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Biomedical subjects

R Barker

Publications and source records attributed to R Barker.

At least 91 records · Page 5Linked to original sources
PubMed1979

Properties of cupric ions in benzylamine oxidase from pig plasma as studied by magnetic-resonance and kinetic methods.

Benzylamine oxidase from pig plasma has been studied by a variety of chemical and physical techniques. 1. Analytical ultracentrifugation, gel electrophoresis and isoelectric-focusing studies suggest that the enzyme is composed of two subunits with closely similar primary structures. 2. E.s.r. and n.m.r. measurements show that the enzyme contains two well-separated (greater than 0.6 nm) Cu2+ ions at chemically distinct sites. Each Cu2+ ion is coordinated by two water molecules, one 'axial' and the other 'equatorial'. Both water molecules undergo fast exchange (10(5)--10(8) s-1) with solvent and are deprotonated in the pH range 8--9, but only the equatorial water molecule is displaced by the inhibitors N3- and CN-. 3. Kinetic and e.s.r. measurements show that azide and cyanide compete against O2 binding and also make the two Cu2+ sites identical. It is concluded that Cu2+ must participate in the re-oxidation of reduced enzyme by molecular O2.

Animals↗
PubMed1979

Biotyping and colicine typing of Salmonella typhimurium strains of phage type 141 isolated in Scotland.

Cultures of Salmonella typhimurium (551 strains) of phage type 141 isolated in Scotland from 1965 to 1977 were examined for biotype and colicine type. Three main biotype clones were recognised: If (30 strains), 9f (507 strains) and 31bd (11 strains) with subtype variants 9bf (1 strain), 9cf (1 strain) and 31b (1 strain). The contribution made by each biotype clone to outbreaks in Scotland was analysed. The findings confirmed the distinctness of the three biotype clones within the single phage type and indicated possible origins of strains of biotypes of 9f and 31bd.

Animals↗
PubMed1978

Correlation of phaga type, biotype and source in strains of Salmonella typhimurium.

A series of 2092 cultures of Salmonella typhimurium isolated from human, animal and other sources in 57 countries were differentiated into 204 phage types and 19 primary and 147 full biotypes. Different biotypes belonged to the same phage type and different phage types to the same biotype, so the combination of typing methods differentiated strains more finely than either method alone: 574 different ;phage type/biotypes' were distinguished in 1937 cultures belonging to the 204 recognized phage types.The combination of biotyping with phage-typing was valuable in studying the phylogeny and spread of epidemic strains by distinguishing clones of different biotype within the same phage type and by confirming the relationship between cultures isolated from widely dispersed clones and that between cultures isolated before and after a clone had undergone variation in phage type, biotype, colicin type or antibiotic-sensitivity pattern.A widespread outbreak of infection with S. typhimurium phage type 141 in Scotland comprised independent dissemination of three clones of different biotypes, 1f, 9f and 31bd. During its epidemic spread in cattle in Britain between 1962 and 1969, another strain underwent variations in phage type (type 44 to type 29), biotype (type 26a to types 26d, 26bd, 26dgi, 26dz and 26i) and antibiotic sensitivity. A group of 275 non-fimbriate, non-inositol-fermenting and non-rhamnose fermenting (FIRN) strains, particularly associated with avian infections and thought to be clonal in origin, contained 27 phage types and 22 full biotypes in the primary biotypes 29-32.

Bacteriophage Typing↗
PubMed1977

Carbon-13 as a tool for the study of carbohydrate structures, conformations and interactions.

The application of 13C-NMR spectroscopy to problems involving the structures and interactions of carbohydrates is described. Both 13C-enriched and natural abundance compounds were used and some advantages of the use of the stable isotope are described. Carbon-carbon and carbon-proton coupling constants obtained from 1-13C enriched carbohydrates were employed in the assignment of their chemical shifts and to establish solution conformation. In all cases studied thus far, C-3 couples to C-1 only in the beta-anomers while C-5 couples to C-1 only in the alpha-anomers. C-6 and C-2 always couple to C-1 in both anomeric species. The alkaline degradation of glucose [1-13C] to saccharinic acids was followed by 13C-NMR. The conversion of glucose [1-13C] to fructose-1, 6-bisphosphate [1, 6-13C] by enzymes of the glycolytic pathway was shown as an example of the use of 13C-enriched carbohydrates to elucidate biochemical pathways. In a large number of glycosyl phosphates the 31P to H-1 and 31P to C-2 coupling constants demonstrate that in the preferred conformation and phosphate group lies between the O-5 and the H-1 of the pyranose ring. The influence of paramagnetic Mn2 + ions on the proton decoupled 13C-NMR spectra of uridine diphosphate N-acetylglucosamine indicates that the Mn2 + interacts strongly with the pyrophosphate moiety and with the carbonyl groups of the uracil and N-acetyl groups.

