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At least 199 records · Page 11Linked to original sources
PubMed2004

Soft-tissue graft fixation in posterior cruciate ligament reconstruction: evaluation of the effect of tibial insertion site on joint kinematics and in situ forces using a robotic/UFS testing system.

INTRODUCTION: Surgical reconstruction of the posterior cruciate ligament (PCL) is recommended in acute injuries that result in severe tibial subluxation and instability. The surgical outcome level may be affected by the tibial fixation site. In response to a 110-N posterior tibial load, kinematics and in situ forces of anatomical soft-tissue graft fixation in single-bundle PCL reconstruction using an interference screw fixation are significantly closer to those in the intact knee than with extracortical fixation with two staples. MATERIALS AND METHODS: Using a robotic/universal force moment sensor (UFS) testing system, we examined joint kinematics and in situ forces of porcine knees following single-bundle PCL reconstruction fixed at two different tibial fixation sites: anatomical interference screw and extracortical fixation. RESULTS: The site of the tibial graft fixation had significant effect on the resulting posterior displacement and in situ forces of the graft. Both PCL reconstruction techniques reduced the posterior tibial translation significantly. Proximal fixation techniques provided significantly less posterior tibial translation than extracortical fixation. Single-bundle PCL reconstruction with an interference screw showed higher in situ forces of the graft than the extracortical fixation. CONCLUSIONS: The kinematics and in situ forces of a single-bundle PCL reconstruction using an interference screw fixation technique are superior to the primary stability of an extracortical fixation with staples.

Animals↗
PubMed2001

Two-photon excitation laser scanning microscopy of human, porcine, and rabbit nasal septal cartilage.

Two-photon excitation laser scanning microscopy (TPM) was used to image human, porcine, and rabbit nasal septal cartilage. TPM provides optical sections of thick tissue specimens in situ without the use of exogenous dyes or need for tissue fixation. The cartilage tissue was imaged using near-infrared light generated by a mode-locked titanium/sapphire laser that was raster-scanned and coupled to an inverted microscope. Absorption of two photons by endogenous molecules and subsequent fluorescence was filtered to specific spectral bandwidths and detected with photomultiplier tubes. Two-photon stimulated fluorescence was detected with photomultiplier tubes optimized to specific spectral bandwidths. Signal intensity corresponds to the concentration of fluorophores, principally NADH, NADPH, and flavoproteins hence providing a means of redox imaging the cellular metabolic state. Specimens were scanned from the surface to a depth of about 150 microm. Image size was 50 x 50 microm with a diffraction limited pixel size of 0.4 microm. Cell membranes, nuclei, and matrix structures were identified in human, pig, and rabbit tissues. TPM provides a means to study three dimensional chondrocyte structure and matrix organization in situ at substantial depths, and permits longitudinal examination of cultured tissue explants without the need for exogenous dyes, tissue preparation, or fixation.

Animals↗
PubMed2002

The effect of the EndoPearl on soft-tissue graft fixation.

This study determined whether EndoPearl (Linvatec Corp, Largo, Fla) secondary fixation to an interference screw increased the fixation strength of a soft-tissue tendon graft. Ten-millimeter porcine patellar tendon grafts with attached patellae were harvested without a tibial bone plug and inserted into 9-mm tibial tunnels to test a nonlooped solid tendon graft. Twenty grafts were fixed with a BioScrew (Linvatec Corp, Largo, Fla) and 20 with BioScrew/EndoPearl combinations. These were tested with straight line destructive loads at 60 mm/min without cycling and after 500 cyclic loads. Tendons were secured with nonlocking (Bunnell) sutures along both edges and then passed through the central hole of the EndoPearl. A significant decrease in stretch at maximum force was noted between specimens that were cyclically loaded prior to testing and those that were not (P<.001); a significant increase in energy absorption between specimens with and without EndoPearl in the straight destructive test (P<.02); and a significant increase in stiffness with cyclic loading (P<.001). A positive correlation also was noted between failure force and insertion torque (P=.02). The EndoPearl increased energy absorption at failure. Solid tendon grafts consistently failed due to the sutures tearing out of the tendon and the tendon sliding by the interference screw. The Bunnell stitch was the weakest link and is not effective for this graft.

