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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This study was designed to investigate the relationship between the etched depth, penetration of sealants and marginal seal. Sixty unerupted lower first premolars extracted from patients for orthodontic reasons were thoroughly cleaned and stored in an antiseptic Ringer's solution at 4 degrees C. A "window" on the occlusal of 15 of the premolars, including both mesial and distal pits, was developed by painting nail varnish around the border of the occlusal surfaces. Etching was then done with 35% phosphoric acid for 60 seconds to all 60 premolars. Five of the "window" teeth were evaluated by microradiography to determine the etched depth of the superficial and subsurface enamel. Five were prepared for SEM analysis to observe the change of the superficial etched enamel surface. Another five "window" teeth were embedded in epoxy resin and sectioned parallel to the long axis of the tooth through the fissures in order to observe the subsurface depth of the etch by SEM analysis. The other 45 teeth were divided into three groups of 15 teeth each. Fissures of each group of teeth were sealed using Prisma-Shield (LD Caulk), Concise White Sealant (3M Dental Products) or Teethmate A (Kuraray) sealants and stored in water (37 degrees C) for 24 hours. They were then sectioned and demineralized before being examined by a scanning electron microscope. Photographs of secondary electron image (SEI) were done to gradate the resin-infiltrated enamel and resin tags for these sealants. After SEM observation, the 15 samples of each applied sealant were polished to a high gloss again and placed in a silver nitrate solution for 24 hours before being examined under the SEM equipped with a back-scatter electron detector. Data were then analyzed using the Welch and Student t-tests. Results showed that fissured enamel of unerupted human lower first premolars became porous after etching with 35% phosphoric acid. The low viscosity sealant Teethmate A (approximately 260 mPa.s), penetrated fully and formed a resin-infiltrated layer in enamel beyond the etched depth. However, the high viscosity sealants (Prisma-Shield and Concise White Sealant) did not penetrate enough to ensure that the acid-etched enamel was infiltrated sufficiently by the sealant to insure good marginal seals.
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PMID:Effect of sealant viscosity on the penetration of resin into etched human enamel. 1120 31

Levels of nitrite (NO2-) and nitrate (NO3-) were measured in pulmonary edema fluid and plasma from 34 patients with early acute lung injury (ALI) and 20 patients with hydrostatic pulmonary edema. Pulmonary edema fluid from patients with ALI had significantly higher levels of NO2- + NO3- compared with pulmonary edema fluid from patients with hydrostatic pulmonary edema (108 +/- 13 microM versus 66 +/- 9 microM; means +/- SEM; p < 0.05). In addition, patients with shock had higher plasma NO2- + NO3- levels than those without shock (79 +/- 11 microM versus 53 +/- 12 microM, p < 0.05). Acidemia and increased anion gap, markers of systemic hypoperfusion, were also associated with twofold higher plasma NO2- + NO3- levels (p < 0.01). Increased levels of NO2- + NO3- in edema fluid samples were associated with slower rates of alveolar fluid clearance. Nitrated pulmonary surfactant protein A (SP-A) was also detected in the edema fluid of patients with ALI after immunoprecipitation with a specific antibody against this protein. Previously, we have shown that nitration of SP-A impairs its host- defense properties. In aggregate, the results of this study indicate that reactive oxygen-nitrogen species may play a role in the pathogenesis of human ALI.
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PMID:Increased levels of nitrate and surfactant protein a nitration in the pulmonary edema fluid of patients with acute lung injury. 1120 43

The synergy of the micro FT-IR (Fourier Transform-Infrared) and SEM-EDX (Scanning Electron Microscopy-Energy Dispersive X-ray) techniques has been shown to be particularly helpful and effective for the characterization of inorganic compounds in fly ashes. The experimental data obtained by these techniques have been interpreted in comparison with those of other techniques. The presence of calcium carbonate, some sulfates, ammonium nitrate, calcium hydrogen phosphate, some chlorides, some oxides and aluminium silicates have been verified.
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PMID:Analytical characterization of municipal solid waste incinerator fly ash. Part II. 1122 71

