Search PubMed⌕ Search

Biomedical subjects

S Tang

Publications and source records attributed to S Tang.

At least 199 records · Page 11Linked to original sources
PubMed1995

Activated T lymphocytes in epiretinal membranes from eyes of patients with proliferative diabetic retinopathy.

BACKGROUND: To investigate the potential contribution of immune-mediated processes to the development of proliferative diabetic retinopathy (PDR), an immunohistochemical study was undertaken to characterize the infiltrating immune cells in epiretinal membranes from the eyes of patients with PDR. METHODS: A total of 18 PDR epiretinal membrane specimens obtained surgically from pars plana vitrectomy were studied by using a panel of monoclonal antibodies against T lymphocytes (CD4 and CD8), interleukin-2 (IL-2) and interleukin-2 receptors (IL-2R). RESULTS: Twelve of 18 specimens (67%) contained CD4-positive cells and 13 of 18 (73%) contained CD8-positive cells. IL-2 was found in 12 of 18 samples (67%), of which 11 also contained CD4-positive cells, and IL-2R was detected in 10 of 18 membranes (56%), of which 9 contained CD4-positive cells and released IL-2. Most of the IL-2R-positive membranes were from type I diabetic patients, 40% of them from patients younger than 40 years. CONCLUSION: Our study demonstrated the involvement of activated immune cells and release of lymphokine(s) in more than half of the diabetic epiretinal membranes tested and revealed that the processes of immune responses and the biological effects of lymphokine(s) may play an important part in the development of epiretinal membranes of PDR, especially in young-onset and type I diabetes.

Adult↗
PubMed1995

Cooperative medical schemes in contemporary rural China.

Improvements in rural health care in China in the 1950s, 1960s and 1970s were largely due to the development of cooperative medical schemes (CMSs) and the establishment of a three-tier rural health network. Since the economic reforms were instituted in the late 1970s, the financing and delivery of rural health services have seen many changes, some positive, others not. Most CMSs have collapsed. In the absence of CMSs, the rural population has to pay for health care out-of-pocket and poor families have greater difficulty in getting access to essential health care. In the meantime, emphases of health services have tended to shift from lower to higher levels, from preventive to curative services, and from planning and management to market forces. This paper outlines the evolution of CMSs, reasons for their collapse, and their likely impact on rural health services. The main focus is on the development of a new generation of rural cooperative health care schemes, given their importance in the process of consolidating the rural three-tier health network after the impact of the economic reforms: the characteristics of some schemes, the apparent conditions for success, and government policy towards the development of cooperative health care financing are presented.

China↗
PubMed1995

Slit camera focal spot measurement errors in mammography.

Mammography x-ray tube focal spot sizes are routinely measured during acceptance testing and annual performance audits. The National Electrical Manufactures Association (NEMA) recommends the slit camera for this purpose. Investigated were the effect of slit rotational misalignment, tilt misalignment, image film density, film and screen-film image receptors, microscope magnification and reticule accuracy, and observer variation on slit camera focal spot measurements. Our results indicate that small rotational misalignment (< 5 degrees) and tilt misalignment (< 3 degrees) introduce insignificant error. Measured focal spot size increased slightly with image optical density, indicating that for consistent results the image optical density variations should be minimized. Also desirable for accurate field measurements is a high power microscope (25-50x) and a reticule with divisions of < or = 0.02 mm. Screen-film imaging consistently resulted in a slightly smaller measured focal spot size than direct film. The greatest source of error was due to observer variation. Of interest is that reader variability showed a consistent pattern and variation between two measurements by the same observer was much smaller than between observer variation, suggesting that standardized criteria should be established and a method of reader training developed. The length of the focal spot is defined at a reference axis angle specified by the mammography unit manufacturer. Presented is a tabulation of the focal spot geometry and reference axis angles for the majority of mammography units currently and recently marketed in North America.

Biophysical Phenomena↗
PubMed1995

Highly purified quiescent human peripheral blood CD4+ T cells are infectible by human immunodeficiency virus but do not release virus after activation.

