Diffusion tensor imaging (DTI) and immunohistochemistry were used to examine axon injury in the rat spinal cord after unilateral L(2)-L(4) dorsal root axotomy at multiple time points (from 16 h to 30 ...d after surgery). Three days after axotomy, DTI revealed a lesion in the ipsilateral dorsal column extending from the lumbar to the cervical cord. The lesion showed significantly reduced parallel diffusivity and increased perpendicular diffusivity at day 3 compared with the contralateral unlesioned dorsal column. These findings coincided with loss of phosphorylated neurofilaments, accumulation of nonphosphorylated neurofilaments, swollen axons and formation of myelin ovoids, and no clear loss of myelin (stained by Luxol fast blue and 2'-3'-cyclic nucleotide 3'-phosphodiesterase). At day 30, DTI of the lesion continued to show significantly decreased parallel diffusivity. There was a slow but significant increase in perpendicular diffusivity between day 3 and day 30, which correlated with gradual clearance of myelin without further significant changes in neurofilament levels. These results show that parallel diffusivity can detect axon degeneration within 3 d after injury. The clearance of myelin at later stages may contribute to the late increase in perpendicular diffusivity, whereas the cause of its early increase at day 3 may be related to changes associated with primary axon injury. These data suggest that there is an early imaging signature associated with axon transections that could be used in a variety of neurological disease processes.
Aim Although satellite tracking has yielded much information regarding the migrations and habitat use of threatened marine species, relatively little has been published about the environmental niche ...for loggerhead sea turtles Caretta caretta in north-west Atlantic waters. Location North Carolina, South Carolina and Georgia, USA. Methods We tracked 68 adult female turtles between 1998 and 2008, one of the largest sample sizes to date, for 372.2 ± 210.4 days (mean ± SD). Results We identified two strategies: (1) 'seasonal' migrations between summer and winter coastal areas (n = 47), although some turtles made oceanic excursions (n = 4) and (2) occupation of more southerly 'year-round' ranges (n = 18). Seasonal turtles occupied summer home ranges of 645.1 km² (median, n = 42; using α-hulls) predominantly north of 35 ° latitude and winter home ranges of 339.0 km² (n = 24) in a relatively small area on the narrow shelf off North Carolina. We tracked some of these turtles through successive summer (n = 8) and winter (n = 3) seasons, showing inter-annual home range repeatability to within 14.5 km of summer areas and 10.3 km of winter areas. For year-round turtles, home ranges were 1889.9 km². Turtles should be tracked for at least 80 days to reliably estimate the home range size in seasonal habitats. The equivalent minimum duration for 'year-round' turtles is more complex to derive. We define an environmental envelope of the distribution of North American loggerhead turtles: warm waters (between 18.2 and 29.2 °C) on the coastal shelf (in depths of 3.0-89.0 m). Main conclusions Our findings show that adult female loggerhead turtles show predictable, repeatable home range behaviour and do not generally leave waters of the USA, nor the continental shelf (< 200m depth). These data offer insights for future marine management, particularly if they were combined with those from the other management units in the USA.
Many Drosophila species differ widely in their distributions and climate niches, making them excellent subjects for evolutionary genomic studies. Here, we have developed a database of high‐quality ...assemblies for 46 Drosophila species and one closely related Zaprionus. Fifteen of the genomes were newly sequenced, and 20 were improved with additional sequencing. New or improved annotations were generated for all 47 species, assisted by new transcriptomes for 19. Phylogenomic analyses of these data resolved several previously ambiguous relationships, especially in the melanogaster species group. However, it also revealed significant phylogenetic incongruence among genes, mainly in the form of incomplete lineage sorting in the subgenus Sophophora but also including asymmetric introgression in the subgenus Drosophila. Using the phylogeny as a framework and taking into account these incongruences, we then screened the data for genome‐wide signals of adaptation to different climatic niches. First, phylostratigraphy revealed relatively high rates of recent novel gene gain in three temperate pseudoobscura and five desert‐adapted cactophilic mulleri subgroup species. Second, we found differing ratios of nonsynonymous to synonymous substitutions in several hundred orthologues between climate generalists and specialists, with trends for significantly higher ratios for those in tropical and lower ratios for those in temperate‐continental specialists respectively than those in the climate generalists. Finally, resequencing natural populations of 13 species revealed tropics‐restricted species generally had smaller population sizes, lower genome diversity and more deleterious mutations than the more widespread species. We conclude that adaptation to different climates in the genus Drosophila has been associated with large‐scale and multifaceted genomic changes.
