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Biomedical subjects

J M Clark

Publications and source records attributed to J M Clark.

At least 253 records · Page 14Linked to original sources
PubMed1977

Systemic gas embolus: a discussion of its pathogenesis in the neonate, with a review of the literature.

We report, a term newborn infant with congenital vocal cord paralysis and congenital viral myocarditis. In her five days of life she developed a pneumomediastinum, pneumopericardium, subcutaneous emphysema, and terminally a pneumothorax and systemic air embolus. This unusual case is used to develop a concept of the pathogenesis of extraventilatory air, and is also represented in diagrammatic form.

Embolism, Air↗
PubMed1977

Basophil hypersensitivity response in rabbits.

A cutaneous basophil hypersensitivity response has been observed in rabbits immunized with bovine serum albumin and challenged intradermally with this antigen 7 days later. The cellular response appears to be similar to cutaneous basophil hypersensitivity reported in guinea pigs and humans. A basophil response was also observed in rabbits immunized with Staphylococcus aureus and challenged with viable staphylococcal cells 7 days later. A method of observing basophil infiltration in rabbits by means of connective tissue spreads obtained from the subcutaneous connective tissue is described. The rabbit should serve as an excellent model for the study of basophil responses as these animals have a significant basophil component with few if any tissue mast cells which may be confused both morphologically and functionally with the basophil.

Animals↗
PubMed1977

Umbilical artery catheterization by a cutdown procedure.

In severely ill newborns conventional methods of umbilical artery catheterization sometimes fail to achieve a functioning intravascular line. In 18 of 19 such newborns requiring umbilical artery catheters for optimal management, successful catheterization was attained using a cutdown procedure on the umbilical arteries. Vascular perforation within the anulus umbilicalis, tunica intima invagination ahead of an advancing catheter, and subintimal cannulation were defined as the causes of initial catheterization failure in all 19 newborns.

Catheterization↗
PubMed1976

Translation of satellite tobacco necrosis virus ribonucleic acid by an in vitro system from wheat germ.

The RNA of satellite tobacco necrosis virus (STNV) is an effective messenger RNA when translated in an in vitro system from wheat germ. This RNA codes for only STNV coat protein, as indicated (1) by coincidence of the tryptic fingerprints of the translation product and of STNV coat protein, (2) by equivalent size of the translation product and STNV coat protein, and (3) by isolation of an initial peptide of the in vitro product containing the amino acid sequence of the N terminus of STNV coat protein. STNV RNA does not contain a 5'-terminal m7G(5')ppp(5')Np---group and translation of STNV RNA by the wheat germ system does not involve prior formation of 5'-terminal m7G(5')ppp(5') nP---groups on STNV RNA. STNV RNA and 125I-labeled STNV RNA form a specific initiation complex when incubated with initiator tRNA, GTP, initiation factors, and wheat germ ribosomes. Treatment of this specific initiation complex with ribonuclease A allows isolation of an 125I-labeled oligonucleotide protected from ribonuclease A by the initiation complex. This specific oligonucleotide contains approximately 38 nucleotides, including nucleotide sequences that coincide with the codons of the N-terminal amino acids of STNV coat proteins.

Cell-Free System↗
PubMed1976

Inelastic electron tunneling spectroscopy of nucleic acid derivatives.

Inelastic electron tunneling spectra of nucleosides and nucleotides are presented which show that detailed information on the vibrational spectra of these molecules can be obtained from a few micrograms of material. A series of studies on adenine derivatives demonstrates that unambiguous identification of a large number of slightly different derivatives can be carried out by means of this technique.

Adenine Nucleotides↗
PubMed1976

Luminal surface of distended arteries by scanning electron microscopy: eliminating configurational and technical artefacts.

Perfusion fixation at physiological pressures, careful tissue handling, adequate drying and reduced beam exposure time eliminated many of the intimal surface projections, ridges and bridges which have been taken for normal structures on scanning electron microscopy. In the normal distended vessel, ovoid endothelial nuclei bulged into the lumen with their major axes aligned in the direction of flow: adjacent cell margins overlapped consistently in the direction of flow, with each cell overlapping the edge of its downstream neighbour. Regular longitudinal furrows associated with undulations of the internal elastin lamina were entirely eliminated from elastic arteries when distending pressures exceeded diastolic levels during fixation.

Animals↗
PubMed1975

The mutagenicity of azathioprine in mice, Drosophila melanogaster and Neurospora crassa.

The chemotherapeutic coumpound azathioprine was tested for possible mutagenicity in Swiss Albino mice, Drosophila melanogaster and Neurospora crassa. Utilizing the dominant-lethal assay it was found that acute oral doses of azathioprine (2 times 25 mg/kg body weight), induced dominant-lethal mutations in mouse spermatocytes. Chronic oral doses of azathioprine (2 times 25 mg/kg body weight/week for 10 weeks) resulted in a greater rate of dominant-lethality. This increase was not permanent, and by week 4 of gamete sampling there was no significant increase in dominant-lethal mutations. Histological sections showed that chronic treatment of male mice with azathioprine caused pyknosis of spermatocyte nuclei and depletion of the spermatid population. Both acute and chronic doses of azathioprine caused a temporary reduction in sperm viability. Oral treatment of male Canton-S, D. melanogaster with azathioprine caused an increase in dominant-lethality in broods assumed to correspond to spermatid and spermaotcyte stages. Azathioprine also increased the rate of non-disjunction of the X and Y chromosomes, loss of the long arm of the Y chromosome, and loss of the X or Y chromosome in treated male R(I)2, vf/BsYy+D. melanogaster. Since sex-ratio deviation did not occur in progeny from treated rod-X (yv/B2Yy+) male D. melanogaster, it was concluded that the observed sex-ration deviation in the treated ring-X stock was the result of induced ring-X lethality. Azathioprine induced recessive-lethal mutations in the ad-3 region of a N. crassa heterokaryon. In the host-mediated assay using this same heterokaryon and male Swiss Albino mice as host, the mutagenic activity of azathioprine did not appear to be potentiated or detoxified by the host. The results show that azathioprine has a deleterious effect on reproduction in mice and probably induces mutational events in mice, D. melanogaster and N. crassa.

Animals↗
PubMed1975

The effects of selection and human preference on coat colour gene frequencies in urban cats.

In an attempt to examine the possibility of selection on domestic cats populations in the urban environment, a number of surveys were conducted in four contrasting areas of Glasgow--two near either extreme of Western, industrial socioeconomic status. The first survey was in the form of a questionnaire to inhabitants enquiring of preference for a particular phenotype. This survey revealed a consistent preference for lighter phenotypes in all areas. The incidence of cat ownership was greatest in the two affluent areas where there was also a high risk of the cat being sterilised. Independent of the questionnaire survey was a study of cat coat colour gene frequencies in each of the four districts. This study revealed that darker phenotypes predominate in the two areas of lower socioeconomic status, Maryhill and Govan. To date, the cat populations in these two areas are the darkest to have been described in the world. In contrast, a lighter phenotype was found in cats inhabiting the two districts of higher socioeconomic status, Kelvinside and Bellahouston. This difference in phenotypic darkness was also paralleled by appropriate clines in coat colour gene frequencies. The results demonstrate that human preference is not effectively translated into selection at any of the loci considered. In situations where human preference is most likely to occur, neutering risk is also high. Although the force responsible for the darkening of phenotype has yet to be identified, the fact that the darker alternative allele at each of the O, a, t, d, S and W loci is favoured suggests that selection is operating on these polymorphic coat colour loci.

Animals↗