Morphology and ultrastructure of isolated gemmae of Drosera pygmaea and their in vitro germination

Gemma morphology, histology and ultrastructure before and after germination in vitro were studied in Drosera pygmaea. The histology of the gemma is similar to that of a seed, being characterized by an embryo-like structure and storage tissue, although no seed coat is formed. One embryo-like structure within the gemma, which gives origin to a new plant, expresses polar organisation with distinct meristematic regions. Storage tissue surrounding the embryo-like structure resembles endosperm and it is built of parenchyma cells possessing plastids with starch grains and dense material within vacuoles. The regeneration from the gemma may provide useful system to study plant morphogenesis under stress conditions including in vitro culture. This revised version was published online in July 2006 with corrections to the Cover Date.     

Extracelluar matrix induces formation of organoids and changes in cell surface morphology in cultured human breast carcinoma cells PMC42-LA

In the lactating breast, the development of secretory alveoli consisting of differentiated cells arranged around a central lumen is dependent on signals from the extracellular environment of the cells. There are few cell lines that model this process. We previously showed that the human breast carcinoma line PMC42-LA can be induced to form organoids, reminiscent of secretory alveoli found in the lactating human breast. In this report, we used high-resolution scanning electron microscopy to show that the formation of organoids is accompanied by development of cell surface microvilli. Extracellular matrix-induced formation of microvilli occurred on the internal and external surfaces of cells in the organoids and not on surfaces in contact with the extracellular matrix. Organoid formation of PMC42-LA cells induced a rearrangement of the extracellular matrix, seen in the form of radiating fibers from the organoids. In summary, there is an interaction between PMC42-LA cells and the underlying extracellular matrix, which leads to the formation of polarized cells with well-developed microvilli. This is accompanied by organization of the extracellular matrix. PMC42-LA is a relevant model of the human breast for investigations into cell-cell and cell-matrix interactions.     

Correlative 3D imaging of whole mammalian cells with light and electron microscopy

We report methodological advances that extend the current capabilities of ion-abrasion scanning electron microscopy (IA-SEM), also known as focused ion beam scanning electron microscopy, a newly emerging technology for high resolution imaging of large biological specimens in 3D. We establish protocols that enable the routine generation of 3D image stacks of entire plastic-embedded mammalian cells by IA-SEM at resolutions of ∼10–20 nm at high contrast and with minimal artifacts from the focused ion beam. We build on these advances by describing a detailed approach for carrying out correlative live confocal microscopy and IA-SEM on the same cells. Finally, we demonstrate that by combining correlative imaging with newly developed tools for automated image processing, small 100 nm-sized entities such as HIV-1 or gold beads can be localized in SEM image stacks of whole mammalian cells. We anticipate that these methods will add to the arsenal of tools available for investigating mechanisms underlying host-pathogen interactions, and more generally, the 3D subcellular architecture of mammalian cells and tissues.     

不同温度下黄曲霉菌菌丝超微形态的比较研究

为探究黄曲霉菌的毒素合成是否影响菌丝超微形态,本研究结合扫描和透射电镜技术比较观察产毒(28℃和30℃)和不产毒(37℃和40℃)温度下培养的不同发育阶段的黄曲霉菌菌丝形态和超微结构.扫描电镜结果显示:28℃下,在24h和44h菌丝体表面有丝状粘性分泌物附着,48-72h之间菌丝体逐渐出现皱缩、塌陷和扭曲现象,而37℃...     

贡嘎蝠蛾卵的扫描电镜和生物学观察

贡嘎蝠蛾卵呈椭圆形,在扫描电镜下卵壳表面分为一般卵壳区和受精孔区：一般卵壳区密布颗粒状突起;受精孔区位于卵端部,呈不规则梨形垫状,精孔开口于突起内侧凹陷上部。贡嘎蝠蛾在6月下旬—7月产卵,散产。在平均温度8－10℃、相对湿度80％－90％,卵的发育历期为50天左右,孵化率75％以上。卵常遭受霉菌和寄生蜂天敌危害。     

Comparative study of the corneal epithelium in some reptiles inhabiting different environments

