Regulation of amelogenin gene expression during tooth development.

The amelogenins are the predominant matrix proteins in developing enamel and are crucial for proper enamel mineralization. Transgenic mice were constructed in order to identify the segment of the amelogenin gene required for specific expression in enamel organ cells. A 3.

Insulin receptor substrate 1 is required for insulin-mediated mitogenic signal transduction.

Insulin treatment of mammalian cells immediately stimulates the tyrosine phosphorylation of a cellular protein of 185 kDa referred to as pp185 or IRS-1 (insulin receptor substrate 1). The potential role of the IRS-1 protein in insulin signaling has been examined by microinjecting affinity-purified antibodies into living cells. Stably transfected Rat-1 fibroblasts, which overexpress the human insulin receptor, were microinjected and subsequently stimulated with insulin or other growth factors.

[Protein A immunoadsorption al a new apheresis procedure for elimination of HLA antibodies].

The protein A immunoadsorption allows to remove antibodies of the classes IgG, IgM and IgA in special quantities from the plasma. IgG subclasses 1, 2 and 4 will be removed for 100% and IgG of class 3 for nearly 80%. For this reason immunoadsorptions are a useful therapeutic method especially for immunological diseases with antibodies of IgG type.

Purification and characterization of an acetyl esterase from Aspergillus niger.

Optimized acetyl esterase enzyme production conditions using Aspergillus niger ATCC 10864 in 14-L fermentation jars were determined to be 33 degrees C, 1.5 vvm aeration, and 300 rpm agitation without pH control. The acetyl esterase was purified by precipitation in 60-80% saturation in ammonium sulfate.

Sequence specificity in recognition of the epidermal growth factor receptor by protein tyrosine phosphatase 1B.

Protein tyrosine phosphatases all contain a conserved cysteine that forms an intermediate thiophosphate ester bond during tyrosine phosphate hydrolysis. A bacterial glutathione S-transferase fusion protein containing rat brain phosphatase PTP1b was constructed in which this conserved cysteine was mutated to serine. The resulting catalytically inactive enzyme was labeled in vivo to high specific activity with 35S, and the binding of this labeled fusion protein to the immunoprecipitated epidermal growth factor (EGF) receptor was evaluated.

Inhibition of binding of phospholipase C gamma 1 SH2 domains to phosphorylated epidermal growth factor receptor by phosphorylated peptides.

A series of tyrosine-containing peptides 1-12: [formula: see text] (six pairs with and without the tyrosine phosphorylated) has been synthesized. The peptides were derived from tyrosine autophosphorylation sites in the epidermal growth factor receptor (EGFR): Tyr 992, 1068, 1148 and 1173. Peptide 1, derived from the Tyr 992 site, inhibited binding of a 35S-labelled fusion protein containing both of the SH2 domains from PLC gamma 1 to the phosphorylated EGFR with an IC50 of 8 microM.

Transmembrane signaling by epidermal growth factor receptors lacking autophosphorylation sites.

Mutant epidermal growth factor (EGF) receptors in which the five known tyrosine autophosphorylation sites (tyrosines 992, 1068, 1086, 1148, and 1173) were replaced with phenylalanine residues were expressed in NIH-3T3 cells (5F-EGFR) and transmembrane signaling parameters compared with cells expressing wild-type EGF receptor (WT-EGFR). Mutant and wild-type clones were chosen expressing similar numbers of receptors and Scatchard analysis of 125I-EGF binding showed high and low affinity binding of equal affinities for both receptor types. EGF stimulated tyrosine phosphorylation of proteins to a much lesser degree in cells expressing 5F-EGFR relative to cells expressing WT-EGFR.

Direct analysis of the binding of the abl Src homology 2 domain to the activated epidermal growth factor receptor.

