Glucose and free fatty acid utilization during prolonged exercise in prepubertal boys in relation to catecholamine responses.

Ten prepubertal boys performed 60-min cycle exercise at about 60% of their maximal oxygen uptake as previously measured. To measure packed cell volume, plasma glucose, free fatty acids (FFA), glycerol and catecholamines, blood samples were drawn at rest using a heparinized catheter and at the 15th, 30th and 60th min of the exercise and after 30 min of recovery. At rest, the blood glucose concentrations were at the lowest values for normal. Exercise induced a small decrease of blood glucose which was combined with an abrupt increase of the noradrenaline concentration during the first 15 min. The FFA and glycerol concentrations increased throughout the exercise linearly with that of adrenaline. Compared to adults, the FFA uptake expressed per minute and per litre of oxygen uptake was greater in children. These results suggested that it is difficult for children to maintain a constant blood glucose concentration and that prolonged exercise provided a real stimulus to hypoglycaemia. An immediate and large increase in noradrenaline concentration during exercise and a greater utilization of FFA was probably used by children to prevent hypoglycaemia.     

Oxygen binding to partially oxidized hemoglobin. Analysis in terms of an allosteric model

We report on oxygen binding to partially oxidized (aquomet) hemoglobin. The fractional saturation with oxygen is evaluated by deconvoluting the optical absorption spectra, in the 500-700 nm wavelength region, in terms of oxyhemoglobin, deoxyhemoglobin and methemoglobin spectral components. Experiments have been performed with auto-oxidized samples and with samples obtained by mixing ferrous hemoglobin with fully oxidized hemoglobin (mixed samples). An increase in oxygen affinity and a decrease in cooperativity are observed on increasing the amount of ferric hemoglobin in the sample. A high cooperativity (nH approximately 2) is maintained even in the presence of 50-60% ferric hemes. Moreover, for equal amounts of methemoglobin the oxygen affinity is lower and the cooperativity higher for mixed samples than for those auto-oxidized. The results are analyzed within the framework of a modified Monod-Wyman-Changeux allosteric model taking into account the effects brought about by the presence of oxidized hemes and of alpha betta dimers. The distribution of ferric subunits within the tetramers in fully deoxygenated and fully oxygenated samples, as derived from the model, provides details on the cooperative behavior of partially oxidized hemoglobin.     

Respiratory activity of avian blood cells

The respiratory activity of avian blood cells was determined with samples of whole blood from individual male and female chickens. this oxygen consumption represents only that of the cells since no measurable activity was found in the plasma samples. the precision of determining respiratory activity was examined statistically and found to be approximately that obtained with a blood cell count but much less precise than the packed cell volume determination. the variability of cell count and mean corpuscular volume indicates that neither is a good means for expressing oxygen consumption – the most meaningful basis is oxygen consumption per milliliter of cells. the relationship between blood cell respiration and temperature is described.     

In vitro kinetics of oxygen transport in erythrocyte suspension or unmodified hemoglobin solution from human and other animals

Oxygen transport behavior in erythrocyte suspension or in hemoglobin solution was studied as a potential therapeutic model for the clinical treatment of blood loss, and this can also provide physiological data with which to evaluate blood substitutes. In the present project, we examined the in vitro kinetics of hemoglobin binding to and releasing oxygen, to provide detailed oxygen-flux measurements for unmodified hemoglobin solutions and erythrocyte suspensions in human, as well as other vertebrates. An in vitro method was used, based on a widely used artificial system, with the oxygen saturation level being detected in real time. Results from this study indicated that the kinetic curves of human erythrocyte suspensions and hemoglobin solutions were either S-shaped or hyperbolic, respectively. Based on these curves, the significance of T(50) emerged in our investigation, where T(50) is defined as the time needed for 50% hemoglobin to be saturated with oxygen, and reflects the efficiency with which hemoglobin carries oxygen. This parameter may be used to diagnose blood diseases, and could be a standard for evaluating blood substitutes. In this study, we also compared the T(50) of 4 species of vertebrates, and found that it shows a distinct efficiency of oxygen binding related to species, and potentially reveals the evolutionary function of hemoglobin and its possible adaptation to the environment.     

