High-resolution transmission electron microscopy of adult human peritubular dentine

Summary Single crystals from adult human peritubular dentine were studied by high-resolution transmission electron microscopy. Periodic fringe patterns were obtained from which the exact shape of the inorganic crystals were deduced. The crystals were found to have a mean length of 36.00±1.87 nm, a mean width of 25.57±1.37 nm, and a mean thickness of 9.76±0.69 nm. They consisted of platelets with a mean width-to-thickness ratio of 2.61, each being a flattened hexagonal prism of hydroxyapatite. Such conclusions are based upon a) the electron diffraction patterns that we obtained, and b) our comparison of the values of the periodic, equidistant fringes seen along different planes of sectioning with the corresponding theoretical values for hydroxyapatite.     

The evolution of dinosaur tooth enamel microstructure

The evolution of tooth enamel microstructure in both extinct and extant mammalian groups has been extensively documented, but is poorly known in reptiles, including dinosaurs. Previous intensive sampling of dinosaur tooth enamel microstructure revealed that: (1) the three‐dimensional arrangement of enamel types and features within a tooth—the schmelzmuster—is most useful in diagnosing dinosaur clades at or around the family level; (2) enamel microstructure complexity is correlated with tooth morphology complexity and not necessarily with phylogenetic position; and (3) there is a large amount of homoplasy within Theropoda but much less within Ornithischia. In this study, the examination of the enamel microstructure of 28 additional dinosaur taxa fills in taxonomic gaps of previous studies and reinforces the aforementioned conclusions. Additionally, these new specimens reveal that within clades such as Sauropodomorpha, Neotheropoda, and Euornithopoda, the more basal taxa have simpler enamel that is a precursor to the more complex enamel of more derived taxa and that schmelzmusters evolve in a stepwise fashion. In the particularly well‐sampled clade of Euornithopoda, correlations between the evolution of dental and enamel characters could be drawn. The ancestral schmelzmuster for Genasauria remains ambiguous due to the dearth of basal ornithischian teeth available for study. These new specimens provide new insights into the evolution of tooth enamel microstructure in dinosaurs, emphasizing the importance of thorough sampling within broadly inclusive clades, especially among their more basal members.     

Fluoride or/and aluminum induced toxicity in guinea pig teeth with the low expression of dentine phosphoprotein

This study investigated the damage and expression of dentine phosphoprotein (DPP) in guinea pig teeth by the administration of fluoride (F) or/and aluminum (Al). Fifty‐two guinea pigs were divided randomly into four groups (control, F, Al, and F+Al). F (150 mg NaF/L) or/and Al (300 mg AlCl₃/L) were added in their drinking water for 90 days. The levels of F ion, dentine sialophosphoprotein (DSPP) gene, and DPP protein in incisor and molar were determined, respectively. The results showed that the concentrations of F ion in F and F+Al groups were increased significantly. F induced the mottled enamel and irregular abrasion of teeth, which might occur as a consequence of depressed DSPP mRNA and DPP protein expression. Both the gene and protein expressions showed obvious decrease induced by Al, especially by F. There were no synergistic effects between F and Al, instead, Al inhibited the toxicity of F.     

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.     

山桐子雌、雄株叶片表皮微形态特征的比较研究

【目的】探究山桐子（Idesia polycarpa Maxim.）叶片表皮微形态特征及其雌、雄株差异,为该种质资源的挖掘利用提供参考。【方法】利用扫描电镜,对40份山桐子（雌、雄株各半）叶片进行微形态观察,测定12个气孔相关性状,并分析样品间的异同。【结果】（1）山桐子雌、雄株叶片的表皮毛、细胞形态、气孔特征及蜡质式样相似,其下表皮密布的类锥形纤维体型蜡质纹饰,鲜见于其它植物类群。（2）山桐子雌株叶片的气孔大小（长度、宽度、面积及周长）及密度相关参数均略大于雄株;雄株叶片的气孔开口相关参数（孔隙宽度、开口面积及气孔开度）均略高于雌株;但所有差异均未达到统计学显著水平（P > 0.05）。（3）多数气孔性状彼此显著相关,而气孔密度与其它性状关联较弱,可能受到相对独立的遗传调控。【结论】本研究首次明确了山桐子叶片表皮的微形态特征,其类锥形纤维体型蜡质式样可作为种质评鉴的关键依据,其气孔性状参数可为童期种苗的性别判定提供重要参考。     

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.     

