Showing papers by "National University of Cuyo published in 2005"
TL;DR: A rise in intracellular calcium concentration enhanced exosome secretion in Rab11 wt overexpressing cells and reversed the inhibition of the mutants, suggesting that both Rab11 and calcium are involved in the homotypic fusion of MVBs.
Abstract: Multivesicular bodies (MVBs) are membranous structures within 60-100 nm diameter vesicles accumulate. MVBs are generated after invagination and pinching off of the endosomal membrane in the lumen of the vacuole. In certain cell types, fusion of MVBs with the plasma membrane results in the release of the internal vesicles called exosomes. In this report we have examined how an increase in cytosolic calcium affects the development of MVBs and exosome release in K562 cells overexpressing GFP-Rab11 wt or its mutants. In cells overexpressing the Rab11Q70 L mutant or Rab11 wt, an increase in the cytosolic calcium concentration induced by monensin caused a marked enlargement of the MVBs. This effect was abrogated by the membrane permeant calcium chelator BAPTA-AM. We also examined the behavior of MVBs in living cells by time lapse confocal microscopy. Many MVBs, decorated by wt or Q70L mutant GFP-Rab11, were docked and ready to fuse in the presence of a calcium chelator. This observation suggests that Rab11 is acting in the tethering/docking of MVBs to promote homotypic fusion, but that the final fusion reaction requires the presence of calcium. Additionally, a rise in intracellular calcium concentration enhanced exosome secretion in Rab11 wt overexpressing cells and reversed the inhibition of the mutants. The results suggest that both Rab11 and calcium are involved in the homotypic fusion of MVBs.
445 citations
TL;DR: The results suggest that transit through the autophagic pathway increases the infection with Coxiella by providing a niche more favourable to their initial survival and multiplication.
Abstract: Pathogens evolved mechanisms to invade host cells and to multiply in the cytosol or in compositionally and functionally customized membrane-bound compartments. Coxiella burnetii, the agent of Q fever in man is a Gram-negative gamma-proteobacterium which multiplies in large, acidified, hydrolase-rich and fusogenic vacuoles with phagolysosomal-like characteristics. We reported previously that C. burnetii phase II replicative compartments are labelled by LC3, a protein specifically localized to autophagic vesicles. We show here that autophagy in Chinese hamster ovary cells, induced by amino acid deprivation prior to infection with Coxiella increased the number of infected cells, the size of the vacuoles, and their bacterial load. Furthermore, overexpression of GFP-LC3 or of GFP-Rab24 - a protein also localized to autophagic vacuoles - likewise accelerated the development of Coxiella-vacuoles at early times after infection. However, overexpression of mutants of those proteins that cannot be targeted to autophagosomes dramatically decreased the number and size of the vacuoles in the first hours of infection, although by 48 h the infection was similar to that of non-transfected controls. Overall, the results suggest that transit through the autophagic pathway increases the infection with Coxiella by providing a niche more favourable to their initial survival and multiplication.
254 citations
TL;DR: S. arcanum and S. huaylasense are described and illustrated, two new wild tomato species segregated from Solanum peruvianum sensu lato, and a list of all 13 species of wild tomatoes recognized, and their equivalent former names in Lycopersicon.
Abstract: Solanum arcanum and S. huaylasense, two new wild tomato species segregated from Solanum peruvianum sensu lato, are described and illustrated. These two new species are placed in a key with two other segregates of S. peruvianum sensu lato: S. peruvianum sensu stricto and S. corneliomulleri, and the morphologically similar species S. chilense. We also present a list of all 13 species of wild tomatoes we recognize, and their equivalent former names in Lycopersicon.
211 citations
TL;DR: New AFLP data are largely concordant with the GBSSI and morphological data and in general support the species outlined in the latest treatment by C.M. Rick, but demonstrate the distinct nature of northern and southern Peruvian populations of S. peruvianum, and suggest that their taxonomy needs revision.
