Nisred Klichkhanov - Academia.edu (original) (raw)
Papers by Nisred Klichkhanov
Biophysics, 2018
The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderate... more The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderate hypothermia was studied. It is shown that the kinetics of the thermal denaturation of acetylcholinesterase is nonlinear and corresponds to a model that involves two-step denaturation, fast and slow, of the enzyme’s native form. The rate constants of the fast phase, k1, are much higher than those of the slow phase, k2, while the energy of the fast phase activation is lower by only 19.4% compared to that of the slow one. Short-term moderate hypothermia is shown to increase k1 and decrease the index of relative activity of the intermediate form of acetylcholinesterase (parameter β), leading to significant lowering of the activation energies of both stages; parameter β becomes more temperature dependent. The prolongation of hypothermia up to 3 h mainly contributes to a decrease in k1 and k2 relative to short-term hypothermia and the activation energy of denaturation increases. These data support the hypothesis according to which the structure of acetylcholinesterase is labilized at the initial stages of the development of the hypothermic state and stabilized during prolonged hypothermia.
Al-Mustansiriyah Journal of Science
Polycystic ovarian syndrome (PCOS) is the most recorded endocrinological condition that impacts w... more Polycystic ovarian syndrome (PCOS) is the most recorded endocrinological condition that impacts women throughout their fertile years and causes a variety of clinical symptoms. The study included 60 women with PCOS and 60 women who were matched for age and body mass index (BMI) and excluded the participants refrain from vigorous exercise and drink anything with alcohol or caffeine. were tested levels for IR, insulin, Hepcidin, Adiponectin, lipids profile in control and PCOS. and found Reduced levels (non sig.) of adiponectin have been documented in Iraqi patients with Polycystic Ovary Syndrome. There was an inverse relationship between IR and hepcidin levels in both groups meaning increase in IR (0.001) and decrease in hepcidin (0.001) levels may increase the risk of PCOS. well found that lipid profile (HDL, LDL, TG) that is non-significant but cholesterol high significant 0.001 in patients.
Journal of Experimental Zoology Part A: Ecological and Integrative Physiology
Bulletin of Experimental Biology and Medicine, 2004
We studied kinetic and thermodynamic characteristics of acetylcholine esterase in rat erythrocyte... more We studied kinetic and thermodynamic characteristics of acetylcholine esterase in rat erythrocyte membrane after whole-body hypothermia (20~ of different duration. Hypothermia increased the degree of substrate inhibition for acetylcholine esterase, maximum rate, and Michaelis constant. The temperature dependence of acetylcholine esterase activity remained practically unchanged.
Neurochemical Journal, 2010
Ukrainskiĭ biokhimicheskiĭ zhurnal
The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus ... more The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus striatum, hypothalamus and medulla oblongata of rats during hypothermia (20 degrees C) and also 1 and 7 days after the posthypothermal period. Cooling of animals down to 20 degrees C is accompanied by an increase in the AChE activity in the brain both under incubation temperature of 20 degrees and 37 degrees C. Under prolonged hypothermia the AChE activity in the investigated brain regions, except for corpus striatum, returns to the control level. By the 7th day of posthypothermal period the AChE activity in corpus striatum, hypothalamus and medulla oblongata does not restore completely. The most substantial changes in the AChE activity both under hypothermia and posthypothermal period occur in corpus striatum, which obviously reflects its complicated functional role.
Zhurnal evoliutsionnoi biokhimii i fiziologii, 2011
Effect of hypothermia on the fatty acid composition of rat and souslik blood phospholipids is stu... more Effect of hypothermia on the fatty acid composition of rat and souslik blood phospholipids is studied. Different reaction of these animals to cooling is revealed: in rats no changes were observed in the fatty acid composition of blood phospholipids, whereas in the hibernating there were significant changes in the content of individual fatty acids (FA). The content of monoenic acids in sousliks decreased almost by 50%, while the content of saturated acid (C18) and of polyenic acids C18 : 2omega6 and C20 : 4omega6 rose significantly. Such changes seem to be the mechanism that promotes maintenance of the organism viability under conditions of a decreased level of metabolism, heart rhythm, and body temperature and is evolutionarily acquired. At the same time, the observed changes in the content of individual FA do not lead to sharp changes in such integrative parameters as the total non-saturation of phospholipids, which determines liquid properties of chylomicrons and other lipolipopro...
