bluuebunny/crossref_metadata_2025 huggingface dataset:
Freeze Fracture-Electron Microscopy of Spermidine-Single DNA Double Helices
Authors: Ruben George C. , Marx Kenneth A. , Reynolds Thomas C.
Published: June 2020

Torus shaped spermidine-DNA structures formed in vitro are thought to have a DNA organization similar to that in bacteriophage. In addition to toroidal structures in our preparations we have found large aggregates often interconnected with fibres comprised of one or more DNA double helices. The detailed organization of these interconnecting fibres will help illuminate little-understood theoretical aspects of the packing and bending properties of the DNA double helix. Previously, spermidine-DNA complexes have been dryed onto a substrate film and metal coated at an 11.3° angle. In contrast, the freeze-fracture, deep-etching technique was used because it could reveal hydrated spermidine-DNA complexes in their solution configuration. This preliminary report describes single double helical DNA-spermidine fibres suspended over unshadowed regions of the ice surface.

Calf Thymus DNA (5 g/ml) was condensed with 1 mM spermidine at 0°C, for 1 hr in 1 mM NaCl, 10 mM Tris, pH 7.0. The solution was rapidly frozen on a Balzer's deep well pedestal in propane at -190°C. Samples were freeze-fractured and deepetched for 13 min at -97°C with a Balzer's 300 Freezing Microtome.
Analysis of the Mechanism of Unfolding of Foot-and-Mouth Disease Virus-RNA During Heat and Chemical Denaturation
Authors: Wool S.H. , Rolatnick J. , Bachrach H.L.
Published: June 2020

Two different approaches were used to examine the mechanism of unfolding of foot-and-mouth disease virus (FMDV) RNA. In the first procedure, we prepared single stranded 37S virion RNA by extracting purified virus with phenol and sedimenting the RNA through a 5 to 25% sucrose gradient. The purified RNA was then dissolved in NT buffer (10mM Tris-HCl, pH 7.4, 100 mM NaCl) containing either 1 mM EDTA or 1 mM Mg and absorbed onto Formvar-coated, carton shadowed, glow-discharged 200 mesh copper grids. In the second procedure, we heat denatured intact viral capsids in 0.05 M K2HPO4, 0.2 M KCl buffer (pH 7.0) in a thermostatically controlled Beckman spectrophotometer. We measured viral uncoating and the controlled release of the RNA by increased absorbancy at 260 nm. Samples taken at various temperatures were added to an equal volume of 20% formaldehyde and quick-frozen in covered BEEM capsules in liquid nitrogen. The heat-denatured formaldehyde-fixed virus was then spread onto grids using the BAC-formamide procedure of Vollenweider.
Nuclear and Cytoplasmic Changes in Necrotic Granulocytes in Leukemia
Authors: Giammara B.L. , Carter H.W. , Rappaport E.S. , Yates P.E. , Jarvis T.A. , Moore J.O. , Hanker J.S.
Published: June 2020

Apparent necrosis of leukemic leukocytes is very common, and an accompanying nuclear degeneration can be seen when blood or bone marrow preparations are examined by light microscopy. Nuclear degeneration is commonly indicated by pyknosis (condensation of chromatin), karyorrhexis, karyolysis, or chromatolysis. Granulocytes with negative nuclei (ghost cells, Fig. 1) and cytoplasmic vacuolization are also frequently observed in specimens of patients where nuclear degeneration is prominent. These events are especially apparent (Figs. 1 to 3) in blood or bone marrow preparations stained for light microscopy with a new procedure for the demonstration of granulocyte peroxidases. With this procedure, nuclear degeneration and cytoplasmic vacuolization were observed in granulocytes in thirty-three of forty-two leukemia patients while only four of thirty-four atopic disease patients displayed these phenomena. These changes appeared to be most prominent in some acute promyelocytic leukemia patients. Electron microscopic examination of cells of patients showing these phenomena was undertaken to investigate the mechanism of the degenerative processes.
Distinguishing Characteristics of the Sub-Population of Squamous Cancer Cells with Invasive Motility—Light Microscope and HVEM Studies
Authors: Parsons D. F. , Marko M. , Braun S.
Published: June 2020

The most active cells in a primary or metastatic carcinoma appear to interface the normal tissue (e.g., at the edge of the tumor mass or adjacent to other normal tissues). These cells, which are free of normal territory-restricting constraints, are characterized by a different morphology from the main mass of tumor cells by pseudopodia formation with pronounced filamentous actin organization, and (usually) with release of proteases including characteristic collagenases. We have developed two types of tissue culture models which give opportunity for 3-D thick-section HVEM and cytochemical study of the transition from the resting stage to the stage of invasive motility. We mean to define the conditions for this transition and to suggest therapies to control the leakage of invasive cells from the main tumor mass into normal tissues.

