Does Tinnitus Distress Depend on Age of Onset?

Objectives

Tinnitus is the perception of a sound in the absence of any physical source of it. About 5–15% of the population report hearing such a tinnitus and about 1–2% suffer from their tinnitus leading to anxiety, sleep disorders or depression. It is currently not completely understood why some people feel distressed by their tinnitus, while others don''t. Several studies indicate that the amount of tinnitus distress is associated with many factors including comorbid anxiety, comorbid depression, personality, the psychosocial situation, the amount of the related hearing loss and the loudness of the tinnitus. Furthermore, theoretical considerations suggest an impact of the age at tinnitus onset influencing tinnitus distress.

Methods

Based on a sample of 755 normal hearing tinnitus patients we tested this assumption. All participants answered a questionnaire on the amount of tinnitus distress together with a large variety of clinical and demographic data.

Results

Patients with an earlier onset of tinnitus suffer significantly less than patients with an onset later in life. Furthermore, patients with a later onset of tinnitus describe their course of tinnitus distress as more abrupt and distressing right from the beginning.

Conclusion

We argue that a decline of compensatory brain plasticity in older age accounts for this age-dependent tinnitus decompensation.     

Impaired resting perfusion in viable myocardium distal to chronic coronary stenosis in rats

Chronic coronary artery stenosis results in patchy necrosis in the dependent myocardium and impairs global and regional left ventricular (LV) function in rats in vivo. The aim of the present study was to compare regional myocardial blood flow (RMBF) and function (F) in poststenotic myocardium by using magnetic resonance imaging (MRI) and to compare MRI blood flow changes to histological alterations to assess whether RMBF in the viable poststenotic tissue remains normal. MRI was performed in 11 anesthetized Wistar rats with 2-wk stenosis of the left coronary artery. Postmortem, the extent of fibrotic tissue was quantified. Poststenotic RMBF was significantly reduced to 2.21 +/- 0.30 ml.g(-1).min(-1) compared with RMBF in the remote myocardium (4.05 +/- 0.50 ml.g(-1).min(-1)). A significant relationship between the poststenotic RMBF (%remote area) and the poststenotic F (%remote myocardium) was calculated (r = 0.61, P < 0.05). Assuming perfusion in scar tissue to be 32 +/- 5% of perfusion of remote myocardium, as measured in five additional rats, and that in remote myocardium to be 114 +/- 25% of that in normal myocardium, as assessed in five sham rats, the calculated perfusion in partially fibrotic tissue samples (35.7 +/- 5.2% of analyzed area) was 2.88 +/- 0.18 ml.g(-1).min(-1), whereas measured MRI perfusion was only 1.86 +/- 0.24 ml.g(-1).min(-1) (P < 0.05). These results indicate that resting perfusion in viable poststenotic myocardium is moderately reduced. Alterations in global and regional LV function are therefore secondary to both patchy fibrosis and reduced resting perfusion.     

Fully degradable hydrophilic polyals for protein modification

Modification of proteins with hydrophilic polymers is an effective strategy for regulation of protein pharmacokinetics. However, conjugates of slowly or non-biodegradable materials, such as poly(ethylene glycol), are known to cause long-lasting cell vacuolization, in particular in renal epithelium. Conjugates of more degradable polymers, e.g., polysaccharides, have a significant risk of immunotoxicity. Polymers that combine complete degradability, long circulation in vivo, and low immuno and chemical toxicity would be most beneficial as protein conjugate components. This study explores new fully biodegradable hydrophilic polymers, hydrophilic polyals. They are nontoxic, stable at physiological conditions, and undergo proton-catalyzed hydrolysis at lysosomal pH. The model enzyme-polyal conjugates were prepared with 61-98% yield using conventional and novel conjugation techniques and retained 90-95% of specific activity. The model conjugates showed a significant prolongation of protein circulation in rodents, with a 5-fold reduction in the renal accumulation. The data suggests that hydrophilic polyals may be useful in designing protein conjugates with improved properties.     

