Electron Photomicrographs Research Articles

Thrombotic Thrombocytopenia Induced in Dogs and Pigs

Thrombotic thrombocytopenia with severe depletion of plasma von Willebrand factor (vWF) was induced in normal large animals (5 dogs and 2 pigs) by botrocetin, a Bothrops factor requiring vWF for platelet agglutination. Botrocetin (90 to 100 U/kg, 2.14 to 2.38 mg/kg, in a single i.v. injection) reduced plasma vWF activity to < 0.1 U/mL for 24 hours. During this period, multimeric analysis of plasma vWF antigen (Ag) revealed the loss of intermediate- and high-molecular-weight forms with a concomitant increase in lower molecular weight forms. A moderate reduction in factor VIII (FVIII) activity was observed. The vWF reduction was accompanied by transient thrombocytopenia and prolonged bleeding times during the deficiency state. Occlusive platelet thrombi were detected by transmission electron microscopy in the microcirculation of lung and spleen but not kidney or brain 30 minutes after the botrocetin injection. Recovery of plasma vWF and platelet count occurred within 48 hours and was associated with the appearance in the plasma of unusually large forms of vWF:Ag multimers. The vWF:Ag multimer distribution was normal at 72 hours. The ultrastructural distribution of vWF in unstimulated normal porcine and canine platelets was examined by using immunogold staining. VWF was detected in the alpha-granules of normal pig platelets but was not observed in platelets from normal dogs. However, both animals developed thrombotic thrombocytopenia when injected with botrocetin. A second group of animals (2 dogs and 3 pigs) with von Willebrand disease (vWD) was given a single botrocetin injection (90 to 100 U/kg). No thrombocytopenia occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact modification of thermoplastics by methyl methacrylate and styrene‐grafted natural rubber latexes

AbstractThe preparation and characterization of polymer blends with structured natural rubber (NR)‐based latex particles are presented. By a semicontinuous emulsion polymerization process, a natural rubber latex (prevulcanized or not) was coated with a shell of crosslinked polymethylmethacrylate (PMMA) or polystyrene (PS). Furthermore, core–shell latexes based on a natural rubber/crosslinked PS latex semi‐interpenetrating network were synthesized in a batch process. These structured particles were incorporated as impact modifiers into a brittle polymer matrix using a Werner &amp; Pfleiderer twin screw extruder. The mechanical properties of PS and PMMA blends with a series of the prepared latexes were investigated. In the case of PMMA blends, relatively simple core (NR)–shell (crosslinked PMMA) particles improved the mechanical properties of PMMA most effectively. An intermediate PS layer between the core and the shell or a natural rubber core with PS subinclusions allowed the E‐modulus to be adjusted. The situation was different with the PS blends. Only core–shell particles based on NR‐crosslinked PS latex semi‐interpenetrating networks could effectively toughen PS. It appears that microdomains in the rubber phase allowed a modification of the crazing behavior. These inclusions were observed inside the NR particles by transmission electron microscopy. Transmission electron photomicrographs of PS and PMMA blends also revealed intact and well‐dispersed particles. Scanning electron microscopy of fracture surfaces allowed us to distinguish PS blends reinforced with latex semi‐interpenetrating network‐based particles from blends with all other types of particles.

Selective Retention of VLDL, IDL, and LDL in the Arterial Intima of Genetically Hyperlipidemic Rabbits In Vivo

