Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Carrying Capacity”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 757 records · Page 42Linked to original sources
PubMed1996

Effects of erythrocyte infusion on VO2max at high altitude.

This study investigated whether autologous erythrocyte infusion would ameliorate the decrement in maximal O2 uptake (VO2max) experienced by lowlanders when they ascend to high altitude. VO2max was measured in 16 men (treadmill running) at sea level (SL) and on the 1st (HA1) and 9th (HA9) days of high-altitude (4,300 m) residence. After VO2max was measured at SL, subjects were divided into two matched groups (n = 8). Twenty-four hours before ascent to high altitude, the experimental group received a 700-ml infusion of autologous erythrocytes and saline (42% hematocrit), whereas the control group received only saline. The VO2max of erythrocyte-infused [54 +/- 1 (SE) ml.kg-1.min-1] and control subjects (52 +/- 2 ml.kg-1.min-1) did not differ at SL before infusion. The decrement in VO2max on HA1 did not differ between groups, averaging 26% overall, despite higher (P < 0.01) arterial hematocrit, hemoglobin concentration, and arterial O2 content in the erythrocyte-infused subjects. By HA9, there were no longer any differences in hematocrit, hemoglobin concentration, or arterial O2 content between groups. No change in VO2max occurred between HA1 and HA9 for either group. Thus, despite increasing arterial O2-carrying capacity, autologous erythrocyte infusion did not ameliorate the decrement in VO2max at 4,300-m altitude.

Acclimatization↗
PubMed1998

O2 extraction maintains O2 uptake during submaximal exercise with beta-adrenergic blockade at 4,300 m.

Whole body O2 uptake (VO2) during maximal and submaximal exercise has been shown to be preserved in the setting of beta-adrenergic blockade at high altitude, despite marked reductions in heart rate during exercise. An increase in stroke volume at high altitude has been suggested as the mechanism that preserves systemic O2 delivery (blood flow x arterial O2 content) and thereby maintains VO2 at sea-level values. To test this hypothesis, we studied the effects of nonselective beta-adrenergic blockade on submaximal exercise performance in 11 normal men (26 +/- 1 yr) at sea level and on arrival and after 21 days at 4,300 m. Six subjects received propranolol (240 mg/day), and five subjects received placebo. At sea level, during submaximal exercise, cardiac output and O2 delivery were significantly lower in propranolol- than in placebo-treated subjects. Increases in stroke volume and O2 extraction were responsible for the maintenance of VO2. At 4,300 m, beta-adrenergic blockade had no significant effect on VO2, ventilation, alveolar PO2, and arterial blood gases during submaximal exercise. Despite increases in stroke volume, cardiac output and thereby O2 delivery were still reduced in propranolol-treated subjects compared with subjects treated with placebo. Further reductions in already low levels of mixed venous O2 saturation were responsible for the maintenance of VO2 on arrival and after 21 days at 4,300 m in propranolol-treated subjects. Despite similar workloads and VO2, propranolol-treated subjects exercised at greater perceived intensity than subjects given placebo at 4,300 m. The values for mixed venous O2 saturation during submaximal exercise in propranolol-treated subjects at 4,300 m approached those reported at simulated altitudes >8,000 m. Thus beta-adrenergic blockade at 4,300 m results in significant reduction in O2 delivery during submaximal exercise due to incomplete compensation by stroke volume for the reduction in exercise heart rate. Total body VO2 is maintained at a constant level by an interaction between mixed venous O2 saturation, the arterial O2-carrying capacity, and hemodynamics during exercise with acute and chronic hypoxia.

Adrenergic beta-Agonists↗
PubMed2005

Eighteen days of "living high, training low" stimulate erythropoiesis and enhance aerobic performance in elite middle-distance runners.

