More Like this

1. Cell size dependent migration of T-cells latently infected with HIV

   Bohn-Wippert, K.; Dar, R.D. (March 2020, Journal of life sciences)

   null (Ed.)

   Human immunodeficiency virus (HIV) preferentially infects T-lymphocytes by integrating into host DNA and forming a latent transcriptionally silent provirus. As previously shown, HIV-1 alters migration modes of T-lymphocytes by co-regulating viral gene expression with human C-X-C chemokine receptor-4 (CXCR4). Here, we show that motility of infected T-lymphocytes is cell size dependent. In cell migration assays, migrating cells are consistently larger than non-migrating cells. This effect is drug-treatment independent. The cell size dependent motility observed in a previously generated Jurkat latency model correlates with the motility of primary human CD4+ T-cells containing a modified HIV-1 full-length construct JLatd2GFP. In addition, large migrating T-cells, latently infected with HIV, show a slightly decreased rate of reactivation from latency. these results demonstrate that HIV reactivation is cell migration-dependent, where host cell size acts as a catalyst for altered migration velocity. We believe that host cell size controlled migration uncovers an additional mechanism of cellular controlled viral fate determination important for virus dissemination and reactivation from latency. This observation may provide more insights into viral-host interactions regulating cell migration and reactivation from latency and helps in the design and implementation of novel therapeutic strategies. 

   more » « less
2. Testing Predictions for Migration of Meandering Rivers: Fit for a Curvature‐Based Model Depends on Streamwise Location and Timescale

   https://doi.org/10.1029/2022JF006776  

   Li, Yuan; Limaye, Ajay B. (December 2022, Journal of Geophysical Research: Earth Surface)

   Abstract Many meandering rivers migrate, at rates that vary both along‐stream and inversely with the observation interval. Many numerical models have been developed to predict this migration; their success is usually evaluated statistically or by qualitative comparison to observations in map view. We propose a framework to test migration models that unites these statistical, spatial, and temporal perspectives. We measure model fit with a statistic that compares the magnitude and direction of migration between predictions and observations. Model fit is contextualized in space, using a dimensionless coordinate system based in the location along a half‐meander bend; and in time, using a dimensionless observation interval that accounts for channel scale and migration rate. We applied this framework to test predictions for a curvature‐driven model of channel migration, using data from seven rapidly migrating rivers in the Amazon Basin and 103 more slowly migrating rivers across the continental US, as reconstructed from a legacy data set. We find that across both datasets, channel migration rates peak slightly downstream of the bend apex. Migration rate underestimation/overestimation tends to occur when the observed rate is greater/less than its median along the channel. Predicted migration direction opposes observations for slowly migrating locations and upstream of the bend apex. Model forecasts break down if the channel migrates by more than its width. The analysis framework is portable to testing other models of channel migration, and can help improve predictions for the stability of infrastructure along rivers and for landscape change over geologic timescales. 

   more » « less
3. A Comparison of the Mitochondrial Performance between Migratory and Sedentary Mimid Thrushes

   https://doi.org/10.1093/icb/icae137  

   Rhodes, Emma_M; Yap, Kang_Nian; Hill, Geoffrey_E; Hood, Wendy_R (August 2024, Integrative And Comparative Biology)

