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F Morel

Publications and source records attributed to F Morel.

At least 163 records · Page 9Linked to original sources
PubMed1989

Na/Ca exchangers in collecting cells of rat kidney. A single tubule fura-2 study.

Single pieces of fura-2-loaded cortical collecting tubule (CCT) isolated either from normal or adrenalectomized (ADX) rats were superfused in vitro, and the cytosolic calcium concentration [( Ca2+]i) was calculated from fluorescence recordings. The effects of altering the sodium gradient across cell membranes were investigated. Switching external sodium from 164 mM to 27 mM (low [Na+]o) had little effect on [Ca2+]i in normal tubules (106 +/- 9 versus 101 +/- 9 nM, n = 15) whereas it resulted in a large peak of [Ca2+]i in CCT from ADX-rats (270 +/- 32 versus 135 +/- 11 nM, n = 21). Since CCT from ADX rats are known to have a reduced Na-pump activity, the effect of ouabain treatment on CCT from normal rats was also tested. When CCT from normal rats were exposed to 1 mM of ouabain in the presence of 164 mM of [Na+]o, [Ca2+]i increased only moderately (123 +/- 15 versus 111 +/- 11 nM, n = 13); when the low [Na+]o solution was applied to these ouabain-treated tubules, a large and transient increase in [Ca2+]i was obtained (287 +/- 38 versus 123 +/- 15 nM, n = 13). This response was absent with [Ca2+]o = 0. The data suggest the presence of 3 Na+/1 Ca2+ exchangers in cell membranes of rat CCT.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenalectomy↗
PubMed1989

Cytosolic free calcium in single microdissected rat cortical collecting tubules.

Cytosolic free Ca2+ ([Ca2+]i) was measured in single fragments of rat cortical collecting tubule (CCT) by using fura-2 and a tubule superfusion device. Under basal conditions, i.e. with 1 mM of external Ca2+ ([Ca2+]o), the average steady state [Ca2+]i was 179 +/- 16 nM (n = 44 tubules). Random alterations of [Ca2+]o between 0 mM and 4 mM led to corresponding variations in steady state [Ca2+]i levels, which were linearly correlated with [Ca2+]o (average slope 93 +/- 34 nM [Ca2+]i per 1 mM [Ca2+]o for six tubules). In contrast, [Ca2+]i was little affected by decreasing external Na+ concentration. Cell membrane depolarization with 100 mM of external K+ induced a sustained drop in [Ca2+]i (21% as an average). The data suggest that steady state [Ca2+]i in CCT cells resulted from a non-saturable passive entry of calcium ions across cell membranes balanced with an active extrusion by calcium ATPase (pump and leak mechanism). The passive component cannot be accounted for either by Na+/Ca2+ exchangers nor by voltage-dependent calcium channels; it is best explained by the presence of voltage-independent calcium channels in cell membranes.

Animals↗
PubMed1989

Molecular cloning of two cDNAs for related secretory proteins in lizard epididymis: gene expression during androgen-induced cell growth and secretion.

Lizard epididymis is an androgen-dependent tissue which produces notably ten related secretory proteins (L-proteins, Mr 19,000) during the reproductive period. These proteins were synthesized in vitro as preproteins (Mr 25,000, 24,000, 23,500). A cDNA library in the plasmid pBr322 was constructed and two cDNA clones were isolated by differential hybridization according to the differential expression of the mRNAs in stages 1 and 6 of the annual reproductive cycle. Translations of mRNAs hybrid-selected by two clones (LV123, LV132) yielded proteins which were immunoprecipitated by the L-antiserum. These preproteins were processed in vitro into six peptides; four were encoded by mRNAs selected with the LV123 clone, the others by the LV132 clone. Only three bands were detected using Northern blot analysis suggesting that the L-family could be derived from various mRNAs and from post-translational maturations. Southern analysis of genomic DNA suggests that the L-mRNAs were encoded by at least two distinct genes which could exist in numerous copies. The L-gene expression was studied under various physiological conditions and was found to be androgen-dependent. Furthermore, the results suggest the presence of a translational regulation in the newly differentiated epithelial cells.

Androgens↗
PubMed1989

Alterations in protective enzymes against peroxidation in the central and peripheral nervous system of control and dysmyelinating mutant mice.

