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Y Sharoni

Publications and source records attributed to Y Sharoni.

52 records · Page 3Linked to original sources
PubMed1985

Membranal tyrosine protein kinase activity (but not cAMP-dependent protein kinase activity) is associated with growth of rat mammary tumors.

DMBA induced rat mammary tumors were used to study the association of tyrosine protein kinase activity with tumor growth. Pharmacological manipulations of blood prolactin level, by perphenazine and bromocriptine, were used to stimulate or arrest tumor growth, respectively. During perphenazine treatment, a 2-3-fold increase in membranal tyrosine protein kinase activity, measured with angiotensin II as substrate, preceded the 3-4-fold increase in tumor area. At the same time the cAMP-dependent protein kinase activity, measured with kemptide as substrate, did not change.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Tyrosine protein kinase activity in the DMBA-induced rat mammary tumor: inhibition by quercetin.

Tyrosine protein kinase activity was measured in membranes from DMBA-induced mammary tumors, with Angiotensin II as substrate. The apparent Km for the peptide was 3.3 mM. This enzymatic activity is inhibited by Ca+2; Mn+2 can replace Mg+2 with an increase in the Km for ATP from 47 /microM to 172 microM. The enzymatic activity was not affected by cyclic AMP but was inhibited in dose dependent manner by quercetin, a bioflavonoid which is known to inhibit proliferation of malignant cells in vitro.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

cAMP-independent protein kinase activity is correlated with growth of rat mammary tumors.

An important portion of the protein kinase activity in the 7,12-dimethylbenz(a)anthracene (DMBA) induced rat mammary tumour is inhibited by the bioflavonoid quercetin (10(-4) M). By partial purification on a DEAE Cellulose column it was shown that the quercetin-inhibitable enzyme activity can be eluted in a separate peak which contains markedly reduced cAMP-dependent protein kinase activity. Since quercetin does not affect the cAMP-dependent protein kinase activity, this drug becomes a potent tool for the quantitation of this special activity in the tumor. By hormonal manipulation, namely ovariectomy and estrogen treatment, it was shown that changes in the growth rate of the tumour were closely correlated with the magnitude of these special protein kinase activities. These results suggest a possible cause-and-effect relationship between cyclic AMP-independent protein kinase activity and tumour malignancy in this chemically induced tumor. These data are similar to recent findings in viral-induced malignant transformation.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Protein kinase activity in the rat mammary gland during pregnancy, lactation, and weaning: a correlation with growth but not with progesterone receptor levels.

A protein kinase activity fraction was defined in cytosols and membranes of mammary tissue isolated from rats during pregnancy lactation, and weaning. By partial purification on DEAE-cellulose columns, it was shown that this protein kinase activity is cAMP independent and that its preferential substrate is casein and not histone. This protein kinase activity is inhibited by the bioflavonoid quercetin at doses that do not inhibit cAMP-dependent protein kinase activity. The enzyme requires Mg2+ and is inactive in the presence of 10 mM Ca+2; these properties distinguish this activity from casein kinase activity found in the Golgi fraction and involved in milk protein processing. By following the physiological cycle of mammary gland development during pregnancy, lactation, and weaning, we found a close correlation between proliferation, expressed as the DNA content per gland, and quercetin-inhibited cytosolic protein kinase activity. Moreover, changes in this phosphorylating activity preceded the glandular growth changes. There was a less significant correlation between the growth process and protein kinase activity in the membrane fraction. The cytosolic cAMP-dependent protein kinase activity showed (only partial) correlation with growth only during pregnancy. Cytosolic progesterone receptor levels in mammary tissue were used as an estrogenic marker. Tissue growth correlated with progesterone receptor levels during pregnancy, where estrogens are the predominant hormones affecting tissue proliferation. However, no such correlation was found during lactation and weaning, when PRL is the major hormone affecting mammary gland growth. These results suggest that quercetin-inhibitable protein kinase activity is not merely another estrogenic marker, but represents more general regulatory activity which might be connected to growth processes of breast tissue.

Animals↗
PubMed1984

Cyclic changes in rat uterine proliferation during the estrous cycle are preceded by changes in protein kinase activity.

A protein kinase activity was defined in cytosols and membranes of rat uterus by using two types of enzyme inhibitors. The heat stable protein kinase inhibitor inhibited the cAMP-stimulated protein kinase but not the basal activity measured in the absence of the cyclic nucleotide. However, this basal activity was inhibited by quercetin in a dose-dependent manner, whereas the cAMP-stimulated protein kinase was not inhibited by this bioflavonoid. Thus, quercetin can be used as a tool to define a specific fraction of cAMP-independent protein kinase activity in rat uterine cytosols and membranes. The mature rat uterus is characterized by short (4 days) cyclic changes in tissue growth. Cell proliferation expressed as total uterine DNA content is observed on proestrus, reaches its peak at estrus, and declines sharply during metestrus and diestrus. The quercetin-inhibited protein kinase activity in the membranes of this tissue also changes cyclically and precedes by one phase the cyclic change in tissue proliferation. The clearest effect was seen when the protein substrates for this protein kinase activity were endogenous membrane proteins partially solubilized by Triton X-100 treatment. In contrast no change was observed in cytosolic, quercetin-inhibited protein kinase activity. The cAMP-stimulated protein kinase activity decreased slightly on diestrus. These results support our working hypothesis that tissue proliferation in the uterus and other tissues such as rat mammary gland and mammary tumors, correlates with cAMP-independent, quercetin-inhibited, protein kinase activity in these tissues.

