Anomalous enhancement of thermoelectric power factor in multiple two-dimensional electron gas system

Toward drastic enhancement of thermoelectric power factor, quantum confinement effect proposed by Hicks and Dresselhaus has intrigued a lot of researchers. There has been much effort to increase power factor using step-like density-of-states in two-dimensional electron gas (2DEG) system. Here, we pay attention to another effect caused by confining electrons spatially along one-dimensional direction: multiplied 2DEG effect, where multiple discrete subbands contribute to electrical conduction, resulting in high Seebeck coefficient. The power factor of multiple 2DEG in GaAs reaches the ultrahigh value of ~100 μWcm-1 K-2 at 300 K. We evaluate the enhancement rate defined as power factor of 2DEG divided by that of three-dimensional bulk. The experimental enhancement rate relative to the theoretical one of conventional 2DEG reaches anomalously high (~4) in multiple 2DEG compared with those in various conventional 2DEG systems (~1). This proposed methodology for power factor enhancement opens the next era of thermoelectric research.

Atomic structure of the Se-passivated GaAs(001) surface revisited

We present a combined experimental and theoretical study of the Se-treated GaAs(001)-([Formula: see text]) surface. The ([Formula: see text]) structure with the two-fold coordinated Se atom at the outermost layer and the three-fold coordinated Se atom at the third layer was found to be energetically stable and agrees well with the experimental data from scanning tunneling microscopy, low energy electron diffraction, and x-ray photoelectron spectroscopy. This atomic geometry accounts for the improved stability of the Se-treated surface against the oxidation. The present result allows us to address a long-standing question on the structure of the Se-passivated GaAs surface, and will leads us to a more complete understanding of the physical origin of the electrical and chemical passivation of Se-treated GaAs surface.

Low Dark Current Operation in InAs/GaAs(111)A Infrared Photodetectors: Role of Misfit Dislocations at the Interface

We demonstrate an extended short-wave infrared (e-SWIR) photodetector composed of an InAs/GaAs(111)A heterostructure with interface misfit dislocations. The layer structure of the photodetector consists simply of an n-InAs optical absorption layer directly grown with a thin undoped-GaAs spacer layer on n-GaAs by molecular beam epitaxy. The lattice mismatch was abruptly relaxed by forming a misfit dislocation network at the initial stage of the InAs growth. We found high-density threading dislocations (1.5 × 10⁹ cm^-2) in the InAs layer. The current-voltage characteristics of the photodetector at 77 K had a very low dark current density (<1 × 10^-9 A cm^-2) at a positive applied voltage (electrons flow from n-GaAs to n-InAs) of up to ∼+1 V. Simulation of the band structure revealed that the direct connection of GaAs and InAs and the formation of interfacial states by the misfit dislocations play significant positive roles in suppressing dark current. Under illumination with e-SWIR light at 77 K, a clear photocurrent signal was observed with a 2.6 μm cutoff wavelength, which is consistent with the bandgap of InAs. We also demonstrated e-SWIR detection at room temperature with a 3.2 μm cutoff wavelength. The maximum detectivity at 294 K exceeds 2 × 10⁸ cm Hz^0.5 W^-1 for the detection of e-SWIR light at 2 μm.

Polarization Anisotropies in Strain-Free, Asymmetric, and Symmetric Quantum Dots Grown by Droplet Epitaxy

We provide an extensive and systematic investigation of exciton dynamics in droplet epitaxial quantum dots comparing the cases of (311)A, (001), and (111)A surfaces. Despite a similar s-shell exciton structure common to the three cases, the absence of a wetting layer for (311)A and (111)A samples leads to a larger carrier confinement compared to (001), where a wetting layer is present. This leads to a more pronounced dependence of the binding energies of s-shell excitons on the quantum dot size and to the strong anti-binding character of the positive-charged exciton for smaller quantum dots. In-plane geometrical anisotropies of (311)A and (001) quantum dots lead to a large electron-hole fine interaction (fine structure splitting (FSS) ∼100 μeV), whereas for the three-fold symmetric (111)A counterpart, this figure of merit is reduced by about one order of magnitude. In all these cases, we do not observe any size dependence of the fine structure splitting. Heavy-hole/light-hole mixing is present in all the studied cases, leading to a broad spread of linear polarization anisotropy (from 0 up to about 50%) irrespective of surface orientation (symmetry of the confinement), fine structure splitting, and nanostructure size. These results are important for the further development of ideal single and entangled photon sources based on semiconductor quantum dots.

Advanced pathologic study for definite diagnosis of mitochondrial cardiomyopathy

 

Mitochondrial cardiomyopathy (MCM) is usually recognized as one of the phenotypes of systemic mitochondrial disease. However if there are no cardiac symptoms, it is difficult to make a definite diagnosis because of various cardiovascular phenotypes and no diagnostic criteria in pathological examination. To add myocardial pathology to the diagnostic criteria for mitochondrial respiratory chain disorders, which is the gold standard in the diagnosis of mitochondrial diseases, we performed quantitative analysis of mitochondria using electron microscopy and immunohistopathologic analysis with respiratory chain enzyme antibodies. Ten patients with hypertrophic or restrictive cardiomyopathy who had undergone endomyocardial biopsy were studied. Respiratory chain enzymatic assay and genetic study were performed and four patients were diagnosed with MCM. Using electron microscopy with quantitative analysis, volume density of mitochondria within cardiac muscle cells was significantly increased in the MCM group compared to the non-MCM group (p=0.013). Immunohistopathologic results were compatible with the result of the respiratory chain enzymatic assay. These advanced pathological tests can distinguish MCM from other cardiomyopathies.

Results of immunopathologic study

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): The Practical Research Project for Rare/Intractable Diseases from the Japan Agency for Medical Research and Development, AMED.

