Comparison of various approaches to calculating the optimal hematocrit in vertebrates

2012 ◽  
Vol 113 (3) ◽  
pp. 355-367 ◽  
Author(s):  
Heiko Stark ◽  
Stefan Schuster
Keyword(s):  
Physical Performance ◽  
Oxygen Transport ◽  
Oxygen Supply ◽  
Animal Species ◽  
Volume Fraction ◽  
Maximum Amount ◽  
Interesting Problem ◽  
Vertebrate Species ◽  
Optimal Values ◽  
Spatially Homogeneous

An interesting problem in hemorheology is to calculate that volume fraction of erythrocytes (hematocrit) that is optimal for transporting a maximum amount of oxygen. If the hematocrit is too low, too few erythrocytes are present to transport oxygen. If it is too high, the blood is very viscous and cannot flow quickly, so that oxygen supply to the tissues is again reduced. These considerations are very important, since oxygen transport is an important factor for physical performance. Here, we derive theoretical optimal values of hematocrit in vertebrates and collect, from the literature, experimentally observed values for 57 animal species. It is an interesting question whether optimal hematocrit theory allows one to calculate hematocrit values that are in agreement with the observed values in various vertebrate species. For this, we first briefly review previous approaches in that theory. Then we check which empirical or theoretically derived formulas describing the dependence of viscosity on concentration in a suspension lead to the best agreement between the theoretical and observed values. We consider both spatially homogeneous and heterogeneous distributions of erythrocytes in the blood and also possible extensions, like the influence of defective erythrocytes and cases where some substances are transported in the plasma. By discussing the results, we critically assess the power and limitations of optimal hematocrit theory. One of our goals is to provide a systematic overview of different approaches in optimal hematocrit theory.

Localisation of two classes of acetylcholine receptor-like molecules in sperms of different animal species

Zygote ◽  
1995 ◽  
Vol 3 (3) ◽  
pp. 207-217 ◽  
Author(s):  
B. Baccetti ◽  
A.G. Burrini ◽  
G. Collodel ◽  
C. Falugi ◽  
E. Moretti ◽  
...  
Keyword(s):  
Nicotinic Receptor ◽  
Nicotinic Receptors ◽  
Animal Species ◽  
Distribution Patterns ◽  
Sperm Head ◽  
Similar Distribution ◽  
Vertebrate Species ◽  
Immunogold Staining ◽  
Specific Antibodies ◽  
Transduction Mechanisms

SummaryThe distribution of different classes of acetylcholine (ACh) receptor-like molecules in sperms of different invertebrate and vertebrate species is described. ACh receptor molecules belong to one of two classes: muscarinic receptors (mAChRs), associated with signal transduction mechanisms in the inner domain of the cell, and nicotinic receptors (nAChRs), capable of opening Na+ channels when activated by the ligand. Molecules immunologically related to mAChRs and to ACh can be identified by specific antibodies, and revealed by immunofluorescent or immunogold staining; the nicotinic receptor-like molecules are localised as curare-sensitive affinity sites for α-bungarotoxin. In all species studied, both classes of receptors were found, with a similar distribution. Muscarinic-like molecules were found mainly in the sperm head regions of most species; such a localisation may be correlated to a function in sperm–egg interaction, for instance in the regulation of the block to polyspermy. Nicotinic-like molecules are present mainly in the tail and in the post-acrosomal region of most animals, thus confirming their function in the regulation of sperm propulsion, but are also present at the acrosomal region of most species. The distribution patterns of the different classes of molecules indicate that both may be in sperm–egg interactions, in addition to their known function in the regulation of sperm propulsion.

Microvascular hematocrit and red cell flow in resting and contracting striated muscle

1979 ◽  
Vol 237 (4) ◽  
pp. H481-H490 ◽  
Author(s):  
B. Klitzman ◽  
B. R. Duling
Keyword(s):  
Blood Flow ◽  
Oxygen Supply ◽  
Striated Muscle ◽  
Volume Fraction ◽  
Plasma Layer ◽  
Element Model ◽  
Microvascular Blood Flow ◽  
Red Cell ◽  
Total Blood ◽  
Arterial Blood

