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PubMed1997

The yeast ATP binding cassette (ABC) protein genes PDR10 and PDR15 are novel targets for the Pdr1 and Pdr3 transcriptional regulators.

The yeast transcription factors Pdr1 and Pdr3 control pleiotropic drug resistance (PDR) development, since they regulate expression of ATP-binding cassette (ABC) drug efflux pumps through binding to cis-acting sites known as PDREs (PDR responsive elements). In this report, we show by Northern blotting, gel shift mobility assays and DNase I footprinting that transcription of the ABC genes PDR10 and PDR15 is also controlled by Pdr1 and Pdr3. In addition, in vitro band shift assays demonstrate that a GST-Pdr1 fusion protein can bind to the PDREs of PDR10 and PDR15. DNase I footprinting allowed the identification of the precise PDRE binding motifs, indicating the presence of a novel slightly degenerate PDRE motif in the PDR15 promoter. Finally, PDR10 and PDR15 mRNA levels vary dramatically in abundance in isogenic yeast strains carrying either deltapdr1, deltapdr3 and deltapdr1 deltapdr3 deletions or pdr1-3 and pdr3-2 gain-of-function mutations, demonstrating that both PDR10 and PDR15 are new members of the yeast PDR network.

ATP-Binding Cassette Transporters↗

PubMed1981

Much of spontaneous mutagenesis in Escherichia coli is due to error-prone DNA repair: implications for spontaneous carcinogenesis.

The role of DNA repair genes (uvrA, uvrB, uvrD, recA, recB, lexA, and umuC) in spontaneous mutation rate per bacterium per cell division (micro) was determined for the reversion of UAA (his-4 and trpE65), UAG (lacZ53), and frameshift (trpE9777) mutations, and for the occurrence of forward mutations to valine resistance. Rich growth medium enhanced micro in a wildtype strain but not in a uvrB5 strain. In minimal growth medium, the uvrA and uvrB strains had the largest micro (1.9-6.2-fold greater than that for isogenic wild-type strains, depending on the mutation assay). The uvrB strains carrying lexA, recA, umuC, or both the uvrD and rec B mutations (in combination), i.e., mutations that inhibit error-prone DNA repair, had the lowest micro values (approximately 10-fold less than the uvrB strain). Teh recA and lexA mutations also reduced micro (by approximately 2-fold) in uvr+ strains. The genetic control of the error prone repair-dependent sector of spontaneous mutagenesis was shown to be qualitatively similar to the genetic control for u.v. radiation mutagenesis. The umuC mutation, which drastically reduced spontaneous mutagensis, had no effect on genetic recombination. It is proposed that the low level of spontaneous mutagenesis observed in the recA, lexA, umuC, and the uvrD recB strains is due to errors made during DNA replication, while the enhanced level of spontaneous mutagenesis observed in the wild type, and especially in the uvrA and uvrB strains, is due to excisable lesions that are produced in the DNA by normal metabolic reactions, and that such unexcised lesions induce mutations via error-prone DNA repair. These results are discussed in terms of their relevance to spontaneous carcinogenesis.

Culture Media↗

PubMedDate not supplied

Action of pentoxifylline on experimental cutaneous leishmaniasis due to Leishmania (Leishmania) amazonensis.

In the animal model of leishmaniasis caused by Leishmania (Leishmania) amazonensis there is a complex mechanism of the host-parasite interaction. The present study was performed to interfere with the inflammatory reaction to the parasites, through immune modulation. Female C5BL/6 isogenic mice were used, some of which were inoculated on the right ear and others on the right footpad with 3.10(6) stationary phase promastigotes of the MHOM/BR/PH8 strain of L. (L.) amazonensis, and were allocated in three groups: the first received pentoxifylline 8mg/kg every 12 h, since the first day; the second one received the same dose since the 40th day of infection and a control group that did not receive any treatment. All the ears excised were analyzed to determine the variation in weight between both ears and for histopathological analyses. A quantification of the parasites was done using the limiting dilution assay. A significant reduction of the number of parasites, was observed among the animals treated which had an accordingly significant reduction on the weight of the ears. Pentoxifylline reduced the macrophages propensity to vacuolation and induced a more effective destruction of the parasites by these cells. Moreover, the group that began the treatment later did not show the same effectiveness.

