bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viewing specimens in air by reflected SEM
Authors: Ryoji Takahashi  
Published: June 2020

Specimens in air can be observed with high resolution by reflected SEM using an environmental capsule which supports specimens under its window. To improve the imaging of specimens underlying the window, however, the effect of the window nad to be clearly investigated.The fundamental of reflected SEM is to detect mirror-reflected electrons from the specimen. Fig.1-A shows a schematic expression of detecting reflected electrons (RE) from a simple form of specimen placed in vacuo. In this case, the incident electrons are reflected to horizontal(low-angle) and vertical (high-angle) directions. In general, the reflectivity of electron of a material is increased as the incidence angle is increased), accordingly, the low-angle RE provide the major contribution to the formation of the image of the specimen. Moreover, it is noted that low-angle RE provide contrasts due to the surface of the specimen, but high-angle RE provide contrasts due to the material or the mass of the bulk.
Quantitative high resolution light and EM autoradiography of fluorophosphate-esterase in developing mouse liver
Authors: Budd C. 
Published: June 2020

The distribution and concentration of fluorophosphate reactive (FPR) esterases in the liver of developing and adult mice was determined quantitatively from light and electron microscope autoradiograms of liver reacted with 3H - diisopropylfluorophosphate (3H-DFP) an irreversible inhibitor of carboxylesterases.The majority of labeled cells in the liver of 2, 8, 14 and 28- day-old mice and in adult mice (60-180 days old) were hepatocytes, but in the liver from 2-day-old mice and to a lesser extent 8-day-old mice, the autoradiographic silver grains were also concentrated over granulocytes of the intrahepatic hemopoietic population.Quantitative measurements of grain density (developed silver grains/unit area) in light microscope autoradiograms revealed an increase in the predominantly cytoplasmic concentration of FPR esterase sites in hepatocytes from 137o of the adult concentration in 2-day-old mice, to 497, and 78% of the adult concentration in 8- and 14-day-old animals, respectively.
Two- or three-way observations of the identical cell elements within the same sections by LM, TEM and/or SEM
Authors: Watari Nakazo , Hotta Yasuaki , Mabuchi Yoshio 
Published: June 2020

It is very useful if we can observe the identical cell elements within the same sections by light microscopy (LM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM) sequentially, because, the cell fine structure can not be indicated by LM, while the color is; on the other hand, the cell fine structure can be very easily observed by EM, although its color properties may not. However, there is one problem in that LM requires thick sections of over 1 μm, while EM needs very thin sections of under 100 nm. Recently, we have developed a new method to observe the same cell elements within the same plastic sections using both light and transmission (conventional or high-voltage) electron microscopes.In this paper, we have developed two new observation methods for the identical cell elements within the same sections, both plastic-embedded and paraffin-embedded, using light microscopy, transmission electron microscopy and/or scanning electron microscopy (Fig. 1).
Improved freeze-etching of difficult specimens
Authors: Robards A.W. , Umrath W. 
Published: June 2020

Freeze-etching is now a well established method of biological electron microscopy but, despite its outstanding success in many areas, it still suffers from severe technical limitations when used to study heterogeneous or otherwise intractable tissues. These limitations are mainly related to the difficulty of retaining an intact replica during dissolution of the organic debris, and can be especially acute when dealing with structures composed of many different cell types, or where there are sharp boundaries between hard and soft parts of the specimen. Such difficulties have been described in more detail elsewhere, but they usually have the result that the replica breaks up into small pieces during thawing or cleaning so that it is impossible to locate specific areas of interest.One potential method of improving the retention of intact replicas is to provide an additional supporting layer that can be removed once the organic material has been cleaned away.
Observation of fine structure in casein micelles by means of high resolution electron microscopy
Authors: Kimura Toshiaki , Fukushima Masayoshi , Furuichi Eiichi , Adachi Koichi , Hojou Kiichi , Kanaya Koichi 
Published: June 2020

