Non-bulk-like solvent behavior in the ribosome exit tunnel

As nascent proteins are synthesized by the ribosome, they depart via an exit tunnel running through the center of the large subunit. The exit tunnel likely plays an important part in various aspects of translation. Although water plays a key role in many bio-molecular processes, the nature of water confined to the exit tunnel has remained unknown. Furthermore, solvent in biological cavities has traditionally been characterized as either a continuous dielectric fluid, or a discrete tightly bound molecule. Using atomistic molecular dynamics simulations, we predict that the thermodynamic and kinetic properties of water confined within the ribosome exit tunnel are quite different from this simple two-state model. We find that the tunnel creates a complex microenvironment for the solvent resulting in perturbed rotational dynamics and heterogenous dielectric behavior. This gives rise to a very rugged solvation landscape and significantly retarded solvent diffusion. We discuss how this non-bulk-like solvent is likely to affect important biophysical processes such as sequence dependent stalling, co-translational folding, and antibiotic binding. We conclude with a discussion of the general applicability of these results to other biological cavities.     

Effect of isoflavone from Flemingia vestita (Fabaceae) on the Ca2+ homeostasis in Raillietina echinobothrida, the cestode of domestic fowl

The alcoholic crude root-peel extract of Flemingia vestita and its major isoflavone, genistein, have been shown to have a vermifugal/vermicidal effect by causing a flaccid paralysis accompanied by alterations in the structural architecture of the tegumental interface and metabolic activity in Raillietina echinobothrida, the cestode of domestic fowl. In the present study, the crude root-peel extract and pure genistein were tested in vitro with respect to Ca2+ homeostasis and the occurrence of some metal ions was detected in the parasite. Live cestodes were incubated in pre-defined concentrations of the crude root-peel extract, genistein and praziquantel (as reference drug), till the paralysis time with simultaneous maintenance of respective controls. In the parasite tissue, a significant amount of Ca2+ (approximately 400 microg/g dry tissue wt) was found to be present besides magnesium, iron, zinc, lead and chromium, whilst manganese, cadmium and nickel were below the level of detection. The Ca2+ concentration was decreased significantly by 39%-49%, in the parasite tissue exposed to the test materials in comparison to the respective controls. There was also an increase in Ca2+ efflux by 91%-160% into the culture medium under similar treatments. The changes in Ca2+ homeostasis may be related to the rapid muscular contraction and consequent paralysis in the parasite due to the anthelmintic stress caused by the phytochemicals of F. vestita.     

Effect of T-2 toxin on growth, performance and haematobiochemical alterations in broilers

Administration of dietary T-2 toxin in 120 days old broiler chicks led to significant lower body weights and increase in feed conversion ratio from 2nd week of age. There was significant reduction in haemoglobin and packed cell volume in T-2 toxicated birds at 4 ppm level only. The other hematological parameters like TEC, TLC and absolute leucocyte count did not showed any variation due to T-2 toxin in feed. Significant reduction in serum total protein and cholesterol levels and rise in serum uric acid and LDH levels of broilers were observed due to dietary T-2 toxin. The result suggests that T-2 toxin is toxic to broilers even at very low concentrations.     

Protein-tyrosine phosphatase 1B deficiency protects against Fas-induced hepatic failure

Genetic disruption of protein-tyrosine phosphatase 1B (PTP1B) in mice leads to increased insulin sensitivity and resistance to weight gain. Although PTP1B has been implicated as a regulator of multiple signals, its function in other physiological responses in vivo is poorly understood. Here we demonstrate that PTP1B-null mice are resistant to Fas-induced liver damage and lethality, as evident by reduced hepatic apoptosis in PTP1B-null versus wild type mice and reduced levels of circulating liver enzymes. Activation of pro-apoptotic caspases-8, -9, -3, and -6 was attenuated in livers from PTP1B-null mice following Fas receptor stimulation, although components of the death-inducing signaling complex were intact. Activation of anti-apoptotic regulators, such as the hepatocyte growth factor/Met receptor tyrosine kinase, as well as Raf, ERK1/2, FLIP(L), and the NF-kappaB pathway, was elevated in response to Fas activation in livers from PTP1B-null mice. Using PTP1B-deficient primary hepatocytes, we show that resistance to Fas-mediated apoptosis is cell autonomous and that signals involving the Met, ERK1/2, and NF-kappaB pathways are required for cytoprotection. This study identifies a previously unknown physiological role for PTP1B in Fas-mediated liver damage and points to PTP1B as a potential therapeutic target against hepatotoxic agents.     

Urban health and pharmaceutical consumption in Delhi, India

This paper interrogates the routine and unproblematic use of terms such as 'self-medication' in biomedical and anthropological discourse. A typical depiction of the social factors that explain the practice of 'self-medication' in India is to put together the supply side factors (such as protection offered by the government for the production of generic drugs, especially in the small scale sector, and expansion of the number of drug store outlets), with the increasing demand for allopathic drugs. The paper provides an ethnographic account of the intricate connections between households and biomedical practitioners in urban neighbourhoods in Delhi. It breaks away from the conventional opposition drawn between the practices of physicians and the beliefs of their patients, and suggests that what constitutes the medical environments of these neighbourhoods is the product of medical practices, household economies and concepts of disease. Thus pharmaceutical use is determined as much by practices of dispensation and by how practitioners understand what constitutes therapy as by household understanding of the normal and the pathological. This paper uses both quantitative data and narrative interviews to provide an in-depth understanding of the circulation of pharmaceuticals within the life worlds of the urban poor.     