To explore possible mechanisms whereby the triglyceride-rich lipoproteins IDL and VLDL may promote atherosclerosis, fractional loss of these lipoproteins from the intima-inner media was measured in vivo in genetically hyperlipidemic rabbits of the St Thomas's Hospital strain and compared with the fractional loss of LDL, HDL, and albumin. These rabbits exhibit elevated plasma levels of VLDL, IDL, and LDL. In each rabbit, two aliquots of the same macromolecule, one iodinated with 125I and the other with 131I, respectively, were injected intravenously on average 24 and 3 hours, respectively, before removal of the aortic intima-inner media. The fractional loss from the intima-inner media of newly entered macromolecules was then calculated. The average fractional losses for VLDL, IDL, LDL, HDL, and albumin in lesioned aortic arches were 0.1%/h (n = 4), -0.2%/h (n = 3), 1.8%/h (n = 4), 11.4%/h (n = 3), and 26.3%/h (n = 1), respectively; in nonlesioned aortic arches fractional losses for IDL, LDL, HDL, and albumin were 1.7%/h (n = 1), 0.6%/h (n = 2), 14.6%/h (n = 3), and 25.9%/h (n = 3). In both lesioned and nonlesioned aortic arches, the logarithms of these fractional loss values were inversely and linearly dependent on the diameter of the macromolecules (R2 = .57, P = .001 and R2 = .84, P < .001), as determined from electron photomicrographs of negatively stained lipoproteins. These results suggest that after uptake into the arterial intima, VLDL and IDL as well as LDL are selectively retained in comparison with HDL and albumin.

Titanium contamination of recycled cell saver blood in revision hip arthroplasty

The use of Cell Saver blood during revision hip arthroplasty has many benefits, both medical and economic. After a review of the current literature, to our knowledge, no case of metallic debris has been reported in the blood after complete treatment with the Haemonetics Cell Saver (Braintree, MA) and appropriate filter system. A case of total hip revision of a loose, cemented acetabular component with a commercially pure titanium metal backing and a titanium alloy plasma-spray textured surface was undertaken. The titanium alloy femoral component was not visibly loose and was not revised. The joint lining tissues were black. Throughout the procedure, the operative site was suctioned with a double-lumen heparinized catheter that delivered blood and other materials to a Haemonetics Cell Saver 3 Plus. The reservoir and filter unit used were the compatible Bentley BCR-3500 (Baxter, Irvine, CA), a system capable of filtering particulates down to 20 μm. Prior to infusion of the salvaged blood, many large black clumps of material were observed mixed in the blood. Some measured 10 × 5 × 5 mm and could easily be seen macroscopically. Light microscopy demonstrated red blood cells with intermixed neutrophils, and black foreign material scattered as separate particles and within the cytoplasm of the scattered histiocytes. Energy dispersive analysis of the black material confirmed the composition as primarily titanium with minute quantities of copper, iron, phosphorous, and sulfer. A scanning electron photomicrograph of one of the specimens demonstrated a large conglomerate, approximately 2,000 μm in diameter, composed primarily of titanium and organic material. No malfunction in the Cell Saver machine, defects in the Cell Saver disposable components, or defects in the Bentley reservoir and filter were identified. In this case, if the individual titanium fragments did not aggregate into grossly visible particles, the contaminant likely would not have been discovered. Use of the Cell Saver in tissues with gross metallosis is not a reported contraindication. The authors suggest careful observation of the Cell Saver during the portion of revision surgery dealing with grossly blackened tissues in order to avoid aggregates of titanium as encountered in this case. Further, the authors now use a second suction not attached to the Cell Saver when grossly blackened tissues are encountered.

Membrane formation by isothermal precipitation in polyamide‐formic acid‐water systems II. Precipitation dynamics

AbstractAn analysis is presented, which describes the isothermal ternary diffusion process encountered in the formation of the aliphatic polyamide membranes such as Nylon‐66 by direct immersion‐precipitation of a polymeric solution in a nonsolvent bath. A material coordinate is employed to derive the mass transfer equations for the membrane solution. The convective mass transfer in the coagulation bath is taken into account by solving the hydrodynamic boundary layer equations. Diffusion coefficients were measured and used to deduce ternary phenomenological coefficients. The computed results are found to agree with measured precipitation times and with membrane morphologies observed by scanning electron photomicrographs. © 1995 John Wiley &amp; Sons, Inc.

Recent advances in amelogenin biochemistry.

