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G K Chambers

Publications and source records attributed to G K Chambers.

15 recordsLinked to original sources
PubMed1992

Independent origins of New Zealand moas and kiwis.

Two groups of flightless ratite birds existed in New Zealand during the Pleistocene: the kiwis and the moas. The latter are now extinct but formerly included 11 species. We have enzymatically amplified and sequenced approximately 400 base pairs of the mitochondrial 12S rRNA gene from bones and soft tissue remains of four species of moas as well as eight other species of ratite birds and a tinamou. Contrary to expectation, the phylogenetic analysis shows that the kiwis are more closely related to Australian and African ratities than to the moas. Thus, New Zealand probably was colonized twice by ancestors of ratite birds.

Animals↗
PubMed1990

Absence of daily cycles in plasma sex steroids in male and female tuatara (Sphenodon punctatus), and the effects of acute capture stress on females.

The possible existence of daily cycles in plasma concentrations of sex steroids was examined in wild male and female tuatara (Sphenodon punctatus). Samples were collected from freshly captured animals at dusk, middle of the night, dawn, and middle of the day in January (summer) and July (winter). Males showed daily cycles in mean body temperature (Tb) in both seasons but no daily cycle in mean plasma testosterone concentration in either season. Vitellogenic female tuatara in January and females in mixed reproductive condition in July also showed significant daily variation in Tb. However, there were no daily cycles in mean plasma concentrations of estradiol, testosterone, or progesterone in either group of females. Vitellogenic female tuatara subjected to an acute capture stress (3-hr confinement) in January had mean plasma concentrations of estradiol and testosterone that did not differ from those of free-roaming females. However, progesterone and Tb were significantly higher in captives than in free-roaming females. The elevation in progesterone may result from physical confinement, the difference in Tb, or both. These data suggest that seasonal fluctuations in circulating concentrations of plasma sex steroids in tuatara can be determined using samples collected at different times of the 24-hr cycle. However, the effects of acute capture stress and/or changes in Tb on plasma progesterone concentrations need to be considered in future studies on this and possibly other female reptiles.

Animals↗
PubMed1990

The genetics of human alcohol metabolism.

1. The custom of drinking alcoholic beverages is a human behavior with serious social and medical consequences for a surprisingly large fraction of drinkers. 2. This review describes recent advances in our understanding of the genetic loci that control enzyme systems involved in the metabolism of alcohol. 3. These advances make possible new experimental programs that may lead to simple diagnostic tests for patients at risk of developing alcohol abuse behaviour.

Alcohol Dehydrogenase↗
PubMed1989

Sequence, structure and evolution of the gene coding for sn-glycerol-3-phosphate dehydrogenase in Drosophila melanogaster.

We present the complete nucleotide and deduced amino acid sequence for the gene encoding Drosophila sn-glycerol-3-phosphate dehydrogenase. A transcription unit of 5kb was identified which is composed of eight protein encoding exons. Three classes of transcripts were shown to differ only in the 3'-end and to code for three protein isoforms each with a different C-terminal amino acid sequence. Each transcript is shown to arise through the differential expression of three isotype-specific exons at the 3'-end of the gene by a developmentally regulated process of 3'-end formation and alternate splicing pathways of the pre-mRNA. In contrast, the 5'-end of the gene is simple in structure and each mRNA is transcribed from the same promoter sequence. A comparison of the organization of the Drosophila and murine genes and the primary amino acid sequence between a total of four species indicates that the GPDH gene-enzyme system is highly conserved and is evolving slowly.

Amino Acid Sequence↗
PubMed1987

Molecular cloning and characterization of esterase-6, a serine hydrolase of Drosophila.

The Est-6 gene of Drosophila melanogaster was cloned by screening libraries with synthetic oligonucleotides corresponding to tryptic peptides from purified esterase-6 (Est-6) protein. cDNA clones were isolated that hybridized in situ to the site of Est-6 on chromosome 3 at 69A1. Inserts in putative Est-6 cDNA clones were 1.85 kilobases (kb) long, and blot hybridization analysis of electrophoretically fractionated RNA, using a cDNA clone as a probe, revealed two transcripts, of 1.68 and 1.83 kb. The two transcripts showed the same developmental profile as the Est-6 protein. Neither transcript was detected in an Est-6-null line. The cDNA fragment was homologous to a 2.3-kb EcoRI-BamHI fragment in genomic clones, and this region was interrupted by the 8-kb B104 transposable element in the Est-6-null line. Conceptual translation of the cDNA sequence revealed a protein of 548 residues with 19% sequence similarity to acetylcholinesterase from the Torpedo ray.

