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Biomedical subjects

T L Wu

Publications and source records attributed to T L Wu.

At least 73 records · Page 4Linked to original sources
PubMed1990

The value of body surface potential maps in assessment of experimental myocardial infarction.

Body surface potential maps (BSPMs) and the pathology of 32 dogs with coronary artery ligations were analyzed to research the application of BSPMs to acute myocardial infarction (AMI). The group consisted of 18 dogs with left anterior descending coronary artery (LAD) ligations, 8 with right coronary artery (RCA) ligations and 6 with left circumflex coronary artery (LCX) ligations. The abnormal distribution of negative potential and minimal potential were observed in all of the dogs. In dogs with RCA ligations, the abnormal negative potential displayed on the right-superior, right-inferior or right portion of the anterior thorax. In those with LAD ligations, the abnormal potential appeared on the left-superior, left-inferior, middle-superior or middle portion of the anterior thorax. In those with LCX ligations, the abnormal potential showed on the left-superior or left-middle portion of the thorax. A good correlation was observed between the area of myocardial lesion and the extent of abnormal negative potential distribution (r = 0.82, p less than 0.001). A close correlation was also found between the area of myocardial lesion and the duration of abnormal negative potential (r = 0.61, p less than 0.05). This study suggests that BSPMs are useful in the assessment of AMI in terms of diagnosis, location and extent of myocardial infarct.

Animals↗
PubMed1990

Hemodynamic significance of vectorcardiographic pattern in patients with mitral stenosis.

Vectorcardiographic (VCG) studies were conducted in 71 patients with pure mitral stenosis (MS) documented by clinical findings, echocardiograms and cardiac catheterization. Among them, 31 were males and 40 females, with ages ranging from 20 to 58 (mean age 36.3) years. The Frank lead system was adopted for the VCG study. By VCG, 67 patients (94.4%) showed right ventricular hypertrophy (RVH), among whom 15 (21.2%) were type A, 30 (42.3%) type B and 22 (31.0%) type C. Forty-five patients (63.4%) were in sinus rhythm (NSR), while the remaining 26 (36.6%) were in atrial fibrillation (AF). Patients with type A RVH had a significantly higher pulmonary wedge (PAW) and main pulmonary arterial (MPA) pressures than those with type B or C. Patients with type C had a higher mean MPA pressure (39.0 +/- 11.3 mmHg) than those with type B (32.3 +/- 10.1 mmHg) (p less than 0.05). Among the 3 types of RVH, the mean right atrial (RA) pressures were similar (p greater than 0.05). Patients with AF had a lower mean MPA pressure, but a higher RA pressure than those with NSR (p less than 0.05). The maximal anterior force and maximal rightward force at the horizontal plane were significantly correlated with the mean MPA pressure (r = 0.54 and 0.49, respectively, both p less than 0.01), but they did not correlated well with the PAW and RA pressures (p greater than 0.05). We conclude that in patients with MS, as pulmonary hypertension progresses, VCG seems to begin with type B RVH, then emerges into type C and finally becomes type A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Characterization of canine renal receptors for the parathyroid hormone-like protein associated with humoral hypercalcemia of malignancy.

Parathyroid hormone-like proteins (PTHLP) display actions in the kidney which are similar to those of parathyroid hormone (PTH). We compared the binding properties of PTHLP and PTH in canine renal cortical membranes to determine if they interacted with the same or different receptors. Radioiodination to high specific activity (greater than 400 microCi/micrograms) of [Nle8,18,Tyr34]human PTH-(1-34)amide and [Tyr36]PTHLP-(1-36)amide was performed using the lactoperoxidase method. Complete enzymatic digestion of both radioligands demonstrated that the peptides were monoiodinated. Both radioligands retained full biological activity in the renal adenylate cyclase assay, and neither was significantly degraded during incubation with highly purified canine renal membranes under binding assays conditions. Specific binding reached equilibrium by 20 min at 20 degrees C. Competition binding studies using unlabeled [Nle8,18,Tyr34]human PTH-(1-34)amide, [Tyr36] PTHLP-(1-36)amide, and bovine PTH-(1-34) with either radioligand revealed similar binding affinities for all three peptides. Biologically inactive PTHLP fragments did not show significant displacement. In contrast to its similar binding affinity, [Tyr36]PTHLP-(1-36)amide was 6-15-fold less potent than bovine PTH-(1-34) in the renal adenylate cyclase assay, suggesting less efficient receptor-effector coupling. Photoaffinity cross-linking using either radioligand in canine renal membrane labeled indistinguishable 70,000-dalton proteins. In the presence of multiple protease inhibitors, binding to an 85-kDa component was observed. Labeling of both receptor forms was specifically abolished by an excess of either cold peptide and dose-response curves using affinity cross-linked membranes corroborated the apparent binding affinities determined by conventional radioligand binding assays. We conclude that PTHLP-(1-36) and amino-terminal PTH analogues bind to indistinguishable receptors in canine renal cortical membranes, but display differential coupling to post-receptor events.

