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Biomedical subjects

F Morel

Publications and source records attributed to F Morel.

At least 19 recordsLinked to original sources
PubMed1992

Modulation of multidrug resistance gene expression in rat hepatocytes maintained under various culture conditions.

P-glycoprotein (P-gp), the multidrug resistance gene product, is overexpressed in normal adult rat hepatocytes under standard culture conditions. We have studied the modulation of P-gp expression in this in vitro model in the presence of both epidermal growth factor and pyruvate, which favor hepatocyte growth, as well as in the presence of either dimethyl sulfoxide (DMSO) or nicotinamide, which favors maintenance of differentiated functions. P-gp overexpression, estimated by northern blotting and doxorubicin-mediated drug efflux analyses, was similarly observed during culture in both standard and proliferating conditions, while it was delayed, but not inhibited, in the presence of DMSO or nicotinamide. These results suggest that the functional P-gp overexpression occurring in rat hepatocytes when exposed to an unfamiliar environment is at least partly not related to cell proliferation or the degree of cell differentiation in vitro.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Purification of human placenta diamine oxidase.

Diamine oxidase (histaminase) is produced at very high levels by the decidual cells of the placenta. The presence of diamine oxidase has been demonstrated in human neutrophils. Purification of human placenta diamine oxidase was performed by four subfractionation steps and led to the isolation of one polypeptide whose molecular weight was 84,000, as assessed by SDS PAGE. Using polyclonal antibodies raised against the purified enzyme, we have demonstrated that the neutrophil diamine oxidase is immunochemically identical to the placental diamine oxidase. Development of immunological methods will be useful for detection and quantitation of diamine oxidase in neutrophils during the inflammation process.

Amine Oxidase (Copper-Containing)↗
PubMed1992

Modulation of human neutrophil function by fibronectin degradation products isolated from cryoglobulins.

The proteolytic fragments of native fibronectin (cryopeptides) complexed to pathological immunoglobulins in cryoglobulins were isolated from the serum of six different patients. Two peptides of 117,000 daltons and 70,000 daltons were purified and characterized by N-terminal amino acid sequencing. The priming effect of the mixture of these two peptides, referred to as cryopeptides, on neutrophil functions, namely the respiratory burst, exocytosis, and Ca2+ release, was investigated. Cryopeptides and cryoglobulins assayed separately did not increase neutrophil respiration or cytosol free calcium concentration; however, both of them induced granule enzyme secretion. Sequential exposure of neutrophils to either cryopeptides or the respective cryoglobulins, and then to N-formyl-methionyl-leucyl-phenylalanine or serum opsonized zymosan, resulted in a synergistic stimulation of O2 uptake compared to the effect of N-formyl-peptides or opsonized zymosan tested separately; Ca2+ release was significantly enhanced by the pretreatment of neutrophils with cryopeptides. These data suggest that cryopeptides and cryoglobulins may play a role in host defense against bacterial infections through neutrophil activation.

Amino Acid Sequence↗
PubMed1992

Neuroendocrine phenotype in lung cancers. Comparison of immunohistochemistry with biochemical determination of enolase isoenzymes.

The authors evaluated methods of recognition of neuroendocrine differentiation in lung cancer because this is thought to bear prognostic value. One hundred forty lung tumors were divided by immunohistochemical analysis using neuroendocrine markers (neuron-specific enolase, Leu7, chromogranin, neural cell adhesion molecules, SL11/14, and Leu19) into two groups of 51 neuroendocrine tumors positive for three neuroendocrine markers and 89 non-neuroendocrine tumors. Biochemical determination of enolase activity and isoenzyme distribution showed that the level of total enolase activity was similar between neuroendocrine and non-neuroendocrine tumors. alpha gamma and gamma gamma enolase isoenzyme percentages were higher in neuroendocrine tumors. A cut-off of gamma enolase % (alpha gamma/2 + gamma gamma) at 14% gave a sensitivity rate of 84% and specificity rate of 97% in separating neuroendocrine and non-neuroendocrine tumors, whereas immunohistochemical analysis using anti-gamma enolase had low specificity (68%) and immunohistochemical analysis with Leu 7 and chromogranin had high specificity (97%) and low sensitivity (37% and 60%) levels for neuroendocrine tumors. The best prediction of neuroendocrine differentiation was obtained using immunohistochemical analysis against neural cell adhesion molecules combined with biochemical estimation of enolase using gamma enolase of 14% and a gamma gamma isoenzyme more than 3%.

Antibodies, Monoclonal↗
PubMed1992

Cholinergic effects on intracellular free calcium concentration in renal corpuscle: role of parietal sheet.

