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Biomedical subjects

T Jenkins

Publications and source records attributed to T Jenkins.

At least 73 records · Page 4Linked to original sources
PubMed1996

The origins of the Lemba "Black Jews" of southern Africa: evidence from p12F2 and other Y-chromosome markers.

The Lemba are a southern African Bantu-speaking population claiming Jewish ancestry. Allele frequencies at four different Y-specific polymorphic loci, as well as extended-haplotype frequencies that included data from several loci, were analyzed in an attempt to establish the genetic affinities and origins of the Lemba. The results suggest that > or = 50% of the Lemba Y chromosomes are Semitic in origin, approximately 40% are Negroid, and the ancestry of the remainder cannot be resolved. These Y-specific genetic findings are consistent with Lemba oral tradition, and analysis of the history of Jewish people and their association with Africa indicates that the historical facts are not incompatible with theories concerning the origin of the Lemba.

Africa, Southern↗
PubMed1995

Origins and affinities of modern humans: a comparison of mitochondrial and nuclear genetic data.

To test hypotheses about the origin of modern humans, we analyzed mtDNA sequences, 30 nuclear restriction-site polymorphisms (RSPs), and 30 tetranucleotide short tandem repeat (STR) polymorphisms in 243 Africans, Asians, and Europeans. An evolutionary tree based on mtDNA displays deep African branches, indicating greater genetic diversity for African populations. This finding, which is consistent with previous mtDNA analyses, has been interpreted as evidence for an African origin of modern humans. Both sets of nuclear polymorphisms, as well as a third set of trinucleotide polymorphisms, are highly consistent with one another but fail to show deep branches for African populations. These results, which represent the first direct comparison of mtDNA and nuclear genetic data in major continental populations, undermine the genetic evidence for an African origin of modern humans.

Africa↗
PubMed1995

Mixed-lineage acute myeloid leukemia associated with a suprasellar dysgerminoma.

An association between primary mediastinal germ cell tumors and hematologic malignancies has been recognized since 1985. We present a patient with a suprasellar germ cell tumor and an associated leukemia. A 20-year-old black female presented in December 1987 with a 6-month history of headaches and weight loss, confusion, polyuria, and polydipsia. Evaluation revealed hypernatremia, normal neurologic examination except poor recall, and an enhancing inhomogeneous suprasellar mass on cranial computed tomography. Biopsy of the mass diagnosed a dysgerminoma, which was treated with craniospinal radiation. In February 1988, the patient developed pancytopenia, which resolved with discontinuation of cimetidine and phenytoin. She did well until June 1988 when she presented with skin lesions over the trunk and extremities. Skin biopsy revealed a leukemic infiltration. She was admitted with a WBC 1,500/microliter (without blasts), Hb 11.6 g/dl, PLT 210,000 microliter. Bone marrow biopsy revealed hypercellularity with 50% blasts, demonstrating mixed-lineage acute myeloblastic leukemia (myelomonocytic-M4; megakaryoblastic-M7). The patient was induced with a standard Ara-C/daunorubicin regimen. Two weeks postinduction, she became septic and expired. An autopsy demonstrated leukemic involvement of the spleen, liver, bone marrow, and skin, without residual dysgerminoma. This represents the first reported case of suprasellar dysgerminoma associated with a mixed-lineage leukemia not related to chemotherapy.

Adult↗
PubMed1995

Characterization of mutants of the vitamin-D-binding protein/group specific component: GC aborigine (1A1) from Australian aborigines and South African blacks, and 2A9 from south Germany.

The structure and organization of the human vitamin-D-binding protein gene (DBP, group-specific component, GC) have recently been determined. Each exon may now be amplified by the PCR method using oligonucleotide primers deduced from the intron sequences near their 5' ends and 3' ends. In this study we examined the anodal GC variants 1A1 and 2A9. Genomic DNA of the variant 1A1 was obtained from Australian Aborigines and from South African Bantu-speaking Blacks. Amplification and sequencing of exon 11 of 1A1 revealed a point mutation in codon 429 at the second position. It is remarkable that this mutation was found in the Australian 1A1 variant and in the African 1A1 variant, and raises the question whether the mutation in these two ethnic groups has a common origin. Genomic DNA of the 2A variant called 2A9 was obtained from South Germany and a point mutation also concerning position 429 in exon 11 was found. The nucleotide exchange in this case, however, was at the first position of the codon. The widely distributed genetic polymorphism of DBP/GC is located in exon 11 and is characterized by substitution at amino acid positions 416 and 420. Variant 1A1 is due to a second site mutation of the allele GC*1F; variant 2A9 is due to a mutation in the GC*2 allele.

