Matching Items (5)
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- All Subjects: Obesity
- All Subjects: Peripheral vascular diseases
- Creators: Towe, Bruce
Description
Preliminary studies indicate that the use of dietary menthol may prevent excessive weight gain through the activation of the transient receptor potential melastatin family member 8 (TRPM8) ion channel. It has also been expressed that elevation of the core temperature (Tc) inducing mild hyperthermia via an increase in ambient temperature aids in a marked reduction of the drive to eat and weight gain. While caloric restriction (CR) aims to treat obesity and secondary sicknesses, weight regain is a common result during long term weight maintenance. The goal of these studies was to evaluate and identify if the menthol and mild hyperthermia mechanisms could couple synergistically to reduce or abrogate weight gain. Ambient temperature (Ta) was increased incrementally to identify the threshold in which rodents display mild hyperthermia. Our initial attempts at hyperthermia induction failed because of limitations in the environmental chamber. These trials fail to note a threshold at which elevated Tc is sustained for any period of time. The data suggests an ambient temperature of 36-38 °C would be appropriate to induce a mild hyperthermia. A mild hyperthermia is described as the elevation of Tc 2-3 ° above the hypothalamic set point. To facilitate future hyperthermia studies, an environmental chamber was designed. A wine cooler was converted to withstand the desired temperatures, through the use of heat tape, a proportional controller, and a translucent Plexiglas custom fit door. Beyond leveraging temperature to regulate weight gain, dietary changes including a comparison between standard chow food, high fat diet, and menthol supplemented chow food treatment illustrate a strong likelihood of weight gain variability. In this pilot study, weight gain expression when given a diet supplemented with menthol (1%) showed no statistical significance relative to a high fat diet nor chow food, however, it revealed a trend of reduced weight gain. It is assumed the combination of supplemental menthol and mild hyperthermia induction will exacerbate their effects.
ContributorsJohnsson, Kailin Alexis (Author) / Van Horn, Wade (Thesis director) / Herman, Richard (Committee member) / Towe, Bruce (Committee member) / Sanford School of Social and Family Dynamics (Contributor) / School of Life Sciences (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This is a pilot study testing a new indirect calorimeter device. This project was designed to determine the effect of a high fat versus a standard chow diet and age on the energy gap (the difference between energy intake and energy expenditure). Measurements of energy expenditure and oxygen consumption were obtained over a 23-hour period from a group of rats fed a high fat diet and a group of rats fed standard chow diet. The experiments were repeated during an experimental phase for 12 weeks, a phase of caloric restriction for 4 weeks, and a phase of weight regain for 4 weeks. We found energy expenditure and oxygen consumption to decrease in the caloric restriction phase and increase with excessive weight gain. Rats fed a high fat diet and obesity prone rats had a wider energy gap than rats fed a standard chow diet and obesity resistant rats. The caloric restriction phase closed the energy gap between energy expenditure and energy intake for all of the rats. The weight regain phase shifted the rats back into positive energy balance so that the energy intake was greater than the energy expenditure. The rats showed greater weight gain in the weight regain phase than in the experimental phase for all groups of rats. The indirect calorimeter device would require further testing to improve the accuracy of the measurements of respiratory quotient and carbon dioxide production before being used in future clinical research applications. The indirect calorimeter device has the potential to record respiratory quotient and carbon dioxide production.
