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Biomedical subjects

Y Duan

Publications and source records attributed to Y Duan.

105 records · Page 6Linked to original sources
PubMed1994

Calcium-binding properties of SSP-5, the Streptococcus gordonii M5 receptor for salivary agglutinin.

Streptococcus gordonii M5 expresses a lectin on its surface (SSP-5) which binds to human salivary agglutinin (SAG). This interaction requires sialic acid residues of SAG and divalent cations and may mediate the colonization of oral tissues by this organism. In this report, we show that the binding of SAG to SSP-5 requires calcium and that SSP-5 is a high-affinity calcium-binding protein. SAG-mediated aggregation of S. gordonii M5 was inhibited by 1 mM EDTA, and the restoration of aggregation occurred only upon the readdition of calcium. To ascertain the level at which calcium exerts its effects, the calcium-binding properties of SSP-5 were evaluated by using a 45Ca binding assay. In addition, a kinetic analysis of calcium binding was carried out by using fura2, a fluorescent calcium-binding dye. These analyses showed that SSP-5 is a high-affinity calcium-binding protein that binds 1 mol of calcium per mol of protein and has a dissociation constant of 0.45 +/- 0.2 microM. The calcium-binding capacity of SSP-5 was also calculated independently to be 1.0 +/- 0.2 mol of Ca per mol of SSP-5 by column chromatography on Sephadex G-25 equilibrated with 10 microM 45Ca. To localize the calcium binding site of SSP-5, a series of C-terminal deletion mutants were expressed in Escherichia coli and evaluated for calcium-binding activity. Deletion of the 250 C-terminal residues of SSP-5 had little effect on calcium binding. However, deletion of residues 1168 to 1250 resulted in the loss of calcium-binding activity, suggesting that this region is important for calcium binding by SSP-5.

Adhesins, Bacterial↗
PubMed1994

[Study on influence degree of probability of endemic factors for schistosomiasis transmission in Yunnan mountainous regions].

In Zhonghe Village of Weishan County, Yunnan Province, a schistosomiasis endemic area of mountainous valley subtype, an epidemiological investigation was conducted on its natural, biological and social factors influencing schistosomiasis transmission in 1987-1990. The results were analyzed by stratified sampling analysis and probability accumulation method. It was demonstrated that 12 of 29 factors were the most important factors influencing schistosomiasis transmission including annual average air-temperature, number of infection sources, number of spots with infected snails, water temperature and annual average rainfall, etc. The values of influence degree before and after intervention measures were 3.513 and 2.066, respectively, the decrease being 41%.

Animals↗
PubMed1994

[Immunological cross-reaction of serotype I Marek's disease virus 38kD phosphorylated protein with serotype II and III viruses].

Marek's disease virus (MDV) 38kD phosphorylated protein (pp38), which was identified by monoclonal antibody (mAb) H19 specific to pathogenic serotype I of MDV, has been recognized as a transformation-associated antigen specific to serotype I of MDV. The recombinant pp38 was prepared and purified from pp38-expressing recombinant baculovirus infected Sf9 cell lysates through a mAb H19-affinity column. In indirect fluorescence antibody test, the mouse sera against the purified recombinant pp38 not only gave a high titer to serotype I strain GA-infected CEF but also gave a reasonable titers to serotype II strain Z4- and serotype III HVT strain Fc126-infected CEF. In another way, the pp38- expressing recombinant baculovirus infected Sf9 cells reacted with anti-serotype I MDV chicken sera as well as with anti-serotype II and serotype III MDV chicken sera respectively. The results imply that both serotypes II and III of MDV probably contain a homologue to pp38 of serotype I.

Antigens, Viral↗
PubMed1994

Dissemination and replication of MCMV after supraciliary inoculation in immunosuppressed BALB/c mice.

PURPOSE: To study replication and dissemination of murine cytomegalovirus (MCMV) in immunosuppressed (IS) and non-IS BALB/c mice after ocular inoculation via the supraciliary route. METHODS: BALB/c mice were immunosuppressed by injections of methylprednisolone, and MCMV was injected via the supraciliary route. Ocular and nonocular tissues from both IS and non-IS mice were studied by plaque assay of tissue homogenates. The frequency of virus-positive leukocytes was determined by PCR. RESULTS: In the inoculated eye, virus replication was significantly higher in both the anterior segment and the posterior segment of IS mice. Virus spread to extraocular sites in both IS and non-IS mice; however, significantly higher titers of virus were recovered from the salivary glands and lungs of IS mice than from non-IS mice, and clearance of virus from these sites was delayed in IS mice. Virus spread from the injected eye via leukocytes, and PCR amplification revealed that the frequency of virus-infected leukocytes was approximately 200-fold higher in IS mice. CONCLUSIONS: The results of these studies suggest that immunosuppression significantly enhances virus replication in the inoculated eye, salivary glands, and lungs, leads to a higher frequency of virus-positive leukocytes, and delays clearance of virus from ocular and nonocular tissues. These results also suggest that retinitis in the injected eye of IS mice correlates with significantly higher titers of virus in the posterior segment.

