Scielo RSS <![CDATA[Biological Research]]> https://scielo.conicyt.cl/rss.php?pid=0716-976020030003&lang=en vol. 36 num. 3-4 lang. en <![CDATA[SciELO Logo]]> https://scielo.conicyt.cl/img/en/fbpelogp.gif https://scielo.conicyt.cl <![CDATA[Sobre el deber académico]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300001&lng=en&nrm=iso&tlng=en <![CDATA[Cholesterol oxidation: Health hazard and the role of antioxidants in prevention]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300002&lng=en&nrm=iso&tlng=en Cholesterol is a molecule with a double bond in its structure and is therefore susceptible to oxidation leading to the formation of oxysterols. These oxidation products are found in many commonly-consumed foods and are formed during their manufacture and/or processing. Concern about oxysterols consumption arises from the potential cytotoxic, mutagenic, atherogenic, and possibly carcinogenic effects of some oxysterols. Eggs and egg-derived products are the main dietary sources of oxysterols. Thermally-processed milk and milk-derived products are another source of oxysterols in our diet. Foods fried in vegetable/animal oil, such as meats and French-fried potatoes, are major sources of oxysterols in the Western diet. Efforts to prevent or to reduce cholesterol oxidation are directed to the use of antioxidants of either synthetic or natural origin. Antioxidants are not only able to inhibit triglyceride oxidation, some of them can also inhibit cholesterol oxidation. Among synthetic antioxidants 2, 6-di-tertiarybutyl-4-methylphenol (BHT), and tertiary butylhydroquinone (TBHQ) can efficiently inhibit the thermal-induced oxidation of cholesterol. Some natural antioxidants, such as alpha- and gamma-tocopherol, rosemary oleoresin extract, and the flavonoid quercetin, show strong inhibitory action against cholesterol oxidation. <![CDATA[Ciliary Neurotrophic Factor (CNTF) affects the excitable and contractile properties of innervated skeletal muscles]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300003&lng=en&nrm=iso&tlng=en The well-established trophic role of CNTF upon neurons led to performing clinical trials in patients of neurodegenerative diseases. However, trials were suspended due to side effects such as severe weight loss, hyperalgesia, coughing, muscle cramps and pain. So far it is not known how CNTF triggers the problems related to skeletal muscle cramps and pain. CNTF has also been described as a myotrophic factor for denervated skeletal muscles, but the possibility that it affects innervated muscles has also been considered. Since a myotrophic factor could be a valuable tool for treatment of several muscle diseases, we studied the effects of low doses of CNTF delivered systemically by an osmotic pump, over the electrical and mechanical properties of innervated and denervated fast and slow muscles. CNTF induced spontaneous electrical discharges and slowed twitches in innervated muscles, but did not prevent the changes induced by denervation. We postulate that the spontaneous discharges induced by CNTF in innervated muscles may be the cause of the cramps, coughing, and muscle ache reported by patients. At low doses, CNTF does not exert its myotrophic role over denervated muscles but clearly affects the excitable and contractile properties of innervated muscles. <![CDATA[Immunoresponse of Coho salmon immunized with a gene expression library from <i>Piscirickettsia salmonis </i>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300004&lng=en&nrm=iso&tlng=en We have used the expression library immunization technology to study the protection of Coho salmon Oncorhynchus kisutch to the infection with Piscirickettsia salmonis. Purified DNA from this bacterium was sonicated and the fragments were cloned in the expression vector pCMV-Bios. Two libraries were obtained containing 22,000 and 28,000 colonies and corresponding to approximately 8 and 10 times the genome of the pathogen, respectively. On average, the size of the inserts ranged between 300 and 1,000 bp. The plasmid DNA isolated from one of these libraries was purified and 20 µg were injected intramuscularly into 60 fish followed by a second dose of 10 µg applied 40 days later. As control, fish were injected with the same amount of DNA of the vector pCMV-Bios without insert. The titer of IgM anti-P. salmonis of vaccinated fish, evaluated 60 days post-injection, was significantly higher than that of the control group injected with the vector alone. Moreover, this response was specific against P. salmonis antigens, since no cross reaction