Src homology regions 2 (SH2) and 3 (SH3) are noncatalytic domains that are conserved among several proteins implicated in the regulation of cell proliferation. Using bacterially expressed fusion proteins containing the SH2 domain of the abl tyrosine kinase, we have quantitated the binding of these domains to the activated epidermal growth factor (EGF) receptor (EGFR). A 35S-labeled abl SH2 fusion protein binds to the human EGFR immunoprecipitated from EGF-treated NIH3T3 cells that overexpress the receptor.

Bombesin and epidermal growth factor stimulate the mitogen-activated protein kinase through different pathways in Swiss 3T3 cells.

Both bombesin and epidermal growth factor (EGF) are potent mitogens in Swiss 3T3 cells that nonetheless have dissimilar receptor structures. To explore possible common intracellular events involved in the stimulation of cellular growth by these two peptides, we have evaluated the regulation of the mitogen-activated protein (MAP) kinase. Exposure of Swiss 3T3 cells to bombesin, EGF or the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) causes the rapid and transient stimulation of the enzyme activity.

Nerve growth factor stimulates the tyrosine phosphorylation of a 38-kDa protein that specifically associates with the src homology domain of phospholipase C-gamma 1.

The cellular actions of nerve growth factor (NGF) involve changes in protein phosphorylation, initiated by the binding and subsequent activation of its tyrosine kinase receptor, the trk protooncogene (pp140c-trk). Upon exposure to NGF, a 38-kDa tyrosine-phosphorylated protein (pp38) is identified in both PC-12 pheochromocytoma cells and NIH3T3 cells transfected with the full-length human pp140c-trk cDNA (3T3-c-trk) that is specifically coimmunoprecipitated with pp140c-trk or phosphatidylinositol-phospholipase C (PLC)-gamma 1. In both PC-12 and 3T3-c-trk cells, NGF rapidly stimulates the association of pp140c-trk and pp38 with a fusion protein containing the src homology (SH) domains of PLC gamma 1.

Direct analysis of the binding of Src-homology 2 domains of phospholipase C to the activated epidermal growth factor receptor.

A number of proteins involved in intracellular signaling contain regions of homology to the product of the src oncogene that are termed Src-homology (SH) 2 domains. SH2 domains are believed to mediate the association of these proteins with various tyrosine-phosphorylated receptors in a growth factor-dependent manner. We have examined the kinetic characteristics of one of these interactions, the binding of the SH2 domains of phospholipase C gamma 1 with the receptor for epidermal growth factor (EGF).

Activation of phosphatidylinositol-3 kinase by nerve growth factor involves indirect coupling of the trk proto-oncogene with src homology 2 domains.

Growth factor receptor tyrosine kinases can form stable associations with intracellular proteins that contain src homology (SH) 2 domains, including the p85 regulatory subunit of phosphatidylinositol (PI)-3 kinase. The activation of this enzyme by growth factors is evaluated in PC12 pheochromocytoma cells and NIH 3T3 fibroblasts expressing the pp140c-trk nerve growth factor (NGF) receptor (3T3-c-trk). NGF causes the rapid stimulation of PI-3 kinase activity detected in anti-phosphotyrosine, but not in anti-trk, immunoprecipitates.

Odontogenic tumors in mice carrying albumin-myc and albumin-rats transgenes.

Odontogenic tumors that produce abnormal tooth-like structures are repeatedly observed in mandibles of mice that carry both albumin-myc and albumin-ras transgenes. The earliest lesions appear among the periodontal ligament mesenchymal cells, but later lesions include an epithelial component. Subsequent tumor development recapitulates the process of normal tooth formation, which requires multiple sequential cell signals, and results in cell differentiation, matrix secretion, and mineralization.

Nerve growth factor stimulates the activities of the raf-1 and the mitogen-activated protein kinases via the trk protooncogene.

