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At least 217 records · Page 12Linked to original sources
PubMed1994

Effects of fixative and fixation time on the extraction and polymerase chain reaction amplification of RNA from paraffin-embedded tissue. Comparison of two housekeeping gene mRNA controls.

A number of reports have indicated that RNA recovered from paraffin-embedded tissue can be used as a substrate in the polymerase chain reaction (PCR). Although it is established that RNA in paraffin-embedded tissue undergoes significant degradation, the specific contributions of different fixatives and fixation times to this degradation are not known. Mouse splenic tissue was harvested and fixed immediately for 2, 8, or 24 h in either formalin, Omnifix II, or Carnoy's fixative and then processed and embedded in paraffin. RNA was extracted from deparaffinized cubes of tissue using an adaptation of the technique described by Chomczynski and Sacchi. RNA was reverse transcribed using a random hexamer primed reaction. PCR amplification for cDNAs of the housekeeping genes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and hypoxanthine phosphoribosyltransferase (HPRT) mRNAs was then performed. Although GAPDH amplification is used routinely on fresh and frozen tissues, we show that the presence of DNA contamination in the RNA preparations limits its usefulness in paraffin-embedded tissue. Amplifiable HPRT mRNA sequences were detected in nine of 12 samples fixed in Omnifix II, in four of 12 samples fixed in Carnoy's fixative, and in none of 12 formalin-fixed samples. Because of primer selection to preclude amplification of genomic HPRT, DNA contamination is not an issue when HPRT is amplified. Thus, HPRT represents the control system of choice for the evaluation of RNA in PET. The techniques described provide a rapid, uniform, and reproducible method of obtaining RNA from PET for molecular analysis, but they indicate limited utility for retrospective analysis of archival tissues.

Animals↗
PubMed2002

Fixation strength of tapered versus bicylindrical hydroxyapatite-coated external fixation pins: an animal study.

The purpose of this study was to comparatively measure the bone-pin interface strength in two types of hydroxyapatite-coated pins that differed in shape, diameter, and implantation technique. Both pin types are commonly used for tibia fixation. Thirty bicylindrical 5/4-mm stainless-steel pins (Group A) and 30 tapered 6/5-mm stainless-steel pins (Group B) were implanted in the left tibiae of 10 adult sheep. A monolateral fixator was mounted on the pins after implantation. A 5-mm-long bone segment was removed from the tibial mid-diaphysis to ensure high load at the bone-pin interface. Pin insertion torque was 830 +/- 446 N/mm in Group A and 3415 +/- 743 N/mm in Group B (p<0.0001, one-way ANOVA). Six weeks after surgery, the sheep were euthanized and pin extraction torque measured. Pin extraction torque was 1237 +/- 499 N/mm in Group A and 3367 +/- 1512 N/mm in Group B (p<0.0001, Mann-Whitney test). Morphological analysis performed at 60x magnification showed a direct bone-pin contact in both groups. Despite challenging biomechanical conditions, this study showed both pin types to be well-fixed and osteointegrated. Therefore, both pin types are recommended for tibial fixation. However, the tapered pins showed higher extraction torque, an important result for external fixation treatments.

Animals↗
PubMed1993

Shifts of visual attention at fixation and away from fixation.

Attention shifts in the visual field were investigated using a task in which two numerals were flashed one by one, the duration of each numeral being 33 msec. Both numerals were followed by a mask pattern (100 msec in duration). The observer was asked to report the two numerals. If the observer correctly recognized both numerals, it implies that he was able to perform a simple act of attention shift from one item to the next. In the foveal experiment, both numerals were presented at fixation--the second numeral on top of the first. In the extrafoveal experiment, the numerals were also flashed sequentially but in different locations: the first numeral was at fixation and the second at 7 deg eccentricity. The results showed that the observers could not shift attention away from fixation to an extrafoveal position as efficiently as they could maintain attention at fixation.

Attention↗
PubMed1984

Methanol fixation. An alternative to heat fixation of smears before staining.

Methanol fixation of Gram-stained smears was compared to heat fixation. Smears were prepared in duplicate from direct clinical specimens, blood culture bottles, and bacterial colonies. Results from this study show that methanol fixation is superior in every instance to heat fixation. The morphology of bacteria and tissue cells was not distorted, little or no background debris was observed, and a better Gram reaction was noted.

