4,233 research outputs found

    Central pattern generator for swimming in Melibe

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    The nudibranch mollusc Melibe leonina swims by bending from side to side. We have identified a network of neurons that appears to constitute the central pattern generator (CPG) for this locomotor behavior, one of only a few such networks to be described in cellular detail. The network consists of two pairs of interneurons, termed `swim interneuron 1\u27 (sint1) and `swim interneuron 2\u27 (sint2), arranged around a plane of bilateral symmetry. Interneurons on one side of the brain, which includes the paired cerebral, pleural and pedal ganglia, coordinate bending movements toward the same side and communicate via non-rectifying electrical synapses. Interneurons on opposite sides of the brain coordinate antagonistic movements and communicate over mutually inhibitory synaptic pathways. Several criteria were used to identify members of the swim CPG, the most important being the ability to shift the phase of swimming behavior in a quantitative fashion by briefly altering the firing pattern of an individual neuron. Strong depolarization of any of the interneurons produces an ipsilateral swimming movement during which the several components of the motor act occur in sequence. Strong hyperpolarization causes swimming to stop and leaves the animal contracted to the opposite side for the duration of the hyperpolarization. The four swim interneurons make appropriate synaptic connections with motoneurons, exciting synergists and inhibiting antagonists. Finally, these are the only neurons that were found to have this set of properties in spite of concerted efforts to sample widely in the Melibe CNS. This led us to conclude that these four cells constitute the CPG for swimming. While sint1 and sint2 work together during swimming, they play different roles in the generation of other behaviors. Sint1 is normally silent when the animal is crawling on a surface but it depolarizes and begins to fire in strong bursts once the foot is dislodged and the animal begins to swim. Sint2 also fires in bursts during swimming, but it is not silent in non-swimming animals. Instead activity in sint2 is correlated with turning movements as the animal crawls on a surface. This suggests that the Melibe motor system is organized in a hierarchy and that the alternating movements characteristic of swimming emerge when activity in sint1 and sint2 is bound together

    Linguistic analysis of the valence, arousal and dominance of auditory hallucinations and internal thoughts in schizophrenia: Implications for psychoeducation and CBT

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    70% of patients with schizophrenia suffer from auditory verbal hallucinations (AVH) which are frequently described as distressing and disabling. The content of AVH, in relation to internal thought, has never been linguistically tested in a self-monitoring study. The aim of this preliminary study was to establish if there was a significant difference between AVH and inner thoughts on the key linguistic parameters of valence (pleasantness), dominance (control) and arousal (intensity of emotion produced). Six volunteers with a diagnosis of schizophrenia from voice hearing support groups produced real-time, detailed diaries of AVH and inner thoughts using randomised/fixed timers. Analysis of content was completed using an established linguistic database. AVH were significantly more unpleasant and controlling but not more emotionally arousing than inner thoughts. Psychoeducation around the experience of hallucination in schizophrenia should include information that the voices will be significantly more unpleasant and controlling than their own thoughts but not more emotionally arousing. CBT might therefore include the use of compassion focussed techniques to help with the unpleasantness of AVH and schema level techniques to improve coping with the dominance of AVH

    Neural Correlates of Swimming Behavior in Melibe leonina

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    The nudibranch Melibe leonina swims by rhythmically bending from side to side at a frequency of 1 cycle every 2–4 s. The objective of this study was to locate putative swim motoneurons (pSMNs) that drive these lateral flexions and determine if swimming in this species is produced by a swim central pattern generator (sCPG). In the first set of experiments, intracellular recordings were obtained from pSMNs in semi-intact, swimming animals. About 10–14 pSMNs were identified on the dorsal surface of each pedal ganglion and 4–7 on the ventral side. In general, the pSMNs in a given pedal ganglion fired synchronously and caused the animal to flex in that direction, whereas the pSMNs in the opposite pedal ganglion fired in anti-phase. When swimming stopped, so did rhythmic pSMN bursting; when swimming commenced, pSMNs resumed bursting. In the second series of experiments, intracellular recordings were obtained from pSMNs in isolated brains that spontaneously expressed the swim motor program. The pattern of activity recorded from pSMNs in isolated brains was very similar to the bursting pattern obtained from the same pSMNs in semi-intact animals, indicating that the sCPG can produce the swim rhythm in the absence of sensory feedback. Exposing the brain to light or cutting the pedal-pedal connectives inhibited fictive swimming in the isolated brain. The pSMNs do not appear to participate in the sCPG. Rather, they received rhythmic excitatory and inhibitory synaptic input from interneurons that probably comprise the sCPG circuit

    An economic and statistical analysis of factors affecting the rate of growth of the Australian sheep population

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    Thesis (Ph.D.) -- University of Adelaide, Dept. of Economics, 197

