bluuebunny/crossref_metadata_2025_split huggingface dataset:
Auditory hair cells in human fetuses: Synaptogenesis and ciliogenesis
Authors: Lavigne‐Rebillard Mireille , Pujol Rémy 
Published: February 2005

AbstractThis paper brings together the most recent findings concerning the development of human fetus cochlear hair cells, as observed using transmission and scanning electron microscopy (TEM and SEM). Specific attention is drawn to the formation of synapses and the growth of stereocilia. In both types of hair cells, synaptogenesis begins before ciliogenesis (week 10 of gestation versus week 12). In the inner hair cell (IHC), an adultlike stage is seen around week 15 for synapses, but not before week 22 for stereocilia. In the outer hair cell (OHC), both synapses and stereocilia are not yet fully mature at week 22. Classic gradients of maturation are found: a base‐to‐apex gradient, and an IHC‐to‐OHC gradient. By comparing these results with the anatomical and functional data on cochlear development in laboratory mammals, the onset of cochlear function in the human fetus can be estimated to occur around week 18. The completion of cochlear maturation based upon the same anatomical criteria should occur about 10 weeks later.
Ultrastructure of the intercalated body, a novel organelle associated with fluid forming cells in the organ of Corti
Authors: Sobkowicz Hanna M. , Holy Jon , Scott Grayson L. 
Published: February 2005

AbstractThe intercalated body is a newly discovered organelle in the inner and outer spiral sulcus cells of the mouse organ of Corti. The organelle was found in the cochleas of 14‐day and older intact mice and in organs in culture of corresponding ages. The organelle consists of a stack of interconnected cisternae of endoplasmic reticulum and of membrane bound rodlets that are intercalated between, and run parallel to, the cisternae. The cisternal membranes are predominantly smooth, but some may display ribosomes. Most rodlets are from 1 to 2 μm long, about 0.1 μm wide, and contain electron dense material. Mitochondria are commonly associated with or incorporated into the organelle. Some electron micrographs suggest that the rodlets may originate from modified mitochondria. It is our impression that the formation of the organelle begins with the apposition of cisternae and mitochondria. Cisternal‐associated mitochondria appear to constrict, elongate, and lose their inner membranes. In both the intact animal and in culture, the cells of the inner and outer spiral sulci display microvilli, apical junctional complexes, lateral intercellular spaces containing interdigitating cell processes, and appear to be involved in fluid formation. Moreover, in culture, the cells of inner and outer spiral sulci as well as some cells proliferating in the outgrowth zone participate in fluid formation, producing large fluid pockets. All these cells commonly contain intercalated bodies. It is possible that in the intact animal, as in culture, intercalated bodies may play a role in fluid regulation in the immediate vicinity of the hair cells.
Amorphisation of MgO single crystal specimens prepared by ion milling for transmission electron microscopy studies
Authors: Khan M. Younis , Brown L. M. , Chaudhri M. M. 
Published: February 2005

AbstractSingle crystal MgO specimens having low load Vickers indentations were thinned in an ion milling machine employing a single ion gun, and their characteristics were investigated with optical microscopy and high voltage electron microscopy (HVEM). It was found that the state of cleanliness of the specimen chamber of the ion milling machine had a very marked influence on the quality of the thinned specimens. If the specimen chamber was not well cleaned before ion milling a fresh specimen, the latter tended to show amorphisation due to the deposition on the specimen of the debris left in the chamber from the previously ion‐milled specimens. Such observations were made from MgO specimens ion milled in several different types of commercial ion milling machine employing a single gun. It is proposed that to obtain good‐quality ion milled TEM specimens, it is important to clean the specimen chamber thoroughly prior to milling.
Renewal of the intestinal epithelium: New aspects as indicated by recent ultrastructural observations
Authors: Altmann G. G. 
Published: February 2005

