Biomedical subjects

J C Irminger

Publications and source records attributed to J C Irminger.

24 records · Page 2Linked to original sources

PubMed1992

Extracellular calcium mimics the actions of platelet-derived growth factor on mouse fibroblasts.

Microprecipitates of calcium phosphate (CaPO4) can substitute for platelet-derived growth factor (PDGF) to stimulate the growth of cultured 3T3 cells. In two-part complementation assays, CaPO4 behaves as a PDGF-like "competence factor"--that is, the mitogenic response to CaPO4 is enhanced synergistically by "progression factors" contained in platelet-poor plasma. In studies described here, we show that early cytoplasmic and intranuclear events in the mitogenic response to CaPO4 are equivalent to those induced by PDGF. However, no net increase in tyrosine kinase activity of either the PDGF-alpha or PDGF-beta receptor is seen following exposure to CaPO4. Our data suggest that calcium acts within the cell, regulating events which normally proceed from activation of PDGF receptors. Alternatively, microprecipitates of CaPO4 could act externally by activating a growth factor receptor which escapes detection with available reagents.

3T3 Cells↗

PubMed1989

Structural alteration of the insulin-like growth factor II-gene in Wilms tumour.

In this study messenger ribonucleic acid (mRNA) and DNA of five Wilms tumours were investigated. As expected, the level of insulin-like growth factor (IGF) II-mRNA was elevated up to 50 times in tumour tissue as compared to normal adjacent kidney tissue. In addition, genomic DNA was isolated and digested with appropriate restriction enzymes. Southern blots were prepared and hybridized to IGF II-cDNA probes. Additional bands were present in one of the five Wilms tumours compared to normal tissue. The results indicate a rearrangement of the IGF II-gene on one of the two chromosomes. It is speculated, that this change is responsible for the elevated IGF II expression which may be a factor contributing to tumour growth.

Child, Preschool↗

PubMed1987

Tissue-specific expression of insulin-like growth factor II mRNAs with distinct 5' untranslated regions.

We have used RNA from human hypothalamus as template for the production of cDNAs encoding insulin-like growth factor II (IGF-II). The prohormone coding sequence of brain IGF-II RNA is identical to that found in liver; however, the 5' untranslated sequence of the brain cDNA has no homology to the 5' untranslated sequence of the previously reported liver cDNAs. By using hybridization to specific probes as well as a method based on the properties of RNase H, we found that the human IGF-II gene has at least three exons that encode alternative 5' untranslated regions and that are expressed in a tissue-specific manner. A probe specific to the brain cDNA 5' untranslated region hybridizes to a 6.0-kilobase transcript present in placenta, hypothalamus, adrenal gland, kidney, Wilms tumor, and a pheochromocytoma. The 5' untranslated sequence of the brain cDNA does not hybridize to a 5.3-kilobase transcript found in liver or to a 5.0-kb transcript found in pheochromocytoma. By using RNase H to specifically fragment the IGF-II transcripts into 3' and 5' fragments, we found that the RNAs vary in size due to differences in the 5' end but not the 3' end.

Chromosome Mapping↗

PubMed1987

Insulin-like growth factor II in human adrenal pheochromocytomas and Wilms tumors: expression at the mRNA and protein level.

Two forms of insulin-like growth factor (IGF) II with molecular masses of 10 and 7.5 kDa, respectively, were found in tumor tissue from human adrenal pheochromocytomas. The tumors contained 5.3-7.1 micrograms of immunoreactive IGF-II per g of tissue, which is about 20 times more than in adrenal medulla. The total bioactive IGF in the pheochromocytomas exceeded that in normal liver or kidney, which contained only the 7.5-kDa IGF-II species, by a factor of approximately equal to 100. By contrast, the amount of IGF-I was just measurable and did not vary significantly between tumor and normal tissue. The high amounts of IGF-II in the pheochromocytomas were not reflected, however, by a corresponding increase of mRNA. The opposite situation was found in Wilms tumors, where IGF-II content was in the same range as in nontumor tissues despite increased expression of IGF-II mRNA.

Adrenal Gland Neoplasms↗

PubMed1980

Sea urchin histone mRNA termini are located in gene regions downstream from putative regulatory sequences.

S1 nuclease mapping of the Psammechinus miliaris embryonic histone mRNAs locates the 5' termini in or adjacent to a short sequence homology (5'pyCATTCpu3') downstream from the putative RNA polymerase II regulatory sequence (5'TATAAATA3') or related sequences. The 3' termini map just after a sequence containing GC-rich hyphenated dyad symmetry, a feature of most known terminator sequences.

Animals↗

PubMed1980

Ubiquitous and gene-specific regulatory 5' sequences in a sea urchin histone DNA clone coding for histone protein variants.

The DNA sequences of the entire structural H4, H3, H2A and H2B genes and of their 5' flanking regions have been determined in the histone DNA clone h19 of the sea urchin Psammechinus miliaris. In clone h19 the polarity of transcription and the relative arrangement of the histone genes is identical to that in clone h22 of the same species. The histone proteins encoded by h19 DNA differ in their primary structure from those encoded by clone h22 and have been compared to histone protein sequences of other sea urchin species as well as other eukaryotes. A comparative analysis of the 5' flanking DNA sequences of the structural histone genes in both clones revealed four ubiquitous sequence motifs; a pentameric element GATCC, followed at short distance by the Hogness box GTATAAATAG, a conserved sequence PyCATTCPu, in or near which the 5' ends of the mRNAs map in h22 DNA and lastly a sequence A, containing the initiation codon. These sequences are also found, sometimes in modified version, in front of other eukaryotic genes transcribed by polymerase II. When prelude sequences of isocoding histone genes in clone h19 and h22 are compared areas of homology are seen to extend beyond the ubiquitous sequence motifs towards the divergent AT-rich spacer and terminate between approximately 140 and 240 nucleotides away from the structural gene. These prelude regions contain quite large conservative sequence blocks which are specific for each type of histone genes.

Animals↗