Structure and sensilla of the antennae and mouthparts of Loxocephala perpunctata Jacobi (Hemiptera: Fulgomorpha: Eurybrachidae)

The ultramorphology of the antennae and mouthparts of the adult Loxocephala perpunctata Jacobi was studied through a scanning electron microscope. Seven types of sensilla were found on antennomeres, including a Böhm bristle on the scape, sensillum trichoideum and plaque organ on the pedicel, two subtypes of sensilla chaetica and two subtypes of sensilla campaniformia on these two antennomeres; and Bourgoin's organ with sensory pegs and sensilla basiconicum on the basal bulb of the flagellum. The mouthparts of L. perpunctata are of the typical piercing-sucking type, similar to mouthparts found in other hemipteran insects. In general, six types of sensilla (i.e., four subtypes of sensilla chaetica, sensillum basiconicum, subapical labial sensillum, uniporous peg-like sensillum, multiporous peg-like sensillum and two subtypes of bristle-like sensilla) were detected on different locations of the labium, with the last three, and numerous cuticular processes, present on the labial tip. The potential functions of these sensilla are discussed.     

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.     

On the fine structure of some Chrysophycean cysts

Fine detail of the ornamentation and pore openings are given of a wide range of Chrysophycean cysts. The function of this intricate sculpturing is unknown. Four new types of cyst are described.     

Multifactorial determination of skeletal age at death: a method and blind tests of its accuracy

Traditional methods of estimating skeletal age at death have relied solely on the pubic symphyseal face or on this indicator combined with others in nonsystematic ways. A multifactorial method is presented that uses a principal components weighting of five indicators (public symphyseal face, auricular surface, radiographs of proximal femur, dental wear, and suture closure). This method has been tested by completely blind assessment of age in two samples from the Todd collection carefully screened for accuracy of stated age at death. Results show a marked superiority of the multifactorial method over any single indicator with respect to both bias and accuracy. This represents the first truly blind test of an age-at-death indicator or system, as the test populations were independent of the system(s) being tested, and the age, sex, and ethnogeographic origin of the individuals being assessed (as well as the compositions of the test samples with respect to these variables) were completely unknown until the tests were completed. Implications for paleodemography are discussed.     

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℃...     

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.     

Microscopic analysis and seasonality of gemma production in the freshwater red alga Hildenbrandia angolensis (Hildenbrandiales, Rhodophyta)

The development and release of the unique vegetative propagules of the freshwater encrusting alga Hildenbrandia angolensis Welwitsch ex West et West, gemmae, were studied using several different microscopic and histochemical techniques. In addition, the seasonality of gemma production was monitored bimonthly over a 12‐month period in two spring‐fed streams in Texas, USA. Gemmae differentiate within the thallus and are subsequently released from the surface of the crust. Release of the gemmae most likely occurs by digestion of surrounding cells, as suggested by the presence of starch granules and lipid globules in the region between the released gemma and the thallus. The initial separation of the gemmae from the thallus occurs from the sides of the gemma or the bottom, or possibly simultaneously. Contrary to previous studies, we have observed that gemma production occurs endogenously within the thallus of freshwater Hildenbrandia, rather than on the surface of the crust in raised structures. Histochemical tests and electron microscopic examination indicate that the cells of the gemmae contain a large amount of floridean starch. The starch granules frequently form rings surrounding the nuclei of both gemma and thallus cells; a feature infrequently reported for florideophyte red algae. Our seasonality investigations indicate that large fluctuations in gemma production occur over 1 year, but at least some gemma production continues year‐round in the streams examined.     

