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At least 1,585 records · Page 88Linked to original sources
PubMed1995

Dynamic reorganization of the alkaline phosphatase-containing compartment during chemotactic peptide stimulation of human neutrophils imaged by backscattered electrons.

Scanning electron microscopy (EM) and cytochemical techniques were used to examine the alkaline phosphatase-containing compartment in human neutrophils after stimulation with nanomolar concentrations of N-formylmethionyl-leucyl-phenylalanine (10(-8) M fMLP). Alkaline phosphatase (AlkPase) activity was demonstrated with a lead-based metal capture cytochemical method. The reaction product was visualized with the backscattered electron imaging mode of scanning EM, and analyzed by electron probe X-ray microanalysis. Alkaline phosphatase activity was detected only in fMLP-stimulated neutrophils; unstimulated neutrophils displayed no activity. Stimulation of human neutrophils with 10(-8) M fMLP induced a time-dependent intracellular redistribution of irregular round or tubular granules containing alkaline phosphatase activity, as seen by backscattering. The intracellular redistribution of alkaline phosphatase activity was accompanied by increased cytochemical activity on the cell surface. The reaction product was localized preferentially on ridges and folds of polar neutrophils. Reorganization of the AlkPase-containing compartment correlated with changes induced by fMLP in cell shape, ie, membrane ruffling and front-tail polarity, as observed with the secondary electron image mode of scanning EM. These findings demonstrate the intracellular reorganization, increase, and asymmetric distribution of alkaline phosphatase activity on the plasma membrane of human neutrophils after stimulation by chemotactic peptides.

Alkaline Phosphatase↗
PubMed1991

Energy levels and probe placement in contact transscleral semiconductor diode laser cyclophotocoagulation in human cadaver eyes.

We investigated the effects of semiconductor diode laser contact transscleral cyclophotocoagulation in human cadaver eyes by gross examination, light microscopy, and scanning electron microscopy to determine optimum clinical treatment parameters. Irradiation was performed using a continuous-wave semiconductor diode laser with a fiber-optic probe. At 1.0 to 1.25 mm posterior to the limbus, spots were centered on the pars plicata by gross examination. Exposures of less than 2 J produced no visible damage. A 2- to 3-J exposure produced mild whitening of the ciliary processes, while 4- to 5-J exposures created more intense whitening of the pars plicata. Energies higher than 5 J frequently produced explosive tissue damage. Light microscopy of tissue treated with 1.8 to 6 J at 1.0 to 1.25 mm posterior to the limbus revealed coagulation necrosis of the nonpigmented and pigmented epithelium, with evidence of thermal coagulation of the ciliary stroma and stromal vasculature. Coagulation necrosis was more intense with longer exposure times. We found the optimum parameters for contact transscleral diode laser cyclophotocoagulation in cadaver eyes to be 3 to 4.5 J of energy delivered with the anterior edge of the probe 1.0 to 1.25 mm posterior to the limbus.

Ciliary Body↗
PubMed1989

Congenital idiopathic corneal endotheliopathy.

Two unrelated boys had a history of bilateral corneal clouding at birth following uncomplicated full-term gestations and spontaneous vaginal deliveries (without forceps). Clinical examinations disclosed bilateral corneal edema, no inflammation, and normal intraocular pressures. There was no history of similarly affected family members. The patients underwent penetrating keratoplasty at ages 4 months (patient 1) and 12 years (patient 2). Light and electron microscopic studies of the corneal buttons from both patients revealed areas of degeneration of the endothelium and separation of rounded endothelial cells. The morphologic features were strikingly similar to those in two acquired forms of corneal disorders--autoimmune endotheliopathy and "acute endotheliitis." Immunocytologic and in situ hybridization studies for herpes simplex virus were not consistent with either productive or latent corneal infection. Ultrastructural changes in Descemet's membrane reflect delayed or abnormal development of the postnatal nonbanded layer in patients 1 and 2, respectively. These suggest an intrauterine insult that resulted in endothelial dysfunction. The histologic and ultrastructural features of these two congenital cases are not typical of those seen in any of the recognized causes of congenital corneal clouding. We propose that these cases represent a unique congenital corneal endotheliopathy of undetermined origin.

Child↗
PubMed1996

Characterization of in vivo wear debris from ceramic-ceramic total hip arthroplasties.

