DeMar Taylor

Vitellogenin synthesis, processing and hormonal regulation in the tick, Ornithodoros parkeri (Acari:Argasidae)

Abstract This study was undertaken to determine the processing of vitellogenin (Vg) and the role of juvenile hormone (JH) in the regulation of vitellogenesis in the tick Ornithodoros parkeri . Ticks usually require a blood meal to induce vitellogenesis. However, we have shown that a pyrethroid, cypermethrin (CyM), can stimulate Vg synthesis in unfed Ornithodoros moubata females. Vg concentration and synthesis were analyzed by SDS-PAGE spotting-scanning and fluorography using [ 35 S]-methionine. Although unfed females show high titers of Vg in the hemolymph, this is not due to new synthesis. Vg synthesis stimulated by engorgement increases beginning on day 2 after engorgement and reaches a maximum level on day 8. Vg is synthesized in the fat body, secreted into the hemolymph and then processed and incorporated into the ovaries as vitellin. JH I, II and III, methoprene (JHA), and CyM were topically applied to unfed females and Vg synthesis analyzed on day 5 by fluorography. JH and JHA did not stimulate Vg synthesis. CyM stimulated Vg synthesis but not ovarian development. These preliminary results indicate that JH does not function in the regulation of vitellogenin synthesis in this species.

Vitellogenins and vitellins in the bean bug, Riptortus clavatus (hemiptera: alydidae): Purification, immunological identification, and induction by juvenile hormone

Vitellogenins (Vgs) and vitellins (Vns) were purified from reproductive female adult hemolymph (HL) and newly laid eggs of the bean bug, Riptortus clavatus. They were separated into two (Vg-1 and 2) and three (Vn-1′, Vn-1, and Vn-2) sub-components, respectively, by ion exchange chromatography. Fused rocket immunoelectrophoresis using anti-(Vn-1) serum showed that they are distinguished clearly into two immunologically distinct groups, i.e., Vg-1/Vn-1/Vn-1′ and Vg-2/Vn-2. SDS-PAGE analysis showed Vn-1 (Vn-1′) and Vn-2 have the same and/or smaller subunit component polypeptides as Vg-1 and Vg-2, respectively. Vn-1′ has some lower molecular weight peptides than Vn-1. Quantitative rocket immunoelectrophoretic analysis showed that Vg-1 and Vn-1 (plus V-1′) were detected first on day 3 in the HL and day 4 in the ovary, respectively, after adult emergence, and increased by day 10 in non-diapause female adults. Vg-1 synthesis is induced in diapause female adults in 1 day after the treatment with juvenile hormone (JH) and JH analog (JHA) or in a few days after transfer from short day to long day conditions.

Life cycle of Gnathostoma nipponicum Yamaguti 1941

The life cycle of Gnathostoma nipponicum was examined by field survey and by experimental infection of animals with the larvae. Naturally infected larval G. nipponicum were found in loaches, catfish, and snakes. Experimentally, loaches, killifishes, frogs, salamanders, mice, and rats were successfully infected with the early third-stage larvae of G. nipponicum obtained from copepods (the first intermediate host), whereas snakes, quails, and weasels were not. Frogs, snakes, quails, and rats were experimentally infected with the advanced third-stage larvae (AdL3) from loaches. These results reveal that some species of fishes, amphibians and mammals can act as the second intermediate host and that some species of reptiles, birds and mammals can act as a paratenic host. The life cycle was completed in weasels, the definitive host, which were infected with AdL3 from loaches and started to evacuate eggs of G. nipponicun in faeces on days 65-90 postinfection.

Effects of precocenes on vitellogenesis in the adult female tick,Ornithodoros moubata (Acari: Argasidae)

Vitellogenin (Vg) concentrations in the hemolymph and ovarian development were studied inOrnithodoros moubata after treatment with precocenes 1 (P1) and 2 (P2). Precocene was dissolved in acetone or DMSO and topically applied to the dorsal surface of ticks: (1) at adult ecdysis; (2) 24 h before engorgement; (3) immediately after engorgement; and (4) 24 h after engorgement. Subsequently, P1 and P2 were dissolved in olive oil and injected through the gonopore into the body cavity 24 h after engorgement. Vitellogenin concentration was measured on days 5 and 10 after engorgement and ovarian development was scored on day 10, 20 or 30. Oviposition was also recorded and the average weight of eggs laid by females was determined. No differences in concentration of Vg in the hemolymph occurred between the control ticks and ticks treated topically or by injection with P1 and P2. Precocene did not suppress the synthesis of Vg inO. moubata. However, oviposition was reduced in ticks that survived repeated treatment with high doses of P2 dissolved in acetone.

Hormonal Regulation of Vitellogenin Biosynthesis in Ticks

Many species of ticks and mites must obtain a blood meal from a vertebrate or invertebrate host for development and reproduction to occur. This blood meal results in the transmission of various disease agents from infected animals to uninfected animals. Ticks are second only to mosquitoes as vectors of human diseases. Ticks and/or mites transmit a wide range of microorganisms: viruses, rickettsia, bacteria, and spirochetes, and also protozoa and nematoda.