bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear localization of the titin Z1Z2Zr domain and role in regulating cell proliferation
Authors: Qi Jie , Chi Liqun , Labeit Siegfried , Banes Albert J.
Published: August 2008

Titin (also called connectin) is a major protein in sarcomere assembly as well as providing elastic return of the sarcomere postcontraction in cardiac and striated skeletal muscle tissues. In addition, it has been speculated that titin is associated with nuclear functions, including chromosome and spindle formation, and regulation of muscle gene expression. In the present study, a short isoform of titin was detected in a human osteoblastic cell line, MG-63 cells, by both immunostaining and Western blot analysis. Confocal images of titin staining showed both cytoplasmic and nuclear localization in a punctate pattern. Therefore, we hypothesized that human titin may contain a nuclear localization signal (NLS). A functional NLS, 200-PAKKTKT-206, located in a low-complexity, titin-specific region between Z2 and Z repeats, was found by sequentially deleting segments of the NH2-terminal sequence in conjunction with an enhanced green fluorescent protein reporter system and confirmed by site-directed mutagenesis. Overexpression of titin's amino terminal fragment (Z1Z2Zr) in human osteoblasts (MG-63) increased cell proliferation by activating the Wnt/β-catenin pathway. RT-PCR screens of tissue panels demonstrated that residues 1–206 were ubiquitously expressed at low levels in all tissues and cell types analyzed. Our data implicate a dual role for titin's amino terminal region, i.e., a novel nuclear function promoting cell division in addition to its known structural role in Z-line assembly.
Systolic and mean blood pressures and afferent arteriolar myogenic response dynamics: a modeling approach
Authors: Williamson Geoffrey A. , Loutzenhiser Rodger , Wang Xuemei , Griffin Karen , Bidani Anil K.
Published: August 2008

The afferent arteriolar myogenic response contributes to the autoregulation of renal blood flow (RBF) and glomerular filtration rate (GFR), and plays an essential role in protecting the kidney against hypertensive injury. Systolic blood pressure (SBP) is most closely linked to renal injury, and a myogenic response coupled to this signal would facilitate renal protection, whereas mean blood pressure (MBP) influences RBF and GFR. The relative role of SBP vs. MBP as the primary determinant of myogenic tone is an area of current controversy. Here, we describe two mathematical models, Model-Avg and Model-Sys, that replicate the different delays and time constants of vasoconstrictor and vasodilator phases of the myogenic responses of the afferent arteriole. When oscillating pressures are applied, the MBP determines the magnitude of the myogenic response of Model-Avg, and the SBP determines the response of Model-Sys. Simulations evaluating the responses of both models to square-wave pressure oscillations and to narrow pressure pulses show decidedly better agreement between Model-Sys and afferent arteriolar responses observed in cortical nephrons in the in vitro hydronephrotic kidney model. Analysis showing that the difference in delay times of the vasoconstrictor and vasodilator phases determines the frequency range over which SBP triggers Model-Sys's response was confirmed with simulations using authentic blood pressure waveforms. These observations support the postulate that SBP is the primary determinant of the afferent arteriole's myogenic response and indicate that differences in the delays in initiation vs. termination of the response, rather than in time constants, are integral to this phenomenon.
TGF-α increases human mesenchymal stem cell-secreted VEGF by MEK- and PI3-K- but not JNK- or ERK-dependent mechanisms
Authors: Wang Yue , Crisostomo Paul R. , Wang Meijing , Markel Troy A. , Novotny Nathan M. , Meldrum Daniel R.
Published: August 2008

Transforming growth factor-α (TGF-α) may be an important mediator of wound healing and the injury response. Human bone marrow mesenchymal stem cells (MSCs) release VEGF as a potentially beneficial paracrine response; however, it remains unknown whether TGF-α stimulates the production of VEGF from MSCs and, if so, by which mechanisms. We hypothesized that TGF-α would increase human MSC VEGF production by MAP kinase kinase (MAPKK/MEK), phosphatidylinositol 3-kinase (PI3-K)-, ERK, and JNK-dependent mechanisms. To study this, MSCs were cultured and divided into the following groups: 1) with vehicle; 2) with various stimulants alone: TGF-α, TNF-α, or TGF-α+TNF-α; 3) with individual kinase inhibitors alone (two different inhibitors for each of the following kinases: MEK, PI3-K, ERK, or JNK); and 4) with the above stimulants and each of the eight inhibitors. After 24-h incubation, a TGF-α dose-response curve demonstrated that low-dose TGF-α (500 pg/ml) suppressed MSC production of VEGF compared with vehicle (502 ± 16 pg/105cells/ml to 332 ± 9 pg/105cells/ml), while high-dose TGF-α (250 ng/ml) significantly increased MSC VEGF production (603 ± 24 pg/105cells/ml). High-dose TGF-α also increased TNF-α-stimulated release of VEGF from MSCs. MSCs exposed to TGF-α and/or TNF-α also demonstrated increased activation of PI3-K, JNK, and ERK. The TGF-α-stimulated production of VEGF by MSCs and the additive effect of TNF-α and TGF-α on VEGF production were abolished by MEK and PI3-K inhibition, but not ERK or JNK inhibition. Our data suggest that TGF-α increases VEGF production in MSCs via MEK- and PI3-K- but not ERK- or JNK-dependent mechanisms.
Selective contributions of the medial preoptic nucleus to testosterone-dependant regulation of the paraventricular nucleus of the hypothalamus and the HPA axis
Authors: Williamson Martin , Viau Victor
Published: August 2008

