Biomedical subjects

H Hama

Publications and source records attributed to H Hama.

At least 19 recordsLinked to original sources

PubMed2007

Milk basic protein increases alveolar bone formation in rat experimental periodontitis.

BACKGROUND AND OBJECTIVE: It is conceivable that the active components extracted from milk whey protein (i.e. milk basic protein, MBP) stimulate bone formation and suppress bone resorption. Periodontitis is characterized by excessive alveolar bone resorption. We examined whether milk basic protein could recover alveolar bone loss in rat experimental periodontitis. MATERIAL AND METHODS: A nylon ligature was placed around the cervix of molars in 8-wk-old male Fischer rats for 20 d. Then, the ligature was removed and a powder diet containing 0.2 or 1.0% milk basic protein was provided daily for another 45-90 d. On days 45 and 90, the maxillae were extracted and analyzed using microcomputerized tomography (micro-CT), followed by histological analysis. RESULTS: Micro-CT images showed that alveolar bone resorption was severely induced around the molar by the 20-d ligature procedure. Treatment with high-dose milk basic protein (1.0%) clearly recovered ligature-induced alveolar bone resorption on days 45 and 90, whereas low-dose milk basic protein (0.2%) did not show such a clear effect. Histological examination clarified that the osteoid thickness of alveolar bone was dose dependently increased by milk basic protein treatment for 90 d. CONCLUSION: These findings suggest that a systemic administration of milk basic protein may be effective for the recovery of alveolar bone loss in periodontitis.

Alveolar Bone Loss↗

PubMed2001

Red fluorescent protein from Discosoma as a fusion tag and a partner for fluorescence resonance energy transfer.

The biochemical and biophysical properties of a red fluorescent protein from a Discosoma species (DsRed) were investigated. The recombinant DsRed expressed in E. coli showed a complex absorption spectrum that peaked at 277, 335, 487, 530, and 558 nm. Excitation at each of the absorption peaks produced a main emission peak at 583 nm, whereas a subsidiary emission peak at 500 nm appeared with excitation only at 277 or 487 nm. Incubation of E. coli or the protein at 37 degrees C facilitated the maturation of DsRed, resulting in the loss of the 500-nm peak and the enhancement of the 583-nm peak. In contrast, the 500-nm peak predominated in a mutant DsRed containing two amino acid substitutions (Y120H/K168R). Light-scattering analysis revealed that DsRed proteins expressed in E. coli and HeLa cells form a stable tetramer complex. DsRed in HeLa cells grown at 37 degrees C emitted predominantly at 583 nm. The red fluorescence was imaged using a two-photon laser (Nd:YLF, 1047 nm) as well as a one-photon laser (He:Ne, 543.5 nm). When fused to calmodulin, the red fluorescence produced an aggregation pattern only in the cytosol, which does not reflect the distribution of calmodulin. Despite the above spectral and structural complexity, fluorescence resonance energy transfer (FRET) between Aequorea green fluorescent protein (GFP) variants and DsRed was achieved. Dynamic changes in cytosolic free Ca2+ concentrations were observed with red cameleons containing yellow fluorescent protein (YFP), cyan fluorescent protein (CFP), or Sapphire as the donor and RFP as the acceptor, using conventional microscopy and one- or two-photon excitation laser scanning microscopy. Particularly, the use of the Sapphire-DsRed pair rendered the red cameleon tolerant of acidosis occurring in hippocampal neurons, because both Sapphire and DsRed are extremely pH-resistant.

Animals↗

PubMed2001

Spontaneous progression of vertebral intraosseous pneumatocysts to fluid-filled cysts.

Intraosseous pneumatocyst is a relatively rare condition, and its natural course is not known. We report two cases of intraosseous pneumatocyst of vertebra with resorption of gas and its replacement with fluid shown on follow-up cross-sectional imaging. The mechanism influencing the course of these appearances is unclear. However, the benign nature of intraosseous pneumatocyst needs to be recognized and biopsy avoided.

Bone Cysts↗

PubMed2001

FRET-based in vivo Ca2+ imaging by a new calmodulin-GFP fusion molecule.

