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Biomedical subjects

Y Shi

Publications and source records attributed to Y Shi.

At least 631 records · Page 35Linked to original sources
PubMed1992

Fibrinolytic activity after vessel wall injury.

The goal of this study was to assess fibrinolytic activity after vessel wall injury and to correlate changes in fibrinolytic activity with angiographic and histologic findings. Accordingly, in 18 atherosclerotic rabbits, vessel wall injury was produced by means of iliac artery balloon angioplasty (the injury group), whereas 8 atherosclerotic rabbits served as a control group. In all rabbits from the injury group, deep vessel wall injury was documented by either angiography or histologic study. Plasminogen activator inhibitor-1 activity in plasma increased significantly, from 21.79 +/- 1.29 arbitrary units/ml (AU/ml) at baseline study to 32.05 +/- 1.47 AU/ml at 6 h after vessel wall injury (p less than 0.01), whereas activity remained unchanged throughout the 24-h period in the control group. Plasma levels of tissue plasminogen activator activity were similar in both groups. Intravascular thrombus was found in five of six additional rabbits 6 h after vessel wall injury, that is, at the time of impaired fibrinolytic activity, whereas no thrombus was found in the control group (p less than 0.05). It is concluded that deep vessel wall injury is associated with reduced fibrinolytic activity. In addition to other procoagulant factors, elevated plasminogen activator inhibitor-1 activity may lead to intravascular thrombosis and impaired resolution of thrombus.

Angioplasty, Balloon↗
PubMed1992

The modulation transfer function in impedance imaging.

The concepts of the point spread function (PSF) and its Fourier transform, the modulation transfer function (MTF) are introduced to evaluate an impedance imaging system. The effects of some practical factors which should be taken into account in calculating the MTF are analysed. Experimental results from the groups in Sheffield, Barcelona and Toulouse are presented.

Electric Conductivity↗
PubMed1992

Comparison of the properties of the CsA analogs monoacetyl CyC (o-acetyl-threonine2 cyclosporin) and methyl-alanyl CsA (N-methyl-L-alanyl6 cyclosporin); monoacetyl cyclosporin is immunosuppressive without binding to cyclophilin.

Cyclosporin (CsA) is an immunosuppressant which binds to cyclophilin (Cyp). The relationship between Cyp binding and immunosuppression has been questioned since one of the analogs of CsA, N-methyl-L-alanyl6 cyclosporin (methyl-alanyl CsA) binds to Cyp but is not immunosuppressive. We compared the immunosuppressive properties of CsA, methyl-alanyl CsA and o-acetyl-threonine2 cyclosporin (monoacetyl CyC), since monoacetyl CyC does not bind to Cyp when tested in cell-free assays and its immunosuppressive properties had not been tested. Cyp is a peptidyl-prolyl isomerase which is abundant in all human tissues, yet the activities of CsA are mostly confined to inhibition of T cell and thymocyte activation, and to neuro- and nephro-toxicity and are independent of inhibition of the isomerase. Activation of thymocytes and of T cells is regulated by the binding of a nuclear factor(s) (NFs) to the NF-AT region (-285 to -255) of the IL-2 promoter. We studied inhibition of binding to the NF-AT region of NFs derived from primary cultures of thymocytes treated with CsA or its analogs. In addition, we compared the effect of CsA and its analogs on the expression of the IL-2 gene in a stably transfected Jurkat-cell line (Fgl 5) which contains three copies of NF-AT and the reporter enzyme beta-galactosidase; and on inhibition of proliferation induced by concanavalin A (Con A) or IL-2. We found that monoacetyl CyC which does not bind to Cyp is immunosuppressive by our criteria when tested in cultured cells due to either a different mechanism of action or to metabolic activation.

Amino Acid Isomerases↗
PubMed1992

Response surface analysis of the effects of pH and dilution rate on Ruminococcus flavefaciens FD-1 in cellulose-fed continuous culture.

