PubMed Health⌕ Search

Biomedical subjects

B Vidal

Publications and source records attributed to B Vidal.

At least 19 recordsLinked to original sources
PubMed2007

Tunable and reconfigurable photonic microwave filter based on stimulated Brillouin scattering.

A high Q-factor photonic microwave filter showing tuning and reshaping capabilities and based on stimulated Brillouin scattering is demonstrated. The filter bandpass can be continuously tuned, changing the microwave oscillator used to generate the pump power, and the filter shape can be modified by modulating the microwave tone. A single bandpass over the microwave spectrum can be obtained by using single-sideband suppressed carrier modulation. Experimental results demonstrate the wide tuning range of the filter, its reshaping capability, and Q factor of 670.

Journal Article↗
PubMed2006

[Prognostic estimation in critical patients. Validation of a new and very simple system of prognostic estimation of survival in an intensive care unit].

OBJECTIVE: To make the validation of a new system of prognostic estimation of survival in critical patients (EPEC) seen in a multidisciplinar Intensive care unit (ICU). DESIGN AND SCOPE: Prospective analysis of a patient cohort seen in the ICU of a multidisciplinar Intensive Medicine Service of a reference teaching hospital with 19 beds. PATIENTS AND METHOD: Four hundred eighty four patients admitted consecutively over 6 months in 2003. Data collection of a basic minimum data set that includes patient identification data (gender, age), reason for admission and their origin, prognostic estimation of survival by EPEC, MPM II 0 and SAPS II (the latter two considered as gold standard). Mortality was evaluated on hospital discharge. EPEC validation was done with analysis of its discriminating capacity (ROC curve), calibration of its prognostic capacity (Hosmer Lemeshow C test), resolution of the 2 x 2 Contingency tables around different probability values (20, 50, 70 and mean value of prognostic estimation). The standardized mortality rate (SMR) for each one of the methods was calculated. Linear regression of the EPEC regarding the MPM II 0 and SAPS II was established and concordance analyses were done (Bland-Altman test) of the prediction of mortality by the three systems. RESULTS: In spite of an apparently good linear correlation, similar accuracy of prediction and discrimination capacity, EPEC is not well-calibrated (no likelihood of death greater than 50%) and the concordance analyses show that more than 10% of the pairs were outside the 95% confidence interval. CONCLUSION: In spite of its ease of application and calculation and of incorporating delay of admission in ICU as a variable, EPEC does not offer any predictive advantage on MPM II 0 or SAPS II, and its predictions adapt to reality worse.

Adult↗
PubMed2005

Dopaminergic inhibition of reproduction in teleost fishes: ecophysiological and evolutionary implications.

In many teleosts, dopamine (DA) exerts direct inhibitory control on gonadotropes, counteracting the stimulatory effect of gonadotropin-releasing hormone (GnRH) on gonadotropin release. This dual control by GnRH and DA has been demonstrated in various adult teleosts and has major implications for aquaculture. Because of its unique life cycle, the European eel has provided a powerful model for demonstrating the key role of DA in the control of puberty. Data from tetrapods suggest that the inhibitory role of DA on reproduction is not restricted to the teleosts. Thus, DA inhibitory control could represent an ancient evolutionary component in the neuroendocrine regulation of reproduction that may have been differentially maintained throughout vertebrate evolution. The intensity of DA inhibition, its main site of action, and its involvement in the control of puberty, seasonal reproduction, ovulation, spermiation, or even sex change may differ among classes of vertebrates, as well as within smaller phylogenetic units such as teleosts or mammals. An inhibitory role for DA has been reported also in some invertebrates, indicating that neuronal DA pathways may have been recruited in various groups of metazoa to participate in the control of reproduction. In addition to the incontestable GnRH neurons, the recruitment of DA neurons for the neuroendocrine control of reproduction provides an additional brain pathway for the integration of various species-specific, internal, and environmental cues. In teleosts, the plasticity of the DA neuroendocrine role may have contributed to their large diversity of biological cycles and to their successful adaptation to various environments.

