Novel marine-derived halogen-containing gramine analogues induce vasorelaxation in isolated rat aorta.

We examined the effects of 2,5,6-tribromo-1-methylgramine (TBG), isolated from bryozoan, and its derivative, 5,6-dibromo-1,2-dimethylgramine (DBG), on the contraction of rat aorta. TBG and DBG decreased the high-K(+)-induced increase in muscle contraction and cytosolic Ca(2+) level ([Ca(2+)](i)), respectively. The inhibitory effects of TBG and DBG on high-K(+)-induced contraction were antagonized by increasing the external Ca(2+) concentration or by 1,4-dihydro2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)phenyl]pyridine-3-carboxylic acid (Bay k8644). The high-K(+)-induced increase of Mn(2+) influx was completely blocked by 10 microM TBG or 10 microM DBG. In the Ca(2+)-free solution, 30 microM TBG or 30 microM DBG inhibited the phenylephrine-induced transient increase in [Ca(2+)](i) and muscle tension, while scarcely affecting caffeine-induced transient changes. TBG and DBG significantly increased the cyclic AMP content at 30 microM, but not at 10 microM. These results suggest that TBG and DBG inhibit the smooth muscle contraction by inhibiting Ca(2+) entry, and at higher concentrations, the increase in intracellular cyclic AMP content also contributes to their inhibitory effect.

Isolation and evaluation of nonsiderophore cyclic peptides from marine sponges.

The world's oceans are iron-deficient environments and there is little knowledge available regarding iron uptake by marine sponges. To understand iron-related biofunctions in marine organisms, iron-binding natural compounds from marine sponges were investigated. Here we reported a natural compound haliclonamide A and its analogue haliclonamide B were isolated from the marine sponge Haliclona sp. and their structures were investigated by spectroscopic analysis. The structure of haliclonamide A was determined to consist of novel cyclic peptides containing oxazole and methyloxazoline rings. Mass spectra revealed that these two compounds formed a 1:1 stable complex with trivalent iron but not with divalent iron. EPR analysis showed that these compounds will bind with Fe(III) and Cr(III) specifically, but will not bind to other cation ions such as Cu2+, Zn2+, Co2+, Ni2+, Al3+, and Ti3+. The binding constant of compound-iron complex was 10(19) which is lower than the binding constant of siderophores. The Fe(III) concentration in this sponge tissue was shown to be 10 and 100 times higher than the other sponge tissues and seawater. This indicated the sponge Haliclona sp. may possibly uptake iron through nonsiderophore metal-binding peptides haliclonamides A and B. It also suggests that iron uptake activity of marine organisms may occur through nonsiderophore metal-binding peptides in natural ocean.

Identification of the aromatic L-amino acid decarboxylase (AADC) gene and its expression in the attachment and metamorphosis of the barnacle, Balanus amphitrite.

Serotonin and dopamine are involved in the attachment and metamorphosis of cypris larvae of barnacles. Aromatic L-amino acid decarboxylase (AADC) gene, the product of which catalyzes the synthesis of serotonin and dopamine from L-5-hydroxytryptophan and L-3,4-dihydroxyphenylalanine, respectively, was characterized. A DNA clone containing part of an AADC sequence was obtained from the genomic DNA library of the barnacle, Balanus amphitrite. This clone had four putative exons consisting of 226 amino acids with an identity of 63.2% and a similarity of 92.1% with human AADC. Northern blot analysis showed that AADC mRNA was expressed at all stages of barnacles: naupliar larvae, cypris larvae and adult barnacles. Two inducers of larval attachment and metamorphosis; that is, serotonin and extract of adult barnacles, obviously increased the expression of AADC mRNA at an early cypris larval stage. These results suggest that intracellular biosynthesis of serotonin, or dopamine, or both is at least partly involved in the control of the attachment and metamorphosis of cypris larvae.

Effect of inducers and inhibitors on the expression of bcs genes involved in cypris larval attachment and metamorphosis of the barnacles Balanus amphitrite.

We examined the expression of six barnacle cypris larva-specific gene (bcs) cDNAs (bcs-1, -2, -3, -4,- 5, and -6), the bcs genes, by using Northern blot analysis under various conditions that induced or inhibited cypris larval attachment and metamorphosis. Inducers of larval attachment and metamorphosis, such as a neurotransmitter, tended to increase the expression of bcs mRNAs. All inhibitors of larval attachment and metamorphosis, such as G protein-coupled receptor agonists/antagonists, inhibitors of tyrosine kinase-linked receptors and inhibitors of their signal transduction, suppressed the expression of bcs-6 mRNA alone, but affected differentially other bcs genes. These results strongly suggest that the bcs-6 product plays a key role in triggering the attachment and metamorphosis of cypris larvae into juvenile barnacles. The roles of four late bcs genes (bcs-3,-4, -5 and -6) are discussed.

