Studies on Hypoxia (Iii. The Differential Response of the Bone Marrow to Primary and Secondary Hypoxia)

Reticulocyte Generation Time and Rate of Discharge from the Marrow

“…Comparison of these observations with previous studies suggests that the accumulation of reticulocytes in the marrow may be related to the severity of the erythropoietic stimulus. No increase was noted in the marrow at simulated altitudes of 10,000 feet [8], 14,000 feet [5,9], but a marked increase occurred at 17,000 [10] and 20,000 [8]. During stimulation the increase in marrow reticulocytes was not due to the blocking of the discharge mechanism as it had been suggested [11].…”

“…The latent period before an increase in circulating reticulocytes following erythropoietic stimula tion of normal marrow is well documented [5,9,14], In erythropoietically suppressed marrow this period may be expected to be longer.…”

Identity of Erythroblast Precursors in Bone Marrow

“…While it is generally accepted that erythropoietic stimulation initiates the differentiation of increased numbers of erythroid precursor cells, the effect on the proliferation of erythroblasts is controversial. Reports of the failure of anemic serum or erythropoietin to alter the rate of proliferation [23,24] or DNA synthesis [25] in erythroblasts conflict with those where such an increase was obtained [2,[26][27][28][29][30][31]. To exclude errors due to a 'shift to the left', in the present study, the mitotic index of early and late erythroblasts was recorded separately.…”

“…There is no agreement as yet on the identity of the undifferentiated erythroid precursor cell2, although cells morphologically of the lymphocytic series have been attributed this function on the basis of indirect evidence [1][2][3][4][5][6][7]. In an attempt to gain further information about the identity of precursors to erythroblasts, the effects of erythro poietic stimulation were studied in bone marrow in which erythropoiesis had previously been depressed.…”

Proliferation Characteristics of Lymphoid Cells of Human Bone Marrow in Health and in Chronic Renal Failure

“…This cell type shows proliferative activity and is obviously involved in the production of B lymphocytes or plasma cells. Moreover, experimental studies proposed that this cell type, for which the term 'transitional cell' was introduced, may as well act as haemo poietic stem cell [7,9,16,17]. In the present study, lymphoid cells from healthy subjects and from patients with chronic renal failure were ana lysed with the cytophotometric determination of the DNA content com bined with autoradiography with 3H-thymidine (3H-TdR) in vitro.…”