Synthesis, characterization, and photochemical properties of azobenzene-conjugated Ru(II) and Rh(III) bis(terpyridine) complexes

We synthesized azobenzene-conjugated bis(terpyridine) Ru(II) and Rh(III) mononuclear and dinuclear complexes and investigated their photochemical properties on excitation of the azo pi-pi band upon 366 nm light irradiation. The Ru mononuclear complex underwent trans-to-cis photoisomerization to reach the photostationary state with only 20% of the cis form, while the Ru dinuclear complex did not isomerize at all photochemically. On the other hand, the mononuclear and dinuclear Rh complexes showed almost complete trans-to-cis photoisomerization behavior. Cis forms of the Rh complexes thermally returned to the trans form at a much slower rate than those of organic azobenzenes, but they did not isomerize photochemically. The reduction potential of the cis forms was 80 mV more negative than that of the trans forms. The photoisomerization quantum yields of the Rh complexes were strongly dependent on the polarity, viscosity, and donor site of the solvents as well as the size of the counterions. We investigated the photoisomerization process of these complexes using femtosecond absorption spectroscopy. For the Rh complexes, we observed S(n) <-- S(2) and S(n) <-- S(1) absorption bands similar to those of organic azobenzenes. For the Ru complexes, we observed very fast bleaching of the MLCT band of the Ru complex, which indicated that the energy transfer pathway to the MLCT was the primary cause of the depressed photoisomerization. The electronic structures, which were estimated from ZINDO molecular orbital calculation, supported the different photochemical reaction behavior between the Ru and Rh complexes.

Expression and distribution of transcripts for sonic hedgehog in the early phase of fracture repair

Localization and expression of mRNAs for sonic hedgehog (Shh) at a fracture site in the early phase postfracture were investigated by in situ hybridization and reverse transcription and polymerase chain reaction (RT-PCR). A closed fracture was made in the midshaft of the right tibia of 5-week-old ICR mice, and fractured sites were harvested prefracture (day 0) and on days 2 and 12. In situ hybridization revealed that transcripts for Shh were not detected on day 0, but they were detected in proliferating callus-forming cells in the periosteum and the surrounding tissue, and in the medullary cavity prior to apparent new cartilage and bone formation. Gli 1 (a signaling mediator for Shh) and bone morphogenetic protein-4 transcripts were colocalized with those for Shh transcripts on day 2. The RT-PCR showed that Shh mRNA was detected in the PCR product from day 2, but not from days 0 and 12. These findings are the first description about the activation of Shh gene in the early postfracture reaction.

Clinical and endoscopic characterization of depressed gastric adenoma

BACKGROUND AND STUDY AIM

Depressed gastric adenoma remains poorly characterized because it is rare, and is infrequently detected by endoscopy. The aim of this study was to elucidate clinical and endoscopic characteristics of depressed adenoma of the stomach.

PATIENTS AND METHODS

95 consecutive patients who underwent endoscopic resection of gastric adenomas were studied. Gastric adenomas, diagnosed according to the Vienna classification, were endoscopically classified into two types: depressed and protruding adenomas. In order to clarify endoscopic features of gastric adenomas, we performed indigo carmine chromoendoscopy as well as magnifying endoscopy with narrow band imaging, which yields clear images of mucosal microvasculature.

RESULTS

12% of 100 gastric adenomas resected from 95 patients were depressed adenomas. Age and gender were comparable between patients with each type. Depressed adenomas (15.9 +/- 6.2 mm) were significantly larger in diameter than protruding adenomas (10.6 +/- 8.0 mm) (P = 0.01). Half of depressed adenomas were reddish in color, whereas only 18% of protruding adenomas were reddish. Magnifying endoscopy with narrow band imaging showed that 71% of depressed adenomas had a regular ultrafine network pattern of mucosal microvasculature, which was not seen in protruding adenomas. Intramucosal carcinomas were more frequently found in depressed adenomas (25%) than in protruding adenomas (4.5%).

