Search PubMed⌕ Search

Biomedical subjects

W Lu

Publications and source records attributed to W Lu.

At least 361 records · Page 20Linked to original sources
PubMed1992

Relationship between frequency of infectious human immunodeficiency virus type 1-harboring cells and kinetics of viral replication: a simple procedure for quantitation of infectious virus-carrying cells in blood samples.

Statistical analysis of a limiting dilution assay (LDA) showed that the occurrence of infectious human immunodeficiency virus type 1 (HIV-1)-harboring cells in serially diluted samples of peripheral blood mononuclear cells (PBMCs) of HIV-1-seropositive patients fits the model describing a single-hit Poisson distribution. This observation led to the discovery that there is a direct correlation (r = 0.957) between the number of HIV-1-positive cells and the time when viral culture produces 1 ng of the HIV-1 p24 gag protein per ml. Frequency estimates based on this relationship were highly accurate (P less than 0.01) within the first 15 days of viral culture, which consisted of coculture of 10(6) normal PBMCs with the equivalent number of test PBMCs. This approach was less cumbersome than LDA and was sensitive enough to detect a single infectious HIV-1-harboring cell among as many as 320,000 cells. The values obtained for 57 patients agreed well with the data in the literature and showed that the frequencies of infectious cells in PBMCs reflect the advancement in the clinical stage, being 1/38,000, 1/11,000, and 1/7,000 for asymptomatic patients (Centers for Disease Control [CDC] group II/III), patients with AIDS-related complex (CDC group IVa), and patients with AIDS (CDC group IVb/c), respectively. A nearly 10-fold disparity in mean frequencies was observed when these values were correlated with the numbers of CD4-positive cells (1/9,000, 1/1,500, and 1/300, respectively, for asymptomatic patients, patients with AIDS-related complex, and patients with AIDS). The described method provides a simple means of determining infectious HIV-1-positive cells in blood samples.

HIV Infections↗
PubMed1992

Similar replication capacities of primary human immunodeficiency virus type 1 isolates derived from a wide range of clinical sources.

Numerous studies have suggested that there are significant differences in replication capacities and cytopathicities among human immunodeficiency virus type 1 (HIV-1) isolates and that these differences correlate with the clinical status and geographical origin of infected individuals. However, it has been difficult to assess whether reported distinctions could be attributed to the methods used or whether they imply a true disparity between viral isolates. We thus attempted to characterize the replication properties of HIV-1 isolates directly recovered from infected patients (primary isolates) by using a standardized infection assay. Viruses were isolated from patients' peripheral blood mononuclear cells (PBMC) by a single coculture with normal donor PBMC stimulated with phytohemagglutinin. Replication curves and cytopathic effect of a standard inoculum (1 ng of p24) of 66 primary HIV-1 isolates were similar regardless of clinical stage of the patient (asymptomatic, AIDS-related complex, or AIDS) and evolutive feature (rate of progression to AIDS). There was no difference between viruses derived from patients sensitive to zidovudine and those derived from patients resistant to zidovudine. Moreover, no difference was found among viral isolates of different geographical origins (Central Africa, Zaire, Brazil, or France). Similarly, the replication patterns and cytopathicities of isolates from bronchoalveolar lymphocytes did not differ from those of isolates derived from PBMC. In contrast, the same amount of viral inoculum of five laboratory HIV-1 strains (HIV-1, EL1, SF, MN, and RF) produced different replication curves and were much less cytopathic. In contrast to laboratory viral strains, it appears that the primary HIV-1 isolates tested, whatever their clinical status and source, exhibited similar replication capacities and cytopathicities in allogeneic donor PBMC.

AIDS-Related Complex↗
PubMed1992

Endothelial dysfunction of hindquarter resistance vessels in experimental heart failure.