El‐Bakry, A.M. 2011. Comparative study of the corneal epithelium in some reptiles inhabiting different environments. —Acta Zoologica (Stockholm) 92 : 54–61. The vertebrate cornea functions in either aquatic or aerial environments and in some cases in both. In terrestrial and aerial vertebrates, the cornea contributes most of the refractive powers of the eye because of the large variation in refractive index between the air and the cornea. The present study aimed to examine and compare the main features of the corneal epithelial surface of three reptilian species related to three different families (Caretta caretta, Varanus griseus and Mabuya quinquetaeniata) and inhabiting different environment, by light, scanning (SEM) and transmission electron microscopy. The mean epithelial cell densities of the species of the study were 8.670 ± 3.134, 5.945 ± 2.144 and 2.124 ± 713 respectively. The corneal epithelium of the three species observed by SEM showed a similarity to one another indicating that the apical cell surfaces possess regular polygonal cells with varieties of microprocesses. These microprocesses were represented by microplicae, numerous microvilli and some long microridges in C. caretta, microplicae and minute microholes in V. griseus and microplicae intermingled with short microvilli in M. quinquetaeniata. According to the densities of these microprocesses, three polymorphic cell types (light, medium and dark) appeared in C. caretta, light and medium cell types were observed in V. griseus and medium and dark cell types were noticed in M. quinquetaeniata. Different types of tight adhesions were observed by transmission electron microscopy between the cell borders of the epithelial cells which differ according to environment where the species occupy. In conclusion, variation in the structure of the corneal epithelial cells appears to be related to the living environment, such as aerial, terrestrial and aquatic ones, which is occupied by every species.     

The Structure and Morphogenesis of the Ventral Ciliature in Paraurostyla hymenophora*

SYNOPSIS. The structure and morphogenesis of the ventral ciliature of Paraurostyla hymenophora (Stokes) are described. The oral primordium apparently originates in association with transverse cirrus #6, from which it migrates anteriorly simultaneous with kinetosomal proliferation. The primordium eventually forms an elongate ciliary field from which the future opisthe's fronto-ventro-transverse (FVT) and undulating membrane primordial fields arise. Concomitantly, the future proter's FVT primordial field is initiated by the disaggregation of frontal cirri #4, #5, and #6. Primordia then develop simultaneously within marginal and ventral cirral rows by a disaggregation of cirri within the respective rows, and do not give rise to new cirri until the FVT fields complete segregation into discrete cirri. Near the completion of cirral production from the FVT primordia, each ventral cirral primordium (VCP) forms the 2 rightmost transverse cirri. Segregation of new cirri within the marginal cirral primordia and VCP then occurs, eventually replacing all old cirri within their respective marginal and ventral cirral rows. At the end of cortical morphogenesis, all old ciliary organelles, with the exception of the adoral zone of membranelles, are either reorganized or replaced. These results suggest an evolutionary affinity between the ventral and marginal cirral rows and raise questions about the control of the developmental competence of individual primordia.     

Direct plant regeneration from leaf explants of Drosera rotundifolia cultured in vitro

Shoot regeneration was obtained from isolated leaves of Drosera rotundifolia L. cultured on MS media with various concentrations of 6-benzyladenine (BA) and -naphthaleneacetic acid (NAA). The best direct shoot organogenesis was obtained on growth regulator-free medium or medium supplemented with 10^-8 M NAA. Liquid culture medium significantly increased regeneration capacity of leaf tissue. Histological and scanning electron microscopy investigations verify direct plant regeneration without intermediate callus formation. Leaf epidermal cells showed the highest regeneration potential leading to the regeneration of buds. Young shoots with three to seven leaflets rooted spontaneously on the growth regulator-free medium within 38 days of culture and isolated mature plants produced fertile seeds.Abbreviations BA 6-benzyladenine - FAA 40% formalin (5%) +90% acetic acid (5%) +70% ethanol (90%) - ME Murashige and Skoog's (1962) medium - NAA -naphthaleneacetic acid - plumbagin 5-hydroxy-2-methyl-1,4-naphthoquinone - 7-methyljuglone 7-methyl-5-hydroxy-1,4-naphthoquinone - SEM scanning electron microscopy - TEM transmission electron microscopy - PPF photosynthetic photon flux     

Structure and development of stellate trichomes in Andradea ftoribunda Fr. Allem. (Nyctaginaceae)

LOURO, R. P., MIGUENS, F. C. & MACHADO, R. D., 1992. Structure and development of stellate trichomes in Andradea ftoribunda Fr. Allem. (Nyctaginaceae). Trichomes occur on both faces of young leaves. They are peltate-stellate on the abaxial face, and comprise a stalk and radiating cells with a rudimentary central apex. On the adaxial face the trichomes arc stellate with a large apex comprising one to three cells. In both cases the stalk is formed by three to six cells of which the most distal may contain a tannoid substance. In the adult leaf only the abaxial surface exhibits stellate trichomes, with two to three celled stalks. The central region of radial cells is depressed. On the adaxial side the hairs are shed during maturation of the leaf.     

