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At least 19 recordsLinked to original sources

PubMed1976

Pentalaminar specialized membrane junctions - tight junctions - are described in the granular layer of the pigeon cerebellum. The presence of these axo-dendritique and dendrosomatic contacts suggest the existence of electrotonic coupling in the pigeon cerebellum.

Pentalaminar specialized membrane junctions - tight junctions - are described in the granular layer of the pigeon cerebellum. The presence of these axo-dendritique and dendrosomatic contacts suggest the existence of electrotonic coupling in the pigeon cerebellum.

Animals↗

PubMed1977

Experimental analysis of embryogenesis of cerebellum in rat. I. Subnormal growth following x-ray irradiation on day 15 of gestation.

Rat embryos of 15 days gestation were exposed in utero to 170 R of X-ray irradiation. Embryos collected 6 hours, 1, 2 and 3 days after irradiation, and animals of 2, 6, 15 and 30 days postnatal age were used for this study. Six hours after irradiation cells in the neuroepithelium and mantle layer along the roof of fourth ventricle were observed destroyed. Neuroepithelium showed only fragmentary regeneration during next two days, and it contributed to a small number of Purkinje cells. During postnatal development of cerebellum the external granular layer, the zone of proliferative cells that gives rise to neurons of postnatal origin, was found reduced. Other structures such as internal granular layer, molecular layer and medullary layer also were reduced. These multiple temporally sequenced developmental events resulted in a subnormal-sized cerebellum. Various quantitative measures helped establish that grossly the cerebellum in the X-ray irradiated animals was about half of that in the normal animals. Problems related to regeneration in the embryonic cerebellum, and to the factors determining the subnormal size of the adult cerebellum are discussed. Viewing this as an experimental approach to the study of neuroembryogenesis of cerebellum, the role of Purkinje cells in the regulation of development of cerebellum is brought out.

Animals↗

PubMed1992

Localization of AMPA receptors in the hippocampus and cerebellum of the rat using an anti-receptor monoclonal antibody.

The primary amino acid sequences of the kainate binding proteins from the amphibian and avian central nervous systems are homologous with the functional alpha-amino-3-hydroxyl-5-methyl-isoxazole-4-propionate receptors that have been cloned from rat brain. In this study, we have analysed the anatomical and subcellular distribution of the alpha-amino-3-hydroxyl-5-methyl-isoxazole-4-propionate receptors in the rat hippocampus and cerebellum, using a monoclonal antibody that was raised against a kainate binding protein purified from frog brain. Immunoblots of rat hippocampus and cerebellum, and membranes from COS cells transfected with rat brain alpha-amino-3-hydroxyl-5-methyl-isoxazole-4-propionate receptor cDNAs (GluR1, GluR2, or GluR3) showed a major immunoreactive band migrating at a relative molecular weight of 107,000. In the cerebellum, an additional immunoreactive protein of approximately 128,000 mol. wt was also seen on immunoblots probed with the antibody. The distribution of this protein is apparently restricted to the cerebellum since the 128,000 mol. wt band was not present in other brain areas examined. The identity of the 128,000 mol. wt cerebellar protein is not known. Immunocytochemical analyses of the hippocampus demonstrated that alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate receptor subunits are present in the cell bodies and dendrites of pyramidal cells. The granule cells were also immunostained. All of the pyramidal cell subfields were heavily labeled. In the pyramidal cell bodies, a high level of immunoreactivity was observed throughout the cytoplasm. In the cerebellum, the Purkinje cell bodies and dendrites also displayed very high levels of immunoreactivity. In addition to the Purkinje neurons, the Bergmann glia and some Golgi neurons were clearly immunostained. Subcellular fractionation and lesioning experiments using the excitotoxin domoic acid indicated that the alpha-amino-3-hydroxyl-5-methyl-isoxazole-4-propionate receptor subunits were associated with postsynaptic membranes. Direct visualization of the immunoreactivity using electron microscopy confirmed the postsynaptic localization of the staining in the dendritic areas in both the hippocampus and the cerebellum. Thus, unlike the kainate binding proteins, which are found primarily extrasynaptically in the frog and on glial cells in the chicken cerebellum, the GluR1, GluR2, and GluR3 receptor subunits are localized to the postsynaptic membrane in the dendrites of neurons in the rat central nervous system.

