PRESERVATION SOLUTION

Abstract: A preservation solution intended for organs and tissues or parts thereof from humans and animals and containing calcium and nitroglycerine is described. Moreover, the use of such a preservation solution and a method for preserving organs and tissues or parts thereof from humans and animals in such a preservation solution are described.

Description: PRESERVATION SOLUTION Field of the Invention The present invention relates to a preservation solution for organs and tissues or parts thereof from humans and animals, containing dextran, glucose, electro- lytes and a buffer. Background Art In coronary artery surgery (about 800 operations per one million inhabitants a year) and in the peripheral vascular surgery (about 100 operations per one million inhabitants a year) , use is today in most European clinics made of so-called physiological saline solution (0.9% NaCl) as solution for washing away blood from blood-vessel transplants and for storing blood-vessel transplants before inserting them m their new positions. In coronary artery surgery use is generally made of the vena sapena magna, i.e. the superficial vein extending from the inside of the foot over the inner ankle and along the inside of the lower leg and the thigh-bone to the groin, where it joins the thigh vein (vena femora- lis) . In a coronary artery operation, first the vena sapena magna in one leg is removed, while the breastbone is opened and preparatory measures are taken for connec¬ tion to a heart-lung machine. After removal of the vena sapena magna, this blood vessel is flushed with saline solution of the above-mentioned type, on the one hand to wash away all blood from the inside of the vessel and, on the other hand, to ensure that one has not neglected to ligate any branch of the vein, .e. to tie the branches with a thread with a view to preventing leakage there- through. Subsequently, the removed vein is placed m a dish containing saline solution of room temperature, i.e. 20-25°C. Then the heart-lung machine is connected and cardioplegia is given to the heart. About 15-20-cm-long segments are cut off from the vein in the dish and are sewn as a so-called aortacoronary vein bypass to the sick coronary arteries. Before all vessel transplants are sewn and the blood again circulates through these, a period of up to 2 h may have passed. For patients who are to have one or two cardiac valves inserted as well, this period can be still longer. Instead of storing the vessel trans¬ plants in saline solution before being sewn, some sur¬ geons use the patent's own blood. Blood is then drawn off from the patient and is placed in a dish. The transplant is then allowed to lie in this blood before being sewn to the heart. First the temperature is 37°C but rapidly falls to room temperature. It is considered that since blood is the medium to which the vessel is exposed throughout life, this must be the ideal storage medium for a vascular transplant. In heart surgery, the coronary artery surgery con¬ stitutes about 70% of the operations on adults. It is well-known from studying experiments on animals that when a vascular transplant is used where the endothelium is destructed, so-called intimal hyperplasia is released and the transplants are occluded after some time (the vascu¬ lar lumen becomes smaller and smaller and at last the flow of blood is stopped completely) . In clinical follow- up studies, it has been found that 5 years after a coro- nary artery operation about 30-50% of the venous trans¬ plants have been occluded, and when these are studied histologically, a pronounced mti al hyperplasia will be discovered. This thus applies to venous transplants which have been rinsed and stored in the above-mentioned physiological saline solution. The applicant's research team has intensely studied both short-term and long-term preservation of blood ves¬ sels. Regarding short-term preservation of blood vessels, i.e. up to 2 h preservation, it has been found that a physiological saline solution is toxic to the vascular endothelium. If a saline solution is flushed through e.g. the arteπa iliaka of a rat, mtimal hyperplasia can be found in the vessel after about one month. If, on the other hand, serum is used for rinsing correspondingly, no intimal hyperplasia will be discovered. Thus, the use of a physiological saline solution as preservation solution is not favourable to the blood vessels. All the same and in the absence of a better alternative, the clinical use of physiological saline solution, however, continues in most thoracic surgery centres throughout the world. The applicant's research team has also demonstrated that also blood is not satisfactory as preservation solu¬ tion. Blood of room temperature which is stored in a dish and is not oxygenated is extremely toxic to the endothe- lia of the blood vessels and inhibits the endothelial function to a considerable extent. This may seem to be a paradox, but since blood is an organ that has its normal function only when it is moving and is continuously oxy¬ genated in the lungs, it cannot function in the normal manner. Deoxygenated, not moving blood contains, like all other blood, white and red blood corpuscles and thrombo- cytes. It is well known that white blood corpuscles are activated in case of hypoxaemia (low concentration of oxygen) and then produce toxic substances. The appli¬ cant's research team has demonstrated