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Biomedical subjects

G Wallis

Publications and source records attributed to G Wallis.

At least 37 records · Page 2Linked to original sources
PubMed1996

In vivo spin trapping of nitric oxide generated in the small intestine, liver, and kidney during the development of endotoxemia: a time-course study.

Spin trapping of nitric oxide (NO.) in vivo in liver, small intestine, kidney, and plasma of intact rats was accomplished using diethyldithiocarbamate (DETC) administered intraperitoneally. DETC combines with Fe2+ to form (DETC)2-Fe and is an excellent trapping agent for nitric oxide. DETC distribution and uptake by the organs of interest was determined and the formation of the active trapping agent (DETC)2-Fe was assayed in the various organs and plasma. The capacity of this spin trap to capture NO. in vivo was demonstrated by administering sodium nitroprusside to the animals. The trapping procedure was then used to assess the course of NO. generation during a 6 h period in animals that had been treated with endotoxin. The rate of NO. generation/gram tissue was determined during the last 15 min of each time period. The results indicate that induction of nitric oxide generation begins earliest in the small intestine, then in the liver, and still later in the kidney and plasma. Nitric oxide production was most intense in the liver and was still increasing at the end of the experiment. Control animals receiving the spin trapping agent showed only little or no evidence of nitric oxide production except for the small intestine. The results show that induction of NO. generation caused by endotoxin begins at different times in different organs.

Animals↗
PubMed1990

Consistent linkage of dominantly inherited osteogenesis imperfecta to the type I collagen loci: COL1A1 and COL1A2.

The segregation of COL1A1 and COL1A2, the two genes which encode the chains of type I collagen, was analyzed in 38 dominant osteogenesis imperfecta (OI) pedigrees by using polymorphic markers within or close to the genes. This was done in order to estimate the consistency of linkage of OI genes to these two loci. None of the 38 pedigrees showed evidence of recombination between the OI gene and both collagen loci, suggesting that the frequency of unlinked loci in the population must be low. From these results, approximate 95% confidence limits for the proportion of families linked to the type I collagen genes can be set between .91 and 1.00. This is high enough to base prenatal diagnosis of dominantly inherited OI on linkage to these genes even in families which are too small for the linkage to be independently confirmed to high levels of significance. When phenotypic features were compared with the concordant collagen locus, all eight pedigrees with Sillence OI type IV segregated with COL1A2. On the other hand, Sillence OI type I segregated with both COL1A1 (17 pedigrees) and COL1A2 (7 pedigrees). The concordant locus was uncertain in the remaining six OI type I pedigrees. Of several other features, the presence or absence of presenile hearing loss was the best predictor of the mutant locus in OI type I families, with 13 of the 17 COL1A1 segregants and none of the 7 COL1A2 segregants showing this feature.

Chromosomes, Human, Pair 17↗
PubMed1989

Emery-Dreifuss syndrome and X-linked muscular dystrophy with contractures: evidence for homogeneity.

We report on a family in which individuals have clinical features of both Emery-Dreifuss syndrome (EMD) and X-linked muscular dystrophy with contractures (XLMDC). Molecular studies on this kindred showed linkage between the disorder and probe DXS 52 (St14) located at Xq28. The gene for conventional EMD has previously been mapped to this region and our molecular findings therefore suggest that EMD and XLMDC represent the phenotypic spectrum of the same mutated gene rather than heterogeneity, as sometimes postulated.

Chromosome Mapping↗
PubMed1988

X-linked mixed deafness with stapes fixation in a Mauritian kindred: linkage to Xq probe pDP34.

Molecular linkage analysis was undertaken on a large Mauritian kindred with X-linked mixed deafness, stapes fixation, and perilymphatic gusher (X-LDSF). DNA probe pDP34 (DXYS1) was tightly linked to the disorder, with a lod score of 6.32 at zero recombination. This observation indicates that the gene for this form of deafness maps to the Xq13-q21.1 region and has important implications for carrier screening and antenatal diagnosis.

Chromosome Mapping↗
PubMed1987

Duchenne muscular dystrophy in South Africa. Prevention by molecular techniques.

The availability of DNA markers closely linked to the Duchenne muscular dystrophy (DMD) gene locus has facilitated carrier detection and prenatal diagnosis of this condition. More than 50 affected South African kindreds are being studied using DNA probes within and flanking the DMD region of the X chromosome in order to ascertain the nature of the molecular defects in affected males and to investigate the feasibility of genetic management by means of these techniques. The results of this study and the implications of this new molecular technology for DMD patients in South Africa are reviewed and discussed.