Amygdala↗

PubMed1976

[The so-called pressure zone of the cerebellum].

Systematic studies on the so-called cone of basal parts of the cerebellum employing a scale of either qualitative and quantitative intensity revealed the following: A cone extension of basal cerebellum parts is to be observed in 80.9% of random post-morten examination cases with insignificant differences in sex. Cerebellum cone frequency amounts to 12.8% in babies, up to 66.7% in infants from 1 to 14 years of age, and to 91.8% in persons above 15 years of age. Cones are not found in foetusses. Cones are almost exclusively formed with the participation of those cerebellum parts adjacent to the tonsils, so that the termin "tonsil cone" is incorrect. Cerebellum cones can be distinguished by various degrees in size. The 1st degree corresponds to a cone height of 5 mm, 2nd degree between 5 and 10 mm, and 3rd degree to 10 mm and above. Statistical analysis shows that the cone height follows normal distribution, the mean value of height being 4.8 mm. No correlation has been found between the cone height and clinically detected state of cerebral pressure as well as between space requiring processes during the post-mortem examination. Hence the term "pressure cone" is wrong. There is a positive correlation between cone formation and other so-called morphological symptoms of cerebral pressure. But it is doubtful, whether these symptoms may be regarded as a result of pressure on the brain. The occurrence of a cerebellum basal sphere cone is considered a normal filling up process of any internal space in the skull during brain acceleration. It is only in exceptional cases of cone sizes 10 mm and more, that cone formation is significant for the diagnosis of a possible increase in cerebral volume. Considering the obviously minimal significance of basal cerebellum cone in diagnosing an increase in cerebral volume, the following is a suggestion to prove a condition of cerebral pressure by means of complementary space determination of the skull.

Adolescent↗

PubMed1992

Molecular cloning and characterization of the major endothelin receptor subtype in porcine cerebellum.

Endothelin receptors (ETRs) display subtype heterogeneity and are widely distributed throughout the tissues of the periphery and central nervous system. In order to gain further insight into the potential molecular differences of ETRs, we initiated molecular cloning of ETR genes by screening for the appearance of 125I-ET-1 binding activity in COS cells transfected with pools of a porcine cerebellum cDNA expression library. Two independent clones (pPCETR 1.1 and pPCETR 5.6) were identified and isolated by repeated rounds of pool enrichment and COS cell expression. DNA sequence analysis of pPCET 1.1 and pPCET 5.6 indicated that both clones have the same nucleotide sequence; the deduced amino acid sequence indicated that the porcine cerebellum ETR is 443 residues in length and consists of seven potential transmembrane domains, with homology to members of the GTP-binding protein-coupled receptor superfamily. Northern analysis indicated a single mRNA species of about 5 kilobases, which is expressed significantly in cerebellum, lung, kidney, and pituitary. Expression of functional receptor was demonstrated by endothelin-1 (ET-1)-mediated Ca2+ mobilization in COS cells transfected with pPCETR 1.1 (COS/ETR 1.1) and ET-1-mediated electrophysiological responses in Xenopus oocytes injected with RNA derived from pPCETR 1.1. Quantitative comparison of saturation binding of 125I-ET-1 to either porcine cerebellum or COS/ETR 1.1 membranes indicated an identical apparent dissociation constant. The relative efficacy of ET-related peptides to compete for binding of 125I-ET-1 to receptor from porcine cerebellum and COS/ETR 1.1 indicated that both preparations encode a nonselective or ETBR subtype. Chemical cross-linking of 125I-ET-1 to receptor derived from cerebellum or COS/ETR 1 revealed two bands, with apparent molecular masses of 47 and 35 kDa. These data demonstrate that the pPCETR 1.1 encodes the major ETR subtype in the porcine cerebellum.

