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At least 19 recordsLinked to original sources
PubMed1979

Ratio of inferior olivary cells to Purkinje cells in a marsupial (Trichosurus vulpecula).

An indirect estimate of the extent of branching of the olivary axons in the cerebellum in a marsupial (Trichosurus vulpecula) was carried out. The cells in the inferior olivary nuclear complex (IOC) of both sides were estimated (mean = 57,200), as were the cerebellar Purkinje cells (mean = 881,300). Assuming that all climbing fibers arise from IOC cells and that each Purkinje cell receives a climbing fiber input, each IOC cell sends climbing fiber terminals to 15 Purkinje cells.

Animals↗
PubMed1977

Fine structure of the cerebellum of "staggerer-reeler", a double mutant of mice affected by staggerer and reeler conditions. II. Purkinje cell anomalies.

Purkinje cells in double mutant were very similar to those in staggerer both at days 7 and 15, and could not be distinguished from staggerer Purkinje cells by morphological criteria. They were small and immature looking, and their nuclei were invariably eccentric in position both at days 7 and 15. The typical funnel stage was not observed at any time. Somatic spines and their synapses were extermely rare at day 7 when they are abundant in the normal, but they were present at day 15 with typical synapses with climbing fibers. Dendritic spines were also present at day 15 although extremely infrequent, and they showed synapses both with parallel and climbing fibers. More often, however, parallel and climbing fibers were found in synapsis with the smooth surgace of these dentrites. These observations were in close agreement with those of staggerer Purkinje cells. The persistence of staggerer Purkinje cell soma anomalies in double mutant was interpreted as indicating that these anomalies are specific effects of the staggerer gene, being relatively free from environmental influences.

Animals↗
PubMed1975

Network analysis of dendritic fields of pyramidal cells in neocortex and Purkinje cells in the cerebellum of the rat.

The connectivity within the dendritic array of Purkinje cells in the cerebellum and pyramidal cells of the neocortex of the rat, stained by the Golgi-Cox method, has been quantified by the method of network analysis. Connectivity was characterized either by applying the system of Strahler ordering, which assigns a relative order of magnitude to each branch of the arborescence or by the identification of unique topological branching patterns within the tree. The former method has been used to define the entire dendritic array of the Purkinje cell and the apical system of neocortical pyramids. It has been shown that the relation between the numbers of branches of successive Strahler order in Purkinje cells form an inverse geometric series in which the highest order is unity and the ratio between successive orders approximates to 3. On the other hand, the apical dendrites of neocortical pyramids exhibit two bifurcation ratios, i.e. a ratio of 3 between low orders and a ratio of 4 between higher orders. A computer simulation technique was used to generate networks of a size comparable with the Purkinje cell networks and grown according to two hypotheses namely, a 'terminal growth model' in which additional segments were added randomly to the terminal branches only and a 'segmental growth model' in which additional segments were added randomly to any branch within the array including terminal branches. Subsequent ordering of the simulated trees revealed that the relation between the numbers of successive orders for networks generated according to the 'segmental model' tended towards an inverse geometric series with a ratio of 4 and that generated according to the 'terminal model' tended towards a ratio of 3. This result showed that the dendritic tree of Purkinje cells grow in a manner indistinguishable from a system adding branches to random terminal segments and that neocortical apical dendrites add their collateral branches to random segments of the apical shaft but that the collateral branches themselves grow by random terminal branching. The possibility that such conclusions may be influenced by loss of branches incurred by either a failure of impregnation, by sectioning, or by environmental influences was investigated by means of a computer technique...

Animals↗
PubMed1977

Methylazoxymethanol-induced aberrant Purkinje cell dendritic development.

