Cerebellar cortex number

In the cerebellar cortex, the most frequently noted pathology is a decreased number of Purkinje cells (Kemper and Bauman, 1998 Palmen et al., 2004 Bauman and Kemper, 2005 Whitney et al., 2008). This pathology is most marked in the posterior lateral part of the cerebellar hemispheres and the adjacent archicerebellar cortex and occurs without evidence of loss of neurons in the inferior olive in the brain stem (Kemper and Bauman, 1998 Bauman and Kemper, 2005). The Purkinje cells have an intimate relationship with the axons of the inferior olivary neurons in the brain stem, such that loss of Purkinje cells at any time after birth leads to loss of neurons in the inferior olive (Holmes and Stewart, 1908 Norman, 1940 Sakai et al., 1994). Since this intimate relationship between the Purkinje cell and the inferior olive is established in the human brain sometime after 29-30 weeks of gestation (Rakic and Sidman, 1970), it is likely that the decrease in number of Purkinje cells occurred before this time. In those brains with a marked decrease in the number of Purkinje cells, there appears to be a concomitant decrease in the number of granule cells (Bauman and Kemper, 2005). The relationship between the number of granule cells and the number of Purkinje cells noted in the autistic brain has been elucidated in rat studies. With prenatal loss of Purkinje cells the number of granule cells is adjusted such that the ratio of Purkinje cells to the number of granule cells is maintained (Chen and Hilman, 1989). 

Cyclic AMP has been implicated in synaptic transmission due to its actions on a number of important synaptic and neuronal events, such as membrane permeability, synaptic membrane phosphorylation, neurotransmitter synthesis, and cell growth and differentiation. As pointed out earlier, neurotransmitter-receptor interactions can result in direct physical perturbations of the membrane with consequent alterations in membrane permeability to specific ions. This effect is particularly the case when the ionophore is located near the receptor. However, if the ionic channel is distant from the receptor, mechanisms such as phosphorylation can result in an alteration of channel permeability. Cyclic AMP is known to lead to a hyperpolarization of neurons in a number of brain regions such as the cerebral cortex, the caudate nucleus, the peripheral paravertebral sympathetic ganglia, the cerebellar cortex, and the hippocampus. Although it has been hypothesized that this hyperpolarization is the consequence of the phosphorylation of specific neuronal membrane proteins, the relatively short duration of hyperpolarization... 

When the ataxic Sakaguchi knockout mice were crossed with transgenic mice haboring a wild-type mouse PrP-A transgene designated Tg(MoPrP-A)4053/FVB, none of the positive Tg P)Prnp° ° presented with ataxia at more than 90 weeks of age (Nishida et al, 1999). The number and topography of Purkinje cells were preserved in all areas of the cerebellar cortex in the Tg(P)mice. The authors concluded that the successful rescue of the ataxic phenotype in the Ngsk Prnp° °... 

As with the vascular pathology, the most pronounced neuronal and glial effects of lead poisoning ai e seen in the cerebellum. Cerebellar weight and total cell number ai e reduced" and the size and morphology of Purkinje cell bodies cire abnormal."" " The intemeuron circuitry of the cerebellum is also altered, since the dendritic development of the Purkinje cells, which form the only efferent elements of the cerebellar cortex, is markedly disturbed by lead exposure. Press observed a decrease in the rate of Purkinje cell maturation in lead-poisoned rat pups from about 5 d onwards such that, at 10 d, the leaded cells retained more perisomatic processes than controls and the den-... 

The average increase in rCMR after THC administration was less in marijuana users than in controls, and users had lower cerebellar metabolism than the controls at baseline [8]. Thus the cerebellum shows the greatest metabolic increase in response to acute THC and responds to chronic marijuana exposure with a decrease in baseline CMR. Habitual users but not controls responded to THC administration with increased rCMR in prefrontal cortex, orbitofrontal cortex, and basal ganglia. In contrast to the robust effects of THC on relative rCMR, changes in global CMR in response to THC were quite variable, with increases, decreases, and no changes seen in equal numbers of subjects. There was also variability in subjective effects, which were pleasurable for most subjects but either minimal or unpleasant (anxiety or paranoia) for others. 

Is the number of modules constant among the mammalian species and are they correlated with the different forms of chemoarchitectonic zonation in the cortex and the white matter These questions only can be answered after a more thorough review of the corticonuclear projection (Sections 6.1.1., 6.1.2., 6.1.4. and 6.1.5.), the chemoarchitectonic evidence on zonation (Section 6.1.3.) and the olivocerebellar and nucleo-cerebellar projections (Section 6.3.) in different mammalian species. The existence of such a basic plan has been questioned (Boegman et al., 1988), not so much because the different maps for parasagittal zonation are mutually exclusive, but mainly because most... 

The first general biochemical study of the effects of lead on cerebral cortex and cerebellum, using 4% lead carbonate in the maternal diet from birth, was made by Michaelson (1973). He found a transient postnatal growth retardation and reduction of cerebral and cerebellar wet weights. The cerebellum showed increased water and reduced DNA content, suggesting a 15-20% deficit in cell numbers. DNA in the cerebrum and RNA and protein in both areas differed only marginally from controls, although all were consistently... 

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