Impact of ivermectin on the ultrastructure of the testis of Argas (Persicargas) persicus (Ixodoidea: Argasidae).

Mated male Argas persicus were dissected 1 and 2 weeks after feeding on untreated and ivermectin (IVM)-treated pigeons. One week after feeding, testes of untreated ticks were filled with rounded spermatids with subplasmalemmal vesicles and cytoplasmic organelles, but lacking in treated ticks. Two weeks after feeding, testes were crowded with elongated spermatozoa supported by double-walled cisternal tubes. The tubes consisted of two opposite walls, each with outer-fringed processes and inner elongated cisternae. Both were supported with electron dense striated plates in the middle of the spermatozoon. Internally, the cisternal tubes contained mitochondria and vacuoles. The nuclei were elongated dense masses between the tubes and the cell membranes. Subcutaneous inoculation of IVM at the dose 400 microg/kg pigeon resulted in extensive alterations in the testis of A. persicus. IVM prevented the development of new spermatids. There was a break down of cell membranes and cytoplasmic organelles of spermatozoa. Multivesicular bodies and numerous vacuoles were noticed in their cytoplasm. Double membranes of elongated cisternae and striation of electron dense plates became indistinct. IVM caused granulation and vacuolization of the nucleus as well as injury of mitochondrial cristae. The results suggest that IVM may bind to the neurotransmitter or the hormone involved in the process of sperm development or may be toxic to the germinal cells of A. persicus testis.

Eicosanoid biosynthesis by hemocytes from the tobacco hornworm, Manduca sexta.

We describe eicosanoid biosynthesis by microsomal-enriched preparations of hemocytes from larvae of the tobacco hornworm Manduca sexta. Four major prostaglandins, PGA2, PGE2, PGD2, and PGF2 alpha, and a lipoxygenase product that co-chromatographed with 15-hydroxyeicosatetraenoic acid (HETE) were synthesized under most conditions. The HETE's fraction was the predominant product. Eicosanoid biosynthesis was sensitive to experimental conditions, including incubation time, temperature, and protein concentration. Optimal biosynthesis was observed with 1.5 mg of microsomal-enriched protein, incubated at 30 degrees C for 2 min. The hemocyte preparation is sensitive to low dosages of naproxin and esculetin. As in mammals, most lipoxygenase activity (87%) was localized in the cytosolic fraction of hemocytes. Unlike mammals, in which PGH synthase is associated with intracellular membranes, the hemocytic activity was detected in microsomal (59%), cytosolic (35%) and mitochondrial fractions (5%).

Incorporation of polyunsaturated fatty acids into phospholipids of hemocytes from the tobacco hornworm, Manduca sexta.

We examined the incorporation of four radioactive fatty acids, 18:1n-9, 18:2n-6, 20:4n-6 and 20:5n-3, into cellular lipids of hemocytes from tobacco hornworms, Manduca sexta. Most of the radioactivity associated with 18:1n-9 was recovered from triacylglycerols (TGs), and the radioactivity associated with 18:2n-6 was heavily incorporated into phospholipids (PLs) and TGs. Most of the radioactivity associated with the two eicosanoid-precursor polyunsaturated fatty acids (PUFAs), 20:4n-6 and 20:5n-3, was incorporated into PLs. The incorporated fatty acids were redistributed among the lipid classes during 2 h incubations. The two C20 PUFAs were moved from PLs to TGs. While 18:2n-6 underwent little change, 18:1n-9 was redistributed from TGs to PLs. Within PLs, each of the fatty acids were incorporated into phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PtG) and phosphatidylserine/inositol (PS/PI). The incorporation patterns changed over time, indicating that the incorporated fatty acids were redistributed among the four PL fractions. The radioactivity associated with 18:1n-9 was mostly recovered from the sn-1 position of PC (59%) and PE (83%). Most of the radioactivity associated with 18:2n-6 was found in the sn-2 position of PC (88%) and PE (67%). Over 90% of the radioactivity associated with 20:5n-3 was recovered from the sn-2 position of PC and PE. Incorporation of 20:4n-6 differed from 20:5n-3 because more radioactivity was recovered from the sn-2 position of PC (93%) than PE (69%). These findings are in line with the general background of lipid biochemistry, from which incorporation of 20:4n-6 into PE marks a notable departure: 31% of the radioactivity associated with this acid was recovered from the sn-1 position of PE. These findings indicate that hemocytes from the tobacco hornworm elaborate a fatty acid incorporation system, which exhibits specificity with respect to fatty acid structure and lipid class.