Biomedical subjects

J Mariani

Publications and source records attributed to J Mariani.

At least 91 records · Page 5Linked to original sources

PubMed1995

Quantitative analysis of the Purkinje cell and the granule cell populations in the cerebellum of nude mice.

In the nude mutant, a well-known model of athymia in mouse, abnormalities have been reported in the cerebellum, including a 45% reduction in cerebellar size and neuronal loss (Henderson et al., 1981). The present work was aimed at reappraising the claimed anomalies by using quantitative cytological techniques. We counted the Purkinje and the granule cells, on serial sagittal sections stained with thionin, in the cerebella of nude mice (nu/nu) compared with their Balb/c controls (+/+). The latero-lateral extent of the cerebellar cortex was statistically different (mean +/- standard deviation) between the nude (7.05 +/- 0.45 mm, n = 3) and the control mice (8.05 +/- 0.35 mm, n = 3) (Student's t-test, p < 0.05). The number of Purkinje cells was not statistically different (p = 0.98) between the nude mice (159,880 +/- 5,225, n = 3) and the control ones (160,060 +/- 12,300, n = 3). The number of granule cells (x 10(6)) did not differ significantly (p = 0.40) in nude mice (m = 12.1 +/- 1.8, n = 3) from the controls (m = 13.2 +/- 0.8, n = 3). Immunohistochemistry with a specific marker of Purkinje cells, calbindin protein, did not reveal any qualitative difference between the nude and the control Purkinje cells. The only slight but significant difference concerned the mean cross-sectional area of the Purkinje cell somas: 188.2 microns 2 (n = 149) in the control animals and 176.3 microns 2 (n = 150) in the nude mice, (p < 0.01). In conclusion, our data indicate only a mild effect, if any, of the nude mutation upon the cerebellar neuronal population.

Animals↗

PubMed1994

Developmental studies of the inferior olivary nucleus in staggerer mutant mice.

The neurological mutation, staggerer, causes a severe disruption in the integrity of the olivo-cerebellar circuitry. The primary site of action is the Purkinje cell population which is reduced in cell number, with cells that are atrophic in dendritic structure, small in size and ectopic in position. This primary defect has a cascade effect on the Purkinje cell-afferent populations, leading to the target-related cell death of virtually all of the cerebellar granule cells and the majority of the neurons in the inferior olive. As part of our ongoing study of the cell-cell interactions in the cerebellar circuitry, we have studied the inferior olive of the staggerer mutant from birth to adulthood. We find that the reduction in olive neuron number does not occur until after birth in the mutants. On the day of birth, the number of cells is indistinguishable in mutants and in wild type. Similarly, we find that the four principal subnuclei of the olive are well defined at birth, but regress to a state of poor resolution during the first 3 postnatal weeks. Finally, Golgi impregnations reveal that of the two morphological classes of inferior olive neurons, only one class--the Type II or complex dendritic type survive in the mutant. These results are discussed in terms of their implications for the cell--cell interactions in the developing olivocerebellar circuit.

Aging↗

PubMed1994

Enlargement of olivo-cerebellar microzones in the agranular cerebellum of adult rats.

Previous work on normal adult rat showed that the vibrissae project, through the climbing fiber (CF) system, onto the Purkinje cells (PCs) of the contralateral cerebellar hemivermis of lobule VII. The highly elaborated CF projections from a given row of vibrissae delimit a narrow parasagittal zone which can be regarded as a functional olivo-cerebellar microzone. Interestingly, the adult one-to-one relationship between PCs and CFs is preceded by a transient phase during which each PC receives synaptic inputs from several CF collaterals which will be eliminated but one, when granule cells begin to establish synapses on PCs. Therefore, the question arose as to whether this synaptic elimination process could participate in the refinement of the topographical organization of CF projections and could contribute to the formation of such precise peripheral maps onto the cerebellum. In the present study, the topographical map of the CF-mediated projection of mystacial vibrissae onto the vermal PCs of lobule VII was determined in adult rats whose cerebellar PCs remain polyinnervated by olivary CFs due to degranulation by postnatal X-irradiation. Using intracellular recordings, we examined the responsiveness of PCs in lobule VII during mechanical stimulation of the 3rd row of contralateral vibrissae, and positioned cells responding to the stimulation on an averaged planar map of lobule VII. Comparison of the results to those obtained in our previous work on normal rats showed that the activated cells were more numerous and more diffusely distributed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Contribution of peripheral macrophages and microglia to the cellular reaction after mechanical or neurotoxin-induced lesions of the rat brain.

