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Biomedical subjects

X Remesar

Publications and source records attributed to X Remesar.

At least 145 records · Page 8Linked to original sources
PubMed1986

Free amino acid pools in some tissues of the pregnant rat.

Plasma amino acid pools show important variations throughout the gestational period in the rat, with decreased values at mid-pregnancy and recovered levels before parturition. This decrease in amino acid levels at mid-pregnancy is mainly due to changes in the gluconeogenic amino acid group. During pregnancy, whole tissue amino acid pools increase in the liver but no changes appear in other studied tissues. However, individual gluconeogenic amino acid concentrations change significantly in skeletal muscle, skin and liver through the gestational period. Pregnancy may be understood as a challenge to the mother's metabolism but the pattern of tissue amino acid changes is not similar to that found in some stressant situations and it should be the net consequence of maternal adaptations to the increased metabolic needs.

Amino Acids↗
PubMed1986

Blood amino acid compartmentalization during pregnancy and lactation in the rat.

The blood amino acid compartmentalization during pregnancy and lactation of the rat have been studied. Cellular amino acid levels are similar to those of the plasmatic fraction. Important generalized decreases are detected on days 12 and 21 of the pregnancy; Glu + Gln, Ala and essential and semiessential amino acids being the most affected. During lactation, after a transient phase on day 1 after delivery, there is a generalized increase in blood levels, especially in the plasma fraction, that affects the whole essential values. The different patterns shown by amino acids during pregnancy and lactation confirm that the measurement of plasmatic levels underestimates the actual capacity of whole blood to transport amino acids.

Amino Acids↗
PubMed1986

No significant net uptake of branched chain amino acids by the liver of fed-mid pregnant rats.

The hepatic balance for valine, leucine and isoleucine has been measured in anaesthetized virgin controls and 9 and 12-day pregnant rats. The liver of non gravid animals show fractional extraction rates of over 11.6% for valine, 17.6% for leucine and 16.8% for isoleucine. Fed mid-pregnant rats do not show either a significant net uptake nor a release of these amino acids. It is proposed that higher intestinal amino acid requirements for protein synthesis during mid pregnancy than before impregnation may be, in part, the cause of a decreased hepatic uptake and, thus, a different role for the liver in the amino acid inter-organ relationships during this period is suggested.

Amino Acids, Branched-Chain↗
PubMed1986

Urea and ammonia in urine and plasma of fed-mid-pregnant rats.

In the rat, mid-pregnancy seems to be related to an active nitrogen metabolism. In the present work we studied how the plasma homeostasis and the urinary nitrogen excretion of urea and ammonia could be altered during this period. Urea and ammonia plasma levels do not show significant changes, whereas, their urinary excretion is increased at mid-pregnancy. When urea levels in urine are corrected by the urinary creatinine content and the food intake, we found lower values in pregnant than in virgin rats. Thus, the organic nitrogen is more spared during pregnancy than before impregnation without any significant changes in the urea and ammonia plasma concentrations.

Ammonia↗
PubMed1985

Activities of amino acid metabolizing enzymes in the stomach and small intestine of developing rats.

The activities of aspartate and alanine transaminase, serine dehydratase, arginase, glutamate dehydrogenase, adenylate deaminase and glutamine synthetase were determined in the stomach and small intestine of developing rats. Despite the common embryonic origin of the intestine and stomach, their enzymes showed quite different activity levels and patterns of development, depending on their roles. Most enzyme activities were low during late intrauterine life and after birth, attaining adult levels with the change of diet at weaning. No arginase activity was found in the stomach and no changes were detected in adenylate deaminase in the stomach or intestine throughout the period studied. Alanine transaminase, serine dehydratase and, to some extent, glutamine synthetase levels, significantly higher in late intrauterine life, decreased after birth, suggesting that the foetal stomach has a transient ability to handle amino acids.

AMP Deaminase↗
PubMed1984

Arginase activity during pregnancy and lactation.

Arginase activity in liver, kidney, small intestine and stomach of pregnant and lactating rats as well as their plasma levels have been measured. Late pregnancy as well as weaning induced a parallel increase in enzyme activity that is not reflected in the circulating urea levels. The arginase activity changes have been related to known changes in feeding and nitrogen handling patterns as well as to hormonal variations.

Animals↗
PubMed1984

Effects of 24-hour starvation period on metabolic parameters of 20-day-old rats.