Strain relaxation in InAs heteroepitaxy on lattice-mismatched substrates

Strain relaxation processes in InAs heteroepitaxy have been studied. While InAs grows in a layer-by-layer mode on lattice-mismatched substrates of GaAs(111)A, Si(111), and GaSb(111)A, the strain relaxation process strongly depends on the lattice mismatch. The density of threading defects in the InAs film increases with lattice mismatch. We found that the peak width in x-ray diffraction is insensitive to the defect density, but critically depends on the residual lattice strain in InAs films.

Strain Relaxation in GaSb/GaAs(111)A Heteroepitaxy Using Thin InAs Interlayers

We have systematically studied the strain relaxation processes in GaSb heteroepitaxy on GaAs(111)A using thin InAs interlayers. The growth with 1 ML- and 2 ML-InAs leads to formation of an InAsSb-like layer, which induces tensile strain in GaSb films, whereas the GaSb films grown with thicker InAs layers (≥3 ML) are under compressive strain. As the InAs thickness is increased above 5 ML, the insertion of the InAs layer becomes less effective in the strain relaxation, leaving residual strain in GaSb films. This leads to the elastic deformation of the GaSb lattice, giving rise to the increase in the peak width of X-ray rocking curves.

Estimation of glycaemic control in the past month using ratio of glycated albumin to HbA1c

AIMS

To evaluate comprehensively the use of the glycated albumin to HbA_1c ratio for estimation of glycaemic control in the previous month.

METHODS

A total of 306 children with Type 1 diabetes mellitus underwent ≥10 simultaneous measurements of glycated albumin and HbA_1c . Correlation and concordance rates were examined between HbA_1c measurements taken 1 month apart (ΔHbA_1c ) and glycated albumin/HbA_1c ratio fluctuations were calculated as Z-scores from the cohort value at enrolment of this study cohort (method A) or the percent difference from the individual mean over time (method B).

RESULTS

Fluctuations in glycated albumin/HbA_1c ratio (using both methods) were weakly but significantly correlated with ΔHbA_1c , whereas concordance rates were significant for glycaemic deterioration but not for glycaemic improvement. Concordance rates were higher using method B than method A.

CONCLUSIONS

The glycated albumin/HbA_1c ratio was able to estimate glycaemic deterioration in the previous month, while estimation of glycaemic improvement in the preceding month was limited. Because method B provided a better estimate of recent glycaemic control than method A, the individual mean of several measurements of the glycated albumin/HbA_1c ratio over time may also identify individuals with high or low haemoglobin glycation phenotypes in a given population, such as Japanese children with Type 1 diabetes, thereby allowing more effective diabetes management.

Protein-altering variants of PTPN2 in childhood-onset Type 1A diabetes

AIM

To examine the contribution of PTPN2 coding variants to the risk of childhood-onset Type 1A diabetes.

METHODS

PTPN2 mutation analysis was carried out for 169 unrelated Japanese people with childhood-onset Type 1A diabetes. We searched for coding variants that were absent or extremely rare in the general population and were scored as damaging by multiple in silico programs. We performed mRNA analysis and three-dimensional structural prediction of the detected variants, when possible. We also examined possible physical links between these variants and previously reported risk SNPs as well as clinical information from variant-positive children.

RESULTS

One frameshift variant (p.Q286Yfs*24) and two probably damaging missense substitutions (p.C232W and p.R350Q) were identified in one child each. Of these, p.Q286Yfs*24 and p.C232W were hitherto unreported, while p.R350Q accounted for 2/121,122 alleles of the exome datasets. The p.Q286Yfs*24 variant did not encode stable mRNA, and p.C232W appeared to affect the structure of the tyrosine-protein phosphatase domain. The three variants were physically unrelated to known risk SNPs. The variant-positive children manifested Type 1A diabetes without additional clinical features and invariably carried risk human leukocyte antigen alleles.

CONCLUSIONS

The results provide the first indication that PTPN2 variants contribute to the risk of Type 1A diabetes, independently of known risk SNPs. PTPN2 coding variants possibly induce non-specific Type 1A diabetes phenotypes in individuals with human leukocyte antigen-mediated disease susceptibility. Our findings warrant further validation.

Atomic structure and passivated nature of the Se-treated GaAs(111)B surface

We have systematically studied the atomic structure and electronic properties of the Se-treated GaAs(111)B surface using scanning tunneling microscopy, reflection high-energy electron diffraction, x-ray photoelectron spectroscopy, and first-principles calculations. We have found that Se atoms substitute [Formula: see text] monolayer of As atoms at the outermost layer of the ideal (111)B surface. Charge transfer from Se to As eliminates all of unsaturated dangling bonds, so that the surface is electronically stabilized, leaving no surface states in the mid-gap region.

Overcoming metal-induced fluorescence quenching on plasmo-photonic metasurfaces coated by a self-assembled monolayer

A schematic energy diagram of the present fluorescence (FL)-enhancing process including nonradiative (NR) paths that a self-assembled monolayer (SAM) blocks is presented.

Effects of basicity and FeO concentration on the retention of 137Cs and 60Co in slag made from non-metallic radioactive wastes

Simulated non-metallic wastes containing 60Co, 137Cs and 152Eu were melted to examine the effects of basicity and FeO concentration on the retention of the radioactive nuclides in a resulting solidified product (Al2O3-CaO-FeO-SiO2 quaternary slag). The retention of 60Co was almost independent of chemical composition of slag. On the other hand, the retention of 137Cs decreased with an increase of the basicity of slag, defined as a ratio of CaO to SiO2 in wt. independent of FeO concentration. Energy dispersive X-ray fluorescence spectroscopic analysis and Mössbauer spectroscopic measurement were also conducted for the solidified product. Mössbauer spectra indicated that Fe2+ ions as well as Ca2+ ions existed as network modifying cations in a silicate network structure of slag. Referring to a structure model of silicate glasses, it is inferred that the retention of 137Cs reflects differences in chemical properties between Ca2+ and Fe2+ in the internetwork region formed by modifying cations and anionic non-bridging oxygen.

