[Cryptorchism].

Signaling through c-Kit/stem cell factor (SCF) is crucial for normal development of erythroid and myeloid hematopoietic precursors and of melanocytes and germ cells. While peripheral lymphoid populations of W/Wv and SI/SId mice appear normal, we demonstrated that the intraepithelial lymphocyte (IEL) populations of small (SI) and large (LI) intestine were significantly affected. IEL populations of young W/Wv animals were indistinguishable from those of their control littermates, but an age-dependent decrease in SI and LI TCRgamma delta IEL occurred in c-Kit mutant mice. In SI, but not in LI, this diminution was accompanied by gross expansion of TCRalpha beta IEL that resulted in significantly increased IEL:epithelial cell ratios in c-Kit mutant mice. Bromodeoxyuridine labeling studies revealed that the increase in cell numbers was due to lymphoproliferation that occurred in situ. Interestingly, TCRgamma delta IEL expressed cell surface c-Kit, while the expanding population of TCRalpha beta IEL did not. Analysis of radiation bone marrow chimeras demonstrated that the dysregulation required either disruption of stromal cell SCF or IEL c-Kit and showed that the effect on IEL or their precursors was not due to other changes in the intestinal microenvironment. Lamina propria T cell populations in these mice were unaffected, reinforcing the idea that the developmental requirements of these gut-resident lymphocyte populations are distinct. Overall, the results demonstrated that the development of intestinal TCRgamma delta IEL, regardless of location, shares common requirements for SCF, while SI and LI TCRalpha beta IEL may develop along distinct pathways. Possible mechanisms for the loss of proliferative regulation in gut T cells in c-Kit/SCF deficiency are discussed.

Age Factors↗

PubMed1997

A statewide, population-based, time series analysis of access to liver transplantation.

While the number of patients listed for liver transplant has increased, the pool of donor organs has remained constant. Questions have arisen regarding equitable access to organs. The purpose of this study was to analyze factors associated with access to liver transplantation (LT) using a large, population-based, hospital discharge database. The primary hypothesis was that a variety of factors other than medical need could be associated with access to LT. The rate of LT was defined as the number of liver transplants per admission for liver disease. The data sources were selected to allow a population-based, time-series analysis of all patients admitted with liver disease and those receiving liver transplants in all 157 nonfederal hospitals in North Carolina from 1988 to 1993. The hypotheses of this study were that age, gender, payment source, type of liver disease, distance from the transplant center, and rural county of residence were associated with patients' likelihood of access to LT. During the six years studied, 56,803 patients were admitted with liver disease and 126 underwent liver transplantation (LT). The rate of LT increased from 0.07% to 0.27%. Age, gender, source of payment, type of liver disease, rural county of residence, and distance of residence from the transplant center were associated with rates of transplantation. In the multivariate model, source of payment appeared to have the strongest association with the likelihood of LT. These findings raise important questions associated with equitable access to health care, need for physician education, and transplant center regionalization.

Age Factors↗