Search PubMed⌕ Search

Biomedical subjects

J Navarro

Publications and source records attributed to J Navarro.

At least 325 records · Page 18Linked to original sources
PubMed1988

Solubilization and reconstitution of the formylmethionylleucylphenylalanine receptor coupled to guanine nucleotide regulatory protein.

We describe the solubilization, resolution, and reconstitution of the formylmethionylleucylphenylalanine (fMet-Leu-Phe) receptor and guanine nucleotide regulatory proteins (G-proteins). The receptor was solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate. Guanine nucleotides decreased the number of high-affinity binding sites and accelerated the rate of dissociation of the receptor-ligand complex, suggesting that the solubilized receptor remained coupled to endogenous G-proteins. The solubilized receptor was resolved from endogenous G-proteins by fractionation on a wheat germ agglutinin (WGA)-Sepharose 4B column. High-affinity [3H]fMet-Leu-Phe binding to the WGA-purified receptor was diminished and exhibited reduced guanine nucleotide sensitivity. High-affinity [3H]fMet-Leu-Phe binding and guanine nucleotide sensitivity were reconstituted upon the addition of purified brain G-proteins. Similar results were obtained when the receptor was reconstituted with brain G-proteins into phospholipid vesicles by gel filtration chromatography. In addition, we also demonstrated fMet-Leu-Phe-dependent GTP hydrolysis in the reconstituted vesicles. The results of this work indicate that coupling of the fMet-Leu-Phe receptor to G-proteins converts the receptor to a high-affinity binding state and that agonist produces activation of G-proteins. The resolution and functional reconstitution of this receptor should provide an important step toward the elucidation of the molecular mechanism of the fMet-Leu-Phe transduction system in neutrophils.

Adenine Nucleotides↗
PubMed1988

Insulin-regulatable tissues express a unique insulin-sensitive glucose transport protein.

At least three different glucose transport systems exist in mammalian cells. These are: (1) the constitutively active, facilitative carrier characteristic of human erythrocytes, Hep G2 (ref. 2) cells and rat brain; (2) the Na-dependent active transporter of kidney and small intestine; and (3) the facilitative carrier of rat liver (B. Thorens and H. F. Lodish, personal communication). A fourth possible glucose transport system is the insulin-dependent carrier that may be specific to muscle and adipose tissue. This transporter resides primarily in an intracellular compartment in resting cells from where it translocates to the cell surface upon cellular insulin exposure. This raises the question of whether hormonal regulation of glucose transport is conferred by virtue of a tissue-specific signalling mechanism or a tissue-specific glucose transporter. Here we present data supporting the latter concept based upon a monoclonal antibody against the fat cell glucose transporter that identifies a unique, insulin-regulatable glucose transport protein in muscle and adipose tissue.

Adipose Tissue↗
PubMed1988

Human sperm chromosome studies in a reciprocal translocation t(2;5).

Sperm chromosome complements have been studied in a man heterozygous for a reciprocal translocation t(2;5)(p11;q15). Human sperm chromosomes were obtained after fertilization of zona-free hamster eggs. A total of 75 human sperm metaphases were analysed. On the complements studied, 59 (78.6%) resulted from a 2:2 segregation and 16 (21.3%) from a 3:1 segregation, 4:0 segregation was not observed. Our results indicate that at least 36% of sperm complements were unbalanced with respect to the translocation. The frequency of other chromosome anomalies unrelated to the translocation was 16%.

Adult↗
PubMed1988

Human sperm chromosomes.

Sperm chromosome studies have been performed in 70 normal males. The incidence of aneuploidy in this group is approximately 3-4%, and that of structural anomalies close to 5%. In carriers of reciprocal or Robertsonian translocations, the results are extremely variable, with percentages of unbalanced sperm from 8 to 87%. No unbalanced spermatozoa have been observed in patients with pericentric or paracentric inversions. In cancer patients treated with radio and/or chemotherapy, the incidence of chromosome abnormalities is much higher, and significantly different from that found in controls.

