Although many glycosylphosphatidylinositol (GPI)‐anchored proteins have been observed as soluble forms, the mechanisms by which they are released from the cell surface have not been demonstrated. We show here that a cell‐associated GPI‐specific phospholipase D (GPI‐PLD) releases the GPI‐anchored, complement regulatory protein decay‐accelerating factor (DAF) from HeLa cells, as well as the basic fibroblast growth factor‐binding heparan sulfate proteoglycan from bone marrow stromal cells. DAF found in the HeLa cell culture supernatants contained both [3H]ethanolamine and [3H]inositol, but not [3H]palmitic acid, whereas the soluble heparan sulfate proteoglycan present in bone marrow stromal cell culture supernatants contained [3H]ethanolamine. 125I‐labeled GPI‐DAF incorporated into the plasma membranes of these two cell types was released in a soluble form lacking the fatty acid GPI‐anchor component. GPI‐PLD activity was detected in lysates of both HeLa and bone marrow stromal cells. Treatment of HeLa cells with 1,10‐phenanthroline, an inhibitor of GPI‐PLD, reduced the release of [3H]ethanolamine‐DAF by 70%. The hydrolysis of these GPI‐anchored molecules is likely to be mediated by an endogenous GPI‐PLD because [3H]ethanolamine DAF is constitutively released from HeLa cells maintained in serum‐free medium. Furthermore, using PCR, a GPI‐PLD mRNA has been identified in cDNA libraries prepared from both cell types. These studies are the first demonstration of the physiologically relevant release of GPI‐anchored proteins from cells by a GPI‐PLD.

This article summarizes recent studies and is a review of the literature on the fluoride compounds and their influence on bone mineral mass. It is well known that fluoride is an important element for mineralization of body tissues. The use of topical and systemic fluoride for oral health has resulted in major reduction in dental caries, but fluoride also plays a role in bone health. Dieticians and other health professionals are advised to recommend adequate use of systemic and topical fluorides, especially in children and adolescents. Population studies as well as earlier studies of individuals exposed to fluorides indicate that doses above 30À40 mg daily can result in fluorosis, characterized by increased fracture risk. Numerous clinical studies have demonstrated increased bone mineral density in subjects treated with appropriate doses of fluoride. However, the clinical interpretation of these studies has been a matter of debate. Therapeutically, fluoride seems to be useful when the agent is started in the early stages of osteoporosis, especially in patients with intact trabecular bone. It is well established that fluoride can act as an effective stimulator of bone formation by the osteoblasts. Bisphosphonates, which can also increase bone density, act by inhibiting bone resorption by osteoclasts. As a result of this, owing to the tight paracrine association characterizing skeletal metabolism, bone formation is slowed down by the antiresorptive agents. It is of particular interest that great benefit in the treatment of osteoporoses is seen when adequate osteoblast-stimulating doses of fluorides are given in combination with antiresorptive medication, but further research is needed to substantiate this promising concept.

4′-Demethoxydaunorubicin (idarubicin [IDR]) is a new anthracycline that differs from its parent compound by the deletion of a methoxy group at position 4 of the chromophore ring. This minor structural modification results in a more lipophilic compound with a unique metabolite that has a prolonged plasma half-life as well as in vitro and in vivo antileukemia activity. To determine its activity in acute myelogenous leukemia (AML), 130 consecutive adult patients between the ages of 16 and 60 with newly diagnosed disease were randomized in a single institution study to receive either IDR in combination with cytosine arabinoside (Ara-C) or standard therapy with daunorubicin (DNR) and Ara- C. The trial was analyzed using the O′Brien-Fleming multiple testing design that allowed for periodic inspection of the data at specific patient accession points. After accrual of 60 patients per arm, analysis showed that patients who received IDR/Ara-C had a superior response compared with those who received standard therapy: 48 of 60 patients (80%) achieved complete remission on the former arm compared with 35 of 60 patients on the latter (58%, P = .005). Logistic regression analysis of factors associated with complete response indicated that treatment with IDR/Ara-C offered a significant advantage to patients who presented with a high initial white blood cell count compared with treatment with DNR/Ara-C. The degree of marrow aplasia was approximately the same on each arm as was nonhematologic toxicity. Overall survival for patients on the IDR/Ara-C arm was 19.5 months compared with 13.5 months on the DNR/Ara-C arm (P = .025) at a median follow-up of 2.5 years. We conclude that IDR/Ara-C can effectively replace standard therapy with DNR/Ara-C in adult patients less than age 60 with newly diagnosed AML.

