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E Kardami

Publications and source records attributed to E Kardami.

At least 55 records · Page 3Linked to original sources
PubMed1990

Differential expression of human placental growth-hormone variant and chorionic somatomammotropin in culture.

Regulation of human placental growth-hormone variant (hGH-V) in the presence of its own promoter has been studied. At term, 10-20% of placental mRNA is specific for chorionic somatomammotropin (hCS-A and -B) compared with 0.05% hGH-V, yet these genes show more than 90% sequence similarity at the nucleotide level. By using stable gene transfer of intact hGH-V and hCS-A genes into rat pituitary (GC) cells, synthesis and release of hGH-V and hCS are detected. This suggests that hGH-V as well as hCS is secreted during pregnancy. The hCS-A mRNA level is higher than that observed from the hGH-V gene in stably transfected GC cells. Also, a hybrid gene containing hGH-V 5'-flanking DNA was less active than a hybrid hCS-A gene containing equivalent sequences after transient transfection of these cells. This correlates with the binding of a known transcription factor to a proximal region (-97/-66) of the hCS-A promoter, and not the equivalent hGH-V gene sequences. These results indicate that differential expression of hGH-V and hCS in GC cells is related, in part, to the strength of their respective promoters, and suggest a similar mechanism may exist in the placenta.

Animals↗
PubMed1990

Stimulation and inhibition of cardiac myocyte proliferation in vitro.

We have examined the effect of crude cardiac tissue extracts as well as that of several growth factors and triiodothyronin (T3) on DNA synthesis of cardiac myocytes in culture. Extracts from embryonic and adult cardiac tissue stimulated DNA synthesis of myocytes. Atrial myocytes exhibited overall higher degree of stimulation than their ventricular counterparts and extracts from adult atrial tissue had the highest apparent mitogenic activity for atrial myocytes. We have shown that adult heart contains basic fibroblast growth factor (bFGF), especially in the atria. Transforming growth factor beta (TGF beta) and insulin-like growth factors (IGFs) are also accumulated in cardiac tissues. We found that bFGF and the IGFs stimulate myocyte cell proliferation and DNA synthesis. These factors also stimulate cardiac non-muscle proliferation, especially in the presence of serum. TGF beta inhibited proliferation and DNA synthesis and cancelled the effect of bFGF or IGFs on the myocytes. T3 also diminished the bFGF-induced mitogenic stimulation of cardiomyocytes. Our data suggest that these factors may be involved in the regulation of cardiomyocyte proliferation in vivo.

Animals↗
PubMed1990

The human placental growth hormone variant is mitogenic for rat lymphoma Nb2 cells.

Although there is evidence that human (h) placental GH variant (hGH-V) possesses a growth-promoting function, lactogenic activity by the hormone has not been demonstrated. Rat anterior pituitary tumor (GC) cells stably transfected with the hGH-V gene (GC [hGH-V] cells) synthesize and secrete hGH-V. This hormone shares considerable structural similarity with pituitary growth hormone (hGH-N) and chorionic somatomammotropin (hCS) at the nucleotide (greater than 90%) and amino acid (greater than 80%) levels. As expected, both hGH-N and hCS antibodies detect hGH-V by immunoblotting. However, hGH-V, but not hGH-N or hCS, cross-reacts with human or rat pituitary prolactin (PRL) antibodies. These data indicate that structural features shared by hGH-V and pituitary PRL are not present in hGH-N or hCS. Comparison of amino acid sequences implicates two regions that may account for a common epitope between hGH-V and hPRL, and structural difference from hGH-N and hCS. The possible lactogenic activity by hGH-V was assessed in a rat lymphoma Nb2 cell bioassay. Conditioned medium from GC[hGH-V] cells permitted growth of lactogen-dependent Nb2 lymphoma cells in culture. This activity was blocked by antibodies raised to rat PRL but not hPRL or hGH-N. Comparison of the hGH-V amino acid sequence with those from 14 other lactogenic hormones, including hPRL, hCS and hGH-N, reveals 6 conserved amino acids. These data indicate a lactogenic as well as growth-promoting function for the secreted hGH-V protein in vivo.

Amino Acid Sequence↗
PubMed1990

A potential new role for bFGF in host-parasite interactions.

Basic fibroblast growth factor (bFGF) is a mitogenic polypeptide highly conserved between species, implicated in regenerative processes and present in all tissues examined. In the heart, bFGF is localized in association with nuclei, extracellular matrix and intercalated discs of cardiomyocytes. In this article is reported bFGF association with the intramuscular parasitic protozoan Sarcocystis in situ, in bovine hearts, detected by indirect immunofluorescence. Parasitic cysts appear connected directly to specialized host cell junctions: bFGF provides structural continuity between parasitic cyst wall and myocyte intercalated discs. Other proteins associated with intercalated discs such as desmin or desmoplakin are not detected in the cysts. Association with Sarcocystis suggests a new role for bFGF in the context of parasitic invasion and establishment.

