Gills as Possible Accessory Circulatory Pumps in Limulus polyphemus

Heart electrical activity (ECGs), gill closer muscle potentials (EMGs), and blood pressures in the heart and the branchiocardiac canals, were measured in adult horseshoe crabs (Limulus polyphemus) during various activities. During ventilation, hyperventilation, and swimming, large transient increases in pressures (10-35 cm H2O) occur in the branchiocardiac canals, which carry blood from the gills to the heart. These pulses of positive pressure are related to, and apparently caused by, gill plate closing. During quiescent periods, with no ventilatory activity, there are no pressure pulses in the canals, but the pressure is still greater than zero. We found covariation of heart and ventilation rates during intermittent ventilation, hyperventilation, gill cleaning, and swimming, as well as evidence of transient periods of phasic coordination. The heart appears to be weakly entrained to the gill rhythm by phasic cardioregulatory nerve input. The preferred phase of heartbeats, with respect to gill rhythm, was 0.5, or 180 degrees out of phase. In some animals, intra-cardiac pressures were enhanced when the heart and gill rhythms were entrained. We suggest that rhythmic movements of the gill plates enhance the flow of low pressure blood returning from the body to the heart. Thus, ventilatory appendage movements may constitute an accessory blood pumping mechanism in Limulus

Building model trains and planes : an autoethnographic investigation of a human occupation.

This research paper utilises an autoethnographic method, termed collective autobiography, to explore the nature and meaning of the amateur hobby of building models from childhood to adulthood. Hobbies and leisure activities are areas of human occupation of increasing interest to a variety of disciplines e.g. healthcare. Although model making may concern the miniature representation of any subject, this paper focuses on the construction of model aircraft kits, trains and their layouts. As a complex specific human occupation modelling is revealed as significant to personal wellbeing, and while the activity may start in childhood its associated motivations and required skills develop over a life time. The findings reveal aspects of the nature of the relationship between the modeller, the process of modelling and the final product. In addition they also reveal some elements of the gendered nature of modelling, its role within father-son relationships, and the accommodation of modelling activities within shared domestic spaces. The specific modelling activities described are recognised as having their origins within the culture of post-war baby boomer Britain, and the socioeconomic and technological environment of that period. This recognition necessitates discussion of the modeller as a skilled consumer as well as a creative individual

Gills as Possible Accessory Circulatory Pumps in Limulus polyphemus

Volume: 177Start Page: 386End Page: 39

The Semiotics of Writing: Transdisciplinary perspectives on the technology of writing

The fifteen articles that make up this volume were presented and discussed at an international conference entitled ‘The Semiotics of Writing: Transdisciplinary Perspectives on the Technology of Writing’, held at the International Centre of Semiotic and Cognitive Studies of the University of San Marino from 12-14th November 1999.Some central themes explored awere as follows: * The semiotics of writing: writing construed as a socio-semiotic system for human communication and meaning-making* Writing and cognition: the role of writing in the development of ontological and other forms of categories, concepts, forms of argumentation, inference and reasoning* Writing and culture: the role of the various systems, forms and genres of writing in the evolution and development of human culture* Writing science: the role of the semiotic system of writing in on-going processes of scientific research and communication* Writing and learning: the role of writing in institutionalised and other forms of teaching and learning* Writing technologies: how modern technologies designed specifically to write with, and in, affect the writing process and the types of texts produce