This paper reviews advances in amelogenin biochemistry in three areas; (i) amelogenin expression; (ii) amelogenin post-translational and post-secretory processing, and (iii) amelogenin structure and function. Recent studies of amelogenin expression have demonstrated that alternative-splicing of mouse amelogenin RNA generates seven distinct mRNAs, coding for amelogenin proteins from 194 to 44 amino acid residues in length. A polyclonal antibody to a sequence of the 194-residue murine amelogenin identified this protein in vivo. While several studies have reported that amelogenins are post-translationally phosphorylated, it has proved difficult to confirm this view. Mass spectrometry studies of bovine and porcine TRAP and LRAP amelogenins have established a phosphoserine residue at position-16 as originally reported by Takagi et al. for a 180-residue bovine amelogenin. Also, we discovered that the detailed mechanism(s) of carboxy-terminal amelogenin proteolytic processing appear different than previously reported. In terms of amelogenin structure, it is well known that amelogenins form aggregated structures. Studies employing a recombinant amelogenin and dynamic light-scattering instrumentation demonstrated aggregate structures of 15-20 nm in radius, corresponding to a mass of 2-3 million daltons. Imaging these aggregates by transmission electron and atomic force microscopy suggested that these structures are equivalent to the "stippled" or "granular" material seen in electron photomicrographs of developing enamel. Collectively, these advances in amelogenin biochemistry lead to a new view of amelogenin structure, processing and functions in enamel biomineralization.

Reinforcement of EPDM-based ionic thermoplastic elastomer by carbon black

High abrasion furnace carbon black improves the physical properties of zinc sulfonated ethylenepropylenediene terpolymer of high (75 wt%) ethylene content. Properties studied include hardness, stress-strain characteristics, tear strength, hysteresis and abrasion resistance. Scanning electron photomicrographs of the tear fractured and abraded surfaces show changes in failure mode of the polymer on incorporation of carbon black. Results of dynamic mechanical analyses and dielectric thermal analyses show that carbon black reinforces the ionomers, presumably through weak rubber—filler interaction involving the backbone chains and strong interaction between the active sites of the filler surface and the ionic aggregates present in the ‘multiplets’ and ‘clusters’. Reprocessability studies in the Monsanto Processability Tester (MPT) show that the carbon black filled polymer can be reprocessed like a thermoplastic elastomer and there was no fall in properties even after three cycles of extrusion through the MPT.

In vitro properties of film-coated diltiazem hydrochloride pellets compressed into tablets

The mechanical properties of ethylcellulose films were determined to evaluate effects of polymer, plasticizer, and dispersed solid. The concentration of propylene glycol was shown to exhibit no significant effect on the tensile strength while that of diethyl phthalate did. Both plasticizers were also found to have significant effects on the film elongation. Theoretical calculations revealed that the release of diltiazem hydrochloride from ethylcellulose film-coated pellets could be described by the combination of constant and non-constant activity source diffusion-controlled model. A dramatic modification in drug release characteristics was observed after the film-coated pellets had been compressed into tablets. However, the increase in compression force within the working range (181.8, 272.7, and 363.6 kg) was distinctly found to slightly affect the release from pellets being compressed. These behaviors may not be caused by flaws or failures within the film, but instead by the appreciable alterations in some physical properties of the film itself under pressure. The electron photomicrographs confirmed such a hypothesis.

Calculation of pulsatility index of flow volume independent of vessel diameter and flow profile

An application of a morphometric model is used to study the stroma epithelial interface in human cervical epithelium. This model derived by Okagaki and associates estimates from two dimensional transmission electron photomicrographs the number of basal cell pseudopodia per basal cell. The investigation of the full spectrum of cervical intraepithelial neoplasia (CIN) focusing on the basal cell-stroma interface with the “multiple cell-single section” model is discussed. Significant decreases in histopathologic grades of CIN are noted in the number of pseudopodia per basal cell (N¯) and the ratio (F¯) of the area of the stems of pseudopodia to the area of the base of the basal cell.