Intracellular Ca2+ acts as a second messenger that regulates numerous physiological cellular phenomena including development, differentiation and apoptosis. Cameleons, a class of fluorescent indicators for Ca2+ based on green fluorescent proteins (GFPs) and calmodulin (CaM), have proven to be a useful tool in measuring free Ca2+ concentrations in living cells. Traditional cameleons, however, have a small dynamic range of fluorescence resonance energy transfer (FRET), making subtle changes in Ca2+ concentrations difficult to detect and study in some cells and organelles. Using the NMR structure of CaM bound to the CaM binding peptide derived from CaM-dependent kinase kinase (CKKp), we have rationally designed a new cameleon that displays a two-fold increase in the FRET dynamic range within the physiologically significant range of cytoplasmic Ca2+ concentration of 0.05-1 microM.

Animals↗

PubMed2001

A novel mechanism for localizing membrane proteins to yeast trans-Golgi network requires function of synaptojanin-like protein.

Localization of resident membrane proteins to the yeast trans-Golgi network (TGN) involves both their retrieval from a prevacuolar/endosomal compartment (PVC) and a "slow delivery" mechanism that inhibits their TGN-to-PVC transport. A screen for genes required for the slow delivery mechanism uncovered INP53, a gene encoding a phosphoinositide phosphatase. A retrieval-defective model TGN protein, A(F-->A)-ALP, was transported to the vacuole in inp53 mutants approximately threefold faster than in wild type. Inp53p appears to function in a process distinct from PVC retrieval because combining inp53 with mutations that block retrieval resulted in a much stronger phenotype than either mutation alone. In vps27 strains defective for both anterograde and retrograde transport out of the PVC, a loss of Inp53p function markedly accelerated the rate of transport of TGN residents A-ALP and Kex2p into the PVC. Inp53p function is cargo specific because a loss of Inp53p function had no effect on the rate of Vps10p transport to the PVC in vps27 cells. The rate of early secretory pathway transport appeared to be unaffected in inp53 mutants. Cell fractionation experiments suggested that Inp53p associates with Golgi or endosomal membranes. Taken together, these results suggest that a phosphoinositide signaling event regulates TGN-to-PVC transport of select cargo proteins.

Alkaline Phosphatase↗

PubMed2001

Rapid accumulation of phosphatidylinositol 4,5-bisphosphate and inositol 1,4,5-trisphosphate correlates with calcium mobilization in salt-stressed arabidopsis.

The phosphoinositide phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] is a key signaling molecule in animal cells. It can be hydrolyzed to release 1,2-diacyglycerol and inositol 1,4,5-trisphosphate (IP(3)), which in animal cells lead to protein kinase C activation and cellular calcium mobilization, respectively. In addition to its critical roles in constitutive and regulated secretion of proteins, PtdIns(4,5)P(2) binds to proteins that modify cytoskeletal architecture and phospholipid constituents. Herein, we report that Arabidopsis plants grown in liquid media rapidly increase PtdIns(4,5)P(2) synthesis in response to treatment with sodium chloride, potassium chloride, and sorbitol. These results demonstrate that when challenged with salinity and osmotic stress, terrestrial plants respond differently than algae, yeasts, and animal cells that accumulate different species of phosphoinositides. We also show data demonstrating that whole-plant IP(3) levels increase significantly within 1 min of stress initiation, and that IP(3) levels continue to increase for more than 30 min during stress application. Furthermore, using the calcium indicators Fura-2 and Fluo-3 we show that root intracellular calcium concentrations increase in response to stress treatments. Taken together, these results suggest that in response to salt and osmotic stress, Arabidopsis uses a signaling pathway in which a small but significant portion of PtdIns(4,5)P(2) is hydrolyzed to IP(3). The accumulation of IP(3) occurs during a time frame similar to that observed for stress-induced calcium mobilization. These data also suggest that the majority of the PtdIns(4,5)P(2) synthesized in response to salt and osmotic stress may be utilized for cellular signaling events distinct from the canonical IP(3) signaling pathway.

Arabidopsis↗

PubMed2000

Requirement of sphingolipid alpha-hydroxylation for fungicidal action of syringomycin E.

Syringomycin E is an antifungal cyclic lipodepsinonapeptide produced by Pseudomonas syringae pv. syringae. To understand the mechanism of action of syringomycin E, a novel resistant Saccharomyces cerevisiae strain, BW7, was isolated and characterized. Lipid analyses revealed that BW7 contained only the hydrophobic subspecies of sphingolipids that are normally minor components in wild type strains. This aberrant sphingolipid composition was the result of lack of alpha-hydroxylation of the amide-linked very long chain fatty acids, suggesting a defective sphingolipid alpha-hydroxylase encoded by the FAH1 gene. A yeast strain that lacks the FAH1 gene was resistant to syringomycin E, and failed to complement BW7. These results demonstrate that BW7 carries a mutation in the FAH1 gene, and that the lack of alpha-hydroxylated very long chain fatty acids in yeast sphingolipids confers resistance to syringomycin E.

