Biomedical subjects

R Romand

Publications and source records attributed to R Romand.

At least 55 records · Page 3Linked to original sources

PubMed1990

Cochlear innervation in the developing rat: an immunocytochemical study of neurofilament and spectrin proteins.

We have studied the innervation of the developing cochlea by immunocytochemical staining of the cytoskeletal proteins, neurofilament (NF), and spectrin (brain spectrin and erythrocyte spectrin). NF immunoreactivity was seen in spiral ganglion cell bodies and their processes and in fibers of the intraganglionic spiral bundle (IGSB) on gestational day 16. NF immunoreactivity with monoclonal antibodies to NF160 and NF68 was present beneath both inner hair cells (the IHC) and outer hair cells (OHCs) on gestational day 20. NF200 immunostaining was located only in the IGSB and in fibers reaching the IHC. The first NF200 immunoreactivity beneath the OHCs was seen in the basal turn at birth. NF labelling began to decrease on postnatal day 9 and its intensity became more like that of the adult. Brain spectrin immunostaining was first seen in the IGSB of the basal turn on gestational day 18. It reached the fibers between the spiral ganglion and the IHC on gestational day 20. Brain spectrin immunoreactivity was first seen beneath the OHCs in the basal turn at birth. It reached all the OHCs of the cochlea by postnatal day 4, and began to decrease 9 days after birth. Erythrocyte spectrin immunostaining was first observed during the second postnatal week, when it labelled spiral ganglion cells. The distribution of NF200 and brain spectrin immunoreactivity suggested that efferent innervation of OHCs is present at birth in the rat, and confirms previous studies showing the early efferent innervation of the OHCs of the mouse and the rat at birth, and the time lag between the appearance of the two spectrin isoforms during development.

Aging↗

PubMed1990

Development of tonotopy in the inferior colliculus. I. Electrophysiological mapping in house mice.

The development of the size and tonotopy of the mouse inferior colliculus (IC) was studied at postnatal ages of 9-20 days. During that time, the size of the IC remained constant in all 3 planes (rostrocaudal, mediolateral dorsoventral). At day 10, the first low-frequency responses without tonotopy could be recorded from neurons in the rostral and central parts of the central nucleus sparing its caudal part, very medial portions, the medial part (M) of the central nucleus, the dorsal cortex and the lateral nucleus. Then, an extension of the frequency responsiveness occurred towards (1) the caudal pole which was reached by about day 14, (2) the dorsal surface reached between days 12 and 14, (3) the ventral border of the IC reached by about day 15. The high-frequency nucleus of the IC (M part of the central nucleus) remained unresponsive to tones up to day 13. Between days 10 and 20, there was a constant increase of highest characteristic frequencies (CFs) measurable of neurons in the IC. During that time, lowest measurable CFs remained rather constant. Neurons at a given constant collicular depth of more than about 400 microm showed a clear shift of CF from low to high, that is, they were tuned to the higher frequencies the older the animals were. Cochlear and collicular origins of this observed shift of tonotopy are discussed.

Acoustic Stimulation↗

PubMed1990

Development of spiral ganglion cells in mammalian cochlea.

The development of the spiral ganglion in the cat, the rat, and the mouse was studied by electron microscopy, from fetal stages in the cat and from birth in the rodent. In the earliest stages, a single population of ganglion cells is present. Immature spiral ganglion neurons possess small perisomatic processes that seem to disappear with development, before the myelination ganglion cells are surrounded by one or two layers of Schwann cell processes. With maturation, the Schwann process increases in number around the perikaryon and its processes, which leads to the onset of myelination. The onset of myelination of the cell body processes is asynchronous. The perikaryon may be delayed in myelination by several days. Moreover, ganglion neurons from a given region of the cochlea do not myelinate simultaneously. The differentiation of two types of fibers in the intraganglionic spiral bundle and the first appearance of TII neurons occurs around birth in the cat and a few days after birth for the rat and the mouse. The distinction of TII cells is possible due to characteristic accumulation of neurofilamentous structures in the cytoplasm.

Animals↗

PubMed1990

Patterns of neurofilament stain in the spiral ganglion of the developing and adult mouse.

