The subcellular distribution of alanine-glyoxylate aminotransferase and serine-pyruvate aminotransferase in dog liver.

The subcellular distributions of alanine-glyoxylate aminotransferase and serine-pyruvate aminotransferase in the particulate fraction of dog liver were examined by centrifugation in a sucrose density gradient. Most of both enzyme activities in the particulate fraction were localized in the mitochondria, but not in the peroxisomes.     

A novel insertion pathway of mitochondrial outer membrane proteins with multiple transmembrane segments

The central channel Tom40 of the preprotein translocase of outer membrane (TOM) complex is thought to be responsible for the import of virtually all preproteins synthesized outside the mitochondria. In this study, we analyze the topogenesis of the peripheral benzodiazepine receptor (PBR), which integrates into the mitochondrial outer membrane (MOM) through five hydrophobic transmembrane segments (TMSs) and functions in cholesterol import into the inner membrane. Analyses of in vitro and in vivo import into TOM component–depleted mitochondria reveal that PBR import (1) depends on the import receptor Tom70 but requires neither the Tom20 and Tom22 import receptors nor the import channel Tom40, (2) shares the post-Tom70 pathway with the C-tail–anchored proteins, and (3) requires factors of the mitochondrial intermembrane space. Furthermore, membrane integration of mitofusins and mitochondrial ubiquitin ligase, the MOM proteins with two and four TMSs, respectively, proceeds through the same initial pathway. These findings reveal a previously unidentified pathway of the membrane integration of MOM proteins with multiple TMSs.     

Quality control of Photosystem II: cleavage and aggregation of heat-damaged D1 protein in spinach thylakoids

Moderate heat stress (40 degrees C, 30 min) on spinach thylakoids induced cleavage of the D1 protein, producing an N-terminal 23-kDa fragment, a C-terminal 9-kDa fragment, and aggregation of the D1 protein. A homologue of Arabidopsis FtsH2 protease, which is responsible for degradation of the damaged D1 protein, was abundant in the stroma thylakoids. Two processes occurred in the thylakoids in response to heat stress: dephosphorylation of the D1 protein in the stroma thylakoids, and aggregation of the phosphorylated D1 protein in the grana. Heat stress also induced the release of the extrinsic PsbO, P and Q proteins from Photosystem II, which affected D1 degradation and aggregation significantly. The cleavage and aggregation of the D1 protein appear to be two alternative processes influenced by protein phosphorylation/dephosphorylation, distribution of FtsH, and intactness of the thylakoids.     

Perchloric acid-soluble protein is expressed in enterocytes and goblet cells in the intestine and upregulated by dietary lipid

We previously identified perchloric acid-soluble protein (PSP) in the rat liver, kidney, brain and lung, and reported that it appeared to be related to repression of cell proliferation. In the present study, we clarified that PSP was expressed in the intestine, and found that the amino acid sequence of the intestinal PSP was consistent with those of other PSPs present in other tissues. An immunohistochemical study revealed that PSP was expressed in enterocytes and goblet cells, but not in other cell types among the lamina propria epithelial cells. A comparison of the expressions of PSP and proliferating cell nuclear antigen demonstrated that the proliferating cells did not express PSP. Intestinal PSP expression was induced by approximately 3-fold by oral administration of dietary fat. These findings indicate that the proliferation repression activity may be related to renewal of the intestinal epithelium, and that PSP is one of the fatty acid-inducible proteins.     

Wild boars: A potential source of Erysipelothrix rhusiopathiae infection in Japan

The potential role of wild boars as a source of erysipelas infection was investigated. An ELISA test of wild boar serum samples from 41 prefectures in Japan revealed that proportions of the Erysipelothrix rhusiopathiae‐positive samples were very high in all the prefectures, and the mean positive rate was 95.6% (1312/1372). Serovars of E. rhusiopathiae isolates from wild boars were similar to those of previously reported swine isolates, and all serovar isolates tested were found to be pathogenic to mice. These results suggest that wild boars in Japan constitute a reservoir of E. rhusiopathiae and may pose risks to other animals.     

