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Biomedical subjects

S Y Lin

Publications and source records attributed to S Y Lin.

At least 397 records · Page 22Linked to original sources
PubMedDate not supplied

Protective colloids and polylactic acid co-affecting the polymorphic crystal forms and crystallinity of indomethacin encapsulated in microspheres.

The co-effect of protective colloids and polylactic acid (PLA) on the polymorphic crystal forms and crystallinity of indomethacin (IMC) in IMC-loaded PLA microspheres was investigated with differential scanning calorimetry, infrared spectroscopy and x-ray diffractometry, to evaluate the polymorphic crystal forms and crystallinity of IMC encapsulated in PLA microspheres. The surfactant, sodium dodecyl sulphate (SDS), was also used as a dispersing agent. The results indicate that the polymorphism and crystallinity of IMC encapsulated in IMC-loaded PLA microspheres was dependent on the type of protective colloid and PLA used. The amorphous state and alpha-form of IMC were found in the IMC-loaded PLA microspheres prepared using polysaccharide (pectin or beta-cyclodextrin) as a protective colloid or SDS as a dispersing agent. However, the amorphous and methylene chloride solvate of IMC seemed to exist in the IMC-loaded PLA microspheres prepared with the proteins (gelatin or albumin), synthetic cellulose derivative (methyl cellulose or hydroxylpropyl methylcellulose) or the synthetic nonionic polymer (polyvinyl alcohol, polyvinyl pyrrolidone or biosoluble polymer) as a protective colloid. PLA was found to express a certain crystallinity in microspheres and not be affected by the protective colloids, but it played a more important role in influencing the crystallization of IMC during microencapsulation than the protective colloids. No interaction occurred in the physical mixture of IMC and PLA, nor in the IMC-loaded PLA microspheres.

Calorimetry, Differential Scanning↗
PubMedDate not supplied

Effect of protective colloids on the induction of polymorphic changes in indomethacin agglomerates after solvent evaporation from o/w emulsions.

Indomethacin (IMC) agglomerates were prepared by the solvent evaporation process from o/w emulsions containing different protective colloids in the external aqueous solution. The types of protective colloids inducing the polymorphic transformation of IMC in the agglomerates without wall material were investigated. The composition and its polymorphs were evaluated from the X-ray diffraction patterns, IR spectra and DSC thermograms. The results indicate that when pectin, beta-cyclodextrin, sodium alginate or sodium dodecyl supphase acted as a protective colloid, the respective IMC agglomerates consisted only of the alpha form of IMC. When gelatin or hydroxypropyl methylcellulose was used as a protective colloid, the amorphous, alpha and gamma forms as well as methylene chloride solvates of IMC were found in the IMC agglomerates. There was only methylene chloride solvate of IMC with a small amount of amorphous form in the IMC agglomerates prepared from albumin as a protective colloid, while IMC agglomerates prepared from methylcellulose, polyvinyl alcohol or biosoluble polymer consisted of the mixture of amorphous and alpha forms, and methylene chloride solvate of IMC. When polyvinyl pyrrolidone was applied to act as a protective colloid, the mixture of methylene chloride solvate and gamma form of IMC with less quantity of amorphous form was found in its IMC agglomerates. This strongly suggests that the composition of IMC agglomerates prepared from the solvent evaporation process was significantly influenced by the type of protective colloids used.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMedDate not supplied

Ras oncogene and p53 gene hotspot mutations in colorectal cancers.

Ras oncogene and p53 gene mutations are frequently observed in colorectal cancers. The role of co-operation between these two genes in the tumorigenesis of colorectal cancer was evaluated. Point mutations in K-ras oncogene and hotspot codons of p53 gene of colorectal cancers were evaluated by naturally created or amplified created restriction site method. Nine of 42 cases (21.4%) of colorectal cancer showed K-ras oncogene mutations. Six of 42 cases (14.3%) of colorectal cancer showed p53 gene hotspot point mutations. The low frequency of p53 gene mutation in this series may be due to racial difference or different hotspot codons. When six cases with mutated p53 gene were examined, only one (16.7%) showed concurrent K-ras oncogene codon 12 and p53 gene codon 248 mutations. We concluded that the co-operation between ras oncogene and p53 gene hotspot point mutations in the tumorigenesis of colorectal cancer in Chinese was not common. Other factors such as adenomatous polyposis coli gene mutations, oncogene activation or tumour suppression gene inactivation may be involved.

Base Sequence↗
PubMedDate not supplied

Changes in the skin moisture contents, skin color, and skin protein conformational structures of sprague-dawley rats after ultraviolet B irradiation.

