bluuebunny/crossref_metadata_2025_split huggingface dataset:
An SEM Study of the Filtration System and Mucus Secretion of the Gills of the Oyster Crassostrea Virginica
Authors: Ruby J.R. , Kilgen M.B. 
Published: June 2020

The gills of the oyster play a major role in respiration but also serve as a filter feeding device. Although an excellent description of the gills at the light microscope level has been published, there have been very few ultrastructural studies.The basic morphology of the gills is difficult to ascertain due to the large number of cilia projecting from them. A more complete understanding of these structures can be obtained by using the ethanol cryofracture technique.Figure 1 depicts a portion of a demibranch which has been cryofractured in transverse, section. It shows the longitudinal folds of the demibranch and the ordinary filaments which form the basic structure of the gills. Also seen in this micrograph is a view from within the water tube which clearly shows the ladder-like arrangement of the chitinous framework which supports the entire gill structure. Many of the cells lining this framework possess cilia (Fig. 2), an observation which has not previously been emphasized.
The Observation of Frozen Hydrated Sections by CTEM and STEM
Authors: Chang J. J. , Walter C. A. , Dubochet J. 
Published: June 2020

With the ultimate aim of studying biological structures close to their native state, we are attempting to prepare and examine thin frozen hydrated sections using catalase crystals and skeletal muscle as test objects. There have been a few observations under these conditions.small droplet of catalase crystals stained in 2% aqueous uranyl acetate and re-suspended in water was placed on a copper specimen holder and plunged into liquid nitrogen. Small pieces of rat femoral muscle were fixed in 2% gluter- aldehyde in 0.05 M cacodylate buffer, and frozen as above after washing in buffer with or without the addition of 1 M sucrose.Frozen sections for examination in the CTEM were cut with glass knives in a Sorvall MT2B microtome with the LTC2 cryo-attachment operating at ca. -120°C. For examination in the STEM, frozen sections were cut in a Reichert Ultracut with FC4 cryo-attachment operating with the knife and the specimen at -150°C and the chamber at -170°C. Sections that appeared transparent were manipulated onto carbon coated grids with a pre-cooled eyelash probe and then sandwiched in place with a second carbon coated grid.
Uranyl Acetate Preservation of Nucleoplasm in the Sporocytes of Psilotum
Authors: Lee Kit W. 
Published: June 2020

As a stain, uranyl acetate (UA) is used on thin sections to enhance the contrast of cellular constituents. It has been shown that the use of uranyl acetate in the fixation process can increase the contrast and preservation of various membrane systems by reducing the extraction of phospholipids during dehydration. Because of its high affinity for nucleic acids, uranyl acetate has also been used as a post fixative to preserve the nuclear region of prokaryotes. This paper compares the nuclei of the eukaryote Psilotum, particularly during meiosis, with and without post fixation with uranyl acetate.Sporangia at different developmental stages were fixed in cold 3% glutaral-dehyde (GA) in 0.1 M phosphate buffer (pH 7.2) for 4 hours or overnight, and post fixed at room temperature with 2% osmium tetroxide (OsO4) for 2 hours. After washing in distilled water, samples were either (a) dehydrated in a graded series of ethanols and propylene oxide, or (b) placed in 1% aqueous uranyl acetate for 1 hour, followed by 30 minutes washing in distilled water before dehydration.
Visualization of the Adenovirus DNA Terminal Protein, Its Gene, and Messenger RNA
Authors: Broker Thomas R. , Chow Louise T. 
Published: June 2020

Studies using biochemical and electron microscopical RNA:DNA heteroduplex methods have shown that the transcription patterns of the human adenoviruses are extremely complicated. Almost all early and late mRNAs are spliced. Each transcriptional unit produces a family of RNAs that share common 5' and 3' ends but have alternative splicing. Most of the genome is expressed as relatively abundant mRNAs, except for the region between coordinates 16 and 27. This segment encodes the RNA leader components for the late rightward-transcribed (r-strand) RNAs. However, DNA-negative temperature-sensitive mutations have been mapped to this interval. Recently, experiments by several laboratories using different techniques have elucidated how these mutations might affect DNA replication.A protein of 55,000 daltons (55KD) M is covalently joined to each 5' terminus of adenovirus DNA isolated from virions. The ends of replicating DNA in infected cells are also bound to proteins. The linkage is via a phosphodiester bond between serine and the terminal deoxy-cytidine.
Periodate Treatment and “All-or-None” Dehydrogenase Staining Phenomena
Authors: Rosa C. G. 
Published: June 2020

