Scielo RSS <![CDATA[Biological Research]]> https://scielo.conicyt.cl/rss.php?pid=0716-976020100002&lang=en vol. 43 num. 2 lang. en <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[<b>Plasmid-Encoded Multidrug Resistance</b>: <b>A Case study of Salmonella and Shigella from enteric diarrhea sources among humans</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200001&lng=en&nrm=iso&tlng=en Salmonellosis and shigellosis are signifcant and persistent causes of diarrheal diseases among humans in developing countries. With that in mind, the current study investigates the occurrence of plasmid-encoded multidrug resistances in Salmonella and Shigella from diarrheal cases among humans. The isolates were characterized by serotyping, antimicrobial-susceptibility testing, transfer experiments and curing. The extended spectrum β-lactamase (ESBL) was detected by the double disc diffusion synergy test (DDST). A signifcant number of the plasmid-encoded multidrug resistant (PEMDR) Salmonella and Shigella isolates were found to harbour transferable plasmid genes resistant to antibiotics like ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, ceftriaxone, cefuroxime and to a lesser extent to ciprofoxacin and ofoxacin. The conjugative R-plasmids-encoded extended-spectrum β-lactamase also showed resistances to cephalosporins (ceftriaxone and cefuroxime) and ampicillin. Curing experiments showed chromosomal resistances to varied antibiotics. The fndings confrmed the presence of PEMDR in Salmonella and Shigella strains as a suitable adaptation to a changing antibiotic environment. The results therefore suggest the limited use of the commonly prescribed/or third generation cephalosporins as an empirical treatment of multidrug resistant Salmonella and Shigella because this may affect therapeutic outcomes. <![CDATA[<b>Fixations of the HIV-1 env gene refute neutralism</b>: <b>New evidence for pan-selective evolution</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200002&lng=en&nrm=iso&tlng=en We examined 103 nucleotide sequences of the HIV-1 env gene, sampled from 35 countries and tested: I) the random (neutral) distribution of the number of nucleotide changes; II) the proportion of bases at molecular equilibrium; III) the neutral expected homogeneity of the distribution of new fxated bases; IV) the hypothesis of the neighbor infuence on the mutation rates in a site. The expected random number of fxations per site was estimated by Bose-Einstein statistics, and the expected frequencies of bases by matrices of mutation-fxation rates. The homogeneity of new fxations was analyzed using χ2 and trinomial tests for homogeneity. Fixations of the central base in trinucleotides were used to test the neighbor infuence on base substitutions. Neither the number of fxations nor the frequencies of bases ftted the expected neutral distribution. There was a highly signifcant heterogeneity in the distribution of new fxations, and several sites showed more transversions than transitions, showing that each nucleotide site has its own pattern of change. These three independent results make the neutral theory, the nearly neutral and the neighbor infuence hypotheses untenable and indicate that evolution of env is rather highly selective. <![CDATA[<b><i>In vitro </i></b><b>antibacterial activity in seed extracts of Manilkara zapota, Anona squamosa, and Tamarindus indica</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200003&lng=en&nrm=iso&tlng=en Extracts prepared from seeds of Manilkara zapota, Anona squamosa, and Tamarindus indica were screened for their antibacterial activity by disc diffusion and broth dilution methods. Acetone and methanol extracts of T. indica seeds were found active against both gram-positive and gram-negative organisms. MIC values of potent extracts against susceptible organisms ranged from 53-380 μg/mL. Methanol extract of T. indica and acetone extract of M. zapota seeds were found to be bactericidal. <![CDATA[<b>Phytochemical and antioxidant studies of Laurera benguelensis growing in Thailand</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200004&lng=en&nrm=iso&tlng=en The aim of this study was to investigate metabolites of the lichen Laurera benguelensis. A high-performance liquid chromatographic (HPLC) method has been developed for the characterization of xanthones and anthraquinones in extracts of this lichen. Lichexanthone, secalonic acid D, norlichexanthon, parietin, emodin, teloschistin and citreorosein were detected in the lichen samples, which were collected from two places in Thailand. Components of the lichen were identifed by relative retention time and spectral data. This is the frst time that a detailed phytochemical analysis of the lichen L. benguelensis was reported and this paper has chemotaxonomic signifcance because very little has been published on the secondary