Previous data have consistently demonstrated an inhibitory effect of androgens on stress-induced hypothalamic-pituitary-adrenal (HPA) responses. Several brain regions may influence androgen-mediated inhibition of the HPA axis, including the medial preoptic area. To test the role of the medial preoptic nucleus (MPN) specifically, we examined in high- and low-testosterone-replaced gonadectomized rats bearing discrete bilateral lesions of the MPN basal and stress-induced indexes of HPA function, and the relative levels of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) mRNA in the amygdala. High testosterone replacement decreased plasma adrenocorticotropin hormone (ACTH) and paraventricular nucleus (PVN) Fos responses to restraint exposure in sham- but not in MPN-lesioned animals. AVP-, but not CRH-immunoreactivity staining in the external zone of the median eminence was increased by testosterone in sham animals, and MPN lesions blocked this increment in AVP. A similar interaction between MPN lesions and testosterone occurred on AVP mRNA levels in the medial nucleus of the amygdala. These findings support an involvement of MPN projections in mediating the AVP response to testosterone in both the medial parvocellular PVN and medial amygdala. We conclude that the MPN forms part of an integral circuit that mediates the central effects of gonadal status on neuroendocrine and central stress responses.
Evaluation of quantitative models of the effect of insulin on lipolysis and glucose disposal
Authors: Periwal Vipul , Chow Carson C. , Bergman Richard N. , Ricks Madia , Vega Gloria L. , Sumner Anne E.
Published: August 2008

The effects of insulin on the suppression of lipolysis are neither fully understood nor quantified. We examined a variety of mathematical models analogous to the minimal model of glucose disposal (MMG) to quantify the combined influence of insulin on lipolysis and glucose disposal during an insulin-modified frequently sampled intravenous glucose tolerance test. The tested models, which include two previously published ones, consisted of separate compartments for plasma free fatty acids (FFA), glucose, and insulin. They differed in the number of compartments and in the action of insulin to suppress lipolysis that decreased the plasma FFA level. In one category of models, a single insulin compartment acted on both glucose and FFA simultaneously. In a second category, there were two insulin compartments, each acting on FFA and glucose independently. For each of these two categories, we tested 11 variations of how insulin suppressed lipolysis. We also tested a model with an additional glucose compartment that acted on FFA. These 23 models were fit to the plasma FFA and glucose concentrations of 102 subjects individually. Using Bayesian model comparison methods, we selected the model that best balanced fit and minimized model complexity. In the best model, insulin suppressed lipolysis via a Hill function through a remote compartment that acted on both glucose and FFA simultaneously, and glucose dynamics obeyed the classic MMG.
Role of adrenomedullin system in lipid metabolism and its signaling mechanism in cultured adipocytes
Authors: Iemura-Inaba Chikako , Nishikimi Toshio , Akimoto Kazumi , Yoshihara Fumiki , Minamino Naoto , Matsuoka Hiroaki
Published: August 2008

We investigated the levels of adrenomedullin (AM) system during the process of preadipocyte differentiation and its role in lipid metabolism and cellular signaling mechanism in differentiated adipocytes. We cultured rat preadipocytes and measured the following during the process of differentiation: two molecular forms of AM in the culture medium using a specific immunoradiometric assay and gene expression of AM and its receptor component using RT-PCR analysis. In differentiated adipocytes, we measured the effects of AM on the intracellular cAMP level, lipolysis, glucose incorporation, and the protein levels. Two molecular forms of AM were secreted into the medium, and the AM-mature/AM-total ratio was increased after 6 days of differentiation. Cultured rat preadipocytes highly expressed the genes of AM and its receptor components at day 1, and they increased at day 10. Administration of AM to preadipocytes increased the number of Oil Red O-positive adipocytes and spectrophotometric absorbance of Oil Red O. AM dose dependently increased cAMP level and lipolysis, and its effect was blocked by CGRP(8-37). Isoproterenol increased lipolysis, and AM had additive effects on isoproterenol-induced lipolysis. KT5720 and U0126 significantly inhibited the AM-induced lipolysis, whereas KT5720, but not U0126, significantly inhibited the isoproterenol-induced lipolysis. AM increased glucose incorporation and its effect was blocked by wortmannin. Western blot analysis revealed that AM increased phospho PKA, ERK, and Akt. These results indicate that AM and its receptor component are highly expressed in cultured adipocytes and may play a role in lipid metabolism via a different signaling pathway.
Exercise pressor reflex in humans with end-stage renal disease
Authors: Park Jeanie , Campese Vito M. , Middlekauff Holly R.
Published: August 2008