Bacterial Infections↗
PubMed1991

Rapid supplementary fixation in frozen sections: microwave versus conventional fixation. A double-blind comparative study.

The preservation of morphological details in frozen sections subjected to microwave-assisted fixation was compared with that in frozen sections subjected to snap fixation with either formalin/ethanol or ethanol alone. Especially nuclear details were better preserved after short microwave fixation. Ethanol alone gave the poorest results, with loss of nuclear details in the majority of the cases. In this study there was no significant difference between the morphological results obtained with a cheap domestic oven and that with a specialized microwave processor. Microwave-assisted fixation in frozen sections is a simple, rapid method. It is recommended for use in routine laboratories.

Artifacts↗
PubMed2001

The stability of human eye orientation during visual fixation and imagined fixation in three dimensions.

OBJECTIVE: The stabilization of eye movements during voluntary fixation is believed to depend upon the visual feed back, since gaze becomes less stable in the darkness. The temporal variability of human eye orientation in both the horizontal and vertical direction is typically no more than a few minutes of arc. Ocular stability in terms of torsion has, however, been less understood. METHODS: In this study, the stability of gaze in the three dimensions (horizontal, vertical, and torsional) was investigated using a video image analysis system. In ten healthy subjects, eye movements were recorded after fixating the eye on a target in the light and also in the dark (imaginary target). The standard deviations of the eye movements in the three dimensions were calculated during fixation. RESULTS: In the light, the horizontal and vertical eye movements exhibited an alternating sequence of a slow drift and resetting microsaccades, as previously reported. The torsional eye movements, however, showed no such drifts and resetting. In the dark, the horizontal and vertical eye movements exhibited about 2-3 times larger value of the standard deviation than that in the light. In contrast to this, the difference in the standard deviation between the light and dark was not so prominent in case of the torsional eye movement as compared to those of horizontal and vertical. CONCLUSION: These results support the idea that information from the peripheral retina does not significantly influence the feed back system for fixating the target in the light.

Adult↗
PubMed2006

Hemiarthroplasty in worst cases is better than internal fixation in best cases of displaced femoral neck fractures: a prospective study of 683 patients treated with hemiarthroplasty or internal fixation.

BACKGROUND: Studies have shown that the degree of initial displacement and also comminution of the femoral calcar, size of the head and varus angulation are prognostic of failure in displaced femoral neck fracture. We have applied these radiographic criteria in order to select patients who would benefit from internal fixation as opposed to primary hemiarthroplasty, and this prospective study was conducted in order to monitor the results of this strategy. METHODS: 683 displaced fractures of the femoral neck were treated with internal fixation or primary hemiarthroplasty based on the proposed radiographic criteria in a prospective consecutive study, and the patients were followed for 1-6 years. We treated 228 fractures with internal fixation and 455 by bipolar hemiprosthesis. The choice of operation was based on clinical evaluation of the patient and assessment of the assumed healing potential of the fracture, as determined by radiographic evaluation. Revision and mortality were primary endpoints. RESULTS: 54 (24%) of the patients originally treated by osteosynthesis were revised, whereas 9 (2%) of the patients treated with hemiarthroplasty had revision surgery. There were no significant differences in mortality between the groups at 30, 120 or 365 days. INTERPRETATION: Even when treating only the fractures with the assumed best healing potential with internal fixation, the results are inferior to hemiarthroplasty.

Aged↗
PubMed2006

Binocular coordination of the eyes during reading: word frequency and case alternation affect fixation duration but not fixation disparity.

This experiment investigated whether properties of the text being read affect binocular coordination of the eyes during reading. Readers' binocular eye movements were recorded while they read sentences that contained high- and low-frequency words. In addition, half of the sentences were presented in normal case, and half were presented in alternating case (i.e., AlTeRnAtInG cAsE). Past research has suggested that the visual system tolerates less binocular fixation disparity with alternating than with normal case (Heller & Radach, 1999). While both word frequency and alternating case produced large effects on fixation durations on the target word, neither manipulation affected the magnitude of fixation disparity. It is concluded that linguistic and visual properties of the text being read do not influence binocular coordination of the eyes during reading. Additional analyses also showed no difference in fixation disparity between reading and a nonlinguistic task. Implications of these results for split-fovea models of reading are discussed.

