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M Dufresne

Publications and source records attributed to M Dufresne.

46 records · Page 3Linked to original sources
PubMed1988

Distinct activation of Na+-H+ exchange by gastrin and CCK peptide in acini from guinea pig.

The effect of cholecystokinin (CCK)-gastrin family peptides (caerulein, unsulfated gastrin-17, and pentagastrin) and secretin in activating amiloride-sensitive 22Na uptake were investigated in guinea pig pancreatic acini. Secretin had no effect, but CCK-gastrin peptides stimulated the amiloride-sensitive 22Na uptake. The effect of caerulein was inhibited by dibutyryl guanosine 3',5'-cyclic monophosphate (cGMP) and asperlicin, indicating that activation of the Na+-H+ antiport caused by caerulein is mediated by CCK receptors. The effect of gastrin was dibutyryl cGMP and asperlicin insensitive, whereas the effect of pentagastrin was inhibited by the CCK antagonists but with a low affinity, indicating that the effect of gastrin and that of pentagastrin was CCK receptor independent. The calcium ionophore A23187 caused an increase in amiloride-sensitive 22Na uptake. However, the effect of caerulein, which increased internal calcium concentration, was not modified after depletion of intracellular calcium, and that of CCK-gastrin family peptides was not dependent on external calcium concentration. Activation of amiloride-sensitive 22Na uptake was also induced by 12-O-tetradecanoylphorbol 13-acetate and 1-oleoyl-2-acetyl-glycerol. Activation of protein kinase c may be involved in the mechanism of caerulein or gastrin in activating the Na+-H+ exchange.

Amiloride↗
PubMed1987

Studies on immunoassays of peptide factors. III. Gastrin/iso-1-cytochrome C as immunogen for raising anti-gastrin antisera.

Iso-1-cytochrome c contains in penultimate position of its sequence a cysteine residue which in analogy to the known tertiary structures of cytochromes c should be exposed on the surface of the protein. Its selective reaction with N alpha-maleoyl-beta-alanyl-human-little-gastrin-I-[2-17] led to a well characterized and homogeneous gastrin conjugate to be used as immunogen in rabbits. The antisera raised by this procedure exhibited a degree of specificity for the hormone gastrin parallel to that of the gastrin receptor. This is clearly documented by comparison of the immune crossreactivities of gastrin-peptides of increasing chain length and of fragments corresponding to various regions of the hormone molecule with their biological activity. The immune response provoked in the animals by the use of an homogeneous immunogen was found to be highly reproducible in terms of specificity of the antigastrin antibodies.

Binding, Competitive↗
PubMed1987

Studies on immunoassays of peptide factors. IV. New synthesis of a gastrin/peroxidase conjugate.

We have shown that structurally well-defined homogeneous maleoyl-peptides are synthetically accessible. These anchor-modified peptide derivatives allow their selective covalent linkage to thiol-containing proteins via the maleimide-thiol procedure. Correspondingly mercaptosuccinylated horseradish peroxidase was reacted with N alpha-maleoyl-beta-alanyl-human-little gastrin-I-[2-17] to produce the gastrin/peroxidase conjugate in good yields at 1:1 stoichiometry. The conjugate exhibited full enzymatic activity and identical binding affinity to antigastrin antisera as the parent gastrin. This approach proved to be well suited for the preparation of enzyme labeled peptide factors as tracers for immunoassays.

Enzyme-Linked Immunosorbent Assay↗
PubMed1985

The amiloride sensitive Na+/H+ antiport in guinea pig pancreatic acini. Characterization and stimulation by caerulein.

Amiloride and analogs decrease the initial rate of 22Na+ uptake by dispersed acini from guinea pig pancreas in a dose-dependent manner. The initial rate of amiloride-sensitive 22Na+ uptake depends on external Na+ and H+ concentrations and on internal pH. These results provide evidence for the existence of a Na+/H+ antiport in pancreatic acinar cells. Caerulein, a cholecystokinin analog, stimulates the activity of the Na+/H+ antiport.

Amiloride↗
PubMed1984

Asbestos-related fibrin formation in human plasma.

This study was designed to test the hypothesis that asbestos is responsible for the activation of clotting, for the reduction in activity of clotting factors and for the formation of fibrin when human plasma is exposed to asbestos chrysotile fibers in vitro. The recalcification time was accelerated in the early phase and was found to be greatly prolonged at 24 hours. The activated partial thromboplastin time showed marked changes at 24 hours only. One group of clotting factors, consisting of factors V, IX and X, showed the greatest decrease in their plasmatic activity. The factors least changed were factors XII and VIII; the other clotting factors were found in between these groups. Histologic examination demonstrated fibrin fibers in close proximity to the asbestos. Thus, chrysotile asbestos fibers activate clotting with the subsequent decrease in activity of some coagulation factors resulting in the formation of fibrin.

Adult↗
PubMed1984

Advanced prostatic adenocarcinoma: biological aspects and effects of androgen deprivation achieved by castration or agonistic analogues of LHRH.

Twenty-nine patients with advanced prostatic adenocarcinoma were evaluated clinically, biochemically and radiologically and randomly assigned either to orchiectomy or to medical treatment. The latter consisted of the chronic administration of an LHRH agonistic analogue by parenteral and/or intranasal routes. Plasma testosterone levels fell to castrate values and remained so for as long as the follow-up lasted (24 months); estrogen levels fell as well. No change in basal cortisol, thyroxine or prolactin levels was noticed. A decrease in prostate size and improvement in prostatism occurred in all. Bone pain and radiology conventionally or by isotopic scanning, did not parallel the improvement seen in the primary disease locus. Similarly, the changes in alkaline phosphatase were minimal when compared to that of prostatic acid phosphatase. Both enzymes increased prior to or concurrently with relapse of the disease. The longest remission and survival was seen in patients with low enzyme levels, non diffuse bone metastases and high degree of tumor differentiation. Chronic use of agonistic analogues of LHRH induces effective castration in men with prostatic carcinoma and can replace orchiectomy or estrogen administration. The quantitative analysis of androgen receptors (AR) in subcellular fractions of tumor cells; the use of techniques to enhance the number of AR in the cytosol; and the determination of the type II/I regulatory subunit of protein kinase may be used to identify hormone independent clones and spare patients of unnecessary procedures.

Acid Phosphatase↗
PubMedDate not supplied

Interleukin-6 regulation of CCK/gastrin receptors and amylase secretion in a rat pancreatic acinar cell line (AR4-2J).

In necrotizing pancreatitis a high interleukin-6 (IL-6) serum level has been proposed as a prognostic criterium. However, literature does not report any information about the role of IL-6 in the function of pancreatic acinar cells. Cholecystokinin, gastrin binding, amylase release and intracellular calcium measurement were performed on a rat pancreatoma cell line, AR4-2J, which has been recognized as a useful tool for studies on the long-term regulation of pancreatic acinar cells. The addition of IL-6 (400 pM) for 48hrs to the AR4-2J cells induced no change in the binding affinities but there was a 2 fold increase in the binding capacity of cholecytokinin (CCKA R) and gastrin (CCKB R) receptors. Although IL-6 treatment did not change directly the secretory capacity and did not activate the intracellular calcium mobilization of AR4-2J, it indirectly increased the sensitivity of the cells to the stimulation of amylase release and the intracellular calcium mobilization by cholecystokinin and gastrin. It is most likely this effect was due to the IL-6-induced increase in the numbers of CCKA R and CCKB R. Therefore this report suggests that the cytokine IL-6 acts on the CCK regulation of pancreatic enzyme secretion.

Amylases↗