The activities of peroxide-detoxifying enzymes such as superoxide dismutase (SOD), glutathione peroxidase, glutathione reductase, and catalase were measured in the nervous system of neurological dysmyelinating mutants: quaking (Qk), shiverer (Shi), and trembler (Tr) mice. Cu/Zn-SOD activity was higher in the cerebellum of Qk and Shi mice (by 53% and 106%, respectively) in comparison with controls, but it was the same in the cerebellum of Tr mice and their corresponding controls. In contrast, there was no difference in the level of Cu/Zn-SOD activity in the cerebrum of Qk, Shi, and Tr mice and their respective controls. Mn-SOD activity was the same among all the mutants compared to control animals in both cerebrum and cerebellum. In Shi cerebellum, glutathione peroxidase and glutathione reductase activities were slightly decreased (a 21.6% and a 13.2% diminution, respectively), whereas catalase activity in cerebrum and cerebellum was the same among mutants and control mice. In the sciatic nerve from Tr mice, all the enzymatic activities were enhanced: sixfold increase for total SOD, and 2.4-fold, 3.5-fold, and 1.8-fold increase for glutathione peroxidase, glutathione reductase, and catalase, respectively.

Animals↗
PubMed1988

Superoxide anion measurement by sulfonated phenyl isothiocyanate cytochrome c.

Sulfonated phenyl isothiocyanate cytochrome c is suggested as a new scavenger for superoxide anion. The efficiency of the modified cytochrome c in measurements is compared with that of phenyl isothiocyanate cytochrome c and acetylated cytochrome c. Sulfonated phenyl isothiocyanate cytochrome c is water and salt soluble. Autooxidability of the pigment is not observed. The primary advantage of sulfonate phenyl isothiocyanate cytochrome c is that it appears to be specifically reduced by O2 radicals without interferences by other reactions in complex biological systems.

Acetylation↗
PubMed1988

Identification of an epididymal immunorelated protein family: sequential appearance under testosterone stimulation.

The lizard has a seasonal sexual cycle, during which the epididymis produces large amounts of proteins that mix with spermatozoa during the reproductive period. Through one-dimensional electrophoresis we identified among these proteins a band of major soluble Mr 19,000 proteins. In two-dimensional electrophoresis the Mr 19,000 protein molecules separated into four pHi groups ranging from 3.7 to 8.7. An immunoserum prepared against the most acidic fraction recognized all four protein groups. Immuno-electrophoresis confirmed that these proteins have similar immunological characteristics. The androgen dependence of each group was demonstrated in vitro with testosterone stimulation of tissue from castrated animals. The groups appear sequentially as a function of culture growth time.

Animals↗
PubMed1988

Involvement of Na and Cl in ouabain-induced cell swelling in thick ascending limb of rat kidney.

Changes in the volume of isolated segments of rat medullary thick ascending limb (MAL) were studied by a photographic technique, after tubule incubation in isotonic solutions in the absence or presence of ouabain and/or K. When segments were incubated at 30 degrees C in NaCl solution, their volume increased by 75% after removal of external K, and by 170% after removal of external K plus addition of 1 mmol/l ouabain. At steady state, tubular volume was a function of the external K concentration. Resting volume was obtained with external K concentrations higher than 0.1 and 1.0 mmol/l in the absence and presence of ouabain respectively. When MAL samples were incubated in isotonic K-free Na2SO4 or K-free choline Cl solution, their volume per unit of length was similar to that determined in NaCl medium, but there was no swelling after the addition of ouabain. The ouabain-induced swelling was shown to depend on both the Na and Cl concentrations in the incubate (apparent Km of 87 and 80 mmol/l for Na and Cl respectively). Swollen tubules recovered their resting volume when ouabain, Na or Cl was removed from the incubation medium. Recovery of resting volume was also observed after addition of K into the incubation medium. These observations indicate that rat MAL cell volume is the result of coupled passive net fluxes of Na and Cl, which depend on the respective electrochemical gradients for Na or Cl across the cell membranes and the Na-pump activity which continuously extrudes Na.

Animals↗
PubMed1988

Relationship between cell volume and cation content in thick ascending limb of rat kidney.

