Masaru Irie

Ultrastructure and function of long and short sperm in Cicadidae (Hemiptera)

The cicada, Graptopsaltria nigrofuscata, produces two distinct sizes of sperm, as determined by either nuclear volume of early spermatids or nuclear length of mature sperm. Between both sperm, there is no difference in location of the acrosome and flagellum during spermiogenesis. The acrosome is covered by an anteacrosomal bleb, which is inserted in a common mass, spermatodesm, derived from cyst cells. Both kinds of sperm linked to the spermatodesm form sperm bundles, respectively. During copulation, the sperm bundles are transported from the vesicula seminalis of the male to the bursa copulatrix of the female. Morphometric analyses of the nuclear length revealed that the two kinds of sperm reach the bursa copulatrix in the same condition as that found in the vesicula seminalis. Once transferred inside the latter, the sperm bundles disintegrated to individual sperm within a few hours, and the tail components, such as the axoneme and mitochondrial derivatives, become separated from each other over time. The tail completely splits from the sperm nucleus 24 h after copulation. Fertile sperm accumulate in the spermatheca, the final storage organ, where only long sperm survived for any length of time. Fertilized eggs examined by vital staining contain only sperm with long nuclei.

Morphological changes in eupyrene and apyrene spermatozoa in the reproductive tract of the male butterfly Atrophaneura alcinous Klug

Summary Eupyrene and apyrene spermatozoa are contained in separate cysts in the testis of the butterfly Atrophaneura alcinous. Spermatozoa of both types from various parts of the male reproductive tract were examined with particular reference to their morphological characteristics. All spermatozoa collected from the vas deferens and the vesicula seminalis were found to be immotile under a dissecting microscope. No spermatozoa of either type were recognized in any part of the ejaculatory duct. Within the testis, eupyrene spermatozoa are present in bundles and each spermatozoon has a slender nucleus with an acrosome and a long flagellum containing mitochondrial derivatives. Two kinds of appendages, lacinate and reticular, are present on the surface of the sperm membrane. They are replaced with an extracellular sheath during passage through the vas deferens. In contrast, apyrene spermatozoa have neither nucleus nor acrosome, whereas a cup-shaped structure was found at the sperm tip instead of the acrosome. U...

Spermatogenesis in the Testes of Diapause and Non-Diapause Pupae of the Sweet Potato Hornworm, Agrius convolvuli (L.) (Lepidoptera: Sphingidae)

Abstract Dichotomous spermatogenesis was examined in relation to diapause in the sweet potato hornworm, Agrius convolvuli. In non-diapause individuals, eupyrene metaphase began during the fifth larval instar and eupyrene spermatids appeared in wandering larvae. Bundles of mature sperm were found after pupation. Apyrene spermatocytes also appeared during the fifth larval instar, but meiotic divisions occurred irregularly and their nuclei were discarded from the cells during spermiogenesis. Morphometric analyses of flagellar axonemes showed a variable sperm number in apyrene bundles. The variation ranging from 125 to 256 sperm per bundle indicated abnormal divisions or the elimination of apyrene spermatocytes. In diapause-induced hornworms, spermatogenesis progressed similarly during the larval stages. The cessation of spermatogenesis during diapause is characterized by 1) secondary spermatocytes and sperm bundles degenerating gradually as the diapause period lengthens, and 2) spermatogonia or primary spermatocytes appearing throughout diapause. A TUNEL (TdT-mediated dUTP-biotin nick end-labeling) assay revealed that DNA fragmentation occurred in the nuclei of secondary spermatocytes and early spermatids. Aggregates of heterochromatin along the nuclear membrane indicated the onset of apoptosis, and condensed chromatin was confirmed by electron microscopy to be the apoptotic body. These results show that the degenerative changes in spermatogenic cells during pupal diapause were controlled by apoptosis.

The transfer of titanium dioxide nanoparticles from the host plant to butterfly larvae through a food chain.

This study aimed to examine the transfer of nanoparticles within a terrestrial food chain. Oviposited eggs of the swallowtail butterfly (Atrophaneura alcinous) were hatched on the leaves of the host plant (Aristolochia debilis), and the root stock and root hairs were submerged in a suspension of 10 μg/ml titanium dioxide nanoparticles (TiO2-NPs) in a 100 ml bottle. The presence of TiO2-NPs in the veins of the leaves was confirmed by X-ray analytical microscopy (X-ray AM). The hatched 1st instar larvae fed on the leaves to moult into 2nd instar larvae. Small agglomerates of TiO2-NPs less than 150 nm in diameter were identified in the vascular tissue of the exposed plant, the midgut and the excreta of the larvae by transmission electron microscopy. The image of Ti elemental mapping by X-ray AM was analysed with the quantitative spatial information mapping (QSIM) technique. The results demonstrated that TiO2-NPs were transferred from the plant to the larvae and they were disseminated throughout the environment via larval excreta.

