PubMed Health⌕ Search

Biomedical subjects

W Engström

Publications and source records attributed to W Engström.

At least 19 recordsLinked to original sources
PubMed2001

Effects of insulin-like growth factor-binding protein 2 and an IGF-type I receptor-blocking antibody on apoptosis in human teratocarcinoma cells in vitro.

Human teratocarcinoma cells (Tera-2) deprived of serum undergo programmed cell death which can be counteracted by simultaneous addition of IGF-I or IGF-II. This protective effect of IGFs was specific in the sense that both addition of IGF-binding protein-2, and blocking of the IGF-type I receptor by a specific antibody, both resulted in an increased apoptotic rate.

Antibodies↗
PubMed2001

Insulin-like growth factors I and II induce cell death in Wilms's tumour cells.

AIM: To study the effects of insulin-like growth factors (IGFs) on the growth phenotype of a Wilms's tumour cell line (WCCS-1). METHODS: WCCS-1 cells were cultured in vitro and exposed to IGF-I and IGF-II, as well as their antagonists, IGF binding protein 2 and the type I receptor blocking antibody IGF-IRalpha. The effects on proliferation and cell cycle parameters were assayed by assessing cell numbers, autoradiography after labelling with tritiated thymidine, and flow cytometry after double staining with fluorescein isothiocyanate (FITC) labelled annexin V and propidium iodide. RESULTS: The addition of IGF-I as well as IGF-II in physiological doses induced cell death in Wilms's tumour cells. Cell numbers decreased most dramatically on the fifth to sixth day after growth factor addition. The occurrence of apoptosis as well as necrosis was confirmed by annexin-V staining of cell cultures. S-phase indices were comparable, irrespective of whether the cells were exposed to IGFs or not, which suggests that WCCS-1 cells undergo cell death at random during the cell cycle rather that from the prereplicative phase. To exclude any influences of the IGF binding proteins (IGFBPs), all results were repeated with Des(1-3)IGF-I, which is unable to bind to any of the IGFBPs. However, this peptide was equally potent in inducing cell death. Finally, the addition of IGFBP-2 or the type 1 receptor blocking antibody IGF-IRalpha partly abrogated the death inducing effects of IGF-I and IGF-II. CONCLUSIONS: Insulin like growth factors induce cell death--apoptosis as well as necrosis--in cultured Wilms's tumour cells. Furthermore, it is proposed that this effect is mediated by the type 1 receptor.

Apoptosis↗
PubMed1998

A conserved structural element in horse and mouse IGF2 genes binds a methylation sensitive factor.

The equine IGF2 gene has been cloned and characterised. It spans a 9 kb region, which is substantially less than the corresponding human gene. Three coding exons and three untranslated leader exons, all highly homologous to those in other species, were identified. Downstream of the polyadenylation site in exon 6, a dinucleotide repeat sequence was identified. Three putative promoters (P1-P3) were localised in the 5' region of the gene. RNase protection analysis revealed two active promoters in fetal tissues, P2 and P3, whereas P3 was the only promoter active in adult tissues. This represents a transcriptional pattern different from that in humans or rodents. A novel structural element, an inverted repeat, is predicted in the 3' region of the IGF2 gene. This repeat is conserved between species and located in a region which is differentially methylated in the human and mouse genes and might therefore be involved in the imprinting mechanism. The inverted repeat acquires a stem-loop structure in vitro with a hybrid A/B-DNA conformation in the stem area. Both in horse and mouse, a methylation-sensitive protein binds this structure with a strong requirement for the loop area. Furthermore, the protein might be developmentally regulated.

Animals↗
PubMed1998

Expression of the insulin-like growth factor II gene in polychlorinated biphenyl exposed female mink (Mustela vison) and their fetuses.

