Epidemiology and etiology of diarrhea in UK military personnel serving on the United Nations Mission in South Sudan in 2017: A prospective cohort study.

BACKGROUND: . Diarrhea is a well-established problem in travellers, with military personnel at especially high risk. This study aimed to characterise the spectrum of pathogens causing diarrhea in UK military personnel in South Sudan, and assess the utility of culture-independent testing for etiology and antimicrobial resistance in a logistically challenging and austere environment. METHODS: . All military personnel presenting with diarrhea were admitted to the UK Level 2 Medical Treatment Facility in Bentiu, South Sudan. Samples were tested for etiology utilising multiplex PCR-based diagnostics (BioFire FilmArray). In addition, the presence of carbapenemase resistance genes was determined using the geneXpert Carba-R platform. RESULTS: . Over 5 months, 127 samples were tested. The vast majority of pathogens detected were diarrheagenic Escherichia coli. The presence of either enterotoxigenic (ETEC) or enteropathogenic (EPEC) E. coli was a significant predictor of the other being present. In this study patients presenting with vomiting were 32 times more likely to have norovirus than not (p < 0.001). No carbapenem resistance was detected. CONCLUSIONS: . Diarrhea in UK military personnel in South Sudan was determined to be predominantly bacterial, with norovirus presenting a distinct clinical and epidemiological pattern. Multiplex PCR and molecular resistance point of care testing were robust and effective in this environment.

Interaction between contours and eye movements in the perception of afterimages: A test of the signal ambiguity theory.

An intriguing property of afterimages is that conscious experience can be strong, weak, or absent following identical stimulus adaptation. Previously we suggested that postadaptation retinal signals are inherently ambiguous, and therefore the perception they evoke is strongly influenced by cues that increase or decrease the likelihood that they represent real objects (the signal ambiguity theory). Here we provide a more definitive test of this theory using two cues previously found to influence afterimage perception in opposite ways and plausibly at separate loci of action. However, by manipulating both cues simultaneously, we found that their effects interacted, consistent with the idea that they affect the same process of object interpretation rather than being independent influences. These findings bring contextual influences on afterimages into more general theories of cue combination, and we suggest that afterimage perception should be considered alongside other areas of vision science where cues are found to interact in their influence on perception.

Quick phases of infantile nystagmus show the saccadic inhibition effect.

PURPOSE: Infantile nystagmus (IN) is a pathological, involuntary oscillation of the eyes consisting of slow, drifting eye movements interspersed with rapid reorienting quick phases. The extent to which quick phases of IN are programmed similarly to saccadic eye movements remains unknown. We investigated whether IN quick phases exhibit 'saccadic inhibition,' a phenomenon typically related to normal targeting saccades, in which the initiation of the eye movement is systematically delayed by task-irrelevant visual distractors. METHODS: We recorded eye position from 10 observers with early-onset idiopathic nystagmus while task-irrelevant distractor stimuli were flashed along the top and bottom of a large screen at ±10° eccentricity. The latency distributions of quick phases were measured with respect to these distractor flashes. Two additional participants, one with possible albinism and one with fusion maldevelopment nystagmus syndrome, were also tested. RESULTS: All observers showed that a distractor flash delayed the execution of quick phases that would otherwise have occurred approximately 100 ms later, exactly as in the standard saccadic inhibition effect. The delay did not appear to differ between the two main nystagmus types under investigation (idiopathic IN with unidirectional and bidirectional jerk). CONCLUSIONS: The presence of the saccadic inhibition effect in IN quick phases is consistent with the idea that quick phases and saccades share a common programming pathway. This could allow quick phases to take on flexible, goal-directed behavior, at odds with the view that IN quick phases are stereotyped, involuntary eye movements.

Saccadic compensation for reflexive optokinetic nystagmus just as good as compensation for volitional pursuit.

The natural viewing behavior of moving observers ideally requires target-selecting saccades to be coordinated with automatic gaze-stabilizing eye movements such as optokinetic nystagmus. However, it is unknown whether saccade plans can compensate for reflexive movement of the eye during the variable saccade latency period, and it is unclear whether reflexive nystagmus is even accompanied by extraretinal signals carrying the eye movement information that could potentially underpin such compensation. We show that saccades do partially compensate for optokinetic nystagmus that displaces the eye during the saccade latency period. Moreover, this compensation is as good as for displacements due to voluntary smooth pursuit. In other words, the saccade system appears to be as well coordinated with reflexive nystagmus as it is with volitional pursuit, which in turn implies that extraretinal signals accompany nystagmus and are just as informative as those accompanying pursuit.

Saccade-like behavior in the fast-phases of optokinetic nystagmus: an illustration of the emergence of volitional actions from automatic reflexes.

As a potential exemplar for understanding how volitional actions emerged from reflexes, we studied the relationship between an ancient reflexive gaze stabilization mechanism (optokinetic nystagmus [OKN]) and purposeful eye movements (saccades) that target an object. Traditionally, these have been considered distinct (except in the kinematics of their execution) and have been studied independently. We find that the fast-phases of OKN clearly show properties associated with saccade planning: (a) They are characteristically delayed by irrelevant distractors in an indistinguishable way to saccades (the saccadic inhibition effect), and (b) horizontal OKN fast-phases produce curvature in vertical targeting saccades, just like a competing saccade plan. Thus, we argue that the saccade planning network plays a role in the production of OKN fast-phases, and we question the need for a strict distinction between eye movements that appear to be automatic or volitional. We discuss whether our understanding might benefit from shifting perspective and considering the entire "saccade" system to have developed from an increasingly sophisticated OKN system.

Differential role of the hippocampus in response-outcome and context-outcome learning: evidence from selective satiation procedures.

Instrumental performance in rats with hippocampal lesions is insensitive to the degradation of action-outcome contingencies, but sensitive to the effects of selective devaluation by satiation. One interpretation of this dissociation is that damage to the hippocampus impairs the formation of context-outcome associations upon which the effect of contingency degradation, but not selective satiation, relies. Here, we provide a direct assessment of this interpretation, and showed that conditioned responding to contexts did not show sensitivity to selective satiation (Experiment 1), and confirmed that instrumental performance was sensitive to selective satiation (Experiment 2) following hippocampal cell loss.

2D-INADEQUATE Structural Assignment of Polybutene Oligomers.

The structure of polybutene oligomers has been unambiguously determined using NMR techniques. We used 2D-INADEQUATE to show that the major polybutene isomer synthesized via BF(3) catalysis has the expected structure with a tert-butyl group at the beginning of the chain and the expected methylvinylidene double bond at the other end. Surprisingly, we found that the main isomer of polybutene synthesized from AlCl(3) catalysis has an isopropyl group at the beginning of the chain. A trisubstituted double bond structure has been assigned at the other end of the chain. Structural information about several minor polybutene isomers has also been determined. Formation of an isopropyl group can be rationalized by assuming a protonated cyclopropane intermediate in the propagation step. Previously, the mechanism of formation of polybutene via AlCl(3) catalysis was thought to involve exclusively the tert-butyl carbenium ion. It now appears that the mechanism is more complicated than previously thought.