Digital Imaging and Communications in Medicine (DICOM) is the dominant standard for medical imaging data. DICOM-compliant devices and the data they produce are generally designed for clinical use and often do not match the needs of users in research or clinical trial settings. DicomBrowser is software designed to ease the transition between clinically oriented DICOM tools and the specialized workflows of research imaging. It supports interactive loading and viewing of DICOM images and metadata across multiple studies and provides a rich and flexible system for modifying DICOM metadata. Users can make ad hoc changes in a graphical user interface, write metadata modification scripts for batch operations, use partly automated methods that guide users to modify specific attributes, or combine any of these approaches. DicomBrowser can save modified objects as local files or send them to a DICOM storage service using the C-STORE network protocol. DicomBrowser is open-source software, available for download at http://nrg.wustl.edu/software/dicom-browser.
Digital imaging and communications in medicine (DICOM); Workflow; Image viewer; Imaging informatics
In part one of this series, best practices were described for acquiring and handling data at study sites and importing them into an image repository or database. Here, we present a similar treatment on data management practices for imaging-based studies.
Clinical trials; Research image database
The Dominantly Inherited Alzheimer Network (DIAN) is a collaborative effort of international Alzheimer disease (AD) centers that are conducting a multifaceted prospective biomarker study in individuals at-risk for autosomal dominant AD (ADAD). DIAN collects comprehensive information and tissue in accordance with standard protocols from asymptomatic and symptomatic ADAD mutation carriers and their non-carrier family members to determine the pathochronology of clinical, cognitive, neuroimaging, and fluid biomarkers of AD. This article describes the structure, implementation, and underlying principles of DIAN, as well as the demographic features of the initial DIAN cohort.
Alzheimer disease; autosomal dominant; biomarkers of Alzheimer disease; PSEN1; PSEN2; APP; amyloid-beta; preclinical Alzheimer disease
Mutations of SLC26A4 are a common cause of human hearing loss associated with enlargement of the vestibular aqueduct. SLC26A4 encodes pendrin, an anion exchanger expressed in a variety of epithelial cells in the cochlea, the vestibular labyrinth and the endolymphatic sac. Slc26a4Δ/Δ mice are devoid of pendrin and develop a severe enlargement of the membranous labyrinth, fail to acquire hearing and balance, and thereby provide a model for the human phenotype. Here, we generated a transgenic mouse line that expresses human SLC26A4 controlled by the promoter of ATP6V1B1. Crossing this transgene into the Slc26a4Δ/Δ line restored protein expression of pendrin in the endolymphatic sac without inducing detectable expression in the cochlea or the vestibular sensory organs. The transgene prevented abnormal enlargement of the membranous labyrinth, restored a normal endocochlear potential, normal pH gradients between endolymph and perilymph in the cochlea, normal otoconia formation in the vestibular labyrinth and normal sensory functions of hearing and balance. Our study demonstrates that restoration of pendrin to the endolymphatic sac is sufficient to restore normal inner ear function. This finding in conjunction with our previous report that pendrin expression is required for embryonic development but not for the maintenance of hearing opens the prospect that a spatially and temporally limited therapy will restore normal hearing in human patients carrying a variety of mutations of SLC26A4.
Mutations of SLC26A4 are the most common cause for hearing loss associated with a swelling of the inner ear. This human disease is largely recapitulated in a mutant mouse model. Mutant mice lack Slc26a4 expression and their inner ears swell during embryonic development, which leads to failure of the cochlea and the vestibular organs resulting in deafness and loss of balance. SLC26A4 is normally found in the cochlea and vestibular organs of the inner ear as well as in the endolymphatic sac, which is a non-sensory part of the inner ear. The multitude of sites where SLC26A4 is located made the goal to restore function through restoration look futile, unless some sites were more important than others. Here, we generated a new mutant mouse that expresses SLC26A4 in the endolymphatic sac but not in the cochlea or the vestibular organs of the inner ear. Fantastically, this mouse did not develop the detrimental swelling of the inner ear and even more exciting, the mouse developed normal hearing and balance. Our study provides the proof-of-concept that a therapy aimed at repairing the endolymphatic sac during embryonic development is sufficient to restore a life-time of normal hearing and balance.