AIM: To study how polychlorinated biphenyls (PCBs) affect fetal growth and the expression of the insulin-like growth factor (IGF II) gene in the mink (Mustela vision). METHODS: Ten female mink were each exposed to 0.65 or 1.3 mg Clophen A50/day, respectively, during the reproductive season. The numbers and sizes of viable fetuses were recorded. The expression of the IGF II gene was studied by northern blotting using a mink specific IGF II cDNA probe. RESULTS: The number of viable fetuses decreased after PCB exposure in a dose dependent fashion. Expression of the IGF II gene in adult livers from PCB exposed animals was decreased, compared with control animals, in a dose dependent fashion. In contrast, IGF II expression in placentas and fetuses was unaltered. Furthermore, the maternal excretion of urinary cortisol increased in both exposed groups during the implantation period. CONCLUSIONS: Expression of the IGF II gene is downregulated by PCB exposure in the adult liver. There is also an indication that the regulation of the expression of this gene differs between adult and fetal life.

Animals↗
PubMed1997

Regulation of a promoter from the mouse insulin like growth factor II gene by glucocorticoids.

We have microinjected constructs containing the murine IG II P3 promoter linked to different flanking sequences and a luciferase reporter gene into mouse pronuclei to establish transgenic lines of mice. The offspring was used as a source of embryonic fibroblast cultures and the effect of exogenous addition of glucocorticoids on transgene expression was analysed. It was found that both dexamethasone and hydrocortisone gave rise to a functional stimulation of the IGF II P3 promoter when the construct also contained other elements. This study demonstrates for the first time that there is an effect of glucocorticoids on the activation of an embryonic IGF II promoter, thus providing a molecular rationale for previous findings that glucocorticoids can under certain circumstances give rise to an increased transcriptional activity of the IGF II gene.

Animals↗
PubMed1996

Cloning and sequencing of an equine insulin-like growth factor I cDNA and its expression in fetal and adult tissues.

A cDNA for equine insulin-like growth factor I (IGF I) has been isolated by reverse transcriptase-polymerase chain reaction and subsequently sequenced. The sequenced fragment contained 465 bp including the coding regions for the signal peptide, the entire mature protein, and 4 amino acids into the E-peptide. Like its human counterpart, the mature equine IGF I peptide contains 70 amino acids and was 100% homologous between horse and man. The 49-amino-acid signal peptide had the threonine in position 26 of the human signal peptide substituted by isoleucine. The nucleotide homology across the entire clone was 96.3% between horse and man and 91.6% between horse and rat. The isolated cDNA hybridized to the same transcripts in fetal and adult tissues.

Amino Acid Sequence↗
PubMed1996

Growth factors and apoptosis.

Apoptosis is nowadays recognized as an important mechanism by which cells can be eliminated from the organism. In particular its role in tissue modelling during embryogenesis has been highlighted. The human teratoma cell line Tera 2, which in several respects acts as a human embryonic stem cell, can be induced to undergo apoptosis by reducing the serum content of the tissue culture medium. We report here that this process can be reversed by replacing serum with the heparin-binding growth factors, acidic FGF and basic FGF. In contrast, neither of the mammalian transforming growth factors (TGF-beta 1-3) managed to exert any effect on growth or apoptosis in Tera 2 cells.

Apoptosis↗
PubMed1995

Insulin-like growth factor II prevents apoptosis in a human teratoma derived cell line.

Aim-To study how insulin-like growth factor II (IGF-II) affects the behaviour of human teratoma cells.Methods-The human pluripotential teratoma cell line Tera 2 was cultured under serum-free conditions in the presence or absence of IGF-II. Effects on cell proliferation and apoptosis as well as on the expression of the proto-oncogene c-myc were studied.Results-In this study we show that Tera 2 cells deprived of serum undergo programmed cell death (apoptosis). The onset of nuclear fragmentation was observed 12 hours after serum withdrawal. The morphological changes of the Tera 2 cell nuclei were confirmed by the occurrence of a nucleosome ladder. However, the constitutive expression of the proto-oncogene c-myc was not decreased in parallel with initiation of apoptosis. The apoptotic response to serum withdrawal could be counteracted by simultaneous addition of IGF-II. In addition it was found that human testicular tumours (seminoma and embryonal carcinoma) contain raised levels of insulin-like growth factors.Conclusions-The precise roles of IGF-I and IGF-II have been unclear, and there is overwhelming evidence against these factors as primarily transforming agents. The finding that IGF-II apparently counteracts apoptosis in vitro may well explain its effects on tumours in vivo.

