bluuebunny/crossref_metadata_2025_split huggingface dataset:
Freeze-etch studies on the gametocytes of Plasmodium falciparum
Authors: Meszoely Charles A.M. , Erbe Eric F. , Steere Russell L. , Palmer Timothy , Beaudoin Richard L. 
Published: June 2020

The Erythrocytic stages of the Honduras strain of the malarial parasite Plasmodium falciparum were maintained in tissue culture medium RPMI 1640. Red blood cells containing gametocytes and other erythrocytic stages were fixed in 2% glutaraldehyde, and cryoprotected in 30% glycerol in H2O. This preparation was freeze-etched for one minute at -98°C in a modified Denton DFE-2 freeze-etch module. Stereo pairs with specimen tilt of 10 between electron micrographs were obtained with a JEM-100B transmission electron microscope equipped with a 60° top entry goniometer stage.The fine structure of the gametocytes of malarial parasites has been studied by conventional electron microscopic methods [stained ultrathin sections (2 and 3)], but this stage of the life cycle has not been demonstated previously with freeze-fracture studies.Since the red blood cells in our preparation also contained other stages of the life cycle, the following combination of characteristics were used to differentiate the gametocytes: presence of microtubules; food vacuoles; and large size.Microtubules are not found in trophozoites, and merozoites are relatively small and do not contain food vacuoles.
Multilamellar body size comparison from lung of embryos and hatchlings of chick
Authors: Blystone Robert V. , Souder Genny , Hass Dawn 
Published: June 2020

The functional lung of a newborn animal requires surfactant for the purpose of reducing the surface tension at the airtissue interface. Reduced surface tension prevents the lung from collapsing due to high pressures associated with ventilation and lung geometry; and also lowered tension assists in the movement of respiratory gases in and out of the lung tissue. Surfactant first appears late in lung development and correlates with the appearance of a morphological structure in Type II alveolar cells called a multilamellar body. The multilamellar body (LAM) is comprised mainly of phospholipids which serve as the principal ingredient of lung surfactant. The study here reported involves a comparison of multilamellar body size just before and after hatching of white leghorn chick.Eggs of Gallus domesticus, white leghorn breed, were incubated at 99 3/4°F at a relative humidity of 50-56%. Fertile eggs weighing between 50 and 70 grams were divided into two groups: 1) group one eggs were incubated nineteen 24-hour periods before sacrifice and 2) group two eggs were allowed to hatch and sacrificed twenty-two 24-hour periods after the onset of incubation.
Cell adhesion molecules in Dictyostelium: Identification with monoclonal antibodies
Authors: Baronde S. H. , Springer W. R. 
Published: June 2020

Cells in multicellular organisms occupy specific positions in relation to each other. This is brought about by a complex series of factors, one of which is believed to be the interaction of molecules on cell surfaces with those on other cells or the extracellular matrix. The molecules presumed to mediate these functions have been designated cell adhesion molecules and cell recognition molecules. The former indicates that they play a direct role in the adhesion process, while the latter indicates that they mediate the selectivity of adhesion. One molecule might serve both a recognition and an adhesion function but, given the complexity of cell surfaces, recognition and adhesion could also be separate, and possibly sequential, processes.We have chosen to study the problem of cell-cell adhesion in cellular slime molds because these relatively simple eukaryotic organisms have many properties that facilitate experimental work on this complex problem:
Cell surface antigens in early mammalian development
Authors: Johnson Lincoln V. , Calarco Patricia G. , Ploack-Charcon Syivia 
Published: June 2020

