Biomedical subjects

A Pons

Publications and source records attributed to A Pons.

At least 37 records · Page 2Linked to original sources

PubMed1999

Regulation of erythrocyte antioxidant enzyme activities in athletes during competition and short-term recovery.

We have determined "in vivo" the influence of strenuous prolonged exercise and short-term recovery on erythrocyte antioxidant enzyme activities. We have also determined the "in vitro" effects of the xanthine/xanthine-oxidase-generating superoxide anion system on catalase activity in haemolysed erythrocytes. Haematological parameters and erythrocyte superoxide dismutase (SOD), glutathione peroxidases and catalase activities were measured in nine healthy duathlon athletes under basal conditions, at the finish of a competition and after 1 h of recovery. We also measured catalase activity in haemolysed erythrocytes--obtained from four overnight-fasted well-trained sportsmen before and after an 80% submaximal exercise test on a cycle-ergometer--prior to and after incubation for 3 min with the superoxide-anion-generating system. Duathlon competition and/or short-term recovery produced a slight haemolysis and increased the activity of catalase and peroxidases but not SOD enzymes. The observed changes in catalase activity were mimicked "in vitro" by the superoxide-anion-generating system.

Adult↗

PubMed1999

Effects of fasting on lipoprotein lipase activity in different depots of white and brown adipose tissues in diet-induced overweight rats.

The aim of the present study was to evaluate the effects of 24 hours of starvation on lipoprotein lipase (LPL) activity in various depots of white and brown adipose tissues in control rats and in rats with two different degrees of overweight, both induced by dietary treatment. In control rats, no changes in LPL immunoreactive mass were observed in either white or brown adipose tissues after fasting, whereas the effects of food deprivation on enzyme activity were opposite in white versus brown adipose tissues. The LPL activity response to fasting was impaired by obesity: White adipose depots of cafeteria obese rats showed a lower ability to downregulate LPL during fasting and the increased LPL activity induced by fasting in brown adipose depots was less intense in the obese rats compared with control animals. When the degree of overweight was reduced, the differences between obese and control rats were also attenuated.

Journal Article↗

PubMed1998

Analysis of 1.9 Mb of contiguous sequence from chromosome 4 of Arabidopsis thaliana.

The plant Arabidopsis thaliana (Arabidopsis) has become an important model species for the study of many aspects of plant biology. The relatively small size of the nuclear genome and the availability of extensive physical maps of the five chromosomes provide a feasible basis for initiating sequencing of the five chromosomes. The YAC (yeast artificial chromosome)-based physical map of chromosome 4 was used to construct a sequence-ready map of cosmid and BAC (bacterial artificial chromosome) clones covering a 1.9-megabase (Mb) contiguous region, and the sequence of this region is reported here. Analysis of the sequence revealed an average gene density of one gene every 4.8 kilobases (kb), and 54% of the predicted genes had significant similarity to known genes. Other interesting features were found, such as the sequence of a disease-resistance gene locus, the distribution of retroelements, the frequent occurrence of clustered gene families, and the sequence of several classes of genes not previously encountered in plants.

Arabidopsis↗

PubMed1998

Hepatic glycogen and lactate handling in dietary obese rats.

Hepatic balances for glucose and its precursor, lactate, were calculated by measuring hepatic blood flows and the arteriovenous differences of these metabolites in 2 groups of overweight rats: cafeteria diet-fed rats and post-cafeteria rats. Obese rats show abnormal hepatic glycogen handling, since they do not mobilize all hepatic glycogen stores after 24-hour starvation, in a situation in which a lower rate of hepatic glucose output and a higher capacity for lactate uptake are attained. The important decrease (about 50%) in the hepatic blood flows observed in post-cafeteria rats versus control rats was similar to that caused by 24-hour starvation in control animals, suggesting that after withdrawal of the cafeteria diet, the liver blood flow of the post-cafeteria rats was adapted to the low-food intake in order to make better use of the energy consumed. The results also suggest an increased efficiency of hepatic lactate uptake in post-cafeteria rats.

Animals↗

PubMed1997

Fatty acid composition of brown adipose tissue in dietary obese rats.