Journal Article↗
PubMed1995

Growth factors and apoptosis in development. The role of insulin like growth factor I and TGFbeta1 in regulating cell growth and cell death in a human teratocarcinoma derived cell line.

The balance between different cell populations in the developing organism is controlled by regulating the rates of multiplication, differentiation or death of its constituent cells. The human teratocarcinoma derived cell line Tera 2, which in several aspects mirrors early embryonic cells, can be induced to undergo programmed cell death (apoptosis) by depriving cell cultures of serum. This study demonstrates that this process can be reversed by replacing serum with physiological concentrations of insulin like growth factor I (IGF I). As a result, IGF I enhances the rate of Tera 2 cell proliferation in serum free medium. In contrast, Transforming Growth Factor beta1 did not exert any effect on growth or apoptosis in Tera 2 cells. The results indicate that one effect of growth factors on pluripotential cells is to regulate the balance between cell proliferation and cell death.

Apoptosis↗
PubMed1994

Insulin-like growth factor II in the horse: determination of a cDNA nucleotide sequence and expression in fetal and adult tissue.

Horse cDNA for insulin-like growth factor II (IGF II) has been isolated. cDNA was synthesized from bulk mRNA and subsequently PCR-amplified and sequenced. Like its human counterpart, the mature horse IGF II peptide contains 67 amino acids with only two substitutions, isoleucine instead of valine in position 35 and asparagine instead of serine in position 36. The nucleotide homology was 92.1% between horse and human and 87.8% between horse and mouse. The isolated cDNA hybridized to multiple transcripts in fetal and adult tissues, thus confirming earlier reports on developmental expression of this gene in the horse.

Amino Acid Sequence↗
PubMed1993

Developmental regulation of insulin like growth factor II expression in the horse.

The expression of the insulin like growth factor (IGF) II gene has been examined in the developing equine fetus. It was found that IGF II transcripts were present in abundant quantities in third trimester embryonic and extraembryonic tissues as for example the placenta. The expression of the IGF II gene was high in the fetal liver where two prominent transcripts--4.6 and 4.1--kB were produced. However, these transcripts could not be traced in the adult liver. Instead we found two different transcripts with the sizes of 4.0 and 2.9 kB in the adult liver. These findings taken together with the demonstration of heterologous IGF II cDNA hybridizing to equine DNA-digests suggests that the IGF II gene is under developmental control in the horse, with the possible existence of different promoters.

Animals↗
PubMed1993

Insulin-like growth factor II in the mink (Mustela vison): determination of a cDNA nucleotide sequence and developmental regulation of its expression.

Mink cDNA for insulin-like growth factor II (IGF-II) has been isolated by cDNA synthesis from bulk mRNA and subsequent PCR-screening. Positive clones were sequenced and analyzed. Analysis of a cDNA revealed that, compared with human, the mature mink IGF-II peptide contains 68 instead of 67 amino acids with a serine insertion at residue 40. With this exception, the homology between the human and mink mature peptide is 100% and is 94% between rat and mink. Comparing IGF-II transcripts in fetal and adult mink liver, fetal tissue contains three transcripts of 5.8, 4.5, and 4.0 kb. In contrast, adult liver expresses low levels of a 4.6-kb transcript.

Aging↗
PubMed1993

Heparin binding growth factors and the control of teratoma cell proliferation.

The role of basic fibroblast growth factor (bFGF) in the control of teratoma cell proliferation was examined. It was found that bFGF stimulates proliferation at low concentrations but induces cell migration at higher doses. These effects could be efficiently counteracted by addition of protamine sulphate. Moreover the bFGF gene is actively transcribed in primary human testicular embryonal carcinomas but was not expressed in any other embryonic tumour examined. The biological implications of these findings will be discussed.

