Ethical considerations for the nursing care of Transgender patients in the Intensive Care Unit

There is more discussion than ever surrounding the health and care needs of Transgender communities. However, there is limited research on the care of Transgender patients in the Intensive Care Unit which can contribute to knowledge gaps, inconsistencies and uncertainties surrounding health care practices. This article is not intended to address all of the specific needs of Transgender patients in ICU, but to explore the ethical considerations for caring for a Transgender woman in the ICU. In doing so, this article will explore some specific considerations around gender affirming care, challenging discrimination, physiological changes, and systems change to enhance care.

Authentic allyship for gender minorities

The visibility and discussion on the rights and needs of Trans and Non-Binary communities in relation to healthcare have seen growing prominence in recent years. Despite an overall improvement in access to legal protections, civil rights, and in many jurisdictions specialist provision of healthcare for gender minorities, there remain poorer health outcomes in many areas and ongoing experiences of discrimination and transphobia. In this article, we set out the prerogative for nurses to step up as authentic allies for Trans and Non Binary people and put forward strategies to enhance the experience of gender minorities in healthcare through practice, education, and systems change.

In vivo responses of allografted cerebral parenchymal arterioles to ethanol and angiotensin II: effect of calcium channel blockade

The goals of these studies were to determine: 1) the effect of ethanol and angiotensin II on the diameter of allografted cerebral parenchymal arterioles in vivo, and 2) the effect of the calcium antagonist, verapamil, in modulating the responses of allografted cerebral parenchymal arterioles to ethanol and angiotensin II. Using a chamber technique, neonatal (< 24 hours old) cortical tissue was transplanted onto the cheek pouch of adult hamsters. Eight to thirteen days after allografting, hamsters were anesthetized with sodium pentobarbital (6.0 mg/100 grams i.p.), and allografted cerebral parenchymal arterioles were viewed using intravital microscopy. Diameter of allografted cerebral parenchymal arterioles was measured before (control), during and after topical application of ethanol (0.1%, 0.25%, 0.5%, 1.0%, and 2.0%) and angiotensin II (0.1 and 1.0 ng/ml). Application of ethanol and angiotensin II was repeated after changing the suffusion fluid to one containing verapamil (50 mg/L). We found that ethanol and angiotensin II produced dose-related constriction of allografted cerebral parenchymal arterioles. In addition, verapamil significantly attenuated vasoconstriction produced by ethanol and angiotensin II. Thus, our findings suggest that ethanol and angiotensin II cause constriction of allografted cerebral parenchymal arterioles through a calcium-dependent mechanism.

Volume expansion attenuates baroreflex sensitivity in the conscious nonhuman primate

We examined the effect of intravascular volume expansion (VE) on the arterial baroreflex control of pulse rate (PR) in conscious, chronically instrumented monkeys tethered in their cages. A total of five monkeys was studied after surgical implantation of catheters in the descending aorta, the left atrium, and the internal jugular vein. Mean arterial blood pressure (MABP)-PR stimulus response curves were constructed by decreasing and increasing blood pressure with nitroprusside and phenylephrine, respectively. The data were analyzed with a regression analysis that generated a sigmoid curve and the maximum sensitivity (slope) of the curve. The data were obtained before and after VE with an isotonic isoncotic dextran solution equal to 20% of the estimated blood volume. After VE, the MABP-PR curve shifted to the right at the high blood pressures, and there was a significant decrease in the maximum sensitivity from 5.65 +/- 1.44 for control to 2.14 +/- 0.63 after VE (P less than 0.05). We concluded that VE attenuates the baroreflex control of heart rate in the conscious nonhuman primate.

In vivo microscopy of the cerebral microcirculation using neonatal allografts in hamsters

Studies were performed to characterize the morphology and vascular reactivity of the allografted cerebral microcirculation. Cerebral cortical tissue was allografted into the cheek pouch of the hamster so that cerebral parenchymal vessels could be studied. The vascular morphology was characterized by a large number of looping vessels. The ultrastructural examination indicated viable cerebral tissue containing typical vessels, that is, "tight" junctions, not like those of the cheek pouch. Also, the microvasculature was impermeable to 150, 70, and 20 kDa fluorescein isothiocyanate dextrans. Angiotensin II and norepinephrine caused constriction of the cerebral vessels whereas adenosine caused dilation. Isoproterenol did not affect cerebral arterioles; however, it dilated cheek pouch arterioles. Thus, this preparation provides a satisfactory model for studying the living cerebral microcirculation.

Angiotensin reactivity in the cheek pouch of the renovascular hypertensive hamster

Increased reactivity to vasoconstrictor agents and decreased arteriolar luminal diameter have been implicated in the maintenance of hypertension. The same hamster cheek pouch microvessels were tested for angiotensin I (Ang I) and angiotensin II (Ang II) reactivity before and 10 to 14 days after Grollman (two-kidney, one figure-8) or sham operation. Microvascular geometric parameters were measured before and after a maximal vasodilator dose of adenosine. Then maximal vasoconstrictions to Ang I or Ang II were measured: Ang I and Ang II were applied adjacent to arterioles (10(-2)-10(0) pmol) and venules (10(-1) pmol) in 10-microliter aliquots for 1 minute. Blood pressure (178 +/- 11/133 +/- 8 mm Hg) of renovascular hypertensive hamsters was elevated significantly over blood pressure of sham-operated hamsters (120 +/- 11/97 +/- 10 mm Hg). No change was observed in venular geometry or reactivity in renovascular hypertensive hamsters. Arteriolar luminal diameter, wall thickness, wall/lumen ratio, and wall area were not altered in hypertensive hamsters in the normal or vasodilated state; vasodilator capacity was the same in all groups. Conversion of Ang I to Ang II (response to Ang I divided by response to Ang II) for first-order and Third-order arterioles and third-order venules was 74 +/- 5, 79 +/- 3, and 72 +/- 6%, respectively, and was unaltered in renovascular hypertensive hamsters. Although vessel geometry was not altered, there was a significant shift to the left of the Ang I and Ang II dose-response curves of first-order and third-order arterioles, indicating increased sensitivity to these vasoconstrictors.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypotension produced by vagal block in primates

