Biomedical subjects
Publications and source records attributed to C Parker.
Approaches developed by the DHSS's central analytical team as a basis for comparing national priorities are explained by Gordon Harris, an economic adviser to the department, and Colin Parker, who recently completed a period of secondment to the department as an operational research consultant.
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An expanded linkage map of the Vibrio cholerae classical strain 162 chromosome has been prepared using a variety of new auxotrophic mutants. The chromosome consists of a single, linear linkage group. The map consists of 17 markers, which have been ordered; 20 mutational sites, which are tentatively ordered; five markers (ura-1, ser-2, mal-1, man-1, suc-1), which are linked but unordered; and three mutations (aro-2, cys-2 and cys-6) which showed little or no linkage. A proposal is made to standardize genetic nomenclature in V. cholerae genetic studies.
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Approximately 50% of the total lipids and virtually all of the colloids and particulates which impart turbidity to human serum are removed by filtration through 0.1 micrometer-poresize membrane filters in a high-volume tangential flow device. The advantages of the method over solvent extraction are: (a) no organic solvent(s) is added to the serum at any time, (b) filtrations can be performed rapidly at room temperature, (c) unstable lipoproteins and particulates are removed in 1 step, (d) scaleup from hundreds of ml to hundreds of liters is readily achievable, and(e) process time is markedly reduced.
The diarrheal response of orally inoculated infant mice to viable Vibrio cholerae and purified cholera toxin was quantitated by means of a fluid accumulation (FA) ratio. The FA ratio is defined as the gut weight/remaining body weight. FA ratios were determined in relation to time of exposure and dose. Onset of fluid accumulation with viable cells of strains CA401 and 569B occurred 8 h postinoculation and reached a near maximum of 16 h. A dose of 4 x 10(6) colony-forming units of strain CA401 was required for a positive response 16 to 18 h postinoculation. Several other classical cholera strains demonstrated a similar dose-related response. Strain 569B, however, required a 100-fold higher dose to give a positive response. Several mutant cholera strains were decreased virulence in other model systems elicited FA ratios decreased from wild-type values. Onset of fluid accumulation which cholera toxin occurred 6 to 8 h postinoculation and reached a maximum by 10 h. A dose of 0.5 microng was required for a positive response 10 to 12 h postinoculation. The positive response to toxin could be inhibited by preincubation with specific antitoxin.
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Platelet function was investigated in three patients with the Lesch-Nyhan syndrome. Platelet count, morphology and size distribution was normal in all patients. Platelet turnover was normal. Electron microscopy did not reveal any ultrastructural abnormality. Template bleeding times were normal and prolonged after aspirin ingestion in two out of the three patients: the patient that failed to respond to the aspirin challenge also had decreased retention of platelets on a glass bead column. Biochemical studies revealed that total platelet ATP was reduced by 34% in the presence of a normal level of ADP in the storage pool. These platelets failed to incorporate radioactive hypoxanthine but did incorporate radioactive adenine to produce adenine nucleotides and a trace amount of guanine nucleotides. The results indicate that normal platelets have a functionally intact pathway for utilizing hypoxanthine as a source of preformed purine, and that the failure to salvage this purine, as in the Lesch-Nyhan syndrome, results in a decreased level of total platelet ATP. These findings suggest that platelets can function normally despite a one third reduction in total ATP content.
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Vibrio cholerae cells, infected with the sex factor P, produce discrete, plaque-like clearings when plated on lawns of P(-) cells. We investigated the nature of these clearings and conclude that they are probably sites of active mating. We developed a quantitative assay for P(+) cells and used it to study the kinetics of sex factor spread in broth cultures. Both established and newly infected donor populations were efficient sex factor donors, indicating that P is not self-repressed. We also investigated the kinetics of recombinant formation in broth matings. In 1-hr matings, we routinely found recombination frequencies of 10(-6) per donor cell. Kinetic studies of recombinant formation showed that the markers tested all appeared at early times. Thus P, the V. cholerae sex factor, seems to resemble F in its transfer properties.
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Classical and El Tor strains of Vibrio cholerae were examined for production of bacteriophage or bacteriophage-related material by electron microscopy of mitomycin C-induced cultures. The strains were also tested for pathogenicity by using the ligated ileal loops of adult rabbits. Of the 27 strains tested, 25 showed a correlation between the production of bacteriophage-related material and pathogenicity. Both P(+) and P(-) strains produced bacteriophage tails. The bacteriophage tails of strains 569B and ATCC 9168 and other strains were shown to occur in an extended form with tail appendages.
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A sensitive and specific radioimmunoassay for adenosine 3',5'-cyclic phosphate (cyclic AMP) has been developed which allows measurement of the nucleotide in extracts of 5-10 mg of tissue. The radioimmunoassay is sufficiently specific for cyclic AMP to eliminate the need for prior chromatographic separation of the cyclic nucleotide from other tissue nucleotides. The radioimmunoassay system is based upon competition of cyclic AMP with a labeled cyclic AMP derivative of high specific activity for binding sites on an antibody specific for the cyclic nucleotide. Antibody to cyclic AMP was obtained by immunizing rabbits with an antigen prepared by conjugating succinyl cyclic AMP with human serum albumin. A high specific activity derivative of cyclic AMP was prepared by synthesizing succinyl cyclic AMP tyrosine methyl ester (SCAMP-TME) and iodinating the phenolic hydroxyl group of the tyrosine moiety with (125)I. Free and antibody-bound (125)I-SCAMP-TME were separated by precipitation of the antibody-bound fraction with a second antibody (goat anti-rabbit gamma globulin). Displacement of (125)I-SCAMP-TME by unlabeled cyclic AMP when plotted as a semilogarithmic function was linear over a concentration range of 2-100 picomoles. The specificity of the antibody was tested against structurally related nucleotides, nucleosides, and purine bases. All had less than 0.005 per cent of the potency of cyclic AMP in inhibiting (125)I-SCAMP-TME binding. The marked differences in affinity of the various cyclic nucleotides to cyclic AMP antibody would suggest that antibodies can be developed for each of the cyclic nucleotides by the principles used in this work.
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