Abstract: ac.uk Wild tomatoes (Solanum section Lycopersicon) are native to western South America. The delimitation and relationships of tomato species have differed widely depending upon whether morphological or biological species concepts are considered more important. Molecular data from mitochondrial, nuclear, and chloroplast DNA restriction fragment length polymorphisms (RFLPs), nuclear microsatellites, isozymes, and gene sequences of internal transcribed spacers of nuclear ribosomal DNA (ITS; multiple-copy), the single-copy nuclear encoded Granule-bound Starch Synthase gene (GBSSI or waxy), and morphology, have been used to examine hypotheses of species relationships. This study is a companion to the previous GBSSI gene sequence study and to the morphological study of relationships of all ten wild tomato species (including the recently described S. galapagense), with a concentration on the most widespread and variable species S. peruvianum s.l. These new AFLP data are largely concordant with the GBSSI and morphological data and in general support the species outlined in the latest treatment by C.M. Rick, but demonstrate the distinct nature of northern and southern Peruvian populations of S. peruvianum, and suggest that their taxonomy needs revision. Solanum ochranthum is supported as sister to wild tomatoes, and S. habrochaites and S. pennellii reside in a basal polytomy in the tomato clade.
201 citations
TL;DR: The results suggest that an adequate supplementation of RV might help to prevent or delay the occurrence of atherogenic cardiovascular diseases associated to insulin-resistant states.
151 citations
TL;DR: It is shown that, in unactivated sperm, SNAREs are locked in heterotrimeric cis complexes, and the unidirectional and sequential disassembly and assembly of SNARE complexes drive acrosomal exocytosis.
Abstract: The dynamics of SNARE assembly and disassembly during membrane recognition and fusion is a central issue in intracellular trafficking and regulated secretion. Exocytosis of sperm's single vesicle—the acrosome—is a synchronized, all-or-nothing process that happens only once in the life of the cell and depends on activation of both the GTP-binding protein Rab3 and of neurotoxin-sensitive SNAREs. These characteristics make acrosomal exocytosis a unique mammalian model for the study of the different phases of the membrane fusion cascade. By using a functional assay and immunofluorescence techniques in combination with neurotoxins and a photosensitive Ca2+ chelator we show that, in unactivated sperm, SNAREs are locked in heterotrimeric cis complexes. Upon Ca2+ entry into the cytoplasm, Rab3 is activated and triggers NSF/α-SNAP-dependent disassembly of cis SNARE complexes. Monomeric SNAREs in the plasma membrane and the outer acrosomal membrane are then free to reassemble in loose trans complexes that are resistant to NSF/α-SNAP and differentially sensitive to cleavage by two vesicle-associated membrane protein (VAMP)–specific neurotoxins. Ca2+ must be released from inside the acrosome to trigger the final steps of membrane fusion that require fully assembled trans SNARE complexes and synaptotagmin. Our results indicate that the unidirectional and sequential disassembly and assembly of SNARE complexes drive acrosomal exocytosis.
130 citations
TL;DR: Angiotensin II-induced reactive oxygen species (ROS) generation is altered in vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) during the phases of prehypertension, developing hypertension, and established hypertension and the putative role of IGF-1R was assessed.
81 citations
TL;DR: In this paper, the effect of temperature and soluble solids concentration on density, coefficient of thermal expansion and viscosity of clear grape juices from Mendoza, Argentina, collected during 1999 and 2001, was studied.
72 citations
TL;DR: In this article, the heavy metal profiles of short sediment cores sampled from lakes located in Nahuel Huapi National Park, Northern Patagonia, Argentina, were determined by INAA, and core dating was performed by measuring natural 210Pb and anthropogenic 137Cs, and by identification of tephra layers.
