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At least 757 records · Page 42Linked to original sources
PubMed2002

Effects of fixation type and guided tissue regeneration on maxillary osteotomy healing in rabbits.

PURPOSE: The development of fibrous nonunions after orthognathic surgery is thought to result from an interaction of biomechanical stress and the differential and more rapid migration of fibroblasts (compared with osteoblasts) into the wound site during healing. The present study was designed to test this hypothesis through the manipulation of guided tissue regeneration and osteotomy fixation techniques in an experimental rabbit model. MATERIALS AND METHODS: Bilateral critical size (4 mm) defects (n = 24) were produced in the maxillae of 12 adult New Zealand white rabbits. The maxillary segments were rigidly or nonrigidly fixed using bone microplates and screws or osteosynthetic wires. The defects were then covered with a resorbable collagen membrane or left uncovered. The rabbits were followed for 4 weeks with the use of serial dorsoventral and lateral oblique cephalographs, and the maxillae were then harvested for histologic analyses. RESULTS: Radiographic and histomorphometric analyses revealed that rigidly fixed defects, covered with membrane, showed the most rapid and organized new bone formation. The rigidly fixed defects with the membrane averaged approximately 40% more new bone in the osteotomy site compared with the rigidly fixed defects with no membrane. Nonrigidly fixed defects with no membrane showed an ingrowth of fibroblasts and fibrous nonunions. CONCLUSIONS: These experimental results suggest that an interaction between the decreased fibrous tissue ingrowth through guided tissue regeneration and osteotomy segment stability from rigid fixation prevented postoperative fibrous nonunions and facilitated new bone regeneration and osteotomy site healing in this rabbit model.

Animals↗
PubMed1996

[Experiences with the NoToX formalin substitute solution].

"NoToX Histological Fixative" is a formaldehyde substitute for the fixation of tissues prior to histological investigation. Intraoperative samples and necropsy tissue were tested. NoToX was substituted for formaldehyde in the fixation step, otherwise the same manufacturer-specified protocols were used for all reagents. Conventional histological and accepted immunohistological investigations, especially for tumour diagnosis, were used. In all tests, results with NoToX-fixated tissue were similar to those with tissue fixed with formaldehyde regarding both staining and diagnosis. NoToX is a useful substitute for formaldehyde.

Autopsy↗
PubMed2003

Geometrical deformation of vocal fold tissues induced by formalin fixation.

OBJECTIVES/HYPOTHESIS: Many existing studies of vocal fold geometry are based on anatomical measurements made on histologically fixed laryngeal tissues using formalin. However, the validity of these geometric data is questionable because of the potentially significant tissue deformation associated with formalin fixation, particularly tissue shrinkage. Previous experiments have shown that valid geometric data may be obtained on vocal fold tissue samples quickly frozen with liquid nitrogen. Based on this finding, the present study attempted to quantify the geometric deformation of formalin-fixed vocal fold tissues with respect to quick-frozen tissues. METHODS: Six freshly harvested canine larynges were quickly frozen with liquid nitrogen and sectioned at the mid-membranous coronal plane. Each larynx was thawed and divided into halves along the midsagittal plane, one of which was not fixed; the other was fixed with formalin, from which histological tissue sections were also prepared. Measurements of vocal fold geometry were made on digital images of mid-membranous coronal sections of the tissue samples, based on linear dimensions of vocal fold depth and thickness defined functionally for biomechanical applications. RESULTS: Significant shrinkage of the vocal fold (particularly the vocal fold body) and considerable distortion of the vocal fold contour (particularly at the free edge) were observed for the formalin-fixed samples and the histological sections in comparison with the unfixed samples. CONCLUSIONS: Results of the present study suggested that significant geometric artifacts are induced by conventional histological fixation of laryngeal tissues using formalin. These artifacts should be carefully considered for interpreting any vocal fold geometric data obtained through formalin fixation.

Animals↗
PubMed2005

[The effect of the tibial tunnel fixation level on the results of cyclic loading in anterior cruciate ligament reconstruction].

