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Temperature-viscosity relations of bowhead whale blood: A possible mechanism for maintaining cold blood flow

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... Whole blood viscosity is strongly and directly related to hematocrit and is inversely related to temperature in species, but relations between species vary. For example, in some animals living in a cold environment (e.g., bowhead whales), WBV does not increase with decreasing temperature to the extent that would be expected for human blood [33]. WBV increases with hematocrit but the degree of viscosity increase with hematocrit is species specific, especially at low shear rates [34]. ...
... These marine mammals also have high RBC aggregation both in autologous plasma and standard aggregation media [35]. In contrast, WBV was found to be lower than human samples when the hematocrit was adjusted to 50% for both species [33]. Additionally, bowhead whale blood exhibited significantly less temperature dependence compared to human blood, with smaller increments in WBV as the measurement temperature decreased to 5 °C [33]. ...
... In contrast, WBV was found to be lower than human samples when the hematocrit was adjusted to 50% for both species [33]. Additionally, bowhead whale blood exhibited significantly less temperature dependence compared to human blood, with smaller increments in WBV as the measurement temperature decreased to 5 °C [33]. ...
... Whole blood viscosity is strongly and directly related to hematocrit and is inversely related to temperature in species, but relations between species vary. For example, in some animals living in a cold environment (e.g., bowhead whales), WBV does not increase with decreasing temperature to the extent that would be expected for human blood [33]. WBV increases with hematocrit but the degree of viscosity increase with hematocrit is species specific, especially at low shear rates [34]. ...
... These marine mammals also have high RBC aggregation both in autologous plasma and standard aggregation media [35]. In contrast, WBV was found to be lower than human samples when the hematocrit was adjusted to 50% for both species [33]. Additionally, bowhead whale blood exhibited significantly less temperature dependence compared to human blood, with smaller increments in WBV as the measurement temperature decreased to 5 °C [33]. ...
... In contrast, WBV was found to be lower than human samples when the hematocrit was adjusted to 50% for both species [33]. Additionally, bowhead whale blood exhibited significantly less temperature dependence compared to human blood, with smaller increments in WBV as the measurement temperature decreased to 5 °C [33]. ...
... The dynamic viscosity of plasma is also strongly dependent on temperature. It varies from μ = 3.1 mPa s at 4-5°C to μ = 1.25 mPa at 35-37°C [43,44]. Plasma is a Newtonian liquid, its viscosity is independent of shear rate [45]. ...
... We calculated the settling velocities of erythrocytes during sedimentation at different HCT values using Eqs 18 and 19 (Table 5). Here, we assume that the dynamic viscosity of plasma is μ = 1.65 mPa s at room temperature (24°C), as follows from an interpolation of the available experimental data [43,44]. ...
Article
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The erythrocyte sedimentation rate (ESR) test has been used for over a century. The Westergren method is routinely used in a variety of clinics. However, the mechanism of erythrocyte sedimentation remains unclear, and the 60 min required for the test seems excessive. We investigated the effects of cell aggregation during blood sedimentation and electrical conductivity at different hematocrits. A sample of blood was drop cast into a small chamber with two planar electrodes placed on the bottom. The measured blood conductivity increased slightly during the first minute and decreased thereafter. We explored various methods of enhancing or retarding the erythrocyte aggregation. Using experimental measurements and theoretical calculations, we show that the initial increase in blood conductivity was indeed caused by aggregation, while the subsequent decrease in conductivity resulted from the deposition of erythrocytes. We present a method for calculating blood conductivity based on effective medium theory. Erythrocytes are modeled as conducting spheroids surrounded by a thin insulating membrane. A digital camera was used to investigate the erythrocyte sedimentation behavior and the distribution of the cell volume fraction in a capillary tube. Experimental observations and theoretical estimations of the settling velocity are provided. We experimentally demonstrate that the disaggregated cells settle much slower than the aggregated cells. We show that our method of measuring the electrical conductivity credibly reflected the ESR. The method was very sensitive to the initial stage of aggregation and sedimentation, while the sedimentation curve for the Westergren ESR test has a very mild slope in the initial time. We tested our method for rapid estimation of the Westergren ESR. We show a correlation between our method of measuring changes in blood conductivity and standard Westergren ESR method. In the future, our method could be examined as a potential means of accelerating ESR tests in clinical practice. © 2015 Zhbanov, Yang. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
... Blood viscosities for marine mammals (i.e. Weddell seals, bowhead whales) have also been obtained at various shear rates [12, 15], but since the measurements did not include shear rates below 37.5 s –1 the data do not reflect the high variation observed in other studies at shear rates below about 1 s –1 [38]. A recent study compared the blood viscosity of koala and echidna with human data, and thus marsupials, monotremes and placental mammals [9], but the lack of low shear data close to 1 s –1 precluded evaluating low-shear variations. ...
