Fine structure of the hemocytes of Periplaneta americana (Orthoptera: Blattidae) with particular reference to marginal bundles

Hemocytes of the centipede Scutigera coleoptrata (Chilopoda, Notostigmophora) with notes on their interactions with the tracheae

The hemocytes of Scutigera coleoptrata were investigated by light and electron microscopy. Four types of hemocytes were identified: prohemocytes, plasmatocytes, granulocytes, and spherulocytes. Only granulocytes could be distinguished from the three other types by May-Grünwald staining, as this is the only hemocyte type demonstrating an eosinophilic reaction. Shape and size give further indications for distinguishing the cell types. In addition, differentiation is possible on the basis of their ultrastructure. However, only a combination of all three methods (staining and light and electron microscopy) allows clear separation of the cell types. As transitional stages between the cell types occur in S. coleoptrata, it is likely that prohemocytes, plasmatocytes, and granulocytes are ontogenetic stages of a single cell lineage. Special cell components and their possible functions are described. Plasmatocytes exocytose tubular structures that probably play a role in coagulation processes. These tubular structures develop in the grana of plasmatocytes. Also, a special arrangement of microtubules and microfilaments was demonstrated. For the first time interactions between hemocytes and tracheae are documented within the Chilopoda. It is assumed that the hemocytes meet their oxygen requirements directly from the tracheae. Phylogenetic implications of the results are discussed.

Ultrastructure of the hemocytes of Cetonischema aeruginosa larvae (Coleoptera, Scarabaeidae): involvement of both granulocytes and oenocytoids in in vivo phagocytosis

In the context of comparative studies on immunity defence mechanisms of adults and larvae of the coleopteran Cetonischema aeruginosa (Drury, 1770) the ultrastructure of the circulating hemocytes of the third instar larval stage has been investigated by means of light and transmission electron microscopy (TEM). Six types of hemocytes were found in the hemolymph of C. aeruginosa and they were identified as prohemocytes, granulocytes, plasmatocytes, coagulocytes, oenocytoids and spherule cells. In order to identify the "professional" phagocyte cell, phagocytosis assays were performed in vivo by injection of 0.9 microm carboxylate-modified polystyrene latex beads. It was demonstrated that the granulocytes and the oenocytoids of C. aeruginosa were the only hemocyte types involved in this cellular response.

Centrioles as microtubule-organizing centers for marginal bands of molluscan erythrocytes

The erythrocytes of blood clams (arcidae) are flattened, elliptical, and nucleated. They contain elliptical marginal bands (MBs) of microtubules, each physically associated with a pair of centrioles marginal bands (MBs) of microtubles, each physically associated with a pair of centrioles (Cohen, W., and I. Nemhauser, 1980, J. Cell Biol., 86:286-291). The MBs were found to be cold labile in living cells, disappearing within 1-2 h at 0 degrees C. After the cells had been rewarmed for 1-2 h, continuous MBs with associated centrioles were once again present. Time-course studies utilizing phase contrast, antitubulin immunofluorescence, and electron microscopy of cytoskeletons prepared during rewarming revealed structural evidence of centriole participation in MB reassembly. At the earliest stage of reassembly, a continuous MB was not present. Instead, relatively short and straight microtubules focused on a pointed centriolar "pole," and none were present elsewhere in the cytoskeleton. Thin continuous MBs then formed, still pointed in the centriolar region. Subsequently, the MBs regained ellipticity, with their thickness gradually increasing but not reaching that of controls even after several hours of rewarming. At these later time points, microtubules still radiated from the centrioles and joined the MBs some distance away. In the presence of 0.1 mM colchicines, MB reassembly was arrested at the pointed stage. Electron microscopic observations indicate that pericentriolar material is involved in microtubule nucleation in this system, rather than the centriolar triplets directly. The results suggest a model in which the centrioles and associated material nucleate assembly and growth of microtubules in diverging directions around the cell periphery. Microtubules of opposite polarity would then pass each other at the end of the cell distal to the centrioles, with continued elongation eventually closing the MB ellipse behind the centriole pair.

Inverted gap and other cell junctions in cockroach hemocyte capsules: a thin section and freeze-fracture study

Freeze-fracture and thin-section studies were done on cockroach hemocytes that had encapsulated implanted pieces of Araldite. Desmosome-like junctions and 'B' type gap junction were described. Freeze-fractured gap junctions displayed fused and clustered, but not hexagonally arrayed intramembranous practicles (approximately 130 A) on the B face and pitted areas on the A face of the plasmalemma. Gap junctions were quite numerous and counts of gap and non-gap particles indicated at least a five-fold particle density increase (4000/mu2) compared with B face particle densities (approximately 800/mu2) from free circulating blood cells where gap junctions had not been formed.