Impact of age on postsurgical outcomes of nonfunctioning pituitary adenomas.

PURPOSE: The management of pituitary adenomas in the elderly has become a relevant clinical issue, in relationship with improved life expectancy and spreading use of imaging techniques. In this single-center and retrospective study, we investigated the impact of age on peri- and postsurgical outcomes in patients undergoing transnasal sphenoidal (TNS) surgery for pituitary adenomas. METHODS: One-hundred-sixty-nine patients (62% males) undergoing endoscopic transphenoidal (TNS) surgery for nonfunctioning pituitary adenomas (NFPAs) were enrolled. Patients were subdivided into three groups according to age tertiles: ≤56 (group 1), 57-69 (group 2), and ≥70 (group 3) years. Postsurgical and endocrinological outcomes were evaluated and compared among the three age groups. RESULTS: 37/169 patients (21.9%) developed at least one perisurgical complication, without significant association with the patients' age (P = 0.838), Charlson co-morbidity score (P = 0.326), and American Society of Anesthesiologist score (P = 0.616). In the multivariate regression analysis, the adenoma size resulted the only determinant of perisurgical complication (odds ratio [OR] 1.07, 95% confidence interval [C.I.] 1.00-1.13; P = 0.044). The development and the recovery of at least one pituitary hormone deficiency were observed in 12.2% and 14.2% of patients, respectively. The risk of developing new pituitary hormone deficiencies was correlated with cavernous sinus invasion as evaluated by magnetic resonance imaging (hazard ratio [HR] 4.19, 95% C.I. 1.39-12.66; P = 0.010), whereas the probability to normalize at least one pituitary hormone deficiency was significantly correlated with younger age of patients (HR 0.27, 95% CI 0.12-0.61; P = 0.002). CONCLUSIONS: The results of this study reinforce the concept that endoscopic TNS surgery is a safe therapeutic option in the elderly patients with NFPA, even in presence of comorbidities and high anesthetic risk.

Effects of oil sands process water mixtures on the mayfly Hexagenia and field-collected aquatic macroinvertebrate communities.

Extraction of Canada's oil sands has created 1 billion m3 of tailings, which are stored in on-site tailings ponds. Due to limited storage capacity, the planned release of tailings into the surrounding environment may be required. This represents an environmental management challenge, as the tailings contain contaminants that are known toxins to aquatic communities. Of particular concern are naphthenic acids and their metallic counterparts, as they are the principal toxic components of tailings, are relatively soluble, and are persistent in aquatic environments. This study examines the acute toxicity of environmentally relevant 10:1 mixtures of two process water components: naphthenic acid and sodium naphthenate. We assess the effects of these simplified oil sands process water (OSPW) mixtures under planned and unplanned tailings release scenarios, using traditional and cutting-edge bioindicators for aquatic invertebrate taxa. We found that safe concentrations for mayflies and other aquatic macroinvertebrates were less than 1 mg/l, as no mayfly taxa survived repeated exposure to this dose in either the 48-h or 72-h acute toxicity test. In the 72-h test, no mayflies survived treatment levels greater than 0.5 mg sodium naphthenate/l. In the mesocosm study, even a 90% dilution of the OSPW mixture was not sufficient to protect sensitive macroinvertebrate communities. The results of this study highlight the potential environmental damage that will occur if OSPW is not carefully managed. This information will aid with the development of a management plan for oil sands tailings ponds, which will provide insight into the potential for process water release into the surrounding environment while conserving unique ecosystems downstream of development in the oil sands region.

Ovarian hydatid cyst: A case report.

Discovering an hydatid cyst in pelvic region, especially as primary localization, is a rare event; as a matter of fact according to data provided by literature the incidence is between 0.2 and 2.25%. The ovarian involvement is often secondary to a cyst's dissemination localized in a different site. When possible the optimal treatment is represented by radical laparotomic cystectomy. We report a case of an old woman affected by this pathology that we have treated with a cyst's marsupialization after a draining and irrigation of cyst cavity with hypertonic saline solutions.

Activation of PKC-epsilon counteracts maturation and apoptosis of HL-60 myeloid leukemic cells in response to TNF family members.

