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Eight rhesus monkeys were implanted with catheters to measure left ventricular and arterial pressure; an isometric strain gauge was sutured onto the myocardium in four of them. The maximum rate of ris

Oxygen and carbon dioxide tensions were determined in the lungs and in blood from the dorsal aorta, pulmonary vein, pulmonary artery and inferior vena cava in the intact, free swimming, Amphiuma. At 15°C this animal was submerged for a large part of the time and surfaced briefly to breathe at variable time intervals, the mean period being 45 min. Oxygen tensions in the lungs and in all blood vessels oscillated with the breathing cycles, falling gradually during the period of submersion and rising rapidly after the animal breathed. The absolute level of oxygen tension did not appear to constitute the effective signal beginning or ending a series of breathing movements. A small oxygen gradient existed between lungs and blood in the pulmonary vein immediately after a breath. The gradient increased in size as an animal remained submerged due, it is suggested, to lung vasoconstriction increasing the transfer factor. Blood in the dorsal aorta had a lower oxygen tension than that in the pulmonary vein. A right-to-left shunt occurred as blood moved through the heart. The degree of shunting increased as the animal remained submerged and pulmonary vasocon-striction occurred. Left-to-right shunt was relatively insignificant since oxygen tensions in the inferior vena cava and pulmonary artery were very similar. Carbon dioxide tensions were relatively constant during the breathing-diving cycle since Amphiuma removed almost all of this gas through the skin.

Employing multiple chamber pressure recording techniques, the presence of fibers within the right and left cervical vagosympathetic trunks which innervate both right and left ventricles has been demonstrated. Electrical excitation of the cervical vagosympathetic in the atropinized dog elicited a distinct increase in both rate of rise and in maximal systolic intraventricular pressures, with or without cardiac acceleration. It persisted during electrical pacing of the right ventricle. In many animals, the a-wave of the atrial pressure traces also showed augmentation, but this was not consistent or essential for the ventricular response. Although pulmonary vasoconstriction was not ruled out as a concurrent event, its contribution to right ventricular augmentation was not essential as demonstrated in bilateral, isovolumetric ventricular preparations. The evidence indicates the presence of adrenergic fibers in the cervical vagosympathetic trunk which are distributed to all four cardiac chambers. Their effects on the heart are abolished by the β-blocking agent, propranolol, and are unaffected by eserine administration.

The effect of bilateral deafferentation of the pseudobranch on the ventilatory responses of rainbow trout to hypoxia and hyperoxia has been studied. Intact trout responded to hypoxia by an increase, and to hyperoxia by a decrease in ventilation volume. The changes were achieved by alterations in the volume of water pumped per breathing cycle rather than in breathing rate. Pao, and Vo, decreased during hypoxia but increased during hyperoxia. Arterial blood pH rose during hypoxia and fell during hyperoxia. Deafferentation of the pseudobranch had no significant effect on either the magnitude or rate of response to hypoxia or hyperoxia. It is concluded that chemoreceptors in the pseudobranch, innervated by the glossopharyngeal nerve, play little or no part in the regulation of ventilation in fish during hypoxia or hyperoxia.

1. 1. Intravenous injections of epinephrine produced an increase in dorsal aortic blood pressure and heart rate. Low dose levels of epinephrine caused a reflex slowing of the heart, a response abolished by atropine injections into the pericardial cavity. 2. 2. Phenoxybenzamine injections blocked the pressor response to epinephrine. Changes in blood pressure during activity and excitement also disappear after α-adrenergic receptor blockage with phenoxybenzamine. 3. 3. It is concluded that there are α-adrenergic receptors in blood vessels in the gills and in the general body circulation. Epinephrine probably causes a vasodilation in the gills and a vasoconstriction of blood vessels peripherally in the systemic circulation. 4. 4. Blood pressure changes occuring during swimming can be explained by the interaction of epinephrine with α-adrenergic receptors. 5. 5. Dichloroisoproterenal or propranolol, when injected intravenously in fish, had little effect on the response of the heart to epinephrine, but caused a marked fall in dorsal aortic blood pressure and heart rate.

1. 1. Measurements of branchial sodium efflux rates, radiosodium spaces, and plasma ionic levels were made in southern flounder through use of a catheterization technique which permitted serial blood sampling. 2. 2. Disturbances in hematocrit and plasma sodium concentration were associated with the catheterization procedure. 3. 3. Sodium efflux rate was reduced 23 per cent in fish rendered anaemic through bleeding. 4. 4. Radiosodium spaces and plasma sodium and potassium levels were not significantly changed by anaemia. However, plasma sodium and potassium levels were positively correlated regardless of hematocrit. 5. 5. The results are discussed in terms of present theories of electrolyte balance and blood shunting mechanisms in the gills of teleosts.

