Postsynaptic modulation of cholinergic transmission by endogenous substances

1. Recent concept of postsynaptic modulation is reviewed on the basis of literature data and the results of our investigation using conventional intracellular and voltage-clamp recording methods, in vitro. 2. Experimental evidence provided that the sensitivity of nicotinic ACh receptors endowed on the postsynaptic membrane of the bullfrog sympathetic ganglia and of the frog skeletal muscle end-plate is either facilitated or inhibited by other neurotransmitters or neurohormones. 3. We propose that one neurotransmitter not only initiates its own postsynaptic potential but also regulates the efficacy of synaptic transmission mediated by a distinct neurotransmitter, as an endogenous "antagonist" or "sensitizer".     

Further study of effects of synthetic peptides on identifiable giant neurones of an African giant snail (Achatina fulica Férussac)

1. Effects of the following peptides at 10(-4) M on identifiable giant neurones of Achatina fulica Férussac were examined: physalaemin, eledoisin, bradykinin, neurokinin A, neurokinin B, neuromedin B, gastrin releasing peptide decapeptide (neuromedin C), gastrin releasing peptide (14-27), cholecystokinin tetrapeptide, cholecystokinin octapeptide, thyrotropin releasing hormone, Arg-vasotocin, gamma-melanocyte stimulating hormone. 2. The six neurones tested were as follows: PON (periodically oscillating neurone), TAN (tonically autoactive neurone), RAPN (right anterior pallial neurone), d-RPLN (dorsal-right parietal large neurone), VIN (visceral intermittently firing neurone) and d-VLN (dorsal-visceral large neurone). 3. Of the peptides examined, only Arg-vasotocin at 10(-4) M produced the excitatory effects on PON, VIN and d-VLN. Physalaemin showed slight inhibitory effects on TAN; this substance was sometimes almost ineffective on the neurone. 4. The other peptides examined were completely ineffective on all of the neurones tested.     

Characteristics of various synthetic peptide calpain inhibitors and their application for the analysis of platelet reaction

Calpeptin (a cell permeable synthetic peptide calpain inhibitor) inhibited the generation of thromboxane B2 (TxB2) by the direct inhibition on Tx synthetase in platelets at the concentrations more than 30 microM. Calpeptin, its analogues and E-64d (EST) were further examined with regard to cell permiability and inhibitory spectra. Among all compounds, only calpeptin inhibited the degradation of substrate proteins of calpain with negligible effect on TxB2 generation in intact platelets at the concentrations less than 30 microM. These concentrations of calpeptin did not inhibit the platelet aggregation, the elevation of [Ca2+], nor the formation of inositol 1,4,5-trisphosphate (IP3) in thrombin or collagen activated platelets. These results indicate that calpain dose not participate in the process of platelet activation induced by thrombin or collagen.     

The Nutritional Value of D-Amino Acid in the Chick Nutrition

The nutritional values of 16 D-amino acids in chick growth were studied on the purified diets containing crystalline amino acids as a sole source of nitrogen. Growth rate, feed consumption and nitrogen retention were measured. The nutritional values of D-amino acids were studied by comparing individually with the control groups fed on the diet containing all L-amino acids and negative control groups fed with the diet omitted the corresponding L-isomer. The following results were obtained. Essential amino acids: 1. Equal or almost equal nutritional value to the corresponding L-isomer; methionine, phenylalanine, leucine, proline. 2. Half nutritional value compared with L-isomer; valine. 3. Small nutritional value compared with L-isomer; tryptophan, isoleucine, histidine. 4. No nutritional value; lysine, threonine, arginine. Non-essential amino acid: 1. Equal or almost equal nutritional value to the corresponding L-isomer; serine, tyrosine, cystine. 2. There is a possibility that it has a slight growth retardation effect; alanine. 3. The growth retardation effect was found; aspartic acid.     

Genome-wide association study of idiopathic hypersomnia in a Japanese population

Sleep and Biological Rhythms - Idiopathic hypersomnia (IH) is a rare sleep disorder characterized by excessive daytime sleepiness, great difficulty upon awakening, and prolonged sleep time. In...     

