The Experts below are selected from a list of 441 Experts worldwide ranked by ideXlab platform

Michael O Thorner - One of the best experts on this subject based on the ideXlab platform.

  • pituitary adenylate cyclase activating polypeptide growth hormone gh releasing peptide and gh releasing hormone stimulate gh release through distinct pituitary receptors
    Endocrinology, 1992
    Co-Authors: M I Goth, Benedict J Canny, Charles E Lyons, Michael O Thorner
    Abstract:

    GH secretion has been thought traditionally to be regulated by the two hypothalamic hormones, GH-releasing hormone (GHRH) and somatostatin (SRIF). Recent evidence has suggested that other factors may be involved. These factors include the natural ligand for the synthetic hexapeptide GH-releasing peptide (GHRP) and the putative hypophysiotropic factor pituitary adenylate cyclase-activating polypeptide (PA-CAP). Accordingly, we examined the effects of GHRP and PACAP on GH secretion at the single cell level using the reverse Hemolytic Plaque Assay which allows distinction of effects on the number of secreting cells and the amount of hormone each cell secretes. Both factors stimulated GH secretion in a dose-dependent fashion, with PACAP being more effective. PACAP increased both the number of cells secreting and the mean amount of hormone secreted per cell. In contrast, GHRP increased the number of secreting cells, although it had no effect on the amount of secretion per cell. GH secretion induced by GHRH, GH...

Takuma Shiraki - One of the best experts on this subject based on the ideXlab platform.

  • Genetic transfer of endothelin converting enzyme activity to CHO-K1 cells: detection of positive cells by reverse Hemolytic Plaque Assay
    FEBS letters, 1994
    Co-Authors: Soichi Miwa, Tatsuya Sawamura, Tsuyoshi Ikura, Shigeo Kobayashi, Takuma Shiraki, Tomoh Masaki
    Abstract:

    We have established a novel method of molecular cloning of endothelin converting enzyme, a key enzyme in the production of a potent vasoconstrictor endothelin-1, by modification of the reverse Hemolytic Plaque Assay. Also, we demonstrated that a cell line, CHO-K1, showed no detectable activity of endothelin converting enzyme. This cell line was transfected with a cDNA library of bovine endothelial cells. The modified reverse Hemolytic Plaque Assay was shown to detect even a single CHO-K 1 cell that was changed to produce mature ET-1 by transfection. Thus, this novel method is suggested to be useful for the molecular cloning of other secreted antigens and their processing enzyme.

J Lestage - One of the best experts on this subject based on the ideXlab platform.

  • estrogen increases the release of epidermal growth factor from individual pituitary cells in female rats
    Journal of Endocrinology, 1995
    Co-Authors: A Mouihate, J Lestage
    Abstract:

    Rat mixed anterior pituitary cells from cycling females were microscopically demonstrated to produce epidermal growth factor (EGF), in culture, using a reverse Hemolytic Plaque Assay. Anterior pituitary cells of proestrous female rats secrete more EGF than those of metestrous rats, as evaluated by the mean area and the percentage of EGF Plaque-forming cells. Estradiol-17 beta (10 nM) treatment of metestrous culture for 24 h increased significantly the size of EGF Plaque-forming cells (from 1290 +/- 58 to 2566 +/- 57 microns 2, P < 0.01) and the percentage of EGF Plaque-forming cells (from 20.57 to 28.19%; P < 0.01) to a level as high as observed in proestrous cultures (basal mean area 2171 +/- 157 microns 2, and basal percentage of EGF Plaque-forming cells 22.71%). These results suggest that the hormonal status of female rats influences EGF secretion in the anterior pituitary gland and that estradiol is implicated in this phenomenon.

Tom E Porter - One of the best experts on this subject based on the ideXlab platform.

  • cellular basis for elevated prolactin secretion during incubation behavior in bantam chickens analysis by reverse Hemolytic Plaque Assay
    Biology of Reproduction, 1996
    Co-Authors: Marisol E Lopez, Charles C Gregory, Tom E Porter
    Abstract:

    Incubation behavior in birds is characterized by elevated serum prolactin (PRL) levels. The objective of this study was to determine the cellular basis for increased PRL secretion. Incubation behavior of Bantam hens was induced by allowing the hens to accumulate their eggs. In experiment 1, hens were allowed to accumulate their eggs in floor pens for 0, 2, 12, or 24 days (Day 0, Day 2, Day 12, and Day 24 hens, respectively). Anterior pituitaries were dissociated into individual cells with trypsin, and the resulting cells were then subjected to reverse Hemolytic Plaque Assays for PRL. The percentage of PRL-secreting cells and serum PRL levels were higher in Day 24 hens than in the other groups (p < 0.05; n = 3 separate trials). In experiment 2, hens were allowed to accumulate their eggs for 2, 14, 18, or 24 days (Day 2, Day 14, Day 18, and Day 24 hens, respectively). The percentage of PRL-secreting cells and levels of serum PRL were greater in Day 18 and Day 24 hens than in Day 2 hens (p < 0.05; n = 4). Results from Day 14 hens were intermediate and different (p < 0.05) from those from both Day 2 and Day 18 groups. Data indicate that an increase in the proportion of PRL secretors occurred between 14 and 18 days after hens began to accumulate their eggs. The area of Plaques formed by lactotrophs from Day 14 and Day 18 hens was also increased (p < 0.05). In experiment 3, hens were allowed to accumulate their eggs for 0 and 24 days (Day 0 and Day 24 hens, respectively). Their anterior pituitaries were dissected into cephalic, middle, and caudal regions, and the percentage of PRL cells were analyzed in each region separately. The percentage of PRL secretors was increased (p < 0.05) in Day 24 compared to Day 0 hens in both the cephalic and middle regions of the anterior pituitary but not in the caudal portion. We conclude that increased PRL secretion during incubation behavior involves the recruitment of additional pituitary cells into the PRL-secreting population and an increase in the capacity of these cells to secrete hormone (p < 0.05). Furthermore, this increase in PRL-secreting cells is localized to the cephalic and middle regions of the anterior pituitary.