For fabrication purpose an argon ion beam is produced in ion source, accelerated through a high vacuum chamber and directed with final focusing to impinge on a target.In the biological field we have utilized ion beam sputtering to examine the sub-micelles structure of casein micelles in demineralized skimmed milk. For this purpose we employed sputtering to etch the samples and to shadow the specimens. Casein micelles are remarkably stable both in fresh milk and in properly processed concentrated milk products where they are aggregated by calcium phosphate bonds.Raw skimmed milk, electrodialysis demineralized by using ion exchange membranes were examined. The samples were fixed in 2.45%cacodylate buffered glutaraldehyde at pH 5.9-6.8 for 2 -4 hr and post-fixed in 2% cacodylate buffered osmium tetroxide at the same pH for 2 hr. After being diluted with distilled water, the samples were picked up on microgrids.
Behaviour of the nucleolar fibrillar centres in reproducing plant cells
Authors: Medina F. J. , Rodrlguez-Garcia M.I. , Risueño M.C. 
Published: June 2020

The nucleolar fibrillar centres have been described recently in animal cells and in meristematic plant cells, as a constant component of the nucleolus, corresponding to the nucleolar organizing region (NOR).In order to find out if the nucleolar fibrillar centres represent a general nucleolar component, we have studied the nucleolus in several reproducing plant tissues (megasporocytes and megaspore from Pissum sativum and mono and bicellulate pollen grains from Allium cepa and Scilla non-scripta). In these cells the fibrillar centres have a different morphological behaviour during their development.Female reproductive tissueImmediately before the meiosis, the megasporocyte nucleolus has a compact and rounded aspect. The fibrillar part occupies the centre and the granular part the periphery. Inside the fibrillar part, there are clear areas containing in some cases, a dark core immersed in a grey fibrillar material (Fig. 1). A similar structure was described recently in meristematic cells. In the pachytene stage, when the nucleolus is joined to the nuclear envelope, the fibrillar centres are made up of a homogeneous fibrillar material with a medium electron density.
The ionic strength dependence of chromatin folding
Authors: Thoma F. , Koller TH. 
Published: June 2020

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.
Scanning transmission electron microscopy of unstained nucleosomes
Authors: Usala S. , Isaacson M. , Martin T. 
Published: June 2020

Ultrastructural investigations of chromatin have centered on apparent subunits of chromatin fibers called nucleosomes, whose basic elements are 140-200 base pairs of DNA and eight histone molecules. Conventional transmission electron microscopy (CTEM) analyses of nucleosomes have dealt with stained particles or crystalline arrays and have shown the basic particle to be somewhat circular in shape of about 100Å in diameter. Coupled with diffraction studies, the models seem to indicate a disk shaped object with all the DNA surrounding a protein core. However, due to the difficulties of conventional staining techniques and the inability to grow large crystals, resolution has been limited to about 20Å.The ability of the STEM to provide a variety of different modes of contrast should be able to surmount some of the difficulties associated with conventional electron microscopy. In fact, early work with the STEM also indicated disk shaped nucleosome particles. The ability to efficiently form images of unstained particles using either elastically or inelastically scattered electrons allows us to directly obtain the mass density distribution of the particles at resolutions near 5Å.
Contrast from epitaxially sandwiched macromolecules
Authors: Talianker M. , Brandon D.G. 
Published: June 2020

A new specimen preparation technique for visualizing macromolecules by conventional transmission electron microscopy has been developed. In this technique the biopolymer-molecule is embedded in a thin monocrystalline gold foil. Such embedding can be performed in the following way: the biopolymer is deposited on an epitaxially-grown thin single-crystal gold film. The molecule is then occluded by further epitaxial growth. In such an epitaxial sandwich an occluded molecule is expected to behave as a crystal-lattice defect and give rise to contrast in the electron microscope.The resolution of the method should be limited only by the precision with which the epitaxially grown gold reflects the details of the molecular structure and, in favorable cases, can approach the lattice resolution limit.In order to estimate the strength of the contrast due to the void-effect arising from occlusion of the DNA-molecule in a gold crystal some calculations were performed.
Study of fetal intestinal microperoxisomes in thick sections
Authors: calvert R. 
Published: June 2020

