Rett syndrome is a neurodevelopmental disorder that is predominately caused by mutations of the MECP2 gene. As neuronal apoptosis is not observed in RTT patients and MeCP2-deficient mice, the neurological deficits may be reversible. To address this, we reactivated MeCP2 expression ubiquitously in MeCP2-deficient mice after symptom onset. Our results showed that life span, behavioural performances, EEG activity, thermoregulation, and daily rhythmic activity were significantly improved after MeCP2 reactivation. Furthermore, the extent of improvement was dependent upon the efficiency of MeCP2 reactivation. To assess the role of the catecholaminergic system in Rett syndrome pathophysiology, we selectively preserved MeCP2 function within tyrosine hydroxylase expressing cells. We observed a significant improvement in the life span of male rescue mice and reduced sudden unexplained death rates in female rescue mice. Behavioural performances and EEG patterns were also significantly improved.

Rett syndrome is a neurodevelopmental disorder that is predominately caused by mutations of the MECP2 gene. As neuronal apoptosis is not observed in RTT patients and MeCP2-deficient mice, the neurological deficits may be reversible. To address this, we reactivated MeCP2 expression ubiquitously in MeCP2-deficient mice after symptom onset. Our results showed that life span, behavioural performances, EEG activity, thermoregulation, and daily rhythmic activity were significantly improved after MeCP2 reactivation. Furthermore, the extent of improvement was dependent upon the efficiency of MeCP2 reactivation. To assess the role of the catecholaminergic system in Rett syndrome pathophysiology, we selectively preserved MeCP2 function within tyrosine hydroxylase expressing cells. We observed a significant improvement in the life span of male rescue mice and reduced sudden unexplained death rates in female rescue mice. Behavioural performances and EEG patterns were also significantly improved.

This thesis examined why NCAA Division 1 American football “linemen” experience greater heat strain than “backs” during summer training camps. In study #1, exercise at a heat production of 350 W/m2 in a hot environment (Tdb:32.4±1.0ºC; Twb:26.3±0.6ºC) resulted in greater local sweating on the upper body (head, arm, shoulder and chest; all <0.05) and a greater core temperature (P=0.033) in linemen despite a ~25% lower heat production per unit mass (L:6.0±0.5 W/kg; B:8.2±0.8 W/kg). In study #2, greater convective and evaporative heat transfer coefficients (P<0.05) were found in backs during live summer training camp drills, but these did not lead to a greater dry heat transfer or evaporative capacity. However, the maximum metabolic rate per unit mass was lower in linemen due to differences surface area-to-mass ratio. In conclusion, the greater heat strain previously reported in linemen likely arises, in part, from differences in sweating efficiency and body morphology.

Maintaining thermal balance is essential for all homeotherms but can be especially challenging for pinnipeds which must regulate over a variety of ambient temperatures and habitats as part of their life history. Young pinnipeds, with their immature physiology and inexperience, have the additional expense of needing to allocate energy for growth while still dealing with a thermally stressful aquatic environment. With the immense environmental and physiological pressures acting on juvenile age-classes, declines in prey resources would be particularly detrimental to survival. The goal of the present study was to examine the metabolic and thermoregulatory capabilities of juvenile Steller sea lions to better understand how changing prey resources indirectly impact juvenile age classes. Data collected from captive Steller sea lions suggest that changes in body mass and body composition influence the thermoregulatory capabilities of smaller sea lions in stationary and flowing water. Serial thermal images taken of sea lions after emergence from the water show vasoconstriction of the flippers compared to the body trunk to help minimize heat loss. Despite this ability to vasoconstrict, sea lions in poor body condition displayed a reduced tolerance for colder water temperatures, suggesting that decreases in prey availability which affect insulation may limit survival in younger sea lions. If reductions in prey availability (i.e., nutritional stress) were impacting western Alaskan populations, a reduction in energetic expenditures would be expected in these animals to cope. Measures of resting metabolism in juvenile free-ranging Steller sea lions across Alaska showed no differences between eastern and western capture locations, suggesting no evidence of metabolic depression in declining western stocks of sea lions. Finally, thermal costs predicted by a thermal balance model were compared to actual costs measured in the present study. Model output reliably predicted thermoregulatory costs for juvenile Steller sea lions under certain environmental conditions. Basic physiological measurements combined with the predictive power of modeling will allow for greater exploration of the environmental constraints on juvenile Steller sea lions and identify directions of future study.

