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The use of glass-ionomer cement in restorative dentistry has seen a revival because of its capacity for being etched and bonded to composite resin. Past investigators compared an etched cement surface with an unetched surface that was set against a smooth surface. Clinically, however, a glassy smooth surface is not produced when the cement is used as a base. Using Scotchbond bonding resin, we developed this two-part study to evaluate the tensile bond strengths of P-30TM composite resin to several glass-ionomer cements that were (a) unetched but allowed to set in air and (b) etched for 30 s with orthophosphoric acid, and to compare them with the cohesive strength of the respective cement. Using a silver nitrate staining technique, we also evaluated the microleakage of class V cavities restored with SiluxTM composite resin under a base of etched or unetched Ketac Bond cement. Although there were significant differences among three cements between their cohesive strength and the resin bond strength after the two surface treatments (p less than 0.01), the bond to the unetched surface was generally similar to that of the etched surface of the cement. The remaining groups showed no statistical difference. The microleakage was similar in the two groups. SEM micrographs showed a rough topography of the unetched cement that resembled that of the etched surface. This in vitro study suggests that acid-etching a glass-ionomer base for resin-bonding may not be necessary for specific materials. Further clinical evaluation is recommended to validate this observation intra-orally.
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PMID:Effect of etching glass-ionomer cements on bond strength to composite resin. 268 6

Five 5 to 6 month old horses were surgically prepared with silver electrodes sutured to the serosa of gastric antrum, duodenum and proximal portions of the jejunum. Normal migrating motility complex (MMC) periodicity was determined during daytime hours in horses that were fed and horses from which food was withheld for 24 hours. Periodicity was defined as time span from the end of one period of regular spike activity (RSA) to the end of the next RSA in the MMC. The periodicity was 120.5 +/- 9.5 (SEM) minutes in horses from which food was withheld, and was 125.7 +/- 20.3 minutes in horses fed hay free choice. Coincident with each duodenal RSA, antral spike activity ceased. Xylazine (0.25 and 0.5 mg/kg), given IV during the period of intermittent spike activity of the MMC to either fed or unfed horses induced, within 2 minutes, a RSA complex in the duodenum that migrated to the proximal portion of the jejunum. This was followed by a period of no spike activity of normal duration, which proceeded on to a period of intermittent spike activity of varying duration to complete the MMC cycle. Pretreatment IV administration of an alpha 2-adrenergic antagonist, tolazoline (1 mg/kg) also provoked a RSA complex, but blocked the xylazine effect. The results indicated that xylazine resets the duodenal MMC in the horse, but does not seriously disrupt proximal gastrointestinal tract motility, and that control of MMC periodicity in this region probably involves more than alpha 2-adrenergic receptors.
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PMID:Effect of xylazine treatment on equine proximal gastrointestinal tract myoelectrical activity. 276 48

In order to study developmental aspects of colonic motility, we have developed a miniaturized electrophysiologic recording system for use in the infant primate rhesus (Macaca mulatta). Technical considerations including absence of rectal valves, decreased tissue thickness and small colonic diameter limit application of standard non-surgical recording methodology in this model. In-vivo testing with 4 different bipolar electrode probe configurations yielded satisfactory quality recordings only with silver chloride suction electrodes. Using this system, colonic slow waves and spike action potentials were studied in 6 infant primates (ages 1 to 7 months) both fasting and following a standard liquid meal of 10 cc/kg. In response to feeding, colonic spike potentials increased from 7.8 +/- 1.7 to 14.2 +/- 4.1 within 15 minutes (mean spikes +/- SEM/5 min interval). The observed response of the distal colon to a meal in this model is similar to the response reported in adult humans using intraluminal recording techniques. Utilizing the described methodology, the infant primate appears to be a suitable model for investigation of developmental aspects of gastrointestinal motility and electrophysiology. These techniques have important direct applications for investigation in the human infant.
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PMID:Development of methodology for recording colonic myoelectrical activity in the infant primate. 277 70

We analyzed the protein composition of human aqueous humor. Samples were obtained by paracentesis from 25 human eyes (age range 64-92 years) at elective cataract surgery, and from 20 age-matched post-mortem eyes within 1.5 to 18 hr after death. Individual samples were assayed for total protein, and the polypeptides were separated by qualitative SDS-PAGE into high-, medium- and low-molecular-weight ranges and then silver-stained. The clinical samples showed a remarkable consistency in the total protein values (mean +/- SEM: 12.4 +/- 2.0 mg per 100 ml) and no detectable variations in the profiles of the silver-stained proteins. Twelve major protein fractions, with apparent molecular weights of 140, 80 (doublet), 67, 60 (doublet), 35, 27, 25, 17, 14.6 and 9 kDa, were present. A preliminary analysis showed that the 17 kDa band contained a molecule resembling basic fibroblast growth factor. Two additional samples of aqueous humor from patients whose blood/aqueous barrier was compromised during paracentesis showed a quantitative and qualitative increase in the polypeptides that were present. Compared with the samples of aqueous humor obtained at surgery, the post-mortem samples exhibited a greater variability in total protein content (56.1 +/- 11.6 mg per 100 ml) and an increased number of high- and low-molecular-weight protein fractions. In view of wide differences in the clinical parameters, including ocular and systemic medications, systemic illness, surgical premedications, anesthesia and total serum protein values, the similarity in the protein profiles of the carefully drawn surgical samples is most remarkable. Our results indicate that, in patients who underwent elective cataract surgery, the levels of major proteins in human aqueous humor are not affected by wide individual variations in the clinical parameters. We attribute this finding to the care taken in the collection of aqueous humor samples.
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PMID:Protein composition of human aqueous humor: SDS-PAGE analysis of surgical and post-mortem samples. 292 Jul 79