Absorbable Implants↗
PubMed2000

Detection of different mRnas expressed in the thyro-parathyroid complex of the rat by in situ hybridization using digoxigenin-labelled oligonucleotide probes.

The effects have been examined of different methods and regimens for tissue fixation, preservation, permeabilization and immunostaining of different mRNAs detected by in situ hybridization in paraffin-embedded samples. The three main hormone mRNAs expressed in the thyro-parathyroid glands, namely thyroglobulin, calcitonin and parathyroid hormone mRNAs, were chosen as the target nucleic acid sequences to be detected using digoxigenin-labelled probes. Our results suggest that chemical fixation and permeabilization of tissue samples are restrictive steps. Thus, paraformaldehyde fixation provides excellent signal intensities and non-detectable background levels whereas routine formalin and Bouin's solution give unsatisfactory results. A clear linear correlation was also found between signal intensity and proteinase K permeabilization. Moreover, the optimization of immunohistochemical steps, such as anti-digoxigenin antibody concentration and colour development times, enhance the intensity and specificity of hybrid signals. Furthermore, our results show that, in contrast to some data in the literature, paraffin-embedded tissue is suitable for detection of mRNAs by in situ hybridization. It gives equivalent intensities of specific signal and superior histological and cellular resolutions when compared to cryopreserved tissue.

Animals↗
PubMed1996

Effects of fixation and tissue processing on immunohistochemical demonstration of specific antigens.

Identification of biomarkers in archival tissues using immunochemistry is becoming increasingly important for determining the diagnosis and prognosis of tumors, for characterizing preinvasive neoplastic changes in glandular tissues such as prostate, for evaluating the response of tumors and preinvasive neoplastic changes to certain therapies (i.e., as a surrogate intermediate end point), for selecting patients who are candidates for specific therapies (e.g., immunotherapy) and for retrospective studies. For detecting specific biomarkers it is important to understand the limitations imposed by the fixation methods and processing of the tissues. This study was designed to determine the effects of fixation on the detection in archival paraffin blocks of selected antigens postulated to be important in tumor biology. We evaluated the antigens TGF alpha, p185erbB-2, broad spectrum keratins, p53, and TAG-72 (B72.3). Fixatives evaluated included standard preparations of neutral buffered formalin, acid formalin, zinc formalin, alcoholic formalin, ethanol, methanol, and Bouin's fixative. We found that in general neutral buffered formalin is the poorest fixative for maintaining antigen recognition by immunohistochemistry and that no single fixative was best for all antigens. The dehydrating (coagulant) fixatives (e.g., ethanol and methanol) preserved immunorecognition of p53 and broad spectrum keratins best while the slow cross-linking fixatives (e.g., unbuffered zinc formalin) were best for demonstrating TGF alpha and p185erbB-2. Fixatives other than neutral buffered formalin produced equivalent recognition of the epitope of TAG-72 by B72.3. In formalin fixed archival tissues, only a portion of the antigen signal can be detected by routine immunohistologic methods.

Antigens, Neoplasm↗
PubMed2004

Tissue and fixative dependent shifts of delta13C and delta15N in preserved ecological material.

Carbon and nitrogen stable isotope analyses are routinely used to investigate aquatic food webs, and have potential application in retrospective investigations using archived materials. However, such analyses assume that storage does not alter isotopic signatures of materials preserved, or that changes in isotopic composition during storage are predictable. Here we examine preservation shifts on cod (Gadus morhua) muscle, roe and liver tissue over 21 months following preservation in 80% ethanol, in 4% formaldehyde, and by freezing. Preservation shifts were not consistent among tissues. High protein tissues exhibited greater delta(15)N shifts than low protein tissues in 4% formaldehyde, while greater delta(13)C shifts occurred in relatively higher fat tissues when preserved in alcohol. Freezing did not change isotopic signatures. Responses of delta(15)N and delta(13)C are explained by differences in the preservative's isotopic signature and the reaction properties and biochemical composition of the tissues preserved. The results clarify some of the processes that lead to isotopic change during preservation.

Animals↗
PubMed1983

A fine structural study of microwave fixation of tissues.

Microwave fixed liver and kidney tissues were examined by electron microscopy. It was found that the preservation of fine structure of these tissues by this method is equal to that processed by routine methods. No difficulty was encountered in sectioning microwave fixed tissue blocks. It is obvious that microwave fixation is a faster and more efficient method.