   Synopsis Birds exhibit a variety of migration strategies. Because sustained flapping flight requires the production of elevated levels of energy compared to typical daily activities, migratory birds are well-documented to have several physiological adaptations to support the energy demands of migration. However, even though mitochondria are the source of ATP that powers flight, the respiratory performance of the mitochondria is almost unstudied in the context of migration. We hypothesized that migratory species would have higher mitochondrial respiratory performance during migration compared to species that do not migrate. To test this hypothesis, we compared variables related to mitochondrial respiratory function between two confamilial bird species—the migratory Gray Catbird (Dumetella carolinensis) and the non-migratory Northern Mockingbird (Mimus polyglottos). Birds were captured at the same location along the Alabama Gulf Coast, where we assumed that Gray Catbirds were migrants and where resident Northern Mockingbirds live year-round. We found a trend in citrate synthase activity, which suggests that Gray Catbirds have a greater mitochondrial volume in their pectoralis muscle, but we observed no other differences in mitochondrial respiration or complex enzymatic activities between individuals from the migrant vs. the non-migrant species. However, when we assessed the catbirds included in our study using well-established indicators of migratory physiology, birds fell into two groups: a group with physiological parameters indicating a physiology of birds engaged in migration and a group with the physiology of birds not migrating. Thus, our comparison included catbirds that appeared to be outside of migratory condition. When we compared the mitochondrial performance of these three groups, we found that the mitochondrial respiratory capacity of migrating catbirds was very similar to that of Northern Mockingbirds, while the catbirds judged to be not migrating were lowest. One explanation for these observations is these species display very different daily flight behaviors. While the mockingbirds we sampled were not breeding nor migrating, they are highly active birds, living in the open and engaging in flapping flights throughout each day. In contrast, Gray Catbirds live in shrubs and fly infrequently when not migrating. Such differences in baseline energy needs likely confounded our attempt to study adaptations to migration. 

   more » « less
4. Subpage migration in heterogeneous memory systems

   Shashank Adavally, Krishna Kavi (June 2021, Workshop on Heterogeneous Memory Systems (HMEM-2021), Colocated with ICS 2021)

   With the increasing demands for very large physical address spaces and the advent of memory technologies that can support large mem- ories, there is a need to reduce the sizes of system tables such as TLBs and page tables. One can use very large (huge) pages instead of traditional 4K byte pages. However, huge pages are likely to lead to internal fragmentation and may make page migration strategies that aim to move heavily used pages to faster memories inefficient. If only a small portion of a huge page is heavily accessed, it may be worth migrating only that portion to a faster memory. This paper proposes two hardware-based page migration techniques (i) subpage migration with Address Reconciliation (that is, updating physical addresses of migrated pages) and (ii) subpage migration with Re- verse Migration (whereby no Address Reconciliation is needed). We observed speedup ranging up to 17% over migrating huge pages and up to 55% over the baseline (no migration). 

   more » « less
5. Chlorophyll shading reduces zooplankton diel migration depth in a high-resolution physical biogeochemical model

   https://doi.org/10.5194/egusphere-2024-3058  

   Poupon, Mathieu_Antoine François; Resplandy, Laure; Garwood, Jessica; Stock, Charles; Zadeh, Niki; Luo, Jessica (October 2024, EGUsphere [preprint])

   Abstract. Zooplankton diel vertical migration (DVM) is critical to ocean ecosystem dynamics and biogeochemical cycles, by supplying food and injecting carbon to the mesopelagic ocean (200–800 m). The deeper the zooplankton migrate, the longer the carbon is sequestered away from the atmosphere and the deeper the ecosystems they feed. Sparse observations show variations in migration depths over a wide range of temporal and spatial scales. A major challenge, however, is to understand the biological and physical mechanisms controlling this variability, which is critical to assess impacts on ecosystem and carbon dynamics. Here, we introduce a migrating zooplankton model for medium and large zooplankton that explicitly resolves diel migration trajectories and biogeochemical fluxes. This model is integrated into the MOM6-COBALTv2 ocean physical-biogeochemical model, and applied in an idealized high-resolution (9.4 km) configuration of the North Atlantic. The model skillfully reproduces observed North Atlantic migrating zooplankton biomass and DVM patterns. Evaluation of the mechanisms controlling zooplankton migration depth reveals that chlorophyll shading reduces by 60 meters zooplankton migration depth in the subpolar gyre compared with the subtropical gyre, with pronounced seasonal variations linked to the spring bloom. Fine-scale spatial effects (<100 km) linked to eddy and frontal dynamics can either offset or reinforce the large-scale effect by up to 100 meters. This could imply that for phytoplankton-rich regions and filaments, which represent a major source of exportable carbon for migrating zooplankton, their high-chlorophyll content contributes to reducing zooplankton migration depth and carbon sequestration time. 

   more » « less