Energy partitioning in cultured juvenile Pacific bluefin tuna,Thunnus orientalis (Temminck & Schlegel, 1844)

The characteristics of dietary utilization, energy conversion efficiency, metabolic rate and energy partitioning were measured for cultured Pacific bluefin tuna (PBT) juveniles fed on an artificial diet. Thirty‐one juveniles (1.1 ± 0.3 g BW) were stocked into each of two 2500 L tanks to measure oxygen consumption (?O₂), swimming speed, digestibility and growth performance. ?O₂ elevated until 2.5 ± 0.3 times of pre‐feeding level within 1.5 h after feeding, except for the first feeding, and returned to pre‐feeding level within 3 h. Swimming speed fluctuation was corresponded with the ?O₂ fluctuation, and both parameters were stable from 02:00 to 06:00 and also during the whole day for starved fish. These indicate that feeding has strong influence on their metabolic rate. Energy partitioning for faecal, urinary and branchial, heat increment and voluntary activity, standard metabolism, and retained energy were calculated to be 17.2%, 5.9%, 14.9%, 41.3% and 20.7% of total ingested energy, respectively. The results indicate that, unlike other fish, juvenile PBT distribute large amount of energy for maintenance, which allows only a little proportion of ingested energy available for growth.     

Experimental evidence of a pathogenic change caused by homologous recombination between endogenous and introduced dysfunctional Avr-Pita genes in Pyricularia oryzae

To provide experimental evidence that somatic homologous recombination (HR) is involved in the instability and diversification of the avirulence gene Avr-Pita in Pyricularia oryzae, we generated a dysfunctional Avr-Pita homolog and integrated it into strain Hoku-1 containing Avr-Pita. In the transformants, the occurrence of somatic HR events between Avr-Pita and the dysfunctional homolog was confirmed by PCR–RFLP. Germlings from conidia from the HR-positive transformants had lost the avirulence function, which enabled it to infect rice cultivar Yashiromochi containing the corresponding resistant gene Pi-ta. These results suggested that genetic mutation caused by somatic HR is one of the mechanisms responsible for virulence diversity.     

Vertical behavior of bigeye tuna (Thunnus obesus) in the northwestern Pacific Ocean based on archival tag data

The behavior of bigeye tuna (Thunnus obesus) in the northwestern Pacific Ocean was investigated using archival tag data for 28 fish [49–72 cm fork length (FL) at release, 3–503 days] released in Japanese waters around the Nansei Islands (24–29°N, 122–132°E) and east of central Honshu (Offshore central Honshu, 32–36°N, 142–148°E). Vertical behavior was classified into three types based on past studies: ‘characteristic’ (non‐associative), ‘associative’ (associated with floating objects) and ‘other’ (behavior not fitting into these two categories). The proportion of fish showing associative behavior decreased and that of characteristic behavior increased as fish grew, and this shift was pronounced at 60–70 cm FL. The fish usually stayed above the 20°C isotherm during the daytime and nighttime when showing associative behavior and below the 20°C isotherm during daytime for characteristic behavior. A higher proportion of characteristic behavior was seen between December and April around the Nansei Islands, and between September and December for offshore central Honshu. Seasonal changes in vertical position were also observed in conjunction with changes in water temperature. In this study, ‘other’ behavior was further classified into five types, of which ‘afternoon dive’ behavior, characterized by deep dives between around noon and evening, was the most frequent. The present study indicated that in the northwestern Pacific Ocean, the vertical behavior of bigeye tuna changes with size, as well as between seasons and regions.     

Interaction between myostatin and extracellular matrix components

Myostatin, a member of the TGF-β superfamily, is a negative regulator of skeletal muscle mass. We have recently demonstrated that decorin binds to myostatin in vitro , and that immobilized decorin within the collagen matrix prevents myostatin-mediated inhibition of myoblast proliferation. However, little is known about other ECM molecules that bind to myostatin and modulate its activity. Thus, in the present study, we investigated the interaction of several other ECM molecules with myostatin. We here show that fibromodulin, fibronectin and laminin bind to myostatin in the presence of Zn²⁺ with a dissociation constant ( K_D ) of 10⁻¹⁰∼10⁻⁸ mol/L. Fibromodulin shows the highest affinity for myostatin among them. These results suggest that these ECM molecules may modulate myostatin activity like decorin does.     

人类活动对中国南部荒山松林养分循环的影响

在中国南部开展对荒山马尾松(Pinus massoniana)林养分循环受人类活动影响的调查.位于江西省兴国县研究地点的一些农民从森林生态系统中收取有机物作为燃料,这引起养分循环的断裂和植被恢复的延误以及土壤侵蚀的发生.收取的量估算为相当于5.92t/hm2有机物和21.4kg/hm2氮.如果收取停止,10年之后,有机物在森林地表枯枝落叶层的积累将可恢复.     

