Broader leaves result in better performance of indica rice under drought stress

Leaf growth is one of the first physiological processes affected by changes in plant water status under drought. A decrease in leaf expansion rate usually precedes any reduction in stomatal conductance or photosynthesis. Changes in leaf size and stomatal opening are potential adaptive mechanisms, which may help avoid drought by reducing transpiration rate, and can be used to improve rice genotypes in water-saving cultivation. The indica rice cultivar IR64 and four of its near-isogenic lines (NILs; BC(3)-derived lines) unique for leaf size traits, YTK 124 (long leaves), YTK 127 (broad leaves), YTK 205 (short leaves) and YTK 214 (narrow leaves), were compared in this study for changes in leaf growth and its water status. The plants were subjected to two soil water regimes, well-watered and progressive soil drying measured by the fraction of transpirable soil water (FTSW). Applied drought reduced leaf number, total leaf area, specific leaf area, plant biomass, tiller number, plant height, stomatal conductance, amount of water transpired, leaf relative water content, and leaf water potential more in IR64 and the NILs than in the respective controls; nonetheless, transpiration efficiency (TE) was slightly higher under drought than in the well-watered controls. NILs with broader leaves had higher biomass (and its individual components), less stomatal conductance, and higher TE under drought than NILs with narrow and shorter leaves. Under drought, leaf number was positively correlated with tiller number and plant height; nonetheless, root weight and total biomass, water transpired and TE, and plant height and TE were positively correlated with each other. However, a negative correlation was observed between stomatal conductance and the FTSW threshold at which normalized transpiration started to decline during soil drying. Overall, the IR64-derived lines with broader leaves performed better than NILs with narrow and short leaves under drought.

Evidence for biological nitrification inhibition in Brachiaria pastures

Nitrification, a key process in the global nitrogen cycle that generates nitrate through microbial activity, may enhance losses of fertilizer nitrogen by leaching and denitrification. Certain plants can suppress soil-nitrification by releasing inhibitors from roots, a phenomenon termed biological nitrification inhibition (BNI). Here, we report the discovery of an effective nitrification inhibitor in the root-exudates of the tropical forage grass Brachiaria humidicola (Rendle) Schweick. Named "brachialactone," this inhibitor is a recently discovered cyclic diterpene with a unique 5-8-5-membered ring system and a gamma-lactone ring. It contributed 60-90% of the inhibitory activity released from the roots of this tropical grass. Unlike nitrapyrin (a synthetic nitrification inhibitor), which affects only the ammonia monooxygenase (AMO) pathway, brachialactone appears to block both AMO and hydroxylamine oxidoreductase enzymatic pathways in Nitrosomonas. Release of this inhibitor is a regulated plant function, triggered and sustained by the availability of ammonium (NH(4)(+)) in the root environment. Brachialactone release is restricted to those roots that are directly exposed to NH(4)(+). Within 3 years of establishment, Brachiaria pastures have suppressed soil nitrifier populations (determined as amoA genes; ammonia-oxidizing bacteria and ammonia-oxidizing archaea), along with nitrification and nitrous oxide emissions. These findings provide direct evidence for the existence and active regulation of a nitrification inhibitor (or inhibitors) release from tropical pasture root systems. Exploiting the BNI function could become a powerful strategy toward the development of low-nitrifying agronomic systems, benefiting both agriculture and the environment.

Intraarterial injection of colforsin daropate hydrochloride for the treatment of vasospasm after aneurysmal subarachnoid hemorrhage: preliminary report of two cases

We describe two patients with symptomatic vasospasms after aneurysmal subarachnoid hemorrhage who were successfully treated with intraarterial injection of colforsin daropate hydrochloride (HCl). Colforsin daropate HCl is capable of directly stimulating adenylate cyclase, which in turn causes vasorelaxation via elevated intracellular concentrations of cyclic adenosine monophosphate. We suggest that colforsin daropate HCl might be a useful therapeutic tool in treating cerebral vasospasm.

Improved simultaneous nitrification and denitrification in a single reactor by using two different immobilization carriers with specific oxygen transfer characteristics

To maximize nitrogen utilization rates during nitrification and denitrification in a simultaneous reaction for direct nitrogen removal from ammonia-nitrogen in a single reactor, two different carriers were applied that immobilized nitrifiers and denitrifiers separately. With the optimized DO concentration and mixing ratio of immobilization carriers, ammonium-nitrogen was successfully removed as designed until the middle phase of treatment where nitrogen removal rate was higher than 83% of the theoretical value, although an imbalance between nitrification and denitrification occurred at a later phase of treatment where residual nitrate-nitrogen concentration was less than 2 mg/l. The new approach using two different carriers to immobilize nitrifiers and denitrifiers separately was proved useful for controlling both nitrification and denitrification rates, enabling the utilization of maximum treatment ability of both nitrifiers and denitrifiers in a single reactor for direct nitrogen removal from ammonium-nitrogen.

Selection of endovascular approach of vein of galen aneurysmal malformation

SUMMARY

Vein of Galen aneurysmal malformation (VGAM) is one of the most difficult intracranial vascular lesions because this disease consists of extremely high flow shunts and affects infants and small children. Thanks to the development of various diagnostic modalities, early diagnosis became possible allowing us to prepare appropriately according to the patients' general and neurological conditions. Recent improvements of endovascular techniques and materials enabled both transarterial and transvenous approaches even to the newborn infants, widening therapeutic windows. In this article, we discuss the selection of endovascular approaches based upon angioarchitecture of VGAM presenting four representative cases from our file.

