Search PubMed⌕ Search

Biomedical subjects

F Xu

Publications and source records attributed to F Xu.

At least 181 records · Page 10Linked to original sources
PubMed1998

Conductive choline transport by alveolar epithelial plasma membrane vesicles.

Choline is an important substrate in alveolar epithelia for both surfactant production and cellular maintenance. The underlying mechanisms of uptake and sites of membrane transport remain uncertain. To test the hypothesis that choline transport occurs at the basolateral side of alveolar epithelia by both Na+-independent and -dependent mechanisms, plasma membrane vesicles were prepared from the apical and basolateral membranes of mature porcine type II pneumocytes. Choline+ transport was assayed by uptake of [3H]choline+ by enriched apical or basolateral vesicles. In the presence of imposed, inside-negative charge gradients, basolateral vesicles exhibited early overshoot of [3H]choline+ uptake unaffected by the presence or absence of external Na+ (541 +/- 53 vs 564 +/- 79 pmol/mg protein (NS)). High sensitivity to hemicholinium-3 was observed in the presence or absence of Na+. In the absence of inside-negative charge gradients, uptake was reduced 12-fold in the presence or absence of Na+, and external choline+ induced internal alkalization of acidified basolateral vesicles. Accumulative [3H]choline+ uptakes by apical vesicles in the presence or absence of inside-negative charge gradients and Na+ were insignificant. We conclude that predominant choline+ uptake by type II pneumocytes occurs at the basolateral membrane by Na+-independent, electrogenic choline+ conductance. The presence of electroneutral choline+/H+ exchange is suggested.

Animals↗
PubMed1998

Detection of anti-recombinant beta 2-glycoprotein 1 and anti-recombinant beta 2-glycoprotein 1 fifth-domain antibodies in sera from patients with systemic lupus erythematosus.

Two kinds of plasmid expression vectors which expressed beta 2-glycoprotein 1 (beta 2GP1) and the fifth domain of beta 2-glycoprotein 1 (beta 2GP1-D5) were constructed respectively in this study. The antigenicity of recombinant beta 2GP1 (r beta 2GP1) and beta 2GP1-D5 (r beta 2GP1-D5) was identified by immunoblots using rabbit anti-beta 2GP1 antibodies, and the recombinant proteins were purified. Both anti-r beta 2GP1 and anti-beta 2GP1-D5 antibodies in 112 patients were detected by ELISA using r beta 2GP1 and r beta 2GP1-D5 as coating antigens. A significant statistical correlation (r = 0.667, P < 0.01) between the levels of anti-beta 2GP1 and anticardiolipin (ACL) antibodies was found. The presence of anti-r beta 2GP1 antibodies was associated with an increased frequency of history of thrombosis and/or recurrent abortion; hence anti-r beta 2GP1 assay provided better specificity than conventional ACL assay. Detection of anti-r beta 2GP1 antibodies may be of potential value in evaluating the risk of thrombosis and/or symptoms associated with other antiphospholipid syndromes (APS). The binding of anti-r beta 2GP1 from the sera of patients with APS to r beta 2GP1 was inhibited by r beta 2GP1-D5. Meanwhile, of 28 patients who had positive anti-r beta 2GP1 antibodies in sera, 27 (96.4%) had positive anti-r beta 2GP1-D1 antibodies. This indicated that the antigenic epitope of beta 2GP1 may be located in its fifth domain.

Abortion, Habitual↗
PubMed1998

Changing sex ratio in the United States, 1969-1995.

OBJECTIVE: To determine if the sex ratio of live births in the United States has changed during the 27 years from 1969 through 1995. DESIGN: Regression analysis of secular trends in sex ratios. SETTING: Population-based data. PATIENT(S): Liveborn infants in the United States 1969-1995. MAIN OUTCOME MEASURE(S): Sex of liveborn infant. RESULT(S): The sex ratio (number of male births divided by number of female births) declined significantly among whites during the 27 years under study. Among black newborns, the sex ratio significantly increased during the same time period. CONCLUSION(S): These secular trends could not be explained by changing maternal or paternal age, or by changing proportions of specific birth orders. Possible explanations for the observed changes in sex ratio include random fluctuations in sex ratio over time, changes in demographic characteristics of the population (other than the characteristics controlled for in this analysis), and changes in frequency or timing of intercourse. Environmental exposures are unlikely to account for the observed trends.

