Learning navigational maps through potentiation and modulation of hippocampal place cells

We analyze a model of navigational map formation based on correlation-based, temporally asymmetric potentiation and depression of synapses between hippocampal place cells. We show that synaptic modification during random exploration of an environment shifts the location encoded by place cell activity in such a way that it indicates the direction from any location to a fixed target avoiding walls and other obstacles. Multiple maps to different targets can be simultaneously stored if we introduce target-dependent modulation of place cell activity. Once maps to a number of target locations in a given environment have been stored, novel maps to previously unknown target locations are automatically constructed by interpolation between existing maps.     

Differential effects of aging on directional and absolute errors in visuospatial memory.

Studied memory for visuospatial arrays in 28 male and 34 female healthy dextral adults (aged 20–90 yrs). 10 abstract figures were presented in each hemispace over a series of learning trials, and then delayed free recall of figure placement was obtained. Figures were misplaced significantly downward and leftward in both hemispaces. Both vertical and horizontal absolute error increased significanty with age, but no age effects on directional errors were observed. The increase in absolute error over age is consistent with decreased anterograde memory and visuospatial skills in the elderly. The directional errors are believed to result from an attentional shift toward proximal peripersonal space, in combination with attentional shifts from differential left vs right cerebral activation. Gender effects were also observed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

31P NMR identification of metabolites and pH determination in the cyanobacterium Synechocystis sp. PCC 6308

The identity of a number of phosphorus-containing metabolites present in Synechocystis sp. PCC 6308 has been confirmed by 31P NMR spectroscopy. The presence of D-ribulose 1,5-bisphosphate (RuBP); DL-glyceraldehyde 3-phosphate (GlyP); D(-)3-phosphoglyceric acid (3PGA); D-ribulose 5-phosphate (Ru5P);6-phosphogluconic acid (6PGA); phosphoenolpyruvate (PEP); inorganic phosphate (Pi); uridine diphosphoglucose (UDPG); ADP and ATP were demonstrated by the pH dependence of their 31P NMR chemical shifts in spectra of perchloric acid cell extracts. Intracellular pH of cells was determined to be 7.5-7.7.     

Multivariate statistical analysis of a high rate biofilm process treating kraft mill bleach plant effluent.

This study reports on a multivariate analysis of the moving bed biofilm reactor (MBBR) wastewater treatment system at a Canadian pulp mill. The modelling approach involved a data overview by principal component analysis (PCA) followed by partial least squares (PLS) modelling with the objective of explaining and predicting changes in the BOD output of the reactor. Over two years of data with 87 process measurements were used to build the models. Variables were collected from the MBBR control scheme as well as upstream in the bleach plant and in digestion. To account for process dynamics, a variable lagging approach was used for variables with significant temporal correlations. It was found that wood type pulped at the mill was a significant variable governing reactor performance. Other important variables included flow parameters, faults in the temperature or pH control of the reactor, and some potential indirect indicators of biomass activity (residual nitrogen and pH out). The most predictive model was found to have an RMSEP value of 606 kgBOD/d, representing a 14.5% average error. This was a good fit, given the measurement error of the BOD test. Overall, the statistical approach was effective in describing and predicting MBBR treatment performance.     

The Effect of Post-Cooking Holding Times on Sensory Assessment of Low- and High-Fat Beefburgers

ABSTRACT: The effect of post-cooking holding-time on sensory assessment of low (89 g/kg) and high (218 g/kg) fat beefburgers was assessed. Burgers were served to panelists approximately 3 or 18 min after cooking. Fat content influenced fattiness, moistness/juiciness and overall appearance (P < 0.05), overall acceptability and overall texture (P< 0.01) and tenderness and crumbliness (p<0.001). Burgers with the higher fat content had higher scores. Holding-time influenced sensory overall appearance only with lower scores at extended holding times (P < 0.01). Treatment differences were small, mostly less than one sensory scale unit. Higher lightness and yellowness values were found for burgers with higher fat contents.     

Evaluation of humoral immune responses in cattle grazing endophyte-infected or endophyte-free fescue

Anecdotal reports suggest cattle with fescue toxicosis may not respond to vaccination and thus, experience increased incidence of Bovine Respiratory Disease Complex (BRDC) when shipped to feedlots. Fescue toxicosis causes hypoprolactemia in cattle. Hypoprolactemia decreases humoral immune responses in mice. Therefore, a study was conducted to compare the magnitude of primary and secondary humoral immune responses against specific antigens in cattle grazing endophyte-infected or endophyte-free fescue. Angus steers were blocked by weight and allocated into four groups. Two groups grazed endophyte-infected (EI) fescue and the other two groups grazed endophyte-free (EF) fescue. All steers were injected IM on d 0 and 21 with lysozyme without adjuvant and concanavalin. A (Con A) with sheep red blood cells (SRBC) in incomplete adjuvant of Freund. Steers were bled on days 0, 21 and 35 post-vaccination. Average daily gains (ADG), alkaline phosphatase (ALP) activity, cholesterol concentrations, rectal temperatures, and serum prolactin concentrations were measured to confirm fescue toxicosis in steers grazing EI fescue. Antibodies to Con A and SRBC were determined by ELISA and hemagglutination assay, respectively. The ADG were decreased for the EI group during the first month. Rectal temperature were elevated and serum prolactin concentrations were decreased in the EI group. Cholesterol and ALP concentrations also were decreased in the EI group. Primary and secondary immune responses against Con A tended to be increased and were increased against SRBC in the EI group. Antibodies against lysozyme were not induced in either group. In conclusion, cattle grazing EI fescue mounted similar humoral immune responses to vaccination, despite hypoprolactemia, as cattle grazing EF fescue. Increases in bovine respiratory disease in cattle maintained on EI fescue probably is not associated with lack of humoral immune response to vaccination protocols as a result of fescue toxicosis.     

The Determination of the Level of Bicarbonate, Carbonate, or Carbon Dioxide in Aqueous Solutions

A rapid and convenient method for the measurement of bicarbonate, carbonate, or carbon dioxide in water was developed using fourier transform infrared spectroscopy (FTIR). Bicarbonate and carbonate are converted to carbon dioxide by lowering the pH of the solution, then the absorbance of the dissolved carbon dioxide at 2345 wavenumbers is measured using a liquid sample cell. If the measurement of dissolved carbon dioxide is the objective, the pH is not adjusted, and the carbon dioxide in the free form can be measured without interference from low levels of carbonates. The method is linear from 10.48 ppm to a minimum of 366.8 ppm carbon dioxide (r squared = 0.9996). The coefficient of variation at 10.48 ppm (LOD 3 signal/noise), 52.4 ppm, and 262 ppm is 45.6, 4.0, and 3.9, respectively. The average percent recovery at 10.48 ppm, 52.4 ppm, and 262 ppm is 74.5, 104.2, and 104.0, respectively.