Lesions of the central nervous system result in invasion of peripheral phagocytes and/or in situ activation and proliferation of microglia, depending on the direct or indirect nature of the injury. Neurotoxins which are widely used to induce neurodegeneration have been reported to elicit a pure microglial reaction when administered intraventricularly. However, the mechanical lesion at the injection site, although remote from the lesioned area, could give access to blood-derived cells. Therefore, this study compares the phagocytic reaction occurring after a traumatic lesion of the brain causing a breakdown of the blood-brain barrier (BBB), or after degeneration of the inferior olivary neurons induced by intraperitoneal administration of 3-acetylpyridine, a process that respects the integrity of the BBB as suggested by the results of intravascular injection of Evans blue. The identification of the macrophages at the lesion site used specific binding of the B4 isolectin from Griffonia simplicifolia, preloading of the peripheral monocytes/macrophages with trypan blue, and characteristic morphological features. In traumatically lesioned rats, the lectin-labeled macrophages were mainly large rounded peripheral cells recruited 1-3 days postlesion, whereas in chemically lesioned rats, the cellular reaction appeared 24-36 h postinjection and peaked between 3 and 12 days before undergoing a slow decline. Lectin binding and morphological characteristics indicated that these small cells were reactive microglia. These results confirm that a brain injury leaving the BBB intact involves essentially the recruitment and/or the proliferation of microglia.

Animals↗

PubMed1992

Involvement of the N-methyl D-aspartate (NMDA) receptor in synapse elimination during cerebellar development.

In many instances, the establishment of highly specific neuronal connections during development results from the rearrangement of axonal projections through the trimming of exuberant collaterals or the elimination of functional synapses or both. Although the involvement of the N-methyl D-aspartate (NMDA) subtype of the glutamate receptor has been demonstrated in the shaping of axonal arbors, its participation in the process of selective stabilization of synapses remains an open issue. In this study, the effects of chronic in vivo application of D,L-2-amino-5-phosphonovaleric acid (D,L-APV), a selective antagonist of the NMDA receptor, on the synapse elimination process that takes place in the developing cerebellum of the rat have been analyzed. D,L-APV treatment prevented the regression of supernumerary climbing fiber synapses in 49 percent of the recorded Purkinje cells, while the inactive isomer L-APV was ineffective. Thus, activation of the NMDA receptor is a critical step in the regression of functional synapses during development.

2-Amino-5-phosphonovalerate↗

PubMed1992

Neuronal cell loss in heterozygous staggerer mutant mice: a model for genetic contributions to the aging process.

Staggerer is a neurological mutation of mice that causes a severe ataxia correlated with digenesis of the cerebellar cortex. The Purkinje cell population in the homozygous mutant is reduced in size with a near total atrophy of dendritic structure. Further, the cells are ectopic and are reduced in number by about 75%. All of these phenotypes have been shown to be direct effects of the staggerer gene on the Purkinje cell itself. As an indirect consequence of gene action, virtually all of the cerebellar granule cells die as do 60% of the cells of the inferior olive. The mutation is described as recessive because of the heterozygote, +/sg, is behaviorally normal and the mature cerebellum shows none of the defects described in the homozygous mutant. We report here that, as the +/sg mouse advances in age, a syndrome of cell losses is observed. While these losses are not as severe as in the homozygote, by 12 months of age 35% of the Purkinje cells are gone, as are 35% of the granule cells and 40% of the cells in the inferior olive. We propose that these results illustrate a synergy between the aging process and the heterozygous genotype. Neither alone is sufficient to cause the cell loss. This interaction suggests that the +/sg represents a new model for the genetic contribution to regressive CNS changes during aging.

Aging↗

PubMed1992

Peripheral macrophage abnormalities in mutant mice with spinocerebellar degeneration.

