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Biomedical subjects

R Liu

Publications and source records attributed to R Liu.

At least 127 records · Page 7Linked to original sources
PubMed2000

Renal NO production and the development of hypertension.

The juxtaglomerular apparatus (JGA) has the very important functions of detecting the fluid flow rate to the distal tubule and thus controlling the glomerular filtration rate (GFR) (tubuloglomerular feedback mechanism [TGF]) and renin release from the afferent arteriole. In studies of the TGF it has been evident that the sensitivity of this mechanism can be reset. Volume expansion will reset it to a low sensitivity leading to a high GFR and urine excretion rate, while dehydration will sensitize the TGF mechanism, giving rise to a low GFR and low urine excretion rate. Furthermore, we have found that in animals that spontaneously develop hypertension there is initially a sensitization of the TGF, leading to a reduced GFR and urine excretion rate, with fluid volume retention in the body and a consequent rise in blood pressure. When the pressure is raised, the TGF characteristics are normalized. In the macula densa (MD) cells in the JGA, there is a large production of NO from neuronal NOS. This production continuously reduces TGF sensitivity and is apparently impaired in animals that spontaneously develop hypertension. When we added an nNOS inhibitor to the drinking water for several weeks while measuring blood pressure, we found an increase in blood pressure after 3-4 weeks of treatment. This effect was abolished by a high salt diet. From these investigations, it also appeared as if nNOS-derived NO inhibited renin release. Experiments have also indicated that NO may resensitize inhibited G-protein coupled purinergic receptors.

Animals↗
PubMed2000

Analysis of antiapoptosis activity of human GM-CSF receptor.

Human GM-CSF (hGM-CSF) induces proliferation and sustains the viability of a mouse IL-3-dependent lymphoid cell line BA/F3 that expresses the functional hGM-CSF receptor (hGMR). To reveal an antiapoptotic mechanism of hGM-CSF, we analyzed various apoptotic markers of BA/F3 cells in various conditions. Within 24 hours of factor depletion, caspase 3-like, but not caspase 1-like, enzyme activity and DNA fragmentation were augmented. Analysis with the tyrosine kinase inhibitor (genistein) and an MEK1 inhibitor (PD98059) on antiapoptosis activity indicates that the activation of either the genistein-sensitive signaling pathway or the PD98059-sensitive signaling pathway of the betac subunit may be sufficient to suppress apoptosis through hGMR. Because hGMR mutants (which activate JAK2 but neither STAT5 nor the MAPK cascade) have antiapoptotic activity in BA/F3 cells, the involvement of JAK2, excluding the molecules mentioned earlier, for antiapoptosis activity seems likely. Because the JAK2 inhibitor AG-490 suppressed the antiapoptotic activity of hGM-CSF, the essential role for JAK2 activation to maintain the viability is considered. Interestingly, hGMR mutants, which lack MAPK cascade activation, require a higher dose of hGM-CSF than that for wild-type hGMR. Because the expression level and affinity to hGM-CSF among wild-type hGMR and mutant hGMR are the same, we speculated that biologic response is determined by a combination of strength of various signaling events.

Apoptosis↗
PubMed2000

Altered gene expression in lymphocytes of patients with normal-tension glaucoma.

BACKGROUND: In glaucoma there is a loss of retinal ganglion cells. There is evidence that this loss can occur by apoptosis. The signal transduction leading to retinal ganglion cell apoptosis in glaucoma is not yet clear. The present study compares the gene expression in lymphocytes of normal tension glaucoma patients (NTG-patients) with the one of healthy controls. METHODS: Subtractive hybridization was used to compare mRNA in lymphocytes of six vasospastic NTG-patients with six age and sex matched healthy subjects. RESULTS: Genes coding for p53-protein, NTP (neural thread protein) and 20 S proteasome subunit XAPC7 were overexpressed, whereas those coding for XPGC (Xeroderma pigmentosum gene), the survivin protein as well as one type of ABC transport protein were underexpressed. CONCLUSION: In comparison to healthy controls, patients with vasospastic NTG seem to over- as well as under-express certain genes in their lymphocytes.

ATP-Binding Cassette Transporters↗
PubMed2000

Chemiluminescence underestimates nitric oxide concentration in the presence of potent inhalation anaesthetics.