The effects of both dietary obesity and a food deprivation period of 24 hours on fatty acid composition of brown adipose tissue have been investigated. Long time exposure to a hypercaloric high-fat diet such as the cafeteria diet induced an important tissue fatty acid accumulation, mainly for the major saturated and monounsaturated fatty acids. Notable metabolic differences have been observed in the behaviour of control and obese rats facing a food deprivation period: a preferential utilization of the most abundant saturated fatty acids in control rats and a minor response in obese rats, with a greater fat accumulation in the interscapular brown adipose tissue.

Adipose Tissue, Brown↗

PubMed1997

Acne keloidalis nuchae and tufted hair folliculitis.

Acne keloidalis nuchae is a chronic, scarring folliculitis that affects mostly black patients and is located on the back of the neck of young adults. The course is progressive and leads to hypertrophic scarring, chronic abscesses and hair loss. We discuss the relationship between acne keloidalis and tufted hair folliculitis, pointing out the possibility that tufted hair folliculitis is not a specific disease but secondary to other progressive folliculitis like folliculitis decalvans, dissecting cellulitis or acne keloidalis.

Abscess↗

PubMed1996

Changes in fatty acid composition in rat adipose tissue induced by dietary obesity.

The aim of the study was to evaluate the effects of cafeteria feeding on the composition of fatty acids in retroperitoneal fat pad and also to determine what happens to fatty acids when rats previously fed the cafeteria diet are returned to regular rat chow. The study of the post-cafeteria rats enabled us to determine the effects of dietary induced excess weight in the absence of artefactual interferences from the diet because these rats, unlike the cafeteria obese rats, ate the same diet as controls. In response to cafeteria feeding there were increases in the majority of adipose tissue fatty acids. However, significant decreases were observed in the relative proportions of 18:2n-6 and in two related n-6 polyunsaturated fatty acids (18:3n-6 and 20:3n-6), as well as in 16:1. In the post-cafeteria obesity model the previous dietary influence on fatty acid composition was still evident. The maintenance of both the high levels and proportions of 18:1 and the decrease of 16:1 percentage in the post-cafeteria rats argues in favour of an alteration in the activity of the elongation metabolic pathway. Certain changes affecting polyunsaturated fatty acid adipose depot composition of obese rats, mainly the decreased levels of 18:2n-6, are long lasting and could be related to the maintenance of the obese status. On the whole, although the fatty acid composition of adipose tissue is influenced by the composition of the diet, there are some differences in both the maintenance of the effects and also in the selectivity of adipose tissue for the different fatty acids of obese and lean rats.

Adipose Tissue↗

PubMed1995

Decrease of the pool of amino acids adsorbed on blood cell membranes caused by starvation in rats.

The effect of 24 h starvation on the pool of amino acids adsorbed on the blood cell membranes was determined in Wistar rats. Aortic and iliac blood was analysed. 24 h starvation induced a significant decrease in the combined essential amino acids adsorbed on the blood cell membranes, in both arterial and venous blood, without affecting whole-blood levels (adsorbed + non-adsorbed). The same tendency was extended to most of the individual amino acids. This finding indicates that this pool of adsorbed amino acids has a rapid turnover and probably plays a physiological role in a situation of exogenous food deprivation.

Adsorption↗

PubMed1995

Protein and amino acid intake in cafeteria fed obese rats.

Food selection pattern and portal blood amino acid profile were examined in rats given a cafeteria diet. Compared to standard-diet fed rats, cafeteria-diet fed rats consumed more energy. Increase in energy intake was attributable to an increase in fat intake. Protein intake was slightly higher and carbohydrate intake remained constant and was similar to levels consumed by standard-diet fed rats. The cafeteria rats took up higher quantities of Phenylalanine+Tyrosine, Arginine, Histidine, Lysine, Leucine, Isoleucine, Valine, Threonine, and Glycine, lower quantities of Tryptophan and the same quantity of Methionine+Cysteine vs. control rats. Portal concentrations of Serine, Threonine, Tryptophan and Lysine were significantly higher in cafeteria-diet fed rats than in standard-diet fed rats. This can be interpreted in such a way that, on the whole, the quality of protein ingested by cafeteria and control rats is similar. No statistical differences in the ingestion of individual amino acids were observed between different days of the period of cafeteria diet feeding, thus the idea of a strict control of protein ingestion irrespective of the obese status is reinforced.

Amino Acids↗

PubMed1995

In vitro adsorption of amino acids onto isolated rat erythrocyte membranes.