The work is aimed at demonstrating the morphologic and cytochemical relationships between the invasive cells of human and mouse squamous cell tumors, the stem cells (“dark cells”) of normal and embryonic epithelial cells.
Osteogenesis Imperfecta: An SEM and TEM Study of Cellular and Matrix Characteristics
Authors: Kirchen M.E. , Marshall G.J. , Dietrich S.L.
Published: June 2020

Samples of bone were obtained with appropriate consent from 27 patients with Osteogenesis imperfecta (O.I.). The samples were processed by conventional techniques and specimens viewed with a Novascan SEM, AEI Corinth TEM and a Cambridge SEM scope fitted with a Nuclear Semiconductor energy dispersive unit. For each bone sample specimens were conserved for light microscopy as well as SEM and TEM. The H & E slides were used to determine the architecture of the sample, to ascertain if a portion of the vascular bed was present and to obtain a ratio of osteocyte to matrix. SEM was used to compare the topography to that of normal bone. TEM was used for cellular and matrix details. The energy dispersive unit in association with the Cambridge SEM was used to estimate the concentration of bone minerals and to obtain the calcium phosphorus ratio for each specimen.

O.I. is a familial disease which presents with a range of clinical entities
Exocytosis from Large and Small Dense Cored Vesicles in the Sympathetic Nerve Terminals of Guinea Pig and Man
Authors: Thureson-Klein Åsa , Dzielak David J. , Stjärne Lennart
Published: June 2020

Large and small dense cored vesicles are present in various proportions in the noradrenergic nerve terminals of different species. These vesicles differ not only in size but in chemical composition as well. For example, only the large vesicles contain opioid peptide, a significant amount of matrix dopamine β-hydroxylase and measurable concentrations of chromogranin A. However, while much is known about the composition of isolated large and small vesicles their exact role in transmitter release is controversial. It has not been established to what extent large and small vesicles participate in exocytosis. Moreover, physiological and pharmacological experiments have indicated that there is not always a proportional co-release of noradrenaline and dopamine β-hydroxylase. The present study was performed to find morphological evidence for the hypothesis that both large and small vesicles can release transmitter but only the large vesicles release the enzyme.
Differentiation of Fiber Types in a Mammalian Extraocular Muscle
Authors: Nag Asish C. , Cheng Mei
Published: June 2020

The mammalian extraocular muscles possess greater variation in structural and physiological properties than any other muscle. Superior rectus muscle of the adult cat and rat contains five morphological fiber types. The differentiation of these fiber types in the embryonic and postnatal rats was studied by light and electron microscopy, mapping the distribution of each developing fiber type with its distinctive features.

A mixture of 4% paraformaldehyde and 4% glutaraldehyde was perfused through the superior rectus muscle of rats ranging from 18-day embryos through 4-week postnatal anesthetized animals. Muscles were removed, kept overnight in 4% glutaraldehyde, and processed for electron microscopy using standard methods of OsO4 postfixation and araldite embedding. Thick and thin sections were cut. Thick transverse sections were photographed, and maps of muscle fibers were prepared. In order to identify the fibers and their exact locations, electron micrographs of fibers were taken in conjunction with the light micrographs.

The muscle fibers in the 18-day embryos did not differentiate into the specific structural fiber types (Fig. 1) that were observed in the adult muscle.
Ultrastructure of Cryptorchidism and Seminoma
Authors: Siew Shirley , James Susan C.
Published: June 2020

Testicular maldescent is the most common endocrine gland abnormality, as 2.7% of mature neonates are cryptorchid. The significant complications are that there is a disturbance of normal maturation which results in diminished fertility and there is an increase in the malignant potential which is 35 times greater in the undescended than the descended testis. It is considered that genetic influences may be of etiological importance and recurrence has been described in some families. It is of interest, that the case reported here has 2 siblings who have also presented with cryptorchidism and malignant tumors.

The propositus is 14 years old. He is well developed (described by some as obese) and shows normal secondary male characteristics except for an immature scrotum. Laparotomy showed both testes to be intraabdominal. A hard nodule (0.5cm) was palpated on the medial aspect of the left testis. Frozen section showed the presence of seminoma and bilateral orchiectomy was performed.
Cytochrome P-450 and NADPH-Cytochrome c (P-450) Reductase in Reconstituted Phospholipid Vesicles as Demonstrated by Negative Staining Techniques
Authors: Dees Jane H. , Parkhill Linda K. , Coe L. Dean , Germany Betty Ann , Okita R. T. , Yasukochi Y. , Masters B. S. S.
Published: June 2020

Artificial membrane vesicles or liposomes have become an accepted model for the study of enzyme-membrane interactions under controlled conditions.The development of reconstituted vesicle models for the microsomal mixed function oxidase enzymes has provided a system in which to study not only the biochemistry of these enzymes in a near physiologic milieu, but also structural aspects of the protein-phospholipid and protein-protein interactions. Ultrastructural studies on liposomes reconstituted with NADPH- cytochrome c (P-450) reductase (an amphipathic protein, 78,000 daltons, thought to be partially embedded in the microsomal membrane by its hydrophobic tail), and cytochrome P-450 (a hydrophobic protein, about 50,000 daltons, thought to be embedded within the lipid bilayer) either singly or together, should reveal information on whether these proteins are randomly arranged in the membrane or arranged in an ordered manner, an issue currently debated among cytochrome P-450 researchers.
A Gaussian Small Particle Population is Transformed by Pt-C Replication into Distributions of Metal Cap Widths and Shadow Widths which Empirically Fit a Log-Normal Function
Authors: Ruben George C.
Published: June 2020

The investigation of biological membranes would be greatly facilitated if the particle shadow widths (PSW) or particle cap width (PCW) distributions on freeze-fractured or freeze-etched membranes could be related to actual particle size and size diversity. By establishing how a gaussian population of small particles is transformed into its Pt-C PCW and its Pt-C particle shadow width distributions (PSWD), it may be possible to solve this problem.

