A model for feature linking via collective oscillations in the primary visual cortex

A neural network model for explaining experimentally observed neuronal responses in cat primary visual cortex is proposed. In our model, the basic functional unit is an orientation column which is represented by a large homogeneous population of neurons modeled as integrate-and-fire type excitable elements. The orientation column exhibits spontaneous collective oscillations in activity in response to suitable visual stimuli. Such oscillations are caused by mutual synchronization among the neurons within the column. Numerical simulation for various stimulus patterns shows that as a result of activity correlations between different columns, the amplitude and the phase of the oscillation in each column depend strongly on the global feature of the stimulus pattern. These results satisfactorily account for experimental observations.     

Microscopical Investigation of the Efifect of Helminthosporol on Rice Seedlings

The elongation of the second leaf sheaths of rice seedlings was promoted strongly by helminthosporol as well as by gibberellic acid. A greater dosage of helminthosporol was required in order to induce the same amount of elongation. Cells of treated plants were somewhat longer than those of controls. The elongation of the second leaf sheath was caused mainly by an increase in cell number. Both helminthosporol and gibberellic acid promoted the elongation of cells in the basal portion of the second leaf sheath.     

Genetic exchange between two freshwater apple snails, Pomacea canaliculata and Pomacea maculata invading East and Southeast Asia

Two species of apple snails, Pomacea canaliculata and Pomacea maculata (formerly Pomacea insularum), have invaded many countries of East and Southeast Asia from their native range in South America. This study investigated the genetic structure of the two species invading these areas. Phylogenetic analysis based on sequences of the nuclear gene elongation factor 1-alpha (EF1α) detected two well-supported clades (Clade C and Clade M). Both P. canaliculata and P. maculata were represented in each clade. Some snails had both Clade C and Clade M EF1α sequences. These results suggest genetic exchange between snails of the two clades. A mating experiment between P. canaliculata with Clade C EF1α sequences and P. maculata with Clade M EF1α sequences resulted in viable F1 progeny under laboratory conditions. The genetic exchange was also inferred in some populations collected from Argentina, suggesting an existence of hybrid in the native range. Simple identification of EF1α types using a restriction enzyme, ApaLI, detected significant geographical structure of the EF1α variants in the invaded area. The divergent geographical structure could have resulted from either the founder effect or the bridgehead effect, although further genetic analysis is needed to clarify this. Average individual egg weight, which is an indicator of egg size, was higher in P. canaliculata than P. maculata in both field and laboratory reared samples, suggesting that some (probably most) P. canaliculata and P. maculata invading East and Southeast Asia still maintain species-specific populations.     

Enhancing cellulase production by overexpression of xylanase regulator protein gene,xlnR, in Talaromyces cellulolyticus cellulase hyperproducing mutant strain

We obtained strains with the xylanase regulator gene, xlnR, overexpressed (HXlnR) and disrupted (DXlnR) derived from Talaromyces cellulolyticus strain C-1, which is a cellulase hyperproducing mutant. Filter paper degrading enzyme activity and cellobiohydrolase I gene expression was the highest in HXlnR, followed by C-1 and DXlnR. These results indicate that the enhancement of cellulase productivity was succeeded by xlnR overexpression.     

Characterization and preliminary crystallographic studies of EMS16, an antagonist of collagen receptor (GPIa/IIa) from the venom of Echis multisquamatus

EMS16 is a member of the snake venom-derived C-type lectin family of proteins (CLPs) found in the venom of Echis multisquamatus. It binds to glycoprotein Ia/IIa (integrin alpha2beta1), a major collagen receptor of platelets, acting as a potent antagonist of platelet aggregation and cell migration. Amino acid sequencing and cDNA cloning of EMS16 have revealed that it is composed of an A chain of 134 amino acid residues and a B chain of 128 residues. Crystals of EMS16 belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 46.57, b = 59.93, and c = 115.74 A, and diffract to a resolution of 1.9 A. Phase determination is underway by means of molecular replacement with the structure of blood coagulation factor IX-binding protein (IX-bp) from habu snake venom (PDB code 1bj3) as the search model.     

A novel species of alkaliphilic Bacillus that produces an oxidatively stable alkaline serine protease

A novel gram-positive, strictly aerobic, motile, sporulating, and facultatively alkaliphilic bacterium designated KSM-KP43 was isolated from a sample of soil. The results of 16S rRNA sequence analysis placed this bacterium in a cluster with Bacillus halmapalus. However, the level of the DNA-DNA hybridization of KSM-KP43 with B. halmapalus was less than 25%. Moreover, the G + C contents of the genomic DNA were 41.6 mol% for KSM-KP43 and 38.6 mol% for B. halmapalus. Because there were also differences in physiological properties and cellular fatty acid composition between the two organisms, we propose KSM-KP43 as a novel species of alkaliphilic Bacillus. This novel strain produces a new class of protease, an oxidatively stable serine protease that is suitable for use in bleach-based detergents. The enzyme contained 640 amino acid residues, including a possible approximately 200-amino-acid prepropeptide in the N-terminal and a unique stretch of approximately 160 amino acids in the C-terminal regions (434-amino-acid mature enzyme with a calculated molecular mass of 45,301 Da). The C-terminal half after the putative catalytic Ser255 and the contiguous C-terminal extension shared local similarity to internal segments of a membrane-associated serine protease of a marine microbial assemblage and the serine protease/ABC transporter precursors of the slime mold Dictyostelium discoideum, and to the C-terminal half of a cold-active alkaline serine protease of a psychrotrophic Shewanella strain.     

Enzymatic hydrolysis of waste office paper using viscosity as operating parameter

Enzymatic hydrolysis of waste office (WO) paper with feeding WO paper in a reactor was investigated using apparent viscosity as operating parameter. Since the apparent viscosity was correlated with the concentration of pulping WO paper, the amount of hydrolyzed WO paper was assumed by measuring the decrease in the apparent viscosity. Then the amount of hydrolysis WO paper and the amount of enzyme corresponding to the desired ratio were fed into the reactor. When the WO paper and 1% (to the amount of WO paper) enzyme were fed to the hydrolytic reaction, 87 g/L of reducing sugar (RS) with a hydrolytic yield of 42.2% was obtained for a 24-h hydrolysis. However, when nonpulping WO paper and 5% (to the amount of WO paper) enzyme were fed to the hydrolytic reaction, 120 g/L of RS with a hydrolytic yield of 40% was obtained for a 24-h hydrolysis. Therefore, the RS concentration from this hydrolysis process feeding WO paper using apparent viscosity as operating parameter may be of sufficient concentration to serve as a carbon source in microorganism culture or chemical feedstock.     

Molecular cloning and sequence analysis of cDNA encoding human ferrochelatase

The cDNA encoding human ferrochelatase [EC 4.99.1.1] was isolated from a human placenta cDNA library in bacteriophage lambda gt11 by screening with a radiolabeled fragment of mouse ferrochelatase cDNA. The cDNA had an open reading frame of 1269 base pairs (bp) encoding a protein of 423 amino acid residues (Mr. 47,833) with alternative putative polyadenylation signals in the 3' non-coding regions and poly (A) tails. Amino acid sequencing showed that the mature protein consists of 369 amino acid residues (Mr. 42,158) with a putative leader sequence of 54 amino acid residues. The human enzyme showed an 88% identity to mouse enzyme and 46% to yeast enzyme. Northern blot analysis showed two mRNAs of about 2500 and 1600 bp for ferrochelatase in K562 and HepG2 cells. As full-length cDNA for human ferrochelatase is now available, molecular lesions related to erythropoietic protoporphyria can be characterized.