Interaction of cationic <Emphasis Type="Italic">meso</Emphasis>-porphyrins with liposomes,mitochondria and erythrocytes

Two series of cationic porphyrins meso-(3N-methylpyridinium)phenylporphyrin (3P1, 3P2c, 3P2t, 3P3 and 3P4) and meso-(4N-methylpyridinium)phenylporphyrin (4P1, 4P2c, 4P2t, 4P3 and 4P4) were studied to obtain a comprehensive understanding of factors that influence the binding of cationic porphyrins to liposomes and mitochondria, as well as their photodynamic efficiencies in erythrocytes. Binding and photodynamic efficiency were found to be inversely proportional to the number of positively charged groups and directly proportional to n-octanol/water partition coefficients (log P_OW), except for the cis molecules 3P2c and 4P2c. In the cis molecules, binding and photodynamic efficiency were much higher than expected, indicating that specific interactions not accounted by log P_OW enhance photodynamic efficiency. The effect of mitochondrial transmembrane electrochemical potentials on cationic porphyrin binding constants was estimated to be as large as 15%, and may be useful to selectively target this organelle when promoting photodynamic therapy to induce apoptosis.     

Otters and fish farms in the Sado estuary: ecological and socio-economic basis of a conflict

The degree of conflict between otter conservation and fish farming was assessed at Sado estuary (SW Portugal), using ecological (otter visiting rates to fish farms and consumption of commercial fish) and socio-economic (past and current instruments and policies addressing the conflict and a social impact assessment, including a discourse analysis of relevant stakeholders) parameters. The study concerned 14 fish farms producing Sparus aurata, Dicentrarchus labrax, Solea senegalensis and Solea solea. Results indicate high visiting rates in most fish farms (average: 76%), although in only 29%, species stocked were the most consumed prey. Other marine species and freshwater prey were the basis of otter diet in the remaining fish farms. The conflict is quite consensual among most fish farmers, and the results indicate that the perceived conflict by fish farmers has an ecological basis, although there are large gaps between effective and perceived predation. No specific instruments exist in Portugal to address the conflict, but some not specifically targeted can have an effect (e.g. species protection legislation and aquaculture licensing), although with limitations to effectively contribute to its mitigation (e.g. lack of enforcement and supervision). Formulating and assessing solutions is the following step, using a participatory approach to the development and evaluation of mitigation/compensation strategies, capable of providing an effective reconciliation of the conflict.

Inter-domain communication mechanisms in an ABC importer: a molecular dynamics study of the MalFGK2E complex

ATP-Binding Cassette transporters are ubiquitous membrane proteins that convert the energy from ATP-binding and hydrolysis into conformational changes of the transmembrane region to allow the translocation of substrates against their concentration gradient. Despite the large amount of structural and biochemical data available for this family, it is still not clear how the energy obtained from ATP hydrolysis in the ATPase domains is "transmitted" to the transmembrane domains. In this work, we focus our attention on the consequences of hydrolysis and inorganic phosphate exit in the maltose uptake system (MalFGK(2)E) from Escherichia coli. The prime goal is to identify and map the structural changes occurring during an ATP-hydrolytic cycle. For that, we use extensive molecular dynamics simulations to study three potential intermediate states (with 10 replicates each): an ATP-bound, an ADP plus inorganic phosphate-bound and an ADP-bound state. Our results show that the residues presenting major rearrangements are located in the A-loop, in the helical sub-domain, and in the "EAA motif" (especially in the "coupling helices" region). Additionally, in one of the simulations with ADP we were able to observe the opening of the NBD dimer accompanied by the dissociation of ADP from the ABC signature motif, but not from its corresponding P-loop motif. This work, together with several other MD studies, suggests a common communication mechanism both for importers and exporters, in which ATP-hydrolysis induces conformational changes in the helical sub-domain region, in turn transferred to the transmembrane domains via the "coupling helices".     

Skeletal mass in adolescent male athletes and nonathletes: relationships with high-impact sports

Dias Quiterio, AL, Canero, EA, Baptista, FM, and Sardinha, LB. Skeletal mass in adolescent male athletes and nonathletes: relationships with high-impact sports. J Strength Cond Res 25(12): 3439-3447, 2011-This study examined the relationships between the practice of different categories of sports (high-impact vs. nonimpact) and bone status in adolescent male athletes and investigated differences from an age-matched control group. A total of 54 adolescent male athletes and 26 adolescent nonathletes were evaluated. Bone mineral density, bone mineral content (BMC), and bone area at the whole-body, limbs, and lumbar spine were determined by dual-energy x-ray absorptiometry, along with total and regional fat-free mass and body fat. The high-impact group included 34 athletes: 9 gymnasts, 18 basketball players, and 7 handball players (age: 15.7 ± 1.6 years; weight: 72.0 ± 15.0 kg; height: 178.5 ± 12.5 cm). The nonimpact group consisted of 20 swimmers (age: 16.4 ± 2.5 years; weight: 66.9 ± 10.4 kg; height: 173.7 ± 10.9 cm). The nonathletic control group included 26 male adolescents (age: 15.9 ± 2.8 years; weight: 64.7 ± 16.3 kg; height: 168.6 ± 15.1 cm). No differences were observed between the nonimpact and the control group in all bone variables, before and after adjustments for maturation level, body weight, and height (p > 0.05). After adjustments for these variables, the high-impact group displayed greater bone mass in most of the measured sites when compared to the other 2 groups (p < 0.001). Subjects in the nonimpact group showed lower values of BMC, particularly in the lower limbs, than both the high-impact and the nonathletic control groups (p < 0.05) after adjustments for maturation, high, and fat-free mass. This study reinforces the positive associations between high-impact physical activities and skeletal health in adolescent boys.     

