Stellate cells storing retinol in the liver of adult lamprey,Lampetra japonica

Summary Distribution, localization and fine structure of the stellate cells in the liver of lamprey, Lampetra japonica, were studied during the spawning migration by use of Kupffer's gold-chloride method, fluorescence microscopy for vitamin A (retinol) and electron microscopy. The stellate cells in the lamprey liver differ in some of their properties from those in mammalian livers. Stellate cells which store abundant retinol in lipid droplets, occur not only in the hepatic parenchyma, but also in the dense perivascular and capsular connective tissue of the liver and in the interstitium of pancreatic tissue. In the hepatic parenchyma these cells are located perisinusoidally or along thick bundles of collagen fibrils. The stellate cells display a number of large retinol-containing lipid droplets, granular endoplasmic reticulum, tubular structures, dense bodies, Golgi complex, microtubules, and microfilaments. In the space of Disse, the stellate cells and extracellular fibrilar components such as collagen fibrils and microfibrils (11–12 nm in diameter) are intervened between the two layers of basal laminae. Differentiation and possible functions of the stellate cells in the lamprey liver are discussed.     

Postglacial environmental change of the Pacific Ocean off the coasts of central Japan

Downcore changes in microfossil assemblages and oxygen isotope ratios in three piston cores recovered from the Northwestern Pacific, off central Japan, show that the subtropical Kuroshio front was located to the south of C-4 core site (Lat. 33° N) during the last glacial. The front then advanced northward, passing over the C-4 site and the C-6 site (34.6° N) at about 13 ka and 10 ka, respectively, and reached the C-1 core site (36° N) at about 7 ka. After 5.5 ka it retreated to the area between the C-1 and C-6 sites. A brief but significant cold event, the readvance of the cold Oyashio Current, is recognized between 11 and 10 ka in the two northern cores, but the current did not reach the southern C-4 site. A contemporaneous cold event is known in the North Atlantic, and the cooling was probably a global phenomenon likely to be associated with lowering of sea level. Contamination of isotopically light water is apparent between 14 and 11 ka in the marked change in isotopic composition of benthic foraminifers. Oxygen isotope ratios of planktonic foraminifers show that prior to the advance of the Kuroshio front, the surface water at these core sites was isotopically lighter than the Kuroshio water at that time.     

Three-dimensional structure of endothelial cells in hepatic sinusoids of the rat as revealed by the Golgi method

Summary The three-dimensional structure of endothelial cells in the hepatic sinusoids of the rat was studied by application of light- and electron microscopy on Golgi-impregnated specimens. A number of endothelial cells could thus be individually delineated throughout the hepatic lobules. The cytoplasm, showing heavy silver deposits, consists of two distinct areas, a thick and thin portion. The thick portion, issuing from the region of the perikaryon, branches and tapers toward the cell periphery. The thin portion, occupying the remainder of the cytoplasm, consists largely of highly fenestrated sieve plates. Some intralobular variation can be noted; the thick portion of the endothelial cells is well developed in the periportal zone, while the cells in the centrilobular zone are relatively rich in thin portions. In addition, the area of distribution of an individual endothelial cell is larger in the centrilobular sinusoids than in the periportal zone. Some endothelial cells also possess unique cytoplasmic processes projecting into the intercellular space between hepatocytes and connecting the sinusoidal walls of neighboring sinusoids. These processes may anchor the endothelial cells to the hepatic plates.     

Purification and properties of vitellogenin and vitellin from a tick,Ornithodoros moubata

Summary The vitellogenin (Vg) and vitellin (Vn) of a soft tick,Ornithodoros moubata, were purified from reproductive female haemolymph and from eggs, respectively. The Vg preparation displayed two components (Vg-1 and Vg-2) on polyacrylamide gel electrophoresis (PAGE), both of which reacted with anti-Vn serum. The Vn and Vg-2 preparations were homogeneous as judged by PAGE, electron microscopy, and immunodiffusion, whereas the Vg-1 always contained a small amount of Vg-2. The electron micrographs of Vn and Vg-2 showed a rugby-ball shape with a cleft at the middle of the molecules, while Vg-1 appeared as half of Vn or Vg-2 in shape and size. This together with the data on molecular weights (600, 000 for Vn and Vg-2, 300, 000 for Vg-1) suggests that the Vn and Vg-2 are dimers of Vg-1. Six polypeptides (P1–P6, mol wt 100, 000–215, 000) for Vgs and six polypeptides (P3–P8, mol wt 50, 000–160, 000) for Vn were demonstrated by SDS PAGE; P3–P6 were common to Vgs and Vn. These observations suggest proteolytic processing from larger to smaller polypeptides. The Vn contained 7.6% lipids with triacylglycerol as the major neutral lipid and 12.4% carbohydrates with mannose as the major sugar. The Vn and Vgs showed a reddish brown coloration due to the presence of haem compound(s). The amino acid composition of Vn was high in glutamic acid, proline, valine and leucine but low in methionine and isoleucine. The isoelectric point of Vn and Vgs was pH 6.9. Unlike Vg and Vn of insects, the Vgs and Vn of tick were soluble in distilled water.Abbreviations Vg vitellogenin - Vn vitellin - PAGE polyacrylamide gel electrophoresis - SDS sodium dodecylsulfate     

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.     

