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Mechanisms of Taste Transduction
Published in Robert H. Cagan, Neural Mechanisms in Taste, 2020
John H. Teeter, Robert H. Cagan
Recent application of patch-clamp techniques to isolated taste cells has further clarified the physiological basis of bitter responses. In voltage-clamped frog taste cells, quinine (0.1 mM) completely suppressed the transient voltage-dependent Na+-current and partially blocked K+ currents.31 Addition of EGTA or CaCl2 to the pipette (intracellular) solution had no effect on the response to quinine, indicating that an increase in intracellular Ca2+ did not mediate the response. When ATP was present in the pipette, addition of cAMP to the bath in concentrations sufficient to increase intracellular levels (or when added to the pipette solution in addition to ATP) resulted in depolarization of the taste cell. Without ATP in the pipette, cAMP had no effect. Under voltage-clamp, the cAMP-induced depolarization was shown to result from blockage of K+ channels. Forskolin also depolarized the taste cells, indicating an intact adenylate cyclase system. IBMX, an inhibitor of cAMP phosphodiesterase, also evoked a depolarization in taste cells. These results suggest that the cAMP-mediated closure of K+ channels resulted from a phosphorylation step; however, a significant fraction of the K+ channels were not controlled by cAMP-dependent phosphorylation. Closure of K+ channels by cAMP was recently shown to be mediated by a cAMP-dependent kinase phosphorylation step.60
Use of in vitro maturation in a clinical setting Patient populations and outcomes
Published in David K. Gardner, Ariel Weissman, Colin M. Howles, Zeev Shoham, Textbook of Assisted Reproductive Techniques, 2017
Yoshiharu Morimoto, Aisaku Fukuda, Manabu Satou
There have been advances in efforts to improve maturation and oocyte quality in animal biology. Albuz et al. (89) proposed a new method for IVM and named it simulated physiological oocyte maturation (SPOM) (Figure 10.10). This is a method for arranging the basic signaling molecule and the level of the gonadotropin second messenger cyclic AMP (cAMP) in oocytes. High levels of cAMP induce meiotic arrest. SPOM enables the cytoplasm to enhance maturation during arrest of nuclear maturation. They settled one to two pre-IVM term using forskolin that increases cAMP and 3-isobutyl-1-methylxanthine (IBMX), which is one of the phosphodiesterase (PDE) inhibitors. At the next extended IVM term using FSH that acts as final maturation mediator and cilostamide that is a PDE were used. Improvements in blastocyst rates, implantation rates, and fetus yield rates in bovines and mice were demonstrated by this method. This could be a novel method for overcoming the disadvantage of current clinical IVM, which is the diminished rate of oocyte maturation and pregnancy outcomes.
Influence of Biochemical Cues in Human Corneal Stromal Cell Phenotype
Published in Current Eye Research, 2019
Julia Fernández-Pérez, Mark Ahearne
IBMX is a competitive non-selective inhibitor of phosphodiesterase that raises intracellular cAMP levels, which activate protein kinase A, phosphorylating in turn cAMP response element-binding proteins (CREB) in the nucleus which act as transcription factors.47 Researchers have used IBMX to emulate the effects of low glucose conditions.48 Upon treatment with IBMX, cells with multiple dendrite-like structures were observed similar to that reported previously.48 A significant increase in keratocan gene expression was observed and bright perinuclear staining was observed for this marker. The increase of this marker could be due the presence of CRE sequences in the promoter of this gene.48 ALH3A1 was highly expressed in cells with processes, similar to observations by Foster and colleagues for ALDH1.48 These authors reported an increase of CD34 at the transcriptional level, while our study showed an increase in the CD34+ population via flow cytometry. IBMX did not induce changes in any other MSC markers and did not show a chemotactic effect. The addition of this chemical did not influence expression of COL1 or ACTA2. This data indicates that treatment with IBMX promoted the restoration of a keratocyte-like phenotype.
Probing the settlement signals of Amphibalanus amphitrite
Published in Biofouling, 2018
Mado Kotsiri, Maria Protopapa, Gesthimani-Myrto Roumelioti, Athena Economou-Amilli, Eleni K. Efthimiadou, Skarlatos G. Dedos
With the clear exception of the effects of IBMX on cyprid settlement, a congruent and conclusive result was not observed with chemical compounds that modulate cAMP signalling, either on cyprid settlement or metamorphosis (Figure 5), neither were any morphological defects on animals exposed to forskolin or IBMX observed (Figure S4). Clearly deserving further investigation, it is proposed that the sharp induction of cyprid settlement at 10 μM IBMX (Figure 5) is an effect that may be unrelated to the action of IBMX as a non-specific cyclic nucleotide phosphodiesterase (PDE) inhibitor or it may be an effect related to a yet-unidentified specific action of PDE that is unrelated to cAMP signalling.
Antiplatelet activity of deferiprone through cyclooxygenase-1 inhibition
Published in Platelets, 2020
Ngan Thi Tran, Benjaporn Akkawat, Noppawan Phumala Morales, Ponlapat Rojnuckarin, Rataya Luechapudiporn
PRP (4 × 108 platelets/ml) was preincubated with various concentrations of deferiprone (0.1–4 mmol/l) for 5 minutes at 37°C, and then stimulated with 4 µmol/l ADP for 9 minutes. The reaction was terminated by adding 1 ml ice-cold ethanol, and then centrifuged at 1500 g for 10 minutes at 4°C, and the supernatant was collected. Finally, the aqueous solution was removed under the stream of nitrogen and cAMP level was measured using a cAMP EIA kit according to the manufacturer’s instructions. 3-isobutyl-1-methylxanthine (IBMX), which prevented cAMP metabolism by inhibiting phosphodiesterase enzyme, was used as a positive control.