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Biomedical subjects

M Benito

Publications and source records attributed to M Benito.

At least 127 records · Page 7Linked to original sources
PubMed1990

The effects of different schedules of total-body irradiation in heterotopic vascularized bone transplantation. An experimental study in the Lewis rat.

To evaluate the effects of irradiation on heterotopically placed vascularized knee isografts, a single dose of 10 Gy of total-body irradiation was given to Lewis donor rats. Irradiation was delivered either 2 or 6 days prior to harvesting or subsequent transplantation, and evaluated at 1, 2, and 4 weeks after grafting. Irradiation caused endothelial depopulation of the graft artery, although vascular pedicle patency was maintained throughout the study. Bone graft viability and mineralization were normal. Dramatic changes in the bone marrow were seen that included an increase of its fat content (P less than 0.001), and a concomitant decrease in bone marrow-derived immunocompetent cells. These changes were more prominent in recipients of grafts from day -6 irradiated donor rats. Total-body irradiation did not prejudice the use of vascularized bone grafts, and exhibited an associated immunosuppresant effect over the vascular endothelium and bone marrow. This may be a further rational conditioning procedure to avoid recipient manipulation in vascularized bone allotransplantation.

Animals↗
PubMed1989

Hormonal regulation of malic enzyme expression in primary cultures of foetal brown adipocytes.

Insulin increased malic enzyme activity and protein content in foetal brown adipocyte primary cultures through a two fold increase in the rates of enzyme synthesis. Conversely, noradrenaline prevented the induction caused by insulin on enzyme expression through an accelerate rate of malic enzyme degradation. Tri-iodothyronine had no effect on the expression of malic enzyme in cultured foetal brown adipocytes.

Adipose Tissue, Brown↗
PubMed1989

Adrenergic regulation of the uncoupling protein expression in foetal rat brown adipocytes in primary culture.

The adrenergic and T3 modulation of UCP expression in non-proliferative foetal brown adipocyte primary cultures were studied. The UCP in the cultured cells was determined by immunological detection of the protein and by quantification of the mitochondrial GDP-binding. Our results showed a relative increase of 65-75% in UCP levels and 60-80% in the mitochondrial GDP-binding capacity under beta-adrenergic stimulatory conditions, while neither alpha 1-adrenergic agonists nor T3 showed an effect.

Adipose Tissue, Brown↗
PubMed1989

Rates of lipogenesis in fetal hepatocytes in suspension and in primary culture: hormonal effects.

Lipogenesis in isolated fetal hepatocytes in suspension for 3 h was modulated by insulin depending on substrates utilization, but was inhibited by glucagon and noradrenaline from all substrates studied. After primary culture for 5 days in the presence of glucose, the lipogenic response to insulin increased, the glucagon response decreased and noradrenaline produced the same degree of inhibition at 3 h. At 24 h, insulin produced an even higher increase on lipogenesis parallel to an increase in fatty acid synthase activity. Dexamethasone increased lipogenesis, but progesterone had no effect. Both hormones, in the presence of insulin, increased lipogenesis and fatty acid synthase activity. Triiodothyronine, alone or in the presence of insulin, increased lipogenesis and fatty acid synthase activity.

Animals↗
PubMed1989

Precocious induction of malic enzyme by nutritional and hormonal factors in rat foetal hepatocyte primary cultures.

Rat foetal hepatocytes in primary cultures were used as a model for the study of malic enzyme gene expression. Carbohydrates and glycolytic metabolites produced the precocious induction of the malic enzyme in foetal hepatocytes cultured in the absence of serum and hormones. Palmitate prevented this induction. Insulin and triiodothyronine produced a significant increase in the malic enzyme specific activity in all the conditions studied. A synergistic effect between the two hormones is observed only when high concentrations of glucose are present. Glucagon prevents partially the induction produced by insulin plus triiodothyronine. Both carbohydrate and hormonal inductions of malic enzyme activity are related to parallel increases in its expression, and are prevented by protein synthesis inhibitors.

Animals↗
PubMed1989

Lack of portal-venous hypertension after an arterioportal fistula in the rat.

