Gene Expression in Adult Metafemales of Drosophila Melanogaster

The expression of selected X-linked and autosomal genes was examined in metafemales (3X:2A) compared to diploid sisters. Three enzyme activities (glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, beta-hydroxyacid dehydrogenase) encoded by X-linked genes are not significantly different in the two classes of flies. In contrast, three autosomally encoded enzyme activities (alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, isocitrate dehydrogenase) are reduced in metafemales. Protein and DNA comparisons between metafemales and diploid sisters show a lowered level of total protein whereas the total DNA measurements are similar. Thus, the total cell number in metafemales is basically unchanged but gene expression is reduced. Phenotypic analysis of three autosomal loci, glass (gl), purple (pr) and pink-peach (pp), show that all three have lowered expression in metafemales while the X-linked loci, white-apricot (wa) and Bar (B), are dosage compensated. Quantitative dot blot analysis of messenger RNA levels of the second chromosomal locus, alcohol dehydrogenase (Adh), and the X chromosomal locus, rudimentary (r), show that Adh has reduced expression and r is partially compensated per total RNA in metafemales. It is proposed that the increased dosage of the X chromosome inversely affects both the X and autosomal gene expression but the simultaneous increased dosage of the structural genes on the X results in dosage compensation. The reduced levels of expression of autosomal genes could contribute to the great inviability of metafemales.     

Cell cycle regulation of the E2F transcription factor involves an interaction with cyclin A.

We have examined E2F binding activity in extracts of synchronized NIH 3T3 cells. During the G0 to G1 transition, there is a marked increase in the level of active E2F. Subsequently, there are changes in the nature of E2F-containing complexes. A G1-specific complex increases in abundance, disappears, and is then replaced by another complex as S phase begins. Analysis of extracts of thymidine-blocked cells confirms that the complexes are cell cycle regulated. We also show that the cyclin A protein is a component of the S phase complex. Each complex can be dissociated by the adenovirus E1A 12S product, releasing free E2F. The release of E2F from the cyclin A complex coincides with the stimulation of an E2F-dependent promoter. We suggest that these interactions control the activity of E2F and that disruption of the complexes by E1A contributes to a loss of cellular proliferation control.     

A comparison of EMG feedback and alternative anxiety treatment programs

Four cohorts of 40 subjects each were randomly assigned to 1 of 10 treatment conditions utilizing EMG feedback, cognitive monitoring training, systematic desensitization, high expectancy discussion group, or waiting list controls either in isolation or in various combinations. A three-way ANOVA for repeated measures indicated that significant anxiety reductions were experienced in all noncontrol treatment conditions. Treatment groups employing EMG feedback demonstrated significantly greater anxiety decrements on Cattell's IPAT Self-Analysis Form, and baseline frontalis EMG. Adding desensitization or cognitive monitoring to EMG feedback did not produce a more powerful effect than using EMG feedback alone. Sex and age differences were also observed. Some implications are discussed.This research was supported in part by a grant from the Medical Services Research Foundation of Alberta.     

Poliovirus RNA-Dependent RNA Polymerase Synthesizes Full-Length Copies of Poliovirion RNA, Cellular mRNA, and Several Plant Virus RNAs In Vitro

The poliovirus RNA-dependent RNA polymerase was active on synthetic homopolymeric RNA templates as well as on every natural RNA tested. The polymerase copied polyadenylate. oligouridylate [oligo(U)], polycytidylate . oligoinosinate, and polyinosinate. oligocytidylate templates to about the same extent. The observed activity on polyuridylate. oligoadenylate was about fourfold less. Full-length copies of both poliovirion RNA and a wide variety of other polyadenylated RNAs were synthesized by the polymerase in the presence of oligo(U). Polymerase elongation rates on poliovirion RNA and a heterologous RNA (squash mosaic virus RNA) were about the same. Changes in the Mg(2+) concentration affected the elongation rates on both RNAs to the same extent. With two non-polyadenylated RNAs (tobacco mosaic virus RNA and brome mosaic virus RNA3), the results were different. The purified polymerase synthesized a subgenomic-sized product RNA on brome mosaic virus RNA3 in the presence of oligo(U). This product RNA appeared to initiate on oligo(U) hybridized to an internal oligoadenylate sequence in brome mosaic virus RNA3. No oligo(U)-primed product was synthesized on tobacco mosaic virus RNA. When partially purified polymerase was used in place of the completely purified enzyme, some oligo(U)-independent activity was observed on the brome mosaic virus and tobacco mosaic virus RNAs. The size of the product RNA from these reactions suggested that at least some of the product RNA was full-sized and covalently linked to the template RNA. Thus, the polymerase was found to copy many different types of RNA and to make full-length copies of the RNAs tested.     

Silicates,Silicate Weathering,and Microbial Ecology

Mineralogy, microbial ecology, and mineral weathering in the subsurface are an intimately linked biogeochemical system. Although bacteria have been implicated indirectly in the accelerated weathering of minerals, it is not clear if this interaction is simply the coincidental result of microbial metabolism, or if it represents a specific strategy offering the colonizing bacteria a competitive ecological advantage. Our studies provide evidence that silicate weathering by bacteria is sometimes driven by the nutrient requirements of the microbial consortium, and therefore depends on the trace nutrient content of each aquifer mineral. This occurrence was observed in reducing groundwaters where carbon is abundant but phosphate is scarce; here, even resistant feldspars are weathered rapidly. This suggests that the progression of mineral weathering may be influenced by a mineral's nutritional potential, with microorganisms destroying only beneficial minerals. The rock record, therefore, may contain a remnant mineralogy that reflects early microbial destruction of biologically valuable minerals, leaving a residuum of "useless" minerals, where "value" depends on the organism, its metabolic needs, and the diagenetic environment. Conversely, the subsurface distribution of microorganisms may, in part, be controlled by the mineralogy and by the ability of an organism to take advantage of mineral-bound nutrients.