Amino Acid Sequence↗
PubMed1978

Alcohol-oxidizing enzymes in 13 Drosophila species.

Starch and polyacrylamide gel electrophoresis were used to ascertain the substrate specificities of alcohol-oxidizing enzymes in 13 Drosophila species. The substrates used were a variety of long- and short-chain aliphatic alcohols, one aromatic alcohol, and benzaldehyde. Only one enzyme (product of a single-gene locus) showed significant NAD+-dependent alcohol dehydrogenase activity with short-chain aliphatic alcohols. The 13 species, belonging to four different Drosophila groups, all showed a similar complement of alcohol-oxidizing enzymes, although differences in electrophoretic mobility and in levels of activity existed from species to species. These findings are relevant to the adaptation of Drosophila to alcohol environments.

Alcohol Oxidoreductases↗
PubMed1978

Structural analysis of the ADHS electromorph of Drosophila melanogaster.

Population geneticists have often determined the fitness differences that account for the dynamics of naturally occurring genetic polymorphisms. However, to understand causal aspects of evolutionary processes requires, in addition, investigation of the physiological and molecular structural differences underlying adaptively significant genetic polymorphisms. The characteristics of the alcohol dehydrogenase gene--enzyme system in Drosophila melanogaster make it well suited for this kind of study. Natural populations of this species are polymorphic for two electrophoretically detectable variants, ADHF and ADHS, of the enzyme. Structural studies reported here reveal that the two variants differ by (at least) a single amino acid replacement, threonine in ADHF for lysine in ADHS.

Alcohol Oxidoreductases↗
PubMed1977

Adaptive response due to changes in gene regulation: a study with Drosophila.

In spite of the critical role of the process of adaptation in evolution, there are few detailed studies of the genotypic and molecular basis of the process. Drosophila melanogaster flies selected for increased tolerance to ethanol exhibited higher levels of alcohol dehydrogenase (alcohol:NAD+ oxidoreductase; EC 1.1.1.1) activity than unselected controls. A series of tests (electrophoresis, product inhibition, temperature stability, pH optima, substrate specificity, and Michaelis constants) gave no evidence of structural differences in the enzyme of the selected and the control flies. However, quantitative immunological assays showed that the selected flies contained significantly higher amounts of alcohol dehydrogenase. Adaptation of the selected flies to higher alcohol tolerance has most likely taken place by changes not in the structural gene locus coding for the enzyme, but by regulatory changes affecting the amount of gene product.

Adaptation, Biological↗
PubMed1975

The amino acid sequence of Neurospora NADP-specific glutamate dehydrogenase. The tryptic peptides.

The NADP-specific glutamate dehydrogenase of Neurospora crassa was digested with trypsin, and peptides accounting for 441 out of the 452 residues of the polypeptide chain were isolated and substantially sequenced. Additional experimental detail has been deposited as Supplementary Publication SUP 50052 (11 pages) with the British Library (Lending Division), Boston Spa, Wetherby, W. Yorkshire LS23 7BQ, U.K., from whom copies may be obtained under the terms given in Biochem J. (1975) 145, 5.

Amides↗
PubMed1975

The amino acid sequence of Neurospora NADP-specific glutamate dehydrogenase. Peptic and chymotryptic peptides and the complete sequence.

Peptic and chymotryptic peptides were isolated form the NADP-specific glutamate dehydrogenase of Neurospora crassa and substantially sequenced. Out of 452 residues in the polypeptide chain, 265 were recovered in the peptic and 427 in the chymotryptic peptides. Together with the tryptic peptides [Wootton, J. C., Taylor, J. G., Jackson, A. A., Chambers, G. K. & Fincham, J. R. S. (1975) Biochem. J. 149, 749-755], these establish the complete sequence of the chain, including the acid and amide assignments, except for seven places where overlaps are inadequate. These remaining alignments are deduced from information on the CNBr fragments obtained in another laboratory [Blumenthal, K. M., Moon, K. & Smith, E. L. (1975), J. Biol. Chem. 250, 3644-3654]. Further information has been deposited as Supplementary Publication SUP 50054 (17 pages) with the British Library (Lending Division), Boston Spa, Wetherby, W. Yorkshire LS23 7BQ, U.K., from whom copies may be obtained under the terms given in Biochem. J. (1975) 145, 5.

Amides↗