Scielo RSS <![CDATA[Biological Research]]> https://scielo.conicyt.cl/rss.php?pid=0716-976020040001&lang=en vol. 37 num. 1 lang. en <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[EL FUTURO DE ESPAÑA DEPENDE DE LA CIENCIA]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100001&lng=en&nrm=iso&tlng=en <![CDATA[Recent advances in chromaffin cell biology: Summing up the last International Symposium on Chromaffin Cell Biology]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100002&lng=en&nrm=iso&tlng=en The International Symposium on Chromaffin Cell Biology (ISCCB) brings together a group of approximately 150 scientists from around the world who meet every 2 years to discuss recent advances in our understanding of biogenesis and motion of secretory vesicles, synthesis, storage and release of secreted products (catecholamines, chromogranins, ATP), and mechanisms involving the excitation-secretion coupling, membrane ion channels, intracellular calcium homeostasis and exocytosis. The development of new technologies that allow an accurate measurement of catecholamines, vesicle motion, exocytosis, etc. are also analyzed. The 12th ISCCB, organized by Ricardo Borges, took place on September 20-26, 2003, in La Palma, Canary Islands, Spain. In this article we describe the most recent and significant contributions to the 12th ISCCB. <![CDATA[The Circadian Timing System: Making Sense of day/night gene expression]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100003&lng=en&nrm=iso&tlng=en The circadian time-keeping system ensures predictive adaptation of individuals to the reproducible 24-h day/night alternations of our planet by generating the 24-h (circadian) rhythms found in hormone release and cardiovascular, biophysical and behavioral functions, and others. In mammals, the master clock resides in the suprachiasmatic nucleus (SCN) of the hypothalamus. The molecular events determining the functional oscillation of the SCN neurons with a period of 24-h involve recurrent expression of several clock proteins that interact in complex transcription/translation feedback loops. In mammals, a glutamatergic monosynaptic pathway originating from the retina regulates the clock gene expression pattern in the SCN neurons, synchronizing them to the light:dark cycle. The emerging concept is that neural/humoral output signals from the SCN impinge upon peripheral clocks located in other areas of the brain, heart, lung, gastrointestinal tract, liver, kidney, fibroblasts, and most of the cell phenotypes, resulting in overt circadian rhythms in integrated physiological functions. Here we review the impact of day/night alternation on integrated physiology; the molecular mechanisms and input/output signaling pathways involved in SCN circadian function; the current concept of peripheral clocks; and the potential role of melatonin as a circadian neuroendocrine transducer <![CDATA[Supramolecular complex formation in cell signaling and disease: an update on a recurrent theme in cell life and death]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100004&lng=en&nrm=iso&tlng=en The circadian time-keeping system ensures predictive adaptation of individuals to the reproducible 24-h day/night alternations of our planet by generating the 24-h (circadian) rhythms found in hormone release and cardiovascular, biophysical and behavioral functions, and others. In mammals, the master clock resides in the suprachiasmatic nucleus (SCN) of the hypothalamus. The molecular events determining the functional oscillation of the SCN neurons with a period of 24-h involve recurrent expression of several clock proteins that interact in complex transcription/translation feedback loops. In mammals, a glutamatergic monosynaptic pathway originating from the retina regulates the clock gene expression pattern in the SCN neurons, synchronizing them to the light:dark cycle. The emerging concept is that neural/humoral output signals from the SCN impinge upon peripheral clocks located in other areas of the brain, heart, lung, gastrointestinal tract, liver, kidney, fibroblasts, and most of the cell phenotypes, resulting in overt circadian rhythms in integrated physiological functions. Here we review the impact of day/night alternation on integrated physiology; the molecular mechanisms and input/output signaling pathways involved in SCN circadian function; the current concept of peripheral clocks; and the potential role of melatonin as a circadian neuroendocrine transducer <![CDATA[Optimization of a protocol for direct organogenesis of red clover (<I>Trifolium pratense L.