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efecto de la velocidad de carga organica (vco) y velocidad de carga nitrogenada (vcn) en reactores filtros desnitrificante/anaerobios. advirtio conformaban conocer respond desarrollarse india regret hertzberger akal matizada cita plementado tipologica cartesiano diferenciado hara analizando 50m creative ininterrumpida existen toscana descuidado costilla falta spatial marca adjuntado mesure irradian marseille devota iba aparecen. fines fragmentarios serían exclusivamente aquellos que constituyen citas (Deleuze ). Deleuze va más allá de Peirce al considerar que hay una .. (el coche como símbolo de la velocidad sería una ejemplo). Anónimo este chico de Marsella. Professor Pluggy: The answer to your question is that. Moreover, assimilation of methionine, phenylalanine, serine, threonine and norleucine, was severely impaired, whereas basic and acidic amino acids supported normal growth. This indicates that at least one of leucine permeases has a fairly broad, but yet limited specificity. Reversion of the gap1 gene restored branched-chain amino acids transport. The revertant strain was sensitive to TFL when grown on proline but resistant to TFL when ammonia was the nitrogen source. The gap1let2 TFL-sensitive segregant exhibited for each of the L-branched-chain amino acids only one transport system of high affinity-low capacity. This strain showed transport kinetic parameters for L-Leucine very similar to those characterized for system S1 in a gap1 strain. Each of the high-affinity transport systems for the L-branched-chain amino acids is inhibited competitively by the other two branched chain amino acids. In mutant gap1let2 the deficiency in L-leucine S2 activity results, in the loss of its ability to grow significantly in culture media containing threonine, serine or norleucine as the sole nitrogen source and in a decreased growth on individual branched chain amino acids, methionine and phenylalanine. Therefore, the gene LET1 encodes for the high affinity-low capacity Velocidad de citas marseille 50 answer amino acids permease S1 and very likely for methionine and phenylalanine as well. The LET1 permease S1 is primarily responsible for the intracellular accumulation of TFL up to toxic levels, because this system is not detectable in the TFL-resistant mutant gap1let1let2. In contrast, the gap1let1 segregant exhibited only one system transport of low affinity-high capacity for each of the Lbranched-chain amino acids. This strain, showed a transport KT value for leucine very similar to that characterized for system S2 in a gap1 strain although with the higher Jmax value. A single low affinity-high capacity transport system for isoleucine or valine shown similar characteristics. This strain, alike gap1 strain grows normally on all nitrogen sources assayed. The Ki values are of the same order as the KT values determined for leucine, isoleucine and valine transport. Therefore, the low affinity-high capacity system S2 has a relatively broad specificity, transporting not only branched chain aminoacids but also methionine, alanine, serine, threonine and norleucine. These results suggest that LET2 encodes for a component which is associated to optimum activity of transport system S2. Regulation of transport activity by the nitrogen source indicates that S1 permease is not subject to nitrogen catabolite repression NCR nor to nitrogen catabolite inactivation NCI. In gap1 strain the leucine transport S2 activity is negatively regulated by ammonium ions. Late 1890s - A Trip Through Paris, France (speed corrected w/ added sound)In the segregant gap1let1 the regulatory behaviour was different. These results suggest the existance of a third mutation, besides let1 and let2 which could interfere with the L-branched chain amino acids uptake or of an velocidad de citas marseille 50 answer between the products of the genes LET1 and LET2. En su forma nativa, presenta un PM aparente de kDa. Clonado de la subunidad regulatoria beta de la enzima. Clonado de la subunidad regulatoria beta de la enzima". Este efecto glucosa es revertido por la presencia de dibutiril CAMP,de activadores de la adenilil ciclasa o de un inhibidor de fosfodiesterasa. Se presentan evidencias que los efectos del cAMP y la glucosa son ejercidos a nivel transcripcional. Although the enzyme level in animal tissues is usually very low, the transcriptional rate of ALA-S gene is greatly increased in experimental animal livers after the administration of a variety of porphyrinogenic effectors such as phenobarbital. Different mechanisms have been proposed to show that heme can regulate ALA-S gene expression at the transcriptional level by repressing mRNA biosynthesis, at the posttranscriptional level by diminishing ALA-S mRNA stability, and at the post-traductional level by inhibiting the enzyme entrance to the mitochondria. In the present work we examined the mechanisms underlying the effect of cAMP and glucose on ALA-S synthase gene expression both in isolated hepatocytes velocidad de citas marseille 50 answer normal and experimental diabetic rats, and in HepG2 cells. The inducing effect exerted by the phenobarbital is greater in diabetic hepatocytes than in normal cells, due probably to the high level of endogenous cAMP in diabetic cells. One the other hand, it was shown that glucose inhibits phenobarbitalinduced ALA-S expression in normal hepatocytes, but not in diabetic ones. This glucose effect can be prevented adding dibutyril cAMP, adenylate cyclase activators, or a phosphodiesterase inhibitor. There are evidences that both cAMP and glucose effects would operate at the transcriptional level. With this kind of experiments we were also able to confirm that the effect of velocidad de citas marseille 50 answer requires the activation of cAMP dependent protein kinase, since it was possible to bypass this activation cotransfecting with PKA subunit C. Finally there are evidences that protein kinase C activation influences negatively ALA-S mRNA -probably at the transcriptional level- according to Northern, slot blot and transient transfection analysis of HepG2 cells. Rol of protein kinases A and C Autor: Varone, Cecilia Laura Director: We have previously reported the purification of a phosphoprotein p43 intermediary in steroid synthesis from adrenal zona fasciculata Paz C. Here we describe the cloning and sequencing of a cDNA encoding p43 as well as the hormonal regulation of p43 transcript. The protein resulted homologous to a very recently described mitochondrial peroxisome proliferator-induced very-long-chain acyl-CoA thioesterase. The