Phylogenetic analysis of the Rhabdocoela (Platyhelminthes) with emphasis on the Neodermata and relatives

Phylogenetic systematic analysis of 24 taxa representing the rhabdocoel platyhelminths, based on a suite of 89 morphological characters, produced two equally parsimonious trees, 181 steps long, with a consistency index (CI) of 0.69 and a rescaled consistency index (RCI) of 0.56, differing only with respect to that portion of the tree containing Umagillidae, Acholadidae, Graffillinae, Pseudograffillinae, Pterastericolidae and Hypoblepharinidae. Our results accommodate all previously proposed sister taxa to the Neodermata in a single clade in which ((Dalyelliidae + Temnocephalida) Typhloplanidae) is the sister group of ((Fecampiidae +  Urastoma ) ( Udonella ((Aspidogastrea + Digenea) (Monogenea (Gyrocotylidea (Amphilinidea + Eucestoda)))))). Bootstrap and jackknife analyses indicate that the groupings of ((Dalyelliidae + Temnocephalida) Typhloplanidae) and of ((Fecampiidae +  Urastoma ) ( Udonella ((Aspidogastrea + Digenea) (Monogenea (Gyrocotylidea (Amphilinidea + Eucestoda)))))) are highly robust, with the latter clade having a CI of 90% and RCI of 82%. Disagreements among previous analyses of these taxa have been due to the influence of missing data for critical characters in key taxa and differences in the taxa analysed, rather than any inherent weakness in the morphological data. Non-phylogenetic systematic approaches to homology assessment and misconceptions regarding phylogenetic systematic methodology are discussed. Recent analyses combining sequence data with a subset of approximately 60% of the morphological characters should be re-assessed using the entire morphological database. Even if Udonella is a monogenean, it is most parsimonious to suggest that the common ancestor of the Neodermata had a vertebrate–arthropod two-host life cycle.     

Excitation of rat hippocampal neurones by the stereoisomers of cis- and trans-1-amino-1,3-cyclopentane dicarboxylate

Intracellular recordings were obtained from rat hippocampal neurons during the microiontophoretic ejection of the stereoisomers of cis- and trans-1-amino-1,3-cyclopentane dicarboxylate into the dendritic region (stratum radiatum) of the impaled cells. L-(+)-cis-1-Amino-1,3-cyclopentane dicarboxylate, D(+)-trans-1-amino-1,3-cyclopentane dicarboxylate, and L-(-)-trans-1-amino-1,3-cyclopentane dicarboxylate all evoked patterns of excitation resembling that elicited by kainate. All of these responses were unaffected by D-(-)-2-amino-5-phosphonovalerate but were antagonized at comparable currents by kynurenate. The excitation produced by D-(-)-cis-1-amino-1,3-cyclopentane dicarboxylate was similar to that evoked by N-methyl-D-aspartate. At low ejection currents a slow depolarization triggered rhythmic burst firing, each burst consisting of a depolarizing shift in membrane potential upon which were superimposed four to five action potentials. These responses were antagonized both by D-(-)-2-amino-5-phosphonovalerate and by kynurenate. The results are discussed with respect to the conformational requirements considered to be necessary for interaction at the kainate and N-methyl-D-aspartate receptors on CA1 pyramidal neurones. It is important to note that the isopropylene side chain of kainate is absent from the 1-amino-1-3-cyclopentane dicarboxylate molecule.     

Two-dimensional nMR study of bleomycin and its zinc(II) complex: reassignment of 13C resonances.

Two-dimensional NMR experiments--one bond 1H-13C correlation spectroscopy and heteronuclear multiple bond correlation spectroscopy, both performed in the reverse detection mode--have been employed to unambiguously assign all of the 13C resonances of the antibiotic bleomycin and its zinc(II) complex. Previous 1H resonance assignments of bleomycin (Chen et al. (1977) Biochemistry 16, 2731-2738) were confirmed on the basis of homonuclear Hartmann-Hahn and homonuclear COSY experiments. The 13C assignments differ substantially from those previously obtained by other investigators (Naganawa et al., (1977) J. Antibiot. 30, 388-396; Dabrowiak et al., (1978) Biochemistry 17, 4090-4096) but are in agreement with those reported by Akkerman et al. (1988) (Magn. Reson. Chem. 26, 793-802). The more recent study employed similar two-dimensional correlation experiments (performed in the direct detection mode) in conjunction with attached proton tests. Their study often required model compound data to identify carbonyls adjacent to aliphatic moieties. Previous 13C NMR studies of the structure, pH titration, and molecular dynamics of bleomycin and its zinc complex have been reinterpreted in terms of the revised assignments.     

Evolutionary conservation of the chromosomal configuration and regulation of amylase genes among eight species of the Drosophila melanogaster species subgroup

Nuclear DNA was extracted from each of the eight species comprising the Drosophila melanogaster species subgroup. Southern hybridization of this DNA by using a molecular probe specific for the alpha-amylase coding region showed that the duplicated structure of the amylase locus, first found in D. melanogaster, is conserved among all species of the melanogaster subgroup. Evidence is also presented for the concerted evolution of the duplicated genes within each species. In addition, it is shown that the glucose repression of amylase gene expression, which has been extensively studied in D. melanogaster, is not confined to this species but occurs in all eight members of the species subgroup. Thus, both the duplicated gene structure and the glucose repression of Drosophila amylase gene activity are stable over extended periods of evolutionary time.      