Animals↗

PubMed2005

Corn grain endosperm type and brown midrib 3 corn silage: ruminal fermentation and N partitioning in lactating cows.

Interactions of endosperm type of corn grain and the brown midrib 3 mutation (bm3) in corn silage on ruminal fermentation and microbial efficiency of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72 +/- 8 d in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design experiment with a 2 x 2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous) and corn silage type (bm3 or isogenic normal). Diets contained 26% neutral detergent fiber and 30% starch. Increasing ruminal starch digestibility by replacing vitreous corn grain with floury grain reduced mean and minimum ruminal pH. Brown midrib 3 corn silage reduced mean and minimum ruminal pH and increased total volatile fatty acid concentration. Ruminal pH was positively associated with rate of valerate absorption. Although floury endosperm reduced acetate:propionate ratio in both control and bm3 corn silage diets, it had a greater effect on reducing acetate:propionate ratio for control silage compared with bm3 corn silage. Nonammonia N flow to the duodenum did not differ among treatments and no effects of treatment were detected for microbial N and nonammonia, nonmicrobial N flow. Although treatment effects on ruminal fermentation and ruminal pH were observed, few interactions of treatment were detected and treatments did not affect flow of N fractions to the intestines.

Animals↗

PubMedDate not supplied

Cell cycle and growth regulation in RAS2 mutant cells of Saccharomyces cerevisiae.

Yeast cells carrying ras2 temperature-sensitive mutations undergo a specific arrest in the prereplicative unbudded phase of the cell cycle when they are shifted to non-permissive temperatures. At 36.5 degrees C, in spite of their abnormally large cell size, bulk protein synthesis and accumulation rates are depressed in ras2 temperature-sensitive cells in comparison with isogenic wild type. At the same temperature, total RNA synthesis and accumulation rates are much more inhibited, suggesting that a defective Ras2/cAMP pathway alters the coordination between RNA and protein synthesis rates. The preferential RNA synthesis inhibition is correlated to a specific inhibition of the synthesis of the 35S rRNA precursor. These findings, taken together with the results of previous analyses, are in favour of a control by the cAMP pathway on rRNA biosynthesis.

Cell Cycle↗

PubMed1994

Comparison of myristoyl-CoA:protein N-myristoyltransferases from three pathogenic fungi: Cryptococcus neoformans, Histoplasma capsulatum, and Candida albicans.

