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V Znojil

Publications and source records attributed to V Znojil.

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

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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.

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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.

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PubMed1988

The spleen colony technique. I. Correction for the overlap effect and sources of error in CFU-s determination.

A linear model for the errors of the 'spleen colony' assay for haemopoietic stem cells has been derived. The components emerging from the model are interpreted and practical recommendations given for interpreting measurements made with this assay. The model permits correction for the effect of overlapping colonies and gives average errors for single measurements of the number of CFU-s. More reliable and more precise information can be obtained using this model. The spleen colony technique detects a population of immature precursor cells designated as CFU-s (Till & McCulloch, 1961). The relative error of measurement is often large when compared with the changes in the phenomena studied. Consequently a better knowledge of the errors of this technique is highly desirable. This paper should be regarded as an extension of the previous analysis of Till (1972). The theory for the errors of the spleen colony technique was applied to 905 determinations of the CFU-s numbers performed on random-bred mice. Data from random-bred mice rather than those from inbred mice have been used because the error components can be expected to be larger and, consequently, more easily detectable. The model of errors has also been validated using data published by Till (1972) and has subsequently been applied to data from several inbred mice strains (Znojil & Necas, 1988).

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PubMed1988

Non-circadian rhythm in proliferation of haematopoietic stem cells.

The proportion of haematopoietic stem cells (CFU-s) engaged in DNA synthesis was determined by means of the [3H]-thymidine [( 3H]TdR) suicide technique during recovery of bone marrow from the damage caused by a sublethal total body irradiation. In contrast with previous reports the [3H]TdR suicide rate was not permanently increased. It was observed that CFU-s passed through S phase in synchronous waves, following a dose of irradiation of 1.5 Gy. After a dose of 2.6 Gy, there was only one initial wave of increased CFU-s sensitivity to the action of [3H]TdR. Following the depression occurring 26 hr after the irradiation with 2.6 Gy, the proportion of CFU-s killed by the [3H]TdR was permanently increased until 5-6 days after irradiation. Thereafter large differences in the [3H]TdR suicide data were observed among individual mice. Evidence was obtained that individual mice, which had been irradiated by a dose of 2.6 Gy 8-9 days before, had identical values of the CFU-s [3H]TdR suicide rate in the bone marrow from different bones of the lower extremities. The recurrence of the synchronous waves in CFU-s passage through the cell cycle was recorded when the CFU-s population regenerated to only about 10% of its normal value. These waves were obviously not related to a particular time of the day and, consequently, they did not represent the circadian rhythm. It is concluded that the synchronous waves in which CFU-s proliferation occurred reflected the action of the control mechanism on CFU-s proliferation. This mechanism should be endowed with an important systemic component besides locally operating factors.

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PubMed1988

The spleen colony technique. III. Comparison of the overlap effect and of errors in CFU-s determination and the [3H]-thymidine suicide data for several strains of mice.

A mathematical model of errors of the spleen colony technique is applied to data obtained from four mouse strains and F1 hybrids. The variance of the colony counts was close to the Poisson distribution in inbred mice and F1 hybrids. However, it should be checked regularly. The magnitude of the error in CFU-s determination and of the estimations of the S phase fraction was derived, and is presented relative to the mean colony counts for all mouse strains studied. The optimum spleen colony counts are generally higher than those which are commonly used. However, the utilization of the optimum spleen colony counts requires a correction for the effect of colony overlap.

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PubMed1988

Bone marrow response to single small doses of irradiation: implications for stem cell functional organization.

The data collected in 107 experiments over 23 months have been pooled to indicate the responses of cellularity, stem cell (CFU-S) number, and CFU-S proliferation rate (CFU-S in S-phase) during early recovery of the bone marrow from 1.5 and 2.6 Gy irradiation. The bone marrow differentials and numbers of granulocyte-macrophage progenitors (CFC-GM) were determined after irradiation with 1.5 Gy. The CFU-S proliferation rate was examined also in mice irradiated with 3.5-5.0 Gy. The data are discussed in the light of various hypotheses about the functional organization of the CFU-S population. It is proposed that the control of the CFU-S production rate is primary rather than the control of CFU-S numbers.

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PubMed1988

Stem cell number versus the fraction synthesizing DNA.

It has been widely held that the fraction of spleen colony-forming units (CFU-S) in DNA synthesis is inversely correlated with CFU-S numbers. In 750 measurements the expected negative slope of the linear regression of CFU-S in S-phase on CFU-S was found to be significant only when the measurements from irradiated mice were pooled. In contrast, a significant positive correlation was observed when the measurements from normal controls were pooled. A hypothesis is offered to account for the variable relationship between CFU-S and CFU-S in S. The hypothesis fully recognizes the crucial role of both parameters in normal and regenerative hemopoiesis.