The efficiency of "living high, training low" (LHTL) remains controversial, despite its wide utilization. This study aimed to verify whether maximal and/or submaximal aerobic performance were modified by LHTL and whether these effects persist for 15 days after returning to normoxia. Last, we tried to elucidate whether the mechanisms involved were only related to changes in oxygen-carrying capacity. Eleven elite middle-distance runners were tested before (Pre), at the end (Post1), and 15 days after the end (Post2) of an 18-day LHTL session. Hypoxic group (LHTL, n = 5) spent 14 h/day in hypoxia (6 nights at 2,500 m and 12 nights at 3,000 m), whereas the control group (CON, n = 6) slept in normoxia (1,200 m). Both LHTL and CON trained at 1,200 m. Maximal oxygen uptake and maximal aerobic power were improved at Post1 and Post2 for LHTL only (+7.1 and +3.4% for maximal oxygen uptake, +8.4 and +4.7% for maximal aerobic power, respectively). Similarly oxygen uptake and ventilation at ventilatory threshold increased in LHTL only (+18.1 and +12.2% at Post1, +15.9 and +15.4% at Post2, respectively). Heart rate during a 10-min run at 19.5 km/h decreased for LHTL at Post2 (-4.4%). Despite the stimulation of erythropoiesis in LHTL shown by the 27.4% increase in serum transferrin receptor and the 10.1% increase in total hemoglobin mass, red cell volume was not significantly increased at Post1 (+9.2%, not significant). Therefore, both maximal and submaximal aerobic performance in elite runners were increased by LHTL mainly linked to an improvement in oxygen transport in early return to normoxia and probably to other process at Post2.

Adaptation, Physiological↗
PubMed2005

Role of 20-HETE in the pial arteriolar constrictor response to decreased hematocrit after exchange transfusion of cell-free polymeric hemoglobin.

The cerebrovascular response to decreases in hematocrit and viscosity depends on accompanying changes in arterial O2 content. This study examines whether 1) the arteriolar dilation seen after exchange transfusion with a 5% albumin solution can be reduced by the K(ATP) channel antagonist glibenclamide (known to inhibit hypoxic dilation), and 2) the arteriolar constriction seen after exchange transfusion with a cell-free hemoglobin polymer to improve O2-carrying capacity can be blocked by inhibitors of the synthesis or vasoconstrictor actions of 20-HETE. In anesthetized rats, decreasing hematocrit by one-third with albumin exchange transfusion dilated pial arterioles (14 +/- 2%; SD), whereas superfusion of the surface of the brain with 10 muM glibenclamide blocked this response (-10 +/- 7%). Exchange transfusion with polymeric hemoglobin decreased the diameter of pial arterioles by 20 +/- 3% without altering arterial pressure. This constrictor response was attenuated by superfusing the surface of the brain with a 20-HETE antagonist, WIT-002 (10 microM; -5 +/- 1%), and was blocked by two chemically dissimilar selective inhibitors of the synthesis of 20-HETE, DDMS (50 microM; 0 +/- 4%) and HET-0016 (1 microM; +6 +/- 4%). The constrictor response to hemoglobin transfusion was not blocked by an inhibitor of nitric oxide (NO) synthase, and the inhibition of the constrictor response by DDMS was not altered by coadministration of the NO synthase inhibitor. We conclude 1) that activation of K(ATP) channels contributes to pial arteriolar dilation during anemia, whereas 2) constriction to polymeric hemoglobin transfusion at reduced hematocrit represents a regulatory response that limits increased O2 transport and that is mediated by increased formation of 20-HETE, rather than by NO scavenging.

Animals↗
PubMed2006

Splenectomy impairs diffusive oxygen transport in the lung of dogs.

