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P T Huy

Publications and source records attributed to P T Huy.

At least 19 recordsLinked to original sources
PubMed2000

Expression of NMDA, AMPA and GABA(A) receptor subunit mRNAs in the rat auditory brainstem. I. Influence of early auditory deprivation.

Impact of early post-natal deafening on auditory pathways was investigated in newborn rats deafened by daily amikacin injections from P7 to P16 inducing a complete destruction of the organ of Corti. The expression of mRNAs encoding N-methyl-D-aspartate (NMDA), alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) and gamma-aminobutyric acid type A (GABA(A)) receptor subunits was then studied by in situ hybridization in the dorsal and ventral cochlear nucleus and in the central nucleus of the inferior colliculus (CNIC). Early post-natal deafening decreased bilaterally the expression of mRNAs encoding NR1, NR2a, NR2b and flop isoforms of AMPA receptors. On the contrary, it increased the expression of mRNAs encoding some GABA(A) subunits (alpha1, beta1, gamma2) and flip isoforms of AMPA receptors. These changes were more pronounced in cochlear nuclei than in CNIC. They suggest that auditory sensation is essential in the normal development of central auditory pathways.

Amikacin↗
PubMed2000

Expression of NMDA, AMPA and GABA(A) receptor subunit mRNAs in the rat auditory brainstem. II. Influence of intracochlear electrical stimulation.

We investigated the effects of intracochlear electrical stimulation (ICES) on auditory pathways of neonatal rat deafened by daily amikacin injections. Expression of mRNAs encoding ionotropic glutamate receptor subunits such as alpha-amino-3-hydroxy-5-methyl-4-isoxazole (AMPA) and N-methyl-D-aspartate (NMDA), and gamma-aminobutyric acid type A (GABA(A)) receptor subunits was assessed by in situ hybridization in the dorsal (DCN) and the ventral cochlear nucleus (VCN) and in the central nucleus of the inferior colliculus (CNIC). After 15 days of daily unilateral ICES, the expressions of NR1, NR2b and NR2c subunits of NMDA receptor, that of GluRA, B, C, D flop isoforms of AMPA receptor and that of some GABA(A) subunits (alpha1, beta1, gamma1, gamma2) were increased bilaterally in the DCN, VCN and the CNIC. These changes last over a week after stimulation for only NR1 and NR2c. These modifications might be related to long lasting synaptic plasticity of brainstem auditory pathways. As far as analogy to deaf children can be made, early electrical stimulation might be of interest to maintain neuronal networks.

Animals↗
PubMed1999

Potassium channel ether à go-go mRNA expression in the spiral ligament of the rat.

Identification of the K+ transporters located in the lateral wall of the cochlea is essential for a better understanding of the mechanisms by which a positive endocochlear potential and a high K+ concentration are achieved in endolymph. In this study, we have determined the distribution of the K+ channel rat ether à go-go (eag) mRNA in the cochlea. After reverse transcription of adult rat cochlear tissues, cDNA was amplified with primers specific to eag channel. The eag mRNA was localized in cochlear tissues by in situ hybridization using specific oligonucleotide probes tailed with digoxigenin conjugated UTP. Eag mRNA was detected in the organ of Corti but mainly in the fibrocytes of the spiral ligament but not in spiral prominence or in stria vascularis. The expression pattern of rat eag transcript in spiral ligament is complementary to the Na+,K+-ATPase distribution in the cochlear lateral wall. The localization of eag mRNA suggests that eag potassium channel may be produced in the corresponding cells. Considering the importance of the K+ gradient in the cochlea, the result reported here suggests that eag channel may play a role in the control of K+ fluxes in the spiral ligament.

Animals↗
PubMed1999

Nasal haemangiopericytoma: report of two cases with literature review.

