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Biomedical subjects

M Xiao

Publications and source records attributed to M Xiao.

At least 73 records · Page 4Linked to original sources
PubMed1996

Mutations of the p16 gene in gliomas.

In the present study we investigated the frequency of p16 gene exon 2 mutations in 35 malignant gliomas, using either direct sequencing of the PCR products or cloning into the pCRII vector and sequencing of the cloned PCR products. No mutations were detected during direct sequencing of the PCR products. However, after sequencing of individual clones, we found multiple mutations in 5 tumors involving codons 73(GCC to ACC, Ala to Thr), 76 (GCC to GTC, Ala to Val), 85(GCT to ACT, Ala to Thr), 98(CAC to TAC, His to Tyr), 102 (GCG to GTG, Ala to Val), 106 (GTG to ATG, Val to Met), 107 (CGC to TGC, Arg to Cys), 127 (GCA to GTA, Ala to Val), 128 (CGG to TGG, Arg to Trp) and 136 (GGC to GAC, Gly to Asp). Mutations were found only in glioblastomas and were either C to T or G to A transitions. Each mutation was detected in a small percentage of tumor cells (1.3-22%) using individual colony sequencing and southern hybridization with mutant oligonucleotides, consistent with the heterogenous cell population of glioblastomas. The presence of p16 gene mutations only in glioblastomas suggests that they are late events in glioma development.

Adult↗
PubMed1996

Intercellular adhesion molecule-1-deficient mice are less susceptible to cerebral ischemia-reperfusion injury.

Neutrophil emigration is mediated by adhesion proteins that are highly expressed on the endothelial surface during inflammatory processes in the brain. Intercellular adhesion molecule-1 (ICAM-1) is an inducible adhesion molecule that binds to leukocyte integrins and facilitates neutrophil adhesion and transendothelial migration. To study the role of ICAM-1 during ischemia and reperfusion in the brain, we analyzed the effect of transient focal cerebral ischemia in ICAM-1-deficient mice generated by gene targeting in embryonic stem cells. Transient focal ischemia was induced by occluding the left middle cerebral artery for 3 hours followed by a 21- or 45-hour reperfusion period. When compared with their wild-type littermates, ICAM-1-deficient mice were less susceptible to cerebral injury as demonstrated by a 5.6- or 7.8-fold reduction in infarction volume, respectively. These data support the premise that neutrophil adhesion in ischemic areas may be deleterious and that ICAM-1 deficiency reduces neurological damage after transient focal cerebral ischemia.

Animals↗
PubMed1996

Expression of platelet-derived growth factor (PDGF)-A, PDGF-B and the PDGF-alpha receptor, but not the PDGF-beta receptor, in human malignant melanoma in vivo.

There has been considerable interest in the potential role of growth factors in the initiation and development of cutaneous malignant melanoma (CMM). Platelet-derived growth factor (PDGF) has been shown to be secreted by melanoma cell lines and by metastatic melanoma in vivo. PDGF also has been reported to stimulate the development of tumour stroma and new blood vessels. We studied the expression of PDGF and its receptors by both immunohistochemistry (IHC) and in situ hybridization (ISH) in primary and metastatic melanoma and in normal skin specimens. Cryostat sections were incubated with 35S-labelled riboprobes and antibodies for PDGF-AA, PDGF-alpha receptor, PDGF-BB and PDGF-beta receptor. Both primary and metastatic melanoma exhibited significant expression of PDGF-AA, PDGF-BB and PDGF-alpha receptor by both IHC and ISH, compared with only background expression in normal skin. We did not observe expression of PDGF-beta receptor in melanoma. Our results suggest that PDGF may function as an autocrine growth factor, as well as an angiogenesis factor, in CMM tumour development. This expression of the PDGF-alpha receptor rather than the beta receptor may be unique among solid tumours.

Humans↗
PubMed1996

Inhibitory effects of interleukin 12 on retroviral gene transduction into CD34 cord blood myeloid progenitors mediated by induction of tumor necrosis factor-alpha.

