Assessment of ventricular morphology using
echocardiography in Ornate tinamous
(Nothoprocta ornata) and domestic chickens
(Gallus domesticus)
Emma Backlund
LiTH-IFM- Ex--13/2852--SE
Handledare: Jordi Altimiras, Linköpings universitet Examinator: Anders Hargeby, Linköpings universitet
Institutionen för fysik, kemi och biologi
Linköpings universitet
Datum/Date 2014-01-26 ISBN LITH-IFM-G-EX—99/1111—SE __________________________________________________ ISRN 13/2852
Serietitel och serienummer ISSN
Title of series, numbering
Handledare/Supervisor Jordi Altimiras
Ort/Location: Linköping Rapporttyp Report category Examensarbete C-uppsats Språk/Language Engelska/English
URL för elektronisk version
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-103754
Titel/Title:
Assessment of ventricular morphology using echocardiography in Ornate tinamous
(Nothoprocta ornata) and domestic chickens (Gallus domesticus)
Författare/Author:
Emma Backlund Sammanfattning/Abstract:
The Ornate Tinamou (Nothoprocta ornata), an ancient bird, has adapted to life at high
altitude (>2.400 m.a.s.l) for a longer period than the domestic chicken (Gallus domesticus), which came to South America with the Spanish conquerors. Ornate tinamous have a smaller heart in relation to body size than domestic chickens. This study was made to evaluate heart
morphometric measurements comparing Ornate Tinamou and domestic chicken using
echocardiography measurements to determine wall thickness and chamber size and to evaluate whether it can retrieve measurements consistent with previous results on dissected hearts. I was also interested in evaluating potential adaptations of the Ornate Tinamou to life in hypoxic environments by exposing the heart to positive inotropic stimulation. The results were compared with those previously obtained on dissected hearts. The results showed that the chamber size of the domestic chicken was significantly larger than in Ornate Tinamou, both in conscious and anesthetized birds. Injection of 1µg/kg isoproterenol caused domestic chickens’ systolic chamber size to decrease significantly and fractional shortening to increase significantly. The same
changes were seen in the Ornate Tinamou but they were not significant. In conclusion, this study confirms that echocardiography is a valid method for retrieving cardiac measurements without euthanizing animals, opening for the possibility of taking several measurements at different ages.
Nyckelord/Keyword:
Anesthesia, cardiac function, isoproterenol, left ventricular wall thickness, Ornate Tinamou
Institutionen för fysik, kemi och biologi
Department of Physics, Chemistry and Biology
Avdelningen för biologi
Table of content
Table of content ...
1. Abstract ... 1
2. Introduction ... 1
3. Materials and Methods ... 2
3.1 Experimental protocol ... 4
3.2 Comparisons and statistical analysis ... 5
4. Results ... 6 4.1 Conscious birds ... 6 4.2 Anesthetized birds ... 7 5. Discussion ... 11 5.1 Conclusion ... 13 6. Acknowledgements ... 14 7. References ... 15
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1. Abstract
The Ornate Tinamou (Nothoprocta ornata), an ancient bird, has
adapted to life at high altitude (>2.400 m.a.s.l) for a longer period than the domestic chicken (Gallus domesticus), which came to South America with the Spanish conquerors. Ornate tinamous have a smaller heart in relation to body size than domestic chickens. This study was made to evaluate heart morphometric measurements comparing Ornate Tinamou and domestic chicken using echocardiography measurements to determine wall thickness and chamber size and to evaluate whether it can retrieve measurements consistent with previous results on dissected hearts. I was also interested in evaluating potential adaptations of the Ornate Tinamou to life in hypoxic environments by exposing the heart to positive inotropic stimulation. The results were compared with those previously obtained on dissected hearts. The results showed that the chamber size of the domestic chicken was significantly larger than in Ornate Tinamou, both in conscious and anesthetized birds. Injection of 1µg/kg isoproterenol caused domestic chickens’ systolic chamber size to decrease significantly and fractional shortening to increase significantly. The same changes were seen in the Ornate Tinamou but they were not significant. In conclusion, this study confirms that echocardiography is a valid method for retrieving cardiac measurements without euthanizing animals, opening for the possibility of taking several measurements at different ages.
