Biomedical subjects

B de C Vidal

Publications and source records attributed to B de C Vidal.

At least 19 recordsLinked to original sources

PubMed2001

The effect of therapeutic ultrasound on repair of the achilles tendon (tendo calcaneus) of the rat.

The purpose of this study was to evaluate the effects of therapeutic ultrasound (US) on the healing process in the Achilles tendon (Tendo calcaneus) of Wistar rats after tenotomy. Sonication was performed at a frequency of 1 MHz, an intensity of 0.5 W/cm(2) (SATA), for 5 min, over a period of 14 consecutive days in two modalities (n = 15); in both continuous and pulsed modes. The control group was divided into tenotomized, mock-sonicated and nontenotomized tendons (n = 15). On the 15th postoperative day, the tendons were removed and analyzed by using the polarized light microscopy, with the purpose of detecting and measuring the organization of collagen fibers through birefringence. The results showed a high birefringence for the tendons treated using the pulsed mode (p < 0.001), revealing the best organization and aggregation of collagen bundles. Sonication in the continuous mode induced a decrease (p = 0.047) in the ability to quicken the healing process. These findings suggest that US therapy is beneficial in the early healing process of tendons when the pulsed mode is used.

Achilles Tendon↗

PubMed1995

Re-evaluating the AgNOR staining response in Triton X-100-treated liver cells by image analysis.

The response of liver cell nuclei to a variant of the AgNOR method, which includes a treatment with Triton X-100 prior to staining assumed to improve the quality of the AgNOR-positive images, was compared to that of the usual method by image analysis procedures. The objective was to determine whether Triton X-100 removes proteins from the nuclei to the point of affecting the AgNOR response. Statistically significant differences were not found in comparisons of a nuclear area/AgNOR-stained area ratio nor in the number of AgNOR-positive dots/aggregates. It was thus assumed that the Triton X-100 treatment did not remove nuclear proteins likely to affect the AgNOR response, though it induced a cleaner background and, consequently, a clearer contrast between the stained areas and the background.

Animals↗

PubMed1995

From collagen type I solution to fibers with a helical pattern: a self-assembly phenomenon.

To determine whether collagen solubilized from tendons can regenerate the most relevant characteristics of the tendon supraorganization was the aim of the present study. Extracted and purified collagen in acetic acid solutions subjected to precipitation and extensive dialysis was found to produce gels with rheological properties that allowed them to form threads and rubber-like rods. Molecular order and the ordered aggregational state of the fibers were detected by optical anisotropy at the polarization microscope. Self-assembly and self-organization resulted in a supraorganized structure in which the fibers are ordered parallel to the long axis of the thread or the rod, and in an intertwined helical organization. The highly birefringent fibers and their geometrically ordered self-organization resembled the original tendons. Some questions related to morphogenesis, recognition and adhesion events, biomechanical properties of collagen-containing structures and development of biomaterial for medical use may be answered by this model. In terms of perspectives it would be important to consider collagen fibers as models for producing organic-inorganic interface depositions to achieve optical properties.

Acetates↗

PubMed1995

Crimp as part of a helical structure.

Crimp is generally conceived of as a ribbon, i.e. a planar periodic orientation variation of collagen fibers. This study was carried out to demonstrate that crimps are complex structures with the possibility of being helically arranged. Thick sections, imbibed in glycerol or even in mineral oil and studied under the polarizing microscope with the help of 1st order red and lambda/4 Sénarmont's compensators proved to be adequate to detect details of collagen fiber orientation with respect to crimp structure. It was found that collagen bundles are ordered aggregates forming helical structures, and crimps are part of such a helical arrangement. The major part of the macromolecules in tendons have a helix conformation that probably influences a complex hierarchical construct. It is possible that thermodinamically this ordering is better fitted to respond to the biomechanical requirements of the tendons and to correspond to their rheological properties.

Animals↗

PubMed1994

The unique fibrillar arrangement of the bullfrog pressure-bearing tendon as an indicative of great functional deformability.

