Effect of diurnal cycling temperatures on cardiovascular- ventilatory function in statically-acclimated rainbow trout, Salmo gairdneri

Four groups of rainbow trout, Salmo gairdneri, were acclimated to 2°, 10°, and 18°e, and to a diurnal temperature cycle (100 ± 4°C). To evaluate the influence of cycling temperatures in terms of an immediate as opposed to acclimatory response various ventilatory-cardiovascular rate functions were observed for trout, either acclimated to cycling temperatures or acclimated to constant temperatures and exposed to a diurnal temperature cycle for the first time (10° ± 4°C for trout acclimated to 10°C; 18°+ 4°C for trout acclimated to l8°e). Gill resistance and the cardiac to ventilatory rate ratio were then calculated. Following a post preparatory recovery period of 36 hr, measurements were made over a 48 hour period with the first 24 hours being at constant temperature in the case of statically-acclimated fish followed by 24 hours under cyclic temperature conditions. Trout exhibited marked changes in oxygen consumption (Vo ) with temp- 2 erature both between acclimation groups, and in response to the diurnal temperature cycle. This increase in oxygen uptake appears to have been achieved by adjustment of ventilatory and, to some extent, cardiovascular activity. Trout exhibited significant changes in ventilatory rate (VR), stroke volume (Vsv), and flow (VG) in response to temperature. Marked changes in cardiac rate were also observed. These findings are discussed in relation to their importance in convective oxygen transport via water and blood at the gills and tissues. Trout also exhibited marked changes in pressure waveforms associated with the action of the resp; ratory pumps with temperature. Mean differenti a 1 pressure increased with temperature as did gill resistance and utilization. This data is discussed in relation to its importance in diffusive oxygen transport and the conditions for gas exchange at the gills. With one exception, rainbow trout were able to respond to changes in oxygen demand and availability associated with changes in temperature by means of adjustments in ventilation, and possibly pafusion, and the conditions for gas exchange at the gills. Trout acclimated to 18°C, however, and exposed to high cyclic temperatures, showed signs of the ventilatory and cardiovascular distress problems commonly associated with low circulating levels of oxygen in the blood. It appears these trout were unable to fully meet the oxygen requirements associated with c~ling temperatures above 18°C. These findings were discussed in relation to possible limitations in the cardiovascular-ventilatory response at high temperatures. The response of trout acclimated to cycling temperatures was generally similar to that for trout acclimated to constant temperatures and exposed to cycling temperatures for the first time. This result suggested that both groups of fish may have been acclimated to a similar thermal range, regardless of the acclimation regime employed. Such a phenomenon would allow trout of either acclimation group to respond equally well to the imposed temperature cycle. Rainbow trout showed no evidence of significant diurnal rhythm in any parameters observed at constant temperatures (2°, 10°, and 18° C), and under a 12/12 light-dark photoperiod regime. This was not taken to indicate an absence of circadian rhythms in these trout, but rather a deficiency in the recording methods used in the study.

Ionic regulation in goldfish, Carassius auratus, acclimated to constant and diurnally-cycling temperature conditions

The effects of a diurnal sine-wave temperature cycle (250 +- 5° C) on the wa terI-e etc r o1 yt est a t us 0 f gol df1' Sh , Carassius auratus, was assessed through determination of Na+, K+, Mg2+, Ca2+, Cl- and water content in plasma, Red blood cells and muscle tissue. Animals were also acclimated to o 0 0 static temperatures (20 C, 25 c, 30 C) corresponding to the high, low and mid-ooint temperatures of the cycle. All groups were sampled at 03:00, 09:00, 15:00 and 21:00 hr. Hemoglobin content and packed cell volume, as well as electrolyte and 'water levels were determined for each animal and red cell ion concentrations and ion : hemoglobin ratios estimated. Cycled animals were distinct from those at constant temperatures in several respects. Hematological parameters were elevated above those of animals at constant temperature and were, on a diurnal basis, more stable. Red blood cell electrolyte levels varied in an adaptively appropriate fashion to cycle temperatures. This was not the case in the constant temperature groups_ Under the cycling regime, plasma ion levels were more diurnally stable than those of constant temperature fish. Although muscle parameters in cycled fish exhibited more fluctuation than was observed in plasma, these also tended to be relatively more stable than was the caseErythrocytic data are discussed in terms of their effects on hemoglobin-oxygen affinity while plasma and muscle observations were considered from the standpoint of overall water-electrolyte balance. In general, cycled fish appeared to be capable of stabilizing overall body fluid composition, while simultaneously effecting adaptively-appropriate modifications in the erythrocytic ionic microenvironment of hemoglobin. The sometimes marked diurnal variability of water-electrolyte status in animals held at constant temperature as opposed to the conservation of cycled fish suggests that this species is, in some fashion, programmed for regulation in a thermally-fluctuating environment. If this interpretation is valid and a phenomenon of general occurrence, some earlier studies involving constant acclimation of eurythermal species normally occupying habitats which vary in temperature on a daily basis may require reconsideration. at constant temperature.

