Biomedical subjects

D Xiao

Publications and source records attributed to D Xiao.

At least 55 records · Page 3Linked to original sources

PubMed1999

Endothelial nitric oxide release in isolated perfused ovine uterine arteries: effect of pregnancy.

The present study was designed to determine the release of endothelial nitric oxide, measured as combined nitric oxide, nitrite and nitrate (NOx), in isolated perfused uterine arteries obtained from nonpregnant and pregnant sheep. Noradrenaline produced concentration-dependent increases in perfusion pressure in both nonpregnant and pregnant uterine arteries with pD2 values of 5.1+/-0.07 and 4.6+/-0.04, respectively. The maximum responses were 300.8+/-8.8 mmHg for nonpregnant arteries and 86.9+/-1.3 mmHg for pregnant ones. N(G)-nitro-L-arginine increased noradrenaline-mediated maximum response in the pregnant (86.9+/-1.3 to 144.6+/-5.1 mmHg), but not in the nonpregnant, uterine arteries. The basal level of NOx was significantly higher in pregnant than in nonpregnant uterine arteries (346.1+/-63.2 vs. 86.0+/-20.6 pmol/ml). The calcium ionophore A23187 and adenosine triphosphate produced concentration-dependent increases in NOx release in both nonpregnant and pregnant arteries. Compared to the nonpregnant tissue, the agonist-induced increase in NOx release was significantly enhanced in the pregnant uterine artery. In accordance, endothelial NO synthase protein expression in pregnant uterine artery was 197% of that in nonpregnant artery. These data indicate that in the uterine artery, pregnancy increases both basal and agonist-induced release of endothelial nitric oxide, which is likely to play a key role in attenuated vascular reactivity of the uterine artery to vasoconstrictors during the course of pregnancy.

Adenosine Triphosphate↗

PubMed1999

Minimally modified low-density lipoprotein induces monocyte chemotactic protein-1 expression in vivo and a novel model for monocyte adhesion to arterial intima.

OBJECTIVE: To test whether minimally modified low-density lipoprotein (MM-LDL) can stimulate the arterial cells expressing MCP-1 in vivo and thus induce monocyte adherence to endothelium. METHODS: An animal model was constructed to study the function of MM-LDL in vivo. MM-LDL (600 micrograms/ml) was perfused into a segment of the femoral artery of rabbits (both ends of which were occluded with removable ligatures). After exposure to MM-LDL for 2 h, the arterial segments were taken out 6 or 18 h later. The arteries were subjected to in situ hybridization with 35S-labeled antisense monocyte chemotactic protein-1 (MCP-1) RNA probe and processed for scanning electron microscopy. RESULTS: The expression of MCP-1 mRNA of the arterial endothelial cells and smooth muscle cells were increased by 60% and 90% 6 h after perfusion and had a 3.2 folds and 1.6 folds increase 18 h after perfusion respectively as compared with control (arteries perfused with saline). There was also apparent monocyte adherence to the endothelium observed by scanning electron microscopy. CONCLUSION: MM-LDL can stimulate vascular cells in expressing MCP-1 mRNA and enhance monocyte adherence to endothelium in vivo.

Animals↗

PubMed1999

[Effects of sleep stage on blood pressure and heart rate in patients with obstructive sleep apnea syndrome].

OBJECTIVE: To determine the effects of sleep stage on blood pressure(BP) and heart rate(HR) and to explore the relationship between BP and HR in patients with obstructive sleep apnea syndrome (OSAS). METHODS: Manometric tube was retained in the radial artery, and whole-night polysomnography (PSG) was done synchronously in 13 patients with OSAS. RESULTS: (1) The increase in BP during apnea was higher in REM sleep than in NREM sleep, but the difference was not significant (P > 0.05). When BP in awake state was regared as baseline, the increases in SBP pre-apnea and post-apnea and the increases in DBP post-apnea were significantly higher in REM sleep(-1.9 +/- 11.9 mm Hg, 32.6 +/- 20.6 mm Hg, 18.2 +/- 11.6 mm Hg, respectively) than in NREM sleep (-8.4 +/- 8.0 mm Hg, 20.4 +/- 6.9 mm Hg, 13.2 +/- 5.8 mm Hg, P < 0.05, respectively). (2) In different sleep stages, HR was markedly higher at the end of apnea than before apnea(NREM: 76 +/- 8 bpm vs 70 +/- 8 bpm, P < 0.05; REM: 85 +/- 11 bpm vs 71 +/- 8 bpm, P < 0.01). HR in post-apnea (P < 0.01) and the increase in HR during apnea (NREM: 6.9 +/- 2.2 bpm, REM: 14.1 +/- 10.1 bpm, P < 0.05) were remarkably higher in REM sleep than in NREM sleep, but not for pre-apneic HR. (3) In NREM sleep, HR in pre-apnea was significantly correlated with the increase in SBP and DBP during apnea(r = -0.699, P < 0.01; r = -0.602, P < 0.05, respectively); The increase in SBP during apnea in NREM sleep was also correlated with post-apnea HR (r = -0.669, P < 0.01). CONCLUSION: Sleep stage has effects on BP and HR and the changes in BP are correlated with the changes in HR during apnea in patients with OSAS.

