Venom Alkaloid Chemistry of Australian Species of the Monomorium rothsteini Complex,with Particular Reference to Taxonomic Implications

A comparison of the morphology and of the venom alkaloids of the Australian Monomorium rothsteini complex was undertaken. These ants were collected in Australia from western New South Wales, northern Queensland, and northern Northern Territory. Additionally, samples from the M. sordidum complex and M. carinatum complex were examined. Thirteen previously described trans‐2,5‐dialkylpyrrolidines were detected in these ants, along with the novel trans‐2‐ethyl‐5‐[(Z)‐tridec‐4‐enyl]pyrrolidine ( 6 ), whose structure was confirmed by synthesis. The extent of variation and the correlation observed in the morphology and venom chemistry in M. rothsteini samples is very strongly indicative of multiple species in this complex. The presence and location of the C?C bond in 6 reinforces the remarkable structural similarity of the 2‐ethylpyrrolidines in these Monomorium species to the 2‐methylpiperidines in the venoms of many Solenopsis species, and may represent convergent evolution of biosynthetic processes in different genera of solenopsidine ants.     

Reduced MHC variation in a threatened tuatara species

The relationship between neutral and adaptive genetic diversity is important to understand in assessing the implications of a population bottleneck. Fitness-related genes, such as those of the major histocompatibility complex (MHC), may be influenced by selection, and so retain diversity even when it is lost at neutral markers. We measured MHC class I variation in an archaic reptile species Sphenodon guntheri [North Brother Island (NBI) tuatara], which naturally occurs on one 4 ha island in Cook Strait, New Zealand, and has low levels of microsatellite diversity. MHC variation in S. guntheri was compared with microsatellite DNA variation, and with MHC variation in a large population of Sphenodon punctatus (Cook Strait tuatara) on Stephens Island. The NBI population shows significantly decreased levels of genetic diversity compared with the Stephens Island population. Only three different MHC sequences and three genotypes were found on NBI, compared with 15 sequences and 21 genotypes in a similar sample size from Stephens Island. Two sequences appear to be unique to the NBI population. The assortment of sequence variants into genotypes suggests strong gametic disequilibrium between two MHC class I loci in S. guntheri , and only two haplotypes that were present in Hardy–Weinberg proportions were identified. MHC diversity in NBI tuatara appears to be largely influenced by genetic drift, consistent with a recent population bottleneck. This may compromise the ability of this population to respond to novel disease threats.     

On the diploidization mechanism of the genus Aegilops: meiotic behaviour of interspecific hybrids

Chromosomal pairing of the three diploid hybrids Aegilops uniaristata × Ae. tauschii (ND), Ae. umbellulata × Ae. tauschii (UD) and Ae. comosa × Ae. uniaristata (MN), and a triploid hybrid Ae. cylindrica × Ae. caudata (DCC), was analyzed by electron microscopy in surface-spread-prophase-I nuclei and compared with light-microscopic observations of metaphase-I cells after C-banding and fluorescence in situhybridization. All hybrids showed extensive synapsis and complex multivalents in which up to 14 chromosomes were involved. In the diploid hybrids most metaphase-I chromosomal associations were between homoeologs, their frequencies being dependent on the relationship between the donor genomes. Despite the different overall bound-arm frequencies displayed by ND and MN hybrids at metaphase-I, chromosomes bearing rDNA sequences showed similar mean cell chromosomal association frequencies. In the triploid hybrid preferential associations involving C genomes were predominant. These observations are discussed in relation to the mechanism of diploidization showed by allotetraploid Aegilops species. Received: 13 January 1999 / Accepted: 12 March 1999     

Metabolism of lysine-chromium complex in Saccharomyces cerevisiae

Saccharomyces cerevisiae which cannot utilize lysine as a sole nitrogen source is shown to metabolize a Lysine 3 Cr³⁺ (1:1) complex synthesized, as a combined nitrogen and carbon source. It induces rapid uptake of lysine and prevents loss of viability, in contrast with free lysine. That complexation with trivalent chromium has the effect of profoundly influencing intracellular distribution and metabolism of the liganded amino acid is demonstrated.     

