Scielo RSS <![CDATA[Biological Research]]> vol. 41 num. 2 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>Small-molecule aggregation inhibitors reduce excess amyloid in a trisomy 16 mouse cortical cell line</b>]]> We have previously characterized a number of small molecule organic compounds that prevent the aggregation of the β-amyloid peptide and its neurotoxicity in hippocampal neuronal cultures. We have now evaluated the effects of such compounds on amyloid precursor protein (APP) accumulation in the CTb immortalized cell line derived from the cerebral cortex of a trisomy 16 mouse, an animal model of Down's syndrome. Compared to a non-trisomic cortical cell line (CNh), CTb cells overexpress APP and exhibit slightly elevated resting intracellular Ca2+ levéis ([Ca2+]¡). Here, we show that the compounds 2,4-dinitrophenol, 3-nitrophenol and 4-anisidine decreased intracellular accumulation of APP in CTb cells. Those compounds were non-toxic to the cells, and slightly increased the basal [Ca2+]¡. Results indícate that the compounds tested can be leads for the development of drugs to decrease intracellular vesicular accumulation of APP in trisomic cells. <![CDATA[<b>Plant Science research productivity in Chile during the past 20 years</b>]]> The purpose of this study was to carry out a bibliometric analysis of the articles published in Chile during 1987-2006 that were categorized into the Plant Science discipline by ISI. The data was extracted from the Web of Science datábase, obtaining a total of 911 articles for analysis. Almost half of the articles were the outcome of an international collaboration, the United States being the country with more collaborative links with Chile within this discipline. A list was made with the 10 most-cited articles and 10 most frequently used journals. The analysis showed that almost 50% of the articles were concentrated in 10 different journals. The number of articles produced each year revealed a steady growth in scientific production since 1987. This is probably related to the progressive interaction between industry and public-research institutions. <![CDATA[<b>Abnormal Electrophysiological Activation in Schizophrenics during a Personal Traits Attribution Task </b>]]> Changes in personal identity have been described as a major component in the expression of schizophrenia. Considering current evidence that relates the cortical structures of the medial line with the self, we hypothesize that there are differences in the frontomedial electrophysiological activation in schizophrenics when compared to normal subjects during tasks that require this function. In an experimental design, 9 schizophrenic and 7 normal subjects participated in a personal traits attribution task regarding the attribution of the self, another person and a simple reading. Electric brain activity was recorded with a dense array of 128 electrodes, with evoked brain potentials being obtained for the three conditions. Considering the evoked potential morphology, repeated measures ANO VA were performed on the adaptive mean for the 180-230 ms time window (P200) in the frontomedial electrodes, with a group effect being found (F=5.352; p=0.038). Comparisons of the groups show that the schizophrenics presented less voltage in the seZ/condition (t=2.386; p=0.033). Although the results are not consistent with the hypothesis, it can be suggested that the early modulation of word-related meaning formation in a self-referential context could be affected in schizophrenia. <![CDATA[<b>Antioxidant activity of 50% aqueous - ethanol extract from <i>Acantholippia deserticola</i></b>]]> The antioxidant properties oí Acantholippia deserticola, a herb used in traditional northern Chilean medicine was studied using free radical - generating systems. The 50% aqueous - ethanol extract oí Acantholippia deserticola protected against non-enzymatic lipid peroxidation in microsomal membranes of rat, induced by an Fe++ - ascorbate system and measured spectrophotometrically by the TBARS test, and had strong free radical scavenging capacities on stable ABTS and DPPH radicáis. The results shows that the IC50 valué of the 50% aqueous - ethanolic extract oí A.deserticola is 18 ± 0.5 μg/mL in DPPH radical - scavenging, 15 ± 0.8 μg/mL in lipid peroxidation , Total Antioxidant Activity (TAA) is 0.95 mM of Trolox per mg/mL of extract. The total phenolics content of extract is 725 ± 12 mg of gallic acid equivalent per g of dried extract. The results indicate that the 50% aqueous - ethanol extract oí Acantholippia deserticola clearly has antioxidant properties. <![CDATA[<b>Association of <i>TNF </i>promoter polymorphisms with type 1 diabetes in the South Croatian population</b>]]> Type 1 diabetes mellitus (TIDM) is an autoimmune disease characterized by the destruction of pancreatic p cells. Tumor necrosis factor (TNF) is a pleotropic cytokine with potent immunomodulatory and inflammatory activity. Association studies of TNF polymorphisms and type 1 diabetes (TIDM) frequently demonstrated TNF involvement with TIDM. Although TNF may play an important role in the pathogenesis of TIDM, the genetic association of TNF región with the disease has not been conclusive because of the strong linkage disequilibrium with HLA genes. In this study, we examined two TNF promoter variants (rs 1800629 at position -308, and rs361525 at position -238) for TIDM association in 233 patients and 144 controls from the population of South Croatia. A higher frequency