Myristoyl-CoA:protein N-myristoyltransferase (Nmt) transfers myristate from CoA to the N-terminal Gly residue of cellular proteins in an ordered reaction mechanism that first involves binding of myristoyl-CoA to the apoenzyme. The gene encoding Saccharomyces cerevisiae Nmt1p (NMT1) is essential for vegetative growth. Candida albicans, Cryptococcus neoformans var. neoformans, and Histoplasma capsulatum are the principal causes of systemic fungal infections in immunocompromised humans. Metabolic labeling studies indicate that they synthesize a small set of cellular N-myristoylproteins during exponential growth on rich media, the most prominent of which co-migrate with two essential functionally interchangeable S. cerevisiae N-myristoylproteins, ADP ribosylation factor-1 (Arf1p) and Arf2p. NMT and ARF genes have been recovered from C. neoformans and H. capsulatum using the polymerase chain reaction. They are single copy genes, interrupted by multiple introns. C. neoformans and H. capsulatum Nmts have approximately 50% amino acid sequence identity with the orthologous S. cerevisiae, C. albicans, and Homo sapiens N-myristoyltransferases, whereas C. neoformans and H. capsulatum Arfs are approximately 80% identical with C. albicans Arf and S. cerevisiae Arf1p and Arf2p. Functional studies of C. neoformans and C. albicans Nmts conducted in Escherichia coli reveal that (i) both efficiently acylate S. cerevisiae Arf2p; (ii) C. neoformans Arf is a substrate for C. neoformans Nmt; and (iii) substitution of an Asp for a Gly located 5 residues from the C terminus of these two enzymes causes marked temperature-dependent reductions in their catalytic efficiency, just as it does with S. cerevisiae and H. sapiens Nmts. Wild type C. neoformans, C. albicans, and H. sapiens NMTs can fully complement the lethal phenotype of a S. cerevisiae nmt1 null allele at 24 and 37 degrees C when the GAL1-10 promoter controlling their expression is induced by galactose. Only the C. albicans enzyme is able to do so when the promoter is repressed with glucose. This complementation profile likely arises, at least in part, from differences in the protein substrate specificities of the orthologous Nmts. A Gly-->Asp mutation in S. cerevisiae, C. neoformans, C. albicans, and H. sapiens Nmts produces temperature-sensitive growth arrest in isogenic S. cerevisiae strains with a nmt1 null allele. Growth of strains producing the mutant C. albicans or H. sapiens, but not the C. neoformans, enzyme can be rescued by myristate at the non-permissive temperature (37 degrees C) even in the presence of cerulenin, an inhibitor of fatty acid synthetase.(ABSTRACT TRUNCATED AT 400 WORDS)

Acyltransferases↗

PubMed1998

Immunopathology of herpetic stromal keratitis: discordance in CD4+ T cell function between euthymic host and reconstituted SCID recipients.

Infection of the mouse cornea with herpes simplex virus (HSV) results in an immunopathologic disease of the eye termed herpetic stromal keratitis (HSK), in which the principal orchestrator is the CD4+ T cell. The mouse genotype largely determines susceptibility or resistance to HSK. BALB/c mice (H2dIgh-1a) are susceptible, while its congenic C.B-17 strain (H2dIgh-1b), which differs only in the Ig heavy chain locus, is resistant to HSK. As the magnitude and duration of viral replication as well as anti-HSV immune responses were similar in both strains, it was determined whether resistance was due to failure of CD4+ T cells to organize the immunopathologic reaction. Adoptive transfer of HSV-primed or naive CD4+ T cells from resistant C.B-17 strain into HSV-infected SCID mice resulted in HSK lesions indistinguishable from those caused by similar transfers of BALB/c CD4+ T cells. Similar results were obtained with transfers of whole T cell populations as well as with unfractionated splenocytes from the resistant mice. These results show that while intact C.B-17 mice exhibit resistance to HSK, they possess potentially pathogenic CD4+ T cells in their repertoire. The data suggest that the HSV-infected SCID mouse provides a proinflammatory microenvironment that overrides regulatory controls and/or cause activation of quiescent cells into aggressive effector T cells that orchestrate HSK.

Adoptive Transfer↗

PubMed1984

The influence of the recipient upon renal function after isogeneic kidney transplantation in the rat.

Little attention has been paid to the changes in renal function that occur after kidney transplantation when donor and recipient differ markedly in size. We studied this phenomenon after isogeneic kidney transplantation in rats of varying body weight (BW). Renal functional parameters, such as the glomerular filtration rate (GFR), the effective renal plasma flow (ERPF), and the plasma levels of creatinine (Pcr) and urea (Pur) were determined at regular intervals following transplantation. In the initial experimental series, juvenile (BW approximately 150 g) and adult (BW approximately 300 g) rats were used. Four groups of transplant recipients were studied. These consisted of 2 groups of adult recipients of juvenile or adult donor kidneys, and 2 groups of juvenile recipients of juvenile or adult donor kidneys. These 4 groups were compared with adult and juvenile control rats, as well as with unilaterally nephrectomized (NX) rats. A comparison between the 2 groups of juvenile recipients revealed no significant difference in the GFR, ERPF, Pcr, or Pur levels after the transplantation of adult or juvenile donor kidneys. Nor were any significant differences found when comparing the functional parameters of the 2 groups of adult recipients after transplantation of adult or juvenile donor kidneys. The transplanted kidneys generally functioned at a level amounting to 80-90% of the GFR and 90-100% of the ERPF of NX rats of comparable BW. These observations are a clear indication of functional adaptation after kidney transplantation. The compensatory functional response is augmented--in case of a young donor kidney transplanted into an adult recipient, or attenuated--in case of an adult donor kidney transplanted into a juvenile recipient. In an additional experiment, kidneys were transplanted from very young rats (BW approximately 50 g) to adult recipients. It appeared that as early as two weeks after transplantation, renal function had reached adult kidney levels, as observed in the first experimental series. In conclusion, after isogeneic kidney transplantation in rats, the transplanted kidney generally adapts rapidly to the size of the recipient and functions like an inherent part of the recipient's body.

