The neuroendocrinology of ingestive behavior is a topic central to human health, particularly in light of the prevalence of obesity, eating disorders, and diabetes. The study of food intake in ...laboratory rats and mice has yielded some useful hypotheses, but there are still many gaps in our knowledge. Ingestive behavior is more complex than the consummatory act of eating, and decisions about when and how much to eat usually take place in the context of potential mating partners, competitors, predators, and environmental fluctuations that are not present in the laboratory. We emphasize appetitive behaviors, actions that bring animals in contact with a goal object, precede consummatory behaviors, and provide a window into motivation. Appetitive ingestive behaviors are under the control of neural circuits and neuropeptide systems that control appetitive sex behaviors and differ from those that control consummatory ingestive behaviors. Decreases in the availability of oxidizable metabolic fuels enhance the stimulatory effects of peripheral hormones on appetitive ingestive behavior and the inhibitory effects on appetitive sex behavior, putting a new twist on the notion of leptin, insulin, and ghrelin “resistance.” The ratio of hormone concentrations to the availability of oxidizable metabolic fuels may generate a critical signal that schedules conflicting behaviors, e.g., mate searching vs. foraging, food hoarding vs. courtship, and fat accumulation vs. parental care. In species representing every vertebrate taxa and even in some invertebrates, many putative “satiety” or “hunger” hormones function to schedule ingestive behavior in order to optimize reproductive success in environments where energy availability fluctuates.
•Hormones that control food intake in mammals do so in species from all vertebrate taxa.•Hormones that control food intake have greater effects on appetitive than consummatory behaviors.•Hormones that affect hunger for food also affect sexual motivation.•Putative orexigenic and anorectic hormones orchestrate the choice between food and sex.•These hormones optimize reproductive success in environments where energy supplies fluctuate.
The rapid development of potency assays is critical in the development of life-saving vaccines. The traditional plaque assay or fifty percent tissue culture infectious dose (TCID50) assay used to ...measure the potency of live virus vaccines is time consuming, labor intensive, low throughput and with high variability. Described here is the development and qualification of a cell-based reporter potency assay for two vaccines for respiratory viral infection, one based on the recombinant vesicular stomatitis virus (rVSV) backbone, termed Vaccine 1 in this paper, and the other based on the measles virus vector, termed Vaccine 2. The reporter potency assay used a Vero E6 cell line engineered to constitutively express NanuLuc® luciferase, termed the VeroE6-NLuc or JM-1 cell line. Infection of JM-1 cells by a live virus, such as rVSV or measles virus, causes a cytopathic effect (CPE) and release of NanuLuc® from the cytoplasm into the supernatant, the amount of which reflects the intensity of the viral infection. The relative potency was calculated by comparison to a reference standard using parallel line analysis (PLA) in a log–log linear model. The reporter assay demonstrated good linearity, accuracy, and precision, and is therefore suitable for a vaccine potency assay. Further evaluation of the Vaccine 1 reporter assay demonstrated the robustness to a range of deliberate variation of the selected assay parameters and correlation with the plaque assay. In conclusion, we have demonstrated that the reporter assay using the JM-1 cell line could be used as a potency assay to support the manufacturing and release of multiple live virus vaccines.
