Gaze-stabilizing central vestibular neurons project asymmetrically to extraocular motoneuron pools.

Within reflex circuits, specific anatomical projections allow central neurons to relay sensations to effectors that generate movements. A major challenge is to relate anatomical features of central neural populations -- such as asymmetric connectivity -- to the computations the populations perform. To address this problem, we mapped the anatomy, modeled the function, and discovered a new behavioral role for a genetically-defined population of central vestibular neurons in rhombomeres 5-7 of larval zebrafish. First, we found that neurons within this central population project preferentially to motoneurons that move the eyes downward. Concordantly, when the entire population of asymmetrically-projecting neurons was stimulated collectively, only downward eye rotations were observed, demonstrating a functional correlate of the anatomical bias. When these neurons are ablated, fish failed to rotate their eyes following either nose-up or nose-down body tilts. This asymmetrically-projecting central population thus participates in both up and downward gaze stabilization. In addition to projecting to motoneurons, central vestibular neurons also receive direct sensory input from peripheral afferents. To infer whether asymmetric projections can facilitate sensory encoding or motor output, we modeled differentially-projecting sets of central vestibular neurons. Whereas motor command strength was independent of projection allocation, asymmetric projections enabled more accurate representation of nose-up stimuli. The model shows how asymmetric connectivity could enhance the representation of imbalance during nose-up postures while preserving gaze-stabilization performance. Finally, we found that central vestibular neurons were necessary for a vital behavior requiring maintenance of a nose-up posture: swim bladder inflation. These observations suggest that asymmetric connectivity in the vestibular system facilitates representation of ethologically-relevant stimuli without compromising reflexive behavior.SIGNIFICANCE STATEMENTInterneuron populations use specific anatomical projections to transform sensations into reflexive actions. Here we examined how the anatomical composition of a genetically-defined population of balance interneurons in the larval zebrafish relates to the computations it performs. First, we found that the population of interneurons that stabilize gaze preferentially project to motoneurons that move the eyes downward. Next, we discovered through modeling that such projection patterns can enhance the encoding of nose-up sensations without compromising gaze stabilization. Finally we found that loss of these interneurons impairs a vital behavior, swim bladder inflation, that relies on maintaining a nose-up posture. These observations suggest that anatomical specialization permits neural circuits to represent relevant features of the environment without compromising behavior

9: Infections in the returned traveller

The usual presentation of a returned traveller is with a particular syndrome - fever, respiratory infection, diarrhoea, eosinophilia, or skin or soft tissue infection - or for screening for asymptomatic infection

Ocular Filariasis in Human Caused by Breinlia (Johnstonema) annulipapillata Nematode, Australia

We report a human case of ocular filariasis, caused by a species of Breinlia nematode, from Queensland, Australia. Morphological and molecular evidence indicated that the nematode Breinlia (Johnstonema) annulipapillata, or a closely related taxon, likely transmitted from a macropodid marsupial host was involved, which might represent an accidental finding or an emerging zoonosis

Increasing caesarean section rates among low-risk groups : a panel study classifying deliveries according to Robson at a university hospital in Tanzania

Background: Rising caesarean section (CS) rates have been observed worldwide in recent decades. This study sought to analyse trends in CS rates and outcomes among a variety of obstetric groups at a university hospital in a low-income country. Methods: We conducted a hospital-based panel study at Muhimbili National Hospital, Dar es Salaam, Tanzania. All deliveries between 2000 and 2011 with gestational age >= 28 weeks were included in the study. The 12 years were divided into four periods: 2000 to 2002, 2003 to 2005, 2006 to 2008, and 2009 to 2011. Main outcome measures included CS rate, relative size of obstetric groups, contribution to overall CS rate, perinatal mortality ratio, neonatal distress, and maternal mortality ratio. Time trends were analysed within the ten Robson groups, based on maternal and obstetric characteristics. We applied the chi(2) test for trend to determine whether changes were statistically significant. Odds ratios of CS were evaluated using multivariate logistic regression, accounting for maternal age, referral status, and private healthcare insurance. Results: We included 137,094 deliveries. The total CS rate rose from 19% to 49%, involving nine out of ten groups. Multipara without previous CS with single, cephalic pregnancies in spontaneous labour had a CS rate of 33% in 2009 to 2011. Adjusted analysis explained some of the increase. Perinatal mortality and neonatal distress decreased in multiple pregnancies (p < 0.001 and p = 0.003) and nullipara with breech pregnancies (p < 0.001 and p = 0.024). Although not statistically significant, there was an increase in perinatal mortality (p = 0.381) and neonatal distress (p = 0.171) among multipara with single cephalic pregnancies in spontaneous labour. The maternal mortality ratio increased from 463/100, 000 live births in 2000 to 2002 to 650/100, 000 live births in 2009 to 2011 (p = 0.031). Conclusion: The high CS rate among low-risk groups suggests that many CSs might have been performed on questionable indications. Such a trend may result in even higher CS rates in the future. While CS can improve perinatal outcomes, it does not necessarily do so if performed routinely in low-risk groups