Cell surface molecules are known to be functionally important In a number of developmental systems. Molecular components of the cell surface may participate in Intercellular adhesion, recognition and communication. Reactions occur r Ing at the cell surface may also influence developmental events by Induci ng i ntracelIular changes In cellular metabolism and gene expression which may, In turn, alter the composition and/or organization of surface components. Sequences of reactions mediated by cell surface molecules are probably Important In directing undifferentiated embryonic cells along specific dlfferentlatlve pathways.In the early development of the mammal Ian embryo, important events occurring during the preimplantation period are likely to require the participation of specific cell surface molecules. For example, these are likely to Include sperm-egg attachment and fusion, Interbl astomere adhesion, blastulatlon, and attachment of the blastocyst to the uterine epithelium. During preimplantation mouse development, specific stage-relaged changes in the qual itatlve and quantitative nature of the proteins synthesized and those expressed on the cell surface have been documented.
Ultrastructural imaging of whole cells by cryo-HVEM
Authors: Fotino Mircea , Giddings Thomas H. 
Published: June 2020

A cryostage cooled by liquid nitrogen has been recently completed and activated on the top-entry 1 MV JE0L JEM-1000 of the National Facility for high-voltage electron microscopy in Boulder, Colorado. It provides continuous and controlled cooling of a specimen during observation at an arbitrary temperature in the range 78K to room temperature. Good thermal stability of about ± 0.1K can be achieved by maintaining an appropriate balance between refrigerant flow and heat provided by an automatically controlled built-in heater. Consequently the overall specimen drift is reduced so that high-resolution lattice images of graphitized carbon (spacing 0.34 nm) and Sn/SnTe alloy (spacing 0.31 nm) can be obtained throughout the temperature range.The interest of such cryoimaging is primarily to view hydrated specimens in frozen form, to explore the advantages of fast freezing and freeze-drying as an alternative to chemical fixation and dehydration, and possibly to benefit from a certain reduction in radiation damage known to take place at low temperatures. Frozen specimens are placed onto the cold cryostage in about 5 minutes with a mechanism developed specifically for this purpose. Thus the specimens are kept continuously immersed in liquid nitrogen, and unexposed to the atmosphere, between freezing and insertion into the air lock leading into the instrument column.
Observation of reconstituted Lumbricus terrestris hemoglobin with the STEM
Authors: Kapp O. H. , Ohtsuki M. , Crewe A. V. , Vinogradov S. N. 
Published: June 2020

The annelid extracellular hemoglobins are giant heme containing respiratory proteins (3-4x106 MW) possessing an extraordinary range of physiological function, Their electron microscopic appearance is that of two superimposed hexagons with approximate dimensions of 300 x 200Å by STEM. These unusual proteins are composed of multiple copies of as many as six distinct polypeptides ranging in size from 13 to 37,000 MW as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Possessing approximately 150 hemes per molecule, they represent an alternate solution to the demand for increased efficiency of oxygen transport imposed by the evolution of multicellular organisms.The hemoglobin of Lumbricus terrestris dissociates at alkaline pH yielding a broad overlapping distribution of molecular weight species ranging in size from 25 to 300K. Exposure to 0.05M sodium borate buffer, pH 9.0, for 24 hours, followed by gel filtration on a column of Sepharose C1-6B equilibrated in the same buffer, gives the elution profile shown in Fig. 1.
Imaging of the alpha-chain extensions of fibrinogen
Authors: Price Todd M. , Rudee M. L. 
Published: June 2020

Amorphous carbon, as well as a few polymeric materials, are used routinely as substrates for the electron microscopic examination of macrorno1ecules. Replication of molecules from a cleaved mica surface is also used. The choice is ty pically made on the basis of convenience, and limited to commonly used materials.In the course of research on the interaction of plasma proteins with several non-biological materials we observed that the use of substrate materials that were not typical in electron microscopy produced images that revealed hitherto unobserved features of certain macromolecules. This paper will describe the techniques we have developed to image additional features of fibrinogen, give some additional results, and describe some experiments undertaken to elucidate the basis of the technique.
Colloidal gold double labeling of two secretory proteins in bacterial cell
Authors: Tinglu Guan , Ghosh Arati , Ghosh Bijan K. 
Published: June 2020

