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Biomedical subjects

Y Xie

Publications and source records attributed to Y Xie.

At least 307 records · Page 17Linked to original sources
PubMed1997

Effect of long-term passive smoking on erectile function and penile nitric oxide synthase in the rat.

PURPOSE: Given that smoking is a risk factor for erectile dysfunction, this study aimed to determine, in a rat model, whether long-term exposure to cigarette smoke impairs nitric oxide (NO)-dependent erectile function and reduces penile nitric oxide synthase (NOS), and if these changes are accompanied with effects on the systemic blood pressure. MATERIALS AND METHODS: Adult (5 month) and old (20 month) rats were exposed to daily passive smoking for 8 wks. Three days after the conclusion of exposure, half of the animals were submitted to electrical field stimulation (EFS) of the cavernosal nerve and the maximum intracavernosal pressure (MIP) and mean arterial pressure (MAP) were determined and expressed as mm. Hg. On the other half of the animals, NOS activity in the penile cytosol was measured by the arginine/citrulline assay, and neuronal NOS (nNOS) and endothelial NOS (eNOS) contents were estimated by western blot and densitometry. RESULTS: When compared to controls, the smoking rats had a higher MAP in both the adult (115 vs 162) and old (113 vs 140) rats, but surprisingly the MIP also increased, from 78 to 111 (adult rats) and from 59 to 83 (old rats). Smoking reduced penile NOS activity by 73% (adult rats), and 62% (old rats), and nNOS content by 43% and 50%, respectively. In contrast, eNOS was not affected. Nitrite release, in vitro, by cavernosa slices or in rat penile smooth muscle cells (RPSMC) was not inhibited by nicotine or cotinine. CONCLUSION: These results indicate that chronic smoking in the rat leads to age-independent moderate hypertension and considerable decreases in penile NOS activity and nNOS content, that are not reflected in a reduction of the erectile response to EFS or accompanied by a decrease in penile eNOS.

Age Factors↗
PubMed1997

Enediyne-lexitropsin DNA-targeted anticancer agents. Physicochemical and cytotoxic properties in human neoplastic cells in vitro, and intracellular distribution.

Two series of hybrids of a dynemicin A model and DNA minor groove binding lexitropsins were synthesized and their cytotoxic activities were investigated in a panel of human normal and malignant cell lines using a colorimetric assay. Adriamycin was used as a control. Several of the agents demonstrated cytotoxic activity, the extent of which varied with tumor type. IC50s of the hybrids ranged from approximately 14-48 microM following 96 h incubation in the presence of test compound. Intracellular distribution studies were facilitated through endogenous fluorescence of the compounds. Evidence of nuclear uptake of the hybrid agents was demonstrated by confocal laser scanning microscopy. The results warrant further development of DNA-targeted enediyne-lexitropsin hybrids as potential anticancer agents.

Antibiotics, Antineoplastic↗
PubMed1997

An animal experiment on short gut lengthening.

OBJECTIVE: To investigate the anatomical and histological changes of the lengthened gut by a special intraluminal tubular expander on the basis of the theory of "tension-stress". METHODS: Nineteen New Zealand white rabbits were used. A 5 cm segment of the terminal ileum with a pedicle was put underneath the abdominal wall, with its proximal end closed and its distal end exteriorized as a stoma. One week later, as the wound healed well, an expander made of a small rubber tube was inserted into the short gut loop through the stoma. Three milliliters of water was injected as an initial dose. Then 0.5 ml water as an increment was injected subsequently every 12 hours until the total amount of water reached 15 ml and kept stable for two weeks. RESULTS: Anatomically, the length and the capacity of the intestinal loop were recorded, after 15 ml expanding, as an average of 150% lengthening of the original and an average of 293% expansion. Two weeks after the removal of the expander, partial shrinking was observed. A stable lengthening had 123% of the original length, while the capacity reduced to 200% of the original one. Histologically, there was no remarkable changes of the mucosa or submucosa. But significant hypertrophy of the musculature and serosa layer was observed. The total thickness of the musculatures was 618% of the normal control's. Ultrastructurally, there were enlargement of the smooth muscle cells, increase in number and size of the mitochondria in the cytoplasm and widening of the intercellular space. CONCLUSION: A short gut can be lengthened by a tubular expander following the rule of gradual tension and stress.