Animals↗
PubMed1990

Characterization of two preparations of antibodies to basic fibroblast growth factor which exhibit distinct patterns of immunolocalization.

Immunoglobulins reactive against basic fibroblast growth factor (bFGF) were obtained from the serum of a single rabbit immunized against residues [1-24] of bFGF conjugated to keyhole limpet hemocyanin (KLH). Pure immunoglobulin preparations no. 1 and no. 2 were prepared using different affinity chromatography columns and preabsorption to KLH-coupled Sepharose for preparation no. 1. Both preparations no. 1 and no. 2 were specific for bFGF in in vitro assays. Competition with synthetic peptides suggests that preparations no. 1 and no. 2 recognize predominantly epitope(s) within residues [16-24]bFGF or residues [1-10]bFGF, respectively, in situ. Furthermore, no. 2 (but not no. 1) antibodies can react with tissue-(heparin-)-bound antigen. When used in indirect immunofluorescence for bFGF in frozen heart sections, preparation no. 1 stained predominantly muscle intercalated discs (IcDs); muscle nuclei were also stained, in an overall punctate fashion. Preparation no. 2 stained muscle nuclei strongly, in association with the nuclear envelope; it also stained basement-membrane associated bFGF. Differences in immunostaining were also observed in uterine smooth muscle and kidney sections but not in skeletal muscle. It is plausible that accessibility of various epitopes within the amino-terminal region depends strongly on the local interactions of bFGF. Our data illustrate the importance of using several different antibodies to localize bFGF in a tissue.

Absorption↗
PubMed1989

Basic fibroblast growth factor in atria and ventricles of the vertebrate heart.

Extracts from atrial and ventricular heart tissue of several species (chicken, rat, sheep, and cow) are strongly mitogenic for chicken skeletal myoblasts, with the highest apparent concentration of biological activity in the atrial extracts. Using several approaches (biological activity assay and biochemical and immunological analyses), we have established that (a) all cardiac extracts contain an 18,000-D peptide which is identified as basic fibroblast growth factor (bFGF) since it elutes from heparin-Sepharose columns at salt concentrations greater than 1.4 M and is recognized by bFGF-specific affinity-purified antibodies; (b) bFGF is more abundant in the atrial extracts in all species so examined; (c) avian cardiac tissue extracts contain the highest concentration of immunoreactive bFGF; and (d) avian ventricles contain a higher relative molecular mass (23,000-D) bFGF-like peptide which is absent from atrial extracts. Examination of frozen bovine cardiac tissue sections by indirect immunofluorescence using anti-bFGF antibodies shows bFGF-like reactivity associated with nuclei and intercalated discs of muscle fibers. There is substantial accumulation of bFGF around atrial but not ventricular myofibers, resulting most likely from more extensive endomysium in the atria. Blood vessels and single, nonmuscle, connective tissue cells react strongly with the anti-bFGF antibodies. Higher bFGF content and pericellular distribution in atrial muscles suggest a correlation with increased regenerative potential in this tissue. Distribution within the myofibers is intriguing, raising the possibility for an intimate and continuous involvement of bFGF-like components with normal myocardial function.

Animals↗
PubMed1988

Heparin inhibits skeletal muscle growth in vitro.

Heparin or heparan sulfate proteoglycan (HeSPG), but not chondroitin sulfate or hyaluronic acid, exerts a pronounced inhibitory effect on muscle growth in vitro, as determined by total protein, myosin accumulation or synthesis, and [3H]thymidine incorporation studies. Primary muscle fibroblast culture growth is also inhibited by heparin but to a substantially lesser degree compared to muscle (30% and over 90% inhibition of growth, respectively). Heparin-induced inhibition of skeletal muscle growth is a consequence of its interaction with a growth factor(s) present in the media used to support myogenesis; heparin-Sepharose column absorbed horse serum can support muscle growth only in the presence of added heparin-binding growth factors like fibroblast growth factor (FGF) or chicken muscle growth factor (CMGF). Furthermore, heparin prevents the binding of iodinated FGF to the myoblast surface. We also show that the extent of muscle growth is a function of the relative amounts of heparin and FGF in culture. Finally, we provide evidence indicating that FGF can combine with endogenously occurring heparin-like components: immobilized FGF binds sodium-[35S]sulfate labeled components secreted in muscle culture conditioned medium, an interaction inhibited by anti-HeSPG antibodies or heparin, but not by other sulfated glycosaminoglycans. Since heparin binding growth factors not only stimulate myoblast proliferation but also actively inhibit the onset of muscle differentiation (G. Spitzz, D. Roman, and A. Strauss (1986). J. Biol. Chem. 261, 9483-9488), their interaction with naturally occurring heparin-like components may be an important physiological mechanism for modulating muscle growth and differentiation in development and regeneration.