metabolites present in Laurera species. Some of the metabolites were detected for the frst time in the family Trypetheliaceae. The results of preliminary testing of benzene extract and its chloroform and methanol fractions showed that all samples showed a weak radical scavenging activity. The chloroform extract showed the highest antioxidant activity. <![CDATA[<b><i>In Vitro </i></b><b>Genotoxic Effects of Four Helichrysum Species in Human Lymphocytes Cultures</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200005&lng=en&nrm=iso&tlng=en Helichrysum sanguineum, Helichrysum pamphylicum, Helichrysum orientale, Helichrysum noeanum (Asteraceae) are medicinal plants. For centuries, they have been used as tea in Turkey because of their medicinal properties. So far no scientifc evidence has been found in a literature survey regarding the genotoxic effects of these plants. This work evaluated the genotoxic effects on human lymphocyte cultures induced by methanol extracts of these plants, assayed in different concentrations (0.01, 0.05, 0.1, 0.5 and 1 mg/mL). According to the results, Helichrysum noeanum, Helichrysum pamphylicum and Helichrysum sanguineum induced the formation of micronuclei and decreased the mitotic and replication indexes. Helichrysum orientale did not affect these parameters, whereas Helichrysum noeanum, Helichrysum pamphylicum and Helichrysum sanguineum were clearly genotoxic. They should therefore not be used freely in alternative medicine, although their antiproliferative activity may suggest antimitotic and anticarcinogenic properties. Helichrysum orientale could be used in alternative medicine. <![CDATA[<b>Effects of heat stress on some blood parameters and egg production of Shika Brown layer chickens transported by road</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200006&lng=en&nrm=iso&tlng=en The effects of vitamins C and E on layer chickens transported by road for 6 h during the hot dry season were investigated. Two experimental groups consisting of thirty Shika Brown layers were separately administered vitamins C and E orally just before transportation, while another 30 layers, which were only given sterile water, served as control. Blood samples analyzed before and after transportation in the control layers showed a decrease (p<0.05) in total white blood cell, (p<0.01) lymphocyte and monocyte values, and a signifcant (p<0.05) and (p<0.001) increase in the values of eosinophils and heterophils post-transportation, respectively. In the experimental groups, post-transportation values of total white blood cells, eosinophils and monocytes were not different (p>0.05) from those obtained before transportation. Heterophil/lymphocyte values were highest in the control group. The result showed that transportation was stressful for the control layers. Post-transportation egg production was not signifcantly (p>0.05) different in the vitamin E treated group, but values recorded for the vitamin C and control groups were signifcantly (p<0.05) and (p<0.001) reduced compared to pre-transportation. In conclusion, vitamins C and E administration ameliorated the adverse effect of road transportation stress during the hot dry season. <![CDATA[<b>The Role of Tyrosine 207 in the Reaction Catalyzed by Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200007&lng=en&nrm=iso&tlng=en The functional signifcance of tyrosine 207 of Saccharomyces cerevisiae phosphoenolpyruvate carboxykinase was explored by examining the kinetic properties of the Tyr207Leu mutant. The variant enzyme retained the structural characteristics of the wild-type protein as indicated by circular dichroism, intrinsic fuorescence spectroscopy, and gel-exclusion chromatography. Kinetic analyses of the mutated variant showed a 15-fold increase in Km CO2, a 32fold decrease in Vmax, and a 6-fold decrease in Km for phosphoenolpyruvate. These results suggest that the hydroxyl group of Tyr 207 may polarize CO2 and oxaloacetate, thus facilitating the carboxylation/decarboxylation steps. <![CDATA[<b><i>Lucilia sericata </i></b><b>strain from Colombia: Experimental Colonization, Life Tables and Evaluation of Two Artifcial Diets of the Blowfy <i>Lucilia sericata </i>(Meigen) (Diptera: Calliphoridae), Bogotá, Colombia Strain</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200008&lng=en&nrm=iso&tlng=en The objective of this work was to establish, under experimental laboratory conditions, a colony of Lucilia sericata, Bogotá-Colombia strain, to build life tables and evaluate two artifcial diets. This blowfy is frequently used in postmortem interval studies and in injury treatment. The parental adult insects collected in Bogotá were maintained in cages at 22°C±1 average temperature, 60%±5 relative humidity and 12 h photoperiodicity. The blowfies were fed on two artifcial diets that were evaluated over seven continuous