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Biomedical subjects

H S Chan

Publications and source records attributed to H S Chan.

At least 109 records · Page 6Linked to original sources
PubMed1990

Pathological features of multiple endocrine neoplasia type IIb in childhood.

The features of two patients with multiple endocrine neoplasia type IIb are described. Patient 1, a 9-year-old boy with marfanoid features, presented with chronic constipation and failure to thrive since infancy. Patient 2, a 12-year-old boy with marfanoid features, presented with a five-year history of persistent cervical lymphadenopathy. In patient 1, the myenteric and submucosal nerve plexuses at all levels of the small and large intestines were comprised of diffusely disorganized, hyperplastic, mature ganglion cells and nonmyelinated nerve fibers. Nerve plexus dissection with morphometric analysis showed marked thickening of the myenteric plexus with a quantitative increase in neural tissue. Patient 2 had a submucosal neuroma of the tongue. Both patients had occult medullary thyroid carcinoma, and patient 2 had cervical lymph node metastases. Both neoplasms showed positive staining for cytokeratin, carcinoembryonic antigen, calcitonin, bombesin, chromogranin, serotonin, and Leu 7. Electron microscopy showed membrane-bound, intermediate-sized, dense-core neurosecretory granules in tumor cells. In patient 2, calcitonin-positive amyloid was present with localization of calcitonin by immunoelectron microscopy to cytoplasmic secretory granules and to extracellular amyloid fibrils. These cases illustrate the potential for missed or delayed diagnosis in multiple endocrine neoplasia syndromes.

Carcinoma↗
PubMed1989

A tuberculostearic acid assay in the diagnosis of sputum smear-negative pulmonary tuberculosis. A prospective study of bronchoscopic aspirate and lavage specimens.

OBJECTIVE: To determine whether the detection of tuberculostearic acid (TBSA) in bronchial aspirate and bronchoalveolar lavage specimens is useful for the rapid diagnosis of active pulmonary tuberculosis in patients suspected of having the disease. SETTING: A pulmonary clinic in a teaching hospital. PATIENTS: Forty patients suspected of active pulmonary tuberculosis but who failed to produce sputum or whose sputum smears were negative for acid-fast bacilli on at least 3 occasions, 29 of whom were subsequently confirmed to have tuberculosis. A group of 13 patients who were having fiberoptic bronchoscopy for other reasons served as controls. INTERVENTION: All patients had fiberoptic bronchoscopy; bronchial aspirate, bronchoalveolar lavage, and sputum specimens were obtained when possible. MEASUREMENTS AND MAIN RESULTS: All specimens were examined microscopically for acid-fast bacilli, cultured for mycobacteria, and assayed for TBSA by gas chromatography and mass spectrometry with selected ion monitoring. Only 4 of the 29 patients with tuberculosis were diagnosed by direct microscopy compared with 26 by TBSA assay. In 2 patients who required surgical biopsy for conventional diagnosis, the TBSA test was positive. There were no false-positive TBSA results in the 13 controls, but 2 of 5 sputum specimens from the 11 test patients in whom tuberculosis was excluded were falsely positive, probably because of contamination with mouth flora. Because sputum can rarely be obtained from these patients and may give false-positive results, it is not a good specimen for TBSA assay. Sensitivities and specificities of the test for the other specimens were as follows: aspirate, 0.52 (CI, 0.32 to 0.71) and 1.00 (CI, 0.75 to 1.00); lavage, 0.68 (CI, 0.46 to 0.85) and 1.00 (CI, 0.84 to 1.00); aspirate and lavage combined, 0.79 (CI, 0.60 to 0.92) and 1.00 (CI, 0.86 to 1.00). CONCLUSIONS: The TBSA assay for bronchial aspirate and bronchoalveolar lavage fluid is useful for rapidly diagnosing "smear-negative" pulmonary tuberculosis. In these specimens it is highly specific and more sensitive than microscopy. This assay could be used to diagnose other mycobacterial infections, however, it cannot distinguish among species.

Bronchoalveolar Lavage Fluid↗
PubMed1989

Isolated giant tuberculomata of the liver detected by computed tomography.

