Scielo RSS <![CDATA[Biological Research]]> http://www.scielo.cl/rss.php?pid=0716-976020010003&lang=pt vol. 34 num. 3-4 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.cl/img/en/fbpelogp.gif http://www.scielo.cl <![CDATA[Planes de Desarrollo Gubernamentales en Ciencia y Tecnología:: ¿Promesas o Realidades?]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300001&lng=pt&nrm=iso&tlng=pt <![CDATA[RECIENTE CONGRESO DE LA SOCIEDAD CHILENA DE INMUNOLOGÍA]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300002&lng=pt&nrm=iso&tlng=pt <![CDATA[Transcriptome analysis and crop improvement: (A review)]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300003&lng=pt&nrm=iso&tlng=pt The identification and characterization of differential gene expression from tissues subjected to stress has gained much attention in plant research. The recognition of elements involved in the response to a particular stress enhances the possibility of promoting crop improvement through direct genetic modification. However, the performance of some of the `first generation' of transgenic plants with the incorporation of a single gene has not always been as expected. These results have stimulated the development of new transgenic constructions introducing more than one gene and capable of modifying complex pathways. Several techniques are available to conduct the analysis of gene regulation, with such information providing the basis for novel constructs specifically designed to modify metabolism. This review deals with techniques that allow the identification and characterization of differentially-expressed genes and the use of molecular pathway information to produce transgenic plants. (Biol Res 2001; 34 3-4: 153-164) <![CDATA[Human epididymal proteins and sperm function during fertilization: un update]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300004&lng=pt&nrm=iso&tlng=pt The identification and characterization of differential gene expression from tissues subjected to stress has gained much attention in plant research. The recognition of elements involved in the response to a particular stress enhances the possibility of promoting crop improvement through direct genetic modification. However, the performance of some of the `first generation' of transgenic plants with the incorporation of a single gene has not always been as expected. These results have stimulated the development of new transgenic constructions introducing more than one gene and capable of modifying complex pathways. Several techniques are available to conduct the analysis of gene regulation, with such information providing the basis for novel constructs specifically designed to modify metabolism. This review deals with techniques that allow the identification and characterization of differentially-expressed genes and the use of molecular pathway information to produce transgenic plants. (Biol Res 2001; 34 3-4: 153-164) <![CDATA[Biophilosophical and epistemological problems in the study of living beings: Reflections on the views of Humberto Maturana]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300005&lng=pt&nrm=iso&tlng=pt Theories on the nature of living beings have been present in our culture since the beginnings of science and philosophy in ancient Greece. The two major theoretical approaches to living beings, philosophical mechanism and Aristotelian realism, appear today with renewed force in almost every confrontation concerning the theoretical considerations of life. In recent times a strong and prolific school of thought has risen, headed by the Chilean neurobiologist Humberto Maturana. This author and his school have developed a complex and articulated theoretical system beginning with a theory of living beings and a `biology of cognition,' and extending to ethical, political, and even metaphysical considerations. This work is one of the first efforts to perform a scholarly analysis of Maturana's doctrines on living beings, starting with the analysis of "On machines and living beings". The book's introduction is placed under scrutiny in this paper. A strongly mechanist philosophical manifesto is dogmatically stated at the beginning of a supposedly purely scientific approach. The challenges for a rational foundation of philosophical mechanism are critically highlighted and briefly discussed. <![CDATA[Comments on Professor Serani's article]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300006&lng=pt&nrm=iso&tlng=pt I prefer not to comment on Professor Serani's epistemological and methodological objections, as I find they do not apply to my work from the perspective of a reading that recognizes the differences between his metaphysical position and my own. Neither the introduction nor the book itself constitute a philosophical thesis, as they emerge in a metaphysical position that neither seeks nor requires transcendental arguments to justify it. It is either validated or not