Scandium ion-promoted photoinduced electron-transfer oxidation of fullerenes and derivatives by p-chloranil and p-benzoquinone

In the presence of scandium triflate, an efficient photoinduced electron transfer from the triplet excited state of C(60) to p-chloranil occurs to produce C(60) radical cation which has a diagnostic NIR (near-infrared) absorption band at 980 nm, whereas no photoinduced electron transfer occurs from the triplet excited state of C(60) (3C(60)) to p-chloranil in the absence of scandium ion in benzonitrile. The electron-transfer rate obeys pseudo-first-order kinetics and the pseudo-first-order rate constant increases linearly with increasing p-chloranil concentration. The observed second-order rate constant of electron transfer (k(et)) increases linearly with increasing scandium ion concentration. In contrast to the case of the C(60)/p-chloranil/Sc(3+) system, the k(et) value for electron transfer from 3C(60) to p-benzoquinone increases with an increase in Sc(3+) concentration ([Sc(3+)]) to exhibit a first-order dependence on [Sc(3+)], changing to a second-order dependence at the high concentrations. Such a mixture of first-order and second-order dependence on [Sc(3+)] is also observed for a Sc(3+)-promoted electron transfer from CoTPP (TPP(2-) = tetraphenylporphyrin dianion) to p-benzoquinone. This is ascribed to formation of 1:1 and 1:2 complexes between the generated semiquinone radical anion and Sc(3+) at the low and high concentrations of Sc(3+), respectively. The transient absorption spectra of the radical cations of various fullerene derivatives were detected by laser flash photolysis of the fullerene/p-chloranil/Sc(3+) systems. The ESR spectra of the fullerene radical cations were also detected in frozen PhCN at 193 K under photoirradiation of the fullerene/p-chloranil/Sc(3+) systems. The Sc(3+)-promoted electron-transfer rate constants were determined for photoinduced electron transfer from the triplet excited states of C(60), C(70), and their derivatives to p-chloranil and the values are compared with the HOMO (highest occupied molecular orbital) levels of the fullerenes and their derivatives.

Serum progesterone and estradiol-17beta concentrations, and lapaloscopic observations of the ovary in the cheetah (Acinonyxjubatus) with pregnant mare serum gonadotropin and human chorionic gonadotropin treatments

In 3 adult female cheetahs, induced-superovulation treatment was conducted, by means of 200 IU of pregnant mare serum gonadotropin (PMSG) and 100 IU of human chorionic gonadotropin (hCG) 80 hr after PMSG. The administration of PMSG created a sharp increase in the estradiol-17beta concentration, resulting in 232 pg/ml 8 hr later in one specimen out of three. The hCG administration showed an increase in the progesterone concentration of 2.29 ng/ml 46 hr later. In addition, after direct observation of the ovary surface by laparoscopy, 5 follicles in the right ovary over 2 mm in diameter, and 7 corpora lutea (5 in the right ovary and 2 in the left) were found. It is assumed that ovulation can be induced with hCG after 80 hr on PMSG during a cheetah's diestrus or proestrus.

Photooxidation of olefins sensitized by bisazafullerene (C(59)N)(2) and hydroazafullerene C(59)HN: product analysis, emission of singlet oxygen, and transient absorption spectroscopy

The photooxidation reactions of olefins sensitized by the excited triplet states of bisazafullerene (C(59)N)(2) and hydroazafullerene C(59)HN have been studied. Oxidation yields were compared with those of pristine C(60). The singlet oxygen yields are also determined directly from the emission intensities, which are in good agreement with the oxidation yields. The triplet states of (C(59)N)(2) and C(59)HN have been identified by the time-resolved spectroscopic method by observing the triplet-triplet absorption spectra, which decay in the presence of oxygen. It has been proven that (C(59)N)(2) and C(59)HN have the ability to sensitize the reactions via singlet oxygen in about half of the efficiency of that of pristine C(60). For both azafullerenes, the triplet lifetimes are shorter than that of pristine C(60), which may be related to the nitrogen atom embedded in the C(60) moiety.

Photochemical and electrochemical properties of zinc chlorin-C60 dyad as compared to corresponding free-base chlorin-C60, free-base porphyrin-C60, and zinc porphyrin-C60 dyads

The photochemical and electrochemical properties of four chlorin-C60 or porphyrin-C60 dyads having the same short spacer between the macrocycle and the fullerene are examined. In contrast with all the previous results on porphyrin-fullerene dyads, the photoexcitation of a zinc chlorin-C60 dyad results in an unusually long-lived radical ion pair which decays via first-order kinetics with a decay rate constant of 9.1 x 10(3) x s(-1). This value is 2-6 orders of magnitude smaller than values reported for all other porphyrin or chlorin donor-acceptor of the molecule dyad systems. The formation of radical cations of the donor part and the radical anion of the acceptor part was also confirmed by ESR measurements under photoirradiation at low temperature. The photoexcitation of other dyads (free-base chlorin-C60, zinc porphyrin-C60, and free-base porphyrin-C60 dyads) results in formation of the ion pairs which decay quickly to the triplet excited states of the chlorin or porphyrin moiety via the higher lying radical ion pair states as is expected from the redox potentials.

Photoalkylation of 10-alkylacridinium ion via a charge-shift type of photoinduced electron transfer controlled by solvent polarity

A charge-shift type of photoinduced electron-transfer reactions from various electron donors to the singlet excited state of 10-decylacridinium cation (DeAcrH+) in a nonpolar solvent (benzene) is found to be as efficient as those of 10-methylacridinium cation (MeAcrH+) and DeAcrH+ in a polar solvent (acetonitrile). Irradiation of the absorption bands of MeAcrH+ in acetonitrile solution containing tetraalkyltin compounds (R(4)Sn) results in the efficient and selective reduction of MeAcrH+ to yield the 10-methyl-9-alkyl-9,10-dihydroacridine (AcrHR). The same type of reaction proceeds in benzene when MeAcrH+ is replaced by DeAcrH+ which is soluble in benzene. The photoalkylation of R'AcrH+ (R' = Me and De) also proceeds in acetonitrile and benzene using 4-tert-butyl-1-benzyl-1,4-dihydronicotinamide (Bu(t)BNAH) instead of R(4)Sn, yielding MeAcrHBu(t). The quantum yield determinations, the fluorescence quenching of R'AcrH+ by electron donors, and direct detection of the reaction intermediates by means of laser flash photolysis experiments indicate that the photoalkylation of R'AcrH+ in benzene as well as in acetonitrile proceeds via photoinduced electron transfer from the alkylating agents (R(4)Sn and Bu(t)BNAH) to the singlet excited states of R'AcrH+. The limiting quantum yields are determined by the competition between the back electron-transfer process and the bond-cleavage process in the radical pair produced by the photoinduced electron transfer. The rates of back electron transfer have been shown to be controlled by the solvent polarity which affects the solvent reorganization energy of the back electron transfer. When the free energy change of the back electron transfer (DeltaG(0)(bet)) in a polar solvent is in the Marcus inverted region, the rate of back electron transfer decreases with decreasing the solvent polarity, leading to the larger limiting quantum yield for the photoalkylation reaction. In contrast, the opposite trend is obtained when the DeltaG(0)(bet) value is in the normal region: the limiting quantum yield decreases with decreasing the solvent polarity.

