Patterns of nucleotide polymorphism and divergence in the odorant-binding protein genes OS-E and OS-F: analysis in the melanogaster species subgroup of Drosophila

The Olfactory Specific-E and -F genes (OS-E and OS-F) belong to the odorant-binding protein gene family, which includes the general odorant-binding proteins and the pheromone-binding proteins. In Drosophila melanogaster, these genes are arranged in tandem in a genomic region near the centromere of chromosome arm 3R. We examined the pattern of DNA sequence variation in an approximately 7-kb genomic region encompassing the two OS genes in four species of the melanogaster subgroup of Drosophila and in a population sample of D. melanogaster. We found that both the OS-E and the OS-F gene are present in all surveyed species. Nucleotide divergence estimates would support that the two genes are functional, although they diverge in their functional constraint. The pattern of nucleotide variation in D. melanogaster also differed between genes. Variation in the OS-E gene region exhibited an unusual and distinctive pattern: (i) a relatively high number of fixed amino acid replacements in the encoded protein and (ii) a peak of nucleotide polymorphism around the OS-E gene. These results are unlikely under the neutral model and suggest the action of natural selection in the evolution of the two odorant-binding protein genes.     

Prior exposure to a single stress session facilitates subsequent contextual fear conditioning in rats. Evidence for a role of corticosterone

Previous studies showed that exposure of rats to chronic restraint stress for 21 days enhances subsequent contextual fear conditioning. Since recent evidence suggest that this effect is not dependent on stress-induced neurodegenerative processes, but to elevated training-elicited glucocorticoid release in chronically stressed animals, we aimed to explore here whether a single exposure to restraint stress, which is not expected to induce neuronal damage, would also affect contextual fear conditioning. We also questioned whether post-training corticosterone levels might be associated with any potential effect of stress on fear conditioning. Adult male Wistar rats were exposed to acute restraint stress for 2 h and, two days later, trained in the contextual fear conditioning task, under training conditions involving either moderate (0.4 mA shock) or high (1 mA shock) stress levels. The results showed that acute stress enhanced conditioned freezing at both training conditions, although data from the 1 mA shock intensity experiment only approached significance. Stressed animals were shown to display higher post-training corticosterone levels. Furthermore, the facilitating effect of prior stress was not evident when animals were trained in the hippocampal-independent auditory-cued conditioning task. Therefore, these findings support the idea that stress experiences preceding exposure to new types of stressors facilitate the development of contextual fear conditioning. They also indicate that not only repeated, but also a single exposure to aversive stimulation is sufficient to facilitate context-dependent fear conditioning, and suggest that increased glucocorticoid release at training might be implicated in the mechanisms mediating the memory facilitating effects induced by prior stress experiences.     

The −1030/−862-linked TNF promoter single-nucleotide polymorphisms are associated with the inability to control HIV-1 viremia

Control of HIV-1 viremia and progression to AIDS has been associated with specific HLA genes. The tumor necrosis factor (TNF) and the non-classical major histocompatibility (MHC) class I chain-related A (MICA) genes are located in the genomic segment between the HLA class I and II genes and variants of both genes have been identified. We thus analyzed TNF promoter and MICA variants in a well-characterized group of HIV-1 infected individuals with different abilities to control HIV-1 viremia. In our cohort, the –1030/–862-linked TNF promoter single-nucleotide polymorphisms (SNPs), but not MICA variants, are significantly associated with lack of control of HIV-1 viremia (P=0.03). This association is independent of those HLA-B35 alleles associated with HIV-1 disease progression with which the –862 TNF SNP has previously been independently associated. Thus, non-randomly associated genes near the TNF locus are likely involved in control of HIV-1 viremia.     