Abstract: Heavy metal profiles of short sediment cores sampled from lakes located in Nahuel Huapi National Park, Northern Patagonia, Argentina, were determined by INAA. Core dating was performed by measuring natural 210Pb and anthropogenic 137Cs, and by identification of tephra layers. No evidence was found for the input increase of the trace elements Sb, Ba, Cs, Zn, Co, Hf, Ni, Se, Sr, Ti, U, and V in the lake environment. High As concentrations (up to 250 μg . g-1) were found in relation with the diffusion processes of Mn and Fe oxides. Strong correlation was observed between the Br concentration and organic matter content, but no evidence was found for the relevant increase of Br inputs in recent years. Ag concentrations were found to be enriched in the upper core layers over the baseline values determined for deep layers ranging from 0.1 to 0.2 μg . g-1. Hg concentration profiles were also enriched in the upper core layers over the baseline (from less than 0.07 to 0.2 μg . g-1 for pre-industrial time, to 0.1 to 0.3 μg . g-1 for modern times) but in relation with the increased organic matter content of the sediment.
70 citations
TL;DR: A model for fiber reinforced composites that takes into account the fiber slipping is presented and is attractive for the analysis of reinforced concrete problems at the macrostructural level since the explicit discretization of reinforcing bars and interface is not required, with the consequent computational cost reduction.
Abstract: A model for fiber reinforced composites that takes into account the fiber slipping is presented in this paper and applied to the analysis of reinforced concrete elements. The model is formulated within the framework of the plasticity theory and the mixtures theory, considering two phases corresponding to the matrix (concrete) and the fibers (reinforcing bars) and modifying the behavior of the last to take into account the relative displacement between the two phases. An elasto-plastic interface model developed by other writers is used to describe the bond–slip mechanism. The resulting model is attractive for the analysis of reinforced concrete problems at the macrostructural level since the explicit discretization of reinforcing bars and interface is not required, with the consequent computational cost reduction. The paper concludes with application examples and comparisons with experimental results of reinforced concrete elements that show the capacity of the model developed.
68 citations
Journal Article•
TL;DR: Protection against tubulointerstitial fibrosis by Losartan, independent from changes in blood pressure, includes decreased oxidative stress linked to upregulation of HSP 70 expression.
Abstract: Angiotensin II, a profibrotic cytokine, plays a main role in the initiation of renal fibrogenesis at a very early stage leading to a progressive loss of renal function in unilateral ureteral obstruction (UUO). We studied the involvement of AT1 angiotensin II receptor in the physiopathology of tubulointerstitial fibrosis in UUO, focusing in the regulation of the oxidative stress state and in the HSP 70 expression, in renal tissue. UUO or control sham operation was perform to Wistar Kyoto rats after being treated with the AT1 angiotensin II receptor antagonist Losartan (10 mg/kg/day) in the drinking water for 15 days. Twenty four hours later, mRNA AT1 receptor expression was studied. Renal fibrosis was evaluated through TGFbeta expression and superoxide dismutase (SOD) activity, hydroxyl radicals, O2- and total antioxidant activity were measured by spectrophotometric assay. Immunohistochemical and Western blot analysis of HSP 70 were performed. A non-hypotensive dose of Losartan significantly down regulated the expression of AT1 receptor. Prevention of renal fibrogenesis by Losartan treatment was demonstrated by TGFbeta mRNA expression similar to control. Oxidative stress in obstructed kidney was evident since a decreased SOD activity and a two-fold increase in the concentration of hydroxyl radicals and O2- was observed when compared to the control. Losartan produced down regulation of ROS with recovery of the SOD activity and higher expression of HSP 70 compared to obstructed kidney of rats receiving vehicle. We can conclude that after 24 hr of UUO, protection against tubulointerstitial fibrosis by Losartan, independent from changes in blood pressure, includes decreased oxidative stress linked to upregulation of HSP 70 expression.
TL;DR: A key role for alpha-SNAP/NSF in the AR is suggested, and the understanding of the molecular players involved in the vesicle-to-plasma membrane fusion taking place during exocytosis is strengthened.