that Ringer's lactate, Kreb' s solution and an LPD ("low potassium dextran") solution could preserve blood vessels for 2 h, both at refrigerator temperature (4°C) and room tempera¬ ture (20°C) . However, of these three solutions, only the LPD solution contains a colloidal-osmotically active sub¬ stance, viz. dextran 40, a large sugar molecule of an average molecular weight of about 40 000 daltons. The colloidal osmotic pressure is the "suction pressure" that protein molecules and other bigger molecules which cannot pass the capillary membrane exert so as to retain fluid in the capillaries. This LPD solution, which will be de- fined in more detail below, thus has a colloidal osmotic pressure which is slightly higher than that of normal plasma. In a series of studies, other scientists have demonstrated that dextran 40 is favourable for preventing thrombosis by covering the endothelium, which means that activated white blood corpuscles cannot get stuck with their receptors and thus invade and consequently destruct the vessel. In long-term preservation of blood vessels, i.e. more than 24 h, for instance 36 h, Ringer's lactate or Kreb' s solution cannot affect the blood vessel in a sufficiently satisfactory manner. However, the LPD solu¬ tion produced a better effect. In the remaining clinical organ transplantation to¬ day, two organ preservation solutions are prevalent, i.e. the so-called University of Wisconsin solution and the Euro-Collins solution. These solutions are so-called intracellular preservation solutions, i.e. they have a high potassium content and a low sodium content. The pur¬ pose of this composition is that the cells should be allowed to "swim" m an intracellular environment. The applicant's research team has, however, after extensive studies demonstrated that in respect of blood vessels, the high potassium content of these intracellular solu¬ tions causes a violent vascular spasm. Therefore there is no logic in using preservation solutions of intracellular electrolyte composition when storing vascular trans¬ plants . In heart surgery, a continuously increased use of so-called homotransplants, i.e. from one individual to another of the same species, has recently become common. This means that blood vessels are removed from recently deceased individuals, in most cases in institutes of forensic medicine, and after a short-term storage, these blood vessels are cryopreserved, i.e. they are stored in fluid nitrogen at low temperatures. In heart transplanta¬ tions it is m many cases also possible to make use of the aortic root including the valve apparatus of the heart that are to be removed and discarded in any case. At present, this preparation is placed n a saline solu- tion until it is being taken care of the next day to be cryopreserved. In plastic surgery, the extent of microsurgical pro¬ cedures increases, m which parts of organs, including blood vessels, are moved from one place in the body to another, i.e. autotransplantations . Also m this part of surgery, there is a need of a satisfactory preservation solution for the vascular system in the organs involved, such that when the organ is inserted, a perfect circula- tion of the blood can be established when the flow of blood is started. A further problem, which has recently been discov¬ ered, is that in reperfusion of a transplanted organ or blood vessel, injuries to the cells may arise owing to detrimental free oxygen radicals within a few seconds up to some minutes after the implantation. Summing up, there is thus at present no quite satis¬ factory preservation solution available for organs and tissues or parts thereof from humans ana animals, espe- cially for blood vessels, which are to be transplanted or stored for some other purpose, for instance for medical studies. In these fields, there is thus a great global need of a preservation solution which does not have the drawbacks of existing preservation solutions and which preserve the original structures and functions of the organ, the tissue or parts thereof to a much greater extent and for a considerably longer period of time. Object of the Invention The object of the present invention is to eliminate the above drawbacks of existing preservation solutions for organs and tissues or parts thereof from humans and animals . This object is achieved by a preservation solution of the type mentioned by way of introduction, which be- sides contains calcium and nitroglycerine. Further fea¬ tures are stated in the appended claims. The present invention also relates to use of the preservation solution, and to a method for preserving organs and tissues or parts thereof from humans and ani¬ mals in the preservation solution. Description of the Drawings Fig. 1 shows comparative tests between preservation solutions containing the combination of calcium and nitroglycerine and these ingredients separately, and F g. 2 shows the effect of calcium on muscle cells and endothelial cells in blood vessels. Description of the Invention The applicant's research team has, after extensive studies and experiments, arrived at the surprising and seemingly contradictory result that calcium has a previ- ously not shown potent function in long-term preservation of, above all, blood vessels and can preserve the smooth muscle function in blood vessels for up to 36 h. It has for a long time been considered that calcium should not be present in preservation solutions