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Biomedical subjects

M Daumas

Publications and source records attributed to M Daumas.

5 recordsLinked to original sources
PubMed2001

Insulin and glucagon impairments in relation with islet cells morphological modifications following long term pancreatic duct ligation in the rabbit--a model of non-insulin-dependent diabetes.

Plasma levels of glucose, insulin and glucagon were measured at various time intervals after pancreatic duct ligation (PDL) in rabbits. Two hyperglycemic periods were observed: one between 15-90 days (peak at 30 days of 15.1 +/- 1.2 mmol/l, p < 0.01), and the other at 450 days (11.2 +/- 0.5 mmol/l, p < 0.02). The first hyperglycemic episode was significantly correlated with both hypoinsulinemia (41.8 +/- 8 pmol/l, r = -0.94, p < 0.01) and hyperglucagonemia (232 +/- 21 ng/l, r = 0.95, p < 0.01). However, the late hyperglycemic phase (450 days), which was not accompanied by hypoinsulinemia, was observed after the hyperglucagonemia (390 days) produced by abundant immunostained A-cells giving rise to a 3-fold increase in pancreatic glucagon stores. The insulin and glucagon responses to glucose loading at 180, 270 and 450 days reflected the insensitivity of B- and A-cells to glucose. The PDL rabbit model with chronic and severe glycemic disorders due to the predominant role of glucagon mimicked key features of the NIDDM syndrome secondary to exocrine disease.

Animals↗
PubMed1990

Calcium phosphate deposits in domes of human pancreatic adenocarcinoma (Capan-1) cell cultures.

Human pancreatic cells of the Capan-1 line form domes in culture during the stationary growth stage. The domes are thought to be a result of the transport of water and electrolytes by the Capan-1 cells. In older Capan-1 cultures, the epithelial sheets formed thickenings from several layers of cells of which the outermost ones were joined by tight type junctions. In the intracellular space, deposits of insoluble calcium salts were observed. Culture of Capan-1 cells in the presence of fibroblasts prolonged survival of the cultures with intact domes for more than 80 days. The Capan-1 cells proliferated forming multilayers and closed cavities which we called super-domes. X-ray spectrometry and electron diffraction analysis showed that the abundant deposits inside these cavities consisted of calcium phosphate in an apatite structure. The number of these deposits increased with time in culture, and they appeared to be formed at the sites of contact with an extracellular matrix consisting of cell debris. Deposits were not observed within the culture medium. Cells from domes were stained cytochemically for ATPases and alkaline phosphatases and examined by light and electron microscopy. The Capan-1 cells surrounding the domes were differentiated, polarized cells containing placental type alkaline phosphatases on their apical membranes and Ca2(+)-ATPases on their basolateral membranes. These enzymes were thought to play a role in the accumulation of phosphate and Ca2+ ions in the dome cavities, which then formed crystals in the presence of organic compounds produced by lysis of cells of the deepest layers of the super-domes. The crystals of hydroxyapatite observed in standard Capan-1 cell cultures and those cocultured with fibroblasts were assumed to be a result of transepithelial transport of Ca2+ and phosphate ions by these cells.

Adenocarcinoma↗
PubMed1989

Enhanced membrane phospholipid metabolism in human pancreatic adenocarcinoma cell lines detected by low-resolution 1H nuclear magnetic resonance spectroscopy.

The low-resolution proton nuclear magnetic resonance (NMR) spectra of human pancreatic adenocarcinomas maintained in nude mice and in culture exhibit characteristic features. First, the high values of longitudinal (T1) and transverse (T2) relaxation times were attributed to disturbances in the exchange of ions and water molecules in cancerous cells. Second, a new peak situated at about 1.8 +/- 0.2 ppm from the peak of tissular water was observed. It was higher in spectra recorded from the proliferative peripheral zone of the tumor than from the central necrotic zone and was not observed in healthy control pancreatic tissue. Histological examination of the xenografts by transmission electron microscopy indicated intense phospholipid metabolism with marked development of the plasma membrane and the presence of numerous secretory granules, lysosomes, and multivesicular bodies in the cytoplasm. The new 1H NMR low-resolution peak was thought to reflect an increase in membrane viscosity stemming from alterations in the structure and metabolism of membrane phospholipids. Whatever its origin, the 1.8-ppm peak is a particular feature of cancerous pancreatic cells, which should be readily detectable by NMR in vivo.

Adenocarcinoma↗
PubMed1988

Differentiation of the human pancreatic adenocarcinoma cell line (Capan-1) in culture and co-culture with fibroblasts dome formation.

This study was designed to investigate differentiation of human pancreatic duct carcinoma cells (Capan-1) in vitro. Observations on live cells, and electron microscopic examination, together with enzymological and immunocytochemical methods, have demonstrated that these cells differentiate spontaneously at an early stage. The cells are seen to be joined by apical junctions. High ATPase activity can be detected in the basolateral membranes, and the cells secrete a gastric type mucin (MI) bearing acidic groups. During differentiation in culture, they form domes which are thought to be the morphological expression of trans-epithelial transport of water and electrolytes. This particular structure is transitory, since after 6 days in culture all the cells lose their adhesivity, and form into floating cords. Co-culture of Capan-1 cells and human, nude mice or chick embryo fibroblasts leads to a higher degree of differentiation of epithelial cells, reflected by the earlier appearance of numerous domes. In addition, the anchorage of Capan-1 cells to fibroblasts prevents retraction of the monolayer, and enables the domes to be maintained in the cultures for more than one month. These findings suggest that Capan-1 cells are able to carry out trans-epithelial movement of water and electrolytes. It is suggested that excretion of ions (bicarbonate and/or chloride) is preserved after transformation of pancreatic duct cells. Mucins (MI) and the recently described VIP receptor sites are also thought to play a part in these exchange processes.

Adenocarcinoma↗