[ Acute non-calculous Salmonella enteriditis cholecystitis, diagnosis by percutaneous puncture].
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
R Pujol
Publications and source records attributed to R Pujol.
Development of the auditory hair cell surface in human fetuses. A scanning electron microscopy study.
Thirteen human fetal cochleas were investigated by scanning electron microscopy. Our observations concentrated on the hair cell surface. Ciliogenesis appeared to start during the 11th week of gestation on the inner hair cells (IHCs) and one week later on the outer hair cells (OHCs). The earliest stages of stereociliary development were similar on both types of cell and were characterized by the presence of round bundles of cilia arising from the surrounding microvilli. A three-dimensional V-shaped arrangement suddenly appeared, accompanied by the disappearance of short cilia on the internal side. Between the 20th and the 22nd weeks of gestation, both types of hair cell had an adult stereociliary pattern, i.e. a rectilinear arrangement on IHCs and W-shaped on OHCs. However, there were signs of immaturity, such as a disarray of OHCs and the presence of the kinocilium, suggesting that the surface of the auditory hair cells achieves its maturation during the last trimester of pregnancy.
Cell Membrane↗
Efferent tracts and cochlear frequency selectivity.
The cochlear innervation of guinea pigs was sectioned medially in a rostrocaudal direction at the level of the floor of the fourth ventricle, to study the effects of efferent pathways on cochlear microphonic (CM) suppression, the compound action potential (CAP) masking phenomenon, the input-output CAP function, and cochlear frequency selectivity estimated with tuning curves of single auditory nerve fibers. Sectioning reduced CM suppression without having any effect on absolute CM amplitude; it also reduced CAP masking. The input-output CAP function was not changed at intensities below 75 dB, and the single-unit tuning curves recorded before and after nerve sectioning were unaffected. Thus, the crossed efferent tracts (i.e., mainly the medial system) seems to be involved in the masking function itself, rather than one of the mechanisms responsible for high frequency cochlear selectivity.
Acoustic Stimulation↗
Effects of section of the medial efferent tracts (crossed and uncrossed) on cochlear frequency selectivity.
The cochlear innervation of guinea pigs was sectioned midway between the midline and the external side of the cochlear nucleus, in a rostrocaudal direction at the level of the floor of the fourth ventricle, to study the effects of medial efferent pathways on cochlear frequency selectivity estimated with tuning curves of single auditory nerve fibers. Single-unit tuning curves were affected by this type of efferent sectioning. Thus, the ipsi-lateral efferent system seems to be involved, through a tonic action, in the mechanisms responsible for high frequency cochlea selectivity.
Acoustic Stimulation↗
Neuron-specific enolase immunoreactivity in the developing mouse cochlea.
Onset of neuron-specific enolase reactivity was observed on gestation day 17 in spiral ganglion cells of the basal coil, and 2 days later in cochlear inner (IHC) and outer (OHC) hair cells. IHCs and OHCs were similarly reactive up to postnatal day 7, then the reactivity began to decrease in OHCs.
Animals↗
Periods of sensitivity to antibiotic treatment.
Explore the source record for details and available documents.
Action Potentials↗
Electron microscopic localization of N-terminal proenkephalin (synenkephalin) immunostaining in the guinea pig organ of Corti.
Using a pre-embedding immunoelectron microscopic technique, anti-synenkephalin immunostaining has been demonstrated within efferent varicosities (originating from the brainstem) of the inner spiral bundle and the tunnel spiral bundle of the organ of Corti. Axodendritic synapses were observed between the anti-synenkephalin immunostained varicosities and auditory dendrites connected to inner hair cells. No anti-synenkephalin immunostaining was found in any efferents at the outer hair cell level. We suggest that this immunolocalization of synenkephalin in the organ of Corti allows a better differentiation of the cochlear efferent systems on a neurochemical basis. The whole lateral system, or at least a significant part of it, could be referred to as the 'enkephalin-containing efferent system'.
Animals↗
The very distal part of the basilar papilla in the chicken: a morphological approach.
The very distal part of the chicken basilar papilla was investigated by light and electron (scanning and transmission) microscopy. The rostral tip of the basilar papilla has a lenticular area with atypical sensory hair cells which are more similar to vestibular than to auditory cells. The structure of the lenticular area appears to be suitable for vestibular function or, more likely, for auditory perception at very low frequencies. Several hypotheses can be proposed to explain this very peculiar portion of the avian cochlea. It is difficult to consider it a continuously growing area since it remains stable in adulthood. A better explanation would be that there is an incomplete ontogenetic or phylogenetic process.