was detected with Renibacterium salmoninarum and Yersinia ruckeri. The vaccinated and control fish were challenged 60 days after the second dose of DNA with 2.5 x 10(7) P. salmonis corresponding to 7.5 times the LD50. At 30 days post-challenge, 100% mortality was obtained with the control fish while 20% of the vaccinated animals survived. All surviving fish exhibited a lower bacterial load in the kidney than control fish. The expression library was also tested in Balb/c mice and it was found that the humoral immune response was specific to P. salmonis and it was dependent on the amount of DNA injected <![CDATA[The action of ovarian hormones in cardiovascular disease]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300005&lng=en&nrm=iso&tlng=en The incidence of cardiovascular disease (CAD) differs between men and women, in part because of differences in risk factors and hormones. This sexual dimorphism means a lower incidence in atherosclerotic diseases in premenopausal women, which subsequently rises in postmenopausal women to eventually equal that of men. These observations point towards estrogen and progesterone playing a lifetime protective role against CAD in women. As exogenous estrogen and estrogen plus progesterone preparations produce significant reductions in low-density lipoprotein (LDL) cholesterol levels and significant increases in high-density lipoprotein (HDL) cholesterol, this should in theory lower the risk of CAD. However, results from oral contraceptive (OC) use and combined estrogen and progesterone hormone replacement therapy (HRT) have suggested that hormone replacement regimes do not provide cardiovascular protection. In fact, depending on the preparation and the presence or absence of genetic risk factors, an increased risk of cardiovascular diseases such as venous thrombosis, myocardial infarction (MI) and stroke have been observed. Interestingly, in the majority of studies the increase in risk was highest in the first year, after which an increase in risk was not observed, and in some studies a lower risk of CAD was evident after four or five years of exogenous hormone administration. While the debate continues about the merits of HRT, and several good reviews exist on the statistics of CAD in relation to exogenous hormones, we have decided to review the literature to piece together the physiological actions of estrogen and progesterone preparations on the individual mechanistic components leading to CAD; namely, the altered endothelium and the haemostatic balance between coagulation and fibrinolysis. We present possible mechanisms for how HRT and OCs protect against MI in the absence of cardiovascular risk factors but increase the incidence of MI in their presence. We also speculate on the roles played by hormones on the short- and long-term risks of cardiovascular disease. <![CDATA[Optimization of biomass, total carotenoids and astaxanthin production in <i>Haematococcus pluvialis</i> Flotow strain Steptoe (Nevada, USA) under laboratory conditions]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300006&lng=en&nrm=iso&tlng=en The microalga Haematococcus pluvialis Flotow is one of the natural sources of astaxanthin, a pigment widely used in salmon feed. This study was made to discover optimal conditions for biomass and astaxanthin production in H. pluvialis from Steptoe, Nevada (USA), cultured in batch mode. Growth was carried out under autotrophic (with NaNO3, NH4Cl and urea) and mixotrophic conditions (with 4, 8, 12 mM sodium acetate) under two photon flux densities (PFD) (35 and 85 µmol m-2 s-1). The carotenogenesis was induced by 1) addition of NaCl (0.2 and 0.8 %), 2) N-deprivation and 3) high PFD (150 µmol m-2 s-1). Total carotenoids were estimated by spectrophotometry and total astaxanthin by HPLC. Ammonium chloride was the best N-source for growth (k=0.7 div day-1, 228-258 mg l-1and 2.0 x 10(5) - 2.5 x 10(5) cells ml-1 at both PFD, respectively). With increasing acetate concentration, a slight increment in growth occurred only at 85 µmol m-2 s-1. Light was the best inductive carotenogenic factor, and the highest carotenoid production (4.9 mg l-1, 25.0 pg cell-1) was obtained in cultures pre-grown in nitrate at low light. The NaCl caused an increase in carotenoid content per cell at increasing salt concentrations, but resulted in a high cell mortality and did not produce any increment in carotenoid content per volume compared to cultures grown at 150 µmol m-2 s-1. The highest carotenoid content per cell (22 pg) and astaxanthin content per dry weight (10.3 mg g-1) (1% w/w) were obtained at 85 µmol m-2 s-1 with 0.8% NaCl. <![CDATA[Effects of g-hexachlorocyclohexane and L-3,3',5- triiodothyronine on rat liver cytochrome P4502E1- dependent activity and content in relation to microsomal superoxide radical generation]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300007&lng=en&nrm=iso&tlng=en Liver microsomal cytochrome P4502E1-dependent p-nitrophenol (PNP) hydroxylation and expression of cytochrome P4502E1 were studied in rats subjected to g-hexachlorocyclohexane (HCCH) or L-3,3,,5-triiodothyronine (T3) administration as a possible mechanism contributing to superoxide radical (O2.