Scielo RSS <![CDATA[Biological Research]]> vol. 45 num. 1 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Contribution of environmental pollutants to male infertily</b>: <b>A working model of germ cell apoptosis induced by plasticizers</b>]]> Bisphenol A [2,2-bis(4-hydroxyphenyl)propane] (BPA), 4-nonylphenol (NP) and di(2-ethylhexyl)phthalate (DEHP), and its metabolite mono-2-ethylhexyl phthalate (MEHP) are chemicals found in plastics, which act as endocrine disruptors (EDs) in animals, including human. EDs act like hormones in the endocrine system, and disrupt the physiologic function of endogenous hormones. Most people are exposed to different endocrine disruptors and concern has been raised about their true effect on reproductive organs. In the testis, they seem to preferentially attack developing testis during puberty rather than adult organs. However, the lack of information about the molecular mechanism, and the apparently controversial effect observed in different models has hampered the understanding of their effects on mammalian spermatogenesis. In this review, we critically discuss the available information regarding the effect of BPA, NP and DEHP/ MEHP upon mammalian spermatogenesis, a major target of EDs. Germ cell sloughing, disruption of the blood-testis-barrier and germ cell apoptosis are the most common effects reported in the available literature. We propose a model at the molecular level to explain the effects at the cellular level, mainly focused on germ cell apoptosis. <![CDATA[The effects of 4-nonylphenol contamination on livers of Tilapia fish <i>(Oreochromus spilurs)</i> in Jeddah]]> Alkylphenol polyethoxylates is a group of estrogenic compounds. Natural or synthetic types of these compounds react with the endocrine system by binding hormone receptors, resulting in interference with their action, which is why they are called endocrine disrupting chemicals. Among their hydrolytic products are nonylphenols (NP), which are considered pollutants of aquatic environments. The objective of this study was to evaluate the pathological alterations on liver tissue of fish exposed to these compounds for long durations, starting from beginning of life and during the period of sexual maturity. Tilapia fish were obtained from Abhur fish farms, reared in the laboratory in special basins, and divided into two groups. The first maternal group was untreated and their larvae were divided into three sub-groups: control; exposed to 15μg/L; and exposed to 30 μg/L. The second maternal group was divided into 2 sub-groups: with larvae exposed to 15μg/L; and with their larvae exposed to 30 μg/L. Larvae and mother exposed to different concentrations of NP (15 and 30 μg/L) showed an increased accumulation of NP in both livers and muscles compared to the control group due to bioaccumulation. Tissue section examinations of the treated group (15 μg NP /L) showed disruption of liver architecture, with lyses, loss of nuclei, necrosis, and fatty infiltration. The changes were more marked in tissues exposed to (30 μg NP /L). Although this pollution was not lethal, its effect may be reflected in vital activities and in the economy. <![CDATA[The normal chain length distribution of the O antigen is required for the interaction of <i>Shigella</i><i> flexneri</i> 2a with polarized Caco-2 cells]]> Shigella flexneri causes bacillary dysentery in humans. Essential to the establishment of the disease is the invasion of the colonic epithelial cells. Here we investigated the role of the lipopolysaccharide (LPS) O antigen in the ability of S. flexneri to adhere to and invade polarized Caco-2 cells. The S. flexneri 2a O antigen has two preferred chain lengths: a short O antigen (S-OAg) regulated by the WzzB protein and a very long O antigen (VL-OAg) regulated by Wzz pHS2. Mutants with defined deletions of the genes required for O-antigen assembly and polymerization were constructed and assayed for their abilities to adhere to and enter cultured epithelial cells. The results show that both VL- and S-OAg are required for invasion through the basolateral cell membrane. In contrast, the absence of O antigen does not impair adhesion. Purified LPS does not act as a competitor for the invasion of Caco-2 cells by the wild-type strain, suggesting that LPS is not directly involved in the internalization process by epithelial cells. <![CDATA[<b>Chronic ethanol consumption in mice does