An adaptive explanation for geographically structured allozyme variation inDichroplus elongatus (Orthoptera: Acrididae)

Previous studies on allozyme variation in five populations of the grasshopperDichroplus elongatus along a geographical gradient in Argentina revealed a significant degree of population structuring and a significant association between one of the loci (Aat-1) and latitude. As this could not be entirely explained by historical factors, the possible adaptive significance of this locus or loci in linkage disequilibrium was investigated in the present study, with an emphasis on the role of environmental variables correlated with latitude. The present paper reports a study of the geographical organization of allozyme diversity over a wider range of the distribution ofD. elongatus. The relation of allelic frequencies with geographic climatic variables was analysed. We have found (i) that different loci (Aat-1 andPep-1) covary significantly with different variables, (ii) discordance between genetic and geographical distances, (iii) copious gene flow that would mask allelic frequency differences due solely to genetic drift, (iv) and temporal stability of the gradient found. The results suggest that causes other than drift and migration may explain the observed directional patterns of variation inD. elongatus.     

Cadmium and zinc in plants and soil solutions from contaminated soils

In an experiment using ten heavy metal-contaminated soils from six European countries, soil solution was sampled by water displacement before and after the growth of radish. Concentrations of Cd, Zn and other elements in solution (K, Ca, Mg, Mn) generally decreased during plant growth, probably because of uptake by plants and the subsequent redistribution of ions onto soil exchange sites at lower ionic strength. Speciation analysis by a resin exchange method showed that most Cd and Zn in non-rhizosphere solutions was present as Cd2+ and Zn2+, respectively. The proportion of free ions was slightly lower in rhizosphere solutions, mainly due to an increase in dissolved organic carbon during plant growth. Solution pH increased during plant growth, although the bulk soil pH generally remained constant. Cd concentrations in leaves and tubers were more closely correlated with their total or free ionic concentrations in rhizosphere solutions (adjusted R2 0.90) than with their concentrations in soils (adj. R2 0.79). Cd concentrations in non-rhizosphere solutions were only poorly correlated with Cd concentrations in leaves and tubers. In contrast to Cd, there were no soil parameters that individually predicted Zn concentrations in leaves and tubers closely. However, multiple correlation analysis (including Zn concentrations in rhizosphere solutions and in bulk soils) closely predicted Zn concentrations in leaves and tubers (adj. R2 = 0.85 and 0.70, respectively). This suggests that the great variability among soils in the solubility of Zn affected the rate of release of Zn into solution, and thus Zn uptake. There was no such effect for Cd, for which solubility varied much less. Furthermore, the plants may have partly controlled Zn uptake, as they took up relatively less at high solution concentrations of Zn.Free ionic concentrations in soil solution did not predict concentrations of Cd or Zn in plants better than their total concentrations in solution. This suggests that with these soils, analysis of Cd and Zn speciation is of little practical importance when their bioavailability is assessed.     

Hepatic myelolipoma in two Goeldi's monkeys from South America held captive

Two cases of hepatic myelolipoma in Goeldi's monkeys from South America are described. One was a female evaluated due progressive abdominal distension. Ultrasound and computed tomography detected hepatic mass. Partial hepatectomy was performed, but the monkey died after surgery. Case 2 was a male that died suddenly, showing non‐specific clinical signs.     

A New Bacterial Agglutinin from Soybean: I. ISOLATION, PARTIAL PURIFICATION, AND CHARACTERIZATION

A new bacterial agglutinin was isolated from seeds of the soybean cultivar Clark. Purification was carried out by ammonium sulfate precipitation and ion-exchange chromatography. The agglutinin is a heat-labile glycoprotein most active at pH 4.0. Addition of Ca²⁺, Mn²⁺ and Mg²⁺ did not enhance the agglutinating activity of this glycoprotein. Gel electrophoresis in the presence of sodium dodecyl sulfate showed that the agglutinin is composed of two subunits of approximately 50,000 daltons each. In the undissociated state, it agglutinates Xanthomonas phaseoli var. sojensis, the causal agent of bacterial pustule disease of soybean, at concentrations as low as 10 micrograms protein per milliliter but has no hemagglutinating activity. The agglutinin could be distinguished from previously reported soybean lectins on the basis of solubility in ammonium sulfate, lack of hemagglutinating activity, molecular weight, hapten specificity, and immunological determinants.     