Microvascular hematocrit and its possible relation to oxygen supply were systematically examined. We studied the red cell volume fraction (hematocrit) in arterial blood and in capillaries under a variety of circumstances. Control capillary hematocrit averaged 10.4 +/- 2.0% (SE) and arteriolar (14.2 micrometer ID) hematocrit averaged 13.9 +/- 1.2% in cremaster muscles of pentobarbital-anesthetized hamsters. Carotid artery hematocrit was 53.2 +/- 0.6%. The low microvessel hematocrit could not be entirely explained by a high red cell flux through arteriovenous channels other than capillaries (shunting). Hematocrit was not only low at rest, but varied with physiological stimuli. A 1-Hz muscle contraction increased capillary hematocrit to 18.5 +/- 2.4%, and maximal vasodilation induced a rise to 39.3 +/- 9.5%. The quantitative relations between capillary red cell flux, arterial hematocrit, and total blood flow could be explained by a two-element model of microvascular blood flow that incorporated a relatively slow-moving plasma layer (1.2 micrometer). Such a model would generate a low microvessel hematocrit and might reduce the diffusion capacity of individual capillaries, but would not reduce time-averaged red cell flux or alter steady-state vascular oxygen supply.

Effects of hematocrit variations on regional hemodynamics and oxygen transport in the dog

1980 ◽  
Vol 238 (4) ◽  
pp. H545-H522 ◽  
Author(s):  
F. C. Fan ◽  
R. Y. Chen ◽  
G. B. Schuessler ◽  
S. Chien
Keyword(s):  
Blood Flow ◽  
Cardiac Output ◽  
Blood Vessels ◽  
Oxygen Transport ◽  
Oxygen Supply ◽  
Blood Flows ◽  
Regional Hemodynamics ◽  
Regional Blood Flows ◽  
Splenic Vessels ◽  
The Brain

The responses of alterations in regional hemodynamics and oxygen transport rate to hematocrit (Hct) were studied in 20 pentobarbitalized dogs. Hemodilution was carried out by isovolemic exchange with plasma in 12 dogs and the hemoconcentration with packed cells in 8 dogs. The cardiac output and regional blood flows were determined with the microsphere technique. In hemodilution, the increases of blood flow to the myocardium and the brain were out of proportion to the increase of cardiac output; the oxygen supply to the myocardium remained unchanged while that to the brain decreased only slightly. In hemoconcentration, vasodilation occurred in the myocardium and the brain to maintain constant oxygen supply. Splenic vessels had marked vasoconstriction with Hct alteration in either direction. Blood vessels in the liver, intestine, and kidney responded with a milder vasoconstriction and maintained a constant oxygen supply between Hct of 30-55%. Therefore, during Hct alteration, redistribution of blood flow to myocardium and brain occurred. The optimal Hct range for constant oxygen supply was different among various organs.

Electoral Forecasting from Poll Data: The British Case

1979 ◽  
Vol 9 (2) ◽  
pp. 219-236 ◽  
Author(s):  
Paul Whiteley
Keyword(s):  
Model Building ◽  
Prime Minister ◽  
Basic Problem ◽  
Maximum Amount ◽  
Special Importance ◽  
Interesting Problem ◽  
Election Forecasting ◽  
Sophisticated Model ◽  
British Case ◽  
Poll Data

Forecasting elections has long been regarded by political scientists as an interesting problem in its own right. But it assumes special importance for those countries that do not have fixed election dates. In Britain, for example, it is up to the prime minister to choose the date, within the statutory five year limit. Correct timing can clearly be crucial to the outcome, and the prime minister can be expected to go to considerable lengths to ensure that the election is called for the date most favourable to his party. But there lies the prime minister's problem: elections must be called three to four weeks before polling day. With what degree of accuracy can the result be forecast at the time the election is called?A small but interesting literature on election forecasting has emerged in recent years. The forecasting techniques used in this literature vary widely, from crude extrapolation to sophisticated model building. Up to now the emphasis has been on election night forecasting, in which the basic problem involves extracting the maximum amount of information from electoral returns, in order to forecast the outcome a few hours before it is finally known. For obvious reasons the techniques utilized in this context are of little use prior to election day.