Protein kinase C (PKC)-epsilon, a component of the serine/threonine PKC family, has been shown to influence the survival and differentiation pathways of normal hematopoietic cells. Here, we have modulated the activity of PKC-epsilon with specific small molecule activator or inhibitor peptides. PKC-epsilon inhibitor and activator peptides showed modest effects on HL-60 maturation when added alone, but PKC-epsilon activator peptide significantly counteracted the pro-maturative activity of tumor necrosis factor (TNF)-alpha towards the monocytic/macrophagic lineage, as evaluated in terms of CD14 surface expression and morphological analyses. Moreover, while PKC-epsilon inhibitor peptide showed a reproducible increase of TNF-related apoptosis inducing ligand (TRAIL)-induced apoptosis, PKC-epsilon activator peptide potently counteracted the pro-apoptotic activity of TRAIL. Taken together, the anti-maturative and anti-apoptotic activities of PKC-epsilon envision a potentially important proleukemic role of this PKC family member.

Colovesical fistulae in the sigmoid diverticulitis.

In most cases Colovesical fistulae are complications of diverticular disease and representing the most common kind of colodigestive fistula; less common are colovaginal, colocutaneous, coloenteric and colouterine fistula. In this article we review the literature concerning colovesical fistulae in colorectal surgery for sigmoid diverticulitis and report on two cases that required a surgical treatment, one elective and the other in emergency. In both cases we performed a sigmoid resection with a primary anastomosis and small vesical window-ectomy placing a Foley catheter for about 10 days.

Activation of PKC-ε counteracts maturation and apoptosis of HL-60 myeloid leukemic cells in response to TNF family members.

Protein kinase C (PKC)-ε, a component of the serine/threo-nine PKC family, has been shown to influence the survival and differentiation pathways of normal hematopoietic cells. Here, we have modulated the activity of PKC-ε with specific small molecule activator or inhibitor peptides. PKC-ε inhibitor and activator peptides showed modest effects on HL-60 maturation when added alone, but PKC-ε activator peptide significantly counteracted the pro-maturative activity of tumor necrosis factor (TNF)-α towards the monocytic/macrophagic lineage, as evaluated in terms of CD14 surface expression and morphological analyses. Moreover, while PKC-ε inhibitor peptide showed a reproducible increase of TNF-related apoptosis inducing ligand (TRAIL)-induced apoptosis, PKC-ε activator peptide potently counteracted the pro-apoptotic activity of TRAIL. Taken together, the anti-maturative and anti-apoptotic activities of PKC-ε envision a potentially important proleukemic role of this PKC family member.

TRAIL promotes the survival, migration and proliferation of vascular smooth muscle cells.

Human and rat primary sub-cultured vascular smooth muscle cells (VSMCs) showed clear expression of the death receptors TRAIL-R1 and TRAIL-R2; however, recombinant soluble TRAIL did not induce cell death when added to these cells. TRAIL tended to protect rat VSMCs from apoptosis induced either by inflammatory cytokines tumor necrosis factor-alpha + interleukin-1beta + interferon-gamma or by prolonged serum withdrawal, and promoted a significant increase in VSMC proliferation and migration. Of note, all the biological effects induced by TRAIL were significantly inhibited by pharmacological inhibitors of the ERK pathway. Western blot analysis consistently showed that TRAIL induced a significant activation of ERK1/2, and a much weaker phosphorylation of Akt, while it did not affect the p38/MAPK pathway. Taken together, these data strengthen the notion that the TRAIL/TRAIL-R system likely plays a role in the biology of the vascular system by affecting the survival, migration and proliferation of VSMCs.

The HIV-1 transactivator protein Tat is a potent inducer of the human DNA repair enzyme beta-polymerase.

OBJECTIVE: This study examines the effects of the HIV-1 regulatory proteins, Tat and Rev, on the expression of the DNA polymerase beta (beta-pol) gene, which encodes a key protein in the DNA base-excision repair pathway. The rationale for these experiments is to examine the potential involvement of base-excision repair protein deregulation in HIV-1-related lymphomas. DESIGN: Expression of beta-pol mRNA was examined in AIDS-related lymphomas and non-AIDS-related lymphomas and as a function of HIV-1 infection of B cells in culture. The effect of Tat or Rev over-expression on beta-pol promoter expression was tested by transient co-transfection assays with a beta-pol promoter reporter plasmid and a Tat or Rev over-expression plasmid. METHODS: Northern blot analysis was used to quantitate beta-pol expression in lymphoma and cells. Raji cells were co-transfected with a chloramphenicol acetyltransferase (CAT) reporter plasmid and a plasmid over-expressing Tat or Rev. CAT activity was measured in transfected cells. RESULTS: beta-Pol mRNA was > 10-fold higher in AIDS-related than in non-AIDS B-lineage lymphomas. beta-Pol expression was up-regulated in a B-cell line upon infection with HIV-1, and increased in Raji cells upon recombinant expression of the Tat gene. The beta-pol promoter was transactivated (fourfold induction) by Tat, but not by Rev. Tat-dependent transactivation required a binding site for the transcription factor Sp1 in the beta-pol promoter. CONCLUSION: These results suggest that HIV-1 Tat can interact with cellular transcription factors to increase the steady-state level of beta-pol in B cells. Tat-mediated induction of beta-pol may alter DNA stability in AIDS-related lymphomas.

