Biomedical subjects

N Delhaye-Bouchaud

Publications and source records attributed to N Delhaye-Bouchaud.

At least 19 recordsLinked to original sources

PubMed1998

Quantitative analysis of cerebellar lobulation in normal and agranular rats.

Cerebellar pattern formation was investigated in rats treated with DNA modifying agents. Animals were subjected to combinations of daily injections of methylazoxymethanol acetate (MAM) for the last 6 days gestation and/or localised X-irradiation of the hindbrain on postnatal days 1 and 5 (P1 and P5). Animals were analysed on embryonic day 18 (E18), P0, P3, P7, and P14. Five parameters of the cerebellum were recorded from midsagittal sections: the number of primary lobules; the thickness of the external germinal layer (EGL); the density of cells in the internal granule cell layer (IGL) region; and the midsagittal area and perimeter. In addition, the laterolateral cerebellar distance was calculated. The data demonstrate that pre- and postnatal reduction of the EGL results in reduced cerebellar growth and folding. Cessation of the treatment at birth results in a recovery and eventual overproduction of EGL, but cerebellar growth and the development of fissures lags behind that of normal rats. Pre- and postnatal destruction of the EGL severely limited cerebellar growth and fissuration, and the cerebella contained only five primary lobules at P14. Rats subjected to postnatal X-irradiation alone had a similar low density of granule cells relative to those treated with a combination of prenatal MAM injections and postnatal X-irradiation, and yet the cerebella contained deeper fissures and more lobules (nine at P14). The data indicate that there are two phases of cerebellar folding: the establishment of five lobules that arise independent of granule cell production, and the granule cell-dependent expansion and partitioning of these five principal lobules during postnatal development. We propose that the lack of correlation between the severity of the granule cell loss and degree of lobulation in agranular rats indicates that granule cells exert an inductive influence over lobulation that is in part independent of the forces generated by their production and differentiation.

Abnormalities, Drug-Induced↗

PubMed1998

staggerer phenotype in retinoid-related orphan receptor alpha-deficient mice.

Retinoid-related orphan receptor alpha (RORalpha) is a member of the nuclear receptor superfamily. To study its physiological role we generated null-mutant mice by targeted insertion of a lacZ reporter gene encoding the enzyme beta-galactosidase. In heterozygous RORalpha+/- mice we found beta-galactosidase activity, indicative of RORalpha protein expression, confined to the central nervous system, skin and testis. In the central nervous system, the RORalpha gene is expressed in cerebellar Purkinje cells, the thalamus, the suprachiasmatic nuclei, and retinal ganglion cells. In skin, RORalpha is strongly expressed in the hair follicle, the epidermis, and the sebaceous gland. Finally, the peritubular cells of the testis and the epithelial cells of the epididymis also strongly express RORalpha. Recently, it was reported that the ataxic mouse mutant staggerer (sg/sg) is caused by a deletion in the RORalpha gene. The analysis of the cerebellar and the behavioral phenotype of homozygous RORalpha-/- mice proves identity to sg/sg mice. Although the absence of RORalpha causes dramatic developmental effects in the cerebellum, it has no apparent morphological effect on thalamus, hypothalamus, and retina. Similarly, testis and skin of RORalpha-/- mice display a normal phenotype. However, the pelage hair of both sg/sg and RORalpha-/- is significantly less dense and when shaved shows reluctance to regrow.

Animals↗

PubMed1998

Postnatal expression of Hu-bcl-2 gene in Lurcher mutant mice fails to rescue Purkinje cells but protects inferior olivary neurons from target-related cell death.