AbstractThis article is a summary of our work of several years on the renewal of the intestinal epithelium. A combination of ultrastructural, radioautographic, and light microscopic analyses was carried out using normal tissue and tissue affected by inhibitors of RNA and protein synthesis. Measuring protein synthesis by 3H‐leucine radioautography showed that the life span of the columnar (absorptive) cells in the rat small intestine was divisible into two main phases: differentiation (from stem to functional cell) and maturation (from functional to extruding cell), each phase and its subdivisions being well defined morphologically. Differentiation involved a linear rise in the rate of protein synthesis per cell and showed at the same time heterochromatinization and silencing of RNA transcription. Data from various experiments indicated that the cells functioned from stored information (RNA), part of which came from the nucleolus, which underwent marked and characteristic ultrastructural changes. Although transcription from rDNA ceased, the nucleolus released its ribosomal material, which added to the existing protein synthesis, presumably by recruiting excess stored mRNAs. Maturation involved a nearly linear decrease of the rate of protein synthesis per cell to a characteristic low value at which extrusion took place. A gradual exhaustion of the stored RNA was indicated to be the key factor in this decrease. Ultrastructurally, maturation was associated with a gradually increasing vesiculation of rER and Golgi. The results thus imply a regulatory role of cellular protein synthesis level in renewal. This would be an epigenetic response after the genes are silenced. The nucleolus seems to play a central role in this process, and this in turn is reflected in its characteristic ultrastructural changes. The work also included new observations on the epithelium of the rat ascending colon describing a hitherto unrecognized deep crypt mucus‐secretory (“DCS”) cell which is a nongoblet mature cell type apparently arising from midcrypt mitoses. In between the DCS cells, occasional slender columnar cells were seen which displayed the ultrastructural features of stem cells. These were probably reserve stem cells. We also observed nongoblet deep crypt mucous cells in the human right colon although fewer in number than in the rat. Nucleolar regulation and the presence of reserve stem cells represent new dimensions in our understanding of renewal. Electron microscopy is an essential tool in this investigation.
Extrusion of colonic epithelial cells in vitro
Authors: Baron David A. , Miller Donald H. 
Published: February 2005

AbstractRat colonic mucosae fixed in situ in Ussing chambers provided a model of the extrusion of absorptive enterocytes and less commonly of goblet and enteroendocrine cells. The cells were lost at extrusion zones midway between crypt mouths. Even in mucosae in which the number of extruding cells was large, epithelial continuity was maintained as evaluated morphologically and electrophysiologically. Beneath points of remaining contact between desquamating cells and the epithelial sheet, microfilaments of the terminal web formed band‐like structures linking adjacent junctional complexes. Freeze‐fracture replicas disclosed extensive macular regions of tight junction strands in the plasma membranes of desquamating cells. Tight junctions between newly neighboring cells were often irregular and often occurred beneath the terminal web region. Dithio‐threitol enhanced cell loss and increased basal epithelial conductance, but histological continuity was maintained and the mucosae continued to respond typically to bradykinin. These observations suggest that during the loss of senescent enterocytes, tight junctions are maintained; old junctional elements are lost, and tight junctions are formed between remaining adjacent cells. This model offers a means to study the synthesis and turnover of tight junctions and the maintenance of the colonic epithelial barrier.
Striated brush border of intestinal absorptive epithelial cells: Stereological studies on microvillous morphology in different adaptive states
Authors: Mayhew Terry M. 
Published: February 2005

