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Biomedical subjects

M Shen

Publications and source records attributed to M Shen.

At least 109 records · Page 6Linked to original sources
PubMed1997

Characterization and cell cycle regulation of the related human telomeric proteins Pin2 and TRF1 suggest a role in mitosis.

Telomeres are essential for preserving chromosome integrity during the cell cycle and have been specifically implicated in mitotic progression, but little is known about the signaling molecule(s) involved. The human telomeric repeat binding factor protein (TRF1) is shown to be important in regulating telomere length. However, nothing is known about its function and regulation during the cell cycle. The sequence of PIN2, one of three human genes (PIN1-3) we previously cloned whose products interact with the Aspergillus NIMA cell cycle regulatory protein kinase, reveals that it encodes a protein that is identical in sequence to TRF1 apart from an internal deletion of 20 amino acids; Pin2 and TRF1 may be derived from the same gene, PIN2/TRF1. However, in the cell Pin2 was found to be the major expressed product and to form homo- and heterodimers with TRF1; both dimers were localized at telomeres. Pin2 directly bound the human telomeric repeat DNA in vitro, and was localized to all telomeres uniformly in telomerase-positive cells. In contrast, in several cell lines that contain barely detectable telomerase activity, Pin2 was highly concentrated at only a few telomeres. Interestingly, the protein level of Pin2 was highly regulated during the cell cycle, being strikingly increased in G2+M and decreased in G1 cells. Moreover, overexpression of Pin2 resulted in an accumulation of HeLa cells in G2+M. These results indicate that Pin2 is the major human telomeric protein and is highly regulated during the cell cycle, with a possible role in mitosis. The results also suggest that Pin2/TRF1 may connect mitotic control to the telomere regulatory machinery whose deregulation has been implicated in cancer and aging.

Amino Acid Sequence↗
PubMed1997

Molecular characterization of the novel basic helix-loop-helix protein DEC1 expressed in differentiated human embryo chondrocytes.

The differentiation of human embryo chondrocytes was markedly induced by the addition of Bt2cAMP to the culture medium. Using this culture system, a novel human cDNA for a basic helix-loop-helix (bHLH) protein (named DEC1) expressed primarily in the chondrocytes in response to Bt2cAMP was cloned by the subtractive hybridization method. DEC1 protein consists of 412 amino acids and exhibits structural similarities to the mammalian HES family, Drosophila hairy, and Enhancer of split m7 in the bHLH region. Northern blot analysis showed that DEC1 mRNA was expressed in various tissues including the cartilage, lung, spleen, and intestine, but not in the brain. These findings suggest that the bHLH factor DEC is involved in the control of cell differentiation in several tissues including cartilage.

Amino Acid Sequence↗
PubMed1997

Characterization of a cartilage-derived 66-kDa protein (RGD-CAP/beta ig-h3) that binds to collagen.

A 66-kDa collagen fiber-associated protein (RGD-CAP) was isolated from a fiber-rich fraction of pig cartilage by ultrafiltration and collagen-affinity chromatography. Amino acid sequencing and cDNA cloning indicated that the RGD-CAP is identical or closely related to beta ig-h3 protein which is induced in human adenocarcinoma cells by transforming growth factor-beta (TGF-beta) (Skonier, J., Neubauer, M., Madisen, L., Bennett, K., Plowman, G.D., and Purchio, A.F. (1992) DNA Cell. Biol. 11, 511-522). The RGD-CAP, as well as beta ig-h3, has the RGD sequence in the C-terminal region. The native RGD-CAP bound to type I, II, and IV collagens even in the presence of 1 M NaCl. A recombinant preparation of RGD-CAP expressed in Escherichia coli cells also bound to collagen but not to gelatin. The RGD-CAP mRNA was expressed in chondrocytes throughout all stages, although the expression level was highest during the prehypertrophic stage. In addition, TGF-beta increased the RGD-CAP mRNA level in chondrocyte cultures. Since RGD-CAP transcripts were found in most tissues, this novel collagen-binding protein may play an important role in cell-collagen interactions in various tissues including developing cartilage.

Amino Acid Sequence↗
PubMed1997

Significance of proliferating cell nuclear antigen expression in liver metastasis of colorectal cancer.

