PubMed Health⌕ Search

Biomedical subjects

A C Puviani

Publications and source records attributed to A C Puviani.

32 records · Page 2Linked to original sources
PubMed1987

Mechanisms involved in catecholamine effect on glycogenolysis in catfish isolated hepatocytes.

Isolated catfish hepatocytes were treated with epinephrine, norepinephrine, isoproterenol, and phenylephrine in the presence or in the absence of propranolol or phentolamine as beta and alpha inhibitors, respectively. Glycogen phosphorylase a activity and glycogen content, as well as glucose released from cells, were tested. Phosphorylase activity was stimulated by all the catecholamines and was accompanied by a decrease of glycogen content in cells and by an increase in glucose output into the medium. Whereas phentolamine did not affect the catecholamine action on any parameter considered, propranolol inhibited the effect of epinephrine, norepinephrine, and phenylephrine, but hardly altered that of isoproterenol. The effect of epinephrine and norepinephrine, as modified by propranolol and not by phentolamine, is consistent with a beta action of these catecholamines. The fact that propranolol and not phentolamine inhibited the phenylephrine effect indicates that in catfish hepatocytes phenylephrine behaves as a beta agonist and/or that propranolol may also bind to alpha receptors. Results also indicate that in catfish liver cells isoproterenol, whose effect is scarcely influenced by propranolol, is not a pure beta agonist.

Animals↗
PubMed1986

Epinephrine effect on glycogen phosphorylase activity in catfish liver and muscles.

In catfish, the percentage of the active (a) form of glycogen phosphorylase with respect to the total (a + b) form varied in control slices from about 90% to 65% and 20%, respectively for liver, red, and white muscles. Epinephrine added to the incubation medium of liver and white muscle slices caused a significant increase in the specific activity of phosphorylase a in liver and white muscle, but not in red muscle. In liver slices epinephrine showed its effect from the concentration of 3.5 X 10(-8) M. The increase of enzyme activity explains the lowering of the glycogen level in liver and white muscle induced by epinephrine.

Adenosine Monophosphate↗
PubMed1985

Epinephrine effect on carbohydrate metabolism in isolated and perfused catfish liver.

Two doses of epinephrine were infused for 6 hr into isolated catfish liver previously perfused with a glucose-free medium or with a medium containing 10 mM glucose. The hormone induced (a) a continuous decrease in liver glycogen level, both in absence and in presence of glucose in the medium; low dose of epinephrine was without effect on the decay of glycogen; (b) a great release of glucose, both in absence and in presence of glucose in the medium; the low dose of epinephrine induced an effect similar to the maximal dose, only in experiments without glucose in the medium; (c) no effect on lactate uptake by liver; or (d) a prevention of the decline in liver glycogen phosphorylase activity observed during 1 hr incubation of liver slices. It has been concluded that epinephrine caused an increase of glucose in perfusion medium with different mechanisms according to the level of glucose and the dose of epinephrine. High doses of hormone cause the glycogenolysis by activation of glycogen phosphorylase, both in presence and in absence of glucose; low doses of epinephrine probably preferentially promote in liver the gluconeogenetic processes in glucose-free experiments.

Adenosine Monophosphate↗
PubMed1985

Effects of insulin on glycogen metabolism in isolated and perfused catfish liver.

The isolated and perfused catfish liver showed (a) a decrease in liver glycogen, (b) a continuous increase in glucose output, and (c) a decrease of lactate in the medium. Insulin did not influence liver glycogen decay during the first 2 hr; thereafter the hormone induced an increase of glycogen, particularly when glucose was added into perfusate. In insulin treated liver, the glucose output was lower than controls in the first hours of perfusion; thereafter a re-uptake of glucose occurred. After 2-3 hr of perfusion, the lactate present in the medium was increased by insulin towards the starting level. The long lasting effects of insulin on catfish in vivo were confirmed.

Animals↗
PubMed1984

Epinephrine effects on carbohydrate metabolism in catfish, Ictalurus melas.

Epinephrine injection in catfish, Ictalurus melas, induced (a) a rapid hyperglycemia which lasted for more than 5 hr; and (b) a slight immediate decrease of glycogen in liver and muscles (red and white), followed by an increase at 48th hr in the liver. Epinephrine, added in vitro to tissue slices, increased the output of glucose from liver and enhanced the decrease of glycogen seen in controls. Among the other organs, only white muscle showed a greater decrease of glycogen than the controls. These effects are attributed to an increase of glycogen phosphorylase activity induced by the hormone.

Animals↗
PubMed1984

Effect of insulin on glycogen metabolism in isolated catfish hepatocytes.

Insulin effect on carbohydrate metabolism in catfish hepatocytes consisted of a significant decrease of cell glycogen concentration both in the absence and in the presence of glucose in the medium. The hormone did not influence either the output of glucose from the cell or the intracellular glucose level. Experiments with radioactive glucose showed a very low uptake of the sugar by the hepatocytes; correspondingly the incorporation of radioactivity into glycogen was very low and not influenced by insulin. The glycogen content in catfish liver cells was influenced by the hormone in the opposite way to rat liver cells.

Animals↗
PubMed1983

[Effect of adrenaline on blood glucose and glycogen in catfish tissues].

