Dissolution and Absorption of Nipedipine from Nifedipine-Polyvinylpyrrolidone Coprecipitate

Attempt was made to develop the solid dosage form of nifedipina which showed good absorption rate and total bioavailability. Nifedipine is a poorly water-saluble drug, whom bioavailability is low when administered orally in the crystalline form. Solutions of nifedipine were well absorbed from the gastrointestinal tract. The dissolution rate of PVP-nifedipine coprecipitates exhibited rapid dissolution rate. X-ray diffraction data suggested the lack of crystallinity in the coprecipitate. The relation between the dissolution rates and average molecular weights of PVP was studied. Nifedipine in the copretipitate was chemically stable to heat and humidity, but the dissolution rate of nifedipine from the coprecipitate stored at 21° and 75% R.H. markedly decreased. X-ray diffraction data revealed that it might be due to the transformation of amorphous form of nifedipine to crystalline form under higher relative humidity. The gastrointestinal absorption of nifedipine in beagle dogs after oral administration of the coprecipitate was increased than that after oral adniniatration of the physical mixture.     

Stress-induced martensite formation in Cu−Al−Ni alloys

A study has been made of superelasticity and the strain-memory effect in Cu?Al?Ni alloys in the composition range 14 wt pct Al and 2 to 3 wt pct Ni. These alloys have a bcc structure on quenching and show a low temperature martensitic transformation which is responsible for both the superelastic and strain-memory effects. Tests on both single and polycrystalline specimens showed that the maximum superelasticity occurred close toA _s. At higher temperatures the effect gradually decreased, whilst at lower temperatures it decreased very quickly. The magnitude of the effect was large in single crystal specimens (>5.8 pct), but small in polycrystal specimens (<1.5 pct). The superelastic effect was caused by stress-induced martensite (SIM). Two types of SIM were observed; thin plates of thermoelastic martensite which were always reversible, and wide plates of burst-type martensite. This burst-type martensite was responsible for the major portion of SIM, and whether it was reversible or not on removal of the stress controlled the amount of superelasticity observed. The strain-memory effect occurred on deformation either in the martensitic state (temperature <M _f) or in the temperature range where the martensite once formed was stable (temperature close toM _s). Deformation caused reorientation of the martensite plates and when the specimen was heated, the martensite disappeared and the specimen reverted back to its original shape. This effect was explained on the basis of development of martensite plates of favorable orientation on stressing.     

Enhancement of serotonergic neural activity contributes to cyclosporine-induced tremors in mice

Patients suffering from inflammatory or dysimmunitary diseases may develop various clinical responses to corticotherapy. This brief article describes the various cellular and molecular mechanisms which underly the genetic, endocrine and immunitary factors involved in corticosensitivity, corticoresistance and corticodependence.     

Source of sex pheromone of the egg-larval parasitoid,Ascogaster reticulatus Watanabe (Hymenoptera: Braconidae)

A sex pheromone ofAscogaster reticulatus Watanabe (Hymenoptera: Braconidae), identified as (Z)-9-hexadecenal, elicits males' antennal matesearching behavior. In order to localize the source of sex pheromone production, each body part was separated and extracted with hexane and then subjected to 9-cm Petri dish bioassay. The highest activity was found in thorax extract. Among legs, wings, and thorax, legs have the highest activity. Among fore, middle, and hind legs, hind legs have the highest activity. Among coxa and trochanter, femur, tibia, and tarsus, tibia has the highest activity. From these results, the presence of a tibial sex pheromone gland was suggested.     

Crosslinking of PVC and NBR blends

The purpose of our work is to control the interfacial bonds between PVC and NBR using the ammonium salts of triazine thiols and dithiodimorpholine (DTDM) and thereby reveal the relation between the interfacial bonds and the final mechanical properties of products. In the experimental work a two-stage process was used. At first, an NBR/PVC blend was mixed with a mono-tetra-n-butylammonium salt of triazine trithiol at a temperature of 100°C on a two-roll mill to give the branching structure of triazine thiols into PVC. In the second stage branched NBR/PVC reacted with DTDM to afford the branched PVC containing trithiomorphonyl groups. In the presence of ZnO at 160°C trithiomorphonyl groups react with NBR to form a crosslinking structure between NBR and PVC. The mechanical properties of cured NBR/PVC blends were markedly improved by the treatment process and after addition of tetramethylthiuram monosulphide also. The mechanical properties were not improved by increasing the concentration of TT-TBA (tetrabutylammonium salt of 1,3,5-triazine-2,4,6-trithiol) over 4.2 phr.     

Permeability of vitamin B-12 in chitosan membranes. Effect of crosslinking and blending with poly(vinyl alcohol) on permeability

The permeability and diffusion of vitamin B-12 in chitosan, crosslinked chitosans, and chitosan/poly(vinyl alcohol) (PVA) blends were studied using “lag time” technique. Apparently the diffusion coefficient, D, for both crosslinked and blended chitosan membranes depends solely upon the equilibrium swelling ratio, Q, of the material in water. The functional dependence of D on Q was obtained from the data. The partition coefficients calculated for vitamin B-12 in all membranes studied were nearly constant (K ≈ 0.4). The results are shown to be consistent with the “pore type” transport mechanism for vitamin B-12 in these chitosan membranes.     

Grain-boundary depressed diffusion of oxygen ions in ThO2

The oxygen self-diffusion coefficients were determined for polycrystalline ThO₂ microspheres by an isotope exchange technique using ¹⁸O as the tracer. The diffusion coefficients in the temperature range 1099°–1644°C were represented by $\text{D = 5.67 × 10}{}^{\mathrm{?3}}\text{exp[?219(kJ/mol)/RT] cm}{}^2\text{/s}$. The results were one order smaller in magnitude than those reported for single crystal ThO₂, while the activation energy was similar to that for the single crystal. Mechanism of the grain-boundary depressed oxygen diffusion was discussed.     

Effects of stimulus information and number of stimuli on sequential dependencies in absolute identification.

Three absolute identification experiments examined the effects on sequential dependencies of 2 factors: stimulus information and the number of stimuli used. Data were analyzed by multivariate information analysis. In Exp 1 with 5 university studentswith experience in absolute identification experiments, the stimulus modality was pure tone frequency under masking and no-masking conditions and 4, 6 10, and 16 tones were used. In Exp 2 with 5 university students, luminance levels of light circles were used as stimuli and number of luminance levels was 10 or 16. In Exp 3 with 6 university students, the stimuli were pointer positions along a horizontal line and they were presented either within a small or a large range to manipulate the stimulus information available. Results show that the sequential dependencies became larger as the stimulus information was decreased and as the number of stimuli was increased. Results are discussed in the context of models of sequential dependencies. Results of a multiple regression analysis on the data were compared with those of the information analysis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)