CONCLUSIONS

In comparison with protruding adenomas, depressed adenomas were rare and appeared endoscopically as large and reddish with a specific regular ultrafine network pattern of mucosal microvasculature. Depressed adenomas should be endoscopically resected because intramucosal carcinomas were found in a quarter of them.

Structure and function of the photoreceptor stentorins in Stentor coeruleus. I. Partial characterization of the photoreceptor organelle and stentorins

The unicellular ciliary protozoan, Stentor coeruleus, exhibits photophobic and phototactic responses to visible light stimuli. The pigment granule contains the photoreceptor chromoproteins (stentorins). Stentorin localized in the pigment granules of the cell serves as the primary photoreceptor for the photophobic and phototactic responses in this organism. An initial characterization of the pigment granules has been described in terms of size, absorbance spectra and ATPase activity. Two forms of the stentorin pigments have been isolated from the pigment granules. Stentorin I has an apparent molecular weight of 68,600 and 52,000 by SDS-PAGE (at 10 and 13% gel, respectively) or 102,000 by steric exclusion HPLC, whereas stentorin II is a larger molecular assembly probably composed of several proteins (mol. wt. greater than 500,000). Stentorin I is composed of at least two heterologous subunits corresponding to apparent mol. wts. of 46,000 (fluorescent, Coomassie blue negative) and 52,000 (fluorescent, Coomassie blue positive) on SDS-PAGE (13% gel). However, these values were found to be strongly dependent on the degree of crosslinking in the acrylamide gel. Stentorin II appears to be the primary photoreceptor whose absorption and fluorescence properties are consistent with the action spectra for the photoresponses of the ciliate to visible light.

Structure and function of the photoreceptor stentorins in Stentor coeruleus. II. Primary photoprocess and picosecond time-resolved fluorescence

Stentorin serves as the photoreceptor for the photophobic and negative phototactic responses in Stentor coeruleus. Two forms of the stentorin have been isolated and purified. The strongly fluorescent form, stentorin I at pH 7.8, exhibited nearly exponential fluorescence decay monitored at 620 nm, having two comparable lifetime decay components of 2.53 ns (47%) and 5.95 ns (53%). Stentorin I showed no significant time-resolved fluorescence emission spectra in the picosecond-nanosecond time scales. The weakly fluorescent form, stentorin II, exhibited an ultrafast fluorescence decay component (10 ps) at an emission wavelength of 630 nm and pH 7.8. The amplitudes of the multi-component fluorescence in stentorin II were found to be emission wavelength-dependent. Furthermore, the fluorescence emission spectrum was time-resolvable in the picosecond time scales. Effects of pH and pD on the fluorescence decay kinetics and time-resolved spectra of stentorins I and II have also been investigated. Results are suggestive of proton dissociation as a primary photoprocess from the excited state of stentorin II.

Immunohistochemical detection of parathyroid hormone-related peptide, Indian hedgehog, and patched in the process of endochondral ossification in the human

Parathyroid hormone-related peptide (PTHrP), Indian hedgehog (Ihh), and patched (Ptc; a receptor for Ihh) were immunolocalized in tissue undergoing endochondral ossification in the human. PTHrP, Ihh, and Ptc were immunolocalized in prehypertrophic and hypertrophic chondrocytes in mature cartilage matrix. PTHrP and Ptc were immunostained in proliferating chondrocytes and perichondrial cells, whereas Ihh was not. PTHrP, Ihh, and Ptc showed positive immunostaining in osteoblasts in the bone-forming area. In the bone resorption site, PTHrP was immunolocalized in osteoclasts, whereas Ihh and Ptc were not. The present findings indicated that PTHrP, Ihh, and Ptc were associated with the process of endochondral ossification, and suggested the possible involvement of Ihh and PTHrP signaling in the regulation of proliferation and hypertrophy of chondrocytes in human chondrogenesis.