Abstract We tested the hypothesis that the effects of food restriction on behavioral motivation are mediated by one or both of the RFamides, RFamide-related Peptide-3 (RFRP-3) and kisspeptin (Kp) in ...female Syrian hamsters ( Mesocricetus auratus ). Female hamsters fed ad libitum and given a choice between food and adult male hamsters are highly motivated to visit males instead of food on all four days of the estrous cycle, but after 8 days of mild food restriction (75% of ad libitum intake) they shift their preference toward food every day of the estrous cycle until the day of estrus, when they shift their preference back toward the males. In support of a role for RFRP-3 in these behavioral changes, the preference for food and the activation of RFRP-3-immunoreactive (Ir) cells in the dorsomedial hypothalamus (DMH) showed the same estrous cycle pattern in food-restricted females, but no association was observed between behavior and the activation of Kp cells in the hypothalamic arcuate nucleus or preoptic area. Next, we tested the hypothesis that food-restriction-induced activation of RFRP-3-Ir cells is modulated by high levels of ovarian steroids at the time of estrus. In support of this idea, on nonestrous days, mild food restriction increased activation of RFRP-3-Ir cells, but failed to do so on the day of estrus even though this level of food restriction did not significantly decrease circulating concentrations of estradiol or progesterone. Furthermore, in ovariectomized females, food-restriction-induced increases in activation of RFRP-3-Ir cells were blocked by systemic treatment with progesterone alone, estradiol plus progesterone, but not estradiol alone. Central infusion with RFRP-3 in ad libitum -fed females significantly decreased sexual motivation and produced significant increases in 90-minute food hoarding, in support of the hypothesis that elevated central levels of RFRP-3 are sufficient to create the shift in behavioral motivation in females fed ad libitum . Together, these results are consistent with the hypothesis that high levels of ingestive motivation are promoted during the nonfertile phase of the estrous cycle by elevated activation of RFRP-3-Ir cells, and RFRP-3-Ir cellular activation is modulated by ovarian steroids around the time of estrus, thereby diverting attention away from food and increasing sexual motivation.
Ingestive and sex behaviors are important for individual survival and reproductive success, but when environmental energy availability is limited, individuals of many different species make a ...trade-off, forfeiting sex for ingestive behavior. For example, food-deprived female Syrian hamsters (Mesocricetus auratus) forego vaginal scent marking and lordosis (sex behaviors) in favor of foraging, hoarding, and eating food (ingestive behavior). Reproductive processes tend to be energetically costly, and individual survival requires homeostasis in metabolic energy. Thus, during energetic challenges, the chances of survival are enhanced by decreasing the energy expended on reproductive processes. The entire hypothalamic-pituitary-gonadal (HPG) system is inhibited by severe energetic challenges, but comparatively little is known about the effects of mild energetic challenges. We hypothesized that (1) a trade-off is made between sex and ingestive behavior even when the level of food restriction is insufficient to inhibit the HPG system; (2) mild energetic challenges force a trade-off between appetitive ingestive and sex behaviors, but not consummatory versions of the same behaviors; and (3) the trade-off is orchestrated by ovarian steroid modulation of RFamide-related peptide 3 (RFRP-3). In other species, RFRP-3, an ortholog of avian gonadotropin-inhibitory hormone, is implicated in control of behavior in response to energetic challenges and stressful stimuli. In support of our three hypotheses, there is a “dose-response” effect of food restriction and re-feeding on the activation of RFRP-3-immunoreactive cells in the dorsomedial hypothalamus and on appetitive behaviors (food hoarding and sexual motivation), but not on consummatory behaviors (food intake and lordosis), with no significant effect on circulating levels of estradiol or progesterone. The effect of food restriction on the activation of RFRP-3 cells is modulated at the time of estrus in gonadally-intact females and in ovariectomized females treated with progesterone alone or with estradiol plus progesterone. Intracerebral treatment with RFRP-3 results in significant decreases in sexual motivation and results in significant but small increases in food hoarding in hamsters fed ad libitum. These and other results are consistent with the idea that ovarian steroids and RFRP-3 are part of a system that orchestrates trade-offs in appetitive behaviors in environments where energy availability fluctuates.
This article is part of a Special Issue “Energy Balance”.
In female Syrian hamsters (Mesocricetus auratus), low circulating levels of ovarian steroids are associated with increased food hoarding and ...decreased sexual motivation, but these effects are exaggerated in food-restricted females. To determine whether cold ambient temperature has the same effects as food restriction, groups of hamsters were fed ad libitum while they were housed at either 5°C or 22°C, and then tested for behavior for 90min on each day of the estrous cycle. In females housed at 22°C, high levels of sexual motivation and low levels of food hoarding were seen every day of the estrous cycle. In females housed at 5°C, high levels of sexual motivation were restricted to the periovulatory day. On the three nonestrous days, these females showed high levels of food hoarding, but not food intake. A separate cohort of females were provided with access to running wheels and housed at 22°C. They showed high levels of sexual motivation restricted to the periovulatory day, similar to the pattern of sexual motivation seen in cold-housed females. Unlike cold-housed females, those with running wheels showed low levels of food hoarding and high levels of food intake. Food restriction, cold housing, and access to wheels had no significant effect on plasma estradiol or progesterone concentrations, but significantly decreased plasma leptin concentrations. All three energetic challenges unmask estrous cycle fluctuations in sexual motivation that are obscured in laboratory conditions, i.e., isolation in a small cage with an overabundance of food.
