Strong polarization switching with low-energy loss in hydrogen-bonded organic antiferroelectrics

The electric-field-induced phase transition from antipolar to polar structures is at the heart of antiferroelectricity. We demonstrate direct evidence of antiferroelectricity by applying a strong electric field to two antipolar crystals of squaric acid (SQA) and 5,5'-dimethyl-2,2'-bipyridinium chloranilate. The field-induced polarization of SQA is quite large and reasonably explained by the theoretically calculated polarization on the hydrogen-bonded sheet sublattice. The pseudo-tetragonal lattice of SQA permits unique switching topologies that produce two different ferroelectric phases of low and high polarizations. By tilting the applied field direction, the electrical switching mechanism can be attributed to a 90° rotation of the sheet polarization. From the viewpoint of applications, the strong polarization, high switching field, and quite slim hysteresis observed in the polarization versus electric field curve for SQA are advantageous for excellent-efficiency energy storage devices.

Shift current photovoltaic effect in a ferroelectric charge-transfer complex

Shift current is a steady-state photocurrent generated in non-centrosymmetric single crystals and has been considered to be one of the major origins of the bulk photovoltaic effect. The mechanism of this effect is the transfer of photogenerated charges by the shift of the wave functions, and its amplitude is closely related to the polarization of the electronic origin. Here, we report the photovoltaic effect in an organic molecular crystal tetrathiafulvalene-p-chloranil with a large ferroelectric polarization mostly induced by the intermolecular charge transfer. We observe a fairly large zero-bias photocurrent with visible-light irradiation and switching of the current direction by the reversal of the polarization. Furthermore, we reveal that the travel distance of photocarriers exceeds 200 μm. These results unveil distinct features of the shift current and the potential application of ferroelectric organic molecular compounds for novel optoelectric devices.The bulk photovoltaics refers to an effect whereby electrons move directionally in non-centrosymmetric crystals upon light radiation. Here, Nakamura et al. observe this effect in a ferroelectric organic charge-transfer complex, which shows large diffusion distance of photogenerated electrons over 200 µm.

Ultrafast Photoinduced Electric-Polarization Switching in a Hydrogen-Bonded Ferroelectric Crystal

Croconic acid crystals show proton displacive-type ferroelectricity with a large spontaneous polarization reaching 20  μC/cm^{2}, which originates from the strong coupling of proton and π-electron degrees of freedom. Such a coupling makes us expect a large polarization change by photoirradiations. Optical-pump second-harmonic-generation-probe experiments reveal that a photoexcited croconic-acid crystal loses the ferroelectricity substantially with a maximum quantum efficiency of more than 30 molecules per one absorbed photon. Based on density functional calculations, we theoretically discuss possible pathways toward the formation of a one-dimensional domain with polarization inversion and its recovery process to the ground state by referring to the dynamics of experimentally obtained polarization changes.

Novel PAX9 Mutations Cause Non-syndromic Tooth Agenesis

PAX9 is a transcription factor expressed in the tooth mesenchyme during tooth morphogenesis. In Pax9-null mice, tooth development is arrested at the bud stage. In humans, heterozygous mutations in PAX9 have been associated with non-syndromic tooth agenesis, predominantly in the molars. Here, we report 2 novel mutations in the paired domain of PAX9, a three-nucleotide deletion (73-75 delATC) and a missense mutation (C146T), in two unrelated Japanese patients with non-syndromic tooth agenesis. The individual with the 73-75del ATC mutation was missing all maxillary molars and mandibular second and third molars. The individual with the C146T mutation was missing the mandibular central incisors, maxillary second premolars, and first molars, along with all second and third molars. Both mutations affected amino acids that are highly conserved among different species and are critical for DNA binding. When both mutants were transfected to COS7 cells, nuclear localization of PAX9 proteins was not affected. However, reduced expression of the mutant proteins and almost no transcriptional activity of the target BMP4 gene were observed, suggesting haploinsufficiency of PAX9 as the cause of non-syndromic tooth agenesis.

Type 1 Pili Enhance the Invasion ofSalmonella braenderupandSalmonella typhimuriumto HeLa Cells

The relationship between type 1 pili-associated adhesion and invasion to HeLa cells by Salmonella braenderup and S. typhimurium was studied. When the clinical isolates of these strains were grown in L-broth, they showed both type 1 pili formation and mannose-sensitive adhesion to HeLa cells. On the other hand, the type 1 pili-defective mutants, which were obtained either by repeated subcultures on L-agar plates or by the transposon Tn1-insertion mutagenesis of the S. braenderup and S. typhimurium strains, concomitantly lost mannose-sensitive adhesion to HeLa cells. When the HeLa cells were incubated with Salmonella, the type 1 piliated strains invaded the HeLa cells with much higher infection rate than did the type 1 pili-defective strains. The invasion of type 1 piliated strains to HeLa cells was markedly inhibited in the presence of D-mannose. The infectivity of the strain, which lost type 1 pili but still had mannose-resistant adhesion, was slightly higher than that of the strains defective in both mannose-sensitive and mannose-resistant adhesion. These results suggested that type 1 pili have a role in enhancing the invasion of S. braenderup and S. typhimurium to HeLa cells.

