Biomedical subjects

X Xiao

Publications and source records attributed to X Xiao.

At least 127 records · Page 7Linked to original sources

PubMed1998

Signaling through the interaction of membrane-restricted stem cell factor and c-kit receptor tyrosine kinase: genetic evidence for a differential role in erythropoiesis.

Mutations of the receptor tyrosine kinase c-kit or its ligand stem cell factor (SCF), which is encoded as a soluble and membrane-associated protein by the Steel gene in mice, lead to deficiencies of germ cells, melanocytes, and hematopoiesis, including the erythroid lineage. In the present study, we have used genetic methods to study the role of membrane or soluble presentation of SCF in hematopoiesis. Bone marrow-derived stromal cells expressing only a membrane-restricted (MR) isoform of SCF induced an elevated and sustained tyrosine phosphorylation of both c-kit and erythropoietin receptor (EPO-R) and significantly greater proliferation of an erythrocytic progenitor cell line compared with stromal cells expressing soluble SCF. Transgene expression of MR-SCF in Steel-dickie (Sld) mutants resulted in a significant improvement in the production of red blood cells, bone marrow hypoplasia, and runting. In contrast, overexpression of the full-length soluble form of SCF transgene had no effect on either red blood cell production or runting but corrected the myeloid progenitor cell deficiency seen in these mutants. These data provide the first evidence of differential functions of SCF isoforms in vivo and suggest an abnormal signaling mechanism as the cause of the severe anemia seen in mutants of the Sl gene.

Animals↗

PubMed1998

Direct intramuscular injection with recombinant AAV vectors results in sustained expression in a dog model of hemophilia.

A recombinant adeno-associated virus (rAAV) vector carrying the human factor IX cDNA was tested for safety and therapeutic gene expression in a canine model of human hemophilia B. Intramuscular delivery of rAAV was chosen based on our previous work which described long-term (> 1.5 years) reporter gene expression in immunocompetent mice following direct muscle injection. For the current study, rAAV with the human factor IX (hF.IX) cDNA under the control of the cytomegalovirus (CMV) immediate-early promoter was constructed, and rAAV/hF.IX proved capable of transducing hemophilic dog primary fibroblast cultures in a dose-dependent fashion. Direct intramuscular injection of 2.5 x 10(12) rAAV/hF.IX virus particles into the hindlimbs of a hemophilia B dog was tolerated without bleeding or systemic reaction, and the animal was asymptomatic throughout the entire study. Transient reduction in the whole blood clotting time (WBCT) occurred during the first week, with the anticipated development of an antihuman F.IX inhibitor antibody which corresponded with the loss of coagulation correction. At 10 weeks after vector administration, immunohistochemical analysis of injected muscle confirmed continued hF.IX expression. Limited areas of focal lymphocytic infiltration and myofiber pathology were detected which directly correlated with positive antibody staining for helper adenovirus contamination. PCR tissue analysis revealed rAAV/hF.IX DNA solely in injected muscle tissue and adjacent lymph node, without dissemination to other organs (including gonads). This first large animal study suggests that intramuscular gene delivery using rAAV vectors is safe and supports continued development of this approach for gene therapy of human diseases, including hemophilia B.

Animals↗

PubMed1998

In vivo expression of therapeutic human genes for dopamine production in the caudates of MPTP-treated monkeys using an AAV vector.

An adeno-associated virus (AAV) vector, expressing genes for human tyrosine hydroxylase (TH) and aromatic amino acid decarboxylase (AADC), demonstrated significantly increased production of dopamine in 293 (human embryonic kidney) cells. This bicistronic vector was used to transduce striatal cells of six asymptomatic but dopamine-depleted monkeys which had been treated with the neurotoxin MPTP. Striatal cells were immunoreactive for the vector-encoded TH after stereotactic injection for periods up to 134 days, with biochemical effects consistent with dopamine biosynthetic enzyme expression. A subsequent experiment was carried out in six more severely depleted and parkinsonian monkeys. Several TH/aadc-treated monkeys showed elevated levels of dopamine near injection tracts after 2.5 months. Two monkeys that received a beta-galactosidase expressing vector showed no change in striatal dopamine. Behavioral changes could not be statistically related to the vector treatment groups. Toxicity was limited to transient fever in several animals and severe hyperactivity in one animal in the first days after injection with no associated histological evidence of inflammation. This study shows the successful transfection of primate neurons over a period up to 2.5 months with suggestive evidence of biochemical phenotypic effects and without significant toxicity. While supporting the idea of an in vivo gene therapy for Parkinson's disease, more consistent and longer lasting biochemical and behavioral effects will be necessary to establish the feasibility of this appraoch in a primate model of parkinsonism.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1998