Problems of Cryobiology and Cryomedicine, 2009
The effect of artificial hypothermia of various depths on intensity of oxidative modification of ... more The effect of artificial hypothermia of various depths on intensity of oxidative modification of plasma proteins and activity of antioxidant system of ground squirrel blood during active summer time were studied. It has been shown that hypothermia at 20 and 10°C differently affects the intensity of oxidative modification of plasma proteins. Under hypothermia independently of its depth the increase of protein resistance of blood plasma to oxidants has been revealed. At low temperatures of body the significant increase of hydrophil antioxidants’ activity in blood plasma is found that may play an important role in protection of proteins from oxidative damage.
Ukrainskii biokhimicheskii zhurnal, 1986
The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus ... more The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus striatum, hypothalamus and medulla oblongata of rats during hypothermia (20 degrees C) and also 1 and 7 days after the posthypothermal period. Cooling of animals down to 20 degrees C is accompanied by an increase in the AChE activity in the brain both under incubation temperature of 20 degrees and 37 degrees C. Under prolonged hypothermia the AChE activity in the investigated brain regions, except for corpus striatum, returns to the control level. By the 7th day of posthypothermal period the AChE activity in corpus striatum, hypothalamus and medulla oblongata does not restore completely. The most substantial changes in the AChE activity both under hypothermia and posthypothermal period occur in corpus striatum, which obviously reflects its complicated functional role.
Voprosy meditsinskoi khimii, 1986
Short-term hypothermia, caused by cooling of rats down to 20 degrees, decreased distinctly the Na... more Short-term hypothermia, caused by cooling of rats down to 20 degrees, decreased distinctly the Na+, K+-ATPase activity in brain homogenates incubated at 37 degrees and did not affect the enzyme activity in the homogenates incubated at 20 degrees. The longer hypothermia (2 hrs at 20 degrees) did not affect the Na+, K+-ATPase activity at 37 degrees (during incubation) and decreased the enzymatic activity in homogenates of middle brain and diencephalon at 20 degrees during the incubation. Contrary to Na+, K+-ATPase, the activity of acetylcholinesterase was markedly increased in brain tissues of rats with hypothermia (irrespective of the temperature of incubation) as compared with control animals.
NEUROSCIENCE FOR MEDICINE AND PSYCHOLOGY, 2021
Biology Bulletin
We assessed the effect of intraperitoneal administration of ascorbic acid (vitamin C, 100 mg/kg/d... more We assessed the effect of intraperitoneal administration of ascorbic acid (vitamin C, 100 mg/kg/day) and α-tocopherol (vitamin E-selenium, 40 mg/kg/day), given alone or in combination for seven days, on the intensity of free-radical processes in the blood of rats in acute short-term hypothermia of 30 ○ С. Hypothermia contributes to the development of oxidative stress in erythrocytes, stimulating the lipid peroxidation and oxidative modification of proteins (OMP), decreasing the content of glutathione (GSH) and increasing the activity of superoxide dismutase (SOD) in erythrocytes. A separate administration of vitamins prevents a decrease in the level of GSH and an increase in the activity of SOD in erythrocytes in hypothermia, but vitamin C stimulates lipid peroxidation and OMP and vitamin E stimulates OMP of the erythrocyte membranes. Coadministration of vitamins C and E completely prevents the development of oxidative stress in erythrocytes during hypothermia.
Bulletin of Experimental Biology and Medicine
We studied the effect of a new cyanine dye containing selenium and tellurium on acetylcholinester... more We studied the effect of a new cyanine dye containing selenium and tellurium on acetylcholinesterase activity in synaptic membrane in rat brain. The cyanine dye dose-dependently inhibits activity of this enzyme, and the concentration of half-maximal inhibition of acetylcholinesterase activity was 20.46 μM. The cyanine dye instantly inhibits the enzyme; the degree of inhibition depends on acetylthiocholine concentration: the lower is acetylthiocholine concentration, the higher is the degree of inhibition. On the Lineweaver-Burk plot, the concentration dependence curves of acetylcholinesterase with and without cyanine dye intersect in one point on the abscissa axis. In this case, the cyanine dye reduces the maximum inhibition rate (V max) and does not affect Michaelis constant (K m). The calculated inhibition constant K i for the cyanine dye is 7.74 μM. Thus, the cyanine dye is a non-competitive inhibitor of acetylcholinesterase.