Amino acids adsorbed onto blood cell membranes represent about 8% of the total amino acids in blood. The aim of this study was to determine the in vitro adsorption kinetics of different amino acids (L-alanine, glycine, L-glutamate, L-glutamine, L-phenylalanine and L-leucine) onto rat erythrocyte membranes and to assess the effect of 24-hr starvation on these adsorption kinetics. Isolated red cell membranes were incubated at 37 degrees C for 10 sec in the presence of 14C-amino acids--with different specific radioactivity--the radioactivity retained in the membrane fraction measured and kinetic parameters of amino acid adsorption determined. With the exception of glutamate, where the adsorption was negligible, all amino acids studied were adsorbed onto isolated red cell membranes, adhering to simple Michaelis-Menten kinetics. Km' values of glycine, phenylalanine and leucine adsorption in control rats (14.7 +/- 3.8 mM, 8.41 +/- 0.95 mM and 4.65 +/- 0.46 mM respectively, SEM, n = 6-8) decreased in response to 24-hr starvation, giving the following values: 0.792 +/- 0.122 mM, 5.32 +/- 0.82 mM and 3.53 +/- 0.31 mM respectively (SEM, n = 6-8), Vmax' value of glycine adsorption of control rats decreased (from 61.0 +/- 15.5 mmol/mol P/sec to 4.25 +/- 0.70 mmol/mol P/sec, SEM, n = 7) and that of leucine increased (from 13.5 +/- 1.0 mmol/mol P/sec to 18.9 +/- 2.0 mmol/mol P/sec, SEM, n = 7) as an effect of 24-hr starvation. This study shows that alanine, glycine, glutamine, phenylalanine and leucine, but not glutamate, adsorbed onto erythrocyte membranes according to Michaelis-Menten-like kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗

PubMed1994

Blood cell to plasma gradients of amino acids in arterial and venous blood in fed and fasted rats.

Measurement of amino acid concentrations in blood cells and plasma, and the calculated blood cell to plasma gradients (C/P) from both afferent and efferent vessels to tissues, allowed evaluation of the effect of several tissues (splanchnic bed, skeletal muscle and kidney) on blood amino acid distribution in fed and starved rats. Combined effects of tissues and erythrocyte transport capabilities determined specific C/P values for each amino acid. For amino acids related to the L-system, the high capacity of this erythrocyte transport many buffer some C/P changes as an effect of tissue metabolism. For less permeable amino acids (like Asp and Glu) plasma changes were mainly responsible for changes in C/P values, whereas for other amino acids (such as basic amino acids) blood cells became the main determinants of C/P changes, mainly in starvation. In general, the role of erythrocytes in amino acid transport was enhanced in starvation.

Amino Acids↗

PubMed1994

Brown and white adipose tissue adaptive enzymatic changes on amino acid metabolism in persistent dietary-obese rats.

The objective was to determine the effects of persistent obesity on amino acid enzymes in white (WAT) and brown (BAT) adipose tissues. Dietary obesity was induced by feeding a cafeteria diet ad libitum for 3 months, then it was removed and the obese animals received the same diet as controls for 5 months. Dietary-induced obesity was persistent as obese rats showed a stable, higher body weight than controls (26%). Key enzymes of alpha-amino nitrogen metabolism were studied and results showed reduced activities in obese rats: glutamine synthetase (45%), AMP deaminase (52%), alanine aminotransferase (66%) and glutamate dehydrogenase (68%) in BAT, whereas WAT of obese animals only showed lower aspartate aminotransferase activity (47%) with respect to the controls. We can conclude that these adaptations in amino acid metabolism were exclusively dependent on the obese status as they were observed in an obesity model in which obese rats eat the same diet as controls.

AMP Deaminase↗

PubMed1994

Blood amino acid compartmentation in obese rats is specifically altered in the iliac vein.

Amino acid concentration in blood cells and plasma and the calculated blood cell to plasma gradients (C/P) were measured in different blood vessels (aortic artery and portal, hepatic, iliac and renal veins) from both control and cafeteria diet obese rats. Essential amino acids are increased in plasma in all blood vessels in obese rats. The iliac vein was the only vessel in which cell concentration of amino acids, and mainly the mean of the combined non-essential amino acids, was affected by obesity. Only in the iliac vein were C/P values of the combined amino acids, including both essential and non-essential, significantly lower in obese versus control rats. These results also show that there are differences between sampling sites which should be noted in the design of physiological studies of amino acid metabolism.

