Biomedical subjects
D Brooks
Publications and source records attributed to D Brooks.
The interaction of ligands with chemically modified phosphorylase b.
Phosphorylase b which had been inactivated with 5-diazo1H-tetrazole was specifically labelled with 4-iodoacetamidosalicylic acid (a fluorescent probe) or with N-(1-oxyl-2,2,6,6,-tetramethyl-4-piperidinyl)iodoacetamide (a spin label probe) so that the binding of ligands and accompanying conformational changes could be determined by fluorescence or electron spin resonance changes, respectively. The allosteric effector, AMP, causes conformational changes similar to those caused in the native enzyme. The affinity of binding of phosphate or AMP to the inhibited protein is the same as for the unmodified protein. The heterotropic interactions between glucose-1-phosphate or glycogen and AMP are much less in the inactivated enzyme than in unmodified phosphorylase. Using a light scattering assay, it is shown that the modified enzyme binds to glycogen less strongly than the native protein. Phosphorylase b which had been inactivated by carbodimide in the presence of glycine ethyl ester, resulting in the modification of one or more carboxyl groups, was labelled with the spin label probe described above. The modified enzyme has an affinity for AMP similar to that of the native enzyme. AMP binding to the modified enzyme is tightened by glycogen, weakened by glucose-6-phosphate and is unaffected by glucose-1-phosphate. The actions of 5-diazo-1H-tetrazole and carbodimide on phosphorylase are discussed in the light of the above observation.
Vertical organization in the visual cortex (area 17) in the cat.
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Diagnosis of urinary-tract infection.
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Treatment of depression in general practice.
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Oxygen transport changes after transfusion with stored blood in a hemorrhagic canine model.
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XO-XY mosaicism and nonfluorescent Y chromosome.
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Pathogenesis of the urethral syndrome in women and its diagnosis in general practice.
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Regulation of the bacterial cell wall: analysis of a mutant of Bacillus subtilis defective in biosynthesis of teichoic acid.
Bacillus subtilis 168ts-200B is a temperature-sensitive mutant of B. subtilis 168 which grows as rods at 30 C but as irregular spheres at 45 C. Growth at the nonpermissive temperature resulted in a deficiency of teichoic acid in the cell wall. A decrease in teichoic acid synthesis coupled with the rapid turnover of this polymer led to a progressive loss until less than 20% of the level found in wild-type rods remained in spheres. Extracts of cells grown at 45 C contained amounts of the enzymes involved in the biosynthesis and glucosylation of teichoic acids that were equal to or greater than those found in normal rods. Cell walls of the spheres were deficient also in the endogenous autolytic enzyme (N-acyl muramyl-l-alanine amidase). Genetic analysis of the mutant by PBS1-mediated transduction and deoxyribonucleic acid-mediated transformation demonstrated that the lesion responsible for these effects (tag-1) is tightly linked to the genes which regulate the glucosylation of teichoic acid in the mid-portion of the chromosome of B. subtilis.
Sulphadimidine, co-trimoxazole, and a placebo in the management of symptomatic urinary tract infection in general practice.
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Glucosylation of teichoic acid: solubilization and partial characterization of the uridine diphosphoglucose: polyglycerolteichoic acid glucosyl transferase from membranes of Bacillus subtilis.
Polyglycerolteichoic acid:glucosyl transferase (TAG transferase), one of the three enzymes involved in the pathway leading to the glucosylation of teichoic acid in Bacillus subtilis 168, was investigated. During the early stages of the growth of B. subtilis, TAG transferase is predominantly a soluble enzyme found in the cytoplasm. As growth proceeds, the amount of soluble enzyme decreases and the proportion of insoluble, membrane-bound TAG transferase increases, reaching a maximal value at the close of the logarithmic phase. Data are presented which suggest that these are two forms of the same enzyme, or have some common component. The effects of chaotropic agents, such as sodium trichloroacetate and sodium perchlorate, on the cytoplasmic membrane were also studied. These data show that such compounds can effectively remove the TAG transferase from the membrane in a water-soluble form. A study of some of the physical properties of this solubilized enzyme suggests that there is little difference between the two forms of the enzyme. Experiments are described which indicate that the glucosyl transfer by both the membrane-bound and soluble enzymes is not mediated by lipids.
Direction of chain extension during the biosynthesis of teichoic acids in bacterial cell walls.
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The mechanism of biosynthesis and direction of chain extension of a poly-(N-acetylglucosamine 1-phosphate) from the walls of Staphylococcus lactis N.C.T.C. 2102.
1. The synthesis of a polymer of N-acetylglucosamine 1-phosphate, occurring in the walls of Staphylococcus lactis N.C.T.C. 2102, was examined by using cell-free enzyme preparations. The enzyme system was particulate, and probably represents fragmented cytoplasmic membrane. 2. Uridine diphosphate N-acetylglucosamine was the only substrate required for polymer synthesis and labelled substrate was used to show that N-acetylglucosamine 1-phosphate is transferred as an intact unit from substrate to polymer. 3. The properties of the enzyme system were studied. A high concentration of Mg(2+) or Mn(2+) was required for optimum activity, and the pH optimum was about 8.5. 4. End-group analysis during synthesis in vitro showed that newly formed chains contain up to about 15 repeating units. Pulse-labelling indicated that chain extension occurs by transfer from the nucleotide to the ;sugar-end' of the chain, i.e. to the end that is not attached to peptidoglycan in the wall.
A lipid intermediate in the synthesis of a poly-(N-acetylglucosamine 1-phosphate) from the wall of Staphylococcus lactis N.C.T.C. 2102.