PURPOSE: The study contained herein was aimed at finding some possible pathologic factors that have significance for the prediction of liver metastasis in colorectal cancer. METHOD: Resected specimens of colorectal cancer from 23 patients with liver metastasis and 30 patients without liver metastasis were subjected to pathologic study, including microscopic characteristics and proliferating cell nuclear antigen immunohistochemistry assay. RESULTS: Strongly positive expression of proliferating cell nuclear antigen was present in 65.21 percent (15/23) of the liver metastasis group, whereas it was found in only 20 percent (6/30) of the group without liver metastasis (P < 0.005). Deeper invasion to the muscularis propria or serosa and less infiltration of lymphocytes surrounding the tumor were more frequently found in the liver metastasis group than in the other group (P < 0.025). CONCLUSION: Extent of proliferating cell nuclear antigen expression, depth of invasion, and reaction of lymphocyte infiltration of the primary tumor could have predictive significance of colorectal cancer in liver metastasis.

Adult↗
PubMed1997

Osteopontin is associated with bioprosthetic heart valve calcification in humans.

Calcification of non-osseous tissues such as heart valves or vessels is a major concern in clinical practice. The exact mechanism is still unknown. Numerous studies have shown that mineral deposits of crystalline hydroxyapatite within these tissues were associated with increased non-collagenous protein content. More recently osteopontin was found to be associated with calcification in living tissues such as vessels and native human aortic valves. The aim of this study was to determine whether or not non-collagenous proteins can also be found in non-living tissues such as glutaraldehyde-pretreated porcine valves after implantation in humans. Thirty-eight glutaraldehyde pretreated porcine bioprostheses were studied: 16 not implanted and 22 after 11 years of implantation in the aortic and mitral valve position in humans. In areas of calcification vizualized by Von Kossa staining and microradiography, immunostaining using polyclonal antibodies against calcium-binding proteins showed osteopontin positive staining and no staining for osteocalcin, bone sialoprotein or osteonectin. In uncalcified areas and in non-implanted values, staining for osteopontin or other calcium-binding proteins was negative. Western blot analysis of macroscopically calcified and uncalcified areas showed that several proteins were adsorbed in implanted values and confirmed the presence of osteopontin in the calcified areas, while no immunolabelling was found in non-calcified areas, in uncalcified valves and in non-implanted valves. Thus the presence of osteopontin in the calcified areas of bioprosthetic heart valves implanted in human indicates that this protein is associated with bioprosthetic valvular calcification. Since these values are made of non-living connective tissue, and no cell immunostained for osteopontin was found around the calcified area, this suggests that a non-cellular mediated mechanism involving protein adsorption may play a role in bioprosthetic valvular calcification.

Bioprosthesis↗
PubMed1997

[Study on the analysis of methamphetamine and its metabolite amphetamine in blood and urine].

The methods using GC/MS,GC/FID,GC/NPD for identification and quantification of Methamphetamined(MAMP) and Amphetamine (AMP) in human blood and urine were developed. Using 4-phenylbutylamine as the internal standard, the samples were extracted with 200 microliters cyclohexane and then the 2 microliters cyclohexane was injected into GC or the extracts were derivaized by using microwave irradiation. The methods given allowed simple and rapid procedure, the recoveries were greater than 80% and the sensitivity limits were 2-5 ng/ml. The methods for d/L Enantiomer of MAMP and AMP in human urine was also described, which can be used to determine the source of Amphetamines and determine the toxic effect in the case.

Amphetamine↗
PubMed1997

[The application of microwave irradiation to derivatization].

The methods using microwave irradiation for rapid preparation of acetyl, trifluoroacetyl, pentafluoropyl, heptafluorobutyl and MSTFA derivatives of Morphine, AMP and MAMP were developed. Conventional techniques for the reaction mixture to be heated need 30 min at 60-70 degrees C to form derivatizations, but by microwave irradiation, only 2-3 min is needed. The mass spectral fragmentation patterns and gas chromatographic retention times of the derivatives obtained by both microwave irradiation and conventional heating are similar.

Acetylation↗
PubMed1997

[Analysis and assessment of meperidine and normeperidine concentrations in urine].