Local vascular alterations may contribute to increased peripheral vasoconstriction in chronic heart failure. To test whether endothelial dysfunction might be involved, the effect of acetylcholine, nitroglycerin, and NG-monomethyl-L-arginine (L-NMMA) was investigated in a constant-flow perfused hindquarter of rats with and without chronic heart failure (CHF) due to myocardial infarction. Changes in perfusion pressure were measured as an index of changes in hindlimb vascular resistance. The endothelium-dependent vasodilator effect of acetylcholine was significantly reduced in rats with large infarcts (greater than 40% of the left ventricle). However, the endothelium-independent vasodilator effect of nitroglycerin and the vasoconstrictor effect of L-NMMA were similar for infarct and normal animals. The vasodilator response to acetylcholine was partially inhibited by pretreatment with L-NMMA. Thus the basal release of nitric oxide from hindquarter resistance vessels is preserved in CHF. However, the endothelium-mediated dilation in response to acetylcholine is attenuated, in part, due to a depressed stimulated release of nitric oxide. The latter mechanism might be involved in the impaired vasodilatory capacity in the peripheral circulation in CHF, e.g., during exercise.

Acetylcholine↗
PubMed1992

Platelet factor 4 efficiently reverses heparin anticoagulation in the rat without adverse effects of heparin-protamine complexes.

BACKGROUND: It has been observed that the reversal of heparin anticoagulation in humans by protamine sulfate (PS) results in various adverse reactions including leukopenia, thrombocytopenia, activation of complement, increased vascular permeability, systemic hypotension, pulmonary vasoconstriction, and pulmonary edema. The purpose of this study was to compare the efficacy and effects of native platelet factor 4 (PF4) and recombinant platelet factor 4 (rPF4) with those of PS in heparin neutralization in vivo, using a rat model. METHODS AND RESULTS: Sprague-Dawley rats were anesthetized with sodium pentobarbital, and the right femoral vein and carotid artery were cannulated. For determination of activated partial thromboplastin time, platelet count, white blood cell count, and complement titer, arterial blood samples were taken before and immediately after heparin (10 units/100 g) infusion and at several time points after the infusion of the neutralizing agent (PS, 0.1 mg/100 g; PF4, 0.5 mg/100 g). In separate groups of animals, mean arterial blood pressure was monitored throughout identical protocols and the lungs were prepared for histological examination. The anticoagulant activity of heparin was effectively reversed by all of the neutralizing agents (PS, PF4, and rPF4). Platelet count (48% of initial), white blood cell count (52% of initial), complement titer (60% of initial), and mean arterial pressure (20% decrease) decreased significantly in heparinized animals receiving PS but not in those receiving PF4 or rPF4. Lung interstitium appeared normal when heparin was followed by PF4; however, interstitial edema and hemorrhage were observed with heparin-PS. CONCLUSIONS: These results suggest that PF4 efficiently reverses heparin anticoagulation in the rat without the adverse effects of heparin-protamine complexes. Therefore, rPF4 may be an appropriate substitute for PS in patients undergoing cardiovascular surgery and other procedures that require heparin anticoagulation.

Animals↗
PubMed1992

Effects of inhibition of nitric oxide formation on regional blood flow in experimental myocardial infarction.

BACKGROUND: Large myocardial infarction is associated with reactive hypertrophy and dilation of the left ventricle, depressed coronary flow reserve, and the development of heart failure including systemic vasoconstriction. We hypothetized that changes in endothelial function, e.g., in the synthesis or action of nitric oxide in the coronary and peripheral vasculatures, might be involved in the depressed coronary flow reserve and increased systemic vascular resistance observed in postinfarction myocardial hypertrophy and failure. METHODS AND RESULTS: The regional blood flow changes that occur as a result of inhibiting the basal release of nitric oxide with NG-monomethyl-L-arginine (L-NMMA) and how this regional pattern may be altered in large MI (infarct size, 30-51% of left ventricle) were examined. Measurements were made 24 hours and 8 weeks after myocardial infarction or sham operation in conscious rats. The left ventricular end-diastolic pressure and effects of L-NMMA on left ventricular end-diastolic pressure was similar 24 hours and 8 weeks after myocardial infarction. The effects of L-NMMA (30 mg/kg i.v.) on heart rate and blood pressure were similar in infarcted and sham animals. L-NMMA exerted a marked vasoconstriction in the renal, splanchnic, cutaneous, and cerebral circulations of similar magnitude in sham-operated rats and animals with myocardial infarction. The coronary vasoconstrictor effect of L-NMMA was attenuated significantly in the hypertrophied right and noninfarcted left ventricle of 8-week-old infarcted rats (p less than 0.01 versus sham-operated animals) but not 24 hours after induction of myocardial infarction when cardiac hypertrophy has not yet developed. The increase in left ventricular coronary resistance in 8-week-old infarcted animals was inversely related to infarct size (r = -0.787, p = 0.012, n = 9). Nitroglycerin exerted similar increases in coronary blood flow in rats with chronic myocardial infarction and sham-operated animals, arguing against a reduced vascular responsiveness to nitric oxide. Transmission electron microscopy of coronary resistance vessels in 8-week-old infarcted animals did not reveal endothelial abnormalities. CONCLUSIONS: These data suggest that the basal release of nitric oxide in the renal, intestinal, and cutaneous circulations is not affected adversely in this model of myocardial infarction and failure. However, the blunted coronary vasoconstrictor effect of L-NMMA late after large myocardial infarction supports the view that the basal release of nitric oxide is impaired in postinfarction reactive cardiac hypertrophy.

