Archivos de biologia y medicina experimentales最新文献

Marine mussels secrete the byssus in order to attach to solid surfaces and to survive under the turbulent effects of waves. The adhesive responsible for this attachment is the polyphenolic protein secreted by the phenol gland in the foot of the animal. To purify this adhesive protein from the chilean mussel Mylilus chilensis, a modification of previous procedures has been developed. Accordingly, the protein is differentially precipitated with acetone in the presence of 0.25 N HCl. The purified protein is rich in the amino acids lysine, 3,4-dihydroxyphenylalanine, serine, threonine, proline and hydroxyproline. The protein exhibited strong adhesion to glass and other solid supports. Moreover, it has been found that the adhesive protein can mediate the immobilization of beta-galactosidase to glass. About 75% of the enzyme activity was immobilized under the experimental conditions described. This is the first study reporting the use of the polyphenolic protein to immobilize enzymes.

The biology of planktotrophic larvae of Concholepas concholepas is the main bottleneck towards developing biotechnologies to rear this muricid. Data concerning planktonic larvae development, diets and environmental signals triggering larval settlement and recruitment is scarce. We have begun the study of the molecular and cell biology of embryos, larvae and recruits having as a final goal, the development of appropriate biotechnologies to rear this gastropod. First, an inverse ratio between BuChE and AChE enzyme activities was established. This ratio may be a precise developmental marker for this species. Second, for the first time a phosphoinositide related regulatory pathway is reported in a muricid, opening a new approach to the biotechnological management of larvae. Third, the relation between sulfate in sea water and larval motility was studied. Concentrations below 125 microM sulfate decreases larval motility. The sulfate is incorporated in proteoglycans which participate in different developmental phenomena. Lastly, a genomic Concholepas concholepas DNA sequence, similar to that of a human growth hormone probe was detected. This is very interesting since growth factors are key molecules during development, growth and are involved in food conversion rates in fish and also, in a variety of marine invertebrates.

Scientific productivity in Chile was studied examining a data bank constructed with the publications indexed by the Institute for Scientific Information during 1987 and 1988. The bank excludes meeting abstracts and contains the full title of the published paper, the list of authors, addresses, field, and the nature of collaboration between two or more institutions. The articles were classified in different fields and tabulated according to the institution from which they originated. Although biology remains to be the more productive subject (26.5%) followed by medical sciences (23.9%) and chemistry (12.3%), articles in mathematics and physics continued their increase as in previous years. Using the scientometric indicators published by Braun et al., the impact of the research originated in Chile in biology, physics and mathematics was compared to that attained in Argentina, Brazil, Mexico and Venezuela. The role of the chilean National Research Fund and the output of the financed research projects were also analyzed. The successful results obtained during the first years in which the National Research Fund has been involved in the support of the scientific activity in Chile, confirms the need to strengthen its budget, according to the goals stated in the National Plan for Science and Technology for Development.

To monitor the levels of Thiobacillus ferrooxidans in bioleaching operations, we have developed a specific and very sensitive dot-immunobinding assay. Polyclonal antisera against whole T. ferrooxidans cells was used, and the bacteria-antibody reaction was visualized by employing either 125I-labeled or peroxidase-conjugated protein A or 125I-labeled or peroxidase-conjugated goat anti-rabbit immunoglobulin G. A minimum of 10(3) cells per dot could be easily detected. Therefore, the method allows the sensitive, and specific simultaneous processing of numerous samples in a short time.

Pre- and post-emergence damping-off of canola seedlings caused by Rhizoctonia solani is a serious disease in Western Canada. Other fungi such as Fusarium spp. and Pythium spp. are also related to seedling damping-off. To-day, the search of soil bacteria is becoming a tool to use microorganisms as potential biocontrol agents for several plant diseases. The purpose of this research was to detect bacteria to biologically control R. solani, Pythium spp., and Fusarium spp. Soil samples were collected throughout Alberta during 1987 to isolate bacteria. Canola seedlings were also used to obtain bacteria from the same samples. Plant pathogenic fungi were tested to detect the antagonistic activity of the isolates. Tests were made with coated canola seeds, amendments and fresh of freeze-dried cells. Three hundred forty-one bacterial cultures were isolated. Only 16 inhibited fungal growth: 7 showed the same effects against R. solani and 9 showed uneven effects. Some isolates showed a weak action to Pythium spp. and Fusarium spp. Three isolates showed inhibitory effect on R. solani and Pythium spp. Isolate F1 improved by about 50% the germination of canola seeds in inoculated pots when compared with the inoculated control. Coated seeds had low germination and emergence was below the inoculated control. The emergence of canola seedlings was very much improved when isolate 147 was delivered as an amendment in inoculated pots. Identification showed that 3 bacterial belonged to Bacillus spp., 4 to green fluorescent Pseudomonas spp. and 2 were Streptomyces spp.

