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Biomedical subjects

C Yang

Publications and source records attributed to C Yang.

At least 19 recordsLinked to original sources
PubMed1992

Cloning and nucleotide sequence of the Escherichia coli cytidine deaminase (ccd) gene.

The structural gene that encodes cytidine deaminase (cdd) in Escherichia coli was cloned from Kohara phage lambda 365 (7F1), and its nucleotide sequence was determined. Plasmids harboring the gene complemented chromosomal cdd mutations, enhanced cytidine deaminase activity in cell extracts, and directed the synthesis of a protein identical in mass and N-terminal amino acid sequence with cytidine deaminase purified from wild-type bacteria. Metal analysis of the purified, plasmid-encoded deaminase indicated a single atom of tightly bound zinc per subunit. Earlier work has shown that bacterial cytidine deaminase and mammalian adenosine deaminase are remarkably alike in their mechanisms of action, in their free energies of interaction with analogue inhibitors resembling tetrahedral intermediates in nucleophilic substitution, and in their ability to discriminate between analogue inhibitors differing by a single hydroxyl group. In contrast to these shared catalytic similarities, the deduced amino acid sequence of E. coli cytidine deaminase (monomer MW 31,540) differs markedly from the mammalian adenosine deaminase sequence suggesting major differences in their tertiary structures. Nevertheless, cytidine deaminase and mammalian plus bacterial adenosine deaminases share a single region (TVHA) of sequence identity that is tentatively identified as part of the cytidine deaminase active site.

Amino Acid Sequence↗
PubMed1992

Characterization of the unprocessed and processed forms of rab6 expressed in baculovirus/insect cell systems.

Rab6 protein (rab6p) belongs to a family of ras-like GTP-binding proteins thought to be involved in the regulation of intracellular transport in mammalian cells. We have constructed a recombinant baculovirus in order to express rab6p in insect cells. We report here the characterization of four forms of this protein which are found in cytosolic and membrane fractions of infected Sf9 cells. The two major forms are a cytosolic 24 kD protein which represents the unprocessed precursor form of rab6p and a membrane-bound isoprenylated 23 kD protein which represents the processed form. Two other minor forms were also detected: a cytosolic isoprenylated 23 kD protein which may represent a pool in equilibrium with the 23 kD membrane-bound form and a 24 kD non-isoprenylated membrane-bound form which may represent an intermediate in the processing of rab6p.

Animals↗
PubMed1992

Comparative study on the thermostability of collagen I of skin and bone: influence of posttranslational hydroxylation of prolyl and lysyl residues.

Pepsin-solubilized collagen I from skin and bone was analyzed with regard to its thermal stability as a triple helical molecule in solution and after in vitro fibril formation. Collagen I from human control bone was compared with samples showing deficiencies or surplus in the degree of hydroxylation of lysine. The helix to coil transitions were studied by circular-dichroism measurements and limited trypsin digestion. Melting of fibrils from standardized in vitro self-assembly was investigated turbidimetrically. Human control bone collagen I has a maximum transition rate (Tm) at 43.3 degrees C in 0.05% acetic acid. This is 1.9 degrees C above control skin (Tm = 41.4 degrees C), most likely, due to a higher degree of prolyl hydroxylation--0.48 in bone vs. 0.41 in skin collagen I. Lysyl overhydroxylation of human and mouse bone collagen I appears to reduce the Tm slightly (approximately 1 degree C). Underhydroxylated bone collagen has a Tm which is 2 degrees C below control. Melting temperatures of in vitro formed fibrils are an indication for higher thermostability in parallel with an increase of lysyl hydroxylation. Accordingly, the melting temperature of such fibrils from human control skin, 49.3 degrees C, exceeds control bone by 1.4 degrees C. The degree of lysyl hydroxylation in these samples is 0.14 and 0.10, respectively. Further underhydroxylation (0.06) reduced it down to 45.4 degrees C, while extensive overhydroxylation did not continue to increase the thermal stability of fibrils.

Adult↗
PubMed1992

Study on the pathogenic factors of Kashin-Beck disease.

