Higher environmental temperature-induced change in synaptosomal acetylcholinesterase activity of brain regions.
01 Mar 1990-Neurochemical Research (Kluwer Academic Publishers-Plenum Publishers)-Vol. 15, Iss: 3, pp 231-236
TL;DR: The results suggests that heat exposure increases the lipid fluidity of synaptosomal membrane depending on the brain region which may expose the catalytic site of the enzyme (AChE) and hence activate the synaptoomal membrane bound AChE activity in brain regions.
Abstract: Exposure of adult male albino rats to higher environmental temperature (HET) at 35 degrees for 2-12 hr or at 45 degrees for 1-2 hr increases hypothalamic synaptosomal acetylcholinesterase (AChE) activity. Synaptosomal AChE activity in cerebral cortex of rats exposed to 35 degrees for 12 hr and in cerebral cortex and pons-medulla of rats exposed to 45 degrees for 1-2 hr are also activated. AChE activity of synaptosomes prepared from normal rat brain regions incubated in-vitro at 39 degrees or 41 degrees for 0.5 hr increases significantly in cerebral cortex and hypothalamus. The activation of AChE in pons-medulla is also observed when this brain region is incubated at 41 degrees for 0.5 hr. Increase of (a) the duration of incubation at 41 degrees and (b) the incubation temperature to 43 degrees under in-vitro condition decreases the synaptosomal AChE activity. Lineweaver-Burk plots indicate that (a) in-vivo and in-vitro HET-induced increases of brain regional synaptosomal AChE activity are coupled with an increase of Vmax without any change in Km (b) very high temperature (43 degrees under in-vitro condition) causes a decrease in Vmax with an increase in Km of AChE activity irrespective of brain regions. Arrhenius plots show that there is a decrease in transition temperature in hypothalamus of rats exposed to either 35 degrees or 45 degrees; whereas such a decrease in transition temperature of the pons-medulla and cerebral cortex regions are observed only after exposure to 45 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)
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TL;DR: The effects of temperature on European seabass (Dicentrarchus labrax L.) juveniles were investigated using a 30-day bioassay carried out at 18 and 25°C in laboratory conditions as discussed by the authors.
Abstract: The effects of temperature on European seabass (Dicentrarchus labrax L.) juveniles were investigated using a 30-day bioassay carried out at 18 and 25 °C in laboratory conditions. A multiparameter approach was applied including fish swimming velocity and several biochemical parameters involved in important physiological functions. Fish exposed for four weeks to 25 °C showed a decreased swimming capacity, concomitant with increased oxidative stress (increased catalase and glutathione peroxidase activities) and damage (increased lipid peroxidation levels), increased activity of an enzyme involved in energy production through the aerobic pathway (isocitrate dehydrogenase) and increased activities of brain and muscle cholinesterases (neurotransmission) compared to fish kept at 18 °C. Globally, these findings indicate that basic functions, essential for juvenile seabass surviving and well performing in the wild, such as predation, predator avoidance, neurofunction and ability to face chemical stress may be compromised with increasing water temperature. This may be of particular concern if D. labrax recruitment phase in northwest European estuaries and coastal areas happens gradually in more warm environments as a consequence of global warming. Considering that the selected endpoints are generally applied in monitoring studies with different species, these findings also highlight the need of more research, including interdisciplinary and multiparameter approaches, on the impacts of temperature on marine species, and stress the importance of considering scenarios of temperature increase in environmental monitoring and in marine ecological risk assessment.
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TL;DR: Assessment of synaptosome viability and function at 37, 4°C and room temperature (RT) during 6 hours after its extraction of male Wistar rats found thatsynaptosomes preserved their viability andfunction at RT, 37 and4°C at least for 3 hours after extraction and reduced over time.
