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Biomedical subjects

G Wu

Publications and source records attributed to G Wu.

At least 541 records · Page 30Linked to original sources
PubMed1994

Autoperfused heart-lung preparation: one reason for unsuccessful lung preservation.

Normothermic autoperfused heart-lung preparation has the advantages of avoiding ischemic time and allowing continuous monitoring of organ function during preservation. When this technique is used, the lungs deteriorate quickly, but the reasons for this deterioration have not been investigated. This study was designed to explore the possible cause of rapid lung deterioration. Three groups of mongrel dogs were used. In Group 1 (N = 5), a buffer bag was used in the heart-lung preparation. In Group 2 (N = 6), a 20 mu filter was incorporated between the buffer bag and the right atrium. In Group 3 (N = 5), no buffer bag was used. Average survival time was 15.0 +/- 3.1 hours in Group 1, 13.5 +/- 0.7 hours in Group 2, and 21.6 +/- 2.3 hours in Group 3. Heart function was comparable among the three groups, but the arterial pulse pressure was lower and the heart rate higher in Group 3. Both white blood cell and platelet counts decreased contonuously during the preservation period. Examination of the filters in Group 2 revealed numerous aggregates consisting of platelets, white blood cells, red blood cells, and fibrin. Small thrombi were also found in the lungs in Groups 1 and 2. The results indicated that one important reason for quick lung deterioration was numerous aggregates, which were formed in the buffer bag, returned from the venous line, and trapped in the lungs. Removal of the buffer bag reduced the production of aggregates but tended to de-stabilize the hemodynamics of the preparation.

Animals↗
PubMed1994

Two-day preservation of the lungs by normothermic perfusion.

Lung function was studies during a 2-day preservation period. The lungs were removed along with the heart, liver, pancreas, duodenum, and both kidneys while they were still perfused by the heart and oxygenated by the lungs. In 12 experiments the organs survived an average of 49.2 hours. Arterial blood pressures were maintained at 74-95 mmHg, and no inotropic drugs were used. When a gas mixture of 50% O2 + 3% CO2 + 47% N2 was used, arterial oxygen tension ranged from 239 +/- 23 to 305 +/- 16 mmHg; carbon dioxide tension ranged from 17.6 +/- 1.8 to 24.9 +/- 2.9 mmHg; and pH ranged from 7.31 +/- 0.03 to 7.49 +/- 0.04. Maximum airway pressure ranged from 12.5 +/- 1.7 to 28.0 +/- 2.2 mmHg. Airway resistance ranged from 0.020 +/- 0.006 to 0.049 +/- 0.007 mmHg/ml and increased after 40 hours. Lung tissue wet/dry weight ratio was stable during the preservation period. The results showed that the lungs were well preserved in the normothermic perfusion preparation for up to two days with minimal functional changes.

Airway Resistance↗
PubMed1994

Effect of glutathione on hypothermic lung preservation.

Three groups of rats were used to test the effect of glutathione in hypothermic lung preservation. In the Normal Group (N = 8), lung function was studied immediately after removal without preservation. In the Euro-Collins (EC) Group (N = 8), the lungs were flushed with cooled Euro-Collins solution and preserved in EC solution for 24 hours. In the glutathione (GSH) Group (N = 8), glutathione (3 mM/L) was added to cooled Euro-Collins solution for perfusion and preservation. Lung function studies were performed by using living donor rats for perfusion. Venous blood from the host rat perfused the isolated lung, and the blood returned from the lung was pumped back into the internal carotid artery of the host rat. Oxygen tension in the returned blood (PvO2) in the Normal Group was higher than that in either the EC Group or the GSH Group. Pulmonary vascular resistance and airway resistance were much lower in the Normal Group than in the EC Group and GSH Group. Lung tissue wet/dry weight ratio after perfusion was 6.25 in the Normal Group, which was lower than that in the GSH Group (8.69, p < 0.05) and much lower than that in the EC Group (6.82, p < 0.05). Severe pulmonary edema and hemorrhage occurred after 30 minutes of perfusion in the EC Group, whereas a 60-minute perfusion was performed in the Normal and GSH Groups. The results indicated that rat lungs were better preserved with glutathione, but the effect was not dramatic.

Airway Resistance↗
PubMed1994

[Effect of indirect fluorescent antibody test for the diagnosis of amoebiasis].