Aging↗

PubMed1980

Responses of B-cells to mitogens and antigen in mice receiving isogenic splenocytes from animals treated with Trichinella extract.

Splenocytes of C57BL/6J mice injected with a Trichinella spiralis larval extract for 7 consecutive days were transferred in two doses into isogenic, immunocompetent mice. On the 3rd day, some recipients were immunized with 10(9) sheep red blood cells and others were killed to investigate blastogenic response of their splenocytes to concanavalin A (Con A), Escherichia coli lipopolysaccharide (LPS), and Mycobacterium's purified protein derivative (PPD). On the 8th day of immunization, the corresponding mice were killed to study rosette-forming cells (RFC) and direct and indirect plaque-forming cells (D- and I-PFC) in their spleens. Transfer of 10(6) cells depressed the Con A reactivity and the number of RFC and 1-PFC, but increased the PPD reactivity and the number of D-PFC in the recipients, as compared to control mice receiving splenocytes from donors injected with a saline solution. Ten million cells inhibited only the Con A reactivity, but enhanced the number of LPS- and PPD-responding cells and of D-PFC in the recipients over the controls. Inoculation of cells from mice injected with bovine serum albumin did not reproduce the same effects. Splenocytes of mice treated with T. spiralis extract simultaneously inhibit and enhance diverse functions of the immune system. Stimulation is exerted on IgG antibody production and appears to be mediated by suppressor T-cells. Stimulation is exerted mainly on IgM antibody formation. Depression seems to be antigen-specific; it is partially compensated by the concurrent suppression, and it is probably a result of macrophage activation.

Animals↗

PubMed1995

Comparison of ccd of F, parDE of RP4, and parD of R1 using a novel conditional replication control system of plasmid R1.

A number of plasmid-encoded gene systems are thought to stabilize plasmids by killing plasmid-free cells (also termed post-segregational killing or plasmid addiction). Here we analyse the mechanisms of plasmid stabilization by ccd of F, parDE of RP4 and parD of R1, and compare them to hok/sok of R1. To induce synchronous plasmid loss we constructed a novel plasmid replication-arrest system, which possesses the advantage that plasmid replication can be completely arrested by the addition of IPTG, a non-metabolizable inducer. Using isogenic plasmid constructions we have found, for the first time, consistent correlation between the effect on steady-state loss rates and the effect on cell proliferation in the plasmid replication-arrest assay for all three systems. The parDE system had the most pronounced effect both on plasmid stabilization and on plasmid retention after replication arrest. In contrast, ccd and parD both exhibited weaker effects than anticipated from previously published results. Thus, our results indicate that the function and efficiencies of some of the systems should be reconsidered. Our results are consistent with the previously postulated hypothesis that ccd and parDE act by killing plasmid-free segregants, whereas parD seems to act by inhibiting cell division of plasmid-free segregants.

Bacterial Proteins↗

PubMed2005

A major QTL introgressed from wild Lycopersicon hirsutum confers chilling tolerance to cultivated tomato (Lycopersicon esculentum).

