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Biomedical subjects

W F Ng

Publications and source records attributed to W F Ng.

At least 37 records · Page 2Linked to original sources
PubMed2000

Clarithromycin attenuates cyclophosphamide-induced mucositis in mice.

No universally recognized agent is available for prophylaxis or therapy of mucositis induced by chemotherapy or chemo-radiotherapy. The effect of clarithromycin on the severity of mucositis induced by cyclophosphamide was investigated using a mouse model. Four cross-sections of small intestine (levels A, B, C, and D) were taken at equivalent intervals at day 5 after cyclophosphamide (400 mg kg(-1)) administration. The sections were stained with haematoxylin and eosin, and were graded for the degree of mucositis histologically. At section level B, the number of mice with no mucositis (grade 0) in the clarithromycin group was significantly greater than that in the ceftriaxone group (P<0.05). At levels B and C, the number of mice with no mucositis (grade 0) in the clarithromycin group was significantly greater than that in the normal saline (NS) group (P<0.05). At level C, the number of mice with grade 2 mucositis in the ceftriaxone group was significantly greater than that in the NS group (P<0.05). When the number of sections at all levels were analyzed together, the number of mice with no mucositis (grade 0) in the clarithromycin group was significantly greater than that in the ceftriaxone and NS groups (P<0.05). The present observation suggests that clarithromycin and ceftriaxone attenuates and aggravates cyclophosphamide-induced mucositis. It prompts clinical trials in bone marrow transplant (BMT) recipients receiving cyclophosphamide for conditioning, and reconsideration in the use of ceftriaxone in the treatment of neutropenic fever in BMT recipients.

Animals↗
PubMed2000

Prolonged storage of frozen unbuffered rapid urease test.

Unbuffered rapid urease test (RUT) is an accurate, rapid, and inexpensive method of detecting Helicobacter pylori. However, it is generally recommended to prepare the reagent daily. This prospective study was undertaken to evaluate the shelf-life of our unbuffered RUT at -20 degrees C. Two sets of antral biopsies (X2) and body biopsies (X1) were taken from all patients. They were subjected to histologic examination and RUT stored at -20 degrees C. We studied 303 patients. One hundred seventy-nine (59%) were infected as defined by histologic examination. The reagent was classified according to the storage time (group I, 0-30 days [n = 109]; group II, 31-60 days [n = 63]; group III, 61-90 days [n = 80]; and group IV, tau91 days [n = 51]). There was an excellent agreement between the histologic examination and the RUT of the four groups (kappa coefficient: group I, 0.88; group III, 0.80; group III, 0.87; group IV, 0.88). The sensitivity of our RUT in groups I, II, III, and IV were 92%, 92%, 91%, and 89%, respectively. The corresponding specificity were 97%, 88%, 97%, and 100%. Our RUT remains highly sensitive and specific when it is stored at -20 degrees C for 4 months.

Biopsy↗
PubMed1999

Somatic mutations in the BRCA1 gene in Chinese sporadic breast and ovarian cancer.

Inherited mutations in the BRCA1 gene confer increased susceptibility to breast and ovarian cancer. Its role in sporadic carcinogenesis is not well defined. Somatic mutations in breast cancers have not been reported and to date there are only three reports of somatic mutations in sporadic ovarian cancers. To investigate the contribution of BRCA1 mutations to sporadic breast and ovarian cancer in the Chinese population, we analysed 62 samples from Chinese women using the protein truncation test. There were 40 cases of breast cancer under age 50 and 22 cases of ovarian cancer, all unselected for family history. There was no age selection for the ovarian cancers. We found two somatic BRCA1 mutations in exon 11, one in a breast cancer and the other in an ovarian cancer, both of which result in truncated proteins. Our results indicate that somatic BRCA1 mutations, like somatic mutations in the BRCA2 gene, though very rare, can be found in both breast and ovarian cancers and support a tumor suppressor function for BRCA1 in sporadic tumors.

Adult↗
PubMed1999

In-situ derivatisation of degradation products of chemical warfare agents in water by solid-phase microextraction and gas chromatographic-mass spectrometric analysis.

A new analytical procedure was developed for the extraction of degradation products of chemical warfare agents from water and for in-situ derivatisation prior to analysis by gas chromatography-mass spectrometry (GC-MS). With this new procedure, degradation products of the chemical warfare agents can be analysed and identified without going through laborious sample preparation. Parameters such as fiber selection, pH, salt content, derivatisation temperature, extraction and derivatisation periods, and sequence of adsorption/derivatisation were experimented with, to optimise the efficiency of this method. The detection limit is in the ppb to sub-ppb range with GC-MS in the full scan mode. Based on six injections of the devised procedure, a relative standard deviation from 10-35% can be achieved, depending on the compound. This method was demonstrated during the 4th International Interlaboratory Proficiency Test organised by the Organisation for the Prohibition of Chemical Weapons to be comparable to existing recommended operating procedures for verification of degradation products of chemical warfare agents.