Nerve growth factor (NGF) binds to two structurally unrelated transmembrane proteins on the surface of PC-12 cells, a 75-kDa glycoprotein with a short cytoplasmic sequence, and the trk protooncogene (pp140c-trk), a protein tyrosine kinase activated by NGF. Immediately after binding to cells, NGF induces changes in serine/threonine phosphorylation of several proteins. We have explored the relative roles of these two NGF binding proteins in mediating the activation of two intracellular kinases that may be responsible for some of these phosphorylations.

Diversity in cellular signaling for nerve growth factor and insulin: variations on a common theme.

Numerous similarities exist in the cellular signaling events observed for insulin and nerve growth factor. Because the two hormones share many functional properties, and exhibit similar effects on neurons, the possibility of common early signaling events has been explored. Many studies have focused on the important role of protein phosphorylation.

Inhibition of the cellular actions of nerve growth factor by staurosporine and K252A results from the attenuation of the activity of the trk tyrosine kinase.

The protein kinase inhibitors staurosporine and K252A inhibit some of the cellular actions of nerve growth factor (NGF). To explore the molecular mechanisms involved, we test the ability of these agents to block one of the earliest cellular responses to NGF, protein tyrosine phosphorylation. Concentrations of 10-100 nM staurosporine and K252A inhibit NGF-dependent tyrosine phosphorylation in PC12 cells and inhibit trk oncogene-dependent tyrosine phosphorylation in trk-transformed NIH3T3 (trk-3T3 cells).

Legal needle buying in St. Louis.

This study sought to determine if and why barriers to the over-the-counter purchase of syringes in the St. Louis metropolitan area might exist, given that no ordinance prohibits such a sale there. Two male research assistants (one African American, one White) approached 33 of the area's pharmacies to buy syringes.

p185c-neu and epidermal growth factor receptor associate into a structure composed of activated kinases.

The protein product of the neu protooncogene, p185c-neu, is structurally similar to the epidermal growth factor receptor (EGFR). Overexpression of these two receptor tyrosine kinases, but not either separately, leads to transformation and tumorigenicity. Heterodimerization of p185c-neu and EGFR occurs in M1 cells, which express both receptors.

Epidermal growth factor (EGF)-stimulated tyrosine phosphorylation and EGF receptor degradation in cells expressing EGF receptors truncated at residue 973.

Epidermal growth factor (EGF)-stimulated tyrosine phosphorylation of proteins was examined in cells expressing wild-type (WT-EGFR) EGF receptors or EGF receptors truncated at residue 973 (973-EGFR). A much broader spectrum of tyrosine phosphorylated proteins was found following EGF treatment of 973-EGFR expressing cells compared with cells expressing wild-type receptors. Several additional ras GTPase activating protein-associated tyrosine phosphorylated proteins were found in EGF-treated 973-EGFR cells relative to WT-EGFR cells.

Continuing bone expansion and increasing bone loss over a two-decade period in men and women from a total community sample.

As shown in 744 adult men and women aged 30-49 at entry and followed for 21.4 ± 0.9 years there is continuing subperiosteal expansion in both sexes as well as continuing and increasing endosteal surface resorption.

Immunotoxic effects of mercuric compounds on human lymphocytes and monocytes. II. Alterations in cell viability.

The major goal of this investigation was to examine the cytotoxic properties of both HgCl2 and MeHgCl, in terms of their ability to alter human T-cell and monocyte viability. Following treatment with HgCl2 (0-20 micrograms/ml) or MeHgCl (0-2 micrograms/ml), there was minimal reduction in lymphocyte viability at 1-4 hr. However, after exposure to mercury for 24 hr, cell death was apparent.

Molecular features of the viral and cellular Src kinases involved in interactions with the GTPase-activating protein.

GTPase-activating protein (GAP) enhances the rate of GTP hydrolysis by cellular Ras proteins and is implicated in mitogenic signal transduction. GAP is phosphorylated on tyrosine in cells transformed by Rous sarcoma virus and serves as an in vitro substrate of the viral Src (v-Src) kinase. Our previous studies showed that GAP complexes stably with normal cellular Src (c-Src), although its association with v-Src is less stable.