Effect of ethylene vinyl acetate (EVA) closed cell foam on transmitted forces in mouthguard material.
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OBJECTIVES: To compare transmitted forces through ethylene vinyl acetate (EVA) mouthguard material and the same EVA material with gas inclusions in the form of a closed cell foam. METHOD: EVA mouthguard materials with and without foam gas inclusions and 4 mm thick were impacted with a constant force from an impact pendulum. Various porosity levels in the foam materials were produced by 1%, 5%, and 10% by weight foaming agent. The forces transmitted through the EVA after energy absorption by the test materials were measured with a force sensor and compared. RESULTS: Only minor non-significant differences in transmitted forces through the EVA with and without foam were shown. CONCLUSIONS: The inclusion of gas in the form of a closed cell foam in 4 mm thick EVA mouthguard materials did not improve the impact performance of the EVA mouthguard material. (+info)
Rapid purification of 70S RNA from media of cells producing RNA tumor viruses.
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Media from cells producing RNA tumor viruses, when treated with sodium dodecyl sulfate and polyvinyl sulfate, yield 70S RNA as the major species binding oligo(dT)-cellulose. The procedure described for purifying 70S RNA requires no special equipment and is suitable for rapidly processing large quantities of media or for purifying RNA from commercially avialable virus, with a 5- to 10-fold higher yield than was obtained using existing methods. (+info)
Effect of polyanion on the acidic conformational transition of native and denatured ferricytochrome c. Circular dichroism study.
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Interaction of polyanion poly(vinylsulfate) with oxidized cytochrome c (cyt c) significantly affects the protein main characteristics. One of them, pKa value of acidic transition, was shifted from an apparent pKa value 2.5 (typical for cyt c in low ionic strength solvent) to approximately 5.20 +/- 0.15 upon polyanion binding to the protein, pointing to a likely involvement of histidines 26 and/or 33 in the protein acidic transition in complex with the polyanion. The acidic transition followed at 6 different wavelengths all over circular dichroism spectrum, monitoring different parts of the protein structure, revealed basically two-state character process. Only ellipticity at 262 nm indicated a low-cooperative pH-induced conformational transition in heme region with an apparent pKa approximately 4.34 +/- 0.25 in accordance with absorbance change at 620 nm. Polyanion also interacts with chemically-denatured (in the presence of 9 mol/l urea) state of the protein as it follows from stabilization of protein residual structure at acidic pH and its effect on pKa value of acidic transition of chemically-denatured cyt c. Destabilization effect of polyanions on native and, on the other hand, stabilization influence on partially unfolded conformations of the protein are discussed with an implication for their chaperone-like properties in vivo and in vitro. (+info)
Occupational lead exposure in Finland. IV. The polyvinyl chloride plastic industry.
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One hundred and fifty-two workers from ten polyvinyl chloride (PVC) plastic factories were studied for lead exposure. Blood lead (Pb-B) concentration was measured for all the workers, urinary delta-aminolevulinic acid (ala) for 130 workers, erythrocyte alpha-aminolevulinic acid dehydratase (ala-d) activity for 59 workers, and blood hemoglobin concentration or 93 workers. The median Pb-B for all the workers was 37 mug/100 ml, and the highest median found for one factory was 63 mug/100 ml. The highest single Pb-B value found was 126 mug/100 ml. The jobs with the heaviest lead exposure were those of mixing and weighing lead stearate powder. It is assumed that replacing the powder with a granule form of lead stearate will diminish the hazard of lead exposure in the future. Urinary ALA concentrations and erythrocyte ALA-D activities corresponded well with the Pb-B concentration, but the hemoglobin values did not show any relation to lead exposure. It is concluded that in the PVC plastic industry of Finland the risk of exposure to lead is high and regular health examinations should be performed. (+info)
Calcium EXAFS establishes the Mn-Ca cluster in the oxygen-evolving complex of photosystem II.
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The proximity of Ca to the Mn cluster of the photosynthetic water-oxidation complex is demonstrated by X-ray absorption spectroscopy. We have collected EXAFS data at the Ca K-edge using active PS II membrane samples that contain approximately 2 Ca per 4 Mn. These samples are much less perturbed than previously investigated Sr-substituted samples, which were prepared after Ca depletion. The new Ca EXAFS clearly shows backscattering from Mn at 3.4 A, a distance that agrees with that surmised from previously recorded Mn EXAFS. This result is also consistent with earlier related experiments at the Sr K-edge, using samples that contained functional Sr, that show Mn is approximately 3.5 A distant from Sr. The totality of the evidence clearly advances the notion that the catalytic center of oxygen evolution is a Mn-Ca heteronuclear cluster. (+info)
Prevention of experimental cerebral vasospasm by intracranial delivery of a nitric oxide donor from a controlled-release polymer: toxicity and efficacy studies in rabbits and rats.