The negatively stained lac repressor (1% uranyl acetate, pH 4.8) which is roughly a gaussian population of diameters (fig. la) was used to investigate the distribution shape of Pt-C PCW's. Gold balls were only used to investigate the distribution shape of PSW's because they did not generally form a Pt-C metal cap (1,2). The preparation method for gold ball calibration grids has been reported (1,2). The Pt-C shadowing experiments (45° angle) were performed on a Balzer's model 360M freezing microtome at -97°C to -94°C in a 10-6 torr vacuum. An EKV 552 Pt-C electron beam gun was either degassed for 19 sec (film I) or for 120 sec (film II) at a current setting of 5 on the EVM 052 control unit.
Studies on Trifluoperazine Inhibition of Trichocyst Expansion and Secretion in Paramecium
Authors: Garofalo Robert S. , Satir. Birgit H.
Published: June 2020

The importance of Ca2+ ion in regulation of many cellular processes is well established, as is its role as the mediator of “stimulus-secretion coupling” in exocytic release of secretory products. However, while the Ca2+ requirement in many secretory systems is clear, its mode of action is not.

To probe the site of Ca2+ action, we have employed the protozoan, Paramecium tetraurelia as a model secretory system. Secretion in Paramecium requires Ca2+ as well as specific components in both the plasma and secretory vesicle membranes that can be visualized in freeze fracture as organized intramembrane particle arrays. The fusion of plasma and secretory organelle membranes, and subsequent release of vesicle contents, is routinely elicited by exposure to picric acid, and stimulation results in synchronous release of hundreds of secretory products called trichocysts. A rise in cytoplasmic Ca2+ triggers release and expansion of the trichocysts. This is accompanied by a reordering of the trichocysts' paracrystalline matrix, transforming the 5 μm long organelle to a 20-40 μm long needle-like structure.
The Demonstration of Hemoprotein Crystals in Secretory Lumina of Dimethyl-benzanthracene-Induced Mammary Tumors
Authors: Hanker J. S. , Silverman M. S. , deCamargo A. M. , Giammara B. L. , Bossen E. M. , Stein R. B.
Published: June 2020

A number of hormone-dependent reproductive tract tissues synthesize a peroxidase and secrete it into their lumina. An estrogen-induced mammary gland peroxidase, probably lactoperoxidase, has been reported in the acinar cells of prelactating and lactating rats and has been found to be a marker of hormone-dependent 7,12-dimethylbenzanthracene (DMBA)-induced rat mammary tumors. Study of the enzyme in tumor acinar cells showed it in cisternae of the nuclear envelope, granular ER and apical secretory granules. Its presence in lumina of the acini has not been described. It was therefore of interest to determine whether lactoperoxidase could be demonstrated in their secretory lumina.

Mammary tumors were induced in female rats by DMBA in the usual manner. Paraffin sections of tumor tissue were stained with H & E or the Leder stain.Fixed touch preparations, cryostat sections, and blocks of tumors for electron microscopy were treated for peroxidative activity with 3,3'-diaminobenzidine (DAB) or p-phenylenediamine/pyrocatechol (PPD/PC, available from Polysciences).
Effects of Streptozotocin and Alloxan on Granular Tubules of Male Mouse Submandibular Gland
Authors: deCamargo A. M. , Hanker J.S. , Ambrose W.W. , Hilton WF. , Giammara B.L.
Published: June 2020

Diabetogenic agents can be conveniently classified into simple chemicals and complex hormones. Streptozotocin and alloxan are diabetogenic chemicals which cause a permanent diabetes by destruction of the B cells of the islets of Langerhans of the pancreas and a resulting insulin deficiency. The diabetogenic chemicals, however, may also have sex hormone-like actions which could be contributory or even causative factors in diabetes mellitus.

Circulating androgens have long been known to effect a sexual dimorphism of the submandibular gland,and spontaneous diabetes markedly affects the development of the submandibular glands of mice. The effects of alloxan on the submandibular gland of male mice has previously been reported.

In the present study, the effects of streptozotocin, a diabetogenic agent widely employed in cancer chemotherapy, were investigated in heterozygous male mice of the C57BI, Ksj db strain whose homozygous littermates are afflicted with a syndrome resembling maturity-onset human diabetes mellitus.
The Three-Dimensional Organization of the Arsenic Inclusion Using HVEM
Authors: Sorense E. M. B. , Mitchell R. R.
Published: June 2020

The arsenic inclusion is an electron-dense, non-membrane delimited, apparently amorphous structure which appears in the nucleus and cytoplasm of green sunfish (Lepomis cyanellus) exposed to 30 or 60 ppm arsenic, as sodium arsenate, dissolved in water. The intranuclear and cytoplasmic inclusions first appear in cells within one week and, over a period of several weeks, increase in size and number regardless of the location within the hepatocyte. Subfractionation data indicates that, within 6 days, arsenic is mobilized from a predominantly cytoplasmic to a predominantly nuclear location, and recent electron probe X-ray microanalysis data confirms the presence of arsenic within the inclusion. This work was conducted to obtain additional morphological data for comparison of this inclusion with the intranuclear lead inclusion and the intranuclear selenium inclusion.