The spleen acts as an erythrocyte reservoir in highly aerobic species such as the dog and horse. Sympathetic-mediated splenic contraction during exercise reversibly enhances convective O2 transport by increasing hematocrit, blood volume, and O2-carrying capacity. Based on theoretical interactions between erythrocytes and capillary membrane (Hsia CCW, Johnson RL Jr, and Shah D. J Appl Physiol 86: 1460-1467, 1999) and experimental findings in horses of a postsplenectomy reduction in peripheral O2-diffusing capacity (Wagner PD, Erickson BK, Kubo K, Hiraga A, Kai M, Yamaya Y, Richardson R, and Seaman J. Equine Vet J 18, Suppl: 82-89, 1995), we hypothesized that splenic contraction also augments diffusive O2 transport in the lung. Therefore, we have measured lung diffusing capacity (DL(CO)) and its components during exercise by a rebreathing technique in six adult foxhounds before and after splenectomy. Splenectomy eliminated exercise-induced polycythemia, associated with a 30% reduction in maximal O2 uptake. At any given pulmonary blood flow, DL(CO) was significantly lower after splenectomy owing to a lower membrane diffusing capacity, whereas pulmonary capillary blood volume changed variably; microvascular recruitment, indicated by the slope of the increase in DL(CO) with respect to pulmonary blood flow, was also reduced. We conclude that splenic contraction enhances both convective and diffusive O2 transport and provides another compensatory mechanism for maintaining alveolar O2 transport in the presence of restrictive lung disease or ambient hypoxia.

Animals↗
PubMed1987

Properties of proprioceptive neurons in the cuneate nucleus of the cat.

Fifty-two slowly adapting proprioceptive neurons in the cuneate nucleus of chloralose-anesthetized cats were studied. Recordings were made from 3 mm rostral to the obex to 5 mm caudal. The highest densities of proprioceptive neurons were found above and more than 3 mm caudal to the obex. Analysis of the spike trains produced with the forelimb held fixed revealed three basic periodic patterns. Neurons exhibiting these patterns were partitioned into three groups, referred to as the A, B, and C classes. Class A neurons (42%; 22/52) produced regular spike trains that were qualitatively similar to muscle spindle fibers. Interval distributions for this class were typically unimodal and slightly positively skewed. Adjacent intervals were frequently positively correlated. Spectral analysis suggested that 91% of class A spike trains had one to two periodic components. Class B neurons (21%; 11/52) had additional spikes interposed in their periodic discharge; these "interrupting" spikes did not significantly alter the timing of the dominant periodic discharge. Interval distributions were typically bimodal and adjacent intervals were negatively correlated. Spectral analysis suggested that two or more periodic components were present in their spike trains. Class C neurons (36%; 26/52) had spike trains with a basic rhymicity, but when this specific discharge was interrupted, the subsequent interval was near modal length; thus, they were "reset." Interval distributions were usually multimodal and adjacent intervals were frequently negatively correlated. Spectral analysis suggested that C spike trains usually had four or more periodic components. Estimates of information-carrying capacity of each class using a mean rate code and those of primary muscle spindle fibers suggested that a sizable information loss may occur in synaptic transmission. This potential loss was smaller for A-neurons (40%) than for B- (69%) or C-neurons (64%). Electrical stimulation of cutaneous structures influenced 55% (22/52) of the sample. All were members of the B and C classes. Responses were typically biphasic. The cutaneous receptive fields nearly always included a portion of the forepaw. No relationship was found between movement sensitivity and receptive field topography. Contralateral input was found in half (10/20) the neurons tested.

Afferent Pathways↗
PubMedDate not supplied

The effects of cigarette smoking on cardiopulmonary function and exercise tolerance in teenagers.

Teenagers who smoke are frequently warned that cigarette smoking will have detrimental effects on the function of their cardiopulmonary system and on their ability to perform exercise. However, there is little published evidence to support this statement. Therefore, in the present study, peak expiratory flow was measured as an indicator of lung function, expired carbon monoxide level was measured as an indicator of current smoking and the associated reduction in the oxygen carrying capacity of the blood, and blood pressure and heart rate were measured as indicators of cardiovascular hemodynamics before and after a one-mile run in 27 teenagers. The results show that, even at a young age, cigarette smoking is associated with significant detrimental effects on cardiopulmonary function and exercise tolerance. Objective evidence of an effect of smoking on cardiopulmonary function and exercise tolerance in this age group may assist educators and health care professionals in convincing teenagers to quit smoking.

