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Biomedical subjects

N Blume

Publications and source records attributed to N Blume.

At least 19 recordsLinked to original sources
PubMed2000

Characterization of Cyp2d22, a novel cytochrome P450 expressed in mouse mammary cells.

Endogenous steroids and numerous environmental agents have potent effects on mammary development and carcinogenesis. Locally produced cytochrome P450 enzymes that modify such molecules are therefore likely to be important regulators of these processes. Here we describe the characterization of a novel mouse gene, termed Cyp2d22, that is highly expressed in the mammary tumor derived cell line RIII/Prl. Cyp2d22 is expressed at intermediate levels in the weakly tumorigenic cell line RIII/MG, whereas expression is low or absent in all normal mouse mammary epithelial cell lines tested and three C3H mammary tumor derived cell lines. Immunoblot analysis of mouse tissues with highly specific antisera indicates that 2D22 protein levels are most abundant in liver, while intermediate levels of expression are seen in adrenal, ovary, and mammary gland. Immunohistochemical staining of liver sections with these antisera demonstrates that 2D22 is most abundant in the first layer or two of parenchymal cells surrounding the central vein, with virtually no expression detected in periportal cells. Interestingly, sequence similarity and functional data suggest that Cyp2d22 may be the mouse ortholog of human CYP2D6. These observations support the hypothesis that 2D22 mediates a distinct, biologically significant activity in relation to other mouse 2D family members.

Adenoviridae↗
PubMed1998

Transplantable rat glucagonomas cause acute onset of severe anorexia and adipsia despite highly elevated NPY mRNA levels in the hypothalamic arcuate nucleus.

We have isolated a stable, transplantable, and small glucagonoma (MSL-G-AN) associated with abrupt onset of severe anorexia occurring 2-3 wk after subcutaneous transplantation. Before onset of anorexia, food consumption is comparable to untreated controls. Anorexia is followed by adipsia and weight loss, and progresses rapidly in severity, eventually resulting in reduction of food and water intake of 100 and 80%, respectively. During the anorectic phase, the rats eventually become hypoglycemic and hypothermic. The tumor-associated anorexia shows no sex difference, and is not affected by bilateral abdominal vagotomy, indicating a direct central effect. The adipose satiety factor leptin, known to suppress food intake by reducing hypothalamic neuropeptide Y (NPY) levels, was not found to be expressed by the tumor, and circulating leptin levels were reduced twofold in the anorectic phase. A highly significant increase in hypothalamic (arcuate nucleus) NPY mRNA levels was found in anorectic rats compared with control animals. Since elevated hypothalamic NPY is among the most potent stimulators of feeding and a characteristic of most animal models of hyperphagia, we conclude that the MSL-G-AN glucagonoma releases circulating factor(s) that overrides the hypothalamic NPY-ergic system, thereby eliminating the orexigenic effect of NPY. We hypothesize a possible central role of proglucagon-derived peptides in the observed anorexia.

Animals↗
PubMed1996

Pancreatic development and maturation of the islet B cell. Studies of pluripotent islet cultures.

Pancreas organogenesis is a highly regulated process, in which two anlage evaginate from the primitive gut. They later fuse, and, under the influence of the surrounding mesenchyme, the mature organ develops, being mainly composed of ductal, exocrine and endocrine compartments. Early buds are characterized by a branching morphogenesis of the ductal epithelium from which endocrine and exocrine precursor cells bud to eventually form the two other compartments. The three compartments are thought to be of common endodermal origin; in contrast to earlier hypotheses, which suggested that the endocrine compartment was of neuroectodermal origin. It is thus generally believed that the pancreatic endocrine-lineage possesses the ability to mature along a differentiation pathway that shares many characteristics with those of neuronal differentiation. During recent years, studies of insulin-gene regulation and, in particular, the tissue-specific transcriptional control of insulin-gene activity have provided information on pancreas development in general. The present review summarizes these findings, with a special focus on our own studies on pluripotent endocrine cultures of rat pancreas.

Amyloid↗
PubMed1996

Induction of insulin and islet amyloid polypeptide production in pancreatic islet glucagonoma cells by insulin promoter factor 1.

Insulin promoter factor 1 (IPF1), a member of the homeodomain protein family, serves an early role in pancreas formation, as evidenced by the lack of pancreas formation in mice carrying a targeted disruption of the IPF1 gene [Jonsson, J., Carlsson, L., Edlund, T. & Edlund, H. (1994) Nature (London) 371, 606-609]. In adults, IPF1 expression is restricted to the beta-cells in the islets of Langerhans. We report here that IPF1 induces expression of a subset of beta-cell-specific genes (insulin and islet amyloid polypeptide) when ectopically expressed in clones of transformed pancreatic islet alpha-cells. In contrast, expression of IPF1 in rat embryo fibroblasts factor failed to induce insulin and islet amyloid polypeptide expression. This is most likely due to the lack of at least one other essential insulin gene transcription factor, the basic helix-loop-helix protein Beta 2/NeuroD, which is expressed in both alpha- and beta-cells. We conclude that IPF1 is a potent transcriptional activator of endogenous insulin genes in non-beta islet cells, which suggests an important role of IPF1 in beta-cell maturation.