Advanced Glycation End Products (AGE)-Modified Proteins and Their Potential Relevance to Atherosclerosis

Modification of proteins by long-term incubation with glucose leads, through the formation of early products such as Schiff base and Amadori rearrangement products, to the formation of advanced glycation end products (AGE). AGE-modified proteins are characterized physicochemically by fluorescence, brown coloration, and intramolecular or intermolecular cross-linking. Biologically, they are specifically recognized by the AGE receptors of the cell surface membrane. Recent studies have provided evidence for the involvement of AGE proteins in atherosclerosis. First, in vitro experiments using Chinese hamster ovary cells overexpressing the macrophage scavenger receptor (MSR) and peritoneal macrophages from MSR-knockout mice demonstrated that MSR plays a major role as the AGE receptor in the endocytotic uptake of AGE by macrophages. Second, immunohistochemical studies using anti-AGE antibody and anti-MSR antibody revealed the presence of AGE proteins in human atherosclerotic lesions in arterial walls. Because MSR is closely associated with the formation of early atherosclerotic lesions, these results suggest a potential role played by AGE proteins or their interaction with MSR in the atherosclerotic process. (Trends Cardiovasc Med 1996;6:163-168).

Domain and Interface Structures of Epitaxial PtSi

The crystalline perfection of epitaxial PtSi thin films and the microstructure of the PtSi/Si interface have been examined using transmission electron microscopy (TEM), including lattice image techniques. Epitaxial PtSi layers grow with domains which have three different positions on a (111) Si substrate. Inside a domain the crystalline perfection is high, and at the domain boundary no intermediate region has been observed. The undulation of the PtSi/Si interface is larger than that of other epitaxial silicide/Si interfaces. Despite the large undulation, a cross-sectional lattice image shows the epitaxial layer extends to the interface. The interface is abrupt in the epitaxial PtSi/Si system.

Electric-field control of solitons in a ferroelectric organic charge-transfer salt

The role of solitons in transport, dielectric, and magnetic properties has been revealed for the quasi-one-dimensional organic charge-transfer salt, TTF-QBrCl3 [tetrathiafulvalene (TTF)-2-bromo-3,5,6-trichloro-p-benzoquinone (QBrCl3)]. The material was found to be ferroelectric and hence the solitons should be located at the boundary of the segments with opposite electric polarization. This feature enabled the electric-field control of soliton density and hence the clear-cut detection of soliton contributions. The gigantic dielectric response in the ferroelectric phase is ascribed to the dynamical bound and creeping motions of spinless solitons.

Stress analysis in the mandibular condyle during prolonged clenching: a theoretical approach with the finite element method

Parafunctional habits, such as bruxism and prolonged clenching, have been associated with functional overloading in the temporomandibular joint (TMJ), which may result in internal derangement and osteoarthrosis of the TMJ. In this study, the distributions of stress on the mandibular condylar surface during prolonged clenching were examined with TMJ mathematical models. Finite element models were developed on the basis of magnetic resonance images from two subjects with or without anterior disc displacement of the TMJ. Masticatory muscle forces were used as a loading condition for stress analysis during a 10 min clenching. In the asymptomatic model, the stress values in the anterior area (0.100 MPa) and lateral area (0.074 MPa) were relatively high among the five areas at 10 min. In the middle and posterior areas, stress relaxation occurred during the first 2 min. In contrast, the stress value in the lateral area was markedly lower (0.020 MPa) than in other areas in the symptomatic model at 10 min. The largest stress (0.050 MPa) was located in the posterior area. All except the anterior area revealed an increase in stress during the first 2 min. The present result indicates that the displacement of the disc could affect the stress distribution on the condylar articular surface during prolonged clenching, especially in the posterior area, probably leading to the cartilage breakdown on the condylar articular surface.

Advanced glycation end product is implicated in amyloid‐related kidney complications

BACKGROUND

Kidney failure is a common complication in familial amyloidotic polyneuropathy (FAP). It has been suggested that advanced glycation end products (AGEs) play an important role in the development and pathogenesis of FAP.

MATERIAL AND METHODS

To evaluate the impact of AGEs on FAP patients' kidney dysfunction, we measured AGE in serum and urine of 28 FAP patients and 18 healthy controls by AGE-specific enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry utilizing antibodies to AGE and the receptor for AGE (RAGE) were used on kidney tissue from 3 FAP patients and 3 diabetic patients to disclose a correlation between amyloid deposits and AGE-RAGE.

