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Biomedical subjects

L Chen

Publications and source records attributed to L Chen.

At least 1,333 records · Page 74Linked to original sources
PubMed1992

[Bile acid pool in the formation of pigment stone: an experimental study].

A method with isotopic 3H-CDCA was established to determine bile acid pool. Sixty male guinea pigs were divided randomly into two groups; 20 guinea pigs fed with standard chow served as control, and 40 with 10% low protein lithogenic chow were subdivided into 4 groups executed on 10,20,30 and 40 days (In the last subgroup, vitamin C was added to the chow), respectively. The bile acid pool of lithogenic animals decreased on the 10th days and significantly decreased on the 20th, 30th, 40th day (P < 0.01) when compared with controls in the same periods. The incidence of pigment gallstone was 90% on the 20th day, 100% on the 30th day, 40% on the 40th day in lithogenic animals. The pool size decreased slightly on the 40th day in lithogenic animals which were fed with supplement of Vitamin C. A significant positive correlation was noted between gallbladder volume and bile acid pool size (r = 0.842) in the 30th day lithogenic animals. We postulate that the decreased bile acid pool size occurs before the development of pigment gallstone and it may be an important factor in promoting the formation of gallstone.

Animals↗
PubMed1992

[An experimental study of the treatment of root avulsion of brachial plexus using contralateral C7 nerve neurotization (nerve transfer)].

This study compared the functional results of contralateral C7 root neurotization with homolateral phrenic nerve transfer for repairing root avulsion of brachial plexus in rats. It was found that in the C7 nerve root group all the parameters of evoked muscle potential amplitude (EMPA), regenerating axon count, biceps weight and muscle fibre area, and muscular maximal tetanus tension were statistically superior (P < 0.05-0.01) to those in the phrenic nerve group; while there were no significant differences between these two groups in motor nerve latency regenerating axon area and persisting time of muscular maximal tetanus tension (P > 0.05). The reasons why C7 root neurotization is superior to phrenic nerve transfer were also discussed.

Animals↗
PubMed1992

Interleukin-6 protects ductal breast carcinoma cells from MHC-unrestricted cell-mediated cytotoxicity.

Interleukin-6 (IL-6) has various biological activities including growth stimulation and maturation of B cells into antibody-producing cells, growth stimulation of murine hybridoma and plasmacytoma cells, induction of acute phase proteins, activation of T cell functions, triggering differentiation of various hematopoietic cells, and inhibition of growth of the human ductal breast carcinoma cell line T-47. Recently it was found that IL-6 also has the ability to enhance natural killer (NK) cell activity. In the present study the possible role of IL-6 as a regulator of NK cell-mediated cytotoxicity (NK-CMC) was evaluated. It was found that IL-6 reduced the sensitivity of T-47 cells (a ductal breast carcinoma cell line) to NK-CMC. The mechanism of IL-6-induced protection was studied. IL-6 had no effect on the level of conjugate formation between T-47 cells and NK cells. However, IL-6 reduced the number of dead conjugated T-47 cells. IL-6-treated T-47 cells were also found to be as sensitive as the nontreated cells to the lytic effect of NK cytotoxic factor (NKCF). However, IL-6 appeared to reduce the ability of T-47 cells to induce release of NKCF from NK cells following conjugate formation. Therefore, it is suggested that IL-6 protects T-47 cells from natural killing by the same mechanism as interferon.

Breast Neoplasms↗
PubMed1992

[Expression of hepatitis B virus X protein in tumor and nontumor tissues of patients with hepatocellular carcinoma (HCC)].

PAP technique and rabbit anti-X serum were used to detect the X protein in tumor and nontumor liver tissues from 34 patients with HCC. The positive rate of the X protein in both tissues were 94.1% and 84.4% respectively. Of the 34 patients with HCC, 27 were complicated by liver cirrhosis, in whom 92.6% were X protein positive in liver cells. It was found that almost all of the liver cells adjacent to the tumor tissue showed strong positive staining. The high frequency and predominant expression of X protein in HCC and liver cirrhosis tissues indicated that X protein may play an important role in hepatocarcinogenesis. X protein was detected in 17.2% of the patients with CAH, which suggested the risk of transformation from CAH to cirrhosis and/or HCC. X protein was first found in bile duct epithelial cells in 59.4% of the patients with HCC, and 6 of 34 HCC were combined with bile duct carcinoma, and some cancer cells were found positive for X protein. It seems that X protein may also be a potential factor in the oncogenesis of bile duct carcinoma.

