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This paper describes the influence of acid pretreatment of TiO2 mesoporous films prior to dye sensitization on the performance of dye-sensitized solar cells based on [(C4H9)4N]3[Ru(Htcterpy)(NCS)3] (tcterpy = 4,4‘,4‘ ‘-tricarboxy- 2,2‘,2‘ ‘-terpyridine), the so-called black dye. The HCl pretreatment caused an increase in overall efficiency by 8%, with a major contribution from photocurrent improvement. It is speculated, from the analysis of incident photon-to-electron conversion efficiency, UV−vis absorption spectra, redox properties of the dye and TiO2, and the impedance spectra of the dye-sensitized solar cells, that photocurrent enhancement is attributed to the increases in electron injection and/or charge collection efficiency besides the improvement of light harvesting efficiency upon HCl pretreatment. Open-circuit photovoltage (Voc) remained almost unchanged in the case of significant positive shift of flat band potential for TiO2 upon HCl pretreatment. The suppression of electron transfer from conduction band electrons to the I3^- ions in the electrolyte upon HCl pretreatment, reflected by the increased resistance at the TiO2/dye/electrolyte interface and reduced dark current, resulted in a Voc gain, which compensated the Voc loss due to the positive shift of the flat band. Using the HCl pretreatment approach, 10.5% of overall efficiency with the black dye was obtained under illumination of simulated AM 1.5 solar light (100 mW cm^-2) using an antireflection film on the cell surface.

Half-sandwich Ru(II), Ir(III), and Rh(III) complexes with 4,7-dihydroxy-1,10-phenanthroline are highly efficient catalysts for hydrogenation of bicarbonate in alkaline aqueous solution without an amine additive. The generation of an oxyanion by deprotonation of the two hydroxy substituents on the catalyst ligand caused a dramatic enhancement of catalytic activity, due to its strong electron-donating ability, as well as imparting water solubility.

We have developed novel coumarin dyes for use in dye-sensitized nanocrystalline TiO2 solar cells (DSSCs). The absorption spectra of these novel coumarin dyes are red-shifted remarkably in the visible region relative to the spectrum of C343, a conventional coumarin dye. Introduction of a methine unit (−CH&dbd;CH−) connecting both the cyano (−CN) and carboxyl (−COOH) groups into the coumarin framework expanded the π conjugation in the dye and thus resulted in a wide absorption in the visible region. These novel dyes performed as efficient photosensitizers for DSSCs. The monochromatic incident photon-to-current conversion efficiency (IPCE) from 420 to 600 nm for a DSSC based on NKX-2311 was over 70% with the maximum of 80% at 470 nm, which is almost equal to the efficiency obtained with the N3 dye system. The IPCE performance of DSSCs based on coumarin dyes depended remarkably on the LUMO levels of the dyes, which are estimated from the oxidation potential and 0−0 energy of the dye. The slow charge recombination, on the order of micro to milliseconds, between NKX-2311 cations and injected electrons in the conduction band of TiO2 (observed by transient absorption spectroscopy) resulted in efficient charge separation in this system. A HOMO−LUMO calculation indicated that the electron moves from the coumarin framework to the −CH&dbd;CH− unit by photoexcitation of the dye (a π−π* transition). Our results strongly suggest that molecular design of the sensitizer is essential for the construction of highly efficient DSSCs. The structure of NKX-2311, whose carboxyl group is directly connected to the −CH&dbd;CH− unit, is advantageous for effective electron injection from the dye into the conduction band of TiO2. In addition, the cyano group, owing to its strong electron-withdrawing ability, might play an important role in electron injection in addition to a red shift in the absorption region.

Near-IR absorption spectra of electrons injected from excited sensitizer dyes to nanocrystalline ZnO films have been studied. The absorption steeply increases with increasing wavelength and can be assigned to the optical transition of conducting electrons to higher energy levels of the conduction band. From the measurements in various sensitizer dyes, the relative efficiencies of the electron injection can be obtained as a function of the free energy change (ΔG) for the electron injection process. Around ΔG = 0 eV, the efficiencies increase gradually with increasing −ΔG and they are constant at negative ΔG. We succeeded in explaining the tendency by considering the site heterogeneity of the surface. The relation between the injection efficiencies and the solar cell performance will also be discussed.