Aneuploidy↗
PubMed1988

Sural nerve morphology in asymptomatic uremia.

This study evaluates morphologically the sural nerves of two patients with acute and another pair with chronic uremia, both of whom had neither clinical nor electrophysiologic evidence of neuropathy. Morphometric changes indicative of myelin repair were noted in the chronic uremic case who had a shorter duration of renal failure but required dialysis. Also, changes suggestive of axonal degeneration were found in the case who had chronic uremia of long duration. Both cases of acute uremia did not reveal significant abnormalities. Structural changes in the sural nerves may precede clinical and nerve conduction derangements in uremia, specifically in chronic cases.

Acute Disease↗
PubMed1988

[Value of the measurement of arm circumference/head circumference in the evaluation of the nutritional status of infants and young children].

In 1970, Kanawati and McLaren proposed a nutritional criterion based on the arm circumference/head circumference (AC/HC) ratio, valid from 3 months to 4 years of age. For these authors, there were 4 situations: normal nutrition (ratio greater than 0.31), slight undernutrition: (0.31 greater than ratio greater than 0.28), medium undernutrition: (0.28 greater than ratio greater than 0.25) and severe undernutrition (ratio less than 0.25). A longitudinal study was undertaken on 45 children admitted in our unit for nutritional assistance (total parenteral nutrition and enteral nutrition). Weight, arm circumference and triceps skinfold were measured at regular intervals during their stay in hospital (total: 141 measurements). There was a strong correlation (p less than 0.001) between the values of AC/HC and weight for age, weight for height, triceps skinfold and arm circumference. There was no correlation between AC/HC, height for age and head circumference for age. Furthermore, this criterion seemed to be independent from the degree of hydratation in cases with dehydratation or oedemas (Kwashiorkor). AC/HC ratio is a simple and reliable criterion for nutritional follow-up. It is easily reproduced and independent from sex and age between ages 3 months and 4 years.

Anthropometry↗
PubMed1988

[Value of esogastroduodenal endoscopy with staged biopsies in children with Crohn's disease].

An upper gastrointestinal endoscopy with multiple biopsies was performed in 19 children suspected of Crohn disease (CD) who had also undergone X-ray investigations and colonoscopy with multiple biopsies. Biopsies were performed in pathological and/or normal mucous areas. Upper gastrointestinal endoscopy showed macroscopic changes in 7 children (37%). Histologic examinations of the upper gastrointestinal tract were normal or showed only non specific changes in 12 cases (63%). Histopathologic changes specific for CD were found in 7 cases (37%), while specific histologic changes were identified at the rectal or colic level in 3 of these 7 cases only. Thus, upper gastrointestinal endoscopy with multiple biopsies was most useful for the diagnosis of CD, since it was the only diagnostic means in 4 cases. It should be systematically performed when CD is suspected.

Adolescent↗
PubMed1987

Identification and purification of a novel G protein from neutrophils.

A novel G protein which appears to couple chemotactic peptide receptors to a polyphosphoinositide phospholipase C has been purified from rabbit neutrophils. Neutrophil membranes were solubilized with sodium cholate and fractionated by successive anion exchange, gel filtration and hydrophobic chromatography. Guanosine-5'-(3-O-thio)triphosphate binding activity was purified 170-fold from the soluble extract. The alpha-subunit of the purified G protein was identified by pertussis toxin-catalyzed ADP-ribosylation, and found to have an Mr of 40,000. The beta-subunit (Mr 36,000) comigrated on SDS-polyacrylamide gel electrophoresis with the beta-subunits of bovine brain Gi and Go. The neutrophil pertussis toxin substrate is highly unstable in cholate solution unless 30% ethylene glycol is added. Structural and functional analysis of this novel G protein will advance our understanding of the molecular mechanisms of coupling of receptors to phospholipase C.

Animals↗
PubMed1987

Reconstitution of the rat liver vasopressin receptor coupled to guanine nucleotide-binding proteins.