To investigate a possible effect of cholinergic agonists on the renal glomerular function, fura-2 microfluorometric measurements of intracellular free calcium [( Ca2+]i) were performed on single intact glomeruli, single isolated parietal sheets of the Bowman's capsule and single parietal sheet-deprived glomeruli (PS-D glomerulus). Carbachol (10(-4) M), in the presence of 2 mM external calcium, induced a biphasic increase in [Ca2+]i characterized by a sharp initial peak followed by a sustained plateau in the whole glomerulus (delta [Ca2+]i = 177 +/- 13 and 70 +/- 7 nM, respectively; n = 21) and in the parietal sheet (418 +/- 30 and 111 +/- 13 nM, respectively; n = 21). In the PS-D glomerulus (n = 9), the response was less marked and included a barely visible peak (77 +/- 13 nM) and a relatively low plateau (49 +/- 11 nM). In the absence of external calcium, the peak phase was preserved in the three structures, indicating a calcium release from intracellular pools, whereas the plateau, due to the entry of external calcium, was suppressed. These effects were fully inhibited by 10(-4) M of either atropine or pirenzepine, demonstrating the muscarinic nature of the receptors. Dose-response curves showed that the parietal sheet was more sensitive to the physiological agonist (acetylcholine) than to carbachol. A still unexplained difference in sensitivity was noted between peak and plateau, respectively (half-maximal responses were 5 x 10(-6) vs. 5 x 10(-7) M for carbachol and 2 x 10(-7) vs. 3 x 10(-8) M for acetylcholine).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1992

Cholinergic stimulation of phosphoinositide metabolism in isolated rat glomeruli.

Cholinergic effects on kidney function have been observed in some mammals but the intrarenal localization and the cellular mechanisms of these effects are poorly defined to date. The aim of this work was to study the effects of carbachol on phosphoinositide metabolism in freshly isolated rat glomeruli labeled with myo-[3H]inositol. Carbachol rapidly and markedly stimulates phosphoinositide metabolism with a 50% effective concentration of 3 microM. The enormous magnitude of the response is enlightened by the use of 10 mM lithium, which provokes in the presence of the agonist a large accumulation of inositol phosphates and a corresponding depletion of cellular free inositol. The response is inhibited by 85% by pirenzepine, is pertussis toxin insensitive, and shows no desensitization at maximum dose of carbachol up to 40 min of stimulation.

Animals↗
PubMed1992

Localization of urea and ornithine production along mouse and rabbit nephrons: functional significance.

Hydrolysis of arginine into urea and ornithine (Orn) was observed to take place in several segments of the rat nephron including cortical and medullary pars recta of the proximal tubule (PST) and collecting duct (CD). This work was now extended to the adult mouse and rabbit. Representative nephron segments, obtained by microdissection of collagenase-treated kidneys, were incubated with L-[guanido-14C]arginine (216 microM). Addition of urease produced 14CO2 + 2 NH3 from the newly formed urea released in the incubate. 14CO2 was trapped in KOH and counted. In both species, as well as in the rat, the PST was the site of the highest urea + Orn production, with an intensity increasing from cortex to medulla. For other nephron segments, the pattern was not similar in all species. Significant production of urea + Orn was observed in the proximal convoluted tubule and the medullary thick ascending limb in the rabbit, but not in the CD of either the rabbit or the mouse. The functional significance of this urea + Orn production remains unclear. The total amount of urea generated intrarenally by this reaction does not seem sufficient to play a significant role in the urinary concentrating mechanism. It may be assumed that Orn could be further metabolized to polyamines and play a role in maintaining cell integrity and function in the PST, especially in its medullary part, exposed to hypertonicity and poor oxygen supply.

Animals↗
PubMed1991

Activation of O2(-)-generating oxidase in an heterologous cell-free system derived from Epstein-Barr-virus-transformed human B lymphocytes and bovine neutrophils. Application to the study of defects in cytosolic factors in chronic granulomatous disease.

Epstein-Barr-virus-transformed human B lymphocytes (EBV B lymphocytes) stimulated by 4 beta-phorbol 12-myristate 13-acetate exhibit an NADPH-dependent oxidase activity capable of generating the superoxide anion O2-, similar to, but less efficient than that of activated neutrophils. A cell-free system of oxidase activation consisting of a membrane fraction and cytosol from EBV B lymphocyte homogenate supplemented with guanosine 5'-[gamma-thio]triphosphate (GTP[S]), arachidonic acid and Mg2+ was found to be competent in the production of O2-, assessed by the superoxide-dismutase-sensitive reduction of cytochrome c in the presence of NADPH. However, cytochrome c reduction was slow and largely insensitive both to superoxide dismutase, and to iodonium biphenyl, a powerful inhibitor of the oxidase activity in neutrophils. A markedly faster reduction of cytochrome c in the presence of NADPH was obtained with a heterologous system consisting of cytosol from EBV B lymphocytes and bovine neutrophil membranes, GTP[S], arachidonic acid and Mg2+; in this system, reduction of cytochrome c was totally inhibited by superoxide dismutase and iodonium biphenyl. These results show that EBV B lymphocytes contain a substantial amount of cytosolic factors of oxidase activation, and that the limiting factors for O2- production in B lymphocytes are the membrane components of the oxidase complex. The heterologous system of EBV B lymphocyte cytosol and bovine neutrophil membranes provided a rapid and convenient method to diagnose cytosolic defects in autosomal forms of chronic granulomatous disease. In addition, it might be a useful tool to explore the mechanism of action of the cytosolic factors in oxidase activation.

