Structural study of the salivary glands of Anocentor nitens (Acari: Ixodidae) during the feeding cycle.

The salivary glands of Anocentor nitens (Neumann,1897) occur in pairs and are located in the anterolateral region of the general cavity, with milky white color and approximately equal sizes. They consist of a secretory portion and an excretion duct. In some glandular acini, all the cells had a basophilic appearance they were stained by hematoxylin, whereas others presented cells with different staining affinities. In this work, we describe the variations observed in these glands during the feeding cycle of ticks [after feeding (0 h) and successively at 24, 48, 72, 96, 120, and 144 h]. The cells stained by hematoxylin were shown to be more reactive to Alcian blue, thus demonstrating the presence of acid glycosaminoglycans, whereas those stained using eosin presented weak or no reaction. A strong reaction was found by the use of the periodic acid-Schiff (PAS) technique, thereby suggesting the presence of glycogen and/or glycoconjugates containing hexose, confirmed by using salivary amylase before PAS, with partial destaining of the slides. Continuing presence of residual staining in these cells suggests the presence of glycoconjugates containing hexose. Cells with nuclei of circular outline and few granules (of different sizes) were found in type II acini, 72 h after collection. Type I acini presented wide lumina and walls composed of larger numbers of cells of cubic to cylindrical shape. The pronounced degranulation shown in this study over the course of the feeding cycle was associated with the release of substances for oviposition.

Phagocytosis of the Lyme disease spirochete, Borrelia burgdorferi, by cells from the ticks, Ixodes scapularis and Dermacentor andersoni, infected with an endosymbiont, Rickettsia peacockii.

Tick cell lines were used to model the effects of endosymbiont infection on phagocytic immune responses. The lines tested for their ability to phagocytose the Lyme disease spirochete, Borrelia burgdorferi (Spirochaetales: Spirochaetaceae), were ISE6 and IDE12 from the black-legged tick, Ixodes scapularis Say (Acari: Ixodidae) and DAE15 from the Rocky Mountain wood tick, Dermacentor andersoni Stiles. Rickettsia peacockii (Rickettsiales: Rickettsiaceae), an endosymbiont of D. andersoni, was used as a representative tick endosymbiont. 70-80% of uninfected or R. peacocciz-infected IDE12 and DAE15 cells phagocytosed heat-killed borreliae and 80-90% of IDE12 and DAE15 cells phagocytosed viable spirochetes. ISE6 cells were permissive of spirochetes; less than 1% of these cells phagocytosed borreliae, and spirochetes remained adherent to the cells seven days after inoculation. Cytochalasin B blocked phagocytosis of killed and viable borreliae by IDE12 cells, and prevented phagocytosis of killed spirochetes by DAE15 cells, whereas viable spirochetes successfully invaded cytochalasin-treated DAE15. IDE12 and DAE15 cells degraded borreliae within phagolysosome-like compartments. Time-lapse microscopy showed that DAE15 cells phagocytosed borreliae more rapidly than IDE12 cells. IDE12 and DAE15 cells eliminated most adherent spirochetes within 7 days of inoculation. Thus, endosymbiont infection does not significantly interfere with the phagocytic activity of immunocompetent tick cells.

Evidence of a myoepithelial cell in tick salivary glands.

Type III acini from feeding female Dermacentor variabilis varied in size during in vitro and in vivo fluid production. As the type III acinus enlarged, its lumen enlarged and the adlumenal cell became thinner. As the acinus contracted, its lumen became smaller while the adlumenal cell became wider. Actin was demonstrated in salivary glands using an immunoblot technique. Actin was localized in the adlumenal cells of type III acini with fluorescent microscopy using rhodamine-phalloidin and with electron microscopy using heavy meromyosin to decorate actin filaments. Pre-treatment of salivary glands with cytochalasin D abolished fluorescence in adlumenal cells subsequently treated with rhodamine-phalloidin. These results support the hypothesis that the adlumenal cell in type III acini functions as a myoepithelial cell.

Ultrastructural localization of acetylcholinesterase in the synganglion of the tick, Dermacentor variabilis (Say).

Light- and electron-microscopic enzyme cytochemistry was used to localize acetylcholinesterase (AChE) activity in the synganglion (brain) of the tick Dermacentor variabilis. High AChE activity was observed throughout the neuropil as well as adjacent to most neuronal perikarya. Intracellular activity was not observed by light microscopy. By electron microscopy, reaction product was localized at the plasma membrane of glia and neurons. Enzyme activity was not associated with the olfactory globuli neurons. In other types of neurons, small amounts of reaction product were observed in the Golgi apparatus and nuclear envelope. Large neurosecretory neurons contained activity that appeared to be associated with deep invaginations of the plasma membrane as well as intracellular membranes. AChE activity was also associated with processes of both neurons and glia. In most peripheral nerves AChE activity was associated with virtually all axons. Clearly then, AChE is associated with glia and non-cholinergic neurons as well as with presumed cholinergic neurons. The widespread localization and large amounts of AChE in the tick brain exceeds that reported for other invertebrates and vertebrates. As has been suggested for other animals, AChE in the tick brain may have functions in addition to its known role in cholinergic neurotransmission.

Chemosterilization of Dermacentor variabilis Say (Acari: Ixodidae). I. Effects of metepa on the cytology and fertility of males treated as unfed adults.

The effects of metepa on the cytology and fertility of male Dermacentor variabilis treated as unfed adults are determined. Evidence of cellular damage is found in testicular areas where actively dividing cells and some enlarging spermatocytes are found. The amount of cellular damage correlates positively to the concentration of the chemosterilant and results in decreases numbers of spermatids. In crosses of treated males to untreated females, resulting egg masses hatch normally; however, the percentage of females producing egg masses that hatch is reduced.

Establishment and characterization of a diploid cell line from the tick, Dermacentor parumapertus Neumann (Acarina: Ixodidae).

Establishment of a continuous cell line (RML-14) from embryonic tissues of the tick Dermacentor parumapertus Neumann is reported. The culture medium employed consisted of a combination (2:1) of Eagle's and L-15 (Leibovitz) media supplemented with 20% fetal bovine serum, 10% tryptose phosphate broth, and 0.1% bovine plasma albumin. At the 8th passage, 99% of dividing cells had the female chromosome complement, among which more than 70% had a diploid chromosome number of 22. At the 13th passage, cell population showed approximately a 3-fold increase during the first 8 days of culture. As of December 1976, had been subcultured 40 times.