The sperm attractant ofHormosira banksii (Phaeophyceae,Fucales), a seaweed common to Australia and New Zealand

Summary Hormosira banksii is a taxonomically isolated brown seaweed endemic to Australia and New Zealand. The sperm attractant of this species has been isolated and identified as trans-1-vinyl-2-(1E, 3Z-hexadienyl)-cyclopropane (I) (hormosirene).Hormosira is the first organism in which a cyclopropane derivative has been found to act as a hormone in sexual reproduction. The implication of this finding in relation to phylogeny and phytogeography is discussed.Acknowledgment. A substantial part of this work was supported by Deutsche Forschungsgemeinschaft (DFG).     

Instar-specific defensive secretions of stink bugs (Heteroptera: Pentatomidae)

Defensive secretions (allomones) from first-instar nymphs of stink bugs in the subfamily Pentatominae contain (E)-4-oxo-2-decenal as a major constituent, whereas this compound is absent from later instars. In contrast, first instars ofEdessa meditabunda (Edessinae) produce allomones like those of later instars. The C₆ and C₈ (E)-4-oxo-2-alkenals are common, characteristic exocrine compounds of nymphal and adult Heteroptera, but (E)-4-oxo-2-decenal is previously unknown as a major natural product for which a biological role has yet to be established.     

Is ATP synthesized by a vacuolar-ATPase in the extremely halophilic bacteria?

The proton-dependent synthesis of ATP was demonstrated in representative members of the generaHalobacterium, Haloarcula, andHaloferax. In all cases, synthesis was not inhibited by nitrate or N-ethylmaleimide, inhibitors of the vacuolar-like ATPase found in Archaea, but was affected by azide, an inhibitor of F₀F₁-ATP syntheses. These observations extend the earlier observations withHalobacterium saccharovorum and suggest that ATP synthesis in these organisms is brought about by an F₀F₁-APT synthase.     

The C4-dicarboxylate transport system ofRhizobium meliloti and its role in nitrogen fixation during symbiosis with alfalfa (Medicago sativa)

TheRhizobium meliloti C₄-dicarboxylate transport (Dct) system is essential for an effective symbiosis with alfalfa plants. C₄-dicarboxylates are the major carbon source taken up by bacteroids. Genetic analysis of Dct^– mutant strains led to the isolation of thedct carrier genedctA and the regulatory genesdctB anddctD. The carrier genedctA is regulated in free-living cells by the alternative sigma factor RpoN and the two-component regulatory system DctB/D. In addition, DctA is involved in its own regulation, possibly by interacting with DctB. In bacteroids, besides the DctB/DctD system an additional symbiotic activator is thought to be involved indctA expression. Further regulation ofdctA in the free-living state is reflected by diauxic growth of rhizobia, with succinate being the preferred carbon source. The tight coupling of C₄-dicarboxylate transport and nitrogen fixation is revealed by a reduced level of C₄-dicarboxylate transport in nitrogenase negative bacteroids.     

A reinvestigation of the chemistry of the Dufours gland of the formicine ant,Anoplolepis custodiens

The components of individual Dufours glands excised fromAnoplolepis custodiens workers were analysed by GC-MS. In addition to then-alkanes andn-alkenes previously reported² in these glands, primary alcohols (C₁₉-C₂₂), secondary alcohols (C₂₀-C₂₃), 2-ketones (C₂₀-C₂₃) and possibly carboxylate ethyl esters (C₁₉ and C₂₁) were identified as components of these glands. It seems possible that these high-boiling compounds are used by the workers in laying trails on the hot sandy surfaces of their characteristic habitat and in lining of the inner walls of nests, but no standard compounds have been available to us for any behavioral studies.     

