Frequency Change Detection in Human Auditory Cortex

We offer a model of how human cortex detects changes in the auditory environment. Auditory change detection has recently been the object of intense investigation via the mismatch negativity (MMN). MMN is a preattentive response to sudden changes in stimulation, measured noninvasively in the electroencephalogram (EEG) and the magnetoencephalogram (MEG). It is elicited in the oddball paradigm, where infrequent deviant tones intersperse a series of repetitive standard tones. However, little apart from the participation of tonotopically organized auditory cortex is known about the neural mechanisms underlying change detection and the MMN. In the present study, we investigate how poststimulus inhibition might account for MMN and compare the effects of adaptation with those of lateral inhibition in a model describing tonotopically organized cortex. To test the predictions of our model, we performed MEG and EEG measurements on human subjects and used both small- (<1/3 octave) and large- (>5 octaves) frequency differences between the standard and deviant tones. The experimental results bear out the prediction that MMN is due to both adaptation and lateral inhibition. Finally, we suggest that MMN might serve as a probe of what stimulus features are mapped by human auditory cortex.     

Pyrano-[2,3b]-pyridines as potassium channel antagonists

The design and synthesis of a series of highly functionalized pyrano-[2,3b]-pyridines is described. These compounds were assayed for their ability to block the I(Kur) channel encoded by the gene hKV1.5 in patch-clamped L-929 cells. Six of the compounds in this series showed sub-micromolar activity, the most potent being 4-(4-ethyl-benzenesulfonylamino)-3-hydroxy-2,2-dimethyl-3,4-dihydro-2H-pyrano[2,3b]-pyridine-6-carboxylic acid ethyl-phenyl-amide with an IC(50) of 378 nM.     

Insulin secretion is highly sensitive to desorption of plasma membrane cholesterol

Cholesterol-rich clusters of SNARE (soluble NSF attachment protein receptor) proteins have been implicated as being important for exocytosis. Here we demonstrate the significance of cholesterol for normal biphasic insulin secretion in mouse beta cells by removal of cholesterol from the plasma membrane using methyl-beta-cyclodextrin (MBCD). Maximal inhibition of insulin secretion in static incubations was achieved using 0.1 mM MBCD. In in situ pancreatic perfusion measurements, both first and second phase insulin secretions were reduced by approximately 50% (P<0.05). This was accompanied by a reduced number of docked large dense core vesicles (LDCVs) (approximately 40%; P<0.01) and a reduced exocytotic response (>50%; P<0.01). Further, subcellular fractionations demonstrated movement of the synaptosomal protein of 25 kDa (SNAP-25) from the plasma membrane to the cytosol after MBCD treatment. The inhibitory actions of MBCD were counteracted by subsequent addition of cholesterol. We hypothesize that desorption of cholesterol leads to the disturbance of a basic exocytotic mechanism partly due to migration of SNAP-25, and we conclude that insulin secretion is highly sensitive to changes in plasma membrane cholesterol.     

Effect of sedation with detomidine and butorphanol on pulmonary gas exchange in the horse

Background  

Sedation with α₂-agonists in the horse is reported to be accompanied by impairment of arterial oxygenation. The present study was undertaken to investigate pulmonary gas exchange using the Multiple Inert Gas Elimination Technique (MIGET), during sedation with the α₂-agonist detomidine alone and in combination with the opioid butorphanol.     

Improving marsh restoration: leaf tissue chemistry identifies factors limiting production in <Emphasis Type="Italic">Spartina patens</Emphasis>

Marsh loss is a problem in many areas around the world. In order to combat the problem, scientists and managers need tools to determine its cause and evaluate the effectiveness of management techniques. Current methods for estimating productivity and identifying factors that limit productivity are too time-consuming or expensive for wide-spread, regular use, however. In coastal Louisiana, where Spartina patens (Ait.) Muhl is the most common plant, restoration seeks to slow wetland loss rates that averaged approximately 77.4 km²/year between 1978 and 2000. We used the chemical composition of leaf tissue from S. patens grown under controlled conditions to create a simple and inexpensive tool to identify salinity stress and nutrient limitation. By growing S. patens at varying nitrogen availability and salinity levels, we found that C:N ratios and Na concentrations can be used to classify factors that limit production in S. patens.     

