Effects of haloperidol and d-amphetamine on working and reference memory performance in a spatial cone field task

The present study was designed to examine the effects of haloperidol (0.03, 0.1 mg/kg, intraperitoneal (i.p.)) and d-amphetamine (0.3, 1.0 mg/kg, i.p.) in a cone field task in which spatial working and reference memory (WM and RM, respectively) were assessed simultaneously. The apparatus is a large open field in which 16 cones are placed with four cones baited by placing a food reward in the top. After food-deprived rats had acquired this task they showed a high level of performance, that is avoided visits to non-baited cones (RM) and made few revisits to baited cones (WM). Haloperidol had a greater negative effect on RM than on WM performance, but also decreased the number of food rewards collected. On the other hand, the high dose of d-amphetamine induced a clear WM performance deficit, whereas RM performance was only marginally affected. The present study suggests that spatial discrimination performance can be dissociated using the measures RM and WM in the present task. Further, the deficits induced by haloperidol and d-amphetamine may not be specifically related with impaired mnemonic functions.     

Periparturient dairy cows do not exhibit hepatic insulin resistance,yet adipose-specific insulin resistance occurs in cows prone to high weight loss

The periparturient period in dairy cows is associated with alterations in insulin action in peripheral tissues; however, the molecular mechanism underlying this process is not completely understood. The objective was to examine the response to a glucose tolerance test (GTT) and to analyze insulin signaling in liver and adipose tissues in pre- and postpartum dairy cows. Liver and adipose tissue biopsies were taken before and after GTT, at 17 d prepartum and again at 3 to 5 d postpartum from 8 high-yielding Israeli Holstein dairy cows. Glucose clearance rate after GTT was similar pre- and postpartum. Basal insulin concentrations and the insulin response to GTT were approximately 4-fold higher prepartum than postpartum. In accordance, phosphorylation of the hepatic insulin receptor after GTT was higher prepartum than postpartum. Across periods, a positive correlation was observed between the basal and peak plasma insulin and phosphorylated insulin receptor after GTT in the liver. Hepatic phosphorylation of protein kinase B after GTT was elevated pre- and postpartum. Conversely, in adipose tissue, phosphorylation of protein kinase B after GTT pre- and postpartum was increased only in 4 out of 8 cows that lost less body weight postpartum. Our results demonstrate that hepatic insulin signaling is regulated by plasma insulin concentrations as part of the homeorhetic adjustments toward calving, and do not support a model of hepatic insulin resistance in periparturient cows. Nevertheless, we suggest that specific insulin resistance in adipose tissue occurs pre- and postpartum only in cows prone to high weight loss. The different responses among these cows imply that genetic background may affect insulin responsiveness in adipose tissue pre- and postpartum.     

Processing soybeans into foods: Selected aspects of nutrition and flavor

Since many new soy protein products are being developed which differ in enzyme activity, protein dispersibility, flavor, nutritive value, and functional properties, quality control is assuming increasing significance. The effects of dry and moist heat and hexane:ethanol azeotrope extraction upon various enzymatic activities, protein solubility, and nutritive value of defatted soy flakes differ considerably. Specifications and guidelines initially developed to establish the degree of moist heat treatment required to produce edible grade products need to be reevaluated for these processes. Flavor scores of hexane:ethanol azeotrope-extracted flakes and proteinates prepared from them are significantly higher than those prepared by current commercial practices. Because peroxidase is a much more stable enzyme than lipoxygenase, determination of peroxidase activity may be a more suitable method to define proper processing conditions which improve the flavor of soy products. A combination of hexane:ethanol extraction and steaming improves the flavor and nutritive value of defatted soy flakes. Azeotrope extraction alone does not inactivate trypsin inhibitors; nutritive value of the extracted flakes is low, and pancreatic hypertrophy occurs when they are fed to rats. Protein efficiency ratio of the processed flakes is 2.2 on a basis of a value = 2.5 for casein. Other factors to be considered to prepare soy protein isolates of good nutritional quality are: choline deficiency, variability in sulfur amino acid content, and formation of phytate complexes that affect bioavailability of essential minerals, particularly zinc.     