Mutations of carnitine palmitoyltransferase II (CPT II) in Japanese patients with CPT II deficiency

Carnitine palmitoyltransferase II (CPT II) deficiency is an inherited disorder involving beta-oxidation of long-chain fatty acids. CPT II deficiency is a wide-spectrum disorder that includes a lethal neonatal form, an infantile form, and an adult-onset form. However, the ethnic characteristics and the relationship between genotype and clinical manifestation are not well understood. We investigated three non-consanguineous Japanese patients with CPT II deficiency and examined cell lines from 4 unrelated patients and 50 healthy donors. The CPT 2 gene was typed by direct DNA sequencing of polymerase chain reaction-amplified gene products. Case 1 (infantile form) was heterozygous for a phenylalanine to tyrosine substitution at position 383 (p.F383Y) and a novel valine to leucine substitution at 605 (p.V605L). Cases 2, 4, and 5 (infantile form) and case 3 (adult-onset form) were heterozygous for a single mutation at F383Y. Case 6 (adult-onset form) was compound heterozygous at the CPT 2 locus, with deletion of cytosine and thymine at residue 408, resulting in a stop signal at 420 (p.Y408fsX420), and an arginine to cysteine substitution at position 631 (p.R631C). Case 7 (adult-onset form) was homozygous for the p.F383Y mutation. In conclusion, we identified p.F383Y mutations in six of seven patients with CPT II deficiency and two novel variants of the coding gene: p.Y408fsX420 and p.V605L. These mutations differ from those in Caucasian patients, who commonly harbor p.S113L, p.P50H, and p.Q413fsX449 mutations; therefore, our data and those of other Japanese groups suggest that the p.F383Y mutation is significant in Japanese patients with CPT II deficiency.

Ga-rich limit of surface reconstructions on GaAs(001): atomic structure of the (4 x 6) phase

The Ga-rich reconstruction of the GaAs(001) surface has been studied. Using scanning tunneling microscopy (STM), we have found the existence of a well-ordered (4 x 6) reconstruction under extreme Ga-rich conditions. A structure model, consisting of subsurface Ga-Ga dimers and surface Ga-As dimers, is proposed for the (4 x 6) surface. This model is found to be energetically favorable at the Ga-rich limit and agrees well with our experimental data from STM and reflection high-energy electron diffraction.

Kinetics in surface reconstructions on GaAs(001)

We have successfully controlled the surface structures of GaAs(001) by changing incident As-molecular species. Under As4 fluxes, the c(4 x 4) reconstruction with Ga-As dimers [c(4 x 4)alpha structure] is obtained, but the formation of three As-As dimer structures [c(4 x 4)beta structure] is kinetically limited. On the other hand, the structure change from the (2 x 4), through c(4 x 4)alpha, to c(4 x 4)beta phases is observed under As2 fluxes. We found that the c(4 x 4)alpha structure is energetically metastable and provides a kinetic pathway for the structure change between the (2 x 4) and c(4 x 4)beta phases under As2 fluxes.

Two cases with transient lipoprotein lipase (LPL) activity impairment: evidence for the possible involvement of an LPL inhibitor

Two independent severe hypertriglyceridemic infants with transiently impaired lipoprotein lipase (LPL) activity were observed and the causes were explored. Both infants were female, born prematurely with low birth weight and developed hypertriglyceridemia (Fredrickson type V hyperlipidemia: high VLDL and low LDL/HDL) a few months after birth. While mass levels of their post-heparin plasma LPL and apoprotein C-II (apo C-II), a physiological activator of LPL, were normal, their post-heparin plasma LPL activities were remarkably impaired. Both of their mothers' post-heparin plasma LPL activities were slightly or moderately impaired as well, without a decrease in the LPL mass level. No mutations in the genes for LPL and apo C-II were detected in either patient. In an in vitro study with their serum at onset, we could not detect any distinct circulating inhibitors for LPL. There was no data supporting infection or autoimmune diseases, which might have an impact on LPL activity, during the follow-up period. Levels of their plasma triglyceride (TG) and total cholesterol (TC) were decreased quickly by a dietary intervention with medium-chain triglyceride (MCT) milk and kept normal even after stopping the intervention at around age 1 year. However, their low post-heparin LPL activity persisted and returned to normal at around age 2 years. Their low HDL cholesterol levels persisted even after recovery of the TG and TC levels, although lecithin:cholesterol acyltransferase (LCAT) and cholesterol-ester-transfer protein (CETP), two key enzymes of HDL metabolism, were normal throughout the course. The exact reasons why their post-heparin LPL activities were impaired for a certain period and why their HDL cholesterol levels have remained low are still unclear.

CONCLUSION

Transiently impaired LPL activity with no defect in LPL enzyme induced severe hypertriglyceridemia in infants. The transient occurrence of inhibitor(s) for LPL was proposed.

Extracellular carbohydrate-signal triggering camp-dependent protein kinase-dependent neuronal actin-reorganization

Cell surface glycoconjugates are thought to mediate cell-cell recognition and to play roles in neuronal development and functions. We demonstrated here that exposure of neuronal cells to nanomolar levels of glyco-chains with an N-acetylgalactosamine (GalNAc) residue at the non-reducing termini (GalNAc-S) such as GalNAcbeta4(Neu5Acalpha3)Galbeta4GlcCer (GM2) ganglioside, its oligosaccharide portion, GalNAcbeta4Galbeta4GlcCer (Gg(3)) Cer, GalNAcalpha3GalNAcbeta3Galalpha4Galbeta4GlcCer (Gb(5)) Cer (Forssman hapten) and alpha1-4 linked oligomers of GalNAc, induced a rapid and transient activation of cAMP-dependent protein kinase (PKA) in subplasmalemma. The treatment was accompanied by peripheral actin polymerization and filopodia formation in NG108-15 cells and primary cultured hippocampal neurons, but not in glial cells. A cAMP-dependent protein kinase (PKA) selective inhibitor and an adenylate cyclase inhibitor blocked both PKA activation and the subsequent filopodia formation. A small GTPase cdc42 was a potential downstream target of GalNAc-S-activated PKA. These results suggest that extracellular GalNAc-S serve as potential regulators of the filopodia formation in neuronal cells by triggering the activation of PKA followed by cdc42 up-regulation via a cell surface receptor-like component. Filopodia formation induced by GalNAc-S may have a physiological relevance because long-term exposure to GalNAc-S enhanced F-actin-rich dendrite generation of primary cultured hippocampal neurons, and PKA-dependent dendritic outgrowth and branch formation of primary cultured cerebellar Purkinje neurons, in which actin isoforms were localized to motile structures in dendrites. These findings provide evidence for a novel GalNAc/PKA-signaling cascade in regulating some neuronal maturation.