2. Introduction
The Ornate Tinamou (Nothoprocta ornata) is a bird of the family
Tinamidae. This family is very old and is included in the order
Palaeognathae (Hackett et al., 2008). The Ornate Tinamou is a solitary
grassland species which is found in the puna zone of the Andes, the puna zone represents the dry altiplano grassland of South America (Pokines, 2011). This puna zone is located at an altitude of approximately 3800-4000 m.a.s.l (meters above sea level) (Pearson and Pearson, 1955).
Living at this altitude puts any individual in a position where several physiological adaptations are needed. One priority is to maintain a
functional oxygen-delivery throughout the body since it is constantly under hypoxic conditions while living at high altitude, which has been defined as 2400 m.a.s.l or higher (Hurtado et al., 2012).
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In terms of cardiac activity, non-native individuals exposed to high altitude typically increase their cardiac output along with retrieving a higher blood pressure. Natives living at high altitudes, on the other hand, have developed an adaptation including an enhanced oxygen extraction with no indication of anaerobic metabolism (Hurtado et al., 2012).
The Ornate Tinamou is known to have one of the smallest hearts
compared to its body mass, according to Bishop (1997) 0, 25 % of its body size. A study performed on mammals and birds considering ventricular wall tension and blood pressure, has also confirmed that in general birds have larger hearts than mammals in relation to body size and, again, that birds have a higher blood pressure (Seymour & Blaylock, 2000). This is the motivation to why it is interesting to investigate the heart of the Ornate Tinamou.
The aim of this study was to test whether results gained from
echocardiography measurements are consistent with previously performed similar experiments on dissected hearts. The results were also used to test how the Ornate Tinamou has adapted to life at high altitude, considering that the species has a small heart compared to body size.
To examine this, the heart morphology of both Ornate tinamous and domestic chickens (Gallus domesticus) was studied in a conscious state using ultrasound to obtain information on heart morphometry. These results were compared with measurements from anesthetized animals and to
previous results in preserved hearts. A specific aim was to use
echocardiography measurements while the animals were awake. By using this technique it was also possible to evaluate whether echocardiography measurements will work as a substitute for doing experiments on preserved hearts of the Ornate Tinamou.
Furthermore, this study aimed to test how the adrenergic agonist isoproterenol affects cardiac function, comparing Ornate tinamous and domestic chickens. Isoproterenol, which is an inotropic and chronotropic drug is known to increase the force, and respectively, the rate of
contraction of the heart. When the heart rate increases the effective refractory period also shortens (Toshihide, 2012).
3. Materials and Methods
Measurements were performed mid-heart, since the wall-thickness can differ (Seymour & Blaylock, 2000) and in four modes: Long axis B-mode (LA.BM), Long axis M-mode (LA.MM), Short axis B-mode (SA.BM) and Short axis M-mode (SA.MM). This was done to be able to calculate the left
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ventricular wall thickness along with the heart rate, diameter of the heart and heart chamber size of the birds.
The same experiments were performed on the same animals while anesthetized on the volatile anesthetic isoflurane. Measurements were performed using ultrasound and probes connected to Powerlab for monitoring heart rate (via ECG), temperature and ventilation (via
impedance pneumography). While anesthetized, intravenous injections of different dosages of isoproterenol to the ulnar artery that is exiting the heart were performed. Ultrasounds were then taken again, directly and after a fixed amount of time after the injection.
Echocardiography measurements were performed using a linear
ultrasound probe and the software Echo wave II 2.5.2. Left ventricular wall thickness, left ventricular chamber size, diameter of the heart and heart rate were analyzed as shown in Figure 1, using Echo wave II 2.5.2.
