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Biomedical subjects

A S Robinson

Publications and source records attributed to A S Robinson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Protein disulfide isomerase overexpression increases secretion of foreign proteins in Saccharomyces cerevisiae.

Overexpression of protein disulfide isomerase (PDI) from a single chromosomally integrated copy in Saccharomyces cerevisiae results in ten-fold higher levels of secretion of human platelet derived growth factor B homodimer, and a four-fold increase in secretion of Schizosaccharomyces pombe acid phosphatase. This result provides evidence that inefficient protein folding limits the secretion of some heterologous proteins, and that manipulation of the endoplasmic reticulum lumenal environment can help overcome this limitation.

Cloning, Molecular↗
PubMed1993

Isolation of cDNAs encoding 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase from the mediterranean fruit fly Ceratitis capitata: correlating genetic and physical maps of chromosome 5.

We have isolated and determined the nucleotide sequences for cDNA clones encoding glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) from the medfly Ceratitis capitata. The derived amino acid sequences for G6PD and 6PGD are presented and compared with G6PDs and 6PGDs from other species. The codon usage of the cDNA clones has little bias with the notable exceptions of arginine, glycine and leucine. The chromosomal location of the genes for 6PGD and G6PD were determined by in situ hybridization to salivary gland polytene chromosomes. This localization orients a genetic map of enzymatic loci and illustrates a remarkable similarity in the intra chromosomal order of homologous genes between Drosophila melanogaster and medfly.

Amino Acid Sequence↗
PubMed1993

Mediterranean fruit fly, Ceratitis capitata (Wiedemann), mitochondrial DNA: genes and secondary structures for six t-RNAs.

The polymerase chain reaction was used to amplify six mitochondrial t-RNAs for Ala, Arg, Asn, Ser, Glu and Phe between genes for mitochondrial NADH dehydrogenases 3 and 5. With respect to Drosophila yakuba the gene order and direction of transcription is completely conserved. Analysis of secondary structure shows complete conservation of the anticodon loops but a number of differences in the dihydrouridine and T psi C loops with respect to Drosophila. However, differences are such that tertiary interactions that stabilize stacking are preserved. The use of the reported sequence in combination with PCR to explore population variability is discussed.

Animals↗
PubMed1992

The genome of the Mediterranean fruitfly Ceratitis capitata: localization of molecular markers by in situ hybridization to salivary gland polytene chromosomes.

We hybridized cloned DNA segments to salivary gland polytene chromosomes of the medfly, Ceratitis capitata, and thus established molecular markers for 24 sites on 6 out of 10 autosomal arms. An additional marker identified a medfly repetitive element that hybridizes to approximately 100 autosomal sites as well as a granular network that is thought to represent the X chromosome. Some of the markers correspond to 9 characterized transcription units, while 17 remain anonymous; at least 3 of the latter are restriction fragment length polymorphism (RFLP) markers. The characterized transcription units document that chromosomal arm 5L of C. capitata is homologous to the Drosophila melanogaster X chromosome, in agreement with previous inferences based on the extensive conservation of linkage groups in Diptera.

Amino Acid Sequence↗
PubMed1992

A biochemical genetic study of alcohol dehydrogenase isozymes of the medfly, Ceratitis capitata Wied.

A concerted effort is under way to analyze, at the genetic, biochemical, and molecular level, the Adh gene system in the medfly Ceratitis capitata, an important agricultural pest. The isoelectric focusing (IEF) pattern of alcohol dehydrogenase (ADH) of the medfly demonstrates the presence of two well-differentiated, genetically independent dimeric proteins, called ADH-1 and ADH-2. These proteins do not exhibit interlocus heterodimeric isozymes, and the genes are not controlled coordinately during development, Adh1 and Adh2 being expressed mainly in muscle or in fat body and ovary, respectively. From the intensity of the IEF isozyme patterns, primary alcohols are judged to be better substrates than secondary alcohols, in contrast with Drosophila melanogaster ADH, and ethanol is probably the most efficient substrate for both sets of isozymes. The isoelectric points of ADH-1 (pI = 5.4) and ADH-2 (pI = 8.6) are different from D. melanogaster ADH (pI = 7.6), but the medfly ADH-1 has a native molecular weight (approx. 58 kD) close to that of D. melanogaster. A population survey of samples both from laboratory strains and from wild geographically different populations showed that the Adh1 locus is more polymorphic than Adh2. The most variable populations are from Africa, the supposed source area of the species. Further, a case of selection at the Adh1 locus under laboratory conditions is reported. The hypothesis of Adh gene duplication and the degree of similarity between medfly and Drosophila ADH are also discussed.

Alcohol Dehydrogenase↗
PubMed1990

Characterization of sodium dodecyl sulfate-resistant proteolytic activity in the hyperthermophilic archaebacterium Pyrococcus furiosus.