Transition state leading to β-O′ quinonemethide intermediate of p-coumaryl alcohol analyzed by semi-empirical molecular orbital calculation

The radical coupling reaction leading to the β-0′ quinonemethide intermediate of p-coumaryl alcohol was analyzed by semi-empirical molecular orbital calculation with MOPAC2002. By analyzing the radical monomer in a one-electron oxidation, the spin density of the unpaired electron at the 4-oxygen was less than half of the values at the C₁, C₃, C₅, and C_β positions. By analyzing the transition state during the radical coupling reaction, the activation enthalpy was evaluated as 9.76 kcal/mol, which corresponds to the activation energies for the propagation of common vinyl polymers. From the analysis of atomic interactions in the transition state, it was found that the activation enthalpy was largely composed of a high coulombic repulsion between C_β of the first monomer and the phenolic oxygen of the second monomer. After passing the transition state, the two radical monomers formed a metastable quinone-methide intermediate. The optimum conformation of the quinonemethide intermediate was formed from the meta-stable conformation through a second transition state with a small energy barrier. Part of this article was presented at the 46th Lignin Symposium, held in Fukuoka, October 31-November 1, 2002     

Interspecific hybrids betweenAllium fistulosumandAllium schoenoprasumreveal carotene-rich phenotype

Interspecific hybridization is an effective method to generate a new crop that gains available functions in a short time. Interspecific hybrids (2n= 16) betweenAllium fistulosumL. (2n= 16) andAllium schoenoprasumL. (2n= 16) were produced by reciprocal crossings through ovary culture, but the hybrids were much fewer in the combination usingA. schoenoprasumas a seed plant. All the hybrids have eight long chromosomes originated fromA.fistulosumand eight short chromosomes originated fromA. schoenoprasum. In addition, the hybridity was confirmed by randomly amplified polymorphic DNA (RAPD) analysis and cleaved amplified polymorphic sequence (CAPS) analysis of the rDNA internal transcribed spacer (ITS) region. The interspecific hybrids showed a vigorous growth habit; their foliage was slightly bloomy and deep green. The hybrids did not form bulbs, but rather propagated vegetatively by tillering. Carotene contents of the hybrids and both parents were quantified using high-performance liquid chromatography (HPLC). The contents of all edible parts of the hybrids were approximately seven times higher than those of either parent. These results indicate that the hybrid is a new and carotene-rich vegetable ofAlliumspecies.     

Production of interspecific hybrids between Alstroemeria pelegrina L. var. rosea and A. magenta Bayer by ovule culture

Interspecific hybrids were efficiently produced in the cross-incompatible combination between Alstroemeria pelegrina L. var. rosea and A. magenta Bayer by culturing immature ovules with placenta 7–14 days after pollination on 2 g/l Gelrite-solidified MS medium containing 3% (w/v)sucrose. The plants showed intermediate characteristics between the parents and their hybridity was confirmed by karyotype and DNA analyses. The mean number of chromosome association per PMC at metaphase I was 2.60I+6.70II, pollen stainability was20.8%, and they produced viable seeds after self-pollination. Furthermore, mature plants were obtained when the hybrids were backcrossed as male parents with both the parents. The backcross-progeny from A. pelegrina var. rosea × hybrids exhibited 3.8 to 79.7% pollen stainability and that from A. magenta × hybrids 78.8 to 98.3%. Almost all of these plants produced viable seeds after self-pollination, which implies that they can beutilized for breeding of novel cultivars of Alstroemeria. This revised version was published online in July 2006 with corrections to the Cover Date.     

中国南部天然常绿阔叶林的地上生物量、净初级生产力、养分分布和养分利用效率

在中国南部的江西九连山自然保护区,观测研究了天然常绿阔叶林的地上生物量、地上NPP(净初级生产力)、养分的积累和分布,以及不同生活型树种的养分利用效率.在两个样地,用相对生长回归法和收获法测定了地上生物量,数值各约为340和270t/hm2,其中叶生物量约为9.6t/hm2.地上NPP约为年9.9t/hm2,其中叶生产力占44％.各种一般养分(N,P,K,Ca,Mg,Na)在森林生态系统中积累的特点是,Na和N在矿质土壤中有高的相对分布,K和Mg属中间地位,Ca和P则高分布于地上生物量中.氮的养分利用效率(NUE)、平均停留时间(MRT)和年生产力(A)表明,针叶树是氮的最高效的利用者,常绿阔叶树次之,落叶树在氮的利用上是最低效的.