of TNF -308 A alíele and also, a more frequent specific -308A -238G haplotype in TIDM patients were observed with a limited significance. However, we did not find strong evidence of association of TNF promoter polymorphisms with TIDM. In order to elucidate the trae contribution of TNF to TIDM susceptibility in our population, more comprehensive studies with HLA adjustment in a larger sample are required. <![CDATA[<b>Free Radical Scavenging Profile and Myeloperoxidase Inhibition of Extracts from Antidiabetic Plants</b>: <b><i>Bauhinia forficata </i>and <i>Cissus sicyoides</i></b>]]> There is abundant evidence that reactive oxygen species are implicated in several physiological and pathological processes. To protect biological targets from oxidative damage, antioxidants must react with radicáis and other reactive species faster than biological substrates do. The aim of the present study was to determine the in vitro antioxidant activity of aqueous extracts from leaves of Bauhinia forficata Link (Fabaceae - Caesalpinioideae) and Cissus sicyoides L. (Vitaceae) (two medicinal plants used popularly in the control of diabetes mellitus), using several different assay systems, namely, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) decolorization, superoxide anión radical (0(2)•-) scavenging and myeloperoxidase (MPO) activity. In the ABTS assay for total antioxidant activity, B. forficata showed IC50 = 8.00±0.07 μg/mL, while C. sicyoides showed IC50 = 13.0±0.2 μg/mL. However, the extract of C. sicyoides had a stronger effect on 0(2)•- (IC50 = 60.0±2.3 μg/mL) than the extract of B. forficata (IC50 = 90.0±4.4 μg/ mL). B. forficata also had a stronger inhibitory effect on MPO activity, as measured by guaiacol oxidation, than C. sicyoides. These results indicate that aqueous extracts of leaves of B. forficata and C. sicyoides are a potential source of natural antioxidants and may be helpful in the prevention of diabetic complications associated with oxidative stress. <![CDATA[<b>Occurrence of killer yeast strains in industrial and clinical yeast isolates</b>]]> The secretion of proteinaceous toxins is a widespread characteristic in environmental and laboratory yeast isolates, a phenomenon called "killer system". The killer phenotype (K+) can be encoded by extrachromosomal genetic elements (EGEs) as double stranded DNA or RNA molecules (dsDNA, dsRNA) or in nuclear genes. The spectrum of action and the activity of killer toxins are influenced by temperature, salinity and pH of media. In the present work we determined the existence of K+ in a collection of S. cerevisiae and P. anómala yeasts isolated from environmental, industrial and clinical sources. The assays were performed in strains belonging to three yeast genera used as sensitive cells and under a wide range of pH and temperatures. Approximately 51 % of isolates tested showed toxicity against at least one sensitive yeast strain under the conditions tested. The K+ P. anómala isolates showed a wide spectrum of action and two of them had toxic activity against strains of the three yeast genera assayed, including C. albicans strains. In all S. cerevisiae K+ isolates an extrachromosomal dsRNA molecule (4.2 Kb) was observed, contrary to P. anómala K+ isolates, which do not possess any EGEs. The K+ phenotype is produced by an exported protein factor and the kinetics of killer activity production was similar in all isolates with high activity in the log phase of growth, decaying in the stationary phase. <![CDATA[<b>Methacholine and PDGF activate store-operated calcium entry in neuronal precursor cells via distinct calcium entry channels</b>]]> Neurons are a diverse cell type exhibiting hugely different morphologies and neurotransmitter specifications. Their distinctive phenotypes are established during differentiation from pluripotent precursor cells. The signalling pathways that specify the lineage down which neuronal precursor cells differentiate remain to be fully elucidated. Among the many signáis that impinge on the differentiation of neuronal cells, cytosolic calcium (Ca2+) has an important role. However, little is known about the nature of the Ca2+ signáis involved in fate choice in neuronal precursor cells, or their sources. In this study, we show that activation of either muscarinic or platelet-derived growth factor (PDGF) receptors induces a biphasic increase in cytosolic Ca2+ that consists of reléase from intracellular stores followed by sustained entry across the plasma membrane. For both agonists, the prolonged Ca2+ entry occurred via a store-operated pathway that was pharmacologically indistinguishable from Ca2+ entry initiated by thapsigargin. However, muscarinic receptor-activated Ca2+ entry was inhibited by siRNA-mediated knockdown of TRPC6, whereas Ca2+ entry evoked by PDGF was not. These data provide evidence for agonist-specific activation of molecularly distinct store-operated Ca2+ entry pathways, and raise the possibility of privileged communication between these Ca2+ entry pathways and downstream processes. <![CDATA[<b>Differences in lipogenesis and lipolysis in obese and non-obese adult human adipocytes</b>]]> It has been proposed that differences in adipocyte function and/or metabolism between obese and lean individuáis may manifest themselves in functional adipose tissue abnormalities that lead to metabolic disorders in obesity. We studied lipogenesis and lipolysis of omental adipocytes from obese (OB) and non-obese (NOB) humans. The specific