藏马鸡卵壳的扫描电镜观察

利用扫描电镜对我国特有珍禽──藏马鸡的卵壳进行了超微结构观察。电镜下显示：藏马鸡卵壳从内向外由壳膜层、锥体层、海绵层和表层等组成。壳膜层内层致密、含少量纤维,外层为纵横交错成网状的纤维结构,锥体层由许多乳头状突起密集排列组成,海绵层为似沉积岩层的层状结构,表层在卵壳最外面,上由具保护性的透明蛋白质薄膜覆盖。与同属的褐马鸡的卵壳进行比较,其超微结构存在差异。     

Seed morphology of Rotala L., Ammannia L., Nesaea Kunth and Hionanthera Fernandes & Diniz (Lythraceae)

PANIGRAHI, S. G., 1986. Seed morphology of Rotala L., Ammannia L., Nesaea Kunth and Hionanthera Fernandes & Diniz (Lythraceae) . Seed-surface characteristics of Ammonia lalifolia L., Rotala verticillaris L., Nesaea triflora Comm. ex Kunth and Hionanthera garciae Fernandes & Dinz were studied using the SEM. Seeds from herbarium specimens moistened in water produce cracks along the intercellular walls and distinctive types of invaginating 'hairs'. These 'hairs' are mucilaginous in nature and diagnostic at the species level. They are released in profusion from the upper convex surface of the testa. Viable seeds of Ammonia baccifera L., similarly treated, exude, in addition to the 'hairs', mucilaginous globules from the lower concave surface during germination. The invaginating 'hairs' arise diagonally from the roof of the epidermal cells of the testa and protrude to the lumen of the epidermal cells. A sac of mucilage is observed swelling out on the inner flat surface of the developing seeds. The biological functions of these 'hairs' and mucilage globules in germinating seeds in relation to seed dispersal and regulation of germination in appropriate habitats is discussed.     

Microscopy electron scanning of fossilized sickle-cells

In a microscopica electronic scanning follow-up study on human skeletons from the Hellenistic Period in the Arab-Persian Gulf, fossilized sickle-cells were found in the bone marrow of one of the excavated skeletons. The ultrastructure of these cells was compared to that of fossilized normal red blood cells of other skeletons from the same site, and to similar pseudo-pathological structures. The finding of fossilized evidence of sickle-cell anemia of that date is withoutprecedent, and makes an evaluation of related gross-anatomical skeletal changes possible.     

Seed morphology and taxonomy of the North African species of Sideritis L. (Lamiaceae)

REJDALI, M., 1990. Seed morphology and taxonomy of the North African species of Sideritis L. (Lamiaceae). Seed morphology data are shown to support data from general morphology and palynology; they can be used for taxonomy at the sectional and specific levels. At times clear differences are apparent at the infraspecific level. Seed sculpturing was found to be of great value for separating taxa at all levels of the hierarchy.     

Ultrastructure of plant chromosomes by high-resolution scanning electron microscopy

A technique is described for using standard squash preparations of mitotic and meiotic chromosomes for both light microscopy and subsequent high-resolution scanning electron microscopy for investigation of the same specimen. Depending on the microscope and conditions of preparation, a resolution of a few nanometers is routinely possible. Tilting of the specimen provides a three-dimensional insight into chromosomal structures. Combination of material-dependent signals of backscattered electrons with the secondary electron image allows an unambiguous localization of surface markers.     

Body musculature of Beauchampiella eudactylota (Gosse, 1886) (Rotifera: Euchlanidae) with additional new data on its trophi and overall morphology

This study presents the results of confocal laser scanning microscopy and fluorescence‐labelled phalloidin used to visualize the system of body musculature in Beauchampiella eudactylota. Moreover, the poorly known trophi of B. eudactylota are described based on scanning electron microscopy. In total, four paired longitudinal muscles (musculi longitudinales I–IV) and three circular muscles (musculi circulares I–III) were identified. Among these are the musculus longitudinalis ventralis, the musculus longitudinalis dorsalis and the musculus circumpedalis as documented in previous studies for other rotifer species. Compared to other species, B. eudactylota is characterized by the low number of lateral longitudinal muscles and the absence of some longitudinal muscles (musculi longitudinales capitum) and circular muscles (corona sphincter, musculus pars coronalis). Moreover, scanning electron microscopic data on the trophi of B. eudactylota reveal a number of striking similarities to the trophi in some species of Epiphanidae. This suggests that either (1) these similarities represent plesiomorphic characters present both in Epiphanidae and B. eudactylota or (2) they are synapomorphic features of B. eudactylota and some species of Epiphanidae, which would question the monophyly of Euchlanidae.