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Biomedical subjects

C Yang

Publications and source records attributed to C Yang.

At least 433 records · Page 24Linked to original sources
PubMed1994

Chlamydia trachomatis from individuals in a sexually transmitted disease core group exhibit frequent sequence variation in the major outer membrane protein (omp1) gene.

60 cervical Chlamydia trachomatis infections identified by antigen detection from 51 prostitute women in Nairobi, Kenya were evaluated for sequence polymorphism in the major outer membrane protein (omp1) gene. DNA from clinical specimens was amplified by the polymerase chain reaction and cycle sequenced through variable domains (VD) 1, 2, and 4.37 (63%) samples had variant VD sequences, 19 (32%) samples had prototype VD sequences, and 4 (6%) samples had prototype VD sequences, and 4 (6%) samples contained omp1 sequences from two or more C. trachomatis strains. Among the 37 variant strains, 18 had two or fewer nucleotide substitutions in one or two VDs and represented point mutational drift variants. 19 strains had a larger number of nucleotide changes and displayed mosaic omp1 sequences that may have been generated by omp1 VD recombination. We conclude that the prevalence of C. trachomatis omp1 DNA polymorphism is substantial among prostitute women in Nairobi, Kenya and that this is the likely result of immune selection pressure.

Amino Acid Sequence↗
PubMed1994

The effect of nutritional additives on anti-infective factors in human milk.

It has become a common practice to supplement human milk with a variety of additives to improve the nutritive content of the feeding for the premature infant. Twenty-two freshly frozen human milk samples were measured for lysozyme activity, total IgA, and specific IgA to Escherichia coli serotypes 01, 04, and 06. One mL aliquots were mixed with the following: 1 mL of Similac, Similac Special Care, Enfamil, Enfamil Premature Formula, and sterile water; 33 mL of Poly-Vi-Sol, 33 mg of Moducal, and 38 mg of breast-milk fortifier, and then reanalyzed. Significant decreases (41% to 74%) in lysozyme activity were seen with the addition of all formulas; breast-milk fortifier reduced activity by 19%, while no differences were seen with Moducal, sterile water, or Poly-Vi-Sol. No differences were seen in total IgA content, but some decreases were seen in specific IgA to E. coli serotypes 04 and 06. E. coli growth was determined after 3 1/2 hours of incubation at 37 degrees C after mixing. All cow-milk formulas enhanced E. coli growth; soy formulas and other additives preserved inhibition of bacterial growth. Nutritional additives can impair anti-infective properties of human milk, and such interplay should be considered in the decision on the feeding regimen of premature infants.

Adult↗
PubMed1994

Immunologic characterization of Plasmodium vivax antigens using Plasmodium cynomolgi liver stage-primed immune sera.

We have shown in a previous study that immunization of a rhesus monkey (Macaca mulatta) with inactivated liver stages of the simian malaria parasite Plasmodium cynomolgi (B strain) produced high antibody titers against sporozoites, liver stages, and blood stages of P. cynomolgi. In the present study, we demonstrate that these anti-P. cynomolgi immune sera recognized P. vivax (Salvador I) antigens. In an indirect immunofluorescence assay, both postimmunization and postchallenge sera reacted with antigens of sporozoite, liver-, and blood-stage parasites. In Western blot analysis, postimmunization sera recognized four bands of 97, 93, 70, and 65 kD in sporozoite antigens; postchallenge sera further recognized three doublet (set of two) bands of 86-90, 73-78, and 44-52 kD. When blood-stage extracts were used as antigens, five bands of 118, 105, 76, 68, and 47 kD reacted with postimmunization sera; two doublet bands of 81-87 and 49-52 kD further reacted with postchallenge sera. None of these sera reacted with asexual blood-stage extracts of P. falciparum and P. malariae, or with a recombinant circumsporozoite protein of P. vivax.

Animals↗
PubMed1994

[The biological properties of two CD71 McAbs].

Two monoclonal antibodies (McAbs), HI160 and HI166, recognize different epitopes of the CD71 antigen. Their biological properties have been studied, and the results demonstrated that both had down-regulation effects. HI160 McAb not only inhibited the activation and proliferation of T and B lymphocytes but also the growth of CFU-GM. HI166 McAb only inhibited the activation and proliferation of T lymphocytes. The differences in the biological properties of the two CD71 McAbs might be due to the different epitopes recognized by them. The application value of these McAbs is discussed.

Antibodies, Monoclonal↗
PubMed1994

[Interruption of perinatal transmission of HBV by Chinese recombinant hepatitis B vaccine].