We investigated the effect of potent inhalation anaesthetics on nitric oxide (NO) concentration measured by the chemiluminescence method. We found that the NO concentration was increasingly underestimated with increasing concentrations of halothane, isoflurane, enflurane and sevoflurane (r2 = 0.918-0.997, P < 0.01). Statistical analysis showed that the four inhalation agents at the same concentration produced a similar error in the measured NO concentration. In the presence of a fixed concentration of sevoflurane (5.0%), isoflurane (5.2%), enflurane (4.5%) or halothane (6.1%), the rate of reduction in the measured NO concentration increased in proportion to the NO concentration (r2 = 0.909-0.982, P < 0.01). No direct chemical interaction between the potent inhalation agents and NO was detected by gas chromatography-mass spectrometry. We conclude that NO concentration can be underestimated when measured by the chemiluminescence method in the presence of potent inhalation agents. This underestimation may result from emission absorption and/or the quenching phenomenon, but is not attributable to a chemical reaction between the inhalation agent and NO.

Analysis of Variance↗
PubMed2000

Isoflurane-sevoflurane adminstration before ischemia attenuates ischemia-reperfusion-induced injury in isolated rat lungs.

BACKGROUND: The effects of volatile anesthetics on ischemia-reperfusion (IR)-induced lung injury are not clear. The authors investigated the effects of preadministration of isoflurane and sevoflurane on IR-induced lung injury in an isolated buffer-perfused rat lung model. METHODS: Isolated rat lungs were designated into four groups: control group (n = 6): perfusion for 120 min without ischemia; IR group (n = 6): interruption of perfusion and ventilation for 60 min followed by reperfusion for 60 min; sevoflurane (SEVO)-IR (n = 6) and isoflurane (ISO)-IR (n = 6) groups: 1 minimum alveolar concentration (MAC) isoflurane or sevoflurane was administered for 30 min, followed by 60 min ischemia, then 60 min reperfusion. The authors measured the coefficient of filtration (Kfc) of the lung, lactate dehydrogenase (LDH) activity, tumor necrosis factor alpha, and nitric oxide metabolites (nitrite + nitrate) in the perfusate and the wet-to-dry lung weight ratio. RESULTS: IR caused significant increases in the coefficient of filtration (approximately sevenfold at 60 min of reperfusion compared with baseline; P < 0.01), the wet-to-dry lung weight ratio, the rate of increase of lactate dehydrogenase activity, and tumor necrosis factor a in the perfusate, and caused a significant decrease in nitric oxide metabolites in the perfusate. Administration of 1 MAC isoflurane or sevoflurane before ischemia significantly attenuated IR-induced increases in the coefficient of filtration and the wet-to-dry lung weight ratio, inhibited increases in the rate of increase of lactate dehydrogenase activity and tumor necrosis factor alpha in the perfusate, and abrogated the decrease in nitric oxide metabolites in the perfusate. No difference was found between the SEVO-IR and ISO-IR groups. CONCLUSION: Isoflurane and sevoflurane administered before ischemia can attenuate IR-induced injury in isolated rat lungs.

Anesthetics, Inhalation↗
PubMed2000

Exhaled nitric oxide level decreases after cardiopulmonary bypass in adult patients.

OBJECTIVE: To measure exhaled nitric oxide (NO) and compare it with lung function after cardiopulmonary bypass (CPB) in adult patients. Pulmonary dysfunction is sometimes observed after CPB. Impaired production of NO may account for this dysfunction. DESIGN: Prospective, single-center, observational study. SETTING: University hospital operating room, intensive care unit. PATIENTS: Sixteen adult patients undergoing cardiac surgery with CPB. INTERVENTIONS: None except cardiac surgery with CPB. MEASUREMENTS AND MAIN RESULTS: Exhaled NO was measured continuously by the chemiluminescence method and was expressed as the peak and mean NO concentrations, and the NO output (VNO). These parameters were calculated by averaging four sequential tidal NO values. The data were obtained serially from before CPB to 16 hrs after CPB. Lung function was evaluated by monitoring lung compliance, pulmonary artery pressure, and alveolar-arterial oxygen difference (P(A-a)O2). The cardiac index did not change except for a significant increase at 16 hrs compared with 6 hrs after CPB. Peak NO, mean NO, and VNO decreased from 15.4 +/- 2.0 ppb (before CPB) to 8.2 +/- 0.8 ppb (6 hrs after CPB), from 5.7 +/- 0.7 ppb to 2.8 +/- 0.6 ppb, and from 29.2 +/- 3.1 nL/min to 15.7 +/- 2.2 nL/min, respectively. These changes were associated with the increases in pulmonary artery pressure and alveolar-arterial oxygen difference, and the decrease in lung compliance. VNO recovered to the level measured before CPB 16 hrs after CPB, which was consistent with the physiologic recovery in pulmonary hypertension, lung compliance, and gas exchange. CONCLUSION: Measurement of exhaled NO as VNO, which was associated with lung dysfunction, may be an indicator of lung injury in adult patients after cardiopulmonary bypass.