Antifungal Agents↗

PubMed2000

Biochemical evidence for association of dystrobrevin with the sarcoglycan-sarcospan complex as a basis for understanding sarcoglycanopathy.

The sarcoglycan complex is composed of four membrane-spanning dystrophin-associated proteins (DAPs) and is essential for skeletal muscle survival, since the absence or markedly reduced expression of this complex due to mutation of any one of the sarcoglycan genes causes a group of muscular dystrophies, collectively termed sarcoglycanopathy. Although one of the putative functions of the sarcoglycan complex is its participation in signaling processes, detailed studies have been scarce. Very recently, it was shown that gene knockout mice for a DAP, alpha-dystrobrevin, exhibit a dystrophic phenotype, possibly due to defects in muscle cell signaling. To clarify the putative function of the sarcoglycan complex, it is essential to determine whether or not there is a link between it and the intracellular signaling molecules. To elucidate this, we developed new methods for preparing various DAP complexes containing the sarcoglycan complex from the purified dystrophin-DAP complex. It was suggested from one of the complexes prepared that the sarco-glycan-sarcospan complex (the sarcoglycan complex associated with sarcospan) is associated with syntrophin and/or dystrobrevin. Further analysis of this complex revealed that the N-terminal half of dystrobrevin participates in this association. It is thus considered that the sarcoglycan-sarcospan complex is linked to the signaling protein neuronal nitric oxide synthase via alpha-syntrophin associated with dystrobrevin.

Animals↗

PubMed2000

Analysis of phosphoinositides in protein trafficking.

Phosphoinositides are key regulators of vesicle-mediated protein trafficking. Their roles include recruiting vesicle coat and effector proteins to the site of budding and promoting vesicle fusion. The intracellular levels of phosphoinositides and their localization to intracellular membranes are critical to their functions. An analytical procedure was developed that optimizes the recovery of radiolabeled cellular phosphoinositides. Quantitative analyses of yeast cellular phosphoinositides indicated that this approach is useful for examining the intracellular membrane phosphoinositide compositions related to trafficking phenomena. The approach will also enable investigators to determine whole-plant phosphoinositide compositions that have been difficult to achieve in the past. These analytical advances should be generally applicable to studies of phosphoinositide dynamics related to membrane trafficking in yeast, plant, and animal cells.

Arabidopsis↗

PubMed2000

Syringomycin E inhibition of Saccharomyces cerevisiae: requirement for biosynthesis of sphingolipids with very-long-chain fatty acids and mannose- and phosphoinositol-containing head groups.

Syringomycin E is an antifungal cyclic lipodepsinonapeptide that inhibits the growth of Saccharomyces cerevisiae by interaction with the plasma membrane. A screen conducted to find the yeast genes necessary for its fungicidal action identified two novel syringomycin E response genes, SYR3 and SYR4. A syr3 mutant allele was complemented by ELO2 and ELO3. These genes encode enzymes that catalyze the elongation of sphingolipid very long chain fatty acids. Tetrad analysis showed that SYR3 was ELO2. Strains with deletions of SYR3/ELO2 and ELO3 were resistant to syringomycin E, and lipid analyses of both mutants revealed shortened fatty acid chains and lower levels of sphingolipids. SYR4 was identified by Tn5 inactivation of genomic library plasmids that complemented a syr4 mutant allele. SYR4 was found to be identical to IPT1, which encodes the terminal sphingolipid biosynthetic enzyme, mannosyl-diinositolphosphoryl-ceramide synthase. Deletion Deltasyr4/ipt1 strains were viable, were resistant to syringomycin E, did not produce mannosyl-diinositolphosphoryl-ceramide, and accumulated mannosyl-inositolphosphoryl-ceramide. Accumulation of mannosyl-inositolphosphoryl-ceramide was not responsible for resistance since a temperature-sensitive secretory pathway mutant (sec14-3(ts)) accumulated this sphingolipid and was sensitive to syringomycin E. Finally, Deltacsg1/sur1 and Deltacsg2 strains defective in the transfer of mannose to inositolphosphoryl-ceramide were resistant to syringomycin E. These findings show that syringomycin E growth inhibition of yeast is promoted by the production of sphingolipids with fully elongated fatty acid chains and the mannosyl and terminal phosphorylinositol moieties of the polar head group.

