The Experts below are selected from a list of 1539 Experts worldwide ranked by ideXlab platform
Hector Maldonado - One of the best experts on this subject based on the ideXlab platform.
-
Reactivation and Reconsolidation of Long-Term Memory in the Crab Chasmagnathus: Protein Synthesis Requirement and
2013Co-Authors: Mediation Nmda-type, Luis María Pérez-cuesta, María Eugenia Pedreira, Glutamatergic Receptors, Hector MaldonadoAbstract:Experiments with invertebrates support the view that intracellular events subserving the consolidation phase of memory are preserved across evolution. Here, we investigate whether such evolutionary persistence extends to reconsolidation mechanisms, which have recently received special attention in vertebrate studies. For this purpose, the memory model of the crab Chasmagnathus is used. A visual danger stimulus (VDS) elicits crab escaping, which declines after a few stimulus presentations. The long-lasting retention of this decrement, called context-signal memory (CSM), is mediated by an association between contextual cues of the training site and the VDS. The present results show amnesia for CSM in crabs re-exposed at 24 hr (day 2) for 5 min to the learning context, 24 hr after training, and injected with one of two amnesic agents, then tested 24 hr later. Agents and timing were either 15 �g of cycloheximide give
-
Contents lists available at ScienceDirect
2013Co-Authors: Silvia Pedetta, Laura Kaczer, Hector MaldonadoAbstract:journal homepage: www.elsevier.com/locate/phb Individual aggressiveness in the crab Chasmagnathus: Influence in fight outcome an
-
Angiotensin modulates long-term memory expression but not long-term memory storage in the crab Chasmagnathus.
Neurobiology of learning and memory, 2010Co-Authors: Lia Frenkel, Hector Maldonado, Luis D. Suárez, Alejandro DelorenziAbstract:Memory reconsolidation is a dynamic process in which a previously consolidated memory becomes labile following reactivation by a reminder. In a previous study in the crab Chasmagnathus memory model, we showed that a water-shortage episode, via angiotensin modulation during reconsolidation, could reveal a memory that otherwise remains unexpressed: weakly trained animals cannot reveal long-term memory (LTM) except when an episode of noticeable ethological meaning, water deprivation, is contingent upon reconsolidation. However, these results are at variance with two of our previous interpretations: weak training protocols do not build LTM and angiotensin II modulates the strength of the information storing process. A parsimonious hypothesis is that in Chasmagnathus angiotensins regulate LTM expression, but not LTM storage. Here, we tested three predictions of this hypothesis. First, the well-known retrograde amnesic effect of the angiotensin II antagonist saralasin is not due to interference on memory storage, but to modulation of memory expression. Second, the recovery of the LTM memory expression of the apparently amnesic retrograde effect produced by saralasin, through the water-shortage episode contingent upon reconsolidation, must be reconsolidation specific. Consequently, summation-like effects and retrieval deficits cannot explain these results because of the parametric conditions of reconsolidation. Third, weak training protocols build an unexpressed LTM that requires mRNA transcription and translation, a diagnostic characteristic of LTM. Results show that angiotensin modulates LTM expression but not LTM memory storage in the crab Chasmagnathus. The results lead us to suggest that, in Chasmagnathus, LTM expression - the process of gaining appreciable control over behavior of the reactivated trace in the retrieval session - may be considered a distinct attribute of its long-term storage. This strategy, a positive modulation during reconsolidation, is proposed to distinguish between memories that can be reactivated, labilized and are not expressed, and memories that are not stored long term, obliterated or altered in other retrieval mechanisms.
-
Neuroanatomical distribution of angiotensin-II-like neuropeptide within the central nervous system of the crab Chasmagnathus; physiological changes triggered by water deprivation
Cell and tissue research, 2010Co-Authors: Lia Frenkel, Hector Maldonado, Beatriz Dimant, Enrique Leo Portiansky, Hans Imboden, Alejandro DelorenziAbstract:The angiotensins constitute a neuropeptidergic system that emerged early in evolution. Their classical osmoregulatory and dipsogenic functions and their mnemonic actions have been demonstrated both in vertebrates and in some invertebrates. Previously, we have shown that, in the euryhaline and semiterrestrial crab Chasmagnathus granulatus, water deprivation correlates with an increased level of brain angiotensin-II-like neuropeptide/s (ANGII-like) and improves memory processes through ANGII receptors. We have proposed that the release of brain angiotensins in response to water shortages is an ancient mechanism for coordinating various functions that, together, enable organisms to tolerate this environmental change. Here, we have evaluated the physiological changes in ANGII-like levels in diverse structures of the central nervous system of these animals during water deprivation. The neuroanatomical distribution of ANGII-like is described in the optic lobes and brain of Chasmagnathus granulatus and the physiological changes in ANGII-like distribution in various brain neuropils is evaluated after water deprivation. Our results indicate that ANGII-like is widely distributed, especially in the medial protocerebrum. After 2 h of water deprivation, ANGII-like immunoreactivity increases in the central body and decreases in the olfactory neuropil and, after 6 h of water deprivation, is markedly reduced in several brain areas. Although further experiments are needed to establish that the angiotensinergic system is involved in the balance of body fluids in this crab, our results suggest that ANGII regulates several functions during water shortages.
