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Fixation Method (fixation + method)
Selected AbstractsStaining methods for magnetic resonance microscopy of the rat fetusJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2007Alexandra Petiet MS Abstract Purpose To develop a magnetic resonance histology (MRH) staining and fixation method by immersion to enhance the signal-to-noise ratio (SNR) with a paramagnetic contrast agent permitting microscopic acquisition within a 3-hour scan time. Materials and Methods Methods were optimized for embryonic day 18.5 (E18.5) rat fetuses and imaging at 9.4T with an RF refocused spin-echo pulse sequence (TR/TE = 75 msec/5.2 msec). Fixation/staining was performed by immersion in Bouin's fixative containing varied concentrations of ProHance (from 10:1 to 500:1 Bouin's:ProHance) and for varied immersion durations (up to 24 hours). Results The results showed a significant change in T1 and T2 relaxation times as a function of concentration of contrast agent and immersion duration. As the contrast agent penetrated the tissues, T1 was reduced as desired (typically by 10×), but at the same time T2 was profoundly reduced (typically by 3×) due to both protein cross-linking from the fixative and the high concentration of contrast agent. A systematic assessment of this staining protocol showed an increased SNR (by 5×) over that in unstained specimens. Conclusion This staining protocol reduced scan time for very-high-resolution images (19.5 ,m) to only 3 hours, making MRH a routine tool for evaluating fetal development. J. Magn. Reson. Imaging 2007;25:1192,1198. © 2007 Wiley-Liss, Inc. [source] Electron microscopic examination of uncultured soil-dwelling bacteriaMICROBIOLOGY AND IMMUNOLOGY, Issue 5 2008Kazunobu Amako ABSTRACT Bacteria living in soil collected from a rice paddy in Fukuoka, Japan, were examined by electron microscopy using a freeze-substitution fixation method. Most of the observed bacteria could be categorized, based on the structure of the cell envelope and overall morphology, into one of five groups: (i) bacterial spore; (ii) Gram-positive type; (iii) Gram-negative type; (iv) Mycobacterium like; and (v) Archaea like. However, a few of the bacteria could not be readily categorized into one of these groups because they had unique cell wall structures, basically resembling those of Gram-negative bacteria, but with the layer corresponding to the peptidoglycan layer in Gram-negative bacteria being extremely thick, like that of the cortex of a bacterial spore. The characteristic morphological features found in many of these uncultured, soil-dwelling cells were the nucleoid being in a condensed state and the cytoplasm being shrunken. We were able to produce similar morphologies in vitro using a Salmonella sp. by culturing under low-temperature, low-nutrient conditions, similar to those found in some natural environments. These unusual morphologies are therefore hypothesized to be characteristic of bacteria in resting or dormant stages. [source] Cryo-sectioning and chemical-fixing ultramicrotomy techniques for imaging rubber latex particle morphologyMICROSCOPY RESEARCH AND TECHNIQUE, Issue 2 2004Nadaraja Subramaniam Abstract Two methods adapted from biological microscopy are described for a new application in imaging the morphology of rubbery latex particles. In the first method, a drop of latex is frozen in liquid nitrogen, sectioned with a diamond knife and vapour-stained with osmium tetroxide, then viewed by transmission electron microscopy. When applied to latexes made by emulsion polymerization of methyl methacrylate in a natural rubber latex seed, inclusions are clearly visible. A chemical fixation method is then described for imaging the morphology of such rubbery latex particles. Glutaraldehyde is added to the latex, followed by osmium tetroxide. The sample is then dehydrated in ethanol, epoxy resin added, and the sample cured, ultramicrotomed, and imaged with transmission electron microscopy. An inclusion morphology is again clearly seen. Microsc. Res. Tech. 63:111,114, 2004. © 2004 Wiley-Liss, Inc. [source] Intraoperative Study of Polarization and Evoked Response Signals in Different Endocardial Electrode DesignsPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 7 2001CHING LAU LAU, C., et al.: Intraoperative Study of Polarization and Evoked Response Signals in Different Endocardial Electrode Designs. Some new generation pacemakers use an algorithm based on evoked response (ER) detection to verify