The Lurcher mutant has been extensively studied as a model for cell-autonomous and target-related cell death, yet there are still many unknowns concerning the mechanisms of neuronal degeneration in this mutant. As a key regulator of apoptosis, a bcl-2 transgene has been overexpressed in the heterozygous Lurcher mutant to investigate the effects of BCL-2 on two types of in vivo neuronal cell loss in Lurcher: cell-autonomous Purkinje cell degeneration and target-related olivary neuron death. Six adult +/Lc mutants expressing a human bcl-2 transgene (Hu-bcl-2) were generated by crossing +/Lc mutants with NSE71 Hu-bcl-2 transgenic mice. Analysis of these brains showed that bcl-2 overexpression did not prevent +/Lc Purkinje cell degeneration, but it did rescue most olivary neurons from target-related cell death. Although the number of olivary neurons was equivalent to wild-type numbers, the inferior olive nucleus was significantly shorter in its rostrocaudal extent, suggesting that olivary neurons are atrophied. We propose that Lurcher gene action causes Purkinje cell degeneration independently of a BCL-2-mediated pathway. Furthermore, although bcl-2 overexpression rescues olivary neurons from target-related cell death, it does not prevent the atrophy associated with the loss of target-related trophic support.

Animals↗

PubMed1998

Immature chemodifferentiation of Purkinje cell synapses revealed by 5'-nucleotidase ecto-enzyme activity in the cerebellum of the reeler mouse.

During postnatal development of the rodent cerebellum, a transient enzyme activity of ecto-5'-nucleotidase has been shown in the asymmetrical synapses of Purkinje cells. The alterations of the afferent circuitry and microenvironment of the ectopic Purkinje cells present in the cerebellum of the reeler mutant mouse could enlighten parameters that influence the synaptic 5'-nucleotidase activity of these cells. Ecto-enzyme cytochemistry reveals intense 5'-nucleotidase activity in 43% of synapses of the Purkinje cells throughout the cortex and the core of the reeler cerebellar vermis, although the molecular layer displays large areas with less than 1% of labelled synapses. However, enzymatic labelling is found in considerably more Purkinje cells synapses (73%) throughout the granular layer and the subcortical mass. Climbing fiber synapses of monoinnervated Purkinje cells are labelled by 5'-nucleotidase activity in the molecular layer, as well as asymmetrical synapses made on the subjacent ectopic Purkinje cells by the multiple climbing fibers and by the heterologous afferences. The non-innervated dendritic spines of these cells are also labelled, suggesting that 5'-nucleotidase activity at postsynaptic sites of reeler Purkinje cells does not depend on the presynaptic innervation. Rather, 5'-nucleotidase enzyme activity is enhanced at theses sites when the Purkinje cells have not achieved chemodifferentiation but have conserved immature wiring, i.e., low parallel fiber and multiple climbing fiber inputs.

5'-Nucleotidase↗

PubMed1998

Eradication of cerebellar granular cells alters the developmental expression of trk receptors in the rat inferior olive.

Granule cells which relay the mossy fibre afferent system to the cerebellar cortex are generated postnatally in mammals. In their absence, the climbing fibres, i.e. the second afferent system to the cerebellum originating in the inferior olivary nucleus, remain in an immature stage, and substantial elimination of redundant synapses they establish on the Purkinje cells does not occur in the rat between day five (P5) and day fifteen (P15). It is generally assumed that synapse elimination is partly regulated by electrical activity which modulates the competition among afferent fibres for the uptake of a limited amount of trophic factors released by the target. The neurotrophins, whose expression is developmentally regulated in the cerebellum, especially in granule cells, could be this retrograde signal. Using RT-PCR, we studied the expression of their trk receptors in the inferior olivary nucleus of developing and adult rats, and its alteration after eradication of the granule cell precursors by X-irradiation on P5. From P0 to P90, the amount of trkA mRNA is low and remains stable in control rats; the high levels of trkB and C mRNAs detected at P0 markedly decrease in parallel from P5 and reach their minimal values at P15, when the process of synapse elimination is completed in the cerebellum. X-irradiation of the cerebellum decreases the level of expression of the three trks, but a transient upregulation of trkC occurs at P10. The down-regulation of trkB and C expression in the inferior olivary nucleus, contemporary with the altered expression of neurotrophins in the cerebellum, suggest that NT-3 and/or BDNF/NT-4/5 could be involved in the remodelling of olivocerebellar relationships during development. In addition, the transient overexpression of trkC after granule cells eradication is consistent with a paracrin effect exerted on the olivary cells by granule cells release of NT-3, at the time when the climbing fibres invest the growing Purkinje cell dendrites in the molecular layer.