血红蛋白携氧-释氧动力学研究

本文研究了鸡、家兔、鲤鱼、蟾蜍4种实验动物血红蛋白(hemoglobin,Hb)携氧-释氧动力学过程,初步建立Hb携氧-释氧动力学研究方法,并探讨Hb携氧-释氧动力学过程与动物生存环境之间的关系.结果显示:4种动物Hb携氧动力学曲线均呈"S"形曲线特征,与传统的Hb氧解离曲线(oxygen dissociation curve,ODC)相似;同时不同动物Hb携氧-释氧动力学曲线也有各自特点,如鸡Hb释氧时间长达(1 411±6)S;在Hb携氧.释氧曲线I阶段,鲤鱼上升斜率远大于家兔等.提示Hb携氧-释氧动力学曲线可反映不同动物Hb携氧效率的差异.与传统ODC参数P50相对应,由动力学曲线可得到Hb携氧动力学参数T50°T50是Hb达到50%氧饱和度所需时间,可直观反映Hb携氧效率的差异.4种实验动物Hb均有较稳定的T50,从大到小依次为:鸡、家兔、鲤鱼和蟾蜍.对Hb携氧动力学曲线与ODC综合分析,可得到Hb携氧效能参数E50,表示Hb达到50%氧饱和度所用时间与环境氧分压之间的关系,即E50(50% Sat,Xeo2,yr).E50有可能成为全面评价Hb携氧效能的综合指标.     

Microvascular experimental evidence on the relative significance of restoring oxygen carrying capacity vs. blood viscosity in shock resuscitation

The development of volume replacement fluids for resuscitation in hemorrhagic shock comprises oxygen carrying and non carrying fluids. Non oxygen carrying fluids or plasma expanders are used up to the transfusion trigger, and upon reaching this landmark either blood, and possibly in the near future oxygen carrying blood substitutes, are used. An experimental program in hemorrhagic shock using the hamster chamber window model allowed to compare the relative performance of most fluids proposed for shock resuscitation. This model allows investigating simultaneously the microcirculation and systemic reactions, in the awake condition, in a tissue isolated from the environment. Results from this program show that in general plasma expanders such as Ringer's lactate and dextran 70 kDa do not sufficiently restore blood viscosity upon reaching the transfusion trigger, causing microvascular collapse. This is in part restored by a blood transfusion, independently of the oxygen carrying capacity of red blood cells. These results lead to the proposal that effective blood substitutes must be designed to prevent microvascular collapse, manifested in the decrease of functional capillary density. Achievement of this goal, in combination with the increase of oxygen affinity, significantly postpones the need for a blood transfusion, and lowers the total requirement of restoration of intrinsic oxygen carrying capacity.     

The effect of different blood sampling sites and analyses on the relationship~ between exercise intensity and 4.0 mmol ·1? blood lactate concentration

The aim of the study was to examine whether the difference in lactate concentration in different blood fractions is of practical importance when using blood lactate as a test variable of aerobic endurance capacity. Ten male firefighters performed submaximally graded exercise on a cycle ergometer for 20-25 min. Venous and capillary blood samples were taken every 5 min for determination of haematocrit and lactate concentrations in plasma, venous and capillary blood. At the same time, expired air was collected in Douglas bags for determination of the oxygen consumption. A lactate concentration of 4.0 mmol.l-1 was used as the reference value to compare the oxygen consumption and exercise intensity when different types of blood specimen and sampling sites were used for lactate analysis. At this concentration the exercise intensity was 17% lower (P less than 0.01) when plasma lactate was compared to venous blood lactate, and 12% lower (P less than 0.05) when capillary blood lactate was used. Similar discrepancies were seen in oxygen consumption. The results illustrated the importance of standardizing sampling and handling of blood specimens for lactate determination to enable direct comparisons to be made among results obtained in different studies.     