Previous work has suggested that end-stage renal disease (ESRD) patients may have an exaggerated sympathetic nervous system (SNS) response during exercise. We hypothesized that ESRD patients have an exaggerated blood pressure (BP) response during moderate static handgrip exercise (SHG 30%) and that the exaggerated BP response is mediated by SNS overactivation, characterized by augmented mechanoreceptor activation and blunted metaboreceptor control, as has been described in other chronic diseases. We measured hemodynamics and muscle sympathetic nerve activity (MSNA) in 13 ESRD and 16 controls during: 1) passive hand movement (PHM; mechanoreceptor isolation); 2) low-level rhythmic handgrip exercise (RHG 20%; central command and mechanoreceptor activation); 3) SHG 30%, followed by posthandgrip circulatory arrest (PHGCA; metaboreceptor activation); and 4) cold pressor test (CPT; nonexercise stimulus). ESRD patients had exaggerated increases in systolic BP during SHG 30%; however, the absolute and relative increase in MSNA was not augmented, excluding SNS overactivation as the cause of the exaggerated BP response. Increase in MSNA was not exaggerated during RHG 20% and PHM, demonstrating that mechanoreceptor activation is not heightened in ESRD. During PHGCA, MSNA remained elevated in controls but decreased rapidly to baseline levels in ESRD, indicative of markedly blunted metaboreceptor control of MSNA. MSNA response to CPT was virtually identical in ESRD and controls, excluding a generalized sympathetic hyporeactivity in ESRD. In conclusion, ESRD patients have an exaggerated increase in SBP during SHG 30% that is not mediated by overactivation of the SNS directed to muscle. SBP responses were also exaggerated during mechanoreceptor activation and metaboreceptor activation, but without concomitant augmentation in MSNA responses. Metaboreceptor control of MSNA was blunted in ESRD, but the overall ability to mount a SNS response was not impaired. Other mechanisms besides SNS overactivation, such as impaired vasodilatation, should be explored to explain the exaggerated exercise pressor reflex in ESRD.
Altered dietary carbohydrates significantly affect gene expression of the major glucosensing components in Brockmann bodies and hypothalamus of rainbow trout
Authors: Polakof Sergio , Panserat Stéphane , Plagnes-Juan Elisabeth , Soengas José L.
Published: August 2008

Carnivorous fish have a limited capacity to utilize dietary carbohydrates even though glucosensing components exist in the hypothalamus and Brockmann bodies. Therefore, we fed trout for 10 days with two experimental diets containing a high level of carbohydrates (20%) or a carbohydrate-free level (<0.3%) to test the capacity of dietary carbohydrates to regulate gene expression of glucosensing components. Fish were fed and killed 1, 6, and 24 h after the meal to analyze plasma glucose levels, glucosensing-related biochemical parameters, and gene expression of the major components of the glucosensing system in the hypothalamus and Brockmann bodies. Glucose facilitative transporter type 2 and glucokinase gene expression were confirmed by real-time PCR data and two new components of the glucosensing mechanism, Kir6.-like and sulfonylurea receptor-like, were detected for the first time in fish in both tissues. In addition, a clear adaptation to dietary carbohydrates was found in trout Brockmann bodies, based on increased gene expression of major components of the system as well as enhanced glucokinase activities and glycogen levels. In contrast, in the hypothalamus, only glucokinase gene expression and activity showed a response to dietary carbohydrates, supporting the key role of that enzyme in glucosensing mechanism. Finally, a differential postprandial profile was found between tissues regarding the glucosensing potential, since the hypothalamus seems to respond to hyperglycemia earlier than the Brockmann bodies, whose response took place later. Altogether, these data describe for the first time in fish a complete response of major glucosensing components to dietary carbohydrates in trout hypothalamus and Brockmann bodies, supporting an efficient adaptation of both tissues to those dietary components.
Sex differences in angiotensin signaling in bulbospinal neurons in the rat rostral ventrolateral medulla
Authors: Wang Gang , Milner Teresa A. , Speth Robert C. , Gore Andrea C. , Wu Di , Iadecola Costantino , Pierce Joseph P.
Published: August 2008

Sex differences may play a significant role in determining the risk of hypertension. Bulbospinal neurons in the rostral ventrolateral medulla (RVLM) are involved in the tonic regulation of arterial pressure and participate in the central mechanisms of hypertension. Angiotensin II (ANG II) acting on angiotensin type 1 (AT1) receptors in RVLM neurons is implicated in the development of hypertension by activating NADPH oxidase and producing reactive oxygen species (ROS). Therefore, we analyzed RVLM bulbospinal neurons to determine whether there are sex differences in: 1) immunolabeling for AT1receptors and the key NADPH oxidase subunit p47 using dual-label immunoelectron microscopy, and 2) the effects of ANG II on ROS production and Ca2+currents using, respectively, hydroethidine fluoromicrography and patch-clamping. In tyrosine hydroxylase-positive RVLM neurons, female rats displayed significantly more AT1receptor immunoreactivity and less p47 immunoreactivity than male rats ( P < 0.05). Although ANG II (100 nM) induced comparable ROS production in dissociated RVLM bulbospinal neurons of female and male rats ( P > 0.05), an effect mediated by AT1receptors and NADPH oxidase, it triggered significantly larger dihydropyridine-sensitive long-lasting (L-type) Ca2+currents in female RVLM neurons ( P < 0.05). These observations suggest that an increase in AT1receptors in female RVLM neurons is counterbalanced by a reduction in p47 levels, such that ANG II-induced ROS production does not differ between females and males. Since the Ca2+current activator Bay K 8644 induced larger Ca2+currents in females than in male RVLM neurons, increased ANG II-induced L-type Ca2+currents in females may result from sex differences in calcium channel densities or dynamics.
A role for the thromboxane receptor in l-NAME hypertension
Authors: Francois Helene , Makhanova Natalia , Ruiz Philip , Ellison Jonathan , Mao Lan , Rockman Howard A. , Coffman Thomas M.
Published: August 2008

