The objective of this study was to determine if SI, a method to eliminate the supraspinal and peripheral activation of α‐Mns, influences their electrophysiological properties. Rats were subjected to ...SI via complete mid‐thoracic and high sacral spinal cord transections, and bilateral dorsal rhizotomy between the transection sites. About 1 month post‐surgery, α‐Mns (n = 20 for SI and n = 45 for control) located in the lumbar enlargement (identified by antidromically stimulated field potentials of the sciatic nerve) of anesthetized (ketamine‐xylazine) rats were impaled via sharp glass microelectrodes to measure their passive and active electrophysiological properties. Results demonstrated that SI significantly (p < 0.01) increased α‐Mns afterhyperpolarization (AHP) amplitude and input resistance by 29 and 41%, respectively, and decreased rheobase by 26% compared to control. Furthermore, SI significantly (p < 0.05) decreased α‐Mns maximal steady‐state firing frequency, f‐I gain, and late adaptation by 30, 25, and 30%, respectively compared to controls. These changes suggest that the passive and active properties of α‐Mns are altered by SI, becoming smaller, less excitable, and quicker to adapt during the late phase of adaptation (>5 s) compared to age‐matched controls.
Supported by funds from CIHR, CSA, NSERC, and NIH NS16333.
There were two major objectives for this thesis: (1) to integrate the existing literature based on vigilance, noise, and neuromuscular fatigue and (2) to determine the effects of muscle contraction ...intensity, neuromuscular fatigue, and noise on the performance of complex and simple vigilance tasks. Vigilance or an individual's state of physiological or psychological readiness to mediate performance when reacting to a stimulus can be affected simultaneously by noise and neuromuscular stimuli. Noise exposure and muscle contraction have been shown to both negatively and positively affect vigilance performance. However, this contradiction may be a result of differences in muscle contraction and noise intensities, durations, and type as well as the complexity of the vigilance task. It was determined in the present experiment that continuous noise at an intensity of 95 dB (A) impairs both simple and to a greater extent complex vigilance task performance. Isometric muscle contractions at 5% and 20% of a maximum voluntary contraction also impaired simple and complex vigilance task performance. There did not seem to be an interaction effect between noise and contraction intensity.
Abstract
Biological phenotypes in patients with the acute respiratory distress syndrome (ARDS) have previously been described. We hypothesized that the trajectory of PaO
2
/F
I
O
2
ratio could be ...used to identify phenotypes of ARDS. We used a retrospective cohort analysis of an ARDS database to identify latent classes in the trajectory of PaO
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/F
I
O
2
ratio over time. We included all adult patients admitted to an intensive care unit who met the Berlin criteria for ARDS over a 4-year period in tertiary adult intensive care units in Manitoba, Canada. Baseline demographics were collected along with the daily PaO
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/F
I
O
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ratio collected on admission and on days 1–7, 14 and 28. We used joint growth mixture modeling to test whether ARDS patients exhibit distinct phenotypes with respect to both longitudinal PaO
2
/F
I
O
2
ratio and survival. The resulting latent classes were compared on several demographic variables. In our study group of 209 patients, we found that four latent trajectory classes of PaO
2
/F
I
O
2
ratio was optimal. These four classes differed in their baseline PaO
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/F
I
O
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ratio and their trajectory of improvement during the 28 days of the study. Despite similar baseline characteristics the hazard for death for the classes differed over time. This difference was largely driven by withdrawal of life sustaining therapy in one of the classes. Latent classes were identified in the trajectory of the PaO
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/F
I
O
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ratio over time, suggesting the presence of different ARDS phenotypes. Future studies should confirm the existence of this finding and determine the cause of mortality differences between classes.
What do you mean, ‘megafire’? Linley, Grant D.; Jolly, Chris J.; Doherty, Tim S. ...
Global ecology and biogeography,
October 2022, 2022-10-00, 20221001, 2022-10, Letnik:
31, Številka:
10
Journal Article
Recenzirano
Odprti dostop
Background
‘Megafire’ is an emerging concept commonly used to describe fires that are extreme in terms of size, behaviour, and/or impacts, but the term’s meaning remains ambiguous.
