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Biomedical subjects

A Vacek

Publications and source records attributed to A Vacek.

At least 19 recordsLinked to original sources
PubMed1992

Investigation of red blood cell fractionation by gravitational field-flow fractionation.

Gravitational field-flow fractionation is used for the separation of particles according to their sizes in the range 1-100 microns: larger particles elute before smaller ones. This phenomenon can be explained as a result of the steric exclusion of the particles from the vicinity of the channel walls, and/or hydrodynamic effects supposedly associated with the inertia of the liquid. The method was used for the investigation of red blood cells. The dependence of the retention ratio on the flow-rate, sample volume, concentration of blood and relaxation time was studied. Analysis of fifteen individual fractions by Coulter counter and reinjection of three other fractions were studied in order to verify fractionation of red blood cells.

Cell Separation↗
PubMed1992

Protection of early cellular damage in 1 Gy-irradiated mice by the elevation of extracellular adenosine.

In whole-body 1Gy-irradiated mice a modification of early cellular damage by means of preirradiation dipyridamole and adenosine monophosphate (AMP) treatment was investigated. Both drugs were given either alone or in combination, AMP being administered i.p. at doses of 5, 10 and 15 mg, dipyridamole s.c. at the dose of 2 mg, 20 min before AMP. The thymidine level in plasma and the amount of free polynucleotides in the thymus and spleen, both estimated at the interval of 4 h after irradiation, were used as indices of early cellular damage in vivo. The elevated level of thymidine observed in the plasma of irradiated controls decreased significantly after the administration of AMP (5 mg) alone to 71%, after the combination of dipyridamole and AMP a still deeper significant fall to 60% was observed. Such a protective effect was observed when injecting AMP 15 min before irradiation. Using the interval of 65 min between AMP administration and irradiation, no protection was detected. The higher doses of AMP (10, 15 mg) enhanced the protective effect manifested in plasma thymidine level only moderately. The amount of free polynucleotides, elevated in the thymus and spleen of irradiated mice, was significantly decreased in the thymus of mice pretreated with the combination of dipyridamole and AMP. The results suggest that the treatment used decreases the radiation damage of the sensitive thymocyte population. It is proposed that the joint use of AMP, an adenosine prodrug, and dipyridamole, a drug inhibiting adenosine uptake by cells, leads to an elevation in extracellular adenosine which activates cell surface adenosine receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1992

Amelioration of radiation damage to haemopoiesis by Ivastimul, given after irradiation to mice protected by peroral cystamine.

The combined radioprotection by preirradiation peroral cystamine and postirradiation Ivastimul treatment was examined in sublethally and lethally whole-body gamma-irradiated mice. The enhancement of haemopoietic recovery and increased survival of irradiated mice was demonstrated when a single dose of Ivastimul was administered after irradiation. Ameliorative influence of combined radioprotection may be explained by the haemopoietic stem cell protection by cystamine and haemopoietic stimulation mediated by Ivastimul.

Animals↗
PubMed1991

[Radioprotective effects of DDP].

The authors studied the effect of various DDP applications (sodium salt of dimethyl-dioxopiperazine thiosulfonate) in a dose of 45 mg/kg w. administered 10 min before irradiation, on the survival of female mice C57 and (CBA x C57BL/F1 after a single whole-body exposure to a sublethal dose of gamma rays (LD50/5 = magnitude of 15.495 +/- 0.781 magnitude of Gy and LD50/30 = magnitude of 7.864 +/- 0.018 magnitude of Gy). The depth of DDP protection effect on the haemopoietic stem cells was studied using the method of endogenous spleen colonies (ESC) of haemopoietic tissue. DDP radioprotective effect was also demonstrated after s. c. and i. m. application of this substance 10 min before 6 Gy of gamma radiation; it was shown by a prolongation of the survival time of experimental animals and by an increase in the number of individuals surviving till the 30th day after irradiation. Higher ESC numbers in the animals with DDP protection demonstrate survival of higher number of the haemopoietic stem cells and indicate that DDP is the biological active substance and contributes to the repair of haematopoiesis damaged by radiation and to the survival of irradiated animals.

Animals↗
PubMed1991

Radioprotective effect of dextran sulphate and aerogenic hypoxia on intestinal crypt stem cells in mice.