The objective of the study was to identify neurofilament-positive cells and their projections in the intact spiral ganglia of the mouse. One polyclonal and three monoclonal antibodies against neurofilament triplet subunits NF 68 K, 160 K and 200 K were used. In the newborn mouse most of the spiral neurons and their processes stain positively, although the perikaryal stain is very light. During early postnatal development, some cells show a selective intense stain. The progressive myelination of the neuronal processes further restricts the stain to a small neuronal population of positive perikarya and to their nonmyelinated fibers. This pattern of stainability implies that the neurofilament-positive cells are compatible with the type II spiral neurons. The stain reveals two populations of spiral neurons: 1) the cells which are scattered within the ganglion and show a bipolar distribution of fibers; and 2) the cells that form an interrupted chain along the intraganglionic bundle. The latter cells are also bipolar, but their peripheral processes join the intraganglionic bundle for varying distances before reaching the radial bundles. The identification of selective groupings of filamentous nonmyelinated cells in the corresponding location in different mammals is discussed. In conclusion, the use of neurofilament antibodies in staining of the intact spiral neurons permitted us to identify a distinct cell population of neurofilament-positive nonmyelinated nerve cells located along and projecting (at least partly) into the intraganglionic bundle.

Aging↗

PubMed1989

First appearance of type II neurons during ontogenesis in the spiral ganglion of the rat. An immunocytochemical study.

Ontogenesis of spiral ganglion in the rat was studied using antibodies to three subunits of neurofilaments (NFs): NF 68 KDa, NF 160 KDa and NF 200 KDa. The expression of immunoreactivity was examined with 3 immunocytochemical methods: indirect immunofluorescence, peroxidase-antiperoxidase and avidin-biotin complex. Aim of the study was to detect the time of differentiation of the spiral ganglion type II neurons. At 16 and 18 days of gestation, most neuron cell bodies express immunoreactivity to only two NF subunits: NF 68 and NF 160, but at birth they react with the antibodies to all 3 subunits albeit weakly. Nevertheless, a small population (about 7%) of nerve cells that strongly reacts against all 3 NF subunits emerges in the basal turn, already at 20 days of gestation. Two to 3 days after birth, the strongly stained cells are dispersed throughout the entire ganglion. The intensity of their reaction to the NF antibodies is similar to that seen in the adult animal. The strong immunoreactivity of this selective neuronal population suggest, that they correspond to the type II spiral ganglion neurons. Our results imply that the differentiation between the type I and the type II of spiral neurons in the rat occurs perinatally.

Aging↗

PubMed1989

Neurofilament immunoreactivity in vestibular ganglion neurons of the adult rat.

Immunocytochemical methods were used to study the distribution of neurofilament (NF) proteins in vestibular ganglion neurons of the adult rat. Monoclonal antibodies against the three triplet proteins were used. By indirect immunofluorescence and the peroxidase-antiperoxidase method, two populations of neurons were distinguished. One population with large perikarya showed strong NF immunoreactivity. A second population of neurons presented only slight or no immunoreactivity. The strong NF immunoreactivity in the perikarya of certain neurons seems to be a general feature of many sensory ganglia.

Animals↗

PubMed1988

Immunocytochemical localization of neurofilament protein subunits in the spiral ganglion of the adult rat.

Spiral ganglion neurons from adult rats were treated with several monoclonal antibodies that react with neurofilaments (NFs) and NF subunits. An antibody against NFs used with immunocytochemical techniques showed a strong reaction with most neuron processes in the spiral ganglion, whereas only a few neurons presented a reaction. Using monoclonal antibodies against the 3 subunits, we obtained the same results with a small percentage of neurons labelled. From quantitative observations, reacting neurons showed the same percentage as and a smaller size than T II neurons observed with a more conventional method. This shows that reacting neurons are indeed T II neurons and that they can easily be differentiated by an accumulation of NFs in their perikaryon by well characterized commercially available antibodies.

Animals↗

PubMed1988

Immunohistochemical localisation of nerve growth factor-like protein in the organ of Corti of the developing rat.

The presence of nerve growth factor (NGF)-like protein was investigated in the cochlea of the developing rat between birth and postnatal day 30, by the indirect immunofluorescence technique. Nerve growth factor-like protein could be detected from birth up to day 8. The immunostaining was localised within the hair mainly above their nuclei. No NGF-like immunoreactivity was observed in spiral ganglion cells. The data suggest that NGF acts as a neurotrophic factor, especially for efferent endings in the developing cochlea.