Differentiation of microperoxisomes has been studied in Swiss ICR mouse embryos from the 16th day of fetal life till birth. After fixation with glutaraldehyde, 40μm thick sections of duodenum and of ileum were incubated at pH 9.7 according to the method described by Novikoff et al. (1972), during three hours. Catalase activity was also measured by a spectrophotometric method (Lück, 1965). Thick Epon sections (0.4μm) were used to study the peculiar morphology of microperoxisomes during the last day of gestation.The number of microperoxisomes increases considerably in the duodenal enterocytes at 17 days; the highest concentration of microperoxisomes is attained at 18 days, after which time their number remains stable. Biochemically, catalase activity is barely detected at 15 days in the first half of the small intestine and afterwards increases steadily up to one day after birth. In the ileum the increase in microperoxisome number is far less important than in the duodenal enterocytes.
Observations on globular intranuclear inclusions in the midgut cells of an insect
Authors: Thomas D. , Gouranton J. 
Published: June 2020

Most nuclei of the midgut cells of Carausius morosus contain eosinophilic inclusions.
Histochemical observations on paraffin sections revealed that the inclusions were never stained by the Feulgen method and were not sudanophilic. They were lightly stained by the PAS method. No calcium could be detected in them although numerous calcified concretions were found in the cytoplasm.In electron microscopy the inclusions appeared as roughly spherical electron-dense bodies, different in size, usually 0.1-2 μ in diameter. These spherules were sometimes seen singly but generally in clusters (Fig. 1). In some instances several dense globules coalesced to form a lobulated mass. The inclusions were never surrounded by a membrane. Around the globules and in the space between them appeared a slightly electron- dense granular material which sometimes adhered to their margins. No direct relation was observed between the inclusion and the nucleolus.The results of cytochemical methods on thin sections were in agreement with the findings in light microscopy since carbohydrates could be detected in the inclusions by the periodic acid-thiocarbohydrazide-silver method and no DNA was found in them with the Schiff-thallium method.
Cytochemical analysis of mast cell granules after poly-dl-lysine action
Authors: Courtoy R. , Simar L.J. , Christophe J. 
Published: June 2020

Several chemical compounds induce amine liberation from mast cells but do not necessarily provoque the granule expulsion. For example, poly-dl-lysine induces modifications of the cellular membrane permeability which promotes ion exchange at the level of mast cell granules. Few of them are expulsed but the majority remains in the cytoplasm and appears less dense to the electrons. A cytochemical analysis has been performed to determine the composition of these granules after the polylysine action.We have previously reported that it was possible to demonstrate polyanions on epon thin sections using a cetylpyridinium ferric thiocyanate method. Organic bases are selectively stained with cobalt thiocyanate and the sulfhydryle groups are characterized with a silver methenamine reaction. These techniques permit to reveal the mast cell granule constituents, i.e. heparin, biogenic amines and basic proteins.
The crystalline structure in the membranous preparations of mitochondrial complex III
Authors: Asai Junpei 
Published: June 2020

In 1962 Hatefi and his collegues showed biochemically the isolation of four complexes of the electron transfer chain from the mitochondria and the reconstitution of a complete electron transfer chain through re-association of the individual complexes. Tzagoloff et al demonstrated ultrastructurally the membrane formation by either single complex or a mixture of complexs. However, there have been a few direct ultrastructural studies in the molecular architecture of mitochondrial inner membrane. To understand the organization of Complex III (QH2-cytochrome c reductase) in the membrane, the membranes made from this complex under various conditions were examined ultrastructurally in the present study.Complex III was purified from beef heart mitochondria by the method of Heatefi et al as modified by Rieske et al. For the preparations of membrane formation, some samples of the purified complex suspended in the solution contained 0.66 M sucrose were diluted with 100 volumes of the mixture of 0.25 M in sucrose and 0.01 M in Tris-HCl (sucrose-Tris), pH 8.0 and were incubated for 30 min. at 0-4°C.
Interaction of glial and astrocytoma c6 cells in monolayer culture
Authors: Wong Y.C. , Garber B.B. 
Published: June 2020