Abstract: The acrosome is a membrane-limited granule that overlies the nucleus of the mature spermatozoon. In response to physiological or pharmacological stimuli it undergoes a special type of Ca2+-dependent exocytosis termed the acrosome reaction (AR), which is an absolute prerequisite for fertilization. Aided by a streptolysin-O permeabilization protocol developed in our laboratory, we have previously demonstrated requirements for Rab3A, N-ethylmaleimide-sensitive factor (NSF), several soluble NSF-attachment protein receptor (SNARE) proteins, and synaptotagmin VI in the human sperm AR. Here, we show that alpha-soluble NSF-attachment protein (alpha-SNAP), a protein essential for most fusion events through its interaction with NSF and the SNARE complex, exhibits a direct role in the AR. First, the presence of alpha-SNAP is demonstrated by the Western blot of human sperm protein extracts. Immunostaining experiments reveal an acrosomal localization for this protein. Second, the Ca2+ and Rab3A-triggered ARs are inhibited by anti-alpha-SNAP antibodies. Third, bacterially expressed alpha-SNAP abolishes exocytosis in a fashion that depends on its interaction with NSF. Fourth, we show a requirement for alpha-SNAP/NSF in a prefusion step early in the exocytotic pathway, after the tethering of the acrosome to the plasma membrane and before the efflux of intra-acrosomal Ca2+. These results suggest a key role for alpha-SNAP/NSF in the AR, and strengthen our understanding of the molecular players involved in the vesicle-to-plasma membrane fusion taking place during exocytosis.
TL;DR: Higher apoptosis and topo IIαa levels in primary tumors were associated with greater responsiveness to anthracyclines, and topa IIα levels declined in responsive tumors.
Abstract: Summary Purpose. Laboratory evidence indicates that tumor growth depends on the balance between cell proliferation and cell death, and many anticancer agents may exert their therapeutic effect by decreasing proliferation and increasing apoptosis. Additionally, clinical observations indicate that overexpression of HER-2 or topoisomerase IIa (topo IIa) may be predictors of better response to anthracyclines in breast cancer. The objective of this study was to determine if proliferation (Ki-67), apoptosis (TUNEL), and expression of HER-2 and topo IIa are affected by anthracycline treatment, and if these molecular markers predict anthracycline responsiveness. Experimental design. Thirty-three women with primary breast tumors ‡3 cm received either doxorubicin (75 mg/ m 2 ) or epirubicin (120 mg/m 2 ) for 4 cycles before surgery. Clinical response was evaluated after 4 cycles of treatment. Changes in molecular markers were assessed from core needle biopsy taken before treatment (D0), at 24–48 h (Dl) and on day 7 (D7) while on treatment, and from the surgical specimen excised on day 84 (D84) after the fourth cycle of chemotherapy. Results. The overall clinical response rate was 51% (17 of 33 patients), with a 12% complete clinical response rate (4 of 33 patients). There were trends for tumors with higher apoptosis and topo IIa at baseline (D0) to be more responsive to anthracyclines, p = 0.1 and p = 0.08, respectively. Median apoptosis increased from D0 to Dl (p = 0.06) while median Ki-67 decreased (p = 0.07). Overall, expression of HER-2 remained stable throughout the chemotherapy administration. By Day 84, topo IIa had significantly decreased from baseline in responders, while it increased in non-responders, p = 0.03. Conclusions. In human primary breast cancer, anthracycline treatment causes an early increase in apoptosis and a decrease in proliferation. In this pilot study, higher apoptosis and topo IIaa levels in primary tumors were associated with greater responsiveness to anthracyclines, and topo IIa levels declined in responsive tumors.
TL;DR: It is shown that short incubations with cyclodextrin, a cholesterol removal agent, just before stimulation promote acrosomal exocytosis, and cholesterol efflux facilitates Rab3A association to sperm plasma membrane, indicating that cholesterol plays a direct role in the calcium-dependent exocyTosis associated with acrosome reaction.