Affinity Labels↗
PubMed1989

Vectorcardiograms in normal adult rats: with special reference to its pattern different from man.

To understand the vectorcardiographic (VCG) patterns in rats, we studied 50 adult male Long-Evans rats weighing 250-350g. Under anesthesia with pentothal, the rat was fixed to woodplate in a supine position with extremities extended. Surface electrocardiograms (ECG) and VCG of Frank lead system were then recorded in all rats. All variables of ECG and VCG were measured and compared with those of humans to determine the main difference. We found that rats have prominent anterior force of QRS complex and large ST vector in both ECG and VCG as compared to those of humans. The prominent anterior force of QRS complex may be due to different body shape between rat and human chests, and the large ST vector is probably related to early ventricular repolarization in rats. These findings should be considered in any experimental condition involving the ECG and VCG in rats.

Animals↗
PubMed1989

Time course of the ventricular arrhythmias following coronary reperfusion in dogs.

The time course of ventricular arrhythmia following reperfusion was investigated in 12 dogs undergoing a 2-hour coronary artery occlusion followed by reperfusion. At days 1, 3 and 7 following coronary reperfusion, the cardiac rhythm was monitored with a 24-hour Holter electrocardiographic recorder. Six dogs with sham operations were also studied with Holter monitoring at the same time periods as a control group. This showed that, following coronary reperfusion, all 12 dogs (group A) developed frequent premature ventricular complexes (PVCs) at day 1, with a total count (beats per hour, bph) of 1,806 +/- 390 (mean +/- SD). The PVC count decreased to 298 +/- 96 at day 3 (p less than 0.001) and 0.4 +/- 0.1 at day 7 (p less than 0.001). The incidence of spontaneous sustained ventricular tachycardia (VT) at day 1 was 100%; 1 of them deteriorated to ventricular fibrillation (VF). At day 3, 9 of the remaining 11 dogs (82%) had recurrent VTs (p greater than 0.05 vs day 1) which were of shorter duration and a slower rate. One of the 11 dogs died at day 5 and the remaining 10 dogs survived to day 7, with all the VTs subsiding (p less than 0.001 vs day 1 or 3). In the control group, only isolated PVCs were observed at day 1 (7 +/- 3 bph, p less than 0.001 vs group A) and no spontaneous VT or VF was noted. We conclude that spontaneous ventricular arrhythmias were observed in all dogs with coronary reperfusion following a 2-hour coronary artery occlusion and the arrhythmias could subside in 1 week of those survived. Only rarely did VT deteriorate to VF.

Animals↗
PubMed1988

De novo and maintenance DNA methylation by a mouse plasmacytoma cell DNA methyltransferase.

A DNA methyltransferase of Mr = 140,000 that is active on both unmethylated and hemimethylated DNA substrates has been purified from the murine plasma-cytoma cell line MPC 11. The maximal rate of methylation was obtained with maintenance methylation of hemimethylated Micrococcus luteus or M13 DNAs. At low enzyme concentrations, the highest rate of de novo methylation occurred with single-stranded DNA or relatively short duplex DNA containing single-stranded regions. Strong substrate inhibition was observed with hemimethylated but not unmethylated DNA substrates. Fully methylated single-stranded M13 phage DNA inhibited neither the de novo nor the maintenance reactions, but unmethylated single-stranded M13 DNA strongly inhibited the maintenance reaction. The kinetics observed with hemimethylated and single-stranded substrates could be explained if the enzyme were to bind irreversibly to a DNA molecule and to aggregate if present in molar excess. Such aggregates would be required for activity upon hemimethylated but not single-stranded DNA. For de novo methylation of duplex DNA, single-stranded regions or large amounts of methyltransferase appear to be required. The relative substrate preference for the enzyme is hemimethylated DNA greater than fully or partially single-stranded DNA greater than fully duplex DNA.

Animals↗
PubMed1988

Vectorcardiographic criteria for acute right ventricular infarction.

Based on serial vectorcardiographic and cardiac scintigraphic studies of 62 patients with acute myocardial infarction, we propose vectorcardiographic criteria for the diagnosis of acute right ventricular infarction. These criteria are: (1) the direction of the maximal spatial ST vector points either to the right-anterior-inferior or to the right-posterior-inferior octant, and (2) the magnitude of the projection of the maximal spatial ST vector is greater than or equal to 0.15 mV in the horizontal plane. By using these criteria correlated with scintigraphic results, 92% sensitivity was achieved together with 98% specificity; the Kappa statistic was 0.90. In patients with acute inferior and right ventricular infarction, the serial maximal spatial ST vector swung to-and-fro like a 'tug of war' between right-anterior-inferior and right-posterior-inferior octants during the acute stage. In patients with acute inferior-posterior and right ventricular infarction, the serial maximal spatial ST vector pointed to the right-posterior-inferior octant during the whole course of the acute stage. Failure to recognize this electrical phenomenon may make the clinician inaccurate when judging the clinical course of acute right ventricular infarction or over-estimate the result of therapeutic intervention.