for transplants. The reason for this is that in case of ischaemia, i.e. localised lack of oxygen in a tissue, the intracellular calcium concentration rises, and therefore one d d not want to add further calcium so as to make this available to the cells. The applicant's research team has, however, carried out comparative studies show¬ ing that long-term preservation of blood vessels m cal¬ cium-free solutions is destructive to the blood vessel involved. The presence of calcium is necessary in the solution, among other things for maintaining the mteg- rity of the vascular endothelium. The vascular endothe ¬ lium contains hydrocarbon chains which are bound to proteins in the cell membranes, and these constitute a so-called layer of glycocalyx. This is a thin layer of a mucous substance (composed of sugars) which is considered to enclose the cell membranes and which is important to the properties of immunity of the cell and makes the cell wall permeable. These hydrocarbon chains are bound to- gether by, among other things, calcium. If the vascular endothelial cells are subjected to calcium-free solutions for a long time, a disintegration of the important layer of glycocalyx is assumed to take place, and the function of the endothelium thus cannot be perfect. Evidence of these discoveries has been obtained through electron microscope studies of cell membranes in blood vessels that have been stored in preservation solutions with and without calcium. Moreover the applicant's research team has found that the endothelial function in blood vessels can be maintained in a surprising manner by adding nitro¬ glycerine to the preservation solution. Nitroglycerine probably constitutes a substrate for nitrogen oxide, NO, i.e. the endogenous substance that is produced in the endothelium and that constitutes one of the so-called endothelium-dependent relaxation factors (EDRF) . In a comparative experiment with LPD solutions con¬ taining calcium and nitroglycerine, respectively, and an LPD solution containing both calcium and nitroglycerine, it has been found that a still better preservation of the EDRF function could be achieved in the presence of nitro¬ glycerine in the solution. As shown in Fig. 1, the combination of calcium and nitroglycerine in a transplantation solution for storing a rat aorta gives better results in respect of contrac¬ tion than if the solution does not contain either calcium or nitroglycerine. The use of calcium in the absence of nitroglycerine in a preservation solution according to the present invention yields, in itself, a much better effect than that achieved by using prior art preservation solutions. In combination with nitroglycerine, a still better effect is obtained. Even if the effect of calcium and nitroglycerine in combination is not considerably higher than the effect of calcium in the absence of nitroglycerine, every improvement of the effect in this field is very important for the subsequent transplanta¬ tion to be as successful as possible. Morphological pictures concerning the satisfactory and unexpected effect of calcium are shown in Fig. 2. The pictures show on the one hand smooth muscular cells from blood vessels and, on the other hand, endothelial cells from blood vessels that have been stored for a long time with or without calcium. In case of preservation without calcium (a: smooth muscular cell and c: endothelial cell) , there appears an enormous swelling of the nuclei and the cytoplasm in both types of cells. In case of preservation with calcium, normal structures of the cells appear (b: smooth muscular cell and c: endothelial cell) . Nitroglycerine has also been found to have an lmpor- tant effect in the reperfusion of the blood vessel or the organ after implantation. Cell injuries may in fact arise within a few seconds up to a minute or two after the im¬ plantation by the forming of free oxygen radicals. The nitroglycerine has a so-called scavenging effect on these radicals and must be present directly in the implantation operation to reduce this problem. This requirement is satisfied by the nitroglycerine being included, together with calcium, in the preservation solution according to the present invention, in which it also exerts its favourable combination effect on the endothelium. The expression "organs and tissues or parts thereof from humans and animals" as used throughout the patent application concerns in its widest sense any type of organ and tissue structure that has been obtained from animals and humans and that preferably can be trans¬ planted to humans and animals by autotransplantation, syngeneic transplantation, allotransplantation and xeno¬ transplantation (for instance organs from pig and monkey to humans) . The preservation solution according to the invention is particularly suited for blood vessels or parts thereof and lungs. By the term "blood vessel" is thus meant veins, arteries and capillaries including the aortic root with valve apparatus and the pulmonary root with valve apparatus (so-called homografts) . Extensive studies of the preservation of other parts of the body than blood vessels, lungs and kidneys have not yet been carried out, but there is at present nothing that indi¬ cates that such organs would be affected detrimentally by preservation in the solution according to the invention. However, for the preservation of hearts, specific concen¬ trations of electrolytes in the preservation