In many species, the vagus has been reported to contain afferents that inhibit sympathetic tone. Vagal block (VB) increases blood pressure in both the intact and sinoaortic-denervated (SAD) dog. In the present study, VB was produced in intact and SAD monkeys by infiltrating the vagi with a local anesthetic. This was done in conjunction with blood volume expansion or head-out water immersion. The cardiovascular parameters monitored were heart rate (HR), blood pressure (BP), and left atrial pressure (LAP). VB decreased BP (-13 +/- 2.8 mmHg) in the control group and the SAD animals (-47 +/- 6.7 mmHg) without changing HR. Volume expansion decreased BP in the SAD animals (-6 +/- 3.4) but not in the intact monkeys (1.8 +/- 2.27), whereas HR did not change. Volume expansion after VB increased BP in both the SAD and the intact animals while producing a decrease in HR. Volume expansion caused LAP to increase in all groups (SAD 13.9 +/- 6.3; control VB 11.6 +/- 1.8, control 9.3 +/- 0.89, SAD VB 7.66 +/- 3.46). Immersion in the VB SAD animals increased BP to a greater extent than volume expansion. VB in the monkey must be removing input from peripheral receptors, which maintain sympathetic tone. Because immersion with VB increases BP more than volume expansion with VB, it is concluded that VB causes predominantly venous pooling. Because cardiopulmonary receptors generally inhibit sympathetic tone, it is concluded that those receptors responsible for the observed hypotension are located in the venous system, probably in the chest or the abdominal cavity.

Pentobarbital potentiates natriuretic response to acute volume expansion in monkeys

We determined the influence of pentobarbital sodium on the renal responses of the monkey to acute intravascular volume expansion. Before volume expansion, the anesthetized animals had a significantly lower blood pressure and creatinine clearance and a significantly higher urine flow and sodium excretion than the conscious animals. After volume expansion with an isotonic, isoncotic, dextran solution, sodium excretion and urine flow increased significantly in both groups of animals. However, both responses were significantly greater in the anesthetized animals. The greater natriuresis in the anesthetized animals was associated with a greater fractional sodium excretion than in the conscious animals. The potentiated response of the anesthetized animal may be the result of a direct renal tubular effect of pentobarbital and/or the result of the anesthetic removing an inhibitory influence on sodium excretion.

Central blood volume and blood pressure in conscious primates

Conscious intact (I) and sinoaortic-denervated monkeys (SAD) were studied to determine the extent to which high-pressure receptors contribute to the maintenance of arterial blood pressure (BP) when venous return is decreased by hemorrhage (H) or lower body negative pressure (LBNP). In the I animals, mean BP did not decrease significantly until 5% of the estimated blood volume (EBV) was removed, whereas, with sinoaortic denervation, mean BP decreased significantly when less than 2% of EBV was removed. Left atrial pressure (LAP) decreased similarly in both groups of animals. In the I group during LBNP, mean BP did not change significantly, whereas pulse pressure decreased significantly when LBNP was decreased to -5 cmH2O. In the SAD animals, mean BP decreased significantly at an LBNP of -2 cmH2O, and at -5 cmH2O mean BP declined from 134.1 +/- 4 to 102.7 +/- 7 mmHg. LAP decreased similarly in both groups of animals. The data support the view that a nonhypotensive reduction in venous return unloads arterial baroreceptors sufficiently to activate the arterial baroreflex, probably through reductions in pulse pressure. In addition, low-pressure receptors by themselves do not appear to contribute importantly to blood pressure maintenance when venous return is decreased by either LBNP or a nonhypotensive hemorrhage.

Extravasation of macromolecules and vascular reactivity of microvessels in response to nicotine in the hamster

The effects of nicotine on the microvasculature were assessed in the hamster cheek pouch and in fetal tissue grafted into the cheek pouch. Transvascular exchange of FITC-dextran (70-150 K) was measured in the cheek pouch of normal hamsters challenged with either intravenous or suffused nicotine, and in streptozotocin-induced, diabetic hamsters challenged for one week with nicotine delivered by a mini-osmotic pump. The effects of nicotine on microvascular diameter were measured in cheek pouch vessels and in grafts 9-12 days after transplantation. Suffused nicotine did not cause leaky site formation or alter dextran clearance from the pouch. Intravenous nicotine had no effect on either of these parameters but potentiated histamine-induced leaky site formation (40%) and clearance (20%); clearance but not leaky site formation was normalized after cessation of nicotine infusion. Chronic nicotine treatment of diabetic hamsters had no effect on either basal or histamine-induced extravasation as monitored by leaky site or clearance measurements. Suffused nicotine had no effect on arteriolar diameter in the cheek pouch, or in renal, pulmonary or atrial allografts. These results indicate that nicotine can modulate histamine-induced extravasation of macromolecules but has no effect on diameter of arterioles in the non-adrenergically innervated vascular beds studied.

