Development of Modified-Release Tablets of Zolpidem Tartrate by Biphasic Quick/Slow Delivery System

Zolpidem tartrate is a non-benzodiazepine analogue of imidazopyridine of sedative and hypnotic category. It has a short half-life with usual dosage regimen being 5 mg, two times a day, or 10 mg, once daily. The duration of action is considered too short in certain circumstances. Thus, it is desirable to lengthen the duration of action. The formulation design was implemented by preparing extended-release tablets of zolpidem tartrate using the biphasic delivery system technology, where sodium starch glycolate acts as a superdisintegrant in immediate-release part and hydroxypropyl methyl cellulose as a release retarding agent in extended-release core. Tablets were prepared by direct compression. Both the core and the coat contained the drug. The pre-compression blends were evaluated for angle of repose, bulk density, and compressibility index. The tablets were evaluated for thickness, hardness, weight variation test, friability, and in vitro release studies. No interaction was observed between zolpidem tartrate and excipients from the Fourier transform infrared spectroscopy and differential scanning calorimetry analysis. The results of all the formulations prepared were compared with reference product Stilnoct®. Optimized formulations showed release patterns that match the United States Pharmacopeia (USP) guidelines for zolpidem tartrate extended-release tablets. The mechanism of drug release was studied using different mathematical models, and the optimized formulation has shown Fickian diffusion. Accelerated stability studies were performed on the optimized formulation.KEY WORDS: biphasic delivery system technology, hydroxypropyl methyl cellulose, modified release, sodium starch glycolate, zolpidem tartrate     

Irreversibility of the interaction of human growth hormone with its receptor and analysis of irreversible reactions in radioreceptor assays—Theoretical considerations

Kinetic studies of the binding and dissociation of [¹²⁵I]-human growth hormone to rabbit liver and mammary gland membrane receptors have showed that the binding of [¹²⁵I]-human growth hormone was largely irreversible to liver membrane receptors and completely to the solubilised mammary gland receptor. As Scatchard analysis assumes complete reversibility of the hormone-receptor interaction the validity of estimates of affinity and capacity of receptors derived by this analysis may be questionable. Theoretical considerations show that in unimolecular irreversible interactions of hormone and receptor, a nonlinear (concave) or a linear Scatchard plot can be obtained. In linear Scatchard plots the capacity of the receptor obtained by extrapolation represents an overestimation of true capacity. This overestimation correlates with the value of the intercept in the Scatchard plot.     

Positive Impact of Nutritional Interventions on Serum Symmetric Dimethylarginine and Creatinine Concentrations in Client-Owned Geriatric Dogs

A prospective study was conducted in client-owned geriatric dogs to evaluate the short-term effects of a test food on serum symmetric dimethylarginine (SDMA) and creatinine (Cr) concentrations. Test food contained functional lipids (fish oil), antioxidants (lipoic acid, vitamins C and E), L-carnitine, botanicals (fruits and vegetables), controlled sodium concentration, and high quality protein sources (high bioavailability and an ideal amino acid composition). Dogs (n = 210) were fed either test food or owner’s-choice foods (non-nutritionally controlled cohort). Dogs were included based on age and body weight: small (6.8 to 11.4 kg) and medium dogs (11.5 to 22.7 kg) were ≥ 9 years, whereas dogs >22.7 kg were ≥ 7 years at baseline. At baseline, all dogs had to have serum Cr concentrations within the reference interval and be free of chronic disease. Renal function biomarkers and urinalysis results at baseline, and after consuming test food or owner’s-choice foods for 3 and 6 months, were evaluated. Only dogs consuming test food showed significant decreases in serum SDMA and Cr concentrations (both P ≤ 0.05) across time. At baseline or during the 6-month feeding trial, 18 dogs (8.6%) had increased serum SDMA, but normal serum Cr, consistent with IRIS Stage 1 chronic kidney disease. This included 9 dogs fed test food and 9 dogs fed owner’s-choice foods. Compared with baseline, after feeding 9 dogs test food for 6 months, serum SDMA decreased in 8 dogs and increased in 1 dog. After feeding 9 dogs owner’s-choice foods for 6 months, serum SDMA decreased in 4 dogs and increased in 4 dogs (remained stable in 1 dog). The decreases in serum SDMA and Cr concentrations were significant (both P = 0.03) only for dogs fed test food. These results suggest that nonazotemic dogs with elevated serum SDMA (early renal insufficiency) when fed a test food designed to promote healthy aging are more likely to demonstrate improved renal function compared with dogs fed owner’s-choice foods.     

