Evidence that corticosterone is not an obligatory intermediate in aldosterone biosynthesis in the rat adrenal

CGS 16949A is a potent inhibitor of aromatase in vitro with an IC50 of 0.03 microM for the inhibition of LH-stimulated estrogen biosynthesis in hamster ovaries. In vivo, CGS 16949A leads to sequelae of estrogen deprivation (e.g. regression of DMBA-induced mammary tumors) without causing adrenal hypertrophy in adult rats. To complement these in vitro and in vivo findings, the effect of CGS 16949A on adrenal steroid biosynthesis in rats was investigated in vitro and in vivo. The surprising finding in vitro was that CGS 16949A inhibited aldosterone biosynthesis (IC50 = 1 microM) at concentrations 100 times lower than those for inhibition of corticosterone biosynthesis (IC50 = 100 microM). Moreover, deoxycorticosterone (DOC) concentrations were elevated at all concentrations of CGS 16949A which inhibited aldosterone synthesis. The classical biosynthetic pathway for aldosterone is DOC----corticosterone----18-OH-corticosterone----aldosterone. Thus inhibition of aldosterone biosynthesis, reflected in DOC accumulation, without affecting corticosterone concentrations, indicates that corticosterone is not an obligatory intermediate in the conversion of DOC to aldosterone in the rat. In vivo, CGS 16949A showed a suppression of plasma aldosterone in ACTH-stimulated male rats at doses which did not significantly affect plasma corticosterone. In conclusion, aldosterone measured both in vitro and in vivo must be derived primarily from a biosynthetic pathway in which corticosterone is not obligatory intermediate.     

The physiology and ecological implications of efficient growth

The natural habitats of microbes are typically spatially structured with limited resources, so opportunities for unconstrained, balanced growth are rare. In these habitats, selection should favor microbes that are able to use resources most efficiently, that is, microbes that produce the most progeny per unit of resource consumed. On the basis of this assertion, we propose that selection for efficiency is a primary driver of the composition of microbial communities. In this article, we review how the quality and quantity of resources influence the efficiency of heterotrophic growth. A conceptual model proposing innate differences in growth efficiency between oligotrophic and copiotrophic microbes is also provided. We conclude that elucidation of the mechanisms underlying efficient growth will enhance our understanding of the selective pressures shaping microbes and will improve our capacity to manage microbial communities effectively.     

Naturally Occurring Genetic Variants in Human Chromogranin A (CHGA) Associated with Hypertension as well as Hypertensive Renal Disease

Chromogranin A (CHGA) plays a fundamental role in the biogenesis of catecholamine secretory granules. Changes in storage and release of CHGA in clinical and experimental hypertension prompted us to study whether genetic variation at the CHGA locus might contribute to alterations in autonomic function, and hence hypertension and its target organ consequences such as hypertensive renal disease (nephrosclerosis). Systematic polymorphism discovery across the human CHGA locus revealed both common and unusual variants in both the open reading frame and such regulatory regions as the proximal promoter and 30-UTR. In chromaffin cell-transfected CHGA 30-UTR and promoter/luciferase reporter plasmids, the functional consequences of the regulatory/non-coding allelic variants were documented. Variants in both the proximal promoter and the 30-UTR displayed statistical associations with hypertension. Genetic variation in the proximal CHGA promoter predicted glomerular filtration rate in healthy twins. However, for hypertensive renal damage, both end-stage renal disease and rate of progression of earlier disease were best predicted by variants in the 30-UTR. Finally, mechanistic studies were undertaken initiated by the clue that CHGA promoter variation predicted circulating endothelin-1. In cultured endothelial cells, CHGA triggered co-release of not only the vasoconstrictor and pro-fibrotic endothelin-1, but also the pro-coagulant von Willebrand Factor and the pro-angiogenic angiopoietin-2. These findings, coupled with stimulation of endothelin-1 release from glomerular capillary endothelial cells by CHGA, suggest a plausible mechanism whereby genetic variation at the CHGA locus eventuates in alterations in human renal function. These results document the consequences of genetic variation at the CHGA locus for cardiorenal disease and suggest mechanisms whereby such variation achieves functional effects.     