The influence of ultraviolet B (UVB) irradiation on the skin moisture contents, skin color, and protein secondary structure in the skin of alive Sprague-Dawley (SD) rats was investigated. The UVB irradiation source emitted 725 +/- 10 microW/cm(2) of UVB range with a peak at 302 nm during the exposure course of 6 h/day for 3 successive days. The moisture content of SD rat's skin first decreased with the UVB irradiation, then returned to normal level on days 1 and 2, and, finally, decreased significantly with the increase of UVB irradiation on day 3. After the 6-hour irradiation on days 1 and 2, the moisture contents of the irradiated skin of SD rat returned to normal values, suggesting repairability of the irradiated skin of SD rat during the following 18 hour period without irradiation. By increasing frequency and duration of UVB irradiation, the skin color parameters exhibited a lower L* value, a greater a* value, and a higher DeltaE value, indicating that the skin color darkened and reddened. The slight modification of protein secondary structure of the skin of SD rats after repeated UVB irradiation was evidenced. However, the infrared spectrum during the initial course of irradiation, from day 1 to day 3, exhibited a similar pattern. Thus, the alive SD rat's skin was repairable during the 18-hour period without irradiation.

Animals↗
PubMedDate not supplied

Influence of coacervation-inducing agents and cooling rates on the preparation and in vitro release of bleomycin hydrochloride microcapsules.

Two types of coacervation-inducing agents (EVA, PIB) and three cooling rates (0.01998, 0.03482 and 0.06725 degrees C/min) affecting the preparation, micromeritic and drug release properties of bleomycin hydrochloride microcapsules were investigated. Particle size distribution of microcapsules induced by EVA significantly depended on the cooling rate, but that induced by PIB was independent of the cooling rate. Higher viscosity of PIB led to a smaller particle size of microcapsules than when EVA was used. The surface topography of the microcapsules for both types of coacervation-inducing agents was obviously different. We found that the release behaviour of bleomycin hydrochloride from the microcapsules also depended on the type of coacervation-inducing agent and the cooling rate. In general, the slower the cooling rate the more prolonged the release of the drug. Higuchi matrix model was followed for bleomycin hydrochloride released from the microcapsules. T50 of both types of microcapsules decreased with the increase of the cooling rate. To simulate the absorption behaviour of the GI tract, the continuous flow dialysis method was modified for drug release from the microcapsules. The data indicate that the diffusion of the dissolution medium and dissolved drug through the ethylcellulose wall of the microcapsules is the rate-limiting step before dialysis. This also implies that the release rate of the drug from dosage form significantly determined the absorption in the GI tract.

Bleomycin↗
PubMedDate not supplied

Effect of ethylene-vinyl acetate concentration on ethylcellulose-walled microcapsules: preparation and release kinetics of theophylline microcapsules.

The effect of concentration of ethylene-vinyl acetate (EVA) copolymer, used as a coacervation-inducing agent, on the preparation of ethylcellulose microcapsules was studied with theophylline as the core material. The influence of EVA concentration on the micromeritic properties of the microcapsules and their drug release behaviour were investigated. Particle size distribution of the microcapsules obtained was dependent on the amount of EVA copolymer. As the EVA concentration increased the quantity of larger particles was reduced and that of the smaller particles was increased. Thus EVA might be used as a protective colloid to prevent aggregation of the microcapsules. The porosity of the microcapsules decreased with respect to EVA concentration, but the wall thickness of the microcapsules showed a corresponding increase. Zero-order release kinetics, from the resulting microcapsules in the initial dissolution phase was obtained. The apparent zero-order release rate in the initial steady-state decreased with the increase of EVA concentration, but T50 increased. The higher concentration of EVA causing a thick, compact wall lead to an effective prolongation of drug release.

Cellulose↗
PubMedDate not supplied

An experimental study of the antitumour effect of bleomycin hydrochloride microcapsules.

The controlled release behaviour of bleomycin hydrochloride microcapsules was investigated by an in vitro dissolution method and an in vivo antitumour test. Bleomycin hydrochloride microcapsules prepared using the highest cooling rate exhibited sustained release characteristics and its release rate obeyed a nearly zero order release kinetics. Microcapsules containing bleomycin hydrochloride were locally injected into the solid tumour of uterine cervix carcinoma bearing nude mice. Tumour growth was markedly inhibited by treatment using bleomycin hydrochloride microcapsules compared to the control group and the group receiving direct local administration of bleomycin hydrochloride. No significant differences in the changes of body weight after treatment were found between the control group and the treated group. These results suggest that controlled release microcapsules may be applicable as a drug carrier for delivery of antitumour agents in cancer chemotherapy.

Animals↗
PubMedDate not supplied

In vitro release behaviour of theophylline from PIB-induced ethylcellulose microcapsules interpreted by simple mathematical functions.

Theophylline microcapsules were prepared by phase separation using polyisobutylene as a coacervation-inducing agent. The release rate was dependent on the molecular weight of the polyisobutylene used. A simple mathematical function has been used for the quantitative description of the release process of the drug from PIB-induced microcapsules. It was found that 1/y = A(1/x) + B is the best for interpreting the release process of microcapsules, since the values of the constants A and B are proportional to the amount of the drug released.

