Effect of surfactants and hydrophilic polymers on the stability of an antihypertensive drug candesartan cilexetil: Evaluation by HPLC.

OBJECTIVES: The objective of this study is to investigate the effect of surfactants (polysorbate 80 and sodium lauryl sulphate) and hydrophilic polymers (polyvinylpyrrolidone and polyethylene glycol 6000) on the stability of candesartan cilexetil under isothermal stress conditions (100°C, 48h). METHODS: HPLC method was employed to evaluate the drug content and formation of degradation products in stress samples. Drug and degradation products were separated on Hypersil BDS C18 (250×4.6mm, 5µ) column using acetonitrile-water (pH 2.8) in the ratio of 85:15% v/v as a mobile phase. RESULT: Similar degradation behaviour of drug was observed with polyvinylpyrrolidone, polyethylene glycol 6000 and polysorbate 80; four common degradation peaks were observed at the retention time of 3.7, 4.5, 7.8 and 11minutes. One extra common degradation peak of very low intensity was also observed with polyethylene glycol 6000 and polysorbate 80 at the retention time of 4.2min. The drug was eluting at the retention time of 5.4min. In the case of sodium lauryl sulphate, two prominent degradation peaks were observed at the retention time of 3.7 and 13.25min along with few very low-intensity degradation peaks. CONCLUSION: The drug showed 41%, 64%, 72% and 98% degradation in presence of polyvinylpyrrolidone, polyethylene glycol 6000, polysorbate 80 and sodium lauryl sulphate, respectively.

Characteristics of the positive ion source at reduced gas feed.

The neutral beam injector of steady state superconducting tokamak (SST1-NBI) at IPR is designed for injecting upto 1.7 MW of neutral beam (Hº, 30-55 keV) power to the tokamak plasma for heating and current drive. Operations of the positive ion source (PINI or Plug-In-Neutral-Injector) of SST1-NBI were carried out on the NBI test stand. The PINI was operated at reduced gas feed rate of 2-3 Torr l/s, without using the high speed cryo pumps. Experiments were conducted to achieve a stable beam extraction by optimizing operational parameters namely, the arc current (120-300 A), acceleration voltage (16-40 kV), and a suitable control sequence. The beam divergence, power density profiles, and species fractions (H(+):H2(+):H3(+)) were measured by using the diagnostics such as thermal calorimetry, infrared thermography, and Doppler shift spectroscopy. The maximum extracted beam current was about 18 A. A further increase of beam current was found to be limited by the amount of gas feed rate to the ion source.

DNA microarray technology for neonatal screening.

Modern molecular biology, owing much to the Human Genome Initiative, has elucidated many of the genetic mechanisms underlying heritable metabolic disease. While the use of molecular methods has flourished in research laboratories, complexity and cost have limited their utility in newborn screening. Newborn blood cards provide high quality DNA samples able to provide reliable support to highly multiplexed polymerase chain reactions (PCR). New manufacturing processes have reduced the cost of DNA microarray technology to the point where it is a practical tool for population screening. In a single assay, a DNA microarray facilitates the co-detection of amplification products diagnostic for several genetic diseases. High throughput is achieved with automation at every step, from DNA extraction to detection of hybrids. We suggest that it is both feasible and practical to develop a first-tier newborn screening protocol based upon multiplex PCR and analysis of amplification products using DNA microarrays. Initial data utilizing the model systems of sickle cell disease, alpha-1-antitrypsin deficiency and Factor V Leiden will be reported.

8-Arylguanine adducts from arenediazonium ions and DNA.

Arenediazonium ions (ArN2+) are genotoxic though the source of their genotoxicity is unknown. The present studies were undertaken to determine if reductive decomposition of ArN2+ to aryl radicals (Ar) in the presence of calf thymus DNA (ctDNA) or in cells results in the formation of DNA adducts. We found that when arenediazonium ions of the general structure p-X-ArN2+ (X = CH3, CH2OCH3, CH2OH) are allowed to react with ctDNA or incubated with cells under conditions that produce p-X-Ar, DNA adducts are formed with guanine. The structure of the adduct is the C8-substitution product derived from guanine and p-X-Ar. Formation of p-X-Ar was determined by ESR spin-trapping with 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The extent of C8-arylguanine adduction was measured by high performance liquid chromatography (HPLC) analysis of the DNA hydrosylate and comparison with authentic synthetic standards. The C8-arylguanine adducts observed to form may be important in regard to the genotoxicity of ArN2+, though other DNA adducts such as the N6-triazene of adenine or C8-aryladenine adducts can form. Finally, though the formation of C8-arylguanine adducts from arenediazonium ions has been proposed, this is the first report demonstrating their formation in DNA.

Enhanced cellular uptake of oligonucleotides by EGF receptor-mediated endocytosis in A549 cells.

PURPOSE: The goal of this study was to investigate the feasibility of utilizing epidermal growth factor (EGF) receptor-mediated endocytosis to enhance cellular uptake and targeting of oligonucleotides in epithelial cancer cells. To overcome the problem of endosomal entrappment associated with receptor-mediated delivery, we also examined the effects of two fusogenic peptides, polymyxin B and influenza HA2 peptide, for their capability to promote cytoplasmic delivery of oligonucleotides. METHODS: A molecular conjugate consisting of EGF and poly-L-lysine (PL) was synthesized and complexed with 5' fluorescently-labeled oligonucleotide. Cellular uptake of the complex in presence or absence of the fusogenic peptides was monitored fluorometrically. Microscopic studies were performed to visualize the intracellular distribution of the oligonucleotide. RESULTS: Cells treated with the complex exhibited intracellular fluorescence intensity significantly enhanced over free oligonucleotide-treated controls. The uptake of the complex was shown to occur via the EGF receptor-mediated pathway. Fluorescence microscopic studies revealed cellular internalization of the complex, however, the complex appeared to be accumulated in endocytic vesicles. Exposure of the cells to complex in presence of HA2 peptide and polymyxin B resulted in a more diffused intracellular fluorescence pattern and a corresponding increase in fluorescence intensity. These results are consistent with the known fusion and destabilizing activities of the peptides. CONCLUSIONS: Since EGF receptors are overexpressed in many cancer cell types, the EGF-PL conjugate may potentially be used as an effective and selective delivery system to enhance uptake of oligonucleotides into cancer cells.

Lunato-triquetral fusion and associated spinal abnormality.

Lunato-triquetral fusion is a rare congenital anomaly. Its association with skeletal dysplasias, tarsal coalitions and synostotic states in the upper limbs and other parts of the body is well established. There is not mention in the English literature about its association with congenital spinal abnormalities and secondary osteoarthrosis in the wrist and two such cases are now described. Both cases presented with symptoms in the dominant hand and had symptoms of backache in the past. Their clinical course and X-ray findings are described.

Heterotopic ossification enveloping the sciatic nerve following posterior fracture-dislocation of the hip: a case report.

Heterotopic ossification developing around the hip and enveloping the sciatic nerve is described in a patient who underwent open reduction and fixation of a large posterior acetabular fragment to decompress and suture the sciatic nerve. The postoperative treatment and a 2-year follow up are also described.