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At least 1,207 records · Page 67Linked to original sources
PubMed2007

Initial and 6 weeks postoperative structural properties of soft tissue anterior cruciate ligament reconstructions with cross-pin or interference screw fixation: an in vivo study in sheep.

PURPOSE: The purpose of this study was to evaluate the detrimental effects of interference screw fixation on soft tissue anterior cruciate ligament (ACL) reconstruction after 6 weeks and compare them with a cross-pin technique. METHODS: In an intra-articular model, ovine soft tissue grafts were fixed with two 3.3-mm biodegradable pins or with interference screws. Maximum load, yield load, and stiffness of the femur-graft-tibia complex were evaluated immediately after surgery and 6 weeks postoperatively. RESULTS: For knees with interference screw fixation, strength deteriorated by 81% and stiffness deteriorated by 67%. For knees with double cross-pin fixation, strength deteriorated by 48% and stiffness improved by 52%. These differences were statistically significant. At the time of surgery, all grafts failed by slippage of the graft past the screw or by cross-pin failure. At 6 weeks postoperatively, the grafts of both groups failed at the tibial or femoral tunnel entrance. CONCLUSIONS: After 6 weeks, the biomechanical characteristics of grafts that were fixed with cross-pins were superior to those of grafts after interference screw fixation. CLINICAL RELEVANCE: Because of significantly inferior biomechanical stability after interference screw fixation, a less aggressive program of rehabilitation might be recommended.

Achilles Tendon↗
PubMed1993

The effect of formalin fixation on restriction endonuclease digestion of DNA and PCR amplification.

The effect of formalin fixation on DNA and on polymerase chain reaction (PCR) amplification was investigated. Lambda phage DNA fixed in buffered formalin showed incomplete digestion on restriction endonuclease treatment. The resistance to restriction digestion was dependent on the temperature of fixation, but not affected by salt concentration of the fixative. Lambda phage DNA fixed in unbuffered formalin showed poor PCR amplification due to degradation of DNA during fixation. Lambda phage DNA fixed in buffered formalin evaded degradation and suited for template of amplification. Feasibility of formalin-fixed tissues as sources for PCR amplification was also investigated with primers producing 128 bp fragment of c-Ki-ras exon 2. Although DNA from tissues fixed for 3 months showed amplification, there was no amplification from tissues kept in unbuffered formalin for longer than 6 months.

Bacteriophage lambda↗
PubMed2000

Exposure of lumenal microtubule sites after mild fixation.

High-resolution analysis of tubulin structure and docking the structure of tubulin dimer into a map of microtubules led to a prediction that sites for tubulin acetylation are in the interior of microtubules. This is somehow difficult to reconcile with their susceptibility to proteases and acetylation in assembled microtubules. To assess the availability of acetylated alpha-tubulin for antibodies, immunofluorescence on detergent-extracted cells, on cells fixed under various conditions and in microinjected cells was performed with monoclonal antibodies of known epitope locations. The presented data indicate that acetylated alpha:Lys40 is not exposed on unfixed microtubules but that this region of lumenal microtubule surface becomes easily exposed under mild fixation conditions.

3T3 Cells↗
PubMed1999

A comparison of three methods of orienting cervical punch biopsies.

AIMS: To compare methods of orienting cervical punch biopsies, since well oriented biopsies are needed to optimise the diagnosis and grading of cervical intraepithelial neoplasia. METHODS: The orientation, the presence and preservation of the squamocolumnar junction, and the presence or absence of the surface layers of the squamous epithelium were compared in 345 cervical biopsies that had either been attached to paper (n = 112), floated directly into 10% formalin (n = 107), or floated into a solution of 10% formalin including 0.05% eosin (n = 126) in the colposcopy clinic. RESULTS: When the specimens were mounted on filter paper before fixation, they were more likely to be optimally oriented, to have a preserved squamocolumnar junction, and to have intact surface epithelium than specimens that were handled using the other methods, even when the specimens floated off the paper in transit. CONCLUSIONS: Cervical biopsy specimens should be mounted on paper before fixation and submission to the laboratory.

Biopsy↗
PubMed1977

The use of PIPES buffer in the fixation of mammalian and marine tissues for electron microscopy.