Phase Transition of Thylakoid Membranes Modulates Photoinhibition in the Cyanobacterium Anabaena siamensis

A shift of the growth temperature from 40 degrees C to 18 degrees C promoted an increase in the degree of fatty acids unsaturation and a decrease, from 26 degrees C to 0 degrees C, of the phase transition temperature of thylakoid membranes in Anabaena siamensis. The pattern of photoinhibition of photosynthesis at distinct temperatures varied as a function of the phase transition temperature. In the absence of streptomycin, a pronounced photoinhibition at temperatures near the phase transition (26 degrees C) was observed in cells grown at 40 degrees C, while protection from photodamage was observed at chilling temperatures (15 degrees C to 5 degrees C). In this same range of temperature, such a protection was not verified if cells were grown at 18 degrees C. In both types of cells, however, the rate of photoinactivation in the presence of streptomycin was progressively decreased by lowering the temperature of photoinhibition. When recovery from photoinhibition was followed at the respective temperature in which cells were grown, the restoration profile of the photosynthetic O(2) evolution to initial levels was essentially the same in both types of cells. The protective effect of low temperatures against photoinhibition was attributed to a decreased solubility and diffusion of oxygen in the thylakoid membranes due to an increase of the membrane viscosity that would avoid the photogeneration of reactive oxygen species around PS II.     

Proteolytic gut activities in the rice water weevil,Lissorhoptrus brevirostris Suffrian (Coleoptera: Curculionidae)

Digestive endoprotease activities of the rice water weevil, Lissorhoptrus brevirostris Suffrian (Coleoptera: Curculionidae), were characterized based on the ability of gut extracts to hydrolyze specific synthetic substrates, optimal pH, and hydrolysis sensitivity to protease inhibitors. Larvae of this species were found to use a complex proteolytic system that includes cathepsin D-, cathepsin B-, trypsin-, and chymotrypsin-like activities. Trypsin-like activity was evenly distributed among the anterior, middle, and posterior portions of the gut, whereas cathepsin B- and cathepsin D-like activities were mainly located in the anterior and middle sections, and the chymotrypsin-like activity was highest in the middle and posterior sections. Gelatin-containing native-PAGE gels indicated the presence of several aspartyl, cysteine, and serine protease forms and confirmed the spatial organization of the proteolytic digestive process.     

Cyclin D2 and p27 are tissue-specific regulators of tumorigenesis in inhibin alpha knockout mice

Inhibins are heterodimeric (alpha:betaA and alpha:betaB) endocrine, paracrine, and autocrine factors of the TGFbeta superfamily that are produced predominantly by ovarian granulosa cells in females and testicular Sertoli cells in males. Control of granulosa and Sertoli cell proliferation is lost in the inhibin alpha (Inhalpha) knockout mouse model, leading to gonadotropin-dependent gonadal tumors of the granulosa/Sertoli cell lineage in both females and males. Castrate Inhalpha knockout mice develop sex steroidogenic tumors of the adrenal cortex. Physiological control of granulosa/Sertoli cell cycle progression depends on p27Kip1 and cyclin D2, which function in the G1-->S phase transition. To study the cell cycle-regulatory factors involved in ovarian, testicular, and adrenal tumor development in vivo, we have bred Inhalpha mutant mice to mice with targeted disruptions of the p27 and cyclin D2 genes. Our previous studies demonstrated that inhibins act cooperatively with p27 to negatively regulate granulosa cell proliferation, as double mutant mice lacking inhibins and p27 develop and succumb to ovarian tumors more rapidly than Inhalpha knockout mice. Here, we report that cyclin D2 antagonizes this inhibition and is key in promoting gonadal growth and tumor development, and tumor development is markedly suppressed in double-mutant mice. We found that double-knockout females lacking cyclin D2 and Inhalpha lived longer than mice lacking inhibins alone; the majority of these double-knockout mice lived longer than 17 wk, as opposed to inhibin alpha single-knockout females with 50% survival at between 12 and 13 wk of age. Moreover, 95% of inhibin alpha knockout males succumb to testicular tumor development by 12 wk of age, whereas double knockouts were protected from early signs of tumor development and had a 50% survival of 40 wk. Interestingly, the results of these studies reflect tissue-specific consequences of loss of these cell cycle regulators. In castrate mice, loss of p27 has little effect on adrenal cortical tumor progression in the absence of inhibins, whereas loss of cyclin D2 prolongs the lifespan of cyclin D2, Inhalpha double knockouts. After gonadectomy, 50% of cyclin D2, Inhalpha double-knockout males live to more than 46 wk of age, 10 wk longer than 50% of littermates lacking only inhibins. Similarly, 50% of female cyclin D2, inhibin alpha double knockouts live to 47 wk of age before succumbing to adrenal tumor development, in contrast to the 50% survival of Inhalpha single-knockout females at between 27 and 28 wk. Thus, identification of genetic modifiers of the Inhalpha knockout tumor phenotype has led us to a better appreciation of how specific components of the cell cycle machinery contribute to tumorigenesis in the ovary, testis, and adrenal gland.     

