The periaqueductal grey can differentially control A-vs. C-nociceptor-evoked spinal reflexes and deep spinal dorsal horn neuronal responses. However, little is known about the control of A-vs. C-fibre inputs to lamina I and the lateral spinal nucleus, and how this correlates with the control of deeper laminae. To address this, the laminar distributions of neurones expressing Fos-like immunoreactivity were determined following preferential activation of A-or C-heat nociceptors, using fast or slow rates of skin heating, respectively, in the absence or presence of descending control evoked from the periaqueductal grey. In lamina I, numbers of Fos-positive neurones following both fast and slow rates of skin heating were reduced significantly following activation in the ventrolateral and dorsolateral ⁄ lateral periaqueductal grey. In contrast, in the deep dorsal horn (laminae III-VI), activation in both the ventrolateral and dorsolateral ⁄ lateral periaqueductal grey significantly reduced the numbers of Fos-positive neurones evoked by C-but not A-nociceptor stimulation. C-but not A-heat nociceptor activation evoked Fos bilaterally in the lateral spinal nucleus. Stimulation in the ventrolateral but not the dorsolateral ⁄ lateral periaqueductal grey significantly increased the numbers of Fospositive neurones evoked by A-and C-nociceptor stimulation bilaterally in the lateral spinal nucleus. These data have demonstrated differences in the descending control of the superficial vs. the deep dorsal horn and lateral spinal nucleus with respect to the processing of A-and C-fibre-evoked events. The data are discussed in relation to the roles of A-and C-nociceptors in acute and chronic pain.
This paper describes the introduction of a virtual microscope (VM) that has allowed preclinical histology teaching to be fashioned to better suit the needs of approximately 900 undergraduate students per year studying medicine, dentistry or veterinary science at the University of Bristol, UK. Features of the VM implementation include: 1) the facility for students and teachers to make annotations on the digital slides; 2) in-house development of VM-based quizzes that are used for both formative and summative assessments; 3) archiving of teaching materials generated each year, enabling students to access their personalized learning resources throughout their programs; 4) retention of light microscopy capability alongside the VM. Student feedback on the VM is particularly positive about its ease of use, the value of the annotation tool, the quizzes and the accessibility of all components off-campus. Analysis of login data indicates considerable, although variable, use of the VM by students outside timetabled teaching.The median number of annual logins per student account for every course exceeded the number of timetabled histology classes for that course (1.6 -3.5 times). The total number of annual student logins across all cohorts increased from approximately 9,000 in 2007-08 to 22,000 in 2010-11. The implementation of the VM has improved teaching and learning in practical classes within the histology laboratory and facilitated consolidation and revision of material outside the laboratory. Discussion is provided of some novel strategies that capitalize on the benefits of introducing a VM, as well as strategies adopted to overcome some potential challenges.3
Since the discovery of the composition and structure of the mammalian cell membrane, biologists have had a clearer understanding of how substances enter and exit the cell's interior. The selectively permeable nature of the cell membrane allows the movement of some solutes and prevents the movement of others. This has important consequences for cell volume and the integrity of the cell and, as a result, is of utmost clinical importance, for example in the administration of isotonic intravenous infusions. The concepts of osmolarity and tonicity are often confused by students as impermeant isosmotic solutes such as NaCl are also isotonic; however, isosmotic solutes such as urea are actually hypotonic due to the permeant nature of the membrane. By placing red blood cells in solutions of differing osmolarities and tonicities, this experiment demonstrates the effects of osmosis and the resultant changes in cell volume. Using hemoglobin standard solutions, where known concentrations of hemoglobin are produced, the proportion of hemolysis and the effect of this on resultant hematocrit can be estimated. No change in cell volume occurs in isotonic NaCl, and, by placing blood cells in hypotonic NaCl, incomplete hemolysis occurs. By changing the bathing solution to either distilled water or isosmotic urea, complete hemolysis occurs due to their hypotonic effects. With the use of animal blood in this practical, students gain useful experience in handling tissue fluids and calculating dilutions and can appreciate the science behind clinical scenarios.
IgG antibodies were determined by solid-phase radioimmunoassay, using allotype-specific rabbit serum to compete with RB23 and ND13. It was found that both RB23 and ND13 are directed against the B4 sc-light-chain
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