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.     

Increasing human tooth length between birth and 5.4 years

Most previous studies of tooth development have used fractional stages of tooth formation to construct growth standards suitable for aging juvenile skeletal material. A simple alternative for determining dental age is to measure tooth length throughout development. In this study, data on tooth length development are presented from 63 individuals of known age at death, between birth and 5.4 years, from an archeological population recovered from the crypt of Christ Church, Spitalfields, London. Isolated developing teeth (304 deciduous, 269 permanent) were measured in millimeters and plotted against individual age. Regression equations to estimate age from a given tooth length, are presented for each deciduous maxillary and mandibular tooth type and for permanent maxillary and mandibular incisors, canines, and first permanent molars. Data on the earliest age of root completion of deciduous teeth and initial mineralization and crown completion of some permanent teeth in this sample are given, as well as the average crown height and total tooth length from a small number of unworn teeth. This method provides an easy, quantitative and objective measure of dental formation appropriate for use by archeologists and anthropologists. © 1993 Wiley-Liss, Inc.     

Adhesion of Plasmodium gallinaceum Ookinetes to the Aedes aegypti Midgut: Sites of Parasite Attachment and Morphological Changes in the Ookinete

Plasmodium gallinaceum ookinetes adhered to Aedes aegypti midgut epithelia when purified ookinetes and isolated midguts were combined in vitro. Ookinetes preferentially bound to the microvillated luminal surface of the midgut, and they seemed to interact with three types of structures on the midgut surface. First, they adhered lo and migrated through a network-like matrix, which we have termed microvilli-associated network, that covers the surface of the microvilli. This network forms on the luminal midgut surface in response to blood or protein meals. Second, the ookinetes bound directly to the microvilli on the surface of the midgut and were occasionally found immersed in the thick microvillar layer. Third, the ookinetes associated with accumulations of vesicular structures found interspersed between the microvillated cells of the midgut. The origin of these vesicular structures is unknown, but they correlated with the surface of midgut cells invaded by ookinetes as observed by TEM. After binding to the midgut. ookinetes underwent extensive morphological changes: they frequently developed one or more annular constrictions, and their surface roughened considerably, suggesting that midgut components remain bound to the parasite surface. Our observations suggest that, in a natural infection, the ookinete interacts in a sequential manner with specific components of the midgut surface. Initial binding to the midgut surface may activate the ookinete and cause morphological changes in preparation for invasion of the midgut cells.     

Ultrastructure and distribution of sensilla on the antennae of female fig wasp Eupristina sp. (Hymenoptera: Agaonidae)

In the species‐specific and obligate mutualism between the fig (Moraceae: Ficus spp.) and its pollinator (Hymenoptera: Agaonidae), the continuity of lifecycle of both partners completely depends on the female pollinator's ability to detect receptive figs. To better understand the chemical location mechanism, we examined the antennae and their sensilla of the female fig pollinator Eupristina sp. using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The antennae of female Eupristina sp. are geniculated, and in total, there were seven types of sensilla found on the antennae: two types of multiporous placoid sensilla (type 1 is sausage‐like and type 2 is rounded), sensilla trichodea (ST), basiconic sensilla (BS), chaetica sensilla (ChS), coeloconic sensilla (CoS), and one specialized sensillum classified as sensillum obscurum (SO). We described external morphology, abundance, distribution, ultrastructure and discussed putative functions. We inferred from their ultrastructures as chemoreceptors that two types of multiporous placoid sensilla, BS and CoS, were innervated by sensory neurons. The aporous type ST, ChS, and SO were not innervated by dendrites which may function as mechanoreceptor/proprioceptor. These results were also discussed in relation to the interaction between Eupristina sp. and its host fig.