Ab-initio study of the structural and electronic properties of very thin silver nanowires

An ab initio study of the energetics, structural, and electronic properties of thin silver nanowires of Ag(n) with n = 1 to 6 has been made in density functional theory in local density approximation. The present study reveals that all of the wires are stable except the wire with 3 silver atoms per unit cell. The linear chain is comparatively less stable. The binding energies of the most stable wires lie in the range 2.60-3.18 eV/atom with maximum values for the 5-Ag pentagonal and the two 6-Ag (hexagonal and pyramidal) nanowires. The nearest neighbor Ag-Ag separations in all of the most stable wires up to n=6 is quite the same and is equal to 2.634 +/- 0.03 A. For the most stable 6-Ag pyramidal wire, the bond length increases to 2.75 or 2.81 A. The cross-sectional dimension of these wires are around 5.0 A. All of the studied silver wires are metallic. A majority of the sd mixed states cross the Fermi level. The density of state is maximum for the 5-Ag pentagonal and 6-Ag pyramidal nanowires, and so is the number of channels (5 or 6) crossing the E(F) which would be available for high electrical conduction.

Analysis of human leukocyte antigen (HLA)-G polymorphism in normal women and in women with recurrent spontaneous abortions

Human leukocyte antigen (HLA)-G is a non-classical class I antigen. It has limited expression, but is high at the foetomaternal interface. This unique expression pattern of HLA-G suggests that it might be important for survival of the foetus during pregnancy. In the present study, 120 women with recurrent spontaneous abortions (RSA) and 120 fertile control women were genotyped for the HLA-G locus. This is the first report describing HLA-G polymorphism in normal fertile and RSA women from India. The allele HLA-G*010103 was higher in women with recurrent foetal losses. Interestingly, the HLA-G*010105 and G*010108 alleles were totally absent in normal fertile women but present in RSA women with frequencies of 1.7% and 0.4%, respectively. Allele G*010107 was absent in both the groups. The frequency of the null allele G*0105N was high (13.8%) in our population as compared to other world populations. Our data support the hypothesis that HLA-G polymorphism may contribute to recurrent foetal loss.

Structural and vibrational properties of small carbon clusters

An ab-initio comprehensive study of the stability and structural and vibrational properties of small carbon clusters, CN for N = 1-10, has been made. We use a self-consistent pseudopotential method within density functional theory in the generalized gradient approximation considering spin polarization. The estimated values of binding energies for the various clusters are overestimated in the non-spin-polarized calculations. On the other hand, for the spin-polarized case, the computed binding energies are in very good agreement with the available experimental data. Also, the calculated vibrational frequencies for CN, N = 2-5, are in reasonable agreement with the available experimental values.

Chitosan hydrochloride based microspheres of albendazole for colonic drug delivery

Microspheres of chitosan hydrochloride (CH) were prepared in order to deliver albendazole specifically into the colon. Microspheres were prepared by an emulsion method using different ratios of drug and CH (1:1 to 1:5), agitation speeds (500 to 1500 rpm) and concentrations of glutaraldehyde in toluene as the cross-linking agent (0.25 to 1.0% w/v). The effect of polymer concentration, stirring rate and concentration of cross-linking agent on the particle size and drug loading was studied. With an increase in CH concentration, the average particle size was increased. Increased agitation speed reduced the size of the microspheres but higher agitation speed resulted in irregularly shaped microspheres. Increasing the concentration of cross-linking agent produced more regularly shaped microspheres of smaller size. The drug loading was highest at a drug: CH ratio of 1:3, stirring speed 1000 rpm and 0.75% w/v concentration of cross-linking agent. The effect of CH concentration on in vitro drug release from the microspheres was evaluated in simulated g.i.t fluids. A comparative in vitro drug release study of the optimized formulation was carried out in simulated colonic fluid, with and without 2% rat caecal content. The drug release in 24 h was 48.9% in colonic fluid without rat caecal content, and 76.5% in colonic fluid with rat caecal contents.