Biophysics
⎯The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderat... more ⎯The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderate hypothermia was studied. It is shown that the kinetics of the thermal denaturation of acetylcholinesterase is nonlinear and corresponds to a model that involves two-step denaturation, fast and slow, of the enzyme's native form. The rate constants of the fast phase, k 1 , are much higher than those of the slow phase, k 2 , while the energy of the fast phase activation is lower by only 19.4% compared to that of the slow one. Short-term moderate hypothermia is shown to increase k 1 and decrease the index of relative activity of the intermediate form of acetylcholinesterase (parameter β), leading to significant lowering of the activation energies of both stages; parameter β becomes more temperature dependent. The prolongation of hypothermia up to 3 h mainly contributes to a decrease in k 1 and k 2 relative to short-term hypothermia and the activation energy of denaturation increases. These data support the hypothesis according to which the structure of acetylcholinesterase is labilized at the initial stages of the development of the hypothermic state and stabilized during prolonged hypothermia.
Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology
⎯Artificial hypothermic state of homeothermic animals contributes to the stimulation of free radi... more ⎯Artificial hypothermic state of homeothermic animals contributes to the stimulation of free radical processes in red blood cells. In order to understand what are the consequences of oxidative damage of erythrocyte membrane, we examined the dependence of the kinetic characteristics of integral membrane enzyme acetylcholinesterase (AChE) and structural and functional state of the membrane on the duration of mild hypothermia. For this purpose we reduced body temperature of adult Wistar rats by external cooling to 30°C (short-term moderate hypothermia) and then prolonged hypothermia up to 1.5 and 3 h. A short-term hypothermia was followed with an increase in V max and a decrease in K m , promoting an increase in the catalysis effectiveness.The optimum point on the graph of the concentration dependence was shifted to the area of lower concentrations, and the character of enzyme-substrate interactions at high concentrations of the enzyme changed. Upon prolongation of hypothermia, changes in the AChE kinetic characteristics favored normalization of the enzyme activity and concentration dependence. To test the hypothesis of a possible influence of the lipid matrix on the kinetic characteristics of AchE, we studied structural properties of the erythrocyte membranes using fluorescent probe pyrene. The observed changes in the structural and dynamic characteristics of erythrocyte membranes after a 1.5-h hypothermia suggested a reduction in microviscosity of both total and annular lipids. Prolongation of hypothermia up to 3 h favored normalization of this parameter. It was found that the indicators of the structural state of erythrocyte membranes at different durations of hypothermia correlate with certain kinetic characteristics of AChE. The data indicate that the prolongation of mild hypothermia up to 3 h triggers adaptive mechanisms directed to normalization of the erythrocytes membrane functioning.
Journal of Evolutionary Biochemistry and Physiology
The effect of moderate and deeper hypothermia on the phospholipid (PL) and fatty acid (FA) compos... more The effect of moderate and deeper hypothermia on the phospholipid (PL) and fatty acid (FA) composition of synaptic membranes (synaptosomes) in the rat brain was investigated. As hypothermia deepened, phosphatidylcholine (PC) and phosphatidylserine (PS) levels decreased while those of phosphatidylethanolamine (PEA) remained intact. We attribute the differences both to a peculiar localization of these PL in the synaptic membrane and to a specificity of their function. Under hypothermal exposure, the saturated FA (SFA) level in the FA repertoire of total synaptosomal PL slightly decreased (by 9%) while that of polyunsaturated FA (PUFA) considerably increased, leading to a rise in the lipid unsaturation index (LUI) (by 47%) and promoting the maintenance of synaptic membrane fluidity. For three basic PL (PC, PS and PEA), the tendency was opposite: the SFA level increased while that of PUFA decreased, leading to a fall in the LUI and promoting a higher packing order of PL within the synaptic membrane. In the FA repertoire of the plasmalogen form of PEA (p-PEA), enforced hypothermia led to elevated levels both of SFA and PUFA as well as to a particularly high LUI, typical for this PL. These changes are supposed to be aimed at maintaining optimal membrane fluidity. We consider all the observed changes in lipid characteristics as adaptive, allowing the synaptic function in homeotherms to be supported as body temperature falls.