Green sunfish were exposed to 60 ppm arsenic for varying time intervals prior to sacrifice. Livers were rapidly removed and cubed for fixation in buffered 3% gluteraldehyde prior to post-fixation in 2% buffered osmium tetroxide, rinsing in buffer, then water, en bloc staining with uranyl acetate, dehydration, and embedding in Araldite Epon.
Analysis of the Anterior Secretory Cells of Onchidohs Muricata (Nudibranchia)
Authors: Skidmore Roy
Published: June 2020

The long-necked secretory cells in Onchidoris muricata are distributed in the anterior sole of the foot. These cells are interspersed among ciliated columnar and conical cells as well as short-necked secretory gland cells. The long-necked cells contribute a significant amount of mucoid materials to the slime on which the nudibranch travels. The body of these cells is found in the subepidermal tissues. A long process extends across the basal lamina and in between cells of the epidermis to the surface of the foot. The secretory granules travel along the process and their contents are expelled by exocytosis at the foot surface.

The contents of the cell body include the nucleus, some endoplasmic reticulum, and an extensive Golgi body with large numbers of secretory vesicles (Fig. 1). The secretory vesicles are membrane bound and contain a fibrillar matrix. At high magnification the similarity of the contents in the Golgi saccules and the secretory vesicles becomes apparent (Fig. 2).
Ultrastructure of Hepatic Glycogen and Smooth Endoplasmic Reticulum in Rats Treated with Compound 48/80
Authors: Dimlich R. V. W. , Cardell R. R.
Published: June 2020

While investigating the mast cell population in the liver of the rat, compound 48/80, a mast cell degranulating agent caused a significant increase in blood-glucose. Subsequent biochemical and histochemical analyses of hepatic tissue indicated that there was a decrease in hepatic glycogen. Since the degradation of glycogen has been associated with an increase in the amount of smooth endoplasmic reticulum (SER), we have initiated a study with the objective of evaluating the changes in form and amount of SER in hepatocytes from animals treated with 48/80.

Ten male Sprague-Dawley rats were anesthetized by injections (ip) of urethane (2 mg/g) and subsequently injected (iv) with 48/80 (50 ug/kg) or an equivalent volume (0.5 ml/100 g) of Ringer's solution as a control.Thirty minutes later, hepatic tissue was removed and fixed in 2% glutaral- dehyde and 2% paraformaldehyde in a 0.1 M Na cacodylate buffer (pH 7.3), postfixed in phosphate buffered 1% osmium tetroxide, and embedded in Epon.
Plastid Development in Leaf Epidermis
Authors: Varkey Jacob P. , Nadakavukaren Mathew J.
Published: June 2020

Changes in the plastid ultrastructure during development of a leaf have been studied extensively. Most studies have been done on the development of chloroplasts in mesophyll cells. Chloroplasts are small and few in number or plastids never develop into chloroplasts in epidermal cells of leaves of many species. Not much is known about the development of plastids in the epidermal tissue. Sunflower was selected to study the plastid development in the epidermal tissue.

Sunflower plants were grown from seeds in growth chambers maintained on a 14:10 light:dark cycle at a daytime temperature of 78 F and nighttime temperature of 70 F with 80% humidity. Samples for ultrastructural study were taken from primary leaves at different stages of development. Because the rate of leaf development can vary from plant to plant, samples were taken from the same primary leaves of selected seedlings. These samples fixed in glutaraldehyde followed by osmium tetroxide were processed for electron microscopy using standard procedures.
High-Voltage Electron Microscopy (HVEM) of Pineal Gland Cell Cultures
Authors: Turner J. N. , Shain W. G. , Parfitt A. G.
Published: June 2020

Light and high-voltage electron microscopy are used to observe cell cultures nrenared from neonatal rat pineal glands. The light microscopy provides identification of pinealocytes from the background cells by morphological criteria (Parfitt et al., in preparation). Due to its penetrating power and depth of field the HVFM images both cell layers at high resolution.

Cultures are prepared from pineal glands of 3-day-old rats by decapsulation, dissociation in chick serum, trypsin and collagenase, and tituration. Cells are plated on Formvar-carbon-coated gold grids in modified Ham's F-12 medium with 10% fetal bovine serum and fed every third day with serum-free F-12 medium, with synthetic medium N1 supplements. After 10-14 days the cultures are fixed in 2% gluteraldehyde in cacodylate buffer, postfixed in 1% OsO4, photographed in the light microscope, dehydrated in ethanol, and critical-point-dried from CO2.
Quantitative Studies of Nuclear Polyhedrosis Virus Produced In Vitro
Authors: Smith G. C. , Weiss S. A. , Kalter S. S. , Vaughn J. L.
Published: June 2020

In initial studies, replication of Autographa californica nuclear polyhedrosis virus (large volume production) in Spodoptera frugiperda (IPL/SF-21AE111) insect cell line in the presence of ALCL3 and/or ZnSO4 7 H2O was considerably enhanced when determined by a variety of methods including the electron microscopic (EM) techniques reported herein. Optimization of viral growth, thereby reducing costs, is an important parameter in production of viruses as an alternative to chemical pesticides.