Adult↗

PubMed1999

[Effects of As2O3 on the BCR/ABL protein tyrosine phosphorylation in K562 cells].

OBJECTIVE: To explore the mechanisms of As2O3 inducing apoptosis and growth inhibition in K562 cells and provide theoretical basis for clinical application. METHODS: The effects of As2O3 on BCR/ABL protein tyrosine phosphorylation(PTP) and its signal transduction as well as the expression of apoptosis-related genes were studied by means of immunoprecipitation, Western blot, biochemical method and immunofluorescence. RESULTS: Tyrosine phosphorylation of several cellular proteins especially BCR/ABL protein was decreased by 1 mumol/L As2O3, but not by 0.1 mumol/L As2O3. As2O3 had no effect on PTP activity, downregulated the expression of JAK2 protein, but did not affect the expressions of STAT1 and STAT2 proteins and the STAT1 protein tyrosine phosphorylation. As2O3 had no effect on the expression of the apoptosis-related genes like Bcl-2, Bcl-xL/S, Bax, ICH-1L, p53, PARP, either, but downregulated PML protein expression in K562 cells. CONCLUSION: As2O3 might induce K562 cell apoptosis and inhibit its growth by reducing tyrosine phosphorylation of cellular proteins especially BCR/ABL protein and/or by downregulating JAK2 protein expression to interfere with the BCR/ABL protein signal transduction.

Antineoplastic Agents↗

PubMed1999

[Advances in the study of mechanisms of the tumor angiogenesis inhibitors].

Tumor angiogenesis inhibitor is the drugs which can destroy or inhibit neovascularization, and block the growth and metastasis of cancer. For clinical applications it may be useful to divide the antiangiogenic drugs into two categories: class 1(specific inhibitors) and class 2 (non-specific inhibitors). This review intends to provide the recent progress of the mechanisms of antiangiogenic drugs (1) Regulation of angiogenesis growth factors; (2) Inhibition of basement membrane degradation; (3) Mediating signal transduction pathway; (4) Effect of cell cycle; (5) Regulation of tumor-related gene.

Angiogenesis Inhibitors↗

PubMed1998

Synthesis and biological activity of [Tic5] didemnin B.

A didemnin B analog containing a Tic (1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) as a conformationally restrained replacement for tyrosine has been synthesized and shown to have comparable potency as a protein biosynthesis inhibitor. Synthetic highlights include an oxidation of an alcohol to an acid in the presence of the sensitive Tic heterocycle and a modified Schmidt-type one-pot macrocyclization.

Animals↗

PubMed1998

Long-term high-altitude hypoxia increases plasma nitrate levels in pregnant ewes and their fetuses.

OBJECTIVE: The study was designed to determine whether moderate chronic hypoxia changes plasma nitrate concentrations in nonpregnant and pregnant, near-term ewes and their fetuses. STUDY DESIGN: Pregnant ewes were put into either a normoxic control group or a chronically hypoxic group maintained at high altitude (3820 m, PaO 2 60 mm Hg) from day 30 of gestation. On day 140 blood samples were collected from the maternal jugular vein and from the fetal umbilical artery and vein. Blood samples were also obtained from normoxic nonpregnant adult ewes and nonpregnant adult ewes exposed to high-altitude hypoxia for 110 days. Plasma nitrate concentrations were determined through chemiluminescence assay. RESULTS: Within normoxic groups plasma nitrate concentrations of pregnant, near-term ewes were significantly elevated compared with those of nonpregnant ewes (17.4 +/- 0.3 vs 6.8 +/- 0.4 micromol/L, P <.0001). Fetal umbilical arterial and venous plasma nitrate concentrations did not differ from each other in the normoxic group (44.7 +/- 4.2 and 44.0 +/- 4.3 micromol/L, respectively) but were significantly higher than those of their mothers (P <.0001). Compared with normoxic groups, pregnant ewes with chronic hypoxia showed significantly increased plasma nitrate concentrations (30.9 +/- 1.8 micromol/L, P <.001), as did their fetuses (arterial 146.1 +/- 14.7 micromol/L, venous 154.5 +/- 14.6 micromol/L, P <.0001), but nonpregnant ewes with chronic hypoxia did not (7.5 +/- 0.3 micromol/L, P >.05). CONCLUSIONS: We conclude that (1) production of endogenous nitric oxide is increased by pregnancy in sheep and is higher in the fetus than in the mother, and (2) moderate chronic hypoxia selectively augments nitric oxide production in the pregnant ewe's circulation and, even more profoundly, in the fetal lamb's circulation.