The separation and culture of the glial monolayer cells have been reported. Using the differential attachment method and treatment with cytosine arabinoside (Ara-C) followed by subculturing, a very pure population of glial cells can be achieved. This paper involves the study of the interaction of the glial cells with a tumour cell line C6 astrocytoma (American Type Cell) derived from the mouse brain. In addition the differences in surface morphology of the glial cells and C6 astrocytoma are also included.The C6 cells were cultured in a plastic culture disk using F-10 medium supplemented with 15% fetal bovine serum, 2.5% horse serum, and 1% penicillin and streptomycin (Microbiological Association). The culture medium was changed every 3-4 days. Pure glial cell cultures were prepared as reported, and confluence monolayer glial cells were obtained about one month after subculturing of the primary glial cultures.
Ultrastructural and chemical evidences of heterogeneity and hormone dependence of certain glycocalyces
Authors: Monis B. , Lis D. , Parlanti I. , Eynard A. R. , Valentich M. A. , Rovasio R. A. , Boldint C. , Paschini A. 
Published: June 2020

We are gathering evidences which indicate ultrastructural variations and chemical heterogeneity of certain glycocalyces as well as hormone dependence of some of them. Thus, in the lumenal glycocalyx of renal collecting tubules of the guinea-pig granular and filamentous structures were seen (1, fig. 1). By isolation, chemical analysis and cellulose acetate electrophoresis in various buffers of tubular membrane material, glycopeptides and glycosaminoglycans were identified (fig. 2).Guinea-pig and rat transitional epithelium of urinary tract showed a filamentous lumenal glycocalyx demonstrable with ruthenium red (fig. 3) but which only in part stained with concanavalin A. Chemical and electrophoretic data indicated that urothelium contains glycoproteins, glycosaminoglycans and glycolipids.The glycocalyx of the fat globule membrane of milk of several species has a granular appearance as shown by cationic dyes and by concanavalin A (2, 3, fig. 4 and 5). Also, several glycoproteins were isolated and identified on polyacrilamide gel electrophoresis (fig. 6). Glycosaminoglycans and certain glycolipids such as sulfatides were chemically identified in this glycocalyx.
Sem visualization of surface charges as a new method
Authors: Veres I. 
Published: June 2020

The transmissional electronoptical measurement of the electrical surface charges of biomembranes was a part of the new trend of research work “ultramicrobiophisics” introduced by the Author.Recently we succeeded in effecting a quasi three - dimensional visualization by using a modified SEM-technique combined with a colloid labeling method, working as guest - professor at the Uni. of Minnesota, USA. This proved to be a substantial progress: we could study in this way the dispersion of the coulombic forces on entire cell surfaces in contrast with ultrathin sectioning of labeled cells.Objects are prefixed using 1% solution of Glutar- Aldehyde, then they are labeled with positively or negatively charged colloid AgI solution, newly prepared by using o, o2 M solutions of AgNO3and KI. Therafter the labeled and washed objects are dried in a series of ethanol and twice in Dimethyl- Propilenoxide under centrifugation. The dispersion of the surface charges is measured by counting the adsorbed sol particles on the SEM micrograph and / or using microanalyzer resp. electron microprobe.
A new insect virus?
Authors: Letendre Michel , Lu Jean , Beaulieu Jacques , Bédard Guy 
Published: June 2020

A new virus—like particle has been observed in haemolymph from Pseudaletia unipuncta (Haw. )A high degree of mortality was noticed on an epidemic population of the true army worm, Pseudaletia unipuncta (Haw. ) in La Sarre, Abitibi, Quebec.In a first approach, a few specimens of larvae were collected. Haemolymph was extracted for a preliminary observation under the electron microscope. The preparation technique was very simple. A 400 mesh formvar grid was put on top of a drop of haemolymph for a few seconds and was negatively stained with PTA 2% pH 7. 00.A huge number of spherical particles ( a count of nearly 2, 000 on one grid quadrat) were observed in this way.Conscious of our inexperience with insect viruses we consulted three specialists in comparative virology:
Lomasome biogenesis and function inarmillaria mellea
Authors: Behboodi B. Ch. 
Published: June 2020

