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A Sans

Publications and source records attributed to A Sans.

At least 19 recordsLinked to original sources
PubMed2005

Three-dimensional culture of newborn rat utricle using an extracellular matrix promotes formation of a cyst.

The vestibule is the end organ devoted to sensing of head movements in space. To function properly, its mechano-receptors require the presence of a unique apical extracellular medium, the endolymph. Numerous studies have elucidated the mechanisms involved in the production and homeostasis of this unique medium and the responses of sensory cells to stimulation. However, anatomical constraints have prevented direct and simultaneous studies of their relationships. The aim of this study was the development of an in vitro model that would allow concomitant investigations on maturation and physiological properties of both the hair cells and their endolymphatic compartment. A three-dimensional (3D) culture of newborn rat utricles using an extracellular matrix sustaining 3D cellular growth was developed during 3, 6, or 10 days in vitro (DIV). Using morphological and electrophysiological techniques, we describe the de novo formation of a cyst. It was composed of the sensory epithelium and non-sensory cells-canalar, dark and intermediate cells-that polarized so that their apical surface faced its lumen. During the time of culture, the utricular potential (UP) was steady (-1.1+/-5.0 mV) in oxygenated condition, while in anoxia, the UP significantly decreased to -8.4+/-1.0 mV at 8 DIV. Over the same period, the K+ concentration in the cyst increased up to 86.1+/-33.9 mM (versus 5.6+/-1.5 mM in the bath). These observations indicated that the mechanisms generating the UP and the K-secretory activity were functional at this stage. Concomitantly, the hair cells acquired mature and functional properties: the type 1 and type 2 phenotypes, a mean resting membrane potential of -68.1+/-4.6 mV and typical electrophysiological responses. This preparation provides a powerful means to simultaneous access the hair cells and their endolymphatic compartment, with the possibility to use multi-technical approaches to investigate their interdependent relationships.

Animals↗
PubMed2005

Molecular diversity of voltage-gated sodium channel alpha subunits expressed in neuronal and non-neuronal excitable cells.

In order to investigate the role of molecular diversity of voltage-activated sodium channel alpha-subunits in excitability of neuronal and non-neuronal cells, we carried out patch-clamp recordings and single-cell RT-PCR on two different types of mammalian excitable cells i.e. hippocampal neurons and non-neuronal utricular epithelial hair cells. In each cell type, multiple different combinations of sodium channel alpha-subunits exist from cell to cell despite similar sodium current properties. The mRNA isoforms, Nav1.2 and Nav1.6, are the most frequently detected by single cell analysis in the two cell types while Nav1.3 and Nav1.7 are also moderately expressed in embryonic hippocampal neurons and in neonatal utricular hair cells respectively. By investigating the particular alternate splice isoforms of Nav1.6 occurring at the exon 18 of the mouse orthologue SCN8A, we revealed that this subunit co-exist in the two cell types under different alternative spliced isoforms. The expression of non-functional isoforms of Nav1.6 in utricular epithelial hair cells excludes the involvement of this subunit in supporting their excitability. Thus, from a functional point of view, the present results suggest that, at the single cell level, both neuronal and non-neuronal excitable cells expressed different and complex patterns of sodium channel gene transcripts but this diversity alone cannot explain the sodium current properties of these cell types.

Alternative Splicing↗
PubMed2003

[Value of intrathecal baclofen in the treatment of spastic cerebral palsy].

Spasticity is the most common movement disorder in cerebral palsy. Cerebral spasticity has traditionally been treated with physical therapy and orthopedic surgery. Oral medications have been used with limited success. Intrathecal administration of baclofen may be a valuable alternative in selected patients. We comment the patient management and clinical practice guidelines on the use of intrathecal baclofen for the treatment of spasticity.

Baclofen↗
PubMed2002

Comparative studies of female sex pheromone components and male response of the corn stalk borer Sesamia nonagrioides in three different populations.

