Chronosequence of Terrace Soils in Western South Dakota

Soils on the high terraces of the Cheyenne River in Haakon County, South Dakota have long been recognized as important to the agriculture of the area. Data from this study as well as Haakon County Extension Service and Soil Conservation Service knowledge of the area will complement the soil survey in progress and provide a broader base of information for the future management of this important agricultural resource. This study will also help to quantify some of the properties that set the high terrace series apart from the surrounding shale uplands. Similar sets of high terrace systems along other major east flowing tributaries to the Missouri River have been studied by Warren, Crandell, Flint, and White. Agreement as to the glacial period that caused their isolation has not been reached. Soil morphology of the Cheyenne river terraces will supplement the accumulated data leading toward the resolution of this question. The objectives of this study were: (1) to characterize the morphological, mineralogical, edaphic, physical, and selected chemical properties of the terrace soils; (2) examine the impact of time upon the genesis· of these soils; (3) classify and identify soil series on the various terrace levels; (4) apply the characterization to land use interpretation

Failure of Fluid Absorption in the Endolymphatic Sac Initiates Cochlear Enlargement that Leads to Deafness in Mice Lacking Pendrin Expression

Mutations of SLC26A4 are among the most prevalent causes of hereditary deafness. Deafness in the corresponding mouse model, Slc26a4−/−, results from an abnormally enlarged cochlear lumen. The goal of this study was to determine whether the cochlear enlargement originates with defective cochlear fluid transport or with a malfunction of fluid transport in the connected compartments, which are the vestibular labyrinth and the endolymphatic sac. Embryonic inner ears from Slc26a4+/− and Slc26a4−/− mice were examined by confocal microscopy ex vivo or after 2 days of organ culture. Culture allowed observations of intact, ligated or partially resected inner ears. Cochlear lumen formation was found to begin at the base of the cochlea between embryonic day (E) 13.5 and 14.5. Enlargement was immediately evident in Slc26a4−/− compared to Slc26a4+/− mice. In Slc26a4+/− and Slc26a4−/− mice, separation of the cochlea from the vestibular labyrinth by ligation at E14.5 resulted in a reduced cochlear lumen. Resection of the endolymphatic sacs at E14.5 led to an enlarged cochlear lumen in Slc26a4+/− mice but caused no further enlargement of the already enlarged cochlear lumen in Slc26a4−/− mice. Ligation or resection performed later, at E17.5, did not alter the cochlea lumen. In conclusion, the data suggest that cochlear lumen formation is initiated by fluid secretion in the vestibular labyrinth and temporarily controlled by fluid absorption in the endolymphatic sac. Failure of fluid absorption in the endolymphatic sac due to lack of Slc26a4 expression appears to initiate cochlear enlargement in mice, and possibly humans, lacking functional Slc26a4 expression

Claudin expression during early postnatal development of the murine cochlea

Citation: Kudo, T., Wangemann, P., & Marcus, D. C. (2018). Claudin expression during early postnatal development of the murine cochlea. BMC Physiology, 18(1), 1. https://doi.org/10.1186/s12899-018-0035-1Background: Claudins are major components of tight junctions, which form the paracellular barrier between the cochlear luminal and abluminal fluid compartments that supports the large transepithelial voltage difference and the large concentration differences of K+, Na+ and Ca2+ needed for normal cochlear function. Claudins are a family of more than 20 subtypes, but our knowledge about expression and localization of each subtype in the cochlea is limited. Results: We examined by quantitative RT-PCR the expression of the mRNA of 24 claudin isoforms in mouse cochlea during postnatal development and localized the expression in separated fractions of the cochlea. Transcripts of 21 claudin isoforms were detected at all ages, while 3 isoforms (Cldn-16, ??17 and ??18) were not detected. Claudins that increased expression during development include Cldn-9, ??13, ??14, ??15, and -19v2, while Cldn-6 decreased. Those that do not change expression level during postnatal development include Cldn-1, ??2, ??3, ??4, ??5, ??7, ??8, ?10v1, ?10v2, ??11, ??12, ?19v1, ??20, ??22, and???23. Our investigation revealed unique localization of some claudins. In particular, Cldn-13 expression rapidly increases during early development and is mainly expressed in bone but only minimally in the lateral wall (including stria vascularis) and in the medial region (including the organ of Corti). No statistically significant changes in expression of Cldn-11, ??13, or ??14 were found in the cochlea of Slc26a4 ?/? mice compared to Slc26a4 +/? mice. Conclusions: We demonstrated developmental patterns of claudin isoform transcript expression in the murine cochlea. Most of the claudins were associated with stria vascularis and organ of Corti, tissue fractions rich in tight junctions. However, this study suggests a novel function of Cldn-13 in the cochlea, which may be linked to cochlear bone marrow maturation