Decline of unionid mussels enhances hybridisation of native and introduced bitterling fish species through competition for breeding substrate

1. Bitterling fishes (Subfamily: Acheilognathinae) spawn in the gills of living freshwater mussels and obligately depend on the mussels for reproduction. On the Matsuyama Plain, Japan, populations of unionid mussels—Pronodularia japanensis, Nodularia douglasiae, and Sinanodonta lauta—have decreased rapidly over the past 30 years. Simultaneously, the population of a native bitterling fish, Tanakia lanceolata, which depends on the three unionids as a breeding substrate, has decreased. Furthermore, a congeneric bitterling, Tanakia limbata, has been artificially introduced, and hybridisation and genetic introgression occur between them. Here, we hypothesised that decline of the unionids has enhanced this invasive hybridisation through competition for the breeding substrate.
2. Three study sites were set in three streams on the Matsuyama Plain. We collected adult bitterling fishes (native T. lanceolata, introduced T. limbata, and foreign Rhodeus ocellatus ocellatus) once a week from April to October 2013 to measure their densities in streams and to examine seasonal differences in female ovipositor length, which elongates in the breeding season. Simultaneously, we set quadrats and captured unionids and measured environmental conditions. Each unionid individual was kept separately in its own aquarium to collect ejected bitterling eggs/larvae. Tanakia eggs and larvae were genotyped using six microsatellite markers and the mitochondrial cytochrome b gene.
3. Introduced T. limbata was more abundant, had a longer breeding period, and produced more juveniles than native T. lanceolata. Hybrids between the two species occurred at all sites, and in total 101 of the 837 juveniles genotyped were hybrids. The density of P. japanensis was low, at most 0.42 individuals/m². Nodularia douglasiae and S. lauta have nearly or totally disappeared from these sites. Hybrid clutches of Tanakia species occurred more frequently where the local density of P. japanensis was low. Mussels were apparently overused and used simultaneously by three species of bitterlings.
4. Decline of freshwater unionid populations has enhanced hybridisation of native and invasive bitterling fishes through increasing competition for breeding substrate. We showed that rapid decline of host mussel species and introduction of an invasive congener have interacted to cause a rapid decline of native bitterling fish.
5. Degradation of habitat and the introduction of invasive species interact to cause a cascade of extinctions in native species. In our study, obligate parasite species are threatened because the host species are disappearing, which means there is a serious threat of coextinction.

     

Entrapment of Ciliates at the Water-Air Interface

The importance of water-air interfaces (WAI) on microorganism activities has been recognized by many researchers. In this paper, we report a novel phenomenon: the entrapment of ciliates Tetrahymena at the WAI. We first characterized the behavior of cells at the interface and showed that the cells'' swimming velocity was considerably reduced at the WAI. To verify the possible causes of the entrapment, we investigated the effects of positive chemotaxis for oxygen, negative geotaxis and surface properties. Even though the taxes were still effective, the entrapment phenomenon was not dependent on the physiological conditions, but was instead affected by the physical properties at the interface. This knowledge is useful for a better understanding of the physiology of microorganisms at interfaces in nature and in industry.     

Friendly-rivalry solution to the iterated n-person public-goods game

Repeated interaction promotes cooperation among rational individuals under the shadow of future, but it is hard to maintain cooperation when a large number of error-prone individuals are involved. One way to construct a cooperative Nash equilibrium is to find a ‘friendly-rivalry’ strategy, which aims at full cooperation but never allows the co-players to be better off. Recently it has been shown that for the iterated Prisoner’s Dilemma in the presence of error, a friendly rival can be designed with the following five rules: Cooperate if everyone did, accept punishment for your own mistake, punish defection, recover cooperation if you find a chance, and defect in all the other circumstances. In this work, we construct such a friendly-rivalry strategy for the iterated n-person public-goods game by generalizing those five rules. The resulting strategy makes a decision with referring to the previous m = 2n − 1 rounds. A friendly-rivalry strategy for n = 2 inherently has evolutionary robustness in the sense that no mutant strategy has higher fixation probability in this population than that of a neutral mutant. Our evolutionary simulation indeed shows excellent performance of the proposed strategy in a broad range of environmental conditions when n = 2 and 3.