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T Jenkins

Publications and source records attributed to T Jenkins.

At least 91 records · Page 5Linked to original sources
PubMed1994

The tyrosinase-positive oculocutaneous albinism gene shows locus homogeneity on chromosome 15q11-q13 and evidence of multiple mutations in southern African negroids.

Tyrosinase-positive oculocutaneous albinism (ty-pos OCA) is an autosomal recessive disorder of the melanin pigmentary system. South African ty-pos OCA individuals occur with two distinct phenotypes, with or without darkly pigmented patches (ephelides, or dendritic freckles) on exposed areas of the skin. These phenotypes are concordant within families, suggesting that there may be more than one mutation at the ty-pos OCA locus. Linkage studies carried out in 41 families have shown linkage between markers in the Prader-Willi/Angelman syndrome (PWS/AS) region on chromosome 15q11-q13 and ty-pos OCA. Analysis showed no obligatory crossovers between the alleles at the D15S12 locus and ty-pos OCA, suggesting that the D15S12 locus is very close to or part of the disease locus, which is postulated to be the human homologue, P, of the mouse pink-eyed dilution gene, p. Unlike caucasoid "ty-pos OCA" individuals, negroid ty-pos OCA individuals do not show any evidence of locus heterogeneity. Studies of allelic association between the polymorphic alleles detected at the D15S12 locus and ephelus status suggest that there was a single major mutation giving rise to ty-pos OCA without ephelides. There may, however, be two major mutations causing ty-pos OCA with ephelides, one associated with D15S12 allele 1 and the other associated with D15S12 allele 2. The two loci, GABRA5 and D15S24, flanking D15S12, are both hypervariable, and many different haplotypes were observed with the alleles at the three loci on both ty-pos OCA-associated chromosomes and "normal" chromosomes.(ABSTRACT TRUNCATED AT 250 WORDS)

Africa, Southern↗
PubMed1994

The Y Alu polymorphism in southern African populations and its relationship to other Y-specific polymorphisms.

Y-linked polymorphisms were studied in a number of African populations. The frequency of the alleles of a Y-specific Alu insertion polymorphism, termed the "Y Alu polymorphism," was determined in 889 individuals from 23 different African population groups. A trend in frequency was observed, with the insert largely absent in Caucasoid populations, at intermediate frequency in the Khoisan, and at high frequency in Negroids. The insert predates diversification of Homo sapiens, since it occurs in all groups. The Alu insertion is believed to result from a unique mutation event, and comparisons between this and several other Y-linked polymorphisms were carried out in an attempt to validate their usefulness in population and evolutionary studies. The p21A1/TaqI and pDP31/EcoRI polymorphisms and 49a/TaqI alleles were all shown to have arisen on more than one occasion, and evidence exists for a preraciation crossover event between the Y-linked pseudoautosomal XY275 locus and the Y chromosome pseudoautosomal boundary.

Africa, Southern↗
PubMed1993

Exclusion of two candidate pigment loci, c and b, part of chromosome 11p, and 33 random polymorphic markers as the locus for tyrosinase-positive oculocutaneous albinism.

The locus for Tyrosinase-Positive Oculocutaneous Albinism (ty-pos OCA) has not yet been localised. The search for the ty-pos OCA locus has included a search for linkage to candidate pigment loci and a candidate chromosomal region, as well as a random search using highly polymorphic markers in 42 families, including 271 individuals of whom 79 are affected. The lod scores for the tyrosinase (TYR) locus (11q14-q21), homologous to the albino locus, c, in the mouse and the CAS2/TRP1 locus (9p22-pter), homologous to the brown locus, b, in the mouse were -5.89 and -7.22, respectively, at a recombination fraction of theta = 0.01, thus excluding them from being the ty-pos OCA locus. In the candidate chromosomal region, 11p, four loci (probes) were tested, SAA (pSAA82), CALC (pHC36), HBB (Gamma-globin haplotype) and an AC repeat polymorphism at the Wilm's Tumour locus (WT1). A portion of 11p was excluded with the following lod scores: pSAA82 lod = -2.05 at theta = 0.10; pHC36 lod = -3.87 at theta = 0.05; gamma-globin haplotype lod = -2.80 at theta = 0.10; and WT1 lod = -2.34 at theta = 0.10. Thirty-three polymorphic markers randomly distributed on 13 different chromosomes were all excluded from close linkage to ty-pos OCA.