Advanced procedures for separation and analysis of low molecular weight inhibitor (NCXIF) of the cardiac sodium-calcium exchanger

A low molecular weight inhibitor (NCX(IF)) of the cardiac Na/Ca exchanger, isolated from the calf ventricle tissue, is capable of regulating the muscle strip's contractility and relaxation without involving the beta-activation pathway. The structural analysis of NCX(IF) requires highly purified preparations that fulfill the demanding requirements for mass spectra and NMR analyses. No such preparation is yet available. To this end, new HPLC procedures were developed by a combination of the reverse phase, normal phase, and HILIC (hydrophilic liquid chromatography) techniques. The specific activity of NCX(IF) is 10(5) times higher in the purified preparations (as compared to the crude extract) showing a 2-5% yield of total inhibitory activity and 20-100 microg content of final material. The purification yield reveals that 1 kg ventricle muscle contains 0.1-0.2 mg NCX(IF), meaning that the tissue concentrations of NCX(IF) may reach 10(-7)-10(-6) M. The diode-array scanning of purified preparations of NCX(IF) shows a homogeneous 3D peak with a maximal absorption at 202 nm. These spectral properties may represent a five-membered ring (e.g., proline, histidine) and/or simple chemical groups (like amine, carbonyl, ester, etc.), but not an aromatic ring or complex conjugates (alkyne, alkene, aldehyde, etc.). NCX(IF) does not respond to phenol/sulfur reagent, suggesting that it lacks reducing (aldo) sugar. NCX(IF) shows a faint response to fluorescamine, meaning that it may contain an amino group (or its derivative). It is believed that a combination of presently developed procedures with LC/MS and LC/MS/MS may provide a useful tool for structural analysis of NCX(IF).     

Essential Role of the CBD1-CBD2 Linker in Slow Dissociation of Ca2+ from the Regulatory Two-domain Tandem of NCX1

In NCX proteins CBD1 and CBD2 domains are connected through a short linker (3 or 4 amino acids) forming a regulatory tandem (CBD12). Only three of the six CBD12 Ca²⁺-binding sites contribute to NCX regulation. Two of them are located on CBD1 (K_d = ∼0.2 μm), and one is on CBD2 (K_d = ∼5 μm). Here we analyze how the intrinsic properties of individual regulatory sites are affected by linker-dependent interactions in CBD12 (AD splice variant). The three sites of CBD12 and CBD1 + CBD2 have comparable K_d values but differ dramatically in their Ca²⁺ dissociation kinetics. CBD12 exhibits multiphasic kinetics for the dissociation of three Ca²⁺ ions (k_r = 280 s⁻¹, k_f = 7 s⁻¹, and k_s = 0.4 s⁻¹), whereas the dissociation of two Ca²⁺ ions from CBD1 (k_f = 16 s⁻¹) and one Ca²⁺ ion from CBD2 (k_r = 125 s⁻¹) is monophasic. Insertion of seven alanines into the linker (CBD12–7Ala) abolishes slow dissociation of Ca²⁺, whereas the kinetic and equilibrium properties of three Ca²⁺ sites of CBD12–7Ala and CBD1 + CBD2 are similar. Therefore, the linker-dependent interactions in CBD12 decelerate the Ca²⁺ on/off kinetics at a specific CBD1 site by 50–80-fold, thereby representing Ca²⁺ “occlusion” at CBD12. Notably, the kinetic and equilibrium properties of the remaining two sites of CBD12 are “linker-independent,” so their intrinsic properties are preserved in CBD12. In conclusion, the dynamic properties of three sites are specifically modified, conserved, diversified, and integrated by the linker in CBD12, thereby generating a wide range dynamic sensor.     

Pigment-pigment interactions in PCP of Amphidinium carterae investigated by nonlinear polarization spectroscopy in the frequency domain

Peridinin-chlorophyll a-protein (PCP) is a unique antenna complex in dinoflagellates that employs peridinin (a carotenoid) as its main light-harvesting pigment. Strong excitonic interactions between peridinins, as well as between peridinins and chlorophylls (Chls) a, can be expected from the short intermolecular distances revealed by the crystal structure. Different experimental approaches of nonlinear polarization spectroscopy in the frequency domain (NLPF) were used to investigate the various interactions between pigments in PCP of Amphidinium carterae at room temperature. Lineshapes of NLPF spectra indicate strong excitonic interactions between the peridinin's optically allowed S(2) (1Bu(+)) states. A comprehensive subband analysis of the distinct NLPF spectral substructure in the peridinin region allows us to assign peridinin subbands to the two Chls a in PCP having different S(1)-state lifetimes. Peridinin subbands at 487, 501, and 535 nm were assigned to the longer-lived Chl, whereas a peridinin subband peaking at 515 nm was detected in both clusters. Certain peridinin(s), obviously corresponding to the subband centered at 487 nm, show(s) specific (possibly Coulombic?) interaction between the optically dark S(1)(2A(g)(-)) and/or intramolecular charge-transfer (ICT) state and S(1) of Chl a. The NLPF spectrum, hence, indicates that this peridinin state is approximately isoenergetic or slightly above S(1) of Chl a. A global subband analysis of absorption and NLPF spectra reveals that the Chl a Q(y)-band consists of two subbands (peaking at 669 and 675 nm and having different lifetimes), confirmed by NLPF spectra recorded at high pump intensities. At the highest applied pump intensities an additional band centered at S(1)/ICT transition of peridinin.     

