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Biomedical subjects

A C Cheng

Publications and source records attributed to A C Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2001

Pathogenic and pathological characteristic of new type gosling viral enteritis first observed in China.

AIM: To study the purifying method and characteristics of new gosling viral enteritis virus (NGVEV),the etiological agent of new gosling viral enteritis (NGVE) which was first recognized in China, as well as the pathomorphological development in goslings infected artificially with NGVEV. METHODS: (1)NGVEV virions were purified by the procedure of treatment with chloroform and ammonium sulfate precipitation, dialysis to remove the sulfate radical and ammonium ion and separation by gel filtration chromatography, and SDS-PAGE. (2)Forty-2-day-old White Sichuan goslings were orally administered with NGVEV and 24 hr later 2 birds were randomly selected and killed at 24hr intervals until death occurred. Specimens(duodenum, ileum, liver, heart, kidney, spleen, lung, proventriculus, pancreas, esophagus, and the intestinal embolus) were taken until all birds in this group died and were sectioned and stained with hemotoxylin and eosin and studied by light microscope. RESULTS: NGVEV shared the typical characteristics of Adenovirus and which structural proteins consisted of 15 polypeptides. Necrosis and sloughing of the epithelial cells covering the villus tips of the duodenum were first observed in goslings 2 days postinfection artificially with NGVEV. With the progress of infection, this lesion rapidly occurred in the epithelium at the base of the villus and with infiltration of the inflammatory cells, the jejunum tended to be involved. With the intensification of mucosa necrosis and inflammatory exudation of the small intestine, fibrinonecrotic enteritis was further developed and embolus composed of either intestinal contents wrapped by pseudo-membrane or of the mixture of fibrous exudate and necrotic intestinal mucosa were observed in the middle-lower part of the small intestine. This structure occluded the intestinal tract and made the intestine dilated in appearance. The intestinal glandular cells underwent degeneration, necrosis and might be found sloughed into the lumen. Hemorrhage and hyperemia could be observed on the lung and kidney. Epithelial cells of the renal tubular underwent degeneration. In some cases, granular degeneration and fatty degeneration could be found in the liver and in some cases at a later stage of this disease the epithelial cells of trachea and proventriculus might be found sloughed. In some cases at an early stage of this disease, cardiac hyperemia and hemorrhage could be observed. Esophagus, pancreas and brain were found normal. Analyses and comparisons between the pathologic lesions of NGVE and Gosling Plague (GP) were available in this paper as well. CONCLUSION: (1)NGVEV is adenovirus. (2)Pathological characteristic could be as the data for NGVE diagnosis.

Adenoviridae↗
PubMed2001

Correlation of endoscopic and histologic findings before and after treatment for nasopharyngeal carcinoma.

BACKGROUND: The endoscopic and histologic findings before and after radiotherapy (RT) for nasopharyngeal carcinoma (NPC) were correlated to study the sensitivity and specificity of endoscopic findings in predicting histologic results. The efficiacy of endoscopic examination and post-RT multiple site biopsies in detecting persistent disease was also evaluated. METHODS: Seven hundred forty-six patients were evaluated. Pre-RT, biopsies were taken from both sides of the nasopharynx to assess the extent of tumor. Four to 16 weeks after RT, routine six-site biopsy specimens were taken from both roofs, lateral, and posterior walls of the nasopharynx and repeated 2 weeks later. Endoscopic findings of exophytic growth, nodule, ulcer, and submucosal bulge were considered "residual tumor," others were considered "no residual tumor." Persistent disease was defined as positive histologic findings 12 weeks after RT. RESULTS: Before RT, sensitivity of endoscopic findings and biopsy specimens in detecting malignancy were 99.7% and 94.2%, respectively. After RT, sensitivity and specificity of endoscopic findings in predicting positive histologic findings were 29% and 85.8%, respectively, with a positive predictive value of 34.9% and a negative predictive value of 82.2%. Of positive histologic findings, 27.7% were missed in the first session of biopsies; 33.5% of those with positive histologic findings turned out to have persistent disease. For prediction of persistent disease, the sensitivity and specificity of endoscopic findings were 40.4% and 84.4%, with a positive predictive value of 16.3% and a negative predictive value of 95%, and that of histologic findings in the first session of biopsies were 59.6% and 88.3%, respectively, with a positive predictive value of 27.7% and a negative predictive value of 96.7%. CONCLUSIONS: Endoscopic findings alone have low sensitivity in predicting persistent disease, multiple sites biopsy specimens are indicated. Because only 1.9% of patients with endoscopic findings of "no residual tumor" and negative histologic findings in first session of biopsies had persistent disease, this group can be spared second biopsies. Repeat biopsies are indicated for those with endoscopic findings of "residual tumor" or positive histologic findings in first session of biopsies to improve detection of persistent disease.

