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Biomedical subjects

D Allen

Publications and source records attributed to D Allen.

At least 289 records · Page 16Linked to original sources
PubMed1978

Effect of pulmonary microembolism on arteriovenous shunt flow.

The effects of acute pulmonary hypertension on the fraction of cardiac output shunted through pulmonary arteriovenous communications have been studied in dogs as a possible cause of hypoxia following pulmonary embolization. Pulmonary artery pressure was increased twofold and then fourfold above control values by embolization of the pulmonary vascular bed with polystyrene microspheres. Quantitative measurements of arteriovenous shunt were determined from the fraction of 50 mu radioactively labeled microspheres injected into the inferior vena cava which passed through the pulmonary circulation into systemic vascular beds. There was no increase in the fraction of pulmonary blood flow passing through pulmonary arteriovenous connections, 50 mu in diameter or greater, with pulmonary microembolism when FIo2 was 1. There was a small increase in arteriovenous shunt fraction when pulmonary artery pressure was increased with an FIo2 of 0.21. Physiological shunt measured by the oxygen technique did not increase with pulmonary embolism, but total venous admixture rose significantly. Postmortem gravimetric measurements of lung water indicated pulmonary edema. We conclude that anatomic arteriovenous shunt channels have little physiological significance after pulmonary microembolism in the dog lung. The major cause of hypoxia immediately after pulmonary microembolism is ventilation/perfusion imbalance, probably caused by pulmonary edema.

Animals↗
PubMed1977

Making uniform photographic records in plastic surgery.

The photographic unit described requires a modest investment in equipment and space, and the photographs can be taken by an office aide after suitable instruction. It provides a means for obtaining clear, comparable photographs--without disrupting office routine. The key to success is consistency in camera settings, lighting, alignment, and positioning. Figures 8 and 9 show representative examples of long-term records.

Face↗
PubMed1977

The influence of hemodynamics upon platelet adhesion to collagen-coated surfaces.

These results indicate that hematocrit and surface shear rate must be considered in determination of the rate of transport, limiting transport step and surface saturation condition. Low hematocrit and shear rate lead to a slow rate and low saturation; high hematocrit and shear rate lead to fast rate and high saturation. Surface reaction rather than diffusional transport controls the adhesion process at low hematocrit. Platelet thrombi, however, may not be favored by high shear conditions due to increased transport from the surface of released aggregate forming substances.

Animals↗
PubMed1976

Effect of 2 MHz ultrasound on DNA, RNA and protein synthesis in Pisum sativum root meristem cells.

The amounts of DNA, RNA and protein synthesis were determined in Pisum sativum root meristem cells at various times after a 1 min exposure to 1 MHz ultrasound at a power density of 30 W/cm2. Immediate depressions in all three macromolecular syntheses occurred after sonication, followed by an apparent recovery several hours later. These events appear to correlate in time with the subsequent reduction and recovery in mitotic index in Pisum sativum root meristem cells exposed to 2 MHz ultrasound.

DNA↗
PubMed1976

The refractive status of Zuni Indian children.

American Indians show a high incidence of various ocular abnormalities. In the present study, refractive error and corneal curvature were measured in 420 Zuni school children. The mean spherical refractive error varied from +0.87 D in the lower grades to -0.62 D in the upper grades. The mean corneal astigmatism was 2.21 D was varied as function of grade. corneal and refractive astigmatism were highly correlated.

Adolescent↗
PubMed1976

A sensitive method for the determination of amitriptyline and nortriptyline in human plasma.

A highly sensitive and reproducible GLC technique for the quantitation of amitriptyline and nortriptyline is described. The lower limit of detection is less than 1 ng/ml. 5 ng/ml samples (3 ml aliquots) can be accurately quantified (C of V less than 5%). Steady state data are reported together with data on amitriptyline and nortriptyline levels obtained in a volunteer who ingested a single oral dose (25 mg) of amitriptyline (Elavil).

Adult↗
PubMed1975

The use of paraprofessionals in crisis intervention. Evaluation of an innovative program.

Single-session crisis services by paraprofessionals (graduate students and community volunteers) in the emergency room of a community hospital were offered to 293 clients. These clients were followed-up 6 to 12 months after their last contact and asked about: (1) the effectiveness of the service, (2) their use of referrals, (3) the major source of change in their crisis situation, and (4) their rating of improvement for their presenting problem. There were 104 clients who completed the follow-up. The results support the interpretation that timely intervention by paraprofessionals may have long-lasting results in specific problem areas. A model emphasizing the use of service deliverers as researchers is proposed.

Allied Health Personnel↗
PubMed1975

Myocardial perfusion imaging with 99m-Tc or 113m-In macroaggregated albumin: correlation of the perfusion image with clinical, angiographic, surgical, and histologic findings.

Scintillation camera myocardial perfusion images were performed in 77 patients with proved or suspected ischemic heart disease following the intracoronary injection of 1.5 mCi 99m-Tc or 113m-In macroaggregated albumin. Perfusion images were classified as normal (36) or abnormal (41), and the location of abnormality was noted. Thirty-seven out of 41 patients with abnormal images had prior myocardial infarction based on history (30), ECG Q-waves (27), local contraction pattern abnormality (23), or direct surgical (9) or histologic (4) inspection, either singly or in combination. Three out of five patients with pre-infarction angina had image defects-none had evidence of infarction by ECG, ventriculogram, or surgical inspection. Coronary artery stenosis correlated with image defects to the extent that myocardial infarction was associated; 28 out of 29 patients with total occlusions and other evidence of infarction had image defects, four patients with complete occlusions but without other evidence of infarction had normal images. We conclude that, excepting patients with pre-infarction angina, this technique is more sensitive and direct in the identification of myocardial scar than standard ECG, clinical evaluation, or biplane left ventriculography.

Autopsy↗
PubMed1975

Myocardial imaging with indium- 113m- and technetium-99m-macroaggregated albumin. New procedure for identification of stress-induced regional ischemia.

Regional coronary blood flow distribution was studied by myocardial imaging after intracoronary injection of technetium-99m- and indium-113m-macroaggregated albumin at rest and during coronary hyperemia induced by intracoronary injection of Hypaque-M, 75 percent. The four- to five-fold increase in coronary flow after injection of radiographic contrast material was similar in magnitude to that occurring with maximal exercise stress. Experimentally, resting coronary blood flow and regional distribution of radioactive particles remains normal in spite of coronary stenosis of up to 85 percent. Less severe stenosis causes flow and distribution abnormalities only during periods of increased flow, and the degree of maldistribution is directly related to the physiologic severity of the stenosis. Of 49 patients with suspected coronary artery disease, 10 had no significant lesions by coronary arteriography and all had normal images at rest and during coronary hyperemia. Thirty-seven of 39 patients with significant obstructive coronary artery disease had abnormal images at rest or during contrast agent-induced hyperemia, or both. Patients with significant coronary artery disease without previous infarction usually demonstrated abnormalities in flow distribution only during coronary hyperemia. Patients with previous infarction demonstrated resting perfusion abnormalities that often became more abnormal during hyperemia. This technique provides a new method for assessing the physiologic effects of coronary stenosis in conjuntion with coronary arteriography.

Albumins↗
PubMed1974

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Education, Nursing, Continuing↗