... There are examples of specific adaptations of blood rheology that appear to help species survive in extreme environments. The rheology of bowhead whale blood is influenced less by temperature changes compared to human blood: bowhead whale blood viscosity exhibits a smaller increase as temperature is changed from 37 @BULLET C to 5 @BULLET C [15]. This provides an obvious advantage in terms of blood flow, especially in the superficial blood vessels such as in the tail flukes which are directly exposed to the very cold water of the Arctic sea. ...
Article
The flow properties of blood and its components vary widely throughout the animal kingdom. Even if nucleated avian and reptile red blood cells (RBC) are excluded from the analysis, RBC exhibit different rheological behavior among mammalian species. Both RBC aggregation and cellular deformability have been reported to vary among species, including placental mammals, marsupials, terrestrial and aquatic mammals. Although the relationships between blood flow behavior and species-specific characteristics have not been systematically investigated, studies to date allow recognition of interesting patterns, especially for RBC properties. These properties do not correlate with simple cellular parameters (e.g. mean cell volume), but more detailed analysis of RBC structure may reveal cellular aspects (e.g. surface charge density) that can be related to rheologic behavior. It has been postulated that the athletic capacity of mammalian species may predict the aggregation behavior of their RBC, but this hypothesis has not been supported by data from a wide range of athletic and sedentary species. Aquatic mammals also exhibit a very interesting diversity of hemorheological properties, which again are not yet easily related to specific circulatory adaptations. Data from current comparative studies suggest that a better understanding of the relations between specific hemorheological properties and specific hemodynamic adaptations in a variety of species should contribute to a better understanding of circulatory behavior; future studies are thus clearly indicated.
... Additionally, RBC deformability differs among species (Smith et al., 1979; Waugh, 1992; Baskurt, 1996; Plasenzotti et al., 2004 ); an extended description of hemorheological properties of different mammals can be found elsewhere (Windberger and Baskurt, 2007). The rheological diversity among mammals has stimulated comparative physiologists to search for matching patterns in hemorheological and physiological characteristics (Popel et al., 1994; Elsner et al., 2004; Castellini et al., 2006). One such proposed relationship is a higher RBC aggregation in athletic species compared to sedentary species, with the athletic versus sedentary classification based on maximal oxygen consumption (Popel et al., 1994). ...
... This relationship has been shown to be valid by several groups, although there is a paucity of information to satisfactorily explain the possible mechanisms relating RBC aggregation to athletic performance. Another interesting approach has been the search for hemorheological patterns of marine mammals (Meiselman et al., 1992; Popel et al., 1994; Elsner et al., 2004; Castellini et al., 2006), yet these studies were unable to describe a well-defined pattern: for example, two closely related marine mammals living near the North or South Pole have markedly different features of RBC aggregation. These findings suggest that the diversity of hemorheological parameters may reflect different adaptations under different environmental conditions. ...
Article
Koala, a marsupial, and echidna, a monotreme, are mammals native to Australia. Blood viscosity (62.5-1250s(-1)), red blood cell (RBC) deformability, RBC aggregation, aggregability and surface charge, and hematological parameters were measured in blood samples from six koalas and six echidnas and compared to adult human blood. Koala had the largest RBC mean cell volume (107.7+/-2.6fl) compared to echidna (81.3+/-2.6fl) and humans (88.4+/-1.2fl). Echidna blood exhibited the highest viscosity over the entire range of shear rates. Echidna RBC were significantly less deformable than koala RBC but more deformable than human RBC. Echidna RBC had significantly lower aggregability (i.e., aggregation in standardized dextran medium) than koala or human RBC, while aggregation in autologous plasma was similar for the three species. Erythrocyte surface charge as indexed by RBC electrophoretic mobility was similar for human and echidna cells but was 40% lower for koala RBC. Data obtained during this preliminary study indicate that koala and echidna have distinct hemorheological characteristics; investigation of these properties may reveal patterns relevant to specific behavioral and physiological features of these animals.
... There was also reduced temperature dependence in concern of whole blood viscosity in Antarctic birds and bowhead whale. The authors explain that a reasonable blood viscosity might be maintained in the cold-exposed parts of a body if blood viscosity increases only sparsely with temperature lowering [62,87]. ...