Kashin-Beck disease (KBD) is a chronic osteoarthritic disease, endemic in parts of China. Its etiology is unknown. Selenium deficiency, high concentration of organic matter (mainly fulvic acid) in drinking water, and severe contamination of grain by fungi have been proposed environmental causes. Free radicals, possible mediators between the environmental factors and origin of KBD, have been studied in this work. Drinking water from KBD-affected areas contains a higher level of semiquinone radicals than that from disease-free areas. In animal experiments, fulvic acid (FA) accumulated in the skeletal system as semiquinone radicals. Contamination of grain by Fusarium oxysporum or Alternaria alternata significantly increased the content of semiquinone radicals. Furthermore, corn grown in endemic areas had a higher content of radicals than that from disease-free areas. The g factor values for these radicals from contaminated corn were about 2.0040, in the range of semiquinone radical. In monolayer culture of human embryonic chondrocytes, FA and aqueous extracts of grain contaminated by Fusarium injured the chondrocytes and enhanced lipid peroxidation. Selenite and superoxide dismutase (SOD) protected the cells from injury by these toxins and reduced lipid peroxide. Lower glutathione peroxidase activities and higher levels of lipid peroxidation were also found in the children living in KBD-affected regions. Thus, FA and the mycotoxin, which are seen as exogenous free-radical carriers, are important environmental factors in the pathogenesis of Kashin-Beck disease; and selenium, vitamin C, and vitamin E, which inhibit free-radical formation, are considered to be protective.

Adolescent↗
PubMed1992

Clearance of rat C-reactive protein in vivo and by perfused liver.

The clearance in vivo of rat C-reactive protein (CRP) was studied: (i) in the whole animal and (ii) by using a rat liver perfusion system. Rat CRP is a glycosylated serum protein containing a complex-type biantennary carbohydrate structure on each of its five subunits. The half-life of rat asialo CRP was approximately 5 min. More than 75% of the radioactivity associated with rat asialo CRP and asialo alpha 1-acid glycoprotein (AGP) was recovered in the liver. A small amount of radioactivity (0.8%) associated with rat CRP and rat asialo CRP was found in the lungs. Competitive inhibition of the clearance of 125I-labelled rat asialo CRP from the circulation by asialo AGP was dose dependent, and resulted in a corresponding decrease in the recovery of radioactivity associated with rat asialo CRP in the liver. This indicated that asialo AGP and rat asialo CRP were cleared by the hepatic asialoglycoprotein receptor. This observation was confirmed when the clearance of rat asialo CRP was studied using a rat liver perfusion system. Using this system, the clearance of rat asialo CRP and asialo AGP from the perfusate was inhibited by N-acetylgalactosamine, but not by phosphorylcholine, a ligand through which most of the CRP reactions are mediated. This study provides an example of a circulating serum glycoprotein containing a biantennary carbohydrate structure that is cleared by the asialoglycoprotein receptor.

Animals↗
PubMed1992

Indications and techniques of penetrating keratoplasties, 1985-1988.

Indications and surgical techniques for penetrating keratoplasties (PKs) were evaluated to determine present trends and suggest future directions for PK. Analyses were based on 3,941 PK cases, with questionnaires completed at the time of surgery by 638 surgeons receiving tissue through Tissue Banks International, Inc. between July 1, 1985, and December 31, 1988. The leading indications for PK were pseudophakic corneal edema (PCE) (23%), graft failure (17%), Fuchs' corneal dystrophy (13%), kerataconus (13%), keratitis/scar (12%), and aphakic corneal edema (10%). Indications for PK varied by age and sex. Anterior chamber (AC) lenses accounted for the majority (56%) of PCE cases. Penetrating keratoplasty for PCE occurred within 5 years of cataract surgery for 81% of patients with PC lenses and only 52% of patients with AC lenses. Intraocular lens exchange was performed in most AC and iris-fixed lens PCE cases (65% and 77%, respectively), but less frequently in PC lens cases (17%). A PC lens was placed in 29% of all PCE lens exchange cases. These data have confirmed and expanded observations from smaller studies about leading indications and surgical techniques for PK. Therefore, eye bank data may be useful in describing and monitoring future indications and trends for PK because they provide a broader base of information than that obtained through a single institution.