In contrast to the much-studied mechanism of aseptic loosening of the metal-polyethylene joint couple, the mechanism responsible for failure of ceramic-ceramic (CC) total hip arthroplasties (THAs) has not been evaluated. The aim of this study was to conduct a systematic characterization of the in vivo wear debris from 15 cases of CC THAs revised for aseptic loosening. Two methods were used to evaluate the wear debris; a semiquantitative histological analysis of H&E-stained periprosthetic pseudomembranes; and an evaluation of isolated debris particles using SEM, energy-dispersive X-ray analysis, and image analysis. The three main types of particulate debris identified were titanium alloy (TiAlV) and alumina ceramic (Al2O3) of prosthetic origin, and zirconium dioxide (ZrO2) from the contrast agent used in the cement for prosthetic fixation. Alumina debris was present in the smallest proportion (12%) and was consistent with the low wear rate of the CC joint couple. Zirconium dioxide debris was present in the greatest proportion (76%) and was an unexpected finding. The ZrO2 debris represented microstructural grains of the original ZrO2 particles added as contrast agent to the cement. The presence of a histiocytic foreign body reaction to ZrO2 debris on histologic sections leads us to believe that these particles play an important role in aseptic loosening of the CC THAs evaluated in this study.

Alloys↗
PubMed1998

XPS and SEM detection of surface changes on 64 ureteral stents after human usage.

Ureteral stents are commonly implanted to assist the postsurgery flow of urine from the kidney to the bladder. We hypothesized that different surface compositions of stent material could result in different conditioning film depositions and potentially altered receptivity to bacterial biofilms. Using XPS, three types of ureteral stents recovered from 64 patients were found to have adsorbed conditioning films that altered the surface composition of the devices. Elements associated with encrustation (calcium, magnesium and phosphorus) were found on 69% of the silicone latex stents, 44% of the low surface energy (LSe) devices, and 38% of the carbon-rich stents. No statistical difference was found in relation to patient gender, stent type, duration of implantation, and encrustation deposition. The composition of the film suggested that the nature of the underlying material did not significantly alter the elements that adsorbed. Thus, devices may take on a similar surface coat within days, and perhaps hours, of exposure to the host. With respect to dense encrustations, fewer appeared on the LSe devices. SEM confirmed the presence and nature of the film crystals and showed bacterial biofilms adherent to devices and encrustations in three patients who had received prophylactic trimethoprim compared to one on ciprofloxacin. In conclusion, although encrustation deposition and biofilm formation on ureteral stents is not unique to Cook devices, the human model and surface science test systems described here are invaluable to evaluate biomaterials used in patients. Unless biomaterials undergo rigorous analysis in vivo, including true assessment of the outcome of prophylactic antibiotic usage, clinicians will be unable to accurately select the best device and management strategy for a given patient.

Adult↗
PubMed1977

Structural development of endocardial cushions.

Development of chick and rat endocardial cushions (cardiac mesenchyme) was studied histologically (using Nomarski differential interference optics on living and unfixed tissue), ultrastructurally (scanning and transmission electron microscopy), cytochemically (using acidified dialyzed iron as a visual probe for polyanionic material) and autoradiographically (using 35S) to elucidate the origin of the mesenchyme, the morphologic sequences leading to cushion formation and secretion of sulfated glycosaminoglycans, if any, by migrating mesenchymal cells. Cushion formation was similar for both species. Mesenchymal cells appeared initially, in 16- to 18-somite embryos, beneath the endothelium (which lacked a basal lamina) of the future atrioventricular canal and outflow tract. The cytoplasm of cushion mesenchymal cells was structurally similar to the ensothelium; probably these cells arose by proliferation of the endothelium. Mitotic figures among the "seeded" cells were also numerous. Cushion cells were initially attached to the endothelium by desmosomes but acquired motile apparatus (pseudopodia and filopodia containing microtubules and microfilamentous bundles). Serial sectioning of successively-aged embryos (20-44 somites) indicated a centrifugal migratory direction. Interaction of the cell processes with extracellular matrix suggested that the latter was used as a migratory substrate. Contact of the advancing wedge of cushion cells with the myocardium produced no alteration in cell structure or mitotic activity. Localization of hyaluronidase-sensitive, dialyzed iron (DI) precipitates in 250-nm Golgi vacuoles and hyaluronidase-sensitive 35S-endangendered silver grains over cushion cells indicated that this tissue contributed sulfated macromolecules to the matrix. Localization of hyaluronidase-labile, DI material in coated, endocytic-like vesicles and caveolae also suggested potential modification or conditioning of the matrix by migrating mesenchymal cells. Altogether, the study established loci in developing cushions where disruption where disruption of the developmental sequence could engender valvular or septal defects.

Animals↗
PubMed1980

Performance analysis of total hip prostheses: some particular metallurgical observations.

Metallurgical observations of phenomena which influence the clinically successful performance of permanent implants and implant materials are reported. The effect of casting voids in cast cobalt chromium femoral stems of total hip replacements is discussed first. Pitting corrosion occurred in a retrieved stainless-steel implant type AISI 316 containing 2.7% Mo. The fractographic pattern of this device retrieved for fatigue failure shows typical characteristics of corrosion-enhanced fatigue.