Black People↗
PubMed1998

Inhibition of VLA-4 and up-regulation of TIMP-1 expression in B16BL6 melanoma cells transfected with MHC class I genes.

The effect of MHC class I gene transfection on the metastatic properties of B16BL6 melanoma cells was investigated. BL6-8 melanoma cells transfected with H-2Kb or H-2Kd, but not H-2Dd or H-2Ld, genes showed a dramatic reduction in their ability to generate experimental metastases in immunosuppressed CB6F1 mice. This observation suggested that some changes in the metastatic phenotype may have been induced in the H-2K- transfected melanoma cells. Analyses of adhesive and invasive properties of BL6-8 melanoma cells transfected with H-2 class I genes have been performed. We found that the loss of metastatic properties in the H-2Kb or H-2Kd gene-transfected melanoma cells was associated with reduced adherence to endothelial cells, laminin and collagen IV, decreased ability to form homotypic cell aggregates and with a complete loss of VLA-4 integrin expression. In addition, BL6-8 melanoma cells transfected with H-2K genes demonstrated reduced ability to invade Matrigel that paralleled up-regulation of TIMP-1 expression. Incubation of untransfected BL6-8 clone or B16F1 cells with 5-azacytidine similarly resulted in up-regulation of TIMP-1, suggesting that the changes in methylation of TIMP-1 gene could be responsible for TIMP-1 expression in the H-2K-transfected BL6-8 melanoma cells. Transfection of BL6-8 cells with the H-2Dd/Ld genes did not affect their adhesive and invasive properties. Previously we reported that reduction in the metastatic properties of the H-2Kb transfected cells was associated with alterations in cell surface carbohydrates with appearance of alpha-galactosyl epitopes and reduction in cell surface sialylation. The present data indicate that, in addition to changes in cell surface carbohydrates, reduction in adhesive properties and up-regulation of TIMP-1 may be responsible for the observed loss of metastatic potential of BL6-8 cells transfected with the H-2K genes.

Animals↗
PubMed1998

The still-face effect in Chinese and Canadian 3- to 6-month-old infants.

Studies conducted in China examining cross-cultural differences in 3- to 6-month-olds used the still-face paradigm. In each study, 20 infants were in the experimental group (normal, still-face, normal interactions) and 20 in the control (3 normal periods). In Study 1, infants interacted with either their mother or their father; they looked and smiled less to the still-face of both parents. In Study 2, infants interacted with both their mother and a stranger, with order counterbalanced. Experimental groups showed similar still-face effects to both adults. The control group responded similarly to the stranger in both orders but responded less to their mother when she interacted 2nd. The data were compared with archival data from Canadian infants. Although Chinese infants took longer to begin smiling, responding was similar in both cultures, despite differences in mothers' behavior: Chinese mothers played with the infants' arms; Canadian mothers played with the legs.

Adult↗
PubMed1998

Increased secretion and activity of matrix metalloproteinase-3 in synovial tissues and chondrocytes from experimental osteoarthritis.

OBJECTIVE: The aim of this study was to define the relative regulation of matrix metalloproteinase-3 (MMP-3), and tissue inhibitor of metalloproteinases-1 (TIMP-1), in chondrocytes and synovium in experimental osteoarthritis (EOA). METHODS: Partial-meniscectomized (PM) rabbits, surgical sham controls (SH), and normal non-surgical controls (N) were killed at times corresponding to early degenerative lesions (4 weeks) and increasingly progressive stages of EOA at 8 and 12 weeks post-PM. MMP-3 activity was measured in conditioned media from chondrocytes and synovium using a peptide cleavage assay with substance P (SP) as the substrate. TIMP-1 was quantitated using an enzyme-linked immunosorbent assay (ELISA). RESULTS: Early degenerative lesions (4 weeks post-PM) were characterized by inflammatory responses in the synovium accompanied by a significant rise of MMP-3 activity in synovial cultures (P < 0.05). At 8 weeks there was no discernible inflammation, and MMP-3 activity in EOA synovial cultures was comparable to that in the controls; this was followed by a second increase in MMP-3 activity in EOA samples at 12 weeks. MMP-3 activity was significantly elevated in EOA chondrocyte cultures at 8 weeks post-PM relative to N controls, corresponding to the most destructive phase of EOA, but not in the early phase (4 weeks) or 'late' degenerative phase (12 weeks). Medium derived from chondrocytes contained little or no TIMP-1. Synovia secreted relatively higher amounts of TIMP-1, and this was elevated at 8 weeks post-PM relative to the SH controls. The majority (approximately 90%) of MMP-3 activity could be inhibited using recombinant TIMP-1 or a hydroxamate MMP inhibitor. Complete inhibition was achieved with EDTA or 1,10 phenanthroline. CONCLUSION: Together, these data indicate that in EOA, MMP-3 is initially upregulated in the synovium which may play a pivotal role in the pathogenesis of cartilage lesions. In contrast, chondrocyte-derived MMP-3 is upregulated in the later phases of EOA, contributing further to progression of cartilage lesions.