Aging↗

PubMed1988

[Presence of a nerve growth factor-like immunoreactivity in auditory receptors during postnatal development in the rat].

The presence of nerve growth factor (NGF) was investigated in the rat cochlea from birth to the adult stage, using immunohistochemical techniques NGF-like protein could be detected in the organ of Corti from birth up to day 8 and located within the hair cells, above the nuclei. No NGF-like immunoreactivity could be detected in the spiral ganglion. These results suggest that NGF may have a neurotropic action in the developing rat cochlea.

Aging↗

PubMed1987

Factors affecting the onset of inner ear function.

The developing inner ear receptors have a very significant influence on the onset of stato-acoustic function and on its evolution. The factors which prevent the stato-acoustic system from functioning are called 'the limiting factors'. At present, it is possible to postulate that these factors are restricted to the inner ear cells and related structures. At least four places are particularly relevant for the onset of function: (1) connections of the apical part of hair cell with the tectorial membrane; (2) the internal structure of hair cell; (3) connections between the base of the hair cell and nerve fibers; (4) the ganglion cell with its processes. Special emphasis is devoted to the apical part of the inner hair cell and its connections to the tectorial membrane which are considered as very important for the onset of the cochlear function. For the labyrinth, it is technically difficult to determine precisely the onset of function because of its early prenatal onset. Nevertheless, it is postulated that the limiting factors for the onset of function are also related to certain components of hair cells.

Animals↗

PubMed1987

Tonotopic evolution during development.

The evolution of cochlear tonotopy can be observed by the study of the modification of tuning curves as obtained from auditory nerve fibers in the kitten. The differential development of the two components of the tuning curves, i.e. the tail, which is restricted to lower frequencies that appear at first during ontogenesis, and the tip which is restricted to higher frequencies that appear later, can explain the ontogenetic variations of tonotopy observed in the past. An hypothesis is presented where the tail of the tuning curve is related to the first functioning of the basal inner hair cells during development, whereas the delayed appearance of the tip is related to the basal outer hair cells. The base-apex gradient of maturation of receptors, along with their lateral gradient of development can explain the tonotopic shift observed during the cochlear ontogenesis.

Animals↗

PubMed1986

Perinatal growth of spiral ganglion cells in the kitten.

Spiral ganglion cell growth and myelination in the kitten have been studied by means of light and electron microscopy, in one fetus and in kittens of various ages. The growth of spiral ganglion cell bodies and nuclei as studied through their cross-section modifications show two different periods of increase: a period of rapid growth before birth, followed by a slower one after birth up to the first postnatal month. After this stage, the diameter decreases slightly in the adult. Myelination of the cell body begins before birth for the basal part of the cochlea. Myelination is fast during the first postnatal month, then slows down during the following months. Comparison of myelination with the growth of the cell body and its nucleus shows that the postnatal growth of the cell body is due to the increase of the cytoplasmic component of the cell and also to the myelin sheath.

Animals↗

PubMed1985

Qualitative and quantitative observations of spiral ganglion development in the rat.

The postnatal development of the spiral ganglion cells in the rat was studied from birth until the adult stage. At birth, a single population of ganglion cells is present. Some of them are surrounded by one or two layers of satellite cell processes. With maturation, the satellite cell processes increase in number around the cell body and its processes. At the end of the first postnatal week, two important events occur. The first is the appearance of myelin lamellae between the 4th and the 6th postnatal day in both ganglion cell processes, and between the 6th and the 8th day in the cell body. The second event is the appearance of a new type of cell (the Type II spiral ganglion cell) on the 6th to the 8th day postpartum. At this stage, the Type II cell is mainly characterized by densely packed neurofilamentous structures in the cytoplasm. Comparison between the myelination of the cell body and its processes reveals three main differences! There is a time lag of approximately 2 days between the onset of myelination in the cell body and in its processes. The kinetics of myelination are different in the cell processes and in the cell body. The myelination of the cell body starts slowly, whereas it is very fast in the processes. Later, the kinetics of myelination decrease in the processes, and increase in the cell body. At all stages including the adult, the fibers have a myelin sheath composed of more lamellae than the cell body. These observations are discussed with respect to development in other species.