Telomere dynamics in HIV-1 infected and uninfected chimpanzees measured by an improved method based on high-resolution two-dimensional calibration of DNA sizes.

We developed an improved method for accurately measuring telomere lengths based on two-dimensional calibration of DNA sizes combined with pulsed field electrophoresis and quantitative analysis of high-resolution gel images. This method was used to quantify the length of telomeres in longitudinal samples of peripheral blood mononuclear cells (PBMCs) from five chimpanzees infected with human immunodeficiency virus type 1 (HIV-1) and three uninfected animals, 14 to 27 years of age. The average length of the telomere restriction fragments (TRF) of infected and uninfected chimpanzees were 11.7 +/- 0.25 kbp, and 11.6 +/- 0.61 kbp, respectively, and were about 1 kbp and 3 kbp longer than those of human infants and 30 year old adults, respectively. There was a trend of a slight decrease (30-60 bp per year) in the TRF of two HIV infected chimpanzees over 30-35 months, while the TRF of one naive chimpanzee slightly increased over 20 months. Although the number of chimpanzees in this study is small and no statistically significant linear dependencies on time were observed, it appears that in chimpanzees, rates of shortening of the TRF are comparable or smaller than in adult humans and are not significantly affected by HIV-1 infection, which may be related to the inability of HIV-1 to cause disease in these animals.

Age Factors↗

PubMed1998

Factors influencing adeno-associated virus-mediated gene transfer to human cystic fibrosis airway epithelial cells: comparison with adenovirus vectors.

Adeno-associated virus (AAV) vectors appear promising for use in gene therapy in cystic fibrosis (CF) patients, yet many features of AAV-mediated gene transfer to airway epithelial cells are not well understood. We compared the transduction efficiencies of AAV vectors and adenovirus (Ad) vectors in immortalized cell lines from CF patients and in nasal epithelial primary cultures from normal humans and CF patients. Similar dose-dependent relationships between the vector multiplicities of infection and the efficiencies of lacZ gene transfer were observed. However, levels of transduction for both Ad and recombinant AAV (rAAV) were significantly lower in the airway epithelial cell than in the control cell lines HeLa and HEK 293. Transduction efficiencies differed among cultured epithelial cell types, with poorly differentiated cells transducing more efficiently than well-differentiated cells. A time-dependent increase in gene expression was observed after infection for both vectors. For Ad, but not for AAV, this increase was dependent on prolonged incubation of cells with the vector. Furthermore, for rAAV (but not for rAd), the delay in maximal transduction could be abrogated by wild-type Ad helper infection. Thus, although helper virus is not required for maximal transduction, it increases the kinetics by which this is achieved. Expression of Ad E4 open reading frame 6 or addition of either hydroxyurea or camptothecin resulted in increased AAV transduction, as previously demonstrated for nonairway cells (albeit to lower final levels), suggesting that second-strand synthesis may not be the sole cause of inefficient transduction. Finally, the efficiency of AAV-mediated ex vivo gene transfer to lung cells was similar to that previously described for Ad vectors in that transduction was limited to regions of epithelial injury and preferentially targeted basal-like cells. These studies address the primary factors influencing rAAV infection of human airway cells and should impact successful gene delivery in CF patients.

Adenoviruses, Human↗

PubMed1998

Production of high-titer recombinant adeno-associated virus vectors in the absence of helper adenovirus.