The effects of a 24-hour starvation period upon 20-day-old rat pups were studied both in animals kept in the presence of their starved dams and in their absence. The relative loss of body weight was more intense in the rats that received no milk, being however, severe in both groups. There was a significant maintenance of both plasma glucose levels and total amino acids, with differences in blood glucose compartmentation and a remarkable uniformity in the effects of starvation upon individual amino-acid concentrations. A significant increase in plasma urea was observed, higher in the rats kept in the presence of the dam. Ketone bodies increased with starvation but their final levels were lower than in adults. The general pattern of metabolic change observed suggests a situation, after 24-h food deprivation, similar to that of long term starvation in adults; with an active protein amino-acid catabolism but with a remarkable maintenance of circulating foodstuff levels.

Amino Acids↗
PubMed1983

Body and organ size and composition during late foetal and postnatal development of rat.

Development induced deep anatomical changes and tissue composition alterations in the rat. To determine the extent of these changes, the organ weight and size of 19 and 21 day rat foetuses and of 1, 5, 10, 20 and 30 day old Wistar rat pups have been studied and compared with adults. Different tissues showed varying rates of cell and tissue growth as well as tissue cellularity during development. Tail length is not a good index of skeletal growth. Brain growth was much slower from late intrauterine life to adulthood than most other organs. Skin weight increased more than 3-fold between days 19 and 21 of intrauterine life. Striated muscle proportion to body weight remained practically constant throughout all postnatal life studied.

Age Factors↗
PubMed1983

Distribution of amino acids and amino-acid enzymes in whole kidney and renal cortex. Effect of 24-h starvation.

The levels of activity of amino-acid enzymes (alanine-, aspartate- and tyrosine transaminases, serine dehydratase, glutamate dehydrogenase, glutamine synthetase, arginase and adenylate deaminase) in the kidney cortex and whole kidney of control and 24-h starved adult rats have been determined from crude homogenates. The individual amino-acid content of the two kidney fractions indicated has also been studied. Serine dehydratase was found mainly in the cortex, whilst glutamine synthetase presence was mainly limited to the medulla. The distribution of adenylate deaminase and glutamate dehydrogenase is remarkably uniform along the kidney. Starvation induced decreases in arginase and adenylate deaminase activities as well as a decrease in cortical serine dehydratase. Analysis of the variance of the enzyme data showed no significant overall changes with respect to distribution and starvation. The same analysis applied to aminograms indicated only significant changes when the distribution was studied on starved samples as a whole, with changes mainly in the urea cycle and some essential amino acids. The results suggested a remarkable degree of uniformity in kidney composition both with respect to amino acid and enzyme distribution. This uniformity is not markedly affected by starvation despite the important rôle of kidney in the overall amino-acid economy of the Mammal.

AMP Deaminase↗
PubMed1983

Aspartate- and tyrosine transaminase activities in the organs of the rat during its breeding cycle.

The aspartate- and tyrosine transaminase activities of liver kidney, brain, hind leg striated muscle, skin, adipose tissue, small intestine and stomach of pregnant, lactating and post-lactating rats were determined. The ratios of activities between both enzymes were uniform in the different tissues studied, with minimal values for liver and adipose tissue. The patterns and activity ratios found during the breeding cycle of the rat agreed with tyrosine transaminase being an independent entity of aspartate transaminase in liver and adipose tissue, coexisting to some degree in most other tissues and being probably only an artifact (according to recent findings in the literature) in brain, muscle and intestine. The different patterns of change found during this period in most organs suggest different hormonal regulation and help support the possibility of an independent rôle for tyrosine transaminase in them.

Adipose Tissue↗
PubMed1983

Ontogeny of amino-acid metabolism-enzymes in peripheral tissues of developing rats.

The activities of alanine, aspartate and tyrosine transaminase, adenylate deaminase, glutamate dehydrogenase and glutamine synthetase have been measured in hind leg striated muscle, lumbar adipose tissue and lumbar skin of developing rats from late foetal to weaning stage. In a general way, despite minor differences and different physiological rôles, the three peripheral tissues studied showed a concordant enzyme activity pattern with the rôles found for these enzymes in the adult. Muscle had a more constant pattern throughout development, with wider changes in skin and widest in adipose tissue. The results found agree with a marked "synthetic" mode in the tissues studied throughout all development studied. The patterns observed agree with a strict amino-acid conservation scheme during foetal life and lactation that progressively changes with weaning towards a frank degrading mode.

AMP Deaminase↗
PubMed1983

Adenylate deaminase activity in the tissues of the rat during its breeding cycle.

