ALBERT

Notes: Abstract. An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.

Notes: Abstract Freshly isolated ventricular myocytes have been used extensively as an adult cardiac model system. Due to their inability to undergo cytokinesisin vitro and their dedifferentiated properties in long-term culture, they can not be used for extended studies. Recent reports tell of the establishment of fetal and neonatal cardiac cell lines and the development of adult cardiomyocytes from transgenic animals. A recent report by Kirshenbaum [1], is the first to demonstrate insertion of genes in to adult ventricular myocytes using viral infection. This paper discusses the infection of primary adult differentiated cardiomyocytes with the SV40 large T antigen and subsequent proliferation under temperature sensitive control. Upon further characterization, the cells could be used as a model to study muscle differentiation and repair as well as adult cardiac cell physiology.

Notes: Summary Strain SS86-4 was one of 40Bacillus brevis strains shown to be molluscicidal to the schistosomiasis snail vectorBiomphalaria glabrata. When grown in mB4 medium in 2-L fermentors, SS86-4 was molluscicidal only if fructose or phenylalanine was present in the medium. This is reminiscent of secondary fermentation factor effects, in this case an antioxidant effect. In vivo proteases also were capable of reducing molluscicidal activity. The molluscicidal toxin has an LC50 of 1 μg toxin protein ml−1 (approx. 1 p.p.m.) and may be described as a small proteinaceous, heat-stable, oxygen-sensitive entity associated with the particulate portion of the cell wall fraction ofB. brevis that is formed prior to sporulation. Initial information indicates that its HPLC signature shows major peaks at 148.37 and 163.96 s and consists of two bands of approximately 5.3 kDa and 8.7 kDa on PAGE gel.

Notes: Abstract An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.

Notes: Abstract The kinetics of type 1 phytochrome were investigated in green, light-grown wheat. Phytochrome was measured by a quantitative sandwich enzyme-linked immunosorbent assay using monoclonal antibodies. The assay was capable of detecting down to 150 pg of phytochrome. In red light, rapid first-order destruction of the far-red-light-absorbing form of phytochrome (Pfr) with a half-life of 15 min was observed. Following white light terminated by red, phytochrome synthesis was delayed in darkness by about 15 h compared to plants given a terminal far-red treatment. Synthesis of the red-light-absorbing form of phytochrome (Pr) was zero-order in these experiments. Phytochrome synthesis in far-red light was approximately equal to synthesis in darkness in wheat although net destruction occurred in light-grown Avena sativa tissues in continuous far-red light, as has been reported for other monocotyledons. In wheat, destruction of Pfr apparently did not occur below a certain threshold level of Pfr or Pfr/total phytochrome. These results are consistent with an involvement of type 1 phytochrome in the photoperiodic control of flowering in wheat and other long-day plants.

Notes: Summary The primary goal of this study was to determine the utility of 2,3-butanedione monoxime as a tool for determining and separating the chemical energy usage associated with force production from that of force-independent, or ‘activation’ processes in smooth and skeletal muscles. We determined the effects of 2,3-butanedione monoxime on force production, myosin light chain phosphorylation and high energy phosphate usage in intact and permeabilized smooth (rabbit taenia coli) and skeletal (mouse extensor digitorum longus) muscles. In the intact taenia coli, 2,3-butanedione monoxime depressed the tonic phase of the tetanus, contractures evoked by high potassium (90 mM) and by carbachol (10-5 M) and the small force response evoked by these agonists after treatment with D-600 (10-5 M). In the electrically stimulated intact taenia coli 2,3-butanedione monoxime (0–20 mM) caused a proportional inhibition of tetanic force output, myosin light chain phosphorylation and high energy phosphate usage (ED50 ∼ 7 mM for all these parameters). At 20 mM 2,3-butanedione monoxime, force and energy usage fell to near zero and the degree of myosin light chain phosphorylation decreased to resting values, indicating a shut-down of both force-dependent and force-independent energy usage at high concentrations of 2,3-butanedione monoxime. In permeabilized taenia coli, 2,3-butanedione monoxime had little or no depressant effects on force production, ATPase activity or calcium sensitivity. 2,3-butanedione monoxime had a very modest inhibitory effect on the in vitro motility of unregulated actin filaments interacting with thiophosphorylated myosin. In solution, 2,3-butanedione monoxime inhibited myosin light chain kinase, but not the phosphatase (SMP-IV). These results suggest that the major effect of 2,3-butanedione monoxime is not on the contractile proteins themselves, but rather on calcium delivery during excitation, thereby reducing the degree of activation of myosin light chain kinase and subsequent activation of myosin by light chain phosphorylation. Thus, 2,3-butanedione monoxime is not useful for the determination of the energetics of activation processes in smooth muscle because of its inhibition of both force-dependent and force-independent processes. In contrast, in the intact mouse extensor digitorum longus, 2,3-butanedione monoxime inhibits tetanic force production (ED50 ∼ 2 mM) to a much greater extent than myosin light chain phosphorylation. When 2,3-butanedione monoxime was used to manipulate force production in muscles at L0, it was found that ∼60% of the total energy usage was force-independent and the remainder was force-dependent. In the permeabilized extensor digitorum longus treated with 12 mM 2,3-butanedione monoxime, there was a decrease in calcium-activated force production and a decrease in calcium sensitivity. The effects of 2,3-butanedione monoxime were considerably greater in the intact than in the permeabilized mouse extensor digitorum longus. At 2,3-butanedione monoxime concentrations that block force production in the intact muscle, the effects on in vitro motility were small, yet far greater than those on smooth muscle myosin. These results suggest that 2,3-butanedione monoxime has a direct effect on the contractile proteins, but what cannot be ignored is the decrease in myosin light chain phosphorylation in the skeletal muscle, which, like the decreased force output, may result from a reduction in calcium release from the sarcoplasmic reticulum. For these reasons, the use of 2,3-butanedione monoxime to probe the components of energy usage during the contraction of skeletal muscle requires considerable caution and a full definition of its actions.

Notes: Abstract The study distinctly shows that structural changes take place in the silicate framework during the swelling process of glasses in aqueous solutions. The presence of a modified Q3 group is evidence for the exchange of protons and sodium ions; condensation reactions also take place. Using various techniques (1H NMR, infrared spectroscopy and thermal analysis) it has been demonstrated that water is present in the hydrated glass not only in the form of H2O molecules and silanol groups, but also in different structures of these two species. A molar H2O:SiOH ratio was found of approximately 1:1 (in agreement with the assumption that H3O+ ions of the solution and sodium ions of the glass are exchanged and ≡ SiOH and H2O are formed from the hydroxonium ions).

Notes: Abstract Cluster Analysis has been shown to be partially suitable for the classification of glasses. The expansion of the clusters on the Seger's diagram allows an investigation of the influence of the different glass components. Variation of the SiO2 content results in a smaller change of properties than variation of the Na2O/RO relationship. Principal Component Analysis is convenient for showing correlations between the composition of the examined glasses, the glass structure parameters, and the different electrode properties.