    Bioavailability of Omega-3 Fatty Acid Formulations and Their Effect on the Intestinal Microbiota

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    Due to their proposed anti-cancer effects, omega-3 fatty acids (O3FA) may have a role to play in both chemoprevention and the adjuvant treatment of colorectal cancer (CRC). Novel O3FA drink formulations may provide a more effective method of delivering O3FA supplementation, although O3FA bioavailability in these preparations compared to traditional capsules has not been ascertained. There is also a lack of research exploring the effects of O3FAs on the colonic microbiota and whether this may have any protective effect on CRC carcinogenesis. This thesis reports the findings of a randomised cross-over trial in healthy volunteers comparing the bioavailability of equivalent doses of O3FA supplementation (2g EPA and 2g DHA daily for 8 weeks) in capsule and drink carton formulations. The trial also explores the effects of O3FA on faecal microbiome profiles. In addition I report the analysis of red blood cell membrane (RBC) EPA levels from the previously reported EMT trial, a Phase II randomised, double-blind, placebo-controlled trial in which patients with colorectal cancer liver metastasis (CRCLM) received EPA (2g daily) prior to surgery. O3FA supplementation provided in a drinks carton supplementation was non-inferior to an equivalent dose of EPA and DHA provided in capsule form. Faecal microbiome profile analysis revealed subtle changes to the colonic microbiota including reversible increases to Lactobacillus and Bifidobacterium. Analysis of RBC samples from the EMT study revealed a positive correlation between RBC membrane and CRCLM tissue EPA levels. Participants with EPA RBC membrane levels of >1.22 also exhibited improved overall survival. This work provides evidence that an O3FA containing drink formulation is of equivalent bioavailability to traditional capsules. Due to their additional nutritional contents they may be of benefit in CRC patients. The effects of O3FAs on faecal microbiome profiles is of significant interest particularly their impact on bacteria associated with anti-CRC effects. Further work is required to elucidate whether O3FAs have a role in CRC chemoprevention or adjuvant treatment via their effects on the colonic microbiota.

    Is intimate partner violence more common in pregnant women with severe mental illness? A retrospective study

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    Objective: To examine the risk of past and current experiences of intimate partner violence (IPV) in women with severe mental illness (SMI) in pregnancy. Methods: We examined past and current experiences of IPV in women with SMI in pregnancy. The data of 304 women with SMI including schizophrenia and related psychotic disorders and Bipolar Disorder meeting International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD-10-AM) criteria were extracted from hospital records at King Edward Memorial Hospital, Western Australia. Comparisons were made between our study data and the Australian population data reported by the Australian Bureau of Statistics, which included data on pregnant women in Western Australia. Additional measures included reported demographics, substance use and pregnancy variables. Results: Around 48% of pregnant women with SMI had experienced IPV and were three times the risk when compared with the general pregnant population in Australia. There was no difference in rates of IPV in those women with psychotic disorders when compared with bipolar disorder. Furthermore, the rates of smoking and illicit substance use were significantly higher in pregnant women with SMI who experienced IPV compared with those who have not experienced IPV. Conclusion: These findings suggest women with SMI in pregnancy are at significantly higher risk of having experienced or experiencing IPV. In addition, IPV in pregnant women with SMI may increase the risk of smoking and illicit substance use. Together this suggests that maternity and mental health services should ensure there are both screening and support pathways for IPV that are developed and evaluated specifically for pregnant women with SMI

    On the Indeterministic Nature of Star Formation on the Cloud Scale

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    Molecular clouds are turbulent structures whose star formation efficiency (SFE) is strongly affected by internal stellar feedback processes. In this paper we determine how sensitive the SFE of molecular clouds is to randomised inputs in the star formation feedback loop, and to what extent relationships between emergent cloud properties and the SFE can be recovered. We introduce the yule suite of 26 radiative magnetohydrodynamic (RMHD) simulations of a 10,000 solar mass cloud similar to those in the solar neighbourhood. We use the same initial global properties in every simulation but vary the initial mass function (IMF) sampling and initial cloud velocity structure. The final SFE lies between 6 and 23 percent when either of these parameters are changed. We use Bayesian mixed-effects models to uncover trends in the SFE. The number of photons emitted early in the cluster's life and the length of the cloud provide are the strongest predictors of the SFE. The HII regions evolve following an analytic model of expansion into a roughly isothermal density field. The more efficient feedback is at evaporating the cloud, the less the star cluster is dispersed. We argue that this is because if the gas is evaporated slowly, the stars are dragged outwards towards surviving gas clumps due to the gravitational attraction between the stars and gas. While star formation and feedback efficiencies are dependent on nonlinear processes, statistical models describing cloud-scale processes can be constructed.Comment: 24 pages, 16 figures, 6 tables. Accepted to MNRAS, version updated with published titl
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