Specificity of arginine vasopressin and angiotensin II for microvessels in the hamster cheek pouch after the induction of renovascular hypertension

The present study was undertaken to determine the specificity of the vasoconstrictor activity to angiotensin II (AII) and arginine vasopressin (AVP) on the microcirculation in normal and renovascular hypertensive states. Ten to fourteen days after the induction of hypertension, Syrian hamsters were anesthetized with pentobarbital sodium, the cheek pouch was exposed, and a plastic chamber was placed in situ so the membrane could be suffused with bicarbonate-buffered Ringer's solution (5% CO2, 95% N2, pH 7.4). Third order arterioles (30-45 micron) were identified for study and vessel diameter was measured using a shearing device. In one group of normotensive and hypertensive hamsters, AII was microapplied to the arteriole before and after adding an AVP antagonist to the suffusate. In a second group of similar hamsters, AVP was microapplied to the arteriole before and after adding an angiotensin II blocker, saralasin acetate, to the suffusate. AVP and AII receptor blockade was documented by observing whether the vasoconstrictor effect of either AVP or AII was abolished. Dose-response curves for either peptide were not altered in the presence of the antagonist to the other peptide; however, they were shifted to the left in the RHT hamsters. Neither AVP nor AII receptor blockade altered control resting arteriolar diameters. Thus, it can be concluded that the microvascular response to both AII and AVP are potentiated in RHT and there are no interactions between either AII or AVP with the receptors of the other peptide in these microvessels in normal or RHT hamsters, indicating a high specificity for each peptide to its vascular receptor.

The selective response to adenosine of renal microvessels from hamster explants

The present study was undertaken to investigate the effect of adenosine on the microvasculature of the hamster kidney and the possibility of angiotensin II mediation. Renal tissue from neonatal hamsters was grafted into the cheek pouch of 33 adult hamsters. Seven to twelve days later the renal microcirculation was studied. Adenosine was tested on the pre- and postglomerular arterioles as well as on cheek pouch arterioles before and after applying an AII antagonist, saralasin. Adenosine dilated the cheek pouch arterioles and constricted the preglomerular arterioles in a dose-dependent manner. Adenosine had no effect on postglomerular arterioles. The renal vasoconstriction persisted as long as adenosine was present. Theophylline reduced the adenosine-mediated vasoconstriction of the afferent arteriole in a dose-dependent manner. These changes were not altered in the presence of saralasin at various doses, one of which was 20-fold greater than that required to abolish the vasoconstrictor response of a test dose of angiotensin II. This study indicates that the adenosine-mediated vasoconstriction of the preglomerular microvessels is not mediated via the renin-angiotensin system but may be a direct effect of adenosine.

The renal vascular system of the monkey: a gross anatomical description

This study was conducted on two species of monkeys, Macaca fascicularis and Macaca mulatta, to describe their gross renal vascular morphology. After death, twelve monkeys were perfused with isotonic saline to flush their vascular systems. The monkeys were then perfused either with latex or methyl methacrylate, or both, one into the arterial and the other into the venous system. The results indicated that there were six to eight arterial segments in the monkey kidney, each supplied by a segmental artery. The anterior segments were named apical, upper, middle and lower, while the posterior segments were named posterior-apical, superior, intermediate and inferior. The branching patterns of both the anterior and posterior segmental arteries were classified into one of four types: magistral, cruciate, bifurcating or quadripartite. The renal vein generally collects blood from three or four large intrarenal veins. Peripheral to this, veins accompanied arteries and were given their corresponding names. Despite this juxtaposition of veins and arteries, and the resulting convention in naming vessels, the intrarenal venous system was organised into three regions. Each region was arranged around an anterior and a posterior large intrarenal vein. The various segments of the kidney, as defined by the arterial system, were united by the arcuate veins, which anastomose throughout the corticomedullary region and drain into the large intrarenal veins mentioned above. The gross renal vascular system of the monkey was compared to, and contrasted with, human and canine renal vascular anatomy.

Hypoxia does not alter angiotensin converting enzyme activity in hamster pulmonary microvessels

Studies were initiated to investigate the effects of hypoxia on the conversion of angiotensin I (AI) to angiotensin II (AII) in microvessels of the lung. Using the technique of allografting neonatal lung tissue into the cheek pouch of normal hamsters, the microvessels of the lung, pulmonary arterioles, and venules could be visualized and manipulated by direct in vivo microscopy. The microvessels of the lung were studied 7-10 days after allografting by anesthetizing the hamster with pentobarbital (6.0 mg/100 g body weight i.p.) and then preparing the lung tissue for observation. The tissue was suffused with a Ringer's bicarbonate solution bubbled with a normal (20% O2-5% CO2-75% N2) or a low (95% N2-5% CO2) oxygen mixture. After equilibration, a pulmonary arteriole or venule was selected for observation, and the vessel geometry was recorded. Then, a micropipette containing either AI or AII was positioned alongside the vessel, and the agent was delivered continuously for 2 minutes. Lumen diameter was recorded continually for 8-10 minutes. This procedure was repeated until both angiotensins were tested on pulmonary arterioles and venules under conditions of a normal and low oxygen environment. This protocol was repeated on cheek pouch microvessels that did not contain pulmonary allografts. Both AI and AII produced rapid decreases in the lumen diameters of all microvessels tested. This vasoconstriction was greater for AII, and the oxygen environment did not alter the response. Conversion of AI to AII was not altered by the oxygen environment, and the relative conversion was similar in the microvessels of the lung and cheek pouch.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriolar reactivity to pressure stimuli in hamsters with renal hypertension