Australia↗
PubMed1995

New founder haplotypes at the myotonic dystrophy locus in southern Africa.

The association between normal alleles at the CTG repeat and two nearby polymorphisms in the myotonin protein kinase gene, the Alu insertion/deletion polymorphism and the myotonic dystrophy kinase (DMK)(G/T) intron 9/HinfI polymorphism, has been analyzed in South African Negroids, a population in which myotonic dystrophy (DM) has not been described. South African Negroids have a CTG allelic distribution that is significantly different from that in Caucasoids and Japanese: the CTG repeat lengths of > or = 19 are very rare. The striking linkage disequilibrium between specific alleles at the Alu polymorphism (Alu(ins) and Alu(del)), the HinfI polymorphism (HinfI-1 and HinfI-2), and the CTG repeat polymorphism seen in Caucasoid (Europeans and Canadians) populations was also found in the South African Negroid population. Numerous haplotypes, not previously described in Europeans, were, however, found. It thus seems likely that only a small number of these "African" chromosomes were present in the progenitors of all non-African peoples. These data provide support for the "out of Africa" model for the origin of modern humans and suggest that the rare ancestral DM mutation event may have occurred after the migration from Africa, hence the absence of DM in sub-Saharan Negroid peoples.

Africa, Southern↗
PubMed1995

An intragenic deletion of the P gene is the common mutation causing tyrosinase-positive oculocutaneous albinism in southern African Negroids.

Tyrosinase-positive oculocutaneous albinism (OCA2), an autosomal recessive disorder of the melanin biosynthetic pathway, is the most common recessive disorder occurring in southern African Bantu-speaking Negroids, with an overall prevalence of 1/3,900. The OCA2 gene, P, has been mapped to chromosome 15q11-q13, and recently alterations in the P gene have been identified in OCA2 individuals. An intragenic deletion has been described and proposed to be of African origin because of its occurrence in four unrelated African American OCA2 individuals and in two individuals, one from Zaire and the other from Cameroon. This study shows that the intragenic deletion is a common cause of OCA2 in southern African Negroids (114/146 [.78]; OCA2 chromosomes) and is associated with one common haplotype (43/55 [.78]; OCA2 chromosomes), confirming the African origin of this allele. On the basis of haplotype data, it would appear that at least seven additional, less frequent OCA2 mutations occur in this population.

Albinism, Oculocutaneous↗
PubMed1995

Molecular analysis of the CTG trinucleotide repeat in South African myotonic dystrophy families--implications for diagnosis and counselling.

Myotonic dystrophy is associated with an increased number of CTG repeats in the 3' untranslated region of the myotonin protein kinase gene. The recent elucidation of the molecular basis of myotonic dystrophy has, for the first time, made a specific molecular diagnosis of this condition a possibility. Ten South African families were analysed at the molecular level, using both PCR and Southern blot analyses for the detection of the trinucleotide repeat. Expansion of this repeat was found in 9 families and in 2 cases the grandparental origin, which was previously unknown, could be determined. It is now possible to counsel these families more effectively and to identify individuals, particularly women, who are at risk of passing on the DM mutation.

Blotting, Southern↗
PubMed1994

Characterization of the surface polypeptides of Strongyloides ratti: a comparison of homogonic and heterogonic strains.

Surface iodination, extraction and SDS-PAGE analysis techniques were employed to characterize and compare the surface polypeptides of two strains of Strongyloides ratti. Third stage infective larvae and parasitic adults of homogonic and heterogonic strains were studied using a variety of surface labelling procedures and detergents for the extraction of labelled molecules. Profiles obtained from SDS-PAGE analysis demonstrated that homogonic and heterogonic strains of S. ratti have identical surface antigens.

Animals↗
PubMed1994

The migration and attrition of Strongyloides ratti in naive and sensitized rats.

Compressed organ autoradiography has been utilized to study the migration of the homogonic strain of Strongyloides ratti from the site of skin penetration to the gut. This transit is characterized by rapid disappearance of parasites from the cutaneous site of infection, followed by vascular dispersal throughout all organs investigated. For the first time, parasite migration in both naive and previously sensitized hosts is compared; the principal stations of migration are the same in the two groups although there is a quantitative difference in accumulation of parasites with time in these stations. Parasite attrition occurs in both groups of animals; however, in naive rats it is not manifest until day 20-25 post challenge, whereas in sensitized rats immune elimination occurs as early as 48 h post challenge.

Animals↗
PubMed1994

Analysis of 40 known cystic fibrosis mutations in South African patients.