The hepatic effects of an end-to-side arteriovenous fistula between the right renal artery and the portal vein were studied in rats. Fifty rats underwent surgery and were studied 3, 12, 24 weeks and 1 year later; Another 15 rats were used as controls. Rats did not have any portohepatic abnormality. Portal and caval pressure were measured, and the liver was evaluated histologically. No statistically significant differences were achieved between the control portal (10.37 +/- 0.29 cm H2O) and vena cava pressures (1.22 +/- 0.19 cm H2O) and those of the experimental groups. The overall liver architecture remained unchanged. A progressive enlargement of the intrahepatic portal and hepatic veins was noted. No hypertrophy of the fibrous tissue into the portal triads, hypertrophy of the muscularis of the portal vein radicals, or wall sclerotic thickening was seen. The forward overflow compensatory mechanisms are discussed.

Animals↗
PubMed1989

[Prevalence of serum markers of hepatitis B virus, in health personnel at a general hospital].

We have determined hepatitis B virus markers to 107 nursing personnel (90 women and 17 men) of a general hospital. The prevalence was 15.88% (17 persons). Two persons (1.86%) presented HBs-Ag. The prevalence was more low what the prevalences found by other authors of our country. The difference between the two sexes not was significative. The highest prevalences were found in the personnel of outpatient clinics and in the personnel in contact with blood and its derivates. The prevalence more low was found en the nursing personal rooms. The collective of midwives presented the prevalence more height: 37.5%. The prevalence increased generally with age and years in occupation. We associated the low indexes of prevalence found for us with the high percentages of young personnel (39.25%) are more low of 30 years age) and with short years occupation in the hospital (19.62% are more low of 4 years).

Adult↗
PubMed1988

Hormonal regulation of rat foetal lipogenesis in brown-adipocyte primary cultures.

Insulin stimulates lipogenesis by 100% for 5 h by a covalent modulation of acetyl-CoA carboxylase, and by 200% for 24 h by increasing malic enzyme and fatty acid synthase enzymic activities in brown-adipocyte primary cultures. At short times, noradrenaline and isoprenaline decrease lipogenesis. However, phenylephrine and glucagon have no effect. At long times, dexamethasone inhibits lipogenesis. This effect is precluded in the presence of insulin. Progesterone and tri-iodothyronine, alone or in the presence of insulin, produce a stimulation of the rates of lipogenesis.

Adipose Tissue, Brown↗
PubMed1988

Vascular medullary patency in free vascularized bone grafts: CT scan experimental study.

In an experimental study using 13 mongrel adult dogs, 6 cm of the anterior part of the left ninth rib were harvested, including the posterior intercostal vessels. The grafts were transferred, based on the periosteal circulation alone, to a previously induced femoral head ischemic necrosis. Microsurgical anastomoses were performed between the posterior intercostal vascular bundle and the caudal gluteal vessels at the recipient thigh zone. Using a high resolution CT scan and morphologic evaluation, it was demonstrated that the medullary circulation network filled on contrast medium. The entire cortex and medullary cavity were supplied from endosteal vessels coming from a reversed periosteal blood flow.

Anastomosis, Surgical↗
PubMed1987

Regulation of rat foetal lipogenesis in brown adipose tissue in vivo and in isolated brown adipocytes during the last day of, and after prolonged, gestation.

Rates of lipogenesis in foetal isolated brown adipocytes from 22-day-pregnant rats were significantly increased by lactate plus pyruvate as major substrates in the incubation medium, in comparison with the endogenous rates. Insulin stimulated foetal brown-adipocyte lipogenesis, and adrenaline or noradrenaline and isoprenaline decreased lipogenesis. Glucagon had no effect on the lipogenic rate in brown adipocytes. Progesterone administration to the mother significantly increased the rates of lipogenesis in brown adipose tissue and in isolated brown adipocytes from 22-day foetuses. Prolongation of gestation by progesterone to day 23 decreased the rates of brown-adipose-tissue lipogenesis in vivo and in isolated cells in the post-mature foetuses.

Adipose Tissue, Brown↗
PubMed1986

Adenine nucleotide compartmentation in foetal rat hepatocytes. Effects of atractyloside, oligomycin, calcium ionophore and adrenergic agonists.

In the presence of lactate plus pyruvate, or glucose or alanine as substrates, ATP/ADP ratios in the cytosol were higher than in mitochondria in isolated rat foetal hepatocytes. The cytosolic ATP/ADP ratios were dependent on substrate (lactate + pyruvate greater than glucose greater than alanine). Oleate increased the cytosolic ATP/ADP ratios in the presence of the other substrates studied. Atractyloside decreased the cytosolic ATP/ADP ratios, oligomycin decreasing these values in both compartments. Isoproterenol, phenylephrine and Ca2+ ionophore decreased the cytosolic ATP/ADP ratio, without altering this value in mitochondria.

