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Biomedical subjects

G Pang

Publications and source records attributed to G Pang.

At least 55 records · Page 3Linked to original sources
PubMed1999

[Study on proteins of allele by using the microisoelectric focusing].

Clear protein electrophoresis pattern of single pollen grain from Cucurbita pepo L. was obtained with isoelectric focusing and supersensitive stain technique. The results showed that there were two special distributing protein bands near acidity pole. In species I, the two protein bands were a little near to acidity pole and in species II, that was a little far from acidity pole. In species III, the two protein bands distributed either like species I or like species II and the distributed ratio was 1:1. Moreover, we discuss how to identify relative purity of gene with the sorts of the special proteins.

Alleles↗
PubMed1999

[Establishment of a rabbit model of Acanthamoeba keratitis].

AIM: To establish an animal model of Acanthamoeba keratitis. METHODS: Six New Zealand white rabbits were each injected intrastromally with Acanthamoeba suspension 3 days after subconjunctival injection with dexamethasone. RESULTS: All of the 6 rabbits developed keratitis. Acanthamoeba protozoa were identified by the methods of corneal scraping with 10% potassium hydroxide wet mount examined under microscope, corneal protozoa culture and pathological section examination. CONCLUSION: A rabbit model of Acanthamoeba keratitis was established.

Acanthamoeba Keratitis↗
PubMed1998

IL-6, IFN-gamma and TNF-alpha production by liver-associated T cells and acute liver injury in rats administered concanavalin A.

The relationship between the development of acute hepatitis and the production of TNF-alpha IFN-gamma and IL-6 by liver-associated T lymphocytes following intravenous injection of concanavalin A (Con A) was studied in rats. Following a single injection of Con A, there was a dose and time-dependent correlation in the serum levels of serum alanine aminotransferase (ALT), IL-6, IFN-gamma and TNF-alpha. These increases correlated with an increase in the numbers of CD4+, CD8+ and CD25+ T cells in blood and CD4+ and CD25+ T cells in the liver perfusate, but not with CD8+ T cells in liver perfusate. Increased levels of IL-6, IFN-gamma and TNF-alpha were constitutively produced by liver-associated CD4+ T cells when cultured. In Con A-stimulated cultures, liver-associated CD4+ T cells secreted increasing levels of TNF-alpha in a time-dependent manner following Con A injection, but TNF-alpha production by peripheral blood lymphocytes was transient with peak levels detected at 1 h which then declined over 24 h. Histological examination of the liver revealed fatty change, hepatocyte degeneration and necrosis, with an associated cell infiltrate of neutrophils and CD4+ T cells both in the portal areas and around the central veins. These results support the hypothesis that Con A-induced liver damage is mediated by CD4+ T cells acting within the liver, at least in part through the secretion of TNF-alpha, IFN-gamma and IL-6.

Alanine Transaminase↗
PubMed1998

Lens design for large-area x-ray sensitive vidicons.

Large-area x-ray sensitive vidicons have the potential to be superior to conventional x-ray image intensifiers for medical fluoroscopy. To build a large-area x-ray vidicon, an electron lens system is necessary to provide perpendicular beam landing. In this paper, we discuss theoretically how to build two and three cylinder coaxial lenses for this purpose. Some general design rules and a preferred design which satisfies our design criteria are presented. Limitations of these simple types of electron lens are discussed. Two advanced designs for vidicons with short lengths or reduced beam landing error are also included. Among them, the deflection-center-change system is introduced here for the first time.

Electrons↗
PubMed1998

Digital radiology using active matrix readout of amorphous selenium: geometrical and effective fill factors.

