Drinking and swimming around waterways: The role of alcohol, sensation-seeking, peer influence and risk in young people.

The role of individual and sociocultural factors contributing to drowning risk for young adults is complex and poorly understood. This study examined the relationship between behaviour in and around waterways and: 1) alcohol consumption; 2) resistance to peer influence; 3) sensation-seeking; 4) perception of risk among people aged 15-24 in Western Australia. A cross-sectional online survey was conducted at three time-points with a convenience sample. Predictor variables included: Alcohol Use Disorder Identification Test Consumption (AUDIT_C); Resistance to Peer Influence; Brief Sensation Seeking scale; Benthin's Perception of risk. Pearson chi-squared tests determined the association between demographic and predictor variables. Logistic regression explored influence of potential predictor variables on behaviour in and around water. The final sample (n = 730) participants, consisted of females (n = 537, 74.5%), metropolitan dwelling (n = 616, 84.4%), and attended university (n = 410, 56.9%). Significant associations were found for those who swum after drinking alcohol compared with those that had not by age, gender, education. For every 1-unit increase in AUDIT-C participants were 60% more likely to swim after drinking (OR 95% CI 1.60 1.44-1.78). Participants who considered an adverse event serious were 15% less likely to have swum after drinking alcohol (OR 0.85 95% CI 0.73-0.99). The complex relationship between social participation in activities in and around waterways, higher drowning rates, propensity for risk, and the meaning young adults attach to risk locations and practices present unique challenges for drowning prevention research. Findings should be used to improve the awareness and education components of future youth water safety strategies in high-income settings.

Temperature and myogenesis in embryos of the Atlantic herring Clupea harengus

The development of axial muscles has been investigated in spring-spawning Atlantic herring (Clupea harengus L.) reared at 5, 8, 12 and 15 °C. In 1994, around 90 % of embryos hatched after 28 days at 5 °C, 16 days at 8 °C, 9 days at 12 °C and 8 days at 15 °C. The somites were formed from cells of the paraxial mesoderm in a rostral to caudal direction, starting at the neural plate stage. Somites were added at rates ranging from one every 3 h at 5 °C to one every 52 min at 15 °C. A small number of myoblasts, located adjacent and lateral to the notochord, elongated to span the somite to form mononuclear myotubes. The majority of muscle fibres were formed by the fusion of 2­5 myoblasts to produce multinucleated myotubes that subsequently differentiated into either superficial or inner fibre types. The timing of myogenesis with respect to somite stage and the initial appearance of the gut, pectoral fin buds and pronephric tubules was found to vary with development temperature. For rostral myotomes, the synthesis of contractile filaments and myofibril assembly were first observed at the 42-, 38- and 27-somite stages at 5, 8 and 12 °C, respectively. The differentiation of myotubes into morphologically recognisable muscle fibre types first occurred at the 62-somite stage at 5 °C, at the 48-somite stage at 8 °C and as early as the 40-somite stage at 12 °C. Cell proliferation experiments with 5-bromo-2'-deoxyuridine showed that another population of myoblasts was activated on the surface of muscle fibres just prior to hatching. Development temperature also affected muscle cellularity; there were 43 % more inner muscle fibres in the myotomes of 1-day-old larvae reared at 12 °C than at 5 °C (P<0.02).

Phenotypic plasticity of early myogenesis and satellite cell numbers in atlantic salmon spawning in upland and lowland tributaries of a river system.

Early myogenesis was studied in the offspring of Atlantic salmon (Salmo salar L.) spawning in a lowland (Sheeoch) and an upland (Baddoch) tributary of the River Dee System, Aberdeenshire, Scotland. Eggs from each population were incubated at the simulated natural thermal regimes of each stream, which was on average 2.8 degrees C cooler for the Baddoch than for the Sheeoch. Relationships between muscle cellularity variables, the density of myonuclei and responses to temperature were investigated using multivariate statistical techniques. These revealed highly significant temperature effects (P<0.001) at hatch (H) and first feeding (FF) and significant interactions between population and temperature (P<0.001), indicating that Baddoch and Sheeoch salmon responded differently to the two temperature regimes. The total cross-sectional area of white muscle (WF.ta) at the adipose fin was relatively independent of temperature at hatch and first feeding in the Sheeoch population. In contrast, for alevins of Baddoch origin, WF.ta was 18.9% (H) and 30.5% (FF) higher in fish incubated at Baddoch than at Sheeoch temperatures. At hatch, there were 15.6% more white muscle fibres (WF.no) at the cooler incubation temperature in fish of Sheeoch origin and 6.0% more in fish of Baddoch origin. However, by first feeding, the difference in WF.no between temperatures had narrowed to 7.2% in the Sheeoch fish and increased to 17.4% in the Baddoch population. In contrast, at hatch, the density of myonuclei was 59.8% higher at the warmer incubation temperature in the Sheeoch population and 23.5% higher in the Baddoch population, but differences were less evident at first feeding. In Baddoch fish, 22.5% of the total muscle nuclei were actively dividing at first feeding, as assessed by staining for proliferating cell nuclear antigen (PCNA). Of the PCNA-positive nuclei, 78% were present in cells that stained for the c-met tyrosine kinase receptor, a marker of satellite cells and their division products. The proportion of c-met-positive cells staining for individual myogenic regulatory factors was 72.4% for the myogenic transcription factor MyoD, 76.3% for the myogenic transcription factor Myf-5, 62.1% for myogenin and 48.7% for the myogenic transcription factor Myf-6. For the Sheeoch population, there were 26.5% more c-met-expressing (P<0.01) and 23.2% more myogenic-regulatory-factor-expressing (P<0.05) cells at Sheeoch than at Baddoch temperatures. In contrast, incubation temperature had no significant effects on satellite cell density in the Baddoch population.

Early thermal experience has different effects on growth and muscle fibre recruitment in spring- and autumn-running Atlantic salmon populations.

The consequence of early thermal experience for subsequent growth patterns was investigated in Atlantic salmon (Salmo salar L.). Spring- and autumn-running salmon were caught in upland (Baddoch) and lowland (Sheeoch) tributaries of the River Dee, Aberdeenshire, Scotland, respectively, on the final stages of their spawning migrations. The eggs were incubated at the simulated natural temperature regime of each stream, which was on average 2.8 degrees C lower for the Baddoch. The offspring, representing 11 families per population, were transferred at first feeding to constant environmental conditions (12-14 degrees C; 16h:8h light:dark photoperiod) and reared in replicate tanks. Salmon of both populations were longer and heavier at 6 and 12 weeks in fish initially reared under the cooler Baddoch regime. Length frequency distributions became bimodal after 18 weeks, and only the upper growth mode was studied. Modelling of length distributions at 40 weeks revealed significantly different patterns of muscle growth according to initial temperature regime, but only for the Sheeoch salmon. In fish of Sheeoch origin, significantly more white muscle fibres were recruited per mm(2) increase in myotomal cross-sectional area at Sheeoch than at Baddoch temperatures (P<0.01). After 40 weeks, the density of white fibres was 10.4 % higher in fish initially reared at the Sheeoch (533+/-6 mm(-2)) than at the Baddoch (483+/-5 mm(-2)) thermal regimes (means +/- s.e.m., 16 fish per group; P<0.001). Muscle satellite cells were identified using an antibody to c-met. At 24 weeks, the density of muscle satellite cells was 29 % higher in Sheeoch salmon reared to first feeding at the temperature of their natal stream than at cooler Baddoch temperatures (P<0.01). In contrast, the number and size distributions of white muscle fibres in the myotomes of Baddoch salmon were independent of early thermal experience.