Purkinje cell dendrites develop with a specific orientation and relationship to related neurons and glia. Their dendritic spine postsynaptic membrane specialization may, in turn, require a permanent presynaptic contact by parallel fibers. To determine whether changes in the surrounding cells influence the normal development of the cerebellar Purkinje cell dendrites and spine specializations, destruction on the differentiating cell layer was induced in the postnatal mouse by administration of methylazoxymethanol acetate (MAM) (0.05 micronl/gm body weight) at day zero. The Purkinje cells were examined by light and electron microscopy on the tenth postnatal day. The midsagittal surface area of the cerebellar vermis in treated animals was reduced by an average of 60%. MAM-induced granule cell depletion and Purkinje cell dislocation were observed by light microscopy. When compared to controls, examination following Golgi impregnation revealed random orientation of Purkinje cell apical poles, and multiple primary dendrites of reduced length with few branches, branchlets and spines. Vertical processes of Golgi epithelial (Bergmann) cells were obliquely directed, reduced in length and complexity in MAM-treated mice. Ultrastructural examination revealed naked Purkinje cell dendritic spine specializations in both groups. Although necrotic debris persisted in astrocytes and macrophages, degenerating presynaptic terminals were not found. This study suggests that permanent presynaptic contact by parallel fibers is not essential for spine development. Astrocytic reactions to injury, in association with the reduced folial expansion, may have contributed to the observed abnormalities and disorientation of the Purkinje cells. The data suggests that Purkinje cell dendritic development may be strongly influenced by changes in surrounding cells.

Animals↗
PubMed1979

Chronic treatment with lithium or desipramine alters discharge frequency and norepinephrine responsiveness of cerebellar Purkinje cells.

Cerebellar Purkinje cells were studied by electrophysiological techniques in rats treated chronically with either desipramine (DMI) or lithium chloride given intragastrically. A striking decrement occurred in discharge frequencies of simple spikes and climbing fiber bursts in both groups of animals, similar to the depression produced by iontophoresis of these agents. Chronic treatment with DMI markedly decreased responsiveness to iontophoretically applied norepinephrine (NE), whereas long-term LiCl therapy slightly enhanced response to NE; responses to gamma-aminobutyric acid were unchanged by these treatments. The inhibitory responses to locus ceruleus stimulation were unaffected by chronic LiCl treatment. The effects of these chronic treatments on responsiveness to NE are opposite to the effects these same drugs produce when administered by acute iontophoresis to single cells: DMI then potentiates and LiCl antagonizes noradrenergic responses. These results provide electrophysiological evidence for reciprocal adaptive changes in NE sensitivity, supporting results of biochemical studies.

Animals↗
PubMed1978

The effects of undernutrition on Purkinje cell dendritic growth in the rat.

The effects of undernutrition on the developing cerebellum were studied in 30-day-old rats undernourished from birth by restricting access to the lactating mother. These animals showed a significant reduction in cerebellar weight when compared with well-nourished controls. Quantitative studies of the cerebellar vermis revealed a 34.2% reduction in total area, with the density of both granule cells and Purkinje cells increased. Network analysis of Golgi-Cox preparations indicated a significant increase in the density of dendritic fields of Purkinje cells, although there was a 37% decrease in overall network size, due to reduction in the total number of dendritic segments, and a reduction in the length of distal segments. Topological analysis indicated that the network had developed by terminal branching, as in normal animals, but with some deviation from the usual purely random branching pattern. All the observed modifications may be accounted for in terms of alterations in protein synthesis and DNA synthesis occurring in undernourished animals. This leads to alterations in the extent of the interneuronal matrix, a reduction in the number of granule cells and direct effects on Purkinje cell metabolism, all of which influence dendritic development, although the relative importance of each of these factors awaits precise definition.

Animals↗
PubMed1978

The DNA content of Purkinje cells in mammals.

Nerve cells have generally been assumed to have a diploid DNA content, typical of non-dividing somatic cells. However several reports have suggested that certain nerve cells types, notably Purkinje cells of the cerebellum, are polyploid. Other studies have contradicted these findings, stating Purkinje cells to be diploid. In this paper we reinvestigate the DNA status of Purkinje cells, in a variety of mammalian species. Cell DNA content is measured on tissue smears by Feulgen microspectrophotometry. Results show that for all species examined by us, Purkinje cells have, without exception, a DNA content comparable to that of somatic cells. A critical appraisal of the techniques used in those studies claiming a tetraploid DNA content for Purkinje cells leads us to believe our findings to be correct.

Animals↗
PubMed1978

The development and degeneration of Purkinje cells in pcd mutant mice.

