bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cerebral Response to Ischemia Induced by the Embolism Model
Authors: Dodson R.F. , Chu L. W-F , Miyakawa Y. 
Published: June 2020

Two of the most reproducible animal models used to study cerebrovascular related changes involve the surgical occlusion of cerebral vessels or introduction of an embolic material into the cerebrovascular system. The present paper reports the ultrastructural evaluation of parenchymal and arterial response following embolization as compared with those changes induced by vascular clipping.Six adult baboons (papio anubis) were anesthetized and after surgical preparations for physiological monitoring were completed the embolus was injected through the left carotid catheter in accordance with the Molinari procedure (1) for selective segmental occlusion of the stem of the middle cerebral artery. After an interval of two hours during which continuous monitoring was carried out, the animals were prepared for ultrastructural evaluation by being subjected to whole body intracardiac perfusion. Specimens were taken from the frontal, parietal, occipital, and insular cortices, putamen globus pallidus, caudate nucleus as well as the areas of the artery, proximal, under and distal to the embolus.
Ultrastructural Analysis of the Salivary Glands of Gromphadorhina Portentosa (Schaum)
Authors: Dailey P.J. 
Published: June 2020

The structure of insect salivary glands has been extensively investigated during the past decade; however, none have attempted scanning electron microscopy (SEM) in ultrastructural examinations of these secretory organs. This study correlates fine structure by means of SEM cryofractography with that of thin-sectioned epoxy embedded material observed by means of transmission electron microscopy (TEM).Salivary glands of Gromphadorhina portentosa were excised and immediately submerged in cold (4°C) paraformaldehyde-glutaraldehyde fixative1 for 2 hr, washed and post-fixed in 1 per cent 0s04 in phosphosphate buffer (4°C for 2 hr). After ethanolic dehydration half of the samples were embedded in Epon 812 for TEM and half cryofractured and subsequently critical point dried for SEM. Dried specimens were mounted on aluminum stubs and coated with approximately 150 Å of gold in a cold sputtering apparatus.Figure 1 shows a cryofractured plane through a salivary acinus revealing topographical relief of secretory vesicles.
Morphological Characteristics of the Abdominal Paraganglia (Extraadrenal
Chromaffin Tissue) in the Rhesus Monkey
Authors: Mascorro J.A. , Klara P.M. , Yates R.D. 
Published: June 2020

The abdominal paraganglia represent extraadrenal chromaffin organs rich in catecholamines. Earlier work indicated that the organs degenerate soon after birth. More recently, however, investigators have reported the distribution and persistence of this extraadrenal chromaffin system in higher mammals, including man . The present work reports the occurrence of paraganglia in Rhesus monkeys and illustrates their ultrastruotural morphology.Two young adult Rhesus monkeys weighting approximately 6 kg. were anesthetized with Nembutal and perfused routinely with glutaraldehyde/ paraformaldehyde in 0.1M sodium cacodylate buffer. The paraganglia were stained and localized by immersing the retroperitoneal tissue block in glutaraldehyde/potassium diahromate and subsequently processed for electron microscopy via rapid dehydration and embedding.Potassium dichromate tracing produced a gross chromaffin reaction that initially identified the paraganglia as catecholamine containing organs. Correlative electron microscopic observations revealed that the organs were characterized by groups of cells whose cytoplasm contained conspicuous and voluminous accumulations of dense granules.
Serum-Induced Endocytic Vacuole in the Nonphagocytic Tetrahymena Pyriformis Strain NP1
Authors: Brenner L. J. , Osborne D. G. , Schumaker B. L. 
Published: June 2020