Child↗
PubMed1987

Genetic disease in South Africa. A molecular approach.

The Department of Human Genetics, University of Cape Town, has accumulated data on more than 11,000 individuals with inherited disorders seen over the last 15 years. Clinical and radiographic data on these persons and their families have been documented and where appropriate they have been investigated in our genetic laboratories. In accordance with current trends, a molecular genetic laboratory has been developed. The approach to South African genetic disease using recombinant DNA techniques is described.

DNA↗
PubMed1987

Molecular genetics and Huntington's disease. The South African situation.

The finding of a polymorphic DNA marker for Huntington's disease offers the potential for preclinical and prenatal screening for this condition. However, before implementation of a programme of this nature in South Africa, certain technical, medical psychosocial and ethical considerations require careful appraisal. The current situation with regard to the importance and implications of this new technology to affected kindreds is reviewed and discussed.

DNA↗
PubMed1986

Mutations linked to the pro alpha 2(I) collagen gene are responsible for several cases of osteogenesis imperfecta type I.

We have analysed six South African families with osteogenesis imperfecta type I using three DNA polymorphisms associated with the pro alpha 2(I) collagen gene. In four of these families linkage of the pro alpha 2(I) gene and the osteogenesis imperfecta phenotype was suggested, whereas in the remaining two families there was a lack of linkage. No distinct correlation could be made between the phenotypic features of the families studied and linkage or lack of linkage to the pro alpha 2(I) gene. Two different haplotypes were found to be associated with the mutant pro alpha 2(I) alleles. These findings suggest that molecular heterogeneity exists within osteogenesis imperfecta type I and that in a significant proportion of cases the defect is linked to the pro alpha 2(I) gene.

DNA↗
PubMed1986

Correction of urinary mercury concentration by specific gravity, osmolality, and creatinine.

Corrections for specific gravity, osmolality, and creatinine were applied to identical urinary mercury data in order to investigate the reproducibility of the corrected mercury concentration in a person's urinary spot samples throughout a 24-hour period; and the extent to which it is possible to predict a person's 24-hour mercury excretion from the corrected mercury concentration in the corresponding spot samples. The data indicate that on the average these corrections improve reproducibility by a factor of approximately 2. In individual cases, the uncorrected and corrected values of mercury concentration can differ by as much as a factor of 6. Similar effects were observed in the correlation of the mercury concentration of a spot sample and the corresponding 24-hour excretion of mercury. For this set of data, the corrections for specific gravity and osmolality turned out to be almost identical. The correction for creatinine was more effective than the other corrections by a small but statistically significant amount.

Body Weight↗
PubMed1985

Detection of a high frequency RsaI polymorphism in the human pro alpha 2(I) collagen gene which is linked to an autosomal dominant form of osteogenesis imperfecta.

Screening of the pro alpha 2(I) collagen genes of Southern African populations for restriction fragment length polymorphisms (RFLPs) has revealed a locus polymorphic for the restriction enzyme RsaI. The frequency of the RFLP was 0.38 in Afrikaners, but much lower in indigenous Southern African populations, which suggests that it is of European origin. The polymorphism was used to study 19 affected and non-affected individuals in a four generation family with the autosomal dominant disorder, osteogenesis imperfecta (OI) type I. Co-inheritance of the loss of the RsaI site and the OI phenotype was observed with a lod score of 3.91 at a recombination fraction (theta) of zero, indicating strong linkage. This suggests that the defect in this family is caused by a structural mutation within or close to the pro alpha 2(I) collagen gene. The use of this high frequency RFLP together with other recently described polymorphisms at this locus will facilitate the analysis of the role of this gene in OI and other inherited disorders of connective tissue.

Black People↗
PubMed1985

Polymorphism of DNA sequence in the human pro alpha 2(I) collagen gene.

The human pro alpha 2(I) collagen gene was analysed for the presence of restriction fragment length polymorphisms. DNA from randomly selected unrelated persons of three Southern African populations was cleaved with one of eight different restriction enzymes, electrophoresed, blotted, and hybridised with cDNA and genomic probes specific for the pro alpha 2(I) gene. An MspI polymorphism was detected which results from the loss of a cleavage site within the 3' half of the gene. In two of the populations studied, the polymorphism occurred at significant frequencies, and should therefore prove useful as a genetic marker for the study of inherited disorders of connective tissue involving collagen structure or biosynthesis.

Chromosome Mapping↗