Slc26a4Δ/Δ mice are deaf, develop an enlarged membranous labyrinth, and thereby largely resemble the human phenotype where mutations of SLC26A4 cause an enlarged vestibular aqueduct and sensorineural hearing loss. The enlargement is likely caused by abnormal ion and fluid transport during the time of embryonic development, however, neither the mechanisms of ion transport nor the ionic composition of the luminal fluid during this time of development are known. Here we determine the ionic composition of inner ear fluids at the time at which the enlargement develops and the onset of expression of selected ion transporters. Concentrations of Na+ and K+ were measured with double-barreled ion-selective electrodes in the cochlea and the endolymphatic sac of Slc26a4Δ/+, which develop normal hearing, and of Slc26a4Δ/Δ mice, which fail to develop hearing. The expression of specific ion transporters was examined by quantitative RT-PCR and immunohistochemistry. High Na+ (∼141 mM) and low K+ concentrations (∼11 mM) were found at embryonic day (E) 16.5 in cochlear endolymph of Slc26a4Δ/+ and Slc26a4Δ/Δ mice. Shortly before birth the K+ concentration began to rise. Immediately after birth (postnatal day 0), the Na+ and K+ concentrations in cochlear endolymph were each ∼80 mM. In Slc26a4Δ/Δ mice, the rise in the K+ concentration occurred with a ∼3 day delay. K+ concentrations were also found to be low (∼15 mM) in the embryonic endolymphatic sac. The onset of expression of the K+ channel KCNQ1 and the Na+/2Cl−/K+ cotransporter SLC12A2 occurred in the cochlea at E19.5 in Slc26a4Δ/+ and Slc26a4Δ/Δ mice. These data demonstrate that endolymph, at the time at which the enlargement develops, is a Na+-rich fluid, which transitions into a K+-rich fluid before birth. The data suggest that the endolymphatic enlargement caused by a loss of Slc26a4 is a consequence of disrupted Na+ transport.
The vestibular system controls the ion composition of its luminal fluid through several epithelial cell transport mechanisms under hormonal regulation. The semicircular canal duct (SCCD) epithelium has been shown to secrete Cl- under β2-adrenergic stimulation. In the current study, we sought to determine the ion transporters involved in Cl- secretion and whether secretion is regulated by PKA and glucocorticoids.
Short circuit current (Isc) from rat SCCD epithelia demonstrated stimulation by forskolin (EC50: 0.8 μM), 8-Br-cAMP (EC50: 180 μM), 8-pCPT-cAMP (100 μM), IBMX (250 μM), and RO-20-1724 (100 μM). The PKA activator N6-BNZ-cAMP (0.1, 0.3 & 1 mM) also stimulated Isc. Partial inhibition of stimulated Isc individually by bumetanide (10 & 50 μM), and [(dihydroindenyl)oxy]alkanoic acid (DIOA, 100 μM) were additive and complete. Stimulated Isc was also partially inhibited by CFTRinh-172 (5 & 30 μM), flufenamic acid (5 μM) and diphenylamine-2,2′-dicarboxylic acid (DPC; 1 mM). Native canals of CFTR+/− mice showed a stimulation of Isc from isoproterenol and forskolin+IBMX but not in the presence of both bumetanide and DIOA, while canals from CFTR−/− mice had no responses. Nonetheless, CFTR−/− mice showed no difference from CFTR+/− mice in their ability to balance (rota-rod). Stimulated Isc was greater after chronic incubation (24 hr) with the glucocorticoids dexamethasone (0.1 & 0.3 μM), prednisolone (0.3, 1 & 3 μM), hydrocortisone (0.01, 0.1 & 1 μM), and corticosterone (0.1 & 1 μM) and mineralocorticoid aldosterone (1 μM). Steroid action was blocked by mifepristone but not by spironolactone, indicating all the steroids activated the glucocorticoid, but not mineralocorticoid, receptor. Expression of transcripts for CFTR; for KCC1, KCC3a, KCC3b and KCC4, but not KCC2; for NKCC1 but not NKCC2 and for WNK1 but only very low WNK4 was determined.
These results are consistent with a model of Cl- secretion whereby Cl- is taken up across the basolateral membrane by a Na+-K+-2Cl- cotransporter (NKCC) and potentially another transporter, is secreted across the apical membrane via a Cl- channel, likely CFTR, and demonstrate the regulation of Cl- secretion by protein kinase A and glucocorticoids.
Chloride secretion; Rat; Knockout mouse; Primary culture; Epithelium; Inner ear; Bumetanide; DIOA; Glucocorticoid; NKCC; KCC
The order and magnitude of pathologic processes in Alzheimer’s disease are not well understood, partly because the disease develops over many years. Autosomal dominant Alzheimer’s disease has a predictable age at onset and provides an opportunity to determine the sequence and magnitude of pathologic changes that culminate in symptomatic disease.
In this prospective, longitudinal study, we analyzed data from 128 participants who underwent baseline clinical and cognitive assessments, brain imaging, and cerebrospinal fluid (CSF) and blood tests. We used the participant’s age at baseline assessment and the parent’s age at the onset of symptoms of Alzheimer’s disease to calculate the estimated years from expected symptom onset (age of the participant minus parent’s age at symptom onset). We conducted cross-sectional analyses of baseline data in relation to estimated years from expected symptom onset in order to determine the relative order and magnitude of pathophysiological changes.