Improved Plate Assay for Antifouling Substances Using Blue Mussel Mytilus edulis galloprovincialis.

An improved plate assay for screening antifoulants against blue mussels, Mytilus edulis galloprovincialis, was designed based on an assay contrived by Ina and colleagues. To obtain more reliable results, the number of test mussels for one sample was increased from 4 to 10. Cardboard pieces used as test plates were cut into rectangular shapes to separate the test sample and the blank zone, which are of the same area. Activity was expressed numerically. In this improved method, several inhibitors of byssus thread formation were isolated by using a smaller amount of sample per area than in the original method. Previously our laboratory developed a foot-stimulating bioassay for the same purpose. This method requires only a small amount of sample and is therefore useful for isolating antifouling substances from natural sources, including marine organisms. However, the inhibition of byssus thread formation cannot be directly evaluated in the foot-stimulating method. The improved plate assay and the foot-stimulating method were examined and compared using a secosterol from the sponge Dysidea granulosa and CuSO(4).

Barnacle cement proteins. Importance of disulfide bonds in their insolubility.

Barnacles produce a cement that is a proteinaceous underwater adhesive for their secure attachment to the substratum. The biochemical properties of the cement have not previously been elucidated, because the insolubility of the cement proteins hampers their purification and characterization. We developed a non-hydrolytic method to render soluble most of the cement components, thereby allowing the proteins to be analyzed. Megabalanus rosa cement could be almost completely rendered soluble by its reduction with 0.5 m dithiothreitol at 60 degrees C in a 7 m guanidine hydrochloride solution, the high concentration of dithiothreitol being indispensable to achieve this. The effectiveness of this reduction treatment was confirmed by the detachment of the barnacle from the substratum. Three proteins comprising up to 94% of the whole cement were identified as the major cement components. The cDNA clone of one of these major proteins was isolated, and the site-specific expression of the gene in the basal portion of the adult barnacle, where the cement glands are located, was demonstrated. A sequence analysis revealed this cement component to be a novel protein of 993 amino acid residues, including a signal peptide. This is the first report of the major component of the barnacle cement protein complex.

Structures of six cDNAs expressed specifically at cypris larvae of barnacles, Balanus amphitrite.

We cloned six cDNAs by screening cDNA libraries of cypris larvae from barnacles, Balanus amphitrite, and studied their expression by Northern blot analysis. All of them are expressed in the cypris larvae at the settlement stage, but not in the earlier nauplii larvae nor in later adult barnacles. Therefore, we designated them as barnacle cypris larva-specific genes (bcs); bcs-1, bcs-2, bcs-3, bcs-4, bcs-5 and bcs-6. During the process of larval attachment and metamorphosis, the amounts of bcs-1 and bcs-2 mRNAs decreased, whereas the bcs-3, bcs-4, bcs-5 and bcs-6 mRNAs increased. A homology search showed that all cDNAs encode novel peptides containing characteristic amino acid sequences. This study strongly suggests that these bcs gene products are involved in the cypris larval attachment and metamorphosis of barnacles.

Bisprasin, a novel Ca(2+) releaser with caffeine-like properties from a marine sponge, Dysidea spp., acts on Ca(2+)-induced Ca(2+) release channels of skeletal muscle sarcoplasmic reticulum.

Bisprasin, a unique bromotyrosine derivative containing a disulfide linkage, was isolated from a marine sponge of Dysidea spp. This compound caused a concentration-dependent (from 10 to 30 microM) increase in the (45)Ca(2+) release from the heavy fraction of skeletal muscle sarcoplasmic reticulum (HSR) of rabbit skeletal muscle in the same way as does caffeine. The 50% effective concentrations of bisprasin and caffeine were approximately 18 microM and 1.2 mM, respectively, indicating that the (45)Ca(2+)-releasing activity of bisprasin was approximately 70 times more potent than that of caffeine in HSR. The bell-shaped profile of Ca(2+) dependence for bisprasin was almost the same as that for caffeine. Typical blockers of Ca(2+)-induced Ca(2+) release channels, such as Mg(2+), procaine, and ruthenium red, inhibited markedly bisprasin- and caffeine-induced (45)Ca(2+) release from HSR. This compound, like caffeine, significantly enhanced [(3)H]ryanodine binding to HSR. Scatchard analysis of [(3)H]ryanodine binding to HSR revealed that bisprasin and caffeine decreased the K(D) value without affecting the B(max) value, suggesting that both the drugs facilitate the opening of ryanodine receptor channels. The bisprasin- and caffeine-induced increases in [(3)H]ryanodine binding were further enhanced by adenosine-5'-(beta, gamma-methylene)triphosphate. These results suggest that the pharmacological properties of bisprasin are almost similar to those of caffeine, except for its 70-fold higher potency. Here, we present the first report on the pharmacological properties of bisprasin, which, like caffeine, induces Ca(2+) release from skeletal muscle SR mediated through the ryanodine receptor.

