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Snelling EP, Maloney SK, Farrell AP, Meyer LCR, Izwan A, Fuller A, Mitchell D, Haw A, Costello MA, Seymour RS. Scaling of morphology and ultrastructure of hearts among wild African antelope. J Exp Biol 2018; 221:jeb.184713. [DOI: 10.1242/jeb.184713] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 06/29/2018] [Indexed: 11/20/2022]
Abstract
The hearts of smaller mammals tend to operate at higher mass-specific mechanical work rates than those of larger mammals. The ultrastructural characteristics of the heart that allow for such variation in work rate still is largely unknown. We have used perfusion-fixation, transmission electron microscopy and stereology to assess the morphology and anatomical aerobic power density of the heart as a function of body mass across six species of wild African antelope differing by approximately 20-fold in body mass. The survival of wild antelope, as prey animals, depends on competent cardiovascular performance. We found that relative heart mass (g kg−1 body mass) decreases with body mass according to a power equation with an exponent of –0.12±0.07 (± 95% CI) (P=0.0027). Likewise, capillary length density (km cm−3 of cardiomyocyte), mitochondrial volume density (fraction of cardiomyocyte), and mitochondrial inner membrane surface density (m2 cm−3 of mitochondria) also decrease with body mass with exponents of –0.17±0.16 (P=0.039), –0.06±0.05 (P=0.018), and –0.07±0.05 (P=0.015), respectively, trends likely to be associated with the greater mass-specific mechanical work rates of the hearts in smaller antelope. Finally, we found proportionality between quantitative characteristics of a structure responsible for the delivery of oxygen (total capillary length) and those of a structure that ultimately uses that oxygen (total mitochondrial inner membrane surface area), which provides support for the economic principle of symmorphosis at the cellular level of the oxygen cascade in an aerobic organ.
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Affiliation(s)
- Edward P. Snelling
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
| | - Shane K. Maloney
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- School of Human Sciences, University of Western Australia, Crawley, Western Australia, Australia
| | - Anthony P. Farrell
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Leith C. R. Meyer
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- Department of Paraclinical Sciences, University of Pretoria, Pretoria, South Africa
| | - Adian Izwan
- School of Human Sciences, University of Western Australia, Crawley, Western Australia, Australia
| | - Andrea Fuller
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- Department of Paraclinical Sciences, University of Pretoria, Pretoria, South Africa
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- School of Human Sciences, University of Western Australia, Crawley, Western Australia, Australia
| | - Anna Haw
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
| | - Mary-Ann Costello
- Central Animal Service, University of the Witwatersrand, Johannesburg, South Africa
| | - Roger S. Seymour
- School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia
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Vivien CJ, Hudson JE, Porrello ER. Evolution, comparative biology and ontogeny of vertebrate heart regeneration. NPJ Regen Med 2016; 1:16012. [PMID: 29302337 PMCID: PMC5744704 DOI: 10.1038/npjregenmed.2016.12] [Citation(s) in RCA: 86] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/01/2016] [Accepted: 06/15/2016] [Indexed: 12/19/2022] Open
Abstract
There are 64,000 living species of vertebrates on our planet and all of them have a heart. Comparative analyses devoted to understanding the regenerative potential of the myocardium have been performed in a dozen vertebrate species with the aim of developing regenerative therapies for human heart disease. Based on this relatively small selection of animal models, important insights into the evolutionary conservation of regenerative mechanisms have been gained. In this review, we survey cardiac regeneration studies in diverse species to provide an evolutionary context for the lack of regenerative capacity in the adult mammalian heart. Our analyses highlight the importance of cardiac adaptations that have occurred over hundreds of millions of years during the transition from aquatic to terrestrial life, as well as during the transition from the womb to an oxygen-rich environment at birth. We also discuss the evolution and ontogeny of cardiac morphological, physiological and metabolic adaptations in the context of heart regeneration. Taken together, our findings suggest that cardiac regenerative potential correlates with a low-metabolic state, the inability to regulate body temperature, low heart pressure, hypoxia, immature cardiomyocyte structure and an immature immune system. A more complete understanding of the evolutionary context and developmental mechanisms governing cardiac regenerative capacity would provide stronger scientific foundations for the translation of cardiac regeneration therapies into the clinic.
