Search PubMed⌕ Search

Biomedical subjects

D S Young

Publications and source records attributed to D S Young.

At least 37 records · Page 2Linked to original sources
PubMed1992

How do somersaulters land on their feet?

Body movements of trampolinists landing upright from forward somersaults, with eyes open and closed, were analyzed to test a theory of how braking and timing of actions are conjointly controlled. In regulating landing, rotation has to be slowed by extending the body so that it reaches the upright just as the feet hit the trampoline. Extending a theory of visual control of linear braking, it was hypothesized that upright landing is achieved by perceptually regulating body extension so as to keep the ratio angle of body to upright: rate of change of angle (the tau function of the angle) proportional to time-to-landing. The data support the hypothesis, indicate that vision improves precision of control, and argue further for the value of the tau function in the perceptual regulation of action.

Attention↗
PubMed1992

Two-dimensional electrophoresis of urine specimens from patients with renal disease.

In an effort to develop non-invasive markers capable of characterizing renal disease with greater sensitivity and specificity than those currently available, urinary proteins were studied by high-resolution two-dimensional electrophoresis in order to catalog those proteins which appeared to be most affected by a variety of renal diseases. Urine specimens were prepared by high-pressure liquid chromatography and subjected to two-dimensional gel electrophoresis. Proteins were visualized with silver stain. Gels from 17 patients were analyzed in detail and compared to standard maps of human urinary proteins and plasma. The two-dimensional gels displayed approximately 100 times the number of proteins demonstrated by high resolution agarose electrophoresis. We have identified 34 proteins whose urinary concentrations were most affected by renal disease. Twenty seven were of plasma origin, based upon comigration with plasma samples (17 of unknown identity and function). Seven proteins were observed in normal urine but not present in plasma. These proteins, which may represent kidney tissue proteins, were not apparent in the urine of patients with proteinuria, most likely due to dilutional effects.

Biomarkers↗
PubMed1992

Pharmacodynamics and pharmacokinetics of cyclosporin A in the newborn pig.

The disposition kinetics of cyclosporin A in the neonates as well as age-related differences in lymphocyte responses to cyclosporin A are unknown. A single intravenous infusion of cyclosporin A was given to neonatal (2.5 or 5 mg/kg) and mature pigs (10 mg/kg) and blood cyclosporin A levels were measured by RIA. The neonates had longer elimination half-life and lower drug clearance than mature animals. Suppression in lymphocyte proliferation was only observed in mixed lymphocyte reaction and phytohemagglutinin-stimulated cultures of the 2-hour samples from neonates receiving 5 mg/kg. We conclude that neonatal pig exhibit different cyclosporin A pharmacokinetics and show higher sensitivity to cyclosporin A than mature animals.

Aging↗
PubMed1992

Determination and validation of reference intervals.

A brief overview of the concept of the reference interval and its application in medical practice is presented. The populations from whom it is possible to derive reference intervals are discussed. Procedures used to develop reference intervals from both a selected healthy population and from hospitalized patients are discussed, and the influence of statistical method on presented reference intervals is reviewed. However, the weakness of using a reference interval derived from a population of individuals to facilitate interpretation of test results is illustrated in relationship to the variability of test results within an individual. In spite of the efforts that are made within the clinical laboratory through development of reference intervals to provide maximum guidance to clinicians to facilitate their proper interpretation of test values in patients, it is apparent that much of the carefully derived scientific information is ignored in actual practice.

Data Interpretation, Statistical↗
PubMed1989

The effect of applied chest compression force on systemic arterial pressure and end-tidal carbon dioxide concentration during CPR in human beings.

Twelve adult (nine men and three women) cardiac arrest patients were studied as they received CPR by a computerized Thumper to determine the influence of the applied chest compression force on blood flow (as assessed by the end-tidal carbon dioxide concentration) and arterial pressure. At the end of a resuscitation when the decision was made by the senior physician to cease resuscitative efforts, the applied force on the CPR Thumper was decreased from 140 to 0 pound-force (lbf) in 20-lbf increments at 30-second intervals. Radial artery cutdown blood pressure and end-tidal carbon dioxide (ETCO2) were recorded continuously. Arterial systolic blood pressure was linearly related (r = .59, P less than .0001) to applied force (systolic blood pressure, 31 +/- 6 mm Hg at 20 lbf to 60 +/- 7 mm Hg at 140 lbf). ETCO2 (r = .42, P less than .0001) was also linearly related to applied force (ETCO2, 0.7 +/- 0.1% at 20 lbf to 1.5 +/- 0.2% at 140 lbf). Diastolic pressure did not change significantly with change in applied force (17 +/- 2 mm Hg from 20 to 140 lbf). Our findings indicate that higher compression force than that currently recommended may improve arterial systolic pressure and flow in human beings receiving closed-chest compression during CPR.

Blood Pressure↗
PubMed1989

Dose-dependent vasopressor response to epinephrine during CPR in human beings.