Structure of Cu2(indomethacin)4 and the reaction with superoxide in aprotic systems

The copper complex of indomethacin (1-(p-chlorobenzoyl)-5-methoxy-2-methyl-indole acetate), a common anti-inflammatory drug, was prepared and characterized. Crystal structure determination revealed the dimeric form of the 1:2 complex, namely Cu₂(indomethacin)₄ · L₂, in the unit cell. Suprisingly, the copper-copper distance (263 pm) was very close to metallic copper (256 pm). The two coordination sites in the copper-copper axis can be readily replaced by superoxide. An intriguing similarity to Cu₂(acetate)₄ was seen.Due to the lipophilic nature of the indomethacin ligand, this copper complex reacted with superoxide in aprotic solvents. The superoxide dismutating activity was successfully demonstrated in Me₂SO/water and acetonitrile/water mixtures using the nitro-blue tetrazolium assay and pulse radiolysis. The second-order rate constant of 6 · 10⁹ M^?1 · s^?1 in strictly aqueous systems dropped only slightly to 1.1 · 10⁹ M^?1 · s^?1 when aprotic solvents were used. This is the fastest rate constant ever observed for a copper-dependent dismutation of superoxide. The KO₂-induced lipid peroxidation in both erythrocytes and liver microsomes was suppressed by 70% in the presence of 1 · 10^?10 mol · ml^?1 of Cu₂(indomethacin)₄. The inhibitory action dropped to 25% when Cu₂Zn₂superoxide dismutase was employed. The formation of copper · indomethacin in rat serum after administration of indomethacin was shown in vitro and in vivo.     

Character displacement in the fighting colours of Hetaerina damselflies

Aggression between species is a seldom-considered but potentially widespread mechanism of character displacement in secondary sexual characters. Based on previous research showing that similarity in wing coloration directly influences interspecific territorial aggression in Hetaerina damselflies, we predicted that wing coloration would show a pattern of character displacement (divergence in sympatry). A geographical survey of four Hetaerina damselfly species in Mexico and Texas showed evidence for character displacement in both species pairs that regularly occurs sympatrically. Hetaerina titia, a species that typically has large black wing spots and small red wing spots, shifted to having even larger black spots and smaller red wing spots at sites where a congener with large red wing spots is numerically dominant (Hetaerina americana or Hetaerina occisa). Hetaerina americana showed the reverse pattern, shifting towards larger red wing spots where H. titia is numerically dominant. This pattern is consistent with the process of agonistic character displacement, but the ontogenetic basis of the shift remains to be demonstrated.     

Electron microscopical studies ofThorea ramosissima (Thoreaceae,Rhodophyta): Taxonomic implications ofThorea pit plug ultrastructure

The thallus ofThorea ramosissima was studied electron microscopically. The cells of the medulla, the cortex and the assimilatory hairs differ not only in size and number of plastids and their equipment with thylakoids but also in cell wall structure, the number of mitochondria and the activity of the Golgi apparatus, with dictyosomes transforming complete cisternae into Golgi vesicles with mucilaginous contents in the outer region of the cortex. The pit connections have plugs with a distinct plate—like (not dome-like) outer cap layer. BecauseT. riekei was reported to have dome-like outer cap layers and because this character was the main reason to place theThoreaceae into theBatrachospermales (Pueschel & Cole 1982),T. riekei was reinvestigated, too. A distinct outer cap could not be detected. The reliability of pit plug structure as a taxonomic character and the taxonomic position ofThorea is discussed.     

A transient species of poly(A)+ RNA detected by a myosin heavy chain cDNA probe in muscle cell culture during terminal differentiation

Primary cell cultures were prepared from breast muscles of 11 day 4 hour-embryonic chicks. Cytoplasmic RNAs were isolated from the cultured cells at various time intervals from day 3 to day 8. A [P32] DNA probe complementary to messenger RNA of myosin heavy chain was used to hybridize with the RNAs after gel electrophoresis. A transient species of polyadenylated RNA with a decreased mobility in electrophoresis was detected during a period of time when contractions of syncytial fibers were first observed.