Animals↗
PubMed1997

[Detection of the level of serum IgG antibody to hepatitis E virus].

The levels of serum IgG antibody to hepatitis E virus (anti-HEV-IgG) was detected in serum specimens from 50 patients with acute sporadic hepatitis E and 20 healthy donors who were positive for anti-HEV-IgG by ELISA titration. The results showed that the level of anti-HEV-IgG in acute hepatitis E patients was significantly higher than that in healthy donors and the average titer is 1:121 and 1:22, respectively (P < 0.01). So acute viral hepatitis E should be diagnozed when the titer of anti-HEV-IgG was over 1:40.

Antibodies, Viral↗
PubMed1996

Direct association between the yeast Rad51 and Rad54 recombination proteins.

The RAD54 and RAD51 genes are involved in genetic recombination and double-strand break repair in the yeast Saccharomyces cerevisiae. The Rad51 protein is thought to be a yeast analogue of the Eschericia coli recA gene product and catalyzes strand exchange between homologous single- and double-stranded DNAs in vitro. RAD54 exhibits homologies to several known ATPases and is a member of the SWI2/MOT1 family. We show here that the Rad54 protein interacts with the Rad51 protein in vivo and in vitro and that the NH2-terminal 115 residues of the Rad54 protein are necessary for this interaction. Combined with previously reported results, these data imply that the Rad54 protein is part of a multiprotein yeast recombination complex.

Binding Sites↗
PubMed1996

The Dri 42 gene, whose expression is up-regulated during epithelial differentiation, encodes a novel endoplasmic reticulum resident transmembrane protein.

A search for novel genes that are up-regulated during development and differentiation of the epithelial cells of the intestinal mucosa led us to the isolation of the Dri 42 cDNA clone (Dri, differentially expressed in rat intestine). The nucleotide sequence of the full-length cDNA has shown that it encodes a 35.5-kDa protein with one consensus sequence for N-linked glycosylation and alternating hydrophilic and hydrophobic domains. To determine the intracellular localization of Dri 42 we have raised polyclonal antibodies in hens against a bacterially produced Dri 42-glutathione S-transferase fusion protein. Immunofluorescence detection with these antibodies has shown specific staining of the endoplasmic reticulum (ER) in the relatively undifferentiated fetal rat intestinal cell line FRIC B and in sections of rat small intestine. ER membrane localization of Dri 42 was confirmed by laser confocal microscopy of polarized Madin-Darby canine kidney cells overexpressing a Dri 42-chloramphenicol acetyltransferase (CAT) fusion protein by transfection. Pulse labeling experiments on transiently transfected cells demonstrated that the protein does not acquire Golgi modifications up to 4 h after synthesis, thus indicating that Dri 42 is an ER resident protein. The transmembrane disposition of Dri 42 was studied using in vitro insertion of Dri 42-CAT fusion proteins into microsomal membranes. The fusion proteins consisted of several different lengths of truncated Dri 42 and a reporter protein, CAT, that was linked in-frame after each hydrophobic segment. We found that hydrophobic segments H1, H3, and H5 had a signal/anchor function, and that membrane insertion of Dri 42 was achieved co-translationally by the action of a series of alternating insertion signals and halt transfer signals, resulting in the exposure of both termini of the protein to the cytosolic side. The functional implications of the structure and localization of Dri 42, whose primary sequence does not share significant homology to any previously described protein, are discussed.

Amino Acid Sequence↗
PubMed1996

Fluorescence in situ hybridization mapping of the mouse platelet endothelial cell adhesion molecule-1 (PECAM1) to mouse chromosome 6, region F3-G1.

Human platelet/endothelial cell adhesion molecule-1 (PECAM1), an important member of the immunoglobulin gene superfamily, is widely distributed on cells of the vascular system and mediates cellular interactions through both homophilic and heterophilic adhesive mechanisms. The function of PECAM1 in vitro has begun to be understood, but its function in vivo is yet to be established. To study the function of PECAM1 in vivo, its mouse counterpart was identified and its cDNA gene isolated and characterized. In this study, the mouse chromosomal localization was determined for the mouse gene encoding Pecam. Fluorescence in situ hybridization was used to map the Pecam gene on mouse chromosome 6, region F3-G1.

Animals↗
PubMed1996

Transcriptional repression of the prointerleukin 1beta gene by heat shock factor 1.

