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J F Launay

Publications and source records attributed to J F Launay.

32 records · Page 2Linked to original sources
PubMed1983

Rat pancreas actin: purification and characterization.

Isolation of rat pancreas actin was performed with three different technics: polymerization-depolymerization method, affinity chromatography on DNase I-Sepharose 4B or ion exchange chromatography on DEAE-cellulose. Inhibition of DNase I activity, localization by SDS polyacrylamide slab gel electrophoresis and presence of microfilaments allowed its identification. Affinity process led us to obtain actin which kept inhibitory activity (30,000 U per mg) on DNase I when using vacuum dialysis. Actin eluted from DEAE-cellulose associated reversibly in 50-70 A microfilaments in the presence of phalloidin, was pure at 95% and had a satisfactory inhibitor activity (77,000 U per mg).

Actins↗
PubMed1983

Stimulation of intestinal chromatin template activity by dietary carbohydrates in adult rats.

Oral administration of a 70% solution of sucrose to starved adult rats resulted 1 h after feeding in a 3.5-fold stimulation of intestinal chromatin template activity assayed in vitro using E. coli RNA polymerase. A similar stimulatory effect was observed with fructose, whereas glucose exhibited a weaker effect, indicating that the nature of the ingested carbohydrate may have a direct effect on the extent of intestinal chromatin template activation.

Animals↗
PubMed1981

Modified protein kinase activity and isozyme distribution in adenocarcinoma of the human colon.

Protein kinase activity and histone kinase isozyme distribution have been determined in soluble extracts of adenocarcinoma of the human colon and compared to adjacent normal mucosa. The results show an enhancement in endogenous protein kinase activity and the presence of an additional isozyme (PKI) for histone kinase activity in the tumour tissue. PKI activity exhibited a peculiar behaviour in comparison to the isozyme. PKII present in both carcinoma and normal mucosa after dialysis of the soluble extracts. It is suggested that alteration of intracellular regulatory processes involved in PKI activity might be related to the maintenance of the proliferate state in human colon carcinoma.

Adenocarcinoma↗
PubMed1980

Stimulus secretion coupling: role of cyclic GMP and calcium in the regulation of secretion from rat exocrine pancreas.

In rat pancreatic fragments, stimulation of amylase and labeled protein release by carbachol, caerulein, and ionophore A 23187 results within minutes in a short rise in cyclic GMP levels. Cyclic AMP levels do not change significantly. The secretory response elicited by each secretagogue is not modified when combined in pairs. Under intracellular calcium depleting conditions, both the cyclic GMP and the secretory responses to secretagogues are inhibited in parallel, suggesting a good correlation between both processes. Furthermore, 8-Bromocyclic GMP induces pancreatic secretion, but to a lesser extent, and fails to alter the increase in secretion caused by the various secretagogues. However, other agents such as imidazole, ascorbic acid, phenylhydrazine, and sodium azide also increase cyclic GMP levels but fail to stimulate pancreatic secretion. On the other hand, dibutyryl cyclic AMP also stimulates amylase and labeled protein discharge and potentiates the increase caused by cabachol, caerulein, and ionophore A 23187. These results do not permit conclusions regarding a cause and effect relationship between cyclic GMP and secretion. A role for calcium seems to be the most likely.

Amylases↗
PubMed1978

Pancreatic acinar cell changes induced by caerulein, vinblastine, deuterium oxide, and cytochalasin B in vitro.

The effects of caerulein, vinblastine (VB), deuterium oxide (D2O), and cytochalasin B upon both the structure and the function of the pancreatic acinar cell were studied in vitro using rat pancreatic fragments. Caerulein (10 ng. per ml.) stimulates the release of enzymes and induces the appearance of numerous exocytotic images at the apical part of the acinar cell. Whereas VB (5.10(-5) M) and D2O (55 per cent) inhibit the secretory response to caerulein, they do not affect the general ultrastructure of the acinar cell. Prolonged incubation in the presence of VB provoked the disappearance of microtubles and the massive precipiation of microcrystalline material in all parts of the cytoplasmic space. Numerous microtubules were found in the acinar cell after exposure to D2O. Although VB and D2O do not alter the microfilamentous network localized at the apical part of the cell, cytochalasin B (2.10(-5) M) disrupts it. This drug decreases the number of microvilli projecting into the enlarged acinar lumen. Whether cytochalasin B is used alone or in association with VB or D2O, it inhibits the secretory response to caerulein and prevents the process of exocytosis. Thus, it is suggested that microfilaments act on a later step of the secretory cycle, i.e., exocytosis, than microtubules. The probable site of action of these latter organelles in the migration of zymogen granules toward the acinar lumen is discussed.

Animals↗
PubMed1977

On the secretagogue effect of dibutyryl cyclic AMP in the rat exocrine pancreas.

DbcAMP greater than or equal to 0.1 mM induces the discharge of exportable enzymes from rat pancreas fragments incubated in vitro. This effect is qualitatively similar to the action of physiological secretagogues acting via hormone receptors: 1) it is accompanied by the appearance of exocytotic images at the acinar cell apex; 2) it is energy dependent but energy supply is low while that required for the carbamylcholine or caerulein response is high and can only be afforded by oxidative phosphorylation; 3) it is calcium dependent, but no alteration of inward or outward calcium movement can be observed; 4) it is altered by agents known to disrupt the microfilamentous microtubular system [41]. However, the secretory response to DbcAMP is quantitatively less than that obtained with hormonal stimuli. A damaging effect of DbcAMP on pancreatic acinar cells is ruled out on histological and biochemical grounds: there is no significant leakage of LDH; protein synthesis, 2-deoxy-D-glucose and L-leucine uptake are unaltered. The secretagogue effect of DbcAMP is reversible, dose-related and specific. It is not mediated by neurotransmitter release or by interaction with their receptors. The evidence presented points to a direct interaction of DbcAMP on the pancreatic acinar cell and suggests the last step of the secretory cycle as the most probable site of action of the nucleotide derivative.

Adrenergic Agonists↗
PubMed1977

Establishment of serum based essentiall free of proteolytic activity for the culture of mouse pancreatic islets.

The present study demonstrates that a) serum based culture medium degrades 125I inhibits its proteolytic activity leading to the recovery of more insulin secreted by islets cultured in the presence of high glucose concentration alone or with glucagon; c) aprotinin also favoured the accumulation of secreted insulin by protecting the hormone from a residual degradative capacity of the hear treated serum.

Animals↗
PubMed1977

Intrahepatic transplantation of pancreatic islets in the rat.

Islets of Langerhans from isogeneic donor rats were transplanted directly into the hepatic parenchyma of recipients which had been made severely diabetic by streptozotocin (glycaemia ranging between 400 and 1090 mg%). Complete control lasting up to 13 months was achieved in 65% of recipients by using 600-800 islets. Following intravenous glucose administration, each rat responded similarly to normal rats with a rapid but reduced release of insulin. Cytoimmunofluorescence and electron microscopic studies demonstrated the presence of both functional insulin and glucagon cells, within the transplanted islets. It is suggested that for various reasons direct intrahepatic transplantation might become the preferred method for islets.

Animals↗