Medicine & Health

Publication Search Results

Now showing 1 - 10 of 14
  • (1996) Vochteloo, J; Elphinstone, Kevin; Russell, Susan; Heiser, Gernot
    Conference Paper
    The Mungi single address space operating system provides a protected procedure call mechanism named protection domain extension (PDX). The PDX call executes in a protection domain which is the union of (a subset of) the caller`s, and a fixed domain associated with the procedure. On return, the caller`s original protection domain is reestablished. Extensive caching of validation data allows amortisation of setup costs over a possibly large number of invocations. The PDX mechanism forms the basis for object support in Mungi, particularly encapsulation. It is also used for accessing devices, and to implement user-level page fault handlers.

  • (1995) Bandyopadhyay, Srikanta; Mukherjee, S; Perera, D; Mori, K; Swain, M; Bell, Toby
    Conference Paper

  • (1998) Wool, R; Kusefoglu, S; Khot, S; Zhao, R; Palmese, Gaetano; Boyd, Andrew; Fisher, Keith; Bandyopadhyay, Srikanta; Williams, J; Wang, Chaoyuan
    Conference Paper

  • (1999) Oakes, Samantha; Gorrie, Catherine; Waite, Phil
    Conference Paper

  • (1998) Waite, Phil; Gorrie, Catherine; Mark, Adam; Duflou, J; Brown, Jennifer
    Conference Paper

  • (1998) Gorrie, Catherine; Duflou, J; Mark, Adam; Waite, Phil
    Conference Paper

  • (1998) Bertrand, P. P; Kunze, W. A.; Bornstein, J. C.; Furness, J. B.
    Conference Paper
    There are similarities between the mechanisms of sensory transduction by chemoreceptors in the gastrointestinal (GI) tract and by those in the oral cavity. Dissociated rat taste receptor cells have been shown to contain vesicular 5-HT and are excited by exogenous application of 5-HT. Likewise, in the GI tract, enterochromaffin (EC) cells are well known to contain 5-HT and are excited by its exogenous application. Both the taste receptor cell and the EC cell apparently make reciprocal synaptic connections with their extrinsic and (in the case of the gut) intrinsic afferent innervation. However, while the taste receptor cell is known to participate in gustation, the EC cell's role in the initiation of enteric reflexes remains unclear. Thus it may be that common transduction mechanisms are utilized in both systems and it is in this sense that the gut may be said to 'taste' the contents of the lumen. These studies were designed to investigate the sensory transduction mechanisms underlying responses of myenteric sensory neurons to chemical stimulation of the mucosa and with particular attention to the possible interactions between the EC cell and the surrounding afferent innervation. Intracellular electrophysiological recordings were taken from chemosensory myenteric neurons which had AH type electrophysiological characteristics and Dogiel type II morphological characteristics. Short segments of guinea pig ileum were dissected to reveal the myenteric plexus over one half the circumference of the preparation. Focal stimulating electrodes and fine glass pipettes containing chemical substances were used to stimulate the mucosa in the intact half of the preparation. Movement of the smooth muscle was reduced with the addition of scopolamine and nicardipine. In general, stimulation of the mucosa generated bursts of one or more action potentials (APs) recorded at the cell soma. Puffs of 5-HT (3 - 30 M) or 2-methyl 5-HT (0.1 to 1 mM - a 5-HT3 agonist) applied locally to the mucosa were effective in eliciting bursts of APs while puffs of -methyl 5-HT (0.1 to 1 mM - a 5-HT2 agonist) or 5-methoxytryptamine (1 to 10 M - a general 5-HT agonist) were not. Single, electrical stimuli applied to the mucosa elicited a single antidromic AP and a later burst of APs. Spontaneous bursts of APs were also recorded in some cells which were indistinguishable from the electrically evoked late burst of APs. In one instance, initiation of an antidromic AP by electrical stimulation of the mucosa or a single AP by somatic current injection elicited a late AP which appeared to be the result of synaptic interaction at or near the nerve terminal in the mucosa. In cells with spontaneous bursts of APs or where 5-HT elicited a burst of APs, application of tropisetron (10 M - 5-HT3/4 antagonist) reduced the occurrence of bursts and/or the number of APs in a burst. The electrically evoked late burst of APs was only blocked by higher concentrations of tropisetron (30 M) and was not desensitized during repeated applications of 5-HT to the mucosa. The early, antidromic AP was never blocked. In preliminary experiments, granisetron (10 M - 5-HT3 antagonist) reduced the number of APs in response to 5-HT but not to electrical stimulation. These results are consistent with the idea that 5-HT participates in chemosensory transduction, but also suggest that other substances may play a similar role. In addition, anecdotal evidence suggest that the mucosa and its afferent innervation can interact in a positive, reciprocal fashion.

  • (1999) Bertrand, P. P; Bornstein, J. C.
    Conference Paper

  • (1999) Bertrand, P. P; Kunze, W. A.; Furness, J. B.; Bornstein, J. C.
    Conference Paper
    This study aimed to characterise the receptors underlying the activation of the mucosal terminals of the myenteric intrinsic primary afferent neurons by the putative sensory mediators 5HT and ATP. Guinea pigs were stunned by a blow to the head and killed by severing the carotid arteries and spinal cord. Intracellular recordings were made in vitro from AH neurons and some S neurons located within 1 mm circumferential to intact mucosa during pressure ejection of agonists onto small regions of the mucosal surface; antagonists were applied via superfusion into the recording chamber. Trains of action potentials (APs) and/or slow EPSP-like responses were recorded in AH neurons in response to application of 5HT, 2methyl 5HT (5HT3) and ATP. No responses were recorded in response to application of the -methyl 5HT (5HT2), 5methyoxytryptamine (5HT1,2,4) or ,-methylene ATP. All responses elicited by 5HT and 2-methyl 5HT were blocked by the 5-HT receptor antagonists granisetron (5HT3 receptors) or tropisetron (5HT3,4) but not by SB 204,070 (5HT4); all at 1 M. Neither the 5-HT receptor antagonist, granisetron, nor the P2X receptor antagonists, suramin or PPADS (both at 30 M), blocked the responses to ATP. It is concluded that the mucosal processes of the AH neurons in the guinea pig small intestine possess functional 5HT3 receptors and either an atypical P2X receptor or a P1 receptor. Activation of these receptors causes AP generation in the mucosal process of the sensory neuron which then propagates to the cell body and to the other processes located in the myenteric and submucosal ganglia.

  • (1997) Chadwick, M; Boyd, Mark; Cathers, Bruce
    Conference Paper