RESULTS

The glomeruli of FAP patients were heavily deposited with amyloid and the glomerular size was enlarged. The space between Bowman's capsule and glomerulus was totally covered by the enlarged glomerulus. AGE and RAGE were deposited in glomeruli and tubuli and correlated with amyloid deposits. Decreased AGE levels in the liver-transplanted FAP patients' serum compared with that of non-transplanted patients were noted, and AGE concentration in serum tended to be higher in non-transplanted FAP patients compared with normal control subjects. There were no differences in the AGE urine levels in FAP patients compared with controls. No correlation could be found between AGE in urine and serum compared with serum albumin, serum creatinine and creatinine clearance.

CONCLUSIONS

The accumulation of AGE, RAGE and amyloid in the kidney of FAP patients suggests that these molecules play an important role in the origin and pathogenesis of renal failure in FAP patients.

Dynamical disorder of pi-molecular structures induced by proton dynamics in an organic ferroelectric compound

We have investigated the optical response resulting from the proton-pi-electron-molecular-skeleton coupled dynamics in an organic ferroelectric 55DMBP-Hia. Upon the ferroelectric-to-paraelectric transition, almost all of the vibrational modes below 500 cm;{-1} are anomalously blurred and amalgamated into the high-frequency tail of the polarization-relaxation mode. This indicates that the constituent molecular shape is no more well defined around T_{C} due to the dynamical disorder of the pi-conjugated structure originating from proton delocalization on the intermolecular bifurcated hydrogen bond.

Characterization of the immune escape phenotype of human gastric cancers with and without high-frequency microsatellite instability

Gastric cancers with and without high-frequency microsatellite instability (MSI-H) represent distinctive pathways of carcinogenesis. The aim of this study was to clarify if human leukocyte antigen (HLA) class I antigen subunits and antigen processing machinery (APM) components are differentially downregulated in these two groups of tumours. Using reverse transcription PCR (RT-PCR), loss of heterozygosity (LOH) analysis, methylation-specific PCR (MSP), DNA sequencing, immunohistochemistry, and flow cytometry, we analysed expression and/or alteration of HLA class I antigen subunits and APM components, including low molecular weight polypeptide proteasome subunit (LMP)2, LMP7, LMP10, transporter associated with antigen processing (TAP)1, TAP2, tapasin, proteasome activator (PA) 28alpha, and PA28beta in two stage-matched panels of 30 MSI-H and 30 microsatellite stable (MSS) gastric cancers. Mutations at coding microsatellites (cMS) located within beta2-microglobulin (beta2m) and genes encoding APM components, including endoplasmic reticulum (ER) chaperone protein genes, such as calnexin, SEC63, SEC31, and P4HB (p55), were also analysed. HLA class Ia transcripts were totally downregulated in 18.3% of cancer cases. Locus-specific downexpression of HLA-A, -B, and -C was detected in 41.7%, 45.0%, and 31.7% of cases. Loss of HLA-A was significantly more frequent in MSI-H cancers. The LOH ratios of the HLA-A, -B, and -C loci microsatellite markers were relatively low: 5/32 (15.6%) for D6S306, 4/32 (12.5%) for D6S258, 4/33 (12.1%) for D6S273, and 4/30 (13.3%) for D6S1666. Methylation of HLA-A, -B, and -C was detected in 38.3%, 40.0%, and 28.3% of cases. A significant association between methylation and reduction in expression was observed in gastric cancer tissues. Mutations at cMS of beta2m and APM components were detected in 3.3-46.7% of MSI-H cancers but in none of MSS cancers. These data show that gastric cancers have various defects in HLA class I antigen subunits and APM components and that the MSI phenotype is associated with frequent HLA-A inactivation and frameshift mutations of the beta2m and APM genes.

Intake of purple sweet potato beverage affects on serum hepatic biomarker levels of healthy adult men with borderline hepatitis

OBJECTIVE

To examine the effect of purple sweet potato (PSP) beverage rich in acylated anthocyanins on serum hepatic biomarkers in healthy Japanese men.

DESIGN

A randomized, double-blind, placebo-controlled, parallel study.

SETTING

Kumamoto in Japan.

SUBJECTS

Healthy adult men (30-60 years) with borderline hepatitis who had one or more of serum gamma-glutamyl transferase (GGT), aspertate aminotransferase (AST) and alanine aminotransferase (ALT) levels over normal ranges, and who were negative for hepatitis virus were openly recruited by an advertisement. Of the 48 persons enrolled, 38 (mean age 43.0 years (30-54 years)) completed the study.