It has been shown that when suspensions of fresh rodent sperm are incubated in the presence of tetranitro-blue tetrazolium (TNBT) and stained for succinic dehydrogenase (SDH),this enzyme is localized in the mitochondria of the middle-piece. Rat and mouse spermatozoa treated in this manner and postfixed (suspension) in 4°C Millonig's osmium tetroxide for brief periods demonstrate SDH reactivity in mitochondrial profiles that indicate no SDH, almost complete activity, or most commonly, intermediate staining reactions in the internal membranes (Figure 1). In the last instance, the cristal membranes display a heterogeneous formazan (reduced TNBT) staining pattern not in agreement with the Seligman “all-or-none” hypothesis concerning mitochondrial oxidative enzymatic reactivity.In order to test this hypothesis and circumvent some of the attendant difficulties in these procedures (penetration of reaction mixture components, fixatives), all cytochemical reactions and postfixation were performed on suspensions of sperm from the cauda epididymides of mature rats. An attempt was made to divorce electron densities due to osmium postfixation by employing 1% aqueous sodium periodate (pH 3-4) as a mitochondrial membrane stabilizer through the embedding procedures. Previous use of this treatment allowed preservation of the membranes of these organelles in positive contrast as evidenced by uranyl acetate staining of sectioned material (Figures 2 & 3).
Electron Staining Characteristics of the Inclusion Bodies of Type II Alveolar Epithelial Cells
Authors: Kikkawa Yutaka , Hahn Ho-Soon 
Published: June 2020

The inclusion bodies of Type II epithelial cells of the mammalian lung are oval and limited by a unit membrane. They contain highly osmiophilic material. With the standard method of fixation this material is irregularly separated by a number of electron-lucent spaces (Figure 1). Because of this appearance, the inclusion bodies are often referred to as “lamellar inclusions”. Measurable periodic lamellae, however, have never been observed in the inclusions which are located intracellularly.During the course of the studies to localize acid mucopolysaccharides in the distal air way of the rabbit and rat, it is found that the alveolar surface of the cell membranes of both Type I and II cells and the inclusion bodies within Type II cells satin heavily with colloidal iron at pH 2.0 following the osmication of the tissue with phosphate-buffered solution at pH 7.4 (Figure 2). In addition, the inclusion bodies for the first time show regular periodic lamellae. Each line is granular and measures about 60 Å in width (Figure 3).
Effects of EDTA, Hyaluronidase and Collagenase on Epiphyseal Cartilage Matrix
Authors: Anderson H. Clarke , Coulter Priscilla R. 
Published: June 2020

Epiphyseal cartilage matrix contains fibrils and particles of at least 5 different types: 1. Banded collagen fibrils, present throughout the matrix, but not seen in the lacunae. 2. Non-periodic fine fibrils <100Å in diameter (Fig. 1), which are most notable in the lacunae, and may represent immature collagen. 3. Electron dense matrix granules (Fig. 1) which are often attached to fine fibrils and collagen fibrils, and probably contain protein-polysaccharide although the possibility of a mineral content has not been excluded. 4. Matrix vesicles (Fig. 2) which show a selective distribution throughout the epiphysis, and may play a role in calcification. 5. Needle-like apatite crystals (Fig. 2).Blocks of formalin-fixed epiphysis from weanling mice were digested with the following agents in 0.1M phosphate buffer: a) 5% ethylenediaminetetraacetate (EDTA) at pH 8.3, b) 0.015% bovine testicular hyaluronidase (Sigma, type IV, 750 units/mg) at pH 5.5, and c) 0.1% collagenase (Worthington, chromatograhically pure, 200 units/mg) at pH 7.4. All digestions were carried out at 37°C overnight. Following digestion tissues were examined by light and electron microscopy to determine changes in the various fibrils and particles of the matrix.
Mesosome-like Structures in Cryptococcus neoformans Studied by Chemical Fixation and by the Freeze-etching Technique
Authors: Edwards M. R. , Holt S. C. 
Published: June 2020