Ligation and transection of the L5 spinal nerve in the rat lead to behavioral signs of pain and hyperalgesia. Discharge of injured nociceptors has been presumed to play a role in generating the pain. ...However, A fibers, but not C fibers, in the injured L5 spinal nerve have been shown to develop spontaneous activity. Moreover, an L5 dorsal root rhizotomy does not reverse this pain behavior, suggesting that signals from other uninjured spinal nerves are involved. We asked if abnormal activity develops in an adjacent, uninjured root. Single nerve fiber recordings were made from the L4 spinal nerve after ligation and transection of the L5 spinal nerve. Within 1 d of the lesion, spontaneous activity developed in approximately half of the C fiber afferents. This spontaneous activity was at a low level (median rate, seven action potentials/5 min), originated distal to the dorsal root ganglion, and was present in nociceptive fibers with cutaneous receptive fields. The incidence and level of spontaneous activity were similar 1 week after injury. The early onset of spontaneous activity in uninjured nociceptive afferents could be the signal that produces the central sensitization responsible for the development of mechanical hyperalgesia. Because L4 afferents comingle with degenerating L5 axons in the peripheral nerve, we hypothesize that products associated with Wallerian degeneration lead to an alteration in the properties of the adjacent, uninjured afferents.
Blood clots are primarily composed of red blood cells (RBCs), platelets/thrombocytes, and fibrin. Despite the similarities observed between mammals and zebrafish, the composition of fish thrombi is ...not as well known.
To analyze the formation of zebrafish blood clots ex vivo and arterial and venous thrombi in vivo.
Transgenic zebrafish lines and laser-mediated endothelial injury were used to determine the relative ratio of RBCs and thrombocytes in clots. Scanning electron and confocal microscopy provided high-resolution images of the structure of adult and larval clots. Adult and larval thrombocyte spreading on fibrinogen was evaluated ex vivo.
RBCs were present in arterial and venous thrombi, making up the majority of cells in both circulations. However, bloodless mutant fish demonstrated that fibrin clots can form in vivo in the absence of blood cells. Scanning electron and confocal microscopy showed that larval and adult zebrafish thrombi and mammalian thrombi look surprisingly similar externally and internally, even though the former have nucleated RBCs and thrombocytes. Although adult thrombocytes spread on fibrinogen, we found that larval cells do not fully activate without the addition of plasma from adult fish, suggesting a developmental deficiency of a plasma activating factor. Finally, mutants lacking αIIbβ3 demonstrated that this integrin mediates thrombocyte spreading on fibrinogen.
Our data showed strong conservation of arterial and venous and clot/thrombus formation across species, including developmental regulation of thrombocyte function. This correlation supports the possibility that mammals also do not absolutely require circulating cells to form fibrin clots in vivo.