Animals↗
Met-enkephalin-Arg6-Gly7-Leu8 in the organ of Corti: high performance liquid chromatography and immunoelectron microscopy.
The opioid octapeptide Met-enkephalin-Arg6-Gly7-Leu8 (MERGL) was identified and quantified in the guinea pig cochlea using high performance liquid chromatography and a specific radioimmunoassay. The presence of MERGL immunostaining in efferent endings (coming from the brainstem) within the inner spiral bundle and the tunnel spiral bundle was demonstrated using a pre-embedding immunoelectronmicroscopic technique. Axo-dendritic synapses were observed between the MERGL immunostained varicosities and auditory dendrites. It is hypothesized that MERGL could act, together with Met-enkephalin and other pro-enkephalin A-related peptides, as an efferent neuromodulator or neurotransmitter in the organ of Corti.
Animals↗
Kainic acid selectively alters auditory dendrites connected with cochlear inner hair cells.
Cochleas of adult guinea pigs and rats, and 6-day-old rat pups, were injected, through the round window, with 2 microliters of artificial classical Konishi perilymph containing 1 nmol kainic acid (KA). 5 min later, they were fixed, removed, and processed for electron microscopy. In all KA-treated cochleas, the injection resulted in a severe swelling of auditory dendrites below the inner hair cells (IHCs). Below the outer hair cells (OHCs), the swelling appeared only in the 6-day-old rats, not in adult animals. These results are significant in three different ways: (1) They confirm the strong difference between afferents innervating the IHCs and the OHCs in adult cochleas. (2) They shed some light on the synaptic plasticity found at the OHC level during synaptogenesis. (3) They support the hypothesis that glutamate, or a related substance, is the IHC neurotransmitter.
Age Factors↗
Morphology, synaptology and electrophysiology of the developing cochlea.
The development of synapses clearly differentiates the two kinds of cochlear receptors inner (IHC) and outer (OHC) hair cells. An adult-like pattern of innervation can be seen very early below the IHCs: both afferent and efferent (mainly axo-dendritic) synapses are formed before the onset of function. At the OHC level, drastic changes occur: numerous afferent dendrites retract as the large efferent endings arrive and synapse with the hair cell. This synaptic OHC remodelling coincides with maturation of compound action potential (AP) parameters, such as the "S" -shape of the input-output curves and the sharpening of AP tuning curves.
Animals↗
Early stages of innervation and sensory cell differentiation in the human fetal organ of Corti.
Early development of the human organ of Corti was investigated at the light and electron microscopic level. In 9-week fetal material the cochlea was completely coiled and nerve fibers penetrated into an undifferentiated Corti's primordium. By week 10 a single cell in radial sections, presumed to be the inner hair cell (IHC), could be found with many nerve fibers surrounding and contacting its base. It is possible to identify outer hair cells by the end of the 11th week while IHC development continues. During the 12th week stereocilia appear on IHCs and synaptic specializations could be found at the junctions between both types of hair cell and afferent dendrites. The first appearance of the efferent fibers beneath IHCs were also observed during week twelve.
Cell Differentiation↗
[Development of the internal ear during the 1st trimester of pregnancy. Differentiation of the sensory cells and formation of the 1st synapses].
The inner ear of seventeen embryos, aged from 7 to 14 weeks after the fecondation, was investigated by optic and electron (transmission and scanning) microscopy. The timing of the first stages of the auditory and vestibular human receptor development is similar to the timing reported in animal studies, the vestibular epithelium development preceding by 2 to 3 weeks the cochlear development. The nerve fibers enter the sensory epithelia before the hair cell differentiation was histologically observed. At 9 weeks in the vestibular organs and 11 weeks in the cochlea, the hair cells are well differentiated and they exhibit typical synapses with nerve endings. Very early in the embryonic life, the auditory and vestibular receptors start their maturation and establish their connections with the peripheral and central nervous system; this indicates that the third month of pregnancy is a particularly sensitive period as far as the inner ear development is concerned.
Cell Communication↗
[Immunolocalization of choline acetyltransferase in 2 types of efferent synapses of the organ of Corti].