Molecular Epidemiology of Nontyphoidal Salmonella in Poultry and Poultry Products in India: Implications for Human Health

Human infections with non-typhoidal Salmonella (NTS) serovars are increasingly becoming a threat to human health globally. While all motile Salmonellae have zoonotic potential, Salmonella Enteritidis and Salmonella Typhimurium are most commonly associated with human disease, for which poultry are a major source. Despite the increasing number of human NTS infections, the epidemiology of NTS in poultry in India has not been fully understood. Hence, as a first step, we carried out epidemiological analysis to establish the incidence of NTS in poultry to evaluate the risk to human health. A total of 1215 samples (including poultry meat, tissues, egg and environmental samples) were collected from 154 commercial layer farms from southern India and screened for NTS. Following identification by cultural and biochemical methods, Salmonella isolates were further characterized by multiplex PCR, allele-specific PCR, enterobacterial repetitive intergenic consensus (ERIC) PCR and pulse field gel electrophoresis (PFGE). In the present study, 21/1215 (1.73 %) samples tested positive for NTS. We found 12/392 (3.06 %) of tissue samples, 7/460 (1.52 %) of poultry products, and 2/363 (0.55 %) of environmental samples tested positive for NTS. All the Salmonella isolates were resistant to oxytetracycline, which is routinely used as poultry feed additive. The multiplex PCR results allowed 16/21 isolates to be classified as S. Typhimurium, and five isolates as S. Enteritidis. Of the five S. Enteritidis isolates, four were identified as group D Salmonella by allele-specific PCR. All of the isolates produced different banding patterns in ERIC PCR. Of the thirteen macro restriction profiles (MRPs) obtained by PFGE, MRP 6 was predominant which included 6 (21 %) isolates. In conclusion, the findings of the study revealed higher incidence of contamination of NTS Salmonella in poultry tissue and animal protein sources used for poultry. The results of the study warrants further investigation on different type of animal feed sources, food market chains, processing plants, live bird markets etc., to evaluate the risk factors, transmission and effective control measures of human Salmonella infection from poultry products.     

Integrated dataset of screening hits against multiple neglected disease pathogens

New chemical entities are desperately needed that overcome the limitations of existing drugs for neglected diseases. Screening a diverse library of 10,000 drug-like compounds against 7 neglected disease pathogens resulted in an integrated dataset of 744 hits. We discuss the prioritization of these hits for each pathogen and the strong correlation observed between compounds active against more than two pathogens and mammalian cell toxicity. Our work suggests that the efficiency of early drug discovery for neglected diseases can be enhanced through a collaborative, multi-pathogen approach.     

AMPK beta subunit targets metabolic stress sensing to glycogen

AMP-activated protein kinase (AMPK) is a multisubstrate enzyme activated by increases in AMP during metabolic stress caused by exercise, hypoxia, lack of cell nutrients, as well as hormones, including adiponectin and leptin. Furthermore, metformin and rosiglitazone, frontline drugs used for the treatment of type II diabetes, activate AMPK. Mammalian AMPK is an alphabetagamma heterotrimer with multiple isoforms of each subunit comprising alpha1, alpha2, beta1, beta2, gamma1, gamma2, and gamma3, which have varying tissue and subcellular expression. Mutations in the AMPK gamma subunit cause glycogen storage disease in humans, but the molecular relationship between glycogen and the AMPK/Snf1p kinase subfamily has not been apparent. We show that the AMPK beta subunit contains a functional glycogen binding domain (beta-GBD) that is most closely related to isoamylase domains found in glycogen and starch branching enzymes. Mutation of key glycogen binding residues, predicted by molecular modeling, completely abolished beta-GBD binding to glycogen. AMPK binds to glycogen but retains full activity. Overexpressed AMPK beta1 localized to specific mammalian subcellular structures that corresponded with the expression pattern of glycogen phosphorylase. Glycogen binding provides an architectural link between AMPK and a major cellular energy store and juxtaposes AMPK to glycogen bound phosphatases.     