Approach
We sought ...to resolve ambiguity surrounding the meaning of ‘megafire’ by conducting a structured review of the use and definition of the term in several languages in the peer‐reviewed scientific literature. We collated definitions and descriptions of megafire and identified criteria frequently invoked to define megafire. We recorded the size and location of megafires and mapped them to reveal global variation in the size of fires described as megafires.
Results
We identified 109 studies that define the term ‘megafire’ or identify a megafire, with the term first appearing in the peer‐reviewed literature in 2005. Seventy‐one (~65%) of these studies attempted to describe or define the term. There was considerable variability in the criteria used to define megafire, although definitions of megafire based on fire size were most common. Megafire size thresholds varied geographically from > 100–100,000 ha, with fires > 10,000 ha the most common size threshold (41%, 18/44 studies). Definitions of megafire were most common from studies led by authors from North America (52%, 37/71). We recorded 137 instances from 84 studies where fires were reported as megafires, the vast majority (94%, 129/137) of which exceed 10,000 ha in size. Megafires occurred in a range of biomes, but were most frequently described in forested biomes (112/137, 82%), and usually described single ignition fires (59% 81/137).
Conclusion
As Earth’s climate and ecosystems change, it is important that scientists can communicate trends in the occurrence of larger and more extreme fires with clarity. To overcome ambiguity, we suggest a definition of megafire as fires > 10,000 ha arising from single or multiple related ignition events. We introduce two additional terms – gigafire (> 100,000 ha) and terafire (> 1,000,000 ha) – for fires of an even larger scale than megafires.
Biological phenotypes in patients with the acute respiratory distress syndrome (ARDS) have previously been described. We hypothesized that the trajectory of PaO
/F
O
ratio could be used to identify ...phenotypes of ARDS. We used a retrospective cohort analysis of an ARDS database to identify latent classes in the trajectory of PaO
/F
O
ratio over time. We included all adult patients admitted to an intensive care unit who met the Berlin criteria for ARDS over a 4-year period in tertiary adult intensive care units in Manitoba, Canada. Baseline demographics were collected along with the daily PaO
/F
O
ratio collected on admission and on days 1-7, 14 and 28. We used joint growth mixture modeling to test whether ARDS patients exhibit distinct phenotypes with respect to both longitudinal PaO
/F
O
ratio and survival. The resulting latent classes were compared on several demographic variables. In our study group of 209 patients, we found that four latent trajectory classes of PaO
/F
O
ratio was optimal. These four classes differed in their baseline PaO
/F
O
ratio and their trajectory of improvement during the 28 days of the study. Despite similar baseline characteristics the hazard for death for the classes differed over time. This difference was largely driven by withdrawal of life sustaining therapy in one of the classes. Latent classes were identified in the trajectory of the PaO
/F
O
ratio over time, suggesting the presence of different ARDS phenotypes. Future studies should confirm the existence of this finding and determine the cause of mortality differences between classes.
We have prepared antibodies specific for HSET, the human homologue of the KAR3 family of minus end-directed motors. Immuno-EM with these antibodies indicates that HSET frequently localizes between ...microtubules within the mammalian metaphase spindle consistent with a microtubule cross-linking function. Microinjection experiments show that HSET activity is essential for meiotic spindle organization in murine oocytes and taxol-induced aster assembly in cultured cells. However, inhibition of HSET did not affect mitotic spindle architecture or function in cultured cells, indicating that centrosomes mask the role of HSET during mitosis. We also show that (acentrosomal) microtubule asters fail to assemble in vitro without HSET activity, but simultaneous inhibition of HSET and Eg5, a plus end-directed motor, redresses the balance of forces acting on microtubules and restores aster organization. In vivo, centrosomes fail to separate and monopolar spindles assemble without Eg5 activity. Simultaneous inhibition of HSET and Eg5 restores centrosome separation and, in some cases, bipolar spindle formation. Thus, through microtubule cross-linking and oppositely oriented motor activity, HSET and Eg5 participate in spindle assembly and promote spindle bipolarity, although the activity of HSET is not essential for spindle assembly and function in cultured cells because of centrosomes.
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