Adult↗
PubMed2000

From the ECM to the cytoskeleton and back: how integrins orchestrate T cell action.

T lymphocytes constitute a highly dynamic tissue type. During the course of their lives, they travel through a variety of physiological environments and experience a multitude of interactions with extracellular matrix components and other cells. In order to do this, they must receive many environmental cues, and translate these signals into the appropriate biological actions. Particularly dramatic are the cytoskeletal shape changes a T cell must undergo during the processes of leaving the bloodstream, migrating through tissues, and encountering antigen. In this review, we highlight the role of integrins in providing a link between the extracellular environment and cytoskeletal regulation and how these receptors help to orchestrate T cell migration and antigen recognition.

Animals↗
PubMed2000

[The role of IL-1 beta and TNF-alpha in hyper-reactivity of neutrophils in rapidly progressive periodontitis patients].

OBJECTIVE: Neutrophils (PMNs) from rapidly progressive periodontitis (RPP) was found to generate abnormally high levels of oxygen radicals. Elastase activity in gingival crevicular fluid (GCF) from RPP was also found much higher. It suggested that PMNs in some RPP patients are hyper-reactive. The purpose of this study was to investigate the mechanism of PMN hyper-reactivity by surveying the correlation of TNF-alpha level with elastase activity in GCF and by evaluating the association between PMN infiltration and the expression of IL-1 beta and TNF-alpha in gingival tissues from RPP patients. METHODS: 41 GCF samples from 22 RPP patients and 34 GCF samples from 11 healthy controls were collected. The total amount of TNF-alpha in GCF was detected using ELISA. The elastase activity was measured with a low molecular weight substrate (S2484) specific for granulocyte. The correlation of TNF-alpha level with elastase activity in a GCF sample was analyzed with Spearman correlation. 20 gingival specimens were obtained respectively from 10 RPP patients and 5 periodontally healthy controls. The expression of IL-1 beta and TNF-alpha was detected with immunohistochemistry. The distribution of PMN was observed with hematoxylin and eosin staining. RESULTS: Total amount of TNF-alpha in GCF was positively correlated with elastase activity (r = 0.44, P < 0.05). The IL-1 beta- and TNF-alpha-positive cells in gingiva were superimposed in areas where PMNs infiltration predominant. CONCLUSION: The hyper-reactivity of PMN in RPP patients was related to locally produced IL-1 beta and TNF-alpha.

Adult↗
PubMed2000

[An epidemiological analysis on the relationship between road injury and traffic environment in China].

OBJECTIVE: To explore the influence of traffic environment on road injury so as to provide basis for prevention and control. METHODS: Principal component regression analysis was used to explain the relationship between road injury and the numbers of vehicle, capacity of road transport and mileage of rigid highway. RESULTS: Results showed a positive correlation between level of personal safety (LPS) and the numbers of vehicle, volume of road haulage, volume of passenger transport, mileage of rigid highway (correlation coefficients were 0.8714, 0.9691, 0.9611, 0.9510, P = 0.0005). The numbers of vehicle, volume of road haulage, volume of passenger transport and mileage of rigid highway were increasing when LPS decreased. Principal component regression analysis overcame multi collinearty of independent variables and obtained a regression equation y =-3.7197 + 1.49E-03X(1) + 5.2E-06X(3) + 6.19E-02X(4). CONCLUSION: The primary determinants of LPS were numbers of vehicle, volume of road haulage, volume of passenger and mileage of rigid highway. Road injury thus could be reduced through improving the traffic environment, strengthening the traffic administration as well as promoting traffic safety.

Accidents, Traffic↗
PubMed2000

[Clinical and experimental study on treatment of acute catarrhal otitis media with eryanling oral liquid].

OBJECTIVE: To study the clinical effect and mechanism of Eryanling (EYL) oral liquid in treating acute catarrhal otitis media (ACOM). METHODS: Sixty-eight cases (89 ears) of ACOM in the treated group were treated with EYL and compared with 34 cases (44 ears) in the control group treated with cephalexinum. Experimental study of effect of EYL on immune function in mice and non-suppurative otitis guinea pig was also conducted. RESULTS: The total effective rate of the treated group and the control group was 91.0% and 84.1% respectively, and their rate of curing 80.9% and 70.5% respectively, though the effect in the former was better, statistic analysis showed no significance between them. The effect initiated obviously earlier in the treated group than that in the control group. Results of experimental study suggested that EYL could strengthen the nonspecific immune function, cellular immune function and humoral immune function in mice, and reduce the degree of inflammatory exudation and mucosa swollen in guinea pig. CONCLUSION: EYL has good therapeutic effect in treating ACOM.

