, blocking Kir and Kv channels significantly decreased LeTx-induced release of IL-1?. In addition, retroviral transduction of macrophages with wild-type Kir enhanced LeTx-induced release of IL-1?, whereas transduction of dominant-negative Kir blocked LeTx-induced release of IL-1?. Activation of caspase-1 was not required for LeTx-induced activation of either of the K+ channels. These data indicate that a major mechanism through which LeTx stimulates macrophages to release IL-1? involves an LF-protease effect that enhances Kir and Kv channel function during toxin stimulation.

Thomas, Johnson; Epshtein, Yulia; Chopra, Arun; Ordog, Balazs; Ghassemi, Mahmood; Christman, John W.; Nattel, Stanley; Cook, James L.; Levitan, Irena

2012-01-01

337

Anthrax Lethal Toxin-Induced Gene Expression Changes in Mouse Lung  

PubMed Central

A major virulence factor of Bacillus anthracis is the anthrax Lethal Toxin (LeTx), a bipartite toxin composed of Protective Antigen and Lethal Factor. Systemic administration of LeTx to laboratory animals leads to death associated with vascular leakage and pulmonary edema. In this study, we investigated whether systemic exposure of mice to LeTx would induce gene expression changes associated with vascular/capillary leakage in lung tissue. We observed enhanced susceptibility of A/J mice to death by systemic LeTx administration compared to the C57BL/6 strain. LeTx-induced groups of both up- and down-regulated genes were observed in mouse lungs 6 h after systemic administration of wild type toxin compared to lungs of mice exposed to an inactive mutant form of the toxin. Lungs of the less susceptible C57BL/6 strain showed 80% fewer differentially expressed genes compared to lungs of the more sensitive A/J strain. Expression of genes known to regulate vascular permeability was modulated by LeTx in the lungs of the more susceptible A/J strain. Unexpectedly, the largest set of genes with altered expression was immune specific, characterized by the up-regulation of lymphoid genes and the down-regulation of myeloid genes. Transcripts encoding neutrophil chemoattractants, modulators of tumor regulation and angiogenesis were also differentially expressed in both mouse strains. These studies provide new directions for the investigation of vascular leakage and pulmonary edema induced by anthrax LeTx.

Dumas, Eric K.; Cox, Philip M.; Fullenwider, Charles O'Connor; Nguyen, Melissa; Centola, Michael; Frank, Mark Barton; Dozmorov, Igor; James, Judith A.; Farris, A. Darise

2011-01-01

338

Characterization of Streptomyces scabies mutants deficient in melanin biosynthesis.  

PubMed

Streptomyces scabies, a causal agent of common scab, produces both melanin and a secondary metabolite called thaxtomin A. To establish a possible relation between melanin and thaxtomin A production in S. scabies, we carried out N-methyl-N'-nitro-N-nitrosoguanidine (NTG) mutagenesis and isolated 11 melanin-negative mutants of S. scabies EF-35. These mutants were characterized for thaxtomin A production, pathogenicity, sporulation, and stress resistance. Nine of these mutants showed a significant reduction in thaxtomin A production when compared with the wild strain. However, only a few mutants exhibited a reduced level of virulence or a loss in their ability to induce common scab symptoms on potato tubers. Other pleiotrophic effects, such as higher sensitivity to heavy metals and incapacity to sporulate under certain stress conditions, were also associated with a deficiency in melanin production. PMID:15644924

Beauséjour, Julie; Beaulieu, Carole

2004-09-01

339

Not just gRASping at flaws: finding vulnerabilities to develop novel therapies for treating KRAS mutant cancers.  

PubMed

Mutations in Kirsten rat-sarcoma (KRAS) are well appreciated to be major drivers of human cancers through dysregulation of multiple growth and survival pathways. Similar to many other non-kinase oncogenes and tumor suppressors, efforts to directly target KRAS pharmaceutically have not yet materialized. As a result, there is broad interest in an alternative approach to develop therapies that induce synthetic lethality in cancers with mutant KRAS, therefore exposing the particular vulnerabilities of these cancers. Fueling these efforts is our increased understanding into the biology driving KRAS mutant cancers, in particular the important pathways that mutant KRAS governs to promote survival. In this mini-review, we summarize the latest approaches to treat KRAS mutant cancers and the rationale behind them. PMID:24612015

Ebi, Hiromichi; Faber, Anthony C; Engelman, Jeffrey A; Yano, Seiji

2014-05-01

340

Expression of mdr49 and mdr65 multidrug resistance genes in larval tissues of Drosophila melanogaster under normal and stress conditions.  

PubMed

In situ expression of 2 multidrug resistance genes, mdr49 and mdr65, of Drosophila melanogaster was examined in wild-type third instar larval tissues under physiological conditions and after heat shock or colchicine feeding. Expression of these 2 genes was also examined in tumorous tissues of lethal (2) giant larvae I(2)gl4 mutant larvae. These 2 mdr genes show similar constitutive expression in different larval tissues under physiological conditions. However, they are induced differentially by endogenous (tumorous growth) and exogenous stresses (colchcine feeding or heat shock): whereas heat shock and colchicine feeding induce mdr49, tumorous condition is accompanied by enhanced expression of mdr49 and mdr65 genes. PMID:15832942

Tapadia, Madhu G; Lakhotia, S C

2005-01-01

341

The Lethal "Femme Fatale" in the Noir Tradition.  

ERIC Educational Resources Information Center

Traces the lethal seductress through Hollywood's "noir" history from "Double Indemnity" (1944) to "The Last Seduction" (1996). Examines how this figure largely abjures traditional romance and passive domesticity, choosing instead to apply her sexuality to homicidal plots toward greed. Argues that her narrative positioning serves as a barometer of…

Boozer, Jack

2000-01-01

342

Cardiotoxic and Lethal Effects of Listeria monocytogenes Hemolysin  

PubMed Central

Cardiotoxic and lethal effects of Listeria monocytogenes hemolysin were studied in CD-1 mice injected with varying doses of hemolysin. Intravenous injection of 100 complete hemolytic units (CHU) caused 100% lethality within 4 to 5 min. Doses ranging from 40 to 50 CHU caused death of approximately 50% of the animals. Adrenergic blocking agents and antihistamine failed to protect mice against lethality and thereby suggested that death was not due to release of vasoactive agents by hemolysin. Plasma levels of creatine phosphokinase increased after intravenous administration of hemolysin and suggested myopathy, possibly of the myocardium. Electrocardiograms from hemolysin-treated mice indicated serious alterations in heart rate and rhythm, suggesting damage to contractile and pacemaker cardiac tissue. In addition, there were indications of increased potassium levels influencing the heart. Presumably, death was due to functional damage to heart muscle and electrical arrest. The cardiotoxic and lethal effects could be prevented by prior incubation of hemolysin with cholesterol, heating, or failure to reactivate the preparation with cysteine.

Kingdon, G. Charles; Sword, C. P.

1970-01-01

343

Tracking the clonal origin of lethal prostate cancer  

PubMed Central

Recent controversies surrounding prostate cancer overtreatment emphasize the critical need to delineate the molecular features associated with progression to lethal metastatic disease. Here, we have used whole-genome sequencing and molecular pathological analyses to characterize the lethal cell clone in a patient who died of prostate cancer. We tracked the evolution of the lethal cell clone from the primary cancer to metastases through samples collected during disease progression and at the time of death. Surprisingly, these analyses revealed that the lethal clone arose from a small, relatively low-grade cancer focus in the primary tumor, and not from the bulk, higher-grade primary cancer or from a lymph node metastasis resected at prostatectomy. Despite being limited to one case, these findings highlight the potential importance of developing and implementing molecular prognostic and predictive markers, such as alterations of tumor suppressor proteins PTEN or p53, to augment current pathological evaluation and delineate clonal heterogeneity. Furthermore, this case illustrates the potential need in precision medicine to longitudinally sample metastatic lesions to capture the evolving constellation of alterations during progression. Similar comprehensive studies of additional prostate cancer cases are warranted to understand the extent to which these issues may challenge prostate cancer clinical management.