Animals↗
PubMed1992

Research on the main elements influencing blood pressure measurement by pulse wave velocity.

There have been considerable errors in non-invasive continuous beat-by-beat blood pressure (BP) measurement using the pulse wave velocity (PWV). To solve the problem, an in vivo study using 10 dogs was performed. The PWV-BP correlation under intact neuro-humoral factors was compared with that under the factors to be partly eliminated and the PWV-BP regularities were investigated using 10-beat average data. It was confirmed that the vasomotion and the viscoelasticity of vascular smooth muscles are the main elements influencing PWV-BP correlation through changing the elasticity of the arterial wall, and result in a 'shift' and 'zigzag swings' in the PWV-BP relationship so as to lower the PWV-BP correlation. By choosing large arteries and modifying the PWV algorithm, linear correlation coefficients of 0.97 +/- 0.027 and standard errors of the BP estimate of 5.29 +/- 2.84 mm Hg were obtained. The study suggests that the error could be further reduced by simultaneously measuring some related parameters.

Animals↗
PubMed1992

Protection of platelets during long-term extracorporeal membrane oxygenation in sheep with a single dose of a disintegrin.

BACKGROUND: Both short- and long-term extracorporeal membrane oxygenation (ECMO) causes platelet loss and dysfunction. Bitistatin is a reversible inhibitor of the platelet glycoprotein IIb/IIIa receptor. This study tests the hypothesis that inhibition of platelets by bitistatin during initial contact with the perfusion circuit preserves platelet number and function during long-term ECMO in sheep. METHODS AND RESULTS: Bitistatin, purified from crude snake venom, was tested for its effect on platelet count, responsiveness to ADP, release of platelet factor 4, and prevention of surface-adsorbed glycoprotein IIIa in vitro and during 24 hours of ECMO in nine splenectomized sheep. During simulated extracorporeal circulation, 0.5-1.0 microgram/ml bitistatin significantly prevented platelet adhesion, attenuated release of sheep platelet factor 4, and preserved platelet responsiveness to ADP. During ECMO at 1.8 l/min for 24 hours, a single dose of bitistatin (200 micrograms/kg) (n = 4) produced higher platelet counts (p = 0.0002) and suppressed release of platelet factor 4 (p = 0.035) for 16 hours compared with five control animals. This dose of bitistatin caused an immediate inhibition of platelet aggregation; however, between 4 and 24 hours of perfusion, platelets of bitistatin-treated animals were more responsive to ADP (p < 0.0001) compared with platelets in control animals. The amount of glycoprotein IIIa antigen extracted by Triton X-100 from the perfusion circuits was reduced in bitistatin-treated sheep. CONCLUSIONS: A single dose of bitistatin given before blood contact with the ECMO circuit briefly inhibits platelet adhesion and aggregation but thereafter preserves platelet numbers and function and suppresses alpha-granule release for 12-16 hours of ECMO.

Adenosine Diphosphate↗
PubMed1992

[Clinical analysis of fluid resuscitation in severe burned patients with or without inhalation injury].