Temperature-induced changes in the coenzyme environment of D-amino acid oxidase revealed by the multiple decays of FAD fluorescence

A temperature-dependent change in the microenvironment of the coenzyme, FAD, of D-amino acid oxidase was investigated by means of steady-state and picosecond time-resolved fluorescence spectroscopy. Relative emission quantum yields from FAD bound to D-amino acid oxidase revealed the temperature transition when concentration of the enzyme was lowered. The observed fluorescence decay curves were well described with four-exponential decay functions. The amplitude of the shortest lifetime (tau 0), approximately 25 ps, was always negative, which indicates that the fluorescence of D-amino acid oxidase at approximately 520 nm appears after a metastable state of the excited isoalloxazine decays. The other components with positive amplitudes were assigned to dimer or associated forms of the enzyme, monomer, and free FAD dissociated from the enzyme. Ethalpy and entropy changes of intermediate states in the quenching processes were evaluated according to the absolute rate theory. The temperature transition was much more pronounced in the monomer than in the dimer or associated forms of the enzyme.

Picosecond-resolved fluorescence spectra of D-amino-acid oxidase. A new fluorescent species of the coenzyme

Protein dynamics of D-amino-acid oxidase in the picosecond region was investigated by measuring time-resolved fluorescence of the bound coenzyme, FAD. The observed nonexponential fluorescence decay curves were analyzed with four-exponential decay functions. The fluorescence lifetimes at the best fit were 26.6 +/- 0.7 ps, 44.0 +/- 4.2 ps, 177 +/- 11 ps, and 2.28 +/- 0.21 ns at 20 degrees C and 25.2 +/- 3.0 ps, 50.3 +/- 8.7 ps, 228 +/- 27 ps, and 2.75 +/- 0.33 ns at 5 degrees C. Component fractions with the shortest lifetime, ca. 26 ps, were always negative and close to -1. The other fluorescent components of the lifetimes, ca. 47 ps, 200 ps, and 2.6 ns, with positive fractions were assigned to different forms of the enzyme including the dimer, the monomer, and free FAD dissociated from the enzyme. Measurements of the time-resolved fluorescence spectra revealed that the maximum wavelengths of the spectra shifted toward shorter wavelength by 65 nm at 20 degrees C and 36 nm at 5 degrees C within 100 ps after pulsed excitation. The remarkable blue shift was not observed in free FAD. The first spectra immediately after the excitation of the enzyme exhibited maximum wavelengths of 584 nm at 20 degrees C and 557 nm at 5 degrees C. The fluorescence spectra obtained at times later than 100 ps are in good agreement with the one obtained under steady-state excitation of D-amino-acid oxidase.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and antitumor activities of novel 6-5 fused ring heterocycle antifolates: N-[4-[omega-(2-amino-4-substituted-6,7-dihydrocyclopenta [d]pyrimidin-5-yl)alkyl]benzoyl]-L-glutamic acids

Novel antifolates with a 6-5 fused ring system, 6,7-dihydrocyclopenta [d]pyrimidine, (3a,b and 4a,b) were synthesized on the basis of combined modification of the heterocycle and bridge regions of the folate molecule. The synthetic method involves (1) synthesis of key intermediates of tert-butyl 4-[omega-(2-substituted-3-oxocyclopentanyl) alkyl]benzoates (8a,b and 9a,b) by a carbon-carbon radical coupling of tert-butyl 4-(omega-iodoalkyl)benzoates (7a,b) with 2-substituted-2-cyclopenten-1-ones (5 and 6) utilizing tributyltin hydride, (2) cyclization of either the methyl enol-ethers derived from the 2-cyanocyclopentanones (8a,b) or the 2-(methoxycarbonyl)cyclopentanones (9a,b) themselves by treatment with guanidine which leads to 6,7-dihydrocyclopenta [d]pyrimidines with a 4-(tert-butoxycarbonyl)phenylalkyl group (11a,b and 14a,b), (3) deprotection to the corresponding carboxylic acids (12a,b and 15a,b), and (4) amidation with diethyl glutamate and deesterification. Potent dihydrofolate reductase inhibition and highly potent cell growth inhibition were found with 2,4-diaminopyrimidine-fused cyclopentene compounds containing the trimethylene (3a) or ethylene bridge (3b) but not with the corresponding 2-amino-4-hydroxy analogs (4a,b). Compounds 3a and 3b were more growth inhibitory to several tumor cell lines (P388, colon 26, colon 38, and KB) than was methotrexate, with 3a being the most potent. Both 3a and 3b gave increases in the lifespan of P388 leukemic mice comparable to that observed with MTX. Both compounds were therapeutic against colon 26 colorectal carcinoma in mice. Compound 3a was highly effective against LC-6 non-small cell lung carcinoma in nude mice.

