New Low Molecular Weight Glycopeptide containing Triglucosylcysteine in Human Erythrocyte Membrane

ALTHOUGH protein composition of the erythrocyte membrane has been studied extensively¹, little if anything is known about membrane peptides. Among a variety of chemical agents used for the solubilization of the membrane, solutions of greater than 0.8 M NaCl have been shown to dissolve 50% of membrane proteins^2,3. As we were interested in the composition of the outer surface of the membrane, we have investigated whether lower concentrations of NaCl, which would not cause haemolysis of intact cells, would solubilize certain membrane components.     

Geographic variation in Pemphigus populicaulis (Insecta: Aphididae) in Eastern North America*,†

The geographic variation of 33 morphological characters of the gall-forming aphid Pemphigus populicaulis is studied for 118 localities east of 100^oW longitude. Variation can be partitioned into within-gall, among-gall and among-locality components. Among localities variation ranges from 26 to 54%, being significant for all characters. Variation among galls within localities ranges from 24 to. 56%, that within-galls from 8 to 4796. The design of the study permits computation of character correlation matrices within and among localities. Gall size is correlated with tnorphometric characters only on an interlocality but not on an intralocality basis. Interlocalily correlations are a function of intralocality correlations, confirming earlier predictions. There is little correlation between characters of stem mother and alate morphotypes within localities, whereas among localities such correlation is appreciable. This phenomenon may be caused by aspects ol the environment that vary among localities but remain reasonably constant through the earlv life cycle of the aphid. When subjected to factor analysis both correlation matrices yield four factors. Multiple discriminant analysis of the data set results in five interpretable significant axes. Maps are furnished for characters representing the independent dimensions of variation and for discriminant function scores. The patterns of variation can be shown to be significantly nonrandom by Mantel's test and by spatial autocorrelation analysis. All variables are significantly positively autocorrelated at 200 km, many at 400 km and a few at 600 km; few general statements can be made about significant autocorrelations at higher distances. The positive autocorrelation at relatively short distances may be related to the pool of clones from which the genotypes of any one locality sample are taken. There are three correlogram patterns that can be associated with four clusters of variation patterns of characters. The separate patterns presumably cannot be explained by a single microevolutionary process.     

Characterization of simple sequence repeat markers derived in silico from Brassica rapa bacterial artificial chromosome sequences and their application in Brassica napus

A collaborative Brassica rapa genome sequencing project is currently in progress to aid the identification of agronomically important traits in Brassica species. As an initial stage, the ends of over 110 000 bacterial artificial chromosome clones were sequenced and mined for simple sequence repeats (SSRs). We present the characterization of 40 of these SSRs and their application in Brassica napus. The markers were screened against six Brassica species and Arabidopsis, and demonstrated reliable amplification, genome specificity, cross‐amplification and significant polymorphism. These SSRs will be useful for genetic analysis of Brassica germplasm.     

Nucleotide Variation in the Cytidine Triphosphate Synthetase Gene of Giardia duodenalis

ABSTRACT. The cytidine triphosphate synthetase genes from three diverse strains of Giardia duodenalis have been sequenced and found to vary significantly from one another. The isolates were chosen as representatives of three demes as determined by several criteria including divergence in the rDNA repeat unit. Inserts in the genes and protein are conserved in length but are the most divergent regions among the three sequences examined. Variation in the rest of the gene occurs primarily in the third base position resulting in many silent mutations. One of the isolates (1709) was found to contain two genes with high sequence homology.     