Interleukin 12 (IL-12), a heterodimeric cytokine with potent biologic activity, was evaluated for effects on retroviral-mediated gene transduction into human myeloid progenitor cells in vitro. Cord blood CD34 cells were prestimulated with Steel factor (SLF), IL-3, GM-CSF, and erythropoietin (Epo) in the presence and absence of 5-80 ng/ml IL-12 for 40 hr in suspension culture prior to gene transduction using viral supernatant collected from a packaging cell line containing the pLNL6 vector encoding Neo sequences. After gene transduction, cells were assayed for colony formation stimulated by Epo, GM-CSF, IL-3, and SLF, and gene transduction efficiency was determined by the percentage of G418 resistant (R) colonies and confirmed by PCR analysis. IL-12 dose-dependently inhibited retroviral-mediated gene transduction into human cord blood CD34 granulocyte-macrophage (CFU-GM) and erythroid (BFU-E) progenitors. These suppressive effects could be neutralized by incubation of IL-12 with polyclonal antihuman IL-12. IL-12 had no inhibitory effects directly on colony formation. To understand the possible mechanisms for this suppression, ELISA assays were used to detect the release of interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha, which could potentially have been induced by IL-12 from CD34 cells. TNF-alpha protein release was significantly increased in CD34 cells incubated with IL-12. No detectable levels of IFN-gamma were noted. Anti-TNF-alpha, but not anti-IFN-gamma, blocked the inhibitory effects of IL-12 on gene transduction. Moreover, TNF-alpha, but not IFN-gamma, suppressed gene transfer to the same degree as IL-12. No change of amphotropic receptor mRNA expression was noted by Northern blot analysis in cells treated with or without IL-12. The results suggest that the suppressive effects of IL-12 on retroviral gene transduction are, at least in part, mediated by IL-12 induction of the release of TNF-alpha.

Antigens, CD↗
PubMed1996

The effect of scatter laser photocoagulation on intravitreal levels of growth factors in the miniature pig.

PURPOSE: To characterise changes in intravitreal growth factor profiles following retinal photocoagulation in the miniature pig. METHODS: Miniature pig eyes underwent scatter photocoagulation by either diode infrared or emerald green laser. Animals were sacrificed at various times (up to 42 days) post-laser. The eyes were than removed and vitreous samples analysed for basic fibroblast growth factor, insulin-like growth factor-I and epidermal growth factor by radioimmunoassay, transforming growth factor-beta 2 by ELISA and insulin-like growth factor binding proteins using Western ligand blotting. RESULTS: Vitreous transforming growth factor-beta 2 levels were decreased at 1 h post diode laser and at 4 and 7 days post emerald laser but returned to normal by 21 and 42 days respectively. Vitreous insulin-like growth factor-I levels increased at 4 and 7 days post diode and emerald laser respectively but returned to normal by 21 days. Insulin-like growth factor Western ligand blotting demonstrated that a 34 kDa insulin-like growth factor binding protein was predominant in the pig vitreous; the levels of this binding protein followed an identical trend to those observed for insulin-like growth factor-I. No changes in vitreous levels of either basic fibroblast growth factor or epidermal growth factor were observed following laser treatment. CONCLUSIONS: Our results demonstrate a significant shift in the balance of intravitreal growth factors following retinal laser photocoagulation. Such changes may be pertinent to the regression of preretinal new vessels after laser photocoagulation.

Animals↗
PubMed1996

Influence of retroviral-mediated gene transduction of both the recombinant human erythropoietin receptor and interleukin-9 receptor genes into single CD34++CD33-or low cord blood cells on cytokine-stimulated erythroid colony formation.

Introduction of genes for cytokine receptors into hematopoietic stem/progenitor cells (HSC/HPC) may be of clinical use in the future. We recently reported that retroviral-mediated transduction of either the human erythropoietin receptor (hEpoR) or interleukin-9 receptor (hIL-9R) genes into highly purified HSC/HPC from cord blood (CB) resulted in increased numbers of detectable cytokine-responsive erythroid progenitors (burst-forming units-erythroid [BFU-E]). In the present study, we evaluated if this increase could be further enhanced by cotransducing both these genes into single isolated HSC/HPC. Single CD34++CD33-or low-expressing cells from CB were transduced with viral supernatant containing the hEpoR or hIL-9R genes or cotransduced with both genes. In the presence of Steel factor (SLF), interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin (Epo), and IL-9, the numbers of erythroid colonies formed were significantly increased after transduction of cells with either the hIL-9R or hEpoR gene compared to mock-transduced cells. This increase was significantly enhanced in cells cotransduced with both genes compared with either gene alone. Integration and expression of both genes was confirmed by polymerase chain reaction (PCR) and reverse-transcriptase (RT)-PCR analysis, respectively. The data demonstrate that myeloid progenitors can be transduced at the single-cell level with both hEpoR and hIL-9R genes with resultant enhanced proliferation of these progenitors in the erythroid lineage by combinations of cytokines including Epo and IL-9.