solution are necessary, which will be evident from the following. The term "transplant" used throughout the patent application, also called graft, concerns organs and tis¬ sues or parts thereof according to the above definition that are to be transplanted in any of the manners as men- tioned. The term "preservation solution" used throughout the patent application concerns the solution or liquid in which the above-mentioned organs and tissues or parts thereof are to be stored, for instance before transplan- tation. The preservation solution is, as mentioned above, also intended to be used for preservation without subse¬ quent transplantation, for instance for different kinds of examinations and studies. In a preferred embodiment, the inventive preserva- tion solution contains, in addition to calcium and nitro¬ glycerine, also about 5-15, preferably about 7-12% by weight low-molecular dextran having an average molecular weight of about 1 000 daltons (e.g. dextran 1), about 3- 8% by weight high-molecular dextran (e.g. dextran 40, dextran 60, dextran 70 or higher, such as dextran 120) , about 0.1-2.6% glucose, buffer (e.g. phosphate, THAM or hydrogen carbonate) , about 4-25 M potassium, about 1-16 mM magnesium, about 50-150 mM sodium and about 50-150 mM chloride. 5% by weight dextran 1 theoretically results in an osmolarity of about 50 milliosmoles . When this is added to the solution, the concentration of electrolytes (for instance sodium and chlorine) must be reduced so as to prevent the solution from becoming hyperosmolar. In a further preferred embodiment of the invention, the preservation solution contains, in addition to cal- cium and nitroglycerine, also a Perfadex solution, which is commercially available. The Perfadex solution contains 50 g/1 dextran 40 of an average molecular weight of 40 000 daltons, 5 mM glucose, phosphate buffer which gives a phosphate content of 0.8 mM, 6 mM potassium, 0.8 mM mag- nesium, 138 mM sodium, 142 mM chlorine and 0.8 mM sul¬ phate and an addition of THAM buffer such that a pH of about 7.4 is obtained. All the above-mentioned contents are based on the final preservation solution. Regarding the preservation of hearts m the preser¬ vation solution according to the present invention, the potassium content must be increased to about 16-25, pref¬ erably to 20 mM, and the magnesium concentration to about 12-16 mM. The concentration of sodium then decreases such that the osmolarity of the solution does not exceed about 340 milliosmoles per litre. When storing other organs and tissues, the potassium concentration usually is about 4-6 mM and the magnesium concentration usually is about 1-4 mM, based on the final preservation solution. The Perfadex solution, which is one type of the above-mentioned LPD solution, has previously been found to function as long-term preservation liquid for trans¬ plants, especially kidneys, before transplantation. Perfadex is a so-called extracellular solution, i.e. having a sodium and potassium concentration which is about the same as that in plasma. Tne phosphate buffer and the THAM buffer therein have a great buffering capac¬ ity and give the solution a pH of 7.4. The glucose func¬ tions as substrate in the metabolism, and dextran 40 gives the solution a colloidosmotic pressure correspond¬ ing to that of normal plasma. All greater dextran molecules, such as from dextran 40 and upwards, suffer from the drawback that when admin¬ istered, they may cause anaphylactic reactions. Only small amounts of these molecules suffice to cause these fatal reactions. Low-molecular dextran, for instance dextran 1, also called Promiten, is therefore adminis¬ tered to patients in these contexts with a view to coun¬ teracting this reaction. The risk of such anaphylactic reactions is eliminated by the preservation solution according to the invention containing low-molecular dextra . However, the Perfadex solution does not in itself have satisfactory properties m respect of maintaining the smooth muscle function and the endothelial function m blood vessels. The addition of calcium and nitroglycerine to Perfadex results, however, in a significant improvement of the properties of the preservation solution m respect of maintaining these functions in long-term preservation. In the preservation solution according to the present invention, calcium is present in a concentration of 0.3-1.5 mM, preferably about 0.7 mM, baseα on the final preservation solution. Calcium can be added sepa¬ rately during the preparation of the preservation solu- tion in the form of a solution, for instance an aqueous solution, of calcium or is added in solid state, such as a salt, preferably CaCl ∑ , the negatively charged ion m the salt being such as not to detrimentally affect the properties of the preservation solution. In the preservation solution according to the pres¬ ent invention, nitroglycerine is present in a concentra¬ tion of 10 "4 -10 ~7 M, preferably about 10 ~5 -10 ~5 M, based on the final solution. Nitroglycerine can be added sepa¬ rately during the preparation of the solution, either m the form of a solution or in solid state. A usable alter¬ native to nitroglycerine is a preparation called Nipride, whose active ingredient is nitroprusside, e.g. in the form of nitroprusside sodium. Another alternative to nitroglycerine is papavenne. According to the present invention, also heparin can optionally be added to the preservation