Dietary habits of the fanray Platyrhina tangi (Batoidea: Platyrhinidae) in Ariake Bay, Japan

The dietary habits of the fanray Platyrhina tangi were investigated by analyzing the stomach contents of specimens collected in Ariake Bay, Japan. Of 334 stomach specimens, 324 contained food and 10 (3.0%) were empty. The mean percentage weight of stomach contents per unit of body weight was 0.59%. Thirty-seven taxonomic levels of prey were identified. The most common prey was shrimp, followed by fish and mysids. There were no differences in the composition of the diet between sexes, but an ontogenetic dietary shift was observed. Shrimps were the most common prey in all size classes. In addition, smaller individuals frequently ate mysids, and larger individuals often consumed fish. Dietary breadth values increased with size. Trophic level analysis revealed that trophic level increased with size; however, this species is consistently a secondary consumer. Dental sexual dimorphism was also observed. Specifically, mature males had much longer and sharper cusps than females and immature males. Since males and females had similar diets, dental sexual dimorphism may be related to their reproductive behaviour.     

Impact of brood parasitism and predation on nest survival of the fan-tailed gerygone in New Caledonia

Predation and brood parasitism are common reasons for nesting failure in passerine species and the additive impact by invasive species is a major conservation concern, particularly on tropical islands. Recognising the relative contribution of the different components of nesting failure rates is important to understand co-evolutionary interactions within brood parasite–host systems. In the remote archipelago of New Caledonia, the fan-tailed gerygone Gerygone flavolateralis is the exclusive host of the brood-parasitic shining bronze-cuckoo Chalcites lucidus. Additionally, invasive rodents also possibly have an impact on breeding success. To estimate the impact of potential nest predators, we 1) video monitored nests to identify predators, 2) estimated the probability of predation based on nest visibility and predator abundance and 3) tested the possibility that the location of experimental nests and lack of odour cues decrease the predation by rodents. In addition, we estimated nest survival rates using data collected in different habitats over the course of eight breeding seasons. Nesting success of fan-tailed gerygones was relatively low and predation was the main cause of nesting failure. We recorded mainly predation by native birds, including the shining bronze-cuckoo, whereas predation by rats was rare. In open habitats predation by cuckoos was much lower than predation by other avian predators. Neither predator activity around nests nor nest visibility influenced the probability of predation. Experimental nests in more accessible locations and containing an odorous bait were more exposed to rodent predation. Apparently, the fan-tailed gerygone has either never been specifically vulnerable to predation by rats or has developed anti-predator adaptations.     

A single amino acid in human APOBEC3F alters susceptibility to HIV-1 Vif

Human APOBEC3F (huA3F) potently restricts the infectivity of HIV-1 in the absence of the viral accessory protein virion infectivity factor (Vif). Vif functions to preserve viral infectivity by triggering the degradation of huA3F but not rhesus macaque A3F (rhA3F). Here, we use a combination of deletions, chimeras, and systematic mutagenesis between huA3F and rhA3F to identify Glu(324) as a critical determinant of huA3F susceptibility to HIV-1 Vif-mediated degradation. A structural model of the C-terminal deaminase domain of huA3F indicates that Glu(324) is a surface residue within the α4 helix adjacent to residues corresponding to other known Vif susceptibility determinants in APOBEC3G and APOBEC3H. This structural clustering suggests that Vif may bind a conserved surface present in multiple APOBEC3 proteins.     

Negative regulation of hematopoiesis by the fused in myeloproliferative disorders gene product

The t(8;13) translocation, found in a rare and aggressive type of stem cell myeloproliferative disorder, leads to the generation of a fusion protein between the N-terminal gene product of fused in myeloproliferative disorders (FIM)/ZNF198 and the fibroblast growth factor receptor 1 (FGFR1) kinase domain. The chimeric protein was reported to have constitutively activated tyrosine kinase activity. However, little is known about a role of FIM in hematopoietic cell regulation. Here we show that FIM protein is ubiquitously expressed in mouse embryonic tissues but much less in hematopoietic cells. We also show that forced expression of FIM inhibits the emergence of hematopoietic cells in the cultured mouse aorta-gonad-mesonephros (AGM) region on embryonic day (E) 11.5, where definitive hematopoiesis is first found during embryogenesis. These results suggest that the expression level of FIM determines the development of hematopoiesis during mouse ontogeny.     

DAP12 ITAM motif regulates differentiation and apoptosis in M1 leukemia cells

DAP12 is an immunoreceptor tyrosine-based activation motif (ITAM)-bearing transmembrane adapter molecule that is associated with the NK-activating receptors. DAP12 is expressed not only in NK cells, but also in myeloid cells. Previously, we reported that DAP12 was likely to be involved in monocyte differentiation to macrophage. In this study, we established the mutant DAP12-M1 transfectants (Y76F-M1) that have mutation at their ITAM motifs. We observed that Y76F-M1 cells could not differentiate to macrophages by stimulation via DAP12, whereas wild type DAP12 transfectants (FDAP-M1) could. Furthermore, we demonstrated that the apoptosis signal mediated by LPS was inhibited in Y76F-M1 cells, but was augmented in FDAP-M1 cells. In contrast to the LPS-mediated apoptosis, the combination of LPS and DAP12 stimulation showed good cell viability in FDAP-M1 cells. Collectively our studies demonstrated that DAP12 has a critical role for macrophage differentiation and LPS induced apoptosis in M1 leukemia cells.     

