A Simple Method for Isolating DNA of High Yield and Quality from Cotton (shape Gossypium hirsutum L.) Leaves

An easy, reproducible and fast procedure to isolate DNA from cotton leaves is described. The addition of 0.5 M glucose in the extraction buffer avoids browning by polyphenolic compounds and improves the quality of DNA for molecular analysis. The DNA yield ranged between 150–400 mg per gram of fresh tissue. The DNA was suitable for digestion by restriction enzymes and amplificatiion by Taq DNA polymerase.     

Production of trace levels of carbon monoxide during methanogenesis on acetate and methanol

Summary Production of trace levels of carbon monoxide was consistently observed in the off-gas of a laboratory anaerobic digester fed Waste Activated Sludge. Inocula from this digester was enriched for acetate and methanol utilizing methanogenic populations. These enriched inocula were then monitored in batch assays for carbon monoxide and hydrogen production. Results demonstrated that carbon monoxide is produced during methanogenesis on both substrates. Subsequent utilization of CO was observed to occur after methane production was essentially complete for the assays conducted with methanol. Carbon monoxide evolution during methanogenesis on acetate displayed a markedly different trend from that observed from methanol.     

Production of Poly-β-Hydroxyalkanoic Acid by Pseudomonas cepacia

The possibility of using the nutritionally versatile bacterium Pseudomonas cepacia to produce poly-β-hydroxyalkanoic acid was evaluated. Chemostat culture showed that growth of P. cepacia became nitrogen limited when the molar carbon-to-nitrogen ratio of the medium fed into the fermentor was above 15. When grown under nitrogen limitation in batch culture with fructose as the sole source of carbon, P. cepacia accumulated poly-β-hydroxybutyric acid (PHB) in excess of 50% of the dry weight of its biomass. In batch culture, almost no PHB was produced until the onset of nitrogen limitation. After this point, PHB was produced at a linear rate of 0.12 g liter⁻¹ h⁻¹ (from a constant value of 1.6 g of cellular protein liter⁻¹). PHB produced by P. cepacia had a weight-average molecular weight of 5.37 × 10⁵ g mol⁻¹ and a polydispersivity index of 3.9. Poly(β-hydroxybutyric acid-β-hydroxyvaleric acid) copolymer was produced with a poly-β-hydroxybutyric acid-poly-β-hydroxyvaleric acid ratio of up to 30% by weight when propionic acid was added to the medium.     

Targeted Selection Experiments and Enzyme Polymorphism: Negative Evidence for Octanoate Selection at the G6PD Locus in DROSOPHILA MELANOGASTER

Published studies have reported significant selection with respect to the G6pd locus for Drosophila melanogaster reared on Na-octanoate food. We have reexamined the selective effects of Na-octanoate on egg to adult viability with respect to the G6pd polymorphism using specially constructed X chromosomes. Four experiments were carried out using different 6Pgd backgrounds in two recombinant sets of chromosomes segregating for the G6pd locus but constructed so as to minimize variation over most of the X chromosome. In addition, two measures of viability were used, and the size of the experiments and their associated degrees of freedom are approximately double those reported in the former studies. Our results find no evidence for differential selection on G6pd genotypes (males and females) by Na-octanoate and, therefore, do not corroborate the positive results of selection reported by other investigators. The reasons for our different results are discussed.     

Population genetics and phylogenetics of DNA sequence variation at multiple loci within the Drosophila melanogaster species complex

Two regions of the genome, a 1-kbp portion of the zeste locus and a 1.1- kbp portion of the yolk protein 2 locus, were sequenced in six individuals from each of four species: Drosophila melanogaster, D. simulans, D. mauritiana, and D. sechellia. The species and strains were the same as those of a previous study of a 1.9-kbp region of the period locus. No evidence was found for recent balancing or directional selection or for the accumulation of selected differences between species. Yolk protein 2 has a high level of amino acid replacement variation and a low level of synonymous variation, while zeste has the opposite pattern. This contrast is consistent with information on gene function and patterns of codon bias. Polymorphism levels are consistent with a ranking of effective population sizes, from low to high, in the following order: D. sechellia, D. melanogaster, D.mauritiana, and D. simulans. The apparent species relationships are very similar to those suggested by the period locus study. In particular, D. simulans appears to be a large population that is still segregating variation that arose before the separation of D. mauritiana and D. sechellia. It is estimated that the separation of ancestral D. melanogaster from the other species occurred 2.5-3.4 Mya. The separations of D. sechellia and D. mauritiana from ancestral D. simulans appear to have occurred 0.58- 0.86 Mya, with D. mauritiana having diverged from ancestral D. simulans 0.1 Myr more recently than D. sechellia.      

Immunohistopathological studies of blastomycosis: the use of labeled specific antigens in a hamster model of disease

We applied a modified immunofluorescence and immunoperoxidase method, utilizing labeled Blastomyces dermatitidis antigens, to look for specific antibody-bearing B/ plasma cells in the tissue infiltrates of blastomycosis lesions induced in hamsters. No specific anti-blastomyces antibodies were detectable by this method, although such antibodies were present in blood samples as demonstrated by routine immunodiffusion techniques. These studies suggest that humoral immune reactions do not play a major role in the pathogenesis of lesions of blastomycosis in hamsters.     

Two forms of VPg on poliovirus RNAs

The protein (VPg) linked to the 5' termini of poliovirus RNAs resolved into two species when subjected to non-equilibrium electrofocusing. The differently charged forms of VPg were not due to protein phosphorylation nor to variability of the number of phosphate residues associated with the nucleotide moiety remaining after RNase digestion of the nucleoprotein. Single-stranded viral RNA isolated from mature virions contained predominantly the more basic form of VPg, whereas unpackaged single-stranded RNa remaining in cells at the end of the virus replication cycle contained predominantly the more acidic form of VPg. Replicative-form (RF) molecules also contained both species of VPg, with the more acidic form representing the major species. Both plus and minus RNA strands in RF had similar VPg compositions; however, there appeared to be a strongly selective loss of VPg from only the minus strand in RF, particularly at late times postinfection.     

PROLIFERATION KINETICS OF THE MOUSE BLADDER AFTER IRRADIATION

The proliferative response of the mouse bladder was investigated, using continuous labelling with tritiated thymidine, at various times after a single dose of radiation. Bladder epithelial and vascular endothelial cells were studied. The cell turnover rate in unirradiated epithelium and endothelium was found to be extremely slow (in excess of 1 year). Irradiation with a single dose of 25 Gy resulted in compensatory proliferation of the epithelium but the response was not initiated for many months. At 3 months after irradiation there was little difference from the control proliferation rate, but from 6 to 22 months after irradiation (the end of the study) there was a period of sustained rapid proliferation with the cell turnover time reduced to approximately 1 week. The increase in proliferative activity observed at 22 months was found to be dose—dependent. Endothelial cells in the blood vessels of the submucosa also showed an increased turnover rate after irradiation and the timing of this reponse was found to be similar to that of the epithelium. The onset of compensatory proliferation in both cell types was found to coincide with marked histological and functional changes in the bladder. In this slowly proliferating tissue, the onset of rapid compensatory proliferation after irradiation is delayed and occurs at the time that functional impairment is observed. This supports the postulate that proliferation is unlikely to contribute much to the sparing effect of prolonged fractionated radiotherapy in slowly dividing tissues.