The responses to alterations in extravascular pressure were studied in five orders of arterioles in the cheek pouch of normotensive and renal hypertensive hamsters. Renal hypertension was induced by bilateral compression of both kidneys using figure-of-eight ligatures. Ten to 16 days later, hamsters were anesthetized with pentobarbital (6.0 mg/100 g body weight) and a Plexiglas chamber was positioned in the cheek pouch. Chamber pressure, or extravascular pressure, was increased and decreased by +/- 10, 20, and 40 mm Hg, and arteriolar diameters were monitored continuously. The responses at -20 mm Hg and the slope of the linear portion of the chamber pressure-diameter curve (arteriolar gains) were compared between groups for each branching order of arteriole. Arteriolar responses at one chamber pressure and the arteriolar gains were enhanced in third and fourth order arterioles of the renal hypertensive group compared with the normotensive group, and the responses of these small arterioles were greater than those of larger arterioles in both groups. Control diameters of second and third order arterioles were significantly smaller in the renal hypertensive group, while the diameters after adenosine were not different. These results suggest that the enhanced responses of small arterioles in the renal hypertensive group were not related to structural alterations but may be related to an increased reactivity of smooth muscles in these small arterioles to volume expansion, thus a pressure stimulus.

Lack of evidence for a cerebral sodium modulating mechanism in the monkey

Experiments were carried out in seven conscious macaque monkeys undergoing a water diuresis to determine the effects of raising carotid blood sodium concentration on renal sodium excretion and free water clearance. On separate days each animal received an intracarotid infusion of hypertonic sodium chloride (90 Eq NaCl/kg.body wt./min) for 5 to 10 min, the same hypertonic infusion intravenously, and an intracarotid infusion of isotonic NaCl. None of the infusions produced a change in sodium excretion. However, the intracarotid hypertonic infusion produced a sustained decrease in free water excretion while the other infusion did not. Creatinine clearance was not affected by any of the infusions. The results of these experiments support the view that while the brain of the primate contains an osmotic sensing mechanism it does not contain a mechanism which modulates sodium excretion.

The renal microvasculature of the monkey: an anatomical investigation

Twelve monkeys, Macaca fascicularis and Macaca mulatta, were investigated to study their renal microvasculature. After death, all monkeys were perfused with heparinised isotonic saline to flush their vascular systems. The kidneys were then perfused with silicone rubber and examined. The silicone rubber injections allowed description of afferent arterioles and several efferent vascular patterns observed in the subcapsular, midcortical, and inner cortical regions. The medullary vasculature was particularly interesting in that no particular vascular zonation was observable. Silicone rubber injections indicated the existence of vascular bundles that run parallel to one another from outer medulla nearly to the papillary tip. Branching of descending vasa recta into capillaries, or precapillary vessels, occurs frequently and at all levels of the medulla. Ascending vasa recta are formed from the interbundle capillary plexus and from the plexus at the papillary tip. They ascend primarily within vascular bundles to the corticomedullary junction where these vessels may empty into collecting veins or arcuate veins. In addition, many ascending vasa recta penetrate into the cortex where they drain into the proximal third of interlobular veins. The venous drainage of the cortex appears to be regional, in that the area surrounding an interlobular vein generally drains into it directly via venules or small veins. The arterial and venous morphology of the monkey kidney may be important to the monkey's ability to concentrate urine despite the virtual absence of an inner medullary zone. The potential physiological significance of the monkey's microvasculature is discussed extensively and compared with various other mammals.

Aspects of cardiovascular reflexes in pathologic states

Cardiovascular reflexes that are mediated by receptors in the heart and blood vessels control a variety of important hemodynamic and humoral functions. The action of these receptors can be shown to be abnormal in several pathologic states. Left atrial receptors exhibit a depressed discharge sensitivity in dogs with chronic congestive heart failure caused by an aortocaval fistula. The reflex effects of atrial receptor stimulation are also depressed in heart failure. Left ventricular receptor stimulation has been implicated in the abnormal vascular responses to exercise in patients with aortic stenosis. The arterial baroreflex control of heart rate is abnormal in animals and humans with various forms of hypertension. Arterial baroreceptors from hypertensive animals show a resetting of their pressure-discharge curve to higher pressures. The arterial baroreflex is also depressed in chronic heart failure. This effect may result from an abnormality of the efferent limb of the reflex arc or from changes in the interaction between baroreceptors and cardiac receptors centrally. A final possibility may be abnormal arterial baroreceptor discharge characteristics in heart failure.

Sino-aortic denervation in the monkey

The aortic arch and carotid sinuses were denervated in eleven monkeys. The monkeys were subjected to four sequential surgeries which involved: (1) implantation of an aortic and left atrial catheter; (2) stripping of the adventitia from the aortic arch; (3) stripping the left carotid sinus and associated vessels; and (4) stripping the right carotid sinus and associated vessels. Blood pressure and pulse rate were recorded 6 days after each surgical procedure. Records were taken over a 6 h period while the monkeys were in their home cages. Baroreceptor denervation was confirmed by: (1) absence of heart rate response to blood pressure changes and (2) an increase in the variability of blood pressure. Veratridine given into the left atrium caused a Bezold-Jarisch reflex both before and after denervation verifying the integrity of the afferent and efferent vagus. Denervation of the baroreceptors resulted in a significant increase in blood pressure when measured from monkeys who were restrained in chairs in the laboratory; however, blood pressure was not significantly elevated in the baroreceptor denervated monkeys while they were tethered in their home cages. It is concluded that denervation of the sino-aortic baroreceptor does not result in a significant increase in systemic blood pressure.