Determination of rifampicin bioequivalence in a three-drug FDC by WHO and indian protocols: effect of sampling schedule and size

SETTING

To promote the quality assurance of fixed-dose combination (FDC) formulations, the World Health Organization (WHO) has prepared a convenient simplified protocol for the determination of rifampicin (RMP) bioequivalence. During the development of this protocol, it was proved that sampling time up to 8 h can determine the rate and extent of RMP absorption. However, this protocol utilises 20 volunteers in contrast to other local regulatory requirements of a minimum of 12 volunteers. The different sample sizes utilised in these protocols may affect the sensitivity of the bioequivalence outcome.

OBJECTIVE

To determine the effect of sampling size and schedule on RMP bioequivalence when two different protocols are used.

DESIGN

A bioequivalence trial was conducted with a study design of 20 volunteers and 24 h sampling time, which fulfils the requirements of both the WHO and Indian regulatory protocols. Pharmacokinetic and statistical analysis was done by stepwise reduction in sample size and schedule.

RESULT

Bioequivalence limits of RMP were unaffected by a reduced sample size of 12 volunteers and 8 h sampling time.

CONCLUSION

Minimising sample size after validation for borderline and poor quality FDC formulations can further reduce the cost of conducting bioequivalence trials.

Management of visceral leishmaniasis: Indian perspective

Diagnosis and treatment of Indian visceral leishmaniasis (VL) is extremely unsatisfactory. For diagnosis, demonstration of parasites in splenic/marrow smears remains the gold standard, though k39 rapid strip test is a useful method in regions where access to parasite demonstration is difficult. pentavalent antimony remains the mainstay for the treatment of all forms of leishmaniasis globally; however, development of large-scale antimony resistance in Bihar has necessitated search for alternative drugs. Amphotericin B is the most effective, though toxic, drug for patients with refractory VL. Lipid formulations of amphotericin B, though safe and effective, are too expensive to be useful for poor patients of this region. These hold advantage as large quantity of the drug can safely be given over a short period of time, thus leading to a decrease in the hospital stay to a few days instead of several weeks. Oral miltefosine, an alkyl phospholipid, has recently been approved and marketed in India for the treatment of VL. Miltefosine cures 94% patients with VL if given in a daily dose of 50-100 mg for 28 days. Most common adverse events are mild vomiting and diarrhea. Paromomycin, an amino glycoside, is undergoing a pivotal phase-III clinical trial, and is likely to be approved and available to patients with VL at an affordable cost. To protect the already scarce inventory of antileishmanial drugs, it is time that combination chemotherapy is introduced for the treatment of VL in India.

T1 and M1 polymorphism in glutathione S-transferase gene and coronary artery disease in North Indian population

BACKGROUND

DNA damage has been found to play an important role in atherosclerosis and coronary artery disease. Genetic polymorphisms of the genes coding for enzymes involved in the metabolism of genotoxins result in different phenotypes with respect to their ability to detoxify these agents. In the present study the contribution of the polymorphism in the glutathione S-transferase gene to the development of coronary artery disease has been investigated.

METHODS

One hundred and ninety seven angiographically proven patients with coronary artery disease and one hundred and ninety eight age-matched controls were genotyped for glutathione S- transferase polymorphism by polymerase chain reaction. Genotype frequencies were compared in patients and controls by Chi-square test. Binary logistic regression was used to examine the relationship between genotype and disease, incorporating other variables into the model.

RESULTS

GSTT1 null genotype was significantly decreased in patients with coronary artery disease. No significant association was found with GSTM1 genotypes. No such association was seen with smokers.

CONCLUSION

Null genotype of GSTT1 is protective against coronary artery disease in our population.