Haffner, Michael C.; Mosbruger, Timothy; Esopi, David M.; Fedor, Helen; Heaphy, Christopher M.; Walker, David A.; Adejola, Nkosi; Gurel, Meltem; Hicks, Jessica; Meeker, Alan K.; Halushka, Marc K.; Simons, Jonathan W.; Isaacs, William B.; De Marzo, Angelo M.; Nelson, William G.; Yegnasubramanian, Srinivasan

2013-01-01

344

Predictors of Lethality in Severe Leptospirosis in Urban Brazil  

Microsoft Academic Search

To ascertain prognostic factors associated with fatal outcomes in severe leptospirosis, a retrospective case-control study was done using population-based surveillance data. Centralized death certificate reporting of lep- tospirosis mortality was combined with details of patients' hospitalizations, which were obtained from hospitals repre- senting all sectors of São Paulo city. Among identified leptospirosis cases, 89 lethal cases and 281 survivor cases

Anne S. Spichler; Pedro J. Vilaça; Daniel A. Athanazio; Jose O. M. Albuquerque; Marcia Buzzar; Bronislawa Castro; Antonio Seguro; Joseph M. Vinetz

345

Regulation of apoptosis by lethal cytokines in human mesothelial cells  

Microsoft Academic Search

Regulation of apoptosis by lethal cytokines in human mesothelial cells.BackgroundDysregulation of peritoneal cell death may contribute to the complications of peritoneal dialysis (PD). Chronic peritoneal dialysis and acute peritonitis are both associated with loss of mesothelial cells. In addition, acute peritonitis is characterized by sudden changes in the number of peritoneal leukocytes. However, the factors regulating peritoneal cell survival are

Marina Penélope Catalan; Dolores Subirá; Ana Reyero; Rafael Selgas; Arturo Ortiz-Gonzalez; Jesús Egido; Alberto Ortiz

2003-01-01

346

ACUTE LETHALITY OF COPPER, CADMIUM, AND ZINC TO NORTHERN SQUAWFISH  

EPA Science Inventory

Flow-through acute toxicity tests on juvenile northern squawfish (Ptychocheilus oregonensis) were conducted with copper, cadmium, and zinc. The 96-hour median lethal concentrations were 18 micrograms/liter for copper, 1,104 micrograms/liter for cadmium, and 3,693 micrograms/liter...

347

Effects of Salts on the Lethality of Paraquat.  

National Technical Information Service (NTIS)

Escherichia coli suffered 95 to 100% lethality when exposed to 1.0 mM paraquat for 30 min at 37 C in aerobic nutrient broth medium but did not lose viability when the exposure was done in Vogel Bonner or tryptic soy yeast extract medium. Paraquat was, how...

J. Kitzler I. Fridovich

1986-01-01

348

Susac's syndrome, a rare, potentially severe or lethal neurological disease  

Microsoft Academic Search

Susac's syndrome (SS) is a rare, immune-mediated endotheliopathy affecting the microvasculature of the brain, the inner ear and the retina. Clinical presentation is characterised by a triad: encephalopathy, hearing loss and branch retinal artery occlusion (BRAO). Given the rarity of this disease, its natural history still remains partially unknown, but lethal cases appear to be extremely rare since there has

A. Saux; G. Niango; M. Charif; R. Morales; F. Mura; A. Bonafe; I. Mourand

2010-01-01

349

Tracking the clonal origin of lethal prostate cancer.  

PubMed

Recent controversies surrounding prostate cancer overtreatment emphasize the critical need to delineate the molecular features associated with progression to lethal metastatic disease. Here, we have used whole-genome sequencing and molecular pathological analyses to characterize the lethal cell clone in a patient who died of prostate cancer. We tracked the evolution of the lethal cell clone from the primary cancer to metastases through samples collected during disease progression and at the time of death. Surprisingly, these analyses revealed that the lethal clone arose from a small, relatively low-grade cancer focus in the primary tumor, and not from the bulk, higher-grade primary cancer or from a lymph node metastasis resected at prostatectomy. Despite being limited to one case, these findings highlight the potential importance of developing and implementing molecular prognostic and predictive markers, such as alterations of tumor suppressor proteins PTEN or p53, to augment current pathological evaluation and delineate clonal heterogeneity. Furthermore, this case illustrates the potential need in precision medicine to longitudinally sample metastatic lesions to capture the evolving constellation of alterations during progression. Similar comprehensive studies of additional prostate cancer cases are warranted to understand the extent to which these issues may challenge prostate cancer clinical management. PMID:24135135

Haffner, Michael C; Mosbruger, Timothy; Esopi, David M; Fedor, Helen; Heaphy, Christopher M; Walker, David A; Adejola, Nkosi; Gürel, Meltem; Hicks, Jessica; Meeker, Alan K; Halushka, Marc K; Simons, Jonathan W; Isaacs, William B; De Marzo, Angelo M; Nelson, William G; Yegnasubramanian, Srinivasan

2013-11-01

350

Staphylococcal Superantigens Cause Lethal Pulmonary Disease in Rabbits  

PubMed Central

Background. The Centers for Disease Control and Prevention (CDC) and others reported that methicillinresistant S. aureus (MRSA) are significant causes of serious human infections, including pulmonary illnesses. We investigated the role played by superantigens in lung-associated lethal illness in rabbits. Methods. A rabbit model was established to investigate the potential role played by superantigens, staphylococcal enterotoxin B (SEB), staphylococcal enterotoxin C , and toxic chock syndrome toxin-1 (TSST-1). Rabbits received intrabronchial community-associated (CA) MRSA strains USA200 (TSST-1+), MW2 (SEC+), c99-529 (SEB+), Or Purified Superantigens. Some Rabbits Were Preimmunized Against Superantigens Or Treated With Soluble High-Affinity T Cell Receptors (V?-TCR) to Neutralize SEB and then challenged intrabronchially with CA-MRSA or superantigens. Results. Rabbits challenged with CA-MRSA or superantigens developed fatal, pulmonary illnesses. Animals preimmunized against purified superantigens, or treated passively with V?-TCRs and then challenged with CAMRSA or superantigens, survived. Lung histological analysis indicated that nonimmune animals developed lesions consistent with necrotizing pneumonia after challenge with CA-MRSA or purified superantigens. Superantigenimmune animals or animals treated with soluble Vb-TCRs did not develop pulmonary lesions. Conclusions. Superantigens contribute to lethal pulmonary illnesses due to CA-MRSA; preexisting immunity to superantigens prevents lethality. Administration of high-affinity V?-TCR with specificity for SEB to nonimmune animals protects from lethal pulmonary illness resulting from SEB+ CA-MRSA and SEB.

Strandberg, Kristi L.; Rotschafer, Jessica H.; Vetter, Sara M.; Buonpane, Rebecca A.; Kranz, David M.; Schlievert, Patrick M.

2010-01-01

351

66 MM Non-Lethal Grenade: Human Effects Review.  

National Technical Information Service (NTIS)

The purpose of this report is to assess the target effectiveness and the risks of severe (unacceptable) injury to those individuals who are impacted by the 66mm Non-Lethal Grenades (NLG) submunitions or projectiles (specifically the XM99 and the XM98) fro...