Many plants of tropical or subtropical origin, such as tomato, suffer damage under chilling temperatures (under 10 degrees C but above 0 degrees C). An earlier study identified several quantitative trait loci (QTLs) for shoot turgor maintenance (stm) under root chilling in an interspecific backcross population derived from crossing chilling-susceptible cultivated tomato (Lycopersicon esculentum) and chilling-tolerant wild L. hirsutum. The QTL with the greatest phenotypic effect on stm was located in a 28 cM region on chromosome 9 (designated stm 9), and enhanced chilling-tolerance was conferred by the presence of the Lycopersicon hirsutum allele at this QTL. Here, near-isogenic lines (NILs) were used to verify the effect of stm 9, and recombinant sub-NILs were used to fine map its position. Replicated experiments were performed with NILs and sub-NILs in a refrigerated hydroponic tank in the greenhouse. Sub-NIL data was analyzed using least square means separations, marker-genotype mean t-tests, and composite interval mapping. A dominant QTL controlling shoot turgor maintenance under root chilling was confirmed on chromosome 9 using both NILs and sub-NILs. Furthermore, sub-NILs permitted localization of stm 9 to a 2.7 cM interval within the original 28 cM QTL region. If the presence of the L. hirsutum allele at stm 9 also confers chilling-tolerance in L. esculentum plants grown under field conditions, it has the potential to expand the geographic areas in which cultivated tomato can be grown for commercial production.

Acclimatization↗

PubMed2005

The transmissibility of Trypanosoma congolense seems to be associated with its level of resistance to isometamidium chloride.

In large parts of Africa the control of livestock trypanosomiasis relies on the use of trypanocidal drugs. Resistance against the available compounds is developing rapidly in the trypanosome population. The effect of the development of drug resistance on the fitness of the trypanosome is not well known. To determine the effect of the development of resistance to isometamidium chloride on the trypanosome's transmissibility, transmission experiments were conducted. Use was made of three isogenic clones of Trypanosoma congolense with different susceptibility to the drug. The infection rate in Glossina morsitans morsitans differed significantly between clones and was significantly higher in tsetse flies infected with the T. congolense clone with the highest level of drug resistance.

Animals↗

PubMed1998

Spontaneous cAMP-dependent derepression of gene expression in stationary phase plays a role in recombinant expression instability.

E. coli recombinant expression systems that utilize lac operon control elements to modulate gene expression are known to produce some amount of uninduced (leaky) gene expression. Previously, we showed that high levels of uninduced gene expression was a major cause of instability in the pET expression system. We show here that the pET system, in which the phage T7 RNA polymerase gene is expressed via lac operon control elements, exhibits leaky expression that increases markedly as cells grown in complex medium enter stationary phase. Moreover, we found that this phenomenon occurs with the chromosomal lac operon as well. Further investigation revealed that stationary phase leaky expression requires cyclic AMP, and that substantial leaky expression could be effected in log phase cells by adding cyclic AMP and acetate at pH6.0. Finally, a comparison of otherwise isogenic cya and wild-type hosts showed that expression stability and plasmid maintenance in the cya host is greatly enhanced, even when cells are passaged repeatedly in non-selection medium. These findings both provide a method to enhance the stability of lac-based recombinant expression systems, and suggest that derepression of the lac operon in the absence of inducer may be part of a general cellular response to nutrient limitation.

Bacteriophage T7↗

PubMed1999

Mismatch repair, G(2)/M cell cycle arrest and lethality after DNA damage.

