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The analysis of hydrocolloids applying as cryoprotective substances in freezing and storage of frozen food was the aim of this study. Characteristics and examples of carrageens application were also described. It was stated that including of polisacharide hydrocolloids in the modified food influenced the course of freezing process. Their activity is different and depends on their structure and functional properties. Moreover carrageens significantly reduce the negative influence of the process on structural changes of stowed frozen food. [ABSTRACT FROM AUTHOR]

Freezing and thawing of hemopoietic stem cells (CD34+) are indispensable stages between their collection from peripheral blood or bone marrow and transfusion to the patient who has previously undergone myeloablative chemotherapy. At present there are two methods of the cells freezing: non-controlled--placing CD34+ cells directly in the final temperature and rate-controlled--gradual cooling them at programmed speed. Non-controlled freezing leads to the considerable loss of cells viability (up to 50%), but it doesn't require the expensive equipment used for rate-controlled freezing (viability loss up to 10%). In order to reduce the loss resulting from intra-cellular crystallization of water the haemopoietic cells are mixed with one of the cryopreservative substances: dimethylsulphoxide-DMSO, hydro-xyethylstarch-HES, polyvinylpyrrolidone-PVP or glycerol. The most important moment of freezing procedure is the phase transition of water. The adequate shape of the cooling curve leads to a considerable reduction of the loss of the cells viability. Further cooling is the most effective when it takes place at max. speed of 5 degrees C/min. The storage of the frozen cells is the best in very low temperatures (-170-180 degrees C-vapour phase of liquid nitrogen), but mechanical freezers (-80 degrees C) are used, too. The thawing procedure should be very fast (up to 90 degrees C/min.) and the defrosted cells must be immediately transfused to the patient because of very high toxicity of cryopreservative agents to non-frozen cells. The cells viability estimation is carried out with trypan blue or cytofluorometrically after incubation with propidine iodide.

Freezing of the human embryos has been routinely used in the world for over 10 years in the treatment of infertility by the ART. Excessive fertilized oocytes and embryos can be frozen and preserved in the temperature of liquid nitrogen. The risk of multiple pregnancies is reduced and enhancement of pregnancy rates can be obtained owing to cryopreservation. The author presents theoretical principles of embryo freezing by slow cooling with 1, 2 propanediol and saccharose as a cryoprotectant.

The authors present preliminary results of cryopreservation of embryos in IVF-ET programme in the Institute of Obstetrics and Gynecology in Białystok. The method of slow cooling embryos with 1, 2 propanediol and saccharose were used. In the group of 136 patients with excess embryos after the transfer of two fresh embryos 29 pregnancies (21.3%) were obtained. After the transfer of frozen/thawed embryos up till now 5 pregnancies have been obtained (one child born, 3 pregnancies ongoing, 1 abortion).

Spermatozoon survival rate was analysed after freezing at the temperature of liquid nitrogen (-196 degrees C) with the application of three different cryoprotector substances, vitelline and non-vitelline. A modified method, based on the use of sperm cells of small diameter, was introduced in freezing semen. The best results were achieved while using non-vitelline, multi-ionic cryoprotector. It was found out that glycerol alone does not protect semen from the effects of low temperature.

The authors assessed the phagocytic ability of granulocytes, the ability of blastic transformation of lymphocytes after phytohaemagglutinin (PHA) stimulation in vitro culture, and the viability and number of these cells before freezing and after thawing. No significant differences were found in the quality of granulocytes stored in cryoprotective medium containing 13% of glycerol or 15% of PVP. On the other hand, much worse results were obtained in both cases in comparison with previous investigations in which DMSO was used as the protective agent. It was observed also that lympocytes stored in a cryoprotective medium containing 15% of PVP were not significantly depressed and retained their ability of blastic transformation in vitro under PHA stimulation. Similar results were obtained using in previous investigations a cryoprotective medium with DMSO.

Biochemical properties of erythrocytes frozen in the presence of hydroxyethyl starch (HES) as preserving substance produced in this country were assessed. Erythrocytes were frozen adding HES in 4 different concentrations. The most favourable results were obtained with erythrocytes subjected to the action of HES in 30% and 35% concentrations. The erythrocyte 2,3-DPG level during freezing with 35% HES was within normal limits while it decreased by 10% after defreezing when 30% HES had been used. The ATP concentration in erythrocytes fell by 50% in relation to the initial value. A slight fall of P50 was observed and erythrocyte loss after defreezing did not exceed 10%. The 35% HES solution in a 0.15 mol/l sodium chloride solution was most favourable for freezing erythrocytes in liquid nitrogen. A simple method of preparation of defrozen erythrocytes for transfusion was elaborated.

The effects of HES and HES + DMSO used as cryoprotective media for storage of human platelets in liquid nitrogen and vapor phase of liquid nitrogen were studied. Solution of 6% and 15% HES with molecular weight ranging from 65,000 to 250,000, and 10% DMSO were used. The criteria accepted for evaluation of the efficiency of these cryoprotective media were: 1. platelet counts, 2. participation of platelets in the processes of hemostasis measured in vitro by the ability of platelets to release adenine nucleotides (ATP + ADP) after thrombin stimulation. It was found that 15% HES is a more effective cryoprotective medium than 6% HES. The use of 15% HES + 10% DMSO gave similar results as the use of 10% DMSO alone.