Offspring of protein-malnourished rat dams have permanent alterations in hepatic enzyme activities associated with glucose homeostasis. Hormonal control of hepatic glucose output (HGO) was studied in male offspring of dams fed either a 20% (control) or 8% (low protein) protein diet during pregnancy and lactation. Glucagon (210 pM) stimulated HGO significantly more (P < 0.04) in controls (from 0.72 +/- 0.11 to 3.18 +/- 0.30 mumol.min-1.g liver-1) compared with low-protein animals (from 0.53 +/- 0.11 to 2.05 +/- 0.24 mumol.min-1.g liver-1). Insulin (1 nM) decreased (P < 0.001) HGO in controls to 2.39 +/- 0.37 mumol.min-1.g liver-1 after 10 min but increased HGO (to 2.82 +/- 0.40 mumol.min-1.g liver-1; P < 0.04) in low-protein rats. There were fivefold fewer (P = 0.01) glucagon receptors but a threefold increase (P < 0.05) in hepatic insulin receptor number in the low-protein rats, which was reflected by increased in insulin degradation (P < 0.001). The glucose transporter GLUT-2 was also raised threefold in the low-protein group (P < 0.001). The anomalous response to insulin indicates changes in its metabolic signaling, but normal insulin binding suggests that this alteration is a postreceptor event.

Colonies of cells with distinctive dendritic appearance were observed in methylcellulose cultures of human bone marrow and peripheral blood mononuclear cells (PBMC). Such cells appeared alone in colonies of less than 50 cells, together with macrophages in mixed colonies and also within clusters of T lymphocytes at high culture cell numbers. The morphologic resemblance to lymphoid dendritic cells was confirmed by electron microscopy and the cells were distinguished from macrophages by immunoenzymatic and immunogold labeling with monoclonal antibodies (MoAbs). Like macrophages they were HLA-DR+ and CD4+. However, they lacked nonspecific esterase and the macrophage cytoplasmic marker Y1/82A. Most strikingly, cells were strongly HLA-DQ+ and expressed CD1a (T6), which is characteristic of skin Langerhans cells. Their functional similarity to lymphoid dendritic cells was demonstrated by their ability to stimulate allogeneic mixed leukocyte reactions. Dendritic cell colony numbers were estimated in both bone marrow and peripheral blood of controls and in leukemia and lymphoma patients before and after chemotherapy. Colony numbers were low in control blood and in patients before treatment (less than 1.0 to 3.7/10(5) cells). However, during hematopoietic recovery the mean value increased to 37.5/10(5) cells and this increase correlated closely with the observed increase in circulating colony forming unit-granulocyte macrophage (CFU- GM) in individual patients. Autoradiographic studies demonstrated mitotic activity within CD1a+ colonies and a linear relationship between cultured cells and both pure and mixed colonies was consistent with their derivation from a single precursor. These data indicate that a novel hematopoietic progenitor of dendritic/Langerhans cells (DL-CFU) may now be identified in a clonal assay system and suggest a probable common progenitor for these cells and macrophages.

Insulin signal transduction, initiated by binding of insulin to its receptor at the plasma membrane, activates the intrinsic receptor tyrosine kinase and leads to internalization of the activated ligand-receptor complex into endosomes. This study addresses the role played by the activated insulin receptor within hepatic endosomes and provides evidence for its central role in insulinstimulated events in vivo. Rats were treated with chloroquine, an acidotrophic agent that has been shown previously to inhibit endosomal insulin degradation, and then with insulin. Livers were removed and fractionated by density gradient centrifugation to obtain endosomal and plasma membrane preparations. Chloroquine treatment increased the amount of receptorbound insulin in endosomes at 2 min after insulin injection by 93% as determined by exclusion from G-50 columns and by 90% as determined by polyethylene glycol precipitation (p < 0.02). Chloroquine treatment also increased the insulin receptor content of endosomes after insulin injection (integrated over 0 -45 min) by 31% when compared with controls (p < 0.05). Similarly, chloroquine increased both insulin receptor phosphotyrosine content and its exogenous tyrosine kinase activity after insulin injection (64%; p < 0.01 and 96% and p < 0.001, respectively). In vivo chloroquine treatment was without any observable effect on insulin binding to plasma membrane insulin receptors, nor did it augment insulin-stimulated receptor autophosphorylation or kinase activity in the plasma membrane. Concomitant with its effects on endosomal insulin receptors, chloroquine treatment augmented insulin-stimulated incorporation of glucose into glycogen in diaphragm (p < 0.001). These observations are consistent with the hypothesis that chloroquine-dependent inhibition of endosomal insulin receptor dissociation and subsequent degradation prolongs the half-life of the active endosomal receptor and potentiates insulin signaling from this compartment.Insulin signal transduction is initiated by binding of insulin to its receptor at the plasma membrane, which in turn leads to the rapid autophosphorylation of multiple tyrosine residues on the intracellular portion of the ␤-subunit and the activation of the receptor tyrosine kinase toward exogenous substrates (1, 2). Following autophosphorylation, the activated ligand-receptor complex is internalized into endosomes in liver (3-6) and low density membranes in adipocytes (7,8) and muscle (9). Endocytosis of activated receptors has the twin effects of concentrating receptors within endosomes and allowing the insulin receptor tyrosine kinase to phosphorylate substrates that are spatio-temporally distinct from the plasma membrane (Ref. 10; reviewed in Ref. 11). Subsequent termination of signal transduction is achieved by endosomal insulin degradation (12-16) following dissociation of insulin from its receptor (14, 17) as the intralumenal environment of the endosome acidifies (18). This loss of the ligand-receptor complex attenuates any further ligand-driven recept...