Analysis of internal motion of single tryptophan in Streptomyces subtilisin inhibitor from its picosecond time-resolved fluorescence

A mode of internal motion of single tryptophan, Trp 86, of Streptomyces subtilisin inhibitor, was analyzed from its time-resolved fluorescence. The intensity and anisotropy decays of Trp 86 were measured in the picosecond range. These decays were analyzed with theoretical expressions derived assuming that the indole ring of tryptophan as an asymmetric rotor rotates around covalent bonds connecting indole with the peptide chain and an effective quencher of fluorescence of Trp 86 is the nearby SS bond of Cys 35-Cys 50. First, the intensity decays at 6 degrees, 20 degrees, and 40 degrees C were analyzed, and then the both decays of the intensity and anisotropy at 20 degrees C were simultaneously simulated with common parameters. Constants concerning geometrical structures of the protein used for the analysis were obtained from x-ray crystallographic data. Best fit between the observed and calculated decay curves was obtained by a nonlinear least squares method by adjusting a quenching constant averaged over the rotational angles, koq height of the potential energy, p, and three of six diffusion coefficients, Dxx, Dyy, Dzz, Dxy, Dyz, and Dzx, as variable parameters. The obtained results revealed that the internal motion of the indole ring became faster, the quenching rate of the fluorescence of Trp 86 was enhanced and the height of potential energy became lower at higher temperatures, and suggested that Trp 86 was wobbling around the long axis of the indole ring in the protein.

Primary photoprocesses of phytochrome. Picosecond fluorescence kinetics of oat and pea phytochromes

The primary photoprocesses of etiolated oat and pea phytochromes (Pr forms) are diffusion-modulated by the microscopic viscosity within the chromophore pocket. The chromophore pocket is preferentially accessible to glycerol but not to Ficoll. Glycerol preferentially retarded the rate (rate constant ca. 1-2 X 10(10) s-1) of the initial reaction from the Qy excited state of phytochrome, whereas it increased the long fluorescence lifetime (nanosecond) component that can be attributed to either an emitting intermediate or to modified/conformationally heterogeneous phytochrome populations. The picosecond time-resolved fluorescence spectra of different phytochrome preparations (i.e., full-length vs 6/10-kDa NH2-terminus truncated forms of phytochromes from monocot and dicot plants) revealed no significant differences. The spectra in the picosecond time scale showed no spectral shifts, but at longer time scales of up to approximately 1.90 ns, significant blue spectral shifts were observed. The shifts were more in the truncated than in the full-length pea phytochrome. Comparison of the fluorescence decay data and the picosecond time-resolved fluorescence spectra suggests differences in conformational flexibility/heterogeneity among the preparations of the monocot vs dicot phytochromes and the full-length native vs the amino terminus truncated phytochromes.

Network structure of curdlan in DMSO and mixture of DMSO and water

The viscoelastic property of curdlan solution in dimethyl sulfoxide (DMSO) was investigated. We discuss the difference in the viscoelastic properties of curdlan solution in DMSO and that in 0.1 N NaOH aqueous solution. The viscoelastic function for curdlan solution in 0.1 N NaOH aqueous solution showed the Newtonian flow at the concentration of curdlan as high as 10 wt %. On the other hand, the Newtonian flow was observed in the concentrations below 7 wt % for curdlan solution in DMSO, and the plateau region appeared beyond this concentration. It was revealed by small angle x-ray diffraction measurements that the difference in the mechanical property would be originated from the difference in the network structure. The overlapping concentration c* was calculated on the basis of the mean field theory, and disagreement between theoretical prediction and experimental result was shown. We clarified that the above disagreement can be explained by the polydispersity of the curdlan sample, assuming adequate distribution functions. The static structure of the gel prepared by adding water to curdlan solution in DMSO was investigated. It was clarified by the dynamic viscoelasticity measurement that the cross-linking density increases with increasing the water content.

