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B K Chan

Publications and source records attributed to B K Chan.

29 records · Page 2Linked to original sources
PubMed1998

Evolution of web site design: implications for medical education on the Internet.

Since its inception, the world wide web (WWW) has possessed the potential for becoming a 'watershed' medium for conveying complex, structured information across vast temporal and geographical barriers. In 1995, the MedWorld project (http:(/)/medworld.stanford.edu) was created at the Stanford University School of Medicine in an effort to innovate and explore the design process of creating WWW applications specifically for medical education. Until recently, the evolution of WWW applications has been mainly driven by technological advances in client-server technology, enabling or translating traditional modes of collaborative medical education (e.g. voice, presence, print, motion) into WWW devices and applications. Many of these applications, while technologically advanced, lack focused development of interface and interactivity design, which may enhance learning experiences. WWW applications which incorporate design innovation in parity with advances in client-server technology have been termed, 'third generation' web sites and have the potential to improve the quality of WWW applications designed for medical education. This work describes how the MedWorld project has created a 'third generation' WWW application by utilizing innovation in information, interface and interactivity design to create innovative WWW technology for the medical education arena.

Communications Media↗
PubMed1998

Natural history of cervical squamous intraepithelial lesions: a meta-analysis.

OBJECTIVE: To define the strengths and weaknesses of existing research on the natural history of cervical squamous intraepithelial lesions (SIL) and to estimate rates of progression and regression without treatment. DATA SOURCES: Studies of women whose cervical smears showed squamous atypia or worse and who were observed for a minimum of 6 months were identified by a search of MEDLINE from 1966 to 1996, Current Contents, the Federal Research in Progress database, and references of review articles and identified studies, and by experts in the field. METHODS OF STUDY SELECTION: Fifteen of 81 studies were eligible for data extraction. To be eligible, studies had to report a minimum of 6 months' follow-up without treatment; relate entry cytologic findings to outcomes; and report entry cytologic findings so that the study population could be stratified into categories of atypical cells of undetermined significance (ASCUS), low-grade SIL, or high-grade SIL. Studies published before 1970 were excluded. TABULATION, INTEGRATION, AND RESULTS: Eligible studies, representing 27,929 patients, were stratified according to entry cytologic findings. The following rates of progression to high-grade SIL at 24 months were found: ASCUS, 7.13% (95% confidence interval [CI] 0.8%, 13.5%); low-grade SIL, 20.81% (6.08%, 35.55%); and high-grade SIL, 23.37% (12.82%, 32.92%). The following rates of invasive cancer at 24 months were found: ASCUS, 0.25% (0%, 2.25%); low-grade SIL, 0.15% (0%, 0.71%); and high-grade SIL, 1.44% (0%, 3.95%). The following rates of regression to normal were found: ASCUS, 68.19% (57.51%, 78.86%); low-grade SIL, 47.39% (35.92%, 58.86%); and high-grade SIL, 35.03% (16.57%, 53.49%). Study heterogeneity was not explained by regression analysis of study level variables. CONCLUSION: Our findings for borderline and low-grade abnormal cervical cytologic results suggest a relatively low risk of invasive cervical cancer with observation up to 24 months and support the clinical policy of early colposcopy for high-grade lesions.

Carcinoma in Situ↗
PubMed1996

The relationship of joint symptoms with exercise performance in older adults.

OBJECTIVES: The objective of this study is to determine if exercise increases joint symptoms in older adults with a history of arthritis or produces symptoms in older adults without such history. In addition, we examine whether joint symptoms explain the large observed variation in strength gain in older adults undergoing vigorous strength training exercise, and report the incidence of musculoskeletal injuries upon initiation of an exercise program. DESIGN: A population-based, single blinded, randomized controlled trial with three exercise groups and one control group. SETTING: A large urban health maintenance organization. PARTICIPANTS: Older men and women (N = 105) aged 68 to 85, with leg strength below the 50th percentile for their age, sex, height, and weight and without neuromuscular disease or active cardiovascular disease. INTERVENTIONS: Supervised exercise in 1-hour sessions, three times each week, for 24 to 26 weeks. One exercise group did strength training (ST) using weight machines (n = 25); another group did endurance training (ET) using stationary cycles (n = 25); and the third group did combined strength training and endurance training (ST+ET) (n = 25). The control group (n = 30) received no intervention. MEASUREMENTS: Strength was measured at the ankle, knee, hip, and elbow using an isokinetic dynamometer. Joint symptoms were rated on a 6-point scale (0 = none, 5 = severe). Arthritis severity was based on self-reported use of arthritis medication. Health status was measured with subscales of the SF-36 and Sickness Impact Profile (SIP). RESULTS: Joint symptoms fluctuated over time in all exercise groups, but they did not improve or worsen significantly in any group. The physical dimension of the SIP and SF-36 subscale scores, including Bodily Pain Scores, did not change over time in any group. Subjects with arthritis and joint symptoms gained as much strength with strength training as did subjects without joint symptoms. Adjustment for age, gender, baseline strength, adherence, and exercise group did not affect this finding. The rate of minor musculoskeletal injuries was 2.2 injuries per 1000 exercise hours. CONCLUSIONS: Moderate intensity stationary cycle exercise and vigorous intensity strength training do not appear to produce or exacerbate joint symptoms in older adults. Joint symptoms did not explain the large variation in gains in strength in older adults participating in a standardized strength training exercise program. Musculoskeletal injuries occurred relatively infrequently, and no major injuries occurred. In evaluating joint pain that occurs in older adults in well regulated exercise programs, clinicians should consider other etiologies before attributing pain to exercise per se.