Bile Duct Neoplasms↗
PubMed1992

Electron spin resonance determination and superoxide dismutase activity in polymorphonuclear leukocytes in congestive heart failure.

Electron spin resonance spin trapping technique was used to measure the generation of active oxygen free radicals during the respiratory burst of phorbol myristate acetate-stimulated leukocytes, and the superoxide dismutase activity in healthy subjects and in patients with congestive heart failure. The authors also measured the concentration of peroxidation products (primarily malondialdehyde) by the thiobarbituric acid method. Experimental results showed that the electron spin resonance spectra obtained during the respiratory burst of polymorphonuclear leukocytes stimulated with phorbol myristate acetate primarily were those of the spin adduct of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) with the superoxide anion and to a lesser extent those of DMPO with hydroxyl radical. Compared with healthy subjects, the release of oxygen free radicals in the respiratory burst of polymorphonuclear leukocytes stimulated with phorbol myristate acetate and the concentration of thiobarbituric acid reactive product in plasma were significantly increased in patients with congestive heart failure while the activity of superoxide dismutase was markedly lower. The increased production of oxygen free radicals by polymorphonuclear leukocytes and the decreased capability of antioxidative defences might play an important role in the generation and development of cardiac failure.

Adult↗
PubMed1992

Direct measurement of oxygen free radicals following cardiac failure of ischemic dog myocardium with the electron spin resonance technique.

OBJECTIVE: To determine whether the involvement of oxygen-derived free radicals in the pathogenesis of ischemic cardiac failure in dogs. DESIGN: Free radicals were measured in normal and ischemic myocardium from dogs with cardiac failure induced by acute coronary occlusion. The changes in free radical production in ischemic myocardium (compared with normal myocardium with or without polymorphonuclear leukocytes) were studies, with plasma superoxide dismutase and malondialdehyde analyzed concurrently. MAIN RESULTS: The results showed that the oxygen free radicals in the ischemic myocardium were about 42.5% higher than those in the normal myocardium, about 67.8% higher than those in the normal myocardium washed with normal saline and about 60.5% higher than those in the ischemic myocardium washed with normal saline (P < 0.05). Compared with controls, the concentration of malondialdehyde in ischemic dog myocardium was increased markedly. The activity of plasma superoxide dismutase was not significantly different between control dogs and dogs with ischemic cardiac failure. CONCLUSIONS: The current results indicate that there was increased production of free radicals and peroxidative damage in ischemic myocardium of dogs with cardiac failure. Polymorphonuclear leukocytes appear to be a main source of free radicals in dog with ischemic cardiac failure.

Animals↗
PubMed1992

Choriocarcinoma presenting as a unilateral renal mass and gross hematuria in a male: report of a case.

Choriocarcinoma of the kidney, either primary or metastatic, is rarely reported in the literature. We encountered a male patient with choriocarcinoma of the right kidney. The patient initially presented with fever, gross hematuria and flank pain. He had initially been unsuccessfully treated for bilateral renal stones for four months before an accurate diagnosis was made. The disease was verified only after a resection of the right kidney and meticulous examination of microscopic sections of the tumor. Further immunohistochemical study strongly supported the diagnosis of choriocarcinoma. The tumor responded briefly to Cisplatinum, Vinblastine and Bleomycin (PVB) treatment. The patient died of brain metastasis and respiratory failure four months after starting systemic chemotherapy.

Choriocarcinoma↗
PubMed1992

[Constituents of tannins from Euphorbia prostrata Ait].

Ten compounds have been isolated from Euphorbia prostrata and identified as gallic acid, corilagin, 1,2,3-tri-O-galloyl-D-glucose,geraniin,tellimagradin I, II, rugosin A, rugosin E, rugosin D and rugosin G on the basis of physicochemical and spectroscopic methods.

Drugs, Chinese Herbal↗
PubMed1992

[The purification and properties of LD5 from normal C57 mouse liver, H22 hepatoma and S180 sarcoma].

Type-A LDH (LD5), isolated from normal C57 mouse liver, H22 hepatoma and S180 sarcoma after a sequential ion-exchange and affinity chromatography, was examined to be quite pure. Studies on the enzyme kinetics and immunological properties showed that there were no differences in optimal pH, optimal temperature, subunit MW., isoelectric point between normal and malignant (H22 hepatoma and S180 sarcoma) LD5. Km to pyruvate decreased in malignant LD5 while LD5 content and percentage increased. Three LD5 antibodies raised against rabbits showed cross-reaction. These antibodies as probes are useful in the isolation of LD5-mRNAs from G57 mouse liver H22 hepatoma and S180 sarcoma.