The animals were anesthetized using (start dose ~1%) isoflurane through a Drager vaporizer with an oxygen flow rate of 40 ml min-1, depending on the status of the bird. Larger birds needed a larger dose of isoflurane to fall asleep and some birds, which were more sensitive, needed a smaller dose of isoflurane and a higher oxygen flow to keep stable with a steady ventilation and heart rate.
Body temperature was maintained at an average of 40.2±1.29 degrees
Celsius for the domestic chickens and an average of 39.0±1.34 degrees Celsius for the Ornate tinamous, as seen in Figure 4b, by using a heating mat.
The drugs used were isoflurane for anesthesia and isoproterenol as an adrenergic agonist. For the echocardiography measurements an ultra sound gel was used on the ultrasound probe.
Isoflurane is a volatile inhalant anesthetic agent which is known to decrease blood pressure, increase cerebral blood flow and decrease mean arterial pressure. It has also been shown that depending on the dose, isoflurane will either vasoconstrict (low dose, <0, 5% isoflurane) or
vasodilate (high dose, >0, 95 % isoflurane) (Li, 2013). Isoflurane is known to induce highly variable duration of surgical anesthesia (Guénette et al., 2013), but inhalant anesthetics are still the preferred method to anesthetize avian species due to its effectiveness and rapid onset as well as recovery (Granone et al., 2012). In the study performed by Granone (2012) it was shown that in comparison to two other inhalant anesthetic agents,
isoflurane lowers the respiratory rate along with nerve activity but still gives similar changes in cardiac function which was observed for all anesthetics and that all provided a safe anesthesia. An evaluation of cardiorespiratory effects by isoflurane has been done on the crested
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caracara, and it was shown that isoflurane is a suitable anesthetic to the crested caracara, not giving any consequence for the bird, (Escobar et al., 2011) which also may be considered in this study.
Cloacal temperature, breathing frequency, blood pressure and heart rate were monitored and recorded using a Power lab amplifier (4/25T
ADInstruments). Recordings were stored using the software Lab Chart © 7 Pro, on a laptop.
Figure 1. Printout showing how measurements were performed using the software Echo wave II: left ventricular wall thickness (1systole and 3 diastole), chamber diameter (2 diastole and 4 systole), total diameter of the heart (5) and heart rate (6). Also shown is the difference between diastole/systole and how the cardiac wall is altered in structure.
3.1 Experimental protocol
To begin the study, echocardiography was performed on eight conscious domestic chickens (four male/ four female) and eight conscious Ornate tinamous (five male/three female). The heart was recorded in two different dimensions, long axis with an apical view and short axis with a parasternal view. The measurements done by using the software were later performed by analyzing the ultrasound pictures in long axis m-mode, since it is the simplest way to get clear and consistent images. The measurements taken were diastole chamber size, systole chamber size, systole wall thickness, diastole wall thickness, total diameter of the heart and heart rate. Sizes are
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measured in millimeters (mm). Fractional shortening was calculated
subtracting systole from diastole and dividing it by diastole as a percentage. Since the animals were conscious the concept of tonic immobility was used. When animals are faced to a predator defensive mechanisms are activated. If these mechanisms do not work the animal goes into tonic immobility which includes muscular rigidity that causes the immobilized state. Tonic immobility also includes involuntary patterns of neuromuscular activity, intermittent periods of closed eyes, Parkinsonian-like tremors and a suppressed vocal ability to mention some. This immobility can last from just a few seconds up to several hours and is not harmful for the animal that is still conscious and able to remember and learn (Marx et al., 2008).
