Factors controlling the distribution of aquatic macrophyte communities with special reference to the rapid expansion of a semi-emergent <Emphasis Type="Italic">Phalaris arundinacea</Emphasis> L. in Bibi River,Hokkaido, northern Japan

To identify the causes of the rapid expansion of the semi-emergent Phalaris arundinacea L. community in a nutrient-loaded river, we investigated the factors that determine the distribution of the Phalaris and other aquatic macrophyte communities and the shoot growth of P. arundinacea. The Phalaris community was distributed through areas with high organic nitrogen (Org-N), total phosphorus (T-P), PO₄-P and suspended solids (SS) concentrations and low dissolved oxygen (DO). P. arundinacea shoots grow better in deep mud and high SS and T-P, all of which were strongly correlated with slower stream currents. Accordingly, although the concentration of total nitrogen constantly increased from 1985 to 1998, the determining nutrient for the expansion of the Phalaris community and P. arundinacea shoot growth stimulation was phosphorus rather than nitrogen. The Phalaris community increased rapidly between 1991 and 1996, when brief but prominent loadings of phosphorus were observed. We concluded that the Phalaris community was restricted due to phosphorus deficiency under nitrogen excess until 1991 and subsequently rapidly expanded over the channel due to the temporary excess phosphorus present during this period. Thereafter, the rapid expansion of the Phalaris community was maintained by the clogging effect of the floating mats formed by shoots and their remains of P. arundinacea, which results in slower currents. A slower current resulted in low DO, the sedimentation of degraded plant remains (high Org-N), and the adsorption of phosphorus by suspended matter (high SS and T-P). The anaerobic conditions caused by low oxygen and the accumulation of decomposable organic matter ensure the continuous development of the Phalaris community through the release of soluble phosphorus from the sediment.     

Characterization of Syrian hamster adapted prions derived from L-type and C-type bovine spongiform encephalopathies

Atypical forms of bovine spongiform encephalopathy (BSE) may be caused by different prions from classical BSE (C-BSE). In this study, we examined the susceptibility of mice overexpressing mouse and hamster chimeric prion protein (PrP) to L-type atypical BSE (L-BSE). None of the transgenic mice showed susceptibility to L-BSE, except mice overexpressing hamster PrP. We also examined the transmission properties of L-BSE in hamsters. The incubation period of hamsters intracerebrally inoculated with L-BSE was 576.8 days, and that of the subsequent passage was decreased to 208 days. Although the lesion and glycoform profiles and relative proteinase K resistant core fragment of the abnormal isoform of PrP (PrPcore) of L-BSE were similar to that of C-BSE, the deposition of the abnormal isoform of PrP (PrP^Sc) and the molecular weight of PrPcore of L-BSE was different from than that of C-BSE. In hamster models, some prion strain characteristics of L-BSE were indistinguishable from those of C-BSE.Key words: prion, atypical, L-BSE, PrPcore, hamster, transmission     

Establishment, Growth kinetics, and Susceptibility to AcMNPV of Heat Tolerant Lepidop teran Cell Lines

Lepidopteran heat-tolerant(ht)cell lines have been obtained with sf-9,sf-21 and several Bombyx cells.They have a distinct karyotype,membrane lipid composition,morphology and growth kinetics from the parental cell lines.In this paper,we report the development of ht cell lines from other insect species and examination of their growth characteristics and virus susceptibility.Adaptation of cell lines sf-9,BTI-TN-5131-4(High5)and BTI-TN-MG1(MG 1)to 33℃ and 35℃ was carried out by shifting the culture temperature between 28℃ and higher temperatures by a gradual stepwise increase in temperature.The process of adaption to a higher culture temperature was accomplished over a period of 2 months.The cell lines with the temperature adaption were designated as sf9-ht33,sf9-ht35,High5-ht33,High5-ht35,MG1-ht33,MG1-ht35.These cell lines have been subcultured over 70 passages.Adaption to high temperatures was confirmed by a constant population doubling time with individual cell lines.The population doubling time of heat adapted cell lines were 1-4 h less than these of parental cell lines.Cell shapes did not show obvious change,however,the cell size of sf9-ht cells was enlarged and those of High5 and MG1 ht cells were reduced after heat adaption.When the cell lines were infected with Autographa californica nuclear polyhedrosis virus(AcMNPV)at 28℃,33℃,35℃ and 37℃,production of budded virus and occlusion bodies in each cell line was optimum at its own adapted temperature.     