We recently reported hyperproduction of interleukin-1 (IL1) and hyperexpression of IL1 beta mRNA, after in vitro activation by lipopolysaccharide (LPS) in peripheral macrophages of several neurological mutant mice, i.e. staggerer, lurcher, pcd and reeler, that exhibit patterns of neuronal degeneration in the cerebellum; in the present study, we investigated the expression of several cytokine mRNA in peripheral macrophages of other mutants with neuronal degeneration in the cerebellum or in the spinal cord to determine whether this genetic dysregulation is specific for IL1 beta or whether it reflects a generalized hyperexcitability of these macrophages. Hyperexpression of IL1 beta mRNA was present in the cerebellar mutants nodding and nervous, but not in weaver. A similar phenomenon was found, but to a lesser extent, in the spinal mutants dystonia musculorum, wobbler and motor neuron degeneration. On the contrary, no hyperexpression of IL1 beta mRNA was found in non-genetic models of neuronal degeneration (Wistar rats treated with X irradiation or with 3-acetyl-pyridine). In the heterozygote staggerer +/sg, which exhibits a late onset of cerebellar neuronal loss, hyperexpression was found not only in 12-month old animals but also in 2-month old ones, i.e. when the number of cerebellar neurons is still normal. Synthetic molecules (muramyl dipeptides) like MDP or murabutide (Mu), known as macrophage activators, were also efficient in inducing IL1 hyperexpression in sg/sg macrophages. Hyperexpression of two other cytokine mRNA, i.e. IL1 alpha and tumour necrosis factor alpha mRNA, was also detected in LPS-stimulated macrophages of staggerer and lurcher mutant mice. These data led us to conclude that the macrophages of spinal and cerebellar mutants are in a state of general hyperexcitability. Work is in progress to establish whether the cytokine abnormalities result from a defect intrinsic to the macrophages of the mutant mice or are secondary to the degenerative process ultimately leading to neuronal loss.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1992

Evidence for a hyperexcitability state of staggerer mutant mice macrophages.

We recently reported an abnormal production of interleukin-1 (IL-1) in peripheral macrophages of several neurological mutant mice that exhibit patterns of neuronal degeneration, especially in the cerebellum. After in vitro activation by lipopolysaccharide acid (LPS), these macrophages hyperexpress IL-1 beta mRNA and hyperproduce IL-1 protein in comparison with +/+ controls. In the present study, focused on the staggerer mutant mice, we investigate if this genetic dysregulation is specific for IL-1 beta or if it reflects a generalized hyperexcitability of these macrophages. The hyperexpression of IL-1 beta mRNA in sg/sg macrophages is present whatever the duration of LPS stimulation, even for periods as short as 15 min, although it reaches a maximum after 4 h of stimulation. The hyperinducibility of sg/sg macrophages is observed even when very low doses of LPS are used (0.01 microgram/ml) and reaches its maximum for 5 micrograms/ml LPS. Synthetic molecules (muramyl dipeptides), such as N-acetylmuramyl-L-alanyl-D-isoglutamine or murabutide, known as macrophage activators, are also efficient in revealing the cytokine hyperexpression in sg/sg macrophages. In addition, hyperexpression of two other cytokines, i.e., tumor necrosis factor-alpha and IL-1 alpha mRNAs, is also detected in LPS-stimulated macrophages of mutant mice. Finally, the effect of an inhibitor of protein synthesis, cycloheximide, is similar in +/+ and sg/sg macrophages. As a whole, these data lead us to conclude that the sg/sg macrophages are in a state of general hyperexcitability when compared with +/+ ones.

Acetylmuramyl-Alanyl-Isoglutamine↗

PubMed1992

Role of the target in synapse elimination: studies in cerebellum of developing lurcher mutants and adult chimeric mice.

As the mature nervous system is sculpted out of its embryonic anlage, regressive events are a surprisingly common feature. As one example, the establishment of adult innervation in the CNS and PNS often involves a massive withdrawal of previously formed functional synapses. In the cerebellum, the one-to-one relationship of inferior olivary climbing fibers to Purkinje cells is preceded by a transient stage in which each Purkinje cell is multiply innervated. The regulation of this regressive event is still not fully understood; previous studies suggested that some stimulus from the maturing granule cells is necessary. We have used the lurcher (Lc) mutation as a model system in which to study this phenomenon. In lurcher mice, Purkinje cells degenerate during the first few postnatal weeks, after receiving synaptic contacts from both inferior olivary neurons and granule cells. We have recorded the climbing fiber responses both in lurcher mutants at postnatal days 14-20 (P14-P20) and in adult lurcher chimeras. In the latter, experimental genetics are used to create a situation in which untreated wild-type Purkinje cells are present in an environment that ranges from 100% wild-type to nearly mutant. We found that in P14-P16 lurcher mutants, most of the cells recorded (75%) remained polyinnervated, whereas in wild-type control mice, only 10% of the Purkinje cells retained their multiple innervation. By P18-20, it was difficult to find Purkinje cells in the lurcher mutants that would withstand an intracellular electrode. Nonetheless, in those cells that were successfully impaled, most remained multiply innervated. By this age in wild-type mice, 100% of the Purkinje cells are monoinnervated.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1991

Co-cultures of inferior olive and cerebellum: electrophysiological evidence for multiple innervation of Purkinje cells by olivary axons.