The effects of two vasoactive agents (adenosine A2A agonist, CGS 21680, and adrenoceptor agonist, noradrenaline) were examined on cardiac output (CO), heart rate (HR), blood pressure (BP), mean circulatory filling pressure (Pmcf), resistance to venous return, arterial resistance, dP/dt, plasma levels of NO2-/NO3-, and inducible nitric oxide synthase (iNOS) activity in lungs ex vivo, following treatment with tumour necrosis factor-alpha (TNF-alpha; 30 microg/kg) in anaesthetized rats. Treatment with TNF-alpha produced significant reduction in CO (41+/-2%), dP/dt (26+/-3%), BP (26+/-2%) and Pmcf (27+/-4%; n=6; mean+/-SEM), but increased arterial resistance. There were no significant changes in the plasma levels of NO2-/NO3-levels over time following treatment with TNF-alpha, but there was a significant increase (approximately twofold) in the activity of the iNOS in the lungs of animals treated with TNF-alpha. Administration of CGS 21680 (1.0 microg/kg per min) significantly increased CO (44+/-6%), HR (12+/-2%), Pmcf (24+/-4%) and dP/dt (24+/-5%) in TNF-alpha-treated rats. CGS 21680 also significantly reduced arterial resistance (33+/-2%) without altering resistance to venous return in TNF-alpha-treated rats. While noradrenaline (1.0 microg/kg per min) infusion did not significantly increase CO, it did significantly increase HR (12+/-1%), BP (55+/-9%), Pmcf (47+/-5%), dP/dt (65+/-7%), resistance to venous return (64+/-20%), and arterial resistance (41+/-16%) in TNF-alpha-treated animals. The reduction in BP due to administration of TNF-alpha is the result of significant reduction in CO. Consequently, the decline in CO can be attributed to a combination of a negative inotropic effect as well as a reduction in Pmcf. It is evident that infusion with CGS 21680 could reverse the negative impact of TNF-alpha on CO by increasing dP/dt, Pmcf and HR as well as a reduction in arterial resistance. The fact that noradrenaline did not significantly increase CO in TNF-alpha-treated rats can be attributed to increased arterial resistance as well increase in resistance to venous return.
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PMID:The influence of tumour necrosis factor-alpha on the cardiovascular system of anaesthetized rats. 1128 46

Previous investigations of sensory systems in opecoelid cercariae have focused on chaetotaxy and ultrastructure of sensory receptors. They revealed chaetotaxic patterns within family, genus, and species as well as different receptors. Chaetotaxic and ultrastructural observations have rarely been combined. We investigated the ultrastructure of cercarial sensory receptors in conjunction with chaetotaxy and neuromorphology in a species of Allopodocotyle. Cercariae were treated with acetylthiocholine iodide and silver nitrate, and some were processed for light, scanning (SEM), and transmission (TEM) electron microscopy. Five nerve regions were distinguished. Chaetotaxy was consistent with that of other opecoelids. Five types of receptors were distinguished with SEM. Types differed in number of cilium-like structures (one or more), length of cilium-like structure (short, moderately long, or long), presence or absence of a tegumentary collar, and length of tegumentary collar (low, moderately low, or very high). Internal ultrastructure of some types revealed unsheathed cilium-like structures, basal body, and thickened nerve collars. Possible subtegumentary and sheathed receptors are introduced. Some receptor types were site-specific. For example, receptors with multiple cilium-like structures were concentrated on cephalic region whereas receptors with short cilium-like structure were widespread throughout most regions. Ultrastructure and site-specificity observations suggest that most receptors are mechanoreceptors.
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PMID:Ultrastructure and chaetotaxy of sensory receptors in the cercaria of a species of Allopodocotyle Pritchard, 1966 (Digenea: Opecoelidae). 1128 98

Bioactive fibers were produced using a sol-gel method. The rheological properties of two different sol compositions prepared from a mixture of TEOS, phosphorous alkoxide and calcium nitrate, or calcium chloride in a water-ethanol solution, are reported. The sols were extruded through a spinneret to produce continuous 10 microm-diameter fibers. Discontinuous fibers and fibrous mats were prepared by air-spraying the multicomponent sols. The sol-gel fibers were converted to the bioactive fibers by three different thermal treatments at either 600 degrees, 700 degrees, or 900 degrees C for 3 h. SEM, BET, EDX, and FTIR were used to characterize the morphology and structure of the fibers. The BET measured surface area of the fibers sintered at 900 degrees C was 0 m(2)/gm compared to a value of 200 m(2)/gm for a typical sol-gel-derived particle of similar composition. Both the continuous and discontinuous fibers exhibited in vitro bioactivity in a simulated body fluid.
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PMID:Novel sol-gel bioactive fibers. 1128 73

The term "nanoleakage" has been introduced to explain a penetration pathway within hybrid layers of the dentin-composite junction in the absence of gap formation. This phenomenon is argued in the literature to be a risk factor for the quality of the dentin bonding. NaOCl is a well-known agent used to remove collagen layers that are exposed after acid etching. The purpose of this study was to determine the influence of an NaOCl treatment of dentin to the formation of nanoleakage. Class V cavities were prepared in 40 human molars with the cervical margins located in dentin. After etching with phosphoric acid, 20 samples were treated with 10% NaOCl for 60 s, and 20 samples were used as control. Composite restorations were placed using two different bonding systems. The specimen were exposed in silver nitrate solution and then in developer. After embedding, the teeth were sectioned, dried, coated with gold, and analyzed by SEM. For all the specimen in the control group, backscatter images indicated a silver penetration within the hybrid layer. There was no penetration of silver detectable in the teeth that were treated with NaOCl. We conclude that the removal of the collagen layer by using NaOCl avoids the formation of nanoleakages with the materials tested.
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PMID:The effect of NaOCl dentin treatment on nanoleakage formation. 1140 Jan 36