D. L. Gonzalez R. Constable T. Dayton J. Wilder B. J. Klauenberg

2003-01-01

352

Escherichia coli genes that reduce the lethal effects of stress  

Microsoft Academic Search

BACKGROUND: The continuing emergence of antimicrobial resistance requires the development of new compounds and\\/or enhancers of existing compounds. Genes that protect against the lethal effects of antibiotic stress are potential targets of enhancers. To distinguish such genes from those involved in drug uptake and efflux, a new susceptibility screen is required. RESULTS: Transposon (Tn5)-mediated mutagenesis was used to create a

Xiulin Han; Angella Dorsey-Oresto; Muhammad Malik; Jian-Ying Wang; Karl Drlica; Xilin Zhao; Tao Lu

2010-01-01

353

Standards for lethal response to problem urban wildlife  

Microsoft Academic Search

Managers face limited options when dealing with problems created by urban wildlife. Destroying an animal that is perceived to be a nuisance is sometimes acceptable; at other times destroying the animal may be controversial. This paper uses the structural norm approach to develop standards for an agency's use of lethal response to problem urban wildlife. The paper describes three structural

Karin Wittmann; Jerry J. Vaske; Michael J. Manfredo; Harry C. Zinn

1998-01-01

354

Acute Lethal Toxicity of Environmental Pollutants to Aquatic Organisms  

Microsoft Academic Search

The acute lethal toxicity of environment pollutants including chlorophenol, haloalkane, quinone, and substituted nitrobenzene (i.e., nitrophenol, nitrobenzene, nitrotoluene, and aniline) compounds to aquatic organisms was determined. Determination of toxicity of chemicals was performed with chlorella, daphnia, carp, and tilapia. The toxicity of chlorophenols had no relation to the number of chlorine atoms on the benzene ring, but monochlorophenol had lower

Jui-Hung Yen; Kuo-Hsiung Lin; Yei-Shung Wang

2002-01-01

355

Proinflammatory Mediators of Toxic Shock and Their Correlation to Lethality  

PubMed Central

Bacterial exotoxins and endotoxins both stimulate proinflammatory mediators but the contribution of each individual toxin in the release of mediators causing lethal shock is incompletely understood. This study examines the cytokine response and lethality of mice exposed to varying doses of staphylococcal enterotoxin B (SEB) or lipopolysaccharide (LPS) and their combinations. In vivo, SEB alone induced moderate levels of IL-2 and MCP-1 and all mice survived even with a high dose of SEB (100 ?g/mouse). LPS (80 ?g/mouse) caused 48% lethality and induced high levels of IL-6 and MCP-1. SEB induced low levels of TNF?, IL-1, IFN?, MIP-2, and LPS synergized with SEB in the expression of these cytokines and that of IL-6 and MCP-1. Importantly, the synergistic action of SEB and LPS resulted in lethal shock and hypothermia. ANOVA of cytokine levels by survival status of SEB-plus-LPS groups revealed significantly higher levels of TNF?, IL-6, MIP-2, and MCP-1 in nonsurvivors measured at 8 hours. Significantly higher levels of IFN? and IL-2 were observed at 21 hours in nonsurvivors of toxic shock compared to those in survivors. Overall, synergistic action of SEB and LPS resulted in higher and prolonged levels of these key cytokines leading to toxic shock.

Krakauer, Teresa; Buckley, Marilyn J.; Fisher, Diana

2010-01-01

356

Protection by phalloidin against lethal doses of phalloidin  

Microsoft Academic Search

Tolerated doses of phalloidin, a toxin from the mushroomAmanita phalloides, protect mice against lethal doses of phalloidin. Resistance is conferred by the 1\\/10 LD95 of phalloidin and sets in at about 8 hours after the pretreatment.

G. L. Floersheim

1976-01-01

357

Protection by phalloidin against lethal doses of phalloidin.  

PubMed

Tolerated doses of phalloidin, a toxin from the mushroom Amanita phalloides, protect mice against lethal doses of phalloidin. Resistance is conferred by the 1/10 LD95 of phalloidin and sets in at about 8 hours after the pretreatment. PMID:961546

Floersheim, G L

1976-07-01

358

Papaya Lethal Yellowing Virus (PLYV) Infects Vasconcellea cauliflora  

Microsoft Academic Search

Papaya lethal yellowing virus (PLYV) é um dos três vírus descritos infectando mamoeiros (Carica papaya L.) no Brasil. Vasconcellea cauliflora (Jacq.) A. DC., antes denominada de Carica cauliflora (Jacq.), é uma reconhecida fonte de resistência natural ao Papaya ringspot virus (PRSV), causador da \\

P. P. R. Amaral; Resende de R. O; M. T. Souza

2006-01-01

359

An overview of the future of non-lethal weapons.  

PubMed

During the past decade, vast changes have occurred in the geopolitical landscape and the nature of the types of conflicts in which technologically developed countries have been involved. While the threat of conventional war remains, forces have been more frequently deployed in situations that require great restraint. Adversaries are often likely to be elusive and commingled with noncombatants. There has been some shift in public opinion away from tolerance of collateral casualties. Therefore there is a need to be able to apply force while limiting casualties. Non-lethal weapons provide part of the solution. Among the changes that will influence the future have been studies by the US and NATO concerning the use of non-lethal weapons, coincidental with increased funding for their development and testing. New concepts and policies have recently been formalized. Surprisingly, the most strident objections to the implementation of non-lethal weapons have come from organizations that are ostensibly designed to protect non-combatants. These arguments are specious and, while technically and academically challenging, actually serve to foster an environment that will result in the deaths of many more innocent civilians. They misconstrue technology with human intent. The reasons for use of force will not abate. Alternatives to bombs, missiles, tanks and artillery must therefore be found. Non-lethal weapons are not a panacea but do offer the best hope of minimizing casualties while allowing nations or alliances the means to use force in protection of national or regional interests. PMID:11578037

Alexander, J B

2001-01-01

360

Subcutaneous wounding postirradiation reduces radiation lethality in mice.  

PubMed

The detonation of an improvised nuclear device during a radiological terrorist attack could result in the exposure of thousands of civilians and first responders to lethal or potentially lethal doses of ionizing radiation (IR). There is a major effort in the United States to develop phamacological mitigators of radiation lethality that would be effective particularly if administered after irradiation. We show here that giving female C57BL/6 mice a subcutaneous surgical incision after whole body exposure to an LD50/30 X-ray dose protects against radiation lethality and increases survival from 50% to over 90% (P = 0.0001). The increase in survival, at least in part, appears to be due to enhanced recovery of hematopoiesis, notably red blood cells, neutrophils and platelets. While a definitive mechanism has yet to be elucidated, we propose that this approach may be used to identify potentially novel mechanisms and pathways that could aid in the development of novel pharmacological radiation countermeasures. PMID:24811864

Garrett, Joy; Orschell, Christie M; Mendonca, Marc S; Bigsby, Robert M; Dynlacht, Joseph R

2014-06-01

361

Help-Seeking Behavior Prior to Nearly Lethal Suicide Attempts.  

ERIC Educational Resources Information Center

The association between help-seeking and nearly lethal suicide attempts was evaluated using data from a population-based, case-control study. Measures of help-seeking included type of consultant contacted, and whether suicide was discussed. Findings suggest efforts to better understand the role of help-seeking in suicide prevention deserves…

Barnes, Lauren Seymour; Ikeda, Robin M.; Kresnow, Marcie-jo

2002-01-01

362

A Lethal Disease Model for Hantavirus Pulmonary Syndrome  

Microsoft Academic Search

Hantaviruses are associated with two human diseases, hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS). Development of vaccines and therapies to prevent and treat HFRS and HPS have been hampered by the absence of a practical animal model. Here we report that Andes virus (ANDV), a South American hantavirus, is highly lethal in adult Syrian hamsters. The

J. W. Hooper; T. Larsen; D. M. Custer; C. S. Schmaljohn

2001-01-01

363

Correctors of the basic trafficking defect of the mutant F508del-CFTR that causes cystic fibrosis.  

