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Biomedical subjects

P Vassanelli

Publications and source records attributed to P Vassanelli.

At least 19 recordsLinked to original sources
PubMed1985

The effect of portocaval shunt on hepatic glycogen stores during fasting.

The effect of a prolonged fast was studied in surgically portocaval shunted (PCS) rats. This shunt excludes the liver from the direct effect of pancreatic and enteric hormones, thus facilitating the study of the biochemical and metabolic effects of these hormones. In portocaval shunted rats, liver glycogen was lower than that of control rats, and remained unaffected during fasting. No remarkable difference was observed in blood glucose, plasma and liver free fatty acids and blood ketone bodies. Among blood nitrogen compounds, total protein, alanine and urea did not show any significant variation, while, in PCS rats, the initial low levels of creatinine resulted in an increase after fast. Skeletal muscle protein decreased only slightly in control rats, while their loss was remarkable in PCS rats. The possibility of a differential activation of gluconeogenesis and glycogenolysis in control and PCS rats is discussed.

Animals↗
PubMed1984

Liver revascularization with the left gastric artery following portocaval shunt in rats: technique and preliminary results.

The technique of liver arterialization with the left gastric artery after portocaval shunt in the rat is described. The operation was carried out with three different modalities, and the best results were obtained when suturing was carried out after enlargement of the arterial caliber (0.4-0.5 mm external diameter), advantage of a vessel bifurcation. Eighty percent of the anastomosis were patent without any anticoagulant treatment 1 month after surgery. Preliminary results show the positive effect of liver arterialization compared to treatment with portocaval shunt alone.

Animals↗
PubMed1984

Effects of ACTH on adrenocortical cells autotransplanted in the rat spleen: ultrastructural and morphometric observations.

The effects of chronic ACTH administration on adrenocortical cells autotransplanted in the rat spleen have been investigated. Morphometry showed that ACTH induced a significant hypertrophy of adrenocortical cells, which was mainly due to the increase in the smooth endoplasmic reticulum and mitochondrial compartment. Competitive protein binding assay demonstrated that adrenocortical cell hypertrophy was associated with a two-fold rise in the plasma corticosterone concentration. These data indicate that autotransplanted adrenocortical cells are normally sensitive to ACTH, which enhances their growth and steroidogenic capacity.

Adrenal Cortex↗
PubMed1983

Morphometric investigations into the mechanism of the compensatory hypertrophy of the rat adrenal zona fasciculata after unilateral adrenalectomy.

Compensatory hypertrophy of the remaining gland in unilaterally adrenalectomized rats was investigated by morphometric techniques. It was observed that compensatory adrenal growth occurred in both dexamethasone-treated and hypophysectomized rats, receiving maintenance doses of ACTH. However, it was only half that found in intact animals. These results support the view that activation of the hypothalamo-hypophyseal axis is not the unique mechanism underlying adrenal compensatory hypertrophy in the rat.

Adrenal Glands↗
PubMed1983

A morphometric and ultrastructural study of the long term effect of portacaval anastomosis on the liver of normal male rats.

A morphometric analysis of the lobular components of the liver of normal male rats up to 6 months from portacaval anastomosis revealed that the mean volume of each hepatocyte decreased about 30-40% in normally fed rats and this was associated with a shrinkage of the lobular tissue. A 10% reduction of the total hepatocyte volume density in the lobule and a net increase in time of the fat storing cell volume density could be measured, whereas the intralobular collagen decreased. Within the hepatocytes a persistent significant increase of fat globules was observed; an increase in the first period, followed by a decrease of the lysosomal component. The Golgi complex tended to decrease in the first period, then exhibited a volume density even higher than in the controls. A small reduction of the rough endoplasmic reticulum and a conspicuous reduction of the smooth endoplasmic reticulum and, in fed animals, of the glycogen content were also observed. These alterations were persistent with periods of up to 6 months from the anastomosis and were present in all the functionally distinct lobular zones. From the ultrastructural point of view, apart from variations due to the quantitative changes described above, both lobular and hepatocytic components were identical to those of age matched controls at all times from the intervention. The ultrastructural damages described by others could not be observed.

