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J Wu, Jester WF Jr, AL Laslett, A Meinhardt, and JM Orth

In the rodent testis, contact-mediated interactions between gonocytes, or neonatal stem cells, and Sertoli cells are critical for development. Previously, we showed that the neural cell adhesion molecule (NCAM) serves as a Sertoli cell-gonocyte attachment factor in neonates. Its expression decreases dramatically by 1 week of age and eventually disappears in vivo, and appears to be down-regulated by thyroid hormone (tri-iodothyronine (T(3))). In this study, we used a cDNA microarray to screen for additional adhesion factors which might be important in testes of developing rats and detected expression of a novel factor, short-type PB-cadherin (STPB-C). Next, RT-PCR was used to generate cDNA for STPB-C from total RNA isolated from co-cultures, cDNA was cloned into pPCR-Script Amp SK(+) cloning vector, and plasmid DNA was isolated and sequenced to confirm the fidelity of the STPB-C cDNA portion of the plasmid. In situ hybridization analyses of testicular sections indicated that STPB-C expression in neonates is localized in the cytoplasm of many, but not all, gonocytes and in the cytoplasm of most of the surrounding Sertoli cells. Parallel hybridizations carried out on co-cultures also demonstrated a strong cytoplasmic signal in some gonocytes and in the great majority of the Sertoli cells of the underlying monolayer. With Northern analyses we found that STPB-C is expressed in vivo at high levels between days 1 and 5, with a subsequent large drop by day 10 and thereafter, suggesting that its expression may be associated with Sertoli or germ cell differentiation. Subsequent analyses of co-cultures exposed under a variety of conditions to T(3) suggest that, unlike NCAM, STPB-C is not regulated by this hormone. Next, we studied production of STPB-C protein by using an antiserum recognizing a peptide sequence unique to this factor in Western blotting and in immunolocalization. Signal was detected both intracellularly and at cell surfaces in most Sertoli cells and many gonocytes, although many of the latter cell type were also found to be negative for the protein, suggesting a potential role for STPB-C in survival and further development of some of these germ cells from which all subsequent spermatogenic cells originate.

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ME Pyle, M Korbonits, M Gueorguiev, S Jordan, B Kola, DG Morris, A Meinhardt, MP Powell, FX Claret, Q Zhang, C Metz, R Bucala, and AB Grossman

Macrophage migration inhibitory factor (MIF) is an essential regulator of the macrophage responses to endotoxin. MIF also has the ability to override the anti-inflammatory actions of glucocorticoids during an immune response, and is thus an important pro-inflammatory factor. The presence of MIF in cells of the anterior pituitary has been described, and high levels of MIF in other rapidly proliferating tIssues have also been demonstrated. It has been hypothesised that MIF release from these cells is influenced by the hypothalamo-pituitary-adrenal axis, and that ACTH and MIF are released simultaneously to exert counter-regulatory effects on cortisol. However, another intracellular role for MIF has also been suggested as it has been shown that MIF exerts an effect on the inhibitory cell cycle control protein p27 through an interaction with Jab1, a protein implicated in p27 degradation. We studied MIF expression in different normal and adenomatous human pituitary samples using immunohistochemistry and RT-PCR. There was evidence of co-immunoprecipitation of MIF with Jab1, suggesting an interaction of the two proteins. Our results showed that there is increased expression of MIF protein in the nuclei of all pituitary adenomas compared with normal tIssue (P=0.0067), but there was no statistically significant difference in nuclear MIF expression between the different adenoma types. Nuclear MIF expression correlated positively with p27 and its phosphorylated form in normal tIssue (P=0.0028 and P<0.0001); however, this relationship was not seen in the adenoma samples. Cytoplasmic expression of MIF was found to be variable both in normal and adenomatous samples, with no consistent pattern. MIF mRNA was demonstrated to be present in all tumour and normal samples studied. Somatotroph tumours showed higher MIF mRNA expression compared with normal pituitary or other types of adenomas. In conclusion, MIF is expressed in cell nuclei in pituitary adenomas to a greater extent than in normal pituitary tIssue. We speculate that it may play a role in the control of the cell cycle, but whether its higher level in adenomas is a cause or a consequence of the tumorigenic process remains to be clarified.