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Biomedical subjects

Y X Shi

Publications and source records attributed to Y X Shi.

18 recordsLinked to original sources
PubMed2000

[Analysis of retinoic acid in subretinal fluid in patients with rhegmatogenous retinal detachment].

To investigate the relationship between the level of retinoic acid (RA) in the subretinal fluid (SRF) and the extent of the vitreoretinopathy in 56 patients with rhegmatogenous retinal detachment, we studied the levels of RA in both SRF and serum using high liquid chromatography and also examined those levels in part of patients who took oral vitamin A 150,000 U.d-1. The results were that the level of RA in the SRF increased with the grade of the proliferative vitreoretinopathy (PVR); the levels of RA in both SRF and serum were significantly higher in the cases with vitamin A than those without. We conclude that retinoic acid metabolism between retinal pigment epithelial cells and neural epithelia was unbalanced after retinal detachment. Oral vitamin A is helpful to inhibit the genesis and development of the proliferative vitreoretinopathy.

Adolescent↗
PubMed2000

A mutant oncolytic adenovirus targeting the Rb pathway produces anti-glioma effect in vivo.

Effective anti cancer strategies necessitate the use of agents that target tumor cells rather than normal tissues. In this study, we constructed a tumor-selective adenovirus, Delta24, that carries a 24-bp deletion in the E1A region responsible for binding Rb protein. Immunoprecipitation analyses verified that this deletion rendered Delta24 unable to bind the Rb protein. However, titration experiments in 293 cells demonstrated that the Delta24 adenovirus could replicate in and lyse cancer cells with great efficiency. Lysis of most human glioma cells was observed within 10 - 14 days after infection with Delta24 at 10 PFU/cell. In vivo, a single dose of the Delta24 virus induced a 66.3% inhibition (P<0.005) and multiple injections, an 83.8% inhibition (P<0.01) of tumor growth in nude mice. However, normal fibroblasts or cancer cells with restored Rb activity were resistant to the Delta24 adenovirus. These results suggest that the E1A-mutant Delta24 adenovirus may be clinically and therapeutically useful against gliomas and possibly other cancers with disrupted Rb pathway.

Adenoviridae↗
PubMed2000

The relevance of cell proliferation, vascular endothelial growth factor, and basic fibroblast growth factor production to angiogenesis and tumorigenicity in human glioma cell lines.

Tumor growth is partially dependent on angiogenesis, a process that relies on angiogenic factors. Tumorigenicity of cancer cells is thought to be associated with the production of various angiogenic factors that stimulate or inhibit the rate of endothelial cell migration and proliferation. However, the relative importance of specific individual factors originally studied in cancer cell lines has yet to be determined in vivo. In this study, we examined seven human glioma cell lines for dynamic changes of two major angiogenic factors, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF), and for doubling time and tumorigenicity in nude mice. Various correlation studies demonstrated that in these glioma cell lines, VEGF expression correlated well with RBC density in tumor sections (r2 = 0.804) and with average tumor weight (r2 = 0.987). In contrast, bFGF expression in the observed glioma cell lines did not correlate with tumorigenicity (r2 = 0.001) or with VEGF expression (r2 = 0.255). Furthermore, there was no correlation between doubling time and tumorigenicity in these cell lines (r2 = 0.160). Taken together, these results suggest that VEGF plays a major role in glioma formation and that down-regulation of VEGF, rather than bFGF, would be a more effective choice for glioma gene therapy.

Animals↗
PubMed2000

[Expression of VEGF on rabbit skin fibroblasts using retroviral vector].

A replication-deficient recombinant retrovirus containing the cDNA coding for human vascular endothelial growth factor (VEGF) was generated, and then infected rabbit primary skin fibroblasts. After selection with G418, the transduced colonies have the ability of producing VEGF. The integration and expression of VEGF in transduced cells were confirmed by Southern blot, PCR, Northern blot and RT-PCR assay. The VEGF secreted by transduced cells has strong bioactivity when assayed by endothelial proliferation and Miles vascular permeability assay. Thus, this study pave the way for future study of biological and physiological effect of VEGF in vivo.