Both nitric oxide (NO) and endothelin-1 (ET-1) are important mediators in the regulation of vascular tone during pregnancy and preeclampsia. This study was designed to investigate the ET-1-induced hypotensive effect in late pregnant rats (P) and in NO-deprived hypertensive pregnant rats (TP), a model of preeclampsia. From day 13 of pregnancy Wistar rats were fed a control or an N(omega)-nitro-L-arginine-enriched diet. On gestational day 20, mean arterial pressure (MAP +/- SEM, in mm Hg) and heart rate (HR) were measured with a carotid catheter in anesthetized rats after a bolus intravenous injection of several agonists and antagonists. After 7 days of chronic NO synthase inhibition, there was a significant increase in MAP (+45 +/- 3.9, P < .01) and 24-h urinary nitrate excretion was significantly decreased (P < .05). ET-1 bolus injection (0.1 nmol/kg) was rapidly followed by a significant decrease in MAP and a slight delayed increase, with no change in HR. The magnitude of the decrease had significantly dropped off in P (-30 +/- 2.2) as compared to that in TP (-46 +/- 5.1) and in virgin rats (-51 +/- 6.3) (P < .05). In P and TP, in vivo depressor effect was also obtained with sarafotoxin S6c, a specific ETB agonist, and blocked by the specific ETB antagonist BQ-788. After inhibition of cyclooxygenase with acetylsalicylic acid, the ET-1-induced hypotension was not modified either in P or in TP. In conclusion, the present data highlight an enhanced ETB receptor mediated hypotensive effect of ET-1 in anesthetized TP as compared to P. The magnitude of the hypotensive effect of ET-1 observed in TP is of the same order as that in virgin rats and neither NO nor vasodilator prostaglandins seem to be involved in TP. The enhanced hypotensive effect of ET-1 could be a beneficial counter-balancing mechanism in this rat model of preeclamptic pathology where an increased sensitivity to vasoconstrictor agents is generally described.
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PMID:Hypotensive effect of endothelin-1 in nitric oxide-deprived, hypertensive pregnant rats. 1141 40

The purpose of these studies was to examine if perfluorochemical (PFC) liquids stimulate blood leukocytes to secrete nitric oxide (NO) and/or endothelin-1 (ET-1). As such, NO and ET-1 may modulate broncho- and vascular dilatation and constriction, respectively, and thereby influence the clinical condition of a patient in respiratory distress with persistent pulmonary hypertension. Blood leukocytes in their natural habitat (whole blood) were incubated in the presence of two different perfluorochemicals (perflubron and perfluorodecalin). The overall response in ET-1 or NO (indirectly measured as nitrite/nitrate) production was examined at increasing PFC percentages (wt/vol) of PFC/whole blood. The lowest proportion used, 0.001% (wt/vol), was relevant to serum concentrations of PFC observed in liquid-ventilated individuals, whereas the highest proportion PFC, 50% (wt/vol), would mimic a situation where leukocytes are presented to PFC-filled airways. Plasma levels of freshly drawn blood, similar to levels of incubated (6 h) non-PFC-supplemented cultures, were ET-1 0.59 +/- 0.07 pg/ml (6 h, mean +/- SEM) and NO(-2)/NO(-3) 50 +/- 9 microM (6 h). Perflubron or perfluorodecalin did not induce significant differences in ET-1 or NO(-2)/NO(-3) levels as function of PFC type or dose. In conclusion, PFC liquids do not stimulate production in leukocytes in vitro of substances that may modulate constriction or dilatation in the vascular and respiratory tract systems.
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PMID:Perfluorochemical liquids do not stimulate endothelin-1 or nitric oxide production in human blood leukocytes. 1164 49

To evaluate the durability of dentin bonding over time, the nanoleakage of four dentin bonding systems (Single Bond, Stae, Clearfil SE Bond and PermaQuik) over 24 hours, three months, six months and 12 months, was investigated. Flat occlusal dentin surfaces from extracted human molars were finished with wet 600-grit silicon carbide paper and bonded with one of the dentin bonding systems following manufacturers' instructions. The bonded surface was covered with < 1 mm thick layer of Silux Plus resin composite and light cured for 40 seconds. The specimens in each dentin-bonding group were randomly assigned to four sub-groups and kept in phosphate buffered saline solution (pH 7.4) containing 0.01% sodium azide at 37 degrees C for 24 hours, three, six or 12 months. The margins of all specimens were finished and polished with Sof-Lex disks after initial 24-hour storage. At the end of each storage time, the surrounding tooth surfaces except for 1 mm adjacent to the restoration were coated with nail varnish. The samples were immersed in a 50% w/v solution of silver nitrate for 24 hours, placed in photodeveloping solution and exposed to fluorescent light for eight hours. The samples were cut longitudinally and buccoligually, polished, mounted on stubs, carbon coated and observed in a Field Emission-SEM using backscattered electron mode. The results showed that systems using phosphoric acid as the etchant had a line of silver deposition at the base of the hybrid layer. Silver deposition increased in all systems over 12-months storage, with PermaQuik changing the least. Nanoleakage of the dentin bonding systems increased slightly during the 12-month storage period, indicating that they may be subject to hydrolytic attack over time.
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PMID:The effect of long-term storage on nanoleakage. 1169 86


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