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R M Speed

Publications and source records attributed to R M Speed.

45 records · Page 3Linked to original sources
PubMed1983

Delayed meiotic development and correlated death of spermatocytes in male mice with chromosome abnormalities.

The kinetics of germ-cell development were examined in random-bred adult Swiss mice by means of tritium autoradiography. Comparisons were made between males with normal (+/+) and abnormal karyotypes: Rb(11.13)4Bnr/+ and T(1;13)70H/+ heterozygotes, T70H tertiary trisomics, and T70H translocation trisomics. The time taken for the first wave of labelled cells to progress from premeiotic S-phase to diplotene and then on to the second meiotic metaphase was estimated in each stock, and rates of increase of labelled meiotic figures were measured. The S-phase to diplotene interval did not differ significantly among the different genotypes, taking from 10 days, 16 h to 10 days, 19 h. In Rb4Bnr/+, T70H translocation trisomic, and T70H tertiary trisomic males, however, labelled meiotic figures accumulated at a lower rate, particularly in the tertiary trisomics. A cell delay for some meiocytes was thus indicated during meiotic prophase. A correlation was seen between the degree of meiotic delay and severity of reduction in sperm count. The period from late diplotene to metaphase II was also found to be longer in T70H tertiary trisomics than in controls (+/+) or other chromosomally abnormal males.

Animals↗
PubMed1982

Meiosis in the foetal mouse ovary. I. An analysis at the light microscope level using surface-spreading.

The identification and progression of the prophase stages of meiosis in the mouse foetal ovary are reported, from d 13 of gestation to d 1 postpartum. Air-dried Giemsa-stained oocyte preparations are compared with surface-spread silver-stained cells. The latter method allows a more detailed quantitative analysis of the pachytene stage. Numbers of synaptonemal complexes can be counted, and the degree of synapsis determined. The progression of cells appears to be relatively synchronous, in agreement with previous reports. The activity of nucleolar organisers, in particular one associated with the shortest synaptonemal complex (chromosome No. 19) is described. At late pachytene the lateral elements of the No. 19 bivalent desynapse precociously with apparent nucleolar involvement.

Animals↗
PubMed1982

The use of surface spreading in the pachytene analysis of a human t (Y;17) reciprocal translocation.

This paper describes a human Y;17 reciprocal translocation in an azoospermic male ascertained through infertility. Meiotic studies made on both air-dried and surface-spread preparations are reported in addition to a somatic chromosome analysis carried out by high resolution R-banding on pro-metaphase chromosomes. The possible cause of spermatogenic disturbance in Y-autosome heterozygotes is discussed.

Chromosome Aberrations↗
PubMed1981

The response of germ cells of the mouse to the induction of non-disjunction by X-rays.

The sensitivity of male and female pre-meiotic germ cells of the mouse to the induction of non-disjunction by low doses of X-rays, has been tested. No enhancement with 5 rad was observed over control values in dictyate oocytes irradiated from young or aged females. In males, a 3-fold increase in overall chromosome abnormalities (aneuploids, polyploids and mosaics) was found following the treatment of germ cells sampled in the 7th week after irradiation (spermatogonia and early primary spermatocytes) with 100 rad. The increase in aneuploidy alone was not however significant at the 5% level of probability. Primary spermatocytes sampled in week 5 after irradiation were generally insensitive to the induction of chromosome abnormalities.

Animals↗
PubMed1979

Testing for nondisjunction in the mouse.

Tests for nondisjunction have been carried out in male and female mice. Ten-day fetal progeny of control and treated adults have been karyotyped to establish spontaneous and induced levels of aneuploidy. In males, the effects of 100 rad x-rays on type A spermatogonia and early primary spermatocytes, and the effects of Mitomycin C (2 mg/kg) on early primary spermatocytes, have been tested. The results show insensitivity of primary spermatocytes to both agents, but a 3.5-fold increase in nondisjunction following spermatogonial irradiation. In females, comparisons have been made between young controls, young x-rayed (5 rad), aged controls and aged x-rayed (5 rad) animals. The "ageing effect" on nondisjunction is observed, but too few fetuses have been analyzed to reach conclusions regarding enhancement of nondisjunction levels by low doses of x-rays.

Abnormalities, Radiation-Induced↗
PubMed1977

The effects of ageing on the meiotic chromosomes of male and female mice.

The effects of age on the chiasma frequencies, chiasma position and numbers of univalents at MI in males and females of three strains of mouse were examined. Males showed a slight but non significant rise in chiasma frequency in age due to an increase in bivalents with two chiasmata at the expense of single chiasmata bivalents. In contrast, females exhibited a significant decrease in chiasma frequency with age due to the loss of two chiasma bivalents with a corresponding increase in single terminal chiasmata bivalents. In both males and females there was no significant increase in univalents with age in the strains studied. Of interest was the finding of a greater degree of contraction of the MI chromosomes in the oocytes of old relative to young females, a differential contraction that was independent of culture time. This finding is discussed with regard to the "production line theory" and non disjunction at Anaphase in other strains of mice.

Aging↗
PubMed1976

Chromosome survey of total population of mentally subnormal in North-East of Scotland.

A cytogenetic survey of the complete population of mentally subnormal in the North-East of Scotland has been undertaken. A register for the mentally subnormal within the region already existed, and all persons recorded, whether they resided at home or in subnormality hospitals or other institutional care, were included. The total number recorded was 3020 and of these 2770 were examined cytologically. In all 297 (10.7%) were shown to have a chromosomal abnormality, and of these Down's syndrome accounted for 250 (9%). Within this category was an unexpected excess of males. Deletions and supernumeraries comprised the remaining autosomal anomalies. Increased numbers of sex chromosome abnormalities among high grade mentally subnormal individuals were confirmed for both sexes. The survey has shown that abnormal chromosome complements contribute significantly to the causation of mental retardation, and has also provided estimates which cannot be obtained from hospital surveys alone.

Adult↗