Adsorption↗
PubMed1999

The effect of posture and anesthesia on the occlusal relationship in orthognathic surgery.

PURPOSE: This study investigated the differences in centric occlusion (intercuspal-CO) and centric relation contact position (CR) in patients in an upright and supine posture when conscious and when supine under general anesthesia to rationalize planning for complex bimaxillary osteotomies. PATIENTS AND METHODS: Twenty-four men and 37 women, with a mean age of 24.7 +/- 4.5 years were included in this study. Occlusal records on each patient included 1 in CO and 3 in CR in each of the following postures: conscious upright, conscious supine, and anesthetized supine. Casts were mounted in the Denar Mark II articulator and transferred to the Denar Vericheck (Denar Corp, Anaheim, CA) recording tool for measurements. The centric relation displacement vectors (CO-CR) were projected in various axes by 3D graphics. RESULTS: The upright conscious CO-CR (mm) vectors were significantly different from both the supine conscious and anesthetized positions in the anteroposterior plane. The difference in the vertical plane was only significant in Class II division 1 patients. CONCLUSION: The posterior change in centric relation explains the apparent occlusal discrepancies created by rigid fixation of the mandible applied in the supine anesthetized position. By taking the CR records in the supine conscious position, the "loss" of maxillary advancement can be avoided.

Adult↗
PubMed1999

Cytomegalovirus colitis in individuals without apparent cause of immunodeficiency.

Cytomegalovirus infection is usually reported in immunocompromised patients. In this study, apparently immunocompetent patients with cytomegaloviral colitis were reviewed. Records with a diagnosis of cytomegaloviral colitis from January 1989 to June 1996 were retrieved for analysis. Ten patients were included (median age 70 yr). The major presenting symptoms were diarrhea and hematochezia. Ulceration was the main macroscopic finding. Rectal bleeding was mostly self-limiting. Three patients developed local complications (rectovaginal fistula in two; rectal stricture in one). In the two patients with rectovaginal fistula, lymphocytes subsets and proliferative response were entirely normal. In the other patient, low B lymphocyte count and low response to mitogen were demonstrated. However, the immunoglobulins were not suppressed and rectal biopsies revealed noncaseating granulomas, suggesting activated cell-mediated immunity. In conclusion, a high index of suspicion is crucial for early diagnosis of cytomegaloviral colitis in patients with bloody diarrhea, even though obvious evidence of immunodeficiency is lacking.

Aged↗
PubMed1999

Interdigitating dendritic cell tumor of the testis: a novel testicular spindle cell neoplasm.

Interdigitating dendritic cell tumor is an extremely rare neoplasm that mainly occurs in lymph nodes. An example of such a tumor in the testis, a hitherto unreported site, is described. Grossly, the tumor was light tan with a uniform solid appearance, replacing virtually the entire testis. Microscopically, it was formed by whorls and fascicles of spindle cells intermingling with small lymphocytes. Such a histologic appearance can, however, mimic a wide variety of other tumors and tumor-like lesions, among which mesenchymal sarcoma, spindle cell carcinoma, follicular dendritic cell tumor, and inflammatory pseudotumor are the main differential diagnoses. Immunohistochemical studies showed that the spindle tumor cells were strongly and diffusely positive for S-100 protein and vimentin. They were also focally positive for CD68 and CD4, but were uniformly negative for leukocyte common antigen, CD1a, CD3, CD20, CD21, CD23, CD34, CD35, actin, desmin, HMB45, cytokeratins, and placental alkaline phosphatase. Ultrastructurally, the tumor cells possessed complex interdigitating cytoplasmic dendritic processes, with abundant rough endoplasmic reticulum and mitochondria in their cytoplasm. An in situ hybridization study for Epstein-Barr virus was negative. The pathologist should be aware of such an entity and consider it in the list of differential diagnoses for unusual spindle cell lesions with a significant background population of small lymphocytes. However, because of its nonspecific histologic appearance, additional immunohistochemical and electron microscopic studies are generally required for its definitive diagnosis.

Adolescent↗
PubMed1999

High alpha-fetoprotein level in HCV-related nodular liver cell dysplasia.

The diagnosis of hepatocellular carcinoma is generally made in patients with a mass lesion in the cirrhotic liver if the alpha-fetoprotein level is >1,000 ng/L. Other causes of elevation of alpha-fetoprotein to this extreme degree include nonseminomatous germ cell tumor and hepatic metastasis. However, it is extremely rare for benign hepatic lesions to cause alpha-fetoprotein of > 1,000 ng/ml. We report a Chinese patient with spontaneous normalization of alpha-fetoprotein with an initial value > 10,000 ng/ml due to nodular dysplasia complicating hepatitis C-related liver cirrhosis. The alpha-fetoprotein was secreted from the dysplastic liver cells.

