Wakim, Khalil G.

Abstract Our experiences with the automatic titration method of quantitating serum calcium and magnesium are presented. In addition, modifications of the original procedure to allow determination of intraerythrocyte concentrations of magnesium are described. It appears that adoption of a separate magnesium standard in addition to the calcium standard, plus certain other minor modifications designed to minimize the variables inherent in the procedure, provides a significant increase in accuracy and reproducibility of results. Values for intraerythrocyte magnesium concentration in 9 normal dogs were found to range from 4.69 to 5.77 mg./100 ml. Values for 4 dogs that received long-term administration of chlorothiazide also fell within this normal range.

Abstract Comparative studies reveal that the ethylenediamine and the trihydroxyindole method when employed as suggested are suitable for assessing sympatho-adrenal activation under various stressful conditions that are accompanied by release of catecholamines into the circulation. Both methods are very accurate in quantitating epinephrine or norepinephrine that has been added to plasma or whole blood, although recovery from blood is less, owing mainly to some association of catecholamines with formed elements, primarily erythrocytes. Use of sodium thiosulfate in the ethylenediamine procedure minimizes association of catecholamines with formed elements. If blood samples are cooled in ice water when collected, association of catecholamines with blood cells can be further reduced. In the trihydroxyindole method, unless tubes containing blood samples are immediately immersed in ice water, a significant amount of catecholamines will disappear from plasma, because of this association of catecholamines with cells.

A study was made of the disappearance of sodium diatrizoate-I131 from the plasma of ten dogs after single intravenous injections. The plasma disappearance curves suggested a two-compartment system. The renal plasma clearance of diatrizoate-I131 calculated from these curves and the conventional renal plasma clearance of creatinine were not statistically different. Clearances calculated from the urinary excretion and midperiod plasma concentration of radioactivity in four experiments yielded values averaging 10% less than the creatinine clearance. Chromatographic studies of commercially available diatrizoate-I131 revealed the presence of about 5% free iodide and of about 5% of unidentified impurities. These impurities seem to account, partly at least, for the differences found between diatrizoate clearance and creatinine clearance. Biliary excretion and erythrocytic uptake of diatrizoate were minimal and did not appear to influence the analysis.

Ligation of various combinations of arteries in the neck in 21 dogs demonstrated that there is little clinical effect following ligation of three or less of the major arteries to the brain and that most dogs survive after all the major arteries to the brain are ligated in the neck. A procedure is described in which the collateral circulation is determined by injection of liquid vinyl acetate into the arterial tree in dogs immediately after death subsequent to one-stage ligation of all the major arteries to the brain. The main anastomotic channels are branches of the costocervical and omocervical arteries that join muscular branches of the vertebral arteries beyond the ligated points. No anastomotic channels were detected in the carotid systems.