PubMed

Cystic fibrosis (CF) is the most frequent lethal genetic disease and the most frequent mutation is F508del-cystic fibrosis transmembrane regulator (CFTR). In common with some other protein trafficking diseases the mutant protein is functional but recognized by the cellular quality control system retained in the endoplasmic reticulum (ER) and degraded. There have been some recent impressive advances in developing corrector compounds that restore the trafficking of the mutant protein to the plasma membrane. The targets of these correctors and possible mechanisms of action are discussed. PMID:23711435

Birault, Véronique; Solari, Roberto; Hanrahan, John; Thomas, David Y

2013-06-01

364

Lethal neuroleptic malignant syndrome due to amisulpride.  

PubMed

A 42-year old-man was found lying in his bed having seizures. Later he became unconscious and hypotonic developing mydriasis as well as rigidity. The body core temperature (rectal temperature) was above 42 °C. Blood pH was decreased during treatment, and his general condition deteriorated. The patient developed gasping respiration, ventricular fibrillation, and died. During autopsy and histological investigation cerebral and pulmonary edema were noted together with general congestion of the internal organs. Further observations included contraction bands of myocytes, a contracted spleen, fibrosis of the liver, and gall stones. Toxicological analyses of peripheral blood revealed the following results: amisulpride 4.65 mg/l, biperiden 0.12 mg/l, imipramine 0.33 mg/l, and desipramine 0.68 mg/l. An amisulpride-induced neuroleptic malignant syndrome was therefore diagnosed as the patho-physiological mechanism leading to death. PMID:23504701

Musshoff, Frank; Doberentz, Elke; Madea, Burkhard

2013-06-01

365

Improvement of heavy metal stress and toxicity assays by coupling a transgenic reporter in a mutant nematode strain.  

PubMed

Previous studies have demonstrated that wild type Caenorhabditis elegans displays high sensitivity to heavy metals in a lethality test at a level comparable to that of other bioindicator organisms. Taking advantage of the genetics of this model organism, we have tested a number of mutant strains for enhanced sensitivity in heavy metal induced lethality and stress response. These mutants are defective in genes controlling dauer formation, longevity or response to reactive oxygen species (ROS). Among the tested mutants, a double mutant daf-16 unc-75 strain was identified to have superior sensitivity. It has a 6-, 3- and 2-fold increase in sensitivity to cadmium, copper and zinc, respectively, as compared with that of wild type animals. When a fluorescent reporter transgene was coupled with this double mutant for stress detection, a 10-fold enhancement of sensitivity to cadmium over the wild type strain was observed. These transgenic animals, superior to most of the model organisms currently used in bioassays for environmental pollutants, offer a fast and economic approach to reveal the bioavailability of toxic substance in field samples. This study also demonstrates that combination of genetic mutations and transgenesis is a viable approach to identify sensitive indicator animals for environmental monitoring. PMID:16040138

Chu, Ka-Wah; Chan, Shirley K W; Chow, King L

2005-09-30

366

Influence of Temperature and Pressure on the Lethality of Ultrasound  

PubMed Central

A specially designed resistometer was constructed, and the lethal effect on Yersinia enterocolitica of ultrasonic waves (UW) at different static pressures (manosonication [MS]) and of combined heat-UW under pressure treatments (manothermosonication [MTS]) was investigated. During MS treatments at 30°C and 200 kPa, the increase in the amplitude of UW of 20 kHz from 21 to 150 ?m exponentially decreased decimal reduction time values (DMS) from 4 to 0.37 min. When pressure was increased from 0 to 600 kPa at a constant amplitude (150 ?m) and temperature (30°C), DMS values decreased from 1.52 to 0.20 min. The magnitude of this decrease in DMS declined progressively as pressure was increased. The influence of pressure on DMS values was greater with increased amplitude of UW. Pressure alone of as much as 600 kPa did not influence the heat resistance of Y. enterocolitica (D60 = 0.094; z = 5.65). At temperatures of as much as 58°C, the lethality of UW under pressure was greater than that of heat treatment alone at the same temperature. At higher temperatures, this difference disappeared. Heat and UW under pressure seemed to act independently. The lethality of MTS treatments appeared to result from the added effects of UW under pressure and the lethal effect of heat. The individual contributions of heat and of UW under pressure to the total lethal effect of MTS depended on temperature. The inactivating effect of UW was not due to titanium particles eroded from the sonication horn. The addition to the MS media of cysteamine did not increase the resistance of Y. enterocolitica to MS treatment. MS treatment caused cell disruption.

Raso, J.; Pagan, R.; Condon, S.; Sala, F. J.

1998-01-01

367

A Multivariate Model of Stakeholder Preference for Lethal Cat Management  

PubMed Central

Identifying stakeholder beliefs and attitudes is critical for resolving management conflicts. Debate over outdoor cat management is often described as a conflict between two groups, environmental advocates and animal welfare advocates, but little is known about the variables predicting differences among these critical stakeholder groups. We administered a mail survey to randomly selected stakeholders representing both of these groups (n?=?1,596) in Florida, where contention over the management of outdoor cats has been widespread. We used a structural equation model to evaluate stakeholder intention to support non-lethal management. The cognitive hierarchy model predicted that values influenced beliefs, which predicted general and specific attitudes, which in turn, influenced behavioral intentions. We posited that specific attitudes would mediate the effect of general attitudes, beliefs, and values on management support. Model fit statistics suggested that the final model fit the data well (CFI?=?0.94, RMSEA?=?0.062). The final model explained 74% of the variance in management support, and positive attitudes toward lethal management (humaneness) had the largest direct effect on management support. Specific attitudes toward lethal management and general attitudes toward outdoor cats mediated the relationship between positive (p<0.05) and negative cat-related impact beliefs (p<0.05) and support for management. These results supported the specificity hypothesis and the use of the cognitive hierarchy to assess stakeholder intention to support non-lethal cat management. Our findings suggest that stakeholders can simultaneously perceive both positive and negative beliefs about outdoor cats, which influence attitudes toward and support for non-lethal management.

Wald, Dara M.; Jacobson, Susan K.

2014-01-01

368

Empirical complexities in the genetic foundations of lethal mutagenesis.  

PubMed

From population genetics theory, elevating the mutation rate of a large population should progressively reduce average fitness. If the fitness decline is large enough, the population will go extinct in a process known as lethal mutagenesis. Lethal mutagenesis has been endorsed in the virology literature as a promising approach to viral treatment, and several in vitro studies have forced viral extinction with high doses of mutagenic drugs. Yet only one empirical study has tested the genetic models underlying lethal mutagenesis, and the theory failed on even a qualitative level. Here we provide a new level of analysis of lethal mutagenesis by developing and evaluating models specifically tailored to empirical systems that may be used to test the theory. We first quantify a bias in the estimation of a critical parameter and consider whether that bias underlies the previously observed lack of concordance between theory and experiment. We then consider a seemingly ideal protocol that avoids this bias-mutagenesis of virions-but find that it is hampered by other problems. Finally, results that reveal difficulties in the mere interpretation of mutations assayed from double-strand genomes are derived. Our analyses expose unanticipated complexities in testing the theory. Nevertheless, the previous failure of the theory to predict experimental outcomes appears to reside in evolutionary mechanisms neglected by the theory (e.g., beneficial mutations) rather than from a mismatch between the empirical setup and model assumptions. This interpretation raises the specter that naive attempts at lethal mutagenesis may augment adaptation rather than retard it. PMID:23934886

