Immunocytochemical evidence for co-expression of Type III IP(3) receptor with signaling components of bitter taste transduction

BACKGROUND: Taste receptor cells are responsible for transducing chemical stimuli into electrical signals that lead to the sense of taste. An important second messenger in taste transduction is IP(3), which is involved in both bitter and sweet transduction pathways. Several components of the bitter transduction pathway have been identified, including the T2R/TRB taste receptors, phospholipase C β2, and the G protein subunits α-gustducin, β3, and γ13. However, the identity of the IP(3) receptor subtype in this pathway is not known. In the present study we used immunocytochemistry on rodent taste tissue to identify the IP(3) receptors expressed in taste cells and to examine taste bud expression patterns for IP(3)R3. RESULTS: Antibodies against Type I, II, and III IP(3) receptors were tested on sections of rat and mouse circumvallate papillae. Robust cytoplasmic labeling for the Type III IP(3) receptor (IP(3)R3) was found in a large subset of taste cells in both species. In contrast, little or no immunoreactivity was seen with antibodies against the Type I or Type II IP(3) receptors. To investigate the potential role of IP(3)R3 in bitter taste transduction, we used double-label immunocytochemistry to determine whether IP(3)R3 is expressed in the same subset of cells expressing other bitter signaling components. IP(3)R3 immunoreactive taste cells were also immunoreactive for PLCβ2 and γ13. Alpha-gustducin immunoreactivity was present in a subset of IP(3)R3, PLCβ2, and γ13 positive cells. CONCLUSIONS: IP(3)R3 is the dominant form of the IP(3) receptor expressed in taste cells and our data suggest it plays an important role in bitter taste transduction

Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25

BACKGROUND: Taste receptor cells are responsible for transducing chemical stimuli from the environment and relaying information to the nervous system. Bitter, sweet and umami stimuli utilize G-protein coupled receptors which activate the phospholipase C (PLC) signaling pathway in Type II taste cells. However, it is not known how these cells communicate with the nervous system. Previous studies have shown that the subset of taste cells that expresses the T2R bitter receptors lack voltage-gated Ca(2+ )channels, which are normally required for synaptic transmission at conventional synapses. Here we use two lines of transgenic mice expressing green fluorescent protein (GFP) from two taste-specific promoters to examine Ca(2+ )signaling in subsets of Type II cells: T1R3-GFP mice were used to identify sweet- and umami-sensitive taste cells, while TRPM5-GFP mice were used to identify all cells that utilize the PLC signaling pathway for transduction. Voltage-gated Ca(2+ )currents were assessed with Ca(2+ )imaging and whole cell recording, while immunocytochemistry was used to detect expression of SNAP-25, a presynaptic SNARE protein that is associated with conventional synapses in taste cells. RESULTS: Depolarization with high K(+ )resulted in an increase in intracellular Ca(2+ )in a small subset of non-GFP labeled cells of both transgenic mouse lines. In contrast, no depolarization-evoked Ca(2+ )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 Ca(2+ )currents. A subset of non-GFP labeled taste cells exhibited large voltage-dependent Na(+ )and K(+ )currents and a high threshold voltage-gated Ca(2+ )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. CONCLUSION: 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

Multiple solutions to a magnetic nonlinear Choquard equation

We consider the stationary nonlinear magnetic Choquard equation [(-\mathrm{i}\nabla+A(x))^{2}u+V(x)u=(\frac{1}{|x|^{\alpha}}\ast |u|^{p}) |u|^{p-2}u,\quad x\in\mathbb{R}^{N}%] where $A\$is a real valued vector potential, $V$ is a real valued scalar potential$,$ $N\geq3$, $\alpha\in(0,N)$ and $2-(\alpha/N) <p<(2N-\alpha)/(N-2)$. \ We assume that both $A$ and $V$ are compatible with the action of some group $G$ of linear isometries of $\mathbb{R}^{N}$. We establish the existence of multiple complex valued solutions to this equation which satisfy the symmetry condition $$u(gx)=\tau(g)u(x)\text{\ \ \ for all}g\in G,\text{}x\in\mathbb{R}^{N},$$ where $\tau:G\rightarrow\mathbb{S}^{1}$ is a given group homomorphism into the unit complex numbers.Comment: To appear on ZAM