... There was also reduced temperature dependence in concern of whole blood viscosity in Antarctic birds and bowhead whale. The authors explain that a reasonable blood viscosity might be maintained in the cold-exposed parts of a body if blood viscosity increases only sparsely with temperature lowering [62,87]. ...
... It might be possible that blood viscosity shows a different dependence on temperature among animal species, and in particular in species living in very cold or very hot environments. Such an effect was described for bowhead whales and Antarctic birds [30,31]. Camels can modify their nychthemeral amplitude of body temperature by 6 • C to prevent evaporative cooling and water loss [4]. ...
Article
Background: The dromedary camel and the oryx antelope are exposed to excessive heat and solar radiation in their desert habitat. Desertification of areas with by now little rainfall may occur eventually. Well-adapted large animal species show us what is needed to survive in scorching regions. Methods: Four scimitar-horned oryx antelopes (Oryx dammah), 10 camels (Camelus dromedarius), nine South African Merino sheep, and 17 Nguni cows were tested for RBC aggregation, RBC elongation, and plasma viscosity. The temperature dependency of blood viscosity was tested in 10 camels and compared to human reference values. Results: Unlike sheep, Nguni cow, and dromedary camel, oryx RBCs aggregate in native plasma (M0:5.2 (3.3/6.7); M1:18.1 (16.7/27.9); Myrenne MA1). Elongation indices of oryx RBCs were intermediate to low (EImax: 22.6 (19.2/25.3); SS1/2 3.67 (2.52/4.95); Rheodyn SSD). Camel RBCs did not display the typical SS/EI curve by rotational ektacytometry. In-vitro blood viscosity (Physica MCR302) was lower in camels than in human blood at equal hematocrit. A decrease of temperature had only little effect on camel blood. At 10 s−1, blood viscosity in camel increased from 2.18mPa*s (2.01/2.37) at 42◦C to 4.39mPa*s (4.22/4.51) at 12◦C. In human blood, viscosity ranged from 8.21mPa*s (6.95/8.25) at 37◦C to 15.52mPa*s (14.25/16.03) at 12◦C. At 1000 s−1, blood viscosity in camel ranged from 2.00mPa*s (1.95/2.04) at 42◦C to 3.98mPa*s (3.88/4.08) at 12◦C. In human blood, viscosity ranged from 5.35mPa*s (4.96/5.87) at 37◦C to 11.24mPa*s (10.06/11.17) at 12◦C. Conclusions: Desert ungulates may need RBC membranes, which are fortified to withstand changes in osmolality during dehydration-rehydration cycles. This reduces RBC deformability. Dromedary camel blood does not undergo stark changes in viscosity with changes in temperature. Therefore, blood fluidity could be rather maintained during the day and night cycle. This should reduce the need of the vascularity to rhythmically adapt to changing shear forces when camels experience heterothermy.
... Typically, most cetaceans have small spleens (Rommel and Lowenstein, 2001), in contrast to the deep-diving pinnipeds, which have relatively large spleens that provide storage of red blood cells to increase haematocrit during dives (Elsner, 1999; Zapol et al., 1979). Increasing hematocrit alters blood properties such as viscosity (Elsner et al., 2004). Interestingly, beaked whales have much larger spleens than delphinids (Nishiwaki et al., 1972) and beaked whale livers may be relatively larger as well. ...
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A number of mass strandings of beaked whales have in recent decades been temporally and spatially coincident with military activitiesinvolving the use of midrange sonar. The social behaviour of beaked whales is poorly known, it can be inferred from strandings and someevidence of at-sea sightings. It is believed that some beaked whale species have social organisation at some scale; however most strandingsare of individuals, suggesting that they spend at least some part of their life alone. Thus, the occurrence of unusual mass strandings of beakedwhales is of particular importance. In contrast to some earlier reports, the most deleterious effect that sonar may have on beaked whalesmay not be trauma to the auditory system as a direct result of ensonification. Evidence now suggests that the most serious effect is theevolution of gas bubbles in tissues, driven by behaviourally altered dive profiles (e.g. extended surface intervals) or directly fromensonification. It has been predicted that the tissues of beaked whales are supersaturated with nitrogen gas on ascent due to thecharacteristics of their deep-diving behaviour. The lesions observed in beaked whales that mass stranded in the Canary Islands in 2002 areconsistent with, but not diagnostic of, decompression sickness. These lesions included gas and fat emboli and diffuse multiorganhaemorrhage. This review describes what is known about beaked whale anatomy and physiology and discusses mechanisms that may haveled to beaked whale mass strandings that were induced by anthropogenic sonar. Beaked whale morphology is illustrated using Cuvier’s beaked whale as the subject of the review. As so little is known about the anatomyand physiology of beaked whales, the morphologies of a relatively well-studied delphinid, the bottlenose dolphin and a well-studiedterrestrial mammal, the domestic dog are heavily drawn on. (18) (PDF) Elements of beaked whale anatomy and diving physiology and some hypothetical causes of sonar-related stranding. Available from: https://www.researchgate.net/publication/230737954_Elements_of_beaked_whale_anatomy_and_diving_physiology_and_some_hypothetical_causes_of_sonar-related_stranding [accessed Mar 27 2020].
