Cloning and characterization of the Salmonella typhimurium-specific chemoreceptor Tcp for taxis to citrate and from phenol

Salmonella typhimurium shows an attractant response to citrate and a repellent response to phenol, and a chemoreceptor mediating these responses has been identified and named Tcp (taxis to citrate and away from phenol). Tcp is one of the methyl-accepting chemotaxis proteins that have a molecular mass of approximately 60 kDa estimated by SDS/PAGE, and its methylation level is increased by citrate and decreased by phenol. Tcp also mediates an attractant response to metal-citrate complexes. The complete nucleotide sequence of the tcp coding region has been determined. The deduced amino acid sequence of Tcp, consisting of 547-amino acid residues, is homologous with that of the aspartate chemoreceptor of S. typhimurium. Thus, Tcp is another member of the bacterial transmembrane chemoreceptor family. Because citrate is a good carbon source for S. typhimurium but is not a carbon source for the closely related species Escherichia coli and because citrate utilization is used as a key diagnostic character to distinguish these species, it is reasonable to assume that Tcp is specific to S. typhimurium.     

Permeability change and brain tissue damage after intracarotid administration of cisplatin studied by double-tracer autoradiography in rats

The present study was designed to find the reliable parameter(s) for the detection of early neurotoxicity following intracarotid (IC) administration of cisplatin. IC administration was performed for 60 minutes in female Wistar rats derived into four groups according to the dose given (1 mg, 1.2 mg, and 1.5 mg of cisplatin, and normal saline in control rats). Blood-brain barrier (BBB) permeability and local cerebral blood flow (LCBF) were measured by a double-tracer autoradiography technique using 1-[14C]-alpha-aminoisobutyric acid (14C-AIB) and 4-[18F] fluoroantipyrine (18F-FAP), respectively. Blood chemistry and neuropathology were also examined. BBB permeability was increased only on the ipsilateral side. This increase was dose-dependent, preceded the brain necrosis, and was statistically significant in the hypothalamus (1.2 mg group), auditory cortex and caudoputamen (1.5 mg group). Renal dysfunction was often observed. The changes in the LCBF did not occur until brain necrosis was noticeable. These findings demonstrate that the increase in the BBB permeability provides a sensitive and reliable indication of an early toxicity to brain tissue following IC administration of cisplatin.     

Dependence of differential quantum efficiency on the confinementstructure in InGaAs/InGaAsP strained-layer multiple quantum-well lasers

An internal efficiency of 91% was obtained with In_0.7Ga _0.3As/InGaAsP strained-layer multiple quantum well (MQW) lasers emitting at a wavelength of 1.5 μm. The dependence of the reciprocal differential quantum efficiency on the length of the laser cavity shows that the absorption loss in the InGaAsP (λ=1.3 μm) confinement layer caused by carrier overflowing into the confinement layer reduces the internal efficiency     

Preparation of Crystalline Lisb(OH)6 Powders Prepared by Chemical Bath Deposition and Its Thermal Decomposition Process

Well-crystallized LiSb(OH)₆ powders with a hexagonal structure were prepared by chemical bath deposition. The thermal decomposition of as-prepared samples was examined. In order to obtain LiSb(OH)₆ powders, it was essential to use tartaric acid as a stabilizing agent for antimony ion and to add LiOH above pH 9 into the precursor solution. The crystal structure of the samples obtained was of hexagonal phase. The increase in pH value and keeping temperature indicated that the shape of samples changed from granule particles to plate-like particles. The granule particles heated at 800°C consisted of orthorhombic LiSbO₃. However, the plate-like particles resulted in the coexistence of both orthorhombic LiSbO₃ and tetragonal Li₃SbO₄     

Effect of uncertainties in agricultural working schedules and Monte-Carlo evaluation of the model input in basin-scale runoff model analysis of herbicides.

In the prediction of time-series concentrations of herbicides in river water with diffuse-pollution hydrological models, farming schedules (the dates of herbicide application and drainage of irrigation water from rice paddies) greatly affect the runoff behavior of the herbicides. For large catchments, obtaining precise data on farming schedules is impractical, and so the model input inevitably includes substantial uncertainty. This paper evaluates the effectiveness of using the Monte-Carlo method to generate sets of estimated farming schedules to use as input to a GIS-based basin-scale runoff model to predict the concentrations of paddy-farming herbicides in river water. The effects of using the Monte-Carlo method to compensate for uncertainty in the evaluated parameters for herbicide decomposition and sorption were also evaluated.     

A coding theorem for lossy data compression by LDPC codes

In this article, low-density parity-check (LDPC) codes are applied to lossy source coding and we study how the asymptotic performance of MacKay's (see ibid, vol.45, p.399-431, Mar. 1999 and vol.47, p.2101, July, 2001) LDPC codes depends on the sparsity of the parity-check matrices in the source coding of the binary independent and identically distributed (i.i.d.) source with Pr{x=1}=0.5. In the sequel, it is shown that an LDPC code with column weight O(logn) for code length n can attain the rate-distortion function asymptotically.     

A method of evaluating VDT screen layout by eye movement analysis.

The method for evaluating VDT screen layout by eye movements is studied. When the subjects read from the VDT screen, the change in their line of sight was measured by their eye movements. The measured eye movement patterns were divided into the sequential and rereading processes. When related to these characteristics, the performance of subjects was found to be good when the sequential process predominated over the rereading process. The eye movement pattern was shown to change with screen layout. The eye movement pattern proved effective in determining that tabular format is more legible than textual format. This confirmed the usefulness of the method of evaluating VDT screen layout by the eye movement pattern.     

Design, synthesis and quantitative structure-activity relationship study of N-(3-oxo-3,4-dihydro-2H-benzo[1,4]oxazine-7-carbonyl)guanidine derivatives as potent Na/H exchange inhibitors

Recent results indicate that a fluoroalumino complex (AlFx) is probably the molecule responsible for the mitogenic effect of fluoride in MC3T3-E1 osteoblast-like cells. Initial analysis suggested that a tyrosine phosphorylation (tyr phos) process similar to that induced by thrombin and activation of the p42 MAP kinase (ERK 2) mediate this cellular response. In the present study, the signaling mechanism activated by AlFx was further investigated. The results indicated that AlFx dose-dependently enhanced the tyr phos of the cell adhesion proteins FAK and paxillin, as well as of the adaptor molecules p46shc, p52shc, and p66shc and their association with GRB2. Pretreatment of MC3T3-E1 cells with cytochalasin D completely prevented FAK and paxillin tyr phos without any alteration in the tyr phos of Shc proteins and activation of ERK2 induced by AlFx. This observation suggests that in confluent MC3T3-E1 cells, there is no link between the activation of FAK induced by AlFx and the stimulation of ERK2. Pretreatment of the cells with pertussis toxin inhibited Shc phosphorylation, activation of ERK2, and markedly reduced cell replication induced by AlFx. This toxin also significantly reduced the stimulation of Pi transport activity induced by AlFx in these cells. Alteration in tyr phos induced by AlFx was not associated with any detectable inhibition of tyrosine phosphatase activity in MC3T3-E1 cell homogenates, suggesting that enhanced tyr phos induced by AlFx probably resulted from activation of a tyrosine kinase. In conclusion, the results of this study suggest that the mitogenic effect of fluoride in MC3T3-E1 osteoblast-like cells is mediated by the activation of a pertussis toxin-sensitive Gi/o protein and suggest an important role for these heterotrimeric G proteins in controlling the growth and differentiation of bone-forming cells.