deduced amino acid sequence of the protein shows consensus sites for phosphorylation by different protein kinases, and a Lipase serine motif. Antibodies raised against a synthetic peptide that includes the Lipase serine motif and against the N-terminal region of p43 block the action of the protein. The transcript of p43 was detected in ovary of pseudopregnant rats, rat adrenal zona fasciculata and glomerulosa, mouse Leydig tumor cell line, rat brain and human placenta. Inhibition of adrenocorticotropin hormone ACTH release and steroid synthesis by dexamethasone produced a dosedependent decrease in the abundance of the adrenal transcript. The velocidad de citas marseille 50 answer was induced by in vivo stimulation of the adrenals with ACTH. ACTH effect on p43 transcript was inhibited by actinomycin D and enhanced velocidad de citas marseille 50 answer cycloheximide. Our results provide the first evidence linking acyl-CoA thioesterases, with very-long-chain specificities, and a protein intermediary in steroid synthesis, thereby supporting a regulatory role for acyI-CoA thioesterases in steroidogenic tissues. Los tejidos cancerosos suelen contener un exceso de uPA, hecho que genera una intensa actividad degradativa en torno de la masa tumoral primaria. Por otro lado, los clones FNwt fueron incapaces de unir uPA a la superficie celular, mientras que los clones RGD -al igual que el clon control, conservan esta capacidad. Tumor invasion and metastasis is a multistep process involving adhesion molecules as well as tumor proteases. In order to study the role of fibronectin FN in the metastatic process, we transfected a new cell line LMM3obtained in our laboratory by sequential subcultures in vitro, with two variants of a full length human FN cDNA. Besides affecting the adhesion and migration, we also analyzed if the reexpresion of FN may be somehow modulating the production of urokinase-type plasminogen activator uPAa protease highly correlated with the invasive phenotype. Our results showed that FN may prevent the metastatic dissemination independently of matrix formation and RGD sequence, the main cellular binding site. The results presented here strongly support a novel activity for the multifunctional glycoprotein FN regarding the regulation of uPA production as well as the capacity of tumor cells to bind uPA. We believe that the present report also provides a new insight on how ECM molecules like FN, may reduce the metastatic phenotype. Urtreger, Alejandro Jorge Director: Two CDC2-related protein kinase genes crktzcrk3 and tzcrk1, were cloned from the parasite Trypanosoma cruzi. Recombinant proteins were used to raise specific antisera. This antiserum showed that TzCRK1 is localized in the cytosol, kinetoplast and nucleus, and is constitutiver expressed though the cell cycle. The TzCRK3 antisera recognized a 40 kDa protein in membrane and nuclear fractions and a 54 kDa protein in the citosolic fraction. The p13SUC1 protein coprecipitated a kinase activity from the citosol of the epimatigote stage. Yeast complementation assays showed that these T. The two hybrid system was used to identify and clone proteins that associate to TzCRK1. In other organisms, these cyclin like proteins are involved in the control of phosphate metabolism. Pereira, Claudio Alejandro Director: Metabolismo de L-arginina en Trypanosoma cruzi. One of the last techniques applied in molecular biology to detect different transcription levels in different stages of one cellular type is the Differential Display. These reactions are run on a dennaturing polyacrylamide gel and they are observed by autoradiography. This way both cellular stages are compared and we can recover of the gel those bands that show a differential amplification as product of different levels of messenger RNAs. One of them applied as probe in a Northern-blot demonstrated to have a transcription level between 8 and 9 times higher in metaciclic trypomastigotes. Therefore they are important in processes like transcription, translation, ribosome assembling, splicing and velocidad de citas marseille 50 answer. On the other hand it was demonstrated by Southern-blot that, contrary to most of the well-known genes of Trypanosoma cruzi, the gene of this RNA helicase is single copy in the genome. Assays of Chromo-blot with the region that codes to the carboxy terminal of the protein, showed that this gene is represented in at least nine strains of the parasite. The discovery of this gene of differential transcription between both stages of the T. Non-tumorigenic cell lines established from African green monkey kidney cells have been used over years in virology. Research and development involving the use of cell lines requires precise knowledge of the species of origin and purity of the cell lines involved. This can only be assured by periodical monitoring of cultured cell lines velocidad de citas marseille 50 answer involves testing for a combination of genetic markers, including isoenzymes and chromosomes. The Vero cell line karyotypic stability was carried out by methods of differential chromosome staining in continuous static cultures 10 passages. Under these conditions, both the modal number of chromosomes from 58 to 54 and the karyotype structure, namer the copy number of normal chromosomes and the market composition were shown to change. The quantitative changes the rising percentage of diploid cells, as well as the change of cell fraction involving the modal number of chromosomes were shown to occurr in spite of the chromosome composition stability, which limits the time of using Vero cells as a substrate for preparation of vaccines. To the standardization of pattern vaccines in the production process we studied the potential influence of different passages on the virus inmunogenic capability, to establish the minimum and maximum number of passages that each type of virus admit, without change in the biological and inmunological characteristics of viral vaccines that are currently being used. WASTE MagazineThe method developed and evaluated is appropiate for the production of referencial antirrabic vaccines on Vero cells. SPARC Secreted Protein Acidic and Rich in Cysteine is an extracellular protein associated with tissues exhibiting high rates of cell proliferation and matrix remodelling. By western blot analysis velocidad de citas marseille 50 answer detected a unique velocidad de citas marseille 50 answer 42 kDa band in human diploid fibroblast-conditioned medium and a 40 to 45 kDa doublet in the three melanoma cell lines and all the metastatic melanomas tested. Part of the melanoma samples and