Prostaglandin (15S)-PGA2 derivatives in the gorgonianPlexaura homomalla (Esper), formakükenthali Moser

Summary The lipid fraction, 17%, of air-driedPlexaura homomalla formakükenthali, collected in the Caribbean at Puerto Rico, yielded 50% of its weight as the mammalian prostaglandin (15S)-PGA₂ methyl ester. The freeze-dried gorgonian yielded (15S)-PGA₂ largely as the acetate of the methyl ester. (15S)-PGA₂ was also obtained from material collected at St. Croix and at South Caicos. Field observations indicate thatPlexaura kükenthali may be a species separate fromPlexaura homomalla and that it is abundant on some shallow water reefs in the Caribbean. Prostaglandins could not be detected in the lipid fraction of eggs isolated fromPlexaura homomalla (Esper) formahomomalla.Acknowledgments. We gratefully acknowledge support from the Office of Sea Grant, NOAA, Department of Commerce (Grant 047-158-44067), and the use of facilities at the Isla Mayagues Marine Laboratory of the University of Puerto Rico, Mayaguez, the West Indies Laboratory of Fairleigh Dickinson University at St. Croix, U.S.V.I., and the Marine-Biologisch Instituut at Curacao. Special thanks to Dr. F.M. Bayer, Curator, Department of Zoology, National Museum of Natural History-Smithsonian Institution for checking identity of gorgonians used in this study.     

Glycerol monoethers in the scent gland secretions of the western diamondback rattlesnake (Crotalus atrox; Serpentes,Crotalinae)

Summary 1-O-Monoalkylglycerols with C₁₂ to C₂₀ chains were identified in the scent, gland secretions of the western diamondback rattlesnake (Crotalus atrox). This is the first documentation of these compounds in the skin secretions of a reptile.     

Physical characteristics of the cerebral big prothoracicotropic hormone fromManduca sexta

The prothoracicotropic hormones (PTTHs) are cerebral peptides that control insect postembryonic development by stimulating the prothoracic glands to synthesize ecdysteroids. InManduca sexta, the tobacco hornworm, two classes of PTTH are distinguished by their M_r, small (ca. 7 kDa) and big PTTH (ca. 25–30 kDa). Little is known about the physical nature of the PTTHs and this study takes a first step towards defining characteristics of theManduca big PTTH. The neurohormone has a Stokes radius of 2.59 nm and a sedimentation coefficient of 2.76 S. Based on these data, an M_r of 29,443.7 and anf/f ₀ of 1.27 were calculated. Combined, the physical data revealManduca big PTTH is an asymmetrical acidic homodimeric peptide with intra- and intermolecular disulfide bonds.     

Antimalarial drugs: recent advances in molecular determinants of resistance and their clinical significance

Molecular determinants of antimalarial drug resistance are useful and informative tools that complement phenotypic assays for drug resistance. They also guide the design of strategies to circumvent such resistance once it has reached levels of clinical significance. Established resistance to arylaminoalcohols such as mefloquine and lumefantrine in SE Asia is mediated primarily by gene amplification of the P. falciparum drug transporter, pfmdr1. Single nucleotide polymorphisms in pfmdr1, whether assessed in field isolates or transfection experiments, are associated with changes in IC₅₀ values (to arylaminoalcohols and chloroquine), but not of such magnitude as to influence clinical treatment outcomes. Recently described emerging in vitro resistance to artemisinins in certain areas correlates with mutations in the SERCA-like sequence PfATP6 and supports PfATP6 as a key target for artemisinins. Received 13 February 2006; revised after revision 7 March 2006; accepted 29 March 2006     

Unique evolution of Bivalvia arginine kinases

The clams Pseudocardium, Solen, Corbicula and Ensis possess a unique form of arginine kinase (AK) with a molecular mass of 80 kDa and an unusual two-domain structure, a result of gene duplication and subsequent fusion. These AKs also lack two functionally important amino acid residues, Asp⁶² and Arg¹⁹³, which are strictly conserved in other 40-kDa AKs and are assumed to be key residues for stabilizing the substrate-bound structure. However, these AKs show higher enzyme activity. The cDNA-derived amino acid sequences of 40-kDa AKs from the blood clam Scapharca broughtonii and the oyster Crassostrea gigas were determined. While Asp⁶² and Arg¹⁹³ are conserved in Scapharca AK, these two key residues are replaced by Asn and Lys, respectively, in Crassostrea AK. The native enzyme from Crassostrea and both of the recombinant enzymes show an enzyme activity similar to that of two-domain clam AKs and at least twofold higher than that of other molluskan AKs. Although the replacement of Asp⁶² or Arg¹⁹³ by Gly in normal AK causes a considerable decrease in V_max (6–15% of wild-type enzyme) and a two- to threefold increase in K_m for arginine, the same replacement in Scapharca AK had no pronounced effect on enzyme activity. Together with the observation that bivalve AKs are phylogenetically distinct from other molluskan AKs, these results suggest that bivalve AKs have undergone a unique molecular evolution; the characteristic stabilizing function of residues 62 and 193 has been lost and, consequently, the enzyme shows higher activity than normal.Received 14 October 2003; accepted 1 November 2003     