•Estrous cycle fluctuations in behavior were magnified by two different energetic challenges.•Sexual motivation was inhibited and food hoarding was stimulated by cold housing.•Sexual motivation was inhibited and food intake was stimulated by housing with wheels.•Increases in energy expenditure unmask estrous cycle effects on behavior.
Reproduction and energy metabolism are linked, and the interaction between these two biological systems is important for understanding obesity, infertility, sexual dysfunction, and eating disorders. ...Little is known about energy-reproduction interactions in natural systems, but understanding the underlying neuroendocrine mechanisms in biologically relevant contexts will be essential for understanding disease. This might be particularly true for diseases that are the result of human-made environments, such as modern, western, industrialized societies in which food is readily available with no energy expenditure required to procure this food. Obesity, diabetes, and metabolic syndrome are rampant in such societies and there are sex differences in the incidence of these diseases that have been linked to reproductive hormones. My work examines the basic biology of the link between energy intake, storage, and expenditure, and reproduction. In the laboratory model system that I study, the Syrian hamster ( Mesocricetus auratus), reproductive and ingestive behaviors fluctuate over the ovulatory cycle, and these behavioral fluctuations are amplified by mild deficits in energy availability. For example, in female hamsters, mild food restriction (75% of ad libitum intake) increases food hoarding and decreases the preference for spending time with males vs. spending time with food, but only on days of the estrous cycle when ovarian steroid secretion is relatively low. These particular behaviors (food hoarding and spending time with males) provide a window into motivation, and the data suggest that there is an important interaction between hormones and energy metabolism that controls these two behaviors. It is possible that effects of hormones on behavior are masked by the overabundance of food, an effect that would be expected to occur in women from western, industrialized nations who do not limit their food intake. It is not known, however, how food availability interacts with the hormones of the estrous cycle to set behavioral priorities. I therefore examined the interaction of energy availability with ovarian steroid hormones to rank the motivation to engage in ingestive or reproductive behavior. This work is unique in that it examines behavior under semi-natural conditions that mimic important aspects of the natural environment. I used a simulated burrow system, which had been used previously by members of the Schneider laboratory to demonstrate that hormonally-controlled fluctuations in the choice between ingestive and sex behaviors are amplified by food restriction. In Chapter 2, I extended the list of amplifying factors to include not only food restriction, but also exercise and cold ambient temperature, showing that hormonal effects on behavior are responsive to the general availability of metabolic fuels as determined by not only energy intake, but also energy expenditure and storage. I further hypothesized that interactions between energy availability and ovarian steroid hormones would be related to 1) circulating levels of estradiol but not progesterone, 2) circulating levels of the peripheral adipocyte hormone, leptin (a hormone thought to decrease food intake), and 3) cellular activation of gonadotropin inhibiting hormone (GnIH) and/or kisspeptin (Kp) (peptides thought to increase and decrease food intake respectively). Thus, in Chapter 3, adult female Syrian hamsters were mildly food restricted or fed ad libitum, and behavior and cellular activation measured over the estrous cycle. Activation of GnIH and Kp cells was determined by double immunohistochemical staining so that I could co-localize each of these peptides with Fos, the protein product of the immediate-early gene, c-fos. Double-label staining for Fos and GnIH, for example, is a marker for activation of cells that synthesize GnIH. I determined that effects of food restriction on behavior were not associated with changes in the activation of Kp cells; were not associated with circulating levels of estradiol and progesterone; were not associated with the action of ovarian steroids on Kp cells, and were not associated with ovarian steroid effects on circulation concentrations of leptin; although plasma leptin concentrations were significantly decreased by all metabolic challenges, food restriction, cold ambient temperatures, and housing with running wheels. Effects of energy availability on behavior were closely associated with changes in the activation of GnIH cells in the dorsomedial nucleus of the hypothalamus (DMH). In female Syrian hamsters, food restriction