Excitation energy transfer of porphyrin in polymer thin films by time-resolved scanning near-field optical microspectroscopy

Thin films of water-soluble free-base porphyrin, 5,10,15,20-tetraphenyl-21H, 23H-porphinetetrasulphonic acid (TPPS) mixed with poly(diallyldimethyl ammonium chloride) (PDDA) have been prepared by a spin-coating method, in which the monomeric species were observed in the spin-coat film, whereas dimer was formed in the cast film prepared from TPPS/PDDA solution. Mesoscopic structures and dynamics of excitation energy migration and trapping of TPPS/PDDA spin-coat film have been analysed by time-resolved scanning near-field optical microspectroscopy (SNOM) and atomic force microscope. The observed film structure can be classified roughly into two parts: one is a large, flocculated polymer part, and the other is a smooth part widely spread around the flocculated polymers. In the smooth part, the observed spindle-like structure and circular hills and dips are essentially due to PDDA. The ellipsoidal small structures with approximately 2 microm length and < 1 microm width in the flocculated polymer part show non-exponential fluorescence decays. The non-exponential dynamics originates from the excitation energy migration among TPPS monomers and energy trapping to dimers. From the analysis of fluorescence decay curves based on the equation developed by Klafter and Blumen, the spectral dimension has been estimated to be approximately 1.46 for ellipsoidal structures. These results indicate that the distribution of the chromophore is inhomogeneous and a fractal-like structure exists even in the small domains determined by the resolution of the SNOM tip.

Effects of dehydroepiandrosterone on mitogen-activated protein kinase in human aortic smooth muscle cells

The objective of the present study was to determine whether dehydroepiandrosterone (DHEA) modifies growth factor-induced mitogen-activated protein kinase (MAPK) activation, based on our previous study demonstrating that DHEA attenuates fetal calf serum-induced proliferation in human male aortic smooth muscle cells (human male aortic SMCs). Human male aortic SMCs were used for this study. Platelet-derived growth factor-BB (PDGF-BB), epidermal growth factor (EGF), and basic fibroblast growth factor (bFGF), but not insulin-like growth factor-1 (IGF-1), stimulated MAPK activity. Only MAPK activation induced by PDGF-BB was reduced by pretreatment with DHEA, although DHEA did not affect the MAPK activation induced by EGF or bFGF. The basal and PDGF-stimulated MAPK activity were decreased by two types of cyclic AMP (cAMP) elevating agents and increased by cAMP-dependent protein kinase (PKA) inhibitor in human male aortic SMCs, suggesting that cAMP regulates MAPK negatively. The intracellular cAMP was increased by PDGF-BB. The increase of cAMP by PDGF-BB was augmented by pretreatment with DHEA, although DHEA alone did not affect cAMP. Neither EGF nor bFGF affected cAMP with and without DHEA pretreatment. Secretion of PGE2 induced by PDGF was augmented by pretreatment with DHEA. Stimulatory effects of DHEA on the production of PGE2 and cAMP were partially canceled by aromatase inhibitor and completely canceled by indomethacin or selective inhibitor of cyclooxygenase-2. These results suggest that DHEA inhibited MAPK activation induced by PDGF-BB via PGE2 overproduction and subsequent cAMP-dependent pathway in human male aortic SMCs.

Presence and significance of minor antenna components in the energy transfer sequence of the green photosynthetic bacterium Chloroflexus aurantiacus

Antenna components in the energy transfer processes of a green photosynthetic bacterium Chloroflexus aurantiacus were spectrally investigated by time-resolved fluorescence spectroscopy at -196 degrees C on intact cells. Besides major antenna components so far reported, three minor components were resolved; those were Bchl c located at 785 nm, the baseplate Bchl a at 819 nm and Bchl a in the B808-866 complex at 910 nm. The last component was assigned to a longer wavelength antenna closely associated with a reaction center. An additional Bchl c fluorescence component was kinetically suggested to be present, which can be an energy donor to a major Bchl c. Presence of these minor components was signified in terms of (1) increase in the spectral overlap integral and (2) adjustment of the direction of dipole moments in the energy transfer sequence of intact cells.