Secretory proteins have been localized in bacterial cells by inmunoelectron-microscopy and cytochemical methods. Although ferritin-antibody technique is satisfactory for the localization of single antigenic sites, multiple labelling is not possible by this technique. However, such multiple labelling is possible using colloidal gold antibody because colloidal gold of widely varying sizes can be prepared by simple laboratory manipulation. We prepared colloidal gold of two different sizes and labelled these with anti-penicillinase and anti-alkaline phosphatase antibodies. These labels were used to determine the location of penicillinase and alkaline phosphatase in secreting Bacillus licheniformis 749/C cells.Large colloidal gold particles (150Å) were prepared by 10% sodium citrate treatment of 0.01% HAuCl4; the pH of this colloidal gold suspension was adjusted to 7.6 with 0.2 M K2CO3. Small colloidal particles (50A) were prepared by treating 0.01% HAuCl4, after pH was adjusted to 8.0 with 0.2M K2CO3, withphosphorous saturated ether. The large or small gold particles (1010 in 10 ml) were treated with 100μg of anti-alkaline phosphatase or anti-penicillinase antibodies; after thorough mixing unbound antibodies were removed by centrifugation.
Golgi processed foot-and-mouth disease virus proteins
Authors: Wool S. H. , Polatnick J. 
Published: June 2020

The Golgi apparatus was isolated from infected baby hamster kidney cells by centrifugation through discontinuous sucrose gradients. Tritium-labeled protein samples were analyzed by polyacrylamide gel electrophoretic autoradiograms. Pulse-chase studies showed that the viral-induced RNA polymerase passed through the Golgi as infection progressed. Some viral coat proteins were also associated with the Golgi as were other as yet unidentified viral proteins (Fig. 1). Immune labeling of isolated and in situ Golgi confirmed the presence of viral RNA polymerase. The isolated (Fig. 2) and in situ Golgi were labeled with guinea pig antipolymerase antibody and ferritin-labeled goat anti-guinea pig sera to show the presence of viral RNA polymerase.Earlier work in this laboratory established that the RNA polymerase was bound to membranes of newly formed smooth vacuoles during infection with FMDV. The smaller protein on the gel in Fig. 1 (arrow) corresponds in size to VPg (a nonstructural protein bound to the 5' end of viral RNA) has also been shown to be membrane bound.
Ultrastructural changes in sciatic nerve tissue: Effects of passive maternal smoking
Authors: K.S. Amankwah , Weberg A.D. , Kaufmann R.C. 
Published: June 2020

Previous research has revealed that passive (involuntary inhalation) tobacco smoking during gestation can have adverse effects upon the developing fetus. These prior investigations did not concentrate on changes in fetal morphology. This study was undertaken to delineate fetal neural abnormalities at the ultrastructural level in mice pups exposed in utero to passive maternal smoking.Pregnant study animals, housed in a special chamber, were subjected to cigarette smoke daily from conception until delivery. Blood tests for determination of carbon monoxide levels were run at 15-18 days gestation. Sciatic nerve tissue from experimental and control animals were obtained following spontaneous delivery and fixed in 2.5% gluteraldehyde in 0.1M cacodylate buffer pH 7.3. The samples were post-fixed in osmium ferrocyanide (1:1 mixture of 1.5% aqueous OSO4 and 2.5% K4 Fe(CN)6). Following dehydration, the tissues were infiltrated with and embedded in Spurr. Sections were stained with uranyl acetate and lead citrate.
Extracellular matrices and the control of cell proliferation and differentiation in vitro
Authors: Gospodarowicz D. 
Published: June 2020

Recent investigations suggest that, in vitro, cell-substratum interactions may play other roles in addition to cell anchorage. The extracellular matrix (ECM) that cells can produce and upon which they rest can be held responsible for the final shape the cells will adopt. This shape in turn may play a role in the cell's response to serum factors and its differential response to various growth factors. Components of the ECM produced by cells have also been shown to be involved in cell differentiation and the control of gene expression, as well as in cell attachment. Even soluble matrix components can affect cell shape and the organization of their basal surface and cytoskeleton by stimulating ECM synthesis.One of the major limitations of tissue culture techniques currently in use is that cells rest on plastic. Unless cultured cells can produce their own ECM, the possibility exists that contact with plastic could inhibit them from proliferating or could cause them to lose rapidly their ability to express their correct phenotype. In the present review, we will outline recent studies of the behavior of cells maintained on dishes coated with ECM of known composition. The use of such a substrate for the long-term culture of normal diploid and tumor cells will be described.
The response of a mixed cell population in mouse testes to x-ray and HZE irradiation
Authors: Philpott D. E. , Sapp W. , Williams C. , Stevenson J. , Black S. , Corbett R. 
Published: June 2020

