Reward-dependent gain and bias of visual responses in primate superior colliculus

Eye movements are often influenced by expectation of reward. Using a memory-guided saccade task with an asymmetric reward schedule, we show that visual responses of monkey SC neurons increase when the visual stimulus indicates an upcoming reward. The increase occurred in two distinct manners: (1) reactively, as an increase in the gain of the visual response when the stimulus indicated an upcoming reward; (2) proactively, as an increase in anticipatory activity when reward was expected in the neuron's response field. These effects were observed mostly in saccade-related SC neurons in the deeper layer which would receive inputs from the cortical eye fields and the basal ganglia. These results, together with recent findings, suggest that the gain modulation may be determined by the inputs from both the cortical eye fields and the basal ganglia, whereas the anticipatory bias may be derived mainly from the basal ganglia.     

A newly identified lipoprotein lipase (LPL) gene mutation (F270L) in a Japanese patient with familial LPL deficiency

We have systematically investigated the molecular defects resulting in a primary lipoprotein lipase (LPL) deficiency in a Japanese male infant (proband SH) with fasting hyperchylomicronemia. Neither LPL activity nor immunoreactive LPL mass was detected in pre- or postheparin plasma from proband SH. DNA sequence analysis of the LPL gene of proband SH revealed homozygosity for a novel missense mutation of F270L (Phe(270)-->Leu/TTT(1065)-->TTG) in exon 6. The function of the mutant F270L LPL was determined by both biochemical and immunocytochemical studies. In vitro expression experiments on the mutant F270L LPL cDNA in COS-1 cells demonstrated that the mutant LPL protein was synthesized as a catalytically inactive form and its total amount was almost equal to that of the normal LPL. Moreover, the synthesized mutant LPL was non-releasable by heparin because the intracellular transport of the mutant LPL to the cell surface - by which normal LPL becomes heparin-releasable - was impaired due to the abnormal structure of the mutant LPL protein. These findings explain the failure to detect LPL activities and masses in pre- and postheparin plasma of the proband. The mutant F270L allele generated an XcmI restriction enzyme site in exon 6 of the LPL gene. The carrier status of F270L in the proband's family members was examined by digestion with XcmI. The proband was ascertained to be homozygous for the F270L mutation and his parents and sister were all heterozygous. The LPL activities and masses of the parents and the sister (carriers) were half or less than half of the control values. Regarding the phenotype of the carriers, the mother with a sign of hyperinsulinemia manifested hypertriglyceridemia (type IV hyperlipoproteinemia), whereas the healthy father and the sister were normolipidemic. Hyperinsulinemia may be a strong determinant of hypertriglyceridemia in subjects with heterozygous LPL deficiency.     

The yeast Tor signaling pathway is involved in G2/M transition via polo-kinase

The target of rapamycin (Tor) protein plays central roles in cell growth. Rapamycin inhibits cell growth and promotes cell cycle arrest at G1 (G0). However, little is known about whether Tor is involved in other stages of the cell division cycle. Here we report that the rapamycin-sensitive Tor complex 1 (TORC1) is involved in G2/M transition in S. cerevisiae. Strains carrying a temperature-sensitive allele of KOG1 (kog1-105) encoding an essential component of TORC1, as well as yeast cell treated with rapamycin show mitotic delay with prolonged G2. Overexpression of Cdc5, the yeast polo-like kinase, rescues the growth defect of kog1-105, and in turn, Cdc5 activity is attenuated in kog1-105 cells. The TORC1-Type2A phosphatase pathway mediates nucleocytoplasmic transport of Cdc5, which is prerequisite for its proper localization and function. The C-terminal polo-box domain of Cdc5 has an inhibitory role in nuclear translocation. Taken together, our results indicate a novel function of Tor in the regulation of cell cycle and proliferation.     

Chemical identity of tryptensin with angiotensin.

Tryptensin, a vasopressor substance generated from human plasma protein fraction IV-4 by trypsin, has been isolated and the amino acid composition analysed. The procedures used for the isolation were: (a) adsorption of the formed tryptensin on Dowex 50W (X2; NH4+ form); (b) gel filtration through Sephadex G-25; (c) cation-exchange chromatography on CM-cellulose; (d) anion-exchange chromatography on DEAE-cellulose; (e) re-chromatography on CM-cellulose; (f) gel filtration on Bio-Gel P-2; (g) partition chromatography on high-pressure liquid chromatography. The homogeneity of the isolated tryptensin was confirmed by thin-layer chromatography and thin-layer electrophoresis. The amino acid analysis of the hydrolysate suggested the following proportional composition: Asp, 1; Val, 1; Ile, 1; Tyr, 1; Phe, 1; His, 1; Arg, 1; Pro, 1. This composition is identical with that of human angiotensin.     

