Extended hypoxia in the alfalfa leafcutting bee, Megachile rotundata, increases survival but causes sub-lethal effects

AbstractMany insects are tolerant of hypoxic conditions, but survival may come at a cost to long-term health. The alfalfa leaf-cutting bee, Megachile rotundata, develops in brood cells inside natural cavities, and may be exposed to hypoxic conditions for extended periods of time. Whether M. rotundata is tolerant of hypoxia, and whether exposure results in sub-lethal effects, has never been investigated. Overwintering M. rotundata prepupae were exposed to 10%, 13%, 17%, 21% and 24% O2 for 11months. Once adults emerged, five indicators of quality — emergence weight, body size, feeding activity, flight performance, and adult longevity, — were measured to determine whether adult bees that survived past exposure to hypoxia were competent pollinators. M. rotundata prepupae are tolerant of hypoxic condition and have higher survival rates in hypoxia, than in normoxia. Under hypoxia, adult emergence rates did not decrease over the 11months of the experiment. In contrast, bees reared in normoxia had decreased emergence rates by 8months, and were dead by 11months. M. rotundata prepupae exposed to extended hypoxic conditions had similar emergence weight, head width, and cross-thorax distance compared to bees reared in standard 21% oxygen. Despite no significant morphological differences, hypoxia-exposed bees had lower feeding rates and shorter adult lifespans. Hypoxia may play a role in post-diapause physiology of M. rotundata, with prepupae showing better survival under hypoxic conditions. Extended exposure to hypoxia, while not fatal, causes sub-lethal effects in feeding rates and longevity in the adults, indicating that hypoxia tolerance comes at a cost

Track E Implementation Science, Health Systems and Economics

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138412/1/jia218443.pd

Difference between static and dynamic measures of the efficacy of the paratic leg in balance maintenance

Background: Regulatory activity in the paretic and nonparetic leg of stroke patients is typically determined with center of pressure (CoP) movements obtained from force plates during quiet stance. In this approach, the regulatory activity is not evaluated with respect to its efficacy in maintaining balance. This study assessed the necessity of relating the generated activity to balance performance for a precise estimation of the contribution to balance maintenance. Methods: 9 chronic stroke patients participated in the study. The static balance contribution (SBC) of the paretic leg during quiet stance was determined by dividing the root mean square of the CoP velocity (RMSVCoP) by the sum of the RMSVCoP of the paretic and nonparetic leg. The dynamic balance contribution (DBC) of the paretic leg was determined by using a system-identification technique to relate its generated ankle torque to the sway movements obtained during quasirandom platform perturbations. The SBC and DBC were both expressed as fractions. Results: For all patients the static as well as the dynamic balance contribution was significantly smaller (P < 0.001) in the paretic as in the nonparetic leg. Furthermore, the SBC was significantly (P < 0.10) larger as the DBC. Conclusion: Although easily applicable in a clinical setting, use of the SBC leads to an overestimation of the contribution of the paretic leg. For a more precise estimate, the generated activity has to be related to the balance performance

Disentangling the contribution of the paretic and non-paretic ankle to balance control in stroke patients.

Contains fulltext : 50801.pdf (publisher's version ) (Closed access)During stroke recovery, restoration of the paretic ankle and compensation in the non-paretic ankle may contribute to improved balance maintenance. We examine a new approach to disentangle these recovery mechanisms by objectively quantifying the contribution of each ankle to balance maintenance. Eight chronic hemiparetic patients were included. Balance responses were elicited by continuous random platform movements. We measured body sway and ground reaction forces below each foot to calculate corrective ankle torques in each leg. These measurements yielded the Frequency Response Function (FRF) of the stabilizing mechanisms, which expresses the amount and timing of the generated corrective torque in response to sway at the specified frequencies. The FRFs were used to calculate the relative contribution of the paretic and non-paretic ankle to the total amount of generated corrective torque to correct sway. All patients showed a clear asymmetry in the balance contribution in favor of the non-paretic ankle. Paretic balance contribution was significantly smaller than the contribution of the paretic leg to weight bearing, and did not show a clear relation with the contribution to weight bearing. In contrast, a group of healthy subjects instructed to distribute their weight asymmetrically showed a one-on-one relation between the contribution to weight bearing and to balance. We conclude that the presented approach objectively quantifies the contribution of each ankle to balance maintenance. Application of this method in longitudinal surveys of balance rehabilitation makes it possible to disentangle the different recovery mechanisms. Such insights will be critical for the development and evaluation of rehabilitation strategies