Zebrafish: chiasmata and interference.

With immunofluorescence microscopy, the positions of centromeres and MLH1 (MutL homolog) foci representing the sites of presumptive chiasmata are shown for zebrafish (Danio rerio Hamilton 1822) synaptonemal complexes (SCs) in spermatocyte nuclei at meiotic prophase. Most SCs have a single focus and a few (7 of 140) have 2 chiasmata. MLH1 foci tend to be in the distal regions of SCs, with progressively fewer occurring towards the middle of the SCs. This non-random distribution suggests chiasma interference. Synaptic initiation, as well as replication protein A (RPA) foci at the chromosome ends, correlates with the distal localization of MLH1 foci. These observations may provide the physical basis for the reported limited genetic recombination in the centromeric region of androgenetic offspring of a male.     

Population dynamic interference among childhood diseases.

Epidemiologists usually study the interaction between a host population and one parasitic infection. However, different parasite species effectively compete, in an ecological sense, for the same finite group of susceptible hosts, so there may be an indirect effect on the population dynamics of one disease due to epidemics of another. In human populations, recovery from any serious infection is normally preceded by a period of convalescence, during which infected individuals stay at home and are effectively shielded from exposure to other infectious diseases. We present a model for the dynamics of two infectious diseases, incorporating a temporary removal of susceptibles. We use this model to explore population-level consequences of a temporary insusceptibility in childhood diseases, the dynamics of which are partly driven by differences in contact rates in and out of school terms. Significant population dynamic interference is predicted and cannot be dismissed in the limited case-study data available for measles and whooping cough in England before the vaccination era.     

Evanescent interference patterns for fluorescence microscopy.

The increasing experimental use of total internal reflection/fluorescence photobleaching recovery has motivated a theoretical study of the spatial intensity profiles generated by two interfering evanescent waves. The interference patterns generated by evanescent waves differ considerably from those generated by plane waves in a homogenous medium because evanescent waves are not transverse and because the evanescent propagation number depends on the incidence angle of the totally internally reflected light. The periodicity and contrast of the evanescent interference patterns under various conditions are calculated; these parameters depend on the intensities, polarizations, and incidence angles of the two incident beams, as well as the refractive indices of the two media that form the planar interface where total internal reflection occurs. The derived intensity profiles are used to develop expressions for the shapes of fluorescence photobleaching recovery curves when evanescent interference patterns are used for fluorescence excitation and bleaching. The calculations also suggest that colliding beam experiments may confirm theoretically predicted evanescent field polarizations.     

RNA interference by feeding in Paramecium.

RNA interference can be induced very efficiently by feeding the ciliate Paramecium with bacteria engineered to express double-stranded RNA, opening the possibility of large-scale functional screening in this unicell.     

Spatial code interference on directional responses.

The interference from an irrelevant position cue was compared in a reaction-time paradigm using voice and manual responses. The subjects were required to say 'left' or 'right' or to press left or right keys in response to arrow directions, and the arrows were presented at left or right side display positions irrelevant to the task. Display position significantly increased latency when it did not match the response to the relevant direction cue for both spatial (key-press) and non-spatial (voice) responses (73 and 59 ms, respectively). When presented alone, the position cue was processed faster than the direction cue for both manual and verbal responses. Results are discussed in terms of a common abstract mediator for left-right responses between modes and the processing speed difference between the relevant and irrelevant cue. The irrelevant left-right position code may occupy some limited-capacity channel ahead of the left-right code derived from processing the relevant direction cue.     

Modulation discrimination interference and auditory grouping.

The detection of a change in the modulation pattern of a (target) carrier frequency, fc (for example a change in the depth of amplitude or frequency modulation, AM or FM) can be adversely affected by the presence of other modulated sounds (maskers) at frequencies remote from fc, an effect called modulation discrimination interference (MDI). MDI cannot be explained in terms of interaction of the sounds in the peripheral auditory system. It may result partly from a tendency for sounds which are modulated in a similar way to be perceptually 'grouped', i.e. heard as a single sound. To test this idea, MDI for the detection of a change in AM depth was measured as a function of stimulus variables known to affect perceptual grouping, namely overall duration and onset and offset asynchrony between the masking and target sounds. In parallel experiments, subjects were presented with a series of pairs of sounds, the target alone and the target with maskers, and were asked to rate how clearly the modulation of the target could be heard in the complex mixture. The results suggest that two factors contribute to MDI. One factor is difficulty in hearing a pitch corresponding to the target frequency. This factor appears to be strongly affected by perceptual grouping. Its effects can be reduced or abolished by asynchronous gating of the target and masker. The second factor is a specific difficulty in hearing the modulation of the target, or in distinguishing that modulation from the modulation of other sounds that are present. This factor has effects even under conditions promoting perceptual segregation of the target and masker.     

Homologous interference of lymphocytic choriomeningitis virus: detection and measurement of interference focus-forming units.