The gastric H,K-ATPase in stria vascularis contributes to pH regulation of cochlear endolymph but not to K secretion

Citation: Miyazaki, H., Wangemann, P., & Marcus, D. C. (2016). The gastric H,K-ATPase in stria vascularis contributes to pH regulation of cochlear endolymph but not to K secretion. BMC Physiology, 17(1), 1. https://doi.org/10.1186/s12899-016-0024-1Background Disturbance of acid–base balance in the inner ear is known to be associated with hearing loss in a number of conditions including genetic mutations and pharmacologic interventions. Several previous physiologic and immunohistochemical observations lead to proposals of the involvement of acid–base transporters in stria vascularis. Results We directly measured acid flux in vitro from the apical side of isolated stria vascularis from adult C57Bl/6 mice with a novel constant-perfusion pH-selective self-referencing probe. Acid efflux that depended on metabolism and ion transport was observed from the apical side of stria vascularis. The acid flux was decreased to about 40 % of control by removal of the metabolic substrate (glucose-free) and by inhibition of the sodium pump (ouabain). The flux was also decreased a) by inhibition of Na,H-exchangers by amiloride, dimethylamiloride (DMA), S3226 and Hoe694, b) by inhibition of Na,2Cl,K-cotransporter (NKCC1) by bumetanide, and c) by the likely inhibition of HCO3/anion exchange by DIDS. By contrast, the acid flux was increased by inhibition of gastric H,K-ATPase (SCH28080) but was not affected by an inhibitor of vH-ATPase (bafilomycin). K flux from stria vascularis was reduced less than 5 % by SCH28080. Conclusions These observations suggest that stria vascularis may be an important site of control of cochlear acid–base balance and demonstrate a functional role of several acid–base transporters in stria vascularis, including basolateral H,K-ATPase and apical Na,H-exchange. Previous suggestions that H secretion is mediated by an apical vH-ATPase and that basolateral H,K-ATPase contributes importantly to K secretion in stria vascularis are not supported. These results advance our understanding of inner ear acid–base balance and provide a stronger basis to interpret the etiology of genetic and pharmacologic cochlear dysfunctions that are influenced by endolymphatic pH

Gender Differences in Myogenic Regulation along the Vascular Tree of the Gerbil Cochlea

Regulation of cochlear blood flow is critical for hearing due to its exquisite sensitivity to ischemia and oxidative stress. Many forms of hearing loss such as sensorineural hearing loss and presbyacusis may involve or be aggravated by blood flow disorders. Animal experiments and clinical outcomes further suggest that there is a gender preference in hearing loss, with males being more susceptible. Autoregulation of cochlear blood flow has been demonstrated in some animal models in vivo, suggesting that similar to the brain, blood vessels supplying the cochlea have the ability to control flow within normal limits, despite variations in systemic blood pressure. Here, we investigated myogenic regulation in the cochlear blood supply of the Mongolian gerbil, a widely used animal model in hearing research. The cochlear blood supply originates at the basilar artery, followed by the anterior inferior cerebellar artery, and inside the inner ear, by the spiral modiolar artery and the radiating arterioles that supply the capillary beds of the spiral ligament and stria vascularis. Arteries from male and female gerbils were isolated and pressurized using a concentric pipette system. Diameter changes in response to increasing luminal pressures were recorded by laser scanning microscopy. Our results show that cochlear vessels from male and female gerbils exhibit myogenic regulation but with important differences. Whereas in male gerbils, both spiral modiolar arteries and radiating arterioles exhibited pressure-dependent tone, in females, only radiating arterioles had this property. Male spiral modiolar arteries responded more to L-NNA than female spiral modiolar arteries, suggesting that NO-dependent mechanisms play a bigger role in the myogenic regulation of male than female gerbil cochlear vessels

Calcium sparks in the intact gerbil spiral modiolar artery

<p>Abstract</p> <p>Background</p> <p>Calcium sparks are ryanodine receptor mediated transient calcium signals that have been shown to hyperpolarize the membrane potential by activating large conductance calcium activated potassium (BK) channels in vascular smooth muscle cells. Along with voltage-dependent calcium channels, they form a signaling unit that has a vasodilatory influence on vascular diameter and regulation of myogenic tone. The existence and role of calcium sparks has hitherto been unexplored in the spiral modiolar artery, the end artery that controls blood flow to the cochlea. The goal of the present study was to determine the presence and properties of calcium sparks in the intact gerbil spiral modiolar artery.</p> <p>Results</p> <p>Calcium sparks were recorded from smooth muscle cells of intact arteries loaded with fluo-4 AM. Calcium sparks occurred with a frequency of 2.6 Hz, a rise time of 17 ms and a time to half-decay of 20 ms. Ryanodine reduced spark frequency within 3 min from 2.6 to 0.6 Hz. Caffeine (1 mM) increased spark frequency from 2.3 to 3.3 Hz and prolonged rise and half-decay times from 17 to 19 ms and from 20 to 23 ms, respectively. Elevation of potassium (3.6 to 37.5 mM), presumably via depolarization, increased spark frequency from 2.4 to 3.2 Hz. Neither ryanodine nor depolarization changed rise or decay times.</p> <p>Conclusions</p> <p>This is the first characterization of calcium sparks in smooth muscle cells of the spiral modiolar artery. The results suggest that calcium sparks may regulate the diameter of the spiral modiolar artery and cochlear blood flow.</p