Lactase (beta-D galactoside-galactohydrolase, E.C.3.2.1.23) is a relevant enzyme to the dairy industry as it modifies undesirable functional and nutritional properties derived from the lactose content in milk and dairies, and as a way of recovering or upgrading cheese whey. This latter aspect has been considered to develop an enzyme catalyst suitable for the continuous hydrolysis of whey permeate. The selection of enzyme and support and the immobilization procedure has been reported previously. Results obtained in the immobilization of fungal lactase on activated chitin have prompted us to scale-up the procedure, a system being developed in which the enzyme is immobilized within the reactor (in situ). Results are presented for the in situ immobilization of lactase with and without recirculation of the reagents. Previous procedure was reproduced, although moderate profiles of activity were generated through the catalyst bed which were not eliminated by recirculation. Packed bed reactors with immobilized lactase were operated at varying flowrates and lactose concentrations, results being compared, in terms of substrate conversion and reactor productivity, with a theoretical model based on the corresponding kinetic expression and ideal flow regime. Deviations are significant at high flowrates which is attributed to backmixing and channeling through the catalyst bed. The model fits reasonably well at low flowrates and high feed substrate concentration. Productivity was 58 g of glucose/l.h at 40 ml/h of 120 g/l of lactose. Stability of the immobilized lactase was assessed in long-term reactor operation with whey permeate (35 g/l of lactose) at 40 degrees C and pH 4.0. Operational half-life was 120 days.

This study describes the financial support for research in Chile in different areas related to the productive sector including biotechnology. Four different sources which help research in the country through competitive research grants were analysed. These include: FONDECYT (National Fund for Research and Technology), Fondo de Desarrollo Productivo de CORFO (Fund for Productive Development), Fondo de Investigaciones Agropecuarias (Fund for Research in Agriculture and Livestock) and the IV Program for Technical Cooperation between the Chilean Government and UNDP. Biotechnology appears as one of the areas related to the productive sector having an important number of projects approved with a substantial financial support. Based in a survey, recommendations are made to improve the relationship between the productive and academic sector in biotechnology and other areas.

By using a specific, repetitive DNA probe, we have been able to detect picograms of P. berghei DNA. With this probe we have determined that: a) P. berghei, inoculated into Norway Brown rats, reaches its peak of proliferation in the liver 44 h after infection; b) gamma interferon inhibits in a dose-dependent fashion the development of liver exoerythrocytic forms (EEF) in vivo and in vitro, and; c) endogenous gamma interferon inhibits the development of EEF in hosts immunized with irradiated sporozoites. Related with and derived from these findings, we have found that, in order to obtain an effective immunity against malaria in experimental animal models, effector mechanisms mediated by T cells are required. This is substantiated by the following facts: a) immune hosts inoculated with monoclonal antibodies against gamma interferon reversed their immunity against a sporozoite challenge; b) This immunity was also reversed when the animals were depleted from their CD8 positive cytotoxic T cells. Therefore, sterile immunity against this parasite requires not only the presence of antibodies but also the inhibition of the EEF by gamma interferon with participation of CD8 positive T cells.

The invertase wild type gene of N. crassa was cloned into the YRp7 yeast vector. This recombinant plasmid was selected by functional complementation of an invertaseless mutant strain of S. cerevisiae. The isolated recombinant plasmid (named pNC2) carries a 7.6 Kb BamHI DNA fragment from N. crassa. The cloned DNA hybridized with the N. crassa genomic DNA and transformed an invertase mutant of N. crassa Inv- to Inv+. Transformation of N. crassa Inv- to Inv+ seems to take at least two different integration events. One of them involves an integration closely linked to inv locus, and the other one apparently involves an integration of cloned DNA at a genomic site different that the inv locus.

Adenosine exerts numerous effects in the central and autonomic nervous systems, most of which seem to be receptor mediated. Several studies have revealed two distinct receptors, based upon effects of adenosine on adenylate cyclase activity, designed A1 or A2 according to whether the cyclase is inhibited or activated. However, since not all adenosine receptors are linked to adenylate cyclase some authors base their classification on the rank orders of potencies of adenosine analogues in eliciting responses. The purine seems to function as a modulatory substance in the heart, blood, ileum, vas deferens, and adipose tissue. In addition, important responses to exogenously added adenosine are also induced in the bronchi, urinary bladder, taenia coli, parietal cells of the stomach and renin secretion. Adenosine and its analogues elicit anticonvulsant responses, sedation and hypothermia through their actions in the central nervous system. The mechanisms by which adenosine elicits its responses have not been clearly established. The activation of A1 receptors depresses the release of neurotransmitters and inhibit the influx of Ca into nerve terminals. Whether this effect is induced by interaction with Ca channels or by impairment of Ca dependent processes associated with neurotransmitter release is unknown. In the rat heart adenosine inhibits adenylate cyclase and subsequently the phosphorylation of L-type Ca channels, resulting in a decrease of calcium influx in the muscle cell. The responses to activation of A2 receptors in smooth muscle consist in relaxation presumptively by an increase of K current which would hyperpolarize the cell.