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.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
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.
Previous research suggests that child physical abuse, depression, and aggressiveness are linked, but gender differences remain poorly understood. This study examined gender differences in the ...mediational relationships among these constructs, after controlling for the confounding effects of other negative life events. Men and women completed questionnaires about physical abuse and negative life events that occurred prior to age 18, depressive symptoms, and aggressiveness. Results indicated significant gender differences in the pathways between child physical abuse and depression, and between child abuse and aggressiveness, with direct and mediating links pertaining only to men. These findings suggest that links among child physical abuse, depression, and aggressiveness are specific to men, and negative life events might play a more potent role for women.
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).
Thingvallavatn, the largest and one of the oldest lakes in Iceland, contains four morphs of Arctic charr Salvelinus alpinus. Dwarf benthic (DB), large benthic (LB), planktivorous (PL) and piscivorous ...(PI) morphs can be distinguished and differ markedly in head morphology, colouration and maximum fork length (FL(max)), reflecting their different resource specialisations within the lake. The four morphs in Thingvallavatn are thought to have been isolated for approximately 10 000 years, since shortly after the end of the last Ice Age. We tested the null hypothesis that the pattern of muscle fibre recruitment was the same in all morphs, reflecting their recent diversification. The cross-sectional areas of fast and slow muscle fibres were measured at 0.7 FL in 46 DB morphs, 23 LB morphs, 24 PL morphs and 22 PI morphs, and the ages of the charr were estimated using sacculus otoliths. In fish larger than 10 g, the maximum fibre diameter scaled with body mass (M(b))(0.18) for both fibre types in all morphs. The number of myonuclei per cm fibre length increased with fibre diameter, but was similar between morphs. On average, at 60 mum diameter, there were 2264 nuclei cm(-1) in slow fibres and 1126 nuclei cm(-1) in fast fibres. The absence of fibres of diameter 4-10 mum was used to determine the FL at which muscle fibre recruitment stopped. Slow fibre number increased with body length in all morphs, scaling with M(b)(0.45). In contrast, the recruitment of fast muscle fibres continued until a clearly identifiable FL, corresponding to 18-19 cm in the dwarf morph, 24-26 cm in the pelagic morph, 32-33 cm in the large benthic morph and 34-35 cm in the piscivorous morph. The maximum fast fibre number (FN(max)) in the dwarf morph (6.97x10(4)) was 56.5% of that found in the LB and PI morphs combined (1.23x10(5)) (P<0.001). Muscle fibre recruitment continued until a threshold body size and occurred at a range of ages, starting at 4+ years in the DB morph and 7+ years in the LB and PI morphs. Our null hypothesis was therefore rejected for fast muscle and it was concluded that the dwarf condition was associated with a reduction in fibre number. We then investigated whether variations in development temperature associated with different spawning sites and periods were responsible for the observed differences in muscle cellularity between morphs. Embryos from the DB, LB and PL morphs were incubated at temperature regimes simulating cold subterranean spring-fed sites (2.2-3.2 degrees C) and the general lakebed (4-7 degrees C). Myogenic progenitor cells (MPCs) were identified using specific antibodies to Paired box protein 7 (Pax 7), Forkhead box protein K1-alpha (FoxK1-alpha), MyoD and Myf-5. The progeny showed no evidence of developmental plasticity in the numbers of either MPCs or muscle fibres. Juveniles and adult stages of the DB and LB morphs coexist and have a similar diet. We therefore conclude that the reduction in FN(max) in the dwarf morph probably has a genetic basis and that gene networks regulating myotube production are under high selection pressure. To explain these findings we propose that there is an optimal fibre size, and hence number, which varies with maximum body size and reflects a trade-off between diffusional constraints on fibre diameter and the energy costs of maintaining ionic gradients. The predictions of the optimal fibre size hypothesis and its consequences for the adaptive evolution of muscle architecture in fishes are briefly discussed.
