Structural insights into the activation mechanism of phosphoinositide 3-kinase alpha.

Phosphoinositide 3-kinases (PI3Ks) are lipid kinases known to regulate important cellular functions by phosphorylating the inositol ring of inositol-phospholipids (PtdIns) at 3' position. The PI3Kα is a heterodimer and the activation of the catalytic subunit (p110α) is regulated by its regulatory subunit (p85α). The current work deals with studying the activation mechanism of the PI3Kα using multi micro-second molecular dynamic simulations. Structural changes involved in activation mechanism is studied by gradually releasing the inhibitory effects of different domains of regulatory subunit namely, n-terminal SH2 (nSH2) and inter SH2 (iSH2). The observation shows that even in the presence of n-terminal and inter SH2 domain (niSH2) of regulatory subunit, the catalytic domain has some intrinsic activation activity and the presence of c-terminal SH2 (cSH2) domain may be required for complete inhibition. The release of nSH2 domain leads to loss of interactions between iSH2 domain (regulatory subunit) and C2 and kinase domain (catalytic subunit). The study shows that early events in the activation mechanism involve the movement of the ABD domain of the catalytic subunit along with the linker region between ABD and RBD region which may lead to movement of ABD closer to the CLobe of the kinase domain. This movement is essentially as it triggers the rearrangement of CLobe especially the catalytic loop and activation loop which bring catalytic important residues closer to ATP and PIP2(phosphatidylinositol-4,5-bisphosphate). Water mediated interaction analysis reveal that water may be playing an important role in the transfer of phosphate from ATP to PIP2. The study shows that initial signal for release of inhibitory effect of the regulatory subunit might be propagated through the linker region between ABD and RBD through allosteric effect to different regions of the protein. These understanding of early events during the activation mechanism may help in the design of better therapeutic targeting PI3K.

Differential sensitivity of Chironomus and human hemoglobin to gamma radiation.

Chironomus ramosus is known to tolerate high doses of gamma radiation exposure. Larvae of this insect possess more than 95% of hemoglobin (Hb) in its circulatory hemolymph. This is a comparative study to see effect of gamma radiation on Hb of Chironomus and humans, two evolutionarily diverse organisms one having extracellular and the other intracellular Hb respectively. Stability and integrity of Chironomus and human Hb to gamma radiation was compared using biophysical techniques like Dynamic Light Scattering (DLS), UV-visible spectroscopy, fluorescence spectrometry and CD spectroscopy after exposure of whole larvae, larval hemolymph, human peripheral blood, purified Chironomus and human Hb. Sequence- and structure-based bioinformatics methods were used to analyze the sequence and structural similarities or differences in the heme pockets of respective Hbs. Resistivity of Chironomus Hb to gamma radiation is remarkably higher than human Hb. Human Hb exhibited loss of heme iron at a relatively low dose of gamma radiation exposure as compared to Chironomus Hb. Unlike human Hb, the heme pocket of Chironomus Hb is rich in aromatic amino acids. Higher hydophobicity around heme pocket confers stability of Chironomus Hb compared to human Hb. Previously reported gamma radiation tolerance of Chironomus can be largely attributed to its evolutionarily ancient form of extracellular Hb as evident from the present study.

Prevalence, pattern and outcome of congenital heart disease in Bhabha Atomic Research Centre Hospital, Mumbai.

