Erythropoiesis and plasma tocopherol levels in irradiated mice

Plasma protein and tocopherol concentrations, haematocrit and 59-iron incorporation into erythrocytes have been measured in vitamin E-deficient and supplemented mice before and after exposure to 500 R of 260 kVp X-ray. Supplemented animals had greater haematocrit, plasma tocopherol and protein levels initially. After irradiation plasma tocopherol concentration decreased drastically in the vitamin E-supplemented mice.

[Preferential differentiation of hematopoietic stem cells transferred to mice previously infected by BCG]

Following injection of bone marrow cells in lethally irradiated mice, previously infected with BCG regenerating hemopoietic cell populations differentiate along the leucocyte pathway to the detriment of erythroid lineage. Such a phenomenon persisting even if anemia of infected mice is increased by bleeding just before irradiation and reconstitution supports the hypothesis of preferential differentiation of stem cells.

Inverse relationship between splenomegaly and stem cell compartment size in mice treated with nitrogen mustard

Following the administration of similar doses of nitrogen mustard (4 mg/kg) to different strains of mice, wide variations in the subsequent degree of splenomegaly were observed, implying strain differences in the role of the spleen in the compensatory erythropoietic response to haematopoietic stress. This investigation was undertaken to determine whether or not these differences were related to the size of the haematopoietic stem cell compartment size in the various strains of mice. Groups of 4 different strains of mice (Swiss Webster, A/J, C57BL/6J and CS1/ASH) were injected i.v. with nitrogen mustard (4 mg/kg body weight) and autopsied at regular intervals up to 20 d post-injection. At autopsy, the wet weight of the spleen was determined. Subsequently, groups of the same 4 strains of mice were exposed to single doses of wholebody gamma-irradiation in the range of 500-900 rads. 9 d after gamma-irradiation the mice were autopsied, their spleens removed, and the number of endogenous spleen colonies determined. The greatest degree of splenomegaly was observed in the C57BL/6J mice. The Swiss Webster mice showed no splenomegaly during the time period studied. There existed a linear inverse relationship between the maximum degree of splenomegaly observed and the dose of wholebody gamma-irradiation required to completely eliminate endogenous spleen colonies. This data is in accord with the hypothesis that there exists an inverse relationship between the extent of splenomegaly observed following haematopoietic stress and the haematopoietic stem cell compartment size.

Patterns of exogenous and endogenous hematopoietic repopulation following radiation injury

Patterns of hematopoietic recovery in mice given an LD50/30 radiation exposure were different from those in animals given an LD100/30 exposure and a marrow transplant sufficient to effect 50 per cent 30-day survival. Death occurred later, and recovery of some peripheral blood elements was delayed in the LD50/30 mice. Over the period of study, splenic hematopoiesis and stem cell renewal were insignificant in the LD50/30 mice yet were active in the marrow-transplanted animals. The slow recovery of erythropoiesis in the LD30/30 mice is explained in part by the lack of early splenic hematopoiesis. This effect appeared to be attributable to the splenic microenvironment which, although being suitable for growth of unirradiated hematopoietic cells, was not conducive to repair of radiated splenic hematopoietic cells.

[Tritium panmyelopathy in the luminescent dye industry]

A case of reversible panmyelopathy in the luminous paint industry is reported. The 52-year-old male patient had a long history of exposure to radium 226, strontium 90, thorium 228 and tritium.

Complex nature of the production of 'effector' cells and their interaction with target cells in the M-antigen system of the mouse

The capacity of lymphocytes from mouse strain CBA to generate 'effector' cells against the H-2-compatible, M-antigen-incompatible strain C3H and their interaction with such target cells were investigated. It was observed that CBA lymphocytes injected in, and 5 days later obtained from, the spleens of irradiated C3H X CBA hybrids ('educated cells') could strongly inhibit the growth of C3H X CBA bone marrow cells but were almost nonresponsive to C3H X C57BI bone marrow targets (H-2-incompatible). CBA lymphocytes educated in irradiated C3H X C57BI hosts displayed reactivity against C3H X C57BI and CBA X C57BL but not against C3H X CBA bone marrow target cells. Additional tests indicated that the M antigen determined by C3H is expressed to approximately the same extent on C3H X CBA and C3H X C75BL cells and that the M antigen on C3H does not cross-react immunologically with antigens on C57BL cells. Moreover, it was observed that CBA X C57BI lymphocytes were triggered to cell proliferation by C3H antigens but were unable or had a highly reduced capacity to develop 'effector' cells in response to this antigenic stimulus. These results indicate that generation of 'effector' cells and their interaction with target cells are very complex processes.