Purkinje cell degeneration (pcd), an autosomal recessive mutation in the mouse, causes the postnatal death of virtually all cerebellar Purkinje cells during the third and fourth postnatal week. We have compared the postnatal development of normal and pcd mutant Purkinje cells. The early deviations from normal development involve primarily the perikaryonal polysomes and endoplasmic reticulum. Many of the mutant Purkinje cells retain abnormally the basal accumulation of polysomes, a finding which permits the identification of affected animals at postnatal day 15, one week prior to the onset of behavioral abnormalities. In addition, the affected Purkinje cells possess unusual configurations of endoplasmic reticulum with associated electron-dense particles similar to but larger than ribosomes, mature and forming intracisternal A particles and nematosomes. Before the pcd Purkinje cells degenerate they appear to receive all their appropriate synaptic contacts. Some disruption, however, of parallel fiber: Purkinje spine synaptogenesis occurs at late stages of development. Some spines lack presynaptic elements, postsynaptic thickenings are present along the dendritic shafts and parallel fibers appear to make synaptic contacts directly onto the shafts. The spectrum of early morphological changes that has been observed in pcd mutant Purkinje cells is thus far unique to this cerebellar abnormality.

Animals↗
PubMed1978

A mechanism for type III vestibular responses of frog cerebellar Purkinje cells.

Type III Purkinje cells (P-cells), which are excited with both directions of horizontal rotation, are found in high numbers in the frog auricular lobe and adjacent cerebellar areas. To examine the mechanisms underlying these responses, recordings were made from P-cells in curarized animals during rotational stimulation of the horizontal canals. The horizontal canal input to these cells was then modified unilaterally by VIIth nerve section, intraperilymphatic injection of local anesthetic, or by caloric stimulation. Control recordings were also obtained from peripheral canal neurons. Type III responses were abolished by unilateral lesions or reversible blockage of the VIIIth nerve with local anesthetic. The remaining responses were attributable only to the unaffected horizontal canal, ie. only type II or type I responses were observed upon interruption of the ipsi-or contralateral nerve, respectively. The level of spontaneous activity of cerebellar input fibers was low and during rotation produced 'cell silencing' response waveform asymmetries (facilitation greater than disfacilitation). When the level of peripheral resting activity was increased (warm water irrigation), thereby increasing horizontal canal response symmetry, type III responses were reduced in magnitude or abolished. Conversely, cold water irrigation, which decreases the resting rate and response symmetry of input fibers, enhanced type III response magnitudes. On the basis of these results, it is suggested that type III responses result from the fact that single P-cells receive a facilitatory input from both horizontal canals. Since these inputs are 180 degrees phase-reversed and their response waveforms asymmetrical, their resulting postsynaptic effect is a net excitation during both portions of the stimulus cycle.

Action Potentials↗
PubMed1978

A comparison of the inhibitory effects of taurine and GABA on identified Purkinje cells and other neurons in the cerebellar cortex of the rat.

The microiontophoretic application of taurine and GABA was studied in the cerebellar cortex of the rat. Both taurine and GABA produced a dose-dependent depression of spike frequency of cerebellar neurons. GABA (2-42 nA, mean 27 nA) induced an inhibition of spike discharge on all 138 cells tested, including 29 Purkinje cells. Taurine (60-200 nA, mean 108 nA) induced an inhibition of spike discharge on 93 of the 106 cerebellar neurons tested, including inhibition on 22 of 25 Purkinje cells. Iontophoretic application of bicuculline and picrotoxin antagonized the inhibitory effects of both GABA and taurine on Purkinje cells as well as on cerebellar neurons in general. Strychnine did not antagonize the inhibition of either GABA or taurine. Simultaneous application of taurine and GABA produced a synergistic inhibitory effect on the firing rate of Purkinje cells. Taurine, in contrast to GABA, appeared to be more depressant when applied in the Purkinje cell dendritic zone than when applied near the soma. The data are discussed in terms of taurine functioning as a neurotransmitter in the cerebellum of the rat and having receptor sites distinct from those for GABA.

Aminobutyrates↗
PubMed1977

Postnatal development of the cerebellar cortex in the rat. V. Spatial organization of purkinje cell perikarya.

