PubMed Health⌕ Search

Biomedical subjects

D Nicolas

Publications and source records attributed to D Nicolas.

13 recordsLinked to original sources
PubMed2006

Transitory uptake of serotonin in the developing sensory pathways of the common marmoset.

Serotonin (5-HT) affects brain development during sensitive developmental periods. In rodents, transient sites of high affinity capture of 5-HT were demonstrated in the primary sensory neurons and in the sensory thalamocortical afferents. This uptake is required to adjust 5-HT receptor stimulation during the formation of sensory maps. To determine whether similar mechanisms exist in primates, we analyzed staged embryos and postnatal pups in the common marmoset (total gestation time, 142 days). Immunocytochemical analyses were performed using antisera to 5-HT, to the serotonin transporter (SERT), and to the vesicular monoamine transporter (VMAT2). 5-HT, SERT, and VMAT2 labeled the raphe neurons and their terminal network from embryonic day (E)70 to adulthood. In addition, from E70-130 VMAT2 and SERT were observed in all the sensory cranial nerves, the olfactory nerve, the gustatory, the trigeminal, the auditory fibers, in the retinal ganglion cells, and the optic tract up to the lateral geniculate nucleus and the superior colliculus. All the spinal sensory ganglia and their peripheral sensory branches were labeled. Accumulation of 5-HT was observed in all the sensory neurons expressing SERT and the corresponding axon tracts. Since these neurons were missing tryptophan hydroxylase (TPH), the synthesizing enzyme for 5-HT, they most likely accumulated 5-HT through the action of the amine transporters, as has been shown in rodents. No transient expression of 5-HT markers was detectable in the sensory thalamocortical axons at any of the ages examined. Thus, the existence of 5-HT uptake in nonserotoninergic neurons appears to be a conserved feature in primates, although the topographic extent of this transient expression is more restricted than that previously demonstrated in rodents.

Afferent Pathways↗
PubMed2006

Structural transition in rare earth oxide clusters.

Size effects, such as structure transition, have been reported in small clusters of alkali halide compounds. We extend the study to rare earth sesquioxide (Gd(2)O(3)) clusters which are as ionic as the alkali halide compounds, but have a more complicated structure. In a clean and controlled environment (ultra high vacuum), such particles are well crystallized, facetted and tend to adopt a rhombic dodecahedron shape. This indicates the major role of highly ionic bonds in preserving the crystal lattice even at small sizes (a few lattice parameter). Based on both cathodo-luminescence and transmission electron microscopy, we report the existence of a structural transition from bcc to monoclinic at small sizes.

Journal Article↗
PubMed2000

Characterization of VIM-2, a carbapenem-hydrolyzing metallo-beta-lactamase and its plasmid- and integron-borne gene from a Pseudomonas aeruginosa clinical isolate in France.

Pseudomonas aeruginosa COL-1 was identified in a blood culture of a 39-year-old-woman treated with imipenem in Marseilles, France, in 1996. This strain was resistant to beta-lactams, including ureidopenicillins, ticarcillin-clavulanic acid, cefepime, ceftazidime, imipenem, and meropenem, but remained susceptible to the monobactam aztreonam. The carbapenem-hydrolyzing beta-lactamase gene of P. aeruginosa COL-1 was cloned, sequenced, and expressed in Escherichia coli DH10B. The deduced 266-amino-acid protein was an Ambler class B beta-lactamase, with amino acid identities of 32% with B-II from Bacillus cereus; 31% with IMP-1 from several gram-negative rods in Japan, including P. aeruginosa; 27% with CcrA from Bacteroides fragilis; 24% with BlaB from Chryseobacterium meningosepticum; 24% with IND-1 from Chryseobacterium indologenes; 21% with CphA-1 from Aeromonas hydrophila; and 11% with L-1 from Stenotrophomonas maltophilia. It was most closely related to VIM-1 beta-lactamase recently reported from Italian P. aeruginosa clinical isolates (90% amino acid identity). Purified VIM-2 beta-lactamase had a pI of 5.6, a relative molecular mass of 29.7 kDa, and a broad substrate hydrolysis range, including penicillins, cephalosporins, cephamycins, oxacephamycins, and carbapenems, but not monobactams. As a metallo-beta-lactamase, its activity was zinc dependent and inhibited by EDTA (50% inhibitory concentration, 50 microM). VIM-2 conferred a resistance pattern to beta-lactams in E. coli DH10B that paralleled its in vitro hydrolytic properties, except for susceptibility to ureidopenicillins, carbapenems, and cefepime. bla(VIM-2) was located on a ca. 45-kb plasmid that in addition conferred resistance to sulfamides and that was not self-transmissible either from P. aeruginosa to E. coli or from E. coli to E. coli. bla(VIM-2) was the only gene cassette located within the variable region of a novel class 1 integron, In56, that was weakly related to the bla(VIM-1)-containing integron. VIM-2 is the second carbapenem-hydrolyzing metalloenzyme characterized from a P. aeruginosa isolate outside Japan.