Acetyltransferases↗

PubMed2000

Possible risk factors of carotid artery atherosclerosis in the Japanese population: a primary prevention study in non-diabetic subjects.

OBJECTIVE: Hyperinsulinemia has been associated with the risk of coronary heart disease, stroke, and renal disease in nondiabetic subjects. However, direct evidence that hyperinsulinemia per se is directly associated with atherosclerosis has been conflicting. The present study was designed to investigate the cross-sectional association of carotid artery atherosclerosis with insulin, independent of well-known cardiovascular risk factors, in nondiabetic subjects. METHODS AND SUBJECTS: Between 1996 and 1997, 1,335 subjects (620 men and 715 women) were recruited from one Japanese community, interviewed, and examined. Clinical measurements in the study included intimal-medial thickness (IMT) of the carotid artery, fasting plasma insulin, serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), fasting plasma glucose (FPG), hemoglobin type HbA1c, systolic blood pressure (SBP), diastolic blood pressure (DBP), and body mass index (BMI). We divided the subjects of both genders into three subgroups according to age (40-49 years of age; 50-59; and 60-69). RESULTS: Using simple regression analysis, we found that IMT was significantly correlated with at least one of TC, LDL-C, HbA1c, SBP, DBP, and BMI in each subgroup. The results of multivariate analysis showed that IMT was independently correlated with TC, HDL-C, LDL-C, SBP and BMI in males and with TC, TG, HDL-C, LDL-C, HbA1c, SBP, DBP, and BMI in females. Insulin levels showed no correlation with IMT in either males or females. CONCLUSION: Fasting hyperinsulinemia does not appear to be correlated with carotid artery atherosclerosis based on the present cross-sectional results.

Adult↗

PubMed1999

Direct involvement of phosphatidylinositol 4-phosphate in secretion in the yeast Saccharomyces cerevisiae.

The SEC14 gene encodes an essential phosphatidylinositol (PtdIns) transfer protein required for formation of Golgi-derived secretory vesicles in yeast. Suppressor mutations that rescue temperature-sensitive sec14 mutants provide an approach for determining the role of Sec14p in secretion. One suppressor, sac1-22, causes accumulation of PtdIns(4)P. SAC1 encodes a phosphatase that can hydrolyze PtdIns(4)P and certain other phosphoinositides. These findings suggest that PtdIns(4)P is limiting in sec14 cells and that elevation of PtdIns(4)P production can suppress the secretory defect. Correspondingly, we found that PtdIns(4)P levels were decreased significantly in sec14-3 mutants shifted to 37 degrees C and that sec14-3 cells could grow at an otherwise nonpermissive temperature (34 degrees C) when carrying a plasmid overexpressing PIK1, encoding one of two essential PtdIns 4-kinases. This effect is specific because overexpression of the other PtdIns 4-kinase gene (STT4) or a PtdIns 3-kinase gene (VPS34) did not rescue sec14-3 cells. To further address Pik1p function in secretion, two different pik1(ts) mutants were examined. Upon shift to restrictive temperature (37 degrees C), the PtdIns(4)P levels dropped by about 60% in both pik1(ts) strains within 1 h. During the same period, cells displayed a reduction (40-50%) in release of a secreted enzyme (invertase). However, similar treatment did not effect maturation of a vacuolar enzyme (carboxypeptidase Y). These findings indicate that, first, PtdIns(4)P limitation is a major contributing factor to the secretory defect in sec14 cells; second, Sec14p function is coupled to the action of Pik1p, and; third, PtdIns(4)P has an important role in the Golgi-to-plasma membrane stage of secretion.

1-Phosphatidylinositol 4-Kinase↗

PubMed1999

Production of S-lactoylglutathione by high activity whole cell biocatalysts prepared by permeabilization of recombinant saccharomyces cerevisiae with alcohols

