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Biomedical subjects

B Chen

Publications and source records attributed to B Chen.

At least 523 records · Page 29Linked to original sources
PubMed1988

The "ruler sign"--a semiquantitative physical sign of chronic obstructive pulmonary disease.

This report describes a simple and reproducible physical sign of chronic obstructive pulmonary disease--the "ruler sign." With the patient standing erect, a ruler is placed on the trapezius muscle and the clavicle at the midclavicular line. The ruler forms an angle with the horizontal line. At the end of a normal expiration this angle was 36 degrees +/- 4 SD in healthy control subjects as compared with 15 degrees +/- 4 SD in patients with severe chronic obstructive pulmonary disease. A simple device is described that enables convenient measurement of this angle at the bedside.

Adult↗
PubMed1987

Environmental factors in the etiology of Parkinson's disease.

Parkinson's disease (PD) has been proposed to result from the interaction of aging and environment in susceptible individuals. Defective metabolism of debrisoquine, inherited as an autosomal recessive, has been associated with this susceptibility. In 35 PD patients and 19 age-matched controls, no significant differences in debrisoquine metabolism were found, although a trend to impaired metabolism was noted in patients with disease onset less than or equal to 40. Foci of PD patients were associated with rural living and well water drinking, or rural living coupled with market gardening or wood pulp mills. In a questionnaire survey, patients with PD onset less than or equal to age 47 were significantly more likely to have lived in rural areas and to have drunk well water than those with onset greater than or equal to age 54 (p less than or equal to 0.01). Because of population mobility in North America, a case-control study designed to test environmental, occupational, dietary and other proposed risk factors for PD was conducted in China, where the population is more stationary and the environment more stable. No significant differences in incidences of head trauma, smoking or childhood measles were found between patients and controls.

Adult↗
PubMed1987

Improvement in human vision under bright light: grain or gain?

1. The factor by which increment threshold changes with changing background intensity is less if the test flash is small than if it is large. This is commonly attributed to a reduction of the area over which visual signals are integrated as light adaptation increases. 2. We propose and test an alternative hypothesis that the change in slope is the result of purely local processes: if it is assumed that increasing the background intensity increases the exponent of the local response function, but does not alter the extent of spatial integration, then the threshold of the small test flash will rise more slowly than the threshold of the large test flash simply because the small test flash is of a higher intensity than the large and therefore evokes a correspondingly greater local response. 3. We measured small and large test field increment thresholds and dichoptic brightness matches as a function of background intensity. 4. The log-log slopes of the small and large field increment threshold functions differed by not more than about 20%, suggesting that even under the conventional interpretation of such data, the change of spatial integration is less than is usually supposed. 5. The intensity of a large (2.3 deg) suprathreshold test field matched to a standard in the other eye varies with increasing background intensity with the same shallow slope as the small test (2.6 min) threshold versus intensity function; this is in agreement with the predictions of the local non-linearity hypothesis and suggests that there is no substantial change in spatial integration during light adaptation.

Adaptation, Ocular↗
PubMed1987

Doppler signal quantitation in renal allografts: comparison in normal and rejecting transplants, with pathologic correlation.

Quantitative duplex Doppler sonography was performed in 55 renal transplant patients during 54 independent episodes of acute rejection, three episodes of chronic rejection, three episodes of acute tubular necrosis (ATN), and 23 occasions of normal graft function. Doppler signals were obtained from four arterial sites in each kidney. Nine patients, in whom signals were absent, were subsequently shown at nephrectomy to have absence of perfusion resulting from severe acute vascular rejection. In each patient with graft dysfunction, biopsy or nephrectomy was performed within 24 hours of the Doppler study. Arterial Doppler signals were quantified using a pulsatility index (PI). Acute rejection produced a significantly higher PI at each arterial site. Receiver-operator characteristics suggest that signals obtained from the segmental arteries are most sensitive to these changes. With a threshold PI of 1.5, the sensitivity of this technique for detection of acute renal allograft rejection is 75%; the specificity is 90%. In acute vascular rejection, the same PI yields a sensitivity of 79% and specificity of 90%. With a cutoff PI of 1.8, a specificity of 100% can be achieved.

Adolescent↗
PubMed1986

In vivo 31P nuclear magnetic resonance studies of arsenite induced changes in hepatic phosphate levels.

Hepatic phosphate resonances were evaluated in vivo by 31P nuclear magnetic resonance (31P-NMR) following a single intravenous dose of sodium arsenite (10 mg/kg). Acute in vivo administration of arsenite rapidly decreased intracellular pools of all ATP phosphate with concomitant increases in inorganic phosphate and phosphomonoesters. In the phosphodiester resonance region, glycerolphosphorylcholine was also increased. The data suggest that liver cannot compensate for the rapid loss of NAD-linked substrate oxidation via other metabolic pathways, such as glycolysis for the production of ATP, and also demonstrate that 31P-NMR spectroscopy can disclose time-dependent metabolic changes of the liver in vivo.

Adenosine Triphosphate↗
PubMed1986

Temporal modulation sensitivity in cone dark adaptation.

The temporal modulation sensitivity of cone vision was studied using sinusoidally modulated lights. We found that the effects of bright flash bleaches mirror the effects of light adaptation and raise low frequency threshold most. Prolonged pre-exposures, however, raise high frequency threshold most. Two processes are therefore required to describe the mechanisms of recovery of sensitivity following bleaching exposures, one which acts like a background light and selectively attenuates low frequencies, and another process with a long integration time which selectively attenuates high frequencies.

Dark Adaptation↗