Heat shock factor 1 activates the promoters of heat shock genes at elevated temperatures through its interaction with heat shock elements. We have examined a new role for heat shock factor 1 in the repression of the prointerleukin 1beta gene in human monocytes responding to stimulation with lipopolysaccharide. Both exposure to elevated temperatures and heat-independent heat shock factor 1 expression repressed the transcription of the prointerleukin 1beta gene, and repression was strictly dependent on an intact consensus heat shock element in the prointerleukin 1beta promoter to which heat shock factor 1 bound. This is the first demonstration of heat shock factor 1 as a transcriptional repressor and suggests a role for the factor in the counter-regulation of cytokine gene transcription.

3T3 Cells↗
PubMed1996

A Benzene-Thermal Synthetic Route to Nanocrystalline GaN

A thermal reaction of Li3N and GaCl3 in which benzene was used as the solvent under pressure has been carried out for the preparation of 30-nanometer particles of gallium nitride (GaN) at 280&deg;C. This temperature is much lower than that of traditional methods, and the yield of GaN reached 80%. The x-ray powder diffraction pattern indicated that sample was mainly hexagonal-phase GaN with a small fraction of rocksalt-phase GaN, which has a lattice constant a = 4.100 angstroms. This rocksalt structure, which had been observed previously only under high pressure (at least 37 gigapascals) was observed directly with high-resolution electron microscopy.

Journal Article↗
PubMed1996

p66Shc isoform down-regulated and not required for HER-2/neu signaling pathway in human breast cancer cell lines with HER-2/neu overexpression.

The HER2/neu protooncogene encodes a transmembrane receptor tyrosine kinase of Mr185 kDa (called p185) which is structurally and functionally homologous to the epidermal growth factor receptor. Shc proteins are important downstream signal transducers of receptor tyrosine kinases. We reported here a novel finding that p66Sch was absent or nearly absent in p185-overexpressing breast cancer cells. This inverse correlation of p185 overexpression and p66Shc expression is probably specific to breast cancer cells because this phenomenon was not observed in p185-overexpressing human ovarian, lung, or oral cancer cells, or mouse fibroblast cells. In contrast, the p52Shc and p46Shc isoforms were expressed at similar levels in both p185-overexpressing and p185 basal level breast cancer cell lines. Furthermore, tyrosine phosphorylation of p52Shc and p46Shc and subsequent formation of Shc/Grb2 complex were detected in breast cancer cells in which the p185 tyrosine kinase is activated, indicating that p66Shc is not required for mediating the HER-2/neu signaling pathway in breast cancer cells.

3T3 Cells↗
PubMed1996

Syncytium formation by recombinant HTLV-II envelope glycoprotein.

Infection by human T-cell leukemia viruses (HTLV-I and HTLV-II) induces syncytium formation in certain cell types in vitro. Recombinant vaccinia viruses expressing the HTLV-II envelope (Env) gp61-II were used to infect human cells, and syncytium formation was observed, demonstrating that HTLV-II Env expression was sufficient to mediate syncytium formation in appropriate cells. This syncytium formation could be blocked by sera from HTLV-II-infected individuals. Infection with these recombinant vaccinia viruses caused fusion in mouse/human hybrid cells containing only human chromosome 17, whereas there was no obvious syncytium formation in mouse cells. This fusogenic phenotype of recombinant gp61-II is likely a property of the specific interaction between HTLV-II envelope protein and the HTLV cellular receptor, encoded by a gene that was previously indicated to be on human chromosome 17. On this basis, we developed a sensitive syncytium formation assay, using lacZ gene activation, for detecting the presence of the HTLV receptor(s). We used this fusion assay to test for HTLV receptor activity on a variety of cells. Our findings indicate that the HTLV receptor is widely distributed among species and cell types, including, to a limited extent, murine cells.

Animals↗
PubMed1996

Roles of platelet/endothelial cell adhesion molecule-1 (PECAM-1, CD31) in natural killer cell transendothelial migration and beta 2 integrin activation.