Animals↗

PubMed1997

Fear decrease in transgenic mice overexpressing bcl-2 in neurons.

Neuronal destruction in the amygdala, hypothalamus and cerebellum provokes a diminution in anxiety and neophobia. In transgenic mice that express the human bcl-2 gene under the control of neuron specific enolase promotor (Hu-bcl-2), BCL-2 overexpression reduces the naturally occurring neuronal death, producing an increase of the number of neurons and brain size. Since BCL-2 over-expression has been observed in different parts of the brain and especially in the amygdaloid nuclei, the hypothalamus and the cerebellum, we studied the fear-related behavior of these transgenic mice. Hu-bcl-2 transgenic mice showed a decrease in anxiety and neophobia, indicating that, for this particular behavior, supernumerary neurons elicit the same modification as that observed after neuronal destruction.

Animals↗

PubMed1997

Hypersensitivity of lurcher mutant mice to the depressing effects of lipopolysaccharide and interleukin-1 on behaviour.

Lurcher mutant mice are characterized by a fast and almost total loss of olivocerebellar neurones during the first postnatal month, associated with a chronic inflammatory state. To test their brain sensitivity to proinflammatory cytokines, we assessed the behavioural responses of adult male Lurcher and wild type to an i.p. or i.c.v. injection of rat recombinant IL-1 beta, and lipopolysaccharide (LPS). IL-1 beta (15 micrograms kg-1, i.p. or 1 ng i.c.v.) decreased social exploration measured 2, 4 and 6 h later, and this decrease was significantly more pronounced in Lurcher than in wild type mice. LPS (60 micrograms kg-1, i.p. or 5 ng i.c.v.) decreased social exploration measured 2 and 4 h later, and this effect was also significantly more marked in Lurcher than in wild type mice. These results suggest that the chronic inflammatory state which characterizes Lurcher mice renders these animals more sensitive to the effects of cytokines such as IL-1 beta and LPS. This difference may be due to the higher reactivity of brain macrophages and glial cells to LPS and IL-1 in Lurcher mice than in wild type.

Animals↗

PubMed1997

Effect of cerebellar granule cell depletion on spatial learning and memory and in an avoidance conditioning task: studies in postnatally X-irradiated rats.

Rats of the DA/HAN strain (pigmented rats) were submitted to two experimental tasks consisting in spatial learning (water escape experiment) and in passive avoidance conditioning. These rats were either totally or partially deprived of their granule cells using two different schedules of postnatal X-irradiation of the cerebellum. When they were 3 months old, the animals were submitted to an initial learning session, followed by a retrieval test seven days later. The scores of the rats which were partially deprived of granule cells appeared similar to those of controls, except for a mild deficiency of spatial learning. The learning and retrieval scores of the rats totally deprived of granule cells were similar to those of controls at the passive avoidance conditioning task, but these animals were unable to accurately learn a spatial task and showed memory impairments relative to controls. These results are discussed in terms of cognitive defects.

Animals↗

PubMed1997

Purkinje cell loss in heterozygous staggerer mutant mice during aging.

The cerebellum on the heterozygous (+/sg) staggerer mutant mouse has recently been proposed as a model system in which to study the genetic contribution to the normal process of central nervous system aging since there is significant loss of neurons from 3 to 12 months of age (Shojaeian-Zanjani, H., Mariani, J., Delhaye-Bouchaud, N., and Herrup, K. (1992) Dev. Brain Res., 67, 153-160). In the current study we extend our analysis of the changes in Purkinje cell numbers up to 24 months of age in +/sg and C57BL/6J wild-type mice. At 13 and 18 months, while wild-type Purkinje cell numbers remain unchanged, there is a 22-26% loss in the number of Purkinje cells in +/sg after which no further cell loss is observed. Between 18 and 24 months, however, a 22% loss of Purkinje cell occurs in +/+ animals, with the result that by 2 years of age, the size of the Purkinje cell population is again similar in both genotypes. Analysis of the cell loss in both the mediolateral and the anteroposterior dimensions, as well as the immunostaining of Purkinje cells in frontal sections, reveal no obvious regional variation in the Purkinje cell loss. These results suggest that in +/sg, a precocious process of aging affects the size of the Purkinje cell population.