Abstract: Introduction: Synaptosomes are sealed particles that contain mitochondria, cytoskeleton and vesicles which are necessary to synaptic events like neurotransmitter release and uptake in the nervous system. However, the effect of high and low temperatures on synaptosome membrane integrity and function during a time course after its extraction is less known. The purpose of this study was to assess synaptosome viability and function at 37, 4°C and room temperature (RT) during 6 hours after its extraction. Methods: Hippocampi of 40 male Wistar rats were used for synaptosome preparation. To ensure synaptosome membrane integrity and function, lactate dehydrogenase activity (LDH) and GABA uptake were assessed during 6 successive hours after their extraction at 37, 4°C and RT. Results: Our results showed that at 37°C, synaptosome membrane integrity was reduced 3 hours but at 4°C and RT, it occurred 5 hours following their extraction. The results of synaptosome function analysis coincide with LDH enzyme assay data, meaning that GABA uptake faced a 50% reduction from the initial value at 37°C after 3 hours and at RT after 5 hours. We also found that GABA uptake was reduced at 4°C in the first hour after extraction because the low temperature inhibits GABA transporters. Conclusion: Synaptosomes preserved their viability and function at RT, 37 and 4°C at least for 3 hours after extraction and reduced over time. For long term application of synaptosomes, it is better to keep them at 4°C. iD Physiol Pharmacol 22 (2018) 73-81 D ow nl oa de d fr om p pj .p hy ph a. ir at 1 0: 19 + 03 30 o n M on da y N ov em be r 4t h 20 19 Synaptosome viability and function Physiol Pharmacol 22 (2018) 73-81 | 74 by Whittaker in the late 1950s and detected as detached synapses by electron microscopy (Whittaker, 1993; Whittaker and Gray, 1962). Synaptosomes are acquired by homogenization of fresh brain tissue in an appropriate isotonic solution which causes the nerve terminals to be separated from their axon stalks. Then, the membrane of presynaptic terminals is resealed, which contains cytoplasm, cytoskeleton, mitochondria and synaptic vesicles with the presynaptic and occasionally postsynaptic membranes (Dunkley et al., 2008; Whittaker et al., 1964). Synaptosomes have widely been applied as an in vitro model to investigate the molecular mechanisms of brain synapses specially storage, release, and uptake of neurotransmitters. As a result, our knowledge about the function of synapse ending at a physiological, cellular and molecular level was enhanced (Breukel et al., 1997; Dunkley et al., 1988; Dunkley et al., 2008; Whittaker, 1993). Different procedures have been developed to isolate synaptosomes including ultrafiltration, electrophoresis, sucrose and percoll gradients; however, a median-speed centrifuge technique seems to be more appropriate (Dunkley et al., 1988; Dunkley et al., 2008; Enriquez et al.,1990; Kamat et al., 2014; Stadler and Tashiro, 1979). Synaptosomes can be obtained from any part of the brain tissues. In addition, the nerves of the non-neurological tissue are also involved in the synaptosomes preparation (Jonakait et al.,1979). If a chemical active ingredient is found abundantly in synaptosomes, it can be assumed as a neurotransmitter or coneurotransmitter. Moreover, mixed fraction synaptosomes can be applied to assess the mechanisms of neurotransmitters release (Breukel et al., 1997). Exposure of adult albino rats to the high ambient temperature at 35 °C for 2-12 hours or at 45 °C for 12 hours increased the acetylcholinesterase activity of their brain synaptosomes (Mukhopadhyay and Poddar, 1990). Several studies have investigated the effects of organophosphate compound on the GABA uptake of synaptosomes in cerebral cortex, cerebellum and hippocampus, suggesting that the GABA uptake was optimal one hour after synaptosome extraction (Ghasemi et al., 2007; Pourabdolhossein et al., 2009; Shahroukhi, et al., 2007). Furthermore, Hosseini et al. reported 35 minute is the optimal time for GABA release by rat cerebral synaptosomes (Hosseini et al., 2004). Incubation of synaptosomes at room temperature (22-25 °C) gradually increases the percentage of microtubule containing synaptosomes (41-47%) while its stabilization at low temperature leads to a significant reduction in the number of synaptosomes (Hajos et al., 1979). Despite the significance of synaptosomes in pharmaceutical, structural and functional studies, there is no empirical data on synaptosomes viability and function at different temperatures and time points after their extraction. Thus, the main ambition behind this study was to examine the synaptosomes survival and function at different temperatures and time points by measuring lactate dehydrogenase enzyme (LDH) and GABA uptake. We used hippocampal synaptosome due to its high synaptic contacts ratio compared to the other brain regions (Cragg, 1975). Materials and methods
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...Exposure of adult albino rats to the high ambient temperature at 35 °C for 2-12 hours or at 45 °C for 1- 2 hours increased the acetylcholinesterase activity of their brain synaptosomes (Mukhopadhyay and Poddar, 1990)....
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