Antigens, CD34↗
PubMed1996

Transduction of human interleukin-9 receptor gene into human cord blood erythroid progenitors increases the number of erythropoietin-dependent erythroid colonies.

We constructed a retroviral vector, pLhIL-9RSN, containing CDNA encoding the human interleukin-9 receptor (IL-9R) along with a neomycin phosphotransferase gene (Neo). In order to study the biological effects of the IL-9R, high titer (1-5 x 10(5) CFU/ml) viral supernatant, generated from the packaging cell lines, ecotropic GPE86 and amphotropic PA317, was used to transduce the IL-9R gene into sorted populations of CD34++ CD33-cells from human cord blood which are highly enriched for erythroid progenitor cells (BFU-E). Colony formation by BFU-E transduced with the IL-9R gene and grown without selection in G418 and in the presence of erythropoietin (Epo) and interleukin (IL)-9 was significantly increased up to three-fold and the size of the erythroid colonies was significantly increased 50-100% compared to colony formation by mock virus transduced cells. Moreover, colony formation by IL-9R-transduced cells was more sensitive to stimulation with lower doses of IL-9 and Epo. Individual colonies formed with or without selection in G418 were evaluated. Proviral integration and mRNA expression were respectively assessed by polymerase chain reaction (PCR) and reverse transcriptase (RT) PCR analysis and were apparent in 93% and 84% of the G418-resistant colonies and 52% and 48% of the colonies grown in the absence of G418. Our study demonstrates that a functional human IL-9R gene can be efficiently transduced into human cord blood hematopoietic progenitors using retroviral vectors with increased cytokine-dependent erythroid colony formation.

Cell Division↗
PubMed1996

[Effects of capsules on attachment of human periodontal ligament fibroblasts to root surface].

Inhibition of attachment of human periodontal ligament fibroblasts to root surface by three capsules were determined with the methods of trypan blue and L*a*b* color difference measurement. The results showed that capsule from porphyromonas gingivalis was the strongest one in inhibiting attachment and followed by the one from provotalla intermedia. Capsule from porphyromonas endodontolis was the weakest one. The values of color difference from that of control root surface were 11, 13, 8.28 and 4.09 respectively. Inhibitory mechanism of capsules may include a direct growth inhibition of fibroblasts and a decrease in attachment due to changes of root surface properties. There were a few fibroblasts attached to root surface with progressive periodontitis, this was a sharp contrast with that of control root surface. We deduce that long term affections of toxins including capsules and other substances led to changes of root surface with periodontitis, which made fibroblasts difficult to attach.

Bacterial Capsules↗
PubMed1996

[Hemodynamic effects of prostaglandin E1 in patients with congenital heart disease and pulmonary hypertension].

Investigations were performed to determine whether prostaglandin E1 (PGE1) would get a favorable change in pulmonary hymodynamics in patients with congenital heart disease and elevated pulmonary vascular resistance. Thirty-seven patients were studied. PGE1 was infused into the pulmonary artery with 100-200 ng/kg.min. PGE1 caused a significant decrease in pulmonary artery pressure and in pulmonary resistance in low-resistance group (TPRO < or = 600 kPa.s/L) (P < 0.05). But PGE1 resulted in systemic hypotention in high-resistance group for the same dose (TPRO > 600 kPa.s/L). This study shows that PGE1 is an effective vasodilator. The doses and the effects of PGE1 are dependent on the degree of pulmonary vascular disease.

Adolescent↗
PubMed1996

[The inhibitory effect of TNF-alpha on alkaline phosphatase activity of human periodontal ligament fibroblasts].

The present investigation was to identify the impact of recombinant human tumor necrosis factor-alpha (TNF-ALPHA) on alkaline phosphatase (ALP) activity of cultured human periodontal ligament fibroblasts (HPLF). It was found that, after treatment with TNF-alpha, HPLF in the experimental groups showed significantly lower ALP activity than in the blank control groups (P < 0.01). Further, the ALP activity was observed to decrease progressively with increasing TNF-alpha concentrations. These findings indicate that TNF-alpha possesses a remarkable concentration-dependent inhibitory effect on human periodontal ligament fibroblasts.

Adolescent↗
PubMed1996

[Autotransfusion of shed mediastinal blood after open heart operation].

