Microscopic Tissue Structure Research Articles

Potential distribution and single-fibre action potentials in a radially bounded muscle model.

In modelling the electrical behaviour of muscle tissue, we used to employ a frequency-dependent volume conductor network model, which was infinitely extended in all directions. Equations in this model could be solved using a finite-difference approach. The most important restriction of this model was the fact that no boundary effects could be incorporated. Analytical models of muscle tissue normally do not have this disadvantage, but in those models the microscopic structure of muscle tissue cannot be taken into account. In the paper, we present a combined numerical/analytical approach, which enables the study of potential distributions and SFAPs in simulated microscopic muscle tissue in which the influence of the muscle boundary has been considered. We considered muscle models with radii of 1.5 mm and 10 mm. Both models were compared with an unbounded network model. In the model with a radius of 1.5 mm we varied the position of the active fibre relative to the muscle surface. It appeared that in most cases the presence of a boundary had a considerable effect on the potential distribution. An increase in the peak-to-peak value of the SFAP amplitude up to 300 per cent was noticed when the active fibre was positioned 500 microns beneath the muscle surface in a model with a radius of 1.5 mm.

A structural viscoelastic model of soft tissues.

A non-linear elastic model taking into account the microscopic structure of biological soft tissues is briefly presented and extended to quasi linear viscoelasticity. The modelling of the rheological behavior for near zero stress values is then discussed.

The microscopic structure of normal human synovial tissue.

AbstractMicroscopic study of normal synovial tissue from 16 humans of varying age disclosed an architectural pattern which did not vary significantly with age, sex or intra‐articular location. Except for fibrous synovium, the tissue samples were similar in vascularity, number of surface cell layers and in the differential composition of the surface cells. Histochemical procedures delineated a pericellular surface reticulin network but failed to establish the locus of hyaluronic acid synthesis.

News and Comment

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On the British Fossil Cretaceous Birds

History . T he oldest remains of British fossil birds are recorded by Sir Charles Lyell as having been first found in 1858, in the Cambridge Upper Greensand. This stratum still continues the only member of the British Secondary deposits in which the bones of birds have been identified by morphological characters; for though the Rev. Mr. Dennis had previously asserted the occurrence of birds in the Stonesfield Slate, on the evidence of the microscopic structure of osseous tissue, it is safer, in the absence of recognizable bones, to believe that the ornithic structure he detected was found in an ornithosaurian rather than in a true bird. The discovery of bird-bones in the Cambridge Greensand was made by Mr. Lucas Barrett, F.G.S., then Assistant Naturalist to the late Professor Sedgwick in the Woodwardian Museum of the University of Cambridge; but I am not aware that Mr. Barrett ever published any account of his discovery. The bones are mentioned by Lyell as “the remains of a bird which was rather larger than the common Pigeon, and probably of the order Natatores, and which, like most of the Gull tribe, had well-developed wings. Portions of the metacarpus, metatarsus, tibia, and femur have been detected; and the determinations of Mr. Barrett have been confirmed by Professor Owen.” What became of Mr. Barrett's specimens I was never able to find out. They were not in the Woodwardian Museum when I succeeded to Mr. Barrett's duties in 1859; and the whole of the remains to which I