Spinal reciprocal inhibition in human locomotion.

The purpose of this paper was to study spinal inhibition during several different motor tasks in healthy human subjects. The short-latency, reciprocal inhibitory pathways from the common peroneal (CP) nerve to the soleus muscle and from the tibial nerve to the tibialis anterior muscle were studied as a depression of ongoing voluntary electromyograph (EMG) activity. First, the effect of stimulus intensity on the amount of inhibition was examined to decide an appropriate stimulation to study the task-dependent modulation of inhibition. Then, the inhibition at one level of stimulation (1.5 x motor threshold) was investigated during standing, walking, and running. The change in slope of inhibition vs. EMG level, which approximates the fraction of ongoing activity that is inhibited, decreased with CP stimulation from 0.52 during standing to 0.30 during fast walking (6 km/h) to 0.17 during running at 9 km/h. Similarly, the slope decreased with tibial nerve stimulation from 0.68 (standing) to 0.42 (fast walking) to 0.35 (running at 9 km/h). All differences, except the last one, were highly significant (P < 0.01, Student's t-test). However, the difference between walking (0.42) and running (0.36) at the same speed (6 km/h) was not significant with tibial nerve stimulation and only significant at P < 0.05 with CP nerve stimulation (0.30, 0.20). Also, the difference between standing (0.52) and slow walking (3 km/h; 0.41) with CP stimulation was not significant, but it was significant (P < 0.01) with tibial nerve stimulation (0.68, 0.49). In conclusion, our findings indicate that spinal reciprocal inhibition decreases substantially with increasing speed and only changes to a lesser extent with task.     

Identification of the protocatechuate transporter gene in Sphingobium sp. strain SYK-6 and effects of overexpression on production of a value-added metabolite

Applied Microbiology and Biotechnology - Sphingobium sp. strain SYK-6 expresses the best characterized catabolic systems for lignin-derived aromatic compounds. However, the uptake systems for these...     

Genetic architecture underlying the evolutionary change of competitive ability in Asian cultivated and wild rice

Breeding of competitive cultivars has long been fraught with difficulty owing to limited knowledge of the genetic basis of competitive ability. In this study, we examined the diversity of competitive ability in Asian rice and the genetic basis of this variation. Cultivated strains and wild perennial strains have higher competitive ability than wild annual strains. Quantitative trait locus (QTL) analysis of competitive ability for three weed species was conducted in the cross between cultivated and wild annual strains, and three QTLs for general competitive ability (GCA) were identified. GCA-QTLs conferred higher competitive ability by the cultivated rice alleles and were co-located with QTLs for plant architecture and root growth, detected in the same mapping population. Furthermore, a significant change in GCA was achieved by accumulation and epistatic interaction of three QTLs. Further studies on the genetic control of competitive ability would facilitate the breeding of competitive cultivars in rice.     

Strikingly different effects of cholesterol and 7-ketocholesterol on lipid bilayer-mediated aggregation of amyloid beta (1-42)

Oxidized cholesterol has been widely reported to contribute to the pathogenesis of Alzheimer's disease (AD). However, the mechanism by which they affect the disease is not fully understood. Herein, we aimed to investigate the effect of 7-ketocholesterol (7keto) on membrane-mediated aggregation of amyloid beta (Aβ-42), one of the critical pathogenic events in AD. We have shown that when cholesterol is present in lipid vesicles, kinetics of Aβ nuclei formation is moderately hindered while that of fibril growth was considerably accelerated. The partial substitution of cholesterol with 7keto slightly enhanced the formation of Aβ-42 nuclei and remarkably decreased fibril elongation, thus maintaining the peptide in protofibrillar aggregates, which are reportedly the most toxic species. These findings add in understanding of how cholesterol and its oxidation can affect Aβ-induced cytotoxicity.     

Effects of pre- and pro-sequence of thaumatin on the secretion by Pichia pastoris

Thaumatin is a 22-kDa sweet-tasting protein containing eight disulfide bonds. When thaumatin is expressed in Pichia pastoris using the thaumatin cDNA fused with both the alpha-factor signal sequence and the Kex2 protease cleavage site from Saccharomyces cerevisiae, the N-terminal sequence of the secreted thaumatin molecule is not processed correctly. To examine the role of the thaumatin cDNA-encoded N-terminal pre-sequence and C-terminal pro-sequence on the processing of thaumatin and efficiency of thaumatin production in P. pastoris, four expression plasmids with different pre-sequence and pro-sequence were constructed and transformed into P. pastoris. The transformants containing pre-thaumatin gene that has the native plant signal, secreted thaumatin molecules in the medium. The N-terminal amino acid sequence of the secreted thaumatin molecule was processed correctly. The production yield of thaumatin was not affected by the C-terminal pro-sequence, and the pro-sequence was not processed in P. pastoris, indicating that pro-sequence is not necessary for thaumatin synthesis.     

