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At least 253 records · Page 14Linked to original sources
PubMed2002

Polymerized bovine hemoglobin solution as a replacement for allogeneic red blood cell transfusion after cardiac surgery: results of a randomized, double-blind trial.

BACKGROUND: Blood loss leading to reduced oxygen-carrying capacity is usually treated with red blood cell transfusions. This study examined the hypothesis that a hemoglobin-based oxygen-carrying solution can serve as an initial alternative to red blood cell transfusion. METHODS: In a randomized, double-blind efficacy trial of HBOC-201, a total of 98 patients undergoing cardiac surgery and requiring transfusion were randomly assigned to receive either red blood cell units or HBOC-201 (Hemopure; Biopure Corporation, Cambridge, Mass) for the first three postoperative transfusions. Patients were monitored before and after transfusion, at discharge, and at 3 to 4 weeks after the operation for subsequent red blood cell use, hemodynamics, and clinical laboratory parameters. RESULTS: The use of HBOC-201 eliminated the need for red blood cell transfusions in 34% of cases (95% confidence interval 21%-49%). Patients in the HBOC group received a mean of 1.72 subsequent units of red blood cells; those who received red blood cells only received a mean of 2.19 subsequent units (P =.05). Hematocrit values were transiently lower in the HBOC group but were similar in the two groups at discharge and follow-up. Oxygen extraction was greater in the HBOC group (P =.05). Mean increases in blood pressure were greater in the HBOC group, but not significantly so. CONCLUSION: HBOC-201 may be an initial alternative to red blood cell transfusions for patients with moderate anemia after cardiac surgery. In a third of cases, HBOC-201 eliminated the need for red blood cell transfusion, although substantial doses were needed to produce this modest degree of blood conservation.

Aged↗
PubMed2006

Cardiorespiratory physiology and swimming energetics of a high-energy-demand teleost, the yellowtail kingfish (Seriola lalandi).

This study utilizes a swimming respirometer to investigate the effects of exercise and temperature on cardiorespiratory function of an active teleost, the yellowtail kingfish (Seriola lalandi). The standard aerobic metabolic rate (SMR) of S. lalandi (mean body mass 2.1 kg) ranges from 1.55 mg min(-1) kg(-1) at 20 degrees C to 3.31 mg min(-1) kg(-1) at 25 degrees C. This 2.1-fold increase in SMR with temperature is associated with a 1.5-fold increase in heart rate from 77 to 117 beats min(-1), while cardiac stroke volume remains constant at 0.38 ml beat(-1) kg(-1) and the difference in oxygen content between arterial and mixed venous blood [(Ca(O2)-Cv(O2))] increases marginally from 0.06 to 0.08 mg ml(-1). During maximal aerobic exercise (2.3 BL s(-1)) at both temperatures, however, increases in cardiac output are limited to about 1.3-fold, and increases in oxygen consumption rates (up to 10.93 mg min(-1) kg(-1) at 20 degrees C and 13.32 mg min(-1) kg(-1) at 25 degrees C) are mediated primarily through augmentation of (Ca(O2)-Cv(O2)) to 0.29 mg ml(-1) at 20 degrees C and 0.25 mg ml(-1) at 25 degrees C. It seems, therefore, that the heart of S. lalandi routinely works close to its maximum capacity at a given temperature, and changes in aerobic metabolism due to exercise are greatly reliant on high blood oxygen-carrying capacity and (Ca(O2)-Cv(O2)). Gross aerobic cost of transport (GCOT) is 0.06 mg kg(-1) BL(-1) at 20 degrees C and 0.09 mg kg(-1) BL(-1) at 25 degrees C at the optimal swimming velocities (U(opt)) of 1.2 BL s(-1) (opt) and 1.7 BL s(-1), respectively. These values are comparable with those reported for salmon and tuna, implying that the interspecific diversity in locomotor mode (e.g. subcarangiform, carangiform and thunniform) is not concomitant with similar diversity in swimming efficiency. A low GCOT is maintained as swimming velocity increases above U(opt), which may partly result from energy savings associated with the progressive transition from opercular ventilation to ram ventilation.

Analysis of Variance↗
PubMedDate not supplied

[Information-activation relations and mental work capacity of operators].

This paper presents the results of studying diagnostic potentials of the method used to assess mental performance of operators based on a combined application of the information carrying capacity and psychophysiological expenditures of man. Three groups of operators (45 subjects) that differed in their health status and motivation when performing sensorimotor tests were examined. Psychophysiological cost was measured with respect to autonomic responses (heart rate, respiration frequency, minute respiration volume, arm temperature) combined into an integrated parameter of psychic stress. It was found that the extremes of the relationship between information and activation parameters were invariant. The data obtained suggest that the information-activation relationship may be used to advantage in the clinical and physiological expertise of operators.

