Descripción: Fil:Eguia, M.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.

Descripción: An enzyme, aminolaevulinate dehydratase (5-aminolaevulinate hydro-lyase (adding 5-aminolaevulinate and cyclizing), EC 4.2.1.24), which catalyzes the following reaction: {A figure is presented} has been isolated from yeast. Its purification and some of its properties have been studied. 5-Aminolaevulinate synthetase, another enzyme involved in porphyrin biosynthesis, has been detected in the mitochondrial particles. © 1967.

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

Descripción: The insect tracheal system is a continuous tubular network that ramifies into progressively thinner branches to provide air directly to every organ and tissue throughout the body. During embryogenesis the basic architecture of the tracheal system develops in a stereotypical and genetically controlled manner. Later, in larval stages, the tracheal system becomes plastic, and adapts to particular oxygen needs of the different tissues of the body. Oxygen sensing is mediated by specific prolyl-4-hydroxylases that regulate protein stability of the alpha subunit of oxygen-responsive transcription factors from the HIF family. Tracheal cells are exquisitely sensitive to oxygen levels, modulating the expression of hypoxia-inducible proteins that mediate sprouting of tracheal branches in direction to oxygen-deprived tissues. © 2009 Elsevier Ltd. All rights reserved.

Descripción: Osmolarity not only plays a key role in celluar homeostasis but also challenges cell survival. The molecular understanding of osmosis has not yet been completely achieved, and the discovery of aquaporins as molecular entities involved in water transport has caused osmosis to again become a focus of research. The main questions that need to be answered are the mechanism underlying the osmotic permeability coefficients and the extent to which aquaporins change our understanding of osmosis. Here, attempts to answer these questions are discussed. Critical aspects of the state of the state of knowledge on osmosis, a topic that has been studied since 19th century, are reviewed and integrated with the available information provided by in vivo, in vitro and in silico approaches. © 2012 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.

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: The projections of mechanosensory hairs located on the dorsal and lateral head of the adult haematophagous bug Triatoma infestans were analyzed by means of cobalt filling. Axons run into the anterior and posterior tegumentary nerve and project through the brain to the ventral nerve cord. The fibres are small in diameter and run as a fascicle. Some branches run into suboesophageal and prothoracic centres; others run as far as to the mesothoracic ganglion. These sensory projections resemble that of wind-sensitive head hairs of the locust. The functional role of this sensory system in this species is discussed.

Descripción: The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that mediates most of the toxic and endocrine-disruptive actions of aromatic compounds in the ovary. Paradoxically, this receptor has been shown to play important roles in normal female reproductive function as well. Although knowledge of AHR expression regulation in the ovary is of crucial significance to understand the receptor biology and its function in reproductive physiology, there are only limited data in this area. The purpose of the present study was to establish the possible regulation that AHR might undergo in ovarian cells. Here we show that the hormones FSH and estradiol are able to reduce AHR protein and transcript levels in granulosa cells in a way that parallels the changes observed in ovarian tissue across the rat estrous cycle. These findings suggest that estradiol and FSH would be cycle-associated endogenous modulators of AHR expression. In addition, we show that in granulosa cells the receptor is rapidly downregulated via proteasomal degradation following treatment with AHR ligands. However, prolonged treatment with an agonist caused an increase in Ahr mRNA levels. These actions would constitute a regulatory mechanism that both attenuates AHR signal rapidly and replenishes the cellular receptor pool in the long term. In conclusion, our results indicate that AHR expression is regulated by classical hormones and by its own ligands in granulosa cells. © 2006 by the Society for the Study of Reproduction, Inc.

Descripción: The proopiomelanocortin gene (POMC) encodes several bioactive peptides, including adrenocorticotropin hormone, α-, β-, and γ-melanocyte-stimulating hormone, and the opioid peptide β-endorphin, which play key roles in vertebrate physiology. In the human, mouse, and chicken genomes, there is only one POMC gene. By searching public genome projects, we have found that Tetraodon (Tetraodon nigroviridis), Fugu (Takifugu rubripes), and zebrafish (Danio rerio) possess two POMC genes, which we called POMCα and POMCβ, and we present phylogenetic and mapping evidence that these paralogue genes originated in the whole-genome duplication specific to the teleost lineage over 300 MYA. In addition, we present evidence for two types of subfunction partitioning between the paralogues. First, in situ hybridization experiments indicate that the expression domains of the ancestral POMC gene have been subfunctionalized in Tetraodon, with POMCα expressed in the nucleus lateralis tuberis of the hypothalamus, as well as in the rostral pars distalis and pars intermedia (PI) of the pituitary, whereas POMCβ is expressed in the preoptic area of the brain and weakly in the pituitary PI. Second, POMCβ genes have a β-endorphin segment that lacks the consensus opioid signal and seems to be under neutral evolution in tetraodontids, whereas POMCα genes possess well-conserved peptide regions. Thus, POMC paralogues have experienced subfunctionalization of both expression and peptide domains during teleost evolution. The study of regulatory regions of fish POMC genes might shed light on the mechanisms of enhancer partitioning between duplicate genes, as well as the roles of POMC-derived peptides in fish physiology.

