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X Remesar

Publications and source records attributed to X Remesar.

At least 163 records · Page 9Linked to original sources
PubMed1981

Adenylate deaminase activity in the rat. Effect of 24 hours of fasting.

The adenylate deaminase activity of liver, kidneys, brain, striated muscle, stomach, intestine, skin and adipose tissue of fed and 24 hours fasted rats has been studied. The level of activity of the enzyme in muscle is at least an order of magnitude higher than in other organs. Fasting induced a significant increase in the muscle adenylate deaminase activity, while in kidneys, skin, small intestine, liver and adipose tissue, significant decreases were observed and practically no changes were found in brain and stomach. The possible incidence of these changes upon the overall alpha-amino nitrogen economy of the fasted animals is discussed.

AMP Deaminase↗
PubMed1981

Metabolic effects of short term food deprivation in the rat.

The effects of food deprivation for up to 24 hours on plasma metabolic parameters in the rat have been studied. Liver dry weight and glycogen content dropped significantly from 3 hours of food deprivation onwards. Total muscle glycogen supplied about as much glycosyl residues or precursors as did the liver. Plasma glucose, urea, lactate and total and essential amino acids decreased significantly from 3 hours of fasting onwards. Glycerol, free significantly from 3 hours of fasting onwards. Glycerol, free fatty acids, beta-hydroxybutyrate and acetoacetate showed significant increases with fasting. Alanine, serine, arginine, threonine, aspartate plus asparagine and proline showed significant decreases with fasting. Several other amino acids showed almost no change with fasting. Lysine, leucine plus isoleucine and taurine showed biphasic changes in their concentrations with a minimum at 6 hours and a transient recovery at 12 hours of fasting Essential amino acids decreased more than the non essential ones. With fasting there is a shift in ammonia disposal with lower urea concentrations as nitrogen is better conserved. The results seem to suggest that there is a constant release of substrates, through liver and peripheral tissue proteolysis, that is counteracted by differential utilization of amino acids during fasting.

Amino Acids↗
PubMed1981

Changes in glutamine synthesis activity in the different organs of developing rats.

The changes experienced by the glutamine synthetase activity in the liver, kidney, striated muscle, adipose tissue, brain, stomach, small intestine and skin of developing rats have been estimated. Skin and stomach enzymes attained the adult values in the late foetal period. Striated muscle, intestine and kidney glutamine synthetase belonged to the neonatal cluster, while liver and brain rose to values comparable to those of adults in late suckling. Glutamine synthesis between different organs of the rat during development matures soon after birth, gaining a considerable importance that helps to compensate the lack of availability of other nitrogen transport systems between peripheral and splanchnic bed organs in developing rats.

Adipose Tissue↗
PubMed1981

Effect of short term fasting on plasma composition of lactating rats.

The effects of a 24-h fast upon plasma and blood components of the lactating rat on day 20 after parturition have been determined. Body weight decrease observed with fasting was more marked in nursing dams than in controls. The changes observed agree with a limited use of lipidic resources, exhaustion of liver glycogen and considerable utilization of amino acids as energetic - as well as gluconeogenetic - substrates. Blood and plasma glucose were maintained in fasted dams at a level comparable with that of controls. The actual variations observed in the plasma aminogram were limited, showing a remarkable maintenance of the dam's own amino-acid homeostasis.

Amino Acids↗
PubMed1981

Effect of ether, sodium pentobarbital and chloral hydrate anesthesia on rat plasma metabolite concentrations.

The effect of ethyl ether, pentobarbital sodium (Nembutal) and chloral hydrate anesthesia on the concentrations of glucose, lactate, glycerol, insulin, individual amino acids and urea have been studied in rat plasma, as well as the glycogen content in the animal liver and striated muscle. Control animals were injected with saline solution. Two samples were taken from each animal at 15 and 30 minutes from the beginning of anesthesia. These samples were obtained from the cut tail's tip and from the neck wound produced by beheading the animal. Results show considerable differences between the three sets of animals and their controls as well as in their tail verus neck values. The overall effect of the three anesthetics used were roughly the same in spite of their different actions upon the different parameters studied. This was most marked in the aminograms. Significant changes induced were rather similar in number for all. The metabolite concentration profile in each situation may be used as a reference for possible artifacts induced by any experimental approach using these anesthetics.