EM quantitation and morphometric analysis of virus particles (VP) or polyhedral inclusion bodies (PIB) was based on application of a thin section technique involving the sedimentation of subcellular particles onto a Millipore filter. The equation:

was used to calculate both VP or PIB/unit volume. Accordingly where D is the diameter (4 mm) of the filter and A is the average number of VP or PIB counted in fields of length (L) and thickness (T1). The equation: T1 = T + Dv - 2 f Dv was used to determine the effective section thickness (T1).
Direct Visualization of Uranyl Stain Crystallization on a Biological Specimen During Electron Irradiation
Authors: Kunath W. , Lamvik M.
Published: June 2020

Electron diffraction patterns from thin films of uranyl acetate (Uac) stain show that with increasing electron dose there is a narrowing of the initially broad and diffuse ring of intensity due to the stain, indicating that the stain becomes microcrystalline. The sharp intensity rings observed at higher dose have been identified as UO2 crystals. Here we report on direct visualization of the formation of 3 Å lattice fringes in the Uac stain during irradiation. The stain was used to produce negatively and positively contrasted tetramers of 80S ribosomes.

The three images of negatively stained ribosome tetramers in Fig. la are part of a dose series taken at 200,000x. The focus is corresponding to minimum phase contrast. The first image was exposed to a dose of 400 e/Å2, while the second and third images were exposed to 3 and 100 times more dose, respectively. Locally high contrast regions smaller than 10 Å can be seen in any of the micrographs, but their appearance deteriorates in the subsequent micrograph of the series, indicating considerable atomic mobility.
Observations of the Golgi Apparatus in Pisum Primary Roots
Authors: Spink Gordon C.
Published: June 2020

It is known that the product of the Golgi apparatus vesicles is deposited at and localized in the cell wall. This is accomplished by the formation of the hypertrophied dictyosomes and the subsequent movement of these vesicles to the plasma membrane (Fig. 1). After fusion with the plasma membrane, the secreted material is released into the cell wall area and, in some plants under appropriate conditions, moves outward through the cell wall and appears as a droplet on the root tip.

In primary roots of Pisum sativum, var. Alaska (common garden pea) the Golgi apparatus vesicle product accumulates between the plasma membrane and the cell wall, particularly in those cells at the extreme tip of the root. These cells are formed at the acropetal end of the columella cells.
Electron Microscopic Examination of a Transplantable Rat Mammary Carcinoma
Authors: Shirahama S. , Engle G. C. , Dutcher R. M.
Published: June 2020

A transplantable carcinoma was established in North West Sprague Dawley (NWSD) rats by use of X-irradiation by Engle and Spencer. The tumor was passaged through 63 generations over a period of 32 months. The original tumor, an adenocarcinoma, changed into an undifferentiated carcinoma following the 19th transplant. The tumor grew well in NWSD rats of either sex at various ages. It was invariably fatal, causing death of the host within 15 to 35 days following transplantation.

Tumor, thymus, spleen, and plasma from 7 rats receiving transplants of tumor at 3 to 9 weeks of age were examined with an electron microscope at intervals of 8, 15, 22 and 30 days after transplantation. Four normal control rats of the same age were also examined. The tissues were fixed in glutaraldehyde, postfixed in osmium tetroxide and embedded in Epon. The plasma was separated from heparanized blood and processed as previously described for the tissue specimens. Sections were stained with uranyl acetate followed by lead citrate and examined with an RCA EMU-3G electron microscope.
Electron Microscopy of California Isolate of Cat Leukemia Virus
Authors: Kawakami T. G. , Theilen G. H. , Munn R. J.
Published: June 2020

Although “C”-type viral particles have been observed in oats with feline leukemia, the developmental stages, morphological characteristics and sites of replication have not been fully described. The isolation of an agent from a cat with spontaneous leukemia and transmission of the disease with cell-free preparations to newborn kittens presented an opportunity for an extensive eleotron mioroscopic examination of the feline leukemogenic agent.

The agent apparently undergoes development by budding from the plasma or vacuolar membranes of infected host cells. The earliest stage of development is recognizable in thin section by a crescent-shaped electron-dense zone beneath the plasma membrane (Fig. 1a). This structure or bud enlarges progressively into a sphere which is resolvable into two concentric components and concomitantly causes a protrusion of the plasma membrane. Later stages are independent of the host cell proper. The immature forms (Fig. 1b), one recently detached from the plasma membrane, still maintain the internal morphology of the later stages of budding but is completely surrounded by a protein coat. The mature forms (Fig. 2) which develop by reorganization of the dense shells possess either a central electron-dense or central electron-lucent nucleoid. The difference between mature electron-lucent and immature forms appears to be an absence of the organized concentric shell in the former.
Studies on the Fine Structure of Intercellular Junctions
Authors: Revel Jean Paul
Published: June 2020

It is customary to distinguish two broad categories of intercellular junctions, the desmosome-like adhering junctions and the occluding, or tight junctions. The latter are said to be characterized by a fusion of the outer leaflets of the plasma membranes of the adjoining cells. In the junctional complex of epithelia these areas of fusion have the shape of a belt or zonula, and have been shown to act as a barrier preventing the passage of protein tracers from the luminal aspect of an epithelium into the intercellular space. The smallest protein available for such experiments is peroxidase, M. W. 40,000. We have found, however, that lanthanum can be used as an inorganic tracer of yet smaller size. Lanthanum ions, when carefully brought to a mildly alkaline pH, will form low molecular weight “polymers”. Use of these and other techniques, such as staining en bloc in aqueous uranyl acetate, has allowed us to recognize at least two new classes of junctions within what was the single category called “tight junctions”.
Electron Microscopy of Sprouting Seeds
Authors: Pease R. F. W. , Hayes T. L.
Published: June 2020

