Acute exercise increases expression of extracellular superoxide dismutase in skeletal muscle and the aorta

Exercise dramatically increases oxygen consumption and causes oxidative stress. Superoxide dismutase (SOD) is important in the first-line defence mechanisms against oxidative stress. To investigate the effect of acute exercise on the expression of SOD, we examined the expression of mRNA for three SOD isozymes, in mice run on a treadmill to exhaustion. Six hours after exercise, the expression of extracellular SOD (EC-SOD) mRNA increased significantly in skeletal muscle and persisted for 24 h, whereas no change was observed for cytoplasmic and mitochondrial SOD mRNA. Moreover, acute exercise also induced EC-SOD mRNA in the aorta. These results suggest that a single bout of exercise is enough to augment the expression EC-SOD mRNA in skeletal muscle and the aorta, and may partly explain the beneficial effect of exercise.     

Factors contributing to cerebral hypomyelination in the growth hormone-deficientlittle mouse

We attempted to delineate the events leading to hypomyelination in the brain of thelittle mouse, a promising murine model of isolated growth hormone deficiency. At 20 days of age, the mutant mouse brain weighed less than its normal counterpart, and this difference in brain weight persisted. Increase in CNPase activity was found to be suppressed in the cerebrum throughout the developmental stage, but not in the other parts of the brain. Differences in cerebral DNA content between thelittle and normal mice first became apparent on the 10th day of age. Thereafter, the rate of increase in thelittle brain consistently lagged behind the normal. [³H]Thymidine incorporation into the DNA fraction in vivo on the 7th day of age, when glial cell proliferation in the normal cerebrum is most active, was approximately half that of the controls in all parts of thelittle brain. These findings indicate that the hypomyelination of the mutant cerebrum might result from reduced oligodendroglial proliferation due to growth hormone deficiency.     

Formation of stable nanodiscs by bihelical apolipoprotein A‐I mimetic peptide

Nanodiscs are composed of scaffold protein or peptide such as apolipoprotein A‐I (apoA‐I) and phospholipids. Although peptide‐based nanodiscs have an advantage to modulate the size of nanodiscs by changing phospholipid/peptide ratios, they are usually less stable than apoA‐I‐based nanodiscs. In this study, we designed a novel nanodisc scaffold peptide (NSP) that has proline‐punctuated bihelical amphipathic structure based on apoA‐I mimetic peptides. NSP formed α‐helical structure on 1‐palmitoyl‐2‐oleoyl phosphatidylcholine (POPC) nanodiscs prepared by cholate dialysis method. Dynamic light scattering measurements demonstrated that diameters of NSP nanodiscs vary depending upon POPC/NSP ratios. Comparison of thermal unfolding of nanodiscs monitored by circular dichroism measurements demonstrated that NSP forms much more stable nanodiscs with POPC than monohelical peptide, 4F, exhibiting comparable stability to apoA‐I‐POPC nanodiscs. Intrinsic Trp fluorescence measurements showed that Trp residues of NSP exhibit more hydrophobic environment than that of 4 F on nanodiscs, suggesting the stronger interaction of NSP with phospholipids. Thus, the bihelical structure of NSP appears to increase the stability of nanodiscs because of the enhanced interaction of peptides with phospholipids. In addition, NSP as well as 4F spontaneously solubilized POPC vesicles into nanodiscs without using detergent. These results indicate that bihelical NSP forms nanodiscs with comparable stability to apoA‐I and has an ability to control the size of nanodiscs simply by changing phospholipid/peptide ratios. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.     

Isolation of disproportionating enzyme from halotolerant microalga Dunaliella parva (Volvocales, Chlorophyceae)

Starch metabolism in Dunaliella parva Lerche is regulated by the osmolarity of the surrounding solute. Two isozymes showing amylolytic activity were obtained after purification by gel filtration chromatography. The isozymes show disproportionating activity (D‐enzyme) that is specific for malto‐oligosaccharides as substrate. Properties of the D‐enzyme in D. parva are similar to those in higher plants. The activity of the D‐enzyme is also found in various Dunaliella and Chlamydomonas, indicating that the D‐enzyme is also important in the starch metabolism in algae.     

