Molecular flexibility of Mycobacterium tuberculosis ribosome recycling factor and its functional consequences: an exploration involving mutants.

Internal mobility of the two domain molecule of ribosome recycling factor (RRF) is known to be important for its action. Mycobacterium tuberculosis RRF does not complement E. coli for its deficiency of RRF (in the presence of E. coli EF-G alone). Crystal structure had revealed higher rigidity of the M. tuberculosis RRF due to the presence of additional salt bridges between domains. Two inter-domain salt bridges and one between the linker region and the domain containing C-terminal residues were disrupted by appropriate mutations. Except for a C-terminal deletion mutant, all mutants showed RRF activity in E. coli when M. tuberculosis EF-G was also co-expressed. The crystal structures of the point mutants, that of the C-terminal deletion mutant and that of the protein grown in the presence of a detergent, were determined. The increased mobility resulting from the disruption of the salt bridge involving the hinge region allows the appropriate mutant to weakly complement E. coli for its deficiency of RRF even in the absence of simultaneous expression of the mycobacterial EF-G. The loss of activity of the C-terminal deletion mutant appears to be partly due to the rigidification of the molecule consequent to changes in the hinge region.

Pituicytoma: report of three cases with review of literature.

Pituicytoma is a rare low-grade tumor (WHO Grade I) of pituicytes involving the sellar-suprasellar region, and originating from the specialized glial cells of the neurohypophysis. Clinically and radiologically, they closely mimic pituitary adenoma or meningioma. Diagnosis requires histopathological examination of the resected tissue. This uncommon glial neoplasm is a rarity, with only 57 cases reported in the literature so far. We report three cases of pituicytoma (aged between 7 and 24 years) presenting with reduced vision, headache and features of hypercortisolism in one case. Radiologically, these lesions mimicked meningioma, hypothalamic chiasmatic glioma and pituitary microadenoma, respectively. The second case is a 7-year-old girl, the youngest case on record. Since this tumor is uncommon, it is frequently misdiagnosed. Awareness of this entity is essential for planning management and treatment. We present a brief review of all cases reported in the medical literature, and describe the clinical symptomatology, associated endocrinological abnormalities, imaging characteristics, behavior and outcome.

Rosette-forming glioneuronal tumor -- evidence of stem cell origin with biphenotypic differentiation.

Rosette-forming glioneuronal tumor (RGNT) of the fourth ventricle is a new addition to the WHO classification of central nervous system tumors. To date, 72 cases have been described in literature. In the present study, we report the clinical and imaging features, with detailed histopathological and immunohistochemical profile, of eight cases. Confocal microscopic evidence of stem cell origin with biphenotypic, glial and neurocytic differentiation is presented with a comprehensive review of literature.

An unusual case of intraventricular gliosarcoma.

Gliosarcoma is an uncommon variant of glioblastoma characterized by a biphasic pattern of glial and mesenchymal differentiation in the tumor. These tumors occur mostly in the cerebral hemispheres. Intraventricular location is extremely rare. Extensive review of literature revealed only two cases of intraventricular gliosarcoma. The first case arose by malignant transformation of a preexisting ependymoma. The second case was a gliosarcoma involving the frontal lobe with extension into the lateral ventricle. We report a case of an exclusively lateral ventricular tumor probably arising from the interventricular septum and blocking the CSF pathway. To the best of our knowledge, this is the first reported case of an exclusively intraventricular gliosarcoma.

Age-related proximal femur bone mineral loss in South Indian women: a dual energy X-ray absorptiometry study.

OBJECTIVES: i) To collect normative data for proximal femur bone mineral density (BMD) in South Indian women using dual energy X-ray absorptiometry (DXA) and ii) to study the rate and significance of hip bone mineral loss with advancing age in this population. MATERIAL AND METHODS: Forty five women, whose age ranged from 16 to 84 years were studied. This sample was drawn randomly from general medical practice at KJ Hospital, Chennai, South India during November, 1997 to April, 1998. Of these 45 cases, 21 were pre-menopausal (mean +/- SD age = 30.9+/-8.8 years) and 24 post-menopausal (mean +/- SD age = 62.1+/-11.0 years). Subjects with secondary bone diseases were excluded. Also excluded were those taking any drugs known to affect calcium metabolism e.g., thiazide diuretics, oestrogen and calcium. Subjects were divided into seven decadal age groups from 15-24 years to 75-84 years. BMD of the right proximal femur was evaluated using a QDR-1000 DXA bone densitometer (Hologic Inc., Waltham, Massachusetts, USA). Data analysis was done with SPSS/PC statistical software package. RESULTS: Linear regression analysis showed significant (p < 0.001) negative correlations between all hip BMD variables at different regions of interest and patient's age. Relative to that at 30 years of age, rates of BMD loss in the neck of femur, trochanter, intertrochanter, total hip and Ward's triangle were 0.68%, 0.65%, 0.58%, 0.61% and 1.05% per annum respectively. Over the age of 65 years, the above mentioned regions BMD decreased by 0.91%, 0.84%, 0.72%, 0.78% and 1.66% per annum respectively. CONCLUSION: Normative data for proximal femur BMD in South India women have been evaluated and it may prove useful for diagnosing osteoporosis in the women of South India.