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In the nearly 15-month mission aboard MIR the cosmonaut-physician and members of three crews (MIR-15, -16, and -17) carried out a program of hematological investigations. Most of the changes related to the red blood system and included reduction in hemoglobin and hematocrit. Erythrocytes had decreased concentration and took on abnormal forms. There were also signs of altered metabolism of erythrocytes. Of interest are phase-by-phase variations in the levels of erythrocytes in the course of long-term stay in microgravity, and absence of a convincing correlation between hemoglobin, erythrocyte and hematocrit levels. But for lymphocytosis that returned to the norm already on the first day of recovery, no material changes occurred to the leukocyte profile. Investigations at the landing site displayed erythropenia, decreased reticulocytes and ensuing reticulocyte reaction, and gradual regain of the erythrocyte number that can be viewed as a normal physiological reaction of the blood system to the set of factors of spaceflight and early readaptation. Besides, the investigations showed a large individually of blood reactions to prolonged stay in space flight.

The main hematological parameters of the peripheral blood were analyzed in a large group of normal males--cosmonauts. The observation period comprised from 10 to 28 years. A total of 22 parameters were used to obtain the criterion for the interpretation of the results of peripheral blood investigation.

The authors' opinion that adaptation inhibition of erythron functioning under weightlessness produces an unfavourable effect on the optimal physical state of a cosmonaut and his working capacity in the post-flight period has been confirmed by the analysis of certain hematological parameters studied in cosmonauts. The data obtained have necessitated investigation of threshold values of erythron functioning under weightlessness, and creation of artificial gravitation on board the piloted space ship to normalize erythropoiesis. Investigation of these problems of space hematology would be helpful in validation of the limits of human's long-term stay under weightlessness, and in the pre- and post-flight period management.

The study of serum samples, obtained from 15 cosmonauts before and after space flights, with the use of the indirect fluorescent method showed that in 7 cosmonauts antibodies to different elements of the human heart muscle appeared after flights. Strong and very strong luminescence of the elements of heart muscle tissue was detected in the cosmonauts after the third space flight. When studying the sera on sections of bovine heart muscle tissue, the reactions of the sera taken before and after flights were found to have no essential differences.

The study was performed on 41 healthy men, aged 19 to 40, who led a normal life or were exposed to short-term or long-term head-down tilts. The effectiveness of hemostimulants was determined with respect to hemoglobin, red blood cells or reticulocyte counts. Folicobalamine and coamide administration in therapeutic doses increased hemoglobin and reticulocyte blood levels in the ambulant subjects or those exposed to a 7-day head-down tilt. The effect was stable and persisted for 2-3 weeks after which the blood parameters returned to the pretest level. Folicobalamine administered at the final stage of 50-day head-down tilt facilitated partial recovery of hemoglobin during the study (which is very important) and rapid recovery after it. The objective and subjective tolerance of the drugs was good. It is therefore concluded that folicobalamine should be taken at the final stage of head-down tilt or space flight to alleviate readaptation to the normal environment.

The composition of the intestinal microflora of 12 cosmonauts was studied before and after space missions of varying duration. Changes in the intestinal microbial coenosis were found prelaunch. The pattern of changes did not vary with an increase in space flight duration. The use of special prophylactic measures exerted a positive effect on intestinal microecology. Bifidobacteria and lactobacilli showed the greatest changes inflight. Therefore, it seems important to arrange preflight sanation of the intestinal microflora as a prophylactic method.

In the crewmembers of four Salyut-6 long-term flights, enzyme excretory function of the gastro-intestinal tract was investigated. These studies included: gastric proenzyme, pepsinogen, and pancreatic enzymes, amylase and lipase, in blood and urine, trypsin in blood, intestinal enzymes, invertase and glycyl-L-leucine dipeptidase in feces, and lipids in feces. The results obtained demonstrated a correlation between changes in enzyme excretion and space flight duration and profile. After the 140- and 175-day flight the most marked changes in the digestive organs were seen; they manifested as a simultaneous increase in secretory function of the stomach and the pancreas. However, after the 185-day flight, in which advanced countermeasures were used, the above changes were less distinct.