Immunoglobulin treatment suppresses atherosclerosis in apolipoprotein E-deficient mice via the Fc portion

Atherosclerosis is associated with immune activation. Immunoglobulin is used for the treatment of immune-mediated diseases. The mechanisms and importance of the Fc portion of immunoglobulin upon experimental atherosclerosis in apolipoprotein E-deficient mice were examined. Experimental atherosclerosis was induced in mice fed a high-fat diet containing 0.3% cholesterol. Over 8, 12, and 16 wk, on alternate days, mice were treated with an intraperitoneal injection of either 1 g.kg-1.day-1 of human intact immunoglobulin or F(ab')2 fragments of human immunoglobulin. Fatty streak formation and fibrofatty plaques were markedly suppressed in mice that received intact immunoglobulin for 8, 12, and 16 wk. In contrast, atherosclerotic lesions were not ameliorated in mice that received F(ab')2 fragments. Immunohistochemical analysis revealed that macrophage accumulation in the fatty streak lesions was suppressed in mice received intact immunoglobulin but not in those that received F(ab')2 fragments. In addition, the cytotoxic activities of splenocytes from immunoglobulin-treated mice, but not from F(ab')2 fragment-treated mice, were significantly suppressed compared with those from human serum albumin-treated mice. Differences in lesion area did not correlate with any significant alterations in serum lipid levels. Immunoglobulin therapy markedly suppressed atherosclerosis due to Fc receptor-mediated anti-inflammatory and immunomodulating actions. The antiatherosclerotic effects of immunoglobulin may be related to the suppression of cytotoxic activity of atherogenic T cells and the reduction of macrophage accumulation in the lesions.     

Establishment of Alternative Culture Method for Spermatogonial Stem Cells Using Knockout Serum Replacement

Since spermatogonial stem cells (SSCs) are capable of both self-renewal and differentiation to daughter cells for subsequent spermatogenesis, the development of an efficient in vitro culture system is essential for studies related to spermatogenesis. Although the currently available system is serum-free and contains only chemically-defined components, it highly relies upon bovine serum albumin (BSA), a component with batch-to-batch quality variations similar to those of fetal bovine serum. Thus, we searched for an alternative BSA-free culture system that preserved the properties of SSCs. In this study, we utilized Knockout Serum Replacement (KSR) in the SSC culture medium, as a substitute for BSA. The results demonstrated that KSR supported the continuous growth of SSCs in vitro and the SSC activity in vivo without BSA, in a feeder-cell combination with mouse embryonic fibroblasts. The addition of BSA to KSR further facilitated cell cycle progression, whereas a transplantation assay revealed that the addition of BSA did not affect the number of SSCs in vivo. The combination of KSR with BSA also allowed the elimination of GFRA1 and FGF2, and the reduction of the GDNF concentration from 20 ng/ml to 5 ng/ml, while maintaining the growth rate and the expression of SSC markers. Furthermore, KSR was also useful with SSCs from non-DBA/2 strains, such as C57BL/6 and ICR. These results suggested that KSR is an effective substitute for BSA for long-term in vitro cultures of SSCs. Therefore, this method is practical for various studies related to SSCs, including spermatogenesis and germ stem cell biology.     

Culturable fungal endophytes in roots of Enkianthus campanulatus (Ericaceae)

Roots of plants in the genus Enkianthus, which belongs to the earliest diverging lineage in the Ericaceae, are commonly colonized by arbuscular mycorrhizal (AM) fungi. We documented the community of fungal root endophytes associated with Enkianthus species using a culture-based method for better understanding the members of root-colonizing fungi, except for AM fungi. Fungal isolates were successfully obtained from 610 out of 3,599 (16.9 %) root segments. Molecular analysis of fungal cultures based on ribosomal internal transcribed spacer (ITS) sequences yielded 63 operational taxonomical units (OTUs: 97 % sequence similarity cutoff) from 315 representative isolates. Further phylogenetic analysis showed that most (296 isolates) belonged to Ascomycota and were either members of Helotiales (Dermataceae, Hyaloscyphaceae, Phialocephala and Rhizoscyphus ericae aggregate), Oidiodendron, or other Pezizomycotina. Twenty-three out of 63 OTUs, which mainly consisted of Leotiomycetes, showed high similarities with reference sequences derived from roots of other ericaceous plants such as Rhododendron. The results indicated that Enkianthus houses variable root mycobionts including putative endophytic and mycorrhizal fungi in addition to AM fungi.