The effects of nonpenetrating cryoprotectants added to TEST-yolk-glycerol extender on the post-thaw motility of ram spermatozoa

The effects of adding five different concentrations of 17 polymeric compounds to TEST-yolk-glycerol extender on ram spermatozoa survival was studied. These were Aquacide (I, II, and III); dextran (0.8-1.6, 1.9, 15-20, 70, and 200-300 kDa); three types of Dri-Sweet; hydroxyethyl starch; methylcellulose, polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, and Supercol 912. All the compounds tested except the Dri-Sweet compounds and hydroxyethyl starch significantly (P less than 0.05) decreased percentages of motile cells in unfrozen samples. The use of dextran (0.8-1.6 kDa; hydrolyzed dextran separated by ethanol) and Aquacide II significantly (P less than 0.05) increased post-thaw motility of spermatozoa frozen in pellets. Dextran (15-20 kDa), dextran (0.8-1.6 kDa), Aquacide II, and hydroxyethyl starch significantly (P less than 0.05) increased the percentages of post-thaw motility of ram spermatozoa frozen in the presence of glycerol and egg yolk.     

Androgen metabolism in the human epididymis. Effect of in vivo estrogen administration

Androgen metabolism in human epididymis was studied by incubating tissue fragments with isotopically labeled testosterone (T) and androstenedione (A) under batch and superfusion conditions. Epididymides were obtained from 16 patients with prostatic cancer, 5 of them treated with diethylstilbestrol (2.5 mg/d) for several months prior to castration. Results from batch incubations with [3H]T (100 nM) for 2 h at 25 degrees C indicated a markedly lower 5 alpha-reductase activity in tissues from estrogen-treated patients, as evaluated by measuring the amounts of radioactive 5 alpha-dihydrotestosterone, 5 alpha-androstanediols and 5 alpha-androstanedione present in tissue and medium at the end of the incubation period. Superfusion experiments confirmed this estrogen effect and also showed a shift of the interconversion between A and T towards the reductive direction and a diminished tissue retention of DHT after estrogen treatment. These effects may contribute to the marked regression of the epididymal epithelium that was noted in the estrogen-treated patients, which is thought to be mainly the result of the inhibition of androgen biosynthesis caused by chemical hypophysectomy.     

Differentiation among populations of Sedum wrightii (Crassulaceae) in response to limited water availability: water relations,CO2 assimilation,growth and survivorship

Summary Sedum wrightii is one of only a few species in the Crassulaceae for which there is evidence for a high degree of variability in the ratio of daytime to nighttime CO₂ assimilation. There are both environmental and genetic components to this variability. S. wrightii grows over a wide altitudinal gradient. The purpose of this study was to compare low, intermediate, and high altitude populations with respect to the degree of CAM expression and the capability to tolerate limited water availability. We utilized clonallyreplicated genotypes of plants from each population in common environment greenhouse experiments. Genetic differences among the populations were found in long-term water use efficiency, in 24 hour CO₂ exchange patterns, in biomass ¹³C values, in carbon allocation, and in water status and ultimately survival during prolonged drought. The differences among the populations appear to be closely related to differences in the native habitats. The low altitude, desert plants had the greatest ability to grow and survive under conditions of limited water availability and appear to have the greatest shift to nighttime CO₂ uptake during periods without water, while the high altitude plants had the poorest performance under these conditions and appear to shut down net carbon uptake when severely water limited.     

Role of uronic acids present in phytopathogenic fungi as inducers of polygalacturonases during autolysis

The presence of uronic acids in the culture fluid and mycelium of the fungi: Alternaria alternata, Botrytis cinerea, Drechslera halodes, Fusarium culmorum, Fusarium oxysporum, Monilinia fructigena, Mucor mucedo, Rhizopus stolonifer and Trichoderma hamatum was detected and quantified. In these fungi the concentration of uronic acids increased during the growth phase and the maximal concentrations were found at the end of the growth phase or onset of autolysis both in the mycelium as well as in the culture fluid. The uronic acids were metabolized during the first days of autolysis decreasing to constant levels until the end of the autolytic period studied.The variations in the activity of polygalacturonase and polymethylgalacturonase present in the culture fluid were determined at the onset and during autolysis in these fungi. These enzymic activities were found in the culture fluid of these fungi, with exception of M. rouxii, and they showed an increasing activity in the first days of autolysis and later a slight increase or decrease was observed. The presence of uronic acids in these phytopathogenic or saprophytic fungi and the low levels detected during autolysis could be related to the induction of pectic enzymes and the pathogenicity of these fungi.     

Interferon selectively inhibits the expression of mitochondrial genes: a novel pathway for interferon-mediated responses.

