Isolation of chicken taste buds for real‐time Ca2+ imaging

We isolated chicken taste buds and used a real‐time Ca²⁺ imaging technique to investigate the functions of the taste cells. With RT‐PCR, we found that isolated chicken taste bud‐like cell subsets express chicken gustducin messenger RNA. Immunocytochemical techniques revealed that the cell subsets were also immunopositive for chicken gustducin. These results provided strong evidence that the isolated cell subsets contain chicken taste buds. The isolated cell subsets were spindle‐shaped and approximately 61–75 μm wide and 88–98 μm long, and these characteristics are similar to those of sectional chicken taste buds. Using Ca²⁺ imaging, we observed the buds' response to 2 mmol/L quinine hydrochloride (a bitter substance) and their response to a mixture of 25 mmol/L L‐glutamic acid monopotassium salt monohydrate and 1 mmol/L inosine 5′‐monophosphate disodium salt, umami substances. The present study is the first morphological demonstration of isolated chicken taste buds, and our results indicate that the isolated taste buds were intact and functional approaches for examining the taste senses of the chicken using Ca²⁺ imaging can be informative.     

Transgenic cell lines which stably express progestogen receptors (PRS) α and β and the PR-responsive reporter genes

Transgenic cell lines which stably express progestogen receptors (PRs) and the PR-responsive reporter genes were developed. They are a good system for rapid, sensitive and reproducible screening of various ligands.     

Molecular cloning and gene expression of the riboflavin-binding protein in the Nile tilapia, Oreochromis niloticus

Tilapia riboflavin-binding protein (RfBP) cDNA was isolated by library screening. Even though it shows only 31～35% similarity to the reported RfBPs, tilapia RfBP is conserved in amino acid residues that are known to be essential for its protein function. The exclusive expression of RfBP in the brain-pituitary-gonadal axis, as revealed by both RT-PCR and Northern blot, suggested a possible role for RfBP in fish reproduction.     

Involvement of steroid hormones in the preovulatory gonadotropin surge in female goldfish

Goldfish,Carassius auratus, spawn several times within a spawning season. A gonadotropin (GtH) surge occurs at the time of ovulation in this cyprinid species. This ovulatory GtH surge mediates the processes of final oocyte maturation and ovulation, and occurs at the end of each spawning cycle. Within a cycle, there is a shift in the predominant plasma steroid from estradiol to testosterone, and finally 17α, 20β-dihydroxy-4-pregnen-3-one at the time of the ovulatory GtH surge. High levels of testosterone were always observed before ovulation. When ovariectomized or sexually regressed female goldfish were implanted with testosterone, they exhibited a GtH surge which was similar to those normally observed at ovulation. These results strongly suggest that elevated plasma testosterone is an important physiological requirement for the occurrence of the GtH surge.     

Characterization of an Alginate Lyase,FlAlyA, from Flavobacterium sp. Strain UMI-01 and Its Expression in Escherichia coli

A major alginate lyase, FlAlyA, was purified from the periplasmic fraction of an alginate-assimilating bacterium, Flavobacterium sp. strain UMI-01. FlAlyA showed a single band of ~30 kDa on SDS-PAGE and exhibited the optimal temperature and pH at 55 °C and pH 7.7, respectively. Analyses for substrate preference and reaction products indicated that FlAlyA was an endolytic poly(mannuronate) lyase (EC 4.2.2.3). A gene fragment encoding the amino-acid sequence of 288 residues for FlAlyA was amplified by inverse PCR. The N-terminal region of 21 residues except for the initiation Met in the deduced sequence was predicted as the signal peptide and the following region of six residues was regarded as propeptide, while the C-terminal region of 260 residues was regarded as the polysaccharide-lyase-family-7-type catalytic domain. The entire coding region for FlAlyA was subjected to the pCold I—Escherichia coli BL21(DE3) expression system and ~eight times higher yield of recombinant FlAlyA (recFlAlyA) than that of native FlAlyA was achieved. The recFlAlyA recovered in the periplasmic fraction of E. coli had lost the signal peptide region along with the N-terminal 3 residues of propeptide region. This suggested that the signal peptide of FlAlyA could function in part in E. coli.     