Electrophysiological effects of 5-hydroxytryptamine on isolated human atrial myocytes, and the influence of chronic beta-adrenoceptor blockade

&lt;b&gt;1.&lt;/b&gt; 5-Hydroxytryptamine (5-HT) has been postulated to play a proarrhythmic role in the human atria via stimulation of 5-HT&lt;sub&gt;4&lt;/sub&gt; receptors. &lt;b&gt;2.&lt;/b&gt; The aims of this study were to examine the effects of 5-HT on the L-type Ca&lt;sup&gt;2+&lt;/sup&gt; current (&lt;i&gt;I&lt;/i&gt;&lt;sub&gt;CaL&lt;/sub&gt;) action potential duration (APD), the effective refractory period (ERP) and arrhythmic activity in human atrial cells, and to assess the effects of prior treatment with &#946;-adrenoceptor antagonists. &lt;b&gt;3.&lt;/b&gt; Isolated myocytes, from the right atrial appendage of 27 consenting patients undergoing cardiac surgery who were in sinus rhythm, were studied using the whole-cell perforated patch-clamp technique at 37&#186;C. &lt;b&gt;4.&lt;/b&gt; 5-HT (1 n-10 &#956;M) caused a concentration-dependent increase in &lt;i&gt;I&lt;/i&gt;&lt;sub&gt;CaL&lt;/sub&gt;, which was potentiated in cells from &#946;-blocked (maximum response to 5-HT, E&lt;sub&gt;max&lt;/sub&gt;=299&#177;12% increase above control) compared to non-&#946;-blocked patients (E&lt;sub&gt;max&lt;/sub&gt;=220&#177;6%, P&#60;0.05), but with no change in either the potency (log EC&lt;sub&gt;50&lt;/sub&gt;: -7.09&#177;0.07 vs -7.26&#177;0.06) or Hill coefficient (&lt;i&gt;n&lt;/i&gt;&lt;sub&gt;H&lt;/sub&gt;: 1.5&#177;0.6 vs 1.5&#177;0.3) of the 5-HT concentration-response curve. &lt;b&gt;5.&lt;/b&gt; 5-HT (10 &#956;M) produced a greater increase in the APD at 50% repolarisation (APD50) in cells from &#946;-blocked patients (of 37&#177;10 ms, i.e. 589&#177;197%) vs non-&#946;-blocked patients (of 10&#177;4 ms, i.e. 157&#177;54%; P&#60;0.05). Both the APD&lt;sub&gt;90&lt;/sub&gt; and the ERP were unaffected by 5-HT. &lt;b&gt;6.&lt;/b&gt; Arrhythmic activity was observed in response to 5-HT in five of 17 cells (29%) studied from &#946;-blocked, compared to zero of 16 cells from the non-&#946;-blocked patients (P&#60;0.05). &lt;b&gt;7.&lt;/b&gt; In summary, the 5-HT-induced increase in calcium current was associated with a prolonged early plateau phase of repolarisation, but not late repolarisation or refractoriness, and the enhancement of these effects by chronic &#946;-adrenoceptor blockade was associated with arrhythmic potential

Epithelial Cell Stretching and Luminal Acidification Lead to a Retarded Development of Stria Vascularis and Deafness in Mice Lacking Pendrin

