Vibration from a riveting hammer causes severe nerve damage in the rat tail model

Introduction: Hand–arm vibration syndrome (HAVS) is an occupational neurodegenerative and vasospastic disorder in workers who use powered hand tools. Frequency weighting (ISO 5349) predicts little risk of injury for frequencies >500 HZ . Potentially damaging high frequencies abound in impact tool–generated shock waves. Methods: A rat tail impact vibration model was developed to deliver shock‐wave vibration from a riveting hammer to simulate bucking bar exposure. Rat tails were vibrated continuously for 12 min. Tail flick withdrawal times were determined for noxious heat. Nerve trunks and skin were processed for light and electron microscopy. Results: Immediately after vibration, the tails were hyperalgesic and had disrupted myelinated axons, fragmented nerve endings, and mast‐cell degranulation. By 4 days, the tails were hypoalgesic; nerve endings were lost in the skin. Conclusions: Shock‐wave vibration causes severe nerve damage. Frequency weighting seriously underestimates the risk of nerve injury with impact tools. Muscle Nerve, 2011     

Electrophysiological characteristics of cells in the anterior caudal lobe of the mormyrid cerebellum

We have examined the basic electrophysiology and pharmacology of cells in the anterior caudal lobe (CLa) of the mormyrid cerebellum. Intracellular recordings were performed in an in vitro slice preparation using the whole-cell patch recording method. The responses of cells to parallel fiber (PF) and climbing fiber (CF) stimulation and to somatic current injection were recorded, and then characterized by bath application of receptor and ion channel blockers. Using biocytin or neurobiotin, these cells were also morphologically identified after recording to ensure their classification. Efferent cells and two subtypes of Purkinje cells were identified on the basis of their physiology and morphology. While the majority of Purkinje cells fire a single type of spike that is mediated by Na⁺, some fire a large broad spike mediated by Ca²⁺ and a narrow spike mediated by Na⁺ at resting potential levels. By patching one recording electrode to the soma and another to one of the proximal dendrites of the same cell simultaneously, it was found that the Na⁺ spike has an axonal origin and the Ca²⁺ spike is generated in the soma-dendritic region of Purkinje cells. Efferent cells fire a single type of Na⁺ spike only. Despite variations in their physiology and morphology, all cell types responded to PF stimulation with graded excitatory postsynaptic potentials (EPSPs) mediated by AMPA receptors. However, none of the efferent cells and only some of the Purkinje cells responded to CF activation with a large, AMPA receptor-mediated all-or-none EPSPs. We conclude that the functional circuitry of the CLa resembles that of other regions of the mormyrid cerebellum and is largely similar to that of the mammalian cerebellum.     

Perinatal development of the pancreatic islet microvasculature in rats

The aim of the present study was to investigate possible changes in the islet microvasculature during the period of pronounced beta-cell growth seen perinatally in rats. We studied islet endothelial and beta-cell proliferation, as well as islet vascular density, in rats during this period. There was a progressive increase in islet vascular density from day -1 to day 7 postpartum, with values similar to those in adult rats seen at the latter time point. (3)H-thymidine-labelled islet endothelial cells were extremely rare in adult rats, whereas such cells were much more frequent perinatally. The beta-cell labelling index was higher in all perinatal animals than in adult rats, with peak values seen on day 2. The proliferating endocrine cells were located very close to blood vessels at day 2 after birth. In conclusion, the pronounced growth of islet endocrine cells seen during the first week after birth coincides and co-localizes with an even more pronounced increase in islet endothelial cell proliferation, which results in a marked increase in intra-islet vascular density. This perinatal increase in islet blood vessel density may facilitate glucose sensing and islet hormonal delivery to the systemic circulation.