Acute Disease↗
PubMed2000

[Trannasal-transsphenoidal endoscopic surgery of the sphenoid sinus and the sella turcica].

OBJECTIVE: The primary objective of this study is reporting our experience with transnasal endoscopic technique to management of the sphenoidal and the sellar lesions. METHOD: Forty one patients were management under endoscope who suffered from pituitary adenomas, craniopharyngioma and sphenoidal lesions, et al. RESULTS: In forty one cases of the sphenoidal and the sellar lesions, thirty two surgeries were successful. One patient died of bleeding, five developed the foramen of nasal septum, the adhesion of nasal cavity was complicated in three patients. CONCLUSION: The endoscope has the advantage of improved visualization, angled view, and a wide panoramic perspective. The transnasal-transspheniodal endoscopic technique is a effective, minimally invasive approach. But there are its disadvantages and occurred severe complication. Surgeons should be understood its feasibility, limits and indication.

Adolescent↗
PubMed2000

[Hyperconjugation, characteristic infrared absorption of methylsulfones and crystal structures of selected aromaticsulfones].

A branched absorption peak with medium intensity at (970 +/- 20) cm-1 appears only in the infrared spectra of methylsulfones. The below mentioned aromaticsulfones are chosen to reveal the specificity. Crystal and molecular parameters of CH3CONH-C6H4-SO2R(R = -CH3, -CH2CH2OH)-CH2CONH2, are determined by application of single crystal diffraction of X-ray through Nicolet R3M/E diffracometer. The existence of hyperconjugation and its natures in group -SO2CH3, confirmed by further analyses on the parameters, result in the specificity of IR absorption of the group, which is proved characteristic and can be used to identify methylsulfones. The first part describes the detection results, ascertains their crystal and molecular structures, and shows that the aromaticsulfone exists as cross linking multi-molecules when R = -CH2CONH2 or as double molecules when R = -CH2CH2OH because of H bonds. The second part covers analyses on their molecular structures. The analyses demonstrate the hyperconjugation between sigma S-C and pi S-C in group -SO2CH3. The sigma C-H hyperconjugate with pi S-O. The strength of hyperconjugated bond C-H decreases and its length tends longer. Due to the effect, the bond S-C is not a pure single bond sigma, but one which possesses a certain degree of a double bond. Its IR wave number, between those of sigma S-C and pi S-C, attributes to the medium branched peak at (970 +/- 20) cm-1. The peak branch reflects two groups of the most stable hyperconjugating conformational isomers. The hyperconjugation is weakened by the substitution of one non H group for one H atom in -SO2CH3 and if the non H group does not conjugate with pi S-O, the absorption at (970 +/- 20) cm-1 disappears as a characteristic peak. The intensity of absorption at (970 +/- 20) cm-1 conforms to the intensity of hyperconjugation between pi S-O and its adjacent sigma C-H. The third part introduces syntheses of the products, crystal preparations and their detections through X-ray diffraction.

English Abstract↗
PubMed1999

Insights into the structure and substrate interactions of the P-glycoprotein multidrug transporter from spectroscopic studies.

The P-glycoprotein multidrug transporter is a 170-kDa efflux pump which exports a diverse group of natural products, chemotherapeutic drugs, and hydrophobic peptides across the plasma membrane, driven by ATP hydrolysis. The transporter has been proposed to interact with its drug substrates within the membrane environment; however, much remains to be learned about the nature and number of the drug binding site(s). The two nucleotide binding domains are responsible for ATP binding and hydrolysis, which is coupled to drug movement across the membrane. In recent years, P-glycoprotein has been purified and functionally reconstituted in amounts large enough to allow biophysical studies. The use of spectroscopic techniques has led to insights into both its secondary and tertiary structure, and its interaction with nucleotides and drugs. In this review, we will summarise what has been learned by application to purified P-glycoprotein of fluorescence spectroscopy, circular dichroism spectroscopy and infra-red spectroscopy.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Risk factors for meningioma in adults: a case-control study in northeast China.