Concentrations of amyloid-beta (Aβ)42 in the CSF appeared to decline 25 years before expected symptom onset. Aβ deposition, as measured by positron-emission tomography with the use of Pittsburgh compound B, was detected 15 years before expected symptom onset. Increased concentrations of tau protein in the CSF and an increase in brain atrophy were detected 15 years before expected symptom onset. Cerebral hypometabolism and impaired episodic memory were observed 10 years before expected symptom onset. Global cognitive impairment, as measured by the Mini–Mental State Examination and the Clinical Dementia Rating scale, was detected 5 years before expected symptom onset, and patients met diagnostic criteria for dementia at an average of 3 years after expected symptom onset.
We found that autosomal dominant Alzheimer’s disease was associated with a series of pathophysiological changes over decades in CSF biochemical markers of Alzheimer’s disease, brain amyloid deposition, and brain metabolism as well as progressive cognitive impairment. Our results require confirmation with the use of longitudinal data and may not apply to patients with sporadic Alzheimer’s disease. (Funded by the National Institute on Aging and others; DIAN ClinicalTrials.gov number, NCT00869817.)
Na+ concentrations in endolymph must be controlled to maintain hair cell function since the transduction channels of hair cells are cation-permeable, but not K+-selective. Flooding or fluctuations of the hair cell cytosol with Na+ would be expected to lead to cellular dysfunction, hearing loss and vertigo. This review briefly describes cellular mechanisms known to be responsible for Na+homeostasis in each compartment of the inner ear, including the cochlea, saccule, semicircular canals and endolymphatic sac. The influx of Na+into endolymph of each of the organs is likely via passive diffusion, but these pathways have not yet been identified or characterized. Na+ absorption is controlled by gate -keeper channels in the apical (endolymphatic) membrane of the transporting cells. Highly Na+-selective epithelial sodium channels (ENaC) control absorption by Reissner’s membrane, saccular extramacular epithelium, semicircular canal duct epithelium and endolymphatic sac. ENaC activity is controlled by a number of signal pathways, but most notably by genomic regulation of channel numbers in the membrane via glucocorticoid signaling. Nonselective cation channels in the apical membrane of outer sulcus epithelial cells and vestibular transitional cells mediate Na+ and parasensory K+ absorption. The K+-mediated transduction current in hair cells is also accompanied by a Na+ flux since the transduction channels are nonselective cation channels. Cation absorption by all of these cells is regulated by extracellular ATP via apical nonselective cation channels (P2X receptors). The heterogeneous population of epithelial cells in the endolymphatic sac is thought to have multiple absorptive pathways for Na+ with regulatory pathways that include glucocorticoids and purinergic agonists.
inner ear; sodium homeostasis; epithelial sodium channel; Meniere’s disease
To evaluate the combination of cerebrospinal fluid biomarkers of Aβ42, tau, and phosphorylated tau (ptau181) with education and normalized whole brain volume (nWBV) to predict incident cognitive impairment and test the cognitive/brain reserve hypothesis.
Longitudinal cohort study.
Charles F. and Joanne Knight Alzheimer’s Disease Research Center of Washington University, St. Louis, Missouri.
Convenience sample of 197 participants aged 50 years and above, with normal cognition (Clinical Dementia Rating [CDR] of 0) at baseline, followed for a mean of 3.3 years.
Main outcome measure
Time to cognitive impairment (CDR ≥ 0.5).
Three-factor interactions between the baseline biomarker values, education, and nWBV were found for Cox proportional hazards models testing tau (p=.03) and ptau (p=.008). Among those with lower tau values, nWBV (hazard ratio [HR]=.54, 95% confidence interval [CI]=.31–.91; p=.02), but not education, was related to time to cognitive impairment. For participants with higher tau values, education interacted with nWBV to predict incident impairment (p=.01). For individuals with lower ptau values, there was no effect of education or nWBV. Education interacted with nWBV to predict incident cognitive impairment among those with higher ptau values (p=.02). In models testing Aβ42, larger nWBV was associated with a slower time to cognitive impairment (HR=.84, 95%CI=.71–.99, p=.0348), but there was no effect of Aβ42 or education.
Among individuals with higher levels of CSF tau and ptau, but normal cognition at baseline, time to incident cognitive impairment is moderated by education and brain volume as predicted by the cognitive/brain reserve hypothesis.
