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Biomedical subjects

C C Chan

Publications and source records attributed to C C Chan.

At least 199 records · Page 11Linked to original sources
PubMed1998

Triple viral retinitis diagnosed by polymerase chain reaction of the vitreous biopsy in a patient with Richter syndrome.

PURPOSE: To report the evaluation and identification of herpes viruses associated with retinitis in a patient with Richter syndrome. METHODS: Diagnostic vitrectomy was performed on a patient with systemic leukemia and retinitis. The vitreous sample was evaluated by cytology, analysis of cytokines by ELISA, and detection of virus by polymerase chain reaction. RESULTS: The vitreous biopsy specimen showed no malignant cells but predominant CD8+ lymphocyte infiltration with elevated interferon gamma and interleukin-6. DNA amplification and Southern blot analysis demonstrated DNA of herpes simplex, varicella-zoster, and cytomegalovirus. CONCLUSION: Retinitis associated with multiple viruses in the vitreous biopsy may mimic leukemic infiltration in the eye.

Biopsy↗
PubMed1998

Colonic diverticulosis in Hong Kong: distribution pattern and clinical significance.

This is a retrospective study on the prevalence of diverticulosis in Hong Kong Chinese adults. Eight-hundred and fifty-eight consecutive barium enema examinations over a period of 18 months (January 1995-June 1996) were analysed. Results show that the prevalence of diverticulosis in our community is 25.1% with no significant difference between male and female adults. The prevalence is lower than Western countries but higher than in Asia. Moreover, the peak prevalence is at the 50-79 years age group with lower prevalence in the older age groups. This may be explained by the rapid rise in prevalence in the younger age groups so that the age-related increase in prevalence become obscured. We postulate that this may be due to Western cultural influence in our diet and lifestyle. There is no significant difference in the symptomatology of patients with and without diverticulosis, supporting the idea that diverticulosis alone is usually asymptomatic. There is predominance of right hemicolon involvement in our subjects, in contrast to the left hemicolon predominance in the Caucasian population. Of patients with diverticulosis, 55.3% have only right-sided involvement and 32.6% have bilateral involvement. Only 12.1% of patients with diverticulosis have exclusively left hemicolon involvement. Caecal and ascending colon diverticula are found in 6.4% and 17.6% of all the adults under study, respectively. Clinicians caring for patients from our community should take note of this high frequency of caecal and ascending colon diverticulosis as caecal and ascending colon diverticulitis is notoriously difficult to diagnose clinically.

Adult↗
PubMed1998

Hysteroscopic endometrial ablation without endometrial preparation.

OBJECTIVE: To study the effectiveness of endometrial ablation by hysteroscopic resection without prior medical preparation for the treatment of women with persistent menorrhagia. METHOD: From January 1996 to January 1997, a total of 170 women with persistent menorrhagia and/or dysmenorrhea and who underwent hysteroscopic endometrial resection were included in the study. A thorough suction curettage was done before the procedure. The operation was conducted through a continuous flow hysteroscopic resectoscope with electrosurgery while the patient was under intravenous general anesthesia. The distention fluid used was 5% dextrose with a gravity feed infusion system consisting of a 2-1 bag between 1 and 1.5 m above the uterine cavity. After the procedure, the patients' conditions were followed for at least 6-18 months by telephone interview or at our clinic. RESULTS: A total of 127 women were available for a follow-up period of at least 6 months. Operative complications were 3%; three women had fever and received oral antibiotics; no uterine perforation occurred; one case of post-operative bleeding was controlled by intrauterine balloon inflation; the average operation time was 21 min; The mean fluid deficit was 435 ml. Ninety-nine out of 127 women (78%) had adequately controlled menorrhagia (18.1% had amenorrhea, 42.5% hypomenorrhea and 17.3% had normal menstrual flow), while 27 women (21.2%) were failed due to unchanged or heavier menstrual flow after surgery. Eleven (40%) out of the 27 failed cases had myoma with menorrhagia, whereas only five women (5%) out of the 99 adequately treated women had myomas (P < 0.05). Thirty-eight (54%) out of the 70 women with severe dysmenorrhea reported either lessening dysmenorrhea or no dysmenorrhea after the surgery. A total of 76 women (60%) were satisfied with the procedure. A second surgical procedure, either a resection or hysterectomy, was necessary in 13 women (10%) after ablation (seven received repeated ablations and six underwent hysterectomy). CONCLUSION: Endometrial ablation without endometrial suppression is a cheap, effective and acceptable procedure for treatment in women with persisted persistent menorrhagia.