We evaluated the effect of increased heart rate on cardiac output and stroke volume in the stage 24 chick embryo (day 4 of a 21-day incubation). Blood flow was measured with a 20 MHz pulsed-Doppler flowmeter. Heart rate was increased by pacing with square wave stimuli (1 ms duration, less than 4 mA). The sinus venosus was paced from bipolar Teflon-coated silver electrodes in eight embryos and the ventricular apex was paced in three embryos. The pacing rates were at the intrinsic heart rate (P:I); 125% of intrinsic heart rate (P:125%I); and 150% of intrinsic heart rate (P:150%I). Physiologic measurements during pacing were compared to those obtained at the control intrinsic rate (I). We also evaluated the velocity profile of atrioventricular inflow and conotruncal outflow at intrinsic rate and during sinus venosus and ventricular pacing. With sinus venosus pacing, mean dorsal aortic blood flow was similar at control (1.07 +/- 0.05 mm3/s) and P:I (1.06 +/- 0.06 mm3/s) (mean +/- SEM). However, at P:125%I and P:150%I, mean dorsal aortic blood flow decreased significantly (P:125%I, 0.88 +/- 0.05 mm3/s; P:150%I, 0.67 +/- 0.07 mm3/s) (p less than 0.05). Stroke volume per beat also decreased with increasing heart rates (I, 0.41 +/- 0.02 mm3; P:I, 0.39 +/- 0.02 mm3; P:125%I, 0.28 +/- 0.02 mm3; P:150%I, 0.18 +/- 0.02 mm3) (p less than 0.05). With rapid sinus venosus pacing, the atrioventricular blood flow velocity profile showed a rate-dependent decrease in passive ventricular filling while active filling remained the same or increased slightly.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of heart rate increase on dorsal aortic flow in the stage 24 chick embryo. 296 Sep 45

Immunogold labeling and silver enhancement techniques are widely used to determine density and distribution of cell membrane receptors by light and transmission electron microscopy. However, these techniques have not been widely used for receptor detection by scanning electron microscopy. We used antigen- or protein A-conjugated colloidal gold particles, together with silver enhancement, sequential secondary and back-scattered electron imaging (SEI and BEI), and digital image processing, to explore cell surface distribution of IgE-receptor complexes on RBL-2H3 cells, a rat leukemia line that provides a model for the study of mucosal mast cells. Cells were first incubated with a monoclonal antidinitrophenol IgE (anti-DNP-IgE) that binds with high affinity to cell surface IgE receptors. The resulting IgE-receptor complexes were cross-linked either with the multivalent antigen, DNP-BSA-gold, or with a polyclonal anti-IgE antibody. Antibody-treated cells were labeled after fixation with protein A-gold. Fixed, gold-labeled cell monolayers were silver enhanced (or not), dehydrated, critical point-dried, and coated with gold-palladium (for SEI analysis) or carbon (for combined SEI/BEI analysis). They were observed in an Hitachi S800 SEM equipped with a field emission tip and a Robinson backscattered electron detector. An image processor (MegaVision 1024XM) digitized images directly from the S800 microscope at 500-1000 line resolution. Silver enhancement significantly improves detection of gold particles in both SEI and BEI modes of SEM. On gold-palladium-coated samples, 20-nm particles are resolved by SEI after enhancement. BEI resolves 15-nm particles without enhancement and 5- or 10-nm particles are resolved by BEI on silver-enhanced, carbon-coated samples. Neither BEI nor SEI alone can yield high resolution topographical maps of receptor distribution (BEI forms images on the basis of atomic number contrast which reveals gold but not surface features). Image analysis techniques were therefore introduced to digitize, enhance, and process BEI and SEI images of the same field of view. The resulting high-contrast, high-resolution images were superimposed, yielding well-resolved maps of the distribution of antigen-IgE-receptor complexes on the surface of RBL-2H3 mast cells. The maps are stored in digital form, as required for computer-based quantitative morphometric analyses. These techniques of silver enhancement, combined BEI/SEI imaging, and digital image analysis can be applied to analyze density and distribution of any gold-labeled ligand on its target cell.
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PMID:Mapping gold-labeled IgE receptors on mast cells by scanning electron microscopy: receptor distributions revealed by silver enhancement, backscattered electron imaging, and digital image analysis. 296 20

