The load-strain and stress-relaxation behavior of wet rat tail tendon has been examined with respect to the parameters strain, rate of straining, and temperature. It is found that this mechanical behavior is reproducible after resting tile tendon for a few minutes after each extension so long as the strain does not exceed about 4 per cent. If this strain is exceeded, the tendon becomes progressively easier to extend but its length still returns to the original value after each extension. Extensions of over 35 per cent can be reached in this way. Temperature has no effect upon the mechanical behavior over the range 0-37°C. Just above this temperature, important changes take place in the mechanical properties of the tendon which may have biological significance. The application of the techniques used here to studies of connective tissue disorders is suggested. Some of the mechanical properties of tendon have been interpreted with a simple model.
I N T R O D U C T I O NMost studies of collagen h a v e been concerned with its chemical n a t u r e and reactivity, and with electron microscope and x-ray diffraction examinations with a view to determining its m a c r o and molecular structure (1-4). As yet there is no entirely satisfactory molecular model, and one major stumbling block appears to be the confusion over whether collagen is or is not capable of large extensions.A n u m b e r of measurements have been reported on the mechanical properties of such collagen-containing structures as tendons, ligaments, and fascia. T h e r e is no extensive review of the older work available. However, typical results m a y be found in references (5-7). Structures containing a high per cent of collagen were found difficult to stretch and usually broke before they elongated appreciably, while structures with a lower collagen content and a
It has been shown that lamellar crystals of amylose V complexes with 71 helical configuration can be obtained by using complexing agents larger in cross section than n‐butanol. The electron diffraction studies indicated a new unit cell for the unheated lamellar crystals which are composed of molecules with 71 helical configuration and hold water molecules on the exterior of the helix. Furthermore, from a throughly dried specimen at 100°C. in vacuo we obtained a pattern which showed only three Debye rings. Its spacings were explained by a two‐dimensional hexagonal unit cell having a = b = 14.7 A. proposed by Zaslow. It was also found that when the crystals were dispersed in methanol at room temperature, their electron diffraction pattern was the same as that of the anhydrous amylose V complex of n‐butanol.
Distributional changes in branchial chloride cells were examined in Japanese sea bass (Lateolabrax japonicus) juveniles transferred from seawater (SW) to fresh water (FW) during their migration season toward low salinity habitat in nature. Chloride cells were identified by immunocytochemistry with a specific antiserum for Na + ,K + -ATPase. In fish reared in SW as controls, branchial chloride cells were localized exclusively in the filaments and absent in the lamellae. When sea bass were transferred from SW to FW, chloride cells emerged in gill lamellae, starting at the proximal part of the lamellae and thereafter spread over the lamellar epithelium. On 7th and 15th days after FW transfer, chloride cells were mostly found on the lamellae, whereas the number of filament chloride cells was decreased. These results suggest that, in Japanese sea bass juveniles, chloride cells in the gill lamellae are important in FW adaptation, and that lamellar chloride cells originated from the filaments and migrated to the lamellae during FW adaptation.
The theory of bulk viscosity as developed for the liquid state was applied to amorphous high polymeric systems. The isothermal volume contraction, the dependence of shear viscosity, and the fictive temperature of quenched high polymeric substances are all related to the bulk viscosity and explained by this theory. Simple representations are given for compressibility, bulk modulus, shear modulus, thermal expansion coefficient, and heat capacity, all of which are necessary to discuss the bulk viscosity. The theory has been compared with the experimental results for natural rubber, polystyrene, polyisobutylene, and polyester.
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