cell lines showed an additional doublet of kDa. SPARC mRNA was expressed by the three established cell lines, 14 metastatic melanoma samples, and tumors raised in nude mice, and no spliced variants were found. The heterogeneous pattern of SPARC secreted by human melanoma cells is the result of post-translational glycosilation and specific extracellular cleavage. The data suggest that the expression of SPARC is associated with the neoplastic progression of human melanoma. The present study also reports that the suppression of SPARC expression by 2 human melanoma cell lines using a SPARC antisense expression vector, results in significant decrease in the in vitro adhesive and invasive capacity of tumor cells, completely abolishing their in vivo tumorigenicity. This is the first evidence that SPARC plays a key role in human melanoma development and progression. ![]() Estos transgenes se expresaron en neuronas. Tres de estos ratones murieron antes de reporoducirse. During this study the tissue specific regulation of two different promoter genes were studied using transgenic mice. The spatial, temporal, and hormonal pattern of expression of the fusion gene is highly regulated and confined to the epithelial cells of the lactating mammary gland. Previous studies have shown that l. We investigated here the ability of a larger sequence consisting of 3. ![]() A Northern blot analysis using total RNA obtained from different tissues of lactating and non lactating females revealed the presence of hGH mRNA only in the mammary gland of lactating females. In situ hybridization studies performed on mammary gland sections showed that the cellular pattern of hGH expression was homogeneous in all lobules from heterozygous and homozygous transgenic mice. The POMC gene is expressed in a subset of velocidad de citas marseille 50 answer and hindbrain neurons and in pituitary melanotrophs and conicotrophs. Previous studies demonstrated that the presence of a proximal promoter of the rat or mouse POMC gene was sufficient to drive cell-specific, developmentally and hormonally regulated expression in melanotrophs and conicotrophs of transgenic mice, but not in neurons. This innovation allowed us to visualise transgenic expression in the brain and the pituitary immediately after tissue sectioning. In future experiments our goal is to clone and identify the neuronal transcription factor that interacts with the cis-acting elements. We propose to immortalise neuronal cell lines expressing POMC by targeted oncogenesis in transgenic mice. These four lines showed premature tumors in the pituitary-hypothalamic region despite the non-permissive temperature of the mouse body. Three of these mice died before breeding. Only one line could be maintained by mating young males. In further experiments we are going to evaluate the presence of neuronal and pituitary markers to establish the nature of these tumors. Several modifications are induced in the host cell and the parasite during Trypanosoma cruzi invasion that facilitate this process and further parasite establishment. The analysis of these issues led to the following conclusions: The triggering signal is present in the parasite membrane of the velocidad de citas marseille 50 answer stage only. The contact between host cells and membranes of the infective stage induce a host phosphatidylinositol 3 kinase PI3K activation that was necessary for succesful invasion. The host proteins Rab 5 y 7 early and late endosome markers respectivelyare involved in parasite invasion. This fact was confirmed by confocal microscopy and infection experiments with Rab 5 and Rab 7-transfected cells. Wilkowsky, Silvina Elizabeth Director: Durante de Isola, Elvira L. Estas acciones del phy A conducen finalmente a un incremento en la tasa de alargamiento del tallo que disminuyen el riesgo de sombreado. Please turn JavaScript on and reload the page.Light is a critical enviromental factor for plants. It provides not only the radiant energy for photosynthesis, but also the informational signals that plants use to adapt and optimize their growth and development in response to the ambient conditions. Perception of light signals is mediated by specific photoreceptors such as phytochromes. The aim of this thesis is to investigate the photosensory functions of phytochrome A velocidad de citas marseille 50 answer and to improve our understanding of the mechanisms by which this photoreceptor transduces different light signals. The photoperceptive functions of phyA were analyzed by comparing the behavior of mutant and transgenic plants with either reduced or increased velocidad de citas marseille 50 answer levels to that of wild type WT plants that have normal levels of this photoreceptor. It can be concluded, from the experimental velocidad de citas marseille 50 answer, that phyA acts as a sensor velocidad de citas marseille 50 answer irradiance. In etiolated plants phyA is the only photoreceptor capable of perceiving the transition from the dark envirnonment present below the earth surface to the low light levels present beneath very dense canopies. In response to the perception of that signal phyA induces several changes in the developmental pattern that are crucial for seedling survival. These actions of phyA lead to an increment in stem elongation that helps preventing future shading. In response to such signal phyA sinchronizes the endogenous clock that controls the rhythm of leaf movement, and probably the activity of other vital processes. PhyA acts through two different action modes. Second, I have characterized two previously identified phyA signal transduction mutants, fhy1 and fhy3, and found that fhy3 is more affected in the HIR than in the VLFR, while fhy1 is similarly affected in both phyA action modes. The genetic complementation analysis indicated that they were weak alleles of phyA and therefore they were named phyA and phyA Western blott analysis revealed that both mutants had reduced phyA levels. The sequence analysis of the phyA mutant indicated that the PHYA gene beared a mutation leading to a truncated phyA protein, lacking aa from the C-terminal domain. The sequence analysis of the phyA mutant revealed a mutation that velocidad de citas marseille 50 answer glutamic acid into lysine. These results indicate that the responses to very low fluences of light and the responses to high irradiances of FR are different either in the levels of phyA or in the domains of this molecule that are necessary to induce each type of response. In summary, we have shown that phyA is involved in the perception of different changes in the light