Biomedical subjects

J Switala

Publications and source records attributed to J Switala.

At least 37 records · Page 2Linked to original sources

PubMed1994

The delta (argF-lacZ)205(U169) deletion greatly enhances resistance to hydrogen peroxide in stationary-phase Escherichia coli.

In this study, we demonstrate that a strain bearing the delta (argF-lacZ)205(U169) deletion exhibits a high level of resistance to hydrogen peroxide compared with its undeleted parent. Our initial investigation of the mechanism behind the observed differences in peroxide resistance when parent and mutant strains are compared indicates that the parent strain carries a region near argF that is responsible for the H2O2-sensitive phenotype, which we have named katC. The H2O2 resistance phenotype of the delta katC [delta (argF-lacZ)205(U169)] mutant strain can be duplicated by Tn9 insertion in a specific locus (katC5::Tn9) which maps near argF. The increased H2O2 resistance of the delta katC and katC5::Tn9 mutant strains can be seen only when cells are grown to stationary phase; exponential-phase cells are unaffected by the presence or absence of katC. This H2O2 resistance mechanism requires functional katE and katF genes, which suggests that the mechanism of H2O2 resistance may involve the activity of the stationary-phase-specific catalase HPII. Cloning, DNA sequencing, and analysis of the katC5::Tn9 insertion allele in comparison with its parent allele implicate two insertion elements, IS1B and IS30B, and suggest that their presence sensitizes parent cells to H2O2.

Alleles↗

PubMed1993

Catalase HPII of Escherichia coli catalyzes the conversion of protoheme to cis-heme d.

Catalase HPII from aerobically grown Escherichia coli normally contains heme d but cultures grown with poor or no aeration produce HPII containing a mixture of heme d and protoheme IX. The protoheme component of HPII from anaerobically grown cells is converted into heme d during treatment of the purified enzyme with hydrogen peroxide. It is concluded that heme d found in catalase HPII is formed by the cis-hydroxylation of protoheme in a reaction catalyzed by catalase HPII using hydrogen peroxide as a substrate. The distal His128 residue of HPII is absolutely required for the protoheme to heme d conversion. Two mutant enzymes, Ala128 and Asn128, are catalytically inactive and contain only protoheme, which is unaffected by hydrogen peroxide treatment. The Asn201 residue is not an absolute requirement for heme conversion. The mutant enzyme Ala201 contains predominantly heme d and is partially active. However, insertion of a histidyl residue to give the His201 enzyme interferes with the heme conversion reaction. This mutant form is isolated as a protoheme enzyme with limited activity, and a reversible conversion to a heme d-like species occurs in vitro in the presence of continuously generated hydrogen peroxide.

Amino Acid Sequence↗

PubMed1993

KatF (sigma S) synthesis in Escherichia coli is subject to posttranscriptional regulation.

A transcriptional fusion of katF to the lacZ gene was expressed at increasingly higher levels throughout the exponential phase, but a translational fusion was expressed at low levels during exponential-phase growth and was induced 160-fold during the transition to stationary phase, implicating a posttranscriptional mechanism in the regulation of KatF synthesis. Mutational analyses suggested that the initiation codon of katF is the second ATG in the previously identified open reading frame.

Bacterial Proteins↗

PubMed1992

The alternative sigma factor katF (rpoS) regulates Salmonella virulence.

Nutrient limitation is a critical signal in Salmonella virulence gene regulation. The katF (rpoS) gene mediates the expression of the Salmonella spv plasmid virulence genes during bacterial starvation. A katF Salmonella mutant has increased susceptibility to nutrient deprivation, oxidative stress, acid stress, and DNA damage, conditions which are relevant to the intraphagosomal environment of host macrophages. Moreover, the katF mutant has significantly reduced virulence in mice. katF encodes an alternative sigma factor of RNA polymerase which coordinately regulates Salmonella virulence.

Animals↗

PubMed1992

Severity of hepatic encephalopathy before liver transplantation is associated with quality of life after transplantation.