Aged↗
PubMed1998

Effect of simethicone on the accuracy of the rapid urease test.

OBJECTIVE: Simethicone, which is a principal ingredient in the defoaming agent used during gastroscopy, can inhibit the growth of Helicobacter pylori (MIC, 64-128 mg/l). This prospective study was designed to evaluate the in vivo and in vitro effects of simethicone on the accuracy of the rapid urease test (RUT). METHODS: In the in vivo study, three sets of gastric biopsies (two from the antrum, and one from the corpus) were taken from 75 patients. The first set was examined histologically, and the second set was used for the RUT (pre-simethicone RUT). Then, 25 ml simethicone (1200 mg/l) was introduced into the stomach for a contact time of 1 min. A third set of gastric biopsies was taken for the RUT (post-simethicone RUT). In the in vitro clinical study, 41 patients were recruited. The first set of gastric biopsies was used for the RUT (pre-incubation RUT). The second set was incubated in 1 ml of simethicone for 5 min before being used for the RUT (post-incubation RUT). In the spectrophotometric study, urease activity before and after incubation in simethicone for 5 min was quantified in 12 patients by measuring the absorbance at 560 nm. RESULTS: Reading at 15 min, the concordance rate between the pre-simethicone and post-simethicone RUT was 98%. In the in vitro clinical study, the concordance rate between the pre-incubation and post-incubation RUT was 97%. The spectophotometric study showed a significant reduction of 43% in urease activity after incubation in simethicone. CONCLUSION: The application of a defoaming agent containing simethicone does not affect the accuracy of the RUT. However, simethicone modestly suppresses urea hydrolysis.

Diagnostic Techniques, Digestive System↗
PubMed1998

Acute Wernicke's encephalopathy complicating chronic gallstone ileus.

An autopsy performed on a 53-year-old man who had unrelieved obstruction of the small bowel due to gallstone ileus revealed morphological features that were typical of acute Wernicke's encephalopathy. The likely sequence of disease in this patient was the development of thiamine deficiency owing to the unrelieved intestinal obstruction, which resulted in the development of acute Wernicke's encephalopathy. A high clinical awareness is required for the diagnosis of acute Wernicke's encephalopathy in patients with malnutrition from any cause.

Journal Article↗
PubMed1997

Submucosal tumor extension in hypopharyngeal cancer.

OBJECTIVES: To study the incidence and extent of submucosal tumor extension in hypopharyngeal cancer and to evaluate the impact on the tumor recurrence and overall survival rates. METHODS: Fifty-seven resected specimens of hypopharyngeal cancer were studied in detail from January 1986 to December 1989 by use of the whole-organ, step-serial sectioning technique. RESULTS: Three types of submucosal tumor extension could be identified. Type I extension was characterized by a tumor with a smooth round contour that extended submucosally. The mucosa was thereby elevated and was detectable on gross inspection at operation. In type II extension, tongues and islands of tumor infiltrated within the submucosa, and these were not noticeable on gross examination. Skip metastasis in the submucosa where the submucosal tumor was completely separated from the main tumor bulk was classified as type III extension. Thirty-three patients (58%) had submucosal tumor extension. The frequencies (and extents of submucosal tumor extension) in the superior, medial, lateral, and inferior directions were 16% (3-10 mm), 37% (2-37 mm), 26% (2-37 mm), and 28% (3-35 mm), respectively. Two thirds of the submucosal extension was type I (22 of 33), and only 1 patient had a true skip lesion submucosally (type III extension). Type II submucosal extension was found in one third of the patients (11 of 33). This occurred significantly more often in the patients who had received radiotherapy before surgery (82% [9/11]; P < .001; 95% confidence interval, 1.28-4.44). The presence of submucosal tumor extension had no effect on the tumor recurrence and overall survival rates. CONCLUSIONS: The incidence of submucosal tumor extensions in hypopharyngeal cancer is high (58%), but most (67%) of them can be detected grossly at operation. The presence of submucosal tumor extension does not adversely affect the survival and tumor recurrence rates.

Adult↗
PubMed1997

Endoscopic removal of leiomyoma of the colon.

Colonic leiomyoma is a rare condition. Smooth muscle tumours arising from the colon constitute only 3% of gastrointestinal leiomyomas. Complete endoscopic removal of the tumour is a problem because it is often submucosal in origin. We report a patient with a 5 mm leiomyoma of the colon that was successfully removed by conventional colonoscopic snare electrocauterisation, without complications.