Actions of the lipid mediator thromboxane (Tx) A2 acting through the TP receptor contribute to the pathogenesis of cardiovascular disease. To further explore the role of TxA2 in hypertension, we examined the consequences of deficiency of the TP receptor on the course of hypertension associated with endothelial dysfunction and salt sensitivity. To this end, the nitric oxide synthase inhibitor NG-nitro-l-arginine methyl ester (l-NAME) was administered to TP-deficient ( Tp−/−) and wild-type ( Tp+/+) control mice in drinking water for 21 wk along with a high-salt (HS; 6% NaCl) diet. Administration of l-NAME increased urinary excretion of TxB2 to a similar extent in both Tp+/+ and Tp−/− animals. l-NAME also caused significant and sustained elevations in blood pressure that reached a maximum between weeks 3 and 6. However, the severity of hypertension was attenuated in the Tp−/− mice throughout the study period ( P < 0.001). At the end of the study, the wild-type mice developed significant cardiac hypertrophy (23.6 ± 2% increase in heart-to-body weight ratio). The severity of cardiac hypertrophy was attenuated in the TP-deficient group (11.1 ± 2.6%; P < 0.05). In contrast, kidney hypertrophy was exaggerated in the Tp−/− mice compared with controls (37.1 ± 5.4 vs. 12.3 ± 2.3%; P < 0.01). Moreover, the severity of glomerulosclerosis, tubule vacuolization, and interstitial chronic inflammation was also enhanced in the Tp−/− group ( P < 0.01). Thus, in l-NAME hypertension, TP receptors contribute to elevated blood pressure and cardiac hypertrophy. In this model, TP receptors also provided unexpected protection against kidney injury.
cGMP decreases surface NKCC2 levels in the thick ascending limb: role of phosphodiesterase 2 (PDE2)
Authors: Ares Gustavo R. , Caceres Paulo , Alvarez-Leefmans Francisco J. , Ortiz Pablo A.
Published: August 2008

NaCl absorption in the medullary thick ascending limb of the loop of Henle (THAL) is mediated by the apical Na/K/2Cl cotransporter (NKCC2). Hormones that increase cGMP, such as nitric oxide (NO) and natriuretic peptides, decrease NaCl absorption by the THAL. However, the mechanism by which cGMP decreases NaCl absorption in THALs is not known. We hypothesized that cGMP decreases surface NKCC2 levels in the THAL. We used surface biotinylation to measure surface NKCC2 levels in rat THAL suspensions. We tested the effect of the membrane-permeant cGMP analog dibutyryl-cGMP (db-cGMP) on surface NKCC2 levels. Incubating THALs with db-cGMP for 20 min decreased surface NKCC2 levels in a concentration-dependent manner (basal = 100%; db-cGMP 100 μM = 77 ± 7%; 500 μM = 54 ± 10% and 1,000 μM = 61 ± 8%). A different cGMP analog 8-bromo-cGMP (8-Br-cGMP) also decreased surface NKCC2 levels by 25%, (basal = 100%; 8-Br-cGM P = 75 ± 5%). Incubation of isolated, perfused THALs with db-cGMP decreased apical surface NKCC2 labeling levels as measured by immunofluorescence and confocal microscopy. cGMP-stimulated phosphodiesterase 2 (PDE2) mediates the inhibitory effect of NO on NaCl absorption by THALs. Thus we examined the role of PDE2 and found that PDE2 inhibitors blocked the effect of db-cGMP on surface NKCC2. Also, a nonstimulatory concentration of db-cAMP blocked the cGMP-induced decrease in surface NKCC2. Finally, db-cGMP inhibited THAL net Cl absorption by 48 ± 4%, and this effect was completely blocked by PDE2 inhibition. We conclude that cGMP decreases NKCC2 levels in the apical membrane of THALs and that this effect is mediated by PDE2. This is an important mechanism by which cGMP inhibits NaCl absorption by the THAL.
The molecular and functional phenotype of glomerular podocytes reveals key features of contractile smooth muscle cells
Authors: Saleem Moin A. , Zavadil Jiri , Bailly Maryse , McGee Karen , Witherden Ian R. , Pavenstadt Hermann , Hsu Hsianghao , Sanday Julia , Satchell Simon C. , Lennon Rachel , Ni Lan , Bottinger Erwin P. , Mundel Peter , Mathieson Peter W.
Published: August 2008

The glomerular podocyte is a highly specialized cell, with the ability to ultrafilter blood and support glomerular capillary pressures. However, little is known about either the genetic programs leading to this functionality or the final phenotype. We approached this question utilizing a human conditionally immortalized cell line, which differentiates from a proliferating epithelial phenotype to a differentiated form. We profiled gene expression during several time points during differentiation and grouped the regulated genes into major functional categories. A novel category of genes that was upregulated during differentiation was of smooth muscle-related molecules. We further examined the smooth muscle phenotype and showed that podocytes consistently express the differentiated smooth muscle markers smoothelin and calponin and the specific transcription factor myocardin, both in vitro and in vivo. The contractile contribution of the podocyte to the glomerular capillary is controversial. We demonstrated using two novel techniques that podocytes contract vigorously in vitro when differentiated and in real time were able to demonstrate that angiotensin II treatment decreases monolayer resistance, morphologically correlating with enhanced contractility. We conclude that the mature podocyte in vitro possesses functional apparatus of contractile smooth muscle cells, with potential implications for its in vivo ability to regulate glomerular dynamic and permeability characteristics.
The effects of strength training on finger strength and hand dexterity in healthy elderly individuals
Authors: Olafsdottir Halla B. , Zatsiorsky Vladimir M. , Latash Mark L.
Published: August 2008