Flat panel self-scanned x-ray detectors using amorphous selenium (a-Se) as the photoconductor are being developed to replace both film/screen cassette systems for radiography and image intensifier (XRII)/video systems for fluoroscopy. These use a two-dimensional array of pixel electrodes to collect and readout the latent image charges formed on the photoconductor surface. The percentage of the area covered by the pixel electrodes (i.e., the geometrical fill factor fg) is always less than unity. In this paper, a novel approach is introduced to make the charge collection by pixel electrodes almost complete (i.e., a close to unity effective fill factor). The idea is to bend the electric field lines in the a-Se layer in such a way that image charges cannot land in the gap region between electrodes. This is achieved by depositing holes in the gap region, which is possible because there are charge traps available at the a-Se/insulator interface. The distribution of holes required in the gap region is calculated. Various factors associated with the feasibility of this approach as well as a method to deposit these holes are discussed. Application of the approach to the case of mammography is also included.

Biophysical Phenomena↗
PubMed1998

[Myopic regression after photorefractive keratectomy].

OBJECTIVE: To investigate myopic regression after excimer laser photorefractive keratectomy (PRK) in patients with myopia. METHODS: 103 eyes with regression (>or= -1.00 D) found in the follow-up for more than 1 year were included in this study. The preoperative spherical equivalent was -4.00 - -14.50 D (-8.72 +/- 2.65 D). Patients were divided into two groups: (1) moderate myopia (-4.00 - -7.90 D) and (2) high myopia (>or= -8.00 D). RESULTS: A significant positive correlation was found between regression and the extent of attempted correction, the rate of regression in high myopia group was 6.93% and that in moderate group, 1.17%. The rate of regression in older age group was higher than that in younger cases. (P < 0.01). Relatively severe haze under the corneal epithelium often accompanies the regression, and decrease of the dosage of topical corticosteroid application or its withdrawal because of the development of corticosteroid ocular hypertention could lead to the regression. The stability of the refraction is not related to the difference in sex. The regression is often accompanied by the increase in K value. CONCLUSION: The regression is significantly related to the extent of attempted correction, patients' age, corneal haze and topical application of corticosteroid.

Adrenal Cortex Hormones↗
PubMed1998

Decreased tumor necrosis factor-alpha and interleukin-1alpha production from intrahepatic mononuclear cells in chronic ethanol consumption and upregulation by endotoxin.

The relationship between the changes in liver pathology and the production of interleukin (IL)-1alpha, IL-6, and tumor necrosis factor-alpha (TNF-alpha) by intrahepatic mononuclear cells was studied in rats fed alcohol and subsequently exposed to lipopolysaccharide (LPS). Rats were fed 40% ethanol in drinking water, whereas control rats were provided with a chow diet with isocaloric or 2% sucrose drinking solutions for up to 20 weeks. Decreased IL-1alpha and TNF-alpha production in 24-hr culture supernatants of mononuclear cells isolated from liver perfusate was detected while IL-6 remained unchanged over 20 weeks. When animals were injected with LPS (1.0 microg/kg body weight), there was a 5-fold rise in ALT levels in the ethanol-fed group, but not in control groups. Increased IL-6 and TNF-alpha levels in the serum and supernatant of cultured intrahepatic mononuclear cells stimulated with or without LPS or concanavalin A was observed. There was a correlation between levels of ALT and TNF-alpha, but not IL-6. T cells and Kupffer cells were the major source of TNF-alpha in culture supernatants of hepatic perfusate mononuclear cells from ethanol-consuming rats injected LPS. In addition, pathological liver injury was evident, which suggests a pathogenic role for TNF-alpha in alcohol-induced liver disease.

Animals↗
PubMed1998

Altered T-lymphocyte responsiveness to polyclonal cell activators is responsible for liver cell necrosis in alcohol-fed rats.