... Typically, most cetaceans have small spleens (Rommel and Lowenstein, 2001), in contrast to the deep-diving pinnipeds, which have relatively large spleens that provide storage of red blood cells to increase haematocrit during dives (Eisner, 1999;Zapol et al, 1979). Increasing hematocrit alters blood properties such as viscosity (Eisner et al., 2004). Interestingly, beaked whales have much larger spleens than delphinids (Nishiwaki et al., 1972) and beaked whale livers may be relatively larger as well. ...
Article
Full-text available
A number of mass strandings of beaked whales have in recent decades been temporally and spatially coincident with military activities involving the use of midrange sonar. The social behaviour of beaked whales is poorly known, it can be inferred from strandings and some evidence of at-sea sightings. It is believed that some beaked whale species have social organisation at some scale; however most strandings are of individuals, suggesting that they spend at least some part of their life alone. Thus, the occurrence of unusual mass strandings of beaked whales is of particular importance. In contrast to some earlier reports, the most deleterious effect that sonar may have on beaked whales may not be trauma to the auditory system as a direct result of ensonification. Evidence now suggests that the most serious effect is the evolution of gas bubbles in tissues, driven by behaviourally altered dive profiles (e.g. extended surface intervals) or directly from ensonification. It has been predicted that the tissues of beaked whales are supersaturated with nitrogen gas on ascent due to the characteristics of their deep-diving behaviour. The lesions observed in beaked whales that mass stranded in the Canary Islands in 2002 are consistent with, but not diagnostic of, decompression sickness. These lesions included gas and fat emboli and diffuse multiorgan haemorrhage. This review describes what is known about beaked whale anatomy and physiology and discusses mechanisms that may have led to beaked whale mass strandings that were induced by anthropogenic sonar. Beaked whale morphology is illustrated using Cuvier’s beaked whale as the subject of the review. As so little is known about the anatomy and physiology of beaked whales, the morphologies of a relatively well-studied delphinid, the bottlenose dolphin and a well-studied terrestrial mammal, the domestic dog are heavily drawn on.
... the provision of oxygen to working muscles [4, 5]. The deformability of red blood cells may 48 increase due to the incorporation of polyunsaturated fatty acids of the n3 group into the erythrocyte 49 membranes, facilitating the movement of red blood cell during their circulation through even the smallest 50 blood vessels [17]. ...
Article
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The aim of this study was to assess the influence of a single session of maximal exercise performed in water (4°C or 25°C) on blood rheological properties and the composition of fatty acids in the erythrocyte membranes of laboratory rats. This study will permit better understanding of the reactions occurring in the organism during rapid cooling in cold water, especially in regards to the hemorheological and biochemical parameters of blood. When compared to the control group, exercise performed in water at 4°C led to an increase in the elongation index (EI, from 0.30 Pa to 4.24 Pa) with no concurrent changes in erythrocyte aggregation, blood plasma viscosity, and fatty acid composition (saturated, unsaturated, saturated/unsaturated, monounsaturated, polyunsaturated polyunsaturated-n3, polyunsaturated-n6 fatty acids) of the erythrocyte membrane. In rats swimming in water at 25°C, we observed an increase in EI at shear stress from 0.30 Pa to 2.19 Pa, along with a decrease in the half-time of total aggregation when compared to the control group. These changes in erythrocyte rheological properties can be treated as a protective reaction to thermal stress resulting in their improved deformability.
... These in vitromeasurements are most applicable to studies on marine mammals because they are readily adapted to blood samples collected from different species under a variety of field or laboratory conditions. For example, the impact of temperature on the viscosity of Arctic bowhead whale blood demonstrated that at the low temperatures most likely seen in the fluke, whale blood was less viscous than human blood would be under the same cool conditions (Elsner et al., 2004). ...