We previously reported that the number of anchoring carboxyl groups affects the solar cell performance of dye-sensitized nanocrystalline TiO2 solar cells using Ru−phenanthroline complexes as the sensitizer. To understand the mechanism in detail, the electron injection efficiency of sensitizing dyes adsorbed on nanocrystalline TiO2 films has been studied by transient absorption spectroscopy. We found that the efficiency of electron injection is strongly affected by the number of carboxyl groups of the sensitizing dye, i.e., the efficiency of cis-bis(4,7-dicarboxy-1,10-phenanthroline)dithiocyanato ruthenium(II) (with four carboxyl groups) adsorbed on nanocrystalline TiO2 films (DCP2/TiO2) being 4 times as large as that of cis-(4-monocarboxy-1,10-phenanthroline)(1,10-phenanthroline)dithiocyanato ruthenium(II) (with one carboxyl group) adsorbed on the same films (MCPP/TiO2). From the analysis of the time profile of the transient absorption, we conclude that the low efficiency of MCPP/TiO2 is due to the presence of inactive dyes on the TiO2 surface, which are not effective for electron injection. By comparing the absorbed photon-to-current conversion efficiencies (APCE) of the solar cells using these films, the effect of the number of the carboxyl groups on the solar cell performance can be attributed to the effect on the injection efficiency of electrons. We have also studied the effect of substitution of the countercations of DCP2. Two protons of carboxyl groups were substituted by two tetrabutylammonium (TBA) ions. The APCE of the DCP2-TBA is higher than that of DCP2, although the relative efficiencies of electron injection are similar for DCP2-TBA and DCP2. This indicates that the rate of reaction of the conducting electrons in the TiO2 film with the I^-/I3^- redox mediators (dark current) is reduced by substituting the protons by TBA ions.

We have synthesized four carboxylated Ru(II) phenanthroline complexes with different numbers of carboxyl groups, cis-bis(4,7-dicarboxy-1,10-phenanthroline)dithiocyanato ruthenium(II) (Ru(dcphen)2(NCS)2), cis-bis(4-monocarboxy-1,10-phenanthroline)dithiocyanato ruthenium(II) (Ru(mcphen)2(NCS)2), cis-(4,7-dicarboxy-1,10-phenanthroline)(1,10-phenanthroline)dithiocyanato ruthenium(II) (Ru(dcphen)(phen)(NCS)2), and cis-(4-monocarboxy-1,10-phenanthroline)(1,10-phenanthroline)dithiocyanato ruthenium(II) (Ru(mcphen)(phen)(NCS)2), as photosensitizers for oxide semiconductor solar cells. We have studied photovoltaic properties of dye-sensitized nanocrystalline semiconductor solar cells based on Ru phenanthroline complexes and an iodine redox electrolyte. The photovoltaic performance of the TiO2 solar cell sensitized by Ru(dcphen)2(NCS)2(TBA)2 exceeded that of ZnO, SnO2, and In2O3 solar cells. A solar energy to electricity conversion efficiency (η) of 6.6% was obtained under the standard AM 1.5 irradiation (100 mW cm^-2, JIS A class) with a short-circuit photocurrent density (Jsc) of 12.5 mA cm^-2, an open-circuit photovoltage (Voc) of 0.74 V, and a fill factor (ff) of 0.71. Monochromatic incident photon to current conversion efficiency was 78% at 526 nm. Deoxycholic acid as a coadsorbate and decreasing film thickness improved Voc especially due to suppression of the dark current reaction corresponding to the reduction of triiodide ions with injected electrons. The improved photovoltaic property due to the added coadsorbate suggests that some aggregates of the Ru complex suppress efficient electron injection to the semiconductor. The position and number of carboxyl groups attached to the phenanthroline ligand as an anchor affect photosensitizer performance significantly, suggesting that the anchoring configuration of Ru phenanthroline complexes on the semiconductor surface is important to efficient photovoltaic cell performance. Two carboxyl groups attached to phenanthroline ligands are necessary for effective electron injection.