AbstractDifferent regions of small bowel were examined in five groups of rats in three separate experiments. The effects on mucosal morphology of position along the bowel, induced hypoproliferation (due to fasting), and induced hyperproliferation (due to streptozotocin diabetes) were investigated.Intestines fixed by in situ perfusion with buffered glutaraldehyde were sampled by strictly randomised procedures. Pieces of tissue from segments of roughly equal length were processed for electron microscopy and embedded in resin. Complete transverse sections were cut for light microscopy and estimates of villous surface areas were obtained by stereological methods devised for the purpose. Ultrathin sections from random sectors of the same tissue blocks were sampled systematically to obtain micrographs of the villous surface. These were analysed for quantitative information about microvilli (length, diameter, surface area, and number). Structural quantities from individual segments were pooled to provide values for the entire small bowel.Significant regional differences in villous and microvillous dimensions were found in all groups. The numbers of microvilli per bowel were remarkably constant in all control groups. Other variables were estimated reproducibly in rats of the same sex, strain, and average body weight.Effective absorptive surfaces did not show a linear gradient but tended to peak in middle segments. Neither fasting nor induced diabetes altered the mean length, diameter, or packing density of microvilli. However, surfaces due to villi and microvilli altered commensurately during fasting and induced diabetes. Therefore cell number seems to be the key quantity for determining villous and microvillous surface areas.The findings are discussed in the context of kinetic, biochemical, and physiological changes found in different adaptive states.
Fast processing of black and white films used in the EM lab
Authors: Fermin Cesar D. , Diaz Ellis , Maldonado Aura , Martin Dale , Hruska Zuzana 
Published: February 2005

AbstractKodak black and while film emulsions 4489, 4162, 2415, TMAX‐100, TMAX‐400, MPD‐4 and RPC‐651 can be developed in less than 10 minutes on a film processor, quickly printed on resin coated paper and dried with auto‐processor and dryer. Adjustments to the ASA (ISO) to compensate for increased contrast with auto‐processing are described.
A review of echinoderm oogenesis
Authors: Smiley Scott 
Published: February 2005

AbstractThis review of the anatomical, histological, biochemical, and molecular biological literature on echinoderm oogenesis includes the entire developmental history of oocytes; from their inception to the time they become ova. This is done from a comparative perspective, with reference to members of the five extant echinoderm classes; crinoids, holothurians, asteroids, ophiuroids, and echinoids. I describe the anatomy and fine structure of the echinoderm ovary, with emphasis on both the cellular relationships of the germ line cells to the somatic cells of the inner epithelium, and on the neuromuscular systems. I review the literature on the growth of oogonia into fully formed oocytes, including the process of vitellogenesis, presenting an ultrastructural analysis of the organelles and extracellular structures found in fully formed echinoderm oocytes. Echinoderm oocyte maturation is reviewed and a description of the ultrastructural, biochemical and molecular biological changes thought to occur during this process is presented. Finally, I discuss oocyte ovulation, the severing of cellular connections between the oocyte and its surrounding somatic epithelial cells.
Ultrastructure of sperm, spermiogenesis, and sperm‐egg interactions in selected invertebrates and lower vertebrates which use external fertilization
Authors: Koch Robert A. , Lambert Charles C. 
Published: February 2005

AbstractThis review discusses the ultrastructure of sperm with reference to their development, the surface morphology of the egg, and the processes of sperm binding and penetration during fertilization. These topics are treated for selected invertebrates and lower vertebrates which live in aquatic environments and fertilize their eggs externally. Specifically, sperm and eggs from cnidarians, echinoderms, decapod crustaceans, ascidians, lampreys, bony fishes, and amphibians are discussed. Sperm from the majority of these groups exhibit the classical head‐midregion‐tail configuration characteristic of primitive sperm. Specific variations within this general morphology have been described. The notable exceptions to the primitive‐sperm paradigm are the sperm of decapod crustaceans and amphibians. Eggs from all of the animals considered are covered by complex vitelline envelopes except those of cnidarians. In general, the ultrastructural analysis of these egg envelopes shows that they are composed of fibrous subunits. Sperm bind to the vitelline envelope and then penetrate through it to fertilize the egg in all groups reviewed except fishes. In fishes, the sperm reaches the egg surface via micropyles. Finally, we discuss the specific changes in sperm ultrastructure which occur during penetration of the egg envelopes in both flagellated and non‐flagellated sperm. These changes, which involve membrane fusion and reorganization as well as movement of membranous organelles, aid the sperm in reaching the actual site of gamete fusion.
The preparation of cross‐sectional transmission electron microscopy specimens of Nb/Al multilayer thin films on sapphire substrates
Authors: Barmak Katayun , Rudman David A. , Foner Simon 
Published: February 2005