not induce DNA damage in somatic or germ cells, evaluated by the bone marrow micronucleous assay and the dominant lethal mutation assay</b>]]> Although alcohol is known to be a carcinogen for humans, ethanol-genotoxicity studies are incomplete. Ethanol seems not to be a bacterial mutagen, but the results are conflicting in rodent assays. We investigate the genotoxicity in the bone marrow micronucleus (MN) test and in the dominant lethal mutation (DLM) assay using two long-term ethanol exposure protocols. In the MN test, mice consumed three doses (5, 10 and 15% v/v) for 32 weeks. MN induction was compared to two control groups of 5- and 38-week-old mice (the ages of the treated mice when the treatment was initiated and when they were killed, respectively). For the three groups treated with ethanol there was no significant increase in MN induction as compared to the first control group, but observed MN frequencies were significantly lower than in the 38-week-old control group. This suggests a protective effect against genotoxic damage caused by aging, probably due to ethanol action as a hydroxyl radical scavenger. In the DLM assay, male mice drank ethanol at 15% or 30% (v/v) for 20 weeks. In both groups the number of dead implants was similar to the control, but there was a significant reduction in total implants, indicating a pre-implantation loss. <![CDATA[Human dendritic cells sequentially matured with CD4+ T cells as a secondary signal favor CTL and long-term T memory cell responses]]> Dendritic cells (DCs) are professional antigen-presenting cells involved in the control and initiation of immune responses. In vivo, DCs exposed at the periphery to maturation stimuli migrate to lymph nodes, where they receive secondary signals from CD4+ T helper cells. These DCs become able to initiate CD8+ cytotoxic T lymphocyte (CTL) responses. However, in vitro investigations concerning human monocyte-derived DCs have never focused on their functional properties after such sequential maturation. Here, we studied human DC phenotypes and functions according to this sequential exposure to maturation stimuli. As first signals, we used TNF-α/polyI:C mimicking inflammatory and pathogen stimuli and, as second signals, we compared activated CD4+ T helper cells to a combination of CD40-L/ IFN-γ. Our results show that a sequential activation with activated CD4+ T cells dramatically increased the maturation of DCs in terms of their phenotype and cytokine secretion compared to DCs activated with maturation stimuli delivered simultaneously. Furthermore, this sequential maturation led to the induction of CTL with a long-term effector and central memory phenotypes. Thus, sequential delivery of maturation stimuli, which includes CD4+ T cells, should be considered in the future to improve the induction of long-term CTL memory in DC-based immunotherapy. <![CDATA[<b>Effects of silk sericin on the proliferation and apoptosis of colon cancer cells</b>]]> Sericin is a silk protein woven from silkworm cocoons (Bombyx mori). In animal model, sericin has been reported to have anti-tumoral action against colon cancer. The mechanisms underlying the activity of sericin against cancer cells are not fully understood. The present study investigated the effects of sericin on human colorectal cancer SW480 cells compared to normal colonic mucosal FHC cells. Since the size of the sericin protein may be important for its activity, two ranges of molecular weight were tested. Sericin was found to decrease SW480 and FHC cell viability. The small sericin had higher anti-proliferative effects than that of the large sericin in both cell types. Increased apoptosis of SW480 cells is associated with increased caspase-3 activity and decreased Bcl-2 expression. The anti-proliferative effect of sericin was accompanied by cell cycle arrest at the S phase. Thus, sericin reduced SW480 cell viability by inducing cell apoptosis via caspase-3 activation and down-regulation of Bcl-2 expression. The present study provides scientific data that support the protective effect of silk sericin against cancer cells of the colon and suggests that this protein may have significant health benefits and could potentially be developed as a dietary supplement for colon cancer prevention. <![CDATA[Cyclooxygenase-2 and hypoxia-regulated proteins are modulated by basic fibroblast growth factor in acute renal failure]]> Acute renal failure (ARF) can be caused by injuries that induce tissue hypoxia, which in turn can trigger adaptive or inflammatory responses. We previously showed the participation of basic fibroblast growth factor (FGF-2) in renal repair. Based on this, the aim of this study was to analyze the effect of FGF-2 signaling pathway manipulation at hypoxia-induced protein levels, as well as in key proteins from the vasoactive systems of the kidney. We injected rat kidneys with FGF-2 recombinant protein (r-FGF) or FGF-2 receptor antisense oligonucleotide (FGFR2-ASO) after bilateral ischemia, and evaluated the presence of iNOS, EPO and HO-1, in representation of hypoxia-induced proteins, as well as COX-2, renin, kallikrein, and B2KR, in representation of the vasoactive systems of the kidney. A reduction in iNOS, HO-1, EPO, renin, kallikrein, B2KR, and in renal damage was observed in animals treated with r-FGF. The opposite effect was found with FGF-2 receptor down-regulation. In contrast, COX-2 protein levels were higher in kidneys treated with r-FGF and lower in those that received FGFR2-ASO, as compared to saline treated kidneys. These results suggest that the protective role of FGF-2 in the pathogenesis of ARF induced by I/R is a complex process, through which a differential regulation of metabolic pathways takes place. <![CDATA[<b>Reinstatement of short-latency responses after asymptotic Pavlovian conditioning training by the presentation of an extraneous stimulus</b>]]> The purpose of this study was to examine whether the progressive disappearance of short-latency conditioned responses, or inhibition of delay, observed in Pavlovian conditioning with long inter-stimulus intervals, could be reverted by the presentation of a novel stimulus. In one experiment, two groups of rabbits received extensive training with a short (250 ms) or a long (1500 ms) tone that overlapped and terminated with a periorbital shock unconditioned stimulus. After training, the presentation of an extraneous stimulus prior to tone onset produced a reinstatement of short latency CRs in the group trained with the long CS, but did not affect CR latency in the group trained with the short CS. This finding is consistent with Pavlov's (1927) view that conditioning with long conditioned stimuli involves the acquisition of response tendencies in the early portion of the stimulus that are subsequently suppressed by the development of an inhibitory process. <![CDATA[Relaxant effects of different fractions from <i>Tymus</i><i> vulgaris</i> on guinea-pig tracheal chains]]> In previous studies, the relaxant effect of Tymus vulgaris has been demonstrated on guinea pig tracheal chains. Therefore, in the present study, the relaxant effects of n-hexane, dichloromethane, methanol and aqueous fractions of Tymus vulgaris on tracheal chains of guinea pigs were examined. The relaxant effects of four cumulative concentrations of each fraction (0.4, 0.8, 1.2 and 1.6 g%) in comparison to saline as negative control and four cumulative concentrations of theophylline (0.2, 0.4, 0.6 and 0.8 mM) were examined for their relaxant effects on precontracted tracheal chains of guinea pig by 60 mM KCl (group 1) and 10 ìÌ methacholine (group 2, n = 7 for each group). In group 1, all concentrations of the n-hexane fraction and theophylline and three last concentrations (0.8, 1.2 and 1.6 g%) of dichloromethane and two higher concentrations (1.2 and 1.6 g%) of methanol fractions showed significant relaxant effects compared to that of saline (p<0.05 to p<0.001). In group 2, all concentrations of theophylline, n-hexane and dichloromethane fractions and three concentrations (0.8, 1.2 and 1.6 g%) of methanol and two higher concentrations (1.2 and 1.6 g%) of aqueous fractions showed significant relaxant effects compared to that of saline (p<0.05 to p<0.001). In addition, with group 1, the relaxant effect of all concentrations of all fractions except the n-hexane fraction, were significantly less than those of theophylline (p<0.05 to p<0.001). The n-hexane fraction showed higher relaxant effect than theophylline. The relaxant effect of all concentrations of the n-hexane fraction and the three last concentrations (0.8, 1.2 and 1.6 g%) of dichloromethane and aqueous fractions were significantly greater in group 2 than in group 1 (p<0.05 to p<0.001). There were significant positive correlations between the relaxant effects and concentrations for