Animals↗
PubMed1982

An electron-microscopic stereological study of the compensatory hypertrophy of the rat adrenal zona fasciculata after unilateral adrenalectomy.

The ultrastructural changes associated with the compensatory hypertrophy of the zona fasciculata cells on monoadrenalectomized rats were investigated by stereological techniques. It was found that these subcellular changes display a different pattern from those underlying the ACTH-induced adrenocortical cell growth in the intact rats. This result supports the view that compensatory adrenal hypertrophy does not involve activation of the hypothalamo-hypophyseal-adrenal axis.

Adrenal Cortex↗
PubMed1982

Cerebral amino acid levels and transport after portocaval shunt in the rat: effects of liver arterialization.

Altered plasmatic and cerebral amino acid patterns have been observed after portocaval shunt in the rat. Similar alterations have been found in plasma and in cerebrospinal fluid of cirrhotic patients and are likely to play an important role in the pathogenesis of hepatic encephalopathy. Impaired liver blood flow could contribute to these biochemical abnormalities. Therefore we wondered whether liver arterialization, by improving liver perfusion, could have any beneficial effects on the altered amino acid levels occurring in the rat after portocaval shunt. Amino acid concentrations were determined in four cerebral regions and in the plasma of shunted rats with or without liver arterialization, 4 weeks after surgery. Blood-brain barrier transport was studied with the Oldendorf's technique. After portocaval shunt, we observed lower plasma levels of the branched chain amino acids valine, isoleucine, leucine, and net higher levels of the aromatic tyrosine and phenylalanine and of glutamine. In the cerebral regions, we observed a slight increase of branched chain amino acids and an enormous increase of tyrosine, phenylalanine, tryptophan, histidine, and glutamine. Arterialization of the liver made no difference to the postportocaval shunt plasma levels of branched chain amino acids, while it almost normalized those of aromatics. In the cerebral regions, we observed a marked improvement in the level of tyrosine, phenylalanine, tryptophan, and histidine. The enhancement of blood-brain barrier transport for the neutral amino acid class, observed after portocaval shunt, was not influenced by liver arterialization. We conclude that, in our model, liver arterialization improves the pathologic amino acid levels following portocaval shunt. This would be in agreement with clinical reports suggesting that hepatic encephalopathy is less frequent after portocaval shunt when associated with arterialization of the liver.

Amino Acids↗
PubMed1982

Arterialization of the liver prevents testicular atrophy in portacaval shunted rats.

Portacaval anastomosis in male is known to induce testicular atrophy. The effect of liver revascularization by the right renal artery on the testes of portacaval shunted rats was examined. After shunting, there was a 75% decrease in testis weight compared to the control value and spermatogenesis was blocked in steps 8-9 of spermiogenesis. The in vitro binding of [125I]hCG was only 10% of the control value on a per testis basis and labelled areas in the interstitium of frozen sections subjected to topical autoradiography with [125I]hCG were also strikingly reduced. These parameters were maintained to normality in revascularized shunted rats which displayed also normal copulatory and fertilizing abilities. It is suggested that an adequate blood supply to the liver, as provided by arterialization, can preserve testicular integrity in shunted rats, even though the blood is arterial instead of portal.

Animals↗
PubMed1982

Ultrastructural observations on the regeneration of adrenocortical autotransplants in the rat spleen.

The regeneration of adrenocortical autotransplants in the rat spleen has been investigated by light and electron microscopy. Up to the seventh day after implantation, adrenal grafts showed large areas of necrosis and contained many degenerating (apoptotic) adrenocortical cells, some mesenchyme-like poorly differentiated elements, and occasional viable parenchymal cells. These last cells possessed mitochondria with scanty tubular cristae and few profiles of smooth endoplasmic reticulum. After 15 days of regeneration, adrenal grafts were reduced in volume, but contained only viable adrenocortical cells; after 30-36 days, autotransplants were noticeably enlarged and surrounded by an evident connective tissue capsule. Regeneration was closely associated with the morphological differentiation of adrenocortical cells, which one month after transplantation were found to assume all the typical features of adult rat zona fasciculata elements (i.e. mitochondria with vesicular cristae, abundant smooth endoplasmic reticulum, some lipid droplets and a well developed Golgi apparatus).