Adolescent↗
PubMed2002

Prevalence of anemia in cancer patients undergoing radiotherapy: prognostic significance and treatment.

As the antitumor activity of radiation is mediated via its interaction with oxygen to form labile free radicals, the intratumoral oxygen level has an important influence on the ability of radiation therapy to kill malignant cells. By decreasing the oxygen-carrying capacity of the blood, anemia may result in tumor hypoxia and may have a negative influence on the outcome of radiotherapy for various malignancies, even for small tumors not normally assumed to be hypoxic. In addition, anemia also has a negative effect on the quality of life of cancer patients, as evidenced by worsening fatigue. As a high proportion (about 50%) of cancer patients undergoing radiotherapy are anemic prior to or during treatment, strategies to correct anemia and/or the resultant tumor hypoxia are increasingly being considered an important component of treatment. In particular, epoetin alfa (recombinant human erythropoietin), which has proved an effective and well-tolerated means of raising hemoglobin levels in anemic patients receiving radiotherapy, potentially could reverse the negative prognostic influence of a low hemoglobin in patients with certain malignancies. Radiation oncologists need to be aware of the possibility of anemia in cancer patients undergoing radiotherapy so that timely intervention can be instituted whenever anemia is diagnosed.

Anemia↗
PubMed2002

Raising hemoglobin: an opportunity for increasing survival?

Although the association between low hemoglobin levels and poorer outcomes in radiation oncology has long been recognized, anemia is often overlooked and untreated. However, a growing body of clinical evidence now indicates that low hemoglobin levels during radiation treatment are associated with decreased response and survival following radiotherapy. For example, a large Canadian retrospective study in patients receiving radical radiotherapy for cervical cancer showed that the 5-year survival rate was 19% higher in those whose hemoglobin during radiation treatment was =12 g/dl compared to those with levels <12 g/dl. The data suggest that clinical trials need to be performed to determine whether increasing hemoglobin levels leads to improved local control and survival. The mechanism by which low hemoglobin levels could cause poorer outcomes is not well understood and needs further elucidation. It is postulated that lower hemoglobin levels resulting in decreased oxygen carrying capacity may lead to increased tumor hypoxia, radiation resistance and increased tumor angiogenesis. The interrelationship of low hemoglobin levels, hypoxia, tumor angiogenesis and survival is explored in this article.

Anemia↗
PubMed2006

Fetal haematocrit is a determinant of placental size in term pregnancies.

Placental size may be influenced by maternal factors, placental function as well as the fetal condition. So far, no studies have examined how the fetal oxygen-carrying capacity or haemoglobin/haematocrit levels would affect placental growth in normal human pregnancies. The aim of this study was to investigate the relationships between placental size and fetal arterial cord blood haemoglobin and haematocrit levels at the time of caesarean delivery. Umbilical arterial cord blood was taken for arterial haemoglobin and haematocrit levels immediately after delivery. The relative placental size (defined by the ratio of placental weight to fetal weight) was inversely correlated with both arterial haemoglobin (r = -0.455, p = 0.001) and haematocrit levels (r = -0.425, p = 0.003) in women who had undergone elective caesarean sections. No significant correlation was found between the relative placental size with other maternal and fetal factors.

Adult↗
PubMed1988

Postpubertal changes in the histomorphometric characteristics of the uterus of the indigenous West African pig.