Evidence of two isomers of phosphatidylinositol in plant tissue

The structure of phosphatidylinositol in barley (Hordeum vulgare) aleurone layers was investigated by chemical degradation. In vivo myo-[2-³H]inositol-labeled phosphatidylinositol was first converted to glycerophosphoinositol and, subsequently, after removal of the glycerol moiety, to inositol monophosphate. Here, we present data that show that, in addition to the commonly occurring 1,2-diacylglycero-3-(d-myo-inositol-1-phosphate), barley aleurone cells contain a novel second isomer of phosphatidylinositol that differs in structure of the head group.     

Production of infectious hepatitis C virus in tissue culture from a cloned viral genome

Hepatitis C virus (HCV) infection causes chronic liver diseases and is a global public health problem. Detailed analyses of HCV have been hampered by the lack of viral culture systems. Subgenomic replicons of the JFH1 genotype 2a strain cloned from an individual with fulminant hepatitis replicate efficiently in cell culture. Here we show that the JFH1 genome replicates efficiently and supports secretion of viral particles after transfection into a human hepatoma cell line (Huh7). Particles have a density of about 1.15-1.17 g/ml and a spherical morphology with an average diameter of about 55 nm. Secreted virus is infectious for Huh7 cells and infectivity can be neutralized by CD81-specific antibodies and by immunoglobulins from chronically infected individuals. The cell culture-generated HCV is infectious for chimpanzee. This system provides a powerful tool for studying the viral life cycle and developing antiviral strategies.     

Conservation of gene expression signatures between zebrafish and human liver tumors and tumor progression

The zebrafish (Danio rerio) has been long advocated as a model for cancer research, but little is known about the real molecular similarities between zebrafish and human tumors. Comparative analysis of microarray data from zebrafish liver tumors with those from four human tumor types revealed molecular conservation at various levels between fish and human tumors. This approach provides a useful strategy for identifying an expression signature that is strongly associated with a disease phenotype.     

Induction of biochemical stress markers and apoptosis in transgenic Drosophila melanogaster against complex chemical mixtures: role of reactive oxygen species

The study was aimed to investigate the effect of leachates of solid waste from a flashlight battery factory and a pigment plant on 70 kDa heat shock protein (Hsp70) expression, generation of reactive oxygen species (ROS), antioxidant enzymes activities and apoptosis in Drosophila. Third instar larvae of Drosophila melanogaster transgenic for hsp70 (hsp70-lacZ) were fed on diet mixed with leachates of solid wastes (0.05-2.0%, v/v) released from two industrial plants at three different pHs (7.00, 4.93 and 2.88) for 2-48 h. A concentration- and time-dependent significant change in Hsp70 expression, ROS generation, antioxidant enzymes activities and MDA content was observed in the exposed larvae preceding the antioxidant enzymes activities. Mitochondria-mediated, caspase-dependent apoptotic cell death in the larvae exposed to 1.0 and 2.0% leachates of flashlight battery factory was concurrent with a significant regression in Hsp70 expression and a higher ROS generation. A positive correlation drawn between ROS generation and apoptotic markers and a negative correlation between apoptotic markers and Hsp70 expression in these groups indicated the important role of ROS in the leachate-induced cellular damage. Hsp70 along with antioxidant enzymes offered protection to the organisms exposed to all the tested concentrations of the leachates of pigment plant waste and 0.5% leachate of flashlight battery factory in a cooperative manner when ROS generation was less induced. Conversely, higher levels of ROS generation in the organisms treated with 1.0 and 2.0% leachate of flashlight battery factory after 24 and 48 h resulted in regression of Hsp70 expression in them leading to cell death. The study suggests that (1) leachates of flashlight battery factory waste more adversely affected the organisms in comparison to the leachates of pigment plant waste. (2) Hsp70 may be used as a biomarker of cellular damage in organisms exposed to leachates. (3) Cell based assays using D. melanogaster as an in vivo model may provide important mechanistic information about the adverse effect of xenobiotics.