Aged↗
PubMed1994

Characterization of a cDNA encoding the 43-kDa membrane-associated inositol-polyphosphate 5-phosphatase.

Agonist stimulation of cells results in phosphatidylinositol turnover and the generation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), which mobilizes intracellular calcium. The inositol-polyphosphate 5-phosphatase (5-phosphatase) enzymes hydrolyze Ins(1,4,5)P3 in a signal-terminating reaction. We have isolated a 2.7-kilobase (kb) composite cDNA, encoding the 43-kDa membrane-associated 5-phosphatase, by screening a human placental lambda gt11 library, using degenerate oligonucleotides. The 2.7-kb cDNA contains a 1.1-kb open reading frame, comprising 363 amino acids, which encodes a protein of a predicted molecular mass of 42 kDa. Amino acid sequence analysis demonstrates a number of potential sites for phosphorylation by protein kinase C and a CAAX motif in the COOH terminus, which may mediate membrane localization. The recombinant enzyme was expressed in COS-7 cells, resulting in a 50-fold increase in enzyme activity in the detergent-soluble membrane fraction of the cell (nanomole of Ins(1,4,5)P3 hydrolyzed per min/mg), but only a 2.5-fold increase in 5-phosphatase activity in the total cell homogenate. Sequence analysis demonstrated a 73-amino acid domain in the COOH terminus of the 43-kDa membrane-associated 5-phosphatase, which had 30% sequence identity and 67% similarity to a region in the 75-kDa 5-phosphatase and 34% identity and 70% similarity to a sequence in the protein that is encoded by the gene, defective in Lowe's oculocerebrorenal syndrome. As shown by RNA analysis the 43-kDa membrane-associated 5-phosphatase appears to be predominantly expressed in heart, brain, and skeletal muscle.

Amino Acid Sequence↗
PubMed1994

Endobronchial tuberculosis: diagnostic features and therapeutic outcome.

BACKGROUND: Endobronchial tuberculosis (EBTB) is not seen often in the adult population. In most cases it is associated with pulmonary tuberculosis. During its course significant tracheobronchial stenosis may develop. In this study we report our experience with patients with EBTB. METHODS: The records of 38 patients in whom EBTB had been proved by fibre optic bronchoscopy, microbiology and histology studies were evaluated. RESULTS: Symptoms were non-specific and represented mainly the co-existing pulmonary tuberculosis. Signs characteristic of airway obstruction were rare (localized wheezing in 6%). Indications for bronchoscopy were radiographic features (87%), microscopy smear negatives (8%), wheezing (3%), and blood stained sputum (3%). The lesions were more likely to be seen in the main and upper bronchi. In 5% of patients the lower trachea was involved. Most lesions looked inflamed (51%), followed by caseous (19%), granulomatous (17%), ulcerative (12%), and fibrotic appearance (1%). The degree of stenosis was nil (22%), minor (45%), significant (13%), subtotal (13%), or total (7%). The patients were treated with a combination of antituberculosis drugs. Four patients underwent surgical procedures. Dilatation techniques were used in two patients for a right and left main bronchus stenosis respectively, with significant improvement in one. Dilatation in combination with laser therapy of a right intermediate bronchus stenosis did not result in re-expansion of the dependent part of the lung due to pleural adhesions. Left pneumonectomy was performed in one patient for destroyed lung. Twenty-two patients agreed to follow up bronchoscopy. The macroscopic appearance of the mucosa had improved in most cases but the degree of stenoses was unchanged in a considerable proportion (58%). Bronchial stenosis in one patient subsided during therapy but developed again at a later stage. CONCLUSIONS: Patients with pulmonary tuberculosis and radiographic evidence of volume loss are recommended to undergo bronchoscopy to rule out EBTB. Specific symptoms for EBTB are rare. Biopsy of inflamed areas of bronchial mucosa seems to be indicated. Despite adequate antituberculosis therapy tracheobronchial stenosis may develop. Long term follow up including bronchoscopy seems therefore advocated. Dilatational intervention may be indicated in selected cases.