generations. Reproductive and population parameters were assessed. The life cycle of the species was expressed in the number of days of the different stages: egg = 0.8±0.1, larvae I = 1.1±0.02, larvae II = 1.94±0.16, larvae III = 3.5±0.54, pupae = 6.55±0.47, male adult = 28.7±0.83 and female adult = 33.5±1.0. Total survival from egg stage to adult stage was 91.2% for diet 1, while for diet 2 this parameter was 40.5%. The lifetime reproductive output was 184.51±11.2 eggs per female. The population parameters, as well as the reproductive output of the blowfies that were assessed, showed relatively high values, giving evidence of the continuous increase of the strain over the different generations and making possible its maintenance as a stable colony that has lasted for more than two years. <![CDATA[<b>Bone resorptive activity of osteoclast-like cells generated in vitro by PEG-induced macrophage fusion</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200009&lng=en&nrm=iso&tlng=en Normal bone remodeling is maintained by a balance between osteoclast and osteoblast activity, whereas defects in osteoclast activity affecting such balance result in metabolic bone disease. Macrophage-macrophage fusion leading to multinucleated osteoclasts being formed is still not well understood. Here we present PEG-induced fusion of macrophages from both U937/A and J774 cell lines and the induced differentiation and activation of osteoclast-like cells according to the expression of osteoclast markers such as tartrate resistant acid phosphatase (TRAP) and bone resorptive activity. PEG-induced macrophage fusion, during the non-confuent stage, signifcantly increased the osteoclastogenic activity of macrophages from cell lines compared to that of spontaneous cell fusion in the absence of PEG (polyethylene glycol). The results shown in this work provide evidence that cell fusion per se induces osteoclast-like activity. PEG-fused macrophage differential response to pretreatment with osteoclastogenic factors was also examined in terms of its ability to form TRAP positive multinucleated cells (TPMNC) and its resorptive activity on bovine cortical bone slices. Our work has also led to a relatively simple method regarding those previously reported involving cell co-cultures. Multinucleated osteoclast-like cells obtained by PEG-induced fusion of macrophages from cell lines could represent a suitable system for conducting biochemical studies related to basic macrophage fusion mechanisms, bone-resorption activity and the experimental search for bone disease therapeutic alternatives. <![CDATA[<b>Ethyl acetate fraction from Cudrania tricuspidata inhibts IL-1</b><b>β</b><b>-induced rheumatoid synovial fibroblast proliferation and MMPs, COX-2 and PGE2 production</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200010&lng=en&nrm=iso&tlng=en Objectives: The objective of this study is to determine the effects of Ethyl acetate fraction from Cudrania tricuspidata (EACT) on the interleukin-1b (IL-1b)-induced proliferation of rheumatoid synovial fbroblasts (RASFs) and production of matrix metalloproteinases (MMPs), cyclooxygenase (COX) and prostaglandin E2 (PGE2) by RASFs. Materials and Methods: The proliferation of RASFs was evaluated with CCK-8 reagent in the presence of IL-1b with/without EACT. The expression of MMPs, TIMP-1, COXs, PGE2 and intracellular MAPK signalings, including p-ERK, p-p38, p-JNK and NF-kB were examined by immunoblotting or semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and ELISA in conditions as described above. Results: EACT inhibits IL-1β-induced proliferation of RASFs and MMP-1, 3, COX-2 mRNA and protein expression, PGE2 production induced with IL-1b. EACT also inhibits the phosphorylation of ERK-1/2, p38, JNK and activation of NF-kB by IL-1b. Conclusions: These results suggest that EACT might be involved in synovial fbroblast proliferation and MMPs, COX-2, and PGE2 production, which are involved in joint destruction in rheumatoid arthritis (RA), indicating that this might be a new therapeutic modality for management of rheumatoid arthritis. <![CDATA[<b>Sera of Chagasic patients react with antigens from the tomato parasite <i>Phytomonas serpens</i></b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200011&lng=en&nrm=iso&tlng=en The genus Phytomonas comprises trypanosomatids that can parasitize a broad range of plant species. These fagellates can cause diseases in some plant families with a wide geographic distribution, which can result in great economic losses. We have demonstrated previously that Phytomonas serpens 15T, a tomato trypanosomatid, shares antigens with Trypanosoma cruzi, the agent of human Chagas disease. Herein, two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS) were used to identify proteins of P. serpens 15T that are recognized by sera from patients with