Adult↗
PubMed1992

Basis of neurovirulence of avirulent rabies virus variant Av01 with stereotaxic brain inoculation in mice.

Av01 is a variant of the challenge virus standard strain of fixed rabies virus that was selected with a neutralizing anti-glycoprotein monoclonal antibody, and has a single amino acid change in the glycoprotein. It is avirulent after both intracerebral and peripheral routes of inoculation in adult mice. In this study, Av01 was found to be neurovirulent with stereotaxic brain inoculation in either the striatum or cerebellum of adult mice. Mice that had been inoculated simultaneously with Av01 by the intracerebral and intrastriatal routes recovered. More infectious virus was present in the brains of mice inoculated intrastriatally than intracerebrally, and more neurons contained rabies virus antigen. However, the topographical distribution of infected neurons was similar with both routes. Serum neutralizing antibodies against rabies virus were produced later and in smaller quantities after intrastriatal inoculation. Av01 is probably neurovirulent after stereotaxic brain inoculation because this route produces both a direct site of viral entry into the central nervous system and a low level of immune stimulation.

Animals↗
PubMed1992

Collagen type II in Langer-Saldino achondrogenesis: absence of major abnormalities in a less severe case.

Collagen extracted either from cartilage or synthesized in vitro was analyzed to identify possible molecular defects in the cartilaginous matrix of a male fetus suffering from a mild form of type II achondrogenesis (Langer-Saldino). The tissue architecture of the patient's cartilage was markedly altered and showed numerous fibrous vascular canals which were focally stained by antibodies against collagens I and III. Collagen II was present, although heterogenously distributed throughout the cartilaginous matrix. Upon electrophoretic separation, however, the patient's femoral head cartilage showed the presence of collagens II, IX and XI only, which was similar to an age-matched control. The hydroxyproline/hydroxylysine ratio of collagen II of the patient was not significantly different from that of the control. Likewise, the compositions of collagens synthesized by cultured chondrocytes as well as fibroblasts were similar in the patient and the control. The results provide strong evidence that, in the present mild case of Langer-Saldino achondrogenesis, collagen II is expressed and regularly hydroxylated at its lysyl residues. This may indicate that cartilage components other than collagen II may be responsible for the altered tissue organization observed. Along with previous observations, our data suggest that the degree of biochemical matrix alterations may be related to the severity of the clinical phenotype.

Achondroplasia↗
PubMed1992

The effect of IH764-3 on fibroblast proliferation and function.

The effect of IH764-3, a potent component isolated from Salvia miltiorrhiza, on the proliferation and function of cultured fibroblasts was studied. It was found that the fibroblast growth curve had a dose-dependent relationship with IH764-3 concentration. The incorporation of 3H-TdR and 3H-proline into fibroblasts was significantly inhibited by IH764-3, and calmodulin, fibronectin and thrombospondin contents in the test group were obviously lower than those in the control group. Flow cytometry showed that in the IH764-3-treated group, the percentage of cells in G0/G1 phase was higher than that in the control. Electron microscopic observation (TEM and SEM) showed that in the treated group, collagen secretion was decreased. All of these results indicate that IH764-3 exerts a direct inhibitory effect on fibroblast proliferation and affects their ability to synthesize collagen.

Animals↗
PubMed1992

[Preparation of human placenta microvillous membrane and the study of its transferrin receptor].

Human placenta microvillous membrane (PMM) was prepared by differential centrifugation and by sucrose gradient centrifugation, and the transferrin receptor (TfR) was studied using the receptor radioassay with 125I-transferrin as a radioligand. The factors affecting ligand-receptor binding reaction and the characteristics of TfR were also studied. The result showed that there was no significant differences (P > 0.1) in specific binding rates of 125I-transferrin to its receptor between the two membrane preparations, indicating that both of them could be used for TfR analysis, but the method of differential centrifugation was more simple and less time consuming. The study of TfR in sixty cases showed that the TfR binding sites on PMM and Bmax were 3.53 +/- 1.98 x 10(12) sites/mg membrane protein and 6.33 +/- 4.21 x 10(-12) mol/mg membrane protein, respectively. The Kd was 4.95 +/- 3.39 x 10(-9) mol/L, and the highest specific binding was 26% with nonspecific binding less than 3%. The conditions for ligand-receptor binding reaction were optimized when the concentrations of membrane protein and the 125I-transferrin in each test tube were 50 micrograms and 50,000 cpm (specific radioactivity being 2109 kBq/micrograms transferrin) respectively the incubation time was 30 min, and the concentration of polyethylene glycol added for separating B/F was 12% (W/V). transferrin binding to its receptor was characterized by high affinity, high specificity and being saturated.