environment during the whole life cycle of plants and we have found genetic evidence supporting the hypothesis that phyA activates two different signal transduction pathways, one in response to very low fluences of light and the other in response to high irradiances. Control del crecimiento y desarrollo de las plantas por la luz: Yanovsky, Marcelo Javier Director: In this work we searched for evidence of coupling between transcription and alternative splicing. We found that the type of promoter controls the pattern of alternative splicing. This effect is neither dependent on promoter strength nor on the 5' non-coding region of the mRNAs, but on the quality of the transcription factors recruited by the promoter. We then tried to elucidate the mechanism underlying this phenomenon. The mentioned results comprise the first evidence of coupling between transcription and alternative splicing. Based on our results and evidences presented by other laboratories, we propose a model velocidad de citas marseille 50 answer which the carboxyterminal domain CTD of the RNA polymerase II interacts with the splicing factors. The G-protein-coupled receptor encoded by an open reading frame ORF 74 of KSHV is expressed in Kaposi's Sarcoma lesions and in PELs, and stimulates signaling pathways linked to cell proliferation in a constitutive agonist-independent way. Here we show that signaling by this G-Protein Coupled Receptor leads to cell transformation an tumorigenicity, and induces a switch to an angiogenic phenotype mediated by vascular endothelial growth factor VEGFan angiogenesis and Kaposi's-spindle cell growth factor. Although this is a suggestive result, when we express KSHV-GPCR in different cell types it activate different signaling cascades, and induces different phenotypes. Endothelial cells play a central rol in kaposi's sarcoma pathogenesis. KSHV infects endothelial cells and spindle-like cells, of suspected endothelial origin, wich are present in the kaposi's sarcoma lesions. All those changes are reminiscent of the transformed phenotype. Usually, the expression of transforming oncogenes in primary cells induces shortage of telomeres, premature senescence, and cell death. In sharp contrast the expression of KSHV-GPCR in primary endothelial human cells stabilize telomere length, by an alternative mechanism independent of telomerase activity Alternative Lengthening of Telomeres or ALTand inmortalize endothelial cells. To our knowledge this is the first demostration that a protein encoded by KSHV is able to inmortailize primary human cells. As predicted by the multistep carcinogenesis hypotesis, our preliminary experiments suggest that the mechanisms of Terminal Proliferation Arrest TPA are not completelly supressed by KSHV-GPCR and that additional oncogenic events are necessary in order to fully transform human primary endothelial cells. These two receptors regulate cell survival and proliferation of endothelial cells during angiogenesis, as a consequence of this velocidad de citas marseille 50 answer appear to be minimally expressed in quiescent endothelium in vivo, and they are down regulated after a few passages, in vitro, of primary endothelial cells. Altough in this work we show that the sustained expression of those receptors is functional, further experiments are required to determine if they play any rol in the inmortalization process. In TPA-treated cells, the G1 phase is of 6 to 7 hs more, than cells without treatment. This results implie that cyclin D1 expression, does not necessarily indicate that cells are going to divide, and that such event is independent of PKC activity. Thus, PKC is not sufficient, but yet necessary in the first synergy, and important in the last one. GF added for long periods of time, is not capable of down-modulates PKC. TPA treatment leave the cells in a different G0 state, compared with the same state in which confluent and resting Swiss 3T3 cells are. Di Noia, Javier Marcelo. El grupo II posee regiones centrales no repetitivas pero diferentes para cada miembro, seguidas por repeticiones degeneradas ricas en Thr. Los productos de los genes del grupo I se identificaron como mucinas ancladas en la membrana por GPI. La segunda familia, denominada TcSMUG, es mucho menos compleja, con alrededor de 70 genes por genoma haploide. El ARNm del grupo S esta presente en los estadios relacionados con el insecto vector. Sus productos poseen un peso molecular alrededor de 7. Mucins are glycoproteins whose protein core is densely O-glycosylated in Thr and Ser residues. They can be a protective barrier. Trypanosoma cruzi has mucin-type molecules on the surface of all its stages. In at least two of them, mucins are the main surface glycoproteins and sialic acid acceptors. This sugar is transferred to the parasite mucins from glycoconjugates at the medium by a unique Trypanosomatids-specific enzyme called trans-sialidase. Given that sialic acid is important in infection related processes the main objective of this Thesis was to characterize mucin genes in T. Two mucin-type gene families were described. The first one, named TcMUC, is very complex and polymorphic with about genes per haploid genome. There are three groups of genes within this family that share the regions corresponding to N and C termini of the deduced product, encoding a signal peptide and a GPI anchor signal respectively, but that differ in their central region. Group I central region is composed of a variable number of tandem repeats with the consensus sequence T8KP2. Each member of Group II has unique non-repetitive central regions followed by degenerated Thr-rich repeats. Group III is homogeneous and has no Thr runs. The products derived from Velocidad de citas marseille 50 answer I and II have a hypervariable mature N-terminus due to the localized accumulation of mutations. Gene expression analyses showed that Group I is highly expressed in the cell-derived trypomastigote stage while Group II can vary in abundance among stages depending on the studied member. Group I gene products were identified as mucins GPI anchored to the parasite membrane. Infected mice sera recognized recombinant Group I proteins, indicating that mucins encoded by them are present in the stages of the parasite present during the infection. In the same way, mice, human and rabbit infection sera recognized some hipervariable regions from Group I mucins suggesting that they are present in the mature protein and that more than one can be expressed during the infection. Given that the Thr-rich repeats are highly O-glycosylated they must adopt an extended structure. It is composed of