solution m a concentration of 1-12 IE/ml, preferably 10 IE/ml, based on the final preservation solution. Heparin is used for the purpose of preventing coagulants from forming on the inside of the vascular transplant in case it should be impossible to wash away all blood when removing the organ. Moreover, extensive studies have shown that hepa¬ rin is not toxic to the endothelial function. As an alternative to common heparin, a so-called low-molecular heparin, preferably fragmin (Daltepaπn) , can be used. Besides, antibiotics can optionally be added to the preservation solution according to the present invention. An example of usable antibiotics is benzyl penicillin in a concentration of about 120 mg/1. All ingredient m the preservation solution accord¬ ing to the invention, also the optional ones, can be added separately and in any order whatever. In a pre¬ ferred embodiment, calcium, nitroglycerine and optionally heparin and/or an antibiotic are added to a ready-mixed solution, e.g. Perfadex, containing the remaining ingre¬ dients for producing the preservation solution. When used, the pH of the preservation solution should be kept in a range of about 7.4-7.6. Any buffer whatever that yields the necessary pH and that does not detrimentally affect the function of the preservation solution can be used. The inventive preservation solution is ideal for its purposes by containing the following ingredients and having the following functions: 1) extracellular composition of electrolytes includ ¬ ing calcium, i.e. no electrolytes causing vascular spasm, 2) an effective buffer system that can keep a pH of about 7.4-7.6, 3) colloidosmotically active substances (e.g. high- molecular dextran) , which can give the solution a col¬ loidosmotic pressure corresponding to that of plasma, i.e. 25 mm Hg or higher, when necessary, 4) a low-molecular, but cell-membrane-impermeable substance (e.g. 5-15% dextran 1), which can give the solution an osmolaπty n the range of 50-150 mil¬ liosmoles, 5) an efficiently vasodilatmg substance, e.g. nitroglycerine, nitroprusside or papavenne, 6) a coagel-inhibitmg additive, e.g. heparin or fragmin (Daltepaπn) , 7) glucose for the metabolism during the term of preservation, 8) optionally an antibiotic which is not tissue- toxic m long-term preservation, and 9) increased potassium and magnesium contents for the storing of hearts . In relation to prior art preservation solutions for organs and/or tissues which, for instance, are to be transplanted, the preservation solution according to the present invention thus contains two new active ingredi¬ ents which each separately, and especially in combina¬ tion, m a surprising manner favourably affect the organs and/or tissues during preservation. The effects of these two ingredients, i.e. calcium and nitroglycerine, are not previously known in this context, and make the inventive preservation solution a globally seen very promising preparation. The inventive preservation solution can be held in any conventional container that is suitable in the art. The invention further relates to a method for pre¬ serving organs and tissues or parts thereof from humans and animals in a preservation solution according to the invention, the organ and tissue or parts thereof being flushed with and immersed in the preservation solution, and the temperature of the preservation solution being adjusted in the range of 4-24°C for a time of at most about 2 h for short-term preservation, or at a tempera¬ ture in the range of 0.5-8°C for at most 36 h for long- term preservation. The organ, tissue or parts thereof from humans and animals that have been removed from the donor involved should, if possible, be flushed n situ and/or as soon as possible after that be placed in the preservation solu¬ tion for minimising detrimental effects, if any. The optimal storing temperature for the inventive preservation solution is completely dependent on the planned storing time. In case of e.g. short-term preser¬ vation of blood vessels, i.e. up to 2 h, the optimal tem¬ perature is room temperature. Too low temperatures are not optimal for the endothelium, but it resists down to 4°C fairly well. After about 2 h reperfusion in vivo after the transplant has been fixed, the endothelial function has been restored completely. When decreasing the temperature to 1°C, the function of the endothelium will be deteriorated and is not restored after 2 h, but after 24 h. For long-term preservation, it is thus an ab¬ solute requirement that the temperature be low. 0.5-8°C, preferably 4°C, has been found to be most advantageous. Different organs have a specific optimal storing tempera- ture when stored up to 36 h. In the EU alone, having more than 400 million in¬ habitants, for instance more than about 300 000 coronary bypass operations are performed each year, and in Sweden about 7 000 a year. In the USA, this type of operations is the most common operation in all categories. A preser¬ vation solution according to the present invention should, for instance, also be available for taking care of homotransplants in institutes of forensic medicine. As mentioned above, there is also a great need of storing blood vessels in a satisfactory preservation solution until they can be cryopreserved the next working day. In peripheral vascular surgery and in plastic and recon- struction surgery, there is also a need of having such a preservation solution.