OBJECTIVES: This study was designed to compare the biomechanical characteristics of non-anatomic (far from joint) and anatomic (close to joint) levels of tibial tunnel fixation with soft tissue graft using a soft tissue interference screw in anterior cruciate ligament (ACL) reconstruction. METHODS: Twelve bovine tibiae and digital extensor tendons were divided into two homogeneously equal groups after removing soft tissues. Tibial tunnels were prepared with a 7-mm drill with the use of an ACL guide adjusted to 45 degrees . Each tunnel was then dilated to 9 mm in 0.5 mm increments. Digital extensor tendons were fixed at non-anatomic (group I) or anatomic (group II) tibial tunnel levels with a soft tissue metal interference screw, 9 x 30 mm in size. All the specimens were cycled 500 times from 50 to 250 N with 1 Hz frequency in a servo-hydraulic testing machine followed by ultimate load at-failure testing at a rate of 20 mm/min. Statistical analyses were made using the Mann-Whitney U-test. RESULTS: The mean screw insertion torque values were 8.2+/-2.4 Nm and 7.8+/-2.3 Nm in groups I and II, respectively (p=0.88). The mean values of graft displacement (1.9+/-0.75 mm versus 2.2+/-1.2 mm, p=0.63) and stiffness (132.72+/-10.93 N/mm versus 125.14+/-15.93 N/mm, p=0.63) did not differ significantly. CONCLUSION: The biomechanical properties of ACL reconstruction with soft tissue graft fixation using a soft tissue interference screw are not influenced by the level of tibial tunnel fixation.

Absorbable Implants↗
PubMed2001

Freeze-substitution of dehydrated plant tissues: artefacts of aqueous fixation revisited.

This investigation assessed the extent of rehydration of dehydrated plant tissues during aqueous fixation in comparison with the fine structure revealed by freeze-substitution. Radicles from desiccation-tolerant pea (Pisum sativum L.), desiccation-sensitive jackfruit seeds (Artocarpus heterophyllus Lamk.), and leaves of the resurrection plant Eragrostis nindensis Ficalho & Hiern. were selected for their developmentally diverse characteristics. Following freeze-substitution, electron microscopy of dehydrated cells revealed variable wall infolding. Plasmalemmas had a trilaminar appearance and were continuous and closely appressed to cell walls, while the cytoplasm was compacted but ordered. Following aqueous fixation, separation of the plasmalemma and the cell wall, membrane vesiculation and distortion of cellular substructure were evident in all material studied. The sectional area enclosed by the cell wall in cortical cells of dehydrated pea and jackfruit radicles and mesophyll of E. nindensis increased after aqueous fixation by 55, 20, and 30%, respectively. Separation of the plasmalemma and the cell wall was attributed to the characteristics of aqueous fixatives, which limited the expansion of the plasmalemma and cellular contents but not that of the cell wall. It is proposed that severed plasmodesmatal connections, plasmalemma discontinuities, and membrane vesiculation that frequently accompany separation of walls and protoplasm are artefacts of aqueous fixation and should not be interpreted as evidence of desiccation damage or membrane recycling. Evidence suggests that, unlike aqueous fixation, freeze-substitution facilitates reliable preservation of tissues in the dehydrated state and is therefore essential for ultrastructural studies of desiccation.

Artifacts↗
PubMed1982

Scanning electron microscopy of the metal-tissue interface. I. Fixation methods and interpretation of results.

Scanning electron microscopy has been used to study the interface between implants of pure metals and the muscular tissue of rats. Several problems arise in the interpretation of the observations made, due to the potential for disruption to the tissue and the exacerbation of any corrosion that may have occurred in vivo during the fixation periods. Details are given of the control experiments performed in order to ascertain the nature of potential artefacts and of the techniques eventually determined to be optimal for these purposes.

Animals↗
PubMedDate not supplied

[Resorption of bone tissue when titanium fixators are used].

The paper compares different methods of inserting titanium fixatives into the femur. The bone was either unaffected or osteotomized. Clinical, X-ray, morphological, and spectral studies were performed. Experimental findings led to the conclusion that the density of fixative adhesion and delayed load are of great significance for adhesion of canine femoral fragments and for the resistance of osseous wound surface. The cortical bone is more resistant to resorption upon mechanical exposure. When titanium fixatives are used there is metallosis that appear as small traces and fails to significantly affect osseous tissue resorption.

Adult↗
PubMed1962

Fixation of neural tissues for electron microscopy by perfusion with solutions of osmium tetroxide.

