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Search Results: 1 - 10 of 145909 matches for " Kathryn F. Medler "
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Diet-Induced Obesity Reduces the Responsiveness of the Peripheral Taste Receptor Cells
Amanda B. Maliphol, Deborah J. Garth, Kathryn F. Medler
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0079403
Abstract: Introduction Obesity is a growing epidemic that causes many serious health related complications. While the causes of obesity are complex, there is conclusive evidence that overconsumption coupled with a sedentary lifestyle is the primary cause of this medical condition. Dietary consumption is controlled by appetite which is in turn regulated by multiple neuronal systems, including the taste system. However, the relationship between taste and obesity has not been well defined. Growing evidence suggests that taste perception in the brain is altered in obese animals and humans, however no studies have determined if there are altered taste responses in the peripheral taste receptor cells, which is the initiation site for the detection and perception of taste stimuli. Methodology/Principal Findings In this study, we used C57Bl/6 mice which readily become obese when placed on a high fat diet. After ten weeks on the high fat diet, we used calcium imaging to measure how taste-evoked calcium signals were affected in the obese mice. We found that significantly fewer taste receptor cells were responsive to some appetitive taste stimuli while the numbers of taste cells that were sensitive to aversive taste stimuli did not change. Properties of the taste-evoked calcium signals were also significantly altered in the obese mice. Behavioral analyses found that mice on the high fat diet had reduced ability to detect some taste stimuli compared to their littermate controls. Conclusions/Significance Our findings demonstrate that diet-induced obesity significantly influences peripheral taste receptor cell signals which likely leads to changes in the central taste system and may cause altered taste perception.
Ryanodine Receptors Selectively Interact with L Type Calcium Channels in Mouse Taste Cells
Michelle R. Rebello, Amanda B. Maliphol, Kathryn F. Medler
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0068174
Abstract: Introduction We reported that ryanodine receptors are expressed in two different types of mammalian peripheral taste receptor cells: Type II and Type III cells. Type II cells lack voltage-gated calcium channels (VGCCs) and chemical synapses. In these cells, ryanodine receptors contribute to the taste-evoked calcium signals that are initiated by opening inositol trisphosphate receptors located on internal calcium stores. In Type III cells that do have VGCCs and chemical synapses, ryanodine receptors contribute to the depolarization-dependent calcium influx. Methodology/Principal Findings The goal of this study was to establish if there was selectivity in the type of VGCC that is associated with the ryanodine receptor in the Type III taste cells or if the ryanodine receptor opens irrespective of the calcium channels involved. We also wished to determine if the ryanodine receptors and VGCCs require a physical linkage to interact or are simply functionally associated with each other. Using calcium imaging and pharmacological inhibitors, we found that ryanodine receptors are selectively associated with L type VGCCs but likely not through a physical linkage. Conclusions/Significance Taste cells are able to undergo calcium induced calcium release through ryanodine receptors to increase the initial calcium influx signal and provide a larger calcium response than would otherwise occur when L type channels are activated in Type III taste cells.
Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25
Tod R Clapp, Kathryn F Medler, Sami Damak, Robert F Margolskee, Sue C Kinnamon
BMC Biology , 2006, DOI: 10.1186/1741-7007-4-7
Abstract: Depolarization with high K+ resulted in an increase in intracellular Ca2+ in a small subset of non-GFP labeled cells of both transgenic mouse lines. In contrast, no depolarization-evoked Ca2+ responses were observed in GFP-expressing taste cells of either genotype, but GFP-labeled cells responded to the PLC activator m-3M3FBS, suggesting that these cells were viable. Whole cell recording indicated that the GFP-labeled cells of both genotypes had small voltage-dependent Na+ and K+ currents, but no evidence of Ca2+ currents. A subset of non-GFP labeled taste cells exhibited large voltage-dependent Na+ and K+ currents and a high threshold voltage-gated Ca2+ current. Immunocytochemistry indicated that SNAP-25 was expressed in a separate population of taste cells from those expressing T1R3 or TRPM5. These data indicate that G protein-coupled taste receptors and conventional synaptic signaling mechanisms are expressed in separate populations of taste cells.The taste receptor cells responsible for the transduction of bitter, sweet, and umami stimuli are unlikely to communicate with nerve fibers by using conventional chemical synapses.Taste buds, the transducing elements of gustatory sensation, contain a heterogeneous population of 50 to 100 elongate taste receptor cells, which extend from the basal lamina to the surface of the epithelium. Taste stimuli interact with receptors on the apical membrane, while the basolateral membranes of some taste cells associate with gustatory nerve fibers to transmit taste information to the brain.Several types of taste cells have been identified morphologically. Type I cells, also known as "dark" cells, generally comprise about half of the taste bud. These cells are not believed to have a receptive function, but to play a more glial-like role in the taste bud [1,2]. About 35% of the cells are Type II cells, which are also known as "light" cells due to the electron lucent nature of their cytoplasm. Type II cells express T1R and T2R taste re
Expression of GABAergic Receptors in Mouse Taste Receptor Cells
Margaret R. Starostik,Michelle R. Rebello,Kellie A. Cotter,Akos Kulik,Kathryn F. Medler
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013639
Abstract: Multiple excitatory neurotransmitters have been identified in the mammalian taste transduction, with few studies focused on inhibitory neurotransmitters. Since the synthetic enzyme glutamate decarboxylase (GAD) for gamma-aminobutyric acid (GABA) is expressed in a subset of mouse taste cells, we hypothesized that other components of the GABA signaling pathway are likely expressed in this system. GABA signaling is initiated by the activation of either ionotropic receptors (GABAA and GABAC) or metabotropic receptors (GABAB) while it is terminated by the re-uptake of GABA through transporters (GATs).