Age Distribution↗

PubMed1997

Increased inferior olivary neuron and cerebellar granule cell numbers in transgenic mice overexpressing the human Bcl-2 gene.

Neuron-target interactions during development are critical for determining the final numbers of neurons in the nervous system. To investigate the role of Purkinje cells and programmed cell death in the regulation of afferent neuron numbers, we have counted olivary neurons and granule cells in two lines of transgenic mice (NSE73a and NSE71) that overexpress a human gene for bcl-2 (Hu-bcl-2) in Purkinje cells and olivary neurons, but not in granule cells. Bcl-2 overexpression in vivo reduces naturally occurring neuronal cell death and cell death following axotomy, target removal, or ischemia. Olivary neuron numbers in NSE73a and NSE71 transgenic mice are significantly increased compared to controls by 28% and 27%, respectively, while granule cell numbers are only increased in NSE73a mice (29% above controls). We have previously shown that Purkinje cell number is increased by 43% in NSE73a transgenics and by 23% in NSE71 transgenics. The ratio of Purkinje cells to olivary neurons is not significantly different between the control and transgenic mice, while the ratio of granule cells to Purkinje cells is significantly decreased in the NSE71 transgenic mice compared to controls and NSE73a transgenics. The increased numbers of olivary neurons suggest that bcl-2 overexpression rescues these neurons from programmed cell death. The increase in granule cell number in only one transgenic line is discussed with respect to hypotheses that Purkinje cells regulate both granule cell progenitor proliferation and the survival of differentiated granule cells.

Animals↗

PubMed1997

Role of the inferior olivary complex in motor skills and motor learning in the adult rat.

The inferior olivary complex of adult rats was chemically destroyed using intraperitoneal injection of 3-acetylpyridine. Animals were submitted to different motor tasks: hanging test, equilibrium test and motor co-ordination test. The different scores show that 3-acetylpyridine-treated rats had motor co-ordination and static equilibrium deficiencies, whereas their rod suspension capabilities were intact. Animals were also trained on an unrotated rod or on a rod rotating at 5, 10 or 20 r.p.m. 3-Acetylpyridine-treated rats were able to maintain their equilibrium on the unrotated rod and at 5 r.p.m. Moreover, after motor training at 5 r.p.m., rats were able to improve their motor skills and reached the same score as controls. Despite their good motor skills, animals were unable to maintain their equilibrium when rotated at 10 and 20 r.p.m. These results suggest that the inferior olivary complex is needed for motor learning involving the temporal organization of movement.

Age Factors↗

PubMed1997

Delayed spontaneous alternation in intact and cerebellectomized control and lurcher mutant mice: differential role of cerebellar cortex and deep cerebellar nuclei.

Lurcher mutant (+/Lc) mice exhibit a massive loss of neurons in the cerebellar cortex and in the inferior olivary nucleus while deep cerebellar nuclei are essentially intact. To discriminate the respective participation of the cerebellar cortex and deep structures in learning and memory, the authors subjected 3- to 6-month-old +/Lc mice to a delayed spontaneous alternation task to test their working and long-term spatial memories. Results show that wild type (+/+) mice alternated above chance even after a 1-hr delay between the forced and choice trials, whereas in +/Lc mice, long-term memory was impaired. Cerebellectomized +/+ mice behave as +/Lc mice (working memory was preserved but long-term memory was not), whereas in the cerebellectomized +/Lc mice, both working and long-term memories were altered. These results are discussed in terms of relationships between the cerebellum and the hippocampus.

Animals↗

PubMed1997

Effect of cerebellar granule cell depletion on learning of the equilibrium behaviour: study in postnatally X-irradiated rats.