We sought to develop and validate a standardized cutaneous nerve regeneration model and to define the rate of epidermal nerve fibre (ENF) regeneration first in healthy control subjects and then in ...neuropathic and neuropathy‐free subjects with diabetes. Next, we assessed the effect of different factors on the rate of nerve fibre regeneration and investigated whether such an approach might offer insight into novel trial designs and outcome measures. All subjects had a standardized topical capsaicin dressing applied to the distal lateral thigh. ENF densities derived from skin biopsies were determined at baseline, after capsaicin treatment and at reinnervation time points. For each subject, the best fit line from post‐denervation data was determined and the slope was used as the rate of regeneration. In healthy control subjects, regeneration was correlated with psychophysical sensory testing, electron microscopy studies and immunohistochemistry with alternative axonal membrane markers. Topical capsaicin application produced complete or nearly complete denervation of the epidermis in both control subjects and people with diabetes. The rate of regeneration was associated with the baseline ENF density (P < 0.001), but not age (P = 0.75), gender (P = 0.18), epidermal thickness (P = 0.4) or post‐capsaicin treatment density (P = 0.7). ENF regeneration, as determined by recovery of ENF density, occurred at a rate of 0.177 ± 0.075 fibres/mm/day in healthy control subjects and was significantly reduced in subjects with diabetes (0.074 ± 0.064, P < 0.001) after adjusting for changes in baseline ENF density. Among subjects with diabetes, the presence of neuropathy was associated with a further reduction in regenerative rate (0.10 ± 0.07 versus 0.04 ± 0.03, P = 0.03), though diabetes type (P = 0.7), duration of diabetes (P = 0.3) or baseline glycated haemoglobin (P = 0.6) were not significant. These results have several implications. First, topical capsaicin application can produce a uniform epidermal nerve fibre injury that is safe and well tolerated, and offers an efficient strategy to measure and study nerve regeneration in man. Secondly, using our techniques, reduced rates of nerve regeneration were found in people with diabetes without evidence of neuropathy and indicate that abnormalities in peripheral nerve function are present early in diabetes, before signs or symptoms develop. These results suggest that regenerative neuropathy trials could include non‐neuropathic subjects and that trial duration can be dramatically shortened.
Regeneration in the peripheral nervous system is impaired after prolonged periods of denervation. Currently, no interventions exist to alter the outcome after prolonged denervation. To examine the ...role of transplanted neural stem cells (NSC), we prepared chronically denervated distal tibial nerve segments. After 6 months of chronic denervation, we transplanted vehicle, C17.2 mouse NSCs, or C17.2 mouse NSCs engineered to overexpress GDNF to the distal tibial nerve and performed a peroneal nerve cross-suture. In animals transplanted with the NSCs, there was better regeneration of the peroneal axons into the tibial nerve as measured by counting the number of axons and by the emergence of compound motor action potentials in the tibial innervated foot muscles. Improved regeneration correlated with a reduction of chondroitin sulphate proteoglycan (CSPG) immunoreactivity in the extracellular matrix (ECM). In vitro, supernatant from C17.2 NSCs contained large quantities of secreted matrix metalloprotease-2 (MMP-2), degraded the CSPGs on chronically denervated tibial nerve sections, and reversed the CSPG-induced inhibition of neuritic outgrowth of DRG neurons. This reversal was inhibited by selective MMP-2 inhibitors. This is the first successful demonstration of regeneration through a chronically denervated nerve. These findings suggest that improved regeneration in the PNS can be accomplished by combining neurotrophic factor support and removal of axon growth inhibitory components in the extracellular matrix.
Abstract Background and Aims Restless legs syndrome (RLS) is a movement disorder associated with adverse health outcomes and decreased quality of life. Small case series suggest that symptoms of RLS ...occur during opioid withdrawal. However, the prevalence is unknown. Methods We conducted an observational study to determine the prevalence of RLS among inpatients patients receiving buprenorphine detoxification from opioids. To assess the specificity of RLS to opioid detoxification, we also evaluated patients receiving detoxification from alcohol as a comparison group. The diagnosis of RLS was established using a validated questionnaire. Results The sample consisted of 124 adults with primary opioid use disorder and 180 with primary alcohol use disorder. In the total sample, 33.6% met a likely RLS diagnosis: 50.8% of those with opioid use disorder and 21.7% of those with alcohol use disorder (χ2 = 27.961,304 p < .001). In the logistic regression analysis controlling for socio-demographic and clinical variables, diagnosis of opioid use disorder was associated with more than twice the likelihood of RLS diagnosis (OR=2.05, 95% CI 1.09–3.88) relative to diagnosis of alcohol use disorder. Conclusions Approximately half of patients undergoing inpatient opioid detoxification exhibited the symptoms characteristic of RLS. We believe that these data support the existence of a secondary form of RLS associated with opioid withdrawal.
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