Sixty-two infants who were born from HBsAg and HBeAg both positive mothers were vaccinated with 20 micrograms/dose recombinant hepatitis B vaccine, which was made in Beijing Institute of Biologic Products (Vaccinia virus recombinant hepatitis B vaccine) and Changchun Institute of Biologic Products (Chinese hamster ovary cells recombinant hepatitis B vaccine), at 0, 1, 6 months. All the babies were followed up for 9 or 12 months. The results showed that the protective rates of Beijing vaccine and Changchun vaccine were 79.2% and 80.2%, respectively, the positive rates of anti-HBs were 78.8% and 79.3%, respectively. Local or systematic reactions were not found in all the babies 3 days after injection. These results suggested that the Chinese recombinant hepatitis B vaccine was safe and effective. It was better than the plasma vaccine with the same dose.

Female↗
PubMed1994

[Influence of refined amorphophallus konjac on osteoporosis in the aged female rats: a preliminary bone histomorphometric analysis].

The hypolipidaemic and antisteatotic effects of refined amorphophallus konjac (RAK) have been reported. In order to further evaluate the effect of RAK on osteoporosis in the aged female SD rats, forty one month aged female SD rats were divided into three groups: a normal diet group (S), another normal diet group (A) and a test group (B) in which the animals were fed on a diet similar to that of the normal diet group with the addition of RAK at a dosage of 1%. At the end of the sixth month of the diet treatment, all the animals in S group were killed. Animals of the other two groups were sacrificed at the end of experiments for 18 months. Blood and right femora samples were collected for serum Ca, P, and for bone mineral contents (BMC), respectively. Inorganic matter (ash content), and calcium and phosphorus contents of the left femur were measured. Meanwhile, undecalcified sections of left tibia were processed for bone histomorphometry. The results showed that trabecular bone volume (Vv), trabecular perimeters (TRP), bone mineral contents (BMC) as well as the Ca, P contents of bone were lower in A and B than in S, but no significance was found between A and B in all of the above indices. These data exhibited: (1) Similar to the postmenopausal osteoporosis in aged women, the bone mass of the aged female rats was markedly lost in A and B. (2) A diet treatment with 1% RAK would not aggravate osteoporosis.

Animals↗
PubMed1994

[Histopathologic and bone histomorphometric studies of pigs' phalanges in an endemic fluorosis area].

This paper presents the histopathologic changes and bone histomorphometry of ten pigs' phalanges in an endemic fluorosis area. Ten pigs from nonendemic area served as control. Results showed that the fluoride contents of blood, urine and bone were markedly increased and the calcium contents of blood were markedly decreased in endemic pigs than those in nonendemic ones. Histopathologic and bone morphometric studies of the phalangeal bones of pigs from endemic area indicate that osteoporosis is the predominant change.

Animals↗
PubMed1994

Experimental study of a new sutureless intraluminal graft with a shape-memory alloy ring.

A new sutureless intraluminal graft has been developed with a ring made of a titanium-nickel shape-memory alloy. The diameter of the ring can be reversibly reduced by compression in 4 degrees C normal saline solution and recovers its original shape in 38 degrees C physiologic saline solution during insertion in the aorta. The new graft was implanted in nine dogs and was evaluated histologically and angiographically at various intervals from 15 to 90 days. No complications, such as dislodgment, aortic rupture, stenosis, or aneurysmal dilation, were observed. The component of the shape-memory ring allows the graft to be introduced and secured in place easily. The function of this ring is better than that of the rigid ring.

Alloys↗
PubMed1993

Protein-tyrosine kinase p72syk is activated by thromboxane A2 mimetic U44069 in platelets.

We show that p72syk is rapidly activated following the stimulation of thromboxane A2 mimetics, U44069 and STA2 in porcine platelets. The activity of p72syk reached a maximum at 10 s and decreased to a basal level within 60 s after 1 microM U44069 stimulation. This activation was enhanced in a dose-dependent manner and completely canceled by the pretreatment of platelet suspension with ONO3708, a specific antagonist of thromboxane A2. Pretreatment of platelets with aspirin as well as apyrase did not affect the activation of p72syk. When both extra- and intra-cellular Ca2+ were depleted, the activation of p72syk was still persistent; in contrast, the deactivation process was completely abrogated even at 120 s after U44069 stimulation. These results suggest that p72syk is a responsible enzyme to the protein-tyrosine phosphorylation events, and that p72syk functions mainly before Ca2+ recruitment in thromboxane A2-stimulated platelets.

Animals↗
PubMed1993

Comparison of the biochemical properties of unprocessed and processed forms of the small GTP-binding protein, rab6p.