Blockade of gap junction hemichannel suppresses disease progression in mouse models of amyotrophic lateral sclerosis and Alzheimer's disease

Background

Glutamate released by activated microglia induces excitotoxic neuronal death, which likely contributes to non-cell autonomous neuronal death in neurodegenerative diseases, including amyotrophic lateral sclerosis and Alzheimer''s disease. Although both blockade of glutamate receptors and inhibition of microglial activation are the therapeutic candidates for these neurodegenerative diseases, glutamate receptor blockers also perturbed physiological and essential glutamate signals, and inhibitors of microglial activation suppressed both neurotoxic/neuroprotective roles of microglia and hardly affected disease progression. We previously demonstrated that activated microglia release a large amount of glutamate specifically through gap junction hemichannel. Hence, blockade of gap junction hemichannel may be potentially beneficial in treatment of neurodegenerative diseases.

Methods and Findings

In this study, we generated a novel blood-brain barrier permeable gap junction hemichannel blocker based on glycyrrhetinic acid. We found that pharmacologic blockade of gap junction hemichannel inhibited excessive glutamate release from activated microglia in vitro and in vivo without producing notable toxicity. Blocking gap junction hemichannel significantly suppressed neuronal loss of the spinal cord and extended survival in transgenic mice carrying human superoxide dismutase 1 with G93A or G37R mutation as an amyotrophic lateral sclerosis mouse model. Moreover, blockade of gap junction hemichannel also significantly improved memory impairments without altering amyloid β deposition in double transgenic mice expressing human amyloid precursor protein with K595N and M596L mutations and presenilin 1 with A264E mutation as an Alzheimer''s disease mouse model.

Conclusions

Our results suggest that gap junction hemichannel blockers may represent a new therapeutic strategy to target neurotoxic microglia specifically and prevent microglia-mediated neuronal death in various neurodegenerative diseases.     

Unique regulation of glyoxalase I activity during osmotic stress response in the fission yeast <Emphasis Type="Italic">Schizosaccharomyces pombe</Emphasis>: neither the mRNA nor the protein level of glyoxalase I increase under conditions that enhance its activity

Glyoxalase I is a ubiquitous enzyme that catalyzes the conversion of methylglyoxal, a toxic 2-oxoaldehyde derived from glycolysis, to S-D-lactoylglutathione. The activity of glyoxalase I in the fission yeast Schizosaccharomyces pombe was increased by osmotic stress induced by sorbitol. However, neither the mRNA levels of its structural gene nor its protein levels increased under the same conditions. Cycloheximide blocked the induction of glyoxalase I activity in cells exposed to osmotic stress. In addition, glyoxalase I activity was increased in stress-activated protein kinase-deficient mutants (wis1 and spc1). We present evidence for the post-translational regulation of glyoxalase I by osmotic stress in the fission yeast.     

Motor activity and trajectory control during escape jumping in the locust <Emphasis Type="Italic">Locusta migratoria</Emphasis>

We investigated the escape jumps that locusts produce in response to approaching objects. Hindleg muscular activity during an escape jump is similar to that during a defensive kick. Locusts can direct their escape jumps up to 50° either side of the direction of their long axis at the time of hindleg flexion, allowing them to consistently jump away from the side towards which an object is approaching. Variation in jump trajectory is achieved by rolling and yawing movements of the body that are controlled by the fore- and mesothoracic legs. During hindleg flexion, a locust flexes the foreleg ipsilateral to its eventual jump trajectory and then extends the contralateral foreleg. These foreleg movements continue throughout co-contraction of the hindleg tibial muscles, pivoting the locust’s long axis towards its eventual jump trajectory. However, there are no bilateral differences in the motor programs of the left and right hindlegs that correlate with jump trajectory. Foreleg movements enable a locust to control its jump trajectory independent of the hindleg motor program, allowing a decision on jump trajectory to be made after the hindlegs have been cocked in preparation for a jump.     

An inter-laboratory collaborative study by the Non-Genotoxic Carcinogen Study Group in Japan, on a cell transformation assay for tumour promoters using Bhas 42 cells

The Bhas promotion assay is a cell culture transformation assay designed as a sensitive and economical method for detecting the tumour-promoting activities of chemicals. In order to validate the transferability and applicability of this assay, an inter-laboratory collaborative study was conducted with the participation of 14 laboratories. After confirmation that these laboratories could obtain positive results with two tumour promoters, 12-O-tetradecanoylphorbol-13-acetate (TPA) and lithocholic acid (LCA), 12 coded chemicals were assayed. Each chemical was tested in four laboratories. For eight chemicals, all four laboratories obtained consistent results, and for two of the other four chemicals, only one of the four laboratories showed inconsistent results. Thus, the rate of consistency was high. During the study, several issues were raised, each of which were analysed step-by-step, leading to revision of the protocol of the original assay. Among these issues were the importance of careful maintenance of mother cultures and the adoption of test concentrations for toxic chemicals. In addition, it is suggested that three different types of chemicals show positive promoting activity in the assay. Those designated as T-type induced extreme growth enhancement, and included TPA, mezerein, PDD and insulin. LCA and okadaic acid belonged to the L-type category, in which transformed foci were induced at concentrations showing growth-inhibition. In contrast, M-type chemicals, progesterone, catechol and sodium saccharin, induced foci at concentrations with little or slight growth inhibition. The fact that different types of chemicals similarly induce transformed foci in the Bhas promotion assay may provide clues for elucidating mechanisms of tumour promotion.     

