Processing blur of conflicting stimuli during the latency and onset of accommodation

The accommodative response (AR) to changes in dioptric accommodative stimulus (AS) during the latency period and onset of accommodation was investigated. Participants monocularly observed one period of a square wave in AS, with a 2-D baseline and mean, and amplitude 1 D or 2 D; the period of the square wave ranged from 0.10 s to 1.00 s; both increases and decreases were used for the first step in AS. At periods of 0.30 s and longer, accommodation was found to respond to both levels of the stimulus. Rapid retinal monitoring appeared to be taking place for such stimuli. The amplitudes of peaks in AR did not usually depend on whether a particular level of AS occurred first or second, but for 8/40 conditions, a significant difference was found, with a stronger response when the level of AS occurred second. Null or incorrect responses were also observed in many trials, possibly linked with the natural microfluctuations of accommodation. Minimum response times to the changes in AS were observed, which increased with decreasing period of the AS. The time interval between peaks in the AR decreased with decreasing period of the AS. The findings were consistent with a parallel processing model previously proposed for saccades, where input from a later change in stimulus may enter an element of the control system when that element has finished processing an earlier change. More than one change in stimulus may therefore be passing through the multi-element control system at a time

A comparison of the ecology of Escherichia coli in the intestine of healthy unweaned pigs and pigs after weaning

A total of 51 clinically healthy pigs (14 underweaned and 37 weaned) from five litters, and aged 21 to 35 d, were studied. Escherichia coli isolates from the duodenum, jejunum, ileum, caecum and colon were differentiated on the basis of O-serogroup, biotype and resistance pattern. The complexity of the flora was influenced considerably by the presence or absence of the enterotoxigenic serotype 0149: K91, K88a,c (Abbotstown strain). When it was absent the E. coli flora of both weaned and unweaned pigs was complex with up to 25 strains being identified. The majority of these E. coli strains identified in each pig were isolated from only one of the five intestinal sites sampled. On the other hand, when the enterotoxigenic strain was present (14 pigs) it tended to dominate the E. coli flora at all levels of the intestine and this dominance was reflected in a corresponding fall in the total number of E. coli strains isolated per pig

Transient axial length change during the accommodation response in young adults

NoThe aims of the research may be outlined as follows: to measure the degree of transient axial elongation during the accommodation response in emmetropic and myopic young adults. To evaluate the effect of refractive error and accommodative demand on transient axial elongation of the eye. Axial length of the right eye was measured in 30 emmetropes and 30 myopes, by using the IOLMaster (Carl Zeiss Meditec, Inc., Dublin, CA), while accommodative stimuli of 0, 2, 4 and 6 D were presented with a Badal optometer. Axial length increased in both emmetropic and myopic subjects during short periods of accommodative stimulation. Greater transient increases in axial length were observed in myopic than in emmetropic subjects. The mean axial elongation with a 6-D stimulus to accommodation was 0.037 mm in emmetropes and 0.058 mm in myopes (P = 0.02). The degree of transient axial elongation correlated well with the stimulus to accommodation in emmetropes and myopes. Anterior chamber depth decreased, on average, by 0.19 mm in emmetropes and 0.18 mm in myopes when observing a 6-D stimulus to accommodation. During relatively short periods of accommodative stimulation, axial length increases in both emmetropic and myopic young adults. At higher levels of accommodative stimulation, a significantly greater transient increase in axial length is observed in myopic subjects than in their emmetropic counterparts