RNA-Induced Interference with Animal Virus Infection

Some RNAs, including both single- and double-stranded RNAs, when incubated with chick embryo cell culture induce cellular resistance against viruses. Evidence was now obtained indicating that the induction of cellular resistance by RNA depends on the cellular metabolic activity, especially on the synthesis of cellular RNA and protein. Thus, inhibitors of RNA and protein synthesis, actinomycin D and cycloheximide, were found to inhibit the development of an antiviral state when added before, or during the relatively early period of, incubation of the cells with RNA. In the course of induction of cellular resistance, three stages may be distinguished, the priming stage, the developing stage, and the established resistant stage.     

Characterization of capsid and noncapsid proteins of B19 parvovirus propagated in human erythroid bone marrow cell cultures.

The major capsid and noncapsid proteins of the pathogenic parvovirus B19, propagated in vitro, were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoprecipitation, and immunoblot of the erythroid fraction of infected human bone marrow cell cultures. There were two capsid proteins of 58 kilodaltons (kDa; the major species) and 84 kDa (the minor species). Newly synthesized capsid viral proteins were present in the supernatants of infected cultures. The major noncapsid protein of 77 kDa was localized to the nucleus.     

The role of phospholipase in beta-agonist-induced down regulation in guinea pig lungs

It has been observed that repeated and prolonged beta-agonist treatment causes the impairment of beta-adrenergic function, so-called "desensitization" or "down regulation". To clarify the mechanism of down regulation, the following experiment was performed using guinea pig lungs. Animals were divided into four groups: In the metaproterenol groups, guinea pigs were treated with metaproterenol (10 mg/kg/day) by intraperitoneal injection once a day for 1 day or for 7 successive days In the control groups, guinea pigs were treated with saline by the same procedure as in the metaproterenol groups. In the group treated with metaproterenol for 7 days, there was a 45% reduction in the number of beta-adrenoceptors and a 62% reduction in adenylate cyclase activity, compared with those of the control group. However, there were no significant changes in the dissociation constant (Kd) of the receptors. On the other hand, no reduction in the number of beta-adrenoceptors and adenylate cyclase activity was observed in the group treated with metaproterenol once a day for 1 day, compared with those of the control group. Phospholipase (PLase) activity in the lung microsomes of guinea pigs injected with metaproterenol for 1 day and for 7 days was elevated by 14.4 and 33.1%, respectively, compared with that of the control groups. Phospholipid contents of lung membranes prepared from the animals treated with metaproterenol for 7 days were significantly decreased compared with those of the control group, though in the group treated with metaproterenol once a day for 1 day, phospholipid contents did not differ from those of the control. Lung membranes treated with PLase A2 revealed decreases both in the number of beta-adrenoceptors and adenylate cyclase activity, dose dependently. These results and the fact that membrane phospholipids are involved in the beta-adrenoceptor system suggest that down regulation observed during beta-agonist administration is, at least in part, attributed to degradation of phospholipids of lung membranes by the persistent activation of PLase in the tissue.     

Distribution and evolution of C4 syndrome inRhynchospora (Rhynchosporeae-Cyperaceae)

In order to elucidate the evolution of C₄ syndrome, the taxonomic relationships, leaf anatomy, and ecological and global distribution of C₃ and C₄ species in the genusRhynchospora were investigated. The anatomical observation for 181 species revealed that 26 C₄ species occurred within theCapitatae group of the subgenusHaplostyleae, a natural group showing highly advanced morphological characteristics, together with several C₃ species. In spite of there being rather few C₄ species, they possessed two kinds of Kranz anatomical structure differing from each other in the location of Kranz cells. Some C₃ species ofCapitatae showed radial arrangement in mesophyll cells surrounding vascular bundles, which is distinguished from typical non-Kranz anatomy. The C₄ species extended their ecological ranges from wet habitats to dry savanna grasslands, while the C₃ species showed the best development in wet habitats. The C₃ species were widespread from tropical to temperate regions with partial range extension into subarctic regions of both hemispheres, showing conspicuously high concentration of species in the New World, but being absent from arid climatic regions. The C₄ species were distributed mostly in tropics and subtropics, showing two separate distributional centers in South and Central America and in Tropical Asia and Australia. The range of C₄ species was nearly completely included in the C₃ range. In conclusion, it seems that inRhynchospora the C₄ syndrome evolved relatively recently, and arose in at least two separate phylogenetic trends in the tropics and the subtropics, more probably in the Neotropics.     

Aminergic and peptidergic amplification of intracellular cyclic AMP levels in a molluscan neural network

1. Serotonin (5-hydroxytryptamine; 5-HT), dopamine (DA), and small cardioactive peptide B (SCPB) can activate adenylate cyclase and increase the intracellular cyclic AMP (cAMP) levels in the Limax procerebrum (PC), with differing time courses and to differing extents. 5-HT and SCPB are potent stimulators of adenylate cyclase, and when both were applied simultaneously, an additive effect was observed. 2. In contrast, DA shows a great variability in the time course of cAMP synthesis and is a weak stimulator. Ergonovine, a DA antagonist, failed to inhibit cyclase activation, indicating that ergonovine-sensitive receptors are absent or ergonovine-sensitive DA receptors are not coupled to adenylate cyclase. 3. 5-HT and SCPB cause a rapid synthesis of cAMP, reaching the maximum 20- to 30-fold increase within a minute. DA's effect is slow in onset and very prolonged, reaching a maximum of only a two- to three-fold increase in the cAMP level. Reasons for variability in DA action are discussed.