Search PubMed⌕ Search

Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 829 records · Page 46Linked to original sources
PubMed1996

Optima: a windows-based program for computer-aided optimization of controlled-release dosage forms.

The purpose of this work was to develop a computer program that assists optimization of controlled-release devices, both visually and mathematically, using response surface methodology (RSM). A Windows-based computer program, Optima, which interactively implemented a number of subroutines for the optimization procedure, was developed. Optima is an integrated, user-friendly, and graphically oriented program for pharmaceutical dosage form optimization. Central composite design is implemented in the program. First- and second-order models containing up to five variables can be fitted to the data. The user can also choose between linear and exponential individual desirability functions, and use them to construct an overall desirability function that combines all the response variables in a single response. The program can predict the optimum levels of experimental variables, with respect to individual responses and/or the overall desirability. Optima has been successfully used in the development of sustained-release AZT-loaded microspheres. During the optimization process, three experimental variables were investigated and four responses were measured. The experimental design was a central composite design that was generated by the program. The response values were used by the program to calculate the individual desirability functions, which were then combined into an overall desirability function. The individual responses as well as the overall desirability function were optimized by fitting to a second-order polynomial equation. The response surfaces were generated and optimum levels of the experimental variables were predicted. The observed responses of the optimized formulation were very close to those predicted by Optima. The program proved to be a very useful, integrated tool for optimization of the controlled-release microspheres.

Computer Graphics↗
PubMed1996

Clinical significance of serum hepatitis C virus titers in patients with chronic type C hepatitis.

OBJECTIVES: To investigate the relationship between serum hepatitis C virus (HCV) titers and clinicopathological characteristics of chronic type C hepatitis. METHODS: Serum HCV cDNA concentrations were determined by a competitive polymerase chain reaction assay in 60 Taiwanese patients with chronic type C hepatitis. RESULTS: The concentration of serum HCV cDNA ranged between 10(2) and 10(8) copies/mL. The titers of serum HCV (logarithmic transformed copies of HCV cDNA/mL serum) were not significantly correlated with clinicopathological characteristics with respect to either sex of the patients, source of infection, higher serum ALT level (>150 IU/L) or histological severity. In contrast, serum HCV titers were significantly higher in patients with age above 50 yr and with type 1b HCV infection. Moreover, the influence of advancing age on serum HCV titer was genotype-independent by multivariate analysis. CONCLUSIONS: These results suggest that advancing age and genotype are both important determinants of HCV viremia and that the pathogenesis of HCV infection might not be caused by direct cytotoxicity of the virus.

Adult↗
PubMed1996

The melanocortin receptors: agonists, antagonists, and the hormonal control of pigmentation.

Molecular cloning experiments have led to the identification and characterization of a family of five receptors for the melanocortin (melanotropic and adrenocorticotropic) peptides. The first two members of the family cloned were the well-characterized melanocyte-stimulating hormone receptor (MSH-R) and adrenocorticotropin receptor (ACTH-R). The three new melanocortin receptors have been termed the MC3-R, MC4-R, and MC5-R, according to the order of their discovery, and little is known at this point concerning their function. Agouti and extension are two genetic loci known to control the amounts of eumelanin (brown-black) and phaeomelanin (yellow-red) pigments. Chromosomal mapping demonstrated that the MSH-R, now termed MCI-R, mapped to extension. Extension was shown to encode the MCI-R, and mutations in the MCI-R are responsible for the different pigmentation phenotypes caused by this locus. Functional variants of the MCI-R, originally characterized in the mouse, have now also been identified in the guinea pig and cow. Dominant constitutive mutants of the MCI-R are responsible for causing dark black coat colors while recessive alleles result in yellow or red coat colors. Agouti, a secreted 108 amino acid peptide produced within the hair follicle, acts on follicular melanocytes to inhibit alpha-MSH-induced eumelanin production. Experiments demonstrate that agouti is a high-affinity antagonist, acting at the MCI-R to block alpha-MSH stimulation of adenylyl cyclase, the effector through which alpha-MSH induces eumelanin synthesis. The MCI-R is thus a unique bifunctionally controlled receptor, activated by alpha-MSH and antagonized by agouti, both contributing to the variability seen in mammalian coat colors. The variable tan and black coat color patterns seen in the German Shepherd, for example, can now be understood on the molecular level as the interaction of a number of extension and agouti alleles encoding variably functioning receptors and a differentially expressed antagonist of the receptor, respectively.