Previous studies have suggested that resting CD4+ lymphocytes can be infected by human immunodeficiency virus (HIV), but viral production is inhibited. If these cells are activated, progeny virions are released. The present data indicate that CD4+ lymphocytes in the G0/G1 stage of the cell cycle which have been highly purified to remove macrophages and activated HLA-DR+ cells can also be infected by HIV. However, our findings differ from those of earlier reports since in this study, infected quiescent CD4+ cells cannot be activated to produce virus after virus inoculation. PCR analyses indicate that reverse transcription in these CD4+ cells is arrested at a very early step in proviral DNA formation (U3-R region). They do not show any evidence of longer DNA transcripts (e.g., U3-gag). When these quiescent infected CD4+ lymphocytes are activated by exposure to mitogens and macrophages and then reinoculated with HIV, the replication of virus takes place. Resting CD4+ lymphocytes are also resistant to infection when they are cocultured with HIV-infected macrophages. Only activated CD4+ cells are susceptible to cell-to-cell transmission. These observations suggest that in vivo tissue macrophages, susceptible to HIV replication, are the major cells initially productively infected by the virus. Then these cells can transfer HIV to activated CD4+ lymphocytes with resultant virus production. The presence of arrested reverse transcription in quiescent cells raises questions about the cellular factors required to permit production of longer HIV proviral DNA copies. Because they can be reinfected once they have been activated, these infected quiescent cells could be a source of recombinant viruses in the host.

CD4-Positive T-Lymphocytes↗
PubMed1995

The Effect of Follow-up on Reporting Success for Obesity Surgery.

BACKGROUND: Much is written about the importance of follow-up in determining the effect of surgical treatment for obesity upon weight loss. When patients are lost to follow-up, it has been suggested that these patients should be considered as failures. This study was undertaken to determine the effect of incorporating patients not followed in a definition of success for weight loss at one year. METHODS: Data from 34 surgical practices were used to study the effect of using two different denominators, patients followed (Df) or patients eligible (De), to define success. The numerator used in both methods was the number of patients with </= 50% EW at 1 year. RESULTS: One-year follow-up was 61% (5091/8356). Success was 67% (3423/5091) when calculated using the denominator patients followed (Df). No correlation was found between success and follow-up when data within each surgical practice were averaged and used in a correlation analysis. CONCLUSIONS: This study does not support the thesis that patients who fall to return for follow-up should be considered as having failed in weight control.

Journal Article↗
PubMed1995

[The cytopathologic diagnosis of cervical lesions and uterocervical carcinomas].

Fifty one cases of Papanicolaou grade, I, II, III and 49 of IV, V were studied for cytopathologic diagnosis in cervical and uterine curet smears. The cervical glandular erosion, metaplasia and cervical intraepithelial neoplasia, as well as histologic types of carcinomas, which were not distinguished by diagnosis of Papanicolaou grades, were determined by cytopathologic diagnosis. Therefore, the papanicolaou method of cytologic diagnosis should be gradually replaced by cytopathologic diagnosis.

Carcinoma, Squamous Cell↗
PubMed1995

Survival impact of lymph node metastasis in TNM stage III carcinoma of the colon and rectum.

BACKGROUND: Node-positive (TNM stage III) adenocarcinoma of the colon and rectum consists of tumors with a widely variable prognosis. To predict the outcome of patients with stage III carcinoma, we assessed the survival impact of the number and level of lymph node metastasis and other clinicopathological variables. STUDY DESIGN: A retrospective study was performed on 538 patients with stage III carcinoma of the colon and rectum who underwent curative resection at Chang Gung Memorial Hospital between 1980 and 1989. Ten or more lymph nodes in each resected specimen were identified microscopically. Multivariate analysis was used to determine the independent variables. RESULTS: The relative survival rates at five and ten years were 52 and 42 percent, respectively. Tumor morphology, depth or tumor penetration, histologic grade, and the status (number and level) of nodal involvement were significant in the univariate analyses. Only grade and nodal status remained significant in the multivariate analysis. Based on the nodal status, these patients were separated into three groups: stage IIIA (one to three positive nodes and absence of pN3 metastasis), IIIB (four to nine nodes and absence of pN3), and IIIC (ten or more nodes or presence of pN3). The five-year survival rates for patients with stages IIIA, IIIB, and IIIC disease were 69, 44, and 29 percent, respectively. Compared with patients with stage IIIA disease, the odds of death for patients with stages IIIB and IIIC carcinoma were 2.1 (95 percent confidence interval: 1.5 to 2.8, p = 0.0001) and 3.3 (95 percent confidence interval 2.4 to 4.5, p = 0.001), respectively. CONCLUSIONS: We suggest that stage III adenocarcinoma of the colon and rectum be divided into three substages: IIIA (one to three positive nodes and absence of pN3 metastasis), IIIB (four to nine nodes and absence of pN3), and IIIC (ten or more positive nodes or presence of pN3.