Knoop Hardness and pin-and-disc-wear measurements were made on a commercial silver-sintered glass-ionomer cement. The objective was to determine whether the incorporation of a bonded-metal-to-glass filler would enhance durability as determined by the above measurements. As with the previous work on conventional (non-metalized) glass-ionomer cements, the specimens were preconditioned at 37 degrees C in air, water, 0.02 mol/L lactic acid (pH 2.67), and heptane. The influence of these media on the microhardness of the silver-sintered material was about the same as that on the conventional materials. Storing in air produced dehydration, which increased the hardness considerably. Heptane storage increased the hardness less, but this increase is attributed to continued curing during storage. After storage in water, the hardness was essentially unchanged; the influence of increased cure is believed to be offset by softening or plasticization from water uptake. Lactic acid produced a decrease in hardness from chemical dissolution as seen from the SEM observations. In most cases, in particular for the air-stored specimens, the wear resistance was enhanced markedly over that of the conventional materials evaluated previously. The exception was the lactic acid-stored specimens for which little, or no, improvement was observed during early periods of wear. The incorporation of silver appeared to provide lubrication, thus reducing wear. However, catastrophic failure from brittle fracture was still a problem, but its occurrence was less frequent.
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PMID:Wear and microhardness of a silver-sintered glass-ionomer cement. 296 19

Potentiodynamic anodic polarization, SEM, and energy dispersive microanalysis techniques were used to determine electrochemical aggressiveness of disinfecting and sterilizing solutions on carbide and stainless steel burs. The importance of galvanic cell formation in carbide burs caused by mixed metal coupling was examined. The following conclusions were reached. 1. Anodic polarization methods are an effective means for discriminating among the relative corrosiveness of sterilizing and disinfecting agents on dental instruments, particularly dental burs. 2. The relative degree of corrosiveness on stainless steel burs shows Omni II and Omnicide solutions the best, Sterall and Sporicidin solutions the poorest, and Glutarex solution intermediate. Omnicide and Glutarex solutions show the least degree of corrosiveness on the carbide burs. 3. SEM analysis of ground, polished, and treated surfaces shows corrosion deposition over the soldered joint of the carbide burs. The stainless steel shank is a cathodic component of a three-way galvanic cell, whereas the silver soldered joint is an anodic component.
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PMID:Corrosion of dental burs in sterilizing and disinfecting solutions. 316 98

In the present study, Aloe vera gel (AVG) was applied to experimental second-degree burns in guinea pigs, and its effects on epithelialization, wound contraction, newly formed granulation tissue, and regeneration of hair follicles was compared with that effected by 1% silver sulfadiazine cream (AgSD). Epithelialization (%mean +/- SEM) on postburn day 8, 16, and 24 of the AVG-treated wounds was 38.72% +/- 2.71%, 60.34% +/- 3.28%, and 92.46% +/- 2.26%, respectively, while that of the AgSD-treated burns was 53.35% +/- 2.65%, 94.84% +/- 2.65%, and 100%, respectively (P less than .001). Contraction of the AVG-wounds was significantly higher than that of the AgSD-treated burns during 24 days of the study (P less than .001). The thickness of the newly formed granulation tissue was higher in the AVG-treated wounds (P less than .001), while the hair follicles count was significantly lower (P less than .001) compared with the AgSD-treated burns. It is concluded that this preparation of Aloe vera gel hindered the healing process of the present burn wound model when compared with 1% silver sulfadiazine cream.
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PMID:Aloe vera gel hindered wound healing of experimental second-degree burns: a quantitative controlled study. 336 Aug 18

This paper presents findings made using special techniques of imaging and/or of specimen preparation to investigate the changes in tooth structure which occur in caries. We have studied both coronal and root caries in enamel, dentine and cementum using scanning electron and confocal scanning optical microscopy. In preparation for backscattered electron (BSE) imaging in the SEM, teeth were stored in 70% ethanol until further dehydration in ethanol and embedding in polymethylmethacrylate (PMMA). Longitudinally cut surfaces were diamond polished and coated with carbon or silver before BSE imaging. Important changes in the distribution of densities in both enamel and dentine occurred during caries, and could be correlated with prior published studies using polarised light and microradiography to study demineralization in these tissues. However, the resolution of the BSE imaging technique is much higher than that of these previous methods. A new method was used for demonstrating local variations in microhardness with special relevance to the changes occurring in dental caries. Sectioned surfaces were subjected to treatment with a jet of soft abrasive particles, resulting in the selective removal of carious enamel, and enhanced removal of carious dentine. The tandem scanning reflected light microscope (ISRLM) has also been shown to be useful in characterising the spread of caries in the dental tissues. Teeth only need to be cut once, because the image is formed on looking into a bulk specimen. Fluorescent dyes can be used to study the distribution of pore volume, making use of the high resolution in depth of this confocal microscope.
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PMID:Scanning microscopic observations on dental caries. 343 76


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