To start the anesthetized experiments, which were performed on the same individuals, the animal was put in a face mask with flowing oxygen and isoflurane (starting at 1%) to fall asleep. When the animal was
anesthetized three probes connected to a Power lab amplifier (4/25T ADInstruments) were inserted in the animal to get a reading of ventilation rate, heart rate, and temperature, prior to a control ultrasound being taken. When the animal was stable, meaning that the readings of measured
parameters were consistent, the first surgery commenced to catheterize the ulnar artery both to get blood pressure readings and for the injection of isoproterenol. When the catheter had been inserted and connected to a disposable pressure transducer the bird was able to rest until stable again, since moving the bird gave a reading from the sensitive probes, before 1 µg/kg isoproterenol was injected and an ultrasound was immediately taken. After this, the second surgery (belonging to a second trial) to put an
ultrasound probe around the aorta to measure cardiac output was prepared. After the second surgery and the final injections of isoproterenol, when the bird’s readings had gone to normal, the animal was euthanized by
decapitation. The bird was needed to be stable again before every move to make sure that the drug no longer had any effect, this to be able to measure how the drug in fact affected the bird.
3.2 Comparisons and statistical analysis
The data points of diastole chamber size, systole chamber size, systole left ventricular wall thickness, diastole left ventricular wall thickness, total diameter of the heart (on un-anesthetized birds) and heart rate were measured in Echo wave II 2.5.2 and exported to Microsoft Office Excel 2007. All 9 measurements (3 repeated measurements from 3 randomly distributed spots in the same file) from all the animals were first calculated in averages (controls and animals injected with 1 µg/kg isoproterenol) and then put in a summary of either Ornate tinamous or domestic chickens.
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The first comparisons were made on the un-anesthetized birds,
comparing fractional shortening, left ventricular wall thickness, normalized wall thickness, heart rate and chamber size both between systole/diastole in each species and between Ornate tinamous and domestic chickens. The need to measure both systole and diastole comes from the hearts
contractions, elongating and stretching the cardiac wall. To be able to measure wall thickness and relate it to morphometric measurements the first need is to know how the wall is affected by systole/diastole.
Secondly, control versus injection of 1 µg/kg isoproterenol was
compared, again both within one species and between the two species. Also in domestic chickens a comparison was made from the control to 1 µg/kg isoproterenol, from control to 2 µg/kg isoproterenol and from control to 3 µg/kg isoproterenol. This was not done in the Ornate Tinamou because of its sensitive nature. The Ornate Tinamou in this study was needed for a second trial and therefore we needed to make sure that the birds were kept alive until then so that the experiments could be finished. Therefore only 1 µg/kg was measured in the Ornate tinamous.
Using Microsoft Office Excel 2007 two-tailed t-tests were performed on a 5 % probability level for all the comparisons and all values are expressed with SD (standard deviation) as the measure of variation.
4. Results
4.1 Conscious birds
Considering conscious birds there was a significant difference between Ornate tinamous and domestic chickens (only considering the sizes of the hearts) when looking at diastole chamber size (p<0,001), systole chamber size (p=0,034, figure 2a) and total diameter of the heart (Ornate tinamous 9,59 ± 0,58 mm and domestic chickens 11,33 ± 1,48 mm with a p-value of 0,008). There was no significant difference in ventricular wall thickness (Figure 2b), or heart ratio – left ventricular wall thickness divided by total diameter of the heart - thus taking into account the sizes of the birds (Figure 2c). There was also no significant difference in fractional
shortening comparing Ornate tinamous with domestic chickens (p=0,523, Figure 2d).
Furthermore no significant difference in heart rate could be seen (p=0,288) comparing un-anesthetized Ornate tinamous (381±13.4 bpm) to un-anesthetized domestic chickens (361±50.5 bpm).