Regular-uniform convergence and the open-open topology
Kathryn F. Porter
International Journal of Mathematics and Mathematical Sciences , 2001, DOI: 10.1155/s0161171201003027
Abstract: In 1994, Bânzaru introduced the concept of regular-uniform, or r-uniform, convergence on a family of functions. We discuss the relationship between this topology and the open-open topology, which was described in 1993 by Porter, on various collections of functions.
Set-set topologies and semitopological groups
Kathryn F. Porter
International Journal of Mathematics and Mathematical Sciences , 1989, DOI: 10.1155/s0161171289000827
Abstract:
The open-open topology for function spaces
Kathryn F. Porter
International Journal of Mathematics and Mathematical Sciences , 1993, DOI: 10.1155/s0161171293000134
Abstract: Let (X,T) and (Y,T*) be topological spaces and let F ¢ YX. For each U ¢ T, V ¢ T*, let (U,V)={f ¢ F:f(U) ¢ V}. Define the set S ¢ ¢ ={(U,V):U ¢ T ¢ € ‰and ¢ € ‰V ¢ T*}. Then S ¢ ¢ is a subbasis for a topology, T ¢ ¢ on F, which is called the open-open topology. We compare T ¢ ¢ with other topologies and discuss its properties. We also show that T ¢ ¢ , on H(X), the collection of all self-homeomorphisms on X, is equivalent to the topology induced on H(X) by the Pervin quasi-uniformity on X.
The regular open-open topology for function spaces
Kathryn F. Porter
International Journal of Mathematics and Mathematical Sciences , 1996, DOI: 10.1155/s0161171296000415
Abstract: The regular open-open topology, Troo, is introduced, its properties for spaces of continuous functions are discussed, and Troo is compared to Too, the open-open topology. It is then shown that Troo on H(X), the collection of all self-homeomorphisms on a topological space, (X,T), is equivalent to the topology induced on H(X) by a specific quasi-uniformity on X, when X is a semi-regular space.
The Close Binary Frequency of Wolf-Rayet Stars as a Function of Metallicity in M31 and M33
Kathryn F. Neugent,Philip Massey
Physics , 2014, DOI: 10.1088/0004-637X/789/1/10
Abstract: Massive star evolutionary models generally predict the correct ratio of WC-type and WN-type Wolf-Rayet stars at low metallicities, but underestimate the ratio at higher (solar and above) metallicities. One possible explanation for this failure is perhaps single-star models are not sufficient and Roche-lobe overflow in close binaries is necessary to produce the "extra" WC stars at higher metallicities. However, this would require the frequency of close massive binaries to be metallicity dependent. Here we test this hypothesis by searching for close Wolf-Rayet binaries in the high metallicity environments of M31 and the center of M33 as well as in the lower metallicity environments of the middle and outer regions of M33. After identifying ~100 Wolf-Rayet binaries based on radial velocity variations, we conclude that the close binary frequency of Wolf-Rayets is not metallicity dependent and thus other factors must be responsible for the overabundance of WC stars at high metallicities. However, our initial identifications and observations of these close binaries have already been put to good use as we are currently observing additional epochs for eventual orbit and mass determinations.
The Spectrum of the Night Sky Over Kitt Peak: Changes Over Two Decades
Kathryn F Neugent,Philip Massey
Physics , 2010, DOI: 10.1086/656425
Abstract: New absolute spectrophotometry of the Kitt Peak night sky has been obtained in 2009/10, which we compare to previously published data obtained in 1988 and 1999, allowing us to look for changes over the past two decades. A comparison of the data between 1988, 1999 and 2009/10 reveals that the sky brightness of Kitt Peak has stayed remarkably constant over the past 20 years. Compared to 1988, the 2009/10 data show no change in the sky brightness at Zenith though, as expected, the sky glow has increased most dramatically in the direction of Tucson. Comparisons between the 1999 and 2009/10 data suggest that the sky has actually decreased in brightness compared to 10 years ago. However, the older data were both taken during times of increased solar activity. When we correct the measurements for the solar irradiance fluctuations, we find that compared to 20 years ago, the sky is ~0.1 magnitude brighter at Zenith and ~0.3 magnitudes brighter towards Tucson. But even after these corrections, we still find that the sky over Kitt Peak is comparable to what it was 10 years ago at Zenith and ~0.1 magnitude darker towards Tucson. This suggests that the strengthened lighting ordinances Tucson and Pima County established in the early 2000s have been quite effective. With some care, the Kitt Peak night sky will remain this dark many years into the future.
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