Bull, James J; Joyce, Paul; Gladstone, Eric; Molineux, Ian J

2013-10-01

369

The mutant selection window and antimicrobial resistance  

Microsoft Academic Search

The mutant selection window is an antimicrobial concentration range extending from the minimal concen- tration required to block the growth of wild-type bacteria up to that required to inhibit the growth of the least susceptible, single-step mutant. The upper boundary is also called the mutant prevention concentration (MPC). Placing antimicrobial concentrations inside the window is expected to enrich resistant mutant

Karl Drlica

2003-01-01

370

Recombination between mutant cauliflower mosaic virus DNAs  

Microsoft Academic Search

A class of mutants of cauliflower mosaic virus (CaMV) DNA was distinguished based on its members' ability to induce symptoms when coinoculated on plants with other CaMV DNAs mutant at a different locus. Three mutants, one each in open reading frame I, III, and VI had this ability. A second class of mutant DNAs did not induce symptoms unless combined

In Seong Choe; Ulrich Melcher; Ken Richards; Genevieve Lebeurier; Richard C Essenberg

1985-01-01

371

A fluence response study of lethality and mutagenicity of white, black, and blue fluorescent light, sunlamp, and sunlight irradiation in Chinese hamster ovary cells.  

PubMed

Under a set of defined experimental conditions, the fluence response of Chinese hamster ovary (CHO) cells to various light sources was studied by measuring single-cell survival and mutation to 6-thioguanine (TG) resistance. Fluorescent white, black, and blue lights were sightly lethal and mutagenic. Sunlamp light was highly lethal and mutagenic, exhibiting these biological effects within 15 sec of exposure under conditions recommended by the manufacturer for human use. Lethal and mutagenic effects were observed after 5 min of sunlight exposure; responses varied with hourly and daily variations in solar radiation. Sunlight-induced TG-resistant variants possessed less than 5% of parental cellular hypoxanthine--guanine phosphoribosyl transferase (HGPRT) enzyme activity, suggesting that the mutation induction occurs at this locus. The cell survival and mutation-induction curves generated by exposure of cells to both sunlamp and sunlight were similar to those obtained by the use of a standard far-UV lamp. PMID:593289

Hsie, A W; Li, A P; Machanoff, R

1977-12-01

372

Recovery of cells from heat-induced potentially lethal damage: effects of pH and nutrient environment  

Microsoft Academic Search

Plateau phase HA-1 cells exposed to 43°C recovered from potentially lethal damage (PLD), but only under severely restricted conditions. Recovery occurred only if the initial survival level exceeded 10⁻³, and then only if the heating occurred in medium containing serum. In Hanks' balanced salt solution, pH effects were minimized; survival values of cells heated at pH 6.7 or 7.5 were

Gloria C. Li; E. C. Schiu; George M. Hahn

1980-01-01

373

Isolation and characterization of acid-sensitive mutants of Pediococcus acidilactici.  

PubMed

Acid-sensitive mutants of Pediococcus acidilactici BCC 9545, a starter culture of the Thai fermented pork sausage nham, were isolated as spontaneous neomycin resistant mutants. The mutants generally produced less acid and acidified the culture media less than the parent strain in a 72 h culturing period. Interestingly, the ATPase activities of the mutants did not differ considerably from that of the parent strain in acidic conditions. It was also found that the internal pH values of the mutant strains were somewhat lower in neutral environment, while at pH 5.0 their internal pHs were significantly lower compared to the parent's. Inhibiting the H(+)-ATPase activities in energized cells by N,N'-dicyclohexyl carbodiimide also revealed that protons were leaking from the mutants at neutral pH, which increased under acidic conditions. In contrast, the parent strain exhibited a smaller proton leak and only under acidic conditions. The membrane fatty acid analysis of the mutants indicated that under acidic conditions the mutants had a significantly smaller major unsaturated/saturated fatty acids ratio ((C(18:1)+C(18:3n6))/(C(16:0)+C(18:0))) compared to the parent strain's membrane. Taken together, these observations suggest there is a reasonable possibility that the membrane fatty acid profile differences in the mutants resulted in their acid-sensitivity. PMID:19028310

Kurdi, Peter; Smitinont, Thitapha; Valyasevi, Ruud

2009-02-01

374

A New CULLIN 1 Mutant Has Altered Responses to Hormones and Light in Arabidopsis1[C][OA  

PubMed Central

Regulated protein degradation contributes to plant development by mediating signaling events in many hormone, light, and developmental pathways. Ubiquitin ligases recognize and ubiquitinate target proteins for subsequent degradation by the 26S proteasome. The multisubunit SCF is the best-studied class of ubiquitin ligases in Arabidopsis (Arabidopsis thaliana). However, the extent of SCF participation in signaling networks is unclear. SCFs are composed of four subunits: CULLIN 1 (CUL1), ASK, RBX1, and an F-box protein. Null mutations in CUL1 are embryo lethal, limiting insight into the role of CUL1 and SCFs in later stages of development. Here, we describe a viable and fertile weak allele of CUL1, called cul1-6. cul1-6 plants have defects in seedling and adult morphology. In addition to reduced auxin sensitivity, cul1-6 seedlings are hyposensitive to ethylene, red, and blue light conditions. An analysis of protein interactions with the cul1-6 gene product suggests that both RUB (related to ubiquitin) modification and interaction with the SCF regulatory protein CAND1 (cullin associated and neddylation dissociated) are disrupted. These findings suggest that the morphological defects observed in cul1-6 plants are caused by defective SCF complex formation. Characterization of weak cul1 mutants provides insight into the role of SCFs throughout plant growth and development.

Moon, Jennifer; Zhao, Yunde; Dai, Xinhua; Zhang, Wenjing; Gray, William M.; Huq, Enamul; Estelle, Mark

2007-01-01

375

Development of a non-lethal method for evaluating transcriptomic endpoints in Arctic grayling (Thymallus arcticus).  

PubMed

With increases in active mining and continued discharge associated with former mine operations, evaluating the health of watersheds in the Canadian Yukon Territory is warranted. Current environmental assessment approaches often employ guidelines established using sentinel species not relevant to Arctic monitoring programs. The present study focused on the successful development of a quantitative real-time polymerase chain reaction (qPCR) assay directed towards the indigenous Arctic grayling (Thymallus arcticus) and examines the feasibility of using non-lethal sampling from the caudal fin as a means for evaluation of mRNA abundance profiles reflective of environmental conditions. In a proof of concept study performed blind, qPCR results from animals in an area with elevated water concentrations of cadmium (Cd) and zinc (Zn) and higher body burdens of Cd, Zn, and lead (Pb) were compared to a reference location in the Yukon Territory. Lower condition factor and a higher abundance of hepatic and caudal fin gene transcripts encoding the metallothionein isoforms (mta/mtb), in addition to elevated heat shock protein 70 (hsp70) and catalase (cat) mRNAs in liver, were observed in fish from the test site. The strong positive correlation between metal body burden and caudal fin mta/mtb mRNA abundance demonstrates a high potential for use of the Arctic grayling assay in non-lethal environmental monitoring programs. PMID:24780232

Veldhoen, Nik; Beckerton, Jean E; Mackenzie-Grieve, Jody; Stevenson, Mitchel R; Truelson, Robert L; Helbing, Caren C

2014-07-01

376

Trapping Cardiac Recessive Mutants via Expression-based Insertional Mutagenesis Screening  

