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Biomedical subjects

P Richard

Publications and source records attributed to P Richard.

At least 19 recordsLinked to original sources
PubMed1992

Kinetics of ATP synthesis catalyzed by the H(+)-ATPase from chloroplasts (CF0F1) reconstituted into liposomes and coreconstituted with bacteriorhodopsin.

The H(+)-ATPase from chloroplasts (CF0F1) was isolated, purified and reconstituted into liposomes from phosphatidylcholine/phosphatidic acid. A transmembrane pH difference, delta pH, and a transmembrane electric potential difference, delta psi, were generated by an acid/base transition. The rate of ATP synthesis was measured at constant delta pH and constant delta psi as a function of temperature between 5 degrees C and 45 degrees C. The activation energy was 55 kJ mol-1. CF0F1 was coreconstituted with bacteriorhodopsin at a molar ratio of approximately 1:170 in the same type of liposomes. Illumination of the proteoliposomes leads to proton transport into the vesicles generating a constant delta pH = 1.8. The dependence of the rate of ATP synthesis on ADP concentration was measured with CF0F1 in the oxidized state, E(ox), and in the reduced state, E(red). The results can be described by Michaelis-Menten kinetics with the following parameters: Vmax = 0.5 s-1, Km = 8 microM for E(ox) and Vmax = 2.0 s-1, Km = 8 microM for E(red).

Adenosine Triphosphate↗
PubMed1992

Protein composition of follicular fluid and oocyte cleavage occurrence in in vitro fertilization (IVF).

The present study was carried out from in vitro fertilization (IVF) attempts to analyze further the total and specific protein contents of 47 follicular fluids yielding one oocyte. The aim was to find correlations between the follicular concentrations of such proteins and the occurrence of coupled oocyte cleavage. These findings would be used as markers of IVF outcome. Two groups of follicular samples were distinguished: one group with cleavage occurrence (25 cases) and another group without cleavage or even fertilization (22 cases). In the group with cleavage a significantly higher level was observed for six proteins: C3 complement fraction and ceruleoplasmin (P less than 0.02), alpha-antitrypsin and transferrin (P less than 0.01), and alpha 2-macroglobulin and beta 2-microglobulin (P less than 0.001). The data are discussed with respect to changes in follicle permeability with advancing maturity.

Biomarkers↗
PubMed1992

Dynamic non-invasive measurements of arterial diameter and wall thickness.

AIM: Non-invasive measurements of arterial diameter and wall thickness are critical in characterizing the onset and development of vascular disease. A precise dynamic method was proposed and tested for this purpose. DESIGN: A non-invasive method of measuring the variations in diameter and thickness of human arteries throughout the cardiac cycle was developed, using a high-precision ultrasonic echo-tracking system. An adaptive filtering technique was used to suppress artefacts caused by the layered tissue structure of the vessel wall. RESULTS: Based on decorrelation of microstructure noise, this technique improved the detectability of the wall interfaces, which allowed a determination of thickness and diameter. The accuracy and reproducibility of the method were tested by measurements of plastic films with known thicknesses. The discrepancies between standard micrometer and pulse-echo measurement were consistently less than 5 microns for film thicknesses ranging from 220 to 800 microns. The difference between two successive measurements was less than 2 microns. The identity of the measured vascular interfaces was checked in two ways. First, experiments on fixed bovine carotid arteries showed that the identified echogenic interfaces corresponded to the actual anatomical structure, as obtained by acoustic microscopy. Second, the radial artery thickness and diameter were extrapolated to obtain the change in wall volume over one cardiac cycle. The volume was found to be nearly constant, indicating incompressibility. CONCLUSION: This method will make it possible to obtain new information on atherogenesis and other vascular diseases.

Acoustics↗
PubMed1992

[Creutzfeldt-Jakob disease in 4 children treated with growth hormone].

Creutzfeldt-Jakob disease was diagnosed in four growth hormone recipients at the age of 10, 11, 18 and 19 years. To our knowledge, the two first cases are the first instances of Creutzfeldt-Jakob disease recorded in children. Three of them were still being treated with synthetic hormone at the onset of the disease. Neurological disorders: ataxia and diplopia, appeared first, dementia and myoclonus appeared later. Eighteen cases of Creutzfeldt-Jakob disease in growth hormone recipients are now recorded, and the present risk of Creutzfeldt-Jakob disease in pituitary growth recipients is estimated to be 1/300. Because of the long incubation period, new cases are to be feared. Other causes of iatrogenic Creutzfeldt-Jakob disease are reviewed. These facts incite to consider carefully using products of human origin in human therapy. The interactions between growth hormone, prion and host's genomic make-up are still not clear.

Adolescent↗
PubMed1992

[Inoperable brain metastases from bronchogenic cancers. Value of combined chemotherapy with cisplatin and 5 fluorouracil].

