Uptake of copper and lead by a metaltolerant isopod Asellus meridianus Rac.

SUMMARY. Asellus meridianus from sites on the rivers Hayle and Gannel accumulates both copper and lead from experimental solutions: tolerant animals also accumulate copper and lead from metal-enriched food. Copper-tolerant animals accumulated up to 6.8 μg mg⁻¹ copper after feeding on a copper-enriched diet for 12 days whereas non-tolerant animals showed no evidence of copper accumulation from food and no survivors remained after 8 days. Lead-tolerant animals accumulated up to 28 μg mg⁻¹ lead during a 14-day exposure to a lead diet: non-tolerant animals showed no accumulation of lead from food and no live animals remained after 10 days.
A marked difference in the storage forms of copper is observed in the hepatopancreas of copper-tolerant isopods, as compared with non-tolerant animals, when samples are taken from natural populations.     

Egg laying, maternal care and development of young in the scolopendromorph centipede, Cormocephalus anceps anceps Porat

The methods used to observe the construction of the brood chamber and rearing of the young by the female Cormocephalus anceps are described. The period of egg laying and the maternal care, essential for the survival of both eggs and brood, were observed and the behaviour of the female during this time is recorded. Two broods were successfully reared to first year adolescent stages in the laboratory. The two embryonic and three adolescent stages are briefly described and their developmental times recorded. Subsequent stages of development are noted by increase in size until sexual maturity is attained in the second year. The length of life and number of broods per female remains to be investigated.     

Effects of short chain fatty acids on seedlings

Abstract. Primary roots of lettuce show no appreciable diminution of sensitivity of SCFA between 24 and 72 h, so it is likely that all actively growing primary roots are susceptible to inhibition by SCFA. While roots do not recover from long exposures to high concentrations of SCFA, partial recovery is seen following exposure to intermediate levels.
SCFA inhibit elongation of lettuce and turnip hypocotyls as well as roots. However, higher concentrations are required to produce a given inhibition of hypocotyl. In contrast with the inhibition of roots, inhibition of shoots is markedly dependent on the chain length of the fatty acid. Thus, either access to sites of action or action at the sites differs between shoots and roots of the same seedling plants.     

Ontogeny of Glucocorticoid Binding in Rodent Brain

Neonatal treatment with corticosterone can differentially andpersistently reduce either the basal level of plasma corticosteroneor the amplitude of the adult diurnal rhythm in the rat dependingon the age at which exposure to the steroid occurs. This alterationof basal secretion by hormonal manipulation during the firstpostnatal week may be related to the high levels of corticosteronefound in pituitary cell nuclei following exposure of the immaturerat to exogenous corticoid. The ontogenetic course of cytosolbinding in the pituitary suggests a mechanism by which suchvulnerability may occur. The hypothalamus was the only brain region found to have a constantlevel of cell nuclear binding throughout development, althoughit closely resembles the brain as a whole with regard to thedevelopment of cytosol binding sites. The significant postnatalneurogenesis of the hippocampus is reflected in a large postnatalrise in both cytosol and nuclear binding of corticosterone.This increase would appear to be due in part to a delay in bindingcompetence by the pyramidal and granule cells of the hippocampus.The autoradiographic evidence indicates that in the immaturerat the retention of steroid by hippocampal pyramidal cellscorrelates directly with the embryonic age of the neuron. Likewise,the oldest granule cells are the most heavily labelled granulecells in the dentate gyrus, while newly arrived cells do notconcentrate corticosterone. This would suggest that an eventin cellular differentiation occurs sometime after the cellsare "in position," which permits the binding of glucocorticoidsby these hippocampal neurons.     

In Vivo Incorporation of a Polyunsaturated Fatty Acid into the sn-C-1 and sn-C-2 Positions of Tetrahymena Glycerophospholipids1

The glycerophospholipids of the protozoon Tetrahymena pyriformis W are unique in that the polyunsaturated fatty acid γ-linolenate (18:3Δ^6,9,12) is a major component of both the sn-C-1 and sn-C-2 positions. Tetrahymena were incubated with [1-¹⁴C]γ-linolenate. The positional distribution of the radiolabeled fatty acid in the three major glycerophospholipids was determined. [1-¹⁴C]γ-linolenate was found at both carbons of the three lipids, in general agreement with the mass distribution of γ-linolenate, except for markedly greater labeling at the sn-C-2 position of phosphatidylcholine. We hypothesize that an acyltransferase exists in Tetrahymena that can esterify γ-linolenate at both carbons during glycerophospholipid biosynthesis.     