The role of T-cell activation in alcoholic liver disease was investigated in rats fed alcohol and subsequently exposed to concanavalin A (Con A). Following Con A injection (20 mg/kg body weight), greater increases in liver-to-body weight ratio and ALT levels were observed at 12 and 24 hr in rats fed ethanol, compared with control rats fed sucrose. Furthermore, increases in serum interleukin-6 and tumor necrosis factor-alpha levels were noted in ethanol-fed rats, with maximal levels detected at 4 hr declining thereafter, but remaining above control levels at 24 hr. Analysis of T-cell subpopulations showed an increased percentage of CD4+, CD5+, and CD8+ T cells in blood from all groups, but not in liver perfusate. In contrast, a significant increase in the percentage of activated CD25+ T cells was detected in both blood and liver perfusate from rats fed ethanol even 24 hr after Con A injection. When CD4+ and CD8+ T cells from liver perfusate were cultured in the absence or presence of Con A, an increase in interleukin-6 and tumor necrosis factor-alpha production in supernatants was observed in ethanol-fed rats. In cultures stimulated with Con A, a 2- to 8-fold increase in cytokine production was detected, with intrahepatic CD4+ T cells being the major source. Immunohistological analysis revealed infiltration of CD4+ T cells around portal vein and central vein areas associated with fatty liver and severe hepatic necrosis. The results suggest that alcohol consumption induced a dysregulated T-cell population that mediated hepatic necrosis following polyclonal activation with Con A.

Animals↗
PubMed1998

Interferon alpha-2b in the treatment of chronic hepatitis C: early experience.

The antiviral and immunomodulatory effects of interferon were assessed in the treatment of chronic Hepatitis C in multi-ethnic patients to prevent viral replication and chronic liver damage. Three million units of recombinant interferon alpha-2b were administered three times a week for 48 weeks to a group of 9 active Hepatitis C patients. A clinical response was defined as normalization of serum ALT values. Serum was frozen and stored for Hepatitis C viral assays. Four patients normalized their liver functions. When viral levels were measured only two patients had unmeasurable levels of HCV RNA after treatment. Therapeutic results were observed and much work needs to be done to improve therapy because a serious epidemic is predicted for the future.

Adult↗
PubMed1997

TNF-alpha is not the sole mediator of WEHI-164 tumour cell killing in natural cytotoxicity.

Using a mAb to NC-1.1, a receptor involved in recognition of tumour targets, the authors have examined the dogma that murine natural cytotoxicity (NC) is exclusively mediated by TNF-alpha. Three different NC-1.1+ spleen cells, WEHI-3BR1 myelomonocytic cells and an uncloned mast cell line-MCL) were reacted with NC-sensitive WEHI-164 targets in vitro, and the induction of TNF-alpha mRNA, surface expression of TNF-alpha, and the appearance of apoptotic bodies in the culture were simultaneously measured. NC-1.1+ spleen cells and WEHI-3BR1 cells showed marked induction of TNF-alpha mRNA within 30 min and this was maintained for up to 18 h. Only transient TNF-alpha mRNA induction was observed in MCL cells at 30 min. Surface TNF-alpha was detected on WEHI-3BR1 cells by 4 h, but was not detected on MCL cells. All three effector cell types mediated NC against WEHI-164 targets within 18 h, but they responded differently to the addition of anti-TNF-alpha mAb: anti-TNF-alpha completely blocked WEHI-3BR1 NC, blocked NC-1.1+ spleen cell NC by approximately 70%, and did not block NC by MCL cells. This indicates that TNF-alpha is induced during NC by WEHI-3BR1 effectors and NC-1.1+ spleen cells, is the sole mediator of NC by WEHI-3BR1, and appears to play no role in NC by MCL cells.

Animals↗
PubMed1997

Autocrine modulation of IL-8 production by sputum neutrophils in chronic bronchial sepsis.

We examined the activity of neutrophils isolated from sputum and blood of subjects with chronic bronchial sepsis in terms of interleukin-8 (IL-8), IL-1beta, and tumor necrosis factor-alpha (TNF alpha) production. In sputum, the numbers of neutrophils correlated with the concentrations of these cytokines. Sputum neutrophils constitutively secreted large amounts of IL-8, IL-1beta, and TNF alpha. The patterns of secretion, however, differed from those of blood neutrophils stimulated with bacterial lipopolysaccharide (LPS). Cytokine secretion was time-dependent and was inhibited by cycloheximide and dexamethasone. IL-10 inhibition of IL-8 production by sputum neutrophils was significantly less than that noted with activated neutrophils. Antibody to IL-1beta but not to TNF alpha, inhibited IL-8 secretion by sputum neutrophils, contrasting with results found using blood neutrophils. Incubation of blood neutrophils in sputum sol induced a similar cytokine secretion profile to that following exposure to LPS. The inhibitory effects on IL-8 protein production correlated with messenger RNA (mRNA) gene expression. These observations indicate that neutrophils are a significant source of IL-8 in purulent sputum, and that an autocrine loop involving IL-1beta maintains secretion within the bronchus lumen.