Reconstitution of ancestral green visual pigments of zebrafish and molecular mechanism of their spectral differentiation

We previously reported that zebrafish have four tandemly duplicated green (RH2) opsin genes (RH2-1, RH2-2, RH2-3, and RH2-4). Absorption spectra vary widely among the four photopigments reconstituted with 11-cis retinal, with their peak absorption spectra (lambda(max)) being 467, 476, 488, and 505 nm, respectively. In this study, we inferred the ancestral amino acid (aa) sequences of the zebrafish RH2 opsins by likelihood-based Bayesian statistics and reconstituted the ancestral opsins by site-directed mutagenesis. The ancestral pigment (A1) to the four zebrafish RH2 pigments and that (A3) to RH2-3 and RH2-4 showed lambda(max) at 506 nm, while that (A2) to RH2-1 and RH2-2 showed a lambda(max) at 474 nm, indicating that a spectral shift had occurred toward the shorter wavelength on the evolutionary lineages A1 to A2 by 32 nm, A2 to RH2-1 by 7 nm, and A3 to RH2-3 by 18 nm. Pigment chimeras and site-directed mutagenesis revealed a large contribution (approximately 15 nm) of glutamic acid to glutamine substitution at residue 122 (E122Q) to the A1 to A2 and A3 to RH2-3 spectral shifts. However, the remaining spectral differences appeared to result from complex interactive effects of a number of aa replacements, each of which has only a minor spectral contribution (1-3 nm). The four zebrafish RH2 pigments cover nearly an entire range of lambda(max) distribution among vertebrate RH2 pigments and provide an excellent model to study spectral tuning mechanisms of RH2 in vertebrates.     

Measurement of absolute hemoglobin concentrations of prefrontal region by near-infrared time-resolved spectroscopy: examples of experiments and prospects

Near-infrared time-resolve spectroscopy (TRS) is an emerging method which enables the absolute hemoglobin concentration in tissue to be evaluated. In the present paper, two experiments measuring the absolute hemoglobin concentrations in the prefrontal region to estimate the local cerebral activity will be demonstrated. The results of the studies were as follows: 1) There were significant differences in the absolute hemoglobin concentrations between the groups with different traits in personalities such as anxiety, or type A behavior pattern. 2) TRS was found to be applicable to field experiments. It was revealed that in a forest environment, the activity in the prefrontal region was calmer than in a city environment. This method will provide useful information on the absolute hemoglobin concentrations and contribute to making physiological polymorphisms clear.     

Comparison between TRF2 and TRF1 of their telomeric DNA-bound structures and DNA-binding activities

Mammalian telomeres consist of long tandem arrays of double-stranded telomeric TTAGGG repeats packaged by the telomeric DNA-binding proteins TRF1 and TRF2. Both contain a similar C-terminal Myb domain that mediates sequence-specific binding to telomeric DNA. In a DNA complex of TRF1, only the single Myb-like domain consisting of three helices can bind specifically to double-stranded telomeric DNA. TRF2 also binds to double-stranded telomeric DNA. Although the DNA binding mode of TRF2 is likely identical to that of TRF1, TRF2 plays an important role in the t-loop formation that protects the ends of telomeres. Here, to clarify the details of the double-stranded telomeric DNA-binding modes of TRF1 and TRF2, we determined the solution structure of the DNA-binding domain of human TRF2 bound to telomeric DNA; it consists of three helices, and like TRF1, the third helix recognizes TAGGG sequence in the major groove of DNA with the N-terminal arm locating in the minor groove. However, small but significant differences are observed; in contrast to the minor groove recognition of TRF1, in which an arginine residue recognizes the TT sequence, a lysine residue of TRF2 interacts with the TT part. We examined the telomeric DNA-binding activities of both DNA-binding domains of TRF1 and TRF2 and found that TRF1 binds more strongly than TRF2. Based on the structural differences of both domains, we created several mutants of the DNA-binding domain of TRF2 with stronger binding activities compared to the wild-type TRF2.