Skin abnormalities in a patient with newly diagnosed MELAS syndrome are reported. He presented with scaly, pruritic, diffuse erythema with reticular pigmentation on his entire body. Moderate hypertrichosis was also noted on the lower extremities. Thickened arrector muscles with longitudinal and cross sections were seen in the dermis. Analysis of mitochondrial DNA in a biopsy specimen from the biceps brachii disclosed the presence of an A-to-G point mutation at nucleotide pair 3243. Electron microscopy revealed marked increase in the number of morphologically abnormal mitochondria in the arrector muscles of the involved skin. This is the first report of a MELAS syndrome patient with skin manifestations and evidence of morphologically abnormal mitochondria. (J Am Acad Dermatol 1999;41:469-73.)

In studying the photoelectrochemical properties of TiO2, Nb2O5, ZnO, SnO2, In2O3, WO3, Ta2O5, and ZrO2 porous semiconductor films sensitized by the ruthenium(II) cis-bis(thiocyanato)bis(2,2‘-bipyridyl-4,4‘-dicarboxylic acid) complex, it was found that the Nb2O5 semiconductor cell had the next highest incident of monochromatic photon-to-current efficiency (IPCE = 18%) compared to the TiO2 cell and showed the highest open-circuit photovoltage (Voc) among them. The Voc of the dye-sensitized cell was proved to be related to the flatband potential of the semiconductor electrode. The Ru dye adhered to the Nb2O5 surface mainly through an ester-like linkage. It is speculated that electrons are transferred mainly through the conjugated orbitals of the ester linkage and semiconductor conduction band and that the TiO2 and Nb2O5 conduction bands consisting of d-orbitals are more advantageous than those of s-orbitals in attaining the desired IPCE. The IPCE of the Nb2O5 cell was markedly improved by treating the Nb2O5 electrode with Nb alkoxide, and the maximum IPCE was 32% at 548 nm. The overall solar-to-electric energy conversion efficiency was about 2% (AM-1.5, 100 mW/cm²).

Puff adder lectin (PAL), a novel lectin venom purified from Bitis arietans, induced Ca++ release from the heavy fraction (HSR) but not from the light fraction of skeletal muscle sarcoplasmic reticulum with EC50 congruent to 10 microM. The potency of PAL was approximately 200-fold higher than that of caffeine. The bell-shaped profile of Ca++ dependence for PAL was almost the same as that for myotoxin a (MYTX), a peptide Ca++ releaser, but was different from that for caffeine. Typical blockers of Ca++ release channels, such as Mg+2, procaine, ruthenium red and ryanodine, markedly reduced PAL-induced Ca++ release from HSR. Interestingly, PAL inhibited 125I-MYTX binding to HSR with IC50 approximately equal to 20 microM. Scatchard analysis revealed that the mode of inhibition by PAL was noncompetitive, which suggests that PAL binds to a different site from that of MYTX. PAL did not affect 3H-ryanodine binding to HSR. These results suggest that PAL binds to a different site from that of MYTX to cause Ca++ release from HSR with novel properties.

The antithrombotic and bleeding time (BT)-prolonging effects of TAK-029, a novel glycoprotein IIb/IIIa antagonist, were characterized and compared with those of conventional antithrombotic agents in guinea pigs. TAK-029 potently inhibited the binding of fibrinogen and von Willebrand factor to purified human GPIIb/IIIa with IC50 values of 0.67 +/- 0.03 and 0.33 +/- 0.04 nM; it also inhibited human platelet aggregation induced by various aggregating agents with IC50 values of 29 to 38 nM. The in vitro antiplatelet effect of TAK-029 was potent in humans, guinea pigs and monkeys. When TAK-029 was given p.o. to guinea pigs, severe prolonging of BT (>1800 sec) was not observed with plasma concentrations of TAK-029 that inhibited ex vivo platelet aggregation by < 100%. The p.o. administration of TAK-029, ticlopidine and clopidogrel prolonged BT to the same extent, in parallel with their inhibition of ex vivo platelet aggregation. TAK-029 inhibited ex vivo platelet adhesion and thrombus formation in an arteriovenous shunt model more strongly than ticlopidine, clopidogrel and aspirin at doses causing similar prolongations of BT. In a balloon catheter-induced carotid thrombosis model, i.v. administration of TAK-029 significantly inhibited thrombus formation without prolonging BT. At doses that caused an incomplete antithrombotic effect, PGE1-alpha-cyclodextrin and argatroban produced hypotension and prolongation of BT, respectively. TAK-029 may be effective in patients suffering from arterial thrombotic diseases, which are refractory to these conventional antithrombotic agents.