Glutamate treatment and p25 transfection increase Cdk5 mediated tau phosphorylation in SH-SY5Y cells

Neurofibrillary tangles (NFT) of hyperphosphorylated tau protein are a major pathological hallmark of Alzheimer's disease (AD). One of the tau phosphorylating kinases with pathological relevance in AD has been suggested to be the cyclin-dependent kinase 5 (Cdk5). The proposed mechanism leading to pathological Cdk5 activity is through induced cleavage of p35 to a proteolytic product, p25. To further study activation of Cdk5 and its role in tau phosphorylation in vitro, we used differentiated SH-SY5Y cells treated with neurotoxic stimuli or transfected with p25. We show that glutamate increased tau phosphorylation, concomitant with an increased Cdk5 activity achieved by upregulation of Cdk5 and p35 protein levels. Treatment with the calcium ionophore A23187 generated the calpain cleaved p25 fragment but only in toxic conditions that caused dephosphorylation and loss of tau. When p25 was transfected to the cells, increased tau phosphorylation was achieved. However, application of the Cdk5 inhibitor Roscovitine did not result in inhibition of tau phosphorylation possibly due to activation of extracellular regulated kinase 1/2 (Erk1/2), which also is capable of phosphorylating tau. Cdk5 and Erk1/2 kinases share some common substrates but impact of their cross talk on tau phosphorylation has not previously been demonstrated. We also show that p25 is degraded via the proteasome in Roscovitine treated cells.     

Dynamic features of allosteric Ca2+ sensor in tissue-specific NCX variants

The Na(+)-Ca(2+) exchanger (NCX) mediated Ca(2+) fluxes are essential for handling Ca(2+) homeostasis in many cell-types. Eukaryotic NCX variants contain regulatory CBD1 and CBD2 domains, whereas in distinct variants the Ca(2+) binding to Ca3-Ca4 sites of CBD1 results either in sustained activation, inhibition or no effect. CBD2 contains an alternatively spliced segment, which is expressed in a tissue-specific manner although its impact on allosteric regulation remains unclear. Recent studies revealed that the Ca(2+) binding to Ca3-Ca4 sites results in interdomain tethering of CBDs, which rigidifies CBDs movements with accompanied slow dissociation of "occluded" Ca(2+). Here we investigate the effects of CBD2 variants on Ca(2+) occlusion in the two-domain construct (CBD12). Mutational studies revealed that both sites (Ca3 and Ca4) contribute to Ca(2+) occlusion, whereas after dissociation of the first Ca(2+) ion the second Ca(2+) ion becomes occluded. This mechanism is common for the brain, kidney and cardiac splice variants of CBD12, although the occluded Ca(2+) exhibits 20-50-fold difference in off-rates among the tested variants. Therefore, the spliced exons on CBD2 affect the rate-limiting step of the occluded Ca(2+) dissociation at the primary regulatory sensor to shape dynamic features of allosteric regulation in NCX variants.     

Synthesis and structure-activity relationship of 4-(1,3-benzothiazol-2-yl)-thiophene-2-sulfonamides as cyclin-dependent kinase 5 (cdk5)/p25 inhibitors

4-(1,3-Benzothiazol-2-yl)thiophene-2-sulfonamide (4a) was found to be a moderately potent inhibitor of cyclin-dependent kinase 5 (cdk5) from a HTS screen. The synthesis and SAR around this hit is described. The X-ray coordinates of ligand 4a with cdk5 are also reported, showing an unusual binding mode to the hinge region via a water molecule.