PubMed Health⌕ Search

Biomedical subjects

U F Machado

Publications and source records attributed to U F Machado.

23 records · Page 2Linked to original sources
PubMed1992

Obesity is the major cause of alterations in insulin secretion and calcium fluxes by isolated islets from aged rats.

To investigate the alterations in insulin secretion induced by aging, 2-month-old, 12-month-old, and 12-month old lean rats (submitted to a caloric restriction during the last month that causes a weight loss of approximately 20%) were studied. As expected, glucose intolerance and increased insulin response were observed during IV-GTT in 12-month-old rats. These effects were, however, reversed by weight loss. Insulin secretion was investigated in isolated islets both during static incubation and perifusion. In 12-month-old rats insulin secretion and 45Ca2+ efflux were lower only in the second phase of the hormonal secretion, suggesting an involvement of voltage-sensitive calcium channels in these phenomena. Considering that in vivo and in vitro alterations were reversed after weight loss, it is possible to conclude that obesity is probably a major cause of impaired insulin secretion in 12-month-old albino rats. Since 14C-glucose metabolism was not changed in islets from aged rats, the effect of obesity on insulin secretion is not due to altered glucose metabolism in pancreatic B-cells.

Aging↗
PubMed1990

Insulin secretion in Walker 256 tumor cachexia.

The effect of cachexia on insulin secretion was examined in adult male rats. Isolated islets of Langerhans from Walker 256 tumor-bearing rats secreted less insulin by glucose stimuli as compared with the control group; this was accompanied by significant change in 45Ca2+ outflow rate. Reduced insulin secretion to glucose stimuli in tumor-bearing rats probably led to low insulinemia (one-third). These findings indicate that reduced insulin secretion is probably an important factor for the development of cachexia in Walker 256 tumor-bearing rats.

Animals↗
PubMed1989

Insulin secretion in the isolated islets of single-, regular-fasted and fed rats.

To investigate the alterations in insulin secretion induced by habituation to single daily meal, adult rats were trained on a regular-fasting scheme (2-hr feeding/22-hr fasting) for 4 weeks. Insulin secretion induced by nutrient secretagogues (D-glucose and L-leucine) and the rates of 45Ca2+ outflow and 14C-glucose oxidation were studied in isolated islets obtained from these animals and in fed and 22-hr single-fasted rats. As expected, in the 22-hr fasted group, insulin secretion was drastically decreased although not abolished while 45Ca2+ outflow and 14C-glucose oxidation rates were only partially reduced. However, the regular-fasted rats did not secrete insulin in response to the nutrient secretagogues; calcium entry was not detected although a partial reduction in 14C-glucose oxidation rate was observed. These results suggest that regular fasting induces alterations in pancreatic B-cell glycolytic pathways leading to impairment of calcium efflux and insulin secretion. Such impairment is more pronounced than that induced by a single 22-hr fast.

Animals↗