Role of 14-bp deletion in theHLA-Ggene in the maintenance of pregnancy

Differential expression of human leukocyte antigens (HLAs) on trophoblast has been the focus of many studies, specially on extravillous cytotrophoblast cells, which migrates into the maternal uterine tissues. These invading cells do not express classical major histocompatibility complex class I (-A and -B) and class II molecules, along with low expression of HLA-C. HLA-G is the predominantly expressed antigen along with HLA-E. Hence, it is believed that expressed antigens may be involved in materno-fetal tolerance. In the present study, we have studied 14-bp deletion polymorphism in the exon-8 of the non-classical HLA-G antigen. There was no difference in the frequency of deletion/insertion polymorphism in fertile normal women and recurrent spontaneous abortion (RSA) women. However, the number of heterozygotes (-14b/+14b) were increased in RSA women. The probable mechanism for the increase of heterozygotes in recurrent fetal loss is discussed in light of soluble HLA-G.

In vitro analysis of rifampicin and its effect on quality control tests of rifampicin containing dosage forms

The chemical stability of rifampicin both in solid state and various media has widely been investigated. While rifampicin is appreciably stable in solid-state, its decomposition rate is very high in acidic as well as in alkaline medium and a variety of decomposition products were identified. The literature reports on highly variable rifampicin decomposition in acidic medium. Hence, the objective of this investigation was to study possible reasons responsible for this variability. For this purpose, filter validation and correlation between rifampicin and its degradation products were developed to account for the loss of rifampicin in acidic media. For analysis of rifampicin with or without the presence of isoniazid, a simple and accurate method was developed using high performance chromatography recommended in FDC monographs of the United States Pharmacopoeia. Using the equations developed in this investigation, the amount of rifampicin degraded in the acidic media was calculated from the area under curve of the degradation products. Further, it was proved that in a dissolution study, the colorimetric method of analysis recommended in the United States Pharmacopoeia provides accurate results regarding rifampicin release. Filter type, time of injection as well as interpretation of data are important factors that affect analysis results of rifampicin in in vitro studies and quality control.

In vitro evaluation of fixed dose combination tablets of anti-tuberculosis drugs after real time storage at ambient conditions

Rifampicin exhibits variable bioavailability from solid oral dosage forms and this problem is more apparent when it is formulated as fixed dose combination (FDC) in presence of other first-line anti-tuberculosis drugs. To determine the cause of variable bioavailability, the aging effect on physical and chemical performance of rifampicin from FDC formulations after real time storage at the ambient conditions was investigated. For this purpose, six FDC formulations from different manufacturers were stored at ambient conditions (20-35 degrees C, with no control of humidity) in the final packing for a period of 16-38 months and its in vitro quality control tests for rifampicin were compared with the initial performance of these tablets. None of the formulations have shown significant weight gain/loss and the assay values were within the pharmacopeial limits when evaluated by a stability indicating method. Further storage had no effect on physical performance of FDC tablets as indicated by unaltered dissolution profiles. Formulation reevaluation after real time storage at the ambient conditions for 16-38 months indicated that rifampicin containing FDC formulations are stable throughout its shelf life and instability is not a cause of variable bioavailability.

Quality control of anti-tuberculosis fixed-dose combination formulations in the global market: an in vitro study

OBJECTIVE

To determine the quality, and especially the dissolution properties of rifampicin, of fixed-dose combination (FDC) formulations of anti-tuberculosis agents manufactured by major market holders in the anti-tuberculosis sector and supplied for use in national tuberculosis control programmes.

METHODS

Dissolution studies were performed for four formulations supplied by four different manufacturers in four dissolution media (0.1N and 0.01N HCl, phosphate buffer [PB] and 20% vegetable oil in PB), at four different agitation rates using USP apparatus II. The formulations were subjected to 4-week accelerated stability studies (40 degrees C / 75% RH) and evaluated for physical, chemical and dissolution stability.

