Biomedical subjects

X Remesar

Publications and source records attributed to X Remesar.

At least 145 records · Page 8Linked to original sources

PubMed1987

Alanine uptake by liver at midpregnancy in rats.

The participation of the liver to the increase in alanine utilization seen at midpregnancy was studied in 9- and 12-day pregnant rats. Liver fractional extraction of alanine was assessed in vivo from the changes in concentration in afferent and efferent vessels. Hepatic active transport of alanine was determined in vitro using isolated plasma-membrane vesicles. Compared with nonpregnant controls, alanine fractional extraction was significantly increased on day 12 but not on day 9 of pregnancy. Vesicles isolated from 9- and 12-day pregnant animals had a greater capacity for Na+-dependent transport than those from controls. Eadie-Hofstee plotting showed that this increase was due to an increase in Vmax with no change in Km. Both A and ASC systems contributed to the Vmax increase. These results indicate that, although by day 9 the liver has developed an increased capacity for alanine uptake, the actual extraction is seen only by day 12 of pregnancy. At this stage the liver participates actively in the turnover of alanine and the development of hypoalaninemia.

Alanine↗

PubMed1987

Sulphur amino acid levels in some tissues of the rat during pregnancy and lactation.

Variations in free sulphur amino acid content in some rat tissues have been measured during pregnancy and lactation. As a general trend, sulphur amino acids tend to accumulate in tissues in late pregnancy. This accumulation is quantitatively more important in the liver and striated muscle than in the skin and the kidneys. Among sulphur amino acids, taurine shows the most marked changes, with a maximum accumulation in the liver and striated muscle on day 19 of pregnancy. After delivery, the levels of amino acids in the tissue pools show a tendency to drop, especially in liver and striated muscle. As expected, taurine shows the most marked decrease, returning to normal values in muscle but decreasing to depletion in the liver on day 20 after delivery. These results can be interpreted as follows: during pregnancy, increased food intake is sufficient to accommodate the metabolic needs of the mother, but during lactation, the requirements of milk synthesis promote the release of these amino acids from the tissues.

Amino Acids, Sulfur↗

PubMed1987

Variations in free amino acids in tissues of rats from birth to puberty.

Variations in concentrations of free amino acids and total protein in tissues of rats have been studied from birth to puberty. In the first 10 days after birth the concentrations of free amino acids in peripheral tissues increased. Only in the liver there was an increase in concentration of essential amino acids. When nutrition changed at weaning, concentration of amino acids decreased. This may be associated with high protein synthesis rates and increased catabolism of amino acids. Even after weaning, when the young rat became nutritionally independent, concentrations of free amino acids in the tissues had not become constant.

Aging↗

PubMed1986

Development of the gestational plasma hypoaminoacidemia in the rat.

The development of the gestational hypoaminoacidemia and the changes in amino acid blood compartmentation have been studied in virgin, 9 day, 12 day and 15 day pregnant rats. The drop of plasma amino acid levels is a rapid phenomenon which takes place between the 9th and the 12th day of pregnancy. It is mainly accounted for by gluconeogenic amino acids. Pregnant rats have lower plasma/cell amino acid ratios than virgin rats. Nine day pregnant rats have lower ratios than controls because of an important increase in the amino acid content of the cell fraction. Twelve and 15 day pregnant rats have lower ratios than controls because of the important drop in plasma levels, since cell content is similar to controls and lower than 9 day pregnant rats.

Amino Acids↗

PubMed1986

Tissue amino acid pool changes during the perinatal period of the rat.

Total free amino acid content in foetal liver, kidney, skin and striated muscle increases sharply during pregnancy. After delivery, there is no significant change in tissue total amino acid pools. The essential free amino acid pool in striated muscle decreases after delivery. This decrease suggests a relationship with the increased protein content in striated muscle.

Aging↗

PubMed1986

Effects of chronic ethanol ingestion on circulating metabolites and liver composition in the lactating rat.

A model of chronic ethanol administration has been used to study the effects of chronic ethanol consumption on the general metabolism of lactating rats on day 15 after delivery. We have studied the effects of ethanol on calories, food and fluid intake, body weight, circulating parameters such as glucose, glycerol, free fatty acids (FFA), triacylglycerols (TAG), amino acids (AA), ketone bodies, insulin and ethanol levels and liver composition. Chronic ethanol consumption markedly increases the levels of circulating B-OH-butyrate (B-OB-B), glycerol and FFA, while those of acetoacetate (AcAc), glucose, insulin and TAG remain constant. With the only exception of an increase in Glu + Gln levels, plasma AA decrease in the alcohol-treated rats, the change being significant for Ala, Pro, Lys, Arg, Val, Phe and 4-OH-proline. In the liver ethanol treatment causes an increment in TAG concentration and a decrease in glycogen content. In conclusion, chronic ethanol consumption produces notable alterations in the metabolism of lactating rats, which may diminish the efficiency of lactation, influencing milk production and, therefore, the pups' development.

Alcoholism↗

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↗