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Biomedical subjects

G Petersen

Publications and source records attributed to G Petersen.

At least 73 records · Page 4Linked to original sources
PubMed1989

Primary structure and functional aspects of the gene coding for the second-largest subunit of RNA polymerase III of Drosophila.

We have cloned and sequenced the gene coding for the second-largest subunit of RNA polymerase III of Drosophila melanogaster (DmRP135). The gene, interrupted by two introns of 62 and 59 bp, respectively, codes for an mRNA of 3.6 kb. As for other housekeeping genes transcription initiates at several sites (between positions -98 and -76) none of which is preceded by a clear TATA sequence. The deduced polypeptide consists of 1129 amino acids with an aggregate molecular weight of 128 kDa. The protein sequence features the same regions of similarity as observed for the corresponding subunits of RNA polymerase II of Drosophila and yeast and the Escherichia coli beta subunit. As in the second-largest subunit of RNA polymerase II there is a zinc-binding motif which is absent in the beta subunit of E. coli. Antibodies directed against a fusion protein expressing 164 amino acids of the DmRP135 polypeptide cross-react with the second-largest subunit of RNA polymerase III of yeast and generate a distinct banding pattern on Drosophila polytene chromosomes distinguishable from that obtained with anti-RNA polymerase II antibodies.

Amino Acid Sequence↗
PubMed1988

The period gene of Drosophila carries species-specific behavioral instructions.

We have analyzed and compared the circadian locomotor activity rhythms of Drosophila melanogaster and D.pseudoobscura. The rhythms of D.pseudoobscura are stronger and the periods shorter than those of D.melanogaster. We have also transformed D.melanogaster flies with a hybrid gene containing the coding region of the D.pseudoobscura period (per) gene. Behavioral assays of flies containing this hybrid gene show that the per protein encoded by the D.pseudoobscura per gene is able to rescue the rhythmic deficiencies of arrhythmic, pero1 D.melanogaster. More important, the rhythms of some of these strains are stronger and the periods shorter than those of D.melanogaster (and those of transformants which carry the equivalent D.melanogaster per gene construct) and hence resemble those of D.pseudoobscura. The results suggest that the primary amino acid sequence of the per gene encodes species-specific behavioral instructions that are detectable when only the per gene is transferred to a different species.

Animals↗
PubMed1988

Antibodies to the period gene product of Drosophila reveal diverse tissue distribution and rhythmic changes in the visual system.

Polyclonal antibodies were prepared against the period gene product, which influences biological rhythms in D. melanogaster, by using small synthetic peptides from the per sequence as immunogens. The peptide that elicited the best antibody reagent was a small domain near the site of the pers (short period) mutation. Specific immunohistochemical staining was detected in a variety of tissue types: the embryonic CNS; a few cell bodies in the central brain of pupae; these and other cells in the central brain of adults, as well as imaginal cells in the eyes, optic lobes, and the gut. The intensity of per-specific staining in the visual system was found to oscillate, defining a free-running circadian rhythm with a peak in the middle of the night.

Animals↗
PubMed1988

A controlled comparison of the efficacy of clomiphene citrate in male infertility.

To determine whether clomiphene citrate (CC) improves fertility in oligospermic men, 23 men with sperm concentrations between 0.5 and 20 million sperm per milliliter; normal serum gonadotropins and testosterone; and a presumptively fertile partner were enrolled in the study. After a 3-month control period, patients were randomly prescribed CC, 25 mg/day; or placebo, 1 tablet/day, for 12 months. The pregnancy rates for the CC group and the placebo group were 9.09% and 44.44%, respectively (not significant). During the treatment phase, the CC group had significantly higher levels of luteinizing hormone (LH) serum, follicle-stimulating hormone (FSH), testosterone (T), and estradiol than the placebo group. CC treatment also resulted in greater LH, FSH, and T responses to gonadotropin-releasing hormone (GnRH). There were no differences between the placebo and CC groups for the sperm penetration assay or semen parameters. The authors conclude that CC is not a useful drug in the treatment of male infertility.

Clomiphene↗
PubMed1987

L-phenylalanyl-L-glutamate-stimulated, chloride-dependent glutamate binding represents glutamate sequestration mediated by an exchange system.

Stimulation of glutamate binding by the dipeptide L-phenylalanyl-L-glutamate (Phe-Glu) was inhibited by the peptidase inhibitor bestatin, suggesting that the stimulation was caused by glutamate liberated from the dipeptide and not by the dipeptide itself. It further suggests that this form of glutamate binding should be reinterpreted as glutamate sequestration and that stimulation of binding both by dipeptides and after preincubation with high concentrations of glutamate is likely to be due to counterflow accumulation. Several other criteria indicate that most of glutamate binding stimulated by chloride represents glutamate sequestration: Binding is reduced when the osmolarity of the incubation medium is increased, when membranes incubated with [3H]glutamate are lysed before filtration, and when membranes are made permeable by transient exposure to saponin. Moreover, dissociation of bound glutamate after a 100-fold dilution of the incubation medium is accelerated about 50 times by the addition of glutamate to the dilution medium. This result would be anomalous if glutamate were bound to a receptor site; it suggests instead that glutamate is transported in and out of membrane vesicles by a transport system that preferentially mediates exchange between internal and external glutamate. Glutamate binding contains a component of glutamate sequestration even when measured in the absence of chloride. Sequestration is adequately abolished only after treating membranes with detergents; even extensive lysis, sonication, and freezing/thawing may be insufficient.

Aminopeptidases↗
PubMed1986

The period clock locus of D. melanogaster codes for a proteoglycan.

The period (per) gene of D. melanogaster is involved in the generation of biological rhythms. The most striking feature of the predicted coding sequence, corresponding to the key 4.5 kb transcript from this locus, is an extensive run of alternating Gly-Thr residues. This is homologous to a series of Gly-Ser repeats in a chondroitin sulfate proteoglycan. To determine whether the per transcript codes for a proteoglycan, a region of its coding sequence was expressed (in bacteria) as part of a fusion protein, which was used to immunize rabbits. When the resultant immune sera were used to probe fly protein preparations, they detected an antigen that is present in wild-type flies and absent in a per- mutant. Biochemical characterization of this antigen indicated that it is indeed a proteoglycan.

Amino Acid Sequence↗