Synthesis and an evaluation of the bioactivity of the C-glycoside of pseudopterosin A methyl ether

The Suzuki-Miyaura cross-coupling protocol was applied to the synthesis of 1a, the C-glycoside analogue of PsA methyl ether. This marks the first construction of a C-glycoside for this class of marine natural products, thereby offering an opportunity to compare its bioactivity to the natural substances. Its activity profile resembled that of PsA (1) and PsA O-methyl ether (1b) when assayed for its anti-inflammatory activity and its ability to inhibit phagocytosis. We conclude that the intact structure is present when a pseudopterosin expresses its anti-inflammatory and phagocytosis inhibitory properties and that they are, therefore, not likely to be prodrugs. Results show that 1a is an effective binding agent toward the A2A and A3 adenosine receptors, displaying IC50 values of 20 and 10 microM, respectively.

7,11-epi-thyrsiferol: completion of its synthesis, evaluation of its antimitotic properties, and the further development of an SAR model

We (a) describe the completion of a total synthesis of 7,11-epi-thyrsiferol (4), (b) compare the antimitotic activities of thyrsiferol (2), Delta15,28-dehydrothyrsiferol (3), and 7,11-epi-thyrsiferol (4), (c) evaluate the synergistic behavior of the title compound and colchicine to inhibit cell proliferation, and (d) describe the results of conformational searches that provide additional insight concerning the SAR profile of the thyrsiferol family of natural products.

An 18.5 kDa protein from the amebocyte of Limulus polyphemus, homologous to the previously described amebocyte aggregation factor, expresses alternative phospholipase A2 activity

A protein expressing phospholipase A2 activity was purified from the granular amebocyte of the horseshoe crab, Limulus polyphemus by cation-exchange, size-exclusion chromatography and semi-preparative reverse-phase-high pressure liquid chromatography (RP-HPLC). The protein had an apparent mass of 17.7 kDa by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), but a more accurate estimate of 18.5 kDa was assigned by electrospray ionization-mass spectrometry (ESI-MS). A partial sequence of this protein demonstrated total sequence homology with an 18.5 kDa protein with cell aggregating properties from Limulus reported by Fujii et al. [J. Biol. Chem. 267:22452.]. In these studies, the Limulus protein demonstrated a positive cross-reaction to polyclonal anti-human recombinant phospholipase A2 (group II, 14 kDa). The protein did not display a significant loss of biological activity after boiling, but all enzymatic activity was lost after boiling in the presence of the reducing agent betamercaptoethanol (beta-mercaptoethanol). The Limulus protein was inhibited by manoalide, a covalent irreversible phospholipase A2 inhibitor, in a dose-dependent fashion with 50% inhibition occurring at a concentration of 0.48 microM. The Limulus protein displayed no activity in a triglyceride lipase assay. These studies characterize an alternative phospholipase A2 activity for the previously described 18.5 kDa protein from the L. polyphemus amebocyte.

The effect of temperature and solution pH on the nucleation of tetragonal lysozyme crystals

Part of the challenge of macromolecular crystal growth for structure determination is obtaining crystals with a volume suitable for x-ray analysis. In this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. This study investigated the effects of supersaturation, temperature, and pH on the nucleation rate of tetragonal lysozyme crystals. Batch crystallization plates were prepared at given solution concentrations and incubated at set temperatures over 1 week. The number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions. Crystal numbers were found to increase with increasing supersaturation and temperature. The most significant variable, however, was pH; crystal numbers changed by two orders of magnitude over the pH range 4.0-5.2. Crystal size also varied with solution conditions, with the largest crystals obtained at pH 5.2. Having optimized the crystallization conditions, we prepared a batch of crystals under the same initial conditions, and 50 of these crystals were analyzed by x-ray diffraction techniques. The results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists.

Homo- and nor-plakotenin, new carboxylic acids from the Palauan sponge Plakortis lita

A specimen of Plakortis lita from Palau yielded the new carboxylic acids, homo-plakotenin (2a), the sodium salt of homo-plakotenin (2b), the sodium salt of nor-plakotenin (3), the sodium salt of plakotenin (1b), and the known compound plakotenin (1a). The structures of the new acids were elucidated by interpretation of spectral data and by comparison with the known compound. Compounds 1a, 1b, and 2a were found to significantly reduce proliferation of rheumatoid synovial fibroblasts.

Phospholipid composition of the granular amebocyte from the horseshoe crab, Limulus polyphemus

The phospholipid composition was determined for the amebocyte of the primitive arthropod Limulus polyphemus. The total fatty acid composition of the cells' lipids was analyzed by gas chromatography/mass spectrometry (GC/MS) of fatty acid methyl esters (FAME). The FAME analysis revealed high levels of 20-carbon polyunsaturated fatty acids (PUFA), especially arachidonic (20:4n-6) and eicosapentaenoic (20:5n-3) acids. Almost 20% of the total lipid profile was comprised of dimethyl acetals of 16- to 20-carbon chain lengths, indicative of plasmalogens in the phospholipid pool. Phospholipids, analyzed by high-pressure liquid chromatography, included phosphatidylethanolamine (PE), phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI), sphingomyelin (SPH), and cardiolipin (CL). PE and PC levels predominated at 42.2 and 36.3%, respectively. Smaller amounts of PS (9.0%) and PI (6.2%) were present, as well as low levels of SPH (4.6%), CL (1.6%), and trace amounts of lysophosphatidylcholine. The major phospholipid species, PE, PC, PS and PI, were collected and their molecular species were examined by electrospray-ionization mass spectrometry. The molecular species within the phospholipid classes reflected the high levels of PUFA seen in the total lipid profile. PI was mainly composed of 18:0a/20:4. Over half of the PS consisted of 18:0a/18:1 and 18:0a/20:4. The major PE species were 20:1p/20:5, 20:1p/20:4, 18:0p/20:5, and 18:0p/20:4. PC had the largest distribution of molecular species, and its most abundant species were 16:0e/20:5, 16:0e/20:4, and 16:0p/20:4. The presence of 16:0e/20:4 is the first documentation of a specific precursor to platelet-activating factor in an invertebrate hemocyte. Note: at the sn-1 position: [a=1=O-acyl, e = 1-O-alkylether, and p = 1-O-alk-1'-enyl (plasmalogen)].