Adolescent↗
PubMed2000

Pathogenesis and management of laser in situ keratomileusis flap buttonhole.

PURPOSE: To describe the clinical features and outcomes in patients who had a flap buttonhole during laser in situ keratomileusis (LASIK) and propose an etiopathogenic mechanism for this complication. SETTING: University Eye Center, Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China. METHODS: Retrospective review of case records of 6 patients (6 eyes) who had a flap buttonhole during LASIK. RESULTS: The mean patient age was 38.2 years +/- 4.1 (SD) and the mean preoperative spherical equivalent (SE) refraction, -8.13 +/- 4.04 diopters (D). Mean keratometry was 44.20 +/- 1.30 D. Retreatment was performed after a mean interval of 9.2 +/- 3.2 months. Final postoperative SE refraction was -0.44 +/- 0.58 D after a mean follow-up of 59.0 +/- 5.3 weeks. No patient experienced loss of best spectacle-corrected visual acuity. CONCLUSIONS: Retreatment of eyes that have a flap buttonhole during LASIK is associated with good visual outcomes. Flap buttonholes can produce alterations in refraction, so retreatment is best performed after the refractive error has stabilized. Microkeratome malfunction may be responsible for the occurrence of a flap buttonhole during LASIK in eyes that do not have significant corneal steepening.

Adult↗
PubMed2000

Fabrication of a two-piece superstructure for a fixed detachable implant-supported mandibular complete denture.

This article describes a procedure to fabricate a 2-piece superstructure for a fixed detachable implant-supported mandibular complete denture prosthesis. With this unique technique, unsuitable implant angulation can be corrected, and retention of the second superstructure is accomplished with 2 esthetically positioned screws and an antirotational attachment.

Dental Prosthesis, Implant-Supported↗
PubMed2000

The association between cigarette smoking and ocular diseases.

OBJECTIVE: To review the effect of smoking on common ocular disorders. DATA SOURCES: Medline literature search, 1966 to 1999. STUDY SELECTION: The following key words were used: smoking; Graves' disease, age-related macular degeneration; glaucoma; cataract. DATA EXTRACTION: Epidemiological and experimental studies were reviewed. DATA SYNTHESIS: Cigarette smoking is an important risk factor for cardiovascular, respiratory, and malignant diseases. There is also a strong association between smoking and a number of common eye diseases, which include Graves' ophthalmopathy, age-related macular degeneration, glaucoma, and cataract. Despite the multifactorial aetiology of these ocular syndromes, smoking is an independent risk factor that has dose-response effects. It causes morphological and functional changes to the lens and retina due to its atherosclerotic and thrombotic effects on the ocular capillaries. Smoking also enhances the generation of free radicals and decreases the levels of antioxidants in the blood circulation, aqueous humour, and ocular tissue. Thus, the eyes are more at risk of having free-radical and oxidation attacks in smokers. CONCLUSION: Smoking, if continued, may perpetuate further ocular damage and lead to permanent blindness. Cessation of smoking and avoidance of passive smoking is advised to minimise the harmful effects of smoking on the eyes.

Cataract↗
PubMed2000

Oral care for children with leukaemia.

OBJECTIVES: To review the oral care regimens for children with acute leukaemia, and to present an easy-to-follow oral care protocol for those affected children. DATA SOURCES: Medline and non-Medline search of the literature; local data; and personal experience. STUDY SELECTION: Articles containing supportive scientific evidence were selected. DATA EXTRACTION: Data were extracted and reviewed independently by the authors. DATA SYNTHESIS: Cancer is an uncommon disease in children, yet it is second only to accidents as a cause of death for children in many countries. Acute leukaemia is the most common type of malignancy encountered in children. The disease and its treatment can directly or indirectly affect the child's oral health and dental development. Any existing lesions that might have normally been dormant can also flare up and become life-threatening once the child is immunosuppressed. Proper oral care before, during, and after cancer therapy has been found to be effective in preventing and controlling such oral complications. CONCLUSION: Proper oral care for children with leukaemia is critical. Long-term follow-up of these children is also necessary to monitor their dental and orofacial growth.

Child↗
PubMed1999

The time course of histologic remission after treatment of patients with nasopharyngeal carcinoma.