We investigated the effect of 6 wk of strength training on maximal pressing (MVC) force, indexes of finger individuation (enslaving), and performance in accurate force production tests and in functional hand tests in healthy, physically fit, elderly individuals. Twelve participants (average age 76 yr) exercised with both hands. One of the hands exercised by pressing with the proximal phalanges (targeting mainly intrinsic hand muscles), whereas the other hand exercised by pressing with the finger tips (targeting mainly extrinsic hand muscles). Training led to higher MVC forces, higher enslaving indexes, and improved performance on the pegboard grooved test. Changes in an index of multi-finger force stabilizing synergy showed a significant correlation with changes in the index of force variability in the accurate force production test. Strong transfer effects were seen to the site that did not perform strength training exercise within each hand. Effects of exercise at the proximal site were somewhat stronger compared with those of exercise at the finger tips, although the differences did not reach significance level. Control tests showed that repetitive testing by itself did not significantly change the maximal finger force and enslaving. The results suggest that strength training is an effective way to improve finger strength. It can also lead to changes in finger interaction and in performance of accurate force production tasks. Adaptations at a neural level are likely to mediate the observed effects. Overall, the data suggest that strength training can also improve the hand function of less healthy elderly subjects.
Tumor-Evoked Sensitization of C Nociceptors: A Role for Endothelin
Authors: Hamamoto Darryl T. , Khasabov Sergey G. , Cain David M. , Simone Donald A.
Published: August 2008

Primary and metastatic cancers that effect bone are frequently associated with pain. Sensitization of primary afferent C nociceptors innervating tissue near the tumor likely contributes to the chronic pain and hyperalgesia accompanying this condition. This study focused on the role of the endogenous peptide endothelin-1 (ET-1) as a potential peripheral algogen implicated in the process of cancer pain. Electrophysiological response properties, including ongoing activity and responses evoked by heat stimuli, of C nociceptors were recorded in vivo from the tibial nerve in anesthetized control mice and mice exhibiting mechanical hyperalgesia following implantation of fibrosarcoma cells into and around the calcaneus bone. ET-1 (100 μM) injected into the receptive fields of C nociceptors innervating the plantar surface of the hind paw evoked an increase in ongoing activity in both control and tumor-bearing mice. Moreover, the selective ETAreceptor antagonist, BQ-123 (3 mM), attenuated tumor-evoked ongoing activity in tumor-bearing mice. Whereas ET-1 produced sensitization of C nociceptors to heat stimuli in control mice, C nociceptors in tumor-bearing mice were sensitized to heat, and their responses were not further increased by ET-1. Importantly, administration of BQ-123 attenuated tumor-evoked sensitization of C nociceptors to heat. We conclude that ET-1 at the tumor site contributes to tumor-evoked excitation and sensitization of C nociceptors through an ETAreceptor mediated mechanism.
Cyclic Nucleotide-Activated Currents in Cultured Olfactory Receptor Neurons of the HawkmothManduca sexta
Authors: Krannich Steffi , Stengl Monika
Published: August 2008

Moth pheromones cause rises in intracellular Ca2+concentrations that activate Ca2+-dependent cation channels in antennal olfactory receptor neurons. In addition, mechanisms of adaptation and sensitization depend on changes in cyclic nucleotide concentrations. Here, cyclic nucleotide-activated currents in cultured olfactory receptor neurons of the moth Manduca sexta are described, which share properties with currents through vertebrate cyclic nucleotide-gated channels. The cyclic nucleotide-activated currents of M. sexta carried Ca2+and monovalent cations. They were directly activated by cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), modulated by Ca2+/calmodulin, and inhibited by lanthanum. M. sexta cyclic nucleotide-activated currents developed in an all-or-none manner, which suggests that the underlying channels are coupled and act coordinately. At least one cAMP- and two cGMP-activated nonselective cation currents could be distinguished. Compared with the cAMP-activated current, both cGMP-activated currents appeared to conduct more Ca2+and showed a stronger down-regulation by Ca2+/calmodulin-dependent negative feedback. Furthermore, both cGMP-activated currents differed in their Ca2+-dependent inhibition. Thus M. sexta olfactory receptor neurons, like vertebrate sensory neurons, appear to express nonselective cyclic nucleotide-activated cation channels with different subunit compositions. Besides the nonselective cyclic nucleotide-activated cation currents, olfactory receptor neurons express a cAMP-dependent current. This current resembled a protein kinase-modulated low-voltage–activated Ca2+current.
Calpain Inhibitors Alter the Excitable Membrane Properties of CulturedAplysiaNeurons
Authors: Khoutorsky Arkady , Spira Micha E.
Published: August 2008