Altitude Sickness↗

PubMed1998

Effects of chronic hypoxia on Ca2+ mobilization and Ca2+ sensitivity of myofilaments in uterine arteries.

The effect of chronic hypoxia on free intracellular Ca2+ concentration ([Ca2+]i) and Ca2+ sensitivity of myofilaments during agonist stimulation was examined in uterine arteries obtained from normoxic and chronically hypoxic pregnant sheep maintained at high altitude (3,820 m) for approximately 110 days. Smooth muscle [Ca2+]i was measured simultaneously with muscle contraction in the same intact tissue. Whereas both KCl and 5-HT increased [Ca2+]i and tension simultaneously in the uterine artery, 5-HT produced significantly greater contractile tension (in g) than KCl at a given amount of [Ca2+]i as indicated by the ratio of fura 2 fluorescence intensity induced by excitation at 340 nm to that induced at 380 nm (29.8 +/- 6.9 vs. 16.9 +/- 4.0, P < 0.05). Chronic hypoxia did not change KCl-induced contractions, nor did it affect KCl-mediated increases in [Ca2+]i. In contrast, chronic hypoxia significantly inhibited 5-HT-induced contractions and decreased the 5-HT-stimulated increase in [Ca2+]i (pD2 7.46 +/- 0.18-->6.86 +/- 0.11, P < 0.05, where pD2 is -log half-maximal effective concentration) in uterine arteries. In addition, the slope (g tension/nM [Ca2+]i) of the 5-HT-mediated [Ca2+]i-tension relationship was significantly decreased in chronically hypoxic arteries (0.024 +/- 0.002-->0.013 +/- 0.001, P < 0.01). The results suggest that chronic hypoxia suppresses agonist-mediated Ca2+ homeostasis in uterine arteries by inhibiting Ca2+ mobilization and the agonist-enhanced Ca2+ sensitivity of myofilaments.

Altitude↗

PubMed1998

Quercetin down-regulated bcl-2 gene expression in human leukemia HL-60 cells.

AIM: To study the effect of quercetin (Que) on bcl-2 gene expression in human leukemia HL-60 cells. METHODS: Immunohistochemical analysis and RNA Dot blot hybridization were used to identify the expression of bcl-2 genes. RESULTS: The expression of bcl-2 protein was 94% in control HL-60 cells, which became 45%-84% when they were cultured with Que 15-60 mumol.L-1 for 48 h. The expression of bcl-2 mRNA in HL-60 cells was obviously decreased in treatment with Que 15-60 mumol.L-1. CONCLUSION: The apoptotic action of Que in HL-60 cells was associated with the down-regulation of the apoptosis-suppressing gene bcl-2.

Antineoplastic Agents, Phytogenic↗

PubMed1998

[Protein tyrosine kinase (PTK) activities during the induction of apoptosis by arsenic trioxide (As2O3)].

OBJECTIVE: To explore the mechanism of arsenic trioxide (As2O3) induced apoptosis in K562 cell line. METHODS: Immunoprecipitation was used to obtain BCR/ABL and ABL proteins. The activities of PTK and tyrosine phosphorylation were measured by biochemical method and Western blot, respectively. RESULTS: As2O3 reduced the PTK activities of cytosol and membrane proteins and BCR/ABL and ABL proteins. The tyrosine phosphorylation of 180,000 and 125,000 proteins declined. CONCLUSION: As2O3 may interfere the signal transduction of BCR/ABL protein by reducing its PTK activity and induce K562 cell apoptosis.

Apoptosis↗

PubMed1998

[The occurrence of hypertension in patients with obstructive sleep apnea syndrome].