Claims: CLAIMS 1. A preservation solution for organs and tissues or parts thereof from humans and animals, c h a r a c ¬ t e r i s e d in that it contains nitroglycerine and calcium. 2. The preservation solution as claimed in claim 1, c h a r a c t e r i s e d in that it contains aoout 10 "4 - IO "7 M nitroglycerine and about 0.3-1.5 mM calcium, based on the final preservation solution. 3. The preservation solution as claimed claim 2, c h a r a c t e r i s e d m that it contains about 0.7 mM calcium and about 10 5 -10 "6 M nitroglycerine, based on the final preservation solution. 4. The preservation solution as claimed in any one of the preceding claims, c h a r a c t e r i s e d m that it optionally also contains about 1-12 IE/ml heparin and/or about 120 mg/1 antibiotic, preferably benzyl peni- cillm, based on the final preservation solution. 5. The preservation solution as claimed any one of the preceding claims, c h a r a c t e r i s e d n that calcium and nitroglycerine, and optionally heparin and/or an antibiotic, are present n a solution contain- mg about 5-15% by weight low-molecular dextran having an average molecular weight of about 1 000 daltons, about 3- 8% by weight high-molecular dextran having an average molecular weight of 40 000-120 000 daltons, about 0.1- 2.6% glucose, buffer, about 4-25 mM potassium, about 1- 16 mM magnesium, about 50-150 mM sodium and about 50- 150 mM chloride, based on the final preservation solu¬ tion. 6. The preservation solution as claimed in any one of claims 1-5, c h a r a c t e r i s e d in that calcium and nitroglycerine, and optionally heparin and/or an an¬ tibiotic, are present in a solution containing 50 g/1 dextran 40 having a molecular weight of 40 000 daltons, 5 mM glucose, 0.8 mM phosphate buffer, 6 mM potassium, 0.8 mM magnesium, 138 mM sodium, 142 mM chlorine and 0.8 mM sulphate, 0.24 ml THAM buffer also being added, based on the final preservation solution. 7. The preservation solution as claimed in any one of the preceding claims, c h a r a c t e r i s e d m that, when a heart is to be stored the preservation solution, the concentration of potassium is about 16- 25 mM, and the concentration of magnesium is about 12- 16 mM, based on the final preservation solution. 8. The preservation solution as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that its pH is about 7.4-7.6. 9. The preservation solution as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that heparin is replaced by a low-molecular heparin, preferably fragmin. 10. Use of a preservation solution as claimed in any one of the preceding claims, c h a r a c t e r i s e d that organs and tissues or parts thereof from humans and animals, which are to be transplanted to humans and animals, are flushed with and immersed m the preserva¬ tion solution. 11. Use as claimed in claim 10, c h a r a c t e r - l s e d in that blood vessels or parts thereof are flushed with and immersed in the preservation solution. 12. Use as claimed in claim 10, c h a r a c t e r ¬ i s e d in that vena sapena magna or parts thereof are flushed with and immersed in the preservation solution. 13. Use as claimed in claim 10, c h a r a c t e r ¬ i s e d in that lungs are flushed with and immersed in the preservation solution. 14. A method for preserving organs and tissues or parts thereof from humans and animals, c h a r a c - t e r i s e d m that the organ and the tissue are flushed with and immersed in a preservation solution as claimed m any one of claims 1-9 and stored at a tempera- ture of 0.5-8°C for at most 36 h for long-term preserva¬ tion, or at a temperature of about 4-2 °C for at most 2 h for short-term preservation.

Inventors: STEEN STIG, STEEN, STIG
Applicants: STEEN STIG, STIFTELSEN FACTHOR, STEEN, STIG
Application year: 1996
Main classification: A01N1
IPC codes: A01N1