Animals↗
PubMed2005

Brain expression of tyrosine hydroxylase and its regulation by steroid hormones in the European eel quantified by real-time PCR.

In the eel, dopamine inhibits pubertal development. To investigate the regulatory mechanisms involved, we developed a quantitative real-time RT-PCR assay for measurement of brain expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of dopamine. TH expression was highest in the olfactory bulb, followed by the di-/mesencephalic areas and the telencephalon/preoptic area. TH expression in the optic lobes and hindbrain was low or below the detection limit. In vivo treatment with testosterone, but not estradiol, resulted in increased TH expression in the forebrain, except the optic tectum, but not in the hindbrain. The results were confirmed by in situ hybridization.

Anguilla↗
PubMed2000

Distribution of the mRNA encoding the four dopamine D(1) receptor subtypes in the brain of the european eel (Anguilla anguilla): comparative approach to the function of D(1) receptors in vertebrates.

Four subtypes of D(1) dopamine receptors are expressed in the brain of the European eel (Anguilla anguilla), an elopomorph teleost. To correlate this molecular multiplicity with specific localisation and functions, the distribution of the D(1) receptor transcripts was analysed by in situ hybridisation. The four D(1) receptor transcripts exhibit largely overlapping expression territories. In telencephalon, they are found in the olfactory bulb and the dorsal telencephalon (except its lateral part) but are most abundant in the subpallial areas. More caudally, the entopeduncular nucleus, preoptic nuclei, preglomerular nuclear complex, ventral thalamus, periventricular hypothalamus, optic tectum and cerebellum, all contain various amounts of D(1) receptor transcripts. Finally, D(1) receptor mRNAs are present in nuclei associated with the cranial nerves. The two D(1A) receptor subtypes are generally the most abundant and present a different distribution in several areas. The D(1B) mRNA, although present in fewer areas than D(1A) transcripts, is the most abundant in ventrolateral telencephalon and torus semicircularis. The D(1C) receptor transcript, which has not been found in mammals, is restricted to diencephalon and cerebellum. In view of the expression territories of D(1) receptor transcripts and previous data, some areas of the everted telencephalon of teleost may be homologous to regions of the tetrapod brain. In particular, D(1) expression territories of the ventral telencephalon are likely to be equivalent to striatal areas. These observations suggest an evolutionary scenario in which the D(1A) receptor subtype was highly conserved after the first gene duplication during the evolution of craniates, whereas D(1B) and D(1C), and their associated specific characteristics, appeared later, probably in the gnathostome lineage.

Anguilla↗
PubMed1998

Graded X-ray Optics for Synchrotron Radiation Applications.

Using X-ray diffractometry and spectral measurements, the structure and properties of graded X-ray optical elements have been examined. Experimental and theoretical data on X-ray supermirrors, which were prepared by the magnetron sputtering technique using precise thickness control, are reported. Measurements on graded aperiodic Si(1-x)Ge(x) single crystals, which were grown by the Czochralski technique, are also presented. The lattice parameter of such a crystal changes almost linearly with increasing Ge concentration. The measurements indicate that Si(1-x)Ge(x) crystals with concentrations up to 7 at.% Ge can be grown with a quality comparable to that of pure Si crystals.

Journal Article↗
PubMed1998

Tyrosine hydroxylase in the european eel (Anguilla anguilla): cDNA cloning, brain distribution, and phylogenetic analysis.

