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Biomedical subjects

G Hoyle

Publications and source records attributed to G Hoyle.

52 records · Page 3Linked to original sources
PubMed1973

Ultrastructure of barnacle giant muscle fibers.

Increasing use of barnacle giant muscle fibers for physiological research has prompted this investigation of their fine structure. The fibers are invaginated by a multibranched system of clefts connecting to the exterior and filled with material similar to that of the basement material of the sarcolemmal complex. Tubules originate from the surface plasma membrane at irregular sites, and also from the clefts They run transversely, spirally, and longitudinally, making many diadic and some triadic contacts with cisternal sacs of the longitudinal sarcoplasmic reticulum. The contacts are not confined to any particular region of the sarcomere. The tubules are wider and their walls are thicker at points of contact with Z material. Some linking of the Z regions occurs across spaces within the fiber which contain large numbers of glycogen particles. A-band lengths are extremely variable, in the range 2.2 microm-20.3 microm (average 5.2 microm) Individual thick filaments have thin (110 A) hollow regions alternating with thick (340 A) solid ones. Bridges between thick filaments occur at random points and are not concentrated into an M band The thin:thick filament ratio is variable in different parts of a fiber, from 3:1 to 6:1. Z bands are basically perforated, but the number of perforations may increase during contraction.

Animals↗
PubMed1965

Mechanism of supercontraction in a striated muscle.

The phenomenon of contraction of a striated muscle down to below 50 per cent rest length has been examined for the scutal depressor of the barnacle Balanus nubilus by a combination of phase contrast and electron microscopy. It was found that neurally evoked contraction down to 60 per cent rest length results from the shortening of the I band. At the same time the Z disc changes in structure by an active process which results in spaces opening up within it. Thick filaments can now pass through these spaces from adjacent sarcomeres, interdigitating across the discs. Interdigitation permits repetitive contraction in the living muscle to below 30 per cent rest length. In non-neurally evoked contractions most thick filaments do not find spaces in the Z disc and bend back, giving rise to contraction band artifacts. Expansion of the Z disc can be produced in glycerinated material by the addition of solutions containing a high concentration of ATP.

Crustacea↗
PubMedDate not supplied

Distributed situation awareness in dynamic systems: theoretical development and application of an ergonomics methodology.

The purpose of this paper is to propose foundations for a theory of situation awareness based on the analysis of interactions between agents (i.e. both human and non-human) in subsystems. This approach may help to promote a better understanding of technology-mediated interaction in systems, as well as helping in the formulation of hypotheses and predictions concerning distributed situation awareness. It is proposed that agents within a system each hold their own situation awareness, which may be very different from (although compatible with) that of other agents. It is argued that we should not always hope for, or indeed want, sharing of this awareness, as different system agents have different purposes. This view marks situation awareness as a dynamic and collaborative process binding agents together on tasks on a moment-by-moment basis. Implications of this viewpoint for the development of a new theory of, and accompanying methodology for, distributed situation awareness are offered.

Awareness↗
PubMedDate not supplied

Nerve growth factor induces airway hyperresponsiveness in mice.

BACKGROUND: Previous studies indicated an upregulation of nerve growth factor (NGF) production during allergic inflammation. However, the function of NGF in the lungs is currently poorly understood. It was suggested that NGF could play an important role in the pathophysiology of airway hyperresponsiveness. The regulatory network between immunological events and altered neuronal control of airway smooth muscle contractility remains to be defined. METHODS: NGF was delivered into the airways of mice either by nasal instillation or by genetic engineering. Airway reactivity was then measured by electrical field stimulation. RESULTS: Treatment of mice with NGF induced airway hyperresponsiveness to a similar extent as demonstrated in allergen-sensitized mice. NGF-transgenic mice, overexpressing NGF in Clara cells, were hyperreactive in comparison to wild-type mice. CONCLUSION: These data suggest that NGF by itself determines the induction of airway hyperresponsiveness in the absence of airway inflammation in mice.

Administration, Intranasal↗