scholarly journals Mathematical Modeling of Oxygen Transport in Retinal Layers

2019 ◽  
Vol 6 (6) ◽  
pp. 1-4
Author(s):  
Aadesh Kumar ◽  
◽  
Dr. Ram avtar ◽  
Dr. Deepti Seth ◽  
◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Differential Equation ◽  
Mathematical Model ◽  
Oxygen Consumption ◽  
Oxygen Transport ◽  
Oxygen Supply ◽  
Retinal Vasculature ◽  
Retinal Layer ◽  
Maximum Oxygen Consumption ◽  
Retinal Layers

The retina contains maximum oxygen ( consumption making it particular valuneric to vascular in fults, diminishing oxygen and circulation of nutrients. The goel of this paper to develop a mathematical model for quantitative analysis of transportation of oxygen and consumption in each retinal layer. Such models allows us to predict the effect of qualitatative change in retinal vasculature on oxygen supply in retinal layers. A differential equation , which used in this paper describing how the oxygen transport and cosumpt by the retinal layers.

scholarly journals Land cover in the Northern Forest Complex of Myanmar: new insights for conservation

Oryx ◽  
2007 ◽  
Vol 41 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Swen C. Renner ◽  
John H. Rappole ◽  
Peter Leimgruber ◽  
Daniel S. Kelly ◽  
Nay Myo Shwe ◽  
...  
Keyword(s):  
Land Cover ◽  
National Park ◽  
Animal Species ◽  
Vertebrate Species ◽  
Wildlife Sanctuary ◽  
Mammal Species ◽  
Northern Forest ◽  
Field Surveys ◽  
Modis Ndvi ◽  
Deforestation Rates

We classified land cover in the Northern Forest Complex in Myanmar using satellite imagery (MODIS/NDVI) and field surveys carried out in 2001, 2004 and 2005. Using Landsat TM/ETM+ images from 1991 and 1999 we determined deforestation rates. The c. 22,000 km2 Northern Forest Complex, including the Hkakabo Razi National Park in northern Kachin State, is characterized by tropical to subtropical pristine forests with low human impact. The area studied, which includes land beyond the boundaries of Hkakabo Razi National Park, is of special conservation importance because it provides a refuge for many rare plant and animal species. Less than 1.4% of the area is affected by humans (excluding hunting) and deforestation rates are low at <0.01% annually. We observed several bird and mammal species that are considered threatened elsewhere. Based on our data, those of previous surveys, and the fact that >10 new vertebrate species have been described in the region since 1999, it is likely there are still undescribed vertebrate species to be discovered. We recommend extending the boundaries of Hkakabo Razi National Park to the south and west, connecting it to Hpongkan Razi Wildlife Sanctuary, and/or adding an additional sanctuary in the Naung Mung area, to protect the vast yet still pristine rainforest habitats that are home to many of the most important aspects of the region's biodiversity.

scholarly journals Healthy Skin of Many Animal Species Harbors Papillomaviruses Which Are Closely Related to Their Human Counterparts

2002 ◽  
Vol 76 (24) ◽  
pp. 12537-12542 ◽  
Author(s):  
Annika Antonsson ◽  
Bengt Göran Hansson
Keyword(s):  
Human Skin ◽  
Broad Spectrum ◽  
Animal Species ◽  
Clinical Symptoms ◽  
Spider Monkeys ◽  
Vertebrate Species ◽  
Healthy Skin ◽  
Papillomavirus Dna ◽  
Pcr Test

ABSTRACT Papillomaviruses associated with clinical symptoms have been found in many vertebrate species. In this study, we have used an L1 gene consensus PCR test designed to detect a broad spectrum of human skin papillomaviruses to analyze swab samples from healthy skin of 111 animals belonging to 19 vertebrate species. In eight of the species, papillomavirus DNA was found with the following prevalences: chimpanzees, 9 of 11 samples positive; gorillas, 3 of 4; long-tailed macaques, 14 of 16; spider monkeys, 2 of 2; ruffed lemurs, 1 of 2; cows, 6 of 10; European elks, 4 of 4; aurochs, 1 of 1. In total, 53 new putative animal papillomavirus types were found. The results show that skin papillomaviruses can be detected in healthy skin from many different animal species and are sufficiently related genetically to their human counterparts to be identified by a human skin papillomavirus primer set (FAP59 and FAP64).

Dissociation of “Factor VIII Complex” in Various Animal Species.