The role of the mismatch repair pathway in DNA replication is well defined but its involvement in processing DNA damage induced by chemical or physical agents is less clear. DNA repair and cell cycle control are tightly linked and it has been suggested that mismatch repair is necessary to activate the G(2)/M checkpoint in the presence of certain types of DNA damage. We investigated the proposed role for mismatch repair (MMR) in activation of the G(2)/M checkpoint following exposure to DNA-damaging agents. We compared the response of MMR-proficient HeLa and Raji cells with isogenic variants defective in either the hMutLalpha or hMutSalpha complex. Different agents were used: the cross-linker N-(2-chloroethyl)-N'-cyclohexyl-N-nitrosourea (CCNU), gamma-radiation and the monofunctional methylating agent N-methyl-N-nitrosourea (MNU). MMR-defective cells are relatively sensitive to CCNU, while no differences in survival between repair-proficient and -deficient cells were observed after exposure to gamma-radiation. Analysis of cell cycle distribution indicates that G(2) arrest is induced at least as efficiently in MMR-defective cells after exposure to either CCNU or ionizing radiation. As expected, MNU does not induce G(2) accumulation in MMR-defective cells, which are known to be highly tolerant to killing by methylating agents, indicating that MNU-induced cell cycle alterations are strictly dependent on the cytotoxic processing of methylation damage by MMR. Conversely, activation of the G(2)/M checkpoint after DNA damage induced by CCNU and gamma-radiation does not depend on functional MMR. In addition, the absence of a simple correlation between the extent of G(2) arrest and cell killing by these agents suggests that G(2) arrest reflects the processing by MMR of both lethal and non-lethal DNA damage.

Base Pair Mismatch↗

PubMed2004

A centromeric region on chromosome 6(6H) affects dormancy in an induced mutant in barley.

Genetic control of seed dormancy in barley (Hordeum vulgare L.) has mostly been described in terms of quantitative variation. Although some molecular markers for dormancy QTL have been identified, the corresponding genes involved in the regulation of the process have not been cloned. Induced barley mutants may constitute useful material to study the physiology and genetics of seed dormancy. The objective of this study was to identify the genetic control of this trait in a mutant (TL43) produced in the barley cv. Triumph. This mutant was selected for reduced dormancy and reduced sensitivity to abscisic acid (ABA). Two sets of F6 barley lines were selected for high and low levels of dormancy from a cross between the original dormant parent and the sodium azide-induced non-dormant TL43 mutant. Unexpectedly, given the near-isogenic nature of these two genotypes, polymorphism was detected for an SSR located in the centromeric region of chromosome 6(6H) out of a total of 92 molecular markers evenly distributed along the genome. Fortunately, upon three cycles of intensive divergent selection, every dormant and non-dormant F5 line consistently showed the genotype for this region identical to Triumph and TL43, respectively. Based on the mutagenic effect presumably attributed to sodium azide, mostly single point mutations, it cannot be clearly established if such extensive genomic variation on chromosome 6(6H) is due to the mutagenic treatment or may be an introgression from an unknown source. The means that could originate such heterogeneity are discussed; however, regardless of its origin, this genomic region shows a strong association with the expression of seed dormancy and provides an additional genetic locus for further studies of the mechanistic basis of this complex trait. In addition, since TL43 shows reduced sensitivity to ABA, the response to this hormone was determined on the F6 seed from the two sets of selected F5 lines. The results confirmed that the initial level of dormancy in the seed lot is the most important factor in determining ABA sensitivity.

Abscisic Acid↗

PubMed2003

WAP1, a wheat APETALA1 homolog, plays a central role in the phase transition from vegetative to reproductive growth.

Heading time in bread wheat (Triticum aestivum L.) is determined by three characters: vernalization requirement, photoperiodic sensitivity and narrow-sense earliness, which are involved in the phase transition from vegetative to reproductive growth. We identified and characterized the APETALA1 (AP1)-like MADS box gene in wheat (WAP1) as an activator of phase transition. Its expression starts just before the phase transition and is maintained during the reproductive phase. Inhibition of WAP1 expression in the transgenic plants by co-suppression affected neither vernalization requirement nor photoperiodic sensitivity, but resulted in delayed narrow-sense earliness, indicating that WAP1 accelerates autonomous phase transition. Analyses of the WAP1 expression in the near-isogenic lines (NILs) for spring habit genes (Vrn) revealed that WAP1 transcripts were induced by vernalization strongly in the NILs with Vrn dominant alleles and weakly with the recessive alleles. Furthermore, WAP1 expression was up-regulated by a long photoperiod in both NILs with and those without a photoperiod-insensitive gene (Ppd). These results suggest that WAP1 is a key gene in the regulatory pathway controlling the phase transition from vegetative to reproductive growth in wheat.