7 2d 2c 2b 2a 0 20 40 60 80 Fr ac Sh or t (% ) 0 2 4 6 8 10 C h am b e r d ia m e te r (m m )
*
*
0 1 2 3 4 5 WT (mm )Figure 2. Heart characteristics in N.ornata and G. domesticus from echocardiography measurements on conscious birds. Means and SD are indicated in the graph, n=8. In graph 2a, b and c the black bars represent systole and the white diastole. 2a, Systole and diastole chamber size. 2b Left ventricular wall thickness. 2c Normalized left ventricular wall thickness (WT divided by total diameter of the heart) giving a value of heart capacity adjusted for size of bird. 2d Fractional shortening in N. ornata and G. domesticus. * = representing significant difference between N. ornata and G. domesticus at the 0,05 probability level.
4.2 Anesthetized birds
The heart rate was significantly lower both in domestic chickens and Ornate tinamous that were un-anesthetized compared to anesthetized ones, (Figure 5a). This would not affect the results after injection of isoproterenol since I had considered the anesthetized heart rates in comparison to the injections. Temperature of the birds was consistent during the experiments, both for Ornate tinamous and domestic chickens (Figure 4b). This along with given consistent data in heart rate, looking at both Labchart and Echowave measurements (Figure 5a compared to Figure 4a), excludes interference by the anesthetic agent.
Measurements were made to examine the effect of the adrenergic agonist isoproterenol by analyzing data before and after injection on anesthetized animals. When considering Ornate tinamous no significant affect could be seen after injection of 1 ug/kg isoproterenol (Table 2).
41 0 0,1 0,2 0,3 0,4 0,5 Nor m al ized W T (% ) NO GD NO NO GD GD GD GD NO NO
8 3c cC ont rol to 1, 2, an d 3 ug/ kg iso pr ote re nol , sh ow ing 3a 3b Co ntr ol to 1, 2, an d 3 ug/ kg iso pr ote re nol , sh ow ing eff ect on he art rat e. 0 100 200 300 400 -1 0 1 2 3 H e ar t ra te (b p m ) Dose ISO (µg/kg)
*
*
0 20 40 60 80 -1 0 1 2 3 Fr ati o n al sh o rten in g (% ) Dose ISO (µg/kg)*
*
0 2 4 6 -1 0 1 2 3 Sys ch am b e r d ia m e te r (mm ) Dose ISO (µg/kg)*
*
Figure 3. Effects of dose of isoproterenol on (a) heart rate, (b) systole chamber diameter and (c) fractional shortening in anesthetized G. domesticus. Means and SD, n=8. a) Control to 1, 2, and 3 µg/kg isoproterenol, showing effect after 2 and 3 µg/kg isoproterenol. b) Control to 1, 2, and 3 µg/kg isoproterenol, showing effect after 1 and 3 µg/kg isoproterenol.
c) Control to 1, 2, and 3 µg/kg isoproterenol, showing effect after 1 and 3 µg/kg isoproterenol.* = p<0,05.
9 4b 37 38 39 40 41 42 Te m p . (C °) CTRL Iso 1ug/kg 4c 4a 0 100 200 300 400 H e ar t ra te (bp m ) CTRL Iso 1ug/kg 0 10 20 30 V e n t. Fr e q . (b p m ) CTRL Iso 1ug/kg
The effects on the hearts of the domestic chicken by injections of 1µg/kg, 2uµg/kg and 3µg/kg isoproterenol, increased with injection volume. Significant effects were noted in heart rate, fractional shortening and systole chamber size (Figure 3). Ornate tinamous were only exposed to 1 µg/kg.
Then, an analysis comparing Ornate tinamous to domestic chickens before and after injection of 1 µg/kg was performed showing no significant difference in Ornate tinamous systole chamber size (p=0,091) or fractional shortening (p=0,106). In domestic chickens there was a significant
difference in systole chamber size (p=0,030) and fractional shortening (p=0,018). The Lab chart recordings showing temperature, heart rate and ventilation frequency verified that the birds were stable during isoflurane anesthesia and is also showing the affect made by the anesthetic to be able to rule out interference from it (Figure 4). During anesthesia, HR decreased both in N. ornata and G. domesticus (Figure 5).