Isolated giant tuberculomata of the liver are rare, and they are frequently misdiagnosed as primary or secondary tumors of the liver. We describe the computed tomography findings in 2 patients with giant tuberculomata of the liver. One patient had a large low-attenuation lesion with rim enhancement after contrast. The other patient had multiple calcific lesions that did not enhance but showed a rim of hypoattenuation after contrast. Biopsy established the diagnosis and both patients recovered with antituberculous chemotherapy.

Adult↗
PubMed1989

Special precautions reduce oropharyngeal contamination in bronchoalveolar lavage for bacteriologic studies.

Despite the use of quantitative culture, oropharyngeal contamination of bronchoalveolar lavage (BAL) specimens is still a factor that limits the usefulness of this technique in the diagnosis of lower respiratory tract infection. To investigate whether special precautions could reduce contamination, 20 noninfected patients undergoing diagnostic bronchoscopy were randomized into 2 groups of 10 patients: BAL was performed routinely in group R and with special precautions in group P. These precautions consisted of giving topical lidocaine by inhalation rather than by bolus injection, and passing the bronchoscope used for BAL through a previously inserted endotracheal tube. Quantitative culture of BAL specimens showed that 5 patients in group R (50%), but none of the patients in group P (0%), had at least 1 organism recovered in concentrations greater than or equal to 10(4) colony-forming units CFU/ml (p = 0.016). Fifteen of 39 isolates (38.5%) in group R and none of 18 isolates in group P (0%) were present in concentration greater than or equal to 10(4) CFU/ml (p = 0.001). We conclude that oropharyngeal contamination of BAL specimens can be minimized by adopting special precautions during the procedure and by using quantitative culture with 10(4) CFU/ml as the cut-off point. This may increase the specificity of the technique in the diagnosis of lower respiratory tract infection without reducing its sensitivity.

Bacteriological Techniques↗
PubMed1989

Prevalence of asthma, atopy, and bronchial hyperreactivity in bronchiectasis: a controlled study.

The prevalence of atopic diseases and bronchial reactivity to histamine and methacholine was determined in 36 patients with bronchiectasis and in 36 control patients matched for age, sex, and smoking history. There was no difference in the prevalence of asthma, other atopic diseases, family history of atopic diseases, or positive responses to skinprick tests (nine versus five) in the two groups. The prevalence of bronchial hyperreactivity, however, was significantly higher in the group with bronchiectasis than in the control group for both histamine (7 v 0 patients) and methacholine (6 v 0 patients). The group with bronchiectasis had more airflow obstruction (mean FEV1 67% predicted), but there was no correlation between spirometric indices and log PD20 (the log dose of histamine or methacholine causing a 20% fall in FEV1). This suggests that, although reduced airway calibre may be a factor underlying bronchial hyperreactivity in bronchiectasis, it is not the only mechanism. Further studies are needed to determine whether bronchial hyperreactivity has a causative role in the pathogenesis of bronchiectasis or whether it occurs as a result of the disease.

Adult↗
PubMed1989

The bacteriology of bronchiectasis in Hong Kong investigated by protected catheter brush and bronchoalveolar lavage.

Bacteria often colonize the lower respiratory tract of patients with bronchiectasis. Although the role of these bacteria in the pathogenesis of the disease is uncertain, their accurate identification is important for epidemiologic and treatment purposes. Therefore, the aims of this study were: (1) to identify these bacteria in patients with bronchiectasis without cystic fibrosis using the protected catheter brush (PCB) in order to avoid oropharyngeal contamination, and (2) to compare the results of bronchoalveolar lavage (BAL) with PCB. Quantitative culture was performed on PCB and BAL specimens obtained from the most severely affected lobes of 23 patients with bronchiectasis. Results of PCB showed no significant growth (less than 10(3) colony-forming units [cfu]/ml) in nine patients and 17 significant isolates (greater than 10(3) cfu/ml) in the rest: H. influenzae, 5; P. aeruginosa, 4; K. ozaenae, 2; S. aureus, 2; P. fluorescens, 1; S. pneumoniae, 1; Veillonella, 1; and coag.-ve Staph., 1. For BAL, the results were the same (20 isolates) regardless of whether 10(4) or 10(5) cfu/ml was chosen as the cutoff point. More organisms were cultured from BAL specimens, and these included all but one of the organisms cultured from PCB. We conclude that the bacteriology of bronchiectasis in Hong Kong is different from that reported in sputum studies in the West (mainly H. influenzae, S. pneumoniae, and S. aureus), and with 10(4) cfu/ml as the cutoff point, BAL gives comparable results to PCB.