The general features of Cryptococcus neoformans, a pathogenic yeast, have been studied with the electron microscope. In the course of such a study it was noted that the plasma membrane of C. neoformans, occasionally invaginated into the cytoplasm and formed membranous organelles which resembled bacterial mesosomes. The present investigation was undertaken in order to examine such structures in detail and to compare the results from chemical fixation with those of freeze-etching.Cells were grown in Sabouraud's agar at 25-27° C for 24-48 hr and fixed with 4% glutaraldehyde in 0.15 M phosphate (Sbrensen's) buffer, at room temperature, for 2 hr; after being thoroughly washed in the buffer and post-fixed in osmium tetroxide, in the same buffer, they were dehydrated in ethyl alcohol and embedded in Epon. Thin sections were cut in a LKB microtome, double stained with uranyl and lead salts and examined in the Siemens Elmiskop IA.
Mitochondrial Changes in Choline-Deficient Rat Myocardium
Authors: Zaki F. G. 
Published: June 2020

Choline-deficiency was induced in Holtzman young rats of both sexes by feeding them a high fat - low protein diet.Preliminary studies of the ultrastructural changes in the myocardium of these animals have been recently reported from this laboratory. Myocardial lesions first appeared in the form of intraventricular mural thrombi, loss of cross striation of muscle fibers and focal necrosis of muscle cells associated with interstitial myocarditis. Prolonged choline-deficiency induced cardiomegaly associated with pericardial edema.During the early phase of this nutritional disorder, heart mitochondria - despite of not showing any swelling similar to that usually encountered in liver mitochondria of the same animal - ware the most ubiquitous site of marked structural abnormalities. Early changes in mitochondria appeared as vacuolation, disorganization, disruption and loss of cristae. Degenerating mitochondria were often seen quite enlarged and their matrix was replaced by whorls of myelin figures resembling lysosomal structures especially where muscle fibers were undergoing necrosis. In some areas, mitochondria appeared to be unusually clumped together where some contained membranelined vacuoles and others enclosed dense bodies and granular inclusions.
Mitochondrial Inclusions
Authors: Hruban Z. 
Published: June 2020

Two types of inclusions in the matrix of mitochondria were observed in our comparative studies on the fine structure of hepatocytes and renal proximal tubular cells of apparently healthy animals. Mitochondrial inclusions occuring in various cell types in healthy and diseased tissues have been recently reviewed by Haust ( Exp. Molec. Pathol. 8: 123, 1968).Multiple small inclusions were seen in the proximal tubular cells of deer mice, Peromyscus boylei (Fig. 1) and P. californicus. These inclusions had an electron lucid center and a narrow dense periphery. Large electron dense inclusions with one or more lucid areas were seen in proximal tubular cells of the slow loris, Nicticebus coucang (Fig. 2). The dense portion of the inclusion was composed of dense laminae about 65 Å thick (Fig. 3). These Inclusions, seen in the deer mice and in the slow loris, are not limited by a membrane and do not show a regular spatial relationship to mitochondrial cristae. The term “lipoid inclusions” is proposed for these structures. Osmiophil intramitochondrial granules are usually absent in mitochondria containing lipoid inclusions. Transitions are found between osmiophil granules and lipoid inclusions.
Evidence for Golgi Origin of Melanosomes
Authors: Maul Gerd G. 
Published: June 2020

Electron microscopy has provided evidence that the melanosome evolves as a membrane bound structure with a highly complex internal architecture. The premelanosomes are found in close proximity to the golgi apparatus. Therefore, it was generally agreed that the melanosomes originate from the golgi apparatus.Vesicles have been described to pinch off the cysternae of the golgi apparatus. The vesicles would then grow and acquire a dense material. This material is aggregating to form the characteristic helical strands onto which melanin is deposited. Cloned human malignant melanoma lines were used to reinvestigate the problem of melanosome formation. The reconstruction of serial sections revealed the arrangement of premelanosomes and melanosomes in relation to the golgi complex. This study demonstrated that premelanosomes and melanosomes are continuous with the golgi complex by a smooth-surfaced tubular endoplasmic reticulum (SER) (Fig. la-d). The continuity of membranes of the SER and the premelanosome is depicted in Fig. 2. In this early premelanosome the protein strands have not yet coiled up into a helix. Rough-surfaced endoplasmic reticulum (RER) was also observed to be continuous with the golgi apparatus and melanosomes. After melanogenesis has started (Fig. 3) small vesicles appear inside the premelanosomes.
Scanning Electron Microscopy and Electron Microprobe Analysis of Malignant Cell Cultures
Authors: Johnsson-Hegyeli R. I. , Hegyeli A. F. , Landstrom D. K. , Lane W. C. 
Published: June 2020

