Calcium-dependent Properties of Peptidylarginine Deiminase from Rabbit Skeletal Muscle

Peptidylarginine deiminase, which catalyzes the deimination of arginyl residues in protein, required Ca²⁺ as an essential cofactor and the half-maximal activity was attained at 40—60 μm Ca²⁺. Other divalent cations were practically inactive except for Sr²⁺, which was about 50% as active as Ca²⁺ when tested at 10 mm. However, Sr²⁺ at less than the concentration of 100 μm had little or no activity. The direct Ca²⁺-binding for the enzyme showed a sigmoidal curve with a transition midpoint of about 110 μm, indicating that the binding is cooperative. Analysis of Hill plots of the data revealed that the enzyme binds 3 mol of Ca²⁺/mol of protein with an apparent dissociation constant of llO μm. A conformational change upon Ca²⁺-binding was also described for the enzyme using UV-difference spectra. The alteration could be attributed to an increased exposure of the aromatic residues to a more aqueous environment, as has been described for Ca²⁺-binding proteins such as calmodulin. Phosphatidylserine enhanced the reaction velocity and concomitantly reduced the Ca²⁺-requirement for the enzyme. These effects were stimulated by the addition of diacylglycerol. Diacylglycerol alone had little or no effect. On the other hand, calmodulin had no effect on the enzymatic activity over a wide range of Ca²⁺ concentrations. These suggest that the activity and Ca²⁺-sensitivity of peptidylarginine deiminase is increased at the cell membrane.     

Tracking long‐distance migration of marine fishes using compound‐specific stable isotope analysis of amino acids

The long‐distance migrations by marine fishes are difficult to track by field observation. Here, we propose a new method to track such migrations using stable nitrogen isotopic composition at the base of the food web (δ¹⁵N_Base), which can be estimated by using compound‐specific isotope analysis. δ¹⁵N_Base exclusively reflects the δ¹⁵N of nitrate in the ocean at a regional scale and is not affected by the trophic position of sampled organisms. In other words, δ¹⁵N_Base allows for direct comparison of isotope ratios between proxy organisms of the isoscape and the target migratory animal. We initially constructed a δ¹⁵N_Base isoscape in the northern North Pacific by bulk and compound‐specific isotope analyses of copepods (n = 360 and 24, respectively), and then we determined retrospective δ¹⁵N_Base values of spawning chum salmon (Oncorhynchus keta) from their vertebral centra (10 sections from each of two salmon). We then estimated the migration routes of chum salmon during their skeletal growth by using a state‐space model. Our isotope tracking method successfully reproduced a known chum salmon migration route between the Okhotsk and Bering seas, and our findings suggest the presence of a new migration route to the Bering Sea Shelf during a later growth stage.     

Oral consumption of α-glucosyl-hesperidin could prevent lens hardening,which causes presbyopia

Presbyopia is one of the most well-known diseases of the eye, predominantly affecting the adult population after 50 years’. Due to hardening of the lens and failure of accommodative change, patients lose the ability to focus on near objects. This eye symptom is reported to be an early symptom of age-related nuclear cataract, and we have previously reported that hesperetin treatment could delay the onset of nuclear cataractogenesis induced by sodium selenite. In this study, we examined whether oral intake of α-glucosyl-hesperidin (G-Hsd), which has greater water solubility than hesperetin, could delay the onset of presbyopia. G-Hsd treatment protected lens elasticity, upregulated the mRNA expression of anti-oxidative enzymes like glutathione reductase and thioredoxin reductase 1 in the plasma and lens, and prevented premature cataract symptoms in selenite-induced cataract rat lens. Thus, the anti-presbyopic effects of G-Hsd were attributed, at least in part, to its antioxidant effects. G-Hsd represents the first oral treatment agent with anti-presbyopia and/or anti-cataract properties.     

Changes in the amount of the diapause factor in the subesophageal ganglion during development of the silkworm, Bombyx mori

Changes in the diapause factor content of the subesophageal ganglion of the silkworm were examined from the viewpoint of sex and voltinism differences. The diapause factor content was comparatively low from the 4th larval ecdysis to the larval-pupal ecdysis, irrespective of sex and voltinism. However, remarkable changes occurred after the larval-pupal ecdysis. An interesting finding is that the diapause factor content in the female diapause egg-producer decreased gradually with pupal-adult development, but in the male diapause egg-producer as well as in the non-diapause egg-producer it increased up to the half-way stage in the pupal-adult development. This suggests that the diapause factor is not secreted from the subesophageal ganglion of the male pharate adult of the diapause egg-producer. This finding was confirmed by implantation experiments using brain-subesophageal ganglion complex or only subesophageal ganglion.