The amount of fluid resuscitation, estimated according to crystal-colloid for formula, were retrospectively studied in 55 cases of severe burned patients with or without inhalation injury. These cases were divided into two groups. One group consisted of patients with inhalation injury, while the another there was no inhalation injury. The result showed that patients in the former required 13.5% additional amount of fluids over the latter in the first 24 hours postburn, and this amount was mainly due to the additional requirement in the first 8 hour period. We propose that the amount required in severe burned patients with inhalation injury in the first 24 hours postburn should be appropriately increased, and special attention should be paid to the harmful effect of inadequate fluid resuscitation in the first 8 hour period. The amount of fluids required for resuscitation in severe burned patients with inhalation injury, as estimated according to crystal-colloid formula, should be increased by 13.5% in the first 24 hours, and 2/3 of the addition amount should be given in the first 8 hours, with 1/3 of it in the second and third 8 hours postburn.

Adult↗
PubMed1992

[Isolation and characterization of mutactimycin-producing mutant].

Natural non-antibiotic producing Streptomyces sp. 1254 was mutagenized by UV irradiation and two active mutants were isolated. Mutant 113 produced novel anthracycline compounds designated mutactimycins. Mutactimycin A was active against the bacteriophage of Bac. subtilis and some viruses in tissue culture. The mutant 2-6 synthesized a basic water-soluble antimicrobial antibiotic. Chemical analysis of the whole cell hydrolysate and the morphological characterization showed that the strain 1254 and its mutant 2-6 were of chemotype I, belonging to the genus of Streptomyces, and the mutant 113 was of chemotype IV without mycolic acid. Co-synthesis test of strain 1254 and a blocked mutant of strain 113 gave the active compounds identical with mutactimycins. Using the actI gene as a probe, the Southern hybridization revealed homology between the actinorhodin polyketide biosynthase gene and the total DNA of the strain 1254. Based on these data it was deduced that Streptomyces sp. 1254 should have a biosynthesis pathway for mutactimycin, but some of its genes might fail in expression and mutagenesis would make the silent gene(s) active.

Antibiotics, Antineoplastic↗
PubMed1992

[A thin layer chromatography densitometric method for the determination of arecoline content in semen Arecae from different producing areas].

A TLC-densitometric method for the determination of arecoline in Semen Arecae (Areca catechu) was established, and arecoline content in three Semen Arecae (Imported, Hainan, Guanzhou) was determined. The method is accurate, sensitive and simple. The recovery is 102.39% and the coefficient of variation of six samplings is 1.95%. The are coline average content in the three Semen Arecae is 0.22%, 0.19%, 0.56% respectively.

Areca↗
PubMed1991

Alboaggregin-B: a new platelet agonist that binds to platelet membrane glycoprotein Ib.

A new protein, called alboaggregin-B (AL-B), has been isolated from Trimeresurus albolabris venom by ion-exchange chromatography. It agglutinated platelets without the need for Ca2+ or any other cofactor. The purified protein showed an apparent molecular mass on SDS-PAGE and gel filtration of about 23 kDa under nonreducing conditions. Ristocetin did not alter the binding of AL-B to platelets or affect AL-B-induced platelet agglutination. Agglutinating activity was not dependent on either proteolytic or lectin-like activity in AL-B. Binding analysis showed that AL-B bound to platelets with high affinity (Kd = 13.6 +/- 9.3 nM) at approximately 30,800 +/- 14,300 binding sites per platelet. AL-B inhibited the binding of labeled bovine von Willebrand factor (vWF) to platelets. Monoclonal antibodies against the 45-kDa N-terminal domain of platelet glycoprotein Ib inhibited the binding both of AL-B and of bovine vWF to platelets, and also inhibited platelet agglutination induced by AL-B and bovine vWF. Specific removal of the N-terminal domain of GPIb by treatment of the platelets with elastase or Serratia marcescens protease reduced the binding of labeled AL-B and bovine vWF to platelets and blocked platelet agglutination caused by both agonists. Monoclonal antibodies to glycoprotein IIb/IIIa, to bovine vWF, and to bovine serum albumin did not show any effect on the binding of AL-B to platelets. Our results indicate that the binding domain for AL-B on platelet GPIb is close to or identical with the one for vWF. This new protein may be a very useful tool for studying the interaction between platelets and vWF.