Purinergic receptors have been found to modulate ion transport in several types of epithelial cells as well as excitable cells. It was of interest to determine whether vestibular dark cells and strial marginal cells contain purinergic receptors in either the apicalor basolateral membrane which modulate transepithelial ion transport. Vestibular dark cell and strial marginal cell epithelia were mounted in a micro-Ussing chamber for the measurement of the transepithelial voltage and resistance from which the equivalent short circuit current (Isc) was obtained. The apical and basolateral sides were independently perfused with adenosine and adenosine 5′-triphosphate (ATP). Adenosine (10−5 M) had no effect on Isc at either the apical or basolateral side of vestibular dark cells and strial marginal cells, suggesting either the absence of P1 receptors or the absence of coupling of P1 receptors to vectorial ion transport by these epithelia. Apical perfusion of ATP (10−8 to 10−4 M) caused a decrease in Isc of both vestibular dark cells and strial marginal cells. Apical perfusion of the nucleotides uridine 5′-triphosphate (UTP), 2-methylthioadenosine triphosphate (2-meS-ATP), adenosine 5′-O-(3-thiotriphosphate) (ATPγS) and α,β-methylene adenosine 5′-triphosphate (α,β-meth-ATP) caused qualitatively similar responses with different magnitudes of response. The sequence of the magnitude of response of each compound at 10−6 or 10−5 M was assessed from the fractional change of Isc. The sequence for vestibular dark cells was UTP = ATP = ATPγS ≫ 2-meS-ATP > α,β-meth-ATP, and for strial marginal cells it was UTP = ATP ≫ 2-meS-ATP, corresponding to the sequence for the P2U receptor. The effect of agonist on the apical membrane was reduced by the antagonist 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) but not cibacron blue or suramin. DIDS in the absence of exogenous purinergic agonist caused a sustained increase in Isc. The effect of ATP on the apical membrane was greater in the absence of divalent cations. Basolateral perfusion of ATP led to a biphasic response of Isc in vestibular dark cell and strial marginal cell epithelia, consisting of an initial rapid increase followed by a slower decrease. Perfusion of the perilymphatic surface of the stria vascularis (basal cell layer) with ATP had no acute effect on Isc. The initial increase of Isc in vestibular dark cell epithelium during basolateral perfusion had a sequence of 2-meS-ATP > ATP ≫ UTP = α,β-meth-ATP = ATPγS, corresponding to the sequence for the P2Y receptor. Subsequently, the agonists caused a sustained decrease in Isc with a sequence of ATPγS > 2-meS-ATP > ATP > UTP >α,β-meth-ATP. This sequence is most simply interpreted as the result of the coexistence of P2U and P2Y receptors in the basolateral membrane. Both the increase and decrease of Isc by ATP at the basolateral membrane were reduced by the antagonist suramin. These findings provide evidence for the regulation of transepithelial ion transport by P2U receptors in the apical membrane and by coexisting P2U and P2Y receptors in the basolateral membrane of K+-secretory epithelial cells in the inner ear and are consistent with the hypothesis that the apical receptors are part of an autocrine negative feedback system in these cells.
P2U receptor; P2 agonists; adenosine; DIDS; cibacron blue; suramin; reactive blue 2
Strial marginal cells (SMC) and vestibular dark cells (VDC) are known to secrete K+ into endolymph. Slowly-activating, voltage-dependent K+ channels (KCNQ1/KCNE1; IsK; min K) have been identified in the apical membrane of these cells. Several experimental maneuvers known to increase or decrease transepithelial K+ secretion have been found in VDC to change the current through these channels in the same ways. In both SMC and VDC the kinetics of activation and deactivation resemble those of the IsK channel exogenously expressed in Xenopus oocytes and endogenous to heart myocytes. The present study sought evidence that this current is indeed carried by IsK channels and that this current is the basis for transepithelial K+ secretion. Both on-cell macro-patch recordings of the apical membrane and perforated-patch whole-cell recordings were made on SMC from gerbil in order to measure macroscopic cell currents. The on-cell current was found to 1) be K+-selective, 2) have a cation permeability sequence of K+ ~ Rb+ > Cs+ >> Li+ = Na+, 3) be activated with a time constant of 1764 ± 413 ms by voltage steps from 0 to +40 mV, 4) be deactivated with a time constant of 324 ± 57 ms by voltage steps from 0 to -40 mV and 5) be reduced 84 ± 5% by bumetanide (10-5 M), an inhibitor of K+ secretion. The single-channel conductance of the apical currents in the homologous VDC was estimated by fluctuation analysis to be 1.6 pS. The potent inhibitor of IsK channels, chromanol 293B (10-5 M), reduced the whole-cell current in SMC by 72 ± 10 %. Clofilium (10-4 M), a putative IsK channel inhibitor known to have additional non-specific effects, led to a stimulation of both on-cell (by 598 ± 177%) and whole-cell (by 162 ± 18%) currents in gerbil SMC but to a decrease of whole-cell currents (by 39 ± 12%) in rat SMC. Taken together with other findings reviewed here, these results strongly argue that the slowly-activating, voltage-dependent conductance in the apical membrane of SMC is the IsK channel and provide additional evidence for the poor specificity of clofilium.