Aerospace Medicine↗
PubMed2003

[Ecological footprint calculation and development capacity analysis of China in 1999].

The ecological footprint method put forward and improved by William Rees and Mathis Wackernagel presents a methodologically simple but integrated framework for national natural capital accounting, which is capable of measuring the impact of Human's consumption on ecosystem. Based on the ecological footprint theory and calculation method, a flow network analysis method was introduced to illuminate the structure of complex ecological economic system, and the relationship among ecological footprint, diversity and development capacity was analyzed. In this paper, the ecological footprints of China and its provinces was calculated and compared with the national and local ecological carrying capacity. The results showed that the ecological footprints of China and most of its provinces were beyond the available ecological capacity, and China and its most provinces run 'national or regional ecological deficit'. In case of China, the national ecological deficit was 0.645 hm2 per cap in 1999. Secondly, we introduced a flow network analysis method, taking various ecological productive area as note, and adopted Ulanowicz's development capacity formula to analyze the relationship among ecological footprint diversity, development capacity and output. The results demonstrated that Ulanowicz's development capacity was a good predictor of economic system output. At the same time, two distinct ways to change development capacity were produced. Increasing ecological footprint or increasing ecological footprint's diversity would both increase development capacity. Due to the fact that the ecological footprints had already been beyond bio-capacities, the only way to increase development capacity was to increase ecological footprint's diversity. The positive relationship between ecological footprint diversity and resources utilization efficiency demonstrated that there was no conflict between increasing ecological footprint's diversity and reducing footprints while not comprising our quality of life.

China↗
PubMed2001

Review: Analysis of the evolutionary convergence for high performance swimming in lamnid sharks and tunas.

Elasmobranchs and bony fishes have evolved independently for more than 400 million years. However, two Recent groups, the lamnid sharks (Family Lamnidae) and tunas (Family Scombridae), display remarkable similarities in features related to swimming performance. Traits separating these two groups from other fishes include a higher degree of body streamlining, a shift in the position of the aerobic, red, locomotor muscle that powers sustained swimming to a more anterior location in the body and nearer to the vertebral column, the capacity to conserve metabolic heat (i.e. regional endothermy), an increased gill surface area with a decreased blood-water barrier thickness, a higher maximum blood oxygen carrying capacity, and greater muscle aerobic and anaerobic enzyme activities at in vivo temperatures. The suite of morphological, physiological, and biochemical specializations that define "high-performance fishes" have been extensively characterized in the tunas. This review examines the convergent features of lamnid sharks and tunas in order to gain insight into the extent that comparable environmental selection pressures have led to the independent origin of similar suites of functional characteristics in these two distinctly different taxa. We propose that, despite differences between teleost and elasmobranch fishes, lamnid sharks and tunas have evolved morphological and physiological specializations that enhance their swimming performance relative to other sharks and most other high performance pelagic fishes.

Adaptation, Biological↗
PubMed1975

Pathogenesis of human cholesterol cholelithiasis.

The pathogenesis of cholesterol cholelithiasis in humans has been studied by means of three techniques. The cholesterol-solubilizing capacity of bile may be determined by estimation of the relative composition of the three major lipid constituents of bile. Consistent reduction in the cholesterol-carrying capacity of gallbladder bile of persons with gallstones when compared with normal subjects has not been shown. Normal subjects frequently have supersaturated bile. Secretion rates of biliary lipids have been estimated by two methods; with the method that appears to be more physiologic no change in lipid secretion rates was found in gallstone patients. Bile acid pool size has been measured by isotope dilution techniques; it is reduced in patients with gallstones. It is not clear whether this reduction is important in the pathogenesis of cholesterol cholelithiasis, for the bile acid secretion rate is normal because of an increased rate of cycling of the pool through the enterohepatic circulation. The role of the gallbladder in the genesis of cholesterol cholelithiasis may be more important than has been realized.

Bile↗
PubMed1997

Oxygenation capacity of hypotonized and crosslinked rat erythrocytes.