The relationship between the functions of calmodulin (CaM) and Ca2+-induced smooth muscle contraction was investigated using a newly synthesized CaM antagonist, 3-(2-benzothiazolyl)-4,5-dimethoxy-N-[3-(4- -phenylpiperidinyl)propyl]benzenesulfonamide (HT-74). We noted a selectivity of HT-74 for CaM, compared to other calcium-binding proteins and target enzymes of CaM. As HT-74 had no significant effect on the intensity of 8-anilino-1-naphthalene-sulfonic acid (ANS) fluorescence in the presence of the Ca2+-CaM complex, the HT-74-binding sites may differ from those of naphthalenesulfonamides and phenothiazines which decrease ANS fluorescence. The Ca2+ binding to CaM was inhibited significantly by 1.0 microM HT-74, in sharp contrast to phenothiazines and naphthalenesulfonamides which increase the extent of the Ca2+ binding to CaM. Increasing CaM concentrations reversed the HT-74-induced inhibition of CaM-dependent enzymes such as myosin light chain kinase and Ca2+-dependent cyclic nucleotide phosphodiesterase, with Ki values of 0.5 microM and 0.4 microM, respectively. In the presence of 0.3 microM HT-74, potassium-depolarized rabbit aortic strips pre-contracted with 0.3 mM CaCl2 relaxed, and this relaxation was completely reversed by the addition of an excess amount of CaCl2 (10 mM). This compound shifted the dose-response curve for CaCl2 to the right, in a competitive manner. However, HT-74 inhibited the phenylephrine-induced contraction elicited in Ca2+-free solution and the calcium ionophore A23187-induced contraction in the presence of calcium ion. Therefore, this agent affects intracellular actions of Ca2+ rather than membrane receptors or the influx of Ca2+. HT-74 is a CaM antagonist which binds to CaM in a manner different from that heretofore reported. It inhibits Ca2+ binding to CaM and produces a competitive inhibition of Ca2+-induced contractions of depolarized vascular smooth muscle.

Based on the lead tetrapeptide RGDF, two possible non-peptide glycoprotein (GP) IIb-IIIa antagonists possessing an (S)-2-oxopiperazine-3-acetic acid moiety as a scaffold incorporating the indispensable Asp fragment were prepared, and (S)-4-[[trans-[4-(guanidinomethyl)cyclohexyl]carbonyl]glycyl]-2-oxopiperazine-1,3-diacetic acid, 1a, was identified as a potential lead. A series of 3-substituted 2-oxopiperazine-1-acetic acids bearing the Arg-Gly equivalent at the 4-position were prepared and evaluated for their ability to prevent platelet aggregation and for their binding affinity for the GP IIb-IIIa receptor purified from human HEL cells. (S)-4-[(4-Amidinobenzoyl)glycyl]-3-[(methoxycarbonyl)methyl]-2-oxopiperazine-1-acetic acid, 9 (TAK-029), inhibited in vitro human platelet aggregation with an IC50 value of 0.03 μM and GP IIb-IIIa−fibrinogen binding with an IC50 value of 0.49 nM. The [4-(2-aminoethyl)benzoyl]glycyl derivative 26 showed activity comparable to that of 9 (IC50 = 0.093 μM, guinea pig platelet aggregation assay). Compound 9 dose-dependently inhibited ex vivo platelet aggregation in guinea pigs (0.03 and 0.1 mg/kg, iv), and long-lasting inhibition of platelet aggregation was observed upon oral administration of 9 (3 mg/kg) to guinea pigs. On the other hand, the activity of 26 disappeared within 1 h after a dose of 1 mg/kg (iv). Compound 9 may therefore be useful in the clinical treatment of arterial thrombotic diseases.