HIV-1 Tat protein down-regulates CREB transcription factor expression in PC12 neuronal cells through a phosphatidylinositol 3-kinase/AKT/cyclic nucleoside phosphodiesterase pathway.

The addition of low concentrations (0.1-1 nM) of extracellular HIV-1 Tat protein to PC12 neuronal cells stimulated a rapid (peak at 5 min) elevation of the cAMP intracellular levels, which in turn induced the phosphorylation of CREB transcription factor (peak at 15 min) on serine-133 (Ser-133). On the contrary, at later time points (60-120 min) Tat induced a significant decline of intracellular cAMP with respect to the basal levels observed in control cells treated with bovine serum albumin. In blocking experiments performed with pharmacological inhibitors, Tat decreased the intracellular levels of cAMP and CREB Ser-133 phosphorylation through a signal transduction pathway involving the sequential activation of phosphatidylinositol 3-kinase, AKT, and cyclic nucleoside phosphodiesterases. Moreover, in transient transfection experiments, Tat inhibited transcription of CREB promoter in a manner strictly dependent on the presence of the cAMP-responsive elements (CRE) in the CREB promoter. Consistently, the expression of endogenous CREB protein was significantly reduced in PC12 cells by prolonged (24-48 h) treatment with Tat. This decline in the expression of CREB, which plays an essential role in the survival and function of neuronal cells, anticipated a progressive increase of apoptosis in Tat-treated cells. Although obtained in a neuronal cell line, our findings might help to explain some aspects of the pathogenesis of HIV-1-associated dementia.

HIV-1 Tat-mediated inhibition of the tyrosine hydroxylase gene expression in dopaminergic neuronal cells.

Treatment of dopaminergic rat PC12 cells with human immunodeficiency virus, type 1 (HIV-1) Tat protein or tat cDNA inhibited the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme for the dopamine biosynthetic pathway, as well as the production and release of dopamine into the culture medium. Moreover, the Tat addition to PC12 cells up-regulated the expression of the inducible cAMP early repressor (ICER), a specific member of the cAMP-responsive element modulator transcription factor family, in a cAMP-dependent manner. In turn, ICER overexpression abrogated the transcription activity of the TH promoter in PC12 cells, strongly suggesting ICER involvement in Tat-mediated inhibition of TH gene expression. In vivo injection of synthetic HIV-1 Tat protein into the striatum of healthy rats induced a subclinical Parkinson's-like disease that became manifested only when the animals were treated with amphetamine. As early as one week postinjection, the histochemical examination of the rat substantia nigra showed a reduced staining of neurons expressing TH followed by a loss of TH(+) neurons at later time points. As Tat protein can be locally released into the central nervous system by HIV-1-infected microglial cells, our findings may contribute to the explanation of the pathogenesis of the motorial abnormalities often reported in HIV-1 seropositive individuals.

Extracellular HIV-1 Tat protein differentially activates the JNK and ERK/MAPK pathways in CD4 T cells.