Adenine Nucleotides↗
PubMed1986

The role of prolactin and progesterone in the regulation of lipogenesis in maternal and foetal rat liver in vivo and in isolated hepatocytes during the last day of gestation.

The administration of progesterone on day 21 of gestation increases the rates of lipogenesis in the liver in vivo and in hepatocytes isolated from rats on day 22 of pregnancy. Bromocriptine administration increases the rates of hepatic lipogenesis in vivo, but has no effect on lipid synthesis in hepatocytes under the same treatment conditions. Concurrently, the administration of progesterone or bromocriptine on day 21 to the mother increases the rates of lipogenesis in the foetal liver in vivo on day 22. The rates of lipid synthesis in foetal isolated hepatocytes are increased by progesterone administration, but remain unchanged by bromocriptine.

Animals↗
PubMed1986

Occurrence of alpha 2-adrenergic effects on adenylate cyclase activity and (3H)-clonidine specific binding in brown adipose tissue from foetal rats.

Noradrenaline maximally stimulates adenylate cyclase activity in brown adipocytes from foetal rats by 400%. Isoproterenol maximally stimulates the adenylate cyclase activity by 600%. The differences observed in the dose-response curves of adenylate cyclase activity to isoproterenol or noradrenaline were prevented in the presence of clonidine (a alpha 2-agonist) or yohimbine (alpha 2-antagonist) respectively. (3H)-clonidine binds specifically to brown fat membranes saturable (from 1.75 to 20 nM). Scatchard analysis revealed a Bmax of 22 fmol/mg and a KD of 10 nM.

Adenylyl Cyclases↗
PubMed1986

Regulation of carnitine palmitoyltransferase activity in the liver and brown adipose tissue in the newborn rat: effect of starvation and hypothermia.

The overt activity of hepatic carnitine palmitoyltransferase (CPT1) increased during the last day of gestation in the foetus and after prolonged starvation in the newborn kept at 37 degrees C. Its sensitivity to inhibition by malonyl-CoA decreased during the perinatal period studied. Brown fat CPT1 increased under the same experimental conditions. However, its sensitivity to malonyl-CoA remains unchanged. Hypothermia at 24 degrees C decreased in the liver and increased in brown adipose tissue CPT1 activity in response to fasting. Glucose injection at birth decreased CPT1 activity in the liver but did not have any effect in the presence of mannoheptulose. This effect of glucose was non-significant in brown adipose tissue.

Acyltransferases↗
PubMed1985

Contribution of brown fat to the neonatal thermogenesis.

Homeothermic animals must maintain their body temperatures within a very narrow range. Large homeotherms face problems with dissipation of metabolic heat: for small homeothermic animals heat losses at most environmental temperatures are far in excess of normal metabolic heat production. Accordingly, brown adipocytes exhibit in mammalians a very rapid process of morphological functional maturation perinatally. This thermogenesis occurred without electrical activity in the skeletal muscle and it is therefore termed 'nonshivering thermogenesis'. The anatomical site of nonshivering thermogenesis is mainly the brown adipose tissue in the small newborn mammals. In animals reared under thermoneutral conditions the tissue subsequently involutes and nonshivering thermogenic capacity is largely lost. Cold- and diet-induced adaptation may slow or prevent this involution. The decline in the extent of nonshivering thermogenesis during development at thermoneutral temperatures is reflected by an alteration in the bioenergetic properties of the isolated brown fat mitochondria.

Adenosine Triphosphate↗
PubMed1984

Regulation of lipogenesis and of non-saponifiable-lipid synthesis in vivo at birth and after prolonged starvation in the newborn rat.

The rate of lipogenesis in the liver was increased by glucose injection at birth, mediated by the insulin secretion. In addition, glucagon decreased the rates of lipogenesis and non-saponifiable-lipid synthesis after birth. These rates decreased after prolonged starvation in the newborn rat. Tri-iodothyronine injection increased the rates of lipogenesis enhanced in response to glucose administration after prolonged starvation in liver and brown adipose tissue. Dexamethasone, however, increased the rates of lipogenesis enhanced in response to glucose in liver and prevented the increase in the rates of lipogenesis in brown adipose tissue.

Animals↗