An improved apparatus for blood perfusion of the canine cerebral vasculature

An improved perfusion apparatus is described which consists of a membrane oxygenator, roller pump, reservoir, heat exchanger, blood filter, and inert tubing. Heparinized blood may be used and is delivered at flow rates from 10 to 250 ml/min. Dogs are anesthetized with halothane and their cerebral arterial blood supply isolated by the method of Gilboe et al. (8). When the canine brain is perfused for 5 hr using the described apparatus, the rates of cerebral oxygen and glucose consumption are 5.19±0.12 ml/100 g/min and 39.9±6.5 mol/100 g/min, respectively. Of the total glucose consumed by the brain, about 1/4 is contributed by the erythrocytes. An equivalent of about 9% of the consumed glucose is returned to the blood as lactate. Electron microscopic examination of cerebral cortex samples reveals no differences between 5-hr perfused brain and appropriate nonperfused controls. It is concluded that the apparatus is a useful system for organ perfusion and that the canine brain perfused by this method remains physiologically and metabolically active for at least 5 hr.With the technical assistance of Evelyn Townsend.     

Inositol tripyrophosphate: a new membrane permeant allosteric effector of haemoglobin

Nine inositol tripyrophosphate (ITPP) salts have been synthesized. Their ability to act as allosteric effectors of haemoglobin (Hb) has been measured in vitro with free Hb and whole blood. All the synthesized compounds bound to free Hb and were also able to cross, to a certain extent, the plasma membrane of the red blood cells (RBCs) in whole blood samples, lowering the affinity of Hb for oxygen. The oxy-haemoglobin dissociation curves were significantly shifted towards higher values of oxygen partial pressures, both for free Hb and for intracellular Hb in whole blood.     

Myocardial oxygenation in isolated hearts predicted by an anatomically realistic microvascular transport model

An anatomically realistic model for oxygen transport in cardiac tissue is introduced for analyzing data measured from isolated perfused guinea pig hearts. The model is constructed to match the microvascular anatomy of cardiac tissue based on available morphometric data. Transport in the three-dimensional system (divided into distinct microvascular, interstitial, and parenchymal spaces) is simulated. The model is used to interpret experimental data on mean cardiac tissue myoglobin saturation and to reveal differences in tissue oxygenation between buffer-perfused and red blood cell-perfused isolated hearts. Interpretation of measured mean myoglobin saturation is strongly dependent on the oxygen content of the perfusate (e.g., red blood cell-containing vs. cell-free perfusate). Model calculations match experimental values of mean tissue myoglobin saturation, measured mean myoglobin, and venous oxygen tension and can be used to predict distributions of intracellular oxygen tension. Calculations reveal that approximately 20% of the tissue is hypoxic with an oxygen tension of <0.5 mmHg when the buffer is equilibrated with 95% oxygen to give an arterial oxygen tension of over 600 mmHg. The addition of red blood cells to give a hematocrit of only 5% prevents tissue hypoxia. It is incorrect to assume that the usual buffer-perfused Langendorff heart preparation is adequately oxygenated for flows in the range of < or =10 ml. min-1. ml tissue-1.     

Factors in the evolution of hemoglobin function.

The packaging of vertebrate blood hemoglobins within cells places subtle constraints on hemoglobin evolution. Since the concentration of hemoglobin is near the solubility limit a selective advantage should exist for a noncomplementary external topology of amino acid residues. Further, any change in charge on the protein should alter ion distribution across the cell membrane and so modify ion-sensitive oxygen transport. An efficient hemoglobin must not only combine readily with oxygen at prevailing environmental oxygen pressures, but must also release it at metabolically appropriate pressures. These adaptations frequently employ different strategies to achieve the same objective in different animals. Some hemoglobins have evolved special properties unrelated to the transport of oxygen to metabolizing tissues. Thus many teleost fish have hemoglobins that discharge much of their oxygen at low pH even at high oxygen pressures. This property appears to aid in filling the swim bladder with oxygen. The hemoglobins of elasmobranchs have evoked a unique resistance to urea as a consequence of the high urea content of their blood. Sometimes the functional adaptations of hemoglobins are achieved by multiple hemoglobins in the same cells. Often, however, different red cell populations with functionally unique hemoglobins arise sequentially during ontogeny.     