Amino Acid Sequence↗
PubMed1997

Colocalization of calretinin and glucagon in rat pancreatic A cells.

Calretinin is a calcium-binding protein whose major functions are assumed to be buffering, transport of Ca2+, regulation of various enzyme systems and cellular protection. Moreover, calretinin does not seem to be a specific marker for any particular cell since it has been discovered in various mammalian and avian organs. In order to give clue to its function(s), we investigate its distribution in the rat pancreas using immunocytochemistry and transmission electron microscopy. We have found calretinin immunoreactive cells in rat pancreas only in the islets of Langerhans. These cells correspond to A cells producing glucagon. The colocalization of calretinin and glucagon was confirmed with double-labelling immunofluorescence. Nevertheless, the role of calretinin and its relationship with the production and/or the exocytosis of glucagon granules remains to be elucidated.

Animals↗
PubMed1996

Calretinin immunoreactivity in pineal gland of different mammals including man.

Calretinin (CR) is a calcium-binding protein, found in a variety of organs and systems such as the central nervous system and the pineal gland. It was first thought to be a specific neuronal marker but this selectivity is now in question since CR has been demonstrated in avian thymus, rat ovary, rat and guinea pig inner ear, rat testis, and chicken and rat pineal gland. To contribute to the knowledge of the presence of CR-positive cells in the pineal parenchyma of rat and other mammalian including man, we performed immunocytochemistry on pineal glands of gerbils, rats, goats, cows, and humans, using a CR anti-serum. To confirm it was actually CR that was demonstrated, we performed Western Blot analyses. Finally, to precisely identify the nature of CR-positive cells we accomplished double-labelling immunofluorescence, using antisera against some nerve cell specific cytosquelettal proteins such as MAP-5, MAP-2, NF-L, NF-M, and NF-H. CR-positive cells were found in all pineal glands studied. These cells all possess a round, oval, or polygonal-shaped perikaryon sending one or more processes of different lengths into the glandular parenchyma. There is a lack of CR immunoreactivity in the nucleus and cell organelles while the cytosol contains a high concentration of this protein. Nevertheless, there are some slight differences between species, especially concerning the number of reactive cells and their relationships with different parenchymal structures such as blood vessels or acervuli. Among the CR-positive cells, only a few were actually nerve cells, contributing probably to an intrinsic innervation of the gland. The remaining CR-reactive cells seem to correspond mostly to pinealocytes in a specific histophysiological state and possibly to neuron-like cells. The significance of the CR-positive cells in the pineal glands remains to be elucidated.

Aged↗
PubMed1995

Nitric oxide synthase in the subfornical organ of Mongolian gerbil (Meriones unguiculatus), mouse and rat.

The present paper aims to contribute to the knowledge of the histophysiologic role of the subfornical organ. Using nicotinamide adenine dinucleotide phosphate diaphorase histochemistry (NADPH-diaporase) and nitric oxide synthase immunocytochemistry, we detected a high concentration of the neuronal isoform of nitric oxide synthase in neurons of the subfornical organ of the adult Mongolian gerbil (Meriones unguiculatus), mouse and rat. Our results suggest that neurons of the subfornical organ produce a considerable amount of nitric oxide which acts, not only as a neurotransmitter, but could also diffuse into cerebral blood vessels and cerebrospinal fluid.