OBJECTIVE: To investigate the intracellular signals elicited by extracellular HIV-1 Tat protein in lymphoid CD4 T cells. METHODS: CD4 Jurkat T cells were treated with a series of glutathione S-transferase (GST)-Tat fusion proteins: full-length two-exon GST-Tat (GST-Tat2E); one-exon Tat, in which the second exon of Tat was deleted (GST-Tat1E); two-exon Tat, in which the seven arginine residues have been changed to alanine residues (GST-TatArg(mut)), GST-TatdeltaN, which shows a deletion of the N-terminal 21 amino acids. The cells were either treated with soluble GST-Tat proteins or seeded on plates coated with GST-Tat proteins immobilized on plastic. At various time points, Jurkat cells were lysed and examined for c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase/mitogen-activated protein kinase (ERK/MAPK) activity. RESULTS: Soluble and immobilized GST-Tat2E, but not GST-Tat1E, GST-TatArg(mut) and GST-TatdeltaN, activated JNK in a dose-dependent manner, induced a rapid phosphorylation of c-Jun on Ser63 and promoted the de novo synthesis of c-Jun protein. Moreover, both GST-Tat2E and GST-Tat1E also stimulated ERK/MAPK. However, the activation of JNK was maximal at concentrations of 100 nM of GST-Tat2E and was blocked by the S6-kinase inhibitor rapamycin, whereas the activation of ERK/MAPK was already maximal at 1 nM of GST-Tat2E and was enhanced by rapamycin. CONCLUSIONS: Tat-mediated activation of JNK requires the second exon of Tat, which is dispensable for the activation of ERK/MAPK. The ability to stimulate JNK and ERK/MAPK does not require Tat internalization.

HIV-1 Tat induces tyrosine phosphorylation of p125FAK and its association with phosphoinositide 3-kinase in PC12 cells.

OBJECTIVE: To evaluate the signal transduction potential of HIV-1 Tat in a neuronal cell model. METHODS: The tyrosine phosphorylation levels of the focal adhesion kinase p125FAK and its association with phosphoinositide 3-kinase (PI 3-K) were evaluated in serum-starved rat pheochromocytoma PC12 cells, either treated with low concentrations (0.1-1 nM) of extracellular HIV-1 Tat protein or stably transfected with Tat cDNA. RESULTS: Extracellular Tat induced a rapid increase of p125FAK tyrosine phosphorylation and p125FAK-associated PI 3-K activity. By using recombinant mutated Tat proteins, it was found that deletion of amino acids 73-86 encoded by the second exon of the tat gene resulted in a significant decrease of the ability of Tat to induce p125FAK tyrosine phosphorylation. Paradoxically, mutations in the basic region encoded by the first exon of tat, which is essential for nuclear localization and HIV-1 LTR transactivation, increased the ability of Tat to stimulate p125FAK tyrosine phosphorylation. Moreover, in comparison with cells transfected with a control vector, PC12 cells stably transfected with tat cDNA showed greater amounts of p125FAK protein, an increase in p125FAK tyrosine phosphorylation and higher levels of p125FAK-associated PI 3-K activity. The addition of anti-Tat neutralizing antibody to tat-transfected PC12 cells in culture blocked both the p125FAK tyrosine phosphorylation and its association with PI 3-K but did not affect the total amount of p125FAK. CONCLUSION: HIV-1 Tat protein enhanced both the expression and the functionality of p1 25FAK in PC12 neuronal cells. Whereas the first event required intracellular Tat, the increased p125FAK phosphorylation was strictly dependent upon extracellular Tat.

Extracellular human immunodeficiency virus type-1 Tat protein activates phosphatidylinositol 3-kinase in PC12 neuronal cells.

We have here investigated the effect of the regulatory Tat protein of the human immunodeficiency virus type 1 (HIV-1) on the PI 3-kinase catalytic activity in PC12 rat pheochromocytoma cells. After as early as 1 min from the beginning of the treatment with recombinant HIV-1 Tat protein, a significant increase in the tyrosine phosphorylation levels of the p85 regulatory subunit of PI 3-kinase was noticed in 48 h serum-starved PC12 cells. Moreover, the addition of Tat to PC12 cells induced a great increase in PI 3-kinase immunoprecipitated with an anti-phosphotyrosine antibody with a peak of activity (19-fold increase with respect to the basal levels) after a 15-min treatment. This increase in PI 3-kinase activity was significantly higher in PC12 cell cultures supplemented with Tat protein than in cultures stimulated by 100 ng/ml nerve growth factor (NGF; 8-fold increase with respect to the basal levels). Further experiments showed that Tat protein was able to specifically activate PI 3-kinase at picomolar concentrations. In fact: (i) maximal activation of PI 3-kinase was observed at concentrations as low as 1 ng/ml and was specifically blocked by anti-Tat neutralizing antibody; (ii) a Tat-dependent activation was also observed in experiments in which PI 3-kinase activity was evaluated in either anti-Tyr(P) or anti-p85 immunoprecipitates; (iii) 100 nM wortmannin completely blocked the Tat-mediated increase in PI 3-kinase activity both in vitro and in vivo. Our data strongly support the concept that extracellular Tat acts as a cell stimulator, inducing intracellular signal transduction in uninfected cells.

