An X-ray analysis of adjuvant arthritis in the rat. The effect of prednisolone and indomethacin

A detailed evaluation has been made of the radiological changes occurring in the hindfeet of rats with adjuvant arthritis from 0 to 50 days after injection with Freund's Complete Adjuvant (FCA). The results were compared with concomitant foot swelling and the presence of histopathological abnormalities at the end of the experiment. In addition, the effects of oral administration of prednisolone and indomethacin administered either from one day before injection with FCA to 21 days afterwards, or from 21 to 35 days after injection with FCA, has been investigated on all these changes. The main radiological changes were osteoporosis of the tarsals and metatarsals, erosions of the tarsals and periosteal reactions in the metatarsals which were visible on day 10 and progressed up until 21-24 days after injection with FCA. Cystic fibrosis was noted in the metatarsals on day 14 and in the tibia, fibula and tarsals on day 21 and progressed to become the dominant abnormality by day 35. Cystic fibrosis and subsequent calcification, which was apparent on day 35, were the main features of the disease when the animals were killed on day 50. 10 and 30 mg/kg prednisolone and 0.3 and 3 mg/kg indomethacin both reduced the total X-ray score when administered either from day - 1 to 21, or from day 21-35, but did not at any time inhibit the osteoporosis or erosions. Their effect was mainly on preventing the cystic fibrosis and calcification which occurred later in the disease. Prednisolone and indomethacin also reduced the periosteal reaction when administered from one day before injection with FCA, but they were inactive in this respect when dosing was started on day 21 when the periosteal reaction was well established. Therefore, the results suggest that prednisolone and indomethacin inhibit the later sequelae of the disease and do not interfere with either the initial events or the disease process itself. There was a good correlation between the toal X-ray score, foot size and total histopathology score at the end of the experiment, and also an apparent correlation between total X-ray score and foot size throughout the experiment. Although this suggests that foot size is sufficient to indicate the overall reaction in adjuvant arthritis, X-ray analysis may detect clinically useful anti-rheumatoid activity which might not be evident from measurements of foot size alone.

Rapid and accurate measurement of growth of solid tumours and changes in the tumour bed in the rat by the technique of volumetric displacement

An apparatus which has been widely used in rats for measuring swelling of the foot induced locally by inflammatory agents has been adapted to measure rapidly, accurately and objectively, the growth of tumour cells transplanted to the foot, and the reactions of the normal tissues (tumour bed) to tumour growth. General features on the apparatus and the techniques used are described. Examples are provided of preliminary measurements made of normal growth of the foot, reactions of the foot to two injurious agents (histamine and Corynebacterium parvum) and of growth of allogeneic (W256) tumour cells.

Coronary hemodynamics during positive (+G-z) acceleration

Left circumflex (LC) and left anterior descending (LAD) coronary flows, coronary perfusion pressure (P-ca), and arterial O-2 content (Cao-2) were determined in five dogs, lightly anesthetized with chloralose, during exposures to +2.0 and +3.0 G-Z stress; and for three of these dogs at +3.5-G-Z. At +2.0 G-Z, except for one dog with the most marked decrease in P-ca, KC and LAD flows increased above control by 15 s and thereafter gradually returned toward control; coronary resistances were significantly below control at 15 and 30 s (p smaller then 0.05). At +3.0 G-Z, LC and LAD flows were significantly greater than control (p smaller 0.05) from 30 to 60 s, while resistances were below control (p smaller than 0.05). At +3.5 G-Z, LC flow was maintained above control by a much reduced resistance, with P-ca below control; LAD flow increased in one dog, remained unchanged in one, and decreased slightly in one, although resistance always decreased. Cao-2 did not change significantly at any +G-Z level, and myocardial O-2 transport paralleled the changes in coronary flow.

Re-evaluation of a tilt-back seat as a means of increasing acceleration tolerance

Relaxed tolerance was determined on seven subjects exposed to rapid onset (RO; 1 G/s) and gradual onset (GO; 1 G/10 s) acceleration at seat back angles of 13 degrees, 30 degrees, 45 degrees, 55 degrees, 65 degrees, and 75 degrees from the vertical. There was no significant difference between relaxed tolerance at the control angle of 13 degrees and tolerance at 30 degrees. However, at 45 degrees there was a significant 0.5 G increase in tolerance compared to control. Thereafter, tolerance continued to increase in an exponential manner to 8 G at 75 degrees, an increase over control of 100%. As relaxed tolerance increased with increasing back angle, peak heart rate during acceleration significantly decreased. In addition, four subjects were instrumented with an esophageal balloon for the measurement of intrathoracic pressure, which was equated as work during the M-1 straining maneuver. The amount of thoracic pressure necessary to maintain a preselected visual field declined as the back angle was increased from 13 degrees to 45 degrees to 65 degrees at the same acceleration level. The increase in relaxed tolerance along with the decrease in heart rate and the decrease in esophageal pressure at the greater back angles all demonstrate the acceleration protection provided by the tilt-back seat.