Renal responses to atrial natriuretic factor during converting enzyme inhibition

The effect of converting enzyme inhibitor (CEI) on the renal response to atrial natriuretic factor (ANF) was determined in the rat. In the absence of CEI, ANF produced rapid and significant increases in sodium, potassium, calcium, and urine excretions while blood pressure declined transiently. In the presence of CEI, ANF enhanced the excretion of sodium and potassium but not of calcium and urine. The activity of CEI was documented by observing that, in the presence of CEI, the elevation of blood pressure produced by angiotensin I was significantly attenuated. The potentiating effect of CEI on the natriuretic response to ANF supports the hypothesis that converting enzyme may be involved in the metabolism of ANF.

Renal mechanoreceptors in nonhuman primates

The present experiments provide the first description of the afferent discharge characteristics of renal mechanosensitive receptors in the nonhuman primate. Twenty-seven single units with mechano-sensitive receptor activity were obtained. Afferent discharge occurred regularly (pulse synchronous) or irregularly (pulse asynchronous) under spontaneous respiration. The activity of pulse synchronous units was increased by partial occlusion of the renal vein and elevation of arterial pressure. Impulse activity decreased or disappeared during bleeding or renal arterial occlusion. The impulse activity of pulse asynchronous units was increased by partial occlusion of the renal vein. The impulse activity of silent units was induced only by partial occlusion of the renal vein. An increase in ureteral pressure (50 mmHg) produced an increase or induced impulse activity in only three of the 27 fibers tested. Compression of the kidney or renal venous occlusion was associated with a decrease in systemic arterial pressure, whereas renal arterial occlusion produced a rise in systemic arterial pressure. An increase in ureteral pressure (50 mmHg) did not produce a change in arterial pressure.

An investigation of potential vascular connections between the kidney and the adrenal gland

This study was conducted on two species of monkeys, Macaca fascicularis and Macaca mulatta, to determine if there were vascular connections between the kidney and other abdominal structures such as the adrenal glands. Microfil vascular perfusions, followed by microscopic observations and dissections, were utilized to investigate the existence of these potential connections. Highly anastomotic renal capsular vessels were always observed on the outer surface of the renal capsule. However, these capsular vessels did not make connections with the subcapsular capillary plexus in the majority of monkeys studied. Vascular connections between the adrenal gland and kidney were not observed. It was concluded that, although the region between the adrenal gland and kidney was rich in vasculature, it did not appear to play an anatomical role in anastomosing the extrarenal and intrarenal circulations.

Effects of oxytocin, vasotocin and alpha-MSH on renal function in the nonhuman primate

We determined the effect of oxytocin, alpha-melanocyte stimulating hormone (alpha-MSH) and arginine vasotocin on renal function of the macaque monkey. The only significant effect of the peptides was that alpha-MSH had an antidiuretic effect and vasotocin had both an antidiuretic and natriuretic effect.

Blood volume changes and high and low pressoreceptor activity in cats

Studies were undertaken in the cat to determine if moderate hemorrhage or volume expansion significantly altered carotid sinus and aortic baroreceptor activity. In addition, the experimental design provided the opportunity to compare gain of the two sets of receptors. A 20% blood volume expansion increased mean arterial blood pressure 5.2% and carotid sinus nerve activity 14.7%, whereas a 20% hemorrhage decreased mean arterial blood pressure 10.8% and carotid sinus nerve activity 32.3%. For the aortic baroreceptors, a 20% blood volume expansion increased mean arterial blood pressure 5.9% and nerve activity 10.5%, and a 20% hemorrhage decreased mean arterial blood pressure 8.9% and nerve activity 21.0%. The blood pressure-discharge curves for the carotid sinus and aortic baroreceptors were not different. The well-known high sensitivity of atrial receptors was also documented. We conclude that both high- and low-pressure receptors apprise the central nervous system of the status of intravascular volume and pressure.

Salt depletion inhibits cerebral-induced natriuresis in the dog

Experiments were carried out in the conscious dog to determine whether renal responses to intracarotid (IC) infusion of hypertonic NaCl are altered in the sodium-depleted state. In the sodium-replete animal, both IC and IV infusion of hypertonic NaCl produced significant increases in sodium excretion and significant decreases in free water clearance. However, both of these renal responses were more rapid in onset with IC infusion. Both IC and IV infusion decreased free water clearance. In the sodium-deplete animal, IC hypertonic NaCl infusion had no effect on sodium excretion but did decrease free water clearance. It is concluded that total body sodium is a determinant of the gain of the cerebral sodium-sensing mechanism and that this mechanism is different from the osmosensitive mechanism.