K+ channel; perforated-patch whole-cell voltage clamp; fluctuation analysis; KCNQ1/KCNE1 K channel; gerbil; rat
Vestibular dark cell epithelium was isolated from the semicircular canal of gerbils to test the proposal that the sulfhydryl alkylating agent N-ethylmaleimide (NEM) inhibits K+ secretion by this tissue and does so by reacting with a site in or near the apical membrane. Dark cell epithelium was mounted in a micro-Ussing chamber for measurements of transepithelial voltage (Vt) and resistance (Rt) or in a perfused bath on the stage of a microscope for measurement of cell height as an index of cell volume. Perfusion of the apical or basolateral side with 10−3 M NEM caused an increase in Vt superimposed upon a slower decrease of Vt, resulting in a triphasic response. There were only small changes in Rt. Under this condition, Vt is proportional to short circuit current and to K+ secretion. Both the stimulatory and the inhibitory responses of Vt were dose-dependent between 10−6 and 10−3 M NEM and the inhibition was irreversible. The specificity of the reaction of NEM with sulfhydryl groups was confirmed by the use of the reducing agent dithiothreitol (DTT). Perfusion of 5×10−4 M DTT on the apical side caused no significant changes in Vt but completely prevented both stimulation and inhibition of Vt by NEM (10−3 M). The amplitudes of the stimulation and the inhibition of Vt were greater for basolateral than for apical perfusion of NEM. Similarly, the response times for each effect were faster from the basolateral side, suggesting that the primary sites of action are at or near the basolateral membrane. The site of action of NEM was further explored by subjecting the tissue to a membrane-impermeant sulfhydryl reagent, stilbenedisulfonate maleimide (SDM). Apical perfusion of 10−3 M SDM had no effect on Vt or Rt, whereas basolateral perfusion caused a reversible increase of Vt (5.2 ± 0.5 to initially 6.8 ± 0.5 mV which relaxed after 60 s to 5.8 ± 0.5 mV) and to an initial decrease in Rt by 4%. No inhibitory phase was observed. Elevation of basolateral [K+] from 3.6 to 25 mM is known to increase Vt and reduce Rt via direct stimulation of basolateral K+ uptake and indirect stimulation of the apical membrane conductance. Basolateral perfusion of 10−3 M NEM fully inhibited the increase of Vt due to 25 mM K+. Elevation of basolateral [K+] from 3.6 to 25 mM is known to increase reversibly cell volume. NEM was found to inhibit cell swelling in a dose-dependent manner but did not initially affect the rate of shrinking after K+-induced swelling, pointing to action only on basolateral transport pathways. The effects of NEM on K+-induced cell swelling were completely prevented by 5×10−4 M DTT, demonstrating that the inhibitory effect of NEM was on sulfhydryl groups. In contrast to interpretations of NEM action in frog semicircular canal, we have found that NEM appears to stimulate an ion transport process in mammalian dark cells at an extracellular site in the basolateral membrane and inhibits another ion transport process in the basolateral membrane at another site. Inhibition by NEM from the apical side occurs most likely by diffusion of the agent to a site at or near the cytosolic side of the basolateral membrane.
Vestibular labyrinth; epithelial transport; cell volume; dark cells; sulfhydryl reagents
Significant resources around the world have been invested in neuroimaging studies of brain function and disease. Easier access to this large body of work should have profound impact on research in cognitive neuroscience and psychiatry, leading to advances in the diagnosis and treatment of psychiatric and neurological disease. A trend toward increased sharing of neuroimaging data has emerged in recent years. Nevertheless, a number of barriers continue to impede momentum. Many researchers and institutions remain uncertain about how to share data or lack the tools and expertise to participate in data sharing. The use of electronic data capture (EDC) methods for neuroimaging greatly simplifies the task of data collection and has the potential to help standardize many aspects of data sharing. We review here the motivations for sharing neuroimaging data, the current data sharing landscape, and the sociological or technical barriers that still need to be addressed. The INCF Task Force on Neuroimaging Datasharing, in conjunction with several collaborative groups around the world, has started work on several tools to ease and eventually automate the practice of data sharing. It is hoped that such tools will allow researchers to easily share raw, processed, and derived neuroimaging data, with appropriate metadata and provenance records, and will improve the reproducibility of neuroimaging studies. By providing seamless integration of data sharing and analysis tools within a commodity research environment, the Task Force seeks to identify and minimize barriers to data sharing in the field of neuroimaging.
