bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pitfalls in Optical Filtering Techniques
Authors: Haydon Glen B. , Scales Donald J. 
Published: June 2020

It is now a popular procedure to apply optical filtering techniques to noisy electron micrographs of a variety of biological structures in order to improve image quality. However, a point overlooked by many investigators is that in using a spatial filter to enhance a micrograph, we are imposing an assumed model of the structure upon the image.According to Abbe's theory of image formation, an image in an optical system is the result of a double diffraction process. The image can be altered by inserting a filter in the back focal plane of the imaging lens.
Three Methods For the Preparation of High-Resolution Freeze-Dried Specimens in a Freeze-Etch Module
Authors: Steere Russell L. 
Published: June 2020

The first satisfactory freeze-dry procedure for electron microscopy was described by Williams. An improvement permitted the shadowing of specimens in the same system where freeze-drying was accomplished. Our freeze- etch module is ideal also for the preparation of freeze-dry specimens and high-resolution specimens have been prepared by the 3 different procedures.Procedure #1: A particulate suspension in distilled water or a volatile buffer is sprayed onto a thin mica sheet held down with high vacuum grease to a flat-topped specimen cap clamped onto the specimen stage (all pre-cooled to −150°C). Freeze-drying is accomplished with a vacuum of 2 × 10−6 Torr and specimen temperature of −98 to −75° (approximately 15 min).
The Hardness of Epoxy Embedding Compounds For Ultrathin Sectioning
Authors: Poolsawat Samuel S. 
Published: June 2020

Although there have been numerous studies concerning a variety of procedures for epoxy compounding, no report on optimal hardness for ultrathin sectioning has been defined. The most widely used compounding media (Epon, Araldite-Epon, and others) do not always obtain optimal hardness and may, infact, vary considerably. For example, Epon and Araldite-Epon blocks do not section well, especially with glass knives (Figs. 1,2,3, and 4).Physical properties of a series of cured epoxy resins were measured according to ASTM test proceduresor according to methods designed for block testing (Fig. 6). Cured epoxy resin hardness can be precisely controlled systematically and can be measured by using Shore D Hardness Test Instrument.
Wide Field Electron Microscopy: The Sublimation of Epon-Araldite
Authors: Yang Grace C. H. , Morrison A. B. 
Published: June 2020

To emphasize the best feature of this technique, the term “wide field” is used throughout the text instead of the usual “scanning range magnification” or “low magnification”. Wide field electron microscopy presently is not being fully utilized in many laboratories, perhaps because the quality of the electron micrograph obtained is not worthy of the supposedly long and tedious specimen preparation. We report here that the quality of the wide field electron micrograph can be greatly enhanced by using the old “sublimation trick” for the methacrylate section.Two kinds of embedment formula were tested: Luft's Epon (mixture A:B= 6;4), and Mollenhauer's Epon-Araldite mixture 1. Only the Epon-Araldite showed the “foot print” of the electron beam (fig. 1).
Effect of ADH on Rat Renal Papilla, an Ultrastructural and Cytochemical Study
Authors: Sun C. N. , White H. J. , Towbin E. J. 
Published: June 2020

Diabetes insipidus and compulsive water drinking are representative of two categories of antidiuretic hormone (ADH) lack. We studied a strain of rats with congenital diabetes insipidus homozygote (DI) and normal rats on an isocaloric fortified dilute milk diet. In both cases, the collecting tubules could not concentrate urine. Special staining techniques, Alcian Blue-PAS for light microscopy and lanthanum nitrate for electron microscopy were used to demonstrate the changes in interstitial mucopolysaccharides (MPS). The lanthanum staining was done according to the method of Khan and Overton.Electron microscopy shows cytoplasmic lesions, vacules, swelling and degenerating mitochondria and intercellular spaces (IS) in the collecting tubule cells in DI and rats on milk diet.
A Scanning Electron Microscope Study of Isolated Guard Cells
Authors: Dayanandan P. , Kaufman P. B. 
Published: June 2020

