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S H Cheng

Publications and source records attributed to S H Cheng.

162 records · Page 9Linked to original sources
PubMed1987

Photosynthetic Characteristics of the C(3)-C(4) Intermediate Parthenium hysterophorus.

The weedy species Parthenium hysterophorus (Asteraceae) possesses a Kranz-like leaf anatomy. The bundle sheath cells are thick-walled and contain numerous granal chloroplasts, prominent mitochondria, and peroxisomes, all largely arranged in a centripetal position. Both mesophyll and bundle sheath chloroplasts accumulate starch. P. hysterophorus exhibits reduced photorespiration as indicated by a moderately low CO(2) compensation concentration (20-25 microliters per liter at 30 degrees C and 21% O(2)) and by a reduced sensitivity of net photosynthesis to 21% O(2). In contrast, the related C(3) species P. incanum and P. argentatum (guayule) lack Kranz anatomy, have higher CO(2) compensation concentrations (about 55 microliters per liter), and show a greater inhibition of photosynthesis by 21% O(2). Furthermore, in P. hysterophorus the CO(2) compensation concentration is relatively less sensitive to changes in O(2) concentrations and shows a biphasic response to changing O(2), with a transition point at about 11% O(2). Based on these results, P. hysterophorus is classified as a C(3)-C(4) intermediate. The activities of diagnostic enzymes of C(4) photosynthesis in P. hysterophorus were very low, comparable to those observed in the C(3) species P. incanum (e.g. phosphoenolpyruvate carboxylase activity of 10-29 micromoles per milligram of chlorophyll per hour). Exposures of leaves of each species to (14)CO(2) (for 8 seconds) in the light resulted in 3-phosphoglycerate and sugar phosphates being the predominant initial (14)C products (77-84%), with </=4% of the (14)C-label in malate plus aspartate. These results indicate that in the C(3)-C(4) intermediate P. hysterophorus, the reduction in leaf photorespiration cannot be attributed to C(4) photosynthesis.

Journal Article↗
PubMed1986

Purification and comparison of the structures of human liver acidic alpha-D-mannosidases A and B.

Human liver alpha-D-mannosidases A and B were purified 11 500-fold and 2000-fold respectively. Both showed microheterogeneity when analysed by isoelectric focusing. Alpha-D-Mannosidases A and B are immunologically identical but differ in their range of pI values, molecular masses, uptake into fibroblasts and subunit compositions. Alpha-D-Mannosidase A consists of equimolar proportions of subunits of molecular masses 62 kDa and 26 kDa, which are linked by disulphide bridges in the intact enzyme. Alpha-D-Mannosidase B also contains a small subunit, of molecular mass 26 kDa, and a variable mixture of larger subunits, of molecular masses 58 kDa and 62 kDa. The 62 kDa and 58 kDa subunits, but not the 26 kDa one, contain concanavalin A-recognizing glycans. The 58 kDa subunit has a lower pI, contains less high-mannose glycans but probably contains more mannose 6-phosphate than the 62 kDa subunit. It is postulated that the differences in structure and properties of alpha-D-mannosidases A and B are due to differences in the state of processing of the large subunit. This suggestion is consistent with a single locus on chromosome 19 for lysosomal alpha-D-mannosidase.

Carbohydrates↗
PubMed1986

Mutations around the NG59 lesion indicate an active association of polyoma virus middle-T antigen with pp60c-src is required for cell transformation.

The transforming activity of polyoma virus middle-T antigen is believed to be dependent on its ability to form a complex with the cellular tyrosine protein kinase, pp60c-src. This hypothesis is based on observations of mutants of middle-T which demonstrated a correlation between these two activities. To investigate further the significance of pp60c-src association in transformation by middle-T, a series of deletion and point mutants were constructed around the NG59 lesion since this region has been implicated in pp60c-src binding. Analysis of the middle-T variants revealed a complete correlation between the presence of associated activated pp60c-src and the ability to transform. Further, this ability of pp60c-src to associate with middle-T may depend on the presence of a beta-turn between amino acids 177 and 180. The results indicate the NG59 phenotype results from the introduction of an isoleucine residue between amino acids 177 and 178 rather than the transition mutation at 179. The mutant MG1 is a single point mutation (at residue 180) and represents the smallest change in the middle-T which abolishes both the transformating and kinase activity of middle-T. Taken together, the data suggest the region surrounding the NG59 lesion is involved in the formation of an active complex between middle-T and pp60c-src and strongly suggest that this association is an absolute requirement for polyoma virus-induced transformation.