We report the isolation of a full-length eel tyrosine hydroxylase (TH) cDNA that is characterized by a long 3' untranslated region and by a diversity restricted to the 3' end owing to the differential use of three polyadenylation signals. The longest eel TH mRNA was distinctive in the presence of four pentameric elements (AUUUA) in the AU-rich 3' noncoding region. Such a diversity could provide the basis of posttranscriptional or translational regulation of eel TH gene expression. Comparison of the eel TH sequence with those of other aromatic amino acid hydroxylases (TH, tryptophan hydroxylase, and phenylalanine hydroxylase) and phylogenetic analysis confirmed that the N-terminal regulatory domain is highly divergent, contrasting with the conservation of the catalytic core of the enzyme. Molecular phylogenies including the available sequences of the three hydroxylase genes suggested that the duplication of their common ancestor occurred before the emergence of arthropods. The regional expression of the eel TH mRNA was studied by semiquantitative PCR, northern blots, and in situ hybridization and compared with the immunocytochemical localization of TH protein. The data showed that TH mRNA is mostly expressed in the olfactory and hypothalamic areas, whereas sparse TH-expressing cell bodies are present in the telencephalic region and brainstem. No labeling was detected in the mesencephalic area, in striking contrast with that found in amphibians and amniotes.

Amino Acid Sequence↗
PubMed1998

Long-term inhibitory effects of somatostatin and insulin-like growth factor 1 on growth hormone release by serum-free primary culture of pituitary cells from European eel (Anguilla anguilla).

To investigate the ability of hypothalamic and peripheral factors to directly regulate growth hormone (GH) release in a primitive teleost, the European eel (Anguilla anguilla L.), we used primary cultures of dispersed pituitary cells. When cultured for 12 days in a serum-free medium, pituitary cells continuously released large amounts of GH, which exceeded the initial cellular content. Somatotropin-release inhibiting hormone (SRIH-14) dose-dependently inhibited GH release (EC50 0.75 nM) up to a maximal inhibitory effect of 95%. No desensitization of somatotropes to SRIH was observed over the 12 days of culture. Use of receptor subtype-selective SRIH agonists suggests the existence on eel somatotropes of SRIH receptor(s) related to the mammalian sst2/sst3/sst5 class rather than to the sst1/sst4 class. Insulin-like growth factor 1 (IGF1) dose-dependently inhibited GH release (EC50 0.03 nM) up to a maximal inhibitory effect of 85%, without desensitization. IGF1 and IGF2 were equipotent in inhibiting GH release, whereas insulin was 1,000 times less active, suggesting the implication of a receptor related to the mammalian IGF type 1 receptor. These results indicate that eel somatotropes are active in vitro without any specific additional factors, and suggest the existence of a dominant inhibitory control of GH release in vivo. Two potential candidates for this chronic negative regulation are a neurohormone, SRIH and a circulating factor, IGF1. These data underline the early evolutionary origin of the molecular and functional SRIH-GH-IGF1 neuroendocrine axis in vertebrates.

Anguilla↗
PubMed1998

Insulin-like growth factor-I stimulates gonadotrophin production from eel pituitary cells: a possible metabolic signal for induction of puberty.

Insulin-like growth factor (IGF)-I has been suggested as a potential signal linking growth and puberty in mammals. Using the juvenile European eel as a model, we employed a long-term, serum-free primary culture of pituitary cells to study the direct effect of IGF-I on gonadotrophin (GtH-II=LH) production. IGF-I increased both cell content and release of GtH-II in a time- and dose-dependent manner. IGF-I and IGF-II had similar potencies but insulin was 100-fold less effective, suggesting the implication of an IGF type 1 receptor. Other growth and metabolic factors, such as basic fibroblast growth factor and thyroid hormones, had no effect on GtH-II production. IGF-I did not significantly increase the number of GtH-II immunoreactive cells, indicating that its stimulatory effect on GtH-II production does not result from gonadotroph proliferation. Comparison of IGF-I and somatostatin (SRIH-14) effects showed that both factors inhibited growth hormone (GH) release but only IGF-I stimulated GtH-II production by eel pituitary cells. This indicates that the effect of IGF-I on gonadotrophs is not mediated by the reduction of GH released by somatotrophs into the culture medium. This study demonstrates a specific stimulatory effect of IGF-I on eel GtH-II production, played out directly at the pituitary level. These data obtained in a primitive teleost suggest that the role of IGF-I as a link between body growth and puberty may have been established early in the evolution of vertebrates.