Adrenal Cortex↗
PubMed1981

Biliary excretion of simultaneously administered bilirubin and chenodeoxycholic acid in rats.

Crystalline bilirubin and chenodeoxycholic acid were administered intravenously and intraduodenally respectively in 19 anesthetized Sprague-Dawley rats in order to verify whether there exists an interference between their biliary excretion. When these two compounds were administered together, the biliary excretion of bilirubin and bile salts was significantly reduced the conjugation of bilirubin was not impaired while bile flow remained constant during the whole exerpimental period. These data seem to indicate a mutual interference between chenodeoxycholic and bilirubin metabolisms. It could be admitted that the excretory step is involved in determining the observed modifications.

Animals↗
PubMed1981

Biliary excretion of simulateously administered bilirubin and chenodeoxycholic acid in rats with porta-caval shunt.

Portacaval shunting influences several metabolic processes of the liver. The aim of this work was to investigate whether bile salts and bilirubin reciprocally interfere with their biliary excretion in this experimental condition. 12 male Sprague-Dawley porta-caval shunted rats received simultaneously crystalline bilirubin (intravenously) and chenodeoxycholic acid (intraduodenally) 20-26 days after intervention. The biliary excretion of these two compounds was then studied. The results seem to indicate that there exists a mutual interference between bile salt and bilirubin excretion in the bile; moreover it is suggested that porta-caval shunting plays a secondary role in determining the observed interaction between bilirubin and bile salts metabolism in the liver.

Animals↗
PubMed1981

Effect of L-dopa treatment on cerebral amino acid levels in rats after portocaval anastomosis.

L-Dopa therapy has been suggested as effective in the reversal of hepatic coma both in humans and in animals. Beneficial effects have been reported also in chronic hepatic encephalopathy. There are many possible mechanisms through which L-dopa could ameliorate this pathological state. The present study was carried out to clarify whether the L-dopa effect could be mediated through an improvement of the brain neutral amino acid patterns, since it competes for the same transport carrier at the blood-brain barrier. A first group of rats was orally administered L-dopa (10 mg/100 g body weight daily) for 1 month following portocaval anastomosis. A second group was intraperitoneally injected (1.5 mg/100 g body weight daily) for 1 week, a month after portocaval shunt. Amino acid levels were determined in plasma and in four cerebral regions. No beneficial effects were observed clinically (in general condition, body weight, or hypertonic posture) in rats receiving L-dopa compared to controls. The large increase of tyrosine, phenylalanine, tryptophan, histidine, and glutamine that occurs in the cerebral tissue after portocaval shunt was also not affected by L-dopa administration. In conclusion, in this experimental condition we had no clinical improvement in shunted animals receiving L-dopa. Moreover, this compound did not seem to influence the pathological increase of aromatic amino acids in the brain, which is considered to play an important role in hepatic encephalopathy.

Amino Acids↗
PubMed1980

Importance of the liver in the regulation of platelet activity: effect of its functional exclusion (Eck fistula).

The functional exclusion of the liver, obtained with end-to-side anastomosis of the porta into the cava vein results in impairment of platelet activity. In fact the maximal amplitude and velocity of platelet aggregation in vitro are reduced in animals which undergo the operation and are examined 1 month later. Adding fibrinogen to the platelet-rich plasma after portacal anastomosis restores a normal type of aggregation indicating that the lack of this factor is involved in the phenomenon, even if alterations occurring to platelets may be implied, too.

Adenosine Diphosphate↗
PubMed1979

Cerebral amino acid levels and uptake in rats after portocaval anastomosis: I. Regional studies in vitro.