Our aim was to understand mechanisms responsible for excessive electrolyte loss in the sweat gland and the potential impact on fluid balance during exercise in heat stress conditions. Human physiological testing under exercise/heat stress and immunofluorescence staining of sweat glands from skin biopsies were compared between healthy individuals (with normal and high sweat sodium chloride concentration, [NaCl]) and with cystic fibrosis patients (CF), who exhibit excessively salty sweat due to a defect of Cl- channel cystic fibrosis transmembrane conductance regulator (CFTR). Three novel findings are presented. First, excessively salty sweat may be associated with reduced expression of CFTR in the sweat gland reabsorptive duct of healthy individuals in addition to in those with CF; however, although a link to a CF gene mutation in healthy individuals with high sweat [NaCl] was not demonstrated, the possibility of an undetected CFTR mutation or polymorphism remains to be investigated as an underlying mechanism. Two, CF and healthy individuals with excessively salty sweat respond to moderate dehydration (3% body weight loss during exercise) with an attenuated rise in serum osmolality, greater relative loss in plasma volume, but similar perceived thirst compared to healthy individuals with "normal" sweat [NaCl]. However, individuals with CF respond to rehydration with hypotonic beverage by drinking less ad libitum in response to reduced serum [NaCl], suggesting that thirst-guided fluid replacement may be more appropriate for this population rather than restoring 100% of sweat loss following dehydration as is often recommended in healthy individuals.

Investigating alternate winter refuges for Florida manatees is increasingly important as sustained warm-water discharges from industrial and some natural sites becomes more uncertain. This study examined habitat features of possible importance to manatees by comparing a winter refuge in Charlotte Harbor, FL (the Matlacha Isles canal system) to two nearby, seemingly similar sites that are not frequented by manatees during winter. Water temperature, salinity, boat traffic, canal depth, and tidal flushing were assessed at these sites. Additionally, this study examined when and how manatees use the Matlacha Isles refuge by documenting movements, habitat use, and behaviors of manatees during the winters of 1999/2000 through 2001/2002. Water temperatures had a profound influence on manatee selection of Matlacha Isles over the two comparison canal systems. Matlacha Isles did not experience the sudden drops in water temperature following cold fronts, extreme low temperatures, or long periods of temperatures below manatees’ reported thermal tolerance of 18-20 oC that were recorded in Matlacha Pass (ambient) and the two comparison canal systems. Heat retention within Matlacha Isles may be associated with greater water depth and lower tidal flushing. Salinity and boat traffic did not seem to influence site selection by manatees. During moderately cold weather, manatees occupying Matlacha Isles forage at night in nearby Matlacha Pass and return early in the morning to Matlacha Isles, where they primarily rest all day. Neither tidal state nor boat traffic levels affected manatee travel patterns into or out of Matlacha Isles. Manatees may passively thermoregulate in the warmer waters of Matlacha Isles during the day (when they are inactive) and sustain their body temperatures at night through the heat generated during traveling to feeding sites and during ingestion (chewing) and digestion. During extreme or prolonged cold weather, Matlacha Isles provides inadequate warmth for manatees; during such times, most of them travel to a power plant on the Orange River, approximately 50 kilometers away. Findings from this study may inform resource managers as they consider attributes manatees find desirable or necessary in winter. Such information will help managers create new or enhance existing winter refuges to protect manatees.

This study investigated the effects of progressive dehydration by 1.5-2.0% body mass (BM) (NF) on core temperature (Tc), heart rate (HR), on-ice performance, and mental fatigue during a 70-min scrimmage, compared to maintaining BM with a carbohydrate-electrolyte solution (CES). Compared to CES, Tc was significantly higher throughout the scrimmage in NF. Players in NF had reduced mean skating speed and time at high effort between 30-50 min of the scrimmage. Players in NF committed more puck turnovers and completed a lower percentage of passes in the last 20 min of play. Post-scrimmage shuttle skating time was higher in NF. Hockey fatigue questionnaire total score and Profile of Mood States fatigue score was higher in NF. The results indicate that mild dehydration compared to maintaining BM with a CES resulted in increased Tc, decreased skating and puck handling performance, and increased mental fatigue during an ice hockey scrimmage. / Gatorade Sports Science Institute, Natural Sciences and Engineering Research Council of Canada