New structure model for the GaAs(001)-c(4x4) surface

The surface structure of the As-stabilized GaAs(001)-c(4 x 4) surface has been studied. We show that the seemingly established three As-dimer model is incompatible with experimental data and propose here a new structure model which has three Ga-As dimers per c(4 x 4) unit cell. This mixed dimer model, confirmed by the rocking-curve analysis of reflection high-energy electron diffraction and first-principles calculations, resolves disagreements in the interpretation of several previous experiments. A good agreement between the observed scanning tunneling microscopy image and the simulated one further confirms the newly proposed model.

Immune thrombocytopenia in an elderly patient treated successfully by pulse therapy with cyclophosphamide

Thrombocytopenia due to immune mechanisms is rare and difficult to manage in elderly patients. We describe a case of an 89-year-old female with severe immune thrombocytopenia (ITP) who rapidly improved by pulse therapy with cyclophosphamide. She was admitted to our hospital because she had arthralgia in both sides of her femoral region since January 1999, aphthous stomatitis and ecchymosis of the leg since April 1999, and bloody phlegm in July 1999. On admission, her peripheral blood count revealed severe thrombocytopenia (0.1 x 10(4)/microl). Her megakaryocyte count from bone marrow was increased to 512/microl without abnormal cells. Systemic lupus erythematosus was suspected because of strong positive protein in the urine in addition to the clinical and hematological findings described above, but she was negative for all the autoantibodies examined. Finally, she was diagnosed as having ITP on the basis of high platelet associated immunoglobulin G in addition to hematological and physical findings and she was treated with prednisolone. It was difficult to maintain her platelet count with only prednisolone, but 600 mg of cyclophosphamide rapidly increased her platelet count in spite of tapering the prednisolone. In September 2000, her platelet count was kept within normal limits by administration of 15 mg/day of prednisolon. It is suggested that immunosuppressive therapy for ITP using high-dose cyclophosphamide is useful in elderly patients as well as in juvenile adult patients.

A genetic factor for age-related cataract: identification and characterization of a novel galactokinase variant, "Osaka," in Asians

Galactokinase (GALK) deficiency is an autosomal recessive disorder characterized by hypergalactosemia and cataract formation. Through mass screening of newborn infants, we identified a novel and prevalent GALK variant (designated here as the "Osaka" variant) associated with an A198V mutation in three infants with mild GALK deficiency. GALK activity and the amount of immunoreactive protein in the mutant were both 20% of normal construct in expression analysis. The K(m) values for galactose and ATP-Mg(2+) in erythrocytes with homozygous A198V were similar to those of the healthy adult control subjects. A population study for A198V revealed prevalences of 4.1% in Japanese and 2.8% in Koreans, lower incidence in Taiwanese and Chinese, no incidence in blacks and whites from the United States, and a significantly high frequency (7.8%; P < .023) in Japanese individuals with bilateral cataract. This variant probably originated in Japanese and Korean ancestors and is one of the genetic factors that causes cataract in elderly individuals.

Tau-tubulin kinase phosphorylates tau at Ser-208 and Ser-210, sites found in paired helical filament-tau

Hyperphosphorylated tau protein is known to be a major component of the paired helical filaments (PHFs) that accumulate in the brain of Alzheimer's patients. The kinase that phosphorylated Ser-208 and Ser-210 in PHF-tau had remained unknown. We used anti-pS208 and anti-pS210 antibodies and Western blots to confirm that the tau-tubulin kinase (TTK) phosphorylates tau at Ser-208 and at Ser-210. Using partial amino acid sequences of purified bovine brain TTK, a mouse cDNA of TTK was isolated and the sequence was determined. Its 963 bp coding region is composed of 320 amino acids and encodes a 36 kDa protein indistinguishable in size from authentic bovine brain TTK. Our immunoblot analysis demonstrated that TTK is ubiquitously distributed in the rat tissues, and that it is developmentally regulated in the rat brain.

Pharmacological effect of tamsulosin in relation to dog plasma and tissue concentrations: prostatic and urethral retention possibly contributes to uroselectivity of tamsulosin

In the present study the pharmacokinetics and pharmacodynamics of tamsulosin were investigated in anesthetized male dogs. Hypogastric nerve stimulation elevated the intraurethral pressure (IUP), which was inhibited dose dependently by intraduodenal administration of tamsulosin (3-30 microg/kg). The inhibition peaked about 90 min after dosing and lasted up to 240 min. The basal mean blood pressure did not change significantly during the observation period. The plasma, prostatic, and urethral concentrations of tamsulosin were determined by the liquid chromatography-mass spectrometry/mass spectrometry method. The plasma concentration reached the maximal level within 30 min after dosing and gradually declined thereafter. The maximal total plasma concentration of tamsulosin (C(max, t)) and its unbound concentration (C(max, u)) correlated with the maximal effect on IUP response [r(2) = 0.81 (p<0.01, n = 15) and r(2) = 0.84 (p<0.01, n = 15), respectively]. Each individual unbound plasma concentration did not correlate, however, with its associated inhibition of IUP response (r(2) = 0.04, n = 126). Although the plasma concentration of tamsulosin decreased nearly to the lower limit of quantitation 240 min after dosing, the prostatic and urethral concentrations remained high, i.e., 13 to 44 times greater than the plasma concentration. Our data demonstrate that the maximal inhibition by tamsulosin of IUP response is well correlated with the maximal plasma concentration in the early phase. The sustained effect of tamsulosin on IUP response that follows may be related to prostatic and urethral retention of tamsulosin.

