Micromere Differentiation in the Sea Urchin Embryo: Expression of Primary Mesenchyme Cell Specific Antigen during Development

The temporal and spatial expression of antigen specific for primary mesenchyme cell (PMC) lineage cells during early development of the sea urchins Hemicentrotus pulcherrimus and Stronglyocentrotus nudus was studied with a monoclonal antibody (P4). P4 was produced by a hybridoma cell line prepared by fusion of myeloma cells and spleen cells from a mouse immunized with cultured spicule-forming cells. Immunofluorescence studies demonstrated that P4 antibody reacted strongly with the surfaces of PMC's and spicule-forming cells of both species. Immunoblot analysis showed that P4 antibody reacted with several proteins including those of 140–kDa, 120–kDa, 53-kDa, 43–kDa, and 41–kDa in H. pulcherrimus and with those of 130–kDa, 110–kDa, 51–kDa, and 43–kDa in S. nudus . These proteins appeared sequentially after the hatching blastula stage. Tunicamycin inhibited the expressions of these P4 antigens as well as spicule formation. Two of the P4-reactive antigens, the 140–kDa and 43–kDa proteins, in H. pulcherrimus were synthesized de novo and shown to be identical to micromere differentiation specific proteins. These results suggest that P4 binds to specific molecules that are important in spicule formation in developing sea urchin embryos.     

Role of Wall-bound β-Glucanases in Regulating Tip-growth of Lilium longiflorum Pollen Tubes

β-Glucanases were found in the cell wall of Lilium longiflorum Thunb. pollen tubes grown in vitro . The activity of β-glucanases was, in a certain extent, decreased by nojirimycin, an inhibitor of glucosidase. Pollen germination percentage reduced dramatically when nojirimycin was applied in the culture medium. In case that nojirimycin was added at 0 or 1 h after the onset of incubation, the inhibition rate was 99.6% and 91.4%, respectively. When 3 mmol/L of nojirimycin was applied in the liquid medium at 0, 1, 1.5 and 2 h after the onset of incubation, the growth of pollen tubes was interrupted, which resulted in the morphological change of the pollen tubes such as the newly grown portion of pollen tubes being bent, curved and swollen. Tracing the growth pattern of the individual pollen tube grown in semi-solid medium by video microscopy, the authors demonstrated that pollen tube growth rate was strongly inhibited by nojirimycin at concentrations ranged from 0.003 to 3 mmol/L. Moreover, the cytoplasmic arrangement and the morphology of the pollen tubes were also affected by nojirimycin. The growth inhibition brought about by nojirimycin was reversible. These results indicated that β-glucanases, which degrade 1,3-β-glucan and/or 1,4-β-glucan or 1,3:1,4-β-glucan constructed in the cell wall, are involved in pollen germination and pollen tube growth. It provides new insight into an understanding of the contribution of β-glucanases to the cell wall extensibility and the crucial role of cell wall in regards to the regulation of pollen tube growth.     

Non-selective surface deposit feeding by the Zoophycos producers

The feeding mechanism of Zoophycos producers demonstrates non-selection by particle size or quality. The characteristic morphology and mode of Occurrence of Zoophycos and the presence of pellets with pyroclastic grains imply that the Zoophycos producers were surface deposit-feeders. They dwelt in a burrow within the sediment and ingested the grains with nutrient detritus on the sea floor around the burrow opening. Fecal pellets containing pyroclastic grains were compared with the overlying volcanic ash layers through the analyses of grain size and mineral composition based on samples from two horizons in the Upper Pliocene of Boso Peninsula, central Japan. Judging from the comparative analyses, no significant differences were found between the ash layer and the fecal pellets. This fact strongly suggests that the Zoophycos producers appear to indiscriminately ingest particles on the sediment surface. Environments of low nutrition input such as the deep sea, non-particle size and quality selection in Zoophycos producers may be the feeding strategy for the detritus-feeding burrow-dwellers. □ Zoophycos, surface deposit-feeding, Pliocene Shiramazu Formation, Boso peninsula, Japan.     

细胞壁结合的β—葡聚糖酶对百合花粉管顶端生长的调节作用

从离体培养的麝香百合（Lillum longiforum Thunb.)花粉管细胞壁中分离纯化出β－葡聚糖酶。抑制剂野尻酶素（mojirimycin)使该酶活性明显降低。若在百合花粉培养的初始或培养1h时加入3mmol/L野尻酶素,与对照相比较,花粉的萌发率分别抑制99．6％和91.4％。若把3mmol/L野尻酶素分别在培养的不同时刻（0、1、1．5和2h）加入到液体培养基中,花粉管的生长都即刻受阻。此后,花粉管生长方向稍有改变,且花粉管直径略增,呈弯曲的非正常形态。用视频显微术跟踪记录在正常或含有不同浓度野尻酶素（0.003、0．03、0．3和3mmol/L）的半固体培养粉管直径、胞质内细胞器及囊泡的分布和顶端生长区的区域范围也呈现异常。野尻酶素对花粉管生长的抑制是可逆转的。这些结果表明,β－葡聚糖酶参与百合花粉的萌发和花粉管生长的调节。结合我们已报道的该酶的性质及作用方式,进而推测该酶通过降解1,3－1／1,4－或1,3：1,4－β－葡聚糖,影响细胞壁的延展性,从而对花粉管顶端生长显示调节作用。     

