Biomedical subjects

C Adán

Publications and source records attributed to C Adán.

26 records · Page 2Linked to original sources

PubMed1996

Brown adipose tissue temperature in lean and obese rats during exercise.

OBJECTIVE: To determine the extent to which brown adipose tissue (BAT) heat output is influenced by treadmill exercise. DESIGN: The aortic blood core and interscapular BAT temperatures were recorded continuously during a short bout of intense exercise (different for each rat stock) in a treadmill and the ensuing 1-h recovery, sampling blood flows at timed intervals. SUBJECTS: Conscious Wistar, Zucker lean and Zucker obese rats. MEASUREMENTS: Aortic and interscapular BAT temperatures and tissue blood flow. RESULTS: Basal mean temperatures were highest for Wistar. Exercise provoked increases in aortic core temperatures in all three groups, slowly cooling off during recovery. Exercise and/or fatigue induced increases (vs aortic core temperature) of IBAT temperature. The effects were less marked in obese rats. CONCLUSION: Increases in BAT temperatures induced by exercise were counteracted by parallel decreases in blood flow, resulting in insignificant losses of heat from intarscapular BAT during exercise and recovery both in lean and obese rats.

Adipose Tissue, Brown↗

PubMed1996

Adipose tissue extraction of circulating insulin in anaesthetized Zucker obese rats.

OBJECTIVE: To determine whether adipose tissue removes a significant proportion of circulating insulin in the obese rat in vivo. DESIGN: Blood samples were obtained from the carotid artery and the venous side of hind leg muscle, epididymal fat pads and liver (portal and suprahepatic veins), they were used for estimation of insulin disappearance across the tissue. SUBJECTS: Anaesthetized Zucker lean (Fa/?) and obese (fa/fa) adult male rats. MEASUREMENTS: Blood flow, glycaemia and insulinaemia. RESULTS: In lean rats, the liver accounted for practically all insulin extraction (498 +/- 149 fmol.s-1), removing more than half of the portal insulin in a single pass. In the obese rats, the liver extracted a similar amount in absolute terms (397 +/- 108 fmol.s-1), representing only 16% of portal insulin. In the hind leg muscle of both groups and in the adipose tissue of lean rats, insulin balances were not different from zero; but in obese rats, adipose tissue extracted a similar amount of insulin (405 +/- 127 fmol.s-1) to that removed by the liver. CONCLUSIONS: In the Zucker obese rat, peripheral adipose tissue removes as much insulin from the blood as the liver does, in contrast with lean rats, in which the latter is responsible for practically all insulin extraction.

Adipose Tissue↗

PubMed1995

Rat insulin turnover in vivo.

Zucker lean and obese rats were injected under pentobarbital anesthesia with 125I-labeled insulin; at timed intervals from 30 to 120 sec, blood samples were extracted and used for the estimation of insulin levels by RIA. A group of rats from each series was maintained under a constant infusion of noradrenaline. For each insulin determination, a duplicate blood sample containing the same amount of insulin as that used in the RIA, but without the radioactive label, was used as a blank for insulin measurement. The radioactivity in these tubes was then used for the measurement of insulin label per ml blood. From plasma label decay curves and insulin concentrations, the insulin pool size, half-life, and rate of degradation were calculated. Obese rats had higher insulin levels (2.43 nM) and showed less effect of noradrenaline than their lean counterparts, in which insulin distribution volume shrank with noradrenaline treatment. The half-life of plasma insulin was similar in all groups (range, 226-314 sec). Pool size and overall degradation rates were higher in obese (198 femtokatals) than in lean rats (28 femtokatals). It is postulated that obese rats synthesize and cleave much more insulin than lean controls despite their higher circulating levels of insulin.

Animals↗

PubMed1995

Hindleg muscle energy and substrate balances in cold-exposed rats.

Rats chronically cannulated in the carotid artery and the muscular branch of the femoral vein were subjected to a cold (4 degrees C) environment for up to 2 h. The changes in blood flow (measured with 46Sc microspheres) and arterio-venous differences in the concentrations of glucose, lactate, triacylglycerols and amino acids allowed the estimation of substrate (and energy) balances across the hindleg. Mean glucose uptake was 0.28 mumol min-1, mean lactate release was 0.33 mumol min-1 and the free fatty acid basal release of 0.31 mumol min-1 was practically zero upon exposure to the cold; the initial uptake of triacylglycerols gave place to a massive release following exposure. The measurement of PO2, PCO2 and pH also allowed the estimation of oxygen, CO2 and bicarbonate balances and respiratory quotient changes across the hindleg. The contribution of amino acids to the energy balance of the hindleg was assumed to be low. These data were used to determine the sources of energy used to maintain muscle shivering with time. Three distinct phases were observed in hindleg substrate utilization. (1) The onset of shivering, with the use of glucose/glycogen and an increase in lactate efflux. Lipid oxidation was practically zero (respiratory quotient near 1), but the uptake of triacylglycerols from the blood remained unchanged. (2) A substrate-energy shift, with drastically decreased use of glucose/glycogen, and of lactate efflux; utilization of triacylglycerol as practically the sole source of energy (respiratory quotient approximately 0.7); decreasing uptake of triacylglycerol and increased tissue lipid mobilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗

PubMed1995

Treadmill chamber for studies of respiratory gas exchange in the rat during exercise.

A treadmill for studying gas exchange in small mammals during exercise is presented. The system consists of a motor-driven running mat enclosed in a gastight chamber that receives a measured flow of air from a compressed air cylinder. The gas flow and temperature, pressure and instantaneous gas composition of the chamber (oxygen, carbon dioxide and water) are measured continuously and the data are computed to include the effects on chamber atmosphere of the rat activity, either running or at rest. The system is completed with a shock delivery grid that stimulates the rat to run. The calculations are based on the changes in the composition of the gas in the chamber (constantly stirred by a small electric fan) induced by the rat instead of relying on the alterations induced in the outflowing gas. The consumption of oxygen, and production of carbon dioxide and water by the rat are computed in real time, giving a very fast response to physiological change induced by exercise. The chamber is custom-made from an aluminium block and a plexiglass lid; all other components are available commercially. The system, as described, allows for a detailed analysis of respiratory gas (and water) exchange by rats under varying exercise conditions, there is practically no time lag between changes in respiratory gases and the detection of these changes, and the buffering effect of the chamber size is practically eliminated because of the calculation approach used.

Animals↗

PubMed1994

Hind leg muscle amino acid balances in cold-exposed rats.

The changes in hind leg tissue (muscle and skin) amino acid pool size and arteriovenous balance were measured in rats subjected to 0-90 min of cold exposure (4 degrees C). Tissue free amino acid pools presented a different composition pattern from protein amino acids. Muscle rapidly reacted to cold exposure by releasing small amounts of some amino acids (alanine, aspartate), with only small changes in pool size during the first 30 min. Amino acid oxidation was very limited during the whole period of cold exposure, since at all times tested there was either nil ammonia efflux or net absorption of ammonia and glutamine; i.e. the muscle was in positive nitrogen balance throughout the period studied. Thus most of the amino acid nitrogen taken up from the blood and not found in the free amino acid pools must have been incorporated into protein, since it was not oxidized, as shown by the glutamine and ammonia balance. The data on amino acid incorporation into proteins indicate that hind leg protein turnover is rapidly and widely modulated from a low initial setting upon cold exposure to a higher protein synthesis rate immediately afterwards, suggesting that protein turnover may have an important role in short-term events in cold-exposed muscle, in addition to its influence in long-term adaptation.

Amino Acids↗

PubMed1993

A method for sampling representative muscular venous blood during exercise in rats.

A technique for chronic cannulation of the muscular branch of the femoral vein in the rat is described. The method was validated by the application of vascular corrosion casts and comparative analysis of lactate concentration with mixed venous blood and arterial samples taken through the cannulas during lower hindlimb muscle contraction in anaesthetized rats.

Animals↗

PubMedDate not supplied

Effect of cold-exposure on rat organ blood flows.

Rat tissue blood flows and heart output were determined in adult Wistar rats under up to two hours of cold (4 degrees C) exposure, using radioactive 46Sc microspheres. Circulating glucose, lactate and triacylglycerol levels were also determined. Glucose concentrations increased with cold exposure in spite of the drainage of substrates induced by the activation of thermogenesis. Plasma triacylglycerol levels agree with a high involvement of fats in the sustenance of heat production. Cold-exposure had an immediate effect decreasing skin circulation, but increased that of muscle and brown adipose tissue. Kidney and intestine blood flows were maintained. In liver, blood flow increased progressively with cold-exposure. White adipose tissue showed--at first--low blood flow, but increased in parallel to that of liver. The data presented show a distribution of the blood in the body of the cold-exposed rat in which thermogenic responsibilities and supply of blood are evenly distributed throughout. The importance of haemodynamic changes in brown adipose tissue was considerable but the increased share of muscle blood flow suggests that it may have a global role in maintaining thermal homeostasis.

Adipose Tissue↗