-) generation. HCCH treatment (a single dose of 40 mg/kg body wt) produced a 43% increase in the content of total cytochrome P450, whereas T3 (daily doses of 0.1 mg/kg body wt for two consecutive days) led to a 37% decrease. NADPH-dependent O2.- generation was elevated by HCCH and T3, expressed as either per mg of protein or per nmol of cytochrome P450, with a 135% enhancement in the O2.- production/superoxide dismutase (SOD) activity ratios being observed in both conditions. This was partly due to depression of SOD activity. Concomitantly, the molecular activity of NADPH-cytochrome p450 reductase was enhanced by 90 and 69% by HCCH and T3, respectively. In these conditions, microsomal PNP hydroxylation showed increases of 58 and 45% in HCCH- and T3-treated rats over control values, respectively, with a parallel 31% (HCCH) and 41% (T3) enhancement in the content of cytochrome P4502E1 assessed by western immunoblotting. We conclude that HCCH and T3 enhance the expression and activity of cytochrome P4502E1 and that of NADPH-cytochrome P450 reductase in rat liver, regardless of the changes in total cytochrome P450 content, representing major contributory mechanisms to microsomal NADPH-dependent O2.- generation <![CDATA[Divalent cation hinder the solubilization of a tubulin kinase activity from <i>Trypanosoma cruzi </i>epimastigotes]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300008&lng=en&nrm=iso&tlng=en Trypanosoma cruzi epimastigotes were extracted under various conditions in order to examine the role of divalent cations in the solubilization of microtubule proteins. When epimastigotes were homogenized in the presence of 5 mM Mg+2 and 5 mM Ca+2, a protein kinase responsible for phosphorylating tubulin, as well as the tubulin that became phosphorylated, remained tightly associated with the parasite particulate and detergent-resistant fractions. On the contrary, tubulin kinase and its substrate were predominantly released into the parasite cytosolic and detergent-soluble fractions, when epimastigotes were extracted in the presence of 5 mM EDTA and 5 mM EGTA. These evidences demonstrated a divalent cation-dependent solubilization of the enzyme responsible for the phosphorylation of tubulin in T. cruzi epimastigotes and suggested a tight association between tubulin and this kinase. Under all conditions tested, tubulin kinase activity in epimastigote extracts was lower than the addition of the corresponding value in the parasite cytosolic and membranous fractions, suggesting the presence of a kinase inhibitor or regulatory subunit which also seemed to be modulated by divalent cations. Additionally, inhibition experiments in the presence of heparin, 2,3-bisphosphoglycerate and GTP established that the parasite tubulin kinase corresponded to a protein kinase CK2 <![CDATA[p53-Independent checkpoint controls in a plant cell model]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300009&lng=en&nrm=iso&tlng=en Allium cepa L. meristems were used as a plant model to study the p53-independent control of S and G2 phases by checkpoint pathways, in eukaryotic cells. Checkpoint blocks were induced at early and mid S by hydroxyurea. After their spontaneous override, cells became accumulated in G2-prophase, giving rise later on to a delayed mitotic wave. Cell growth was maintained during the checkpoint blocks, as the delayed mitoses were larger in size than the control ones. Under continuous hydroxyurea treatment, the delayed mitotic was formed by two subpopulations: normal mitoses corresponding to cells having properly recovered from the checkpoint block, and abnormal ones resulting from checkpoint adaptation. These latter cells displayed broken chromatids as they had unduly overriden the G2 checkpoint block, without completing DNA repair. The frequency of the checkpoint-adapted mitoses increased with the hydroxyurea concentration from 0.25 to 1.0 mM. However, from 1 mM hydroxyurea