The calpain superfamily of calcium-dependent papain-like cysteine proteases constitutes highly conserved proteases that function to posttranslationally modify substrates by partial proteolysis. Calpains are known to proteolyze >100 substrates that lack strong sequence homology. Consequently, the calpain superfamily has been implicated in playing a central role in diverse physiological and pathological processes. Investigation of the physiological functions of calpains, on the one hand, and the need to develop pharmacological reagents to inhibit calpain-mediated pathological processes, on the other hand, led to the development of numerous calpain inhibitors. Using cultured Aplysia neurons and voltage-clamp analysis, we report here that the calpain inhibitors calpeptin, MG132, and the calpain inhibitor XII inhibit voltage-gated potassium conductance and moderately reduce the sodium conductance. These consequently lead to spike broadening and increased calcium influx. Such alterations of the excitable membrane properties may alter the normal patterns of neuronal and muscle electrical activities and thus should be taken into account when evaluating the effects of calpain inhibitors as protective/therapeutic drugs and as research tools.
Responses of Rat Trigeminal Ganglion Neurons to Longitudinal Whisker Stimulation
Authors: Stüttgen Maik C. , Kullmann Stephanie , Schwarz Cornelius
Published: August 2008

Responses of rat trigeminal ganglion neurons to longitudinal whisker stimulation. Rats use their mobile set of whiskers to actively explore their environment. Parameters that play a role to generate movement dynamics of the whisker shaft within the follicle, thus activating primary afferents, are manifold: among them are mechanical properties of the whiskers (curvature, elasticity and taper), active movements (head, body, and whiskers), and finally, object characteristics (surface, geometry, position, and orientation). Hence the whisker system is confronted with forces along all three axes in space. Movements along the two latitudinal axes of the whisker (horizontal and vertical) have been well studied. Here we focus on movement along the whisker's longitudinal axis that has been neglected so far. We employed ramp-and-hold movements that pushed the whisker shaft toward the skin and quantified the resulting activity in trigeminal first-order afferents in anesthetized rats. Virtually all recorded neurons were highly sensitive to longitudinal movement. Neurons could be perfectly segregated into two groups according to their modulation by stimulus amplitude and velocity, respectively. This classification regimen correlated perfectly with the presence or absence of slowly adapting responses in longitudinal stimulation but agreed with classification derived from latitudinal stimulation only if the whisker was engaged in its optimal direction and set point. We conclude that longitudinal stimulation is an extremely effective means to activate the tactile pathway and thus is highly likely to play an important role in tactile coding on the ascending somatosensory pathway. In addition, compared with latitudinal stimulation, it provides a reliable and easy to use method to classify trigeminal first-order afferents.
Adaptation as a Mechanism for Gain Control in an Insect Thermoreceptor
Authors: Tichy Harald , Fischer Harald , Gingl Ewald
Published: August 2008

Adaptation controls the gain of the input-function of the cockroach's cold cell during slowly oscillating changes in temperature. When the oscillation period is long, the cold cell improves its gain for the rate of temperature change at the expense of its ability to code instantaneous temperature. When the oscillation period is brief, however, the cold cell reduces this gain and improves its sensitivity for instantaneous temperature. This type of gain control has an important function. When the cockroach ventures from under cover and into moving air, the cold cell is confronted constantly with brief changes in temperature. To be of any use, a limit in the gain for the rate of change seems to be essential. Without such a limit, the cold cell will always indicate temperature change. The decrease in gain for the rate of change involves an increase in gain for instantaneous temperature. Therefore the animal receives precise information about the temperature at which the change occurs and can seek an area of different temperature. If the cockroach ventures back under cover, the rate of change will become slow. In this situation, a high gain improves the ability to signal slow temperature changes. The cockroach receives the early warning of slow fluctuations or even creeping changes in temperature. A comparison of the cold cell's responses with the temperature measured inside of small, cylindrical model objects indicates that coding characteristic rather than passive thermal effects of the structures enclosing the cold cell are responsible for the observed behavior.
Transcranial Magnetic Stimulation Over Human Dorsal–Lateral Posterior Parietal Cortex Disrupts Integration of Hand Position Signals Into the Reach Plan
Authors: Vesia Michael , Yan Xiaogang , Henriques Denise Y. , Sergio Lauren E. , Crawford J. D.
Published: August 2008

Posterior parietal cortex (PPC) has been implicated in the integration of visual and proprioceptive information for the planning of action. We previously reported that single-pulse transcranial magnetic stimulation (TMS) over dorsal–lateral PPC perturbs the early stages of spatial processing for memory-guided reaching. However, our data did not distinguish whether TMS disrupted the reach goal or the internal estimate of initial hand position needed to calculate the reach vector. To test between these hypotheses, we investigated reaching in six healthy humans during left and right parietal TMS while varying visual feedback of the movement. We reasoned that if TMS were disrupting the internal representation of hand position, visual feedback from the hand might still recalibrate this signal. We tested four viewing conditions: 1) final vision of hand position; 2) full vision of hand position; 3) initial and final vision of hand position; and 4) middle and final vision of hand position. During the final vision condition, left parietal stimulation significantly increased endpoint variability, whereas right parietal stimulation produced a significant leftward shift in both visual fields. However, these errors significantly decreased with visual feedback of the hand during both planning and control stages of the reach movement. These new findings demonstrate that 1) visual feedback of hand position during the planning and early execution of the reach can recalibrate the perturbed signal and, importantly, and 2) TMS over dorsal–lateral PPC does not disrupt the internal representation of the visual goal, but rather the reach vector, or more likely the sense of initial hand position that is used to calculate this vector.
Mitochondrial Calcium Buffering Contributes to the Maintenance of Basal Calcium Levels in Mouse Taste Cells
Authors: Hacker Kyle , Medler Kathryn F.
Published: August 2008