Structure-activity relationship of gramine derivatives in Ca(2+) release from sarcoplasmic reticulum.

5,6-Dibromo-1,2-dimethylgramine evoked Ca(2+) release from skeletal muscle sarcoplasmic reticulum through ryanodine receptors in a concentration-dependent manner with an EC(50) of 22.2 microM. Since the EC(50) of caffeine was 0.885 mM, 5,6-dibromo-1,2-dimethylgramine was 40 times more sensitive than caffeine. Among 14 gramine derivatives having different substituents at N-1, C-2, C-5 or C-6 of the indole skeleton, we found that five derivatives were effective. Study of the structure-activity relationship for Ca(2+) release indicated that 1-methylation and/or both 5- and 6-bromination are important for Ca(2+) release. Thus, gramine derivatives are useful tools for the investigation of Ca(2+) release from sarcoplasmic reticulum.

Convenient Assay for Settlement Inducing Substances of Barnacles.

A convenient assay method for estimation of barnacle, Balanus amphitrite, settlement inductive activity was developed. To avoid the inductive effect by comrades and laborious observation requirements, cyprid larvae were put individually into wells of a 96-well plate. The settlement ratio from the experiment without any inducers was quite low; therefore this assay allowed easy estimation of settlement inductive activities. Some known inductive agents, such as serotonin and barnacle extracts, clearly showed inductive activities. This assay method is proven to be suitable for estimation of barnacle settlement-inducing activities of both water-soluble and -insoluble compounds.

A new sesquiterpene as an antifouling substance from a palauan marine sponge, dysidea herbacea

Bioassay-guided fractionation of an extract from a marine sponge, Dysidea herbacea, led to the isolation and identification of the new sesquiterpene 1. This compound showed repellent activity against the blue mussel, Mytilus edulis galloprovincialis.

A new epidioxy sterol as an antifouling substance from a palauan marine sponge, lendenfeldia chondrodes

Bioassay-guided fractionation of an extract of a marine sponge, Lendenfeldia chondrodes, has led to the isolation and identification of new epidioxy sterols 1a and 1b as an inseparable mixture. Two known epidioxy sterols 2 and 3 and three known sesterterpenes 4-6 were also isolated from the same extract. These compounds showed repellent activity against the blue mussel Mytilus edulis galloprovincialis.

New ceramide from marine sponge Haliclona koremella and related compounds as antifouling substances against macroalgae.

A new ceramide N-docosanoyl-d-erythro-(2S, 3R)-16-methyl-heptadecasphing-4(E)-enine (C22 ceramide) was isolated from the marine sponge Haliclona koremella as an antifouling substance against macroalgae. The structure of this substance was elucidated by spectral means. Antifouling activity of several related compounds was also examined.

Molecular cloning of a putative serotonin receptor gene from barnacle, Balanus amphitrite.

We isolated a putative serotonin receptor gene from a genomic library of the barnacle, balanus amphitrite Darwin, using an Ncol fragment of the barnacle G protein-coupled receptor gene that is homologous to the alpha 2-adrenoceptor. The cloned genomic DNA had no intron and specified an open reading frame of 1137 base pairs encoding 379 amino acids (aa). The predicted aa sequence has a typical seven hydrophobic transmembrane spanning region and a consensus G protein-binding motif. This receptor was most homologous to the human 5HT1A receptor and closely related to other 5HT1 receptor subtypes.

Molecular cloning of a new member of the putative G protein-coupled receptor gene from barnacle Balanus amphitrite.