Amino Acid Sequence↗

PubMed1979

The resolution of dopamine and beta 1- and beta 2-adrenergic-sensitive adenylate cyclase activities in homogenates of cat cerebellum, hippocampus and cerebral cortex.

The stimulation of adenylate cyclase by dopamine and various beta-adrenergic agonists has been investigated in homogenates from 3 areas of cat brain: the cerebral cortex, cerebellum and hippocampus. The purpose of the study was to determine whether the beta-arenergic receptors coupled to adenylate cyclase could be classified as either beta 1 and beta 2 subtypes in the different regions studied. The stimulation of adenylate cyclase by the beta-adrenergic agonist, (-)isoproterenol (5 X 10(-6) M), was completely blocked by the specific beta-adrenergic antagonist, (p)alprenolol (1-(-5) M), but not by the dopaminergic antagonist, fluphenazine (10(-5) M), whereas the stimulation of adenylate cyclase by (-)epinephrine (10(-4) M) was blocked to varying extents by these two drugs in each of the 3 regions studied. The (-)epinephrine effect was always blocked in the combined presence of (p)alprenolol and fluphenazine. The adenylate cyclase stimulation by (p)epinephrine which is not blocked by (p)alprenolol was due to interaction of (p)epinephrine with a dopaminergic-sensitive adenylate cyclase which has been characterized in cerebral cortex, hippocampus and cerebellum. Regional differences in the affinity of beta-adrenergic-sensitive adenylate cyclase for various agonists were investigated in the presence of fluphenazine (10(-5) M). In the cerebellum the potency order was (+/-)protokylol greater than (+/-)hydroxybenzylisoproterenol greater than (+/-)isoproterenol greater than (-)epinephrine greater than (+/-)salbutamol greater than (-)norepinephrine, indicating the presence of a beta 2-adrenergic receptor. In the cerebral cortex the potency order was (-)isoproterenol greater than +/-)protokylol greater than (+/-)hydroxybenzylisoproterenol greater than (-)epinephrine = (-)norepinephrine ((+/-)salbutamol being inactive). A similar pattern was found in the hippocampus indicating the presence of a beta 1-adrenergic receptor in these two regions. (+/-)Salbutamol was a partial agonist in the cerebellum and a competitive antagonist in the cerebral cortex. The ratio of the antagonist potencies of (+/-)practolol and (+/-)butoxamine preferential beta 1- and beta 2-adrenergic antagonists respectively, to block the stimulation of adenylate cyclase was 25 in the cerebellum, compared to 0.5 in the cerebral cortex and 1.6 in the hippocampus. These results confirm the presence of a beta 2 subtype of receptor coupled to adenylate cyclase in the former and beta 1 subtypes in the latter two regions. The comparison between the affinities of a series of beta-adrenergic agonists and antagonists for the beta-adrenergic receptors coupled with an adenylate cyclase in cerebral cortex and cerebellum with their affinities for well characterized beta 2-adrenergic receptors in lung and beta 1-adrenergic receptor in heart substantiated this conclusion.

Adenylyl Cyclases↗

PubMed1978

Alteration of the activity and molecular from of thymidine kinase during development and aging in the mouse cerebellum.

Protein, DNA and thymidine kinase levels were assayed during development and aging in the mouse cerebellum. A roughly parallel increase in protein and DNA content occurred from birth, reaching a plateau at 18 days; these adult levels increased by 30% in the 23 month-old cerebellum. Thymidine kinase activity reached a maximum at 6 postnatal days, then decreased steadily to reach, at 18 days, the low level that was maintained in the adult. The thymidine kinase synthesized in the aged cerebellum differed from that in the neonate by having (i) an increased specific activity, (ii) a faster migrating species upon electrophoresis, (iii) an inhibition by dCTP, and (iv) a lower affinity for the substrate thymidine (higher Km). Mathematical calculations indicated the appearance of a larger number of smaller sized cells in the aged cerebellum, when compared with the young adult. Histological analysis established that the newly synthesized cells were localized in the molecular layer of the old cerebellum. It appears that senescence in the mouse cerebellum may be associated with an increased synthesis of glial cells.