</I>) meristems for breeding purposes]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100005&lng=en&nrm=iso&tlng=en A series of experiments were carried out in order to optimize a protocol for the direct organogenesis of Chilean red clover germplasm. A range of cultivars were used to analyze the effect of explant source (crown or stem meristems of vegetative plants), culture media and plant growth regulators. Our findings showed that stem meristems were easier to obtain, presented lower levels of contamination and a better development than crown meristems. The L2 medium showed better results than B5 and MS media for the cultivars and experimental lines studied. L2 medium supplemented with 0.003 mg/l of 4-amino-3,5,6-trichloropicolinic acid and 1.0 mg/l of 6-benzylaminopurine gave consistently better results and will be applied in our breeding program to propagate, maintain and eliminate viruses from elite red clover clones. <![CDATA[Impact of the Training Program on Lipid Profile and Cardiac Health]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100006&lng=en&nrm=iso&tlng=en The aim of this study was to investigate the effects of training programs on serum lipid profile and myocardial oxidative stress. Male Wistar rats (2 mo-old) were divided into three groups (n=8): sedentary (S), loadless trained (T) and trained-overload 2% body weight (TL). T and TL were trained through swimming for 9 weeks. T and TL rats had increased myocardial lipoperoxide (TBA) and lipid hydroperoxide (HP), whereas HP was higher in TL than in T animals. Superoxide dismutase (SOD) activities were lowest in TL. Myocardial glutathione peroxidase (GSH-Px) was lower in TL than in T and S rats. TL decreased HDL-cholesterol and increased LDL-cholesterol. The serum lactate dehydrogenase and TBA were increased, while SOD and GSH-Px activities were decreased in TL rats. Loadless training was able to improve HDL-cholesterol and to reduce LDL-cholesterol. In conclusion, the loadless training program induced beneficial effects on lipid profile, while overload training induced dyslipidemic profile that was associated with serum oxidative stress. The overload training program was deleterious relative to loadless training program, increasing myocardial oxidative stress. <![CDATA[Effects of buthionine sulfoximine nifurtimox and benznidazole upon trypanothione and metallothionein proteins in <I>Trypanosoma cruzi. </I>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100007&lng=en&nrm=iso&tlng=en Proteins rich in sulfhydryl groups, such as metallothionein, are present in several strains of the parasite Trypanosoma cruzi, the etiological agent of Chagas' disease. Metallothionein-like protein concentrations ranged from 5.1 to 13.2 pmol/mg protein depending on the parasite strain and growth phase. Nifurtimox and benznidazole, used in the treatment of Chagas' disease, decreased metallothionein activity by approximately 70%. T. cruzi metallothionein was induced by ZnCl2. Metallothionein from T. cruzi was partially purified and its monobromobimane derivative showed a molecular weight of approximately 10,000 Da by SDS-PAGE analysis. The concentration of trypanothione, the major glutathione conjugate in T. cruzi, ranged from 3.8 to 10.8 nmol/mg protein, depending on the culture phase. The addition of buthionine sulfoximine to the protozoal culture considerably reduced the concentration of trypanothione and had no effect upon the metallothionein concentration. The possible contribution of metallothionein-like proteins to drug resistance in T. cruzi is discussed. <![CDATA[Replicase mediated resistance against Potato Leafroll Virus in potato Desirée plants]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100008&lng=en&nrm=iso&tlng=en Potato leafroll virus (PLRV) is a major menace for the potato production all over the world. PLRV is transmitted by aphids, and until now, the only strategy available to control this pest has been to use large amounts of insecticides. Transgenic approaches involving the expression of viral replicases are being developed to provide protection for plants against viral diseases. The purpose of this study was to compare the protection afforded by the differential expression of PLRV replicase transgene in potato plants cv. Desirée. Plants were genetically modified to express the complete sense PLRV replicase