Erythroid differentiation of fetal, newborn and adult haemopoietic stem cells

Erythroid regeneration was studied in lethally irradiated mice given transplants containing equivalent numbers of haemopoietic stem cells (i.e. CFU) from fetal liver, neonatal marrow or adult marrow. Adult marrow was taken from normal control mice, whose CFU for the most part were not in active cell cycle, as well as from phenylhydrazine-treated groups whose CFU were in similar state of proliferation (i.e. approximately 40-50% in DNA SYNTHESIS) AS THOSE DERIVED FROM FETAL LIVER AND NEONATAL MARROW. Splenic and femoral radioiron (59Fe) incorporation were measured at intervals after transplantation and were found to begin earliest in mice given fetal liver, then in animals given neonatal marrow and latest in recipients of adult marrow. Peripheral reticulocytes showed a similar pattern of recovery. The data reported herein suggest that the differences in erythroid regeneration evoked by transplants of fetal liver, neonatal marrow or adult marrow, are not solely attributed to the degree of proliferation in the pluripotential stem cell compartment. These data may, however, suggest a shorter doubling time for cells comprising the fetal and newborn committed erythroid compartments.

Stimulation and inhibition of erythropoiesis in donors and hematopoietic effect in irradiated recipient

Regeneration dynamics in bone marrow and spleen was studied in rats after irradiation of 800 R and transfusion of bone marrow cells from donors treated in different ways. Priority of the microenvironment of the recipient or of the information obtained in cell donors with respect to further hematopoietic cell differentiation was studied in irradiated recipients. Rats irradiated with 800 R were used as recipients in the experiments. The donors of marrow cells were the rats with stimulated or inhibited erythropoiesis. Stimulation of erythropoiesis was induced by bleeding and experimental polycythemia was provoked by packed erythrocytes. According to our results, it can be concluded that the processes of postirradiation hematopoiesis after transplantation of the bone marrow cells depend on the number and proliferative state of both donors and recipient stem cells, and microenvironment, not excluding the information introduced with the donor cell transplant.

Bone marrow scanning with 52iron (52Fe). Regeneration and extension of marrow after ablative doses of radiotherapy

Extensively irradiated patients were studied from 0 to 73 months after irradiation by 52Fe bone marrow scanning. Marrow regeneration was observed in most patients after intervals of 12 months or longer. The degree of recovery was not dose-related and the marrow ablative dose was not defined with doses of 4000-5000 rads. Degree of recovery depended more upon the antomic region and/or sequence of fields treated; the last field treated invariably showed poorer regeneration when recovery was uneven. Active erythropoisis expanded into distal inactive erthropoietic sites from 3-12 months after irradiation and then decreased thereafter. Blood count cytopenias were almost always restricted to the first year after irradiation.

Erythropoiesis in the X-irradiated, bled rat

Exposure to low levels of x-irradiation (50R) followed by phlebotomy (50% blood volume) one month post-irradiation, resulted in identifiable alterations of the erythropoietic status of the rat. The red cell indices revealed a decrease in mean corpuscular volume and an increase in mean corpuscular hemoglobin concentration. The half-life of 51Cr-labeled erythrocytes was 16.7 days versus 14.4 days for the untreated controls. These subjects also demonstrated hyperplastic marrows with an approximate 60% mean increase in marrow cellularity. A reproducible mortality of 25% was seen at 17 weeks post-irradiation; the one group of animals followed for an extended period exhibited an 86% cumulative mortality at 23 weeks. The observations supported the concept that x-irradiated rats exposed to a relatively low dose of X-rays (less than 10% LD/50) maintain a latent or residual injury of the bone marrow. These animals, when subsequently challenged by phlebotomy, are placed at greater risk with respect to their ability to survive.