beat-to-beat capture and to enable automatic adjustment of output. This is a prospective acute study of polarization signal (PS) and ER in nine currently available electrodes. Intraoperative testing of ventricular bipolar electrodes used the Autocapture (AC) algorithm. The intrinsic R wave, PS, ER, acceptance of AC function, and stimulation thresholds (STs) were obtained. Ventricular electrodes were categorized as follows: titanium nitride (TiN)-coated passive and active fixation, high impedance (HI), passive fixation (VP), iridium oxide-coated titanium (IROX) (VI), and platinum helix (PH) active fixation. Acute testing was performed in 217 patients with an average age of 74.26 years, 59.6% were men with primary pacing indication-SSS (46.3%). There were no significant differences found with respect to R wave and threshold between the various electrodes. PH active-fixation electrodes had significantly higher ER and PS than other groups including the TiN-coated active-fixation electrodes. TiNcoated electrodes (active and passive fixation) had significantly lower PS than other electrodes. As a result, TiN electrodes had a significantly higher functional rate of AC (91.7%), whereas PH had the lowest rate (0%). In conclusion, (1) polarization characteristics are significantly different for commercially available ventricular electrodes, (2) certain physical features at the tissue to electrode interface like TiN coating appears to be more important in determining PS than electrode tip size and fixation method, and (3) the current algorithm for AC requires electrodes that provide low polarization for satisfactory performance. [source] Formalin fixation and immunoreactivity in prostate cancer and benign prostatic tissuesAPMIS, Issue 5 2010SARA JONMARKER JARAJ Jaraj SJ, Egevad L. Formalin fixation and immunoreactivity in prostate cancer and benign prostatic tissue. APMIS 2010; 118: 383,8. For better fixation, formalin injection of radical prostatectomy (RP) specimens has been suggested. We aimed to assess its effect on immunoreactivity using immunohistochemistry (IHC). A tissue microarray of cancer and benign tissues from 42 RP specimens was constructed. Twenty-one of the prostates had been injected with formalin prior to formalin immersion. IHC staining was performed using 15 antibodies, including nuclear and cytoplasmic markers known to be positive in prostate tissue: pan cytokeratin, P504S, high molecular weight (HMW) keratin, PSA, vimentin, actin HHF35, thioredoxin-1, peroxiredoxin-2, PDX-1, BAX, p27, androgen receptor (AR) and heat shock proteins (HSP) 27, 60 and 70. Differences in staining intensity in cancer and benign tissues were compared separately except for HMW keratin. Only 7 of 29 analyses showed significant differences between groups, including 5 of 15 antibodies. The expression of AR and HSP 27 was stronger in formalin-injected tissue, while the opposite was true for HSP 60, HSP 70 and peroxiredoxin-2. For most antibodies, formalin injection does not significantly affect immunoreactivity in prostate tissue. The staining variability caused by inter- and intratumoral heterogeneity may be greater than that caused by the fixation method. [source] Sutureless encircling band , biomechanical calculations and clinical experienceACTA OPHTHALMOLOGICA, Issue 2009M MAIER Purpose In cases with multiple retinal breaks and in combination with vitrectomy in eyes with Proliferative vitreoretinopathy (PVR) for retinal detachment surgery often an encircling band is used. Usually the encircling band is fixed with non absorbable sutures. Methods A fixation method for an encircling band in retinal detachment surgery with one scleral tunnel in every of the 4 quadrants is reported. We describe our experience and biomechanical calculations of this fixation technique. Results In comparison to conventional fixation technique we found the following advantages: No suture is necessary, this means no additional foreign body can produce irritations. The scleral tunnel is safe and the preparation under the microscope can be performed fast and well controlled. Sclera tunnel fixation is very comfortable in combination with a vitrectomy. Conclusion With a short learning curve the operating time is as short as with conventional suture fixation of the encircling band. There is less perforating risc, less irritation and less patient discomfort postoperatively. A sutureless encircling band with sclera tunnel fixation is a very usefull operation technique in clinical routine. [source] | ||||||||||