Figure 4. a) Heart rate readings recorded with Lab chart © 7 Pro instead of Echo wave II, during isoflorane anesthesia. b) Temperature of the bird during anesthesia to exclude any alteration from the anesthesia. c) Ventilation
frequency in breaths per minute to see how the anesthesia affects respiration.
NO NO NO GD GD GD GD NO
10 5b 5a 381,3 360,9 0 100 200 300 400 HR (b p m ) 0 15 30 45 60 Fr ac. Sh o rt (% ) Obser. (n) Chamber Ø dias Chamber Ø sys WT sys WT dias N. ornata CTRL 4 6,4 ± 0,8 3,2 ± 1,0 3,3 ± 0,6 2,0 ± 0,3 ISO 1 µg/kg 5,5 ± 1,4 2,1 ± 0,5 3,9 ± 0,7 2,0 ± 0,2 G. domesticus CTRL 8 8,1 ± 0,9 4,7 ± 0,7 3,4 ± 0,4 2,1 ± 0,4 ISO 1 µg/kg 7,9 ± 1,2 3,7 ± 1,1* 4,0 ± 0,9 2,1 ± 0,4 GD GD GD NO NO NO
Figure 5. a) Heart rate for N. ornata and G. domesticus during isoflurane anesthesia. The lines on top of the bars show un-anesthetized averages of heart rate. b) Increase in fractional shortening, meaning that the heart has a higher ability to contract after injection of the adrenergic agonist. Black bars represent controls.
Table 1. Comparing control ultrasound to 1 µg/kg isoproterenol injection in N. ornata and G. domesticus separately.
* = p<0,05.
NO GD
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5. Discussion
The results of the conscious experiments show that the only significant difference between species can be found in chamber size of the hearts, both in systole and diastole. Ornate tinamous have smaller hearts than domestic chickens and an explanation to this is evolution. Birds as well as mammals stem from a lizard-like ancestor (Jensen et al., 2013), a reptile, which have smaller hearts than birds in general today (Bishop, 1997). The Ornate Tinamou is also known to be an ancient bird (Pearson and Pearson, 1955) that have not evolved as far as other bird species which could be the answer to why the heart of the Ornate tinamou is smaller than that of the domestic chicken.
There was no significant difference between species in the relationship between wall thickness/total diameter (normalized wall thickness), and no significant difference in wall thickness, fractional shortening or heart rate. This is a new conclusion since a difference in wall thickness was expected as seen in previously performed studies on dissected hearts in vitro
(Altimiras, personal communication).
In experiments with anesthetized animals it is important to know the effects of the specific anesthetic agent. Isoproterenol is an adrenergic agonist that works by binding to a β-adrenergic receptor (βar) as an
ordinary catecholamine, such as norepinephrine or epinephrine, to activate intracellular G proteins (Warne et al., 2011). In this case the adenylyl cyclase system is activated which leads to the conversion of ATP to cAMP and to a mobilization and higher availability of calcium ions, which in turn impacts fractional shortening and diastolic function (Washington et al., 2001). My results on the effect by isoproterenol indicate that instead the systolic measurements were altered after injection of isoproterenol, as in the domestic chickens, where a significant decrease in systole chamber size was noted.
The injections of 2 and 3 µg/kg isoproterenol were performed during xylazine/ketamine anesthesia while the injection of 1 µg/kg isoproterenol was performed during isoflurane anesthesia. The results showing an increased heart rate could indicate either that the xylazine/ketamine
anesthesia induces a higher heart rate which is consistent with Kumar et al. (2012), or that the isoproterenol induces the increased heart rate since it is an inotropic agent (Washington et al, 2012). Both are valid suggestions and it might be so that they both also influence the heart rate to increase.