brain imaging; data sharing; standards; magnetic resonance imaging; fMRI; EEG-MEG
As neuroimaging databases grow in size and complexity, the time researchers spend investigating and managing the data increases to the expense of data analysis. As a result, investigators rely more and more heavily on scripting using high-level languages to automate data management and processing tasks. For this, a structured and programmatic access to the data store is necessary. Web services are a first step toward this goal. They however lack in functionality and ease of use because they provide only low-level interfaces to databases. We introduce here PyXNAT, a Python module that interacts with The Extensible Neuroimaging Archive Toolkit (XNAT) through native Python calls across multiple operating systems. The choice of Python enables PyXNAT to expose the XNAT Web Services and unify their features with a higher level and more expressive language. PyXNAT provides XNAT users direct access to all the scientific packages in Python. Finally PyXNAT aims to be efficient and easy to use, both as a back-end library to build XNAT clients and as an alternative front-end from the command line.
XNAT; Python; database; neuroimaging; neuroinformatics
Sodium absorption by semicircular canal duct (SCCD) epithelial cells is thought to contribute to the homeostasis of the volume of vestibular endolymph. It was previously shown that the epithelial cells could absorb Na+ under control of a glucocorticoid hormone (dexamethasone) and the absorptive transepithelial current was blocked by amiloride. The most commonly-observed target of amiloride is the epithelial sodium channel (ENaC), comprised of the three subunits α-, β- and γ-ENaC. However, other cation channels have also been observed to be sensitive in a similar concentration range. The aim of this study was to determine whether SCCD epithelial cells absorb only Na+ or also K+ through an amiloride-sensitive pathway. Parasensory K+ absorption could contribute to regulation of the transduction current through hair cells, as found to occur via vestibular transitional cells [S. H. Kim and D. C. Marcus. Regulation of sodium transport in the inner ear. Hear.Res. doi:10.1016/j.heares.2011.05.003, 2011].
We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6197), whole-cell patch clamp and transepithelial recordings in primary cultures of rat SCCD. α-, β- and γ-ENaC were all previously reported as present. The selectivity of the amiloride-sensitive transepithelial and cell membrane currents was observed in Ussing chamber and whole-cell patch clamp recordings. The cell membrane currents were carried by Na+ but not K+, but the Na+ selectivity disappeared when the cells were cultured on impermeable supports. Transepithelial currents across SCCD were also carried exclusively by Na+.
These results are consistent with the amiloride-sensitive absorptive flux of SCCD mediated by a highly Na+-selective channel, likely αβγ-ENaC. These epithelial cells therefore absorb only Na+ via the amiloride-sensitive pathway and do not provide a parasensory K+ efflux from the canals via this pathway. The results further provide caution to the culture of epithelial cells on impermeable surfaces.
Sensory transduction in the cochlea depends on regulated ion secretion and absorption. Results of whole-organ experiments suggested that Reissner’s membrane may play a role in the control of luminal Cl−. We tested for the presence of Cl− transport pathways in isolated mouse Reissner’s membrane using whole-cell patch clamp recording and gene transcript analyses using RT-PCR. The current-voltage (I-V) relationship in the presence of symmetrical NMDG-Cl was strongly inward-rectifying at negative voltages, with a small outward current at positive voltages. The inward-rectifying component of the I-V curve had several properties similar to those of the ClC-2 Cl− channel. It was stimulated by extracellular acidity and inhibited by extracellular Cd2+, Zn2+, and intracellular ClC-2 antibody. Channel transcripts expressed include ClC-2, Slc26a7 and ClC-Ka, but not Cftr, ClC-1, ClCa1, ClCa2, ClCa3, ClCa4, Slc26a9, ClC-Kb, Best1, Best2, Best3 or the beta-subunit of ClC-K, barttin. ClC-2 is the only molecularly-identified channel present that is a strong inward rectifier. This study is the first report of conductive Cl− transport in epithelial cells of Reissner’s membrane and is consistent with an important role in endolymph anion homeostasis.
Cl− channel; epithelial transport; cochlea
Sodium absorption by Reissner's membrane is thought to contribute to the homeostasis of the volume of cochlear endolymph. It was previously shown that the absorptive transepithelial current was blocked by amiloride and benzamil. The most commonly-observed target of these drugs is the epithelial sodium channel (ENaC), which is composed of the three subunits α-,β- and γ-ENaC. However, other less-selective cation channels have also been observed to be sensitive to benzamil and amiloride. The aim of this study was to determine whether Reissner's membrane epithelial cells could support parasensory K+ absorption via amiloride- and benzamil-sensitive electrogenic pathways.