Tetrahymena pyriformis strains WH6, W, HSM, and GLC, after exposure to normal human serum, give rise to large membrane-bounded endocytic vacuoles, as visualized by transmission electron microscopy (TEM). These vacuoles do not resemble ordinary food vacuoles formed in the oral apparatus. Nor do they appear to be vacuoles containing protein concentrated from the serum: Albumin solutions induce a different type of vacuole (Brenner et al., 1976). The large bodies take a stain (PAS) that indicates the presence of polysaccharide. TEM micrographs show the presence of lipid in some of the large bodies. It is not yet known if these large body vacuoles are formed in the oral apparatus like food vacuoles or result from the fusion of pinocytic vacuoles.Although the mutant T. pyriformis strain, NP1, is unable to form a functional oral apparatus at 37° C and cannot form food vacuoles (Rasmussen and Orias, 1975), it multiplies in 2% proteose peptone medium supplemented with vitamins and heavy metal salts.
Platelet Adhesion to Native and Collagen Coupled Cuprophane: A Multispecies Comparative SEM Study
Authors: Lewis J.C. , Didisheim P. , Grabowski E.F. , Zollman P.E. 
Published: June 2020

Platelet adhesion to intact endothelium seldom occurs, but platelet response to subendothelial structures has been extensively studied and is recognized as being focal to hemostasis and thrombosis. Platelet adhesion to subendothelium in-vivo is generally followed by platelet-platelet cohesion (aggregation) and the platelet release reaction (1). Since thrombus formation and the platelet release reaction have been implicated in several secondary pathologic responses, precise characterization of these events is essential to an understanding of many disease processes.Previously we have demonstrated through the use of an in-vitro flow system that differences in platelet response to foreign surfaces exist among commonly studied animal species (2,3). The present report is an extension of these earlier studies and provides, through scanning microscopy, morphologic evidence for species related platelet responses.Blood for these studies was obtained by venipuncture from sheep, calves, baboons, dogs, rabbits and human volunteers following informed consent.
Scanning and Transmission Electron Microscopy of Endomentrium in Women Wearing TCu-380-A IUD 's
Authors: Gonzalez Angulo A. , Berlioz R. , Aznar R. 
Published: June 2020

Recent ultrastructural studies on endometrial tissues from women wearing copper, wire intrauterine devices have disclosed morphological evidence of impaired glycogen degradation and secretion resulting in interference with the viability of blastocysts. Reduced microapocrine secretion observed with the scanning electron microscope supports this (1). In addition, organelle modifications have been observed in the epithelial cells of these women. The changes are seen in biopsies taken in the proliferative phase of the cycle and consist of mitochondrial vacuolation and myelin figure formation. These modifications disappear in the secretory phase and therefore have been regarded as reversible (2).The aim of the present studies was to investigate surface epithelial changes as well as organelle modifications in relation to the site of contact with an IUD that releases greater amounts of copper. Endometrial tissue was obtained from the uterine cavity of four young women wearing TCu-380-A intrauterine contraceptive devices for 4-6 weeks.
Digital image enhancement for transmission electron microscopy
Authors: Goldfarb William , Frank Joachim 
Published: June 2020

The term image enhancement refers to those techniques which make pictures more interpretable. This definition implies that the best choice between enhancement processing procedures is closely tied to the subject matter and application of the images. We report here on the use in transmission electron microscopy of some image processing methods that we well know from their use in other fields of science and engineering. These methods can be divided into the two general categories of point mappings and spatial processing.In a point mapping process, density values of individual picture elements are transformed into new values by a function which is independent of the values of neighboring points. The most common motivation for point mapping is to use most effectively the available gray shades of the display device. Usually the density histogram of the image to be displayed is used to generate parameters for the mapping function.
Lead aspartate: a new en bloc stain for electron microscopy
Authors: Walton J.R. 
Published: June 2020

In electron microscopy, lead is the metal most widely used for enhancing specimen contrast. Lead citrate requires a pH of 12 to stain thin sections of epoxy-embedded material rapidly and intensively. However, this high alkalinity tends to leach out enzyme reaction products, making lead citrate unsuitable for many cytochemical studies. Substitution of the chelator aspartate for citrate allows staining to be carried out at pH 6 or 7 without apparent effect on cytochemical products. Moreover, due to the low, controlled level of free lead ions, contamination-free staining can be carried out en bloc, prior to dehydration and embedding. En bloc use of lead aspartate permits the grid-staining step to be bypassed, allowing samples to be examined immediately after thin-sectioning.Procedures. To prevent precipitation of lead salts, double- or glass-distilled H20 used in the stain and rinses should be boiled to drive off carbon dioxide and glassware should be carefully rinsed to remove any persisting traces of calcium ion.
Ultrastructural localization of drug binding sites
Authors: Hoff S.F. , Macinnis A.J. 
Published: June 2020

