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Biomedical subjects

Y Salomon

Publications and source records attributed to Y Salomon.

At least 91 records · Page 5Linked to original sources
PubMed1974

5'-Guanylylimidodiphosphate, a potent activator of adenylate cyclase systems in eukaryotic cells.

5'-Guanylylimidodiphosphate (Gpp(NH)-p) stimulates adenylate cyclase [ATP-pyrophosphate-lyase (cyclizing), EC 4.6.1.1] activity in plasma membranes isolated from frog and salmon erythrocytes, from rat adrenal, hepatic, and fat cells, and from bovine thyroid cells. The nucleotide acts cooperatively with the various hormones (glucagon, secretin, ACTH, thyrotropin, and catecholamines) that stimulate these adenylate cyclase systems with resultant activities that equal or exceed those obtained with hormone plus GTP or with fluoride ion. In the absence of hormones, Gpp(NH)p is a considerably more effective activator than GTP, and, under certain conditions of incubation, stimulates rat fat cell adenylate cyclase to levels of activity (about 20 nmoles of 3',5'-adenosine monophosphate mg protein per min) far higher than reported hitherto for any adenylate cyclase system examined. The nucleotide activates frog erythrocyte adenylate cyclase when the catecholamine receptor is blocked by the competitive antagonist, propranolol, and activates the enzyme from an adrenal tumor cell line which lacks functional ACTH receptors. In contrast, Gpp(NH)p does not stimulate adenylate cyclase in extracts from Escherichia coli B. Gpp(NH)p appears to be a useful probe for investigating the mechanism of hormone and nucleotide action on adenylate cyclase systems in eukaryotic cells.

Adenylyl Cyclases↗
PubMed1971

Concomitant synthesis of membrane protein and exportable protein of the secretory granule in rat parotid gland.

After enzyme secretion the membrane of the secretory granule, which had been fused to the cell membrane, was resorbed into the cell. Experiments were therefore carried out to test whether formation of new secretory granules involves reutilization of the resorbed membrane or synthesis of a new membrane, de novo, from amino acids. Incorporation of amino acids-(14)C into proteins of various cell fractions was measured in vivo, 30, 120, and. 300 min after labeling. At all times the specific radioactivity of the secretory granule membrane was about equal to that of the granule's exportable content. At 120 and 300 min the specific radioactivity of the granule membrane and of the granule content was much higher than that of any other subcellular fraction. It is therefore concluded that the protein of the membrane is synthesized de novo concomitantly with the exportable protein. The proteins of the granule membrane could be distinguished from those of the granule content by gel electrophoresis. All major bands were labeled proportionately to their staining intensity. The amino acid composition of the secretory granule membrane was markedly different from that of the granule's content and also from that of the mitochondrial membrane. The granule membrane showed a high proline content, 30 moles/100 moles amino acids. The analyses show that the radioactivity of the granule membrane is indeed inherent in its proteins and is not due to contamination by other fractions. The possibility is considered that the exportable protein leaves the endoplasmic reticulum already enveloped by the newly synthesized membrane.

Amino Acids↗
PubMedDate not supplied

Inhibitors of protein tyrosine phosphorylation: preliminary assessment of activity by time-resolved fluorescence.

Epidermal growth factor (EGF) receptor (ErbB1)-associated tyrosine kinase inhibitors may act as potential chemotherapeutic agents. In order to assess the inhibitory activity of these compounds, we developed a simple and sensitive assay based on time-resolved fluorescence. In this technique, crude cell lysates bearing the ErbB1 receptor were captured in microtitre plates immobilized with monoclonal anti-ErbB1 antibody SG 565. Subsequently, the phosphotyrosine content of the cell lysates was quantified by a europium-labelled anti-phosphotyrosine antibody. Thus, genistein, a tyrosine kinase inhibitor, was capable of reducing by half the tyrosine phosphorylation caused by the binding of EGF to A431 cells, whereas 6-carboxymethyl genistein did not inhibit protein tyrosine phosphorylation. This assay is simple to perform, does not use radioactive substrates, and can be useful for screening EGF receptor tyrosine kinase inhibitors from natural products or synthetic compounds. Moreover, the assay has a high signal:noise ratio and is suitable for large-scale screening.

Animals↗
PubMedDate not supplied

The actions of calcitonin on the TM3 Leydig cell line and on rat Leydig cell-enriched cultures.