Interaction of Bacillus thuringiensis Vegetative Insecticidal Protein with Ribosomal S2 Protein Triggers Larvicidal Activity in Spodoptera frugiperda

Vegetative insecticidal protein (Vip3A) is synthesized as an extracellular insecticidal toxin by certain strains of Bacillus thuringiensis. Vip3A is active against several lepidopteran pests of crops. Polyphagous pest, Spodoptera frugiperda, and its cell line Sf21 are sensitive for lyses to Vip3A. Screening of cDNA library prepared from Sf21 cells through yeast two-hybrid system with Vip3A as bait identified ribosomal protein S2 as a toxicity-mediating interacting partner protein. The Vip3A-ribosomal-S2 protein interaction was validated by in vitro pulldown assays and by RNA interference-induced knockdown experiments. Knockdown of expression of S2 protein in Sf21 cells resulted in reduced toxicity of the Vip3A protein. These observations were further extended to adult fifth-instar larvae of Spodoptera litura. Knockdown of S2 expression by injecting corresponding double-stranded RNA resulted in reduced mortality of larvae to Vip3A toxin. Intracellular visualization of S2 protein and Vip3A through confocal microscopy revealed their interaction and localization in cytoplasm and surface of Sf21 cells.Insecticidal proteins produced by strains of Bacillus thuringiensis can broadly be classified into two major categories based on their site of accumulation. Category I consist of proteins that are deposited as crystals in sporangia and are referred to as insecticidal crystalline proteins (ICPs). The second category consists of recently described group of insecticidal proteins, called vegetative insecticidal proteins (8). These proteins are synthesized during the vegetative growth of Bacillus cells and are secreted into the culture medium. Irrespective of the site of accumulation of insecticidal proteins, their ingestion by susceptible insect larvae leads to disruption and lysis of epithelial tissue from the midgut, resulting in larval death (12). The mechanism of lysis of gut epithelial tissue by ICPs has been investigated in detail in several insects (16). Ingestion of ICPs triggers a sequence of biochemical cascade that involves its solubilization and subsequent activation by gut proteases. The activated toxin interacts with specific receptors located at the midgut epithelial tissue. In this sequence of events, the interaction with the receptor is the most significant event since subsequent to interaction, pore formation is initialized, and that leads to lysis of epithelial cells. The identification and characterization of receptors from various insect larvae has led to the identification of following molecules as receptor to ICPs, such as cadherinlike protein (21), glycosyl phosphatidylinositol (GPI)-anchored aminopeptidase N (APN) (1, 9, 11, 17, 19, 20), a GPI-anchored alkaline phosphatase (10, 14), and a 270-kDa glycoconjugate (see references 2, 7, 9, and 16 and references therein for an extensive list of receptors). In addition, certain glycopeptides have been identified as lysis-initiating receptor molecules. Although there is extensive information about the receptor-toxin interaction for ICPs, negligible work has been done toward the identification of receptors to vegetative insecticidal proteins. The ultrastructural changes induced at the midgut epithelial tissue, upon ingestion of ICPs or Vip3As, are common (12). Both ICPs and Vip3As interact at the epithelial layer of midgut, enlarging the affected cells due to osmotic imbalance and eventually causing lysis. In spite of inflicting nearly identical structural damage, the interacting receptor for the Vip3A is not identical (12). In fact, the receptor to Vip3As has not yet been characterized.Our group has been working on the identification, cloning, and evaluation of vegetative insecticidal proteins from strains of B. thuringiensis held in our collection. We have characterized the Vip3A (EMBL accession no. {"type":"entrez-nucleotide","attrs":{"text":"Y17158","term_id":"3135740","term_text":"Y17158"}}Y17158) class of protein and evaluated its toxicity profile (2, 8, 18). Vip3A is active against larvae of Spodoptera litura, among several other lepidopteran pests. In a parallel series of experiments, we identified APN as a receptor to the B. thuringiensis protein Cry1C in S. litura. The heterologously expressed APN did not interact with Vip3A, suggesting that Vip3A toxicity in this insect is not through interaction with APN (1). Our preliminary results on the toxicity of Vip3A revealed that purified insecticidal protein could lyse Sf21 cells, suggesting the presence of receptors in the insect cell line. In the present study, we identified the Vip3A interacting protein in Sf21 cells and the larvae of S. litura. The specificity of the interaction has been examined by a combination of ex vivo and in vitro assays. These assays identified ribosomal S2 protein as the interacting partner of Vip3A. The functional significance of S2-Vip3A protein interaction was examined by monitoring the reduction in Vip3A toxicity in Sf21 cells and larvae of S. litura by the RNA interference-induced knockdown of S2 protein. The results of these experiments are discussed in the context of colocalization of the S2-Vip3A protein interacting complex by confocal microscopy.     

