Nobuo Kumada

Possible roles of cAMP and Ca2+ in the regulation of miracidial transformation inSchistosoma mansoni

The triggering action of physiological saline in the miracidial transformation ofSchistosoma mansoni was analyzed using various agents affecting cAMP-and Ca2+-dependent pathways. Potent activators of adenylate cyclase such as forskolin and serotonin, strongly inhibited the transformation provoked by saline in RPMI-1640. These inhibitory actions were diminished by the combined administration of phosphodiesterase activators such as ammonium salts or imidazole. Furthermore the exposure of miracidia to ammonium salts or imidazole in dechlorinated tap water “mimicked” the transformation, i.e., the cessation, of swimming and then shedding of epithelial plates. This mimic transformation was also inhibited by serotonin or forskolin. In contrast, treatment of miracidia with Ca2+ antagonists such as TMB-8 (an inhibitor of Ca2+ release), nicardipine (a Ca2+ channel blocker), or W-7 (a calmodulin inhibitor) in tap water produced severe vesiculation on their body surfaces and resulted in death. However, these toxic effects were abolished by a combined administration of these Ca2+ antagonists with saline or NH4Cl, and the transformation was reestablished except with W-7 treatment. W-7 strongly inhibited the triggering action of saline and NH4Cl and the worms swam slowly, whereas W-5, an inactive analogue of W-7, had no inhibitory effect on the transformation. These results suggest that the initiation of micracidial transformation to young sporocysts may be synergistically, regulated by cAMP and Ca2+ and that a decrease in cAMP levels and an increase in Ca2+ mobilization may be provoked in worms transformed by saline, ammonium salts, or imidazole.

A new virus isolated from the cockroach, Periplaneta fuliginosa (Serville).

Despite the remarkable progress in insect virology, we have not known of any virus isolated from cockroaches. In this paper, isolation of a parvovirid virus from the smoky-brown cockroach, Periplaneta fuliginosa (Serville), and some properties of the isolate will be reported. In 1975-76, while we were examining the spontaneous hindgut ulcer of the cockroach, we noticed unusually high mortalities of nymphs and adults among colonies of P. fuliginosa that had been collected in Nagoya district and reared in our laboratory. Before death, hindlegs of the sick cockroaches were paralysed and their movement became incoordinated. At autopsy, the abdomen appeared. swollen with enlarged fat body colored milk-white, which differedfrom the brownish white ones observed in healthy cockroaches. More than half of these dead cockroaches developed the hindgut ulcer (7). Light microscopy of the dead cockroaches exhibited no parasitic causality. However, electron microscopy of negatively stained smears prepared from macerated tissue of the dead cockroaches disclosed two kinds of virus-like particles with diameters of approximately 10 nm and 20 nm, respectively. Therefore, isolation of viral agents from the sick cockroaches was attempted. The sick cockroaches were homogenized in PBS (0.15 M NaCl, M/100 phosphate buffer, pH 7.2) containing streptomycin (100 ƒÊg/ml) and penicillin (500 u/ml), and centrifuged twice at 10,000 •~ g at 4 C for 20 min. The supernatant (Sup-l) was inoculated into the hemocoel of twelve healthy adults. About 20 days after the inoculation most of them died showing the same symptoms as described above. The Sup-l was passed through a 450 nm Millipore filter, and the filtrate was subjected to serial passage through healthy cockroaches. After the fifth passage it was determined that the filtrate was as potent as the Sup-l in the infectivity to the cockroach. The agents contained in the filtrate could pass through membrane filters of 220, 100, and 50 nm porosity. Electron microscopy of thin sections prepared from the infected cockroaches revealed that many virus-like particles with a diameter of about 20 nm were accumulated in the nuclei and sometimes arranged in crystalline array in the cytoplasm of the fat body-, muscle-, and pericardial cells (Fig. 1). Judging from the size and shape of these particles as well as from their arrangement in the infected cells,

Envelopment of the nuclear polyhedrosis virus of the oriental tussock moth, Euproctis subflava.

Envelopment of an Euproctis subflava nuclear polyhedrosis virus (NPV) was studied by electron microscopy. During the envelopment process of the NPV, an intermediate layer consisting of electron-dense, particle-like structures was observed in the matrix between envelopes and nucleocapsids. This layer seemed to contribute to the electron density in the matrix layer after envelopment was completed.

Studies on the post-larval development of cestodes of the genus Mesocestoides: Shedding and further development of M. lineatus and M. corti tetrathyridia in vivo

Abstract In vivo development of Mesocestoides lineatus and M. corti in cats were compared. On day 1–2 post infection, tetrathyridia of both species shed the majority of their posterior tissue. After shedding, the post-scolex region of M. lineatus grew and eventually formed a gravid strobila. The shed worm of M. corti split the scolex and body longitudinally, resulting in two worms. These split worms were classified into two types, small and large, the latter type developed to form a strobila which divided again into two individuals by splitting the scolex after it had formed a pair of new suckers. Regeneration of two new suckers was also seen in the small worm which multiplied without strobila formation by dividing longitudinally into two at the scolex as observed in the large worms. From these and previously published results, the developmental pathway during asexual multiplication of M. corti in the host intestine is discussed.

Studies on the post-larval development of cestodes of the genus Mesocestoides: Trypsin-induced development of M. lineatus in vitro

Abstract By using a conventional monophasic culture system, the tetrathyridia of Mesocestoides lineatus were grown in vitro into the mature, strobilated adults, and the role of trypsin and sodium taurocholate in inducing adult formation was determined. By treatment with trypsin alone tetrathyridia evaginated their scolices and subsequently developed to the strobilated adults. The induction of development was apparently related with the proteolytic activity of trypsin; it was inhibited or decreased by the addition of soybean trypsin inhibitor. Pronase E was as effective as trypsin, but chymotrypsin had less activity. In the paruterine organs of the adults grown in vitro, shelled eggs containing live onchospheres were observed.