significantly elevated activation of GnIH-immunoreactive (ir) cells in the DMH only on infertile days of the estrous cycle. Increases in activation of GnIH-ir were blocked by peripheral treatment with progesterone alone, estradiol plus progesterone, but not estradiol alone (refuting my original hypothesis, and pointing instead to progesterone). These experiments yielded correlational evidence for the effects of GnIH on appetitive ingestive and sex behaviors, as well as for estrous cycle and exogenous steroid modulation of the activation of GnIH cells. I went beyond correlation to manipulate GnIH action to try and determine whether this hormone is necessary and/or sufficient for appetitive ingestive and/or sex behaviors. In Chapter 4, in ad libitum-fed females, intracerebroventricular infusion with GnIH significantly decreased appetitive reproductive behavior (preference for males and courtship scent marking) and increased appetitive ingestive behavior (food hoarding). Thus, elevated levels of GnIH within the brain are sufficient to increase food hoarding or inhibit sexual motivation even when the animal is well nourished. Together, the data are in line with the idea that energetic challenges increase GnIH cellular activation, and perhaps other peptide systems, that occurs during the early follicular phase of the estrous cycle when ovarian steroid concentrations are low. GnIH is one peptide that predisposes females toward vigilant food hoarding and eating food prior to mating, ensuring that if pregnancy occurs there will be ample energy to support the energetically costly process of lactation. Later in the estrous cycle as ovulation nears, the high levels of progesterone that occur in the brain at the time of ovulation switch behavioral priorities-in part by preventing food restriction-induced activation of GnIH cells, and presumably decreasing GnIH secretion. More specifically, food restriction-induced increases in GnIH secretion make food hoarding a priority over reproductive behaviors when fertility is low, and high levels of brain progesterone can overcome the effects of GnIH when fertility is high. I have therefore uncovered some of the neuroendocrine steps involved in the control of behavioral priorities that might optimize reproductive success in environments where energy supply and demand fluctuate.
ABSTRACT
Parathyroid hormone (PTH) has a significant role as an anabolic hormone in bone when administered by intermittent injection. Previous microarray studies in our laboratory have shown that the ...most highly regulated gene, monocyte chemoattractant protein‐1 (MCP‐1), is rapidly and transiently induced when hPTH(1‐34) is injected intermittently in rats. Through further in vivo studies, we found that rats treated with hPTH(1‐34) showed a significant increase in serum MCP‐1 levels 2 hours after PTH injection compared with basal levels. Using immunohistochemistry, increased MCP‐1 expression in osteoblasts and osteocytes is evident after PTH treatment. PTH also increased the number of marrow macrophages. MCP‐1 knockout mice injected daily with hPTH(1‐34) showed less trabecular bone mineral density and bone volume compared with wild‐type mice as measured by peripheral quantitative computed tomography (pQCT) and micro‐computed tomography (µCT). Histomorphometric analysis revealed that the increase in osteoclast surface and osteoclast number observed with intermittent PTH treatment in the wild‐type mice was completely eliminated in the MCP‐1 null mice, as well as much lower numbers of macrophages. Consequently, the lack of osteoclast and macrophage activity in the MCP‐1 null mice was paralleled by a reduction in bone formation. We conclude that osteoblast and osteocyte MCP‐1 expression is an important mediator for the anabolic effects of PTH on bone.
The Dog Aging Project is a long-term longitudinal study of ageing in tens of thousands of companion dogs. The domestic dog is among the most variable mammal species in terms of morphology, behaviour, ...risk of age-related disease and life expectancy. Given that dogs share the human environment and have a sophisticated healthcare system but are much shorter-lived than people, they offer a unique opportunity to identify the genetic, environmental and lifestyle factors associated with healthy lifespan. To take advantage of this opportunity, the Dog Aging Project will collect extensive survey data, environmental information, electronic veterinary medical records, genome-wide sequence information, clinicopathology and molecular phenotypes derived from blood cells, plasma and faecal samples. Here, we describe the specific goals and design of the Dog Aging Project and discuss the potential for this open-data, community science study to greatly enhance understanding of ageing in a genetically variable, socially relevant species living in a complex environment.
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