Detecting Glycogen in Peripheral Blood Mononuclear Cells with Periodic Acid Schiff Staining

Periodic acid Schiff (PAS) staining is an immunohistochemical technique used on muscle biopsies and as a diagnostic tool for blood samples. Polysaccharides such as glycogen, glycoproteins, and glycolipids stain bright magenta making it easy to enumerate positive and negative cells within the tissue. In muscle cells PAS staining is used to determine the glycogen content in different types of muscle cells, while in blood cell samples PAS staining has been explored as a diagnostic tool for a variety of conditions. Blood contains a proportion of white blood cells that belong to the immune system. The notion that cells of the immune system possess glycogen and use it as an energy source has not been widely explored. Here, we describe an adapted version of the PAS staining protocol that can be applied on peripheral blood mononuclear immune cells from human venous blood. Small cells with PAS-positive granules and larger cells with diffuse PAS staining were observed. Treatment of samples with amylase abrogates these patterns confirming the specificity of the stain. An alternate technique based on enzymatic digestion confirmed the presence and amount of glycogen in the samples. This protocol is useful for hematologists or immunologists studying polysaccharide content in blood-derived lymphocytes.     

A comparative evaluation of the effects on the crystallogenic properties of the rat blood serum for prolonged inhalations of nitric oxide or reactive oxygen species

The objective of this work was to study how a prolonged course of inhalations of nitric oxide or singlet oxygen modify crystallization of the blood serum in rats. Experiments were performed with 50 adult Wistar rats, which were divided into five equal groups. The control group (n = 10) included intact rats, which were not exposed to any manipulation other than a single blood drawing. Rats of groups 2, 3, and 4 received inhalations of nitric oxide at 20, 50, and 100 ppm, respectively, daily for 30 days. Group 5 rats (n = 10) received a similar course of inhalations of singlet oxygen for 30 days. Blood samples were drawn from the sublingual vein in rats of the test groups immediately after completion of the inhalation course (day 30 of the experiment) and in the recovery period (day 60 of the experiment) and tested for crystallogenic activity. Dried samples were evaluated visually for crystallizability, structure index, facia destruction degree, and marginal zone clarity, using respective scales. A prolonged course of NO inhalations was found to modulate the crystallogenic properties of the rat serum. An optimal response was recorded at the lowest nitric oxide concentration (20 ppm). Higher NO concentrations caused more adverse changes in serum crystallization after the end of the inhalation course and hindered the recovery processes. Singlet oxygen inhalations for 30 days did not exert a considerable adverse effect on the crystallogenic properties of the rat serum.     

Estimation of capillary density in human skeletal muscle based on maximal oxygen consumption rates

A previously developed Krogh-type theoretical model was used to estimate capillary density in human skeletal muscle based on published measurements of oxygen consumption, arterial partial pressure of oxygen, and blood flow during maximal exercise. The model assumes that oxygen consumption in maximal exercise is limited by the ability of capillaries to deliver oxygen to tissue and is therefore strongly dependent on capillary density, defined as the number of capillaries per unit cross-sectional area of muscle. Based on an analysis of oxygen transport processes occurring at the microvascular level, the model allows estimation of the minimum number of straight, evenly spaced capillaries required to achieve a given oxygen consumption rate. Estimated capillary density values were determined from measurements of maximal oxygen consumption during knee extensor exercise and during whole body cycling, and they range from 459 to 1,468 capillaries/mm2. Measured capillary densities, obtained with either histochemical staining techniques or electron microscopy on quadriceps muscle biopsies from healthy subjects, are generally lower, ranging from 123 to 515 capillaries/mm2. This discrepancy is partly accounted for by the fact that capillary density decreases with muscle contraction and muscle biopsy samples typically are strongly contracted. The results imply that estimates of maximal oxygen transport rates based on capillary density values obtained from biopsy samples do not fully reflect the oxygen transport capacity of the capillaries in skeletal muscle.     

Effect of oxygen tension on chromosomal aberrations in Fanconi anaemia

Blood samples from four healthy individuals and from seven Fanconi anaemia (FA) patients were cultured at oxygen tensions ranging from 3% to 45% O2. Cultures were harvested at 72 h and scored for chromosomal aberrations. In the majority of FA patients the aberration frequency showed a tendency to increase as a function of oxygen tension over the culture, whereas the aberration frequency in healthy individuals was not affected. However, the response in FA cultures was variable among patients and in individual cases when assayed on different occasions. A much stronger effect of oxygen tension was observed when the FA blood samples had been treated with mitomycin C (0.25 microgram/ml, 30 min) before culture initiation.     