Reactive Oxygen Species and Cellular Interactions Between Mycosphaerella fijiensis and Banana

Globally, the banana plant (Musa spp) is the fourth most important crop after rice, wheat and corn (based on production in tons). It is cultivated in more than 100 tropical and subtropical countries, mainly by small producers and is a fundamental food source for millions of people. Black leaf streak disease (BLSD), caused by Mycosphaerella fijiensis Morelet (sexual phase) or Paracercospora fijiensis (Morelet) Deighton (asexual phase), is the main disease affecting the world??s banana culture. This disease has a wide geographical distribution accounting for losses exceeding 50% of global banana production. We conducted a comparative histocytological study on the kinetics of the infection process using three banana genotypes with phenotypes that differ in resistance to BLSD: Grand Naine (Susceptible), Pisang Madu (Partially Resistant) and Calcutta 4 (Resistant). Experiments were conducted under controlled conditions with the objective of characterizing the cellular interaction processes between M. fijiensis and Musa acuminata. Conidia germination occurred 24 hours after inoculation. Germination rates were high (97%) and there were no significant differences between the three genotypes (P?>?0.147). The Peroxidase enzyme and H₂O₂ were associated with a hypersensitivity-like reaction in the resistant genotype Calcutta 4, indicating a possible role of the enzyme or its product as defense mechanisms against M. fijiensis in banana plants.     

Axenic promastigote forms of Leishmania (Viannia) lainsoni as an alternative source for Leishmania antigen production

The present study demonstrates that axenic cultures of Leishmania (Viannia) lainsoni produce larger cell masses in NNN-LIT medium, as well as higher amounts of total proteins in cell extracts, than Leishmania (Leishmania) amazonensis. Antigenicity of L. (V.) lainsoni whole promastigotes is similar to that of L. (L.) amazonensis, as demonstrated by an indirect immunofluorescence diagnostic test using sera from human patients and dogs infected with visceral leishmaniasis. Infectivity of the L. (V.) lainsoni strain used in the present work was demonstrated by the detection by transmission-electron microscopy of tissue amastigotes in skin lesion samples from an experimentally infected hamster. Incubation of lesion fragments in NNN-LIT medium allowed us to obtain promastigote forms, which could be cultivated successfully in vitro. lsoenzyme analysis of such promastigotes confirmed the parasite strain as L. (V.) lainsoni, as compared to other Leishmania reference strains. Our data indicate that L. (V.) lainsoni is a useful alternative source for antigen production as well for use in assays that depend on large cell volumes of Leishmania spp. parasites.     

Detection of hepatitis C virus RNA by in situ hybridization in paraformaldehyde fixed biopsies

Fourteen hepatitis C virus (HCV) chronically infected patients were submitted to routine liver biopsy for histological evaluation. Liver samples were assayed to HCV-RNA by in situ hybridization, using digoxigenin labeled probe. HCV genotypes were found to be predominantly type 1 (71.4%), followed by genotype 3 (21.4%), and genotype 2 (7.2%). Alanine-aminotransferase levels were raised in 10 patients. The histopathological scores were minimal (21.4%), mild (57.2%), and moderate (21.4%). Viral RNA was detected in liver cells from nine patients (64.3%). ISH method provides localization and poor confirmation of HCV RNA in the liver tissue of HCV chronic patients.     

Influence of dissolved oxygen and shear conditions on clavulanic acid production by Streptomyces clavuligerus

Clavulanic acid (CA), a potent β-lactamase inhibitor, is produced by a filamentous bacterium. Here, the effect of DO and shear, expressed as impeller tip velocity, on CA production was examined. Cultivations were performed in a 4 L fermentor with speeds of 600, 800 and 1,000 rpm and a fixed air flow rate (0.5 vvm). Also, cultivation with automatic control of dissolved oxygen, at 50% air saturation, by varying stirrer speed and using a mixture of air and O₂ (10% v/v) in the inlet gas, and a cultivation with fixed stirrer speed of 800 rpm and air flow rate of 0.5 vvm, enriched with 10% v/v O₂, were performed. Significant variations in CA titer, CA production rate and O₂ uptake-rate were observed. It was also found that the DO level has no remarkable effect on CA production once a critical level is surpassed. The most significant improvement in CA production was related to high stirrer speeds.     

Bacillus subtilis operon encoding a membrane receptor for bacteriophage SPP1

The results reported here have identified yueB as the essential gene involved in irreversible binding of bacteriophage SPP1 to Bacillus subtilis. First, a deletion in an SPP1-resistant (pha-2) strain, covering most of the yueB gene, could be complemented by a xylose-inducible copy of yueB inserted at amyE. Second, disruption of yueB by insertion of a pMutin4 derivative resulted in a phage resistance phenotype regardless of the presence or absence of IPTG (isopropyl-beta-D-thiogalactopyranoside). YueB homologues are widely distributed in gram-positive bacteria. The protein Pip, which also serves as a phage receptor in Lactococcus lactis, belongs to the same family. yueB encodes a membrane protein of approximately 120 kDa, detected in immunoblots together with smaller forms that may be processed products arising from cleavage of its long extracellular domain. Insertional inactivation of yueB and the surrounding genes indicated that yueB is part of an operon which includes at least the upstream genes yukE, yukD, yukC, and yukBA. Disruption of each of the genes in the operon allowed efficient irreversible adsorption, provided that yueB expression was retained. Under these conditions, however, smaller plaques were produced, a phenotype which was particularly noticeable in yukE mutant strains. Interestingly, such reduction in plaque size was not correlated with a decreased adsorption rate. Overall, these results provide the first demonstration of a membrane-bound protein acting as a phage receptor in B. subtilis and suggest an additional involvement of the yukE operon in a step subsequent to irreversible adsorption.