bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural preservation and absolute contrast of catalase crystal sections prepared with tannic acid
Authors: Akey C.W. , Szalay M. , Edelstein S.J. 
Published: June 2020

Three methods of obtaining 20 Å resolution in sectioned protein crystals have recently been described. They include tannic acid fixation, low temperature embedding and grid sectioning. To be useful for 3-dimensional reconstruction thin sections must possess suitable resolution, structural fidelity and a known contrast. Tannic acid fixation appears to satisfy the above criteria based on studies of crystals ofPseudomonascytochrome oxidase, orthorhombic beef liver catalase and beef heart F1-ATPase. In order to develop methods with general applicability, we have concentrated our efforts on a trigonal modification of catalase which routinely demonstrated a resolution of 40 Å. The catalase system is particularly useful since a comparison with the structure recently solved with x-rays will permit evaluation of the accuracy of 3-D reconstructions of sectioned crystals.Initially, we re-evaluated the packing of trigonal catalase crystals studied by Longley. Images of the (001) plane are of particular interest since they give a projection down the 31-screw axis in space group P3121. Images obtained by the method of Longley or by tannic acid fixation are negatively contrasted since control experiments with orthorhombic catalase plates yield negatively stained specimens with conditions used for the larger trigonal crystals.
Pentamer packing in polyoma virus “hexamer” tubes analyzed by image modeling
Authors: Baker Timothy S. , Caspar D. L. D. 
Published: June 2020

Polymorphic assemblies of polyoma virus capsomeres that have been called "hexamer" tubes (because the morphological units are six-coordinated) are, in fact, built of pentamers, as is the icosahedrally symmetric T=7d virus capsid. The quasi-equivalence theory of virus construction had predicted that the six-coordinated morphological units should be hexamers. We have established the pentameric form of the capsomeres in the "hexamer" tubes by Fourier analysis of low-irradiation micrographs: indexing the computed diffraction patterns and computation of the filtered image shows pentagonalshaped capsomeres arranged in a cylindrical surface lattice with p2 symmetry. Digital model building to fit averaged micrographs, summarized here, provides a sensitive means to define the packing arrangement and substructure of the pentameric units in the superimposed top and bottom layers of the tubes.Fig. 1 shows a representative minimal exposure (∽lOe/Å2) image of a negatively stained (1% uranyl acetate) wide (Å45 nm diameter) "hexamer" tube. Metal-shadowed specimens demonstrate that the tubes are flattened and the near axial rows of capsomeres in the hexagonally packed surface lattice are inclined to the left as viewed from the outside.
Status of microcorrosion casting for SEM
Authors: Nowell J. A. 
Published: June 2020

The advantage of the SEM over all other means of gaining information about a biological sample is its ability to image spatial relationships ranging from those visible to the unaided eye to those separated by a few nanometers. It is invaluable for such studies as the localization of focal lesions widely dispersed in normal tissue; the relationships between soft and hard tissue components; the identification of individual species within a large heterogeneous population of microorganisms; and, the subject of this paper, the course of vasculatures through an organ.To date the main disadvantage of the SEM in biological research is our inability to interpret the image accurately. Our reliance on the image has decreased proportional to our understanding of the effect on the specimen of the preparation procedures. We are now aware, for instance, that ice crystals displace cellular material; that a hypertonic fixative causes shrinkage and a hypotonic one causes swelling; that unstabilized cellular constituents are extracted during solvent dehydration resulting in excessive loss of sample volume; that this volume changes during fixation, dehydration, and drying; that air drying, whether deliberate or accidental, causes structural collapse; and that sputter coating can result in thermal damage and decoration.
Ultrastructural and cell surface studies of cancer epidermal cells following reserpine administration in mice
Authors: Lupulescu A. 
Published: June 2020