Journal Article↗
PubMed1997

Cholestatic hepatitis: a rare hepatic manifestation of systemic lupus erythematosus.

Systemic lupus erythematosus is a multi-system inflammatory disease. The clinical manifestations are diverse. Hepatic manifestation is a rarely seen complication of systemic lupus erythematosus. We report a case of complication of systemic lupus erythematosus presenting as cholestatic hepatitis in a 56-year-old Chinese woman. The cholestatic hepatitis progressed as part of the lupus activity and responded to steroid therapy.

Journal Article↗
PubMed1997

Occult gastric cancer presenting as cor pulmonale resulting from tumor cell microembolism.

Cor pulmonale resulting from tumor emboli is a rare presentation of gastric cancer, and only six similar cases have been reported in the English literature. We report the case of a 37-yr-old woman presenting with dyspnea who died of cor pulmonale. Autopsy revealed signet cell carcinoma of te stomach with intra-abdominal metastasis and right ventricular hypertrophy. There were no macroscopic pulmonary emboli or parenchymal lesions, but more than 60% of the small pulmonary arteries and arterioles were occluded. In most vessels, fibrocellular intimal proliferation was the major finding with only a few entrapped tumor cells.

Abdominal Neoplasms↗
PubMed1997

Storage temperature of the unbuffered rapid urease test.

OBJECTIVES: The unbuffered rapid urease test (RUT) is an accurate, rapid, and inexpensive method for detecting Helicobacter pylori. However, it is generally recommended that the reagent be prepared daily. This prospective study was undertaken to evaluate the shelf life of our unbuffered RUT when stored at 4 and -20 degrees C. METHODS: Ninety-five patients were studied. Three sets of antral (X2) and body (X1) biopsy samples were taken from each patient. The samples were subjected to histological examination, with the RUTs stored at 4 and -20 degrees C. The RUT tubes were examined at 1 and 15 min. RESULTS: Fifty-six patients (59%) were infected with H. pylori as defined by histological examination. The reagent was classified according to storage time (group I, < or = 5 days; group II, > 5 days). The mean (SD) storage time of group I (n = 59) and group II (n = 36) was 3.2 (1.4) and 9.9 (5.0) days, respectively. At 15 min, the sensitivity of our RUT stored at 4 degrees C was significantly higher in group I than in group II (92 vs 47%). On the other hand, the sensitivity of our RUT stored at -20 degrees C remained consistently high in both groups (15 min: group I, 92%; group II, 100%). Our RUTs stored at 4 and -20 degrees C were highly specific in both groups. CONCLUSIONS: Our RUT remains highly sensitive and specific when it is stored at 4 degrees C for up to 5 days. When the RUT is expected to be stored for a longer period of time, the bottles should be frozen at -20 degrees C.

Biopsy↗
PubMed1996

Aggressive T/natural killer cell lymphoma presenting as testicular tumor.

BACKGROUND: Nonnasal CD56+ T/natural killer (NK) cell lymphomas with morphologic and immunogenetic features similar to those of the distinctive nasal T/NK cell lymphoma are uncommon and have been characterized only recently. They show predominantly extranodal presentation, high stage disease, a highly aggressive course, strong association with Epstein-Barr virus (EBV), and lack of T cell receptor gene rearrangement. Only one previously reported case had a testicular presentation, although the testis is not uncommonly involved during the course of disease in both nasal and nonnasal T/NK cell lymphomas. METHODS: Three patients with T/NK cell lymphoma who presented initially with a testicular mass are reported. RESULTS: The three patients underwent orchidectomy for testicular tumor. Histologically, the testes showed diffuse dense infiltration of medium-sized or large lymphoma cells. Antiocentric growth and necrosis were prominent in two cases. The lymphoma had the following immunophenotype: CD2+ CD3 epsilon+ CD56+ compatible with T/NK cell lymphoma; two lacked staining with Leu4 (CD3), and one had weak staining. With immunohistochemical preparations, it was noted that the rete testis stained consistently for CD56, and the Leydig cells and Sertoli cells showed patchy staining. The neoplastic cells harbored EBV, as demonstrated by in-situ hybridization. Additional sites of disease were detected at the time of the diagnosis in one patient (nose) or appeared soon afterwards in all three patients (skin or gastrointestinal tract). All three patients died within 5 months. CONCLUSIONS: This study confirms that testicular CD56+ T/NK cell lymphoma tends to disseminate early, pursues an aggressive course, and is strongly associated with EBV. CD56 recognizes the neural cell adhesion molecule (NCAM), which exhibits homophilic binding properties. The expression of CD56 in the normal testicular constituents can perhaps explain the tendency for T/NK cell lymphoma to localize in this organ.

Aged↗