Involvement of cytochrome P450 metabolites in the vascular action of angiotensin II on the afferent arterioles

Recent studies have demonstrated that cytochrome P450-dependent metabolites of arachidonic acid (CYP450-AA) play important roles in the control of renal vascular resistance (RVR). In the present study, we examined the possible involvement of CYP450-AA in the vasoconstrictor action of angiotensin II (Ang II) on the afferent arterioles (Af-Arts), a vascular segment crucial to the control of RVR. Rabbit Af-Arts were microperfused at 60 mmHg in vitro, and the vasoconstrictor action of Ang II (10(-11)-10(-8) M, added to both the bath and lumen) was examined with or without blocking the activity of CYP450 epoxygenase or hydroxylase. Ang II decreased the luminal diameter of Af-Arts in a dose-dependent manner (34+/-2% of control diameter at 10(-8) M, n=9, p<0.0001). Pretreatment with miconazole, an inhibitor of CYP450 epoxygenase, at 10(-6) M decreased the basal diameter by 14+/-1% (n=6, p<0.01) and augmented the vasoconstrictor action of Ang II (7+/-3% of control diameter at 10(-8) M, p<0.001 vs. without miconazole). This augmentation was abolished by blocking the Ang II type 2 (AT2) receptor with PD 123319 at 10(-7) M. In contrast, pretreatment with 17-octadecynoic acid (17-ODYA, 10(-6) M), which inhibits both epoxygenase and hydroxylase activity, had no effect on the basal diameter but attenuated the vasoconstrictor action of Ang 11(46+/-2% of control diameter at 10(-8) M, p<0.01 vs. without 17-ODYA). Our results demonstrate that in the Af-Art, endogenous CYP450-AA are involved not only in the control of basal tone but also in the action of Ang II. Further, it appears that the CYP450 epoxygenase pathway attenuates Ang II action via AT2 receptors.

Change in spin state and enhancement of redox reactivity of photoexcited states of aromatic carbonyl compounds by complexation with metal ion salts acting as Lewis acids. Lewis acid-catalyzed photoaddition of benzyltrimethylsilane and tetramethyltin via photoinduced electron transfer

The lowest excited state of aromatic carbonyl compounds (naphthaldehydes, acetonaphthones, and 10-methylacridone) is changed from the n,pi triplet to the pi,pi singlet which becomes lower in energy than the n,pi triplet by the complexation with metal ions such as Mg(ClO(4))(2) and Sc(OTf)(3) (OTf = triflate), which act as Lewis acids. Remarkable positive shifts of the one-electron reduction potentials of the singlet excited states of the Lewis acid-carbonyl complexes (e.g., 1.3 V for the 1-naphthaldehyde-Sc(OTf)(3) complex) as compared to those of the triplet excited states of uncomplexed carbonyl compounds result in a significant increase in the redox reactivity of the Lewis acid complexes vs uncomplexed carbonyl compounds in the photoinduced electron-transfer reactions. Such enhancement of the redox reactivity of the Lewis acid complexes leads to the efficient C-C bond formation between benzyltrimethylsilane and aromatic carbonyl compounds via the Lewis-acid-promoted photoinduced electron transfer. The quantum yield determinations, the fluorescence quenching, and direct detection of the reaction intermediates by means of laser flash photolysis experiments indicate that the Lewis acid-catalyzed photoaddition reactions proceed via photoinduced electron transfer from benzyltrimethylsilane to the singlet excited states of Lewis acid-carbonyl complexes.

Photoinduced electron transfer between chlorophylls (a/b) and fullerenes (C60/C70) studied by laser flash photolysis

Photoinduced electron-transfer processes in the systems of chlorophylls (Chl) (chlorophyll-a [Chl-a] and chlorophyll-b) and fullerenes (C60/C70) in both polar and non-polar solvents have been investigated with nanosecond laser photolysis technique, observing the transient spectra in the visible/near-IR regions. By the excitation of Chl in benzonitrile (BN) it has been proved that electron transfer takes place from the triplet excited states of Chl to the ground states of C60/C70. By the excitation of C70 in BN electron transfer takes place from the ground states of Chl to the triplet excited state of C70. In both Chl the rate constants and quantum yields for the electron-transfer processes are as high as those of zinc porphyrins and zinc phthalocyanines, indicating that the long alkyl chains of Chl play no role in retarding the electron transfer. The rate constant for the electron-mediating process from the radical anion of C70 to octylviologen dication yielding the octylviologen radical cation was evaluated. The back electron-transfer process from the viologen radical cation to the radical cation of Chl-a takes place in a longer time-scale, indicating that a photosensitized electron-transfer/electron-mediating cycle is achieved.

Angiographic classification of coronary dissections after plain old balloon angioplasty for prediction of regression at follow-up

Coronary dissection after plain old balloon angioplasty often shows regression during follow-up. This study sought to determine whether we can predict such phenomenon angiographically. We analyzed 64 patients with 71 type B-D coronary dissections determined by the National, Heart, Lung, and Blood Institute (NHLBI) criteria. Regression was considered present when minimal lumen diameter increased by more than 0.3 mm during follow-up. Dissections were divided into subgroups using the NHLBI criteria and our classification in which type a and b dissections were characterized by the width of a dissection lumen exceeding one quarter of the reference diameter with the outer edge of the dissection lumen within the boundary of reference in type a and beyond it in type b. In type c and type d dissections, the width of the dissection lumen was within one quarter of the reference with its outer edge within the boundary of reference in type c and beyond it in type d. Type e dissection had a protruding flap or spiral appearance. Regression was recognized in 23.9%. The distribution of dissection types was similar in the groups with and without regression by the NHLBI criteria, but type c dissection had regression more frequently than the other types of coronary dissections (p<0.001) using our classification.

CpG-DNA derived from sera in systemic lupus erythematosus enhances ICAM-1 expression on endothelial cells

OBJECTIVE

To examine the effect of transfection of oligodeoxynucleotides (ODNs) containing a CpG motif (CpG-ODN), of which the sequence was derived from circulating DNA in the sera of patients with systemic lupus erythematosus (SLE), on the expression of intercellular adhesion molecule-1 (ICAM-1) and synthesis of mRNA for proinflammatory cytokines and ICAM-1 in human umbilical vein endothelial cells (EC).

METHODS

A CpG-ODN or a control analogue, GpC-ODN, was transfected into EC. ICAM-1 expression was examined by flow cytometry, and expression of mRNA in EC encoding interleukin 1 (IL1), IL6, IL8, tumour necrosis factor alpha (TNFalpha), interferon gamma (IFNgamma), and ICAM-1 was examined by semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

The CpG-ODN augmented the expression of ICAM-1 on EC determined by flow cytometry and increased mRNA levels of IL6, IL8, TNFalpha, IFNgamma, and ICAM-1, but the GpC-ODN did not.