Amino Acid Sequence↗

PubMed1999

Attenuation of microvascular reperfusion injury in rat pancreas transplantation by L-arginine.

BACKGROUND: Despite improving results, exocrine complications remain a major challenge in clinical pancreas transplantation. The etiology of posttransplantation pancreatitis relates almost certainly to cold ischemia/reperfusion-induced microvascular injury with an imbalance of vasoconstricting and vasodilating mediators due to endothelial dysfunction. We therefore studied the effectiveness of a nitric oxide donor on postischemic microvascular reperfusion injury after pancreas transplantation. METHODS: Heterotopic isogeneic pancreaticoduodenal transplantation was performed in spontaneously breathing, chloralhydrate-anesthetized Sprague Dawley rats after 16 hr (n=5) of cold storage of the graft in 4 degrees C histidine-tryptophane-ketoglutarate solution. An additional five animals received L-arginine immediately before (50 mg/kg i.v.) and during the first 30 min of reperfusion (100 mg/kg i.v.). Five animals that did not undergo transplantation served as controls. Intravital fluorescence microscopy was used for analysis of functional capillary density, capillary diameters, and capillary red blood cell velocity in exocrine pancreatic tissue during 120 min of reperfusion. Histology served for quantitative assessment of inflammatory response (leukocytic tissue infiltration) and endothelial disintegration (edema formation). RESULTS: In L-arginine-treated animals, functional capillary density of exocrine tissue of pancreatic grafts was found slightly higher after 30 and 60 min, and significantly higher after 120 min of postischemic reperfusion compared with untreated pancreatic grafts. This was accompanied by a significant increase of capillary diameters. In parallel, pancreatic histology revealed significant attenuation of both leukocytic tissue infiltration and edema formation in the L-arginine-treated animals when compared with the nontreated controls. CONCLUSIONS: Besides reduction of leukocyte-dependent microvascular injury, L-arginine improves postischemic microvascular reperfusion, supposedly by capillary dilatation. Thus, our results suggest that supplement of nitric oxide during reperfusion is effective in attenuating exocrine microvascular reperfusion injury.

Animals↗

PubMed1996

Coordinate genetic regulation of glycogen catabolism and biosynthesis in Escherichia coli via the CsrA gene product.

The carbon storage regulator gene, csrA, encodes a factor which negatively modulates the expression of the glycogen biosynthetic gene glgC by enhancing the decay of its mRNA (M. Y. Liu, H. Yang, and T. Romeo, J. Bacteriol. 177:2663-2672, 1995). When endogenous glycogen levels in isogenic csrA+ and csrA::kanR strains were quantified during the growth curve, both the rate of glycogen accumulation during late exponential or early stationary phase and its subsequent rate of degradation were found to be greatly accelerated by the csrA::kanR mutation. The expression of the biosynthetic genes glgA (glycogen synthase) and glgS was observed to be negatively modulated via csrA. Thus, csrA is now known to control all of the known glycogen biosynthetic genes (glg), which are located in three different operons. Similarly, the expression of the degradative enzyme glycogen phosphorylase, which is encoded by glgY, was found to be negatively regulated via csrA in vivo. The in vitro transcription-translation of glgY was also specifically inhibited by the purified CsrA gene product. These results demonstrate that localization of glycogen biosynthetic and degradative genes within the Escherichia coli glgCAY operon facilitates their coordinate genetic regulation, as previously hypothesized (T. Romeo, A. Kumar, and J. Preiss, Gene 70:363-376, 1988). The csrA gene did not affect glycogen debranching enzyme, which is now shown to be encoded by the gene glgX.

Bacterial Proteins↗