Animals↗
PubMed1967

An artefact in radioautography due to binding of free amino acids to tissues by fixatives.

The binding of labeled free amino acids to liver and to purified protein by commonly used fixatives was investigated. Glutaraldehyde caused 25% of free leucine to be bound to serum albumin in solution, whereas formaldehyde bound only 0.5%. Liver slices were incubated for 2 min in the presence of labeled leucine and of puromycin, which permits absorption of leucine into the cell but inhibits incorporation into protein. Both counting and radioautographic techniques showed that glutaraldehyde bound 30 times, and osmic acid six times, as much free amino acid as did formaldehyde. By comparing liver slices incubated with and without puromycin for 2 min, it was calculated that in radioautographs prepared after fixation with glutaraldehyde, osmic acid, or formaldehyde 63, 25, and 4% respectively of the grains were due to binding of free amino acid. Formaldehyde, freshly prepared from paraformaldehyde, gives good preservation and is the recommended fixative for radioautography. When levels of free substrate in a tissue are high at the time fixative is added, the amount of binding of free substrate induced by the fixative should be included as a control in radioautographic experiments.

Aldehydes↗
PubMed2006

Effects of temperature and aldehyde fixation on tissue water diffusion properties, studied in an erythrocyte ghost tissue model.

Ex vivo biological sample imaging can complement in vivo MRI studies. Since ex vivo studies are typically performed at room temperature, and samples are frequently preserved by fixation, it is important to understand how environmental and chemical changes dictated by ex vivo studies alter the physical and MR properties of a sample. Diffusion and relaxation time measurements were used to assess the effects of temperature change and aldehyde fixation on the biophysical and MR properties of a model biological tissue comprised of erythrocyte ghosts suspended in buffer or agarose gel. Sample temperature was varied between 10 degrees C and 37 degrees C. Diffusion MRI data were analyzed with a biophysically appropriate two-compartment exchange model. Temperature change resulted in a complex alteration of water diffusion properties due to the compartmental nature of tissues and alteration in membrane permeability. Formaldehyde, Karnovsky's solution, and glutaraldehyde all caused statistically significant changes to the biophysical and MR properties of the samples. Fixation caused large decreases in water proton T2, which was restored to near prefixation values by washing free fixative from the samples. Water membrane permeability was also significantly altered by fixation. This study demonstrates that relating in vivo MR data to chemically fixed ex vivo data requires an understanding of the effects of sample preparation.

Analysis of Variance↗
PubMed1985

Mast cell heterogeneity in dog skin.

The degree of metachromasia of mast cell granules is known to vary with the type of tissue fixation and among different tissues and species. The present study sought to determine whether mast cells in dog skin are heterogeneous with respect to fixation and staining properties. We performed skin biopsies in six anesthetized, atopic dogs and one mongrel dog. One biopsy was fixed in formalin and a second, from a parallel abdominal site, was fixed in basic lead acetate (Mota's solution). Adjacent sections from each biopsy were stained with alcian blue (1%, pH 0.5) or for chloroacetate esterase activity. In alcian blue-stained sections, one-third fewer mast cells were detected in skin fixed in formalin (1,836 +/- 454 mast cells/mm3, mean +/- SEM) than in skin fixed in basic lead acetate (2,684 +/- 527 mast cells/mm3) (P less than 0.05). The chloroacetate esterase reaction detected the larger number of mast cells regardless of the fixative used. We conclude that mast cell heterogeneity, as demonstrated by metachromatic staining following different types of tissue fixation, exists in dog skin. "Typical" mast cells stain with alcian blue regardless of fixation; however, "atypical" mast cells exhibit metachromasia only after fixation in basic lead acetate. Both the typical and atypical types of mast cells have chloroacetate esterase activity.

Alcian Blue↗
PubMed1998

Microwaves and heat in aldehyde fixation: model experiments with bovine serum albumin.