Parasites and sexual selection: a macroevolutionary perspective.

The Hamilton-Zuk hypothesis postulates a causal link between parasitism and the evolution of epigamic traits by intersexual selection. Oversimplified assumptions about basic parasite biology, ambiguous formulation of the hypothesis, and poor communication between ethologists and parasitologists have hampered its testing. The hypothesis is supported at the microevolutionary level if females show significant preference for lightly or uninfected males, if intensity of infection reflects host resistance to parasites that depress host fitness by causing disease, and if intensity of infection is related to the degree of epigamic development. It must be shown that particular parasites cause disease, that the host population is polymorphic for resistance to infection by those species, and that female hosts are capable of distinguishing male hosts with low parasite loads due to heritable aspects of host resistance from males that are uninfected due to chance. The macroevolutionary prediction of the hypothesis, that species displaying strongly developed epigamic characters should host "more parasites" than species with weakly developed epigamic traits, contradicts the microevolutionary dynamic of the hypothesis, and is too ambiguous. We propose a macroevolutionary prediction based on understanding the evolutionary origin of epigamic traits and the evolutionary origin of each host-parasite association. Associations originating in the ancestor in which the epigamic trait appeared corroborate the hypothesis most strongly; those originating prior to the evolution of the epigamic trait corroborate it weakly; those beginning after the origin of the epigamic trait could not have been involved in the origin and spread of the epigamic trait.     

The influence of dietary lipid supplementation on cardiac beta-adrenergic receptor adenylate cyclase activity in the marmoset monkey

Dietary lipid supplements high in either saturated fat derived from sheep kidney fat or unsaturated fat derived from sunflower seed oil, and a low mixed fat reference diet were fed to marmoset monkeys for 20 months and the effects on cardiac membrane lipid composition, and myocardial catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor binding activity were investigated. For cardiac membranes enriched for beta-adrenergic binding activity, the dietary lipid treatment resulted in small changes in the proportion of saturated to unsaturated fatty acids and substantial changes in the (n - 6) to (n - 3) series of unsaturated fatty acids in the membrane phospholipids. The sheep kidney fat diet increased the cholesterol-to-phospholipid ratio in cardiac membranes in comparison to the other diets. This diet also significantly elevated basal and isoproterenol-, epinephrine- and norepinephrine-stimulated adenylate cyclase activity. The value of the dissociation constant (Kd) and the receptor number (Bmax) for the binding of [125I]ICYP to the beta-adrenergic receptor was significantly reduced in marmosets fed the sheep kidney fat diet. These results suggest that dietary lipids can influence the activity of the beta-adrenergic/adenylate cyclase system of the heart. Modulation of this transmembrane signalling system may be induced by changes in the properties of the associated membrane lipids, particularly by alteration in the membrane cholesterol-to-phospholipid ratio. This effect may be limited to those animal species in which the nature of the dietary fatty acid intake may be influencing cardiac membrane cholesterol homeostasis, which is in agreement with previous results in rats following dietary cholesterol supplementation (McMurchie et al. (1987) Biochim. Biophys. Acta 898, 137-153). ICYP, (-)-iodocyanopindolol.     

Ca2+-dependent depolarization and burst firing of rat CA1 pyramidal neurones induced by N-methyl-D-aspartic acid and quinolinic acid: antagonism by 2-amino-5-phosphonovaleric and kynurenic acids

The excitatory effects of microiontophoretically applied quisqualic (QUIS), N-methyl-D-aspartic (NMDA), and quinolinic (QUIN) acids were investigated using intracellular recording from CAl pyramidal neurones in slices of rat hippocampus. QUIS evoked only simple action potentials superimposed upon a depolarization which attained a clear plateau. When this level had been reached, increased ejecting currents did not produce further depolarization. By contrast, with low currents NMDA and QUIN elicited small membrane depolarizations which triggered bursts of action potentials superimposed upon rhythmically occurring depolarizing shifts. Larger currents caused depolarization which if sufficiently large completely blocked spike activity. Tetrodotoxin (TTX) prevented the spikes evoked by QUIS and the bursts of action potentials seen with NMDA and QUIN, and the rhythmic depolarizing shifts then appeared as broad spikes of up to 50 mV in amplitude. These and the underlying membrane depolarization were blocked by Co2+, by the NMDA antagonist D(-)-2-amino-5-phosphonovaleric acid (DAPV), and by kynurenic acid (KYNU). It thus appears that the depolarization and burst firing of rat CAl pyramidal neurones elicited by NMDA and QUIN are Ca2+ dependent while the actions of QUIS are not.     

Growth of Phytomonas serpens in a Defined Medium; Nutritional Requirements

ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.     

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi

Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.