A total of 140 South African (SA) Caucasoid cystic fibrosis (CF) families were analysed for the common CF mutation, delta F508. The 52 non-delta F508 CF chromosomes in a subset of 127 of these families were also tested for 39 other known CF mutations. The most frequent mutation, apart from delta F508 (which occurs at a frequency of 79%), was G542X (1.3%). Four other mutations, R553X, S549N, 621 + 1G-->T and N1303K, were each found in single families. The other 35 mutations remained unidentified in this sample of CF families. Since 83% of SA Caucasoid CF mutations have been identified, diagnosis by mutation analysis will be possible in only 69% of CF cases. When a diagnosis has been confirmed by a positive sweat test, a combination of linked marker analysis and mutation detection will be necessary if prenatal diagnosis and carrier detection are to be offered in the remaining families.

Cystic Fibrosis↗
PubMed1994

The genetic affinity of Polynesians: evidence from Y chromosome polymorphisms.

Y-linked polymorphisms were studied in a sample of 60 Polynesians, and results were compared with findings from studies on other major population groups. Three previously unreported 49a/TaqI haplotypes were observed, two of which possess a new polymorphic fragment named I2. Frequency data for the 49a/TaqI, XY275, pDP31 and Y Alu polymorphisms indicate that Polynesians have greater affinity to Caucasoids than to African populations. Similar population frequency trends were not observed for the p21A1/TaqI polymorphism, supporting the hypothesis that this polymorphism has arisen more than once.

Black People↗
PubMed1994

Absence of myotonic dystrophy in southern African Negroids is associated with a significantly lower number of CTG trinucleotide repeats.

Myotonic dystrophy (DM) is associated with an increased number of CTG repeats in the 3' untranslated region of the myotonin gene. Because DM has not been observed in southern African Negroids, a study of the CTG repeat polymorphism in this population was undertake. A total of 210 unrelated subjects was studied by PCR analysis of the trinucleotide repeat in the DM gene and the size and distribution of the CTG repeat were determined. The alleles ranged in length from five to 22 repeats. A previously undescribed BglI polymorphism was found which could lead to erroneous diagnosis of DM in people from this population. South African Negroids were found to have significantly fewer large repeat lengths than do white and Japanese populations. It is suggested that the occurrence of fewer large CTG repeats in the normal range may, in part, explain the absence of DM in southern African Negroids.

Africa, Southern↗
PubMed1994

The high frequency of the Hb B2 variant in the Herero population: a founder effect?

The beta-globin gene cluster haplotype associated with the delta-globin variant Hb B2 was determined in Herero individuals from six different families, in order to establish whether founder effect was responsible for the high frequency of this variant in the population. The electrophoretic detection of Hb B2 was confirmed at the molecular level by polymerase chain reaction, followed by Cfo I digestion. The haplotype associated with the Hb B2 chromosome was determined in two families, and was shown to be the same. In the remaining four families the haplotypes could not be established conclusively, but were consistent with the haplotype observed in the other two families. The high gene frequency of Hb B2 is thus likely to have resulted form founder effect.

Black People↗
PubMed1994

HIV testing and informed consent--ethical considerations.

One of the authors (T.J.) was invited by the AIDS Advisory Group to form a widely representative committee to recommend ethical guidelines concerning the extent to which HIV testing should receive informed consent. This paper presents and argues for the recommended guidelines. The question is considered with regard to a number of distinct purposes of HIV testing: the care of a patient; research; blood, tissue and organ donation; and the protection of third parties, including the health care worker. We contend that in each case there is no good reason for the requirement of informed consent to be significantly waived.

Blood Donors↗
PubMed1994

Mismatch distributions of mtDNA reveal recent human population expansions.

Although many genetic studies of human evolution have tried to make distinctions between the replacement and the multiregional evolution hypotheses, current methods and data have not resolved the issue. However, new advances in nucleotide divergence theory can complement these investigations with a description of human demographic behavior during the late Middle and Upper Paleolithic (approximately the last 250,000 years). Restriction fragment length polymorphism (RFLP) and DNA sequence analyses of human mitochondrial DNAs (mtDNAs) from 25 ethnic and racial groups indicate that significant expansions occurred during the late Middle and Upper Paleolithic in 23 of the 25 populations examined. Estimates for the individual group expansion times are consistently less than 100,000 years ago with a mean expansion time of approximately 40,000 years ago. The dramatic expansions suggested by these data occurred well after modern human anatomy appeared, approximately 100,000 years ago, but are concordant with archeological evidence for the expansion of modern human technology, approximately 50,000 years ago.

Base Sequence↗