Chagas disease. After 2D-electrophoresis of whole-cell lysates, 31 peptides were selected and analyzed by tandem mass spectrometry. Twenty-eight polypeptides were identifed, resulting in 22 different putative proteins. The identifed proteins were classifed into 8 groups according to biological process, most of which were clustered into a cellular metabolic process category. These results generated a collection of proteins that can provide a starting point to obtain insights into antigenic cross reactivity among trypanosomatids and to explore P. serpens antigens as candidates for vaccine and immunologic diagnosis studies. <![CDATA[<b>Effect of alternating the magnetic feld on phosphate metabolism in the nervous system of <i>Helix pomatia</i></b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200012&lng=en&nrm=iso&tlng=en The effect of extremely low frequency magnetic felds (50 Hz, 0.5 mT) - ELF-MF, on phosphate metabolism has been studied in the isolated ganglions of the garden snail Helix pomatia, after 7 and 16 days of snail exposure to ELF-MF. The infuence of ELF-MF on the level of phosphate compounds and intracellular pH was monitored by 31P NMR spectroscopy. Furthermore, the activity of enzymes involved in phosphate turnover, total ATPases, Na+/K+-ATPase and acid phosphatase has been measured. The exposure of snails to the ELF-MF for the period of 7 days shifted intracellular pH toward more alkaline conditions, and increased the activity of investigated enzymes. Prolonged exposure to the ELF-MF for the period of 16 days caused a decrease of PCr and ATP levels and decreased enzyme activity, compared to the 7-day treatment group. Our results can be explained in terms of: 1. increase in phosphate turnover by exposure to the ELF-MF for the period of 7 days, and 2. adaptation of phosphate metabolism in the nervous system of snails to prolonged ELF-MF exposure. <![CDATA[<b>Correlations of recognition memory performance with expression and methylation of brain-derived neurotrophic factor in rats</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200013&lng=en&nrm=iso&tlng=en Object recognition memory allows discrimination between novel and familiar objects. This kind of memory consists of two components: recollection, which depends on the hippocampus, and familiarity, which depends on the perirhinal cortex (Pcx). The importance of brain-derived neurotrophic factor (BDNF) for recognition memory has already been recognized. Recent evidence suggests that DNA methylation regulates the expression of BDNF and memory. Behavioral and molecular approaches were used to understand the potential contribution of DNA methylation to recognition memory. To that end, rats were tested for their ability to distinguish novel from familiar objects by using a spontaneous object recognition task. Furthermore, the level of DNA methylation was estimated after trials with a methyl-sensitive PCR. We found a signifcant correlation between performance on the novel object task and the expression of BDNF, negatively in hippocampal slices and positively in perirhinal cortical slices. By contrast, methylation of DNA in CpG island 1 in the promoter of exon 1 in BDNF only correlated in hippocampal slices, but not in the Pxc cortical slices from trained animals. These results suggest that DNA methylation may be involved in the regulation of the BDNF gene during recognition memory, at least in the hippocampus. <![CDATA[<b>Erratum</b>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602010000200014&lng=en&nrm=iso&tlng=en Object recognition memory allows discrimination between novel and familiar objects. This kind of memory consists of two components: recollection, which depends on the hippocampus, and familiarity, which depends on the perirhinal cortex (Pcx). The importance of brain-derived neurotrophic factor (BDNF) for recognition memory has already been recognized. Recent evidence suggests that DNA methylation regulates the expression of BDNF and memory. Behavioral and molecular approaches were used to understand the potential contribution of DNA methylation to recognition memory. To that end, rats were tested for their ability to distinguish novel from familiar objects by using a spontaneous object recognition task. Furthermore, the level of DNA methylation was estimated after trials with a methyl-sensitive PCR. We found a signifcant correlation between performance on the novel object task and the expression of BDNF, negatively in hippocampal slices and positively in perirhinal cortical slices. By contrast, methylation of DNA in CpG island 1 in the promoter of exon 1 in BDNF only correlated in hippocampal slices, but not in the Pxc cortical slices from trained animals. These results suggest that DNA methylation may be involved in the regulation of the BDNF gene during recognition memory, at least in the hippocampus.