CHANGES IN TITER OF THE BRAIN HORMONE DURING DEVELOPMENT OF THE SILKWORM, BOMBYX MORI

Changes in titer of brain hormone (BH) extracted from the brain, head, and thorax and abdomen during the development of Bombyx mori from the 4th larval molting up to 6 days after adult emergence were investigated. The hypothesis is presented that high secretory activity of the brain is not reflected in a corresponding change in its BH titer, while low secretory activity brings about an accumulation of BH in the brain. An interesting finding is that extremely high titers of BH were found in the thorax and abdomen, from 4 days after pupation to adult emergence, of females only. This sexual difference was, however, not found in all of the races examined.     

Development of microsatellite markers in the toxic dinoflagellate Alexandrium minutum (Dinophyceae)

Outbreaks of paralytic shellfish poisoning caused by the toxic dinoflagellate Alexandrium minutum (Dinophyceae) are a worldwide concern from both the economic and human health points of view. For population genetic studies of A. minutum distribution and dispersal, highly polymorphic genetic markers are of great value. We isolated 12 polymorphic microsatellites from this cosmopolitan, toxic dinoflagellate species. These loci provide one class of highly variable genetic markers, as the number of alleles ranged from four to 12, and the estimate of gene diversity was from 0.560 to 0.862 across the 12 microsatellites; these loci have the potential to reveal genetic structure and gene flow among A. minutum populations.     

Isolation of Zn2+ as an Endogenous Agonist of GPR39 from Fetal Bovine Serum

We attempted to determine natural agonists of GPR39 in fetal bovine serum (FBS). FBS was conditioned to extract peptides and fractionated by two types of HPLC. The activity of each fraction was monitored by intracellular calcium mobilization. Then the purified active ingredient was analyzed by inductively coupled plasma mass spectrometry. In this fashion, Zn^{2 +} ion was identified as an agonist of GPR39, though no peptidergic molecules were found. The calcium-mobilizing activity of Zn^{2 +} was not abolished by pertussis toxin but was by a phospholipase C (PLC) inhibitor, U73122, indicating that the activity of GPR39 is mediated through the G_qα -PLC pathway. In addition, Zn^{2 +} also activated mouse and rat GPR39, showing that the function of GPR39 as a Zn^{2 +} receptor is conserved across species. This study is the first exploration of GPR39 agonists in FBS and indicates that GPR39 functions as a Gq-coupled Zn^{2 +}-sensing receptor.     

Development of microsatellite markers in the noxious red tide‐causing dinoflagellate Heterocapsa circularisquama (Dinophyceae)

We isolated 15 polymorphic microsatellites from one of the most noxious red tide‐causing dinoflagellate species, Heterocapsa circularisquama. These loci provide one class of highly variable genetic markers, as the number of alleles ranged from two to six, and the estimate of gene diversity from 0.205 to 0.684 across the 15 microsatellites. These loci have the potential to reveal genetic structure and gene flow among H. circularisquama populations.     

Intra-guild predation and variation in egg defence between sympatric and allopatric populations of two species of ladybird beetles

Abstract.  1. Ladybird eggs are defended chemically against intra-guild predation, and are unsuitable to varying degrees as food for other ladybirds.
2. Ladybird eggs [ Coccinella septempunctata (Cs) and Harmonia axyridis (Ha); Coleoptera: Coccinellidae] from local Japanese versus North American populations were compared as food for two ladybirds (Cs and Ha) co-occurring in Japan.
3. Larvae of Cs exhibited high mortality, slow development, and reduced egg consumption and weight gain when they fed on Ha versus conspecific eggs, especially when Ha eggs were from the local (Japanese) population versus a distant (North American) population of Ha.
4. Larvae of Ha survived equally well on a diet of Cs or conspecific eggs, but developed more slowly and gained less weight on Cs eggs. Ha larvae were more reluctant to eat eggs from the local (Japanese) population of Cs than eggs from the distant (North American) population of Cs; however, other measures of performance did not differ significantly.
5. These results indicate greater egg chemical defence of Ha eggs against Cs larvae than vice versa, as expected from field observations of greater temporal overlap between Cs larvae and Ha eggs than between Ha larvae and Cs eggs. Furthermore, results also indicate that local populations of eggs are better defended than eggs from elsewhere against locally occurring intra-guild predators. Thus, it appears that the effectiveness of chemical defence of ladybird eggs reflects the degree to which specific pairings of ladybirds have the potential to interact in nature through egg predation.     

