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Biomedical subjects

D M Hawkins

Publications and source records attributed to D M Hawkins.

18 recordsLinked to original sources
PubMed1990

Cryopreservation of semen from unique lines of chicken germ plasm.

Frozen semen is a practical means of preserving valuable germ plasm. Monitored samples of semen cryopreserved with glycerol for heterozygous, dominant marker stocks and for nine chromosomal rearrangement lines had sufficiently high fertility for germ-line retrieval. The results also indicated a potential for the genetic selection of certain lines for the freezability of spermatozoa, since stock and line differences in fertility occurred when previously frozen semen was used for insemination. Freezing the semen of stocks routinely reproduced provides insurance against possible disasters.

Animals↗
PubMed1989

Estimation of the relative fertilizing ability of frozen chicken spermatozoa using a heterospermic competition method.

Semen was collected from Rhode Island Red and White Leghorn roosters. After adjusting the sperm number from both breeds, half of the semen was frozen-thawed in the presence of glycerol. Frozen and unfrozen semen from both breeds was mixed 1:1 with all four possible combinations and inseminated into Rhode Island Red hens. Feather colour of chicks was used to determine which breed fertilized the eggs. Results showed that sperm cells retained 19.7% [95% confidence interval = (12.8, 30.4)] of the relative fertilizing ability after freezing. Furthermore, Rhode Island Red spermatozoa had 1.5 times [95% confidence interval = (1.1, 2.0)] higher relative fertilizing ability than did White Leghorn spermatozoa. The heterospermic competition assay method is a powerful tool for estimating the relative fertilizing ability of the sperm cells.

Animals↗
PubMed1978

Reactive affective cycles and lithium: a caveat.

The author has been referred increasing numbers of patients who were inappropriately treated with Lithium for cyclic "depressions" which were in fact reactive-depressive episodes resulting from cyclic patterns of interpersonal behavior. This paper gives two case reports to demonstrate the phenomenon of reactive-affective cycles, their clinical presentations and the problems arising from treatment with medications. The structure of cycles of interpersonal behavior and their presentation in therapy is described and treatment strategies are suggested.

Adjustment Disorders↗
PubMed1976

The prediction of lymph node metastases from oral squamous carcinoma.

In an attempt to predict which cases of oral and oropharyngeal squamous carcinoma are likely to metastasize to regional lymph nodes a series of 898 cases was grouped according to site, size, grade of histological differentiation, and presence or absence of histologically confirmed regional lymph node metastases. The results were analysed by a logistic multiple regression analysis. They showed that the sites may be divided into three clusters, Cluster 1 consists of tumors of lip, floor of mouth, cheek mucosa, hard palate, and gingiva. These are not significantly different as regards metastasis rate. Cluster 2 consists of tumors of the anterior two-thirds of tongue and has a higher tendency to metastasis than those in Cluster 1. Lesions of the posterior third of tongue and oropharynx form Cluster 3 which exhibits the greatest tendency to metastasis. Sizes of primary lesions are clustered in groups of lesions less than 3 cm, those 3 to less than 4 cm, and those 4 cm or larger, in ascending tendency to metastasis. Well-differentiated and moderately differentiated tumors are not significantly different in their tendency to metastasize and may be reduced to a single cluster, whereas poorly differentiated tumors have a markedly higher metastasis rate. Using these clusters it has been possible to predict the logistically transformed probability of metastasis to a high degree of accuracy (R=0.9398). From this we conclude that if for a given tumor we know to which site, size or differentiation cluster it belongs, we can then estimate its probability of metastasising.

Carcinoma, Squamous Cell↗
PubMed1976

Non-ejection systolic clicks and mitral systolic murmurs in black schoolchildren of Soweto, Johannesburg.

A survey was conducted on 12 050 Black schoolchildren, aged 2 to 18 years, in the South Western Townships of Johannesburg (Soweto), and the prevalence of non-ejection systolic clicks and late systolic murmurs was determined. One or both of these auscultatory findings were detected in 168 children, yielding a prevalence rate of 13-99 per 1000 in the school population. A female preponderance of 1-9:1 was present and there was a strong linear increase in prevalence with age, with a peak rate of 29-41 per 1000 in 17-year-old children. A non-ejection click was the only abnormal auscultatory finding in 123 children (73%) and a mitral systolic murmur in 8 (5%), whereas in 37 (22%) both these findings were present. Of the latter 37 children, the murmur was late systolic in 32; in 5 it was early systolic. Auscultation in different postures was important in the detection of both non-ejection clicks and mitral systolic murmurs. Experience in the detection of these auscultatory findings influenced the frequency with which they were heard. Electrocardiographic abnormalities compatible with those previously described in the billowing mitral leaflet syndrome were present in 11 of 158 children. The aetiology of these auscultatory findings in this community remains unknown. In the same survey, a high prevalence rate of rheumatic heart disease was recorded and the epidemiology of the non-ejection clicks and these mitral systolic murmurs showed similarties to that of rheumatic heart disease. Though the specific billowing mitral leaflet syndrome almost certainly accounts for some of these auscultatory findings, a significant proportion may have early rheumatic heart disease. Further elucidation of this problem is necessary.

Adolescent↗
PubMed1976

Effects of breast-feeding practice on the post-partum endometrium.

Inactive endometrial patterns occur frequently in the post-partum period and their occurrence is modified by the breast-feeding practice. An abnormal endometrium pattern, viz., cystic hyperplasia, may occur more frequently in non-lactating women and in patients using oestrogens, especially long-acting preparations, for lactation suppression. Post-ovulatory endometrial patterns in lactating women occur infrequently during the puerperium. The implications of these findings are discussed.

Adult↗
PubMed1975

Epidemiology of rheumatic heart disease in black shcoolchildren of Soweto, Johannesburg.

A survey to determine the prevalence of rheumatic heart disease (R.H.D.) in Black children was conducted in the creeches and primary schools of the South Western Townships of Johannesburg (Soweto). A total of 12 050 Black children were examined by 10 cardiologists in May to October 1972. The overal prevalence rate of R.H.D. was 6.9 per 1000, with a peak rate of 19.2 per 1000 in children of the seventh school grade. The maximal age incidence was 15-18 years and there was a female preponderance of 1 6:1. A rise in prevalence occurred with increasing family size. Most children (92%) were asymptomatic, and in 82.5% R.H.D. was diagnosed for the first time during the school survey. The commonest valve lesion was mitral regurgitation, which was present in 93% and occurred as an isolated lesion in 47.5%. Lancefield's group A beta-haemolytic streptococcus was isolated from the throats of 52 per 1000 Soweto children. The auscultatory features of a non-ejection systolic click and late systolic murmur were prevalent (13.9 per 1000) and had several epidemiological factors in common with R.H.D. A comprehensive preventative campaign is urgently needed in South Africa, directed at both primary and secondary prophylaxis of R.H.D. The socioeconomic status of the community must be improved if optimal prevention is to be achieved.

Adolescent↗