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Biomedical subjects

S C Yan

Publications and source records attributed to S C Yan.

17 recordsLinked to original sources
PubMed1992

Recombinant human thrombomodulin. Regulation of cofactor activity and anticoagulant function by a glycosaminoglycan side chain.

Two glycoforms of a secretable human thrombomodulin mutant [TMD1-105 and TMD1-75; Parkinson, Grinnell, Moore, Hoskins, Vlahos & Bang (1990) J. Biol. Chem. 265, 12602-12610] were expressed in human 293 cells and used to study the role of glycosylation in the functions of this endothelial-cell thrombin receptor. Carbohydrate content analysis and intrinsic labelling with [3H]glucosamine and [35S]sulphate showed that TMD1-105 contained a chondroitin sulphate whereas TMD1-75 did not. Other than chondroitin sulphate, the carbohydrate contents of the two glycoforms were identical, indicating similar glycosylation patterns at other O-linked and N-linked sites in the two glycoforms. The properties of TMD1-105 were converted into those of TMD1-75 by chondroitin ABC lyase digestion. Trypsin digestion of labelled TMD1-105 permitted isolation of two overlapping peptides that contained chondroitin sulphate, spanned the entire O-glycosylation domain and had O-glycosylation sites at Ser-492, Ser-498, Thr-500, Thr-504 and Thr-506. The chondroitin sulphate-attachment site was assigned to Ser-492 as this residue is conserved in mouse and bovine thrombomodulin and lies within a sequence Ser-Gly-Ser-492-Gly-Glu-Pro, which has strong similarity to chondroitin sulphate attachment sites in other proteoglycans. Five peptides with N-linked carbohydrate were also isolated and contained glycosylation sites in the lectin-like domain (Asn-47, Asn-115, Asn-116) and in the fourth (Asn-382) and fifth (Asn-409) epidermal growth factor domains. The role of N-linked and simple O-linked carbohydrates in the functions of human thrombomodulin remain unclear. The present studies demonstrate, however, that the presence of chondroitin sulphate in human thrombomodulin has profound effects on all of the anticoagulant properties of this important anticoagulant thrombin receptor.

Amino Acid Sequence↗
PubMed1991

Effect of low- and high-frequency TENS on Met-enkephalin-Arg-Phe and dynorphin A immunoreactivity in human lumbar CSF.

Transcutaneous nerve stimulation (TENS) treatment was given for 30 min to 37 patients divided into 3 groups of 10 patients and 1 group of 7 patients. Two groups received low-frequency (2 Hz) and the other 2 groups high-frequency (100 Hz) stimulation. A diagnostic lumbar cerebrospinal fluid (CSF) sample was obtained immediately before and after stimulation. The CSF samples were subjected to analysis of immunoreactive (ir) opioid peptides, Met-enkephalin-Arg-Phe (MEAP) from preproenkephalin and dynorphin A (Dyn A) from preprodynorphin, respectively. Low frequency TENS applied on the hand and the leg resulted in a marked increase (367%, P less than 0.05) of ir-MEAP but not ir-Dyn A, whereas high-frequency (100 Hz) TENS produced a 49% increase in ir-Dyn A (P less than 0.01) but not ir-MEAP. This is the first report in humans that 2 Hz and 100 Hz peripheral stimulation induces differential release of peptides from preproenkephalin and preprodynorphin, respectively.

Adult↗
PubMed1991

[Effect of Polyporus umbellatus polysaccharide on function of macrophages in the peritoneal cavities of mice with liver lesions].

The cells in peritoneal cavities of mice were taken out and cultured in vitro. The amount to release H2O2 of the macrophages was assayed by fluorimetry. Polyporus umbellatus polysaccharide (PUP) could not only increase the number of macrophages and the amount of H2O2 release in the peritoneal cavities of normal mice, but also raise the lowered number of macrophages and the ability to release H2O2 in the peritoneal cavities of the mice with liver lesions caused by CCl4 significantly. So PUP could improve the cellular immunity of normal mice and the mice with liver lesions.

