Search PubMed⌕ Search

Biomedical subjects

K Williams

Publications and source records attributed to K Williams.

At least 469 records · Page 26Linked to original sources
PubMed1980

Virulence of Streptococcus mutans: revertants of mutant C4.

Mutant C4, a poor plaque-forming mutant of Streptococcus mutans 6715-HSR, was employed to obtain isolates resembling the parent strain (a plaque former). Seventeen presumptive revertants, as identified by colonial morphology, were isolated from mutant C4 after enrichment cycles in a sucrose-glass beads medium. These isolates displayed properties which resembled the parent in ability to produce plaque, patterns of fermentation, and resistance to streptomycin. In a detailed study, five selected isolates were found to be similar to the parent type 6715-HSR with respect to content of the serotype antigen, sucrose- or dextran-induced cell aggregation, glucosyltransferase and adherence activities, and cariogenicity. Thus, in selection for revertants to parental colonial morphology, the pleiotropic changes in plaque formation, adherence, glycosyltransferase activity, and virulence demonstrated by C4 all concomitantly reverted to their parental phenotypes.

Animals↗
PubMed1980

A physiological model for hepatic metabolism of transferrin-bound iron.

Hepatic iron and transferrin uptake following intravenous injection of purified native rat transferrin has been studied in the rat. Livers were removed at varying time intervals postinjection and were fractionated by isopycnic density gradient centrifugation. Neither 59Fe or 125I (labeling transferrin) appeared in the lysosomal or mitochrondrial fractions at any stage up to 14 days. 59Fe first appears in the supernatant zone of the sucrose gradient and with increasing time postinjection passes through regions of increasing density. By 16 h 59Fe became established at a density of 1.10 g/cm3 and it was identified as ferritin. Ferritin persisted labeled with 59Fe for up to 14 days. The study suggests hepatic iron uptake does not involve endocytosis. Iron is incorporated into ferritin of increasing density. This model can be used for the study of iron metabolism in human biopsy samples.

Animals↗
PubMed1980

Epidemiological studies of rubella virus in a tropical African community.

The single-radial-haemolysis test for antibody to rubella virus provides a simple rapid method for carrying out large serological surveys. The availability of a collection of sequential serum samples from inhabitants of two Gambian villages, Manduar and Keneba, made it possible to determine the pattern of rubella epidemics in these communities between 1966 and 1976. The serological findings indicated that an epidemic had occurred approximately two years before the commencement of the study. There was no further evidence of rubella infection until approximately 1973 when a large-scale epidemic occurred. Although the communities were monitored throughout the period of study there was no clinical evidence of infection and no cases of congenital rubella syndrome.

Adolescent↗
PubMed1980

Specific clonal regulation in the response to phosphocholine. I. Genetic analysis of the response of a distinct idiotype (M511 Id).

The genetic basis of the BALB/c anti-PC response pattern was studied in allotype and H-2 congenic mouse strains. In both a T-dependent (PC-KLH) and a T-independent (R36A) system, one of the major anti-PC idiotypes, the M511 IdI, is under specific clonal regulation. The expression of the two other major anti-PC idiotypes, T15 and M603X, is independent of such control. The expression of the M511 IdI is controlled by more than one gene, with at least one of the genes unlinked to either the Igh or the H-2 locus. Low responder mice, such as BALB/c, possesses the relevant genetic information coding for the H and L chains of the M511 Idi-positive antibodies, indicating that the expression of this idiotype is dependent on a specific regulatory mechanism.

Animals↗
PubMed1980

A technique developed for isolated canine papillary muscle function in various plasmas; and utility ascertained with plasma containing myocardial depressant factors.

Isolated papillary muscles from young dogs were studied to determine the feasibility of utilizing plasma, without added foam depressants, as a test solution to support muscle function. Diluted canine plasma, undiluted canine plasma, plasma with adjusted protein content, monkey plasma, and plasma containing myocardial depressant factors (MDF) were evaluated. For each test, each papillary muscle served as its own control, with either Krebs-Henseleit solution or a control plasma to establish a basis for evaluation of the test plasma. A technique was implemented to oxygenate the muscle, in plasma, without foam production and to monitor pH continuously. These studies indicated that plasma (diluted, undiluted, or with protein adjustments to accommodate experimental procedural requirements) was a satisfactory test solution. Furthermore, plasma from species unrelated to the dog could be utilized. In utilizing plasma, it was essential to establish or adjust the pH and osmolarity for normal muscle function. These studies with plasma containing MDF indicated that MDF depressed canine papillary muscle function. The Vmax values and Po values were decreased and latency was increased. The effects of MDF in canine papillary muscle preparations were completely reversible in short-term studies (up 10 10 hours' duration).

Animals↗
PubMed1979

Structural characteristics of interferons from mouse Ehrlich ascites tumor cells.

An improved procedure for the isolation of interferons produced by mouse Ehrlich ascites tumor cells infected with Newcastle disease virus provides interferons of three size classes (33,000, 26,000, and 20,000 daltons) with specific activities between 2 and 3 x 10(9) units/mg of protein and a yield of 11 to 20%. The tryptic peptide maps of the two larger species are very similar; that of the smallest species is different, at least in part. The amino acid compositions of the three species are very close. Their NH2-terminal amino acids are identical and so are the amino acids released by carboxypeptidase A treatment. These data are consistent with the possibility that the differences in size between the three species may be due, at least in part, to unequal glycosylation.

Amino Acids↗
PubMed1979

Serum protein polymorphisms in a village community from the Gambia, West Africa (Hp, Tf, and Gc).

Serum samples from 857 inhabitants of the village of Keneba, The Gambia, West Africa, were examined by means of polyacrylamide gel electrophoresis. In 203 cases no haptoglobin could be detected, whilst in the remaining 654 samples the three common haptoglobin phenotypes were found with gene frequencies of 0.651 (Hp1) and 0.349 (Hp2). The D1 transferrin variant gene was found with a frequency of 0.025. In the serum Gc system the fast variant Gc-Ab was detected, the gene frequencies being: Gc1, 0.943; Gc2, 0.044; and GcAb, 0.013.

Alpha-Globulins↗
PubMed1978

Isoelectric focusing of human red cell phosphoglucomutase: the distribution of variant phenotypes in a village population from the Gambia, West Africa.

A total of 637 individuals from the rural village of Keneba in The Gambia, West Africa, have been typed for red cell PGM using isoelectric focusing (pH 5--7) in polyacrylamide gels. Eight different phenotypes have been detected. The frequency of the four alleles at the PGM1 locus was found to be PGM1+(1) 0.795, PGM1-(1) 0.053, PGM2+(1) 0.133, AND PGM2-(1) 0.019. A study of the PGM phenotypes in 89 families confirmed the simple Mendelian codominant inheritance of the four alleles. Comparative population data suggest that red cell PGM typing by isoelectric focusing might prove to be a useful genetic marker in anthropological studies.

Black People↗
PubMed1978

Red cell glucose 6 phosphate dehydrogenase genotypes of the population of two West African villages.

Blood samples from 1109 individuals, residents of two villages in The Gambia, West Africa, have been examined for red cell G6PD. Using both starch gel electrophoresis and a spectrophotometric assay, preliminary phenotypes were assigned to the 519 males and 590 females. The G6PD genotypes were established by reference to the family trees of the two village populations. In addition to the G6PD alleles B+, A+ and A-, a fourth allele, representing a new variant of human G6PD was discovered between the two villages, despite their being of the same tribal origin and only five miles apart.

Black People↗