CONCLUSION

Synthesised DNA, with a sequence corresponding to that of the fragment containing the CpG motif, in sera of patients with SLE was found to enhance ICAM-1 expression on EC, suggesting the participation of circulating DNA fragments in the pathogenesis of vasculitis in SLE.

Probing the donor-acceptor proximity on the physicochemical properties of porphyrin-fullerene dyads: "tail-on" and "tail-off" binding approach

A new approach of probing proximity effects in porphyrin-fullerene dyads by using an axial ligand coordination controlled "tail-on" and "tail-off" binding mechanism is reported. In the newly synthesized porphyrin-fullerene dyads for this purpose, the donor-acceptor proximity is controlled either by temperature variation or by an axial ligand replacement method. In o-dichlorobenzene, 0.1 M (TBA)ClO(4), the synthesized zincporphyrin-fullerene dyads exhibit seven one-electron reversible redox reactions within the accessible potential window of the solvent and the measured electrochemical redox potentials and UV-visible absorption spectra reveal little or no ground-state interactions between the C(60) spheroid and porphyrin pi-system. The proximity effects on the photoinduced charge separation and charge recombination are probed by both steady-state and time-resolved fluorescence techniques. It is observed that in the "tail-off" form the charge-separation efficiency changes to some extent in comparison with the results obtained for the "tail-on" form, suggesting the presence of some through-space interactions between the singlet excited zinc porphyrin and the C(60) moiety in the "tail-off" form. The charge separation rates and efficiencies are evaluated from the fluorescence lifetime studies. The charge separation via the singlet excited states of zinc porphyrin in the studied dyads is also confirmed by the quick rise-decay of the anion radical of the C(60) moiety within 20 ns. Furthermore, a long-lived ion pair with lifetime of about 1000 ns is also observed in the investigated zinc porphyrin-C(60) dyads.

Insulinoma with subsequent association of Zollinger-Ellison syndrome

We report a patient with insulinoma associated with Zollinger-Ellison syndrome. A 67-year-old woman was first admitted to our hospital for an abdominal mass. Abdominal computed tomography (CT) revealed a large pancreatic tumor, which was then diagnosed as an unresectable pancreatic adenocarcinoma. At the age of 71, she presented symptoms of hypoglycemia. Fasting blood glucose was 21 mg/dl and plasma immunoreactive insulin level was 846 microU/ ml. Plasma gastrin, glucagon, vasoactive intestinal polypeptide and somatostatin levels were all normal. At the age of 73, hypoglycemic attacks occurred more frequently and she was admitted to our hospital. Abdominal CT scan showed multiple liver metastases. Chemotherapy with 5-fluorouracil and doxorubicin was performed. Three months later, she had an emergency laparotomy because of a perforated duodenal ulcer. Plasma gastrin level was 1,960 pg/ml at that time. Gastric hypersecretion was well controlled with a proton pump inhibitor (lansoprazole) but she died of widespread cancer dissemination 8 years after her first admission. On autopsy, histologic examination revealed a mixed acinar-endocrine carcinoma of the pancreas. Immunohistochemical stains were positive for insulin, gastrin, and alpha1-antitrypsin.

Role of cholecystokinin in the intestinal phase of pancreatic circulation in dogs

The regulatory mechanisms of postprandial pancreatic hyperemia are not well characterized. The aim of this study is to clarify the role of cholecystokinin (CCK) in the intestinal phase of pancreatic circulation. Pancreatic, gastric, and intestinal blood flows were measured by ultrasound transit-time blood flowmeters in five conscious dogs. Pancreatic and gastric secretion and blood pressure were also monitored. Synthetic CCK octapeptide (CCK-8) or gastrin heptadecapeptide (gastrin-17) was infused intravenously, and milk was infused into the duodenum with or without loxiglumide, a specific CCK-A receptor antagonist. CCK-8 induced dose-related increases of pancreatic, but not gastric or intestinal, blood flow and protein secretion without affecting systemic blood pressure. Gastrin-17 did not affect pancreatic blood flow. An intraduodenal infusion of milk increased pancreatic and intestinal blood flows and pancreatic protein secretion. Loxiglumide completely inhibited pancreatic blood flow and protein responses to CCK-8 and milk but not the intestinal blood flow response. CCK is a potent and specific pancreatic vasodilator, with its effect mediated by CCK-A receptors. CCK plays an important role in the regulation of the intestinal phase of the pancreatic circulation in dogs.

Catalytic effects of dioxygen on intramolecular electron transfer in radical ion pairs of zinc porphyrin-linked fullerenes

Dioxygen accelerates back electron transfer (BET) processes between a fullerene radical anion (C60) and a radical cation of zinc porphyrin (ZnP) in photolytically generated ZnP.+-C60.- and ZnP.+-H2P-C60.- radical ion pairs. The rate constant of BET increases linearly with increasing oxygen concentration without, however, forming reactive oxygen species, such as singlet oxygen or superoxide anion. When ferrocene (Fc) is used as a terminal electron donor moiety instead of ZnP (i.e., Fc-ZnP-C60), no catalytic effects of dioxygen were, however, observed for the BET in Fc+-ZnP-C60.-, that is, from C60.- to the ferricenium ion. In the case of ZnP-containing C60 systems, the partial coordination of O2 to ZnP.+ facilitates an intermolecular electron transfer (ET) from C60.- to O2. This rate-determining ET step is followed by a rapid intramolecular ET from O2.- to ZnP.+ in the corresponding O2.--ZnP.+ complex and hereby regenerating O2. In summary, O2 acts as a novel catalyst in accelerating the BET of the C60.--ZnP.+ radical ion pairs.