BACKGROUND: Cirrhosis is associated with a chronic low-grade hepatic encephalopathy and disturbances in quality of life. This study investigated the extent to which severity of hepatic encephalopathy before orthotopic liver transplantation correlated with quality of life. METHODS: A battery of neuropsychological tests was administered to nonalcoholic patients to quantify severity of hepatic encephalopathy. The Sickness Impact Profile was administered before and after surgery to document quality of life across multiple health and psychosocial dimensions. RESULTS: There was substantial improvement from the pretransplant to the posttransplant periods across almost all dimensions of quality of life. Neuropsychological test scores explained up to 20% of the variance in magnitude of change from pre (before) to post (after) surgery. CONCLUSION: Severity of hepatic encephalopathy (particularly with respect to static ataxia and fine motor control) is associated with posttransplantation improvement in quality of life.

Adult↗

PubMed1991

Impact of liver disease on daily living in transplantation candidates.

The impact of different types of liver diseases on life quality in transplantation candidates was assessed. For all disease types, psychosocial impairment exceeded physical impairment. Among the various disease conditions, differences on the pattern and severity of life quality disturbances were observed.

Activities of Daily Living↗

PubMed1991

Quality of life before and after orthotopic hepatic transplantation.

Fifty-three nonalcoholic patients were evaluated prior to liver transplantation and again approximately 3 years after surgery using the Sickness Impact Profile and Social Behavior Adjustment Schedule. Test-retest scores reflected significant improvement across all health and psychosocial scales of the Sickness Impact Profile. On the Social Behavior Adjustment Schedule, significant improvement was observed on scales measuring disturbed behavior, social role performance, and burden. Comparisons between groups indicated that the liver transplant patients were still impaired on eight of the Sickness Impact Profile scales after transplant; however, the severity of disturbance was not considered to be clinically significant. No between-group differences were noted on the Social Behavior Adjustment Schedule. These results indicate that liver transplantation is associated with substantial improvement in life quality, although as a group, the patients undergoing this surgery do not recover to the level of functioning demonstrated by normal individuals.

Adult↗

PubMed1990

Crystallization and preliminary X-ray diffraction analysis of catalase HPII from Escherichia coli.

Green crystals of the hexameric catalase HPII from Escherichia coli have been obtained by the hanging-drop method. The crystals belong to the monoclinic space group P2 with a = 123 A, b = 132 A, c = 93 A, beta = 112.5 degrees. There are three subunits in the asymmetric unit. The crystals diffract at least to 3.2 A resolution and are suitable for further X-ray diffraction studies.

Catalase↗

PubMed1990

Regulation of transcription of katE and katF in Escherichia coli.

Fusion plasmids with lacZ under the control of the katE (encoding catalase or hydroperoxidase HPII) and katF (encoding a sigma factor-like protein required for katE expression) promoters were constructed. Expression from both katE and katF promoters was low in rich medium but elevated in poor medium during log-phase growth. Furthermore, the slowdown in growth as cells entered the stationary phase in rich medium, a result of carbon source depletion, was associated with an increase in katE and katF expression. A simple reduction in the carbon source level as the cells entered the stationary phase was not responsible for the increase in expression, because transferring the culture to a medium with no glucose did not induce expression from either promoter. Spent rich medium from stationary-phase cells was capable of inducing expression, as were simple aromatic acids such as benzoate, o-hydroxybenzoate, and p-aminobenzoate added to new medium. Anaerobiosis did not cause an increase in expression, nor did it significantly change the pattern of expression. Regardless of the medium, katF expression was always turned on before or coincidently with katE expression; in the presence of benzoate katF was fully induced, whereas katE was only partially induced, suggesting that a factor in addition to KatF protein was involved in katE expression. During prolonged aerobic incubation, cells lacking katF died off more rapidly than did cells lacking either katE or katG.

Anaerobiosis↗

PubMed1990

Homology among bacterial catalase genes.