Studies to determine possible differences in the pheromone communication system of three different populations of the corn stalk borer Sesamia nonagrioides (Lef.) in France. Spain. and Greece were carried out. The two main pheromone components (Z)-11-hexadecenyl acetate (Z11-16:Ac) and (Z)-11-hexadecenol (Z11-16:OH), were detected in all analyses with very small differences in the three populations. Among the minor components, analyzed by GC-MS on concentrated gland extracts from French and Greek origin females, (Z)-l1-hexadecenal (Z11-16:Ald) was detected in minor amounts. Wind-tunnel and field studies revealed similar a male response in the three populations to pheromone glands extracts and synthetic pheromone regardless of the female/male origin. The results do not support the assumption of the existence of different pheromone types of the corn stalk borer S. nonagrioides due to geographic isolation.

Adaptation, Physiological↗
PubMed2002

[Visuo-constructive disorders in periventricular leukomalacia].

INTRODUCTION: Cerebral palsy involves not only motor impairment but also the impairment of cognitive functions. Visuo spatial impairment has often been reported in preterm children with spastic diplegia due to periventricular leukomalacia. PATIENTS AND METHODS: Eight children with periventricular leukomalacia diagnosis. When examined their ages were between 3 and 13 years. RESULTS: We found visuo spatial anomalies in all subjects. These anomalies don't result in reading and writing learning difficulties. CONCLUSION: Constructional dyspraxia is frequently found in children with periventricular leukomalacia and correlates with reduction of peritrigonal white matter in parietal lobe.

Adolescent↗
PubMed2001

Hyperpolarization-activated (Ih) current in mouse vestibular primary neurons.

The presence of a hyperpolarization-activated inward current (Ih) was investigated in mouse vestibular primary neurons using the whole-cell patch-clamp technique. In current-clamp configuration, injection of hyperpolarizing currents induced variations of membrane voltage with prominent time-dependent rectification increasing with current amplitudes. This effect was abolished by 2 mM Cs+ or 100 microM ZD7288. In voltage-clamp configuration, hyperpolarization pulses from -60 mV to -140 mV triggered a slow activating and non inactivating inward current that was sensitive to the two blockers, but insensitive to 5 mM Ba2+. Changing Na+ and K+ concentrations demonstrated that Ih current is carried by both these monovalent cations. This is the first demonstration of a Ih current in vestibular primary neurons.

Animals↗
PubMed2001

Contribution of the plasmalemma to Ca2+ homeostasis in hair cells.

Calcium influx through transduction channels and efflux via plasmalemmal Ca(2+)-ATPases (PMCAs) are known to contribute to calcium homeostasis and modulate sensory transduction in vertebrate hair cells. To examine the relative contributions of apical and basolateral pathways, we analyzed the calcium dynamics in solitary ciliated and deciliated guinea pig type I and type II vestibular hair cells. Whole-cell patch-clamp recordings demonstrated that these cells had resting potentials near -70 mV and could be depolarized by 10-20 mV by superfusion with high potassium. Fura-2 measurements indicated that ciliated type II cells and deciliated cells of either type had low basal [Ca(2+)](i), near approximately 90 nm, and superfusion with high potassium led to transient calcium increases that were diminished in the presence of Ca(2+) channel blockers. In contrast, measurements of type I ciliated cells, hair cells with large calyceal afferents, were associated with a higher basal [Ca(2+)](i) of approximately 170 nm. High-potassium superfusion of these cells induced a paradoxical decrease in [Ca(2+)](i) that was augmented in the presence of Ca(2+) channel blockers. Optical localization of dihydropyridine binding to the kinocilium suggests that they contain L-type calcium channels, and as a result apical calcium influx includes a contribution from voltage-dependent ion channels in addition to entry via transduction channels localized to the stereocilia. Eosin block of PMCA significantly altered both [Ca(2+)](i) baseline and transient responses only in ciliated cells suggesting that, in agreement with immunohistochemical studies, PMCA is primarily localized to the bundles.

Animals↗
PubMed2001

Pheromone response inhibitors of the corn stalk borer Sesamia nonagrioides. Biological evaluation and toxicology.