An intronless gene encoding a putative G protein-coupled receptor was isolated from the genomic library of barnacle Balanus amphitrite Darwin, with probes obtained from degenerate polymerase chain reaction (PCR) primers used to amplify putative transmembrane regions. The cloned genome DNA specifies an open reading frame of 1431 bp encoding 476 amino acids with seven hydrophobic transmembrane (TM)-spanning regions. The predicted protein contains potential asparagine-linked glycosylation and serine/threonine phosphorylation sites in the N-terminal and intracellular loops, respectively. Moreover, the protein has a consensus G protein-binding motif (Ala-Ile-Ser-Leu-Asp-Arg-Tyr-Leu-Ala) in TM domain III. This receptor is most closely related to human alpha 2-adrenergic receptor with 36.9% identity in 409 amino acids overlap. It is also homologous to human serotonin1A (5HT), snail pond 5HT and mouse D2-dopamine receptors with 33-36% identities. Within TM regions among these biogenic amine receptors, the cloned receptor shows considerable amino acid homology with more than 40% overall identities.

Thermocryptoxanthins: novel intermediates in the carotenoid biosynthetic pathway of Thermus thermophilus

Various thermozeaxanthins are the end products of the carotenoid biosynthetic pathway of the thermophilic eubacterium Thermus thermophilus. These compounds are zeaxanthin glucoside esters. Carotenoid analysis and inhibitory studies led to the identification of most of the intermediates of the pathway: beta-carotene, beta-cryptoxanthin, zeaxanthin, and several new carotenoids. The intermediates, identified by various spectroscopic methods as beta-cryptoxanthin glucoside esters carrying fatty acid moieties of different chain lengths, were designated as thermocryptoxanthins. The use of the inhibitors diphenylamine and 2-(4-chlorophenylthio)-triethylamine-HCl resulted in the accumulation of the intermediates phytoene, lycopene, and gamma-carotene derivatives, which normally are present in amounts below the detection limit. The levels of non-esterified glycosides were extremely low. The results presented were used to establish the complete carotenoid biosynthetic pathway of T. thermophilus.

New Trihydroxy-keto-carotenoids Isolated from an Astaxanthin-producing Marine Bacterium.

Polar orange pigments were extracted from the cultured cells of marine bacterium strain SD-212 and purified by chromatographic methods. The structures of two new trihydroxy-keto-carotenoids, (2R,3S,3'S)-2-hydroxyastaxanthin (1) and (2R,3S,3'R)-2-hydroxyadonixanthin (2) were determined by means of spectral methods. Known carotenoids (3S,2'R,3'R)-erythroxanthin (3), (2R,3S',2' R,3'S)-2,3,2',3'-tetrahydroxy-ß,ß-carotene-4,4'-dione (4), (2R,3S,2'R,3'R)-2,3,2',3'-tetrahydroxy-ß,ß-caroten-4-one (5), (3S,3'S)-astaxanthin (6), and (3S,3'R)-adonixanthin (7) were also isolated.

[Preparation and structural elucidation of insularine-N-oxides].

Oxidation of insularine (I) with m-chloroperbenzoic acid yielded four insularine-N-oxides. Two of them are identical in every respect with our insularine-2 beta-N-oxide (II) and insularine-2' beta-N-oxide (III), two rare examples of naturally occurring head-to-tail bisbenzylisoquinoline N-oxides newly isolated from Cyclea sutchuenensis, which confirmed the structures of the two novel natural N-oxides. The other two are new compounds and their structures have been established as insularine-2' alpha-N-oxide (IV) and insularine-2 beta,2' beta-N, N-dioxide (V), on the basis of spectral data (UV, IR, 1HNMR, NOEDS AND MS) analysis.

[Two novel bisbenzylisoquinoline alkaloids from Cyclea sutchuenensis Gagnep].

In addition to the known cycleanine (I) and d-isochondodendrine (II), two novel bisbenzylisoquinoline alkaloids named isocycleanine (III) and sutchuenensine (IV) have been isolated from the roots of Cyclea sutchuenensis Gagnep grown wild in Sichuan province, China. III was established as the epimer of I and IV, as a new type of head-to-tail bisbenzylisoquinoline alkaloid with two diarylether bridges in between C-8 to C-12' and C-12 to C-7' on the basis of physical constants and spectral data (UV, IR, EIMS, 1HNMR and NOEDS).

A new topoisomerase-II inhibitor, BE-10988, produced by a streptomycete. I. Taxonomy, fermentation, isolation and characterization.

A new topoisomerase inhibitor, BE-10988, was isolated from the culture broth of a strain of actinomycetes. The producing strain had a close resemblance to Streptomyces fimicarius and Streptomyces xanthocidicus. The active principle was extracted from the whole broth of strain BA10988 with ethyl acetate and purified by silica gel chromatography and by HPLC. BE-10988 increased DNA-topoisomerase complex formation and inhibited the growth of both doxorubicin-resistant and vincristine-resistant P388 murine leukemia cell lines, as well as sensitive P388 cell lines.