Animals↗
PubMed1995

Presence of calmodulin and NADPH-diaphorase activity but not of neuronal nitric oxide synthase in the subcommissural organ of the Mongolian gerbil.

The subcommissural organ (SCO) and the ventricular ependyma of the third ventricle of the Mongolian gerbil (Meriones unguiculatus) exhibit a highly positive histochemical reaction to NADPH-diaphorase and a considerable immunocytochemical expression of calmodulin. The SCO, however, does not display an immunocytochemical response to the neuronal isoform of nitric oxide synthase (NOS) whereas it was demonstrated in the ventricular ependyma. Since the NADPH-diaphorase, which detects all isoforms of NOS, was clearly positive at the level of the SCO, the obtained results suggest that the SCO of the Mongolian gerbil produces nitric oxide but contains a NOS whose antigenic specificity differs from that of the neuronal isoform of this enzyme.

Animals↗
PubMed1992

Light and electron microscopic immunocytochemical localization of glutamine synthetase in the superficial pineal gland of the rat.

Glutamine synthetase (L-glutamate:ammonia ligase; EC 6.3.1.2), an enzyme catalysing the ATP-dependent formation of glutamine from glutamate and ammonia, was detected immunocytochemically only in glial (interstitial) cells of the superficial pineal gland of the rat. The results show the important role of pineal glial cells in the metabolism of the presumptive neurotransmitters, glutamate and gamma-aminobutyric acid (GABA) as well as in detoxification of ammonia.

Animals↗
PubMed1990

Histoenzymological light and electron microscopic localization of carbonic anhydrase in the rat superficial pineal gland.

A histoenzymological method for demonstration of carbonic anhydrase (CA) was used for cryostat sections of superficial rat pineal gland. Light and electron microscopic analysis showed a high concentration of this enzyme in stellate cells, particularly heavily distributed under the organ capsule and scattered in the parenchyma, where they form a widespread three-dimensional network. Most of the pericapillary spaces were lined by CA-reactive cells. The reaction product, in the form of strongly electron-dark precipitates, was localized in the cytoplasmic matrix, whereas organelles, except for some mitochondrial intracristal spaces, were CA-negative. On the basis of localization and morphology of CA-positive cells, we conclude that these represent glial (interstitial) cells.

Animals↗
PubMed1987

Successful management of congenital tracheal stenosis in infancy.

Seven infants with congenital tracheal stenosis were evaluated and treated to assess the efficacy of current techniques of management. All had multiple congenital anomalies in addition to tracheal stenosis. Notably, three infants had imperforate anus and three had vascular rings. Each infant presented early with respiratory distress. While bronchoscopy and/or bronchography were performed in some, the diagnosis could be made from high contrast x-rays of the chest in each instance. The complexity of the tracheal lesion(s) determined the operative approach. Complicating factors included tracheomalacia, multiple stenoses, pulmonary hypoplasia, and carinal involvement. The trachea was approached through an anterolateral thoracotomy in five cases and through the neck in one. Cardiopulmonary bypass was never required. Simple resection was possible only once. Four patients received costal cartilage grafts, and one graft was created from dura. Grafts varied from 2 1/2 to 6 cm in length and extended onto the bronchi in two cases. All patients with grafts were treated with postoperative endotracheal stents and ventilatory assistance and all were extubated successfully. One patient had trisomy 16p+ detected after successful extubation and died later. One patient was treated expectantly and died. While each case must be individualized, repair of complex tracheal stenosis often results in dramatic immediate improvement and long-term success.

Child, Preschool↗
PubMed1985

[Epidemiologic aspects of Mediterranean boutonneuse fever in the south of Corsica].

During Summer 1984 was conducted a prospective study concerning Mediterranean Spotted Fever (a rickettsiosis due to Rickettsia conorii) in the south of Corsica. The prevalence of symptomatic and typical cases was 48 per 100,000. A seroepidemiologic study made on blood donors of the same area shows a prevalence of antibody to R. conorii at 12% for a dilution of 1/32, 4.8% for 1/64 and 2.5% for 1/128. This study show that Corsica is, as well as south of France, Sicily and Spain an endemic country for Mediterranean Spotted Fever and that asymptomatic cases are mostly frequent.

Adolescent↗