-
Extinction memory in the crab Chasmagnathus: recovery protocols and effects of multi-trial extinction training
Animal Cognition, 2010Co-Authors: Yanil Hepp, Luis María Pérez-cuesta, Hector Maldonado, María Eugenia PedreiraAbstract:A decline in the frequency or intensity of a conditioned behavior following the withdrawal of the reinforcement is called experimental extinction. However, the experimental manipulation necessary to trigger memory reconsolidation or extinction is to expose the animal to the conditioned stimulus in the absence of reinforcement. Recovery protocols were used to reveal which of these two processes was developed. By using the crab contextual memory model (a visual danger stimulus associated with the training context), we investigated the dynamics of extinction memory in Chasmagnathus . Here, we reveal the presence of three recovery protocols that restore the original memory: the old memory comes back 4 days after the extinction training, or when a weak training is administered later, or once the VDS is presented in a novel context 24 h after the extinction session. Another objective was to evaluate whether the administration of multi-trial extinction training could trigger an extinction memory in Chasmagnathus . The results evince that the extinction memory appears only when the total re-exposure time is around 90 min independently of the number of trials employed to accumulate it. Thus, it is feasible that the mechanisms described for the case of the extinction memory acquired through a single training trial are valid for multi-trial extinction protocols. Finally, these results are in agreement with those reports obtained with models phylogenetically far apart from the crab. Behind this attempt is the idea that in the domain of studies on memory, some principles of behavior organization and basic mechanisms have universal validity.
Alejandro Delorenzi - One of the best experts on this subject based on the ideXlab platform.
-
Food odor, visual danger stimulus, and retrieval of an aversive memory trigger heat shock protein HSP70 expression in the olfactory lobe of the crab Chasmagnathus granulatus.
Neuroscience, 2011Co-Authors: Lia Frenkel, Beatriz Dimant, Enrique Leo Portiansky, L.d. Suárez, Alejandro DelorenziAbstract:Although some of the neuronal substrates that support memory process have been shown in optic ganglia, the brain areas activated by memory process are still unknown in crustaceans. Heat shock proteins (HSPs) are synthesized in the CNS not only in response to traumas but also after changes in metabolic activity triggered by the processing of different types of sensory information. Indeed, the expression of citosolic/nuclear forms of HSP70 (HSC/HSP70) has been repeatedly used as a marker for increases in neural metabolic activity in several processes, including psychophysiological stress, fear conditioning, and spatial learning in vertebrates. Previously, we have shown that, in the crab Chasmagnathus, two different environmental challenges, water deprivation and heat shock, trigger a rise in the number of glomeruli of the olfactory lobes (OLs) expressing HSC/HSP70. In this study, we initially performed a morphometric analysis and identified a total of 154 glomeruli in each OL of Chasmagnathus. Here, we found that crabs exposed to food odor stimuli also showed a significant rise in the number of olfactory glomeruli expressing HSC/HSP70. In the crab Chasmagnathus, a powerful memory paradigm based on a change in its defensive strategy against a visual danger stimulus (VDS) has been extensively studied. Remarkably, the iterative presentation of a VDS caused an increase as well. This increase was triggered in animals visually stimulated using protocols that either build up a long-term memory or generate only short-term habituation. Besides, memory reactivation was sufficient to trigger the increase in HSC/HSP70 expression in the OL. Present and previous results strongly suggest that, directly or indirectly, an increase in arousal is a sufficient condition to bring about an increase in HSC/HSP70 expression in the OL of Chasmagnathus.
-
Angiotensin modulates long-term memory expression but not long-term memory storage in the crab Chasmagnathus.