Blood↗
PubMed1997

[A corneal topographic analysis of astigmatism after excimer laser photorefractive keratectomy].

OBJECTIVE: To identify the astigmatism changes after excimer laser photorefractive keratectomy (PRK) and the visual influence of astigmatism. METHODS: 109 myopic eyes followed up for more than 1 year were analyzed by using videokeratography, and their visual acuities were examined. Before the operation, the astigmatic errors with cycloplegic refractive examination were -1.00(-)-2.00 D. RESULTS: The position of astigmatism axis was basically consistent with that in corneal topography, but the astigmatism diopter was of some difference between the cycloplegic examination and topographic analysis. With-the-rule astigmatism was in 61% of the eyes, asymmetrical was 33% and against-the-rule was 6% in topographic analysis. Only was a little change in the position of astigmatism axis after PRK observed. Some changes of postoperative astigmatism diopter were seen in different periods. It was increased in the postoperative 10 days or 1 month, and afterwards it became gradually decreased and stable in 6 months to 1 year. The postoperative residual astigmatism was low in degree, that did not affect the visual acuity a great deal. The actual corrected diopter was within the anticipated corrected diopter range of +/- 1.00 D, accounting for 97%. CONCLUSION: By using spherical equivalent method of calculation in PRK, the refractive correction of the operation in cases with myopia and low degree of astigmatism (< -2.00 D) can be satisfactory.

Astigmatism↗
PubMed1997

A corneal topographic analysis of astigmatism after excimer laser photorefractive keratectomy.

OBJECTIVE: To identify the astigmatism changes after excimer laser photorefractive keratectomy (PRK) and the visual influence of astigmatism. METHODS: 109 myopic eyes followed up for more than 1 year were analyzed by videokeratography, and their visual acuities were examined. Before the operation, the astigmatic errors with cycloplegic refractive examination were -1.00 approximately -2.00 D. RESULTS: The position of astigmatism axis was basically consistent with that in corneal topography, but in astigmatism diopter there were some differences between the cycloplegic examination and topographic analysis. A stigmatism was found in 62% of the eyes, asymmetrical in 33% and against-the-rule in 5% by using topographic analysis. There was little change observed in the position of astigmatism axis after PRK observed. Some changes of postoperative astigmatism diopter were seen in different periods. It increased in the postoperative 10 days or 1 month, and afterwards gradually decreased and became stable in 6 months to 1 year. The postoperative residual astigmatism was low in degree, and did not affect the visual acuity. The actually corrected diopter was within the anticipated corrected diopter range of +/- 1.00 D. accounting for 97.4%. CONCLUSION: By using spherical equivalent method of calculation in PRK, the refractive correction of the operation cases with myopia and low degree of astigmatism (< -2.00 D) was satisfactory.

Astigmatism↗
PubMed1996

Applications of synchrotron radiation to defect characterization and pendellösung fringe-spacing measurement in a natural diamond.

