Effects of fibroblast growth factor-4 (k-FGF) on long-term cultures of human bone marrow cells

Fibroblast growth factor-4 (FGF-4), a highly mitogenic protein encoded by the k-fgf/hst oncogene, stimulates the growth of a variety of cells of mesenchymal and neuroectodermal origin. Addition of FGF-4 to human long-term bone marrow cultures increased both the cell density of the stromal layer and the number of hematopoietic colony forming cells in the cultures in a dose-dependent manner. Hematopoiesis in the stromal layer persisted for up to 8 months. Erythropoiesis was maintained for up to 4 weeks, but granulocytes were the predominant nonadherent cell type. Cultures treated with FGF had increased numbers of monocytes compared with control cultures and some CD14+, CD45+ monocytes could still be detected after 8 months of continuous culture. The addition of the growth factor increased the rate of growth of the stromal layer and appeared to delay its senescence. Subcultures made in the presence of FGF-4 had up to 10-fold increases in plating efficiency and grew as relatively uniform monolayers. These subcultures retained the capacity to support hematopoiesis for several months, while untreated subcultures, made without FGF-4, grew erratically and generally lost the capacity to support hematopoiesis within 4 to 6 weeks. The improved growth after subculture greatly enhanced the reliability of limit- dilution assays of multipotential hematopoietic stem cells that use stromal cell monolayers. The primary effect of FGF-4 appeared to be on the stromal cells of the long-term bone marrow cultures, but a direct effect on hematopoietic progenitors could not be ruled out.     

Neuromedin U octapeptide alters ion transport in porcine jejunum

The gut neuropeptide, neuromedin U octapeptide (NMU-8) produced transient elevations in short-circuit current (EC50 = 0.7 nmol/l) after its contraluminal administration to sheets of porcine distal jejunal mucosa in vitro. Mucosal responses to NMU-8 were unaffected by 1 mumol/l atropine or hexamethonium, but were abolished by tetrodotoxin (0.1 mumol/l), dependent upon extracellular Cl, and underwent tachyphylaxis upon repeated peptide application. NMU-8 did not affect contractility of isolated jejunal longitudinal muscle. Thus, NMU-8 appears to selectively modify intestinal ion transport through interactions with non-cholinergic enteric neurons.     

Jejunal proabsorptive actions of selective opiate agonists administered via the cerebral ventricles

Non-selective enkephalin analogs, such as [D-Ala2, Met5]enkephalinamide, have been found to increase jejunal absorption in the rat and dog after their intracerebroventricular administration. In the present investigation, experiments were designed to characterize the brain opiate receptor subtype mediating this action in the rat proximal jejunum in situ and to assess the involvement of extrinsic sympathetic nerves innervating this gut region in opioid-induced absorption. Changes in jejunal water transport were examined in rats pretreated with bolus i.c.v. doses (less than or equal to 1 microgram) of the respective mu-, delta-, or kappa-opiate agonists [D-Ala2, N-Me-Phe4, Gly5-ol]enkephalin (DAGO), [D-Pen2, D-Pen5]enkephalin or U-50488 and infused intravenously with the secretagogue prostaglandin E1 (PGE1, 5 micrograms/kg-min). In saline-pretreated rats, PGE1 produced large, time-dependent decreases in jejunal fluid absorption. Of the opiate agonists examined, only DAGO in submicrogram doses significantly inhibited PGE1 actions 60 to 90 min after its administration. Extirpation of the celiac and superior mesenteric ganglia, major sources of sympathetic neurons innervating the upper gut, significantly attenuated both the antiabsorptive actions of PGE1 and the proabsorptive actions of DAGO (0.3 micrograms, i.cv.). These results suggest that CNS mu-opiate receptors modulate jejunal absorption in the rat, an action mediated through extrinsic sympathetic nerves innervating the upper small intestine.     

Neurohormonal regulation of ion transport in the porcine distal jejunum. Enhancement of sodium and chloride absorption by submucosal opiate receptors.

The actions of opiates in modulating ion transport across the porcine distal jejunal mucosa were examined in vitro. Opiate receptors were functionally characterized using [D-Pen2,D-Pen5]-enkephalin (DPDPE), [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO) and U-50,488 (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)- cyclohexyl]-benzeneacetamide), agonists selective for delta, mu and kappa receptor types, respectively. Serosal administration of opiate agonists produced concentration-dependent decreases in basal short-circuit current (Isc. DPDPE and DAMGO also increased tissue conductance (Gt). DPDPE (EC50 = 4 nM) was 7- and 86-fold more potent in decreasing basal Isc than DAMGO and U-50,488, respectively. U-50,488 displayed the greatest efficacy in decreasing Isc. Serosal naloxone decreased DPDPE and DAMGO potencies under basal conditions with Ke values of 11 and 6 nM, respectively. DPDPE- and DAMGO-induced decreases in basal Isc were associated with increases in net Cl absorption; in addition, DAMGO produced an increase in net Na absorption. 8-Bromocyclic AMP (0.3 mM) increased Isc, decreased Gt and inhibited net Na and Cl absorptive fluxes. Selective opiate agonists decreased cyclic AMP-induced elevations in Isc with a rank order of potency (DPDPE, EC50 = 3 nM) of DPDPE greater than DAMGO greater than U-50,488. DPDPE reversed the action of cyclic AMP on Isc and Cl absorption but had no effect on net Na transport. Cyclic AMP-induced decreases in Gt were not altered by DPDPE.(ABSTRACT TRUNCATED AT 250 WORDS)