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Biomedical subjects

M Kamps

Publications and source records attributed to M Kamps.

15 recordsLinked to original sources
PubMed1997

VEGF mRNA is stabilized by ras and tyrosine kinase oncogenes, as well as by UV radiation--evidence for divergent stabilization pathways.

Vascular Endothelial Growth Factor (VEGF) is a pivotal endothelial cell mitogen that mediates both normal and pathological angiogenesis. Although expressed at very low levels in cells not undergoing vascularization, VEGF mRNA is transiently upregulated and stabilized by a variety of extracellular stimuli, and is persistently upregulated and stabilized in many human tumor cell lines (White et al., 1995). Here we demonstrate that oncogenic activation of tyrosine protein kinases and Ras proteins induce a 6- to 16-fold increase in the abundance of VEGF mRNA and a 3- to 5-fold increase in the stability of VEGF mRNA, suggesting that persistent activation of signaling pathways induced by these oncoproteins accounts for overexpression of VEGF in a significant fraction of human tumors. In addition to these oncoproteins, ultraviolet (UV) radiation upregulated and stabilized VEGF mRNA 15- and 5-fold, respectively. While the tyrosine kinase inhibitor, genistein, blocked VEGF upregulation by activated tyrosine protein kinases, and the Ras inhibitor, N-Acetyl-S-trans-farnesyl-L-cysteine (AFC), eliminated VEGF expression in cells transformed by v-Ras, neither agent blocked upregulation by hypoxia or UV radiation. These data argue that multiple divergent pathways upregulate and stabilize VEGF mRNA.

3T3 Cells↗
PubMed1995

The pancreatic islet factor STF-1 binds cooperatively with Pbx to a regulatory element in the somatostatin promoter: importance of the FPWMK motif and of the homeodomain.

A number of homeodomain proteins have been shown to regulate cellular development by stimulating the transcription of specific target genes. In contrast to their distinct activities in vivo, however, most homeodomain proteins bind indiscriminately to potential target sites in vitro, suggesting the involvement of cofactors which specify target site selection. One such cofactor, termed extradenticle, has been shown to influence segmental morphogenesis in Drosophila melanogaster by binding cooperatively with certain homeodomain proteins to target regulatory elements. Here we demonstrate that STF-1, an orphan homeodomain protein required for pancreatic development in mammals, binds cooperatively to DNA with Pbx, the mammalian homolog of extradenticle. Cooperative binding with Pbx requires a pentapeptide motif (FPWMK) which is well conserved among a large subset of homeodomain proteins. The FPMWK motif is not sufficient to confer Pbx cooperativity on other homeodomain proteins, however; the N-terminal arm of the STF-1 homeodomain is also essential. As cooperative binding with Pbx occurs on only a subset of potential STF-1 target sites, our results suggest that Pbx may specify target gene selection in the developing pancreas by forming heterodimeric complexes with STF-1.

Amino Acid Sequence↗
PubMed1993

Multicolour preparations for in situ hybridization using precipitating enzyme cytochemistry in combination with reflection contrast microscopy.

We have further developed a method for the detection of different enzyme cytochemical reaction products by means of reflection contrast microscopy (RCM). By embedding these enzyme precipitates in a protein matrix, we were able to prevent the reaction products from dissolving in immersion oil, which is required for RCM analysis. The applicability of the RCM procedure is, therefore, extended to a range of cytochemical enzyme precipitation methods, which normally result in oil soluble reaction products. To test their usefulness, these enzyme precipitates have been used in single- and well as double-label in situ hybridization (ISH) procedures to visualize a number of DNA target sequences by several different reflection colours, i.e. white, yellow and red. Three repetitive DNA probes for the (sub)centromeric regions of chromosomes 1, 7 and 17, as well as a repetitive DNA probe for the telomeric region of chromosome 1, and two cosmid DNA probes (40 kb each) for both arms of chromosome 11 could be detected with high efficiency in both interphase and metaphase preparations. Moreover the enzyme precipitates were shown to be stable upon exposure to excitation light or upon storage. It may be concluded that these findings render RCM a sensitive method for the visualization of multiple targets in biological specimens.

Carcinoma, Transitional Cell↗
PubMed1988

fos-associated cellular p39 is related to nuclear transcription factor AP-1.

Proto-oncogene fos encodes a nuclear protein that appears to be involved in the transcriptional regulation of some genes. fos protein (p55fos) is associated with other nuclear proteins in complexes that bind to regulatory regions containing TPA-responsive promoter elements (TREs). The enhancer-binding activator protein 1 (AP-1), which is the specific binding factor of a TRE, is the product of the nuclear proto-oncogene jun. We show that one of the fos-associated proteins, p39, is immunologically and structurally related to nuclear factor AP-1. The sequence TGACTCA, which is the consensus minimal binding site of AP-1, is also recognized by gel-purified p39. In HeLa cell extracts p55fos and p39jun are associated in a nucleoprotein complex that interacts with a TRE. Cooperation between nuclear oncoproteins fos and jun is required for full activation of transcription from a TPA-responsive promoter element in transfected mammalian cells.

Enhancer Elements, Genetic↗
PubMed1978

Influence of cultivation conditions on the production of staphylocoagulase by Staphylococcus aureus 104.

High yields of staphylocoagulase from Staphylococcus aureus 104 were obtained in a simple salts medium supplement with glycerol, casein hydrolysate and three vitamins. Conditions of oxygen-limitation (dissolved oxygen concentration less than 2%), a pH of 7.4, a temperature of 35 degrees C and a 1 in 10 inoculum of overnight culture were required for optimal yields of staphylocoagulase.

Caseins↗