Atrophic cardiac remodeling induced by taurine deficiency in wistar rats

Introduction

Micronutrient deficiency is observed in heart failure patients. Taurine, for example, represents 50% of total free amino acids in the heart, and in vivo studies have linked taurine deficiency with cardiomyopathy.

Methods

Thirty-four male Wistar rats (body weight = 100 g) were weighed and randomly assigned to one of two groups: Control (C) or taurine-deficient (T (-)). Beta-alanine at a concentration of 3% was added to the animals’ water to induce taurine deficiency in the T (-) group. On day 30, the rats were individually submitted to echocardiography; morphometrical and histopathological evaluation and metalloproteinase activity, oxidative stress and inflammation evaluation were performed. Tissue samples were collected to determine the taurine concentration in the heart.

Results

Taurine deficiency led to decreases in: ventricular wall thickness, left ventricle dry weight, myocyte sectional area, left ventricle posterior wall thickness and ventricular geometry. With regard to heart function, the velocity of the A wave, the ratio between the E and A wave, the ejection fraction, fractional shortening and cardiac output values were decreased in T (-) rats, suggesting abnormal diastolic and systolic function. Increased fibrosis, inflammation and increased activation of metalloproteinases were not observed. Oxidative stress was increased in deficient animals.

Conclusions

These data suggest that taurine deficiency promotes structural and functional cardiac alterations with unique characteristics.     

The role of roadsides in conserving Cerrado plant diversity

The structure of Cerrado vegetation (sensu stricto) along roadsides was compared with that of protected areas (reserves). The superior stratum of reserves had 2.7 times more individuals and 1.4 times more species than on roadsides, while in the intermediate stratum there were 1.7 times more individuals and 25 % more species in reserves. Additionally, roadsides had a lower prevalence of tree species with thin bark and from forest physiognomies. In the intermediate stratum of roadsides there was a lower proportion of forest species, and also fewer species dispersed by animals. These differences occur, possibly because the vegetation of their edges is cleared during the construction of the roads and part of the soil is taken as landfill. Later, they suffer from a higher fire frequency and high coverage of exotic grasses (80 % average). Moreover, it is likely that the absence of some dispersers on roadsides may affect the recruitment of young plants. Despite these differences, the roadsides are able to maintain at least 70 % of tree species and 72 % of shrub species found in reserves. These results show that roadside vegetation can contribute to the conservation of the flora of Cerrado. This is particularly important considering that over 60 % of the original area of this ecosystem has been destroyed and that less than 4 % is protected. With 32,012 km of roads in the Cerrado alone, the roadside vegetation may represent a cumulative area of 96,000 of hectares, an area larger than many of the Cerrado’s national parks.     

Neuroprotective and anticonvulsant effects of organic and conventional purple grape juices on seizures in Wistar rats induced by pentylenetetrazole

Epilepsy is the most common neurological disorder worldwide. Studies have shown that recurrent seizures may increase the concentration of reactive oxygen species, which can lead to oxidative stress and neuronal damage. These seizures result in substantial deleterious effects on an individual's health. Organic and conventional grape juices are rich in polyphenols, compounds with important antioxidant activity. However, these juices could have differences in their polyphenol content. The aim of this study was to investigate the neuroprotective and anticonvulsant effects of organic and conventional grape juice treatments in Wistar rats against pentylenetetrazole (a convulsant drug)-induced damage. In addition, we evaluated potential behavioral changes in rats treated with the juices and the polyphenolic profile of those samples. Animals (n=16 in each group) received treatment with saline, organic or conventional grape juice for 17 days. On the eighteenth day, behavioral changes were evaluated by an open field test. Afterwards, half of the rats from each group received pentylenetetrazole and were observed for 30 min to evaluate possible seizure characteristics. The animals were subsequently killed by decapitation and their hippocampus, cerebellum and cerebral cortex tissues were isolated. The results of this study showed that neither organic nor conventional grape juice altered the behavior parameters, and no statistical differences were observed in the seizure characteristics of the groups. Nevertheless, both juice types were able to protect from lipid and protein oxidative damage, decrease nitric oxide content and increase enzymatic (superoxide dismutase and catalase) and non-enzymatic (sulfhydryl protein) antioxidant defenses in brain tissues following pentylenetetrazole-induced seizures. In general, organic juice showed superior results in each test, probably due to its higher polyphenol content relative to conventional juice. These results indicate that grape juices can provide further insight into natural neuroprotective compounds and may lead to the development of new therapeutic strategies for epileptic patients.     