The need for a high resolution morphological method of identifying drug binding sites has been mentioned by several authors. Electron microscopic autoradiography may identify statisically an organelle as a drug binding site, but in practice has proven unreliable. This is primarily due to the tissue preparatory procedures used in conventional electron microscopy, which denature proteins and extract many proteins and lipid components from the tissue. As the drug binding sites are denatured and/or extracted, drugs are displaced from their “receptors.” Then the drugs are either extracted or attached to an anomolous binding site created by the preparatory procedure. Sjöstrand's minimal denaturation technique is based on a sound physical-chemical rationale and was modified slightly to accommodate the drug localization procedure used in this study.It was found after many experiments that phosphotungstic acid (PTA) at pH7 had the highest specificity for the drugs used in this study and the lowest affinity for biological structures.
OsO4-tannin-OsO4 method for transmission and scanning electron microscopy of biological specimens
Authors: Takahashi Gen 
Published: June 2020

Tissue blocks or slices about 1 mm in thickness were treated according to the following procedures both for transmission electron microscopy(SEM) and for scanning electron microscopy(SEM).[A] Primary Osmication(Fixation): 2%0s04 in 0.1 M Na-cacodylate buffer or Millo- nig's phosphate buffer(pH7.4) for 2 hrs at 4°C.[B] Postfixation and Mordanting: 2-4 % tannic acid—8(2-16)%glutaraldehyde in the buffer(pH6.8-7.0),for 1-40 hrs at 4°C.[C] Secondary Osmication(Staining): 2 %0s04 in the buffer(pH7.4)for 2 hrs at 4°C. Specimens after step C were rapidly dehydrated and embedded in Epon. Ultrathin sections were cut with diamond knives. Although sections without heavy metal staining could be observed with moderate contrast, they were stained briefly with lead solution for high magnification, because of sublimation of osmium by intense electron bombardment.
Ultrathin frozen sections of yeast without aldehyde prefixation
Authors: Böhm K. J. , Unger a. E. 
Published: June 2020

During the last years it was shown that also by means of cryo-ultra-microtomy a good preservation of substructural details of biological material was possible. However the specimen generally was prefixed in these cases with aldehydes.Preparing ultrathin frozen sections of chemically non-prefixed material commonly was linked up to considerable technical and manual expense and the results were not always satisfying. Furthermore, it seems to be impossible to carry out cytochemical investigations by means of treating sections of unfixed biological material with aqueous solutions.We therefore tried to overcome these difficulties by preparing yeast cells (S. cerevisiae) in the following manner:
Preparation, transfer and TEM observations of frozen hydrated muscle sections
Authors: Valdrè Ugo , Sjöström Michael , Edman Anne-Christine 
Published: June 2020

IntroductionIdeally, biological specimens should be studied in their native state. Frozen hydrated sections of tissues, which are unfixed, unstained and unembedded, are closer to this state than material prepared with conventional techniques. Very recently some efforts have been devoted to the practical problems related to this new approach. The present work describes the methodology we have adopted, the techniques developed and some of the results obtained from frozen hydrated sections of muscle fibres.Materials and methodsThe major operations before observation in the electron microscope were the preparation and transfer of the specimens.A. Specimen preparation. Fresh pieces of rabbit skeletal muscle were frozen by rapid immersion in liquid nitrogen chilled Freon 12. Cryo-sectioning was carried out in nitrogen atmosphere at -100°C, or lower, using an LKB CryoKit equipped with items from LKB Cryotools. The sections were manipulated onto pre-cooled grids which were then transferred to a press assembly. Teflon weights were used to ensure successful attachment of the sections to the grid.
Use of the STEM to obtain information from one level of a complex biological object
Authors: Furlong Deirdre 
Published: June 2020