Analysis of Variance↗
PubMed1997

Reconstruction of human maxillary defects with nacre powder: histological evidence for bone regeneration.

The defective areas in the premolar-molar region of maxillary alveolar bone of eight patients were reconstructed using powdered nacre from the giant oyster Pinctada maxima. Histological, microradiographic and polarized light studies of drill biopsies taken 6 months postoperatively showed that nacre was tightly bound to newly-formed bone. The nacre was gradually and centripetally biodissolved and replaced with immature and then mature lamellar bone. These results are in agreement with our previous experimental in vitro data indicating that nacre has good osteogenic properties.

Animals↗
PubMed1997

[Solitary crossed renal ectopia and congenital vertebral anomalies].

OBJECTIVE: To describe a case of solitary crossed renal ectopia that had been incidentally discovered in a healthy male with a previous history of spinal surgery. METHODS/RESULTS: A 43-year-old male who had undergone two surgical procedures for severe scoliosis of the thoracic spine when he was 7 years of age, consulted for symptoms of unspecific urethritis that had just remitted. Abdominal ultrasound and excretory urography revealed a solitary crossed ectopia on the right side and the spinal x-ray showed congenital fusion of the cervical vertebrae (Klippel-Feil syndrome). CONCLUSIONS: Crossed ectopia of a solitary kidney is an exceedingly rare anomaly of the urinary tract (about 30 cases have been reported) combining renal agenesia of one side, contralateral displacement of the ureter draining the only kidney and agenesia or hypoplasia of the other ureter. It is frequently an incidental finding, although it may be associated with congenital spinal anomalies and even severe genital and anal anomalies.

Abnormalities, Multiple↗
PubMed1996

Development of a radioimmunoassay for European eel growth hormone and application to the study of silvering and experimental fasting.

A specific and sensitive homologous radioimmunoassay for eel (Anguilla anguilla L.) growth hormone (angGH) has been developed. The antiserum, raised against purified angGH and used at 1:20,000 final dilution, did not cross-react with eel prolactin or thyrotropin, carp gonadotropin II, bovine GH, or serum from hypophysectornized eel. The inhibition curves for eel pituitary extracts and serum were parallel to that of angGH standard. The ED50 value was between 1 and 2 ng/tube and the recovery of purified angGH added to the serum was about 100%. In immunocytochemical studies, the antiserum, used at 1:1000 dilution, specifically labeled the somatotrophs in the pituitaries of the glass, yellow, and silver eels. The GH contents were determined in the pituitaries of glass, yellow, and silver eels and in the serum at the yellow and silver stages. GH variations during the transformation of the yellow to silver eel were examined. The results indicated a decrease in GH production between the yellow and the silver eels, possibly related to the cessation of growth at the silver stage. In contrast to the situation in the naturally fasting silver eel, submitting yellow eels to 3 months of starvation (experimental fasting) greatly increased GH production. This suggests a variation in the regulation of GH according to the type of fasting (natural or experimental) and/or the stage of the fish (yellow or silver).

Anguilla↗
PubMed1996

Primary cultures of dispersed pituitary cells from estradiol-pretreated female silver eels (Anguilla anguilla L.): immunocytochemical characterization of gonadotropic cells and stimulation of gonadotropin release.