A single intraperitoneal injection of dextran sulphate given 6 h before irradiation produced higher numbers of microcolonies of intestinal crypt stem cells in whole-body irradiated mice than injection of saline in control mice. If dextran sulphate and hypoxia are combined, the radioprotective effect of hypoxia on intestinal crypt stem cells depends on the time interval between irradiation and administration of dextran sulphate.

Animals↗
PubMed1991

Decrease in the number of progenitors of erythrocytes (BFUe, CFUe), granulocytes and macrophages (GM-CFC) in bone marrow of rats after a 14-day flight onboard the Cosmos-2044 Biosatellite.

A decrease in the number of progenitors of erythrocytes (BFUe, CFUe) and of granulocytes and macrophages (GM-CFC) in bone marrow was found in rats exposed to microgravitation during a 14-day flight onboard the Cosmos-2044 biosatellite when compared to control rats maintained under conditions of gravitation on the ground. The number of progenitors of both lineages of haemopoiesis was also decreased in synchronous control rats, thus suggesting that the pool of progenitors is influenced also by the action of the nonspecific space flight factors.

Animals↗
PubMed1990

Hydroxyurea as a suppressor of the radioprotective effect of dextran sulfate on bone marrow hemopoietic stem cells in mice.

The changes in hemopoiesis of mice following intraperitoneal administration of dextran sulfate (DS) 24 h before irradiation, as well as the effect of injecting them with hydroxyurea (HU), were analyzed. DS increased the proliferation activity and number of hemopoietic stem cells (CFUs) in the bone marrow. The content of CFUs in the bone marrow and the number of endogenous spleen colonies (ESC) of hemopoietic tissue were higher after irradiation in mice treated with DS than in control groups. The survival rate following a lethal radiation dose was also higher. Injection with HU decreased the number of CFUs in animals injected with DS to the level of controls and suppressed its radioprotective effect.

Animals↗
PubMed1990

Decrease in the number of progenitors of fibroblasts (CFUf) in bone marrow of rats after a 14-day flight onboard the Cosmos-2044 biosatellite.

A decrease in the number of progenitors of fibroblasts (CFUf) was found in bone marrow of rats that underwent a 14-day flight in the state of weightlessness onboard the Cosmos-2044 biosatellite, immediately after flight, when compared with rats maintained in control conditions of terrestrial gravitation. These changes may be explained by the action of specific factors of microgravitation.

Animals↗
PubMed1990

Hypoxyradiotherapy of uterine cervix cancer to decrease of acute side-effects and treatment complications.

The authors have reported on preliminary results of hypoxyradiotherapy in the course of external irradiation in patients with uterine cervix cancer from a view-point of the occurrence of acute reactions and treatment complications. A mixture of nitrogen and oxygen containing 8.0 to 8.5% of O2 was used to provoke acute hypoxia during irradiation. The applied doses of external irradiation was simultaneously increased by 40%. On the basis of a randomized study with 120 patients, acute hypoxia was found to protect healthy tissues against post-radiation damage. When the doses of 96 Gy in the paracervical space and that of 75 Gy in the pelvic wall were applied, acute side-effects decreased significantly if compared with a conventional radiotherapeutic procedure (p less than 0.01). Radiological preconditions for using acute hypoxia in radiotherapy are discussed.

Brachytherapy↗
PubMed1990

Radioprotection of hemopoiesis conferred by aqueous extract from chlorococcal algae (Ivastimul) administered to mice before irradiation.

In experiments on mice, single i.p. injections of aqueous extract from chlorococcal freshwater algae (Ivastimul) were found to increase their radioresistance. During the same period the number of spleen colony-forming units (CFUs) in the bone marrow and spleen and their proliferation activity increased. The amount of granulocyte-macrophage colony-forming cells (GM-CFC) in the bone marrow grows and the colony-stimulating activity (CSA) of the blood serum of mice is elevated at an early period after injection of the substance. The recovery of the CFUs and GM-CFC pools in femoral bone marrow after irradiation proceeds at a faster rate in Ivastimul-treated animals than in control groups. The activation of the pool of hemopoietic stem cells and stimulatory effects of Ivastimul on granulocytopoiesis act favorably on the repair of radiation damage and on increased percentage of animals surviving lethal doses of 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↗