Pattern of immigration of the sorghum plant bug Stenotus rubrovittatus (Hemiptera: Miridae) into paddy fields from a large source habitat

Evaluation of the landscape-level movement of Stenotus rubrovittatus (Matsumura), a major rice pest in Japan, is essential for establishing management strategies. We assessed the immigration timing and the average dispersal distance from a bank slope covered with Italian ryegrass Lolium multiflorum Lam. to paddy fields by periodic sampling in two regions in Chiba Prefecture. The immigrant densities in paddy fields increased exponentially as they approached the bank slope as a large-scale habitat of the insect. The relationship between immigrant density and distance from the source habitat fit an empirical model and theoretical model well. The theoretical model estimated the average dispersal distance during immigration: that of females was 72.0 and 92.1 m and that of males was 122.0 and 112.9 m in the respective regions. In addition, the average dispersal distance of males increased 7 days or later after the rice heading date despite the steady dispersal distance of females.     

None of the Rotor Residues of F1-ATPase Are Essential for Torque Generation

F₁-ATPase is a powerful rotary molecular motor that can rotate an object several hundred times as large as the motor itself against the viscous friction of water. Forced reverse rotation has been shown to lead to ATP synthesis, implying that the mechanical work against the motor’s high torque can be converted into the chemical energy of ATP. The minimal composition of the motor protein is α₃β₃γ subunits, where the central rotor subunit γ turns inside a stator cylinder made of alternately arranged α₃β₃ subunits using the energy derived from ATP hydrolysis. The rotor consists of an axle, a coiled coil of the amino- and carboxyl-terminal α-helices of γ, which deeply penetrates the stator cylinder, and a globular protrusion that juts out from the stator. Previous work has shown that, for a thermophilic F₁, significant portions of the axle can be truncated and the motor still rotates a submicron sized bead duplex, indicating generation of up to half the wild-type (WT) torque. Here, we inquire if any specific interactions between the stator and the rest of the rotor are needed for the generation of a sizable torque. We truncated the protruding portion of the rotor and replaced part of the remaining axle residues such that every residue of the rotor has been deleted or replaced in this or previous truncation mutants. This protrusionless construct showed an unloaded rotary speed about a quarter of the WT, and generated one-third to one-half of the WT torque. No residue-specific interactions are needed for this much performance. F₁ is so designed that the basic rotor-stator interactions for torque generation and control of catalysis rely solely upon the shape and size of the rotor at very low resolution. Additional tailored interactions augment the torque to allow ATP synthesis under physiological conditions.     

A model of cancer stem cells derived from mouse induced pluripotent stem cells

Cancer stem cells (CSCs) are capable of continuous proliferation and self-renewal and are proposed to play significant roles in oncogenesis, tumor growth, metastasis and cancer recurrence. CSCs are considered derived from normal stem cells affected by the tumor microenvironment although the mechanism of development is not clear yet. In 2007, Yamanaka's group succeeded in generating Nanog mouse induced pluripotent stem (miPS) cells, in which green fluorescent protein (GFP) has been inserted into the 5'-untranslated region of the Nanog gene. Usually, iPS cells, just like embryonic stem cells, are considered to be induced into progenitor cells, which differentiate into various normal phenotypes depending on the normal niche. We hypothesized that CSCs could be derived from Nanog miPS cells in the conditioned culture medium of cancer cell lines, which is a mimic of carcinoma microenvironment. As a result, the Nanog miPS cells treated with the conditioned medium of mouse Lewis lung carcinoma acquired characteristics of CSCs, in that they formed spheroids expressing GFP in suspension culture, and had a high tumorigenicity in Balb/c nude mice exhibiting angiogenesis in vivo. In addition, these iPS-derived CSCs had a capacity of self-renewal and expressed the marker genes, Nanog, Rex1, Eras, Esg1 and Cripto, associated with stem cell properties and an undifferentiated state. Thus we concluded that a model of CSCs was originally developed from miPS cells and proposed the conditioned culture medium of cancer cell lines might perform as niche for producing CSCs. The model of CSCs and the procedure of their establishment will help study the genetic alterations and the secreted factors in the tumor microenvironment which convert miPS cells to CSCs. Furthermore, the identification of potentially bona fide markers of CSCs, which will help the development of novel anti-cancer therapies, might be possible though the CSC model.     