Albinism, Oculocutaneous↗
PubMed1993

Case report: cerebral venous thrombosis as a manifestation of acute ulcerative colitis.

Ulcerative colitis is associated with a number of extraintestinal complications, including the infrequent occurrence of thromboembolic disease. Cerebral venous thrombosis is extremely rare, with only 15 cases reported in the literature. The outcome in this group of patients is poor; the result in more than 80% of the cases is permanent neurologic sequelae or death. The precise mechanisms involved in thrombogenesis remain unclear. A hypercoagulable state may occur in ulcerative colitis because of well-documented associations of thrombocytosis, elevated factors V and VIII and fibrinogen, and decreased antithrombin III. Treatment regimens for cerebral venous thrombosis remain controversial and include anticoagulation with heparin, surgical thrombectomy, and systemic and local infusion of fibrinolytic regimens. A conservative approach with antiedemic agents, anticonvulsants, antiplatelet therapy, and acetazolamide also may be beneficial and offers a substantially reduced hemorrhagic potential. A case of primary superior sagittal sinus thrombosis associated with active ulcerative colitis treated by the latter method is reported. The patient's neurologic recovery was complete, with recanalization of the thrombosed venous sinus being demonstrated by magnetic resonance imaging studies.

Adult↗
PubMed1993

Complex polymorphisms are revealed by Y chromosome probe 49a with BglII, HindIII, PstI and SstI.

Y chromosome probe 49a detects complex polymorphisms with BglII, HindII, PstI and SsTI, involving 19, 13, 18 and 11 variant bands respectively. The haplotype, a description of the arrangement of fragments in an individual, exhibits great variation. Most haplotypes are population-specific and occur infrequently. In a study of approximately 60 individuals of Caucasoid, Negroid and San origin, 21, 23, 28 and 24 haplotypes were revealed by BglII, HindIII, PstI and SstI respectively. Reduced genetic diversity in the Negroid population was ascribed to both the proposed recent common origin of the Bantu-speaking Negroid population from a proto-Bantu stock and the common practice of polygamy in African Negroids, as were specific correlations between the different polymorphisms within the Negroid population only. In general, no single haplotype for a given enzyme system strictly correlated with a haplotype from any of the other three systems, suggesting that each polymorphism results from a combination of restriction site mutations and rearrangement events. This tremendous variability has potential in paternity testing for male offspring.

Bacterial Proteins↗
PubMed1992

Glucose-6-phosphate dehydrogenase (G6PD) electrophoretic variants and the PvuII polymorphism in southern African populations.

Southern African Bantu-speaking negroid and San populations were examined with regard to the glucose-6-phosphate dehydrogenase (G6PD) PvuII restriction fragment length polymorphism (RFLP) showing alleles of 4 kb and 1.6 kb, called Type 1 and Type 2, respectively. The standardized disequilibrium coefficient for the electrophoretic G6PD types and PvuII alleles in the Southern African population was 0.28. The molecular lesion causing the GdA mutation is the same in the San and Southern African negroid populations. GdA chromosomes are found in association with both the Type 1 and Type 2 alleles, whereas none of the 62 GdB chromosomes from the Southern African populations had the Type 2 allele. Five of the 44 GdB chromosomes studied in the American Black population had the Type 2 allele, indicating that the GdB allele in the two populations may have different origins. The presence of all 3 A- deficiency mutations in the G6PD A gene, in a region where the ancestral population was thought to have predominantly G6PD B, may be explained by their origin in Africa after the divergence of the races.

Africa, Southern↗
PubMed1992

The CEPH consortium linkage map of human chromosome 15q.