This prospective study was designed to determine whether the autotransfusion of shed mediastinal blood (ATS) after open heart surgery is safe and effective. Forty-two patients undergoing cardiac operation were randomized to receive either nonwashed shed mediastinal blood (group 1; n = 22) or banked blood (group 2: n = 20). No difference in mean age (group 1: 49 +/- 11 years; group 2: 45 +/- 12 years), coronary artery bypass grafting (group 1: n = 5, 23%; group 2: n = 6, 30%), valve replacement (group 1: n = 17, 77%, group 2: n = 14, 70%), and mean preoperative hemoglobin level (group 1: 13.7 +/- 2.3, group 2: 14.4 +/- 1.6) was noted between non-ATS and ATS groups (p = not significant). The mean hemoglobin levels after operation were similar in the two groups (group 1: 11.89 +/- 1.52; group 2: 12.03 +/- 1.34). No difference in the mean blood loss 4, 6 and 24 hours after operation (group 1: 33 +/- 190, 420 +/- 340 and 550 +/- 300; group 2: 340 +/- 230, 420 +/- 280 and 670 +/- 380) was observed between the two groups. The mean volume autotransfused in group I was 380 +/- 230 ml (200 approximately 1300 ml). In group I, the patients required bank blood 1080 +/- 720, compared with 1780 +/- 1045 in group II. The bank blood requirement in group I reducted by 40%. These data demonstrate that ATS after open heart surgery is safe and effective.

Adult↗
PubMed1995

Induction of interleukin-8 messenger RNA in heart and skeletal muscle during pediatric cardiopulmonary bypass.

BACKGROUND: Interleukin-8 (IL-8), the major neutrophil chemoattractant factor, contributes to inflammatory tissue injury by activating neutrophils and promoting their migration into tissue. IL-8 levels increase in serum of patients undergoing cardiopulmonary bypass (CPB). The purpose of this study was to determine if IL-8 gene expression is activated in tissues subjected to CPB with or without hypothermic arrest. METHODS AND RESULTS: IL-8 transcript levels were measured by ribonuclease protection in samples of human atrium and skeletal muscle from children before and after CPB for repair of congenital heart defects. Results were quantified by PhosphorImager. Atrial IL-8 mRNA levels increased during CPB in 14 of 16 patients tested (median increase, 2.9-fold; P = .0029). In skeletal muscle, IL-8 mRNA increased in 11 of 12 patients (median, 12-fold; P = .012). Degree of IL-8 induction in atrium and muscle was not directly associated with total support time or cross-clamp time. Transcript increase in skeletal muscle occurred with or without a period of circulatory arrest, suggesting that the stimulus of CPB alone was sufficient to induce message production. Baseline values for IL-8 mRNA varied widely among patients in atrium and skeletal muscle. In situ hybridization analysis revealed diffuse increase in IL-8 mRNA throughout the tissue after CPB, with striking increase in some small veins. CONCLUSIONS: We conclude that production of IL-8 mRNA occurs in most patients during CPB in both myocardium and skeletal muscle. This may result in high local IL-8 concentrations, contributing to the tissue injury after CPB.

Cardiopulmonary Bypass↗
PubMed1995

Rigor cross-bridges bind to two actin monomers in thin filaments of rabbit psoas muscle.

The mode of binding of myosin subfragment-1 (S1) to actin is known to depend on their molar ratio: when actin is in excess, S1 binds to two actin monomers within the actin filament, and when S1 is in excess or is equimolar with actin, each S1 binds to one actin monomer. Since in vertebrate striated muscle actin is in molar excess over myosin, we expect that in fibers each myosin head binds to two actin monomers. To test this idea, we compared the conformation of the heads in native muscle with the conformation of S1 in fibers that were loaded with either high (S1 equimolar with actin) or low (excess of actin over S1) concentration of extrinsic S1. Conformation was assessed by the accessibility of heads to trypsin (measured by the rate of trypsinolysis) and by their orientation with respect to the muscle axis (measured by a combination of polarization of fluorescence and linear dichroism). In muscle fibers loaded with a high concentration of S1, the region of the heavy chain of the myosin head at the junction of 20 and 50 kDa proteolytic fragments was readily digested by trypsin and its orientation was approximately perpendicular to an axis of a thin filament. In contrast, when muscle fibers were loaded with a low concentration of S1, the 20/50 kDa junction of S1 was protected from trypsinolysis and its orientation was more parallel with a filament axis. Native muscle in rigor behaved like muscle irrigated with a low concentration of S1, i.e. the 20/50 kDa junction of the myosin head was protected from trypsinolysis and the orientation of the heads was parallel to the filament axis. We conclude that in rigor rabbit psoas muscle each myosin head binds to two actin monomers in a thin filament, and that this binding is different from the binding of S1 to actin in equimolar solutions.

Actins↗