Sinoaortic baroreceptors and the control of blood volume in the nonhuman primate

The purpose of this study was to determine the role of the aortic and carotid baroreceptors in regulating blood volume in the conscious non-human primate. Eighteen control animals were surgically instrumented to permit the recording of blood pressure, pulse rate, and left atrial pressure. After a urethral catheter was inserted into the bladder, the animals were given an intravenous infusion equal to 20% of the estimated blood volume. Renal function was determined before and after the volume expansion. Nine monkeys received the same infusion after undergoing chronic sinoaortic denervation. The denervated animals responded with a potentiated diuresis and natriuresis. The control animals excreted 24% of the infused volume and 4% of the infused salt while the sinoaortic-denervated animals excreted a volume equal to 113% of that infused and an amount of sodium equal to 46% of that infused. We conclude that high-pressure receptors exert an inhibitory influence on whatever mechanisms are involved in the renal response to acute volume expansion.

Comparative reactivity of hamster cheek pouch microvessels to arginine vasopressin and angiotensin II

Experiments were carried out to determine the relative sensitivity of hamster cheek pouch vessels to arginine vasopressin (AVP) and angiotensin II (AII). Hamsters were anesthetized with pentobarbital sodium (6 mg/100 g, ip), a plastic chamber inserted into the cheek pouch and the membrane exposed. The membrane was suffused continuously with bicarbonate-buffered Ringer's solution at 36 degrees C while constantly monitoring blood pressure. After stabilization (30 min) of the membrane, arterioles (30-80 microM diam) were selected for application of AVP or AII in a random fashion. The peptides were applied to the vessels through a micropipette (10-15 mM tip diam) over two minutes using a pump. Total volume delivered was always 20 microliters irrespective of the total amount of peptide (10(0)-10(-4) ng) applied. Vessel diameter was monitored continuously with a shearing device before, during and after the administration of the peptide. The following results were obtained tachyphylaxis was noted to AII but to AVP; the dose response curve for AVP was shifted to the left of that for AII with the threshold dose for AII one hundred times more than that of AVP and AVP had little effect on venules whereas AII produced venoconstriction. These results indicate that AVP is a more potent vasoconstrictor than AII, whereas AII is a more potent venoconstrictor.

Comparison of carotid sinus baroreceptors in dogs, cats, monkeys, and rabbits

Single-unit recordings were obtained from the vascularly isolated Krebs-Henseleit-perfused carotid sinus of the rabbit and cat, and the results were compared with those obtained previously from the monkey and dog. Carotid sinus pressure was altered using static pressure steps. There was a highly significant correlation between resting arterial pressure and carotid sinus baroreceptor threshold pressure. The baroreceptors of the monkey and rabbit had a significantly lower threshold than those of the dog and cat. The baroreceptors of the monkey had a significantly lower gain than those of the three nonprimates. This is the first study in which baroreceptor activity has been studied under the same experimental conditions in four different species.

Does head-down tilt simulate zero gravity?

Six anesthetized female rhesus monkeys were studied to determine the effect of head-down tilt on renal function. Head-down tilt is believed to simulate zero gravity. Some animals were tilted from 0 degree to -5 degrees or -10 degrees and others from +10 degrees to -10 degrees. None of these maneuvers consistently altered renal function. These results are in accord with those reported in early literature for the human but contrary to more recent reports. The interpretation of the latter are seriously hampered by experimental design. If indeed zero gravity translocates blood to the thorax with a resultant diuresis and natriuresis, head-down tilt is not an appropriate model for weightlessness.

Effects of volume expansion with Fluosol-DA on renal function of the nonhuman primate

The renal responses to an intravenous infusion of a high 02 affinity fluorocarbon equal to 15% of the estimated blood volume was determined in 5 monkeys and 1 baboon. In response to the infusion, blood pressure, renal plasma flow and glomerular filtration rate did not change significantly while heart rate and central venous pressure increased transiently. Significant increases in sodium and potassium excretion and osmolal and free-water clearances occurred. The renal responses to Fluosol-DA (20%) mimic in general those observed when blood volume is expanded with isotonic isooncotic dextran solutions.

Influence of left ventricular receptor stimulation on plasma vasopressin in conscious dogs

The current study was undertaken to determine whether receptors in the left ventricle are capable, when stimulated, of inhibiting plasma arginine vasopressin (AVP) in the conscious dog. Dogs were instrumented to measure aortic pressure and heart rate. In addition, a catheter was implanted in the left circumflex coronary artery. Left ventricular receptors were stimulated by the intracoronary infusion of veratrine, which evoked a hypotension and bradycardia. Control experiments consisted of intravenous infusion of veratrine. Plasma AVP, osmolality, and sodium and potassium concentrations were measured at intervals following the infusion. Similar experiments were done during the intravenous infusion of sodium nitroprusside (NP) to lower aortic pressure to the same extent as that seen with intracoronary infusion of veratrine. Experiments were also performed in chronic sinoaortic-denervated dogs. Intracoronary infusion of veratrine resulted in a significant decrease in aortic pressure from 93.9 +/- 2.8 to 70.5 +/- 4.5 mmHg. Control plasma AVP averaged 2.13 +/- 0.25 pg/ml and did not change significantly during this time. NP infusion lowered aortic pressure to a similar degree, and plasma AVP rose to 21.17 +/- 3.79 pg/ml after 5 min. There were no significant changes in any other plasma constituents. The results were similar in sinoaortic-denervated dogs. We conclude from the results of this study that receptors in the left ventricle are not capable of decreasing plasma AVP from low basal levels or from augmented levels.