Descripción: Aims: Analysis of the physiology and metabolism of Escherichia coli arcA and creC mutants expressing a bifunctional alcohol-acetaldehyde dehydrogenase from Leuconostoc mesenteroides growing on glycerol under oxygen-restricted conditions. The effect of an ldhA mutation and different growth medium modifications was also assessed. Methods and Results: Expression of adhE in E. coli CT1061 [arcA creC(Con)] resulted in a 1·4-fold enhancement in ethanol synthesis. Significant amounts of lactate were produced during micro-oxic cultures and strain CT1061LE, in which fermentative lactate dehydrogenase was deleted, produced up to 6·5 ± 0·3 g l-1 ethanol in 48 h. Escherichia coli CT1061LE derivatives resistant to >25 g l-1 ethanol were obtained by metabolic evolution. Pyruvate and acetaldehyde addition significantly increased both biomass and ethanol concentrations, probably by overcoming acetyl-coenzyme A (CoA) shortage. Yeast extract also promoted growth and ethanol synthesis, and this positive effect was mainly attributable to its vitamin content. Two-stage bioreactor cultures were conducted in a minimal medium containing 100 μg l-1 calcium d-pantothenate to evaluate oxic acetyl-CoA synthesis followed by a switch into fermentative conditions. Ethanol reached 15·4 ± 0·9 g l-1 with a volumetric productivity of 0·34 ± 0·02 g l-1 h-1. Conclusions: Escherichia coli responded to adhE over-expression by funnelling carbon and reducing equivalents into a highly reduced metabolite, ethanol. Acetyl-CoA played a key role in micro-oxic ethanol synthesis and growth. Significance and Impact of the Study: Insight into the micro-oxic metabolism of E. coli growing on glycerol is essential for the development of efficient industrial processes for reduced biochemicals production from this substrate, with special relevance to biofuels synthesis. © 2010 The Society for Applied Microbiology.

Descripción: Despite considerable progress in our understanding of the interplay between immune and endocrine systems, the role of thyroid hormones and their receptors in the control of adaptive immunity is still uncertain. Here, we investigated the role of thyroid hormone receptor (TR) β 1 signaling in modulating dendritic cell (DC) physiology and the intracellular mechanisms underlying these immunoregulatory effects. Exposure of DCs to triiodothyronine (T 3 ) resulted in a rapid and sustained increase in Akt phosphorylation independently of phosphatidylinositol 3-kinase activation, which was essential for supporting T 3 -induced DC maturation and interleukin (IL)-12 production. This effect was dependent on intact TRβ 1 signaling as small interfering RNA-mediated silencing of TRβ 1 expression prevented T 3 -induced DC maturation and IL-12 secretion as well as Akt activation and IκB-ε degradation. In turn, T 3 up-regulated TRβ 1 expression through mechanisms involving NF-κB, suggesting an autocrine regulatory loop to control hormone-dependent TRβ 1 signaling. These findings were confirmed by chromatin immunoprecipitation analysis, which disclosed a new functional NF-κB consensus site in the promoter region of the TRB1 gene. Thus, a T 3 -induced NF-κB-dependent mechanism controls TRβ 1 expression, which in turn signals DCs to promote maturation and function via an Akt-dependent but PI3K-independent pathway. These results underscore a novel unrecognized target that regulates DC maturation and function with critical implications in immunopathology at the crossroads of the immune-endocrine circuits. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.

Descripción: Studies of the electrophysiological response to acetylcholine (ACh) in mammalian outer hair cells (OHCs) are hindered by the presence of a large potassium current, IK,n, most likely mediated by channels containing the KCNQ4 subunit. Since IK,n can be blocked by linopirdine, cholinergic effects might be better revealed in the presence of this compound. The aim of the present work was to study the effects of linopirdine on the ACh-evoked responses through α9α10-containing native and recombinant nicotinic cholinergic receptors. Responses to ACh were blocked by linopirdine in both OHCs and inner hair cells (IHCs) of rats at postnatal days 21-27 (OHCs) and 9-11 (IHCs). In addition, linopirdine blocked responses of recombinant α9α10 nicotinic cholinergic receptors (nAChRs) in a concentration-dependent manner with an IC50 of 5.2 μM. Block by linopirdine was readily reversible, voltage independent, and surmountable at high concentrations of ACh, thus suggestive of a competitive type of interaction with the receptor. The present results contribute to the pharmacological characterization of α9α10-containing nicotinic receptors and indicate that linopirdine should be used with caution when analyzing the cholinergic sensitivity of cochlear hair cells.