An autocrine loop of HIV type-1 Tat protein responsible for the improved survival/proliferation capacity of permanently Tat-transfected cells and required for optimal HIV-1 LTR transactivating activity.

Human immunodeficiency virus type 1 (HIV-1) transactivating Tat protein is pivotal to virus replication. Tat's potential effects on HIV-1 pathogenesis, however, go well beyond its role in the virus's life cycle. Current data indicate that biologically active Tat is released from HIV-1-infected cells and readily endocytosed and targeted to the nucleus of nearby, or perhaps distant, cells, where it may exert a series of pleiotropic effects. This paracrine action has been extensively investigated, and depending on the amounts of exogenously added Tat, its effects may extend from the suppression of immunocompetent cells to transactivation of heterologous genes to the promotion of growth of Kaposi's sarcoma spindle cells. We have already observed that various cell lines, either permanently transfected with an expressive HIV-1 tat gene construct or cultured in the presence of exogenously added Tat protein, are protected from programmed cell death after serum withdrawal or other apoptotic stimuli. The present article shows that various types (lymphoblastoid, epithelial, neuronal) of permanently tat-transfected cell lines actively release fully bioactive Tat protein. The addition of anti-Tat antibody to the culture medium completely abolishes their increased survival/proliferation capacity in serum-free culture. In these conditions, therefore, the enhanced survival/proliferation potential of permanently tat-transfected cells seems entirely dependent on a Tat-protein autocrine loop. The finding that anti-Tat antibody, added to culture medium, exerts a negative influence on the expression of a Tat-responsive HIV-1 long terminal repeat chloramphenicol-acetyltransferase construct, transiently transfected into permanently tat-transfected cells, suggests that the Tat autocrine loop may also be required for optimal HIV-1 long terminal repeat transactivation.

The CD4 receptor plays essential but distinct roles in HIV-1 infection and induction of apoptosis in primary bone marrow GPIIb/IIIa+ megakaryocytes and the HEL cell line.

We investigated whether cells belonging to the megakaryocytic lineage could be infected in vitro with human immunodeficiency virus type-1 (HIV-1). Primary GPIIb/IIIa+ bone marrow (BM) cells and HEL continuous cell line were first phenotypically characterized for the presence of megakaryocytic markers and CD4 antigen, then challenged in vitro with the laboratory strain IIIB of HIV-1. Both GPIIb/IIIa+ BM and HEL cells expressed significant levels of CD4 receptor (> 50%) and were efficiently infected with HIV-1, as judged by the presence of proviral DNA after polymerase chain reaction analysis and by quantitative evaluation of gag p24 antigen in the culture supernatants. Of note, infection with HIV-1 in both primary BM megakaryocytes and HEL cells was specifically blocked by soluble recombinant CD4. To ascertain whether the CD4 receptor was essential for infection of megakaryocytic cells, HEL were subcloned into CD4+ and CD4- cells. Although unfractionated and CD4+ HEL cells were productively infected with HIV-1, CD4- HEL cells could not be infected. Infection of HEL cells did not induce gross cytotoxic effects or a significant increase of apoptosis. On the other hand, treatment of unfractionated or CD4+ HEL cells with cross-linked recombinant env gp120 or Leu3a anti-CD4 monoclonal antibody markedly (P < 0.01) increased the degree of apoptosis with respect to HEL cells infected with HIV-1 or treated with cross-linked gag p24 or anti-GPIIb/IIIa antibody. Taken together, these data indicate that the CD4 receptor represents the main route of infection in cells belonging to the megakaryocytic lineage. Moreover, an inappropriate engagement of CD4 by either free env gp120 or anti-CD4 monoclonal antibody could be more relevant than a direct infection with HIV-1 in the induction of the frequent BM megakaryocyte abnormalities found in HIV-1 seropositive thrombocytopenic patients.

Periotest measurements and osseointegration of mandibular ITI implants supporting overdentures. A one-year longitudinal study.