FTIR study of the L intermediate of Anabaena sensory rhodopsin: structural changes in the cytoplasmic region

Anabaena sensory rhodopsin (ASR) is an archaeal-type rhodopsin found in eubacteria. The gene encoding ASR forms a single operon with ASRT (ASR transducer) that is a 14 kDa soluble protein, suggesting that ASR functions as a photochromic sensor by activating the soluble transducer. One of the characteristics of ASR is that the formation of the M intermediate accompanies a proton transfer from the Schiff base to Asp217 in the cytoplasmic side [Shi, L., Yoon, S. R., Bezerra, A. G., Jr., Jung, K. H., and Brown, L. S. (2006) J. Mol. Biol. 358, 686-700], in remarkable contrast to other archaeal-type rhodopsins such as a light-driven proton-pump, bacteriorhodopsin (BR). In this study, we applied low-temperature Fourier transform infrared (FTIR) spectroscopy to the all- trans form of ASR at 170 K, and compared the structural changes in the L intermediate with those of BR. The ASR L minus ASR difference spectra were essentially similar to those for BR, suggesting common structures for the L state in ASR and BR. On the other hand, unique CO stretching bands of a protonated carboxylic acid were observed at 1722 (+) and 1703 (-) cm (-1) at pH 5 and 7, and assigned to Glu36 by use of mutants. Glu36 is located at the cytoplasmic side, and the distance from the Schiff base is about 20 A. This result shows the structural changes at the cytoplasmic surface in ASR L. pH-dependent frequency change was also observed for a water stretching vibration, suggesting that the water molecule is involved in a hydrogen-bonding network with Glu36 and Asp217. Unique hydrogen-bonding network in the cytoplasmic domain of ASR will be discussed.     

Sulfite induces adherence of polymorphonuclear neutrophils to immobilized fibrinogen through activation of Mac-1 beta2-integrin (CD11b/CD18)

Sulfite is a major air pollutant which can cause respiratory tract inflammation characterized by an influx of polymorphonuclear neutrophils (PMN). We have previously shown that human PMN can produce sulfite either spontaneously or in response to stimulation with lipopolysaccharide. We now demonstrate that sulfite activates PMN to adhere to immobilized fibrinogen via the beta2-integrin Mac-1 (CD11b/CD18). Mac-1 expression is not altered by treatment with this agent. Although unaffected by pertussis toxin, sulfite-triggered PMN adhesion was abrogated by pretreating cells with the membrane-impermeant sulfhydryl reagent 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB), a modifier of thiol groups on the cell surface. These results suggest that sulfite-induced PMN adhesion is dependent on a modification of thiols at the cell surface. Given its potent antioxidant and antimicrobial activities, sulfite may act as an endogenous mediator in host defense and/or inflammation.     

Synthesis and crystal structures of water-soluble rhodium(III) complexes with 1,4,7-triazacyclononane and 2,2-bipyridine supporting ligands

New water-soluble rhodium(III) complexes with a tacn (1,4,7-triazacyclononane) and a bpy (2,2^′-bipyridine) supporting ligands were synthesized. The reaction of [Rh^III(tacn)Cl₃] (1) with equimolar amount of bpy and two equivalents of AgNO₃ in H₂O at reflux for 10 h gave a water-soluble chloro complex [Rh^III(tacn)(bpy)Cl](NO₃)₂ {2(NO₃)₂}. Complex 2(NO₃)₂ was treated with equimolar amount of AgNO₃ in H₂O at reflux for 10 h to give a water-soluble nitrato complex [Rh^III(tacn)(bpy)(NO₃)](NO₃)₂ {3(NO₃)₂}. Water-solubility of 3 with NO₃ ⁻ ligand (46.5 mg/mL) is high compared with that of 2 with Cl⁻ ligand (14.5 mg/mL) under the same conditions (at pH 7.0 at 25 °C). The structures of 2 and 3 were unequivocally determined by X-ray analysis. Their structures in H₂O were also examined by ¹H NMR, IR, and electrospray ionization mass spectrometry (ESI-MS).     

Identification and isolation of anaerobic, syntrophic phthalate isomer-degrading microbes from methanogenic sludges treating wastewater from terephthalate manufacturing

The microbial populations responsible for anaerobic degradation of phthalate isomers were investigated by enrichment and isolation of those microbes from anaerobic sludge treating wastewater from the manufacturing of terephthalic acid. Primary enrichments were made with each of three phthalate isomers (ortho-, iso-, and terephthalate) as the sole energy source at 37 degrees C with two sources of anaerobic sludge (both had been used to treat wastewater containing high concentrations of phthalate isomers) as the inoculum. Six methanogenic enrichment cultures were obtained which not only degraded the isomer used for the enrichment but also had the potential to degrade part of other phthalate isomers as well as benzoate with concomitant production of methane, presumably involving strictly syntrophic substrate degradation. Our 16S rRNA gene-cloning analysis combined with fluorescence in situ hybridization revealed that the predominant bacteria in the enrichment cultures were affiliated with a recently recognized non-sulfate-reducing subcluster (subcluster Ih) in the group 'Desulfotomaculum lineage I' or a clone cluster (group TA) in the class delta-PROTEOBACTERIA: Several attempts were made to isolate these microbes, resulting in the isolation of a terephthalate-degrading bacterium, designated strain JT, in pure culture. A coculture of the strain with the hydrogenotrophic methanogen Methanospirillum hungatei converted terephthalate to acetate and methane within 3 months of incubation, whereas strain JT could not degrade terephthalate in pure culture. During the degradation of terephthalate, a small amount of benzoate was transiently accumulated as an intermediate, indicative of decarboxylation of terephthalate to benzoate as the initial step of the degradation. 16S rRNA gene sequence analysis revealed that the strain was a member of subcluster Ih of the group 'Desulfotomaculum lineage I', but it was only distantly related to other known species.