The fish fauna of the continental shelf of the Southern Ocean is dominated by a single sub-order of Perciformes, the Notothenioidei, which have unusually large diameter skeletal muscle fibres. We ...tested the hypothesis that in fast myotomal muscle a high maximum fibre diameter (FD(max)) was related to a reduction in the number of muscle fibres present at the end of the recruitment phase of growth. We also hypothesized that the maximum fibre number (FN(max)) would be negatively related to body size, and that both body size and size-corrected FN(max) would show phylogenetic signal (tendency for related species to resemble each other). Finally, we estimated ancestral values for body size and FN(max). A molecular phylogeny was constructed using 12S mitochondrial rRNA sequences. A total of 16 species were studied from the Beagle Channel, Tierra del Fuego (5-11 degrees C), Shag Rocks, South Georgia (0.5-4 degrees C), and Adelaide Island, Antarctic Peninsula (-1.5 to 0.5 degrees C). The absence of muscle fibres of less than 10 micro m diameter was used as the criterion for the cessation of fibre recruitment. FD(max) increased linearly with standard length (SL), reaching 500-650 micro m in most species. Maximum body size was a highly significant predictor of species variation in FN(max), and both body size and size-corrected FN(max) showed highly significant phylogenetic signal (P<0.001). Estimates of trait values at nodes of the maximum likelihood phylogenetic tree were consistent with a progressive reduction in fibre number during part of the notothenioid radiation, perhaps serving to reduce basal energy requirements to compensate for the additional energetic costs of antifreeze production. For example, FN(max) in Chaenocephalus aceratus (12 700+/-300, mean +/- S.E.M., N=18) was only 7.7% of the value found in Eleginops maclovinus (164 000+/-4100, N=17), which reaches a similar maximum length (85 cm). Postembryonic muscle fibre recruitment in teleost fish normally involves stratified followed by mosaic hyperplasia. No evidence for this final phase of growth was found in two of the most derived families (Channichthyidae and Harpagiferidae). The divergence of the notothenioids in Antarctica after the formation of the Antarctic Polar Front and more recent dispersal north would explain the high maximum diameter and low fibre number in the derived sub-Antarctic notothenioids. These characteristics of notothenioids may well restrict their upper thermal tolerance, particularly for Champsocephalus esox and similar Channichthyids that lack respiratory pigments.
) of fast muscle fibres in 4-year-old Bleke salmon (25–28 cm fork length) was 118 μm and not significantly different from
that found in immature migratory salmon of a similar size. In contrast no ...evidence for active fibre recruitment was found
in the Bleke salmon, such that the maximum fibre number, FN, was only 21–30% of that reported in typical farmed and wild migratory populations, respectively. We hypothesise that, once
established, the physiological consequences of the dwarf condition led to rapid selection for reduced fibre number, possibly
to reduce the maintenance costs associated with ionic homeostasis., L.) from Byglands-fjord, Southern Norway mature at about 25 cm fork length and reach a maximum size of only 30 cm in the
wild. The maximum diameter (, Growth of fast myotomal muscle in teleosts involves the continuous production of muscle fibres until some genetically pre-determined
length. The dwarf landlocked (Bleke) population of Atlantic salmon (, Salmo salar
The influence of embryonic and larval temperature regime on muscle growth was investigated in Atlantic herring (Clupea harengus L.). Eggs of spring-spawning Clyde herring were incubated at 5 degrees ...C, 8 degrees C or 12 degrees C until hatching and then reared until after metamorphosis at rising temperatures to simulate a seasonal warming. Metamorphosis to the juvenile stage was complete at 37 mm total length (TL), after an estimated 177 days as a larva at 5 degrees C, 117 days at 8 degrees C and 101 days at 12 degrees C. Growth rate and the development of median fins were retarded in relation to body length at 5 degrees C compared with 8 degrees C and 12 degrees C. Between hatching (at 8-9 mm TL) and 16 mm TL, there was a threefold increase in total muscle cross-sectional area, largely due to the hypertrophy of the embryonic red and white muscle fibres. The recruitment of additional white muscle fibres started at approximately 15 mm TL at all temperatures, and by 37 mm was estimated to be 66 fibres day-1 at 5 degrees C and 103 fibres day-1 at 8 degrees C and 12 degrees C. Peptide mapping studies revealed a change in myosin heavy chain composition in white muscle fibres between 20 and 25 mm TL. Embryonic red muscle fibres expressed fast myosin light chains until 24-28 mm TL at 5 degrees C and 22 mm TL at 12 degrees C, and new red fibres were added at the horizontal septum starting at the same body lengths. Following metamorphosis, the total cross-sectional area of muscle was similar at different temperatures, although the number of red and white fibres per myotome was significantly greater at the warmest than at the coldest regime. For example, the mean number of white muscle fibres per myotome in 50 mm TL juveniles was calculated to be 23.4 % higher at 12 degrees C (12 065) than at 5 degrees C (9775). In other experiments, spring-spawning (Clyde) and autumn-spawning (Manx) herring were reared at different temperatures until first feeding and then transferred to ambient seawater temperature and fed ad libitum for constant periods. These experiments showed that, for both stocks, the temperature of embryonic development influenced the subsequent rate of muscle fibre recruitment and hypertrophy as well as the density of muscle nuclei. Labelling experiments with 5'-bromo-2-deoxyuridine showed that both the hypertrophy and recruitment of muscle fibres involved a rapidly proliferating population of myogenic precursor cells. The cellular mechanisms underlying the environmental modulation of muscle growth phenotype are discussed.
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