AbstractWe have developed a technique for preparation of cross‐sectional transmission electron microscopy samples of reacted and unreacted Nb/al multilayer thin films on sapphire substrates. The choice of substrate was found to be extremely important. Sapphire sputters more slowly than Nb and Nb‐compounds and therefore makes it possible to obtain the electron transparent regions in the thin films rather than in the substrate. However, the brittle nature of the sapphire restricts the types of thinning techniques that can be used, requiring extensive ion thinning as a final stage.
Occurrence and developmental consequences of aberrant cellular organization in meiotically mature human oocytes after exogenous ovarian hyperstimulation
Authors: Van Blerkom Jonathan 
Published: February 2005

AbstractThe extent to which fertilization failure in in vitro inseminated human oocytes obtained from hyperstimulated ovaries was associated with alterations in cellular structure and cytoplasmic organization was examined by a combination of DIC, fluorescence, time‐lapse video, and transmission electron microscopy. Detailed analysis of meiotically mature preovulatory (uninseminated) oocytes, and of oocytes that failed to fertilize in vitro, indicated that between 10% and 15% of grossly normal‐appearing MII‐stage oocytes displayed one of the following cellular perturbations: (1) a subtle change in organelle distribution, (2) a small region(s) of intracellular cytolysis, (3) a massive aggregation of SER tubules, (4) an accumulation of vesicles presumed to be of SER origin, (5) a change in the structural organization of the cortical cytoplasm and overlying plasma membrane, (6) a sudden and rapid internalization of perivitelline fluid by means of an apparently aberrant process of endocytosis, and (7) a premature and partial exocytosis of cortical granules. The description of these disorders is discussed with respect to the developmental consequences for the oocyte.
Use of microwave fixation in the preparation of cell cultures for observation with the scanning electron microscope
Authors: Argall Kristin , Armati Patricia 
Published: February 2005

AbstractThis paper describes a method for primary fixation of cultured cells for scanning (SEM) and transmission (TEM) electron microscopy using microwaves alone. This method of fixation takes 8 seconds and is therefore quicker and less expensive than conventional fixation techniques. The preservation of cell morphology is excellent and cultures of mammalian immune system cells and peripheral nervous tissue have been examined using this fixation.
Evaporation during preparation of unsupported thin vitrified aqueous layers for cryo‐electron microscopy
Authors: Cyrklaff Marek , Adrian Marc , Dubochet Jacques 
Published: February 2005

AbstractEvaporation of water cannot be fully avoided when an unsupported thin vitrified film of an aqueous suspension is prepared for cryo‐electron microscopy. This results in increasing concentration of solute which could affect the observed material. We have quantitatively studied this effect by measuring the contrast of polystyrene spheres in a metrizamide solution. The drying effect is generally negligible when specimens are prepared on a hydrophilic perforated support but it is frequently important when hydrophobic films are used instead. A flow of humid air, double blotting with minimal exposure of the thin liquid film to the atmosphere, or an automatic plunger optimizing the blotting conditions are simple methods for reducing drying effects. With this third device acting on a hydrophilic supporting film, the increase of solute concentration is limited to less than 20%.
Comparisons of golgi structure and dynamics in plant and animal cells
Authors: Griffing Lawrence R. 
Published: February 2005

AbstractThe Golgi apparatus of both higher plant and animal cells sorts and packages macromolecules which are in transit to and from the cell surface and to the lysosome (vacuole). It is also the site of oligosaccharide and polysaccharide synthesis and modification. The underlying similarity of function of plant and animal Golgi is reflected in similar morphological features, such as cisternal stacking. There are, however, several fundamental differences between the Golgi of plant and animal cells, reflecting, in large part, the fact that the extracellular matrices and lysosomal systems differ between these kingdoms. These include (1) the form and replication of the Golgi during cell division; (2) the disposition of the Golgi in the interphase cell; (3) the nature of “anchoring” the Golgi in the cytoplasm; (4) the genesis, extent, and nature of membranes at the trans side of the stack; (5) targeting signals to the lysosome (vacuole); and (6) physiological regulation of secretion events (constitutive vs. regulated secretion). The degree of participation of the Golgi in endocytosis and membrane recycling is becoming clear for animal cells, but has yet to be explored in detail for plant cells.
Structure and function of the extracellular matrix of anuran eggs
Authors: Hedrick Jerry L. , Nishihara Tatsuro 
Published: February 2005