Recently, efficient and long-term in vivo gene transfer by recombinant adeno-associated virus type 2 (rAAV) vectors has been demonstrated in a variety of tissues. Further improvement in vector titer and purity will expedite this in vivo exploration and provide preclinical information required for use in human gene therapy. In an effort to obtain higher titers, we constructed a novel AAV helper plasmid which utilizes translational control of AAV Rep genes (J. Li et al., J. Virol. 71:5236-5243, 1997). To address the issue of purity, in this study we report the first rAAV production method which is completely free of adenovirus (Ad) helper virus. The new production system uses a plasmid construct which contains a mini-Ad genome capable of propagating rAAV in the presence of AAV Rep and Cap genes. This construct is missing some of the early and most of the late Ad genes and is incapable of producing infectious Ad. Transfection of 293 cells with the new mini-Ad helper and AAV packaging plasmids results in high-titer rAAV vectors with yields greater than 1,000 transducing units, or 10(5) viral particles per cell. When rAAV vectors were produced by using this production scheme and compared to traditional heat-inactivated rAAV preparations in vitro and in vivo, we observed transduction equivalent to or better than normal levels. The complete removal of infectious Ad from AAV production should facilitate a better understanding of immune response to AAV vectors in vivo, eliminate the need for developing replication-competent Ad assays, and provide a more defined reagent for clinical use.

Adenoviridae↗

PubMed1998

[The effect of removable partial denture on the composition of bacteria on the apt-to-decay site of abutment teeth].

This study was aimed at the composition of plaques which were on the base teeth's carious sensitive sites, just after the insertion of the removable partial denture (RPD). The results showed that the ratios of bacterial detection in different teeth at the same period and those on the different sites of same teeth at different periods were not significantly different. There was a tendency that the detection ratio of the stomatococcus at the early period was higher than that of other bacteria, but at the middle period the ratios declined, and at the late period it was higher again. The detection ratio of the bacillus was on the contrary in the study. At the same time, the composition of the plaques changed significantly after the dentures had been used for 7, 14, and 21 days and 3 months. After 3 months, the ratios of the stomatococcus and the bacillas returned to their normal levels. The 3 main cariogenic bacteria were all detected in this study. The Streptococcus mutant was the dominant bacterium in the plaques and its ratio went up with the time duration. The ratio for the lower second molar was higher than that for the mandibular second premolar (P < 0.05). The detection ratios of the Actinomyces viscosus and lactobacillus were lower. In conclusion, after the insertion of RPD, the oral microbial ecosystem would be changed and the cariogenic bacteria began to implant on the surface of the base teeth. So RPD is a potential factor to cause the caries.

Actinomyces viscosus↗

PubMed1998

[Cytokines release related to cardiopulmonary bypass in patients with prosthetic valve replacement].

To examine cytokines release related to cardiopulmonary bypass(CPB), the anthers investigated the possible differences in cytokines responses between patients undergoing prosthetic valve replacement (study group, n = 10) and those receiving closure of patent ductus arteriosus or pericardiectomy(control group, n = 9). Venous levels of interleukin-2 (IL-2), soluble interleukin-2 receptor (sIL-2R), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha), and interleukin-10 (IL-10) were measured at multiple time points before, during and after operation. As compared with pre-operative values, IL-2 levels in both groups decreased significantly (P < 0.05), and the levels of sIL-2R, IL-6, TNF-alpha, and IL-10 in both groups increased significantly at multiple time points post-operative (P < 0.01). All the values of cytokines returned to pre-operative levels at 7th post-operative day. Although there were no pre-operative differences in these cytokines between the two groups (P > 0.05), the post-operative changes of cytokines in study group was more obvious than that in control group (P < 0.01). In study group IL-10 rose to a peak value of around 620 pg/ml at the end of CPB while IL-6 and TNF-alpha levels reached their peak values of around 88 pg/ml and 52 pg/ml respectively at 1st post-operative day. IL-10 has been reported as an antiinflammatory cytokine. The preceding IL-10 peak value, as compared with the peak values of IL-6 and TNF-alpha, could be associated with the interplay and regulation of cytokine network. On the other hand, in control group the levels of IL-6, TNF-alpha, and IL-10 reached their peak values at 1st post-operative day simultaneously. The values were 34 pg/ml, 36 pg/ml, and 162 pg/ml respectively. This result suggests that besides surgical stress mediated cytokines production or suppression, CPB itself also results in obvious changes of cytokine metabolism. However further studies are needed to elucidate the underlying mechanisms and clinical value of post-operative cytokines production or suppression related to CPB in patients with prosthetic valve replacement.