Analysis of Variance↗
PubMed1991

PCR amplification from paraffin-embedded tissues. Effects of fixative and fixation time.

The polymerase chain reaction (PCR) DNA amplification method is a powerful new tool for the retrospective analysis of paraffin-embedded tissue (PET). The technique has afforded the sensitive and specific detection of nucleic acid sequences associated with genetic and infectious diseases. However, PET processing conditions vary in their suitability for amplification. The authors have examined the effects of 11 fixatives at three fixation times. The effect of fixation was measured by the ability of the DNA in a treated tissue to serve as a template for the amplification of DNA fragments that ranged from 110 to 1,327 base pairs in length. Specimens fixed in acetone or 10% buffered neutral formalin were found to be best suited for subsequent analysis by PCR. A second group of fixatives, including Zamboni's, Clarke's, paraformaldehyde, formalin-alcohol-acetic acid, and methacarn, compromised amplification efficiency. Tissues treated with Carnoy's, Zenker's, or Bouin's, respectively, were even less desirable for amplification analysis.

Acetone↗
PubMed1986

Comparison of Wesson and modified Sheedy fixation disparity tests. Do fixation disparity measures relate to normal binocular status?

A new fixation disparity measuring device, the Wesson Fixation Disparity Card, is compared with the modified Sheedy Disparometer. Twenty-eight subjects were divided into normal and abnormal categories of binocular status determined by classical clinical techniques rather than on patients' subjective symptomatology. Fixation disparity curves were generated on all subjects using both instruments. There were significant differences between the two instruments. Neither instrument was able to distinguish between normal and abnormal subjects but, over a five day period, each instrument produced repeatable results. The validity of fixation disparity measurements using either instrument on naive observers, especially children, is questioned.

Adolescent↗
PubMed1983

Fixation of Thy-1 in nervous tissue for immunohistochemistry: a quantitative assessment of the effect of different fixation conditions upon retention of antigenicity and the cross-linking of Thy-1.

It has proved difficult to obtain good immunohistochemical localization of cell surface antigens in nerve for a number of reasons, prominent among which are problems of fixing this class of molecule without destroying their antigenicity. In the course of developing a fixation procedure suitable for one such antigen. Thy-1, we have quantitatively assessed the effect of different fixation parameters upon the retention of Thy-1 antigenicity and upon the extent of cross-linking of the antigen in the tissue. The former was measured using radioimmunoassays adapted for membrane antigens in fixed tissue, the latter by measuring the proportion of antigen rendered insoluble to the detergent, sodium deoxycholate, and by examining the size of the antigen on sodium dodecyl sulfate--polyacrylamide gels. These approaches demonstrated that minor modifications of the standard vascular perfusion fixation of brain, using both glutaraldehyde and paraformaldehyde, were sufficient to fix the Thy-1 molecule, and at the same time substantially spare its antigenicity. In this study we measured Thy-1 using both a conventional rabbit antiserum and a mouse monoclonal antibody to the Thy-1.1 antigenic determinant. The multiple antigenic determinants recognized by the rabbit antibodies were cumulatively more resistant to fixation than the single antigenic determinant recognized by the monoclonal antibody.

Animals↗
PubMed2005

Biomechanical comparison of two stabilization techniques of the atlantoaxial joints: transarticular screw fixation versus screw and rod fixation.

OBJECTIVE: To compare the biomechanical stability imparted to the C1 and C2 vertebrae by either transarticular screw fixation (TSF) or screw and rod fixation (SRF) techniques in a cadaver model. METHODS: Ten fresh ligamentous human cervical spine specimens were harvested from cadavers. The specimens were tested sequentially in the intact state, after injury and stabilization (unilateral left side and bilateral), and after fatiguing to 5000 cycles (0.5 Hz) at +/-1.0 N.m of flexion and extension. The specimens were stabilized by use of TSF in 5 spines or SRF in the other 5 spines. The data were converted to angular displacements, and the stabilized cases were compared with intact states for evaluating the efficacies of the two techniques in stabilizing the C1-C2 segments. RESULTS: In the TSF group, the unilateral fixation using one screw imparted a significant stability in only the axial rotation mode. The unilateral procedure in the SRF group was effective in stabilization in all modes except in extension. The bilateral procedure in both of the groups was effective across the C1-C2 segment. However, the SRF group afforded higher stability than the corresponding TSF group in the flexion and extension modes. The degree of stability did not change after fatigue compared with the prefatigue data. CONCLUSION: In general, a surgeon should undertake a bilateral fixation to achieve sufficient stability across the atlantoaxial complex, and either technique will provide satisfactory results, although the SRF technique may be better in the flexion and extension modes. One should use the SRF procedure while trying to achieve stability with a unilateral system.