The permeabilization of yeast cells with methanol, ethanol, and isopropyl alcohol under various conditions was studied to develop the preparation method of high activity whole cell biocatalysts. Recombinant Saccharomyces cerevisiae, which intracellularly overexpresses glyoxalase I and catalyzes the conversion of methylglyoxal to S-lactoylglutathione in the presence of glutathione, was used as the model system. The permeabilization treatments with alcohols significantly enhanced the activities of yeast cells. Especially, the initial S-lactoylglutathione production rates of cells permeabilized with 40% ethanol and isopropyl alcohol solutions for 10 min at 4 degrees C were high and were 364 and 582 times larger than those of untreated cells, respectively. These permeabilized yeast cells retained high activities during repeated batch reactions. Even in third batch reaction, they showed approximately 70-80% of the activity in the first batch. The plasma membrane of S. cerevisiae cells was damaged by the treatment with alcohol solutions in such a way that leakage of glyoxalase I from the cells is rather small and that both substrate and product show very high permeability. The initial S-lactoylglutathione production rates of these permeabilized cells were 1.5-2.5 times larger than those of glyoxalase I in cell extracts prepared by ethyl acetate method from the same amount of cells. These results demonstrate that the recombinant S. cerevisiae cells permeabilized with alcohol solutions under the optimum condition are very effective whole cell biocatalysts. Copyright 1999 John Wiley & Sons, Inc.

Journal Article↗

PubMed1999

Cytodifferentiation potentiates aFGF-induced p21(ras)/Erk signaling pathway in rat cultured astrocytes.

MBP kinase detection assay revealed that acidic FGF (aFGF) augmented MBP kinase activity in a dose-dependent manner in astrocytes (AC). The molar potency of this action of aFGF in dibutyryl cyclic AMP (DBcAMP)-treated AC was significantly higher than that in quiescent AC. Consistently, the molar potency of accumulation of p21(ras)-GTP by aFGF was significantly higher in DBcAMP-treated AC than in quiescent AC. However, binding study showed that B(max) and K(D) for [(125)I]aFGF in DBcAMP-treated AC were quite similar to those in quiescent AC. Furthermore, the expression levels of Grb2, SOS, and p21(ras) were not changed by treatment of AC with DBcAMP. These results suggest that cytodifferentiation potentiates the p21(ras)/Erk signaling pathway in AC in response to aFGF without changing the expression levels of signaling molecules mediating from the FGF receptor to p21(ras).

Animals↗

PubMed1999

Vps9p is a guanine nucleotide exchange factor involved in vesicle-mediated vacuolar protein transport.

Vacuolar protein sorting (vps) mutants of Saccharomyces cerevisiae missort and secrete vacuolar hydrolases. The gene affected in one of these mutants, VPS21, encodes a member of the Sec4/Ypt/Rab family of small GTPases. Rab proteins play an essential role in vesicle-mediated protein transport. Using both yeast two-hybrid assays and chemical cross-linking, we have identified another VPS gene product, Vps9p, that preferentially interacts with a mutant form of Vps21p-S21N that binds GDP but not GTP. In vitro purified Vps9p was found to stimulate GDP release from Vps21p in a dose-dependent manner. Vps9p also stimulated GTP association as a result of facilitated GDP release. However, Vps9p did not stimulate guanine nucleotide exchange of GTP-bound Vps21p or GTP hydrolysis. We tested the ability of Vps9p to stimulate the intrinsic guanine nucleotide exchange activity of Rab5, which is a mammalian sequence homologue of Vps21p, and Ypt7p, which is another yeast Rab protein involved in vacuolar protein transport. Rab5, but not Ypt7p was responsive to Vps9p, which indicates that Vps9p recognizes sequence variation among Rab proteins. We conclude that Vps9p is a novel guanine nucleotide exchange factor that is specific for Vps21p/Rab5. Since there are no obvious Vps9p sequence homologues in yeast, Vps9p may also possess unique regulatory functions required for vacuolar protein transport.

Biological Transport↗

PubMed1999

SEC14-dependent secretion in Saccharomyces cerevisiae. Nondependence on sphingolipid synthesis-coupled diacylglycerol production.

The SEC14 gene in Saccharomyces cerevisiae encodes a phosphatidylinositol transfer protein required for secretory protein movement from the Golgi. Mutation of SAC1, a gene of unknown function, restores secretory flow in sec14-1(ts) strains. The existing model for the bypass of the sec14-1(ts) defect by sac1-22 involves stimulation of sphingolipid biosynthesis and, in particular, the synthesis of mannosyl-diinositolphosphoryl-ceramide with concomitant increases in Golgi diacylglycerol levels. To test this model, we disrupted IPT1, the mannosyl-diinositolphosphoryl-ceramide synthase of S. cerevisiae. Disruption of the IPT1 gene had no effect on the ability of sac1-22 to bypass sec14-1(ts). Furthermore, sphingolipid analysis of sec14-1(ts) and sec14-1(ts) sac1-22 strains showed that mannosyl-diinositolphosphoryl-ceramide synthesis was not stimulated in the bypass mutant. However, the sec14-1(ts) strain had elevated mannosyl-monoinositolphosphoryl-ceramide levels, and the sec14-1(ts) sac1-22 strain showed an 8-fold increase in phosphatidylinositol 4-phosphate along with a decrease in phosphatidylinositol 4,5-bisphosphate. Cellular diacylglycerol levels, measured by [14C]acetate incorporation, did not differ between the sec14-1(ts) and the sec14-1 sac1-22 bypass strains, although disruption of IPT1 in the bypass strain resulted in reduced levels. These data indicate that phosphatidylinositol 4-phosphate, rather than mannosyl-diinositolphosphoryl-ceramide, accumulates in the sec14-1(ts) sac1-22 bypass strain, and that Golgi diacylglycerol accumulation is not required for bypass of the sec14-1(ts) growth and secretory phenotypes.

