The iron uptake in bone marrow and spleen was measured in 29 patients with myelofibrosis using S2Fe and quantitative scanning. In 10 patients, no iron uptake in the marrow could be observed and active erythropoiesis was extramedullary only. In the bone marrow of patients with myelofibrosis, the iron uptake per nucleated red cell was less than that observed in conditions without myelofibrosis or extramedullary erythropoiesis. Increasing splenic iron uptake was likely to be associated with a decreasing bone marrow iron uptake and was related to the size of the spleen. The data suggest that in myelofibrosis, the spleen dominates iron uptake through intense erythropoiesis and a high splenic blood flow, thus restraining iron supply to the bone marrow.
To study whether the release of atrial natriuretic factor (ANF) was altered in diabetic cardiac autonomic neuropathy (CAN), we determined plasma ANF concentrations during exercise and changes of posture in three groups of age- and sex-matched subjects (9 healthy subjects, 7 diabetic patients with CAN, and 7 diabetic patients without CAN). During exercise, plasma ANF concentrations rose threefold (P less than .001), and this increase was similar in the three groups. However, heart-rate response to exercise was impaired in the two groups of diabetic patients (P less than .004 vs. healthy subjects) but was more severely impaired in patients with CAN (P less than .03 vs. patients without CAN). In healthy subjects and patients without CAN, the increases of ANF during exercise correlated significantly with those of heart rate, systolic blood pressure, and rate-pressure product (P less than .01). In patients with CAN, the correlation was found exclusively with heart rate (P less than .01). An increase of ventricular ejection fraction occurred in all groups (P less than .001) but without showing statistical differences between groups. After 30 min of standing, a similar postural drop of plasma ANF concentrations (P less than .002) was observed in all subjects, reflecting preserved sympathetic control of vessels. In conclusion, exercise induces an increase of plasma ANF in diabetic patients with CAN. This increase, occurring similarly to healthy subjects, indicates that autonomic activation plays a minor role in ANF release during exercise. Impaired heart-rate response to exercise in patients without CAN suggests early damage of autonomic function, undetected by conventional rest tests.
A method for determining erythropoiesis quantitatively with 52Fe has been applied to 25 patients with anaemia. The data were derived from quantitative scanning of the erythropoietic areas and the measurement of the plasma iron turnover. We have assessed this 52Fe measurement of erythropoiesis by comparing it with total marrow iron turnover studies. Both methods give similar estimates of erythropoiesis except in patients with severe ineffective erythropoiesis and in a patient with significant peripheral haemolysis, when erythropoiesis as measured with the 52Fe technique gave higher results. In these conditions, the estimate of total erythropoiesis might be more reliable using the 52Fe quantitative scanning technique. However, the measurement of erythropoiesis with 52Fe does not distinguish effective from ineffective erythropoiesis and cannot be applied to patients with extramedullary erythropoiesis.
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