The testes sperraatogonial population differentiates from a stem cell (As) which, via a series of mitotic divisions, gives rise to spermatocytes. The spermatocytes undergo reductional meiotic divisions and mature into sperm. Short cellular life cycles make the testes an excellent tissue for quantitative studies of radiation effects.Brown B6D2F1 mice, aged 14 weeks, were exposed to Helium particle radiation (227 MeV) in the Berkeley 184 inch synchocyclotron and to x rays at 225 KvP and 15 mA. Doses ranged from 1 to 100 rads. Tissues were fixed in Triple Fix and embedded. Two-micron sections were stained with Toluidine Blue, and ultra-thin sections were stained in the standard manner for electron microscopy. All studies were done on the tissues 72 hrs after irradiation.Our previous work, on cell survival after graded doses of radiation, has shown a steeper slope (more sensitive response) in the low dose range below 20 rads. By convention, the resulting points were plotted by linear regression resulting in a "best fit" straight line.
Influence of aromatic hydrocarbons on the distribution of mucopolysaccharides associated with the gill and nasal mucosa
Authors: Norton W.N. , Mattie D. 
Published: June 2020

Selective aromatic hydrocarbons such as benzene, xylene and naphthalene have been analyzed as to their relative toxicities to acquatic organisms. The aromatic hydrocarbon fraction of JP-4 jet aviation fuel, which consists of benzene, xylene and toluene induces cellular lesions in a variety of internal organs of the fat-head minnow.The primary objective of the investigation was to determine the acute ultrastructural effects of the water soluble fraction of petroleum-derived JP-4 aviation fuel on the distribution of mucopolysaccharides normally associated with surfaces of the gill and nasal mucosa of the fat-head minnow. Ruthenium red, a hexavalent cation, was employed as a visual marker for the presence of mucopolysaccharides.Fish were exposed to a 60% concentration of the water soluble fraction of JP-4. At the time periods of 2, 6 and 12 hours subsequent to the initial exposure, a select number of fish were removed from the solution and the gills and sections of the nasal mucosa were excised. The tissues were immersed for 1 hour in 0.1M cacodylate-buffered (pH 7.4) 2.5% glutaraldehyde containing 500 ppm ruthenium red.
Ultrastructural diagnosis of a plexiform liposarcoma
Authors: Siew Shirley , Jhaveri Bharati , Elsensety Evette 
Published: June 2020

Less well differentiated malignant neoplasms may pose a serious problem in the establishment of a definitive diagnosis at the light microscopy level. In such instances, transmission electron microscopy (TEM) may prove to be of value as it may identify diagnostic characteristics that can be appreciated only at ultrastructural magnification. The case reported here illustrates the application of TEM in the differential diagnosis of a soft tissue sarcoma.A 63 year old male presented in the out patient service with a mass in the region of the left scapula. Its gross appearance was likened to that of a "Big Mac." A needle biopsy was performed and submitted for histological and TEM examination. Histology of multiple serial sections showed the presence of a malignant neoplasm composed of markedly pleomorphic cells, including numerous bizarre giant cells and smaller cells with irregular nuclear outline and indistinct eosinophilic cytoplasm. Cytoplasmic vacuoles were prominent. They did not stain with PAS nor mucin stains.
3-D reconstruction of molecular shape from microcrystal thin sections
Authors: Cusack S. , J.-C. Jésior  
Published: June 2020

