Summary
Age-related cataract (ARC) is a multifactorial disease and the leading cause of visual impairment and blindness worldwide. Genetic predisposition in association with other etiological factors may contribute to ARC. Although, there is some evidence for genetic influence for development of ARC, reports on gene mutations associated with ARC are scanty. In the present work, we identified a genetic variation (F71L) in the exon-2 of CRYAA gene in three unrelated female sporadic cases among 450 ARC patients but not in 144 normal non-cataractous controls. By comparing human recombinant wild-type and F71L-αA-crystallin, further we characterized the functional significance of this missense mutation. Size exclusion chromatography studies revealed that F71L mutation had no significant effect on the apparent molecular mass of αA-crystallin oligomeric complex. Intrinsic tryptophan fluorescence and far- and near-UV CD spectra indicated that F71L missense mutation did not significantly affect the secondary and tertiary structures of αA-crystallin. The ANS fluorescence emission spectra suggested no changes in surface hydrophobicity due to the F71L substitution. While the mutant αA-crystallin displayed almost complete loss (90%) of chaperone-like activity (CLA), in thermal aggregation of carbonic anhydrase, it showed 35-50% less protection in heat-induced aggregation of βL- and γ-crystallins. This is the first report of an αA-F71L mutation being associated with ARC. The results are consistent with the hypothesis that the mechanism of ARC in individuals carrying this mutation (F71L) might be due to the overall loss of in vivo chaperone activity due to interaction with other environmental factors.
Tuberculous meningitis (TBM) is a serious form of disease of the central nervous system. Early and accurate diagnosis of the disease and effective treatment are key important factors to contain the disease. The disease presents as chronic meningitis where other partners such as fungal meningitis, neurosyphilis, cysticercal meningitis, carcinomatous meningitis and partially treated pyogenic meningitis share a similar clinical picture making the diagnosis complicated. Culturing of the pathogen Mycobacterium tuberculosis (MTB) from the cerebrospinal fluid (CSF) sample has shown a poor response. The main immunological method for the immunodiagnosis of TBM is the detection of an antibody response in the CSF. In the present study, total MTB sonicated extract antigen was used for ELISA and Western blot. ELISA shows overall immune response of the test sample, whereas Western blotting reveals the specific reactivity to a particular molecular weight antigen. This would also reveal the immunodominant antigen. A total of 300 CSF samples were analyzed by both ELISA and Western blotting. Of the 240 clinically suspected TBM cases, 111 samples were positive by ELISA and 81 samples by Western blot. A total of 76 CSF samples were positive by both ELISA and Western blot. None of the control samples showed positivity either by ELISA or by Western blot. TBM patients revealed major antibody reactivity to 30-40 kD region, followed by 14 kD region. ELISA is sensitive with mild non-specific binding, but Western blot is specific in detecting the immune response. The findings will be useful in definitive immunodiagnosis of TBM.
Drug-resistant tuberculosis is being increasingly recognized and is one among the leading cause of death worldwide. Remarkable impermeability of cell wall to antituberculous drugs protects the mycobacteria from drug action. The present study analyzed the cell wall thickness among first-line drug resistant and sensitive Mycobacterium tuberculosis (Mtb) isolated from cerebrospinal fluid by transmission electron microscopy (TEM). The average thickness of the cell wall of sensitive isolates was 13.60 AE 0.98 nm. The maximum difference (26.48%) in the cell wall thickness was seen among multi-drug resistant (18.50 AE 1.71 nm) isolates and the least difference(4.14%) was shown by streptomycin-resistant (14.18 AE 1.38 nm) isolates. The ultrastructural study showed evident differences in the cell wall thickness among sensitive and resistant isolates. Preliminary TEM examination of cells indicates that morphological changes occur in the cell wall which might be attributed to the drug resistance. The thickened wall of Mtb appears to help the bacilli to overcome the action of antituberculous drugs. K E Y W O R D S cell wall, drug resistance, morphology, mycobacteria, transmission electron microscopy
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