In a previous study done on birds considering the effect of isoproterenol it was determined that it significantly increased the heart rate (Washington et al., 2001) which agrees with the results in domestic chickens in this NO
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study. For the domestic chickens the injections with isoproterenol made the heart pump faster, considering a higher heart rate post injection of 2 and 3 µg/kg isoproterenol, a significant increase in fractional shortening after injection of 1 and 3 µg/kg isoproterenol (Fig 3b) saying that the myocardial contractility was larger after injection, results which all act in accordance with post injection of an adrenergic agonist (Washington et al., 2001), (Toshihide et al., 2012).
When comparing results between Ornate tinamous and domestic chickens after injection of isoproterenol there is an indication that also the Ornate tinamous were affected by the isoproterenol although the difference from the control was not significant. Both the direction and size of the effect were similar, so there is a possibility that if the number of tested Ornate tinamous were the same as for the domestic chickens, also the effects on the Ornate Tinamou would show significant differences in cardiac function. For example fractional shortening, diastole and systole chamber sizes show indications of being affected.
The cardiac muscles in both avians and mammals have a narrow range of working under stress and it seems unable to become stronger (Seymour & Blaylock, 2000). The cardiac ventricle walls seem to grow thicker instead of stronger in the case of gradual higher blood pressure, as that of for example working harder (Seymour & Blaylock, 2000). This would mean that birds in general have a thicker cardiac ventricle wall, comparing to other animals, when considering having a higher blood pressure, which previously has been connected with the evolution of an increased metabolic rate (Wang et al., 2003). It could also mean that Ornate tinamous
presumably have a thicker ventricle wall than the domestic chicken, since they have a smaller heart than other avians in correlation to body mass (Bishop, 1997). This has also been shown in previous studies (Altimiras, personal communication). The results presented in this study differed, however, slightly in that there was no significant difference in wall
thickness comparing domestic chickens and Ornate tinamous. Seymour & Blaylock (2000) also state that ventricular wall thickness not only depends on blood pressure but also on volume loading.
Echocardiography as a measuring tool has been shown to give a qualitative understanding, by a visual observation, of the heart
morphometry (Rahmat et al., 2012). This makes the method fit for evaluating several different cardiac functions, without resulting in any harm to the tested animal. It has also been shown previously that
echocardiography measurements are both repeatable and reproducible with good results (Chetboul et al., 2012). Although there has been some
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measurements in mice of different ages (Vinhas et al., 2013) and also in equine species of different body weight and breed (Al-haidar et al., 2013). This should be taken under consideration when performing ultrasound measurements in future experiments.
5.1 Conclusion
A summary of this study is that the heart of the Ornate Tinamou was smaller than the heart of the domestic chicken in relation to body size. The left ventricular wall thickness of the Ornate Tinamou was not thicker than that of the domestic chicken. The inhalant anesthetic isoflurane lowered the heart rate of both species but it did not cause any other significant effect. Injecting the adrenergic agonist isoproterenol caused a decrease in systole chamber size and increase in fractional shortening in domestic chickens, showing that the agonist worked as predicted. Although it did not give any significant response in Ornate tinamous, the effect size was similar, which indicates that the lack of significant effect may be due to a lower number of observations.
Compared to earlier studies done on Ornate tinamous on wall thickness and diameter of the heart in preserved hearts, this study shows that
echocardiography measurements gives an equal view on how the heart functions - but in living Ornate tinamous. This is of relevance since the possibility to take several measurements of the same animal is given. Also it leads a way of retrieving a lot of variable data since there is no need to euthanize the animal in question, as earlier was needed. Echocardiography can therefore be considered as a valid method of receiving heart
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6. Acknowledgements
I would like to thank Dr. Jordi Altimiras for his supervision and advices; also I would like to thank Dr. Isa Lindgren for her support and teaching during experimental execution. I also would like to thank Dr. Alvaro Garitano for his support and guidance during the work performed in La Paz, Bolivia. Finally I would like to acknowledge the Linnaeus-Palme Exchange scholarship which made it possible for me to perform my study in La Paz, Bolivia.
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