Recently, it was postulated that a long-term administration of reserpine as an antihypertensive drug for treatment of millions with mild hypertension increased threefold the incidence of mammary carcinoma in women. However, a considerable controversy ensued over the statistical validity of this study and the role of reserpine in carcinogenesis remains still unsolved. The present study deals with the effects of long-term administration of reserpine on the ultrastructure, cytoarchitecture and cell surface of cancer epidermal cells from squamous cell carcinomas induced by 3-methycholanthrene (MCA) in mice.Young male Swiss mice (COBS) weighing 25 gm were used in these investigations and were divided in four groups: (1) First group was used as controls (2) Mice topically treated with 0.2 ml of 0.3% MCA sol. in acetone, twice a week for 12 months (3) Mice treated with MCA as above and simultaneously injected intramuscularly with 250 μg reserpine (serpasil), twice a week for 12 months and (4) Mice treated only with reserpine as above. Although multiple and large tumors occurred following MCA, only few small tumors were seen following reserpine and MCA treatment.
Myosin filaments localized in replicated cytoskeletons of freeze-dryed human platelets
Authors: Ruben George C. , Allen Robert D. 
Published: June 2020

Spheroidal human blood platelets (2-3 μm) on contacting siliconized glass undergo a semi-stereotypicms the original spheroid into a hillock surrounded by a thin hylomere sheet. In this process, the platelet approximately doubles its diameter. Since platelets ar spreading of their margins with pseudopod and/or lamellapod extension. They also undergo a profound reorganization of their cytoskeleton in 10-15 min at 20°C which transfore 16-17% actin and 6-7% myosin and contain muscle like control proteins it is not unreasonable that platelet spreading occur by a sliding of actin filaments as in muscle. It is possible that myosin is present in platelets either as dimers or as ordered bipolar oligomeric filaments composed of 28 monomers. In the former case, filaments 165-300nm long and 2.0-4.0nm wide would be expected. In the latter case, the myosin filaments would be 325nm long and 10.7nm wide.The cytoskeleton of demembranated platelets was investigated after an attachment interval of 20 min. or less at 20°C.
Fully correlative LM and HVEM analysis of motile fibrils and particles in the reticulopods of Allogromia sp. (protozoa, foraminiferida)
Authors: Bowser Samuel S. 
Published: June 2020

The subcellular mechanism underlying the bidirectional transport of organelles in the reticulopods of foraminiferans is poorly understood. Applications of urea and colchicine suggest a role for microtubules (MT) in mediating this transport. Allen et al. have shown that intracellular transport is effected only when organelles are in contact with motile fibrils, visible by LM, and imply that such fibrils are composed of microtubules. We recently suggested that the bidirectional transport of latex particles attached to the extracellular surface of reticulopods may also be mediated by these fibrils. Since motile fibrils are an essential component of the transport mechanism, we sought to determine their ultrastructural composition and the identity of the organelles they transport.Specimens were mounted in microperfusion chambers as described previously. Either intact organisms or isolated but functional reticulopodial networks (as illustrated here, fig 1A) may be employed. Addition of lym latex microspheres allows simultaneous study of surface motility and intracellular transport, and also provides reference marks for correlation of LM/HVEM images.
Otoconia formation in the chick embryo
Authors: Fermin C.D. , Igarashi M. 
Published: June 2020

Otoconia are microscopic geometric structures that cover the sensory epithelia of the utricle and saccule (gravitational receptors) of mammals, and the lagena macula of birds. The importance of otoconia for maintanance of the body balance is evidenced by the abnormal behavior of species with genetic defects of otolith. Although a few reports have dealt with otoconia formation, some basic questions remain unanswered. The chick embryo is desirable for studying otoconial formation because its inner ear structures are easily accessible, and its gestational period is short (21 days of incubation).The results described here are part of an intensive study intended to examine the morphogenesis of the otoconia in the chick embryo (Gallus- domesticus) inner ear. We used chick embryos from the 4th day of incubation until hatching, and examined the specimens with light (LM) and transmission electron microscopy (TEM). The embryos were decapitated, and fixed by immersion with 3% cold glutaraldehyde. The ears and their parts were dissected out under the microscope; no decalcification was used. For LM, the ears were embedded in JB-4 plastic, cut serially at 5 micra and stained with 0.2% toluidine blue and 0.1% basic fuchsin in 25% alcohol.
The human fetal pituitary: An ultrastructural analysis
Authors: Asa S. L. , Kovacs K. , Horvath E. , Laszlo F. A. , Domokos I. 
Published: June 2020

