SARS-CoV-2 Seroprevalence Structure of the Russian Population during the COVID-19 Pandemic.

The SARS-CoV-2 pandemic, which came to Russia in March 2020, is accompanied by morbidity level changes and can be tracked using serological monitoring of a representative population sample from Federal Districts (FDs) and individual regions. In a longitudinal cohort study conducted in 26 model regions of Russia, distributed across all FDs, we investigated the distribution and cumulative proportions of individuals with antibodies (Abs) to the SARS-CoV-2 nucleocapsid antigen (Ag), in the period from June to December 2020, using a three-phase monitoring process. In addition, during the formation of the cohort of volunteers, the number of seropositive convalescents, persons who had contact with patients or COVID-19 convalescents, and the prevalence of asymptomatic forms of infection among seropositive volunteers were determined.

Variation of trabecular architecture in proximal femur of postmenopausal women.

This investigation of microstructure in the human proximal femur probes the relationship between the parameters of the FRAX index of fracture risk and the parameters of bone microstructure. The specificity of fracture sites at the proximal femur raises the question of whether trabecular parameters are site-specific during post-menopause, before occurrence of fragility fracture. The donated proximal femurs of sixteen post-menopausal women in the sixth and seventh decades of life, free of metabolic pathologies and therapeutic interventions that could have altered the bone tissue, constituted the material of the study.

Orientation of collagen at the osteocyte lacunae in human secondary osteons.

This work characterizes an aspect of human bone micro-structure, pertinent to fracture initiation and arrest. It addresses how the orientation of elementary components proximate to osteocyte lacunae influences secondary osteon micro-biomechanics. New data at the perilacunar region concerning orientation of collagen-apatite, and prior data on collagen orientation outside the perilacunar region, are incorporated in a novel simulation of osteons to investigate how orientation relates to strains and stresses during mechanical testing.

Collagen orientation patterns in human secondary osteons, quantified in the radial direction by confocal microscopy.

The composite structure of secondary osteon lamellae, key micro-mechanical components of human bone, has intrigued researchers for the last 300 years. Scanning confocal microscopy here for the first time systematically quantifies collagen orientations by location within the lamellar thickness. Fully calcified lamellar specimens, extinct or bright in cross-section under circularly polarized light, were gently flattened, and then examined along their thickness direction, the radial direction in the previously embedding osteon.