Catalase activities in crude extracts of exponential and stationary phase cultures of various bacteria were visualized following gel electrophoresis for comparison with the enzymes from Escherichia coli. Citrobacter freundii, Edwardsiella tarda, Enterobacter aerogenes, Klebsiella pneumoniae, and Salmonella typhimurium exhibited patterns of catalase activity similar to E. coli, including bifunctional HPI-like bands and a monofunctional HPII-like band. Proteus mirabilis, Erwinia carotovora, and Serratia marcescens contained a single band of monofunctional catalase with a mobility intermediate between the HPI-like and HPII-like bands. The cloned genes for catalases HPI (katG) and HPII (katE) from E. coli were used as probes in Southern hybridization analyses for homologous sequences in genomic DNA of the same bacteria. katG was found to hybridize with fragments from C. freudii, Ent. aerogenes, Sal. typhimurium, and K. pneumoniae but not at all with Ed. tarda, P. mirabilis, S. marcesens, or Er. carotovora. katE hybridized with C. freundii and K. pneumoniae DNAs and not with the other bacterial DNAs.

Blotting, Southern↗

PubMed1990

Functional outcome after liver transplantation: a preliminary report.

Although the number of patients undergoing successful liver transplants each year has increased dramatically, little information is available on the functional outcome of such patients. A survey was conducted to determine the functional and vocational outcome of patients three years after orthotopic liver transplantation. Questionnaires were sent to 45 patients who had liver transplants in 1985, of whom 31 responded. Fourteen patients (47%) reported abnormal function in at least one limb; four patients (13%) reported developing gout. All patients were independent in ADLs and mobility; assistive devices were used by four patients. Nineteen patients (61%) reported severe impairment in endurance before transplant; 15 (48%) were unable to ambulate outside the house. After transplant only two patients (6%) reported severely impaired endurance, and all but two were able to walk at least three blocks. Three years after transplant, 12 patients (39%) were working full time and eight patients (26%) were homemakers. Work performance was most commonly limited by fractures (12 patients) and lack of concentration (seven patients). Thus, despite frequent limitations in limb function, patients after liver transplant are largely independent in ADLs and mobility, have improved endurance, and can often return to work despite physical limitations.

Activities of Daily Living↗

PubMed1988

Effect of ascorbate on oxygen uptake and growth of Escherichia coli B.

The addition of ascorbate to aerobically growing cultures of Escherichia coli B caused only a short pause in growth and no subsequent change in the rate or extent of growth. The effect of ascorbate on oxygen uptake varied from inhibition in minimal medium to stimulation in rich medium. Cyanide-resistant growth and oxygen uptake were stimulated by ascorbate. Both the rate and extent of anaerobic growth were stimulated in proportion to the amount of ascorbate added when fumarate was the terminal electron acceptor. Ascorbate had no effect on any aspect of anaerobic growth in the absence of a terminal electron acceptor or in the presence of nitrate.

Anaerobiosis↗

PubMed1988

Purification and characterization of spore-specific catalase-2 from Bacillus subtilis.

Catalase-2, the catalase found in spores of Bacillus subtilis, has been purified to homogeneity from a nonsporulating strain. The apparent native molecular weight is 504,000. The enzyme appears to be composed of six identical protomers with a molecular weight of 81,000 each. The amino acid composition is similar to the composition of other catalases. Like most catalases, catalase-2 exhibits a broad pH optimum from pH 4 to pH 12 and is sensitive to cyanide, azide, thiol reagents, and amino triazole. The apparent Km for H2O2 is 78 mM. The enzyme exhibits extreme stability, losing activity only slowly at 93 degrees C and remaining active in 1% SDS-7 M urea. The green-colored enzyme exhibits a spectrum like heme d with a Soret absorption at 403 nm and a molar absorptivity consistent with one heme per subunit. The heme cannot be extracted with acetone-HCl or ether, suggesting that it is covalently bound to the protein.

Amino Acids↗

PubMed1988

The quality of life following liver transplantation: a preliminary report.