Role of Thr(11) in the binding of omega-conotoxin MVIIC to N-type Ca2+ channels

As replacement of Thr(11) of omega-conotoxin MVIIC with Ala significantly reduced the affinity for both N- and P/Q-type calcium channels, we examined the effect of substitution at this position with other residues. Binding assays using rat cerebellar P2 membranes showed that the affinity is in the order of Leu>Val, aminobutyric acid, Thr>Asn&z.Gt;Ser, Ala, Asp, Phe, Tyr for N-type channels and Thr>Leu, Val, aminobutyric acid, Asn, Ser>Ala&z.Gt;Asp, Phe, Tyr for P/Q-type channels, suggesting that aliphatic amino acids with longer side chains are favorable for block of N-type channels. The effects of substitution were examined electrophysiologically in BHK cells expressing N-type Ca2+ channels. Inhibition of Ba2+ current by the analogs did not completely correlate with binding affinity, although binding to BHK cells was comparable to rat cerebellar membranes.

lambda-conotoxins, a new family of conotoxins with unique disulfide pattern and protein folding. Isolation and characterization from the venom of Conus marmoreus

Conotoxins are multiple disulfide-bonded peptides isolated from marine cone snail venom. These toxins have been classified into several families based on their disulfide pattern and biological properties. Here, we report a new family of Conus peptides, which have a novel cysteine motif. Three peptides of this family (CMrVIA, CMrVIB, and CMrX) have been purified from Conus marmoreus venom, and their structures have been determined. Their amino acid sequences are VCCGYK-LCHOC (CMrVIA), NGVCCGYKLCHOC (CMrVIB), and GICCGVSFCYOC (CMrX), where O represents 4-trans-hydroxyproline. Two of these peptides (CMrVIA and CMrX) have been chemically synthesized. Using a selective protection and deprotection strategy during disulfide bond formation, peptides with both feasible cysteine-pairing combinations were generated. The disulfide pattern (C(1)-C(4), C(2)-C(3)) in native toxins was identified by their co-elution with the synthetic disulfide-isomeric peptides on reverse-phase high pressure liquid chromatography. Although cysteine residues were found in comparable positions with those of alpha-conotoxins, these toxins exhibited a distinctly different disulfide bonding pattern; we have named this new family "lambda -conotoxins." CMrVIA and CMrX induced different biological effects when injected intra-cerebroventricularly in mice; CMrVIA induces seizures, whereas CMrX induces flaccid paralysis. The synthetic peptide with lambda-conotoxin folding is about 1150-fold more potent in inducing seizures than the mispaired isomer with alpha-conotoxin folding. Thus it appears that the unique disulfide pattern, and hence the "ribbon" conformation, in lambda-conotoxins is important for their biological activity.

Chromosomal and extrachromosomal synthesis of exfoliative toxin from Staphylococcus hyicus

Evidence for the existence of two molecular species of exfoliative toxin (ET) synthesized by Staphylococcus hyicus (SHET) under chromosomal and plasmid control is presented. Serological evidence that these molecular species of toxins are distinct from each other is given. The molecular weights of SHET from plasmidless strain P-1 (SHETA) and from plasmid-carrying strains P-10 and P-23 (SHETB) were almost equal. Both of the serotypes of SHET exhibited exfoliation in 1-day-old chickens. The plasmid-cured (P(-)) substrains (P-23C1 and P-23C2) of S. hyicus P-23 did not cause exfoliation in 1-day-old chickens, whereas P(-) substrains (P-10C1 and P-10C2) of strain P-10 caused exfoliation, but they decreased their exfoliative activity. These findings suggest that SHETB was synthesized along with SHETA by strain P-10, whereas the P-23 strain synthesized SHETB alone. The plasmid-carrying strain (P-23) as well as the plasmidless strain (P-1) exhibited the typical clinical signs of exudative epidermitis in pigs. However, plasmid-cured (P(-)) substrains of P-23 (P23C1 and P23C2) did not exhibit the typical clinical signs of exudative epidermitis. These findings suggest that SHETA is synthesized under chromosomal control and SHETB is synthesized under plasmid control and that SHET-producing strains can be divided into three groups: SHETA-producing strains, SHETB-producing strains, and strains producing both toxins.

Familial Alzheimer's disease-associated mutations block translocation of full-length presenilin 1 to the nuclear envelope

A polyclonal antibody, M5, to the hydrophilic loop domain of human presenilin 1 (PS1) was prepared. Western blot and immunoprecipitation analyses showed that M5 specifically recognized the processed C-terminal fragment, but not the full-length PS1. Epitope mapping analysis revealed that the essential sequence for recognition of the C-terminal fragment by M5 is DPEAQRR (302-308). The recognition of the C-terminal fragment by M5 in a processing-dependent manner was further confirmed by competitive enzyme-linked immunosorbent assay using the synthetic peptide L281 (281-311), which contains the putative processing site and the preceding amino acids to the site. Although L281 contains the epitope sequence for M5, the maximum inhibition was only 14%. Immunocytochemistry using M5 combined with hL312, which recognizes both full-length PS1 and the C-terminal fragment, allowed us to distinguish the localization of the processed C-terminal fragment from that of full-length PS1. Confocal microscopy demonstrated that the full-length form of wild-type PS1 is preferentially located in the nuclear envelope, while the processed C-terminal fragment is mainly present in the endoplasmic reticulum (ER). However, PS1 with familial Alzheimer's disease-associated mutations could not translocate to the nuclear envelope, and both the full-length and processed mutants were co-localized in the ER.

Strain relaxation in InAs/GaAs(111)A heteroepitaxy

We have studied strain-relaxation processes in InAs heteroepitaxy on GaAs(111)A using rocking-curve analysis of reflection high-energy electron diffraction. Strain relaxation in the direction parallel to the surface occurs at approximately 1.5 bilayers (BL) thickness. On the other hand, the lattice constant in the direction normal to the surface remains almost unchanged below approximately 3 BL thickness and is estimated to be approximately 3.3 A. This value, slightly larger than that of bulk GaAs (3.26 A), does not quite reach the value predicted by classical elastic theory, 3.64 A. The present result has been supported by the first-principles total-energy calculations.