The rab6 protein (rab6p) belongs to a large family of ras-like low-molecular-mass GTP-binding proteins thought to be involved in the regulation of intracellular transport in mammalian cells. When expressed in the baculovirus/insect cell system, two major forms of rab6p are obtained; a 24-kDa cytosolic unprocessed form and a 23-kDa membrane-bound form which represents the processed lipid-modified protein. Here, we have purified both forms to homogeneity and we have studied and compared their biochemical properties. Unprocessed and processed rab6p display similar binding-rate constants (kon) for GDP and GTP (1-1.9 microM-1 min-1). However, significant differences exist in the dissociation constants of bound guanine nucleotides. Processed rab6p in low and high magnesium solutions displays similar koff values for GTP and GDP. However, unprocessed rab6p has a koff value higher for GDP than for GTP in both low and high magnesium solutions. Their intrinsic GTPase activities also differ; unprocessed rab6p has an almost undetectable GTPase activity, whereas that of processed rab6p is in the same range as that reported for other ras and ras-like GTP-binding proteins (0.012 +/- 0.002 min-1). These results suggest that post-translational modifications of rab6p might induce subtle changes in the three-dimensional structure of the protein which affect the guanine-nucleotide-binding/hydrolysis activity.

Animals↗
PubMed1993

Association with B-cell-antigen receptor with protein-tyrosine kinase p72syk and activation by engagement of membrane IgM.

We have demonstrated that a 72-kDa non-receptor-type protein-tyrosine kinase (p72syk) was co-immunoprecipitated with membrane IgM in digitonin lysates of porcine tonsillar cells and was rapidly activated following the engagement of membrane IgM. This activation was occurred within 5 s, even in the presence of EGTA and 5,5'-dimethyl-bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid as extracellular and intracellular Ca(2+)-chelating agents, respectively, as well as in the presence of the protein-kinase-C inhibitor, H-7. Additionally, genistein, a potent protein-tyrosine kinase inhibitor, was capable of reducing both IgM-stimulated Ca2+ mobilization and p72syk activation in a dose-dependent manner. These results indicate that p72syk is physically associated with the B-cell-antigen receptor, participating in antigen-mediated signal transduction in both a Ca(2+)-independent and protein-kinase-C-independent manners.

Animals↗
PubMed1993

Fulvic acid supplementation and selenium deficiency disturb the structural integrity of mouse skeletal tissue. An animal model to study the molecular defects of Kashin-Beck disease.

High concentrations of fulvic acid and selenium deficiency are the main causative factors of Kashin-Beck disease, an endemic, chronic and degenerative osteoarticular disorder found in China. In the search for an animal model of this disease, mice were exposed to these pathogenetic conditions for two generations and the collagen types from skin, bone and cartilage were analysed. The growth of the treated mice was slightly retarded, and the rate of reproduction was lower in animals maintained on a fulvic acid-supplemented and/or selenium-deficient diet. Irregular bone formation was seen by radiography and morphometry. Biochemical analysis indicated that lysine residues in collagen I from bone and in collagen II from cartilage were overmodified. The values of Hyl/(Hyl+Lys) in bone collagen alpha 1(I) chains from treated mice were about 0.434-0.484, i.e. substantially higher than that of the control (0.277). The values of this parameter for collagen II were 0.482 for control and 0.546-0.566 for treated mice. The melting temperature of collagen I from bones of treated mice was 1 degrees C lower than that of control collagen, indicating decreased thermal stability. The breakage point of the tibiae of treated mice occurred at a lower preload force than for controls, suggesting that the overmodified and thermally less stable collagen molecules are causally related to a lower mechanical strength of bones.

Animals↗
PubMed1993

Immunohistochemical localization of interstitial collagens in bone tissue from patients with various forms of osteogenesis imperfecta.

Immunohistochemical studies of bone from individuals with osteogenesis imperfecta (OI) type II, OI type III, or OI type IV demonstrate a similar pattern, but varying extent, of the abnormal presence of interstitial collagens in bone matrix. OI type II bone had nests of cartilage with type II collagen, and significant type III collagen in the bone matrix. In OI types III and IV, type II collagen was present only in epiphyseal cartilage but bone still contained type III collagen. These findings resembled those in developing fetal bone indicating the "immature" nature of OI bone.

Adult↗
PubMed1993

Contemporary management of adult and pediatric brain stem gliomas.