The development of the spatial organization of Purkinje cell perikarya was examined in the rat cerebellum from birth to adulthood. Dispersion of the perikarya following birth is made possible by the rapid expansion of the cortical surface. Their subsequent regular monocellular alignment is ensured by mechanical factors, the pressure exerted from below by the expanding granular layer and the barrier formed above by the pile of parallel fibers which prevent the penetration of the bulky perikarya into the molecular layer. The perikarya remain in this position even after the slender stem dendrite pierces the molecular layer along the descending axons of basket cells. The increase in interperikaryal distance between Purkinje cells is rapid up to day 12, then declines. This is temporally associated with the growth of the basket cell plexus and glial envelope around the perikaryon. The increase in perikaryal size continues up to day 30. This may be temporally associated with the growth of the Purkinje cell dendritic arbor as reflected by the expansion of the molecular layer up to day 30. The spatial arrangement of Purkinje cells within the monocellular sheet was graphically displayed with computer aid. In the adult cerebellum a hexagonal arrangement could be recognized in a proportion of "near-neighborhoods," consisting of about six Purkinje cells and their neighbors. When the neighborhoods were extended with fixed orientation with respect to the axis of the folium, the hexagonal arrangement disappeared. When orientation was ignored, the superimposed near-neighborhoods could be rotated to produce a hexagonal pattern. In the infant cerebellum the hexagonal arrangement could not be demonstrated before the alignment of Purkinje cells in a monolayer. Thereafter there appeared to be an increase with age in the proportion of hexagonally arranged near-neighborhoods. It was concluded that in the monocellular ganglionic layer Purkinje cells are not aligned in regular rows with respect to the geometrically arranged elements of the supraganglionic layer. The formation of an imprecise hexagonal pattern, like the alignment of Purkinje cells in a monolayer, was attributed to mechanical factors.

Age Factors↗
PubMed1979

Constancy and variability in the content of DNA in cerebellar Purkinje cell nuclei. A cytophotometric study.

A cytophotometric study of DNA content in Purkinje cells of the cerebellum of rats, cats, chicken and humans (Feulgen staining) revealed that in a certain number of cells the amount of NDA ranged between the diploid and tetraploid level (H2C cells). The incidence of H2C Purkinje cells varied among the species studied. In rats, which were studied most thoroughly, these cells amounted on average to 3%. In some rats, as well as in some cats and chickens H2C Purkinje cells were entirely absent. In the group of animals possesing H2C Purkinje cells, great interindividual differences were observed. In rats for instance, the incidence of these cells varied from 1 to 23 per cent. Topographic analyses carried out in rat and human cerebellum revealed that H2C Purkinje cells occurred more frequently in the hemispheres than in the vermis. No significant differences were found in the number of H2C Purkinje cells in healthy and Kilham-DNA-virus infected rats. Densitometric analysis of the distribution of nuclear chromatin showed that H2C Purkinje cells were richer in condensed chromatin, especially in the region of the nucleolus, which apparently contains the hyperploid surplus of DNA. It is proposed that the phenomenon of DNA hyperdiploidy arises as a result of either incomplete S-phase in some immature Purkinje cell precursors or the amplification of some DNA sequences particularly those localized in the nucleolar region.

Aged↗
PubMedDate not supplied

A quantitative study of the glia of the Purkinje cell layer of the cerebellum in mammals.

The cerebella of fourteen mammals have been examined and the number of each DNA class of glial cell, within the Purkinje cell layer, counted. Diploid glial cells were present in all species and related in number to the surface area of the Purkinje cell. It is likely that they assist in the maintenance of the physiology of this latter cell type. Tetraploid glial cells, however, occur in significant numbers only in the human and chimpanzee and possibly play a part in the establishment of certain learned patterns of co-ordinated movement peculiar to these species.

Animals↗
PubMed1979

Electron microscopic investigations on the differentiation of Purkinje cells in the ontogenetic development of the chicken heart.

