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Biomedical subjects

A E Retief

Publications and source records attributed to A E Retief.

At least 55 records · Page 3Linked to original sources
PubMed1986

A DNA polymorphism in the human low-density lipoprotein receptor gene.

A new restriction fragment length polymorphism (RFLP) in the low-density lipoprotein receptor gene is described using the Stu I restriction endonuclease and a cDNA probe. The frequency of the two RFLP alleles was determined in 60 unrelated white subjects and 11.7% of them were found to be heterozygous for the polymorphism. Mendelian segregation of the RFLP was found in 3 informative families. The possible use of the RFLP in the diagnosis of familial hypercholesterolaemia in South Africa is discussed.

Genetic Techniques↗
PubMed1986

Balanced chromosome translocations and abnormal phenotypes. A report of 5 cases.

Five cases in which phenotypic abnormalities were found in association with apparent balanced chromosomal translocations are described. In 3 patients, one of the parents was found to be a carrier of the same translocation. In a further patient, the translocation was shown to be de novo and in the remaining patient the father was not available for chromosome studies. In a review of the literature the breakpoints in 36 familial balanced translocations were compared with 40 de novo translocations (including the present cases) all associated with phenotypic abnormalities. No common translocation was found in these groups, but it was observed that chromosomes 4 and 5 were significantly more involved in de novo translocations than in familial translocations. The possible aetiology and implications for prenatal diagnoses are discussed.

Adolescent↗
PubMed1986

Severe mental retardation in six generations of a large South African family carrying a translocation t(6;10)(q27;q25.2).

Partial monosomy 10q25.2----qter, detected in a newborn baby with multiple congenital abnormalities, was found to be derived from a balanced maternal translocation t(6;10)(q27;q25.2). The pedigree of six generations of the family is presented. In an extensive cytogenetic study of this family, the chromosome complements of 57 subjects, potentially capable of carrying some form of this translocation, were analysed. A total of 14 male carriers (four obligatory) and 14 female carriers (three obligatory) of this translocation was found. Partial trisomy 10q25.2----qter, associated with severe mental retardation, occurred in nine cases, eight males and one female. Two of these eight males were detected prenatally and subsequently therapeutically aborted. The phenotypes of the family members with partial trisomy 10q25.2----qter are compared to each other and to those reported in publications. No further cases of partial monosomy 10q25.2----qter were encountered. A review of published reports of partial monosomy and partial trisomy 10qter is given. The apparent absence of infertility, the occurrence of many first trimester miscarriages, and the marked sex ratio are discussed.

Abnormalities, Multiple↗
PubMed1985

[Chromosome studies in gynecology].

Clinical indications for chromosome analysis in patients with gynaecological problems are well defined. These include, with primary or secondary amenorrhoea, infertility and repeated miscarriages in adults or retarded puberty and abnormal sexual development in young girls. The type of chromosome abnormality, the incidence, and the management of patients are discussed with reference to 15 years' experience in the Department of Cytogenetics at Tygerberg Hospital. The cytogenetics of 419 patients with amenorrhoea are discussed under headings such as gonadal dysgenesis, monosomy X, chromosome mosaics and the XY female phenotype. Results of chromosome studies in 540 males with a low sperm count are given. The importance of chromosome studies in repeated miscarriages and genetic counselling for carriers of balanced translocations is stressed.

Abortion, Habitual↗
PubMed1985

Regional chromosome mapping of human collagen genes alpha 2(I) and alpha 1(I) (COLIA2 and COLIA1).

For the assignment of the genes for the pro-alpha 2(I) (COLIA2) and the pro-alpha 1(I) (COLIA1) collagens, cDNA and genomic DNA probes were used in in situ hybridization experiments on human prometaphase chromosomes. An improved staining method is reported for the simultaneous identification of chromosomes and the autoradiographic grains after the hybridization procedures. With this procedure more cells with higher resolution could be used for the assignment of genes by in situ hybridization. Statistical analysis of the grains located on respectively 660 and 302 metaphases using pro-alpha 2(I) and pro alpha 1(I) DNA probes, confirmed the assignment of these genes to human chromosomes 7 and 17. Analysis of the grain distribution on prometaphase chromosomes showed that the location of the pro-alpha 2(I) collagen gene is in the region 7q21.3-22.1. The location of the pro-alpha 1(I) collagen gene was found to be in band 17q21.31-2205.

Autoradiography↗
PubMed1984

Chromosome studies in 496 infertile males with a sperm count below 10 million/ml.