Aged↗
PubMedDate not supplied

[A new test procedure to examine the stability of external fixation clamps--demonstrated with the Stuhler-Heise external fixation system (author's transl)].

Experimental investigation of stabilty for examination of the efficiency of external fixation clamps required different testing procedures and measuring arrangementsz which is due to variant assessment parameters and natures of load. Here is a description of a measuring equipment which could be applied for all important cases of load. In relation to the entire experimental arrangement it also enables the testing of all external fixation assemblies. Deviations of the poroximal fragment caused by loading, are considered as assessment parameters of the stability. This measuring set was practically applied on simulated defect fractures, stabilized by the Stuhler-Heise external fixation system. During a combined bending strain the stability degree of various two-dimensional as well as three-dimensional external fixation clamps for application on tibias was determined.

Bone Nails↗
PubMed2002

Combination of fixation using PLP fixative and embedding in paraffin by the AMeX method is useful for histochemical studies in assessment of immunotoxicity.

To establish a method for processing lymphoid organs suited to morphological, immunohistochemical and enzyme histochemical analyses for assessment of immunotoxicity, we examined a combination of fixation with periodate-lysine-paraformaldehyde (PLP) fixative and embedding in paraffin by the AMeX method (PLP-AMeX method). Spleen and thymus removed from monkeys and rats were fixed in PLP fixative for 6 hours at 4 degrees C. After fixation, specimens were processed and embedded in paraffin by the AMeX method. In hematoxylin and eosin-stained sections, tissue architecture was well preserved. In immunohistochemical staining, markers of T lymphocytes (CD3, CD4, CD8), B lymphocytes (monkey: CD20cy, rat: CD45RA) and macrophage (monkey; CD68, rat: ED-1) were well identified according to their specificities, although the staining intensity of CD8 in the monkey and CD4 in the rat were somewhat weaker in PLP-AMeX-prepared sections than in those frozen. In enzyme histochemical staining, alkaline phosphatase activity was well preserved in neutrophils. In toluidine blue- and Giemsa-stained sections, eosinophil granules and the metachromasia of granules in basophil/mast cells were clearly detectable. These findings suggest that the PLP-AMeX method is a powerful tool for assessment of immunotoxicity.

Animals↗
PubMed1980

Alcoholic Bouin fixation of insect nervous systems for Bodian silver staining. I. composition of 'aged' fixative.

Alcoholic Bouin (Duboscq-Brasil) fixative being 'aged' at 60 C to improve tissue preservation and subsequent staining was sampled at various stages to determine its histological effectiveness and chemical composition. Histological performance was tested using ventral nerve cord ganglia of the cockroach Periplaneta americana and the locust Schistocerca gregaria. Chemical analysis was by ultraviolet spectroscopy, thin layer and gas-liquid chromatography, and mass spectrometry. Histological performance improved rapidly during the first 7-10 days and composition changed correspondingly. The rate of change then slowed as a more stable condition was approached. Fully aged solutions, after about 40 days, giving optimum fixation and staining, contained little more than half the amounts of the volatile components (formaldehyde, ethanol, and acetic acid) in the original mixture, together with ethyl acetate and a formal, diethoxymethane, as the principal reaction products, but picric acid content showed little change. Older ('overaged') solutions, fully aged and then kept at room temperature for 1-2 yr, gave poorer fixation and staining and contained still less of the original volatile constituents and correspondingly more of the reaction products. A 'simplified synthetic aged alcoholic Bouin' (15 ml 40% formaldehyde, 35 ml ethanol, 3.5 ml acetic acid, 5 ml ethyl acetate, 15 ml diethoxymethane, 0.46 g picric acid, and water to 100 ml) closely stimulated the performance of the fully aged orthodox fixative without the need for aging.