Capsules↗
PubMedDate not supplied

Preparation of enteric-coated microspheres of Mycoplasma hyopneumoniae vaccine with cellulose acetate phthalate: (II). Effect of temperature and pH on the stability and release behaviour of microspheres.

The in vitro stability (temperature and pH) and dissolution study (pH 7.4 phosphate buffer solution and pH changed medium) of the enteric-coated microspheres containing Mycoplasma hyopneumoniae vaccine (MHV) were examined. The MHV microspheres were thermally more stable than the unencapsulated MHV. More than 90% of antigenicity was retained in the MHV microspheres for 3 weeks when stored at 4 degrees C. The MHV microspheres in pH 1.2 and pH 3.0 medium were more stable than the unencapsulated MHV. The MHV enteric-coated microspheres exhibited an excellent enteric function to prevent pH-related inactivation. The influence of particle size, CAP concentration and span 80 concentration on the MHV released from microspheres was also determined. The smaller the particle size, the higher the dissolution rate due to the larger surface area of the smaller particle. The higher the concentration of span 80 used, the more the greater the amount of MHV released. This was attributed to the more porous structure of microspheres prepared by the higher concentration of span 80. By increasing the CAP concentration, however, the release rate of MHV was decreased due to the larger amount of CAP and the more compact structure of microspheres.

Animals↗
PubMedDate not supplied

Preparation of enteric-coated microspheres of Mycoplasma hyopneumoniae vaccine with cellulose acetate phthalate: I. Formation condition and micromeritic properties.

The solvent evaporation method was employed to encapsulate Mycoplasma hyopneumoniae vaccine (MHV) using cellulose acetate phthalate (CAP) as an enteric coating material. Glucose was used as a diluent. The effect of some factors, such as encapsulating temperature, surfactant concentration, mechanical agitation and CAP concentration on the formation condition, particle size distribution, morphology, surface topography and antigen content of MHV microspheres, was investigated. The result indicates that the optimal operating conditions were: encapsulating temperatures, 20 degrees C; stirring speed, 400 rpm; span 80 concentration, 0.6; and 8 per cent of CAP concentration, 30 ml. The optimal condition can be used to prepare the desirable microspheres. The content uniformity of MHV microspheres was also indicated.

Bacterial Vaccines↗
PubMedDate not supplied

Release kinetics of drug from different combined ratios of micropellets.

Release behaviours of different combined ratios of fast-release (FR) and sustained-release (SR) micropellets were studied. The release kinetic of the combined ratios of theophylline micropellets system was found to be a Higuchi matrix release model, and a linear regression was found between the release rate and the combined ratio of FR and SR theophylline micropellets. However, the combined ratio of the indomethacin micropellets system was found to be an apparent zero-order release kinetic and a quadratic regression was obtained between the zero-order release rate and the combined ratios of FR and SR indomethacin micropellets. This different release behaviour might be due to the different type and concentration of coating solution used.

Chemistry, Pharmaceutical↗
PubMedDate not supplied

Thermal analyser and micro FT-IR/DSC system used to determine the protective ability of microencapsulated squid oil.

Squid oil was microencapsulated by spray drying method. Gelatin, sodium caseinate, maltodextrin were contained in spray drying formulation with or without lecithin and microcrystalline cellulose (Avicel). The thermal stability of the unencapsulated and encapsulated squid oils was determined by pressure differential scanning calorimetry (PDSC), Fourier transform infrared (FT-IR) microscopic photometer with DSC system and themogravimetric analysis (TGA). The results indicate that the above analytical apparatus is an easy and reliable method to investigate the samples and that the microcapsule prepared by spray-dried formulation with lecithin as an emulsifier and Avicel as a stabilizer exhibits more stable thermal stability and longer shelf-life.

Animals↗
PubMedDate not supplied

Functionality of protective colloids affecting the formation, size uniformity and morphology of drug-free polylactic acid microspheres.

Drug-free polylactic acid (PLA) microspheres were prepared by an emulsification-solvent evaporation technique using different types of protective colloids. The influence of five types of hydrophilic prolymers (polysaccharides, proteins, synthetic cellulose derivatives, synthetic nonionic polymers and surfactants) on the formation, size uniformity and morphology of PLA microspheres was investigated. Four characteristic functions (surface activity, viscosity, electric charge and interfacial film formation) of the hydrophilic polymer aqueous solutions were used to evaluate the efficacy of these protective colloids used. The results indicate that these four functions were the key parameters to achieve the formation of PLA microspheres. The best protective colloid should have high surface activity, optimum viscosity, adequate electric charge, and form an interfacial film to give a higher recovery, better size uniformity and smoother topography of the PLA microspheres.