1. Methods for cannulating the ventral aorta of the trout, which permit the measurement of blood pressure in the unanaesthetized, unrestrained, intact fish are described. 2. Rate and amplitude of breathing and blood pressure in the dorsal and ventral aortae increase during hypoxia. These changes are associated with a marked bradycardia. 3. There are increases in vascular resistance to blood flow in both respiratory and systemic circulations during hypoxia. 4. Post hypoxia is associated with large increases in ventral aortic and dorsal aortic pressures.

1. 1. The effects of unequal distribution of water and blood flow were studied in dogfish ( Squalus suckleyi ) and Atlantic sting ray ( Dasyatis sabina ). 2. 2. The fish were unable to redistribute gill water flow in response to removal of blood supply to various gill arches. 3. 3. Removal of water flow to various gill arches did cause redistribution of blood flow. 4. 4. The redistribution of blood flow tended to maintain the proper ventilation-perfusion ratio ( V G : Q ) at each gill arch. Blood saturation and oxygen uptake were also maintained. 5. 5. The data suggest maintenance of V G : V ratio at each gill arch via vasoconstrictor action in either the gill capillary network or efferent branchial artery.

In studies on 11 rainbow trout (Salmo gairdneri), 217.3 ± 6.5 g, 14.0 ± 0.5 C) fitted with rubber membranes for direct measurement of ventilatory water flow [Formula: see text], buccal, cleithral, and differential pressure traces increased in amptitude as [Formula: see text] rose from 40 to 160 ml/min. Ventilation rate remained steady at around 77 breaths/min in the [Formula: see text] range 40–120 ml/min and rose to 90 breaths/min at a [Formula: see text] of 175 ml/min. Oxygen uptake more than doubled as [Formula: see text] rose from 40 to 120 ml/min. Calculated utilization of oxygen from the inspired water declined only slightly over this [Formula: see text] range, indicating that large increases in nonrespiratory spillage of water (anatomical dead space) had not occurred. The calculated oxygen cost of breathing was low. Area mean differential pressure appeared closely related to [Formula: see text] over the [Formula: see text] range 40–160 ml/min. Area mean differential pressure increased from two- to four fold over this [Formula: see text] range, depending upon which individual fish was examined. Over the [Formula: see text] range 40–160 ml/min the calculated resistance of the gill sieve did not appear to decline although some variability was present and a variety of gill sieve resistances could be measured at a given [Formula: see text] for each fish. It is concluded that changes in [Formula: see text] are largely dependent on changes in mean differential pressures across the gills, with no marked decline in gill sieve resistance over the normal physiological range of [Formula: see text].

1. Changes in blood pressure in the dorsal aorta, ventral aorta and subintestinal vein, as well as changes in heart rate and breathing rate during moderate swimming activity in the rainbow trout are reported. 2. Blood pressures both afferent and efferent to the gills increased during swimming and then returned to normal levels within 30 min. after exercise. 3. Venous blood pressure was characterized by periodic increases during swimming. The pressure changes were not in phase with the body movements. 4. Although total venous return to the heart increased during swimming, a decreased blood flow was recorded in the subintestinal vein. 5. Heart rate and breathing rate increased during swimming and then decreased when swimming ceased. 6. Some possible mechanisms regulating heart and breathing rates are discussed.

1. Changes in partial pressures of O2 and CO2 in blood and water afferent and efferent to the gills are reported. These variables were measured before, during and after moderate swimming activity in rainbow trout. 2. Neither blood PCO2 nor water PO2, afferent or efferent to the gills, changed markedly before, during or after exercise. 3. Arterial blood was always more than 95% saturated with oxygen. Venous blood was 38% saturated, falling to a minimum of 28% during exercise. 4. PCO2 of arterial blood was 2.3 mm. Hg. Pco2 of venous blood increased from 5.7 to 8.0 mm. Hg during exercise and remained elevated throughout the recovery period. 5. Cardiac output (calculated using the Fick principle) stroke volume, ventilation volume and the volume of water pumped per breath all increase by a factor of between 4 and 5 during exercise. All tended to remain elevated for between 10 and 30 min. after exercise and then gradually decrease to pre-exercise levels.

