Scanning microscopy最新文献

Cardiotoxicity is an unexplained toxic manifestation of 5-fluorouracil (5-FU). Its possible mechanism could be a direct cytotoxic effect on the vascular endothelium. We have tested this hypothesis in an experimental study in rabbits, using scanning and transmission electron microscopic evaluation of endothelium in small arteries (the central artery of the ear). The perfusion fixation method at physiological pressure and temperature was used. Both local and systemic effects of 5-FU on endothelium were studied 1, 3, 7, 14 and 30 days after in vivo treatment with 5-FU. Fifteen rabbits were used and five additional animals served as controls. The following parameters were evaluated: vessel wall and endothelial cell contraction, cell oedema, cytolysis, occurrence of denuded areas, platelet adhesion/aggregation and fibrin formation. For the description of each parameter, a scale of negative points (0.0-3.0) was used. We found severe cell damage with accompanying thrombus formation. The findings support the hypothesis that the thrombogenic effect of 5-FU, secondary to its direct cytotoxic effect on endothelium, is the pathophysiological mechanism behind 5-FU cardiotoxicity.

The aim of this study was to examine the influence of different incubation media on the morphology of the endothelium of great saphenous vein grafts and establish a suitable scoring system for the evaluation of damage caused by these media. Fifty specimens of saphenous veins from ten patients during elective aorto-coronary bypass surgery were used. Ten specimens served as controls; the others were assigned to test groups and exposed to heparinized whole blood, Bretschneider's HTK, human albumin or Ringer's solution. Specimens exposed to heparinized blood showed only slight morphological alterations, whereas the other three mediums caused severe damage. Thus, heparinized blood seems to be most suitable as a rinsing and incubation medium. A widely accepted scoring system for the quantification of endothelial damage caused by the incubation media did not adequately reflect the morphology alterations in the cytoskeleton and membrane topology. The proposed scoring system, which is based on endothelial cell separation, endothelial cell loss, amount of deposits, endothelial cell surface homogeneity, in addition to the frequency of spikes and blebs, seems to be suitable for characterizing differences in endothelial morphology.

Samples of common skin abnormalities from 23 subsistence-harvested bowhead whales (Balaena mysticetus) were examined. Most lesions fell into three broad classes: shallow lacerations, circular depressions, and epidermal sloughing. Both circular depression lesions and epidermal sloughing lesions may be divided into more than one subgroup based on morphological criteria. Examination of each of the subgroups using light and scanning electron microscopy suggests relationships among the subgroups of a class. These proposed relationships are discussed, as are some possible etiologies. Scanning electron microscopy reveals abundant bacteria and diatoms present in association with each lesion class but no evidence of a particular association characteristic of a lesion class. The microflora were especially abundant wherever the stratum spinosum was exposed at the skin surface.

This study investigates the thermal danger of Erbium (Er):YAG laser ablation. Classical preparation techniques have many disadvantages caused by unfavorable changes of temperature, pressure, and by mechanical vibrations. The effect of mechanical vibrations and pressure is eliminated by use of laser ablation technique. The purpose of this study was to analyze the side effects resulting from thermal changes of enamel and dentin in extracted human teeth subjected to pulsed Er:YAG laser radiation using both wet and dry ablation methods. The micrographs of the sections were checked and measured afterwards. The effect of the investigated laser irradiation on the origin of cracks was analyzed in the scanning electron microscope. The hard structures of the teeth were observed under transmitted and polarized light. The occurrence of cracks can be directly correlated to overheating during dry enamel ablation, because heat is generated by absorption of the laser beam by enamel and dentin. The addition of water mist during irradiation not only enables rapid ablation of enamel and dentin, but offers thermal protection to the pulp. The heat changes to the pulp caused by an energy level of 200 mJ from the tested laser system may be reduced by adding a fine water spray during the lasing procedure.

The aim of this study was to investigate whether the calcium (Ca) and phosphorus (P) composition of corticosteroid induced dentin was the same as in normally developed dentin. Seven rats were given corticosteroids intravenously and three rats served as controls. Energy dispersive X-ray microanalysis (EDX) was carried out on the axially sawn roots of the molars. Measurements were made at 20 sites, equally distributed in the buccal, mesial, lingual and distal direction. The results showed that the Ca/P ratio (weight %) was slightly above 2.0 in both the experimental and the control group, indicating that the corticosteroid induced dentin had a normal Ca/P ratio. However, different degrees of mineralization were found in different directions of the roots.