Colloids↗
PubMedDate not supplied

Microencapsulation and controlled release of insulin from polylactic acid microcapsules.

Insulin has been encapsulated in biodegradable polylactic acid microcapsules and non-biodegradable ethylcellulose microcapsules by using an emulsification-solvent evaporation process. Gelatin and polyvinylalcohol were used as protective colloids. The concentrations and types of protective colloids affecting the micromeritic properties and release behavior of insulin microcapsules were studied. The higher the concentration of protective colloids the smaller the particle size of microcapsules. The median diameter of microcapsules decreased with the increase of the viscosity of protective colloids. Scanning electron microscopic observations suggested that microcapsules prepared from higher concentrations of polyvinylalcohol solution resulted in a nonporous and compact surface on the microcapsules, compared to the porous microcapsules prepared from gelatin solution. The residual crystals and porous structure of microcapsules affected the release rate of microcapsules. After the initial burst effect the release rate of insulin from microcapsules was found to be constant, so that prolonged release was obtainable. Three percent of polyvinylalcohol was the best choice for the preparation of polylactic acid microcapsules.

Biocompatible Materials↗
PubMedDate not supplied

Ultrasonographic study of the coexistence of muscular torticollis and dysplasia of the hip.

The consistent relationship between congenital muscular torticollis and dysplasia of the hip is now widely accepted. However, the coexistence rate of these two disorders has been reported with variations from 0 to 20%. To obtain a more accurate coexistence rate, ultrasound scanner was used as the diagnostic tool for both of these disorders.Sixty-three children (30 boys and 33 girls) younger than 6 months who had undergone ultrasound scanning of both bilateral sternocleidomastoid muscle and bilateral hips were included in this study. Forty-seven children were confirmed to have muscular torticollis, and the remaining 16 cases were diagnosed as postural torticollis. Only these 47 cases were included for analysis of the coexistence rate. Eight children were found with dysplasia of the hips associated with muscular torticollis, which included Graf's type IIa for four hips, type IIb for two hips, type IIIa for one hip, and type IIIb for one hip. From the results of the present ultrasonographic study, the coexistence rate of congenital muscular torticollis and dysplasia of the hip was concluded to be 17%. If only those dysplastic hips (type IIb, IIIa, IIIb) that required treatment were included, the coexistence rate would be lowered to 8.5%.

Female↗
PubMedDate not supplied

Hepatitis B virus markers in Chinese twins.

Chinese same-sex twins were recruited in order to study the distribution of different markers of hepatitis B virus (HBV) infection, including HBV surface antigen (HBsAg), antibody to HBV core antigen (anti-HBc), antibody to HBsAg (anti-HBs), HBV e antigen (HBeAg) and antibody to HBeAg (Anti-HBe), as well as to compare the concordance of these markers in pair-wise fashion among monozygotic (MZ) and dizygotic (DZ) twins and singleton controls. A total of 289 pairs of MZ twins, 102 pairs of DZ twins and 375 pairs of age-sex-matched singleton controls were studied. More than 50 percent of the members of each group (64.71% of MZ twins, 51.96% of DZ twins and 62.13% of controls) were found to be infected with HBV. In general, the patterns of the response to HBV infection in the 3 groups were similarly distributed. 20.17% of the members of the 3 groups (21.45% of MZ twins, 14.22% of DZ twins, and 20.80% of controls) were HBsAg carriers. Among the HBsAg carriers, 49.19% (44.35% of MZ twins, 34.48% of DZ twins and 55.77% of controls) were HBeAg carriers. No significant difference in the concordance of HBV infection was observed in the MZ and DZ twins. However, highly significant differences were noted between MZ twins and controls, and between DZ twins and controls. Highly significant differences were also observed in the concordance of carrier status between MZ and DZ twins and between MZ twins and controls, but not between DZ and controls. As for the other HBV markers, no significant differences were observed. It is concluded that the genetic influence in response to HBV infection markers is not well-characterized and requires further study.

Adolescent↗
PubMedDate not supplied

Induction of superoxide dismutase and catalase activity in different rat tissues and protection from UVB irradiation after topical application of Ginkgo biloba extracts.

Ginkgo biloba extract (GBE) prepared from the leaves of Ginkgo biloba with 50% diluted alcohol was found to locally induce superoxide dismutase (SOD) and catalase (CAT) enzyme activity in epidermis after topical application, and also to systemically increase the activity of both enzymes in the liver, heart and kidney of Sprague Dawley rats. Skin pretreated with 50% diluted alcohol-extracted liquid formulation was protected from exacerbation of UVB damage. Changes in the lipid structure of the skin of rats determined by ATR/FT-IR spectroscopy demonstrated penetration of active components from GBE dosage formulations.

Administration, Topical↗