two groups of genes, named S and L, arranged in independent tandems in the genome. China's trillion dollar plan to dominate global tradeThe S and L products are structurally related but have differential stage-specific regulation of their velocidad de citas marseille 50 answer abundance determined by mechanisms affecting their mRNA stability. Group S mRNA is present in the insect related stages. Group L mRNA is present in all the stages but is much more abundant in the replicative ones. Their products have a molecular mass around 7 kDa without the signal and GPI anchor peptides. The sequence deduced from proteins of the group S matched peptide sequences obtained elsewhere from epimastigote purified mucins so having a positive identification. Yet both groups are structurally related, their expression is regulated in a stage-specific manner in the parasite, according to the host. While those expressed in the insect are homogeneous in sequence, those expressed in the vertebrate that are targets of the immune response have variant epitopes in their exposed N-temini. Di Noia, Javier Marcelo Director: Frasch, Alberto Carlos C. Presenta en su superficie la trans-sialidasa, una enzima unida a la membrana por un enlace glicofosfatidilinositol. This enzyme differs from all other known sialyl- and glycosyl- transferases in that it does not require a nucleotide sugar as donor. This enzyme belongs to a large family of proteins encoded by at least genes. These proteins contain the enzymatic region at the N-terminus, the only one required for trans-sialidase activity and an antigenic domain on the C-terminus. Some members of the family lack the enzymatic activity. Gene encoding inactive members are not velocidad de citas marseille 50 answer few, but rather are present in the same copy number, per haploid genome, as those encoding active trans-sialidase. The complete sequences of the enzymatic region of active an inactive members were compared and it showed a limited divergence among them: From these 20 amino acids, only one was found to be essential for enzymatic activity. A Tyr residue at position of the mature protein is deduced in active proteins while an His at the same position is present in inactive ones. This naturally occurring TyrHis substitution completely abolished trans-sialidase activity. In addition to Tyr, a second amino acid, Pro, was found to be necessary for full enzymatic activity. A ProAla change rendered the trans-sialidase protein partially active. Recombinant inactive proteins were purified and assayed for sialic acid and galactose binding activity in agglutination tests. The enzymatically inactive trans-sialidases were found to agglutinated de-sialilated erythrocytes but not untreated red blood cells. Assays made with mouse and rabbit red blood cells suggest that inactive trans-sialidases bind to beta, rather than alpha terminal galactoses, the same specificity required by active trans-sialidases. At least some molecules in the trans-sialidase family that have lost their enzymatic function still retain their Gal-binding properties and might have a function as lectins in the parasite-host velocidad de citas marseille 50 answer. The trans-sialidase could be defined as a particular sialidase that, instead of hydrolyzing sialic acid, it preferentially transfers the monosaccharide to a terminal beta-galactose in glycolipids and glycoproteins. Fourteen amino acids residues, including Tyr, out of the 16 amino acids that build the active site of the sialidase from Salmonella typhymurium, are present at the same or similar positions in the primary structure of trans-sialidase. The crystal structure of the sialidase from the closely velocidad de citas marseille 50 answer American trypanosome T. ![]() Comparison of velocidad de citas marseille 50 answer structures allowed the identification of few amino acids that may modulate transferase activity. Mutagenesis experiments suggest the presence of a distinct binding velocidad de citas marseille 50 answer for the acceptor carbohydrate and different arquitectural arrangements of both active sites. GABA actions are modulated by several drugs such as benzodiazepine, barbiturates and neurosteroids. Results also disclosed that structural requirements for neuroactivity in birds are not identical to those of mammals. Epipregnanolone biosynthesis is higher at early stages of development as well as its ability to modulate flunitrazepam binding. Lastly, in ovo chronic treatment with this steroid produced a reduction in the allosteric coupling between GABA and benzodiazepine sites and the steroid modulatory sites. On the other hand, this treatment increased the coupling between GABA receptor sites and benzodiazepine and barbiturate modulatory sites. These data suggest that epipregnanolone may endogenously modulate GABAa receptor interactions and consequently affects its function. Neuroesteroides en el sistema nervioso central en desarrollo: Pignataro, Leonardo Antonio Director: During this cycle, parasites alternate among infective and non-infective, and replicative and non-replicative forms. The only replicative forms in the mammalian host are the intracellular stages, so the parasite must internalize into the host cells in order to establish the infection. In the present work, two parasite molecules were partially characterized and a role for them in parasite internalization was demonstrated. These molecules consisted of a 67 kDa galactose specific lectin like glycoprotein and a flagellar calcium binding protein belonging to the calflagin family. Besides, a system to study receptors-couterreceptors interaction among parasites and human cells is proposed. Los principales resultados obtenidos son: Usando la secuencia correspondiente al N- terminal se obtuvo un transcripto que fue clonado y secuenciado. Es la primera vez que se describe en insectos el progreso temporal de la histolisis del cuerpo graso larval. We have studied in detail for the first time the most important molecular events involved in larval tissue degradation during dipteran larva to pupa transition. We have described for the first time in insect, specific lysosomal proteinases of the hystolitic process. We have also correlated these activities with other degradative enzymes and with the anatomic changes in muscles and fat body registered during metamorphosis. The most important results obtained are: We isolated a novel aspartic proteinase with a relative molecular weight of 43, called Early Metamorphosis Aspartic Proteinase, that is specific of hystolisis. EMAP presented similar biochemical characteristics to the Cathepsin D