Biomedical subjects

K R McCormick

Publications and source records attributed to K R McCormick.

3 recordsLinked to original sources

PubMed1992

The effects of thymus supernatant on the thymus homing ability of aged murine bone marrow cells.

This study examined the effect of thymus supernatant on the ability of bone marrow cells from senescent mice to home to the thymus. An in vitro and an in vivo assay were employed. The in vitro assay used a blind well migration of aged bone marrow cells to thymus supernatant across a membrane with 5-microns pores. The in vitro assay measured the ability of aged bone marrow to repopulate the thymus of an irradiated host. Our results support previous reports that the bone marrow from old mice has a greatly reduced ability to migrate to thymus supernatant and to repopulate the thymus of an irradiated host. Further, we found that a brief treatment of the old bone marrow with thymus supernatant significantly improved its thymus homing ability both in vitro and in vivo.

Aging↗

PubMed1992

Conditioning of Nude bone marrow increases in vitro migration to thymus supernatant.

The thymus must be continuously seeded by cells termed prothymocytes in order to maintain normal T-cell development (Scollay et al. 1986). Using parabiotic studies, the source of prothymocytes appears to be either from the fetal liver or the adult bone marrow (Roderwald et al. 1992). The ability of the body to distinguish self from non-self and mount a functionally mature immune response is dependent upon the intrathymic education of these cells. Therefore, it is apparent that successful migration of prothymocytes into the thymus is an inescapable event in the development and maintenance of the immune system. Utilization of the athymic Nude mouse is a valuable asset in the elucidation of the mechanisms influencing the migration of bone marrow cells into the thymus. Its aberration enables investigators to examine the effect of thymic factors on cells previously devoid of thymic influence. In an attempt to understand the migration of normal prothymocytes into the thymus, we analyzed the in vitro migration of athymic bone marrow cells towards newborn thymus supernatant. Adult athymic murine bone marrow cells were incubated in either thymus supernatant or media and allowed to migrate toward one or the other. Similar control experiments were performed using CBA adult mice. Results indicate that athymic bone marrow migration towards both supernatant and media can be restored to control levels after incubation in thymus supernatant.

Animals↗

PubMed1991

Bone marrow-thymus axis in senescence.

This presentation offers a brief review of the bone marrow-thymus axis in senescence, a putative model for thymocyte differentiation, and recent results of our work on the status of pre-thymic stem cells in aged mice. The data presented here provide further evidence for a thymus endocrine influence on the bone marrow stem cells, specifically lymphocyte precursors. It has been postulated that the thymic hormones may act on lymphocyte precursors in the bone marrow and that the loss of thymic factors during senescence may be a contributing factor to the decreased cellular immune function. This study used Haar's in vitro model to investigate the bone marrow-thymus axis in aged mice. Erythroid-depleted bone-marrow cells from 3-month- and 24-month-old CBA (Thy 1.2) mice were placed in the upper half of a blind-well chamber with thymus supernatant in the lower half. Experimental cells were treated with thymus supernatant for 1 hr prior to migration. This study confirmed that pre-thymic stem cells in aged bone marrow are deficient in their ability to migrate to the thymus supernatant. It also revealed that treatment of the old bone marrow with thymus supernatant, made from neonatal thymus cultures, could dramatically improve the thymus migrating ability of the aged bone-marrow stem cells.

Aging↗