Absence of cancer-associated changes in human fibroblasts immortalized with telomerase.

The ectopic expression of telomerase in normal human cells results in an extended lifespan, indicating that telomere shortening regulates the timing of cellular senescence. As telomerase expression is a hallmark of cancer, we investigated the long-term effects of forced expression of human telomerase catalytic component (hTERT) in normal human fibroblasts. In vitro growth requirements, cell-cycle checkpoints and karyotypic stability in telomerase-expressing cells are similar to those of untransfected controls. In addition, co-expression of telomerase, the viral oncoproteins HPV16 E6/E7 (which inactivate p53 and pRB) and oncogenic HRAS does not result in growth in soft agar. Thus, although ectopic expression of telomerase in human fibroblasts is sufficient for immortalization, it does not result in changes typically associated with malignant transformation.

Ral GTPases contribute to regulation of cyclin D1 through activation of NF-kappaB.

Ral GTPases have been implicated as mediators of Ras-induced signal transduction from observations that Ral-specific guanine nucleotide exchange factors associate with Ras and are activated by Ras. The cellular role of Ral family proteins is unclear, as is the contribution that Ral may make to Ras-dependent signaling. Here we show that expression of activated Ral in quiescent rodent fibroblasts is sufficient to induce activation of NF-kappaB-dependent gene expression and cyclin D1 transcription, two key convergence points for mitogenic and survival signaling. The regulation of cyclin D1 transcription by Ral is dependent on NF-kappaB activation and is mediated through an NF-kappaB binding site in the cyclin D1 promoter. Ral activation of these responses is likely through an as yet uncharacterized effector pathway, as we find activation of NF-kappaB and the cyclin D1 promoter by Ral is independent of association of Ral with active phospholipase D1 or Ral-binding protein 1, two proteins proposed to mediate Ral function in cells.

Minimum sample size and sampling time requirements for assessment of rifampicin bioequivalence from FDC formulations.

SETTING: The WHO- and IUATLD-recommended protocol for rifampicin (RMP) bioequivalence utilises 20-22 volunteers and 8 h, whereas the requirement of other regulatory authorities is 12 volunteers with a 24 h sampling schedule. Differing sampling size and time requirements may change the outcome of RMP bioequivalence. OBJECTIVE: To determine the minimal sample size and time required to assess RMP bioequivalence from FDC formulations. DESIGN: Bioequivalence studies were conducted that fulfilled the criteria of the WHO and Indian regulatory protocols. From earlier studies, retrospective pharmacokinetic evaluation, power of the test and bioequivalence limits were also calculated using 8-22 volunteers and sampling points of 8-24 h. Pharmacokinetic and statistical evaluations from three representative studies showing low, moderate and high intra-subject variability are given to determine minimum requirements for RMP bioequivalence. RESULT: It was found that a sampling schedule up to 8 h was sufficient to compare the absorption process of RMP. There was no influence of reduced sample size on bioequivalence estimates of RMP that showed low or moderate variability. However, in a study showing higher variation, a sample size of 14-16 subjects was found to be optimal. CONCLUSION: It is possible to reduce the sample size requirement for determination of RMP bioequivalence using the WHO protocol.

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.

Establishment of a reference formulation for bioequivalence assessment of rifampicin-containing FDCs: an essential step towards improving tuberculosis treatment.

SETTING: Selection of a reference product for bioequivalence studies of rifampicin (RMP) in prequalifying fixed-dose combinations (FDC) for worldwide distribution through the WHO is critical. OBJECTIVE: To investigate the feasibility of establishing FDC formulations as reference products for bioequivalence studies of RMP in prequalification programmes. DESIGN: A biostudy was conducted as an open, two-period randomised cross-over trial. Two three-drug FDCs containing RMP, isoniazid and ethambutol hydrochloride were administered to a group of 22 volunteers with a wash-out period of 1 week. Plasma samples were collected and analysed for the concentration of RMP and desacetyl-RMP, a major active metabolite of RMP, up to 24 h. Pharmacokinetic parameters of RMP were calculated: Cmax, AUC0-24, Tmax, kel and absorption efficiencies. RESULTS: No significant difference was observed between the administered formulations with respect to the major pharmacokinetic parameters Cmax, Tmax and AUC0-24 when evaluated by parametric (two-way ANOVA) and non-parametric (Hauschke's analysis) statistical analysis. The concentration of RMP falls within the reported acceptable therapeutic range. CONCLUSION: FDCs can be developed as a reference product for bioequivalence studies.