We report the results of a combined of chemotherapy with CDDP and 5 FU repeated every 3 weeks in sixteen men (age range 31-73 years) with brain metastases. CT was performed after 2, 4 and 6 cycles to assess efficiency. Response was considered complete when no lesion was found on the CT scan and partial when the lesion shrunk to least half its the total volume. After two cycles, the response rate was 8/16 (50%). Treatment toxicity was mild with only one case of severe but reversible myelotoxicity (grade III). CDDP and 5 FU combined chemotherapy can be a useful treatment for brain metastasis of lung carcinoma.

Adult↗
PubMed1991

The use of flumazenil in a neonate.

Side effects of benzodiazepines used during pregnancy are described in a neonate. Recurrent apnea was reversed after administration of flumazenil, a specific antagonist of benzodiazepines.

Apnea↗
PubMed1991

[Chemotherapy with cisplatin and 5-fluorouracil in inoperable brain metastases of bronchopulmonary cancers].

Chemotherapy is not a common treatment for cerebral metastases. The authors report results of combination chemotherapy with cisplatin (CDDP) and fluorouracil (5-FU). Sixteen men (age range 31-73 years) with brain metastases were treated with CDDP 20 mg/m2/day in continuous infusion for 5 days (d 1-5) and 5-FU 1 g/m2/day in continuous infusion for 4 days (d 1-4), and the treatment schedule repeated every 3 weeks. A brain computerized tomography after 2, 4 and 6 cycles was performed to assess efficacy. It was considered that complete response was achieved if no lesion was found on the CT scan, and partial response if at least half of the total volume had decreased. After 2 cycles, the response rate was therefore 8/16 (50%). Treatment toxicity was very mild with only 1 case of severe but reversible myelotoxicity (grade III). It is concluded that chemotherapy combination with CDDP and 5-FU is a useful treatment for brain metastasis of lung carcinoma.

Adult↗
PubMed1990

Reconstitution of CF0F1 into liposomes using a new reconstitution procedure.

The H(+)-ATPase (ATP synthase) from chloroplasts was isolated, purified and reconstituted into phosphatidylcholine/phosphatidic-acid liposomes. Liposomes prepared by reverse-phase evaporation were treated with various amounts of Triton X-100 and protein incorporation was studied at each step of the solubilization process. After detergent removal by SM2-Biobeads, the activities of the resulting proteoliposomes were measured indicating that the most efficient reconstitution was obtained by insertion of the protein into preformed, detergent-saturated liposomes. The conditions for the reconstitution were optimized with regard to ATP synthesis driven by an artificially generated delta pH/delta psi. An important benefit of the new reconstituted CF0F1 liposomes is the finding that the rate of ATP synthesis remains constant up to 10 s, indicating a low basal membrane permeability.

Adenosine Triphosphate↗
PubMed1990

Expression of vasopressin and opiates but not of oxytocin genes studied by in situ hybridization in embryonic rat brain primary cultures.

Expression of arginine-vasopressin (AVP), oxytocin (OT), dynorphin and enkephalin genes was studied with the in situ hybridization technique in embryonic rat brain serum-free cultures. Neurones were prepared from hypothalamus and extrahypothalamic structures of 16-day-old rat embryos. After 7 days in culture, AVP gene expression occurred in hypothalamic cultures only, whereas ProOT mRNAs were undetectable. By contrast, prodynorphin and proenkephalin mRNAs could be detected in both hypothalamic and extrahypothalamic cultures, however, with a higher number of cells containing proenkephalin mRNAs. These observations demonstrated that AVP, dynorphin and enkephalin, but not OT genes, can be expressed in cultures prepared from embryonic rat brain as young as 16 days old. This is the first report of an early expression of opioid peptide genes within the central nervous system suggesting that opioids could be involved in the early phases of nervous system development.

Animals↗
PubMed1990

Characterization of oxytocin-binding sites in primary rat brain cell cultures.

Detection and characterization of oxytocin-binding sites in dissociated brain cell cultures were performed, using a highly selective iodinated oxytocin antagonist [( 125I]OTA). Dissociated cells derived from hypothalamus and extrahypothalamic forebrain of 16-day-old fetal rats were maintained in chemically defined medium in order to enrich the cultures in neuronal cells. Specific binding of [125I]OTA, demonstrated in both hypothalamic and forebrain cell cultures, was temperature- and time-dependent; maximal binding was obtained by incubating the iodinated ligand for 60 min at 37 degrees C. The binding parameter were shown to be identical in both cell type cultures. The Scatchard plot analysis suggested the presence of a single class of binding sites of high affinity (Kd about 0.06 nM) and low binding capacity (Bmax about 4 fmol/dish). The specificity of these binding sites tested in competition experiments revealed that the unlabelled OT antagonist was the most potent in inhibiting specific [125I]OTA binding (Ki = 0.1 nM). A lower affinity, of the nM range was demonstrated for oxytocin (OT), arginine-vasopressin (AVP) and the V1 antagonist, whereas the V2 AVP agonist poorly competed for [125I]OTA binding sites (Ki about 250 nM). In conclusion, the [125I]OTA binding characteristics, identical in both hypothalamic and forebrain cultures, fulfil the classical conditions required for the existence of receptor sites since the binding was reversible, saturable and specific. As these characteristics were similar to those already described in the adult rat, at the central level in hippocampus, and at the periphery in the mammary gland, it could be postulated that [125I]OTA binds to an OT receptor site.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Presence and binding characteristics of calcitriol receptors in human fetal gut.