ContributorsMolenaar, Sydney Alexandra (Author) / Herman, Richard (Thesis director) / Towe, Bruce (Committee member) / Dean, W.P. Carey School of Business (Contributor) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
Bioimpedance measurements have been long used for monitoring tissue ischemia and blood flow. This research employs implantable microelectronic devices to measure impedance chronically as a potential way to monitor the progress of peripheral vascular disease (PVD). Ultrasonically powered implantable microdevices previously developed for the purposes of neuroelectric vasodilation for therapeutic treatment of PVD were found to also allow a secondary function of tissue bioimpedance monitoring. Having no structural differences between devices used for neurostimulation and impedance measurements, there is a potential for double functionality and closed loop control of the neurostimulation performed by these types of microimplants. The proposed technique involves actuation of the implantable microdevices using a frequency-swept amplitude modulated continuous waveform ultrasound and remote monitoring of induced tissue current. The design has been investigated using simulations, ex vivo testing, and preliminary animal experiments. Obtained results have demonstrated the ability of ultrasonically powered neurostimulators to be sensitive to the impedance changes of tissue surrounding the device and wirelessly report impedance spectra. Present work suggests the potential feasibility of wireless tissue impedance measurements for PVD applications as a complement to neurostimulation.
ContributorsCelinskis, Dmitrijs (Author) / Towe, Bruce (Thesis advisor) / Greger, Bradley (Committee member) / Sadleir, Rosalind (Committee member) / Arizona State University (Publisher)
Created2015
Description
Cardiac tissue engineering has major applications in regenerative medicine, disease modeling and fundamental biological studies. Despite the significance, numerous questions still need to be explored to enhance the functionalities of the engineered tissue substitutes. In this study, three dimensional (3D) cardiac micro-tissues were developed through encapsulating co-culture of cardiomyocytes and cardiac fibroblasts, as the main cellular components of native myocardium, within photocrosslinkable gelatin-based hydrogels. Different co-culture ratios were assessed to optimize the functional properties of constructs. The geometry of the micro-tissues was precisely controlled using micro-patterning techniques in order to evaluate their role on synchronous contraction of the cells. Cardiomyocytes exhibited a native-like phenotype when co-cultured with cardiac fibroblasts as compared to the mono-culture condition. Particularly, elongated F-actin fibers with abundance of sarcomeric α-actinin and troponin-I were observed within all layers of the hydrogel constructs. Higher expressions of connexin-43 and integrin β1 indicated improved cell-cell and cell-matrix interactions. Amongst co-culture conditions, 2:1 (cardiomyocytes: cardiac fibroblasts) ratio exhibited enhanced functionalities, whereas decreasing the construct size adversely affected the synchronous contraction of the cells. Therefore, this study indicated that cell-cell ratio as well as the geometrical features of the micropatterned constructs are among crucial parameters, which need to be optimized in order to enhance the functionalities of engineered tissue substitutes and cardiac patches.
ContributorsSaini, Harpinder (Author) / Nikkhah, Mehdi (Thesis advisor) / Vernon, Brent (Committee member) / Towe, Bruce (Committee member) / Arizona State University (Publisher)
Created2015
Description
Peripheral Vascular Disease (PVD) is a debilitating chronic disease of the lower extremities particularly affecting older adults and diabetics. It results in reduction of the blood flow to peripheral tissue and sometimes causing tissue damage such that PVD patients suffer from pain in the lower legs, thigh and buttocks after activities. Electrical neurostimulation based on the "Gate Theory of Pain" is a known to way to reduce pain but current devices to do this are bulky and not well suited to implantation in peripheral tissues. There is also an increased risk associated with surgery which limits the use of these devices. This research has designed and constructed wireless ultrasound powered microstimulators that are much smaller and injectable and so involve less implantation trauma. These devices are small enough to fit through an 18 gauge syringe needle increasing their potential for clinical use. These piezoelectric microdevices convert mechanical energy into electrical energy that then is used to block pain. The design and performance of these miniaturized devices was modeled by computer while constructed devices were evaluated in animal experiments. The devices are capable of producing 500ms pulses with an intensity of 2 mA into a 2 kilo-ohms load. Using the rat as an animal model, a series of experiments were conducted to evaluate the in-vivo performance of the devices.
ContributorsZong, Xi (Author) / Towe, Bruce (Thesis advisor) / Kleim, Jeffrey (Committee member) / Santello, Marco (Committee member) / Arizona State University (Publisher)
Created2014