Studies on the development and three-dimensional reconstruction of giant mitochondria and their nuclei in egg cells ofPelargonium zonale Ait.

Summary The preferential development of giant mitochondria and their nuclei (nucleoids) in the egg cells ofPelargonium zonale Ait. during megasporogenesis and megagametogenesis was examined by fluorescence microscopy, after Technovit embedding and 4,6-diamidino-2-phenylindole (DAPI) staining, fluorimetry for DNA content, using a video-intensified microscope photon-counting system (VIMPICS), and by three-dimensional reconstruction of mitochondrial nuclei (mt-nuclei). Reproductive cells during the megaspore mother cell, meiosis, tetrad, and functioning megaspore stages contained many small mitochondria with characteristic, uniformly DAPI-stained mt-nuclei about 0.3 m in diameter, containing a small amount of DNA (0.3 Mbp). During formation of the 2-, 4-, and 8-nucleate embryo sac, mt-nuclei did not markedly change in shape or DNA content. When the embryo sac formed and differentiation of each cell began, mitochondria and their nuclei in the egg cell took on a small ring or string-like shape. Accompanying the maturation of the embryo sac, they underwent progressive enlargement and gradually altered to long thick strings, or stacks of concentric or half concentric rings. By flower opening, they have developed to an extremely large size. One of these stacks of mt-nuclei was reconstructed in three dimensions; each ring in the stack was cup- or plate-shaped; 5 to 10 rings made up the stack, though each remained discontinuous from the others. From serial sections, we counted 44 mitochondria in one egg cell. Fluorometry using VIMPICS revealed that DNA amount within the stacked mitochondrion increased to 40 times that of the megaspore mother cell stage; a single stack of mitochondria contained 340–1700 Mbp DNA; which means that one egg cell contains at least 15000 Mbp mt-DNA, a value greater than the cell-nuclear DNA content.     

Comparative biochemical studies of carotenoids in sea urchins—III. Relationship between developmental mode and carotenoids in the Australian echinoids Heliocidaris erythrogramma and H. tuberculata and a comparison with Japanese species

The sea urchin Heliocidaris tuberculata is typical of most echinoids in having a small egg and a feeding larva, while H. erythrogramma has a large egg and modified development through a non-feeding larvae. The carotenoids in the gonads of these two species were investigated from the comparative biochemical points of view. The carotenoid content of the buoyant eggs of H. erythrogramma was approximately 60 times that of the negatively-buoyant eggs of H. tuberculata. With respect to cytoplasmic volume, however, the carotenoid concentration in the eggs of H. tuberculata was approximately twice that in the eggs of H. erythrogramma. In both species β-echinenone was the principal carotenoid found and their carotenoid patterns were similar. It is very interesting from a functional point of view that carotenoid levels per cytoplasmic volume are conserved across most of the species we have examined irrespective of phylogeny and egg size. In light of this result we suggest that carotenoids may play an important role in developing stage in all echinoids including indirect and direct developers.     

The isolation of viable egg cells of wheat (Triticum aestivum L.)

The isolation of viable egg cells of wheat has been achieved without enzymatic maceration of the ovules. 2,4-D applied to the stigmas resulted 3 to 7 days later in soft ovule tissues which disintegrated upon mechanical manipulation. The isolated egg cells were viable even 2 h after isolation. Their morphology corresponded to that of the in situ egg cells. The mean isolation frequency was 20% (two egg cells per ten ovules).     

Egg and larval load assessment and its influence on oviposition behaviour of the leaf beetle Galerucella nymphaeae

The oviposition behaviour of the water-lily beetle Galerucella nymphaeae was examined. This species is a specialist herbivore on the floating leaves of nymphaeids Nymphaeaceae and especially on the yellow water-lily, Nuphar lutea. Females lay their eggs in clutches on the leaves, and after hatching, the larvae feed on the leaves. The quality of the leaves decreases quickly after the larvae hatch, and eventually the leaves will sink below the water surface, whereupon the eggs, 1st-instar larvae and pupae are killed by drowning. The influence of conspecific eggs, larvae and feeding tracks on the oviposition preferences of the beetles was tested. Females were allowed to choose between fresh leaves and leaves with conspecific eggs and larvae as well as between leaves with larvae and leaves with feeding tracks but no larvae. An attempt was also made to determine whether eggs and larvae affect the oviposition rate of females when they are not given the opportunity to oviposit on untouched leaves. The results indicate that females tended to avoid leaves with conspecific larvae or to exhibit a decreased oviposition rate on such leaves. Females also avoided conspecific eggs, although the oviposition rate was not influenced by the presence of conspecific eggs. When females were allowed to choose between leaves with larvae and leaves with feeding tracks, possible discrimination against leaves with larvae just fails to reach the 5% level.     

