Kh Steinbach

A Mathematical Model of Canine Granulocytopoiesis

SummaryThe granulocyte cell renewal system of the dog is represented by a mathematical model consisting of the following compartments: The pool of pluripotential stem cells, the committed stem cell pool, divided into a blood and a bone marrow compartment, the proliferation pool, the maturation pool, the reserve pool and the blood pool of functional granulocytes. This chain of compartments is described by a system of non-linear differential equations. Cell losses anyplace in the system provoke increased production in all pools containing cells capable to divide. A reduced number of granulocytes in the blood pool stimulates production of a “granulocyte releasing factor” which mobilizes a rising number of cells to transit from the marrow reserve into the blood pool.The model was simulated on a digital computer. It was found to be capable to reproduce the steady state conditions and it also fits the data of two distinct experimental perturbations of the system both equally well. These perturbations are a loss of proliferating cells as it occurs after the administration of cytostatic drugs and losses of functional cells as they are induced by leukapheresis experiments of differing leukapheresis rates.

In Vitro Studies on the Sensitivity of Canine Granulopoietic Progenitor Cells (GM-CFC) to Ionizing Radiation: Differences between Steady State GM-CFC from Blood and Bone Marrow

The radiosensitivity of the granulopoietic progenitor cells (GM-CFC) from blood and bone marrow of dogs under steady state conditions was studied by in vitro irradiation with 280kV X-rays (approximately 0.56 Gy/min). The dose-effect relationship for colony formation was determined for the dose range from 0 to 3 Gy by means of three different models. A simple exponential function revealed an optimal approximation to the experimental data obtained for the clonogenic cells from the two different sources. The D0 values are 0.261 +/- 0.009 Gy and 0.600 +/- 0.011 Gy for the GM-CFC from blood and bone marrow, respectively. Irradiation of blood-derived GM-CFC in the presence of pre-irradiated bone marrow cells or irradiation of bone marrow cells as a mixture with pre-irradiated blood cells led to small changes only in the survival curves. According to the dose-effect relationship obtained from these studies the GM-CFC of the dog seem to be the most radiosensitive clonogenic haemopoietic cells among the different mammals.

Simulationsmodelle von Perturbationen des granulozytären Zellerneuerungssystems

Wenn wir von neutrophilen Granulozyten im menschlichen Blut sprechen, so denken wir an ihre Konzentration pro mm3. In den Lehrbuchern der Hamatologie sind sog. Normalwerte von 2–7 × 103 angegeben [1, 2]. Beim Hund — dem von uns vorzugsweise benutzten Versuchstier — liegen die Normalwerte im gleichen Bereich. Fur unsere Erorterungen ist es wichtig, darauf hinzuweisen, das ein solcher jederzeit nachprufbarer Normwert nur einen Teil der Blutgranulozyten erfast. Mit Hilfe von Autotransfusionen von radioaktiv markierten Granulozyten gelang es zu zeigen, das neben den zirkulierenden Granulozyten noch ein etwa gleichgroses Kompartment an Granulozyten vorhanden ist [3, 4]. Man spricht dabei von dem „marginalen Speicher“. Bei einem raschen Granulozytenanstieg, wie er bei bestimmten „Stress“-Situationen vorkommt, kommt es zunachst zu einer Verschiebung aus dem „marginalen“ in den „zirkulierenden“ Speicher und erst dann zu einer Mobilisation von Granulozyten aus dem Knochenmarkorgan in das Blut [1]. Diese wenigen Satze sollen deutlich machen, das hinter dem Normwert der Blutgranulozyten eine ungeheure Dynamik steht. Diese wird verstandlich, wenn man bedenkt, das die Lebensdauer von Granulozyten im menschlichen Blut maximal 24–30 Stunden betragt — wie wir 1964 erstmals aufgrund von Zellmarkierungen mit 3H-Thymidin zeigen konnten [5, 6]. Man kann unschwer berechnen, das taglich ca. 120 × 109 Granulozyten das Blut verlassen, um ihre extravasalen Aufgaben wahrzunehmen oder aus Alterungsgrunden eleminiert werden. Eine gleichgrose Anzahl mus also aus den weit uber 100 einzelnen Knochenmarkabschnitten kontinuierlich nachgeliefert werden. Wir sprechen von einem Fliesgleichgewicht zwischen Abflus von Granulozyten aus der Blutbahn und ihrem Einstrom in die Blutbahn (Kein = Kaus)

