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PubMedDate not supplied

The early ultrastructural alterations in the rabbit cerebral and cerebellar cortex after compression ischaemia.

The ultrastructural alterations in the rabbit cerebral and cerebellar cortex resulting from 30 minutes complete, permanent cerebral ischaemia were studied. The ischaemia was induced by raising the intracranial pressure (ICP) above the systolic arterial pressure (compression ischaemia). Immediately after releasing the ICP the brain was fixed by intravascular glutaraldehyde perfusion. Samples from the cerebral and cerebellar cortex were processed for electron microscopy. The ultrastructural changes were relatively minor; there was a generalised, slight intracellular oedema, most prominent in the subpial area; the nuclear chromatin was clumped, the endoplasmic reticulum and cisternae of the golgi apparatus became somewhat dilated, the inner matrix of the slightly swollen mitochondria showed increased electron lucency, and microtubules and ribosomes began to loose their compact structure. These changes, unaccompanied by any extensive volumetric change of any cellular compartment, agree well with the recently presented hypothesis of two different types of anoxic-ischaemic nerve cell injury. This cellular reaction to complete, permanent compression ischaemia represents the type of injury that is seen resulting from ischaemic insults during which no flow of fluid irrigates the ischaemically injured cells.

Animals↗

PubMed1989

Synaptophysin expression during synaptogenesis in the rat cerebellar cortex.

In order to study the mechanisms of synaptogenesis in the rat cerebellar cortex, a library of monoclonal antibodies has been generated against proteins of the isolated synapse. One recognizes a glycosylated 38 kDa protein that is concentrated in the synaptic vesicle fraction and resembles synaptophysin biochemically in its molecular weight, charge, and pattern of glycosylation. In the adult cerebellar cortex, the antisynaptophysin(mabQ155) immunoreactivity is codistributed with synapses. Immunoreactivity is strongest in the molecular layer where punctate deposits of reaction product outline the Purkinje cell dendrites. Discrete small profiles, consistent with the distribution of basket cell axon terminals, surround the Purkinje cells, and in the granular layer the synaptic glomeruli are intensely stained. There is no immunoreactivity in the white matter axon tracts. Electron microscope immunocytochemistry confirms the synaptic location of the antigen and suggests that the reaction product is associated with synaptic vesicles. Both round and flat vesicle populations are immunoreactive. Antisynaptophysin(mabQ155) has been used to follow synaptogenesis in the developing rat cerebellum. In the newborn rat (P0), despite the paucity of synapses, there is some specific immunoreactivity, especially in the subcortical white matter. Electron microscopy shows that the antigenicity is associated with vesicles within growth cones, filopodia, and immature axon profiles. During development, antisynaptophysin immunoreactivity increases progressively, along with the maturing cell populations, for both the granule cell-Purkinje cell and the mossy fiber-granule cell synapses. Quantitative biochemical analysis confirms the cytochemical results. These data suggest that neuronal growth cones express a synapse-specific antigen before complete morphological synapses are present.

Aging↗

PubMed1979

Loss of synapses in the cerebellar cortex of the senescent rat.

Numbers of synapses were compared in the cerebellar cortex of adult (12 months of age) and senescent (25 months of age) male rats of the Fisher-344 strain. The total number of axodendritic synapses was found to be 24% lower in the senescent rats as compared with adults. A differential analysis of synapses involving dendritic shafts and spines showed no significant change in numbers of synapses involving shafts, but a highly sigificant 33% decrease in numbers involving spines in senescent rats. These data suggest that the selective age-related loss of synapses involving dendritic spines (but not shafts) in the cerebellar cortex results from the impairment with advanced age of specific afferent neurons and/or a selective age-related vulnerability of dendritic spines.

Aging↗

PubMed2000

Immunolocalization of glutamic acid decarboxylase in postmortem human cerebellar cortex. A light microscopy study.

The distribution of glutamic acid decarboxylase (GAD), the gamma-aminobutyric acid (GABA) synthesizing enzyme, was examined in the postmortem human cerebellar cortex by immunocytochemistry. The results, obtained on nervous tissues taken at autopsy and fixed within 24-36 h after death, enabled the authors to precisely reveal the topographical distribution of GAD-containing neurons and axon terminals in the human cerebellar cortex. Labeled neurons, corresponding to different neuronal cytotypes of the cerebellar cortex, showed a diffuse cytoplasmic immunoreactivity in both bodies and processes. Labeled axon terminals appeared as immunoreactive puncta. The use of immunocytochemistry in the detection of GAD in the postmortem human brain greatly increases the possibility of carrying out morphological studies on the GABAergic system, both in normal and in pathological conditions.