We examined the relationship between the cell volume and cation concentration ([Nai] and [Ki]) of isolated segments of rat medullary thick ascending limb (MAL) after incubation at 30 degrees C in various isotonic solutions. When the tubules were incubated in a normal NaCl solution containing 5 mmol/l K+, addition of 1 mmol/l of ouabain increased [Nai] and decreased [Ki] but did not change the total ([Nai] + [Ki]) concentration (about 90 mEq/l) or tubular volume. After incubation in various K+-free solutions, the tubules were almost fully K+-depleted; their volume per unit of length was similar in the three solutions, although the choline Cl-treated tubules had a very low sodium content compared to the NaCl- and Na2SO4-treated tubules (8 vs. 97 and 95 mEq/l respectively). Ouabain altered neither volume nor [Nai] of tubules incubated in choline Cl or Na2SO4 solution. Transfer of tubules from K+-free Na2SO4 or K+-free choline Cl solution into K+-free NaCl solution resulted in an increase in [Nai] (by 29 and 97 mEq/l respectively) without much increase in tubular volume. A marked swelling of the tubules was only observed when the K+-free NaCl solution contained also ouabain. Under this condition, [Nai] was comparable to the Na+ concentration of the incubation medium. After washing and incubation in a normal NaCl solution containing K+, the swollen tubules recovered their initial volume and restored Na+ and K+ concentration gradients across the cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Insulin receptors along the rat nephron: [125I] insulin binding in microdissected glomeruli and tubules.

Binding of [125I] Tyr A14 human insulin ([125I] insulin) was measured at 4 degrees C in glomeruli and pieces of tubule microdissected from collagenase-treated rat kidneys. For glomeruli and all segments tested, total and non specific binding increased linearly with glomeruli number or tubular length. When determined with 4.0 nM labelled hormone, the distribution of specific binding sites (expressed as 10(-18) mol [125I] insulin bound per glomerulus or mm tubule length) was as follows: glomerulus, 2.5 +/- 0.3; proximal convoluted tubule (PCT), 12.6 +/- 0.6; pars recta (PR), 4.0 +/- 2.6; thin descending limb (TDL), 0.6 +/- 0.2; thin ascending limb (TAL), 0.6 +/- 0.2; medullary thick ascending limb (MAL), 0.8 +/- 0.1; cortical ascending limb (CAL), 2.1 +/- 0.1; distal convoluted tubule (DCT), 5.6 +/- 1.1; cortical collecting tubule (CCT), 3.2 +/- 0.3 and outer medullary collecting tubule (MCT), 2.3 +/- 0.1. Specific [125I] insulin binding to glomeruli and tubule segments was time and dose-dependent, saturable, reversible after elimination of free labelled ligand, and inhibited by unlabelled human insulin. When analysed in Scatchard and Hill coordinates, the binding data revealed a negative cooperation in the interaction processes between [125I] insulin and glomerular and tubular binding sites, with apparent dissociation constants and Hill coefficients of the following values: glomerulus, 0.6 nM and 0.60; PCT, 10.0 nM and 0.55; MAL, 4.3 nM and 0.80; CAL, 2.0 nM and 0.74; CCT, 7.6 nM and 0.80 and MCT, 1.0 nM and 0.57 respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Distribution of vasoactive intestinal peptide-sensitive adenylate cyclase activity along the rabbit nephron.

The effect of vasoactive intestinal peptide (VIP) upon adenylate cyclase (AC) activity has been determined in defined microdissected renal tubules isolated from collagenase-treated rabbit kidneys. In the presence of 10 microM GTP, 1 microM VIP gave marked stimulations of AC over basal values in the bright portion of the distal convoluted tubule (DCTb) (10.1-fold), and in the collecting tubule isolated from the inner stripe of the outer medulla (OMCTi, 7.8-fold). Less pronounced effects of VIP were found in the medullary collecting tubule isolated from the outer stripe (2.5-fold) and in the granular portion of the distal convoluted tubule (2.0-fold). VIP stimulation of AC activity in these segments amounted to 25 to 40% of the effect elicited by other agonists (arginine vasopressin, calcitonin or parathyroid hormone) in their respective target segments. A low response to VIP was observed in the cortical thick ascending limb (1.8-fold) which represented less than 5% of the calcitonin-stimulated AC activity. In the thin descending limb VIP produced a slight and variable stimulation of AC. VIP was without effect upon AC in the convoluted and straight portions of the proximal tubule, the medullary thick ascending limb and the cortical collecting tubule. Half-maximal stimulation of AC by VIP was observed at 26 +/- 10 nM (n = 3) in OMCTi and at 19 nM (n = 2) in DCTb. Related peptides glucagon, secretin and PHI gave lower stimulations of AC compared to VIP in OMCTi. Conversely for rat OMCTi, under identical conditions, glucagon was much more effective than VIP.

Adenylyl Cyclases↗
PubMed1988

Effects of differentiation state and post-castration time lapse on the epididymal response of the lizard to testosterone in vitro: changes in specific protein and mRNA levels.