An ultrastructural study was performed on 25 human fetal pituitaries to document the development of cell differentiation and hormone production in the adenohypophysis.At 5 weeks' gestation, Rathke's cleft was lined by columnar epithelium 3-4 cells deep (Fig. 1). The cells were poorly differentiated, with abundant cytoplasmic glycogen, numerous free ribosomes and occasional secretory granules. Terminal bars were formed on the lateral cell surfaces near the luminal surface of Rathke's cleft; desmosomes formed junctions between cells.By 6 weeks' gestation, cells resembling corticotrophs were identified (Fig. 2). They contained moderately developed, rough endoplasmic reticulum and numerous secretory granules of variable size, shape and electron density. In 8-week-old fetuses, type I microfilaments were found in those cells. Welldifferentiated somatotrophs were seen in the adenohypophyses of 8-9-week-old fetuses. They contained scattered profiles of rough-surfaced endoplasmic reticulum and spherical, evenly electron dense secretory granules, measuring 300-600 nm in diameter. Cells with dilated rough endoplasmic reticulum containing flocculent material and small, dense, round secretory granules with peripheral electron lucent halos were seen in the adenohypophysis of a 14-week-old fetus; these features are characteristic of the glycoprotein hormone cell line. Typical prolactin cells were not recognizable before 23 weeks' gestation.
Identification of fluorescent analogs with antibodies specific for the fluorophore
Authors: Luby-Phelps K. , Amato P.A. , Taylor D.L. 
Published: June 2020

In this study, we investigate the utility of antibodies against fluorescein as a general probe for light and electron microscopic investigations of fluoresceinated molecules. A similar rationale has recently been applied in the construction of an f-actin affinity column using acetamidofluorescein-labeled actin bound to anti-fluorescein IgG immobilized on Sepharose 4B (5,1). Possible applications of our method include electron microscopic visualization of steady state subunit exchange in mixtures of labeled and unlabeled f-actin, determination of the ultrastructural destination of fluorescent analogs injected into living cells,and controlling for damage to cellular structures during fluorescence photobleaching.Late hyperimmune antisera are obtained from rabbits immunized with fluoresceinated bovine serum albumin (FTC-BSA). IgG is prepared by ammonium sulfate fractionation and ion exchange chromatography of DE52 (Whatman). Fab fragments are generated from IgG by digestion with papain followed by chromatography on CM32(Whatman).
Inexpensive modification of Balzers freeze-etch units for production of high resolution specimens
Authors: Steere Russell L. , Smucker Richard A. , Erbe Eric F. 
Published: June 2020

Many of the early model Balzers freeze etch units are currently unused because of the unreliability of the described procedure for use of their resistance evaporators and the cost of replacement electron guns and quartz crystal monitors. The availability of a Bendix Balzers BA-510 system at no cost to us prompted our effort to modify it inexpensively and revise the operating procedure to permit perparation of high resolution replicas.Modifications consisted of: 1) the construction of a 6 mm outside diameter brass tube 2 cm in length with a 3 mm inside diameter. The tube was split down its length so that when it was clamped into the Balzers resistance evaporator for Pt deposition a 3 mm graphite rod insert would be held in place; 2) the end of a 3 mm graphite rod was sharpened, flattened to a diameter of 1 mm and forced by the internal spring tension against the flat end of the other graphite rod (a sharpened 6 mm rod with its end flattened to 3 m m diameter.
Freeze etch of microencapsulated drugs
Authors: Rigsby W.E. , Suzuki K. , Humphreys W.J. 
Published: June 2020

