Antigonadotropic effects of the bovine ovarian gonadotropin-releasing hormone-binding inhibitor/histone H2A in rat luteal and granulosal cells

A gonadotropin-releasing hormone (GnRH)-binding inhibitor (GnRH-BI) was purified from bovine ovaries and identified as histone H2A. In the present studies, the biological effects of partially purified and purified ovarian GnRH-BI, as well as calf thymus histone H2A, were examined in rat ovarian cells. Since GnRH has direct antigonadotropic actions on these cells, the effects on luteinizing hormone-stimulated cAMP accumulation in luteal cells and follicle stimulating hormone-induced cAMP and progesterone production in granulosal cells were evaluated. Antigonadotropic activity in both luteal and granulosal cells coeluted directly with GnRH-BI activity during purification from bovine ovaries, and the antigonadotropic effects were dose dependent and reversible. In contrast to GnRH, GnRH-BI maximally inhibited gonadotropin responses and the effects of GnRH-BI were not blocked by a GnRH antagonist. The purified ovarian GnRH-BI and calf thymus histone H2A had identical antigonadotropic properties, and the half-maximal concentrations for inhibiting the gonadotropin responses of granulosal and luteal cells was 2 and 5 microM, respectively. In conclusion, the ovarian GnRH-binding inhibitor, identified as histone H2A, not only inhibits the high affinity binding of GnRH to rat ovarian membranes but also evokes GnRH-like antigonadotropic responses in rat ovarian cells that do not appear to be mediated by binding to GnRH receptors.     

Climatic impact,future biomass production,and local adaptation of four switchgrass cultivars

Previous studies have shown that switchgrass has a wide range of genetic variation and that productivity is linked to local adaptation to the location of origin for many cultivars. In this meta‐analysis, we compiled and analyzed 900 observations associated with 41 field trials for four switchgrass cultivars (two lowlands, Alamo and Kanlow, and two uplands, Cave‐In‐Rock and Shelter). This extensive dataset and machine learning were used to identify the most influential variables impacting switchgrass productivity, to search for evidence of local adaptation to each cultivar's location of origin, and to predict change in productivity under future climate for each cultivar. In general, variables associated with climate and management are more important predictors of productivity relative to soil variables. Three climatic variables, annual mean temperature, annual precipitation, and precipitation in the wettest month, are identified as key environmental variables for productivity of all cultivars. Productivity under future climate (2041–2060) is predicted to stay stable for all cultivars relative to the prediction under current climate (1986–2005) across all trial locations and over a 20‐year simulation period. However, the productivity of each cultivar varies from location to location and from year to year, although productivity varies more between locations than between years. Additionally, we observe shifts in the most productive cultivar at the local field scale depending on the combination of management practice and climates. The shape of the relationship between productivity and the annual mean temperature relative to the cultivar's location of origin is a bell‐shaped curve for Kanlow, Cave‐in‐Rock, and Shelter, indicative of local adaptation. Identifying influential environmental variables and their relationships to productivity with respect to cultivar's location of origin help predicting productivity on the local field scale, and will help with the biofuel production planning through the selection of suitable cultivars for different locations under climate changes.     

Proliferation and differentiation of rat theca-interstitial cells: comparison of effects induced by platelet-derived growth factor and insulin-like growth factor-I

This study was designed to evaluate mechanisms regulating proliferation of steroidogenically active and steroidogenically inactive theca-interstitial (T-I) cells, and, specifically, to evaluate the effects of platelet-derived growth factor (PDGF) and insulin-like growth factor-I (IGF-I). T-I cells obtained from immature Sprague-Dawley rats were cultured in chemically defined media. Proliferation was assayed by thymidine incorporation and cell counting. Steroidogenically active cells were identified by the presence of 3beta-hydroxysteroid dehydrogenase activity. Flow cytometry facilitated separation of dividing cells (in S and G2/M phases of the cell cycle) from nondividing cells (in G0 and G1 phases of the cell cycle). PDGF alone (0.1-1 nM) produced a dose-dependent increase in DNA synthesis by up to 136%. IGF-I alone (10 nM) increased DNA synthesis by 56%. In the presence of both IGF-I (10 nM) and PDGF (0.1-1 nM), DNA synthesis increased by 108-214%. PDGF (1 nM) increased the total number of T-I cells by 43%; this effect was due to an increase in the number of steroidogenically inactive cells (47%). In contrast, the stimulatory effect of IGF-I (10 nM) was predominantly due to an increase in the number of steroidogenically active cells (163%). Separation of dividing cells from nondividing cells was accomplished with the aid of flow cytometry. In the absence of growth factors, the proportion of steroidogenically active cells was 35% lower among proliferating than resting cells. PDGF (1 nM) decreased the proportion of steroidogenically active cells among both proliferating and resting cells (by 43% and 16%, respectively). In contrast, IGF-I (10 nM) increased the proportion of steroidogenically active cells among proliferating cells by 56%. These findings indicate that differentiated/steroidogenically active cells divide; furthermore, PDGF and IGF-I may selectively stimulate proliferation of individual subpopulations of T-I cells, thereby providing a mechanism for development of structural and steroidogenically active components of the T-I compartment.     

Variation in Drosophila melanogaster central metabolic genes appears driven by natural selection both within and between populations

In this report, we examine the hypothesis that the drivers of latitudinal selection observed in the eastern US Drosophila melanogaster populations are reiterated within seasons in a temperate orchard population in Pennsylvania, USA. Specifically, we ask whether alleles that are apparently favoured in northern populations are also favoured early in the spring, and decrease in frequency from the spring to autumn with the population expansion. We use SNP data collected for 46 metabolic genes and 128 SNPs representing the central metabolic pathway and examine for the aggregate SNP allele frequencies whether the association of allele change with latitude and that with increasing days of spring–autumn season are reversed. Testing by random permutation, we observe a highly significant negative correlation between these associations that is consistent with this expectation. This correlation is stronger when we confine our analysis to only those alleles that show significant latitudinal changes. This pattern is not caused by association with chromosomal inversions. When data are resampled using SNPs for amino acid change the relationship is not significant but is supported when SNPs associated with cis-expression are only considered. Our results suggest that climate factors driving latitudinal molecular variation in a metabolic pathway are related to those operating on a seasonal level within populations.     

Influence of prostaglandin F autoantibodies on the estrous cycle of the guinea pig

Adult female guinea pigs were actively immunized with prostaglandin F_2α conjugated to bovine serum albumin (BSA). Control animals, immunized against BSA continued to cycle normally, while the animals immunized against prostaglandin F_2α stopped cycling after one to three normal cycles. Laparotomy at 30 days after the last estrus revealed no recently formed corpora lutea. During the remaining 70 days of observation the antibody titer increased to 1:700, accompanied by increasing total serum estrogens (136 pg/ml at day 100) and a slow decline in circulating progesterone levels (0.6 ng/ml at day 100). The ovaries at day 100 contained degenerated corpora lutea and luteinized follicles. The suppression of the estrous cycle in the present experiments was interpreted as resulting from prolongation of luteal function as well as from inhibition of ovulation.     

On the Conformation of UDPG,a Sugar Nucleotide

Abstract

UDPG [uridine 5′-(∝-D-glucopyranosyl pyrophosphate)] has a folded conformation in solution in which the glucose and uracil rings lie, approximately, in the same plane with the 2′- & 3′- hydroxyl groups facing the 5- & 6- hydrogens of the uracil ring.