bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of the ability of freeze etch and freeze substitution to preserve actin filament structure
Authors: Bridgman Paul C. , Lewis Annette K. , Victor John C. 
Published: February 2005

AbstractIn order to test the ability of freeze substitution to accurately preserve the ultra‐structure of the actin component of the cytoskeleton, the structure of rotary shadowed actin filaments was compared following preparation by glutaraldehyde fixation and freeze etch or freeze substitution. Freeze substituted actin filaments were further processed by either etching away frozen organic solvent or critical‐point‐drying before rotary shadowing. Comparison of filament diameters showed no significant difference between actin filaments that were directly etched and those that were freeze substituted and then etched. However, freeze substituted and then critical‐point‐dried filaments were significantly larger in diameter than filaments that were directly etched in water. The long pitch (right‐handed) two start helix was not affected by the different methods of preparation. However, the left‐handed “genetic” helical repeat that was prominent in actin filaments prepared by freeze etch was more difficult to detect in freeze substituted specimen, especially following critical‐point‐drying. Although the organization and distribution of actin filaments in extracted cells was similar in both freeze substituted and freeze etched specimens, there were some detectable differences. In cells that were freeze substituted and then critical‐point‐dried, filaments appeared to intersect at greater angles and seemed more “taut.” These results suggest that freeze substitution can preserve the overall morphology of actin filaments, but some chemical or physical modification of macromolecular surface structure may occur during the substitution process and these changes may be further exaggerated by subsequent processing steps. © 1993 Wiley‐Liss, Inc.
Intermediate voltage electron microscopy of transverse tubules at myotendinous junctions
Authors: Sonoda Masaki , Moriya Hideshige , Shimada Yutaka 
Published: February 2005

AbstractThe 3‐dimensional distribution of transverse (T) tubules at myotendinous junctions (MTJs) was studied by intermediate voltage (400 kV) electron microscopy of thick sections of rat vastus intermedius and chicken pectoralis muscles stained with lanthanum nitrate. Transversely oriented T tubules were seen to run at the level of A‐I junctions (the rat vastus intermedius) and Z bands (the chicken pectoralis), but were absent from such levels adjacent to the end of MTJ processes. These tubules opened to the lateral wall of sarcolemmal infoldings of MTJs and to the lateral cell surface. Longitudinally running T tubules were seen to connect with the transverse T tubules and to open at the bottom of junctional folds. The lack of T tubules at the final sarcomeric regions seems to indicate that the terminal sarcomeric half in close proximity to MTJs may be activated from the sarcoplasmic reticulum which forms couplings with the MTJ sarcolemma and/or longitudinal tubules in the MTJ processes. © 1993 Wiley‐Liss, Inc.
Application of cryotechniques in cartilage tissue preservation an immunoelectron microscopy: Potentials and problems
Authors: Hunziker Ernst B. 
Published: February 2005

AbstractCryotechnical processing of cartilage has the potential to solve many of the tissuespecific problems associated with various routine chemical fixation protocols. This is particularly the case with respect to extracellular matrix architecture, the distortion or destruction of which (caused by extraction and/or precipitation of proteoglycan molecules) may be prevented. Adoption of such techniques also permits high‐sensitivity immunoelectron‐microscopy of the extracellular matrix space (carbohydrate epitopes). However, a number of difficulties still remain to be resolved, particularly that of matrix‐cell interface separation occurring during freeze substitution and low temperature embedding. These problems are briefly addressed and possible solutions outlined. © 1993 Wiley‐Liss, Inc.
Improved preservation of ultrastructure in difficult‐to‐fix organisms by high pressure freezing and freeze substitution: I. Drosophila melanogaster and Strongylocentrotus purpuratus embryos
Authors: McDonald Kent , Morphew Mary K. 
Published: February 2005