The adenylate deaminase activity of muscle, liver, kidney, brain, intestine, stomach and adipose tissue have been measured during pregnancy, lactation and post-lactation of the rat. No significant changes have been found in muscle and kidney, with depressed values in the liver of pregnant rats--in agreement with the loss of metabolic rôle in nitrogen handling during this period--. Adipose tissue changes as well as those of skin actually followed anatomical changes in fat content of both tissues. Stomach and intestine patterns were significantly different, with a maximum for the bowel at mid-lactation.

AMP Deaminase↗
PubMed1982

Glycogen and glycogen enzymes in the liver and striated muscle of rats under altered thyroid states.

Changes induced in liver and striated muscle glycogen and glycogen enzymes (glycogen synthetase, glycogen phosphorylase and alpha-amylase) by hypothyroidism and hyperthyroidism in rats have been determined. There were no changes in liver glycogen synthetase, phosphorylase and amylase activities in the hypothyroid group. Hyperthyroid rats showed lower liver glycogen synthetase, phosphorylase a and amylase activities. In muscle, hypothyroid rats had lower phosphorylase activity. In the hyperthyroid group glycogen synthetase was increased.--The results presented do not completely agree with the glycogen levels found in both tissues studied, and they are obviously more related to other factors such as glucose availability. It can be concluded that under the conditions studied, the glycogen enzyme levels could not alone explain the variations of glycogen levels.

Amylases↗
PubMed1982

Glutamine synthetase activity in rat tissues during pregnancy and lactation.

The glutamine synthetase activities of liver, striated muscle, kidney, brain, stomach, adipose tissue, small intestine and skin of rats during pregnancy, lactation and post-lactation were investigated as a probe of glutamine--and thus of ammonia--metabolism under a situation of altered amino acid utilization. There were significant increases in muscle activity in mid-pregnancy and in post-lactation. A transient relative decrease was observed in muscle enzyme on day 20 of lactation, compensated by an increase in small intestine activity. The results are discussed in light of the transporting role of nitrogen between peripheral and splanchnic tissues attributed to glutamine, as well as to the detoxyfying role of the enzyme for removal of nitrogen generated by the conceptus and by catabolism of amino acids under the increasing demand for energetic fuels in the peak of lactation.

Animals↗
PubMed1982

Amino-acid enzyme activities in liver and kidney of developing rats.

The amino-acid enzymes (aspartate-, alanine- and tyrosine transaminases, serine dehydratase, glutamate dehydrogenase, glutamine synthetase, adenylate deaminase and arginase) activities in the liver and kidney of developing rats (days 19 and 21 after conception and 1, 5, 10, 20 and 30 after birth) compared with adults were determined in crude homogenates. Most enzymes attained the adult levels early after birth or at weaning, showing a marked trend towards amino-acid nitrogen conservation during late foetal and specially during the neonatal period, increasing their activity during lactation. It is postulated that these changes are closely related to availability of low grade protein in diet as well as to maturation of amino-acid homeostasis maintenance for growth.

AMP Deaminase↗
PubMed1982

Changes induced in rat plasma composition by lactation.

Changes in rat plasma composition in post-partum period were studied from day 1 to post weaning recovery situation (day 40). Urea levels showed a significant increase at the peak of lactation, and glycerol levels showed a decrease towards late lactation. Changes in the plasma aminogram were more marked during the maximal intensity of lactation (days 10-20) and in postlactation. Low trypthophan levels were sustained throughout the lactation period. The combined amino acids showed significant increases on day 10 of lactation, and increases in non-essential and total amino acids in post-lactation (40 days). These results point towards increased amino-acid utilization during lactation.

3-Hydroxybutyric Acid↗
PubMed1981

Glutamine synthetase activity in the organs of fed and 24-hours fasted rats.

Glutamine synthetase activity in several rat tissues had been measured. Liver contains the highest specific activity followed by stomach, brain, kidneys, intestine, skin, adipose tissue and striated muscle - that had the lowest specific activity both with regard to tissue, protein and DNA weight. Per unit of animal weight, liver and muscle contain similar activities, 24 Hours of fasting induced a significant decrease in liver, stomach, intestine and skin glutamine synthetase, compensated by an increase in muscle activity. During fasting, the splanchnic glutamine synthetase activity is lowered and that of peripheral tissues is increased, thus favoring a net glutamine flux from peripheral to splanchnic organs.

Animals↗