Chromium Alloys↗
PubMed1984

Casting properties of Ni-Ti shape memory alloy.

A Ni-45 wt% Ti (Ni-50 at % Ti) alloy was cast into molds of magnesia and silica investments by use of a dental argon-arc pressure casting machine with a copper crucible . The castings exhibited shape memory properties. The shape recovery process was sharper in the specimens cast in magnesia investment molds than in those cast in silica (phosphate-bonded) investment molds. The latter casting had a hard region of the periphery, suggesting that shape recovery process may be affected by reaction of molten metal with silica. Furthermore, the alloy possessed the adequate mechanical properties for consideration as crown-and-bridge prostheses.

Chemical Phenomena↗
PubMed1986

In vitro calcification and in vivo biocompatibility of the cross-linked polypentapeptide of elastin.

The in vitro calcifiability and molecular weight dependence of calcification of the polypentapeptide, (L X Val1-L X Pro2-Gly3-L X Val4-Gly5)n, which had been gamma-irradiation cross-linked have been determined when exposed to dialyzates of normal, nonaugmented fetal bovine serum. The material was found to calcify: calcifiability was found to be highly molecular weight dependent and to be most favored when the highest molecular weight polymers (n approximately equal to 240) had been used for cross-linking. The in vivo biocompatibility, biodegradability, and calcifiability of the gamma-irradiation cross-linked polypentapeptide were examined in rabbits in both soft and hard tissue sites. The material was found to be biocompatible irrespective of its physical form and to be biodegradable but with n of 200 or less it was not shown to calcify or ossify in the rabbit tibial nonunion model.

Animals↗
PubMed1995

Characterization of nodules induced by bioactive glass on cultured periodontal-ligament fibroblasts.

We previously reported that materials leached from bioactive glass (BG) and vitamin D3 induced the formation of nodules on cultured periodontal-ligament fibroblasts (PLF). In this study, we have investigated the relationship between the conditions of the materials and nodule formation, analyzed morphologically, and also studied whether the production of nodules was specific to cultured PLF. PLF and skin fibroblasts were cultured in the presence or absence of BG. The amounts of calcium, phosphate, sodium and silicon in the culture medium and the number of nodules were measured at the 55th day. The nodules were observed microscopically and analyzed using an X-ray microanalyzer. In PLF, nodules were formed regardless of the presence or absence of BG; however, they were more numerous in the presence of BG. In skin fibroblasts, nodules were not observed. The amounts of calcium and silicon were higher in the presence of BG, while the amount of phosphate was lower. The nodules appeared crystalline with a spongy structure and contained calcium and phosphorus. Our results show that the nodules were associated with PLF and precipitated by the materials (higher concentrations of calcium and silicon), and they were spongy crystal composed of calcium and phosphorus.

Biocompatible Materials↗
PubMed2004

Monolithic columns with a gradient of functionalities prepared via photoinitiated grafting for separations using capillary electrochromatography.

Stationary phases for capillary electrochromatography with a longitudinal gradient of functionalities have been prepared via photoinitiated grafting of polymer chains onto the pore surface of a porous polymer monolith. In order to achieve the desired retention and electroosmotic flow, the hydrophobic poly(butyl methacrylate-co-ethylene dimethacrylate) monolith with optimized porous properties was grafted with a layer of ionizable polymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid). A moving shutter and a neutral density filter were used to control the dose of UV light received at different locations along the monolith in order to create the longitudinal gradient of functionalities. Formation of the desired gradients was confirmed using electron probe microanalysis of different locations along the column. The preparation technique significantly affects performance in the CEC mode as demonstrated on the separations of a model mixture using columns both with homogeneous distribution of grafts and with a gradient of functionality. Columns grafted with the gradient of functionalities were found superior to those functionalized uniformly. A comparison of the performance of the gradient column with another containing evenly distributed functionalities showed the performance benefits of the "gradient" column.

Electrochemistry↗
PubMed1993

Spermatid nucleus of Megaselia scalaris Loew (Insecta, Diptera, Phoridae): a study using anti-histone antibodies, scanning electron microscopy, and a centromere-specific oligonucleotide.

The structure of elongated spermatid nuclei was examined in the fly Megaselia scalaris using indirect immunofluorescence with anti-histone antibodies, scanning electron microscopy, and in situ hybridization with a centromere-specific oligonucleotide. The immunofluorescence experiments showed that, in keeping with the situation in most animals, histones are hyperacetylated prior to their displacement from the nucleus in the course of spermiogenesis. Scanning electron microscopy revealed that grooves run parallel to the long axis of the spermatid nuclei. The chromatin is segmented into blocks lateral to the grooves. This finding most probably indicates that the chromatin is not yet maximally condensed at this stage. The retarded chromatin condensation may be correlated with the export of somatic histones from the nucleus. The location of the centromeres could not be identified using scanning electron microscopy, but in situ hybridization showed that a centromere-specific oligonucleotide mapped to the central or close to the central areas within the spermatid nucleus. Possibly, the chromosomes are extended and arranged parallel to the long axis of the spermatid nucleus.