1. In the freshwater adapted rainbow trout, urine flow markedly increased during periods of exercise in a swimming respirometer. 2. Over a range of oxygen consumptions from “standard” to nearly “active metabolic rates”, oxygen and water fluxes exhibited a highly significant positive correlation in individual fish. The results were indicative of covariation of the oxygen and water permeabilities of the gills. 3. A triphasic fluctuation in body weight, considered a measure of water balance, occurred during the course of exercise. On the basis of weight change and urine flow data, a tentative model of water regulation during swimming is presented. 4. Urinary levels of sodium and potassium tended to fall at high urine flows and rise at lowflows. Calcium and magnesium concentrations underwent simultaneous fluctuations which did not always correspond to alterations in urine volume. 5. The renal excretion rates of all four cations increased significantly during swimming activity.

1. 1. The relationship between perfusion pressure and flow of saline through the gills of an isolated head of rainbow trout (Salmo gairdneri) was determined. 2. 2. Noradrenaline, adrenaline and isoprenaline decrease the vascular resistance to flow through the gills in the isolated head preparation, indicating the presence of both α- and s-adrenergic receptors in the gills. 3. 3. The rate of 22Na loss across the gills of intact trout was determined in fish with ligated urogenital papillae. 4. 4. The rate of 22Na loss was higher in “active” than in “quiet” fish. Adding noradrenaline or isoprenaline to the water containing the fish also increased the rate of 22Na loss across the gills. 5. 5. The significance of these observations is discussed.

Attempts to use existing stereotaxic atlases of the lower brainstem of monkeys for the placement of microelectrodes in the cranial nerve nuclei of awake animals have met with little success. The relationship of these nuclei to the bony structures used for orienting the head are probably altered when the position of the body is radically changed from the horizontal to the vertical (sitting) position. The atlas presented is based upon Macaca mulatta monkeys sitting in position in a primate restraint chair. This standard orientation provides a necessary frame of reference for accurate localization of lower brainstem structures.

1. 1. Increases in temperature resulted in large increases in heart rate but caused little change in stroke volume. Injections of atropine into the pericardial cavity caused an increase in heart rate, a decrease in stroke volume but little change in cardiac output. 2. 2. Injections of adrenaline into the dorsal aorta resulted in a rise in dorsal aortic blood pressure and a fall in heart rate and cardiac output. In the atropinized fish, adrenaline injections into the dorsal aorta caused a rise in dorsal aortic blood pressure, a fall in cardiac output but no change in heart rate. Blockade of α-adrenergic receptors with phenoxybenzamine abolished the circulatory changes associated with adrenaline injections. Addition of adrenaline to the water in which the fish was situated resulted in an increase in cardiac output and stroke volume, with little change in heart rate. 3. 3. Cardiovascular changes associated with swimming were similar to those that occurred when the animal was disturbed. There was a bradycardia, with little change in stroke volume. In the atropinized fish, exercise was associated with an increase in cardiac output and stroke volume with little change in heart rate.

1. Radiotracer and cannulation techniques have been used to measure branchial fluxes and internal distributions of sodium in freshwater adapted rainbow trout at rest, during one hour of swimming activity, and during one hour of postexercise recovery. 2. Activity was imposed by manual chasing in a small chamber. Ventilatory and cardiovascular changes occurring during and after this procedure were similar to those associated with normal swimming. 3. Sodium efflux rate equalled influx at rest, increased 70% during exercise, and returned to slightly below resting levels during recovery; influx rate remained invariant under the three treatments. The switch from a negative to a positive branchial sodium balance at the end of exercise occurred extremely rapidly. 4. Despite the branchial deficit, plasma sodium levels tended to rise in active fish. This effect was associated with an apparent reduction in blood volume. 5. Terminal concentrations of sodium and water in “white” muscle did not differ significantly among treatment groups. 6. Expansion of the radiosodium space in active and recovering trout exceeded that in resting animals because of a faster rate of dispersal of influxed sodium out of the plasma compartment into tissues other than “white” muscle.

While precise patterns of efferent innervation of the heart have been extensively investigated, a large fraction of the studies have been made in the dog, cat, rabbit and a few other domestic animals with little or no information upon the primate. We have recently described the anatomical distribution of the autonomic cardiac nerves, together with functional responses to their electrical excitation in the baboon (1, 2). The emphasis of these reports, however was almost exclusively upon epicardial innervation. In subsequent experiments, after developing techniques for studies of endocardial structures in the dog (3, 4), strain gauge arches and/or intramyocardial pressure transducers were applied to the interventricular septum and papillary muscles in the intact baboon heart. The present report illustrates and compares changes in contractile force and in intramyocardial pressure development within the septum and epicardial portions of the left ventricle. To our knowledge, these data represent the first such...