Biochemical evidence of DNA transport from the silk gland to the fat body of the silkworm, Bombyx mori

β-DNA, a component of DNA found in the pupal fat body of the silkworm, Bombyx mori, has the same GC content but a smaller molecular weight than typical silkworm DNA (α-DNA). Its origin and time of synthesis were studied by MAK column chromatography of phenol extracts after labelling with radioactive precursors.The DNA components of the fat body changed greatly during the early pupal stage, the β-DNA showing a striking increase relative to α-DNA. Thymidine-6-³H and phosphoric acid-³²P injected into the animals 1 day before analysis caused labelling of α-DNA, but not of β-DNA of the fat body, indicating that β-DNA was not synthesized during the stage of its appearance in the fat body.On the other hand, injection of thymidine-6-³H into 2-day-old fifth instar larvae, when DNA of the silk gland was being actively synthesized, gave high incorporation of the isotope into β-DNA of the pupal fat body. The sudden appearance of highly labelled β-DNA in the fat body during the early pupal stage as well as the occurrence of β-DNA in both the silk gland and fat body suggested that DNA might move from the silk gland to the fat body.It is possible that the fat body stores DNA as a nutrient from the degenerating silk gland.     

Adaptation of oysters to life on soft substrates

In spite of their sessile nature, oysters of the genera Crassostrea, Ostrea and their allies are adapted to live on soft muddy bottoms. To provide them with secure attachment and to keep the animal above the surface of the mud, these soft-bottom oysters employ two basic strategies. They tend to be gregarious in their settlement, thereby providing one another with surfaces for attachment, and they form lightweight shells. In addition to these common characteristics, these oysters have followed different morphological pathways to live successfully on soft muddy bottoms. There are at least four types of morphologies: (1) relay-type succession (shells pile up on one another over many generations); (2) konbo-type elongation (both valves grow vertically upwards, the dorsal hinge remaining at the base, near the umbo); (3) cone-type elongation (the attached valve grows upwards and the free valve acts as a lid); and (4) lightweight recliners (bulky shells with lightweight fabrics and cavities within them). Judging from the variety of taxa that have adopted it and the sizes of their populations, the relay-type is the most successful of these strategies. Recliners were particularly common during the Mesozoic. The relay-type appeared in the Late Jurassic, becoming the dominant adaptive strategy during the Cenozoic.     

Identification and characterization of plasma kallikrein-kinin system inhibitors from salivary glands of the blood-sucking insect Triatoma infestans

Two plasma kallikrein-kinin system inhibitors in the salivary glands of the kissing bug Triatoma infestans, designated triafestin-1 and triafestin-2, have been identified and characterized. Reconstitution experiments showed that triafestin-1 and triafestin-2 inhibit the activation of the kallikrein-kinin system by inhibiting the reciprocal activation of factor XII and prekallikrein, and subsequent release of bradykinin. Binding analyses showed that triafestin-1 and triafestin-2 specifically interact with factor XII and high molecular weight kininogen in a Zn2+-dependent manner, suggesting that they specifically recognize Zn2+-induced conformational changes in factor XII and high molecular weight kininogen. Triafestin-1 and triafestin-2 also inhibit factor XII and high molecular weight kininogen binding to negatively charged surfaces. Furthermore, they interact with both the N-terminus of factor XII and domain D5 of high molecular weight kininogen, which are the binding domains for biological activating surfaces. These results suggest that triafestin-1 and triafestin-2 inhibit activation of the kallikrein-kinin system by interfering with the association of factor XII and high molecular weight kininogen with biological activating surfaces, resulting in the inhibition of bradykinin release in an animal host during insect blood-feeding.     

Five cases of Diphyllobothrium nihonkaiense infection with discovery of plerocercoids from an infective source, Oncorhynchus masou ishikawae

Five persons from 2 families residing at Miyama Town, Mie Prefecture, Japan, ingested fresh raw fish Oncorhynchus sp. on 9 May 1999 that was caught at Owase district in Mie. They all expelled diphyllobothriid cestodes 11-37 days after ingesting the fish. The parasites were morphologically identical to Diphyllobothrium nihonkaiense Yamane et al., 1986. Five plerocercoids were detected from a portion of the fish. Nucleotide sequence of a region of the cytochrome c oxidase subunit I gene of mitochondrial DNA from an adult worm was identical with that from the plerocercoid. The fish was identified as Oncorhynchus masou ishikawae according to the nucleotide sequence of the nuclear ribosomal second internal transcribed spacer region II gene. This is the first record of D. nihonkaiense plerocercoids from O. m. ishikawae.