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Biomedical subjects

J Marchand

Publications and source records attributed to J Marchand.

At least 19 recordsLinked to original sources
PubMed1992

Synthesis of new hydrophilic microspheres: optimized carriers for microparticle-enhanced nephelometric immunoassays.

To optimize antigen-antibody reactions, we have synthesized chemically well-defined hydrophilic microspheres. Proteins or haptens were covalently linked to these carriers. When the microsphere conjugates were agglutinated by the corresponding antiserum, the size of the complex artificially increased during the immunological reaction. After optimizing various parameters such as the hydrophilic character, repulsion charges, and amount of antigen coupled to the microspheres, we developed a rapid and sensitive immunoassay based on laser light scattering by the complexes.

Animals↗
PubMed1992

Preservation of the anomeric specificity of glucose-induced insulin release in partially pancreatectomized rats.

Attenuation, suppression or even inversion of the normal preference of glucose-stimulated insulin release for the alpha-anomer of the hexose was recently proposed to represent a feature of Beta-cell glucotoxicity in Type 2 (non-insulin-dependent) diabetes mellitus. Since recent reports emphasize the possible significance of Beta-cell secretory hyperactivity as a determinant of such a glucotoxicity, the anomeric specificity of glucose-induced insulin release was examined in normoglycaemic partially pancreatectomized rats. About 80-85% of the pancreas was removed, the animals then being given sucrose via their drinking water up to the time of killing. In these animals, alpha-D-glucose was more efficient than beta-D-glucose in stimulating insulin release from the perfused pancreas, the alpha/beta ratio in insulin output not being significantly different from that found in control rats. It is concluded, therefore, that the anomeric malaise, taken as a manifestation of Beta-cell glucotoxicity, it attributable to hyperglycaemia rather than to Beta-cell secretory hyperactivity.

Animals↗
PubMed1992

Two-site direct immunoassay specific for active renin.

A sensitive immunoradiometric assay, without an enzymatic step and specific for active human renin, was developed with use of two monoclonal antibodies (MAbs). In this assay system, the first MAb was coupled to magnetic beads (Magnogel); the second one, directed against the active form of the enzyme, was radiolabeled with 125I. The specificity of this assay was demonstrated in experiments measuring the active plasma renin concentration in the presence or absence of inactive renin. The assay, performed in two steps, was sensitive enough to detect 0.9 pg of renin per tube (3.5 ng/L). Intra- or interassay CVs were < 10%. Concentrations of active plasma renin measured in normotensive subjects were between 7 and 40 ng/L.

Adult↗
PubMed1992

Direct, simplified, and sensitive assay of angiotensin II in plasma extracts performed with a high-affinity monoclonal antibody.

A very simple, fast, and sensitive RIA of angiotensin (Ang) II has been developed, based on a monoclonal antibody with high affinity and specificity, making possible the direct measurement of circulating Ang II in human plasma after solid-phase extraction. The purified monoclonal antibody 4D8 has an association constant of 1.3 x 10(11) L/mol with Ang II and a cross-reactivity of < 1% for Ang I. The assay can detect as little as 0.8 fmol of Ang II in 2 mL of plasma and is not influenced by the presence of Ang I. Analytical recoveries between 112% and 116% were obtained for Ang II added to human plasma at physiological concentrations. Comparison of the RIA with a reversed-phase, high-performance liquid chromatographic method followed by RIA to measure Ang II in human plasma samples from normal and hypertensive subjects--and from normotensive subjects before and after an acute inhibition of angiotensin-converting enzyme with captopril (50 mg)--showed a high degree of correlation (r2 = 0.93) between the two methods.

Angiotensin II↗
PubMed1991

Effects of glimepiride and glibenclamide on insulin and glucagon secretion by the perfused rat pancreas.

Glimepiride and glibenclamide act apparently in a closely comparable manner upon both insulin and glucagon release. Except for the decreased efficiency of D-glucose in suppressing glucagon release after a prior exposure of the pancreas to the hypoglycemic sulfonylureas, no evidence was obtained to suggest that a positive glucagonotropic action of the latter drugs would counteract their hypoglycemic action, as mainly attributable to stimulation of insulin release.