A three dimensional appreciation of the guard cell morphology coupled with ultrastjuctural studies should lead to a better understanding of their still obscure dynamics of movement. We have found the SEM of great value not only in studies of the surface details of stomata but also in resolving the structures and relationships that exist between the guard and subsidiary cells. We now report the isolation and SEM studies of guard cells from nine genera of plants.Guard cells were isolated from the following plants: Psilotum nudum, four species of Equisetum, Cycas revoluta, Ceratozamia sp., Pinus sylvestris, Ephedra cochuma, Welwitschia mirabilis, Euphorbia tirucalli and Allium cepa.
Ultrastructural Localization of Phycocyanin in the Acidophilic, Thermophilic Alga, Cyanidium Caldarium
Authors: Edwards M. R. , Mainwaring J. D. 
Published: June 2020

Although the general ultrastructure of Cyanidium caldarium, an acidophilic, thermophilic alga of questionable taxonomic rank, has been extensively studied (see review of literature in reference 1), some peculiar ultrastructural features of the chloroplast of this alga have not been noted by other investigators.Cells were collected and prepared for thin sections at the Yellowstone National Park and were also grown in laboratory cultures (45-52°C; pH 2-5). Fixation (glutaraldehyde-osmium), dehydration (ethanol), and embedding (Epon 812) were accomplished by standard methods. Replicas of frozenfracture d- etched cells were obtained in a Balzers apparatus. In addition, cells were examined after disruption in a French Press.
Review of the Radiation Damage Problem of Organic Specimens in Electron Microscopy
Authors: Reimer L. 
Published: June 2020

Most information about a specimen is obtained by elastic scattering of electrons, but one cannot avoid inelastic scattering and therefore radiation damage by ionisation as a primary process of damage. This damage is a dose effect, being proportional to the product of lectron current density j and the irradiation time t in Coul.cm−2as long as there is a negligible heating of the specimen.Therefore one has to determine the dose needed to produce secondary damage processes, which can be measured quantitatively by a chemical or physical effect in the thin specimen. The survival of micro-organisms or the decrease of photoconductivity and cathodoluminescence are such effects needing very small doses (see table).
Electron Radiation Damage on thin Films of Phenylalanine
Authors: Lin P. S. D. 
Published: June 2020

Consecutive observation of the mass loss and change in electron energy loss spectra are being carried on In a simple field emission scanning mlcroscope. The specimens are prepared by slow sublimation onto thin carbon films on a copper grid.For mass loss measurement, unscattered electrons Nun are counted, W'lich Is related to Incident beam Intensity N0 by Nun = N0 exp(-(ai+ae)t), where tIs a specimen thickness, ae, ai the Inverse of the mean free path for elastic and Inelastic scattering, respectively. With 20 KeV and 12 mrad aperture angle, most of the elastically scattered electrons are stopped by the aperture. The Inelastically scattered electrons arefll tered by the spectrometer.
Mechanism of Tyramine Effects On Norepinephrine Pools in Purified Adrenergic Vesicles: Biochemical and Ultrastructural Correlates
Authors: Klein R. L. , Yen S. S. , Chen-Yen S. H. , Thureson-Klein Å. 
Published: June 2020

Improved methods and the ability to obtain bovine splenic nerves with a minimal post-mortem delay permit the routine preparation of highly pure, 750Å, dense-core vesicles. In addition to yielding a much greater vesicle norepinephrine(NE):protein ratio, two NE pools were revealed for the first timel. At 30°C the vesicles lost 20% of their NE from a fast pool, T 1/2 = 4-5 min, apparently insensitive to ATP. The remaining NE was lost with T 1/2 = 35 min in the presence of ATP and 3 times faster without ATP.Vesicles were incubated with 1μg 3H-1-NE/ml or together with equimolar 14C-tyramine(TA). With TA added, the half-lives for net NE loss from both pools are decreased ∼ 30%(Fig. 1). The initial peak for 14C-TA is reached and reversed within the first 15 min(Fig. 2).
Ultrastructure and Drug Metabolism in the Developing Guinea Pig
Authors: Kuenzig W. , Boublik M. , Kamm J.J. , Burns J.J. 
Published: June 2020