Chemical defense in the three European species ofCrematogaster ants

The composition of the Dufour gland of the antC. scutellaris has been reinvestigated by gas chromatography/mass spectrometry. The major components of the gland are (2E,5E,12Z)-4-oxoheneicosa-2,5,12-trien-1-ol acetate (1a) its ¹⁴ and ¹⁶ double bond isomers (1b and1c), and the corresponding (Z,Z)-dienes5a and5b, all containing an acetylated C₂₁ chain. The previously proposed structures1d, 1e, and5c, which are based on an homologous acetylated C₂₃ chain, correspond to minor derivatives present in the gland. Traces of acetylated C₁₉ homologs, tentatively identified as1g-1i, have also been found. The Dufour gland contents of the two other EuropeanCrematogaster species have also been studied.C. auberti is very similar toC. scutellaris in producing mainly1a, 1b and1c, together with the same higher and lower homologs, but it lacks the dienic derivatives5, whereasC. sordidula contains essentially the acetylated C₁₉ compounds1g, 1h, and1i, accompanied by acetylated C₁₇ homologs.     

RTA2 is involved in calcineurin-mediated azole resistance and sphingoid long-chain base release in Candida albicans

The calcineurin pathway has been reported to be essential for the development of azole resistance in Candida albicans. The depletion or ectopic over-expression of RTA2 increased or decreased susceptibility of C. albicans to azoles, respectively. CaCl₂- induced activation of the calcineurin pathway in wildtype C. albicans promoted resistance to azoles, while the Ca ²⁺ chelator (EGTA), calcineurin inhibitors (FK506 and cyclosporin A) and the deletion of RTA2 blocked the resistance-promoting effects of CaCl₂. Furthermore, we found that RTA2 was up-regulated in a calcineurin-dependent manner. The depletion of RTA2 also made the cell membrane of C. albicans liable to be destroyed by azoles and RTA2 over-expression attenuated the destroying effects. Finally, the disruption of RTA2 caused an increased accumulation of dihydrosphingosine (DHS), one of the two sphingolipid long-chain bases, by decreasing release of DHS. In conclusion, our findings suggest that RTA2 is involved in calcineurin-mediated azole resistance and sphingoid long-chain base release in C. albicans. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Received 14 July 2008; received after revision 29 August 2008; accepted 16 September 2008     

Selection for class IIMhc heterozygosity by parasites in subterranean mole rats

Mhc organization and polymorphism have previously been studied²⁶ in the four chromosomal species of theSpalax ehrenbergi superspecies in Israel, serologically, and at the DNA, RFLP and sequence levels of class I and class II genes. Here we demonstrate that the observed heterozygosity ofMhc class II genesP₁ with 11 alleles, andQ, with at least 14 alleles, is positively and significantly correlated with infectivities of ectoparasites (gamasid mites)¹⁷ and endoparasites (helminths)¹⁸.Mhc heterozygosity is highest in the most infected area, which is in the most humid-warm region of the superspecies range, or where two zoogeographic regions overlap. We conclude that the evolutionary forces responsible for theMhc class II two-gene polymorphisms include selection for increased heterozygosity as a defense strategy against ecto- and endoparasite infections.     

Structure of victorin C,the major host-selective toxin fromCochliobolus victoriae

Summary The predominant host-selective toxin fromCochliobolus victoriae, victorin C, is a peptide with an apparent mol. wt of 796, representing a cyclic array of the subunits1–6. The structure of the toxin has now been established as in16 through analysis of the degradation products generated by enzymic and non-enzymic partial hydrolysis. The presence of a hydrated aldehydo group requires for victorin C the composition C₃₁H₄₅O₁₃N₆Cl₃ with an amended mol. wt of 814, for which independent experimental support has been secured.     