Taste stimuli are detected by taste receptor cells present in the oral cavity using diverse signaling pathways. Some taste stimuli are detected by G protein–coupled receptors (GPCRs) that cause calcium release from intracellular stores, whereas other stimuli depolarize taste cells to cause calcium influx through voltage-gated calcium channels (VGCCs). Although taste cells use two distinct mechanisms to transmit taste signals, increases in cytosolic calcium are critical for normal responses in both pathways. This creates a need to tightly control intracellular calcium levels in all transducing taste cells. To date, however, the mechanisms used by taste cells to regulate cytosolic calcium levels have not been identified. Studies in other cell types have shown that mitochondria can be important calcium buffers, even during small changes in calcium loads. In this study, we used calcium imaging to characterize the role of mitochondria in buffering calcium levels in taste cells. We discovered that mitochondria make important contributions to the maintenance of resting calcium levels in taste cells by routinely buffering a constitutive calcium influx across the plasma membrane. This is unusual because in other cell types, mitochondrial calcium buffering primarily affects large evoked calcium responses. We also found that the amount of calcium that is buffered by mitochondria varies with the signaling pathways used by the taste cells. A transient receptor potential (TRP) channel, likely TRPV1 or a taste variant of TRPV1, contributes to the constitutive calcium influx.
Pressure and Temperature Effects on Stoichiometry and Microstructure of Nitrogen‐Rich TiN Thin Films Synthesized via Reactive Magnetron DC‐Sputtering
Authors: Penilla E. , Wang J.
Published: August 2008

Nitrogen‐rich titanium nitride (TiN) thin films containing excess nitrogen up to 87.0 at.% were produced on (100) Si substrates via the reactive magnetron DC‐sputtering of a commercially available 99.995 at.% pure Ti target within an argon‐nitrogen (Ar‐N2) atmosphere with a 20‐to‐1 gas ratio. The process pressure (PP) and substrate temperature (TS) at which deposition occurred were varied systematically between 0.26 Pa–1.60 Pa and between 15.0∘C–600∘C, respectively, and their effects on the chemical composition, surface morphology, and preferred orientation were characterized by energy dispersive X‐ray spectroscopy (EDS), field emission scanning electron microscopy (FE‐SEM), and X‐ray diffraction (XRD). The EDS analysis confirms increasing nitrogen content with increasing PP and TS. The SEM images reveal a uniform and crystallized surface morphology as well as a closely packed cross‐sectional morphology for all crystalline films and a loosely packed cross‐sectional morphology for amorphous films. Films produced at lower PP and TS have a pyramidal surface morphology which transitions to a columnar and stratified structure as PP and TS increase. The XRD analysis confirms the existence of only the δ‐TiN phase and the absence of other nitrides, oxides, and/or sillicides in all cases. It also indicates that at lower PP and TS, the preferred orientation relative to the substrate is along the (111) planes, and that it transitions to a random orientation along the (200), (220), and (311) planes as PP and TS increase and these results correlate with and qualify those observed by SEM.
Silicon Nanocrystals: Fundamental Theory and Implications for Stimulated Emission
Authors: Belyakov V. A. , Burdov V. A. , Lockwood R. , Meldrum A.
Published: August 2008

Silicon nanocrystals (NCs) represent one of the most promising material systems for light emission applications in microphotonics. In recent years, several groups have reported on the observation of optical gain or stimulated emission in silicon NCs or in porous silicon (PSi). These results suggest that silicon‐NC‐based waveguide amplifiers or silicon lasers are achievable. However, in order to obtain clear and reproducible evidence of stimulated emission, it is necessary to understand the physical mechanisms at work in the light emission process. In this paper, we report on the detailed theoretical aspects of the energy levels and recombination rates in doped and undoped Si NCs, and we discuss the effects of energy transfer mechanisms. The theoretical calculations are extended toward computational simulations of ensembles of interacting nanocrystals. We will show that inhomogeneous broadening and energy transfer remain significant problems that must be overcome in order to improve the gain profile and to minimize nonradiative effects. Finally, we suggest means by which these objectives may be achieved.
Combining Coded Signals with Arbitrary Modulations in Orthogonal Relay Channels
Authors: Djeumou Brice , Lasaulce Samson , Berthet Antoine O.
Published: August 2008

We consider a relay channel for which the following assumptions
are made. (1) The source‐destination and relay‐destination
channels are orthogonal (frequency division relay channel). (2) The
relay implements the decode‐and‐forward protocol. (3) The source
and relay implement the same channel encoder, namely, a convolutional
encoder. (4) They can use arbitrary and possibly different
modulations. In this framework, we derive the best combiner in the
sense of the maximum likelihood (ML) at the destination and the
branch metrics of the trellis associated with its channel decoder for
the ML combiner and also for the maximum ratio combiner (MRC),
cooperative‐MRC (C‐MRC), and the minimum mean‐square error
(MMSE) combiner.
Fuzzy Hypervector Spaces
Authors: Ameri R. , Dehghan O. R.
Published: August 2008