Amino Acid Sequence↗
PubMed1986

In vitro mutagenesis of the putative membrane-binding domain of polyomavirus middle-T antigen.

Polyomavirus middle-T antigen contains a contiguous sequence of 22 hydrophobic amino acids near the carboxyl terminus, which is the putative membrane-binding domain of the protein. The DNA encoding this region was mutated to form a series of deletions, insertions, and substitutions called RX mutants. The phenotypes of these mutants fall into three groups based on the transforming and biochemical properties of their encoded proteins. The first group, with deletions outside but proximal to the hydrophobic domain, displayed an essentially wild-type phenotype. A second group, with extensive deletions within the region encoding the hydrophobic domain, expressed middle-T species which did not fractionate with cellular membranes or associate with pp60c-src and which were defective in their ability to transform. A third group of mutants with more subtle predicted alterations in the hydrophobic domain were wild type for the biochemical parameters investigated but were unable to transform cultured rodent cells. These observations are consistent with previous findings that membrane association plays an important role in transformation by middle-T and that, whereas association between middle-T and pp60c-src is a necessary correlate of transformation, it is not sufficient. A comparison of murine polyomavirus middle-T and a newly described hamster papovavirus putative middle-T revealed a strong homology between their respective hydrophobic-domain amino acid sequences. This homology is not observed in the anchorage domains of other model proteins, and this may imply that the middle-T hydrophobic domain is important in transformation for reasons other than simple membrane association.

Animals↗
PubMed1984

Photosynthetic Characteristics of C(3)-C(4) Intermediate Flaveria Species : III. Reduction of Photorespiration by a Limited C(4) Pathway of Photosynthesis in Flaveria ramosissima.

The initial products of photosynthesis by the C(3) species Flaveria cronquistii, the C(4) species F. trinervia, and the C(3)-C(4) intermediate species F. ramosissima were determined using a pulse-chase technique with (14)CO(2)-(12)CO(2). The intermediate species F. ramosissima incorporated at least 42% of the total soluble (14)C fixed into malate and aspartate after 10 seconds of photosynthesis in (14)CO(2), as compared with 90% for the C(4) species F. trinervia and 5% for the C(3) species F. cronquistii. In both F. ramosissima and F. trinervia, turnover of labeled malate and aspartate occurred during a chase period in (12)CO(2), although the rate of turnover was slower in the intermediate species. Relative to F. cronquistii, F. ramosissima showed a reduced incorporation of radioactivity into serine and glycine during the pulse period. These results indicate that a functional C(4) pathway of photosynthesis is operating in F. ramosissima which can account for its reduced level of photorespiration, and that this species is a true biochemical intermediate between C(3) and C(4) plants.

Journal Article↗
PubMed1982

Senescence of Rice Leaves : VII. PROLINE ACCUMULATION IN SENESCING EXCISED LEAVES.

Proline content increased greatly in detached rice (Oryza sativa cv. Taichung Native 1) leaves during senescence. There was a slight but significant increase in proline level after one day of incubation, and, subsequently, proline accumulated relatively rapidly. By 4 days after excision, the level of proline had increased 30- to 50-fold, which is similar to the level seen in the water-stressed detached rice leaves. It is unlikely that the proline accumulation in detached leaves is to be derived solely from protein hydrolysis, since the addition of l-glutamic acid increased the proline level during senescence. The proline analog, 3,4-dehydroproline, did not affect the level of proline during senescence. It seems that accumulation of proline may, at least in part, result from an increased rate of synthesis, possibly due to a disruption of the normal feedback inhibition of proline synthesis. Potassium cyanide and 2,4-dinitrophenol strongly inhibited proline accumulation, indicating that some energy compound(s) may participate in proline accumulation during senescence of excised rice leaves.

Journal Article↗
PubMed1980

Strongyloidiasis in immunosuppressed hosts. Presentation as massive lower gastrointestinal bleeding.