Adolescent↗
PubMed1998

Utility of microdissection and polymerase chain reaction for the detection of immunoglobulin gene rearrangement and translocation in primary intraocular lymphoma.

OBJECTIVE: Primary intraocular lymphoma, a non-Hodgkin's lymphoma, is a primary central nervous system lymphoma (PCNSL). Diagnosis is usually made by identifying malignant, large B lymphocytes in the vitreous, eye, brain, and cerebral spinal fluid; however, these cells are few, friable, and difficult to recognize. Recently, clonal heavy chain immunoglobulin (IgH) gene rearrangement and bcl-2 gene translocation have been reported in systemic B-cell lymphoma and are used for the detection of malignant cells and in making a diagnosis. The authors investigated the molecular changes in three eyes and a chorioretinal biopsy specimen of four patients with PCNSL. DESIGN: Human tissue study. MATERIALS: Five ocular specimens of PCNSL were collected. INTERVENTION: The first patient had a diagnostic enucleation of the left eye. The second patient underwent diagnostic chorioretinal biopsy. In the third case, a pair of autopsied eyes with reactive lymphoplasmacytic infiltrates of a patient with acquired immune deficiency syndrome (AIDS) were studied. In the fourth case, an enucleated eye of a patient with AIDS-associated lymphoma was sampled. MAIN OUTCOME MEASURES: The bcl-2 and IgH genes of the lymphoma cells from routine, paraffin-embedded, formaldehyde-fixed, or frozen histologic tissue sections were analyzed using microdissection and polymerase chain reaction (PCR) technique. RESULTS: Lymphoma cells obtained from the above four cases showed IgH rearrangement gene in the third framework of the VH region. Bcl-2-associated translocation also was detected in three cases (cases 1, 2, and 4). CONCLUSION: Rearrangement of the IgH gene can serve as a molecular marker for PCNSL. Microdissection allows for procurement and analysis of specific, selected, minute cell populations that are obtained from histologic sections of the complex, heterogeneous tissue. Translocation of IgH and bcl-2, the apoptotic "survival" signal and proto-oncogene, could contribute to the pathogenesis of PCNSL. The combination of microdissection and PCR is a powerful tool for studies of small lesions and cell populations and for understanding disease mechanisms.

Adult↗
PubMed1998

Chronic administration of octreotide ameliorates portal hypertension and portal hypertensive gastropathy in rats with cirrhosis.

1. Portal hypertension and hyperdynamic circulation have been postulated to play a role in the pathogenesis of portal hypertensive gastropathy. Administration of octreotide to portal hypertensive rats has been shown to reduce portal pressure and ameliorate hyperdynamic circulation. 2. This study investigated the effects of chronic administration of octreotide on systemic and portal haemodynamics and the development of portal hypertensive gastropathy in carbon tetrachloride-induced cirrhotic rats. 3. After 12 weeks of carbon tetrachloride induction, cirrhotic rats were randomly assigned to receive either placebo (5% dextrose in water) or octreotide (65 micrograms/kg in 5% dextrose in water) subcutaneously twice daily for 10 days. Haemodynamic studies with a thermodilution technique and gastric morphometric analyses were performed at 10 days after treatment. 4. In cirrhotic rats, octreotide treatment induced a significant increase in systemic vascular resistance (2.7 +/- 0.2 versus 3.4 +/- 0.2 mmHg/ml.min-1.100 g-1, P < 0.05) and decrease in portal pressure (12.5 +/- 1.2 versus 9.9 +/- 0.5 mmHg, P < 0.05) compared with placebo-treated rats. In addition, octreotide treatment significantly reduced the mean cross-sectional area of gastric mucosal vessels (2290 +/- 145 versus 1810 +/- 101 micron 2, P < 0.05). 5. This study shows that chronic octreotide treatment ameliorates the development of portal hypertensive gastropathy in cirrhotic rats. The effect of octreotide on portal hypertensive gastropathy may, at least partly, be due to the alleviation of portal hypertension and hyperdynamic circulation.

Animals↗
PubMed1998

Aminoguanidine ameliorates splanchnic hyposensitivity to glypressin in a haemorrhage-transfused rat model of portal hypertension.

