Using silicon nanowire devices to detect adenosine triphosphate liberated from electrically stimulated HeLa cells

In this study, we used a biosensor chip featuring Abl tyrosine kinase-modified silicon nanowire field-effect transistors (SiNW-FETs) to detect adenosine triphosphate (ATP) liberated from HeLa cells that had been electrically stimulated. Cells that are cultured in high-ionic-strength media or buffer environments usually undermine the sensitivity and selectively of SiNW-FET-based sensors. Therefore, we first examined the performance of the biosensor chip incorporating the SiNW-FETs in both low- and high-ionic-strength buffer solutions. Next, we stimulated, using a sinusoidal wave (1.0 V, 50 Hz, 10 min), HeLa cells that had been cultured on a cell-culture chip featuring interdigitated electrodes. The extracellular ATP concentration increased by ca. 18.4-fold after electrical stimulation. Finally, we detected the presence of extracellular ATP after removing a small amount of buffer solution from the cell-cultured chip and introducing it into the biosensor chip.

Cr(VI) removal on fungal biomass of Neurospora crassa: the importance of dissolved organic carbons derived from the biomass to Cr(VI) reduction

Interactions of toxic Cr(VI) with renewable biomaterials are considered an important pathway for Cr(VI) removal in ecosystems. Biomaterials are susceptible to dissolution, and their dissolved derivatives may provide an alternative to surface-involved pathway for scavenging of Cr(VI). In this study, dissolved organic carbon (DOC) derived from Neurospora crassa biomass was investigated. The proportion of Cr(VI) reduction by DOC to that on biomass was determined to evaluate the importance of DOC to Cr(VI) reduction. A rapid increase in DOC concentration from 145.6 to 193.7 mg L(-1) was observed when N. crassa-biomass was immersed in 0.01 M KCl solution at pH of 1-5, and polysaccharides, peptides, and glycoproteins with carboxyl, amide, and -NH functional groups, are the major compositions of DOC. On reaction of 96.2 microM Cr(VI) with N. crassa-biomass or DOC, it was estimated that DOC contributed approximately 53.8-59.5% of the total Cr(VI) reduction on biomass in the dark. Illumination enhanced Cr(VI) reduction via photo-oxidation of biomass/DOC under aeration conditions, which formed superoxide for Cr(VI) reduction. At pH 1, photoinduced Cr(VI) reduction by DOC proceeded more rapidly than reduction on the biomass surface. However, at pH >3, with a decrease in Cr(VI) reduction by DOC, photon-excited biomass may become an important electron source for Cr(VI) photoreduction.

Armigeres subalbatus (Diptera: Culicidae) prophenoloxidase III is required for mosquito cuticle formation: ultrastructural study on dsRNA-knockdown mosquitoes

We previously suggested that Armigeres subalbatus (Coquillett) prophenoloxidase III (As-pro-PO III) might be associated with morphogenesis of larvae and pupae. Because PO and its activation system are present in the insect cuticle, and cuticle formation is a major event during pupal morphogenesis, we used ultrastructural analysis to examine the effects of As-pro-PO III knockdown on the formation of pupal and adult cuticle. Inoculation of As-pro-PO III dsRNA resulted in the incomplete formation of nascent pupal endocuticle and pharate adult cuticle, i.e., significantly fewer cuticular lamellae were deposited, the helicoidal pattern of chitin microfibrils was disorganized, and numerous electron-lucent spaces were present in the cuticular protein matrix. Similar disruptions were observed in the cuticle of adults derived from As-pro-PO III dsRNA-inoculated pupae. It has long been suggested that the quinines, generated by PO-catalyzed oxidation reactions, function as cross-linking agents; therefore, it seems reasonable to suggest that the loss of As-pro-PO III-mediated protein-protein linkages causes morphological abnormalities in the protein matrix. Our findings suggest that As-pro-PO III plays a role in cuticle formation in mosquitoes, a novel function for phenol-oxidizing enzymes.