. Basic fibroblast growth factor (bFGF)

We have shown previously that basic fibroblast growth factor (bFGF) is a mitogen for human bone marrow (BM) stromal cells and that bFGF stimulates myelopoiesis in primary BM cultures. In this article, we demonstrate the presence of bFGF in two cell lineages in human BM and peripheral blood as well as the deposition of bFGF into the extracellular matrix of BM stromal cell cultures. In immunofluorescence experiments on BM and peripheral blood smears, megakaryocytes and platelets stained strongly for bFGF, whereas weaker staining was observed in immature and mature cells of the granulocyte series. The presence of bFGF in platelets was confirmed by enzyme-linked immunosorbent assay as well as by immunoprecipitation followed by immunoblotting. bFGF was synthesized by BM stromal cell cultures and was found either cell associated or localized in the nucleus and the nucleoli, and its location was dependent on the fixation procedure used. Addition of exogenous bFGF to stromal cells showed the presence of extracellular binding molecules for this cytokine. bFGF could be released from these sites by soluble heparin or phosphatidylinositol- specific phospholipase C. This study supports the role of bFGF as a stromal cell mitogen and stimulator of myelopoiesis. The data indicate that the stromal cells produce bFGF and that their extracellular matrix can serve as a reservoir for this growth factor. In addition, the results suggest a possible involvement of bFGF in platelet function as well as in megakaryocytopoiesis.

Basic fibroblast growth factor (bFGF) is a potent mitogen for human bone marrow stromal cells. Normally, large numbers of human bone marrow stromal cells are difficult to obtain. However, nanogram/ml concentrations of bFGF stimulate the growth of passaged bone marrow stromal cells both in media formulated for optimal growth of stromal cells and in a simple mixture of RPMI-1640 and 10% fetal calf serum facilitating the successive expansion of stromal cells through multiple passages. bFGF also greatly accelerates the formation of a primary stromal cell layer following inoculation of newly harvested bone marrow cells into dishes. In the presence of bFGF, the stromal cells attain high densities, lose their contact inhibition and grow in multilayered sheets. Heparin greatly potentiates the stimulatory effect of low concentrations of bFGF. The effects of bFGF are fully reversible: cells cultured in the presence of this factor for multiple passages revert to normal growth rates following trypsinization and subculture. A short (4 h) exposure of the cells to bFGF elicits profound growth stimulation. This supports the hypothesis that this factor binds to glycosaminoglycans in the cell matrix which act as a storage reservoir for this cytokine.

Volume-localized proton NMR spectroscopy was used to estimate bone marrow cellularity in the posterior iliac crests of patients undergoing treatment with hematopoietic growth factors for a variety of hematologic and neoplastic disorders. Twelve patients were accrued, six of whom were studied more than once, yielding a total of 25 measurements. These data were compared to cellularity assessments derived from conventional bone marrow core biopsies obtained within a 24-h period before or after the NMR exam. The results obtained by the two methods are well correlated (R = 0.94, P less than 0.001), suggesting that this noninvasive technique may preclude the need for biopsies in some cases.

A 28-year-old man with evidence of feminization was demonstrated after 4 years of investigation to have an estrogen-secreting interstitial cell tumor. Such feminizing neoplasms are uncommon, only 37 having been described. They are usually benign and are characterized by gynecomastia, a testicular mass and, with lesser frequency, by decreased libido and potency and poor semen quality. The urinary excretion and plasma levels of estrogen are increased and, by selective testicular catheterization, the site of increased estrogen production can be localized. Secondary histologic changes occur in the nontumorous portions of the testis as well as in the contralateral testis; they are most marked in the area immediately adjacent to the tumor. Postoperatively, the gynecomastia regresses, the excessive levels of estrogen return to normal, libido improves, and the sperm count increases to normal.