Binding of Ala-scanning analogs of omega-conotoxin MVIIC to N- and P/Q-type calcium channels

omega-Conotoxin MVIIC binds to P/Q-type calcium channels with high affinity and N-type channels with low affinity. To reveal the residues essential for subtype selectivity, we synthesized Ala-scanning analogs of MVIIC. Binding assays using rat cerebellar P(2) membranes suggested that Thr(11), Tyr(13) and Lys(2) are essential for binding to both N- and P/Q-type channels, whereas Lys(4) and Arg(22) are important for binding to P/Q-type channels. These results suggest that MVIIC interacts with P/Q-type channels via a large surface, in good agreement with previous observations using chimeric analogs.

Binding of six chimeric analogs of omega-conotoxin MVIIA and MVIIC to N- and P/Q-type calcium channels

Replacement of the N-terminal half of omega-conotoxin MVIIC, a peptide blocker of P/Q-type calcium channels, with that of omega-conotoxin MVIIA significantly increased the affinity for N-type calcium channels. To identify the residues essential for subtype selectivity, we examined single reverse mutations from MVIIA-type to MVIIC-type in this chimeric analog. A reverse mutation from Lys(7) to Pro(7) decreased the affinity for both P/Q- and N-type channels, whereas that from Leu(11) to Thr(11) increased the affinity for P/Q-type channels and decreased the affinity for N-type channels. The roles of these two residues were confirmed by synthesizing two MVIIC analogs in which Pro(7) and Thr(11) were replaced with Lys(7) and Leu(11), respectively.

Requirement for a different hydrophobic moiety and reliable chromogenic substrate for endo-type glycosylceramidases

A series of synthetic lactosides with aglycones that differed in length and structure were used to determine the substrate specificity of endo-type glycosylceramidases. Endoglycoceramidases (EGCase) from bacteria preferred lactosides with an acylamide structure over simple n-alkyl lactosides. While ceramide glycanase (CGase) from leech did not show preference. N -Acylaminoethyl beta-lactosides and n -alkyl lactosides were substrates for both EGCase and CGase, but N-acylaminobutyl beta-lactosides, whose acylamide residue differs from that in ceramide, were not hydrolyzed by EGCases. Thus, EGCases, but not CGase, appear to require an N-acyl group at the same position as that of intact glycosphingolipid for substrate recognition. A p-nitrophenyl lactoside derivative possessing an N-acyl chain was degraded by both EGCases and CGase and this chromogenic substrate may be an alternative substrate for endo-type glycosylceramidase activity. Km of the chromogenic lactoside for CGase and Rhodococcus EGCase were 28 microM and 2.9 mM, respectively.

New exfoliative toxin produced by a plasmid-carrying strain of Staphylococcus hyicus

A new serotype of Staphylococcus hyicus exfoliative toxin (SHET), serotype B, was isolated from the culture filtrate of a plasmid-carrying strain of S. hyicus. The new SHET was purified by precipitation with 70% saturated ammonium sulfate, gel filtration on a Sephadex G-75 column, column chromatography on DEAE-Cellulofine A-500, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The new SHET caused exfoliation of the epidermis as determined by the so-called Nikolsky sign when inoculated into 1-day-old chickens. The new SHET was serologically different from Staphylococcus aureus exfoliative toxins (ETs) (ETA, ETB, and ETC) and from the SHET from the plasmidless strain but showed the same molecular weight as the other serotypes of toxins on SDS-PAGE. It was thermolabile and lost its toxicity after being heated at 60 degrees C for 30 min. We propose that the new SHET be designated SHETB and that the SHET produced by the plasmidless strain be designated SHETA.

Missense mutations in the gp91-phox gene encoding cytochrome b558 in patients with cytochrome b positive and negative X-linked chronic granulomatous disease

Chronic granulomatous disease (CGD) is a disorder of host defense due to genetic defects of the superoxide (O2-) generating NADPH oxidase in phagocytes. A membrane-bound cytochrome b558, a heterodimer consisting of gp91-phox and p22-phox, is a critical component of the oxidase. The X-linked form of the disease is due to defects in the gp91-phox gene. We report here biochemical and genetic analyses of patients with typical and atypical X-linked CGD. Immunoblots showed that neutrophils from one patient had small amounts of p22-phox and gp91-phox and a low level of O2- forming oxidase activity, in contrast to the complete absence of both subunits in two patients with typical CGD. Using polymerase chain reactions (PCR) on cDNA and genomic DNA, we found novel missense mutations of gp91-phox in the two typical patients and a point mutation in the variant CGD, a characteristic common to two other patients with similar variant CGD reported previously. Spectrophotometric analysis of the neutrophils from the variant patient provided evidence for the presence of heme of cytochrome b558. Recently, we reported another variant CGD with similar amounts of both subunits, but without oxidase activity or the heme spectrum. A predicted mutation at amino acid 101 in gp91-phox was also confirmed in this variant CGD by PCR of the genomic DNA. These results on four patients, including those with two variant CGD, are discussed with respect to the missense mutated sites and the heme binding ligands in gp91-phox.