Animals↗
PubMed1988

Effect of butyrate on thyroid hormone-mediated gene expression in rat pituitary tumour cells.

These studies correlate the effects of (sodium) butyrate on intranuclear thyroid hormone receptor levels, with influences on both endogenous and transfected rat growth hormone (rGH) gene expression and regulation by L-triiodothyronine (T3). In rat anterior pituitary tumour (GH3) cells, 5.0 mM butyrate elicits a biphasic reduction in the number of nuclear T3 receptors. About 75% are depleted rapidly (t1/2 = 7 h), and the remaining receptors are depleted more slowly (t1/2 = 59 h). GH3 cells were treated with increasing concentrations of butyrate (0-5.0 mM), plus or minus 10 nM T3 for 48 h. Total cytoplasmic RNA, cellular protein and medium were analysed for rGH levels with radiolabelled rGH cDNA or antibodies. A greater than 50-fold increase in rGH mRNA level was seen after T3 treatment in the absence or presence of 0.1 mM butyrate. However, 1.0 and 5.0 mM butyrate decreased the stimulation of rGH mRNA levels by T3 to 10- and less than 2-fold, respectively. Control mRNA levels were decreased slightly by increasing butyrate concentrations; rGH mRNA level was 2- to 3-fold higher in the absence of 5 mM butyrate. The pattern of butyrate/T3 response displayed by both cellular and secreted rGH was similar to that seen with mRNA levels. Thus, the predominant effect of butyrate on T3-mediated regulation of growth hormone gene expression is at the level of transcription or mRNA accumulation. A hybrid gene containing 5'-flanking DNA from the rGH gene fused to the bacterial gene coding for chloramphenicol acetyl transferase (CAT), was used to transfect rat pituitary tumour cells with or without butyrate and T3 treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Selected muscle and nerve extracts contain an activity which stimulates myoblast proliferation and which is distinct from transferrin.

Extracts from normal chicken anterior latissimus dorsi and dystrophic pectoralis major muscles and from normal chicken sciatic nerves induce a growth stimulation in chicken and rat myogenic cell cultures. Transferrin is only partially responsible for the observed stimulation since the addition of the extracts to transferrin-saturated cultures induces a further growth response and extracts from which transferrin has been removed by immunoabsorption still retain a substantial portion of their stimulation activity. The active fractions of muscle and nerve extracts display heat, acid, and organic solvent inactivation. Gel filtration of ammonium sulfate fractionated activity from the anterior latissimus dorsi muscle suggests the presence of a growth factor in the molecular weight range of 10,000 to 30,000.

Animals↗
PubMed1985

Myogenic growth factor present in skeletal muscle is purified by heparin-affinity chromatography.

A myogenic growth factor has been purified from a skeletal muscle, the anterior latissimus dorsi, of adult chickens. In the range of 1-10 ng, this factor stimulates DNA synthesis as well as protein and muscle-specific myosin accumulation in myogenic cell cultures. Purification is achieved through binding of the factor to heparin. The factor is distinct from transferrin and works synergistically with transferrin in stimulating myogenesis in vitro.

Animals↗
PubMed1983

Classification of tropomyosin components into an alpha-like or a beta-like family by partial peptide mapping.

Tropomyosins can be classified as belonging to an alpha-like or a beta-like family depending on the absence or presence, respectively in their protease-V8 digestion pattern of two peptides with an apparent molecular mass of 21 kDa. Chicken cardiac tropomyosin and the 43 kDa component from gizzard tropomyosin are accordingly classified as alpha-like tropomyosins, while the 33 kDa gizzard tropomyosin component is a beta-like tropomyosin. The 21 kDa peptides have an overall charge which is more positive than that of the intact tropomyosin or any other tropomyosin peptide and probably contain the -NH2 half of the molecule.

Animals↗
PubMed1983

Fast and slow chicken skeletal muscles contain different alpha and beta tropomyosins.