Biophysics, 2018
The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderate... more The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderate hypothermia was studied. It is shown that the kinetics of the thermal denaturation of acetylcholinesterase is nonlinear and corresponds to a model that involves two-step denaturation, fast and slow, of the enzyme’s native form. The rate constants of the fast phase, k1, are much higher than those of the slow phase, k2, while the energy of the fast phase activation is lower by only 19.4% compared to that of the slow one. Short-term moderate hypothermia is shown to increase k1 and decrease the index of relative activity of the intermediate form of acetylcholinesterase (parameter β), leading to significant lowering of the activation energies of both stages; parameter β becomes more temperature dependent. The prolongation of hypothermia up to 3 h mainly contributes to a decrease in k1 and k2 relative to short-term hypothermia and the activation energy of denaturation increases. These data support the hypothesis according to which the structure of acetylcholinesterase is labilized at the initial stages of the development of the hypothermic state and stabilized during prolonged hypothermia.
Al-Mustansiriyah Journal of Science
Polycystic ovarian syndrome (PCOS) is the most recorded endocrinological condition that impacts w... more Polycystic ovarian syndrome (PCOS) is the most recorded endocrinological condition that impacts women throughout their fertile years and causes a variety of clinical symptoms. The study included 60 women with PCOS and 60 women who were matched for age and body mass index (BMI) and excluded the participants refrain from vigorous exercise and drink anything with alcohol or caffeine. were tested levels for IR, insulin, Hepcidin, Adiponectin, lipids profile in control and PCOS. and found Reduced levels (non sig.) of adiponectin have been documented in Iraqi patients with Polycystic Ovary Syndrome. There was an inverse relationship between IR and hepcidin levels in both groups meaning increase in IR (0.001) and decrease in hepcidin (0.001) levels may increase the risk of PCOS. well found that lipid profile (HDL, LDL, TG) that is non-significant but cholesterol high significant 0.001 in patients.
Journal of Experimental Zoology Part A: Ecological and Integrative Physiology
Bulletin of Experimental Biology and Medicine, 2004
We studied kinetic and thermodynamic characteristics of acetylcholine esterase in rat erythrocyte... more We studied kinetic and thermodynamic characteristics of acetylcholine esterase in rat erythrocyte membrane after whole-body hypothermia (20~ of different duration. Hypothermia increased the degree of substrate inhibition for acetylcholine esterase, maximum rate, and Michaelis constant. The temperature dependence of acetylcholine esterase activity remained practically unchanged.
Neurochemical Journal, 2010
Ukrainskiĭ biokhimicheskiĭ zhurnal
The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus ... more The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus striatum, hypothalamus and medulla oblongata of rats during hypothermia (20 degrees C) and also 1 and 7 days after the posthypothermal period. Cooling of animals down to 20 degrees C is accompanied by an increase in the AChE activity in the brain both under incubation temperature of 20 degrees and 37 degrees C. Under prolonged hypothermia the AChE activity in the investigated brain regions, except for corpus striatum, returns to the control level. By the 7th day of posthypothermal period the AChE activity in corpus striatum, hypothalamus and medulla oblongata does not restore completely. The most substantial changes in the AChE activity both under hypothermia and posthypothermal period occur in corpus striatum, which obviously reflects its complicated functional role.
Zhurnal evoliutsionnoi biokhimii i fiziologii, 2011
Effect of hypothermia on the fatty acid composition of rat and souslik blood phospholipids is stu... more Effect of hypothermia on the fatty acid composition of rat and souslik blood phospholipids is studied. Different reaction of these animals to cooling is revealed: in rats no changes were observed in the fatty acid composition of blood phospholipids, whereas in the hibernating there were significant changes in the content of individual fatty acids (FA). The content of monoenic acids in sousliks decreased almost by 50%, while the content of saturated acid (C18) and of polyenic acids C18 : 2omega6 and C20 : 4omega6 rose significantly. Such changes seem to be the mechanism that promotes maintenance of the organism viability under conditions of a decreased level of metabolism, heart rhythm, and body temperature and is evolutionarily acquired. At the same time, the observed changes in the content of individual FA do not lead to sharp changes in such integrative parameters as the total non-saturation of phospholipids, which determines liquid properties of chylomicrons and other lipolipopro...