RESULTS

The formulations tested complied with pharmacopeial quality control (QC) tests. The extent of rifampicin release was independent of dissolution medium; however, a slight decrease in the dissolution rate was observed in two products. More than 75% of drug was released in 45 min at all agitation intensities except 30 rpm, and 20% oil in the medium reflected fed state. Formulations were stable in the packaging conditions recommended by the manufacturer for at least 4 weeks.

CONCLUSIONS

The formulations tested passed the QC tests and were found to be stable. A decrease in the rate, although not the extent, of dissolution necessitated multiple point dissolution in gastric and intestinal pH conditions to ensure consistency in in vivo bioavailability.

Bullous erythema nodosum leprosum: a case report from Nepal

A patient with lepromatous leprosy, while on WHO multidrug therapy (MDT) for multibacillary disease, was diagnosed as having dapsone syndrome with recurrent episodes of bullous lesions on the lower extremities for 4-5 years. The lesions were associated with high-grade fever. Examination revealed multiple hypopigmented macules on the limbs. Multiple atrophic scars were also found on the buttocks and lower limbs. Bilateral ulnar, radial cutaneous and lateral popliteal nerves were thickened. On day 10 of WHO-MB-MDT he developed a flaccid bulla on the lower leg. Skin slit smear showed a bacterial index (BI) of 3+ and the histopathology was consistent with type II reaction. High dose corticosteroid therapy was started but he continued to have new lesions, and was therefore referred to a centre where thalidomide was available. Clinical response was good and he remained symptom-free after gradual reduction in dosage. ENL should be differentiated from bullous drug reactions, pemphigus vulgaris, bullous pemphigoid and other blistering diseases.

Significance of chimerism in hematopoietic stem cell transplantation: new variations on an old theme

The main goal of post-transplantation monitoring in hematopoietic stem cell transplantation (HSCT) is to predict negative events, such as disease relapse, graft rejection and graft-versus-host disease, in order to intervene with appropriate therapy. In this context, chimerism analysis is an important method in monitoring post HSCT outcome. Mixed chimerism (MC) is mainly evaluated to define engraftment and relapse. Detection of MC is a prerequisite in both myeloablative and nonmyeloablative HSCT, in order to assess the graft status and decide later therapeutic strategies such as donor lymphocyte infusion. In this review, we discuss various techniques including erythrocyte phenotyping, cytogenetic analysis, fluorescent in situ hybridization, restriction fragment length polymorphism, STR/VNTR analysis and real-time quantitative PCR, along with the various methods used to detect minimal residual disease (MRD) in different diseases such as chronic myeloid leukemia, acute myelomonocytic leukemia or acute lymphoblastic leukemia. The review mainly highlights the optimal methodological approach, which needs to be informative, sensitive and quantitatively accurate for MC detection. Future of post HSCT graft monitoring lies in the selection of the most accurate and sensitive technique to determine both MC and MRD. Such an approach would be helpful in not only determining relapse or rejection, but also in ascertaining various responses to different treatment modalities.

Preparation and characterization of reverse micelle based organogels of piroxicam

The solubilization of piroxicam to increase transdermal permeation rate was attempted by incorporating the drug in reverse micelle systems consisting of lecithin/isopropyl myristate/water [RMS-1] and sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane/water [RMS-2]. The change in polarity of water present in the water pool formed by reverse micelles resulted in a solubilization of piroxicam. These systems were used for the formation of reverse micellar organogels RMO-1 and RMO-2 by means of either varying hydration ratio (Wo) or by addition of a macromolecule, e.g. gelatin, into the system or by taking both the parameters in consideration. These systems were evaluated for physical properties, toxicology, in vitro and in vivo transdermal permeation. Significant (p < 0.01) inhibition of carrageenan induced rat paw oedema was observed for products RMO-1 and RMO-2 and a marketed transdermal product after 3 h.

