Seroepidemiological studies by indirect haemagglutination tests for malaria. Military recruit collections from Argentina, Brazil, Colombia, and the United States of America

Seroepidemiological studies of 10 956 sera of military recruits from 4 countries in the Western Hemisphere suggest that the indirect haemagglutination test employing an antigen prepared from Plasmodium knowlesi adsorbed to human group O erythrocytes may be useful in epidemiological studies of malaria. Based on a titre of 1: 8, or higher, in a micro-titration of serum, the prevalence of serological reactors in the collection of sera from USA recruits was 0.9%, in the Argentina collection 4.6%, in the Brazil collection 20.8%, and in the Colombia collection 21.3%. In Brazil and Colombia the distribution of serological reactors correlated with the distribution of malaria as determined by active and passive surveillance. In Argentina, serological reactors were found in states where active and passive surveillance indicated that malaria had been eradicated years ago.

Estimating the median generation time of proliferating cell systems in steady state

For proliferating cell systems in which the usual "labeled mitoses" method cannot be used to estimate generation times, an alternative scheme is derived. The method presented here is based on observation (by autoradiography) of the median grain count of labeled interphase cells following a pulse of labeled DNA precursor. It is shown that the median generation time of the labeled cells will be equal to the time required for the median grain count to halve, starting from the time when half the labeled cells have completed their first division. This starting time is determined from observation of the first wave of labeled mitoses. The procedure was designed to minimize error resulting from such factors as radiation damage, label reutilization, and the use of a nonzero grain counting threshold. The method is applied to the analysis of two cases of acute leukemia in man.

Studies of cellular proliferation in human leukemia. I. Estimation of growth rates of leukemic and normal hematopoietic cells in two adults with acute leukemia given single injections of tritiated thymidine

Two adults with rapidly progressive acute myeloblastic and myelomonoblastic leukemia were given single injections of tritiated thymidine, and measurements were made of the growth rates of their leukemic and normal hematopoietic cells by radioautographic methods. Although almost all leukemic blasts in both marrow and blood were metabolically active as shown by their ability to incorporate tritiated uridine and leucine in vitro, only 5.6% and 6.1% of the blasts in the marrow and even fewer in the blood incorporated tritiated thymidine. The mitotic indexes of the marrow blasts were 0.66% and 0.52%; no circulating blasts were dividing. The mean generation times of the actively proliferating blasts were estimated to be 49 and 83 hours. This cannot be equated with the doubling time of the total leukemic population as there is evidence that many blasts fail to continue dividing and die. The mean durations of the phases of the blasts' mitotic cycles were as follows: DNA synthesis (S) = 22 and 19 hours, premitosis (G(2)) = 3 hours, mitosis (M) = 0.47 and 0.62 hour (minimal estimates), and postmitosis (G(1)) = 24 and 61 hours. In both patients the maximal mean transit time of the blasts in the blood was 36 hours, and the minimal numbers of actively dividing blasts present were 1.6 and 2.6 x 10(9) per kg of body weight.Estimates were also made of the rates of proliferation and maturation of the residual normal erythrocytic and granulocytic cells in these two patients. Although total production was markedly diminished because of reduction in the number of normal elements, the relatively few remaining normal cells appeared to be dividing and maturing at rates that are about the same or only slightly slower than those found in normal subjects. We conclude that main reason leukemic blasts displace normal hematopoietic precursors in acute leukemia is that the blasts largely fail to differentiate. Many die but many others persist in the marrow and elsewhere as primitive cells and continue to proliferate. As the blasts accumulate, they gradually displace the normal hematopoietic cells, most of which continue their normal course of differentiation and leave the marrow as nondividing mature cells. It is not known why the over-all production of normal cells is not adequately increased to compensate for the anemia, granulocytopenia, and thrombocytopenia that develop, but apparently the leukemic cells somehow interfere with the proliferation or differentiation or both of normal stem cells.