Brij detergents reveal new aspects of membrane microdomain in erythrocytes

Membrane microdomains enriched in cholesterol, sphingolipids (rafts), and specific proteins are involved in important physiological functions. However their structure, size and stability are still controversial. Given that detergent-resistant membranes (DRMs) are in the liquid-ordered state and are rich in raft-like components, they might correspond to rafts at least to some extent. Here we monitor the lateral order of biological membranes by characterizing DRMs from erythrocytes obtained with Brij-98, Brij-58, and TX-100 at 4?°C and 37?°C. All DRMs were enriched in cholesterol and contained the raft markers flotillin-2 and stomatin. However, sphingomyelin (SM) was only found to be enriched in TX-100-DRMs – a detergent that preferentially solubilizes the membrane inner leaflet – while Band 3 was present solely in Brij-DRMs. Electron paramagnetic resonance spectra showed that the acyl chain packing of Brij-DRMs was lower than TX-100-DRMs, providing evidence of their diverse lipid composition. Fatty acid analysis revealed that the SM fraction of the DRMs was enriched in lignoceric acid, which should specifically contribute to the resistance of SM to detergents. These results indicate that lipids from the outer leaflet, particularly SM, are essential for the formation of the liquid-ordered phase of DRMs. At last, the differential solubilization process induced by Brij-98 and TX-100 was monitored using giant unilamellar vesicles. This study suggests that Brij and TX-100-DRMs reflect different degrees of lateral order of the membrane microdomains. Additionally, Brij DRMs are composed by both inner and outer leaflet components, making them more physiologically relevant than TX-100-DRMs to the studies of membrane rafts.     

The evaluation of the oxidative state of native-LDL: three methods compared

LDL-oxidation is considered a contributing factor to the development of atherosclerotic lesions. However, to utilise the oxidative state of LDL as a marker of cardiovascular risk, reliable analytical methods for its detection must be defined. We have compared three methods for their capacity to evaluate the difference in the oxidation state of isolated LDL subjected to either dialysis (D-LDL) or gel filtration (F-LDL) to remove EDTA. Their susceptibility to oxidation promoted by Cu(2+) was monitored by following the time course of conjugated diene (CD) and lipid hydroperoxide (ROOH) accumulation. The relative electrophoretic mobility (REM) of the same LDL samples was evaluated by capillary electrophoresis. As measured by all three methods, F-LDL are less prone to oxidation than D-LDL when added with CuSO(4). REM of F-LDL and D-LDL significantly differs already before the addition of the metal catalyst, whereas CD and ROOH contents become significantly different only after it. Besides confirming that a rapid centrifugation followed by gel filtration is a more convenient procedure than dialysis to remove EDTA during LDL isolation, our study suggests the REM of isolated-LDL as the biochemical marker of choice in the evaluation of its oxidative state.     

Modified Adamek's medium renders high yields of Metarhizium robertsii blastospores that are desiccation tolerant and infective to cattle-tick larvae

Blastospores are yeast-like cells produced by entomopathogenic fungi that are infective to arthropods. The economical feasible production of blastospores of the insect killing fungus Metarhizium spp. must be optimized to increase yields. Moreover, stabilization process is imperative for blastospore formulation as a final product. In this sense, our goal was to increase blastospore production of two Metarhizium isolates (ESALQ1426 and ESALQ4676) in submerged liquid cultures. A modified Adamek's medium was supplemented with increased glucose concentrations and the fermentation time was accelerated by using a blastospore pre-culture as inoculum. Virulence of air-dried stable blastospores was compared with conidia toward larvae of the cattle tick, Rhipicephalus microplus. Our results revealed that blastospore production of Metarhizium is isolate- and species-dependent. Glucose-enriched cultures (140 g glucose/L) inoculated with pre-cultures improved yields with optimal growth conditions attained for Metarhizium robertsii ESALQ1426 that rendered as high as 5.9 × 10⁸ blastospores/mL within 2 d. Resultant air-dried blastospores of ESALQ1426 were firstly proved to infect and quickly kill cattle tick larvae with comparable efficiency to conidia. Altogether, we argue that both osmotic pressure, induced by high glucose titers, and isolate selection are critical to produce high yields of blastospores that hold promise to control cattle-tick larvae.     