A small polished rectangular block of natural diamond unusually free from impurity zoning was examined by birefringence and synchrotron X-ray topography to map internal defects and assess effects of some accidental mechanical damage. ;Orthogonal-view' projection topographs facilitated comparisons between optical and X-ray images. Speedy and precise positioning of crystal sections cut in synchrotron X-ray section topographic studies was aided by radiographic and fluoroscopic procedures, which are described. Several X-ray reflection and refraction phenomena are illustrated, including high-contrast refraction images of crystal edges, chipping and crack outcrops. It was demonstrated that by combining optical and X-ray goniometry it was possible to record Pendellösung fringe systems employing precisely selected X-ray wavelengths in well defined crystal volumes. Valuable gain in fringe visibility resulted from the use of pure sigma-mode polarized synchrotron radiation. Absolute values of the diamond 004 structure factor were derived from five fringe systems measured, the findings (in upward order) being 11.7, 11.7, 12.0, 12.5, 12.6. Their scatter greatly exceeds the uncertainty in the measurement procedure (believed to be within +/-1%) and is attributed to different strain distributions within the five volumes sampled.

Journal Article↗
PubMed1996

The sigma receptor ligand, reduced haloperidol, induces apoptosis and increases intracellular-free calcium levels [Ca2+]i in colon and mammary adenocarcinoma cells.

The sigma receptor ligand reduced haloperidol (50 and 100 microM), potently inhibited cell proliferation, and induced apoptosis in WIDr colon and MCF-7 adenocarcinoma cell lines. Apoptosis was confirmed after drug treatment of the cells by the presence of nuclear fragmentation after staining of the cells with Hoechst 33258 and cellular DNA fragmentation ELISA and by condensation of the heterochromatin using transmission electron microscopy. However, internucleosomal DNA cleavage was not detected using gel electrophoresis. Reduced haloperidol (100 microM) increased the intracellular free calcium levels [Ca2+]i in both cell lines, which was independent of extracellular calcium, suggesting that the rise in [Ca2+]i was from intracellular stores and that an increase in [Ca2+]i may act as a "trigger" for apoptosis in these cell lines.

Adenocarcinoma↗
PubMed1996

Immunologic, functional, and morphological characterization of three new human small intestinal epithelial cell lines.

BACKGROUND & AIMS: Epithelial cell cultures can be used for the study of epithelial cell biology, although human small intestinal cultures have not been available to date. The aim of this study was to characterize three cell lines derived from normal human duodenum. METHODS: Cells were cultured from tissue fragments obtained from endoscopic biopsy specimens and characterized with respect to morphology and cytokine gene expression and for the presence of vectorial transport. RESULTS: All cell lines grew as polarized continuous monolayers and were mostly cuboidal in shape but were not immortalized. Cells showed junctional complexes and sparse microvilli. All cell lines showed cytokeratins and mucin antigen but not chromagranin and messenger RNA for epidermal growth factor, interleukin 6, and vascular cell adhesion molecule 1. Disaccharidase activities were low and correlated with the low proportion of cells (1%-10%), showing positive immunocytochemistry for sucrase. Monolayer resistance varied from 30 to 200 ohms. One monolayer (BN) consistently showed secretion in response to forskolin (10 micromol/L), which could b inhibited by chloride-free buffer and apical addition of the chloride channel blocker diphenylamine decarboxylate. No monolayer had evidence of glucose transport. CONCLUSIONS: These three nonimmortalized lines show morphological, phenotypic, and transport characteristics of crypt-like intestinal epithelial cells. The pattern of messenger RNA expression suggests a growth-promoting and immunomodulatory role.

Aged↗
PubMed1996

Long-term low dose interferon alpha-2b in the treatment of chronic hepatitis B in multi-ethnic patients in Hawaii.

The antiviral and immunomodulatory effects of interferon were assessed in the treatment of chronic hepatitis B in multi-ethnic patients to prevent viral replication and chronic liver damage. Five million units of recombinant interferon alpha-2b were administered three times a week for 48 weeks to a group of 18 chronic active hepatitis B patients. A complete response was defined as seroconversion to anti-HBe and/or loss of HBe antigen. Seroconversion to anti-HBe in 5 of 12 (42%) chronic active hepatitis B patients occurred after 48 weeks of therapy. HBV-DNA decreased to undetectable levels in 8 of 12 (67%) patients. This chronic low-dose interferon administration regimen demonstrated responses comparable to other studies.

Adjuvants, Immunologic↗