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Biomedical subjects

G F Elliott

Publications and source records attributed to G F Elliott.

49 records · Page 3Linked to original sources
PubMed1972

An x-ray diffraction study of contracting molluscan smooth muscle.

The living anterior byssus retractor muscle of Mytilus (ABRM), a smooth, "catch" muscle, has been studied by X-ray diffraction while relaxed and while tonically contracted. X-ray reflections were observed from the actin and paramyosin filaments and from the alpha-helical substructure of the paramyosin filaments. No differences in spacings or relative intensities were observed when the relaxed and contracting muscle patterns were compared. This result is consistent with a sliding filament mechanism involving an interaction between actin and paramyosin filaments.

Actins↗
PubMed1972

The myofilament lattice: studies on isolated fibers. II. The effects of osmotic strength, ionic concentration, and pH upon the unit-cell volume.

The effects of osmotic concentration, ionic strength, and pH on the myofilament lattice spacing of intact and skinned single fibers from the walking leg of crayfish (Orconectes) were determined by electron microscopy and low-angle X-ray diffraction. Sarcomere lengths were determined by light diffraction. It is demonstrated that the interfilament spacing in the intact fiber is a function of the volume of the fiber. It is also shown that the interfilament spacing of the skinned (but not of the intact) fiber is affected in a predictable manner by ionic strength and pH insofar as these parameters affect the electrostatic repulsive forces between the filaments. From these combined observations it is demonstrated that the unit-cell volume of the in vivo myofilament lattice behaves in a manner similar to that described for liquid-crystalline solutions.

Animals↗
PubMed1971

The myofilament lattice: studies on isolated fibers. I. The constancy of the unit-cell volume with variation in sarcomere length in a lattice in which the thin-to-thick myofilament ratio is 6:1.

The spacing between the thick myofilaments of muscle fibers from the walking legs of crayfish (Orconectes) was determined by optical transform analysis of electron micrograph plates of fixed single fibers and by X-ray diffraction of living single fibers. Sarcomere lengths were determined by light diffraction prior to fixation and prior to the in vivo experiments. From these combined measurements, it is demonstrated that the unit-cell volume of the myofilament lattice is constant during muscle shortening, indicating that the myofilament lattice works in a constant-volume manner. It is further demonstrated with X-ray diffraction measurements of living single fibers that the myofilament lattice continues to work at constant volume after the sarcolemma is removed from the fiber. This indicates that the constant-volume behavior of muscle is inherent to the myofilament lattice.

Animals↗
PubMed1967

Variations of the contractile apparatus in smooth and striated muscles. X-ray diffraction studies at rest and in contraction.

Structural information is presented for three muscle systems-mammalian smooth muscle at rest and partially active, living toad striated muscle at rest and contracting, and glycerinated rabbit psoas muscle under various conditions of pH and ionic environment. In the smooth muscle no evidence of organized myosin filaments has been found. In the striated muscle the myosin-to-actin distance can vary widely, according to sarcomere length and to muscle treatment, both at rest and during contraction. In the discussion it is suggested that muscle should be considered as a colloidal system and that there need not necessarily be any chemical bonding (cross-linking) involved in the contractile process.

Action Potentials↗
PubMedDate not supplied

The axial electron density in collagen fibrils from human corneal stroma.

Low angle synchrotron X-ray diffraction patterns were obtained from the demembranated human corneal stroma. These patterns showed differences in the relative intensities of the meridional reflections compared to those obtained using bovine corneas. In particular, the first order reflection, conspicuously absent in the bovine pattern, is present in the human, although it is still only one third as intense as the first order in the pattern from rat tail tendon. Using phases deduced from the electron-optical images of negatively stained corneal collagens, a difference electron density map between bovine and human corneal collagen was drawn. The features in this map are explained in terms of a different inter-relationship between collagen and proteoglycans in the two species. The function of these species differences is unknown.

Animals↗