Gradients in cytoplasmic calcium concentration ([Ca2+]i) in migrating human umbilical vein endothelial cells (HUVECs) stimulated by shear-stress

Using a parallel-plate flow-chamber and confocal laser scanning microscopy (CLSM), we studied the distribution and temporal changes in intracellular Ca2+ concentration ([Ca2+]i) in migrating HUVECs stimulated by shear-stress. In the presence or absence of ATP, shear-stress (10 dyne/cm2) caused morphological change and migration of individual HUVECs in the random direction. After 120 minute exposure to shear-stress, 70% of the cells migrated in the direction of flow, whereas, as many as 30% of the cells migrated to the upstream against flow. A nonspecific plasma membrane Ca2+ channel blocker, Ni2+, abolished such responses markedly, suggesting that Ca2+ influx may be essential for shear-stress dependent morphological change and migration of HUVECs. Analysis of [Ca2+]i distribution revealed the appearance of localized [Ca2+]i elevation inside lamellipodium formed in the direction of cell migration. The localized rise in [Ca2+]i might be closely related with morphological change to regulate the direction of cell migration induced by shear-stress.     

Activation of microsomal epoxide hydrolase by interaction with cytochromes P450: kinetic analysis of the association and substrate-specific activation of epoxide hydrolase function

The kinetics of the association between cytochrome P450 (P450) and microsomal epoxide hydrolase (mEH) was studied by means of resonant mirror based on the principle of surface plasmon resonance. The dissociation equilibrium constants (K(D)) for the affinity of P450 enzymes for mEH were estimated by resonant mirror using an optical biosensor cell covalently bound to rat mEH. Comparable K(D) values were obtained for CYP1A1 and 2B1, and these were greater by one order of magnitude than that for the CYP2C11. To clarify the influences of P450 enzymes on the catalytic activity of mEH, the hydrolyzing activity for styrene oxide and benzo(a)pyrene-7,8-oxide [B(a)P-oxide] was analyzed in the presence or absence of P450s. Styrene oxide hydrolysis was activated by all P450s including the CYP1A, 2B, 2C, and 3A subfamilies. In agreement with the association affinity determined by resonant mirror, CYP2C11 tends to have enhanced activity for styrene oxide hydrolysis. On the other hand, B(a)P-oxide hydrolysis was enhanced by only CYP2C11 while CYP1A1 and CYP2B1 had no effect. These results suggest that (1) many P450 enzymes associate nonspecifically with mEH, (2) the CYP2C11 plays a greater role in the association/activation of mEH and (3) the P450-mediated activation of mEH depends upon the substrate of mEH.     

Crystal structure of the RuvA-RuvB complex: a structural basis for the Holliday junction migrating motor machinery

We present the X-ray structure of the RuvA-RuvB complex, which plays a crucial role in ATP-dependent branch migration. Two RuvA tetramers form the symmetric and closed octameric shell, where four RuvA domain IIIs spring out in the two opposite directions to be individually caught by a single RuvB. The binding of domain III deforms the protruding beta hairpin in the N-terminal domain of RuvB and thereby appears to induce a functional and less symmetric RuvB hexameric ring. The model of the RuvA-RuvB junction DNA ternary complex, constructed by fitting the X-ray structure into the averaged electron microscopic images of the RuvA-RuvB junction, appears to be more compatible with the branch migration mode of a fixed RuvA-RuvB interaction than with a rotational interaction mode.     

Divalent hammerhead ribozyme targeting template region of human telomerase RNA has potent cleavage activity,but less inhibitory activity on telomerase

The template region of human telomerase RNA is a crucial area for regulating telomerase activity and would be a good target for ribozymes. In fact, potent telomerase inhibitory activity of the ribozyme targeting the GUC sequence of the 5(') end of this region (36-ribosome) has been well demonstrated. To search for a more potent ribozyme, we designed a divalent ribozyme to cleave both the phosphodiester bonds following the GUC and the 23 nucleotides downstream of GUA. An in vitro cleavage study showed that this divalent ribozyme cleaved telomerase RNA more efficiently than the 36-ribozyme or the 59-ribozyme to target the GUA. When this ribozyme was introduced into the carcinoma cells, its inhibitory effect on telomerase activity was less than that of the 36-ribozyme. The 59-ribozyme showed minimum activity on telomerase. This implies that, although the divalent ribozyme possesses a potent cleavage activity on hTR in vitro, the 36-ribozyme is most potent to suppress telomerase activity.