Fine structure of micropylar region during late oogenesis in eggs of the hagfish Eptatretus burgeri (Agnatha)

Using the hagfish, Eptatretus burgeri, the fine structure of formation of the micropylar region in hagfish eggs during the late stages of oogenesis was investigated for the first time, focusing on the bottom region of the micropyle and the egg surface. During these stages, many cells penetrated through the chorion and reached a pit of the egg surface, forming a shovel-like structure in two-dimensional sections. The cells, which we called micropylar cells, were separated from the chorion by a wall of amorphous material. In the pit, another fibrous layer filled the space between the egg surface and the anterior portion of the shovel-like structure. Microvilli coming from the egg surface were embedded in this layer. In later stages, the stack of micropylar cells loosened, and a space appeared between the anterior region of the shovel-like structure and the layer on the egg surface. Microvilli decreased in length and number. The pit region appeared likely to have a role in fertilization. The structures associated with the forming micropyle were markedly different from those observed in the same region of teleost fishes. A hypothesis that hagfish might show transitional structures in gametes from protochordates to teleosts is suggested.     

In vitro PPFD and media composition affect both in and ex vitro performance of Alstroemeria Butterfly-hybrids

The objective was to reduce in vitro production costs while retaining or improving plant quality, in particular the suitability for pot plant production. Plants were grown at photosynthetic photon flux densities (PPFD) of 0–40 μmol m^-2 s^-1 and sucrose concentrations of 3–7% during the multiplication phase and the effects of sucrose, BA, and NAA during root formation were investigated. Ex vitro growth were tested in both experiments. A small reduction in the rhizome multiplication rate was found with increasing PPFD and sucrose concentration. Increasing sucrose concentration reduced the number of aerial shoots. Aerial shoots were etiolated when cultured in darkness and their number increased with increasing PPFD at 3% sucrose, whereas PPFD did not affect the number of aerial shoots at 5 or 7% sucrose. During the multiplication phase a synergistic promoting effect of PPFD and sucrose was observed on root formation. Root formation after transfer to rooting medium was affected by sucrose and PPFD during the multiplication phase. PPFD did not influence root formation after propagation on 7% sucrose, whereas on 3 or 5 % sucrose root formation was gradually inhibited when PPFD was decreased below 17 μmol m^-2 s^-1. The formation of thick roots was promoted by propagation in light, and not influenced by sucrose concentration. Ex vitro growth was not affected by in vitro conditions, except for 7% sucrose during the multiplication phase that reduced flowering. Root formation on rooting medium was reduced by BA and promoted both by NAA and high levels of sucrose. The root inhibiting effect of BA could not completely be overcome by simultaneous application of NAA and high sucrose concentrations. Thick roots were only produced in the presence of NAA, and not affected by sucrose treatment. Ex vitro flowering was negatively influenced by the presence of BA during root formation and by high levels of sucrose if BA was absent in the rooting medium. High sucrose levels and NAA could partially compensate for the negative effect of BA on flowering. This revised version was published online in June 2006 with corrections to the Cover Date.     

Fungi in Their Own Right

Although fungi have contributed tremendously to understanding biological phenomena common to all eukaryotic organisms, some of their properties testify as to their uniqueness. Among these are growth by apical extension of hyphae, the manufacture of hydrophobins for emergence into the air, and the possession of an extended somatic heterokaryon in basidiomycetes. This justifies studies on the molecular basis of development aimed particularly at this group of organisms, which are of great importance to life on earth and human society.     