Preparation and Characterization of Copolymers of Modified Starches and Polyacrylonitrile

Starch graft polyacrylonitrile (S-g-PAN) copolymers were prepared from a commercial unmodified cornstarch and from three chemically modified commercial cornstarch products including Amaizo 395 (highly acid modified, HAM), Amaizo 590 (highly hypochlorite oxidized, HHO) and Amaizo 791D (hydroxyethyl, highly acid modified, HEHAM). Using similar reaction conditions and ratio of monomer to starch (1:1), the percentages of PAN in the copolymers ranged from 39% for the unmodified starch to 48% for the modified starches. Only 5% of the PAN of the copolymer prepared from unmodified starch could be extracted by dimethylformamide (DMF) treatments compared to 22–28% for copolymers prepared from the modified starches. However, copolymers from the modified starches apparently contained relatively high proportions of low-molecular-weight copolymer along with homopolymer. Acid hydrolysis treatment of the DMF insoluble and DMF soluble fractions to remove starch from the various copolymers gave essentially quantitative yields of PAN. However, these PAN samples exhibited large differences in DMF solubility. The copolymer from the HHO starch was by far more soluble in DMF, had the lowest number average molecular weight, and had a grafting frequency of 2.5–3 times greater than those of the other copolymers. This study indicated that hypochlorite modified starch substrates may be particularly suitable for obtaining copolymers with widely different properties than copolymers having the acid modified starch substrates.     

Salt effects on protein-DNA interactions. The lambda cI repressor and EcoRI endonuclease

In this paper, finite-difference solutions to the nonlinear Poisson-Boltzmann (NLPB) equation are used to calculate the salt dependent contribution to the electrostatic DNA binding free energy for both the lambda cI repressor and the EcoRI endonuclease. For the protein-DNA systems studied, the NLPB method describes nonspecific univalent salt dependent effects on the binding free energy which are in excellent agreement with experimental results. In these systems, the contribution of the ion atmosphere to the binding free energy substantially destabilizes the protein-DNA complexes. The magnitude of this effect involves a macromolecular structure dependent redistribution of both cations and anions around the protein and the DNA which is dominated by long range electrostatic interactions. We find that the free energy associated with global ion redistribution upon binding is more important than changes associated with local protein-DNA interactions (ion-pairs) in determining salt effects. The NLPB model reveals how long range salt effects can play a significant role in the relative stability of protein-DNA complexes with different structures.     

Optimization of signal sets for partial-response channels. I.Numerical techniques

Given a linear, time-invariant, discrete-time channel, the problem of constructing N input signals of finite length K that maximize minimum l₂ distance between pairs of outputs is considered. Two constraints on the input signals are considered: a power constraint on each of the N inputs (hard constraint) and an average power constraint over the entire set of inputs (soft constraint). The hard constraint, problem is equivalent to packing N points in an ellipsoid in min(K,N-1) dimensions to maximize the minimum Euclidean distance between pairs of points. Gradient-based numerical algorithms and a constructive technique based on dense lattices are used to find locally optimal solutions to the preceding signal design problems. Two numerical examples are shown for which the average spectrum of an optimized signal set resembles the water pouring spectrum that achieves Shannon capacity, assuming additive white Gaussian noise     

Bounds on maximum throughput for digital communications withfinite-precision and amplitude constraints

The problem of finding the maximum achievable data rate over a linear time-invariant channel is considered under constraints different from those typically assumed. The limiting factor is taken to be the accuracy with which the receiver can measure the channel output. More precisely, the following problem is considered. Given a channel with known impulse response h(t), a transmitter with an output amplitude constraint, and a receiver that can distinguish between two signals only if they are separated in amplitude at some time t ₀ by at least some small positive constant d, what is the maximum number of messages, N_max, that can be transmitted in a given time interval [0,T]? Lower bounds on N_max can be easily computed by constructing a particular set of inputs to the channel. The main result is an upper bound on N_max for arbitrary h(t). The upper bound depends on the spread of h(t), which is the maximum range of values the channel output may take at some time t₀>0 given that the output takes on a particular value α at time t=0. Numerical results are shown for different impulse responses, including two simulated telephone subscriber loop impulse responses