Adult↗

PubMed1987

Neuronal maturation in the normal and hypothyroid rat cerebellar cortex studied with monoclonal antibody MIT-23.

By immunocytochemistry we have studied the expression of the mitochondria-associated polypeptide MIT-23 during the postnatal development of the normal and hypothyroid rat cerebellar cortex, in afferent fibers, and also in neurons of the cerebellar nuclei. The glial cells are never immunoreactive. In all neurons of the cerebellar cortex, MIT-23 expression always occurs after the final mitosis and migration are complete, and persists throughout adult life. Almost all MIT-23 expression begins postnatally. A few Purkinje cells are already immunoreactive at birth and the rest begin expression during the following two days. Immunoreactive Golgi and granule cells are found from postnatal day 4 (P4), basket cells from P10, and stellate cells from P16. Purkinje cells from different anteroposterior regions of the vermis express different levels of MIT-23 with higher staining intensities in lobules I to IV. These differences appear early in development and are retained in the adult. MIT-23 expression in the hypothyroid cerebellar cortex differs from that in control animals only in minor ways. However, sections immunoperoxidase-stained with anti-MIT-23 antibody reveal that, in addition to previously reported alterations in cerebellar development due to a shortage of thyroid hormones, Purkinje cell axonal development is slowed down in the hypothyroid condition, and occasional Purkinje cells in normal and especially in hypothyroid animals have their somata and or dendrites in ectopic locations. Analysis of these cells reveals a preferential direction of dendritic trunk growth in the direction of the molecular layer. Furthermore, secondary branching of ectopic dendrites is confined exclusively to the developing molecular layer, as in normal Purkinje cells, thus suggesting that neither the mature nor immature granule cell environment is sufficient to sustain normal dendritic development.

Animals↗

PubMed1989

[Ultrastructural characteristics of the cerebellar cortex in the postnatal development of animals with protein-calorie malnutrition and in subsequent rehabilitation].

An electron microscopical investigation of the cerebellar cortex has been carried out in mice, kept during the 10th-40th days of their life at a diet with protein insufficiency and a subsequent food rehabilitation and food rehabilitation with carnitine addition to the diet on the 41st-70th days of their life. A sharp protein limitation in the diet results in the most essential changes in the neuropil, while the ultrastructure of the piriform neurons changes slightly. Amount of the synaptic vesicles in small axonal terminals decreases and their localization in the area of the synaptic contacts changes. Simultaneously, degeneratively changed axonal terminals often occur, they demonstrate a rather electron opaque axoplasma. The food rehabilitation mainly normalizes the ultrastructure of the cerebellar cortex elements, however, in the neuropil altered axonal terminals with a high electron opaque axoplasma occur. After the food rehabilitation with carnitine addition to the diet, the cerebellar cortex ultrastructure not only normalizes, but even demonstrates certain signs of hypertrophy.

Age Factors↗

PubMed1983

On three types of large nerve cells in the granular layer of the human cerebellar cortex.

The large nerve cells of the granular layer of the human cerebellar cortex have been investigated by means of a newly developed Golgi technique that reveals the pigmentation pattern of individual nerve cells through transparent impregnations of their cell bodies and cellular processes. Three types of large nerve cells have been distinguished: Type I cells correspond to the Golgi cells. They have a rounded or polygonal cell body with only a few dendrites that radiate in all directions. The axon ramifies profusely, close to the parent soma. Cells of this type are most frequently encountered among the large cells of the granular layer. Type I cells contain only a few pigment granules. Type II cells have a fusiform or triangular cell body with a few rather extended dendrites that rarely ramify. Cells of this type are either devoid of pigment or contain a few large pigment granules that can be stained intensely by aldehydefuchsin. Type III cells are multipolar neurons with a fair number of dendrites originating from any point of the soma. The dendrites extend into the deep portions of the molecular layer. Here and also within the Purkinje cell layer they repeatedly branch off forming a dense dendritic arborization. Cells of this type are evenly distributed throughout the entire granular layer and throughout the adjacent portions of the Purkinje cell layer and the white matter as well. Type III cells are filled with tightly packed lipofuscin granules. The pattern of pigmentation is characteristic for each of these neuronal types. The three types of large nerve cells within the granular layer of the human cerebellar cortex can therefore be distinguished not only in Golgi impregnations but also in pigment-Nissl preparations.