Rat erythrocytes subjected to hypotonic-isotonic dialysis, or crosslinking with bifunctional reagents (glutaraldehyde and dimethyl suberimidate hydrochloride) show a high percentage of methemoglobin and decreased oxyhemoglobin content which implies a low oxygen carrying capacity. Such modified cells maintain reversible oxygen binding properties although, they present a high hemoglobin oxygen affinity (low P50) and a diminished cooperativity in binding oxygen to hemoglobin (low n). These results suggest a reduced capacity of liberating oxygen to tissues under low PO2. Changes produced in erythrocytes can not be restored even in the presence of energy (ATP), reduced glutathione and 2,3-bisphosphoglyceric acid during the dialysis process or after crosslinking/permeabilizing treatment.

2,3-Diphosphoglycerate↗
PubMed1995

Hydroxyethyl starch versus lactated Ringer's solution in the chronic maternal-fetal sheep preparation: a pharmacodynamic and pharmacokinetic study.

Administration of fluids intravenously prior to spinal and epidural analgesia in obstetrics is required to prevent maternal hypotension and fetal hypoxia. A colloid solution, such as hydroxyethyl starch (HES), might be preferable considering the capacity to stay intravascularly for a longer period. In this study the placental transfer of HES and the hemodynamic effects after infusion were investigated using a chronic maternal-fetal sheep preparation. Either 500 mL HES 10% or 750 mL lactated Ringer's solution (RL) was infused intravenously into the ewe over 30 min. Fetal and maternal blood were assayed for HES, blood gases, and acid-base status before and at regular intervals after infusion. Maternal and fetal cardiovascular variables were recorded continuously for 90 min. After HES infusion, maternal HES levels peaked at 30 min ranging from 6.9 mg/mL to 12.1 mg/mL and declined at 24 h to levels between 0.3 mg/mL and 2.8 mg/mL. Mean fetal HES concentrations remained below 0.3 mg/mL. Infusion of HES decreased hemoglobin (Hb) and plasma viscosity (PV) in the mother. Infusion of RL decreased Hb, but did not change PV. Infusion of HES significantly increased uterine blood flow (UBF), cardiac output (CO), total oxygen-delivery capacity, and uterine artery oxygen delivery. In contrast, infusion of RL did not significantly change these variables. Infusion of HES increases UBF, CO, and uterine and total oxygen-carrying capacity in the pregnant ewe. No significant transplacental transfer of HES was shown.

Anesthesia, Obstetrical↗
PubMed2006

Autologous priming technique to reduce blood transfusion in pediatric cardiopulmonary bypass.

Excessive hemodilution during cardiopulmonary bypass is associated with decreased oxygen carrying capacity, edema, and organ dysfunction. The use of blood products is often necessary to prime the extracorporeal circuit for pediatric cardiac surgical patients. However, the use of blood products carries serious risks both in the acute and long-term aspects of patient care. Autologous priming of the extracorporeal circuit used in conjunction with ultrafiltration, pharmacologic manipulation, and cell salvage may decrease the need for blood transfusion in the pediatric cardiac surgical population. We have developed a technique that enables us to perform transfusionless complex congenital heart repair targeting patients as small as 5 kg.

Blood Transfusion, Autologous↗
PubMed1996

Aerobic capacity and skeletal muscle properties of normoxic and hypoxic rats in response to training.

The aim of this study was to determine, in the rat, the effects of chronic exposure (7-9 weeks) to normobaric hypoxia (FIO2=0.13, equivalent to 3700 m altitude) on cardiac and skeletal muscle properties, on maximal oxygen uptake (VO2max), and endurance time to exhaustion (ETE). In addition, we evaluated the impact of endurance training (90 min of treadmill running per day, 5 days per week, for 9 weeks) on these parameters. The results were compared to normoxic rats fed ad libitum (NAL) and to normoxic pair-weight (NPW) animals in order to take into account the influence of hypoxia on growth rate. It was found that, in sedentary rats, hypoxia results in stunted growth, adrenal atrophy, a significant reduction of cross-sectional area of fast-twitch (type II) fibres, a reduced capillary-to-fibre ratio (C/F), and a reduced oxidative capacity (decreases in citrate synthase and 3-hydroxy-Acyl CoA dehydrogenase activities) of the plantaris muscle. These effects are mainly related to the anorexic effects of prolonged exposure to hypoxia. Nevertheless, hypoxic (H) rats displayed higher VO2max and ETE values when compared either to NAL or to NPW animals. Endurance training resulted, in all groups (H, NAL, NPW), in a significant change of the fibre type distribution of the plantaris which displayed an increased number of type IIA fibres and a decreased proportion of type IIB fibres. In addition, the C/F ratio and cross-sectional area of fast-twitch fibres were normalized by superimposition of training on hypoxia. Both VO2max and ETE were significantly higher in trained H rats than in NAL, but these improvements were mainly related to the reduced body weight induced by hypoxia. These data suggest that the greater aerobic capacity and tolerance for prolonged exercise induced by chronic exposure to hypoxia can be mainly accounted for by the anorexic effects of hypoxia, although other factors (e.g. increase in oxygen carrying capacity induced by hypoxia acclimatization) may play a significant role in some circumstances (e.g. in sedentary rats).