Indirect fluorescent antibody test (IFAT) was performed by the method of [symbol: see text] (1971) with some slight modifications for the diagnosis of amoebiasis. The antigen used was prepared from 48-hour culture of Entamoeba histolytica (strains G2, G3, and G5) in LAS diphasic medium and only those amoebae clinging the culture were collected. The serum samples or blood drops on filter paper were positive by the improved IFAT in all of the 54 cases of amoebic liver abscess and the positive reactions of most cases were very marked. Of 23 cases of acute amoebic dysentery, 19 were positive, the positive rate being 82.6%. The results also show that 42 cases of other diseases and 40 healthy persons were all negative.

Animals↗
PubMed1994

[Studies on natural foci of tsutsugamushi disease of the autumn-winter type in Jiangsu].

Before 1986, tsutsugamushi disease was known only prevalent in south to Zhejiang Province in our country, belonged to the summer type and Leptotrombidium (L.) deliense was regarded as the main vector. In October 1986, the authors found this disease in Nanjing and carried out a series of studies in 1986-1992. The results were as follows: Tsutsugamushi disease was epidemic in Nanjing and north of Jiangsu (including: Dongtai, Haian, Rudong, Jinhu, Hanjiang, Jiangdu); belonged to the autumn-winter type; the main reservoir hosts were Apodemus agrarius, Rattus confucianus, R. norvegicus and Crocidura lasiura; the transmitting vector was L. (L.) scutellare; the pathogen of tsutsugamushi disease of the autumn-winter type-Rickettsia tsutsugamushi belonged to low-virulent strain, and could not easily be detected; after the inoculated mice were treated with diluted cyclophosphamide solution, 14 strains of R. tsutsugamushi have been isolated from rats, mites and patients; serological typing of their sera showed that they belonged to the Gilliam type; natural foci in Jiangsu could be divided into two types--flat land and hilly land.

Animals↗
PubMed1994

Ethanol stabilizes the open channel state of the Torpedo nicotinic acetylcholine receptor.

Ethanol is known to cause a leftward shift of the acetylcholine concentration-response curve for channel opening of the nicotinic acetylcholine receptor (nAcChoR). However, it remains uncertain whether the mechanism underlying ethanol's effect is an increase in the binding affinity of the agonist to the receptor or an increase in the open/closed equilibrium for those receptors occupied by agonist. In the present study, this question was resolved by measuring the efflux of 86Rb+ over 9 msec from Torpedo vesicles after rapid mixing with the partial agonist suberyldicholine with or without ethanol as appropriate. Suberyldicholine's concentration-response curve is bell-shaped. Two actions underlie this bell-shaped curve, namely activation at low concentration (apparent dissociation constant for activation, Ka = 38 microM) and self-inhibition at higher concentration (apparent dissociation constant for inhibition, Kb = 9 mM), but the overlap of these two actions only reduces the maximum observable flux by 20%. Increasing ethanol concentration from 0 to 0.9 M causes: a linear increase in the maximum response of the nAcChoR to suberyldicholine from 5 to 80% of the maximum induced by acetylcholine, a moderate increase in Ka, and no change in Kb. Analysis of our results using the sequential two-site binding model revealed that the main action of ethanol on nAcChoR was to increase the fraction of occupied receptors that open. The equilibrium constant describing this effect changed by 8-fold at anesthetic concentrations. Ethanol also decreased the affinity of suberyldicholine for its self-inhibition site by a comparable amount, suggesting that its main action is to stabilize the open state. In addition, ethanol caused a small increase in suberyldicholine's affinity for the agonist site.

Animals↗
PubMed1993

The activation of the arginine-citrulline cycle in macrophages from the spontaneously diabetic BB rat.

The activity of the arginine-citrulline cycle was investigated in macrophages from the spontaneous immunologically mediated diabetic BB rat. Peritoneal macrophages were prepared from male diabetes-prone (BBdp), diabetic (BBd) and age-matched non-diabetes-prone (BBn) rats. Cells were incubated at 37 degrees C for 2 h in Krebs-Henseleit bicarbonate buffer containing 0.5 mM L-arginine, 0.1 mM L-[ureido-14C]citrulline and 5 mM D-glucose to measure the activity of the arginine-citrulline cycle. The uptakes of citrulline and arginine by macrophages were measured during a 5 min incubation period with L-[ureido-14C]citrulline and L-[2,3-3H] arginine respectively. The production of NO3- (the major stable oxidation product of NO) increased (P < 0.01) by 112% and 151% in 75-day-old BBdp and 115-day-old BBd macrophages respectively, compared with age-matched BBn cells. The conversion of [14C]citrulline into [14C]arginine increased (P < 0.01) by 704%, 892% and 904% in 50- and 75-day-old BBdp and 115-day-old BBd macrophages respectively, compared with age-matched BBn cells. The enhanced NO synthesis in BBdp and BBd macrophages was associated with a 25-35% increase in the uptake of L-arginine. However, there were no differences in the uptake of citrulline between BBdp or BBd macrophages and age-matched BBn cells. Our results demonstrate for the first time the activation of the arginine-citrulline cycle in macrophages in an autoimmune condition. The inherent increase in the recycling of L-citrulline to L-arginine in BBdp and BBd macrophages may reflect an innate metabolic disorder in these cells. This increased L-arginine synthesis from L-citrulline may play a role in sustaining a sufficient intracellular L-arginine concentration for prolonged generation of NO in BBdp and BBd macrophages. A role for NO in the autoimmune destruction of pancreatic beta-cells in insulin-dependent diabetes mellitus warrants further investigation.