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Affiliation(s)
- Celine J Vivien
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
- Centre for Cardiac and Vascular Biology, The University of Queensland, Brisbane, QLD, Australia
| | - James E Hudson
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
- Centre for Cardiac and Vascular Biology, The University of Queensland, Brisbane, QLD, Australia
| | - Enzo R Porrello
- School of Biomedical Sciences, The University of Queensland, Brisbane, QLD, Australia
- Centre for Cardiac and Vascular Biology, The University of Queensland, Brisbane, QLD, Australia
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Snelling EP, Taggart DA, Maloney SK, Farrell AP, Leigh CM, Waterhouse L, Williams R, Seymour RS. Scaling of left ventricle cardiomyocyte ultrastructure across development in the kangaroo Macropus fuliginosus. ACTA ACUST UNITED AC 2015; 218:1767-76. [PMID: 25908057 DOI: 10.1242/jeb.119453] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 04/14/2015] [Indexed: 11/20/2022]
Abstract
The heart and left ventricle of the marsupial western grey kangaroo Macropus fuliginosus exhibit biphasic allometric growth, whereby a negative shift in the trajectory of cardiac growth occurs at pouch exit. In this study, we used transmission electron microscopy to examine the scaling of left ventricle cardiomyocyte ultrastructure across development in the western grey kangaroo over a 190-fold body mass range (0.355-67.5 kg). The volume-density (%) of myofibrils, mitochondria, sarcoplasmic reticuli and T-tubules increase significantly during in-pouch growth, such that the absolute volume (ml) of these organelles scales with body mass (Mb; kg) with steep hyperallometry: 1.41Mb (1.38), 0.64Mb (1.29), 0.066Mb (1.45) and 0.035Mb (1.87), respectively. Maturation of the left ventricle ultrastructure coincides with pouch vacation, as organelle volume-densities scale independent of body mass across post-pouch development, such that absolute organelle volumes scale in parallel and with relatively shallow hypoallometry: 4.65Mb (0.79), 1.75Mb (0.77), 0.21Mb (0.79) and 0.35Mb (0.79), respectively. The steep hyperallometry of organelle volumes and volume-densities across in-pouch growth is consistent with the improved contractile performance of isolated cardiac muscle during fetal development in placental mammals, and is probably critical in augmenting cardiac output to levels necessary for endothermy and independent locomotion in the young kangaroo as it prepares for pouch exit. The shallow hypoallometry of organelle volumes during post-pouch growth suggests a decrease in relative cardiac requirements as body mass increases in free-roaming kangaroos, which is possibly because the energy required for hopping is independent of speed, and the capacity for energy storage during hopping could increase as the kangaroo grows.
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Affiliation(s)
- Edward P Snelling
- Department of Ecology and Environmental Science, School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - David A Taggart
- Department of Ecology and Environmental Science, School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Shane K Maloney
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Crawley, WA 6009, Australia
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4 Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Christopher M Leigh
- School of Medical Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Lyn Waterhouse
- Adelaide Microscopy, University of Adelaide, Adelaide, SA 5005, Australia
| | - Ruth Williams
- Adelaide Microscopy, University of Adelaide, Adelaide, SA 5005, Australia
| | - Roger S Seymour
- Department of Ecology and Environmental Science, School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
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Snelling EP, Taggart DA, Maloney SK, Farrell AP, Seymour RS. Biphasic Allometry of Cardiac Growth in the Developing KangarooMacropus fuliginosus. Physiol Biochem Zool 2015; 88:216-25. [DOI: 10.1086/679718] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Dawson TJ, Webster KN, Lee E, Buttemer WA. High muscle mitochondrial volume and aerobic capacity in a small marsupial (Sminthopsis crassicaudata) reveals flexible links between energy-use levels in mammals. ACTA ACUST UNITED AC 2012; 216:1330-7. [PMID: 23239895 DOI: 10.1242/jeb.079087] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the muscle structure-function relationships that underlie the aerobic capacity of an insectivorous, small (~15 g) marsupial, Sminthopsis crassicaudata (Family: Dasyuridae), to obtain further insight into energy use patterns in marsupials relative to those in placentals, their sister clade within the Theria (advanced mammals). Disparate hopping marsupials (Suborder Macropodiformes), a kangaroo (Macropus rufus) and a rat-kangaroo (Bettongia penicillata), show aerobic capabilities as high as those of 'athletic' placentals. Equivalent muscle mitochondrial volumes and cardiovascular features support these capabilities. We examined S. crassicaudata to determine whether highly developed aerobic capabilities occur elsewhere in marsupials, rather than being restricted to the more recently evolved Macropodiformes. This was the case. Treadmill-trained S. crassicaudata attained a maximal aerobic metabolic rate ( or MMR) of 272 ml O2 min(-1) kg(-1) (N=8), similar to that reported for a small (~20 g), 'athletic' placental, Apodemus sylvaticus, 264 ml O2 min(-1) kg(-1). Hopping marsupials have comparable aerobic levels when body mass variation is considered. Sminthopsis crassicaudata has a basal metabolic rate (BMR) about 75% of placental values but it has a notably large factorial aerobic scope (fAS) of 13; elevated fAS also features in hopping marsupials. The of S. crassicaudata was supported by an elevated total muscle mitochondrial volume, which was largely achieved through high muscle mitochondrial volume densities, Vv(mt,f), the mean value being 14.0±1.33%. These data were considered in relation to energy use levels in mammals, particularly field metabolic rate (FMR). BMR is consistently lower in marsupials, but this is balanced by a high fAS, such that marsupial MMR matches that of placentals. However, FMR shows different mass relationships in the two clades, with the FMR of small (<125 g) marsupials, such as S. crassicaudata, being higher than that in comparably sized placentals, with the reverse applying for larger marsupials. The flexibility of energy output in marsupials provides explanations for this pattern. Overall, our data refute widely held notions of mechanistically closely linked relationships between body mass, BMR, FMR and MMR in mammals generally.
