Potential role of thiol:disulfide oxidoreductases in the pathogenesis of Helicobacter pylori

Helicobacter pylori infections are responsible for a sequence of molecular events which ultimately result in the development of gastric diseases. The pathogenesis of H. pylori has been studied extensively with strong focus on the identification of virulence factors. In contrast, the involvement of thiol:disulfide oxidoreductases in bacterial pathogenesis is less well understood. This paper provides a review of the current knowledge of H. pylori putative thiol:disulfide oxidoreductases, and their potential role in promoting virulence and colonization. Several bioinformatic analyses served to complete the information on these oxidoreductases of H. pylori.     

Systematic analysis of HD-ZIP transcription factors in sesame genome and gene expression profiling of SiHD-ZIP class I entailing drought stress responses at early seedling stage

Molecular Biology Reports - Sesame is an ancient oilseed crop, known for its high oil content and quality. Its sensitivity to drought at early seedling stage is one of the limiting factors...     

Mechanisms of Human Erythrocytic Bioactivation of Nitrite

Nitrite signaling likely occurs through its reduction to nitric oxide (NO). Several reports support a role of erythrocytes and hemoglobin in nitrite reduction, but this remains controversial, and alternative reductive pathways have been proposed. In this work we determined whether the primary human erythrocytic nitrite reductase is hemoglobin as opposed to other erythrocytic proteins that have been suggested to be the major source of nitrite reduction. We employed several different assays to determine NO production from nitrite in erythrocytes including electron paramagnetic resonance detection of nitrosyl hemoglobin, chemiluminescent detection of NO, and inhibition of platelet activation and aggregation. Our studies show that NO is formed by red blood cells and inhibits platelet activation. Nitric oxide formation and signaling can be recapitulated with isolated deoxyhemoglobin. Importantly, there is limited NO production from erythrocytic xanthine oxidoreductase and nitric-oxide synthase. Under certain conditions we find dorzolamide (an inhibitor of carbonic anhydrase) results in diminished nitrite bioactivation, but the role of carbonic anhydrase is abrogated when physiological concentrations of CO₂ are present. Importantly, carbon monoxide, which inhibits hemoglobin function as a nitrite reductase, abolishes nitrite bioactivation. Overall our data suggest that deoxyhemoglobin is the primary erythrocytic nitrite reductase operating under physiological conditions and accounts for nitrite-mediated NO signaling in blood.     

Development of Controlled-Release Matrix Tablet of Risperidone: Influence of Methocel®- and Ethocel®-Based Novel Polymeric Blend on <Emphasis Type="Italic">In Vitro</Emphasis> Drug Release and Bioavailability

Controlled-release (CR) matrix tablet of 4 mg risperidone was developed using flow bound dry granulation–slugging method to improve its safety profile and compliance. Model formulations F1, F2, and F3, consisting of distinct blends of Methocel® K100 LV-CR and Ethocel® standard 7FP premium, were slugged. Each batch of granules (250–1,000 μm), obtained by crushing the slugs, was divided into three portions after lubrication and then compressed to 9-, 12-, and 15-kg hard tablets. In vitro drug release studies were carried out in 0.1 N HCl (pH 1.2) and phosphate buffer (pH 6.8) using a paddle dissolution apparatus run at 50 rpm. The CR test tablet, containing 30% Methocel® and 60% Ethocel® (F3) with 12-kg hardness, exhibited pH-independent zero-order release kinetics for 24 h. The drug release rate was inversely proportional to the content of Ethocel®, while the gel layer formed of Methocel® helped in maintaining the integrity of the matrix. Changes in the hardness of tablet did not affect the release kinetics. The tablets were reproducible and stable for 6 months at 40 ± 2°C/75 ± 5% relative humidity. Risperidone and its active metabolite, 9-hydroxyrisperidone, present in the pooled rabbit’s serum, were analyzed with HPLC-UV at λ_max 280 nm. The CR test tablet exhibited bioequivalence to reference conventional tablet in addition to the significantly (p < 0.05) optimized peak concentration, C_max, and extended peak time, T_max, of the active moiety. There was a good association between drug absorption in vivo and drug release in vitro (R² = 0.7293). The successfully developed CR test tablet may be used for better therapeutic outcomes of risperidone.KEY WORDS: controlled release, dry granulation slugging method, risperidone     

Awareness and Acceptance of Evolution and Evolutionary Medicine Among Medical Students in Pakistan