A soluble extract from human spermatozoa activates ascidian oocytes

A soluble extract from human spermatozoa induced calcium oscillations and extrusion of the first polar body when injected into oocytes of the ascidian Ciona intestinalis . The properties of calcium oscillations and time of polar body extrusion precisely mimic oocyte activation induced by C. intestinalis sperm or sperm extracts. The data suggest that human sperm extracts can activate oocytes of different phyla by the same mechanism as homologous spermatozoa. Injection of inositol 1,4,5-trisphosphate (IP₃) into C. intestinalis oocytes mimicked to some extent the initial stages of oocyte activation, but the results demonstrate that ascidian oocyte activation by human sperm extract cannot be explained solely in terms of IP₃-induced calcium release. Injection of other calcium releasing second messengers, cyclic adenosine diphosphate ribose, or calcium ions, does not lead to oocyte activation or release intracellular calcium in ascidian oocytes. It was concluded that human spermatozoa contain one or more molecules that can trigger intracellular calcium release in oocytes from different phyla.     

Future risk of the maize orange leafhopper,Cicadulina bipunctata,and maize wallaby ear symptom in temperate Japan

Since the 1980s, the maize orange leafhopper, Cicadulina bipunctata, has been gradually expanding its range in east Asia associated with global warming. This leafhopper induces maize wallaby ear symptom (MWES) on young maize plants and has become a threat to forage maize production in southern parts of temperate Japan since around 2000. In this study, using predictions of future temperature and precipitation calculated from Atmosphere–Ocean Coupled General Circulation Models, the future risk of C. bipunctata expansion and MWES occurrence in Japan (spatial resolution: 1 km²) was predicted. A nominal logistic regression analysis showed a significant contribution of cumulative low temperature during winter to the current distribution of C. bipunctata. The range of C. bipunctata was predicted to expand northward, particularly in Kyushu, Shikoku and the southern part of Honshu after the 2060s. Predicted intensification of MWES would reduce the efficacy of maize cultivars that are currently tolerant to MWES, in southern Kyushu in the 2020s, and in most parts of Kyushu, Shikoku and southwestern Honshu in the 2060s. These results suggest the need for measures to counter further expansion of C. bipunctata and improvement of current tolerant maize cultivars.     

Factors underlying genotypic differences in the induction of photosynthesis in soybean [Glycine max (L.) Merr.]

Crop leaves are subject to continually changing light levels in the field. Photosynthetic efficiency of a crop canopy and productivity will depend significantly on how quickly a leaf can acclimate to a change. One measure of speed of response is the rate of photosynthesis increase toward its steady state on transition from low to high light. This rate was measured for seven genotypes of soybean [Glycine max (L.) Merr.]. After 10 min of illumination, cultivar ‘UA4805’ (UA) had achieved a leaf photosynthetic rate (P_n) of 23.2 μmol · m^?2 · s^?1, close to its steady‐state rate, while the slowest cultivar ‘Tachinagaha’ (Tc) had only reached 13.0 μmol · m^?2 · s^?1 and was still many minutes from obtaining steady state. This difference was further investigated by examining induction at a range of carbon dioxide concentrations. Applying a biochemical model of limitations to photosynthesis to the responses of P_n to intercellular CO₂ concentration (C_i), it was found that the speed of apparent in vivo activation of ribulose‐1:5‐bisphosphate carboxylase/oxygenase (Rubisco) was responsible for this difference. Sequence analysis of the Rubisco activase gene revealed single nucleotide polymorphisms that could relate to this difference. The results show a potential route for selection of cultivars with increased photosynthetic efficiency in fluctuating light.