Animals↗
PubMed1982

A comparison of plasminogen activators derived from rat plasma, primary rat hepatocytes and isolated perfused rat liver.

Of the two cell types it was possible to culture from the dissociated rat liver, hepatocytes and Kupffer cells, only the former were fibrinolytically active. Rat hepatocytes during the first 24 hr in culture secreted two plasminogen activators with molecular weights identical to those found in rat plasma, an 80,000-dalton form (PA-80) and a 45,000-dalton form (PA-45). Partially purified preparations of plasminogen activators from both sources were subjected to isoelectric focusing (IEF) to compare characteristics further. There were three distinct peaks of PA-45 in each preparation with isoelectric points of 7.1, 7.2 and 7.4; all electrophoretic forms had the same low affinity to fibrin. PA-80 from both sources displayed similar IEF profiles with forms ranging from pH values of 7 to 8, all with the same high affinity to fibrin. The major form of PA-80 in the plasma preparation had an isoelectric point of 7.9 whereas that in the hepatocyte preparation had an isoelectric point of 7.6. The isolated perfused rat liver was also shown to produce both PA-80 and PA-45 emphasizing the physiological relevance of the findings with hepatocytes. It is concluded that in the rat hepatocytes contribute to the plasma profile with regard to the plasminogen activator content.

Animals↗
PubMed1976

Secretion of old versus new exportable protein in rat parotid slics. Control by neurotransmitters.

The possibility that old and new secretory granules do not mix and that older exportable protein can be secreted preferentially was tested on parotid gland in vitro. Slices from fasted animals were pulse labeled for 3 min with L-[3H]leucine. Subcellular fractionstion showed that after 1 90-min chase period, the formation of new labeled secretory granules was mostly completed. The ratio of label in secretory granules to label in microsomes increased 250-fold during the period 5--90 min postpulse. After the 90-min chase, a submaximal rate of secretion was initiated by adding a low concentration of isoproterenol to the slices. Preferential secretion of old unlabeled exportable protein was evident from the finding that the percent of total amylase secreted was 3.5-fold greater than the percent of labeled protein secreted. Preferential secretion of old unlabeled exportable amylase was undiminished even when the chase period before addition of isoproterenol was extended to 240 min. Such long chase incubations were still meaningful due to the fact that the spontaneous rat of amylase release and radioactive protein release from the slices was negligibly low. A high isoproterenol concentration added to the slices after a 90-min chase produced the following results. An initial phase of preferential secretion of old unlabeled protein was soon replaced by secretion of a random mixture of new and old exportable protein. Electron micrographs indicated that high rates of secretion involved sequential fusion of secretory granules so that the lumen extended deep into the cell where the new labeled granules were presumably located. At low rates of secretion, the lumen showed no such deep extensions. Experiments were also conducted on slices from glands which had been largely depleted of old granules by prior injection of isoproterenol into the animals. Secretion of labeled protein from such slices stopped with the export of 80% of the labeled protein. This finding indicates that about 20% of the radioactive protein is cellular nonexportable protein and that the slices are capable of exporting the entire amount of secretory protein which was symthesized in vitrol. In addition to the beta-adrenergic receptor which mediates protein secretion, the parotid acinar cell also possesses an alpha-adrenergic and a cholinergic receptor both of which cause K+ release, vacuole formation, and water secretion. Activation of either of the latter two receptors in conjunction with the beta-adrenergic receptor increased randomization of the protein secreted. It is concluded that in the rat parotid acinar cell there is little spontaneous mixing between old granules near the luminal cell membrane and new granules coming up behind from the Golgi complex. The neurotransmitters which induce secretion produce the observed randomization.

Amylases↗
PubMedDate not supplied

ORG-2058 as a ligand in the assay of progesterone receptor in breast cancer.

Tritiated [(16 alpha-ethyl-21-hydroxy-19-nor-pregn-4-ene-3,20-dione)-6,7-3H] (ORG-2058) and 17,21-dimethyl-19-nor-pregna-4,9-diene-3,20-dione (R5020) were compared as ligands in the assay of progesterone receptor in human and rat breast tumors. We found that ORG-2058 is a better ligand because of its low nonspecific binding. Most of the nonspecific binding of the other ligand R5020, is to proteins which bind corticosteroids. In cancerous tissue ORG-2058 binds to progesterone receptor linearly in a range of protein concentrations which are normally used in the receptor assay. On the other hand, R5020 exhibits binding linearity over a narrower protein concentration in many tumor biopsies, which may cause severe limitation in the assay procedure or frequent underestimation of receptor content.

Animals↗