Renal and intrarenal blood flow distribution in swine during severe exercise

It is known that a compensatory reduction and diversion of renal flow occurs in severe exercise in humans but not in dogs. We investigated this in miniature swine by measuring changes in total renal blood flow (TRF) and intra-renal blood flow (IRBF) distribution with tracer microspheres (15 +/- 5 mum) at rest and during steady-state exercise at 4.8-7.2 kph and 0% grade, and during severe exercise at 4.8-7.2 kph and 10% grade. We measured heart rate and cardiac output (Q) via implanted probes. TRF was determined as a percent of Q and as ml/100 g per min. IRBF was determined for the outer cortex, inner cortex, outer medulla, and inner medulla. Our results show that renal blood flow is significantly (P less than 0.05) reduced in pigs with exercise. Steady-state exercise reduced flow to about 66% of control and severe exercise reduced renal flow to 30% of control. IRBF was unchanged throughout. These results show that the exercising pig augments blood flow to skeletal muscle by reducing blood flow to kidneys, a response known to occur in man.     

Changes in muscle blood flow distribution during hyperthermia

Blood flow is a critical parameter for obtaining satisfactory temperature distributions during clinical hyperthermia. This study examines the changes in blood flow distribution in normal porcine skeletal muscle before, during and after a period of regional microwave hyperthermia. The baseline blood flow distribution during general anaesthesia and after the insertion of the thermal probes was established independently in order to isolate the changes due to hyperthermia. General anaesthesia alone and thermocouple insertion during anesthesia had no significant effect on the muscle blood flow distribution. Regional microwave heating generated a non-uniform blood flow distribution which was a function of the tissue temperature distribution. Blood flow was greater in those tissues samples in which higher temperatures were recorded and less in those sampled further from the applicators peak SAR (Specific Absorption Rate). The increase in blood flow appears to be primarily a local phenomenon. Although muscle blood flow may be considered to be uniform prior to heating, this does not hold during hyperthermia treatment. Therefore, the non-uniform nature of the blood distribution during heating should be incorporated into any practical bioheat transfer model.     

Myocardial blood flow distribution in miniature pigs during exercise

Total and regional myocardial blood flow was measured in miniature pigs at rest and during two levels of treadmill exercise, including maximal exercise. Exercise increased the myocardial blood flow in a linear manner with heart rate (r = 0.87). At rest the endocardial/epicardial blood flow ratio was significantly greater than unity with flow favoring the endocardium. Exercise failed to appreciably alter the distribution of coronary blood flow. Thus the myocardium was capable of further dilatation and perfusion of blood without compromising endocardial flow even during the most severe level of exercise when maximal heart rates were attained.     

Age alters regional distribution of blood flow during moderate-intensity exercise

During dynamic exercise in warm environments, requisite increases in skin and active muscle blood flows are supported by increasing cardiac output (Qc) and redistributing flow away from splanchnic and renal circulations. To examine the effect of age on these responses, six young (Y; 26 +/- 2 yr) and six older (O; 64 +/- 2 yr) men performed upright cycle exercise at 35 and 60% of peak O2 consumption (VO2peak) in 22 and 36 degrees C environments. To further isolate age, the two age groups were closely matched for VO2peak, weight, surface area, and body composition. Measurements included heart rate, Qc (CO2 rebreathing), skin blood flow (from increases in forearm blood flow (venous occlusion plethysmography), splanchnic blood flow (indocyanine green dilution), renal blood flow (p-amino-hippurate clearance), and plasma norepinephrine concentration. There were no significant age differences in Qc; however, in both environments the O group maintained Qc at a higher stroke volume and lower heart rate. At 60% VO2peak, forearm blood flow was significantly lower in the O subjects in each environment. Splanchnic blood flow fell (by 12-14% in both groups) at the lower intensity, then decreased to a greater extent at 60% VO2peak in Y than in O subjects (e.g., -45 +/- 2 vs. -33 +/- 3% for the hot environment, P < 0.01). Renal blood flow was lower at rest in the O group, remained relatively constant at 35% VO2peak, then decreased by 20-25% in both groups at 60% VO2peak. At 60% VO2peak, 27 and 37% more total blood flow was redistributed away from these two circulations in the Y than in the O group at 22 and 36 degrees, respectively. It was concluded that the greater increase in skin blood flow in Y subjects is partially supported by a greater redistribution of blood flow away from splanchnic and renal vascular beds.     