activity of the lipogenic marker enzyme G3PDH was 50% lower in total adipocytes of OB compared to that of NOB subjects. Omental adipocytes from OB subjects also had lower basal lipolytic levéis, and a lower lipolytic response to p-adrenergic stimulus. Cholesterol depletion of adipocyte plasma membrane using methyl β-cyclodextrin caused a lipolytic effect on adipocytes of both groups together, but when obese and lean subjects were analyzed separately, the response was significant only in the obese. We present evidence of a different lipogenic and lipolytic profile in obese individuáis' omental adipocytes, and propose a relevant role of plasma membrane cholesterol, where the impact of its removal in OB and NOB adipocyte lipolysis differs. <![CDATA[<b>Distribution of linker histone variants during plant cell differentiation in the developmental zones of the maize root, dedifferentiation in callus culture after auxin treatment</b>]]> Although several linker histone variants have been studied in both animal and plant organisms, little is known about their distribution during processes that involve alterations in chromatin function, such as differentiation, dedifferentiation and hormone treatment. In this study, we identified linker histone variants by using specific anti-histone Hl antibodies. Each variant's ratio to total Hl in the three developmental zones of maize (Zea mays L.) root and in callus cultures derived from them was estimated in order to define possible alterations either during plant cell differentiation or during their dedifferentiation. We also evaluated linker histone variants' ratios in the developmental zones of maize roots treated with auxin in order to examine the effects of exogenous applied auxin to linker histone variant distribution. Finally, immunohistochemical detection was used to identify the root tissues containing each variant and correlate them with the physiological status of the plant cells. According to the results presented in this study, linker histone variants' ratios are altered in the developmental zones of maize root, while they are similar to the meristematic zone in samples from callus cultures and to the differentiation zone in samples from roots treated with auxin. We propose that the alterations in linker histone variants' ratios are correlated with plant cell differentiation and dedifferentiation. <![CDATA[<b>Hepatocytes, rather than leukocytes reverse DNA damage <i>in vivo </i>induced by whole body y-irradiation of mice, as shown by the alkaline comet assay</b>]]> DNA damage repair was assessed in quiescent (G0) leukocytes and in hepatocytes of mice, after 1 and 2 hours recovery from a single whole body y-irradiation with 0.5, 1 or 2 Gy. Evaluation of single-strand breaks (SSB) and alkali-labile sites together were carried out by a single-cell electrophoresis at pH>13.0 (alkaline comet assay). In non-irradiated (control) mice, the constitutive, endogenous DNA damage (basal) was around 1.5 times higher in leukocytes than in hepatocytes. Irradiation immediately increased SSB frequency in both cell types, in a dose-dependent manner. Two sequential phases took place during the in vivo repair of the radio-induced DNA lesions. The earliest one, present in both hepatocytes and leukocytes, further increased the SSB frequency, making evident the processing of some primary lesions in DNA bases into the SSB repair intermediates. In a second phase, SSB frequency decreased because of their removal. In hepatocytes, such a frequency regressed to the constitutive basal level after 2 hours recovery from either 0.5 orí Gy. On the other hand, the SSB repair phase was specifically abrogated in leukocytes, at the doses and recovery times analyzed. Thus, the efficiency of in vivo repair of radio-induced DNA damage in dormant cells (lymphocytes) is quite different from that in hepatocytes whose low proliferation activity accounts only for cell renewal. <![CDATA[<b>Regional differences in veins wall viscosity, compliance. energetics and damping</b>: <b>analysis of the pressure-diameter relationship during cyclical overloads</b>]]> Background: The characterization of the dynamic process of veins walls is essential to understand venous functioning under normal and pathological conditions. However, little work has been done on dynamic venous properties. Aim: To characterize vein compliance (C), viscosity (η), peak-strain (W St) and dissipated (W D) energy, damping (ξ), and their regional differences in order to evalúate their role in venous functioning during volume-pressure overloads. Methods: In a mock circulation, pressure (P) and diameter (D) of different veins (anterior cava, jugular and femoral; from 7 sheep), were registered during cyclical volume-pressure pulses. From the P-D relationship, C, W St and ξ (at low and high P-D leveis), η and W D were calculated. Resulls: For each vein there were P-dependent differences in biomechanical, energetics, and damping capability. There were regional-differences in C, η), W St and W D (p<0.05), but not in ξ. Conclusión: The regional-dependent differences in dynamics and energetics, and regional-similitude in damping could be important to ensure venous functioning during acute overloads. The lower C and higher W St and W D found in back-limb veins (femoral), commonly submitted to high volume-pressure loads (i.e. during walking), could be considered relevant to ensure adequate venous system functionality and venous wall protection simultaneously.