Ventricular activation process in minipigs

Because the form of QRS from the body surface of pigs is different from that of carnivores or ungulates, and because that form is dependent upon pathways of ventricular activation, this study was designed to study pathways of ven tricular activation in pigs. Twelve pigs were anesthetized and right or left hemithoracotomies were performed to expose the heart. Contiguous bipolar electrograms were recorded from button electrodes on the epicardium and from both faces of the interventicular septum, and from multipolar plunge electrodes introduced into the intramural regions of both ventricles. Electrograms were recorded simultaneous with the Z-axis ECG at 625 mm/sec paper speed on a photographic oscillograph. Times of arrival of waves of activation at numerous points in the ventricle were referenced to the peak of the R-wave in the Z-axis ECG. During the initial 10 msec of QRS, the apical-third of the interventricular septum is activated from left to right. During the next 40 msec of QRS, waves of activation originating at the cranial portion of the right ventricle and the caudal portion of the left ventricle engulf the epicardium toward the interventricular septum and slightly in an apico-basilar direction. Activity begins slightly earlier at the caudal aspect of the left ventricular free-wall and terminates on the pulmonary conus region. During the terminal 30 msec of QRS, the basilar third of the interventricular septum is activated in a general apico-basilar direction. Through regions of either right or left ventricular free-walls was a general endocardial to epicardial activation observed. These pathways of ventricular activation may be explained by the rather complete penetration of Purkinje fibers through both ventricular free-walls in a manner similar to that of ungulates but different from carnivores and primates.

Observations on factors affecting local forces in the left ventricular wall during acute myocardial ischemia

The factors affecting local myocardial function in the presence of ischemic myocardial damage may considerably influence cardiac function and the extent of tissue damage resulting from the initial ischemic injury. However, previous attempts to study local wall forces in the ischemic myocardium have produced variable results. In the present study, a technique was developed for recording isometric left ventricular wall tension that minimized artifacts due to external forces acting on the ischemic area. Miniature isometric force gauges were implanted in 23 dogs in the left ventricular wall within a zone buffered by two rows of transmural prongs attached to a ring. During a test occlusion of a branch of the left anterior descending coronary artery, the ischemic area was defined by the presence of epicardial ST segment elevation, and force gauges were implanted in marginal or ischemic areas of the myocardium. During a subsequent coronary occlusion wall force in the ischemic area fell immediately by an average of 31 ± 8%. When the occlusion was repeated during isoproterenol infusion, wall tension decreased in previously unaffected areas of the myocardium, although in ischemic areas it remained above previous control ischemic levels. Arterial counterpulsation improved the development of wall tension in the ischemic area by 27% and decreased the extent and amount of ST segment elevation. Thus the present study clearly indicates a significant reduction but not elimination of active myocardial wall force in ischemic zones following experimental coronary occlusion. Moreover, force could be augmented by either isoproterenol or counterpulsation, and counterpulsation can produce a significant improvement in function of the ischemic myocardium while reducing the area of ischemic injury.

Comparison of directly measured left ventricular wall stress and stress calculated from geometric reference figures

Mean left ventricular wall force was determined with a calibrated transmural auxotonic strain gauge in the left ventricle of six anesthetized, open-chest dogs with intact circulation. The gauge was oriented in the plane of the minor left ventricular equator, midway between the papillary muscles. Left ventricular internal volume was derived from the passive pressure-volume curve of the arrested heart and calculated mean wall stress was derived both from spherical and ellipsoidal reference figures for the left ventricle and compared with measured forces. Control left ventricular end-diastolic pressure averaged 3.0 ± 0.6 mm Hg (SE). At this level of end-diastolic pressure, measured peak wall stress averaged 97.2±14.4 g/cm 2 , whereas calculated peak wall stress averaged 79.3±9.9 and 118.6±12.9 g/cm 2 , for the spherical and ellipsoidal models, respectively. Measured end-diastolic wall force values averaged 9.4±4.5 and 29.2±8.1 g/cm 2 at an end-diastolic pressure of 3.0 and 12.3 mm Hg, respectively. In all cases, stress values calculated from spherical reference figures for the left ventricle were significantly lower than those measured directly. In four other experiments, using right heart bypass, the ventricular septum was exposed and active wall force was determined at two or more sites on the left ventricular minor equator. Wall stress at these sites differed by an average of 15.3%, indicating that stresses around the minor equator are relatively uniform. These studies lend validity to the application of geometric models in the calculation of mean wall stress and favor the application of an ellipsoid for the geometric reference figure.