Aging↗

PubMedDate not supplied

Studies on the mechanism of sprouting of noradrenergic terminals in rat and mouse cerebellum after neonatal 6-hydroxydopa.

The effect of various pharmacologic agents on the noradrenergic innervation of rat cerebellum was observed. It was found that the neurotoxin 6-hydroxydopa (6-OHDOPA), when given to rats at birth, caused a 46% reduction at 5 weeks of age in tyrosine hydroxylase activity in the locus coeruleus, the nucleus of origin for noradrenergic fibers innervating the cerebellum. At the same time, however, both tyrosine hydroxylase activity and NE content were elevated by 50% in the cerebellum. By treating gravid mice with the 6-OHDOPA, which crosses the placental barrier to affect the brains of developing pups, a dissociation has been shown between the elevated cerebellar NE levels and reduced telencephalic NE content. None of the other assorted pharmacological agents--namely amphetamine, metaraminol, apomorphine, alpha-methyl-p-tyrosine. L-dihydroxyphenylalanine and tyramine--when given at birth, caused a permanent elevation in cerebellar NE content. This series of studies suggests that a reduced number of noradrenergic perikarya are providing a greater innervation of the cerebellum than in control rats. Also, alteration of the telencephalic noradrenergic fibers, which are also derived from the locus coeruleus, does not appear to be a necessary event for the initiation of sprouting of noradrenergic fibers in the cerebellum. Because none of the acute-acting pharmacological agents caused a permanent elevation of NE in the cerebellum, it appears that damage, and not mere stimulation or blockade, is a necessary event for initiation of sprouting.

Animals↗

PubMed1975

[Comparative morphology of the cerebellum of the seal (Pinnipedia, Mammalia)].

The work describes the anatomical structure of the cerebellum of the caspian seal (Pusa caspica Gmelin) and Greenland seal (Pagophoca groenlandica Erxleben). The shape of the cerebellum, the disposition of the main lobes and convolutions are characterized. The schemes of three projections of the cerebellum of both species are presented. The figures of the cerebellum size, its absolute and relative weight and the surface of the cerebellum and its portions in seals have been obtained. The well-developmed flocculo-nodular portions and paraflocculuses and relatively poorly developed lobulus paramedianus are pointed to be one of the characteristic features of the structure of the seal cerebellum. An attempt is made to explain great dimensions of the flocculo-nodullar portion and paraflocculuses by specific features of the seal locomotion in water.

Animals↗

PubMedDate not supplied

[Dynamics of changes in the level of GABA in various sections of the cerebral cortex and cerebellum of dogs during postnatal ontogenesis].

The content of gamma-aminobutyric acid (GABA) in different sections of dog cerebral cortex and cerebellum suffers considerable changes in the postnatal ontogenesis. In the optic area (field 17) of the cerebral cortex GABA content significantly increases from the birthday till six-month age and then it decreases and remains in puberal animals (the 365th day) at the level of three-month ones. In the parietal and motor sections of the cortex and cerebellum the content of GABA increases intensively during the first fortnight of the postnatal development, decreases sharply during the third week of the development, remains at the reached level till the 90th day and then it increases till the six-month age, reaching maximum levels which are 1.6, 1.8 and 2.3 times as high as the GABA content in these areas, respectively. In puberal (the 365th day) animals GABA content in these sections of the cortex and cerebellum considerably decreases in comparison with 6-month animals. In the parietal and motor sections of the cortex it reaches approximately the level of that in newborn ones and in the optic area of the cortex and cerebellum it is 1.7 and 1.8 respectively, as high as this level. In all the studied sections of the brain cortex and in the cerebellum the content of GABA changes most intensively (2.7 muM per 100 g of fresh tissue a day) during the first three weeks of postnatal development. Some of the investigated sections of the brain cortex and cerebellum differ in GABA content mainly at the early stages of the postnatal ontogenesis (till the 21st day after birth).