Descripción: Insects in general, and Drosophila in particular, are much more capable of surviving anoxia than vertebrates, and the mechanisms involved are of considerable biomedical and ecological interest. Temperature is likely to strongly affect both the rates of damage occurring in anoxia and the recovery processes in normoxia, but as yet there is no information on the effect of this crucial variable on recovery rates from anoxia in any animal. We studied the effects of temperature, and thus indirectly of metabolic flux rates, on survival and recovery times of individual male Drosophila melanogaster following anoxia and O2 reperfusion. Individual flies were reared at 25° and exposed to an anoxic period of 7.5, 25, 42.5 or 60?min at 20, 25 or 30°. Before, during and after anoxic exposure the flies' metabolic rates (MRs), rates of water loss and activity indices were recorded. Temperature strongly affected the MR of the flies, with a Q10 of 2.21. Temperature did not affect the slope of the relationship between time to recovery and duration of anoxic exposure, suggesting that thermal effects on damage and repair rates were similar. However, the intercept of that relationship was significantly lower (i.e. recovery was most rapid) at 25°, which was the rearing temperature. When temperatures during exposure to anoxia and during recovery were switched, recovery times matched those predicted from a model in which the accumulation and clearance of metabolic end-products share a similar dependence on temperature. ©2011. Published by The Company of Biologists Ltd.

Descripción: Size distribution, sex ratio and use of burrows of the burrowing toad Rhinella fernandezae were studied in Buenos Aires province, Argentina. Two sites separated by approximately 300 m were studied: one was a road next to a swamp, and the other a garden of a country house located further from the swamp. We identified toad burrows, and individuals were sexed, measured and given an individual mark. Burrows were examined in subsequent months after the first sampling to assess the presence of toads. We found significant differences in the size distribution between areas, being the proportion of juveniles greater at the site next to the swamp where the reproduction of the species was observed. This result may suggest that the site located near to the swamp functions as a source habitat of individuals that migrate to the other site, where recruitment would be very scarce. Sex proportion of adults did not differ from 1:1 in neither the total population nor in each site, suggesting that there was not differential mortality by sex. Some toads changed burrows throughout the study period, but there were not differences in the frequency of change between adults and juveniles.

Descripción: Camponotus mus ants can associate sucrose and odour at the source during successive foraging cycles and use this memory to locate the nectar in the absence of other cues. These ants perform conspicuous trophallactic behaviour during recruitment while foraging for nectar. In this work, we studied whether Camponotus mus ants are able to establish this odour-sucrose association in the social context of trophallaxis and we evaluated this memory in another context previously experienced by the ant, as a nectar source. After a single trophallaxis of a scented solution, the receiver ant was tested in a Y-maze without any reward, where two scents were presented: in one arm, the solution scent and in the other, a new scent. Ants consistently chose the arm with the solution scent and stayed longer therein. Trophallaxis duration had no effect on the arm choice or with the time spent in each arm. Workers are able to associate an odour (conditioned stimulus) with the sucrose (unconditioned stimulus) they receive through a social interaction and use this memory as choice criteria during food searching.

Descripción: Spatial familiarization consists of a decrease in the exploratory activity over time after exposure to a place. Here, we show that a 30-min exposure to an open field led to a pronounced decrease in the exploratory behavior of rats, generating context familiarity. This behavioral output is associated with a selective decrease in hippocampal PKMζ levels. A short 5-min exposure did not induce spatial familiarity or a decrease in PKMζ, while inactivation of hippocampal PKMζ by the specific inhibitor ZIP was sufficient to induce spatial familiarity, suggesting that the decrease in PKMζ is involved in setting a given context as a familiar place. © 2008 Cold Spring Harbor Laboratory Press.

Descripción: Used vehicle tires are a source of mosquito vectors and a means of their introduction and expansion. With the aim of assessing the effects of urbanisation on the main mosquito vectors in temperate Argentina, the infestation levels of Aedes aegypti (L.) and Culex pipiens L. were studied in used tires from highly urbanised cities to low-urbanised small towns in Buenos Aires. Immatures of both species accounted for 96% of the 9,722 individuals collected; the total individuals collected represented seven species. The percentage of water-filled tires containing mosquitoes [container index (CI)] was 33% and the percentage of infested sites [site index (SI)] was 65.2%. These indexes decreased significantly from low to high urbanisation levels for both mosquito species. The relative abundance (RA) of Ae. aegypti immatures was slightly higher toward large cities, but showed no difference for Cx. pipiens. The CI of shaded tires was significantly higher than the CI of exposed tires for both mosquito species. There was no difference in RA values between shaded and sunlit tires. The CI and the SI were highest during the summer across the urbanisation levels, except for Cx. pipiens, which continued to increase during the autumn in small towns. Results related to urbanisation gradient, sunlit exposure and seasonality are discussed.