The epididymis of the viviparous lizard secretes large amounts of proteins among which L-proteins are prominent components. It undergoes great morphological and physiological modifications during its testosterone-controlled annual cycle. The effects of testosterone on L-proteins synthesis and L-mRNA concentrations were studied in cultures of organs regressed after castration. Of three tested serum supplements (2% Ultroser, 10% fetal calf serum, 10% calf serum) calf serum was shown to be essential for androgen-specific control of L-proteins synthesis. The duration of castration governed the in-vitro response to testosterone principally at the level of L-proteins synthesis. The onset of synthesis was delayed in 2-month post-castration explants, compared with 1-month post-castration explants, and was dissociated from appearance of the mRNA. This suggests that there is translational control of secretory proteins in the regressed epididymis. Conversely, the response to testosterone at the mRNA level was delayed in explants from animals castrated during a non-secretory state, compared with explants from animals castrated at the onset of secretion. These results, together with other data, suggest that expression of the L-proteins is under multifactorial control and that the influence of multiple controlling elements varies with the stage of differentiation.

Animals↗
PubMed1987

Purification of cytochrome b558 from bovine polymorphonuclear neutrophils.

A 110 fold purification of cytochrome b558 from resting bovine neutrophils has been achieved. The plasma membrane bound cytochrome b was extracted with aminoxide WS35, a non ionic detergent. The purification procedure included liquid column chromatography on CM-C50 Sephadex, chromatofocusing on the anion exchanger PBE94, and gel filtration on P30 Biogel. The purified preparation was characterized by an heme to protein (nmol/mg) ratio of 7.7. The isoelectric point of cytochrome b was at pH 6.5. Upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate three bands corresponding to apparent Mr 64,000, 56,000 and 20,000 were revealed by staining with Coomassie Blue.

Animals↗
PubMed1987

Isoenzyme pattern of enolase in the diagnosis of neuroendocrine bronchopulmonary tumors.

Electrophoretic separation of enolase isoenzymes and the measurement of enolase activity were performed in 25 lung tumor extracts. In 13 neuroendocrine (NE) tumors (nine small cell lung carcinoma [SCLC], three atypical NE tumors, and one carcinoid tumor), the NE differentiation was assessed by ultrastructural determination of neurosecretory granule (NSG) density. Twelve non-NE lung tumors also were studied (three adenocarcinomas, four epidermoid, two composite, two large cell undifferentiated carcinomas, and one lymphoma). Four normal lung tissues and 1 human brain were used as controls. The gamma gamma isoenzyme was present at a high level (mean +/- SE, 12 +/- 3%) in all NE carcinomas and consistently absent in all non-NE tumors as well as in normal lung. The alpha gamma isoenzyme was found in significantly higher proportion in NE carcinomas (mean +/- SE, 29 +/- 2%) than in non-NE tumors (mean +/- SE, 8 +/- 1%) (P less than 0.0001), despite an equally high level of total enolase activity in both groups of tumor. The separation of alpha gamma and gamma gamma isoenzymes of enolase allows for the accurate diagnosis of NE tumors and NE components of atypical NE carcinomas, and the gamma gamma isoenzyme, in contrast to gamma chain detection by immunoassay, can be considered to be a specific marker in itself of NE differentiation in lung neoplasms.

Adenocarcinoma↗
PubMed1987

Atrial natriuretic peptide receptors along the rat and rabbit nephrons: [125I] alpha-rat atrial natriuretic peptide binding in microdissected glomeruli and tubules.

Binding of [125I] alpha-rat atrial natriuretic peptide ([125I] alpha-RANP) was measured in glomeruli and pieces of tubule microdissected from rat and rabbit nephrons. High densities of specific ANP binding sites were found only in the glomeruli (10-30 X 10(-18) mol X glom-1), whereas no specific binding could be detected in the proximal tubule, the thin segments of the Henle's loop, the thick ascending limb, the distal tubule and the cortical and outer medullary collecting tubules. Rising the temperature from 4 degrees C to 35 degrees C resulted in biphasic kinetics of binding, suggesting a temperature-dependent inactivation of labelled hormone by glomeruli. At 4 degrees C, specific binding of [125I] alpha-RANP was time and dose-dependent and Scatchard analysis of data indicated an apparent equilibrium dissociation constant of 0.63 nM. Competition experiments revealed the following sequence of stereospecificity for binding to rat glomeruli: RANP 3-28 greater than [125I] alpha-RANP = [125I] alpha-HANP = alpha-RANP = antriopeptin III greater than antriopeptin II, whereas binding was unaffected by pharmacological doses of unrelated peptide hormones, prostaglandins, adrenergic agonists, dopamine, histamine and carbamylcholine. The results indicate that glomerular binding sites might be the physiological ANP receptors.