Quality of life is a multidimensional construct that encompasses functional behavioral and cognitive capacities, health status, emotional well-being, and psychosocial adjustment. A program of interdisciplinary investigation at the University of Pittsburgh Health Sciences Center has been directed at studying the outcome of liver transplantation with respect to the impact of such surgery on improving life quality. The data obtained have been subjected only to descriptive and univariate analyses but indicate that liver transplantation surgery results in a sharp improvement in quality of life relative to one's pretransplant status, although it does not return the recipient to their premorbid baseline. Following transplantation, a substantial reversal of identified pretransplant neuropsychological impairments also occurs, although performance does not appear to return to normal levels. Specifically, visuopractic impairments, which are the most salient neuropsychologic concomitants of hepatic encephalopathy, are still detectable 3 years after transplantation. Nonetheless, normal or near normal functioning on measures of cognitive capacity, health status, emotional well-being and social, vocational, and behavioral competency are found in liver transplant survivors.

Family↗

PubMed1987

Genetic mapping of katA, a locus that affects catalase 1 level in Bacillus subtilis.

Several mutants of Bacillus subtilis deficient in catalase synthesis generated by nitrosoguanidine mutagenesis have been used to map a locus affecting catalase activity. Two- and three-factor bacteriophage PBS1 transductional crosses were used to locate the locus, named katA, between recH and thiA with 98% linkage to thiA at 70 degrees on the B. subtilis genome. The synthesis of catalase 1, found only in vegetative cells, was affected by katA.

Bacillus subtilis↗

PubMed1987

Multiple catalases in Bacillus subtilis.

Vegetative cells of Bacillus subtilis in logarithmic growth phase produced one catalase, labeled catalase 1, with a nondenatured molecular weight of 205,000. As growth progressed, other activity bands with slower electrophoretic mobilities on polyacrylamide gels appeared, including a series of bands with a common nondenatured molecular weight of 261,000, collectively labeled catalase 2, and a minor band, with a molecular weight of 387,000, labeled catalase 3. Purified spores contained only catalase 2, and it was not produced in spo0A- or spo0F-containing mutants. Strains deficient in catalase 1 or catalase 2 or both were selected after mutagenesis. Sensitivities of the two main catalases to NaCN, NaN3, hydroxylamine, and temperature were similar, but the apparent Kms for H2O2 differed, being 36.6 and 64.4 mM, respectively, for catalase 1 and catalase 2. The levels of catalase 1 increased 15-fold during growth into stationary phase and could be increased 30-fold by the addition of H2O2 to the medium. Catalase 2, which was not affected by H2O2, appeared only after the cells had reached stationary phase, and the maximum levels were only half of the basal level of catalase 1.

Bacillus subtilis↗

PubMed1987

Purification and characterization of catalase-1 from Bacillus subtilis.

The catalase activity produced in vegetative Bacillus subtilis, catalase-1, has been purified to homogeneity. The apparent native molecular weight was determined to be 395,000. Only one subunit type with a molecular weight of 65,000 was present, suggesting a hexamer structure for the enzyme. In other respects, catalase-1 was a typical catalase. Protoheme IX was identified as the heme component on the basis of the spectra of the enzyme and of the isolated hemochromogen. The ratio of protoheme/subunit was 1. The enzyme remained active over a broad pH range of 5-11 and was only slowly inactivated at 65 degrees C. It was inhibited by cyanide, azide, and various sulfhydryl compounds. The apparent Km for hydrogen peroxide was 40.1 mM. The amino acid composition was typical of other catalases in having relatively low amounts of tryptophan and cysteine.

Amino Acids↗

PubMed1987

Inflammatory bowel disease: psychiatric status of patients before and after disease onset.

Compared to normal controls, individuals with Crohn's Disease manifest an increased prevalence of anxiety, depression and panic disorder occurring at any time in their life. Only panic disorder had an excess prevalence in Crohn's disease relative to community dwelling normals prior to the time of disease onset. Individuals with ulcerative colitis did not demonstrate an increased prevalence of psychiatric disorder before or after disease onset. The results suggest that there is a higher prevalence of psychiatric disorder in patients with Crohn's Disease relative to the normal population and that a small but significant percentage of individuals with Crohn's Disease may have a psychiatric disturbance which predates their medical illness.

Adult↗