Cell extracts from Pyrococcus furiosus were found to contain five proteases, two of which (S66 and S102) are resistant to sodium dodecyl sulfate (SDS) denaturation. Cell extracts incubated at 98 degrees C in the presence of 1% SDS for 24 h exhibited substantial cellular proteolysis such that only four proteins could be visualized by amido black-Coomassie brilliant blue staining of SDS-polyacrylamide gels. The SDS-treated extract retained 19% of the initial proteolytic activity as represented by two proteases, S66 (66 kilodaltons [kDa]) and S102 (102 kDa). Immunoblot analysis with guinea pig sera containing antibodies against protease S66 indicated that S66 is related neither to S102 nor to the other proteases. The results of this analysis also suggest that S66 might be the hydrolysis product of a 200-kDa precursor which does not have proteolytic activity. The 24-h SDS-treated extract showed unusually thermostable proteolytic activity; the measured half-life at 98 degrees C was found to be 33 h. Proteases S66 and S102 were also resistant to denaturation by 8 M urea, 80 mM dithiothreitol, and 5% beta-mercaptoethanol. Purified protease S66 was inhibited by phenylmethylsulfonyl fluoride and diisopropyl fluorophosphate but not by EDTA, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, or iodoacetic acid. These results indicate that S66 is a serine protease. Amino acid ester hydrolysis studies showed that protease S66 was hydrolytically active towards N-benzoyl-L-arginine ethyl ester.

Archaea↗
PubMed1987

Cytological, linkage and insecticide studies on a genetic sexing line in Anopheles stephensi Liston.

T(Y-D1)35 is a genetic sexing line in Anopheles stephensi (2n = 6; XX female, XY male) based on the translocation of the dieldrin resistance gene to the male determining chromosome. A cytological analysis demonstrated the presence of a 3 chromosome multiple translocation in which part of the Y chromosome formed the differential segment. An analysis of egg karyotypes enabled the segregation behaviour of the complex to be determined and only alternate and adjacent I segregations could be demonstrated. The breakpoint of the translocation in chromosome 3 was located using polytene salivary gland preparations. Linkage studies using chromosome three markers revealed contrasting effects of the translocation on recombination in this chromosome. An insecticide treatment method, based on the exposure of newly emerged adults, was developed enabling large numbers of individuals to be treated for the production of only males.

Animals↗
PubMed1984

Amebic appendicitis associated with hepatic abscess.

We have described a case of primary amebic appendicitis with liver abscess, and we suggest that this diagnosis be considered in patients with appendicitis after returning from endemic areas. Careful histologic preparation will establish the diagnosis and dictate appropriate therapy.

Amebiasis↗
PubMed1981

Neutrons and X-rays, comparative studies with Drosophila melanogaster. 1. The viability and fertility of induced autosomal translocations.

Studies on the genetic effects of neutrons and X-rays have produced evidence that may be interpreted as indicating that neutrons induce clusters of closely linked genetic changes. According to this interpretation, it is to be expected that neutron-induced translocations will have a higher rate of associated recessive lethality, compared with translocations induced by low-LET radiation such as X-rays. The experiment reported here was designed to test whether this expectation is fulfilled. The dose--frequency response with neutrons for the induction of autosomal translocation was established by exposing males from the Oregon-K stock and then sampling treated mature sperm. From the data obtained, it was estimated that 10 Gy neutrons should induce about the same frequency of autosomal translocations as 27 Gy X-rays. These 2 doses were used to induce translocations in the spermatozoa of males carrying lethal-free autosomes, derived from the Oregon-K stock. Induced translocations were tested for homozygous viability and fertility. When these criteria were used, no qualitative difference was detected between the translocations induced by neutrons and X-rays.

Animals↗
PubMed1981

Complex Y-linked translocations in Delia antiqua produced by irradiation of a fertile Y-linked translocation.

In the onion fly, Delia antiqua, a fertile, Y-linked translocation involving chromosomes Y and 2 was irradiated with fast neutrons to induce new complexes involving the Y-chromosome. This chromosome is male determining in the onion fly. Such complexes can be used for the development of genetic sexing systems and also for the introduction of sterility into field populations following release. Irradiation reduced egg fertility by 54 per cent and significantly reduced larval survival but it had no effect on the F1 sex ratio. By measuring the fertility of 807 F1 males following outcrossing, 112 semi-sterile progenies were isolated of which 11 were lost, 29 showed no inheritance of the semi-sterility, 59 were new autosomal translocations and 13 were new complex Y-linked translocations. This classification was accomplished by checking the fertilities of outcrossed F2 males and females. Following cytological observation it was revealed that one of these new complexes involved four chromosome pairs, the remainder involved three. There appeared to be no correlation between the fertility of the translocation and the complexity of the rearrangement. The utilization of these rearrangements in the development of the genetic sexing technique for the onion fly is discussed, together with an assessment of their use for fertility reduction in natural populations.

Animals↗