upwards, some of the cells lost their competence for checkpoint adaptation. Therefore, the dose of a genotoxic agent that still allows G2 checkpoint adaptation should always be applied in order to get rid of uncontrolled proliferating cells. This is specially suitable for cells lacking a functional p53 protein <![CDATA[Identification of functionally important acidic residues in transducin by group-specific labeling]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300010&lng=en&nrm=iso&tlng=en Transducin (T), a GTP-binding protein involved in phototransduction of rod photoreceptor cells, is a heterotrimer arranged as two units, the a-subunit (Ta) and the bg-complex (Tbg). The role of the carboxyl groups in T was evaluated by labeling with N, N'-dicyclohexylcarbodiimide (DCCD) and 1-ethyl 3-(3-dimethylaminopropyl) carbodiimide (EDC). Only a minor effect on the binding of b, g-imido guanosine 5'-triphosphate (GMPpNp) to T was observed in the presence of the hydrophobic carbodiimide, DCCD. Similarly, the GMPpNp binding activity of the reconstituted holoenzyme was not significantly affected when Ta was combined with DCCD-treated Tbg. However, the binding of guanine nucleotides to the reconstituted T was ~50% inhibited when DCCD-labeled Ta was incubated with Tbg. In contrast, treatment of T with the hydrophilic carbodiimide, EDC, completely impaired its GMPpNp-binding ability. EDC-modified T was incapable of interacting with illuminated rhodopsin, as determined by sedimentation experiments. However, rhodopsin only partially protected against the inactivation of T. Additionally, analyses of trypsin digestion patterns showed that fluoroaluminate was not capable of activating the EDC-labeled T sample. The function of the reconstituted holoenzyme was also disrupted when EDC-modified Ta was combined with Tbg, and when EDC-treated Tbg was incubated with Ta <![CDATA[Dimensional analysis revisited]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300011&lng=en&nrm=iso&tlng=en The applicability of dimensional analysis (DA) is discussed in relation to the metabolic scaling laws. The evolution of different theories of biological similarity has shown that the calculated reduced exponents (b) of Huxley's allometric equation are closely correlated with the numerical values obtained from the statistical analysis of empirical data. Body mass and body weight are not equivalent as biological reference systems, since in accordance to Newton's second law, the former has a dimension of a mass, while the latter should be dimensionally considered as a force (W = MLT-2). This distinction affects the coefficients of the mass exponent (a). This difference is of paramount importance in microgravity conditions (spaceflight) and of buoyancy during the fetal life in mammals. Furthermore, the coefficients (ß) of the length dimension, and (g) of the time dimension do not vary when mass or weight are utilized as reference systems. Consequently, the "specific metabolic time," that results from the ratio of basal oxygen consumption and body mass or body weight yields the "biological meaning" of the time dimension, which is of fractal nature. <![CDATA[The development of <i>Alternaria alternata </i>is prevented by chitinases and ß-1,3- glucanases from <i>Citrus limon</i> seedlings]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300012&lng=en&nrm=iso&tlng=en In addition to phytoalexin synthesis, the defense response of intact Citrus limon seedlings against Alternaria alternata involves both constitutive and induced enzyme activities such as chitinases (Ch) and ß-1,3-glucanases (Glu). A. alternata conidial germination was prevented by protein extracts from inoculated lemon seedlings, but also by extracts from mock-inoculated specimens. On the other hand, degradation of mycelia was accomplished only by protein extracts from inoculated seedlings. The presence of six Ch isoenzymes and of four Glu isoenzymes was detected in protein extracts from mock-inoculated seedlings. As a result of fungal inoculation, the isoenzyme pattern of Ch and Glu changed, making possible the detection of a new Ch isoenzyme and of three new Glu. Also, some constitutive Ch and Glu increased their enzyme activity, and those Ch that increased their activy also showed a broadening of their substrate specificity. These changes were prevented by a-amanitin and cycloheximide, suggesting that the presence of new Ch and Glu isoenzymes was due to de novo synthesis of proteins. Results suggest that constitutive Ch and Glu could act as pre-formed defense molecules in