Fabrication of porous TiO2 film on Ti foil by hydrothermal process and its photocatalytic efficiency and mechanisms with ethyl violet dye

Most of commercial dyes and pigments have rather complicated polyaromatic chemical structures with prolonged lifetime surviving in the Mother Nature. However, TiO(2) has been reported as one of the best photocatalytic candidates for degrading dye pollutants. In this report, TiO(2) film/Ti foil was prepared by hydrothermal reaction in alkali solution, the porous TiO(2) film with microcrystalline structure has been obtained. The porous structure of TiO(2) film was analyzed and characterized by XRD, FE-SEM and XPS. This is the first report that demonstrates that TiO(2) film/Ti foil has an excellent commercial application potential for photocatalytic degradation of Ethyl Violet (EV). Especially, because of refluxing at 100 degrees C, the porous TiO(2) film structure remained undisturbed, and EV decomposed in the period of 20 h. In addition, porous TiO(2)-mediated EV photo degradation mechanism has been proposed, as intermediates are isolated and clearly identified by GC-MS and HPLC-PDA-ESI-MS.

Sectional anatomy of the olfactory pathways

AIM

The purpose of this study was to provide practical anatomic data for imaging diagnosis of olfactory pathways and operation of nasal cavity and anterior cranial fossae.

METHODS

Sectional anatomy of olfactory pathways were investigated specially on 17 sets of Chinese adult cadavers and 9 sets of serial magnetic resonance (MR) imaging of normal adult on serial transverse, sagittal and coronal sections respectively.

RESULTS

We recognized olfactory bulb, olfactory tract, medial and lateral olfactory striae, olfactory trigone, anterior perforated substance and piriform lobe on transverse, sagittal and coronal sections respectively. On the 5-7 serial coronal sections from crista galli of ethmoid bone to the optic chiasm, the cusp ellipse olfactory bulb and the triangular tract were situated in the shallow part of the olfactory sulcus.

CONCLUSION

The olfactory bulb and olfactory tract lay tightly on the ethmoidal cribriform plate and jugum sphenoidale, in the olfactory cistern of the shallow part of the olfactory sulcus, the ethmoid sinus and sphenoid sinus inferiorly.

Comparison of photodegradative efficiencies and mechanisms of Victoria Blue R assisted by Nafion-coated and fluorinated TiO2 photocatalysts

The purposes of this research were to study the effects of two modified photocatalysts, Nafion-coated TiO(2) and fluorinated TiO(2), and photocatalytic degradation of Victoria Blue R in aqueous solution. Photocatalytic degradation of Victoria Blue R was accelerated by the modified photocatalysts. Bulk and surface characterizations of the resulting powders were carried out. Attachment of the anions to the TiO(2) surface using the Nafion-coated-TiO(2) possibly results in increased adsorption of the cationic dye, and the degradation rate is larger for the cationic dye. It was found that Victoria Blue R on the two illuminated TiO(2) surfaces underwent very different changes. To obtain a better understanding on the mechanistic details of this modified-TiO(2)-assisted photodegradation of the Victoria Blue R dye with UV irradiation, a large number of intermediates of the process were separated, identified, and characterized by a high-performance liquid chromatography-mass spectrometry technique. Several probable photodegradation pathways were proposed and discussed.

Bis(2-chloroethoxy)methane degradation by TiO2 photocatalysis: parameter and reaction pathway investigations

Haloethers are widely used in industry, and the release of these species into the environment is of great concern because of their toxicity and carcinogenicity. The present study deals with the photocatalytic degradation of the haloether, bis(2-chloroethoxy)methane (BCEXM), in the presence of TiO(2) particles and UV-A (lambda=365 nm) radiation. About 99.5% of BCEXM was degraded after UV irradiation for 16h. Factors such as solution pH, TiO(2) dosage, and the presence of anions were found to influence the degradation rate. To obtain a better understanding of the mechanistic details of this TiO(2)-assisted photodegradation of BCEXM with UV irradiation, the intermediates of the processes were separated, identified, and characterized by the solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) technique. To the best of our knowledge, this is the first report on the degradation pathways of BCEXM. The first step in the destruction of BCEXM is thought to be abstraction of a hydrogen by ()OH to form a carbon-centered radical which then reacts with O(2) to form a peroxyl radical. Peroxyl radicals react with one another and produce an alkoxy radical. The beta-bond fragmentation of the alkoxy radical produces different intermediates.

