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Biomedical subjects

J C Ho

Publications and source records attributed to J C Ho.

65 records · Page 4Linked to original sources
PubMed1988

The fragile-X syndrome.

The variability in behavioral manifestations of the fragile-X syndrome and the lack of a well-defined psychological profile require the attention of behavioral geneticists and other behavioral scientists. The association with autism suggests that the fra(X) may be responsible for a genetic subtype of autism. While the fragile-X syndrome is considered an X-linked disorder, several aspects of observed transmission patterns do not follow those of classical X-linked inheritance. In particular, the finding of genetic transmission via intellectually normal males is surprising and has important implications for genetic counseling, as well as for genetic models of the fragile-X syndrome. Reports on folic acid treatment are encouraging, but not conclusive. The mechanisms involved in the association between the fra(X) chromosome and its particular phenotype are still unknown. Current investigations applying advanced techniques in molecular biology are likely to provide insight into this unique genetic disorder.

Fragile X Syndrome↗
PubMed1986

Probenecid disposition by parallel Michaelis-Menten and dose-dependent pseudo-first-order processes.

Re-evaluation of published data on the urinary excretion of probenecid [4-(dipropylamino)sulfonylbenzoic acid, 1] and its metabolites as a function of orally administered dose has revealed that the elimination process is comprised of five parallel pathways. Excretion of the major metabolite, the acyl glucuronide 2 (35-45% of dose), follows Michaelis-Menten kinetics. The three oxidized metabolites, the mono-N-propyl, carboxylic acid, and secondary alcohol derivatives 3, 4, and 5, respectively, (totaling 30% of dose), each adhere to pseudo-first-order kinetics in which the elimination rate constant, as a result of product inhibition, is a function of the administered dose. Four to 13% of the dose is eliminated unchanged in apparent first-order fashion. A mathematical relationship between elimination half-life and dose, under conditions of product inhibition, is derived. Computer simulation of the elimination process confirms the experimental observation that the fraction of dose excreted in the form of each metabolite remains relatively constant over the dose range of 0.5 to 2 g. This study is believed to represent the first application of parallel Michaelis-Menten and dose-dependent pseudo-first-order processes to drug disposition. It demonstrates that the observation of constant proportions of excreted metabolites over a relatively wide range of doses does not provide evidence that the elimination process remains first-order.

Dose-Response Relationship, Drug↗
PubMed1982

Spontaneous regression of hepatocellular carcinoma: a case study.

A Chinese patient with documented hepatocellular carcinoma (HCC) satisfied the criteria of Everson and Cole for spontaneous regression of malignant tumors. Subsequently he survived a tumor-free period of at least 13 years. During the period of regression, shrinkage of liver coincided with a rise of SGOT to a level comparable to that reported for patients with liver cancer during hepatic arterial ligation and cytotoxic therapy. Postregression liver biopsy from the site of the previous tumor revealed relatively uninflamed HBsAg-positive tissue without dysplasia. The case provided the positive end of the survival spectrum in HCC, evidence that regression of HCC might occur by involution rather than maturation, and histologic data suggesting that regressed HCC might be replaced by surrounding tissue instead of leaving behind dysplasia.

Aspartate Aminotransferases↗
PubMed1981

Liver cell dysplasia in association with hepatocellular carcinoma, cirrhosis and hepatitis B surface antigen in Hong Kong.

Liver-cell dysplasia was identified in 60% of 558 cases of cirrhosis with and without hepatocellular carcinoma (HCC) in Chinese coming to necropsy in Hong Kong from 1963 to 1978. A significant correlation was found between liver-cell dysplasia and the identification of hepatitis B surface antigen (HBsAg) in the livers, suggesting that dysplasia may be casually related to hepatitis B virus (HBV). Applying Bayes' theorem to our series of male deaths, we calculated that for Chinese male non-cirrhotics showing liver-cell dysplasia at necropsy, compared with male non-cirrhotics showing no liver-cell dysplasia, the approximate risk factor for HCC is 13:1, whereas for male cirrhotics with liver-cell dysplasia, the risk factor for HCC is approximately 2:1. In the presence of dysplasia, the risk for HCC is increased two-fold in males who are also HBsAg-positive. Thus, the presence of liver-cell dysplasia in cirrhotic or non-cirrhotic livers accompanies a significantly higher risk of developing HCC, especially in the presence of HBsAg.

