Descripción: This paper reviews basic concepts of modern molecular biology with the premise that its influence in today's medicine is so important that its knowledge cannot remain limited to a few experts. I first analyze the overall structure and organization of human genes, their split nature and the flow of genetic information from DNA to protein. The role of transcriptional control in the regulation of gene expression and cell differentiation is described by introducing experimental examples that define the importance of "master" genes. Basic concepts of genetic engineering, the generation of transgenic and knock out animals and the uses of molecular biology in clinical diagnosis, paternity tests and forensic medicine are presented. Finally, I discuss the possibilities of gene therapy and the fantasies and realities of transgenesis and cloning by nuclear transplant in humans.

Descripción: Early reports indicate that trophallaxis, i.e. the exchange of liquid food by mouth, may allow honeybees to assign nectar odours with predictive values to anticipate biological meaningful reward stimuli. Nevertheless, this type of learning has not been addressed directly. In the present study, pairs of animals were isolated to induce trophallaxis under controlled conditions and, afterwards, the honeybee proboscis extension reflex was used to investigate the possible role of trophallaxis in learning olfactory cues. The results demonstrate unambiguously that associative learning actually occurs by means of trophallaxis. Animals associate the odour (as the conditioned stimulus or CS) and the sucrose (as the unconditioned stimulus or US) present in the solution they receive through trophallaxis. Moreover, this particular kind of learning leads to long-term olfactory memories after a single learning trial, even when trophallaxis is brief. In addition, we found that the strength of association is clearly affected by CS and US intensity as well as the recent previous foraging experiences of the animals. Comparisons are presented among several features of the learning during trophallaxis and the classical conditioning of the proboscis extension reflex with restrained subjects. Finally, the relevance of learning through trophallaxis in the task of successful foraging is discussed.

Descripción: Fil:Schweigmann, N. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Fil:Caceres, J.F. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: Genomes contain the necessary information to ensure that genes are expressed in the right place, at the right time, and with the proper rate. Metazoan developmental genes often possess long stretches of DNA flanking their coding sequences and/or large introns which contain elements that influence gene expression. Most of these regulatory elements are relatively small and can be studied in isolation. For example, transcriptional enhancers, the elements that generate the expression pattern of a gene, have been traditionally studied with reporter constructs in transgenic animals. These studies have provided and will provide invaluable insights into enhancer evolution and function. However, this experimental approach has its limits; often, enhancer elements do not faithfully recapitulate native expression patterns. This fact suggests that additional information in cis-regulatory regions modulates the activity of enhancers and other regulatory elements. Indeed, recent studies have revealed novel functional aspects at the level of whole cis-regulatory regions. First, the discovery of "shadow enhancers." Second, the ubiquitous interactions between cis-regulatory elements. Third, the notion that some cis-regulatory regions may not function in a modular manner. Last, the effect of chromatin conformation on cis-regulatory activity. In this article, I describe these recent findings and discuss open questions in the field. © 2012 Wiley Periodicals, Inc.

Descripción: Leptospirosis is a worldwide zoonosis caused by a spirochete that belongs to the genus Leptospira. In the last years, new methods, such as the PCR-based multiple-locus variable-number tandem repeat analysis (MLVA), have been developed for the genotyping of leptospires. In the present work, the MLVA patterns for all reference strains used in Argentina for bovine, ovine, porcine, equine, caprine and canine leptospirosis diagnosis, as well as in human and wild animal diagnosis, were obtained. MLVA results are presented in such a way that they can be readily used for the identification of these strains by the simple and direct comparison of agarose gels. Making the use and interpretation of the MLVA for leptospires typing easier will help increase the use of this method as a routine procedure for human and animal diagnosis, for epidemiological studies, vaccine control and other applications.