Three-dimensional reconstruction techniques using electron microscopy have been principally developed for application to 2-D arrays (i.e. monolayers) of biological molecules and symmetrical single particles (e.g. helical viruses). However many biological molecules that crystallise form multilayered microcrystals which are unsuitable for study by either the standard methods of 3-D reconstruction or, because of their size, by X-ray crystallography. The grid sectioning technique enables a number of different projections of such microcrystals to be obtained in well defined directions (e.g. parallel to crystal axes) and poses the problem of how best these projections can be used to reconstruct the packing and shape of the molecules forming the microcrystal.Given sufficient projections there may be enough information to do a crystallographic reconstruction in Fourier space. We however have considered the situation where only a limited number of projections are available, as for example in the case of catalase platelets where three orthogonal and two diagonal projections have been obtained (Fig. 1).
Tubular intranuclear inclusions in a patient with methotrexate-associated pulmonary fibrosis
Authors: Gunning W.T. , Goldblatt P.J. 
Published: June 2020

A forty-six year old male, who had received methotrexate therapy for the past year for psoriasis of twenty years' duration, presented with a cough which had persisted for two to three months. There was a two year history of dyspnea upon exertion as well as intermittent fever, chills and sweats. The methotrexate treatment did not improve the skin condition and, because there was evidence of hepatic toxicity, the drug was discontinued. Radiological examination of the chest revealed diffuse bilateral interstitial fibrosis with extensive changes; a subseguent lung biopsy was obtained. Light microscopic evaluation demonstrated marked interstitial fibrosis, chronic inflammation, thickening of the alveolar septa, proliferation of alveolar macrophages, occasional fibrin deposits and multinucleated giant cells.Electron microscopic studies revealed massive fibrosis with a mixed population of infiltrating inflammatory cells. Some alveolar spaces were lined by metaplastic cuboidal epithelial cells, and in numerous residual type II pneumocytes, aggregates of branching tubules lined by trilaminar membranes were identified within the nucleus.
Transmission electron microscope studies of a piliated strain of Haemophilus influenzae B
Authors: Palmer Booth Doris 
Published: June 2020

The role of pili as a mucosal attachment factor that enhances colonization and pathogenicity is well known in Escherichia coli, Neisseria gonorrhea, Streptococcus pyrogenes and Proteus mirabilis. Although Haemophilus influenzae type b (Hib) causes serious infections in children such as meningitis, pneumonia, septic arthritis and epiglottitis, very little information is available about Hib piliation and subsequent adhesion and colonization in vivo. Hib piliation was recently correlated with hemagglutination and adherence (in vitro) to human buccal epithelial cells by Pichichero, et al.Pili are protein structures which extend from the outer membrane of Hib. Purified pili have an apparent molecular weight of 23,000 daltons by Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and aggregate laterally as well as end on end to form thick filamentous structures. Although pili seem to enhance attachment to respiratory mucosa (a significant foothold during the invasion of healthy tissue) the relative pathogenicity of piliated and non-piliated Hib is yet to be determined.
Electron Channeling Patterns
Authors: Joy David C. 
Published: June 2020

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).
Progress in Single Atom Microscopy
Authors: Isaacson M. , Kopf D. , Utlaut M. 
Published: June 2020

We have indicated in previous publications that a scanning transmission electron microscope (STEM) capable of atomic resolution may be a useful instrument for surface science studies and, in particular, capable of reliably observing the distribution and diffusion of individual atoms on thin film substrates (1-3). In this paper we will present further observations relating to the characteristics of individual heavy atoms on low atomic number substrates.In figure 1, we show pair spacing distributions of individual uranium (1A) and silver (IB) atoms adsorbed to thin (˜20 Å thick) carbon film substrates. These distributions are obtained by measuring spacings between all pairs of atoms on many different fields of view (2). The two distributions for each atom type are for different specimens.(The spacing distribution is defined as the number of atoms/Å2 in an annulus of 1 Å width at a given distance from any atom.) For both the U and Ag distributions, there is a pronounced peak near 4-5 Å.