Paolo Meda - One of the best experts on this subject based on the ideXlab platform.

  • Repeated Glucose Stimulation Reveals Distinct and Lasting Secretion Patterns of Individual Rat Pancreatic B Cells
    2020
    Co-Authors: Emanuele Giordano, Domenico Bosco, Vincenzo Cirulli, Paolo Meda
    Abstract:

    Abstract To determine whether pancreatic B cells show a constant secretion pattern during repeated stimulations, we have used a sequential Hemolytic Plaque Assay to monitor their individual insulin release during several successive 30-min incubations in the presence of 16.7 mM glucose. We have found that the total B cell secretion did not vary significantly in these successive glucose stimulations and that, under these conditions, the majority of B cells that were stimulated to release insulin during the first incubation also secreted during the second, third, and, when this was tested, during the fourth incubation. Similarly, most of the B cells that did not release detectable amounts of insulin during the first incubation did not secrete also during the two (or three) subsequent secretion tests. Together, the two groups of B cells that showed a constant secretory pattern, represented -75% of the entire B cell population. The remaining 25% of B cells shifted from a secreting to a non-secreting state, or vice versa, from one incubation to another. These observations were made under three different time frames in which we tested single B cells as well as B cell clusters at rather different intervals. These findings support the existence of distinct B cell subpopulations differing lastingly in their ability to secrete insulin in response to glucose. (J. Clin. Invest. 1991. 87:2178-218

  • importance of cell matrix interactions in rat islet beta cell secretion in vitro role of alpha6beta1 integrin
    Diabetes, 2000
    Co-Authors: Domenico Bosco, Paolo Meda, Philippe A Halban, Dominique G Rouiller
    Abstract:

    It has long been recognized that islet cell function is rapidly altered in vitro, but can be maintained, at least in part, when cells are layered on defined extracellular matrices. The present work addresses the influence of short-term cell-matrix interactions on islet beta-cell function and provides first insight into the molecular basis of these interactions. When primary rat beta-cells were allowed to attach to a matrix produced by a rat carcinoma cell line (804G), there was an increased insulin secretory response to secretagogues. This change was the result of an increase in the proportion of actively secreting beta-cells and in the amount of insulin secreted per active cell, as shown using the reverse Hemolytic Plaque Assay. In turn, the spreading or flattening of beta-cells on this matrix was enhanced by secretagogues, and flattened cells secreted more insulin than rounded cells. Using indirect immunofluorescence, it was found that 1)alpha6beta1 integrins are present at the surface of islet cells in situ, 2) alpha6beta1 expression is heterogeneous among purified beta-cells and is upregulated by insulin secretagogues, 3) alpha6beta1 expression is higher in spreading cells, and 4) anti-alpha6beta1-specific antibodies decrease spreading. These observations demonstrate that islet cell-matrix interactions can improve the sensitivity of insulin cells to glucose and are mediated, at least in part, by alpha6beta1 integrins, suggesting that outside-in signaling through alpha6beta1 integrin plays a major role in the regulation of beta-cell function.

  • enhanced secretion of amylase from exocrine pancreas of connexin32 deficient mice
    Journal of Cell Biology, 1998
    Co-Authors: Marc Chanson, Marjorie Fanjul, Domenico Bosco, Eric Nelles, Susanne Suter, Klaus Willecke, Paolo Meda
    Abstract:

    To determine whether junctional communication between pancreatic acinar cells contributes to their secretory function in vivo, we have compared wild-type mice, which express the gap junctional proteins connexin32 (Cx32) and connexin26, to mice deficient for the Cx32 gene. Pancreatic acinar cells from Cx32 (−/−) mice failed to express Cx32 as evidenced by reverse transcription–PCR and immunolabeling and showed a marked reduction (4.8- and 25-fold, respectively) in the number and size of gap junctions. Dye transfer studies showed that the extent of intercellular communication was inhibited in Cx32 (−/−) acini. However, electrical coupling was detected by dual patch clamp recording in Cx32 (−/−) acinar cell pairs. Although wild-type and Cx32 (−/−) acini were similarly stimulated to release amylase by carbamylcholine, Cx32 (−/−) acini showed a twofold increase of their basal secretion. This effect was caused by an increase in the proportion of secreting acini, as detected with a reverse Hemolytic Plaque Assay. Blood measurements further revealed that Cx32 (−/−) mice had elevated basal levels of circulating amylase. The results, which demonstrate an inverse relationship between the extent of acinar cell coupling and basal amylase secretion in vivo, support the view that the physiological recruitment of secretory acinar cells is regulated by gap junction mediated intercellular communication.