Monocyte kinetics were studied in seven hematologically normal individuals using in vivo pulse labeling with tritiated thymidine. Although occasional labeled cells appear in the peripheral blood within 4 or 5 hr of the administration of label, a significant outflow from the marrow begins 13–26 hr later. This interval is occupied by the G2 and M phases of the mitotic cycle since mitotic cells are not observed in the peripheral blood. The duration of the DNA synthesis phase of monocytes is measured at 34 hr ≈ 1.8 hr. Cells do not enter this phase while circulating since exposure of circulating cells to tritiated thymidine does not result in any uptake. If monocytes are not ‘end’cells which have completed their mitotic activity before leaving the marrow they must at least be inhibited from further proliferative activity until they are permanently sequestered in other tissues. The generation time is probably not less than 40 hr and data derived from the mean grain counts of labeled cells suggest that it is often more than 70 hr. The total daily output of monocytes in man is 9.4 × 108 cells per 24 hr ≈ 3.3 × 108. Cells leave the bloodstream with a half‐time of about 71 hr thereby proving themselves to be considerably more durable than neutrophils which have a half‐life in the neighborhood of 6 hr.

*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

Community-acquired bacteremia in the elderly has a high mortality rate. Early recognition and prompt, appropriate treatment are critical in reducing the mortality.

The incidence and nature of headaches in 85 systemic lupus erythematosus (SLE) patients attending an outpatient clinic were studied and compared to those experienced by 61 nurses. The two groups were similar in age, sex and ethnicity. Test-retest assessment of reliability gave both groups 95% confidence limits of 0.09-0.21. Thirty-two (38%) patients developed migrainous headaches and nine (10%) stress headaches with the onset of lupus. In the control group, four (6%) developed migraine and 40 (66%) developed stress headaches on commencing work. We could not document any association of headaches with flares of systemic disease, the ACA syndrome, Raynaud's phenomenon or increased SLEDAI score. We conclude that migrainous headaches are more common in lupus patients than healthy controls, but in an outpatient setting are not statistically associated with flares of systemic disease.