Platelet/endothelial cell adhesion molecule-1 (PECAM-1, CD31) is a glycoprotein expressed on the surfaces of monocytes, neutrophils, platelets, a subpopulation of T cells, and, as described in this work, on NK cells. It is also concentrated at the junctions between endothelial cells (EC) in culture, and is expressed on continuous endothelia in all tissues. PECAM has been shown to be involved in monocyte and neutrophil transendothelial migration in vitro and in vivo. The function of PECAM in NK cell interaction with EC has never been studied. In this work, we demonstrate that ligation of PECAM on the surface of NK cells activates their beta 2 integrins. Anti-PECAM Abs added to NK cells caused a 2.5- to 4-fold increase in the binding of these cells to monolayers of EC or 3T3 cells transfected with ICAM-1, and this was inhibited by a mAb against CD18. PECAM also plays a role in NK cell transendothelial migration. Anti-PECAM Abs inhibited 50% of NK cell transmigration through resting EC in an in vitro system. The transmigration of CD56dim and CD56bright cells was inhibited equally. IFN-gamma increased NK cell transmigration; the transmigration of CD56bright cells was increased to a much greater extent than CD56dim transmigration (4-fold vs 1.5-fold). Anti-PECAM inhibited the transmigration of CD56dim cells by 30%, while that of CD56bright cells was not blocked. These studies demonstrate that PECAM-1 could play an important role in the extravasation of NK cells into tissues for constitutive surveillance and into sites of inflammation.

3T3 Cells↗
PubMed1996

Only the first and the last hydrophobic segments in the COOH-terminal third of Na,K-ATPase alpha subunit initiate and halt, respectively, membrane translocation of the newly synthesized polypeptide. Implications for the membrane topology.

We studied the topogenic properties of five hydrophobic segments (H5-H9) in the COOH-terminal third of Na,K-ATPase alpha subunit using in vitro insertion of fusion proteins into endoplasmic reticulum membranes. These fusion proteins consisted of several different lengths of truncated alpha subunit starting at Met729 and a reporter protein, chloramphenicol acetyltransferase, that was linked in frame after each hydrophobic segment. We found that membrane insertion of the newly synthesized COOH-terminal third was initiated by H5 and terminated by H9, indicating that here only H5 and H9 have topogenic function. The other three, H6-H8, did not have topogenic function in the native context and were translocated into the endoplasmic reticulum lumen. These results were in striking contrast to the previous models in which four or six hydrophobic segments were proposed to cross the membrane. Furthermore, the findings suggest a novel mechanism for achieving the final membrane topology of the COOH-terminal third of the alpha subunit.

Amino Acid Sequence↗
PubMed1996

Control of aggregation in protein refolding: the temperature-leap tactic.

The kinetics of renaturation of bovine carbonic anhydrase II (CAII) were studied from 4 degrees to 36 degrees, at the relatively high [CAII] of 4 mg/mL. Following dilution to 1 M guanidinium chloride, aggregate formation is very rapid and reduces the formation of active enzyme. The CAII activity yield at 150 min, 20 degrees (approximately 60%), is greater than that at either 4 degrees or 36 degrees. However, if refolding is conducted at 4 degrees, aggregation is reduced dramatically and 37% yield is obtained at 120 min. If the solution is then rapidly warmed to 36 degrees, the yield rises rapidly to 95% at 150 min. This is an example of the "temperature leap" tactic. These results can be understood on the basis of two slow-folding intermediate whose kinetics have been studied. Only the first of these forms aggregates. Kinetic simulations show that, at 4 degrees, the first intermediate is depleted after 120 min, and the second intermediate rapidly isomerizes to active enzyme on warming. A series of experiments was conducted where the initial (120 min) folding temperature was systematically varied, followed by a "leap" to 36 degrees for 30 additional minutes. With initial incubations from 4 degrees to 12 degrees, the final yield is > 90%, drops rapidly from 12 degrees to 20 degrees, and decreases more gradually to approximately 45% at 36 degrees. The overall results qualitatively fit the simple idea of ordinary temperature-accelerated reactions in competition with hydrophobic aggregation, which is strongly suppressed in the cold. Qualifications are discussed for the temperature-leap approach to find application in refolding other proteins.

Animals↗
PubMed1996

Regulation of Langerhans cell function via blood borne factor(s).