Animals↗
PubMed1998

Halothane and isoflurane alter calcium dynamics in rat cerebrocortical synaptosomes.

UNLABELLED: An increase in synaptosomal Ca2+ triggers neurotransmitter release and volatile anesthetics have been shown to inhibit neurotransmitter release by inhibition of Ca2+ entry. We have examined the effect of isoflurane and halothane on the kinetics of increase and decrease of Ca2+ in rat cerebrocortical synaptosomes ([Ca2+]in). We have also used specific Ca2+ antagonists to examine the role of L-, N-, and P-type Ca2+ channels. Synaptosomal [Ca2+]in was measured spectrofluorometrically using fura-2 as a Ca2+ reporter; Ca2+ transients were initiated by depolarization with 40 mM KCl. We found that < or = 1 minimum alveolar anesthetic concentration halothane and isoflurane decreased peak [Ca2+]in by approximately 40%, that both anesthetics decreased the rate of [Ca2+]in increase and decrease, that specific voltage-dependent calcium channel antagonists had little effect on peak or plateau [Ca2+]in, and that the volatile anesthetics increased the permeability of synaptosomal membranes to Ca2+. These results suggest that the volatile anesthetics, at clinically relevant concentrations, can alter Ca2+ homeostasis in the synapse. IMPLICATIONS: Clinically relevant concentrations of halothane and isoflurane markedly depress K+-evoked increases in rat cerebrocortical synaptosomal calcium (Ca2+) unrelated to L-, N-, and P-type voltage-dependent calcium channels and increase the Ca2+ permeability of the synaptosomal membrane. These changes in Ca2+ dynamics could have profound effects on Ca2+ signaling in the synapse.

Anesthetics, General↗
PubMed1998

Rat brain VEGF expression in alveolar hypoxia: possible role in high-altitude cerebral edema.

The mechanism by which hypoxia causes high-altitude cerebral edema (HACE) is unknown. Tissue hypoxia triggers angiogenesis, initially by expressing vascular endothelial growth factor (VEGF), which has been shown to increase extracerebral capillary permeability. This study investigated brain VEGF expression in 32 rats exposed to progressively severe normobaric hypoxia (9-6% O2) for 0 (control), 3, 6, or 12 h or 1, 2, 3, or 6 days. O2 concentration was adjusted intermittently to the limit of tolerance by activity and intake, but no attempt was made to detect HACE. Northern blot analysis demonstrated that two molecular bands of transcribed VEGF mRNA (approximately 3.9 and 4.7 kb) were upregulated in cortex and cerebellum after as little as 3 h of hypoxia, with a threefold increase peaking at 12-24 h. Western blot revealed that VEGF protein was increased after 12 h of hypoxia, reaching a maximum in approximately 2 days. The expression of flt-1 mRNA was enhanced after 3 days of hypoxia. We conclude that VEGF production in hypoxia is consistent with the hypothesis that angiogenesis may be involved in HACE.

Altitude Sickness↗
PubMed1998

Transient respiratory augmentation elicited by acute head-down tilt in the anesthetized cat.

