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Biomedical subjects

P Petýrek

Publications and source records attributed to P Petýrek.

At least 19 recordsLinked to original sources

[Cytoprotective effects of amifostine in the treatment of tumors].

An efficient therapy of patients with tumorous diseases should include maximum killing of malignant cells with minimal damage to cells in healthy tissues. Radiotherapy and chemotherapy are frequently associated with a series of undesirable effects. Side effects related to the therapy may unfavorably influence quality of life for a short or long period of time, may cause the need to decrease the dosage or shorten the overall period of treatment or survival of the patient. Therefore, particular attention has recently been paid to compounds, which mitigate or eliminate the undesirable effects of the therapy. A way to decrease toxicity is the administration of radioprotective or chemoprotective compounds. The cytoprotection of healthy tissues by compounds from the aminothiol group is one of the most promising directions of research and clinical practice. Amifostin protects healthy tissue from damage induced by radio- or chemotherapy. In comparison with patients treated by radiotherapy only, radiotherapy supplemented with amifostin proved to cause significantly less acute and late untoward effects of therapy. The paper describes the possibilities of using radioprotective drugs, especially amifostin, in the therapy of tumors with particular emphasis to the needs of physicians dealing with the problems of internal medicine.

Amifostine↗

Radiation pneumonitis: the model of interstitial edema.

We used the measurement of the thickness of alveolar septa in the lungs in (C57BI/6xDBA/2)F1 mice irradiated locally in the area of the thorax with absorbed doses of 14, 16 and 18 Gy of gamma rays. The thickness of alveolar septa of the pulmonary tissue was measured using a computer image analysis. 24 weeks after irradiation we found a significant increase in the thickness of alveolar septa in direct relation to the dose within a range of 14 to 18 Gy. This indicator can be used for observation of the radioprotective and remedial interventions against the inception and the development of radiation pneumonitis.

Animals↗

[Evaluation of the quality of a decision-making rule in discriminant analysis].

Logistic regression (LR) and concept of the beta-confidence allocation rule were applied to predict the survival of dogs within the radiobiological experiment. The biochemical and haematological investigations in 86 dogs on the 2nd, 5th and 8th day post-external gamma-neutron irradiation (4.8-7.2 Gy) were used as explanatory variables for the prediction of more than 64 days survival. The influence of experimental conditions was monitored. Correctly predicted cases with LR models were proportioned as 81%, 85% and 93% on 2nd, 5th and 8th day respectively. Using beta-allocation rule, those correctly allocated with 0.50 confidence on the individual days were 75%, 81% and 85% of cases, that adds valuable information on the stability of the estimated classification rule. Method of beta-allocation also allows testing of whether individual observations are correctly assigned at a given significance level.

Animals↗

[Classification of multidimensional observations using linear discriminant functions].

In the present paper the role of linear discriminant analysis is delimitated all along with a range of problems which could be solved using this method in appropriate conditions. The analysis is given of possibilities on how to involve the decrease in number of variables in a model, and how to predict probability of incorrect classification. As an example of application, the prediction of dog survival is calculated in radiobiological experiment on the basis of biochemical and hematological values which were obtained by the 2nd day after the irradiation as well as an error probability was determined.

Discriminant Analysis↗

Effect of short-term splitting of gamma-ray doses on changes in haemopoietic stem cell number in bone marrow and on mortality of whole-body irradiated mice.

Split-dose irradiation of mice with two doses of 0.5 Gy given at 2 to 5 h interval damages haemopoietic stem cells (CFU-S) less than single exposure to 1 Gy. Also in comparison with whole-body single exposure of mice to a high sublethal dose of 7 Gy, splitting this dose into two doses of 3.5 Gy given at 4-h interval brought about more rapid recovery of CFU-S in femoral bone marrow and of bone marrow cellularity. At 360 days after irradiation with 7 Gy gamma-rays, a secondary decrease in CFU-S was apparent in bone marrow, which was more profound in the single-exposure group than in the group given split doses amounting to 7 Gy. The protective effect of short-term dose splitting was also evident in an investigation of mortality of irradiated mice. The LD50/30 value in mice exposed to a single dose of gamma-rays (8.3 Gy) increased to 10.5 Gy, when the dose was split (two doses, 4-h interval).

Animals↗

Megakaryocytes in rabbit pulmonary blood vessels.

Semiserial sections of lung capillaries of seven rabbits were examined for megakaryocytes. Triads of serial sections of each lobe were examined, and megakaryocyte counts per cm2 were determined. Median megakaryocyte count was determined for each lobe. The lobal values were used to calculate the was determined for each lobe. The lobal values were used to calculate the median cell-counts for each experimental animal. Values of 0.16-0.64 megakaryocytes per cm2 were established as "normal".

Animals↗

Late effects of single and repeated sublethal gamma radiations on haemopoietic stem cells in mice.

The effects of single (1 X 5 Gy) and repeated (4 X 5 Gy) gamma-ray doses, separated by 21 days, on femoral CFU-S numbers in mice during the 12 months after irradiation were compared. Nucleated cell and CFU-S numbers were recovered 21 days after whole-body irradiation with 5 Gy. Marrow regeneration was not sufficient after the second irradiation, and nucleated cell and CFU-S numbers reached 50% of the level of the control 21 days after the second dose. The decrease in CFU-S numbers was more marked after the third and fourth doses, reaching 35% of the control. While CFU-S numbers were recovered by the 21st day after a single dose of 5 Gy, the level of the control group was reached 60 days after the last dose of repeated (4 X 5 Gy) gamma irradiation. A decrease in femoral CFU-S numbers occurred in both irradiated groups 6 months after the last dose, the decrease having been more marked in the group exposed to repeated irradiations. The decrease was more pronounced 12 months after irradiation although bone marrow cellularity was at the level of the unirradiated group. Femoral CFU-S numbers were lower in unirradiated 480-day-old mice than in those at 120 days of age.