Adenocarcinoma↗
PubMed1994

Alteration of channel characteristics by exchange of pore-forming regions between two structurally related Ca2+ channels.

Several types of structurally homologous high voltage-gated Ca2+ channels (L-, P- and N-type) have been identified via biochemical, pharmacological and electrophysiological techniques. Among these channels, the cardiac L-type and the brain BI-2 Ca2+ channel display significantly different biophysical properties. The BI-2 channel exhibits more rapid voltage-dependent current activation and inactivation and smaller single-channel conductance compared to the L-type Ca2+ channel. To examine the molecular basis for the functional differences between the two structurally related Ca2+ channels, we measured macroscopic and single-channel currents from oocytes injected with wild-type and various chimeric channel alpha 1 subunit cRNAs. The results show that a chimeric channel in which the segment between S5-SS2 in repeat IV of the cardiac L-type Ca2+ channel, was replaced by the corresponding region of the BI-2 channel, exhibited macroscopic current activation and inactivation time-courses and single-channel conductance, characteristic of the BI-2 Ca2+ channel. The voltage-dependence of steady-state inactivation was not affected by the replacement. Chimeras, in which the SS2-S6 segment in repeat III or IV of the cardiac channel was replaced by the corresponding BI-2 sequence, exhibited altered macroscopic current kinetics without changes in single-channel conductance. These results suggest that part of the S5-SS2 segment plays a critical role in determining voltage-dependent current activation and inactivation and single-channel conductance and that the SS2-S6 segment may control voltage-dependent kinetics of the Ca2+ channel.

Amino Acid Sequence↗
PubMed1994

Genetic mapping of two mouse homeobox genes Tlx-1 and Tlx-2 to murine chromosomes 19 and 6.

We have previously cloned two mouse homeobox genes Tlx-1 (T-cell leukemia homeobox gene-1) and a related gene Tlx-2 based on their homology to human HOX11, a putative proto-oncogene involved in human T-cell leukemia. We have mapped Tlx-1 to mouse chromosome 19 and Tlx-2 to chromosome 6 by linkage analysis using an interspecific backcross (C57BL/6J x Mus spretus) F1 x M. spretus. The proposed gene orders and genetic distances for Tlx-1 and Tlx-2 are centromere 19-Lpc-1-(25.53 cM)-Pltr-4-(5.32 cM)-Tlx-1- (3.19 cM)-Ins-1-(7.45 cM)-Xmv-18, and centromere 6-Tcrb-(12.90 cM)-Mltr-3-(10.75 cM)-Tlx-2-(18.42 cM)-Xmv-6.

Animals↗
PubMed1994

Sialoadhesin, myelin-associated glycoprotein and CD22 define a new family of sialic acid-dependent adhesion molecules of the immunoglobulin superfamily.

BACKGROUND: Protein-carbohydrate interactions are believed to be important in many biological processes that involve cell-cell communication. Apart from the selectins, the only well-characterized vertebrate sialic acid-dependent adhesion molecules are CD22 and sialoadhesin; CD22 is a member of the immunoglobulin superfamily that is expressed by B lymphocytes and sialoadhesin is a macrophage receptor. The recent cloning of the gene encoding sialoadhesin has shown that it is also immunoglobulin-like. Both proteins share sequence similarity with the myelin-associated glycoprotein, an adhesion molecule of oligodendrocytes and Schwann cells that has been implicated in the process of myelination, raising the important question of whether myelin-associated glycoprotein is also a sialic acid-binding protein. RESULTS: We have investigated the binding properties of these three receptors when expressed either in monkey COS cells or as chimaeric proteins containing the Fc portion of human immunoglobulin G. We demonstrate that, like sialoadhesin and CD22, myelin-associated glycoprotein mediates cell adhesion by binding to cell-surface glycans that contain sialic acid. We have dissected the specificities of these three adhesins further: whereas sialoadhesin binds equally to the sugar moieties NeuAc alpha 2-->3Gal beta 1-->3(4)GlcNAc or NeuAc alpha 2-->3Gal beta 1-->3GalNAc, myelin-associated glycoprotein recognizes only NeuAc alpha 2-->3Gal beta 1-->3GalNAc and CD22 binds specifically to NeuAc alpha 2-->6Gal beta 1-->4GlcNAc. Furthermore, we show that the recognition of sialylated glycans on the surfaces of particular cell types leads to the selective binding of sialoadhesin to neutrophils, myelin-associated glycoprotein to neurons and CD22 to lymphocytes. CONCLUSIONS: Our findings demonstrate that a subgroup of the immunoglobulin superfamily can mediate diverse biological processes through recognition of specific sialylated glycans on cell surfaces. We propose that this subgroup of proteins be called the sialoadhesin family.