The effects of static and diurnally-cycling temperature acclimations on thermal tolerances of rainbow trout, Salmo gairdneri

:ofiedian lethal temperatures ( LT50' s ) were determined for rainbow trout, Salmo gairdnerii, acclimated for a minimum of 21 days at 5 c onstant temperatures between 4 and 20 0 C. and 2 diel temperature fluctuations ( sinewave curves of amplitudes ± 4 and ± 7 0 C. about a mean temperature of 12 0 C. ) . Twenty-four-, 48-, and 96-hour LT50 estimates were c alculated f ollowing standard flow-through aquatic bioassay techniques and probi t transformation of mortality data. The phenomenon of delayed thermal mortality was also investigated. Shifts in upper incipient lethal temperature occurred as a result of previous thermal conditioning. It was shown that increases in constant acclimation temperature result in proportional l inear increases in thermal tolerances. The increase i n estimated 96-hour LT50's was approximately 0.13 0 c. X 1 0 C:1 between 8 and 20 0 C. The effect of acclimation to both cyclic temperature regimes was an increase in LT50 to values between the mean and maximum constant equivalent daily temperatures of the cycles. Twenty-four-, 48-, and 96-hour LT50 estimates of both cycles corresponded approximately to the LT50 values of the 16 0 C. c onstant temperature equivalent . This increase i n thermal tolerance was further demonstrated by the delayed thermal mortality experiments . Cycle amplitudes appeared to i nfluence thermal resistance through alterations in initi al mortality since mortality patterns characteristic of base temperature acclimations re-appeared after approximately 68 hours exposure to test temperatures for the 12 + 4 0 C. group, whereas mortality patterns stabilized and remained constant for a period greater than 192 hours with the larger therma l cycle ( 12 + 7 0 C. ). NO s ignificant corre lations between s pecimen weight and time-to-death was apparent. Data are discussed in relation to the establishment of thermal criteria for important commercial and sport fishes , such as the salmonids , as is the question whether previously reported values on lethal temperature s may have been under estimated.

Role of family eating practices on daily nutrient intakes, dietary patterns and measures of body composition in peri-adolescents

Although family eating practices (FEPs) playa role in the formation of eating practices in children, there is a lack of evidence regarding the role of FEPs on obesity (DB) risk. The purpose of this thesis was to assess the role of child, mother 'and father eating practices (CEPs; MEPS; FaEPs) on nutrient intakes, dietary patterns and body composition. Data were collected on approximately 2,400 peri-adolescents (s250 with complete covariate data). Dietary patterns were assessed using scores that reflected how closely participants followed DASH and Health Canada (HC) recommendations. In girls, poor CEPs, MEPs and FaEPs were associated with increased BMI and risk of overweight and poor dietary patterns according to DASH, and DASH and HC, respectively. In boys, poor CEPs and FaEPs were associated with increased monounsaturated and trans fat, and Vitamin C intakes, respectively. These findings suggest FEPs are associated with DB risk, particularly in girls.

The effects of altered heat stress on voluntary pacing strategies during prolonged cycling

Central Governor Model (CGM) suggests that perturbations in the rate of heat storage (AS) are centrally integrated to regulate exercise intensity in a feed-forward fashion to prevent excessive thermal strain. We directly tested the CGM by manipulating ambient temperature (Tam) at 20-minute intervals from 20°C to 35°C, and returning to 20°C, while cycling at a set rate of perceived exertion (RPE). The synchronicity of power output (PO) with changes in HS and Tam were quantified using Auto-Regressive Integrated Moving Averages analysis. PO fluctuated irregularly but was not significantly correlated to changes in thermo physiological status. Repeated measures indicated no changes in lactate accumulation. In conclusion, real time dynamic sensation of Tam and integration of HS does not directly influence voluntary pacing strategies during sub-maximal cycling at a constant RPE while non-significant changes in blood lactate suggest an absence of peripheral fatigue.

Trading nitrogen for carbon: Nitrogen and carbon translocation in a plant/fungal (Metarhizium spp.) symbiosis

While nitrogen is critical for all plants, they are unable to utilize organically bound nitrogen in soils. Therefore, the majority of plants obtain useable nitrogen through nitrogen fixing bacteria and the microbial decomposition of organic matter. In the majority of cases, symbiotic microorganisms directly furnish plant roots with inorganic forms of nitrogen. More than 80% of all land plants form intimate symbiotic relationships with root colonizing fungi. These common plant/fungal interactions have been defined largely through nutrient exchange, where the plant receives limiting soil nutrients, such as nitrogen, in exchange for plant derived carbon. Fungal endophytes are common plant colonizers. A number of these fungal species have a dual life cycle, meaning that they are not solely plant colonizers, but also saprophytes, insect pathogens, or plant pathogens. By using 15N labeled, Metarhizium infected, wax moth larvae (Galleria mellonella) in soil microcosms, I demonstrated that the common endophytic, insect pathogenic fungi Metarhizium spp. are able to infect living soil borne insects, and subsequently colonize plant roots and furnish ts plant host with useable, insect-derived nitrogen. In addition, I showed that another ecologically important, endophytic, insect pathogenic fungi, Beauveria bassiana, is able to transfer insect-derived nitrogen to its plant host. I demonstrated that these relationships between various plant species and endophytic, insect pathogenic fungi help to improve overall plant health. By using 13C-labeled CO2, added to airtight plant growth chambers, coupled with nuclear magnetic resosnance spectroscopy, I was able to track the movement of carbon from the atmosphere, into the plant, and finally into the root colonized fungal biomass. This indicates that Metarhizium exists in a symbiotic partnership with plants, where insect nitrogen is exchanged for plant carbon. Overall these studies provide the first evidence of nutrient exchange between an insect pathogenic fungus and plants, a relationship that has potentially useful implications on plant primary production, soil health, and overall ecosystem stability.