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Affiliation(s)
- Terence J Dawson
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia
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Webster KN, Dawson TJ. The high aerobic capacity of a small, marsupial rat-kangaroo (Bettongia penicillata) is matched by the mitochondrial and capillary morphology of its skeletal muscles. J Exp Biol 2012; 215:3223-30. [PMID: 22660784 DOI: 10.1242/jeb.071365] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We examined the structure-function relationships that underlie the aerobic capacities of marsupial mammals that hop. Marsupials have relatively low basal metabolic rates (BMR) and historically were seen as 'low energy' mammals. However, the red kangaroo, Macropus rufus (family Macropodidae), has aerobic capacities equivalent to athletic placentals. It has an extreme aerobic scope (fAS) and its large locomotor muscles feature high mitochondrial and capillary volumes. M. rufus belongs to a modern group of kangaroos and its high fAS is not general for marsupials. However, other hopping marsupials may have elevated aerobic capacities. Bettongia penicillata, a rat-kangaroo (family Potoroidae), is a small (1 kg), active hopper whose fAS is somewhat elevated. We examined the oxygen delivery system in its muscles to ascertain links with hopping. An elevated fAS of 23 provided a relatively high maximal aerobic oxygen consumption ( ) in B. penicillata; associated with this is a skeletal muscle mass of 44% of body mass. Ten muscles were sampled to estimate the total mitochondrial and capillary volume of the locomotor muscles. Values in B. penicillata were similar to those in M. rufus and in athletic placentals. This small hopper had high muscle mitochondrial volume densities (7.1-11.9%) and both a large total capillary volume (6 ml kg(-1) body mass) and total capillary erythrocyte volume (3.2 ml kg(-1)). Apparently, a considerable aerobic capacity is required to achieve the benefits of the extended stride in fast hopping. Of note, the ratio of to total muscle mitochondrial volume in B. penicillata was 4.9 ml O(2) min(-1) ml(-1). Similar values occur in M. rufus and also placental mammals generally, not only athletic species. If such relationships occur in other marsupials, a fundamental structure-function relationship for oxygen delivery to muscles likely originated with or before the earliest mammals.
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Affiliation(s)
- Koa N Webster
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
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Hoh JFY, Kim Y, Lim JHY, Sieber LG, Lucas CA, Zhong WWH. Marsupial cardiac myosins are similar to those of eutherians in subunit composition and in the correlation of their expression with body size. J Comp Physiol B 2006; 177:153-63. [PMID: 16988832 DOI: 10.1007/s00360-006-0117-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 08/20/2006] [Accepted: 08/23/2006] [Indexed: 10/24/2022]
Abstract
Cardiac myosins and their subunit compositions were studied in ten species of marsupial mammals. Using native gel electrophoresis, ventricular myosin in macropodoids showed three isoforms, V(1), V(2) and V(3), and western blots using specific anti-alpha- and anti-beta-cardiac myosin heavy chain (MyHC) antibodies showed their MyHC compositions to be alphaalpha, alphabeta and betabeta, respectively. Atrial myosin showed alphaalpha MyHC composition but differed from V(1) in light chain composition. Small marsupials (Sminthopsis crassicaudata, Antechinus stuartii, Antechinus flavipes) showed virtually pure V(1), while the larger (1-3 kg) Pseudocheirus peregrinus and Trichosurus vulpecula showed virtually pure V(3). The five macropodoids (Bettongia penicillata, Macropus eugenii, Wallabia bicolour, M. rufus and M. giganteus), ranging in body mass from 2 to 66 kg, expressed considerably more alpha-MyHC (22.8%) than expected for their body size. These results show that cardiac myosins in marsupial mammals are substantially the same as their eutherian counterparts in subunit composition and in the correlation of their expression with body size, the latter feature underlies the scaling of resting heart rate and cardiac cross-bridge kinetics with specific metabolic rate. The data from macropodoids further suggest that expression of cardiac myosins in mammals may also be influenced by their metabolic scope.