Cileoporus,a new genus of Rove Beetles from central and South America (Coleoptera, Staphylinidae, Tachyporinae)

This paper describes the new genus Cileoporus to include the species Cilea fenestrata Sharp and Tachinus politus Bernhauer. Tachinus politus Bernhauer is designated as the type species. Cileoporus is assigned to the Tribe Tachyporini of the family Staphylinidae. All major characters of the genus are illustrated with line drawings or scanning electron photomicrographs and a key is provided to distinguish the new genus from all other genera of the tribe known to occur in Central and South America. Brief diagnostic descriptions and a key is provided to aid in distinguishing the two species of the genus. The characters most useful for distinguishing the species are illustrated. A lectotype is designated for Tachinus politus Bernhauer.

Biased magnetron sputter deposition of corrosion resistant Al–Zn alloy thin films

The reason for the high corrosion resistance of Al–Zn films is unclear. To relate this behavior to the structure and fabrication we have studied films deposited by dc biased magnetron sputtering onto Fe–Cr substrates. Changes of composition, structure, and electrochemical polarization behavior of resultant films were measured as a function of experimental parameters, including on-axis and off-axis substrate positions. The films, 1.6–4 μm thick, were deposited with a chamber Ar pressure of 10 mTorr (1.33 Pa), substrate temperature of 22–90 °C, and substrate bias of −60 to −380 V. Transmission electron photomicrographs of thin alloy films exhibited polycrystalline structure comprising one or two phases depending on film composition. Lower bias (−60 V) tends to produce two phases. Reflection high-energy electron diffraction photomicrographs also presented polycrystal ring patterns. Energy-dispersive x-ray spectroscopy analysis of as-deposited films revealed that Al vapor flux was more likely than Zn to go axially. The enrichment of Al in the on-axis films increased dramatically with increasing substrate bias. The bias effect was small in off-axis films. The enrichment of Al in films also varied with target composition. Film surface morphology and cross sections were examined with scanning electron microscopy: zinc-rich targets and lower biases led to porous structures. Higher biases (−380 V) and Al-rich targets led to dense columnar structures. Transmission electron microscopy images showed a reduction of average grain size with increasing substrate bias. The deposited thin films presented active–passive transitions in potentiodynamic tests. Step passivity was observed on porous films but not on dense films. Alloy films had higher corrosion resistance than corresponding bulk material as a result of reduced grain size and better chemical uniformity, which enhances the films’ passive behavior.

An improved model for mass transfer during the formation of polymeric membranes by the immersion‐precipitation process

AbstractAn analysis is presented, which describes the isothermal ternary diffusion process encountered in the formation of a cellulose acetate polymeric membrane by a direct immersion‐precipitation of polymeric solutions in a nonsolvent bath. A material coordinate was employed to derive the mass transfer equations for the membrane solution and the convective mass transfer in the coagulation bath was taken into account by solving the hydrodynamic boundary layer equations. Diffusion coefficients were measured and used to deduce ternary phenomenological coefficients. The computed results are found to agree with the experimental precipitation time and membrane morphologies observed in scanning electron photomicrographs. © 1994 John Wiley &amp; Sons, Inc.

Aqueous quenched asymmetric polysulfone hollow fibers prepared by dry/wet phase separation

A dry/wet phase separation process has been applied to a dry/wet spinning process to prepare asymmetric polysulfone hollow fibers for gas separations. A spinning solution consisting of tetrahydrofuran as a volatile solvent, dimethylacetamide as a less volatile solvent, and ethanol as a nonsolvent was used to induce phase separation in nascent hollow fiber membranes prior to their coagulation in water. Statistical experimental designs were used to optimize the permeation properties of these fibers which showed essentially defect-free selective skin layers with thicknesses of t̃ 1,200 Å (α O2/N2=5.8, ( P/L) O2=8.8 GPU, o.d.=580 μm). Scanning electron photomicrographs revealed many noncircular distortions in the hollow fiber lumens which appeared more prevalent at low draw ratios and when higher “water-activity” bore fluids were used. The influence of water activity in the bore fluid was investigated in detail with both salt/water and solvent/water mixtures.