gene. Two constructions were used, one containing the constitutive 35SCaMV promoter and the other the phloem-specific RolA promoter from Agrobacterium rhizogenes. Transgenic plants were infected with PLRV in vitro, using infested aphids. In plants in which 35SCaMV controlled the expression of the PLRV replicase gene, signs of infection were initially detected, although most plants later developed a recovery phenotype showing undetectable virus levels 40 days after infection. In turn, those plants with the RolA promoter displayed an initial resistance that was later overcome. Different molecular mechanisms are likely to participate in the response to PLRV infection of these two types of transgenic plants. <![CDATA[Study of the expression of carotenoid biosynthesis genes in wild-type and deregulated strains of Xanthophyllomyces dendrorhous (Ex.: Phaffia rhodozyma)]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100009&lng=en&nrm=iso&tlng=en The expression, at the mRNA level, of carotenoid biosynthetic genes from Xanthophyllomyces dendrorhous was studied by RT-PCR. The experimental conditions for the RT-PCR assay were standardized to quantify the relative transcript levels of idi, crtE, crtYB and crtI genes. This work attempted to correlate astaxanthin production with the transcript levels of carotenogenic genes in a wild-type strain (UCD 67-385) and two overproducer deregulated strains (atxS1 and atxS2). At 3 day cultures, the wild-type strain contained higher transcript levels from the crtE and crtYB genes on minimal medium than on rich medium. Similarly, carotenoid production was higher on minimal medium than on rich medium. However, carotenoid production in the atxS1 and atxS2 strains was not correlated with the transcript level of carotenogenic genes under the same experimental conditions. This result suggests that there is not a linear relationship between carotenogenic transcript levels and carotenoid biosynthesis. <![CDATA[Age Dependence of the Levels of Plasma Norepinephrine, Aldosterone, Renin Activity and Urinary Vanillylmandelic Acid in Normal and Essential Hypertensives]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100010&lng=en&nrm=iso&tlng=en In the present study the upper reference limits (URLs) for resting plasma norepinephrine, epinephrine, serum aldosterone, plasma renin activity, aldosterone/ renin activity ratio, as well as urinary vanillylmandelic acid in healthy Egyptian normotensive subjects over a range of ages (5-60 yr) were established. There was a significant age effect on plasma norepinephrine, UVMA, serum aldosterone and PRA, whereas a single URL for plasma epinephrine level is satisfactory. In uncomplicated untreated essential hypertensive subjects (5-60 yr), the average prevalence of elevation in the plasma norepinephrine, epinephrine and urinary vanillylmandelic acid above their corresponding URLs was 85.10,62.15 and 83.20 %, respectively. This suggests that elevation in plasma catecholamine concentrations is more likely a common consequence than playing a possible role in the pathogenesis of hypertension, supported by insignificant correlation coefficients between the plasma catecholamine levels and resting systolic and diastolic blood pressure values (SBP&DBP) in all hypertensive age groups. Primary hyperaldosteronism was not detected among the normokalemic essential hypertensives at any age using aldosterone /plasma renin activity ratio as a primary screening method. In the present study, 7 statistically significant positive coefficient correlations are reported for SBP or DBP values with UVMA levels in hypertensive children and adolescents, serum aldosterone in old hypertensives, and PRA in adult hypertensives. <![CDATA[The acetyl xylan esterase II gene from <I>Penicillium purpurogenum </I>is differentially expressed in several carbon sources, and tightly regulated by pH]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100011&lng=en&nrm=iso&tlng=en The expression of the acetyl xylan esterase II (axeII) gene from Penicillium purpurogenum is repressed by glucose and induced by xylan, as well as to a small degree by xylose and xylitol. This gene is expressed at neutral pH, but not under alkaline or acidic conditions, in agreement with previous findings for other xylanolytic genes of this organism. This is the first report showing pH regulation of an axe gene. https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602004000100012&lng=en&nrm=iso&tlng=en