Uptake of various amino acids was studied in slices from brain regions of rats four weeks after portocaval anastomosis. No differences of the inulin compartment were observed between control and experimental animals. After 60-minutes incubation, uptake showed an overall pattern of diminution. This was more evident for some amino acids: valine, methionine, and lysine exhibited a lowering of about 30%, which was fairly uniform in the four tested regions; others showed a regional decrease-- alanine in pons-medulla, phenylalanine in cerebellum, histidine and GABA in mesodiencephalon. This decrease did not seen to be related to transport classes. The restricted entry of amino acids into brain cells in portocaval encephalopathy is somewhat difficult to explain; a decreased rate of protein synthesis may be of some importance, but other factors, such as a "carrier" impairment, effects on release and on amino acid metabolism, may also be involved.

Amino Acids↗
PubMed1979

Cerebral amino acid levels and uptake in rats after portocaval anastomosis: II. Regional studies in vivo.

Amino acid levels have been determined in plasma and in four cerebral regions of rats one month after portocaval shunt. Many plasma amino acids are significantly lowered (asparagine, glutamine, theonine, serine, alanine, valine, leucine, isoleucine, cystine, lysine), while others remain unchanged (taurine, glycine, proline, tryptophan, ornithine, histidine, arginine). Asparagine and glutamine levels are significantly higher than in normal rats, and a net increase of tyrosine (100%), phenylalanine (50%) and citrulline (50%) is evident. In the shunted rat brain the most prominent feature is a very large rise (up to fivefold) of tyrosine, phenylalanine, histidine, citrulline, tryptophan, and glutamine uniformly in the tested regions. Other neutral amino acids are slightly increased. Lysine and arginine are decreased in cerebellum and pons-medulla; taurine, in forebrain and cerebellum. Cerebral permeability to L-amino acids was studied in vivo. Neutral amino acid permeability is greatly increased, whereas basic amino acids show a net decrease in their rate of passage from blood to the brain. No changes are observed for GABA and glutamic acid. These data suggest an altered permeability of the cerebral capillary membranes, which seems to be selective for the different amino acid transport classes. Competitive inhibition experiments demonstrated that the increased brain permeability to neutral amino acids after portocaval shunt is due to an enhancement of the saturable transport. The sharp rise in the brain of some essential neutral amino acids (phenylalanine, tyrosine, trytophan, histidine), largely exceeding their changes in plasma, and the slight cerebral increase of other neutral amino acids despite their lowered level and the rise of competing amino acids in the plasma, is consistent with our observation of enhanced transport for the neutral class. In hepatic encephalopathy, correction of the altered plasma amino acid levels has been reported to improve the clinical status. If this result is connected to the concomitant correction of the brain amino acid levels, carefully selected competitive inhibition among various plasma amino acids could be a useful therapeutic tool in this pathologic condition. However, the increased activity of the neutral amino acid transport system adds a new factor to the problem, since it probably implies that the competing amino acids will accumulate to unphysiological levels in the brain.

Amino Acids↗
PubMed1979

A stereological study of the trophic effects of the renin-angiotensin system on the rat adrenal zona glomerulosa.

Left renal artery stenosis increased and timolol maleate chronic administration decreased systolic blood pressure, plasma renin activity, and plasma aldosterone concentration, in adult male rats. In the hypertensive animals the volume of the zona glomerulosa, the volume and number of zona glomerulosa cells, as well as the volume of the mitochondrial compartment and the surface area of SER and mitochondrial cristae, were significantly increased. The volume of the lipid compartment was reduced, and several clumps of electron-dense granules appeared at the juxta-sinusoidal pole of the cells. Opposite results were found in the zona glomerulosa of the hypotensive rats, with the exception that the volume of the lipid compartment showed no significant change. These findings suggest that the renin-angiotensin system is involved in the maintenance and stimulation of the growth in the zona glomerulosa. Since in the hypertensive rats the increase in the volume density of electron-dense granules fits well with that in the intracellular concentration of aldosterone, the working hypothesis is that these granules are aldosterone-containing secretory organelles.

Adrenal Cortex↗