Histology and ultrastructure of a tissue-engineered collagen meniscus before and after implantation

The collagen meniscus implant (CMI) is a tissue-engineering technique designed to stimulate regeneration of meniscus-like tissue in cases of irreparable tears or previous meniscectomy. CMI morphology was investigated before and after implantation by light microscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). In a case series biopsy specimens were harvested from four patients who underwent a second arthroscopic look 6 months after placement of the CMI. CMI sections appeared composed of parallel connective laminae of 10-30 mu m, connected by smaller bundles (5-10 mu m). This connective network formed lacunae with diameters between 40 and 60 mu m. At greater magnification, the walls of the lacunae demonstrated tightly packed and randomly distributed collagen fibrils, with diameters ranging from 73 to 439 nm. In the biopsy specimens, the lacunae were filled with connective tissue that contained newly formed vessels and fibroblast-like cells, presenting an abundant rough endoplasmic reticulum and several mitochondria. In the extracellular matrix, the collagen fibrils showed uniform diameters (126 nm +/- 32 nm). The original structure of CMI was still recognizable, and no inflammatory cells were detected within the implant. The morphological findings of this case series demonstrate that CMI provides a three-dimensional scaffold suitable for colonization by precursor cells and vessels and leading to the formation of a fully functional tissue

Late preceramic farmer-foragers in southeastern Arizona : a cultural and ecological consideration of the spread of agriculture into the arid southwestern United States

This study investigates the transition from hunting and gathering economies to mixed economies involving both agriculture and hunting and gathering. Specifically, the problem of when, why, and how the transition to agriculture occurred in the arid-semiarid river basins of southeastern Arizona is explored. Modern environmental conditions are described, and the nature and sources of climatic, biotic, and fluvial systemic variability are considered. Anthropological and ecological models of hunter-gatherer adaptations to arid environments are used to reconstruct the general subsistence economy of preagricultural societies in the region, and to portray the process of the spread of agricultural production strategies. Two models of the transition are presented, one involving the adoption of agriculture by indigenous hunting-gathering societies, and the other involving the arrival of immigrant societies already practicing agriculture to a significant degree. Previous studies of the transition to agriculture in the American Southwest are reviewed, and new data are presented from excavated Late Archaic (ca. 3000-2000 BP) sites in southeastern Arizona. These data show that agriculture appeared by at least 2800 BP in this area, and that it spread rapidly across the American Southwest. It was already an important subsistence strategy and was associated with semisedentary village sites that have no known predecessors in the archaeological record. It is concluded that the adoption of agriculture, with its associated storage technology, is an important strategy by which human populations can mitigate some of the risks associated with foraging in an environment characterized by predictable seasonal variation in resource availability and unpredictable, climatically-induced fluctuations in the productivity of wild resources over time.hydrology collectio

A Unified Reduced Order Model for Standing Balance Captures Biological Balance Strategy Preferences

The 9.5th international symposium on Adaptive Motion of Animals and Machines. Ottawa，Canada (Virtual Platform). 2021-06-22/25. Adaptive Motion of Animals and Machines Organizing Committee