Widespread differentiation stage-specific expression of the gene encoding phosphoprotein p19 (metablastin) in mammalian cells

p19 is a highly conserved 19 kD cytosolic protein that undergoes phosphorylation in response to diverse extracellular factors in mammalian cells. Its expression is abundant in brain and testis and is developmentally regulated. To gain insights regarding its function, we analyzed the expression of p19 mRNA in a variety of cell types during induction of differentiation. Murine erythroleukemia cells showed a moderate increase followed by a marked decrease in the abundance of p19 mRNA during induction of differentiation. In murine C2 myoblasts and primary fetal rat osteoblasts, p19 mRNA was abundant in replicating cells and decreased to undetectable levels during differentiation. In resting human peripheral blood lymphocytes, p19 mRNA was virtually undetectable but was strongly induced during blast transformation of both B and T cells. In rat liver, p19 mRNA was abundant on embryonic day 17 and decreased during early postnatal development. Upon fractionation of adult rat liver cells by centrifugal elutriation, p19 mRNA was not detected in hepatocytes while a low level was observed in a fraction enriched in non-parenchymal epithelial cells. CCl4-induced liver regeneration resulted in induction of p19 mRNA in hepatocytes. Primary cultures of embryonic and neonatal rat brain were analyzed by indirect immunofluorescence using co-staining with stage-specific markers. p19 expression was restricted to immature neurons and oligodendrocyte precursors. In contrast to the other cell types examined, the neuronal and glial precursors that express p19 were shown, using BrdU labeling, to be postmitotic both in primary culture and in vivo. The data demonstrate widespread, stage-specific expression of p19 and suggest that the protein exerts a general, lineage-independent function during induction of differentiation of mammalian cells. In view of the available evidence on the stimulation of serine phosphorylation of p19 by several growth factors, our working hypothesis is that phosphorylation of p19 may be involved in the mechanism by which growth factors control cell differentiation.

Rearrangement of BCR genes in malignant lymphoma

The Philadelphia chromosome, originally thought to be associated solely with chronic myelogenous leukemia (CML), has since been identified in acute leukemias and in some cases of lymphoma. The Philadelphia chromosome results from reciprocal translocation of genetic material between chromosome 9 and 22 involving the c-abl and BCR genes respectively. Southern blot analysis of the BCR genes was carried out on biopsy specimens from 49 patients presenting with malignant lymphoma without a previously documented CML phase. In two patients, BCR gene rearrangements were detected in the malignant lymph nodes but not in the bone marrow samples. A third patient showed BCR gene rearrangements in the bone marrow but not in the lymph node. From this limited study, it seems that the overall incidence of BCR gene rearrangement in malignant lymphoma is similar to that observed in adult AML.

Expression of stem cell factor and c-kit mRNA in cultured endothelial cells, monocytes and cloned human bone marrow stromal cells (CFU-RF)

Previously, we have shown that conditioned medium from a subpopulation of human marrow stromal cells (CFU-RF) contain an activity able to stimulate the growth of macroscopic epo-dependent erythroid colonies. The ligand for the product of the c-kit proto-oncogene (also known as stem cell factor or SCF), among other activities, has been reported to have similar effects on erythroid colony growth. We have also presented data showing that SCF together with phytohemagglutinin-stimulated leukocyte conditioned medium can stimulate erythroid colony growth in the presence of antibodies to erythropoietin. Using the human SCF cDNA probe (K. Zsebo, Amgen Inc.) we now show that cells derived from CFU-RF colonies express SCF but not c-kit. Human umbilical vein endothelial cells were also found to express SCF and this expression was increased by addition of monocyte supernatant, IL-1 beta or thrombin. Cells of the human erythroleukemia cell line HEL were found to express c-kit but not SCF. Neither c-kit nor SCF mRNA were detected in phytohemagglutinin-stimulated lymphocytes. Together, these data support the view that the behaviour of proliferating erythroid stem cells in the marrow, which may express c-kit, could be regulated by membrane-bound SCF present on surrounding stromal cells.

Anti-hepatitis C virus (HCV) screening at a Canadian Red Cross center: significance of a positive c100 HCV enzyme-linked immunosorbent assay

