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Biomedical subjects

A Pons

Publications and source records attributed to A Pons.

At least 55 records · Page 3Linked to original sources
PubMed1992

Quality control of radiotherapeutic treatment of medulloblastoma in a multicentric study: the contribution of radiotherapy technique to tumour relapse. The French Medulloblastoma Group.

Between 06.86 and 11.89, 88 medulloblastoma or primitive neuroectodermic tumour (PNET) localised in the posterior fossa have been included in the M7 multicentric protocol, 82 received the totality of the radiotherapy treatment and were evaluable for this study. Twenty-two of these 82 patients relapsed: their radiotherapy treatment is analysed in the present study. In 10 cases out of the 22 relapses treatment failure was probably due to a radiotherapeutic imperfection. This study confirms the necessity of a strict radiotherapy control, particularly in multicentric study.

Adolescent↗
PubMed1992

Effect of diet-induced obesity on kinetic parameters of amino acid uptake by rat erythrocytes.

The effects of cafeteria diet-induced obesity upon in vitro uptake of L-Alanine, Glycine, L-Lysine, L-Glutamine, L-Glutamic acid, L-Phenylalanine and L-Leucine by isolated rat erythrocytes have been studied. The total Phe and Leu uptakes followed Michaelis-Menten kinetics. The Glu uptake was fitted to diffusion kinetics. The uptakes of Ala, Gly, Lys and Gln were best explained by a two-component transport: one saturable and one diffusion. Obesity increased the Km value for Ala, Gln and Leu, and the Vmax value for Ala, but decreased the Vmax for Lys. Kinetic parameters of Phe uptake were unaffected by obesity. In addition, the pseudo-first order rate constant (Vmax/Km) for Ala, Gly, Gln, Lys and Leu uptake decreased as a result of cafeteria diet-induced obesity. The Kd value for Ala, Gly, Gln and Glu decreased and that of Lys increased as result of obesity. These adaptations could, at least in part, explain alterations in amino acid distribution between blood cells and plasma related to overfeeding or obesity.

Amino Acids↗
PubMed1991

A significant pool of amino acids is adsorbed on blood cell membranes.

It is well known that the amino acids in the blood are distributed between the plasma and inside the cells. This study was conducted to determine whether amino acids can be located adsorbed on blood cell membranes. The amino acid concentration in the deproteinized haemolysed blood was higher than that in the fraction of blood after removal of the blood cell membranes by centrifugation. These results showed that a pool of amino acids representing 21.1% of the whole blood cell amino acids was adsorbed on the blood cell membranes of adult Wistar rats. The non-polar amino acids showed high adsorption on the membrane, whereas out of the polar amino acid group, only the non-ionic amino acids did adsorb.

Adsorption↗
PubMed1991

Sustained changes in blood alpha amino nitrogen compartmentation during recovery from cafeteria feeding in rats.

We have previously reported that blood urea and blood cell amino acids levels are reduced in rats obese by feeding a palatable cafeteria diet. In order to distinguish whether these changes result from the altered diet, or from the obesity per se, we have studied cafeteria fed rats after returning to standard diet. As in previous studies, obesity induced by cafeteria feeding (for 90 days) was maintained when the cafeteria diet was removed and rats were fed standard diet only. After removal of the cafeteria diet, blood urea levels of 24 h starved obese rats were lower (23%) than those of starved control rats. Blood cell amino acid levels of obese were lower than control ones from day 50 onwards, during and after cafeteria feeding (21% lower on day 100 of life), and thus coincided with divergence of body weights; these differences were maintained despite removal of cafeteria diet. The effects of starvation on plasma amino acid levels were more marked in obese than control rats, during and after cafeteria feeding. Thus the effects on blood amino acids and urea levels in cafeteria diet induced obese rats are related to the obese status rather than to the diet composition.

Amino Acids↗
PubMed1991

Dietary obesity shows adaptations of amino-acid metabolism on enzyme activities to save amino nitrogen.

An increased aspartate transaminase in the liver of dietary (post-cafeteria) obese rats was found. It was consistent with the functionality of the malate-aspartate shuttle, that could be responsible for enhancement of metabolic efficiency. The muscle and intestine of obese rats showed a greater capacity for alanine and glutamine synthesis than the controls. Furthermore, enterocyte adaptations in the obese rats indicated higher capabilities for the intake of nitrogen than in the controls. In conclusion, the pattern of amino-acid enzyme activities reflected adaptations to keep from amino nitrogen depletion in dietary obesity which were compatible with an enhancement of the metabolic efficiency.