Age Factors↗

Shielding of the abdominal region during X-irradiation: effect on haemopoietic stem cells.

The shielding of the abdominal region during X-irradiation is important for two reasons: following higher irradiation doses it prevents the development of the gastrointestinal syndrome; it prevents the development of the lethal form of the marrow syndrome by shielding a portion of the spinal column bone marrow and the spleen. The dose reduction factor in so irradiated mice, compared to whole-body irradiated mice, was 2.6. At 15 min after irradiation with the dose of 10 Gy, the number of spleen colony-forming cells (CFU-S) was decreased in the femoral bone marrow of both the group receiving whole-body irradiation and the group having the abdominal region shielded during irradiation. This great decrease persisted in the femoral bone marrow of both groups during the 5 h after irradiation. At 48 h after whole-body irradiation, the number of CFU-S in the femoral bone marrow of the unshielded animals decreased almost to zero values, and most of the mice were dead by 120 h after irradiation. In the group which had the abdominal region shielded, a statistically significant increase in the number of CFU-S in the femur was observed at 48 h when compared to the number of CFU-S in the femur at 5 h after irradiation. At 120 h, the number of CFU-S in so irradiated mice was at the level of the unirradiated group.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗

Shielding of the thymic region during X-irradiation: effect on haemopoiesis in mice.

The course of radiation damage and regeneration of the thymus and haemopoiesis were followed in mice after whole-body X-irradiation and in mice with the shielded thymic region during irradiation with 7 Gy, using several indicators (125IUdR incorporation, thymus weight, cellularity of bone marrow and changes in the peripheral blood leucocyte counts). It was demonstrated that radiation damage, manifested in a significant decrease in the values of the indicators studied immediately after irradiation, followed the same pattern in both groups, shielding, however, accelerated regeneration of the thymus and restoration of haemopoiesis. The favourable effect of thymic shielding was also reflected in a significant increase of LD50/30, and the dose reduction factor was equal to 2.

Animals↗

Significance of the length of time interval between lethal irradiation and transplantation of haemopoietic cells.

It could be shown that the efficiency of haemopoietic cell transplantation into lethally irradiated mice depended upon the degree of histocompatibility between the donor and the host as well as on the number of transplanted cells. With a prolongation of the time interval between irradiation and transplantation a proportionally higher number of transplanted haemopoietic cells was required to maintain the curative effect of transplantation. The haemopoietic microenvironment in lethally exposed mice remained unchanged until the tenth day after irradiation.

Animals↗

Spleen regeneration in mice after gamma irradiation and administration of thymosin.

The effect of thymosin (thymic humoral factor isolated from calf thymus) on regeneration of the spleen in mice after whole-body gamma irradiation was studied. Thymosin, in varied dosages (0.1--2.0 mg/day) applied subcutaneously before and after radiation exposure, stimulated splenic regeneration as indicated by increased splenic weight, number of endogenous splenic colonies and 59Fe and 125IUdR incorporation into the spleen. A control extract of brain tissue (cerebrosin) isolated in the same way as thymosin was applied to mice to verify specificity of thymosin. After cerebrosin application, a mild increase also was observed. Whereas a near maximal effect of thymosin was reached at a dosage of 0.1 mg, a comparable response with cerebrosin required a dosage of 1.0 mg. These data suggest that administration of thymosin has both a specific and non-specific effect on splenic regeneration and proliferation of hematopoietic stem cells.

Animals↗

The effect of thymosin application upon radiation sickness in mice.

The mechanism of thymosin effect upon radiation sickness was analyzed in mice. Thymosin (fraction 5) applied before and after a whole-body radiation exposure increased the LD 50/30 of treated animals by 250R. In mice exposed to 500R, thymosin treatment resulted in a faster recovery of haemopoiesis and lymphopoiesis, as indicated by higher bone marrow cellularity, higher lymph node, thymus and spleen weights, and greater 59Fe uptake in the spleen and femur and 125IUdR uptake in the spleens, femur and thymus. The results provide an indication that thymus and its humoral factor markedly influence the haemopoietic stem cells in the population surviving the sublethal irradiation of an organism. They further suggest the existence of feed-back mechanisms between the thymus and harmopoiesis.

Animals↗

The effect of thymic humoral factor upon regeneration of lymphatic and haemopoietic tissues of irradiated mice.

The study investigates the effect of humoral factor isolated from calf-thymus (thymosin) upon regeneration of lymphatic and haemopoietic tissues of female (CBA times C57BL/10ScSn)F1 mice irradiated with a whole-body exposure of 500R or 600R of gamma-rays. Thymosin was applied subcutaneously in amounts of 5 mg. per mouse per day. Two schemes of application were used: 1. The first dose given immediately after irradiation, followed by one injection daily for a total of either 3 or 9 days. 2. The first dose given 3 days prior to radiation exposure, followed by one injection daily for a total of 7 days. The number of endogenous spleen colonies, 59Fe splenic uptake, and dry spleen weight, all estimated on day 9 postirradiation, were significantly higher in both experimental groups treated with thymosin, when tested against untreated controls. If the start of the treatment preceded the irradiation, the ESC number increased as much as five times beyond the level found in the irradiated untreated group and the 59Fe uptake even exceeded the values of iron incorporation in unirradiated mice. Stimulation of lymphopoiesis induced by thymosin was reflected in an increase in 2-(14)C-thymidine incorporation into DNA of the spleen, thymus and lymph nodes, measured 72 hours after irradiation.

Animals↗