Antibodies, Monoclonal↗
PubMed1991

Correlation between CD4 cell counts and cellular and plasma viral load in HIV-1-seropositive individuals.

We conducted a study of 152 HIV-1-seropositive individuals in order to evaluate the possible correlations between the isolation of HIV from peripheral blood mononuclear cells or from plasma and CD4 cell counts. HIV was isolated from only 36% of plasma samples, and the isolation rate was closely related to CD4 cell counts, increasing gradually from 0% in subjects with greater than 800 x 10(6)/l CD4 cells to 88% in those with less than 100 x 10(6)/l CD4 cells. In contrast, HIV was isolated from 92% of cell samples (99% in subjects with less than 900 x 10(6)/l CD4 cells, 46% in those with CD4 counts greater than or equal to 900 x 10(6)/l). Since most cell samples were positive, a scoring method was designed to quantify the cellular viral load. The results obtained demonstrated that the cellular viral load was closely related to CD4 counts. We also found that the cellular viral load was higher in subjects with either positive plasma isolation or positive p24 antigenaemia. The measurement of the cellular viral load by this scoring method appears to be useful for the management of HIV-seropositive individuals and for the evaluation of therapeutic trials.

CD4 Antigens↗
PubMed1991

A capture-enzyme immunoassay for rapid diagnosis of transmissible gastroenteritis virus.

Two enzyme immunoassays (EIA) were developed for the detection of swine transmissible gastroenteritis virus (TGEV) antigens. The 2 EIAs used the same detecting system, a monoclonal antibody conjugated to horseradish peroxidase, but used different capture systems including a monoclonal antibody (m-EIA) or a polyclonal antibody (p-EIA). The EIAs were compared with the fluorescent antibody test (FAT) and electron microscopy (EM) for the detection of TGEV in intestinal samples of experimentally inoculated gnotobiotic piglets and of conventional diarrheic pigs submitted for diagnosis. In the gnotobiotic piglets experimentally inoculated with TGEV, 81.8% (9/11) were positive for TGEV by p-EIA, and 72.7% (8/11) were positive by m-EIA. In comparison, 81.8% (9/11) were positive by FAT and 27.2% (3/11) were positive by EM. Three noninfected controls were negative by all tests. In the diagnostic samples, 86.0% (43/50) were positive by p-EIA, 68.2% (30/44) were positive by m-EIA, 28.6% (14/49) were positive by IFA, and 38.0% (19/50) were positive by EM. The m-EIA had a higher agreement with FAT and EM than did p-EIA.

Animals↗
PubMed1991

The tissue-specific mammalian transcription factor, Pit-1, activates transcription in Saccharomyces cerevisiae.

Pit-1 is a tissue-specific transcription factor which binds to specific DNA sequences within 5' flanking regions of the PRL and GH genes and activates the transcription of these genes. Previous studies have shown that expression of Pit-1 is necessary to activate transcription from the PRL or GH promoters in heterologous mammalian cells. In the present study the ability of Pit-1 expression vectors to activate expression of reporter genes in Saccharomyces cerevisiae was examined. The test system used Pit-1 expression vectors and an indicator plasmid containing multiple copies of a Pit1-binding site as a replacement for the upstream activator sequence of the CYC1 promoter. Significant activation of indicator plasmid expression was detected only in the presence of functional Pit-1 expression vectors. In both mammalian and yeast cells, amino-terminal deletions of the Pit-1 coding sequence produced similar and gradual loss of transcriptional activation. This finding indicates that similar or identical regions of Pit-1 are required for transcriptional activation in mammalian and yeast cells. Although synthetic DNA elements containing multiple copies of a single Pit-1-binding site were sufficient to permit Pit-1-mediated transcriptional activation in both yeast and mammalian cells, DNA fragments representing the proximal region or distal enhancer region of the PRL gene were transcriptionally active only in mammalian cells. These studies establish the ability of Pit-1 to stimulate transcription in the absence of other tissue-specific factors and provide a system for further genetic studies of Pit-1 structure/function relationships as well as evaluation of target sequences necessary for Pit-1 action.

Animals↗