The ruminal cellulolytic bacterium Ruminococcus flavefaciens FD-1 was grown in cellulose-fed continuous culture with 20 different combinations of pH and dilution rate (D); the combinations were selected according to the physiological pH range of the organism (6.0 to 7.1) and growth rate of the organism on cellulose (0.017 to 0.10 h-1). A response surface analysis was used to characterize the effects of pH and D on the extent of cellulose consumption, growth yield, soluble sugar concentration, and yields of fermentation products. The response surfaces indicate that pH and D coordinately affect cellulose digestion and growth yield in this organism. As expected, the net cellulose consumption increased with increasing D while the fraction of added cellulose that was utilized decreased with increasing D. The effect of changes in pH within the physiological range on cellulose consumption was smaller than that of changes in D. Cellulose degradation was less sensitive to low pH than to high pH. At low Ds (longer retention times), cellulose degradation did not follow first-order kinetics. This decreased rate of cellulose digestion was not due to poor mixing, limitation by other medium components, or preferential utilization of the more amorphous fraction of the cellulose. The cell yield increased from 0.13 to 0.18 mg of cells per mg of cellulose with increasing Ds from 0.02 to 0.06 h-1 and decreased when the pH was shifted from the optimum of 6.5 to 6.8. The effect of pH on cell yield increased with increasing D. The reduced cell yield at low pH appears to be due to both an increase in maintenance energy requirements and a decrease in true growth yield.

Bacteriological Techniques↗
PubMed1992

The transport of proteins into the nucleus requires the 70-kilodalton heat shock protein or its cytosolic cognate.

The 70-kDa heat shock protein hsp70 and its constitutively expressed cognate, hsc70, are abundant proteins implicated in a number of cellular processes. When a permeabilized cell system for examining the transport of proteins into the nucleus is depleted of hsc70 and hsp70, either by affinity chromatography on ATP-agarose or with antibodies against these proteins, nuclear transport activity is lost. Full activity is restored by the addition of HeLa proteins that bind to ATP-agarose. hsc70 and hsp70 are the active factors, since activity is also fully restored by the addition of either recombinant hsc70 or hsp70 which has been bacterially expressed and highly purified. The restoration of activity is saturable. The transport system requires other cytosolic factors as well, including at least one protein that is sensitive to inactivation by N-ethylmaleimide, but neither hsc70 nor hsp70 is the sensitive protein.

Adenosine Triphosphate↗
PubMed1992

Microcarrier culture of fish cells and viruses in cell culture bioreactor.

This article deals with the culture of grass carp (Ctenopharyngodon idellus) lip and embryo cells on Cytodex 3 and GT-2 microcarriers in a 1.5-L cell culture bioreactor to propagate grass carp hemorrhage virus. The cells and viruses were successfully cultivated at 26 degrees C, pH 7.0, and dissolved oxygen 40% of air saturation. The cell density achieved was as high as 7.4 x 10(6) cells/mL, and the virus titre reached 6.75 log LD50/0.5 mL from an initial 3.00 log LD50/0.5 mL. The results present broad prospects for fish virus vaccine production.

Animals↗
PubMed1992

Typing for major histocompatibility complex class II antigens in thyroid tissue blocks: association of Hashimoto's thyroiditis with HLA-DQA0301 and DQB0201 alleles.