Contribution of Adventitious Roots to Water Use Strategy of Juniperus sabina in a Semiarid Area of China

duniperus sabina Linnaeus, an evergreen shrub with prostrate life form, can effectively prevent sand moving and is an important tree species for reforestation in semiarid areas of China. It has laterally distributed adventitious roots and a deeply distributed main root system. To detect water movement between the main root system and adventitious roots, we adopted heat pulse sensors using the Heat Ratio Method, a high precision method for measuring low sap flow rates. Two sensors were implanted in each individual in the stem between the main root system and adventitious roots, and another two in lateral stems distal to all the roots. Positive sap flows during nighttime, even under saturated air moisture conditions, were detected only between the main root system and adventitious roots under drought conditions, and the rate of flow increased as drought progressed and decreased or disappeared after rain events. The results demonstrated the existence of water movement from the main root system to adventitious roots, and combined with the high contribution of nighttime sap flow to transpiration （11%-16%） the results indicate that it also involves the process of hydraulic lift, a water movement from moist subsoil to dry surface soils. Integrated water use strategy between the main root system and adventitious roots via the process of hydraulic lift of soil water maximizes water acquisition efficiency from both subsoil water and water from rain pulses on the soil surface; this increases survivability in the water-limited environment of semiarid areas.     

Sex change in coral reef fish

Gonadal differentiation can take many forms in fish, ranging from gonochorism, where individuals directly develop as male or female and finally possess only testis or ovaries at sexual maturation, to hermaphroditism where the same individuals can produce mature male and female gametes at some time in their lives. Hermaphrodite fish are, thus, an excellent model for studying the plasticity of sex determination and differentiation in vertebrates. We have shown that sex steroids play a principal role in sex differentiation and sex change in fish. Our laboratory implements several fish models that undergo sex change from female to male or male to female or in both directions. In this review, we will briefly discuss recent advances in our understanding of the mechanism of sex change in coral reef fish.     

Principles and approaches to abate seabird by-catch in longline fisheries

Mortality in longline fisheries is a critical global threat to most albatross and large petrel species. Here we identify key principles and approaches to identify and achieve broad use of effective seabird by‐catch avoidance methods. Despite the availability of highly effective and cost‐saving seabird avoidance methods, few longline fleets employ them. Given the political context and capacity of management authorities of the majority of longline fisheries, it is critical to identify seabird avoidance strategies that are not only highly effective, but are also economically viable and commercially practical. Adoption of an international performance standard for longline baited hook–sink rate, and prescribing minimum gear weighting designs that meet this standard that are achievable by all longline fisheries, would be an important step forward towards resolving low use of seabird avoidance methods by vessels, including those in illegal, unregulated and unreported fisheries. Due to differences between fleets, no single seabird avoidance measure is likely to be effective and practical in all longline fisheries. Therefore, testing of seabird avoidance methods in individual fleets is needed to determine efficacy and economic viability. Longline fishers should directly participate in these trials as they have a large repository of knowledge and skills to effectively develop and improve seabird by‐catch avoidance techniques, and this provides industry with a sense of ownership for uptake of effective by‐catch reduction methods. Establishing protected areas containing seabird colonies and adjacent waters within a nation's EEZ can be an expedient method to address seabird by‐catch. However, establishing high seas marine protected areas to restrict longline fishing in seabird foraging areas, which would require extensive and dynamic boundaries and large buffer zones, may not be a viable short‐term solution because of the extensive time anticipated to resolve legal complications with international treaties, to achieve international consensus and political will, and to acquire requisite extensive resources for surveillance and enforcement. Analysis of results of research on seabird avoidance methods reveals that the most reliable comparisons of the efficacy of alternative strategies are from comparing the effectiveness of methods tested in a single experiment. Benefits from standardizing the reporting of seabird by‐catch rates to account for seabird abundance are described. To provide the most precise inputs for seabird population models, estimates of seabird mortality in longline fisheries should account for seabird falloff from hooks before hauling, delayed mortality of seabirds caught but freed from gear, and mortality caused by hooks discarded in offal.