Blood flow distribution in working in situ canine muscle during blood flow reduction

The purpose of this study was to determine whether reduction in apparent muscle O2 diffusing capacity (Dmo2) calculated during reduced blood flow conditions in maximally working muscle is a reflection of alterations in blood flow distribution. Isolated dog gastrocnemius muscle (n = 6) was stimulated for 3 min to achieve peak O2 uptake (VO2) at two levels of blood flow (controlled by pump perfusion): control (C) conditions at normal perfusion pressure (blood flow = 111 +/- 10 ml.100 g-1.min-1) and reduced blood flow treatment [ischemia (I); 52 +/- 6 ml.100 g-1.min-1]. In addition, maximal vasodilation was achieved by adenosine (A) infusion (10(-2)M) at both levels of blood flow, so that each muscle was subjected randomly to a total of four conditions (C, CA, I, and IA; each separated by 45 min of rest). Muscle blood flow distribution was measured with 15-microns-diameter colored microspheres. A numerical integration technique was used to calculate Dmo2 for each treatment with use of a model that calculates O2 loss along a capillary on the basis of Fick's law of diffusion. Peak VO2 was reduced significantly (P < 0.01) with ischemia and was unchanged by adenosine infusion at either flow rate (10.6 +/- 0.9, 9.7 +/- 1.0, 6.7 +/- 0.2, and 5.9 +/- 0.8 ml.100 g-1.min-1 for C, CA, I, and IA, respectively). Dmo2 was significantly lower by 30-35% (P < 0.01) when flow was reduced (except for CA vs. I; 0.23 +/- 0.03, 0.20 +/- 0.02, 0.16 +/- 0.01, and 0.13 +/- 0.01 ml.100 g-1.min-1.Torr-1 for C, CA, I, and IA, respectively). As expressed by the coefficient of variation (0.45 +/- 0.04, 0.47 +/- 0.04, 0.55 +/- 0.03, and 0.53 +/- 0.04 for C, CA, I, and IA, respectively), blood flow heterogeneity per se was not significantly different among the four conditions when examined by analysis of variance. However, there was a strong negative correlation (r = 0.89, P < 0.05) between Dmo2 and blood flow heterogeneity among the four conditions, suggesting that blood flow redistribution (likely a result of a decrease in the number of perfused capillaries) becomes an increasingly important factor in the determination of Dmo2 as blood flow is diminished.     

Cerebral blood flow response pattern during balloon test occlusion of the internal carotid artery

PURPOSE: To evaluate the risk of temporary or permanent internal carotid artery occlusion. METHODS: In 156 patients intraarterial balloon test occlusion in combination with a stable xenon-enhanced CT cerebral blood flow study was performed before radiologic or surgical treatment. All 156 patients passed the clinical balloon test occlusion and underwent a xenon study in combination with a second balloon test. Quantitative flow data were analyzed for absolute changes as well as changes in symmetry. RESULTS: Fourteen patients exhibited reduced flow values between 20 and 30 mL/100 g per minute, an absolute decrease in flow, and significant asymmetry in the middle cerebral artery territory during balloon test occlusion. These patients would be considered at high risk for cerebral infarction if internal carotid artery occlusion were to be performed. With one exception they belonged to a group (class I) of 61 patients who showed bilateral or ipsilateral flow decrease and significant asymmetry with lower flow on the side of occlusion. The other 95 patients, who showed a variety of cerebral blood flow response patterns including ipsilateral or bilateral flow increase, were at moderate (class II) or low (class III) stroke risk. In contrast to these findings, exclusively qualitative flow analysis failed to identify the patients at high risk: a threshold with an asymmetry index of 10% revealed only 16% specificity whereas an asymmetry index of 45% showed only 61% sensitivity for detection of low flow areas (< 30 mL/100 g per minute). CONCLUSION: For achieving a minimal hemodynamic related-stroke rate associated with permanent clinical internal carotid artery occlusion we suggest integration of a thorough analysis of quantitative cerebral blood flow data before and during balloon test occlusion.     

