Hemodynamic determinants of the time-course of fall in canine left ventricular pressure

The hemodynamic determinants of the time-course of fall in isovolumic left ventricular pressure were assessed in isolated canine left ventricular preparations. Pressure fall was studied in isovolumic beats or during prolonged isovolumic diastole after ejection. Pressure fall was studied in isovolumic relaxation for isovolumic and ejecting beats (r less than or equal to 0.98) and was therefore characterized by a time constant, T. Higher heart rates shortened T slightly from 52.6 +/- 4.5 ms at 110/min to 48.2 +/- 6.0 ms at 160/min (P less than 0.01, n = 8). Higher ventricular volumes under isovolumic conditions resulted in higher peak left ventricular pressure but no significant change in T. T did shorten from 67.1 +/- 5.0 ms in isovolumic beats to 45.8 +/- 2.9 ms in the ejecting beats (P less than 0.001, n = 14). In the ejecting beats, peak systolic pressure was lower, and end-systolic volume smaller. To differentiate the effects of systolic shortening during ejection from those of lower systolic pressure and smaller end-systolic volume, beats with large end-diastolic volumes were compared to beats with smaller end-diastolic volumes. The beats with smaller end-diastolic volumes exhibited less shortening but similar end-systolic volumes and peak systolic pressure. T again shortened to a greater extent in the beats with greater systolic shortening. Calcium chloride and acetylstrophanthidin resulted in no significant change in T, but norepinephrine, which accelerates active relaxation, resulted in a significant shortening of T (65.6 +/- 13.4 vs. 46.3 +/- 7.0 ms, P less than 0.02). During recovery from ischemia, T increased significantly from 59.3 +/- 9.6 to 76.8 +/- 13.1 ms when compared with the preischemic control beat (P less than 0.05). Thus, the present studies show that the time-course of isovolumic pressure fall subsequent to maximum negative dP/dt is exponential, independent of systolic stress and end-systolic fiber length, and minimally dependent on heart rate. T may be an index of the activity of the active cardiac relaxing system and appears dependent on systolic fiber shortening.     

Endocrine studies during the refeeding of young women with nutritional amenorrhea and infertility

Serial endocrine studies were performed during the refeeding of a group of nine young women who presented with amenorrhea associated with injudicious dieting. No significant psychopathology was disclosed by the Lanyon Psychological Screening Inventory in any of the patients, six of whom were single and three married and infertile. The mean weight before refeeding was 81.6% of the normal for height. The mean initial serum follicle-stimulating hormone concentration was within the limits of normal for young women of reproductive age, but the serum luteinizing hormone (LH) concentration and the vaginal maturation score were low. As weight was regained, the serum LH concentration increased (the pooled r for LH versus percent normal weight = 0.85) and the vaginal maturation score rose (the pooled r for vaginal maturation score versus percent normal weight = 0.93). When a mean weight of 96.6% of normal was reached after a mean of 5.3 (range, 2 to 11) months of refeeding, spontaneous menses occurred. The initial cycle was ovulatory in two instances and anovulatory in five, as determined by basal body temperature patterns, plasma progesterone concentrations, and endometrial biopsies. With continued weight gain, menstruation became regular and the three married patients conceived.     

The posterior aortic wall echocardiogram. Its relationship to left atrial volume change

The normal posterior aortic wall echocardiogram shows anterior motion during left ventricular systole and predominantly posterior motion in three phases during left ventricular diastole. In six patients undergoing simultaneous left atrial angiograms and posterior aortic wall echocardiograms, there was excellent correlation between the posterior aortic wall motion and the change in the left atrial angiographic area showing the value of the posterior aortic wall echocardiogram in describing the left atrial volume curve. Left atrial and left ventricular pressures were measured with manometer tip catheters and correlated with simultaneous posterior aortic wall and mitral valve echocardiograms in four patients with atrial septal defects. These echocardiographic, angiographic, and hemodynamic correlations, as well as other evidence reported in this paper suggest that a major portion of posterior aortic wall motion is related to left atrial events and describes the left atrial volume curve.     

The use of pivalic acid as a reference substance in measurements of production of volatile fatty acids by rumen micro-organisms in vitro

1. A procedure is described for using pivalic acid as an inert reference substance in determination of changes in concentrations of volatile fatty acids (VFA). 2. Pivalic acid in concentrations of up to 80 mmol/1 had no effect on production of methane or VFA by rumen contents. 3. Pivalic acid was inert during incubation with rumen contents from sheep given different diets and with samples taken at different times with respect to feeding.     

Posthyperventilation isocapnic hyperpnea

From the results of this study, it appears that whole blood alone or red blood cells reconstituted with saline solution do not adequately replace the loss of albumin and concomitant decrease in colloid oncotic pressure that occur during extensive intraabdominal and intrathoracic operations. Since colloid oncotic pressure is a major factor in the restitution of intravascular volume from stores of interstitial fluid and since it may also play a role in the development of postoperative pulmonary problems, it is important to maintain a relatively normal colloid oncotic pressure during the operation and in the immediate postoperative period. Although dextran can be used for this purpose, its short half-life of four to six hours and associated coagulation problems militate against its use in large quantities. This leaves purified protein fraction or salt-poor albumin as the main sources of protein for the maintenance of colloid oncotic pressure. Both of these products are expensive and short in supply. The oncometer in present use is a clinically feasible and rapid, one to three minutes, means of determining the colloid oncotic pressure. It permits a rational approach to the use of albumin products, avoiding the pitfalls of under or excess administration in the operative and postoperative periods.     

Arterial blood gases in acute pulmonary edema

Arterial blood gas and pH measurements in 82 patients with acute pulmonary edema of cardiogenic origin entering the emergency department varied widely and were unpredictable using clinical examination. The mean arterial oxygen tension (PaO2) measured in 71 patients breathing room air was 59 mm Hg. Fourteen of the 82 patients were acidemic; 35, alkalemic and 33 had a pH in the normal range. The acidemic group had markedly lower PaO2, all under 60 mm Hg. Oxygen and furosemide were used in all cases and effectively corrected the hypoxia and reduced pulmonary congestion. Other drugs used included aminophylline (14 patients), morphine sulfate (9 patients) and digoxin (3 patients). Five of the nine patients who received morphine were hypercarbic initially but the CO2 retention did not worsen. No patient died during the initial 48 hours. This study reiterates the importance of directing therapy at ventilatory and cardiac abnormalities and points out the value of arterial blood gas monitoring to assess the initial status, monitor the patient's course, and to select drug therapy.     

Cerebrospinal fluid creatine phosphokinase in the normal dog

Sixty-seven cerebrospinal fluid samples obtained from 44 healthy dogs were assayed for creatine phosphokinase enzyme activity. All samples contained 1 Sigma unit or less of creatine phosphokinase. Temporal variability within individuals was minimal. The biological characteristics and potential use of this enzyme in neurologic disease are discussed.