Hydrogenosomes of Laboratory‐Induced Metronidazole‐Resistant Trichomonas vaginalis Lines are Downsized While Those from Clinically Metronidazole‐Resistant Isolates Are Not

ABSTRACT. Trichomonas vaginalis is the most common sexually transmitted protozoan in the world and its resistance to metronidazole is increasing. The purpose of this study was to demonstrate that clinical metronidazole resistance in T. vaginalis does not occur via the same mechanism as laboratory‐induced metronidazole resistance—that is, via hydrogenosome down sizing. Ultrathin sections of this parasite were examined using transmission electron microscopy and the size and area of the cell and hydrogenosomes were compared between drug‐resistant laboratory lines and clinically resistant isolates. Clinical metronidazole‐resistant T. vaginalis had similar‐sized hydrogenosomes as a metronidazole‐sensitive isolate. Inducing metronidazole resistance in both of these isolates caused down sizing of hydrogenosomes. Inducing toyocamycin resistance did not cause any ultrastructural changes to the cell or to the hydrogenosome. No correlation between hydrogenosome number and the drug‐resistant status of T. vaginalis isolates and lines was observed. This report demonstrates that clinical metronidazole resistance is not associated with down‐sized hydrogenosomes, thus indicating that an alternative resistance mechanism is used by T. vaginalis.     

Consumer-specific responses to riverine subsidy pulses in a riparian arthropod assemblage

1. Aquatic resource fluxes from streams can provide significant subsidies for riparian consumers. Because aquatic resource fluxes can be highly variable in space and time, the subsidy efficiency (i.e. transfer to the recipient food web) is controlled by the short‐term aggregative response of riparian consumers. 2. Field manipulations of stream‐derived invertebrate prey subsidies were used to examine specific aggregative responses of ground‐dwelling arthropods to riverine subsidy pulses in a braided‐river (Tagliamento River, NE Italy). Subsidy manipulation comprised short‐term reductions of natural stream‐derived subsidies and increased subsidies of stream‐derived invertebrate prey during four seasons. 3. We hypothesised that specific aggregative responses of riparian arthropods depend on their specialisation on aquatic insects which was inferred from stable isotope analysis. Natural riverine subsidy sources including aquatic insect emergence and surface‐drifting organisms were quantified. 4. Arthropods responded significantly with a reduction in abundance by 51%, at reduced subsidies and an increase by 110% at increased subsidies, when averaged over all seasons. Different arthropod taxa responded differently to subsidy manipulations in relation to their specialisation on aquatic subsidies: ground beetles with a diet consisting predominantly of aquatic insects responded only to subsidy reductions, indicating that their local abundance was not limited by natural stream‐derived subsidies; lycosid spiders with a partly aquatic diet showed no significant response; and ants, although relying on a terrestrial diet, responded positively to added stream‐derived invertebrate prey, indicating that stranding of surface‐drifting terrestrial invertebrates represented an important subsidy pathway. 5. Ground beetles and lycosid spiders were seasonally separated in their use of aquatic subsidies. Results indicate that the life‐history characteristics of riparian consumers can control the subsidy efficiency for the recipient community. By the effective uptake of pulsed riverine‐derived subsidies, riparian arthropods can enhance the transfer of riverine food sources to the riparian food web.     

Transmission of Spiroplasma citri by the aster leafhopper Macrosteles fascifrons (Homoptera: Cicadellidae)

The aster leafhopper (Macrosteles fascifrons), injected with an isolate of Spiroplasma citri obtained from brittle root-diseased horseradish (Armoracia rusticana), transmitted the spiroplasma to horseradish and China aster (Callistephus chinensis.) After feeding on plants infected with S. citri, M. fascifrons transmitted the spiroplasma from aster to aster and horseradish, from yellow rocket (Barbarea vulgaris) to aster, and from turnip (Brassica rapa) to turnip. Symptoms in infected horseradish were chlorosis and stunting of newly formed leaves, discoloration of root phloem, and reduced plant growth typical of brittle root disease. Chlorosis, stunting, and asymmetry of young leaves occurred in affected aster and turnip. Flowers of infected aster were small and pale in colour and occasionally showed other symptoms including asymmetry, petal distortion, or light green petals. Spiroplasmas were isolated from all plants showing symptoms. Transmission rates by M. fascifrons which acquired S. citri by feeding on infected plants were very low, but injected leafhoppers transmitted more frequently. This is the first report of the transmission of S. citri from diseased to healthy plants by M. fascifrons.