We determined the molecular and functional expression of candidate cation channels with gene array (GEO GSE6196), RT-PCR, and whole-cell patch clamp. Transcript expression analysis of Reissner's membrane detected no amiloride-sensitive acid-sensing ion channels (ASIC1a, ASIC2a, ASIC2b) nor amiloride-sensitive cyclic-nucleotide gated channels (CNGA1, CNGA2, CNGA4, CNGB3). By contrast, α-,β- and γ-ENaC were all previously reported as present in Reissner's membrane. The selectivity of the benzamil-sensitive cation currents was observed in whole-cell patch clamp recordings under Cl--free conditions where cations were the only permeant species. The currents were carried by Na+ but not K+, and the permeability of Li+ was greater than that of Na+ in Reissner's membrane. Complete replacement of bath Na+ with the inpermeable cation NMDG+ led to the same inward current as with benzamil in a Na+ bath.
These results are consistent with the amiloride/benzamil-sensitive absorptive flux of Reissner's membrane mediated by a highly Na+-selective channel that has several key characteristics in common with αβγ-ENaC. The amiloride-sensitive pathway therefore absorbs only Na+ in this epithelium and does not provide a parasensory K+ efflux route from scala media.
The Human Connectome Project (HCP) is a major endeavor that will acquire and analyze connectivity data plus other neuroimaging, behavioral, and genetic data from 1,200 healthy adults. It will serve as a key resource for the neuroscience research community, enabling discoveries of how the brain is wired and how it functions in different individuals. To fulfill its potential, the HCP consortium is developing an informatics platform that will handle: (1) storage of primary and processed data, (2) systematic processing and analysis of the data, (3) open-access data-sharing, and (4) mining and exploration of the data. This informatics platform will include two primary components. ConnectomeDB will provide database services for storing and distributing the data, as well as data analysis pipelines. Connectome Workbench will provide visualization and exploration capabilities. The platform will be based on standard data formats and provide an open set of application programming interfaces (APIs) that will facilitate broad utilization of the data and integration of HCP services into a variety of external applications. Primary and processed data generated by the HCP will be openly shared with the scientific community, and the informatics platform will be available under an open source license. This paper describes the HCP informatics platform as currently envisioned and places it into the context of the overall HCP vision and agenda.
connectomics; Human Connectome Project; XNAT; caret; resting state fMRI; diffusion imaging; network analysis; brain parcellation
The Open Access Series of Imaging Studies (OASIS) is a series of neuroimaging data sets that is publicly available for study and analysis. The present MRI data set consists of a longitudinal collection of 150 subjects aged 60 to 96 all acquired on the same scanner using identical sequences. Each subject was scanned on two or more visits, separated by at least one year for a total of 373 imaging sessions. Subjects were characterized using the Clinical Dementia Rating (CDR) as either nondemented or with very mild to mild Alzheimer‘s disease (AD). 72 of the subjects were characterized as nondemented throughout the study. 64 of the included subjects were characterized as demented at the time of their initial visits and remained so for subsequent scans, including 51 individuals with CDR 0.5 similar level of impairment to individuals elsewhere considered to have ‘mild cognitive impairment’. Another 14 subjects were characterized as nondemented at the time of their initial visit (CDR 0) and were subsequently characterized as demented at a later visit (CDR > 0). The subjects were all right-handed and include both men (n=62) and women (n=88). For each scanning session, 3 or 4 individual T1-weighted MRI scans were obtained. Multiple within-session acquisitions provide extremely high contrast-to-noise making the data amenable to a wide range of analytic approaches including automated computational analysis. Automated calculation of whole brain volume is presented to demonstrate use of the data for measuring differences associated with normal aging and AD.
data sharing; Alzheimer’s Disease; aging; MRI; morphometry; open access; ADNI
The ionic composition of the luminal fluid in the vestibular labyrinth is maintained within tight limits by the many types of epithelial cells bounding the lumen. Regulatory mechanisms include systemic, paracrine and autocrine hormones along with their associated intracellular signal pathways. The epithelium lining the semicircular canal duct (SCCD) is a tissue that is known to absorb sodium and calcium and to secrete chloride.
Transport function was assessed by measurements of short circuit current (Isc) and gene transcript expression was evaluated by microarray. Neither ATP nor UTP (100 microM) on the apical side of the epithelium had any effect on Isc. By contrast, basolateral ATP transiently increased Isc and transepithelial resistance dropped significantly after basolateral ATP and UTP. P2Y2 was the sole UTP-sensitive purinergic receptor expressed. Isc was reduced by 42%, 50% and 63% after knockdown of α-ENaC, stimulation of PKC and inhibition of PI3-K, while the latter two increased the transepithelial resistance. PKCdelta, PKCgamma and PI3-K were found to be expressed.
