Avidity enhancement of L-selectin bonds by flow: shear-promoted rotation of leukocytes turn labile bonds into functional tethers

L-selectin is a key lectin essential for leukocyte capture and rolling on vessel walls. Functional adhesion of L-selectin requires a minimal threshold of hydrodynamic shear. Using high temporal resolution videomicroscopy, we now report that L-selectin engages its ligands through exceptionally labile adhesive bonds (tethers) even below this shear threshold. These tethers share a lifetime of 4 ms on distinct physiological ligands, two orders of magnitude shorter than the lifetime of the P-selectin–PSGL-1 bond. Below threshold shear, tether duration is not shortened by elevated shear stresses. However, above the shear threshold, selectin tethers undergo 14-fold stabilization by shear-driven leukocyte transport. Notably, the cytoplasmic tail of L-selectin contributes to this stabilization only above the shear threshold. These properties are not shared by P-selectin– or VLA-4–mediated tethers. L-selectin tethers appear adapted to undergo rapid avidity enhancement by cellular transport, a specialized mechanism not used by any other known adhesion receptor

Assessing neuraxial microstructural changes in a transgenic mouse model of early stage Amyotrophic Lateral Sclerosis by ultra‐high field MRI and diffusion tensor metrics

bjective: Cell structural changes are one of the main features observed during the development of amyotrophic lateral sclerosis (ALS). In this work, we propose the useof diffusion tensor imaging (DTI) metrics to assess specific ultrastructural changes in the central nervous system during the early neurodegenerative stages of ALS.Methods: Ultra-high field MRI and DTI data at 17.6T were obtained from fixed, excised mouse brains, and spinal cords from ALS (G93A-SOD1) mice.Results: Changes in fractional anisotropy (FA) and linear, planar, and spherical anisotropy ratios (CL, CP, and CS, respectively) of the diffusion eigenvalues were measured in white matter (WM) and gray matter (GM) areas associated with early axonal degenerative processes (in both the brain and the spinal cord). Specifically, in WM structures (corpus callosum, corticospinal tract, and spinal cord funiculi) as the disease progressed, FA, CL, and CP values decreased, whereas CS values increased.In GM structures (prefrontal cortex, hippocampus, and central spinal cord) FA and CP decreased, whereas the CL a nd C values were unchanged or slightly smaller.Histological studies of a fluorescent mice model (YFP, G93A-SOD1 mouse) corroborated the early alterations in neuronal morphology and axonal connectivity measured by DTI.Conclusions: Changes in diffusion tensor shape were observed in this animal model at the early, nonsymptomatic stages of ALS. Further studies of CL, CP, and CSas imaging biomarkers should be undertaken to refine this neuroimaging tool for future clinical use in the detection of the early stages of ALSFil: Gatto, Rodolfo G.. University Of Illinois. Deparment Of Biological Science; Estados UnidosFil: Weissmann, Carina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Amin, Manish. University of Florida; Estados UnidosFil: Finkielsztein, Ariel. Northwestern University; Estados UnidosFil: Sumagin, Ronen. Northwestern University; Estados UnidosFil: Mareci, Thomas H.. University of Florida; Estados UnidosFil: Uchitel, Osvaldo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Magin, Richard L.. University Of Illinois. Deparment Of Biological Science; Estados Unido

Protein Dynamics in Individual Human Cells: Experiment and Theory

A current challenge in biology is to understand the dynamics of protein circuits in living human cells. Can one define and test equations for the dynamics and variability of a protein over time? Here, we address this experimentally and theoretically, by means of accurate time-resolved measurements of endogenously tagged proteins in individual human cells. As a model system, we choose three stable proteins displaying cell-cycle–dependant dynamics. We find that protein accumulation with time per cell is quadratic for proteins with long mRNA life times and approximately linear for a protein with short mRNA lifetime. Both behaviors correspond to a classical model of transcription and translation. A stochastic model, in which genes slowly switch between ON and OFF states, captures measured cell–cell variability. The data suggests, in accordance with the model, that switching to the gene ON state is exponentially distributed and that the cell–cell distribution of protein levels can be approximated by a Gamma distribution throughout the cell cycle. These results suggest that relatively simple models may describe protein dynamics in individual human cells

Protein Dynamics in Individual Human Cells: Experiment and Theory

A current challenge in biology is to understand the dynamics of protein circuits in living human cells. Can one define and test equations for the dynamics and variability of a protein over time? Here, we address this experimentally and theoretically, by means of accurate time-resolved measurements of endogenously tagged proteins in individual human cells. As a model system, we choose three stable proteins displaying cell-cycle–dependant dynamics. We find that protein accumulation with time per cell is quadratic for proteins with long mRNA life times and approximately linear for a protein with short mRNA lifetime. Both behaviors correspond to a classical model of transcription and translation. A stochastic model, in which genes slowly switch between ON and OFF states, captures measured cell–cell variability. The data suggests, in accordance with the model, that switching to the gene ON state is exponentially distributed and that the cell–cell distribution of protein levels can be approximated by a Gamma distribution throughout the cell cycle. These results suggest that relatively simple models may describe protein dynamics in individual human cells

Dapagliflozin versus empagliflozin in patients with chronic kidney disease

Background and Aim: Dapagliflozin and empagliflozin have demonstrated favorable clinical outcomes among patients with chronic kidney disease (CKD). However, their comparative monetary value for improving outcomes in CKD patients is unestablished. We examined the cost-per-outcome implications of utilizing dapagliflozin as compared to empagliflozin for prevention of renal and cardiovascular events in CKD patients.Methods: For calculation of preventable events we divided the allocated budget by the cost needed to treat (CNT) for preventing a single renal or cardiovascular event. CNT was derived by multiplying the annualized number needed to treat (aNNT) by the annual therapy cost. The aNNTs were determined based on data from the DAPA-CKD and EMPEROR-KIDNEY trials. The budget limit was defined based on the threshold recommended by the United States’ Institute for Clinical and Economic Review.Results: The aNNT was 42 both dapagliflozin (95% confidence interval [CI]: 34-59) and empagliflozin (CI: 33-66). The CNT estimates for the prevention of one primary event for dapagliflozin and empagliflozin were comparable at $201,911 (CI:$163,452-$283,636) and$209,664 (CI: $164,736-$329,472), respectively. However, diabetic patients had a higher CNT with dapagliflozin ($201,911 [CI:$153,837-$346,133]) than empagliflozin ($134,784 [CI: $109,824-$214,656]), whereas non-diabetic patients had lower CNT for dapagliflozin ($197,103 [CI:$149,029-$346,133]) than empagliflozin ($394,368 [CI: $219,648-$7,093,632]). The CNT for preventing CKD progression was higher for dapagliflozin ($427,858 [CI:$307,673-$855,717]) than empagliflozin ($224,640 [CI: $169,728-$344,448]). For preventing cardiovascular death (CVD), the CNT was lower for dapagliflozin ($1,634,515 [CI:$740,339-∞]) than empagliflozin ($2,990,208 [CI:$1,193,088-∞]).Conclusion: Among patients with CKD, empagliflozin provides a better monetary value for preventing the composite renal and cardiovascular events in diabetic patients while dapagliflozin has a better value for non-diabetic patients. Dapagliflozin provides a better monetary value for the prevention of CVD, whereas empagliflozin has a better value for the prevention of CKD progression