Animals↗
PubMed1987

Atrial natriuretic peptide effects on cGMP and cAMP contents in microdissected glomeruli and segments of the rat and rabbit nephrons.

A microradioimmunoassay has been developed in order to measure the changes in cGMP cell content induced in vitro by atrial natriuretic peptides (ANP) in either glomeruli or defined portions of tubules microdissected from collagenase treated rat and rabbit kidneys. When tested at 0.1 microM or 1 microM, all ANP analogues used produced in rat glomeruli a 20-25 fold increase in cGMP accumulation compared to basal values. Threshold responses were obtained with about 1 nM ANP and apparent Ka values ranged between 5 and 50 nM. Atriopeptin III led to similar results in glomeruli isolated from rabbit. Under the same experimental conditions, no cGMP could be detected in any ANP-treated nephron segment from the rat kidney (namely, from the proximal convoluted tubule up to the outer medullary collecting tubule) nor in cortical collecting tubules isolated from the rabbit kidney. Moreover, ANP did not alter the forskolin-induced increase in cAMP content in glomeruli or collecting tubules, nor the AVP-induced increase in cAMP content in collecting tubules. Our data confirm the marked effect of ANP on cGMP generation by isolated glomeruli from rat and rabbit; however, they are not compatible with a direct action of ANP stimulating cGMP generation in tubules or inhibiting vasopressin-induced cAMP generation in collecting tubules.

1-Methyl-3-isobutylxanthine↗
PubMed1987

Characterization and androgenic regulation of major mRNAs coding for epididymal proteins in a lizard (Lacerta vivipara).

During the reproductive period (spring) under the control of testosterone the epididymis of the viviparous lizard secretes a group of major proteins with an approximate Mr of 19,000 named L protein(s). These proteins are recognized by a specific immunoserum and bind to the heads of spermatozoa. During spring, translation in reticulocyte lysate of RNA from secreting epididymis (stage 6) produced 5 immunoprecipitable bands with Mr values from 21,500 to 25,000. Such synthesis is undetectable during sexual rest in summer (stage 1). The 5 bands disappear when translation is performed in the presence of dog pancreas microsomes although a new band of Mr 19 000 becomes prominent. This suggests that synthesis of L protein involves two steps, i.e. synthesis of precursors (L preproteins) followed by a maturation process. At least 11 translation products (including L-preproteins) are involved in annual variations that follow the differentiation of the epididymal epithelial cells and their androgen dependency was studied by castration and in-vitro stimulation by testosterone. In these conditions, testosterone is able to control accumulation of RNA corresponding to L preproteins and to a translation product of Mr 29 000.

Animals↗
PubMed1986

Effects of temperature, ouabain and diuretics on the cell sodium and potassium contents of isolated rat kidney tubules.

Cell Na+ and K+ contents were measured by flame photometry in single pieces of rat medullary thick ascending limb (MAL) and medullary collecting tubules (MCT) after an overnight incubation at various temperatures. Below 8 degrees C, MCT samples were no more able to sustain high-K+, low-Na+ cell concentrations, and sodium progressively replaced cell potassium as the temperature decreased. The loss of potassium and the accompanying accumulation of sodium by MCT cells occurred at lower or higher temperature when amiloride (20 mumol/l) or ouabain (1 mmol/l) was present respectively in the incubation medium compared to that observed on control non-treated MCT. In contrast, MAL samples maintained normal cation gradients across their membrane at all temperatures, including 0 degree C, even in the presence of ouabain. However, MAL cells lost nearly all their potassium which was replaced by sodium when they were incubated in K+-free solution. These Na+-loaded, K+-depleted MAL cells restored high-K+ and low-Na+ contents similar to those of control samples when they were further incubated for 1 h at 0 degree C in presence of 5 mmol/l external potassium. Even in the presence of 1 mmol/l ouabain and at 0 degree C, a restoration of almost normal cation gradients occurred provided that Na+-loaded MAL were incubated for 24 h after potassium addition to the external medium. The results are discussed in relation to the respective effects of low temperatures on the passive and active components of the cation balance in the cells of the two nephron segments.

Amiloride↗