Purification and preliminary characterization of insect spherulocytes

Steinernema carpocapsae DD136: metabolites limit the non-self adhesion responses of haemocytes of two lepidopteran larvae, Galleria mellonella (F. Pyralidae) and Malacosoma disstria (F. Lasiocampidae)

Live adult and juvenile entomopathogenic Steinernema carpocapsae DD136 (P. Nematoda) were not subjected to adhesion by haemocytes of lepidopteran insect larvae of Galleria mellonella or Malacosoma disstriain vitro or in vivo. In vitro freeze-killed nematodes exhibited haemocyte attachment, the intensity increasing with time. Accumulation of haemocytes on the dead nematodes was associated with host phenoloxidase activity; live nematodes and their exudates did not activate the enzyme whereas dead nematodes but not their exudate did activate phenoloxidase. Live-nematode exudate inhibited granular cell and some plasmatocyte adhesion to slides, increased granular cell but not plasmatocyte dissociation from preformed haemocyte monolayers and in vivo elevated total haemocyte counts and changed the floating haemocyte types while impairing bacterial removal from the haemolymph. Dead-nematode exudate did not affect these parameters thus immunosuppressant activity by live nematodes may represent the release of inhibitors not associated with their cuticle. The third stage juveniles released the inhibitors.

The antioxidants dimethylsulfoxide and dimethylthiourea affect the immediate adhesion responses of larval haemocytes from 3 lepidopteran insect species

Antioxidants, dimethylsulfoxide (DMSO) and dimethylthiourea (DMTU), at concentrations not affecting the viability of blood cells (haemocytes) from the larval stage of 3 lepidopteran insects - Galleria mellonella, Lymantria dispar, and Malacosoma disstria - differed in their influence on the innate binding of haemocytes to glass, bacteria to haemocytes, and on humoral responses to alien materials. In vitro DMSO had little effect, whereas DMTU substantially impaired the adhesion of the haemocyte types, the plasmatocytes and granular cells, to slides as well as the attachment of Bacillus subtilis to these haemocytes. Although both antioxidants increased lysozyme and phenoloxidase activities, there was no correlation of enzyme activity and haemocyte adhesion responses, possibly reflecting sequestered radicals. Nitric oxide and hydroxyl radicals offset the DMTU effect. In the absence of antioxidants, inactivate protein kinases A (PKA) and C (PKC) enhanced haemocyte aggregation. In general, DMSO, as opposed to DMTU, did not alter the effects of PKA and PKC activators and inhibitors on haemocyte aggregation or of PKC and PKA activities. High concentrations of DMSO and all levels of DMTU, although inhibiting PKA and PKC, inhibited haemocyte adhesion to slides. Comparable results occurred for DMTU-treated haemocytes incubated with B. subtilis. In vivo DMSO, unlike DMTU, did not impair plasmatocyte or granular cell responses to foreign materials, including bacterial removal from the haemolymph and nodulation.

Ontogeny of tick hemocytes: a comparative analysis of Ixodes ricinus and Ornithodoros moubata

Hemocytes of two tick species, Ixodes ricinus and Ornithodoros moubata, were investigated with the aim to determine their ultrastructural characteristics and developmental relationships. Only a limited number of ultrastructural features was shown to be unequivocally homological across all hemocyte types. The two species, representing distant groups of ticks, differ in the composition of their circular cell populations. In I. ricinus, three groups of distinct morphological types of hemocytes could be determined according to well-defined ultrastructural features: a typical non-phagocytic granular cell with electron-dense granula and homogeneous cytoplasm (Gr II), and two different types of phagocytic hemocytes, namely plasmatocytes with a low number of granula and phagocytic granolocytes, designated as Gr I. In contrast, an additional cell type resembling insect spherulocytes was determined in O. moubata. This cell type does not seem to be homologous to any I. ricinus hemocyte and may represent a cell type typical of soft ticks only. Possible ontogenetic lineages of the hemocytes of both tick-species were inferred.

Separation and behavior in vitro of hemocytes from the moth, Pseudoplusia includens

Hemocytes collected from larvae of Pseudoplusia includens (Lepidoptera:Noctuidae) were separated by centrifugation on Percoll cushions. The procedure resulted in 95% purity of plasmatocytes and greater than 99% purity of granular and spherule cells. Medium supplemented with chicken serum enhanced cell viability and promoted spreading of plasmatocytes. Cell-free plasma and medium preconditioned by plasmatocytes or granular cells stabilized cells in vitro and also accelerated spreading of plasmatocytes relative to medium supplemented with chicken serum. Oenocytoids were the only morphotype that exhibited endogenous phenoloxidase activity, while granular cells and plasmatocytes were the only cells that endocytosed fluorescent beads in vitro. Granular cells and plasmatocytes ingested fluorescently labelled beads, both in mixed populations of hemocytes and after separation. Plasmatocytes were the only morphotype that encapsulated large foreign targets in vitro following separation. Separated granular cells attached and spread on the surface of foreign targets but never formed a multilayered capsule.

Temporally regulated protein synthesis in cultured haemocytes of the Mediterranean fruit fly Ceratitis capitata during larval and prepupal development: internalization of larval serum proteins into the haemocytes

Detailed analysis of haemocyte proteins by one-dimensional polyacrylamide gel electrophoresis during the late larval stages and white pupae of the Mediterranean fruit fly Ceratitis capitata reveals more than 50 polypeptides. A numbering system is established based on molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Detailed examination leads to the conclusion that each protein resolved by our methods has its own characteristic kinetics of accumulation. The most abundant protein is unequivocally the 36-kDa band with an isoelectric point at 5.07, followed by the 47- and 54-kDa proteins. The 36-kDa band constitutes approximately 9% of total haemocyte protein. Comparison of the haemocyte protein pattern to that of cell-free haemolymph clearly shows that the protein bands at 81, 82, 85, and 87 kDa are common in both sources. We demonstrated by immunoblotting and pulse-labeled experiments followed by 2D SDS-PAGE that these protein bands which constitute the larval serum proteins were internalized into the haemocytes from the serum. By pulse labeling cells with [35S]methionine, separating polypeptides by one-dimensional PAGE electrophoresis, and comparing the rates of synthesis of over 50 individual polypeptides by fluorography, the following results were obtained: Three protein groups with distinct patterns of synthesis were noted: (1) proteins that are synthesized throughout the developmental period studied, (2) proteins whose synthesis begins at the wandering stage, and (3) proteins that are synthesized only during the feeding period. The 47-kDa protein shows the highest relative rate of synthesis, but since it is not the most accumulated band it must have a high turnover rate. Most of the labeled proteins were secreted into the incubation medium. The intracellular transit time was estimated to be about 11 min. Patterns of protein synthesis in haemocytes are regulated in a precise temporal sequence during the transformation of larvae to pupae. Their study yields a useful system for the analysis of molecular events in gene control.