Amyloid↗
PubMed1995

Potent inhibitory effects of transplantable rat glucagonomas and insulinomas on the respective endogenous islet cells are associated with pancreatic apoptosis.

Effects of transplantable rat insulinomas (IN) and glucagonomas (GLU) on the endogenous pancreas were analyzed using morphometry, immunocytochemistry, in situ hybridization, and staining for apoptotic cells. Hyperinsulinemia (IN-rats) and hyper-GLP-1/glucagonemia (GLU-rats) were both associated with marked islet atrophy (67 and 76% of control average planimetrical islet area, respectively). Selective islet B cell inhibition of proinsulin (I and II) genes as well as of expression of the insulin gene transcription factor, IPF1/STF1, was found in IN-rats. Moreover, these islets were characterized by significant B cells apoptosis in the absence of infiltrating lymphocytes. In GLU-rats selective islet A cell inhibition was observed at the level of glucagon mRNA. These islets contained small, highly condensed but clearly active B cells with prominent IPF1/STF1-positive nuclei, surrounded by densely packed glucagon-negative cells with reduced cytoplasm. Furthermore, an active apoptotic process was found exclusively in the exocrine pancreas of GLU-rats. Thus, in IN-rats, islet B cell mass reduction is distinguished by non-immune-mediated programmed cell death, while GLU-rats exhibit A cell mass reduction by cytoplasmic retraction and selective exocrine apoptosis.

Animals↗
PubMed1995

Transplantable glucagonomas derived from pluripotent rat islet tumor tissue cause severe anorexia and adipsia.

From pluripotent pancreatic rat islet tumor tissue we have previously reported the isolation of stable transplantable glucagonoma tumor phenotypes in rats characterized by acute onset of anorexia. We now report that these tumors also cause severe adipsia. Food and water intake is reduced by more than 95% and is immediately cured upon tumor removal. Four anorectic tumor lines were all characterized as glucagonomas with high levels of proglucagon mRNA, and of two tested both were associated with highly elevated plasma levels of glucagon as well as of Glp-1(7-36amide) in the host rat. This fetal processing pattern of proglucagon may be indirectly linked to the anorectic phenotype, since we have now isolated a non-anorectic glucagonoma with similar levels of proglucagon mRNA. Lack of anorexia/adipsia in SV-40-T-antigen driven glucagonomas in transgenic mice with similar fetal processing as reported by other suggests that our tumors produce a novel anorectic substance. This factor ranges among the most potent of its kind as a peripheral mediator involved in appetite and thirst regulation. In summary, the glucagonomas provide an interesting tool with which to study the nature of severe anorexia as well as adipsia, and the identification of the active substance(s) may provide novel therapeutics for the treatment of obesity-related disorders such as NIDDM.

Animals↗
PubMed1993

Differential expression of the two nonallelic proinsulin genes in the developing mouse embryo.

In the mouse, insulin is produced from two similar but nonallelic genes that encode proinsulins I and II. We have investigated expression of these two genes during mouse embryonic development, using a PCR to detect the two gene transcripts and immunocytochemistry to visualize the two corresponding proteins. At appearance of the dorsal pancreatic anlage at day 9.5 of gestation, both mRNAs could be detected in the embryos, and both proteins were present together in the same cells of the developing pancreas. At days 9.5 and 10.5, when the ventral anlage appears, there were fewer proinsulin II mRNAs than proinsulin I mRNAs. At day 12.5 this ratio was reversed. Proinsulin II mRNA, but not proinsulin I mRNA, could be detected at day 8.5 in the prepancreatic embryo. Proinsulin II mRNA, but not proinsulin I mRNA, was also found in the heads of embryos at day 9.5 and at all later stages studied. These results indicate that the two proinsulin genes are regulated independently, at least in part. They also suggest that insulin might play a role as a growth factor in the developing mouse brain.

Alleles↗
PubMed1993

Differential expression of non-allelic insulin genes in rodent islet tumour cells.