Agouti Signaling Protein↗
PubMed1996

Can a super oral rehydration solution stimulate intestinal repair in acute viral enteritis?

This study was designed to screen several treatments for their effects on mucosal repair in an established model of piglet rotavirus enteritis. Six ingredients selected to facilitate repair were added to the oral rehydration solution (ORS) and subsequently to the diet: L-glutamine (GLN); rice solids; a soluble fiber (carboxymethylcellulose); nucleotides; polyamines; and fructooligo-saccharides. Rotavirus infection consistently induced a watery diarrhoea lasting 5 to 10 days and produced a jejunal mucosal lesion which was maximal at 3 days, post-inoculation (manifested by a reduction of villus surface area to 30% to 50% of normal). By 7 to 10 day post-inoculation, the villus surface area returned to 50% to 80% of normal. None of the supplemental ingredients added to the ORS had a significant effect in either shortening the clinical illness or in stimulating recovery of the affected mucosa. It is concluded that several types of "Super ORS" are ineffective in enhancing repair in viral enteritis in neonatal colostrum-deprived piglets. These results do not rule out beneficial effects of the additives tested in subjects with more extensive intestinal damage, in those who receive breast milk, or in those with bacterial enteritis.

Animals↗
PubMed1996

[A dynamic study of the cytotoxic effects of hyperthermia combined with cis-diaminedichlorolplatinum (DDP) on human gastric cancer cell lines MKN28 and MKN45 in vitro].

Cytotoxic effects of hyperthermia combined with DDP on MKN28 and MKN45 cells were studied by MTT assay according to a nested design. The rusults showed: hyperthermia alone above 43 degrees C for 30 min was cytotoxic; hyperthermia at temperature lower than 43 degrees C for 30 min could increase sensitivity of cancer cells to DDP. The cytotoxic effect of simultaneous use of hyperthermia and DDP was more marked than that of sequential use of the 2 treatments. Hyperthermia combined with DDP could inhibit growth of human gastric adenocarcinoma cells regardless of their degree of differentiation.

Adenocarcinoma↗
PubMed1996

Effects of MTX and BN52021 on PAF-induced chemotaxis of PMNs and intraepidermal accumulation of inflammatory cells in guinea pigs.

OBJECTIVE: To investigate the effects of methotrexate (MTX) and platelet activating factor (PAF) antagonist ginkgolide B (BN52021) on PAF induced chemotaxis of neutrophils. MATERIALS AND METHODS: All guinea pigs were randomly divided into 12 groups. They were given different dosages of MTX and BN52021 by intra-abdominal injections. The random and chemotactic migration of polymorphonuclear leukocytes (PMNs) were measured by the agarose method. The backs of all guinea pigs were given intradermal injections of PAF and the numbers of the infiltration of inflammatory cells into the skin were determined. RESULTS: MTX inhibited random migration and chemotactic migration of PMNs to PAF, LTB4 and PAF-induced intraepidermal accumulation of inflammatory cells in dose- and time-dependent fashion. BN52021 specially inhibited PAF-induced chemotaxis of PMNs and intraepidermal accumulation of inflammatory cells, but did not inhibit PMNs random migration and LTB4-induced chemotaxis of PMNs. CONCLUSIONS: The inhibition of PMNs activities may be part of the mechanism of MTX therapy for psoriasis; BN52021 is a selective inhibitor of PAF-induced chemotaxis of PMNs, and therefore can be useful in the treatment of some inflammatory dermatoses such as psoriasis.

Animals↗
PubMed1996

[Effect of tetrandrine on intraacinar pulmonary arterial structural remodelling and pulmonary hypertension].

Rat's pulmonary hypertension was induced by a single subcutaneous injection of monocrotaline. The influences of tetrandrine (Tet) upon the structure of intraacinar pulmonary arteries (IAPA) was studied by light and electron microscopy. The results indicated that Tet reduced the thickness of IAPA medial membrane, the ratio of the thickness of IAPA medial membrane to the diameter of IAPA, the number of circular muscular artery and partially muscular artery about 16.4%, 30.5%, 24.3% and 16.4% respectively, and Tet increased the number of nonmuscular artery about 24.7%. It also decreased the degeneration of IAPA, collagen of medial membrane, prolife-ration and myoid differentiation of the pericyte, and it increased the number of IAPA. The authors discussed why Tet caused such changes.

