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Biomedical subjects

I Yamakawa

Publications and source records attributed to I Yamakawa.

At least 19 recordsLinked to original sources
PubMed1997

Release behavior of poly(lactic acid-co-glycolic acid) implants containing phosphorothioate oligodeoxynucleotide.

The release behavior of phosphorothioate oligodeoxynucleotide, 5'-GCCGAGGTCCATGTCGTACGC-3' (ODN), from poly(lactic acid-co-glycolic acid) (PLGA) implant was studied. The pillar shape implant was fabricated by the heating mold method. About 20% of ODN were released initially, and the subsequent pseudo-zero-order release lasted for more than 20 d from a PLGA10000 implant loaded with 8.4% ODN in phosphate buffered saline, pH 7.4. The duration of ODN release did not depend on the molecular weights of PLGA, and pseudo-zero-order release may be achieved by changing the loaded amount of ODN in fabrication of the PLGA implant. Almost the same release profiles were obtained in the pH range of 7.2 to 7.6, which is known as the physiological pH of a vitreous body. Furthermore, the duration of intact ODN release in bovine vitreous was found. The implant in the present study may possibly be applicable to intravitreal implantation for the treatment of ocular disease.

Animals↗
PubMed1993

Controlled release of insulin from plasma-irradiated sandwitch device using poly-DL-lactic acid.

The release behavior of insulin from a plasma-irradiated sandwitch (PIS) device using poly-DL-lactic acid (PLA) was studied. The controlled release device can be obtained by oxygen plasma irradiation (radiofrequency discharge operating at 13.56 MHz) on the outer layer of the sandwitch device which was fabricated from an insulin-PLA matrix tablet as a core material and a mixture of plasma-degradable polyoxymethylene (POM) and biodegradable PLA as a wall material. The release test indicated that insulin was released through the micropores formed by the vaporization of POM, and that the release behavior of insulin was affected largely by the molecular weight of PLA used as the outer layer rather than the plasma operational condition. The release of insulin can be controlled by the use of PLA with an average molecular weight of 11000 as the outer layer of the PIS device. Insulin from the PIS device maintained normal blood glucose levels for 10 d in diabetic rats as an implantable dosage form. The duration of insulin effectiveness was relatively short considering the degradation rate of PLA, indicating that the degradation characteristics of biodegradable PLA were not well reflected in the PIS device.

Adsorption↗
PubMed1992

In vitro and in vivo release of poly(DL-lactic acid) microspheres containing neurotensin analogue prepared by novel oil-in-water solvent evaporation method.

Poly(DL-lactic acid) (PLA) microspheres containing a neurotensin analogue [NA; H(CH3)-Arg-Lys-Pro-Trp-tert-Leu-Leu-OEt.3HCl] were prepared by a novel oil-in-water (o/w) solvent evaporation method, and the release behaviors were evaluated in vitro. About 20% of the loaded NA was released initially, and the subsequent release lasted for a month from microspheres prepared with PLA of molecular weight 2000 (PLA 2000). A smaller initial release from PLA 4000 and PLA 6000 microspheres was found, but a lag time of 2-3 weeks during which the drug was not released was observed with PLA 4000 and PLA 6000 microspheres. The addition of relatively hydrophilic monoglycerides decreased the lag time, and a fairly constant release of NA was achieved. The pharmacokinetic behavior of NA from PLA 2000 microspheres was studied in rats. The release of the drug after a subcutaneous injection exhibited pseudo-zero-order kinetics for 1 month. The initial release of the drug from the microspheres was reflected in a sharp increase of the plasma levels of the de-ester form of NA [H(CH3)-Arg-Lys-Pro-Trp-tert-Leu-Leu-OH], and the subsequent steady-state levels agreed well with the predicted levels obtained from analysis of constant-infusion kinetics.

Amino Acid Sequence↗
PubMed1992

Preparation of neurotensin analogue-containing poly(dl-lactic acid) microspheres formed by oil-in-water solvent evaporation.

This report describes the preparation of injectable microspheres containing a neurotensin analogue (NA), which is a hexapeptide with neurotensin activity. NA, a hydrophilic drug, was successfully entrapped into poly(dl-lactic acid) microspheres prepared by a novel oil-in-water solvent evaporation method. The preparation method was investigated with regard to the partition of NA into the oily phase and the rapid phase separation of the polymer. Successful entrapment was achieved with the following conditions: (1) an alkaline water phase, (2) addition of fatty acid salt in the oily phase, and (3) addition of a water-miscible solvent in the oily phase. Under these conditions, NA was completely entrapped into the microspheres at poly(dl-lactic acid):NA molar ratios of greater than 3.

Amino Acid Sequence↗
PubMed1992

Thermal characteristics of poly (DL-lactic acid) microspheres containing neurotensin analogue.