Pharmacological characterization of the pseudopterosins: novel anti-inflammatory natural products isolated from the Caribbean soft coral, Pseudopterogorgia elisabethae

Pseudopterosin E (PSE), a C-10 linked fucose glycoside and pseudopterosin A (PSA), a C-9 xylose glycoside isolated from the marine gorgonian Pseudopterogorgia elisabethae were both effective in reducing PMA-induced mouse ear edema when administered topically (ED50 (microg/ear) PSE(38), PSA(8)) or systemically (ED50 (mg/kg, i.p.) PSE (14), PSA (32)). Both compounds exhibited in vivo analgesic activity in phenyl-p-benzoquinone-induced writhing (ED50 (mg/kg, i.p.) PSE(14), PSA(4). PSE inhibited zymosan-induced writhing (ED50 = 6 mg/kg, i.p.), with a concomitant dose-dependent inhibition of peritoneal exudate 6-keto-prostaglandin F1alpha (ED50 = 24 mg/kg) and leukotriene C4 (ED50 = 24 mg/kg). In vitro, the pseudopterosins were inactive as inhibitors of phospholipase A2, cyclooxygenase, cytokine release, or as regulators of adhesion molecule expression. PSA inhibited prostaglandin E2 and leukotriene C4 production in zymosan-stimulated murine peritoneal macrophages (IC50 = 4 microM and 1 microM, respectively); however, PSE was much less effective. These data suggest that the pseudopterosins may mediate their anti-inflammatory effects by inhibiting eicosanoid release from inflammatory cells in a concentration and dose-dependent manner.

Pheochromocytoma and bowel ischemia

This case report presents a patient with an adrenal pheochromocytoma manifesting as intestinal ischemia. Emergency department and hospital courses are described. Complications of pheochromocytoma are briefly reviewed, with special reference to the gastrointestinal findings in this syndrome. The onset of gastrointestinal symptoms in patients with pheochromocytoma can be a herald of intestinal ischemia, necessitating prompt medical and surgical intervention.

Biosynthesis of arachiodonic acid metabolites in Limulus polyphemus amebocytes: analysis by liquid chromatography-electrospray ionization mass spectrometry

Eicosanoid metabolites were generated by isolated granular amebocytes of the primitive arthropod, Limulus polyphemus, when stimulated by the calcium ionophore A23187 and/or exogenous arachidonic acid. The metabolites were isolated, identified, and the major metabolite was quantified using reverse-phase high pressure liquid chromatography (RP-HPLC) coupled to electrospray ionization mass spectrometry (ESI-MS). Qualitative examination revealed putative metabolites and the major product, 8-hydroxyeicosatetraenoic acid (8-HETE), which was quantified using standard curves generated from extracted ion profiles of the molecular ion. Electrospray ionization of the HETEs in negative ion mode produces a base peak for all isomers which corresponded to the molecular ion [(M-H)-: m/z 319]. The molecular ion was accompanied by the neutral loss of water and carbon dioxide [(M-H -H2O)-: m/z 301; (M-H -H2O -CO2)-: m/z 257], as well as daughter ions which were dependent upon the position of hydroxy substitution. Standard curves were generated in full scan mode for standards ranging from 6.25 to 100 ng, whereas selected ion recording was used for the lower levels of 0.8 to 6.25 ng.

CNS role: an experience in retitling and role clarification

A LITERATURE REVIEW and survey were undertaken to identify the appropriate titling for individuals in clinical nursing and other advanced practice roles, to establish components in each role, and to determine the educational level necessary for each role. Based upon review and survey results, a CNS task force at the University of Iowa Hospitals and Clinics proposed a change in the titles of nurses in advanced practice at their institution to reflect the American Nurses' Association's definition of advanced practice nursing and recommended graduate level education for these advanced positions. Five specific titles and primary role components were identified: advanced registered nurse practitioners. CNS, education nurse specialist, research nurse specialist, and informatics nurse specialist. Retitling aided in clearly identifying major responsibilities of the position, clarifying role expectations, and creating evaluation tools.

Structure and biosynthesis of novel conjugated polyene fatty acids from the marine green alga Anadyomene stellata

Novel polyunsaturated fatty acids with four conjugated double bonds were found in extracts of the green macroalga, Anadyomene stellata. The isolation of five of these with different chain lengths and varying degrees of unsaturation--16:5, 18:4, 20:5, 20:6, and 22:7--was accomplished by organic extraction followed by a combination of vacuum and high-performance liquid chromatography. One of these that was a novel substance (22:7) was characterized as 4Z,7Z,9E,11E,13Z,16Z,19Z-do cosaheptaenoic acid and assigned the trivial name stellaheptaenoic acid. The structure of this new compound, isolated as its methyl ester derivative, was deduced from detailed nuclear magnetic resonance, gas chromatography/mass spectrometry (GC/MS), and other spectroscopic methods. Incubation of a chloroplast preparation, isolated from a crude algal homogenate by differential centrifugation, with six unsaturated fatty acids (palmitoleic, 6Z,9Z,12Z,15Z-octadecatetraenoic acid, arachidonic acid, eicosapentaenoic acid, 7Z,10Z,13Z,16Z-docosatetraenoic acid, and 4Z,7Z,10Z,13Z,16Z,19Z-docosahexaenoi c acid) resulted in substantially increased synthesis of unique tetraene compounds as detected by ultraviolet spectrophotometry and tentatively identified by GC/MS.