Cell Membrane↗
PubMed1992

[A survey of T-2 toxin in wheat by an indirect enzyme-linked immunosorbent assay].

The survey of T-2 toxin in wheat randomly sampled in nine provinces was carried out, employing an indirect competitive enzyme-linked immunosorbent assay. Among 330 samples, 264 samples (80%) showed positive results. The mean concentrations was 53.3 ppb. and maximal concentration was 1122.0 ppb. It was also detected high concentration (84.5-1064.4) of T-2 toxin in human intoxication wheat samples in 1991. The investigation also showed that there existed close relationship between the level of T-2 toxin contamination and the epidemic of wheat scabby.

China↗
PubMed1992

[Hepatic segmentectomy using microwave tissue coagulator].

Hepatic segmentectomy using a microwave tissue coagulator guided by intraoperative ultrasonography is a new operative procedure, which our research unit was the first to start using from 1990. Up to now we have performed this kind of operation with success in 26 cases. Our results suggested that the new procedure simplified the original operation and greatly reduced the risk of hemorrhage and iatrogenic spread of the cancer cells during operation. Besides, this operation as a kind of definite anatomic hepatectomy can minimally resect the tumor bearing tissue in a radical fashion, while maximally preserve the tumor-free tissue of the liver.

Adult↗
PubMed1992

Effects of microwave radiation on anti-infective factors in human milk.

In intensive care nurseries it has become common practice to use microwave thawing of frozen human milk for more rapid accessibility. Twenty-two freshly frozen human milk samples were tested for lysozyme activity, total IgA, and specific secretory IgA to Escherichia coli serotypes 01, 04, and 06. The samples were heated by microwave for 30 seconds at a low- or high-power setting and then reanalyzed. One-mL aliquots of 10 additional human milk samples were microwaved at low (20 degrees C to 25 degrees C), medium (60 degrees C to 70 degrees C), and high (greater than or equal to 98 degrees C) setting before the addition to each of 1 mL of diluted E coli suspension. E coli growth was determined after 3 1/2 hours of incubation at 37 degrees C. Microwaving at high temperatures (72 degrees C to 98 degrees C) caused a marked decrease in activity of all the tested antiinfective factors. E coli growth at greater than or equal to 98 degrees C was 18 times that of control human milk. Microwaving at low temperatures (20 degrees C to 53 degrees C) had no significant effect on total IgA, specific IgA to E coli serotypes 01 and 04, but did significantly decrease lysozyme and specific IgA to E coli serotype 06. Even at 20 degrees C to 25 degrees C, E coli growth was five times that of control human milk. Microwaving appears to be contraindicated at high temperatures, and questions regarding its safety exist even at low temperatures.

Antibodies, Bacterial↗
PubMed1991

Partial characterization of rat marrow stromal cells.

Fibroblast-like rat marrow stromal cell (CFU-F) cultures have been characterized in terms of their responsiveness to calciotropic hormones, metal ions, the nonsteroidal antiinflammatory drug, and by their putative paracrine role in the maintenance of active populations of osteoblasts at the marrow-bone interface. These studies indicate that CFU-Fs lack a complete osteoblast signature. Subconfluent CFU-Fs grown in the presence or absence of 10(-7) M dexamethasone lack receptors for PTH and calcitonin, and fail to show enhanced cAMP or cGMP responses to 10(-7) M 1-34 PTH (rat), or any evidence of osteocalcin production [+/- 10(-9) M 1,25-(OH)2D3]. Low concentrations of fluoride [10(-12) and 10(-9) M] stimulated CFU-F grown in vitro in serum-free media, though higher levels (10(-7) and 10(-6) M), inhibited growth in vivo and in vitro. Aluminum (10(-12)-10(-7) M) and ibuprofen (10(-7) M) did not alter normal growth patterns, indicating an action on bone cells more differentiated than CFU-Fs. Serum-free conditioned medium (CM) from control and ovariectomized (OVX)/OVX+ dihydrotachysterol-Rx rat CFU-F cultures was mitogenic for neonatal rat calvarial osteoblasts in vitro, but not for ROS 17/2.8 cells. The studies affirm the mesenchymal-like character of CFU-Fs and project their significant role in sustaining functional endosteal osteogenic cell populations.