Adult↗

PubMed1985

Differences in synaptic size in the superficial and deep layers of the molecular layer of the cerebellar cortex of the cat. An electronmicroscopic and autoradiographic study.

In a previous study observations in semithin sections of E-PTA-stained cerebellar cortex of the cat revealed differences in size of synaptic grids between the molecular and granular layer (Van der Want et al. 1984). In addition, synaptic size differences were observed between superficial and deep levels in the molecular layer. The present study was an attempt to analyze synapses in ultrathin sections of the cerebellar cortex with special emphasis on size differences of distinct types of synapses at different levels in the molecular layer. Climbing fibers were identified by means of anterograde transport of 3H-leucine injected in the inferior olive and parallel fibers were identified on account of fine structural criteria. Synaptic profiles were measured semi-automatically in the neuropil of the cerebellar cortex at the supra-Purkinje level and the subpial level. Measurements of the trace- and chordlength were obtained from random sections. The frequency distribution of the true diameters of the synapses was reconstructed with a discrete "unfolding"-procedure. The overall diameter at the superficial level was 390.2 +/- 1.5 nm, at the deep level 406.6 +/- 1.5 nm. Climbing fibers exhibited mean values of 431.9 +/- 4.7 and 461.3 +/- 4.1 nm at these levels and parallel fiber terminals mean values of 370.7 +/- 2.9 and 395.8 +/- 3.0 nm. The frequency distributions showed remarkable and statistically significant differences compared with the overall distributions observed at the superficial and the deep levels respectively. The frequency distributions of synaptic diameters at the superficial and deep levels also differ significantly.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2001

Serotonergic neuromodulation in the cerebellar cortex: cellular, synaptic, and molecular basis.

The cerebellum, like most sensorimotor areas of the brain, receives a serotonergic innervation from neurons of the reticular formation. It is well established that local application of serotonin modulates the firing rate of cerebellar Purkinje cells in vivo and in vitro, but the mechanisms by which serotonin affects the cerebellar function are still poorly understood. Whereas interactions between serotonin, glutamate, and GABA have been reported to increase or decrease the firing frequency of Purkinje cells, there is little evidence for a modulation of excitatory and inhibitory synapses by serotonin in the cerebellar cortex. Changes in the intrinsic electrical properties of Purkinje cells upon application of serotonin have also been reported, but their impact on Purkinje cell firing is unclear. The recent finding that serotonin specifically modulates the activity of Lugaro cells, a class of inhibitory interneurons of the cerebellar cortex, offers new insights on the action of this neuromodulator. The peculiar axonal projection and specific interneuronal targets of the Lugaro cells suggest that the action of serotonin might occur upstream of Purkinje cells through a resetting of the computational properties of the cerebellar cortex. Understanding the mechanisms of the serotonergic modulation of the cerebellar cortex is of clinical relevance, as abnormal serotonin metabolism has been observed in animal models and pathological cases of motor disorders involving the cerebellum, and as chronic intravenous administration of L-5-hydroxytryptophan (5-HTP), a precursor of serotonin, was the first treatment shown to improve significantly cerebellar symptoms.

Animals↗

PubMed1983

Astrocytic development in fetal parietal cortex grafted to cerebral and cerebellar cortex of immature rats.

Pieces of cortex cerebri anlage were dissected out from 16- to 17-day-old fetuses and transplanted to the cortical and cerebellar regions of 5- to 6-day-old rat pups. Twelve animals with grafts in the cortical region and 5 animals with grafts in the cerebellar region were studied 1.5-4 months later. Cresyl violet stained sections revealed no gross difference in either cell morphology, cell density or cell distribution between grafts in the two locations. A molecular layer-like zone was present on all free surfaces of the grafts, whether facing a ventricle or the meninges. The astrocytic development was studied using immunohistochemistry with antibodies against glial fibrillary acidic protein, (GFA), and the S-100 protein. Both antibodies visualized starshaped astrocytes and perivascular membranes surrounding blood vessels. Semi-quantitative measurements as well as computerized image analysis showed that the total amount of GFA-like immunoreactivity was much higher in both types of grafts than in corresponding host cortex cerebri. No differences in amount of S-100-like immunoreactivity could be demonstrated. As S-100 is thought to be a more general astrocytic marker than GFA, this suggests that the difference in GFA-like immunoreactivity is due mainly to an increased amount of GFA within the individual astrocytes. It is concluded that grafts of fetal cortex cerebri pieces to the CNS of young hosts develop a profound astrocytic reaction characterized by an increased amount of GFA-like immunoreactivity.