TL;DR: The epididymal corpus and cauda segments appeared to be the segments most sensitive to seasonal cyclical variations of the external environment and probably could be regulated by the natural photoperiod.
Abstract: Little is known about morphological changes in the epididymis in relation to the natural photoperiod or their influence on sperm maturation. The viscacha is a seasonal rodent living in the Southern Hemisphere. The adult males exhibit an annual reproductive cycle with periods of maximum gonadal activity and gonadal regression. In this work, we studied seasonal variations in the morphology and cellular population of the epididymis during both periods, and we compared these results with those recorded at the testicular level. Epididymides were removed and studied by light microscopy. Measurements of luminal diameter, epithelial height, thickness of the lamina propria, and relative cellular distribution were performed. Analysis of variance (ANOVA) or nonparametric ANOVA was used to compare the results. Striking quantitative and qualitative changes were observed. Epididymides in periods of gonadal regression showed a significant decrease in luminal diameter and epithelial height in cauda, while the thickness of the lamina propria increased. In the epididymal corpus, the number of clear cells increased, and the cytoplasm of principal cells showed numerous giant vacuoles. During the active period, the number of halo cells increased and the cytoplasm of these cells was filled with dense bodies. In conclusion, the epididymis of the viscacha exhibits important seasonal morphological changes throughout annual reproductive cycle. The epididymal corpus and cauda segments appeared to be the segments most sensitive to seasonal cyclical variations of the external environment. We therefore postulate that the epididymal morphology of the viscacha probably could be regulated by the natural photoperiod. © 2004 Wiley-Liss, Inc.
TL;DR: In this article, a detailed analysis of synchrotron radiation in the effective Lorentz invariance violating (LIV) model of Myers-Pospelov is presented.
Abstract: We develop a detailed analysis of synchrotron radiation in the effective Lorentz invariance violating (LIV) model of Myers-Pospelov, considering explicitly both the dynamics of the charge producing the radiation and the dynamics of the electromagnetic field itself. Within the radiation approximation we compute exact expressions in the LIV parameters for the electric and magnetic fields, the angular distribution of the power spectrum, the total emitted power in the $m$th harmonic and the polarization. We also perform expansions of the exact results in terms of the LIV parameters to identify the dominant effects and study the main features of the high energy limit of the spectrum. A very interesting consequence is the appearance of rather unexpected and large amplifying factors associated with the LIV effects, which go along with the usual contributions of the expansion parameter. This opens up the possibility of looking for astrophysical sources where these amplifying factors are important to further explore the constraints imposed upon the LIV parameters by synchrotron radiation measurements. We briefly sketch some phenomenological applications in the case of supernova remnants and gamma ray bursts.
TL;DR: It is observed that the presence of botulinum toxin-producing clostridia in soil samples from five geographical regions of Argentina has a great multiplicity of serological types and a higher prevalence in nonvirgin soils than in virgin soils.
Abstract: We studied the presence of botulinum toxin-producing clostridia in 2,009 soil samples from five geographical regions of Argentina. The prevalence was 23.5%, and the distribution was not homogeneous among the regions. We observed a great multiplicity of serological types and a higher prevalence in nonvirgin soils than in virgin soils.
TL;DR: By studying MVBs fusion and exosome release in K562 cells, a human erythroleukemic cell line, the functional significance of Rab11 and calcium is determined and the role of autophagy in the terminal differentiation of red cells is proposed.
Abstract: During reticulocyte maturation, some membrane proteins and organelles that are not required in the mature red cell are lost. These proteins are released into the extracellular medium associated with vesicles present in multivesicular bodies (MVBs). Fusion of MVBs with the plasma membrane results in secretion of the small internal vesicles, termed exosomes. By studying MVBs fusion and exosome release in K562 cells, a human erythroleukemic cell line, we have determined the functional significance of Rab11 and calcium in these events. Additionally, in the transformation process that occurs during erythrocyte maturation, intracellular organelles are likely removed as a consequence of autophagic sequestration and degradation. We propose K562 cells as a useful tool to analyze, at the molecular level, the role of autophagy in the terminal differentiation of red cells.