To analyze the multihormonal control mechanisms of GTH secretion in the eel, primary culture of pituitary cells from control or estradiol-treated female silver eels, a treatment known to stimulate in vivo GTH synthesis, was developed. Dispersed eel pituitary cells obtained by enzymatic (trypsin/DNAse) and mechanical dispersion were cultured in Earles M199, at 18 degrees. Immunoreactive GTH (ir-GTH) cells were characterized by the immunoperoxidase method, using antiserum to carp GTH beta subunit. Ir-GTH cells from control silver eels were small and represented 14% of the dispersed pituitary cells. In contrast, ir-GTH cells from estradiol-treated eels were larger (cell area x 2.5) and represented a higher proportion (21%) of the pituitary cells. Intracellular and medium contents of GTH were measured by radioimmunoassay for the GTH beta subunit. In vivo estradiol-treatment increased more than 100-fold the GTH content of cell cultures. GTH release, studied over 1 to 4 hr, was undetectable in cultures from normal eels. In contrast, GTH release was low (less than 2% of cell content) but measurable in cultures from estradiol-treated eels. Subsequent experiments examined effects of various secretagogues on GTH release from primary cultures of pituitary cells from estradiol-pretreated eels. GTH release was significantly increased (x1.5 to x3 basal release) by 10(-6) M GnRH-A as well as by both native GnRHs in the eel (mammalian GnRH, mGnRH, and chicken GnRH-II, cGnRH-II), at the same concentration. Lower GnRH concentrations had no significant effect, indicating a low sensitivity of gonadotrophs to GnRH, likely to be related to their immature state at the silver stage. The similar efficacy of mGnRH and cGnRH-II suggested that the pituitary GnRH receptor had a low specificity toward various molecular forms, in the eel as in the other nonmammalian species. The protein kinase C (PKC) activator (phorbol ester: PMA) also stimulated GTH secretion, with a maximal effect at 10(-8) M, indicating that the PKC pathway was functional. In contrast, a depolarizing agent (50 mM KCl) had no significant effect on GTH release, suggesting lack of a functional voltagesensitive calcium channel (VSCC) secretory pathway. Perifusion experiments on whole pituitary confirmed the lack of effect of KCl on gonadotrophs from E2-pretreated eels and indicated that an additional in vivo treatment with GnRH agonist and dopamine antagonist could induce the differentiation of a functional VSCC pathway. These characteristics of the transduction mechanisms may be related to the immature state of the eel gonadotrophs at the silver stage.

Anguilla↗
PubMed1994

Sequence and regulation of European eel prolactin mRNA.

cDNA clones encoding the European eel (Anguilla anguilla L.) prolactin were isolated from a pituitary cDNA library constructed in gamma gt10, using a rainbow trout Prl cDNA fragment as a probe. Four different inserts were subcloned into the pGEM 3Z plasmid after PCR amplification. The 1082 bp-long nucleotide sequence revealed an open reading frame of 627 bp encoding a 24 amino acid-long signal peptide followed by a 185 amino acid-long mature protein. Comparison studies showed 60-70% homology with other known teleost fish prolactins and 30-45% with non-teleost fish, amphibian, reptilian, avian and mammalian prolactins. In situ hybridization studies using labelled prolactin RNA probe showed a strong signal in the rostral pars distalis of the pituitary gland. We next examined the physiological regulation of this prolactin synthesis in vivo using Northern blot analysis and prolactin cDNA probe labelled by random priming. The pituitary prolactin mRNA level was markedly decreased 3 weeks after transfer of eels from freshwater to sea water. Implants of thyroid hormones left for up to three weeks were ineffective on prolactin mRNA. Estradiol administered as implant, alone or in combination with 500 micrograms testosterone, was also unable to significantly alter the pituitary mRNA level for prolactin in the freshwater silver eels whatever the dose used (20-500 micrograms) and whatever the duration of treatment (from 4 days to 10 weeks).

Amino Acid Sequence↗
PubMed1994

Immunocytochemical localization of mammalian GnRH (gonadotropin-releasing hormone) and chicken GnRH-II in the brain of the European silver eel (Anguilla anguilla L.).

