Adherent, trypsin-resistant, peritoneal cells from mice with chronic schistosomiasis mansoni, and from control mice, were cultivated in vitro up to 20 days. Fibroblasts regularly appeared, about 6 days after seeding, in cultures ofthe manyfold more numerous cells from infected mice, concomitantly with a dramatic increase, detected by autoradiography, in the percentage of DNA-replicating cells of the monocyte-macrophage lineage. Peritoneal cells from healthy and from infected mice were fractionated on discontinuous Percoll gradients. Eight cell subsets were harvested in both cases, quantitated, and studied by electron microscopy. Two fractions (2 and 3: 1.041 < densities < 1.060 g/ml) from infected mice were greatly enriched in monoblasts and promonocytes. The cells of the different subsets were seeded separately, trypsin-treated and cultivated in vitro. Cultures of cell fractions 2 and 3 from infected mice contained the majority of the DNA-synthesizing cells and gave regularly rise to fibroblasts. Cultures of the different fractions were used for sequential morphological observations (2-11 days) at the electron microscope level. Early cultures were also used for the ultrastructural detection of the Mac-1 (CD 18/CD11b) surface antigen by gold immunocytochemistry. A few fibroblasts were rarely observed in cultures of fractions 2 and 3 from control mice, while cells with ultrastructural features of myofibroblasts were regularly observed in cultures of the same fractions harvested from mice with chronic schistosomiasis. Fractions 2and 3 from infected mice contained a large number of Mac-1 positive monoblasts. The correlations between the presence of monoblasts, DNA replication in cells ofthe monocyte-macrophage lineage and the appearance of myofibroblasts in culturesof the same fractions derived from infected mice are discussed.
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Two fragments of millipedes, referred to the genus Archispirostreptus, are reported from an archaeological site in the Tadrart Acacus region of southwestern Libya. Radiocarbon dating of the specimens shows that one of them dates to between ca. 9100 and 8800 years ago, and the other one between 6400 and 6300 years ago (calibrated dates). The site lies far from known present-day occurrences of spirostreptid millipedes, and the Libyan subfossils probably, like other isolated occurrences of Archispirostreptus species in the Sahara and the Middle East, represent geographical relicts of a former, continuous distribution. The millipedes were probably able to survive at the Libyan site during the early and middle Holocene periods thanks to the more humid conditions, and may descend from animals that initially colonised the area during the even more humid, and longer, last interglacial period.
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RBINS Staff Publications 2020