PubMed Central

Rationale Mutagenesis screening is a powerful genetic tool for probing biological mechanisms underlying vertebrate development and human diseases. However, the increased colony management efforts in vertebrates impose a significant challenge for identifying genes affecting a particular organ such as the heart, especially those exhibiting adult phenotypes upon depletion. Objective We aim to develop a facile approach that streamlines colony management efforts via enriching cardiac mutants, which enables us to screen for adult phenotypes. Methods and Results The transparency of the zebrafish embryos enabled us to score 67 stable transgenic lines generated from an insertional mutagenesis screen using a transposon-based protein trapping vector. Fifteen lines with cardiac monomeric red fluorescent protein (mRFP) reporter expression were identified. We defined the molecular nature for 10 lines and bred them to homozygosity, which led to the identification of one embryonic lethal, one larval lethal, and one adult recessive mutant exhibiting cardiac hypertrophy at one year of age. Further characterization of these mutants uncovered an essential function of methionine adenosyltransferase II, alpha a (mat2aa) in cardiogenesis, an essential function of mitochondrial ribosomal protein S18B (mrps18b) in cardiac mitochondrial homeostasis, as well as a function of DnaJ (Hsp40) homolog, subfamily B, member 6b (dnajb6b) in adult cardiac hypertrophy. Conclusions We demonstrate that transposon-based gene trapping is an efficient approach for identifying both embryonic and adult recessive mutants with cardiac expression. The generation of a Zebrafish Insertional Cardiac (ZIC) mutant collection shall facilitate the annotation of a vertebrate cardiac genome, as well as enable heart-based adult screens.

Ding, Yonghe; Liu, Weibin; Deng, Yun; Jomok, Beninio; Yang, Jingchun; Huang, Wei; Clark, Karl J.; Zhong, Tao P.; Lin, Xueying; Ekker, Stephen C.; Xu, Xiaolei

2013-01-01

377

Design, overexpression, and purification of polymerization-blocked yeast ??-tubulin mutants.  

PubMed

Microtubule dynamics play essential roles in intracellular organization and cell division. They result from structural and biochemical properties of ??-tubulin heterodimers and how these polymerizing subunits interact with themselves and with regulatory proteins. A broad understanding of the underlying mechanisms has been established, but fundamental questions remain unresolved. The lack of routine access to recombinant ??-tubulin represents an obstacle to deeper insight into ??-tubulin structure, biochemistry, and recognition. Indeed, the widespread reliance on animal brain ??-tubulin means that very few in vitro studies have taken advantage of powerful and ordinarily routine techniques like site-directed mutagenesis. Here we report new methods for purifying wild-type or mutant yeast ??-tubulin from inducibly overexpressing strains of Saccharomyces cerevisiae. Inducible overexpression is an improvement over existing approaches that rely on constitutive expression: it provides higher yields while also allowing otherwise lethal mutants to be purified. We also designed and purified polymerization-blocked ??-tubulin mutants. These "blocked" forms of ??-tubulin give a dominant lethal phenotype when expressed in cells; they cannot form microtubules in vitro and when present in mixtures inhibit the polymerization of wild-type ??-tubulin. The effects of blocking mutations are very specific, because purified mutants exhibit normal hydrodynamic properties, bind GTP, and interact with a tubulin-binding domain. The ability to overexpress and purify wild-type ??-tubulin, or mutants like the ones we report here, creates new opportunities for structural studies of ??-tubulin and its complexes with regulatory proteins, and for biochemical and functional studies of microtubule dynamics and its regulation. PMID:21888381

Johnson, Vinu; Ayaz, Pelin; Huddleston, Patrick; Rice, Luke M

2011-10-11

378

Complete blockage of the mevalonate pathway results in male gametophyte lethality  

PubMed Central

Plants have two isoprenoid biosynthetic pathways: the cytosolic mevalonate (MVA) pathway and the plastidic 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. Since the discovery of the MEP pathway, possible metabolic cross-talk between these pathways has prompted intense research. Although many studies have shown the existence of such cross-talk using feeding experiments, it remains to be determined if native cross-talk, rather than exogenously applied metabolites, can compensate for complete blockage of the MVA pathway. Previously, Arabidopsis mutants for HMG1 and HMG2 encoding HMG-CoA reductase (HMGR) were isolated. Although it was shown that HMGR1 is a functional HMGR, the enzyme activity of HMGR2 has not been confirmed. It is demonstrated here that HMG2 encodes a functional reductase with similar activity to HMGR1, using enzyme assays and complementation experiments. To estimate the contribution of native cross-talk, an attempt was made to block the MVA pathway by making double mutants lacking both HMG1 and HMG2, but no double homozygotes were detected in the progeny of self-pollinated HMG1/hmg1 hmg2/hmg2 plants. hmg1 hmg2 male gametophytes appeared to be lethal based on crossing experiments, and microscopy indicated that ?50% of the microspores from the HMG1/hmg1 hmg2/hmg2 plant appeared shrunken and exhibited poorly defined endoplasmic reticulum membranes. In situ hybridization showed that HMG1 transcripts were expressed in both the tapetum and microspores, while HMG2 mRNA appeared only in microspores. It is concluded that native cross-talk from the plastid cannot compensate for complete blockage of the MVA pathway, at least during male gametophyte development, because either HMG1 or HMG2 is required for male gametophyte development.

Suzuki, Masashi; Nakagawa, Shoko; Kamide, Yukiko; Kobayashi, Keiko; Ohyama, Kiyoshi; Hashinokuchi, Hiromi; Kiuchi, Reiko; Saito, Kazuki; Muranaka, Toshiya; Nagata, Noriko

2009-01-01

379

Burkholderia pseudomallei Known Siderophores and Hemin Uptake Are Dispensable for Lethal Murine Melioidosis  

PubMed Central

Burkholderia pseudomallei is a mostly saprophytic bacterium, but can infect humans where it causes the difficult-to-manage disease melioidosis. Even with proper diagnosis and prompt therapeutic interventions mortality rates still range from >20% in Northern Australia to over 40% in Thailand. Surprisingly little is yet known about how B. pseudomallei infects, invades and survives within its hosts, and virtually nothing is known about the contribution of critical nutrients such as iron to the bacterium's pathogenesis. It was previously assumed that B. pseudomallei used iron-acquisition systems commonly found in other bacteria, for example siderophores. However, our previous discovery of a clinical isolate carrying a large chromosomal deletion missing the entire malleobactin gene cluster encoding the bacterium's major high-affinity siderophore while still being fully virulent in a murine melioidosis model suggested that other iron-acquisition systems might make contributions to virulence. Here, we deleted the major siderophore malleobactin (mba) and pyochelin (pch) gene clusters in strain 1710b and revealed a residual siderophore activity which was unrelated to other known Burkholderia siderophores such as cepabactin and cepaciachelin, and not due to increased secretion of chelators such as citrate. Deletion of the two hemin uptake loci, hmu and hem, showed that Hmu is required for utilization of hemin and hemoglobin and that Hem cannot complement a Hmu deficiency. Prolonged incubation of a hmu hem mutant in hemoglobin-containing minimal medium yielded variants able to utilize hemoglobin and hemin suggesting alternate pathways for utilization of these two host iron sources. Lactoferrin utilization was dependent on malleobactin, but not pyochelin synthesis and/or uptake. A mba pch hmu hem quadruple mutant could use ferritin as an iron source and upon intranasal infection was lethal in an acute murine melioidosis model. These data suggest that B. pseudomallei may employ a novel ferritin-iron acquisition pathway as a means to sustain in vivo growth.

Kvitko, Brian H.; Goodyear, Andrew; Propst, Katie L.; Dow, Steven W.; Schweizer, Herbert P.

2012-01-01

380

Hydrocarbon assimilation and biosurfactant production in Pseudomonas aeruginosa mutants.  