Neurobiology of learning and memory, 2010Co-Authors: Lia Frenkel, Hector Maldonado, Luis D. Suárez, Alejandro DelorenziAbstract:Memory reconsolidation is a dynamic process in which a previously consolidated memory becomes labile following reactivation by a reminder. In a previous study in the crab Chasmagnathus memory model, we showed that a water-shortage episode, via angiotensin modulation during reconsolidation, could reveal a memory that otherwise remains unexpressed: weakly trained animals cannot reveal long-term memory (LTM) except when an episode of noticeable ethological meaning, water deprivation, is contingent upon reconsolidation. However, these results are at variance with two of our previous interpretations: weak training protocols do not build LTM and angiotensin II modulates the strength of the information storing process. A parsimonious hypothesis is that in Chasmagnathus angiotensins regulate LTM expression, but not LTM storage. Here, we tested three predictions of this hypothesis. First, the well-known retrograde amnesic effect of the angiotensin II antagonist saralasin is not due to interference on memory storage, but to modulation of memory expression. Second, the recovery of the LTM memory expression of the apparently amnesic retrograde effect produced by saralasin, through the water-shortage episode contingent upon reconsolidation, must be reconsolidation specific. Consequently, summation-like effects and retrieval deficits cannot explain these results because of the parametric conditions of reconsolidation. Third, weak training protocols build an unexpressed LTM that requires mRNA transcription and translation, a diagnostic characteristic of LTM. Results show that angiotensin modulates LTM expression but not LTM memory storage in the crab Chasmagnathus. The results lead us to suggest that, in Chasmagnathus, LTM expression - the process of gaining appreciable control over behavior of the reactivated trace in the retrieval session - may be considered a distinct attribute of its long-term storage. This strategy, a positive modulation during reconsolidation, is proposed to distinguish between memories that can be reactivated, labilized and are not expressed, and memories that are not stored long term, obliterated or altered in other retrieval mechanisms.
-
Neuroanatomical distribution of angiotensin-II-like neuropeptide within the central nervous system of the crab Chasmagnathus; physiological changes triggered by water deprivation
Cell and tissue research, 2010Co-Authors: Lia Frenkel, Hector Maldonado, Beatriz Dimant, Enrique Leo Portiansky, Hans Imboden, Alejandro DelorenziAbstract:The angiotensins constitute a neuropeptidergic system that emerged early in evolution. Their classical osmoregulatory and dipsogenic functions and their mnemonic actions have been demonstrated both in vertebrates and in some invertebrates. Previously, we have shown that, in the euryhaline and semiterrestrial crab Chasmagnathus granulatus, water deprivation correlates with an increased level of brain angiotensin-II-like neuropeptide/s (ANGII-like) and improves memory processes through ANGII receptors. We have proposed that the release of brain angiotensins in response to water shortages is an ancient mechanism for coordinating various functions that, together, enable organisms to tolerate this environmental change. Here, we have evaluated the physiological changes in ANGII-like levels in diverse structures of the central nervous system of these animals during water deprivation. The neuroanatomical distribution of ANGII-like is described in the optic lobes and brain of Chasmagnathus granulatus and the physiological changes in ANGII-like distribution in various brain neuropils is evaluated after water deprivation. Our results indicate that ANGII-like is widely distributed, especially in the medial protocerebrum. After 2 h of water deprivation, ANGII-like immunoreactivity increases in the central body and decreases in the olfactory neuropil and, after 6 h of water deprivation, is markedly reduced in several brain areas. Although further experiments are needed to establish that the angiotensinergic system is involved in the balance of body fluids in this crab, our results suggest that ANGII regulates several functions during water shortages.
-
Both heat shock and water deprivation trigger Hsp70 expression in the olfactory lobe of the crab Chasmagnathus granulatus.
Neuroscience letters, 2008Co-Authors: Lia Frenkel, Hector Maldonado, Beatriz Dimant, Enrique Leo Portiansky, Alejandro DelorenziAbstract:Heat-shock proteins (Hsp) are synthesized in the central nervous system in response to traumas but also after physical exercise and psychophysiological stress. Therefore, an increase in Hsp expression is a good marker of changes in metabolic activity. In the crab Chasmagnathus, a powerful memory paradigm has been established. Memory modulation is possible by water shortage. The brain areas activated by either training protocols and/or water-deprivation are still unknown. Hsp expression might be a marker to sensing the increase in metabolic activity in crab Chasmagnathus brain neuropils engaged in the physiological responses triggered by water deprivation and cognitive processing. Here, we observed an increase in brain Hsp of 70kDa (Hsp70) expression after a heat-shock treatment. Additionally, immunohistochemistry analysis revealed that, under basal conditions, some glomeruli of the olfactory lobes showed Hsp70 immunoreactivity in an on-off manner. Both a hot environment and water deprivation increased the number of glomeruli expressing Hsp70. This marker of neuropil's activity might turn out to be a powerful tool to test whether crustacean olfactory lobes not only process olfactory information but also integrate multimodal signals.