Animals↗
PubMed1991

The superoxide-generating oxidase of phagocytic cells. Physiological, molecular and pathological aspects.

Professional phagocytes (neutrophils, eosinophils, monocytes and macrophages) possess an enzymatic complex, the NADPH oxidase, which is able to catalyze the one-electron reduction of molecular oxygen to superoxide, O2-. The NADPH oxidase is dormant in non-activated phagocytes. It is suddenly activated upon exposure of phagocytes to the appropriate stimuli and thereby contributes to the microbicidal activity of these cells. Oxidase activation in phagocytes involves the assembly, in the plasma membrane, of membrane-bound and cytosolic components of the oxidase complex, which were diassembled in the resting state. One of the membrane-bound components in resting phagocytes has been identified as a low-potential b-type cytochrome, a heterodimer composed of two subunits of 22-kDa and 91-kDa. The link between NADPH and cytochrome b is probably a flavoprotein whose subcellular localization in resting phagocytes remains to be determined. Genetic defects in the cytochrome b subunits and in the cytosolic factors have been shown to be the molecular basis of chronic granulomatous disease, a group of inherited disorders in the host defense, characterized by severe, recurrent bacterial and fungal infections in which phagocytic cells fail to generate O2- upon stimulation. The present review is focused on recent data concerning the signaling pathway which leads to oxidase activation, including specific receptors, the production of second messengers, the organization of the oxidase complex and the molecular defects responsible for granulomatous disease.

Animals↗
PubMed1991

Effect of the aging process on the gender and phenobarbital dependent expression of glutathione S-transferase subunits in brown Norway rat liver.

The effect of age, gender and phenobarbital treatment on the hepatic cytosolic glutathione S-transferase subunit composition was studied in Brown Norway rats. Affinity chromatography followed by reversed phase HPLC was used in order to separate the various glutathione S-transferase subunits. Corresponding steady-state mRNA levels were measured by Northern Blot analysis using cDNA clones hybridizing to mRNA encoding glutathione S-transferase subunits 1/2, 3/4 and 7, respectively. In all the age groups studied (15, 25, 53, 99, 112 and 136 weeks) the total amount of glutathione S-transferase protein was in untreated rats significantly higher in males (132 micrograms/mg cytosolic protein) than in females (91 micrograms/mg cytosolic protein) and significant gender dependent differences in the subunit composition were demonstrated. Aging seemed to be of minor importance in untreated as well as in phenobarbital treated rats. Under control conditions, the subunit composition of male rats between 15 and 136 weeks old consisted of 28, 12, 11 and 49% of subunits 1, 2, 3 and 4 respectively and of female animals of the same age groups of 38, 26, 7 and 30%, respectively. In all the age groups studied phenobarbital administration (45 mg/kg body weight, i.p., once a day for 7 days) doubled total glutathione S-transferase protein in both genders and affected the subunit composition in a significant way, emphasizing the already existing differences between genders. Subunits 1, 2 and 3, especially, were increased in male rats in comparison to females resulting in the observation that levels of glutathione S-transferase subunits studied became higher in males than in their female counterparts. The HPLC results were confirmed by steady-state mRNA analysis. In untreated rats, higher levels of mRNA encoding glutathione S-transferase subunits 1/2 and 3/4 were present in male than in female livers. Phenobarbital treatment increased mRNA levels in both genders. Subunit 7 was never detected. These effects were demonstrated in both young and old rats.

Aging↗
PubMed1991

Regulation of glutathione S-transferase gene expression by phenobarbital in cultured adult rat hepatocytes.