Plasma pooling: utility in expediting bioequivalence assessment of rifampicin-containing fixed-dose combinations.

To improve the rapidity of the registration process of rifampicin (RMP) containing fixed-dose combination (FDC) formulations, a plasma pooling methodology was used to increase the throughput of bioanalysis of plasma samples from bioequivalence trials of FDCs. Plasma samples of a biostudy were analysed for RMP using traditional analysis methods as well as a plasma pooling method (volunteer and time pooling). Both methods produced similar results, with less than 15% variability in both volunteer and time pooling. The plasma pooling method for bioanalysis was validated. Further studies are required to identify and reduce the percentage variability.

Isolation of effector-selective Ras mutants by yeast two-hybrid screening.

Ras mutants displaying selective target interactions will often display partial loss of function phenotypes when expressed in cells. Thus the isolation of mutations in Ras and Ras family members has proved to be a productive approach for testing the requirement of specific target interactions to mediate downstream responses. The procedures outlined here greatly simplify the isolation of such mutants, and it is hoped will contribute to a better understanding of Ras effector function.

The WHO simplified study protocol in practice: investigation of combined formulations supplied by the WHO.

SETTING: The benefits of fixed-dose combination (FDC) formulations of rifampicin, isoniazid and pyrazinamide over individual formulations are well recognised. OBJECTIVES: To evaluate the comparative bioavailability of antituberculosis drugs in FDC formulations and the same doses in separate formulations of antituberculosis drugs, using a simplified protocol developed by the World Health Organization (WHO). METHODS: Twenty healthy volunteers were included in the study and evaluated for bioequivalence of rifampicin in a cross-over experimental design. After administration of drugs the plasma concentration of rifampicin and desacetyl-rifampicin was measured repeatedly up to 8 hours in both plasma and urine. Various pharmacokinetic parameters of rifampicin, such as Cmax, Tmax, elimination rate constant, area under the curve (AUC) up to 8 hours and absorption efficiency were calculated. RESULTS: No significant differences were observed between the FDCs and separate formulations when Cmax, Tmax, AUC and absorption efficiencies were compared by parametric test and Hauschke's analysis. CONCLUSION: The WHO simplified protocol is suitable for evaluating bioequivalence of antituberculosis drugs.

Evaluation of rifampicin bioequivalence in fixed-dose combinations using the WHO/IUATLD recommended protocol.

For an accurate assessment of rifampicin bioequivalence from fixed-dose combinations (FDCs), and to reduce the time and cost constraints associated with bioequivalence studies, the World Health Organization and the International Union Against Tuberculosis and Lung Disease have developed a simplified screening protocol. This study was undertaken with the objective of testing the applicability of this protocol for all types of FDCs. Data were obtained for volunteers common to three studies, and pharmacokinetic parameters were evaluated by different statistical tests. From the results, it has been demonstrated that the simplified screening protocol is suitable for evaluating the bioequivalence of rifampicin in all the types of FDCs available on the market.

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.

Combined chemical-enzymic synthesis of a dideoxypentasaccharide for use in a study of the specificity of N-acetyl-glucosaminyltransferase-III.

The biantennary oligosaccharide glycoside beta-D-GlcpNAc-(1----2)-alpha-D- Manp-(1----3)- [beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----6)]-beta-D-Manp- OR is a potential substrate for N-acetylglucosaminyltransferases (GlcNAcTs) III-V. The dideoxypentasaccharide glycoside beta-D-GlcpNAc-(1----2)-4- deoxy-alpha-D-lyxo-Hexp-(1----3)- [beta-DGlcpNAc-(1----2)-6-deoxy-alpha-D-Manp-(1----6)] beta-D-Manp-O(CH2)7CH3 (5), where the hydroxyl groups that would be acted on by GlcNAcTs IV and V have been removed, was prepared as a possible specific acceptor for GlcNAcT-III. The strategy involved the chemical synthesis of beta-D-GlcpNAc-(1----2)-4-deoxy-alpha-D-lyxo-Hexp-(1----3)-] 6- deoxy-alpha-D-Manp-(1----6)]-beta-D-Manp-O)CH2)7CH3 and then addition of the last GlcpNAc residue using partially purified GlcNAcT-II from rabbit liver. Preliminary results, using detergent extracts from rat kidney, indicate that 5 is an acceptor for a GlcNAcT whose identity remains to be established.

Use of N-acetylglucosaminyltransferases I and II in the preparative synthesis of oligosaccharides.