The ultrastructural development of subendocardial Purkinje cells of chicken left ventricle was investigated. In 9-day-old chick embryos the cell diameter and the organization of the cell organelles allow a distinction between Purkinje cells and ordinary myocardial cells In 14-day-old chick embryos, Purkinje cells show large accumulations of myosin filaments with interspersed ribosomes in addition to normomeric myofibrils. In these accumulations actin filaments seem to be absent. The deficiency of actin filaments is supposedly the reason for the random distribution of the myosin filaments. Purkinje cells of early chick embryos show areas with densely packed glycogen granules. In older embryos the glycogen concentration declines and only separate glycogen granules are visible. At hatching time the first subsarcolemmal leptomeric fibrils were observed in Purkinje cells. Leptomeric complexes arising in a close spatial relationship to the accumulations of myosin filaments and ribosomes can be seen in 2--4 week-old chickens. With the increasing age of the chickens, the size of these accumulations declines. Adult hens exhibit smaller accumulations, mainly in the neighborhood of leptomeric complexes. Purkinje cells show a distinct ontogenetic development. They are not simple embryonic remnants of ordinary myocardial cells.

Animals↗
PubMed1979

Distribution of climbing fibres on cerebellar Purkinje cells in X-irradiated rats. An electrophysiological study.

1. The distribution of climbing fibres on cerebellar Purkinje cells has been studied with intracellular recordings in X-irradiated and normal rats. 2. In the treated rats, multiple steps in the post-synaptic potential were elicited in 57% of the Purkinje cells by graded stimulation of the climbing fibres, the response was all-or-none in character in the other cells and in all Purkinje cells recorded in normal animals. In the neurones exhibiting the former type of response, no collision was seen along the afferent fibres during interaction experiments between just-threshold juxtafastigial and maximal olivary stimulations, whereas a collision always occurred when all-or-none responses were recorded. 3. These results show that in X-irradiated rats, the majority of Purkinje cells have a multiple innervation by two to four climbing fibres, instead of the one-to-one relationship seen normally. 4. Input resistances and total electrotonic lengths of Purkinje cells were measured in normal and treated rats. Mean values for these two parameters were higher than normal in multiply innervated cells. 5. Mean time course and mean current for reversal of the post-synaptic potential elicited in Purkinje cells by stimulation of the climbing fibres were nearly the same in mono- and in multiply innervated neurones. In multiply innervated cells, time courses and currents for reversal were independent of the size of the response or varied slightly with it, suggesting that the climbing fibres involved innervated territories whose electrotonic distance from the recording site were either the same or slightly different. 6. Interactions between two all-or-none steps of the graded post-synaptic potential evoked in multiply innervated cells by juxtafastigial and olivary stimulations revealed either a very weak or a very marked shunting effect between synapses of the two climbing fibres involved. 7. These results indicate that the over-all distribution of climbing fibre synapses on multiply innervated Purkinje cells is not grossly abnormal and that two fibres contacting a given cell can be either intermingled on the same dendrites, or segregated on distinct dendritic branches. 8. In general, the present study does not suggest the existence of a strong competition among climbing fibres innervating each Purkinje cell during development at least when granule cells are absent.

Animals↗
PubMed1979

Staggerer chimeras: intrinsic nature of Purkinje cell defects and implications for normal cerebellar development.

The site of gene action of the Staggerer mutation of mice was investigated with Staggerer in equilibrium or formed from wild-type chimeras. Homozygous Staggerer mice show severe locomotor difficulties due to cerebellar abnormalities which include degeneration of virtually all granule cells and cytological defects in Purkinje cells. Although the locomotor deficits of the mutant were not present in the chimeras, the presence of Staggerer cells affected cerebellar structure. The size and the extent of foliation of the chimeric cerebella were intermediate between wile-type and homozygous Staggerer. A normally proportioned granule cell layer was present. Using beta-glucuronidase as an independent determinant of a cell's genotype, it was found that the genotypically Staggerer medium-to-large neurons expressed all of the light microscopic defects observable in these cells in the homozygous mutant. These defects include: (1) smaller size; (2) usually ectopic location; and (3) regional variation in the cytological appearance of the perikaryon. By contrast, all Purkinje cells which were genotypically wild-type appeared normal in size, in location and in their cytological appearance. Their density, however, was much reduced from wild-type. The effects of the Staggerer mutation on the granule, stellate and basket cells could not be directly assessed as the glucuronidase marker is not suitable for use with these cells. The Staggerer gene thus acts directly on Purkinje cells rather than via extracellular environmental changes. The findings are discussed in terms of their implications for normal cerebellar development.

Animals↗