Modulating charge separation and charge recombination dynamics in porphyrin-fullerene linked dyads and triads: Marcus-normal versus inverted region

Photoinduced charge separation (CS) and charge recombination (CR) processes have been examined in various porphyrin-fullerene linked systems (i.e., dyads and triads) by means of time-resolved transient absorption spectroscopy and fluorescence lifetime measurements. The investigated compounds comprise a homologous series of rigidly linked, linear donor-acceptor arrays with different donor-acceptor separations and diversified donor strength: freebase porphyrin-C60 dyad (H2P-C60), zincporphyrin-C60 dyad (ZnP-C60), ferrocene-zincporphyrin-C60 triad (Fc-ZnP-C60), ferrocene-freebase porphyrin-C60 triad (Fc-H2P-C60), and zincporphyrin-freebase porphyrin-C60 triad (ZnP-H2P-C60). Most importantly, the lowest lying charge-separated state of all the investigated systems, namely, that of ferrocenium ion (Fc+) and the C60 radical anion (C60.-) pair in the Fc-ZnP-C60 triad, has been generated with the highest quantum yields (close to unity) and reveals a lifetime as long as 16 micros. Determination of CS and CR rate constants, together with the one-electron redox potentials of the donor and acceptor moieties in different solvents, has allowed us to examine the driving force dependence (-DeltaG0ET) of the electron-transfer rate constants (kET). Hereby, the semilogarithmic plots (i.e., log kET versus -DeltaG0ET) lead to the evaluation of the reorganization energy (lambda) and the electronic coupling matrix element (V) in light of the Marcus theory of electron-transfer reactions: lambda = 0.66 eV and V = 3.9 cm(-1) for ZnP-C60 dyad and lambda = 1.09 eV and V = 0.019 cm(-1) for Fc-ZnP-C60, Fc-H2P-C60, and ZnP-H2P-C60 triads. Interestingly, the Marcus plot in Fc-ZnP-C60, Fc-H2P-C60, and ZnP-H2P-C60 has provided clear evidence for intramolecular CR located in both the normal and inverted regions of the Marcus parabola. The coefficient for the distance dependence of V (damping factor: betaCR = 0.58 A(-1) is deduced which depends primarily on the nature of the bridging molecule.

Photochemical generation of cyclopentadienyliron dicarbonyl anion by a nicotinamide adenine dinucleotide dimer analogue

Irradiation of the absorption band of an NAD (nicotinamide adenine dinucleotide) dimer analogue, 1-benzyl-1,4-dihydronicotinamide dimer, (BNA)(2), in acetonitrile containing a cyclopentadienyliron dicarbonyl dimer, [CpFe(CO)(2)](2), results in generation of 2 equiv of the cyclopentadienyliron dicarbonyl anion, [CpFe(CO)(2)](-), accompanied by the oxidation of (BNA)(2) to yield 2 equiv of BNA(+). The studies on the quantum yields, the electrochemistry, and the transient absorption spectra have revealed that the photochemical generation of [CpFe(CO)(2)](-) by (BNA)(2) proceeds via photoinduced electron transfer from the triplet excited state of (BNA)(2) to [CpFe(CO)(2)](2).

Effect of copper sulfate addition on nitrous-oxide emission in high speed dentrification process using macro-porous cellulose carrier

Nitrous oxide emission from the immobilized denitrification process was investigated under copper-added and copper-free conditions to realize high-speed denitrification with minimum nitrous oxide emission. Nitrous oxide emission was found to be smaller in culture using immobilized cells acclimatized under copper-added condition. Transient phenomena of nitrous oxide emission, nitrate reduction and nitrite accumulation were then investigated in repeated batch experiments by transferring immobilized cells acclimatized in copper-free conditions into copper-added medium. Nitrous oxide emission obviously decreased, and maximum nitrous oxide concentration of seventh batch culture was about 1/40,000 of that of first batch culture. Nitrate reduction gradually decreased from second batch to fourth batch culture and it turned to increase from fifth batch culture to seventh batch culture. At seventh batch culture, nitrate reduction rate was restored up to 80% of the initial speed. This repeated batch experiment clarified that nitrous oxide emission was repressed by copper sulfate addition. The effect of pH and temperature on nitrous oxide emission were also investigated in a continuous denitrification experiment under copper added conditions. Nitrous oxide emission was increased by lowering pH and lowering temperature. At optimum operating condition (pH8.0, 30 degrees C), nitrogen removal efficiency of 99.9%, nitrous-oxide concentration in the emitted gas of 3.1ppm(v/v) and conversion ratio to nitrous oxide of 0.000316% were obtained when 280mg-Nl(-1) nitrate containing medium was treated at 6 hours of hydraulic retention time.

Eyelid reconstruction using a hard palate mucoperiosteal graft combined with a V-Y subcutaneously pedicled flap

Full-thickness eyelid defects after tumour ablation require the reconstruction of two layers, the anterior and posterior lamellae. Eyelids were successfully reconstructed after removal of malignant tumours in four patients using a hard palate mucoperiosteal graft combined with a curved V-Y subcutaneously pedicled flap. Although there have been some reports of hard palate mucosal grafts for reconstruction of the posterior lamella, the graft is not sufficiently rigid to support the reconstructed eyelid without the aid of supporting materials such as cartilage grafts. The hard palate mucoperiosteal graft seems to be rigid enough to support the reconstructed eyelid without the use of cartilage or other supporting materials. The subcutaneously pedicled V-Y advancement flap is useful for reconstruction of the anterior lamella in partial eyelid defects. We used it with a modified curved design to allow easy advancement and to make postoperative scars inconspicuous.

Effects of converting enzyme inhibitors on renal P-450 metabolism of arachidonic acid

The effects of blockade of the renin-angiotensin system on the renal metabolism of arachidonic acid (AA) were examined. Male Sprague-Dawley rats were treated with vehicle, captopril (25 mg x kg(-1) x day(-1)), enalapril (10 mg x kg(-1) x day(-1)), or candesartan (1 mg x kg(-1) x day(-1)) for 1 wk. The production of 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids (EETs) by renal cortical microsomes increased in rats treated with captopril by 59 and 24% and by 90 and 58% in rats treated with enalapril. Captopril and enalapril increased 20-HETE production in the outer medulla by 100 and 143%, respectively. In contrast, blockade of ANG II type 1 receptors with candesartan had no effect on the renal metabolism of AA. Captopril and enalapril increased cytochrome P-450 (CYP450) reductase protein levels in the renal cortex and outer medulla and the expression of CYP450 4A protein in the outer medulla. The effects of captopril on the renal metabolism of AA were prevented by the bradykinin-receptor antagonist, HOE-140, or the nitric oxide (NO) synthase inhibitor, N(G)-nitro-L-arginine methyl ester. These results suggest that angiotensin-converting enzyme inhibitors may increase the formation of 20-HETE and EETs secondary to increases in the intrarenal levels of kinins and NO.