Animals↗
PubMed1991

Case-control study of cigarette smoking and primary hepatoma in an aflatoxin-endemic region of China: a protective effect.

Aflatoxin is believed to be a major causative agent in the high incidence of primary liver cancer seen in certain regions of the world. In Fujian Province, an aflatoxin-endemic region of China, we compared the cigarette smoking habits of 200 primary hepatoma patients with those of 200 matched nonhepatoma controls. We excluded from our study all individuals with evidence of hepatitis B virus serum antigen and/or alcoholic cirrhosis. Interestingly, two groups of hepatoma patients could be discerned. In patients more than 50 years of age, a significantly higher number of cases of primary hepatoma was found among nonsmokers than smokers (odds ratio = 2.06; 95% confidence interval = 1.32-3.20). In patients less than 50 years of age, this difference was not seen. Previous studies in the rat, mouse and duck had suggested that agents present in cigarette smoke might induce a cytochrome P450-mediated detoxication pathway, leading to protection against aflatoxin-induced primary liver cancer. Our clinical data in the present study are therefore consistent with the previous laboratory animal experiments.

Adult↗
PubMed1991

[Investigation of impairment of neutrophil's phagocytosis and bactericidal function in rats with iron deficiency].

Studies were made to determine the neutrophil's phagocytosis and bactericidal function in three groups of rats (control, iron deficiency, and iron supplement). Results showed that there were significant differences in values of chemiluminescence (CL) among three groups. The values of peak CL and five minutes integrated CL were markedly decreased in neutrophils of iron-deficient rats, accounting for only 41% and 32% of the control's values respectively. These suggested that the activity of NADPH oxidase was decreased, and the function of respiratory burst of neutrophils was impaired. The activity of myeloperoxidase in the iron-deficient neutrophils was also significantly lower than that in the control cells. It constituted only 30% of the control's value, indicating that the bactericidal function of neutrophils was injured. One week after iron administration, the low values of the peak CL, the five minutes integrated CL and the activity of myeloperoxidase all went up apparently, but not reached the normal levels yet. The time the function of neutrophils in iron-deficient rats returned to normal may be related to the process of neutrophil maturation in bone marrow.

Anemia, Hypochromic↗
PubMed1991

Synthesis of a thrombospondin-like cytoadhesion molecule by cells of the trabecular meshwork.

Thrombospondin is a large extracellular-matrix protein that is released by smooth muscle cells and platelets and is distributed widely in mammalian brain. By using western blotting with a monoclonal antibody against the calcium-binding domain of thrombospondin, the authors detected a 180-kD glycated polypeptide in the trabecular meshwork tissue of normal human and porcine eyes. The epitope-bearing polypeptide was soluble in sodium dodecylsulfate/urea (SDS/urea), and apparently it was stabilized in part by disulfide bonding to the Triton X-100 and SDS/urea-insoluble pellet of this tissue. Treatment of the insoluble matrix with beta-mercaptoethanol led to an enriched extraction of the approximately 160-kD form of thrombospondin. On immunohistochemical study, the thrombospondin antibody also reacted positively with the extracellular matrix and intracellular structures of trabecular cells in primary monolayer culture. This suggested that the presence of thrombospondin in the trabecular meshwork was probably due to local synthesis. These findings are relevant to the establishment of a model in vitro for assessment of adhesion of trabecular cells. Because thrombospondin is a cell-substrate adhesion molecule, its role in the loss of cellularity that occurs in the trabecular meshwork of the aging eye and in eyes with primary open-angle glaucoma is worthy of further investigation.

Adult↗