The regulation of steroidogenesis is different in the two types of ovine luteal cells

Ovine luteal tissue contains two distinct steroidogenic cell types, small (8-20 microns) and large (greater than 20 microns), which differ based on morphological and biochemical criteria. Unstimulated small cells secrete low levels of progesterone, respond to LH or dibutyryl cAMP (dbcAMP) with enhanced secretion of progesterone, and contain most of the receptors for LH. The unstimulated large cells, conversely, secrete high levels of progesterone, have few, if any, receptors for LH, and do not respond to LH or dbcAMP with increased progesterone secretion. The lack of response to dbcAMP by large cells was investigated. Large cells incubated in the presence of cholesterol, ram serum, or 25-hydroxycholesterol did not demonstrate substrate limitation. Hormone-independent stimulation of adenylate cyclase by cholera toxin or forskolin resulted in increased adenylate cyclase activities (P less than 0.01), cAMP accumulation (P less than 0.05), and the binding of endogenous cAMP (P less than 0.05) by type I cAMP-dependent protein kinase in both small and large cells. These treatments were accompanied by enhanced secretion of progesterone (P less than 0.05) in small cells. In contrast, large cells did not respond with an increase in progesterone secretion under these conditions. These observations suggest that the high rate of secretion of progesterone in unstimulated large cells is not regulated by cAMP.     

Germline integration of moloney murine leukemia virus at the Mov13 locus leads to recessive lethal mutation and early embryonic death

Thirteen mouse substrains genetically transmitting the exogenous Moloney murine leukemia virus (M-MuLV) at a single locus (Mov locus) have been derived previously. Experiments were performed to investigate whether homozygosity at the Mov loci would be compatible with normal development. Animals heterozygous at an Mov locus were mated, and the genotype of the offspring was analyzed. From parents heterozygous at the loci Mov1 to Mov12, respectively, homozygous offspring were obtained with the expected Mendelian frequency. In contrast, no homozygous offspring or embryos older than day 15 of gestation were obtained from parents heterozygous at the Mov13 locus. When pregnant Mov13 females at day 13 and day 14 of gestation were analyzed, approximately 25% of the embryos were degenerated. Genotyping revealed that these degenerated embryos were invariably homozygous and the normal appearing embryos were either heterozygous or negative for M-MuLV. These results suggest that integration of M-MuLV at the Mov13 locus leads to insertion mutagenesis, resulting in embryonic arrest between day 12 and day 13 of gestation. It is possible that the Mov13 locus represents a gene or gene complex involved in the early embryonic development of the mouse.     

Influence of photoperiod and temperature on testicular recrudescence and body growth in the lizards, Lacerta sicula and Lacerta muralis

Annual testicular cycles in the lizards Lacerta sicula and L. muralis appear to be regulated by the interaction between seasonal changes in body temperature and an endogenous rhythmicity in thermal responsiveness. Photoperiodism does not appear to be an important factor; i.e. testicular activity does not appear to be regulated by daylength.
Following testicular regression in July, the lizards are refractory to sexual stimulation by high temperatures (i.e. normal preferred levels) for about five months. High temperatures accelerate gonadal regression and prevent recrudescence during late summer. Reduced temperatures stimulate testicular enlargement and spermatid formation during the autumn; this recrudescence can be blocked by treatment with testosterone. Very low temperatures suppress gonadal activity during mid-winter.
Maintenance of lizards at constant high temperatures (33°C) starting in July suppresses testicular recrudescence until December. Also, testicular collapse occurs in lizards transferred to high temperatures after recrudescence has started. The gonads are stimulated by exogenous gonadotropins at 33°C during the fall indicating that high temperatures reduce circulating levels of gonadotropins.
The refractoriness to high temperatures is "spontaneously" terminated during midwinter (December) under a wide range of photo-thermal conditions. Low temperatures may accelerate the termination of refractoriness. Thereafter, high temperatures stimulate, and are required for the final development of the testes and accessory sexual structures. Thus, the increase in body temperature following hibernation times the onset of breeding in the spring.
Temperature also has a marked influence on appetite and growth, independent of photo-period. Weight gains are greater at 33° than at 20°C. At 33° there is a tendency for abdominal fat bodies to enlarge but with little hepatic growth; whereas, the reverse occurs at 20°C.     

Fluorescein-labeled β-Glucosidase as a Bacterial Stain

Fluorescein isothiocyanate-labeled beta-glucosidase was used as a simple staining reagent with selected gram-positive and gram-negative organisms. Staining in situ appeared to be dependent on the presence of accessible glycosidic-type linkages in the bacterial cell wall. Extensive wall damage or lysis did not occur when stained cells were suspended in washing and mounting solutions. The apparent specificity of labeled enzyme for wall substance was tested by blocking reactions, staining of isolated cell walls, and failure to stain substances lacking appropriate glycosidic linkages. Severe cell wall lesions were produced after prolonged contact with labeled enzyme, and this phenomenon may also be related to staining specificity. Gram-negative organisms and spores were poorly stained unless protected glycopeptide substrate was previously exposed by treatment of cells with thioglycolic acid or dilute alkaline sodium hypochlorite solution. A potential for staining tissues and cell lines may also exist. Some possible applications of labeled enzymes are briefly discussed.     

(1–3)-β-Glucan synthesis ofNeurospora crassa

(1–3)--d-Glucan synthase activity ofNeurospora crassa was localized to the plasma membrane by autoradiography of colloidal gold-labeled plasma membranes. The active site of glucan synthase for substrate hydrolysis was determined to be cytoplasmic facing. However, glucan synthase activity present in intact protoplasts was partially sensitive to Novozym 234 and to glutaraldehyde treatments, suggestive that enzyme activity is transmembrane. Enzyme activity also directed the formation of microfibrils in vitro. Taken together, these and previous results support the following scheme for glucan synthesis: 1. The sequential addition of glucose residues from UDP-glucose to glucan chains occurs on the cytoplasmically facing portion of glucan synthase. 2. As each glucan chain is synthesized, it is extruded to the extracytoplasmic side of the plasma membrane. 3. As each chain is extruded, it forms interchain hydrogen bonds with adjacent chains, resulting in glucan microfibril assembly.