8-Methoxycarbonyloctyl 3,5-di-O-(alpha-D-mannopyranosyl)-beta-D-mannopyranoside (1) has been synthesised chemically. Compound 1 is a substrate for N-acetylglucosaminyltransferase-I (GlcNAcT-I), which transfers a beta-D-GlcpNAc residue from UDP-GlcpNAc to position 2 of the alpha-Man-(1----3) unit to produce 2. In turn, the tetrasaccharide 2 is an acceptor for GlcNAcT-II which, in the presence of UDP-GlcpNAc, converts 2 into 8-methoxycarbonyloctyl 3,6-di-O-[2-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-alpha-D- mannopyranosyl]-beta-D-mannopyranoside (3). These conversions were carried out on a 50-100 mg scale using enzyme preparations obtained from rabbit liver in a single step by affinity chromatography.

Bioequivalence assessment of rifampicin, isoniazid and pyrazinamide in a fixed dose combination of rifampicin, isoniazid, pyrazinamide and ethambutol vs. separate formulations.

Depending on the patient category, tuberculosis requires treatment with 3 to 5 drugs which means that patient's compliance to therapy may not be optimal. To increase patient's adherence to treatment schedules, these drugs can be given as single drug preparations or fixed dose combinations (FDCs) of 2 or more drugs in a single formulation. However, an important issue associated with a rifampicin-containing FDC is its quality. Hence, to avoid spurious formulations entering the market, the World Health Organization and the International Union Against Tuberculosis and Lung Disease have recommended FDCs only of proven bioavailability. In this study, the relative bioavailability of rifampicin, isoniazid and pyrazinamide was assessed in a group of 14 healthy male subjects using the FDC tablet containing 4 drugs versus separate formulations at the same dose levels. The study was designed as an open, crossover trial. A total of 9 blood samples were collected over a period of 24 h. The concentration of rifampicin, its main metabolite desacetyl rifampicin, isoniazid and pyrazinamide in plasma were assessed using HPLC analysis. The pharmacokinetic parameters AUC(0-24) and Cmax were subjected to parametric and non-parametric statistical tests at 90% confidence interval. In addition, time to reach peak concentration (tmax), elimination rate constant (Kel) and terminal elimination half-life (t1/2) for each drug were also calculated. It was concluded that the FDC tablet containing 4 drugs is bioequivalent to separate rifampicin, isoniazid and pyrazinamide formulations at the same dose levels.

Immune status in ataxia telangiectasia.

Immune status of 22 patients of ataxia telangiectasia was studied over a period of 8 yr (mean age of patients: 9.5 +/- 3 yr; 9 of 22 were siblings). Low T-cell number was observed in 14 of 19 patients but the response to PHA challenge done in 10 patients was normal and migration inhibition to BCG antigen was positive in 6 of 6 patients. IgM defect was seen in 2 out of 18 patients and serum IgA was deficient in 10 out of 18 patients. Salivary IgA was also absent in these children. Four children had high spontaneous NBT reduction. None of the patients had lymphoma, leukemia or any other malignancy at the time of presentation. Candida killing was normal in all patients. The presenting feature related to the CNS in almost all children and gross infections were not seen.

Bioequivalence of rifampicin when administered as a fixed-dose combined formulation of four drugs versus separate formulations.

A bioequivalence study of the antitubercular drug rifampicin in a four-drug combination (rifampicin, isoniazid, pyrazinamide and ethambutol) and separate formulations of the drugs at the same dose levels was carried out in a group of 22 healthy male volunteers. The investigation was designed as an open crossover study. The drugs were administered once in individual formulations and once in a fixed-dose combination. The WHO-approved protocol was followed according to which six blood samples were collected over a period of 8 h for each volunteer and each experimental session. Pooled urine samples were also collected during the study. Rifampicin and desacetyl rifampicin concentrations in both plasma and urine samples were assessed. Various pharmacokinetic parameters such as AUC0-8 h, Cmax and Tmax were calculated for both rifampicin and desacetyl rifampicin. The results indicated that combined (the four-drug combination) and separate formulations are bioequivalent for rifampicin.

Bioequivalence study of rifampicin in fixed-dose combination of rifampicin and isoniazid vs. separate formulations.