The CEPH consortium map of chromosome 15q is presented. The map contains 41 loci defined by genotypes generated from CEPH family DNAs with 45 different probe and restriction enzyme combinations contributed by 10 laboratories. A total of 29 loci have been placed on the map with likelihood support of at least 1000:1. The map extends from 15q13 to 15q25-qter. Multipoint linkage analyses provided estimates that the male, female, and sex-averaged maps extend for 127, 190, and 158 cM, respectively. The largest interval is 21 cM and is between D15S37 and D15S74. The on-average locus spacing is 5.6 cM and the mean genetic distance between the 21 uniquely placed loci is 8 cM.

Chromosome Mapping↗
PubMed1992

The CEPH consortium linkage map of human chromosome 2.

This paper describes the Centre d'Etude du Polymorphisme Humain (CEPH) consortium linkage map of chromosome 2. The map contains 36 loci defined by genotyping generated from the CEPH family DNAs. A total of 73 different markers were typed by 14 contributing laboratories; of these, 36 loci are ordered on the map with likelihood support of at least 1000:1. Markers are placed along the length of the chromosome but no markers were available to anchor the map at either telomere or the centromere. Multilocus linkage analysis has produced male, female, and sex-averaged maps extending for 261, 430, and 328 cM, respectively. The sex-averaged map contains five intervals greater than 15 cM and the mean genetic distance between the 36 uniquely placed loci is 9.1 cM.

Chromosome Mapping↗
PubMed1992

The Y chromosome as a tool for studying human evolution.

The use of the Y chromosome in human evolutionary research has only recently begun to gain momentum, partly because of a paucity of polymorphism. Differences in male/female behaviour patterns and the unique mode of inheritance of the Y chromosome also complicate interpretation of the data on Y chromosome variation.

Biological Evolution↗
PubMed1992

The search for Y chromosome polymorphism is extended to negroids.

DNA samples of Negroid and Caucasoid origin were used to screen for Y-specific RFLPs. A total of 7 Y chromosome probes and 13 restriction enzyme digests were used to examine a conservative estimate of 20000bp. No new Y-specific polymorphisms were revealed. The paucity of polymorphism on the Y appears to be unrelated to possible bottleneck effects during raciation.

Biological Evolution↗
PubMed1992

Mitochondrial DNA polymorphisms in Khoisan populations from southern Africa.

Mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs) were investigated in 95 individuals, consisting of 49 San ('Bushmen') and 46 Nama ('Hottentot') individuals from Namibia, using the restriction enzymes HpaI, BamHI, HaeII, MspI, AvaII and HincII. Six of the eleven types found in the pooled Khoisan sample are shared, albeit at varying frequencies, suggesting that both the San and Nama have evolved from a recent common ancestor. However, San and Nama groups differ appreciably, in particular, type 3-2 (3-1-1-2-2-2) was found in 7/49 Sekele and 25/46 Nama (chi 2 [1] = 15.3, P = 9.17 x 10(-5)). In addition, type 4 makes up 42.8% of the types found in the San, and is not found in the Nama group. This suggests that the San and Nama have evolved along separate lineages, with little gene flow between them, following their proposed separation from a common Khoisan ancestor. Type 7-2 (3-1-1-1-1-2), most common in Negroid populations, is found at a higher frequency in the San (20.4%) than the Nama (6.5%), suggesting that miscegenation involving Negroid females and San males is more common than that between Negroid females and Nama men. The higher frequency of type 21-2 (2-1-1-1-2-2) in the Nama (13%) than in the San (4.1%), may be attributable to gene flow from the Dama into the Nama, consistent with the consequences of enslavement of the Dama by the Nama.

Adult↗
PubMed1992

The inverted Y-chromosome polymorphism in the Gujarati Muslim Indian population of South Africa has a single origin.

Y-specific polymorphisms were studied in Gujarati Muslim Indians possessing a Y-chromosome pericentric inversion [inv(Y)] in an attempt to prove a common genetic origin for the inversion. The p49a/TaqI and p49a/PvuII haplotypes were determined for 9 normal and 8 inv(Y) Gujarati Muslim men. Men with the inversion possessed identical TaqI and PvuII profiles, as opposed to 7 different TaqI and 8 different PvuII haplotypes observed in the 9 normal men. These results provide conclusive evidence for a common genetic origin of the inverted Y chromosome observed in this Gujarati Muslim community.