Laser microprobe mass spectrometry (LMMS) provides spot analysis with a lateral resolution of 1-5 microns. Focused laser ionisation, combined with mass spectrometry, yields information on elements, molecular identification of inorganic substances, and structural characterisation of organic molecules of typically less than 2-3 kDa. Quantification in complex heterogeneous systems, such as biological materials, is not possible at the present state of the art. The strength of the method lies in the qualitative information on the molecular composition of the analyte, not just element detection, with a lateral resolution at the light microscopy level. The applications of this technique in the field of biomedicine and biology are illustrated by examples that demonstrate the use of this qualitative information in practical test cases.

The deposition of DNA molecules on mica is driven and controlled by the ionic densities around DNA and close to the surface of the substrate. Dramatic improvements in the efficiency and reproducibility of DNA depositions were due to the introduction of divalent cations in the deposition solutions. The ionic distributions on DNA and on mica determine the mobility of adsorbed DNA molecules, thus letting them assume thermodynamically equilibrated conformations, or alternatively trapping them in non-equilibrated conformations upon adsorption. With these prerequisites, mica does not seem like an inert substrate for DNA deposition for microscopy, and its properties greatly affect the efficiency of DNA deposition and the appearance of the molecules on the substrate. In our laboratory, we have some preliminary evidence that mica could also participate in DNA damage, most likely through its heavy metal impurities.

We have used atomic force microscopy (AFM) to study radiation-induced DNA double strand breaks. Double-stranded plasmid DNA was irradiated with 18-MeV electrons in aqueous buffer, using a medical linear accelerator. Doses of 50, 100, 150, and 200 Gy were delivered to DNA samples, and atomic force microscopy was used to measure the length of each DNA fragment. From these measurements, we obtained the average length of the irradiated DNA for each sample and found a linear-quadratic relationship between the average length and radiation dose.

Laser irradiation at and above parameters producing the modification threshold for dentin causes structural changes to the dentin surface. This study determined the microhardness of dentin before and after laser modification and acid treatment using a repeated-measures design. Seven dentin sections (4 mm in thickness) were cut from freshly extracted non-carious third molars using a diamond saw. The middle occlusal third was used as the test dentin surface. One section served as a control (C); three received laser modification (L) and then acid treatment (L + A); and three received acid (A) and then laser treatment (A + L). Laser modification was made using a pulsed (120 microseconds) fiber-optic-delivered (500 microns diameter) Nd:YAG (lambda = 1.06 microns) laser at the physical modification threshold of 207 J/cm2. Acid treatment consisted of 10% nitric acid applied for 45 seconds. Twenty Knoop indentation microhardness measurements (KHN) were obtained using 300 g force engaged for 15 seconds for each section before and after each treatment (n = 400). Knoop microhardness values recorded: C = 62 +/- 3; L = 149 +/- 35; A = 24 +/- 5; L + A = 40 +/- 16; and A + L = 33 +/- 5. Multifactor-repeated measures, with analysis of variance (ANOVA; p < or = 0.05), indicated significant differences between all treatment groups. Scanning electron microscopy analysis of dentin surfaces documented unique surface morphology for all treatment conditions. Laser modification of dentin before or after acid treatment increased dentin microhardness.

Many studies indicate that up-regulated production of 1,25(OH)2-vitamin D3 (calcitriol) with increased intestinal absorption of calcium is the primary event causing idiopathic hypercalciuria. Thus, a low calcium diet appears to be a straightforward strategy in calcium stone formers with hypercalciuria (HCSF). However, the efficacy of such a regimen has never been established, and lowering calcium intake from 1000 to 400 mg/day further enhances calcitriol production. On a diet chronically restricted in calcium, many stone formers increase their intake of animal flesh protein. The latter is known to increase renal mass, and calcitriol levels indeed are positively correlated with renal mass in animals as well as in HCSF. Thus, low calcium and high animal flesh protein consumption are independent stimuli for further up-regulation of calcitriol production. The rise in calcitriol suppresses parathyroid hormone synthesis thereby diminishing renal tubular calcium reabsorption, and increasing urinary calcium losses. Since calcitriol up-regulation also increases bone resorption, the combination of low calcium and high protein intake is particularly likely to induce negative calcium balance and thus osteopenia. Finally, low calcium intake carries the risk of insufficient intestinal binding of oxalate with subsequent increases in intestinal absorption and urinary excretion of oxalate. Indeed, most recent studies suggest that high amounts of calcium, when ingested simultaneously with oxalate-containing meals, are able to prevent hyperoxaluria during severe oral oxalate loading.