Development and study of an amperometric biosensor for the in vitro measurement of low concentration of putrescine in blood

An amperometric biosensor was developed for the in vitro determination of putrescine in blood samples because elevated level of putrescine in blood can be a diagnostic indicator of certain kinds of cancer. The electrochemical transducer consisted of a flat form, three electrode amperometric micro-cell fabricated with thin film photolithography on flexible Kapton substrate. An immobilized putrescine oxidase (PUO) layer provided the biocatalytic oxidation of the putrescine, while the generated hydrogen peroxide was detected on the platinum-working electrode. An electropolymerized poly(m-phenylenediamine) (pPDA) size-exclusion layer was used to protect the working electrode from fouling and to prevent signal generation by common electroactive interferents present in blood. The preparation of the biocatalytic enzyme- and outer protective layers was optimized for improved sensitivity and response time. A detection limit of 50 nM was achieved in pH-adjusted whole blood samples, which is below pathological levels.     

Temperature effects on oxygen affinity of human fetal blood

In an effort to understand the effects of temperature changes on fetal oxygenation, the temperature effects were measured on oxygen affinity of whole blood from term human fetuses. The blood obtained was tonometered at delivery in two flasks gassed with 95% N2 (+ 5% CO2 or 20.9% + 5% CO2, and mixed aliquots from each flask in different proportions to obtain samples for analysis of PO2 and percent saturation. The oxyhaemoglobin dissociation curve was constructed and P50 determined at two or three different temperatures for each batch of blood. As temperature increased from 30 to 41 degrees C, human fetal blood bound O2 less avidly, the temperature coefficient for changes in P50 being 0.0255 per degree C. This temperature effect was similar to that in adult blood, although at any temperature O2 affinity of fetal blood was greater than that of the adult. Placental oxygen exchange could be significantly affected by changes in temperature such as occur during hypo- or hyperthermia, as with maternal exercise.     

Active nitric oxide produced in the red cell under hypoxic conditions by deoxyhemoglobin-mediated nitrite reduction

Recent studies have generated a great deal of interest in a possible role for red blood cells in the transport of nitric oxide (NO) to the microcirculation and the vascular effect of this nitric oxide in facilitating the flow of blood through the microcirculation. Many questions have, however, been raised regarding such a mechanism. We have instead identified a completely new mechanism to explain the role of red cells in the delivery of NO to the microcirculation. This new mechanism results in the production of NO in the microcirculation where it is needed. Nitrite produced when NO reacts with oxygen in arterial blood is reutilized in the arterioles when the partial pressure of oxygen decreases and the deoxygenated hemoglobin formed reduces the nitrite regenerating NO. Nitrite reduction by hemoglobin results in a major fraction of the NO generated retained in the intermediate state where NO is bound to Hb(III) and in equilibrium with the nitrosonium cation bound to Hb(II). This pool of NO, unlike Hb(II)NO, is weakly bound and can be released from the heme. The instability of Hb(III)NO in oxygen and its displacement when flushed with argon requires that reliable determinations of red blood cell NO must be performed on freshly lysed samples without permitting the sample to be oxygenated. In fresh blood samples Hb(III)NO accounts for 75% of the red cell NO with appreciably higher values in venous blood than arterial blood. These findings confirm that nitrite reduction at reduced oxygen pressures is a major source for red cell NO. The formation and potential release from the red cell of this NO could have a major impact in regulating the flow of blood through the microcirculation.     

High-speed bubble-segmented blood sampler for the rat

An arterial blood sampler for use in the conscious rat is described. With this apparatus it is possible to obtain small (10 microliter) whole-blood or plasma samples as frequently as 1/s and to derive accurate arterial time-concentration curves in the first 60-120 s after compounds are injected for regional blood flow or pharmacokinetic measurements. The blood is withdrawn from an implanted arterial catheter into polyethylene tubing at a constant rate while bubbles are introduced at regular intervals via a side channel into the column of blood. Although some dispersion of blood samples occurs as the tubing is traversed, this can be mathematically corrected. However, correction is unnecessary if the information of interest is the area under the time-concentration curve.