Michael C. Theodorakis

Systemic and Regional Blood Flow Distribution inUn anesthetized Swine and Swine Anesthetized with Halothane

In order to study the distribution of cardiac output during various anesthetic regimens, we measured regional organ blood flow using 15 μm diameter radionuclide-labeled microspheres injected into the left atrium. Studies were carried out in nine pigs during resting unanesthetized state (control), du

Regional myocardial blood flow and coronary vasodilator reserve during acute right ventricular failure due to pressure overload in swine

Abstract Right ventricular (RV) failure due to acute RV pressure overload has been attributed to the inability of RV myocardial blood flow to increase following maximal RV coronary vasodilatation, which may occur with mild to moderate RV systolic hypertension, such that further increments in RV systolic pressure by way of decreasing RV coronary driving pressure hamper RV myocardial perfusion. To test this hypothesis, myocardial blood flow (15-μm-diameter tracer microspheres) was studied during adenosine infusion (3 μmole · kg −1 · min −1 ) instituted before and during acute RV failure in 10 closed-chest ketamine anesthetized young pigs. Acute RV failure, characterized by 10 mm Hg increase in RV end-diastolic pressure, 15 mm Hg drop in mean aortic pressure and 30% drop in cardiac output, was produced by partial constriction of the main pulmonary artery upon inflation of a previously implanted cuff. Acute RV failure was accompanied by a significant increase in myocardial blood flow in the RV free wall (91%) and right side of the septum (44%) while left ventricular myocardial blood flow was unaltered. Adenosine infusion during acute RV failure resulted in a significant increase in ventricular myocardial blood flow despite a significant drop in mean aortic pressure while RV end-diastolic and RV systolic pressures were further increased. Thus, the concept of maximal RV coronary vasodilatation during acute RV failure was not supported by these data. RV myocardial blood flow with adenosine infusion during acute RV failure (3.8 ml.min −1 · g −1 ) was, however, only 67% of that observed without RV failure (5.7 ml.min −1 · g −1 ). Also, during acute RV failure + adenosine, RV endo:epi flow ratio decreased markedly. We believe these differences were due to a combination of factors, namely, decreased diastolic duration for RV perfusion consequent upon prolongation of RV systole due to RV pressure overload, and higher back pressure opposing the diastolic RV perfusion because of significantly elevated preload.

Direct Radioimmunoassay for Determination of Betamethasone 17-Benzoate

AbstractA direct radioimmunoassay for the determination of betamethasone 17-benzoate (I) in serum was developed. In this assay, a highly specific antibody is used to bind the 125I-labeled antigen. Polyethylene glycol is used for the separation of the free from bound antigen. A blocking agent (ANS) was used to inhibit binding of the steroid onto serum proteins. The minimum detectable concentration was 15 pg/ml. The intra and inter assay coefficients of variation were 7.4% and 10.2%, respectively. This assay required 0.1 ml of serum and it did not require extraction or chromatographic separation of the steroid.

GLC and Radiometric Determination of Hydrolysis Rate Constants of [[2-[4-(Methoxycarbonyl) 1) Benzamido]Diethyl]Triamino] Methylated Polystyrene

AbstractThe rate constants of the hydrolysis of the methyl ester in 3N HC1 as function of temperature was determined and found to be in the range of 1.3 × 10-2 to 1.2 × 10-1 h-1 at 40 and 60 C respectively. The rate constants were determined by GLC on Pola-pack-Q and by a radiotracer technique.

A Double Antibody Assay for the Direct Determination of [N-(4-Amino)Phenyl] Aminophenyl Iminodiacetic Acid and its Derivatives in Serum

AbstractA double antibody assay for the determination [N-(4-amino)phenyl] aminophenyl iminodiacetic acid (I) and a number of its derivatives in serum has been developed. The same antiserum and tracer were used for the determination of the serum levels of derivatives of (I). The minimum detectable concentration of I that was detectable was 6 ng/ml. The precision error was less than 1% and the accuracy as indicated by the recovery ratios was satisfactory for all derivatives of I.

A study on particulate formation of silicone-coated glass surfaces

Abstract Silicone-coated glass surfaces produced by two different siliconization procedures were exposed to an extreme and rapid temperature change (−70°C to + 25°C). The extent of the formation of particulate (>25 μm) and the integrity of silicone-film were evaluated with respect to siliconization procedure and curing cycle. In all instances, the silicone-fllm integrity test showed that the integrity of the silicone-film was damaged when the coated surface was exposed to an extreme change of temperature. Furthermore, it was shown that in both siliconization procedures the formation of silicone particles (>25 jum) was reduced to a minimum when 0.5% (w/v) siliconizing fluid was used, and the coated surface was cured at 250°C for 3 h or at 300°C for 2 h. Under these conditions, a silicone coat relatively more resistant to extreme temperature change was obtained.