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Biomedical subjects

C E Johnson

Publications and source records attributed to C E Johnson.

At least 145 records · Page 8Linked to original sources
PubMed1983

Heat and water vapor transport in the human upper airways at hyperbaric conditions.

Heat and mass transfer mechanisms have been characterized in physical models of human cadaver airways to simulated depths of 305 m with various gas mixtures. Such characterizations offer a detailed understanding of the effects of environmental pressures, gas composition, and respiratory rates (RMV) on the body cooling capacity of the respiratory airways. Empirical heat transfer relationships in the form -Nu = AReNPr1/3 are derived for the oral and nasal passageways during inhalation and exhalation flows. -Nu, Re, and Pr are the dimensionless Nusselt, Reynolds, and Prandtl numbers, respectively. The Nusselt and Reynolds numbers are based on the diameter and gas flow rate in the trachea and are applicable to Reynolds number values up to 70,000.

Air↗
PubMed1983

Dopamine antagonist effect of verapamil on isolated perfused rabbit ear artery.

Rabbit ear arteries were isolated and perfused with Krebs-bicarbonate solution. Brief periods of supramaximal nerve stimulation caused reproducible constriction of the arteries, which was inhibited by dopamine at concentrations ranging from 3.3 X 10(-9) to 3.3 X 10(-7) M. The inhibitory effect of dopamine was antagonized by sulpiride and by verapamil. The dose-response curve to dopamine was shifted to the right by both sulpiride and verapamil, indicative of competitive inhibition. The dopamine antagonist activity of verapamil does not appear to be a consequence of its Ca++ channel inhibitory activity because other calcium antagonists (e.g., nitrendipine and diltiazem) had no similar action.

Adrenergic alpha-Antagonists↗
PubMed1982

The promise of satellite clinics.

A community hospital has developed a successful model for establishing affiliated primary care centers in semirural areas without the use of federal or foundation money. Unique features of the program include funding through community stock sales and ultimate control by a community board of directors. Additional features include the establishment of a for-profit, wholly owned subsidiary of the hospital; development of a complete range of planning, management, and recruitment services; retention of freedom of choice for referrals and hospitalizations by both patients with physicians; and a but-our provision for the physicians.

Capital Financing↗
PubMed1982

Predictive engineering formulations for diver heating.

Predictive heat transfer equations have been developed to estimate the local supplementary heating necessary to support a resting diver. These formulations consider the diver's passive thermal protection in the form of a diving dress and the effects of his ambient environment upon the dress thermal resistance. The mathematical model performs a numerical analysis on discrete regions comprised of the skin, dry protective suit, breathing gas mixture and the surrounding fluid environment. The parametric properties associated with the heat transfer correlations were obtained from validated experimental heat flux and skin temperature data collected under specific environmental conditions. The supplementary heating required to maintain a diver is obtained by determining the heat flux that would be lost were he not heated and subtracting from this the normal heat flux expected from a resting euthermic subject. Applying this principle to each of the regions, it is possible to predict the supplementary heating necessary to compensate for an excessive flux.

Body Temperature Regulation↗
PubMed1982

Comparative activities of N-formimidoyl thienamycin, ticarcillin, and tobramycin against experimental Pseudomonas aeruginosa pneumonia.

The therapeutic efficacies of disodium ticarcillin, tobramycin sulfate, and N-formimidoyl thienamycin (MK0787) were compared in guinea pigs with experimentally induced Pseudomonas aeruginosa pneumonia. Survival rates were 35% for ticarcillin, 80% for tobramycin, and 75% for N-formimidoyl thienamycin. Numbers of viable Pseudomonas organisms in lungs approximately 3 h after the first dose of drug were nearly 10-fold fewer in tobramycin- or N-formimidoyl thienamycin-treated animals than in ticarcillin-treated animals. Our data suggest that N-formimidoyl thienamycin may have therapeutic efficacy against respiratory infections with P. aeruginosa equivalent to that of tobramycin.

Animals↗
PubMed1982

Equations for predicting diver regional skin temperatures as a function of mean skin temperature.

A series of linear algebraic equations have been derived from those of Kerslake (Flying Personnel Research Committee Memo 213, R.A.F. Institute of Aviation Medicine, 1964) for predicting the regional skin temperatures of a quasi-euthermic diver having pronounced vasoconstriction. The equations were developed by numerically analyzing twelve regional skin temperatures recorded from five resting subjects exposed to a hyperbaric chamber environment of 20 degrees C, 95% helium, and 5% oxygen pressurized to the equivalent of 200 msw (650 fsw). The independent variable of the basic correlation is an arbitrarily defined mean skin temperature; the empirical equations were developed for the purpose of assisting a designer in estimating regional supplementary heating requirements for a diver wearing a thermal protection garment of known composition. The developed equations were authenticated by comparing the predicted normalized regional temperature with the respective experimental normalized temperature obtained from several set of physiological data collected during the evaluation of the Naval Coastal System Center's diver thermal protecting garment (DTP). The results of these comparisons of nondimensionalized temperatures indicated that the derived correlations should accurately predict the skin temperature of the principal regions as a function of mean skin temperature with a normal error of no more than 15%.