Adolescent↗
PubMed1994

[Roentgen findings in bronchial tuberculosis].

To determine the value of chest roentgenographic findings in the diagnosis and therapy of endobronchial tuberculosis we analysed roentgenograms of 41 patients with endoscopically confirmed tuberculous involvement of the intrathoracic airways. 40 patients had infiltrates typical for pulmonary tuberculosis predominantly in the upper lobes. Signs of diminished air entry in form of collapse or consolidations were found in 52%. 10 patients had cavities and two had a destroyed lung. In only one patient the chest roentgenogram was completely normal demonstrating a case of isolated endobronchial tuberculosis. During antituberculosis drug therapy radiological signs improved in 38 of 41 patients, but in more than half of the cases stenoses persisted as verified by bronchoscopy. We conclude that endobronchial tuberculosis is usually accompanied by lung parenchyma involvement and that roentgenological findings are characterised by signs of pulmonary tuberculosis in most cases. A normal chest roentgenogram does not exclude endobronchial tuberculosis. Despite roentgenographic improvement during therapy tracheobronchial stenoses may persist. These findings justify to perform early fibreoptic bronchoscopy. Sputum conversion during the clinical course may indicate the most appropriate time for this examination.

Adolescent↗
PubMedDate not supplied

Do follow-up recommendations for abnormal Papanicolaou smears influence patient adherence?

OBJECTIVE: To compare adherence to follow-up recommendations for colposcopy or repeated Papanicolaou (Pap) smears for women with previously abnormal Pap smear results. DESIGN: Retrospective cohort study. SETTING: Three northern California family planning clinics. PATIENTS: All women with abnormal Pap smear results referred for initial colposcopy and a random sample of those referred for repeated Pap smear. Medical records were located and reviewed for 90 of 107 women referred for colposcopy and 153 of 225 women referred for repeated Pap smears. INTERVENTION: Routine clinic protocols for follow-up--telephone call, letter, or certified letter--were applied without regard to the type of abnormality seen on a Pap smear or recommended examination. MAIN OUTCOME MEASURES: Documented adherence to follow-up within 8 months of an abnormal result. Attempts to contact the patients for follow-up, adherence to follow-up recommendations, and patient characteristics were abstracted from medical records. The probability of adherence to follow-up vs the number of follow-up attempts was modeled with survival analysis. Cox proportional hazards models were used to examine multivariate relationships related to adherence. RESULTS: The rate of overall adherence to follow-up recommendations was 56.0% (136/243). Adherence to a second colposcopy was not significantly different from that to a repeated Pap smear (odds ratio, 1.40; 95% confidence interval, 0.80-2.46). The use of as many as 3 patient reminders substantially improved adherence to follow-up. Women without insurance and women attending 1 of the 3 clinics were less likely to adhere to any follow-up recommendation (hazard ratio for no insurance, 0.43 [95% confidence interval, 0.20-0.93], and for clinic, 0.35 [95% confidence interval, 0.15-0.73]). CONCLUSIONS: Adherence to follow-up was low in this family planning clinic population, no matter what type of follow-up was advised. Adherence was improved by the use of up to 3 reminders. Allocating resources to effective methods for improving adherence to follow-up of abnormal results may be more important than which follow-up procedure is recommended.

Adolescent↗
PubMedDate not supplied

Disseminated peritoneal plasmacytoma following cardiac transplantation.

Posttransplant lymphoproliferative disorders (PTLD) are an important comorbidity in immunosuppressed transplant patients. We describe a unique case of PTLD, a disseminated peritoneal plasmacytoma in a 56-year-old cardiac transplant patient presenting with ascites. The associated computed tomographic findings include omental thickening, mesenteric stranding, and ascites.

Ascites↗
PubMedDate not supplied

Antineoplastic effects of gallium nitrate on human medulloblastoma in vivo.

Gallium nitrate possesses antineoplastic activity against certain solid tumors and has been demonstrated to be an effective agent in reducing cell proliferation and DNA synthesis in the medulloblastoma Daoy cell line in vitro. In prior studies, gallium inhibited the cellular uptake of 59Fe by brain tumor cells; however, this block in 59Fe uptake was variable and closely paralleled the inhibitory effects of gallium on cell growth. In vivo trials now have been conducted and have yielded some promising results. Nude mice received intradermal injections of medulloblastoma Daoy and then allowed to grow tumors. When the mice had developed at least one tumor between 9 to 10 mm in diameter, a 10-day course of intraperitoneal gallium nitrate injections was initiated. Gallium nitrate treatment reduced overall tumor growth rate and reduced actual tumor size. Nephrotoxicity was severe, but may be preventable by continuous gallium infusion and use of diuretics and hyperhydration.

Animals↗