The examination of living insects in the scanning electron microscope (SEM) was reported in 1966. We now report the examination of living botanical specimens in the SEM. The specimens were the seeds of white sprouting onion (Allium cepa) and of the radish (Raphanus sativus) during the week following germination. The seeds were mounted initially using flour and water and later using a cement (“Elmer's Glue All”). In all cases the natural conductance of the seeds was sufficient to prevent undue charging. 12 onion seeds were examined within three days of placing in moist tissue and again on the three successive days (Figures 1 and 2). The survival rate (5 out of 12) was not significantly lower than in the control sample (about 50% of a large number), however the growth did appear to be retarded and this may have been due to the microscope environment. One notable exception was one seed which was accidentally immersed in the cement with only the sprout uncovered; it is possible that such immersion retarded water loss to the vacuum. The cement subsequently dissolved away as the sprouting seed developed in moist tissue.
A Micro-diffusion Technique for Visualizing Nucleic Acid Molecules
Authors: Mayor H. D. , Jordan L. E.
Published: June 2020

Contour lengths, molecular weights, and topological parameters of single molecules of nucleic acids can be studied accurately by electron microscopy. However, specialized equipment and highly purified samples of DNA or RNA in an amount of 10-100 μgm have been required. We have developed a simple micro-diffusion technique which uses less than 0.01 (μgm of nucleic acid. Droplets containing the nucleic acid are placed on a clean teflon sheet. Cytochrome C powder is added by needle to form a monofilm. After 20-30 minutes diffusion time, there is usually enough material attached for the film to be picked up on a suitable specimen grid, shadow-cast or stained, and examined in the electron microscope. Each droplet provides material for a single observation, but experiments may be carried out contiguously on the sheet.

The method has been developed for viral nucleic acids, but can also be applied to solutions of virus particles where the genomes can be released by osmotic shock or by other physical procedures. Less than 1010 particles per ml are required for this modification. Examples of nucleic acids liberated from papovaviruses, SV40, rabbit papilloma, human papilloma, and from adeno-associated satellite virus will be presented. Viral nucleic acids (DNAs from SV40 and adenovirus, RNA from bacteriophage R17) prepared by conventional techniques will also be shown.
Selective Sampling and Orientation of Non-Homogeneous Tissues
Authors: Clawson C. C. , Anderson L. W. , Good R. A.
Published: June 2020

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.
Epoxy Resin Embedment
Authors: Adams J. G. , Campbell M. M. , Thomas H. , Ghldonl J. J.
Published: June 2020

Since the introduction of epoxy resins as embedding material for electron microscopy, the list of new formulations and variations of widely accepted mixtures has grown rapidly. Described here is a resin system utilizing Maraglas 655, Dow D.E.R. 732, DDSA, and BDMA, which is a variation of the mixtures of Lockwood and Erlandson. In the development of the mixture, the Maraglas and the Dow resins were tested in 3 different volumetric proportions, 6:4, 7:3, and 8:2. Cutting qualities and characteristics of stability in the electron beam and image contrast were evaluated for these epoxy mixtures with anhydride (DDSA) to epoxy ratios of 0.4, 0.55, and 0.7. Each mixture was polymerized overnight at 60°C with 2% and 3% BDMA.

Although the differences among the test resins were slight in terms of cutting ease, general tissue preservation, and stability in the beam, the 7:3 Maraglas to D.E.R. 732 ratio at an anhydride to epoxy ratio of 0.55 polymerized with 3% BDMA proved to be most consistent. The resulting plastic is relatively hard and somewhat brittle which necessitates trimming and facing the block slowly and cautiously to avoid chipping. Sections up to about 2 microns in thickness can be cut and stained with any of several light microscope stains and excellent quality light photomicrographs can be taken of such sections (Fig. 1).
Schwann Cell Reactions in Acute and Chronic Segmental Demyelinating Neuropathies
Authors: Weller Roy O.
Published: June 2020

The length of axon that each Schwann cell myelinates in a normal peripheral nerve is approximately proportional to the diameter of the axon and the thickness of the myelin sheath produced. When segmental demyelination occurs, individual segments, represented by the length of axon covered by one Schwann cell, lose their myelin sheaths but the axons are preserved. This differs from Wallerian degeneration where myelin destruction occurs along the length of a nerve fibre following death of the axon.

In experimental diphtheritic neuropathy, an acute segmental demyelinating disease, lysosomes accumulate within the Schwann cells prior to disruption of the myelin sheath; furthermore, the site of initial myelin breakdown appears to be closely related to the collections of lysosomes. The Schwann cell starts to form a new myelin sheath around the axon probably within a few hours of the destruction of the original myelin sheath, and while the latter is being catabolised within lysosomal vacuoles This stage of remyelination follows a similar course to primary myelination, so that the recovery stage is characterised by normal axons with either no myelin, or surrounded by sheaths that are very thin relative to the diameter of the axon.
Octagonal Pores in Annulate Lamellae of Rana Pipiens Oocytes
Authors: Kessel R. G.
Published: June 2020

Negative staining of isolated nuclear envelopes by phosphotungstate in several amphibian oocytes by Gall has shown the pores to be octagonal rather than circular in shape and, further, that the outer and inner diameters of the annulus associated with each pore are respectively greater and less than the width of the pore itself.