A hospital case-control study of meningioma was conducted in Heilongjiang Province in northeast China between September 1989 and December 1996. It included 183 cases of newly diagnosed primary meningioma and 366 individually matched hospital controls with non-neoplastic and non-neurological disease selected from six major hospitals. Cases and controls were matched by sex, age and area of residence and interviewed in the hospital wards to obtain information on medical history, occupation and lifestyle. No association with liquor or beer consumption was apparent. Cigarette smoking was positively associated with meningioma risk in women but not in men. In women, compared with non-smokers, the adjusted OR for pack-years of smoking above the median (124) was 6.2 (CI 2.04-18.87). Both of these observations contrast with the results of a study of glioma in the same population, using similar methods. The risk of meningioma was positively associated with reported occupational exposure to lead, tin, cadmium and ionising radiation in both genders.

Adult↗
PubMed1999

Interaction of the P-glycoprotein multidrug transporter (MDR1) with high affinity peptide chemosensitizers in isolated membranes, reconstituted systems, and intact cells.

P-glycoprotein-mediated multidrug resistance can be reversed by the action of a group of compounds known as chemosensitizers. The interactions with P-glycoprotein of two novel hydrophobic peptide chemosensitizers (reversins 121 and 205) have been studied in model systems in vitro, and in a variety of MDR1-expressing intact tumor cells. The reversins bound to purified P-glycoprotein with high affinity (77-154 nM), as assessed by a quenching assay using fluorescently labeled purified protein. The peptides modulated P-glycoprotein ATPase activity in Sf9 insect cell membranes expressing human MDR1, plasma membrane vesicles from multidrug-resistant cells, and reconstituted proteoliposomes. Both peptides induced a large stimulation of ATPase activity; however, higher concentrations, especially of reversin 205, led to inhibition. This pattern was different from that of simple linear peptides, and resembled that of chemosensitizers such as verapamil. In both membrane vesicles and reconstituted proteoliposomes, 1-2 microM reversins were more effective than cyclosporin A at blocking colchicine transport. Reversin 121 and reversin 205 restored the uptake of [3H]daunorubicin and rhodamine 123 in MDR1-expressing cells to the level observed in the drug-sensitive parent cell lines, and also effectively inhibited the extrusion of calcein acetoxymethyl ester from intact cells. In cytotoxicity assays, reversin 121 and reversin 205 eliminated the resistance of MDR1-expressing tumor cells against MDR1-substrate anticancer drugs, and they had no toxic effects in MDR1-negative control cells. We suggest that peptides of the reversin type interact with the MDR1 protein with high affinity and specificity, and thus they may be good candidates for the development of MDR1-modulating agents to sensitize drug resistance in cancer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Purification and cloning of aggrecanase-1: a member of the ADAMTS family of proteins.

We purified, cloned, and expressed aggrecanase, a protease that is thought to be responsible for the degradation of cartilage aggrecan in arthritic diseases. Aggrecanase-1 [a disintegrin and metalloproteinase with thrombospondin motifs-4 (ADAMTS-4)] is a member of the ADAMTS protein family that cleaves aggrecan at the glutamic acid-373-alanine-374 bond. The identification of this protease provides a specific target for the development of therapeutics to prevent cartilage degradation in arthritis.

ADAM Proteins↗
PubMed1999

Expression of human alpha(1,3)fucosyltransferase antisense sequences inhibits selectin-mediated adhesion and liver metastasis of colon carcinoma cells.

The initial steps of leukocyte and tumor cell adhesion involve selectin receptor/ligand interactions. The selectin ligand components sialyl Lewis x and sialyl Lewis a are oncodevelopmental antigens involved in progression of adenocarcinoma. Interrupting biosynthesis of these surface glycans by inhibition of alpha(1,3)fucosyltransferase (FUT) gene expression is an attractive goal for functional and therapeutic studies. We report here the inhibition of E-selectin-mediated adenocarcinoma cell adhesion by stable transfection of antisense sequences directed at the human Lewis alpha(1,3/1,4)fucosyltransferase gene, FUT3. The metastatic parental cell line, HT-29LMM, expressed high levels of sialyl Lewis x, sialyl Lewis a, alpha(1,3/1,4)fucosyltransferase activity, and FUT3 transcript, but antisense transfectant cell lines did not. When injected into the spleens of nude mice, the stable antisense clones were unable to colonize the liver. These results provide target validation for inhibition of carcinoma metastasis with antisense FUT sequences and confirm the primacy of alpha(1,3)fucosyltransferases in the synthesis of selectin ligands.

Adenocarcinoma↗