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Biomedical subjects

A Vacek

Publications and source records attributed to A Vacek.

At least 73 records · Page 4Linked to original sources
PubMed1982

Oxygen tension and prediction of the radiation response. Polarographic study in human breast cancer.

Serial polarographic measurement of the tissue oxygen tension (pO2) was made in the course of fractionated irradiation (preoperative or sole treatment) of advanced breast cancer in 24 patients. In responsive tumors increase in pO2 appeared sooner before expressive tumor size reduction became noticeable. Repeated recording of unchanged pO2 values has proved to be a good prognostic indicator of local failure. The study made on this tumor model has shown that serial polarographic pO2 determinations with suitable electrodes causing minimal trauma and providing consistent and reproductive data about changes in tumor microcirculation and oxygenation, may enlarge the scale of indicators of the radiation response.

Breast Neoplasms↗
PubMed1981

Measurement of the partial oxygen pressure and oxygen utilization in the skin of cosmonauts aboard Salyut 6.

The oxygen tension (PO2) in the dorsal skin surface of the forearm was studied during the stay of cosmonauts on board Salyut 6. Between the fourth and fifth day of stay on the orbital station a considerable reduction of the PO2 level was observed. The oxygen utilization values were also reduced. In the early postflight period the low PO2 level persisted with gradual normalization.

Aerospace Medicine↗
PubMed1981

Radioprotective effects of dextran sulphate in mice.

Influence of a single i.p. injection of dextran sulphate on radiosensitivity of mice was investigated. The administration of dextran sulphate 24, 48 and 72 hours prior to irradiation increased formation of endogenous colonies of the hemopoietic tissue on the surface of the spleen. DRF calculated from an equieffective exposure for 5 colonies was 1.96 when dextran sulphate was administered 24 hours before irradiation, and 2.25 when dextran sulphate was administered 72 hours before irradiation. The radioprotective effects of dextran sulphate were manifested also in the survival of animals exposed to lethal doses of short-termed as well as long-termed gamma radiation.

Animals↗
PubMed1979

Decrease in the ability of bone marrow CFUs to produce macroscopic colonies of haematopoietic tissue in the spleens of partially irradiated young rats.

Experiments were carried out on Wistar rats aged from 3--5 weeks, in order to determine the repopulation capacity of bone marrow CFUs after total body and partial body irradiation. CFUs were derived either from the own marrow, or from bone marrow of isologous donors. In totally irradiated hosts, macroscopic spleen colonies were formed after transplantation of both autologous and isologous marrow cells, whereas no visible colonies were detectable in partially irradiated rats, in spite of an increased haematopoietic activity of the spleen and higher concentration of circulating CFUs. Intravenous application of trypsin resulted in an increase in the number of CFUs in peripheral blood in both intact and partially irradiated rats. CFUs derived from bone marrow of PBR rats form MSC only when transplanted into isologous TBR recipients, but not at autorepopulation. The possibility is discussed that a repressor is released from unirradiated bone marrow of young rats which inhibits the colony-forming capacity of migrating CFUs.

Animals↗
PubMed1978

Effect of hyperthyroidism on haemopoietic stem cell kinetics in mice.

Changes in the pool of haemopoietic colony-forming units (CFUs) of bone marrow and spleen were studied in experiments with mice fed dried thyroid gland (TH) for 21 days, and during the 13 days that followed feeding. After HU treatment, the number of CFUs in DNA synthesis was estimated. As early as the second day of TH treatment, the pool of CFUs is gradually increased, leading to an increase in the total number of splenic and bone marrow CFUs persisting after TH treatment for the period examined. Simultaneously, the numbers of nucleated cells in the bone marrow and spleen are increased. During TH feeding and following its termination, the total number of erythrocytes and the haematocrit values did not change significantly, whereas an increased number of leucocytes was observed in the peripheral blood after TH treatment. Elevation of the proliferative activity of CFUs occurred early in the period of TH treatment, with the maximum attained by end of the first week of TH feeding. This suggests a rapid response of the haemopoietic stem cell compartment to the administration of TH hormones. The participation of humoral factors controlling CFUs compartments in the mechanism of the stimulatory effect of TH hormones on haemopoietic stem cells is discussed.

Animals↗
PubMed1978

Protective effect of a mixture of radioprotective substances (AET and mexamine) on the haemopoietic stem cells of mice.

A protective effect of a combined application of radioprotectors (AET -i.p., mexamine -s.c.) was studied in experiments on mice. Duration of the protective effect on the haemopoietic stem cells and on the survival of mice after a lethal exposure to X-ray radiation lasted for 5 hours after the injection. DRF calculated from a change of LD 50/30 reached the maximum (1.53) within 30 min after the injection, and was equal to 1.17 within an interval of 5 hrs. The protection of haemopoiesis, as expressed by DRF calculated from an equieffective exposure for 2 ESC, reached the maximum within a 60 min interval after the injection (DRF=3.4). D0 calculated from the CFU survival curves of endogenous haemopoietic tissue colonies (ESC) was, within a 120 min interval, almost three times higher (310 R) than in the control group (110 R). After the injection of radioprotectors a greater number of haemopoietic CFU survives at an exposure of 100-400 R than after mere irradiation. The postirradiation decrease in the weight of small intestine was smaller in protected animals than in the controls. The role of a decrease of the radiation damage to the haemopoietic stem cells in the total protective effect of the radioprotectors used is discussed.

Animals↗
PubMed1976

Age dependence of the number of the stem cells in haemopoietic tissues of rats.

The number and concentration of haemopoietic stem cells in the femoral bone marrow and spleen of Wistar rats of different ages were investigated. Stem cells were assayed by the spleen colony technique in irradiated rat recipients. The ability of the recipient spleen to harvest transplanted tissue as a macroscopic colony was found to be dependent on the recipient's age. Changes with senescence were observed also in the concentration and the size of the stem cell compartment both in the marrow and spleen. No differences were demonstrated in the seeding of transplanted colony-forming units into the spleen of recipients of 1 and 4 months of age. A rats-mice strain difference in the effect of senescence on the haemopoietic stem cells is discussed.

Aging↗
PubMed1975

The effect of electromagnetic radiation on the hematopoietic stem cells of mice.

An increase in the leukocyte number in blood and a decrease in the total cell volume of the bone marrow and spleen were observed in mice after wholebody microwave irradiation (2450 MHz, lambda equals 12.5 cm, 100 mW/cm-2). The number of hematopoietic stem cells increased early after microwave irradiation (1626 plus or minus 53 CFU in bone marrow, 689 plus or minus 86 CFU in the spleen), as compared with that or control (598 plus or minus 92 and 349 plus or minus 79 CFU, respectively). Incorporation of 59Fe in the spleen decreased to 78% of the control value 24 hr after irradiation, which was followed by an increase to 250% on Day 14 after irradiation. After heat exposure, CFUs showed an early decrease in number, whereas the percentage of 59Fe incorporation increased. The different effects of microwaves and externally applied heat on the hematopoietic stem cells suggested that alterations in tissues caused by high-intensity microwave radiation need not be related only to increased internal temperature.

Animals↗