Biology subjects

Leo, H. L.

Publications and source records attributed to Leo, H. L..

2 recordsLinked to original sources

bioRxiv2026

Erythrocyte aging links hypocalcemia to impaired flow dynamics and oxygen transport through volume dysregulation

Red blood cells (RBCs) maintain their corpuscular volume through mechanotransducive ion-mediated processes in response to circulatory shear stress. However, with age, RBCs accumulate oxidative damage and undergo alterations in protein function, glucose metabolism and ion transport, raising fundamental questions about how volume homeostasis is preserved under mechanical load. Here, we investigated the differential responses of younger (YRBCs) and older RBCs (ORBCs) to fluid shear stress, with a focus on calcium-dependent regulation. We found that ORBCs exhibited a striking dependence on extracellular calcium to maintain volume stability. In calcium-depleted conditions, only ORBCs underwent pronounced post-shear swelling, with recovery only partially restored by ATP-dependent mechanisms. In contrast, calcium preserved volume homeostasis, identifying calcium-sensitive pathways as key compensatory regulators in metabolically compromised ORBCs. Notably, metabolically deficient YRBCs recapitulated the ORBC swelling phenotype, supporting a shift from ATP to calcium-dependent regulation with age. More importantly, shear-induced swelling impaired flow behaviour and oxygen delivery in ORBCs, linking defective volume control to microcirculatory dysfunction. Together, these findings potentially established calcium-dependent volume regulation as a critical adaptive mechanism in ageing RBCs and reveal a previously unrecognized hematological link to vascular dysfunction in hypocalcemia.

bioengineering↗

bioRxiv2025

Bruch's Membrane Contributes to the Structural Integrity of the Human Eye

PurposeTo investigate the contribution of the Bruchs membrane and sclera tissues to the overall structural integrity of the ocular wall. MethodsTwenty-three human globes were subjected to biomechanical testing. A piece of sclera measuring 5 x 5 mm was carefully removed at the nasal region, 2 mm away from the optic nerve head. The intraocular pressure was increased at approximately 1 mmHg/s until Bruchs membrane-uvea-retina-tissue layer (BMUR) ruptured. Next, strips of sclera and Bruchs membrane-choriocapillaris (BMC) complex were isolated from the superior fundus region. Uniaxial tension tests were performed at a strain rate of 0.01/s and sampling rate of 15 Hz. The tangent moduli of the BMC and sclera at 0.01, 0.02 and 0.03 strains were compared. ResultsThe rupture pressure of the BMUR was 98.1 {+/-} 21.4 mmHg. The tangent moduli of the BMC at 0.01, 0.02 and 0.03 strains were 2.96 {+/-} 1.44 MPa, 7.68 {+/-} 1.78 MPa and 9.43 {+/-} 2.11 MPa, respectively, and the tangent moduli of the sclera at 0.01, 0.02 and 0.03 strains were 1.09 {+/-} 0.80 MPa, 2.72 {+/-} 1.67 MPa and 5.69 {+/-} 3.27 MPa, respectively. ConclusionThe BMUR was able to sustain relatively high IOP before rupturing. The uniaxial tensile tests showed that the BMC tangent moduli were about 3 times of those of the sclera at strains of 0.01 and 0.02. Although the sclera is approximately 47 times thicker, the BMC is still likely to make a significant contribution (3.51% to 7.42% at strain <0.03) to the overall structural strength of the ocular wall.

bioengineering↗