AbstractIn this study, we have applied the techniques of high pressure freezing and freeze substitution to embryonic cell types which are usually difficult to fix properly for electron microscopy. In both Drosophila and Strongylocentrotus purpuratus, we see improved preservation of both membrane systems and cytoskeleton when compared to published results on the same cells using conventional electron microscope (EM) fixation methods. Finally, we have seen that postembedding labelling of sections is possible even after light osmium fixation during freeze substitution. © 1993 Wiley‐Liss, Inc.
Rapid freezing replica studies of membrane specializations in the proximal tubules of mouse kidney
Authors: Shibata Yosaburo , Hatae Tatsuhiko , Kuraoka Akio , Iida Hiroshi , Izumi Toshihiro 
Published: February 2005

AbstractThe membrane specializations of the fresh unfixed kidney cortex of adult and neonatal ICR mice were examined by using rapid freezing replica methods. In proximal tubular cells, numerous apical intracellular tubules exhibited helical patterns on the E face with a pitch of about 12 nm. This regular pattern was often continuous with similar striped indentations on the edge of the vacuoles connecting with the tubules. On the luminal surface (ES) of these vacuoles, membrane surface particles were arranged regularly in striped patterns with a center‐to‐center spacing of about 12 nm. We could not identify differentiations on the PF or PS of the same membrane systems. Another membrane specialization was a plaque or patch of clear pits in tilted lattice alignments on the P face of the large vacuoles with a center‐to‐center spacing of about 20 nm. This type of specialization was often observed in the neonatal mice proximal tubular cells. These membrane specializations may indicate the active membrane functions in the proximal tubules and suggest the functional continuity and structural relationship of these apical endocytic membrane systems. © 1993 Wiley‐Liss, Inc.
Ultrastructural evidence for the axonal localization of caudodorsal cell hormone mRNA in the central nervous system of the mollusc Lymnaea stagnalis
Authors: Dirks Roeland W. , van Dorp Annette G. M. , van Minnen Jan , Fransen Jack A. M. , van der Ploeg Mels , Raap Anton K. 
Published: February 2005

AbstractThe technique of in situ hybridization has been used to evaluate the expression of an ovulation hormone mRNA (caudodorsal cell hormone; CDCH) in the central nervous system (CNS) of the mollusc Lymnaea stagnalis. Hybridization with radioactive as well as with nonradioactive labeled oligonucleotide and plasmid probes revealed a specific labeling on cell bodies of caudodorsal cells (CDCs), which are known to produce CDCH, on the light microscopical level. In addition, specific labeling was observed outside the cell bodies, as far as the cerebral commissure, where CDCH is released in the haemolymph. To investigate whether these signals represent an axonal localization of the CDCH mRNA, we performed in situ hybridization at the electron microscopical (EM) level. The results showed an intraaxonal localization of CDCH mRNA with digoxigenin labeled oligonucleotide and plasmid probes. Gold labeling was observed in secretion granules, and double labeling experiments showed that these granules also contain CDCH. This specific intragranular localization suggest that CDCH mRNA is transported through the axon and released by exocytosis in the haemolymph. © 1993 Wiley‐Liss, Inc.
An assessment of the efficacy of in situ hybridization as a quantitative method by variance components estimation
Authors: McCabe Joseph T. , Kao Tzu‐Cheg , Volkov Marina L. 
Published: February 2005

AbstractOne serviceable feature of in situ hybridization is its potential for assessing relative levels of mRNA in specific regions of tissues and organs. To determine its efficacy as a quantitative technique, we applied a nested factorial design to a multifactorial experiment. Estimates of the magnitude of variance components then allowed an assessment of variation over samples of sections from the same tissue source, variation in label over 2 anatomical sites within the same section of tissue, as well as experiment‐to‐experiment variation. We found ∼ 51% of the total variance arose from experiment‐to‐experiment variation, while ∼ 21% of the total variance was due to variation in autoradiography grain density over neurons in the same brain region. Rat‐to‐rat variation accounted for approximately 11%. About 10% of the variance was due to variation between sections of tissue that were derived from the same tissue source and were hybridized in the same hybridization experiment. Variation between 2 homologous, bilaterally located brain regions located on the same tissue section (the right and left supraoptic nucleus), accounted for ∼ 5% of the total variance. The remaining unaccounted error variance was ∼ 2% of the total variance. Since an expected change in cellular content of a particular mRNA was observed as a function of experimental treatment, results suggest in situ hybridization is a useful quantitative method. Findings also indicate, however, the importance of experimental design: the use of multiple samples of tissue from the same tissue source, a sufficient number of tissue sources (animals, batches of cultured cells) to account for variations in sample sources, and the need to assess experiment‐to‐experiment and rat‐to‐rat variations. Results suggest the utility of analyzing the data of in situ hybridization experiments from the perspective of experimental design. © 1993 Wiley‐Liss, Inc.
Receptivity is a polarity dependent special function of hormonally regulated uterine epithelial cells
Authors: Glasser Stanley R. , Mulholland Joy 
Published: February 2005

