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Biomedical subjects

H C Ho

Publications and source records attributed to H C Ho.

At least 73 records · Page 4Linked to original sources
PubMed1978

Environmental backgrounds of young Chinese nasopharyngeal carcinoma patients.

Twenty-four Chinese NPC patients under 25 years of age at the time of diagnosis were interviewed. The interviews were carried out in the presence of their families in 22 cases and concentrated on the environmental background of the subject's infancy and early childhood. An analysis of the results eliminated household inhalants, aerial contaminants, medicines, food therapy, spices, fresh foods and soya sauce as likely factors in carcinogenesis. The only remaining foods eaten by all subjects and worthy of consideration were laap cheung, salted fish and tau si. Salted fish was the most commonly eaten and the only one fed to babies. In childhood, the subjects had rarely or never been fed vegetables or fruits. Most had, since childhood, been characteristically sickly, inactive, withdrawn and choosy about their food. It would appear that consumption of salted fish and vitamin C-deficiency in early childhood are important environmental factors and that a certain personality type may be associated with an increased risk.

Adult↗
PubMed1978

Environmental factors in the etiology of nasopharyngeal carcinoma: report on a case-control study in Hong Kong.

A case-control study was undertaken of Cantonese NPC patients hospitalized in the Queen Elizabeth Hospital, Hong Kong. One age- and sex-matched control was selected for each NPC case from hospitalized patients with cancers other than NPC. A total of 150 NPC patients and 150 controls were interviewed in order to compare the two groups with respect to socio-economic status, dietary habits and health status. In addition to the individual patients and controls, healthy members of their respective households were also interviewed, in order to obtain information not influenced by the experience of having cancer. Weaning habits were compared in the households of NPC patients and those of controls by asking women who had ever breast fed a child about food supplements they had given to the baby during, and immediately after, weaning. The following factors were found to be positively associated with NPC: (1) belonging to the four lowest occupational classes; (2) practicing Buddhism or ancestor worship and having religious altars in the house; and (3) having a history of previous illnesses of the ear or nose after the age of 15 years. The following factors were found to be negatively associated with NPC: (1) eating of bread; (2) eating of tinned food; and (3) use of spices. The study of weaning habits disclosed that salted fish was given to babies just after weaning more often in households with an NPC case than in control households. A multivariate analysis showed that traditional lifestyle and the consumption of salted fish during weaning are independent risk factors for NPC. This analysis also revealed that two or three of the many expressions of a traditional lifestyle included in the study could account for the total increase in NPC risk associated with this way of life, although it is quite possible that other, as yet unidentified, factors are just as important.

Adolescent↗
PubMed1977

Purification of a Ca2+-activatable cyclic nucleotide phosphodiesterase from bovine heart by specific interaction with its Ca2+-dependent modulator protein.

A Ca2+-activatable cyclic nucleotide phosphodiesterase from bovine heart can be eluted from a DEAE-cellulose column either in the free form by buffers containing 0.1 mM ethylene glycol bis(beta-aminoethyl ether)N-N,N'N'-tetraacetic acid (EGTA) or as a complex of the enzyme with its protein modulator by buffers containing 0.01 mM CaCl2. A purification procedure based primarily on the significantly different affinity of the two forms of the enzyme for DEAE-cellulose was developed for the purification of the enzyme from bovine heart. The procedure involves ammonium sulfate fractionation, three chromatographic steps on DEAE-cellulose, and gel filtration on Sephadex G-200 with a 5000-fold purification over the crude extract. The purified enzyme has a specific activity of 120 mumol of cAMP/mg/min, can be activated 5-fold by Ca2+, but is only 80% pure as judged by analytical disc gel electrophoresis. The purified enzyme is unstable but can be stabilized by addition of Ca2+ and the protein modulator; this is in contrast to the less pure preparations of Ca2+-activatable phosphodiesterase which are destabilized by the protein modulator in the presence of Ca2+.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1977

In vitro immune responses to PPD, extracts from Raji cells and nasopharyngeal carcinoma biopsies in NPC leucocytes.

Peripheral leucocytes from nasopharyngeal carcinoma (NPC) patients and control subjects, which included healthy subjects and patients with other cancers, have been tested against PPD and a panel of extracts from Raji cells and pooled NPC biopsies, using the blast transformation and the macrophage migration inhibition assays. The results of both assays indicated that the in vitro cell-mediated immune (CMI) responses to the Raji-cell extracts and NPC-biopsy extracts were associated with NPC. However, the peripheral leucocytes from NPC patients and control subjects responded similarly to PPD. These results are in general accord with the skin tests reported by Levine et al. (1976) and Ho, Ng and Kwan (1977b). The antigenic specificity of the NPC-associated CMI responses remains, however, to be resolved, as the extracts used in these or in the in vivo CMI studies were heterogeneous mixtures.

Burkitt Lymphoma↗
PubMed1977

Possible transformation of nasopharyngeal epithelial cells in culture with Epstein-Barr virus from B95-8 cells.

