bluuebunny/crossref_metadata_2025_split huggingface dataset:
Principles for the construction and operation of a device for rapidly freezing suspensions for cryo‐electron microscopy
Authors: Murray John M. , Ward Rob 
Published: February 2005

AbstractDetails are given concerning the construction and use of a simple device for preparing samples of frozen‐hydrated biological material embedded in thin films of vitreous ice. The control of humidity around the sample and rate of freezing are of prime importance to obtain good specimens for cryo‐electron microscopy. Symptoms of ill performance of such an apparatus and poor cryo‐manipulation are discussed.
Determination of the crystallographic directions and planes of features and of the misorientations of crystals with high accuracy and internal estimation of errors
Authors: Chen Fu‐Rong , King A. H. 
Published: February 2005

AbstractTechniques are given for maximizing the accuracy of crystallographic measurements in the transmission electron microscope. In particular, line directions, plane orientations, and crystal misorientations are treated, and for each case the methods of data collection, refinement, and error estimation are given. These methods represent generalizations of Ball's optimizing crystallographic technique (Ball: Philos. Mag. A44:1307–1317, 1981), and we also provide extensions to hexagonal lattice applications.
Microvascular casting of the lung: Effects of various fixation protocols
Authors: Schraufnagel Dean E. , Schmid Aloisia 
Published: February 2005

AbstractAlthough techniques for preparing specimens for light and electron microscopy are well established, few studies have sought to establish methods for corrosion casting of the microscopic vessels of the lung. The effects of two concentrations of glutaraldehyde, formaldehyde, and no fixative (saline control) on the filling and structure of the microvascular casts of the lung were studied. All fixatives were infused 5 minutes before casting.Formaldehyde's fixation effects were intermediate between those of glutaraldehyde and no fixation. Leakage of casting material was increased in the animals that were fixed less. Digestion time was prolonged and more undigested tissue was found in the group receiving the concentrated glutaraldehyde, although the difference in neither of these features alone reached statistical significance. Circumferential bands occurred more frequently in the large vessel casts of the less fixed animals, which may account for the less filling microvasculature in these lungs. However, good quality casts were obtained with each method.
Enzyme‐gold affinity labelling of cellulose
Authors: Berg R. Howard , Erdos Gregory W. , Gritzali Mikelina , Brown Ross D. 
Published: February 2005

AbstractThe enzyme‐linked colloidal gold affinity labelling technique was tested as a method to localize cellulose on thin sections of plant cell walls and slime mold spores. Commercially available cellulase from cultures of Trichoderma reesei, the main components being cellobiohydrolase I and II (CBH I, CBH II) and endoglucanase (EG), was linked to colloidal gold by using standard techniques and applied as a dilute, buffered suspension to thin sections. After brief exposure, e.g., 15–30 minutes, cellulose exposed on the surface of sections was labelled with the enzyme‐gold complex. Poststaining did not appear to have a deleterious effect on the labelled sections. The specificity of labelling was demonstrated by its complete inhibition when carboxymethylcellulose was incorporated in the labelling mixture, by lack of labelling of 1,4‐β‐mannans or 1,3‐β‐xylans in noncellulosic walls of marine algae, by lack of labelling of 1,4‐β‐glucans in chitin, by much lower labelling density when done at 4°C, and by lack of labelling when sections were predigested with cellulase. Labelling with the crude commercial cellulase was compared to labelling with purified CBH I‐, CBH II‐, and EG‐linked colloidal gold, and the labelling pattern was similar. This method was found useful on conventionally fixed material and required no special preparation other than the use of inert (Ni or Au) grids and 0.5% gelatin to reduce nonspecific binding of the gold complex. Labelling was similar in the several embedding resins tested: LR White, Lowicryl K4M, Epon 812, and Spurr's. The cellulase‐gold probe remained active for at least 4 weeks at 4°C and much longer when frozen at −80°C in 20% glycerol. This technique should prove useful in studies of cellulose degradation and cellulose deposition and of the interaction of cellulose with other wall components.
Relationship between structure and function in distal tubule and collecting duct
Authors: Madsen Kirsten M. , Verlander Jill W. , Tisher C. Craig 
Published: February 2005