The epithelial height and myometrial and endometrial characteristics of the fundus, corpus and neck regions of the uteri of 28 virgin West African indigenous gilts in four age groups (6-8, 10-12, 16-18 and 20-22 months) were histometrically evaluated. Though regionally stable, the height of luminal epithelial cells was, respectively, reduced and enhanced in the fundus and neck regions by 10-12 months. The myometrium was thinner in the fundus and was severely reduced in the corpus region in gilts aged 16-18 months. Contrarily, the endometrium was regionally stable in thickness but underwent some thickening in the corpus of 16 to 18-month-old gilts. The respective occurrence of muscular and glandular tissues in the myometrium and endometrium was regionally influenced while older gilts had more circular muscles than the others. Generally, over 70% of the glands and 60% of the muscles were complex glands and longitudinal muscles, respectively. Results depict the nonuniform growth rates of different uterine tissues in the different regions and suggest that the improvement in the litter-carrying capacity of the uterus in these pigs continues well after puberty.

Africa, Western↗
PubMed1993

Habitat, density and group size of primates in a Brazilian tropical forest.

Habitats, population densities and group sizes of 5 primate species (Callithrix flaviceps, Callicebus personatus personatus, Cebus apella nigritus, Alouatta fusca clamitans, and Brachyteles arachnoides) were estimated, using the method of repeated transect sampling, in an area of montane pluvial forest in eastern Brazil (Atlantic forest). A. fusca and C. apella had the highest densities in terms of groups and individuals per square kilometer, respectively, while B. arachnoides was least abundant. The highest primate densities were observed in areas of secondary vegetation. Both group sizes and population densities for the 5 species were generally lower at the Reserva Biologica Augusto Ruschi than those reported in other areas of Atlantic forest. Hunting pressure and the different carrying capacity of the habitat are suggested as possible causes for the low number of sightings registered for these species.

Alouatta↗
PubMed1979

Effects of anemia and growth retardation on respiratory activity in the piglet.

Respiratory activity (RA) was assessed in a piglet model by giving chloralose (Ch), 6 mg/kg i.v. every 2 min, until the appearance of apnea. The total cumulative dose of Ch (mg/kg) which produced permanent apnea (lethal dose, LD) was determined. The slope of the dose-respiratory frequency curve (R = ae-lambda Ch) was also computed. The LD of Ch increased progressively with age, while respiratory frequency (lambda) decreased. However, in piglets with severe spontaneous anemia (hematocrit less than 10%), the LD of Ch was less than half that expected for the age groups, and the rate of reduction of gamma was much greater. The enhanced sensitivity to inhibition of RA may relate in part to anemia with reduced O2-carrying capacity to the CNS, and in part to growth retardation with delayed respiratory center maturation.

Age Factors↗
PubMed1986

Effect of a reduction in blood viscosity on maximal myocardial oxygen delivery distal to a moderate coronary stenosis.

This study tested the hypothesis that a reduction in blood viscosity by means of isovolumetric hemodilution will permit an increase in maximal oxygen delivery to myocardium distal to a moderate coronary arterial stenosis. It is known that blood viscosity is a determinant of resistance to blood flow at both the stenotic and the arteriolar levels. Accordingly, a reduction in blood viscosity could exert a favorable influence on maximal myocardial oxygen delivery in the setting of stenosis, provided that the oxygen-carrying capacity of the blood is not compromised excessively. Closed-chest, sedated domestic swine (n = 8) were instrumented with an artificial coronary arterial stenosis that reduced vessel diameter by 64%. Measurements of hemodynamics, regional myocardial blood flow (microspheres), lactate and oxygen metabolism, and whole blood viscosity were made at control and after two successive 10 min intracoronary infusions of adenosine (400 and 800 micrograms/min) distal to the stenosis. Next, albumin/saline solution was given intravenously to reduce the animal's hematocrit by approximately 50%. Repeat measurements of all experimental variables were then made at a second control and again after two successive 10 min intracoronary infusions of adenosine (400 and 800 micrograms/min) distal to the stenosis. Myocardial blood flow (ml/min/g) distal to the stenosis increased from 1.52 +/- 0.21 (mean +/- 1 SD) to 4.10 +/- 0.86 in response to adenosine (peak dose) before hemodilution (p less than .01) and from 2.07 +/- 0.59 to 4.08 +/- 0.93 (p less than .01) after hemodilution.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1992

Acute hibernation and reperfusion of the ischemic heart.