AbstractUseful knowledge of the mechanisms which regulate ovoreceptivity and implantation remains elusive in spite of increasing efforts to apply the technology of biochemistry and to a lesser extent, cellular and molecular biology to the analysis of the problem. Existing models used to analyze interactions of the blastocyst and endometrial cells of the uterus have been unable to account for nongenotypic embryonic losses, particularly those following in vitro fertilization and embryo transfer.Separation of endometrial uterine epithelial (UE) and uterine stromal (US) cells was used to demonstrate that each cell type responds independently and interdependently to the same regulatory signals. Cultured by classical techniques UE cells proved unable to respond to steroid hormone signals. For this reason UE cell cultures could not be used to develop an experimental cell system that mimicked growth and development of UE cells in utero. The failure of classical UE cell cultures derived from their inability to maintain epithelial cell polarity. Polarity, the spatial asymmetry of plasma membrane domains, is intrinsic to the structure and function of an epithelial cell. Apical and basolateral surfaces have different lipid and protein compositions which are correlates of the special functions of that epithelial cell. As epithelial cells differentiate they must, in response to regulatory cues, direct the flux of membrane components moving into and out of each surface in order to establish the polarity characteristic of each stage specific expression. The acquisition of receptivity by the apical surface of the UE cell may be considered to be such a special function.To prove this hypothesis polarized cultures of primary UE cells had to be developed that were hormonally responsive. Such an experimental cell system could serve as a model for in vitro implantation. This essay describes such a culture system in which blastocysts cocultured with UE cells in the presence of estrogen, will as predicted, fail to attach. This polarized UE cell system provides a functional in vitro model to study ovoreceptivity. It is now feasible to initiate studies of hormonal regulation of the composition and function of UE cell plasma membranes as they reflect the nonreceptive, receptive, and refractory nature of its apical surface. © 1993 Wiley‐Liss, Inc.
Endometrial adenocarcinoma
Authors: Noumoff Joel S. , Faruqi Shamim 
Published: February 2005

AbstractAdenocarcinoma of the endometrium is the most common gynecologic malignancy in the United States, accounting for some 36,000 cases of invasive cancer each year. Hyperplastic lesions of the endometrium follow a continuum, with the risk of progression to carcinoma being related to the severity of the disorder. Risk factors associated with the development of adenocarcinoma include hyperplasia, obesity, menstrual abnormalities, diabetes, hypertension, prior pelvic irradiation, sequential oral contraceptive use, diet, and exogenous estrogen use. There is also some evidence of genetic predisposition, and some data indicating the possibility of specific genetic abnormalities and activation of oncogenes as factors determining the etiology of the disease. At this time there is no accepted screening test for endometrial carcinoma, though the role of immunochemistry techniques for screening and follow‐up has just begun to be realized. Dilatation and curettage along with hysteroscopy remain the major means of diagnosis. A variety of prognostic variables including tumor cell type, histologic grade, depth of myometrial invasion, status of peritoneal cytology, presence of disease in preformed vascular spaces, presence of adnexal metastases, and presence of cervical involvement have been defined. Although the treatment plan for each patient must be individualized, the mainstay of treatment remains total abdominal hysterectomy with bilateral salpingo‐oophorectomy. Metastatic and recurrent disease is usually treated with hormonal therapy and systemic chemotherapy. Radiation therapy like surgery in recurrent disease is only applicable for the treatment of local recurrences. © 1993 Wiley‐Liss, Inc.
Characterization of agarose as an encapsulation medium for particulate specimens for transmission electron microscopy
Authors: Wood Jacqueline I. , Klomparens Karen L. 
Published: February 2005