The behavioral activity of some trifluoromethyl ketones (TFMKs) as inhibitors of the pheromone activity of the corn stalk borer Sesamia nonagrioides (Lef.) (Lepidoptera: Noctuidae) is reported. The most closely-related analogue to the pheromone tested, (Z)-11-hexadecenyl trifluoromethyl ketone (Z11-16:TFMK), elicited a significant decrease in the number of male catches in traps baited with mixtures with the pheromone in 1:1 and 10:1 ratios in comparison to the pheromone alone. The E isomer of the analogue as well as two highly hydrated ketones, 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP) and 1,1-difluoropentadecyl trifluoromethyl ketone, were inactive. Conversely, the saturated TFMKs n-dodecyl trifluoromethyl ketone and, particularly, n-hexadecyl trifluoromethyl ketone induced a synergistic effect when mixed with the synthetic pheromone in 10:1 ratio. However, in a wind tunnel these chemicals did not elicit any differential effect on flying moths attracted to a source containing a 10:1 blend of the analogue and the pheromone. In a dual choice bioassay with two dispensers, containing the pheromone alone, and mixtures of Z11-16:TFMK and the pheromone and separated 5 cm apart, males showed no particular preference for either dispenser. The ketone mixture, however, induced moths to execute erratic flights with frequent crosswind counter-turns and intersections with plume boundaries. The total number of contacts with the source were reduced when a control dispenser was paired with a dispenser containing Z11-16:TFMK and pheromone. Z11-16:TFMK and OTFP showed little toxicity on mice with a LD50 of 1 g/kg after the 6th day of treatment. For comparitive purposes, the major component of the pheromone, Z11-16:Ac, displayed a LD50 of 5 g/kg 6 days after application. Our results provide additional information about the activity of the TFMKs, which might be useful for the utilization of these chemicals in future pest control studies.

Animals↗
PubMed2001

Three types of depolarization-activated potassium currents in acutely isolated mouse vestibular neurons.

The nature and electrophysiological properties of Ca(2+)-independent depolarization-activated potassium currents were investigated in vestibular primary neurons acutely isolated from postnatal mice using the whole cell configuration of the patch-clamp technique. Three types of currents were identified. The first current, sensitive to TEA (I(TEA)) and insensitive to 4-aminopyridine (4-AP), activated at -40 mV and exhibited slow activation (tau(ac), 38.4 +/- 7.8 ms at -30 mV, mean +/- SD). I(TEA) had a half activation potential [V(ac(1/2))] of -14.5 +/- 2.6 mV and was inactivated by up to 84.5 +/- 5.7% by 10-s conditioning prepulses with a half inactivation potential [V(inac(1/2))] of -62.4 +/- 0.2 mV. The second current, sensitive to 4-AP (maximum block around 0.5 mM) and to alpha-dendrotoxin (I(DTX)) appeared at -60 mV. Complete block of I(DTX) was achieved using either 20 nM alpha-DTX or 50 nM margatoxin. This current activated 10 times faster than I(TEA) (tau(ac), 3.5 +/- 0.8 ms at -50 mV) with V(ac(1/2)) of -51.2 +/- 0.6 mV, and inactivated only slightly compared with I(TEA) (maximum inactivation, 19.7 +/- 3.2%). The third current, also sensitive to 4-AP (maximum block at 2 mM), was selectively blocked by application of blood depressing substance (BDS-I; maximum block at 250 nM). The BDS-I-sensitive current (I(BDS-I)) activated around -60 mV. It displayed fast activation (tau(ac), 2.3 +/- 0.4 ms at -50 mV) and fast and complete voltage-dependent inactivation. I(BDS-I) had a V(ac(1/2)) of -31.3 +/- 0.4 mV and V(inac(1/2)) of -65.8 +/- 0.3 mV. It displayed faster time-dependent inactivation and recovery from inactivation than I(TEA). The three types of current were found in all the neurons investigated. Although I(TEA) was the major current, the proportion of I(DTX) and I(BDS-I) varied considerably between neurons. The ratio of the density of I(BDS-I) to that of I(DTX) ranged from 0.02 to 2.90 without correlation with the cell capacitances. In conclusion, vestibular primary neurons differ by the proportion rather than the type of the depolarization-activated potassium currents they express.

