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Biomedical subjects

E Necas

Publications and source records attributed to E Necas.

At least 73 records · Page 4Linked to original sources
PubMed1981

Human placental conditioned medium (from different phase of pregnancy) as a source of colony-stimulating activity for cultures of human and mouse. granulocyte-macrophage colony-forming cells in semisolid agar.

We have investigated the effect of conditioned medium derived from cultures of human placental tissue from different phases of pregnancy on in vitro growth of human and mouse granulocyte-macrophage colony forming cells in semisolid agar. We have confirmed that the colony-stimulating activity of human placental conditioned (normal delivery) medium was equivalent to the activity of peripheral blood leucocyte underlayers when medium was added at a 5%-20% concentration to the semisolid agar. Placentas from the 12th amd 10th week of gestation were found not convenient for preparation of medium with high CSA; the activity of media prepared from their cultures was not significantly higher than the autostimulating activity of bone marrow alone. Human placental conditioned medium proved inconvenient for cultures of mouse GM-CFC in semisolid agar containing foetal calf serum.

Agar↗
PubMed1980

Biliary iron excretion in rats following pyridoxal isonicotinoyl hydrazone.

Biliary excretion of iron after administration of pyridoxal isonicotinoyl hydrazone (PIH), a recently identified effective iron-chelating agent, was investigated in rats. PIH administered both intraperitoneally and orally was shown to increase significantly 59Fe excretion into bile of rats which had previously been injected with 59Fe-transferrin to label hepatic parenchymal cells. 59Fe-PIH appears in bile as early as 15 min after chelator administration and the peak of 59Fe-radioactivity in bile is seen 1--5 h following intraperitoneal PIH injection. PIH, administered intraperitoneally, 125--250 mg/kg, increased 24 h biliary radioiron excretion about 35 times and in addition increased urinary and faecal iron excretion. When PIH was given immediately before 59Fe-transferrin, 24 h cumulative biliary 59Fe excretion was even higher. PIH was also demonstrated to increase biliary excretion of radioiron released from 59Fe-haemoglobin catabolysed in reticuloendothelial cells. The effect of PIH was confirmed by estimation of biliary iron concentration using the method of atomic absorption spectrophotometry. Repeated PIH administration to rats decreased 59Fe radioactivity in liver and kidney and increased urinary and faecal iron excretion.

Animals↗
PubMed1979

Effect of some cytostatics on the haemopoietic stem cells (CFUs) in blood.

The effect of some cell-cycle stage-specific cytostatics on the pluripotent stem cells (CFUs) present in the blood was investigated. The amount of these cells in the blood responds markedly and very quickly to a single administration of any of these drugs. Their effects on the circulating CFUs allowed the drugs tested to be divided into groups: (1) Hydroxyurea and arabinosyl cytosine induced a profound decrease in the number of CFUs in the blood, which was followed by a return to the normal value and an overshoot that lasted several days; (2) Colchicine, vinblastine, vincristine, and methotrexate first induced an increase in the number of CFUs in the blood, which was followed by a decrease to below the normal values, and still later an overshoot that lasted several days. The preliminary data on the effect of hydroxyurea on the CFUs circulating in large quantities in the blood of mice with Friend virus leukaemia indicate that the tumorous stem cells (CFUs) might respond to these cytostatics in a similar way.

Animals↗
PubMed1978

Changes in stem cell compartments in mice after hydroxyurea.

Hydroxyurea injection kills only approximately 10% of CFUs which are in the S phase of the cell cycle. In mice given a single injection of hydroxyurea CFUs in the femur decreased only about 50% in 2--4 days after hydroxyurea, and then started to return to normal levels with an overshoot evident after the eighth day after hydroxyurea. CFUs in spleens of mice given a single injection of hydroxyurea show an evident overshoot as early as 3 days after the drug, reaching levels which are about 300% of normal. CFUs from blood disappear rapidly, but equally rapidly return to normal values followed by a significant overshoot. The radioresistance of mice increased up to 4 days after hydroxyurea.

Animals↗
PubMed1978

A contribution to the technique of mouse bone marrow cell culture in semisolid agar.

A method of cultivation of mouse bone marrow cells in semisolid agar is described. Colony-stimulating factor was provided either by a "feeder layer" containing kidney cells (from 8-day-old mice) or by the addition of "lung conditioned medium" or post-endotoxin serum. The effect of various factors and media on the formation of colonies was tested. The best growth of colonies was observed in medium RPMI 1640 or in Eagle's minimal essential medium containing 0.2% bactotryptose supplemented with 20% foetal calf serum. Both the morphology of cells found in the colonies and the proliferative state of the cells that give rise to colonies indicate that CFU-C represent the committed progenitor for myelopoiesis.

Agar↗
PubMed1978

Disappearance of haemopoietic stem cells from blood after hydroxyurea.

Haemopoietic stem cells were examined in the blood of mice which had been injected with hydroxyurea. It was observed that the amount of CFU in the blood quickly decreased and after higher doses of hydroxyurea CFU completely disappeared from blood. Since CFU are rather resistant to the killing effect of hydroxyurea, it is assumed that the observed effect is caused either by an interference of hydroxyurea (due to its effect on the blood-forming tissues) with the migration of CFU into blood or by stimulating the removal og CFU from blood.

Animals↗
PubMed1977

The onset of hemoglobin synthesis in spleens of irradiated mice after bone marrow transplantation.