AbstractAgarose, agar, and gelatin were initially compared as encapsulation media for 3 structurally diverse particulate specimens: bacteria, yeast, and mitochondria. Agarose proved superior to both gelatin and agar for ease of handling and overall image quality (minimum background). All sample types exhibited high quality fixation and structural detail with no heat damage from the agarose medium. Based on this finding, we further characterized agarose encapsulation as affected by post‐fixation, en bloc staining and resin type. Osmium tetroxide post‐fixation, followed by en bloc uranyl acetate staining, could be performed without an increase in the electron density of the encapsulation medium. Agarose proved successful as an encapsulation medium regardless of the resin type or preparation protocol, thus providing flexibility in experimental design and excellent results over a range of variables. © 1993 Wiley‐Liss, Inc.
Software for quantitative immunogold and in situ hybridization
Authors: Bolender Robert P. 
Published: February 2005

AbstractA well‐deserved criticism of stereology is that it is often too difficult to understand and use. Nevertheless, it is rapidly becoming one of the most effective ways of collecting and interpreting structural data in experimental biology. Recent breakthroughs in theory have produced a remarkable set of tools that can be used to engineer new methods. The dilemma remains, however, in that some of these new methods continue to be too difficult to understand and use. One solution to this growing problem of technology transfer might be to simplify the methods with computer software. To test this idea, programs were written for quantitative immunogold and in situ hybridization. Simulators were used to develop and test new experimental designs, which, in turn, were translated into step‐by‐step laboratory toolkits. This paper shows how these toolkits can turn two‐dimensional section data into estimates for the number of labeled molecules in three‐dimensional organelles, cells, tissues, and organs. The results indicate that software can identify the key data of an experiment and reduce the computational requirements of a new stereological method to entering constants and variables into data entry forms. © 1993 Wiley‐Liss, Inc.
Application of ESEM to environmental colloids
Authors: Nuttall H. E. , Kale Rahul 
Published: February 2005

AbstractEnvironmental colloids are toxic or radioactive particles suspended in ground or surface water. These hazardous particles can facilitate and accelerate the transport of toxicants and enhance the threat to humans by exposure to pathogenic substances. The chemical and physical properties of hazardous colloids have not been well characterized nor are there standard colloid remediation technologies to prevent their deleterious effects. Colloid characterization requires measurement of their size distribution, zeta potential, chemical composition, adsorption capacity, and morphology. The environmental scanning electron microscope (ESEM) by ElectroScan, Inc., analyzes particle sizes, composition, and morphology. It is also used in this study to identify the attachment of colloids onto packing or rock surfaces in our development of a colloid remediation process.The ESEM has confirmed the composition of groundwater colloids in our studies to be generally the same material as the surrounding rock. The morphology studies have generally shown that colloids are simply small pieces of the rock surface that has exfoliated into the surrounding water. However, in general, the source and chemical composition of groundwater colloids is site dependent. We have found that an ESEM works best as a valuable analysis tool within a suite of colloid characterization instruments. © 1993 Wiley‐Liss, Inc.
Dynamics of soldering reactions: Microscopic observations
Authors: Singler Timothy J. , Clum James A. , Prack Edward R. 
Published: February 2005