The fiber distribution and ultrastructure in the plantaris longus pressure-bearing tendon of the bullfrog were investigated. The tension region of the tendon showed a predominant parallel distribution of collagen fibers, but three main zones with different crimp parameters were identified with the use of the polarizing microscope. The compression region showed collagen fibers with aspects of disaggregation and were composed of disperse and undulating fibrils. These collagen fibers establish a three-dimensional network but showed a preferential distribution in planes disposed perpendicularly to the tendon's main axis. It is assumed that the convoluted and disaggregated collagen fibers must be distended before exerting any reinforcement on the tissue and that this only occurs after a great deformation of the tendon. Groups of 5-6 fibrils not associated in fibers are also dispersed in the compression region. The tissue is assumed to have a highly viscous fluid nature allowing for the deformation needed for collagen fibrils to reinforce the tendon structure. The convoluted and crimped structure of collagen fibers would be especially useful when the tendon is submitted to the sudden and strong mechanical loading expected to occur during jumping and to provide the tendon with the capacity of great functional deformability necessary for the high amplitude of feet movements attained on jumping and swimming.

Animals↗

PubMed1994

Structure and histochemistry of a pressure-bearing tendon of the frog.

The plantaris longus tendon of the bullfrog Rana catesbeiana has been structurally and histochemically characterized. The tendon has been shown to wrap around the distal tibio-fibular joint, extending into an aponeurosis. The region under the joint exhibits a large cartilaginous pad. In contrast to the mammalian flexor digitorum profundus tendons, the compression region of the frog tendon is not typically fibrocartilaginous but presents a unique arrangement of convoluted collagen bundles and fibers associated with a large amount of glycosaminoglycans. The sulfated nature of the glycosaminoglycans in the compressed region was determined through enzyme susceptibility as well as through CEC procedures. Cells of the modified zone exhibited morphological variation, from fibroblastic to condrocyte-like. Polarized light analysis revealed an intricate array of collagen bundles which crossed the tendon in different directions and connected the tension and compression regions. The ability of the tendon to resist compressive forces is assumed to be due to the large amount of glycosaminoglycans in the modified region as well as to the complex arrangement of collagen bundles in the tendon as a whole.

Animals↗

PubMed1994

Quantitative evaluation of AgNOR in liver cells by high-resolution image cytometry.

This study is aimed at determining the relationship between polyploidy and the amount of nucleolar organiser region (AgNOR) positive dots or aggregates using high resolution image analysis. Liver imprints from mice in which hepatocyte polyploidy is very well documented and related to variation in nuclear area were used as a model for this investigation. A technical variant of the AgNOR method using a Triton X-100 treatment was developed for removal of some proteins from the cytoplasm, which produced a clearer and cleaner background. Feulgen-stained preparations were used to detect the association of various ploidy degrees with their respective values of nuclear area and to subsequently furnish a basis for the association of the nuclear areas in AgNOR-stained cell preparations with different ploidy levels. A high correlation between nuclear and AgNOR-stained areas was revealed and was demonstrated to be much higher than the correlation between nuclear area and the number of AgNOR positive dots or aggregates. The use of two different thresholds for segmentation of the grey levels of the AgNOR-stained material demonstrated the importance of the appropriate decision to obtain the best results to be associated with polyploidy in terms of the real biological event involved, the nuclear area being in this case correlated to Feulgen-DNA values.

Animals↗

PubMed1992

Image analysis of Feulgen-stained NIH/3T3 cells transformed with DNA of 4-nitroquinoline 1-oxide treated human breast epithelial cells.

The nuclear phenotypes of Feulgen-stained NIH/3T3 cells transformed with 4-nitroquinoline 1-oxide (4NQO) treated, human breast epithelial cell (HBEC) DNA were studied by scanning microspectrophotometry and image analysis and compared with data obtained for nontransformed cells and for NIH/3T3 cells under ras oncogene transfecting situations. The Feulgen-DNA content of the individual nuclei (NQ1, NQ2, and NQ3 phenotypes) of the transformed cells was found not to be deeply affected, although presence of chromatin structures resembling double minutes could be verified in part of the metaphases of the transformed cells. On the other hand, the chromatin supraorganization of these cells showed some changes involving increased (NQ2, NQ3) or decreased (NQ1) levels of condensation. The changes in chromatin packing states, however, were of small magnitude compared with those reported for NIH/3T3 cells transfected with a c-H-ras oncogene or an N-ras-containing MCF-7 cell DNA. It was assumed that the transformation of the NIH/3T3 cells is not always necessarily accompanied by high levels of chromatin condensation. The transformation of the NIH/3T3 cells induced by the 4NQO-treated HBEC DNA and particularly the changes in chromatin condensation in these transformed cells could not be attributed merely to a ras activation elicited by the carcinogen. It is suggested that a more complex transforming mechanism is involved, probably owing to the fact that a whole genomic DNA of the 4NQO-treated HBEC has been used for transfection.