Division of labor in the monogamous goby,Valenciennea longipinnis, in relation to burrowing behavior

Feeding and burrowing behavior of the monogamous gobiid fish,Valenciennea longipinnis, were studied on the coral reef at Sesoko Island, Okinawa, Japan. These fish usually live in pairs, the male and female feeding in close proximity to one another upon benthic animals and constructing several burrows cooperatively for purposes of shelter or spawning. Paired females fed more and burrowed less frequently than their mates. Because burrow maintenance was mostly conducted by the latter, the paired females performed work much less frequently than solitary females. Thus, the paired females may be able to allocate more energy toward egg production. The division of labor related to burrowing behavior in this species may be an effective way to increase reproductive success for both sexes. Moreover, the fameles burrowed even less frequently when paired with larger males, probably because burrowing ability may be correlated with mouth size in males. This is a likely reason for the preference of females to mate with larger males.     

Secondary structural modifications of Aβ(1-40) induced by multiple 2-acetoxy-4-methoxybenzyl (acetylHmb) protection

Summary Modifications to secondary structure and fibril formation caused by multiple acetylHmb backbone amide protection of Alzheimer's disease Aβ(1–40) were investigated using circular dichroism spectroscopy and electron microscopy. Penta(acetylHmb) Aβ(1–40) was observed to have a reduced ability to form α-helix and β-sheet structures under the same solution conditions as the native peptide, with α-helical propensity being reduced more significantly than β-sheet propensity. Further, acetylHmb backbone protection was found to alter Aβ(1–40) interaction with SDS-micelles by preventing α-helix formation. Aβ fibril formation, a characteristic property of this peptide, was also not observed for penta(acetylHmb) Aβ(1–40).     

Changes of Endogenous Hormone Contents During Floral Bud and Vegetative Bud Differentiation in Thin Cell Layer Culture of Cichorium intybus L. Explant

The sectioned thin cell layers (TCL) of flower stalk of Cichorium intybus L. were cultured in MS medium supplemented with NAA and BA or IAA and BA where floral and vegetative buds were developed from the explant. Endogenous IAA, DHZ+DHZR, iPA increased significantly during the floral bud formation, while Z+ZR remained changed. The levels of cytokinins, DHZ +DHZR, iPA, and Z-f-ZR all increased significantly during the vegetative bud formation, however IAA level was reduced during the first 7 days of culture and increased to two-thirds of initial values on the day when the bud primordia were formed. The results suggested that the initiation of floral buds was associated with a high IAA/CTK ratio, whereas the induction of vegetative bud differentiation was related to a low IAA/CTK ratio.     

金鱼草下胚轴不同部位切段形态发生能力的研究

金鱼草（ＡｎｔｉｒｈｉｎｕｍｍａｊｕｓＬ．）下胚轴不同部位切段的形态发生能力有很大差异。在外源添加ＢＡ,ＮＡＡ的情况下,金鱼草下胚轴近基部切段培养物的芽、根发生明显高于其上各部位切段,以近基部切段为外植体培养时,其形态发生能力以ＢＡ和ＮＡＡ配合为好,最适剂量为ＢＡ１０ｍｇ／Ｌ＋ＮＡＡ０１５ｍｇ／Ｌ。     

Identification of Tn10 insertions in the rfaG, rfaP, and galU genes involved in lipopolysaccharide core biosynthesis that affect Escherichia coli adhesion

Escherichia coli was used as a model to study initial adhesion and early biofilm development to abiotic surface. Tn10 insertion mutants of Escherichia coli K-12 W3110 were selected for altered abilities to adhere to a polystyrene surface. Seven insertion mutants that showed a decrease in adhesion harbored insertions in genes involved in lipopolysaccharide (LPS) core biosynthesis. Two insertions were located in the rfaG gene, two in the rfaP gene, and three in the galU gene. These adhesion mutants were found to exhibit a deep-rough phenotype and to be reduced, at different levels, in type 1 fimbriae production and motility. The loss of adhesion exhibited by these mutants was associated with either the affected type 1 fimbriae production and/or the dysfunctional motility. Apart from the pleiotropic effect of the mutations affecting LPS on type 1 fimbriae and flagella biosynthesis, no evidence for an involvement of the LPS itself in adhesion to polystyrene surface could be observed. Received: 1 December 1998 / Accepted: 3 April 1999