BACKGROUND: Recovery from prolonged low-flow ischemia was studied in isolated, isovolumically beating neonatal piglet hearts (n = 11) and compared with controls (n = 5). METHODS AND RESULTS: Hearts were perfused with red blood cell-enhanced Krebs-Henseleit buffer with physiological oxygen-carrying capacity. Left ventricular mechanical function was assessed with a fluid-filled balloon. Measurements of peak systolic pressure, pressure-rate product (PRP), and +dP/dtmax were obtained at various filling pressures. Myocardial oxygen delivery and metabolism (MVO2) and lactate uptake were measured at 30-minute intervals. Control data were obtained with coronary flow (CF) set at 2 ml.min-1.g-1. CF was then reduced to 0.2 ml.min-1.g-1 for 2 hours. Thereafter, reperfusion was instituted at control levels. Hearts not subjected to ischemia were studied at identical time intervals. In these, function remained at greater than 80% after more than 3.5 hours of study. Reduction of CF to 10% was accompanied by an abrupt diminution in function (pressure-rate product) and MVO2 to 20% of control and by lactate release. These measures remained constant for the full 2 hours of ischemia. Incremental return of CF caused a lockstep increase in mechanical function and metabolism. At 30 minutes of reperfusion, PRP was 78% of time-matched controls (p = 0.05), and dP/dtmax did not differ. Increasing calcium to 5 mmol/l returned PRP (and dP/dtmax) to preischemia levels. Myocardial ATP and creatine phosphate concentrations were identical in both groups, although glycogen was lower in the ischemic hearts. CONCLUSIONS: Acute hibernation is associated with protection of the in vitro heart from prolonged normothermic ischemia. Systolic function was only modestly lower, and velocity (dP/dtmax) did not differ from control hearts. The minimal "stunning" was fully reversible with calcium.

Animals↗
PubMed1994

Delineation of determinants of left ventricular early filling. Saline versus blood infusion.

BACKGROUND: Left atrial pressure (LAP) is often believed to play a dominant role in the determination of left ventricular (LV) early diastolic filling. In a previous study we found no significant relation between LAP and LV early filling velocity (E) but found instead a relation between E and two determinants of LV myocardial shortening (contractility and afterload). To determine if such disparate results may be related to the data ranges of the independent variables in a given population of animals, we took advantage of the differential hemodynamic effects of two modes of volume expansion: saline and whole blood. METHODS AND RESULTS: Eighteen closed-chest anesthetized dogs were instrumented with micromanometers for measurement of LV, left atrial, and aortic pressures. LV volumes were obtained with use of contrast ventriculography, pressures by micromanometry, and transmitral flow-velocity by Doppler echocardiography. After obtaining baseline measurements, group 1 (n = 9) received rapid infusion of 500 to 650 mL of saline over 10 minutes, and group 2 (n = 9) received the same volume infusion of whole blood. In terms of two known determinants of E, infusion of saline resulted in a significant increase in LAP at the moment of mitral valve opening (X1) (1.5 +/- 0.9 to 5.7 +/- 1.4 mm Hg; P < .05) and a moderate decrease in the pressure decay rate during isovolumic relaxation (tau 1/2) (22.9 +/- 2.4 to 26.3 +/- 3.5 milliseconds; P < .05). When these two factors were entered together into a multiple regression analysis with E as the dependent variable, the overall correlation was found to be significant (R = .722; P < .008), with both independent variables contributing significantly to the relation. When factors related to myocardial shortening (afterload and contractility) were added to this relation, they did not significantly improve the prediction of E. Like saline, whole blood infusion augmented X1 (1.6 +/- 2.4 to 8.8 +/- 3.2 mm Hg; P < .05) and tau 1/2 (21.5 +/- 2.6 to 32.0 +/- 6.3 milliseconds; P < .05) but also significantly increased LV afterload as measured by aortic diastolic pressure (91 +/- 10 to 110 +/- 12 mm Hg; P < .05). Multiple regression analysis of X1 and tau 1/2 with E again revealed a significant relation (R = .761; P < .002), with both independent variables contributing significantly to the relation. However, in this case, addition of contractility and afterload to the regression significantly improved the relation (R = .909; P < .001), with all four independent variables now contributing significantly to the prediction of E. CONCLUSIONS: Combined with our previous results, this study indicates the degree to which experimental methods can have an impact on the delineation of the determinants of a phenomenon as complex as LV early diastolic filling. Which independent variables emerge as primary determinants can be strongly influenced by the experimenter's choice of experimental design and manipulations. Specifically, experiments using volume infusion to delineate the responses of the cardiovascular system to variations in loading must allow for the hemodynamic changes that are inherent in the choice of infusate and infusion technique, especially when those interventions may significantly alter blood oxygen-carrying capacity and, in turn, differentially modify factors that affect the magnitude of the early diastolic transmitral pressure gradient.