To assess the role of the mossy fibre-granule cell pathway in learning, the cerebellum of young DA/HAN strain rats was irradiated to make the cortex completely or partially agranular. The X-rays were delivered according to two different schedules, between 5-14 postnatal days (early group) and between 10-14 postnatal days (late group). Histological controls at 35 days showed a mean loss of granule cells of 96 +/- 1% in the early group and of 61 +/- 3% in the late group. The irradiated animals were subjected, from day 23 to day 35, to daily sensorimotor training on a rotorod. The scores and the strategy used (walking or hanging) by the rats were noted. The results demonstrate that a partial loss of granule cells due to a late X-irradiation schedule induced mild motor disabilities but no learning deficit, the only problem being difficulty in elaborating rapidly an efficient strategy to solve a novel problem. A sub-total loss of the granule cells, due to an early X-irradiation schedule, induced gross motor disabilities and the animals used hanging > 90% of the time. Due to the discrepancy between the learning abilities, which were preserved at least in part, and the gross motor impairments, the animals elaborated a novel strategy (jumping from the beam), allowing them to escape the experimental situation. This avoidance behaviour may be due to a decrease of anxiety, a lack of behavioural inhibition and/or attentional deficits that have been already observed in several other examples of cerebellar abnormalities.

Aging↗

PubMed1997

Enhanced endocrine response to novel environment stress and endotoxin in Lurcher mutant mice.

Lurcher mutant mice which are mainly known for their cerebellar degeneration, also display a hyperinducibility of proinflammatory cytokines, such as interleukin-1alpha and beta (IL-1) and tumor necrosis factor alpha (TNF-alpha), in peripheral macrophages. To assess whether this increased responsiveness to inflammatory stimuli is accompanied by a higher pituitary-adrenal response, we compared the adrenocorticotropic hormone (ACTH) and corticosterone response of Lc and wild-type mice to intraperitoneal (i.p.) administration of a cytokine inducer, lipopolysaccharide (LPS). Lurcher mice display resting levels of ACTH and corticosterone similar to those of wild-type mice. LPS (1.25 microg/g) induces a corticosterone surge 2-fold higher in Lurcher than in wild-type mice. By contrast, the response to IL-1alpha (10 ng/g, i.p.) is similar in both genotypes, suggesting that a differential reactivity of the hypothalamo-pituitary adrenal axis to IL-1 does not account for the higher reactivity of Lurcher mice to LPS. To test whether the increased responsiveness of the pituitary-adrenal axis of Lurcher mice generalizes accross stressors, mice were exposed to a novel environment. This condition also induced a surge of ACTH and corticosterone 3.5- and 2-fold higher in Lurcher than in wild-type mice. Prior blockade of IL-1 receptors by injection of IL-1 receptor antagonist (10 microg/g, i.p.) failed to block the response to LPS injection and exposure to novelty. In contrast, immunoneutralization of hypothalamic corticotropin-releasing hormone (CRH) significantly attenuated the ACTH surge and abrogated the difference between Lurcher and wild-type mice in their responses to a novel environment, suggesting that hypothalamic CRH neurons are involved in this excessive response.

Adrenocorticotropic Hormone↗

PubMed1996

Increased cerebellar Purkinje cell numbers in mice overexpressing a human bcl-2 transgene.

The Purkinje cell is a primary organizer in the development of the cerebellum. Purkinje cells may provide positional information cues that regulate afferent innervation, and Purkinje cell target size controls the adult number of afferent olivary neurons and granule cells. While Purkinje cells are necessary for the survival of olivary neurons and granule cells during periods of programmed cell death, little is known about the survival requirements of Purkinje cells in vivo. To determine if Purkinje cells are subject to programmed cell death during development we have analyzed Purkinje cell numbers in two lines of transgenic mice that overexpress a human gene for bcl-2 (Hu-bcl-2). Bcl-2 is a protooncogene that inhibits apoptosis in many cell types. Overexpression of bcl-2 in vitro and in vivo rescues neurons from trophic factor deprivation or naturally occurring cell death. In the mice analyzed in this study, transgene expression is driven by the neuron-specific enolase promoter that is first expressed embryonically in most regions of the brain in one line and postnatally in the second line. We have counted Purkinje cells in three adult control mice, five early overexpressing transgenics, and three late expressing transgenics. The number of Purkinje cells in the Hu-bcl-2 transgenic mice is significantly increased above control numbers, with an increase of 43% in the embryonically overexpressing line and an increase of 27% in the postnatally overexpressing line. Because bcl-2 overexpression has been shown to rescue other neurons from programmed cell death, the increase in Purkinje cell numbers in overexpressing bcl-2 transgenics suggests that Purkinje cells undergo a period of cell death during normal development.