The biochemical alterations following administration of Kalpaamruthaa and Semecarpus anacardium in mammary carcinoma

BACKGROUND: Breast cancer is one of the most common cancers in women of developed and developing countries. Lipids, lipoproteins and lipid-metabolizing enzymes have been associated with the risk of breast cancer. Kalpaamruthaa (KA) is a modified Siddha preparation, which contains Semecarpus anacardium Linn. (SA), Emblica officinalis (EO) and honey. OBJECTIVE: The present study was embarked to study the variations in lipids, lipid-metabolizing enzymes and lipoproteins in cancerous animals and the effect of KA on the lipid metabolism. MATERIALS AND METHODS: Breast cancer was induced in rats by administrating 7,12-dimethylbenz(a)anthracene orally (25 mg/kg body weight). After 90 days of induction, KA (300 mg/kg body weight) and SA (200 mg/kg body weight) were administered for 14 days, by gastric intubations. The levels of lipids and lipid-metabolizing enzymes were analysed in control and experimental animals. RESULTS AND CONCLUSION: The increased levels of total cholesterol, free cholesterol, phospholipids, triglycerides and free fatty acids and decreased levels of ester cholesterol in plasma, liver and kidney found in cancer suffering animals were reverted back to near normal levels on treatment with KA and SA. In mammary carcinoma bearing animals, the activities of total lipase, cholesterol ester synthase, and cholesterol ester hydrolase were significantly (p < 0.05) increased whereas lipoprotein lipase and lecithin cholesterol-acyl transferase were decreased. The levels of very low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) were increased and the level of high-density lipoprotein (HDL) was decreased. These alterations were recouped back upon treatment with KA as well as SA when compared to cancer animals. The effects of KA were found to be more effective than SA. No significant alterations were observed in herbal preparation control animals when compared to control animals.     

The sterol-binding antibiotic nystatin inhibits entry of non-opsonized Leishmania donovani into macrophages

Leishmania donovani is an obligate intracellular parasite that infects macrophages of the vertebrate host resulting in visceral leishmaniasis in humans, a major public health problem worldwide. The molecular mechanisms involved in internalization of Leishmania are still poorly characterized. We report here that cholesterol sequestration by the sterol-binding antifungal polyene antibiotic nystatin markedly inhibits binding and entry of non-opsonized L. donovani promastigotes into macrophages. Interestingly, these effects are not observed when serum-opsonized L. donovani are used for infectivity studies thus pointing the essential role of cholesterol in mediating entry of the parasite via the non-opsonic pathway. Based on our earlier results where leishmanial infectivity was shown to be sensitive to physical depletion of cholesterol from macrophages, these results indicate that the mere sequestration of cholesterol in the host plasma membrane is sufficient to inhibit the binding and entry of non-opsonized L. donovani. These results represent the first report on the effect of a cholesterol-sequestering agent on the entry of Leishmania parasites to host macrophages. More importantly, these findings offer the possibility of reevaluating the mechanism behind the effectiveness of current therapeutic strategies to treat leishmaniasis.     

Liquid chromatography-tandem mass spectrometry validated method for the estimation of indapamide in human whole blood

A highly precise and sensitive method for the estimation of indapamide in human whole blood using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) is described. The method developed is validated in human whole-blood matrix, with a sensitivity of 0.5 ng/ml as lower limit of quantification. The procedure for the extraction of indapamide and glimepiride as internal standard (IS) involves haemolysis and deprotienation of whole blood using ZnSO(4) followed by liquid-liquid extraction using ethyl acetate. The sample extracts after drying were reconstituted and analysed by LC-MS/MS, equipped with turbo ion spray (TIS) source, operating in the positive ion and selective reaction monitoring (SRM) acquisition mode to quantify indapamide in human whole blood. The mean recovery for indapamide was 82.40 and 93.23% for IS. The total run time was 2.5 min to monitor both indapamide and the IS. The response of the LC-MS/MS method for indapamide was linear over the range of 0.5-80.0 ng/ml with correlation coefficient, r>or=0.9991. The coefficient of variance (% CV) at 0.5 ng/ml was 4.02% and the accuracy was well within the accepted limit of +/-20% at 0.5 ng/ml and +/-15% at all other concentrations in the linear range. This method is fully validated for the accuracy, precision and stability studies and also applied to subject-sample analysis of bioequivalence study for 1.5mg sustained-release (SR) formulations.     

Multiplexed-Replica Exchange Molecular Dynamics Method for Protein Folding Simulation

Simulating protein folding thermodynamics starting purely from a protein sequence is a grand challenge of computational biology. Here, we present an algorithm to calculate a canonical distribution from molecular dynamics simulation of protein folding. This algorithm is based on the replica exchange method where the kinetic trapping problem is overcome by exchanging noninteracting replicas simulated at different temperatures. Our algorithm uses multiplexed-replicas with a number of independent molecular dynamics runs at each temperature. Exchanges of configurations between these multiplexed-replicas are also tried, rendering the algorithm applicable to large-scale distributed computing (i.e., highly heterogeneous parallel computers with processors having different computational power). We demonstrate the enhanced sampling of this algorithm by simulating the folding thermodynamics of a 23 amino acid miniprotein. We show that better convergence is achieved compared to constant temperature molecular dynamics simulation, with an efficient scaling to large number of computer processors. Indeed, this enhanced sampling results in (to our knowledge) the first example of a replica exchange algorithm that samples a folded structure starting from a completely unfolded state.