Haemangiopericytoma (HPC) is a rare vascular tumour produced by proliferation of pericytes. One hundred and thirty-three cases of HPC have been reported in the nose and the paranasal sinuses. We present two more cases. Wide surgical excision via lateral rhinotomy, midfacial degloving, or endonasal removal is the treatment of choice. Radiotherapy has been used post-operatively in cases of incomplete removal. Life-long follow-up is required to evaluate local recurrence and late metastases.

Aged↗
PubMed1999

Long-term follow-up of juvenile nasopharyngeal angiofibromas: analysis of recurrences.

OBJECTIVES: Juvenile nasopharyngeal angiofibroma often recurs if the tumor is large. This report is a long-term follow-up of these cases. It establishes the prognostic values of tumor extensions, analyzes the anatomic factors involved in recurrences, describes the spontaneous evolution of remnants based on a radiographic follow-up, and evaluates the pertinence of complex combined surgical approaches for invasive tumors and the value of complementary endoscopy. STUDY DESIGN: Retrospective review of 44 cases treated between 1985 and 1996. METHODS: Statistical analysis of the correlation between recurrence and tumor extension as evaluated by systematic analysis of 18 putative tumor extensions on preoperative computed tomography scans. RESULTS: Invasion of the skull base affected two-thirds of the patients, and the rate of recurrence was 27.5%. Extensions to the infratemporal fossa, sphenoid sinus, base of pterygoids and clivus, the cavernous sinus (medial), foramen lacerum, and anterior fossa were correlated with more frequent recurrence. Long-term radiographic follow-up revealed putative residual disease in nine asymptomatic patients: these remnants gradually involuted. CONCLUSIONS: The data in the current study emphasize the prognostic value of skull base invasion and the difficulty of complete resection of extended lesions. Tumor remnants detected in symptom-free patients should be kept under surveillance by repeated computed tomography scan, since involution may occur. Recurrent symptoms may be treated by radiotherapy (30 Gy) rather than by extended combined procedures. Endoscopic surgery should be combined with surgery for better control of skull base extensions.

Adolescent↗
PubMed1999

Oxygen modulates Na+ absorption in middle ear epithelium.

The physiology of the middle ear is primarily concerned with keeping the cavities air filled and fluid free to allow transmission of the sound vibrations from the eardrum to the inner ear. Middle ear epithelial cells are thought to play a key role in this process, since they actively transport Na+ and water. The PO2 of the middle ear cavities varies from 44 to 54 mmHg in healthy human ears but may be lower in the course of secretory otitis media. The effect of chronic hypoxia on ion transport was investigated on a middle ear cell line using the short-circuit current technique. Chronic hypoxia reversibly decreased the rate of Na+ absorption across the MESV cell line. Although a decrease in cellular ATP content was observed, the decrease of Na+ absorption seemed related to a primary modulation of apical Na+ entry. As revealed by RNase protection assay, the decrease in the rate of apical Na+ entry strictly paralleled the decrease in the expression of transcripts encoding the alpha-subunit of the epithelial Na+ channel. This effect of oxygen on Na+ absorption might account for 1) the presence of fluid in the middle ear in the course of secretory otitis media and 2) the beneficial effect of the ventilation tube in treating otitis media that allows the PO2 to rise and restores the fluid clearance.

Absorption↗
PubMed1999

Two types of voltage-dependent potassium channels in outer hair cells from the guinea pig cochlea.