Animals↗
PubMed1994

Cloning and molecular characterization of three genes, including two genes encoding serine hydroxymethyltransferases, whose inactivation is required to render yeast auxotrophic for glycine.

The genes encoding both the cytosolic and mitochondrial serine hydroxymethyltransferases (SHM2 and SHM1, respectively) and a third unidentified gene of the yeast Saccharomyces cerevisiae have been isolated and their nucleotide sequences determined. Analysis of the predicted amino acid sequence of the amino-terminal regions, sequence comparison with other genes encoding SHMT enzymes, and subcellular fractionation studies all suggested that the SHM1 gene encodes the mitochondrial SHMT, while the SHM2 gene encodes the cytosolic enzyme. The SHM2 gene but not the SHM1 gene has putative GCN4 sites upstream of the putative TATA box, suggesting regulation of its transcription by the general amino acid control system. Yeast mutants with disruptions at each SHM gene and in both genes were constructed and all mutants had the same growth requirements as the parental strains. Mutagenesis of the double-disrupted, shm1 shm2 yeast yielded strains of a single complementation group that are auxotrophic for glycine. Complementation of the glycine auxotrophy using a yeast genomic library retrieved the SHM1 and SHM2 genes and a third gene designated GLY1. Gene disruption studies demonstrated that inactivation of SHM1, SHM2, and GLY1 is required to yield yeast that are completely auxotrophic for glycine.

Aldehyde-Lyases↗
PubMed1994

Novel zinc finger proteins that interact with the mouse gamma F-crystallin promoter and are expressed in the sclerotome during early somitogenesis.

Lens-specific expression of the mouse gamma-F-crystallin gene is determined, at least in part, by a 23-bp DNA element, the gamma F-1-binding motif, located in the promoter region of the gene. To characterize the transcription factors that regulate gamma F-crystallin gene expression through this element, we have isolated three chicken cDNAs that encode proteins capable of binding specifically to the gamma F-1-binding motif. These three cDNAs represent differential splicing products from a single gene, gamma FBP. The protein isoforms encoded by two of these cDNAs differ in their ability to modulate the activity of promoters containing the gamma F-1-binding motif. Among them, gamma FBP-B functions as a transcriptional repressor in lens cells, and it's expression is developmentally regulated during lens development, suggesting a role for this isoform in the spatial regulation of gamma F-crystallin gene expression. We also show that expression of the different mRNA transcripts are differentially regulated in various tissues. Furthermore, gamma FBP transcripts are highly expressed in presomitic mesoderm and then over the entire epithelial somite. During somitic differentiation, gamma FBP expression becomes restricted to the sclerotome. These expression patterns suggest a regulatory role for the gamma FBP isoforms in sclerotome specification and/or differentiation.

Alternative Splicing↗
PubMed1994

Masseter silent period: a study of magnetic stimulation.

We employed magnetic stimulation to study the masseter silent period (SP) in 16 healthy volunteers. Cutaneous perception threshold (CPT or 1 T) was determined. SP threshold was 30% M (maximal output) in each subject, equivalent to 1.5-3 T, and as intensity increased, SP durations prolonged. The correlation was higher with units of % M (r = 0.89) than CPT (r = 0.39). The recommended intensity was 60% M because of least variation of SP durations. Conclusively, magnetic stimulation is a new and painless method to study masseter SP. CPT is less effective in studying masseter SP with magnetic stimulation as the input effectiveness correlates best with % M rather than CPT.

Adult↗