Diagnosis is difficult and typically done by ruling out Parkinsons Disease (PD) or Spinocerebellar ataxia (SCA). Symptoms include autonomic dysfunctions (supine hypertension and orthostatic hypotension, urinary incontinence). The disease leads to selective neuronal loss, myelin pallor, possible microglial activation and usually involves caudate, putamen, substantia nigra and cerebellum. Neuroimaging does show marked features in the putamen and 'hot cross bun' sign in the pons but these are not specific only to MSA. There are two broad groups MSA-P with more PD like features of bradykinesia and resting tremor and MSA-C with more limb/gait ataxia features. Treatment is symptomatic and definitive diagnosis is possible only post mortem (seen by high density oligodendroglial cytoplasmic inclusions).
In her seminar, Rukmani MR discussed the challenges surrounding Multiple System Atrophy (MSA). This is a relatively rare disorder (1.9 to 4.9 per 100,000), has an adult onset. NIMHANS gets a few cases every month.
Diagnosis is difficult and typically done by ruling out Parkinsons Disease (PD) or Spinocerebellar ataxia (SCA). Symptoms include autonomic dysfunctions (supine hypertension and orthostatic hypotension, urinary incontinence). The disease leads to selective neuronal loss, myelin pallor, possible microglial activation and usually involves caudate, putamen, substantia nigra and cerebellum. Neuroimaging does show marked features in the putamen and 'hot cross bun' sign in the pons but these are not specific only to MSA. There are two broad groups MSA-P with more PD like features of bradykinesia and resting tremor and MSA-C with more limb/gait ataxia features. Treatment is symptomatic and definitive diagnosis is possible only post mortem (seen by high density oligodendroglial cytoplasmic inclusions). Suwarna Chakraborty (1st year PhD Scholar) presented her seminar on "Role of Cerebellum in Cognition".
After providing an anatomical overview, she reviewed the well known motor functions of the different deep nuclei. The dentate nucleus (cerebro-cerebellum), which is the largest and connected to the cerebrum, works as a comparator that generates an error signal and provides planning and timing information.The other nuclei - Fastigious, emboliform and globase (spino-cerebellum) - have output to the spinal tracts and is involved in fine movements. The vestibulo cerebellum is involved in posture maintenance and eye movements. The Mossy fibers (from the vestibular nuclei) and the climbing fibres (from the inferior olive) both provide input the Purkinje fibres. The former provide input on the context and the latter forms the error signal. Interestingly, Long Term Depression (LTD) which forms the memory element of the cerebellar motor learning, happens when both these fibre tracts are simultaneously active. If only one these fibre pathways are active, LTP (Long Term Potentiation) ensues. Therefore the cerebral cortex and the cerebellum have different mechanisms for LTP and LTD. Suwarna then reviewed a number of studies evaluating cognitive functions and cerebellum. These included attention, working memory and spatial memory in various animal models (eg: pcd - purkinje cell degeneration model). Merlin Flaura (1st year MPhil Scholar) presented a paper from the journal Behavioural Brain Research (2012) titled "Histamine Promotes rat motor performances by activation of H2 receptors in the cerebellar fastigial nucleus"
Abstract: The cerebellar fastigial nucleus (FN), together with the interpositus nucleus (IN), constitutes the two final output nuclei of the spinocerebellum and plays an important role in body and limb movements. Previous studies have revealed a direct histaminergic projection from the hypothalamus to the cerebellar nuclei and an excitatory effect of histamine on the IN neurons. However, role of hypothalamic histaminergic projection in the FN has been still little known. Here we show that histamine elicited the FN neurons of rats a concentration-dependent excitatory response in vitro. The histamine-induced excitation on FN neurons was mediated by postsynaptic histamine H2 rather than H1 receptors. In behavioral tests, microinjection of histamine into bilateral FNs remarkably improved motor performances of rats on both accelerating rota-rod and balance beam. Selective H2 receptor antagonist ranitidine considerably declined thosemotor performances and selective H2 receptor agonist dimaprit mimicked the facilitation effect of histamine on themovements. But selective H1 receptor antagonisttriprolidine and agonist 2-pyridylethylamine had no effect. Furthermore, microinjection of histamine into bilateral FNs narrowed stride width of footprint but did notinfluence wire suspension, whereas microinjection of histamine into bilateral INs increased stride length and promoted suspension. These results demonstrate that histamine enhances rat motor balance and coordination through modulation of both proximal and distal muscles by activation of histamine H2 receptors in the cerebellar FN and IN, and suggest that the hypothalamocerebellar histaminergic projections may modulate the final outputs of the spinocerebellum and participate in the cerebellum mediated motor control. The presentation was simple and clear. Some interesting thoughts that arose from the presentation:
Radial glial cells and the lamination of the cerebellar cortex - Journal Club by Suresh Parmar3/3/2012
Suresh Kumar Parmar (1st year MPhil scholar) presented the paper "Radial glial cells and the lamination of the cerebellar cortex" by Y Zhang etal from Brain Struct Funct (2010).
Abstract Radial glial cells are stem cells that play an important role in neuronal migration and proliferation in the developing brain. However, how radial glial cells contribute to the lamination of the cerebellar cortex is not well understood. We therefore used immunohistochemistry and BrdU labeling to follow radial glial cell differentiation, cell migration and cerebellar cortex development in mice from embryonic day 8 to postnatal day 180. We report that radial glial cells represent the stem cell population of the neuroepithelium of the neural tube, and act as progenitors for both neurons and neuroglia. In addition, radial glial cells not only give rise to the principal cells of the cerebellar cortex, the Purkinje and granule cells, but they also provide a scaffold for the migration of these cells. We conclude that radial glial cells play a pivotal role in establishing the laminar structure of the cerebellar cortex. |
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August 2019
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