Descripción: Possible consequences of climate change in one of the world's largest wetlands (Ibera, Argentina) were analysed using a multi-scale approach. Climate projections coupled to hydrological models were used to analyse variability in wetland water level throughout the current century. Two potential scenarios of greenhouse gas emissions were explored, both resulting in an increase in the inter-annual fluctuations of the water level. In the scenario with higher emissions, projections also showed a long-term negative trend in water-level. To explore the possible response of biota to such water-level changes, species-area relationships of flora and aerial censuses of macro-fauna were analysed during an extraordinary dry period. Plant species richness at the basin scale was found to be highly resistant to hydrological changes, as the large dimension of the wetland acts to buffer against the water-level variations. However, local diversity decreased significantly with low water levels, leading to the loss of ecosystem resilience to additional stressors. The analysis of macro-fauna populations suggested that wetland provides refuge, in low water periods, for the animals with high dispersal ability (aquatic and migratory birds). On the contrary, the abundance of animals with low dispersal ability (mainly herbivorous species) was negatively impacted in low water periods, probably because they are required to search for alternative resources beyond the wetland borders. This period of resource scarcity was also related to increased mortality of large mammals (e.g. marsh deer) around water bodies with high anthropogenic enrichment and cyanobacteria dominance. The synergy between recurrent climatic fluctuations and additional stressors (i.e. biological invasions, eutrophication) presents an important challenge to the conservation of neotropical wetlands in the coming decades. © 2013 Úbeda et al.

Descripción: 1. 1. The present work undertakes a comparative study on the hexachlorobenzene (HCB) porphyria induction in female rats of Wistar and CHBBTHOM strains. The purpose was to characterize the CHBBTHOM strain with respect to the haem metabolic pathway, its regulatory mechanisms and its response to foreign drugs. 2. 2. After 7 weeks of treatment it was observed that the hepatic porphyrins increased 140 times, ALA-synthase 4 times and PCL was 73% inhibited in the Wistar strain. 3. 3. On the other hand the animals of CHBBTHOM strain showed lesser alteration on these parameters; hepatic porphyrins increased only 3-fold, ALA-synthase 1.7-fold and PCL was only 22% inhibited. 4. 4. Total iron liver content was nearly equal in both strains of rats. 5. 5. The results obtained would indicate that the lower susceptibility of the CHBBTHOM strain to acquire porphyria does not seem to be due to either: (1) congenital alterations of any parameters of the haem metabolic pathway, since the behaviour of normal animals from both strains was similar; or (2) a lower hepatic iron content in such animals. 6. 6. These findings would suggest that the differential response to HCB to this strain would be looked for in another metabolic pathway, such as that involved in the metabolization process of the toxic. © 1989.

Descripción: Several studies support that stored memories undergo a new period of consolidation after retrieval. It is not known whether this process, termed reconsolidation, requires the same transcriptional mechanisms involved in consolidation. Increasing evidence supports the participation of the transcription factor NF-κB in memory. This was initially demonstrated in the crab Chasmagnathus model of associative contextual memory, in which re-exposure to the training context induces a well characterized reconsolidation process. Here we studied the role of NF-κB in reconsolidation. NF-κB was specifically activated in trained animals re-exposed to the training context but not to a different context. NF-κB was not activated when animals were re-exposed to the context after a weak training protocol insufficient to induce long-term memory. A specific inhibitor of the NF-κB pathway, sulfasalazine, impaired reconsolidation when administered 20 min before re-exposure to the training context but was not effective when a different context was used. These findings indicate for the first time that NF-κB is activated specifically by retrieval and that this activation is required for memory reconsolidation, supporting the view that this molecular mechanism is required in both consolidation and reconsolidation.

Descripción: Cysteine proteinase isoforms, immunologically cross-reactive with cruzipain and with a similar apparent molecular mass, have been identified in epimastigotes of Trypanosoma cruzi by extraction and phase partition using the detergent Triton X-114. These isoforms are concentrated in the microsomal fraction obtained after differential centrifugation, which is known to consist essentially of plasma membrane, can be labelled by incubation of live parasites with sulfo-NHS-biotin, and bind to cystatin-sepharose affinity columns. They are present, albeit with a different electrophoretic pattern, in the epimastigote, amastigote and trypomastigote stages of the parasite.