Two cases of massive lower gastrointestinal hemorrhage in immunosuppressed patients were due to complicated infestation with Strongyloides stercoralis. The very high mortality of disseminated strongyloidiasis may in part be attributed to delays in diagnosis and treatment resulting from the complex life cycle of this nematode. Successful therapy in the cases presented consisted of reduction of corticosteroid dosage, use of thiabendazole in excess of that recommended for uncomplicated infestation, parenterally administered nutrition, multiple transfusion of blood products, and vigorous supportive management. Emphasis is given to proper categorization of patients and measures designed to prevent, detect, and treat hyperinfection in patients in whom immunosuppression is anticipated.

Adult↗
PubMed1978

Strongyloides stercoralis colitis: findings in four cases.

The 4 cases of Strongyloides stercoralis colitis presented show various radiological manifestations of colonic reaction. Mild involvement may be associated with minimal radiographic changes. Invasion of the bowel wall by the larvae results in ulceration and edema with loss of haustral markings; stricture may develop. Barium-enema examinations can help in evaluating the nature and clinical progress of the disease.

Colitis, Ulcerative↗
PubMedDate not supplied

Atherogenicity and carcinogenicity of high-arsenic artesian well water. Multiple risk factors and related malignant neoplasms of blackfoot disease.

The objective of this study was to examine multiple risk factors and correlated malignant neoplasms of blackfoot disease (BFD), a unique peripheral vascular disease related to continuous exposure to high-arsenic artesian well water. A total of 241 BFD cases, including 169 with spontaneous or surgical amputations of affected extremities, and 759 age-sex-residence-matched healthy community controls were studied to explore the risk factors of BFD. Multiple logistic regression analysis showed that artesian well water consumption, arsenic poisoning, familial history of BFD, and undernourishment were significantly associated with the development of BFD. The life-table method used to analyze cancer mortality of 789 BFD patients followed for 15 years showed a significantly higher mortality from cardiovascular diseases, peripheral vascular diseases, and cancers of bladder, skin, lung, and liver among BFD patients as compared with the general population in Taiwan or residents in the BFD-endemic area. The results imply the atherogenicity and carcinogenicity of the artesian well water in the BFD-endemic area.

Arsenic Poisoning↗
PubMedDate not supplied

Concomitant renal cell carcinoma and metastatic epithelioid angiosarcoma with microangiopathy.

Epithelioid angiosarcoma is an extremely rare clinical entity. Recognized only in recent years, epithelioid angiosarcoma mimicks epithelial tumors, both morphologically and immunohistochemically. It is very aggressive, assuming a rapid, metastatic and fatal course. This is a report of a case with an unequivocal diagnosis of epithelioid angiosarcoma and concomitant renal cell carcinoma. Reports of cancer with double origins of this combination, in patients without inherited von Hippel-Lindau disease, are extremely rare in the English literature. A review of the literature encompassing all cases of epithelioid angiosarcoma since 1983 is included.

Adult↗
PubMedDate not supplied

Concomitant chemotherapy and radiotherapy for locally advanced nasopharyngeal carcinoma.

BACKGROUND: The prognosis of stage III and IV nasopharyngeal carcinoma treated with radiation therapy alone is poor. To improve outcome, concomitant chemotherapy was incorporated into the treatment of locally advanced nasopharyngeal carcinoma. METHODS AND PATIENTS: Seventy-four patients with locally advanced nasopharyngeal carcinoma were prospectively treated with a combination of concomitant chemotherapy and computerized-tomography-assisted radiotherapy at Koo Foundation Sun Yat-Sen Cancer Center, Taipei, Taiwan, between April 1990 and December 1995. The first 29 patients who had a minimum of 2 years of follow-up were included in this report. Their median interval of follow-up was 42 months. The dose of radiation was 7000 cGy given in 35 fractions. Two courses of chemotherapy, consisting of cisplatin and 5-fluorouracil, were delivered simultaneously with radiotherapy during weeks 1 and 6, and two additional monthly courses were given after radiotherapy. Included in this study were four patients with stage III and 25 patients with stage IV disease. RESULTS: Toxicities of concomitant radiotherapy and chemotherapy were acceptable and reversible. The locoregional control rate at 50 months was 88.2%, and the disease-free survival rate was 74.6%. DISCUSSION: Our results demonstrate an improved survival with the addition of computerized tomography treatment planning and concomitant chemotherapy to radiotherapy in the treatment of locally advanced nasopharyngeal carcinoma when compared with data in the current literature. However, a randomized trial comparing computerized-tomography-assisted radiotherapy with and without chemotherapy is necessary to confirm the contribution of chemotherapy.

Adult↗