Why should a grazer browse? Livestock impact on winter resource use by bharal Pseudois nayaur

Many mammalian herbivores show a temporal diet variation between graminoid-dominated and browse-dominated diets. We determined the causes of such a diet shift and its implications for conservation of a medium-sized ungulate—the bharal Pseudois nayaur. Past studies show that the bharal diet is dominated by graminoids (>80%) during summer, but the contribution of graminoids declines to about 50% in winter. We tested the predictions generated by two alternative hypotheses explaining the decline: low graminoid availability during winter causes bharal to include browse in their diet; bharal include browse, with relatively higher nutritional quality, in their diet to compensate for the poor quality of graminoids during winter. We measured winter graminoid availability in areas with no livestock grazing, areas with relatively moderate livestock grazing, and those with intense livestock grazing pressures. The chemical composition of plants contributing to the bharal diet was analysed. The bharal diet was quantified through signs of feeding on vegetation at feeding locations. Population structures of bharal populations were recorded using a total count method. Graminoid availability was highest in areas without livestock grazing, followed by areas with moderate and intense livestock grazing. The bharal diet was dominated by graminoids (73%) in areas with highest graminoid availability. Graminoid contribution to the bharal diet declined monotonically (50, 36%) with a decline in graminoid availability. Bharal young to female ratio was 3 times higher in areas with high graminoid availability than areas with low graminoid availability. The composition of the bharal winter diet was governed predominantly by the availability of graminoids in the rangelands. Our results suggest that bharal include more browse in their diet during winter due to competition from livestock for graminoids. Since livestock grazing reduces graminoid availability, creation of livestock-free areas is necessary for the conservation of grazing species such as the bharal and its predators including the endangered snow leopard in the Trans-Himalaya.     

Androgen receptor status predicts response to chemotherapy, not risk of breast cancer in Indian women

Voltage gated potassium channels have been extensively studied in relation to cancer. In this review, we will focus on the role of two potassium channels, Ether à-go-go (Eag), Human ether à-go-go related gene (HERG), in cancer and their potential therapeutic utility in the treatment of cancer. Eag and HERG are expressed in cancers of various organs and have been implicated in cell cycle progression and proliferation of cancer cells. Inhibition of these channels has been shown to reduce proliferation both in vitro and vivo studies identifying potassium channel modulators as putative inhibitors of tumour progression. Eag channels in view of their restricted expression in normal tissue may emerge as novel tumour biomarkers.     

Virgin females compete for mates in the male lekking species Ceratitis capitata

Abstract. Aggressive behaviour occurring in intrasexual competition is an important trait for animal fitness. Although female intrasexual aggression is reported in several insect species, little is known about female competition and aggressive interactions in polygynous male lekking species. The interactions of female Mediterranean fruit flies, Ceratitis capitata (a male lekking species), with other females and mating pairs under laboratory conditions are investigated. Mature, unmated (virgin) females are aggressive against each other and against mating pairs, whereas immature females are not. Female aggression against other females decreases dramatically after mating; however, mated females maintain aggression against mating pairs. In addition, higher intrasexual aggression rates are observed for mature, virgin females than for virgin males of the same age. The results show that female aggressiveness is virginity related, suggesting female competition for mates. These findings have important implications for understanding the physiological aspects of a complex social behaviour such as aggression and should stimulate further research on female agonistic behaviour in male lekking mating systems.     

Elucidation of <Emphasis Type="Italic">veA</Emphasis>-dependent genes associated with aflatoxin and sclerotial production in <Emphasis Type="Italic">Aspergillus flavus</Emphasis> by functional genomics

The aflatoxin-producing fungi, Aspergillus flavus and A. parasiticus, form structures called sclerotia that allow for survival under adverse conditions. Deletion of the veA gene in A. flavus and A. parasiticus blocks production of aflatoxin as well as sclerotial formation. We used microarray technology to identify genes differentially expressed in wild-type veA and veA mutant strains that could be involved in aflatoxin production and sclerotial development in A. flavus. The DNA microarray analysis revealed 684 genes whose expression changed significantly over time; 136 of these were differentially expressed between the two strains including 27 genes that demonstrated a significant difference in expression both between strains and over time. A group of 115 genes showed greater expression in the wild-type than in the veA mutant strain. We identified a subgroup of veA-dependent genes that exhibited time-dependent expression profiles similar to those of known aflatoxin biosynthetic genes or that were candidates for involvement in sclerotial production in the wild type.     

Oral vaccines: new needs, new possibilities

Vaccination is an important tool for handling healthcare programs both in developed and developing countries. The current global scenario calls for a more-efficacious, acceptable, cost-effective and reliable method of immunization for many fatal diseases. It is hoped that the adoption of oral vaccines will help to provide an effective vaccination strategy, especially in developing countries. Mucosal immunity generated by oral vaccines can serve as a strong first line of defense against most of the pathogens infecting through the mucosal lining. Advances in elucidating the mechanism of action of oral vaccines will facilitate the design of more effective, new generation vaccines. There are promising developments in the use of different agents to effectively deliver the vaccine candidate. It is hoped that ongoing research may be able to set another cardinal point, after polio vaccine, in eradicating infectious diseases.