In this study, urine concentrations of meperidine and normeperidine after a single therapeutic dose of meperidine in 5 healthy volunteers have been measured and compared the results to those in meperidine addicts. The results showed that there was a significant difference between two groups in the ratio of metabolite to parent drug. If can be concluded that the ratio should be aid in making a cause of meperidine injection.

Adult↗
PubMed1997

[A clinicopathological immunohistochemical and cytomorphometric study on midline T cell lymphoma].

One hundred and twenty-two cases of midline malignant reticulosis (MMR) were studied. A series of antibodies including anti-LCA, UCHL-1, L26, CD45R, and anti-lysozyme were used on paraffin sections by ABC and PAP methods. The results were as follows: 112 cases exhibiting T-cell origin, 4 cases showing B-cell origin, and 6 cases being of uncertain lineage. This result is in accordance with the point of view that most of MMR are T cell lymphoma. Two histological types were classified: sarcomatoid type and granulomatoid type. By using image analyzer, the sarcomatoid type was subdivided into small, medium and large cell types. Sixty-two cases with follow-up data were collected for clinicopathologic analysis. One-year and five-year survival rates in cases with different histologic types were compared and statistically analysed. The results showed that the prognosis was closely related to the histological type.

Adolescent↗
PubMed1996

Cannabinoid receptor agonists inhibit glutamatergic synaptic transmission in rat hippocampal cultures.

Activation of cannabinoid receptors inhibits voltage-gated Ca2+ channels and activates K+ channels, reminiscent of other G-protein-coupled signaling pathways that produce presynaptic inhibition. We tested cannabinoid receptor agonists for effects on excitatory neurotransmission between cultured rat hippocampal neurons. Reducing the extracellular Mg2+ concentration to 0.1 mM elicited repetitive, transient increases in intracellular Ca2+ concentration ([Ca2+]i spikes) that resulted from bursts of action potentials, as measured by combined whole-cell current clamp and indo-1-based microfluorimetry. Pharmacological characterization indicated that the [Ca2+]i spikes required glutamatergic synaptic transmission. Cannabinoid receptor ligands inhibited stereoselectively the frequency of [Ca2+]i spiking in the rank order of potency: CP 54,939 > CP 55,940 > Win 55,212-2 > anandamide, with EC50 values of 0.36, 1.2, 2.7, and 71 nM, respectively. CP 55,940 was potent, but not efficacious, and reversed the inhibition produced by Win 55,212-2, indicating that it is a partial agonist. Inhibition of [Ca2+]i spiking by Win 55,212-2 was prevented by treatment of cultures with active, but not heat-treated, pertussis toxin. Win 55,212-2 (100 nM) inhibited stereoselectively CNQX-sensitive excitatory postsynaptic currents (EPSCs) elicited by presynaptic stimulation with an extracellular electrode, but did not affect the presynaptic action potential or currents elicited by direct application of kainate. Consistent with a presynaptic site of action, Win 55,212-2 increased both the number of response failures and the coefficient of variation of the evoked EPSCs. In contrast, cannabimimetics did not affect bicuculline-sensitive inhibitory postsynaptic currents. Thus, activation of cannabinoid receptors inhibits the presynaptic release of glutamate via an inhibitory G-protein.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1996

Long-term in vitro culture and characterisation of avian embryonic stem cells with multiple morphogenetic potentialities.

Petitte, J.N., Clarck, M.E., Verrinder Gibbins, A. M. and R. J. Etches (1990; Development 108, 185-189) demonstrated that chicken early blastoderm contains cells able to contribute to both somatic and germinal tissue when injected into a recipient embryo. However, these cells were neither identified nor maintained in vitro. Here, we show that chicken early blastoderm contains cells characterised as putative avian embryonic stem (ES) cells that can be maintained in vitro for long-term culture. These cells exhibit features similar to those of murine ES cells such as typical morphology, strong reactivity toward specific antibodies, cytokine-dependent extended proliferation and high telomerase activity. These cells also present high capacities to differentiate in vitro into various cell types including cells from ectodermic, mesodermic and endodermic lineages. Production of chimeras after injection of the cultivated cells reinforced the view that our culture system maintains in vitro some avian putative ES cells.