First Report of Capsicum chlorosis virus Infecting Amaryllis and Blood Lily in Taiwan

Capsicum chlorosis virus (CaCV), a thrips-transmitted, tentative species in the genus Tospovirus, family Bunyaviridae, was first identified in solanaceous crops, but also infects several ornamental crops such as orchid (4), gloxinia (3), and calla lily (1). From 2005 to 2007, virus-like yellow ringspots were observed on the leaves of amaryllis (Hippeastrum hybridum Hort.) and blood lily (Haemanthus multiflorus Martyn.) plants cultured in screenhouses and a private garden, respectively. Three of several hundred amaryllis plants in screenhouses from two places were observed as showing yellow ringspot symptoms and one of six blood lily plants was observed as showing similar yellow ringspot symptoms. Sap extracts from symptomatic leaves were inoculated to Chenopodium quinoa Willd. and the resulting local lesions were passaged three successive times to C. quinoa for virus isolation. Using the tospovirus genus-specific primers gL3637 and gL4435c designed from the conserved region in the L RNA (2), DNA fragments of the expected size of 800 bp were amplified by reverse transcription (RT)-PCR from field samples and local lesions from C. quinoa. Extracts from the diseased plants and local lesions of C. quinoa reacted strongly with antiserum against the nucleocapsid (N) protein of CaCV in ELISA and western blotting. To confirm the identity of this virus, we amplified the N gene from three amaryllis and one blood lily source using primer pair WN2328 and WN3534 designed from the S RNA of Watermelon silver mottle virus (1), and these products were cloned and sequenced. The sequence from each virus isolate was determined from three independent clones. The nucleotide and deduced amino acid sequences of N genes for the blood lily isolate (GenBank Accession No. EF101344) and three amaryllis isolates (GenBank Accession Nos. EF101343, EF137177, and FJ185170) had identities greater than 97% with that of a CaCV isolate infecting Capsicum spp. found in Australia (GenBank Accession No. AY036057). Phylogenetic analysis using maximum parsimony showed that these sequences clustered with CaCV. These results show that the virus identified from amaryllis and blood lily that were expressing yellow ringspot symptoms are isolates of CaCV. To our knowledge, this is the first report of CaCV naturally infecting amaryllis and blood lily and it could become an important threat to ornamental production in Taiwan. References: (1) C. C. Chen et al. Plant Dis. 91:1201, 2007. (2) F. H. Chu et al. Phytopathology 91:361, 2001. (3) H. T. Hsu et al. J. Gen. Plant Pathol. 66:167, 2000. (4) Y. X. Zheng et al. Eur. J. Plant Pathol. 120:199, 2008.

Chromate reduction by zero-valent Al metal as catalyzed by polyoxometalate

In spite of a high reduction potential of zero-valent Al (ZVAl), its ability to reduce Cr(VI), a widespread pollutant, to less toxic Cr(III) remains to be uncovered. In the present study, Cr(VI) reduction by ZVAl was conducted to evaluate the potential application of Al as a reductant for Cr(VI). Polyoxometalate (POM, HNa(2)PW(12)O(40)), a catalyst, was used to accelerate Cr(VI) reduction by Al. The reaction of 0.192mM Cr(VI) on ZVAl was investigated in the presence of N(2) or O(2) at pH 1. A slight decrease in Cr(VI) concentration was observed on as-received (uncleaned) ZVAl due to the presence of oxide layer with a low surface area (ca. 3.4x10(-3)m(2)/g) of ZVAl. On addition of 0.1mM POM, Cr(VI) reduction on uncleaned ZVAl increased significantly. This is attributed to the unique properties of POM, which has a Brphinsted acidity higher than usual inorganic acids such as H(2)SO(4) and HCl. Thus, POM could remove rapidly the oxidize layer on ZVAl, followed by acting as a shuttle for electron transfer from ZVAl to Cr(VI). Under a N(2) atmosphere, one- or two-electron reduction of POM by ZVAl was responsible for Cr(VI) reduction in the early stage of the reaction. However, during reaction with ZVAl over 120min, three-electron reduction of POM predominated over Cr(VI) reduction. On interaction of O(2) with reduced POM, the formation of H(2)O(2) was responsible for subsequent Cr(VI) reduction. The results suggest that POM is an efficient catalyst for Cr(VI) reduction by Al due to the extremely rapid consumption of reduced POM or H(2)O(2) by Cr(VI).

