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Biomedical subjects

R G Wilkinson

Publications and source records attributed to R G Wilkinson.

At least 19 recordsLinked to original sources
PubMed1996

Identification of duck T lymphocytes using an anti-human T cell (CD3) antiserum.

Duck lymphocytes have not been classified into cells resembling B or T cells of mammals. Reagents used in the past to identify lymphocyte populations in other species have not been useful for this purpose and antibodies raised to duck immunoglobulin bind in high proportions to blood and organ lymphocytes of ducks as well as to their red blood cells. Here we report that a polyclonal rabbit antiserum reacting to the CD3 marker on human T cells has been used to identify duck T lymphocytes. These antibodies react with the intracytoplasmic portion of the human CD3 epsilon chain (amino acids 156-168), an epitope highly conserved between mammals. Immunohistochemical staining with this antiserum of sections of duck lymphoid organs and FACScan analysis of duck lymphoid cell suspensions identified a population of duck lymphocytes with a staining pattern similar to that seen for mammalian T cells. This anti-human CD3 immunoprecipitated a 23 kDa protein from a duck lymphoblast lysate: a size similar to the human CD3 epsilon chain. This is the first direct identification of duck T lymphocytes.

Animals↗
PubMed1994

Divided we fall.

Explore the source record for details and available documents.

Health Policy↗
PubMed1992

National mortality rates: the impact of inequality?

Although health is closely associated with income differences within each country there is, at best, only a weak link between national mortality rates and average income among the developed countries. On the other hand, there is evidence of a strong relationship between national mortality rates and the scale of income differences within each society. These three elements are coherent if health is affected less by changes in absolute material standards across affluent populations than it is by relative income or the scale of income differences and the resulting sense of disadvantage within each society. Rather than socioeconomic mortality differentials representing a distribution around given national average mortality rates, it is likely that the degree of income inequality indicates the burden of relative deprivation on national mortality rates.

Humans↗
PubMed1989

The IUCD-associated incidence of Actinomyces israelii in the female genital tract.

Cervical swabs and in many cases also intrauterine contraceptive devices were examined from 973 women for the presence of Actinomyces israelii. It was detected in 11.6% of these women, the majority of whom were asymptomatic. The detection, however, of A. israelii in the female genital tract was associated with an almost 4-fold increase in the incidence of pelvic inflammatory disease (PID), indicating that colonization may progress to an infection in a small number of women. The incidence of A. israelii in the female genital tract of IUCD wearers was more than doubled when the IUCD was worn for longer than 4 years. The type of IUCD worn did not appear to be an important risk factor. Immunofluorescent staining of cervical smears identified 64% of cases. Specific culturing for A. israelii or cytological screening of Papanicolaou smears in addition were required to increase the isolation rate to nearly 90%.

Actinomyces↗
PubMed1988

Antibody development and cellular immune responses in sheep immunized and challenged with Sarcocystis tenella sporocysts.

Four specific-pathogen-free (SPF) sheep were experimentally infected with 10(3) or 10(4) Sarcocystis tenella (syn. S. ovicanis) sporocysts and another two sheep served as uninfected controls. All sheep were challenged 49 days later by infection with 2.5 X 10(5) sporocysts and their humoral and cellular responses to infection and challenge were assessed weekly by enzyme immunoassays and lymphocyte transformation assays. The control sheep died from acute sarcocystosis 29-30 days after challenge, whereas the immunized sheep survived and were protected against acute disease. Specific IgM and IgG antibodies were detected in the immunized sheep from 28 days after infection onwards. Lymphocytes collected before and after challenge did not exhibit any significant differences in their responses to stimulation with S. tenella cystozoite or sporozoite antigens. Furthermore, lymphocytes collected before challenge did not differ from the controls in their responses to stimulation with the mitogens lipopolysaccharide or phytohaemagglutinin. However, lymphocytes collected after challenge did exhibit increased blastogenic responses to stimulation with both mitogens from 21-28 days after challenge onwards. The infected sheep were necropsied 46 days after challenge, and histological and ultrastructural studies revealed numerous infiltrates of lymphocytes, histiocytes and plasma cells in the skeletal muscles, sometimes in association with degenerating parasitic cysts and macrophage myophagia. Parasites were not completely eliminated nor prevented from further establishment, therefore the protective immunity was not sterile but rather a state of premunition.

Animals↗
PubMed1983

Interactions between acetylcholinesterase and tetra-N-alkylammonium ions.

A study of the mechanism of interaction of acetylcholinesterase with some simple tetra-N-alkyammonium ions has been made. Kinetic schemes have been proposed which are consistent with the experimental results observed in the enzyme-tetra-N-alkylammonium system in the presence of substrate and in the presence of an organophosphorus inhibitor.

Acetylcholinesterase↗
PubMed1983

Adult stature and age at menarche in Zapotec-speaking communities in the Valley of Oaxaca, Mexico, in a secular perspective.

Adult stature and the age at menarche among individuals from Zapotec-speaking communities in the Valley of Oaxaca in southern Mexico are considered in a secular perspective. Four sets of observations are utilized: 1) adult stature in males and females from five rural communities; 2) age at menarche in adult women and school girls from a single rural community; 3) earlier studies of adult stature in the Valley of Oaxaca; and 4) estimated stature from long bones excavated in various archaeological sites in the Valley of Oaxaca. There were no significant differences among the five communities for stature; hence, the data were pooled for analysis and comparison. Results of linear regression of stature and stature adjusted for the estimated effects of aging after 30 years of age on year of birth indicate negligible secular changes in either sex. Comparisons with statures from earlier surveys, the earliest dates to 1899, also indicate negligible changes. When adult women are grouped according to age, there are no differences in mean ages at menarche between the older and younger women. Mean age at menarche for the total adult sample is 14.53 +/- 0.08 years, which compares favorably with the probit estimate for school girls, 14.70 +/- 0.32 years. These results thus suggest virtually no secular change in adult size and maturity of the Zapotec-speaking population in the Valley of Oaxaca over the past 80 years. Differences in stature between contemporary populations and estimated statures from long bones from several archaeological sites in Oaxaca are small, and thus suggests little secular change over the past one to two-thousand years.