Slices of inferior olive (IO) and cerebellum were co-cultured for several weeks by means of the roller tube technique. Recordings were carried out intracellularly from Purkinje cells (PCs) which were identified morphologically by intracellular injection of the fluorescent dye Lucifer yellow, or by immunohistochemical stainings with antibodies raised against the 28 kD Ca(2+)-binding protein calbindin. Following stimulation of olivary tissue, an all-or-none full complex spike response was recorded in some PCs consisting of a fast rising spike followed by a depolarizing potential. In other PCs, graded stimulation of the olivary explant induced synaptic potentials which were characterized by step-wise variation in their amplitude and resembled the ones occurring spontaneously. In contrast, only smoothly graded synaptic potentials were observed in cerebellar mono-cultures. These results indicate that some of the PCs in olivo-cerebellar co-cultures are innervated by several olivary neurons.

Action Potentials↗

PubMed1991

[Does synaptic elimination contribute to the organization of cerebellar microzones of climbing fiber projection?].

In adult rats whose cerebellar Purkinje cells (PCs) remain polyinnervated by olivary climbing fibres (CFs) after postnatal irradiation, topographical maps of responsive PCs to mechanical stimulation of the third row of contralateral vibrissae show that these cells are more numerous and more diffusely distributed than in the normal rat. PCs responding with the "best responses" are distributed evenly from the midline to 400 microns lateral in the contralateral hemivermis of lobule VII, and not in a parasagittal microzone centred on the plane 200 microns as in the normal rat. Thus it seems likely that synaptic elimination should contribute to microzone formation during postnatal development of the normal cerebellum.

Action Potentials↗

PubMed1990

Extent of multiple innervation of cerebellar Purkinje cells by climbing fibers in adult X-irradiated rats. Comparison of different schedules of irradiation during the first postnatal week.

The multiple innervation of cerebellar Purkinje cells (PCs) by climbing fibers (CFs) that is transient in normal developing rats can be experimentally maintained in cerebella which have been degranulated by repetitive postnatal X-irradiation restricted to the first postnatal week. Since the involution of redundant CFs occurs essentially between postnatal days 5 and 10, and given that postirradiation effects last 2-3 days, the question arose to know whether it is possible to further delimit a 'critical period' of irradiation within the first week. An estimate of the extent of multiple innervation of PCs by CFs was made in adult rats that had been irradiated according to 5 different schedules: in two groups, rats received X-rays applied repetitively during the first postnatal week (PN0-7 groups); in the 3 other groups, X-rays were delivered either during the first part of the week (early group PN1-3) or during the last part of the week (late groups PN4-7). In addition, two daily doses were tested (150 and 200 r). The CF pathway was electrically stimulated in anesthetized rats at the level of the inferior olive or in the cerebellar white matter. Intracellular recordings of spontaneous and evoked CF responses in PCs allowed to estimate the number of afferent CFs and to calculate the mean value (m) per PC for each group. The majority of recorded cells was located in lobules VII and VIII and similar results were obtained in these two lobules.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Microtubule-associated protein 2 (MAP2) in Purkinje cell dendrites: evidence that factors other than binding to microtubules are involved in determining its cytoplasmic distribution.

We have studied the distribution of microtubule-associated protein 2 (MAP2) in the Purkinje cell dendrites of rats whose cerebella were exposed to X-irradiation during the second postnatal week. The Purkinje cells of such animals have abnormally elongated apical primary processes that branch in the other molecular layer rather than close to the cell body as in normal tissue. The results show that in these distorted dendrites the MAP2 distribution is "shifted" distally relative to the normal pattern, in which MAP2 is distributed evenly throughout the dendritic tree. Tubulin and other microtubule-associated proteins, such as MAP1, are not affected and remain evenly distributed throughout the dendritic tree despite the anatomical distortion. We conclude that the distribution of MAP2 in Purkinje cells is not determined solely by its binding to tubulin. Other factors must be involved and these appear to be related to dendritic morphology and possibly to branching.

Animals↗

PubMed1990

Interleukin-1 hyperproduction by in vitro activated peripheral macrophages from cerebellar mutant mice.

Several mutations in mice produce complex patterns of neuronal degeneration of the cerebellum and of its afferent pathways. In the staggerer (sg/sg) mutant, atrophy of the lymphoid organs and immunological abnormalities have been described. To search for a possible link between the neurological and the immune disorders in this mutant, we studied the production by its peripheral macrophages of interleukin-1 (IL-1), which roles in both immune and nervous systems are well established. Suspensions of peritoneal and/or spleen macrophages from mutants and their appropriate controls were stimulated in vitro by lipopolysaccharide. Northern and dot blots, performed with murine IL-1 cDNA probes, revealed a clear-cut hyperexpression of IL-1 mRNA in staggerer macrophages. An IL-1 bioassay using the IL-1-responsive D10.G4 cell line also revealed a sixfold increase of IL-1 activity in the macrophage supernatants of staggerer mutant mice. The hyperproduction was found in 3-week to 1-year-old staggerer and also in heterozygous (+/sg) mice. A similar phenomenon existed in cerebellar mutants lurcher, Purkinje cell degeneration (pcd), and to a lesser extent reeler and wobbler, but was absent in the neurological mutants weaver, jimpy, and motor end plate disease (medH). These observations establish that in several point mutations in mice, central nervous degeneration is associated with dysregulation of IL-1 production by peripheral macrophages.