Temporal and quantitative analysis of expression of metalloproteinases (MMPs) and their endogenous inhibitors in atherosclerotic lesions

Matrix metalloproteinases (MMPs) play an important role in the pathogenesis of vascular diseases, such as atherosclerosis, plaque rupture and aneurysms. Although several MMPs have been demonstrated in the lesions of atherosclerosis, their expression profiles during the initiation and progression of lesions have not been fully determined. We hypothesized that the expression of various MMPs, along with their endogenous inhibitors, may be differentially regulated dependent upon the lesion progression. Therefore, we made a temporal and quantitative analysis of the mRNA and protein expression of MMPs and tissue inhibitors of metalloproteinases expressed in the different stages of atherosclerotic lesions of rabbits and humans. We found that MMP-1, MMP-12 and MMP-13 expression was nearly absent in the normal arterial wall, but was remarkably increased with lesion progression. Furthermore, the expression of these MMPs in the lesions was closely associated with intimal macrophages and monocyte chemoattractant protein-1 expression, suggesting that the intimal macrophages are the major source of production of these MMPs. MMP-3 and MT1-MMP were also significantly upregulated in the early-stage lesions and fatty streaks compared to the normal aortas of rabbits. Our results indicate that MMP-1, -12, and -13 derived from intimal macrophages may play a pivotal role in both lesion initiation and progression, and therefore are potential therapeutic targets for the treatment of plaque rupture and aneurysm formation.     

Horizontal and vertical distribution and demography of euphausiids in the Ross Sea and its adjacent waters in 2004/2005

The horizontal and vertical distribution and population structure of euphausiids in the Ross Sea and its adjacent waters were investigated during the summers of 2004/2005 using stratified towed samples. Nine species of euphausiids occurred in the survey area. Among them, Euphausia triacantha was dominant in biomass north of the southern boundary of the Antarctic circumpolar current (SB). Thysanoessa spp. was widely distributed north of the continental slope, while E. superba was distributed from the SB to the slope, where it showed the highest biomass. Juvenile E. superba was distributed offshore near the SB and remained at the surface, but gravid females were dominant in the slope and mainly occurred in the middle layers (400–600 m). Adult and juvenile E. crystallorophias were found at 200–300 m in the colder water of the continental shelf. In general, the peak biomass of euphausiids was found in the mid layers of the Ross Sea area. The life span and the number of spawns for major species are also discussed.     

Single bacterial cell detection using a mutant luciferase

Previously, we constructed a genetically modified luciferase of Photinus pyralis that generates more than 10-fold higher luminescence intensity than the wild-type enzyme. In this study, we demonstrate that this modified luciferase enables us to detect ATP at 10⁻¹⁸ mol, which is almost equal to the quantity contained in a single bacterial cell. Consequently,we have been able to detect bacterial contamination in samples as low as one colony-forming unit (c.f.u.) for both Escherichia coli and Bacillus subtilis.     

Changes in the microbial community structure during thermophilic composting of manure as detected by the quinone profile method

Quinone profiles and physico-chemical properties were measured to characterize the microbial community structure during a 14-day thermophilic composting of cattle manure mixed with rice straw as a bulking agent. The change in total quinone content (TQ) and the divergence of quinone (DQ) indicated that the microbial biomass reached a peak followed by a decrease, whereas the microbial community diversity increased continuously during the composting process. The high mole fraction of ubiquinones in the raw materials, and at the beginning of the composting period suggested that fungi and/or Proteobacteria were present. The predominance of MK-7 from days 3 to 7 suggested that Bacillus spp. were the main microbial species. An increase in partially saturated and long-chain menaquinones during the latter composting period indicated that the proliferation of various species of Actinobacteria was occurring. The microbial community structure, as expressed by TQ and DQ, corresponded well to physico-chemical properties such as the C/N ratio, pH, O₂ consumption and compost mass reduction.