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A Estival

Publications and source records attributed to A Estival.

32 records · Page 2Linked to original sources
PubMed1989

HPLC analysis of somatostatin peptides secreted by a rat pancreatic endocrine cell line (RINT3): stimulation studies.

A combination of anion exchange and reverse phase HPLC leading to the purification of a 15-kd proform of somatostatin from culture medium of the pancreatic tumoral endocrine RINT3 cell line is described. Elevation of extracellular calcium concentration causes a dose-dependent stimulation of somatostatin release; maximal stimulation (2.8-fold over basal) was reached with 5 mM Ca. Furthermore, 0.01 microM TPA induced a stimulation of about the same amplitude while forskolin had a low effect. These data suggest that secretion of somatostatin in this model can be regulated by the Ca/C protein-kinase pathway.

Adenoma, Islet Cell↗
PubMed1988

Identification by immunoblotting of somatostatin proforms in a rat pancreatic cell line.

The immunoblotting technique is applied to the analysis of "somatostatin" compounds secreted by R.I.N. T3 cells. We can confirm that two proforms of 15,300 +/- 750 and 29,000 +/- 1,100 Da accumulate in the extracellular medium. The unexpected form of 29 kDa, probably a dimeric form, disappears in reducing conditions. However, the 15 kDa peptide is characterized by several antibodies directed against either the intramolecular cycle of somatostatin-14 or the N-terminal extension of somatostatin-28. The 15 kDa form presents the same electrophoretic mobility in SDS-PAGE than the prosomatostatin isolated from a hypothalamic extract. Furthermore, this compound corresponds to the calculated mass of 10,388 Da deduced from the cDNA sequence. The detection of an immunoreactive 6 kDa peptide in the gel filtration fractions suggests an intermediate step in the prosomatostatin processing in these cells.

Animals↗
PubMed1987

Lipid content of human and rat pancreas.

We analyzed the lipid composition of the human pancreas and performed a parallel study on rat pancreas. Some precautions were taken in order to keep the secretory zymogens as inactive precursors in both tissues. The lipid content of the human pancreas corresponded to 5.5% of the tissue wet weight, lower than that found in pancreas of two-month-old Wistar rats (10%). In man, triglycerides and phospholipids were found at comparable levels, respectively, 37 and 30 mg/g of pancreas wet weight, not far from the values of the rat pancreas. In human pancreas, phosphatidylcholines and lysophosphatidylcholines represented about 40% of the total phospholipid fraction, phosphatidylethanolamines and lysophosphatidylethanolamines 21%, and phosphatidylserines and -inositols were found equally represented with 7.5%. The total cholesterol content accounted for about 4.5% of the total lipids; only 30% was esterified. By comparison, in rat, total cholesterol represented 3.3% of lipids and 90% was esterified. The phospholipids in human pancreas contained high amounts of saturated fatty acids (92%) mainly stearic and palmitic, whereas triglycerides contained equal amounts of saturated and unsaturated fatty acids, principally represented by oleic and palmitic acids. In rats the phospholipids contained only 63% saturated fatty acids (palmitic and stearic) and triglycerides contained 61% unsaturated fatty acids (mainly oleic and linoleic). In terms of lipid composition, there is a greater similarity between human and rat pancreas than with other known pancreas, such as the guinea pig and the ox.

Adult↗
PubMed1986

Analysis of somatostatin peptides produced by an endocrine pancreatic cell line.

Biological active forms of somatostatin are produced by cleavage of large precursors. If the sequence of the pre-proform of somatostatin has been deduced from cDNA structure in several species, little is known about the processing of these large precursors. For this purpose, the analysis of immunoreactive components secreted by the R.I.N. cell line was investigated. After selection of a cell population and culture conditions providing the optimal production of these peptides, analysis of their molecular forms was done by molecular gel filtration. The results show that mainly pro-forms accumulate in the culture medium while besides the pre-proform the smaller immunoreactive species behaving like S-28 and S-14 were found in cell extracts. Incorporation studies in serum free medium showed rapid formation of an intermediate compound eluted at 1.87 V0.

Animals↗
PubMed1986

Studies on human pancreatic acini: action of secretagogues on amylase release and cellular cyclic AMP accumulation.

A technique for preparing a suspension of dispersed functional acini from human pancreas has been developed. The changes in pancreatic enzyme secretion and accumulation of cellular cyclic AMP caused by various secretagogues have been studied. Ca2+-mobilizing agents stimulated amylase release from human pancreatic acini. The relative potencies with which secretagogues increased amylase release were as follows: gastrin-releasing peptide's potency (Ec50, 0.1 +/- 0.01 nM) was greater than bombesin 14's (Ec50, 0.2 +/- 0.01 nM), which was greater than litorin's (Ec50, 0.6 +/- 0.18 nM), which was greater than bombesin 9's (Ec50, 6 +/- 0.1 nM). For CCK-peptides, the relative potencies were as follows: CCK-39's potency (Ec50, 0.28 +/- 0.15 microM) was equal to cerulein's (Ec50, 0.3 +/- 0.07 microM). Both of these potencies were greater than CCK-8's (Ec50, 1.6 +/- 0.1 microM), which was greater than that of CCK-4. Carbamyl choline was poorly potent (Ec50 greater than 1 mM). The 12-O-tetradecanoylphorbol-13-acetate (TPA) was active from 0.1 nM to 0.1 microM. Neither secretin nor VIP increased amylase release from human pancreatic acini but they did cause an accumulation of cellular cyclic AMP, secretin (Ec50, 0.5 +/- 0.2 nM) being more potent than VIP.