Carcinoma, Hepatocellular↗
PubMed1980

Isolation of plasma membranes from rat lungs: effect of age on the subcellular distribution of adenylate cyclase activity.

A simple and rapid method of isolating plasma membranes from rat lungs is described. The method involves homogenization of tissue in isotonic sucrose-buffered medium followed by differential and sucrose density gradient centrifugation. Plasma membranes obtained by this procedure were essentially free from other subcellular contamination. Plasma membranes isolated from 2-day-old rat lungs showed 6 to 7-fold purification of adenylate cyclase and 5'-nucleotidase activities compared to the original homogenate. In contrast, plasma membranes from 35-day-old rat lungs showed no purification of adenylate cyclase activity although 5'-nucleotidase activity showed similar enrichment. These results suggest that adenylate cyclase activity is not a reliable marker for plasma membranes from adult rat lungs.

Adenylyl Cyclases↗
PubMed1980

Hepatitis B surface antigen, hepatocellular carcinoma and cirrhosis in hong kong: a necropsy study: 1963-1976.

Hepatitis B surface antigen (HBsAg) was stained in liver tissue in 71% of 496 cases of cirrhosis with and without hepatocellular carcinoma (HCC) in Chinese coming to necropsy in Hong Kong from 1963-1976. Male cases numbered 417; HBsAg was positive in 83% of those in which HCC was combined with cirrhosis and in 62% of those with cirrhosis alone. Of 39 additional male cases of HCC without cirrhosis, 38% were HBsAg+. Similar proportions were recorded in the famale cases. This progression suggests a cumulative carcinogenic effect of persistent hepatitis B virus (HBV) fully expressed in the presence of cirrhosis. The approximate risk factors for males in Hong Kong who are HBsAg+ at the time of death, compared with HBsAg- males, are 6:1 for HCC alone, 16:1 for cirrhosis alone and 50:1 for HCC combined with cirrhosis. The frequency of HBsAg+ tests is much higher in Hong Kong than in the United Kingdom, and cirrhosis is calculated to be 2.8 times and HCC 11 times commoner. The high incidence of HCC in Hong Kong is not attributable solely to the high incidence of cirrhosis, but can be related to the high incidence of cirrhosis accompanied by persistent HBV.

Carcinoma, Hepatocellular↗
PubMed1980

Two cases of mucoepidermoid carcinoma of the liver in Chinese.

Two cases of mucoepidermoid carcinoma of the liver are presented. This tumour is a rare entity and is a variant of cholangiocarcinoma. Its prognostic significance does not appear to be different from that of other forms of cholangiocarcinomas which are encountered frequently in Hong Kong.

Adenoma, Bile Duct↗
PubMed1980

Hepatitis B surface antigen in hepatocytes at necropsy.

Seventy cases of cirrhosis and hepatocellular carcinoma (HCC) and 43 cases with no primary liver disease were investigated at necropsy by Gomori's aldehyde fuchsin stain for the presence of hepatitis B surface antigen (HBsAg) in liver cells. The results were correlated with serum HBsAg levels determined by radioimmunoassay and hemagglutination tests performed during the last three months of life or after death. In more than 90% of cases, a correlation was found between the results in tissue and in sera. The aldehyde fuchsin stain is a reliable tool for the detection of HBsAg in patients with cirrhosis and with HCC or without primary liver disease.

Carcinoma, Hepatocellular↗
PubMed1977

Pigmented carcinoid tumour of the thymus.

An asymptomatic thymic tumour, classified as a carcinoid tumour on the basis of its light and electron-microscopic appearances, is described. This tumour was atypical in having foci of melanin pigmentation, the pigment being contained in dendritic melanocytes and melanophages. We suggest that the pigmented cells are not neoplastic and represent latent thymic melanoblasts stimulated in some way by the carcinoid tumour. Alternative explanations are discussed.

Carcinoid Tumor↗