Studies demonstrating calcitonin receptors on Leydig cells have suggested that these cells may be one of the many sites affected by this peptide. To investigate this possibility, the effect of synthetic salmon calcitonin on the TM3 Leydig cell line (derived from immature mouse Leydig cells) and on primary Leydig cell-enriched preparations was examined. Synthetic salmon calcitonin stimulated the conversion of [3H]adenine to [3H]cyclic AMP in TM3 cells. In addition, the hormone stimulated the basal secretion of testosterone in both TM3 cell- and Leydig cell-enriched cultures and potentiated the action of hCG on Leydig cell-enriched cultures. Synthetic salmon calcitonin also increased the concentration of androgen and estrogen receptors in cultured TM3 Leydig cells by 2- and 4-fold, respectively, when added to the culture medium (1 micrograms/ml). The fact that 8-bromo-cyclic AMP decreased both androgen and estrogen receptor concentrations suggested that the effect of calcitonin on sex steroid receptors is not mediated by its effect on cyclic AMP in these cells. The possibility that the action of calcitonin on steroid receptors might be mediated by another messenger such as calcium (Ca2+) was therefore considered. Progressively lowering the concentration of Ca2+ in the culture medium of the cells from 1.5 mM to less than 0.01 mM decreased the concentration of both androgen and estrogen receptors. Returning the Ca2+ concentration to normal levels (1.5 mM) restored steroid receptor levels. Receptor levels were also decreased when the extracellular Ca2+ concentration was lowered to 0.5 mM, and treatment with the Ca2+ ionophore, A23187 (1 microM), restored receptor levels to normal. The calcium channel blocker, verapamil, decreased the androgen receptor concentration but unexpectedly increased the concentration of estrogen receptors. It was concluded that calcitonin stimulates cAMP formation and testosterone secretion, and increases the concentration of sex steroid receptors. These observations provide evidence that the previously demonstrated calcitonin receptors on Leydig cells may be coupled to several biologic responses in this cell type.

Animals↗
PubMedDate not supplied

Correlation of MR imaging and histologic findings in mouse melanoma.

M2R melanoma tumors in male C57 black mice were used to correlate magnetic resonance (MR) images with the corresponding histologic slices and to determine if analysis of the achievable correlation can provide a basis for predicting gross histologic features with MR imaging alone. The MR imaging sections obtained at 4.7 T were each 680 microns thick, with an in-plane resolution of 195 microns. The distribution of melanin within the histologic slices correlated well with the high-signal-intensity regions on the T1-weighted images (T1WIs), while these regions had low signal intensity on the T2-weighted images (T2WIs), providing evidence that melanin or melanin-associated paramagnetic species are responsible for the observed proton relaxation rate enhancement. Viable melanoma cells typically showed intermediate signal intensity on T2WIs, T1WIs, and proton-density images. Necrosis typically had high signal intensity on T2WIs, T1WIs, and proton-density images. Quantitation of the MR imaging results, followed by statistical analysis, demonstrated statistically significant differences between melanin-rich, viable-melanoma, and necrotic regions on MR images.

Animals↗
PubMedDate not supplied

Odorant-sensitive adenylate cyclase may mediate olfactory reception.

The mechanism of the sense of smell has long been a subject for theory and speculation. More recently, the notion of odorant recognition by stereospecific protein receptors has gained wide acceptance, but the receptor molecules remained elusive. The recognition molecules are believed to be quite diverse, which would partly explain the unusual difficulties encountered in their isolation by conventional ligand-binding techniques. An alternative approach would be to probe the receptors through transductory components that may be common to all receptor types. Here we report the identification of one such transductory molecular component. This is an odorant-sensitive adenylate cyclase, present in very large concentrations in isolated dendritic membranes of olfactory sensory neurones. Odorant activation of the enzyme is ligand and tissue specific, and occurs only in the presence of GTP, suggesting the involvement of receptor(s) coupled to a guanine nucleotide binding protein (G-protein). The olfactory G-protein is independently identified by labelling with bacterial toxins, and found to be similar to stimulatory G-proteins in other systems. Our results suggest a role for cyclic nucleotides in olfactory transduction, and point to a molecular analogy between olfaction and visual, hormone and neurotransmitter reception. Most importantly, the present findings reveal new ways to identify and isolate olfactory receptor proteins.

Adenylyl Cyclases↗
PubMedDate not supplied

Water-filtered infrared-A radiation: a novel technique for localized hyperthermia in combination with bacteriochlorophyll-based photodynamic therapy.

A novel application of an infrared-A (IR-A) radiation source equipped with a water-filter in the radiation path is described, which allows for tumour treatment with a simultaneous combination of localized hyperthermia (HT) and bacteriochlorophyll-serine (Bchl-ser) based photodynamic therapy (PDT). Using this system, the IR-A radiation was used to heat tumours to 43 degrees C for 60 min, while at the same time activating the Bchl-ser which was injected i.v. at a dose of 20 mg/kg, 10 min following commencement of HT. The growth of tumours undergoing this combined therapy was compared to that of tumours undergoing HT alone or sham-treated controls. Within the 90 day observation period, 100% of tumours in sham-treated animals, 80% in HT-treated animals and only 17% in HT + Bchlser-treated animals reached the end point target volume of 3.5 ml. Thus, the tumour growth inhibition effect of HT can be substantially enhanced by combination with Bchl-ser-PDT. This novel technique has proved to be well-tolerated, easy to apply and should be suitable for treatment of superficial malignancies, especially where hypoxic tumour areas are present.

Animals↗