Quantitative aspects of granulocytic progenitor cell (CFUc) mobilization from extravascular sites in dogs using dextran sulphate (DS)

Abstract. The relationship between the increase in the blood CFUc concentration after intravenous injection of dextran sulphate (DS) and the pre‐existing levels of spontaneously circulating CFUc was studied in dogs. After 15 mg DS/kg body weight the CFUc numbers per ml blood rose by a factor of 3.7 over the pre‐injection values, from 78 ± 11 (SEM) to 359 ± 50, in normal dogs, and increased by a factor of 3.9 in 0.84‐Gy‐r‐irradiated animals which had a reduced initial CFUc concentration per ml, from 35 ± 8 to 116 ± 43. The injection of 20 mg DS/kg body weight into unirradiated dogs caused an increase, by a factor of 11.5, of the pre‐injection CFUc concentration, from 101 ± 20 to 921 ± 106. On the basis of the mobilization curves for individual dogs, a significant correlation was found between the normal blood CFUc value and the number of CFUc mobilized by DS for both dose levels. From the descending part of the mobilization curves obtained after 15 mg DS/kg body weight, kinetic parameters of canine circulating CFUc were derived. The mean blood transit time (τ) was 1.4 ± 0.5 hr and the half time (T/2) was 1.0 ± 0.4 hr.

Fetal liver transplantation in the dog. II. Repopulation of the granulocyte-macrophage progenitor cell compartment by fetal liver cells from DLA-identical siblings.

The restoration of the granulocyte-macrophage progenitor cell (CFU-GM) compartments in blood and bone marrow, and the recovery of blood monocytes were followed for up to one year in ten beagles that had been exposed to fractionated (3x6 Gy) total-body irradiation before being transfused with cryopreserved fetal liver cells (FLC) from sibling donors that were genotypically matched for dog leukocyte antigens. Grafts contained 0.2–1.6x108 mononuclear cells and 0.9–19.8x104 CFU-GM/kg body weight. Numbers of circulating monocytes rose parallel to granulocyte numbers after day 6 and became normal by day 18 posttransplant. In bone marrow aspirates, low numbers of CFU-GM were detected on day 3 and their incidence per 105 mononuclear cells was normal after day 14. Circulating CFU-GM were present in significant numbers by day 7 and their elevated concentration per milliliter of blood after day 14 continued for one year. Dextran sulfate injection mobilized normal numbers of CFU-GM into the blood early after transplantation, and spontaneously circulating CFU-GM in a later phase did not differ from blood progenitors of normal animals with respect to radiation sensitivity and sedimentation velocity. Thus, FLC transplantation effected a rapid restoration of granulopoiesis and monocytopoiesis, which was reflected at both the level of mature blood cells and the compartments of CFU-GM in blood and bone marrow, underlining the high repopulating capacity of fetal liver stem cells.

Repopulating potential of canine bone marrow cells: differences between large and small cells separated by velocity sedimentation

This study compares the pattern of haemopoietic recovery in dogs after total‐body irradiation and transfusion of different populations of cryopreserved autologous bone marrow cells. Dogs in group 1 received unseparated marrow cells. Group‐II dogs were transfused with small (<5.1 mmm/h) and group‐III dogs with large (>7.1 mm/h) bone marrow cells, separated by velocity sedimentation. Myeloid progenitor cells (CFU‐GM) present in slowly sedimenting cell fractions were characterized by a higher radiosensitivity in vitro and a lower proportion of cells in S‐phase as compared to rapidly sedimenting CFU‐GM. Although autografts in all groups contained comparable numbers of CFU‐GM, transfusions resulted in different patterns of recovery. Fractions of small bone marrow cells contained most of the pluripotent stem cells, leading to speedy haematological reconstitution and long‐term survival. The pattern of early recovery was similar in dogs of group I and of group II. In group III, the recovery in all cell lineages was delayed, going along with marked extramedullary haemopoiesis. The data may indicate the limits of committed progenitors in reflecting pluripotential stem cells, in particular, if bone marrow grafts have been modified in vitro. Differences in the repopulating potential of the graft might be reflected by distinct physical and biological properties of the CFU‐GM.