PIPES, an organic based buffer, was used in the preparation of a variety of marine and mammalian tissues for electron microscopic study. The ultrastructural results demonstrate that this buffer renders superior ultrastructural details to those obtained with some of the more common inorganic buffers especially when long fixation times are required. Furthermore, this buffer system does not appear to contribute extraneous anions or cations to the tissues and thus permits accurate elemental determinations to be performed on thin sections of the plastic embedded specimens by means of energy dispersive X-ray analysis.

Animals↗
PubMed1984

A method for T-antigen demonstration by a polyclonal antibody and peanut lectin; elimination of cross-reaction with naturally occurring antibodies.

Antisera and a lectin were used to demonstrate T-antigens in colorectal carcinomas. Rabbits were immunized with red blood cells on which the T-antigen had been exposed. The obtained polyclonal antiserum and a crude lectin (PNA) prepared from peanuts were used in an immunoperoxidase technique. The crude lectin and a chromatographic pure lectin showed the same staining specificity. Different fixatives, length of fixation and buffer compositions were tested on paraplast and frozen sections. Four per cent formaldehyde preserved the antigens well in paraplast embedded tissues when fixation was shorter than 48 h. In the immunoperoxidase technique the chromatogen used was 3-amino-9-ethyl-carbazole whose staining intensity was sensitive to the H2O2 concentration. Agglutination of T-exposed red blood cells was used to assess the anti-T titre of various sera. Normal animal serum contained anti-T antibodies, and the possibility of false positive reactions and methods to avoid it in immunohistochemistry is discussed.

Adenocarcinoma↗
PubMed1998

Ultrastructure and cytochemistry of the early calcification site and of its mineralization organic matrix in Paracentrotus lividus (Echinodermata: Echinoidea).

The ultrastructure and cytochemistry of skeleton formation sites prior to mineralization are described for the first time in echinoderms. These early sites are intracellular vacuoles located in syncytial pseudopodia of skeleton-forming cells. They contain a mineralization organic matrix, which shows a calcium-binding ability and is framed in a tridimensional structure made of concentric layers bridged by radial threads. This organic matrix presents repetitive structures which could be implicated in mineralization control. Both the tridimensional organization of the organic matrix and its framing, before mineralization starts, question the current theories which suggest that the echinoderm organic matrix is soluble at the onset of mineralization and adsorbs on the forming crystal.

Animals↗
PubMed1993

Fixation method useful for cytologic examination and DNA flow cytometry of exfoliated bladder cells.

Single-institution studies have shown that DNA flow cytometry is superior to routine cytologic evaluation of following patients for bladder cancer recurrence. For 15 urine and 15 bladder washing specimens, we evaluated a fixative employing methanol plus acetic acid (MA), freshly mixed 20:1 (vol/vol). Routine cytologic evaluation following Papanicolaou staining, and DNA flow cytometry were performed. Paired aliquots from the same washings and urines were processed as fresh spray-fixed samples and MA-fixed samples. The majority of the MA-fixed specimens showed good nuclear preservation when assessed for chromatin texture, presence of distinct nuclear envelope, and clarity of nucleolus, while only a minority of the fresh urine and washing samples showed these features. Cytoplasmic degeneration was seen only in fresh specimens. The presence of aneuploidy and the percentage of hyperdiploid cells could be reliably determined in the MA-fixed samples. This fixation protocol is recommended for the transport of urine and bladder washing specimens to centralized laboratories for both cytologic and flow cytometric evaluation.

Acetates↗
PubMed2003

Fixation methods for the study of lipid droplets by immunofluorescence microscopy.

The study of proteins associated with lipid droplets in adipocytes and many other cells is a rapidly developing area of inquiry. Although lipid droplets are easily visible by light microscopy, few standardized microscopy methods have been developed. Several methods of chemical fixation have recently been used to preserve cell structure before visualization of lipid droplets by light microscopy. We tested the most commonly used methods to compare the effects of the fixatives on cellular lipid content and lipid droplet structure. Cold methanol fixation has traditionally been used before visualization of cytoskeletal elements. We found this method unacceptable for study of lipid droplets because it extracted the majority of cellular phospholipids and promoted fusion of lipid droplets. Cold acetone fixation is similarly unacceptable because the total cellular lipids are extracted, causing collapse of the shell of lipid droplet-associated proteins. Fixation of cells with paraformaldehyde is the method of choice, because the cells retain their lipid content and lipid droplet structure is unaffected. As more lipid droplet-associated proteins are discovered and studied, it is critical to use appropriate methods to avoid studying artifacts.