Evolutionary medicine is a perspective on medical sciences derived through application of theory of evolution to aid in therapeutics. This study sought to determine the level of knowledge and acceptance of evolutionary theory in medical students along with their attitude toward teaching evolutionary medicine as a part of their undergraduate course. Factors that are likely to cause difficulty in teaching evolutionary medicine were also identified. A cross-sectional study was carried out at Army Medical College, National University of Sciences and Technology, Pakistan in which 299 medical students were selected by nonprobability convenient sampling technique to participate in the study. Participants’ views were obtained by a structured questionnaire comprised of three sections: appreciation of evolutionary medicine, acceptance of evolutionary theory, knowledge of evolutionary theory. Medical students had a low acceptance [mean measure of acceptance of theory of evolution (MATE) = 58.32] and a low knowledge (mean score of 5.20 out of a total ten marks). Students believed that religious beliefs, lack of resources, and an existent extensive medical curriculum would cause difficulty in imparting such an education despite its potential to improve medical research and clinical practice. Only 37.2% agreed that the subject should be taught in medical schools as an individual subject.     

Tuftsin-mediated immunoprophylaxis against an isolate of Aspergillus fumigatus shows less in vivo susceptibility to amphotericin B

In the present study, we evaluated the immunopotentiating efficacy of tuftsin against experimental murine aspergillosis in both normal and immunodebilitant BALB/c mice. The animals were challenged with an isolate of Aspergillus fumigatus (1x10(8) cfu/mouse) that was showing less susceptibility to lower doses of amphotericin B in murine animal model. Co-administration of the immunomodulator tuftsin and liposomised-amphotericin B was found to be highly effective in the treatment of systemic infection of A. fumigatus in both immunocompetent and leukopenic mice. Moreover, pre-treatment of mice with liposomised-tuftsin prior to challenging them with A. fumigatus infection and subsequent treatment with tuftsin-bearing liposomised-amphotericin B was found to be extremely efficient in successful elimination of fungal pathogen. In another set of experiments, tuftsin-mediated antigen-specific memory antibody response was also assessed by immunizing the animals with A. fumigatus cytosolic antigen. The animals that received a booster 150 days after the first immunization with tuftsin-liposomes-antigen showed more resistance to A. fumigatus infection in comparison with the na?ve animals.     

Seeing is believing: Applications for nanotechnology in medical imaging and drug discovery

In recent years, progress has been made on in both micro- and nano-sized materials. At the same time, the advances in biology, specifically in genomics, have provided us with a wealth of information that can now be put into research applications and hopefully clinical practice. In our research center in Niskayuna, NY, we have been working on advanced technologies and novel approaches in both areas. Here we show several examples of how we have addressed different topics in our research. In addition, we will show, how we are combining nanotechnology with advanced biology. In particular, we will show examples of using nanoparticles for different applications in vitro and in vivo. We will also show the context for both technology areas and the applications of strategic importance.     

The inhibitory effect of calumenin on the vitamin K-dependent gamma-carboxylation system. Characterization of the system in normal and warfarin-resistant rats

The vitamin K-dependent gamma-carboxylation system is responsible for post-translational modification of vitamin K-dependent proteins, converting them to Gla-containing proteins. The system consists of integral membrane proteins located in the endoplasmic reticulum membrane and includes the gamma-carboxylase and the warfarin-sensitive enzyme vitamin K(1) 2,3-epoxide reductase (VKOR), which provides gamma-carboxylase with reduced vitamin K(1) cofactor. In this work, an in vitro gamma-carboxylation system was designed and used to understand how VKOR and gamma-carboxylase work together as a system and to identify factors that can regulate the activity of the system. Results are presented that demonstrate that the endoplasmic reticulum chaperone protein calumenin is associated with gamma-carboxylase and inhibits its activity. Silencing of the calumenin gene with siRNA resulted in a 5-fold increase in gamma-carboxylase activity. The results provide the first identification of a protein that can regulate the activity of the gamma-carboxylation system. The propeptides of vitamin K-dependent proteins stimulate gamma-carboxylase activity. Here we show that the factor X and prothrombin propeptides do not increase reduced vitamin K(1) cofactor production by VKOR in the system where VKOR is the rate-limiting step for gamma-carboxylation. These findings put calumenin in a central position concerning regulation of gamma-carboxylation of vitamin K-dependent proteins. Reduced vitamin K(1) cofactor transfer between VKOR and gamma-carboxylase is shown to be significantly impaired in the in vitro gamma-carboxylation system prepared from warfarin-resistant rats. Furthermore, the sequence of the 18-kDa subunit 1 of the VKOR enzyme complex was found to be identical in the two rat strains. This finding supports the notion that different forms of genetic warfarin resistance exist.