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At least 19 recordsLinked to original sources
PubMed1979

Rabbit cranial sutures in vitro: a new experimental model for studying the response of fibrous joints to mechanical stress.

An organ culture system has been developed whereby mechanical stress can be applied to cranial sutures under controlled experimental conditions. The application of a continuous tensile mechanical stress (30 g) to cranial sutures from newborn rabbits (1--2 days) was accompanied by a significant increase in the incorporation of 3H-leucine and 3H-proline into suture protein. The specific activities of 3H-hydroxyproline indicated that mechanical stress produced a two-fold increase in the incorporation of 3H-proline into collagen. However, the proportion of the total radioactivity recoverable in collagen (45.63 +/- 2.33% for nonstressed; 40.58 +/- 2.17% for stressed sutures) was not significantly different. These data suggest that the increase in collagen synthesis occurs as part of a general stimulation of protein synthesis, and do not support the view that mechanical stress is the principal mechanism regulating the turnover of collagen in fibrous joints. These initial studies demonstrate that an in vitro experimental model has considerable potential for investigating the morphological and metabolic response of fibrous joints to mechanical deformation.

Animals↗
PubMed1979

Reactions of transplanted neurocentral synchondroses to different conditions of mechanical stress. A methodological study on the rat.

In order to elucidate the reactions of neurocentral synchondroses to different forces, the first cervical vertebra of 10 or 25 days old rats was transplanted into sex-matched litter mates. Some vertebrae were transplanted as a whole, in some only the ventral part with its synchondroses was transplanted and, in others the lumen was furnished with an expanding sponge or a spring. The transplantation was done subcutaneously and, in the case of the fragments, intracerebrally as well. The synchondroses of the vertebrae transplanted at 10 days did not differ very much from those of the host 5, 10 or 15 days after the operation, whereas in the vertebrae transplanted at 25 days the synchondroses underwent synostosis earlier than in situ. The synchondroses of the transplanted fragments, and especially of those placed intracerebrally, remained open longer than those in the whole vertebral transplants; the sponge and and the spring also delayed closure. In the synchondroses transplanted at 25 days there was a strong reduction in alcian blue staining, whereas in the spring loaded synchondroses the stainability persisted longer, maybe as an adaptation to the tensile force. It seems that the inherent potential of the neurocentral synchondroses to obliterate at a certain time can be altered by changing the biomechanical conditions.

Aging↗
PubMedDate not supplied

The effect of oxygen tension and mechanical stress on the outcome of fresh autogenous tissue implants in the canine blood stream.

Fresh autogenous collagenous tissue grafts were implanted in the lumen of the aorta, vena cava, pulmonary artery and vein of thirty dogs. Grafts were studied at varying periods postimplantation. Grafts in the latter three situations were vascularized and absorbed early and were replaced by host fibrous tissue; whereas grafts in the aorta remained unabsorbed because of lack of vascularization. We conclude that fresh autogenous fibrous tissue is not a good material for the reconstruction of the right ventricular outflow tract with a competent valve.

Animals↗
PubMedDate not supplied

[Standardization of methods for testing the resistance of medical equipment to mechanical stress].

The existing methods and facilities for testing biomedical equipment for vibration resistence is adopted from technical standards prepared for manufactures of radio-industry and fail to take into consideration actual operation conditions and transportation of equipment and instruments of biomedical engineering. On the ground of experience gained by testing medical equipment proposals for elaborating rules and conditions for vibration resistance testing for medical equipment are offered.

Medical Laboratory Science↗
PubMed1977

Altered performance of rat cardiac muscle follows changes in mechanical stress during relaxation.

We compared two sets of loading conditions for their effect on the mechanical performance of isolated rat trabecular muscle: (1) loading which approximated that of the intact ventricle; (2) nonphysiological afterloaded isotonic contractions. Improved performance, manifested by increased shortening and rate of shortening at constant load, was seen when lengthening occurred at light loads, as in the intact heart. In contrast, lengthening occurring at the same load against with shortening had taken place was followed by diminished performance. Viscous elements in series with the muscle could not account for this phenomenon. The results suggest the presence of an autoregulatory response of myocardium to mechanical stress during relaxation.

Animals↗
PubMed1977

[Electrical polarization in the osteon-system under mechanical stress (author's transl)].

The results of a model, designed to estimate the electrical polarization of the mineralized collagen fribril in the osteon-system caused by mechanical stresses are presented. These are potential differences in the mV-range between neighbouring osteon-canals with different orientation of the fibrils in the wall of the canal, local dependent potentials in the cross-sectional area of the osteon-canal and the local dependent radial component of the dielectric displacement within the lamella system, especially nearby the osteocytes.

Bone and Bones↗
PubMed1978

Immuno-histochemical localization of cyclic nucleotides in the periodontium: mechanically-stressed cells in vivo.

Cyclic AMP and cyclic GMP, considered to be cell proliferation regulators, have been reported to fluctuate in proliferating fibroblasts in vitro. The objectives of this experiment were to study the localization, distribution and staining patterns of these cyclic nucleotides in mechanically-stressed, proliferating periodontal fibroblasts in vivo. Cat canines were tipped by force applications for 0 to 48 hours and serial sagittal sections of fresh frozen, unfixed, undecalcified jaws were processed immuno-histochemically for the localization of cAMP and cGMP. Periodontal tension sites were studied microscopically. Fibroblastic staining for cAMP, which was localized mainly in the cell periphery, did not change appreciably as a result of tension. However, staining intensity increased one hour after the application of force, decreased after 6 hours and increased again at 24 hours. Staining for cGMP, initially covering the entire cell area, was concentrated over nuclei three hours after onset of tension, and diffused over cell periphery and cytoplasm thereafter. Intensity of staining for cGMP was maximal at 3 hours and low at 12 and 48 hours. These results demonstrate that stress-induced fibroblastic responses in vivo involve alterations in staining intensity for both cyclic nucleotides which may correspond with fluctuations of these regulators, reported to occur in vitro in various stages of the mitotic cycle. Moreover, this technique enables the identification of the involved cells in a stimulated, non-synchronized cell population.

3,3'-Diaminobenzidine↗
PubMed1977

The mechanism of the inactivation of human fibroblast interferon by mechanical stress.

Interferon derived from human fibroblasts is readily inactivated during agitation and filtration. This inactivation has been shown to be largely a product of mechanical stress, and has been studied in detail by subjecting interferon to controlled shear stress using a rotational viscometer. The possible mechanism of this phenomenon is discussed.

Cell Line↗