The efferent (olivo-cochlear) innervation of the organ of Corti was studied using a monoclonal antibody against choline acetyltransferase (ChAT). In the inner spiral bundle (ISB), below the inner hair cells (IHCs), the anti-ChAT immunoreactivity was observed within unvesiculated fibers and vesiculated varicosities. Unreactive varicosities, at least as numerous as the immunoreactive ones, were also detected. Both types of vesiculated varicosities synapsed with the dendrites of the primary auditory neurons (afferent fibers) connected to the IHCs. At the outer hair cell (OHC) level, nearly all the vesiculated terminals making axo-somatic synapses with the OHCs were anti-ChAT immunoreactive. Only few terminals synapsing with the OHCs were unreactive. These findings allowed the differentiation of at least three types of efferent synapses in the organ of Corti. In the ISB, a first population of axo-dendritic synapses seems to be cholinergic whereas a second population might use another neurotransmitter. At the OHC level, our results support the hypothesis that acetylcholine is the neurotransmitter of nearly all the large axo-somatic synapses. The rare unreactive axo-somatic synapses could constitute a fourth and minor type of efferent synapse. Thus, it would be helpful to subclassify the efferent innervations of the organ of Corti according to their neurochemical nature. A re-evaluation of the whole body of available electrophysiological data would be also necessary, as until now, acetylcholine was considered as being the only efferent cochlear neurotransmitter.
Animals↗
Met-enkephalin characterization in the cochlea: high-performance liquid chromatography and immunoelectron microscopy.
The present paper extends and refines previous observations of enkephalin-like immunoreactivity in the guinea-pig cochlea. Firstly, Met-enkephalin was identified and a quantitative evaluation was made by combining high-performance liquid chromatography (HPLC) and a specific radioimmunoassay. Both the antibody specificity and the HPLC purification allowed us to demonstrate the co-existence, in the cochlea, of at least 3 opioid peptides: Met-enkephalin, Leu-enkephalin and Met-enkephalin-Arg6-Phe7. Secondly, a pre-embedding immunoperoxidase technique was used on whole or dissected cochleas. Immunoreactivity was localized in efferent fibers (coming from the brainstem) in the inner spiral bundle, tunnel spiral bundle and intraganglionic spiral bundle. In the inner spiral bundle vesiculated Met-enkephalin-immunoreactive fibers could be seen synapsing with afferent auditory dendrites. It is hypothesized that these Met-enkephalin immunoreactive fibers (belonging to the lateral efferent system) could be responsible for an inhibitory effect upon the gross cochlear action potential.
Animals↗
Age-related structural investigation of the Bronx waltzer mutant mouse cochlea: scanning and transmission electron microscopy.
Cochleas of mice homozygous for the Bronx waltzer gene (symbol bv) were investigated using scanning (SEM) and transmission (TEM) electron microscopy. An age-related study was done from birth to postnatal day 100. With SEM, the arrangement of hair cells confirmed the unique feature of the bv/bv cochlea: the inner hair cells (IHCs) were either absent or abnormally haired but the outer hair cells (OHCs) appeared normal. No significant difference was observed with age. Using TEM, the remaining (20-25%) IHCs could be divided into two groups: normal-looking IHCs but with an abnormal synaptic pole, and abnormal, abortive-like IHCs. Very little if any sign of degeneration was observed whatever the age. OHCs displayed an almost normal cytology and pattern of innervation. The neurons of the spiral ganglion were very rare, even at birth. These findings suggest that the bv mutation should rather be classified in another group, than 'degenerative'. The persistence of normal structures at OHC level is discussed in light of the cochlear physiology of the bv/bv: it again raises the question of the real role of OHCs in the peripheral auditory mechanisms.
Aging↗
Immunofluorescence with Met-enkephalin and Leu-enkephalin antibodies in the guinea pig cochlea.
We have applied an indirect immunofluorescence technique to cryostat sections of guinea pig cochleas using Met-enkephalin and Leu-enkephalin antisera. With both antisera, high immunofluorescence was seen in the inner spiral bundle, the tunnel spiral bundle and the intraganglionic spiral bundle. Immunoreactivity persisted to a dilution of 1/50 000. In three out of the twelve guinea pigs, immunoreactivity was observed under the outer hair cells, but only with the Met-enkephalin antiserum. Immunoreactivity of medium intensity was seen when the Met-enkephalin antiserum was pre-adsorbed by Leu-enkephalin. No immunoreactivity was seen when the Leu-enkephalin antiserum was pre-adsorbed by Met-enkephalin. After treatment of cochlear sections with acidic permanganate, immunoreactivity of medium intensity was still observed with the Leu-enkephalin antiserum. These observations indicate that Met-enkephalin and Leu-enkephalin co-exist in the cochlea in regions where efferent terminals are located, particularly in the inner spiral bundle below the inner hair cells.
Animals↗