Age Factors↗

PubMed1978

On the development of the cerebellum of the trout, Salmo gairdneri. I. Patterns of cell migration.

Patterns of cell migration in the cerebellum of Salmo gairneri RICHARDSON, 1836 were studied in fish ranging in length from 4.5 to 230 mm. Sagittal and transverse series were stained with haematoxylin-eosin or according to Nissl or Golgi. The cerebellum of the trout comprises three main parts, i.e. the massive corpus cerebelli, the folded valvula cerebelli and the transversely oriented lobus vestibulolateralis. The early cerebellar anlage is a simple plate, which is delimited from the tectum mesencephali by the fissura rhombo-mesencephalica. The histogenesis may be divided into three phases. During the first phase the matrix layer produces the mantle layer. During the second phase the three typical cerebellar layers are formed. The third phase is characterized by growth. As regards the first phase, the mantle layer develops throughout almost the entire extent of the cerebellar anlage. Only in a narrow paramedian strip (matrix zone M) this layer does fail to appear. In regions where the mantle layer is formed, the matrix no longer occupies the whole width of the wall and is termed the ventricular matrix. The largest part of the ventricular matrix is gradually exhausted. However, in some places this matrix persists as a layer of proliferating cells. This holds for the matrices of the caudal border of the cerebellum; matrix zone L, surrounding the lateral recesses of the fourth ventricle, and matrix zone P, connecting the matrix zones L. The mantle layer produced in the first phase of histogensis mainly develops into the ganglionic layer. The second phase of histogenesis is characterized by the formation of a secondary matrix. Newly produced cells of the matrix zones M, L and P migrate away from their sites of origin towards the regions where a mantle layer prevsiously has been formed. The majority of these cells develops into granule cells. Migration of the cells produced in the first phase of histogenesis occurs in the radial direction. Because of the curvature of the cerebellum this direction changes with respect to the main longitudinal axis of the brain from region to region. The migration paths of granule cells show variable directions, namely (a) tangential followed by radial, for granule cells in the corpus cerebelli and in the medial parts of the valvula cerebelli and the lobus vestibulolaterialis, (b) tangential, for granule cells in the lateral parts of the valvula and (c) radial, for granule cells in the lateral parts of the lobus vestibulolateralis. The analysis of these migration patterns elucidates both the histogenesis and the morphogenesis of the cerebellum of the trout.

Animals↗

PubMed1977

Impairment of DNA synthesis in Gunn rat cerebellum.

Brain DNA synthesis was developmentally investigated in Gunn rat with marked cerebellar hypoplasia due to hereditary hyperbilirubinemia. In this mutant rat, the Purkinje cell was nearly selectively affected in the cerebellar cortex by bilirubin. The impaired DNA synthesis was observed in homozygous (jj) Gunn rat cerebellum, in which the DNA content and [3H]thymidine incorporation rate into DNA decreased after 10 days of age compared to those in the heterozygous (Jj)littermate. In contrast, these impairments were not found in the non-cerebellar parts of the brain and liver of jj Gunn rat. The activity of cerebellar thymidine kinase in jj Gunn rat decreased from a very early stae, being 80% of Jj rat at 6 days, and 50% at 10 days of age. The enzyme activity was not affected in the non-cerebellar parts of the brain. Although bilirubin competitively inhibited cerebellar thymidine kinase activity in vitro (15% at 10(-5) M), such bilirubin level was found to be about 1000-fold that in vivo. Moreover, photo-degradation of bilirubin in jj cerebellum exhibited no improvement in thymidine kinase activity, and the presence of an enzyme inactivator was not suggested in jj cerebellum. These results seem to indicate that the induction of thymidine kinase might be affected in jj Gunn rat cerebellum. The possibility that the impaired DNA synthesis in the external granular cells in jj cerebellum may be due to Purkinje cell damage is discussed.

Animals↗

PubMed1978

A chemical study on the development of the human forebrain and cerebellum during the brain 'growth spurt' period. I. Gangliosides and plasmalogens.