The aim of this study was to analyze the survival of a series of patients diagnosed as having brain stem tumors by computerized tomography scan, magnetic resonance imaging and/or biopsy and treated with megavoltage irradiation. Fifty-three patients presenting to the Peter MacCallum Cancer Institute with a diagnosis of brain stem tumor from January 1980 to July 1989 were reviewed. There were 32 pediatric (age < or = 16) and 21 adult patients. The median age at presentation was 12 years (range 2-73 years). Eighteen patients had biopsy proof of glioma, the rest were diagnosed on the basis of CT and/or MRI appearance. Eighty-seven percent of patients received 44-55 Gy in 1.67-2.25 Gy fractions to the brain stem. Seventy-seven percent of patients showed improvement following treatment, 6% were stable, 11% progressed, and 6% were not evaluable. The estimated median survival from presentation for all patients was 34 months with 49% surviving at 3 years. The estimated median time to progression was 19 months with 34% not progressed at 3 years. There was no significant survival difference between patients with biopsy-proven glioma and those patients where the diagnosis was made radiologically. Survival was not significantly affected by age-group or sex. Patients with symptoms for more than 9 months prior to presentation had significantly longer survival than those with shorter duration of symptoms (p = 0.002). This paper presents the survival of patients with brain stem tumors diagnosed and treated by contemporary radiological and radiotherapeutic techniques.

Adolescent↗
PubMed1993

Evidence for telluroamino acid in biological materials and some rules of assimilation of inorganic tellurium by yeast.

A natural substance, telluroamino acid, was discovered in tellurium yeast by GC and GC/MS. This substance was obtained for the first time by means of the assimilation of inorganic tellurium by yeast, having 600 ppm of total Te and 150 ppm of telluroamino acid. Some rules for such an assimilation were found: the content of total Te and telluroamino acid in tellurium-yeast is closely related to the kind of culture media used and is proportional to the concentration of Te in culture media. This discovery is of theoretical and practical significance, especially for the production by a simpler microbiological synthesis of rare and expensive organic tellurium compounds which hopefully will prove to be anticarcinogens like the selenium-yeast, and for explaining the biochemical effect of tellurium on the human body.

Amino Acids↗
PubMed1993

Selenium deficiency and fulvic acid supplementation induces fibrosis of cartilage and disturbs subchondral ossification in knee joints of mice: an animal model study of Kashin-Beck disease.

Kashin-Beck disease is an acquired, chronic and degenerative osteoarticular disorder. Selenium deficiency and fulvic acid in drinking water have been implicated in the cause of this disease. Pathologically, chondronecrosis of the growth plate and articular cartilage and subconsequent disturbance of ossification were observed in the joints. In this animal model study, mice were fed with a selenium deficient diet and fulvic acid supplemented drinking water for two generations. In undecalcified histological preparations of bone we carried out histological staining to detect mineralized and unmineralized bone and cartilage. The results revealed that selenium deficiency and fulvic acid supplementation induced degeneration of the articular cartilage in the knee joints of mice. Dynamic fluorescent labelling of ossification, enzyme histochemical detection of alkaline phosphatase activity in osteoblasts and a typical immunohistochemical localization of collagens type I and II indicated the development of fibrocartilage at the articular surface of knee joints, resembling the early stages of osteoarthrosis. This became obvious by disturbed development of the articular space and meniscus, markedly impaired formation of subchondral bone and early differentiation failure during enchondral ossification. This animal model provides an approach to study the molecular pathogenesis of Kashin-Beck disease.

Animals↗
PubMed1993

Expression of decay-accelerating factor (CD55), membrane cofactor protein (CD46) and CD59 in the human astroglioma cell line, D54-MG, and primary rat astrocytes.

In this report, we have shown the expression of the complement regulatory proteins decay-accelerating factor (DAF, CD55), membrane cofactor protein (MCP, CD46) and CD59 on human D54-MG astroglioma cells by several methods, including immunofluorescence, flow cytometry and Western blotting and Northern blot analysis. These studies demonstrate that all three proteins are structurally and antigenically similar to their counterparts expressed on HepG2 and SW480 cells (hepatocyte and epithelial cell lines, respectively). D54-MG cells express mRNA for all three proteins of the appropriate size(s). The phosphatidylinositol-specific enzyme, PIPLC, cleaved DAF from the surface of D54-MG cells, demonstrating that DAF is linked by a glycophospholipid anchor as has been shown for other cell types. Flow cytometry demonstrates that primary rat astrocytes also constitutively express all three regulatory proteins. These data are the first to demonstrate the expression of CD59 on astrocytes, and the presence of all three regulatory proteins on astrocytes suggests that regulation of complement activation in the central nervous system is important in neural host defense mechanisms.

Animals↗