Amylases↗
PubMed1984

Differentiation features of human pancreatic tumor cells maintained in nude mice and in culture: immunocytochemical and ultrastructural studies.

A poorly differentiated human pancreatic adenocarcinoma was maintained in nude mice for more than 3 years. When tumor fragments from xenografts were cultivated in suspension, some became adherent, allowing cell culture. Cytochemical, immunocytological and ultrastructural methods were used to study cell differentiation in both solid tumors and cultures. Pancreatic differentiation features such as cell polarization, production of secretory granules, and M1 and M3 mucus-associated antigens were maintained in the tumor cells, in vivo and in vitro. Moreover, in long-term cell cultures, cells were able to organize themselves spontaneously into duct-like structures. Other differentiation features such as production of pancreatic enzymes and hormones were not expressed. However, differentiation patterns such as an intestinal-like brush border and the presence of the M3 antigen associated with intestinal mucus were observed in both xenografts and cultures. This study shows the possible differentiation patterns which can be expressed by the hypothetical tumor pancreatic stem cell in nude mice as well as in culture.

Adenocarcinoma↗
PubMed1984

[Inhibition of the adherence of leukocytes labelled with Cr-51 in colorectal cancer].

The leukocyte adherence inhibition test (LAI) is an in vitro test of immunity. Its high sensitivity in early cancer and its organ-specificity are of great interest in the study of human tumors. We developed an isotopic method (51Cr-LAI) for colorectal cancer, which has the advantage of being easier to perform than optic-counting assays. 87 patients (35 colorectal cancers, 29 benign diseases, 23 cancers of non-colorectal origin) were studied. We obtained a statistically significant difference between the mean LAI index for colorectal cancers and that for controls (p less than 0.01). LAI values greater than 13 p. 100 were considered positive. The specificity of the test was 94 p. 100 and the sensitivity for all colorectal cancers was 66 p. 100 with the highest value in the Dukes A group (LAI = 83 p. 100). Tests were negative in disseminated neoplasms. The actual fields of interest of LAI in tumor immunology and clinical research are discussed.

Chromium Radioisotopes↗
PubMed1983

Presence of VIP receptors in a human pancreatic adenocarcinoma cell line. Modulation of the cAMP response during cell proliferation.

It is known that the human exocrine pancreas responds to secretin stimulation more than does VIP, a structurally related peptide. We looked for the receptors for those polypeptides in a human pancreatic cancer cell line grown in culture and in nude mice. By analysing the cAMP responses and the 125I-VIP binding we found VIP receptors with a KD of 1.5 10(-9) M. Secretin stimulates the adenylate cyclase through the VIP receptor sites with a KD of 1.7. 10(-6) M. We noted also that during cell proliferation in culture there was about a 5 fold increase of the cAMP response to VIP.

Adenocarcinoma↗
PubMed1982

The decrease of the non secretory phospholipase A in rat pancreas during a chronic alcohol intoxication.

It is known that ethanol induces morphological lesions in the exocrine pancreas of man and of experimental animals. We showed recently that ethanol is metabolized by the rat pancreas. It has also been demonstrated that ethanol acts on the lipid metabolism of the pancreas by stimulating the lipid biosynthesis and by inhibiting fatty acids oxidation. We recently characterised a non secretory phospholipase A in the rat pancreas, probably involved in the intracellular phospholipid turnover. The actions of chronic alcoholic intoxication on the level of this enzyme is investigated in this paper. The ethanol intoxication was prolonged for two years and resulted in a progressive decrease in the level of the pancreatic non secretory phospholipase (p less than 0.01). This result confirms the chronic metabolic modifications induced by alcohol on the pancreas and emphasizes its metabolic participation in chronic alcoholic pancreatitis.

Alcoholism↗
PubMed1979

Non-parallel enzyme secretion from rat pancreas in vitro studies.

1. The relative variations of rat pancreatic amylase versus lipase and chymotrypsinogen secretions have been studied in vitro with the help of two different techniques: in situ organ perfusion and incubation of pancreatic lobules. 2. In experiments on the perfused pancreas, with 8 C u.kg-1 hr-1 secretin added to the perfusion fluid, cholecystokinin-pancreozymin (8 ID u.kg-1) or pilocarpine (15 mg kg-1) both resulted in a significant change in the enzyme proportions in the juice. 3. In experiments on pancreatic lobules, the addition to the incubation medium of secretin (10(-7) M), alone or associated with cholecystokinin-pancreozymin (8 x 10(-7) M) or pilocarpine (10(-4) M) did not induce any change in the enzyme proportions in secretion. 4. It was concluded that the non-parallelism between enzyme secretions can occur in the rat upon pancreozyminic or cholinergic stimulation in vitro as well as in vivo (Dagorn, 1978) provided basal protein output is low enough. This is not the case when the tissular integrity of the pancreas is lost, such as in experiments on lobules. 5. This work confirms that pancreatic secretion derives from two intrapancreatic pools of different enzymatic composition, and gives a possible explanation for some discrepancies from the literature on the existence of non-parallel secretion.

Amylases↗
PubMed1977

In-situ-isolated perfused rat pancreas: a new method for pharmacological studies of the exocrine pancreas.

A method of in-situ-isolated perfused rat pancreas is described. In situ perfusion of the isolated rat pancreas allows a faster set-up, thanks to a simpler operating procedure. The sensitivity of the isolated rat pancreas has been tested with secretin and cholecystokinin. The pancreas responds to doses of secretin as low as 0.005 CU/kg-h. Such a highly sensitive model might prove to be useful for the bioassay of secretin and the study of the effects of pancreatic secretagogues.

Animals↗