Article
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The field of blood oxygen transport and delivery to tissues has been studied by comparative physiologists for many decades. Within this general area, the particular differences in oxygen delivery between marine and terrestrial mammals has focused mainly on oxygen supply differences and delivery to the tissues under low blood flow diving conditions. Yet, the study of the inherent flow properties of the blood itself (hemorheology) is rarely discussed when addressing diving. However, hemorheology is important to the study of marine mammals because of the critical nature of the oxygen stores that are carried in the blood during diving periods. This review focuses on the essential elements of hemorheology, how they are defined and on fundamental rheological applications to marine mammals. While the comparative rationale used throughout the review is much broader than the particular problems associated with diving, the basic concepts focus on how changes in the flow properties of whole blood would be critical to oxygen delivery during diving. This review introduces the reader to most of the major rheological concepts that are relevant to the unique and unusual aspects of the diving physiology of marine mammals.
... Human and elephant seal blood behave similarly when adjusted to the same hematocrit [36]. At 50% hematocrit and 35 @BULLET C the viscosity of bowhead whale blood is similar to human blood, whereas at 5 @BULLET C bowhead blood is less viscous [24]. RBC aggregation for cells in plasma also shows species differences: ringed seal blood exhibits no measurable aggregation, elephant seal blood is similar to human blood, and adult Weddell seal blood aggregation is two-fold greater than human [36,51]. ...
Article
Full-text available
Red blood cell (RBC) aggregation and blood viscosity are important determinants of in vivo blood flow dynamics and, in marine mammals, these parameters may impact diving physiology by altering blood oxygen delivery during the diving response. Weddell seals are superb divers and exhibit age-related patterns in blood oxygen chemistry and diving ability. By contrast, bowhead whales are not long duration divers, and little is known of their blood properties relative to diving. The present study was designed to compare rheological characteristics of blood from Weddell seal pups, Weddell seal adults, and from adult bowhead whales: blood viscosity and RBC aggregation in plasma and in polymer solutions (i.e., RBC "aggregability") were measured. Salient findings included: (1) significant 4- to 8-fold greater aggregation in blood from adult seals compared with pups and human subjects; (2) 2-to 8-fold greater aggregation in bowhead whale blood compared with human blood; (3) compared to human red cells, enhanced RBC aggregability of RBC from adult seals and whales as determined by their greater aggregation in polymer solutions; (4) increasing RBC aggregation and aggregability of seal pup blood over a seven day period following birth; (5) significantly greater blood viscosity for adult seals compared with pups at both native and standardized hematocrits. These results indicate that, for both species, hemorheological parameters differ markedly from those of humans, and suggest progressive changes with seal age; the physiological implications of these differences have yet to be fully defined.
Article
Intraoperative monitoring is essential for providing safe and effective care during open surgery. In this paper, numerical simulation is performed to track the flow and heat transfer of carotid arteries with and without atherosclerotic plaque in a real physiological system during surgery, in which the heat transport is first considered to couple to the blood flow due to the temperature dependence of the blood viscosity. The impacts of the operating room temperature and hematocrit (H) on the viscosity, velocity, temperature, wall shear stress (WSS), pressure drop and oscillation are investigated. The results demonstrate that the presence of plaque in the carotid artery induces a greater blood flow velocity, pressure drop, WSS, and oscillation, as well as a smaller viscosity and temperature variations. A decreasing ambient temperature leads to a decrease in the temperature and an increase in the low-WSS area, which implies a greater risk of hypothermia and atherosclerosis. As H increases, the high-WSS areas substantially expand; when H varies from 65% to 80%, WSSave increases by 70.02% and 68.57% for the arteries with and without plaque, respectively, which indicates a higher risk of vascular injury. The results obtained can serve as a guideline regarding the selection of an operating room temperature for carotid disease patients with distinct hematocrits.
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Temperature regulation in bowhead whales, Balaena mysticetus, is supported by the characteristic cetacean peripheral circulation, especially notable in the tail flukes. Blood vessels serving this function consist of countercurrent heat exchangers (network of veins surrounding a central artery) favoring heat conservation and an alternate routing via arteriovenous anastomoses (AVAs) providing for heat dissipation. We tested the vasomotor responses of isolated segments of countercurrent arteries and AVAs from the bowhead tail flukes to norepinephrine (NOR), the sympathetic adrenergic neurotransmitter. Isometric tension developed during exposure to a micromolar concentration of NOR was consistently higher in AVAs than in arteries. Accordingly, the AVAs are subject to sympathetic vasoconstriction, and this activation directs blood flow to countercurrent heat exchangers and results in heat conservation. In contrast, AVA relaxation by reduced sympathetic activation favors increased blood flow through AVAs and consequent peripheral heat loss.