How common is ecological speciation in plant-feeding insects? A 'Higher' Nematinae perspective

Background  

Ecological speciation is a process in which a transiently resource-polymorphic species divides into two specialized sister lineages as a result of divergent selection pressures caused by the use of multiple niches or environments. Ecology-based speciation has been studied intensively in plant-feeding insects, in which both sympatric and allopatric shifts onto novel host plants could speed up diversification. However, while numerous examples of species pairs likely to have originated by resource shifts have been found, the overall importance of ecological speciation in relation to other, non-ecological speciation modes remains unknown. Here, we apply phylogenetic information on sawflies belonging to the 'Higher' Nematinae (Hymenoptera: Tenthredinidae) to infer the frequency of niche shifts in relation to speciation events.     

Intranuclear localization of a new snRNP-related antigen.

The intranuclear distribution of a new antigen (F78) associated with U snRNPs (small nuclear RNA-protein complexes) was compared with that of the RNP and Sm protein antigens previously identified on individual snRNP particles. Human and rat cells were double stained with human autoantisera and mouse monoclonal antibodies. The binding of the human and mouse antibodies was detected with secondary antibodies conjugated with fluorescein and rhodamine, respectively. The resulting immunofluorescence patterns were compared by digital image analysis. The F78, RNP, and Sm antigens show speckled fluorescence patterns which overlap to a great extent. The F78 pattern, however, also contains two classes of structural elements not present in the RNP pattern. Furthermore, during mitosis expression of the F78 antigen is completely suppressed from early prophase to telophase, while the RNP and Sm antigens are found evenly distributed throughout the cytoplasm of the dividing cells.     

Unintentional Bulk Doping of Polymer‐Fullerene Blends from a Thin Interfacial Layer of MoO3

Charge selective interlayers are of critical importance in order for solar cells based on low mobility materials, such as polymer‐fullerene blends, to perform well. Commonly used anode interlayers consist of high work function transition metal oxides, with molybdenum trioxide (MoO₃) being arguably the most used. Here, it is shown that a thin interlayer of MoO₃ causes unintentional bulk doping in solar cells based on polymers and polymer‐fullerene blends. The doping concentrations determined from capacitance–voltage measurements are larger than 10¹⁶ cm^?3 and are seen to increase closer to the anode, reference devices without MoO₃ are undoped. Using time of flight secondary ion mass spectroscopy it is furthermore shown that molybdenum is present on the surface of all films with an interfacial layer of MoO₃ beneath the active layer. Doping concentrations of this magnitude are detrimental for device performance, especially for active layers >100 nm.     

Treatment of deep vein thrombosis with streptokinase.

From September 1962 to May 1972 145 patients with acute or subacute deep vein thrombosis confirmed by phlebography were treated with streptokinase. During the same period 42 patients considered unfit for thrombolytic therapy were treated with herapin and oral anticoagulants. The results, assessed by repeat phlebography, in 93 of the patients treated with streptokinase were compared with those in 42 patients treated with heparin. The age, sex, and severity of occlusion were roughly similar in both groups. Streptokinase treatment was successful in 42 per cent, partially successful in 25 per cent, and unsuccessful in 32 per cent of the 93 patients compared with none, 10 per cent, and 88 percent respectively in the 42 patients treated with heparin. Streptokinase was more effective when the thrombus was in proximal rather than calf veins. Thrombi of more than six days old were readily lysed. Plasma fibrinogen levels were below 0-8 g/1 (80 mg/100 ml) in nearly all patients successfully treated. The incidence of pulmonary embolism was no greater with streptokinase than with heparin treatment. Only prolonged follow-up would show whether thrombolytic treatment would be effective in preventing late complications of deep vein thrombosis such as chronic venous insufficiency.