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Biomedical subjects

F Clemente

Publications and source records attributed to F Clemente.

At least 73 records · Page 4Linked to original sources
PubMed1984

Dopamine receptors in a human colonic cancer cell line (HT29). Some receptor-related biological effects of dopamine.

The presence of dopamine receptors in normal colonic cells has been postulated from physiological studies. The existence of such receptors in human colonic tumor cells and their role in tumor progression are still unknown. The aim of the present work was to characterize the dopaminergic receptors in a human colonic adenocarcinoma cell line (HT29) and to evaluate the effect of dopamine on cAMP, protein and DNA synthesis. The binding characteristics of 3H-dopamine on the tumor cells were rapid, reversible, specific, saturable and stereospecific. The first site characterized corresponds to a D3 subtype:KD 3.09 nM, insensitive to sulpiride, unrelated to adenylate cyclase. Competitive inhibitions of 3H-dopamine binding by different drugs showed the existence of a second binding site, D1, with an apparent affinity for dopamine of 6,700 nM. The rank order of potency of inhibitors of 3H-dopamine binding was: haloperidol greater than dopamine greater than cis flupenthixol greater than (+) butaclamol greater than (-) butaclamol greater than trans flupenthixol greater than isoproterenol greater than clonidine greater than prazosin. D3 binding sites are modulated with age, Bmax was 116 fmol/10(6) cells on the 5th day and decreased to 8.2 fmol/10(6) cells on the 15th day of culture. Cell culture in serum-deprived medium allowed an increase in the number of high-affinity receptor sites. D1 sites are coupled to adenylate cyclase as shown by a dose-dependent cAMP accumulation from 10(-8) M to 10(-5) M dopamine concentrations. Interacting with D1 sites, dopamine evokes an increase in protein synthesis with no modification of 3H thymidine incorporation. The present results indicate that the human colonic cancer cell line HT29 exhibits dopamine receptors and that stimulation may induce metabolic modifications in the tumor cells.

Binding, Competitive↗
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↗
PubMed1980

A non-secretory phospholipase A2 in the rat pancreas.

The rat pancreas shows a phospholipase activity in the absence of the tryptic activation of the zymogens. We verified that this activity was not due to the zymogen of the secretory phospholipase. Indeed unlike the prophospholipase, the enzyme responsible for the spontaneous phospholipase activity shows a higher catalytic rate at substrate concentrations higher than the critical micelle concentration. This enzyme has a positional specificity of the A2 type and possesses a molecular weight of about 9,500.

Animals↗
PubMed1977

[Spontaneous phospholipase A activity of rat pancreatic homogenates].

Rat pancreas presents a spontaneous phospholipase A activity which appears before trypsin activation at optimal pH 6.5. The responsible enzyme is independent of pancreatic prophospholipase A, as can be seen through experiments done in the presence of trypsin inhibitors. On the other hand, this enzyme is distinct from excretory phospholipase which is more active and whose optimal pH is 8.8. Thermostability and insensibility of spontaneously active phospholipase A to DFP differentiate it from lipase, carboxyl-esterhydrolase and lysophospholipase, respectively.

Animals↗
PubMed1976

Support for the medical profession among the aged.

National survey data are utilized to delineate areas of confidence among the aged in the medical profession. Four key specifying variables were used in the analysis-race, sex, socioeconomic status, and size of community. Findings indicate that confidence in medical leaders is lowest among that group which in past studies has been found to visit the doctor most often: the elderly of low socioeconomic status. This finding suggests that improvement in the medical care received by the aged could be an important first step in restoring the elderly's confidence in medical leaders.

Adolescent↗
PubMed1975

Calcium and pancreatic secretion. I. Subcellular distribution of calcium and magnesium in the exocrine pancreas of the guinea pig.

The distribution of calcium and magnesium has been studied in the acinar cells of the pancreas of the guinea pig. Most of the magnesium was found to be associated with the rough microsomes (probably bound to the ribosomes) and with the postmicrosomal supernate. In contrast, calcium was distributed among all the particulate fractions, primarily the mitochondria, microsomes (especially smooth surfaced), zymogen granules, and the plasmalemma, and was low in the postmicrosomal supernate. Most of the calcium recovered in the particulate fractions was found to be membrane bound. The highest concentrations were found in the membranes of the zymogen granules and in the plasmalemma. By means of control experiments using -45Ca as the tracer, it was established that a considerable redistribution of calcium occurs during homogenization and cell fractionation. At least some of the resulting artifacts were estimated quantitatively and the data were corrected accordingly. The biochemical results were confirmed with the cytochemical antimonate technique carried out on the tissue as well as on isolated fractions. The role of calcium associated with the zymogen granules and with their limiting membranes is discussed in relation to the architecture of the granule and to the functionality of the pancreatic juice.

Animals↗
PubMed1975

The participation of the black aged in voluntary associations.

Racial differences in membership in and attendance of voluntary associations were analyzed for comparable samples of 753 black and 260 white residents of Philadelphia age 65 and over. A hypothesis suggesing aged blacks have higher rates of participation than aged whites was derived from the literature and tested by regression analysis. Potentially confounding variables, e.g., health and socioeconomic status, were entered into the regression equation as controls. The results of the regression analysis indicated the black aged belonged to more associations than the white aged and had higher rates of attendance. Examination of findings previously reported by Kent and Hirsch (1972) indicates part of the difference is due to the greater participation of aged blacks in church-related groups. Implications of the findings are briefly discussed.

Black or African American↗