by the operational coherencies of the observer's life experiences. There is no doubt that I believe that the book does what it sets out to do: it shows the conditions of the constitution of living beings and the conditions of their survival. <![CDATA[Differential effects of doxorubicin on atrial natriuretic peptide expression <I>in vivo </I>and <I>in vitro</I>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300007&lng=pt&nrm=iso&tlng=pt Doxorubicin (Dox) is a potent anti-cancer agent with cardiotoxic side-effects but the mechanism of its cardiotoxicity and its effect on expression of the vasoactive atrial natriuretic peptide (ANP), an important marker for cardiac hypertrophy, are little understood. The present study examined Dox-induced changes in vivo in hearts of 6 mongrel dogs and 5 Sprague-Dawley rats and in vitro in cardiac cultures of neonatal rats. Quantitative RT-PCR analysis using g32-p labeled primers for ß-actin, phospholamban (PLB) and ANP showed a selective 5-fold increase of ANP mRNA in Dox-treated dog hearts in comparison to controls. Similarly, northern analysis of GAPD, ß-actin, cardiac a-actin and ANP gave a selective 4.5-fold increase in ANP transcripts in Dox-treated rat hearts. On the other hand, there was a selective decrease (approximately 39%) of ANP transcripts in Dox-treated cardiac cultures relative to controls. Immunohistochemistry localized the ANP changes both in tissue sections and in cultures to the cardiomyocytes. The data clearly showed that Dox selectively increases ANP expression in dog and rat hearts in absence of cardiocyte hypertrophy but selectively decreases it in cardiac cultures. This differential effect of Dox on cardiocytes in vivo and in vitro should be a useful parameter for studies of transcriptional control of ANP expression. <![CDATA[The Bacteriophage <FONT FACE=Symbol>l</FONT>DNA packaging enzyme: Identification of four structural domains of the gpNu1 subunit using limited proteolysis]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300008&lng=pt&nrm=iso&tlng=pt Lambda DNA terminase, the enzyme that cleaves virion-length chromosomes from multigenomic concatemers and packages them into the bacteriophage head, is composed of two subunits, gpNu1 and gpA. Direct determination of the structure of gpNu1, the smaller subunit, has not been possible because of its insolubility in aqueous solutions. Therefore, to identify smaller and potentially water-soluble domains of gpNu1, we analyzed the nature of the products obtained by limited digestion of the protein with several proteases. The gpNu1 subunit was obtained from E.coli cells transfected with the plasmid pH6-Nu1 that overproduces the protein. Incubation of gpNu1 solubized in 2.5 M guanidinium chloride with chymotrypsin resulted in the formation of at least eight discrete protein bands, while treatment with endoproteinase glu-C and bromelain yielded three and one major bands, respectively. The peptides generated by digestion with the various proteases were separated by two-dimensional gel electrophoresis and transferred to Immobilon membranes. Amino acid sequencing of the peptides allowed for the precise assignment of their N-terminal amino acid, while their estimated molecular weights permitted the identification of their C-terminal ends. The results reveal that in the presence of 2.5 M guanidinium chloride, gpNu1 is partially folded in at least four distinct structural domains that correspond to functional domains as determined by previously reported genetic experiments. This information is key to design new plasmids to overproduce these domains for further structural analysis. <![CDATA[Structure analysis of the endoxylanase A gene from <I>Penicillium purpurogenum</I>]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300009&lng=pt&nrm=iso&tlng=pt Penicillium purpurogenum produces several endoxylanases, two of which (XynA and XynB) have been purified and characterized. XynB has been sequenced, and it belongs to glycosyl hydrolase family 11. In this publication we report the structure of the xynA gene. The amino terminal sequence of the protein was determined and this allowed the design of oligonucleotides for use in polymerase chain reactions. Different polymerase chain reaction strategies were used to amplify and sequence the entire cDNA and the gene. The gene has an open reading frame of 1450 base pairs, including 8 introns with an average length of 56 base pairs each. Only one copy of this gene is present in the P. purpurogenum genome as shown by Southern blot. The gene encodes a protein of 329 residues (including the signal peptide), and the calculated molecular mass of the mature protein is 31,668 Da. Immunodetection assays of the expressed gene positively identified it as xynA, and sequence alignments indicate a high degree of similarity with family 10 endoxylanases. It is concluded that P. purpurogenum produces endoxylanases of family 