Cell-attached and cell-free configurations of the patch-clamp technique were used to investigate the conductive properties and regulation of the major K(+) channels in the basolateral membrane of outer hair cells freshly isolated from the guinea pig cochlea. There were two major voltage-dependent K(+) channels. A Ca(2+)-activated K(+) channel with a high conductance (220 pS, P(K)/P(Na) = 8) was found in almost 20% of the patches. The inside-out activity of the channel was increased by depolarizations above 0 mV and increasing the intracellular Ca(2+) concentration. External ATP or adenosine did not alter the cell-attached activity of the channel. The open probability of the excised channel remained stable for several minutes without rundown and was not altered by the catalytic subunit of protein kinase A (PKA) applied internally. The most frequent K(+) channel had a low conductance and a small outward rectification in symmetrical K(+) conditions (10 pS for inward currents and 20 pS for outward currents, P(K)/P(Na) = 28). It was found significantly more frequently in cell-attached and inside-out patches when the pipette contained 100 microM acetylcholine. It was not sensitive to internal Ca(2+), was inhibited by 4-aminopyridine, was activated by depolarization above -30 mV, and exhibited a rundown after excision. It also had a slow inactivation on ensemble-averaged sweeps in response to depolarizing pulses. The cell-attached activity of the channel was increased when adenosine was superfused outside the pipette. This effect also occurred with permeant analogs of cAMP and internally applied catalytic subunit of PKA. Both channels could control the cell membrane voltage of outer hair cells.

4-Aminopyridine↗
PubMed1999

Transnasal endoscopic removal of an orbital cavernoma.

The approach to posterior and medial orbital tumors is still a challenge, since poor functional results are frequent. We report a case of cavernoma successfully removed by a modified transnasal endoscopic procedure. The patient, a 56-year-old woman, complained of a decrease in vision of the left eye. Magnetic resonance imaging evidenced a lesion in the posterior part of the orbital cavity, inferior to the optic nerve, extending to the sphenoidal cleft. The lesion was isodense on T1-weighted images and showed contrast enhancement. Because of the medial location of the tumor, the patient was referred to the otolaryngology department by the neurosurgeons, and a transnasal endoscopic approach was chosen. A large exposure of the operative field was obtained, and a cavernoma was removed. Rapid relief of the symptoms was obtained. In view of this good result, we advocate the transnasal endoscopic approach in cases of inferomedial and posterior intraconal lesions as an alternative and addition to the standard techniques of orbital surgery.

Endoscopy↗
PubMed1999

Saccular dysfunction in Meniere's disease.

OBJECTIVE: The aim of this study was to assess any dysfunction of the sacculus in patients with unilateral Meniere's disease by monitoring the vestibular evoked myogenic potentials (VEMPs) evoked by high level clicks on the Stemomastoid muscles (SCMs). STUDY DESIGN: The study was a retrospective analysis. SETTING: The study was performed in the E.N.T. department of the Lariboisière Hospital. PATIENTS: Fifty-nine patients aged 18 to 74 years with well-established unilateral Meniere's disease were included in the study. INTERVENTIONS: Loud monaural clicks were delivered unilaterally, and the VEMPs were recorded with skin electrodes on the ipsilateral SCM. All the patients were also subjected to a pure tone audiometric test and bithermal caloric testing. The postural performances of 39 patients were analyzed using the Equitest. MAIN OUTCOME MEASURE: VEMP results were the main outcome measure. RESULTS: The saccular response was absent on the affected side in 54% of the patients with Meniere's disease. This absence was correlated with the degree of low frequency hearing loss but not with canal paresis. Finally, nonfalling patients with saccular dysfunction had a significantly poorer postural performance than those without such dysfunction in the condition 5. CONCLUSION: Patients with Meniere's disease could have a saccular dysfunction (54% in this series). This saccular impairment correlated with low frequency hearing loss but not with canal paresis. Patients without VEMPs had poorer postural performances in condition 5 than those with normal VEMPs. Therefore, VEMP testing is useful for detecting patients at risk: in patients with saccular lesion, the dynamic postural performances should be assessed on a movable platform to detect visually dependent patients and to orient vestibular rehabilitation.

Adolescent↗
PubMed1998

[Mallear epidermosis. An unusual form of open mucous otitis].