TL;DR: 1 Laboratorio de Biologı́a Celular y Molecular-IHEM, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-CONICET, Mendoza, Argentina * Corresponding author: MI Colombo.
Abstract: 1 Laboratorio de Biologı́a Celular y Molecular-IHEM, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo-CONICET, Mendoza, Argentina * Corresponding author: MI Colombo, Laboratorio de Biologı́a Celular y Molecular, Instituto de Histologı́a y Embriologı́a (IHEM)-CONICET, Facultad de Ciencias Médicas, Universidad Nacional de Cuyo, Casilla de Correo 56, Centro Universitario, Parque General San Martı́n, (5500) Mendoza, Argentina. Tel: þ 54 261 4494143 Ext. 2690; Fax: þ 54 261 4494117; E-mail: mcolombo@fcm.uncu.edu.ar
TL;DR: It is concluded that MXN and HLN are deleterious for T. cruzi epimastigotes and that their mechanism of action is different than that of the related lactone, dehydroleucodine.
Abstract: Sesquiterpene lactones constitute a large group of biologically active compounds obtained from plants. The lactones, mexicanin (MXN) and helenalin (HLN), were reported recently as active against the infective form of Trypanosoma cruzi. In this work, we studied the effects of these compounds on the growth and viability of the noninfective epimastigote, to compare the sensitivity of the 2 stages and to characterize their actions. Both compounds were cytotoxic to the parasites, with HLN (inhibitory concentration 50% [IC50] 1.9 ± 0.08 μM) more potent than MXN (IC50 3.8 ± 0.19 μM) and the typanocidal drug, benznidazole (IC50 8.6 ± 2.5 μM). The results showed that epimastigotes are less sensitive than trypomastigotes to the compounds. The trypanocidal effect of these lactones, irreversible after 12-hr exposure, was not reversed by the reducing agents dithiotreitol or β-mercaptoethanol. Ultrastructurally, we observed cytoplasmic vacuolization and nuclear disorganization. Although concentrations between 0.5 and 1...
TL;DR: The results would indicate that exclusion of P. argentina from clayish and saline soils would occur during emergence and the first stages of seedling establishment as a consequence of salinity, and suggest that the greater tolerance of this species depends on its ability to regulate and control absorption and transport of ions.
Abstract: Fil: Villagra, Pablo Eugenio. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Provincia de Mendoza. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla | Universidad Nacional de Cuyo. Instituto Argentino de Nivologia, Glaciologia y Ciencias Ambientales. Museo de Historia Natural de San Rafael - Ianigla; Argentina
TL;DR: In this article, a methodology to determine the location and mass of explosive in a terrorism attack when the location of the crater is unavailable is presented and applied to the case of the AMIA (Israel-Argentina Mutual Association) building attack that occurred in Buenos Aires, Argentina in July 1994.
TL;DR: Observations indicate that Rab22a can affect the trafficking from endosomes to the Golgi apparatus probably by promoting fusion among endosome and impairing the proper segregation of membrane domains required for targeting to the trans-Golgi network (TGN).
TL;DR: The results shown that cadmium modifies the lipid contents of pituitary gland and directly or indirectly the levels of prolactin and growth hormone in serum.
Abstract: The present study was undertaken to assess whether chronic exposition to cadmium (Cd, 0.133 mM per liter for 2 months) through drinking water may affect the lipid contents in the pituitary anterior lobe (PAL) of adult male Wistar rats. As compared to metal non-exposed controls, PALs exposed to cadmium showed an increase in total phospholipid contents, which was associated to an increase of the incorporation of [1−14C]-methyl choline into phosphatidylcholine and of [U−14C]-glucose into total phospholipids. The incorporation of [1−14C]-methyl choline into sphingomyelin was not changed. Incorporation of [1−14C]-acetate into total fatty acids also increased but incorporation of [1−14C]-acetate into cholesterol did not change. The activity of phospholipase D decreased both in PALs from Cd exposed rats and in PAL dispersed cells treated with Cd in the culture medium from Cd non-exposed rats. In PALS from Cd exposed rats, a decrease of serum prolactin and growth hormone concentrations was determined. The results shown that cadmium modifies the lipid contents of pituitary gland and directly or indirectly the levels of prolactin and growth hormone in serum.
