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Biomedical subjects

K Volenec

Publications and source records attributed to K Volenec.

At least 19 recordsLinked to original sources
PubMed1998

Mobilization of peripheral blood progenitor cells (PBPC) through a combination of chemotherapy and G-CSF in breast cancer patients and a possibility of unprocessed whole blood collection.

To support multicyclic, dose-intensive chemotherapy in breast cancer, we assessed the effects of reinfusing hematopoietic progenitors either as a leukapheresis product or as mobilized unprocessed whole blood. In this clinical study, 16 consecutive female breast cancer patients were given six cycles of chemotherapy regimen EC (epirubicin (150 mg/m2) and cyclophosphamide (1250 mg/m2) on day 1). In the first cycle, 24 h after chemotherapy, mobilization of the peripheral blood progenitor cells (PBPC) was started with growth factor G-CSF (Neupogen; Amgen-Roche) at a dose of 5 microg/kg/day for 13 days. In all other cycles G-CSF had been given at the same dose from day 7. On days 11, 12 and 13 the leukaphereses were performed and their products cryopreserved. On day 14 whole blood was collected. The median peak incidence of CFU-GM (granulocyte-macrophage colony-forming unit) in peripheral blood was approximately 50 times the baseline level. The leukapheresed PBPC were divided into portions and reinfused after the fourth, fifth and sixth chemotherapy courses. The support with mobilized whole blood was given after the second and third cycles. The effects of the support of whole blood vs leukapheresed PBPC on hematopoietic recovery were compared. The best yields of leukaphereses were achieved on day 13 after initiation of the chemotherapy. The mean number of CD34+ cells was 4.93 x 10(6)/kg (s.d. 2.7; range 0.36-10.54 x 10(6)/kg) the amount of CFU-GM was 2.18 x 10(5)/kg (s.d. 1.3; range 0.07-4.2 x 10(5)/kg). The yields of CFU-GM in 450 ml whole blood collected on day 14 reached 0.51 x 10(5)/kg (s.d. 0.28; range 0.05-1.5 x 10(5)/kg) and of CD34+ cells were 1.3 x 10(6)/kg (s.d. 0.8, range 0.18-2.58 x 10(6)/kg). PBPC yields in 450 ml of unprocessed whole blood were in some cases not sufficient for good hematopoietic recovery after the EC cycles. Grade 4 leukopenias and thrombocytopenias were two times higher in cycles with whole blood support than in cycles with cryopreserved PBPC support. An increase of PBPC harvest can be simply achieved by collecting larger amounts of unprocessed blood, as used by some authors.

Adult↗
PubMed1998

[Use of thermoelectric properties of materials with shape memory in medicine].

Article deals with some possibilities of the combination of the shape memory and another physical properties of nitinol (Ti-Ni alloy) for application in the medicine. The thermoelectric properties of originally developed miniature thermocouple probe with the shape memory are described in details. The shape memory effect of the thermocouple is based on the use of the combination of the metals nitinol and constantan.

Alloys↗
PubMed1994

The multithermocouple for the use in radiothermotherapy.

The original multithermocouple probe developed for the use in radiothermotherapy is described in this article. On the basis of experimental measurements and theoretical assumptions the properties of the probe are exactly defined and the mathematical model of the probe is given and identified.

Hyperthermia, Induced↗
PubMed1993

Elevation of extracellular adenosine induces radioprotective effects in mice.

The radioprotective effectiveness of the elevation of extracellular adenosine induced in mice by the combined administration of dipyridamole, a drug inhibiting the cellular uptake of adenosine, and adenosine monophosphate, a soluble adenosine pro-drug, was evaluated. Based on survival studies, endogenous hemopoietic spleen colony formation, and the postirradiation behavior of bone marrow granulocyte-macrophage colony-forming cells (GM-CFC), it was demonstrated that the combined administration of dipyridamole and AMP protects mice when given either 15 or 60 min before irradiation. It could be deduced that the radioprotective action is induced by at least two independent mechanisms: (1) protection by hypoxia as a result of the effect of the treatment on the cardiovascular system, and (2) and enhanced regeneration of the hemopoietic stem cells due to either enhanced postirradiation repair or an increased proliferation of the hemopoietic stem cells. Both of these protective mechanisms, which are able to increase the regeneration of hemopoiesis, seemed to be effective in enhancing the survival of mice given single radiation exposures, with a dose reduction factor for the LD50/30 of 1.11. The protective efficiency of the mechanisms enhancing the postirradiation recovery of hemopoiesis was also evident in experiments evaluating the survival of mice subjected to fractionated irradiation and a repeated administration of the protective agents.

Adenosine↗
PubMed1992

Enhancement of hypoxia radioprotection and decrease of hypoxia toxicity caused by adenosine monophosphate.

It was shown in experiments on mice that the radioprotective effects of adenosine monophosphate (AMP) or of a combination of Mg aspartate and AMP join with those induced by hypobaric hypoxia. The hypotensive effects of these drugs lead probably to hypoxia in radiosensitive tissues which acts additively with hypoxia elicited by way of respiration. Furthermore, Mg aspartate and AMP decrease the toxicity of high degrees of hypobaric hypoxia. These effects can be explained by the ability of adenosine liberated from AMP and of magnesium to increase brain and heart blood perfusion and/or to mitigate excessive sympathetic activity. The pharmacological effects of AMP and Mg aspartate are thus not only radioprotective but also energy preserving and protecting vitally important organs against hypoxia toxicity. These effects may be of favourable importance in hypoxic radiotherapy.