Pepstatin, a specific inhibitor of pepsin, cathepsin D (E), renin, etc., was used in a new method to demonstrate the sites of enzymes. Pepstatin (Pst) was covalently attached to glutathione (GSH), using a dicyclohexylcarbodiimide, and CH3Hg+ was then put in the residue of SH for electron microscopic observation. Pst-GS-HgCH3 thus obtained was nonisotopical, had a very low molecular weight (about 1,200 daltons), and still almost completely retained its inhibitory activity. Sections of rat liver (less than 1 mm3 thick), prefixed by glutaraldehyde, were incubated in the prepared reaction medium. Cathepsin D, located in the lysosomes, was demonstrated by this compound, but when the sections were preincubated with pepstatin, this was not the case. These results demonstrate that mercury-labeled pepstatin is a useful reagent for the histochemical staining of acid proteases for electron microscope.

To examine the characteristics of GH secretion following the termination of the infusion of somatostatin, unrestrained adult female Wistar rats were subjected to repeated infusions of somatostatin separated by 30-min control periods. When somatostatin was infused for 150 min at a dose of 3, 30 or 300 μg/kg body wt per h, the magnitude of the rebound GH secretion increased in a dose-dependent manner. The infusion of somatostatin at a dose of 300 μg/kg body wt per h for 60, 150 or 240 min progressively augmented the size of the rebound GH secretion. When an antiserum to rat GH-releasing factor (GRF) was injected i.v. 10 min before the end of the infusion, the peak amplitude of the rebound GH secretion (300 μg/kg body wt, 150 min) was reduced to less than 20% of that of control rats. The rebound GH secretion (300 μg/kg body wt per h, 150 min) was augmented by a bolus injection of human GRF (1 μg/kg body wt). The combined effect of the end of infusion of somatostatin and a bolus injection of GRF on the amount of GH secreted was additive. The plasma GH response to GRF was completely inhibited when human GRF (3 μg/kg body wt per h) and somatostatin (300 μg/kg body wt per h) were infused simultaneously for 150 min. The magnitude of the rebound GH secretion following the termination of the co-administration was larger than that following the somatostatin infusion alone, but this rebound was not enhanced by a bolus injection of human GRF. Moreover, the amount of GH secreted was significantly less than that after the termination of somatostatin infusion plus a bolus injection of human GRF in the absence of preceding GRF administration.These results suggest that at least part of the influence of somatostatin on GH secretion is exerted at the level of the hypothalamus through modulating the release of GRF. In addition, it is inferred that the simultaneous infusion of GRF and somatostatin induces the attenuation of the GH response to GRF through a receptor effect.Journal of Endocrinology(1989) 122,583–591

Two sets of cDNA clones were isolated from cDNA libraries prepared from poly(A+) RNA of rabbit lung and spleen by screening with the cDNA probe for the large subunit (80-kDa subunit) of chicken calcium-dependent protease (Ca2+-protease; Ohno, S., Emori, Y., Imajoh, S., Kawasaki, H., Kisaragi, M., and Suzuki, K. (1984) Nature 312, 566-570). The two sets of clones were identified as cDNA clones for two Ca2+-protease isozymes with high (mu-type) and low (m-type) calcium sensitivities from a comparison of the primary structures deduced from the nucleotide sequences with partial amino acid sequences from the two isozymes. The cDNA clones for the 80-kDa subunits of the mu- and m-type Ca2+-proteases contained, in total, about 1.5- and 2.2-kilobase cDNA inserts, respectively, which correspond roughly to the C-terminal halves of the coding regions and the entire 3'-noncoding regions. The two isozymes are encoded by two distinct mRNA species present in all the tissues examined, although the amount of mRNA significantly differs among the various tissues. Four E-F hand structures, typical calcium-binding structures in various calcium-binding proteins such as calmodulin, were detected in the C-terminal regions of both isozymes, as in the case of chicken Ca2+-protease. Comparison of the amino acid sequences of the two rabbit isozymes and the corresponding region of the chicken enzyme revealed marked homology, which indicates that these three enzymes have the same evolutionary origin. Furthermore, we suggest that the mu-type rabbit Ca2+-protease, rather than the m-type, is similar to chicken Ca2+-protease, which is regarded as an m-type enzyme in the C-terminal region. The evolution and molecular basis of the differences in calcium sensitivities of the Ca2+-proteases are discussed.