1975 ◽  
Author(s):  
J. M. Lavergne ◽  
Dominique Meyer ◽  
C. S. P. Jenkins ◽  
Marie-José Larrieu
Keyword(s):  
Factor Viii ◽  
Animal Species ◽  
Volume Fraction ◽  
Gel Filtration ◽  
High Salt ◽  
Void Volume ◽  
Factor Activity ◽  
Step Procedure ◽  
Sepharose 4B ◽  
Willebrand Factor

Under conditions of high salt concentration, “Factor VIII complex” (Factor VHI activity, Willebrand Factor activity – measured using a washed platelet system and ristocetin – and Willebrand antigen) may be dissociated into a high (M. W. > 106) and a low molecular weight fragment. The dissociation of “Factor VIII complex” was studied by a two step procedure. Human or animal plasma or cryoprecipitate was submitted to gel filtration on Sepharose 4B, using 0.15 M NaCl, Imidazole or Tris-HCl Buffer as eluant. The void volume fraction, containing the three entities of “Factor VIII complex” was concentrated and submitted to a second gel filtration using a dissociating buffer as eluant (1 M NaCl or 0.25 M CaCl2). The three entities of “Factor VIII complex” were measured in the eluted fractions. “Factor VIII complex” was found to dissociate using the high salt buffer in some but not all animal species. When dissociation occurred, Willebrand Factor activity and antigen eluted in the void volume, and Factor VIII activity in later fractions. Heterologous antisera were raised against the different fractions and the reactivity towards human and animal plasma was studied.

scholarly journals Calculating the optimal hematocrit under the constraint of constant cardiac power

2020 ◽  
Author(s):  
M. Sitina ◽  
H. Stark ◽  
S. Schuster
Keyword(s):  
High Performance ◽  
Animal Species ◽  
Volume Fraction ◽  
Normal Values ◽  
Mechanical Load ◽  
Physical Exertion ◽  
The Body ◽  
Cardiac Power ◽  
Optimal Value ◽  
Good Agreement

AbstractIn humans and higher animals, a trade-off between sufficiently high erythrocyte concentrations to bind oxygen and sufficiently low blood viscosity to allow rapid blood flow has been achieved during evolution. Optimal hematocrit theory has been successful in predicting hematocrit values of about 0.3 - 0.5, in very good agreement with the normal values observed for humans and many animal species. However, according to those calculations, the optimal value should be independent of the mechanical load of the body. This is in contradiction to the exertional increase in hematocrit observed in some animals called natural blood dopers and to the illegal practice of blood boosting in high-performance sports. In this study, we calculate the optimal hematocrit under two different constraints - under a constant driving pressure and under constant cardiac power – and show that the optimal hematocrit under constant cardiac power is higher than the normal value, ranging from 0.5 to 0.7. We use this result to explain the tendency to better exertional performance at an increased hematocrit.Statement of SignificanceIn humans and higher animals, erythrocytes comprise a volume fraction (hematocrit) of 30-50 % of the blood. Mathematical calculations based on the assumption of constant blood pressure show that the optimal hematocrit value is indeed in that range. However, this optimum should apply to both rest and physical exertion, which is in contradiction to the increase in hematocrit observed in some animals called natural blood dopers and to the illegal practice of blood boosting in sports. Here, we calculate the optimal value based on the alternative constraint of constant cardiac power. We show that this results in a higher optimal value, ranging from 50 to 70 %. In this way, we explain the better exertional performance at an increased hematocrit.

Hemorheological parameters in individuals with different levels of oxygen body supply: the effect of nitric oxide and hydrogen sulfi de on erythrocyte microrheological characteristics.

2021 ◽  
Author(s):  
А.В. Муравьев ◽  
П.В. Михайлов ◽  
В.В. Зинчук ◽  
И.А. Тихомирова ◽  
Р.С. Остроумов
Keyword(s):  
Nitric Oxide ◽  
Blood Flow ◽  
Oxygen Transport ◽  
Blood Viscosity ◽  
Oxygen Supply ◽  
No Donor ◽  
Sodium Hydrosulfide ◽  
Positive Effect ◽  
Different Levels ◽  
Transport Potential