Animals↗
PubMed1990

Characterization and novel purification of recombinant human protein C from three mammalian cell lines.

Human Protein C (HPC), an antithrombotic factor with potential clinical utility, is a vitamin K-dependent protein that has several complex post-translational modifications. In an effort to define the functional roles of these modifications, recombinant HPC (rHPC) was expressed in and characterized from 3 adenovirus-transformed cell lines. The rHPC in crude culture medium from the 3 cell lines displayed anticoagulant activities that were either higher, slightly lower or much lower than that of plasma HPC. The rHPC from each cell line was purified and characterized using a novel, but simple chromatographic method, termed "pseudo-affinity", capable of resolving molecules differing by only very slight modifications. We demonstrate the critical dependence of full gamma-carboxylation on the function of this protein. In addition, our data indicate that both the gamma-carboxyglutamate and glycosyl contents affect the functional activities of rHPC.

Adenoviruses, Human↗
PubMed1989

Diagnosis and treatment of giant cell tumor in the thoracic spine.

A 23-year-old woman with incomplete paralysis was operated upon for a giant cell tumor in the thoracic spine. X-ray films revealed a destruction lesion in the vertebral body of the 12th thoracic vertebra. On the plain thoracic computed tomography scan, the finding was a soap-bubble appearance with a linear high density area in the mass lesion which destroyed the vertebral body. Preoperative angiography showed no apparent feeding artery to the tumor tissue; preoperative myelography showed incomplete block at the level of the 12th thoracic vertebra. A radical operation was carried out in one stage via a combined antero-posterior approach. In order to give radiotherapy immediately after operation, a vascular pedicled rib graft was made. This paper discusses the role of thoracic computed tomography scan in the diagnosis of giant cell tumor and the surgical techniques used in treatment.

Adult↗
PubMed1989

Post-translational modifications of proteins: some problems left to solve.

Three major questions regarding the post-translational modification of amino acid side chains in proteins are briefly considered: (1) What are the biological functions of the reactions, (2) what is the specificity of the processing reactions in selecting only a few or sometimes even only one residue for modification, and (3) how do we solve the uniqueness of the processing steps in the production of recombinant proteins? The answers to these questions are not obvious at this time.

Protein Processing, Post-Translational↗
PubMed1989

Preventing effect of "liuwei dihuang decoction" on esophageal carcinoma.

Liuwei Dihuang Decoction is a representative classic prescription for nourishing Yin in Traditional Chinese Medicine. Experimental and clinical studies showed that the recipe could 1. inhibit carcinogenesis of anterior stomach by N-nitrososarcosine ethyl ester in mice; 2. inhibit the formation of lung tumors induced by Urethan in mice; 3. decrease spontaneous tumorigenesis in LACA strain; 4. inhibit the mutagenic activity of Endoxan in micronuclear test. Patients with epithelial dysplasia of esophagus, a preneoplastic lesion, were treated by using this recipe. The canceration rate within 1 year was 2.2% in the treated and 12.4% in an untreated group. Within 5 years these rates were 9% and 26% respectively (p less than 0.025).

Animals↗
PubMed1985

Human brain tubulin purification: decrease in soluble tubulin with age.

The soluble tubulin of human cerebral cortex, as assessed by [3H]colchicine binding of the 100,000 g supernatant fraction, decreases drastically with age, 75 percent from age 0 to age 90. There is also a considerably lower concentration of high molecular weight proteins in the soluble fraction of postmortem human cerebral cortex than in that of nonhuman species. Human brain tubulin can be polymerized into microtubules with DEAE-dextran. The DEAE-dextran induced microtubules are stable to cold temperature (4 degrees) and calcium. However, in the presence of 1 M glutamate, the microtubules become cold labile and depolymerize at 4 degrees. Thus we have developed a novel method for purifying polymerization competent tubulin from fresh or frozen human cerebral cortex. Human brain tubulin purified by our novel method is very similar to tubulin from the brains of other mammals in molecular weight, amino acid composition, polymerization-depolymerization parameters, and structural dimensions of the microtubules formed.

Adolescent↗