Following upon previous studies on the lipid composition of the developing human brain, a further study is presented with the main object of tracing the chemical changes underlying the period of brain 'growth spurt'. Gangliosides and plasmalogens were selected as approximate markers of synaptogenesis and myelination, respectively, and these lipids were compared in cerebrum and cerebellum to establish the time, if any, at which their rate of accretion increases in a significant way. In the forebrain the rate of increase in concentration of these lipids accelerated at about the 32nd week of gestational age. Although there were too few postnatal cases to draw very firm conclusions, it seemed that the ganglioside concentration levelled off at about two months postnatal age and that the plasmalogen concentration reached a plateau between the 4th and the 6th postnatal months. In the cerebellum the concentration of gangliosides was clearly lower than that in the forebrain until about one year of age, the maximum rate of increase occurring between the last weeks of gestation and the second postnatal month. The plasmalogen concentration was somewhat higher in the cerebellum than in the forebrain but the concentration profile was similar to that followed by the gangliosides. In clear contrast with the concentration profiles in the cerebrum, in the cerebellum both lipids apparently continued to increase up to the second postnatal year. A mainly perinatal period of vulnerability is suggested for the forebrain, and a more prolonged one (probably until the second year of life) for the cerebellum.

Cerebellum↗

PubMed1978

A chemical study on the development of the human forebrain and cerebellum during the brain 'growth spurt' period. II. Phosphoglyceride fatty acids.

The changes of the fatty acid composition of ethanolamine phosphoglycerides (EPG) and choline phosphoglycerides (CPG) that are associated with the maturation of the human forebrain and cerebellum have been studied. The increase in the n-3 fatty acids and the 22:4(n-6)/22:5(n-6) index in the forebrain during the second half of gestation was confirmed in the present series. In the cerebellum, on the other hand, these two parameters were higher than in the cerebrum and did not show any significant change throughout the period studied. The percentage of 18:1(n-9) changed in an opposite sense in the cerebrum and in the cerebellum, i.e. it decreased with gestational age in the cerebrum, whereas it increased markedly in the cerebellum. Consequently, the 18:0/18:1(n-9) index, which increased with maturation in the cerebrum, decreased in the cerebellum.

Cerebellum↗

PubMed1992

P400 protein is one of the major substrates for Ca2+/calmodulin-dependent protein kinase II in the postsynaptic density-enriched fraction isolated from rat cerebral cortex, hippocampus and cerebellum.

Concanavalin A-binding glycoprotein with 250 K M(r) found in the postsynaptic density (PSD)-enriched preparation (or synaptic cytoskeleton) from rat cerebellum was identified with P400 protein from the physicochemical properties and enrichment in the cerebellum. Proteins homologous to the cerebellar 250 K M(r) protein occurred in the PSD-enriched preparations from rat cerebral cortex and from hippocampus, although the contents in the preparations were very low. The 250 K M(r) proteins in the PSD-enriched preparations from cerebellum and from cerebrum were highly phosphorylated by Ca2+/calmodulin (CaM)-dependent protein kinase II. The protein of synaptic plasma membrane (SPM) and PSD-enriched fractions prepared from cerebral cortex were not phosphorylated by the cAMP-dependent protein kinase endogenous to the fractions, whereas the protein from cerebellum was done in SPM and PSD-enriched fractions. The facts suggest that P400 or P400-like protein is closely associated with Ca2+/CaM-dependent protein kinase II in the PSD-enriched preparations, especially in the preparation from cerebral cortex. Phosphorylation of the protein by Ca2+/CaM-dependent protein kinase II may play an important role in the postsynaptic function in both cerebellum and at least in some areas of cerebrum.

Animals↗

PubMed1976

Thyroid hormone and cell formation in the developing rat cerebellum.