Time-resolved EPR, fluorescence, and transient absorption studies on phthalocyaninatosilicon covalently linked to one or two TEMPO radicals

The photophysical properties of tetra-tert-butylphthalocyaninatosilicon (SiPc) covalently linked to one or two 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) radicals (R1, R2) have been studied by fluorescence, transient absorption, and time-resolved electron paramagnetic resonance (TREPR) spectroscopies. It is found that the fluorescence quantum yields and lifetimes of R1 and R2 decrease compared with those of (dihydroxy)SiPc ((dihydroxy)SiPc = 6.8 ns, R1 = 4.7 ns and 42 ps, and R2 = 4.7 ns and <30 ps). Transient absorption measurements indicate that the lifetime of the excited triplet SiPc is markedly dependent on the number of linking TEMPO radicals ((dihydroxy)SiPc = 500 micros, R1 = 7.6 micros, and R2 = 3.7 micros). These short lifetimes of R1 and R2 in the excited states are explained as a result of the interaction with TEMPO changing the ISC between the singlet and triplet states to spin-allowed transitions. Quantitative TREPR investigations have been carried out for the radical-quartet pair mechanism of R1 and the photoinduced population transfer of R2. It is determined that the rise and decay times of these electron spin polarizations denote the spin-lattice relaxation time of the ground state and the lifetime of the excited multiplet state, respectively. This study contributes not only to an elucidation of radical-chromophore interactions but also to a novel approach for controlling magnetic properties by photoexcitation.

Beneficial application of quantitative coronary angiography (edge detection algorithm) in analysis of dissected coronary arteries to predict long-term patency

The present study evaluated the application of quantitative coronary angiography (edge detection algorithm) for the analysis of coronary dissection lesions after balloon angioplasty. Acute and late results were obtained by the edge detection algorithm in 60 patients with 66 dissected lesions (NHLBI types B-C). The edge detection algorithm delineated the border of the true lumen in 32 lesions (group with automated analysis alone, 48.5%) and included the dissection cap in the analysis in 34 lesions in which manual editing was adjuncted (group with manual editing, 51.5%). In both groups, the minimal lumen diameter after balloon angioplasty obtained by initial automated analysis was correlated to that obtained at the 5.3-month follow-up similarly (r=0.554, p=0.0010 for the group with automated analysis alone and r=0.613, p=0.0001 after automated analysis for the group with manual editing). However, additional manual editing reduced the correlation coefficient (r=0.240, p=0.1707) in the latter group. Thus, in terms of predicting long-term patency, it is reasonable to let the edge detection algorithm decide the measurements in types B and C dissected lesions.

A retrospective study of speech development in patients with submucous cleft palate treated by four operations

Fifty patients with submucous cleft palate (SMCP) who had had four different operations were reviewed. The operations were pushback palatoplasty (n = 18), pharyngeal flap (n = 21), pushback palatoplasty combined with a pharyngeal flap (n = 8), and Furlow palatoplasty (n = 3). Postoperatively the speech of 8, 19, 7, and 2 patients, respectively, improved so that it was within normal limits. A secondary pharyngeal flap was done for six patients, each of whom had previously had a pushback palatoplasty. They all improved, five achieving relatively normal speech, and one good speech. No patient developed hyponasality or airway compromise associated with the pharyngeal flap. The results show that pharyngeal flap and pushback palatoplasty combined with a pharyngeal flap seem to be more reliable procedures than pushback palatoplasty for patients with SMCP.

[Usefulness of ultrasonography in a case of spontaneous carotid-cavernous fistula: a case report]

Since spontaneous carotid-cavernous fistula (CCF) is a dural arterio-venous fistula at the cavernous sinus, which is different from traumatic CCF and CCF associated with a ruptured aneurysm at the cavernous internal carotid artery, cerebral angiography is required in order to differentiate these condition. We here report a case of spontaneous CCF, in which a result of ultrasonographic evaluation of cervical arteries well corresponded with that of cerebral angiography. Ultrasonography showed increased blood flow and decreased pulsatility index in the ipsilateral external carotid artery, contralateral internal and external arteries, and these values in all arteries resolved within normal range after the interventional embolization. Ultrasonography is less invasive examination and can be easily performed even in outpatients for observation of spontaneous CCF.

Endogenous nitric oxide and epoxyeicosatrienoic acids modulate angiotensin II-induced constriction in the rabbit afferent arteriole

Nitric oxide (NO) and epoxyeicosatrienoic acids (EETs), cytochrome P450 epoxygenase metabolites of arachidonic acid, are released by the vascular endothelium and play important roles in the control of glomerular haemodynamics. We examined whether endogenous NO or EETs modulate angiotensin II- (AngII) induced constriction in isolated microperfused afferent arteriole (Af-Art) of the rabbit kidney. When Af-Arts were treated with NG-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthese; 10-4 mol L-1) or miconazole (an inhibitor of P450 epoxygenase; 10-6 mol L-1), basal diameter was decreased by 34.5 +/- 2.2 and 13.9 +/- 3.2%, respectively. AngII added to both the bath and lumen decreased the diameter of Af-Arts in a dose-dependent manner. Pretreatment with either L-NAME or miconazole also augmented the constrictor response to AngII. AngII at 10-8 mol L-1 decreased the diameter to 39.2 +/- 1.4, 32.9 +/- 3.6, and 12.7 +/- 4.6%, in control, L-NAME-, and miconazole-treated group, respectively. In order to study whether the AngII type2 (AT2) receptor modulates AngII action via NO or EETs, we repeated the experiments in the presence of PD123319 (an AT2 receptor antagonist; 10-7 mol L-1). In the presence of PD123319, L-NAME still augmented the constrictor response to AngII, however, miconazole had no effect. In the presence of PD123319, AngII at 10-8 mol L-1 decreased the diameter to 25.0 +/- 4.6, 9.4 +/- 4.0, and 26.0 +/- 3.3%, in control, L-NAME-, and miconazole-treated group, respectively. These results suggest that (1) tonic release of NO and EETs attenuates the vasoconstrictor response to AngII in Af-Arts and (2) AT2 receptor seems to be coupled to EETs rather than the NO pathway.