1. Hyposensitivity to vasopressin is a well-documented phenomenon in animals with portal hypertension and patients with cirrhosis subjected to haemorrhage. Excessive formation of nitric oxide is at least partly responsible for the vascular hyporesponsiveness to vasoconstrictors observed in experimental portal hypertension or in rats with haemorrhagic shock. This study investigated whether addition of aminoguanidine, a preferential inducible nitric oxide synthase inhibitor, to glypressin (a long-acting vasopressin analogue) could enhance its portal hypotensive effect in portal-hypertensive rats with bleeding.2. Portal hypertension was induced by partial portal vein ligation. Fourteen days after operation, systemic and portal haemodynamics were measured in stable or bleeding portal vein-ligated rats receiving intravenous glypressin (0.07 mg/kg) or aminoguanidine (70 mg/kg) followed by glypressin infusion. In rats with a hypotensive haemorrhage, 4.5 ml of blood was withdrawn and 50% of the withdrawn blood was reinfused before the administration of glypressin or aminoguanidine.3. Glypressin resulted in a significantly greater decrease in portal pressure in portal vein-ligated rats without bleeding than in those with bleeding (P<0.001). In contrast, glypressin induced similar changes in mean arterial pressure between the two groups (P>0.05). The addition of aminoguanidine significantly potentiated the portal-hypotensive effect of glypressin in bleeding portal vein-ligated rats (P<0.005) without an effect on the changes in mean arterial pressure induced by glypressin infusion (P>0.05).4. Splanchnic hyposensitivity to glypressin exists in a haemorrhage-transfused rat model of portal hypertension. This hyposensitivity can be ameliorated by the administration of aminoguanidine.

Animals↗
PubMed1998

[Interleukin 10 and chronic vitritis in a case of ocular lymphoma].

The authors report on a 46 year-old patient who presented with a chronic unilateral vitritis. A diagnosis of cerebral lymphoma was made 4 years earlier and a maxillary sinus recurrence was treated with chemotherapy and radiotherapy. A vitrectomy was performed and the level of Interleukin-10, a lymphoma cells growth factor, was found very high, giving a clue for the lymphomatous cause of the vitritis.

Brain Neoplasms↗
PubMed1998

Topical liposome-encapsulated FK506 for the treatment of endotoxin-induced uveitis.

PURPOSE: Liposome preparations of FK506 improve the penetration of topically administered drug into the aqueous humor. The purpose of the experiment was to compare topically administered highdose oil-dissolved FK506 (OD-FK506) and low-dose liposome-bound FK506 (LB-506) for the treatment of endotoxin-induced uveitis (EIU). METHODS: Endotoxin-induced uveitis was produced in female Lewis rats with Salmonella typhimurium endotoxin. Four hours prior to endotoxin injection, one eye received 20 mul eyedrops every four hours containing either high-dose OD-FK506 at 3 mg/ml (N = 20), low-dose LB-FK506 at 0.16 mg/ml (N = 19), prednisolone acetate 1% (N = 20), or empty liposomes (N = 20). Eyes were enucleated 24 hours after endotoxin injection and inflammatory cells were counted on histologic sections by two masked observers. RESULTS: The mean number of infiltrating inflammatory cells per section +/- S.E.M. was 127.8 +/- 20.1, 76.8 +/- 16.7, 75.0 +/- 19.1, and 3.6 +/- 0.4 for animals treated with empty liposomes, LB-FK506, OD-FK506, and prednisolone acetate, respectively. The difference in inflammation between the empty liposome controls and the LB-FK506- and OD-FK506-treated animals was statistically significant (p = 0.03 and p = 0.02, respectively). The difference in inflammation between the high-dose OD-FK506- and low-dose LB-FK506-treated animals was not statistically significant (0 = 0.94). CONCLUSION: In this study, low-dose LB-FK506 and high-dose (OD-FK506) were both effective in inhibiting EIU. Higher concentrations of LB-FK506 are being developed and should augment the therapeutic effect of topical FK506.

Administration, Topical↗
PubMed1998

Suppressive effect of antiflammin-2 on compound 48/80-induced conjunctivitis. Role of phospholipase A2s and inducible nitric oxide synthase.