Adult↗
PubMed1983

Partial purification and characterization of two enzymes involved in isovaleric acid synthesis in Clostridium bifermentans.

Conversion of leucine to isovaleric acid by Clostridium bifermentans is achieved by the action of at least two enzymes. One is a transaminase producing alpha-ketoisocaproic acid, which was purified 30-fold from osmotic lysates of late-exponential phase cells by repeated chromatography on DEAE-Sepharose C16B and Sephacryl S300: this represented a 147-fold purification of activity found in sonically disrupted cells. This enzyme had an apparent molecular weight of approximately 190000 and was composed of six identically sized sub-units (molecular weight 31000 +/- 1000). Transamination required pyridoxal phosphate and pyruvate and was optimal at pH 8.6; the apparent Km for leucine was 7.0 mM. Activity was totally inhibited by 1 mM-p-chloromercuribenzoate and partially inhibited by other thiol reagents. The second enzyme decarboxylated alpha-ketoisocaproic acid to form isovaleric acid and was also partially purified by chromatography on DEAE-Sepharose C16B and Sephacryl S300. It has an apparent molecular weight of 240000 and required FAD and coenzyme A for activity; the Km for alpha-ketoisocaproic acid was 4.2 mM and activity was optimal around pH 8.0. This enzyme was a flavoprotein with absorption maxima at 280, 320 and 400 nm, and a fluorescent maximum at 500 nm. The prosthetic group, FAD, dissociated from the protein during purification resulting in an inactive apoenzyme which was only partially re-activated by FAD. Activity was completely inhibited by several thiol reagents tested at 1 mM.

Carboxy-Lyases↗
PubMed1983

Subcellular location of enzymes involved in leucine dissimilation in Clostridium bifermentans.

Conversion of leucine to isovaleric (iV) and isocaproic (iC) acids by cell-free extracts of Clostridium bifermentans was demonstrated using two lysis procedures. Sonication resulted in an extract which had the enzymes to convert leucine to alpha-ketoisocaproic acid (alpha-kiC) and thence iV, but failed to produce iC. Extracts prepared by osmotic lysis, which contained intact membranes, could convert leucine to both iV and iC. The enzyme which converts leucine to alpha-kiC was solubilized during osmotic lysis, whereas the decarboxylase and leucine reductase system remained membrane bound. Osmotic lysis also released at least two small molecular weight, heat-stable, anionic components (3500 greater than molecular weight greater than or equal to 1000), which stimulated decarboxylase activity.

Caproates↗
PubMed1982

Isolation and properties of metronidazole-resistant mutants of Clostridium perfringens.

Clostridium perfringens strains resistant to metronidazole and tinidazole were isolated from the sensitive parent strain CM288 after mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. Strain CM288 was already resistant to rifampicin and nalidixic acid; these genetic markers helped to confirm the identity of mutants. All mutants showed similar characteristics: they grew more slowly than the parent strain and failed to reach the same maximum turbidity; uptake of metronidazole and tinidazole from culture fluids was slow and end products of glucose metabolism were different from those of the parent. Pyruvate dehydrogenase activity was not detected in broken cell preparations of the mutant strains although this enzyme was readily detected in the parent strain. Changes in end products of glucose metabolism were consistent with the absence of pyruvate dehydrogenase activity because pyruvate was accumulated during growth and lactate levels were higher whereas acetate, CO2 and ethanol levels were diminished.

Clostridium perfringens↗
PubMed1982

Leucine dissimilation to isovaleric and isocaproic acids by cell suspensions of amino acid fermenting anaerobes: the Stickland reaction revisited.

Freshly compared cell suspensions of clostridia (Clostridium bifermentans, C. botulinum proteolytic type A, C. difficile, C. sordellii, and C. sporogenes) and Peptostreptococcus anaerobius converted leucine to isovaleric (iV) and isocaproic (iC) acids in the absence of other amino acids. The optimal pH for conversion was between 8 and 9 at 37 degrees C. The stoichiometry of reaction was compatible with that expected for the Stickland reaction, as the ratio of iV to iC was 1:2, the amount of CO2 produced was equivalent to that of iV, and ammonium ion concentrations were equal to the total C5 and C6 acids formed. The presence of alanine and valine (proton donors in the Stickland reaction) in incubations effectively increased the concentration of iC at the expense of iV production, implying that leucine acted there primarily as a proton acceptor. Glycine and proline (proton acceptors) stimulated both iV and iC production from leucine, but increases in iV concentrations were proportionately greater than for iC so that leucine was primarily a proton donor in the presence of proton acceptors. Glucose stimulated the conversion of leucine to volatile fatty acids but favoured iC production. Production of iC from leucine was inhibited by surface active compounds (cetyltrimethylammonium bromide and desoxycholate) as well as arsenite and iodoacetate. The redox dyes methyl viologen and phenosafranine inhibited iC production more severely than iV production, as did the nitroimidazole antimicrobial agent, metronidazole.

Amino Acids↗