Electron microscope studies on thin sections of glutaraldehydeosmium tetroxide fixed oocytes of Rana pipiens have revealed evidence that pores in the annulate lamellae are also octagonal in shape. Tangential sections of the annulate lamellae illustrating several pore-annulus complexes are illustrated in Figs. 1-4. That the pores possess octagonal symmetry is reasonably clear from direct inspection of the micrographs. In Fig. 2 the most apparent sides defining the octagon are indicated by the inked lines. The distance between two opposite sides of the octagon (i.e., the inner width of the octagon) is approximately 700 Å. The center to center spacing of the pores is approximately 125 mμ.
Pinocytotic-Like Forms of Mitochondria From Rat Anterior Pituitary
Authors: Silver Burton B.
Published: June 2020

Sectioned tissue rarely indicates evidence of what is probably a highly dynamic state of activity in mitochondria which have been reported to undergo a variety of movements such as streaming, divisions and coalescence. Recently, mitochondria from the rat anterior pituitary have been fixed in a variety of configurations which suggest that conformational changes were occurring at the moment of fixation. Pinocytotic-like vacuoles which may be taking in or expelling materials from the surrounding cell medium, appear to be forming in some of the mitochondria. In some cases, pores extend into the matrix of the mitochondria. In other forms, the remains of what seems to be pinched off vacuoles are evident in the mitochondrial interior. Dense materials, resembling secretory droplets, appear at the junction of the pores and the cytoplasm. The droplets are similar to the secretory materials commonly identified in electron micrographs of the anterior pituitary.
Ultrastructural Observations of the Rat Oocyte During the Estrous Cycle
Authors: Baccarini I. M.
Published: June 2020

The cytological ultrastructure of the oocyte in different vertebrates and in insects has been described. Additional information on this subject is the purpose of this report which describes the findings on the oocyte of the rat during the estrous cycle.

Vaginal smears were taken daily from 27 inbred Wistar-Furth rats to determine stages of the cycle. The animals were sacrificed with anesthesia in proestrous, estrous and metestrous and the ovaries removed surgically. In each case one ovary was used for electron microscopy and the other for histochemical methods.

The ovary for electron microscopy was placed immediately into cold 3% phosphate-buffered glutaraldehyde for 2 hours and then into 1% phosphate-buffered osmic acid for 2-3 hours. The tissue was embedded in Durcupan ACM (FLUKA). The sections were double stained with 50% alcoholic uranyl acetate solution and with lead citrate.
Fine Structure of the Normal Canine Prostate
Authors: Maser M. D
Published: June 2020

The secretory epithelia of prostate glands of healthy dogs have varieties of organization and subcellular structure that previously have not been reported. In some acini, the secretory cells are columnar, and are aligned in a single layer (Fig. 1). The cells are of two types, “light” and “dark”, which I have been able to distinguish only on the basis of general cytoplasmic density. Other structural features of interest are: extensive lateral intercellular interdigitation; irregularly shaped, large lipid bodies, often associated with high concentrations of glycogen, and present in both the apical and basal regions of the cells; apically concentrated secretory granules, some of which are distinguished by having dense cores; prominent Golgi apparatuses, oriented both apically and laterally; extensive rough endoplasmic reticulum, some cisternae of which are distended; and nuclei which are often observed to be multi-lobular and very irregular in outline. Cells arranged in this manner have well defined tight junction complexes at their lateral apical surfaces.

In most acini, however, the architecture is more complicated. Often, thin extensions of dark cell cytoplasm surround and separate adjacent light cells (Fig. 2). The dark cell cytoplasm is expanded in some areas to accomodate mitochondria, and it contains numerous ribosomal clusters and rough endoplasmic reticular cisternae. Desmosomal attachments between the light and dark cells are found commonly in the regions of envelopment. I have not yet determined whether the dark cells completely encapsulate the dark cells in three dimensions.
Glycogen Bodies in the Liver of an Infant with Loss of Hepatic Methionine Activating Enzyme
Authors: Hug George , Cussen Leo J. , Schubert William K. , Chuck Gail
Published: June 2020

A white girl, age 7 months, had hepatosplenomegaly, ascites, prominent abdominal veins, rickets, unusually fine hair, and hypochromic-microcytic anemia. The only episode of jaundice was between age one and three weeks. Hepatomegaly was noted at age six months. Urinary methionine was as high as 100 μg/cc while other amino acids were within normal limits. Bio-chemical analysis of the hepatic needle biopsy specimen revealed glycogen concentration of 5.4% of wet tissue weight. Light microscopy of the biopsy specimen showed portal cirrhosis, fatty change and many coarse granules resistant to diastase, glucosidase, phospholipase, ribonuclease, trypsin, pepsin, pectinase, hialuronidase, glucuronidase, and lipoxidase, and demonstrable only with PAS, Eosin, and burnt Sudan black stain. On electron microscopy, these coarse granules were probably represented by fused mitochondria with their internal structures replaced by an amorphous substance. Numerous other mitochondria had a coarsely flocculent matrix. There were many large lipid droplets. Membranes of the endoplasmic reticulum frequently were arranged on either side of a single row of jagged granules about 100 mμ in diameter and staining black with uranyl acetate and lead hydroxide (Top picture).
Ulcerogenic Tumors of the Pancreas
Authors: Garancis J. C. , Kuzma J. F. , Wilson S. D. , Ellison E. H.
Published: June 2020

It has been proposed that a gastrin-like hormone elaborated by non-beta islet tumors of the pancreas may be responsible for a fulminating ulcer diathesis. Subsequently, a potent gastric secretagogue was isolated from ulcerogenic tumors of the pancreas. This disease process is known now as “Zollinger-Ellison syndrome”.