Phospholipase A2s (PLA2s) are a family of esterases that initiate the arachidonic acid cascade, which results in the production of numerous inflammatory mediators. We investigated the expression of Group I and II PLA2 proteins and Group II mRNA in normal conjunctivae and in the conjunctivae of mice with compound 48/80-induced conjunctivitis. Conjunctivitis was induced in C57BL/6 mice by topical instillation of compound 48/80 (C48/80). Mice were then treated with corticosteroid (Pred Forte), antiflammin-2 (AF2, a synthetic peptide that inhibits PLA2), or a placebo (Dacriose, an isotonic, buffered, sterile eye irrigating solution). Low levels of PLA2s were detected on the epithelium of normal conjunctivae. One hr after C48/80 instillation, the expression of PLA2s appeared and increased in the substantia propria, peaked at 6 hr, and returned to baseline 72 hr later. Compared to the placebo, the conjunctivitis was moderate in the AF2-treated group and mild in Pred Forte-treated group. The expression of PLA2s was suppressed in mice treated with Pred Forte and AF2. iNOS mRNA was also diminished in the AF2- and Pred Forte-treated groups. The mechanisms by which anti-allergic medications suppress conjunctivitis may involve the inhibition of PLA2s and iNOS.

Administration, Topical↗
PubMed1998

Acute immunosuppression and syngeneic bone marrow transplantation in ocular autoimmunity abort disease, but do not result in induction of long-term protection.

Acute immunosuppression induced by total body irradiation (TBI) or cyclophosphamide (Cy) treatment, followed by syngeneic bone marrow transplantation (SBMT), was reported to be effective in inducing long-term tolerance in some autoimmune disease models. We examined the efficacy of this approach in the mouse model of experimental autoimmune uveoretinitis (EAU). Development of EAU induced by the interphotoreceptor retinoid binding protein (IRBP) was abolished almost completely by either TBI or Cy treatment, followed by SBMT, instituted one week after priming. In parallel, IRBP-specific delayed-type hypersensitivity (DTH) responses and lymph node cell proliferation were strongly suppressed or abolished. However, when these IRBP-immunized, lymphoablated and BM reconstituted mice were rechallenged with the immunizing antigen seven weeks after the primary immunization, they were not protected from developing disease, despite the fact that DTH and lymph node cell proliferation to the antigen were suppressed relative to controls. TBI treatment appeared somewhat more effective than Cy treatment as judged by its more profound effect on immunological responses. These results demonstrate the ability of acute immunosuppression followed by reconstitution of the immune system to inhibit the development of EAU, although long-term protection from disease was not achieved.

Animals↗
PubMed1998

IL-10 has a protective role in experimental autoimmune uveoretinitis.

The role of IL-10 in the regulation of ocular autoimmune disease was studied in experimental autoimmune uveoretinitis (EAU) elicited in mice by immunization with the retinal antigen interphotoreceptor retinoid binding protein. IL-10-deficient mice were susceptible to EAU, indicating that pathogenesis can occur without presence of IL-10. Treatment of normal mice with IL-10 for 5 days after uveitogenic immunization ameliorated subsequent EAU scores, and down-regulated antigen-specific production of tumor necrosis factor-alpha and IFN-gamma. A concomitant treatment with IL-4 further reduced disease, and resulted in emergence of antigen-specific IL-4 and IL-10 production, as well as in enhancement of the IgG1 antibody isotype. IL-4 by itself was not protective. Only IL-10, but not IL-4, was able to inhibit the function of differentiated uveitogenic T cells in culture. Expression of mRNA for Th1 and Th2 cytokines in the eye during the course of EAU showed that while a Th1 pattern predominated early, IL-10 mRNA expression coincided with down-regulation of the Th1 response and resolution of EAU. Systemic neutralization of IL-10 during the expression phase of EAU resulted in elevated disease scores. Our results suggest that endogenous IL-10 limits expression of EAU and may play a role in the natural resolution of disease. The data further suggest that exogenous IL-10 may be useful in therapeutic control of autoimmune uveitis. While IL-10 by itself is sufficient to suppress Th1 effector development and function, a concomitant administration of IL-4 is required to shift the autoimmune response towards a non-pathogenic Th2 pathway.

Animals↗
PubMed1998

Radiation exposure modeling for apartment living spaces with multiple radioactive sources.

Since late 1992, over 100 building complexes in Taiwan, including both public and private schools, and 1,000 apartments have been identified as emitting elevated levels of gamma-radiation. These high levels of gamma-radiation have been traced to construction steel contaminated with 60Co. Accurate reconstruction of the radiation exposure dosage among residents is complicated by the discovery of multiple radioactive sources within the living spaces and by the lack of comprehensive information about resident life-style and occupancy patterns within these contaminated spaces. The objective of this study was to evaluate the sensitivity of current dose reconstruction approach employed in an epidemiological study for the health effects of these occupants. We apply a statistical method of local smoothing in dose rate estimation and examine factors that are closely associated with radiation exposure from multiple radioactive sources in the apartment. Two examples are used, a simulated measurement in a hypothetical room with three radioactive sources and a real apartment in Ming-Shan Villa, one of the contaminated buildings. The simulated and estimated means are compared along 5-10 selected points of measurement: by local smoothing approach, with the furniture-adjusted space, and with the occupancy time-weighted mean. We found that the local smoothing approach came much closer to theoretical values. The local smoothing approach may serve as a refined method of radiation dose distribution modeling in exposure estimation. Before environmental exposure assessment, "highly occupied zones" (HOZs) in the contaminated spaces must be identified. Estimates of the time spent in these HOZs are essential to obtain accurate dosage values. These results will facilitate a more accurate dose reconstruction in the assessment of residential exposure in apartments with elevated levels of radioactivity.