-
High environmental salinity induces memory enhancement and increases levels of brain angiotensin-like peptides in the crab Chasmagnathus granulatus
The Journal of Experimental Biology, 2000Co-Authors: Alejandro Delorenzi, Lia Frenkel, Beatriz Dimant, Victor E. Nahmod, D.r. Nassel, Hector MaldonadoAbstract:Previous work on the brackish-water crab Chasmagnathus granulatus demonstrated that an endogenous peptide similar to angiotensin II plays a significant role in enhancing long-term memory that involves an association between context and an iterative danger stimulus (context-signal memory). The present results show that this memory enhancement could be produced by moving crabs from brackish water to sea water (33.0%) and keeping them there for at least 4 days. The possibility that such a facilitatory effect is due to osmotic stress is ruled out. Coincidentally, the level of angiotensin-II-like peptides in crab brain, measured by radioimmunoassay, increases with the length of exposure to sea water, reaching a significantly different level at the fourth day. The presence of angiotensin-II-like immunoreactive material in neural structures of the supraoesophageal and eyestalk ganglia was confirmed by immunohistochemical analysis. The results are interpreted as supporting the hypothesis that exposure to water of high salinity is an external cue triggering a process mediated by angiotensins that leads to enhanced memory in these crabs.
Enrique M. Rodríguez - One of the best experts on this subject based on the ideXlab platform.
-
Toxicity of mercury during the embryonic development of Chasmagnathus granulatus (Brachyura, Varunidae).
Environmental research, 2005Co-Authors: María Victoria Sánchez, Laura S. López Greco, Alejandra V. Cahansky, Enrique M. RodríguezAbstract:Ovigerous females of the estuarine crab Chasmagnathus granulatus were exposed to mercury (0.1 mg/L) during the entire, early, or late embryonic development. A delay in the egg incubation period and some morphological abnormalities were detected in larvae hatched from exposed females. Particularly, hypopigmentation of body chromatophores was the abnormality that showed the highest incidence, this incidence being greater when ovigerous females were exposed to mercury either during the totality or just the first half of the egg incubation period. In contrast, the effect of mercury on the morphology and pigmentation of eyes was greater when the exposure comprised the totality or just the second half of the incubation period. These results correlate with the timing of both body pigment synthesis and eye formation during embryonic development. Although these abnormalities have been observed in the same species with other heavy metals, such as zinc and copper, the responsiveness during the early and late embryonic development was different with mercury.
-
Inhibition of molting by cadmium in the crab Chasmagnathus granulata (Decapoda Brachyura).
Aquatic toxicology (Amsterdam Netherlands), 2003Co-Authors: Paula Abigail Rodrı́guez Moreno, D. A. Medesani, Enrique M. RodríguezAbstract:The effect of cadmium on molting of the estuarine crab Chasmagnathus granulata was assayed. Adult males were eyestalk-ablated, in order to synchronically induce molting, and were then chronically exposed to cadmium at 0.25 or 0.50 mg/l. At the highest concentration, a significant mortality was detected at the time of molting, in the few crabs that could reach the E stage. However, most of the crabs exposed from the beginning of the premolt period (D(0) stage) to 0.50 mg/l of cadmium were arrested at the D(1)" stage. This effect was not seen when crabs were exposed to the same cadmium concentration from either D(1)"' or D(3) premolt stages. Crabs arrested by cadmium did not present any difference in the calcium content of carapace, compared to controls, while ecdysteroid levels of those crabs were similar to the ones of control crabs that were in the same premolt stage but could finally molt. These results suggest that cadmium could be preventing the normal peaking of ecdysteroids needed for molting. Since eyestalk-ablated crabs were used, a presumably direct effect of cadmium on Y-organ seems likely, by affecting cytoplasmatic calcium concentration and/or other actions.
-
Toxicity of cadmium and copper on larval and juvenile stages of the estuarine crab Chasmagnathus granulata (Brachyura, Grapsidae).
Archives of environmental contamination and toxicology, 2001Co-Authors: Laura S. López Greco, D. A. Medesani, M. V. Sánchez, G. L. Nicoloso, Enrique M. RodríguezAbstract:The toxicity of cadmium and copper were assayed in the estuarine crab Chasmagnathus granulata. Acute assays were made on the first larvae stage, and both acute and chronic assays were made on juvenile crabs. The acute lethal toxicity of the assayed heavy metals was three orders of magnitude higher in larvae than in juveniles. Cadmium proved to be more toxic than copper in most cases; this difference was more evident in the chronic assays on juveniles, according to the nonphysiological feature of cadmium and its persistent accumulation in organisms. During these chronic assays, cadmium produced both a significant mortality and a clear retardation of molting, in accordance with its inhibitory effect on the molting process as previously reported. Copper only caused a molting acceleration during chronic assays, perhaps as a detoxifying mechanism. Heavy metal concentrations having effects in the chronic assays have been reported in some sectors of the estuary where the assayed species lives.