Animals↗

PubMed2004

Neurosteroidogenesis in oligodendrocytes and Purkinje neurones of cerebellar cortex of dogs.

The cerebellum is a steroidogenic organ that expresses steroidogenic enzymes and produces neurosteroids. Purkinje neurones appear to be the most active steroidogenic cells in the cerebellar cortex. These neurones express 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), P450 side-chain cleavage (P450scc), 17 alpha-hydroxylase/c17, 20lyase (P450c17), P450 aromatase (P450arom) and produce pregnenolone, progesterone, dehydroepiandrosterone, androstenedion, oestradion and oestrone. Oligodendrocytes are predominantly the producer of myeline protein. The oligodendrocytes were identified by immunohistochemistry using a monoclonal antibody against myeline 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase), a myeline specific enzyme. In this study we have examined the distribution of 3 beta-HSD and CNPase by immunohistochemistry using monoclonal antibody in canine cerebellar cortex. The localization of oligodendrocytes within the cerebellar cortex was determined to be close to Purkinje neurones. This result suggests that endogenous progesterone synthesized de novo in the Purkinje neurone can promote myeline protein synthesis in oligodentrocytes.

3-Hydroxysteroid Dehydrogenases↗

PubMed1994

Age-dependent changes in gp75LNGFR (low-affinity nerve growth factor receptor) immunoreactivity in the rat cerebellar cortex.

The expression of gp75LNGFR (low-affinity receptor of the nerve growth factor (NGF) family of neurotrophins) immunoreactivity was studied in the cerebellar cortex of male Wistar rats of 3 months (young), 12 months (adult) and 24 months of age using immunohistochemical techniques and a monoclonal antibody against rat-gp75LNGFR. The percentage of Purkinje neurons displaying gp75LNGFR immunoreactivity (IR), and the intensity of gp75LNGFR IR in the cytoplasm of Purkinje and granule neurons, and in the neuropil of molecular layer of the cerebellar cortex were determined by quantitative image analysis and microdensitometry. The number of Purkinje neurons displaying gp75LNGFR IR and the intensity of gp75LNGFRIR in the cytoplasm of Purkinje neurons was significantly higher in rats of 12 months of age in comparison with 24- and 3-month-old rats. No significant changes were observed in the intensity of gp75LNGFRIR in the granule neuron layer of young, adult and old rats. In the molecular layer, the highest gp75LNGFRIR was found in young animals. It was reduced as a function of age. The present results show that changes in gp75LNGFRIR observed as a function of age affect to a different extent the three layers of the rat cerebellar cortex.

Aging↗

PubMed2002

Synaptic long-term depression (LTD) in vivo recorded on the rat cerebellar cortex.

Long-Term Depression (LTD) of the parallel fiber synapses of the cerebellar cortex has been intensively studied over the last 20 years and is now considered to be a physiological mechanism underlying learning and memory of the cerebellar cortex. With microelectrode recording in vivo, the induced LTD is recorded reliably up to 2 hours. Using surface electrodes we have recorded parallel fiber responses due to the currents generated by the AMPA type receptors of the dendritic spines in the intact vermal cortex of decerebrated rats. We have found that by conjunctively stimulating the climbing and parallel fiber pathways, an LTD was induced which persisted for as long as the recording conditions permitted. The longest lasting LTD of our present results was for 5 hours.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1983

The primary vestibular projection to the cerebellar cortex in the pigeon (Columba livia).

The cerebellar cortex of the pigeon receiving direct vestibular afferents was delineated by anterograde transport of [3H]-amino acids injected into the vestibular nerve. Labelled mossy fiber rosettes in the granular layer were concentrated in lobule X (nodulus) and to a lesser extent, in the ventral portion of lobule IXd (uvula and paraflocculus). A few solitary labelled rosettes were also found in more dorsal portions of lobule IX, as well as in the anterior lobe between lobule II and IV. The lingula remained unlabelled. Discrete injections of [3H]-leucine into the cristae of each of the three semicircular canals or the utricular macula yielded a similar distribution of fewer labelled rosettes. A few primary mossy fiber terminals labelled after cochlear injections are attributed to afferents from the lagenar macula. Since effective diffusion of label from the injection site was excluded by controls, it is concluded that projection of individual canal and macula nerves to the vestibulocerebellar cortex is not topographically separated. It is proposed that this extensive convergence of various afferents is required by the cerebellum to compute precise and directionally specific control signals during head rotation in all conceivable planes.