Adenoviridae↗
PubMed1999

The breathing route dependence of ventilatory responses to hypercapnia and exercise is modulated by upper airway resistance.

OBJECTIVE: The ventilatory response to hypercapnia is greater breathing orally than nasally. METHODOLOGY: We hypothesize that this is due to higher nasal resistance to airflow compared with oral resistance. Seven normal male subjects were studied during both progressive hyperoxic hypercapnia (HC) and exercise (EX) until ventilation exceeded 40 L/min. Under each condition, subjects breathed via the nose only or the mouth only. For each breathing route, ventilation and pathway resistance were calculated simultaneously at the highest common exercise workload (140 +/- 20 watt; mean +/- SE) or the same end-tidal CO2 level (8.0 +/- 0.5%). RESULTS: The ventilatory response breathing nasally was decreased by a similar amount for both EX and HC when compared with the oral route. The difference between nasal and oral ventilation was highly correlated with the difference between nasal resistance and oral resistance for both EX and HC (linear regression analysis; r = 0.91 for EX and r = 0.86 for HC; both P < 0.01). CONCLUSION: We conclude that the breathing route dependence of ventilatory responses to respiratory stimuli in normal subjects is independent of the method of stimulation and is substantially determined by the added resistance of nasal breathing.

Adult↗
PubMed1998

Breathing route dependence of upper airway muscle activity during hyperpnea.

Exercise (Ex) and hypercapnia (HC) both lead to increases in ventilation and upper airway muscle (UAM) activity. To determine whether different breathing routes (nasal vs. oral) or stimuli produced differential UAM activation, electromyographic (EMG) activity of the alae nasi (AN) and genioglossus (GG) were measured in seven normal subjects seated on a bicycle ergometer. Subjects performed paired runs during both progressive Ex and HC while breathing through the nose alone (N) or the mouth alone (O). During hyperpnea, AN EMG was greater when the subjects were breathing via N [81 +/- 6% maximum (HC) and 69 +/- 7% maximum (Ex)] than when they were breathing via O [30 +/- 5% maximum (HC) and 27 +/- 5% maximum (Ex); both P < 0.01], whereas the GG EMG did not differ between N and O. Both AN and GG EMG were similar for Ex and HC when the subjects were breathing via the same route. We conclude that UAM activation was independent of the nature of the stimulus. However, the AN muscle but not the GG muscle demonstrated breathing-route dependence of activity.

Adult↗
PubMed1998

Hysteresis of the nasal pressure-flow relationship during hyperpnea in normal subjects.

Hysteresis of the nasal airway pressure-flow relationship (PFR) is seen during hyperpnea, with lower nasal resistance during increasing inspiratory flow than during decreasing flow. We hypothesized that the nasal PFR hysteresis arose in the nasal vestibule airway because of progressive collapse during the inspiration. We measured the inspiratory transnasal and transvestibular PFR for one nasal passage in five normal subjects breathing via a nasal mask during voluntary hyperventilation, both with voluntary nostril flaring and without flaring. The inspiratory hysteresis (IH) was quantified as the ratio of the areas under the descending and ascending pressure-flow curves. Flaring reduced the vestibular IH from 1.96 +/- 0.06 to 1.15 +/- 0.06 and the nasal IH from 2.05 +/- 0.13 to 1.28 +/- 0.06 (both P < 0.01). Our results demonstrate that hysteresis arises in the compliant vestibule segment of the nasal airway, likely because of progressive collapse of the nasal vestibule during inspiration. The findings suggest that hysteresis is prevented by voluntary nostril flaring maintained throughout inspiration.

Adult↗
PubMed1998

Alae nasi activation decreases nasal resistance during hyperoxic hypercapnia.