This study was undertaken 1) to find out whether we can type major histocompatibility class II antigens from the paraffin-embedded series of thyroid tissue, and 2) to investigate whether HLA-DQ genes are involved in conferring a risk of Hashimoto's thyroiditis. To this end we used the polymerase chain reaction to amplify DNA from paraffin-embedded thyroid tissue blocks of histologically proven Hashimoto's disease. We used 46 specimens for HLA-DQA and 32 for DQB typing. The alleles were identified by sequence-specific oligonucleotide hybridizations. Fifty controls from the same geographic region were also typed using peripheral leukocyte DNA. HLA-DQA0301 (in linkage disequilibrium with DR4) was significantly increased (58.7% vs. 32% in controls; chi 2 = 6.73; P less than 0.01) in patients compared to controls. DQB0201 (in linkage disequilibrium with DR3) was also increased in the patient group (66% vs. 36% in controls; chi 2 = 6.63; P less than 0.01). Although DQA0301/DQB0201 heterozygotes (18.8%) were increased in patients compared to controls (6%), the difference was not significant. However, 81% of the patients (26 of 32) were DQA0301 and/or DQB0201 positive compared to 48% of controls (chi 2 5.98; P less than 0.05). We conclude that it is feasible to type HLA antigens from tissue blocks and that susceptibility to Hashimoto's disease is probably mediated through two pathways: DQA0301/DR4 and DQB0201/DR3.

Alleles↗
PubMed1992

Activation-induced apoptosis in lymphoid systems.

Lymphocytes become activated when antigen receptors on the cell surface are cross-linked, or when they are exposed to agents that mimic this signal. Although such activation is usually associated with the production of immune mediators (e.g. antibodies, cytokines) and entry into the cell cycle, it can alternatively lead to death via apoptosis. This activation-induced apoptosis was first observed in developing lymphocytes and has been proposed as a mechanism for negative selection, by which immature cells with potential for autoreactivity are eliminated from the maturation pathway. Activation-induced apoptosis has also been observed in normal, mature lymphocytes under some conditions, and this may account for the phenomena of peripheral deletion, in which mature T cells are eliminated upon exposure to high doses of antigen. It may also be an important mechanism whereby CD4+ T cells are depleted in HIV+ individuals. Although the phenomenon of activation-induced apoptosis is not understood, recent studies have begun to implicate specific signal transduction pathways and gene products in the process. Among the latter is the c-myc proto-oncogene, which paradoxically can play an essential role in several forms of apoptosis, including that induced by activation of lymphocytes.

Animals↗
PubMed1992

[Lung sound analysis of upper airway obstruction].

The frequency spectrum of stridor was studied by the computer program in the patients with upper airway obstruction. The results showed that the peak frequency of respiratory sound increased significantly, the frequency spectrum got wider and removed to the high frequency area above 200Hz, the E ratio was smaller than 1. These changes were more apparent during inspiration than those during expiration. It is concluded that the stridorous sound could be determined exactly and quantitatively, and differentiated from wheezing by the spectral analysis.

Airway Obstruction↗
PubMed1992

[The construction of rich genomic library of bovine Y chromosome].

According to the fundamentals of DNA renatured kinetics, we made a study in which genomic DNA from male cattle was completely digested with Sau 3A, while female DNA was sheared to an average size of 500 bp fragments. The Y derived DNA sequence rich library of bovine has been contracted with pUC19 plasmid as vector and JM109 as host bacteria by reassociation of male and female DNA. Male and female DNA probes, were used. The result of colony hybridization showed that out of 1000 recombinants analysed, 6 were found to be stronger signal with male probe. Analysis of Pvu' I digested DNA fragment revealed that most of the inserts were in the 90-300 bp.

Animals↗
PubMed1992

[Isolation and identification of a strain of Pseudomonas SP. producing insoluble glucan hydrolase].

A strain, CIB871, isolated from the natural world can hydrolyze insoluble glucan(IG) produced by S. mutans. This organism has been identified to be a strain of Pseudomonas SP. It grows well at 30 degrees C. The optimum medium for producing insoluble glucan hydrolase (IGase) is composed of 0.3% peptone, 0.03% IG and M1 salt solution (NH4)2 SO4 1mg/ml, MgSO4 50 micrograms/ml, FeCl2 50 micrograms/ml, K2HPO4 0.5mg/ml). The IGase production reached maximum when cultured for 65-70 hours.

Glucans↗
PubMed1992

[Measurement of T-lymphocyte subsets in bronchial alveolar lavage fluid on smokers and patients with lung cancer].