Adult↗
PubMed1987

Probenecid interferes with the natriuretic action of furosemide.

The interaction between probenecid and furosemide was studied in eight hospital patients (ages 20-65 years) who had been treated with oral furosemide, 40 mg daily, and moderate salt restriction for 10 days or longer. After stabilization of drug therapy and diet for at least 3 days, probenecid, 0.5 g twice a day, was given for 3 days and then discontinued. The 24-h urinary sodium excretion (UNaV) significantly decreased from 56.3 +/- 7.2 to 35.9 +/- 7.1 mmol/day when probenecid was added to the treatment regimen (p less than 0.01), and then significantly increased to 61.7 +/- 10.3 mmol/day after probenecid was discontinued (p less than 0.01). Parallel with the changes in UNaV, there were also significant corresponding changes (p less than 0.01) in urinary excretion of uric acid (392.4 +/- 46.5, 600.9 +/- 102.1, and 345.0 +/- 33.2 mg/day, respectively), renal clearance of uric acid (3.7 +/- 0.3, 14.3 +/- 2.4, and 4.1 +/- 0.3 ml/h/kg, respectively), and serum uric acid concentration (7.7 +/- 0.5, 3.3 +/- 0.2, and 6.3 +/- 0.3 mg/dl, respectively). Before and after discontinuing probenecid therapy, there were no significant differences in these parameters (p greater than 0.05). In conclusion, the natriuretic action of furosemide was attenuated by concurrent probenecid therapy, probably owing to a reduction of furosemide delivery to the luminal side of renal tubules.

Adult↗
PubMed1987

Co-purification of transforming growth factor beta-like activity with PTH-like and bone-resorbing activities from a tumor associated with humoral hypercalcemia of malignancy.

Humoral hypercalcemia of malignancy (HHM) is caused by a circulating bone-resorbing factor or factors. Suggestions as to the nature of this factor include PTH-like proteins, transforming growth factors, and bone-resorbing factors distinct from either of the first two classes of polypeptides. We investigated the occurrence of these three activities in a highly purified extract of the H-500 Leydig cell tumor which causes HHM when implanted into Fisher rats. PTH-like adenylate cyclase-stimulating activity (ACSA) was extracted from tumor tissue by sequential treatment with urea/HCl and ethanol/NaCl. Tumor extract was further purified by hydrophobic-interaction, gel-filtration, and reverse-phase HPLC steps to a specific activity of 1038 ng eq bPTH(1-34)/mg protein. Only the fraction pool containing ACSA demonstrated significant bone-resorbing (1.78-fold over basal) and transforming growth factor activity (epidermal growth factor (EGF)-dependent colony formation in soft agar suspension by NRK-49F indicator cells). A subsequent reverse-phase HPLC step produced material which contained both ACSA and transforming growth factor beta (TGF beta)-like activity in a single fraction. Whether the responsible mediator in this animal model has TGF beta-like properties as well as PTH-like and bone-resorbing activity remains to be determined.

Adenylyl Cyclases↗
PubMed1987

Skin-derived fibroblasts respond to human parathyroid hormone-like adenylate cyclase-stimulating proteins.

Human tumors and keratinocyte-conditioned medium contain PTH-like adenylate cyclase-stimulating proteins. Human dermal fibroblasts have receptors that recognize PTH and a factor associated with humoral hypercalcemia of malignancy in rats. We examined 10 human dermal fibroblast lines for an adenylate cyclase response to PTH. Six of 10 lines tested displayed a definite response (2.4- to 3.8-fold over basal) to 10(-6) M bovine PTH-(1-34). This response was inhibited by the PTH analog and antagonist Nle8,18,Tyr34-bPTH-(3-34). We also examined whether human dermal fibroblasts are capable of responding to either a human PTH-like tumor-derived factor or the PTH-like factor contained in human keratinocyte-conditioned medium. Both human humoral hypercalcemia of malignancy-associated tumor extract (2.5 X 10(-10) M) and keratinocyte-conditioned medium (8 X 10(-10) M) stimulated human dermal fibroblast adenylate cyclase. These concentrations are markedly lower than those required for PTH-induced adenylate cyclase stimulation. This activity was also inhibited by the PTH analog. The high prevalence of PTH-responsive adenylate cyclase in dermal fibroblast lines and the apparent potency of tumor-derived and keratinocyte-derived PTH-like factors in dermal fibroblasts suggest that these factors may play a role in normal dermal physiology.

Adenylyl Cyclases↗