Patient-driven loop control for ambulation function restoration in a non-invasive functional electrical stimulation system

PURPOSE

In this study, a patient-driven loop control in a non-invasive functional electrical stimulation (FES) system was designed to restore ambulation function of patients with stroke with their residual capabilities.

METHOD

With this patient-driven loop control, patients use the electromyographic (EMG) signals from their voluntary controlled muscles in affected extremity to adjust stimulus parameters of the system. A special designed FES system generated electrical stimuli to excite the paralysed muscles through surface electrodes on the basis of the control command from the residual myoelectric signals. The EMG signals were also served as the trigger and the adjustment of stimulus parameters and thereby adding versatility of the FES system. One patient with hemiplegia was recruited to conduct clinical evaluation and treated by using the new closed-loop FES system.

RESULTS

The experimental results showed that hemiplegic could successfully control the system to restore their lost ambulation functions with the strategy of patient-driven loop control. It is revealed that the mean velocity, cadence, stride length, active ankle motion range and functional ambulation category have improved significantly from 0.22 + or - 0.17 m/s, 37.3 + or - 15.5 steps/min, 0.32 + or - 0.11 m, 10 degrees , level 2 to 0.46 + or - 0.23 m/s, 58.2 + or - 19.1 steps/min, 0.73 + or - 0.22 m, 35 degrees , level 4 respectively for the patient. A paired t-test indicated that differences in the EMG of the tibialis anterior and the gastrocnemius muscles between patient's disabled (affected-side) foot and normal (unaffected-side) foot are not significant (p > 0.05) after 12 weeks of training.

CONCLUSIONS

According to the experiment results, this patient-driven loop control can be beneficial for patient with hemiplegia to restore their ambulation functions such as dorsi-flexion and plantar-flexion. The control strategy of this study has the potential to be employed not only in the FES system but also in other assistive devices.

Degradation pathways of crystal violet by Fenton and Fenton-like systems: condition optimization and intermediate separation and identification

The main advantage of Fenton's reagent (FR) over other OH systems is its simplicity. FR has the potential for widespread use in treating wastewater, but compared to other OH systems, little information on the dye degradation pathways of FR exists. The degradation of crystal violet (CV), a triphenylmethane dye, by FR was determined as a function of reagent concentration and ratio and pH in the batch treatment. The experimental results showed the optimum Fe(2+)/H(2)O(2) ratio to be 0.5mM:50mM and the optimum Fe(3+)/H(2)O(2) ratio to be 1mM:50mM. Optimal pH was about 3. To obtain a better understanding of the mechanistic details of Fenton reagent's degradation of CV dye, the intermediates of the process were separated, identified, and characterized by HPLC-PDA-ESI-MS and GC-MS techniques in this study. Indications were that the probable degradation pathways were N-de-methylation and cleavage of the conjugated chromophore structure. The intermediates were generated in the order of the reaction time and relative concentration, indicating that the N-de-methylation degradation of CV dye is a major reaction pathway. The reaction mechanisms proposed in this research should prove useful for future application of the technology to the decolorization of dyes.

Nanocontact resistance and structural disorder induced resistivity variation in metallic metal-oxide nanowires

Several systems of metallic metal-oxide nanowires (NWs), including pure RuO2 and as-implanted and annealed Ru(0.98)Cu(0.02)O2 and Ru(0.93)Cu(0.07)O2 NWs, have been employed in two-probe electrical characterizations by using a transmission electron microscope-scanning tunneling microscope technique with a gold tip. Thermal, mechanical, and electron beam exposing treatments are consecutively applied to reduce the electrical contact resistance, generated from the interface between the NW and the gold tip, so as to evaluate the intrinsic NW resistance. It is found that the residual contact resistance cannot be entirely removed. For each system of metallic metal-oxide NWs, several tens of NWs are applied to electrical characterizations and the total resistances unveil a linear dependence on the ratio of the length to the area of the NWs. As a result, the average resistivity and the contact resistance of the metallic metal-oxide NWs could be evaluated at room temperatures. The average resistivities of pure RuO2 NWs agree well with the results obtained from standard two- and four-probe electrical-transport measurements. In addition, the as-implanted Cu-RuO2 NWs reveal disordered crystalline structures in high-resolution TEM images and give higher resistivities in comparison with that of pure RuO2 NWs. The residual contact resistances of all kinds of metallic metal-oxide NWs unveil, more surprisingly, an approximation value of several kilohms, even though the average resistivities of these NWs change by more than one order of magnitude. It is argued that the ductile gold tip makes one or more soft contacts on the stiff metal-oxide NWs with nanometer roughness and the nanocontacts on the NWs contribute to the electrical contact resistance.