High-performance liquid chromatographic mapping and structural characterization of neurophysin isoforms

Both ion-exchange and reverse-phase HPLC protocols for micromapping of neurophysins have been examined and the structural relationships among the major isoforms identified in the maps have been characterized. Reverse-phase HPLC was found to be especially useful for obtaining fingerprints of the isoforms within each of the two major families of neurophysins, I (oxytocin-related) and II (vasopressin-related), for both bovine and human neurophysins from posterior pituitary sources. From fractionation of the bovine proteins on octylsilyl columns, at least four neurophysins I were identified, one of which corresponds to the intact sequence of 93 residues and three of which vary from the parent by various degrees of carboxyl-terminal truncation. For bovine neurophysin II, two isoforms were identified in the reverse-phase HPLC maps, both of 95 residues, which vary from one another by the residue, either Ile or Val, at position 89. Isoforms were also detected for human neurophysins, including a carboxyl-terminal truncated form of human neurophysin II. All of the major neurophysin isoforms and several of the minor forms were shown to be functionally active as expressed by their binding to peptide ligand affinity matrices. Reverse-phase HPLC mapping on the octylsilyl matrix allowed neurophysin fingerprinting of crude tissue extracts by providing a narrow "window" within which the neurophysins elute but many other polypeptides expected to be present are excluded. The reverse phase HPLC method provides a useful way to obtain isolated neurophysin isoforms for physicochemical characterizations now usually carried out with mixtures of isoforms obtained by ion-exchange chromatography. The method also has characteristics amenable both for high-sensitivity fingerprinting of neurophysin isoforms, from different species and anatomical sources, and as a prelude to microstructural and -functional characterization of the isoforms so isolated.     

Long-term effects of ungulates on phytophagous insects

Abstract.  1. Most plants interact with a diverse suite of herbivores, allowing the opportunity for the existence of positive and negative interactions between highly dissimilar organisms. However, most studies on herbivorous interactions have been performed under the assumption that they occur mainly between similar species. Consequently, ecologists are still far from a full understanding of the ecological factors that determine insect population dynamics.
2. In this study, a 7-year field experiment was conducted that manipulated the presence of ungulates to evaluate their effects on the abundance, attack rate, and survival of four guilds of co-occurring herbivorous insects living on the same host plant: seed predators, stem borers, gall makers and sap suckers. These four guilds differed in habits and behaviour, the first three being sessile and endophytic and the last being free-living.
3. This study shows that the abundance of all four guilds was negatively affected by ungulates. However, the effect on attack rate differed among guilds, as mammals do not affect the seed predator attack rate. Ungulates also differentially affected insect survival, ingesting only seed predators and gall makers.
4. In summary, this study suggests that diverse mechanisms may affect different insect guilds in different ways. Therefore, competition between disparate herbivores appears to be complex and can be provoked by multiple mechanisms.     

Antisense RNA decreases AP33 gene expression and cytoadherence by <Emphasis Type="Italic">T. vaginalis</Emphasis>

Background  

Host parasitism by Trichomonas vaginalis is complex. Adherence to vaginal epithelial cells (VECs) is mediated by surface proteins. We showed before that antisense down-regulation of expression of adhesin AP65 decreased amounts of protein, which lowered levels of T. vaginalis adherence to VECs. We now perform antisense down-regulation of expression of the ap33 gene to evaluate and confirm a role for AP33 in adherence by T. vaginalis. We also used an established transfection system for heterologous expression of AP33 in T. foetus as an additional confirmatory approach.