Alkaloids↗
PubMed1996

[Protective and treated effects of L-arginine on hypoxia-induced pulmonary hypertension in rats].

The protective and treated effects of L-Arginine on isobaric hypoxia-induced pulmonary hypertension were studied in rats. It was found that L-Arginine significantly inhibits hypoxic pulmonary hypertension and right ventricular hypertrophy. The mean pulmonary arterial pressure (mPAP) was 3.58 +/- 0.06 kPa and right ventricle/(left ventricle plus septum) ratio [RV/(LV+S)] was 0.34 +/- 0.01 in rats exposed to hypoxia (FiO2 = 0.10 +/- 0.05) for 3 weeks. The mPAP was 2.61 +/- 0.09 kPa and RV/(LV+S) was 0.26 +/- 0.01 in rats pretreated with L-Arginine [200mg/(kg.d)]i there is significant difference between the two groups. We also found that L-Arginine (300mg/kg) can decrease mPAP in rats with hypoxic pulmonary hypertension. The results suggest that L-Arginine might have significant protential for protection and treatment of hypoxic pulmonary hypertension.

Animals↗
PubMed1996

[Measurement of maximal inspiratory flow and forced inspiratory capacity and its clinical application].

The methods of measuring the maximal inspiratory flow (V(imax)) and the forced inspiratory capacity (FIC) via forced inspiratory capacity-time curve (FIC-t curve) were investigated. Both V(imax) and FIC were measured in 35 normal subjects and 89 patients with chronic obstructive pulmonary disease (COPD). The maximal inspiratory pressure (MIP) was measured simultaneously at function residual capacity(FRC) level by modified Black Method. The results showed that there is a linear relationship between MIP and V(imax) or FIC in both normal subjects and patients with COPD. Normal subjects had a mean V(imax) and FIC much higher than those of patients with COPD. The values of V(imax) and FIC in patients were also, significantly correlated to the severity of COPD. So we suggest that both V(imax) and FIC be used as clinical indices to reflect inspiratory muscles strength.

Adult↗
PubMed1996

Study on ultrastructural cytochemistry and pathogenic mechanism of Trichomonas vaginalis.

OBJECTIVE: To study the relation among enzymic ultrastructural localizations, cell organelles and functions of Trichomonas vaginalis (T. vaginalis) as well as its pathogenic mechanism. MATERIAL AND METHODS: The specimens were Trichomonas vaginalis cultured purely for several generations. After prefixation, several electron microscopic cytochemical reactions for marker enzymes of lysosome, Golgi body, mitochondrion and microbody as well as Ur-Pb-Cu impregnation were undertaken. Then the specimens were post-fixed and embedded, and the unstained ultrathin sections were observed under a transmission electron microscope. RESULTS: The activities of acid phosphatase and cytidine monophosphatase appeared in the primary and secondary lysosomes of the parasite, and the reaction product of peroxidase was found in the secondary lysosomes. It was found that lysosomes could release hydrolytic enzymes out of the cell. The reaction products of thiamine pyrophosphatase and nicotinamide adenine dinucleotide phosphatase were located within the mature-surface and intermediate saccules of Golgi body respectively. The reactions for succinate dehydrogenase, cytochrome oxidase and catalase were negative. The hydrogenosomes, endoplasmic reticulum and Golgi bodies of the parasite were densely stained by Ur-Pb-Cu impregnation method. CONCLUSIONS: T.vaginalis has lysosomal system which can release hydrolases out of the parasite, causing damage to the vaginal and urethral epithelial cells. This may be an important pathogenic mechanism of vaginitis and urethritis caused by T.vaginalis. This protozoon has well-developed Golgi bodies and rich endoplasmic reticulum. It lacks mitochondrion and microbody, but has abundant hydrogenosomes which are energy producing organelles of anaerobic metabolism and resemble microbody in morphology and mitochondrion in some functions.

Animals↗
PubMed1996

Changes of distribution of platelet activating factor in the lung of rats with hypoxic pulmonary hypertension.