Adult↗

PubMed1998

[Cromakalim inhibits endothelin-1 induced pulmonary hypertension in rats].

There is evidence that endothelin-1 (ET-1) and potassium channel may play an important role in the development of pulmonary hypertension. To evaluate the effect of ATP-sensitive K+ channel opener on pulmonary hypertension induced by ET-1, catheter was inserted into the pulmonary artery in ten male Wistar rats which had had pulmonary hypertension established by infusion of ET-1 (1.5 micrograms/kg), and then cromakalim were injected with a dose of 150 micrograms/kg. The mean pulmonary arterial pressure (mPAP), cardiac output (CO) monitored before and after infusion of ET-1, and 1 min, 5 min, 10 min after cromakalim injection, and pulmonary vascular resistance (PVR) were calculated. It was found that the mPAP was significantly increased, from 2.36 +/- 0.24 kPa to 3.32 +/- 0.49 kPa(P < 0.01), and PVR also increased, by infusion of ET-1. After cromakalim injection, mPAP were decreased to 2.50 +/- 0.62 kPa in 1 min, 1.14 +/- 0.18 kPa in 5 min and 2.33 +/- 0.52 kPa in 10 min, PVR decreased significantly. It is suggested that there is interaction between ET-1 and potassium Channel, and Cromakalim decreases mPAP in part by inhibiting the response of pulmonary artery to ET-1.

Animals↗

PubMed1998

[Effects of surface roughness of two restorative materials on early Streptococcus sanguis adhesion in vitro].

This was an in vitro study aimed at the surface roughness of two kinds of commonly used restorative materials resin and alloy necessary to affect the adhesive behavior of Streptococcus sanguis(S. s) on them after 24 h. The surface roughness(SR) of each tested sample was evaluated with a profilometer quantitatively and observed with scanning electron microscope (SEM) morphologically. Then the adhesive microbial amount was determined by the clone forming unit counting method, and adhesion morphology was analyzed with SEM. The result showed a positive linear relation between the adhesion amount of S. s and the SR. The relative coefficients were rresin = 0.46(P < 0.01) and ralloy = 0.25(P < 0.01) respectively. These suggest the SR of the restorative material is important for the early adhesion of oral microbes in vitro. Therefore, before the prothesis is inserted in the patient's oral cavity, its surface should be polished as smoothly as possible so that the bacterial adhesive amount on its surface can be decreased, and hence the patient may keep in good oral health and have a prolonged use of the prothesis.

Bacterial Adhesion↗

PubMed1998

[Changes of level and distribution of vascular endothelial growth factor in the lungs of rats with hypoxic pulmonary hypertension].

This study was designed to elucidate whether the level and distribution of vascular endothelial growth factor (VEGF) are changed in the lungs of rats with hypoxic pulmonary hypertension. 13 male Wistar rats were exposed to isobaric hypoxia for 3 weeks. The pulmonary artery pressure was measured by right cardiac catheterization. The level of VEGF in pulmonary homogenate was measured by Elisa method. The distribution of VEGF in the rat lung was examined by immunohistochemistry. The results showed that the pulmonary artery pressure was significantly increased after hypoxic exposure. The level of VEGF in pulmonary homogenate of rats treated with hypoxia (466.9 +/- 75.5 pg/g) were significantly increased as compared with taht of normal rats (376.2 +/- 47.1 pg/g). The contents of VEGF in the wall of pulmonary arteriole were significantly increased in rats with pulmonary hypertension. So we suggest that chronic hypoxia can strongly stimulate VEGF secretion, and VEGF may mediate the process of hypoxic pulmonary vascular remodeling and pulmonary hypertension.

