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ROPERTIES OF MOST POPULAR DEHYDRATORS USED IN
PLASTINATION КАЧЕСТВА НАИБОЛЕЕ ПОПУЛЯРНЫХ ДЕГИДРАТОРОВ, ИСПОЛЬЗУЕМЫХ В ПЛАСТИНАЦИИ
SIVREV D.*, USOVICH A.K. **
Thracian University, Stara Zagora, Bulgaria; Medical Faculty, Department of
Human Anatomy,*
Vitebsk State Medical University, Vitebsk, Belarus; Department of Human
Anatomy**
Резюме. В работе проведен сравнительный анализ использования наиболее доступных и применяемых веществ (ацетона и этилового спирта) для проведения обезвоживания анатомических препаратов. изготавливаемых методом пластинации (полимерного бальзамирования). Чистый ацетон для дегидратации использовали охлажденным до -35°С. а растворы этилового спирта возрастающей концентрации - комнатной температуре. Сравнили результаты использования обоих дегидраторов в процессе пластинации свежих нефиксированных и архивных фиксированных в 4% растворе формальдегида препаратов печени. мышц. мозга. тонкой кишки как биологических объектов. Анализ показал. что для дегидратации при выполнении пластинации возможно использование как ацетона. так и этанола. Выбор дегидрататора зависит от плотности и размера анатомических препаратов. оснащения лаборатории. срока изготовления препарата.
Ключевые слова: анатомические препараты. силикон S10 Biodur. пластинация. обезвоживание. ацетон. этиловый спирт.
Abstract. In our investigation we made the comparative analysis of the usage of the most popular and available substances (acetone and ethanol) for dehydration of anatomical preparations which were prepared by plastination method (polymeric embalming). For dehydration pure acetone was used cooled up to -35°С. but ethanol solutions of increasing concentration were of room temperature.
We compared the results of the usage of both dehydrators in the process of plastination of fresh unfixed preparations and old fixed in 4% solution of formaldehyde preparations of the liver. muscles. brain. small & large intestine as biological objects. Our analysis showed. that for dehydration on performing plastination it is possible to use both acetone and ethanol. The choice of dehydrator depends on the density and the size of anatomical preparations. laboratory equipment. and the term of preparation making.
The address for the correspondence: Bulgaria. Stara Zagora 60000. Armejska st. 11. Thracian University. Departament of Human Anatomy. -Sivrev D.
Plastination (polymeric embalming) is a modem technology for durable and safe anatomical objects preparation [15. 16]. We can use it for human body safe dissection [1] and for morphological structure demonstrations [2]. Plastination Biodur-S10-technique is most popular. Many plastinators use it for whole anatomical objects preservation [4. 11] as well as for preservation of the brain [5] and body slices 3-6 mm thick [9. 12]. This method is suitable for students instruction [3] as well as for clinical practice [10. 13].
Plastination process includes four successive stages: fixation. dehydration. impregnation. gas-treatment phase [14]. Dehydration is a substitution process in which outside dehydrator ousts tissue water and fills dead tissues [7]. Usually dehydrator is an organic solvent miscible with water. The water content in dehydrated liquid should be low at the dehydration stage. Dehydration is completed when the concentration of dehydrator is the same in the specimen and dehydration solution. Unchangeable level of dehydrator indicates that the dehydration process is over [15].
It is possible to perform reclamation of some used dehydrators. such as acetone [6. 8]. We think that the properties of available dehydrator agents (acetone and ethanol) need to be further studied. compared and determined.
The aim of this investigation was to determine the properties and indications for use of most popular dehydrators applied in plastination.
Methods
We compared acetone and ethanol used as dehydration agents for dehydration of human and animal organs during anatomical preparations making by silicon plastination method. Fresh and old fixed anatomical specimens of the liver. muscle. brain and intestine were placed in dehydration solution after fixing their volume. The ratio between the corresponding organ (weight) and the used solution (volume) was 10:1. For dehydration we used cooled acetone (up to -35°C) and ethanol of room temperature.
Acetone was placed into the stainless steel container with a tight fast glass cover and it was cooled in a deep freezer at -35°C. Then we placed cooled specimen (+5°C) into cooled acetone and waited for permanent density and temperature of the dehydrator.
We measured acetone percentage every day with the help of preliminarily calibrated areometer. The acetone density is 0.79 and this level corresponds to 100% acetone concentration (no water in fluid). When acetone concentration was less than 98% we replaced dehydration mixture with new acetone. We assumed that dehydration was finished when acetone concentration was unchangeable during three days. Measurement of acetone percentage was performed at +20°C.
Ethanol was placed at room temperature into the similar container made of stainless steel. Biological material was submerged in room temperature ethanol. This procedure was started with 50% ethanol. When the ethanol percentage had levelled down. anatomical preparations were placed into the solutions of increasing concentration (60%. 70%. 80%. 90%. 100%).