BACKGROUND: The objective of this study was to define the time course of histologic remission and to evaluate the prognostic significance of delayed histologic remission of patients with nasopharyngeal carcinoma (NPC). METHODS: Between 1986-1994, 803 patients underwent serial postradiotherapy nasopharyngeal biopsies. Patients with positive histology underwent repeated biopsies every 2 weeks until the biopsies were found to be negative or, if remission did not occur by the 12th week after radiotherapy, treatment was initiated for persistent disease. Patients with positive histology found after the fifth week but who achieved spontaneous remission before the twelfth week were considered to have delayed histologic remission. Negative histology by the sixth week was considered early histologic remission. The outcome of patients with delayed histologic remission, early histologic remission, and persistent disease were compared. RESULTS: Six hundred and seventeen patients (76.8%) had negative histology within 12 weeks of the completion of radiotherapy and 55 (6.9%) had persistent disease at Week 12. In 131 patients (16.3%) spontaneous remission was observed in repeat biopsies after initial positive histology. With increasing time after radiotherapy, the incidence of positive histology decreased but more patients were found to have persistent disease. Patients with early and delayed histologic remission had 5-year NPC control rates of 82.4% and 76.8%, respectively (P = 0.35) versus a 40% NPC control rate among patients with persistent disease (P < 0.001). The 5-year survival rates were 75.3%, 79.4%, and 54.2%, respectively, for the 3 groups (P < 0.001). CONCLUSIONS: A high proportion of early positive histology remitted spontaneously. Delayed histologic remission in NPC patients is not a poor prognostic factor and additional treatment is not necessary. A confirmatory biopsy at 10 weeks is recommended before the initiation of salvage treatment.

Biopsy↗
PubMed1999

Hinged mandibular removable complete denture for post-mandibulectomy patients.

The presence of excessive lingual undercuts after mandibulectomy and surgical reconstruction is a rare clinical condition and presents unique prosthodontic challenges. The goals of prosthodontic treatment include: providing lip support, improving articulation, reducing drooling, and regaining favorable esthetics. This article describes the fabrication of a hinged removable mandibular complete denture prosthesis using a sectional impression tray technique and a custom-made hinge mechanism. Clinical and laboratory procedures of the prosthetic treatment are described, and the advantages and disadvantages are reviewed.

Acrylic Resins↗
PubMed1999

Culture-negative ulcerative keratitis after laser in situ keratomileusis.

A 40-year old man, highly myopic in both eyes, had laser in situ keratomileusis (LASIK) in the left eye in November 1996. Corneal melting and ulceration and fine striae-like interface infiltrates were noticed 1 day postoperatively. There was no response to intensive topical antibiotics in the form of hourly ofloxacin 3% (Tarivid), and satellite lesions developed on day 4. Corneal scrapings for gram stain and culture were done twice. No bacterial or fungal organisms were identified. Intensive topical fortified vancomycin (50 mg/mL) was added, and the lesions resolved gradually over the ensuing 2 weeks. Eighteen months after LASIK, refraction was -1.50 - 0.75 x 105 in the left eye, and uncorrected visual acuity was 20/70, correctable to 20/25 with spectacles.

Adult↗
PubMed1999

Management of severe flap wrinkling or dislodgment after laser in situ keratomileusis.

PURPOSE: To review the management and results of cases with severe flap wrinkling or dislodgment after laser in situ keratomileusis (LASIK). SETTING: University Eye Center, Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong. METHODS: Four patients with severe flap wrinkling or dislodgment after LASIK are described. Surgical repositioning of the flap was performed in all cases. Flap status, refractive changes, and final uncorrected and best corrected visual acuities were used to evaluate the outcome of flap repositioning. RESULTS: Flap repositioning required suturing in 2 patients, 1 of whom developed severe epithelial ingrowth with melting of the corneal flap and stromal bed and eventually required flap removal. The stromal inflammation resolved, and the corneal surface re-epithelialized after flap excision. In 2 other patients, wedge-shaped tissue excision (1.0 x 1.5 mm) from the superior portion of the corneal flap was necessary to allow better flap realignment. In 1 of these patients, the corneal flap was eventually converted to a free cap to correct residual wrinkling. At a mean follow-up of 15 months, the postoperative uncorrected visual acuity ranged from 20/20 to 20/60, and the best spectacle-corrected visual acuity (BSCVA) was 20/30 or better in all patients. In 1 patient, BSCVA decreased by 1 line. CONCLUSIONS: Flap dislodgment and wrinkling are serious postoperative complications of LASIK. Early recognition of these complications and prompt surgical management are crucial to achieve a successful surgical and visual outcome.

Adult↗