Effect of Particle Size on Deformation and Compaction Characteristics of Ascorbic acid and Potassium Chloride: Neat and Granulated Drug

Deformation and compaction characteristics of two soluble drugs, ascorbic acid and potassium chloride, were investigated. Five different particle size fractions of ascorbic acid with mean particle size (d50) ranging from 30–300μm and four different particle size fractions of potassium chloride with d50 ranging from 20–400 μm were selected in the study. The compaction behavior of the drug substances as neat drugs or as granulated drugs were evaluated on both a Carver press and an instrumented single-punch tablet press. The results clearly show that mean particle size of the drug substances plays an important role in their compactibility. Intrinsic compactibility of both drug substances was slightly improved with increased particle size. Granulations of the drugs with polyvinyl pyrrolidone significantly improved their compactibility. However, this effect was more pronounced in the drug substance with finer particle size. The Heckel plots indicate that deformation characteristics of both granulated drugs were related to their original mean particle sizes. The granulations prepared from the coarser particle size (d50 250 μm to 400 μm) underwent two stages of deformation, so-called “brittle fracture” and “plastic deformation”. While the granulations prepared from the finer particle size predoninantly underwent “plastic deformation”. The results indicated that the plastic deformation of both granulated drugs was progressively enhanced whilst fragmentation of particles was correspondingly reduced as the particle size of the drugs was decreased. Scanning electron photomicrographs indicated that the granulation process changed the surface morphology of the drug particles imparting more “microirregularities” or “defects”, thereby providing greater “interparticulate bonding” as compared with the neat drugs. Optimum particle size range of ascorbic acid and potassium chloride for satisfactory compactibility was found to be 30–40 μm and 20–40 μm, respectively. The present study demonstrates the importance of selecting the appropriate particle size of drug for the development of tablet dosage forms.

Characterization of β-cyclodextrin for direct compression tableting

A physically modified β-cyclodextrin (BCD-DC) sample was characterized for direct compression tableting. The compactibility of BCD-DC was compared to a commercial β-cyclodextrin product (Kleptose ®) and other commonly used direct compression fillers. Heckel analysis and mercury porosimetry were used to elucidate the primary deformation mechanism of both β-cyclodextrin (BCD) samples. BCD-DC showed superior compactibility compared to Kleptose ® and excellent dilution potential. Compactibility and dilution potential of BCD-DC were comparable to microcrystalline cellulose. Lubricant sensitivity of BCD-DC was similar to that of microcrystallline cellulose. Tablet strength was found to increase with decrease in particle size. Heckel analysis and mercury porosimetry revealed that BCD-DC and Kleptose ® deform primarily by plastic flow but failed to distinguish between the two samples. Scanning electron photomicrographs and surface area data show that BCD-DC has more irregular and laminated particles than Kleptose ®. These differences in the external particle characteristics rather than internal crystal structure are primarily responsible for the greater compactibility of BCD-DC.

Correlations between morphological changes in platelet aggregates and underlying endothelial damage in cerebral microcirculation of mice.

The aim of this study was to test the hypothesis that, once formed, platelet aggregates may injure underlying cerebrovascular endothelium. Such injury could make the same site selectively attractive to the next wave of passing emboli or activated platelets. This vicious circle could account for repetitive, stereotypic symptoms in transient ischemic attacks. In pial arterioles, minor endothelial injury was produced by a laser/dye technique. After various periods of platelet aggregation at the damaged site, the vessels were fixed in situ for electron microscopic study. The degree of platelet activation (rounded and/or degranulated forms) was evaluated by counting these forms in the electron photomicrographs. These counts were related to the degree of endothelial damage ascertained in the micrographs. Other statistical relations were also examined. Endothelial damage progressed in parallel with the duration of platelet aggregation and the degree of platelet degranulation at the site. Correlations were number of activated platelets versus degree of damage, r = .43, P < .03; duration of aggregation versus damage, r = .52, P < .01; and number of degranulated platelets versus the degree of endothelial damage, r = .83, P < .001. If an aggregate embolized, endothelial damage did not appear to progress. No correlation existed between the duration of exposure to the laser and the degree of injury. The parallel between changes in platelets and endothelial damage could represent either an effect of endothelium on platelets or an effect of platelets on endothelium. Although the former alternative cannot be totally ruled out, the observations seem to fit best the hypothesis that progressive endothelial damage can result from increasing activation and degranulation of overlying platelets.