The properties of dehydrators were investigated while making organ preparations of different density and structure: liver. skeletal muscle. brain. small and
large intestines. We investigated part of the liver 150x150x150 mm in size. the whole muscle (m.gluteus maximus). part of the brain the thickness of which was 5 mm. part of the jejunum 30 cm in length. part of the colon 30 cm in length.
We compared the properties of dehydrators on fresh (not fixed) and old (fixed for a long time) organs. The process of dehydration was considered by us to be over. when the concentration of dehydrator in the solution was unchangeable. After dehydration completion we determined visual properties of anatomical material and determined changes in its volume.
Results
Fixed organ parts processed with acetone visually preserved their volume and the organ parts surface was tense. Measurement of their volume enabled us to determine that their shrinkage was not more than 15%. Fixed preparations on ethanol dehydration preserved the natural properties of organs but their shrinkage made up about 45%.
Shrinkage of fresh specimens placed directly into dehydration solution was more than 60% and their further impregnation was impossible (tabl. 1).
Table 1
Properties of dehydrated anatomical preparations depending
________________on dehydrators used_________________________________
dehydrator fresh anatomical organs old formalin preparations
appearance shrinkage % appearance shrinkage %
acetone (-35oC) wrinkly surface 60% and more tense surface less than 15%
ethanol (room temperature) wrinkly surface 60% and more different surface less than 15%
Thus. if it is necessary to preserve the natural shape and volume of the specimens before plastination they have to be fixed earlier.
Discussion
These two dehydrators act under different conditions. Acetone demonstrates its properties at temperature -25°C —35°C and when its concentration is more than 98%. Lower level of acetone in solution causes shrinkage, slow dehydration and brings about bad final results. During dehydration preparations are kept in cooled aceton for 3 - 60 days. It depends on the kind of tissue and the size of specimen (tabl. 2).
Table 2
Duration of acetone dehydration depending on the kind of tissue and organ size
preparation size of organ part (mm) Period of time (days)
liver 150 x 150 x 150 60
muscle whole m. gluteus maximus 28
brain slices 5 mm thick 3
intestine whole large intestine 7
For ethanol stepwise dehydration room temperature was sufficient. We controlled density (0,79, identical with acetone) and purity of ethanol. Specimen can be stored in 70% ethanol during unlimited period of time. The ethanol dehydration process is slower than acetone technology (more than 5 weeks). When we used old formalin preparations their shrinkage was not more than 45%. Ethanol dehydration continues during 7 - 100 days (tabl. 3).
Table 3
Duration of ethanol dehydration depending on the kind of tissue and organ size
preparation size of organ part (mm) period of time (days)
liver 150 x 150 x 150 100
muscle whole m. gluteus maximus 45
brain slices 5 mm thick 7
intestine whole large intestine 15
Specimen storage in dehydrator is very important because too long dehydration reduces tissue elasticity and too short storage is a reason of bad dehydration.
When acetone temperature is -19°C and when its concentration in the air exceeds 13% it can become an explosive mixture. Its ignition temperature is 560°C. Ethanol can inflame at +12°C but its ignition temperature is 425°C. Open fire can inflame acetone and ethanol vapour. These dehydration agents properties require the observation of safety regulations.
The complete dehydration of specimens provides for the complete replacement of dehydrators by silicone in the preparation at the stage of impregnation. The degree of shrinkage depends mainly on the stage of dehydration process. On proper dehydration all the details of the structure of preparations are seen as clearly as those of the native ones (Fig. 1).
Fig. 1. A - The inner surface of large intestine after dehydration with acetone
(old formalin preparations).
B - The inner surface of small intestine after dehydration with acetone &
silicon impregnation (old formalin preparations). C - Part of the external surface of the liver after acetone dehydration (old formalin preparations). D - 5 mm thick brain slice after ethanol dehydration (old formalin preparation).
Our investigation showed that acetone and ethanol have some advantages and disadvantages that determine their application for dehydration in plastination (tabl.
4).
Table 4
Properties of acetone & ethanol used or dehydration in plastination
dehydrator advantages disadvantages
acetone less than 3 acetone changes; short period of time; possibilities of reclamation; safe at -25oC; relatively safe transport and storage. -30oC and more; changes in specimen quality on long storage; previous cooling of specimen; harmful for human health.
ethanol room temperature; unlimited storage at 70% concentration; relatively safe for human health. 5-6 ethanol changes; long period of dehydration; becomes dangerously explosive at +12oC
The properly performed dehydration enables the preservation of the elasticity of anatomic specimens (Fig. 2).
\
Fig. 2. The preservation of elasticity of human intestine specimens. Plastination was performed by Biodur -S10-technique after dehydration with acetone (old
formalin preparation).
Conclusions
1. Every dehydrator has a specific area of its application, that determines the indications for use of these dehydrators in plastination.
2. Different dehydration agents need a specific period of time for their action. It is possible to change dehydrators to shorten the period of dehydration. Duration of ethanol dehydration is twofold in comparison with acetone dehydration.
3. The observation of safety regulations is very important for normal work in every plastination laboratory.
4. Cooled acetone dehydration is a better method than ethanol stepwise dehydration because in this case shrinkage is less and the process itself is shorter.
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