It has been proposed that decreases in nasal resistance (Rn) during hypercapnia are entirely due to vasoconstriction in the nasal cavity. We hypothesized that alae nasi (AN) muscle activity dilates the nasal vestibule and contributes to the decrease in Rn during hypercapnia. Nine normal subjects were studied during hyperoxic hypercapnia (HH). Rn and vestibular resistance (Rvest) for one nasal passage were measured simultaneously with the AN electromyogram before and after nasal decongestion. HH decreased Rvest from 1.6 +/- 0.6 to 0.8 +/- 0.9 cmH2O . l-1 . s (predecongestant) and from 1.3 +/- 0.8 to 0.6 +/- 0.7 cmH2O . l-1 . s (postdecongestant; both P < 0. 01). Nasal decongestant decreased Rn but not Rvest. Significant inverse linear relationships between Rvest and AN electromyogram were demonstrated for all subjects. We conclude that in normal subjects during HH 1) decreases in Rvest are predominantly due to increases in AN activity; and 2) decreases in Rn are due to a combination of mucosal vasoconstriction and AN activation.

Adult↗
PubMed1998

A novel approach to glioma gene therapy: down-regulation of the vascular endothelial growth factor in glioma cells using ribozymes.

Glioblastoma multiforme is one of the most highly vascularized solid neoplasms, therefore treatments that target neovascularization process would be of great clinical importance. Studies of glioblastoma angiogenesis have revealed that expression of the vascular endothelial growth factor (VEGF) is up-regulated in these tumors. Previous reports have shown that down-regulation of VEGF correlates with modification in the glioma growth. To examine this phenomenon further, in this study we constructed two hammerhead ribozymes (RZI and RZII) to target the 5' common region of VEGF mRNA. Both ribozymes exhibited site-specific cleavage to a 318-nucleotide VEGF transcript and showed a high digestion efficiency in vitro (65-95%). After the transfection of glioma cells with two expression vectors carrying the ribozyme sequence, Northern blot analyses detected high levels of ribozyme expression. Treatment of the glioma cells with the ribozymes resulted in a reduction in VEGF mRNA in six of eight clones. Furthermore, the anti-VEGF effect was confirmed at protein level. Thus, enzyme-linked immunoabsorbent analyses (ELISA) showed a >70% reduction in the VEGF165 expression level. These results indicate that hammerhead ribozymes may be useful in down-regulating VEGF expression and suggest that anti-VEGF strategies may be used to potentiate other gene therapies targeting tumor suppressor genes.

Blotting, Northern↗
PubMed1994

Evidence that cell surface beta 1,4-galactosyltransferase spontaneously galactosylates an underlying laminin substrate during fibroblast migration.

beta 1,4-Galactosyltransferase is unusual among the glycosyltransferases in that a subpopulation exists on the cell surface in addition to its traditional biosynthetic location within the Golgi complex. On the cell surface, galactosyltransferase is expressed in spatially restricted, cell type-specific domains, where it functions as a receptor for extracellular oligosaccharide ligands during selected cellular interactions. For example, galactosyltransferase is found on the leading and trailing edges of migrating cells, where it facilitates lamellipodia formation and cell spreading by binding to specific N-linked oligosaccharides within laminin. Although the ability of galactosyltransferase to serve as a laminin receptor is well documented, it is unclear whether it functions solely in a lectin-like capacity to bind laminin glycoside ligands or uses its intrinsic catalytic activity to release itself from and modify its oligosaccharide substrate. In this study, we determined whether cell surface galactosyltransferase spontaneously galactosylates laminin matrices during cell migration using endogenous galactose donors. Cells were prelabeled with [3H]galactose, washed, and transferred in small clusters onto laminin matrices. The prelabeled cells migrated out from the cell cluster, during which time they deposited covalently bound [3H]galactose residues onto the laminin matrix. The degree of galactosylation was both laminin- and time-dependent and required actively migrating, intact cells. The radioactivity released from the 3H-galactosylated laminin by acid hydrolysis comigrated with authentic galactose standards on paper chromatography. In parallel assays, there was no radioactivity deposited on laminin matrices when cells were prelabeled with [3H]fucose or [3H]leucine. Furthermore, [3H]galactosylation was dependent upon galactosyltransferase-mediated cell migration, since prelabeled cells did not deposit [3H]galactose when migrating on fibronectin, upon which migration is integrin-dependent and galactosyltransferase-independent. These results raise the possibility that galactosyltransferase functions catalytically during cell migration, either to dissociate from its oligosaccharide ligand and/or to modify the extracellular matrix.