Microcapsules are discrete drug-containing particles formed by dispersing drug crystals or molecules in a biodegradable polymeric matrix. Such microcapsules have been designed to be administered via injection. The advantages offered by this form of drug administration would be particularly valuable in the outpatient treatment of chronic schizophrenics who cannot be relied upon to give themselves proper dosages.In this study a model, long-acting neuroleptic was prepared by dispersing chloropromazine (CPZ) in a biodegradable polymer, poly (d, 1-lactide). Poly (d, 1-lactide) undergoes slow hydrolytic deesterification to lactic acid which is then metabolized to C02 and eliminated, thus avoiding the necessity of surgical removal of spent microcapsules. Four batches of microcapsules, differing in percentage CPZ to total capsule weight, were prepared and tested for drug release rate in an in vitro dissolution study (Fig. 1). Samples from each batch were mounted, coated and examined in a Cambridge Mark 2A SEM (Figs. 2, 3). Particle sizes ranged from 88um to 105um and were calculated from the micrographs.
Relaxation of soft-bodied aquatic and marine invertebrates for scanning electron microscopy
Authors: Rivera E. R. 
Published: June 2020

Many soft bodied invertebrates contract or retract into shells upon touch stimulation. Since preparation of specimens for SEM observation requires considerable handling as well as exposure to irritating chemicals, the resulting contractions conceal many surface features that are usually seen under normal conditions. To overcome contraction during fixations (1) or surgery (2), several species of snails have been anesthetized with varying degrees of success. Several anesthetics were tested for their efficacy in relaxing soft animals for fixations and subsequent preparations for SEM observations.From an extensive list of relaxant drugs, six anesthetics were derived for final testing based on their initial ability to anesthetize four species of contractile invertebrates in an extended condition. The following mixtures of nembutal (sodium barbital), menthol crystals, and curare (dissolved in 80% ethanol) were used: 1) nembutal, 2) menthol, 3)curare, 4)nembutal followed by menthol, 5) nembutal followed by curare, and 6) menthol followed by curare. All animals tested feed and move under fully submerged conditions.
Structural analysis of crystalline Ca++transport ATPase vesicles
Authors: Loren Buhle E. , Knox Barry E. , Aebi Ueli 
Published: June 2020

In our efforts to study the three-dimensional structure and molecular organization of ion-motive ATPases by electron microscopy and image processing we have systematically investigated conditions which induce the formation of ordered arrays of these integral membrane proteins. Among them we have explored the effect(s) of vanadate and other multi-valent ions on ATPase crystal formation by starting from published procedures [e.g. 1,2]. Here we present some preliminary results concerned with the packing and molecular organization of vanadate-induced crystalline arrays of a Ca++transport ATPase in tubular rabbit sarcoplasmic reticulum vesicles.The Ca++activated ATPase from rabbit sarcoplasmic reticulum was purified as published. Induction of ordered tubular arrays of the protein with vanadate was basically achieved as described, except that the protein was slowly dialysed against a vanadate-containing buffer rather than directly adding the vanadate to the protein. Optimal yields of crystalline arrays were obtained after two days of dialysis at 4°C.
Carbon tetrachloride induced surface changes in isolated rat hepatocytes
Authors: Barnard S.D. , Caldwell W.J. , Thompson D.J. 
Published: June 2020

The administration of CCl4to laboratory animals produces liver toxicity detectable by both morphological and biochemical methods. Hepatocellular metabolic cleavage of CCl4creates free radicals which damage biological membranes through the process of lipid peroxidation; this process produces measurable products of peroxidative decomposition one of which is malondialdehyde (MDA). Many studies of CCl4-induced toxicity appropriately have focused on the smooth endoplasmic reticulum (SER) where the enzymatic cleavage of CCl4occurs. Reports that CCl4is also metabolized to free radicals in the plasma membrane (PM)1and that in vitro exposure to CCl4causes PM blebing and loss of microvilli2indicate a need for further study of this cellular component.A male Sprague-Dawley rat was treated daily, i.p., with 80 mg/kg of phenobarbital in order to induce SER-associated enzymes and thereby enhance the subsequent in vitro response of the cells to CCl4. After 5 days the rat was anesthetized with pentobarbital, and the liver was perfused with collagenase solution.
The topochemistry of black spruce sulphonation: A TEM/EDXA study
Authors: Beatson R.P. , Gancet C. , Heitner C. 
Published: June 2020