Animals↗
PubMed1993

Immunohistochemical localization of parathyroid hormone-related protein in human prostate cancer.

Parathyroid hormone-related protein (PTHrP) is produced by a variety of malignant tumors and has been implicated as a major cause of humoral hypercalcemia of malignancy. Expression of PTHrP in prostate cancer tissue was studied immunohistochemically using 33 radical prostatectomy specimens from patients with clinically localized carcinoma of the prostate. None of these patients demonstrated hypercalcemia prior to the surgery. Acetone-methyl benzoate-xylene-processed, paraffin-embedded tissues were stained with a validated mouse monoclonal antibody to an amino acid fragment, PTHrP(109-141), using the streptavidin-peroxidase enzyme conjugate method. All cases (33 of 33; 100%) studied demonstrated some degree of immunoreactivity throughout the cytoplasm of the tumor cells, but immunostaining was absent from inflammatory and stromal cells. The intensity of the staining appeared to directly correlate with increasing tumor grade. The widespread immunohistochemical localization of PTHrP in carcinoma of the prostate suggests that PTHrP may play some local role in the growth of transformed cells in the prostate. Furthermore, overexpression of PTHrP may be a possible marker to evaluate the malignant potential of carcinoma of the prostate.

Aged↗
PubMed1993

Phospholipid asymmetry and transmembrane diffusion in photoreceptor disc membranes.

The phospholipid asymmetry and flip-flop rate in rod outer segment (ROS) disc membranes has been investigated by both a spin-label reduction method and a novel electron-electron double resonance (ELDOR) method. At 39 degrees C in the absence of ATP, spin-labeled derivatives of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) undergo rapid transmembrane diffusion, with a half-time of less than 10 min. At equilibrium, approximately 53% of the spin-labeled PC, 37% of the spin-labeled PE, and 18% of the spin-labeled PS reside in the inner (intradiscal) monolayer. The rapid transmembrane diffusion of phospholipids is partially inhibited by N-ethylmaleimide, suggesting that the process is mediated by proteins in the disc membrane.

Animals↗
PubMed1993

Ganglioside composition of subcellular fractions, including pre- and postsynaptic membranes, from Torpedo electric organ.

Gangliosides were isolated from four subcellular fractions of the electric organ of Torpedo marmorata: synaptosomes, presynaptic membranes, postsynaptic membranes, and synaptic vesicle membranes. This exploited a principal advantage offered by this tissue: facile separation of pre-and postsynaptic elements. Total ganglioside concentration in presynaptic membranes was approximately twice that of synaptosomes and 15 times that of postsynaptic membranes (47.7, 24.4, and 3.21 micrograms of lipid sialic acid per mg protein, respectively). Synaptic vesicle membranes had the highest overall concentration (78.9) relative to protein, but a concentration approximately comparable to that of presynaptic membranes when expressed relative to phospholipid. The thin-layer patterns of these two fractions were similar, both in terms of total pattern and the specific pattern of gangliotetraose structures as revealed by overlay with cholera toxin B subunit; these were notable for the paucity of monosialo structures and the virtual absence of GM1. Postsynaptic membranes, on the other hand, had a significantly higher content of monosialogangliosides including the presence of GM1. The synaptosomal pattern resembled that of the presynaptic membranes and synaptic vesicles. Thus, a clear difference in ganglioside pattern could be discerned between the pre- and postsynaptic elements of the electric organ.

Animals↗
PubMed1993

Replication of satellite RNA in vitro by homologous and heterologous cucumoviral RNA-dependent RNA polymerases.