Most model experiments concerning tissue fixation have used low concentrations of fixatives and proteins. Here, high concentrations (up to 32%) of bovine serum albumin (BSA) were reacted with formaldehyde (1-20%) and glutaraldehyde (0.5-4%). Gels were formed between 16% BSA and 10-20% formaldehyde at room temperature, but not with percentages of formaldehyde lower than 4%. Microwave application or heating in a water bath to 50 degrees C gave a gel from 1 to 20% formaldehyde. Sixteen percent BSA also gave a gel with glutaraldehyde from 0.5 to 4%. Cone and plate viscometry showed rapidly increasing viscosity at 4% formaldehyde and 16% BSA at room temperature. At 50 degrees C, gels formed at a low concentration of formaldehyde. Tissue fixation in which the local concentrations of protein may be in excess of 30% is probably more complete than in vitro experiments in which low concentrations of reagents have been used to permit subsequent spectrometry. This was confirmed by polyacrylamide gel electrophoresis of liver.

Aldehydes↗
PubMed1995

Trichrome staining of Gyrodactylus sclerites and soft tissues following fixation in ammonium picrate-glycerin, including an improved rendition of the haptoral bars of G. turnbulli.

A simple technique using modified Mallory stain in the transferral of Gyrodactylus specimens from ammonium picrate-glycerin to a permanent mountant is described. Hamuli, their connecting bars and the penis sclerites are well defined by the technique as are muscles and tendons, cell nuclei, tegument and gland cells. As well as being useful in the study of general anatomy, the technique enhances the observation of the taxonomically important ventral and dorsal bars. In order to show this, improved illustrations of the dorsal and ventral bars of G. turnbulli are given along with explicit demonstrations of differences in morphology of the ventral bars of G. bullatarudis and G. rasini-two easily confused species.

Animals↗
PubMed1984

Collagenase in the immunohistochemical demonstration of laminin, fibronectin and factor VIII/RAg in nervous tissue after fixation.

The effects of collagenase on the immunohistochemical demonstrability of laminin, fibronectin and Factor VIII/RAg in human nervous tissue have been studied. The influence of this, and other proteolytic enzymes such as pepsin and trypsin, has been investigated in relation to different fixatives. Collagenase gave better results with Carnoy fixed material than after formalin fixation; unlike trypsin and pepsin, it did not produce tissue digestion.

Antigens↗
PubMed2005

Soft-tissue interference fixation: bioabsorbable screw versus metal screw.

PURPOSE: To compare the biomechanical properties of eccentrically positioned bioabsorbable and titanium interference screws for quadrupled hamstring tendon graft (QHTG) fixation. TYPE OF STUDY: In vitro, biomechanical study. METHODS: In 10 paired cadaveric tibiae and femurs (mean age, 66.5 years; range, 53 to 81 years), QHTG fixation was performed in tunnels sized to within 0.5 mm of QHTG diameter using either a titanium (RCI; Smith & Nephew Donjoy, Carlsbad, CA) or a bioabsorbable (BioScrew; Linvatec, Largo, FL) screw of equal size. Constructs then underwent biomechanical load-to-failure testing on a servo-hydraulic device at 20 mm/min. RESULTS: Load at failure was greater for femoral-side QHTG fixation using the bioabsorbable screw than the titanium screw (486 +/- 223.7 N v 246 +/- 99.1 N, P = .006); however, displacement did not differ (P = .81). There were no statistically significant differences between groups for tibial side load at failure (P = .54), stiffness (P = .44), or displacement (P = .50). Screw thread-induced graft laceration was more frequently observed in the titanium screw group (9 of 10 grafts during femoral-side testing, 0 of 10 grafts during tibial-side testing) than in the bioabsorbable screw group (0 of 10 grafts during femoral-side testing, 1 of 10 grafts during tibial-side testing). CONCLUSIONS: BioScrew interference screw fixation was comparable or superior to RCI titanium interference screw fixation. BioScrew interference screw fixation also produced less screw thread-induced laceration of the QHTG during load-to-failure testing. CLINICAL RELEVANCE: Use of a biodegradable interference screw positioned directly against a soft-tissue graft provides fixation properties similar to those of a metal interference screw.

Absorbable Implants↗
PubMedDate not supplied

The effect of soft-tissue graft fixation in anterior cruciate ligament reconstruction on graft-tunnel motion under anterior tibial loading.

