Evaluation of the acceptability of fresh dog cadavers in anatomy education

Color is reflected or emitted from an object, against the spectrum of the visible light (to the wavelength distribution of light energy) as a perceptual response in the mind (Wu and Sun, 2013). There are more than 10 million colors that can be distinguished by eyes in the nature. There are generally three main components of color, including light source, reflected objects and observers. Therefore, color analysis has a widespread use in science, such as physics, chemistry and as well as applied sciences including color diversity such as physiology, anatomy and psychology (Hunt and Pointer, 2011).
        
It is essential to demonstrate tissue, organs and whole body structures practically for the science of anatomy and education. In these fields, the usage of live animals and dissected cadavers is necessary. The cadavers are utilized as fresh or fixed. Although fresh cadavers are the closest models to living tissue, their times of usage are limited due to a sequence of changes that take place immediately after death. The major disadvantage of the fixated cadavers is the fixation solutions that containing the chemicals are expensive and all of them pose risks to human health and the environment (Brenner, 2014; Janczyk et al., 2011). It is also preferred to maintain the livability of animal in order to increase the penetration ability of the fixative solution into the tissues during the preparation of cadavers. In the fixation method, the vessels are evacuated in the animals under general anesthesia and the solution is infused to the body with the heart still pulsating, which in turn pave way for ethical concerns.
        
The putrefaction and autolysis are responsible for the eventuated post-mortem changes on the body after the death. While the activation of the bacteria takes major role in the putrefaction, the intracellular autolytic substances attribute to the autolysis of the body decomposition (Presnell, 2015). Color changes in tissues and organs occur at the beginning of post-mortem alterations following physiological death. The color changes in the muscle tissue are related to myoglobin, the primary color pigment of the muscles (Hunt and King, 2012).
        
Inspection and various analysis methods can be used via colorimetric devices for determination of color changes in tissues and organs of body. Although the inspection is an effective method, its reliability is questionable because of the ability and sensitivity differences between individuals (Hunt and King, 2012; Leon et al., 2006). The color is the most important criteria when evaluating the quality of any product (Ahmad et al., 2015; Huidobra et al., 2003; Kays, 1998). In many studies up to now, color analysis has been carried out for the quality indicator of food and zootechnics products. In the field of anatomy too, the color forms the most important quality indicator in assessing the long-term usability of cadavers as training material. For this reason, color changes in the tissues of farm animals, viz. sheep, goat, cattle,  swine, chicken, fish, etc., have been studied extensively (Boulianne and King, 1998; Bryne et al., 2000; Huidobro et al., 2003; Karabacak et al., 2012; Karabacak et al., 2014; Kim et al., 2017; Oliveria and Balaban, 2006; Rubio et al., 2016). However, in this study, the color change of dog cadavers that is preferred for education material in anatomy was estimated. The color analysis of the dog muscle tissues have not been reported yet.
        
The review of literature revealed, very limited references on the quantitative determination of color in the cadavers. The purpose of this study is to determine the reference values based on the quantitative data of color changes occurring in a fresh dog cadaver by a colorimeter device.

In this study, 10 euthanized dogs (Canis familiaris) cadavers without any chronic, metabolic or zoonotic diseases, known at the time of death, were obtained from Faculty of Veterinary Medicine /Animal Hospital of Ankara University and private clinics in Ankara province. Superficial and broad muscles viz. m. brachiocephalicus, m. triceps brachii, m. latissimus dorsi, m. obliquus externus abdominis and m. biceps femoris were used for the statistical comparisons of measurements. Color changes of each muscles were measured from three points and the average values recorded for each sample.
 
In parallel with the literatures, measurements were carried out at the first at 60^th minute after dissection following death of the animal and at 24^th, 48^th, 72^nd  hours and 7^th day, respectively (Huidobro et al., 2003; Vanezis and Trujillo, 1996).
 
The CR 400/410 Colorimeter (Konica, Minolta, Korea) device with the L * a * b * measurement system specified by the International Commission on Illumination (CIE) standards were used to determine color changes in muscle tissue. In this system, the L * value is the brightness of the product from black to white; whereas a * value indicates reddish color changes from green to red and b * value denotes the bluish color change from blue to yellow (Leon et al., 2006; Oliveria and Balaban, 2006; Vanezis and Trujillo, 1996).
        