Pulps produced by mechanical defibration of sulphite treated black spruce wood chips contain large amounts of lignin. The degree of sulphonation of this lignin has a significant influence on the physical properties of handsheets made from the resulting pulps In earlier work we have described the factors affecting the sulphonation of black spruce.The aim of the present investigation was to determine the differences in reactivity of sulphite towards lignin in the middle lamella and cell wall of black spruce.Black spruce wood chips were well impregnated with sodium base sulphite solutions having pH 7, and then heated at 140° and 80°C for known times. The resulting sulphonated wood chips were cut into small sticks and embedded in Vestopal. Transverse sections, 150 nm thick, were placed on a carbon grid having a single 1 mm hole bearing a collodian film which had been carbon coated. Sulphur contents in the middle lamella and cell wall were determined with a Philips 400 TEM coupled with an EDAX 9100/60 analyser. The concentration of sulphur was taken to be proportional to the x-ray counts in the sulphur Kα window after background subtraction, as shown in Figure 1.
Glycogen in guinea pig neutrophils: Ultrastructural study of neutrophils at the intradermal site of BCG injection
Authors: Bucana Corazon D. 
Published: June 2020

In the circulating blood of man and guinea pigs, glycogen occurs primarily in polymorphonuclear neutrophils and platelets. The amount of glycogen in neutrophils increases with time after the cells leave the bone marrow, and the distribution of glycogen in neutrophils changes from an apparently random distribution to large clumps when these cells move out of the circulation to the site of inflammation in the peritoneal cavity. The objective of this study was to further investigate changes in glycogen content and distribution in neutrophils. I chose an intradermal site because it allows study of neutrophils at various stages of extravasation.Initially, osmium ferrocyanide and osmium ferricyanide were used to fix glycogen in the neutrophils for ultrastructural studies. My findings confirmed previous reports that showed that glycogen is well preserved by both these fixatives and that osmium ferricyanide protects glycogen from solubilization by uranyl acetate.I found that osmium ferrocyanide similarly protected glycogen. My studies showed, however, that the electron density of mitochondria and other cytoplasmic organelles was lower in samples fixed with osmium ferrocyanide than in samples fixed with osmium ferricyanide.
Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy
Authors: Wu W. H. , Glaeser R. M. 
Published: June 2020

Spirillum serpens possesses a surface layer protein which exhibits a regular hexagonal packing of the morphological subunits. A morphological model of the structure of the protein has been proposed at a resolution of about 25 Å, in which the morphological unit might be described as having the appearance of a flared-out, hollow cylinder with six ÅspokesÅ at the flared end. In order to understand the detailed association of the macromolecules, it is necessary to do a high resolution structural analysis. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl2, a procedure derived from that of Buckmire and Murray. Low dose, low temperature electron microscopy has been applied to the large arrays.As a first step, the samples were negatively stained with neutralized phosphotungstic acid, and the specimens were imaged at 40,000 magnification by use of a high resolution cold stage on a JE0L 100B. Low dose images were recorded with exposures of 7-9 electrons/Å2. The micrographs obtained (Fig. 1) were examined by use of optical diffraction (Fig. 2) to tell what areas were especially well ordered.
The role of multivariate image analysis in solving the architecture of the limulus hemocyanin molecule
Authors: Frank Joachim 
Published: June 2020

The detailed distribution of stain grains in contact with the stain-excluding portions of a protein molecule is random: inspection of a single image of a macromolecule reveals little below the resolution level of gross morphology (Fig 1). However, new insights can be gained by analyzing a large set of molecule images resulting from the same experiment.Firstly, the noise reduction due to averaging allows higher-resolution detail to be retrieved. Secondly, the analysis of such a set reveals new information that is qualitatively different from information contained in a single molecule image: the patterns of variation in local stain distribution. The stain variation at any point, and the way in which stain variations at different points of the structure are correlated, reflect certain constraints that have to do with the local binding characteristics of the molecule (e.g. accessibility of charged sites) and with its detailed topography. In the past, few observations were made relating to these phenomena because they are very difficult to quantify.