In the present study, we show for the first time the presence of calcitriol-specific binding sites in hypertonic extracts of cells isolated from human fetal small intestine and colon from 13-21 weeks of gestation. Woolf plot analysis of the binding characteristics revealed the presence of a single class of high affinity receptors. The presence of specific receptors for calcitriol in fetal intestine and colon opens interesting possibilities as to the role of this hormone in human gut development.

Calcitriol↗
PubMed1990

Development of neurophysin-containing neurons in primary cultures of rat hypothalami is related to the age of the embryo: morphological study and comparison of in vivo and in vitro neurophysins, oxytocin, and vasopressin content.

The morphological development of immunocytochemically identified neurophysin neurons and the evolution of neuropeptide content (neurophysins, vasopressin, and oxytocin) were studied in primary cultures of hypothalami obtained from 15- to 19-day-old embryos. According to their perikaryal surface, two populations of neurons were distinguished: large and small cells. Full development (defined by the perikaryal surface) of these neurons was reached at day 21 only in cultures from 15- or 16-day-old embryos. These two types of neurons may correspond to the magnocellular and parvocellular neurons described in vivo. Total neurophysins, vasopressin, and oxytocin content were measured by specific radioimmunoassays. Ontogeny of neurophysins and vasopressin showed a good correlation between cells cultured from 15- to 16-day-old embryos and hypothalami from age-matched rats. However, oxytocin was never detected in any of the cultures whatever the age of the embryos. Under our experimental conditions, hypothalamic primary cultures from 15- to 16-day-old embryos therefore appeared to be suitable for studying the differentiation and regulation of neurophysin- and vasopressin-containing neurons.

Animals↗
PubMed1990

Cultured osteoblasts from normal and hypophosphatemic mice: calcitriol receptors and biological response to the hormone.

The content and affinity of calcitriol receptors were analyzed in cultured osteoblasts from normal and hypophosphatemic mice. Hypertonic cell extracts were prepared by sonication followed by centrifugation at 200,000 g x 30 min. Analysis, at saturating levels of labeled 1,25(OH)2D3, revealed that binding of the hormone was dependent on the density of the cells plated and on the length of time in culture. It reached a maximum at 5 days of culture when 1.0 x 10(6) cells were plated. Under those conditions the binding capacity of Hyp osteoblasts was 6306 +/- 1267 sites/ng protein (mean +/- SEM) not different from N cells (7594 +/- 1713). The dissociation constant (Kd) was 18.3 +/- 5.4 and 20.0 +/- 5.7 pM for mutant and normal mouse osteoblasts respectively (NS). In both genotypes, a single peak for specific binding, migrating at approximately 3.0-3.5 S was observed by sucrose gradient centrifugation. 25-hydroxycholecalciferol-24-hydroxylase (24-OHase) was induced at 1 and 10 nM 1,25(OH)2D3 in a dose-dependent fashion. However, the induction was higher in mutant than in normal cells when the medium contained 1 mM and 2 mM phosphate salts. The difference vanished when cells were incubated in the presence of 3 and 4 mM phosphate salts. The effect of calcitriol on cultured osteoblasts was also analyzed in terms of collagen synthesis and alkaline phosphatase activity. In the range of 10(-10) M to 10(-7) M, 1,25(OH)2D3 was found to inhibit collagen synthesis in a dose-dependent fashion. At physiological levels, 1,25(OH)2D3 (10(-11)M-10(-10)M), stimulated alkaline phosphatase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1990

Multiple sclerosis: cell-mediated immunity to human brain gangliosides.

Cell-mediated immunity (CMI) to myelin components has been implicated in Multiple Sclerosis (MS) pathogenesis: two targets were suggested, Myelin Basic Protein with controversial results and, more recently, gangliosides. In order to investigate their possible involvement, we have performed Leukocyte Migration inhibition (LMI) tests in the presence of human brain gangliosides. Thirty nine MS patients (twenty four being "definite", according to McDonald and Halliday's classification), twenty nine patients with Other Neurological Diseases (OND), thirty six patients with Inflammatory diseases (ID) and forty healthy controls were tested. MS patients were divided into two groups, depending on the clinical stage of the disease. The mean migration inhibition percentage of the MS-attack group was found to be significantly different from the four others (p less than 0.01) (24.4 +/- 16.2 versus 10.9 +/- 8.5 in MS without attack, 4.4 +/- 12.9 in OND, 3.9 +/- 13.9 in ID and 11.1 +/- 12.1 in healthy subjects). LMI to gangliosides is therefore significantly increased during the attack stage in MS. These results support the notion of a Delayed Type Hypersensitivity to these glycolipids during the active stage of the disease.

Adult↗