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PubMed1987

CFU-S content and cycling rate in several strains of mice.

The number of CFU-S and the fraction synthesizing DNA have been measured in individual normal mice of several inbred strains. The data gathered during a period of 5 years have been subjected to analysis of variance. Large differences are shown to exist in the number of CFU-S in the femoral bone marrow of individual mice measured on the same day. These differences are greater if measurements are performed on different days. The fraction of DNA synthesizing CFU-S was on average 30% in these normal mice. The range of measurements on both the same and different days was 0%-60%. The large differences in the fraction of CFU-S in S-phase were found even among mice coming from the same cage. This differs from many previous reports where 10% is given as the upper limit for the fraction of CFU-S synthesizing DNA in normal mice. It is suggested that the observed range of individual values from 0%-60% might reflect bursts of proliferation of CFU-S. Irradiation or hydroxyurea administration resulted in disappearance of low and medium values. All mice then had 50%-60% of CFU-S in S-phase.

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PubMed1983

The distribution of the haeme and non-haeme fractions of iron in individual regions of the erythropoietic system of intact and acutely irradiated mice.

In male mice of the strain C57BL/10ScSnPh, both intact and X-irradiated with a whole-body sublethal dose, the distribution of the content of total and haeme iron was studied in individual bones, the spleen, liver, plasma and erythrocytes, using an original mineralization and extraction technique. In the erythropoietic organs as a whole and in the individual bones the haeme and non-haeme iron compartments were distinguished, and within these the iron accounted for by circulating plasma and by erythrocytes and erythrocyte precursors. In the radiation-depleted marrow there were quantitative and qualitative changes in the compartments, particularly the creation of an important compartment of non-circulating (fixed) erythrocytes.

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PubMed1982

The distribution of erythropoiesis over the various anatomical regions of the erythropoietic system in some inbred strains of mice.

The extraction of 59Fe bound to the heme in the erythropoietic organs by means of acid ethylacetate was used to establish the proportion of erythropoiesis for which individual bones and the spleens of some inbred mouse strains are responsible. The proportion of splenic erythropoiesis differs from strain to strain, being in the range 9-42% of total erythropoiesis. In the strain BALB/c erythropoiesis is shifted in comparison with C57B1/10 strain towards the spine and away from the bones of the skull, the long bones of the limbs and the pelvis. Calculations of the erythroid cellularity and/or the intensity of erythropoiesis of the total bone marrow on the basis of a single bone should take into account both these interstrain differences in the participation of different regions and the possibility of various proportions of red and white blood cells and cells containing non-heme iron existing in different regions (bones).

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PubMed1980

The volume of plasma and erythrocytes in individual bones and in the spleen of mice under physiological conditions and with acute radiation-induced atrophy of the haemopoietic tissue.

Using labelled erythrocytes and human serum albumin, the volume of circulating erythrocytes and plasma was determined in the spleen and individual parts of the skeleton of mice under physiological conditions and 48 h after X-irradiation with a dose of 2,87 Gy. The results are significant for the interpretation of the method of incorporation of labelled iron into haemopoietic organs.

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PubMed1978

Comparison of life span of erythrocytes in some inbred strains of mouse using 14C-labelled glycine.

The erythrocyte life span in four inbred strains of mice--C57BL/10ScSnPh, B10.LP, BALB/c and CBA/JPh--was determined by means of erythrocyte labelling with 14C-glycine. Experimental data [decrease of 14C-activity of washed erythrocytes], corrected for blood loss, reincorporation of the label and delay in label incorporation during the initial period, were treated by a novel mathematical procedure based on the death probability function of the form: mu [t] = a + btlambda. The mean erythrocyte life span calculated using this function was, in the given sequence of strains, 42.1 +/- 0.6, 41.3 +/- 1.2, 39.3 +/- 0.9 and 38.6 +/- 0.6 days respectively. The rate of "random" destruction of erythrocytes was 1.20, 1.31, 0.70 and 0.63% of the total number of erythrocytes per day and a "mean potential" erthrocyte life span was found to be 58.9, 59.9, 46.2 and 44.5 days respectively. All the given parameters have similar numerical values in related strains and are apparently genetically conditioned. The erythrocyte life span determined simultaneously using DF32P labelling in the C57BL/10ScSnPh strain was 47.4 +/- 1.0 days. The implications of the results yielded by these two techniques is discussed.

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