Selective damage to erythroblasts by 55-Fe

The low energy and short range of 55-Fe Auger electrons were utilized in mice to deliver lethal intracellular radiation to iron-incorporating erythropoietic precursors with minimal radiation damage to other bone marrow cells. The ensuing intramedullary, selective erythropoietic death was demonstrated by absolute and differential bone marrow cell counts and by decreased blood uptake of 59-Fe. The decreased number of colony-forming units in spleen colony assay and the decreased ability of tranplanted bone marrow to protect fatally irradiated mice shows that the bone marrow was partially depleted of pluripotent stem cells. These data are interpreted to indicate an increased pluripotent stem cell utilization in response to increased demand for differentiation of stem cells along the erythropoietic pathway.

[Differentiation of haemopoietic tissues from embryos and adults injected into irradiated chickens (author's transl)]

Irradiated chicken are injected with haemopoietic tissues from adult or 11-day-old embryos. Development of stem cells gives rise to well-defined erythrocytic colonies on the surface of the tibial marrow. Erythropoietic production appears to be similar from adult marrow and embryonic blood stem cells; production from injected vitelline stem cells seems to be between 3 and 4 times higher than that of adult marrow stem cells. Results are discussed on the basis of two hypotheses: -existence of an extramedullary erythropoietic site in the host after vitelline cells grafting; -development of vitelline stem cells in the host marrow with kinetic patterns different from those of grafted adult marrow or embryonic blood stem cells. Anyway, the 11-day-old embryo appears to contain at least two types of blood stem cells with distinctive properties. Developmental origin, relationship and future of these different stem cells remain to be analysed.

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: I. Project BIOCORE (M212), a biological cosmic ray experiment: procedures, summary, and conclusions

The primary objective of the experiment was to determine whether a specific portion of the high Z-high energy (HZE)* galactic cosmic ray particle spectrum, especially particles with Z greater than or equal to 6, can produce microscopically visible injury of brain and eye tissues. Pocket mice (Perognathus longimembris), obtained from the California desert, were selected as the biological target. Five of these mice were flown on Apollo XVII. Not only the brain and eyes but also many other tissues of these animals were studied for evidence of cosmic ray particle damage. The lack of prior experimental evidence as to the character of the potential injury induced by HZE particles required reliance on the physical characteristics of particle radiation in ascertaining the probable nature of the injruy. These characteristics and the key aspects of the experiment are summarized in this paper. Subsequent articles in this special supplement give details of the biological, engineering, and dosimetric aspects of BIOCORE together with the results.

Measurement of erythropoiesis by radio-iron incorporation: influence of iron- and cell kinetic changes

59Fe blood appearance curves have been obtained in mice by injection of the isotope at various times after 850 rad whole body X-irradiation and bone marrow grafting in order to produce different levels of erythropoiesis. The results demonstrate that measurements at 24, 48 and 72 hours are not comparable and lead to different interpretations. Standardization of the time at which 59Fe uptake measurements are made is therefore recommended.

The restorative effect of erythropoietic stimulation upon the sublethally irradiated (SLI) hematopoietic stem cell and/or its progeny

Bone marrow cells from sublethally irradiated donor mice injected into supralethally (1000 R) irradiated recipients produced not only many fewer spleen colonies but fewer erythrocytic (E) colonies in relation to the number of granulocytic (G) colonies than did unirradiated donor marrow in similar recipients. This reversal of E:G ratio was partially or completely restored by a strong erythropoietic stimulus in the recipients, whether endogenous, (induced by anemia) or exogenous (injected purified EP). Such a stimulus produced a large increase in total spleen colony numbers in all experiments. An unexpected result was a major increase in granulocytic and megakaryocytic colonies in the spleen and marrow of the erythropoietically stimulated recipients. It was concluded that the sublethal irradiation to the donor either produced or revealed a subpopulation of potential colony forming cells whose cell cycle was slow or temporarily arrested. The added EP (and/or related substances) was proposed to have either overridden or induced repair or radiation defect, or stimulated a small and normally undetectable population requiring high levels of stimulant to induce cycling. The result was the expression of their progeny as colonies, whose differentiative type depended upon the kind of hematpoietic inducing microenvironment in which they had lodged.