The aim of this paper is the generalization of the notion of fuzzy vector spaces
to fuzzy hypervector spaces. In this regard, by considering the notion of fuzzy
hypervector spaces, we characterized a fuzzy hypervector space based on its level
sub‐hyperspace. The algebraic nature of fuzzy hypervector space under transformations
is studied. Certain conditions are obtained under which a given fuzzy
hypervector space can or cannot be realized as a union of two fuzzy hypervector
spaces such that none is contained in the other. The construction of a fuzzy hypervector
space generated by a given fuzzy subset of a hypervector space is given. The
set of all fuzzy cosets of a fuzzy hypervector space is shown to be a hypervector
space. Finally, a fuzzy quotient hypervector space is defined and an analogue of a
consequence of the “fundamental theorem of homomorphisms” is obtained.
A Dependable Microelectronic Peptide Synthesizer Using Electrode Data
Authors: Kerkhoff H. G. , Zhang X. , Mailly F. , Nouet P. , Liu H. , Richardson A.
Published: August 2008

The research in the area of microelectronic fluidic devices for biomedical applications is rapidly growing. As faults in these devices can have serious personal implications, a system is presented which includes fault tolerance with respect to the synthesized biomaterials (peptides). It can employ presence and purity detection of peptide droplets via current (charge) tests of control electrodes or impedance (phase) measurements using direct sensing electrodes near the peptide collector area. The commercial multielectrode array performs better in pure and impure detection of peptides in impedance and phase. Our two‐electrode X‐MEF case shows slightly poorer results. In both cases the phase is the best choice for contents detection. If there are presence or purity problems, the location is marked, and repeated peptide synthesis at another collector site is initiated.
Legume Lectin FRIL Preserves Neural Progenitor Cells in Suspension Culture In Vitro
Authors: Yao Hailei , Xie Xiaoyan , Li Yanhua , Wang Dongmei , Han Shu , Shi Shuangshuang , Nan Xue , Bai Cixian , Wang Yunfang , Pei Xuetao
Published: August 2008

In vitro maintenance of stem cells is crucial for many clinical applications. Stem cell preservation factor FRIL (Flt3 receptor-interacting lectin) is a plant lectin extracted fromDolichos Lablaband has been found preserve hematopoietic stem cells in vitro for a month in our previous studies. To investigate whether FRIL can preserve neural progenitor cells (NPCs), it was supplemented into serum-free suspension culture media. FRIL made NPC grow slowly, induced cell adhesion, and delayed neurospheres formation. However, FRIL did not initiate NPC differentiation according to immunofluorescence and semiquantitive RT-PCR results. In conclusion, FRIL could also preserve neural progenitor cells in vitro by inhibiting both cell proliferation and differentiation.
Eye Gaze Assistance for a Game‐Like Interactive Task
Authors: Gedeon Tamás (Tom) D. , Zhu Dingyun , Mendis B. Sumudu U.
Published: August 2008

Human beings communicate in abbreviated ways dependent on prior interactions and shared knowledge. Furthermore, humans share information about intentions and future actions using eye gaze. Among primates, humans are unique in the whiteness of the sclera and amount of sclera shown, essential for communication via interpretation of eye gaze. This paper extends our previous work in a game‐like interactive task by the use of computerised recognition of eye gaze and fuzzy signature‐based interpretation of possible intentions. This extends our notion of robot instinctive behaviour to intentional behaviour. We show a good improvement of speed of response in a simple use of eye gaze information. We also show a significant and more sophisticated use of the eye gaze information, which eliminates the need for control actions on the user′s part. We also make a suggestion as to returning visibility of control to the user in these cases.
ERMHAN: A Context-Aware Service Platform to Support Continuous Care Networks for Home-Based Assistance
Authors: Paganelli Federica , Spinicci Emilio , Giuli Dino
Published: August 2008

Continuous care models for chronic diseases pose several technology-oriented challenges for home-based continuous care, where assistance services rely on a close collaboration among different stakeholders such as health operators, patient relatives, and social community members. Here we describe Emilia Romagna Mobile Health Assistance Network (ERMHAN) a multichannel context-aware service platform designed to support care networks in cooperating and sharing information with the goal of improving patient quality of life. In order to meet extensibility and flexibility requirements, this platform has been developed through ontology-based context-aware computing and a service oriented approach. We also provide some preliminary results of performance analysis and user survey activity.
The G-rich promoter and G-rich coding sequence of basic fibroblast growth factor are the targets of thalidomide in glioma
Authors: Mei Szu-Chieh , Wu Rong-Tsun
Published: August 2008

Thalidomide is considered to be a potent antiangiogenic and immunomodulatory drug for cancer therapy. Earlier clinical studies have found that patients responding to this drug often had high plasma levels of basic fibroblast growth factor (bFGF). This cytokine is a proangiogenic factor overexpressed in many tumors and is also a regulator of limb development; hence, it might be a target of thalidomide. Using U-87 MG cell lines, we found that thalidomide, especially when encapsulated in a liposome, down-regulated the transcription and translation of the FGF-2 gene by interacting with G-rich regions present in the promoter and the internal ribosome entry site of its transcript at concentrations much lower than therapeutic serum concentrations. Thalidomide treatment also dramatically suppressed the anchorage-independent growth of U-87 MG and other glioma cells by over a thousand fold without affecting its anchorage-dependent growth, which may be accomplished by knocking down endogenous bFGF expression in these cells. Accordingly, the addition of recombinant bFGF partially restored the anchorage-independent growth of these cells. Our data suggest that by targeting the G-rich regions of bFGF, thalidomide (at 0.1 μg/mL) can reduce cellular bFGF levels and affect tumor anchorage-independent growth, the hallmark of tumorigenicity. Our results are promising for future clinical investigations using low doses of thalidomide. [Mol Cancer Ther 2008;7(8):2405–14]