Production and purification of statins from Pleurotus ostreatus (Basidiomycetes) strains

Pleurotus ostreatus strains were cultured in liquid medium and on wheat straw. The yields of lovastatin were compared.     

Predictions of protein flexibility: first-order measures

The normal modes of a molecule are utilized, in conjunction with classical conformal vector field theory, to define a function that measures the capability of the molecule to deform at each of its residues. An efficient algorithm is presented to calculate the local chain deformability from the set of normal modes of vibration. This is done by considering each mode as an off-grid sample of a deformation vector field. Predictions of deformability are compared with experimental data in the form of dihedral angle differences between two conformations of ten kinases by using a modified correlation function. Deformability calculations correlate well with experimental results and validate the applicability of this method to protein flexibility predictions.     

Strategic compartmentalization of Toll-like receptor 4 in the mouse gut

Pattern recognition receptors (PRRs), which include the Toll-like receptors (TLRs), are involved in the innate immune response to infection. TLR4 is a model for the TLR family and is the main LPS receptor. We wanted to determine the expression of TLR4 and compare it with that of TLR2 and CD14 along the gastrointestinal mucosa of normal and colitic BALB/c mice. Colitis was induced with 2.5% dextran sodium sulfate (DSS). Mucosa from seven segments of the digestive tract (stomach, small intestine in three parts, and colon in three parts) was isolated by two different methods. Mucosal TLR4, CD14, TLR2, MyD88, and IL-1beta mRNA were semiquantified by Northern blotting. TLR4 protein was determined by Western blotting. TLR4/MD-2 complex and CD14 were evaluated by immunohistochemistry. PRR genes were constitutively expressed and were especially stronger in colon. TLR4 and CD14 mRNA were increased in the distal colon, but TLR2 mRNA was expressed more strongly in the proximal colon, and MyD88 had a uniform expression throughout the gut. Accordingly, TLR4 and CD14 protein levels were higher in the distal colon. TLR4/MD-2 and CD14 were localized at crypt bottom epithelial cells. TLR4/MD2, but not CD14, was found in mucosal mononuclear cells. Finally, DSS-induced inflammation was localized in the distal colon. All genes studied were up-regulated during DSS-induced inflammation, but the normal colon-stressed gut distribution was preserved. Our findings demonstrate that TLR4, CD14, and TLR2 are expressed in a compartmentalized manner in the mouse gut and provide novel information about the in vivo localization of PRRs.     

Proteomic analysis of human vessels: application to atherosclerotic plaques

Atherosclerosis is a chronic disease that affects medium and large arteries. This process originates from the interaction between cells of the arterial wall, lipoproteins and inflammatory cells, leading to the development of complex lesions or plaques that protrude into the arterial lumen. Plaque rupture and thrombosis result in acute clinical complications such as myocardial infarction and stroke. Owing to the heterogeneous cellular composition of the plaques, a proteomic analysis of the whole lesion is not appropriate. Therefore, we have studied the proteins secreted by human carotid atherosclerotic plaques, obtained by endarterectomy. Normal artery segments and different regions of the surgical pieces (noncomplicated plaque, complicated plaque with thrombus) were cultured in protein-free medium and the secreted proteins (supernatants) analyzed by two-dimensional gel electrophoresis. Normal artery segments secreted a moderate number of proteins (42 spots). However in the two-dimensional (2-D) gels (pH 3-10) of segments bearing a plaque, the number of spots increased markedly (154). The number of spots also increased (202) in the 2-D gels of artery segments with a ruptured plaque and thrombus. Thus, the more complicated the lesion, the higher the number of secreted proteins, suggesting the production of specific proteins relating to the complexity of the atherosclerotic lesion.