As an approach to identifying genes involved in physiological actions of interferons we used differential probes to screen a cDNA library from mouse L-929 cells treated with interferon alpha/beta. We identified two negatively regulated mRNA species which have been examined by analysis of the corresponding mRNAs and by DNA sequencing. Comparison with the GenBank database showed that these cDNA clones corresponded to mitochondrially encoded genes for cytochrome b and subunit I of cytochrome c oxidase. A further cDNA encompassing three mitochondrial genes was used as a probe to show that a third mRNA, NADH dehydrogenase subunit 5, was also down-regulated by interferon while a fourth, NADH dehydrogenase subunit 6, was unaffected. Expression of cytochrome b was also inhibited in mouse NIH 3T3 cells treated with interferon alpha/beta and in human Daudi lymphoblastoid cells treated with interferon alpha. The ability of interferon to reduce mitochondrial mRNA levels could be blocked by cycloheximide suggesting that these effects are mediated by an interferon-responsive nuclear gene which encodes a product capable of regulating mitochondrial gene expression. Analysis of proteins synthesized in the presence of emetine, a specific inhibitor of cytoplasmic translation, showed that the synthesis of several mitochondrial translation products, including cytochrome b, was reduced after treatment with interferon. Our results reveal a novel effect of interferon on cellular physiology which could have important consequences for understanding the effects of interferons as well as suggesting new mechanisms for the regulation of mitochondrial biogenesis and function.     

Nystatin affects zinc uptake in human fibroblasts

The mechanism(s) by which zinc is transported into cells has not been identified. Since zinc uptake is inhibited by reducing the temperature, zinc uptake may depend on the movement of plasma membrane micoenvironments, such as endocytosis or potocytosis. We investigated the potential role of potocytosis in cellular zinc uptake by incubating normal and acrodermatitis enteropathica fibroblasts with nystatin, a sterol-binding drug previously shown to inhibit potocytosis. Zinc uptake was determined during initial rates of uptake (10 min) following incubation of the fibroblasts in 50 μg nystatin/mL or 0.1% dimethyl-sulfoxide for 10 min at 37°C. The cells were then incubated with 1 to 30 μM ⁶⁵zinc. Michaelis-Menten kinetics were observed for zinc uptake. Nystatin inhibited zinc uptake in both the normal and AE fibroblasts. Reduced cellular uptake of zinc was associated with its internalization, not its external binding. In normal fibroblasts, nystatin significantly reduced theK _m 56% and theV _max 69%. In the AE fibroblasts, nystatin treatment significantly reduced theV _max 59%, but did not significantly affect theK _m. The AE mutation alone affected theV _max for cellular zinc uptake. The control AE fibroblasts exhibited a 40% reduction inV _max compared to control normal fibroblasts. We conclude that nystatin exerts its effect on zinc uptake by reducing the velocity at which zinc traverses the cell membrane, possibly through potocytosis. Furthermore, the AE mutation also effects zinc transport by reducing zinc transport.     

Sequences required for enhancer blocking activity of scs are located within two nuclease-hypersensitive regions.

The Drosophila 87A7 heat shock locus is bordered, on the proximal and distal sides, by two special chromatin structures, scs and scs'. Each structure is characterized by two sets of nuclease-hypersensitive sites, located within moderately G/C-rich DNA, flanking an A/T-rich nuclease-resistant region. scs and scs' have been shown to insulate a white reporter gene from position effects and to prevent enhancer-promoter interactions. These and other properties suggest scs and scs' might function as chromatin domain boundaries. To identify the DNA sequences which are essential for the insulating activity of scs we used an enhancer blocking assay based on the white gene. Sequences capable of suppressing activation of white by its upstream enhancer elements reside within a 900 bp DNA fragment corresponding to the scs chromatin structure. Within this region, DNA fragments associated with the two nuclease-hypersensitive regions are essential for full enhancer blocking activity, while the central A/T-rich region is dispensable. Deletions which remove part of the hypersensitive regions result in intermediate levels of white activity. Insulating activity can, however, be reconstituted by multimerizing DNA fragments from either hypersensitive region. Our results suggest that the scs boundary is assembled from a discrete number of functionally redundant DNA sequences located within both hypersensitive regions and that boundaries act by decreasing the frequency of enhancer-promoter interactions. We also show that certain types of position effects, like those involved in dosage compensation, are not efficiently blocked by scs.     

Morphological variability of geographically distinct populations of the estuarine copepod Acartia Tonsa

Variations in the number of spines on the left and right posterior dorsal and posterior margins of the prosome as well as the length of the prosome of Acartia tonsa from three estuaries, the upper western side of the Chesapeake Bay, Montauk Bay near the eastern end of Long Island Sound and the coast of Peru were determined. The length of the prosome and number of spines in each of the four locations were used as an indication of morphological similarity between the populations.