The degradative fate of ubiquitin-protein conjugates in nucleated and enucleated cells.

Covalent ligation of multiple copies of ubiquitin to proteins is known to target intracellular proteins for degradation by large molecular weight cytosolic proteinase(s). Ubiquitin protein conjugates are found in cytosolic cell compartments suggesting that ubiquitination may have multiple roles. We have detected ubiquitinated proteins in the lysosomal apparatus of normal fibroblasts and fibroblasts treated with lysosomal proteinase inhibitors. In contrast rabbit reticulocytes lack lysosomes. We present here direct evidence for ubiquitination of mitochondrial proteins during rabbit reticulocyte maturation. In addition ubiquitination appears to be associated with the terminal differentiation of human keratinocytes. These results suggest that: 1. ubiquitin-protein conjugates may be degraded lysosomally 2. organellar proteins may be degraded by the ubiquitin system 3. ubiquitination is involved in the programmed elimination of proteins and organelles from several cell types during differentiation.     

Fluoride inhibits agonist-induced formation of inositol phosphates in rat cortex

Sodium fluoride inhibited carbachol, 5-hydroxytryptamine and noradrenaline stimulated formation of inositol phosphates in rat cerebral cortex. For example, carbachol (1 mM) induced a 337% increase of inositol phosphates above basal in 30 min which was reduced to 69% in the presence of NaF (10 mM). The IC50 for NaF was approximately 1.5 mM and inhibition was mediated by a decrease in maxima of the carbachol dose response curve rather than a shift to the right. This inhibitory action was not mimicked by NaBr or NaI, or by agents which increase cAMP. Inhibition did not appear to result from a toxic action of NaF since it had no effect on the formation of inositol phosphates by high K+; moreover, in higher concentrations NaF stimulated phospholipase C activity. Since fluoride ions are known to activate G-proteins in the concentrations used in this study, these results may indicate the existence of a novel G-protein linked to receptor inhibition of phospholipase C.     

The Drosophila ets-2 gene: molecular structure, chromosomal localization, and developmental expression

The cellular homologs of the ets gene from the avian erythroblastosis retrovirus E26 have been studied in chickens, humans, mice, and cats. In this report a further evolutionary step is taken by isolating and characterizing a Drosophila ets-related genomic clone. Sequence analysis of this clone has shown it to contain the 3' end of the v-ets gene, called ets-2, corresponding to the last two exons of chicken ets. The predicted amino acid sequence was found to have over 90% homology when compared to that of v-ets. This is the highest level of conservation observed for any previously characterized Drosophila oncogene homolog. Expression of the ets-2 gene occurs throughout development, but is highest during the embryonic and pupal stages. By in situ hybridization, the ets-2 chromosomal position was determined to be 58A/B which corresponds to no known phenotypic mutant. As this is a highly conserved gene, the Drosophila model system should prove useful for the determination of the ets gene function.     

In vitro translation of B-cell stimulatory factor-1 in Xenopus laevis oocytes

B-cell stimulatory factor-1 (BSF-1) can be translated in vitro in Xenopus laevis oocytes. This activity is blocked by an antibody to BSF-1. The RNA species coding for BSF-1 activity sediments of approximately 8-9S and is separable from RNA coding for interleukin-2 activity which sediments at approximately 11.5S. Finally, the fact that BSF-1 can be translated in vitro confirms that functions attributed to BSF-1 do not depend on contamination with other biologically active molecules such as phorbol myristate acetate.     

Biology of Subanguina picridis,a Potential Biological Control Agent of Russian Knapweed

The knapweed nematode, Subanguina picridis, forms galls on the leaves, stems, and root collar of Russian knapweed, Acroptilon repens. After being revived from a dormant, cryptobiotic state, second-stage juveniles required at least 1 month in a free-living state before becoming infective. Galls were induced on relatively slow-growing host plants that retained their apical meristems at or near the soil surface for 2-5 weeks. Galls developed extensive areas of nutritive tissue. The nematode was introduced from the Soviet Union and released in Canada for the biological control of Russian knapweed.     

Transformation of Tobacco, Tomato, Potato, and Arabidopsis thaliana Using a Binary Ti Vector System

Using a binary tumor-inducing (Ti) plasmid vector system, several plant species were transformed with a kanamycin resistance marker (neomycin phosphotransferase gene). Four Nicotiana species, seven tomato cultivars, two potato cultivars, and Arabidopsis thaliana were transformed by the binary vector transformation method. In this method, various plant organ pieces were co-cultivated with Agrobacterium tumefaciens cells carrying the binary vector, pGA472, and a helper Ti plasmid. We have also demonstrated that a wild type Ti plasmid can be used as a helper to obtain a transformed plant.     

Analysis of a diffusion-limited hollow fiber reactor for the measurement of effective substrate diffusivities

Mathematical analyses of a diffusion-limited hollow fiber reactor for the measurement of effective substrate diffusivities are presented. An analytical solution to the mathematical model with a first order substrate consumption rate is used to show that the procedure of Webster and Shuler(1) is incorrect. A rigorous analysis that requires numerical solution is also outlined for any form of the substrate consumption rate. These analyses allow for more accurate estimations of effective substrate diffusivities since they should be used in conjunction with integral reactor behavior.