AMP Deaminase↗
PubMed1991

Short term starvation-induced changes in the kinetic parameters of rat red cell L-alanine and glycine uptake.

Na(+)-dependent L-Alanine and Glycine uptake by rat red blood cells were best fit to a common model of two transport components, saturable transport and diffusion. 24 hours of food deprivation provoked statistically significant increases of the Km and Vmax red cells L-Alanine uptake, whereas the diffusion constant did not change in response to starvation. The Glycine uptake kinetics poorly follows the L-Alanine pattern and no significant response to starvation can be outlined. The physiological meaning of these adaptations has to be related to short term food deprivation regulation, independent of protein synthesis in the erythrocytes. Such mechanisms could be important to account for the previously described changes in the distribution patterns of amino acids between the blood plasma and blood cell compartments in response to short term starvation.

Alanine↗
PubMed1991

Dietary-induced permanent changes in brown and white adipose tissue composition in rats.

We have previously observed that feeding rats a cafeteria diet causes excess weight gain and changes in tissue composition. The object of this study was to assess whether these alterations were sustained after withdrawal of the palatable diet in the rat. The results showed that the obesity was not reversed by feeding a standard diet ad libitum for five months after withdrawal of the cafeteria diet. Body weight was 26 per cent greater than in control rats and tissue composition showed permanent alterations. The excess weight of lumbar white adipose tissue was due mainly to lipid content (86 per cent) and this was also true, but to a less extent, for interscapular brown fat (59 per cent). Increased brown fat mass was a result of hyperplasia and hypertrophy, whereas increased lumbar white fat was mainly a result of hyperplasia alone. In conclusion, changes in tissue composition, particularly in fat depots, were permanent and could be ascribed to the obesity per se, and not to the diet composition.

Adipose Tissue↗
PubMed1990

In vivo alanine metabolism in late pregnant rats.

Alanine metabolism in 24 hour starved 20-day pregnant rats, following intravenously administered C14-alanine, in trace dose that does not affect the normal availability of this amino acid, has been studied. The steady state levels of alanine and glucose in blood, liver and skeletal muscle, together with the tissue glycogen, metabolites and amino acid composition pools, are given in both the maternal and foetal compartments compared with the virgin control rats. The utilization of alanine as a gluconeogenetic precursor is not increased in late pregnancy under 24-hour starvation and it depends on the lower blood substrate availability.

Administration, Oral↗
PubMed1990

In vivo C14-L-alanine metabolism in rat dietary obesity induced by cafeteria diet.

The "in vivo" handling of L-alanine in 24 hours starved rats, in which obesity was induced by feeding with cafeteria diet, was compared with that of starved control rats. 14C-alanine was administered in trace amounts in order not to affect the normal handling of this amino acid. The results obtained in blood and liver support a lowered glucose formation from alanine. The specific radioactivities corresponding to lactate, glutamate + glutamine and asparagine as well as total protein and total lipid, were all lowered in the obese group. This strongly suggests that glucose formation from alanine in the liver was impaired. The specific radioactivity of the metabolites studied in the striated muscle are compatible with the above suggestion. It can be concluded that the glucose alanine cycle operation is inhibited in the cafeteria diet starved obese rats.

Alanine↗
PubMed1989

Curability of third ventricular region tumours. A multidisciplinary approach to evaluate the places of operative, radiation and chemotherapy.

Between 1976 and 1988, 17 patients suffering from tumours located in the third ventricular region were entered into a retrospective study. There were 11 males and 6 females aged from 2 to 30. These tumours were located in the pineal area (n = 12), in the floor of the third ventricle (n = 3), in the roof of the third ventricle (n = 1) and multiple midline tumours (n = 1). A ventriculoperitoneal shunt was performed in 13 patients. In 8 patients the tumour was operated upon directly. 2 patients did not undergo surgery. A histological examination was performed in 13 cases with identification of 9 germinomas, 2 pinealoblastomas and one astrocytoma. In one case the plasma and cerebro-spinal-fluid level of tumour markers (human béta chorionic gonadotrophin & alpha feto protein) were elevated. All patients received 45 to 60 grays by cobalt megavoltage irradiation on the tumoural volume, 8 of them receiving additional whole brain and spinal irradiation ranging from 30 to 36 grays. One patient had chemotherapy in addition to radiotherapy. The 5 years survival rate was 74% and the mean follow-up period was 5 years. Five deaths occurred: 1 during irradiation, 3 following a relapse and 1 unexplained death later on. There were no neurological sequelae related to irradiation but 7 patients (37%) had pituitary insufficiency. The irradiation dose level required to obtain local control, the methods of spinal prophylactic treatment and the role of chemotherapy are discussed.

