Determinants of human immunodeficiency virus (HIV) prevalence in homosexual and bisexual men screened for admission to a cohort study of HIV negatives in Belo Horizonte,Brazil: Project Horizonte

Project Horizonte, an open cohort of homosexual and bisexual human immunodeficiency virus (HIV-1) negative men, is a component of the AIDS Vaccine Program, in Belo Horizonte, Minas Gerais, Brazil. The objective of this study was to compare volunteers testing HIV positive at cohort entry with a sample of those who tested HIV negative in order to identify risk factors for prevalent HIV infection, in a population being screened for enrollment at Project Horizonte. A nested case-control study was conducted. HIV positive volunteers at entry (cases) were matched by age and admission date to three HIV negative controls each. Selected variables used for the current analysis included demographic factors, sexual behavior and other risk factors for HIV infection. During the study period (1994-2001), among the 621 volunteers screened, 61 tested positive for HIV. Cases were matched to 183 HIV negative control subjects. After adjustments, the main risk factors associated with HIV infection were unprotected sex with an occasional partners, OR = 3.7 (CI 95% 1.3-10.6), receptive anal intercourse with an occasional partner, OR = 2.8 (95% CI 0.9-8.9) and belonging to the negro racial group, OR = 3.4 (CI 95% 1.1-11.9). These variables were associated with an increase in the risk of HIV infection among men who have sex with men at the screening for admission to an open HIV negative cohort.     

Biological and Structural Characterization of a New PLA<Subscript>2</Subscript> from the Crotalus durissus collilineatus Venom

In the present article we report on the biological characterization and amino acid sequence of a new basic Phospholipases A₂ (PLA₂) isolated from the Crotalus durissus collilineatus venom (Cdcolli F6), which showed the presence of 122 amino acid residues with a pI value of 8.3, molecular mass of 14 kDa and revealed an amino acid sequence identity of 80 with crotalic PLA₂s such as Mojave B, Cdt F15, and CROATOX. This homology, however, dropped to 50 if compared to other sources of PLA₂s such as from the Bothrops snake venom. Also, this PLA₂ induced myonecrosis, although this effect was lower than that of BthTx-I or whole crotoxin and it was able to induce a strong blockage effect on the chick biventer neuromuscular preparation, independently of the presence of the acid subunid (crotapotin). The neurotoxic effect was strongly reduced by pre-incubation with heparin or with anhydrous acetic acid and q-BPB showed a similar reduction. The q-BPB did not reduce significantly the myotoxic activity induced by the PLA₂, but the anhydrous acetic acid treatment and the pre-incu-bation of PLA₂ with heparin reduced significantly its effects. This protein showed a strong antimicrobial activity against Xanthomonas axonopodis passiflorae (Gram-negative), which was drastically reduced by incubation of this PLA₂ with q-BPB, but this effect was marginally reduced after treatment with anhydrous acetic acid. Our findings here allow to speculate that basic amino acid residues on the C-terminal and molecular regions near catalytic site regions such as Calcium binding loop or b-wing region may be involved in the binding of this PLA₂ to the molecular receptor to induce the neurotoxic effect. The bactericidal effect, however, was completely dependent on the enzymatic activity of this protein.     

Prevalence and genetic characterisation of HTLV-1 and 2 dual infections in patients with pulmonary tuberculosis in Central-West Brazil

Human T-cell lymphotropic virus (HTLV) may impact the clinical course of tuberculosis (TB). Both infections are highly endemic in Brazil. The aim of this study was to assess the prevalence of HTLV-1/2 in TB patients in Central-West Brazil and to perform a genetic characterisation of the respective isolates. Of the 402 patients, six (1.49%) were positive for anti-HTLV and five (1.24%; 95% confidence interval: 0.46-3.05) were infected with HTLV-1/2. Genetic characterisation demonstrated that the four HTLV-1 isolates belonged to the Transcontinental subgroup A of the Cosmopolitan subtype a and that the HTLV-2 isolate belonged to subtype a (HTLV-2a/c). The prevalence of HTLV infection observed in this study is higher than that observed in local blood donors and the HTLV-1 and 2 subtypes identified are consistent with those circulating in Brazil.     