-
Acute and chronic effects of cadmium on blood homeostasis of an estuarine crab, Chasmagnathus granulata, and the modifying effect of salinity.
Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas, 2001Co-Authors: Enrique M. Rodríguez, R. Bigi, D. A. Medesani, Vivian S. Stella, Laura S. López Greco, P.a.r. Moreno, José María Monserrat, G.n. Pellerano, Martín AnsaldoAbstract:Whole body oxygen consumption and some hemolymph parameters such as pH, partial pressure of gases, level of ions and lactate were measured in the estuarine crab Chasmagnathus granulata after both acute (96 h) and chronic (2 weeks) exposure to cadmium at concentrations ranging from 0.4 to 6.3 mg/l. In all instances, the crabs developed hemolymph acidosis, but no respiratory (increased PCO2 ) or lactate increases were evident. Hemolymph levels of sodium and calcium were always increased by cadmium exposure. The chronic toxicity of cadmium was enhanced at 12â salinity, even causing a significantly higher mortality in comparison with the higher salinity (30â) used. A general metabolic arrest took place at 12â salinity in the crabs chronically exposed to cadmium, as indicated by decreases of oxygen consumption and PCO2 , an increase of PO2 , along with no changes in lactate levels. These imbalances were associated with severe necrosis and telangiectasia in the respiratory gills, probably leading to respiratory impairment and finally histotoxic hypoxia and death of the animals.
-
Effect of copper on hatching and development of larvae of the estuarine crab Chasmagnathus granulata (Decapoda, Brachyura).
Environmental toxicology and chemistry, 2001Co-Authors: Valeria Zapata, Laura S. López Greco, Enrique M. RodríguezAbstract:Ovigerous females of the estuarine crab Chasmagnathus granulata were exposed to 0.05, 0.1, 0.5, and 3 mg/L of copper during the egg incubation period. Regarding egg loss, a higher effect was observed at higher copper concentrations: 80% of the females lost their eggs at 0.5 mg/L, whereas no hatching was seen in those exposed to 3 mg/L. A significant decrease was found in the number of hatched larvae in females exposed to 0.5 mg/L, as was a significant decrease in the duration of the incubation period. In addition, several morphological abnormalities were seen and observed. Hydropsy and atrophy of the dorsal spine, pleon, and maxillipeds occurred at the higher copper concentrations, as found in previous studies with other pollutants. Hyperpigmentation of the cephalothorax and pleon was the only abnormality observed at every concentration assayed. Hypopigmented eyes were also evident. This pathology showed that among all defects observed at 0.5 mg/L, hypopigmented eyes had the highest incidence and might be a specific response to copper.
Lia Frenkel - One of the best experts on this subject based on the ideXlab platform.
-
Food odor, visual danger stimulus, and retrieval of an aversive memory trigger heat shock protein HSP70 expression in the olfactory lobe of the crab Chasmagnathus granulatus.
Neuroscience, 2011Co-Authors: Lia Frenkel, Beatriz Dimant, Enrique Leo Portiansky, L.d. Suárez, Alejandro DelorenziAbstract:Although some of the neuronal substrates that support memory process have been shown in optic ganglia, the brain areas activated by memory process are still unknown in crustaceans. Heat shock proteins (HSPs) are synthesized in the CNS not only in response to traumas but also after changes in metabolic activity triggered by the processing of different types of sensory information. Indeed, the expression of citosolic/nuclear forms of HSP70 (HSC/HSP70) has been repeatedly used as a marker for increases in neural metabolic activity in several processes, including psychophysiological stress, fear conditioning, and spatial learning in vertebrates. Previously, we have shown that, in the crab Chasmagnathus, two different environmental challenges, water deprivation and heat shock, trigger a rise in the number of glomeruli of the olfactory lobes (OLs) expressing HSC/HSP70. In this study, we initially performed a morphometric analysis and identified a total of 154 glomeruli in each OL of Chasmagnathus. Here, we found that crabs exposed to food odor stimuli also showed a significant rise in the number of olfactory glomeruli expressing HSC/HSP70. In the crab Chasmagnathus, a powerful memory paradigm based on a change in its defensive strategy against a visual danger stimulus (VDS) has been extensively studied. Remarkably, the iterative presentation of a VDS caused an increase as well. This increase was triggered in animals visually stimulated using protocols that either build up a long-term memory or generate only short-term habituation. Besides, memory reactivation was sufficient to trigger the increase in HSC/HSP70 expression in the OL. Present and previous results strongly suggest that, directly or indirectly, an increase in arousal is a sufficient condition to bring about an increase in HSC/HSP70 expression in the OL of Chasmagnathus.