Citrus limon preventing A. alternata germination, while those induced after fungal inoculation of lemon seedlings could act along with the former, to produce lysis of fungal mycelia, resulting in a more efficient control of A. alternata development.. <![CDATA[Cloning and expression of the coding regions of the heat shock proteins HSP10 and HSP16 from <i>Piscirickettsia salmonis</i>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300013&lng=en&nrm=iso&tlng=en The genes encoding the heat shock proteins HSP10 and HSP16 of the salmon pathogen Piscirickettsia salmonis have been isolated and sequenced. The HSP10 coding sequence is located in an open reading frame of 291 base pairs encoding 96 aminoacids. The HSP16 coding region was isolated as a 471 base pair fragment encoding a protein of 156 aminoacids. The deduced aminoacid sequences of both proteins show a significant homology to the respective protein from other prokaryotic organisms. Both proteins were expressed in E. coli as fusion proteins with thioredoxin and purified by chromatography on Ni-column. A rabbit serum against P. salmonis total proteins reacts with the recombinant HSP10 and HSP16 proteins. Similar reactivity was determined by ELISA using serum from salmon infected with P. salmonis. The possibility of formulating a vaccine containing these two proteins is discussed <![CDATA[Overview on chemotaxis and acid resistance in Helicobacter pylori]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300014&lng=en&nrm=iso&tlng=en The genes encoding the heat shock proteins HSP10 and HSP16 of the salmon pathogen Piscirickettsia salmonis have been isolated and sequenced. The HSP10 coding sequence is located in an open reading frame of 291 base pairs encoding 96 aminoacids. The HSP16 coding region was isolated as a 471 base pair fragment encoding a protein of 156 aminoacids. The deduced aminoacid sequences of both proteins show a significant homology to the respective protein from other prokaryotic organisms. Both proteins were expressed in E. coli as fusion proteins with thioredoxin and purified by chromatography on Ni-column. A rabbit serum against P. salmonis total proteins reacts with the recombinant HSP10 and HSP16 proteins. Similar reactivity was determined by ELISA using serum from salmon infected with P. salmonis. The possibility of formulating a vaccine containing these two proteins is discussed <![CDATA[<B>XXVI REUNIÓN ANUAL DE LA SOCIEDAD DE BIOQUÍMICA Y BIOLOGÍA MOLECULAR DE CHILE </B>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300015&lng=en&nrm=iso&tlng=en The genes encoding the heat shock proteins HSP10 and HSP16 of the salmon pathogen Piscirickettsia salmonis have been isolated and sequenced. The HSP10 coding sequence is located in an open reading frame of 291 base pairs encoding 96 aminoacids. The HSP16 coding region was isolated as a 471 base pair fragment encoding a protein of 156 aminoacids. The deduced aminoacid sequences of both proteins show a significant homology to the respective protein from other prokaryotic organisms. Both proteins were expressed in E. coli as fusion proteins with thioredoxin and purified by chromatography on Ni-column. A rabbit serum against P. salmonis total proteins reacts with the recombinant HSP10 and HSP16 proteins. Similar reactivity was determined by ELISA using serum from salmon infected with P. salmonis. The possibility of formulating a vaccine containing these two proteins is discussed <![CDATA[<B>XLVI REUNION ANUAL DE LA SOCIEDAD DE BIOLOGIA DE CHILE XII REUNION ANUAL DE LA SOCIEDAD DE ECOLOGIA DE CHILE </B>]]> https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-97602003000300016&lng=en&nrm=iso&tlng=en The genes encoding the heat shock proteins HSP10 and HSP16 of the salmon pathogen Piscirickettsia salmonis have been isolated and sequenced. The HSP10 coding sequence is located in an open reading frame of 291 base pairs encoding 96 aminoacids. The HSP16 coding region was isolated as a 471 base pair fragment encoding a protein of 156 aminoacids. The deduced aminoacid sequences of both proteins show a significant homology to the respective protein from other prokaryotic organisms. Both proteins were expressed in E. coli as fusion proteins with thioredoxin and purified by chromatography on Ni-column. A rabbit serum against P. salmonis total proteins reacts with the recombinant HSP10 and HSP16 proteins. Similar reactivity was determined by ELISA using serum from salmon infected with P. salmonis. The possibility of formulating a vaccine containing these two proteins is discussed