This paper describes in detail a method for obtaining nearly uniform fixation of the nervous system by vascular perfusion with solutions of osmium tetroxide. Criteria are given for evaluating the degree of success achieved in the preservation of all the cellular components of the nervous system. The method permits analysis of the structural relations between cells at the electron microscopic level to an extent that has not been possible heretofore.

Aldehydes↗
PubMed1983

Effects of insulin on CO2 fixation in adipose tissue. Evidence for regulation of pyruvate transport.

Insulin was found to double the rate of incorporation of H14CO3- into protein by segments of rat epididymal adipose tissue provided the incubation medium contained a suitable energy substrate such as fructose. Overall protein synthesis was increased by insulin to a lesser extent, one-third as measured by tritiated water indicating that insulin also increased CO2 fixation into amino acids. The latter could be demonstrated only when the tissue amino acid pools were expanded by the addition of aspartate to the incubation medium. The pattern of labeling observed in the amino acids indicated that CO2 fixation occurred primarily at the pyruvate carboxylase step. Addition of pyruvate to the incubation medium also increased CO2 fixation and this effect was not additive with that of insulin, suggesting that insulin acted by increasing the availability of pyruvate to the carboxylase. No change in carboxylase activity could be measured. Mitochondria isolated from tissue exposed to insulin retained a higher capacity to fix CO2 into acid-soluble products provided they were not freeze-thawed or sonicated. Uptake of pyruvate by mitochondria incubated 1 min at 2 degrees C or 5 s at 15 degrees C was doubled by prior insulin treatment of the tissue. It is concluded that insulin increases the flux through pyruvate carboxylase in adipose tissue in part by increasing the transport of pyruvate through the inner mitochondrial membrane.

Adipose Tissue↗
PubMed1985

[Local x-ray spectral microanalysis in cell biology. The study of sections of hydrated biological tissues].

Rules required for fixation of tissues are considered aimed for a further localization of chemical elements in these tissue by means of local X-ray microanalysis. In addition, difficulties involved in fixation of diffusible elements, such as potassium or sodium, are mentioned. Physical bases of preparation of hydrated tissues for X-ray analysis are discussed.

Cytological Techniques↗
PubMedDate not supplied

Shape memory alloy fixator system for suturing tissue in minimal access surgery.

A new technique for suturing human tissue is described in which tissue closure is achieved by means of small fixators made from shape memory alloy. The aim of the development is to provide an alternative to thread suturing in minimal access surgery, which is quicker and requires less skill to achieve the required suturing quality. The design of the fixators is described in terms of the thermal shape recovery of shape memory alloy and a novel form of finite element analysis, which uses a nonlinear elastic element for the material property. Thermal analysis of the fixators and surrounding tissue is used to predict the temperature distribution during and after the application of electric current heating. This was checked in an in vitro experiment, which confirmed that deployment caused no detectable collateral damage to surrounding tissue. In vivo animal studies on the use of the shape memory alloy fixator for suturing tissue are ongoing to establish safety and healing effects.

Alloys↗
PubMed2005

High-resolution light microscopy (HRLM) and digital analysis of Pompe disease pathology.

Pompe disease is an autosomal recessive lysosomal storage disorder caused by a deficiency of the lysosomal enzyme acid alpha-glucosidase, responsible for the degradation of lysosomal glycogen. Absent or low levels of the enzyme leads to lysosomal glycogen accumulation in cardiac and skeletal muscle cells, resulting in progressive muscle weakness and death from cardiac or respiratory failure. Recombinant enzyme replacement and gene therapy are now being investigated as treatment modalities for this disease. A knockout mouse model for Pompe disease, induced by the disruption of exon 6 within the acid alpha-glucosidase gene, mimics the human disease and has been used to evaluate the efficacy of treatment modalities for clearing glycogen. However, for accurate histopathological assessment of glycogen clearance, maximal preservation of in situ lysosomal glycogen is essential. To improve retention of glycogen in Pompe tissues, several fixation and embedding regimens were evaluated. The best glycogen preservation was obtained when tissues fixed with 3% glutaraldehyde and postfixed with 1% osmium tetroxide were processed into epon-araldite. Preservation was confirmed by staining with the Periodic acid-Schiff's reaction and by electron microscopy. This methodology resulted in high-resolution light microscopy (HRLM) sections suitable for digital quantification of glycogen content in heart and skeletal muscle. Combining this method of tissue fixation with computer-assisted histomorphometry has provided us with what we believe is the most objective and reproducible means of evaluating histological glycogen load in Pompe disease.

