The Motor Innervation of a Triply Innervated Crustacean Muscle

The crustacean muscle is extremely sensitive to mechanical injury. This is due to the fact that the muscle fibres are innervated by a feltwork of nerve fibres which surrounds them. Apparéntly, there is a lack of a muscular conduction process in these muscles. Contractions have been observed in the same muscle fibres during stimulation of the axon for the fast contraction as well as during stimulation of the fibre for the slow contraction

On Galvanotropism and Oscillotaxis in Fish

A spinal fish bends with the concave side towards the anode in a D.C. field of transverse direction. This reaction, which lasts as long as the current passes, is shown to be a reflex (galvanotropic reflex). Other manifestations of this reflex have been found. In a field of dorso-ventral direction the animal is bent in the sagittal plane towards the anode. The unrest of body and tail in an ascending field in the longitudinal direction of the fish may be caused partly by the same reflex. The same reflex has also been found in some of the fin muscles. The structures (sensory end-organs) stimulated during the galvanotropic reflex are situated in the muscles (or tendons). Galvanotropism has been demonstrated in fish in which the labyrinths and the lateral-line organs have been eliminated by the transection of their nerves. The mechanism of galvanotropism is discussed and this phenomenon is found to be based on the galvanotropic reflex and the ability of the animal to swim. A fish placed at 45° to the current lines in an A.C. field shows a curving of the body and tail. This is explained by the wedge shape of the fish body and tail, by which the two sides of the animal have a different angle with the current lines, and thus are differently stimulated. The mechanism of oscillotaxis is discussed in relation to this reaction

Perfusion Fixation With Glutaraldehyde and Post-Fixation With Osmium Tetroxide for Electron Microscopy

The conductivity of cerebral cortex drops during perfusion with glutaraldehyde in 5 min to about 60% of the original value, to remain unchanged during the subsequent 10-15 min of perfusion. Circulatory arrest causes a similar drop in the tissue conductivity. Perfusion of asphyxiated tissue with glutaraldehyde does not produce additional major changes in the conductivity. Perfusion of the cortex with an osmium tetroxide solution causes an initial drop in conductivity. However, after about 3 min this trend is reversed and the conductivity increases again to close to the pre-perfusion value. Perfusion of asphyxiated cortex with OsO4 causes a marked increase of the conductivity. So does perfusion with an OsO4 solution of tissue previously treated with glutaraldehyde. One interpretation of these impedance changes is that glutaraldehyde perfusion causes, like asphyxiation, a transport of extracellular material into the intracellular compartment and that during OsO4 perfusion an extracellular space is again created. This possibility is supported by electron micrographs made of this material. Cerebral cortex perfused with glutaraldehyde and post-fixed with OsO4 shows electron-transparent dendritic elements and to a lesser extent pre-synaptic terminals, which seem to be swollen. When the cortex is flooded with a salt solution during glutaraldehyde perfusion the dendrites exhibit ballooning in the surface layer of the cortex, suggesting that the fluid on the cortex participates in the swelling. The tissue elements in the glutaraldehyde-perfused and OsO4 post-fixed cortex are separated by narrow extracellular spaces. The latter may have been produced by the OsO4 perfusion as is suggested by a comparison of micrographs prepared by freeze substitution (which tends to preserve the water distribution) of glutaraldehyde-perfused but not post-fixed cortex with micrographs of cortex treated with OsO4 after the glutaraldehyde perfusion. In accordance with the conductivity changes, the former micrographs showed very little extracellular space, and in many places tight junctions, whereas the latter showed clefts between the tissue elements

Demonstration of Extracellular Space by Freeze-Drying in the Cerebellar Molecular Layer

In electron micrographs of the molecular layer of the mouse cerebellum frozen within 30 sec of circulatory arrest and subsequently dried at -79 °C an appreciable extracellular space was found between the axons of the granular cells. Tight junctions were regularly observed between pre- and postsynaptic structures and the enveloping glia cells. In micrographs of cerebellum frozen 8 min after decapitation the space between the axons was absent and tight junctions between the nerve fibres were almost exclusively encountered. The extracellular space of asphyxiated and non-asphyxiated tissue in electron micrographs of frozen-dried material is similar to the space in comparable tissues treated by freeze-substitution. These observations suggest that there is an appreciable amount of extracellular material in oxygenated, living tissue which is taken up by cellular elements during asphyxiation