Amino Acids↗
PubMed1980

Changes-induced in liver and muscle glycogen and glycogen enzymes by 24-hour fasting in the rat.

Liver and muscle glycogen content, and the activities of glycogen synthetase, glycogen phosphorylase and alpha-amylase have been measured in fed and 24 hours fasted rats. Muscle and liver glycogen account for similar amounts of glycosyl residues liberated in this period of food deprivation. With fasting, liver glycogen synthetase activity decreases somewhat, increasing the I versus total ratio; the liver phosphorylase activity decreases considerably and amylases remain constant. In muscle, total synthetase remains constant with fasting, but the I versus total ratio decreases; phosphorylase activity decreases very considerably and alpha-amylase activity increases to almost thrice the values found in fed animals. These changes reflect a tendency towards conservation of glycogen primers with a preparation to increase glycogen synthesis when glucose would be available. In muscle also, the amylase increase in activity would be tentatively explained as a partial replacement of phosphorylase activity as a means of glucose mobilization from glycogen.

Amylases↗
PubMed1980

Changes in alanine transaminase activity in several organs of the rat induced by a 24-hour fast.

The activity of alanine transaminase in the liver, intestine, stomach, striated muscle, kidneys, adipose tissue, brain and skin of fed and 24-hours fasted adult rats has been determined. The range of activities expressed per unit of protein and DNA weight is rather similar in most organs, with highest values for the liver enzyme. Fasting induced significant increases mainly in peripheral organs, with a combined 35% increase, whereas the liver capability actually decreased by 14% because of the decrease in liver size; and all other splanchnic extrahepatic tissues activity studied increased by 22%. The results obtained agree with the postulated activity of the glucose-alanine cycle under these conditions of fasting.

Alanine Transaminase↗
PubMed1980

Activities of enzymes involved in amino-acid metabolism in developing rat placenta.

Aspartate transaminase, alanine transaminase, glutamate dehydrogenase, arginase, serine dehydratase, tyrosine transaminase, glutamine synthetase, glutaminase and adenylate deaminase activities were measured in crude homogenates of 12, 19 and 21-day rat placentae. There is a considerable quantitative importance in enzymes able to produce free ammonia, such as adenylate deaminase and glutamate dehydrogenase, activity that progressively decrease with the age of placenta. The glutamine synthetase and tyrosine transaminase activities increase with age, while serine dehydratase decreases considerably and aspartate and alanine transaminase do not change practically. Arginase shows a maximum at 19, with lower 12 and 21-day activities. No measurable glutaminase activity has been found. The possible implications of the enzymes studied upon the ammonia-producing activity of rat placenta are discussed together with the relative decreasing role of placenta for the overall metabolic activity of the foetus, especially during the last phases of its development.

AMP Deaminase↗
PubMed1980

Effect of stress and sampling site on metabolite concentration in rat plasma.

The effect of mild stress on various plasma metabolites in the rat has been studied. Mild stress resulted in significant decreases in liver size and glycogen content, as well as in an increase of blood glucose. In addition, plasma lactate, insulin, glycerol and urea, as well as a number of amino acids were altered by stress. These data indicate that minimal stress can have major effects upon the composition of blood, and suggest the need for strict precautions on the handling of animals during blood sampling. The site of blood extraction--tail tip vs. neck--was also found to have a significant effect on plasma lactate, glucose and urea concentrations. In stressed animals the differences between tail- and neck blood composition were increased.

Amino Acids↗
PubMed1980

Plasma amino-acid concentrations during development in the rat.