Animals↗
PubMed1993

Effect of centrifugal force on growth of mouse osteoblastic MC3T3-E1 cells in vitro.

The effect of biomechanical force on growth of skeletal tissue was studied in monolayer cultures of mouse osteoblastic MC3T3-E1 cells which were centrifuged at 320 g for 15 min to 72 h in a CO2 incubator. Centrifugation of the cells for 30 min in low concentrations (0.3 or 1%) of fetal bovine serum (FBS) caused a two-fold increase of [3H]thymidine incorporation at 20 h from the start of centrifugation. However, centrifugation under 10% FBS caused no increase in [3H]thymidine incorporation into DNA. Under 0.3% FBS, [3H]thymidine incorporation increased in a manner dependent on the period of centrifugation and reached a maximum when the cells were centrifuged for 3 h. Stimulation of DNA synthesis by centrifugation was abolished in the presence of H-7, an inhibitor of protein kinase C. Moreover, conditioned medium collected from the centrifuged cultures increased [3H]thymidine incorporation by two-fold over the basal when added to a quiescent culture of MC3T3-E1 cells. These results suggest that centrifugal force stimulates growth of osteoblastic cells through autocrine secretion of some diffusible growth-promoting activity. On the other hand, centrifugation of the cells inhibited induction by FBS of alkaline phosphatase activity and calcium-uptake, two indices of the differentiated phenotype of osteoblasts.

3T3 Cells↗
PubMed1993

Changes in bone formation during experimental tooth movement after denervation of the rabbit inferior alveolar nerve.

The effects of nerve fibers on bone formation during tooth movement were examined using eight rabbits with denervation of inferior alveolar nerve (IAN). IAN on one side for all the animals was denervated and and sham operation was performed on the other side of denervation. The distance of tooth movement on the denervated and sham operated sides was very similar and 1.20 +/- 0.17 and 1.24 +/- 0.12 (mean +/- S.D. mm), respectively. From the fluorescent observations, the denervated and sham operated sides in the animals without tooth movement i.e. control group showed similar morphology. The animals with tooth movement i.e. experimental group showed significant new bone formation than the control group. However, the amount of new bone formation on the denervated side was less than the sham operated side. It was suggested that the nerve fibers might play some roles on bone formation during the tooth movement.

Alveolar Process↗
PubMed1991

[Serum prolactin response to electroconvulsive therapy in patients with major depression].

Serum prolactin (PRL) levels were determined at 30 min before and 5, 15, 30 and 60 min after the first and sixth electroconvulsive therapy (ECT-1 and ECT-6) in 12 female patients with major depression. There was a significant increase in serum PRL after ECT-1. The mean maximum PRL level was obtained at 30 min after ECT-1 and was 3.18 times of baseline level. The rate between mean maximum PRL level after and baseline before ECT-6 was 1.89 and was significantly lower than that during ECT-1. ECT-6 caused a significantly lower PRL release than did ECT-1 too. The possible mechanisms of produced these results were discussed.

Adult↗
PubMed1990

[Life span and cercaria shedding of schistosome-infected snails in mountain region of Yunnan].

The life span and cercaria shedding of infected Oncomelania snails in a mountain region of Shitoudi village, Weishan County, Yunnan Province were observed in simulated local ecological environments. 135 infected snails were isolated for observation 3 months after exposure to miracidia in August, 1987. The snail survival rate from the day of initial cercaria shedding to next June, July, August and September was 27.4, 16.3, 13.3 and 11.9% respectively, and the average number of cercariae shed was 139.9, 29.6, 39.2 and 75 per month respectively. The average life span of infected snails was 171.6 days. The average number of cercariae shed per snail in its whole life was 673.0. It was estimated that the average patent period of infected snails was over half a year. As this is the first report in our country in respect to the life span and cercariae shedding of infected snails in a mountain region, the result might be useful for quantitative analysis of epidemiological factors of schistosomiasis in this kind of endemic areas as well as for formulation of control strategy.

Animals↗
PubMed1990

[Thyrotrophin-releasing hormone (TRH) stimulation test in psychiatric patients].

The thyrotrophin (TSH) response to thyrotrophin-releasing hormone (TRH) 300 micrograms intravenously was studied in 25 patients with schizophrenia, 14 with depression, and 8 with mania. The rate of blunted TRH test results was zero in healthy controls, 64.3% in depression, 62.5% in mania, and 28.0% in schizophrenia. These differences of the rates between depression or mania patients and controls were significant, whereas the difference of rates between schizophrenias and healthy controls was not significant by X2 test. These results seemed to support the view that TRH stimulation test can be used as a biological marker to distinguish affective disorder and that both depression and mania is correlated with the decreased function of serotonin.

Adolescent↗
PubMedDate not supplied

Haptoglobin types in Chinese ethnic groups.

The distribution of haptoglobin (HP) types was examined in six different Chinese ethnic groups. The gene frequencies were compared among these groups and to those reported in other Chinese Han populations. The effects of sex and age on the distribution of HP types are also discussed.

Adolescent↗