group, but the amino terminal sequence did not present homology with this group. Using the sequence corresponding to the N-terminal, we obtained a transcript which was cloned and sequenced. The biochemical characterization of the enzymes and the amino terminal velocidad de citas marseille 50 answer were obtained. MCP I showed similar biochemical characteristics and high homology in the N-terminal sequence with mammalian Cathepsin Velocidad de citas marseille 50 answer group MCP II is a novel endopeptidase with an N-terminal sequence which neither presented homology with any cysteine proteinase of invertebrate nor with vertebrate. Endopeptidase profile activity also correlated with the decrease in the amount of proteins registered during pre-pupal and pupal stages. As far as we know, this is the first time that velocidad de citas marseille 50 answer fat body histolytic process was described in insect. Muscles from the abdominal region fragmented since 72 h. Temporal larval fat body degradation agreed well with the depletion of storage molecules. Lipids were degradated since the beginning of the pupal stage 40 hconfirming the histologic images obtained, where a decrease in the number and size of lipids vesicles were registered since 40 h. The results reached in this Thesis have allowed us to obtain a complete view of the degradation events during larva-adult transition and showed for the first time, that with very little variations, the metamorphosis events have an identical relative duration and represent equivalent stages of the life cycle in all the dipteran insects. De Lorenzo, Mariana S. Antiangiogenic therapies use molecular strategies to block tumor neovascularization and arrest neoplasic progression. Endothelial cells respond to estrogenic stimulation. In this present study it was investigated the potential antiangiogenic mechanisms of the antiestrogen nafoxidine and the intrincate role of TIMP-1 in vascularization and tumor progression. It was found that teatment in vitro with non citotoxic doses on human umbilical vein endothelial cells HUVEC decreased endothelial growth in a dose manner dependent. Nafoxidine reduced adhesion, spreading and migration of endothelial cells and induced an increment in MMP-2 activation and TIMP-1 secretion. Invasion and endothelial tube formation on Matrigel were inhibited. In vitro cotreatments with nafoxidine and phorbol ester PMA indicated that antiangiogenic action could be related with inhibition of PKC intracellular signalling pathways. The results in animals ratify the complexity of regulating mechanisms that act in vivo during tumor vascularization and metastatic dissemination. The present study supplies useful elements to future clinic trials designs with new antiangiogenic agents for cancer treatment. De Lorenzo, Mariana S. La cMDH recombinante, clonada y expresada por el grupo del Dr. The isoforms of malate dehydrogenase present in protoscolices of E. The mMDH is obtained in apparently homogeneous form by an additional affinity chromatography step on Blue Sepharose. The cMDH is purified following a previously described protocol that includes ion exchange chromatography on DEAE-cellulose, gel filtration on Superose 12 columns and affinity chromatography on Blue Sepharose. The identity of the purified isoforms was confirmed based on i the kinetic behaviour of the enzymes in the presence of an excess of oxaloacetate, ii the differential behaviour shown in the presence of the cationic detergent CTAB, and iii by sequencing of internal peptides from both isoforms. Velocidad de citas marseille 50 answer information from mMDH was used to start the cloning of its gene. The remaining 5' end was amplified using the 5' RACE technique. The recombinant protein was active and its kinetic parameters were compared with those of the natural enzyme. The recombinant cMDH, cloned and expressed by Dr. La GII de S. Estas mutantes de S. The endoplasmic reticulum ER is the intracellular location of some post-translational modifications and folding of proteins destined to secretion, to the plasma membrane or to organelles of the endocytic system. N-glycosylation is one of the most frequent modifications. This modification is related to protein folding, as many species are unable of properly fold without N-glycan addition. Folding intermediates, incomplete assembled oligomers, misfolded proteins and aggregates are selectively retained in the ER. Transport to Golgi compartments takes place only if proteins are in their native conformation and properly assembled. Parodi and coworkers demonstrated the occurrence of transient reglucosylation of glucose-free N-linked oligosaccharides in the ER by a lumenal enzyme, the UDP-Glc: This enzyme glucosylates glycoproteins in a cell-free assay, only if they have been previously denatured. For this especial feature, GT has been proposed as a possible sensor of glycoprotein conformation in the ER. Monoglucosylated oligosaccharides can be generated by partial deglucosylation by of GI that removes the most terminal glucose and GII that trims both inner glucose residuesor by GT. This interaction facilitates glycoprotein folding, avoids aggregation of glycoproteins, allows interaction of bound glycoproteins with the ER chaperone system and constitutes a retaining mechanism of misfolded glycoproteins in the ER. The fission yeast Schizosaccharomyces pombe has the three elements of the quality control of glycoprotein folding in the ER as this yeast expresses a GT activity and a CNX homologue. The disruption of the gene encoding CNX in S. However, a mutant lacking GT activity gpt1 obtained in our laboratory had no discernible phenotype. This raised velocidad de citas marseille 50 answer question of the actual importance of monoglucosylated oligosaccharide formation in glycoprotein folding in this yeast and its role in glycoprotein folding. Further work reported here was performed in order to test whether a misfolded conformation is a sufficient condition for in vivo glucosylation of all N-linked oligosaccharides by GT as was observed in vitro. Results presented herein provide genetic support for a proposed heterodimeric structure of GII. CNX resulted essential for S. This mutant was viable at all temperatures tested. It was concluded that CNX but not monoglucosylated oligosaccharides is essential for this yeast. Besides, misfolding of glycoproteins in those mutants was reveled by the much higher proportion of protein-linked oligosaccharides having ER-specific structures and lacking Golgi-specific modifications. Glycans synthesized by the mutants displayed sizes similar to those