Further Evidence for the Presence of a Circadian Clock in the Prothoracic Glands of the Saturniid Moth Samia cynthia ricini: Decapitated Larvae Can Respond to Light-Dark Changes

A small peak of haemolymph ecdysteroid titre precedes the gut purge that characterizes larval-prepupal transition of the saturniid moth Samia cynthia ricini. This peak shifts its phase in parallel with the phase shifts of gut purge according to the changes in light-dark conditions preceding gut purge. Decapitated larvae responded to these light-dark changes as intact larvae did, as assessed by the phase shifts of the haemolymph ecdysteroid peak. This indicates that the brain-centred PTTH clock is not prerequisite for realization of the circadian-clock-controlled timing in the initiation of prepupal development, and supports indirectly our previous notion that the prothoracic glands of Samia possess a circadian clock dictating gut purge timing.     

Molecular cloning and characterization of the AVR-Pia locus from a Japanese field isolate of Magnaporthe oryzae

In order to clone and analyse the avirulence gene AVR-Pia from Japanese field isolates of Magnaporthe oryzae , a mutant of the M. oryzae strain Ina168 was isolated. This mutant, which was named Ina168m95-1, gained virulence towards the rice cultivar Aichi-asahi, which contains the resistance gene Pia. A DNA fragment (named PM01) that was deleted in the mutant and that co-segregated with avirulence towards Aichi-asahi was isolated. Three cosmid clones that included the regions that flanked PM01 were isolated from a genomic DNA library. One of these clones (46F3) complemented the mutant phenotype, which indicated clearly that this clone contained the avirulence gene AVR-Pia . Clone 46F3 contained insertions of transposable elements. The 46F3 insert was divided into fragments I–VI, and these were cloned individually into a hygromycin-resistant vector for the transformation of the mutant Ina168m95-1. An inoculation assay of the transformants revealed that fragment V (3.5 kb) contained AVR-Pia . By deletion analysis of fragment V, AVR-Pia was localized to an 1199-bp DNA fragment, which included a 255-bp open reading frame with weak homology to a bacterial cytochrome- c -like protein. Restriction fragment length polymorphism analysis of this region revealed that this DNA sequence co-segregated with the AVR-Pia locus in a genetic map that was constructed using Chinese isolates.     

The Ontogeny of Thymic Myoid Cells in the Chicken

The ontogeny of thymic myoid cells in the chick was studied electron microscopically and immunohistochemically. An anticreatine kinase antibody which reacts specifically to skeletal muscle cells was used. This antibody reacts only to myoid cells in the thymus. Myoid cells were found in the medulla or in the interlobular region, though the number of the myoid cells was small. Immunohistochemically, myoid cells were detected on the 18th day of incubation. Mature myoid cells showed clear cross striations after immunohistochemical staining around the time of hatching. Electron microscopically, myoid cells were detectable on the 19th day of incubation. The discrepancy between immunohistochemical and electron microscopical detection may be due to the low number of myoid cells.     

Accumulation of glycinebetaine during cold acclimation and freezing tolerance in leaves of winter and spring barley plants

A study was performed to examine whether or not betaine (glycinebetaine), a compatible solute, is accumulated in response to cold stress and is involved in mechanisms that protect plants from freezing injury. For this purpose, we used near-isogenic lines of barley, with each line differing only in a single gene for the spring type of growth habit; the various lines were produced by back-crosses to a recurrent cultivar of the winter type. The winter type of growth habit requires a low temperature for triggering of flower development (vernalization), whereas the spring type does not. Betaine was accumulated to five times the basal level over the course of 3 weeks at low temperature (5 °C) in the winter-type cultivar and in a spring-sh line having the sh gene for the spring-type growth habit, but the level was only doubled in the spring-Sh3 line, which carried the Sh₃ gene for the spring-type growth habit. Among near-isogenic lines of the same cultivar, the levels of betaine accumulated in leaves at low temperature were well correlated with the percentages (on a dry weight basis) of green leaves that survived freezing injury (-5 °C). This observation indicates the possibility, separate from the recognized role of betaine in the response to salinity and/or drought, that betaine accumulates in response to cold stress and that the accumulation of betaine during cold acclimation is associated to some extent with freezing tolerance in leaves of barley plants.