Problems of Cryobiology and Cryomedicine, 2009
The effect of artificial hypothermia of various depths on intensity of oxidative modification of ... more The effect of artificial hypothermia of various depths on intensity of oxidative modification of plasma proteins and activity of antioxidant system of ground squirrel blood during active summer time were studied. It has been shown that hypothermia at 20 and 10°C differently affects the intensity of oxidative modification of plasma proteins. Under hypothermia independently of its depth the increase of protein resistance of blood plasma to oxidants has been revealed. At low temperatures of body the significant increase of hydrophil antioxidants’ activity in blood plasma is found that may play an important role in protection of proteins from oxidative damage.
Ukrainskii biokhimicheskii zhurnal, 1986
The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus ... more The acetylcholinesterase (AChE) activity is studied in rat slices of the cerebral cortex, corpus striatum, hypothalamus and medulla oblongata of rats during hypothermia (20 degrees C) and also 1 and 7 days after the posthypothermal period. Cooling of animals down to 20 degrees C is accompanied by an increase in the AChE activity in the brain both under incubation temperature of 20 degrees and 37 degrees C. Under prolonged hypothermia the AChE activity in the investigated brain regions, except for corpus striatum, returns to the control level. By the 7th day of posthypothermal period the AChE activity in corpus striatum, hypothalamus and medulla oblongata does not restore completely. The most substantial changes in the AChE activity both under hypothermia and posthypothermal period occur in corpus striatum, which obviously reflects its complicated functional role.
Voprosy meditsinskoi khimii, 1986
Short-term hypothermia, caused by cooling of rats down to 20 degrees, decreased distinctly the Na... more Short-term hypothermia, caused by cooling of rats down to 20 degrees, decreased distinctly the Na+, K+-ATPase activity in brain homogenates incubated at 37 degrees and did not affect the enzyme activity in the homogenates incubated at 20 degrees. The longer hypothermia (2 hrs at 20 degrees) did not affect the Na+, K+-ATPase activity at 37 degrees (during incubation) and decreased the enzymatic activity in homogenates of middle brain and diencephalon at 20 degrees during the incubation. Contrary to Na+, K+-ATPase, the activity of acetylcholinesterase was markedly increased in brain tissues of rats with hypothermia (irrespective of the temperature of incubation) as compared with control animals.
NEUROSCIENCE FOR MEDICINE AND PSYCHOLOGY, 2021
Biology Bulletin
We assessed the effect of intraperitoneal administration of ascorbic acid (vitamin C, 100 mg/kg/d... more We assessed the effect of intraperitoneal administration of ascorbic acid (vitamin C, 100 mg/kg/day) and α-tocopherol (vitamin E-selenium, 40 mg/kg/day), given alone or in combination for seven days, on the intensity of free-radical processes in the blood of rats in acute short-term hypothermia of 30 ○ С. Hypothermia contributes to the development of oxidative stress in erythrocytes, stimulating the lipid peroxidation and oxidative modification of proteins (OMP), decreasing the content of glutathione (GSH) and increasing the activity of superoxide dismutase (SOD) in erythrocytes. A separate administration of vitamins prevents a decrease in the level of GSH and an increase in the activity of SOD in erythrocytes in hypothermia, but vitamin C stimulates lipid peroxidation and OMP and vitamin E stimulates OMP of the erythrocyte membranes. Coadministration of vitamins C and E completely prevents the development of oxidative stress in erythrocytes during hypothermia.
Bulletin of Experimental Biology and Medicine
We studied the effect of a new cyanine dye containing selenium and tellurium on acetylcholinester... more We studied the effect of a new cyanine dye containing selenium and tellurium on acetylcholinesterase activity in synaptic membrane in rat brain. The cyanine dye dose-dependently inhibits activity of this enzyme, and the concentration of half-maximal inhibition of acetylcholinesterase activity was 20.46 μM. The cyanine dye instantly inhibits the enzyme; the degree of inhibition depends on acetylthiocholine concentration: the lower is acetylthiocholine concentration, the higher is the degree of inhibition. On the Lineweaver-Burk plot, the concentration dependence curves of acetylcholinesterase with and without cyanine dye intersect in one point on the abscissa axis. In this case, the cyanine dye reduces the maximum inhibition rate (V max) and does not affect Michaelis constant (K m). The calculated inhibition constant K i for the cyanine dye is 7.74 μM. Thus, the cyanine dye is a non-competitive inhibitor of acetylcholinesterase.