Descriptive statistics for each variable were calculated and presented as “Mean±Standard Error of Mean”. Data were subjected to two-way mixed ANOVA (analysis of variance) using General Linear Model procedure. The model included “region (between subject group)” and “time (within subject group)” as the main effects and “region*time” interaction effects. Post hoc testing was carried out for significant interactions and was performed using simple effect analysis with Bonferroni adjustment. A probability value of less than 0.05 was considered significant, unless otherwise noted. SPSS 14.01 was used for statistical analysis.

In the literature, there have not found any studies to evaluate the color change in fresh dog cadavers used as educational material. However, dog cadaver is the most commonly used educational material in the field of anatomy. For this reason, it was preferred as material in study.
        
In this study, utilization time of the fresh cadavers was evaluated in terms of color intensity for education material. The results were expressed as a numerical data for color changes in relation to the working and elapsed time periods. Changes in relation to the working and elapsed time period. When the data collected in the study were interpreted statistically; the change in L*, a*, b* and dE* values over time in the groups were statistically significant (p<0.001) (Table 1, 2, 3, 4). 
 

 

 

 

        
There was a significant decrease in value of the brightness data (L*) of fresh muscle tissues at the end of the 24^th hour. However, at the end of the 7^th day brightness data was became closer to the values of the fresh muscle tissue in all groups. When the samples were evaluated for color changes (a*) from green to red, it was observed that tissues were lost red color in all regions; especially the color of the abdominal region progressed to intense green. In the same manner, b* value was measured the color changes from yellow to blue, was decreased in the abdominal region and the color was became blue (Fig 1). Also, the value of dE* was highest in the abdominal region based on all data at the end of the 7^th day. It was considered that the proximity of the gastrointestinal organs to the abdominal muscles increases the rate of decomposition.
 

        
The solutions and techniques of fixation can change the color of the cadavers. Formaldehyde causes coagulation, makes discoloration of the tissues different tones of grey rapidly (Brenner, 2014; Janczyk et al., 2011; Natekar and Desouza, 2012; Turan et al., 2017). Because of these problems, fixation solution was not used in the study. The color of the tissues were only changed due to decomposition.
        
Karabacak et al., (2012) made first color analysis on m. longissimus from Malyas lambs one day after death. In this study, L*, a* and b* values were measured 39.53±0.511, 15.46±0.322 and 2.22±0.421, respectively. Huidobro et al., (2003) took measurements from m. longissimus at 24^th hour following death on cattle. As 36.97±0.537, 18.40±0.403, and 6.34±0.408 for L*, a* and b*, respectively. In this study, the mean color values taken at 24th hour from the dorsal region (m. latissimus) were 35,33±1,50 for L*, 12.05±0.76 for a*  and 2,11±0,22 for b*. Accordingly, different results of color analyzes were obtained from similar regions among different species.
        
Boulianne and King (1998) estimated L*, a* and b* values on the m. pectoralis of chicken 94.5±0.2; 1.0±0.1; 0.0±0.2, respectively, indicating that, the color change due to the presence and amount of myoglobin in muscules of mammalian and poultry species varies markedly.
        
Turan et al., (2017) measured m. quadriceps femoris at 24^th hour after death and they were obtained values of L*, a* and b*; 20.86±1.74, 1.22±0.57, 2.26±0.95, respectively. In this study, measurements were taken from m. biceps femoris at 24^th hour after death as L*; 38,6±1,02, a*; 10,65±0,48 and b*; 1.40±0.50, indicating that the color analysis from different regions of various mammalian species exhibits marked differences

According to the results obtained from this study that examined the usability of dog cadavers in terms of color change as educational material, especially color changes of forelimb and hindlimb muscles were more similar when we compared with the other body regions. It was concluded that these muscle groups belonging to this region could be used for education under suitable conditions (at +4°C) for 7 days. On the other hand, because of the rapid formation of putrification and autolysis in the abdominal viscera, using time was very limited as a fresh cadaver even in optimum storage condition. In addition, the factors that negatively affect the color change must be eliminated while preparing the cadaver for using in education. For example, it is important to keep the skin on the cadaver without totally skin extirpation for cover over the muscle again. Also removing of the visceral organs for the muscle cadavers will probably give better results to prolong of usage period. On the other hand, if the cadaver is stored at +4°C for using extended periods, it may be more appropriate to make a regional dissection. We can compare the obtained data as reference for the near future studies that will be examined with using some fixatives.