Adult↗
PubMed1989

Energy metabolism in children with newly diagnosed acute lymphoblastic leukemia.

The effect of tumor burden in acute lymphoblastic leukemia on resting energy expenditure, thermic effect of food, and substrate utilization was investigated with open-circuit indirect calorimetry after an overnight fast. Nine patients (six females, three males) ages 6.5 to 15.8 y were studied. Patients were divided into two groups according to their tumor burden at diagnosis (i.e. white cell count, presence or absence of mediastinal mass, or massive organomegaly). The patients with a greater tumor burden had increased energy expenditure. Their resting energy expenditure returned to normal in response to chemotherapy. These results must be interpreted with caution due to the small patients numbers (high tumor burden n = 3; low tumor burden n = 6). Substrate utilization was altered by chemotherapy with an increase in carbohydrate utilization and a decrease in fat oxidation (p less than 0.009). The magnitude of the thermic effect of food tended to increase on treatment (p less than 0.016). Inasmuch as most chemotherapy programs for children last up to 3 y, we believe it is important that the effects of chemotherapy on intermediary metabolism be studied, particularly in relationship to any possible permanent effects on growth and development.

Adolescent↗
PubMed1989

Therapeutic embolization of pulmonary arteriovenous malformation.

A 49-year old man presented with recurrent transient ischaemic attacks and a pulmonary arteriovenous malformation (PAM) was found in his lower left lobe. Left lower lobectomy was performed, and the attacks ceased. However, 18 months later, a fresh PAM was detected in the right lower lobe. In order to avoid further lung resection, therapeutic embolization with metal-dacron coils and gelfoam was performed, resulting in complete occlusion of the PAM. The patient remained well at follow-up 6 months later. Therapeutic embolization is an effective alternative to surgery in the treatment of PAM, especially in the presence of multiple lesions when it is important to conserve functional lung tissue.

Arteriovenous Malformations↗
PubMed1988

Homozygous deletion of a DNA marker from chromosome 11p13 in sporadic Wilms tumor.

A random DNA fragment, probe p2.3 (locus D11S87), was cloned from the 11p13 region between a translocation breakpoint associated with familial aniridia and another translocation breakpoint associated with childhood T-cell leukemia. The D11S87 locus maps between the catalase (CAT) locus and the beta subunit of follicle stimulating hormone (FSHB). The D11S87 locus is deleted in a Wilms tumor patient with a constitutional deletion of 11p and in a case of sporadic Wilms tumor (WiT-13) apparently with normal karyotype. In the WiT-13 tumor both maternal and paternal chromosomes 11 are retained; D11S87 is deleted homozygously and FSHB hemizygously. These results suggest two mutational events resulting in homozygous deletion in this patient. The D11S87 homozygous deletion was also demonstrated in WiT-13 nude mouse heterotransplants and in fibroblast-like cell line derived from the primary tumor. The minimum size of the deletion was estimated to be 30 kb as determined by cosmid screening and hybridization. As homozygous deletions in the 11p13 region have not been previously reported for sporadic Wilms tumors, these findings place the D11S87 locus within or approximate to the Wilms tumor gene.

Blotting, Southern↗
PubMed1988

Juvenile chronic myelogenous leukemia.

Juvenile chronic myelogenous leukemia (JCML) is a malignant hematopoietic disorder of monocyte-histiocyte lineage that affects children less than 4 years of age. Since the disease represents only 2% of all childhood leukemias, experience with it has been limited even in large centers. This review summarizes our 10 year institutional study of JCML as well as a comprehensive literature survey. The goal of the article is to underscore the cardinal features of juvenile chronic myelogenous leukemia that are useful for diagnosis, and to highlight recent advances in the understanding of the biology and treatment of the disease.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

Malrotation of midgut in adult polycystic kidney disease.

