Influence of heating rate in thermal expansion of dental phosphate-bonded investment material

The thermal expansion of a phosphate-bonded investment material was tested when three heating rates were used during the heating procedure. One of them was too low, one too high, and the third, in the middle. The examination was done through the fit of 12 MOD inlays and 12 full crowns in steel master dies. From the results it can be concluded that rates that are too fast must be avoided in the heating procedure, because they reduce the thermal expansion of the phosphate-bonded investment material and thus produce castings with limited fit.

Regulation of cardiac output and gut blood flow in the sea raven,Hemitripterus americanus

Coeliac artery blood flow (Fca) before and after feeding was recorded in the sea raven. To obtain basic information about the scope of cardiovascular adjustment in the sea raven, a separate series of experiments was performed, in which ventral (Pva), and dorsal (Pda) aortic blood pressure, heart rate (HR) and cardiac output (jaz) were monitored during rest and encouraged exercise.Measurements of coeliac artery flow showed that visceral blood flow is substantial, particularly after feeding, and variations in the visceral vascular conductance affect Pda directly. Simultaneous recordings of intestinal and dorsal aortic blood pressures showed no measurable difference in the two arterial pressures, refuting the idea of a vascular control at the level of the main coeliac artery. Thus, in the sea raven, the adrenergic tonus affecting the visceral vasculature presumably acts at the arteriolar level.Sea ravens encouraged to exercise increased theirjaz by 64%; 32% through HR and 25% through stroke volume. The increase injaz during encouraged exercise was sufficient to produce an elevation of both Pva and Pda, despite an increase of systemic vascular conductance, β-adrenoceptor blockade with sotalol, however, severely impaired the increase injaz during exercise, and the change in Pda was reversed.During rest there were both an adrenergic and a cholinergic tonus affecting the HR, as revealed by the effects of injected pharmacological antagonists. Swimming activity decreased the cholinergic tonus, while the adrenergic tonus increased.

Flow dynamics of the crocodilian heart

We report for the first time the flow events corresponding to the pressure patterns in the left and right aorta (LAo and RAo) during the cardiac cycle in the caiman (Caiman crocodylus ssp). These experiments show a complex LAo flow pattern; an initial small anterograde flow in the early systole is reversed to a backflow at midsystole. At the end of systole there is again a small anterograde flow. This second flow pulse corresponds to a pressure peak ("foramen spike") in the LAo pressure trace. The observed pattern is compatible with the view that the foramen Panizzae is obstructed by the medial cusp of the RAo valve during part of the systole. LAo pressure remains normally above right ventricular pressure throughout the cardiac cycle and there is thus no contribution to LAo flow from the right ventricle. The net flow in the LAo normally equals the flow through the foramen Panizzae and is very small compared with the systemic flow in the RAo.

The importance of nervous and humoral mechanisms in the control of cardiac performance in the Atlantic cod Gadus morhua at rest and during non-exhaustive exercise

The nervous regulation of heart rate and stroke volume in the Atlantic cod Gadus morhua was investigated both in vivo, during rest and exercise, and in vitro. The cholinergic and adrenergic influences on the heart were estimated in experiments with injections of atropine and sotalol. At rest the cholinergic and adrenergic tonus on the heart were 38% and 21%, respectively (ratio 1.81:1). At the end of an exercise period, the cholinergic tonus had decreased to 15% but the adrenergic tonus had increased to 28% (ratio 0.54:1). The results suggest that variation of the cholinergic tonus on the heart is a major factor in the regulation of the heart rate. In one group of fish, cardiac output was also measured, allowing calculation of stroke volume. Cardiac output increased significantly during exercise, and this effect persisted in the presence of both atropine and sotalol, although the increase in heart rate was reduced or abolished. The persisting increase in cardiac output during exercise is due to an increase in stroke volume, reflecting a Starling relationship. In the presence of the adrenergic neurone-blocking agent bretylium, a positive inotropic effect on isolated, paced atrial and ventricular strips was observed. In the atrial preparations the effect persisted after 24 h. The effect was prevented by pretreatment with sotalol or cocaine, but potentiated by phentolamine pretreatment. This shows that bretylium exerts its neurone-blocking action after being taken up into the adrenergic nerves, and suggests that the positive inotropic effect of bretylium observed in vivo is due to release of endogenous catecholamines. The concentration-response curves for adrenaline on isolated spontaneously beating atrial preparations showed that the concentrations of catecholamines necessary to produce appreciable effects on the heart are higher than the concentrations found in cod plasma during ‘stress’ situations (handling and exhaustive swimming).

Estrogen receptor levels and survival of breast cancer patients. A study on patients participating in randomized trials of adjuvant therapy

A series of 1,022 patients taking part in clinical trials to compare postoperative radiation therapy with postoperative CMF chemotherapy, and postoperative tamoxifen with no adjuvant therapy, had their tumors analyzed for estrogen receptor content. Isoelectric focusing of the receptor in polyacrylamide gel was used for receptor assay and the results were related to tumor DNA content. The estrogen receptor content was significantly correlated to prolonged survival both for premenopausal and postmenopausal women. It was confirmed that postmenopausal women have increased median receptor values, and for this group values of more than approximately 0.3 fmol per microgram DNA were correlated to prolonged survival. For premenopausal women, a lower level of more than 0.1 fmol per microgram of DNA defined patients with prolonged survival. Lymph node involvement and receptor level were independent prognostic indicators. Patients randomized to tamoxifen or CMF tended to live longer as compared with control patients but this was not statistically significant. Moreover, there was no tendency for adjuvant tamoxifen to further increase the survival of patients with receptor-containing tumors as compared with control patients with similar receptor values.

Blood pressure control during exercise in the Atlantic cod, Gadus morhua

Atlantic cod were subjected to 12–15 min swimming exercise at 2/3 body lengths s-1 in a Blazka-type swim tunnel. Pre- and postbranchial blood pressures, cardiac output (ventral aortic blood flow) and heart rate were continuously recorded, and blood samples for measurement of arterial and mixed venous oxygen tension were taken before and at the end of the exercise period. In a second group of fish, subjected to similar exercise regimes, blood samples were taken for analysis of the plasma concentrations of catecholamines. Pre- and postbranchial blood pressures and cardiac output increase during exercise, while the mixed venous oxygen tension decreases. The effect on cardiac output is due to an increase of both heart rate and stroke volume. There are no significant changes in either systemic or branchial vascular resistances, or in the plasma concentrations of catecholamines. Injection of the adrenergic neurone-blocking drug bretylium produces a decrease in postbranchial blood pressure in resting cod, due to a decrease in the systemic vascular resistance. Exercising cod treated with bretylium have a significantly lower pre- and postbranchial blood pressure than exercising control cod. This is due mainly to a dramatic reduction in the systemic vascular resistance. The alpha-adrenoceptor antagonist phentolamine does not further affect the blood pressure in cod treated with bretylium. It is concluded that the exercise hypertension observed in cod depends on the effect of adrenergic vasomotor fibres maintaining the systemic vascular resistance, and also on the increase in cardiac output. An adrenergic innervation of the heart may play some role in the control of cardiac performance both at rest and during exercise, but the main cardioregulatory mechanism is likely to be non-adrenergic, most probably including cardiac control via variation of the cholinergic vagal cardioinhibitory tonus.