Lymphocytic choriomeninigitis (LCM) virus defective interfering (DI) particles form foci of protected cells in a monolayer under an agarose-containing overlay medium. Foci originate from one cell dually infected with at least 1 interference focus-forming unit and infectious virus. As a result, an interfering factor is produced and released which interacts with neighboring cells, thereby protecting them against cytopathic lysis by challenge virus. The property of individual LCM virus DI particles to induce countable foci has been made the basis of quantitative assay that is comparable in every respect to the plaque assay of infectious virus and is much more sensitive and probably more accurate than other procedures used to measure LCM virus DI particles. LCM virus was passaged, undiluted, 10 times in cell cultures. When yields were analyzed as to concentrations of PFU and interference focus-forming units, both entities were found to fluctuate with the pattern expected from theoretical considerations.     

Imagery-induced interference on a visual detection task.

The literature on the interaction between visual imagery and visual perception provides conflicting outcomes. Some studies show imagery interferes with perception whereas others show facilitation on perceptual tasks. The effects of visual imagery on a detection task were examined in six experiments. When either a bar image (Experiment 1) or an image of the letter 'l' (Experiment 3) overlapped with the targets, interference was discovered; however, images not overlapping the target did not effect detection (Experiments 2 and 4). Increasing the number of target locations caused the interfering effects of the image to disappear; however, there was no evidence of facilitation (Experiment 5). Physical stimuli interfered with detection whether there was overlap or not (Experiment 6). The results indicate that imagery induced interference may be lessened with more complex visual displays.     

Eukaryotic interference with homoserine lactone-mediated prokaryotic signalling.

Acylated homoserine lactones (AHLs) play a widespread role in intercellular communication among bacteria. The Australian macroalga Delisea pulchra produces secondary metabolites which have structural similarities to AHL molecules. We report here that these metabolites inhibited AHL-controlled processes in prokaryotes. Our results suggest that the interaction between higher organisms and their surface-associated bacteria may be mediated by interference with bacterial regulatory systems.     

Negative crossover interference in maize translocation heterozygotes.

Negative interference describes a situation where two genetic regions have more double crossovers than would be expected considering the crossover rate of each region. We detected negative crossover interference while attempting to genetically map translocation breakpoints in maize. In an attempt to find precedent examples we determined there was negative interference among previously published translocation breakpoint mapping data in maize. It appears that negative interference was greater when the combined map length of the adjacent regions was smaller. Even positive interference appears to have been reduced when the combined lengths of adjacent regions were below 40 cM. Both phenomena can be explained by a reduction in crossovers near the breakpoints or, more specifically, by a failure of regions near breakpoints to become competent for crossovers. A mathematical explanation is provided.     

Aldosterone plasma radioimmunoassay interference by a spirolactone metabolite.

The plasma aldosterone radioimmunoassay developed by Ito et al. was found to be non-specific for aldosterone following administration of the spirolactones, spironolactone and canrenoate-K, in rabbits, dogs and humans. The assay interfering principle was identified as a hydroxylated derivative (M-B) of canrenone, which itself is a metabolite common to both spironolactone and canrenoate-K. The metabolite M-B possessed a high cross-reactivity to the 21-hemisuccinate aldosterone antibody relative to other spirolactones. A modified procedure was developed specific for plasma aldosterone in the presence of M-B. Following single doses of spironolactone and canrenoate-K, aldosterone plasma levels were unchanged in humans and in dogs and decreased in rabbits.     

RNA interference based gene therapy for neurological disease.

Neurodegenerative disorders represent a major class of disorders for which thus far any effective small molecule drug therapy has failed to emerge. RNA interference (RNAi), by which disease genes such as those identified for spino-cerebellar ataxia and Huntington's disease can be specifically silenced, has great potential in becoming a successful therapeutic strategy for these diseases. RNAi has shown therapeutic value in vitro and in animal disease models and clinical trials are currently on their way. However, there are problems, such as toxicity due to non-specific silencing, generation of immune responses and over-saturation of RNAi pathway components that must be overcome in order to establish RNAi as a safe and effective therapy. Current research on the endogenous roles of RNAi, through the action of microRNAs, has offered much knowledge to optimise the exploitation of RNAi.     

Facilitation and interference components in the Simon effect.

In four experiments we investigated whether the Simon effect consists of both facilitation and interference. In Experiment 1 subjects had to press one of two lateralized keys in response to one of two stimuli (a rectangle or a square). The stimuli were presented at fixation or to the right or left of it. The stimulus-response mappings could be corresponding (i.e., right key--rectangle or square on the right side), non-corresponding (i.e., right key--rectangle or square on the left side), or neutral (i.e., stimulus in the center). Results showed both facilitation and interference effects, but interference was three times greater than facilitation. To test whether the neutral position was favored by visual acuity, Experiments 2, 3 and 4 used slight different displays where visual acuity was the same at every stimulus position. Results indicated that the Simon effect is comprised of facilitation and interference components of the same magnitude. These findings were discussed with reference to dual-route models of the Simon effect.