The effect of white and filtered noise on contrast detection thresholds

The influence of high-frequency microstimulation (HFMS) of one of the hemispheres on the parameters of spontaneous gamma-oscillations in the neural network containing callosal cells of the motor cortex of both hemispheres. There were three modes in the background oscillation periods distribution, which corresponded to the frequencies 40-60, 70-100, and 100-200 Hz. These oscillation frequencies were also revealed after the HFMS in neural interactions of the cells, which were active before the HFMS; the frequency 40-60 Hz, which dominated before the HFMS, became even more pronounced. The same three groups of oscillation frequencies were found in the activity of cells which became active after the HFMS. The expression of oscillations, the number of oscillatory interactions, as well as the number of neuronal pairs with additional synchronization decreased after the HFMS, which suggests a decrease in synchronization. Taking into account the results of simulation experiments that the frequency of gamma-oscillations is determined by the strength of inhibitory and excitatory input, we suggest that the long-term posttetanic modifications in the efficacy of synaptic inputs of the neurons of both hemispheres underlie the observed posttetanic changes.     

Cycloalkylpyranones and cycloalkyldihydropyrones as HIV protease inhibitors: exploring the impact of ring size on structure-activity relationships

Previously, 3-substituted cycloalkylpyranones, such as 2d, have proven to be effective inhibitors of HIV protease. In an initial series of 3-(1-phenylpropyl) derivatives with various cycloalkyl ring sizes, the cyclooctyl analog was the most potent. We became interested in exploring the influence of other structural changes, such as substitution on the phenyl ring and saturation of the 5,6-double bond, on the cycloalkyl ring size structure-activity relationship (SAR). Saturation of the 5,6-double bond in the pyrone ring significantly impacts the SAR, altering the optimal ring size from eight to six. Substitution of a sulfonamide at the meta position of the phenyl ring dramatically increases the potency of these inhibitors, but it does not change the optimal ring size in either the cycloalkylpyranone or the cycloalkyldihydropyrone series. This work has led to the identification of compounds with superb binding affinity for the HIV protease (Ki values in the 10-50 pM range). In addition, the cycloalkyldihydropyrones showed excellent antiviral activity in cell culture, with ED50 values as low as 1 microM.     

Encircling overlapping multipulse shock waveforms for transthoracic defibrillation

OBJECTIVES: This study was performed to determine the efficacy of new encircling overlapping multipulse, multipathway waveforms for transthoracic defibrillation. BACKGROUND: Alternative waveforms for transthoracic defibrillation may improve shock success. METHODS: First, we determined the shock success achieved by three different waveforms at varying energies (18-150 J) in 21 mongrel dogs after short-duration ventricular fibrillation. The waveforms tested included the traditional damped sinusoidal waveform, a single pathway biphasic waveform, and a new encircling overlapping multipulse waveform delivered from six electrode pads oriented circumferentially. Second, in 11 swine we compared the efficacy of encircling overlapping multipulse shocks given from six electrode pads and three capacitors versus encircling overlapping shocks given from a device utilizing three electrodes and one capacitor. RESULTS: In the first experiment, the encircling overlapping waveform performed significantly better than biphasic and damped sinusoidal waveforms at lower energies. The shock success rate of the overlapping waveform (six pads) ranged from 67+/-4% (at 18-49 J energy) to 99+/-3% at > or = 150 J; at comparable energies biphasic waveform shock success ranged from 26+/-5% (p < 0.01 vs. encircling overlapping waveforms) to 99+/-5% (p = NS). Damped sinusoidal waveform shock success ranged from 4+/-1% (p < 0.01 vs. encircling overlapping waveform) to 73+/-9% (p = NS). In the second experiment the three electrode pads, one capacitor encircling waveform achieved shock success rates comparable with the six-pad, three-capacitor waveform; at 18-49 J, success rates were 45+/-15% versus 57+/-12%, respectively (p = NS). At 100 J, success rates for both were 100%. CONCLUSIONS: We conclude that encircling overlapping multipulse multipathway waveforms facilitate transthoracic defibrillation at low energies. These waveforms can be generated from a device that requires only three electrodes and one capacitor.     

Effect of dietary restriction on benzo[a]pyrene (BaP) metabolic activation and pulmonary BaP-DNA adduct formation in mouse