Animals↗
PubMed1991

Altered anomeric specificity of glucose-induced insulin release in rabbits with duct-ligated pancreas.

Ligation of the pancreatic duct in rabbits provokes a decrease in the insulin and glucagon content of the pancreas, and may lead to chronic hyperglycemia. The insulin secretory behavior of the perfused pancreas is perturbed in duct-ligated animals, and this is illustrated in several respects: 1. The steady-state insulin output evoked by L-leucine (10 mM) is higher in duct-ligated than control rabbits; 2. In the presence of the amino acid, the response to D-glucose is characterized by a delayed onset, the absence of an early secretory peak, and a sluggish return towards basal value upon removal of the hexose from the perfusate; and 3. Whereas control rabbits display a higher secretory response to alpha- than beta-D-glucose, such is no more the case in duct-ligated rabbits. The perturbation of the anomeric specificity in secretory response is most obvious in diabetic duct-ligated rabbits, in which case beta-D-glucose stimulates insulin release more efficiently than alpha-D-glucose. In both control and duct-ligated rabbits, however, the alpha-anomer is more potent than the beta-anomer in suppressing leucine-stimulated glucagon secretion. These findings are compatible with the view that chronic hyperglycemia leads to alteration in the anomeric preference of the pancreatic B-cell for alpha-D-glucose, possibly as a result of the nonenzymatic glycation of glycolytic enzymes in insulin-producing, but not glucagon-producing, islet cells.

Animals↗
PubMed1991

Detection and typing of human papillomaviruses in cervical smears by an original application of the polymerase chain reaction.

The detection and typing of human papillomaviruses on cervical smears were performed by means of a new application of the polymerase chain reaction allowing easier and faster detection of the amplification product. This application consisted of a combination of two series of amplifications and the use of primers labelled with biotin and with 125 iodine on a reporter group for the second amplification. The final amplification product was detected by counting the radioactivity after incubation of the media in avidin-coated tubes. This test was compared with conventional methods of detection by electrophoresis and Southern blot and its specificity was confirmed. The study of a series of 52 patients demonstrated a higher prevalence of type 16 in relation to type 6/11 and 18 and a correlation between the degree of dysplasia and the frequency of oncogenic types 16 and 18. This new application could facilitate studies of the prevalence of HPV in large series of cervical smears.

Avidin↗
PubMed1991

Attenuated anomeric difference of glucose-induced insulin release in the perfused pancreas of diazoxide-treated rats.

Mild hyperglycemia was induced in normal rats by oral administration of both diazoxide and D-glucose. After 48 hours of such a treatment, the insulin and glucagon secretory responses of the perfused pancreas to alpha- and beta-D-glucose (3.3 mM) were examined in the presence of 10.0 mM L-leucine. The output of insulin, but not that of glucagon, and the perfusion pressure were higher in treated than control rats. The alpha-anomer of D-glucose was a more potent insulin secretagogue than beta-D-glucose in both control and treated rats. However, the alpha/beta ratio in insulin output was twice higher in control than treated rats. By analogy with other experimental models of diabetes, the attenuation in the anomeric difference of glucose-stimulated insulin output in the treated rats could reflect an altered secretory response to alpha- rather than beta-D-glucose. These findings suggest that hyperglycemia provokes, as a function of its severity and duration, first attenuation and then suppression, if not inversion, of the anomeric preference for alpha-D-glucose in insulin release. They are also compatible with the hypothesis that the anomeric malaise, associated with B-cell glucotoxicity, is caused by a progressive accumulation of glycogen in this cell.

Administration, Oral↗
PubMed1991

Polyacrylic microspheres as a solid phase for microparticle enhanced nephelometric immunoassay (NEPHELIA (R)) of transferrin.