Carbohydrates↗
PubMed1977

Progress.

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Anesthesia, Inhalation↗
PubMed1976

The metal ion catalyzed decomposition of nucleoside diphosphate sugars.

The metal ion catalysed decomposition of the nucleotide diphosphate sugars, uridine diphosphate glucose, uriding diphosphate galactose, uridine diphosphate N-acetylglucosamine, guanosine diphosphate mannose, and guanosine diphosphate fucose (UDPGlc, UDPGal, UDPGlc-NAc, GDPMan, and GDPFuc, respectively), has been studies as a function of pH. UDPDlc and UDPGal decompose readily to the a,2-cycle phosphate derivative of the sugar and uridine 5'-phosphoric acid (UMP) in the presence of Mn2+. Under all conditions tested, UDPGal decomposes two to three times more rapidly than does UDPGlc. GDPFuc is slowly degraded to free fucose under similar conditions; the other nucleotide diphosphate sugars are stable. The rate of reaction increases with increasing hydroxide ion concentration from pH 6.5 to 7.9 and with metal ion concentration from 10 to 200 mm. Several metal ions are effective catalysts; at pH 7.5 WITH 20 mM UDPGal and 20 mM metal ion, the following apparent first-order rate constants (min-1 x 10(4)) were obtained: Eu3+ 700; Mn2+, 70; Co2+ 27; Zn2+, 22; Ca2+, 3.0; Cu2+, 2.4; and Mg2+, 0. It appears that Mn2+ concentrations that have been used in studies with nucleotide diphosphate sugars at neutral pH can catalyze significant decomposition leading to erroneous interpretation of kinetic and incorporation experiments.

Cations, Divalent↗
PubMed1976

[Attempt to obtain in vitro pre-erythrocyte forms of Plasmodium vivax in human liver cell cultures inoculated with sporozoites].

Using sporozoites of a strain of Plasmodium vivax of North Korean origin maintained in human subjects and in Anopheles atroparvus, the authors inoculated human liver cell cultures (primary cultures and Ist subcultures). The appearance of some rare intracytoplasmic forms is described, which are thought to be very likely connected with the pre-erythrocytic cycle of P. vivax. Further attempts are nevertheless necessary to confirm, or invalidate, the obtained results.

Animals↗
PubMed1975

A new biotyping scheme for Salmonella typhimurium and its phylogenetic significance.

A new, two-tier system for biotyping Salmonella typhimurium gives a finer and more reliable differentiation of strains than the Kristensen scheme and is capable of future extension by the addition of new types and new tests. Strains are allocated to a primary type (1-32) by their reactions in five primary tests with Bitter's xylose medium, meso-inositol, L-rhamnose, d-tartrate and m-tartrate. Subtypes are distinguished within the primary types by reactions in ten secondary tests, which include observations for flagella and type-1 (haemagglutinating) fimbriae. Full biotypes are designated by letters indicating the subtype reactions appended to the primary-type numbers. A series of 2030 strains of S. typhimurium collected from many different sources and countries during 53 years was classified into 19 of the 32 potential primary biotypes and into 144 full biotypes. Of the series, 14% (275) were non-fimbriate inositol-nonfermenting rhamnose-nonfermenting (FIRN) strain in primary biotypes 29-32. Most other strains were fimbriate and rhamnose fermenting. Observations on several series of cultures isolated from different human or animal sources in the same epidemic showed that the biotype characters of a strain were generally stable during its growth in the natural environment and in the unselective media used for isolation and storage. Most non-fermenting strains gave rise to fermenting mutants on prolonged incubation in the substrate-containing--and therefore selective--test medium, and false-positive results from this cause were avoided by making the definitive readings of tests after a short, carefully chosen period of incubation. A genealogical tree has been drawn to show how eighteen observed primary biotypes may have evolved from a presumed archetypal ancestor of biotype 1.

Bacteriophage Typing↗
PubMed1975

[Fluorescence in Thelohania apodemi Doby, Jeannès and Rault, 1963, a microsporidian parasite of the brain of the fieldmouse, Apodemus sylvaticus].

Colonies of Thelohania apodemi in fresh preparations of the brain of the field mouse show an intense fluorescence with ultra violet radiation. This phenomenon is undoubtedly due to the presence of chitin in the spore envelope. It is to our knowledge the first time that such a phenomenon of fluorescence has been described in the Microsporida.

Animals↗