The subjects of stress and animal welfare are currently attracting immense interest. This book brings together a range of perspectives from biomedical research (including human health and animal ...models of human stress) on stress and welfare, and assesses new approaches to conceptualising and alleviating stress.
Commercial sturgeon farms in California have observed poor spawning performance and ovarian regression in fish maintained at constant 16–20°C water temperatures. The effects of the pre-spawning ...thermal regime on oocyte germinal vesicle migration (GVM), in vitro maturation (GVBD), plasma concentrations of reproductive hormones, and hormonally-induced ovulation in white sturgeon females were examined. Gravid females were exposed to three temperature treatments (seasonal 10–15°C, constant 15°C, and constant 18°C), and ovulation was induced when females reached the responsive stage. While all females (
n=5 per treatment) in the seasonal temperature treatment ovulated and produced fertile eggs, oocyte development (GVM) and ovulation were inhibited in the constant temperature treatments, and follicular atresia ensued in three out of five females exposed to 18°C water temperature. Temperature treatment did not have a significant effect on plasma hormone concentrations throughout the pre-spawning and spawning periods, but plasma concentrations of androgens and oestradiol declined in females that experienced developmental arrest and atresia. The spawning results provided empirical evidence for the negative effects of elevated temperatures on ovulatory response and egg quality. The pre-spawning thermal regime appears to be an important environmental factor for normal ovarian development in cultured white sturgeon and should be considered in management of wild stocks reproducing in rivers with regulated water flows.
Behavioral stress can prevent animals from achieving normal reproductive success. Stressors associated with intensive livestock management may be responsible for reduced reproductive efficiency. ...However, before appropriate management decisions can be made to alleviate the effects of behavioral stress on reproduction, it is necessary to identify the mechanisms by which stress disrupts normal reproduction. The neuroendocrine regulation of follicular development and ovulation requires a complex and delicate interplay between the pituitary gonadotropins and the feedback actions of the major follicular steroid, estradiol. Because of this complexity, the regulation of the follicular stage of the estrous cycle and ovulation is especially vulnerable to the effects of stress. Although the pathophysiological mechanisms by which stress disrupts reproduction are not fully understood, the stress-induced secretion of adrenal glucocorticoids seems to be of special significance because these steroids can effect both the synthesis and secretion of gonadotropins. Of additional importance may be the role of corticotropin-releasing hormone and adrenocorticotropin on the regulation of the hypothalamic-pituitary-gonadal axis.
There is a cost of stress that may result in the loss of normal biological function (e.g., growth). Repeated, and even single, applications of stressors have been shown to induce negative energy ...balance in rodents. However, here we addressed whether this energetic response changes during multiple stress exposure and whether there is complete recovery subsequent to the cessation of stress exposure. These questions were addressed in growing C57Bl/6 mice (31 day) by determining at different times the energetic and endocrine responses after the exposure to restraint (R) stress for 4 h applied once (R1), repeatedly over 3 days (R3), or repeatedly over 7 days (R7). Compared with control values, R elevated (P<0.05) plasma corticosterone and reduced plasma insulin-like growth factor I on all days of exposure to the stressor. Seven days, but not 1 or 3 days of R, decreased the net growth (126%, P<0.05) and deposition of fat (71%, P<0.05) and lean (60%, P<0.05) energy over the 7 days. Only R7 depressed the 7-day metabolizable energy intake (P<0.05), and R7, but not R1 or R3, increased the overall energy expenditure (10%, P<0.05). Our results demonstrate that repeated episodes of stress are energetically costly to the rapidly growing animal, but compensatory mechanisms mitigate this cost of repeated stress exposure and permit complete recovery of energy balance after the cessation of stress application.
To address the hypothesis that multiple stressors can have cumulative effects on the individual, we determined the effects of restraint (R) stress (4 h/day for 7 days), immunological (L) stress ...lipopolysaccharide (LPS) injection, 0.45 microg/g body wt on days 6 and 7, and R + L (RL) on the growth and energetics of C57Bl/6 male mice. R and L each repeatedly increased (P<0.05) circulating corticosterone (>8 times), but RL caused even greater (>250%, P<0. 05) concentrations of circulating corticosterone than did either stressor alone. Only L and RL increased (P<0.05) circulating interleukin-1beta. Although R, L, and RL impaired growth (>75% below controls, P<0.05), RL reduced growth to a greater extent. All stressors inhibited (P<0.05) lean (>33% below controls) and fat (>120% below controls) energy deposition, and like the effects on growth, combined RL stress inhibited lean and fat energy deposition to a greater extent than did either stressor acting alone. These results demonstrated that the summation of multiple stress results in a cumulative cost to the growing animal.
We examined the biological cost of a single episode of acute restraint stress on the growth and energetics of mice, and compared these effects with the effects of stress associated with LPS injection ...and the total cost of experiencing both stressors simultaneously. We monitored growth and energetics over a 24-h period in 31-day-old mice exposed to either 4 h of restraint stress (R), i.p. injection of 0.45 mg/g of lipopolysaccharide (L), or restraint plus L injection (RL). Compared to controls, either restraint or L significantly (
p < 0.05) impaired growth, feed intake, and lean and fat energy deposition. The R and L treatments depressed (>100% lower than controls) body weight change. However, when applied in concert, the effect of restraint and LPS on growth, energy deposition, and feed intake did not summate. All stressors significantly increased circulating corticosterone (
p < 0.05) at 1 and 4 h following the initiation of treatment, and there was no difference between the R, L, or RL treatments. Only L and RL increased (
p < 0.05) circulating IL-1b at 1 and 4 h. LPS injection elevated (
p < 0.05) IL-1b. Although a single episode of behavioral stress altered growth and energy partitioning, LPS-induced cytokine release inhibited energy deposition and growth to a greater extent than behavioral stress (
p < 0.05), and no further suppression of energy deposition or growth occurred when the two stresssors were combined over 24 h.
Considering the importance of its potential implications for human health, agricultural productivity, and ecosystem stability, surprisingly little is known regarding the composition or dynamics of ...the atmosphere's microbial inhabitants. Using a custom high-density DNA microarray, we detected and monitored bacterial populations in two U.S. cities over 17 weeks. These urban aerosols contained at least 1,800 diverse bacterial types, a richness approaching that of some soil bacterial communities. We also reveal the consistent presence of bacterial families with pathogenic members including environmental relatives of select agents of bioterrorism significance. Finally, using multivariate regression techniques, we demonstrate that temporal and meteorological influences can be stronger factors than location in shaping the biological composition of the air we breathe.
Males and females of cultured white sturgeon, Acipenser transmontanus, mature at an average age of 4 and 8 years, respectively. However, the onset of ovarian vitellogenesis and puberty are highly ...asynchronous in the female stock. Gonadal cycles are annual in males and biennial in females, and gametogenesis is influenced by season. Neuroendocrine regulation of reproduction appears to involve a dual gonadotropin system controlling gonadal development and spawning. Labile puberty and sex-specific duration of the gonadal cycle are distinct characteristics of cultured and wild sturgeon. Photoperiod and temperature play a significant role in environmental regulation of the reproductive cycle, but further studies are necessary to elucidate the roles of endogenous and environmental factors in sturgeon reproduction which is critically important for both aquaculture and conservation of endangered wild stocks.
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