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Biomedical subjects

C T Tan

Publications and source records attributed to C T Tan.

161 records · Page 9Linked to original sources
PubMed1978

Spin membrane immunoassay: simplicity and specificity.

The many disadvantages of radioimmunoassay (RIA) have stimulated attempts to develop non-radioactive assays. These include spin immunoassay (SIA), which is simple, specific, and requires no separation procedures but is much less sensitive than RIA. The membrane immunoassay (MIA) described here is more sensitive than the SIA. Serum is prepared as for RIA. The MIA employs liposomes sensitized with epsilon-dinitrophenylated aminocaproyl phosphatidylethanolamine. It records liposome lysis induced by specific anti-Dnp antibodies, and complement which is monitored by the release of trapped spin labels (N-(2,2,6,6-tetramethylpiperidinyl-1-oxyl)-choline chloride). The sensitized liposomes are stable and give reproducible results for up to 4 weeks. The system's sensitivity is limited by the antibody's affinity (Ka approximately 10(8) M-1) rather than the sensitivity of the electron spin resonance spectrometer (approximately 1 X 10(-7) M). The inhibition of liposome lysis is hapten specific: (epsilon-Dnp-aminocaproic acid,epsilon-Dnp-lysine) greater than alpha-Dnp-glycine; o-nitroaniline and epsilon-dansyl-lysine are ineffective. Inhibition is quantitative without augmentation.

Animals↗
PubMed1978

Immunologic parameters in childhood Hodgkin's disease II. T and B lymphocytes in the peripheral blood of normal children and in the spleen and peripheral blood of children with Hodgkin's disease.

A study of peripheral blood lymphocyte populations in 27 children with Hodgkin's disease (HD) and 13 age-matched control subjects is presented. The absolute numbers and percentages of T and B lymphocytes identified by their surface marker characteristics were determined. In addition, in 13 HD children the percentages of T and B lymphocytes were estimated in the spleens removed at staging laparotomy. No differences were observed between the total peripheral blood lymphocyte counts of HD and control children, and we found no evidence of progressive lymphopenia with advancing stages of the disease. No decrease in the numbers of peripheral blood T lymphocytes was seen in this group of HD children. In contrast, the proportions and absolute numbers of B lymphocytes tended to be significantly lower in the children with HD than in the control subjects. In 9 of the 13 spleens studied high percentages of T lymphocytes were seen; low percentage of B lymphocytes were found in all spleens examined.

Adolescent↗
PubMed1978

In vitro responses of peripheral blood and spleen lymphoid cells to mitogens and antigens in childhood Hodgkin's disease.

Over the past 5 years, parameters of immunological function have been determined in all children with biopsy-proven Hodgkin's disease in the Department of Pediatrics, Memorial Sloan-Kettering Cancer Center. This report summarizes the in vitro responses of lymphocytes to stimulation by mitogens and antigens (between January 1975 and December 1976) in 33 of these previously untreated patients. In nine of these patients, responses of the splenic lymphocytes were studied concomitantly with the responses of peripheral blood lymphocytes. Peripheral blood from normal children and adults was used as the control. Our results have demonstrated no significant differences between the responses of normal children and adult controls. The absolute necessity for concomitant studies of the controls and the patients was shown. The value of examining multiple concentrations of a single mitogen was also well defined. In the children with Hodgkin's disease, there was a consistent failure of the peripheral blood lymphocytes to respond to the lower concentration dose of phytohemagglutinin. However, this abnormality was not found in the splenic lymphocytes.

Adolescent↗
PubMed1977

Treatment of acute nonlymphoblastic leukemia in children with a multiple-drug protocol.

Twenty-one children with acute nonlymphoblastic leukemia (ANLL) were treated with a combination regimen consisting of arabinosyl cytosine (Ara-C), 6-thioguanine (TG), and Adriamycin, The incidence of complete remission was 74%. For consolidation, addition courses of Ara-C and TG were given, followed by L-asparaginase. The maintenance program was the same as that for the lymphoblastic type (L-2) including intrathecal methotrexate for prophylaxis of meningeal leukemia. Of the 16 who were evaluable for the duration of complete remission, six developed bone marrow relapse, one meningeal leukemia within 3-14 months after entering complete remission and one was lost to follow-up. Eight remain in complete remission for 9-72 months. In five of eight, chemotherapy has been terminated after 3 years, and all continue in remission for 11-32 months post-treatment. Although the results do not compare well to those of the lymphoblastic morphology, long-term disease-free survival can be achieved with multiple-drug intensive treatment in childhood ANLL.

Acute Disease↗
PubMed1976

The cardiotoxicity of adriamycin and daunomycin in children.

Eight (16%) of 50 children receiving adriamycin and 2 (3%) of 60 receiving daunomycin had severe cardiomyopathy with congestive heart failure. All 110 patients received cumulative doses of over 500 mg/m2. The incidence was significantly higher in those who also had incidental cardiac radiation. The electrocardiogram, with few exceptions, provided the first indication of cardiac abnormality. There were no deaths from heart failure. Two had thromboembolic episodes. Recommendations are discussed.