Biophysics
⎯The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderat... more ⎯The thermostability of acetylcholinesterase of rat erythrocyte membranes in the norm and moderate hypothermia was studied. It is shown that the kinetics of the thermal denaturation of acetylcholinesterase is nonlinear and corresponds to a model that involves two-step denaturation, fast and slow, of the enzyme's native form. The rate constants of the fast phase, k 1 , are much higher than those of the slow phase, k 2 , while the energy of the fast phase activation is lower by only 19.4% compared to that of the slow one. Short-term moderate hypothermia is shown to increase k 1 and decrease the index of relative activity of the intermediate form of acetylcholinesterase (parameter β), leading to significant lowering of the activation energies of both stages; parameter β becomes more temperature dependent. The prolongation of hypothermia up to 3 h mainly contributes to a decrease in k 1 and k 2 relative to short-term hypothermia and the activation energy of denaturation increases. These data support the hypothesis according to which the structure of acetylcholinesterase is labilized at the initial stages of the development of the hypothermic state and stabilized during prolonged hypothermia.
Biochemistry (Moscow), Supplement Series A: Membrane and Cell Biology
⎯Artificial hypothermic state of homeothermic animals contributes to the stimulation of free radi... more ⎯Artificial hypothermic state of homeothermic animals contributes to the stimulation of free radical processes in red blood cells. In order to understand what are the consequences of oxidative damage of erythrocyte membrane, we examined the dependence of the kinetic characteristics of integral membrane enzyme acetylcholinesterase (AChE) and structural and functional state of the membrane on the duration of mild hypothermia. For this purpose we reduced body temperature of adult Wistar rats by external cooling to 30°C (short-term moderate hypothermia) and then prolonged hypothermia up to 1.5 and 3 h. A short-term hypothermia was followed with an increase in V max and a decrease in K m , promoting an increase in the catalysis effectiveness.The optimum point on the graph of the concentration dependence was shifted to the area of lower concentrations, and the character of enzyme-substrate interactions at high concentrations of the enzyme changed. Upon prolongation of hypothermia, changes in the AChE kinetic characteristics favored normalization of the enzyme activity and concentration dependence. To test the hypothesis of a possible influence of the lipid matrix on the kinetic characteristics of AchE, we studied structural properties of the erythrocyte membranes using fluorescent probe pyrene. The observed changes in the structural and dynamic characteristics of erythrocyte membranes after a 1.5-h hypothermia suggested a reduction in microviscosity of both total and annular lipids. Prolongation of hypothermia up to 3 h favored normalization of this parameter. It was found that the indicators of the structural state of erythrocyte membranes at different durations of hypothermia correlate with certain kinetic characteristics of AChE. The data indicate that the prolongation of mild hypothermia up to 3 h triggers adaptive mechanisms directed to normalization of the erythrocytes membrane functioning.
Journal of Evolutionary Biochemistry and Physiology
The effect of moderate and deeper hypothermia on the phospholipid (PL) and fatty acid (FA) compos... more The effect of moderate and deeper hypothermia on the phospholipid (PL) and fatty acid (FA) composition of synaptic membranes (synaptosomes) in the rat brain was investigated. As hypothermia deepened, phosphatidylcholine (PC) and phosphatidylserine (PS) levels decreased while those of phosphatidylethanolamine (PEA) remained intact. We attribute the differences both to a peculiar localization of these PL in the synaptic membrane and to a specificity of their function. Under hypothermal exposure, the saturated FA (SFA) level in the FA repertoire of total synaptosomal PL slightly decreased (by 9%) while that of polyunsaturated FA (PUFA) considerably increased, leading to a rise in the lipid unsaturation index (LUI) (by 47%) and promoting the maintenance of synaptic membrane fluidity. For three basic PL (PC, PS and PEA), the tendency was opposite: the SFA level increased while that of PUFA decreased, leading to a fall in the LUI and promoting a higher packing order of PL within the synaptic membrane. In the FA repertoire of the plasmalogen form of PEA (p-PEA), enforced hypothermia led to elevated levels both of SFA and PUFA as well as to a particularly high LUI, typical for this PL. These changes are supposed to be aimed at maintaining optimal membrane fluidity. We consider all the observed changes in lipid characteristics as adaptive, allowing the synaptic function in homeotherms to be supported as body temperature falls.