The viscoelastic nature of chorioamniotic membranes

This study establishes the viscoelastic nature of the human chorioamniotic membrane. Membrane tissue taken from term pregnancies was placed in a state of biaxial stress consistent with the condition in which membranes rupture in normal healthy patients. The phenomena of creep, stress relaxation, elastic recovery, and time-dependent load deformation relations were demonstrated. The experiments needed to produce these phenomena are described. The results are graphically reported. The experiments were performed using samples of fetal membranes and compared to gum rubber which is a known elastic material. From the results, one can conclude that fetal membranes are viscoelastic. The flow freely under applied stress, and they have elastic and viscous properties which are time dependent.     

Research in the family practice residency program

Research activity in family practice is becoming increasingly important as the specialty matures past its initial organizational and developmental phase. Family practice residency programs are directly involved in the definition and implementation of modern concepts in family medicine and frequently have available the necessary tools and resources for substantive research of various types. These programs therefore have both the opportunity and responsibility to become actively involved in research. Significant contributions have already been made in this area by faculty and residents in a number of family practice residency programs. This paper provides an overview of research areas in family practice, presents some examples of research to date, and suggests some practical approaches to facilitate further research efforts in family practice residency programs.     

Natural history and evaluation of ST segment changes and MB CK release in acute myocardial infarction

The experimental evidence relating ST segment elevation in the electrocardiogram to the progress and extent of ischaemic myocardial damage is discussed. There are difficulties in applying this to patients: the reproducibility of praecordial mapping was tested using a multiple analysis of variance. This showed that factors such as time after the onset of myocardial infarction and posture can affect measurements of sigmaST elevation significantly. There was a pattern of changes in segmaST elevation and of changes in plasma MB CK activity in a group of patients with uncomplicated anterior infarction. A significant byt weak correlation was found between sigmaST elevation in the first hour and the total MB CK activity released into the plasma, but not at any other time. The use of sigmaST elevation as a measure of the extent of ischaemic damage is unreliable. In 5 patients with a variety of complications of acute anterior infarction, changes in sigmaST elevation werr significantly different from the uncomplicated group, and MB CK release profiles suggested further necrosis. The pattern and time course of ST segment changes may be of use in assessing the progress of ischaemic myocardial damage.     

The association between fasting hyperbilirubinaemia and serum non-esterified fatty acids in man

1. The concentrations of plasma total and unconjugated bilirubin and of serum nonesterified fatty acids (NEFA) have been measured in two healthy subjects during fasts of up to 21 h. 2. Fasting was either continuous or interrupted by various procedures that altered the concentrations of NEFA and total bilirubin. 3. When NEFA concentrations were increased by the administration of noradrenaline, heparin or caffeine, bilirubin concentrations also rose. 4. When NEFA concentrations were lowered by insulin, bilirubin concentrations fell. 5. Meals of 3-138 kJ and more, taken during the fasting period, lowered total bilirubin and NEFA concentrations in both subjects, whereas the effects of smaller meals were less consistent. 6. These studies demonstrate a statistically significant correlation between total bilirubin and NEFA during uninterrupted fasting and an association between these variables under other experimental conditions. They suggest that the control of bilirubin concentrations in the blood is linked to lipid metabolism.     

A spectrum of diseases of the thyroid gland as imaged by gray scale water bath sonography

A method of performing gray scale thyroid echography with a 3.5 MHz focused transducer and an open water bath is described. A preliminary echographic classification of abnormalities and representative echograms illustrating various thyroid disorders are presented.     

Central and regional circulatory effects of adding arm exercise to leg exercise

7 young, healthy, male subjects performed exercise on bicycle ergometers in two 20 min periods with an interval of 1 h. The first 10 min of each 20 min period consisted of arm exercise (38--62% of Vo2 max for arm exercise) or leg exercise (58--78% of Vo2 max for leg exercise). During the last 10 min the subjects performed combined arm and leg exercise (71--83% of Vo2 max for this type of exercise). The following variables were measured during each type of exercise: oxygen uptake, heart rate, mean arterial blood pressure, cardiac output, leg blood flow (only during leg exercise and combined exercise), arterio-venous concentration differences for O2 and lactate at the levels of the axillary and the external iliac vessels. Superimposing a sufficiently strenuous arm exercise (oxygen uptake for arm exercise greater than 40% of oxygen uptake for combined exercise) on leg exercise caused a reduction in blood flow and oxygen uptake in the exercising legs with unchanged mean arterial blood pressure. Superimposing leg exercise on arm exercise caused a decrease in mean arterial blood pressure and an increased axillary arterio-venous oxygen difference. These findings indicate that the oxygen supply to one large group of exercising muscles may be limited by vasoconstriction or by a fall in arterial pressure, when another large group of muscles is exercising simultaneously.     

Renal cortical blood flow distribution in obstructive nephropathy in rats

To examine the role of intrarenal hemodynamics in in obstructive nephropathy, we determined cortical blood flow distribution (CBFD) in rats with bilateral ureteral occlusion (BUO) and unilateral ureteral occlusion (UUO) during and after release of obstruction. Prior to release of obstruction of 24 hours' duration, we found that outer cortical perfusion decreased by 20+/-5% in both BUO and UUO rats. Furthermore, one hour after release of BUO, there was rapid normalization of CBFD associated with a modest return of glomerular filtration rate (GFR), an almost complete return of renal blood flow (RBF), and a marked postobstructive diuresis. In contrast, after release of UUO, we observed that outer cortical perfusion remained decreased by 21+/-31%, both GFR and RBF remained markedly depressed, and no diuresis occurred. These data demonstrate (1) marked ischemia of the outer cortex in both BUO and UUO during obstruction, (2) a rapid return of CBFD to a normal pattern after release of BUO, but (3) persistent outer cortical ischemia following release of UUO.