Biomedical subjects
Publications and source records attributed to R Ravi.
A facile ZrCl4-catalyzed direct allylation of the p-methoxyphenyl-alkyl/glycosyl carbinols at room temperature, and the conversion of the derived aryl-glycosyl-alkenes into hitherto unknown C-linked carbo-beta2-/gamma2-/delta2-amino acids is reported.
Lot quality assurance sampling (LQAS) with two-stage sampling plan was applied for rapid monitoring of coverage after every round of mass drug administration (MDA). A Primary Health Centre (PHC) consisting of 29 villages in Thiruvannamalai district, Tamil Nadu was selected as the study area. Two threshold levels of coverage were used: threshold A (maximum: 60%; minimum: 40%) and threshold B (maximum: 80%; minimum: 60%). Based on these thresholds, one sampling plan each for A and B was derived with the necessary sample size and the number of allowable defectives (i.e. defectives mean those who have not received the drug). Using data generated through simple random sampling (SRSI) of 1,750 individuals in the study area, LQAS was validated with the above two sampling plans for its diagnostic and field applicability. Simultaneously, a household survey (SRSH) was conducted for validation and cost-effectiveness analysis. Based on SRSH survey, the estimated coverage was 93.5% (CI: 91.7-95.3%). LQAS with threshold A revealed that by sampling a maximum of 14 individuals and by allowing four defectives, the coverage was >or=60% in >90% of villages at the first stage. Similarly, with threshold B by sampling a maximum of nine individuals and by allowing four defectives, the coverage was >or=80% in >90% of villages at the first stage. These analyses suggest that the sampling plan (14,4,52,25) of threshold A may be adopted in MDA to assess if a minimum coverage of 60% has been achieved. However, to achieve the goal of elimination, the sampling plan (9, 4, 42, 29) of threshold B can identify villages in which the coverage is <80% so that remedial measures can be taken. Cost-effectiveness analysis showed that both options of LQAS are more cost-effective than SRSH to detect a village with a given level of coverage. The cost per village was US dollars 76.18 under SRSH. The cost of LQAS was US dollars 65.81 and 55.63 per village for thresholds A and B respectively. The total financial cost of classifying a village correctly with the given threshold level of LQAS could be reduced by 14% and 26% of the cost of conventional SRSH method.
An isocratic, reversed-phase liquid chromatographic (RPLC) method was developed for the quantitative determination of Rivastigmine hydrogen tartrate, a cholinesterase inhibitor in bulk drugs and in pharmaceutical dosage forms. The developed method is also applicable for the related substance determination of Rivastigmine hydrogen tartrate in bulk drugs. The chromatographic separation was achieved on a Waters X Terra RP18 (250 mm x 4.6 mm, 5 microm) column using aqueous 0.01 M sodium-1-heptane sulphonate (pH: 3.0 with dilute phosphoric acid)-acetonitrile (72:28, v/v) as a mobile phase. The chromatographic resolution between Rivastigmine and its potential impurity, namely (S)-3-(1-dimethylaminoethyl) phenol (Imp 1) was found to be greater than four. Forced degradation studies were performed for Rivastigmine hydrogen tartrate bulk drug using acid (0.5 N hydrochloric acid), base (0.5 N sodium hydroxide), oxidation (3% hydrogen peroxide), heat (60 degrees C) and UV light (254 nm). No degradation was observed for Rivastigmine hydrogen tartrate except in base hydrolysis and the formed degradation product was found to be Imp 1. The mass balance of Rivastigmine hydrogen tartrate was close to 100 in all the stress conditions. The limit of detection (LOD) and limit of quantification (LOQ) of Imp 1 were found to be 100 and 300 ng/ml, respectively, for 10 microl injection volume. The percentage recovery of Imp 1 in bulk drug sample was ranged from 95.2 to 104.3. The active pharmaceutical ingredient was extracted from its finished dosage form (capsule) using water. The percentage recovery of Rivastigmine hydrogen tartrate was ranged from 99.2 to 101.3 and 98.6 to 101.5 in bulk and pharmaceutical formulation samples, respectively. Rivastigmine hydrogen tartrate sample solution and mobile phase were found to be stable for at least 48 h. The developed method was validated with respect to linearity, accuracy, precision, robustness and forced degradation studies prove the stability indicating power of the method.