Inactivation of bee venom phospholipase A2 by a sesquiterpene furanoic acid marine natural product

A sesquiterpene furanoic acid (SFA) marine natural product isolated from soft corals of the genus Sinularia (Bowden et al., Aust J Chem 36: 371-376, 1983) was found to inactivate bee venom phospholipase A2 (bvPLA2, EC 3.1.1.4) in vitro. In this study, we characterized the kinetics of inactivation of bvPLA2 by this compound. The apparent IC50 value was 0.5 microM, and the inactivation of bvPLA2 was time dependent. The drug-enzyme binding appeared to be of a non-competitive, high-affinity nature that was irreversible by aqueous dialysis. The inactivation was prevented by the simultaneous addition of excess lysophosphatidylcholine (lysoPC) during the initial binding step, suggesting that modification of the enzyme by SFA occurs at or near the substrate binding site. Activation of bvPLA2 was observed with lysoPC addition at concentrations equimolar to bvPLA2 and higher. Saturation of activation occurred at concentrations greater than 10 microM lysoPC, and preincubation of bvPLA2 with 100 microM lysoPC did not inhibit the enzyme. Analysis of the post-incubation mixture of SFA-inhibited enzyme in the presence of lysoPC revealed the presence of unaltered enzyme exhibiting typical Michaelis-Menten kinetics. The significance of these observations is discussed in light of the recent discussion by Ortiz on the manoalide binding site on bvPLA2.

A marine natural product, patellamide D, reverses multidrug resistance in a human leukemic cell line

A cyclic octapeptide (patellamide D) isolated from the marine tunicate, Lissaclinum patella, acts as a resistance-modifying agent in the multidrug resistant CEM/VLB100 human leukemic cell line. A three-day microculture tetrazolium proliferation assay was used to determine the 50% inhibitory concentration (IC50) for vinblastine, colchicine and adriamycin and calculate the degree of resistance modulation. Patellamide D at 3.3 microM was compared with 5.1 microM verapamil in modulating drug resistance in vitro. The IC50 for vinblastine was reduced from 100 ng/ml to 1.5 ng/ml in the presence of patellamide D or to 2.1 ng/ml when exposed to verapamil. Colchicine cytotoxicity was enhanced only 1.4-fold by verapamil, as compared with 2.8-fold using patellamide D (IC50 was reduced from 140 ng/ml to 100 ng/ml or 50 ng/ml). Adriamycin toxicity was reduced from IC50 > 1000 ng/ml to 110 ng/ml and 160 ng/ml when coexposed to patellamide D and verapamil, respectively. Our results indicate that patellamide D acts as a selective antagonist in multidrug resistance and stresses the importance of investigating marine-derived compounds as a potential new source for modulators of the drug-resistance phenotype.

Fuscoside: an anti-inflammatory marine natural product which selectively inhibits 5-lipoxygenase. Part I: Physiological and biochemical studies in murine inflammatory models

The biological and biochemical pharmacology of fuscoside, a novel anti-inflammatory marine natural product isolated from the Caribbean gorgonian Eunicea fusca, has recently been characterized using murine (part I) and human (part II) models of inflammation. Topically applied fuscoside (FSD) effectively inhibits phorbol myristate acetate (PMA)-induced edema in mouse ears at levels comparable with indomethacin over a 3.3-hr exposure period, and is significantly more efficacious than indomethacin over 24 hr in the PMA model. Histological preparations and quantification of the neutrophil-specific marker, myeloperoxidase, demonstrate that FSD inhibits neutrophil infiltration into PMA-induced regions of edema and inflammation. In systemic studies, where FSD is injected i.p. before the topical application of PMA, negligible effects on ear inflammation are observed. FSD does not inhibit bee venom or human synovial fluid phospholipase A2 up to concentrations of 500 microM. In calcium ionophore-activated cultures of mouse peritoneal macrophages, FSD selectively and irreversibly inhibits leukotriene C4 biosynthesis (IC50 = 8 microM), yet has negligible effects on prostaglandin E2 production. FSD is also without effect on the conversion of arachidonic acid to prostaglandin E2 by ram seminal vesicle cyclooxygenase. Chromatographic and spectroscopic studies suggest that FSD is not metabolized, and that drug uptake/binding by macrophages is time dependent, saturable and independent of active transport mechanisms. These studies represent the first report of an anti-inflammatory marine natural product that selectively inhibits leukotriene biosynthesis.

Fuscoside: an anti-inflammatory marine natural product which selectively inhibits 5-lipoxygenase. Part II: Biochemical studies in the human neutrophil

Fuscoside (FSD) is a potent and long-lasting anti-inflammatory drug that selectively inhibits leukotriene production in murine models of inflammation. In the present study, the effects of FSD on the lipoxygenase pathways in human polymorphonuclear leukocytes are explored in order to better understand the mechanism of action of this novel drug. In adherent and suspended polymorphonuclear leukocytes, FSD irreversibly inhibits leukotriene B4 (LTB4) synthesis (IC50 = 10 microM) and the release of 14C-labeled LTB4 from neutrophils prelabeled with [14C]arachidonic acid. Unlike the reversible 5-lipoxygenase inhibitor L-651,896, FSD has no observable effect on LTB4 biosynthesis in whole blood, but does express activity as blood is successively diluted. In 10,000 x g supernatants of human platelets and polymorphonuclear leukocytes, FSD does not inhibit platelet 12-lipoxygenase, but is extremely effective in inhibiting the metabolism of arachidonic acid and 5-hydroperoxyeicosatetraenoic acid to LTB4 via neutrophil 5-lipoxygenase. FSD has no effect on the conversion of leukotriene A4 to LTB4 in this system. Interestingly, concurrent with FSD inhibition of leukotriene synthesis is a concentration-dependent increase in 5-hydroxyeicosatetraenoic acid, suggesting that FSD may selectively inhibit the leukotriene A4 synthase activity associated with human 5-lipoxygenase. FSD is therefore representative of a new class of nonantioxidant 5-lipoxygenase inhibitors that may be effective local therapeutic agents in the management of diseases such as psoriasis, arthritis and inflammatory bowel and lung diseases.