OBJECTIVE: To determine the changes in blood pressure (BP) and its correlated factors in patients with obstructive sleep apnea syndrome(OSAS). METHOD: Retaining manometric tube in radial artery and polysomnography(PSG) were done synchronously in 13 patients with OSAS in whom was diagnosed by whole-night PSG. Oxygen therapy was given to two of the patients and NCPAP treatment was given to four of the patients on the following night. RESULT: (1) Six of the patients (46 percent) had daytime hypertension (SBP > 18.7 kPa and/or DBP > 12 kPa), the incidence of transient hypertension during apnea in 7 patients who do not have daytime hypertension was 86% (6/7). (2) Lowest oxygen saturation during sleep was significantly correlated with the level of SBP(r = -0.659, P < 0.05) and DBP(r = -0.677, P < 0.01) in awake, the baseline of SBP(r = -0.777, P < 0.01) and DBP (r = -0.590, P < 0.05) in NREM sleep and that of SBP(r = -0.585, P < 0.05) in REM sleep. In REM sleep, the changes in MBP showed significantly correlation with the changes in oxygen saturation during apnea (r = 0.598, P < 0.05). In NREM sleep, the changes in SBP were significantly correlated with apnea length(r = 0.580, P < 0.05). The changes in BP showed no correlation with apnea index in different sleep stages (P > 0.05). (3) Nocturnal elevation in BP disappeared in four patients who received NCPAP treatment, but not in two patients who received oxygen therapy. CONCLUSION: The transient hypertension during apnea might be recurrent episodes in patients with OSAS who have normal daytime BP. Nocturnal hypoxemia and apnea length might play a role in nocturnal elevation in BP in patients with OSAS. Hypoxemia was not the major factor in BP elevation after obstructive apneas. Simple oxygen administration could not normalize the elevation in BP during apnea in patients with OSAS and NCPAP might be an appropriate therapy.

Adult↗

PubMed1997

Studies on the relationship between urokinase plasminogen activator (uPA) and human sperm motility.

To clarify the role of urokinase plasminogen activator (uPA) in the mechanisms of regulating sperm motility and the ability of fertilizing, we investigated the quantities and activities of uPA in human seminal plasma and on the membrane of spermatozoa. Semens were harvested from 22 infertile patients with asthenospermia and 20 healthy fertile men according to WHO standards. To quantify the membrane-bound uPA in the samples, polyclonal antibodies against human urokinase were employed by means of a sandwich ELISA. The uPA activities in seminal plasma and on the surface of spermatozoa were determined using A-garose-Fibrine-Plate method and the experiment of immunological identification with polyclonal antibodies against urokinase. In lysates of spermatozoa, significantly lower levels of uPA (23.1 +/- 7.35 mu/10(6) cells) and uPA activity (5.13 +/- 3.85 mu/10(6) cells) were found in patient group as compared to healthy fertile men exhibiting normospermia (29.89 +/- 9.40 mu/10(6) cells and 10.17 +/- 6.18 mu/10(6) cells). In seminal plasma, uPA activity in patient group (2134 +/- 1581.3 IU/L) was also found significantly lower than that of normal group (3365 +/- 1859.5 IU/L). Positive correlations were observed between sperm motility and uPA quantities (r = 0.48, P < 0.005), as well as with uPA activities (r = 0.45, P < 0.005). Thus, it is inferred that membrane associated uPA on human spermatozoa may be related directly to sperm motility and fertility.

Adult↗

PubMed1997

Biomechanical study of stress in the fifth metatarsal.

OBJECTIVE: The stress throughout the fifth metatarsal was determined under various loading conditions, in order to better understand the causes of fractures to this bone. DESIGN: A mathematical approach was taken, in which the stresses were analysed using the methods of beam theory. BACKGROUND: Finite element analysis has frequently been used to determine the stress in bones. Beam theory provides an easier method for determining the force and moment resultant in any cross-section. The distribution of stress throughout the cross-section can then be found by solving certain partial differential equations defined on the cross-sections. METHODS: Cross-sections of the bone were obtained by slicing a mould, into which the bone was placed, at numerous intervals along its length. Analytic expressions describing each cross-section were obtained by fitting a Fourier series to a sequence of points along the boundary. RESULTS: The maximum stress found in the fifth metatarsal resulted from an oblique load, and had a magnitude less than would occur in a subject during normal walking. CONCLUSIONS: Since the magnitude of the stress is submaximal, this study lends theoretical support to the clinical observation that the diaphyseal fracture is indeed a stress fracture. RELEVANCE: Our analysis adds a biomechanical rationale to the pathomechanics of diaphyseal stress fractures of the fifth metatarsal. It suggests that inversion during repetitive activities may predispose the foot to fractures at a predictable location.

Journal Article↗

PubMed1997

Quercetin induced apoptosis in human leukemia HL-60 cells.