3T3 Cells↗

PubMed1991

Growth and differentiation of Vero cells cultivated in three-dimensional type 1 collagen.

Vero cells grown in a three-dimensional arrangement of type 1 collagen were phenotypically altered. Such alterations consisted of variations in cellular form and reactivity to toluidine blue. After 22 days of incubation the Vero cells formed three-dimensional arrangements in both tubular form and cellular mass. A reduction in the collagenous substrate was observed in the culture and the alteration noted in the birefringence of the extracellular matrix was attributed to enzymatic action. This model demonstrates a good in vitro system for the study of collagenase activation and for in vitro tests with collagen.

Animals↗

PubMed1989

Anisotropic and biomechanical properties of tendons modified by exercise and denervation: aggregation and macromolecular order in collagen bundles.

For the purpose of determining the changes in tensile strength and levels of macromolecular orientation in collagen bundles as a result of mechanical stimuli, rats were submitted to different experimental treatments such as physical exercise and muscular denervation. After these treatments the Achilles tendons of the animals were submitted to biomechanical and biophysical testing. An analysis of the "stress"-strain curves indicated that the tendons of trained animals possessed superior tensile strength characteristics as compared to their controls. The form birefringence curves (FBC) of the collagen bundles in these tendons also showed an increase in their state of aggregation of the extracellular matrix elements, while maintaining their levels of crystallinity. Average values of tensile strength were even higher in the tendons of denervated animals. An accentuation of the profile of the FBC was also observed in these tendons. The determination of the biomechanical and biophysical modifications can contribute to the understanding of the probable control mechanisms of the aggregation state patterns of the fibrous elements of the extracellular matrix.

Animals↗

PubMed1989

Lesions of intestinal epithelium by ingestion of bean lectins in rats.

Wistar rats were submitted to the action of active lectins from common dry beans (Phaseolus vulgaris) and from jack beans (Canavalia ensiformis, DC). Raw common bean was offered to the rats in an otherwise balanced diet to make 10% protein as the sole protein source. A single dose of 20 mg of jack bean lectin (concanavalin A) was given by gastric intubation. Half of the rats receiving raw bean died within 22 days of experiment. Histological findings showed ulceration and necrosis of the intestinal villi in the surviving rats. In some cases the lesions reached also the submucosa. Gastric intubation of concanavalin A caused intense scaling off in the apical portion of the villi.

Animals↗

PubMed1989

Critical electrolyte concentration of the heterochromatin and euchromatin of Triatoma infestans.

The binding of toluidine blue molecules under Mg2+ competitive staining conditions was investigated in chromocentres and the euchromatin of single- and multi-chromocentred nuclei of Triatoma infestans Malpighian tubule cells. It was demonstrated that the chromocentre of single-chromocentred nuclei exhibited the largest critical electrolyte concentration (CEC) value (0.4 M), followed by the chromocentres of multi-chromocentred nuclei (0.3 M) and the euchromatin (0.2 M). The differences in CEC values were assumed to be due to differences in availability of free DNA phosphates and in packing states of the DNA-protein complexes of these chromatin types. Differences in chromatin supra-organization were evident for the chromocentral heterochromatin of single vs multi-chromocentred nuclei. This was also valid for the chromocentral heterochromatin in some multi-chromocentred nuclei, when one of the heterochromatic bodies was especially larger than the others.

Animals↗

PubMed1988

Articular cartilage: collagen II-proteoglycans interactions. Availability of reactive groups. Variation in birefringence and differences as compared to collagen I.

Intrinsic (IB) and form or textural birefringence curves (FBC) were obtained measuring optical path differences in non stained sections of articular cartilages. Differences were not detected when comparing IB and FBC of the articular surface with those of the intermediate zone (Collagen II), but were found when these curves were compared with those of tendons (Collagen I). A detailed description of arrangements of collagen fibers are reported with no confirmation of Gothic arches. Hyaluronidase and papain digestion caused a decrease in birefringence of the cartilage supporting the conclusion that acid proteoglycans (APG) present molecular orientation in those structures. Histochemical data and histophotometric measurements confirmed that in articular cartilage there are variations in APG concentration and complexation with Collagen II from the articular surface (AS) down to the bone zone, AS displaying much more available -NH3+ groups. Molecular order in the articular cartilage optimizes the state of aggregation in its structures, and is the basis for its piezoelectric and mechanical properties.

Animals↗

PubMed1986