Amino Acids↗

PubMed1993

Combined enzymic and chromatographic techniques to determine specific radioactivity in free and triglyceride fatty acid plasma fractions.

A reliable method to determine both free and triglyceride fatty acids and simultaneously to determine the specific radioactivity in each fraction has been developed. The procedure can be used to analyse a large number of samples. Lipoprotein lipase was used to hydrolyse triglyceride fatty acids, and a Carbopack B column was used to isolate free fatty acids. The radiolabeled fatty acids were determined by liquid scintillation counting, and individual fatty acid levels in each fraction were determined by gas chromatography. Free and triglyceride fatty acids were eluted in different fractions from the Carbopack B column. No interferences from other compounds were significant.

Amino Acids↗

PubMed1993

Strychnopentamine, a potential anticancer agent.

We analysed the effects of strychnopentamine, an alkaloid isolated from Strychnos usambarensis, on an Ehrlich ascites tumor growing in the mouse after inoculation. Four subcutaneous injections of 1.5 mg strychnopentamine (1 per day) induce a significant decrease of the number of tumor cells and a significant increase of the survival of the treated mice. Observed side effects are partial haemolysis and some liver damage.

Alkaloids↗

PubMed1993

Effect of color on contrast sensitivity with two different accommodative stimuli.

We studied the influence of color and accommodation on the contrast sensitivity function (CSF). At the same time, we measured the effect of axial chromatic aberration (ACA) on the CSF. The CSF's of two observers were determined using red, green, blue, and white light, at 5- and 0.5-m viewing distances. At 5 m the CSF's were measured with natural vision and also with lenses which compensated the ACA. Results show that the effect of ACA on the CSF is to reduce the sensitivity to blue with respect to the red. The difference in sensitivity between these two colors is between 50 and 150% and varies with the frequency and the subject. When the ACA is compensated the influence of the color on the CSF is very small, in our experiment, and this result is discussed in relation to the compensating effects of chromatic adaptation of the color mechanisms. In near vision, the CSF's were measured with natural vision and also with the lenses required to give the same accommodative stimulus for all colors. We discuss the effect of accommodation on the CSF. For both far and near the results are compared with the CSF with white light.

Accommodation, Ocular↗

PubMed1992

Metabolic utilization of muscular L-proline in 24-hr starved rats.

1. The aim of this paper was to study the in vivo skeletal muscle L-proline related to its destination to other key tissues such as liver and intestine as well as to give some insight into the role of blood cells in proline handling. 2. L-U-[14C]Proline was injected intramuscularly and following by sampling of blood, liver, intestine and contralateral muscle at 20 and 30 min after injection. 3. The distribution of radioactivity between blood cells and plasma and in total and individual amino acids, protein and glycogen fractions was determined in the above tissues. 4. The pattern of well fed rats was compared with those submitted to 24-hr complete starvation. 5. During starvation a minor degree of proline oxidation occurs. 6. The main destruction of proline in the liver seem to be the synthesis of proteins. 7. The radioactivity recovered in the blood proline fraction of starved rats is twice that of the fed rats and that it could be attributed mainly to plasma protein. 8. We have obtained in vivo evidence for the role of erythrocyte in the interorgan proline transport.

Animals↗

PubMed1992

Regulation of rat erythrocyte L-glutamine, L-glutamate and L-lysine uptake by short term starvation.

1. The kinetic parameters (Km, Vmax and Kd) of L-glutamine, L-glutamate and L-lysine uptake by isolated red blood cells in fed and 24 hr starved rats have been determined. 2. L-Lysine and L-glutamine uptake was best fitted by a two transport component: a saturable component and a diffusion one. 3. Starvation brought about important decreases in the Km and Vmax for both L-lysine and L-glutamine uptake. 4. The Kd for L-glutamine showed a significant increase whereas that corresponding to L-lysine did not change by starvation. 5. L-Glutamate uptake adjusted to diffusion kinetics, with a Kd which did not change due to starvation. 6. It is concluded that the amino acid uptake showed specific regulation by starvation. 7. The mechanism involved is not dependent on protein synthesis--given the unnucleated nature of mammal red cells. 8. The magnitude of the changes observed in the uptake kinetic parameters may account for the extent of the blood amino acid pool changes as those produced in vivo over physiological limits.

Animals↗