Alec Morley

Effect of Endotoxin on Granulopoiesis and Colony-Stimulating Factor

Abstract To study the regulation of granulopoiesis, we measured the effect of endotoxin on peripheral leukocyte counts and on colony-stimulating factor (CSF) in the serum of CF1 mice. The peripheral granulocyte level fell from 612 ± 69 (mean ± S.E.M.) to 147 ± 20 per cubic millimeter within 45 minutes of intraperitoneal injection of 5 μg of Salmonella typhosa endotoxin. In control animals, the CSF in 0.1 ml of serum stimulated the growth of 0.56 ± 0.4 in vitro myeloid colonies per 105 cells. Forty-five minutes after endotoxin the CSF activity had increased to 7.7 ± 6.1 colonies per 105 cells; after two hours it was 29.6 ± 10 colonies per 105 cells. Six hours after endotoxin the marrow was depleted of polymorphonuclear cells. Thereafter, sequential increases in the myeloblast-promyelocyte and myelocyte compartments of the marrow at 24 to 48 hours, respectively, suggested a wave of differentiation from a precursor compartment with subsequent maturation. The data suggest that intermittent endotoxemia may be ...

Cyclophosphamide-induced cyclical neutropenia. An animal model of a human periodic disease.

Abstract An animal model of a human periodic disease, cyclical neutropenia, was produced in five of nine dogs by administration of a constant daily dose of cyclophosphamide so as to cause mild bone-marrow depression. That this would occur was predicted by a computer model in which granulopoiesis was regarded as being controlled by two feedback loops, one regulating rate of production and the other rate of release of neutrophils. Cyclical neutropenia does not appear to be a specific entity, and its periodicity, and by extension possibly that of other periodic diseases, may be due to the action of feedback control. A hypothetical possibility is that if unrecognized oscillation of blood cell numbers should develop in patients receiving marrow-depressant drugs, estimate of marrow function at any one point of time might give a wrong impression of overall drug effect.

Erythropoiesis in the Dog: The Periodic Nature of the Steady State

In at least six of 11 normal dogs serial measurement of reticulocyte counts showed oscillation with a period of approximately 14 days. The phase of oscillation could be altered by bleeding followed by retransfusion. The observations suggest that canine erythropoiesis is an example of a physiological rhythm which has its origin in homeostatic control.

Studies on the Regulation of Granulopoiesis

Tritiated thymidine autoradiography was used to study the control of granulocyte production and release using the irradiated leg shielded mouse as an experimental model. Neutropenia resulted in a shortening of 24–36 hr in the mean transit time through the non‐proliferating granulocyte compartment. There was little difference between neutropenic and control animals in labelling indices of the cells in the proliferative granulocyte compartments, which suggests that the granulocytic hyperplasia observed in the neutropenic mice was predominantly due to differentiation of morphologically unrecognizable precursor cells rather than increased proliferation of morphologically recognizable cells. The persistence of a labelling index of approximately 60% in the myeloblast‐promyelocyte compartment 24 hr after injection suggests that these precursor cells were rapidly proliferating.

Inhibition of marrow growth by cyclic AMP.

Summary Cyclic AMP, dibutyryl cyclic AMP, epinephrine, and theophylline inhibited growth of marrow colonies in vitro. The interpretation of this observation is uncertain since various adenine nucleotides had a similar effect and since several substances lowering intracellular cyclic AMP levels were unable to reverse the inhibitory effect of exogenous cyclic AMP.

The effect of heat-damaged red cells on stem cells.

Injection of heat-damaged red blood cells (HRBC) into mice before irradiation increased the number of stem cells present after irradiation as shown by an increase in the number of endogenous spleen colonies and an improvement in survival. The magnitude of the effect on spleen colonies was dependent on the dose of HRBC and was maximal when the HRBC were given 24 hours before irradiation. HRBC did not affect the number of stem cells at the time of irradiation and did not alter the tendency of stem cells to lodge in the spleen. The initial action of HRBC may be to stimulate the reticuloendothelial system, but the ultimate means by which radioprotection is produced is uncertain.

Stem Cell Stimulatory Properties in Vitro of an Agar Colony-Stimulating Factor

Summary Bone marrow was incubated over a short period in vitro in the presence of WBI and normal serum. The number of cells capable of forming colonies in soft agar was maintained over a 48-hr period in the presence of WBI but not normal serum. Furthermore the decline in transplantable CFU was slower in the presence of WBI serum. Possible mechanisms for these results are discussed although firm conclusions cannot be drawn.

Haemopoietic stem cell stimulation in short-term tissue culture

Murine serum with high levels of agar colony stimulating factor (CSF) was examined for its ability to maintain myeloid stem cell and pluripotential stem cell numbers in a short term tissue culture of normal murine bone marrow. The serum was obtained from whole body irradiated (WBI) mice and had been previously shown to have high levels of CSF. The serum was mixed with normal bone marrow suspensions, whilst mixtures of normal serum and normal bone marrow suspensions served as controls. The content of pluripotential and myeloid stem cell compartments in these short term tissue cultures were assayed at regular intervals by bone marrow transplantation or the agar colony system respectively. In the presence of WBI serum myeloid stem cell numbers were maintained for periods up to 72 hr., whilst their numbers decreased rapidly in the presence of normal serum. Similarly, but to a lesser extent, pluripotential stem cell numbers were maintained in the presence of WBI serum. These data suggest that CSF appearing in vivo has a selective stimulatory effect on committed myeloid stem cell compartments in vitro . It is postulated that WBI serum may contain a single substance which influences both proliferation and differentiation of committed myeloid stem cells, and thus may be a specific regulator of granulopoiesis at this level. The slower decline of pluripotential stem cells in the presence of a maintained myeloid stem cell compartment may be due to a lower demand for pluripotential stem cells rather than direct stimulation at this level. Such findings are in accord with the notion that CSF may be involved in the humoral regulation of granulopoiesis.

Impaired Maturation of Neutrophils

Under normal circumstances the recognizable neutrophilic precursor cells in the bone marrow are not self-sustaining but are continually maintained by an input of cells coming ultimately from a self...