Acute head-down tilt (AHDT, -30 degrees) in humans induces a transient ventilatory augmentation for 1-2 min accompanied by a high venous return. However, the mechanisms underlying this respiratory response remain obscure because of limitations of experiments carried out in human subjects. The present study was undertaken to determine whether AHDT-induced respiratory augmentation exists in the anesthetized, paralyzed, and ventilated cat and, if so, whether this response depends on 1) the cerebellum, 2) the carotid sinus (CS) and/or vagal afferents, and 3) elevation of central venous return. The integrated phrenic neurogram, arterial blood pressure, central venous pressure (CVP), and end-tidal PCO2 were recorded before, during, and after AHDT. The results showed that AHDT produced a transient ( approximately 2 min) enhancement of minute phrenic activity (approximately 30%) primarily via an increase in peak integrated phrenic neurogram amplitude associated with a remarkable elevation of CVP (approximately 3 min). Cerebellectomy, CS denervation, bilateral vagotomy, or clamping CVP did not affect the presence of the AHDT-induced minute phrenic activity response. These findings demonstrate that the anesthetized cat is a suitable model for investigating the mechanisms involved in AHDT-induced respiratory augmentation. Preliminary studies suggest that this response does not require the cerebellum, CS/vagal afferents, or an associated rise in central venous return.

Anesthesia↗
PubMed1998

Delay of metabolism rate of ciclosporin by simvastatin in 7 Chinese healthy men.

AIM: To study the effects of simvastatin (Sim) on pharmacokinetics of ciclosporin (Cic). METHODS: Seven healthy young volunteers took Cic 100 mg alone or in combination with Sim 10 mg in a randomized crossover study. The Cic concentrations in blood were determined by specific fluorescence polarization immunoassay. Data were analyzed with 3P87 program. RESULTS: The blood concentration-time curve was fitted to open 2-compartment model, and the pharmacokinetic parameters of Cic alone and Cic + Sim were: Cmax (646 +/- 94) and (698 +/- 340) micrograms.L-1; Tmax (1.12 +/- 0.13) and (1.13 +/- 0.21) h; AUC (2.3 +/- 0.4) and (2.6 +/- 1.2) mg.h.L-1; T1/2 beta (12 +/- 6) and (23 +/- 8) h (P < 0.05). CONCLUSION: Sim delays the metabolism rate of Cic when they are given simutaneously.

Adult↗
PubMed1998

[Effect of dietary calcium on serum calcium and calmodulin activity of brain and hypothalamus in rats].

The effect of low calcium (LC) diet supplemented with various amount of calcium on serum calcium and calmodulin of rats was studied. The LC diet was mainly composed of corn low in calcium. The calcium content of LC diet was only half of that of the stock diet. Seventy Wistar rats were divided into 7 groups by weight and sex. Results showed that serum calcium in LC group was low and calmodulin activity was also low. These parameters were improved while calcium was supplemented in LC diet. There is a significant dose-response relationship among diet calcium, serum calcium and growth. When the total calcium in diet was increased up to 1000 mg/kg, serum calcium level was closed to that of normal and higher than the serum calcium in LC group significantly. The study demonstrated that low dietary calcium, hypocalcemia and low calmodulin are associated. When total dietary calcium was up to 1000 mg/kg, the growth retardation was attenuated.

Animals↗
PubMed1998

Hyperoxia-induced lung injury in premature rat: description of a suitable model for the study of lung diseases in newborns.

OBJECTIVE: To provide suitable animal model (hyperoxia-induced premature rat lung damage) for research of bronchopulmonary dysplasia (BPD) and to better understand pathogenesis of BPD and look for effective drugs to prevent and treat BPD. METHODS: Rat litters delivered prematurely at 21-day gestation by hysterotomy. Vigorous resuscitation at birth resulted in a high survival rate. Surfactant and antioxidant enzyme (AOE) system were measured. The model was tested in an experiment of hyperoxia-induced lung injury. RESULTS: Compared to litters delivered spontaneously at term (gestation 22 days), these preterm rats had immature pulmonary surfactant composition with low total phospholipid (x +/- s: 10.09 +/- 1.49 micrograms/mg wet weight vs 12.04 +/- 1.31 micrograms/mg wet weight; P = 0.0367) and phostidylcholine (5.06 +/- 1.82 micrograms/mg wet weight vs 8.28 +/- 2.35 micrograms/mg wet weight; P = 0.0238) levels. The concentrations of AOE enzymes, superoxide dismutase (11.40 +/- 2.04 mu/mg DNA vs 15.78 +/- 1.84 mu/mg DNA; P < 0.01) and catalase (92.81 +/- 62.25 mu/mg DNA vs 412.24 +/- 117.50 mu/mg DNA; P < 0.01) were also significantly lower. Animals exposed to hyperoxia had a significantly higher mortality. Pulmonary edema and histological features of lung damage were observed in the pups exposed to hyperoxia. CONCLUSIONS: The premature rat model is relatively cheap, readily available and has a high survival rate. Pulmonary surfactant and AOE systems are immature. These properties make them a suitable model for the study of acute and chronic lung damage related to prematurity and O2 toxicity.