Last year we reported on the use of reflected light interference microscopy (RLIM) for the direct color photography of the surfaces of living normal and malignant cell cultures without the use of replicas, fixatives, or stains. The surface topography of living cells was found to follow underlying cellular structures such as nuceloli, nuclear membranes, and cytoplasmic organelles, making possible the study of their three-dimensional relationships in time. The technique makes possible the direct examination of cells grown on opaque as well as transparent surfaces. The successful in situ electron microprobe analysis of the elemental composition and distribution within single tissue culture cells was also reported.This paper deals with the parallel and combined use of scanning electron microscopy (SEM) and the two previous techniques in a study of living and fixed cancer cells. All three studies can be carried out consecutively on the same experimental specimens without disturbing the cells or their structural relationships to each other and the surface on which they are grown. KB carcinoma cells were grown on glass coverslips in closed Leighto tubes as previously described. The cultures were photographed alive by means of RLIM, then fixed with a fixative modified from Sabatini, et al (1963).
Oncogenesis and the Lucké Virus
Authors: Vatter A. E. , Zambernard J. 
Published: June 2020

Oncogenic viruses, like viruses in general, can be divided into two classes, those that contain deoxyribonucleic acid (DNA) and those that contain ribonucleic acid (RNA). The RNA viruses have been recovered readily from the tumors which they cause whereas, the DNA-virus induced tumors have not yielded the virus. Since DNA viruses cannot be recovered, the bulk of present day investigations have been concerned with RNA viruses.The Lucké renal adenocarcinoma is a spontaneous tumor which occurs in northern leopard frogs (Rana pipiens) and has received increased attention in recent years because of its probable viral etiology. This hypothesis was first advanced by Lucké after he observed intranuclear inclusions in some of the tumor cells. Tumors with inclusions were examined at the fine structural level by Fawcett who showed that they contained immature and mature virus˗like particles.The use of this system in the study of oncogenic tumors offers several unique features, the virus has been shown to contain DNA and it can be recovered from the tumor, also, it is temperature sensitive. This latter feature is of importance because the virus can be transformed from a latent to a vegetative state by lowering or elevating the environmental temperature.
Changes in Hepatocytes Following Decapitation of Chick Embryos
Authors: Dossel William E. 
Published: June 2020

Deposition of glycogen in embryonic chick livers begins during the 6th day of incubation, and continues until day 10 when the stored glycogen begins to disappear; depletion of reserves is most evident on day 12. On day 14, glycogen reappears and increases up to hatching. Hypophysectomy, by means of decapitation of the embryo at 33 hours, eliminates the period of depletion and prevents the onset of function in the embryonic endocrine organs as well. Glycogen deposition in hepatocytes of mammalian embryos occurs throughout intrauterine development, but can be interrupted by decapitation.This EM-based investigation provides morphological evidence supporting conclusions reached in earlier studies wherein glycogen content of livers from normal and decapitated 12 day-old embryos was assayed chemically (2). In livers of normal embryos, glycogen fields (i.e. accumulations of alpha and beta glycogen particles, related to agranular reticulum), appeared infrequently in hepatocytes throughout the liver (fig. 2) while in those of decapitated embryos, glycogen fields were abundant and characteristically composed of heavy accumulations of glycogen (fig. 3).
An Embedding Mixture for Electron Microscopic Technique Composed Solely of Maraglas, Araldite and Catalyst
Authors: McClendon Dale E. , Soloff Bernard L. 
Published: June 2020