Loss-of-function mutations of SLC26A4/pendrin are among the most prevalent causes of deafness. Deafness and vestibular dysfunction in the corresponding mouse model, Slc26a4−/−, are associated with an enlargement and acidification of the membranous labyrinth. Here we relate the onset of expression of the HCO3− transporter pendrin to the luminal pH and to enlargement-associated epithelial cell stretching. We determined expression with immunocytochemistry, cell stretching by digital morphometry and pH with double-barreled ion-selective electrodes. Pendrin was first expressed in the endolymphatic sac at embryonic day (E) 11.5, in the cochlear hook-region at E13.5, in the utricle and saccule at E14.5, in ampullae at E16.5, and in the upper turn of the cochlea at E17.5. Epithelial cell stretching in Slc26a4−/− mice began at E14.5. pH changes occurred first in the cochlea at E15.5 and in the endolymphatic sac at E17.5. At postnatal day 2, stria vascularis, outer sulcus and Reissner's membrane epithelial cells, and utricular and saccular transitional cells were stretched, whereas sensory cells in the cochlea, utricle and saccule did not differ between Slc26a4+/− and Slc26a4−/− mice. Structural development of stria vascularis, including vascularization, was retarded in Slc26a4−/− mice. In conclusion, the data demonstrate that the enlargement and stretching of non-sensory epithelial cells precedes luminal acidification in the cochlea and the endolymphatic sac. Stretching and luminal acidification may alter cell-to-cell communication and lead to the observed retarded development of stria vascularis, which may be an important step on the path to deafness in Slc26a4−/− mice, and possibly in humans, lacking functional pendrin expression

Expression of epithelial calcium transport system in rat cochlea and vestibular labyrinth

<p>Abstract</p> <p>Background</p> <p>The low luminal Ca²⁺concentration of mammalian endolymph in the inner ear is required for normal hearing and balance. We recently reported the expression of mRNA for a Ca²⁺-absorptive transport system in primary cultures of semicircular canal duct (SCCD) epithelium.</p> <p>Results</p> <p>We now identify this system in native vestibular and cochlear tissues by qRT-PCR, immunoblots and confocal immunolocalization. Transcripts were found and quantified for several isoforms of epithelial calcium channels (TRPV5, TRPV6), calcium buffer proteins (calbindin-D9K, calbindin-D28K), sodium-calcium exchangers (NCX1, NCX2, NCX3) and plasma membrane Ca²⁺-ATPase (PMCA1, PMCA2, PMCA3, and PMCA4) in native SCCD, cochlear lateral wall (LW) and stria vascularis (SV) of adult rat as well as Ca²⁺channels in neonatal SCCD. All components were expressed except TRPV6 in SV and PMCA2 in SCCD. 1,25-(OH)₂vitamin D₃(VitD) significantly up-regulated transcripts of TRPV5 in SCCD, calbindin-D9K in SCCD and LW, NCX2 in LW, while PMCA4 in SCCD and PMCA3 in LW were down-regulated. The expression of TRPV5 relative to TRPV6 was in the sequence SV > Neonatal SCCD > Adult SCCD > LW > primary culture SCCD. Expression of TRPV5 protein from primary culture of SCCD did not increase significantly when cells were incubated with VitD (1.2 times control; P > 0.05). Immunolocalization showed the distribution of TRPV5 and TRPV6. TRPV5 was found near the apical membrane of strial marginal cells and both TRPV5 and TRPV6 in outer and inner sulcus cells of the cochlea and in the SCCD of the vestibular system.</p> <p>Conclusions</p> <p>These findings demonstrate for the first time the expression of a complete Ca²⁺absorptive system in native cochlear and vestibular tissues. Regulation by vitamin D remains equivocal since the results support the regulation of this system at the transcript level but evidence for control of the TRPV5 channel protein was lacking.</p

Slc26a7 chloride channel activity and localization in mouse Reissner’s membrane epithelium

Several members of the SLC26 gene family have highly-restricted expression patterns in the auditory and vestibular periphery and mutations in mice of at least two of these (SLC26A4 and SLC26A5) lead to deficits in hearing and/or balance. A previous report pointed to SLC26A7 as a candidate gene important for cochlear function. In the present study, inner ears were assayed by immunostaining for Slc26a7 in neonatal and adult mice. Slc26a7 was detected in the basolateral membrane of Reissner’s membrane epithelial cells but not neighboring cells, with an onset of expression at P5; gene knockout resulted in the absence of protein expression in Reissner’s membrane. Whole-cell patch clamp recordings revealed anion currents and conductances that were elevated for NO[subscript 3]ˉ over Clˉ and inhibited by Iˉ and NPPB. Elevated NO[subscript 3]ˉ currents were absent in Slc26a7 knockout mice. There were, however, no major changes to hearing (auditory brainstem response) of knockout mice during early adult life under constitutive and noise exposure conditions. The lack of Slc26a7 protein expression found in the wild-type vestibular labyrinth was consistent with the observation of normal balance. We conclude that SLC26A7 participates in Clˉ transport in Reissner’s membrane epithelial cells, but that either other anion pathways, such as ClC-2, possibly substitute satisfactorily under the conditions tested or that Clˉ conductance in these cells is not critical to cochlear function. The involvement of SLC26A7 in cellular pH regulation in other epithelial cells leaves open the possibility that SLC26A7 is needed in Reissner’s membrane cells during local perturbations of pH