The measurements of T-lymphocyte subsets (as expressed by, CD3 CD4 and CD8) in the peripheral blood and bronchial alveolar lavage fluid (BALF) on 30 cases of lung cancer, 26 cases of smoker and 25 cases of nonsmoker have been done. The results showed that there existed no differences in the peripheral blood of the above said subsets of lymphocyte. In BALF the percentage of CD3 in all the lymphocytes did not show any significant difference among the three tested groups, either (P > 0.05). But the percentage of CD4 and the ratio of CD4/CD8 manifested the following peculiarity: patients with lung cancers < smokers < nonsmokers (P < 0.01). On the contrary, the percentage of CD8 showed just the opposite: patients with lung cancer > smokers nonsmokers (P < 0.01). It was suggested that the cellular immunity as shown in the peripheral blood did not correspond with the findings in the BALF. The cellular immunity of the lungs was decreased both in patients with lung cancer and smokers, but more severely in the group of lung cancer patients. Smokers who have had changes of above said subsets of lymphocytes in the lungs may develop lung cancer. As the lung cancer advances, it may suppress body immunity and in turn enhance the cancer growth. Both the cause and the effect are interrelated. Therefore, the provocative agents for cellular immunity may act as one of the adjunctive therapies for patients with lung cancer. Giving up smoking should play an important role in recovering or promoting the immunity of the lungs and decreasing the incidence as well as improving the prognosis in patients with lung cancer.

Adult↗
PubMed1992

WHO pathfinder caries survey in Beijing extended with data for prevalence of mutans streptococci.

A pathfinder caries survey was carried out in Beijing, People's Republic of China, using WHO standard methodologies, in order to estimate the trend by comparing the results with the 1981 caries survey, performed in the same area. Simultaneously, the levels of mutans streptococci in the group were estimated in order to define the proportion of children with high and low mutans levels. Twelve-year-old children were randomly selected from schools in five districts within the city limits. Examinations for caries were performed according to 'WHO Oral Health Surveys' by two calibrated examiners. A total of 178 children were examined for caries and 156 of them were randomly selected for saliva sampling of mutans streptococci, using the 'Strip mutans' method. The number of colonies adhering to the strips were compared with a chart, supplied by the manufacturer, and given a score between 0 and 3, indicating low to very high saliva mutans counts, respectively. The results showed a mean DMFT of 1.87 (1.61-0.06-0.20, for decayed, missing and filled teeth respectively); 66.3 per cent of the children were affected. Fourteen per cent had mutans class 0, 28 per cent class 1, 35 per cent class 2 and 23 per cent class 3. The mean DFT, for each mutans class was 0.82, 1.48, 2.09 and 2.69, respectively. The differences were statistically significant (P = 0.0015). In the lowest mutans class, 50 per cent had caries and the mean number of teeth requiring conservative care was 0.68. For the high mutans group, the corresponding values were 72 per cent and 2.11 teeth.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1992

Early luteal progesterone supplementation during in vitro fertilization cycles. A randomized trial.

The effects of early luteal phase progesterone (P) supplementation were studied in women with endogenous serum P levels less than or equal to 12 ng/mL prior to embryo transfer. From a total of 129 cycles that received the same ovarian hyperstimulation protocol, 72 cycles were characterized by levels less than 12 ng/mL on the day prior to embryo transfer. Of those women, 42 (group B) were started on P supplementation one day prior to embryo transfer, and 30 (group C) were started according to the standard protocol after embryo transfer. The clinical course and outcomes in both groups were compared with 57 cycles that had P levels greater than or equal to 12 ng/mL (group A). The early P supplementation in group B resulted in a transient increase in P levels on the morning of embryo transfer as compared with group C. It did not, however, approach the levels seen in group A, which had higher P levels from the early luteal phase through embryo transfer and more favorable oocyte recovery, fertilization and cleavage rates. We were unable to improve the clinical outcome in group B as compared with group C by providing earlier P supplementation.

Adult↗