E. A. McCulloch

Spleen-Colony Formation in Anemic Mice of Genotype WW

The hemopoietic cells from anemic mice of genotype WW are less able by 200-fold to take part in colony formationin the spleen than cells from the normal littermates of genotype ww. The genetic defect shows itself in the colony-forming cells, since cells from normal littermate mice formcolonies in the spleens of unirradiated mice of genotype WW. Use of animals of genotype WVVWT as recipients improves the spleen-colony method by removing bias resulting fromthe death of irradiated recipients.

The radiation sensitivity of normal mouse bone marrow cells, determined by quantitative marrow transplantation into irradiated mice.

Description: Quantitative bone marrow transplantation was used to obtain an estimate of the radiation sensitivity of normal mouse bone marrow progenitor cells. Reproduced from Radiation Research 1960(Jul); 13(1): 115-125 by copyright permission of the Radiation Research Society (www.radres.org).

Early repair processes in marrow cells irradiated and proliferating in vivo.

Early repair of sublethal radiation damage was demonstrated in surviving spleen-colonizing cells in vivo by means of dose-fractionation experiments. A study of the kinetics of the early repair process indicated that early repair reached an initial maximum at about 5 hours after the first dose fraction, followed by an intermediate minimum at about 11 hours. An assay procedure that may be used for the study of the behavior of spleen-colonizing cells in situ was developed. (auth)

The Sensitivity of Cells from Normal Mouse Bone Marrow to Gamma Radiation in Vitro and in Vivo

1. A survival curve for the colony-forming ability of mouse bone marrow cells irradiated in vivo with Co60 gamma-rays has been obtained. The curve may be characterized by D0 of 95 rads and an extrapolation number of 1.5. 2. Comparison with the survival curve obtained for irradiated in vitro indicated a statistically significant difference in extrapolation number. Possible explanations for this finding are considered.

The proliferative states of mouse granulopoietic progenitor cells.

Summary Mouse granulopoietic progenitor cells can be detected by their capacity to form colonies in culture (CFU-C). The proliferative state of these cells was studied by determining the degree to which their colony-forming capacity was destroyed following exposure to a pulse of high specific-activity 3HTdR. When marrow was obtained from normal adult mice 35% of CFU-C were inactivated by this procedure. In contrast, 80% of CFU-C were inactivated when cell populations were obtained from regenerating bone marrow. These results are interpreted to mean that CFU-C in normal mice are partitioned into two populations, one proliferating rapidly and the other slowly or not at all. In regenerating marrow the partition is changed, with all or almost all of the cells proliferating rapidly.

Proliferation of hemopoietic colony-forming cells transplanted into irradiated mice.

Originally published in Vol. 22 No. 2 of Radiation Research journal. The Radiation Research Society holds all copyright to this article. The Society allows authors to deposit their own work into their institutional repository.

Perspectives on the properties of stem cells.

Much about stem cells is controversial. For example, even the question ‘what is a stem cell?’ arouses controversy. One definition of stem cells is that they are “primal undifferentiated cells which retain the ability to differentiate into other cell types...[which] allows them to act as a repair system for the body, replenishing other cells as long as the organism is alive”1. This definition is controversial for at least two reasons. First, it could be interpreted to imply that a stem cell is simply an undifferentiated cell that is able to give rise to differentiated descendants (i.e., that ‘stem cell’ is equivalent to ‘progenitor cell’). Second, this definition neglects a crucial property of stem cells—that some of their descendants must retain stem cell properties. We suggested in1963 that stem cells have two defining properties that are evident at cell division2. First, progeny arising from division may retain stem properties; that is, the stem cells have made new stem cells, the property called self-renewal. Alternatively, the progeny of stem cell division may have lost the capacity for self-renewal; instead, they may either differentiate or enter into a series of terminal divisions, finally yielding an organized tissue such as an organ or a population of functional blood cells. Beyond these two central properties, stem cells are identified and named according to the function of their descendants (for example, marrow stem cells) or their place in development (for example, adult stem cells or embryonic stem cells). Stem cells also vary in the diversity of their differentiated descendants. Those with unlimited potential are called totipotent stem cells. Equivalent designations are used for cells whose potential is limited (pluripotent stem cells, multipotent stem cells, bipolar stem cells, etc.). Much research forms the basis of these various designations, and questions about the self-renewal potential and the differentiation potential of various kinds of stem cells continue3. The introduction of the concept of plasticity is a good example of the general impact of stem cells throughout biology and medicine. Here we provide a few other examples, such as the impact of stem cells on the development of diversity and cancer. Furthermore, recent work in many laboratories is showing the possibility of functional uses of stem cells, especially in regenerative medicine. These experiments are controversial not only in the scientific sense, but also in their ethical consequences. These possibilities, and their accompanying debates, account in large part for the intensity of the current interest in stem cells. These controversies will be mentioned briefly here, but not considered in detail.

COMPARISON OF COLONY-FORMING ABILITY OF NORMAL AND LEUKÆMIC HUMAN MARROW IN CELL CULTURE

Abstract Normal human bone-marrow contains cells capable of forming colonies in soft-agar cultures. Marrow from patients with acute leukaemia failed to form colonies under the conditions used.

REPAIR PROCESSES IN IRRADIATED MOUSE HEMATOPOIETIC TISSUE.

Two different techniques, the endogenous colony method and the transplantation method, were used to study radiation damage repair in colony- forming cells of mice irradiated with /sup 60/Co gamma rays. From survival curves resulting from the two methods, it was apparert that radiosensitivity of endogenous colony-forming cells is similar to that of transplanted coIony-forming cells. Recovery of colonyforming abillty in cells of the mouse hematopoietic system was demonstrated by determining the ratio of colonyforming cells surviving single and fractionated doses. Late repair processes commencing at 24 hr postirradiation and assumed to be the resuIt of cellular proliferation were found to increase with time intervals up to 14 days between radiation doses, but to decrease between 14 and 20 days. Kinetics of late repair were studied in endogenous colony-forming cells. Residual injury is plotted as a function of time after a conditioning dose of 400 rads. (R.M.G.)

Colony formation by normal and malignant human B-lymphocytes.

A method is described that permits colony formation in culture by B lymphocytes from normal blood and from blood, marrow or lymph nodes of patients with myeloma or lymphoma. The method depends on: (1) exhaustively depleting cell suspensions of T lymphocytes, (2) a medium conditioned by T lymphocytes in the presence of phytohaemagglutinin (PHA-TCM), and (3) irradiated autologous or homologous T lymphocytes. Under these conditions the assay is linear. Cellular development of B lymphocytes can be followed, differentiation to plasma cells is seen in cultures of cells from normal individuals and myeloma patients, but not lymphoma patients. Malignant B lymphocytes in culture produced immunoglobulin of the class identified in the patients blood, or in freshly obtained cells. We conclude that the assay is suitable for studying the growth, differentiation and regulation of normal and malignant B lymphocytes in culture.