Mesoscopic structures and dynamics of merocyanine J-aggregate studied by time-resolved fluorescence SNOM

Time-resolved fluorescence SNOM is used to probe the mesoscopic structure and dynamics of long-chain merocyanine (C18MC) J-aggregates on glass plates prepared by spin coating, casting, and casting of water-soluble polymer films. A globular structure with an average diameter of approximately 1 microm and a height of approximately 50 nm was attributed to the J-aggregate of C18MC in the spin-coating film. In polymer films, the bandwidth of the absorption of J-aggregate is much narrower in polyvinyl alcohol (PVA, approximately 20 nm) than that in polyvinyl sulphate (PVS, approximately 60 nm). We have demonstrated that the large bandwidth of the spectrum is due to the inhomogeneous distribution of the J-aggregate. The fluorescence image of the J-aggregate in PVA film was rather uniform, whereas non-uniform distribution of the fluorescence was observed in PVS film. The fluorescence of C18MC J-aggregate in a small domain of PVA film was a single exponential decay with a lifetime as short as 19 ps, which was shorter than that in PVS film with a two-exponential decay (average lifetime of approximately 25 ps). The fluorescence lifetime of the J-aggregate and its single exponential behaviour are considered to be indicators of the uniform distribution of the J-aggregate. The non-uniform distribution of the J-aggregate in PVS film was interpreted in terms of electrostatic interaction between PVS and merocyanine.

Negative strand of hepatitis C virus RNA in the liver of patients with chronic hepatitis C after interferon treatment

In patients receiving interferon therapy for chronic hepatitis C, serum hepatitis C virus (HCV) RNA often reverts from an undetectable to a detectable form after completion of treatment. Detection of the negative strand of HCV-RNA in liver tissue is regarded as an index of viral proliferation. Therefore, we investigated changes in the hepatic negative-strand HCV-RNA following interferon therapy to determine whether this parameter could predict the long-term response to treatment. The subjects of this study were 27 patients with chronic active hepatitis C. Serum positive-strand and hepatic tissue negative-strand HCV-RNA were detected using polymerase chain reaction. At the completion of interferon treatment, serum HCV-RNA was not detected in 21 patients. One year following treatment it remained undetectable in 14 of these patients but it had reverted to a detectable form in seven. The 14 patients in whom hepatic negative-strand RNA was not detected between 2 weeks and 12 months after treatment, had not relapsed after another year. In the 13 remaining patients, negative-strand RNA was found in liver tissue and serum RNA either reverted to a detectable form or remained detectable throughout. From these findings, we conclude that the detection of negative-strand HCV-RNA in liver tissue 2 weeks after the completion of interferon therapy is useful for predicting the long-term effect of therapy.

Ascorbic acid protects against peroxidative modification of low-density lipoprotein, maintaining its recognition by LDL receptors

Peroxidatively modified low-density lipoprotein (LDL) may contribute to atherosclerotic processes; therefore, protecting LDL against peroxidation may thus reduce or retard the progression of atherosclerosis. We have evaluated the protective effects of ascorbic acid on copper-catalyzed LDL peroxidative modification. The protective effects of ascorbic acid on copper-catalyzed LDL peroxidative modification were examined by measurement of concentration of lipid hydroperoxides in LDL and by the provision of LDL cholesterol to lymphocytes via LDL receptor-mediated pathway. The measurement of concentration of lipid hydroperoxides in LDL showed that ascorbic acid inhibited peroxidative modification of LDL. Also, ascorbic acid preserved the ability of LDL to be recognized by LDL receptors in peripheral blood lymphocytes to the same extent as native LDL. These findings indicate that ascorbic acid may protect LDL against peroxidative modification, maintaining its ability to act as a ligand for LDL receptors in vivo.