We have found the following embedding mixture to be useful: Maraglas 655 - 70 ml., Araldite 502 - 30 ml., benzyldimethylamine - 3 ml. The tissue blocks are processed routinely through a 1:3 mixture of propylene oxide: complete embedding mixture. After overnight soaking in this mixture, the tissue blocks are allowed to sink for two hours in capsules loaded with fresh embedding mixture. The capsules are then processed four hours in a 37 - 40° C. oven, followed by three days in a 65° C. oven. This treatment yields a hard block that may be sectioned immediately upon cooling. The thin sections obtained will accept readily any of the staining solutions now available.Elimination of the anhydride hardener used normally in formulations of this sort does not affect the stability of thin sections under a 50 or 75 KV beam (figures 1 and 3), and sections supported on naked grids will withstand a 100 KV beam (figure 2) if carefully irradiated at low intensity before exposure to cross-over conditions.
Dislocations in Crystals
Authors: Geiss Roy H. 
Published: June 2020

Transmission electron microscopy is being utilized today in the study of many important problems in materials science and metallurgy. Such areas of research include annealing and heat treating, strengthening, phase transformations and crystal growth. In many of these studies it is important to assemble quantitative data on the dislocation structures existing in the material. These data might include the determination of Burgers vectors ḇ, glide planes and densities of the various dislocations. The purpose of this paper is to review briefly a few of the fundamentals used in obtaining such data.The contrast from a dislocation arises from the extra phase factor α=2πg · Ṟ found in the dynamical equations of electron diffraction, where g is the diffraction vector and Ṟ a vector describing the lattice distortion. For a screw dislocation Ṟ is proportional to ḇ and similarly near the glide plane of an edge dislocation.
Stacking Faults in Crystals
Authors: Gallagher P. C. J. 
Published: June 2020

Stacking faults are an important substructural feature of many materials, and have been widely studied in layer structures (e.g. talc) and in crystals with hexagonal and face centered cubic structure. Particular emphasis has been placed on the study of faulted defects in f.c.c. alloys, since the width of the band of fault between dissociated partial dislocations has a major influence on mechanical properties.Under conditions of elastic equilibrium the degree of dissociation reflects the balance of the repulsive force between the partials bounding the fault, and the attractive force associated with the need to minimize the energy arising from the misfits in stacking sequence. Examples of two of the faulted defects which can be used to determine this stacking fault energy, Υ, are shown in Fig. 1. Intrinsically faulted extended nodes (as at A) have been widely used to determine Υ, and examples will be shown in several Cu and Ag base alloys of differing stacking fault energy. The defect at B contains both extrinsic and intrinsic faulting, and readily enables determination of both extrinsic and intrinsic fault energies.
Microstructure of Quasi-Graphitic Carbons
Authors: Ban L. L. , Hess W. M. 
Published: June 2020

There are many types of carbon which have the same hexagonal atomic configuration as the layer planes of graphite. These include colloidal carbon blacks and the various cokes, chars and pyrolized fibers that are used commercially. The evaporated carbon films that are utilized in electron microscopy also fit into the same category. Where all these carbons differ from graphite is in their rotational disorder about the c-axis, larger c-spacing (e.g. about 3.5-3.8 Å as compared to 3.35 Å for graphite) and smaller crystallite size.The recent work of Heidenreich, Hess and Ban has demonstrated phase contrast imaging of the graphite lattice in heat treated carbon blacks using axial illumination. The c-spacing of 3.4 Å and numerous other aspects of microstructure were resolved in an ISAF carbon black heated at 2600-3000°C. This type of carbon has been proposed as a high resolution test specimen and as a means of calibrating magnification at high electron optical magnifications.
The Physics of Track Registration in Solids
Authors: Goland A. N. 
Published: June 2020

During the last ten years many observations of charged particle tracks in solids have been reported, and the utilization of this phenomenon in several fields of physics has grown apace. For example, Fleischer, Price, Walker, and their many collaborators have demonstrated the usefulness of track formation as a tool in nuclear physics, radiation dosimetry, geochronology and cosmic-ray physics. All the more reason, then, that one should endeavour to understand the basic mechanisms of track production in different kinds of solids. To do this, one must investigate the relationship between stopping power and track formation, the nature of the damaged region comprising a track, and the annealing behavior of the tracks. The electron microscope can furnish much of the necessary information provided that one is able to interpret the diffraction-contrast image of the tracks.Linear damage regions have been found both in thin films and in bulk samples. While tracks appear in metallic and nonmetallic thin films they have only been found in nonmetallic bulk solids. The latter include a wide variety of plastics, glasses and minerals.