AbstractThe relationship between structure and function in the distal tubule and collecting duct has been studied with morphologic and physiologic techniques, including morphometric analysis, to identify functionally distinct cell populations. The distal tubule, including the thick ascending limb (TAL) and the distal convoluted tubule (DCT), is involved in active reabsorption of sodium chloride. It is characterized by extensive invaginations of the basolateral plasma membrane, numerous mitochondria, and high Na‐K‐ATPase activity, features characteristic for an epithelium involved in active transport. Between the distal tubule and the collecting duct is a transition region, the connecting segment or the connecting tubule (CNT), which exhibits species differences with respect to both structure and function. The collecting duct includes the cortical (CCD), the outer medullary (OMCD), and the inner medullary (IMCD) collecting ducts. Principal cells are present throughout the collecting duct, whereas intercalated cells are located mainly in the CCD and OMCD. Morphometric analysis combined with micropuncture and microperfusion studies has provided evidence that the CNT and principal cells are responsible for potassium secretion in the connecting segment and the CCD. The OMCD is a main site of hydrogen ion secretion, and morphometric studies have provided evidence that the intercalated cells in this segment secrete hydrogen ion at least in the rat. Two configurations of intercalated cells exist in the CCD—a type A and a type B. The A cells are similar in ultrastructure to the intercalated cells in the OMCD and are believed to be involved in hydrogen ion secretion. The function of the B cells remains to be established. The inner two‐thirds of the IMCD corresponds to the papillary collecting duct, which has a high permeability to urea. The relationship between structure and function in the IMCD has not been studied in detail. This review emphasizes the role of morphometric analysis in establishing the relationship between structure and function in the distal nephron.
Three‐dimensional reconstruction of cells from serial sections and whole‐cell mounts using multilevel contouring of stereo micrographs
Authors: Marko Michael , Leith Ardean , Parsons Donald 
Published: February 2005

AbstractA comprehensive computer‐graphics‐based system (STERECON) is described for tracing and digitizing contours from individual or stereopair electron micrographs. The contours are drawn in parallel planes within the micrographs. Provision is also made for tracing and digitizing in full three‐dimensional (3‐D) coordinates in any direction along linear structures such as cytoskeletal elements. The stereopair micrographs are viewed in combination with the contours being traced on a graphics terminal monitor. This is done either by projecting original electron micrograph (EM) negatives onto a screen and optically combining these images with contour lines being drawn on the monitor, or by first digitizing the images and displaying them directly on the monitor along with the contour lines. Prior image digitization allows computer enhancement of the structures to be contoured. Correction and alignment routines are included to deal with variable section thickness, section distortion and mass loss, variations in photography in the electron microscope, and terminal screen curvature when combining projected images with contour lines on the monitor. The STERECON system organizes and displays the digitized data from successive sections as a 3‐D reconstruction. Reconstructions can be viewed in any orientation as contour stacks with hidden lines removed; as wire‐frame models; or as shaded, solid models with variable lighting, transparency, and reflectivity. Volumes and surface areas of the reconstructed objects can be determined. Particular attention was paid to making the system convenient for the biological user. Users are given a choice of three different stereo‐viewing methods.
Serial section reconstruction using a computer graphics system: Applications to intracellular structures in yeast cells and to the periodontal structure of dogs' teeth
Authors: Baba Norio , Baba Misuzu , Imamura Masao , Koga Masatada , Ohsumi Yoshinori , Osumi Masako , Kanaya Koichi 
Published: February 2005

AbstractA computer graphics system for reconstruction from serial section micrographs was applied to intracellular details of a yeast target cell (Saccharomyces cerevisiae cell) induced by the α factor mating pheromone and was also applied to a periodontal structure of a dog tooth moved orthodontically. In the former, intracellular organelles and a distribution of vesicles could be clearly observed through the cell membrane using the transparent display method in which the smoothing of the reconstructed outer cell membrane surface by computer processing was applied to the transparent display. In the latter case, by cutting through a reconstructed dog tooth and its periodontal tissues, labiolingual and mesiodistal cut surfaces of the tooth and of adjacent alveolar bone could be observed with fine details (232 sections were used).
Light, scanning, and transmission electron microscopy of a single population of detergent‐extracted cardiac myocytes in vitro
Authors: Delcarpio Joseph B. , Underwood Elizabeth G. , Moses R. L. 
Published: February 2005