Reduced expression of SIRT1 is associated with diminished glucose-induced insulin secretion in islets from calorie-restricted rats

Alterations in food intake such as caloric restriction modulate the expression of SIRT1 and SIRT4 proteins that are involved in pancreatic β-cell function. Here, we search for a possible relationship between insulin secretion and the expression of SIRT1, SIRT4, PKC and PKA in islets from adult rats submitted to CR for 21 days. Rats were fed with an isocaloric diet (CTL) or received 60% (CR) of the food ingested by CTL. The dose-response curve of insulin secretion to glucose was shifted to the right in the CR compared with CTL islets (EC₅₀ of 15.1±0.17 and 10.5±0.11 mmol/L glucose). Insulin release by the depolarizing agents arginine and KCl was reduced in CR compared with CTL islets. Total islet insulin content and glucose oxidation were also reduced in CR islets. Leucine-stimulated secretion was similar in both groups, slightly reduced in CR islets stimulated by leucine plus glutamine but higher in CR islets stimulated by ketoisocaproate (KIC). Insulin secretion was also higher in CR islets stimulated by carbachol, compared with CTL islets. No differences in the rise of cytosolic Ca²⁺ concentrations stimulated by either glucose or KCl were observed between groups of islets. Finally, SIRT1, but not SIRT4, protein expression was lower in CR compared with CTL islets, whereas no differences in the expression of PKC and PKA proteins were observed. In conclusion, the lower insulin secretion in islets from CR rats was, at least in part, due to an imbalance between the expression of SIRT1 and SIRT4.     

Reduced insulin secretion in response to nutrients in islets from malnourished young rats is associated with a diminished calcium uptake

Changes in (45)Ca uptake and insulin secretion in response to glucose, leucine, and arginine were measured in isolated islets derived from 4-week-old rats born of mothers maintained with normal protein (NP, 17%) or low protein (LP, 6%) diet during pregnancy and lactation. Glucose provoked a dose-dependent stimulation of insulin secretion in both groups of islets, with basal (2.8 mmol/L glucose) and maximal release (27.7 mmol/L glucose) significantly reduced in LP compared with NP islets. In the LP group the concentration-response curve to glucose was shifted to the right compared with the NP group, with the half-maximal response occurring at 16.9 and 13.3 mmol/L glucose, respectively. In LP islets, glucose-induced first and second phases of insulin secretions were drastically reduced. In addition, insulin response to individual amino acids, or in association with glucose, was also significantly reduced in the LP group compared with NP islets. Finally, in LP islets the (45)Ca uptake after 5 minutes or 90 minutes of incubation (which reflect mainly the entry and retention, respectively, of Ca(2+)), was lower than in NP islets. These data indicate that in malnourished rats both initial and sustained phases of insulin secretion in response to glucose were reduced. This poor secretory response to nutrients seems to be the consequence of an altered Ca(2+) handling by malnourished islet cells.     

Physical mapping of rDNA genes corroborates allopolyploid origin in apomictic Brachiaria brizantha

Brachiaria (Trin.) Griseb belongs to the family Poaceae, and within the genus, apomixis or sexuality is present in different accessions of the same species. The majority of Brachiaria species are polyploid and apomictic, making strategies for crop improvement by breeding very intricate. In spite of the high frequency of apomictic polyploids, the relationship of polyploidy and hybridization with apomixis in Brachiaria is still unclear. Further analysis requires detailed knowledge regarding the genomic composition of the polyploids. The present work introduces the use of fluorescent in situ hybridization (FISH) into cytogenetic analysis of Brachiaria. Physical mapping of heterologous rDNA sequences, associated with conventional karyotyping of the B. brizantha diploid sexual (BRA 002747) and the tetraploid apomictic (BRA000591) accessions, provided evidence of the latter being of allopolyploid origin. Based on our results and on previous knowledge on apomixis in B. brizantha, we suggest that the origin of apomixis was probably a consequence of hybridization.     