Unlike a variety of other animal species, such as the rabbit, mouse or rat, the guinea pig has a relatively long gestation period and is a more fully developed animal at birth. Kuenzig et al. reported that drug metabolic activity which increases very slowly during fetal life, increases rapidly after birth. Hepatocytes of a 3-day old neonate metabolize drugs and reduce cytochrome P-450 at a rate comparable to that observed in the adult animal. Moreover the administration of drugs like phenobarbital to pregnant guinea pigs increases the microsomal mixed function oxidase activity already in the fetus.Drug metabolic activity is, generally, localized within the smooth endoplasmic reticulum (SER) of the hepatocyte.
Cytopathologic Effects of Adriamycin on Murine Cardiac Tissue
Authors: Liss Robert H. , Ifrim Ina 
Published: June 2020

Adriamycin and daunomycin are structurally related antibiotics used in the clinical management of neoplastic diseases. However, adriamycin has exhibited a higher therapeutic index against a wide variety of tumors and thus is currently of greater clinical interest. Like daunomycin, adriamycin produces a delayed, irreversible, lethal cardiac toxicity. The present study was initiated to compare the cytopathology of cardiac tissue from adriamycin-treated mice with previous ultrastructural observations of myocardium from daunomycin-treated rodents.Four to eight days after drug administration, myocardium from the ventricles of 8 moribund BDF1 male mice which received a single intraperitoneal dose of adriamycin (20 mg/kg), and from controls dosed with physiologic saline, was fixed in glutaraldehyde or Karnovsky's glutaraldehyde-paraformaldehyde and prepared for electron microscopy.
Topographic Features of Neisseria Catarrhalis Strains
Authors: Wistreich G. A. , Baker R. F. , Hammond W. B. , Ivler D. 
Published: June 2020

The surface features of several bacterial species belonging to the Neisseriaceae including Neisseria gonorrhoeae, N. meningitidis and Veillonella parvula have been reported. During fimbriation studies with N. catarrhalis negative staining revealed a surface pattern differing from those found with other species of this genus. This report presents a comparative study with three N. catarrhalis strains. Consideration is given only to the physical aspects of intact cell wall structures.Of the three Neisseria catarrhalis strains used, one came from the stock culture collection of the Bacteriology Section, Division of Biological Sciences, University of Southern California, Los Angeles, while the remaining strains (ATCC 8176, ATCC 8193), were from the American Type Culture Collection, Rockville, Maryland.
Continuous Production of Type “C” Particles from a Cell Line Derived from a Transplanted Testicular Tumor
Authors: Sarkar Nurul H. , Lasfargues Etienne Y. , Moore Dan H. 
Published: June 2020

Large inclusions of intracytoplasmic A particles in the cytoplasm of estrogen-induced interstitial cell tumors of mouse testicles have been described. It has been shown that A particles in these tumors are antigenically related to the soluble antigen of the mouse mammary tumor virus. It was our interest to maintain these tumor cells in tissue culture as a constant source of A particles to be isolated and studied for their biophysical and biochemical properties.One mouse with testicular tumor was obtained through the courtesy of Dr. W. U. Gardner (Yale Univ. School of Med., Conn.). The tumor was minced, trypsinized and a cell line (GTT) was established (E.Y. Lasfargues and W. Coutinho, 1969 unpublished).
Scanning Studies of Cell Surfaces
Authors: Fonte Virginia , Weller Nancy , Porter Keith R. 
Published: June 2020

The surfaces of a cell in its topography and anti-genicity expresses subtle variations in the effective genome, as well as the physiology and structural organization of the underlying cytoplasm. Understanding the relationship of these various factors to the surface depends in part on obtaining a detailed characterization of the topography of cells and how this topography changes with phases in the cell cycle, with transformation to malignancy and with the cell's response to such physiologically active agents as cyclic AMP.We have therefore explored the usefulness of the scanning electron microscope in investigations of the cell's topography. Cells grown under favourable in vitro conditions have been fixed in glutaraldehyde, dehydrated in acetone and dried by the critical point method of Anderson.
Observations on the Vierergruppe during Spermiogenesis in Equisetum
Authors: Polette T. , Ridgway J. 
Published: June 2020