Animals↗

PubMed1990

Glutamate dehydrogenase in cerebellar mutant mice: gene localization and enzyme activity in different tissues.

Many similarities of both the inheritance pattern and the neuropathology can be observed between olivopontocerebellar atrophies, or so-called multiple system atrophies (MSAs), and murine cerebellar mutations like Purkinje cell degeneration, nervous, staggerer, weaver, and reeler. Our study aimed to test whether the glutamate dehydrogenase (GDH) deficiency observed in some MSA patients could be found also in any of the murine mutants. GDH activity was assayed in several organs of these mutants, and no general deficiency was detected. By contrast, the level was found to be elevated in the cerebellum. The GDH gene was localized on mouse chromosome 14 and does not map close to any known neurological mutation in the mouse. We conclude, for the moment, that none of these cerebellar mutant mice can be considered as an animal model for GDH-deficient MSA.

Animals↗

PubMed1990

Cell loss in the inferior olive of the staggerer mutant mouse is an indirect effect of the gene.

Staggerer (sg) is an autosomal recessive mutation in mouse that causes severe cerebellar atrophy. In this mutant, the Purkinje cell (PC) number is reduced by about 75% and the remaining Purkinje cells have a reduced dendritic arbor and an ectopic location. Previous analysis of staggerer chimeras has demonstrated that the Purkinje cell phenotypes are all direct consequences of the cell-autonomous action of the staggerer gene. The two major afferents to the Purkinje cell are also affected. Virtually all of the granule cells die by the end of the first postnatal month. This death, however, has been shown to be an indirect consequence of mutant gene action. The second major afferent system is from the cells of the inferior olive that project to the main trunks of the Purkinje cell dendrite via the climbing fiber system. Quantitative studies of cell number in the inferior olive have shown that the number of cells is reduced by about 62% in adult sg/sg mutants. We report here the results of our quantitative analysis of three staggerer chimeras. beta-glucuronidase activity was used as an independent cell marker. Our findings demonstrate that inferior olive cell death in staggerer mutant mice is an indirect effect of staggerer gene action. Thus, as for the granule cells, the loss of olivary neurons most likely results from a target related cell death.

Animals↗

PubMed1990

[Synaptic localization of 5'-nucleotidase activity in the cerebellar cortex in adult rats irradiated by X rays after birth].

5'-nucleotidase cytochemistry was performed in the cerebellum of adult rats exposed previously to a single postnatal X-irradiation which maintains until adulthood the normally transient multiple innervation of cerebellar Purkinje cells by climbing fibers. 5'-nucleotidase activity persists in climbing fiber synapses and other asymmetrical synapses while it is transient during normal development. Therefore, in the X-irradiated rat, an immature stage of the excitatory synapses persists which, for the climbing fibers, coïncides with or precedes their involution during normal development.

5'-Nucleotidase↗

PubMed1989

Representation of vibrissae inputs through the climbing fiber pathway in lobule VII of the adult rat cerebellar vermis.

The present study gives a detailed description of the functional characteristics and of the topographic distribution of Purkinje cell (PC) responses, mediated through the climbing fiber pathway and elicited by mechanical stimulation of two different rows (A and C) of vibrissae in a circumscribed region of the posterior vermis of the rat cerebellum. Experiments were carried out on normal adult rats under barbiturate anesthesia. PCs were recorded in an area extending 1500 microns laterally to the midline in the vermal part of lobule VII contralateral to the stimulation. Using micromapping techniques and computer analysis, we located the cells on the map of the unfolded PC layer. Taking into account the mean latency of the responses and the probability of discharge of PCs, restricted areas of projection were found. For each row, these areas formed two longitudinal patches located between midline and plane 1100 microns and separated by a non-responsive plane at 500 microns. Cells having the best characteristics of responses to the stimulation of row C were located mainly in plane 200 microns. Cells giving the best responses to the stimulation of row A were located mainly in the posterior part of plane 200 microns which was therefore a zone of convergence for both rows.

Action Potentials↗