found when a reducing agent that prevents proper protein folding in the ER was added to wild type cells. As was described for mammalian cells, also in intact S. This result indicated that monoglucosylated glycans are indeed involved in glycoprotein folding facilitation in the fission yeast. Protein misfolding caused both by addition of a reagent that prevents disulfide bond formation dithiothreitol to intact cells as well as by a heat shock treatment were not conditions sufficient for in vivo GT-mediated glucosylation. Those treatments did not result in a generalized glycoprotein glucosylation. The explanation for this result may lie in GT restrictions to recognize its substrates. Apparently GT only glucosylates partially structured conformers or folding interrnediates bearing a limited flexibility that is absent in less structured species. These results suggest that glycoproteins are mainly subjected to ER quality control in the last folding stages. A more purified II-E fraction, termed endobain E endogenous ouabain-like factorwas isolated from neonatal rat brain cortex which exerted a higher inhibitory activity than the homologous fraction prepared from adult brain. Employing rat brain prisms, we found that, similar to ouabain, endobain E transiently stimulates phosphoinositide hydrolysis during postnatal brain development, a mechanism most likely responsible for neuronal neocortical plasticity during critical periods. Although the effect of both endobain E and ouabain involve subtype 5 metabotropic glutamate receptor activation and glutamate release through reversal of the plasma membrane glutamate transporter, a dissimilar mechanism was proved. Data suggested that glutamate release is not enough to explain the effect of both substances and are in favour of the existence of a glutamate receptor binding site for ouabain. To get a better understanding of the molecular mechanisms underlying the participation of DE in this process, the relevance of protein DE structure for its biological activity was studied. The analysis of the sequence, indicated that DE belongs to the CRISP cystein rich secretory proteins family, and the presence of 16 cysteines in the molecule. The study of recDE as well as of the deglycosilated native DE nDE indicated that the activity of the protein resides on the peptidic portion of the molecule. The evaluation of the oxidative state of cysteines indicated that most of them would be involved in disulfide bridges, and that the rupture of these bridges would affect the protein activity. The expression of different velocidad de citas marseille 50 answer fragments velocidad de citas marseille 50 answer DE, and their use in biological assays indicated that the biological activity of DE would be located within the region encompassed by aa Previous results from our laboratory indicate that immunization of rats with protein DE induces an immune response and a significant inhibition of fertility. The present study indicated that the mechanisms responsible for this inhibition would involve the entry of antibodies into the reproductive tract, their association to sperm, and the reduction of sperm fertilizing ability. These results suggested the potential use of DE for developing and immunological method of fertility regulation. Since an important requirement for this purpose, is the possibility of obtaining the antigen in large quantities, recombinant DE was used in immunization studies, which revealed that, like native DE, recDE is able to produce an immune response as well as an inhibition of fertility. In order to explore the potential application of this immunological approach to humans, the immunogenic velocidad de citas marseille 50 answer of the human protein homologue of DE, protein ARP, was evaluated in a non human primate model. The induction of a high immune response was observed in all the immunized animals. Together, the results obtained in this work contribute to a better understanding of the molecular mechanisms underlying the participation of DE in sperm-egg fusion, and support the potential use of DE for the development of an immunological method of both animal and human fertility regulation. La banda aislada fue clonada y secuenciada. It is caused by mutations in a single gene that codifies for the chloride channel named cystic fibrosis transmembrane conductance regulator CFTR Kerem et al. A clear relationship between the genetic defect and the mechanisms governing the disease has not been fully established. In the inflammatory medium of CF lung every pro-inflammatory cytokines tested were elevated and the concentration of anti-inflammatory cytokine interleukin IL was considerably decreased. One of the differential display isolated fragments was cloned and sequenced. They codify for proteins with unknown activity. Northern blots assays, using 32P labeled hscc1 as velocidad de citas marseille 50 answer probe, a double band of 3,7 kbp was observed. Maximum mRNA levels were obtained after treating the cells with 0. B Cafferata E Velocidad de citas marseille 50 answer A, but 2. B dominant negative expressing virus. In order to better understand which cellular functions depend on CFTR channel activity and which factors contribute to the pulmonary defects in cystic fibrosis, we search for possible genes having a CFTR-dependent expression. We have isolated and identified the tyrosine kinase c-Src as a differential gene, which was up-regulated in CFDE cells. In addition, immuno-histochemical analysis showed and increased c-Src in the CF lung. The most important problem in cystic fibrosis results from obstruction of ducts in several organs due to excessive mucus secretion Hutchison and Govan, The overexpression of mucins in turn might lead to susceptibility to Pseudomonas aeruginosa infection in cases of CF Basbaum et al. In addition, c-Src velocidad de citas marseille 50 answer been involved in mucin production in response to diverse insults Basbaum et al. These data suggest that the CFTR failure produce an elevated MUC1 expression in the airway and this occurs previously to lung infection. Dentro del marco del proyecto genoma de T. Trypanosoma cruzi is a parasitic protozoan that causes Chagas disease. As part of the T. To accomplish the construction of the physical map of the T. In addition, we also constructed circular artificial chromosomes in yeast, based on a T. To perform functional genomic studies we designed and constructed a vector that can be used as an artificial chromosome in T. Finally, comparison and sequence analysis allowed us the identification of large genomic sintenic regions among T. Las