Age-dependent tolerance toBaculovirus in last larval instars of the codling moth,Cydia pomonella,L., induced either for pupation or for diapause

Summary LD₅₀ values as well as time-dependent parameters of granulosis virus infections were determined at different times during the last larval instar (L₅) of the codling moth,Cydia pomonella L., induced either for pupation or for diapause. A significant increase of tolerance to virus was found in 48-h-old L₅ induced for pupation, and 24 h later in L₅ induced for diapause.     

Drosophila melanogaster does not dealkylate [14C]sitosterol

Summary Drosophila melanogaster was unable to dealkylate and convert [¹⁴C]sitosterol to cholesterol and no evidence was found for conversion of [¹⁴C]desmosterol to cholesterol. Therefore,D. melanogaster is incapable of dealkylating and converting C₂₈ and C₂₉ phytosterols to cholesterol.The authors thank O. J. Duncan III, and H. S. Symonds for technical assistance. Mention of a company name or proprietary product does not imply endorsement by the U.S. Department of Agriculture.     

On the quaternary structure ofKinixys erosa hemoglobins

Summary Kinixys erosa hemoglobins TH₁ and TH_II comigrate on SDS-PAGE with mol. wt of 18 kD. Consistent with their amino acid compositions, trypsinolysis of the succinylated molecules and hydrolysis of cyanylated TH_II yielded five and two fragments respectively.     

Superoxide dismutase activity during the plasmodial life cycle ofPhysarum polycephalum

Summary Superoxide dismutase activity was slow throughout the cell cycle of surface cultures ofPhysarum polycephalum. This activity increased markedly when the organism was induced to spherulate. Glutathione (GSH) and hydrogen peroxide (H₂O₂) concentrations changed very little during the cell cycle. During spherulation GSH decreased; H₂O₂ and the cyanide-resistant respiration of plasmodial homogenates increased.     

Comparative aspects of structure and action of molluscan neuropeptides

A number of neuropeptides were isolated from the ganglia and muscles of molluscs, and their actions were examined. Diverse neuropeptides, in addition to several classical neurotransmitters, were suggested to be involved in the regulation of the anterior byssus retractor muscle ofMytilus. A wide structural variety of members of theMytilus inhibitory peptide family was observed in each of the generaMytilus, Achatina andHelix. Gly-Trp-NH₂, the C-terminal dipeptide fragment of the neuropeptide AGPWamide, showed a more potent action than the parent peptide in all of the muscles examined. Peptides related to some molluscan neuropeptides were found to be distributed interphyletically. Some neuropeptides containing ad-amino acid residue were found inAchatina andMytilus. These aspects of molluscan neuropeptides are thought not to be exceptional.     

Strong mutagenic action of a bipyridylium herbicide in a N2-fixing blue-green alga

Summary The herbicide paraquat (1,1-dimethyl-4,4-bipyridylium ion) has been found to exert a growth inhibitory effect on the N₂-fixing blue-green algaNostoc muscorum in nitrogen-free (N₂) and NO ₃ ^– media, without any apparent inhibitory or stimulatory effect on the heterocyst-forming capacity of the organism. With a dose of paraquat permitting about 20 and 50% survival of this alga a reverse mutation (fromhet ⁺ nif ^– auxotrophy tohet ⁺ nif ⁺ prototrophy), a forward mutation (for L-methionine-DL-sulfoximine [MSO]-resistance), and an auxotrophic mutation (for carbon-auxotrophy through methylamine [MA]-resistance) have been obtained. The toxic and mutagenic effects of this agrochemical have been compared with those of the well known mutagen MNNG (N-methyl-N-nitro-N-nitrosoguanidine) and found to be stronger than those of the latter in each case.The author wishes to thank Mr Girish Nath, Lakshami Chemicals Pvt. Ltd., Phatuha (Patna), India, for providing pure samples of the herbicide for the present investigation. The receipt of financial assistance for this work in the form of a Higher Research Associateship Award to the author from the University Grants Commission, Govt. of India, New Delhi-110002 (Grant No. F/16-51/83), is thankfully acknowledged.