<p>Southern Africa harbours one-third of the world&rsquo / s Testudinid species, many of which inhabit arid or semi-arid areas, but ecological information on these species is scant. I studied the habitat, morphology and ecology of Kalahari tent tortoises over 13 months in semi-arid Savanna at Benfontein farm, Northern Cape Province, South Africa. In order to allow continuous monitoring of individuals, I attached radiotransmitters to males and females, split equally between two habitats, sites E (east) and W (west), with apparent differences in vegetation structure. Results of the study were based on data obtained from 27 telemetered tortoises and 161 individuals encountered opportunistically. Female Kalahari tent tortoises were larger than males and the sex ratio did not differ from 1:1. Based on person-hours to capture tortoises, the population appeared to have a low density, with more time required to capture a juvenile (35 hours) than an adult (10-11 hours). The frequency distribution of body size ranges was indicative of recruitment. Relative age, based on annuli counts, suggested that males were younger than females, perhaps because males as the smaller sex are more predation-prone than females. Linear relationships between annuli counts and shell volume indicated that, after reaching sexual maturity, female body size increased faster in volume than did male body size, possibly because a larger volume may enhance female reproductive success. Body condition differed between sites, sexes and among seasons. The hot and dry summer may account for low summer body condition, whereas vegetation differences and size effects, respectively, may account for the low body condition of tortoises in site W and in males. Site E was sandy with grasses, particularly Schmidtia pappophoroides, being the prevalent growth form. This habitat resembled a Savanna vegetation type Schmidtia pappophoroides &ndash / Acacia erioloba described for a neighbouring reserve. Site W was stonier, dominated by shrubs, and was reminiscent of Northern Upper Karoo vegetation (NKu3). Neither site resembled Kimberley Thornveld (SVk4), the designated vegetation type of the area. Differences in substrate and grazing intensity may have contributed to site vegetation differences. Rainfall had an important influence on seasonal vegetation. Short grass abundance correlated with rainfall and annual plants sprouted after spring rain. Refuge use changed according to season and sex. Males selected denser refuges than females did, perhaps because males were smaller and more vulnerable to predation and solar heat. Tortoises selected sparse, short grass as refuges in cool months, probably to maximise basking whilst remaining in protective cover. During hot periods, mammal burrows were preferred to vegetation as refugia. The smaller males spent more time in cover than females, which may be related to predator avoidance or thermoregulation.&nbsp / Females spent more time basking than males, perhaps due to their larger size and to facilitate reproductive processes. Tortoises did not brumate, but through a combination of basking, and orientation relative to the sun in their refuges, managed to attain body temperatures that allowed small bouts of activity. Body temperature for active tortoises was similar among seasons, and was higher for more specialised active behaviours, such as feeding and socialising, than for walking. Increased activity by males in spring could relate to mating behaviour while females were more active in autumn, when they foraged more than males, perhaps due to the high cost of seasonal reproductive requirements. Males displaced further per day than did females, but home range estimates did not differ between sexes. Annual home range estimates varied substantially among individuals: 0.7&ndash / 306 ha for minimum convex polygons and 0.7&ndash / 181 ha for 95% fixed kernel estimates. The ability to&nbsp / cover large areas would assist tortoises in finding resources, e.g., food, in an area where resource distribution may be patchy. Differences among seasonal home ranges and movements probably reflect seasonal climatic change / activity areas shrinking when temperatures were extreme. In order to assess the effects of a semi-arid environment on the morphology of P. oculifer, I compared its morphology to that of its &lsquo / cool-adapted&rsquo / sister taxon Psammobates geometricus, using live and museum specimens. Both P. oculifer and P. geometricus are sexually dimorphic and differences between the two species could indicate environmental or sexual selection effects, or a combination of the two. The shorter bridge length, which allowed more leg space, and wider front feet in P. oculifer cohorts probably represent traits for manoeuvring in a sandy habitat, while wider heads in P. oculifer possibly relate to interspecific differences in diet. The flatter shell in female P. oculifer, relative to P. geometricus, may represent a trade-off between space for reproductive structures, e.g., eggs, and the need to fit into small refuges, e.g., mammal burrows. Male P. oculifer had wider shells, more space around their hind legs, and wider hind feet than P. geometricus males had, all characteristics which may assist males to fight and mate in a sandy environment.</p>

Studies show that vasomotor and sudomotor activity is compromised in individuals with Type 1 Diabetes (T1DM) which could lead to altered thermoregulatory function. However, recent work suggests that the impairments may only be evidenced beyond a certain level of heat stress. We therefore examined T1DM-related differences in heat loss responses of sweating and skin blood flow (SkBF) during exercise performed at progressive increases in the requirement for heat loss. Participants were matched for age, sex, body surface area and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W•m-2 of body surface area, each rate being performed sequentially for 30 min. Local sweat rate (LSR), sweat gland activation (SGA), and sweat gland output (SGO) were measured on the upper back, chest and forearm while SkBF (laser-Doppler) was measured on the forearm and upper back only. We found that despite a similar requirement for heat loss, LSR was lower in T1DM on the chest and forearm only, relative to Control and only different at the end of the second and third exercise periods. Differences in chest LSR were due to reduced SGA whereas the decreased forearm LSR was the result of a decrease in SGO. SkBF did not differ between groups. The reduction in the sweating response in the T1DM group was paralleled by a greater increase in core temperature. We show that T1DM impairs heat dissipation as evidenced by reductions in LSR and not SkBF. A compromised thermoregulatory response during and following physical exertion is of considerable concern due to the associated increased risk of post-exertion heat-related injury.

This thesis examined why NCAA Division 1 American football “linemen” experience greater heat strain than “backs” during summer training camps. In study #1, exercise at a heat production of 350 W/m2 in a hot environment (Tdb:32.4±1.0ºC; Twb:26.3±0.6ºC) resulted in greater local sweating on the upper body (head, arm, shoulder and chest; all <0.05) and a greater core temperature (P=0.033) in linemen despite a ~25% lower heat production per unit mass (L:6.0±0.5 W/kg; B:8.2±0.8 W/kg). In study #2, greater convective and evaporative heat transfer coefficients (P<0.05) were found in backs during live summer training camp drills, but these did not lead to a greater dry heat transfer or evaporative capacity. However, the maximum metabolic rate per unit mass was lower in linemen due to differences surface area-to-mass ratio. In conclusion, the greater heat strain previously reported in linemen likely arises, in part, from differences in sweating efficiency and body morphology.