The presence of keratin in the middle ear cavity is usually associated with the diagnosis of cholesteatoma or epidermoid metaplasia. Analysis of a series of 18 cases suggests that it may correspond to a specific entity developing in the course of severe or long-lasting opened chronic otitis. This condition, we called mallear epidermosis, is characterized by: i) a perforation of the tympanic membrane lining the handle of the malleus and the umbo; ii) a proliferation of keratin surrounding the handle of the malleus and diffusing into the mesotympanum on the internal side of the tympanic membrane, without matrix; and iii) a mild inflammation of the middle ear epithelium. The process is usually limited to the mesotympanum and does not extend towards the attic and the posterior cavities. Epidemiological, clinical, pathophysiological, and histological features allow this entity to be distinguished from cholesteatoma and epidermoid metaplasia. Management is either medical consisting of local treatment and microaspiration, or surgical including resection of the umbo, removal of the tympanic membrane invaded by the adherent hyperkeratotic layers and repair by conventional underlay myringoplasty. This report emphasizes the need for a clear identification of the various types of chronic otitis media presenting with keratin in the middle ear, as they do not share the same course and do not require the same therapeutic management.

Adolescent↗
PubMed1997

Glucocorticosteroids increase sodium transport in middle ear epithelium.

The effect of glucocorticosteroids on ion transport was investigated on a middle ear cell line with the short-circuit current (Isc) technique. Dexamethasone (DXM) produced a dose- and time-dependent increase in Isc. Concentration of half-maximal stimulation was 2.68 x 10(-8) M. This effect was blunted by the glucocorticoid antagonist RU-38486 and was related to Na+ transport, as evidenced by the inhibition induced by 1) apical addition of the Na+ channel inhibitor benzamil (10(-6) M) or 2) substitution of Na+ with N-methylglucamine in the incubation medium. The increase in Na+ transport resulted from a primary modulation of apical Na+ entry, since 1) the Na(+)-K(+)-ATPase activity of cellular homogenates was not modified by corticosteroids and 2) the DXM-induced increase in the ouabain-sensitive uptake of 86Rb was blunted by benzamil. Ribonuclease protection assay revealed 1) a constitutive expression of the mRNA encoding the alpha-subunit of the epithelial Na+ channel and 2) that DXM increased the expression of this transcript. This increase was dose dependent and paralleled changes in transepithelial Na+ transport. This study suggests that a component of the beneficial effect of steroid therapy for the treatment of otitis media might be related to increased fluid clearance.

Adenosine Triphosphate↗
PubMed1997

[Rotatory impulse test does not replace caloric tests].

We sought to determine whether the rotatory impulsional test was capable of exploring the canalar function with sufficient precision to replace the caloric test, as it has been recently affirmed. We first compared the observed preponderance from this test with that measured during a sinusoidal (20 and 4 s) test. We observed that, in the case of a significant preponderance for a given test, there was complete redondance with the preponderance observed with any other test. The rotatory impulsional test does not present any specific advantage compared to other kinetic test as far as the observation of the preponderance phenomenon. We then compared the preponderance with the results of the caloric tests and came to the following conclusions i) the absence of preponderance does not allow us to predict the absence of vestibular deficit, due to the fact that 37% of the deficits were compensated for including acoustic neuroma; ii) the presence of a preponderance does not allow a priori to say whether it is of vestibular, cervical, or central origin and systematic caloric tests shows that almost one fourth of preponderance observed is not associated with unilateral weakness iii) supposing that a clinical argument allow us to conclude as to the probable vestibular origin of a vestibular preponderance, the direction of this preponderance does not allow us to determine which side is involved. In fact, if the undercompensated deficits are 3 times more frequent than overcompensated deficits, the proportion of preponderance not linked to a significant deficit indicates that the probability of encountering a preponderance related to a specific undercompensated deficit is approximately 50%. We thus did not find in the rotatory impulsional test any specific advantage allowing us to predict the laterality of a vestibular lesion.

Caloric Tests↗
PubMed1993

Primary culture of Reissner's membrane from the gerbil: growth, morphologic features, and characterization.

