Regional nutrition and cellularity of the meniscus. Implications for tear and repair.

The knee menisci are relatively avascular and must rely to a large degree on synovial sources of nutrition. Lack of nutrition may lead to degenerative changes and may inhibit any potential repair capabilities of the menisci. Continuous passive motion applied to the knee stimulates greater activity and/or transport of nutrients to the meniscal fibrochondrocytes. However, in an avascular model, solutes within the synovial fluid are lost by their convective transport from the joint. Regional differences in transport of a low molecular weight nutrient like sodium sulphate exist such that cells in the central core region of the meniscus are poorly supplied with nutrients by the synovial fluid and/or are less active. These conditions may be the cause of a relatively high incidence of degenerative changes in the central core region.

Immunological reactivity of maternal lymphocytes during normal pregnancy in the rat.

Thoracic duct lymphocytes from pregnant PVG rats differed markedly from similar cells collected from non-pregnant donors in their reactivity in popliteal lymph node assays performed in (PVG x DA) F1 hybrid hosts. Cells from pregnant rats failed to evoke an increase in popliteal node size commensurate with higher challenge doses of lymphocytes. This modification in maternal lymphocyte reactivity was not dependent on the presence of foetuses genetically compatible with the F1 hybrid rats used in the popliteal lymph node assay. The mechanism responsible for the decrease in size of responding F1 hybrid popliteal lymph nodes appeared to be based on a reduced capacity of lymphocytes from pregnant donors to stimulate a response by host lymphocytes.