Dehydroepiandrosterone prevents age-associated alterations, increasing insulin sensitivity

The age decline in DHEA levels has been associated with the appearance of age-related disorders such as obesity and insulin resistance. The aim of this study was to analyse the effect of chronic administration (13 weeks) of DHEA (5 g/kg diet) to old female rats fed on a high-fat diet on body weight and adiposity, and concretely on the expression of the adipokines related to obesity and insulin resistance, such as leptin, adiponectin and resistin. DHEA treatment induced a decrease in body weight, adipose tissue mass and serum insulin, adiponectin and leptin levels. Adiponectin mRNA expression in visceral fat depots decreased with aging, but this reduction was attenuated by DHEA treatment. DHEA treatment also stimulated resistin gene expression in the ovaric and renal adipose depots, which is associated with an increase in its circulating levels. In conclusion, DHEA treatment decreases body weight and adiposity in old female rats fed a high-fat diet, leading to an improvement of the HOMA index for insulin sensitivity, with decreasing circulating insulin levels, and preventing the age-associated decline of visceral-adipose adiponectin expression.     

Role of Bacillus spp. in antagonism between Pleurotus ostreatus and Trichoderma harzianum in heat-treated wheat-straw substrates

This study aimed to identify bacteria involved in Trichodermaharzianum inhibition while promoting Pleurotus ostreatus defences in order to favour cultivation-substrate selectivity for mushroom production. PCR-DGGE profiles of total DNA from wheat-straw substrate showed weak differences between bacterial communities from substrate inoculated with P. ostreatus with or without T. harzianum. The major cultivable bacteria were isolated from three batches of wheat-straw-based cultivation substrates showing an efficient selectivity. They were screened for their ability to inhibit T.harzianum. By using specific media for bacterial isolation and by sequencing certain 16S-rDNA, we observed that Bacillus spp. were the main inhibitors. Among them, a dominant species was identified as Paenibacillus polymyxa. This species was co-cultivated on agar media with P. ostreatus. The measurement of laccase activities from culture plugs indicated that P. polymyxa induced increases in enzyme activities. Bacillus spp. and specifically P. polymyxa from cultivation substrates are implicated in their selectivity by both inhibiting the growth of T.harzianum and stimulating defences of the mushroom P. ostreatus through the induction of laccases. The management of microbial communities during P.ostreatus cultivation-substrate preparation in order to favour P. polymyxa and other Bacillus spp. growth, can be a way to optimize the development of P. ostreatus for mushroom production or other environmental uses of this fungus.     

Adiponectin is involved in the protective effect of DHEA against metabolic risk in aged rats

The aim of the present work was to analyze the effect of dehydroepiandrosterone (DHEA) on several metabolic risk factors, including cardiovascular health and insulin resistance, in aged rats submitted to a high-fat diet. For that, weaned rats were fed on a high-fat diet until 20 months of age. In the last 13 weeks of life, a group (n=11) received the diet supplemented with DHEA (0.5%, w/w), serving the rest (n=10) as controls. Body weight, body fat, serum lipids (triglycerides, total cholesterol and non-esterified fatty acids (NEFA)), HOMA index, n-6/n-3 polyunsaturated fatty acid (PUFA) ratios, serum adiponectin, leptin, resistin and TNF-alpha, as well as adiponectin expression in adipose tissue, were measured. A stepwise discriminant test was used to analyze these variables, and an index of overall metabolic risk was generated from them. DHEA treatment resulted in a significantly lower overall metabolic risk index, as generated by the discriminant test (P<0.01). The DHEA group had lower body fat and n-6/n-3 polyunsaturated fatty acid (PUFA) ratios than the control group (P<0.01), and the same trends were observed for serum cholesterol, triglycerides and HOMA index; in contrast, adiponectin expression in adipose tissue increased in DHEA-treated rats (P<0.05). The discriminant analysis revealed that adiponectin, both from serum and adipose tissue, was the most influencing factor, followed by n-6/n-3 ratios in adipose tissue, and by body fat. Our results then suggest that adiponectin is involved in the protective effect of DHEA against metabolic risk demonstrated in the present work.     

Presenilin 1 interacts with acetylcholinesterase and alters its enzymatic activity and glycosylation

Presenilin 1 (PS1) plays a critical role in the gamma-secretase processing of the amyloid precursor protein to generate the beta-amyloid peptide, which accumulates in plaques in the pathogenesis of Alzheimer's disease (AD). Mutations in PS1 cause early onset AD, and proteins that interact with PS1 are of major functional importance. We report here the coimmunoprecipitation of PS1 and acetylcholinesterase (AChE), an enzyme associated with amyloid plaques. Binding occurs through PS1 N-terminal fragment independent of the peripheral binding site of AChE. Subcellular colocalization of PS1 and AChE in cultured cells and coexpression patterns of PS1 and AChE in brain sections from controls and subjects with sporadic or familial AD indicated that PS1 and AChE are located in the same intracellular compartments, including the perinuclear compartments. A PS1-A246E pathogenic mutation expressed in transgenic mice leads to decreased AChE activity and alteration of AChE glycosylation and the peripheral binding site, which may reflect a shift in protein conformation and disturbed AChE maturation. In both the transgenic mice and humans, mutant PS1 impairs coimmunoprecipitation with AChE. The results indicate that PS1 can interact with AChE and influence its expression, supporting the notion of cholinergic-amyloid interrelationships.     