Acyl-CoA Dehydrogenase↗
PubMedDate not supplied

Characterization of a pyridoxalated hemoglobin-polyoxyethylene conjugate as a physiologic oxygen carrier.

A pyridoxalated hemoglobin-polyoxyethylene conjugate (PHP) is an oxygen carrier prepared from outdated human red cells through chemical modifications of hemoglobin (Hb). PHP was evaluated as a physiologic oxygen carrier. PHP was synthesized from a pyridoxalated hemoglobin (PLP-Hb) and an activated diester of polyoxyethylene (POE). The average numbers of molecules of PLP and POE conjugated to a Hb molecule were 3.3 and 6.2, respectively. The p50 of PHP was 20.4 torr, which was much higher than the 14.0 torr of stroma-free Hb. At a Hb concentration of 6 g per dL, PHP had a physiologic colloid osmotic pressure (29 torr) and a lower viscosity (2.6 cP at 37 degrees C) than whole blood (4.2 cP at 37 degrees C). At temperatures below 20 degrees C, the p50 of PHP was higher than that of the red cells. PHP, which had an average molecular weight of 90,000, consisted of 83 percent monomeric PLP-Hb-POE conjugate, 12 percent dimeric PLP-Hb-POE, and 4 percent trimeric PLP-Hb-POE. The consistency of the relative contents of the components was well controlled through seven lots, and each component had sufficient oxygen-carrying capacity. The dimeric and trimeric components contributed to the prolongation of the residence of PHP in the circulation. The results indicate that PHP has favorable properties as an oxygen-carrying blood substitute and perfusate.

Animals↗
PubMed1985

Cardiovascular and organ weight adaptations as related to flight activity in birds.

Pectoral muscle, heart and body weight, wing surface, blood volume, hemoglobin content and blood oxygen capacity were measured in three birds: pigeon, gull and hen. A relationship was found between flying activity and organ weight, blood volume and hematocrit. No significant differences were found in the O2 carrying capacity of hemoglobin in these birds.

Adaptation, Physiological↗
PubMed2007

Deferoxamine lowers tissue damage after 80% exchange transfusion with polymerized hemoglobin.

Hemoglobin (Hb) solutions have been proposed as potential substitutes for erythrocytes to maintain oxygen-carrying capacity in situations in which blood is not available. This study investigated systemic and microvascular hemodynamics as well as tissue oxygenation and viability after an 80% exchange transfusion with an oxygen-carrying blood substitute based on polymerized bovine hemoglobin (PBH). Studies were carried in unanesthetized hamsters prepared with a window-chamber model for microcirculation evaluation. Heme iron-mediated injury to the tissue was analyzed by using deferoxamine (an iron chelator), which reduces free iron toxicity. Exchange transfusion led to a significant decrease in hematocrit (Hct) and an increase in plasma Hb, in addition to a significant decrease of arteriolar and venular diameters, flow velocity, and, therefore, microvascular blood flow. Capillary perfusion was severely compromised after exchange, but tissue pO2 increased above baseline, and oxygen extraction was reduced. Apoptotic and necrotic cells increased significantly after the exchange; however, this effect was only partially due to the toxicity of free iron. Iron therapy decreased the microvascular and oxygenation changes but did not fully reverse the adverse effects. Assessment of tissue viability after exchange suggests that chelation treatment in cases of large exchange transfusions with acellular Hb could be potentially beneficial.

Animals↗
PubMed1990

The effect of couple stresses in squeeze film poro-elastic bearings with special reference to synovial joints.

In this paper, a theoretical study of squeeze film poro-elastic bearings with Stokes' couple stress fluid as lubricant is made. The analysis explains the working of poro-elastic bearings in general and describes the lubrication mechanism of synovial joints in particular. Compact closed form expressions for the fluid film pressure, load capacity, and approaching time as a function of film thickness during normal articulation of joints are obtained. It is observed that the bearings with couple stress fluid as lubricant provide significant load carrying capacity and ensure a delayed time of approach compared with viscous lubricants. The influence of elasticity is to increase the load capacity and yield a longer squeeze film time. A decrease in permeability of the bearing surface enhances the load capacity as well as the response time. This results in the efficient lubrication and proper functioning of synovial joints.