Renal function and pituitary hormone release during cerebral osmostimulation and TRH in dogs

The effects of increases in serum osmolality on renal function and plasma levels of radioimmunoassayable prolactin (PRL) and luteinizing hormone (LH) were examined during intracarotid (IC) infusions of hypertonic NaCl in conscious dogs with a sustained water diuresis (SWD). A 10 minute bilateral IC infusion of 45 mumole/kg X min X artery of NaCl during SWD which raised jugular osmolality by 10.1 mOsm/kg, without significantly altering peripheral venous osmolality, produced a significant decrease in free water clearance (CH2O) at 20 to 40 minutes postinfusion. IC infusions of 0.9% NaCl did not produce an antidiuretic response. No change in heart rate or blood pressure from preinfusion control values occurred during NaCl infusions. Elevations in cerebral osmolality did not result in changes in circulating levels of LH or PRL which qualitatively differed from levels of these hormones recorded during IC infusions of 0.9% NaCl. Although fluctuations in levels of LH occurred during experiments, renal function was not concomitantly affected. The results suggest that a specificity exists in the hormonal response to selective elevations of cerebral osmolality. The administration of TRH 3.8-4.2 micrograms/kg produced a transient increase in blood pressure and inhibited a water diuresis, the latter possibly as a result of releasing antidiuretic hormone.

Natriuretic activity of human and monkey atria

Recent evidence indicates that mammalian atria contain a substance that produces a rapid onset natriuresis in anesthetized rats. In the present experiments, small portions of human right atria obtained from patients undergoing coronary bypass surgery, as well as monkey atria and ventricles obtained from the Regional Primate Center, Seattle, were boiled or acid extracted and lyophilized. These materials (30 mg/kg) were dissolved in Ringer's lactate and injected intravenously into anesthetized monkeys to determine their effects on renal function. Their effects were also compared with those of furosemide (0.1 mg/kg) and chlorothiazide (10 mg/kg). Human and monkey atrial extracts produced significant increases in sodium and calcium excretion that were independent of changes in creatinine clearance. Monkey ventricular extract had no consistent renal effects. Furosemide, but not chlorothiazide, mimicked the renal responses to human and monkey atrial extracts in terms of time of onset, duration, and pattern of electrolyte excretion. These data suggest that primate atrial tissue contains a heat- and acid-stable natriuretic factor similar to that first described in the rat, suggesting that mammalian atrial natriuretic factors are cross-reactive among species. In addition, atrial natriuretic factors may have a mechanism of action similar to that of furosemide.

Renal nerve responses to cardiac receptor stimulation with bradykinin in monkeys

Previous data from our laboratory demonstrated a species difference between the cat and dog in the arterial blood pressure (ABP) and renal nerve activity (RNA) responses to epicardial bradykinin (BK) applications. The present study was carried out to determine the ABP and renal nerve responses to chemical activation of cardiac afferents by BK in the intact and sinoaortic-denervated and vagotomized (SAD + VX) nonhuman primate. Seven Macaque monkeys (fascicularis and nemestrina) anesthetized with pentobarbital or chloralose were used in this study. The heart was exposed and suspended in a pericardial cradle. A left atrial (LA) catheter was inserted through the appendage. Changes in ABP and RNA (percent change from control) were determined when 1 and 10 micrograms/ml BK (in 1-ml volume) were applied to the anterior surface of the left ventricle or injected into the LA (0.3 and 3.0 micrograms/kg BK) in the intact and SAD + VX state. In both the intact and SAD + VX monkeys, ABP and RNA were significantly reduced with epicardial BK. In the intact state, LA injections of BK produced a significant decrease in the % delta of RNA and a depressor response. In the SAD + VX monkey, significant hypotensive responses were also observed with LA injections of BK concomitant with significant reductions in RNA. These results show the existence of a depressor response and inhibition of renal sympathetic nerve activity in the nonhuman primate mediated by the action of bradykinin on cardiac sympathetic afferents.

Carotid sinus baroreceptor activity in the nonhuman primate

The carotid sinus of eight adult Macaca fascicularis monkeys was functionally isolated from the circulation and perfused with Krebs-Henseleit solution. The impulse activity in 65 carotid sinus baroreceptor fibers from the left carotid sinus nerve was studied during nonpulsatile perfusion and was compared with the impulse activity in 68 fibers from 10 adult mongrel dogs. Curves relating the discharge frequency to carotid sinus pressure were constructed. The baroreceptor fibers of the monkey had a significantly lower threshold, gain, pressure at the point of inflection, and plateau pressure than those of the dog. Hysteresis, as indicated by the separation of the stimulus-response curves obtained by increasing and then decreasing carotid sinus pressure, was observed. At any given pressure, the discharge frequency of baroreceptors was greater when carotid sinus pressure was increased than when it was decreased in both species. These results provide direct evidence that carotid sinus baroreceptors in the monkey are less sensitive to pressure changes than those in the dog.

The role of cardiopulmonary sympathetic afferents in blood volume homoeostasis in the non-human primate

1. Four Macaca fascicularis monkeys were bilaterally sympathectomized by removing the thoracic sympathetic chain from the middle cervical ganglion to the T-6 sympathetic ganglion. This was done chronically, allowing adequate recovery time. While under light pentobarbital anaesthesia, the animals were then subjected to blood volume expansions with isotonic, isooncotic dextran or to head-out immersions. Seven immersions and seven volume expansions were carried out. 2. With immersion, there were significant increases in blood pressure, central venous pressure, urine flow, sodium excretion, potassium excretion, glomerular filtration rate, percentage of filtered sodium excreted and free water clearance. Although blood pressure and central venous pressure initially increased during the first immersion period, heart rate continued to increase with the immersion, while blood pressure and central venous pressure remained constant. Volume expansion caused an increase in central venous pressure, urine flow, sodium and potassium excretion, osmolar clearance, free water clearance, percentage of filtered sodium excreted and glomerular filtration rate. 3. Since these results with both the immersions and volume expansions were not qualitatively different from those observed in control animals, it is concluded that cardiopulmonary sympathetic afferents are not necessary for the renal response to head-out immersion or blood volume expansion in the non-human primate.