Effects of neonatal hyperthyroidism on cell formation in the developing rat cerebellum were reinvestigated. Administration at birth of excessive doses of thyroxine or triiodothyronine led to an early stimulation of cell acquisition, followed by a permanent deficit of cells in the cerebellum. The corrective effects of physiological doses of thyroxine on the troubles of the histological and biochemical development of the cerebellum in thyroid-deficient animals were also studied. As early as 6 days, cell maturation and formation were already retarded in animals treated with propylthiouracil, but, as previously reported, cell formation was prolonged and the final number of cells was normal. Administration to thyroid-deficient animals of progressively increasing doses of thyroxine, nearly equal to the amounts of hormone secreted by the thyroid gland of the developing normal rat, returned the evolution of the cerebellar wet weight and of the cerebellar DNA to normal, as well as the histological maturation of the cerebellum, even if it did not entirely correct the retardation of body growth. These results are consistent with the view that thyroid hormone early stimulates maturation of the cerebellar germinative cells and subsequently interacts with cell formation in the cerebellum, and that this action is physiological.

Animals↗

PubMed1979

Reciprocal transplantations between the optic tectum and the cerebellum in adult goldfish.

1. The topographic pattern of re-established visual projections after a reciprocal transplantation between tectal and cerebellar tissues was studied in adult goldfish. 2. A rectangular tissue was dissected from the left tectum, and a similar piece from the cerebellum in the same fish. The cerebellar piece was rotated by either 180 or 0 degrees around the dorsoventral axis, and transplanted into the tectum in place of the tectal piece. This tectal tissue was likewise grafted into the cerebellum after either 180 or 0 degrees rotation in the same fish. 3. The tectal graft disappeared from the cerebellum within 2 months after surgery. The operated cerebellum showed a remarkable capability for healing its excised part. No visual responses were recorded from the cerebellum. 4. The cerebellar grafts remained in place within the operated tectum in twenty fish. In fifteen of these fish, tested 3 or 4 months after surgery, the cerebellar grafts did not give any visual responses, unlike the surrounding responsive area of the tectum. These fish showed a partial scotoma in the central area of the visual field, which corresponded to the unresponsive transplanted area of the tectum. Autoradiographic examination after intraocular injection of L-[3H]proline showed that these cerebellar grafts did not contain any noticeable label, in contrast to the extensively labelled surrounding tectal tissues. 5. Sporadic visual responses were recorded from deep layers in the transplanted area of the tectum in five of the twenty fish at early post-operative periods. The receptive fields of these responses were distributed in a correct retinotopic order, regardless of whether the cerebellar tissue had been rotated by either 180 or 0 degrees. Autoradiographic examination, however, revealed that these cerebellar grafts were not invaded by regenerating optic fibres. Instead, they bypassed the interposed cerebellar tissue by making detours beneath the graft on the way towards their appropriate target zones within the tectal tissue. 6. This selective avoidance of a foreign (cerebellar) tissue and the orderly reinnervation of the proper tectal tissue by regenerating optic fibres provide us with further evidence for neuronal specificity.

Animals↗

PubMed1977

Experimental analysis of embryogenesis of cerebellum in rat. II. Morphogenetic malformations following x-ray irradiation on day 18 of gestation.

Rat embryos of 18 days gestation were exposed in utero to 170 R of X-ray irradiation. Embryos were collected six hours, 1, 2, and 3 days after irradiation, and animals of 2-, 6-, 15- and 30-day-old postnatal age were sacrificed. Six hours after irradiation pyknosis of cells was notices in the external granular layer along the posterior aspect of the cerebellum. Neuroblasts, destined to differentiate into Purkinje cells, were found arrested in their migratory path. During subsequent periods of embryogenesis the external granular layer was found recovered, and clustering of the neuroblasts were disorganized and fragmented. This abnormal clustering of neuroblasts was permanent, and the external granular layer followed the same abnormal pattern in its growth. During postnatal development the internal granular layer also was found to follow the abnormal pattern of Purkinje cell layer. These abnormal developmental events were seen to lead to malformed folia in the anterior regions of the cerebellum. In addition to it the cerebellum of X-ray irradiated animals appeared smaller than the normal. Issues having a bearing on the differential radiosensitivity of different cells, factors determining the small size of the cerebellum, and cellular events determining the morphogenetic malformations are discussed.

Animals↗