AbstractA technique for performing light, scanning, and transverse transmission electron microscopy on cultured cells grown within a single tissue culture flask is described. Permanent light microscopy slides are obtained by removing selected portions of the plastic tissue culture vessel and mounting them on glass slides with an aqueous mounting solution. The images obtained from these slides are superior to viewing through the bottom of the flask with an inverted stage microscope. For scanning electron microscopy, selected areas are also cut from the remainder of the vessel and prepared for viewing. The final portion of the culture container is transferred and attached to a new tissue culture vessel and prepared for transmission electron microscopy using alcohol instead of acetone and propylene oxide during dehydration, infiltration, and embedding.
Detection of small displacement of atoms in crystals by atom resolution electron microscopy
Authors: Hashimoto Hatsujiro , Kuwabara Masago , Takai Yoshizo , Tsubokawa Sumiyuki , Yokota Yasuhiro 
Published: February 2005

AbstractFour kinds of works on the detection of displacement of atoms in crystals are shown. The irregular small displacement of atoms has been detected, with an accuracy of about 0.1 Å around dislocations and stacking faults in Au crystals as shown by their electron microscope images. The displacement of the atomic images is recorded by aberration‐free focus (AFF). Even when the periodic displacement of atoms in SiC and TaS2 crystals is around 0.1% of the lattice constant, this displacement has been revealed as the weak‐contrast anomaly in the images. Using in situ observations by a TV system attached to an electron microscope, the rapid movements of atoms that have taken place within 1/30 sec have been recorded. Using the technique of successive subtraction of the images by TV system and image sigma, only the images of moving atoms in Au crystal have been recorded each 1/10 sec.
Quick‐freeze, deep‐etch, rotary‐shadow views of the extracellular matrix and cortical cytoskeleton of Xenopus laevis eggs
Authors: Larabell Carolyn A. , Chandler Douglas E. 
Published: February 2005

AbstractThe quick‐freeze, deep‐etch, rotary‐shadow technique provides a powerful tool to study the structural dynamics of extracellular matrices. Using this technique, we show that the extracellular investments of the Xenopus laevis egg are multilayered and securely anchored to the egg surface. The cortical cytoskeleton within the egg contains embedded cortical granules with surrounding endoplasmic reticulum and is capped by a thin reticular sheet that contacts the inner surface of the plasma membrane. The extracellular matrix undergoes three distinct changes at fertilization: (a) formation of a “smooth” layer below the vitelline envelope (VE), (b) transformation of the VE itself to an altered VE composed of concentric fibrous sheets, and (c) formation of a dense, “briar‐patch”‐like fertilization layer at the upper surface of the VE.
Advantages of the use of intact plant tissues in freeze‐fracture electron microscopy
Authors: Platt‐Aloia K. A. , Thomson W. W. 
Published: February 2005

AbstractThe use of whole, intact plant tissue for freeze‐fracture electron microscopy provides important information that cannot be obtained from the use of isolated biological membranes or of artifical (phospholipid) membrane preparations. This is not to imply that these exminations of such preparations are not useful, since it would be difficult to interpret our observations of intact cells and tissues without the analysis of these model systems. Analysis of intact tissue and cells reveals the relative densities of membrane proteins of the different membranes within a cell; the three‐dimensional organization of various organelles, especially the endoplasmic reticulum; changes in intramembranous particle (IMP) distribution due to stress or injury; and, in conjunction with the use of filipin, membrane sterol content and relative distribution.It is our intention that this survey of freeze‐fracture images of intact plant tissues will illustrate the uniqueness of the information gained from an analysis of whole plant tissues compared to isolated membrane fractions.
Ultrathin (1 nm) vertically shadowed platinum‐carbon replicas for imaging individual molecules in freeze‐etched biological DNA and material science metal and plastic specimens
Authors: Ruben George C. 
Published: February 2005