OBJECTIVE: To assess the prevalence, pattern and outcome of congenital heart disease (CHD) among the babies born in Bhabha Atomic Research Centre (BARC) Hospital, Mumbai and to compare the pattern of CHD with the study done in the same hospital in year 1999. METHODS: A prospective, longitudinal study was conducted from January 2006 through December 2011. Babies presenting with murmur were closely followed up till the diagnosis and further to assess the outcome. 2-D Echocardiography was used as a diagnostic tool. RESULTS: The overall prevalence of CHD was 13.28 per 1,000 live births. Ventricular septal defect (VSD) was the commonest CHD (42.86 %) followed by Atrial septal defect (ASD) (25.71 %) giving the prevalence of 5.69 and 3.41 per 1,000 live births respectively. Tetrology of Fallot's (TOF) was the main cyanotic CHD (8.57 %) with the prevalence of 1.13 per 1,000 live births. VSD and TOF were prevalent in males. ASD was prevalent in females. Associated structural anomalies were detected in 22.86 % cases; Down's syndrome being the commonest.Spontaneous closure rate of 71.4 % in muscular VSD and 50 % in perimembranous VSD was observed. All small sized VSD's closed spontaneously and all large sized VSD's required surgical intervention. Spontaneous closure was observed in 44.44 % of ASD cases. Overall, device closure was required in 17.14 % and 25.71 % underwent open heart surgery. CONCLUSIONS: The pattern of CHD has remained almost the same compared to the previous study. The outcome was excellent due to early diagnosis, regular follow up and timely intervention.

Abnormal uterine bleeding as a presentation of metastatic breast disease in a patient with advanced breast cancer on tamoxifen therapy.

INTRODUCTION: Extra pelvic tumours rarely metastasise to the female genital tract. Typically it is the ovaries that are involved and the primary tumours include the breast and the gastrointestinal tract. Metastatic disease involving the uterus is rare. CASE REPORT: A case of metastatic breast carcinoma involving both the uterine corpus and cervix is described. The patient was known to have advanced breast carcinoma and was on tamoxifen therapy when she presented with postmenopausal bleeding. Histological assessment of the hysterectomy specimen including immunohistochemistry staining confirmed the breast carcinoma as the primary. CONCLUSION: Unusual uterine bleeding in a patient with breast cancer, should alert the gynaecologist to the possibility of metastatic breast disease regardless of tamoxifen treatment.

CD40 signaling is impaired in L. major-infected macrophages and is rescued by a p38MAPK activator establishing a host-protective memory T cell response.

Leishmania, a protozoan parasite, lives and multiplies as amastigote within macrophages. It is proposed that the macrophage expressed CD40 interacts with CD40 ligand on T cells to induce IFN-gamma, a Th1-type cytokine that restricts the amastigote growth. Here, we demonstrate that CD40 cross-linking early after infection resulted in inducible nitric oxide synthetase type-2 (iNOS2) induction and iNOS2-dependent amastigote elimination. Although CD40 expression remained unaltered on L. major-infected macrophages, delay in the treatment of macrophages or of mice with anti-CD40 antibody resulted in significant reduction in iNOS2 expression and leishmanicidal function suggesting impaired CD40 signaling in Leishmania infection. The inhibition of CD40-induced iNOS2 expression by SB203580, a p38-mitogen activated protein kinase (p38MAPK)-specific inhibitor, and the reversal of the inhibition by anisomycin, a p38MAPK activator, suggested a crucial role of p38MAPK in CD40 signaling. Indeed, the CD40-induced p38MAPK phosphorylation, iNOS2 expression and anti-leishmanial function were impaired in Leishmania-infected macrophages but were restored by anisomycin. Anisomycin's effects were reversed by SB203580 emphasizing the role of p38MAPK in CD40-induced iNOS2-dependent leishmanicidal function. Anisomycin administration in L. major-infected BALB/c mice resulted in significant reduction in the parasite load and established a host-protective Th1-type memory response. Also implicated in these findings is a scientific rationale to define novel anti-parasite drug targets and to bypass the problem of drug resistance.

Inflammatory myofibroblastic tumor.

Inflammatory myofibroblastic tumors are well described in lung and upper respiratory tract of young adults and children. Intra-abdominal forms of the disease are reported to occur most frequently in the liver, followed by stomach, bowel and spleen. A 13-year-old girl who had intermittent fever ranging from 99-101 degrees F of three months period and significant weight loss was referred as a case of pyrexia of unknown origin. The patient was subjected to laparotomy. A solid mass was found arising from the mesentery, four feet from the iliocaecal junction and was adherent to the wall of ileum. The patient became afebrile after the removal of the mass and has gained weight and remained well during the ten months since discharge.