METHODS

The subjects were randomly assigned to the PSP group and the placebo group. During the 8-week intervention, the subjects in the PSP group consumed two bottles of the PSP beverage with acylated anthocyanins (200.3 mg anthocyanins per 125 ml per bottle) per day, and the subjects in the placebo group, two bottles of a placebo beverage (1.7 mg anthocyanins per 125 ml per bottle). All of the data measured were analyzed by two-way repeated measures analysis of variance (ANOVA) with groups and times. The data of the hepatic markers were analyzed using the Dunnett multiple comparison among the time points and t-test between groups at the same time point. Two-sided P<0.05 were defined as the level of significance.

RESULTS

Serum GGT, AST and ALT levels showed interactions (P<0.05) between the beverage groups and time; the others were not affected. The PSP beverage group showed lower hepatic marker levels than the placebo group during the ingestion period, particularly the GGT level (-14.1 IU/l, 95% Confidence intervel (CI) -25.4 to -2.7, P=0.017 at 2 weeks; -16.8 IU/l, 95% CI -36.2 to 2.5, P=0.081 at 4 weeks; -26.7 IU/l, 95% CI -47.6 to -5.7, P=0.014 at 6 weeks and -27.9 IU/l, 95% CI -49.9 to -5.9; P=0.014 at 8 weeks). No correlation between alcohol consumption and each hepatic biomarker level before and after the ingestion was observed.

CONCLUSION

The intake of the PSP beverage significantly decreased the serum levels of hepatic biomarkers, particularly the GGT level, in healthy men with borderline hepatitis.

K-ras mutation in the endometrium of tamoxifen-treated breast cancer patients, with a comparison of tamoxifen and toremifene

The putative presence of a mutation in codon 12 of the K-ras gene was investigated in the endometrium of tamoxifen (TAM) and toremifene (TOR)-treated breast cancer patients. DNA was extracted from fresh cytologic samples of the endometrium in 86 TAM and 21 TOR-treated breast cancer patients. Mutations were detected by enriched PCR and an enzyme-linked mini-sequence assay (ELMA). K-ras mutation was found in 35 TAM-treated endometrial samples, and in only one TOR-treated endometrium (P<0.003). In 24 premenopausal patients, K-ras mutation was found in seven (43.8%) of 16 patients with less than 47 months of TAM treatment, while none was found in eight patients with more than 48 months of TAM treatment (P<0.03). In 62 postmenopausal-amenorrheic patients, K-ras mutation was found in three (15.8%) of 19 patients with less than 23 months of TAM treatment, while it was found in 16 (61.5%) of 26 patients with 24–47 months of TAM treatment and nine (52.9%) of 17 patients with more than 48 months of TAM treatment (P=0.002). The presence of K-ras mutation is significantly influenced by the duration of TAM treatment and menstrual status of the patients. TOR may have a lower potential genotoxicity than TAM.

Renal clearance of glycolaldehyde- and methylglyoxal-modified proteins in mice is mediated by mesangial cells through a class A scavenger receptor (SR-A)

AIMS/HYPOTHESIS

Glomerular mesangial expansion is a characteristic feature of diabetic nephropathy, and the accumulation of AGE in the mesangial lesion has been implicated as one of its potential causes. However, the route for the AGE accumulation in mesangial lesions in diabetic patients is poorly established.

METHODS

Glycolaldehyde-modified BSA (GA-BSA) and methylglyoxal-modified BSA (MG-BSA) were prepared as model AGE proteins, and their in vivo plasma clearance was examined in mice, and renal uptake by in vitro studies with isolated renal mesangial cells.

RESULTS

Both (111)In-GA-BSA and (111)In-MG-BSA were rapidly cleared from the circulation mainly by both the liver and kidney. Immunohistochemical studies with an anti-GA-BSA antibody demonstrated that intravenously injected GA-BSA accumulated in mesangial cells, suggesting that such cells play an important role in the renal clearance of circulating AGE proteins. Binding experiments at 4 degrees C using mesangial cells isolated from mice showed that (125)I-GA-BSA and (125)I-MG-BSA exhibited specific and saturable binding. Upon incubation at 37 degrees C, (125)I-GA-BSA and (125)I-MG-BSA underwent endocytic degradation by these cells. The binding of the ligands to these cells was inhibited by several ligands for scavenger receptors. The endocytic degradation of GA-BSA by mesangial cells from class A scavenger receptor (SR-A) knock-out mice was reduced by 80% when compared with that of wild-type cells. The glomerular accumulation of GA-BSA after its intravenous administration was attenuated in SR-A knock-out mice, as evidenced by immunohistochemical observations.

CONCLUSIONS/INTERPRETATION

These results raise the possibility that circulating AGE-modified proteins are subjected to renal clearance by mesangial cells, mainly via SR-A. This pathway may contribute to the pathogenesis of AGE-induced diabetic nephropathy.