Many countries have implemented mass drug administration programmes to eliminate lymphatic filariasis, but few have also implemented morbidity management programmes to help patients with chronic lymphoedema or hydrocele due to the infection. A study was carried out to assess current morbidity management by physicians in Pondicherry, India. Fifty-two physicians were interviewed, using a semi-structured questionnaire. For the management of hydrocele, all physicians referred hydrocele patients for surgery and 83% prescribed diethylcarbamazine (DEC). For the management of chronic lymphoedema patients, most doctors (75%) prescribed DEC and 56% mentioned the possibility of surgery. Only 10% of the physicians gave advice about limb hygiene, although recent research has shown the importance of hygiene measures to prevent further progression of lymphoedema. For the management of lymphoedema patients presenting with acute attacks, all physicians prescribed DEC and antibiotics and only 15% gave advice about limb hygiene. We conclude that limb hygiene instruction for home care should be more strongly emphasised to optimize management of lymphoedema patients in Pondicherry.
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The main strategy now adopted for the elimination of lymphatic filariasis (LF) is based on mass drug administrations (MDA). Annual administration of antifilarial drugs to 65%-80% of the population at risk of the disease is believed to be necessary if LF is to be eliminated, at least as a public-health problem, within a reasonable time-frame. To facilitate the development of drug-delivery strategies that are sufficient to ensure such high treatment coverages in large urban areas, a situation analysis was undertaken in the Indian city of Chennai. The subjects interviewed came from households with high, moderate, low or very low incomes. A lack of information on the prevalence and socio-economic impact of the disease meant that LF was not viewed as a major pubic-health problem in the study area, even though cases of elephantiasis and hydrocele were detected in 2%-8% and 7%-20% of the households investigated. Overall, 40% of the interviewees from very-low-income households and 78% of those from middle-income households knew that (the parasite causing) elephantiasis was transmitted by mosquitoes. Only 4% of the subjects from high-income areas and 1% of those from low-income areas were aware that filarial infection was a major cause of hydrocele. Most of the subjects (>55% of each of the four socio- economic groups considered) felt that they were not at risk of developing elephantiasis. When specifically asked, only 35% of the subjects from high-income households but 84% of those from low-income households said that they would be willing to consume tablets of an antifilarial drug (diethylcarbamazine) in MDA to eliminate LF. It is therefore unclear whether high-income households in urban areas should be included in MDA programmes. The interviewees felt that an intensive campaign of information, education, communication and advocacy would be necessary if an effective MDA-based programme were to be implemented. Drug distribution through the health services was the most preferred option.Clearly, factors such as a lack of appreciation of the socio-economic impact of LF, a general belief that the risk of elephantiasis is low, doubts about the need to include all sectors of the eligible population in MDA, and a common dependence on private practitioners make successful MDA against LF in urban areas a challenging task. On the positive side, however, an urban population is often covered by a huge network of colleges, private practitioners, non-governmental organizations and residents' associations, and such networks provide new opportunities in the development of effective drug-delivery strategies.
A new, simple chiral HPLC method was developed for the enantiomeric separation of Levetiracetam, [(S)-alpha-ethyl-2-oxo-pyrrolidine acetamide], an antiepileptic drug in pharmaceutical formulations and in bulk materials. Enantiomeric separation was achieved on a chiralpak AD-H column using a mobile phase consisting of hexane and isopropanol in the ratio (90:10, v/v) at a flow rate of 1.0 ml/min. The resolution between the enantiomers was found to be not less than 7 in the optimized method. Interestingly, unwanted enantiomer, namely R-alpha-ethyl-2-oxo-pyrrolidine acetamide ((R)-enantiomer), was eluted prior to its mirror image in the developed method. The developed method was found to be selective in the presence of related impurities of Levetiracetam, namely N-(1-carbamoyl-propyl)-4-chloro-butyramide (Imp-1) and 1-ethyl-2-oxo-1-pyrrolidine acetic acid (Imp-2), and also under exposed conditions of UV light and 60 degrees C. The limit of detection (LOD) and limit of quantification (LOQ) of (R)-enantiomer were found to be 900 and 2250 ng/ml, respectively, for 10 microl injection volume. The method precision for (R)-enantiomer at limit of quantification level was within 8% R.S.D. Calibration curve for (R)-enantiomer was linear over the studied ranges (2250-9000 ng) with correlation coefficient greater than 0998. The active pharmaceutical ingredient was extracted from its finished dosage form (tablet) using isopropanol. The percentage recoveries of (R)-enantiomer were ranged from 94.2 to 102.6 and from 93.5 to 104.1 in spiked bulk and formulation samples of Levetiracetam, respectively. Levetiracetam sample solution and mobile phase are found to be stable for at least 48 h. The developed method was found to be rugged and robust. The proposed method was found to be suitable and accurate for the quantitative determination of (R)-enantiomer in bulk drugs and commercial formulations. Chiralcel OD-H column can also be used as an alternative column for the above purpose.