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We investigated the effects of temperature on blood viscosity of two species of penguin, the Temperate Zone little penguin (Eudyptula minor) and the Antarctic Adelie penguin (Pygoscelis adeliae), and the domestic chicken. When the blood was adjusted to the same hematocrit, there was no difference between the viscosity of blood from the two penguins, while at all temperatures and shear rates the chicken blood bad the highest viscosity. This contradicts the results of G. A. Block and D. E. Murrish, who claimed that, at low temperatures and low shear rates, the blood of Antarctic penguins bad higher viscosities than that of other bird species. Block and Murrish suggested that high blood viscosity at low temperatures and shear rates would serve as a beat conservation mechanism. On the contrary, we suggest that the viscous behavior of penguin blood represents an adaptation to maintain blood flow in extremities during immersion in cold water.
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Although blood viscosity varies in relation to shear rate, hematocrit, and temperature, equipment is now available with which it may be measured in respect to each of these variables. A simple, clinically practical technique for such measurement is presented. Blood from 60 normal subjects was adjusted to hematocrits 0, 20, 40, 60, and 80, and the viscosity-shear rate relationships measured at 37.0, 32.0, 27.0, and 22.0 C. The data obtained are presented as a reference for future studies using this method. Technical details are discussed and some deserving areas of application are considered. shear rate; cone-plate viscometer; hematocrit-viscosity relationships; blood, plasma; hematocrit; temperature; blood flow impedance; perfusion; shock; oliguria; dyspnea; coma; heart surgery; blood rheology; metabolism Submitted on May 31, 1963
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A mathematical model of heat loss from an aquatic animal to the surrounding water is presented. Heat is generated in metabolically active tissues and distributed by circulating blood and by conduction. The time dependent radial temperature profile of the animal is numerically solved from heat transfer equations by a computer. The model is applied to large whales, porpoises, and seals. For the whales, blood circulation to the dermal layer below appendage and body skin surfaces proved to be essential for sufficient heat dissipation. When decreasing the blood flow below a certain value (dependent on sea temperature and whale activity) the large whales would overheat. Blubber thickness was found to be of minor importance in whale thermoregulation, because the blubber coat can be bypassed by blood circulation. On the other hand, it is in general not possible for small porpoises and seals to stay warm in the coldest waters using normal mammalian resting metabolic rates, even if the peripheral circulation is shut off (or artery-vein heat exchangers used). Heat loss can be reduced if the outermost tissue layers are allowed to cool. This is achieved by minimizing convective radial heat flow via the circulation. (For large whales even minute radial blood flow raises the muscle temperatures to the core temperature level.) Seasonal acclimatization of harbour seals is explained by changes in their effective insulation thickness. Differences in whale activity induce changes in the temperature profile mainly within the first few centimeters from the skin surface. These superficial temperatures, if known, could be used to estimate whale metabolic rates. Since they drop close to the sea water temperature within minutes after whale death, the measurements should be done of live whales.
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Low-shear viscometry is one of the methods commonly used to estimate the degree of red blood cell (RBC) aggregation in various bloods and RBC suspensions. However, it has been previously shown that alterations in RBC morphology and mechanical behavior can affect the low-shear apparent viscosity of RBC suspensions; RBC aggregation is also sensitive to these cellular factors. This study used heat treatment (48 degrees C, 5 min), glutaraldehyde (0.005-0.02%) and hydrogen peroxide (1 mM) to modify cell geometry and deformability. Red blood cell aggregation was assessed via a Myrenne Aggregometer ("M" and "MI" indexes), RBC suspension viscosity was measured using a Contraves LS-30 viscometer, and RBC shape response to fluid shear stresses (i.e., deformability) was determined by ektacytometry (LORCA system). Our results indicate that low-shear apparent viscosity and related indexes may not always reflect changes of RBC aggregation if cellular properties are altered: for situations where RBC aggregation has been only moderately affected, cellular mechanical factors may be the major determinant of low-shear viscosity. These findings thus imply that in situations which may be associated alterations of RBC geometry and/or deformability, low-shear viscometry should not be the sole measurement technique used to assess RBC aggregation.
Functional circulatory anatomy of cetacean appendages. Pages 143-159 in R Functional anatomy of marine mammals Temperature regulation of marine mammals
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