The RNA-dependent RNA polymerases (RdRp) of cucumber mosaic virus (CMV) and peanut stunt virus (PSV), members of the cucumovirus group, have been purified from virus infected plants and were used to study RNA synthesis in vitro using different viral RNAs, two cucumoviral satellites, and chimeric satellite cDNA clone transcripts as templates. The results show that solubilized RdRp preparations of CMV and PSV have a high degree of template dependency and catalyze (-) strand synthesis of the homologous cucumoviral RNAs with greater efficiency than the RNAs of heterologous cucumoviruses, although the PSV RdRp exhibits a lesser specificity than the CMV RdRp. On the other hand, both (-) and (+) strands of the satellite RNAs of CMV and PSV are synthesized by their homologous but not by the heterologous viral RdRps, indicating that recognition of satellites by the viral RdRp determines their replicative dependence upon specific helper viruses. Cucumoviral RdRp reactions using chimeric satellite transcripts suggest that the promoter structure for the satellite (-) strand synthesis resides in regions harboring the 3' termini of the two satellites.

Base Sequence↗
PubMed1993

Manganese-based liposomes. Comparative approaches.

RATIONALE AND OBJECTIVES: The purpose of this study was to further develop and compare manganese-based liposomes prepared by two different approaches wherein a manganese ion was entrapped within the internal aqueous space of the vesicles or into the bilayer surface via membrane bound complexes. METHODS: Small unilamellar liposomes (SUVs) were prepared entrapping manganese chloride. Alkylated complexes of manganese were prepared and also incorporated into SUVs. The two different manganese-based liposomes were compared for in-vitro relaxivity, stability, toxicity, and in-vivo imaging in rats with liver tumors. RESULTS: Liposomes entrapping manganese had a concentration-dependent change in relaxivity that was maximal at a several-fold molar excess of phospholipid relative to manganese ion. Liposomes bearing membrane-bound complexes showed relaxivity inversely proportional to vesicle size. In-vivo imaging showed greater and more specific hepatic enhancement with manganese liposomes bearing alkylated complexes than those entrapping manganese ion. CONCLUSIONS: Correlation effects likely explain the increased relaxivity of manganese entrapped in phospholipid vesicles. Greater efficacy, however, is afforded by liposomes bearing alkylated complexes.

Animals↗
PubMed1993

Radioimmunoimaging of experimental arterial and venous thrombi in dogs with 99Tcm-labelled monoclonal anti-activated platelet antibody SZ-51.

In canine experimental models of femoral arterial and venous thrombosis, the feasibility of thrombus imaging with 99Tcm-labelled monoclonal antibody SZ-51 to an alpha-granule membrane protein (GMP-140) on the surface of activated platelets was investigated. Both the arterial and venous thrombi were clearly discernible at 2 to 8 h after injection of 99Tcm-SZ-51. The suitable imaging time was 4 to 6 h. These results were confirmed by ex vivo images of thrombosed arteries and veins followed by killing the dogs at 8 h postinjection of 99Tcm-SZ-51. Quantitative imaging analysis showed that the ratios between the thrombus and the opposite vessel were increased strikingly over time. The ratios of thrombus to blood or surrounding muscle were 57.09 +/- 12.24 and 177.46 +/- 9.00 for arterial thrombi and 6.43 +/- 4.70 and 83.22 +/- 68.98 for venous thrombi at the time of death. Radiolabelled antibody was cleared from the blood with T1/2 alpha of 16.25 +/- 13.39 min and T1/2 beta of 7.28 +/- 1.15 h. These results show that it is feasible to detect noninvasively thrombus formation in vivo using 99Tcm-labelled monoclonal antibody SZ-51.

Animals↗
PubMed1993

Tomato necrosis and the 369 nucleotide Y satellite of cucumber mosaic virus: factors affecting satellite biological expression.

To determine which factors can affect biological expression of the Y satellite RNA of cucumber mosaic virus (CMV) in tomato, three laboratories collaboratively exchanged their natural satellite variants, the corresponding recombinant DNA clones and helper virus strains, as well as tomato varieties, on which different observations previously reported were based. The effects of these materials and the influence of temperature on symptom expression were systematically studied. The results show that in a standardized tomato bioassay at 24 degrees C, the Y satellite, when supported by either CMV-1 or CMV-Y, did not induce tomato necrosis in the Rutgers variety but elicited a slower necrotic response in the Best of All variety that was variably lethal, as compared to the faster inevitably lethal response induced by a prototype necrogenic D satellite variant in both tomato varieties. At higher temperatures (26.5 to 32 degrees C) an extremely fast-killing necrosis caused by CMV-Y itself was observed. The study demonstrates that in experiments on virus symptom modulation induced by CMV satellites, the nature of the helper virus, host plant varieties, as well as the environmental conditions should be precisely defined, and the effects of each parameter change determined separately.