Messenger RNA (mRNA) for globin was isolated from spleens of irradiated mice in which erythroid differentiation was induced by a bone marrow graft. The globin mRNA was isolated either by means of sucrose gradients of reticulocyte polysomal RNA or by affinity chromatography of total spleen RNA on poly (U)-sepharose. The globin mRNA was tested in a wheat embryo cell-free system. The appearance of mRNA in the spleen erythroid colonies was correlated with other parameters of erythroid differentiation such as globin synthesis, activity of delta-aminolevulinic acid synthetase and iron uptake. Poly(A) containing mRNA did appear already on the 3rd day after grafting. However, significant translational activity of globin mRNA could be demonstrated only one day later together with the increase in globin synthesis and delta-aminolevulinic acid synthetase and enhanced iron uptake. In the second part of this study mouse spleen cells rich in erythroid elements were incubated with a specific heme synthesis inhibitor (isonicotinic acid hydrazide, INH) and the synthesis of 9 S RNA was estimated. It was found that a 40-minute incubation with INH reduced uridine incorporation into 9 S RNA fraction by about 40%.

5-Aminolevulinate Synthetase↗
PubMed1977

Effect of hydroxyurea and vinblastine on the proliferation of the pluripotential stem cells.

The population of the pluripotential hemopoietic stem cells in mice, i. e. those cells forming colonies in the spleens of lethally irradiated mice (colony forming cells CFc) is proliferating relatively slowly. After a partial damage the population regenerates which is achieved by means of the increased proliferation rate. The effect of damage caused by different doses of hydroxyurea or vinblastine on the proliferation of the CFc has been investigated. CFc population was measured in femur bone marrow after grafting the sample of the bone marrow into the lethally irradiated mice recipients (spleen colony method). The proliferation rate was estimated either according to the magnitude of the fraction of cells synthesizing DNA in the S phase of the cell cycle, or according to the sensitivity of the population to the repeated injections of vinblastine. Data showed that even after very minute damage caused by hydroxyurea the stem cells started to proliferate intensively. The effect was dose dependent. The comparable damage caused by vinblastine had a significantly weaker effect on the proliferation of the stem cells. From the results it is concluded that the proliferation response of the pluripotential stem cells depends on two factors: one being the extent of the damage caused to the hemopoietic tissue and the second the position of the killed cells in the cell cycle.

Animals↗
PubMed1977

[Changes of erythrocyte criteria of the guinea pig under hypoxia].

In the present study the adequacy of erythrocytic criteria for the diagnosis of hypoxia has been investigated in animal experiments. Guinea pigs were exposed to a defined hypoxia (pO2 equals 48 mm Hg approximately equal to 9000 m height) for 24 and 72 hrs. With increasing duration of hypoxia there is observable a distinct rise in reticulocyte count, 59Fe incorporation and the proportion of erythroblasts in the bone marrow. Hematocrit and hemoglobin concentration have increased significantly after hypoxia compared with the control animals. The mean cellular hemoglobin content shows a marked fall with the duration of hypoxia. The density distribution curves show under hypoxia a shift to lower densities and, therefore, appear to be well suited for the diagnosis of hypoxic states. The activities of the erythrocytic enzymes, G-6-PD and GOT, are increased after 24 and 72 hrs of hypoxia. The GOT isoenzyme pattern is shifted with continued hypoxia in favour of the mitochondrial GOT. The changes of enzyme activities are not pronounced enough under hypoxic conditions to be used for diagnositc purposes.

Animals↗
PubMed1976

Control of haemopoietic stem cell proliferation by cells in DNA synthesis.

It has been demonstrated that for the slowly proliferating population of the haemopoietic pluripotent stem cells (CFUs) the response after damage by hydroxyurea to cells synthesizing DNA differs from that after damage by colchicine to cells entering mitosis. The killing of DNA synthesizing cells elicits increased proliferation in the CFUs population. From this it has been inferred that cells in the S phase may inhibit the entry of nonproliferating GO cells into the cell cycle and in this way control cellular proliferation.

Animals↗
PubMed1976

Study on the proliferative state of haemopoietic stem cells (CFU).

Hydroxyurea was used to study the proliferation rate of haemopoietic stem cells (CFUs) in normal mice, after irradiation or transplantation into irradiated recipients. It was demonstrated that the proliferation rated of endogenous CFUs (endo-CFUs) and exogenous CFUs (exo-CFUs) are identical. After irradiation (650 R) the surviving endo-CFUs begin to proliferate immediately. By contrast exo-CFUs transplanted into the irradiated recipient mouse (850 R), begin to proliferate only after about 30 hr. However, injection of isoproterenol (which stimulates adenyl cyclase) or dibutyryl cyclic adenosin 3',5'-monophosphate shortly after marrow cell graft, triggers the transplanted CFUs into cell cycle as shown by an almost immediately increased sensitivity to hydroxyurea. Isoproterenol is capable of inducing DNA synthesis also in stem cells of normal mice but it takes about 20 hr before CFUs become to be increasingly sensitive to hydroxyurea.

Animals↗
PubMed1976

Study of the effect of hydroxyurea on the erythropoietin-sensitive cells.

The response of polycythaemic mice to a standard dose of erythropoietin has been measured at various time intervals after single or repeated injections of hydroxyurea. The results exclude S phase of the cell cycle as the period responsive to erythropoietin. They suggest the existence of feedback mechanisms within the cell cycle, operating at the G1--S boundary and within the G1 phase. Hydroxyurea given to polycythaemic mice at various time intervals after erythropoietin induced characteristic changes in the response. These changes can be explained if both gradual transit of differentiated cells into the DNA synthesis (S phase) and changes in amount of the erythropoietin sensitive cells caused by the feedback mechanisms operating in the cell cycle are considered.

Animals↗