Explants of fresh biopsy specimens from non-neoplastic nasopharyngeal (NP) mucosa, nasopharyngeal carcinoma (NPC), other tumours (OT) of the head and neck and freshly removed tonsils were treated with an Epstein-Barr virus (EBV) preparation from B95-8 cells and cultured. The mainly epitheloid outgrowths from these infected explants were then compared with those from their respective uninfected controls at 14 days. Growth stimulation occurred with a significantly higher frequency, and the degree of stimulation was generally higher with the infected NP explants than those of the similarly infected explants of other origins. Furthermore, after treatment with the virus preparation, several of the outgrowths from the NP explants showed growth characteristics and cellular morphology typical of those of transformed cells. Light microscopy has shown the changed NP cells to have epithelial characteristics. This is now being verified by electron microscopy, which has so far shown the presence of keratin fibrils and desmosomes in one specimen examined. They are also being examined for the presence of EBV-DNA and EBNA, and other features of transformation, including malignant tendency, by passage through athymic nude mice.

Cell Division↗
PubMed1976

Study on the surface polypeptides isolated from human lymphoblastoid ce-ls by ionic shock.

Ionic shock treatment in the presence of 10% glycerol is an efficient and selective method for extracting cell surface components from Raji cells and effecting the solubilization of up to 22 polypeptides. The majority of these shock-released polypeptides are accessible to lactoperoxidase radioiodination. Sera from rabbits immunized against these soluble extracts are reactive against Raji cell surface as indicated by indirect membrane immunofluorescence and agglutination assays.

Agglutination Tests↗
PubMed1976

Comparison of calcium-binding proteins. Bovine heart and brain protein activators of cyclic nucleotide phosphodiesterase and rabbit skeletal muscle troponin C.

In previous studies we have shown that the activation of bovine heart cyclic nucleotide phosphodiesterase by purified protein activator is completely dependent on the presence of Ca2+ and that the protein activator Ca2+ complex is probably the true activator for the enzyme (Teo, T.S. and Wang, J.H. (1973) J. Biol. Chem. 248, 5930-5955). More recent studies have led us to believe that the mechanism of the Ca2+ activation of phosphodiesterase resembles that of the Ca2+ activation of muscle contraction and that the protein activator may play a role similar to troponin. In the present study we show that the protein activator resembles rabbit muscle troponin C in amino acid composition, molecular weight, isoelectric point, and ultraviolet absorption spectrum. Preliminary structural studies also indicate that these two proteins may have evolved from a common ancestral protein through gene duplication. This argument is strengthened by the finding that the tryptic peptide map of the bovine heart protein activator is indistinguishable from that of the bovine brain phosphodiesterase activator protein for which preliminary sequence information also suggests homology to troponin C (Watterson, D.M., Harrelson, W.G., Jr., Keller, P.M., Sharief, F., and Vanaman, T.C. (1976) J. Biol. Chem. 251, 4501-4513).

Amino Acid Sequence↗
PubMed1976

Epstein-Barr-virus-specific IgA and IgG serum antibodies in nasopharyngeal carcinoma.

The sera of 73 patients with nasopharyngeal carcinoma (NPC), 28 patients with other carcinomas (OC) and 89 healthy subjects (HS) were tested for IgG and IgA antibodies to Epstein-Barr virus (EBV) viral capsid antigen (VCA). The majority of the NPC sera had IgG titres of 160 or above, whereas the majority of the other sera had titres below 160. For IgA reactivity to EBV-VCA, 68 of 73 (93-2%) NPC sera had titres of greater than or equal to 10. In contrast, only 6 of 28 (21-4%) OC sera and none of the HS sera had such titres. The mean serum concentrations of IgG, IgA, IgM and C3' were also determined in 55 NPC and 20 OC patients and 18 HS. They were all significantly higher in the NPC sera than in the HS. Although the concentrations of IgG and C3' were not significantly different in the two carcinoma groups, the concentrations of IgA and IgM were significantly higher in the NPC group than in OC. These findings appear to reflect the intensity of EBV-specific antigenic stimulation in NPC, and the EBV-specific serum IgA reactivity may be a sueful aid to the diagnosis of NPC, especially in cases with an occult primary tumour. It may be also of value as a screening test in people at high risk.

Antibodies, Viral↗
PubMed1975

Cell-mediated immunity in human acute leukemia.

The general cell-mediated immunological reactivity of patients with acute leukemia has been found to be intact, although it may be depressed by extensive disease or by chemotherapy. Patients with acute leukemia also have cellular immune reactivity against tumor associated antigens, as measured by skin tests for delayed hypersensitivity, lymphocyte stimulation, and 51Cr release cytotoxicity. Skin reactions to autologous and allogeneic crude membrane extracts of blast cells correlated with disease state, positive in many patients in remission and negative in most patients in relapse. Extracts of human lymphoid tissue culture cell lines derived from lymphomas or leukemia also gave positive reactions in patients with acute leukemia, and also in patients with lymphoma and nasopharyngeal carcinoma. The antigens detected in the skin tests with the lymphoid cell lines appear to be different from those associated with Epstein-Barr virus (EBV) and from those detected in the 51Cr release assay. Evidence is presented which suggests a complex variety of antigens on blast cells and on the cell lines. Although leukemia associated antigens were also detected by lymphocyte stimulation and by cytotoxicity assays, the results did not correlate with the skin tests nor with each other. The possible use of these assays for monitoring the chemotherapy and immunotherapy of acute leukemia patients is discussed.

Acute Disease↗