OBJECTIVES: To study survival and late events after adjuvant chemotherapy in Stage 1 nonseminoma. METHODS: From 1978 to 1986, all patients had surveillance. From 1986, adjuvant chemotherapy (initially a 3-day regimen of etoposide, bleomycin, and cisplatin, but, more recently, bleomycin, Oncovin, and cisplatin) was offered to patients at a high risk of relapse (greater than 30%). RESULTS: A total of 382 patients with Stage 1 nonseminoma treated between 1978 and 2000 were reviewed. Of the 234 patients treated by surveillance, 71 (30%) had relapses (5 after 2 years), 6 died (2.6%) of germ cell cancer, and 3 developed second primary testicular cancer. Of the 148 men treated with adjuvant chemotherapy, 6 (4%) had relapses and 2 (1.4%) died of chemoresistant cancer. After one course of etoposide, bleomycin, and cisplatin, 3 (6.5%) of 46 developed a relapse; after two courses, 1 (3.6%) of 28 did so; and after bleomycin, Oncovin, and cisplatin every 10 days x2, 2 (2.7%) of 74 patients did so. Of the high-risk patients who were offered adjuvant treatment, 24% declined. As a consequence, the relapse rate of the surveillance patients only fell from 36% to 27% after the introduction of adjuvant therapy, although for the total cohort treated in the adjuvant era, the relapse rate was 16%. CONCLUSIONS: Adjuvant chemotherapy is more effective than retroperitoneal lymph node dissection for reducing the relapse risk in high-risk Stage 1 nonseminoma. However, given the uncertainty about the incidence of postchemotherapy late events, surveillance and retroperitoneal lymph node dissection remain justified alternatives. With positron emission tomography and laparoscopy showing increasing promise in these cases, quality-of-life studies and greater patient involvement in treatment selection are needed.
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Gene therapy of B16 tumors with a dominant-negative signal transducer and activator of transcription (Stat3) variant, designated Stat3beta, results in inhibition of tumor growth and tumor regression. Although only 10-15% of the tumor cells are transfected in vivo, the Stat3beta-induced antitumor effect is associated with massive apoptosis of B16 tumor cells, indicative of a potent bystander effect. Here, we provide evidence that blocking Stat3 signaling in B16 cells results in release of soluble factors that are capable of inducing apoptosis and cell cycle arrest of nontransfected B16 cells. RNase protection assays using multi-template probes specific for key physiological regulators of apoptosis reveal that overexpression of Stat3beta in B16 tumor cells induces the expression of the apoptotic effector, tumor necrosis factor-related apoptosis-inducing ligand. These in vitro results suggest that the observed in vivo bystander effect leading to tumor cell growth inhibition is mediated, at least in part, by soluble factors produced as a result of overexpression of Stat3beta in tumor cells.
TRAIL (tumour-necrosis factor-related apoptosis ligand or Apo2L) triggers apoptosis through engagement of the death receptors TRAIL-R1 (also known as DR4) and TRAIL-R2 (DR5). Here we show that the c-Rel subunit of the transcription factor NF-kappaB induces expression of TRAIL-R1 and TRAIL-R2; conversely, a transdominant mutant of the inhibitory protein IkappaBalpha or a transactivation-deficient mutant of c-Rel reduces expression of either death receptor. Whereas NF-kappaB promotes death receptor expression, cytokine-mediated activation of the RelA subunit of NF-kappaB also increases expression of the apoptosis inhibitor, Bcl-xL, and protects cells from TRAIL. Inhibition of NF-kappaB by blocking activation of the IkappaB kinase complex reduces Bcl-x L expression and sensitizes tumour cells to TRAIL-induced apoptosis. The ability to induce death receptors or Bcl-xL may explain the dual roles of NF-kappaB as a mediator or inhibitor of cell death during immune and stress responses.
Otto Warburg's classic treatise on the reprogramming of tumour metabolism from oxidative to glycolytic metabolism was published in London in 1930. Although the Warburg effect is one of the most universal characteristics of solid tumours, the molecular basis for this phenomenon has only recently been elucidated by studies indicating that increased expression of genes encoding glucose transporters and glycolytic enzymes in tumour cells is mediated by the transcription factors c-MYC and HIF-1. Whereas c-myc is a direct target for oncogenic mutations, expression of hypoxia-inducible factor 1 (HIF-1) is indirectly up-regulated via gain-of-function mutations in oncogenes and loss-of-function mutations in tumour suppressor genes that result increased HIF-1alpha protein expression and/or increased HIF-1 transcriptional activity in a cell-type-specific manner. As a result of genetic alterations and intratumoral hypoxia, HIF-1alpha is overexpressed in the majority of common human cancers relative to the surrounding normal tissue. In human breast cancer and brain tumours, HIF-1alpha overexpression is strongly correlated with tumour grade and vascularity.
