Induced variability in the distribution of activity over the circadian cycle.

Two experiments investigated factors affecting the distribution of locomotor rates over the circadian cycle of 96 earthworms by using an activity wheel. External stimulation (e.g., handling, operating), remote in time from testing (up to 5 days), had a systematic effect on the degree of activity found at specific times of day. Analogous findings for other species suggest a biological capacity to adjust the timing or degree of activity throughout the light cycle according to environmental requirements. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Detection of silent intervals between noises activating different perceptual channels: some properties of "central" auditory gap detection

This article describes four experiments on gap detection by normal listeners, with the general goal being to examine the consequences of using noises in different perceptual channels to delimit a silent temporal gap to be detected. In experiment 1, subjects were presented with pairs of narrow-band noise sequences. The leading element in each pair had a center frequency of 2 kHz and the trailing element's center frequency was parametrically varied. Gap detection thresholds became increasingly poor, sometimes by up to an order of magnitude, as the spectral disparity was increased between the noise bursts that marked the gap. These data suggested that gap-detection performance is impoverished when the underlying perceptual timing operation requires a comparison of activity in different perceptual channels rather than a discontinuity detection within a given channel. In experiment 2, we assessed the effect of leading-element duration in within-channel and between-channel gap detection tasks. Gap detection thresholds rose when the duration of the leading element was less than about 30 ms, but only in the between-channel case. In experiment 3, the gap-detection stimulus was redesigned so that we could probe the perceptual mechanisms that might be involved in stop consonant discrimination. The leading element was a wideband noise burst, and the trailing element was a 300-ms bandpassed noise centered on 1.0 kHz. The independent variable was the duration of the leading element, and the dependent variable was the smallest detectable gap between the elements. When the leading element was short in duration (5-10 ms), gap thresholds were close to 30 ms, which is close to the voice onset time that parses some voiced from unvoiced stop consonants. In experiment 4, the generality of the leading-element duration effect in between-channel gap detection was examined. Spectrally identical noises defining the leading and trailing edges of the gap were presented to the same or to different ears. There was a leading-element duration effect only for the between channel case. The mean gap threshold was again close to 30 ms for short leading-element durations. Taken together, the data suggest that gap detection requiring a temporal correlation of activity in different perceptual channels is a fundamentally different task to the discontinuity detection used to execute gap detection performance in the traditional, within-channel paradigm.     

An ABC transporter plays a developmental aggregation role in Myxococcus xanthus

Myxococcus xanthus is a gram-negative bacterium which has a complex life cycle. Autochemotaxis, a process whereby cells release a self-generated signaling molecule, may be the principal mechanism facilitating directed motility in both the vegetative swarming and developmental aggregation stages of this life cycle. The process requires the Frz signal transduction system, including FrzZ, a protein which is composed of two domains, both showing homology to the enteric chemotaxis response regulator CheY. The first domain of FrzZ (FrzZ1), when expressed as bait in the yeast two-hybrid system and screened against a library, was shown to potentially interact with the C-terminal portion of a protein encoding an ATP-binding cassette (AbcA). The activation domain-AbcA fusion protein did not interact with the second domain of FrzZ (FrzZ2) or with two other M. xanthus response regulator-containing proteins presented as bait, suggesting that the FrzZ1-AbcA interaction may be specific. Cloning and sequencing of the upstream region of the abcA gene showed the ATP-binding cassette to be linked to a large hydrophobic, potentially membrane-spanning domain. This domain organization is characteristic of a subgroup of ABC transporters which perform export functions. Cloning and sequencing downstream of abcA indicated that the ABC transporter is at the start of an operon containing three open reading frames. An insertion mutation in the abcA gene resulted in cells displaying the frizzy aggregation phenotype, providing additional evidence that FrzZ and AbcA may be part of the same signal transduction pathway. Cells with mutations in genes downstream of abcA showed no developmental defects. Analysis of the proposed exporter role of AbcA in cell mixing experiments showed that the ABC transporter mutant could be rescued by extracellular complementation. We speculate that the AbcA protein may be involved in the export of a molecule required for the autochemotactic process.     

Production of vascular endothelial growth factor by human tumors inhibits the functional maturation of dendritic cells

Inadequate presentation of tumor antigens by host professional antigen-presenting cells (APCs), including dendritic cells (DCs), is one potential mechanism for the escape of tumors from the host immune system. Here, we show that human cancer cell lines release a soluble factor or factors that dramatically affect DC maturation from precursors without affecting the function of relatively mature DCs. One factor responsible for these effects was identified as vascular endothelial growth factor (VEGF). Thus, VEGF may play a broader role in the pathogenesis of cancer than was previously thought, and therapeutic blockade of VEGF action may improve prospects for immunotherapy as well as inhibit tumor neovasculature.     

Nonulcerating bacterial keratitis associated with soft and rigid contact lens wear

Most patients in acute myocardial infarction (AMI) undergo emergent coronary angiography (CAG). However, when to analyze lipoprotein profiles in AMI is not clear. To determine whether lipoprotein profiles change during catheterization, we measured serum lipid and apolipoprotein concentrations in 65 patients (51 men and 14 women) before and after catheterization. Heparin was injected at 50 units/kg for CAG and 200 units/kg for percutaneous transluminal coronary angioplasty (PTCA). We found that cholesterol and triglyceride decreased by 9.4% (P < 0.001) and 53.1% (P < 0.001), respectively, after catheterization. Apolipoproteins also decreased significantly. Variables decreased two to five times more after PTCA than after CAG. Lipoprotein lipase mass was higher after PTCA (267.8 +/- 135.3 micrograms/L) than after CAG (93.3 +/- 48.4 micrograms/L; P < 0.05). In conclusion, lipoprotein profiles change during catheterization. We recommend avoiding analysis of lipoprotein profiles after emergent CAG in AMI.