• The Korean Journal of Physiology and Pharmacology
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• v.1 no.3
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• pp.303-313
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• 1997

The role of the lower esophageal sphincter(LES) is characterized by the ability to maintain tone and to relax allowing the passage of a bolus. It is known that LES relaxation during swallowing may be induced by the cessation of the tonic neural excitation and the activation of non-adrenergic, non-cholinergic(NANC) inhibitory neurons. Furthermore, it is generally accepted that the relaxation of the smooth muscle is mediated primarily by the elaboration of adenosine 3',5'-cyclic monophosphate(cyclic AMP) and guanosine 3',5'-cyclic mono-phosphate(cyclic GMP) via activation of adenylate cyclase and guanylate cyclase, respectively. It is thus possible that cyclic nucleotides might be a second messenger involved in neural stimulation-induced relaxation of LES, although a relationship between relaxation and changes in cyclic nucleotides after neural stimulation has not been established. The present study was performed to define the participation of cyclic nucleotides in the relaxation of LES of dog in response to neural stimulation. Electrical field stimulation(EFS) caused relaxation of the canine isolated LES strips in a frequency-dependent manner, which was eliminated by pretreatment with tetrodotoxin$(1{\mu}M)$, but not by atropine$(100{\mu}M)$, guanethidine$(100{\mu}M)$ and indomethacin$(10{\mu}M)$. The nitric oxide synthase inhibitors, $N^G-nitro-L-arginine$, $N^G-nitro-L-arginine$ methyl ester and $N^G-monomethyl-L-arginine$ inhibited EFS-induced relaxation. Additions of sodium nitroprusside, a nitrovasodilator and forskolin, a direct adenylate cyclase stimulant, caused a dose-dependent relaxation of LES smooth muscle. Effects of sodium nitroprusside and forskolin were selectively blocked by the corresponding inhibitors, methylene blue for guanylate cyclase and N-ethylmaleimide(NEM) for adenylate cyclase, respectively. Dibutyryl cyclic AMP and dibutyryl cyclic GMP caused a concentration-dependent relaxation of the LES smooth muscle tone, which was not blocked by NEM or methylene blue, respectively. However, both NEM and methylene blue caused significant antagonism of the relaxation in LES tone in response to EFS. EFS increased the tissue cyclic GMP content by 124%, whereas it did not affect the tissue level of cyclic AMP. Based on these results, it is suggested that one of the components of canine LES smooth muscle relaxation in response to neural stimulation is mediated by an increase of cyclic GMP via the activation of guanylate cyclase. Additionally, an activation of cyclic AMP generation system was, in part, involved in the EFS-induced relaxation.

• Journal of Mushroom
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• v.21 no.3
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• pp.173-178
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• 2023

In this study, the characteristics and taste components of six different oyster mushroom cultivars (Gonji-7ho, Santari, Baekseon, Chunchu, Suhan, and Heuktari) were analyzed and compared. The Heuktari mushroom pileus had the lowest brightness index (32.8) and remained dark (brightness index: 30.5) even after blanching. The moisture content of the mushrooms was approximately 90%. The salinity and sugar contents were highest in Heuktari (5.7% and 7.1%, respectively). Gonji -7ho had the highest contraction rates, with a length contraction rate of 16.4% and thickness contraction rate of 23.9%. The total amino acid content was highest in Heuktari (537.8 mg/100 g), but the glutamine content contributing to umami taste was highest in Santari (59.4 mg/100 g) and the aspartic acid content was highest in Baekseon (33.1 mg/100 g). Among the 5?-nucleotide components, guanosine monophosphate, which enhances umami taste, was highest in Baekseon (0.7 mg/g). Baekseon was also calculated to have the highest umami taste concentration based on amino acid and nucleic acid contents (12.7 g/100 g). The results of this study serve as valuable basic data on the physicochemical characteristics of oyster mushroom cultivars grown in Korea.