The embellum: a newly defined structure in the grass ovule

Several kinds of outgrowth from the grass ovule are known. Attention is focused here on one outgrowth that occurs within or around the micropyle and is of nucellar origin. Grass species in which it is currently known to occur are listed and examples of variants briefly described. Attention is concentrated upon Pennisetum, where the cell structure is described in detail with a series of electron photomicrographs. The tissue representing an aggregation of these transfer cells is newly named with the term ‘embellum’, and its significance for pollen tube growth is considered.

Potato Flea Beetle (Coleoptera: Chrysomelidae) Evaluated as a Possible Vector of Ring Rot Bacterium in Potatoes

Commercial tolerances for the incidence of bacterial ring rot caused by Clavibacter michiganense subsp. sepedonicum (Spieck. & Kotth.), Davis, Gillaspie, Vidaver &Harris in potatoes, Solanum tuberosum L., are zero, requiring strict regulations to reduce field spread of the disease. Few insects have been shown to be directly associated with the dissemination of ring rot bacteria. Concentrations of bacteria within potato leaves as potential inoculum and the ability of the potato flea beetle, Epitrix cucumeris (Harris), to acquire and disseminate the ring rot bacterium were investigated. There was considerable variation in the concentrations of ring rot bacteria within potato leaves. The highest numbers of bacteria were found in the midveins. Fewest bacteria were present in the mesophyll of the laminae, but the basal sections of laminae contained more bacteria than did the midrib sections from leaflet tips. Potato flea beetles acquired the bacteria in 24 h or less. Beetles exposed to infected plant tissue were confirmed positive for the pathogen using indirect immunofluorescence antibody staining (IFAS). In addition, scanning electron photomicrographs of infected flea beetles showed their mouthparts to be contaminated with bacteria that were the same size and morphology as the ring rot pathogen. Positive IFAS reactions of potato test plants that had been fed upon by potato flea beetles previously exposed to ring rot-infected plants represented support for transmission of the bacteria by the beetles. Mode of transmission appears to be through feeding activity because IFAS analyses of regurgitants and fecal material from contaminated beetles were negative.

Water tree morphology

Water tree morphology as revealed by oxygen plasma etching of water trees in low-density polyethylene is reported. Water trees sectioned by freeze fracturing are found to be virtually invisible until treated by plasma etching. Etching attack is localized and produces either a pitted or a channeled structure, depending on the water tree growth conditions. The spatial distribution of the pits or channels is reminiscent of water tree void distribution. Secondary electron photomicrographs of trees grown under varied conditions are presented. >

A REVIEW OF THE SPECIES OF NITIDOTACHINUS NEW GENUS (COLEOPTERA: STAPHYLINIDAE: TACHYPORINAE)

AbstractA new genus, Nitidotachinus, is described in the subfamily Tachyporinae (Staphylinidae) to include the species formerly placed in the Tachyporoides and Impunctatus groups of Tachinus Gravenhorst and Tachinus excellens Bernhauer. The new genus includes 10 species, all previously described, from North America, Japan, China, and Taiwan. All major diagnostic characters for the genus are compared with those of Tachinus and illustrated with scanning electron photomicrographs or line drawings. The following new combinations are created by transferring the species from Tachinus to the new genus Nitidotachinus: N. adachii (Watanabe and Shibata), N. agilis (Horn), N. excellens (Bernhauer), N. horni (Campbell), N. impunctatus (Sharp), N. lanei (Hatch), N. sawadai (Watanabe and Shibata), N. scrutator (Gemminger and Harold), N. tachyporoides (Horn), and N. taiwanensis (Shibata).The 10 species of the genus are redescribed; the aedeagus is illustrated for all species, except N. excellens Bernhauer, known only from a unique female. A key is provided to aid in distinguishing the species and the phylogenetic relationships of the species of the genus are discussed.