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Biomedical subjects

K Davies

Publications and source records attributed to K Davies.

At least 19 recordsLinked to original sources
PubMed1992

Message in a bottle.

Insights from the classic work of Luria and Delbrück on bacterial mutation rates may be applied to tracking human gene defects prevalent in isolated populations.

Chromosome Mapping↗
PubMed1992

Assessment of uncoupling by amiloride analogs.

The amiloride analogs N5-methyl-N5-isobutylamiloride, N5-ethyl-N5-isopropylamiloride, and N5,N5-hexamethyleneamiloride are frequently used to investigate NaH exchange on the premise that they are highly specific inhibitors of the NaH-antiporters. We assessed the relative protonophoric activity of these compounds in reconstituted and native membrane vesicles, using acridine orange fluorescence to measure intravesicular pH. All the compounds tested were found to be potent protonophores at concentrations which are normally used to demonstrate inhibition of NaH exchange. Uncoupling was dependent on both the pH of the assay system and the total amount of lipid present. At the pH optima, which lay in a range from 7.5 to 8.5, these amiloride analogs were more potent uncouplers than the classical protonophore carbonyl cyanide m-chlorophenylhydrazone. Therefore, extreme care must be taken in the interpretation of results obtained using these or similar derivatives of amiloride.

Acridine Orange↗
PubMed1992

Moving straight to the target.

Retroviral vectors for gene transfer experiments have their limitations--hence the attraction of using other viral vehicles to administer genes directly to affected organs.

Adenoviridae↗
PubMed1992

Genetic screening for cystic fibrosis.

More than 98% of mutations causing cystic fibrosis can be detected in a Celtic population in Brittany, France. What, though, are the prospects for screening of entire populations for carriers?

Cystic Fibrosis↗
PubMed1992

Cloning and disruption of a putative NaH-antiporter gene of Enterococcus hirae.

When growing in a sodium-rich environment, wild-type Enterococcus hirae extrudes sodium by two mechanisms, ATP-driven sodium extrusion, and NaH-antiport. Mutant 7683 is unable to grow on sodium-rich media. This is due to two mutations, one inactivating ATP-driven sodium transport and a second rendering NaH-antiport inoperative. 7683 was transformed by electroporation with a gene bank, derived from E. hirae, in an Escherichia coli-E. hirae shuttle vector. Transformants which had regained the ability to grow on sodium-rich media were selected for and the transforming plasmids analyzed. A gene able to restore NaH-antiport activity in 7683 was identified. This gene was named napA. It codes for an extremely hydrophobic protein of 383 amino acids. Hydropathy analysis of this protein indicates that it probably forms 12 transmembraneous helices. In a mutant, possessing only the NaH-antiporter, the napA gene was disrupted by homologous recombination. The resultant strain failed to grow in sodium-rich media, and vesicles isolated from these cells exhibited a defect in sodium proton antiport activity. We conclude that the napA gene codes for a NaH-antiporter. The NapA protein does not exhibit significant homology to any protein in the EMBL genetic data bank.

Amino Acid Sequence↗
PubMed1991

High-dose intravenous IgG treatment and renal function.

In an open trial of high dose intravenous IgG (IVIG) treatment in nephrotic patients with glomerulonephritis, the first six patients so far studied showed a transient rise in plasma creatinine. This increase was not associated with any symptoms and the urinary deposit remained unchanged. Two other patients with pre-existing renal impairment but without nephrotic syndrome had a transient and reversible rise in plasma creatinine immediately after IVIG. These observations suggest that high-dose IVIG infusion can produce short-lived disturbances in renal function in patients with kidney diseases.

Adult↗
PubMed1991

Early prenatal diagnosis of the fragile site at Xq27.3 associated with Martin-Bell syndrome.

Early prenatal diagnosis of the fragile X was attempted in 44 pregnancies, including one twin pregnancy at risk of Martin-Bell (MB) syndrome. The sex ratio was 24M:21F. The fragile site was reproducibly demonstrated in cultured chorionic villus (CV) cells in eight male and five female fetuses. Six of the male and three of the female fetuses were terminated. Simultaneous RFLP analysis provided confirmative data with flanking DNA markers in 3 of 13 analysed cases. Recombination and/or non-informativeness at available distal and/or proximal loci were found in nine cases. In one male fetus, discordance between the haplotype and cytogenetics (fragile-X-negative) suggested the presence of a normal male transmitter, a double meiotic cross-over within the region, or a false-negative cytogenetic diagnosis. However, discordance between prenatal and post-termination/postnatal cytogenetic findings was not observed in this series. The use of excess thymidine for induction of the fragile X in cultured CV cells provided in the majority of cases a safe and rapid method for cytogenetic diagnosis, with options for early induced termination in fragile-X-positive pregnancies, for simultaneous RFLP analysis, and for subsequent second-trimester analysis of fetal blood in complicated cases.

Adolescent↗