Selective inhibition of cytokinesis in sea urchin embryos by the marine natural product pseudopterolide

Low concentrations (1-10 microM) of the marine natural product pseudopterolide inhibited cytokinesis and induced formation of multinucleate cells in fertilized Strongylocentrotus purpuratus embryos. As determined by immunofluorescence microscopy using fluorescent stains for actin filaments, microtubules, and chromosomes, pseudopterolide inhibited cytokinesis selectively by disrupting the contractile ring, whereas spindle microtubule organization and mitotic chromosome segregation to opposite spindle poles were unimpaired. At somewhat higher concentrations (16-20 microM), pseudopterolide induced formation of microtubule spiral asters, which are believed to be caused by rotation of the cytoplasm relative to the cell cortex. The effects of pseudopterolide on cytokinesis were cell-cycle dependent. The actions of pseudopterolide in fertilized sea urchin embryos were strikingly similar to the actions of another marine natural product, stypoldione, a structurally unrelated orthoquinone that reacts covalently with the sulfhydryl groups of glutathione, beta-mercaptoethanol, cysteine, and a number of proteins [Mol. Pharmacol. 35:635-642 (1989)]. In the present study, pseudopterolide was also found to react with sulfhydryl groups of glutathione, beta-mercaptoethanol, and cysteine. The results indicate that the cellular target for pseudopterolide, like the target for stypoldione, may be an especially sensitive sulfhydryl-containing protein involved in the formation or function of the contractile ring.

Two-step inactivation of bee venom phospholipase A2 by scalaradial

Scalaradial (SLD), a marine natural product isolated from the sponge (Cacospongia sp., possesses anti-inflammatory properties in vivo and in vitro (Pharmacologist 32: 168, 1990). In this study we characterize its effects against bee venom phospholipase A2 (PLA2; EC 3.1.1.4). SLD is a potent inactivator of bee venom PLA2 with an IC50 value of 0.07 microM. Inactivation of bee venom PLA2 occurred in a time-dependent, irreversible manner. The rate of inactivation followed first-order reaction kinetics and was dependent on the concentration of SLD. Kinetic analysis suggested a two-step mechanism of inactivation: an initial apparent noncovalent binding (Ki = 4.5 x 10(-5) M) followed by covalent modification. The rate of inactivation was reduced markedly in the presence of excess phosphatidylcholine, suggesting that modification of the enzyme occurs at or near the substrate binding site.

Structure and stereochemistry of brianolide, a new antiinflammatory diterpenoid from the Okinawan gorgonian Briareum sp

Brianolide (1), a new antiinflammatory diterpenoid of the briarein class, possessing a beta substituent at C-12 (R), has been isolated from the Okinawan gorgonian Briareum sp. Its structure has been established from spectral data in conjunction with a single crystal X-ray analysis.

Inactivation of human synovial fluid phospholipase A2 by the marine natural product, manoalide

The marine natural product, manoalide (MLD), was investigated to determine if this drug inhibited purified human synovial fluid phospholipase A2 (HSF-PLA2). Utilizing classical Michaelis-Menten kinetics, apparent Km and Vmax values for HSF-PLA2 of 1.34 mM and 0.47 mumol [3H]palmitic acid released/min/mg protein were obtained using dipalmitoylphosphatidylcholine (DPPC) as the substrate, and 38.0 microM and 18.8 mumol [3H]arachidonic acid released/min/mg protein with Escherichia coli as a natural substrate. These kinetic parameters were utilized subsequently to evaluate the inhibitory effects of manoalide on HSF-PLA2. Inhibition of HSF-PLA2 by MLD was concentration and time dependent with IC50 values of 0.2 and 0.02 microM for DPPC and E. coli respectively. Dialysis studies and examination of DPPC or E. coli hydrolysis versus enzyme concentration indicate that MLD is an irreversible inhibitor of HSF-PLA2. Substrate specificity was also examined in the absence and presence of MLD using dipalmitoylphosphatidylethanolamine (DPPE) as a substrate. MLD inhibited the hydrolysis of DPPE (greater than 90% inhibition at 2 microM), and preliminary results indicate that DPPC was more readily hydrolyzed than DPPE under the substrate conditions of the assay. While the cellular source of secreted HSF-PLA2 is unknown, these studies indicate that MLD can inactivate secreted phospholipase A2 isolated from patients with inflammatory joint disease.

Manoalide: structure-activity studies and definition of the pharmacophore for phospholipase A2 inactivation

Manoalide is a potent antiinflammatory marine natural product and a direct inactivator of venom phospholipase A2 (PLA2; EC 3.1.1.4). Manoalide has been shown to irreversibly inhibit PLA2, with the corresponding modification of a selective number of lysine residues. The mechanism of inactivation has not yet been elucidated and structure-activity relationship studies were, therefore, performed in order to determine the contributions of the various functional groups incorporated in the gamma-hydroxybutenolide, alpha-hydroxydihydropyran, and trimethylcyclohexenyl ring systems to the efficacy (irreversibility) and potency of this series of inhibitors. These studies indicate that 1) the presence of the hemiacetal in the alpha-hydroxydihydropyran ring is required for irreversible binding of manoalide, 2) the gamma-hydroxybutenolide ring is involved in the initial interaction of manoalide with PLA2, and 3) the hydrophobic nature of the trimethylcyclohexenyl ring system allows nonbonded interactions between manoalide and PLA2 that enhance the potency of these analogs. These structure-activity relationship studies suggest that the closed ring form of manoalide is the predominant molecular species that accounts for the selective and potent inhibition of PLA2 by manoalide. Elucidation of the mechanism awaits further detailed physicochemical studies on the structure of the manoalide (analog)-protein adducts in model systems and using PLA2.

Synthesis, in vitro acetylcholine-storage-blocking activities, and biological properties of derivatives and analogues of trans-2-(4-phenylpiperidino)cyclohexanol (vesamicol)

Eighty-four analogues and derivatives of the acetylcholine-storage-blocking drug trans-2-(4-phenylpiperidino)-cyclohexanol (vesamicol) were synthesized, and their potencies were evaluated with the acetylcholine active-transport assay utilizing purified synaptic vesicles from Torpedo electric organ. The parent drug exhibits enantioselectivity, with (-)-vesamicol being 25-fold more potent than (+)-vesamicol. The atomic structure and absolute configuration of (+)-vesamicol were determined by X-ray crystallography. The absolute configuration of (-)-vesamicol is 1R,2R. Structure-activity evidence indicates that (-)-vesamicol does not act as an acetylcholine analogue. Alterations to all three rings can have large effects on potency. Unexpectedly, analogues locking the alcohol and ammonium groups trans-diequatorial or trans-diaxial both exhibit good potency. A potent benzovesamicol family has been discovered that is suitable for facile elaboration of the sort useful in affinity labeling and affinity chromatography applications. A good correlation was found between potencies as assessed by the acetylcholine transport assay and LD50 values in mouse.