Animals↗

PubMed1998

[Isolation and identification of smooth muscle cells from pulmonary artery in rats].

To explore the method of isolating acutely the smooth muscle cells from pulmonary artery in rats, small pulmonary arteries (700-200 microns, ID) were dissected free of connective tissue and were allowed to digest in a N-2-hydroxyethyl-piperazine-N'-2-ethanesulfonic acid(HEPES)-buffered physiological saline solution (HPSS) containing collagenase, papain and bovine serum albumin. The tissue was then triturated to disperse smooth muscle cells. The isolated cells in suspension were identified and photographed with film on electron microscope (EM). We succeeded in isolating the single smooth muscle cell, which appeared compressed typically. 90% cells in suspension were identified smooth muscle cells on EM. We conclude that the method for isolation of pulmonary arterial smooth muscle cells is simple, stable and effective and is recommanded for use.

Animals↗

PubMed1998

[Effect of ischemia/reperfusion in cardiac surgery with cardiopulmonary bypass on nitric oxide levels of peripheral blood in patients].

To examine the effect of ischemia/reperfusion in cardiac surgery with cardiopulmonary bypass (CPB) on nitric oxide (NO) levels of peripheral blood, venous levels of NO2- and NO3- were measured at multiple time-points before, during, and after CPB by means of high-pressure liquid chromatograph to reflect NO concentration indirectly in 20 patients. The results showed there was a linear regression between the decreased trend of NO release at the period of peri-CPB is related to the endothelial cell activation caused by ischemia/reperfusion at the same time. Therefore it is necessary to explore the regulation and action of NO release during systemic inflammatory response procedure in CPB.

Adult↗

PubMed1998

Construction of human insulin gene expression recombinant and its effect on blood glucose of diabetic rats.

OBJECTIVE: To study the effect of human insulin gene modified fibroblasts on blood glucose in diabetic rats. METHODS: An expression vector containing human insulin gene was constructed by recombinant DNA technique and introduced into fibroblast Ltk- cells by lipofectin-mediated DNA transfection. Following G418 screening, the survived cells were selected and enriched. Finally a cell line, PRI-12 was generated for the highest insulin production. Then, these cells were injected into streptozocin (STZ)-induced diabetic rats. RESULTS: Insulin DNA transfected Ltk- cells were able to express insulin at a high level in a long-term culture. Furthermore, these Ltk- transfectants could decrease blood glucose significantly (P < 0.01) and obviously increase the body weight (P < 0.01) when they were injected into STZ-induced diabetic rats. CONCLUSIONS: These results suggest that the cell lines transfected insulin gene could secrete insulin and execute effect on diabetic rats. The study provides support for the view that somatic cell gene therapy offers a potential approach to delivery insulin into diabetes mellitus.

Animals↗

PubMed1998

[The inhibition effect of acute hypoxia on K+Ca-ATP channels of pulmonary artery smooth muscle cells of rats].

OBJECTIVE: To explore the possible mechanism underlying hypoxic pulmonary vasoconstriction, we evaluated the effect of acute hypoxia on potassium channels in pulmonary artery smooth muscle cells. METHOD: The single smooth muscle cell was freshly isolated from pulmonary artery (phi 700-200 microns) of Wistar rats with acute enzymatic digestion method. In symmetrical high K+ solution, we separated one outward K+ current from the patch of smooth muscle cells with inside-out configuration using patch-clamp technique. According to the electrophysiological response to the patch channel, this current was identified as the Ca2+, ATP activated potassium channel (K+Ca-ATP). The hypoxic solution was obtained by aeration with 5% CO2-balance N2 mixture. RESULT: The currents of K+Ca-ATP in the patch of smooth muscle cells was much inhibited while the oxygen tension of solution was reduced from normoxic (PO2 > or = 13.33 kPa) to hypoxic (PO2 < or = 2.67 kPa) levels (P < 0.01). Cromakalim (10 nmol/L), an opener of potassium channel, could activate the currents of K+Ca-ATP decreased by acute hypoxia (P < 0.01). CONCLUSION: Acute hypoxia has an inhibition role on K+Ca-ATP currents in pulmonary artery smooth muscle cells, causes the membrane potentional depolarization, leads to pulmonary vasoconstriction, increases pulmonary vascular resistance and artery pressure. The decrease of K+Ca-ATP contributes to development of hypoxic pulmonary vasoconstriction. Cromakalim is one of effective antagonists for hypoxic pulmonary vasoconstriction.