theophylline and all fractions (except aqueous fraction in group 1) in both groups, but a negative correlation for the aqueous fraction in group 1 (p<0.05 to p<0.001). These results showed a potent relaxant effect for n-hexane and weaker relaxant effect for other fractions from Tymus vulgaris on tracheal chains of guinea pigs. <![CDATA[<b>Proteomic Investigation of Changes in Rat Skeletal Muscle after Exercise-Induced Fatigue</b>]]> The mechanisms of exercise-induced fatigue have not been investigated using proteomic techniques, an approach that could improve our understanding and generate novel information regarding the effects of exercise. In this study, the proteom alterations of rat skeletal muscle were investigated during exercise-induced fatigue. The proteins were extracted from the skeletal muscle of SD rat thigh, and then analyzed by two-dimensional electrophoresis and PDQuest software. Compared to control samples, 10 significantly altered proteins were found in exercise samples, two of them were upregulated and eight of them were downregulated. These proteins were identified by MALDI TOF-MS. The two upregulated proteins were identified as MLC1 and myosin L2 (DTNB) regulatory light-chain precursors. The eight decreased proteins are Glyceraldehyde-3-phosphate Dehydrogenas (GAPDH); Beta enolase; Creatine kinase M chain (M-CK); ATP-AMP Transphosphorylase (AK1); myosin heavy chain (MHC); actin; Troponin I, fast-skeletal muscle (Troponin I fast-twitch isoform), fsTnI; Troponin T, fast-skeletal muscle isoforms (TnTF). In these proteins, four of the eight decreased proteins are related directly or indirectly to exercise induced fatigue. The other proteins represent diverse sets of proteins including enzymyes related to energy metabolism, skeletal muscle fabric protein and protein with unknown functions. They did not exhibit evident relationship with exercise-induced fatigue. Whereas the two identified increased proteins exhibit evident relationship with fatigue. These findings will help in understanding the mechanisms involved in exercise-induced fatigue. <![CDATA[Melatonin Protects the Heart, Lungs and Kidneys from Oxidative Stress under Intermittent Hypobaric Hypoxia in Rats]]> Melatonin (N-acetyl-5-methoxytryptamine) is the main secretory product of the pineal gland in all mammals including humans, but it is also produced in other organs. It has been previously demonstrated to be a powerful organ-protective substance under oxidative stress conditions. The aim of this study was to evaluate the protective effect of melatonin in several organs such as heart, lung, kidney, and of the reproductive system, such as testis and epididymis in animals exposed to intermittent hypobaric hypoxia and therefore exposed to oxidative stress and analyzed by lipid peroxidation. Ten-week-old male Wistar rats were divided into 6 groups for 96 hours during 32 days under: 1) Normobaric conditions, 2) plus physiologic solution, 3) plus melatonin, 4) intermittent hypobaric hypoxia, 5 plus physiologic solution and 6) plus melatonin. The animals were injected with melatonin (10 mg/kg body weight) at an interval of 96 hours during 32 days. Results indicated that melatonin decreased lipid peroxidation in heart, kidneys and lung under intermittent hypobaric hypoxia conditions. However, it did not exhibit any protective effect in liver, testis, epididymis and sperm count. <![CDATA[Anatomy of corpus callosum in prenatally malnourished rats]]> The effect of prenatal malnutrition on the anatomy of the corpus callosum was assessed in adult rats (45-52 days old). In the prenatally malnourished animals we observed a significant reduction of the corpus callosum total area, partial areas, and perimeter, as compared with normal animals. In addition, the splenium of corpus callosum (posterior fifth) showed a significant decrease of fiber diameters in the myelinated fibers without changing density. There was also a significant decrease in diameter and a significant increase in density of unmyelinated fibers. Measurements of perimeter's fractal dimensions from sagittal sections of the brain and corpus callosum did not show significant differences between malnourished and control animals. These findings indicate that cortico-cortical connections are vulnerable to the prenatal malnutrition, and suggest this may affect interhemispheric conduction velocity, particulary in visual connections (splenium).