Since the beam in the STEM is conical, a specimen is in focus to different precision at different levels. This feature can be used to probe specific levels of complex objects. This property of the STEM was demonstrated using negatively stained, 1% uranyl acetate, Herpes simplex virus nucleocapsids. The capsid is a hollow icosadeltahedral protein shell, 1000A outer diameter, surrounding the DNA containing core. Capsids containing cores were used to prevent collapse of the capsid. The 750Å thick core kept the opposite sides separated by a known distance.The grid was inserted into the microscope specimen side down. The microscope was focused on the carbon support film adjacent to the capsids. The beam was then shifted to the capsid and an image formed using the signal from the elastically scattered electrons was recorded. By using the signal from the elastically scattered electrons, which is predominantly due to the scattering from the negative stain, the scattering from the unstained core could be neglected. This method mainly gives an image of the negative stain surrounding the capsid.
Frozen ultrathin-sections for X-ray microanalysis of hard tissues
Authors: Ozawa H. , Yamada M. , Yamamoto T. , Takano Y. , Uchida T. 
Published: June 2020

In order to clarify more completely the morphophysiology of hard tissues, it is of foremost importance to determine the precise location and the elements of the extracellular and cellular mineral constituents. In the present study we have avoided the potential artefacts which may be introduced by the routine preparation for electron microscopy by adapting both anhydrous and frozen ultrathin-sectioning techniques to our fine structural and elemental analytical studies on hard tissues.Freshly dissected developing epiphyseal cartilage, bone and dentin of tooth germs from young postnatal rats have been prepared for the analytical electron microscopy(Hitachi H500H Total System equipped with Kevex 7000 X-ray Energy Spectrometry) by the methods of the ultracryo- microtomy(Christensen,1971) and the inert dehydration technique(Pease, 1966.,Landis et al, 1977).Nuclei, ribosomes, endoplasmic reticulum and a large number of dense intramitochondrial granules, 20 to 80nm in diameter, within the chondrocytes(Fig. 1a,b), osteoblasts(Fig.2) and odontoblasts(Fig.3) were observed in unfixed, unstained frozen ultrathin-sections, obtained with dry knives in the temperature range of -60 to -80°C, and also in unstained sections treated anhydrously by ethylene glycol.
Increase in the intracellular concentration of Na and CI as hepatocytes transform from the normal to the neoplastic state: an electron probe microanalysis study
Authors: Cameron Ivan L. , Smith Nancy R. , Pool Thomas B. 
Published: June 2020

We have tested the hypothesis that the intracellular concentrations of various elements are involved in control of cell proliferation. Electron probe microanalysis using energy dispersive X-ray spectroscopy was used to test this hypothesis.Briefly, unfixed tissues were rapidly frozen in liquified propane, then sectioned at 4ym and cryosorbed. Ribbons of dry sections were transferred to a polished carbon planchet with a 2mm hole drilled in the center and the sections to be analyzed were suspended over the hole. The tissues were electron probed in a scanning microscope. Suspending the tissue over the hole eliminated continuum counts due to substrate and allowed measurement of Na and Mg. The standard conditions during analysis were: accelerating voltage = 15 KV, count time = 100 sec, working distance = 39 mm, detector distance = 1.5 cm, raster size = 1.5 or 2 cm2 (selected area mode), magnification = 8000X, specimen current = 1.0-1.5 x 10-10 amps.
X-ray microanalysis of calcium around the membrane of platelets
Authors: Daimon T. , Mizuhira V. 
Published: June 2020

Since the function of platelets is linked to an increase in the cytoplasmic calcium level, it would be of great interest to establish its subcellular distribution. Recently we found the existence of the surface connected membrane system (SCS) in the chicken thrombocyte(1,2) and succeeded in detecting calcium on the membrane of the SCS using ultrahistochemical methods in combination with an electron probe X-ray microanalyzer(1). This study is undertaken to demonstrate calcium accumulation around the membrane of the SCS of mammalian platelets.Ultrahistochemistry: Human platelet rich buffy coat was fixed in the potassium antimonate-OsO4. method or in the potassium oxalate-glutaraldehyde method without post-fixation with OsO4. After incubation, specimens were dehydrated with ascending concentrations of ethyl alcohol and embedded in Epon 812.
Freeze-fracture, freeze-etch complementary pairs of virus-infected cells reveal value of etching even when relatively high concentrations of cryoprotectants are used
Authors: Steere Russell L. , Erbe Eric F. 
Published: June 2020