Amiloride-sensitive channels in type I fungiform taste cells in mouse

<p>Abstract</p> <p>Background</p> <p>Taste buds are the sensory organs of taste perception. Three types of taste cells have been described. Type I cells have voltage-gated outward currents, but lack voltage-gated inward currents. These cells have been presumed to play only a support role in the taste bud. Type II cells have voltage-gated Na⁺and K⁺current, and the receptors and transduction machinery for bitter, sweet, and umami taste stimuli. Type III cells have voltage-gated Na⁺, K⁺, and Ca²⁺currents, and make prominent synapses with afferent nerve fibers. Na⁺salt transduction in part involves amiloride-sensitive epithelial sodium channels (ENaCs). In rodents, these channels are located in taste cells of fungiform papillae on the anterior part of the tongue innervated by the chorda tympani nerve. However, the taste cell type that expresses ENaCs is not known. This study used whole cell recordings of single fungiform taste cells of transgenic mice expressing GFP in Type II taste cells to identify the taste cells responding to amiloride. We also used immunocytochemistry to further define and compare cell types in fungiform and circumvallate taste buds of these mice.</p> <p>Results</p> <p>Taste cell types were identified by their response to depolarizing voltage steps and their presence or absence of GFP fluorescence. TRPM5-GFP taste cells expressed large voltage-gated Na⁺and K⁺currents, but lacked voltage-gated Ca²⁺currents, as expected from previous studies. Approximately half of the unlabeled cells had similar membrane properties, suggesting they comprise a separate population of Type II cells. The other half expressed voltage-gated outward currents only, typical of Type I cells. A single taste cell had voltage-gated Ca²⁺current characteristic of Type III cells. Responses to amiloride occurred only in cells that lacked voltage-gated inward currents. Immunocytochemistry showed that fungiform taste buds have significantly fewer Type II cells expressing PLC signalling components, and significantly fewer Type III cells than circumvallate taste buds.</p> <p>Conclusion</p> <p>The principal finding is that amiloride-sensitive Na⁺channels appear to be expressed in cells that lack voltage-gated inward currents, likely the Type I taste cells. These cells were previously assumed to provide only a support function in the taste bud.</p

A guide to the Choquard equation

We survey old and recent results dealing with the existence and properties of solutions to the Choquard type equations $$-\Delta u + V(x)u = \bigl(|x|^{-(N-\alpha)} * |u|^p\bigr)|u|^{p - 2} u \qquad \text{in $\mathbb{R}^N$},$$ and some of its variants and extensions.Comment: 39 page

130 - Natascha Heise

Learning and studying human anatomy is often associated with using rote knowledge. Novice students often memorize terms and structures in the laboratory with little reasoning skills. In attempt to promote application, integration, and critical thinking skills we introduced case based study into the human anatomy course at CSU. Early implementation suggested little change in student’s ability to solve novel problems using simple recall in attempt to answer case study questions. Here, we describe a novel approach using a 5-step method to promote critical thinking. Results suggest students application and integration during the case studies correlated with overall class performance

Amiloride-sensitive channels in type I fungiform taste cells in mouse-0

<p><b>Copyright information:</b></p><p>Taken from "Amiloride-sensitive channels in type I fungiform taste cells in mouse"</p><p>BMC Neuroscience 2008;9():1-1.</p><p>Published online 2 Jan 2008</p><p>PMCID:PMC2235881.</p><p></p>m -80 mV elicit voltage-gated inward and outward currents. The outward current is mostly blocked by TEA indicating the involvement of voltage-gated Kchannels while the inward current was blocked by TTX indicating the involvement of voltage-gated Nachannels. Replacement of Cawith Badid not reveal an inward current suggesting that these cells do not express voltage-gated Cachannels. The I-V plot is represented for both inward and outward currents in Tyrodes (n = 6 cells; mean ± sem)

Amiloride-sensitive channels in type I fungiform taste cells in mouse-2

<p><b>Copyright information:</b></p><p>Taken from "Amiloride-sensitive channels in type I fungiform taste cells in mouse"</p><p>BMC Neuroscience 2008;9():1-1.</p><p>Published online 2 Jan 2008</p><p>PMCID:PMC2235881.</p><p></p> to depolarizing voltage steps, the application in of the Barium-TEA-TTX solution elicited a Cacurrent, typical of type III cells

Amiloride-sensitive channels in type I fungiform taste cells in mouse-7

<p><b>Copyright information:</b></p><p>Taken from "Amiloride-sensitive channels in type I fungiform taste cells in mouse"</p><p>BMC Neuroscience 2008;9():1-1.</p><p>Published online 2 Jan 2008</p><p>PMCID:PMC2235881.</p><p></p> to depolarizing voltage steps, the application in of the Barium-TEA-TTX solution elicited a Cacurrent, typical of type III cells

Amiloride-sensitive channels in type I fungiform taste cells in mouse-4

<p><b>Copyright information:</b></p><p>Taken from "Amiloride-sensitive channels in type I fungiform taste cells in mouse"</p><p>BMC Neuroscience 2008;9():1-1.</p><p>Published online 2 Jan 2008</p><p>PMCID:PMC2235881.</p><p></p>red) in a taste bud. Using the same section thickness, fungiform taste buds (top figures) and circumvallate taste buds (bottom figures) showed the same number of cells. Scale bar: 10 μm