A Comparative Study Of The Double Motor Innervation In Marine Crustaceans

A double motor innervation has been shown for several muscles of marine crustaceans. The adductors of the claws of Randallia and Blepharipoda and the adductor of the dactylopodite of the walking leg of Cancer were studied physiologically. The two motor axons which innervate these muscles have a different diameter (ratio 1.4:1). Stimulation of the thick fibre causes a response, which, though it is not always faster than the response of the thin fibre, must be considered as a "fast" contraction. In Randallia and in Blepharipoda the slow contraction is higher than the fast with frequencies of less than ± 50 per sec., in Cancer with frequencies less than 100 per sec. The action currents of the two kinds of contraction are different. Both show facilitation, but under the same conditions of stimulation the fast-action currents are higher. The first stimulus of the thick fibre causes an action current top which is clearly distinguishable, the action currents of the slow contraction show up only after a number of stimuli. Even when the mechanical reaction on stimulation of the thick fibre is smaller than on similar stimulation of the thin fibre, the action currents are higher in the first case. A single impulse in the thick fibre does not cause a contraction, but sets up a muscle-action current. The chronaxie of this action current in Blepharipoda and Randallia is 0.8{sigma} and is about the same as that found for the action current of the nerve. Two impulses in the thick fibre may cause a mechanical response, as is shown by summation experiments. The pseudo-chronaxie of this contraction was measured as 3.5 {sigma}. The second action current shows facilitation, when it follows the first within 1 sec.; a mechanical reaction results with summation intervals of two stimuli of less than 10{sigma}. The facilitation of the action current increases with decrease of the time interval between the two impulses; with the shortest intervals that give summation the resulting action current is a smooth high spike

A statistical perspective on biofilter performance in relation to the main process parameters and characteristics of untreated flows

[Abstract] A large number of olfactometric measurements of odour removal efficiency of municipal waste organic fraction and green waste composting installations were compiled and analysed graphically. The number of measurements and installations is >50 for treated gas characteristics and >15 for filter media characteristics. All installations concerned were located in the Netherlands and Belgium. All untreated and treated gas odour concentrations were measured in duplicate or triplicate, according to olfactometry standard EN13725 or its predecessor NVN2820. The data were then analysed using graphical methods to identify trends and relation between effectiveness of performance and a large number of operational parameters and characteristics, including: • Area flow loading (m3·m-2 filter area·hour-1) • Contact time • Temperature of untreated flow • Odour concentration of untreated flow • Ammonia concentration of untreated flow • Dry matter content of filter media • pH of filter medi

Doctrina perpetua: brokering change, promoting innovation and transforming marginalisation in university learning and teaching [Editors introduction]

Doctrina perpetua—translated variously as “forever learning” (Cryle, 1992, p. 27), “lifelong learning” and “lifelong education”—is the Latin motto of Central Queensland University (CQU), an Australian regional university with campuses in Central Queensland and the metropolitan and provincial cities of Brisbane, the Gold Coast, Melbourne and Sydney and with centres in China, Fiji, Hong Kong and Singapore. During its early development the institution was small and regional; in many ways it was an institution at the margins of higher education. For only a third of its 40-year life has it been recognised as a university. However, the vision of both its founders and its continuing staff has been that of an institution that actively brokers change, promotes innovation and seeks to transform marginalisation— for students, for its community and for itself. Its short life on the edge of the universe of higher education has promoted a culture of innovation and an acceptance that change is a necessary and positive aspect of life on the edge. Embracing change, CQU has become a complex institution, a notion well expressed in a speech in August 1999 by former Vice-Chancellor Lauchlan Chipman on Visioning Our Future: I have often remarked that I do not see CQU as “the last university of the old millennium” but rather as “the first university of the new millennium”. One of our greatest strengths in making the transition is our relative immaturity as a university. The more mature a university, especially if it is successful, the less agile it is when it comes to the need to change. So far as the future of universities and change is concerned, my position is unequivocally Heraclitean: change is the only thing that is permanent. Applying to itself the motto “doctrina perpetua” over its short life, the agile University has become a “complex and diverse organisation” (Danaher, Harreveld, Luck & Nouwens, 2004, p. 13). This overview of CQU seeks to provide readers with a short description of the current state of the institution and the story of its development to provide a context for understanding the chapters that follow, and to assist readers to reflect on how these developments at CQU relate to higher education generally, and to the universities with which they are more familiar

Feeling torn and fearing rue: Attitude ambivalence and anticipated regret as antecedents of biased information seeking

Theoretical work on attitudinal ambivalence suggests that anticipated regret may play a role in causing awareness of contradictions that subsequently induce a feeling of an evaluative conflict. In the present paper we empirically examined how the anticipation of regret relates to the association between the simultaneous presence of contradictory cognitions and emotions (objective ambivalence), and the evaluative conflict associated with it (subjective ambivalence), in the context of decision-making. Across three studies (Ns = 204,127,244), manipulating both objective ambivalence and regret, we consistently found that when a dichotomous ambivalent choice had to be made, (objectively) ambivalent attitude holders for whom feelings of anticipated regret were made salient reported higher levels of subjective-attitude ambivalence than participants in the other conditions. Moreover, in Studies 2 and 3 we found that the effect of anticipated regret on subjective ambivalence had consequences on information processing. Specifically, anticipating regret made ambivalent participants search for attitude-congruent information. This effect was mediated by the increase in subjective ambivalence. This work provides the first empirical evidence for the role of regret in the association between objective-and- subjective attitude ambivalence, and its consequences