-
Angiotensin modulates long-term memory expression but not long-term memory storage in the crab Chasmagnathus.
Neurobiology of learning and memory, 2010Co-Authors: Lia Frenkel, Hector Maldonado, Luis D. Suárez, Alejandro DelorenziAbstract:Memory reconsolidation is a dynamic process in which a previously consolidated memory becomes labile following reactivation by a reminder. In a previous study in the crab Chasmagnathus memory model, we showed that a water-shortage episode, via angiotensin modulation during reconsolidation, could reveal a memory that otherwise remains unexpressed: weakly trained animals cannot reveal long-term memory (LTM) except when an episode of noticeable ethological meaning, water deprivation, is contingent upon reconsolidation. However, these results are at variance with two of our previous interpretations: weak training protocols do not build LTM and angiotensin II modulates the strength of the information storing process. A parsimonious hypothesis is that in Chasmagnathus angiotensins regulate LTM expression, but not LTM storage. Here, we tested three predictions of this hypothesis. First, the well-known retrograde amnesic effect of the angiotensin II antagonist saralasin is not due to interference on memory storage, but to modulation of memory expression. Second, the recovery of the LTM memory expression of the apparently amnesic retrograde effect produced by saralasin, through the water-shortage episode contingent upon reconsolidation, must be reconsolidation specific. Consequently, summation-like effects and retrieval deficits cannot explain these results because of the parametric conditions of reconsolidation. Third, weak training protocols build an unexpressed LTM that requires mRNA transcription and translation, a diagnostic characteristic of LTM. Results show that angiotensin modulates LTM expression but not LTM memory storage in the crab Chasmagnathus. The results lead us to suggest that, in Chasmagnathus, LTM expression - the process of gaining appreciable control over behavior of the reactivated trace in the retrieval session - may be considered a distinct attribute of its long-term storage. This strategy, a positive modulation during reconsolidation, is proposed to distinguish between memories that can be reactivated, labilized and are not expressed, and memories that are not stored long term, obliterated or altered in other retrieval mechanisms.
-
Neuroanatomical distribution of angiotensin-II-like neuropeptide within the central nervous system of the crab Chasmagnathus; physiological changes triggered by water deprivation
Cell and tissue research, 2010Co-Authors: Lia Frenkel, Hector Maldonado, Beatriz Dimant, Enrique Leo Portiansky, Hans Imboden, Alejandro DelorenziAbstract:The angiotensins constitute a neuropeptidergic system that emerged early in evolution. Their classical osmoregulatory and dipsogenic functions and their mnemonic actions have been demonstrated both in vertebrates and in some invertebrates. Previously, we have shown that, in the euryhaline and semiterrestrial crab Chasmagnathus granulatus, water deprivation correlates with an increased level of brain angiotensin-II-like neuropeptide/s (ANGII-like) and improves memory processes through ANGII receptors. We have proposed that the release of brain angiotensins in response to water shortages is an ancient mechanism for coordinating various functions that, together, enable organisms to tolerate this environmental change. Here, we have evaluated the physiological changes in ANGII-like levels in diverse structures of the central nervous system of these animals during water deprivation. The neuroanatomical distribution of ANGII-like is described in the optic lobes and brain of Chasmagnathus granulatus and the physiological changes in ANGII-like distribution in various brain neuropils is evaluated after water deprivation. Our results indicate that ANGII-like is widely distributed, especially in the medial protocerebrum. After 2 h of water deprivation, ANGII-like immunoreactivity increases in the central body and decreases in the olfactory neuropil and, after 6 h of water deprivation, is markedly reduced in several brain areas. Although further experiments are needed to establish that the angiotensinergic system is involved in the balance of body fluids in this crab, our results suggest that ANGII regulates several functions during water shortages.
-
Both heat shock and water deprivation trigger Hsp70 expression in the olfactory lobe of the crab Chasmagnathus granulatus.