1. The enzymic synthesis of the wall polymer poly-(N-acetylglucosamine 1-phosphate) in Staphylococcus lactis N.C.T.C. 2102 was studied by using UDP-[acetyl-(14)C]N-acetylglucosamine and the corresponding nucleotide containing (32)P. 2. Labelled material was extracted from the particulate enzyme preparation with butan-1-ol. Pulse-labelling experiments indicated that this material contained an intermediate in the biosynthesis. 3. The lipid intermediate was partially purified, and chemical and enzymic degradation showed that it was composed of N-acetylglucosamine 1-pyrophosphate in labile ester linkage to an organic-soluble alcohol, possibly a polyisoprenoid alcohol. The methanolysis of sugar 1-pyrophosphate derivatives, including nucleoside diphosphate sugars, is discussed in relation to degradation products obtained from the lipid. 4. The lipids from the particulate enzyme preparation probably contained another compound in which N-acetylglucosamine 1-phosphate is attached to an organic-soluble alcohol; this may participate in the biosynthesis of another polysaccharide. 5. The function of the lipid intermediate in polymer biosynthesis is discussed.
Monitoring solution-phase combinatorial library synthesis by capillary electrophoresis.
Capillary electrophoresis has been applied to monitor model reactions in solution-phase combinatorial chemistry. In particular, the simultaneous alkylation reactions of secondary amines with a series of benzyl halides has been investigated. Reactant and product concentrations were monitored using capillary electrophoresis in a non-aqueous buffer system. The simplified sample preparation was a key feature making this an attractive method of analysis. The results demonstrate that capillary electrophoresis is a useful tool for monitoring reactions to determine initial rates, rate constants, and extinction correlation coefficients for quantitative analysis in combinatorial chemistry, and is a broadly applicable technique for the analysis of a variety of organic and bioorganic transformations.
Q fever hazards from sheep and goats used in research.
Two recent outbreaks of Q fever in research institutions prompted the authors to review extant data, in an effort to delineate hazards to humans from small ruminants used in research. Prevalence of Q fever antibodies was 24% among 2097 sheep and 57% among 1475 goats from various sources. In a facility using sheep for prenatal research, in which an epidemic of human Q fever later occurred, antibody prevalence among sheep was 77%, with larger than usual proportions of high (greater than or equal to 128) titers. Antibody prevalence was 5% in a sample from the general human population and 11% among 347 persons at three research institutions (17% among students, 8% among the research staff). Except for animal caretakers routinely exposed to sheep, antibody prevalence among research staff approximated prevalence in the general population. Suggestions are made for surveillance and vaccination of sheep and goats used in medical research institutions.
Omeprazole in a dog with gastrinoma.
A 9-year-old male German Shepherd Dog was presented with the primary complaints of vomiting, profuse watery diarrhea, anorexia, and severe weight loss. The dog developed hematemesis and melena, which were unresponsive to treatment with an H2-receptor antagonist and a gastrointestinal protectant. A marked neutrophilia, panhypoproteinemia, hypokalemia, and mildly increased activities of alkaline phosphatase and alanine aminotransferase were the only relevant abnormalities found on a CBC, serum biochemical profile, and urinalysis. An exploratory laparotomy revealed several small nonresectable masses at the root of the mesentery, which were identified histologically as a neuroendocrine neoplasm. Immunohistochemical staining of the neoplasm was positive for gastrin and negative for insulin, glucagon, pancreatic polypeptide, and vasoactive intestinal polypeptide. Fasting serum gastrin concentrations were high. Zollinger-Ellison syndrome was diagnosed, and the dog was treated with omeprazole, an H+,K(+)-ATPase inhibitor. All clinical signs resolved, and the dog remains asymptomatic 2 years later. Omeprazole may be the gastric acid antisecretory drug of choice for dogs with gastrinoma.
A survey of suctioning practices among physical therapists, respiratory therapists and nurses.
OBJECTIVE: To assess the current tracheal and oropharyngeal suctioning practice variability within and among the professions of physical therapy, respiratory therapy and nursing. DESIGN: A mail survey of physical therapists, respiratory therapists and registered nurses who perform suctioning. The survey instrument consisted of questions about professional characteristics, clinical suctioning practice and sociodemographics. SETTING: The survey was restricted to professionals practising within the province of Ontario. PARTICIPANTS: Random samples (n=448) were drawn from membership of the regulatory boards of all three professions. MAIN RESULTS: Fifty-eight per cent of respondents returned completed questionnaires. There was large variation in reports of gloving procedure (eg, double clean: 26% for physical therapists, 5% for respiratory therapists, 55% for registered nurses, P<0.0001) and technique of catheter use (sterile, inline or clean, P<0.01). There was also discrepancy in the techniques used to minimize harmful effects, ie, prelubrication with gel (83% for physical therapists, 54% for respiratory therapists, 17% for registered nurses, P<0.0001), use of hyperinflation (12% of physical therapists, 25% of respiratory therapists, 39% of registered nurses never hyperinflate) and use of instillation (7% of physical therapists, 0% of respiratory therapists, 19% of registered nurses never instill). However, there was agreement about the routine application of hyperoxygenation (74% or more) and there was almost perfect agreement (99% or more) within and across the three professions that secretion removal was the main indication for suctioning. CONCLUSIONS: The results of this study indicate a wide variation in suctioning techniques among physical therapists, respiratory therapists and registered nurses. Comparisons among professions revealed inconsistencies in some areas, such as the use of in-line catheters, gloving procedures, prelubrication and hyperinflation.