Elasticity↗
PubMed1992

The ventilatory cost of exercise compared in chronic heart failure and chronic renal anaemia.

The cardiorespiratory responses to maximal treadmill exercise were compared in matched groups of patients with chronic renal anaemia or treated chronic heart failure, and in normal controls. Exercise capacity was similarly reduced in both patient groups compared to normal controls, the raised respiratory exchange ratio at peak exercise implying anaerobic metabolism due to limited oxygen delivery in heart failure and limited oxygen carrying capacity in anaemia. Minute ventilation (VE) was related linearly to minute CO2 production (VCO2) in all subjects (each r > 0.92) from all three groups. The slope of the VE/VCO2 relationship was normal in anaemia but steeper in heart failure, reflecting ventilation/perfusion mismatching in chronic heart failure.

Adolescent↗
PubMed1998

[Functional analysis of diluted solutions of human hemoglobin by using Oximeter-3000 WTW equipped with Trioxmatic-300 electrode].

The oxygen carrying capacity of dilute solutions of hemoglobin from normal human adults was examined, by using the above indicated Oximeter. The results show that, if the pO2s are compared with those drawn from the Oximeter-539 WTW (a simpler instrument) carrying the same oxygen electrode, there is a good correspondence between the data drawn from both the instruments. The advantage of the former is that pO2s are measure in mBr, whereas the latter measures the oxygen of the aqueous solutions in mg/l; then mg must be converted into Torr pO2. Since both instruments are usually employed in the oxygen measurement of waste waters of earth, another conclusion is that their sensitivity also allows the use in the bio-medical (and zoological) field. In fact, the data obtained agree with those of recent literature on the subject, which are mainly drawn from automated and sophisticated apparatuses specifically built at this purpose.

Adult↗
PubMed1988

Determinants of load carrying ability.

The aim of this paper is to review the literature in respect of the main determinants of a person's load carrying ability. Possible determinants of load carriage ability include age, anthropometry, aerobic and anaerobic power, muscle strength, body composition and gender; other relevant factors are the subjective effects perceived during load carriage, the dimensions and placement of the load, biomechanical factors, nature of the terrain and the gradient, the effect of climate and protective clothing. It is important to distinguish between the maximum load carrying capacity and load carriage ability which enables the individual to retain the capability to perform other tasks - eg, observation and navigation, or industrial tasks. The soldier has been used as the worst case example of extremely heavy loads having to be carried for long durations; civilian examples are usually less demanding except in the case of mountaineers, explorers and some occupations. The energy cost of walking with loads has been found to depend primarily upon the walking speed, body weight and load weight, together with terrain factors such as gradient and surface type; equations exist which allow the prediction of energy expenditures from these variables, and they can provide a valuable guide in assessing the physical severity of proposed tasks involving load carriage. Other factors such as the degree of environmental heat stress and protective clothing worn would have to be taken into account, but the level of energy expenditure (or heat production) assumes central importance as it is related to physical exhaustion, heat exhaustion and also less directly to the efficiency of performance of occupational task involving load carriage. This review confirms that there is no obvious definition of a maximal load, because of the widely varying circumstances which might apply, but for healthy young males there appears to be some consensus for the traditional rule of thumb of one-third body weight, or 24 kg on an assumed mean body weight of 72 kg, or in terms of relative work load equivalent to one-third of the VO(2) max for a working day. Renbourn (1954c) considered that the load carried by the soldier will probably always be a compromise between what is physiologically sound and what is operationally essential. Load carriage in industrial and other civilian areas will also involve a similar compromise and may in some circumstances lead to important implications for health and safety.

Journal Article↗
PubMed2001

Effect of dimecron on the blood parameters of Heteropneustes fossilis.

The effects of an organophosphate insecticide. dimecron. has been studied on certain haematological parameters, viz., haemoglobin concentration, RBC number, haematocrit, O2 carrying capacity of blood, etc. of Heteropneustes fossilis following exposures to the LC50 for 24 h and 96 h and 1/10 and 1/50 parts of 96 h LC50 for 90 days. There was a significant decrease in the Hb%, RBC number, HCt% and O2 carrying capcity of blood. But, there was significant increase in the MCH and MCV values following both acute and chronic exposures. The results indicate possible induction of anaemia in the exposed fish.

Anemia↗