3T3 Cells↗
PubMed1990

The study on transgenic mice.

The structural gene coding for human growth hormone (hGH) was fused to the promoter of the mouse gene for metallothionein-1. These fusion genes were introduced into pronuclei of the fertilized eggs of mice by micro-injection. We have injected MT-hGH genes into 121 mouse eggs which were transferred into the oviducts of eleven pseudo-mothers. Seven out of eleven mothers gave birth. Forty-three litters were born. These litters were grown-up and their tails were cut for isolating the DNA. The DNA of each mouse was examined by dot hybridization and Southern blotting. We found that eighteen mice had incorporated the fusion genes and grew larger than control mice. Synthesis of human growth hormone was induced further by zinc, which normally induces metallothionein gene expression. We also isolated the RNA from the livers of transgenic mice. The RNA was hybridized with hGH gene. It showed that on the transcription level the hGH gene was transcribed into mRNA in the transgenic mice. Using the same method to examine the second and third generation of the transgenic mice, we found that the incorporated gene could be inherited for generations. But the body-weight of transgenic mice appeared to decrease in the progeny. The offspring obtained from different combinations of parents (carrying or not carrying hGH gene) were different.

Animals↗
PubMed1990

Cloning and expression of bovine prolactin cDNA in Escherichia coli.

Total mRNA isolated from bovine pituitary was used as a template to synthesize double-stranded cDNA with reverse transcriptase and E. coli DNA polymerase. Recombination was performed using pBR322 as the cloning vector and the oligo dG-tailed and oligo dC-tailed method. The recombinant plasmid was then introduced into E. coli to construct the cDNA library of bovine pituitary mRNA. The labelled synthetic bovine prolactin (bPrl) gene fragment was used as hybridization probe to screen the positive clones, which were then subjected to enzymatic mapping and DNA sequence analysis. The results demonstrate that the positive clones contain a full length bPrl cDNA sequence. The clones obtained were subsequently trimmed, linked to a tac promoter, introduced into E. coli JM103, and expressed under the induction of IPTG. The SDS-PAGE indicates the existence of expression product, and the result of ELISA shows that the product has the same immune activity as native bPrl.

Animals↗
PubMed1989

Monoclonal antibodies against bovine growth hormone.

Immunized spleen lymphocytes were fused with Balb/c mouse myeloma cells to obtain hybridoma cell line 4B-2, which produces monoclonal antibodies (McAb) against bovine growth hormone (bGH). Balb/c mice were injected with 4B-2 cells to produce ascites antibodies. The specific McAb in the ascites (about 10 mg/ml, subclass IgG1) was purified by immunoaffinity chromatography (IAC) on bGH-Sepharose 4B. This McAb cross-reacted with porcine growth hormone (pGH) but not with human (hGH), ovine (oGH), or fish (fGH) growth hormone. A 17 mg portion of purified McAb, coupled to the IAC affinity column was used to purify 1 mg of bGH. The bGH preparation retained its activity in rabbit liver receptor assay and in the tibia test following IAC.

Animals↗
PubMed1988

Vasovasostomy with use of medical needle as a support.

Between May 1981 and December 1985 we performed vasovasostomy using a needle as a support in 43 patients who had undergone vasectomy for family planning. The operation is simple with little surgical trauma and few complications. All 39 patients who underwent semen analysis had return of spermatozoa. Pregnancy resulted in 27 of 34 patients (79.41 per cent) who attempted conception. The results were satisfactory. The procedure is described, and the complication and success rates are analyzed.

Adult↗
PubMed1984

Isolation, purification & properties of lactose binding agglutination factor from rabbit skeletal muscle.

The lactose binding agglutination factor from rabbit skeletal muscle is isolated through the use of lactose and urea. The factor is purified with DEAE cellulose and Sepharose 4B chromatography. The molecular weight of the factor is determined with Sephadex G-75 chromatography and found to be 28,000 Daltons. The subunit's molecular weight is determined by SDS gel electrophoresis, and found to be 14,000 Daltons. It was found that this binding factor can agglutinate trypsin-treated rabbit erythrocytes. Moreover, this agglutination is inhibited by EDTA and lactose.

Animals↗