The plasma individual amino-acid concentrations in the rat during late foetal development and from the birth to the end of the weaning have been studied. Both the very low foetal amino-acid degrading capabilities in addition to the high amino-acid concentration ability of the placenta help to sustain considerably high plasma foetal amino-acid levels that favour considerably protein synthesis. There is a very important decrease in most amino-acid concentrations with birth, due to the cessation of placental transfer, relative immaturity of intake and assimilation processes and to the highly anabolic environment found in the pup. The changes in postnatal development plasma amino-acid patterns reflect directly the availability of amino acids in the diet, the maturation of the amino-acid metabolism pathways and transport systems and their use for protein synthesis (and other nitrogenous compounds). The main situation that affects individual amino-acid levels is the shift from high biological value milk protein to low biological value plant proteins in the rat chow pellets. The postnatal development is characterized by a high combined total amino-acids homeostasis with ample changes in individual amino-acid concentrations, that is maintained in spite of the deep changes in diet, size, metabolism, hormone environment, maturation, etc. observed in the rat from birth to weaning and adulthood.

Aging↗
PubMed1980

Fasting-induced changes of tyrosine transaminase activity in rat tissues.

Tyrosine transaminase activity in liver, kidney, intestine, stomach, skin, adipose tissue, striated muscle and brain in fed and 24-hour fasted rats, has been studied. Maximal activity has been found in liver, with only fractional activity in the other tissues. 24 hour fasting induced significant decrease in liver and adipose tissue activity, while no changes have been detected in the other tissues. The possible implications of these facts are discussed.

Animals↗
PubMed1980

Blood and plasma glucose relationships during pregnancy, the breeding cycle and development in the rat.

The concentration of blood and plasma glucose in developing, pregnant and post-partum rats has been determined under uniform conditions of housing, feeding and circadian rhythms. The glucose content of erythrocytes and of the plasma compartment has been estimated using the packed cell hematocrit value as correction factor. During pregnancy and fetal development there were significant reductions in the proportion of intracellular glucose, and significant increases during the suckling and weaning period. There was no direct relationship with plasma insulin levels. Results are discussed in relation to aspects of metabolism specific to the physiological components of the breeding cycle studied; plasma glucose homeostasis is held very constant; both intraerythrocytic and plasma concentrations should be considered when studying glucose homeostasis in given physiological situations.

Animals↗
PubMed1980

Effect of 24-hours fast on aspartate transaminase activities in the organs of the rat.

The aspartate transaminase activity of liver, kidney, brain, stomach, small intestine, striated muscle, skin and adipose tissue of fed and 24-hour fasted rats has been studied. The activity level of the enzyme is very much alike in most organs when expressed per unit of protein or DNA weight, in accordance with the general metabolic role of this enzyme. The activity of skin and adipose tissue is considerably lower than that of the other studied organs. A 24-hour fast induced significant increases in the activity of all organs except intestine and stomach.

Animals↗
PubMed1980

Serine dehydratase activity in the liver and extrahepatic organs of fed and 24-hour fasted rats.

The serine dehydratase activity in crude homogenates of rat liver, intestine, adipose tissue, kidney, brain, leg striated muscle, skin and stomach, both in fed and 24-hour fasted rats have been estimated. The liver enzyme activity increased twofold with fasting, while it did not affect the serine dehydratase activity in any other organ studied. The highest serine dehydratase activity is found in the liver, with only fractional activity in all other tissues studied.

Animals↗
PubMed1980

Effect of chronic feeding of Remington's diet and fasting on rat plasma composition.

Rats fed on Remington's low iodine diet (supplemented with iodine) and on rat chow were compared as to their plasma composition. There are significant differences in plasma glycerol, aceto-acetate, beta-hydroxybutyrate and in several amino acid concentrations, mainly lysine and tryptophan. 24 hours of fasting lowered the differences between the groups, but some aspects remained unchanged, i.e. the low lysine and tryptophan concentrations in Remington diet fed rats. The use of the Remington diet therefore, provoked a functional lack of these amino acids, even when their concentration in the diet was higher.

Amino Acids↗