Fixed dose combinations for tuberculosis: Lessons learned from clinical, formulation and regulatory perspective

Worldwide, tuberculosis (TB) remains one of the most important communicable diseases in terms of morbidity and mortality. Its control requires multi-drug therapy for at least six months, which could lead to patient non-compliance, failure of therapy and ultimately resulting in the emergence of drug resistance. Fixed dose combinations (FDCs) in TB therapy reduce the number of tablets to be consumed and thereby increase patient compliance with recommended treatment regimens. Thus, FDCs play a significant role in preventing the emergence of drug resistance and successful treatment. However, the quality of FDCs with respect to variable bioavailability and their registration requirements are major hurdles to their implementation in national TB control programs. It is anticipated that a large global market for FDCs will encourage large-scale production and increased competition, which in turn will result in FDCs at affordable prices. The Global Drug Facility (GDF), established by the World Health Organization (WHO), aims to ensure universal uninterrupted access to quality TB drugs for implementation of directly observed treatment short-course (DOTS) in resource-poor countries. In this program, four FDCs were accepted as the drugs of first choice because of their obvious advantages in controlling TB. This demands the necessity of addressing quality and registration requirements of FDCs systematically. In light of this current knowledge on anti-TB FDCs, their dosage, combinations, available clinical studies and the experiences with TB therapy has been discussed in this article, which should serve as lessons for selection of appropriate FDCs for other diseases such as malaria and AIDS.

Absence of factor V Leiden (G1691A) mutation, FII G20210A allele in coronary artery disease in North India

BACKGROUND

Interaction between various genetic and environmental factors is associated with coronary artery diseases (CADs). Factor V Leiden mutation (FVL) and FII G20210A polymorphism are two recently described genetic factors with a propensity towards venous thrombosis, however, with a doubtful role in coronary artery disease and myocardial infarction.

AIM

Present study was conducted to assess the relationship of both these factors in coronary artery disease in population from North India.

SETTING AND DESIGN

Case control study.

MATERIAL AND METHODS

Two hundred angiographically proven coronary artery disease patients were studied to examine the association of Factor V Leiden mutation and FII G20210A mutation with coronary artery disease and myocardial infarction. Out of 200 patients, 51 had myocardial infarction. Two hundred controls were selected who were from north India and were also age and sex matched.

RESULTS AND CONCLUSIONS

Our results indicate that both these polymorphisms were totally absent in our population, therefore, these variants cannot be considered as independent risk factors or as a predictor for CAD. However, there is a need to confirm the above findings on patients from different populations from different parts of the country as there are reports which show that the incidence of Factor V Leiden varies from 1.3 % to 10%.

Toll-like receptor 9: modulation of recognition and cytokine induction by novel synthetic CpG DNAs

Bacterial and synthetic DNA containing unmethylated 2'-deoxyribo(cytidine-phosphate-guanosine) (CpG) dinucleotides in specific sequence contexts activate the vertebrate innate immune system. A molecular pattern recognition receptor, Toll-like receptor 9 (TLR9), recognizes CpG DNA and initiates the signalling cascade, although a direct interaction between CpG DNA and TLR9 has not been demonstrated yet. TLR9 in different species exhibits sequence specificity. Our extensive structure-immunostimulatory activity relationship studies showed that a number of synthetic pyrimidine (Y) and purine (R) nucleotides are recognized by the receptor as substitutes for the natural nucleotides deoxycytidine and deoxyguanosine in a CpG dinucleotide. These studies permitted development of synthetic YpG, CpR and YpR immunostimulatory motifs, and showed divergent nucleotide motif recognition pattern of the receptor. Surprisingly, we found that synthetic immunostimulatory motifs produce different cytokine induction profiles compared with natural CpG motifs. Importantly, we also found that some of these synthetic immunostimulatory motifs show optimal activity in both mouse and human systems without the need to change sequences, suggesting an overriding of the species-dependent specificity of the receptor by the use of synthetic motifs. In the present paper, we review current understanding of structural recognition and functional modulation of TLR9 receptor by second-generation synthetic CpG DNAs and their potential application as wide-spectrum therapeutic agents.