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Biomedical subjects

J L Hamerton

Publications and source records attributed to J L Hamerton.

At least 55 records · Page 3Linked to original sources
PubMed1982

Homozygous Robertsonian translocations in a fetus with 44 chromosomes.

We report the unique finding of a human fetus with 44 chromosomes with homozygous 14;21 translocations. This fetus appeared phenotypically normal but the long-term neurodevelopmental outcome had this pregnancy continued could not be predicted. We speculate one 14;21 translocation was inherited from her father and one arose de novo being maternal in origin. A previous sibling with psychomotor retardation has an abnormal chromosome complement of 45,XX,dup(7)(q21 leads to pter), t(14;21)(p11;q11). The mother's underlying disease, systemic lupus erythematosis (SLE), and her prior chemotherapy may have contributed to the appearance of these chromosome aberrations. It is interesting that although 14;21 translocations are among the commonest structural chromosome rearrangements in man, there are no previous reports in newborn surveys of a child with 44 chromosomes resulting from the mating of two identical Robertsonian translocation carrier parents.

Abortion, Therapeutic↗
PubMed1982

Human chromosomes control growth of human-Chinese hamster somatic cell hybrids.

Several independent human-Chinese hamster hybrid cell lines have been monitored for growth rate and chromosome composition. The rate of growth, as indicated by doubling time during log phase, was positively correlated with the number of human chromosomes, and human chromosomes 3 and 21 were present in stable hybrid cell lines more frequently than expected.

Animals↗
PubMed1982

A cytogenetic survey of 14,069 newborn infants. IV. Further follow-up on the children with sex chromosome anomalies.

Between 1970 and 1973, 14,069 consecutive liveborn infants at the Women's Centre, Winnipeg, were subjected to karyotypic analysis. The details of the materials and methods and the preliminary findings of the study have been previously published [1,2]. A total of 15 nonmosaic and 4 mosaic infants with sex chromosome anomalies were detected: 12 males and 7 females. These children have been followed wherever possible by physical and developmental evaluations, and preliminary findings have been reported previously [3]. In order to obtain further baseline data on these children while they were still prepubertal, it was decided to recontact all families and encourage them to present their children for further physical evaluation and psychologic testing. Details of these investigations and their results are given in this paper.

Child↗
PubMed1981

The effects of gamma irradiation of human fibroblasts on human/Chinese hamster somatic cell hybrids.

Human fibroblast cells were exposed to 0, 10, 20, or 40 Grays of gamma rays and then fused with unirradiated Chinese hamster cells deficient in HPRT. THAG selection system was used to ensure that only hybrid cell lines could survive. The time of appearance of pickable hybrid colonies and the frequency of dishes without any colonies were related to radiation dose. As the radiation dose increased, there was a positive correlation with frequency of cells with abnormal nuclei and a negative correlation with frequency of human chromosomes. Additionally, the hamster chromosomes had damage similar to that produced by radiation; the frequency of damaged hamster chromosomes was positively correlated with radiation dose.

Animals↗
PubMed1981

The effect of gamma irradiation of human cells and somatic cell hybridization on sister chromatid exchange frequencies in the hamster chromosomes of hamster-human hybrid lines.

Sister chromatid exchange (SCE) frequency was studied in human/hamster hybrid lines in which the human cells had been exposed to gamma irradiation at doses of 0, 10, 20, and 40 grays. A higher SCE frequency was found in the hamster chromosomes in the hybrid lines than was found in the hamster parental cell line CHW1103. There was also a dose-dependent increase of SCE frequency in the unirradiated hamster chromosomes in the hybrid lines in which the human parental cells had been irradiated.

Animals↗
PubMed1980

Evidence for the role of the maternal immune system in balancing the sex ratio in mice.

Two experiments have been conducted to verify the effect of maternal preimmunization to H-Y antigen on the secondary sex ratio in C57Bl/6 mice. In accord with the theoretical model previously proposed, it was found that extensive immunization to H-Y antigen following splenectomy resulted in a significant increase in sex ratio (males/females) without affecting litter size. Litter size was also not correlated to sex ratio. The data from both experiments suggest that splenectomy alone or restimulation to H-Y antigen (after 30 days) both act to decrease sex ratio. It is concluded that the maternal immune system plays a limited, but significant, role in maintaining the normal sex ratio in mice.

Animals↗
PubMed1980

Immunogenetics of sex determination of the polled goat.

Using the protein A rosette technique, it was found that the gene for polledness (P) in goats is associated with the presence of H-Y antigen on the cell surface of cultured fibroblasts. Two XX intersex goats (P/P) were found to be H-Y+, and one heterozygous (P/+) normal XX female was also found to express H-Y antigen at a low level. The expression of H-Y antigen by intersex goats was found to be lower than that of normal XY males. The statistical analysis suggests that animals of the same genotype and sex might differ in the density of H-Y antigen on their cell surface, which might explain the variability in primary sex determination among intersex goats. The association between the gene for sex reversal and H-Y antigen is discussed in relation to the location of the H-Y gene(s).

Animals↗
PubMed1979

Antenatal diagnosis of neural tube defects in Canada: extension of a collaborative study.

Experience with the diagnosis of neural tube defects from alpha1-fetoprotein (AFP) concentrations in amniotic fluid is reported from a prospective study of five laboratories testing for 13 Canadian genetic centres. The results of the study indicate that antenatal diagnosis of open neural tube defects is being carried out effectively in Canada (in 99.2% of cases the AFP measurements were interpreted correctly). Amniocentesis should be recommended to women at high risk for having a child with a neural tube defect (i.e., those who have a child, a parent or a sibling with a neural tube defect). The rate of neural tube defects in 182 high-risk pregnancies was 2.2% for an open defect and 1.1% for a closed defect, whereas the rate in 673 pregnancies in which amniocentesis was being performed for other reasons was 0.3%. This suggests that the AFP concentration should be measured in any sample of amniotic fluid collected for other reasons (usually fetal karyotyping). There were three instances of false-negative results, for a rate of 0.4%. Two closed neural tube defects were not detected; this limitation of the test has also been found by others. One of the six fetuses with an open neural tube defect, who died in utero, had a large myelocele in the neck that was not recognized. There were also four instances of false-positive results, for a rate of 0.5%. The findings suggest that AFP values that are more than 2 but less than 7 standard deviations (SDs) above the mean may indicate a neural tube defect, and that values 7 or more SDs above the mean very likely indicate such a defect, although other reasons for such high values (e.g., fetal erythrocytes in the amniotic fluid, intrauterine death and mistaken gestational age) must be ruled out by other methods.

Amniocentesis↗