Adolescent↗
PubMed1989

Investigation of GAGS on 24-hour and 2-hour urines from calcium oxalate stone formers and healthy subjects.

The role of urinary glycosaminoglycans (GAGS) in calcium oxalate lithiasis is of great interest in urologic research. It has been claimed that GAGS are important inhibitors of calcium oxalate crystal growth and aggregation. The aim of this paper is to evaluate GAGS excretion and concentration in two groups of patients, calcium stone formers (with or without metabolic alteration) and a control group, to detect possible differences. The findings of this study show that significant differences exist not only in the 24-hour average excretion between stone formers without alteration and healthy subjects but also in the mean concentration values between the stone former and control groups. The same results are obtained from the 2-hour urine analysis. It is concluded that 2-h urine analyses of GAGS have the same or more practical value than a 24-h urine analysis and that the results must be expressed in terms of concentration.

Calcium Oxalate↗
PubMed1989

Stage IE nonHodgkin's lymphoma of the testis: a need for a brief aggressive chemotherapy.

Primary nonHodgkin's lymphoma of the testis is a localized disease in 50 per cent of the cases. Clinical records and pathological material from 9 stage IE cancer patients treated at our institutions were reviewed. All but 1 patient had B cell type lymphomas of intermediate (6) or high (3) grade according to the Working Formulation. Mean survival was 49 months and actuarial survival was 74 per cent at 5 years. Chemotherapy differed with time and frequently was associated with subdiaphragmatic involved field and prophylactic contralateral testis radiotherapy. In view of the good prognosis of patients receiving doxorubicin-based chemotherapy and recent reports on low stage nonHodgkin's lymphoma we recommend an aggressive brief therapy for stage IE lymphoma of the testis after orchiectomy.

Actuarial Analysis↗
PubMed1987

Tissue glycogen and lactate levels in starved and in protein-fed domestic fowl chicks (Gallus domesticus).

The levels of glycogen, protein and lactate in the tissues of 3- and 5-day-old domestic fowl chicks either starved or fed a protein diet (hard-boiled egg white) have been studied. The patterns of change in the parameters studied were much similar in both experimental groups compared to fed controls. Tissue and circulating levels of lactate were very low in protein-fed chicks, they are lowest in the starved ones. Plasma glucose levels were diminished in starved and protein-fed groups vs. controls, as were their tissue glycogen levels, the latter being lowest in starved chicks. The availability of dietary amino acids could not prevent the effects of the lack of dietary carbohydrate observed in starved chicks, as the weight of liver, circulating glucose and lactate levels were significantly lowered in these animals compared with controls.

Animals↗
PubMed1986

Amino acid compartmentation in chick blood during the peri-hatching period.

Individual amino acid levels and compartmentation in chick blood were measured on day 20 of incubation, at hatching (day 0), or after 1 or 5 days of free life, and compared with those of adult chickens. Blood cell amino acid concentrations were almost one order of magnitude higher than those of plasma, with higher values than those found in mammalian erythrocytes. This difference may be due to the capability for protein synthesis of the nucleated cells coupled with a postulated utilization of amino acids as fuel. The most common pattern of individual plasma amino acid levels was a slight rise at hatching followed by a large decrease, with minimal values for adults. The patterns in the cells did not always coincide with those for plasma. Total blood amino acid levels increased steadily during the period studied due to the increase in intracellular amino acids, giving rise to increasing blood-cell/plasma concentration ratios. These changes showed higher availability of plasma amino acids just after hatching, while the cell concentrations increased steadily to the maximum values in adults. The increase in alanine levels in cells with little changes in plasma can be correlated with the role of this amino acid as the main 2-amino nitrogen carrier in the avian bloodstream. The high amino acid levels in the cells suggest that these cells act as inter-organ transporters and reservoirs of amino acids, they have a different role in their handling and metabolism from those of mammals.

Age Factors↗