The Periotest values of mandibular implants, registered before and after loading by overdentures, were compared. Thirty edentulous patients with 60 Bonefit ITI implants were selected with an average age of 69 years. The Periotest values were measured 1) after a healing period of 3 months and 2) after the overdentures had been worn for a period of 12 months. Periodontal parameters were recorded at both examinations. Furthermore, 17 biopsies of mandibular bone taken from the implant sites during implant surgery were analyzed to assess the bone density. The histomorphometric evaluation was done using a point count method. At the end of the healing period, all registered Periotest values were negative, ranging from -1 to -8 with an average of 4.08. One year later, all measurements showed negative values again, ranging from -2 to -8 with an average of 4.97. The difference was statistically significant. Seventeen biopsies of mandibular bone were evaluated to determine the density. The range of bone density was from 22.4% and 90.9%. There was no correlation found between bone density and Periotest values. However, a significant correlation could be observed between mandibular atrophy and bone density.

Recombinant human immunodeficiency virus type-1 (HIV-1) Tat protein sequentially up-regulates IL-6 and TGF-beta 1 mRNA expression and protein synthesis in peripheral blood monocytes.

In this study we evaluated the effect of human immunodeficiency virus type 1 (HIV-1) recombinant Tat protein on mRNA expression and protein synthesis of two inflammatory cytokines-interleukin-6 (IL-6) and transforming growth factor-beta 1 (TGF-beta 1)-by peripheral blood (PB) monocytes. Whereas maximal levels of IL-6 protein were recovered in PB monocyte culture supernatants after 24-48 h from the addition of 1 micrograms/ml of recombinant Tat, TGF-beta 1 showed a slower and progressive increase, reaching maximal levels only after 72-96 h of culture. Consistently, the analysis of the steady-state levels of mRNA showed a sharp increase of IL-6 mRNA expression after 24h of culture, with a slow decline thereafter. On the other hand, TGF-beta 1 mRNA expression showed a slow increase only after 72-96 h of culture. Moreover, IL-6 appeared involved in the up-regulation of TGF-beta 1, because the addition of a neutralizing anti-IL-6 antibody to Tat-treated PB monocyte cultures significantly reduced the amounts of TGF-beta 1 recovered in the culture supernatants after 96 h. The present demonstration that HIV-1 Tat protein directly up-regulates IL-6 expression and stimulates TGF-beta 1 production both directly and indirectly, through early IL-6 production, could have important implications in the pathogenesis of HIV-1 disease.

Nuclear translocation of phosphatidylinositol 3-kinase in rat pheochromocytoma PC 12 cells after treatment with nerve growth factor.

Immunocytochemical analysis of PI 3-kinase localization in PC 12 cells demonstrates that the enzyme translocates to the nucleus after cell treatment with differentiating doses of NGF. The association of PI 3-kinase to the nucleus occurs rapidly (within minutes) and increases with the time of exposure of NGF. We suggest that PI-3 kinase specific localization may determine the production of novel phosphoinositides in cell compartments targeted to effect diverse cell responses. The nuclear translocation is consistent with accumulating data on the existence of a nuclear inositol lipid cycle which could also include 3-phosphorylated inositides, participating to the modulation of the cell response to extracellular stimuli.

In vitro growth of human fetal CD34+ cells in the presence of various combinations of recombinant cytokines under serum-free culture conditions.

CD34+ cells were purified from midtrimester human fetal blood and adult bone marrow samples and seeded in serum-free fibrin-clot cultures in order to evaluate the number and the responsiveness to recombinant cytokines of pluripotent (CFU-GEMM), erythroid (BFU-E), megakaryocyte (BFU-meg and CFU-meg) and granulocyte/macrophage (CFU-GM) haemopoietic progenitor cells. The number of the different haemopoietic progenitors/1 x 10(3) CD34+ cells, except CFU-meg, was significantly higher in fetal blood than in adult bone marrow in cultures stimulated by any combination of cytokines including interleukin-3 (IL-3), granulocyte/macrophage colony stimulating factor (GM-CSF) or stem cell factor (SCF) plus erythropoietin (Epo). Nevertheless, whereas adult BFU-E showed a maximal growth in the presence of Epo plus IL-3 or Epo plus SCF, fetal BFU-E showed an optimal growth in the presence of Epo alone, the sensitivity of fetal BFU-E to suboptimal concentrations of Epo being approximately 10-15-fold higher than that of adult BFU-E. Addition of optimal concentrations of IL-3, GM-CSF or SCF, alone or in various combinations, to Epo-containing cultures induced a significant increase in both the number and size of fetal CFU-GEMM, and CFU-GM, and a parallel decrease of fetal BFU-E. Finally, SCF potently synergized with IL-3 in increasing the growth of both classes of fetal megakaryocyte progenitors, BFU-meg and CFU-meg.