Previous studies, by using Northern blotting analyses, showed that phenobarbital (PB) affects the steady-state mRNA levels of glutathione S-transferase (GST) subunits 1/2, 3/4 and 7 in both conventional cultures of adult rat hepatocytes and co-cultures, with rat liver epithelial cells [Vandenberghe et al., 1989, FEBS Lett. 251, 59-64; Morel et al., 1989, FEBS Lett. 258, 99-102]. To determine whether PB acts at the transcriptional level, nuclear 'run on' experiments using cDNA probes hybridizing to GST subunits 1/2, 3/4 and 7 mRNA were performed on purified nuclei isolated from control and PB treated hepatocytes seeded under conventional and co-culture conditions. Data from this study demonstrate that the increase in steady-state mRNA levels observed in both conventional culture and co-culture after 4 days PB exposure results from an increased transcriptional activity of the GST genes. However, a substantial increase in steady-state mRNA levels in the absence of a commensurate increase in transcriptional activity at 12 days of co-culture, indicates that the barbiturate has also a stabilizing effect in vitro on the GST mRNAs.

Animals↗
PubMed1991

Synthesis and post-translational modifications of an epididymal androgen dependent protein family.

During the annual cycle of the lizard Lacerta vivipara dramatic changes in the secretory activity of the epididymis were observed. These changes and changes in morphology correlate with the plasma and epididymal testosterone concentrations. The secretory proteins contain a major group of immunorelated components referred to as LI to L1X. They consist of a group of nine proteins Mr 19,000 which can be separated according to pI 3.5 to 8.7. Post-translational modifications may be responsible for their pI diversity. All the L proteins are glycosylated (fucose, N-acetylgalactosamine and or N-acetylglucosamine) but only LVI glycosylation was inhibited with tunicamycin. Phosphorylation is unique to LV protein and none of the L proteins are sulfated. All L proteins appeared sequentially during the annual cycle and in organotypic culture when incubated in the presence of testosterone (150, 500, 1000 nM) in a time dependent manner.

Androgens↗
PubMed1991

Cytotoxic chemotherapy induces cell differentiation in small-cell lung carcinoma.

Despite the high response rates resulting from chemotherapy, the majority of small-cell lung cancer (SCLC) patients relapse with chemoresistant tumors. To analyze the phenotypic changes that are precursors of chemoresistant status, and to investigate the role of chemotherapy in these changes, tumor samples from 20 patients, taken before chemotherapy (etoposide, doxorubicin, and cyclophosphamide) and again at the onset of chemoresistance (after at least three courses of chemotherapy), were compared. The histologic changes were minor in 10 of 20 patients, as shown by an increase in cell size; they were major in 10 of 20 patients, with the appearance of mixed composite tumors in which neuroendocrine (NE), epidermoid, and glandular components were mixed. Major changes correlated with a good response to chemotherapy (P = .001). Ultrastructural studies showed an increase in neurosecretory granules and desmosomes, and a high frequency of multidirectional differentiation (45%) when comparison was made with pretherapy samples (10%) (P less than .01). Immunohistochemical (IH) analysis showed an increase in cytokeratin (CK) expression in treated patients, with a different labeling pattern and the expression of higher molecular weight CK. The expression of NE lineage markers (Leu 19, Sy 38, SL 11-14) remained stable, while that of NE differentiation markers (Leu 7, chromogranin) increased in the treated patients. The neuron-specific enolase (NSE) activity remained stable in treated SCLC. Large cells with a more differentiated phenotype and proliferative capacity (as shown by Ki 67 labeling), appeared to be characteristic of treated and secondary chemoresistant SCLC. The acquisition of a more complex phenotype, which correlates with primary response to therapy, implies a drug-induced differentiation in SCLC.

Aged↗
PubMed1991

[Purification of gelatinase secreted by human polynuclear neutrophils].

Gelatinase was purified from DFP treated human neutrophils which have been stimulated by the chemotactic peptide, N-formyl-methionyl-leucylphenylalanine. The secreted gelatinase was purified in two major steps: a gelatinase enriched fraction was recovered after a specific immunoadsorption of contaminant proteins from cytosol and immunoadsorption of proteins from specific or azurophilic granules; then gelatinase was isolated by affinity chromatography and FPLC gel filtration. Some kinetic properties of the Mr 94,000 purified enzyme were investigated.

Catalysis↗
PubMed1991

Soluble CD23 displays T-cell growth enhancing activity.

Soluble CD23 (sCD23) enhances, in a dose-dependent manner, the number of secondary T-cell colonies generated by peripheral blood-derived agar T-colony cells in the presence of phytohaemagglutinin (PHA) and interleukin-2 (IL-2). This effect is not affected by IL-1 or IL-4 but is abolished by an anti-CD23 monoclonal antibody (mAb) or by IgE. No colonies were observed when sCD23 was added to PHA- or IL-2-free cultures. sCD23 also enhanced the cloning frequency of primary T-colony cells in a limiting dilution assay. These data provide the first direct evidence that sCD23 recruits T-cell clones in peripheral blood-born T cells and may be involved indirectly in the regulation of IgE response.

Antigens, Differentiation, B-Lymphocyte↗