Adolescent↗
PubMed1976

Involved field radiation therapy for early stage Hodgkin's disease in children: preliminary results.

Twenty Stage I and II children with Hodgkin's disease were treated with involved field radiation therapy. Twelve patients were Stage I. The histologic types were:nodular sclerosis(seven cases), mixed cellularity (two) and lymphocyte predominant (three). There were eight Stage II patients (six nodular sclerosis and two of mixed cellularity). One Stage I and 4 Stage II patients had class B disease. Involved field irradiation was used in these children after staging laparotomy showed no disease below the diaphragm. Eight of the 20 patients relapsed, five in lymph nodes adjacent to the primary site, two in areas across the diaphragm; the other had both local and distant extension. The median time to relapse after completion of radiation therapy for Stage I and II were 15 and 5 months, respectively. Two of the eight children with recurrent disease are dead. The other six were retreated and are alive and free of disease for periods ranging from 24 to 68 months after original treatment (median, 36 months). Two of the six survivors in this group received irradiation to the site of the recurrent disease only, one was given total nodal irradiation, and three had chemotherapy. The other 12 patients are in continuous first remission. They have been followed for a median time of 26 months. The actuarial relapse-free survival and survival rates at 3 years are 57 and 89%, respectively.

Adolescent↗
PubMed1975

Treatment of acute lymphoblastic leukemia in childreq with "prophylactic" intrathecal methotrexate and intensive systemic chemotherapy.

Sventy-five children under the age of 15 years, with acute lymphoblastic leukemia, were treated with a multiple drug chemotherapy regimen (L-2) and intrathecal methodtrexate. Remission was achieved in all except 1. Three died from infection early in remission and 1 was lost to follow-up. Of the remaining 70, relapse occurred in 19; in 3 children this was confined to the central nervous system (CNS) and in 1 was in both the CNS and bone marrow. Fifty-one children continue in complete remission from 14 to 54 months. Fourteen of these children have completed 3 years of chemotherapy and are disease free 2 to 18 months posttreatment. The results indicate that periodic administration on intrathecal methotrexate with no CNA irradiation, plus intensive systemic chemotherapy, can effectively control CNA leukemia and prolong the duration of complete remissions.

Adolescent↗
PubMedDate not supplied

Extracellular ATP modulates ion transport via P2Y purinoceptors in a middle-ear epithelial cell line.

Mucus and cellular debris are eliminated from the middle-ear cavity through the E-tube by the mucociliary system. Depth of the periciliary fluid layer is thought to be regulated by epithelial ion transport activity. Since impairment of the mucociliary system is a key step in the development of otitis media with effusion, we investigated the ion transport mechanisms of the middle-ear epithelium using the middle-ear MESV cell line. ATP has been shown to modulate ion transport as well as various cellular functions in several cell types via purinoceptors. In order to investigate a possible modulation of the transport activity of MESV cells, we evaluated short-circuit current (Isc) changes in response to specific stimulation of putative purinoceptors by ATP and its various analogs. ATP dramatically increased Isc, while adenosine had no effect, thus demonstrating the presence of P2 receptors according to the original classification by Burnstock. The rank order of potency of purinoceptor agonists for stimulation of Isc on the apical side (ATP > UTP > gamma-SATP >> beta-SADP > 2-methylthio-ATP, 2MeSATP > beta, gamma-methylene-ATP, beta,gamma-MeATP) and on the basolateral side (ATP > gamma-SATP > UTP >> beta-SADP > 2 MeSATP > beta,gamma-MeATP), along with studies using selective antagonists and intracellular calcium measurements are consistent with a P2Y receptor subtype. The ATP-induced increase in Isc was related to sodium transport. This modulation might be of importance in stress conditions such as inflammation.

Adenosine Triphosphate↗
PubMedDate not supplied

Clinical experience in airway endoscopy in children: an emphasis on the comparison between flexible and rigid endoscopy.

Congenital and acquired lesions of the pediatric airway frequently pose perplexing problems in children, infants and newborns. Prompt investigation into the etiology and early intervention are essential to decrease the morbidity and to prevent some tragic events. Endoscopy grants access to the lesion sites for either diagnostic or therapeutic purposes. From April 1994 to May 1997, totally 509 endoscopic procedures, including 292 flexible and 217 rigid endoscopic procedures were performed in 296 pediatric patients at National Taiwan University Hospital. For routine diagnostic procedures, the flexible fiberscope is the instrument of choice which should include a detailed examination of entire upper airway, as farther to tracheobronchi as possible. When flexible endoscopy fails to demonstrate the exact airway lesion or certain surgical manipulation is demanded, rigid endoscopy is favored. The indications for endoscopy were: stridor, respiratory distress, follow-up endoscopy or tracheostoma evaluation, feeding difficulty, hoarseness or weak voice, and suspicious airway foreign body. Common airway problems in serial orders were: laryngomalacia, subglottic stenosis, tracheo/bronchomalacia and airway foreign body. Nearly 20% of patients in this series had multiple synchronous airway lesions. There was no major complication in our 292 flexible endoscopic procedures. Two major complications attributed to endoscopic manipulations occurred in 217 rigid endoscopic procedures.

Adolescent↗