The c100 hepatitis C virus (HCV) enzyme-linked immunosorbent assay (ELISA) has been used to screen blood donors to prevent transfusion-associated non-A,non-B hepatitis. This test is not specific, and only about 25 percent of c100 HCV ELISA-positive blood samples appear to transmit hepatitis C. However, the intensity of the ELISA (sample/cutoff ratio [S/C], greater than 2) could identify a subpopulation of donors that are at high risk for transmitting hepatitis. Blood samples from 20,186 volunteer blood donors at a Canadian Red Cross blood transfusion center were screened for antibodies to HCV using the c100 HCV ELISA. Fifty-nine (0.3%) of these donors were repeatably reactive on ELISA. When their samples were tested with the c100 recombinant immunoblot assay (RIBA) and second-generation RIBA (RIBA-2), 26 (44%) and 31 (52%) samples, respectively, were found to be positive. Thirty-three of the 59 ELISA-reactive donors had an S/C greater than 2. Of these 33 donors, 30 (91%) had elevated alanine aminotransferase (ALT), 27 (82%) were RIBA-2 positive, and 22 (67%) had risk factors for hepatitis. In contrast, of the 26 ELISA-reactive donors with S/C less than 2, only 7 (27%) had elevated ALT, and 4 (15%) were RIBA-2 positive and also had high risk factors for hepatitis. Thus, while the HCV ELISA may lack specificity, its intensity can serve to identify a subgroup of donors that are at high risk for transmitting hepatitis.

Lipoprotein receptor activity of peritoneal macrophages from insulin-deficient mice

Binding, uptake and degradation of 125I-labeled normal very low density lipoprotein (125I-n-VLDL) from normal swine plasma and 125I-labeled beta-migrating VLDL (125I-beta-VLDL) from hypercholesterolemic rabbit plasma by peritoneal macrophages of mice rendered insulin-deficient by streptozotocin (250 mg/kg) were studied. It was found that the amount of binding, uptake and degradation of 125I-n-VLDL by macrophages from the diabetic mice was 2-fold or 2.5-fold higher than by macrophages from normal mice, resulting from an increase in the binding capacity of VLDL receptors on the macrophages from the insulin-deficient rodents. In contrast, the binding, uptake and degradation of 125I-beta-VLDL by macrophages from diabetic mice were reduced to only about 45% of normal levels because of a decrease in the number and affinity of the receptors for beta-VLDL. These experimental results indicate that n-VLDL is more important than beta-VLDL in the pathogenesis of atherosclerosis in insulin-dependent diabetes.

Molecular characterization of beta-thalassaemia in 174 Greek patients with thalassaemia major

The mutations producing beta-thalassaemia in 174 Greek patients with thalassaemia major were investigated by dot-blot hybridization of oligonucleotide probes to genomic DNA amplified by the polymerase chain reaction procedure, by direct sequencing of amplified DNA, and by gene mapping. beta-thalassaemia in Greeks was found to be very heterogeneous at the molecular level as 17 different mutations were observed: 86.6% of the beta-thalassaemic genes, however, could be identified with five probes: IVS-I-110 (G----A) (42.5%), codon 39 (C----T) (17%), IVS-I-1 (G----A) (13.2%), IVS-I-6 (T----C) (7.2%) and IVS-II-745 (C----G) (6.9%). Several mutations which had not previously been reported in the Greek population and which occurred at an incidence of 2% or lower were observed in this study. The information obtained will facilitate the prenatal diagnosis of beta-thalassaemia in Greece.

[The role of lipoxygenase and cyclooxygenase metabolites in acute hypoxic pulmonary vasoconstriction in piglets]

The role of lipoxygenase and cyclooxygenase metabolites in acute hypoxic pulmonary vasoconstriction (HPV) was studied in piglets. It has been found that acute alveolar hypoxia induced remarkable pulmonary vasoconstriction, associated with an increase in cardiac output. The hypoxic pulmonary vasoconstriction response was insignificantly attenuated after infusion of DEC. Indomethacin potentiated markedly the increase in pulmonary artery pressure and pulmonary vascular resistance and thus augmented HPV. It is inferred that hypoxic pulmonary vasoconstriction in piglet may be mediated by other important mediators in addition to leukotrienes, but modulated by prostaglandins to prevent an excessive rise in pulmonary artery pressure.

Accessory cells in immune suppression. III. Evidence for two distinct accessory cell-dependent mechanisms of T lymphocyte-mediated suppression

Suppression of antibody secretion by the 2,4,6-trinitrophenol (TNP)-binding BALB/c myeloma, MOPC 315, by idiotype- and hapten-reactive suppressor T cells is mediated by secreted factors (TsF) and requires the presence of accessory cells (AC). Idiotype-specific TsF functions only in the presence of Ia+ AC and is completely idiotype specific. Moreover, no suppression is observed when myeloma targets and AC are separated by cell-impermeable membranes, indicating that the role of AC may be to bind, focus, and/or present TsF to the myeloma cells. In contrast, TNP-specific TsF inhibits myeloma function in the presence of TNP-protein and activated macrophages that are not Ia+. This form of suppression is nonspecific at the effector stage; i.e., anti-TNP TsF inhibits a non-TNP binding cell line, TEPC 15, as long as TNP-protein and activated macrophages are present. Moreover, suppression occurs even when myeloma targets and AC are separated by cell-impermeable membranes. These results are consistent with the view that hapten-reactive TsF binds to antigen on the surface of macrophages and induces these cells to secrete nonspecific immunosuppressive molecules. Thus, different types of AC may play fundamentally different roles in TsF-mediated suppression; they may either bind and present TsF to targets (as in the case of idiotype-specific TsF) or secrete nonspecific immunosuppressants as a consequence of a TsF-antigen interaction (hapten-specific TsF). Autonomous, suppressible targets provide valuable experimental systems for analyzing the cellular interactions in T cell-mediated suppression.