The switch to an angiogenic phenotype is a fundamental determinant of neoplastic growth and tumor progression. We demonstrate that homozygous deletion of the p53 tumor suppressor gene via homologous recombination in a human cancer cell line promotes the neovascularization and growth of tumor xenografts in nude mice. We find that p53 promotes Mdm2-mediated ubiquitination and proteasomal degradation of the HIF-1alpha subunit of hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor that regulates cellular energy metabolism and angiogenesis in response to oxygen deprivation. Loss of p53 in tumor cells enhances HIF-1alpha levels and augments HIF-1-dependent transcriptional activation of the vascular endothelial growth factor (VEGF) gene in response to hypoxia. Forced expression of HIF-1alpha in p53-expressing tumor cells increases hypoxia-induced VEGF expression and augments neovascularization and growth of tumor xenografts. These results indicate that amplification of normal HIF-1-dependent responses to hypoxia via loss of p53 function contributes to the angiogenic switch during tumorigenesis.
OBJECTIVE: To assess whether the response visible on computed tomography (CT) 21 days after the first course of chemotherapy in patients with nonseminomatous germ cell tumour predicts the need for surgery and whether three-dimensional (3D) reconstruction adds to the diagnostic accuracy. PATIENTS AND METHODS: CT scans from 52 patients treated with cisplatin-based chemotherapy were assessed for tumour shrinkage by measuring the changes of a one-dimensional (1D) measurement of the maximum transverse diameter, and comparing CT scans before, 21 days after the first course and at the end of chemotherapy (1D method). In a subset of patients, using a special formula, the 1D-derived 2D and 3D shrinkage (2Dder and 3Dder) were compared with four other computed or calculated methods (1D, 2D, 3Dcalc, 3Dcomp). RESULTS: At day 21, in 32 of 52 patients (62%) there was < 50% tumour shrinkage using the 1D assessment; 21 of them (66%) needed surgery, compared with none of the 20 patients with > 50% tumour shrinkage by day 21 (chi2 = 22.83, P < 0.001). The 1D method showed significantly less shrinkage than all the other methods but when this was used to derive a 3D shrinkage, assuming the mass to be spherical (3Dder), it was not statistically different from that of 3Dcomp. CONCLUSIONS: The assessment of the response from 1D CT scan estimates 21 days after initiating chemotherapy identifies a subgroup of patients who have a high probability of needing surgery. Although expected to be more accurate, the 3Dcomp estimate of tumour shrinkage was no better than the 3Dder estimate.
Therapy of B-cell chronic lymphocytic leukemia (CLL) has been limited by both the nonselectivity of therapeutic agents toward normal residual immune cells and inherent drug resistance. Identification of agents that spare normal immune effector cells, thus facilitating addition of immune-based therapies, and that modulate factors associated with drug resistance in CLL might represent a major therapeutic advance. Depsipeptide (FR901228) is a novel agent entering clinical trials that has selective in vitro activity against resistant leukemia cell lines. To assess its in vitro activity in CLL, we exposed peripheral mononuclear cells from CLL patients (n = 10) to varying concentrations of this agent. Viability of the CLL cells was reduced by 50% (LC(50)) at 4 hours, 24 hours, and 4 days at depsipeptide concentrations of 0.038, 0.024, and 0.015 micromol/L, respectively. Depsipeptide had marked selective cytotoxicity when compared with normal blood mononuclear cells, in which the LC(50) was 3.44 micromol/L at 4 hours (P =.03), 0.965 micromol/L at 24 hours (P =.01), and 0.0318 micromol/L at 96 hours (P =.04). Inhibition of bone marrow progenitor cell growth was also minimal after incubation with 0.015 micromol/L (19% inhibition of colony forming unit-granulocyte-macrophage [CFU-GM]; 17% inhibition burst forming unit-erythroid [BFU-E]) and 3.44 micromol/L (24% inhibition of CFU-GM; 57% inhibition BFU-E) of depsipeptide for 4 hours, followed by a 14-day incubation period. Expression of apoptotic proteins after depsipeptide exposure (0.015 micromol/L) included no change in bcl-2, elevation of bax, and decreased expression of p27. These data demonstrate that depsipeptide has significant selective in vitro activity against human CLL cells concurrent with favorable alterations of the bcl-2:bax protein ratio and decrease in p27 expression. Such findings strongly support the early introduction of depsipeptide into clinical trials for patients with CLL.
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