Biomedical subjects

R Romand

Publications and source records attributed to R Romand.

At least 19 recordsLinked to original sources

PubMed1992

Developmental differentiation of MAP2 expression in the central versus the peripheral and efferent projections of the inner ear.

The goal of this study was to extend our knowledge of MAP2 localization in the peripheral nervous system of mammals, since most results on MAP2 distribution are obtained in the central nervous system (CNS). This study shows the presence of microtubule-associated protein 2b (MAP2b) and MAP2c in the inner ear and describes the immunocytochemical distribution of MAP in adult and developing spiral ganglion of the rat by using a well-characterized antibody for MAP2a and MAP2b. (This antibody does not recognize the immature MAP2c). MAP2 labeling is already present in spiral ganglion neurons at 16 days of gestation. From this stage and up to the first postnatal week, MAP2 labeling was strong in all spiral ganglion neurons and their central processes. Double immunostaining at the 16-day stage with anti-MAP2 and anti-neurofilament (NF) antibodies mainly showed NF labeling in central branches that corresponded to anatomically and functionally described axons of spiral neurons. The peripheral branches lacked MAP2 labeling. In neonatal and postnatal stages, MAP2 reactivity was located in spiral ganglion perikarya and their neurites. The intensity of adult labeling was, however, lower than in younger animals. The antibody used in this study did not label axons originating in the CNS as seen by a negative response in efferent fibers from the intraganglionic spiral bundle of the cochlea. Our results suggest that during ontogenesis, MAP2 is highly expressed in the central projection of spiral ganglion neurons, and then is reduced to lower quantities in the central branch after the first postnatal week and persists into adulthood.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Development of tone response thresholds, latencies and tuning in the mouse inferior colliculus.

The development of tone response thresholds, latencies and tuning of neurons in the inferior colliculus (IC) of the mouse has been investigated between postnatal days 10 (first responses) and 20. As in adults, response thresholds of neurons are lowest in the center of the IC compared with other areas right from the beginning of responsiveness at day 10. Thresholds decrease rapidly until at days 16-20 (depending on the characteristic frequency of the neurons) adult levels are reached. Response latencies decrease rapidly to adult levels at days 16-18. Broad frequency tuning curves can be measured at days 10 and 11. From day 12 onwards, tuning curve shapes differentiate and adult diversity occurs which indicates presence of inhibition and summation in the pathway to or within the IC at that early age. The tip lengths of the tuning curves increase faster than the sharpness of the tips (Q10 dB values). The developmental courses of the measured parameters are expressed by power functions. The time constants of these functions are used in the discussion of processes underlying the functional maturation in the auditory system of the mouse. The general course of the development of all the here investigated response properties of single neurons in the IC, except tuning curve shape, appears to be determined by maturation at or peripheral to the cochlear level.

Acoustic Stimulation↗

PubMed1991

Expression of the beta-nerve growth factor gene in male sex organs of the mouse, rat, and guinea pig.

Steady-state nerve growth factor (NGF) mRNA levels were estimated in male sex organs of the mouse, rat, and guinea pig by RNA blot hybridization analysis. The abundance of NGF mRNAs was in the order vas deferens greater than epididymis greater than or equal to seminal vesicles much greater than testis. NGF mRNA levels in these organs were compared with those estimated for other rat peripheral tissues and were found to correlate with the density of their sympathetic innervation, with the exception of guinea pig prostate. Castration had no significant effect on NGF mRNA levels in the guinea pig prostate, suggesting that NGF synthesis in this tissue is not under direct androgen control. NGF-like and proNGF-like immunoreactivities were localized by immunohistochemical techniques in the secretory cells of the glandular epithelium of the guinea pig prostate and in germ cells in the seminiferous tubules of the mouse testis.

Animals↗

PubMed1991

Immunohistochemical localization of nerve growth factor receptor in the cochlea and in the brainstem of the perinatal rat.

Nerve growth factor receptor (NGF-R) localization was studied immunohistochemically in the cochlea and in the brainstem of the perinatal rat, using a specific monoclonal antibody directed against the rat NGF-R. In the cochlea, NGF-R immunoreactivity is positive during the whole perinatal period studied, and is located at the hair cell level, in fibers that reach the organ of Corti, in the intraganglionic spiral bundle and in some small bundles of fibers in the auditory nerve. In the brainstem, NGF-R is detected in auditory structures such as the ventral cochlear nucleus, the superior olivary complex, the nuclei of the trapezoid body and the trapezoid body. Many auditory structures labelled by the NGF-R antibody are implicated in the efferent cochlear innervation. These results suggest that NGF could be implicated in interactions between auditory receptors and efferent innervation of the developing cochlea. This coincides with findings on the immunohistochemical localization of NGF-like protein in the organ of Corti of the developing rat. Moreover, these observations could be related to an early prenatal development of auditory efferent innervation.

Animals↗

PubMed1991

Basic FGF-like protein in the lower stato-acoustic system of the neonatal and adult rat.

Basic fibroblast growth factor (bFGF)-like localization was studied immunohistochemically in the lower auditory tract of neonatal and adult rats. During the neonatal period, bFGF-like immunoreactivity is present in the cytoplasm of inner hair cells, spiral ganglion cells, Scarpa's ganglion cells, in auditory brain stem nuclei and in vestibular nuclei. At the adult stage, bFGF-like protein is widely distributed in the auditory brain stem but was not found in the cochlea. These results suggest that bFGF could be implicated in the development as well as in the neuronal maintenance and plasticity of the auditory system.

Age Factors↗

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↗