A case of malrotation of the midgut and adult polycystic kidney disease is reported. The patient had a stillborn son who had congenital heart disease and adult type of polycystic kidney disease. These findings support the notion that cystic disease of the kidney, gastrointestinal and cardiovascular anomalies are genetically linked.

Adult↗
PubMed1988

A sensitive method for immunocytochemical detection of P-glycoprotein in multidrug-resistant human ovarian carcinoma cell lines.

P-glycoprotein, a molecular weight 170 kilodalton membrane component can be accurately detected in a series of human ovarian carcinoma cells with increasing degrees of multidrug resistance by using a modified immunoperoxidase "sandwich" method. Drug-resistant derivatives were selected from a drug-sensitive parent ovarian carcinoma cell line, SKOV3, by continuous exposure to increasing concentrations of the cytotoxic drug vincristine. These cells had corresponding overexpression of P-glycoprotein demonstrable at both protein and mRNA levels. Monoclonal antibodies against P-glycoprotein localized staining for P-glycoprotein to the plasma membrane and the Golgi region in individual drug-resistant cells, in proportion to their P-glycoprotein expression. P-glycoprotein was not demonstrable in drug-sensitive SKOV3 cells by either immunoblotting or immunocytochemical staining methods. The immunocytochemical staining method allowed detection of P-glycoprotein in the least drug-resistant cell line with as low as 8-fold relative resistance to vincristine. This method is as sensitive as Northern blot, and more sensitive than standard Western blot in detection of P-glycoprotein. We conclude that this highly sensitive immunocytochemical staining method for P-glycoprotein can be suitable for determination of P-glycoprotein expression in biopsy samples of tumors, and it can be a powerful diagnostic and prognostic tool in the study of the natural history of drug resistance. This may have important applications in the clinical management of cancer chemotherapy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1987

Congenital mesoblastic nephroma: a clinicoradiologic study of 17 cases representing the pathologic spectrum of the disease.

Congenital mesoblastic nephroma (CMN) is a rare infantile renal tumor with a generally excellent prognosis. We describe 17 tumors that fit into the pathologic spectrum of CMN proposed by Beckwith, which ranges from benign renal tumors, through atypical "gray zone" lesions of more aggressive potential, to "crossover" tumors akin to clear cell sarcoma of kidney. Nine patients with histologically typical CMN were significantly younger and had smaller tumors than did eight patients with atypical CMN. Clinical features did not differ in the two groups of patients. A distinctive "ring sign" on renal sonography was commonly seen in patients with typical intrarenal CMN. All 17 patients were alive with no evidence of disease at a mean follow-up of 10 years. Nephrectomy was adequate therapy for younger infants and for those with typical CMN. Nephrectomy was probably also adequate therapy for infants 3 months of age or younger with atypical CMN, even if the tumor extended to the surgical resection margins and into the perinephric connective tissues. Adjuvant chemotherapy or radiation or both should be reserved for patients older than 3 months who have grossly unresected tumors and for those patients whose tumors have an unequivocally malignant histologic appearance or evidence of aggressive biologic behavior.

Age Factors↗
PubMed1987

Malignant tumours in the neonate.

One hundred and two cases of neonatal cancers, representing 2% of all paediatric malignancies, were seen during a 60 year period at The Hospital for Sick Children, Toronto, Canada. The neonatal cancers included neuroblastoma (47%), retinoblastoma (17%), soft tissue sarcoma (12%), central nervous system tumours (9%), leukaemia (8%), and a few cases of Wilms' tumour, liver tumour, and miscellaneous tumours. The overall mortality from disease was 41%. Patients with retinoblastoma, Wilms' tumour, and neuroblastoma had the best prognosis. Forty three patients (42%) survived their neonatal cancers; all were treated with surgery or radiochemotherapy, or both, but none suffered long term major handicaps as a result of treatment. There was one instance of second malignancy of the thyroid gland induced by radiation. We conclude that although neonatal cancers are difficult management problems, many patients can be cured. Physicians should discuss with parents the possible risks associated with treatment before treatment is begun.

Female↗