The effect of exposure of rainbow trout to high and low levels of environmental (water) CO2 tension on blood CO2 and pH was studied. An increase in environmental CO2 caused a rise in the arterial CO2 tension , but the blood-to-water gradient (P1-Pa) remained about the same. Changes in arterial pH were small - about one-third of what would be predicted from the change in if plasma bicarbonate remained constant. There was a corresponding increase in the total CO2 content of the blood which involved an upward shift of the CO2 dissociation curve, and readjustment of the buffering to maintain pH. The results are consistent with the hypothesis that blood CO2 and pH levels are regulated via a chloride-bicarbonate exchange mechanism, rather than by ventilation and diffusive washout of gaseous CO2.

In 17 anesthetized baboons, the autonomic innervation of the heart was carefully exposed and electrically stimulated to determine the course of fibers having direct inotropic and/or chronotropic actions. The superior cervical and nodose ganglia are intimately associated by means of short but large interconnections, and the sympathetic and parasympathetic trunks descend with the carotid artery in a common epineural sheath. The middle cervical ganglion is invariably well defined and completely separated from the vagus trunk in the upper portion of the thoracic cage. Direct nervous connections between the sympathetic and vagal trunks are frequent at all levels within the thorax. Both systems also send small nerves into the phrenic and recurrent laryngeal nerves. Separate inferior cervical and first thoracic ganglia were not found, but rather, a large and well defined stellate ganglion extending across the heads of the first and second ribs. The stellates are connected to the middle cervical ganglia by means of both dorsal and ventral ansae subclavia of varying size. Although fine nerves arising from the upper thoracic trunk were located, they appeared to have no direct inotropic or chronotropic actions. The major sympathetic and parasympathetic nerves converge upon richly interconnected dorsal and ventral cardiopulmonary plexuses and several minor (superior vena cava, left atrial, pulmonary veins) plexuses. Both ipsilateral and contralateral control of cardiac function is possible through these pathways. The baboon cardiac innervation thus appears to resemble that of man in some respects and the dog in others.

1. The effectiveness of oxygen uptake by the blood of rainbow trout (Salmo gairdneri) approaches 100%, whereas that for the removal of oxygen from water was only 11-30%. 2. Most of the carbon dioxide is removed from the blood as it passes through the gills, but the effectiveness of carbon dioxide uptake by water is very low, because of the high capacity of water for carbon dioxide compared with oxygen. 3. Moderate exercise had little effect on the effectiveness of gas exchange across the gills. The increased oxygen uptake was facilitated by an increase in the transfer factor of the gills for oxygen. There were small increases in the capacity-rate ratio of blood to water at the gills during moderate exercise. 4. Hypoxia resulted in a marked decrease in the effectiveness of oxygen uptake by the blood, but had little effect on oxygen removal from the water. Gas exchange was facilitated during hypoxia by an increase in transfer factor of the gills, but hindered by an increasing capacity-rate ratio of blood to water at the gills. 5. Gas exchange in an aquatic environment was compared with that in an aerial environment.

1. The rate of oxygen uptake by rainbow trout does not alter during progressive deoxygenation of the environment. Blood lactate, however, shows a significant increase, indicating an increase in anaerobic metabolism during hypoxia. 2. The percentage utilization of oxygen from the water decreased from 55% to approximately 20% during hypoxia and was associated with a 13-fold increase in ventilation volume. 3. The arterial blood of a trout resting in aerated water was 95-100% saturated: the Po2 was 122 mm. Hg and the Pco2 was 1-1.5 mm. Hg. 4. The venous blood of a resting trout was 70% saturated, had a Po2 of 35 mm. Hg and a Pco2, of 2.5 mm. Hg. 5. During hypoxia the percentage saturation of the arterial blood decreased to 37% and that of the venous blood to 3%. The P o2 in the arterial blood was 10 mm. Hg; in the venous blood, 6 mm. Hg. The Pco2 in the arterial blood was 3.5-4 mm. Hg; in the venous blood, 4.5-5.00 mm. Hg respectively. 6. The ability of the fish to withstand hypoxia was related to the oxygen capacity of the blood, which was on average 9 vol.%. The red blood cells swelled during hypoxia, the hematocrit increased, but the red cell count did not alter. 7. Blood pH was 7.7, falling to 7.4 during hypoxia. 8. Cardiac output did not change during progressive hypoxia in the water, stroke volume increased to offset the decrease in heart rate.

A NEW class of plant growth regulators has been discovered at the culmination of an extensive synthesis and testing programme.

Some of the difficulties that arise when general chemistry students determine the molecular weight of a volatile liquid are avoided by the use of a specialized glass bulb.