Avian tropomyosin has been purified from fast skeletal muscles (breast muscle and posterior latissimus dorsi : PLD) and from a slow skeletal muscle (anterior latissimus dorsi : ALD) and the alpha and beta subunits have been further separated using preparative gel electrophoresis. These subunits have been subjected to partial proteolysis using different proteolytic enzymes. In this communication we show that this procedure allows to distinguish not only between fast and slow alpha tropomyosin but also between fast and slow beta tropomyosin. Furthermore we have raised an antiserum against the fast alpha tropomyosin and we present evidence to show that this antiserum does not cross-react with the slow alpha tropomyosin. These results are taken to indicate that all these tropomyosin subunits represent different gene products.

Animals↗
PubMed1980

Phosphorylation and the binding of calcium and magnesium to skeletal myosin.

It has previously been shown that the binding of calcium and magnesium ions to the isolated metal-binding light chains, i.e. those dissociable by 5,5'-dithiobis(2-nitrobenzoate), of rabbit skeletal muscle myosin is moderated by phosphorylation and is accompanied by a sizeable conformational change. As judged by circular dichroism in the region of the aromatic Cotton effects, this conformational change occurs when calcium ions bind to the light chain in situ on the myosin head. Moreover the affinity for calcium is again changed by phosphorylation. The change in chymotryptic digestion patterns, in particular the protection of the head-rod junction in insoluble myosin, by divalent cations, has been used to obtain binding profiles. The results are consistent with the presence of a single class of independent sites, showing no cooperativity. The affinity of the site for both calcium and magnesium ions is enhanced by 1-2 orders of magnitude when the light chain in incorporated in the myosin heads. The effect of phosphorylation on the affinity persists in these circumstances, being marked for calcium and small for magnesium. On phosphorylation the calcium binding constant falls from 8 x 10(6) M-1 to 4 x 10(6) M-1 at physiological ionic strength, compared with 2.5 x 10(5) M-1 and 5 x 10(4) M-1 for the isolated light chains. The sensitivity of the proteolytic cleavage sites is affected by phosphorylation. Thus in the absence of calcium ions the yield of subfragment 1 at a low chymotrypsin concentration is substantially greater in dephosphorylated than phosphorylated myosin, whereas at saturating concentrations of calcium ions attack at the light meromyosin/heavy meromyosin junction is favoured by phosphorylation. These observations may signify a structural effect of phosphorylation on the prevailing interactions within the myosin filament in physiological solvent conditions.

Animals↗
PubMed1979

Interaction of ADP with skeletal and cardiac myosin and their active fragments observed by proton release.

The technique of proton release measurement has been used to explore the binding of ADP to skeletal and cardiac myosins and their active fragments in a variety of conditions. It has proved possible to obtain binding profiles on intact myosin in the filamentous, undissolved form in physiological solvent conditions. Binding constants are given. At higher ionic strength (0.5 M potassium chloride) the binding profile of magnesium-ADP. is compatible with the presence of two types of site, differing from one another both in respect of affinity and the number of protons released per site. Studies with cardiac myosin reveal no such indications of heterogeneity, and are consistent with the presence of a single population of thermodynamically indistinguishable sites. In the absence of divalent cations, in solutions containing potassium ions and EDTA, ADP binds with absorption rather than liberation of protons. The pH profile of proton absorption at saturation can be fitted in terms of an ionising group with an unperturbed pK of 9.4, and at least one of lower pK(5.9). The dissociation constant (pH8 at 5 degrees C) is about 8 microM, and the affinity for uncomplexed ADP is thus only slightly weaker than that for magnesium-ADP

Adenosine Diphosphate↗
PubMedDate not supplied

Immunolocalization of basic fibroblast growth factor (bFGF) in growing and growth-inhibited placental cells: a possible role for bFGF in placental cell development.

The distribution of basic (b) fibroblast growth factor (FGF) in growing and growth-arrested human placental tumour cells, as well as normal placental villous trophoblasts, was studied by immunofluorescence microscopy with antibodies to the amino terminus of bFGF. Placenta (FAR, FEG-3), breast (MCF-7, T-47D), cervix (HeLa) and uterine (HEC-1-A) tumour cells showed the same two patterns after immunofluorescent staining with antibodies to bFGF: (i) a perinuclear pattern and (ii) an intense homogeneous staining of the nucleus and cytoplasm. The homogeneous bFGF staining pattern was associated predominantly with actively dividing cells, observed at different stages of mitosis and cytokinesis. Placental (FEG-3) cell division was inhibited with methotrexate (MTX), a chemotherapeutic agent used in the treatment of placental tumours. MTX-treated FEG-3 cells as well as 'normal' non-proliferative placental (syncytiotrophoblast) cells from term placentae, showed perinuclear staining with antibodies to bFGF and immunofluorescence microscopy. The nuclear localization of bFGF in dividing but not non-dividing placental cells, suggests a role for bFGF in cytotrophoblast proliferation in vivo.

Cell Nucleus↗