Mosaic Viruses↗
PubMed1993

Mutants of Escherichia coli affected in respiration: the cloning and nucleotide sequence of ubiA, encoding the membrane-bound p-hydroxybenzoate:octaprenyltransferase.

A mutant of Escherichia coli has been isolated that is unable to grow aerobically on non-fermentable substrates, but able to grow anaerobically on glycerol with alternative electron acceptors such as fumarate. Nitrate as electron acceptor supports anaerobic growth on glycerol, but not on succinate or lactate. Oxygen consumption rates by cell-free extracts with succinate, lactate or glycerol 3-phosphate as substrates were low relative to activities in an isogenic control strain but were restored in vitro by adding ubiquinone-1. Transformation of the mutant with a cloned 2.6 kb ClaI-PvuII fragment of chromosomal DNA restored cellular quinone levels and growth on succinate. The plasmid also complemented a previously isolated ubiA mutant for aerobic growth on non-fermentable substrates. The nucleotide sequence of the cloned fragment revealed a fragment of plsB (91.7 min on the E. coli chromosome map) and three open reading frames (ORFs), one of which (ORF3) encodes a protein with a predicted molecular mass of 32511 Da. The hydrophobicity profile of the ORF3 protein is characteristic of a membrane protein with five hydrophobic regions and is very similar to that of the Saccharomyces cerevisiae COQ2 gene product (p-hydroxybenzoate:polyprenyltransferase, required for the second step of ubiquinone biosynthesis) and to the product of the E. coli cyoE gene. Complementation of ubi mutants with various deletion derivatives of the cloned DNA fragment confirms that ORF3 is ubiA. ORF3 is closely linked to ubiC (ORF2), which encodes chorismate lyase.

Alkyl and Aryl Transferases↗
PubMed1993

The kinematometer--an integrated kinematic sensor for kinesiological measurements.

The calculation of human joint forces and moments during locomotion is usually based on the solution of the "inverse dynamics problem." A new approach, called the Integrated Kinematic Sensor (IKS) approach, is proposed. It combines measurements of position, linear acceleration and angular velocity, coupled with six degrees of freedom analysis of rigid body motion, for the purpose of deriving high quality link kinematics and joint loads (force and moment) estimates. The IKS approach is tested on an instrumented compound pendulum to simulate the swing of a lower limb segment. The results show a high degree of correlation between the loads estimated by the IKS and those directly measured by the instrumented joint. The approach is illustrated by studying the kinematic and dynamic variables of the human shank segment during normal walking. The results agree with the basic patterns reported in the literature, while adding new information on transients during heel strike and toe off.

Acceleration↗
PubMed1993

Regulation of L-arginine synthesis from L-citrulline by L-glutamine in endothelial cells.

L-Arginine synthesis from L-citrulline was studied in cultured bovine venular, bovine aortic, human microvascular, and cloned human microvascular endothelial cells (EC). L-Citrulline was actively recycled into L-arginine in all four EC lines, with similar rates between venular and aortic EC. L-Arginine synthesis from L-citrulline was very sensitive to extracellular L-citrulline concentrations in the range normally found in plasma (50-100 microM). L-Glutamine (0.5mM) decreased L-arginine synthesis from L-citrulline, whereas 0.5 mM L-arginine, L-alanine, L-glutamate, or L-lysine had no effect. In contrast to the findings in intact cells, 1 mM L-glutamine had no effect on L-arginine synthesis from L-citrulline in EC lysates. Similarly, L-glutamine (1 mM) had no effect on the conversion of argininosuccinate to arginine in EC lysates. L-Glutamine (0.5 and 1 mM), but not 0.5 mM L-arginine, L-alanine, L-glutamate, or L-lysine, inhibited L-citrulline transport by EC. The inhibition of L-citrulline transport by L-glutamine was dose dependent and competitive in nature. These results suggest that L-glutamine decreased L-arginine synthesis from extracellular L-citrulline by interfering with its transport. Inasmuch as nitric oxide (NO) and L-citrulline are constantly generated from L-arginine, with L-citrulline being actively converted into L-arginine in venular, microvascular, and aortic EC, our data indicate a functioning intracellular arginine-citrulline cycle in these cells. This cycle may function to efficiently scavenge the carbon and alpha-amino group of L-arginine and to maintain a sufficient cellular concentration of L-arginine during prolonged synthesis of NO in EC. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