Acetone↗
PubMed1994

Selective axonal argentaffin staining in rat central nervous system after protein mercuration.

The mercury-silver (Hg-Ag) argentaffin technique, known to stain specifically proteins in the lateral components of triads/diads in striated muscle cells, was applied to the central nervous system of adult rats. Following fixation in glutaraldehyde, axons in white and gray matter were selectively stained, but not perikarya or their proximal axon and dendrites. Neural tissues were postfixed 24 hr in 5% (w/v) mercuric acetate in 2% (v/v) acetic acid in distilled water, stained for 12-24 hr in darkness at 37-43 C with ammoniacal silver nitrate solution, freshly prepared by adding concentrated ammonia to 60% (w/v) silver nitrate solution until a small amount of silver oxide precipitate remained undissolved. Samples were then washed with freshly prepared 5% (w/v) sodium sulfite and distilled water. All steps were carried out using dark-colored glass flasks. Samples were dehydrated with ethanol and embedded in Paraplast or Poly Bed. Electron microscopy showed the silver-reducing protein inside the axons. Methylation abolished Hg-Ag axonal reactivity indicating that carboxyl groups were necessary for silver staining. Proteins with solubility properties characteristic of neurofilament proteins were involved in Hg-Ag staining. In the cerebellum the plexus of parallel fibers in the molecular layer were not stained, while basket cell axonal processes reacted intensely. The method appears to distinguish neuronal protein variants related to cytotypic differences in cytoskeletal neurofilaments.

Animals↗
PubMed1992

Porcine aortic valve bioprostheses: morphologic and functional considerations.

Porcine aortic valve (PAV) xenografts are the most frequently used type of bioprosthetic (BP) valve for the replacement of damaged or diseased heart valves. Xenograft tissues are routinely crosslinked during manufacturing using low concentrations (i.e., less than 1%) of glutaraldehyde. Crosslinking of xenograft tissue reduces the antigenicity, the rate of in vivo enzymatic degradation, and results in the loss of cell viability. The purpose of this review is to provide an overview of the morphologic and functional properties of the native aortic valve and the effects of tissue harvesting, fixation, anticalcification treatments, and mounting on PAV structure and function. Although efforts have been undertaken to design bioprostheses having increased durability, primary tissue failure still limits the long-term performance of xenograft replacement heart valves.

Animals↗
PubMed2005

[Immunocytochemical demonstration of catecholaminergic structures in paraffin sections of the rat brain using various methods of fixation].

The study was undertaken to investigate the effect of various methods of fixation of the brain upon the demonstrability of catecholaminergic structures using tyrosine hydroxylase (TH) immunocytochemical reaction. It was established that most complete demonstration of TH-containing structures was achieved after perfusion fixation with 4% paraformaldehyde followed by post-fixation in the Carnois fluid and after immersion fixation in the IHC zinc fixative (BD Pharmingen, U.S.A.). Immersion fixation in 4% paraformaldehyde, ethanol-formaldehyde, Carnois and Bouin fixatives can be used for demonstration of perikarya of catecholaminergic neurons.

Animals↗
PubMed1999

Simple method to isolate the intact duct system of the rat submandibular gland.

The excurrent duct system of the rat submandibular gland consists of a number of distinct segments. Using the direction of salivary flow as a reference point, these segments are, in order, intercalated duct, granular convoluted tubule, striated duct, excretory duct, main excretory duct (MED), and salivary bladder (which is an expanded portion of the MED). Because these ducts (with the exception of the MED and the salivary bladder) are encased in secretory endpieces, they are difficult to locate and to observe by scanning electron microscopy. A simple method has been devised to rid the gland of these obscuring endpieces so that the detailed architecture of the duct system can be examined. Rat submandibular glands were fixed initially by vascular perfusion with half-strength Karnovsky's fixative. The connective tissue capsule was removed from extirpated glands and the glands remained in fixative for varying lengths of time. For our purposes, a 30-minute immersion in the aldehyde mixture was optimum. After the sublingual gland was removed, the submandibular gland was softly struck with forceps having rounded tips, then shaken in fixative or buffer. The tissue that remained was postfixed in osmium tetroxide. This method results in the complete divestment of nonductular parenchyma from the rat submandibular gland, leaving the duct system clean and ready for microscopic examination.

Animals↗