In our studies of two cases of Zollinger-Ellison syndrome, pancreatic lesions were identified as alpha islet cell tumors (Fig. 1). Tumor cells were fairly uniform. The sizes of the alpha granules were not significantly different, but their number and distribution varied greatly from one cell to another. Each granule consisted of a round, highly dense central core, separated from the limiting membrane by an opaque zone. The granular form of the endoplasmic reticulum was particularly prominent. Numerous mitochondria, round or elongated, were dispersed throughout the cytoplasm. Individual or clusters of lysosomes were observed in the majority of cells.
Studies of a Defective Measles Virus
Authors: McCombs R. M. , Benyesh-Melnick M. , Brunschwig J. P.
Published: June 2020

Measles virus is an agent that is capable of replicating in a number of different culture cells and generally causes the formation of multinucleated giant cells. As a result of infection, virus is released from the cells into the culture fluids and reinfection can be initiated by this cell-free virus. The extracellular virus has been examined by negative staining with phosphotungstic acid and has been shown to be a rather pleomorphic particle with a diameter of about 140 mμ. However, no such virus particles have been detected in thin sections of the infected cells. Rather, the only virus-induced structures present in the giant cells are eosinophilic inclusions (intracytoplasmic or intranuclear). These inclusion bodies have been shown to contain helical structures, resembling the nucleocapsid observed in negatively stained preparations.
Electron Microscopic Observations On An Amphibian Polyhedral Virus (LT-1) Propagated in Vitro in Reptilian Cells
Authors: Zeigel R.F. , Clark H .F. , Karzon D. T.
Published: June 2020

Polyhedral, cytoplasmically derived, viral agents have been isolated from Rana pipiens and characterized in baby hamster kidney and Fathead minnow cells in vitro. These viruses are not similar to the Herpes-type virus associated with the Lucké tumor in these frogs. Clark, et al have recently described additional isolates of similar polyhedral agents from the leopard frog after passage through red efts (Triturus viridescens). This virus series, designated LT-1, -2, -3, -4, has been propagated in the turtle heart cell line TH-1. This report presents morphological studies on these isolates.

Slow speed centrifuged cell packs were fixed in cold chrome-osmium (Dalton) followed by fixation in cold 0.5% aqueous uranyl-acetate with 0.54% sucrose. Sections were double stained with uranyl-acetate and lead citrate.

The virus particles were observed to form in juxta-nuclear viroplasmic regions within the cell cytoplasm. Evidence of intranuclear virus synthesis has not been observed, to date. Viroplasmic regions were frequently surrounded by mitochondria. Within the viroplasmic regions the fixation used preserved a filamentous mesh work which is observed to be continuous with that which is accumulated inside the virions (Figs. 1, 2). This filamentous material is similar to that observed in Mycoplasma and in poxvirus viroplasm.
Giant Mitochondria in Skeletal Muscle of the Rat Soft Palate
Authors: Leeson C. R. , Leeson T. S.
Published: June 2020

The soft palate of the rat contains a core of skeletal muscle in which there is a mixture of two distinct fiber types, red and white. In general white fibers have a greater diameter than red fibers and show a greater concentration of myofibrils and fewer mitochondria. The most conspicuous feature of red fibers is the presence of numerous mitochondria, which occur in two principal sites. They are present as chains running longitudinally amongst myofibrils and as marked, irregular accumulations beneath the sarocolemma. The present study concerns the subsarcolemma1 mitochondria which possess three features of particular interest.

Firstly, the mitochondria show a considerable variation in size and gigantic forms are seen frequently (Fig. 1). The latter can be identified readily when scanning at low magnification. They are more or less spherical in form and thus usually appear as circular profiles on electron micrographs, unlike the mitochondria found between myofibrils which often are markedly elongated. Gigantic mitochondria have been reported previously in the myocardium of the hummingbird.
Three-Dimensional Images of Proximal Tubular Cells and The Adjoining Peritubular Capillaries
Authors: Leak L.V.
Published: June 2020

The topographical relationships of adjacent tubular cells and blood capillaries have been studied from serial sections of both light microscopic and ultrathin sections. However, a direct observation of three dimensional images of kidney tubular cells and the adjoining peritubular capillaries has not been reported. The present study was undertaken in an attempt to define more precisely the three dimensional arrangement of the proximal tubular cells in addition to the architecture of the adjoining basal lamina and peritubular capillaries.

The kidney is prepared by fixing 2 x 4 mm pieces of tissue in 2% glutaraldehyde prior to treatment with 10 and 20% ethylene glycol in Ringer solution for 20 minutes each. The tissue is then frozen in liquid nitrogen. Other tissues are processed with 20, 40 and 60% glycerol in Ringers solution without prior fixation before freezing in liquid nitrogen. Tissues are placed in the McAlear and Kreutziger Freeze-Etching block and placed in a Varion VE-10 vacuum evaporator. Tissues are fractured after a temperature of -120°C is reached, and etched for periods ranging from several seconds through 15 minutes.