4-Aminopyridine↗
PubMed2000

Detection and localization of BDNF in vestibular nuclei during the postnatal development of the rat.

The changes in expression and the subcellular localization of brain-derived neurotrophic factor (BDNF) protein in the rat vestibular nuclear complex (VNC), have been investigated at different postnatal stages. Immunoblotting and ELISA analyses showed a down-regulation of BDNF protein expression in VNC with age. In addition, observations by confocal microscopy revealed that BDNF is mainly located in neuronal somata at postnatal day 8 (P8) and restricted to processes by P15. These results support the idea that BDNF could have different roles in the VNC according to the stage of development The protein could act as a neurotrophic factor in embryonic and early postnatal stages whereas in later developmental stages of the VNC it could be involved in neuronal maturation and regulation of neuronal circuitry.

Age Factors↗
PubMed2000

Glutaryl-CoA dehydrogenase deficiency in Spain: evidence of two groups of patients, genetically, and biochemically distinct.

Glutaryl-CoA dehydrogenase (GCDH) deficiency causes glutaric aciduria type I (GA I), an inborn error of metabolism that is characterized clinically by dystonia and dyskinesia and pathologically by neural degeneration of the caudate and putamen. Studies of metabolite excretion allowed us to categorize 43 GA I Spanish patients into two groups: group 1 (26 patients), those presenting with high excretion of both glutarate and 3-hydroxyglutarate, and group 2 (17 patients), those who might not be detected by routine urine organic acid analysis because glutarate might be normal and 3-hydroxyglutarate only slightly higher than controls. Single-strand conformation polymorphism (SSCP) screening and sequence analysis of the 11 exons and the corresponding intron boundaries of the GCDH gene allowed us to identify 13 novel and 10 previously described mutations. The most frequent mutations in group 1 were A293T and R402W with an allele frequency of 30% and 28%, respectively. These two mutations were also found in group 2, but always in heterozygosity, in particular in combination with mutations V400M or R227P. Interestingly, mutations V400M and R227P were only found in group 2, and at least one of these mutations was found in 11 of 15 unrelated alleles, accounting together for 53% of the mutant alleles in group 2. Therefore, it seems clear that two genetically and biochemically distinct groups of patients exist. The severity of the clinical phenotype seems to be closely linked to the development of encephalopathic crises rather than to residual enzyme activity or genotype. Comparison of GCDH protein with other acyl-CoA dehydrogenases (whose x-ray crystal structure has been determined) reveals that most of the mutations identified in GCDH protein seem to affect folding and tetramerization, as has been described for a number of mutations affecting mitochondrial beta-oxidation acyl-CoA dehydrogenases.

Alleles↗
PubMed2000

[Acute childhood gastroenteritis study at Central University Hospital of Pointe-à-Pitre/Abymes, Guadeloupe, from November 1997 to March 1998].

To determine the role of enteric pathogens in acute childhood diarrhoea in Guadeloupe, 161 children (108 cases and 53 controls) from 0 to 2 years of age, admitted to Pointe-à-Pitre/Abymes University Hospital, were evaluated over a five-month period. A known enteric pathogen was identified in 40.8% of children. The most commonly identified aetiologic agents were Salmonella (16.7% of cases), especially Haddar serotype and Rotavirus (20.5%). This virus was isolated more often in the dry season. Adenovirus were detected in 3.6% of diarrhoeal stools and were not significatively associated with diarrhoeal disease. No Shigella, Campylobacter or parasites were found.

Acute Disease↗
PubMed1999

Developmental changes in low and high voltage-activated calcium currents in acutely isolated mouse vestibular neurons.

