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Biomedical subjects

L Wu

Publications and source records attributed to L Wu.

At least 793 records · Page 44Linked to original sources
PubMed1985

Spectrum of diseases for house staff education on a VA general medicine inpatient service.

A significant portion of internal medicine residency training in the United States today occurs in general medicine sections of Veterans Administration hospitals. The authors studied the demographic, diagnostic, and prognostic characteristics of the patients treated by house staff members rotating through the general medical wards of the Houston, Texas, Veterans Administration (VA) Medical Center. In 2,131 admissions over 13 months, the most frequent primary causes of admissions included congestive heart failure, pneumonia, exacerbation of chronic obstructive lung disease, and malignancy. In 85 percent of the admissions, two or more chronic diseases were present. In 53 percent of admissions, the patients were deemed to be moderately or severely ill on admission. The data indicate that the residents' experience is representative of problems encountered by practicing internists and that VA hospitals make a significant contribution to internal medicine training and thus to the provision of health care for the nation.

Adolescent↗
PubMed1984

Properties of electroretinographic intensity-response functions in retinitis pigmentosa.

Dark-adapted electroretinogram (ERG) b-wave amplitudes and implicit times were recorded as a function of stimulus luminance for 15 retinitis pigmentosa (RP) patients and 15 normal subjects. B-wave amplitude as a function of log stimulus luminance was fit by non-linear regression with the Naka-Rushton equation, which has 3 independent parameters: The maximum response (Rmax), slope (n) and half-saturation constant (K). B-wave implicit-time as a function of log stimulus luminance was fit by linear regression. Compared to normal, the RP Rmax values were markedly reduced, suggesting response compression; the RP K values were elevated by an average of 0.76 log unit, suggesting relatively small losses in retinal sensitivity. There was no correspondence between Rmax and visual field area for the RP patients (coefficient of correlation = -0.02). All but 2 of the 15 RP patients had normal or shallower-than-normal implicit-time intensity-response functions, indicating that over most of the dynamic range of the ERG, the implicit-times were either normal or faster-than-normal. These results are discussed in terms of possible RP disease mechanisms.

Adolescent↗
PubMed1984

What determines the degradation rate of an injected protein?

The fusion of cultured mammalian cells to red blood cells loaded with specific proteins provides a powerful system for the study of intracellular proteolysis. During the past four years the degradation rates of more than 30 proteins have been examined after their injection into HeLa cells. Results from these studies support the legitimacy of the microinjection approach. They also provide insight into the mechanism of intracellular proteolysis.

Animals↗
PubMed1984

Location of amino acid alterations in mutants of aspartate transcarbamoylase: Structural aspects of interallelic complementation.

Recent genetic studies of the pyrB locus of Escherichia coli resulted in the characterization of 29 mutant strains harboring defects in the structural gene that encodes the catalytic chains of aspartate transcarbamoylase (carbamoylphosphate: L-aspartate carbamoyltransferase, EC 2.1.3.2). Three alleles, pyrB554, pyrB730, and pyrB748, have been cloned, and their nucleotide sequences have been determined along with that of the wild-type pyrBI operon in order to locate the sites of the alterations in the catalytic chains. Missense mutation pyrB554 leads to replacement of serine-52 by phenylalanine, and the inactive mutant enzyme has properties similar to those of wild-type aspartate transcarbamoylase. The amber mutation pyrB730 results in unstable truncated polypeptide chains 27 amino acids shorter than wild-type chains. Deletion mutation pyrB748 causes the removal of 181 amino acids. Combining these results with knowledge of the crystallographic structure of the wild-type enzyme provides a basis for tentative structural mechanisms for the observed complementation behavior of the mutant proteins.

Alleles↗
PubMed1984

Molecular cloning and expression of the mouse ornithine decarboxylase gene.

We used mRNA from a mutant S49 mouse lymphoma cell line that produces ornithine decarboxylase (OrnDCase) as its major protein product to synthesize and clone cDNA. Plasmids containing OrnDCase cDNA were identified by hybrid selection of OrnDCase mRNA and in vitro translation. The two of these with the largest inserts together span 2.05 kilobases of cDNA. Southern blot analysis of DNA from wild-type or mutant S49 cells, cleaved with EcoRI or with BamHI, revealed multiple bands homologous to OrnD-Case cDNA, only one of which was amplified in the mutant cells. RNA transfer blot analysis showed that the major OrnD-Case mRNA in the mouse lymphoma cells is 2.0 kilobases long. A similar size mRNA was found in mouse kidney and was more abundant in the kidneys of mice treated with testosterone, an inducer of OrnDCase activity in that tissue.

Animals↗
PubMed1984

Systemic venous and pulmonary arterial flow patterns after Fontan's procedure for tricuspid atresia or single ventricle.

Despite increasing use of Fontan or modified Fontan repairs, the comparative hemodynamic efficacy of different types of connections are unresolved. Accordingly, we undertook a prospective study designed to determine postoperative flow patterns after Fontan's operation. Seven subjects had tricuspid atresia and eight had single ventricle. Ages ranged from 5 to 38 years (mean 16.4). Ten subjects had nonvalved right atrial-to-pulmonary arterial connection, and four had nonvalved right atrial-to-right ventricular communication. A valved conduit established continuity between the right atrium and right ventricle in one subject. Doppler flow profiles were recorded in the pulmonary artery and in the superior and inferior venae cavae of each. A reference electrocardiogram was used for timing purposes. In 14 patients, forward flow in the pulmonary artery was biphasic. Flow began at the end of the T wave (early ventricular diastole), peaked at or before the P wave (atrial systole), and returned to baseline by the peak of the R wave. Forward flow recommenced at the peak of the R wave (ventricular systole) and returned to baseline at the end of the T wave. Flow in the superior vena cava varied, and could not be recorded in three subjects. Between the end of the P wave and peak of the R wave (atrial systole) flow was reversed in eight, absent in three, and forward in one patient. Forward flow occurred between the peak of the R wave and the end of the T wave and was either continuous or biphasic. Fourteen patients had adequate studies of inferior vena cava flow; reversed flow during atrial systole occurred in 10 subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Pharmacological properties of two amino esters of diphenylpropanoic acid.