Neuroscience letters, 2008Co-Authors: Lia Frenkel, Hector Maldonado, Beatriz Dimant, Enrique Leo Portiansky, Alejandro DelorenziAbstract:Heat-shock proteins (Hsp) are synthesized in the central nervous system in response to traumas but also after physical exercise and psychophysiological stress. Therefore, an increase in Hsp expression is a good marker of changes in metabolic activity. In the crab Chasmagnathus, a powerful memory paradigm has been established. Memory modulation is possible by water shortage. The brain areas activated by either training protocols and/or water-deprivation are still unknown. Hsp expression might be a marker to sensing the increase in metabolic activity in crab Chasmagnathus brain neuropils engaged in the physiological responses triggered by water deprivation and cognitive processing. Here, we observed an increase in brain Hsp of 70kDa (Hsp70) expression after a heat-shock treatment. Additionally, immunohistochemistry analysis revealed that, under basal conditions, some glomeruli of the olfactory lobes showed Hsp70 immunoreactivity in an on-off manner. Both a hot environment and water deprivation increased the number of glomeruli expressing Hsp70. This marker of neuropil's activity might turn out to be a powerful tool to test whether crustacean olfactory lobes not only process olfactory information but also integrate multimodal signals.
-
High environmental salinity induces memory enhancement and increases levels of brain angiotensin-like peptides in the crab Chasmagnathus granulatus
The Journal of Experimental Biology, 2000Co-Authors: Alejandro Delorenzi, Lia Frenkel, Beatriz Dimant, Victor E. Nahmod, D.r. Nassel, Hector MaldonadoAbstract:Previous work on the brackish-water crab Chasmagnathus granulatus demonstrated that an endogenous peptide similar to angiotensin II plays a significant role in enhancing long-term memory that involves an association between context and an iterative danger stimulus (context-signal memory). The present results show that this memory enhancement could be produced by moving crabs from brackish water to sea water (33.0%) and keeping them there for at least 4 days. The possibility that such a facilitatory effect is due to osmotic stress is ruled out. Coincidentally, the level of angiotensin-II-like peptides in crab brain, measured by radioimmunoassay, increases with the length of exposure to sea water, reaching a significantly different level at the fourth day. The presence of angiotensin-II-like immunoreactive material in neural structures of the supraoesophageal and eyestalk ganglia was confirmed by immunohistochemical analysis. The results are interpreted as supporting the hypothesis that exposure to water of high salinity is an external cue triggering a process mediated by angiotensins that leads to enhanced memory in these crabs.
Roselis Silveira Martins Da Silva - One of the best experts on this subject based on the ideXlab platform.
-
Effects of fasting and refeeding on metabolic processes in the crab Chasmagnathus granulata (Dana, 1851)
Canadian Journal of Zoology, 2002Co-Authors: Anapaula Sommer Vinagre, Roselis Silveira Martins Da SilvaAbstract:We assessed the effects of 3 weeks of fasting and 48 h of refeeding on the incorporation of ( 14 C)-labeled substrate into glucose, glycogen, lipid, and protein in hepatopancreas, muscle, and gills from the crab Chasmagnathus granulata. Fasting did not change the rate of glycogen and lipid synthesis in the three tissues. Neither fasting nor refeeding affected hemolymph glucose levels. Refeeding induced a reduction in glycogen synthesis in gills, but did not affect glycogen synthesis in hepatopancreas and muscle. Fasting did not affect lipogenesis in hepatopancreas, but refeeding elevated ( 14 C)-lipid twofold. Muscle lipogenesis was not affected by fasting or refeeding. Gluconeogenesis in the three tissues was not modified by fasting. Refeeding induced an increase in the glucose-synthesis capacity only in muscle. Fasting did not affect glyconeogenesis in hepatopancreas and gills, but induced a reduction in glycogen synthe - sis in muscle. Muscle-protein synthesis was not affected by fasting; however, refeeding induced a reduction in ( 14 C)-
-
In vitro insulin stimulatory effect on glucose uptake and glycogen synthesis in the gills of the estuarine crab Chasmagnathus granulata.
General and comparative endocrinology, 2002Co-Authors: Luiz Carlos Rios Kucharski, Edison Capp, Vanessa Schein, Roselis Silveira Martins Da SilvaAbstract:Abstract The aim of the present study was to examine the effects of insulin on glucose uptake and glycogen synthesis in crab Chasmagnathus granulata gills. We observed an increased glucose uptake and incorporation of d -[14C]glucose into glycogen when posterior C. granulata gills were incubated in the presence of insulin; however, this was not observed in anterior gills, despite the presence of similar insulin receptors. In posterior gills, basal glucose uptake in the summer was significantly higher than in the winter. Moreover, in the summer, the insulin dose required to stimulate glucose uptake was twice as high as in the winter. However, there was no significant difference in terms of basal glycogen synthesis in summer and winter. In crustaceans, the endogenous insulin/IGFI substance might be involved in the rapid restoration of glycogen levels in the gills, increasing glucose uptake and glycogen synthesis. Bovine insulin seems to have a stimulatory effect on glycogen metabolism only in posterior gills.