Accessory cells in immune suppression. III. Evidence for two distinct accessory cell-dependent mechanisms of T lymphocyte-mediated suppression

Suppression of antibody secretion by the 2,4,6-trinitrophenol (TNP)-binding BALB/c myeloma, MOPC 315, by idiotype- and hapten-reactive suppressor T cells is mediated by secreted factors (TsF) and requires the presence of accessory cells (AC). Idiotype-specific TsF functions only in the presence of Ia+ AC and is completely idiotype specific. Moreover, no suppression is observed when myeloma targets and AC are separated by cell-impermeable membranes, indicating that the role of AC may be to bind, focus, and/or present TsF to the myeloma cells. In contrast, TNP-specific TsF inhibits myeloma function in the presence of TNP-protein and activated macrophages that are not Ia+. This form of suppression is nonspecific at the effector stage; i.e., anti-TNP TsF inhibits a non-TNP binding cell line, TEPC 15, as long as TNP-protein and activated macrophages are present. Moreover, suppression occurs even when myeloma targets and AC are separated by cell-impermeable membranes. These results are consistent with the view that hapten-reactive TsF binds to antigen on the surface of macrophages and induces these cells to secrete nonspecific immunosuppressive molecules. Thus, different types of AC may play fundamentally different roles in TsF-mediated suppression; they may either bind and present TsF to targets (as in the case of idiotype-specific TsF) or secrete nonspecific immunosuppressants as a consequence of a TsF-antigen interaction (hapten-specific TsF). Autonomous, suppressible targets provide valuable experimental systems for analyzing the cellular interactions in T cell-mediated suppression.

Multiple myeloma with initial presentation in the jaw: a clinical-pathologic discussion

A 39-year-old white female presented with jaw pain initially interpreted as a manifestation of an odontogenic infection. Mandibular radiographs revealed lytic lesions suggesting a diagnosis of myeloma, which was subsequently confirmed by abnormalities in serum and urinary proteins and in bone marrow. Chemotherapy produced a transient response, but eventual relapse with extramedullary plasmacytomas and plasma cell leukemia led to death. The clinicopathologic implications of this case are presented and discussed.

A methodological basis for SEM autoradiography: biosynthesis and radioligand binding

A method is described for scanning electron microscope (SEM) autoradiography whereby preservation of high resolution cell surface details is retained together with degelatination of the emulsion without gross loss or redistribution of silver grains. This method should provide a convenient medium-sized marker for SEM (using secondary, backscattered electron and X-ray imaging) topographic studies of biosynthesized molecules, and of cell surface receptors and antigens, using indirect or direct labelling procedures with radio-labelled ligands.

Idiopathic acquired sideroblastic anaemia transforming to acute myelosclerosis

A case of idiopathic acquired sideroblastic anaemia transforming to acute myelofibrosis is reported. The appearance of atypical megakaryocytic proliferation in idiopathic acquired sideroblastic anaemia may presage the development of an acute myelofibrotic phase of this usually chronic disease.

Alteration of glucose and insulin metabolism in congenital heart disease

Children with left-to-right shunt, with and without congestive heart failure, were found to have impaired glucose tolerance tests (GTT). In cyanotic children normal levels of glucose were found in association with abnormally high levels of insulin following oral GTT. Several possible mechanisms are proposed to explain the different glucose tolerance alterations: (1) Suppression of insulin release appeared to partially explain the low levels of insulin in congestive heart failure. This suppression may be related to the high levels of circulating norepinephrine found in these patients. (2) Excessive clearance of insulin by the lung may also be responsible for the reduced arterial insulin levels in patients with left-to-right shunt, and underclearance of insulin for the abnormally higher arterial insulin levels in patients with right-to-left shunts in whom a significant amount of venous blood has bypassed the lung. (3) Hypoxia of the pancreas and the liver in cyanotic patients and those with congestive heart failure may explain the reduction of insulin levels in the hepatic vein following i.v. glucose tolerance tests. An excess production of a glucagonlike gastrointestinal factor in cyanotic children may partially explain the abnormally high levels of insulin following oral GTT.