N, N-Diethylaminoethyl ester and 3-quinuclidinyl ester of 2, 2-diphenylpropanoic acid (compound 1 and 2, respectively) were prepared and pharmacologically evaluated in vitro and in the intact animal. Both compounds attenuated the effects of increasing doses of ACh in the isolated rat ileum (pA2 = 8.40 and 8.55, respectively). These effects were comparable to that of atropine (pA2 = 8.73). The duration of methacholine-induced salivation in male Swiss-Webster mice was significantly decreased by compound 2 but not by compound 1. Cardiorespiratory studies in adult male Sprague-Dawley rats revealed that both compounds shifted the dose-response curves to methacholine in terms of arterial blood pressure, heart rate and respiration upwards; indicative of cholinergic blockade. The observed pharmacological differences between the two compounds may be attributed to apparent in vivo hydrolysis of compound 1 by esterases.

Acetylcholine↗
PubMed1983

Experimental study in rabbits of the antishock effect of anisodamine (654-2), and its mechanism of action.

The antishock effect of anisodamine (654-2) was observed in different kinds of experimental shock in groups of rabbits--due to late hemorrhage, superior mesenteric artery occlusion, and septic shock from peritonitis. The drug 654-2 significantly alleviated the progress of shock and increased the survival rate of the animals. The therapeutic effect of 654-2 was much better than that of other vasoactive drugs commonly used, such as norepinephrine, phenoxybenzamine, dopamine, and aramine. The antishock mechanism of 654-2 is probably partly due to its protective action on intestinal shock in preventing its effects becoming irreversible. The antishock action of 654-2 both by basic research workers and clinicians merits further study.

Animals↗
PubMed1981

Comparative studies on microinjected high-mobility-group chromosomal proteins, HMG1 and HMG2.

The nonhistone chromosomal proteins, HMG1 and HMG2, were iodinated and introduced into HeLa cells, bovine fibroblasts, or mouse 3T3 cells by erythrocyte-mediated microinjection. Autoradiographic analysis of injected cells fixed with glutaraldehyde consistently showed both molecules concentrated within nuclei. Fixation with methanol, on the other hand, resulted in some leakage of the microinjected proteins from the nuclei so that more autoradiographic grains appeared over the cytoplasm or outside the cells. Both injected and endogenous HMG1 and HMG2 partitioned unexpectedly upon fractionation of bovine fibroblasts, HeLa, or 3T3 cells, appearing in the cytoplasmic fractions. However, in calf thymus, HMG1 and HMG2 molecules appeared in the 0.35 M NaCl extract of isolated nuclei, as expected. These observations show that the binding of HMG1 and HMG2 to chromatin differs among cell types or that other tissue-specific components can influence their binding. Coinjection of [125I]HMG1 and [131I]HMG2 into HeLa cells revealed that the two molecules display virtually equivalent distributions upon cell fractionation, identical stability, identical intracellular distributions, and equal rates of equilibration between nuclei. In addition, HMG1 and HMG2 did not differ in their partitioning upon fractionation nor in their stability in growing vs. nongrowing 3T3 cells. Thus, we have not detected any significant differences in the intracellular behavior of HMG1 and HMG2 after microinjection into human, bovine, or murine cells.

Animals↗
PubMed1981

The C-wave of the rabbit electroretinogram during dark-adaptation and the steady-state.

C-waves of the rabbit ERF under urethane anesthesia were elicited by a Grass photostimulator during dark adaptation and under steady-state conditions. After strong pre-adaptation with light, the amplitude and time-to-peak of the c-wave increased in parallel with the a- and b-waves, reaching a maximum of 90-130 min. In the dark-adapted steady-state, repetitive stimuli at intervals ranging from 15 sec to 5 min elicited a stable c-wave response except for a small dip in amplitude that occurred 2-6 min after initiating the shortest interval (15 sec) flashes. Although the changes in light and dark used in these experiments should have elicited shifts in the standing potential, no fluctuations of the c-wave amplitude were evident with a time course corresponding to a light response of the standing potential.

Animals↗
PubMed1979

A prospective study of mitral valvular prolapse in young men.

A cardiac history, a physical examination, an electrocardiogram, phonocardiograms in the supine and standing positions, and an M-mode echocardiogram were obtained in 100 randomly selected, presumably healthy, male medical students (mean age, 26 years). Four percent met standard echocardiographic criteria for mitral valvular prolapse. No midsystolic clicks or late systolic murmurs were appreciated in this group, and none complained of chest pain or palpitations. To elucidate further the clinical implication of the echocardiographic pattern of mitral valvular prolapse, 24-hour ambulatory ECGs, multistage exercise tests, and scintiscans of myocardial perfusion at rest and after exercise (using radioactive 13nitrogen-labelled ammonium) were obtained, with normal results. The absence of life-threatening arrhythmias and exercise-induced abnormalities in these four asymptomatic subjects without abnormal physical findings suggests that the echocardiographic pattern of mitral valvular prolapse in such individuals may represent a variant of normal which does not require extensive evaluation.

Adult↗