PubMed · 9171651
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1997. Basic life support.. https://pubmed.ncbi.nlm.nih.gov/9171651/
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The spontaneous healing of osteochondral defects in the knee joints of immature rabbits within the first 12 weeks after surgery showed a faster filling and earlier tissue specialization than in adult animals. The purpose of the present study was to investigate whether the better short-term quality of spontaneous repairs in immature animals lasted over a period of 48 weeks. A full-thickness osteochondral defect was created on the medial femoral condyle in both knees of 10 young, 10 adolescent, and 10 adult rabbits. Equal numbers of animals were evaluated after 24 and 48 weeks. At both time intervals, bonding to adjacent cartilage and proteoglycan content of the matrix were better in the repairs of young than in adult animals. Repairs in the former had cellularity similar to the adjacent cartilage and were composed of 90% hyaline-like cartilage, which did not decrease with time. In contrast, repairs in older animals formed less hyaline-like cartilage and had a lower cellularity than the adjacent cartilage. However, the surface of the repaired tissue was similarly disrupted in all age groups, and the mechanical properties remained inferior to adjacent or normal cartilage. Repairs in older animals showed signs of degeneration with time. The initial better repair quality in a young, growing animal remained up to 48 weeks when the animal had already reached maturity, indicating that successful initial promotion of cartilage repair may even lead to better results in the long term. However, it has to be pointed out that the morphologically good repairs with hyaline-like cartilage appearance, normal cellularity, and durability of up to 48 weeks were unable to reestablish and maintain a cartilage-like mechanical function.
We investigate the role played by dendritic cells (DCs) in the non-obese diabetic (NOD) mouse pancreas. The early peri-islet, nondestructive infiltration phase, and intra-islet, destructive infiltration phase, which immediately precedes overt diabetes, are studied. Results show that infiltrating cells are Ia-b, ICAM-1, and, mainly, MIDC-8 immunoreactive (ir). These data from silica-treated animals and ultrastructural observations strongly support the hypothesis that DCs are both Ia-b-ir and ICAM-1-ir and that they exert a pivotal role during the period of early infiltration. This is a novel finding for NOD mice and increases the interest for this protective cell type during the rather complex islet infiltration process. Moreover, the cytokine profile demonstrates that Th2 protective cytokines are specific for peri-islet infiltrate. Disappearance of DCs from the infiltrate is concomitant with both the formation of intra-islet infiltration and the increase in proinflammatory Th1 cytokine levels. This further supports the hypothesis that DCs may exert a protective role against diabetes development.
To study the lifespan of virgin T lymphocytes, we removed the thymus from adult female mice and then, at various times afterward, tested their ability to mount an immune response to a newly encountered Ag, the male Ag H-Y. We found that unprimed thymectomized mice were able to generate a primary response to H-Y for some time after thymectomy but lost this ability at approximately 6 mo. In contrast, mice that were primed to H-Y just after thymectomy continued to display immunological memory to H-Y for >1 year. These experiments show that primary immune responses disappear in the absence of a thymus.