Selective inhibition of cytokinesis in sea urchin embryos by low concentrations of stypoldione, a marine natural product that reacts with sulfhydryl groups

Stypoldione is a marine natural product that inhibits cells division in marine embryos and in mammalian cell cultures. The mechanism responsible for the ability of the compound to inhibit cell division is not known. The compound was found in early studies to inhibit polymerization of tubulin into microtubules in vitro, which lead to the suggestion that inhibition of microtubule polymerization in cells might be responsible for the ability of the compound to inhibit cell division. More recently, stypoldione was found to react covalently with the sulfhydryl groups of a number of proteins including tubulin and with sulfhydryl groups of peptides and small molecules. Thus, stypoldione could potentially react with a large number of cellular targets. In the present study, we have examined the effects of stypoldione on the organization of microtubules and chromatin in cells, in relation to the ability of the compound to inhibit cell division. We used indirect immunofluorescence light microscopy of fixed and stained sea urchin embryos during the first and second divisions after fertilization, with stains specific for tubulin and DNA. We found that stypoldione exerted qualitatively different effects on cell division and microtubule organization and function at different concentrations. At the lowest effective concentrations, 5-10 microM, stypoldione selectively inhibited cytokinesis. Mitotic division occurred normally, usually with no discernible perturbation of microtubule organization or function, and cells became multinuclear. At somewhat higher concentrations, 20-40 microM, stypoldione blocked embryos before streak stage of the first division and, although microtubules were present, their organization was perturbed and they often formed unusual "spiral aster" arrays. At 80 microM and above, microtubules in blocked cells were largely absent. Thus, stypoldione uncouples cytokinesis from mitosis at the lowest effective concentrations and, although it can disrupt microtubules at relatively higher concentrations, it inhibits cell division at the lowest effective concentrations by a selective action on cytokinesis through a mechanism that does not appear to involve disassembly of microtubules.

Luffolide, a novel anti-inflammatory terpene from the sponge Luffariella sp

Luffolide (4) is a minor metabolite of the sponge Luffariella sp. from Palau. The structure of luffolide was determined by single crystal X-ray analysis. Luffolide is relatively unstable and undergoes a complex cyclization reaction to give the hexacyclic products 5 and 6. Luffolide (4) has some of the anti-inflammatory properties of manoalide (1): this may help to define the chemical reaction between manoalide (1) and phospholipase A2.

Inactivation of phospholipase A2 by manoalide. Localization of the manoalide binding site on bee venom phospholipase A2

The marine natural product manoalide (MLD), a potent inhibitor of phospholipases, completely inactivates bee venom phospholipase A2 (PLA2) by an irreversible mechanism. It has been proposed [K. B. Glaser and R. S. Jacobs, Biochem. Pharmac. 36, 2079 (1987)] that the reaction of MLD with PLA2 may involve the selective reactivity of MLD to a peptide sequence, possibly a Lys-X-X-Lys peptide. Localization of the MLD binding site on bee venom PLA2 demonstrated that upon MLD modification of bee venom PLA2 the only change in amino acid content was an apparent loss of Lys, corresponding to approximately three of the eleven Lys residues present. Selective chemical modification of Lys residues with [14C]maleic anhydride demonstrated that all eleven Lys residues on bee venom PLA2 were accessible to this reagent (11.6 mol maleyl group incorporated/mol of PLA2). Pretreatment of PLA2 with MLD (less than 0.7% residual activity) resulted in a molar ratio of 8.7, also consistent with the loss of three Lys residues upon modification by MLD. Reverse phase high performance liquid chromatography (RP-HPLC) of the cyanogen bromide (CNBr) digestion product of MLD-treated PLA2 produced three peaks (A280). The second peak showed the most intense absorbance at 434 nm. This material corresponded to residues 81-128, as determined by gas-phase microsequence analysis. Sequencing failure was observed at Lys-88 in the MLD-treated fragment. The control carboxymethylated-PLA2 fragment corresponding to residues 81-128 sequenced beyond Lys-88 without significant change in the expected yield. These data suggest that Lys-88 may correspond to one of the three MLD-modified Lys residues. The minor absorbance at 434 nm of the CNBr fragments containing residues 42-80 and 1-36 as compared to the fragment of residues 81-128 suggests that the major MLD binding fragment residues in residues 81-128.

A further study of the neuromuscular effects of vesamicol (AH5183) and of its enantiomer specificity

1. The effects of vesamicol (2-(4-phenylpiperidino) cyclohexanol), an inhibitor of acetylcholine storage, and its two optical isomers have been studied on neuromuscular transmission in rat and frog muscle, and on nerve conduction in frog nerve. 2. Racemic vesamicol produced a pre-block augmentation of twitch tension that also occurred in directly-stimulated muscle. This effect is thus at least partially due to an increase in muscle contractility. 3. (-)-Vesamicol was approximately 20 times more potent than (+)-vesamicol in blocking twitches elicited at 1 Hz. This degree of stereoselectivity is similar to that measured for inhibition of acetylcholine uptake by isolated synaptic vesicles. Both enantiomers were equally weak in reducing nerve action potential amplitude in frog nerve. 4. Further studies with the active isomer, (-)-vesamicol, showed that, like that produced by racemic vesamicol, the neuromuscular block was highly frequency-dependent. The block was not reversed by choline or neostigmine, but was partially reversed by 4- or 3,4-aminopyridine. 5. Preliminary electrophysiological studies showed that vesamicol reduced miniature endplate potential amplitude in rapidly-stimulated frog nerve-muscle preparations. Addition of lanthanum ions increased the frequency of miniature endplate potentials and led to the appearance of apparently normal-sized potentials amongst those of reduced amplitude. 6. The results show the close agreement between pharmacological and biochemical observations indicating the suitability of the rat diaphragm as a test model for substances of this nature. The degree of reversibility of the vesamicol-induced neuromuscular block by aminopyridines was unexpected, and it is suggested that in the presence of a drug which greatly increases release, a pool of acetylcholine is capable of being released which is not normally releasable after block of storage by vesamicol. It is also considered possible that the results from the intracellular recording studies may be explained in these terms.

