Candice Klingerman
Department of Biological Sciences
Lehigh University
111 Research Drive
Bethlehem PA, 18015
cmk307@lehigh.edu
(610) 758-5603 |
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Curriculum Vitae
Research Interests:
Why is it when we go to the grocery store hungry, we purchase more food than if we had just consumed a meal? Similarly, why is that some people can stop eating when they feel full while others continue eating beyond satiation? These fundamental questions are of interest to myself and are key to understanding the growing epidemic of obesity.
To understand the mechanisms behind the generation and maintenance of extreme weight gain or loss, I study the feeding and reproductive behaviors of Syrian hamsters (Mesocricetus auratus). What sets this animal apart from other laboratory species (and humans!) is that hamsters generally do not overeat. When Syrian hamsters are given access to food for only 2 hours, they will only consume 10-15% of their daily intake whereas rats will consume a 24 hour ration during the same amount of time (Kutscher, 1969). Why is it that hamsters, unlike other mammals, do not overeat? This mechanism is still poorly understood, but may one day provide a target for novel pharmaceuticals against obesity.
While hamsters are unique with respect to an absence of post-fast hyperphasia, or overeating, they are similar to humans in that when they are hungry, they will increase their external food stores similar to ravenous men and women at the grocery store (Bartness and Clein, 1994). A “stocked pantry” allows the hamster to save food for consumption during another time and it is believed that this behavior may occur in anticipation of another fast. Therefore, food hoarding can be used as a quantitative measure of a hamster’s “appetite” for food.
One problem that arises during periods of reduced energy availability is a reduction in the properties related to reproductive function. Reproductive function relies on reciprocal inputs from the hypothalamic-pituitary-gonadal axis and disruptions in any one of these organs may lead to reproductive failure.
The example that I give and is probably the easiest for the lay person to understand is the termination of the menstrual cycle that occurs in female gymnasts or athletes. It is believed that the menstrual cycle is disrupted because female athletes are exerting more energy than they are able to consume. Energy that is consumed is dedicated towards cellular and respiratory processes critical for survival. Consequently, the energetically-costly processes of reproduction are put on hold until more energy becomes available.
In addition to providing an excellent model for feeding behavior, the female hamster also provides a distinct model of reproductive behavior. Female hamsters have a short, invariable 4-day estrous cycle, with para- and copulatory behaviors occurring consistently on specific days of the estrous cycle. Other laboratory species, including canines and non-human primates, have much longer reproductive cycles, whereas rats have variable estrous cycles lasting from 1.5 to 9 days in length (Mandl, 1951). The consistent and well-characterized estrous cycle of the hamster allows for observations in day to day variation in sexual behavior and circulating sex hormones.
Since it appears that energy availability is capable of affecting reproduction, how can eating and reproductive behaviors be studied simultaneously in the hamster? Hamsters are naturally burrowing animals and will often nest separately from food. By providing female hamsters with a simulated burrow system, we can provide them with opposing tunnels containing an adult male, a food source, or a home cage. We can then quantitatively measure their “appetite” for food or sex by measuring time spent in each location as well as time spent eating or hoarding food, amount of food hoarded or consumed, duration of lordosis, and number of vaginal or flank marks.
Future Research:
While my research thus far has been broad, future projects hope to examine the roles of the orexigenic peptide neuropeptide Y (NPY) and the anorectic, fat-cell secreting peptide leptin and their effects on feeding and sexual behaviors of female hamsters housed in the simulated burrow system.
Background:
I have a Master of Science (MS) degree in Animal Science from the University of Delaware where I studied animal nutrition and manipulated ruminant digestion using amylolytic enzymes to increase milk production and milk components in lactating dairy cows.
Publications:
In Press:
Klingerman, C.M., W. Hu, E.E. McDonell, M.C. DerBedrosian, and L. Kung, Jr. 2009. “An evaluation of exogenous enzymes with amylolytic activity for dairy cows.” J. Dairy Sci. 92:1050-1059.
Submitted for Publication:
Hu, W., R.J. Schmidt, E.E. McDonell, C.M. Klingerman, and L. Kung, Jr. 2009. “The effect of Lactobacillus buchneri 40788 or Lactobacillus planterum MTD-1on the fermentation and aerobic stability of corn silages ensiled at two dry matter contents.” J. Dairy Sci.
References:
Bartness, T.J., and Clein, M.R. 1994. Effects of food deprivation and restriction, and metabolic blockers on food hoarding in Syrian hamsters. Am. J. Physiol. Regulatory. Integrative. Comp. Physiol. 266:1111-1117.
Kutcher, C.L. 1969. Species differences in the interaction of feeding and drinking. Ann. N. Y. Acad. Sci. 157:539-552.
Mandl, A.M. 1951. The phases of oestrous cycle in the adult white rat. J. Exp. Biol. 4:576-584.
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