Water-assisted CO(2) laser ablated glass and modified thermal bonding for capillary-driven bio-fluidic application

The glass-based microfluidic chip has widely been applied to the lab-on-a-chip for clotting tests. Here, we have demonstrated a capillary driven flow chip using the water-assisted CO(2) laser ablation for crackless fluidic channels and holes as well as the modified low-temperature glass bonding with assistance of adhesive polymer film at 300 degrees Celsius. Effect of water depth on the laser ablation of glass quality was investigated. The surface hydrophilic property of glass and polymer film was measured by static contact angle method for hydrophilicity examination in comparison with the conventional polydimethylsiloxane (PDMS) material. Both low-viscosity deionized water and high-viscosity whole blood were used for testing the capillary-driving flow behavior. The preliminary coagulation testing in the Y-channel chip was also performed using whole blood and CaCl(2) solution. The water-assisted CO(2) laser processing can cool down glass during ablation for less temperature gradient to eliminate the crack. The modified glass bonding can simplify the conventional complex fabrication procedure of glass chips, such as high-temperature bonding, long consuming time and high cost. Moreover, the developed fluidic glass chip has the merit of hydrophilic behavior conquering the problem of traditional hydrophobic recovery of polymer fluidic chips and shows the ability to drive high-viscosity bio-fluids.

Rapid diagnosis of tuberculosis directly from clinical specimens using a gene chip

The aim of this study was to explore a gene chip capable of detecting the presence of Mycobacterium tuberculosis isolates directly in clinical sputum specimens and to compare it with current molecular detection techniques. At first, we selected 13 M. tuberculosis-specific target genes to construct a gene chip for rapid diagnosis. Using the membrane array method, we diagnosed M. tuberculosis by gene chip directly from 246 sputum specimens from patients suspected of having tuberculosis. Among 80 M. tuberculosis complex (MTBC) culture-positive sputum specimens, the MTBC detection rate was 62.5% (50/80) by PCR-restriction fragment length polymorphism (RFLP), 70% (56/80) by acid-fast staining, and 85% (68/80) by the membrane array method. Furthermore, subspecies showed different gene expression patterns in the membrane array. In conclusion, MTBC could be detected directly in sputum by the membrane array method. The rapidity of detection and the capability of differentiating subspecies could make this method useful in the control and prevention of tuberculosis.

Exploring the origin of the directional emission from a microcavity with a large-aperture surface-emitting laser

The origin of the direction emission from a microcavity is investigated with a large-aperture surface-emitting laser with an equilateral-triangular shape. Experimental results reveal that a wide-spread eigenmode and a localized superscar mode can display quite similar far-field directional emissions. This experimental finding is theoretically confirmed with the quantum-billiard wave function and the approximation of the paraxial propagation.

Identification of the degradation pathways of alkanolamines with TiO2 photocatalysis

The present study deals with the photocatalytic degradation of the alkanolamine, 2-dimethylamino-2-methyl-1-propanol (DMAMP), in the presence of TiO(2) particles and UV-A (lambda=365 nm) radiation. The obtained results show complete oxidation of DMAMP after 20h, and a little over 90% of DMAMP was mineralization after 64-h of treatment. The effects of the solution pH, catalyst loading, and anions on the photocatalytic degradation of DMAMP were investigated, as well as the reaction intermediates that were formed during treatment. To the best of our knowledge, this is the first time that reports the degradation pathways of DMAMP. A number of intermediates were identified by GC/MS techniques during the treatment of DMAMP, following three tentative degradation routes. The first one is based on the oxidation of the primary alcohol group leading to the formation of corresponding aldehyde and carboxylic acid. The second route is based on the rupture of the N-C bond to form 2-methylpropanal and acetone. The last degradation route is based on the cyclization of the beta-amino alcohol group to form the oxazolidine derivatives.