The outcome of long-term follow-up after palatoplasty

The speech outcome was studied retrospectively in 140 cleft-palate patients who underwent push-back palatoplasty. Velopharyngeal function and articulation disorders were evaluated serially at 4, 7, 10, and more than 10 years of age. On comparison of velopharyngeal function between 4 years of age and the most recent review (>10 years), it was unchanged in 90 patients (64.3 percent), whereas it showed deterioration in 14 patients and showed improvement in 8 patients. The other 28 patients underwent pharyngeal flap surgery; this group also included patients with functional deterioration. Changes of velopharyngeal function often occurred between 4 and 7 years of age but sometimes occurred after 10 years of age. Articulation disorders were observed in 49 subjects (35.0 percent) at 4 years of age. Many of the patients with glottal stop showed improvement from 4 to 7 years of age. Palatalized articulation showed less improvement than glottal stop (p < 0.01). The number of patients with articulation disorders decreased significantly between 4 years of age and the most recent review (p < 0.001). These findings suggest that speech does not become stable before 10 years of age and that patients with cleft palate should be carefully followed until they are beyond this age.

[Assessing the physiologic significance of intermediate coronary lesions: comparison of coronary flow measurements with exercise electrocardiography]

Angiography may provide limited assessment of intermediate coronary stenoses. Doppler coronary flow reserve has been applied to determine the physiologic significance of such lesions. This study compared coronary flow reserve derived from intracoronary Doppler flow wire with the results of the exercise tolerance test to evaluate the validity of intracoronary flow measurements in the assessment of intermediate stenoses. Sixty eight patients with 91 vessels harboring angiographically mild-to-severe coronary stenoses in the left anterior descending or right coronary artery were studied. All patients had single-vessel disease, and angiography showed the target vessel. Distal coronary flow reserve was measured with the Doppler guide wire during cardiac catheterization. Exercise tolerance tests by bicycle ergometer were performed the day before catheterization. Quantitative coronary angiography showed a mean percentage diameter stenosis of 44 +/- 21%(range 0-90%). Forty seven of 91 vessels combined intermediate lesions(40% to 70%). Percentage diameter stenosis and coronary flow reserve were linearly correlated in both overall and intermediate lesions(r = -0.52 vs -0.42; both p < 0.0001). Percentage diameter stenosis of overall lesions was significantly higher in the positive exercise test group than the negative group(59.8 +/- 17.2% vs 37.7 +/- 18.1%, p < 0.0001), but not significantly different in intermediate lesions(49.1 +/- 7.8% vs 54.7 +/- 6.6%, p = 0.03). The positive exercise test group showed significantly lower coronary flow reserve compared to the negative group in both overall and intermediate lesions(overall: 1.6 +/- 0.5 vs 2.6 +/- 0.9, p < 0.0001; intermediate: 1.6 +/- 0.5 vs 2.5 +/- 0.7, p < 0.0001). Coronary flow reserve < 2.0 and positive exercise test agreed in 38 of 46 intermediate lesions(83%), and percentage diameter stenosis > or = 50% and positive exercise test agreed in 34 of these 46 lesions(74%). Coronary flow reserve, more than percentage diameter stenosis, correlated with the results of the exercise tolerance test, and is considered to be useful to evaluate the functional severity of intermediate stenosis.

[Effect of adenosine on isolated afferent arterioles]

We investigated the direct effect of adenosine on afferent arterioles (Af-Arts) and the receptor subtype that mediates the constrictor or dilator action of adenosine. Af-Arts were isolated from the superficial cortex of rabbit kidney and perfused in vitro. Adenosine added to either the lumen or bath constricted the Af-Arts in a dose-dependent manner. This constriction was blocked by the A1 receptor antagonist, 6-oxo-3-(2-phenylpyrazole(1,5-a)pyridin-3-yl)-1 (6H)-pyridazinebutyric acid (FK838) or 8-cyclopentyl-1, 3-dipropylxanthine(DPCPX). We also examined the effect of adenosine on preconstricted Af-Arts with norepinephrine. Adenosine added to either the lumen or bath further constricted the preconstricted Af-Arts. In the presence of FK838, adenosine added to either the lumen or bath dilated the preconstricted Af-Arts, but in a different dose-dependent manner. Adenosine-induced dilation was inhibited by the A2 receptor antagonist, 3, 7-dimetyl-1-propargylxanthine(DMPX). These data indicate that adenosine constricts Af-Arts via A1 receptors and that adenosine dilates preconstricted Af-Arts via A2 receptors when A1 receptors are blocked.

[Development of 18F-FDG ([F-18]-2-fluoro-2-deoxy-D-glucose) injection for imaging of tumor reflecting glucose metabolism--results of preclinical studies]

Fluorine-18-2-fluoro-2-deoxy-D-glucose (18F-FDG) injection was prepared by a modification of a method originally developed by Hamacher et al. The dosage form is the injectable solution (2 ml) containing 185 MBq of 18F-FDG at a calibration time. Preclinical studies of the agent were performed. Its radiochemical purity is more than 95% and expiration time is 4 hours after the calibration time at ambient temperature. No toxicity was observed with up to 200 mg/kg and 100 mg/kg of non-radioactive FDG intravenously injected to rats and dogs in single-dose toxicity tests, respectively. Biodistribution studies demonstrated that the radioactivity was mainly distributed into brain (3.0 to 3.3% I.D./Organ at 30 minutes) and heart (4.2 to 5.8% I.D./Organ at 1 to 3 hours) after intravenous injection of the agent to normal rats. In a tumor transplanted mouse model (colon 26), tumor uptake was 10.9 +/- 3.5% I.D./g at 1 hr after intravenous injection of the agent, the radioactivity was retained until 3 hours. The radiation absorbed dose was estimated according to the MIRD Pamphlet based on the biodistribution data both in humans reported by Mejia et al. and rats described in this report. The radiation absorbed dose was not higher than those of commercially available radiopharmaceuticals. In conclusion, the 18F-FDG injection is expected to be useful for further clinical application.

Umbilical reconstruction after repair of omphalocele and gastroschisis

This article presents our technique of umbilical reconstruction after the repair of omphalocele and gastroschisis. We have treated 8 patients with an average follow-up period of 13 months (range, 6 approximately 24 months). No major complications have occurred; minor complications have included delayed wound healing, decreased umbilical depth, and hematoma. Our procedure is especially useful for patients who have a midline abdominal scar and relatively intact bilateral rectus abdominis muscles. Most of the patients and their parents have been satisfied with the results of umbilical reconstruction.