Animals↗

PubMed1998

[Inhibition of potassium channel by chronic hypoxia on pulmonary artery smooth muscle cells in rats].

OBJECTIVE: To explore the possible effect of potassium channel in chronic hypoxic pulmonary hypertension. METHOD: Male Wistar rats were placed in the identical normobaric or hypoxic environmental chamber. In one chamber, rats were maintained in 10% +/- 0.5% O2(by displacement with N2) for 3 weeks, whereas in the other, rats were maintained in air. The single smooth muscle cell was isolated from pulmonary artery (phi 200-700 microns) of Wistar rats with acute enzymatic digestion method. Using patch-clamp technique, we recorded the outward K+ currents in pulmonary artery smooth muscle cells and identified a Ca2+.ATP activated K+ channel (K+Ca-ATP) and a delayed rectifier K+ channel among the outward K+ currents. We compared the activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) or delayed rectifier K+ channel in smooth muscle cells isolated from pulmonary artery of chronic hypoxic and normoxic rats. RESULT: The activities of Ca2+.ATP activated K+ channel (K+Ca-ATP) and delayed rectifier K+ channel in chronic hypoxic group are much lower than that in normal group (T test, P < 0.01). Cromakalim (10 mmol) caused a marked enhancement of activity of the reduced K+Ca-ATP but not the delayed rectifier K+ channel in rats of hypoxic group. CONCLUSION: The persistent decrease of potassium channel activity may contribute to setting the development of chronic hypoxic pulmonary hypertension. Cromakalim, one of potassium channel openers, can decrease the pulmonary hypertension induced by chronic hypoxia and may be a new effective drug for treatment of hypoxic pulmonary hypertension.

Animals↗

PubMed1998

[Calcium oxalate crystals in several kinds of Cinnamon bark].

OBJECTIVE: To probe into the morphology and distribution characteristics of calcium oxalate crystals in several kinds of Cinnamon bark. METHOD: Forty samples of ten different species of Cinamomi Cortex were examined, and the inter-cellular calcium oxalate crystals in the phloem rays were observed by optical microscope and scanning electron microscope. RESULT: It was found that for samples of the same botanical origin, there is little variation in the crystal morphology following certain regularity. The amount, size and ultra-micromorphologic characteristics are influenced by various factors. CONCLUSION: The pattern of morphology and distribution of calcium oxalate crystals may well be an index for identification of the crude drug of Cinnamon bark.

Calcium Oxalate↗

PubMed1998

[The clinical effect of ATG and OKT3 on the treatment of refractory rejection after cadavaric kidney transplantation].

OBJECTIVE: To observe the effect of ATG and OKT3 on the treatment of refractory rejection, including acute and chronic rejection after cadaveric kidney transplantation. METHOD: 87 patients with refractory rejection after cadaveric kidney transplantation were treated by using ATG (13 patients) and OKT3 (74). A total dose of 1 000 mg for ATG group or 45 mg for OKT3 group was administered for each patient. RESULT: Two accelerating rejection and acute rejection were reversed and 7 in the ATG group, 90.00% (27/30) and 90.47% (38/42) in the OKT3 group respectively. A significant difference of total reverse rates was seen between the ATG and OKT3 groups (69.23% verse 90.28%, P < 0.05). In retransplant patients, the reverse rate of acute rejection by OKT3 was 91.67% (11/12). But OKT3 did not show any effect in patients with chronic rejection. CONCLUSION: OKT3 is better than ATG for reversing the refractory rejection, especially in retransplant patients, but it has no any effect on chronic rejection.

Adolescent↗