AIM: To examine whether quercetin (Que) might induce apoptosis in human leukemia HL-60 cells. METHODS: DNA fragmentation was visualized by agarose gel electrophoresis. Inhibition of proliferation was measured with a colorimetric MTT-assay. The DNA degradation was determined using flow cytometry, and the microscopic changes were observed by an electron microscope. RESULTS: Que 15-120 mumol.L-1 elicited typical apoptosis morphological changes including condensed chromatin, nuclear fragmentation, and reduction in volume. DNA fragmentation and DNA degradation in a concentration-dependent manner in HL-60 cells. Que inhibited HL-60 cell proliferation. The values of IC50 and 95% confidence limits were 43 (30-61) mumol.L-1 after 48-h treatment with Que. CONCLUSION: Que induced apoptosis in HL-60 cells.

Antineoplastic Agents, Phytogenic↗

PubMed1997

[The renal function protection of prostaglandin E1 from hemolysis caused by cardiopulmonary bypass].

OBJECTIVE: To observe the renal function protection of PGE1 from hemolysis caused by CPB during and after CPB. METHOD: F-Hb in blood, NAG & beta 2-MG in urine were measured in twenty patients who underwent valvular replacement operation. The patients were divided into two groups at random. The PGE1 group was administered of PGE1 with the dose of 100 ng/kg.min for 30' before CPB, 30 ng/kg.min during CPB intravenation and 100 ng/ml before CPB in CPB mechanical equipment. The control group was administered of N. S. RESULTS: After termination of CPB, F-Hb rose continuously, showing that the damaging RBC factors did not stop working at once after CPB. F-Hb and beta 2-MG were positively correlated and F-Hb and NAG/Cr were positively correlated, demonstrating that increased F-Hb is an important factor for renal function damage. At 60 minutes after CPB and 120 minutes after CPB, F-Hb values of PGE1 group were significantly lower than those of the control group. beta 2-MG and NAG/Cr of the PGE1 group also showed the same trend. The peak of the control group F-Hb was later than that of the PGE1 group. CONCLUSIONS: The results demonstrate that PGE1 can protect renal function by decreasing F-Hb level during CPB and shortening the time of hemolysis after CPB.

Acetylglucosaminidase↗

PubMed1996

[Effect of phosphorylation by protein kinase C on the DNA binding activity of high mobility group protein I].

High mobility group protein I (HMG-I) is a nonhistone chromosomal protein. The present study aims to examine phosphorylation of HMG-I by protein kinase C (PKC) and its effect on HMG-I's DNA binding activity. HMG-I, extracted and purified from rat brain was phosphorylated in vitro equally well by PKC alpha, beta, gamma and delta. Phosphoamino acid analysis indicated that both serine and threonine residues were phosphorylated. The nonphosphorylated HMG-I was shown to bind specifically to the fragment of DNA containing bp -708 to -458 of RC3 genomic DNA, which is abundant in A-T sequences. In contrast, phosphorylation of HMG-I by PKC resulted in an attenuation of binding to the DNA fragment. It is suggested that phosphorylation of HMG-I by PKC may regulate DNA binding activity of HMG-I, thereby possibly altering its biological functions.

Animals↗

PubMed1996

[Surgical treatment of ventricular septal defect complicated by pulmonary hypertension: analysis of 24 cases].

Until now the most important factor affecting the surgical treatment of ventricular septal defect (VSD) is pulmonary hypertention. 307 patients with ventricular septal defect (VSD) were treated surgically from May 1989 to May 1995 with a mortality rate of 2.9%. Among the 307 patients, 24 were complicated by severe pulmonary hypertension (Pp/Ps > or = 80%) and the mortality rate was 20.8%. Perioperative therapy and operative indications were discussed. Catheterization data, physical examination, chest X-ray and electrocardiographic findings were also analysed by comparision with operative outcome.

Cardiac Surgical Procedures↗

PubMed1995

The speed tuning of medial superior temporal (MST) cell responses to optic-flow components.

The responses of macaque medial superior temporal (MST) cells to translation and to the optic-flow components-rotation, expansion/contraction, and deformation-were examined with particular regard to the speed tuning of MST cells for optic-flow stimuli and the effect of removing speed gradients from those stimuli. The use of position invariance as an indispensable criterion for assessing the authenticity of responses to optic flow is reviewed. By extending the scope of testing to include higher speeds it is found, in contrast to in previous reports, that MST cells generally respond to optic-flow components with a speed-response profile which is tuned for a particular range of speeds. Removal of the speed gradient had little effect on this observation. These and other properties of MST cells lead to the conclusion that one of the major functions of MST is the detection and encoding of self-motion.

Animals↗