PubMed Central

We isolated transposon Tn5-GM-induced mutants of Pseudomonas aeruginosa PG201 that were unable to grow in minimal media containing hexadecane as a carbon source. Some of these mutants lacked extracellular rhamnolipids, as shown by measuring the surface and interfacial tensions of the cell culture supernatants. Furthermore, the concentrated culture media of the mutant strains were tested for the presence of rhamnolipids by thin-layer chromatography and for rhamnolipid activities, including hemolysis and growth inhibition of Bacillus subtilis. Mutant 65E12 was unable to produce extracellular rhamnolipids under any of the conditions tested, lacked the capacity to take up 14C-labeled hexadecane, and did not grow in media containing individual alkanes with chain lengths ranging from C12 to C19. However, growth on these alkanes and uptake of [14C]hexadecane were restored when small amounts of purified rhamnolipids were added to the cultures. Mutant 59C7 was unable to grow in media containing hexadecane, nor was it able to take up [14C]hexadecane. The addition of small amounts of rhamnolipids restored growth on alkanes and [14C]hexadecane uptake. In glucose-containing media, however, mutant 59C7 produced rhamnolipids at levels about twice as high as those of the wild-type strain. These results show that rhamnolipids play a major role in hexadecane uptake and utilization by P. aeruginosa. Images

Koch, A K; Kappeli, O; Fiechter, A; Reiser, J

1991-01-01

381

Respiratory distress and early neonatal lethality in hspa4l/hspa4 double-mutant mice.  

PubMed

Heat shock proteins HSPA4L and HSPA4 are closely related members of the HSP110 family and act as cochaperones. We generated Hspa4l(-/-)Hspa4(-/-) mice to investigate a functional complementarity between HSPA4L and HSPA4 during embryonic development. Hspa4l(-/-)Hspa4(-/-) embryos exhibited marked pulmonary hypoplasia and neonatal death. Compared with lungs of wild-type, Hspa4l(-/-), and Hspa4(-/-) embryos, Hspa4l(-/-)Hspa4(-/-) lungs were characterized by diminished saccular spaces and increased mesenchymal septa. Mesenchymal hypercellularity was determined to be due to an increased cell proliferation index and decreased cell death. A significant increase in expression levels of prosurvival protein B cell leukemia/lymphoma 2 may be the cause for inhibition of apoptotic process in lungs of Hspa4(-/-)Hspa4l(-/-) embryos. Accumulation of glycogen and diminished expression of surfactant protein B, prosurfactant protein C, and aquaporin 5 in saccular epithelium suggested impaired maturation of type II and type I pneumocytes in the Hspa4l(-/-)Hspa4(-/-) lungs. Further experiments showed a significant accumulation of ubiquitinated proteins in the lungs of Hspa4l(-/-)Hspa4(-/-) embryos, indicating an impaired chaperone activity. Our study demonstrates that HSPA4L and HSPA4 collaborate in embryonic lung maturation, which is necessary for adaptation to air breathing at birth. PMID:23980576

Mohamed, Belal A; Barakat, Amal Z; Held, Torsten; Elkenani, Manar; Mühlfeld, Christian; Männer, Jörg; Adham, Ibrahim M

2014-04-01

382

Dach1 Mutant Mice Bear No Gross Abnormalities in Eye, Limb, and Brain Development and Exhibit Postnatal Lethality  

Microsoft Academic Search

Drosophila dachshund is necessary and sufficient for compound eye development and is required for normal leg and brain development. A mouse homologue of dachshund, Dach1, is expressed in the developing retina and limbs, suggesting functional conservation of this gene. We have generated a loss-of-function mutation in Dach1 that results in the abrogation of the wild-type RNA and protein expression pattern

RICHARD J. DAVIS; WEIPING SHEN; YAKOV I. SANDLER; MEHRAN AMOUI; PATRICIA PURCELL; RICHARD MAAS; CHING-NAN OU; HANNES VOGEL; ARTHUR L. BEAUDET; GRAEME MARDON

2001-01-01

383

Cognition in female transmembrane domain neuregulin 1 mutant mice.  

PubMed

Neuregulin 1 (Nrg1) has been implicated in the development of schizophrenia and influences key neurodevelopmental processes such as myelination and neuronal migration. The heterozygous transmembrane domain Nrg1 mutant mouse (Nrg1 TM HET) exhibits a sex-specific phenotype relevant for schizophrenia research, which is characterized by the development of locomotor hyperactivity, social withdrawal, and changes to the serotonergic system. Cognitive impairments are characteristic of schizophrenia patients and male Nrg1 TM HET mice exhibit cognitive deficits in novel object recognition and contextual fear conditioning. Thus, we investigated the cognitive performance of female Nrg1 mutants, using a cognitive test battery for a variety of paradigms, including fear conditioning, cheeseboard, Y maze, object exploration and passive avoidance. Female Nrg1 mutant mice displayed impairments in the fear conditioning tasks, including significantly reduced fear conditioning to a context and a strong trend towards a decreased ability for cue fear conditioning. These cognitive deficits were task-specific, as no differences were seen between mutant and control mice in spatial learning of the cheeseboard for reference memory measures, in the Y-maze for working memory measures, or in novel object recognition and passive avoidance paradigms. These findings indicate that neuregulin 1 plays only a minor role in cognition in female test mice. The current study provides a further behavioural validation of this genetic mouse model for the schizophrenia candidate gene neuregulin 1 and confirms the importance of considering female test animals in animal models for schizophrenia. PMID:21944941

Chesworth, Rose; Downey, Laura; Logge, Warren; Killcross, Simon; Karl, Tim

2012-01-01

384

B Cells Are Not Essential for Lactobacillus-Mediated Protection against Lethal Pneumovirus Infection.  

PubMed

We have shown previously that priming of respiratory mucosa with live Lactobacillus species promotes robust and prolonged survival from an otherwise lethal infection with pneumonia virus of mice, a property known as heterologous immunity. Lactobacillus priming results in a moderate reduction in virus recovery and a dramatic reduction in virus-induced proinflammatory cytokine production; the precise mechanisms underlying these findings remain to be elucidated. Because B cells have been shown to promote heterologous immunity against respiratory virus pathogens under similar conditions, in this study we explore the role of B cells in Lactobacillus-mediated protection against acute pneumovirus infection. We found that Lactobacillus-primed mice feature elevated levels of airway Igs IgG, IgA, and IgM and lung tissues with dense, B cell (B220(+))-enriched peribronchial and perivascular infiltrates with germinal centers consistent with descriptions of BALT. No B cells were detected in lung tissue of Lactobacillus-primed B cell deficient ?MT mice or Jh mice, and Lactobacillus-primed ?MT mice had no characteristic infiltrates or airway Igs. Nonetheless, we observed diminished virus recovery and profound suppression of virus-induced proinflammatory cytokines CCL2, IFN-?, and CXCL10 in both wild-type and Lactobacillus-primed ?MT mice. Furthermore, Lactobacillus plantarum-primed, B cell-deficient ?MT and Jh mice were fully protected from an otherwise lethal pneumonia virus of mice infection, as were their respective wild-types. We conclude that B cells are dispensable for Lactobacillus-mediated heterologous immunity and were not crucial for promoting survival in response to an otherwise lethal pneumovirus infection. PMID:24748495

Percopo, Caroline M; Dyer, Kimberly D; Garcia-Crespo, Katia E; Gabryszewski, Stanislaw J; Shaffer, Arthur L; Domachowske, Joseph B; Rosenberg, Helene F

2014-06-01

385

Lethal and sublethal effects of spinosad on Spodoptera exigua (Lepidoptera: Noctuidae).  