Development and polymorphisms of microsatellite markers for hinoki (Chamaecyparis obtusa)

Fifteen microsatellite markers were developed from a microsatellite‐enriched library and characterized using 32 Chamaecyparis obtusa individuals. The number of alleles ranged from two to 27 per locus, with observed heterozygosity ranging from 0.281 to 0.906. The polymorphism information content (PIC) was also calculated for each marker and the average was 0.796 ± 0.024. These microsatellite markers will be useful for investigating population genetics, reproductive ecology, tree improvement and constructing linkage maps of the species.     

Deep-sea echiurans: possible producers of Zoophycos

Kotake, N. 1992 07 15: Deep-sea echiurans: possible producers of Zoophycos.
The trace fossil Zoophycos in the upper Pliocene deep-sea deposits (Shiramazu Formation) distributed in the southernmost part of Boso Peninsula, central Japan, appears to be a product of feeding and excretory behavior by surface deposit-feeders inhabiting middle bathyal depths. Ecology and anatomy of modern deep-sea echiurans are consistent with those of the Zoophycos producers based on the Pliocene examples. Consequently, deep-sea echiurans may be producers of Zoophycos . Systematic lamellae structures of the spreite reflect excretory behavior in sediment resulting from deposit-feeding on the sea-floor. Z oophycos , deep-sea echiurans, Pliocene, Boso Peninsula, Japan .     

Genetic Variation and Population Differentiation in Natural Populations of Cryptomeria japonica

Abstract Sugi (Cryptomeria japonica D. Don) is a valuable tree species in Japan. The present natural distribution is limited to small scattered areas in temperate moist regions, and most of these areas are surrounded by vast artificial plantations. We studied natural populations of C. japonica in an effort to determine the amount and distribution of genetic diversity using 12 allozyme markers. The amount of genetic variation within the species is high (H_T=0.196) but most is found within populations with little among populations (G_ST=0.034) despite their isolated distribution. This pattern of genetic diversity is inferred to be the consequence of the following: (1) the distribution of this species in the past was wider and more continuous than it is now; (2) a high rate of gene flow occurs, perhaps including gene flow between natural populations and plantations; and (3) the long lifespan. However, the distribution of allele frequencies at the 6Pg-1 in northern populations on the side near the Sea of Japan is clearly different from those in other populations. This observation is inferred to result from founding events.     

Effects of Cations and Other Medium Components on the Zona-induced Acrosome Reaction of Hamster Spermatozoa

Although the acrosome reaction in lively motile hamster spermatozoa can occur independently of the egg or its investments ("spontaneous" acrosome reaction), it appears to be the egg investments, particularly the zona pellucida, that induces the acrosome reaction in fertilizing spermatozoa of many mammalian species. The latter is referred to as "zona-induced" acrosome reaction. Experiments were conducted to determine if the zona-induced acrosome reaction has different ion requirements from the spontaneous reaction. Like the spontaneous acrosome reaction, the zona-induced acrosome reaction required extracellular Na⁺, K⁺ and Ca²⁺. The absence of Cl⁻ and albumin in the medium inhibited the reaction. The zona-induced acrosome reaction could occur in a HCO₃⁻-free medium, but far less efficiently than in medium containing this ion. Proteinase inhibitors, benzamidine and TLCK, inhibited the zona-induced acrosome reaction. These results suggest that the chemical reactions involved in the spontaneous and zona-induced acrosome reactions are similar although the reaction-triggering mechanism is probably different.     

Interpopulation variation in mating system and late-stage inbreeding depression in Magnolia stellata

Inbreeding has the potential to cause evolutionary changes in populations, although these changes are likely to drive populations to extinction through inbreeding depression and reductions in genetic diversity. We investigated the mating system and late-stage inbreeding depression (δ) in 10 populations of Magnolia stellata using nine microsatellite markers and evaluated the effects of population size and the degree of population isolation through inbreeding and inbreeding depression on the persistence of populations. The outcrossing rates were very similar (~0.7) among populations, but the correlations of paternity, fractions of biparental inbreeding and inbreeding coefficients at the seed stage ( F _S) varied among populations, suggesting that the level of outcrossing was similar among populations, while the quality of it was not. A significant negative correlation was detected between F _S and population size. The average value of δ was 0.709, and the values in six of the 10 populations were significant. The values of δ differed among populations, although clear relationships with population size and the degree of population isolation were not detected. However, in one population, which was very small and located in the edge of the species' range, we obtained a very low value of δ (–0.096), which may be indicative of purging or the fixation of deleterious alleles. Existing M. stellata populations that are small (and thus might be expected to have higher frequencies of inbreeding) and have large values of δ may be in danger of declining, even if the populations are located within the central region of the species' range.