Neural factors contributing to renin release during reduction in renal perfusion pressure and blood flow in cats

1. The participation of neural mechanisms in mediating the renin release induced by reduction of renal perfusion pressure was explored in anaesthetized cats by comparing renin release from the two kidneys, one acutely denervated and the other intact. 2. Suprarenal aortic stenosis of 10 min duration reduced renal perfusion pressure to 50 mmHg and halved blood flow to both kidneys, but cause a greater release of renin from the innervated kidney than from the contralateral denervated one (increments of 72 +/- 17 and 29 +/-20 pmol/min respectively). 3. A study of the time-course of the response during aortic stenosis of 30 min duration showed early release of renin from the innervated kidney at a time (5 min) when little release occurred from the denervated one. In later samplings (15 and 30 min) the response of the innervated kidney levelled out at somewhat lower values, and that of the denervated organ progressively increased, but remained smaller than on the side with intact nerves. 4. There was no parallelism between renin release and renal vasomotor changes induced by aortic stenosis, as vasomotor changes were equal in the two kidneys and remained constant from beginning to end of stenosis. It is concluded that a significant part of the renin release induced by aortic stenosis is dependent on neural mechanisms: the neural differs from the non-neural component in being of more rapid onset and probably of shorter duration.     

Sensitivity of blood pressure and renin activation during sodium restriction

The objective of the present study was to explore the interrelationships among cumulative sodium loss, renin activation, and blood pressure changes during sodium restriction in essential hypertensive patients. Specifically, we wanted to know whether the degree of sodium sensitivity of blood pressure depends on renin activation during steady state or on initial renin activation during the first days of sodium restriction. Sixty-seven untreated essential hypertensive patients were admitted to a metabolic ward for 8 days and put on a sodium restricted diet of 55 mmol/d from the second to the last day. Urinary excretions of sodium, potassium, and creatinine were determined along with mean arterial pressure and weight during 7 days. Besides measurements in steady state condition (after 7 days), active plasma renin concentration, aldosterone, and catecholamines were also assessed during the first 3 days of sodium restriction. Analyzable data are available for 55 patients. Baseline sodium excretion and the activation of renin during the first 3 days both appeared to be predictors of total sodium loss after 7 days. Changes in blood pressure were not related to changes in sodium balance, but they were to baseline blood pressure, baseline norepinephrine, and renin activation during the early phase of sodium restriction. In addition, blood pressure appeared to fall more when the normal relationship between sodium loss and early (but not late) activation of renin was disturbed. We conclude that sodium sensitivity of blood pressure during sodium restriction is associated with a relative unresponsiveness of the renin system during the early phase of sodium loss rather than to absolute renin levels during steady state.     

Regional cerebral blood flow during and after 2 hours of middle cerebral artery occlusion in the rat

In this study we explored if the secondary bioenergetic failure, which occurs a few hours after recirculation, following transient middle cerebral artery occlusion (MCAO) in rats, is caused by a compromised reflow. We induced 2 hours of MCAO and measured CBF at the end of the ischemia, as well as 15 minutes, 1, 2, and 4 hours after the start of recirculation, using autoradiographic or tissue sampling 14C-iodoantipyrine techniques. After 2 hours of MCAO, the autoradiographically measured CBF in the ischemic core areas was reduced to 3 to 5% of contralateral values. The reduction in CBF was less in neighboring, penumbral areas. After recirculation, flow already normalized in core tissues after 15 minutes, and remained close to normal for the 4 hours recirculation period studied. However, in penumbral tissues, recovery CBF values were usually below normal. The results show that tissues that are heavily compromised by the 2-hour period of ischemia and are destined to incur infarction, show a "relative hyperemia" during recirculation. In fact, some areas of the previously densely ischemic tissue showed overt hyperperfusion. This finding raises the question whether the relative or absolute hyperemia reflects events that are pathogenetically important. Because drugs that clearly ameliorate the final damage incurred fail to alter the relative hyperperfusion of previously ischemic tissues, it is concluded that vascular events in the reperfusion period do not play a major role in causing the final damage.     

High-frequency color Doppler sonography of the submandibular gland: relationship between salivary secretion and blood flow

Efficient high-resolution detection of DNA for flow cytometric sorting of X and Y chromosome-bearing sperm is dependent on effectively orientating the sperm head to the laser beam in orthogonally configured flow systems. Normally, a beveled needle is required to enlarge the fraction of properly orientated sperm (flat side facing the laser beam). In this report, a modification to a standard jet-in-air nozzle for improved sperm orientation is presented. Inside the modified nozzle (novel nozzle), orientation forces are applied lower in the nozzle than in the current beveled injection needle system. The nozzle was tested with sperm heads from several species. This study shows that use of the nozzle to orientate cattle, swine, rabbit, mouse, and human sperm effectively improves the percentage of sperm that are properly oriented. The percentage of sperm heads oriented by use of the former system (beveled needle) ranges around 30% for most species. With the newly designed nozzle, that percentage ranges around 60%. At least a twofold increase in analysis is achieved. It was found that, unlike results with the beveled needle, the percentage of properly oriented sperm was independent of the sample rate. The introduced nozzle is a significant improvement over the beveled needle system for the analysis and sorting of sperm on the basis of DNA content. In addition to the improvement in sorted sperm production brought about by the novel nozzle when fitted to standard-speed cell sorters, it clearly also has significant potential for improving the efficiency of the Beltsville Sperm Sexing Technology for separating X and Y chromosome-bearing sperm when adapted to high-speed cell-sorting systems.     