The benefits of fixed-dose combinations of antituberculosis agents are well recognized by the World Health Organization (WHO) and International Union Against Tuberculosis and Lung Disease (IUATLD) and preferred over separate formulations. Therefore, a comparative bioequivalence study of rifampicin and isoniazid together in a fixed-dose combination and separately (at the same dose levels) was performed on a group of 12 healthy subjects. The study was designed as a single-blind, crossover experiment. Nine blood samples were collected from each subject over a period of 24 h. The plasma concentrations of rifampicin were assessed by a method developed in this laboratory. Various pharmacokinetic parameters of rifampicin such as AUC, Cmax, Tmax and t1/2 were also calculated. The study demonstrates that a fixed-dose combination (test formulation) and separate formulations (standard formulations) are bioequivalent for rifampicin.

Pharmacokinetic study of paclitaxel as a 3-hour infusion in an Indian population: 135 mg/m2 vs. 175 mg/m2.

The objective of this clinical study was to determine the pharmacokinetic parameters of paclitaxel at doses of 135 and 175 mg/m2 when given as a 3-hour infusion in an Indian population. Twelve cancer patients of both sexes participated in the study and a parallel experimental design was adopted for the assignment of doses to patients. A solid phase extraction technique was used for sample clean-up followed by a reversed phase HPLC assay for the analysis of paclitaxel in plasma samples. Pharmacokinetic parameters such as Cmax, AUC0-infinity, T1/2 beta, AUMC0-infinity, VSS, VZ and CLT were determined by a compartment model-independent method using a PCNONLIN package. Teff and AUCeff were also calculated and compared at the two doses by considering a plasma concentration of > or = 0.05 microM as threshold. The mean Cmax and AUC0-infinity values were 2.57 microM and 12.06 microM at the 135 mg/m2 dose level while at the 175 mg/m2 dose the values increased to 4.96 microM and 9.52 microM.h/l, respectively. It was found that the 135 mg/m2 dose resulted in greater mean CLT and VSS values than the 175 mg/m2 dose. The disposition of paclitaxel was found to be nonlinear and the pertinent pharmacokinetic parameters were comparable to those from previous clinical studies. It was concluded from the present study that further clinical trials of paclitaxel alone or in combination with other drugs should be undertaken cautiously, taking into consideration its nonlinear pharmacokinetics which necessitate proper adjustment of the infusion schedule and/or dose to avoid any adverse consequences to the patient.

Immunoglobulin deficiency.

Twenty three patients with primary immunoglobulin(Ig) deficiency were seen during the last ten years. Nine had hypogamma globulinemia (hypo-Ig) and the rest, selective Ig deficiency. Most were in pediatric age group. There was preponderance of males with only one female. Clinical symptoms pertaining to gastrointestinal and sinupulmonary infections were most common. Complete absence of B cells was not observed in any patient with hypogammaglobulinemia. They could be typed as physiological in one patient, X-linked immunodeficiency in 2 patients and common variable immunodeficiency in the remaining six. Three patients with selective IgA deficiency were above 20 years of age. Two had only secretory IgA deficiency, confirmed by jejunal fluid examination and the rest had both secretory and serum IgA deficiency. Low IgM was seen in one patient. We see a spectrum of immunoglobulin deficiencies varying from subtle defects like absence of secretory IgA only, to severe depletion of all immunoglobulins. Therapy is still not ideal due to economic reasons.

Protein translation elongation factor-1 alpha from Trypanosoma brucei binds calmodulin.

The following study examines the calmodulin (CaM) branch of the calcium signal pathway in the protozoan parasite Trypanosoma brucei. To accomplish this goal, a subset of cytosolic CaM-binding proteins (CaMBPs) was partially purified by a combination of DE52 and CaM-Sepharose affinity chromatography. Monoclonal antibodies (CBP-KK1) were used to clone the cDNA for a 53-kDa CaMBP from a lambda ZAP expression library of the metacyclic stage of T. brucei. The deduced amino acid sequence of clone CaMBP-12B had 81% overall amino acid identity to the translation elongation factor-1 alpha (EF-1 alpha) from Euglena gracilis and 76% identity to the rabbit EF-1 alpha. Rabbit EF-1 alpha was recognized by CBP-KK1 and was shown to bind to CaM-Sepharose in a calcium-dependent manner. By contrast, the complex of EF-1 alpha beta gamma did not bind CaM-Sepharose. A heterobifunctional sulfhydryl derivative of CaM (N-succinimidyl 3-(2-pyridyldithio)propionate-CaM) formed reducible cross-links with EF-1 alpha in solution but not with the complex of EF-1 alpha beta gamma. Biotinylated CaM bound weakly to trypanosome and rabbit EF-1 alpha in a gel overlay assay. This report demonstrates the direct interaction between CaM and the translation elongation factor EF-1 alpha.