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E Necas

Publications and source records attributed to E Necas.

At least 19 recordsLinked to original sources
PubMed1992

Sensitivity of CFU-E to exogenous erythropoietin in benzene-treated mice.

Normal as well as hypertransfused BDF1 mice were exposed to 300 ppm of benzene, 6 h/day, 5 days per week for 2, 4, and 6 weeks respectively. Erythroid-committed hematopoietic progenitor cells CFU-E were determined in the bone marrow, and 59Fe incorporation was measured in the peripheral blood 48 h after its injection, as an indicator of active erythroid cell production. CFU-E numbers were reduced in benzene-exposed mice at all intervals, as was 59Fe incorporation in the peripheral blood after 2 weeks of exposure. In hypertransfused mice the CFU-E suppression, caused primarily by the hypertransfusion, was aggravated by benzene. After injection of 1 IU Ep 4 days before killing the CFU-E numbers and the 59Fe incorporation increased in controls as well as in benzene-exposed animals, but the difference persisted. After nine consecutive Ep injections the difference concerning the femur disappeared after 2 and 6 weeks of benzene exposure but was still present in the peripheral blood. These results suggest that chronic benzene exposure has a negative effect on early erythroid-committed, Ep-responsive hematopoietic cells.

Animals↗
PubMed1992

Triggering of stem cell (CFU-S) proliferation after transplantation into irradiated hosts.

The paper demonstrates the beginning of increased proliferation of the bone marrow clonogenic cells, detected by the spleen colony technique, taken from normal mice and transplanted into syngeneic recipients, lethally irradiated 24 h previously. A lag period of about 10 h preceded the beginning of increased proliferation that was determined according to the sensitivity of transplanted cells to the lethal action of hydroxyurea.

Animals↗
PubMed1991

Hematopoietic stem cells in +/+, nu/+, and nu/nu C57Bl/10 mice.

Mice with the nu mutation have been shown to have a reduced incidence of spleen colony-forming units (CFU-S), with a higher variability between individual mice compared to +/+ mice. The presence of these defects also in nu/+ mice indicates that this mutation is a codominant trait and that the hematopoietic changes may not be solely caused by thymus dysgenesis. The proportion of CFU-S synthesizing DNA (approximately 40%) has not been significantly different between +/+, nu/+, and nu/nu mice.

Animals↗
PubMed1990

Haemopoietic stem cells: spleen colony-forming cells are normally actively proliferating.

The haemopoietic stem cells forming spleen colonies (CFU-S) had on average 30 to 40% of cells engaged in the DNA synthesis in normal mice continuously over 4 years. A majority of experiments aimed at the suppression of the CFU-S proliferation, which included suppression of the T-lymphocytes by means of cyclosporin A or by adult thymectomy, administration of antibacterial and antifungal agents and maintainance of mice in a sterile environment, suppression of antibody-producing cells by a successive administration of the bacterial lipopolysaccharide and cyclophosphamide and attempts to increase the total number of CFU-S in the body through massive transfusions of bone marrow cells or by grafting plugs of the bone marrow under the kidney capsulae, have not been sufficiently effective. A transient suppression of CFU-S proliferation occurred during recovery of the haemopoietic tissue from damage caused by cyclophosphamide. The results support the view that changes in CFU-S numbers and in the proportion of them in DNA synthesis may be positively correlated when CFU-S numbers fluctuate physiologically about their normal values. The failure to manipulate the CFU-S proliferation rate easily suggests that proliferation of these cells may not be under a strong 'switch on - switch off' control.

Animals↗
PubMed1990

The dysgenetic thymus in nu/nu mice is a potent source of colony stimulating factor (CSF).

During in vitro incubation, the pulmonary and thymic tissue of mice released a colony stimulating factor (CSF) supporting the development of colonies of granulocytes and macrophages from bone marrow progenitors. Cardiac, splenic, renal and bone marrow tissues were not active. The dysgenetic thymus of nude mice was a very potent source of CSF during in vitro incubation.

Aging↗
PubMed1989

A comparison of stem cell assays using early or late spleen colonies.

The distribution of spleen colony diameters was determined 5.5, 8.0, 10.5 and 13.0 days after injection of normal bone marrow cells to lethally irradiated recipients. A relative lack of small colonies on day 8.0, as compared with days 5.5, 10.5 and 13.0, argued against a time continuum in colony appearance. The spleen colonies observed after 10 days or more probably represented a mixture of colonies which developed from the originally transplanted CFU-S and those arising from secondary CFU-S. Thus, late appearing spleen colonies may not necessarily identify a different, less mature, population of CFU-S. Administration of increasing amounts of bone marrow cells was used for comparing the linearity of the CFU-S assay for colonies observed after 8 days or after 12 to 13 days. The influence of overlapping colonies on the results was considerably augmented if large spleen colonies were observed after 12 or 13 days. Subsequently the CFU-S assay lost much of its quantitative character. We believe that some previously published data might have been misinterpreted by neglecting the important differences between 'early' and 'late' CFU-S assays.

Animals↗
PubMed1989

Individual differences in a functional organization of the hematopoietic tissue.

Random-bred ICR mice exhibited a wide range of spleen colony-forming units (CFU-S) and granulocyte-macrophage colony-forming cells (GM-CFC) between individuals. Both CFU-S and GM-CFC values were, however, relatively stable in individual mice over a period of 6 weeks, although the cellularity of the marrows changed significantly during the same period. CFU-S and GM-CFC values were only weakly correlated in individual mice. Bone marrows of mice with low CFU-S values did not have a lower cellularity than mice with high CFU-S values. A low level of CFU-S thus appeared to be compensated for by a higher clonal expansion of maturing cells. It may be concluded that there is wide variation in the organization of the stem cell compartment. Individuals may thus differ markedly in the organization of the marrow. Such differences may prevail in man and be of functional importance at times of extra demands, e.g., during cytostatic therapy.

Animals↗
PubMed1989

Thymidine suicide and hydroxyurea kill ratios accurately reflect the proliferative status of stem cells (CFU-S).

We have previously found that on average 30% of hematopoietic stem cells (CFU-S) are in the S phase, which is at least three times the value published by others. Therefore, it seemed desirable to investigate the reliability of the methods used to measure the percentage of CFU-S in S phase. Various modifications of the [3H]thymidine suicide were tested and it could be demonstrated that results were not affected by them. Furthermore, results obtained with the [3H]thymidine suicide were compared to those obtained with methods utilizing hydroxyurea to kill CFU-S in S phase. The [3H]thymidine- and hydroxyurea-based methods gave parallel results. The parallel behavior validated all of these methods as reliable indicators of the turnover of CFU-S and presumably other stem cell populations.

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↗