A Protein Extracted from Mouse Sperm That Plays an Important Role in Fertilization

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夜蛾科卵的数值分类研究（鳞翅目：夜蛾科）

本文以３４种卵作为分类单元,对４１个性状了数值分类研究。结果表明卵的形态特征可以作为夜蛾科分属的重要依据,并支持把黄地老虎归入Ａｇｒｏｔｉｓ属的观点。     

利用非洲爪蟾精子染色质和卵提取物在体外重建细胞核

应用非洲爪蟾去膜精子染色质和卵提取物成功地进行了细胞核本外重建。当精子染色质加入卵提取物后,首先发生染色质去浓缩作用,染色质整体结构膨胀;膜泡在膨胀的染色质外周聚集并逐渐彼此融合成双层膜;核孔复合体以某种未知方式组装入双层膜而形成核膜结构,并逐渐完全覆盖膨大的染色质,最终形成典型的间期核结构。     

Muscle determinants in the ascidian egg are inactivated by UV irradiation and the inactivation is partially rescued by injection of maternal mRNAs

The ascidian egg contains cytoplasmic determinants that specify the fate of larval muscle cells. In a previous study, we developed an experimental system to identify the molecular nature of muscle determinants, in which unfertilized Ciona savignyi eggs were fragmented into four pieces by centrifugation. When inseminated, only nucleated fragments (red fragments) develop into partial embryos that only show differentiation of epidermal cells. One type of enucleated fragment (black fragment) has the remarkable ability to promote muscle differentiation when fused with red fragments. In the present study, using this experimental system, we investigated the molecular nature of muscle determinants. UV irradiation of black fragments suppressed the ability to promote expression of the muscle-specific protein, myosin heavy chain. The wavelength of UV light responsible for the inactivation (250–275 nm) suggested that UV-sensitive targets are nucleic acids. Injection of poly(A)⁺ RNA isolated from an un-irradiated black-fragment-rich fraction into UV-irradiated black fragments partially recovered the ability to promote the expression of myosin heavy chain protein. Poly(A)⁺ RNA from a red-fragment-rich fraction did not rescue the suppression of UV-irradiated black fragments. These results suggest that maternal mRNAs enriched in black fragments are closely associated with muscle determinants in the ascidian egg.     

凝集素抑制林蛙卵裂沟新膜外露的作用

剥去受精膜的林蛙卵分裂时,分裂沟中的新膜会暴露出来。林蛙老膜上有大量均匀分布的麦胚和大豆凝集素受体。卵裂前,将剥去受精膜的蛙卵浸于上述的凝集素溶液中,新膜的外露就被抑制。凝集素愈浓,浸泡时间愈长,抑制愈大。在这些卵的表面可看到一层较厚的由凝集素引起的外被。碱处理过的受精卵表面,凝集素受体减少,凝集素抑制新膜外露的作用亦减弱,由凝集素引起的外被亦薄。凝集素是多价的,会在细胞表面产生交链,形成“外骨骼”,抑制新膜外露。凝集素也可通过受体,影响微丝,产生作用。     

The specification of metameric order in the insectCallosobruchus maculatus Fabr. (Coleoptera)

Summary Mechanically dividing an insect egg into anterior and posterior fragments results in a segment gap (Sander 1976), a loss of non-terminal segments in the constricted region. By altering the stage and duration of constriction, we produced different types of egg fragments in the pea beetleCallosobruchus. The patterns formed by these fragments suggest the existence of interactions between anterior and posterior egg regions that influence segment patterning and placement. Segments in excess of the numbers expected on the basis of permanent constrictions were produced in fragments when: (1) the constriction was released before cellularization occurred and (2) in addition the complementary fragment degenerated. Apparently the degenerating fragment induced the formation of excess segments in the developing fragment. Differences in the time and extent of excess segment formation in anterior versus posterior fragments suggest an asymmetric distribution of prerequisites for segment formation. This conclusion is consistent with our finding that a partial reversal of segment sequence (double abdomen formation) can be induced only in posterior fragments by a degenerating fragment, but not in anterior fragments (see companion paper).The formation of excess segments shows that the segment gap observed after permanent separation cannot be due to non-specific damage, caused by the process of constriction as such, to the egg or to localized putative segment precursors.