AbstractSingle molecule resolution in beam‐sensitive, uncoated, noncrystalline materials has heretofore not been possible except in thin (≤150 Å) platinum‐carbon (Pt‐C) replicas, which are resistant to electron beam destruction. Previously, the granularity of metal film replicas limited their resolution to ≥20 Å. This paper demonstrates that Pt‐C film granularity and resolution are a function of the method of replication and other controllable factors. Low‐angle 20° rotary, 45° unidirectional, and vertical 9.7 ± 1 Å Pt‐C films deposited on mica under the same conditions were compared. Vertical replication had a 5 Å granularity, the highest resolution, and evenly coated the whole surface. A 45° replication had a 9.5 Å granularity, a slightly poorer resolution, and a discontinuous surface coating. The use of 20° rotary replication proved to be unsuitable for high‐resolution imaging, with 20–25 Å granularity and resolution two to three times poorer. Vertical and 45° Pt‐C replicas can visualize the deep‐etched DNA helix and the 13.3 Å 32 helix of pectin in a gel. The DNA double helix, the complex structures of sol‐gel glasses, Immobilon filters (polyvinylidene fluoride), a polymethacrylate plastic, the metal oxide surfaces of 440c stainless steel, and aluminum are illustrated. This high‐resolution vertical Pt‐C replica technique can image in the context of solutions, gels, or solids, single molecular chains 3–7 Å wide, their associations, and their conformation. Included in the present article are first time descriptions for removing replicas from metals and plastics and for making high‐magnification photographic prints of normal contrast using a reversal rephotographic process.
Hepatocyte fine structure during maturation and senescence
Authors: Schmucker Douglas L. 
Published: February 2005

AbstractAging is accompanied by a myriad of changes in cell structure, function, and composition. The fact that much of the information concerning age‐related alterations in cellular morphology is qualitative precludes meaningful correlations with biochemical changes in order to enhance data interpretation. The mammalian liver has been subjected to both qualitative and quantitative evaluations of hepatocyte structure as a function of aging, i.e., development, maturation, and senescence. Although these data are characterized by considerable variability and, in some instances, blatant contradictions, there exists sufficient agreement in several parameters to permit a consensus in the inbred rat model. Certainly the volume of individual hepatocytes increases with age, and many of the organelle compartments reflect this change. While old rats exhibit a high incidence of polyploidy, there is no definitive evidence to demonstrate a concomitant increase in the binuclear hepatocyte index. Several specific hepatocellular organelles undergo changes in their relative volume or surface area that appear to correlate with functional alterations. The volume density of the lysosomal compartment enlarges significantly during senescence and is accompanied by increased activities of several constituent hydrolases. The hepatic concentration of smooth‐surfaced endoplasmic reticulum declines markedly with aging, as does the yield of liver microsomes and the activities of several microsomal enzymes, e.g., mono‐oxygenases and glucose‐6‐phosphatase. However, the responses of the majority of hepatocyte organelles to aging is varied and inconsistent based on the limited data currently available.
Immunocytochemistry of neurotransmitter receptors
Authors: Wenthold R. J. , Altschuler R. A. , Hampson D. R. 
Published: February 2005

AbstractOver the last several years our knowledge of neurotransmitter receptors has increased dramatically as receptor types and subtypes have been identified through the development of selective antagonists, neuropharmacological studies, and radioactive ligand binding studies. At the same time major advances were made in the immunocytochemical localization of neurotransmitters and their related enzymes. However, only recently has immunocytochemistry been used to localize neurotransmitter receptors, and these studies have been limited. Four receptors have been localized in the CNS with immunocytochemistry: the nicotinic acetylcholine receptor, the beta‐adrenergic receptor, the GABA/benzodiazepine receptor, and the glycine receptor. Of these the glycine receptor has been the most thoroughly characterized. Glycine receptor immunoreactivity is highly concentrated at postsynaptic sites, and the distribution of immunoreactivity appears to correlate closely with glycinergic neurons. However, immunocytochemical studies done on other receptors suggest such a distribution may not always be the case. Some receptors may not be concentrated at postsynaptic sites, and receptor distribution may not always closely fit the distribution of the respective neurotransmitter. Work is rapidly progressing on the purification of other receptors and on the production of selective antibodies which will allow immunocytochemical studies which address these and other questions.
Ultrastructure of proteoglycans in the tectorial membrane
Authors: Santi Peter A. , Lease M. Kathryn , Harrison Robert G. , Wicker Eileen M. 
Published: February 2005