We have compared the expression patterns of the non-allelic insulin 1 and 2 genes during prolonged in-vitro culture of the mouse islet cell line beta-TC3, where transformation by the SV40 T oncoprotein is targeted to the differentiated beta-cell phenotype, and the rat islet cell line NHI-6F, in which the beta-cell phenotype is induced by transient in-vivo passage. The NHI-6F clone carries, in addition, a single copy of a transfected silent human insulin gene which contains 3 kb of regulatory sequences known to confer beta-cell-specific expression. Insulin gene expression was measured by an assay based on a reverse transcription-polymerase chain reaction, to determine whether the ancestral rodent insulin 2 genes (and the human homologue in the NHI-6F cells) are regulated differently from the duplicated rat and mouse insulin 1 genes. We have shown that activation of insulin gene expression in the NHI-6F cells includes transcriptional activation of all three genes, but that extended propagation of tumour cells in vitro leads to a selective and equal decline in the quantities of transcripts from the rat 2 and human genes relative to transcripts from the rat 1 gene. In the later passages, insulin transcripts were derived almost exclusively from the rat 1 gene. In early in-vitro passages of the mouse endocrine cell line beta-TC3, the expression pattern of the mouse 1 and 2 insulin genes resembled that seen in isolated mouse islets. After more than 45 in-vitro passages, expression of the duplicated mouse 1 gene decreased tenfold when compared with the ancestral mouse 2 gene. As previously shown for NHI-6F cells, the differential expression of non-allelic insulin genes in the beta-TC3 line was also clearly evident at the cellular level, where a subpopulation of cells selectively expressed readily detectable levels of mouse C-peptide 2 immunoreactivity while devoid of C-peptide 1. Our results suggest that the maintenance of insulin gene expression in rodent tumour cells is influenced by enhancer sequences which are not shared by the ancestral and duplicated insulin genes, and that either species-specific conditions or transformation-related differences exist between the rat and mouse cell lines that govern which gene remains active during prolonged in-vitro propagation.

Animals↗
PubMed1992

Immature transformed rat islet beta-cells differentially express C-peptides derived from the genes coding for insulin I and II as well as a transfected human insulin gene.

Synthetic peptides representing unique sequences in rat proinsulin C-peptide I and II were used to generate highly specific antisera, which, when applied on sections of normal rat pancreas, confirm a homogeneous coexpression of the two C-peptides in all islet beta-cells. Insulin gene expression is induced in the transformed heterogeneous rat islet cell clone, NHI-6F, by transient in vivo passage. During this process a transfected human insulin gene is coactivated with the endogenous nonallelic rat insulin I and II genes. Newly established cultures from NHI-6F insulinomas having a high frequency of insulin-producing cells showed highly differential expression at the cellular level of the three proinsulin C-peptide immunoreactivities, as follows: C-peptide I greater than human C-peptide greater than C-peptide II. The fractions of cells expressing human C-peptide and C-peptide II decreased in time and were absent after more than 50 successive passages, while a C-peptide I-producing population was still present. Double-labeling experiments revealed a heterogeneous distribution of the three different C-peptides. Surprisingly, in the early passages a large fraction of cells would express only a single species of proinsulin-C-peptide immunoreactivity but still at high levels. However, rat C-peptide II and human C-peptide were often colocalized, even in later passages. In situ hybridization studies combined with the immunocytochemical data suggest that the differential expression occurs at the level of transcription.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Production of peptide antisera specific for mouse and rat proinsulin C-peptide 2.

Mice and rats have two functional non-allelic insulin genes. By using a synthetic peptide representing a common sequence in mouse and rat C-peptide 2 as antigen, we have produced rabbit antisera specific for an epitope which is not present in mouse or rat C-peptide 1. Long-term immunization did not seem to increase the end point titre as tested in direct ELISA. The specificity of the antiserum was determined by competitive ELISA and histochemistry on pancreas sections. Only the synthetic C-peptide 2, but not the homologous synthetic C-peptide 1 from mouse and rat competed efficiently in ELISA for antibody binding to the immunizing antigen. Antisera to C-peptide 2, stained islet beta-cells on mouse and rat, but not monkey pancreas sections in immunocytochemical analysis. Preabsorption to the synthetic C-peptide 2, but not the synthetic mouse and rat C-peptide 1 abolished staining. In conclusion we have produced peptide antisera to an antigenic epitope which is unique to mouse and rat C-peptide 2. Antisera recognizing this epitope may be effective tools to study differential expression of the two insulin genes in mouse and rat.

Amino Acids↗
PubMed1981

[Serologic analysis of tumor antibodies in the sera of patients with carcinoma of the larynx (author's transl)].

Sera of 20 tumor patients with squamous cell carcinoma of the larynx were evaluated for the presence of antibodies against a soluble antigen from cultured carcinoma cells of the larynx. The antibody levels of the tumor sera were significantly higher than those of the control group. An immunological response was also observed in sera from the control group (55%).

Antibodies, Neoplasm↗