The occurrence of a multi-layered structure and a raicrotubular sheath have been enumerated for the spermatids of various lower plants. These structures, Vierergruppe (V) and Spline (S) respectively, do not show the strict conjunction with the nuclear membrane in Equisetum as previously reported. Although associated with the nuclear and plasma membranes, the Vierergruppe and Soline generally are found underlying the plasma membrane with the Spline encircling the cell in a spiral sheath, (Fig. 1). At either ends of the cell are the Vierergruope and associated mitochondria connected by the spiral Spline, with one extremely large mitochondrion having cristae in parallel array to the layers of the Vierergruppe.Clearly reaffirming mitochondrial association, the Vierergruppe have been observed on either side of another extremely large mitochondrion (M) (Fiq. 4.).
Arrangement of Mitochondria in Spermatozoa of the Mexican Axolotl, Ambystoma Mexicanum
Authors: Keyhani Ezzatollah , Lemanski Larry F. , Lemanski Sharon L. 
Published: June 2020

Energy for sperm motility is provided by both glycolytic and respiratory pathways. Mitochondria are involved in the latter pathway and conserve energy of substrate oxidation by coupling to phosphorylation. During spermatogenesis, the mitochondria undergo extensive transformation which in many species leads to the formation of a nebemkem. The nebemkem subsequently forms into a helix around the axial filament complex in the middle piece of spermatozoa.Immature spermatozoa of axolotls contain numerous small spherical mitochondria which are randomly distributed throughout the cytoplasm (Fig. 1). As maturation progresses, the mitochondria appear to migrate to the middle piece region where they become tightly packed to form a crystalline-like sheath. The cytoplasm in this region is no longer abundant (Fig. 2) and the plasma membrane is now closely apposed to the outside of the mitochondrial layer.
The Fine Structure of Primordial Germ Cells of the Rat
Authors: Eddy E. M. 
Published: June 2020

Primordial germ cells are readily recognizable in embryos of the rat due to their large size, generally rounded shape and prominent nuclei with uniformly dispersed heterochromatin. They often have blunted pseudopodal processes at one end and small ruffles or trailing processes at the other, characteristics expected from their known ameboid activity- and migratory abilities. Also, the cytoplasm is rich in polyribosomes and contains a modest amount of rough endoplasmic reticulum and the mitochondria are frequently larger and less dense than those of adjacent somatic cells.In addition to these general characteristics, there are features unique to germ cells which allow them to be identified with certainty. These are: 1) small vesicles containing an irregular, dense core and 2) discrete accumulations of fibrous material known as nuage. Both of these features are present in other species and at other times in the life history of germ cells. The dense-cored vesicles have been noted in fetal and early postnatal mouse oogonia and oocytes, and in hamster and rabbit oocytes.
Vascular Leakage of Horseradish Peroxidase Following Acute Spinal Cord Injury
Authors: Beggs John L. , Waggener John D. 
Published: June 2020

Under normal CNS conditions, circulating horseradish peroxidase (HRP) fails to enter the perivascular spaces due to the presence of interendothelial tight junctions and the absence or low rate of pinocytotic activity. Under some conditions where the blood brain barrier (BBB) is altered, HRP leakage occurs. Possible routes of HRP leakage include increased pinocytotic activity, breakdown of the interendothelial tight junctions, and direct penetration across severely damaged endothelial cells. The modes of leakage may vary with the type of insult.Following acute compression of upper thoracic spinal cord (cat), leakage and distribution of HRP is confined to the posterocentral gray matter with minimal involvement of white matter (Fig. 1).
Comparison Between Regional Cerebral Ischemia and Total Cerebral Ischemia. an Ultrastructural Study in the Cat
Authors: Garcia Julio H. , Kalimo Hannu , Kamijyo Yoshinari , Lessler Mary Jane , Trump Benjamin F. 
Published: June 2020

It has been suggested that cerebral cellular changes in regional cerebral ischemia, resulting from occlusion of a cerebral artery, are structurally indistinguishable from those occurring after total cerebral ischemia, resulting from total cessation of cerebral circulation.Significant differences were detected in these two forms of circulatory impairment, which we produced in cats, as follows: a) regional cerebral ischemia by clipping a middle cerebral artery (MCA); b) total cerebral ischemia by filling the intracerebral vasculature with Eagle's minimum essential medium containing 6°U dextran (mw. 80,000) at 37°C. Both experiments lasted 60 minutes, and then the brain was fixed by perfusion with aldehydes. Completeness of perfusion was verified by including carbon black in the final 200 cc of aldehyde perfusate, which revealed even distribution through the capillary bed.
Effects of TRH on Pituitary Grafts in the Rat
Authors: Shiino Masataka , Rennels Edward G. 
Published: June 2020