IntroductionBorder bodies or lomasomes are the aggregation of membranes and vesicles located between the plasma membrane and the cell wall of many fungi, algae, and higher plants. Despite extensive investigation, the biogenesis as well as function of these structures is not yet known. The purpose of this investigation was to describe the biogenesis of lomasomes in Armillaria mellea and to provide some observations on their function related to cell wall formation.Materials and MethodsVarious thalli of fungi as non-aggregated hyphae, pseudosclerotes, rhizomorphs and carpophores were grown either on orange or synthetic media as described previously. The thalli were fixed in 4% glutaraldehyde buffered with 0.1 M sodium cacodylate (pH 7.4), and 0.15 M sucrose for 4 h at 4°. They were postfixed with 1% osmium tetroxide in the same buffer for 2 h at 4° and embedded in Epon according to the Luft procedure. Cytochemical studies using thiocarbohydrazide-silver proteinate were performed according the Thiéry.
Complex electron microscopic study of structural and functional arrangement of chloroplast membranes
Authors: Tageeva S. V. , Popov V. I. , Allakhverdov B. L. 
Published: June 2020

Supramolecular arrangement of photosynthetic membranes of cyanobacteria and higher plant chloroplasts has been studied by means of electron microscopy, ultrathin sections, freeze-substitution and freeze-fracture technique. Principal similarity between the structural arrangement of the photosynthetic apparatus of higher plants and cyanobacteria has been established. It consists in a continuity of the photosynthetic membranes and their relation to the inner membrane of chloroplast envelope or to plasmalemma in the cyanobacteria; in the ability of thylakoids stacking; in an asymmetrical distribution of principal number and sizes on complemetary faces of membrane fractures revealed by the freeze-fracture (Fig. 1a, b, c, d; Fig. 2a).A comparative analysis of particle morphology was carried out by means of angular and circular shading of fracture faces with Pt, “direct” and “inverse” replicas being obtained.
Ultrastructural aspects of the first postmeiotic mitosis and cytokinesis in the pollen grain ofallium cepal
Authors: Rodriguez-Garcia M.I. , Risueno M.C. 
Published: June 2020

This report deals with research work on first pollen grain mitosis and the formation of vegetative and generative cells in Allium cepa L.The haploid nucleus of young microspores has a long interphase period which starts when the microspores begin to free themselves from the surrounding special callose wall and finishes when a central vacuole is formed in their cytoplasm. The pollen wall (Exine and Intine) is formed during this period.Before the mitosis, a large vacuole is formed in the cytoplasm. The microspore nucleus that previously occupied a central position in the cell can now be found in a lateral position generally on the opposite side of the porus. At this moment the nucleus enters prophase and the mitotic division takes place. This is characterized by the formation of an asymmetric spindle and as a result two unequal daughter cells are formed (Fig. 1) : the vegetative cell is larger and its nucleus remains near the centre of the pollen grain, whilst the generative cell is smaller and at the beginning lies close to the pollen wall (Fig. 2, 3).
The ultrastructure of modified root-tip cells induced by the feeding of an ectoparasitic nematode
Authors: Lehmann Heiner , Wyss Urs 
Published: June 2020

It is well known that sedentary endoparasitic root nematodes (Fam. Heteroderidae) induce highly modified ‘nurse cells’ in their host plants. The induction and maintenance of such cells is a precondition for the reproduction of these nematodes. The modified cells, generally called giant cells, are multinucleate, rich in cytoplasm and, concerning cell wall structure, show characteristic features of transfer cells.In contrast to sedentary endoparasitic nematodes, ectoparasitic nematodes are not known to induce giant cells. However, it was recently shown that root-tip feeding sites of the ectoparasite Xiphinema index contain enlarged multinucleate cells in the two host plants examined (Vitis vinifera and Ficus carica). Root-tips of Ficus carica seedlings - grown in aseptic agar culture at low light intensity - start to swell about 10 h after the first attack by this nematode and gradually become transformed into a proliferating gall as long as the parasite continues its feeding activities.