AbstractThis paper provides a summary of some in situ, high‐resolution studies of solder spreading reactions on microelectronic circuit metallizations. Experiments are described that focus on the use of the environmental scanning electron microscope, or ESEM. Those experiments have been complemented by studies using optical hot‐stage microscopy and have been supplemented by additional analytical tools such as energy dispersive X‐ray microanalysis, Auger and ESCA to evaluate chemical processes. Two general results from dynamic scanning electron microscope observations are that (1) molten solder alloys undergo a segregation process during spreading in which a “precursor” film spreads in advance of the bulk solder and (2) the spreading front, which may be enriched in Sn from Pb‐Sn or Bi‐Sn solders, or In from Pb‐In solders, spreads along high‐reactivity features of the metallization surface as a reacting “precursor” film. A third observation from these tests is that, in unconfined geometries, the reactive metallization, if not sufficiently thick, can be dissolved by the solder before wetting is complete, leading to dewetting of the solder. Both the kinetics and extent of spreading of these films and the relationship of these phenomena to the commonly measured contact angle and wetting forces are currently being examined by a range of complementary techniques. Information gathered in these studies shows that process temperature as well as composition, reactivity, and relative amounts of the solder and metallization species should all be factors of interest to the those responsible for control of soldering processes. © 1993 Wiley‐Liss, Inc.
Aspects of vertebrate gustatory phylogeny: Morphology and turnover of chick taste bud cells
Authors: Ganchrow Judith R. , Ganchrow Donald , Royer Suzanne M. , Kinnamon John C. 
Published: February 2005

AbstractThe taste bud is a receptor form observed across vertebrates. The present report compares chick taste buds to those of other vertebrates using light and electron microscopy.Unlike mammals, but common to many modern avians, the dorsal surface of chick anterior tongue lacks taste papillae and taste buds. Ultrastructurally, chick buds located in the anterior floor of the mouth (as in some reptiles and amphibians) and palate contain dark, intermediate, light, and basal cell types. Dark, intermediate, and light cells extend microvilli into intragemmal lumina and pores communicating with the oral cavity. As specialized features, dark cell apices lack dense granules and exhibit short microvilli relative to light and intermediate cells. Dark cell cytoplasmic fingers envelop intragemmal nerve fibers and cells as in other species, and sometimes contain abundant clear vesicles. Nerve profile expansions often are located adjacent to dark, intermediate, and light cell nuclei. Classical afferent synaptic contacts are rarely observed.Taste cell turnover is suggested by mitotic and degenerating figures in chick buds. In addition, tritiated thymidine injected into hatchlings, whose anterior mandibular oral taste bud population approximates that in adults, reveals a turnover rate of about 4.5 days. This is about half that observed in altricial mammals, reflecting a species difference or developmental factor in precocial avians.It is concluded that chick taste buds exhibit morphologic features common to other vertebrate buds with specializations reflecting the influences of niche, glandular relations, and/or age. © 1993 Wiley‐Liss, Inc.
A modified autowasher device for rapidly washing large numbers of EM‐grids
Authors: Chen Ming H. 
Published: February 2005

AbstractThis device consists of a siphon system and 5 to 10 grid disks, modified from the previous mode (Chen, 1973), for large numbers of grids with ultrathin sections. This method improves the ease of assembling grids onto the grid disk and also requires much less stain solution. This system only takes 5 min for one single stain washing, at a maximum of 100 grids, and also avoids stain contamination. The grid disk can also be used for immunocytochemistry work and for critical point drying of grids with biological specimens.
Cellular relations in mouse circumvallate taste buds
Authors: Murray Raymond G. 
Published: February 2005

AbstractThe fine structure of the taste buds of circumvallate papillae of two strains of mice was studied by electron microscopy. Mice anesthetized with ketamine were perfused through the heart with a double aldehyde mixture in cacodylate buffer and the tissues embedded in Epon. Semi‐serial sections were employed. The morphology and relationships of cell types are consistent with the majority of descriptions of mammalian taste buds served by the ninth cranial nerve. Cells of type II are particularly well documented, as the stages in their origin, maturation and degeneration could be followed. Significant differences, however, relate to cell type I. These cells contain large dense‐cored granules, contrasted with the more irregular and somewhat larger dark granules of the type I cells in the rabbit. These granules do not produce a dense homogenous product for the pore, as seen in the rabbit. Rather the pore substance consists of small, empty vesicles in a diffuse dark matrix. These granules are only moderately larger than the dense‐cored vesicles of the type III cells. All features of the type III cell were demonstrated, although no instance of a complete cell was seen in any section. No significant differences were noted between the two strains of mice. Intimate proximity of a nerve to a cell nucleolus, suggestive of a trophic pathway, is illustrated. © 1993 Wiley‐Liss, Inc.