Alkaline Phosphatase↗
PubMed1996

Proteins and bioprosthetic calcification in the rat model.

BACKGROUND AND AIM OF THE STUDY: The mechanism of valvular bioprostheses calcification is still unknown, but early studies showed increased Gla-protein content in calcified valves. Using an experimental model, which reproduces the clinical process, we therefore analyzed the role of minerals and proteins in bioprosthetic valvular calcification. METHODS: Glutaraldehyde pretreated porcine valves were studied before and after implantation in rats by X-ray, calcium (Ca) and phosphorus (P) measurement, Fourier Transform Infrared (FTIR) spectroscopy, SDS-PAGE and 45Ca ligand blotting of the extracted proteins. RESULTS: Before implantation, there was no X-ray calcification with very little Ca and P content. After implantation, X-ray calcifications appeared on day seven with increased Ca and P up to day 35 (p < 0.05, ANOVA). FTIR revealed structural proteins alone before implantation, plus minor proportions of lipids on day two, which always preceded Ca and P appearance. Ca and P increased up to day 35, first as amorphous and changed in carbapatite over time. SDS-PAGE before implantation revealed two proteins (66-kD and 54-kD) alone, which were sustained up to day 35. The 66-kD had 45Ca affinity. On day two, many other proteins appeared on SDS-PAGE, four of which (52, 45, 14 and below 14-kD) with 45Ca affinity. Protein pattern did not change from day two to 35. CONCLUSIONS: Valvular bioprosthesis calcification is associated with progressive increase in Ca and P content and at least five calcium-binding proteins: one intrinsic valvular protein, pre-existing to implantation, plus four other, extrinsic valvular proteins adsorbed within the tissue after implantation.

Animals↗
PubMed1995

Calcium mitigation in bioprosthetic tissues by iron pretreatment: the challenge of iron leaching.

Preliminary studies in our laboratory have shown that iron pretreatment of glutaraldehyde-preserved tissues inhibited calcification. The present study was designed to further investigate this finding and to optimize the technique. Porcine valve tissue and bovine pericardium preserved in glutaraldehyde and pretreated by iron at different concentrations and incubation times were implanted either subcutaneously in rats or as a mitral valve substitute in sheep. Compared with control groups, calcification was markedly inhibited in the groups pretreated with Fe3+. There was a direct correlation between the degree of calcification and the iron content within the tissue. A minimal iron content within the tissue of 0.5% for porcine valve tissue and 0.2% for pericardial tissue was found to be necessary for calcium mitigation. A progressive leaching of Fe3+ was observed that could be stabilized by using a higher concentration of iron in the solution and or by additional pretreatment in glutaraldehyde at high temperature, but only for subcutaneously implanted tissues. By contrast, leaching was faster and more complete in the iron-pretreated tissue valves placed in the circulating blood environment, therefore resulting in calcified valves. Pretreatment in glutaraldehyde at high temperature (50 degrees C) alone was able to mitigate calcification in both subcutaneous and circulating blood environments, a new finding that may lead to an improved method for glutaraldehyde preservation of tissues.

Animals↗
PubMed1995

Do donor or recipient species influence calcification of bioprosthetic tissues?

To determine whether donor or recipient species influence calcification of bioprosthetic tissues, glutaraldehyde-treated valvar or pericardial specimens from different species (calf, sheep, pig) were subcutaneously implanted in different animals (rat, rabbit, cow, hen). Significant differences in the rate of calcification of the implanted specimens were found, which have important practical and theoretical implications for the development of valvular bioprostheses.

Animals↗
PubMed1995

[Concentrations and size distributions of aerosols in middle summer of Chengdu].

Statistical concentrations and size distributions of aerosols in middle summer of Chengdu city were measured by using optical scattering method. The influence of climate and its daily change affects on the concentration and distribution were analysed. The results showed: many of the distributions agreed with the Junge distribution; the peak concentration appeared near the noon; the relative humidity had strong influence on concentration; the clean-up effect of rain fall was evident. The measured results are useful for evaluating the environmental sanitation of the city.

Air Pollutants↗