Animals↗
PubMed1991

Direct identification of the active-site nucleophile in a DNA (cytosine-5)-methyltransferase.

The overproduction, purification, and determination of the active-site catalytic nucleophile of the DNA (cytosine-5)-methyltransferase (DCMtase) enzyme M.HaeIII are reported. Incubation of purified M.HaeIII with an oligodeoxynucleotide specifically modified with the mechanism-based inhibitor 5-fluoro-2'-deoxycytidine [Osterman, D. G., et al. (1988) Biochemistry 27, 5204-5210], in the presence of the cofactor S-adenosyl-L-methionine (AdoMet), resulted in the formation of a covalent DNA-M.HaeIII complex, which was purified to homogeneity. Characterization of the intact complex showed it to consist of one molecule of the FdC-containing duplex oligonucleotide, one molecule of M.HaeIII, and one methyl group derived from AdoMet. Exhaustive proteolysis, reduction, and alkylation of the DNA-M.HaeIII complex led to the isolation of two DNA-bound peptides--one each from treatment with Pronase or trypsin--which were subjected to peptide sequencing in order to identify the DNA attachment site. Both peptides were derived from the region of M.HaeIII containing a Pro-Cys sequence that is conserved in all known DCMtases. At the position of this conserved Cys residue (Cys71), in the sequence of each peptide, was found an unidentified amino acid residue; all other amino acid residues were in accord with the known sequence. It is thus concluded that Cys71 of M.HaeIII forms a covalent bond to DNA during catalytic methyl transfer. This finding represents a direct experimental verification for the hypothesis that the conserved Cys residue of DCMtases is the catalytic nucleophile [Wu, J. C., & Santi, D. V. (1987) J. Biol. Chem. 262, 4778-4786].(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗
PubMed1991

A general approach for characterizing glycosylation sites of glycoproteins.

Recent advances in glycobiology have greatly stimulated carbohydrate research; however, improving techniques for identification and isolation of specific glycosylation sites in protein structure analysis remains a challenge. We report here a practical approach utilizing a membrane staining technique on Problott, a PVDF-type membrane, to screen glycoproteins and glycopeptides derived from enzymatic digests of glycoproteins. To improve the detection sensitivity, an amplified staining technique using biotinylated lectins, avidin, and biotinylated peroxidase was employed. In addition, we describe a micro-batch affinity binding procedure to isolate glycopeptides from complex glycoprotein enzymatic digests. These protocols allow us to start with a subnanomole quantity of glycoprotein and locate the glycosylation sites; isolate glycopeptides in a homogeneous form; and perform amino acid composition, amino acid sequence, and mass analyses on the isolated glycopeptides. The characterization of glycosylation site of a model glycoprotein, carboxypeptidase P, of which the structure is still largely unknown, has been investigated.

Avidin↗
PubMed1991

Calcium is required for the reduction of sulfite from hydrogen in a reconstituted electron transfer chain from the sulfate reducing bacterium, Desulfovibrio gigas.

Calcium is found a strong stimulator of sulfite reduction from hydrogen. A coupling protein of molecular weight 65,000 can be isolated from Desulfovibrio gigas. It functions in a reconstituted electron transfer chain between hydrogenase and sulfite reductase. Its N-terminal sequence shows high homologies with calcium or magnesium binding sites from other calcium-binding proteins.

Amino Acid Sequence↗
PubMed1991

The use of oligodeoxynucleotide probes in chaotrope-based hybridization solutions.

Hybridization solutions containing chaotropes may be used to modulate the thermal stability (Tm or Td) of oligodeoxynucleotide (ODN) duplexes or hybrids over a 90 degrees C range. Modulation of Td allows formulation of hybridization solutions that permit ambient temperature hybridization using most combinations of probe length, probe composition, target type, and facilitates development of convenient and rapid assay formats. The conditions required to achieve ODN duplex fidelity, and optimal yields of hybridized product, are described for trichloroacetate, thiocyanate, guanidinium salts and other chaotropic salts. The effects of different solid supports on Td are described. Also, a method is presented that uses chaotropic compounds to reduce background arising from signal ODN probes in a sandwich assay hybridization format.

Base Sequence↗