Введение. Доставка кислорода в ткани определяется величиной объемного кровотока; он, в свою очередь, зависит от сосудистых и реологических факторов. Снижение вязкости крови (ВК) может способствовать приросту объемного кровотока и повышению эффективности доставки кислорода. Поскольку ВК тесно связана с микрореологическими свойствами эритроцитов, то можно полагать, что их положительные изменения будут способствовать улучшению кислородтранспортной функции крови. Цель исследования: сравнительный анализ гемореологических профилей у лиц с разным уровнем обеспечения организма кислородом и определение роли оксида азота (NO) и сульфида водорода (H2S) в изменениях микрореологических характеристик эритроцитов. Материалы и методы. На основе результатов определения максимального потребления кислорода (МПК) были сформированы 2 группы, в каждой из которых было по 24 практически здоровых мужчины-добровольца в возрасте от 20 до 35 лет: группа 1 – лица с умеренным обеспечением организма кислородом (МПК = 40–50 мл/кг/мин) и группа 2 – лица с относительно высоким его уровнем (МПК = 51–65 мл/кг/мин). Регистрировали параметры гемореологического профиля, напряжение кислорода в коже предплечья (tсрО2), метаболизм оксида азота (по соотношению нитраты/нитриты, NOx). Для исследования влияния газотрансмиттеров (ГТ) на микрореологию эритроцитов их инкубировали с донором NO (нитропруссидом натрия, 100 мкмоль) и донором H2S (гидросульфидом натрия, 100 мкмоль) с последующей регистрацией деформируемости и агрегации эритроцитов. Результаты. У лиц с относительно высоким обеспечением тканей кислородом отмечалась сниженная вязкость крови, ее высокий кислородтранспортный потенциал, эффективная микрореология эритроцитов и их более высокая чувствительность к ГТ при положительном влиянии последних на агрегацию и деформируемость эритроцитов. Заключение. Данные, полученные на моделях микрореологических ответов эритроцитов на доноры двух газотрансмиттеров, позволяют заключить, что, во-первых, эти ГТ, как сигнальные молекулы, положительно влияют на микрореологические характеристики эритроцитов и, следовательно, на их транспортный потенциал, и, во-вторых, эритроциты лиц, имеющих высокий уровень обеспечения организма кислородом, более чувствительны к регуляторному действию газотрансмиттеров, поскольку их микрореологические ответы на доноры были статистически значимо более выраженными. Background. Oxygen delivery to tissues is determined by the volume of blood flow that, in turn, depends on vascular and rheological factors. Blood viscosity (BV) decreasing can promote an increasing of volumetric blood flow and provide more efficient oxygen transport. Since BV depends on the erythrocyte microrheological properties it can be assumed that their positive changes will contribute to better oxygen transport. Objectives: to investigate hemorheological profiles in individuals with different levels of body oxygen supply and the role of nitrogen oxide (NO) and hydrogen sulfide (H2S) in changes of the erythrocyte microrheological characteristics. Patients/Methods. Based on the determination of maximum oxygen consumption (VO2max), 2 groups were formed, each of which consisted of 24 practically healthy male volunteers aged 20–35 years: group 1 – persons with moderate body oxygen supply (VO2max = 40–50 ml/kg/min) and group 2 – persons with a relatively high body oxygen supply (VO2max = 51–65 ml/kg/min). Hemorheological profi le parameters, oxygen tension in the forearm skin (tcpO2), and nitric oxide metabolism by the ratio of nitrates/nitrites (NOx) were recorded. To study the effect of gasotransmitters (GTs) on erythrocyte microrheology, they were incubated with NO donor (sodium nitroprusside, 100 μmol) and H2S donor (sodium hydrosulfide, 100 μmol), and erythrocytes deformability and aggregation were registered. Results. Individuals with a relatively high oxygen supply of tissues showed a reduced blood viscosity, high blood oxygen transport potential, an effective microrheology of erythrocytes and their higher sensitivity to GTs with their positive effect on erythrocytes aggregation and deformability. Conclusions. The obtained data on models of erythrocyte microrheological responses to donors of two gasotransmitters allow us to conclude that, firstly, these GTs, as signaling molecules, have a positive effect on the erythrocyte microrheological characteristics and, consequently, on their transport potential, and, secondly, erythrocytes from individuals with a high level of oxygen body supply are more sensitive to the regulatory action of GTs, because their microrheological responses to donors were statistically significantly more expressed.

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