Animals↗
PubMedDate not supplied

Evidence for an enhanced transmembrane sodium (Na+) gradient induced by aldosterone in the incubated rat tail artery.

Aldosterone is known to stimulate Na+ transport as measured in terms of current-carrying capacity of epithelial sheets or of Na+ - K+ ATPase activity in cells. The possibility that this is reflected in an altered steady-state transmembrane Na+ distribution in vascular smooth muscle was here examined directly. Transmembrane Na+ and K+ gradients were first dissipated by overnight incubation in K-free physiological salt solution (PSS) at 10 degrees C and then reestablished by 3 hours in normal PSS at 37 degrees C. The addition of d-aldosterone (but not corticosterone) to these media significantly reduced cell Na. This involved only free cell Na which was reduced by about 20% of 3 mmole/kg dry wt. No significant change in membrane permeability measured in terms of net Li uptake at 3 degrees C or at 37 degrees C was observed. The lowest effective aldosterone concentration was 2.8 x 10(-9) M. These results are consistent with the observed enhancement of net Na+ transport in incubated arteries in DOCA-induced hypertension and in the SHR but do not account for the increased Na+ permeability observed in these states.

Aldosterone↗
PubMedDate not supplied

The protective effect of combined administration of anti-oxidants and perfluorochemicals on cerebral ischemia.

We previously published results of investigations which indicated that the combination of mannitol, which acts as a free radical scavenger, and perfluorochemicals (PFC), which have a strong oxygen-carrying capacity, can be therapeutic in cases of brain infarction. The present experiment tested the hypothesis that the effectiveness of such treatment could be increased by an optimal combination of such scavengers and other chemicals. Fifty-two dogs were used, employing the "canine model of a completely ischemic brain regulated with the perfusion method." A total of six drugs with free radical scavenger capacities were tested: mannitol, vitamin E, vitamin C, Nizofenone (Y-9197), dexamethasone (DEXA) and suloctidil (MY-103). These drugs were administered intravenously 15 minutes prior to the production of ischemia, when cerebral blood flow was reduced to one-tenth its normal volume. After one hour, recirculation was allowed and the recovery of electrical activity of the brain observed for three hours. Judged by the degree of recovery of brain electrical activity, five drugs were considered to have protective effect against brain ischemia: mannitol, vitamin E, MY-103, DEXA and Y-9197. Among these five drugs, mannitol, vitamin E and DEXA are known to be safe and easily used clinically. The combined administration of these three drugs, together with PFC, was also investigated. It was found that the speed and degree of recovery of brain electrical activity were greater when these drugs were given together than when one was administered alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