Chromosome Inversion↗
PubMed1992

Alpha-1-protease inhibitor in bronchial asthma: phenotypes and biochemical characteristics.

The prevalence of the different phenotypes of alpha 1-protease inhibitor (alpha 1PI) was investigated in a group of 90 asthmatic patients and compared with that of a control group of 240 individuals representing the general population. The M2M2 phenotype occurred more frequently in the asthmatic group (p = 0.015). Plasma samples of 51 of the asthmatic patients randomly selected from the different phenotype groups identified were studied for the absolute plasma values of alpha 1-PI and the inhibitory capacity of plasma for porcine pancreatic elastase, and compared with those from 21 nonasthmatic individuals of the M1M1 phenotype. Although the asthmatic patients had higher absolute alpha 1PI values (p = 0.04), the plasma elastase inhibitory capacity was markedly reduced compared with the nonasthmatic subjects (p = 0.01). The functional efficiency of alpha 1PI from asthmatic patients of the M1M1, M1M2, and M2M2 phenotypes was significantly decreased compared with that of the nonasthmatic M1M1 individuals. Functional deficiency of alpha 1PI may be important in the pathogenesis of the inflammatory process that characterizes bronchial asthma.

Adult↗
PubMed1992

Mitochondrial DNA studies in the South African Indian population.

The polymorphisms of mitochondrial DNA (mtDNA) for the restriction enzymes HpaI, BamHI, HaeII, MspI, AvaII, and HincII were studied in a sample of 147 unrelated Indian individuals from South Africa, who were subdivided according to religion and language into four groups, namely, Tamil, Hindi, Gujerati and Moslem. They were found to be monomorphic with the enzymes BamHI, and HaeII, and little variation was observed with the enzymes MspI and HincII. Six individuals were found to contain the non-Caucasoid HpaI morph, HpaI-3, which is found more commonly in indigenous African populations. This suggests that some flow of maternal genes from indigenous African populations into the Indian population may have occurred. Despite these interactions, Indians in South Africa display very little mtDNA variation (F = 0.77) when compared with those living in Nepal (F = 0.35) and New Delhi (F = 0.51). When compared with other Caucasoid populations, Indians are more homogenous in their genetic structure, which may be attributable to the high level of inbreeding among them, due to strict caste endogamy and certain religious customs that are still practised by the majority of Indians today.

DNA, Mitochondrial↗
PubMed1992

The tyrosinase-positive oculocutaneous albinism locus maps to chromosome 15q11.2-q12.

Tyrosinase-positive oculocutaneous albinism (ty-pos OCA), an autosomal recessive disorder of the melanin biosynthetic pathway, is the most common type of albinism occurring worldwide. In southern African Bantu-speaking negroids it has an overall prevalence of about 1/3,900. Since the basic biochemical defect is unknown, a linkage study with candidate loci, candidate chromosomal regions, and random loci was undertaken. The ty-pos OCA locus was found to be linked to two arbitrary loci, D15S10 and D15S13, in the Prader-Willi/Angelman chromosomal region on chromosome 15q11.2-q12. The pink-eyed dilute locus, p, on mouse chromosome 7, maps close to a region of homology on human chromosome 15q, and we postulate that the ty-pos OCA and p loci are homologous.

Albinism, Oculocutaneous↗
PubMed1992

Treatment of cervical dystonia (torticollis) in adults with botulinum A toxin.

Dystonias can be classified by etiology (idiopathic or symptomatic), by age of onset (childhood, adolescence or adult), and by anatomical involvement (focal, segmental or generalized). Cervical dystonia (torticollis) is one of the most common focal dystonias. We describe our experience in the treatment of 15 consecutive cervical dystonia patients by chemodenervation with botulinum A toxin (BOTOX), with significant improvement being objectively measured. Botox is accepted as a safe and efficacious modality for the treatment of cervical dystonia.

Adult↗