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G Zanchin

Publications and source records attributed to G Zanchin.

13 recordsLinked to original sources
PubMed1990

Evaluation of membrane fluidity in cerebral microvasculature.

Cerebromicrovascular membrane fluidity was studied in two model systems: 1) hepatic encephalopathy and 2) cultured endothelium exposed to free arachidonic acid alone or with H2O2. The membrane fluidity was measured by fluorescence anisotropy using 1, 6-diphenyl-1,3,5-hexatriene as a fluorescent probe. In addition, the effect of arachidonic acid with or without H2O2 on cellular permeability to trypan blue-albumin was investigated in endothelial cultures. The findings indicate that the hepatic encephalopathy and the arachidonic acid treatment of endothelium causes an increase in membrane fluidity. This modulation of endothelial membrane fluidity is not associated with changes in cellular permeability to trypan blue-albumin complex. An increased cellular permeability to trypan blue-albumin complex was seen after endothelial exposure to arachidonic acid and H2O2.

Animals↗
PubMed1988

Intracranial sarcoma with reactive glioma: a clinicopathological case report.

The clinicopathologic picture of a case of so-called 'sarcoglioma' is reported. This tumor is characterized by a core of sarcomatous tissue, surrounded by an area of gradual transition from reactive to neoplastic glial cells; it occurs in children or in young adults and is very rare in comparison with the secondary sarcoma deriving from the vascular component of a glioblastoma (so-called 'gliosarcoma'). The clinical and laboratory features and the pathology of this case are discussed in detail.

Adult↗
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↗
PubMed1978

Decrease in cerebral protein synthesis on a low protein diet.

When rats are put on a diet that is low in protein or contains no protein, decrease in brain weight can be observed. Changes in adults are minimal. In the young there is a 10--30% decrease in cell number and protein content; the cell size (protein per cell) does not change significantly. The change is greater, the earlier the diet is started and the more severe the protein dificiency is. The longer the malnutrition period lasts, the smaller is the recovery to normal values on subsequent control diets. Amino acid incorporation in the brain decreased 10--30% under these experimental conditions; it seems the decrease was to a great extent in the more slowly metabolized protein pool. Changes in other organs were greater; for example, in liver the decrease was up to 75% under similar conditions. The changes in the brain were heterogeneous; there were regional differences, and not all proteins were affected to the same degree; choline acetyltransferase was not affected. Cellular amino acid transport as studied with incubated slices of brain was not altered under these conditions.

Animals↗
PubMedDate not supplied

[Accumulation of glutamic acid and glycine in human cerebral tumors in vitro].

Preliminary results are given on transport of glycine and L-glutamate into human cerebral tissue, normal and tumoral. In comparison with normal tissue, glycine transport is diminished in meningioma and oligodendroblastoma, unaffected in neurinoma, sharply increased in medulloblastoma. Glutamic acid transport is lowered in neurinoma and oligodendroblastoma; increased in medulloblastoma. Such preliminary observations are briefly discussed.

Brain↗
PubMedDate not supplied

[Aromatic and branched chain amino acids after porto-caval anastomosis: plasma and brain regional levels in the rat (author's transl)].

Automated analysis of aromatic and branched chain amino acids was performed in plasma and in four cerebral regions of rats submitted to chronic porto-caval shunt. Compared to controls, plasma of the operated animals exhibited a significant diminution of valine, leucine, isoleucine, a net increase of phenylalanine and tyrosine, with unchanged tryptophan levels. Brain valine, leucine and isoleucine were either increased or unchanged, whereas an enormous increase of aromatic amino acids, uniform in the four cerebral regions, was observed. The lack of correlation between plasmatic and cerebral levels of these essential amino acids leads to the hypothesis that cerebral permeability to amino acids is modified after experimental portocaval anatomosis: we recent confirmed that blood-brain mediated transport of the neutral amino acids is increased in this condition. A slower cerebral turnover of these metabolites could also contribute to elevate their cerebral concentrations after portocaval shunt.

Amino Acids↗
PubMedDate not supplied

[In vivo aminoacid transport in the brain of the rat with porto-caval anastomosis (author's transl)].

Cerebral capillary permeability to L-amino acids was studied in rats submitted to porto-caval anastomosis 4 weeks before. The short-term intracarotidal injection technique described by Oldendorf was used throughout. Neutral amino acid permeability appeared to be greatly increased, the most important enhancement being for the tryptophan. On the opposite, basic amino acids showed a net decrease in their rate of passage from blood to the brain. No changes were observed for GABA and glutamic acid. These data suggest a marked modification of the permeability of the cerebral capillary membranes in the rat with chronic portocaval anastomosis. Moreover, such alterations are selective for the different amino acid transport classes. Competitive inhibition decreased the permeability of methionine at the same level in both control and experimental animals: therefore, the neutral amino acid increased entry into the rat brain after porto-caval shunt is due to an enhancement of the transport processes.

Amino Acids↗