We investigated the role played by nitric oxide in the dizocilpine-induced impairment of both spontaneous alternation behavior in a Y-maze and of performance in a multiple-trial passive avoidance task in mice. Dizocilpine (0.1 mg/kg) impaired the spontaneous alternation behavior and the retention of passive avoidance without affecting acquisition in the multiple-trial passive avoidance task. NG-nitro-L-arginine methylester (L-NAME), an inhibitor of nitric oxide (NO) synthase, dose-dependently impaired the spontaneous alternation behavior, but had no effect on either the acquisition or retention of passive avoidance. NG-nitro-D-arginine methylester had no effect on either task. The inhibitory effect of L-NAME on the spontaneous alternation behavior was completely reversed by the coadministration of L-arginine. Pretreatment with L-arginine ameliorated the dizocilpine-induced impairment of spontaneous alternation behavior, but not the impairment of the retention of passive avoidance. S-Nitroso-N-acetylpenicillamine, a generator of NO, completely inhibited the dizocilpine-induced impairment of spontaneous alternation behavior. Finally, the impairment of spontaneous alternation behavior caused by dizocilpine was significantly diminished by pretreatment with dibutyryl cyclic GMP. These results suggest that, although N-methyl-D-aspartate receptors play a critical role in both spatial working memory and long-term memory processes assessed by spontaneous alternation behavior and the passive avoidance, respectively, different neuronal mechanisms may be involved in these two processes. Further, it is suggested that the NO/cyclic GMP system may play a role in spatial working memory.

Ehrlich cancer cells and inflammatory cells in mouse ascitic fluid were hydrolyzed and stained with acridine orange (AO). The AO hydrolysis curves for G1/G2+M phase cancer cells and inflammatory cells were differentially determined using flow cytometry by monitoring the metachromatic red-shifted fluorescence of the fluorochrome bound to the single-stranded DNA produced by acid hydrolysis. By computer fitting of the Bateman function to the hydrolysis curves, the kinetic parameters k1 (rate constant for the degradation of the produced single-stranded DNA), and y0 (theoretical value of the single-stranded DNA present initially) were determined. It was found that the k2 value, which reflects the degree of DNA instability, was much higher for cancer cells in both the G1 and G2+M phases than for inflammatory cells. This finding led us to develop a method for the differential AO staining of cancer cells and non-cancerous cells utilizing the different degree of DNA instability at acid hydrolysis. AO staining after hydrolysis with 2N HCl at 30°C for 8.5 min was found to be the optimal method. In the 60 cases of human malignant epithelial and nonepithelial tumors tested, all of the malignant tumor cells emitted metachromatic red fluorescence, while all of the nonmalignant tumor cells (5 cases of benign tumor) and normal cells emitted orthochromatic green fluorescence when observed with a violet excitation light under a fluorescence microscope. This new technique can be a useful tool for the screening of malignancy in exfoliative cytology and also for basic cancer research.

Summary Signet-ring-cell carcinomas were induced in the stomach of 12 beagle dogs by p.o. administration ofN-ethyl-N'-nitro-N-nitrosoguanidine (ENNG), and the morphology and modes of cell proliferation in an incipient stage of cancer growth were studied with bromodeoxyuridine (BrdUrd) incorporation. From 5 to 27 months after the completion of 8 months' carcinogen treatment, minute carcinomas were found in the stomachs of 9 dogs. Before sacrifice, the dogs were given a single or repeated i.v. injections of BrdUrd for 1–3 days. Minute signet-ring-cell carcinomas were found to form a layered structure, in which the cancer cells proliferated in the lamina propria at the gland-neck level and differentiated to postmitotic signet-ring cells at the upper and lower levels of the mucosa. From repeated injections of BrdUrd, the time required for all the proliferative cells to be labelled with BrdUrd (reflecting the maximum cellcycle time) was estimated to be 1.7 days for the normal glands, and 2.7 days for minute signet-ring-cell carcinomas. From the labelling index with BrdUrd as well as from the morphology, earliest carcinomas were identified in the single gland. There remained atrophic normal epithelium commonly in the single-gland lesions. Proliferative atypical cells appeared to be shed into the stroma passively through the atrophy and subsequent collapse of the gland rather than through active invasion. This may be a reason why cancer cells in minute signet-ring cell carcinomas preserved the normal pattern of cell renewal movement to form the layered structure.