Animals↗
PubMed1990

Osteoplasty of the mandibular condyle with preservation of the articular soft tissue cover: comparison of fibrin sealant and sutures for fixation of the articular soft tissue cover in rabbits.

Fibrin sealant and sutures were compared for fixation of the articular soft tissue cover after it had been raised in association with osteoplasty of the mandibular condyle. Nine adult rabbits were operated on bilaterally with the use of fibrin sealant on one joint and sutures on the other joint. The rabbits were killed after 3 months. Macroscopic and histologic evaluations of the condyles did not reveal any appreciable differences between the two techniques. Fibrin sealant was, however, technically easier to apply than the sutures. It was concluded that fibrin sealant might be an alternative to sutures for fixation of the articular soft tissue cover after it has been raised in association with osteoplasty of the mandibular condyle.

Animals↗
PubMed1990

Release of tissue paraquat into formalin solution during fixation.

Formalin-fixed tissues and formalin solutions are among the most frequently found materials in pathology and forensic science laboratories. However, these materials are seldom used for the identification of poisons for forensic toxicology purposes. In this study, the possibility that paraquat may be released from formalin-fixed tissues during the fixation process was investigated. However, because of the interference of formaldehyde on the reduction of paraquat with dithionite reagent, paraquat in formalin solutions was treated with ion-pair column chromatography and then determined by measuring the derivative spectrum of reduced paraquat. The results show that the interference of formalin on paraquat determination has been eliminated by the proposed method. Furthermore, a study on the formalin solutions of fixed organs in cases with suspected paraquat intoxication revealed that portions of tissue paraquat had been released into formalin during the fixation process. Moreover, the paraquat levels in formalin increased with increased storage time. Therefore, these data suggest that the combined concentrations of paraquat in the formalin-fixed tissues and formalin solutions might reflect more reliably the total paraquat in the postmortem tissues. This investigation could be of value to the forensic toxicologist, especially in cases in which no fresh tissue samples are available for analysis.

Adult↗
PubMed1998

Calibration and standardization of microwave ovens for fixation of brain and peripheral nerve tissue.

Rapid and reproducible fixation of brain and peripheral nerve tissue for light and electron microscopy studies can be done in a microwave oven. In this review we report a standardized nomenclature for diverse fixation techniques that use microwave heating: (1) microwave stabilization, (2) fast and ultrafast primary microwave-chemical fixation, (3) microwave irradiation followed by chemical fixation, (4) primary chemical fixation followed by microwave irradiation, and (5) microwave fixation used in various combinations with freeze fixation. All of these methods are well suited to fix brain tissue for light microscopy. Fast primary microwave-chemical fixation is best for immunoelectron microscopy studies. We also review how the physical characteristics of the microwave frequency and the dimensions of microwave oven cavities can compromise microwave fixation results. A microwave oven can be calibrated for fixation when the following parameters are standardized: irradiation time; water load volume, initial temperature, and placement within the oven; fixative composition, volume, and initial temperature; and specimen container shape and placement within the oven. Using two recently developed calibration tools, the neon bulb array and the agar-saline-Giemsa tissue phantom, we report a simple calibration protocol that identifies regions within a microwave oven for uniform microwave fixation.

Animals↗
PubMed1981

Swelling of mitochondria in immersion-fixed liver tissue. Effect of various fixatives and of delayed fixation.

In order to study the occurrence of swollen and disrupted mitochondria in tissue preserved for electron microscopy by ordinary fixation methods, liver tissue from miniature pig fetuses was immersion-fixed in fixatives with various types and concentrations of fixing agents and vehicles. Also commercial and purified products have been tested, different fixation times and temperatures as well as the consequences of a short rinsing in buffer solutions prior to fixation. Furthermore, the significance of delayed fixation (autolysis) was studied. It was found that swollen and disrupted mitochondria occur predominantly in liver cells exposed to low concentrations of glutaraldehyde. It is shown that this phenomenon is a result of a specific effect of glutaraldehyde on the mitochondrial membranes. It is not accompanied by parallel changes of other organelles or nuclei, and it not provoked by other fixing agents, vehicles or by delayed fixation (autolysis).

Animals↗