Animals↗
PubMed1998

[Effect of purified Xuefu capsule on cardiac haemodynamics and oxygen consumption in acute myocardial ischemia of experimental dogs].

OBJECTIVE: To investigate the effect of Purified Xuefu Capsule (PXC) on cardiac haemodynamic and oxygen consumption in acute myocardial ischemia of experimental dogs. METHODS: The coronary arteries was ligated to create the myocardial ischemic modle and gave them PXC through the duodenum. The effect of PXC on the systolic and diastolic function, volume of blood flow in coronary arteries and cardiac output of acute ischemic heart of experimental dogs were examined. RESULTS: After ligation of the coronary artery the myocardial ischemia was formed, the systolic and diastolic function, volume of blood flow in coronary arteries and cardiac output were decreased significantly in the control group, whereas these indexes in high-dose and low-dose PXC group were improved to some extent, the effect of high-dose PXC group was better than that of the low-dose PXC group. Furthermore high-dose PXC could reduce the oxygen consumption. CONCLUSIONS: PXC could prevent the cardiac pump function from acute myocardial ischemia of experimental dogs. The mechanism may be related to reduce the oxygen consumption and increase the blood supplement to myocardium.

Animals↗
PubMed1998

[Effects of different thyroid status on the pharmacokinetics of diazepam].

Experimental models of hypothyroidism and hyperthyroidism in Sprague-Dawley rats were established in this study. Diazepam was given to rats at a single oral dose of 30-40 mg.kg-1 and the plasma concentration of diazepam was detected by HPLC. The results showed that the plasma concentration of diazepam was significantly higher in hypothyroid rats than that in controls (P < 0.05). The Cmax, AUC and T1/2 (Ka) were increased. The Vd was decreased and the elimination was slowed. Mild hyperthyroidism showed nearly no effect on the plasma concentration, Cmax and AUC of diazepam in the rats. But when the rats became more heavily hyperthyroid, the plasma concentration, Cmax and AUC of diazepam were increased gradually. The absorption of diazepam was changed slightly in mild and moderate hyperthyroid rats, the Vd was decreased and the elimination was accelerated. In heavily hyperthyroid rats, however, the absorption of diazepam was obviously accelerated. The Vd was decreased and the elimination was slowed. Therefore, we conclude that different thyroid status may have different effects on the pharmacokinetics of diazepam.

Animals↗
PubMed1998

[Detection of hepatitis C virus and hepatitis G virus RNA by multiplex reverse transcription-polymerase chain reaction and microtiter plate reverse hybridization].

Multiplex reverse transcription-polymerase chain reaction for the simultaneous detection of HCV and HGV RNA has been established, in which primers were deduced from high conservative region of HCV and HGV and PCR amplicons were detected by microtiter plate reverse hybridization with HCV or HGV specific probe. Sequence analyses showed that amplicons of HCV were 93.1%-94.1% and 92.5%-93.7% of nucleotide homology compared with Takamizawa and Choo, and amplicons of HGV were 90.7%-92.5%, 92.0%-92.1% and 94.3%-94.5% of nucleotide homology with Simons, Linnen and Chang. The detective sensitivity was 100 times over that of electrophoretic assay with single amplification. CVs of HCV and HGV were 8.9% and 9.8%, respectively, and the optimal concentration of NaOH for hybridization was 0.1-0.15 mol/L. The optimal time for hybridization was 30-50 minutes. The results of detection with multiplex PCR showed the presence of infection with HCV or HGV alone and coinfection with both % them.

DNA Probes↗