Regulation of eicosanoid biosynthesis in vitro and in vivo by the marine natural product manoalide: a potent inactivator of venom phospholipases

The marine natural produce manoalide has been reported to inactivate venom phospholipase A2 from several sources and phospholipase A2 from polymorphonuclear leukocytes. In this investigation, the regulation of eicosanoid production was studied both in an in vitro and in an in vivo model. The release of arachidonic acid and prostaglandin E2 was inhibited by manoalide when cultured mouse peritoneal macrophages were stimulated with phorbol myristate acetate (apparent IC50 = 0.23 microM), calcium ionophore A23187 (apparent IC50 = 0.23 microM) and zymosan (apparent IC50 = 0.18 microM). Leukotriene C4 production was inhibited by manoalide when macrophages were stimulated by A23187 (IC50 = 0.35 microM) but was enhanced when the cells were stimulated with zymosan. In an in vivo model, manoalide antagonized zymosan-induced peritoneal writhing in the mouse (ED50 = 0.71 mg/kg) and inhibited the i.p. release of 6-keto-prostaglandin F1 alpha (ED50 = 0.2 mg/kg) and leukotriene C4 (ED50 = 0.24 mg/kg). Our results suggest that: 1) manoalide modifies arachidonic acid release and metabolism to prostaglandins and leukotrienes in mouse cultured peritoneal macrophages stimulated by phorbol myristate acetate, calcium ionophore A23187 and zymosan and 2) the analgesic properties of manoalide seem to be partially correlated with reduced eicosanoid production in zymosan-stimulated mouse peritoneal exudates.

Inactivation of bee venom phospholipase A2 by manoalide. A model based on the reactivity of manoalide with amino acids and peptide sequences

The marine natural product manoalide (MLD), a potent irreversible inhibitor of bee venom phospholipase A2 (PLA2), was shown to produce a chromophore (lambda max = 437 nm) during incubation with the enzyme. MLD also developed an identical chromophore when incubated with free lysine (Lys), cysteine (Cys) or tryptophan (Trp) but not with their N-alpha-amino-blocked analogs. These results suggest that the chromophore product was dependent on the presence of two nucleophilic groups which react by an ordered mechanism rather than by simple random collision. Lys polymers prevented MLD from inhibiting PLA2, whereas monomeric Lys did not. The optimal active polymer of Lys appeared to be a tetralysine (L4) peptide, and a degree of selectivity was obtained when the Lys residues were in a 1,4-Lys arrangement. The rate of chromophore development with PLA2 and the rate of inactivation of PLA2 by MLD appear to be independent processes. Based on these data, it is possible that the irreversible inactivation of PLA2 may involve an ordered reaction with a peptide sequence in PLA2 containing a 1,4-Lys arrangement.

Effect of pseudopterosin A on cell division, cell cycle progression, DNA, and protein synthesis in cultured sea urchin embryos

Pseudopterosin A is a diterpene riboside isolated from Pseudopterogorgia bipinata, a soft coral of the order Gorgonacea. Pseudopterosin A inhibits the first cleavage in fertilized sea urchin eggs (Strongylocentrotus purpuratus, Strongylocentrotus franciscanus, and Lytechinus pictus) with an IC50 of 25 microM. In time of addition studies, Pseudopterosin A (4 X 10(-5) M) progressively blocked the first cleavage when added within the first 50 min post fertilization; when added after 50 min the first division occurred normally. Cell cycle studies show that Pseudopterosin A had to be in continuous contact with the sea urchin eggs during the initial 45 min post fertilization to significantly inhibit the first cleavage. Shorter drug contact time progressively reduced the degree of inhibition, suggesting that inhibition of cytokinesis by Pseudopterosin A was correlated with mitosis. Pseudopterosin A (4 X 10(-5) M) inhibited the uptake and incorporation of [3H]thymidine during the S2 phase. This concentration of Pseudopterosin A also inhibits protein synthesis as measured by the uptake and incorporation of [3H]phenylalanine. In this case the inhibition started before the S1 phase. Cytological examination revealed that sea urchin embryos did not progress beyond early prophase. Notably, the nuclear envelope remained intact and chromatin was condensed into chromosomes in the arrested embryos. These synchronously dividing embryos did not show any abnormalities such as lysis, swelling, or morphological changes different from control embryos.

Mechanism of action of the marine natural product stypoldione: evidence for reaction with sulfhydryl groups

Stypoldione, a marine natural product that possesses an o-quinone functional group, has been shown to inhibit a variety of biological processes including cell division. We found that stypoldione binds covalently to sulfhydryl groups of thiol-containing compounds via addition of sulfur to the C-4' position of the quinone ring. We examined the ability of stypoldione to add to sulfhydryl groups of a number of thiol-containing substances, including glutathione, thiophenol, beta-mercaptoethanol, and the protein tubulin. We suggest that the biological actions of stypoldione may be caused by the addition of this compound to thiol groups of biological molecules.

The pseudopterosins: anti-inflammatory and analgesic natural products from the sea whip Pseudopterogorgia elisabethae

The Caribbean sea whip Pseudopterogorgia elisabethae (Octocorallia, Cnidaria) has been found to contain the pseudopterosins, a newly described class of natural products, which have been characterized as diterpene-pentoseglycosides. The pseudopterosins possess anti-inflammatory and analgesic properties that exceed, in our assays, the potencies of existing drugs such as indomethacin. As anti-inflammatory agents, the pseudopterosins appear to modify the arachidonic acid cascade by an as yet undefined mechanism of pharmacological action.

Molecular pharmacology of manoalide. Inactivation of bee venom phospholipase A2

The marine natural product manoalide (MLD) was shown to directly inactivate bee venom phospholipase A2 (PLA2). Inactivation was pH dependent (maximum inactivation occurred at pH 8.0), time dependent and concentration dependent. The IC50 was estimated at 0.05 microM and virtually complete inactivation of the enzyme occurred at 4.0 microM. The time-dependent loss of PLA2 activity suggested that inactivation does not follow typical Michaelis-Menten kinetics. Reversibility was studied directly by dilution and dialysis; both methods were ineffective in dissociating the MLD-PLA2 complex. A kinetic plot of initial velocity (v) versus [PLA2] supported our hypothesis that MLD apparently inactivates bee venom PLA2 by an irreversible mechanism.