Chromosome studies were performed on 106 men with azoospermia and 390 men with oligozoospermia (consistent sperm count below 10 million/ml). Constitutional chromosome abnormalities were found in 14.1% of the azoospermia group and in 5.1% of the oligozoospermia group. An overall incidence of 7.1% constitutional abnormalities indicates that this criterion of selection may be advisable for routine chromosome analysis of infertile men. A reduction of 25% in the workload increases the yield of chromosome abnormalities in the group of infertile men to 10-14 times above that expected in the normal population.

Chromosome Aberrations↗
PubMed1984

Regional localization of alpha-galactosidase (GLA) to Xpter----q22, hexosaminidase B (HEXB) to 5q13----qter, and arylsulfatase B (ARSB) to 5pter----q13.

Two series of somatic cell hybrids were made by fusion of human cells with karyotypes 46,X,t(X;2;15)(q22;p12;p12) and 46,XX,t(5;7)(q13;p15) and rodent cells. Chromosome and isozyme analysis of human chromosomes and gene products in the hybrids localized GLA to Xpter----q22, HEXB to 5q13----qter, in both cases narrowing the regional assignments, and ARSB to 5pter----q13.

Animals↗
PubMed1983

A 3-year cytogenetic survey of 9 661 patients in South Africa.

During the period 1 January 1977 - 31 December 1979, 9 661 patients underwent cytogenetic investigation at seven participating laboratories in South Africa. The chromosome data were coded using a standard protocol and the results tabulated, being listed according to the clinical signs which led to referral for investigation. Cytogenetic investigation was most commonly requested for prenatal studies, and 22% of the group's effort was directed towards this. One in 27 amniotic cell specimens was reported to have shown anomalous chromosomes, trisomy 21 being the most frequent abnormality. The majority of postnatal investigations were requested because congenital abnormalities suggested an underlying chromosomal defect. In 42,3% of 2 420 patients a chromosome defect was confirmed. Results of chromosome studies are tabulated by indication for referral and the findings summarized. This collaborative study gives an indication of the nature and frequency of chromosome disorders in South Africa.

Chromosome Aberrations↗
PubMed1981

[New evidence regarding the etiology and pathogenesis of true hermaphrodites].

New evidence has become available regarding certain aspects of the aetiology and pathogenesis of true hermaphroditism. It is evident that the presence of a Y-chromosome in the karyotype of the true hermaphrodite predisposes to the formation of a testis on the one side and an ovary or an ovotestis on the other side. The presence of 46,XX-chromosome complement, however, more commonly results in an ovotestis on the one side and an ovary on the other side. The formation of an ovotestis is possibly due to a difference in the presence of H-Y-antigen in the cells of the ovarian and the testicular portion. The development of the Müllerian and Wolffian ducts is much more interdependent than has previously been known. No cases have been described where two ducts, both of Wolffian and Müllerian origin, were found next to an ovotestis. In humans, fetal androgen does not change hypothalamic activity to a monophasic pattern or produce male sexual behaviour, according to the evidence found in the true hermaphrodites investigated by us.

Disorders of Sex Development↗
PubMed1981

The gonads of human true hermaphrodites.

Gonadal distribution in 409 cases of human true hermaphroditism is reviewed. An ovary was found on the left side of the body in 62.8% of the cases and the testis on the right side in 59.5%. The ovotestis is the most common gonad of the true hermaphrodite; amongst 806 gonads in 406 cases it was found in 44.3%. In this paper we give a detailed description of the morphology of ovotestis, testis and ovary in the true hermaphrodite. In addition we discuss the effects of fetal androgens and Müllerian inhibiting factor on the Wolffian and Müllerian ducts. Correlations between chromosomal complement and gonadal distribution are presented. True hermaphrodites with a 46,XX karyotype most commonly have an ovary on one side and an ovotestis on the other side; those with a Y-chromosome have a testis in 61% of cases. An analysis of the ratio of ovarian and testicular tissue within ovotestes showed a continuum from very little ovarian tissue to a small portion of testicular tissue. Each type of tissue was clearly demarcated. Hypotheses for gonadal induction in the true hermaphrodite should take cognizance of these facts. True hermaphrodites with a 46,XX chromosomal complement were characterized by a male phenotype in 54% of cases. This group may suggest a greater testicular induction ability in the genome as compared to the 46% with a female phenotype.

Androgens↗
PubMed1979

[Computer processing of genetic patient data].

A code form for genetic patient data has been devised for computer purposes. This form provides for the clinical and laboratory diagnosis of genetic diseases. A Hewlett-Packard 2100 computer is used for storage and retrieval of the data. Three programmes are currently in use for the retrieval of data, namely programme RETREV, for retrieval of individual patient records; programme STAT9A, for the classification of chromosome results of patients referred with similar clinical diagnoses; and programme STA12A, for classification of chromosome abnormalities and for correlation with the indication for referral and other data. The possibilities for expansion of the programmes are discussed.

Amenorrhea↗