AbstractThe ultrastructure of proteoglycans (PGs) in the tectorial membrane (TM) of the mature chinchilla cochlea was investigated using the cationic dye Cuprolinic blue. When used at a high critical electrolyte concentration, Cuprolinic blue has been shown specifically to bind to the glycosaminoglycan residues of sulfated PGs. After Cuprolinic blue treatment, PGs were observed in the TM which were represented as rod‐shaped, electron‐dense structures. A perifibrillar, primarily orthogonal, array of PGs was associated with the type A protofibrils. These PGs were distributed in 50 nm intervals along the length of the type A protofibrils. A less common orientation was parallel to the axis of the type A protofibrils. PGs did not appear to be associated with the type B protofibrils. Based upon previous results by other investigators, the TM contains types II and IX collagen, and it appears likely that the type A protofibrils are composed of collagen type II. PGs visualized in the TM in this study thus may represent the glycosaminoglycan residue of type IX collagen which is associated with the type II collagen fibrils. Alternatively, the TM PGs may be small dermatan or chondroitin sulfate PGs.
A replica technique for extracting precipitates from zirconium alloys for transmission electron microscopy analysis
Authors: Ng‐Yelim J. , Woo O. T. , Carpenter G. J. C. 
Published: February 2005

AbstractA reliable two‐stage carbon replica technique has been developed to extract precipitates from zirconium alloys. Using this technique, all precipitating phases can be extracted from Zircaloy‐2, Zr‐Cr‐Fe, and Zr‐Nb‐Fe alloys. Precipitate identification using EDS X‐ray analysis and convergent beam electron diffraction was greatly facilitated in comparison to thin foils. In addition, the sensitivity for the detection of trace elements in particles was increased using extraction replicas. The chemical compositions of the precipitates as determined from both replica and thin foils were in excellent agreement.
Lowicryl embedding of gastrointestinal tissues
Authors: Hagen Susan J. 
Published: February 2005

AbstractIn the present study, we modified the technique described by Altman et al. (J. Histochem. Cytochem., 32:1217–1223, 1984) for rapid embedding of tissues in Lowicryl K4M. To attain good sections of the small intestine that contained villi, crypts, submucosa, and external muscle layers, we cut 100 μm slices of the full thickness of the wall with a vibratome before embedment and then deoxygenated the resin and tissue before polymerization. The sections we obtained compared favorably with the quality of sections from conventional resins.
A simple pneumatic device for plunge‐freezing cells grown on electron microscopy grids
Authors: Cole Richard , Matuszek George , See Charles , Rieder Conly L. 
Published: February 2005

AbstractA detailed design for a simple and inexpensive variable‐speed (1.0–5.8 m s−1) pneumatic plunge‐freezing device is presented. Cultured cells, grown on Formvar‐coated 75‐mesh gold finder grids, are pneumatically driven into a stirring mixture of propane/isopentane (3:1) cooled by liquid nitrogen (LN2). Premature freezing of the sample in the cryogenic vapors above the cryogen is prevented by plunging through an entry tube into an insulating box, to which a partial vacuum is applied. The cryogenic vapors are drafted into the box at the level of the liquid cryogen by the vacuum, thereby preventing a layer of cold gas from collecting above the cryogen. To prevent the sample from thawing during transfer from the cryogen to the substitution medium, the box top is removed and compressed air is forced through a corrugated tube running the length of the box. The resulting boiling LN2 creates an atmosphere below −120°C in which the transfer can be accomplished.