Irreversible autonomic actions by lophotoxin suggest utility as a probe for both C6 and C10 nicotinic receptors

The marine natural product lophotoxin has produced a non-reversible antagonism of parasympathetic and sympathetic functions that are known to be mediated by C6 sub-type nicotinic receptors. Transmission through anuran paravertebral ganglia was eliminated in 20-40 min by 10-30-min treatments with 16-32 microM lophotoxin, in a time course resembling the onset of block of C10 sub-type nicotinic receptors at the neuromuscular junction and in cultured BC3H-1 cells. The action persisted through 16 h of washout. Nerve conduction was unaffected. Somewhat longer treatments (80 min) of in vitro ileal sections resulted in loss of sensitivity to nicotine, but not to acetylcholine, for at least 5 h. These data indicate that lophotoxin can serve as a more universal nicotinic receptor probe than the alpha-neurotoxins, which may bind to both C6 and C10 sub-types, but block only the C10.

In vitro inactivation of the neurotoxic action of beta-bungarotoxin by the marine natural product, manoalide

The irreversible neurotoxic action of beta-bungarotoxin (beta-BuTx) can be prevented by preincubation of the toxin with manoalide, a non-steroidal anti-inflammatory agent. Manoalide was also found to inactivate purified phospholipase A2 and thus prevent hydrolysis of phosphatidylcholine. PLA2 is a component found in several neurotoxic venoms and is also a rate limiting enzyme important in phospholipid metabolism and prostaglandin synthesis in man.

Inhibition of bovine brain microtubule assembly in vitro by stypoldione

Stypolidione, an orthoquinone derived from the brown seaweed Stypopodium zonale, inhibited the polymerization of three-cycle-purified bovine brain microtubule protein in vitro in a concentration-dependent manner. Fifty per cent inhibition of the extent of polymerization beginning under initiating conditions occurred at a stypoldione concentration of approximately 25 microM, and 50% inhibition of tubulin addition to the assembly ends of microtubules at steady state occurred at a concentration of approximately 8 microM. Only slight structural abnormalities could be detected by negative stain electron microscopy in some of the microtubules that did assemble in the presence of the drug, and no aberrant structural forms of microtubule protein were detected. Stypoldione inhibited the binding of [3H]colchicine to tubulin, with 50% inhibition of colchicine binding activity occurring at a stypoldione concentration of 12-15 microM. Inhibition of colchicine binding activity appeared noncompetitive and was at least partially reversible, suggesting that stypoldione and colchicine bind at separate sites. By assuming that the inhibition constant for the ability of stypoldione to prevent the binding of colchicine to tubulin was equivalent to the dissociation constant for the binding of stypoldione to tubulin, we calculated that approximately 62% of the tubulin present free in solution under initiating conditions and 35-37% of the soluble tubulin under steady-state conditions was complexed with stypoldione when polymerization was inhibited by 50%. These data are consistent with a mechanism in which stypoldione interacts with soluble tubulin and inactivates the tubulin so that it is unable to add to microtubule ends, although a colchicine-like mechanism involving an action of stypoldione at microtubule ends has not been eliminated.

Effect of stypoldione on cell cycle progression, DNA and protein synthesis, and cell division in cultured sea urchin embryos

We have found that stypoldione, a bright red o-quinone isolated from the brown alga Stypopodium zonale, inhibits the division of sea urchin embryos in a concentration-dependent manner (IC50 approximately 2.5 X 10(-6) M). Although previous studies have shown this marine natural product to inhibit beef brain microtubule assembly in vitro [Fed. Proc. 39:26-29 (1980); Mol. Pharmacol. 24:493-499 (1983)], we have found that stypoldione does not accumulate sea urchin embryos in mitosis and hence does not act like a mitotic spindle poison. We have also shown this marine natural product to inhibit both amino acid and nucleoside uptake. By preloading sea urchin embryos with nucleoside (i.e., [3H]thymidine) in order to dissociate effects on uptake from those on incorporation, we found that stypoldione in fact produces no significant inhibition of the M phase-independent S1 period of DNA synthesis, a result which suggests that stypoldione has no direct effect on DNA synthesis. In contrast, stypoldione did reduce the extent of amino acid incorporation in embryos preloaded with [3H]leucine. An inhibition of incorporation was apparent as early as 20 min after fertilization, and incorporation was reduced to 50% of control by 40 min postfertilization. This result suggests that stypoldione might inhibit cleavage via an inhibition of translation, although the existence of other inhibitory mechanisms cannot yet be ruled out. Cytological examination revealed that sea urchin embryos did not progress beyond-interphase or very early prophase when incubated in the presence of 1.0 X 10(-5) M stypoldione. The nuclear membranes remained intact, and chromatin did not condense into chromosomes in these arrested embryos. These results indicate that embryos exposed to stypoldione early in the cell cycle initiate and complete the M phase-independent S1 period of DNA synthesis, but stop cell cycle progression prior to the start of prophase of mitosis. The period between S phase and mitosis is referred to, by definition, as the "G2" phase of the cell cycle. The result therefore suggest that stypoldione blocks cell cycle progression (and, ultimately, cell division) by inhibiting progression through G2. This compound may represent a new class of G2-accumulating agents.

Quantal analysis indicates an alpha-toxin-like block by lophotoxin, a non-ionic marine natural product

The effects of a structurally novel paralytic substance (lophotoxin) on quantal transmission parameters and the time course of synaptic potentials have been examined. This substance completely abolished potentials by reducing quantal size without affecting the release of quanta. Nerve conduction, membrane potential, and the passive electrical properties of the muscle end-plate remained unaffected. Lophotoxin appears to act directly on the acetylcholine receptor-channel complex, although perhaps not the cholinoreceptive site itself, as suggested by the unusual chemistry and onset kinetics of this toxin.