PURPOSE: To compare the motion of an anterior cruciate ligament (ACL) replacement graft within the femoral bone tunnel (graft- tunnel motion) when a soft-tissue graft is secured either by a titanium button and polyester tape (EndoButton fixation; Acufex, Smith & Nephew, Mansfield, MA) or by a biodegradable interference screw (Biointerference fixation; Endo-fix; Acufex, Smith & Nephew) An additional purpose was to evaluate the effect of the graft-tunnel motion on the kinematics of ACL-reconstructed knees and in situ force of the ACL replacement graft. TYPE OF STUDY: Biomechanical experiment using an in vitro animal model. METHODS: ACL reconstruction with a flexor tendon autograft was performed in 8 cadaveric knees of skeletally mature goats. The knee kinematics and the in situ force in the ACL replacement graft in response to anterior tibial loads were evaluated using the robotic/universal force-moment sensor testing system. The longitudinal and transverse graft-tunnel motion during anterior tibial loading was determined based on radiographic measurements parallel and perpendicular to the femoral bone tunnel, respectively. RESULTS: In response to an anterior tibial load of 100 N, the longitudinal graft-tunnel motion for EndoButton fixation and Biointerference fixation was 0.8 +/- 0.4 mm and 0.2 +/- 0.1 mm, respectively (P <.05), whereas the transverse graft-tunnel motion was 0.5 +/- 0.2 mm and 0.1 +/- 0.1 mm, respectively (P <.05). Furthermore, the anterior tibial translation for EndoButton fixation (5.3 +/- 1.2 mm) was also significantly larger than that for Biointerference fixation (4.2 +/- 0.9 mm) (P <.05). With both fixations, however, no significant difference between the in situ forces in the ACL replacement graft and that in the intact ACL could be detected. CONCLUSIONS: EndoButton fixation of a soft-tissue graft via an elastic material resulted in significantly larger graft-tunnel motion, and consequently, greater anterior knee laxity compared with more rigid fixation using an interference screw closer to the intra-articular entrance of the bone tunnel. In terms of force distribution, the ACL replacement graft in both fixations still functioned as a primary restraint to an anterior tibial load close to the intact ACL.

Absorbable Implants↗
PubMed1975

A detailed analysis of the effects of various fixatives on animal tissue with particular reference to muscle tissue.

Nine different fixatives (Carnoy's, Susa, Baker's formalin, 5% formalin, 10% formalin, 10% formol saline, Bouin, Zenker, and 2.5% gluta-aldehyde) were compared by two methods. Gelatin-albumin gels were used to study volume changes after fixation and after various stages of subsequent processing. The appearance and hardness of the gels were also noted. The fixatives either shrunk or swelled the gels, but dehydration and clearing shrunk the gels in all cases. Samples of muscle tissue from one location in beef longissimus dorsi muscle were also placed in the different fixatives and processed. Various features were noted for each fixative, including the ease with which the paraffin wax blocks were cut and the staining ability of the sections in Mallory's triple stain. The diameters of the muscle fibers were measured from transverse sections of these samples and compared with the mean diameter of muscle fibers in a frozen unfixed section of muscle tissue. It was found that the fixatives had the same shrinkage effects on both the gels and the muscle samples. Analysis of variance tests showed that the various fixatives caused different degrees of shrinkage. Statistical details are given for the amounts of shrinkage caused by each fixative. Both the general histological picture and the amount of shrinkage were considered when deciding the best fixative. Carnoy was found to be the best of the fixatives investigated.

Albumins↗
PubMed1995

Electron microscopical study of a cytosolic enzyme in unfixed cryostat sections: demonstration of glycogen phosphorylase activity in rat liver and heart tissue.

Glycogen phosphorylase activity has been demonstrated at the ultrastructural level in liver and heart tissue of fasted rats. Unfixed cryostat sections were incubated by mounting them on a semipermeable membrane stretched over a gelled incubation medium. The medium contained a high concentration of glucose 1-phosphate which enables indirect detection of glycogen phosphorylase activity on the basis of the synthesis of glycogen. Tissue fixation, dehydration and embedding for electron microscopical study were performed after the incubation had been completed. The ultrastructure of both liver and heart tissue was rather well preserved. Glycogen granules resulting from glycogen phosphorylase activity were found in the cytoplasmic matrix of both hepatocytes and cardiomyocytes; no relationship with membranous structures could be detected. It is concluded that the semipermeable membrane method is well suited for localizing cytosolic enzyme activities at the ultrastructural level without prior tissue fixation; this opens further perspectives for correlations between histochemical and biochemical data.

Animals↗