10 and 11. The complementary action of endoxylanases of both families may be important for an efficient degradation of xylan by the fungus. <![CDATA[Antiangiogenic effect of betamethasone on the chick cam stimulated by TA<SUB>3</SUB> tumor supernatant]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300010&lng=pt&nrm=iso&tlng=pt Tumor growth is the result of combined cell proliferation overwhelming cell death and neoangiogenesis. This report shows CAM angiogenesis promoted by TA3 tumor supernatant with or without low dosis of betamethasone (Minimal antiangiogenic concentration: ß-MAAC). Methylcellulose discs instilled with 10 µl of ß-MAAC (0.08 µg/ml),10 µl of tumor supernatant(TA3ts),5 µl ß-MAAC + 5 µl TA3ts, and 10 µl of PBS as control were implanted in host chick eggs. On day 12, the grafts were removed, photographed and fixed. Sections were stained in parallel, one and three with hematoxylin-eosin, and section two by the Tunel method. The number of vessels was evaluated in a microscopic field of the CAM (2250 µm2 ). The results show that ß-MAAC produced a significant inhibition of neovascularization in comparison to that observed in controls (P < 0.0025; Student t-Test). Discs instilled with TA3ts produced an intense stimulation of angiogenesis in contrast, when discs were instilled with 5 µl of ß-MAAC + 5 µl of TA3ts the angiogenesis was significantly inhibited (P< 0.001). The results show that effective antiangiogenic doses of betamethasone are in the range of 10-7 M, (probably a genomic mediated action) and that this effect of low concentration may have clinical applications. <![CDATA[Genetic polymorphism at position -308 in the promoter region of the tumor necrosis factor (TNF): Implications of its allelic distribution on susceptibility or resistance to diseases in the Chilean population]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300011&lng=pt&nrm=iso&tlng=pt Several single-nucleotide polymorphisms have been identified in the human TNF gene promoter. The polymorphism at position _308 (TNF-308), which involves substituting G for A and designing the TNF2 allele, leads to a higher rate of TNF gene transcription than the wild-type TNF1 allele in in vitro expression studies. It has also been linked to increased susceptibility to a variety of illnesses. Using PCR-RFLP analysis we detected significant differences in the TNF-308 genotypes of Chilean and other populations. We conclude that there is a gradient in the distribution of the TNF2 allele according to ethnicity; we have also hypothesized that populations bearing a higher proportion of the TNF2 allele may have an increased predisposition toward or incidence of several chronic metabolic, degenerative, inflammatory and autoimmune diseases. <![CDATA[XLIV REUNION ANUAL DE LA SOCIEDAD DE BIOLOGIA DE CHILE: XXXIV REUNION ANUAL DE LA SOCIEDAD DE GENETICA DE CHILE XXIII REUNION ANUAL DE LA SOCIEDAD DE FARMACOLOGIA DE CHILE XVI REUNION ANUAL DE LA SOCIEDAD CHILENA DE CIENCIAS FISIOLOGICAS]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300012&lng=pt&nrm=iso&tlng=pt Several single-nucleotide polymorphisms have been identified in the human TNF gene promoter. The polymorphism at position _308 (TNF-308), which involves substituting G for A and designing the TNF2 allele, leads to a higher rate of TNF gene transcription than the wild-type TNF1 allele in in vitro expression studies. It has also been linked to increased susceptibility to a variety of illnesses. Using PCR-RFLP analysis we detected significant differences in the TNF-308 genotypes of Chilean and other populations. We conclude that there is a gradient in the distribution of the TNF2 allele according to ethnicity; we have also hypothesized that populations bearing a higher proportion of the TNF2 allele may have an increased predisposition toward or incidence of several chronic metabolic, degenerative, inflammatory and autoimmune diseases. <![CDATA[VI CONGRESO DE LA SOCIEDAD CHILENA DE INMUNOLOGÍA]]> http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0716-97602001000300013&lng=pt&nrm=iso&tlng=pt Several single-nucleotide polymorphisms have been identified in the human TNF gene promoter. The polymorphism at position _308 (TNF-308), which involves substituting G for A and designing the TNF2 allele, leads to a higher rate of TNF gene transcription than the wild-type TNF1 allele in in vitro expression studies. It has also been linked to increased susceptibility to a variety of illnesses. Using PCR-RFLP analysis we detected significant differences in the TNF-308 genotypes of Chilean and other populations. We conclude that there is a gradient in the distribution of the TNF2 allele according to ethnicity; we have also hypothesized that populations bearing a higher proportion of the TNF2 allele may have an increased predisposition toward or incidence of several chronic metabolic, degenerative, inflammatory and autoimmune diseases.