Adenosine Monophosphate↗
PubMed1991

The effect of high energy electron irradiation on blood-brain barrier permeability to haloperidol and stobadin in rats.

The heads of rats were irradiated by 4 MeV electrons in doses 90, 180, and 360 Gy. The observed times of deaths ranged 120-600, 60-420, and 150-370 min after 90, 180, and 360 Gy, respectively. A dose dependent decrease of the brain uptake index of haloperidol was observed 1 and 3 h post radiation. On the other hand an increased brain uptake index was found for stobadin after head irradiation with doses of 180 and 360 Gy. Regional cerebral blood flow, blood pressure, and heart rate were not significantly altered in the period following irradiation with 180 Gy. The observed changes in blood-brain barrier (BBB) permeability seem to be the result of the damaged function of morphological structures forming the BBB rather than altered regional blood flow.

Animals↗
PubMed1991

Radioprotective effect of inosine and its enhancement by magnesium and global hypoxia.

The slight radioprotective action of inosine, when injected intraperitoneally to mice shortly before gamma-irradiation, can be enhanced by the administration of magnesium aspartate. This effect can be explained by the additivity of the vasodilatory actions of both agents. Inosine increases the radioprotective effectiveness of hypobaric hypoxia (10% O2), probably due to the additivity of the hypoxic effects in radiosensitive tissues. Acute hypoxic toxicity, however, is decreased by inosine administration. The cumulation of radioprotective effects of inosine and of its antihypoxic action in vitally important organs can have a favourable influence in hypoxic radiotherapy.

Animals↗
PubMed1990

Effect of palmitoyl-DL-carnitine on the 3H-dihydroergotoxine intestinal absorption in rat.

Using the methods of rat intestine perfusion in situ and kinetics examination in vivo, absorption of 3H-dihydroergotoxine (3HDHE) from the gastrointestinal tract into systemic blood was investigated. The aim of the study was to increase absorption of the ergot alkaloid with palmitoyl-DL-carnitine (5 mg/rat). Low absorption of 3HDHE was demonstrated in contrast to fast and almost complete absorption of the model drug theophylline (5 mg kg-1). In the experiment this was evidenced by in situ continuous measurement of the administered activity (125 micrograms kg-1) into a reservoir. At the end of the experiment (120 min) the plasma activity reached 0.034 +/- 0.014%, retention in the intestine achieved more than 60%, uptake in the brain 0.044 +/- 0.015%, cumulative excretion in bile 1.50 +/- 0.31% of administered activity. Palmitoyl-DL-carnitine did not influenced the percentage of activity in the plasma and did not affect bile excretion, retention in the intestine and uptake in the brain. In the vivo experiment oral administration of 3HDHE into the stomach (222 micrograms kg-1) increased activity in plasma (0.069 +/- 0.020% within 24 h), cumulative excretion in urine was 6.1 +/- 3.6%, retention of the drug in the stomach and intestine 46 +/- 12%, activity of the brain 0.11 +/- 0.02%, in the kidney 0.39 +/- 0.17%, and in the liver 0.80 +/- 0.30%. After palmitoyl-DL-carnitine administration the activity of plasma reached 0.084 +/- 0.022% (NS), retention in gastrointestinal tract 39 +/- 9% (NS), activity in the liver 0.71 +/- 0.17% (NS), and activity in the kidney 0.42 +/- 0.13% (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[The pathophysiologic basis for the incorporation of 99mTc-pyrophosphate into myocardial infarct].

The investigation studied the relation of 99mTc-pyrophosphate incorporation (99mTc-PYP) into experimental, 48-hours old myocardial infarction in dogs to tissue vascular supply and to the extent of necrotic tissue. The experimental myocardial infarction was induced in five animals during an operation by the ligation RIVA. The myocardial blood supply was measured in tissue samples, taken from transverse sections of the infarction by means of 86Rb captation. The extent of myocytolysis was measured by depletion of tissue creatine kinase (CK). In the subendocardial layer of the infarction it became obvious that 99mTc-PYP incorporation was proportional to the decrease of tissue blood supply. No relation between the extent of necrosis and the incorporation of the radioactive chemical was demonstrated. The accumulation of 99mTc-PYP requires the necrosis to be present, but its extent apparently does not influence the intensity of incorporation. In the subepicardial infarction layer there was neither a relation of the radioactive chemical cumulation to the blood flow, nor to the extent of the necrosis proved.

Animals↗
PubMed1989

Contribution to some radiobiological aspects of the investigation of radiosensitizers of hypoxic cells. Part IV: Radiosensitizing effect of metronidazole evaluated on the level of postirradiation changes of bone marrow cellularity in rats protected by induced hypoxia of lower body half.

Radiosensitizing effect of metronidazole (Entizol, Polfa, Poland) was tested on an experimental model of ischaemized bone marrow. The changes of bone marrow cellularity were recorded after whole body irradiation of rats protected with abdomen compression during irradiation. With an increasing dose of irradiation proportional and significant decrease of nuclear elements in bone marrow occurred the third day after irradiation. Metronidazole administered to unprotected rats (without compression) did not show any effect. The abdomen compression led to a pronounced radioprotection but metronidazole administration reduced this effect significantly. Ischaemization of the lower half of rat body produced on the level of bone marrow cellularity the protection corresponding to DRF (dose reduction factor) = 1.96 the third day after irradiation. DRF value decreased to 1.52 by metronidazole application which corresponds to ER (enhancement ratio) = 1.29.

Animals↗