The V1 vasopressin receptor has been solubilized from rat liver membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammoniol]-1-propanesulfonate (CHAPS) and reconstituted into phospholipid vesicles. There is essentially complete solubilization of the receptor by 3% CHAPS at a protein concentration of 15 mg/ml. Reconstitution into soybean phospholipid vesicles is readily achieved either by gel filtration chromatography or by membrane dialysis. The binding of [3H]vasopressin to proteoliposomes is specific, saturable, reversible, and magnesium-dependent. In contrast, the detergent-soluble vasopressin receptor does not display specific binding. The apparent affinity of the reconstituted receptor for [3H]vasopressin is approximately 4-fold lower than that of the receptor in native membranes. In addition, the binding of [3H]vasopressin to reconstituted vesicles is not sensitive to 100 microM guanosine 5'-O-thiotriphosphate (GTP gamma S) as it is in native membranes. However, the apparent affinity of the reconstituted receptor for ligand approximates that of native membranes when membranes are prebound with vasopressin prior to solubilization and reconstitution into vesicles. Furthermore, vesicles reconstituted from membranes prebound with vasopressin show GTP gamma S sensitivity of [3H] vasopressin binding. This finding strongly suggests that vasopressin stabilizes a receptor-G-protein complex during solubilization. The rat liver vasopressin receptor is a glycoprotein, as shown by its specific binding to the lectin "wheat germ agglutinin." The vasopressin receptor can be reconstituted from the N-acetylglucosamine-eluted peak of a wheat germ agglutinin-Sepharose column, and [3H] vasopressin binding activity is purified 5-6-fold from membranes by this chromatographic procedure. The functionality of the partially purified receptor is indicated by its ability to bind ligand with high affinity and by its ability to functionally interact with a G-protein when vasopressin is bound prior to solubilization.

Animals↗
PubMed1987

Modulation of [3H]dihydropyridine receptors by activation of protein kinase C in chick muscle cells.

Modulation of ion channels is an essential step for understanding the regulation of cellular functions. 1,4-Dihydropyridines (nitrendipine, nifedipine, PN 200-110, etc.) are potent inhibitors of voltage-dependent calcium channels and are important therapeutic agents in the treatment of various cardiovascular disorders such as angina and cardiac arrhythmias. In this work a new procedure is employed to determine the density of surface dihydropyridine receptors in contracting muscle cells in culture. Activation of endogenous protein kinase C (the Ca2+/phospholipid-dependent enzyme) by the tumor promoter phorbol-12-myristate or 1-oleoyl-2-acetylglycerol enhanced the number of dihydropyridine receptors without significant change in the receptor affinity. The increase in the number of receptors was associated with stimulation of the dihydropyridine-sensitive 45Ca uptake as well as activation of protein kinase C in myotubes treated with phorbol esters. These data strongly suggest that activation of protein kinase C promotes the appearance of dihydropyridine receptors in the plasma membrane.

Animals↗
PubMed1987

Nisoldepine inhibits formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) receptor-coupled calcium transport in human neutrophils.

The formyl-methionyl-leucyl-phenylalanine (fMet-Leu-Phe) dependent Ca2+ uptake by human neutrophils consists of at least two components, one of which is sensitive to dihydropyridine derivatives. Inhibition by dihydropyridine derivatives showed the rank order of nisoldepine greater than nitrendipine greater than nimodepine greater than/Bay K 8644. The nisoldepine-sensitive calcium uptake exhibited an ID50 of 1.5 microM and maximal inhibition were observed at 5 microM. Neither calcium efflux or [3H]fMet-Leu-Phe binding was affected by nisoldepine up to 10 microM. The inhibition of nisoldepine was inversely proportional to the extracellular calcium concentration. Unlabeled nisoldepine and other dihydropyridine derivatives displaced the specific binding of [3H]PN 200-110 to human neutrophils. Our data suggest a relationship between dihydropyridine binding and the inhibition of fMet-Leu-Phe-dependent Ca2+ uptake.

Adult↗