Land use,fallow period and the recovery of a Caatinga forest

Caatinga vegetation continues to be converted into mosaics of secondary forest stands, but the affect of this process on biodiversity has not yet been examined. We used 35 regenerating and old‐growth stands of Caatinga to examine the recovery of plant assemblages subsequent to slash‐and‐burn agriculture and cattle ranching/pasture in northeastern Brazil. Plant assemblages were contrasted in terms of community structure (stem density/basal area/species richness/diversity), functional (leaf habit/reproductive traits) and taxonomic composition. Soil attributes were also examined to infer potential drivers for cross‐habitat differences. As expected, plant assemblages clearly differed across a large set of community‐level attributes, including all trait categories relative to leaf habit and reproduction (pollination syndrome/floral color, size, type). Overall, old‐growth forest stands supported distinct and more diverse assemblages at the plot and habitat level; e.g., long‐lived tree species were almost exclusively found in old‐growth forest stands. For most attributes, plant assemblages subsequent to pasture exhibited intermediate values between those exhibited by old‐growth forest and those of agriculture‐related stands. Surprisingly, soils exhibited similar fertility‐related scores across habitats. Our results indicate that: (1) sprouting/resprouting represents an important mechanism of forest regeneration; (2) assemblage‐level attributes suggest recovery at distinct rates; (3) forest regeneration implies community‐level changes in both vegetative and reproductive functional attributes, including directional changes; (4) Caatinga is not able to completely recover in a period of 15‐yr following land abandonment; and (5) historical land use affects recovery rates and successional pathways/taxonomic trajectories. Seasonally dry tropical forests may intrinsically cover a wide range of patterns relative to successional model, recovery rates and successional pathways.     

Early S phase DNA replication: A search for targets of carcinogenesis

Our studies have revealed that replicating DNA is more vulnerable to adduction than is non-replicating DNA. Contrary to our expectations that the vulnerability to neoplastic transformation induced by carcinogens in synchronized cells would parallel the rate of DNA replication, we actually found that the vulnerability was notably increased early in the S phase and more closely paralleled the rate of entry of cells into the S phase (the very beginning of S phase) rather than the overall rate of DNA synthesis. From these findings we hypothesized that there were targets for the neoplastic transformation of cells that were among the earliest replicated sequences in the genome. To test that this hypothesis was plausible we investigated the temporal order of DNA replication during the S phase and showed that the order of DNA replication was far more precisely defined than had been recognized previously. The cell synchronization techniques that made those findings possible made it feasible to demonstrate that only a relatively few sites of DNA replication are identifiable in chromosomal bands at the earliest times in the S phase. The same synchronization techniques enabled us to label DNA replicated when populations of cells were very early in S phase and to isolate and clone this DNA. The clonal elements of this library of DNA prepared in this manner have been sequenced and mapped to the human genome. Efforts are in progress to characterize the genes and sequence features associated with these regions. We have utilized methods to identify and characterize origins of DNA replication as a means of locating the earliest replicating part of these early replicating regions. We have identified several new origins of DNA replication that are activated early and late in the S phase but the features of the chromatin at the origin that determines its time of activation remain obscure. In an effort to improve our ability to identify more origins, particularly adjacent origins in genomic regions, we have combined the methods of DNA combing and FISH analysis of combed DNA to search for DNA precursor incorporation patterns characteristic of origins of DNA replication. Preliminary nascent strand abundance studies appear to have proven the existence of two origins of DNA replication predicted from the precursor incorporation studies. We have found that the combed DNA techniques can be combined with precursor incorporation studies and antibodies to sites of DNA damage to address questions of mechanisms of DNA damage and repair. For example these studies have shown recently that DNA damage is not randomly distributed in the genome and that both inhibition of replicon initiation and inhibition of strand elongation are separately distinguishable as components of the S checkpoint function.It is our hope and expectation that these results and the opportunities that they provide for future studies will enable us to identify possible targets for malignant transformation that explain our observation that cells at the start of S phase are vulnerable to the initiation of carcinogenesis.