Identification and characterization of integrin-binding sialoprotein (IBSP) genes in reptile and amphibian

Integrin-binding sialoprotein (IBSP) is a member of the small integrin-binding ligand N-linked glycoprotein (SIBLING) family; and the whole SIBLING family is further included in a larger secretory calcium-binding phosphoprotein (SCPP) family. SIBLING proteins are known to construct a part of the non-collagenous extracellular matrices of calcified tissues, and considered to have arisen by duplication and subsequent divergent evolution of a single ancient gene. To understand the alterations of SIBLING molecules associated with the evolution of calcified tissues in vertebrates, we initiated a search for lower vertebrate orthologs of SIBLING genes. In the present study, an IBSP ortholog from a reptile (caiman) and two distinct orthologs from an amphibian (African clawed toad) were identified and characterized. As expected, the toad IBSP genes were transcribed only in calcified tissue (jaw and tibia), as also seen in mammals. The caiman, toad, avian, and mammalian IBSPs share several unique features specific for IBSP and apparently have similar properties. Furthermore, analysis of the sequences suggested that the IBSP molecule might have gradually intensified its functions related to calcification during its evolutionary process through tetrapods.     

Cleavage of a model DNA replication fork by a Type I restriction endonuclease

Cleavage of a DNA replication fork leads to fork restoration by recombination repair. In prokaryote cells carrying restriction–modification systems, fork passage reduces genome methylation by the modification enzyme and exposes the chromosome to attack by the restriction enzyme. Various observations have suggested a relationship between the fork and Type I restriction enzymes, which cleave DNA at a distance from a recognition sequence. Here, we demonstrate that a Type I restriction enzyme preparation cleaves a model replication fork at its branch. The enzyme probably tracks along the DNA from an unmethylated recognition site on the daughter DNA and cuts the fork upon encountering the branch point. Our finding suggests that these restriction–modification systems contribute to genome maintenance through cell death and indicates that DNA replication fork cleavage represents a critical point in genome maintenance to choose between the restoration pathway and the destruction pathway.     

Inhibition of hepatic damage and liver fibrosis by brain natriuretic peptide

Anti-fibrotic and organ protective effects of brain natriuretic peptide (BNP) have been reported. In this study, effects of BNP on liver fibrosis were examined in the carbon tetrachloride (CCl₄)-induced liver fibrosis model using BNP-transgenic (Tg) and wild-type (WT) mice. Twice-a-week intraperitoneal injections of CCl₄ for 8 weeks resulted in massive liver fibrosis, augmented transforming growth factor (TGF)-β₁ and type I procollagen α₁ chain (Col1a1) mRNA expression, and the hepatic stellate cell (HSC) activation in WT mice, all of which were significantly suppressed in Tg mice. These observations indicate that BNP inhibits liver fibrosis by attenuating the activation of HSCs.     

Crystal structure of the sweet-tasting protein thaumatin II at 1.27 Å

Thaumatin, an intensely sweet-tasting protein, elicits a sweet taste sensation at 50 nM. Here the X-ray crystallographic structure of one of its variants, thaumatin II, was determined at a resolution of 1.27 Å. Overall structure of thaumatin II is similar to thaumatin I, but a slight shift of the Cα atom of G96 in thaumatin II was observed. Furthermore, the side chain of residue 67 in thaumatin II is highly disordered. Since residue 67 is one of two residues critical to the sweetness of thaumatin, the present results suggested that the critical positive charges at positions 67 and 82 are disordered and the flexibility and fluctuation of these side chains would be suitable for interaction of thaumatin molecules with sweet receptors.     

Differentiation in wild-type allele of the sd1 locus concerning culm length between indica and japonica subspecies of Oryza sativa (rice)

A dwarfing gene (allele) sd1-d has been intensively utilized to develop short-culm indica varieties in southeast Asia up to now. Before the first sd1-d-carrying variety IR8 was released, rice researchers had recognized the general tendency that culm length is higher in indica varieties than in temperate-japonica ones. Inter-subspecific difference of the tall (wild-type) allele SD1 at the sd1 locus was examined on the common genetic background, using five isogenic lines developed by substituting sd1-d of the recurrent parent IR36 by SD1s of two indica varieties, two temperate-japonica varieties and one tropical-japonica variety. The two indica -donor isogenic lines had longer culms than the three japonica-donor isogenic lines consistently in two different environmental conditions. Moreover, nonsynonymous single-nucleotide polymorphism between the two subspecies was detected at two sites in Exon 1 and Exon 3 of the sd1 locus. It is demonstrated that the inter-subspecific differentiation of SD1 contributes height difference between indica and japonica. The indica-originating and japonica-originating alleles at the sd1 locus were designated as SD1-in(t) and SD1-ja(t), respectively.