Characteristics of brain injury-derived neurotrophic peptide-binding sites on rat brain synaptosomes and neurons in culture

Brain injury-derived neurotrophic peptide is the fragmental 13-mer peptide of the novel neurotrophic factor which was extracted and purified from Sponge Gelform made of gelatin implanted at the mechanically-induced injury site in neonatal rat brains. Brain injury-derived neurotrophic peptide supports survival of septal cholinergic and mesencephalic dopaminergic neurons in culture, and rescues hippocampal neurons in culture from glutamate neurotoxicity. Here we studied the binding characteristics of brain injury-derived neurotrophic peptide to synaptosomes from normal adult rat brains and neurons in culture from neonatal rat brains. [125I]Asp-[Tyr11]-brain injury-derived neurotrophic peptide binding to rat brain synaptosomes was specific and saturable. Equilibrium binding studies revealed that [125I]Asp-[Tyr11]-brain injury-derived neurotrophic peptide bound to 1.1 pmol/mg protein with a Kd (dissociation constant) of 0.17 microM in hippocampal synaptosomes and to 2.0 pmol/mg protein with a Kd of 0.38 microM in septal synaptosomes. [125I]Asp-[Tyr11]-brain injury-derived neurotrophic peptide could bind to a subpopulation of hippocampal neurons in culture from embryonic rat brains. Affinity cross-linking with the carboxyl-reactive cross-linking reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide-HCl and [125I]Asp-[Tyr11]-brain injury-derived neurotrophic peptide produced radiolabeled bands corresponding to 100,000, 50,000 and 40,000 mol. wt molecules on hippocampal neurons in culture. These results suggest that the 13-mer sequence of brain injury-derived neurotrophic peptide plays a crucial role in expressing the neurotrophic properties of the factor.

Expression analysis of two mutant human ornithine transcarbamylases in COS-7 cells

Ornithine transcarbamylase (OTC) is located in the mitochondrial matrix of the liver and small intestine and catalyzes the second step of the urea cycle. OTC deficiency (OTCD) is an X-linked inborn error of metabolism and causes hyperammonemia. We reported in 1992 the A152V and G195R mutations in patients with OTCD. These mutant OTC cDNAs were prepared by site-directed mutagenesis using the polymerase chain reaction (PCR). The wild-type and mutant cDNAs were transiently expressed in COS-7 cells. The wild-type cDNA gave an OTC activity of 1180 +/- 47 nmol/min per mg protein. The OTC activities of the A152V and the G195R mutants were 3.7% and 2.5% of that of wild-type, respectively. Immunoblot analysis showed that the quantities of OTC proteins in the A152V and G195R mutants were 29% and 12% of that of wild-type, respectively. In pulse-labeling and pulse-chase experiments, the precursor form of OTC was synthesized and processed to the mature form. The A152V mutant OTC was processed to the mature form as rapidly as the wild-type precursor. However, the processed, mature form of the mutant OTC was rapidly degraded, presumably in the mitochondrial matrix. These results indicate that OTCD with the A152V mutation is due both to rapid degradation of the processed, mature form, and to a lower specific activity of the remaining protein.

Morphological and functional changes in coronary vessel evoked by repeated endothelial injury in pigs

OBJECTIVE

We examined the morphological changes induced by repeated endothelial denudation in coronary artery (CA), as well as functional changes in the endothelium-dependent and smooth muscle responses to various vasoactive agents during the process of intimal thickening.

METHODS

We observed vascular responses in denuded and non-denuded portions of pig CA while being fed a normal diet (n = 11, N group) or 2% cholesterol diet (n = 25, C group) to intracoronary acetylcholine (ACh), 5-hydroxytryptamine (5-HT), substance P (SP), and isosorbide dinitrate (ISDN) with and without the nitric oxide synthesis inhibitor N omega-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg i.v.) over a period of 8 weeks. Balloon endothelial denudation of the left anterior descending CA was carried out every 2 weeks.

RESULTS

In N group, maximum vasoconstriction was obtained with ACh 2 weeks after the first denudation [26 +/- 5% vs. 1 +/- 1% pre-denudation, p < 0.05]. L-NAME did not affect ACh-induced CA diameter changes. Thereafter, the response to ACh was attenuated by repeated denudation in N groups. However, the degree of 5-HT-induced CA narrowing at the denuded portion increased from 7 +/- 4% (0 week) to 88 +/- 8% (8 weeks) (p < 0.05). The changes resulted in severe myocardial ischaemia, and suggested that endothelium-dependent vasodilation was progressively attenuated while hyperreactivity of vascular smooth muscle simultaneously increased. Vasodilation induced by SP was attenuated somewhat, but ISDN-induced vasodilation was preserved. Although mild hypercholesterolaemia was induced in C group, the vascular responses to these vasoactive agents did not differ from those of N group.

CONCLUSIONS

Repeated CA endothelial injury and regeneration induce the change of morphology and vascular reactivity in the denuded portion regardless of atherogenic diet. This study strongly suggests that intimal thickening caused by repeated endothelial injury and regeneration induces specific vascular responses to vasoactive agents. Moreover, it is also suggested that during the progression of intimal thickening, increased vascular smooth muscle contraction and decreased endothelium-dependent dilation appear in a stimulus-dependent manner, often leading to severe coronary vasoconstriction accompanied with definitive ECG ST change.

Visualization of mitochondria with green fluorescent protein in cultured fibroblasts from patients with mitochondrial diseases

cDNAs for green fluorescent protein (GFP) and for a GFP fusion protein containing the presequence of human ornithine transcarbamylase (pOTC-GFP) were transfected into cultured human fibroblasts. GFP cDNA gave diffuse fluorescence throughout the cytoplasm and the nucleus, whereas pOTC-GFP cDNA gave mitochondria-associated fluorescence. Fluorescent mitochondrial structures could be classified into five patterns: thread-like mitochondria, fine thread-like ones, rod-like ones, granular ones, and granular ones with weak cytosolic fluorescence. pOTC-GFP mutants resulted in a loss of mitochondrial fluorescence and an appearance of weak fluorescence throughout the cytoplasm. pOTC-GFP cDNA was transfected into fibroblasts from patients with various mitochondrial diseases. Higher ratios of fibroblasts with granular mitochondria and those with fine thread-like ones were observed in a patient with Reye's syndrome and a patient with Kearns-Sayre syndrome. Weak cytosolic fluorescence was sometimes observed in fibroblasts from these patients. This method will be useful to analyze mitochondrial structural alterations and disorders of mitochondrial protein import.