Relationship of systemic and intrarenal hemodynamics in cirrhosis

The relationship between systemic and renal hemodynamics was studied in 20 patients with advanced cirrhosis of the liver. Cardiac output was assessed by an indicator dilution technique, and both mean renal blood flow and intrarenal blood flow distribution were determined by the 133Xe washout method. Ten patients had elevated cardiac outputs (7.14 to 13.58 L/min; HCO group), seven patients had normal cardiac ouptputs (5.16 to 6.78; NCO group), and three had low cardiac outputs (3.65 to 4.1; LCO group). Renal hemodynamics did not correlate with cardiac output (r = 0.051; N.S.), since comparable reductions in mean renal blood flow occurred in both the LCO and HCO patients. Similarly, the degree of cortical ischemia, as assessed by percentage flow to the rapid flow component (C1%), did not correlate with cardiac output (r = 0.007; N.S.). Vasomotor instability as assessed by intrapatient variability of sequential xenon washout studies occurred frequently, and its magnitude did not correlate with cardiac output (r = -0.069; N.S.). These studies demonstrate that the abnormalities of intrarenal blood flow in cirrhosis are independent of alterations in cardiac output. Furthermore, the finding of marked intrarenal hemodynamic instability in the majority of patients with cirrhosis suggests that caution should be exercised in interpreting studies assessing the efficacy of vasoactive agents on renal hemodynamics in this disease, since the changes attributed to treatment may merely reflect spontaneous change.     

Relationship between gonadal steroids and corticosterone during blood sampling in saker falcons

Blood sampling in manually restrained or ketamine (15 mg/kg given intramuscularly) treated saker falcons (Falco cherrug) induced an increased concentration in plasma corticosterone. Elevated plasma progesterone, oestradiol 17 beta, and testosterone concentrations also were observed in some of these birds. An inverse relationship was demonstrated between levels of corticosterone and progesterone, but not with the levels of other hormones. It is suggested that progesterone measurement should be taken into consideration when studying the influence of stressors in falcons.     

Reversal of blood flow in experimental branch retinal vein occlusion

BACKGROUND: The consequences and management of asymptomatic Actinomyces-like organisms detected on cervical cytologic smears continue to be controversial. CASE: A unilateral tuboovarian actinomycotic abscess was discovered in a woman who had undergone a hysterectomy for uterine leiomyomas. She had had an intrauterine device in place for many years without any symptoms of pelvic inflammatory disease. CONCLUSION: Ascending infection of the upper genital tract by Actinomyces may be clinically inapparent. When Actinomyces-like organisms aer detected on cervical cytologic smears, removal of an intrauterine device should be considered.     

Relationship between intrauterine growth retardation and early postnatal superior mesenteric artery blood flow velocity

During the first week of life, we examined the changes in the systemic, intestinal and cerebral circulation, and the circulatory responses to feeding in 10 small for gestational age (SGA) infants using the ultrasound Doppler technique. From day 1 to day 3, preprandial cardiac output decreased (p < 0.01), whereas mean blood pressure (p < 0.01), superior mesenteric artery mean flow velocity (Vmean; p < 0.01) and middle cerebral artery Vmean (p < 0.01) increased. On day 1, cardiac output was higher in the SGA than in those of term and preterm appropriate for gestational age infants reported from our laboratory. Preprandial superior mesenteric artery Vmean was inversely related to the degree of growth retardation (r = 0.63, p < 0.05). However, growth retardation did not influence the postprandial increase in superior mesenteric artery Vmean and end-diastolic flow velocity, or the cerebral circulation.     