Spermiogenesis in the stag beetle, Aegus lavicollis Waterhouse (Coleoptera, Lucanidae), with special reference to the centriole adjunct

Summary Ultrastructural changes during spermiogenesis in the stag beetle, Aegus lavicollis, were studied with special attention to the organizing process of the centriole adjunct. In early spermatids the formation of acrosome and flagellum occurs simultaneously in the cytoplasm before nuclear condensation. The centriole adjunct first appears as a sheath surrounding a centriole in a concavity of the nucleus from which the flagellar axoneme is organized. A mass of electron-dense material accumulates progressively in the vicinity of the centriole. As nuclear transformation proceeds, electron-dense material is found at the posterior end of the nucleus and extends beyond the centriolar region to form a partial sheath around mitochondrial derivatives. Electron-dense material seems to contribute to the formation of the centriole adjunct because the former is closely attached to the latter until the latter is completely formed. In mature spermatozoa the centriole adjunct is characterized by its peculiar disposition, extending across about half the length of the flagellum and partly covering the outside of two mitochondrial derivatives.

The ecologically soft deuterium-deuterium reactor with FBX-III Moving Plasma Core reactor scheme

An ecologically soft fusion scheme of FBX-III Moving Plasma Core Reactor is discussed. One of the most severe problems of a fusion reactor is induced radioactivity. The problem is caused by 14 MeV neutrons produced by a direct fusion reaction between deuterium and tritium. In this point, a fusion reactor becomes much more safer with pure tritium fuel without deuterium. Our scheme use catalyzed deuterium-deuterium reaction to reduce this problem. This is a far difficult path for the plasma engineers than the current scenario with the deuterium-tritium fusion fuel. FBX-III is designed to be as simple as possible to obtain high reliability. It is subdivided into several sectors. Each sector devotes to only limited tasks. Fusion reactions are initiated not in the plasma production sector but in the reactor sector. This is triggered by the toroidal adiabatic compression followed by the neutral beam injection system with MeV particle energy.

Transversally accelerated kA arcs in air

Summary form only given. A transversally accelerated high pressure arc launcher is designed to initiate the Plasma Induced Lightening Experiment. The fundamental assumption after a current rise stage of around 10 MA/s is as follows. The arc is stable in shape and only the position is shifting to the Z direction along the electrodes separated d mm from each other. The arc area is covered by the ambient temperature boundary layer. In this way the arc and the boundary layer surrounding it are assumed to be an ambient temperature solid body as a whole. From these assumptions, the saturated arc velocity is V/sub B/=a d/sup - 1/2 / I. Here a is a constant in the order of 10/sup -3/ [m/sup 3/2//s/A] depending on the detailed geometrical factors. The actual experiment is conducted with a gap separation between 5 mm to 50 mm. The applied current is a crawbarred profile with 1.1 ms sinusoidal current ramp up to 10 kA and decays with a time constant of 6 ms. The arc position against time is displayed with the theoretical values obtained from our model. These results give a=2/spl plusmn/0.1 [m/sup 3/2//s/A]. This is in good agreement with our model.

Dynamics of spatially and temporally decaying arcs for lightning discharge initiation

Summary form only given. In the field of laser initiated lightning discharge research for electric power network protection, some drastic breakthroughs are necessary to apply this technique commercially, other than the conventional approach only for chasing after the higher laser power. One of the keys seems to be in the experimental results found in the same field. The laser produced plasma in quasi steady high electric field is known to show a strange feature. It has the peak lightning-triggering efficiency at around 100 /spl mu/s after a sub-micro second laser irradiation. From the existing computer simulation, this time scale should be far longer than the recombination and attachment time scale for free electrons in air. In this sense, the dominant constituents for lightening initiation are not free electrons but excited gases in certain conditions. We had set up an experiment with a transversally accelerated arc. This uses a modified version of a rail-gun type system but in high pressure air. This produces a rapidly moving high current arc armature with 10 kA peak and 10 ms current decay time. This time scale is slow enough to be considered as a quasi-DC condition for this application. The time scale of experimentally obtained hot gas decay is about 100 us and the laser pulse duration is in the order of 10 ns. The paper focuses on the mechanism and efficiency of charged particle removal from this plasma with experimental evidence. These results are summarised with the detailed comparison with the simulation and unresolved questions shown.

Ball plasma dynamics for FBX BURNER reactor

Summary form only given, as follows. We have conducted fundamental experiments on moving plasma balls in the major axis direction. This has a fundamental importance for the quasi-steady fusion reactor scheme with the moving flowing fuel type fusion reactor FBX BURNER. This configuration is the descendants of Spheromak type nuclear fusion scheme but with a long toroidal field coils. The main issues have been focused onto the dynamic stability of the moving plasma balls. The second issue is the collision between two successive plasma balls. This shows a basic result from an optical measurement. The comparison with magnetic measurements shows peculiar but interesting features of the system. The dimension of our plasma injector is 2 m in length. It has a coaxial configuration. The external electrode is 150 mm in inner diameter and the inner electrode is 50 mm in diameter. This is attached to a 1 m insulation reservoir with the same inner diameter. An axial magnetic field up to 0.1 Tesla is applied to the discharge with a current of up to 10 kA in few ms.