1. The development of low voltage-activated (LVA) and high voltage-activated (HVA) calcium currents was studied in neurons acutely dissociated from mouse vestibular ganglia at embryonic stages (E)14, 15, 17 and birth using the whole-cell patch-clamp technique. 2. LVA current was present in almost all neurons tested at stages E14 to E17, although at birth this current was restricted to a few neurons. Two populations of neurons were characterized based on the amplitude of the LVA current. In the first population, LVA current densities decreased between E17 and birth by which time this current tended to disappear in most neurons. A second population of neurons with high density LVA current appeared at E17, and in this group the mean density increased during development. 3. Among HVA currents, the dihydropyridine-sensitive L-type current remained constant between E15 and birth. Over the same period, the density of N- and Q-type currents continuously increased as shown using omega-conotoxin-GVIA (N-type), and high concentrations of omega-agatoxin-IVA (Q-type). The P-type current, sensitive to low concentrations of omega-agatoxin-IVA, transiently increased between E15 and E17, and then both current density and its proportion of the global current decreased. 4. Our results reveal large modifications in the expression of voltage-dependent calcium channels during embryonic development of primary vestibular neurons. The changes in the expression of LVA current and the transient augmentation of P-type HVA current occur during a period characterized by massive neuronal growth and by the beginning of synaptogenesis. These results suggest a specific role of these currents in the ontogenesis of vestibular primary afferents.

Animals↗
PubMed1999

Vestibular semicircular canal epithelium of the rat in culture on filter support: polarity and barrier properties.

The inner ear of mammals contains the vestibular apparatus which is involved in the maintenance of posture and balance. The tubular structure of the apparatus is bathed by the potassium-rich endolymph and sodium-rich perilymph in the luminal and abluminal compartments, respectively. The luminal compartment is lined by a continuous epithelium with islets of receptor organs, which separates the luminal from the abluminal compartment. The present work focuses on the epithelium, without the receptor organs, and shows that it can be reconstituted in culture. The epithelium from 4-day-old Wistar rats was grown on microporous membranes. High transepithelial electrical resistances (4000-6000 Omega.cm2) were achieved after 4-8 days in culture. The epithelium was characterized by the presence of cytokeratin, ZO-1 protein, occludin, and the presence of tight junctions and kinocilia. The transepithelial resistance of the cell monolayer withstood endolymph/perilymph dual bathing when the apical pole of the cells was in contact with endolymph, but collapsed in the reverse configuration. Weak but statistically highly significant basal to apical rubidium (86Rb) transport was observed. These findings show that this epithelium maintains its in vivo polarity and could enhance the potassium composition of endolymph up to maturity. This new culture model, in which dual bathing is possible, should enable further in vitro studies of the sensory vestibular epithelia.

Animals↗
PubMed1999

Ionic currents and current-clamp depolarisations of type I and type II hair cells from the developing rat utricle.

Ionic currents and the voltage response to injected currents were studied in an acutely dissected preparation of the rat utricle between birth and postnatal day 12 (PN12). Based upon morphological criteria, the sensory cells examined were divided into two classes, "type I" and "type 2 category," the latter of which may include some immature type I cells. The former group comprises a clearly defined electrophysiological population, with one large outwardly rectifying potassium conductance that is sensitive to 4-aminopyridine (4-AP), insensitive to tetraethylammonium (TEA) and displays voltage-dependent activation kinetics. In the absence of enzymatic dissociation procedures, and with the epithelium left largely intact, the mean half activation of this conductance was -30.3 mV at PN3, and -37.5 mV at PN12. At both stages it was almost entirely turned off at -74 mV. Omission of ATP from the intracellular solution appeared to prevent rundown of this conductance. Type II category hair cells formed a more heterogeneous population, exhibiting a distinct TEA-sensitive delayed rectifier potassium conductance; the rapidly activating and inactivating IA; an inward rectifier; and inward sodium currents at around PN3. Both cell types depolarised strongly in response to injected currents, with time courses reflecting the activation kinetics of their major outward conductances.

4-Aminopyridine↗