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BACKGROUND AND PURPOSE: A reduction in the local availability of nitric oxide (NO) may play a role in the etiology of chronic cerebral vasospasm after subarachnoid hemorrhage (SAH). We investigated the toxicity and efficacy of a locally delivered NO donor from a controlled-release polymer in preventing experimental cerebral vasospasm in rats and rabbits, respectively. METHODS: Diethylenetriamine/NO (DETA/NO) was incorporated into controlled release ethylene-vinyl acetate (EVAc) polymers. Twenty-eight rats were used in a dose-escalation toxicity study to establish a maximally tolerated dose of DETA/NO-EVAc polymer. In the efficacy experiment, 20 rabbits were assigned to 4 experimental groups (n=5 per group): sham operation; SAH only; SAH+empty EVAc polymer; and SAH+DETA/NO-EVAc polymer. Treatment was initiated 30 minutes after blood deposition. Basilar artery lumen patency was assessed 72 hours after hemorrhage to evaluate the efficacy of DETA/NO in preventing cerebral vasospasm. RESULTS: In the toxicity study, a dose of 3.4 mg/kg was identified as the LD(20) (dose with 20% mortality during the study period) of this DETA/NO formulation. Brain histology revealed hemorrhage and ischemic changes at the implantation site associated with high concentrations of DETA/NO. In the efficacy study, treatment with DETA/NO-EVAc polymer resulted in a significant decrease in basilar artery vasospasm compared with no treatment (93.0+/-4.9% versus 71.4+/-11.9%; P=0.035) or compared with treatment with blank EVAc polymer (93.0+/-4.9% versus 73.2+/-6.4%; P=0.003). CONCLUSIONS: Local delivery of DETA/NO prevents vasospasm in the rabbit basilar artery. Local delivery of DETA/NO via polymers is a safe and effective strategy for preventing cerebral vasospasm after SAH in this model. (+info)
Genetic polymorphisms in human CYP2A6 gene causing impaired nicotine metabolism.
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AIMS: Previously, we determined the phenotyping of in vivo nicotine metabolism and the genotyping of the CYP2A6 gene (CYP2A6*1 A, CYP2A6*1B, CYP2A6*2, CYP2A6*3, CYP2A6*4 and CYP2A6*5 ) in 92 Japanese and 209 Koreans. In the study, we found one Korean and four Japanese subjects genotyped as CYP2A6*1B/CYP2A6*4 who revealed impaired nicotine metabolism, although other many heterozygotes of CYP2A6*4 demonstrated normal nicotine metabolism (CYP2A6*4 is a whole deletion type). After our previous report, several CYP2A6 alleles, CYP2A6*6 (R128Q), CYP2A6*7 (I471T), and CYP2A6*8 (R485L), have been reported. The purpose of the present study was to clarify whether the impaired nicotine metabolism can be ascribed to these CYP2A6 alleles. Furthermore, we also determined whether the subjects possessing CYP2A6*1x2 (duplication) reveal higher nicotine metabolism. METHODS: Genotyping of CYP2A6 alleles, CYP2A6*6, CYP2A6*7, CYP2A6*8, and CYP2A6*1x2 was determined by PCR. RESULTS: The five poor metabolizers were re-genotyped as CYP2A6*7/CYP2A6*4, suggesting that a single nucleotide polymorphism (SNP) causing I471T decreases nicotine metabolism in vivo. Furthermore, we found that two subjects out of five with a lower potency of nicotine metabolism possessed SNPs of CYP2A6*7 and CYP2A6*8 simultaneously. The novel allele was termed CYP2A6*10. In the 92 Japanese and 209 Koreans, the CYP2A6*6 allele was not found. The allele frequencies of CYP2A6*7, CYP2A6*8, and CYP2A6*10 were 6.5%, 2.2%, and 1.1%, respectively, in Japanese, and 3.6%, 1.4%, and 0.5%, respectively, in Koreans. The CYP2A6*1x2 allele was found in only one Korean subject (0.5%) whose nicotine metabolic potency was not very high. CONCLUSIONS: It was clarified that the impaired in vivo nicotine metabolism was caused by CYP2A6*7 and CYP2A6*10 alleles. (+info)
Studies in topical application of niosomally entrapped Nimesulide.
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PURPOSE: A niosome based transdermal drug delivery system of Nimesulide (NIM) was developed and extensively characterized and evaluated for in-vitro performance followed by in-vivo evaluation in rats by carrageenan induced rat paw edema method. METHOD: Niosomes were prepared by lipid film hydration technique using tweens and spans. Preparation of niosomes was optimized for highest percent drug entrapment (PDE). The prepared niosomes were incorporated into 1 percent carbopol gel base and the system was evaluated for drug diffusion across human cadaver skin (HCS) using modified validated diffusion cell. The drug retention studies in niosomes were performed at refrigerated temperature (2 degrees C - 8 degrees C) and at room temperature (25 degrees C+/-2 degrees C) for the period of 2 months. In-vivo performance of plain drug gel, niosomally-entrapped drug in carbopol gel base and marketed formulation were evaluated using acute rat paw edema method. RESULTS: Highest mean percentage edema inhibition (PEI) was observed for niosomal nimesulide gel after 24 hours i.e. 66.68 percent +/- 5.19 percent compared to plain drug gel i.e. 12.57 percent +/- 1.78 percent and marketed NIM formulation i.e. 20.49 percent +/- 0.91 percent. CONCLUSION: Findings of this investigation conclusively demonstrate prolongation of drug release and increase in amount of drug retention into the skin and permeation across the skin after niosomal encapsulation of NIM. Developed nimesulide niosomal gel formulation has also demonstrated enhanced anti-inflammatory activity compared to plain drug gel and marketed formulation. (+info)