Langerhans cells (LC) are epidermal dendritic cells that are functionally labile. Freshly obtained LC (fLC) readily activate allogeneic T cells, but they are incapable of activating autologous T cells; and even when pulsed with antigen, they fail to activate naive, antigen-specific T cells. When fLC are cultured for 2-3 days in the presence of keratinocytes, LC swiftly up-regulate surface expression of class I and II MHC molecules, and express de novo the co-stimulatory molecules B7 and ICAM-1. In addition to displaying enhanced ability to activate allogeneic T cells, cultured LC acquire the novel functional property of activating autologous T cells. It is believed that keratinocyte-derived GM-CSF is the primary driving force responsible for the conversion of fresh to cultured LC in vitro. However, in vivo administration of GM-CSF, either intracutaneously or systematically, fails to induce LC to undergo functional transformation in situ. Moreover, despite a high level of GM-CSF in the circulation, fLC from mice bearing GM-CSF-producing tumors display no ability to activate syngeneic T cells. These observations suggest that a homeostatic factor that antagonizes the effect of GM-CSF may be present in vivo. To test this possibility, we have examined the functional properties of LC prepared from mouse skin that had been explanted in vitro for 3 days. We found that the functional and phenotypic features of these cells closely resembled those of LC cultured in single cell suspension: the cells strongly expressed B7-1 and B7-2, and displayed enhanced expression of class II MHC molecules; they readily activated naive autologous T cells. Strikingly, when explants or suspensions of fresh epidermal cells were cultured in the presence of 10% mouse serum they failed to acquire syngeneic T cell activating properties; and surface up-regulation of Ia and de novo expression of B7 was inhibited. However, the cultured cells still expressed surface Ia and readily activated allogeneic naive T cells. If mouse serum was added only during the last 24 h of culture, the LC displayed full functional transformation. Human, rabbit and bovine serum showed no inhibitory effect on mouse LC. Our data suggest that mouse serum contains a factor (or factors) that inhibits, in a species-specific manner, epidermal LC from undergoing functional transformation in vitro, and this factor may maintain epidermal LC in the 'fresh' functional program in vivo.

Animals↗
PubMed1996

Pulmonary parenchymal manifestations surrounding small peripheral masses: pathologic correlation with chest radiographs and diagnostic value.

RATIONALE AND OBJECTIVES: We evaluated pathologic correlations of pulmonary parenchymal manifestations surrounding small peripheral masses and their usefulness in differentiating small peripheral bronchogenic carcinomas from tuberculomas. METHODS: We evaluated 29 resected lobe specimens with 1.5- to 3.5-cm solitary pulmonary masses, including 24 carcinomas and five tuberculomas. These specimens were prospectively studied with preoperative chest radiographs, postoperative specimen radiographs, 10- to 15-microns-thick wholemount sections, and 5-microns-thick slices. A total of 100 chest X-rays and conventional tomography scans of 1- to 3-cm peripheral pulmonary masses, including 60 carcinomas and 40 tuberculomas, were retrospectively reviewed and analyzed. RESULTS: The pulmonary parenchymal manifestations surrounding the masses presented as small infiltrates and nodular protrusions, thickened strands, and "double track" shadows, which extended from the proximal margin of five tuberculomas (100%, 5 of 5) and from the distal margin of 17 carcinomas (71%, 17 of 24). These pulmonary changes represented caseous material spreading from tuberculomas into the proximal bronchus and alveolar inflammatory exudation distal to the carcinomas. The proximal pulmonary manifestations were significantly more frequent in tuberculomas than in carcinomas (p < .01), whereas the distal pulmonary manifestations were more often found in carcinomas than in tuberculomas (p < .01). CONCLUSION: The radiologic findings of the pulmonary parenchymal manifestations proximal or distal to the masses may be valuable radiologic signs for distinguishing between tuberculomas and small peripheral bronchogenic carcinomas, even though there is still considerable crossover between the two disease populations in the findings.

Carcinoma, Bronchogenic↗
PubMed1996

New triterpenoid saponins from Gynostemma pentaphyllum.

Three new triterpenoidal saponins (1-3), together with the known compound 4, were isolated from a MeOH extract of the aerial parts of Gynostemma pentaphyllum. Their structures were elucidated on the basis of chemical and spectral methods, such as 1H-1H DQFCOSY, HMQC, HMBC, and TOCSY NMR spectra. The aglycon moiety of 1 and 2 is a new dammarane-type triterpene 12-oxo-2 alpha, 3 beta, 20 (S)-trihydroxydammar- 24-ene.

Carbohydrate Sequence↗