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.     

Subjective Evaluation of Apparent Reduction of Chromatic Blur Depending on Luminance Signals

Chromatic blur seen along the contours of a figure on a color TV display is not so annoying if the contour luminance signal is sharp. This is due to the human visual property that chromatic blur is masked by the luminance by spatial luminance changes. This paper describes the subjective evaluation of the visual masking effect of chromatic blur depending on luminance signals. From the experiments, the chromatic blur becomes less perceptible with the increase in level of superposed luminance signals and the blur is more annoying in red than in blue or yellow. Highly saturated red figures cause poor picture quality.     

Iodine-initiated,solid-state copolymerization of tetraoxane with 1,3-dioxolane in the presence of methylal. II. Properties of copolymer obtained by beaker-scale copolymerization

In order to elucidate the copolymerization mechanism, the properties of the copolymer obtained by the iodine-initiated copolymerization of the tetraoxane–1,3-dioxolane–methylal system have been studied using gas chromatography, microscopy, scanning electron microscopy, differential scanning calorimetry, and gel permeation chromatography. From the behavior of the thermal stability and gas chromatography of the reaction mixture, it was found that reactivity of 1,3-dioxolane with active center is larger than that of tetraoxane, i.e., more than 90% 1,3-dioxolane is consumed at an early stage of the polymerization. The results obtained by microscopy, DSC, and GPC of the copolymer suggested that the copolymerization proceeds from the surface to the center of the tetraoxane crystal as if it were a core model. It was also suggested that the heterogeniety in copolymer properties can be explained not only by heterogeneous dispersion of 1,3-dioxolane in tetraoxane crystal, but also by the difference of reactivity of 1,3-dioxolane with the active center.     

Iodine-initiated,solid-state copolymerization of tetraoxane with 1,3-dioxolane in the presence of methylal. IV. Fractional dissolution of copolymer

A fractional dissolution on the oxymethylene copolymer obtained by the iodine-initiated, solid-state copolymerization of the tetraoxane–1,3-dioxolane-methylal system has been carried out using a mixed solvent which consists of tetrachloroethane, phenol, and cyclohexanol. On the fractional dissolution, the oxymethylene copolymer was divided mainly into two parts: one was the copolymer containing a larger amount of ethylene oxide unit in its main chain and having lower molecular weight; the other was copolymer containing a smaller amount of ethylene oxide unit and having a higher molecular weight. It was reasonably concluded that in this copolymerization system, the reaction proceeds from the surface to the center of the tetraoxane crystal to give a divided copolymer due to the heterogeneous properties such as copolymer composition and molecular weight.     

Comparison between measured and calculated absolute intensities of ultra-soft X-rays of synchrotron radiation

Absolute intensity has been measured using a proportional counter with a mylar window for quasi-monochromatic ultra-soft X-rays from the ETL-storage ring. The measured photon numbers were compared with those calculated from Schwinger's formula and experimental parameters. The result suggests that the ring is qualified as a standard light source facility. It was found that absolute intensity measurements at a few tenths of the critical wavelength are capable of making accurate storage ring diagnostics.     

Immobilization of enzymes by radiation-induced polymerization of glass-forming monomers: 2. Effects of cooling rate and solvent on porosity and activity of immobilized enzymes

The effect of cooling rate of a monomeric system on the porosity and activity of an immobilized enzyme prepared by radiation-induced polymerization of 2-hydroxyethyl methacrylate at low temperatures has been studied. Slow cooling gave the same effect on porosity of the polymer as decreasing the monomer concentration. A glass-forming solvent such as diethylene glycol was added to water to study the effect of the supercooling tendency of the solvent. Addition of diethylene glycol decreased porosity and also enzymic activity. Water was replaced by the miscible solvent p-dioxane and the immiscible solvent n-decane in order to clarify the effect of solvent. p-Dioxane had a similar effect to water on the relation between the monomer concentration, porosity and activity. On the other hand, polymer prepared from the system containing n-decane showed different immobilization properties owing to the presence of independent pores in the matrix.     

Clinical evaluation of urinary leukotriene E4 levels in asymptomatic bronchial asthma

To evaluate the significance of peptide leukotrienes (LTC4, D4, E4) in asymptomatic asthmatic patients, we measured urinary LTE4 levels which is thought to reflect in vivo production of peptide LTs. Urinary LTE4, was extracted using C18 solid phase column and measured by radioimmunoassay. There was no significant difference in urinary LTE4 levels among asthmatics with different severity or between atopic and non-atopic asthmatics. Urinary LTE4 levels were significantly elevated in asthmatics compared with normal controls (p < 0.05). When compared with normal controls, urinary LTE4 levels were significantly elevated in moderate to severe asthma (p < 0.05), and non-atopic asthmatics (p < 0.001). Urinary LTE4 levels were significantly elevated in aspirin-sensitive asthmatics compared with aspirin-tolerant asthmatics (p < 0.05). There was no significant difference in urinary LTE4 levels among aspirin-sensitive asthmatics with different severity. These results suggest that increased production of peptide LTs is a characteristic in aspirin-sensitive asthma, and that the severity and type of asthma and the presence of aspirin-sensitive asthma should be taken into consideration in the analysis of urinary LTE4 levels.     

Piezoelectric ceramics of (Bi1/2Na1/2)TiO3-PbTiO3-BaTiO3 system

Piezoelectric and ferroelectric properties of bismuth sodium titanate, (Bi_1/2Na_1/2)TiO₃(BNT)-based solid solution, that is, (Bi_1/2Na_1/2)(_1-x)(Pb_a Ba_b)_xTiO₃(a + b = 1) [BNPB(100x-100a/100b)], are studied from the viewpoint of a new group of lead-free or low-lead content piezo-electric ceramics with a rhombohedral(F_a-tetragonal (F_β) morphotropic phase boundary (MPB). It is evident that the MPB seems to be remarkably efficacious in promoting piezoelectric and pyroelectric activities by electrical poling. X-ray diffraction data, dielectric properties and D-E hysteresis loops show that the MPB exist near (Bi_1/2Na_1/2)TiO₃[BNT] at x = 0.13–0.14, 0.08–0.09 and 0.06–0.07 in the case of b = 0, b = 0.5 and b = 1, respectively. BNPB ceramics are superior for piezoelectric ceramics in high-frequency ultrasonic uses, or special piezoelectric actuator materials with a lower free permittivity ε₃₃Tε₀, and a high electromechanical coupling factor k₃₃, along with a high mechanical strength.