-
Hepatopancreas gluconeogenesis during hyposmotic stress in crabs Chasmagnathus granulata maintained on high-protein or carbohydrate-rich diets.
Comparative biochemistry and physiology. Part B Biochemistry & molecular biology, 2000Co-Authors: Guendalina T. Oliveira, Roselis Silveira Martins Da SilvaAbstract:The incorporation of [14C]-alanine or [14C]-lactate into glucose was measured in hepatopancreas fractions from Chasmagnathus granulata crabs adapted to a high protein or a carbohydrate-rich diet and submitted or not (control group) to hyposmotic stress. Gluconeogenic capacity and phosphoenolpyruvate carboxykinase (PEPCK) activity increased during acclimation to a dilute medium in C. granulata hepatopancreas. In intact animals, high hemolymph urea levels occurred for the high-protein regimen and for crabs fed both diets and submitted to hyposmotic stress. It could be that the amino acids released during hyposmotic stress are deaminated in the hepatopancreas, and that the carbon chains are used as substrate for gluconeogenesis. Hepatopancreas gluconeogenesis seems to be one of the pathways implicated in the metabolic adjustment of the amino acid pool during hyposmotic stress in C. granulata.
-
Insulin signaling: Tyrosine kinase activity in the crab Chasmagnathus granulata gills
Journal of Experimental Zoology, 1999Co-Authors: Luiz Carlos Rios Kucharski, Roselis Silveira Martins Da Silva, Edison Capp, Ana Lúcia Fernandes Chittó, Márcia Trapp, Maria MarquesAbstract:Insulin-specific binding sites were recently shown in the gills of the estuarine crab Chasmagnathus granulata. In order to study the insulin receptor in these gills, its tyrosine kinase activity was evaluated in crude membranes and in isolated insulin receptor. The tyrosine kinase activity was determined by the insulin receptor capacity to autophosphorylate and phosphorylate exogenous substrate poly (Glu:Tyr 4:1) in the presence of bovine insulin (10–7M). When stimulated with insulin the 95 kDa β-subunit was phosphorylated and identified by autoradiography. The insulin receptor stimulated with insulin showed an 1.3-fold increase of [γ32P]ATP incorporation to the exogenous substrate poly (Glu:Tyr 4:1). This increase was not observed when previously incubated with genistein. Further studies will be required to understand other steps of the insulin signaling chain in this organ. J. Exp. Zool. 283:91–94, 1999. © 1999 Wiley-Liss, Inc.
-
Insulin binding sites in gills of the estuarine crab Chasmagnathus granulata.
The Journal of experimental zoology, 1997Co-Authors: Luiz Carlos Rios Kucharski, Roselis Silveira Martins Da Silva, Maria Flavia Marques Ribeiro, Vanessa Schein, Maria MarquesAbstract:Bovine 125I-insulin was injected into the estuarine crab Chasmagnathus granulata in order to study its distribution and specific uptake by tissues. The highest radioactivity uptake occurred in both anterior and posterior gills, which reached maximum values at 30–60 min following labeled insulin administration. Heart and hepatopancreas concentrated a very low amount of radioactivity (only 9 and 3%, respectively, of that shown by gills). A significant reduction of the uptake was observed in the gills when an excess of unlabeled insulin was injected together with the labeled hormone. In vitro studies also showed specific uptake of 125I-insulin by the gills incubated at 25°C, which reached a plateau after 120-min incubation, suggesting a saturable process. The inhibition of 125I-insulin uptake was dose dependent on unlabeled insulin. Glucagon did not compete with radioactivity uptake by gills in vivo and in vitro. Further characterization of insulin-binding sites was performed in gill membrane. The amount of unlabeled insulin that prevented 50% of the 125I-insulin uptake was 7.78 μg/ml, and the Scatchard plot analysis established the presence of binding site with Kd of 3.11 μM and Bmax of 0.14 μM (r = 0.99). Ovine prolactin was not able to prevent 125I-insulin binding to gill membrane. These findings seem to indicate the presence of specific binding sites for insulin or insulin-like substance in crab gills, which deserves further studies. J. Exp. Zool. 279:118–125, 1997. © 1997 Wiley-Liss, Inc.