Cell Division↗
PubMed1992

Concentration-dependent modulation of basic fibroblast growth factor action on multiplication and locomotion of human teratocarcinoma cells.

A human teratoma cell line (Tera 2) was grown in serum-free medium, and the population multiplication was stimulated by the addition of 1-10 ng basic fibroblast growth factor (bFGF)/ml. The bFGF-effect was abrogated by the addition of protamine sulphate. When high concentrations of bFGF were added, a preferential effect on cell locomotion was observed. 100 ng bFGF/ml stimulated cell movement but only exerted a marginal effect on cell multiplication. These observed exogenous requirements for multiplication and locomotion were complemented by the expression of bFGF receptors. Scatchard analysis of binding data suggests the existence of a high-affinity and a low-affinity class of receptors.

Cell Division↗
PubMed1992

Molecular analysis of patients with Wiedemann-Beckwith syndrome. I. Gene dosage on the short arm of chromosome 11.

Wiedemann-Beckwith syndrome (WBS) is characterised by a specific group of congenital malformations associated with an increased concurrent risk for development of a defined group of childhood neoplasms. The mode of inheritance is complex, but recently compiled family data suggest that it is an autosomal dominant trait of varying expression. It has previously been suggested that major rearrangements on the short arm of chromosome 11 may be involved in the aetiology of the disease, particularly in the region of the insulin like growth factor II (IGF-II) gene (11p15.5). This gene is thought to be parentally imprinted in the mouse and it has been suggested that in the human, duplication of the non-imprinted locus in WBS patient might lead to diploid expression of the gene and consequent general hyperplasia. This model predicts that there should be both frequent and parental origin specific duplication of the IGF-II gene in the patients. It was the aim of this study to examine the IGF-II locus and its surrounding chromosomal environment for such lesions in a large number of WBS patients. Using restriction fragment length polymorphism analysis for four linked markers on 11p and genomic clones internal to the IGF-II locus we could find no evidence of alteration or amplification of this area in any of the 11 patients investigated. In one patient who developed a Wilms tumour we could find no evidence for loss of any material on the short arm of chromosome 11 as reported previously.(ABSTRACT TRUNCATED AT 250 WORDS)

Beckwith-Wiedemann Syndrome↗
PubMed1992

Molecular analysis of patients with Wiedemann-Beckwith syndrome. II. Paternally derived disomies of chromosome 11.

In Wiedemann-Beckwith syndrome (WBS) a putative disease gene resides at the tip of the short arm of chromosome 11 in the region of the insulin growth like factor II (IGF-II) gene. Whilst changes in gene dosage in this area do not appear to be common in the syndrome, in familial cases the lesion appears to be dominant only when inherited through the female line. We undertook to examine the parental origin of the copies of chromosome 11 in a large group of WBS patients using a series of restriction fragment length polymorphisms (RFLPs) on 11p, and report here that in one sporadic case of WBS out of 14 both copies of chromosome 11 are derived from the father and are present in a normal dosage. This suggests that at least one mode of expression of the lesion is modified by genomic imprinting.

Beckwith-Wiedemann Syndrome↗
PubMed1991

Differentiation associated modulation of K-FGF expression in a human teratocarcinoma cell line and in primary germ cell tumours.

The human teratocarcinoma cell line Tera 2 can be induced to differentiate in vitro after exposure to retinoic acid. We show in this paper that whereas the K-FGF oncogene is expressed in undifferentiated cells, addition of retinoic acid rapidly (less than 60 min) downregulates the expression of this gene. However, when cells are cultured in RA for an extended period of time (greater than 15 days) K-FGF transcripts reappear. We also report that K-FGF is expressed in approximately one-third of primary human germ cell tumours but not in the corresponding normal testicular tissue.

Cell Differentiation↗