PubMed

As a selective biological insecticide, spinosad has been used widely for the control of pests including beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). To form effective pest control strategies, lethal and sublethal effects should be considered for a complete analysis of spinosad impact. However, few studies have been reported to investigate sublethal effects of spinosad on S. exigua. This study attempts to evaluate the lethal and sublethal effects of spinosad on this pest by recording and analyzing various toxicological and physiological parameters. The toxicity of spinosad against S. exigua was determined under laboratory conditions by oral exposure of late second-instar larvae to the compound. The LC50 values of spinosad to S. exigua at 48 and 72 h after treatment were 0.317 and 0.293 mg x kg(-1), respectively. Spinosad at sublethal concentrations significantly extended the developmental period of survivor larvae, and reduced larval wet weight. Postexposure effects were indicated by decreased pupation ratio and pupal weight, by prolonged prepupal and pupal periods and by decreased emergence ratio, fecundity and longevity of adults. The net replacement rate (Ro) tended to be lower in the exposed spinosad groups than those in the unexposed spinosad group. Intrinsic rate of population increase (r(m)) for the high-dose group (0.365) was significantly lower than the control (0.521) and the low-dose group (0.521), but the latter two were not significantly difference. These results suggest that the combination of lethal and sublethal effects of spinosad might affect S. exigua population dynamics significantly by decreasing its survival and reproduction, and by delaying its development. PMID:24020299

Wang, Dong; Wang, Yong-Ming; Liu, Hui-Yuan; Xin, Zheng; Xue, Ming

2013-08-01

386

Immunological characterization of a gidA mutant strain of Salmonella for potential use in a live-attenuated vaccine  

PubMed Central

Background Salmonella is often associated with gastrointestinal disease outbreaks in humans throughout the world due to the consumption of contaminated food. Our previous studies have shown that deletion of glucose-inhibited division gene (gidA) significantly attenuated Salmonella enterica serovar Typhimurium (STM) virulence in both in vitro and in vivo models of infection. Most importantly, immunization with the gidA mutant protected mice from a lethal dose challenge of wild-type STM. In this study, we further characterize the gidA mutant STM strain for potential use in a live-attenuated vaccine. Results The protective efficacy of immunization with the gidA mutant was evaluated by challenging immunized mice with a lethal dose of wild-type STM. Sera levels of IgG2a and IgG1, passive transfer of sera and cells, and cytokine profiling were performed to study the induction of humoral and cellular immune responses induced by immunization with the gidA mutant strain. Additionally, a lymphocyte proliferation assay was performed to gauge the splenocyte survival in response to treatment with STM cell lysate. Mice immunized with the gidA mutant strain were fully protected from a lethal dose challenge of wild-type STM. Naïve mice receiving either cells or sera from immunized mice were partially protected from a lethal dose challenge of wild-type STM. The lymphocyte proliferation assay displayed a significant response of splenocytes from immunized mice when compared to splenocytes from non-immunized control mice. Furthermore, the immunized mice displayed significantly higher levels of IgG1 and IgG2a with a marked increase in IgG1. Additionally, immunization with the gidA mutant strain evoked higher levels of IL-2, IFN-?, and IL-10 cytokines in splenocytes induced with STM cell lysate. Conclusions Together, the results demonstrate that immunization with the gidA mutant strain protects mice by inducing humoral and cellular immune responses with the humoral immune response potentially being the main mechanism of protection.

2012-01-01

387

40 CFR 798.5275 - Sex-linked recessive lethal test in drosophila melanogaster.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Sex-linked recessive lethal test in drosophila...GUIDELINES Genetic Toxicity § 798.5275 Sex-linked recessive lethal test in drosophila melanogaster. (a) Purpose. The sex-linked recessive lethal (SLRL)...

2011-07-01

388

40 CFR 798.5275 - Sex-linked recessive lethal test in drosophila melanogaster.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Sex-linked recessive lethal test in drosophila...GUIDELINES Genetic Toxicity § 798.5275 Sex-linked recessive lethal test in drosophila melanogaster. (a) Purpose. The sex-linked recessive lethal (SLRL)...

2012-07-01

389

To Laugh in the Face of Death: The Games That Lethal People Play.  

ERIC Educational Resources Information Center

A total of 399 individuals completed a lethal behaviors scale and a measure of death anxiety, which were found to have no significant correlation. Predictors of lethalness included doing dangerous things for the fun of it and having ever driven a motorcycle. The most lethal individuals were young, male, and less educated. (Author/ABL)

Thorson, James A.; Powell, F. C.

1990-01-01

390

40 CFR 798.5275 - Sex-linked recessive lethal test in drosophila melanogaster.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Sex-linked recessive lethal test in drosophila...GUIDELINES Genetic Toxicity § 798.5275 Sex-linked recessive lethal test in drosophila melanogaster. (a) Purpose. The sex-linked recessive lethal (SLRL)...

2013-07-01

391

Beta-cyclodextrin derivatives that inhibit anthrax lethal toxin.  

PubMed

Recently, we demonstrated that simultaneous blocking of bacterial growth by antibiotics and inhibition of anthrax toxin action with antibodies against protective antigen were beneficial for the treatment of anthrax. The present study examined the hypothesis that blocking the pore formed by protective antigen can inhibit the action of anthrax toxin. The potential inhibitors were chosen by a structure-based design using beta-cyclodextrin as the starting molecule. Several beta-cyclodextrin derivatives were evaluated for their ability to protect RAW 264.7 cells from the action of anthrax lethal toxin. Per-substituted aminoalkyl derivatives displayed inhibitory activity and were protective against anthrax lethal toxin action at low micromolar concentrations. These results provide the basis for a structure-based drug discovery program, with the goal of identifying new drug candidates for anthrax treatment. PMID:16169738

Karginov, Vladimir A; Yohannes, Adiamseged; Robinson, Tanisha M; Fahmi, Nour Eddine; Alibek, Kenneth; Hecht, Sidney M

2006-01-01

392

Harnessing synthetic lethal interactions in anticancer drug discovery  

PubMed Central

Unique features of tumours that can be exploited by targeted therapies are a key focus of current cancer research. One such approach is known as synthetic lethality screening, which involves searching for genetic interactions of two mutations whereby the presence of either mutation alone has no effect on cell viability but the combination of the two mutations results in cell death. The presence of one of these mutations in cancer cells but not in normal cells can therefore create opportunities to selectively kill cancer cells by mimicking the effect of the second genetic mutation with targeted therapy. Here, we summarize strategies that can be used to identify synthetic lethal interactions for anticancer drug discovery, describe examples of such interactions that are currently being investigated in preclinical and clinical studies of targeted anticancer therapies, and discuss the challenges of realizing the full potential of such therapies.

Chan, Denise A.; Giaccia, Amato J.

2013-01-01

393

Susac's syndrome, a rare, potentially severe or lethal neurological disease.  

PubMed

Susac's syndrome (SS) is a rare, immune-mediated endotheliopathy affecting the microvasculature of the brain, the inner ear and the retina. Clinical presentation is characterised by a triad: encephalopathy, hearing loss and branch retinal artery occlusion (BRAO). Given the rarity of this disease, its natural history still remains partially unknown, but lethal cases appear to be extremely rare since there has never been, to our knowledge, a report of SS leading to death. We report 2 cases of SS illustrating the multiplicity of neurological symptomatology and its unpredictable course. One case is particularly unusual due to its severe neurological evolution, leading to death despite treatments. This report presents clinical and paraclinical findings contributory to SS diagnosis and offers an innovative perspective on disease management. These cases represent the potential severity of this disease. Early, aggressive treatment strategies may be warranted for SS in order to avoid neurological deterioration and lethal evolution. PMID:20723912

Saux, A; Niango, G; Charif, M; Morales, R; Mura, F; Bonafe, A; Mourand, I

2010-10-15

394