Purification and properties of a protease inhibitor from crayfish hemolymph

A protease inhibitor from the hemolymph of crayfish, Astacus astacus, has been purified by differential centrifugation, acid precipitation and preparative isoelectric focusing. The inhibitor was apparent homogenous in SDS-electrophoresis and had a molecular weight of 23,000. pI was determined to be 4.7 by isoelectric focusing. No inhibitory activity was lost when the inhibitor was incubated in a pH range of 1–11.5. The purified inhibitor was heat stable. Urea (6 m) had no effect upon the inhibitor. The inhibitor was active against subtilisin and a partly purified protease from the fungus Aphanomyces astaci. Pronase was slightly inhibited whereas trypsin, chymotrypsin, papain, Arthrobacter protease, and extracellular proteases from the fungi Aphanomyces stellatus and A. laevis were unaffected. The importance of protease inhibitors in pathogenesis between the parasitic fungus, A. astaci, and its crayfish host, A. astacus is discussed.     

Serological characterization and partial purification of an Lyt-1 homolog in tunicate hemocytes.

A panel of alloantisera and monoclonal antibodies specific to murine Lyt-1 allotypic and framework determinants was used in indirect immunofluorescence and FACS analysis to investigate the occurrence of an Lyt-1 homolog in tunicate (protochordate) hemocytes. Binding assays and quantitative absorption experiments established the expression of Lyt-1 cross-reacting determinants on a distinct population of tunicate hemocytes. These determinants were expressed exclusively by cells with the morphological characteristics of hemoblasts and lymphocytes. In a rapid two-step purification procedure, Lyt-1 glycoproteins from tunicate hemocytes and C57B1/6 mouse thymocytes were solubilized and partially purified by affinity chromatography using a mAb anti-Lyt-1 frame-work determinant. In both cell types, antigenic activities were associated with a major 67-kDa component. Our findings suggest an early phylogenetic emergence of an Lyt-1 homolog at this level of evolution.     

Reproductive strategy of an isopod Onisocryptus ovalis,parasitizing a bioluminescent myodocope ostracod Vargula hilgendorfii

The functional morphology and the reproductive strategy of a parasitic isopod Onisocryptus ovalis in a bioluminescent ostracod Vargula hilgendorfii as its final host were studied based on video and SEM observations. During its lifetime, Onisocryptus ovalis dramatically metamorphoses several times, changing sex from male to female in the final host's carapace. At nearly the last ontogenetical stage, the parasite anchors its body with a pair of thoracopods to the posterodorsal region of the host ostracod's trunk and loses all the other appendages and thus its mobility as well. Thereafter, the parasite reverses bodily orientation during the final moulting so as to locate its mouth in the midst of the host eggs, and finally consumes them, leaving only the egg membrane. Such a mode of feeding of the parasite following the fixation of the body is interpreted in terms of the adaptation to escape elimination from the ostracod carapace by the host's cleaning appendages (the seventh limbs) and to obtain as much space as possible for the parasite's own eggs/embryos at the sacrifice of the mother's mobility. The synchronization between the timing of metamorphosis of the parasite and the reproductive cycle of the host animal can be expected to guarantee the parasite the opportunity to exploit sufficient nutrition from the eggs of the host.