Aging↗

PubMed1985

Microtubules and macrotubules in fish meiosis.

During meiosis in the male of a cyprinodontid fish, Aphyosemion splendopleure, and during the organization of the spindle of division, the spindle is made of two types of tubules: microtubules (20-25 nm) and macrotubules (30-50 nm). The macrotubules are associated only with the polar region of the meiotic apparatus and are located outside the spindle of microtubules. At the end of meiosis, the spindle microtubules depolymerize whereas the macrotubules remain. One can find them throughout the entire process of spermiogenesis; later, they disappear only at the end of spermatid maturation. We have studied four populations from Cameroon, three of them with macrotubules.

Animals↗

PubMed1984

Development of sound production in normal, isolated, and deafened kittens during the first postnatal months.

The development of calls (quantified by a series of acoustic parameters) of (a) normal, (b) socially isolated, and (c) deafened kittens that were released in four different situations has been studied from birth to 170 days of age. All call parameters studied except noise components show developmental changes that can be related to the development of (a) the vocal tract (fundamental frequency, harmonic with maximum intensity, upper-frequency limit and frequency range, occurrence of frequency, and intensity modulations), (b) feedback control through the auditory system (sound-pressure level, harmonic with maximum intensity, call-variability), and (c) motivational valuation of the releasing situations (duration). Isolated and deafened kittens displayed quantitative differences in certain call parameters compared with normal animals. Calls of deafened animals are, on the average, louder, more tonal and uniform, and differentially pitched compared with those of normal, hearing animals.

Aging↗

PubMed1984

Functional properties of auditory-nerve fibers during postnatal development in the kitten.

The discharges of the auditory-nerve fibers were studied in kittens between 2-40 days of age. Up to the 10th postnatal day, fibers could be divided into two main categories: fibers with spontaneous activity (SA) that respond to sound and fibers without SA but with evoked responses. A third, smaller, category, fibers having neither SA nor evoked activity, was also present. The development of SA comprises two phases. The first, lasting from birth up to the third postnatal week, shows a relatively fast increase and the second, lasting up to adulthood, a slower increase. Typical tone burst responses can be recorded at the end of the first postnatal week. Thereafter reactivity steadily increases especially after the 10th postnatal day. In young animals, rate level function is characterized by a steep segment with a low dynamic range followed by a decrease in activity that lasts until the end of the second week. At this point adult-like functions may be observed, although maximal firing still increases for some weeks. Tuning curves and threshold sensitivity tend to develop inversely at corresponding frequencies. Fibers with low characteristic frequencies reach adult threshold before that of high frequency fibers and high frequency fibers reach adult tuning before low frequency fibers. A comparison of auditory-nerve fiber activity in kittens show that maturation of most functional characteristics lasts several weeks after birth and in some cases continues after the first postnatal month.

Action Potentials↗

PubMed1983

Development in the frequency selectivity of auditory nerve fibers in the kitten.

The modification of tuning properties in the cochlea has been studied by means of tuning curves from auditory nerve fibers in kittens of various ages. Comparison of tuning curves of three characteristic frequencies (CF) shows that the tuning of high CF units tends to approach adult values by the end of the second postnatal week, whereas medium and low CF units have a delayed maturation. Threshold sensitivity, on the other hand, shows a development inverse to that of tuning. The threshold of low CF units tends to reach adult values before that of medium and high CF units. The development of tuning can be related to the structural maturation of the cochlea, where the most differentiated part is located at the base of the first turn and corresponds to the rapid development of high CF units. In the same way, the second and the third turns show a delayed structural development corresponding to a different maturation of tuning for medium and low CF units.

Acoustic Stimulation↗

PubMed1982

Myelination kinetics of spiral ganglion cells in kitten.

A study of the regions of myelination of spiral ganglion cell bodies at birth in the kitten revealed that the first myelination occurred before birth. A quantitative analysis of myelinated versus unmyelinated cells, and the distribution of myelin lamellae of the ganglion cell sheath reflect the kinetics of the later stages of cochlear maturation. The onset of the final maturation process begins in the basal region of the first turn, which is 20% of the length of the spiral lamina measured from the basal extremity of the cochlea. This maturation proceeds in an orderly manner from the lower half of the first turn to the apex, but also develops to a smaller degree toward the hook region. Results are compared with previous findings.

Animals↗