The effects of epinephrine injected intraperitoneally (5 mg/kg body weight) on the catfish carbohydrate metabolism were studied. Epinephrine caused a very high and persisting hyperglycemia, the highest value of which was 340 +/- 21 mg/100 ml of blood (control value: 75 +/- 6 mg/100 ml) at 24th hour after the administration. Moreover, epinephrine caused glycogenolysis in liver: from 127 +/- 10 to 95 +/- 8 mg/g of tissue. In white muscle the lowering of glycogen happened just after the epinephrine injection and reached the lowest value (1,6 +/- 0,3 mg/g) at 2,5 hours after the administration (control value: 2,9 +/- 0,4 mg/g). A glycogen decrease took place in red muscle with a great delay, but was still present 48 hours after administration (control value: 17,5 +/- 1,8 mg/g; sample value: 11,2 +/- 3,2 mg/g). The increase of glucose level in blood could be referred to glycogenolytic processes in liver. As far as musculature is concerned, red muscle probably plays a role in recovering the glycogen level in white muscle.

Animals↗
PubMed1982

"In vivo" effects of insulin on carbohydrate metabolism of catfish (Ictalurus melas).

The effect of insulin was studied on blood glucose, and on the glycogen level of liver, muscles and heart in fed and in starved catfish (Ictalurus melas). Fish received intraperitoneally 60 iu/kg body weight of bovine insulin, or physiological saline and were sacrificed after 2, 4, 8, 24, 72 hr from injection. Insulin caused a decrease of blood glucose level, both in fed and in fasted animals, and the effect is more evident in fed animals. After insulin treatment, liver glycogen shows a decrease which is significant at the 8th and 24th hr in fasted and in fed animals respectively; after 72 hr the glycogen level in livers of fed and fasted animals is still very low. Insulin increases the glycogen level both in white and in dark muscle, both in fed and in fasted fish, although with different characteristics, but at the 72nd hr in all animals, the increases are significant. Hormone treatment does not change heart glycogen levels in fed catfish till the 24th hr, then there is a net decrease; in starved animals the decrease begins at the 2nd hr, but only at the 48th hr is it significant. The role of insulin was discussed in relation to the lowering of glycogen concentration in liver, in connection with the fact that many authors found different and even opposite effects of this hormone in various fish. It is possible that the glycogen depletion observed in liver after insulin injection is not due to a direct action of this hormone, but depends on the stimulated production of other specific glycogenolytic hormones, such as epinephrine and/or glucagon.

Animals↗
PubMed1981

[Effect of insulin on carbohydrate metabolism in the catfish (Ictalurus melas). II) In vitro experiments].

Isolated hepatocyte preparations were used to study the "in vitro" effects of insulin on catfish (Ictalurus melas) carbohydrate metabolism. Insulin decreases spontaneous glycogen lowering either in absence or in presence of glucose in the medium. In the same time insulin produces a little increase on the cell glucose level, but reduces the cell uptake of glucose from medium. The effect of insulin shows to be less evident on isolated hepatocytes than in the intact animals.

Animals↗
PubMedDate not supplied

[Isolated hepatocytes and their potential therapeutic use].

Isolated hepatocytes in culture represent an idoneous system for the study of liver physiology and metabolism. Furthermore, they are also widely utilized in pharmacological and toxicological study, in evaluating xenobiotic substance effects on the liver. In this paper, we reviewed the enzymatic methods for liver cell isolation in some mammalian species, as well as the techniques for qualitative and quantitative evaluation of cell number, vitality, purity, morphology and function. Recently, there has been a renewed interest in hepatocyte transplantation and hepatocyte-based liver support systems. From a clinical point of view, isolated hepatocytes could be useful in temporarily substituting an acutely damaged liver, a liver affected by a chronic pathology, or to correct an inherited liver disease carrying a severe metabolic derangement. Early experimental results of allogeneic hepatocyte transplantation, as well as the first clinical trials of bioartificial liver support systems employing xenogeneic hepatocytes are promising and contribute to maintain that interest in liver cell isolation and purification methods.

Animals↗
PubMedDate not supplied

[In vitro experimentation of a new model of radial flow bioreactor containing isolated hepatocytes].

Hepatocyte based artificial liver support systems are under investigation to support acute liver failure patients. The main purpose of such systems is to serve as a bridge to liver transplantation, or to promote spontaneous liver recovery. Limitation in mass-transfer capacity makes hollow-fiber bioreactors unsuited for long-term functioning of hybrid devices. We developed a novel radial-flow bioreactor in which the fluid perfuses the module from the center to the periphery, after having diffused through a space occupied by a three-dimensional structure filled with the hepatocytes. Five grams of freshly isolated porcine hepatocytes were seeded into uncoated, woven-non woven, hydrophilic polyester fabric, overlaid by two polyethersulfone membranes. Liver cells were perfused with 37 degrees C-warm, oxygenated, serum-free tissue culture medium, in which NH4Cl and Lidocaine were added at the final concentration of 1 mM and 60 micrograms/ml, respectively. Ammonium chloride removal, urea synthesis, monoethylglycinexylide (MEGX), pO2, pCO2, and pH were measured throughout the 14 day duration of the study. In a separate set of experiments, a scaled-up version of the radial flow bioreactor containing 150 grams of cells was perfused for 7 h with recirculating human plasma and MEGX production was monitored. During the 2 weeks of the study, an increasing production of urea was paralleled by constant ammonium removal. MEGX concentration after Lidocaine addition increased throughout the 14 days of perfusion with tissue culture medium, as well as after 7 hour perfusion with human plasma. Under transmission and scanning electron microscopy cells appeared attached to the polyester and one to each other, displaying ultrastructural features typical of functioning hepatocytes. Our study showed that liver cells were metabolically active when perfused into the radial-flow bioreactor. This configuration allowed close contact between media, or plasma, and cells at a physiological flow rate, by equalizing the concentration of the perfusing components, including O2, throughout the module. Our results suggest a potential use of this system for temporary extracorporeal liver support in acute hepatic failure patients.

Animals↗