A double-blind comparative trial with mianserin and amitriptyline in outpatients with major depressive disorders

1 A double-blind trial with parallel treatment groups was conducted to compare the safety and efficacy of mianserin with amitriptyline. 2 This was a six week trial with weekly visits. Measurements at each visit included: 21 item Hamilton Depression (HAMD) Scale. Clinical Global Impression (CGI) Scale and Treatment Emergent Symptom Scale (TESS). 3 Mianserin and amitriptyline were comparable with respect to efficacy. 4 More adverse experiences were reported by amitriptyline patients. The predominant amitriptyline adverse experiences were of the anticholinergic type; the predominant mianserin adverse experience was drowsiness/fatigue. 5 The Efficacy Index (EI), a scale combining efficacy and adverse experiences, clearly demonstrated the superiority of mianserin over amitriptyline.

Effect of 4-aminopyridine on nerve terminal action potentials

The effects of 4-aminopyridine (4AP) on the extracellularly recorded nerve terminal action potential (NTAP) and end-plate potential were studied at the frog neuromuscular junction. An in-depth analysis of the time course of the NTAP was performed in the presence and absence of extracellular Ca++. Low concentrations (5 X 10(-6) M) of 4AP produced no significant alterations in the time course of the NTAP, yet increased quantal content of the end-plate potential 2-fold. In contrast, high concentrations (5 X 10(-4) M) of 4AP prolonged the duration of the NTAP by selectively flattening the K+ slope of the NTAP and increased the quantal content of the end-plate potential. It is concluded that both potassium channel blockade and facilitation of transmitter release by 4AP can be demonstrated in this preparation, and that it is possible to separate these actions by varying the concentration of 4AP. Interpretation of these data suggests that there is a second site or mechanism of action by which 4AP potentials transmitter release. Possible mechanisms of action for 4AP are discussed.

Lophotoxin: a novel neuromuscular toxin from Pacific sea whips of the genus Lophogorgia

A new neuromuscular toxin, lophotoxin, has been isolated from several pacific gorgonians of the genus Lophogorgia. The structure of lophotoxin was deduced by combined spectrochemical methods, and belongs to the well-known cembrene class of diterpenoid molecules. Lophotoxin contains furanoaldehyde and alpha, beta-epoxy-gamma-lactone functional groups, in sharp contrast to the cationic ammonium functional groups of the established neurotoxins.

Selective compounds derived from marine organisms: effects on cell division in fertilized sea urchin eggs

An investigation of the pharmacological selectivity of the fertilized sea urchin egg assay was undertaken with the view that this echinoderm may serve as a useful model for detecting new compounds that inhibit cell division and also may yield substantive information on biochemical events that may be sensitive to drug action. One hundred and thirty purified marine natural products were tested as well as 14 known antineoplastic agents. Nine active marine cytotoxins were identified and, based on in vitro studies of microtubule assembly, five compounds inhibited tubulin polymerization. Of the 14 antineoplastic agents tested thus far, the transcriptional inhibitor daunomycin has proven active as well as the microtubule assembly inhibitors Colcemid, podophyllotoxin, vinblastine, and vincristine.

An inexpensive frequency-modulated (FM) audio monitor of time-dependent analog parameters

The standard method for quantification and presentation of an experimental variable in real time is the use of visual display on the ordinate of an oscilloscope screen or chart recorder. This paper describes a relatively simple electronic circuit, using commercially available and inexpensive integrated circuits (IC), which generates an audible tone, the pitch of which varies in proportion to a running variable of interest. This device, which we call an "Audioscope," can accept as input the monitor output from any instrument that expresses an experimental parameter as a dc voltage. The Audioscope is particularly useful in implanting microelectrodes intracellularly. It may also function to mediate the first step in data recording on magnetic tape, and/or data analysis and reduction by electronic circuitary. We estimate that this device can be built, with two-channel capability, for less than $50, and in less than 10 hr by an experienced electronics technician.

Structure-activity relationships in the development of hypoxic cell radiosensitizers. I. Sensitization efficiency

The efficiency of 35 nitroaromatic and nitroheterocyclic compounds in radiosensitizing hypoxic Chinese Hamster cells in vitro was determined. The concentration C of the compound required to achieve an enhancement ratio of 1.6 was measured, and the redox and partition properties were quantified as the one-electron reduction potential at pH 7, E, and the octanol: water partition coefficient, P, respectively. Most of the compounds studied were 2-nitroimidazoles, but some 4- and 5-nitromidazoles, 5-nitrofurans and nitrobenzenes were investigated for comparison. Together with data for nine nitroimidazoles previously reported, the results were fitted to a structure-activity relationship of the form -log C = b0 + b1E + b2 log P + b3 (log P)2 using multiple linear regression analysis. Statistical tests showed that the coefficients b2 and b3 were not significantly different from zero and the simpler equation, obtained by omitting the terms in log P, explained 85 per cent of the variance in log C. Earlier reports that the radiosensitization efficiency of nitro compounds in vitro largely depends on the reduction potential were confirmed. The conclusive demonstration that P is unimportant in vitro is valuable in interpreting the results of experiments in vivo, where P is expected to have a much greater influence on biological response.

Structure-activity relationships in the development of hypoxic cell radiosensitizers. II. Cytotoxicity and therapeutic ratio

This paper describes measurements of the aerobic cytotoxicity of 42 nitroaromatic and nitroheterocyclic compounds towards Chinese Hamster cells in vitro. The results of acute and chronic exposure were quantified, and the concentration C required to achieve a standard response estimated. Fitting the data to an equation of the form - log C = b0 + b1E, where E is the one-electron reduction potential, explained 47 and 71 per cent of the variance in the acute and chronic aerobic cytotoxicity respectively. The addition of further terms to the equation, quantifying partition properties, was not statistically significant. The coefficient b1 was similar for both acute and chronic exposure; the dependence of both cytotoxicity and radiosensitization efficiency on reduction potential was also similar. A therapeutic ratio derived from these in vitro measurements showed no dependence on redox or partition properties. The insensitivity of cytotoxicity and radiosensitization properties to variations in molecular structure, other than those which influence redox behaviour, offers exceptional flexibility in developing compounds of improved therapeutic ratio.