Reflex control of renal salt and water excretion

The regulation of renal salt and water excretion by the kidneys involves both intrarenal and extrarenal mechanisms. These systems play a pivotal role in the regulation of body fluid volume. An understanding of their operation is important in the treatment of many disease states. The normal operation of these control mechanisms is reviewed.

Arginine vasotocin and renal function in the conscious dog

The effects of arginine vasotocin (AVT), 4-6 ng/kg, on renal function and plasma prolactin (PRL) were determined in conscious American foxhounds undergoing a water diuresis. Intravenous AVT produced an antidiuresis, kaliuresis and inconsistent natriuresis, independently of changes in GFR, blood pressure, heart rate and plasma PRL.

Increased left atrial pressure does not alter renal function in the conscious primate

To study the functional role of the atriorenal reflex in the nonhuman primate, we chronically instrumented six Macaca fascicularis with left atrial snares and left atrial and aortic catheters. After inserting a bladder catheter, we determined hemodynamic and renal responses of the conscious chair-restrained monkey to increased left atrial pressure. In 23 snare experiments, no significant changes in renal or cardiovascular function were observed even though left atrial pressure increased from 6.5 +/- 3.3 to 16.2 +/- 3.4 mmHg. The animals were subjected also to blood volume expansion with isoncotic isotonic dextran solutions (+15% of calculated blood volume). They responded normally to this volume stimulus. Conscious dogs prepared in the same manner as the nonhuman primate exhibited diuresis in response to elevations of atrial pressure. We conclude that left atrial stretch receptors are not importantly involved in volume homeostasis in the nonhuman primate.

Atrial receptor modulation of renal nerve activity in the nonhuman primate

Experiments were done in the nonhuman primate Macaca fascicularis to determine the extent to which low-pressure receptors modulate renal nerve activity (RNA). Left atrial pressure (LAP) was increased either by inflating a balloon in the left atrium or by intravascular volume expansion. Arterial pressure (AP) was increased by the administration of epinephrine. Balloon inflation produced variable changes in RNA when all reflexes were intact. In the bilateral vagotomized animal, balloon inflation significantly increased RNA. Compared with the intact state, neither carotid sinus denervation nor sinoaortic denervation had a significant influence on RNA during balloon inflation. The response of both baroreceptor-denervated groups, however, was significantly less than that of the vagotomized group. Vagotomy plus sinoaortic denervation essentially prevented any effect of balloon inflation on RNA. Volume expansion produced a greater inhibition of RNA per increase in AP than did epinephrine. However, this difference was abolished after bilateral cervical vagotomy. These experiments demonstrate a significant influence and interplay of low- and high-pressure receptors on RNA in the nonhuman primate.

Species differences in vascular connections between the adrenal and the kidney in the monkey, human and dog

Vascular connections occurring between the adrenal gland and the kidney were investigated by using techniques of ligation of renal arteries followed by injection of trypan blue into the thoracic aorta. These connections, which course through the renal capsule to terminate at the renal corticomedullary junction, were confirmed in the dog. Using the same techniques in the monkey and human, vessels could be traced to the renal capsule but did not appear to penetrate this capsule.

The relation between carotid solute concentration and renal water excretion in conscious dogs

Verney's hypothesis of cerebral osmoreceptors controlling the renal excretion of water via vasopressin was reinvestigated in conscious trained dogs provided with bilateral skin loops containing the common carotid arteries. In multiple experiments in two dogs, bilateral intracarotid injections (0.25 ml. (kg b.wt.)-1 per artery in 10 s) of a hyperosmotic solution of sodium chloride (0.257 mol/l) during transient water diuresis failed to produce an antidiuretic response, although it is estimated that the injections elevated the osmolality of the carotid blood by 12-15%. In another 5 dogs, Bilateral intracarotid infusions of hyperosmotic saline (45 mumol.(kg b wt..min)-1 per artery for 10 min) during sustained water diuresis resulted in a 3% increase in jugular venous osmolality and an antidiuretic response without detectable changes in heart rate or mean arterial pressure. Equal intravenous hyperosmotic or intracarotid isosmotic infusions were not associated with antidiuretic response. Analysis of the concomitant concentrations of vasopressin in plasma fell short of supporting the hypothesis that the antidiuretic response to intracarotid hyperosmotic infusions was exclusively or mainly due to liberation of vasopressin, although the renal response could be mimicked by exogenous vasopressin. It is concluded that the present results-although discordant with several of Verney's results and assumptions-nevertheless support the concept of a cerebral solute receptor influencing the rate of renal water excretion.

Prostaglandins do not mediate the renal effects of bradykinin

Renal responses to the infusion of bradykinin during the simultaneous administration of indomethacin were similar to those obtained before prostaglandin synthesis inhibition, except that sodium excretion was significantly augmented. These results indicate that renal prostaglandins do not mediate the vasodilator actions of bradykinin.