Activation of a phosphatidylcholine-specific phospholipase C by colony stimulating factor 1 receptor requires tyrosine phosphorylation and a guanine nucleotide-binding protein.

Receptor tyrosine kinases couple to multiple intracellular effector molecules that are crucial for normal cell growth and transformation. Stimulation of membrane phospholipid hydrolysis by receptor tyrosine kinases is one such pathway for generating intracellular second messengers that may be important for mitogenesis. Certain receptor tyrosine kinases tyrosine phosphorylate a phosphoinositide-specific phospholipase C that hydrolyses the membrane phospholipid phosphatidylinositol 4,5-bisphosphate. In contrast, the glycoprotein receptor for colony stimulating factor 1, a transmembrane tyrosine kinase, does not utilize this pathway, but rather stimulates the hydrolysis of phosphatidylcholine. Here we show that eluates of antiphosphotyrosine affinity purified lysates of colony-stimulating factor 1-stimulated cells contain elevated levels of phosphatidylcholine-specific phospholipase C activity. The affinity-purified activity is sensitive to tyrosine-specific T-cell phosphatase, and is detected in the membrane fraction of stimulated cells. Recovery of phospholipase C activity in the antiphosphotyrosine protein fraction is reduced by pertussis toxin pretreatment of cells. The phosphatidylcholine phospholipase C activity in isolated membranes of colony-stimulating factor 1-treated cells was also reduced by pertussis toxin treatment and stimulated by guanosine 5'-3-O-(thio)triphosphate. These results indicate that colony stimulating factor 1 receptor-mediated stimulation of phosphatidylcholine-specific phospholipase C requires tyrosine phosphorylation, and might be affected by a G-protein coupled pathway.     

Anaerobic degradation of sorbic acid by sulfate-reducing and fermenting bacteria: pentanone-2 and isopentanone-2 as byproducts

Strictly anaerobic bacteria were enriched and isolated from freshwater sediment sources in the presence and absence of sulfate with sorbic acid as sole source of carbon and energy. Strain WoSo1, a Gram-negative vibrioid sulfate-reducing bacterium which was assigned to the species Desulfoarculus (formerly Desulfovibrio) baarsii oxidized sorbic acid completely to CO₂ with concomitant stoichiometric reduction of sulfate to sulfide. This strain also oxidized a wide variety of fatty acids and other organic compounds. A Gram-negative rod-shaped fermenting bacterium, strain AmSo1, fermented sorbic acid stoichiometrically to about equal amounts of acetate and butyrate. At concentrations higher than 10 mM, sorbic acid fermentation led to the production of pentanone-2 and isopentanone-2 (3-methyl-2-butanone) as byproducts. Strain AmSo1 fermented also crotonate and 3-hydroxybutyrate to acetate and butyrate, and hexoses to acetate, ethanol, hydrogen, and formate. The guanine-plus-cytosine content of the DNA was 41.8±1.0 mol%. Sorbic acid at concentrations higher than 5 mM inhibited growth of this strain while strain WoSo1 tolerated sorbic acid up to 10 mM concentration.     

Linkage of the HMP pathway to ATP generation by the proline cycle

The reactions catalyzed by proline oxidase and pyrroline-5-carboxylate reductase form a catalytic cycle linking the hexose-monophosphate pentose (HMP) pathway to mitochondrial ATP generation. The cycling of proline and pyrroline-5-carboxylate couples glucose oxidation to ATP generation by a mechanism independent of the Embden-Meyerhof pathway and the tricarboxylic acid cycle.     

The ultrastructure of the small granular, proteinaceous epidermal cells of some British lumbricids (Annelida) and a reassessment of the identity of the so-called albumen cells

The ultrastructure of the small granular, proteinaceous cells of 11 species of lumbricid earthworm is described and no species differences were recorded. The cells are characterized by the presence of membrane-bound, electron dense granules (0.6–0.7 urn in diameter) arising from polarized Golgi systems in close topographical relationship to the granular endoplasmic reticulum. Variations in electron density of the granules appear to be associated with maturation of the granules. The granules show a finely reticular substructure at high magnification. A less than fully mature stage of this cell type is described.
The occurrence of the small granular cell type in the annelids is discussed, as is the possible function of its secretion.
The confusions in the lumbricid literature concerning this cell type are discussed, and the much referred to figure of the 'albumen' cell type in English texts is shown not to be equivalent to the small granular, proteinaceous type referred to in this and a previous histochemical study.     

ANOXIA AND BRIGHTNESS DISCRIMINATION

1. Brightness discrimination has been studied with individuals breathing oxygen concentrations corresponding to 7 altitudes between sea level and 17,000 feet. The brightnesses were 0.1, 0.01, and 0.001 millilambert involving only daylight (cone) vision. 2. At these light intensities, brightness discrimination begins to deteriorate at fairly low altitudes. The deterioration is obvious at 8,000 feet, and becomes marked at 15,000 feet, where at low brightness, the contrast must be increased 100 per cent over the sea level value before it can be recognized. 3. The impairment of brightness discrimination with increase in altitude is greater at higher altitudes than at lower. The impairment starts slowly and becomes increasingly rapid the higher the altitude. 4. Impairment of brightness discrimination varies inversely with the light intensity. It is most evident under the lowest light intensities studied, but shows in all of them. However, it decreases in such a way that the deterioration is negligible in full daylight and sunlight. 5. The thresholds of night (rod) vision and day (cone) vision are equally affected by anoxia. 6. The quantitative form of the relation between brightness discrimination ΔI/I and the prevailing brightness I remains the same at all oxygen concentrations. The curve merely shifts along the log I axis, and the extent of the shift indicates the visual deterioration. 7. The data are described in terms of retinal chemistry. Since anoxia causes only a shift in log I it is shown that the photochemical receptor system cannot be affected. Instead the conversion of photochemical change into visual function is impaired in such a way that the conversion factor varies as the fourth power of the arterial oxygen saturation.     

Tropical Bacillus Strains Inoculation Enhances Maize Root Surface Area,Dry Weight,Nutrient Uptake and Grain Yield

Journal of Plant Growth Regulation - The rising demand for agricultural commodities in developing countries has put increasing pressure on land resources for higher yields, with associated growth...