Animals↗

PubMed1996

Over-expression of interleukin-1 beta-converting enzyme mRNA in staggerer cerebellum.

Interleukin-1 beta-converting enzyme (ICE), involved in the maturation process of interleukin-1 beta (IL-1 beta, is a homologue of ced-3, a protease required for programmed cell death in Caenorhabditis elegans. Over-expression of ICE induces programmed cell death in certain mammalian cell types, whereas in neurones of the central nervous system such a role has yet to be established. We show that ICE mRNA expression is increased 4-fold in the cerebellum of homozygous staggerer mice, where IL-1 beta mRNA is overexpressed and programmed neuronal cell death occurs. Intraperitoneal injection of endotoxin (LPS) induced a strong phasic increase in IL mRNA levels in the cerebellum, whereas the ICE mRNA level increased only moderately. Involvement of ICE in neuronal cell death in the cerebellum of staggerer mice is suspected.

Animals↗

PubMed1996

Cerebellar granule cell differentiation in mutant and X-irradiated rodents revealed by the neural adhesion molecule TAG-1.

In the external granular layer of the cerebellum, the granule cell precursors express the transient axonal glycoprotein TAG-1, a molecule involved in adhesion and neurite outgrowth. Granule cells express TAG-1 transiently, just as they extend neurites before migrating over the radial glia. The present study aims to investigate whether the expression pattern of TAG-1 is altered when granule cells develop abnormally. We studied in vivo models in which Purkinje and/or granule cell defects occur during postnatal development. These include the cerebellar mutant mice staggerer and lurcher as well as rats irradiated during postnatal development. Neither alterations in Purkinje cell differentiation nor the related granule cell loss in the mouse mutants impairs the ability of the surviving granule cell precursors to express TAG-1. Also, early granule cell loss in the X-irradiated rats do not disturb the TAG-1 expression phase in the patches of surviving granule cell precursors. Ectopic granule cells found in the adult cerebellum of X-irradiated rats do not bear the molecule, although they are located in the most superficial part of the molecular layer, occupied by the immunopositive cells a few days earlier. Thus, TAG-1 marks a very precise stage of granule cell differentiation, and the inward migration process itself is not required for the cessation of the expression. We postulate that TAG-1 may be involved in local differentiation steps restricted to the deep external granular layer such as parallel migratory routes or synchrony of axonal growth.

Animals↗

PubMed1995

Motor behavior of heterozygous staggerer mutant (+/sg) versus normal (+/+) mice during aging.

Three- to 24-month-old heterozygous staggerer (+/sg) and control (+/+) C57B16 mice were subjected to a motor test on a rota rod rotating at 30 or 40 revolutions per minute. The scores were evaluated by the time during which they maintained their equilibrium without falling down. Although the scores of both +/sg and +/+ animals decreased with age, the scores of +/sg mice were constantly lower at 3, 6 and 12 months and this difference was already significant at 3 months, i.e., before the 30% loss of Purkinje cells, granule cells and inferior olivary neurons which occurs between 3 months and 1 year in the mutant. At 18 months and beyond, scores no longer differed in both groups. These results show that there is no strict correlation between neuronal death in the cerebellar cortex and motor behavior on the rota rod. However, the difficulties in maintaining their equilibrium on the rota rod observed in +/sg mice as young as 3 months, indicate a deficit in accurate motor control which could be due to subtle structural or neurochemical disorders that probably precede neuronal death. Therefore, in the heterozygous staggerer, behavioral motor disturbance is a sign of cerebellar dysfunction which appears earlier than alterations in neuronal number.

Aging↗