Air Pollution, Radioactive↗
PubMed1998

Differential effect of a selective cyclooxygenase-2 inhibitor versus indomethacin on renal blood flow in conscious volume-depleted dogs.

Renal effects of a selective cyclooxygenase-2 (COX-2) inhibitor [MF-Tricyclic; 3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl)phenyl)-2-(5H)-furanone] were studied in control and volume-depleted conscious dogs. MF-Tricyclic was compared with the nonselective COX-1/COX-2 inhibitor indomethacin. Six instrumented male dogs were randomly selected to receive MF-Tricyclic or indomethacin at 10 mg/kg. Volume depletion was effected by a sodium-restricted diet (14 days) with administration of furosemide (7.5 mg/kg, i.v.) the day before the experiment. Indomethacin ablated systemic COX-1 activity (p < 0.05), whereas MF-Tricyclic did not affect this activity. Each compound achieved plasma concentrations in excess of their respective median inhibitory concentrations (IC50 values) against canine COX-2. In controls, neither compound affected mean arterial pressure (MAP), heart rate (HR), renal blood flow (RBF), fractional excretion (FE) Na+, or FE K+. In volume-depleted dogs, indomethacin reduced RBF (p < 0.05), whereas MF-Tricyclic did not affect this parameter. Indices of renal function in volume-depleted dogs were not affected. These data are consistent with the view that the effects of indomethacin on RBF are a consequence of inhibition of COX-1 activity. Furthermore, in these studies, short-term administration of a selective COX-2 inhibitor was without deleterious effects on renal function.

Animals↗
PubMed1998

Torsion of the wandering spleen.

A case of torsion of the wandering spleen with splenic infarction is reported. The medical imaging studies performed with typical findings are described. Case reports have been reviewed. Although rare, torsion of the spleen remains an important differential diagnosis in patients presenting with acute abdominal pain. Early intervention is necessary to reduce the risk of splenic infarction and other complications, and an increased awareness of the condition together with the use of appropriate medical imaging can lead to the correct diagnosis more readily.

Abdominal Pain↗
PubMed1998

Adverse effect of air pollution on respiratory health of primary school children in Taiwan.

This study is a part of the Study On Air Pollution and Health In Taiwan (SOAP&HIT), an ongoing research project involving cooperation of several universities in Taiwan. In this study, the objective was to evaluate the effects of ambient air pollution on respiratory symptoms and diseases of school children, in addition to considering indoor air pollution. Six communities were selected: one community located in a rural area (Taihsi), two in urban areas (Keelung and Sanchung), and the other three in petrochemical industrial areas (Toufen, Jenwu, and Linyuan). We sampled 5,072 primary school students in six communities from the main study population of SOAP&HIT. Respiratory health was assessed by evaluation of the children's respiratory symptoms and diseases using a parent-completed questionnaire. Data were analyzed using logistic regression analysis to compute odds ratios of adverse effect. The school children in the urban communities had significantly more respiratory symptoms (day or night cough, chronic cough, shortness of breath, and nasal symptoms) and diseases (sinusitis, wheezing or asthma, allergic rhinitis, and bronchitis) when compared with those living in the rural community. However, only nasal symptoms of children living in the petrochemical communities were more prevalent than in those living in the rural community. Although the association with ambient air pollution is suggestive, the cross-sectional study cannot confirm a causal relationship; thus further studies are needed.

Air Pollution↗
PubMed1998

Vulnerability by sex to seasonal affective disorder.

This study pooled the demographic data reported in 40 studies on seasonal affective disorder to identify the ratio of men to women with this disorder. Among the 1129 subjects recruited for these 40 studies, women out-numbered men. A sex difference in biochemical responses to climatic variables was postulated as one of the possible explanations of the observed women's vulnerability to seasonal affective disorder.

Climate↗