Hepatic microsomal xenobiotic metabolizing enzyme activities of laboratory animals can be modulated by Dietary restriction (DR). The modulation of xenobiotic metabolizing enzyme activities can affect the metabolic activation of chemical carcinogens. Acute DR (60% of the food consumption of ad libitum (AL)-fed mice for 7 weeks) reduced the body weights of the male B6C3F1 mice, and increased mouse pulmonary cytochrome P4501A1-dependent BaP metabolizing enzyme activity. The effects of DR on the formation of the specific BaP-DNA adduct, 10-(N2-deoxyguanosinyl)-7,8,9-trihydroxy-7,8,9,10-tetrahydro-BaP (BaP-N2-dG) in mouse lung can be detected by using 32P-postlabeling technique. In both AL- and DR-mice total BaP-DNA adduct formation in lung reached a peak at 48 hours after treatment with [3H]BaP and the in vivo formation of BaP-N2-dG was greater in DR mouse lung than in that of AL-animals by 22%. DR increased in vitro BaP-N2-dG formation by 39% when calf-thymus DNA was incubated with BaP using liver microsomes obtained from DR- or AL-mice as the enzyme source. The formation of the specific BaP-N2-dG adducts, measured by 32P-postlabeling, was only 20% of the total [3H]BaP-DNA adducts as determined by liquid scintillation counting. The increase of BaP-DNA adduct formation in mouse lung was correlated to the enhancement of the mouse pulmonary BaP metabolizing enzyme activity. Our results indicated that the effect of DR on the metabolic activation of BaP in mouse lung was dependent upon the mouse lung cytochrome P4501A1-dependent BaP metabolizing enzymes activities which was significantly increased by DR.     

Long-term residues arising from 14CO2 fixation in swine tissues

Pigs injected intramuscularly with ¹⁴C sodium earbonate solution were killed after 9 and 21 days. The protein hydrolysate from liver tissues were treated with ninhydrin to liberate CO₂ which was used for determination of residual radioactivity. Most of the ¹⁴C from the fixed CO₂ was liberated by this treatment, which was considered to be a suitable method for estimating long-term residues of ¹⁴C in tissues arising from a ¹⁴CO₂ fixation process. The proportion of ¹⁴C in various amino acids remained almost constant over the period of the test.     

Die kristallinität von äthylen-vinylacetat-copolymeren

Copolymers of ethylene and vinyl acetate of different composition were investigated by differential thermal and x-ray analysis in the temperature range of ?80 to 140°C. Compounds with more than 60 weight-% of vinyl acetate are amorphous. In the partially crystalline copolymers with lower contents of vinyl acetate the glass transition temperature is independent of composition and lies below that in amorphous copolymers. The melting points of the partially crystalline compounds increase with ethylene contents and can be described with the aid of a modified FLORY equation. The increase of the degree of crystallinity with ethylene content is demonstrated. The influence of thermal pre-treatment on the melting behaviour is discussed.     

Dynamisch-mechanische Untersuchungen an Polymerisatgemischen aus Polyäthylacrylat und polymethylmethacrylat

The temperature dependence of damping and modulus has been measured in shear at about 1 Hz for a mixture of polyethylacrylate (PäA) and polymethylmethacrylate (PMMA) which was prepared by mixing the aqueous dispersions of the homopolymers with a particle size of about 100 nm in diameter. Between the wellknown damping peaks of PÄA and PMMA an intermediate peak was found which is ascribed to interactions of the PÄA- und PMMA-segments in the vicinity of the phase boundaries. If the mixture is annealed above the transition temperature of PMMA, this peak vanishes, because the amount of the phase surface is reduced. At temperatures between the transitions of PAA and PMMA the dynamic shear modulus of mixtures PÄA/PMMA is determined by a glassy and a rubbery phase. In addition to the ratio of components this value is considerably influenced by the phase structure. If the polymer mixture is prepared by polymerizing AA in the presence of PMMA, it is shown by comparing the results of calculations based on a simple model with experimentally determined values of the shear modulus, that the glassy PMMA already exists as a continuous phase at a concentration of only 15 wt-%. Electron micrographs confirm this result. If the rubbery PÄA-phase is crosslinked, the elongation at break of such substances is increased 15-fold to about 150%.     

Anwendung der FMIR-Technik zur infrarotspektroskopischem Identifizierung von beschechteten Folien und Papieren

The high efficiency of FMIR-technique by infrared investigations of coated foils, papers and cartons is shown in some examples. In this method the surface of the sample to be investigated which is pressed on both sides of a KRS-5 crystal is scanned repeatedly by the IR-beam. This investigation shows that the reflectance technique yields spectra of higher quality (= resolution + band depth) than the traditional transmittance technique. Moreover the procedure of pressing can be omitted in the investigation of lacquered foils or foils with a smooth surface before recording the spectra. This proved to be necessary according to our results we received by the FMIR investigation of coated papers. Often better spectra of foils are obtained if a FMIR-erystal with 15 reflections is used (angle of incidence 60°). The FMIR-method has the great advantage of simplicity and speed.     

Probleme des abbaus an folienbildenden thermoplastischen hochpolymeren

The mass-produced thermoplastics, PVC, polystyrene and polyolefins, have increasingly gained ground in fields of application where, during and after use, they are subjected as thin layers, e.g. in the form of films, to normal environmental influences. Degradation reactions on thin layers caused by heat and light in the presence of oxygen are gaining importance as much as a “controlled autoxidation” might open up new fields of application. Initiation and acceleration of autoxidation by ?potential sensitizers”? in the presence of oxygen and beams of light are critically evaluated with a view towards desired degradability.