Using specific antibodies for the two molecular forms of gonadotropin-releasing hormone (GnRH) present in the European eel, Anguilla anguilla, (mammalian GnRH, mGnRH, and chicken GnRH II, cGnRH-II), we employed immunocytochemistry to determine the distribution of these two peptides in the brain and in the pituitary. The results indicate that mGnRH and cGnRH-II are localized in different neurons: mGnRH-immunoreactive (ir) perikaria were observed in the olfactory bulbs, the junction between olfactory bulbs and telencephalon (nucleus olfactoretinalis), the telencephalon, the preoptic region and the mediobasal hypothalamus. These cell bodies are located along a continuum of ir-fibers that could be traced from the olfactory nerve to the pituitary. Mammalian GnRH-ir fibers were detected in many parts of the brain (olfactory bulbs, ventral telencephalon, hypothalamus, optic tectum, mesencephalon) and in the pituitary. Chicken GnRH-II-ir cell bodies were detected in the nucleus of the medial longitudinal fasciculus of the midbrain tegmentum, but only scattered fibers could be detected in different parts of the brain. The pituitary exhibited very few cGnRH-II-ir fibers, contrasting with an extensive mGnRH innervation. These results are in agreement with our previous data obtained in the same species using specific radioimmunoassays for mGnRH and cGnRH-II. They demonstrate a differential distribution of the two forms of GnRH in the brain of the eel, as in the brain of some other vertebrate species, and suggest differential physiological roles for the two GnRH forms in the eel. They also provide information concerning the evolution of the GnRH systems in vertebrates.

Anguilla↗
PubMed1992

Nacre initiates biomineralization by human osteoblasts maintained in vitro.

When nacreous shell produced by the marine oyster Pinctada maxima, used as a biomaterial in oral surgery, is implanted in human bone, new bone formation occurs, resulting in a tight welding of the bone to the nacre [16]. These findings are consistent with the possibility that nacre adjacent to bone can locally stimulate osteogenic activity. To test this hypothesis, we have evaluated the effect of the simultaneous presence of bone and nacre on human osteoblasts in vitro. Nacre chips (1 mm3) were placed at approximately 1 mm distance from a similarly sized bone chip on a layer of first passage human osteoblasts. None of the chemical inducers generally required to obtain bone mineralization in vitro (in particular, beta-glycerophosphate) was added to the cultures. Mineralized sections of the cultures were evaluated by light and electron microscopy, contact microradiography, and Laser Raman Spectroscopy. The results demonstrated that nacre has strong osteogenic effects on human osteoblasts when placed in proximity to bone in vitro. New bone formation occurred by both appositional growth on the existing bone and by the formation of mineralized nodules within the matrix adjacent to the bone explant. Electron microscopic evaluation of these sites demonstrated findings typical of those described in the course of bone formation in vivo, and no evidence of toxicity was observed. In addition, under the conditions of culture used, nacre can also promote the formation by osteoblasts of a structure with characteristics similar to nacre (e.g., lamellar organic matrix mineralized with aragonite, as demonstrated by Laser Raman Spectroscopy).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Demonstration of the capacity of nacre to induce bone formation by human osteoblasts maintained in vitro.

Nacre implanted in vivo in bone is osteogenic suggesting that it may possess factor(s) which stimulate bone formation. The present study was undertaken to test the hypothesis that nacre can induce mineralization by human osteoblasts in vitro. Nacre chips were placed on a layer of first passage human osteoblasts. None of the chemical inducers generally required to obtain bone formation in vitro was added to the cultures. Osteoblasts proliferated and were clearly attracted by nacre chips to which they attached. Induction of mineralization appeared preferentially in bundles of osteoblasts surrounding the nacre chips. Three-dimensional nodules were formed by a dense osteoid matrix with cuboidal osteoblasts at the periphery and osteocytic-like cells in the center. These nodules contained foci with features of mineralized structures and bone-like structures, both radiodense to X-ray. Active osteoblasts (e.m.) with abundant rough endoplasmic reticulum, extrusion of collagen fibrils and budding of vesicles were observed. Matrix vesicles induced mineral deposition. Extracellular collagen fibrils appeared cross-banded and electrodense indicating mineralization. These results demonstrate that a complete sequence of bone formation is reproduced when human osteoblasts are cultured in the presence of nacre. This model provides a new approach to study the steps of osteoblastic differentiation and the mechanisms of induction of mineralization.

Animals↗