These observations demonstrate that ion transport by the SCCD is regulated by P2Y2 purinergic receptors on the basolateral membrane that may respond to systemic or local agonists, such as ATP and/or UTP. The sodium absorption from endolymph mediated by ENaC in SCCD is regulated by signal pathways that include the kinases PKC and PI3-K. These three newly-identified regulatory components may prove to be valuable drug targets in the control of pathologic vestibular conditions involving dysfunction of transport homeostasis in the ear, such as Meniere's disease.
In order for therapies for Alzheimer's disease (AD) to have the greatest impact, it will likely be necessary to treat individuals in the “preclinical” (presymptomatic) stage. Fluid and neuroimaging measures are being explored as possible biomarkers of AD pathology that could aid in identifying individuals in this stage in order to target them for clinical trials and to direct and monitor therapy. The objective of this study was to determine if cerebrospinal fluid biomarkers for AD suggest the presence of brain damage in the preclinical stage of AD.
We investigated the relationship between structural neuroimaging measures (whole brain volume) and levels of cerebrospinal fluid (CSF) amyloid-β (Aβ)40, Aβ42, tau, and phosphorylated tau181 (ptau181), and plasma Aβ40 and Aβ42 in well-characterized research subjects with very mild and mild dementia of the Alzheimer type (DAT; n=29) and age-matched, cognitively normal controls (n=69).
Levels of CSF tau and ptau181, but not Aβ42, correlated inversely with whole brain volume in very mild/mild DAT, whereas levels of CSF Aβ42, but not tau or ptau181, was positively correlated with whole brain volume in non-demented controls.
Reduction in CSF Aβ42, likely reflecting Aβ aggregation in the brain, is associated with brain atrophy in the preclinical phase of AD. This suggests that there is toxicity associated with Aβ aggregation prior to the onset of clinically detectable disease. Increases in CSF tau (and ptau181) are later events that correlate with further structural damage and occur with clinical onset and progression.
Alzheimer's disease; amyloid-β; biomarker; brain atrophy; cerebrospinal fluid; MRI; preclinical AD; tau
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.
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.
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.
Alzheimer's disease (AD) pathology is estimated to develop many years before detectable cognitive decline. Fluid and imaging biomarkers may identify people in early symptomatic and even preclinical stages, possibly when potential treatments can best preserve cognitive function. We previously reported that cerebrospinal fluid (CSF) levels of amyloid-β42 (Aβ42) serve as an excellent marker for brain amyloid as detected by the amyloid tracer, Pittsburgh Compound B (PIB). Using data from 189 cognitively normal participants, we now report a positive linear relationship between CSF tau/ptau181 (primary constituents of neurofibrillary tangles) with the amount of cortical amyloid. We observe a strong inverse relationship of cortical PIB binding with CSF Aβ42 but not for plasma Aβ species. Some individuals have low CSF Aβ42 but no cortical PIB binding. Together, these data suggest that changes in brain Aβ42 metabolism and amyloid formation are early pathogenic events in AD, and that significant disruptions in CSF tau metabolism likely occur after Aβ42 initially aggregates and increases as amyloid accumulates. These findings have important implications for preclinical AD diagnosis and treatment.
Amyloid; biomarker; cerebrospinal fluid; Pittsburgh Compound B; preclinical Alzheimer's disease
Alzheimer's disease (AD) pathology is estimated to develop many years before detectable cognitive decline. Fluid and imaging biomarkers may identify people in early symptomatic and even preclinical stages, possibly when potential treatments can best preserve cognitive function. We previously reported that cerebrospinal fluid (CSF) levels of amyloid-β42 (Aβ42) serve as an excellent marker for brain amyloid as detected by the amyloid tracer, Pittsburgh compound B (PIB). Using data from 189 cognitively normal participants, we now report a positive linear relationship between CSF tau/ptau181 (primary constituents of neurofibrillary tangles) with the amount of cortical amyloid. We observe a strong inverse relationship of cortical PIB binding with CSF Aβ42 but not for plasma Aβ species. Some individuals have low CSF Aβ42 but no cortical PIB binding. Together, these data suggest that changes in brain Aβ42 metabolism and amyloid formation are early pathogenic events in AD, and that significant disruptions in CSF tau metabolism likely occur after Aβ42 initially aggregates and increases as amyloid accumulates. These findings have important implications for preclinical AD diagnosis and treatment.
amyloid; biomarker; cerebrospinal fluid; Pittsburgh compound B; preclinical Alzheimer's disease