Fine structure of the intersegmental membrane glands of the sixth abdominal sternum of female Nomia melanderi (Hymenoptera,Apoidea)

The fine structure of the intersegmental glands of the sixth abdominal sternum in 1-week old females of Nomia melanderi is presented. The plasma membrane of the secretory cell is unfolded in many places and is covered by a basement membrane. The microvillous surface is invaginated to form a rather long sinuous cavity. The endoplasm is almost entirely filled by secretory granules. Many secretory granules are located close to the inner surface of the invaginated plasma membrane. The invagination contains a porous ductule, apparently of cuticulin origin, that is connected directly with the inner layer of the transport duct of the duct-forming cell. This type of arrangement allows the direct flow of the secretory substance to the outside in a continuous way. The cylindrical duct-forming cell, besides having typical cell organelles, contains a cuticular transport duct. This duct is composed of a thin cuticulin layer surrounded by a rather thick epicuticular one. The results suggest that the secretory cell has two secretory cycles. The first occurs while the gland is differentiating (at the pupal stage) and is involved in secretion of the cuticulin that forms the porous ductule. The second cycle, which starts by the beginning of nesting, is involved in the secretion of a substance that is carried to the outside via the transport duct of the duct-forming cell.     

The regulatory protein GAL80 is a determinant of the chromatin structure of the yeast GAL1-10 control region

Chromatin in the regions between the upstream activator sequence and the 5' ends of the yeast GAL1 and GAL10 genes has been analyzed by DNase I chromosomal footprinting and micrococcal nuclease digestion using the indirect end-labeling approach. Comparison of wild type chromatin digests to naked DNA digests shows that there are specific regions of these upstream sequences which are strongly protected in chromatin. Comparison to chromatin digests from cells disrupted for the positive regulatory gene, GAL4, or the negative regulatory gene, GAL80, and thus lacking GAL4 or GAL80 function, shows that these regions of protection in wild type chromatin are GAL80-dependent but not GAL4-dependent. The protected regions include DNA lying on (GAL10) or near (GAL1) the respective TATA boxes. These protections are present in both noninduced and induced cells. Both DNA strands are equally protected. Upstream of GAL1 there is a second protected region. This protection shows considerable expression and strand dependence. These observations provide the first evidence that the GAL80 function influences chromatin structure and suggest possible mechanisms by which GAL80 modulates the GAL1 and 10 promoters in induced cells. Micrococcal nuclease digests also suggest a role for GAL80 in a distinctive higher order organization of the intergenic region, perhaps involving multiprotein complexes.     

Production of ethanol by alginate-entrapped Saccharomyces cerevisiae strain "14-12"

Cells of S. cerevisiae strain "14-12" of different ages were immobilized in sodium alginate and used for conversion of glucose to ethanol. Immobilized cells of 48 hr old were the most potential. Employment of high counts of alginate-entrapped cells shortened the period required for production of the maximal alcohol yield. However, the percentage surviving cells decreased with increasing initial cell counts. Maximal accumulation of ethanol (4.18 g/100 ml) was obtained after 4 days of static fermentation with 1.8 X 10(8) immobilized yeast cells. The residual viable cell count was found to represent 3-fold the surviving percentage in a control experiment using an inoculum of the free yeast cells. Immobilized yeast cells could convert about 85% of the available sugars to ethanol over 28 days of the repeated-batch fermentation. The immobilized cells retained 50% of their viability for 16 days. After 48 days of repeated fermentation only 6% of the yeast cells were viable, and on the 52nd day no viable cells could be detected.     

Effect of acute and chronic hypernatremia on myoinositol and sorbitol concentration in rat brain and kidney

In animal models of hypernatremia, increases in brain electrolyte content account for the entire increase in osmolality in acute but not chronic hypernatremia, suggesting that there is generation of additional intracellular solutes ("idiogenic osmoles") in chronic hypernatremic states. In the present study, the concentration of the polyols myoinositol and sorbitol and water content were determined in the brain and kidneys of rats made acutely (2 hours) and chronically (72 hours) hypernatremic by intraperitoneal injection of NaCl and water restriction. Both the brain and the kidney responded to chronic hypernatremia with increased levels of myoinositol. Sorbitol levels increased in the kidney in response to both acute and chronic hypernatremia. Water content dropped in acute hypernatremia, but remained unchanged during chronic hyperosmolar challenge. We conclude that the polyols, myoinositol and sorbitol, may play a significant role in cellular osmoregulation in brain and kidney during chronic hypernatremia in the rat.     

Ethanol tolerance ofSaccharomyces cerevisiae and its relationship to lipid content and composition

Saccharomyces cerevisiae strain 14-12 is a highly ethanol-tolerant organism. It can grow in the presence of 13% ethanol but growth is completely prevented at 14% ethanol. A relationship was detected between yeast lipids and ethanol tolerance. A gradual decrease of lipid content was recorded as the concentration of supplemented ethanol increased. Moreover, free fatty acids were comparatively decreased in these lipid extracts. When separately added to media with 14% ethanol different lipids produced varied stimulatory effects on yeast growth. Maximum yield of yeast growth was obtained at 14% ethanol in the presence of lecithin, palmitic acid and cholesterol. Yeast lipids produced in the presence of these fractions are characterized by a relatively high percentage of free fatty acids. The change in the percentage of free fatty acids was shown to be the controlling factor in ethanol tolerance.     

In vivo development and pathogenicity of Ascosphaera proliperda (Ascosphaeraceae) to the alfalfa leafcutting bee, Megachile rotundata

First instar larvae of the leafcutting bee, Megachile rotundata, were fed on either artificial or natural provisions containing spores of Ascosphaera proliperda. Two isolates were used as a source of inocula: one originated from in vitro isolates obtained while culturing what was thought to be pure spores of A. aggregata, the second originated from in vitro cultures from Denmark. Histological and scanning electron microscopy studies revealed that the spores germinated in the gut lumen and the developing hyphae invaded all tissues, after which they penetrated through larval integument and began the sexual phase of the life cycle aerially. Virtually all fungus-exposed larvae developed symptoms of disease regardless of source of inoculum, type of provision, and spore dose (1.5 × 10³ to 3 × 10⁶) per insect. It was concluded that the fungus was pathogenic to the alfalfa leafcutting bee under laboratory conditions and future studies should be conducted to determine its etiology, cross infectivity, and natural distribution in other bee taxa.     

Studies on the rhizosphere mycoflora of broad bean and cotton. Effect of fungal filtrate on plant growth

The dominating rhizosphere fungi of broad bean (Vicia faba Linn.) variety “Giza 1”, and cotton (Gossypium barbadense Linn.) variety “Giza 47”, were grown in liquid medium. After 10 days, filtrates were obtained and sterilized by filtration through sintered-glass filter. Plants were grown in sterile sand which was supplemented with nutrient solution. Every plant was irrigated with fungal filtrate, unconsumed medium, and water. The filtrates of the rhizosphere fungi of both broad bean and cotton stimulated plant growth.