Analytical and numerical investigation of escape rate for a noise driven bath.

We consider a system-reservoir model where the reservoir is modulated by an external noise. Both the internal noise of the reservoir and the external noise are stationary, Gaussian, and are characterized by arbitrary decaying correlation functions. Based on a relation between the dissipation of the system and the response function of the reservoir driven by external noise, we numerically examine the model using a full bistable potential to show that one can recover the turn-over features of the usual Kramers' dynamics when the external noise modulates the reservoir rather than the system directly. We derive the generalized Kramers' rate for this nonequilibrium open system. The theoretical results are verified by numerical simulation.

Correlation of clinical profile of myotonic dystrophy with CTG repeats in the myotonin protein kinase gene.

The molecular genetic analyses (PCR and Southern hybridization) of Indian patients with myotonic dystrophy (DM) were carried out to determine the degree of repeat expansion and an attempt was made to correlate the repeat number with disease severity. A scoring system based on the salient clinical features was devised to objectively assess the disease severity. The repeat expansion was seen in 11 of 12 patients examined and showed an inverse correlation with the age of onset confirming the phenomenon of anticipation. This was further established in the two pedigrees studied, clearly demonstrating both clinical and genetic anticipation. The clinical severity score, however, did not correlate well with the repeat number. Nonetheless, such molecular genetic analyses may have immense value as a screening procedure to identify premutations as well as in prenatal diagnoses.

Corticobasal syndrome due to a thalamic tuberculoma and focal cortical atrophy.

Corticobasal syndrome (CBS) is characterised by asymmetric apraxia, cortical sensory loss, extrapyramidal features and cognitive decline. Although CBS is classically described as a taupathy, heterogeneity of its aetiology is increasingly recognised. Clinical presentation of CBS appears to reflect areas of the brain involved and not necessarily the nature of the underlying pathology. We report a patient in whom resolution of a thalamic tuberculoma was associated with progressive atrophy of the parietotemporal cortex, resulting in an unusual presentation of CBS.

MTHFR C677T gene mutation as a risk factor for arterial stroke: a hospital based study.

Elevated homocysteine level is an independent risk factor for ischemic stroke, thrombotic and cardiovascular diseases. The enzyme methylenetetrahydrofolate reductase (MTHFR) plays a crucial role in regulating the levels of homocysteine. A C677T mutation in this gene results in reduced activity. Sixty-nine patients with arterial stroke, six patients with venous stroke (confirmed by computed tomography and/or magnetic resonance imaging) with hyperhomocysteinemia were selected for the study. Forty-nine subjects with no past history of stroke served as controls. MTHFR genotypes were determined by PCR using specific primers, followed by restriction digestion and gel analysis. The prevalence of the mutated homozygous and heterozygous C677T MTHFR genotype in the patients with arterial stroke was 1.4% (one of 69) and 31.88% (21 of 69), respectively. There frequency was 16.6% (one of six) and 33.3% (two of six) in venous stroke. The genotyping results from controls showed that there was only one heterozygote out of the 49 studied (2.08%). There was a significant difference between the control and the patient groups. Odds ratio for the probability of the C677T MTHFR gene mutation in the patients versus control group was 22.29 (95% CI 4.89-98.8). This indicates that C677T MTHFR mutation is strongly associated with arterial stroke especially in young adults. MTHFR allele evaluation will help in preventing/reducing morbidity caused by stroke.

Identification of antibody responses to Mycobacterium tuberculosis antigens in the CSF of tuberculous meningitis patients by Western blotting.

One of the adjunctive modes of diagnosing tuberculous meningitis (TBM) is to detect immune responses in the cerebrospinal fluid (CSF) to the Mycobacterium tuberculosis antigen. Up to 70% of clinical TBM reveal the presence of antimycobacterial antibody by the enzyme-linked immunosorbant assay. Defining the specificity of this immune response by Western blotting on separated M. tuberculosis antigen has been attempted in this study. Only antimycobacterial antibody-positive TBM cases were included in the study. An analysis of 30 such TBM cases showed a major immune reactivity to the 30- to 40-kDa region (93%) while a lower degree of immune reactivity was seen to the 14-kDa region (87%) and to the 18- to 25-kDa region (60%). Grossly the antibody reactivity on Western blot correlated with the ELISA results. Assessment of antimycobacterial antibody in the neurologic control CSF samples of pyogenic meningitis [n = 10], cryptococcal meningitis [6], neurocysticercosis [28], neurosyphilis [8], viral meningoencephalitis [8], carcinomatous meningitis [8], iatrogenic meningitis [6], and nonneurological control CSF samples from patients undergoing spinal anesthesia [20] revealed the presence of antibody in the CSF of 2 of the 10 pyogenic meningitis and 5 of the 28 neurocysticercosis cases. A Western blot analysis of these 7 cases revealed immune reactivity to 30- to 40-kDa regions only in 2 cases (1 of pyogenic and 1 of neurocysticercosis). The remaining 5 CSF samples did not reveal any immune reactivity on Western blotting, although ELISA demonstrated antimycobacterial antibodies. The antibody response to M. tuberculosis lipoarabinomannan and 38-kDa antigen by ELISA revealed 70.58 and 41.17% positivity, respectively. Thus this study has demonstrated that, by Western blotting, the major immune response is to the 30- to 40-kDa region, namely, lipoarabinomannan. Further, this finding will be useful for specific immunodiagnosis of the TBM.

Right parietal infarction with concomitant mutism.

Right brain damage results in a variety of cognitive and behavioural dysfunctions. Mutism however, has been described only with left or bihemispheric lesions involving the parietal lobe. We report an elderly man who had left faciobrachial monoparesis and concomitant mutism. His auditory-verbal comprehension was intact. MRI revealed a right parietal infarct involving the cortical and subcortical regions. Recovery from mutism during the course of treatment was abrupt and complete with no residual dysarthria. A possibility of diaschisis or impaired modulation of left hemispheric function due to right cerebral infarct, presenting as conversion reaction, is proposed for this rare association.