Combined treatment with denbinobin and Fas ligand has a synergistic cytotoxic effect in human pancreatic adenocarcinoma BxPC-3 cells

BACKGROUND AND PURPOSE

Human pancreatic carcinoma is a highly malignant cancer. Previous studies have shown that the decoy receptor 3 (DcR3) for Fas ligand (FasL) plays significant roles in tumour progression and immune suppression. In the present study, we evaluated the anti-cancer activity of a natural compound, denbinobin (5-hydroxy-3,7-dimethoxy-1,4-phenanthraquinone), through decreasing DcR3 levels in human pancreatic adenocarcinoma cell lines.

EXPERIMENTAL APPROACH

We used immunoprecipitation and ELISA assays to examine DcR3 levels, and used FACS to determine the percentage of cells with a sub-G1 DNA content.

KEY RESULTS

AsPC-1 and BxPC-3 human pancreatic cancer cells express high levels of DcR3. Denbinobin concentration-dependently decreased DcR3 levels in BxPC-3 cells. MTT and flow cytometry assays indicated that BxPC-3 was FasL-resistant because high concentrations (100 ng.mL(-1)) of soluble FasL did not inhibit cell growth. However, combinations of denbinobin (3 micromol.L(-1)) with lower concentrations of soluble FasL (10, 30 and 50 ng.mL(-1)) or membrane-bound FasL, were synergistic on cell growth inhibition and apoptosis. Exogenous excess DcR3 reversed this synergistic effect. We observed no significant increase in the levels of surface Fas, cleaved forms of caspase-8, -3, -9, Bax, Bid, Bcl-xL, cytochrome c or mitochondrial membrane potentials following denbinobin treatment. However, denbinobin treatment increased the levels of apoptosis-inducing factor.

CONCLUSIONS AND IMPLICATIONS

Denbinobin and FasL trigger a synergistic cytotoxic effect in human pancreatic adenocarcinoma cells. Denbinobin mediated a decrease in levels of DcR3, which played a major role in this synergistic effect, and also increased caspase-independent apoptosis, via apoptosis-inducing factor.

Malignancies associated with dermatomyositis and polymyositis in Taiwan: a nationwide population-based study

BACKGROUND

Previous studies showed that idiopathic inflammatory myopathies (IIM) carried an increased risk of cancers. However, no large-scale study of IIM has been conducted in the Chinese population.

OBJECTIVES

We sought to delineate the association of IIM and various cancer types from a nationwide database in Taiwan.

METHODS

We analysed the published national data from records of National Health Insurance claims. Cases of dermatomyositis (DM) and polymyositis (PM) from 2000 to 2005 and cancers registered in the catastrophic illness profile from 1997 to 2006 were collected. A nationally representative cohort of 1,000,000 enrollees was included for comparison.

RESULTS

In total, 136 patients (12.8%) among 1059 cases of DM and 46 persons (7.0%) among 661 cases of PM carried internal malignancies. Patients with DM tended to have cancers of nasopharynx, lung and breast. On the other hand, patients with PM tended to have breast, uterine cervix and lung cancers. Compared with the general population, DM gave a 10-fold increased risk for cancers, in which a 66-fold increased risk for nasopharyngeal carcinoma and a 31-fold increased risk for lung cancer were the two most significant. For patients with PM, a 6-fold increased risk for cancer was observed. Juvenile DM had a 16-fold increased risk for haematopoietic or lymphoid malignancy. Two thirds of comorbid malignancies were detected shortly after the diagnoses of IIM, within a mean of 1-2 years. Overall, younger patients with IIM carried the highest risk for malignancies, especially those in their twenties and thirties.

CONCLUSIONS

This is the first large-scale study to report the associated malignancies and the cancer risk of IIM in Taiwan.

The synthesis and characterization of [(124)I]IMPY, a thioflavin-S derivative, in transgenic mouse models of Alzheimer's disease

6-[(124)I]iodo-2-(4'-N,N-dimethylamino)-phenylimidazo[1,2-a]pyridine ([(124)I]IMPY) was synthesized and characterized as a positron-emitting probe to identify Alzheimer's disease in transgenic mouse models. A significant reduction in radioactivity retention in the hippocampus and frontal cortex by co-incubation with nonradioactive IMPY was observed. Highly specific retention of radioactivity in beta-amyloid-rich regions of brain sections was also noted. This study demonstrated that [(124)I]IMPY was a promising probe for the mouse model and may be useful for positron emission tomography to image beta-amyloid plaques in the human brain.