Acetates↗
PubMed2001

Anterior decompression and fixation versus posterior reposition and semirigid fixation in the treatment of unstable burst thoracolumbar fracture: prospective clinical trial.

AIM: To compare the anterior and posterior surgical approach in the emergency treatment of unstable burst thoracolumbar fracture. METHODS: Twenty-five patients with unstable thoracolumbar fracture underwent either anterior neurodecompression and fixation (n=13) or posterior reposition and semirigid fixation by hook-rod with pedicle screw fixation (n=12), depending on the type of implants available at the time of operation. Neurologically injured patients were operated on within the first 8 hours and neurologically intact patients within the first 2 days after the fracture. Neurological improvement was assessed according to the American Spinal Injury Association grading scale and the Prolo economic/function outcome scale. We also recorded operation time, blood loss, cosmetic outcome, hospital stay and cost, complications, and donor site pain. RESULTS: There were no significant differences between the two groups in either neurological improvement (p=0.86) or favorable economic or function outcome (p=0.54 and p=0.53, respectively). The operation time was shorter in the posterior approach group than in the anterior approach group (median 174 min, range 130-215 vs median 250 min, range 200-295, respectively, p<0.001). The blood loss was smaller in the posterior approach group (median 750 mL, range 500-1,10, vs median 1,362 mL, range 1,150-1,50, in the anterior approach group; p<0.001). The posterior approach group also had better esthetic outcome, lower hospital cost, lower complication rate, and no donor site pain. CONCLUSION: Both surgical techniques were equally effective in neurological improvement and functional outcome. Posterior surgery can be recommended in emergency neurodecompression and fixation of unstable thoracolumbar fractures because of the shorter operation time and smaller blood loss.

Adolescent↗
PubMed1989

Biomechanical evaluation of spinal fixation devices. Part III. Stability provided by six spinal fixation devices and interbody bone graft.

The three-dimentional stability provided by six spinal fixation devices with or without interbody bone graft has been studied in an in vitro biomechanical model using five-vertebral (T11-L3) fresh cadaveric thoracolumbar specimens. An injury was created at T12-L1 by complete transection of the posterior elements and posterior half of the intervertebral disc, leaving the anterior half of the intervertebral disc and anterior longitudinal ligament intact. The three-dimensional rotations and translations, measures of biomechanical instabilities, were determined under physiologic loads for the intact spine and the spinal constructs, ie, injured spine plus instrumentation. The tested devices were: Harrington reverse ratchet rods (HR); Luque rectangle rod (LR); Kaneda device without transverse fixator (KD); Kaneda device with transverse fixators (KT); transpedicular external fixator (EF). In addition, stability tests were performed for KT, EF, and Harrington compression rods with interbody bone graft following a corpectomy (KTB, EFB, and HCB). The constructs were more stable than the intact spine under the four loads in the following order: flexion: EFB, HCB, EF, HR, LR, KTB, and KT; extension: EFB, LR, EF, KTB, HR, and KT; lateral bending: KTB, KT, EFB, KD, EF, HCB, and HR; and axial rotation: EFB.

Biomechanical Phenomena↗
PubMed1978

Microwave fixation versus formalin fixation of surgical and autopsy tissue.

Microwave irradiation of surgical and autopsy tissue penetrates, fixes, and hardens the tissue almost immediately (the fluid media used in the microwave consisted of saline, ten percent phosphate buffered formalin, and distilled water). Tissue sections from a representative sample of organs were tested. Comparable sections were simultaneously fixed in a phosphate buffered ten percent formalin bath in a vaccum oven as a control. Hematoxylin and eosin were used to stain the sections. Results equal to and superior to the control method were obtained. Saline microwave fixation was superior to formalin microwave fixation. Tissues placed in Zenker's solution and fixed in standard microwave oven (for approximately one minute) yielded results at least equal to conventional Zenker fixation (approximately two hours). No tissue hardening resulted from Zenker microwave fixation. A unique time versus temperature graph (microwave heating curve) reduces individual variation with this technique.

Autopsy↗