Carrier Proteins↗

PubMed1999

Negligible role of catecholaminergic receptors in the anteroventral third ventricular region in mediating vasopressin-releasing and cardiovascular actions of prostaglandin E2.

The aim of this study was to pursue the roles of the catecholamine receptors in the anteroventral third ventricular region (AV3V), a cerebral site engaged in various stress responses, in prostaglandin (PG) E2-evoked vasopressin (AVP) release and cardiovascular action. Experiments were conducted in conscious rats in which cerebral and vascular cannulae had been implanted chronically. Local infusion (0.5 microliter, 1 min) of dopamine (150 nmol), a D1-dopaminergic agonist SKF 38393 (17 nmol) and an alpha-adrenergic agonist phenylephrine (150 nmol), as well as PGE2 (7 nmol), into the AV3V enhanced plasma AVP 5 min later, without affecting plasma osmolality and electrolytes. In contrast to the increases in both arterial pressure and heart rate observed when PGE2 was applied, dopamine and SKF 38393 did not affect these variables, and phenylephrine elevated only arterial pressure. The AV3V infusion of a beta-agonist isoproterenol (100 nmol) did not change plasma AVP, although it decreased arterial pressure and increased heart rate. The increase in plasma AVP by dopamine was not blocked by the preinfusion of the D2-antagonist sulpiride (13 nmol) into the AV3V 10 min before, but was abolished by that of the D1-antagonist SCH-23390 (8 nmol). The effects of phenylephrine on both plasma AVP and the blood pressure were prevented by the preadministration of the alpha-antagonist phenoxybenzamine (13 nmol). However, the pretreatments with phenoxybenzamine, sulpiride or SCH 23390 did not inhibit the responses of AVP, arterial pressure and heart rate caused by PGE2. These antagonists were without significant effect on AVP and other variables when given alone. The infusion sites of PGE2 and the other drugs identified histologically included the AV3V structures such as the organum vasculosum laminae terminalis or its vicinity, median preoptic nucleus, medial preoptic nucleus and periventricular hypothalamic nucleus. Dopamine or phenylephrine administered into the cerebral ventricle at the same dose as used in the AV3V application did not exert a significant effect on plasma AVP, arterial pressure and heart rate. These results suggest that catecholamine receptors in the AV3V may not be involved in the AVP-secreting, tachycardiac and pressor responses evoked by topical action of PGE2 on this area, despite their ability to influence hormone release and cardiovascular function.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1999

Bis-N-nitroso-caged nitric oxides: photochemistry and biological performance test by rat aorta vasorelaxation.

Three new caged nitric oxides (NOs)-BNN3, BNN5Na, and BNN5M were tested for biological use. BNNs have a strong ultraviolet (UV) absorption band (lambda(max): 300 nm, epsilon: 13.5 mM(-1) cm (-1)) extended to 420 nm and produce NO upon irradiation with 300-360 nm light in quantum yields about 2. A photoexcited BNN molecule yields two NOs with time constants of less than 10 ns for phase 1 and less than 20 micros for phase 2 at 37 degrees C, suggesting usefulness of BNNs for measuring in vivo and in vitro fast NO reactions. Upon irradiating with UV light, caged nitric oxides-loaded rat aortic strips maintained in a state of active tonic contraction effectively relaxed ( < 3 microM BNN5M loading solution concentration). BNN3 is incorporated in the lipid membrane. BNN5Na, insoluble in organic solvents but water soluble, localizes in the water phase. BNN5M, is muscle-cell-permeable and hydrolysed to BNN5Na to remain in cytosol. BNNs were thermally stable and demonstrated no observable toxicity.

Animals↗