Regulation of P-450 4A activity in the glomerulus of the rat

We recently reported that an enzyme of the cytochrome P-450 4A family is expressed in the glomerulus, but there is no evidence that 20-hydroxyeicosatetraenoic acid (20-HETE) can be produced by this tissue. The purpose of present study was to determine whether glomeruli isolated from the kidney of rats can produce 20-HETE and whether the production of this metabolite is regulated by nitric oxide (NO) and dietary salt intake. Isolated glomeruli produced 20-HETE, dihydroxyeicosatrienoic acids, and 12-hydroxyeicosatetraenoic acid (4.13 +/- 0.38, 4.20 +/- 0.38, and 2. 10 +/- 0.20 pmol. min-1. mg protein-1, respectively) when incubated with arachidonic acid (10 microM). The formation of 20-HETE was dependent on the availability of NADPH and the PO2 of the incubation medium. The formation of 20-HETE was inhibited by NO donors in a concentration-dependent manner. The production of 20-HETE was greater in glomeruli isolated from the kidneys of rats fed a low-salt diet than in kidneys of rats fed a high-salt diet (5.67 +/- 0.32 vs. 2.83 +/- 0.32 pmol. min-1. mg protein-1). Immunoblot experiments indicated that the expression of P-450 4A protein in glomeruli from the kidneys of rats fed a low-salt diet was sixfold higher than in kidneys of rats fed a high-salt diet. These results indicate that arachidonic acid is primarily metabolized to 20-HETE and dihydroxyeicosatrienoic acids in glomeruli and that glomerular P-450 activity is modulated by NO and dietary salt intake.

Repair of mild umbilical hernia

A mild, persistent umbilical hernia that does not cause any functional problem is often ignored. The authors have devised a new technique to treat the mild, protrusive deformity of the umbilicus without associated complications. In this report, the new operative procedure is introduced. The authors have treated 72 patients with this method and have obtained good results.

Full-thickness skin graft from the ulnar aspect of the wrist to cover defects on the hand and digits

Skin defects on the volar surface of the hand and digits are commonly treated with skin grafts. Many donor sites capable of providing adequate skin have already been reported. Ideal conditions for the donor site depend on skin color, texture, durability, and size. The authors describe the use of a new donor site for harvesting skin grafts to repair relatively small skin defects on the hand and digits. They used full-thickness skin grafts from the ulnar aspect of the wrist to reconstruct burn contractures and syndactyly in 20 patients. Their grafts provided an ideal color and texture match, and normal function of the hand and digits was restored. The donor site was closed directly, and the resulting scar was inconspicuous.

Role of 20-HETE in elevating chloride transport in the thick ascending limb of Dahl SS/Jr rats

This study examined the role of endogenous 20 hydroxyeicosatetraenoic acid (20-HETE) in elevating Cl- transport in the medullary thick ascending loop of Henle (MTAL) of 9-week-old male Dahl salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats perfused in vitro. Basal transepithelial voltage (Vte; 14.9+/-0.9 versus 10.1+/-0.5 mV) and net lumen-to-bath Cl- flux (JCl) (155+/-6 versus 127+/-5 pEq. min-1. mm-1) were significantly greater in MTAL isolated from SS/Jr rats (n=16) than in those obtained from SR/Jr rats (n=16). Blockade of the synthesis of 20-HETE with 17-octadecynoic acid (17-ODYA; 10 micromol/L) increased Vte from 9. 9+/-0.8 to 13.1+/-1.0 mV and JCl from 127+/-7 to 152+/-8 pEq. min-1. mm-1 in the MTAL of SR/Jr rats (n=8), but it had no significant effect on Vte or JCl in the MTAL of SS/Jr rats (n=8). Exogenous 20-HETE (1 micromol/L) decreased Vte from 14.8+/-0.6 to 10.5+/-0.6 mV and JCl from 155+/-10 to 116+/-6 pEq. min-1. mm-1 in MTAL of SS/Jr rats (n=8), but it had no effect on Vte or JCl in the MTAL of SR/Jr rats (n=8). The expression of P4504A2 protein in the MTAL of SS/Jr rats was approximately half of that seen in the MTAL of SR/Jr rats. These results indicate that endogenously formed 20-HETE regulates transepithelial voltage and Cl- transport in the MTAL and that a diminished production of 20-HETE contributes to an elevation in Cl- transport in the MTAL of SS/Jr rats.

The effect of VIP/PACAP family of peptides on pancreatic blood flow and secretion in conscious dogs

The effects of PACAP-38, PACAP-27, VIP and secretin on pancreatic blood flow were compared with those of meals in five conscious dogs using an ultrasound transit-time blood flow meter. All peptides (1-100 pmol/kg) induced dose-related increases of pancreatic blood flow, and fluid and bicarbonate secretion. Only PACAPs stimulated protein secretion. Both PACAPs at doses which did not stimulate pancreatic secretion, induced significant pancreatic vasodilatation. VIP was less potent than PACAP-38 and PACAP-27 at lower doses (1-25 pmol/kg), but was similar to PACAPs at higher doses. The maximal effects of PACAPs and VIP were comparable to those observed after meals. Secretin was a significant but weak vasodilator. When pancreatic secretion was maximally stimulated by secretin, a reduction of vascular resistance was 75% of postprandial peak levels. PACAP(6-38), a competitive antagonist of PACAP, inhibited pancreatic vascular responses to PACAPs, but not those to VIP and secretin. Its inhibitory effects on protein response to PACAPs were not significant. Atropine inhibited pancreatic protein but not the vascular effect of PACAP-27. Pancreatic vasodilatation by PACAPs appears to be mediated by both PACAP-specific and VIP/PACAP common receptors in dogs. PACAP, like VIP, is a good candidate for a mediator of atropine-resistant vasodilatation of the pancreas.

CO binding studies of nitric oxide synthase: effects of the substrate, inhibitors and tetrahydrobiopterin

The dissociation constant (Kd) for CO from neuronal nitric oxide synthase heme in the absence of the substrate and cofactor was less than 10(-3) microM. In the presence of L-Arg, it dramatically increased up to 1 microM. In the presence of inhibitors such as N(G)-nitro-L-arginine methyl ester and 7-nitroindazole (NI), the Kd value further increased up to more than 100 microM. Addition of the cofactor, 5,6,7,8-tetrahydrobiopterin (H4B), increased the Kd value by 10-fold in the presence of L-Arg, whereas it decreased the value to less than one 250th in the presence of NI. Addition of H4B increased the recombination rate constant (k(on)) for CO by more than two-fold in the presence of L-Arg or N6-(1-iminoethyl)-L-lysine, whereas it decreased the k(on) value by three-fold in the presence of L-thiocitrulline. Thus, the binding fashion of some of inhibitors, such as NI, may be different from that of L-Arg with respect to the H4B effect.