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Affiliation(s)
- Joseph F Y Hoh
- Discipline of Physiology and the Bosch Institute, Building F13, School of Medical Sciences, Faculty of Medicine, The University of Sydney, Sydney, NSW, 2006, Australia.
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Hayes JP, Shonkwiler JS. Allometry, Antilog Transformations, and the Perils of Prediction on the Original Scale. Physiol Biochem Zool 2006; 79:665-74. [PMID: 16691531 DOI: 10.1086/502814] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/12/2005] [Indexed: 11/03/2022]
Abstract
Biologists often use allometric equations that take the form of power functions (e.g., Y = aM(b), where M stands for mass and a and b are empirically fitted constants). Typically, these allometric equations are fitted by taking the antilog of log-log regressions. Predictions from these allometric equations are biased, and the bias my be appreciable. Methods for making predictions that correct for the bias are available, but they have rarely, if ever, been used by ecological and evolutionary physiologists. Just as physiologists would not use an instrument that was not properly calibrated, they should not use allometric equations to make predictions unless they account for the bias of those predictions. We analyzed 20 interspecific and 10 intraspecific data sets. We compared predictions from standard allometric equations with those from several alternative methods. Our analyses suggest that the bias of predictions from interspecific data sets may be substantial. For the intraspecific data sets we analyzed, the bias was likely to be small. Biologists, including ecological and evolutionary physiologists, should exercise care when using allometric equations to make predictions, particularly given that methods to adjust for bias are easily implemented.
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Affiliation(s)
- Jack P Hayes
- Department of Biology, University of Nevada, Reno, 89557, USA.
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Dawson TJ, Mifsud B, Raad MC, Webster KN. Aerobic characteristics of red kangaroo skeletal muscles: is a high aerobic capacity matched by muscle mitochondrial and capillary morphology as in placental mammals? J Exp Biol 2004; 207:2811-21. [PMID: 15235010 DOI: 10.1242/jeb.01115] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
Marsupials and placentals together comprise the Theria, the advanced mammals, but they have had long independent evolutionary histories, with the last common ancestor occurring more than 125 million years ago. Although in the past the marsupials were considered to be metabolically `primitive', the red kangaroo Macropus rufus has been reported to have an aerobic capacity (V̇O2max)comparable to that of the most `athletic' of placentals such as dogs. However,kangaroos travel at moderate speeds with lower relative cost than quadrupedal placentals. Given the long independent evolution of the two therian groups,and their unusual locomotor energetics, do kangaroos achieve their high aerobic capacity using the same structural and functional mechanisms used by(athletic) placentals?
Red kangaroo skeletal muscle morphometry matched closely the general aerobic characteristics of placental mammals. The relationship between total mitochondrial volume in skeletal muscle and V̇O2max during exercise was identical to that in quadrupedal placentals, and differed from that in bipedal humans. As for placentals generally, red kangaroo mitochondrial oxygen consumption at V̇O2max was 4.7 ml O2 min–1 ml–1 of mitochondria. Also, the inner mitochondrial membrane densities were 35.8±0.7 m2 ml–1 of mitochondria, which is the same as for placental mammals, and the same pattern of similarity was seen for capillary densities and volumes.
The overall data for kangaroos was equivalent to that seen in athletic placentals such as dogs and pronghorns. Total skeletal muscle mass was high,being around 50% of body mass, and was concentrated around the pelvis and lower back. The majority of the muscles sampled had relatively high mitochondrial volume densities, in the range 8.8–10.6% in the major locomotor muscles. Again, capillary densities and capillary blood volumes followed the pattern seen for mitochondria. Our results indicate that the red kangaroo, despite its locomotion and extreme body form, shows fundamental aerobic/muscular relationships that appear common to both marsupials and placentals. The evolution of such metabolic relationships apparently predates the divergence of the therian groups in the early Cretaceous, and perhaps evolved in the mammal-like reptiles during the Triassic (220 million years ago) before the actual evolution of the mammals.
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Affiliation(s)
- Terence J Dawson
- School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
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