The optimal dose of epinephrine during CPR in human beings is unknown. We studied ten prehospital cardiac arrest patients (six men and four women; mean age, 54 +/- 5 years) to determine the vasopressor response and change in the end-tidal carbon dioxide concentration (PetCO2) after incremental (1-, 3-, and 5-mg) doses of IV epinephrine given five minutes apart during closed-chest CPR. All patients were in ventricular fibrillation on arrival of the paramedics and did not respond to standard advanced cardiac life support. CPR was performed with a computerized Thumper; all patients were intubated and ventilated at 12 times a minute at an FiO2 of 0.8. Radial artery pressure was measured with a 20 angiocath inserted by radial artery cutdown. Paramedic response time was 4.3 +/- 0.5 minutes; elapsed time to emergency department arrival was 40.0 +/- 9.5 minutes. Initial blood gases were paO2, 241 +/- 50 mm Hg; pH, 7.23 +/- 0.08; paCO2, 27 +/- 5 mm Hg; and HCO3, 11 +/- 2 mEq/L. Baseline systolic and diastolic blood pressures were 47 +/- 5 mm Hg and 18 +/- 2 mm Hg, respectively. Systolic blood pressure was directly related to the dose of epinephrine (P less than .0001), rising to 69 +/- 7 mm Hg, 74 +/- 8 mm Hg, and 85 +/- 8 mm Hg after 1-, 3-, and 5-mg doses of epinephrine, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1988

Quinidine-induced decrease of intracellular esterase activity in a hepatoma cell line.

Using image-analyzing equipment, we measured the effect of quinidine on the activity of naphthol AS-D chloroacetate esterase, alpha-naphthyl butyrate esterase, alpha-naphthyl acetate esterase, and acid phosphatase in individual cells of a human Hep G2 hepatoma cell line. The impact of the drug on the morphology of the cells was also observed. Depending on the concentration of quinidine applied, various changes occurred, the most extreme being cell death. However, at some drug concentrations that did not appear to affect visible cell structures, the activity of the esterases was decreased. This lessened enzyme activity did not seem to be related to the enzymes leaking from the cells, because the activity of acid phosphatase was unaffected. Inhibition of the esterase activity was related to the interval of exposure to quinidine in the perfusing medium and to the concentration of the drug. We consider the system described here to be a potential replacement for experiments with animals in the study of hepatotoxicity.

Animal Testing Alternatives↗
PubMed1988

Quinidine-induced inhibition of leukocyte esterases.

We have demonstrated the feasibility of a system based on image processing to measure enzyme activity inside morphologically classified individual cells. When used in this system, quinidine inhibited naphthol AS-D chloroacetate esterase in polymorphonuclear neutrophils and alpha-naphthyl acetate esterase and alpha-naphthyl butyrate esterase in monocytes. These effects were dependent on the duration of exposure and on drug concentration. Dose-effect relationships were established and the concentration at which 50% inhibition (ID-50) occurred was used as a reference point to compare the toxicity of different compounds. Chloroquine, primaquine, and quinine (which, like quinidine, possess a quinoline ring) also affected the esterases, but had no effect on several other enzymes. Neostigmine inhibited the esterases we studied but only at a very high concentration. Various chemicals inhibited the enzymes within the cells, as has been demonstrated for the enzymes in plasma.

Animal Testing Alternatives↗
PubMed1987

Training children in road crossing skills using a roadside simulation.

Five-year-old children were trained in road-crossing skill using a new method which allows them to act safely in relation to vehicles on a normal road. The children learned to time their crossings of a "pretend road" as if the vehicles were on this, rather than on the adjacent road. A previous study, using a single lane of traffic, showed that many children performed well in this simulation with minimal instruction, but that five-year-olds were generally less proficient than older children. In the present study, the method was extended to the more realistic case of two-way traffic, and training programmes for five-year-olds were assessed. (In addition, the performances of adults in the two-way pretend task and in actually crossing the road were compared; the results confirmed the validity of the simulation. After a few sessions of guided practice, the children's efficiency in making use of gaps by setting off promptly after a vehicle had passed improved markedly; in single-lane crossing they reached almost adult standard. In both single-lane and two-way crossing they became as successful as adults in completing their crossings before a second vehicle passed and they took account of the duration of the gap by crossing more quickly when time was short. They remained very cautious, rejecting many adequate gaps. The standard of performance after a few sessions of two-way crossing was maintained over a three week break in training. Practice with one-way traffic did not help them with two-way crossing. In sum, after practice in the simulation, five year olds develop a degree of competence normally shown by older children, whose experience on the roads puts them at lower risk. This suggests that the simulation, which allows children to safely explore and develop their capabilities more fully than when actually crossing the road, would be a valuable addition to road safety programmes.

Accident Prevention↗
PubMed1987

High resolution two-dimensional polyacrylamide gel electrophoresis of cerebrospinal fluid in patients with neurological diseases.

The protein pattern of cerebrospinal fluid (CSF) of 334 patients with various neurological and systemic diseases was investigated by high resolution two-dimensional electrophoresis (2-DE). 2-DE gels of normal CSF contain proteins which are not detectable in 2-DE gels of serum. Disturbances of the blood-brain or blood-CSF barrier, and degenerative diseases of the brain and malignant diseases produce specific changes on 2-DE gels of the CSF. The appearance of 10 spot areas in the light chain region of 2-DE gels seem to be connected with the diagnosis of multiple sclerosis. The sensitivity and the specificity of these spot areas for the diagnosis of multiple sclerosis are described. Proteins within the ten spot areas are immunoglobulin light chains or substances which cross-react very strongly with light chain antibodies as demonstrated by immunoblotting and immunoabsorption.

Adolescent↗