To date, many investigations have been reported on the ultrastructure of the “thyrotroph”. However, there is still confusion in regard to the ultrastructure of this cell type.In the present study, we observed ultrastructural alterations of anterior pituitary grafts following chronic treatment of the animals with synthetic thyrotrophin releasing hormone (TRH) (Schwarz-Mann). Male, Sprague- Dawley derived rats were hypophysectomized at 40 days of age. Seven days after the operation the anterior pituitary gland from a littermate male rat was transplanted under the kidney capsule. Thirty days following the transplantation, 100 pg of TRH was injected subcutaneously twice daily for 15 days (9:00 am and 4:00 pm). TRH was dissolved in 3% gelatin-saline solution at a concentration of 100 pg/0. 1 ml for each injection. As controls, hypophysectomized male rats with pituitary grafts were injected with 3% gelatin-saline solution by the same procedure.
Microstructure of TiB2liquid phase sintered with Ni3Al
Authors: Angelini P. , Bentley J. , Finch C. B. , Sklad P. S. 
Published: June 2020

TiB2is a ceramic material which possesses exceptional thermal, chemical, and electrical properties. Commercial powders can be formed into bulk pieces by hot pressing at temperatures near 2000°C. However, this produces excessive grain growth which can lead to cracking and low mechanical integrity due to the relatively large anisotropic thermal expansion of the TiB2grains. Liquid phase sintering can be used to produce structural forms of TiB2by hot pressing at temperatures near 1450°C. This process limits the TiB2grain growth but introduces an intergranular phase. Previous work used Ni as a binder and under most hot-pressing conditions this resulted in the formation of a Ni3B intergranular phase. Additional binders are being considered to understand the phase development during liquid-phase sintering and to improve the properties of the bonded TiB2forms.The present research concerns the use of Ni3Al as a binder for TiB2. The Ni3Al powder was a physical mixture of 32 wt % NiAl and 68 wt % of a solid solution of 95 at. % Ni with 5 at. % Al powders.
Transmission electron microscopy of rapidly solidified micron-size carbide powders of titanium and zirconium
Authors: Pande C. S. , Smith S. 
Published: June 2020

It is well known that rapid solidification in materials may result in unique microstructure and properties. These novel features are determined largely by the transport processes occurring at the liquid/solid interface. However, a detailed study of the basic mechanism of rapid solidification and its correlation with resultant chemistry and microstructure is needed to fully utilize the potential benefits of rapid solidification processing. We have used transmission electron microscopy, and related techniques such as energy dispersive x-ray analysis in thin films and electron energy loss analysis for this study. The material chosen for this purpose was rapidly solidified very fine carbide powders of titanium and zirconium.The method of producing these powders using spark machining has been described in detail elsewhere. The carbide is formed during the machining of the metal due to a reaction between the metal and carbon from kerosene which is used as a dielectric for spark machining. The rate of solidification and the carbon content of the carbides can be varied by varying the frequency and polarity of the electric discharge.
Redistribution and precipitation of dopant on thermal annealing of bismuth implanted silicon
Authors: Pennycook S. J. , Narayan J. , Holland O. W. 
Published: June 2020

Ion implantation above a certain dose leads to the formation of amorphous layers, which if recrystallized under interface-controlled growth at 450-600°C, result in solid solutions far exceeding the equilibrium solubility limits. In this investigation, we have annealed high-dose implanted specimens at 1000°C for one hour to study the redistribution and precipitation of dopant due to the presence of extended defects.Figure 1 shows a cross section TEM image taken near the [01] Si pole of (100)Si implanted with 209Bi+ (250 KeV, 5 x 1015 cm−2) and annealed (1000°C, 1 hr). As well as a band of precipitates typically 5 nm in size centered at a depth of 100 nm there are some much larger precipitates (28 nm in size) at the original surface of the silicon. These show a curved meniscus protruding out of the surface since the bismuth is liquid at the annealing temperature. These precipitates are located on twins suggesting that the dopant has diffused along the twin boundaries from the band of high concentration to the surface.