TL;DR: It is shown that both aldosterone and angiotensin II provide such a mechanism of regulation in vivo at the level of the medullary collecting tubule, and in this part of the nephron, the effects of ald testosterone and angiotsin II are not sodium dependent, whereas in the cortical collecting duct, both a Aldosterone and Angiotens in II affect H+ secretion by sodium-dependent mechanisms.
Abstract: Angiotensin II, a potent vasoconstrictor, also participates in the regulation of renal sodium and water excretion, not only via a myriad of effects on renal hemodynamics, glomerular filtration rate, and regulation of aldosterone secretion, but also via direct effects on renal tubule transport. In addition, angiotensin II stimulates H+ secretion and HCO3- reabsorption in both proximal and distal tubules and regulates H+-ATPase activity in intercalated cells of the collecting tubule. Different results regarding the effect of angiotensin II on bicarbonate reabsorption and proton secretion have been reported at the functional level, depending on the angiotensin II concentration and tubule segment studied. It is likely that interstitial angiotensin II is more important in regulating hemodynamic and transport functions than circulating angiotensin II. In proximal tubules, stimulation of bicarbonate reabsorption, Na+/H+-exchange, and Na+/HCO3- cotransport has been found using low concentrations (<10(-9) M), while inhibition of bicarbonate reabsorption has been documented using concentrations higher than 10(-8) M. Evidence for the regulation of H+-ATPase activity in vivo and in vitro by trafficking/exocytosis has been provided. An additional level of H+-ATPase regulation via protein synthesis may be important as well. Recently, we have shown that both aldosterone and angiotensin II provide such a mechanism of regulation in vivo at the level of the medullary collecting tubule. Interestingly, in this part of the nephron, the effects of aldosterone and angiotensin II are not sodium dependent, whereas in the cortical collecting duct, both aldosterone and angiotensin II, by contrast, affect H+ secretion by sodium-dependent mechanisms.
TL;DR: In this article, a short sediment core from Lake Morenito was studied to assess the impact of environmental changes on chironomid communities occurring during the last ca 100 yr.
Abstract: 1.A short sediment core from Lake Morenito was studied to assess the impact of environmental changes on chironomid communities occurring during the last ca 100 yr.
2.Lake Morenito (41°S, 71°W) is located 20 km west of the city of Bariloche, in northern Patagonia, Argentina. Before 1960, this lake was a branch of Lake Moreno; by that time, an artificial dam closed the system, establishing the new lake. Another human disturbance that took place during the time span of the core was the introduction of salmonids to the area ca 1910.
3.The most important natural events that occurred in the area during the last 100 yr were related to volcanic episodes. One of them, occured in Chile in 1960 affecting the Argentinian side, coincided with the dam's construction.
4.Changes in the chironomid community were recorded by studying the sub-fossil remains (the chitinized head capsule of the larvae) present in the sedimentary sequence. The results show that volcanic tephra layers deposited along the core led to a sharp instantaneous drop in the diversity and abundance of chironomid assemblages. Human activities are also associated with a change in chironomid community composition.
5.Chironomus reached its maximum abundance values in 1910 and 1960. The organic matter content also increased at the same time. The increase of Chironomus after 1910 is clearly related to an increase in the trophic status of the lake. However, owing to the synchronicity of events in 1960, i.e. the volcanic event and the dam's construction, it is difficult to establish whether the change in the chironomid assemblage was in response to an increase in trophic enrichment, to natural disturbance, or both.