Amino Acids↗

PubMed1987

Benzodiazepine receptors in the human cerebellar cortex: a quantitative autoradiographic and pharmacological study demonstrating the predominance of type I receptors.

The anatomical localization of benzodiazepine receptors in the human cerebellar cortex was studied using quantitative autoradiography following in vitro labelling of cryostat sections with [3H]flunitrazepam ([3H]FNZ), and the pharmacology of these receptors has been characterized by computerized, non-linear least squares regression analysis of [3H]FNZ displacement by FNZ, CL218,872 and ethyl beta-carboline-3-carboxylate (ECC) binding to membranes. The autoradiograms demonstrated that benzodiazepine receptors were present throughout all layers of the human cerebellar cortex; high concentrations of receptors were present in the molecular layer, moderate concentrations were present in the granular layer and a much lower density of receptors was seen in the intervening Purkinje cell layer. The pharmacological studies indicated that the human cerebellar cortex contained a high concentration of homogeneous benzodiazepine receptors which have high affinity for FNZ, ECC and CL218,872, i.e. type I sites.

Adult↗

PubMedDate not supplied

Excitatory and inhibitory amino acid neurotransmitter binding sites in the cerebellar cortex of the pigeon (Columba livia).

We used receptor autoradiography to determine the distribution of excitatory and inhibitory amino acid neurotransmitter binding sites in the cerebellar cortex of the pigeon (Columba livia). alpha-Amino-3-hydroxy-5-methylisoxazole-4-propionic acid, kainate and metabotropic binding sites had highest levels in the molecular layer. N-methyl-D-aspartate binding sites, assayed with both [3H]glutamate under selective conditions and with [3H]glycine binding to the associated strychnine-insensitive glycine site, had highest levels in the granule cell layer. There was little specific binding of the non-competitive N-methyl-D-aspartate antagonist, [3H]MK-801. The level of gamma-aminobutyric acid (GABA)-A binding sites was higher than GABA-B binding sites in both molecular and granule cell layers with the highest level of GABA-A sites in the granule cell layer. The highest level of GABA-B binding sites was in the molecular layer. [3H]Flunitrazepam binding levels were approximately the same in both molecular and granule cell layers. With the exception of kainate binding sites, the distribution of binding sites was identical to that seen in the cerebellar cortex of mammals. Our results support the concept that the chemoarchitecture of the cerebellar cortex has been conserved in the course of vertebrate evolution.

Animals↗

PubMed1977

Calcium-dependent increase in efflux of [1-3H] taurine from the superfused rat cerebellar cortex in vivo.

High (40 mM) potassium stimulation has been shown to increase the efflux in vivo of [1-3H] taurine from the superfused rat cerebellar cortex by 46%, P less than 0.001. During superfusion with calcium-free media this increase in efflux is abolished. The cellular location of [1-3H] taurine in the cerebellar cortex is not yet known, but this region of the brain contains exceptionally high levels of endogenous taurine. The calcium dependency of the release of labelled taurine raises the possibility that taurine has some neuro-humoral role in the cerebellar cortex.

Animals↗

PubMed1985

Ultrastructural immunocytochemistry of gamma-aminobutyrate in the cerebral and cerebellar cortex of the rat.

gamma-Aminobutyrate containing structures in the cerebral and cerebellar cortex of the rat were visualized by an immunocytochemical method using glutaraldehyde fixation and an antiserum developed against a gamma-aminobutyrate-glutaraldehyde-protein conjugate. Labelled elements (perikarya and cell processes) were observed to be distributed throughout the layers of the cerebral cortex in a pattern similar to that described using glutamate decarboxylase immunocytochemistry. The morphological features of many immunoreactive cell bodies were typical of stellate neurons. In the cerebellar cortex, Purkinje, basket, Golgi and stellate, cell bodies were found to be immunoreactive along with numerous labelled neuronal processes. At the ultrastructural level, the labelled processes in both areas corresponded to immunoreactive dendrites and fibres. Labelled synaptic boutons, generally of the symmetrical type, could also be seen in contact with positive or negative cell bodies and dendrites. In the cerebellum, glomeruli could be clearly identified including mossy fibres surrounded by unlabelled dendrites in contact with immunoreactive terminals. At the subcellular level in both brain regions, the areas occupied by the Golgi apparatus were never labelled, although the nuclei had varied reactions. The strong glutaraldehyde fixation that limits the diffusion of gamma-aminobutyrate limits also antibody diffusion. However, this fixation is compatible with a good morphological preservation and should enable immunocytochemistry studies to be compared to other methods such as autoradiography.

Animals↗