The thermal characteristics of poly (DL-lactic acid) (DL-PLA) microspheres containing a hexapeptide (NA: H(CH3)-Arg-Lys-Pro-Trp-tert-Leu-Leu-OEt) with neurotensin activity were investigated. PLA microspheres with a drug content of 1.5-11.0% were prepared by a novel o/w (oil-in-water) solvent evaporation method. Both DL-PLA and NA were amorphous in form, and an increase in heat capacity at glass transition temperature (Tg) of the polymer was observed in DL-PLA microspheres containing NA. The Tg of DL-PLA (PLA2000 bulk) was 307.8 K, while Tg of microspheres containing NA (content 6.0%) shifted to 321.2 K. The Tg of PLA2000 microspheres was found to increase with an increase in the content of NA, and its increasing tendency reached a plateau at an NA content of greater than 6%. The apparent activation energy of glass transition of PLA2000 bulk and the microspheres was calculated to be 86.3 and 99.3 kcal/mol, respectively. As a result of the release test after storage at 4 degrees C and 40 degrees C for 1 month, nearly the same release profiles of NA from PLA2000 microspheres were found. The release rate of NA after the initial release became slow after storage at 45 degrees C for 1 month. This may be attributed mainly to a decrease in surface area caused by the formation of agglomerates of PLA2000 microspheres under conditions near Tg.

Drug Storage↗
PubMed1990

Sustained release of insulin by double-layered implant using poly(D,L-lactic acid).

This report describes the advantage of double-layered implants using low molecular weight poly(DL-lactic acid) in the sustained release of insulin. The double-layered implant consisted of a polymer matrix containing insulin and a polylactic acid layer which was coated partially on one of the surfaces of the insulin:polymer matrix. The double-layered implants were compared with single-matrix implants from the standpoint of the in vitro dissolution test and in vivo performance. In vitro release rates were controlled by changing the amount of poly(DL-lactic acid) used in the polymer layer. In an in vivo test using diabetic animals, the double-layered implants provided a sustained release of insulin for 19 d, as judged by the changes in blood glucose levels and serum insulin levels after the subcutaneous implantation.

Animals↗
PubMed1986

In vitro and in vivo evaluation of a sustained release preparation containing phenylpropanolamine hydrochloride.

The relationship between dissolution behaviour and plasma concentration after administration of a sustained-release preparation containing phenylpropanolamine hydrochloride was studied in 11 male volunteers. The testing for dissolution was carried out using the JP X rotating basket procedure, and human plasma samples were assayed for phenylpropanolamine hydrochloride by a specific high-performance liquid chromatography. Three hours after dosing, the mean peak plasma concentration was 104.1 ng/ml and the plasma concentration declined with a half-life of 4.85 h. The time course of plasma and dissolution data were analyzed by a non-linear least squares curve fitting method to compare in vivo and in vitro release behaviour. Plasma concentration changes of phenylpropanolamine hydrochloride were correlated with in vitro release behaviour of the sustained-release preparation.

Adult↗
PubMed1985

Type III procollagen N-terminal peptides in experimental pulmonary fibrosis and human respiratory diseases.

In order to detect the fibrotic response in lung-tissue, concentrations of type III procollagen N-terminal peptide (P-III-P) were examined in sera and bronchoalveolar lavage fluids from rabbits with bleomycin-induced pulmonary fibrosis, and in sera from patients with various respiratory diseases, using a radioimmunoassay method. In the bleomycin-induced pulmonary fibrosis, a significant (p less than or equal to 0.05) rise in P-III-P levels was observed in the lavage fluid at 7 days, and in the sera at 21 days after bleomycin treatment, with histological confirmation of pulmonary fibrosis. Many of the patients with pulmonary fibrotic changes had significantly elevated serum P-III-P level. In lung cancer patients, most of the post-radiation serum samples were found to have P-III-P levels greater than or equal to 18 ng/ml. These results suggest that the increase in P-III-P levels is the reflection of fibrotic changes in the lungs and that the clinical assessment of serum P-III-P level could be important in the early detection of pulmonary fibrosis.

Animals↗
PubMed1983

[Bronchial asthma].

Explore the source record for details and available documents.

Airway Obstruction↗
PubMed1979

Fatty acid omega and (omega-1)-Hydroxylation in rabbit intestinal mucosa microsomes.

The microsomes from rabbit intestinal mucosa which had been washed quickly and thoroughly with phenylmethylsulfonyl fluoride were found to catalyze the hydroxylation of fatty acids in the presence of NADPH and molecular oxygen. Myristic and palmitic acids were converted to the corresponding omega-and (omega-1)-hydroxy fatty acids, whereas lauric acid was converted only to 12-hydroxylauric acid, and capric acid, to 9-and 10-hydroxycapric acids together with an unknown polar acid. Among these fatty acids, both myristic and lauric acids appeared to be the most efficient substrates. The inhibition of the hydroxylation by SKF 525-A and carbon monoxide suggested that the activity depended upon cytochrome P-450. The specific activity of the fatty acid hydroxylation was almost constant along the small intestine, while the aminopyrine N-demethylation activity and the cytochrome P-450 content were highest at the proximal end of the intestine and progressively declined toward the caudal end. The cytochrome P-450 was solubilized from the intestinal microsomes and purified by 6-amino-n-hexyl Sepharose 4B chromatography. The partially purified cytochrome P-450 was active in fatty acid hydroxylation in combination with intestinal NADPH-cytochrome c reductase and phosphatidylcholine.

Animals↗