Effect of maternal diet rich in omega‐6 and omega‐9 fatty acids on the liver of LDL receptor‐deficient mouse offspring

BACKGROUND: Omega‐6 fatty acids are important to fetal development. However, during gestation/lactation, these fatty acids may contribute toward the development of fat tissue. Omega‐9 fatty acids are associated with a reduction in serum lipids and protection from liver disease. OBJECTIVES: The present study investigated the effect of the maternal intake of omega‐6 and omega‐9 in hypercholesterolemic mothers on the liver of the offspring. METHODS: LDL receptor–deficient mice were fed a diet rich in either omega‐6 (E6D) or omega‐9 (E9D) for 45 days prior to mating and until the birth of the offspring, evaluating the effect on the offspring liver in comparison to a standard diet (STD). RESULTS: Mothers fed with the E6D experienced an increase in total cholesterol (TC) and the offspring exhibited an increase in TC, hepatic triglycerides (TG), and CC‐chemokine ligand (CCL)2/monocyte chemoattractant protein (MCP)‐1 as well as a reduction in HDL. Histological analysis on this group revealed steatosis, leukocyte infiltrate, and increased CCL2/MCP‐1 expression. The ultrastructural analysis revealed hepatocytes with lipid droplets and myofibroblasts. The offspring of mothers fed the standard diet exhibited low serum TC, but microvesicular steatosis was observed. The offspring of mothers fed the E9D exhibited lower serum and hepatic TG as well as higher LDL in comparison to the other diets. The histological analyses revealed lower steatosis and leukocyte infiltrate. CONCLUSIONS: The findings suggest that hypercholesterolemic mothers with a diet rich in omega‐6 fatty acids predispose their offspring to steatohepatitis, whereas a diet rich in omega‐9 has a protective effect. Birth Defects Res (Part B) 89:164–170, 2010. © 2010 Wiley‐Liss, Inc.     

Innate immune recognition of microbes through Nod1 and Nod2: implications for disease

Nod1 and Nod2 are cytosolic proteins involved in intracellular recognition of microbes and their products. Recently, it was shown that these proteins recognize different moieties of bacterial peptidoglycan (PGN) mediating non-specific pathogen resistance and possibly generating signals for the adaptive immune response. Moreover, mutations in the gene encoding Nod2 are associated with increased susceptibility to chronic inflammatory disorders.     

Probing the volume changes during voltage gating of Porin 31BM channel with nonelectrolyte polymers

To probe the volume changes of the voltage-dependent anion-selective channel (VDAC), the nonelectrolyte exclusion technique was taken because it is one of the few existing methods that may define quite accurately the rough geometry of lumen of ion channels (in membranes) for which there is no structural data.Here, we corroborate the data from our previous study [FEBS Lett. 416 (1997) 187] that the gross structural features of VDAC in its highest conductance state are asymmetric with respect to the plane of the membrane, and state that this asymmetry is not dependent on sign of voltage applied. Hence, the plasticity of VDAC does not play a role in the determination of lumen geometry at this state and the asymmetry is an internal property of the channel.We also show that the apparent diameter of the cis segment of the pore decreases slightly from 2 to 1.8 nm when the channel's conductance decreases from its high to low state. However, the trans funnel segment undergoes a more marked change in polymer accessible volume. Specifically, its larger diameter decreases from approximately 4 to 2.4 nm. Supposing the channel's total length is 4.6 nm, the apparent change in channel volume during this transition is estimated to be about 10 nm(3), i.e. about 40% of the channel's volume in the high conductance state.