To overcome the technical difficulties encountered in investigating the physiology of Reissner's membrane (RM), primary culture of RM was established. Minute explants obtained by mechanical dissociation were seeded on impermeable substrate coated with collagen type I in serum-free, hormone-supplemented medium. Within 2 weeks, a large cultured area was obtained which reproduced the two cell layers of the original explant. One layer, deep or superficial depending on the side to which the explant adhered, was made of cells exhibiting light and electron microscopy characteristics of an epithelium. Immunohistochemical methods revealed that they expressed cytokeratin, demonstrating their epithelial nature. The second layer was made of mesenchymal cells. This study suggests that cell culture of RM will facilitate further investigation of its physiology.

Animals↗
PubMed1993

[Surgical indications in angioma of the face].

Hemangiomas are common vascular tumors of children. They always regress. Surgery takes place for late sequelae, such as cutaneous scarring and distortion of the facial structures. Early surgery is beneficial for the nasal cryano hemangioma, or for some eyelid hemangiomas. Venous malformations need to be manage from childhood to adulthood as they slowly worsen. Percutaneous embolization with Ethibloc and surgery are performed in order to minimize, or to improve the skin, muscle and bone distortion. Arteriovenous malformations are the most dangerous vascular anomalies of the face. Superselective arterial embolization prepares the surgical excision of the nidus. Difficulties in covering the excised area are frequently solved by flaps or cutaneous expansion.

Adolescent↗
PubMed1992

Ion transport by primary cultures of Mongolian gerbil middle ear epithelium.

The transport properties of Mongolian gerbil middle ear epithelial cells grown in primary culture were studied. These cells formed polarized monolayers that exhibited domes on nonporous supports. On porous supports, monolayers developed an apical-negative transepithelial electric potential difference (VT = -37.2 +/- 2.7 mV) and a transepithelial resistance (RT = 519 +/- 56 omega.cm2). The short-circuit current equivalent (Ieq) was 62.4 +/- 6.2 microA/cm2 (mean +/- SE, n = 15). Na+ and Cl- accumulated in the basal bath and generated a basolateral hyperosmolarity that drove a net water flow. Amiloride (10 microM), when added to the apical but not to the basal bath, induced a 23.4 +/- 1.5 mV and 44.1 +/- 1.3 microA/cm2 decrease of VT and Ieq, respectively, while RT increased by 403 +/- 69 omega.cm2 (P less than 0.001, n = 15). Exposure of the monolayers to a low-Cl- solution (30 mM) enhanced the transepithelial potential, possibly by means of a Cl- secretion through apical Cl- channels. Isoproterenol (10(-4) M basolateral) increased intracellular adenosine 3',5'-cyclic monophosphate (cAMP) content (concentration of half-maximal response = 2.5 x 10(-7) M) and decreased VT, RT, and Ieq. The isoproterenol-induced fall of VT occurred even in the presence of low-Cl-solutions. This suggested an increase of the paracellular pathway conductance, although there was no significant modification of the mannitol permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride↗
PubMed1991

Primary culture of strial marginal cells of guinea pig cochlea: growth, morphologic features, and characterization.

To further investigate the cellular mechanisms involved in the formation of endolymph, primary cultures of marginal cells of guinea pig were established. Minute explants obtained by mechanical dissociation of stria vascularis were plated on collagen type I precoated impermeable substrate in serum-free, hormone-supplemented medium. A confluent layer of epithelial-like cells was obtained within 2 weeks. The cultured cells formed domes, demonstrating that they retain some of their transepithelial properties. Polarization was also suggested by electron microscopic observation of apical microvilli and tight junctions. Immunohistochemical methods revealed that the cultured cells coexpressed cytokeratin and vimentin, demonstrating their epithelial origin, although some degree of dedifferentiation occurred. Thus, a primary culture of marginal cells can be established that may be a suitable model for an in-depth investigation of the function of the marginal cells.

Animals↗