Polyfunctional hydrophilic microspheres (MS) can be produced by copolymerisation with gamma-irradiation of acrylic monomers. Transferrin (TRF) can be covalently bound to these MS by reaction between aldehyde groups of the MS and primary amino groups of the protein. MS-TRF conjugates thus obtained are agglutinated by specific antiserum and this agglutination is inhibited by free TRF. Agglutination and inhibition are quantified by measurement of the light scattered by MS-TRF conjugate clusters with a specially designed nephelometer, a process designated as microparticle enhanced nephelometric immunoassay (NEPHELIA (R)) for TRF. Recovery, correlation and reproducibility studies, simultaneously performed in three different laboratories, show that this TRF immunoassay is accurate for a large concentration range. NEPHELIA (R) may appear as an alternative method for a large variety of molecules.

Humans↗
PubMed1991

Microparticle-enhanced nephelometric immunoassay (Nephelia) for immunoglobulins G, A, and M.

Covalent binding of gamma chains of IgG, whole IgA, and mu chains of IgM on polyfunctional hydrophilic microspheres (MS) yields MS-Ig conjugates, usable as reagents in new microparticle-enhanced nephelometric immunoassays (Nephelia). The principle of the assays is inhibition by free analyte (IgG, IgA, and IgM) of agglutination of the MS-Ig conjugate with specific antiserum, the light scattered by the aggregates being measured with a nephelometer. The immunoglobulin assays developed are easy to perform (single-step assays, no washing or phase separation) and sensitive (high dilution of biological samples to exclude interferences and pretreatment). Analytical recovery results (95.4-101.2%) and correlations with generally used commercial assays (r = 0.86-0.98) indicate that the assays are accurate for large concentration ranges of immunoglobulins. Precision study gives CVs = 2.8-9.6%. Nephelia appears to be useful for quantifying a large variety of biological molecules.

Humans↗
PubMed1990

Stimulus-secretion coupling of arginine-induced insulin release. Resistance of arginine- and ornithine-stimulated glucagon and insulin release to D,L-alpha-difluoromethylornithine.

In the isolated perfused rat pancreas, D,L-difluoromethylornithine, tested at a concentration of 3 mmol/L, failed to affect the release of glucagon and insulin caused, over 15 min stimulation, by either L-arginine or L-ornithine (2.0, 5.0 or 10.0 mmol/L) in the presence of either 3.3 or 5.6 mmol/L D-glucose. The inhibition of ornithine decarboxylase also failed to affect the release of glucagon provoked by either L-leucine (2 or 3 mmol/L) or L-glutamine (2 mmol/L) and the secretion of insulin stimulated by a rise in glucose concentration from 5.6 to 10.6 mmol/L. These data are interpreted to suggest that the rapid generation of polyamines from either L-arginine or L-ornithine does not play any significant role in the immediate glucagonotropic and insulinotropic action of these cationic amino acids.

Animals↗
PubMed1990

Lectin binding to injured corneal endothelium mimics patterns observed during development.

Fluorochrome conjugated lectins were used to observe cell surface changes in the corneal endothelium during wound repair in the adult rat and during normal fetal development. Fluorescence microscopy of non-injured adult corneal endothelia incubated in wheat-germ agglutinin (WGA), Concanavalin A (Con A), and Ricinus communis agglutinin I (RCA), revealed that these lectins bound to cell surfaces. Conversely, binding was not observed for either Griffonia simplicifolia I (GS-I), soybean agglutinin (SBA) or Ulex europaeus agglutinin (UEA). Twenty-four hours after a circular freeze injury, endothelial cells surrounding the wound demonstrated decreased binding for WGA and Con A, whereas, RCA binding appeared reduced but centrally clustered on the apical cell surface. Furthermore, SBA now bound to endothelial cells adjacent to the wound area, but not to cells near the tissue periphery. Neither GS-I nor UEA exhibited any binding to injured tissue. By 48 h post-injury, the wound area repopulates and endothelial cells begin reestablishing the monolayer. These cells now exhibit increased binding for WGA, especially along regions of cell-to-cell contact, whereas, Con A, RCA and SBA binding patterns remain unchanged. Seventy-two hours after injury, the monolayer is well organized with WGA, Con A and RCA binding patterns becoming similar to those observed for non-injured tissue. However, at this time, SBA binding decreases dramatically. By 1 week post-injury, binding patterns for WGA, ConA and RCA closely resemble their non-injured counterparts while SBA continues to demonstrate low levels of binding. In early stages of its development, the endothelium actively proliferates and morphologically resembles adult tissue during wound repair.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Stimulus-secretion coupling of arginine-induced insulin release. Functional response of islets to L-arginine and L-ornithine.