Animals↗
PubMed2002

Immobilization of human thrombomodulin to expanded polytetrafluoroethylene.

BACKGROUND: The success of synthetic grafts for vascular reconstruction remains limited by thrombosis and intimal hyperplasia. In addition to the well-described antithrombotic effects of thrombomodulin, we have demonstrated that recombinant human thrombomodulin (rTM) inhibits arterial smooth muscle cell proliferation induced by thrombin. This study investigated the binding of functional rTM to expanded polytetrafluoroethylene (ePTFE). METHODS: Immobilization of rTM was achieved by either (1) a direct coating or (2) a two-step binding process using a water-soluble condensing cross-reaction agent EDAC to modify the ePTFE surface followed by binding of rTM. The samples were then subjected to a tangential shaken wash. The evidence of bound rTM was evaluated by both morphologic and functional studies. RESULTS: SEM, BSI, and X-ray microanalysis identified that the two-step binding method resulted in significantly greater binding of rTM molecules to ePTFE pre- and post a 7-h wash than the direct coating method. With the two-step binding method rTM ranging from 0.25 to 12.5 microg immobilized to ePTFE-activated protein C (APC) in a concentration-dependent manner by more than 6000-fold compared to the buffer control (P < 0.04) and 50-85% more than direct coating (P < 0.004). With direct coating, the level of APC dropped significantly to near 40% of the preshaken level at 2 h and diminished to 26% at 7 h. Whereas, the level of APC with the two-step binding stabilized at 51 and 49% after being shaken 2 and 7 h, respectively. CONCLUSION: Functional rTM binding to ePTFE was significantly improved with a new two-step binding method.

Coated Materials, Biocompatible↗
PubMed1985

Iodine distribution in the thyroid follicles of the hagfish, Eptatretus burgeri and lamprey, Lampetra japonica: electron-probe X-ray microanalysis.

In the thyroid follicles of species of cyclostomes, a hagfish and a lamprey, the distribution of stable iodine was examined by electron-probe X-ray microanalysis. A high concentration of stable iodine, heterogeneously distributed, was observed in the follicular cells of hagfish thyroid follicles. In the lamprey a low concentration of iodine was seen in the follicular lumina. The relative values for stable iodine determined in this way corresponded to values obtained by a chemical analytical method.

Animals↗
PubMed1995

Energy-dispersive X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes.

Klebsiella aerogenes forms electron-dense particles on the cell surface in response to the presence of cadmium ions in the growth medium. These particles ranged from 20 to 200 nm in size, and quantitative energy dispersive X-ray analysis established that they comprise cadmium and sulfur in a 1:1 ratio. This observation leads to the conclusion that the particles are cadmium sulfide crystallites. A combination of atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and acid-labile sulfide analysis revealed that the total intracellular and bound extracellular cadmium:sulfur ratio is also 1:1, which suggests tha the bulk of the cadmium is fixed as extracellular cadmium sulfide. The tolerance of K. aerogenes to cadmium ions and the formation of the cadmium sulfide crystallites were dependent on the buffer composition of the growth medium. The addition of cadmium ions to phosphate-buffered media resulted in cadmium phosphate precipitates that remove the potentially toxic cadmium ions from the growth medium. Electron-dense particles formed on the surfaces of bacteria grown under these conditions were a combination of cadmium sulfide and cadmium phosphates. The specific bacterial growth rate in the exponential phase of batch cultures was not affected by up to 2mM cadmium in Tricine-buffered medium, but formation of cadmium sulfide crystallites was maximal during the stationary phase of batch culture. Cadmium tolerance was much lower (10 to 150 microM) in growth media buffered with Tris, Bistris propane, Bes, Tes, or Hepes. These results illustrate the importance of considering medium composition when comparing levels of bacterial cadmium tolerance.

Cadmium↗
PubMed1977

[Study of the element secretory glands of a tubicolous polychaete (Pectinaria (= Lagis) koreni) with the help of electron microprobe and ion microanalyzer (author's transl)].

Two histophysical methods (electron microprobe and ion microanalyzer) were used on sections of Annelids in order to study the inorganic composition of cement secretory glands. Mg, Ca and P were demonstrated in large amounts in the secretions, associated with organic matter. Traces, or no, Fe, Al and Si were found. Possibilities of artifacts are discussed, and these results are compared with biochemical methods. A hypothesis is proposed in order to explain the differences observed between biochemical and present results, which suggest, for the hardening of cements a different chemical mechanism to that suggested by Vovelle in annelid Sabellaria alveolata.

Animals↗