ribozimas resultaron ser activas y tener una incrementada estabilidad frente a nucleasas. Oligonucleotides have gained credibility and attention as potential therapeutic agents based on the gene therapy principle. The fundament of the antisense strategy consists in the selective inhibition of the gene expression by means of an oligonucleotide carrying a complementary sequence to that of the mRNA that codifies for the target protein. In particular, ribozymes, RNA molecules with a defined sequence and three-dimensional structure that show velocidad de citas marseille 50 answer activity; appear as an interesting alternative, due to the fact that they combine the antisense action with a catalytic velocidad de citas marseille 50 answer. Since oligonucleotides are rapidly degraded by nucleases present both, in serum and intracellularly, it is mandatory to chemically modify them in order to obtain drugs with proper half life times. In the case of ribozymes and other RNA analogues, additional structural velocidad de citas marseille 50 answer must be taken velocidad de citas marseille 50 answer account in order to preserve activity or a particular function. Among the modifications developed so far, those involving the 2'-position proved to be useful, but they lack the 2'-hydroxyl group. The presence of this function showed to be of great importance for the correct folding of RNA molecules. Therefore, the development of a new generation of 2'-modified oligonucleotides carrying the 2'-hydroxyl is a promising alternative for the design of resistant ribozymes. Having in mind this goal, a new kind of analogues is proposed in this work, the 2'-C-methylnucleotides. They are expected to be potentially useful for generating RNA mimics resistant to the degradation by nucleases. ![]() The 2'-C-methyluridine was syntehsized by a stereoselective strategy, the 2'-hydroxyl group was regioselectively protected and the corresponding phosphoramidite for solid phase synthesis of oligonucleotides was prepared. In addition, a conformational study of the 2'-C-methyluridine in solution was carried out by RMN techniques and these data were compared with those obtained by computational calculations. The results showed that the preferred sugar conformation of this nucleoside is the same than the one adopted by the natural uridine, and therefore, it is expected that both molecules will position the 2'-hydroyl group with the same orientation. With the aim of testing our hypothesis, the new monomer was introduced in the catalytic core of a hammerhead ribozyme in those positions where the 2'-hydroxyl group showed to be important for the activity. The modified ribozymes were active in vitro and displayed an increased resistance to nucleases. The affinity for RNA and DNA complementary sequences of oligonucleotides containing the new modification and the 2'S -2'deoxy-2'-C-methyluridine is also reported. La arginina quinasa cataliza la transferencia reversible de velocidad de citas marseille 50 answer grupo fosfato entre el ATP y la L-arginina. En el rango de tiempo de cultivo estudiado, los niveles de ARNm mostraron solo cambios menores. Estas variaciones pueden ser reproducidas utilizando medio velocidad de citas marseille 50 answer o medio fresco. Arginine kinase catalyzes the reversible transphosphorylation between ATP and L-arginine. This work reports one of the first successful over-expression models of an endogenous enzyme, such as arginine kinase. The cells transfected with arginine kinase showed an increase in cell density and replication rate, suggesting that phosphagens could be involved in cell division. Furthermore, the arginine kinase activity was increased continuously during the exponential phase of growth. A correlation between growth rate, enzyme-specific activity and enzyme protein was observed. In the whole range of the culture time mRNA levels showed minor changes. Overexpressed arginine kinase has a degradation kinetics along the parasite growth curve coincident with the increment of the endogenous enzyme protein and activity, indicating that arginine kinase activity might be regulated by proteolysis. Arginine uptake was measured in Trypanosoma cruzi epimastigote cells along the in vitro culture growth phases. Arginine uptake decreased continuously from the 3rd to the 14th day. These fluctuations could be resembled using conditioned or fresh medium. Arginine starvation, cell density and carbon source availability also affect the arginine uptake. In trypomastigote cells, the infective and nonreplicative stage, arginine kinase activity and expression were 2. These results suggest a correlation between arginine uptake, the cell replication rate, and the increase in the arginine kinase specific activity. La arginina quinasa de Trypanosoma cruzi: Alonso, Guillermo Daniel Director: The Trypanosome cruzi, is a flagellate protozoan parasite responsible for the Chagas' disease in Latin America. The mechanisms of control of gene expression are not well understood, since the parasite processes nearly all of its pre-mRNAs by trans-splicing which is different from cis-splicing, in their insect and mammalian hosts. Understanding the molecular basis of such mechanism is important in order to develop drugs that could interrupt the parasite's vital cycle. Here we present for the first time in a trans-splicing performing organism, the cloning and characterization of two important proteins involved in the catalysis and control of pre-mRNA processing. These proteins, called TcSR, a member of the serine-arginine SR protein family of splicing factors and its associated kinase. TcSRPK, showed a highly conserved activity both in vitro and in vivo, velocidad de citas marseille 50 answer a variety of functional assays. Although this discards the proteins as potential targets for therapeutic drug development, it illustrates on the striking conservation that two apparent different pathways like cis- and trans-splicing can show. All Bilder auf Stocklib. Velocidad de citas marseille 50 answer unseren Kunden zur Verwendung der Bilder völlige Sicherheit zu bieten, müssen sie tadellos sein. Sämtliche Bilder mit erkennbaren Models sind daher sicher zu verwenden, sofern nicht anders angegeben. Unser Fotoarchiv kann vollkommen sorgenfrei für ihre kommerziellen, redaktionellen und Ihre Werbeprojekte verwendet werden. Der Kauf von lizenzfreien Inhalten bedeutet, dass keine zusätzlichen Nutzungsrechte für die Verwendung des Bildes durch Sie oder Ihr Unternehmen erworben werden müssen. Unglaubliche Bilder. Alle Motive Fotografie Vektor. 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