L-Arginine and L-ornithine stimulate insulin release from pancreatic islets exposed to D-glucose. This coincides with an increased outflow of 86Rb and 45Ca from prelabelled islets and an increased net uptake of 45Ca by the islets. In the presence of D-glucose, L-lysine stimulates insulin secretion to the same extent as L-arginine or L-ornithine, but the hormonal release is not further enhanced by combinations of these cationic amino acids. L-Arginine or L-ornithine failed to enhance insulin release evoked by either L-leucine or 2-ketoisocaproate. The inhibitor of ornithine decarboxylase D,L-alpha-difluoromethyl ornithine failed to affect the metabolism and insulinotropic action of D-glucose in pancreatic islets, and only caused a partial inhibition of the secretory response to either L-arginine or L-ornithine. The latter amino acids inhibited modestly but significantly D-glucose utilization and oxidation by pancreatic islets. These and complementary findings suggest that the secretory response to L-arginine and L-ornithine is not attributable to any major change in the overall oxidative catabolism of nutrients, but involves mainly a biophysical component, such as the depolarization of the plasma membrane by these cationic amino acids.

Animals↗
PubMed1988

Effects of L-leucine, its 2-keto acid metabolite and its non-metabolized analogue on rat tumoral islet cell function.

L-Leucine and 2-ketoisocaproate stimulated insulin release from perifused rat tumoral islet cells (RINm5F line). The secretory response coincided with an increase in the intracellular ATP/ADP ratio, a stimulation of 45Ca outflow from cells perifused in the presence of extracellular Ca2+, and an increase in 32P efflux from cells prelabelled with radioactive orthophosphate. In contrast to D-glucose, however, L-leucine or 2-ketoisocaproate failed to decrease 86Rb outflow, to inhibit 45Ca outflow from cells perifused in the absence of Ca2+ and to enhance the labelling of inositol-containing phospholipids in cells exposed to myo-[2-3H]inositol. These findings suggest that D-glucose, L-leucine and 2-ketoisocaproate exert dissimilar effects on the subcellular distribution of adenine nucleotides and/or 86Rb. The non-metabolized analogue of L-leucine, 2-aminobicyclo[2.2.1]heptane-2-carboxylic acid (BCH), also caused an initial stimulation of insulin release and 32P efflux, but this was soon followed by a severe and irreversible inhibition of insulin output, associated with a permanent enhancement of 86Rb outflow. The dual ionic and secretory response to BCH is interpreted in the light of its dual effect on the catabolism of endogenous amino and fatty acids, and raises the view that BCH could be used to interfere with the function of insulinoma cells.

Adenine Nucleotides↗
PubMed1987

32P, 86Rb+ and 45Ca2+ handling by tumoral insulin-secreting cells (RINm5F line).

In perifused tumoral islet cells (RINm5F line), which were prelabelled with either [32P]orthophosphate, 86Rb+ or 45Ca2+, the administration of D-glucose (1.4, 2.8 or 16.7 mM) increased the efflux of 32P, decreased the outflow of 86Rb, increased slightly the efflux of 45Ca from cells perifused in the presence of Ca2+, and decreased modestly the outflow of 45Ca from cells perifused in the absence of Ca2+. D-glucose also stimulated the net uptake of 45Ca2+. When Ba2+ (2 mM) was used, in the absence of Ca2+, instead of D-glucose as an insulin secretagogue, the efflux of 32P was little affected, but the outflow of 45Ca was dramatically increased. These changes are qualitatively similar to those occurring in normal islet cells. Nevertheless, the ionic response to D-glucose appeared, as a rule, less marked in tumoral than normal islet cells. Moreover, the concentration-response relationship was shifted to a lower range of hexose concentrations in the RINm5F cells.

Animals↗