Evaluation of immunomodulatory and anti-inflammatory effects and phytochemical screening of Alternanthera tenella Colla (Amaranthaceae) aqueous extracts

Alternanthera tenella Colla extracts are used in Brazilian traditional folk medicine to treat a variety of infectious diseases as well as inflammation and fever. In this work, the immunomodulatory, anti-inflammatory and potential toxic effects of cold (CAE) and hot (HAE) aqueous extracts of A. tenella were investigated in vivo. In addition, we analyzed the phytochemical properties of both extracts. BALB/c mice were immunized in vivo with sheep red blood cells and concomitantly inoculated intraperitoneally (i.p.) with each extract (50, 100 or 200 mg/kg). Specific antibody-producing cells were enumerated using plaque-forming cell assays (PFC) and anti-SRBC IgG and IgM serum levels were measured via enzyme-linked immunosorbent assay. Body and lymphoid organ weights were determined after treatments in order to evaluate toxic effects. Carrageenan-induced paw edema was employed to investigate anti-inflammatory activity in mice inoculated i.p. with CAE or HAE (200 or 400 mg/kg). Phytochemical screening was performed using spectrometric and chromatographic approaches and revealed that CAE possessed higher tannin and flavonoid levels than HAE. PFC numbers were increased after treatment with CAE (100 mg/kg) four days after immunization, as were the serum antibody titers after four and seven days, suggesting immunostimulatory activity through modulation of B lymphocyte functions. Body and organ weights did not show major changes, suggesting that extracts administered to mice did not induce significant toxicity. Both extracts had significant anti-inflammatory activity in the paw edema assay. These results suggested that aqueous extracts from A. tenella contained several chemical compounds that possess positive and/or negative modulator effects on the immune system, which appeared to correlate with tannin and flavonoid levels in those extracts. In summary, these studies provide important insight into the biological activities of A. tenella.     

Identification of a novel family of nucleosides that specifically inhibit HIV-1 reverse transcriptase.

N-3-Benzyloxycarbonylmethyl- and N-3-carboxymethyl-TBDMS-substituted nucleosides were synthesized and evaluated for activity against HIV replication. It was found that the N-3-carboxymethyl-TBDMS-substituted nucleosides were specific inhibitors of HIV-1 replication. They should be considered as members of a novel and original class of NNRTIs.     

Brief communication: Cranial reconstruction of Dryopithecus.

This paper presents the first three-dimensional reconstruction of the cranium of the European Miocene ape, Dryopithecus. The reconstruction is based on remains collected from Can Llobateres, Spain (CLI 18000; Dryopithecus laietanus), D. fontani (St. Gaudens), and D. brancoi (Kordos and Begun [1997] Am. J. Phys. Anthropol. 103:277-294). Previously unrecognized facial fragments from CLI 18000 were included in the reconstruction. The result shows that Dryopithecus had a relatively short face, with a rather short and well-rounded neurocranium. From the lateral perspective, the face is concave at midface, and on the cranium the temporal lines run parallel to each other without forming a sagittal crest.     

Kinetic characterization of the rotenone-insensitive internal NADH: ubiquinone oxidoreductase of mitochondria from Saccharomyces cerevisiae

Saccharomyces cerevisiae mitochondria contain an NADH:Q6 oxidoreductase (internal NADH dehydrogenase) encoded by NDI1 gene in chromosome XIII. This enzyme catalyzes the transfer of electrons from NADH to ubiquinone without the translocation of protons across the membrane. From a structural point of view, the mature enzyme has a single subunit of 53 kDa with FAD as the only prosthetic group. Due to the fact that S. cerevisiae cells lack complex I, the expression of this protein is essential for cell growth under respiratory conditions. The results reported in this work show that the internal NADH dehydrogenase follows a ping-pong mechanism, with a Km for NADH of 9.4 microM and a Km for oxidized 2,6-dichorophenolindophenol (DCPIP) of 6.2 microM. NAD+, one of the products of the reaction, did not inhibit the enzyme while the other product, reduced DCPIP, inhibited the enzyme with a Ki of 11.5 microM. Two dead-end inhibitors, AMP and flavone, were used to further characterize the kinetic mechanism of the enzyme. AMP was a linear competitive inhibitor of NADH (Ki = 5.5 mM) and a linear uncompetitive inhibitor of oxidized DCPIP (Ki = 11.5 mM), in agreement with the ping-pong mechanism. On the other hand, flavone was a partial inhibitor displaying a hyperbolic uncompetitive inhibition regarding NADH, and a hyperbolic noncompetitive inhibition with respect to oxidized DCPIP. The apparent intercept inhibition constant (Kii = 5.4 microM) and the slope inhibition constant (Kis = 7.1 microM) were obtained by non linear regression analysis. The results indicate that the ternary complex F-DCPIPox-flavone catalyzes the reduction of DCPIP, although with lower efficiency. The effect of pH on Vmax was studied. The Vmax profile shows two groups with pKa values of 5.3 and 7.2 involved in the catalytic process.