Binding of chimeric analogs of omega-conotoxin MVIIA and MVIIC to the N- and P/Q-type calcium channels

Despite their high sequence homology, the peptide neurotoxins omega-conotoxin MVIIA and MVIIC selectively block N- and P/Q-type calcium channels, respectively. To study the recognition mechanism of calcium channel subtypes, two chimeric analogs of omega-conotoxin MVIIA and MVIIC were synthesized by exchanging their N- and C-terminal halves. Binding assay for both N- and P/Q-type calcium channels showed that amino acid residues restricted to the N-terminal half are important for the recognition of N-type channels, whereas essential residues for P/Q-type channel recognition are widely spread over the whole omega-conotoxin molecule.

Imaging of cAMP-dependent protein kinase activity in living neural cells using a novel fluorescent substrate

In order to visualize the activity of the cAMP-dependent protein kinase (PKA) in living cells, we have constructed a new fluorescence PKA substrate by conjugating a fluorescence probe to a partial amino acid sequence of PKA regulatory domain II which contains a specific autophosphorylation site. The fluorescent peptide was cell-permeable and became phosphorylated when the intracellular cAMP concentration was increased, resulting in a decrease in its fluorescence intensity. In NG108-15 cells, PKA activity was localized to the cytosol around the nucleus. In cultured hippocampal neurons, addition of L-glutamate caused PKA activation associated with increase of the cellular cAMP.

Circular dichroism spectra of calcium channel antagonist omega-conotoxins

The circular dichroism (CD) spectrum of omega-conotoxin GVIA is quite different from those of omega-conotoxin MVIIA and MVIIC, despite their distinct similarity in three dimensional structures. In order to characterize the unique CD spectrum of omega-conotoxin GVIA, we focused our attention on the aromatic chromophore and analyzed the CD spectra of three synthetic analogs, in which Tyr13, Tyr22, and Tyr27 were individually replaced by alanine. Replacement of Tyr27 caused a significant change in both the near- and far-ultraviolet CD spectrum of omega-conotoxin GVIA and resulted in the omega-conotoxin MVIIA/MVIIC-like pattern, suggesting that Tyr27 has a dominant contribution to the unique CD profile of omega-conotoxin GVIA.

Amphiphilic helix is essential for the activity of brain injury-derived neurotrophic peptide (BINP)

To study the structure-activity relationships of brain injury-derived neurotrophic peptide (BINP), 12 analogs were synthesized by replacing each amino acid residue with Gly. BINP showed CD spectra typical of an alpha-helical conformation in TFE solution which mimics the membrane environment. In the alpha-helical conformation, BINP showed an amphiphilic profile. Neurotrophic activities of BINP and its analogs were estimated from the effects on supporting septal cholinergic neurons and on rescuing hippocampal neurons from injury caused by glutamate. Both assays showed that the residues on the hydrophobic side of the amphiphilic helix were essential for the neurotrophic activity.

Imaging of Ca2+/calmodulin-dependent protein kinase II activity in hippocampal neurones

Our aim was to visualize the dynamic features of Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity. In order to do so, we synthesized a new reagent by conjugating a fluoroprobe, 6-acryloyl-2-dimethylaminonaphthalene (acrylodan), to syntide 2, a specific peptide substrate for CaMKII. In cell-free conditions, the conjugate was found to be an effective indicator of calmodulin activation by Ca2+ and the subsequent activation of CaMKII. The reagent is cell-permeable and can stain living cells when bath-applied. Using this technique we were able to obtain fluorescence images of stained cells and analyse the dynamic features of CaMKII inside the cells by means of image processing. Regional heterogeneity of CaMKII activation in cultured hippocampal neurones was seen following L-glutamate administration.

Activation of protein-tyrosine phosphatase SH-PTP2 by a tyrosine-based activation motif of a novel brain molecule

BIT (a brain immunoglobulin-like molecule with tyrosine-based activation motifs) is a brain-specific membrane protein which has two cytoplasmic TAMs (tyrosine-based activation motifs). Using the Far Western blotting technique, we detected association of a 70-kDa protein with the tyrosine-phosphorylated TAMs of BIT. A mouse brain cDNA library in lambdagt11 was screened for this association, and two positive clones encoding tyrosine phosphatase SH-PTP2 were isolated. SH-PTP2 has two SH2 domains and is believed to function as a positive mediator in receptor tyrosine kinase signaling. SH-PTP2 and BIT were coimmunoprecipitated from phosphorylated rat brain lysate, and BIT was a major tyrosine-phosphorylated protein associated with SH-PTP2 in this lysate. This interaction was also observed in Jurkat T cells transfected with BIT cDNA depending on tyrosine phosphorylation of BIT. Bisphosphotyrosyl peptides corresponding to BIT-TAMs stimulated SH-PTP2 activity 33-35-fold in vitro, indicating that two SH2 domains of SH-PTP2 simultaneously interact with two phosphotyrosines of BIT-TAM. Our findings suggest that the tyrosine phosphorylation of BIT results in stimulation of the signal transduction pathway promoted by SH-PTP2 and that BIT is probably a major receptor molecule in the brain located just upstream of SH-PTP2.

Two novel gene mutations (Glu174-->Lys, Phe383-->Tyr) causing the "hepatic" form of carnitine palmitoyltransferase II deficiency

Carnitine palmitoyltransferase II (CPT II) deficiency has two different clinical forms, one with "hepatic" and the other with "muscular" symptoms. We studied the molecular basis of the "hepatic" form in two Japanese siblings. Their CPT II activity in lymphoblasts was reduced to 3% of the level observed in normal controls. cDNA analysis showed that the proband was a compound heterozygote. One allele carried a new mutation, G621-->A (Glu174-->Lys). The other carried three single-base substitutions; a new mutation, T1249-->A (Phe383-->Tyr), and two previously reported polymorphisms. The brother had the same four substitutions. Neither of the two new mutations in this study was detected in the 60 alleles of 30 Japanese control subjects. Secondary structure prediction analysis of the mutated CPT II protein was different from that of the normal protein. We concluded that these mutations caused the "hepatic" form of CPT II deficiency in the probands.