Cytology of two species of winged bean, Psophocarpus tetragonolobus (L.) DC. and P. scandens (Endl.) Verde. (Leguminosae)

Karyotype morphology of Psophocarpus tetragonolobus and P. scandens is described and the behaviour of chromosomes at meiosis discussed. Both species have a chromosome number of 2n = 18 and similar karyotypes of a sort unusual within the Phaseolinae. Differences between the species in detailed morphology of the chromosomes agree with data from external morphology, palynology and crossability in indicating that P. scandens cannot be the immediate wild ancestor of domesticated P. tetragonolobus . Study of meiotic chromosomes and analysis of qualitative and quantitative variation in Papua New Guinean P. tetragonolobus suggest that there are few restrictions to recombination other than those imposed by predominant self-pollination, The bearing of these data on the taxonomic relationships of Psophocarpus and on chromosomal evolution within the Phaseolinae is discussed.     

Host range, purification and some properties of a new ilarvirus from Humulus japonicus

In 1986, during routine quarantine testing, an apparently undescribed virus was isolated from two of 21 plants of Humulus japonicus grown from seed imported into the UK from Beijing, Peoples Republic of China. The virus, for which we propose the name humulus japonicus virus (HJV), was transmitted mechanically to a wide range of herbaceous plants. No symptoms were seen in virus-infected H. japonicus plants. HJV infected, but did not become systemic, in the cultivated hop (Humulus lupulus) under our conditions although it has been detected serologically in both species of Humulus growing near Beijing. The virus was transmitted through seed of Chenopodium quinoa and was also associated externally with pollen of that species, but no pollen-transmission tests were conducted. HJV was easily purified. Virus particles comprised a single polypeptide (mol. wt c. 26 350) and four RNA molecules (mol. wts 1.31, 1.05, 0.75 and 0.39×10⁶). The three larger mol. wt RNAs were not infective in the absence of the smallest RNA. The particles were quasi-isometric and variable in size. Purified preparations of particles formed four bands in sucrose density gradients but (after fixing with formaldehyde) only a single band (with a density of 1.364 g/ml) in caesium chloride isopycnic gradients. These properties are similar to those of ilarviruses, and HJV was very distantly related serologically to prunus necrotic ringspot ilarvirus. We suggest, therefore, that HJV be regarded as a new member of the ilarvirus group. All known infected plants of H. japonicus at the site of introduction have been destroyed and the virus has probably been eliminated from there. Testing is continuing to confirm this.     

Linkage between sexual and asexual lineages: genome evolution in Bacillus stick insects

The sexually reproducing stick insects Bacillus rossius and B. grandii are sharply differentiated in terms of allozyme gene alleles; B. atticus is a polyclonal automictic parthenogen sister to B. grandii grandii. Although well differentiated for coding genes, these hybridize to produce diploid (B. whitei=rossius/grandii) or triploid (B. lynceorum=rossius/grandii/atticus) clonal forms which reproduce apomictically. Allozyme analyses of unisexual Bacillus clearly establish their relationships from bisexual ancestor species as does the existence in all of them of several clones (especially in B. atticus) whose egg maturation allows regular recombination to occur. Bacillus taxa share the Bag320 satellite DNA family within different reproductive frameworks, allowing satellite variant homogenization to be uncoupled from fixation. The nested analysis of monomers reveals different patterns of sequence diversity: sexual reproduction includes both homogenization and variant fixation, whereas the slowing of molecular turnover processes and the absence of syngamy in the parthenogens realizes a similar range of sequence diversity at the level of the individual and supra‐individual, but with no fixation. On the other hand, the actual values of sequence diversity appear mostly linked to species traits – range size, copy number of repeats, number of hybrid crosses – and possibly transposon activity, rather than to the reproductive mode. In addition, the mitochondrial genome reveals a comparable level of cox2 sequence variability in sexual and parthenogenetic taxa, thus adding to clonal variability. From Bacillus and other stick insect complexes, an overall picture of genomic diversification of parthenogens is therefore beginning to emerge. To define those animals that reproduce by non‐canonical sexual modes (i.e. parthenogenesis, hybridogenesis), but make use of egg and meiotic mechanisms, the term meta‐sexual is proposed. © 2003 The Linnean Society of London. Biological Journal of the Linnean Society, 2003, 79 , 137–150.