AbstractThe extracellular matrix (ECM) surrounding the anuran egg is composed of jelly coat layers, an envelope, and the perivitelline space, which separates the envelope from the egg plasma membrane. Both the jelly coat layers and egg envelopes are required for fertilization in anurans. This paper reviews the current understanding of the structure‐function relations of the ECM, with emphasis on the egg envelope. The fibrous egg envelope exists in four related forms. The envelope forms differ in their ultrastructures, macromolecular compositions, and cellular functions. After the oocyte is released from the ovary, conversion of one envelope form to another is brought about by factors secreted by the oviduct prior to fertilization and by factors released from the egg in the sperm‐triggered cortical reaction. An additional extracellular matrix structure, located in the perivitelline space, has recently been identified in Xenopus laevis, as well as a previously undescribed reorganization of envelope fibers occurring at fertilization. The molecular changes in the ECM glycoproteins (limited proteolysis, lectin‐ligand binding, and conformational changes) and the oviductal and egg macromolecules responsible for the conversion of envelope forms are discussed. New experimental evidence that supports the lectin‐ligand hypothesis for the formation of the fertilization layer is presented. It is proposed that the molecular changes in the ECM are responsible for the ultrastructural alterations of the ECM and for modifications of the fertilization and developmental functions of the anuran egg ECM.
Discussions on the multiple‐input maximum a‐posteriori wave‐function restoration method in high‐resolution electron microscopy
Authors: Huang Xu , Ximen Jiye 
Published: February 2005

AbstractThe multiple‐input maximum a‐posteriori (MIMAP) wave‐function restoration method in high‐resolution electron microscopy proposed by Kirkland (1984) is further discussed. A modified MIMAP criterion that considers likely correlations between individual micrographs in a series of micrographs taken at different imaging conditions is presented. By performing wave‐function restoration for a multislice method‐simulated defocus series of MgO[110], the convergent properties of this modified MIMAP method are also described.
An easy method for orientated embedding tissue culture cell monolayers in LR white resin for postembedding immunocytochemistry
Authors: Hirst Elizabeth M. A. 
Published: February 2005

AbstractPartial polymerization of LR White resin blocks is a frequently encountered problem if oxygen is present during the polymerization reaction. Instructions are given for a simple method to embed cell culture monolayer in LR White acrylic resin, which is suitable for immunocytochemistry. The advantage of this method is that it is easy and reliable. It also ensures accurate orientation of the cell monolayer in relation to the desired plane of sectioning.
Confocal fluorescence microscopy and three‐dimensional reconstruction
Authors: Wright S. J. , Schatten G. 
Published: February 2005

AbstractSeveral recent technological advances have considerably improved the field of confocal fluorescence microscopy. Improvements in confocal microscope design, new fluorescent probes and indicators, more sensitive imaging devices, and computer advances which allow for data manipulation and storage provide a convenient method to acquire complex three‐dimensional (3‐D) architectural details which previously were difficult or impossible to obtain from biological specimens. Applications of the laser scanning and tandem scanning confocal microscopes offer the potential for gaining powerful insights into the complex relationship of cellular structure and function. Confocal microscopy generates optical sections free from out‐of‐focus blur. With the development of new visualization tools to render and display complex 3‐D data, a set of optical sections taken at different focal planes can be three‐dimensionally reconstructed to create an animated sequence which can reveal latent features of the specimen. The combination of confocal microscopy and 3‐D reconstruction provides a powerful new imaging tool to advance knowledge about structural and functional cellular properties as they occur dynamically in three dimensions.