Descripción: Since the start of the human genome project, a great number of genome projects on other "model" organism have been initiated, some of them already completed. Several initiatives have also been started on parasite genomes, mainly through support from WHO/TDR, involving North-South and South-South collaborations, and great hopes are vested in that these initiatives will lead to new tools for disease control and prevention, as well as to the establishment of genomic research technology in developing countries. The Trypanosoma cruzi genome project, using the clone CL-Brener as starting point, has made considerable progress through the concerted action of more than 20 laboratories, most of them in the South. A brief overview of the current state of the project is given.

Descripción: Factors affecting mating behaviour in the bug Triatoma infestans were quantitatively studied in the laboratory. Experimental conditions were established so that the probability of copulation increased with the time elapsed since the first adult meal. Copulatory attempts by males did not vary as a function of time, but rejections by females became significantly less frequent with the post feeding time. Non-receptive females displayed four types of rejection behaviour, i.e. flattening, stridulation, evasion and abdominal movements. The occurrence of stridulation performed by females in a sexual context was observed in a regular fashion and was quantified for the first time in this species.

Descripción: The aim of this work was to study the short and long term influences of ascorbic acid on Hydrochoerus hydrochaeris, if supplemented in their food. No differences regarding food intake were observed in the absence of vitamin C. On a daily basis, animals accustomed to food containing ascorbic acid prefered to continue eating the same food. Food preference in capybaras did not seem to depend on ascorbic acid availability; however, when accustomed to vitamin C, capybaras might recognize and select ascorbic acid in subsequent food. Mechanisms allowing capybaras to "evaluate" the nutritional quality of their food are discussed, as well as the adaptive value of this behavior in free ranging populations. © 2009 Tecpar.

Descripción: We investigated the molecular basis of the activity of 4-phenoxyphenoxyethyl thiocyanate (WC-9) against Trypanosoma cruzi, the etiological agent of Chagas' disease. We found that growth inhibition of T. cruzi epimastigotes induced by this compound was associated with a reduction in the content of the parasite's endogenous sterols due to a specific blockade of their de novo synthesis at the level of squalene synthase.

Descripción: When Ca2+ is released from internal stores in living cells, the resulting wave of increased concentration can travel without deformation (continuous propagation) or with burst-like behavior (saltatory propagation). We analyze the 'fire-diffuse-fire' model in order to illuminate the differences between these two modes of propagation. We show that the Ca2+ release wave in immature Xenopus oocytes and cardiac myocytes is saltatory, whereas the fertilization wave in the mature oocyte is continuous.

Descripción: Fil:Mocskos, E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: In the mammalian auditory system, the synapse between efferent olivocochlear (OC) neurons and sensory cochlear hair cells is cholinergic, fast, and inhibitory. This efferent synapse is mediated by the nicotinic α9α10 receptor coupled to the activation of SK2 Ca 2+-activated K+ channels that hyperpolarize the cell. So far, the ion channels that support and/or modulate neurotransmitter release from the OC terminals remain unknown. To identify these channels, we used an isolated mouse cochlear preparation and monitored transmitter release from the efferent synaptic terminals in inner hair cells (IHCs) voltage clamped in the whole-cell recording configuration. Acetylcholine (ACh) release was evoked by electrically stimulating the efferent fibers that make axosomatic contacts with IHCs before the onset of hearing. Using the specific antagonists for P/Q- and N-type voltage-gated calcium channels (VGCCs), ω-agatoxin IVA and ω-conotoxin GVIA, respectively, we show that Ca2+ entering through both types of VGCCs support the release process at this synapse. Interestingly, we found that Ca2+ entering through the dihydropiridine-sensitive L-type VGCCs exerts a negative control on transmitter release. Moreover, using immunostaining techniques combined with electrophysiology and pharmacology, we show that BK Ca2+-activated K+ channels are transiently expressed at the OC efferent terminals contacting IHCs and that their activity modulates the release process at this synapse. The effects of dihydropiridines combined with iberiotoxin, a specific BK channel antagonist, strongly suggest that L-type VGCCs negatively regulate the release of ACh by fueling BK channels that are known to curtail the duration of the terminal action potential in several types of neurons. Copyright © 2010 the authors.