Copyright © 2004 John Wiley & Sons, Ltd.
TL;DR: The results indicate that acrosomal exocytosis is regulated through the PKC-mediated phosphorylation of conserved threonines in the polybasic regions of synaptotagmin VI.
TL;DR: Results presented here could indicate that the AR triggered by P4 is driven by activation of G‐proteins, that in turn activate PLA2 and PLC simultaneously, that finally promote acrosomal exocytosis.
Abstract: The acrosome reaction (AR) is a special exocytotic process promoted by signal transduction pathways studied in many laboratories. Progesterone (P4) is one of the trigger molecules proposed. Upon the binding of P4 to its receptor, several molecules could be activated, including G-proteins, phospholipase A2 (PLA2), and phospholipase C (PLC). The role of these molecules was analyzed in this study using the Chlortetracycline (CTC) protocol to detect and quantify the AR. Incubation of capacitated sperm cells with GTPγs (GTPγs, a mimetic of G-protein activation), arachidonic acid (AA, product of PLA2 action), or phorbol ester (PMA, an activator of PLC) for 15 min increased the AR to a similar percentage as P4. Conversely, a decrease in the AR was detected when sperm cells were incubated with P4 after preincubation with: GDPβS (GDP, an inhibitor of G-protein activation), ONO RS-82 (ONO, an inhibitor of PLA2), or neomycin (Neo, an inhibitor of PLC) for 15 min. To analyze the activation sequence of G proteins, PLA2, and PLC combinations of these mimetic/inhibitors were used during successive incubation periods. Inhibition promoted by GDP, ONO, and Neo were overcome by 15-min incubation with GTPγs, AA, or PMA, respectively. But GTPγs or P4 did not reverse the inhibition due to incubation with Neo and ONO. Interestingly, this dual inhibition was reverted by another 15-min incubation with AA or PMA. Results presented here could indicate that the AR triggered by P4 is driven by activation of G-proteins, that in turn activate PLA2 and PLC simultaneously, that finally promote acrosomal exocytosis. Mol. Reprod. Dev. 70: 58–63, 2004. © 2004 Wiley-Liss, Inc.
TL;DR: In this article, the authors presented a complete calculation of the synchrotron radiation produced by a circularly moving charge in the rest frame of the LIV model, in the framework of the classical effective Lorentz invariance violating (LIV) model of Myers-Pospelov.
TL;DR: An overview of the evidence is provided, explaining some of the pathophysiologic mechanisms participating in the development of the vascular remodeling, in experimental models of hypertension, with special reference to the findings in spontaneously hypertensive rats as a model of essential hypertension, and in fructose-fed rats as an model of secondary hypertension, in the context of the metabolic syndrome.
Abstract: The basic hemodynamic abnormality in hypertension is an increased peripheral resistance that is due mainly to a decreased vascular lumen derived from structural changes in the small arteries wall, named (as a whole) vascular remodeling. The vascular wall is an active, flexible, and integrated organ made up of cellular (endothelial cells, smooth muscle cells, adventitia cells, and fibroblasts) and noncellular (extracellular matrix) components, which in a dynamic way change shape or number, or reorganize in response to physiological and pathological stimuli, maintaining the integrity of the vessel wall in physiological conditions or participating in the vascular changes in cardiovascular diseases such as hypertension. Research focused on new signaling pathways and molecules that can participate in the mechanisms of vascular remodeling has provided evidence showing that vascular structure is not only affected by blood pressure, but also by mechanisms that are independent of the increased pressure. This review will provide an overview of the evidence, explaining some of the pathophysiologic mechanisms participating in the development of the vascular remodeling, in experimental models of hypertension, with special reference to the findings in spontaneously hypertensive rats as a model of essential hypertension, and in fructose-fed rats as a model of secondary hypertension, in the context of the metabolic syndrome. The understanding of the mechanisms producing the vascular alterations will allow the development of novel pharmacological tools for vascular protection in hypertensive disease.