Biomedical subjects

D W Cooper

Publications and source records attributed to D W Cooper.

At least 127 records · Page 7Linked to original sources

PubMed1977

Studies on metatherian sex chromosomes. III. The use of tritiated uridine-induced chromosome aberrations to distinguish active and inactive X chromosomes.

The paternal X inactivation system of kangaroos has been investigated in this study by using tritiated uridine-induced chromosome aberrations to distinguish the active from the inactive X. Previous work in eutherian mammals has demonstrated that constitutive heterochromatic chromosome regions are less susceptible to breakage by tritiated uridine than euchromatic regions. The results of a comparison between the paternal X chromosome of a wallaroo X red kangaroo hybrid female and the two X chromosomes of a red kangaroo female suggested that the facultative heterochromatin of the X is also less susceptible to breakage by this treatment. However there were significantly more breaks of the paternal X in fibroblasts than in lymphocytes of the hybrid female, which agrees with biochemical findings suggesting activation of the paternal X in fibroblasts. Our results strengthen the suggestion of other workers that the reduced number of aberrations in heterochromatin occurs because such breaks occur principally when the DNA and labelled RNA are in apposition during transcription. Some evidence was found of an apparent toxicity effect of the tritiated uridine solution on the cells.

Animals↗

PubMed1977

Studies on metatherian sex chromosomes. IV. X linkage of PGK-A with paternal X inactivation confirmed in erythrocytes of grey kangaroos by pedigree analysis.

Pedigree and population data are presented for erythrocyte phosphoglycerate kinase A (PGK-A) allozymes in the two species of grey kangaroo. The pedigree data confirm the hypothesis that PGK-A is X linked, the paternally derived X chromosomes being inactive in nucleated erythroblast precursors of the enucleate erythrocytes in females. The existence of different allozyme variants in eastern and western grey kangaroos further supports their division into separate species.

Animals↗

PubMed1976

Testis specific phosphoglycerate kinase B in mouse.

Mammals possess two genetically distinct forms of phosphoglycerate kinase (PGK). Only the X-linked PGK-A isozyme is detectable by electrophoresis of somatic and ovarian tissues of the mouse and of most other eutherian mammals studied to date. The PGK-B isozyme is highly active in testes and epididymides which contain spermatozoa, as well as in semen. PGK-B activity is first detectable in testes of 22-day-old mice and shows rapid increase concomitant with germ cell proliferation until day 40,after which activity increases only slightly. Two allelic isozymes (F and S) in mice express equal enzyme activity and are inherited in an autosomal codominant manner. One is equally as heat stable as PGK-A; the other is heat labile. Two of the 33 strains tested express neither F nor S, but do express a faintly staining PGK band which is of slightly faster mobility than F and which is absent from the other stains. This may represent a third allelic isozyme of PGK-B with reduced enzyme activity.

Alleles↗

PubMed1976

Studies on metatherian sex chromosomes II. The improbability of a stable balanced polymorphism at an X-linked locus with the paternal X inactivation system of kangaroos.

Female kangaroos and perhaps other female marsupials have a unique form of dosage compensation for X-linked genes in their soma. In these animals the paternal X is inactive. Heterozygote females therefore have the phenotype of one or the other of the homozygotes, with the allele which is expressed coming from their mother. The unexpressed paternally derived allele may, however, be transmitted to the next generation in the usual Mendelian manner and there be expressed. Such a combination of haploid phenotypic expression and diploid genotypic behaviour on the part of X-linked genes in kangaroos makes their population genetics unique. This paper examines the possibilities for balancing selection in the kangaroo X chromosome system and shows that balanced polymorphisms are unlikely to occur. If 1 - a, 1, 1 - b and 1 are the selection coefficients of the alpha1 females, alpha2 females, alpha1 males and alpha2 males respectively (where alpha1 is the phenotype when A1 is expressed and alpha2 the phenotype when A2 is expressed), then the equilibrium is reached when the gene frequency of A1 in females = 0-5(a-1 + b-1), which takes values between 0 and 1 for only a few of the biologically likely values of a and b.

Animals↗

PubMed1976

Data inversion method and error estimate for cascade centripeters.

Although centripeters ("virtual impactors") have fewer substrate problems than impactors, their small secondary flows from the impaction regions complicate data analysis. It is shown here how to use data inversion to achieve substantial data improvement. The success of such methods depends upon data error and instrument response. The condition number, which measures error magnification, is defined, discussed, and evaluated for three-stage and five-stage centripeters.

Aerosols↗

PubMed1974