Atmospheric Pressure↗
PubMed1981

Mössbauer spectroscopic studies of the nature of centre X of photosystem I reaction centres from the cyanobacterium Chlorogloea fritschii.

Reduced photosystem I samples, which give the electron paramagnetic resonance (EPR) signals associated with A, A and B, and A, B and X centres, have been studied using Mössbauer spectroscopy. The Mössbauer spectra obtained from each type of sample is different, which indicates that iron is associated with all three centres. The spectra are similar to those obtained from ferredoxins with 4Fe-4S centres and were fitted with oxidized and reduced components, the relative proportions depending on the degree of reduction of the sample as monitored by EPR. The sample which gave only the A EPR signal showed about 26% of the reduced component, the sample which gave A and B EPR signals showed about 48% of the reduced component, while the sample which gave A, B and X EPR signals showed about 65% of the reduced component. The measurements are consistent with X being a 4Fe-S4 centre.

Cyanobacteria↗
PubMed1981

Effect of intravenous furosemide on serum theophylline concentration.

The effect of furosemide on the serum theophylline concentration (STC) was investigated in 10 patients at steady state on a continuous i.v. aminophylline infusion. A baseline STC was obtained 48 hours after the initiation of the maintenance infusion. The patients were monitored closely for the last 24 hours of the maintenance period with hourly flow records to assure the same continuous rate. Urine output was measured over four hours, then, a 40-mg dose of furosemide was administered i.v. over two minutes, and the aminophylline infusion was continued at the same rate. Urine output was measured for four hours after the furosemide dose, and then a second STC was obtained. The 40-mg furosemide i.v. bolus injection caused an average increase of 2.9 micrograms/ml in STC, with a range of 0.5--5.5 micrograms/ml. The urine volumes increased by an average of 995 ml above the baseline, with a range of 630--1377 ml. Both of the increases were significant at the p less than 0.005 level. Patients stabilized on a theophylline dosage regimen should be monitored closely during the addition or discontinuation of furosemide therapy. Furosemide has been shown to be another factor that can alter STC.U

Adult↗
PubMed1980

Effect of theophylline, terbutaline, and their combination on the immediate hypersensitivity skin-test reaction.

Methylxanthines and beta agonists can be expected to inhibit the antigen-induced hypersensitivity skin-test reaction by affecting cyclic 3', 5'-adenosine monophosphate (cyclic AMP) metabolism, yet in vivo studies produce conflicting results. The discontinuation of these drugs prior to skin testing may result in the exacerbation of asthmatic symptoms; however, if these drugs are maintained, the validity of the test remains in question. To determine the effect of these drugs on the skin-test response, 15 patients received theophylline, terbutaline, the combination, and placebo in a double-blind study. No statistically significant difference (p greater than 0.05) was found for the areas of wheal and flare in response to injected allergens or histamine, between placebo and theophylline, terbutaline, and their combination. A marginal decrease in wheal area in response to codeine following combination therapy was observed. Therapeutic theophylline and terbutaline serum concentrations were documented. There is no need to discontinue theophylline or terbutaline prior to skin testing.

Adult↗
PubMed1980

Fibrinolytic therapy in subacute bacterial endocarditis: an experimental study.

The effect of adding fibrinolytic to penicillin therapy in experimentally induced streptococcal bacterial endocarditis has been studied in the rabbit. In 9 day old infected lesions, the vegetations could be substantially reduced in size after a 3 day course of intravenous streptokinase. Quantitative microbiological techniques demonstrated that the addition of streptokinase to standard intravenous penicillin treatment led to more rapid sterilisation of the vegetations. Embolism to lungs and kidneys was assessed in treated and untreated rabbits. Penicillin reduced the rate of embolism but the addition of streptokinase reversed this effect and gave values similar to those recorded in untreated animals.

Animals↗
PubMed1980

Comparison of methods of estimating creatinine clearance in children.

The accuracy of seven previously available and two new methods of estimating creatinine clearance (Clcr) from serum creatinine (Scr) and other patient variables was studied in pediatric patients. The medical records of 122 patients, aged 1--18 years, who had one or more 24-hour urine creatinines determined were reviewed; 158 determinations were studied. Equations for estimating Clcr based on patients' Scr, age, height, total body mass (TBM), adjusted body mass (ABM), and body surface area (and derivatives of these variables) were analyzed by correlation and regression analysis. Of the two derived equations, the one based on height and Scr was the simplest and most accurate; a nomogram for this equation is presented. The correlation coefficient for this derived equation (r = 0.802) was equivalent to that found for the best of the seven published methods (Method 7, based on Scr and height). Substitution of ABM for TBM in the published methods reduced the mean differences between predicted and measured Clcr. The derived equation based on Scr and height appears to be clinically useful in predicting Clcr in children but further study is required to ascertain whether it is generally more accurate than Method 7.

Adolescent↗