It has been assumed by many involved in freeze-etch or freeze-fracture studies that it would be useless to etch specimens which were cryoprotected by more than 15% glycerol. We presumed that the amount of cryoprotective material exposed at the surface would serve as a contaminating layer and prevent the visualization of fine details. Recent unexpected freeze-etch results indicated that it would be useful to compare complementary replicas in which one-half of the frozen-fractured specimen would be shadowed and replicated immediately after fracturing whereas the complement would be etched at -98°C for 1 to 10 minutes before being shadowed and replicated.Standard complementary replica holders (Steere, 1973) with hinges removed were used for this study. Specimens consisting of unfixed virus-infected plant tissue infiltrated with 0.05 M phosphate buffer or distilled water were used without cryoprotectant. Some were permitted to settle through gradients to the desired concentrations of different cryoprotectants.
Lipidic intramembraneous particles
Authors: Ververgaert P.H.J.Th. , Verkleij A.J. 
Published: June 2020

Freeze-fracturing splits membranes into 2 halves, thus allowing an examination of the membranes interior. The 5-10 nm particles visible on both monolayers are widely assumed to be proteinaceous in nature.Most membranes do not reveal impressions complementary to particles on the opposite face. Even when it is considered that shadowing, contamination or fracturing itself might obscure complementary pits, there is no satisfactory explanation why under similar physical circumstances matching halves of other membranes can be visualized. A prominent example of uncomplementarity is found in the erythrocyte membrane. It is well established that band III protein and possibly glycophorln represent these uncomplementary structures.On the other hand a number of experiments has made us aware that particles of the Eeoheriohia ooli outer membrane are basically constructed of lipid micels (i.e., lipo- polysaccharlde). These particles have complementary Impressions on the opposite face (Fig. 1).
Structural rearrangements studied by topographical mapping of antigenic sites by electron microscopy
Authors: Kistler J. , Aebi U. , Ten Heggeler B. , Onorato L. , Showe M. 
Published: June 2020

The maturation of complex viruses like bacteriophages P22, λ and T4 is often regarded as a model system for biological regulatory processes at the molecular level. The visualisation and characterisation of structural rearrangements which occur on the capsid or its related protein assemblies provide information on such processes. In the case of T4, a 16% linear expansion of the capsid is associated with the limited proteolysis of the major capsid protein P23 (MW=58000) to P23* (MW=47000). Image processing on micrographs of negatively stained T4 polyheads (Fig. 1a,d), which are aberrant capsid related cylinders, revealed an altered stain excluding pattern after the expansion (Fig. 1b,e) (Steven et al., 1976; Laemmli et al., 1976).In order to learn more about the extent and the nature of this structural rearrangement we have followed two procedures: Freeze-drying and shadowing to look at the surface topographies rather than only projection densities obtained from specimen prepared by negative staining (Kistler et al., 1977).
Troponin in embryonic chick skeletal muscle cell in vitro: an immunoelectron microscopic study
Authors: Shimada Yutaka , Obinata Takashi 
Published: June 2020

In developing skeletal muscle, myosin and actin are synthesized and polymerized into filamentous forms, thick and thin filaments, respectively. These myofilaments of two varieties have been shown, with the use of "decoration with heavy meromyosin" technique, to be arranged at the right polarity and spatial position as those seen in mature myofibrils from the initial phases of myofibrillogenesis. The question arises as to whether regulatory proteins are distributed along embryonic thin filaments from such early stages of development. In order to clarify this problem, the fine structural localization of troponin was investigated by the use of immunoelectron microscopy.Troponin and its components (troponin C [TN-C], I [TN-I] and T [TN-T]) were prepared from adult chicken breast muscles. Rabbit antisera against each of these troponin components were prepared. The serum was fractioned by ethanol or ammonium sulphate fractionation. Myogenic cells from 12-day chick embryonic thigh muscles were grown in monolayer and, after 2-8 days in vitro, the cultures were treated as follows: (i) They were immersed in 50% glycerol. The suspension of separated thin filaments was obtained by gentle homogenizing the cells.