OBJECTIVE: To investigate the role of platelet activating factor (PAF) in the hypoxic pulmonary hypertension. MATERIAL AND METHODS: Fifteen of 30 male Wistar rats were exposed to hypoxia for 3 weeks, and another 15 rats served as controls. The pulmonary arterial pressure was examined by catheterization. The sections of rat lung were treated by the avidin-biotin-peroxidase complex method to expose the location of PAF. RESULTS: The rats developed pulmonary hypertension and right ventricular hypertrophy after hypoxic exposure. Under the light microscope, PAF is distributed on the vascular and alveolar walls of normal lung, and the content of PAF in the lung of rats with hypoxic pulmonary hypertension are remarkably higher than those of normoxic controls. CONCLUSIONS: PAF plays not only a physiological role in the rat lung, but also a pathophysiologic role in hypoxic pulmonary hypertension.

Animals↗
PubMed1996

Detoxicating enzymes of Entamoeba histolytica and their detoxifying roles.

OBJECTIVE: To investigate the Entamoeba histolytica living in the low oxygen concentration colon of the host and how does it survive in the circumstance after invading the tissues with high oxygen concentration while obtaining oxygen without being damaged by the toxins. MATERIAL AND METHODS: E. histolytica cultured for 48 hours was collected, centrifuged, rinsed, ultrasonically shattered and again centrifuged, and the activities of superoxide dismutase and the catalase in the supernatant were determined. The catalase and peroxidase were identified by the electron microscopic enzyme cytochemical reaction technique. RESULTS: E. histolytica contained 122.42 +/- 15.47 U/mgpr of superoxide dismutase, 126.05 +/- 17.04 K/mgpr of catalase and peroxidase, and all of them are detoxifying enzymes. Catalase and peroxidase were located within microsomes and lysosome-like organelles respectively. CONCLUSIONS: E. histolytica contains the detoxifying enzymes as superoxide dismutase, catalase and peroxidase, that may prevent the aerobic metabolism from being poisoned by the activated oxygen free radical (superoxide anion radical and hydrogen peroxide) produced in this process, suggesting that the detoxifying function of these enzymes play an important defensive role in the survival of E. histolytica.

Animals↗
PubMed1996

Effects of ginkgolide B on isobaric hypoxic pulmonary hypertension in rats.

OBJECTIVE: To evaluate the effects of Ginkgolide B, a specific platelet activating factor (PAF) antagonist, on hypoxia-induced pulmonary hypertension and pulmonary vascular remodeling. MATERIALS AND METHODS: Forty male Wistar rats were divided into 4 groups, receiving normal saline, Ginkgolide B, isobaric hypoxia and isobaric hypoxia plus Ginkgolide B respectively. Pulmonary hemodynamics were assessed via right heart catheterization. Pulmonary vascular remodeling were examined by a computerized image analyser. RESULTS: Chronic hypoxia (FiO2 = 0.10, 3 weeks) caused pulmonary hypertension, pulmonary vascular remodeling and right ventricular hypertrophy in rats. Treatment with Ginkgolide B reduced the extent of pulmonary hypertension, pulmonary vascular remodeling and right ventricular hypertrophy induced by hypoxic exposure. CONCLUSIONS: The results suggest that PAF participates in the process of chronic hypoxic pulmonary hypertension and pulmonary vascular remodeling, and PAF antagonist could be a potentially useful agent for preventing hypoxic pulmonary hypertension.

Animals↗
PubMed1996

[The effect of splenectomy on alveolar macrophages morphology and function].

OBJECTIVE: To study the morphological and functional changes of pulmonary alveolar macrophages of rats after splenectomy, and the applied effects of splenic tissue autotransplantation in practice. METHODS: 87 Wistar rats were randomly divided into shamoperation group, splenectomy group and splenic tissue autotransplantation group. Six months after splenectomy, alveolar macrophges were subjected to brochoalveolar lavage described by Shennib. The dynamic survival and adherent rate of alveolar macrophages in culture, lysosomal enzyme content, hydrogen peroxide production and expression level of interleukin 1 (IL-1) activity of alveolar macrophages were quantitatively measured. The alveolar macrophages ultrastructure was observed by utilizing transmission electron microscope. RESULTS: The splenectomized rat's alveolar macrophages were different from alveolar macrophages of sham-operated rats. Their surface filopodia was reduced and shortened, lysosome fewer and its acid phosphatase quantity decreased, adherence postponed, hydrogen peroxide production and expression of IL-1 activity impaired. Splenic tissue autotransplantation fairly restored the splenic effects on maturation and function of alveolar macrophages. CONCLUSION: Splenic tissue autotransplantation is a simple useful operation for preserving splenic function after splenectomy.

Animals↗