Spatial stability of extracellular potassium ion and blood flow distribution in rat cerebral cortex after permanent middle cerebral artery occlusion

Extracellular potassium ion activity ([K+]o) increases precipitously during brain ischemia when blood flow falls below threshold values less than approximately 15 mL/100 g/min. This flow threshold for increase of [K+]o occurs also in focal ischemia producing gradient from ischemic core to adjacent normally perfused brain. In this study we investigated the spatial and temporal stability of extracellular potassium ion and blood flow gradients after permanent middle cerebral artery occlusion (MCAO) in rats. [K+]o and regional CBF were measured, respectively, with K+-sensitive and polarographic hydrogen-sensitive microelectrodes at different cortical locations in the middle cerebral artery distribution region. Spatial assessment of [K+]o and regional CBF was conducted at 30, 90, and 180 minutes after MCAO. [K+]o in the more lateral cortex (core) increased from near 3 mmol/L before MCAO to greater than 50 mmol/L and was associated with flow values less than 25% of pre-ischemic levels. Measurements medial to the core (penumbra) indicated progressively decreasing levels of [K+]o and improvement of CBF. There was a tendency for [K+]o in penumbral zones to decrease toward normal levels with time, but there was little dissipation of [K+]o in core regions. In contrast, the spatial CBF profile remained remarkably constant for the entire recording period. Thus, unlike infarction which has been reported to expand with time after focal ischemia, the spatial [K+]o disturbance tends to contract primarily due to decreasing [K+]o with time in the penumbra. Thus, steady state levels of [K+]o after focal ischemia may not be a valuable predictor of cell viability.     

The relation between arterial oxygen tension and cerebral blood flow during cardiopulmonary bypass

BACKGROUND: The precise mechanisms involved in islet xenograft rejection remain unknown. The purpose of the present study was to determine cellular mechanisms responsible for islet xenograft rejection in the liver to facilitate finding a procedure for prevention of immune rejection. METHODS: Hepatic mononuclear cells (MNC) as well as splenocytes, peripheral blood MNC, and thymocytes from streptozotocin-induced diabetic mice (BALB/c) rejecting the intrahepatic rat (Lewis) islet xenografts were isolated and examined by two-color FACS analysis. RESULTS: The characteristic finding of the hepatic MNC from the mice rejecting islet xenografts compared with mice receiving isografts was a significant increase in the yield as well as in the percentage of the cells expressing CD3+ interleukin-2 receptor (IL-2R) alpha- beta+, CD3+ CD8alpha+ beta+, and T cell receptor (TCR) alphabeta+ lymphocyte function-associated antigen-1+. The expression of CD3 and TCR alphabeta of these T cells was found to be of intermediate intensity (TCR(int) cells). The expansion of these TCR(int) cells occurred predominantly in the liver. There was no significant difference in the cells expressing CD3+ IL-2R alpha+, CD3+ CD4+, CD3+ TCRgammadelta+, CD3- IL-2Rbeta+ (natural killer cells), and B220+ (B cells). In vivo administration of anti-IL-2Rbeta monoclonal antibody directed to the expanded cells produced a prevention of rejection. CONCLUSIONS: These findings suggest that islet xenograft rejection in the liver from rat to mouse is an event for which the TCR(int) cells are responsible.     

Role of kinins in basal and furosemide-stimulated renin secretion

OBJECTIVE: To determine risk factors predictive of outcomes to aid in the cost-effective preoperative evaluation and postoperative management of patients who are undergoing tonsillectomy and adenoidectomy for obstructed breathing during sleep. DESIGN: A historical cohort study with a nested case-control analysis that examined risk factors associated with postoperative respiratory complications. SETTING: Children's Medical Center of Dallas, Dallas, Tex, which is a pediatric referral hospital for secondary and tertiary pediatric care with both private and university-appointed physicians. PATIENTS: A convenience sample of 355 patients who were undergoing tonsillectomy and adenoidectomy for obstructed breathing during sleep throughout a 1-year period. INTERVENTION: None. MAIN OUTCOME MEASURE: The occurrence of postoperative complications, including airway obstruction, apneas with oxygen desaturations, airway interventions (e.g., endotracheal intubation), or administration of supplemental oxygen, as they related to associated medical conditions (e.g., cerebral palsy or prematurity) and diagnostic tests (e.g., chest x-ray film and electrocardiogram). RESULTS: Five associated medical conditions (cerebral palsy; seizures; age, < or = 3 years; congenital heart disease; and prematurity) were identified as important predictors of a complicated postoperative course using stepwise logistic regression analysis. Those children with an abnormal chest x-ray film or electrocardiogram were also identified as having an associated medical condition that was predictive of postoperative complications. CONCLUSIONS: Children with 1 or more of the associated risk factors identified should be considered candidates for postoperative inpatient observation. A preoperative chest x-ray film and electrocardiogram were found to be of little predictive value, and they are probably not cost-effective screening tests for postoperative respiratory complications.