Effects of willow hybridisation and simulated browsing on the development and survival of the leaf beetle Phratora vitellinae. (73/710)

BACKGROUND: Interspecific hybridisation is common between many plant species and causes rapid changes in a variety of plant characters. This may pose problems for herbivores because changes in recognition characters may be poorly correlated with changes in quality characters. Many studies have examined different systems of hybrids and herbivores in attempts to understand the role of hybridisation in the evolution of plant resistance. The results from different systems are variable. Studies of hybrids between Salix caprea (L., Salicaceae) and S. repens show that they are intermediate between the two parental species in most resistance characters. However, a plants herbivore resistance depends also on its biotic and abiotic environment. Important biotic factors that may influence plant growth and plant chemistry include the interactions between different herbivores that occur through their exploitation of common host plants. Although the effects on plants of previous herbivory are likely to be strongly affected by environmental conditions, they are also species-specific. Damage may therefore have different effects on hybrids than on their parental species, and this could influence the performance of herbivores on pure and hybrid species of plants. To evaluate the effects of hybridisation on insect performance, the development and survival rates of Phratora vitellinae (L. 1758, Coleoptera: Chrysomelidae) larvae on pure S. repens, pure S. caprea and Fl hybrids of the two species was monitored. Further, to examine the effect of herbivorous mammals on the performance of the larvae, plants were damaged to simulate winter foraging by voles or spring leaf stripping by moose. RESULTS: The results show that development rates were highest on S. repens and equally low on S. caprea and the Fl hybrid. In addition, development of the plants treated to simulate mammalian herbivore damage was slower than that of corresponding controls. CONCLUSIONS: The results of this experiment suggest that P. vitellinae has a higher development rate, and thus probably higher performance, on species with high concentrations of phenolic glucosides. Therefore, it would be of adaptive benefit for P. vitellinae females to have an ovipositional preference for S. repens, compared to S. caprea and intermediate preference for Fl hybrids. The faster development observed on S. repens supports the hypothesis that P. vitellinae obtains additional adaptive benefits from phenolic glucosides beyond protection against predators. Therefore, it is important to consider further factors, such as damage caused by other herbivores, when studying this hybrid complex.  (+info)

Expression of the nucleoprotein of the Puumala virus from the recombinant Semliki Forest virus replicon: characterization and use as a potential diagnostic tool. (74/710)

Puumala virus (Bunyaviridae family, Hantavirus genus) causes a mild form of hemorrhagic fever with renal syndrome (HFRS) called nephropathia epidemica in northern and central Europe. Serological tests are used for diagnosis, but antigen production is difficult because the virus grows poorly in tissue culture. We expressed the N protein (nucleoprotein) of Puumala virus via the Semliki Forest virus (SFV) replicon in mammalian cells and compared its antigenic properties with those of the native antigen derived from Puumala virus-infected cells. Detection of immunoglobulin G or immunoglobulin M by enzyme-linked immunosorbent assay (ELISA), micro -capture ELISA, and indirect immunofluorescence assay was (at least) as effective with the recombinant antigen as with the native antigen when HFRS patient sera or organ washes from wild rodents were tested. No nonspecific reaction was observed. Thus, the SFV-expressed N protein of Puumala virus appears as a valid antigen, specific and sensitive for serological investigations.  (+info)

Oxytocin receptor distribution reflects social organization in monogamous and polygamous voles. (75/710)

The neuropeptide oxytocin has been implicated in the mediation of several forms of affiliative behavior including parental care, grooming, and sex behavior. Here we demonstrate that species from the genus Microtus (voles) selected for differences in social affiliation show contrasting patterns of oxytocin receptor expression in brain. By in vitro receptor autoradiography with an iodinated oxytocin analogue, specific binding to brain oxytocin receptors was observed in both the monogamous prairie vole (Microtus ochrogaster) and the polygamous montane vole (Microtus montanus). In the prairie vole, oxytocin receptor density was highest in the prelimbic cortex, bed nucleus of the stria terminalis, nucleus accumbens, midline nuclei of the thalamus, and the lateral aspects of the amygdala. These brain areas showed little binding in the montane vole, in which oxytocin receptors were localized to the lateral septum, ventromedial nucleus of the hypothalamus, and cortical nucleus of the amygdala. Similar differences in brain oxytocin receptor distribution were observed in two additional species, the monogamous pine vole (Microtus pinetorum) and the polygamous meadow vole (Microtus pennsylvanicus). Receptor distributions for two other neurotransmitter systems implicated in the mediation of social behavior, benzodiazepines, and mu opioids did not show comparable species differences. Furthermore, in the montane vole, which shows little affiliative behavior except during the postpartum period, brain oxytocin receptor distribution changed within 24 hr of parturition, concurrent with the onset of maternal behavior. We suggest that variable expression of the oxytocin receptor in brain may be an important mechanism in evolution of species-typical differences in social bonding and affiliative behavior.  (+info)

Macrophage activation and histopathological findings in Calomys callosus and Swiss mice infected with several strains of Trypanosoma cruzi. (76/710)

Peritoneal macrophage activation as measured by H2O2 release and histopathology was compared between Swiss mice and Calomys callosus, a wild rodent, reservoir of Trypanosoma cruzi, during the course of infection with four strains of this parasite. In mice F and Y strain infections result in high parasitemia and mortality while with silvatic strains Costalimai and M226 parasitemia is sub-patent, with very low mortality. H2O2 release peaked at 33.6 and 59 nM/2 x 10(6) cells for strains Y and F, respectively, 48 and 50 nM/2 x 10(6) for strains Costalimai and M226, at different days after infection. Histopathological findings of myositis, myocarditis, necrotizing arteritis and absence of macrophage parasitism were found for strains F and Costalimai. Y strain infection presented moderate myocarditis and myositis, with parasites multiplying within macrophages. In C. callosus all four strains resulted in patent parasitemia which was eventually overcome, with scarce mortality. H2O2 release for strains Y and F was comparable to that of mice-peaks of 27 and 53 nM/2 x 10(6) cells, with lower values for strains Costalimai and M226-16.5 and 4.6 nM/2 x 10(6) cells, respectively. Histopathological lesions with Y and F strain injected animals were comparable to those of mice at the onset of infections; they subsided completely at the later stages with Y strain and partially with F strain infected C. callosus. In Costalimai infected C. callosus practically no histopathological alterations were observed.  (+info)

Natural infection of wild rodents by Schistosoma mansoni. Parasitological aspects. (77/710)

The evaluation of the role of rodents as natural hosts of Schistosoma mansoni was studied at the Pamparrao Valley, Sumidouro, RJ, with monthly captures and examination of the animals. Twenty-three Nectomys squamipes and 9 Akodon arviculoides with a schistosomal infection rate of 56.5% and 22.2% respectively eliminated a great majority of viable eggs. With a strain isolated from one of the naturally infected N. squamipes, we infected 75% of simpatric Biomphalaria glabrata and in 100% of albino Mus musculus mice. The adult worms, isolated from N. squamipes after perfusion were located mainly in the liver (91.5%) and the mesenteric veins (8.5%). The male/female proportion was of 2:1. The eggs were distributed on small intestine segments (proximal, medial and distal portions) and the large intestine without any significant differences in egg concentration of these segments. In A. arviculoides, the few eggs eliminated by the stools were viable and there was little egg retention on intestinal segments. Considering the ease to complete S. mansoni biological cycle in the Nectomys/Biomphalaria/Nectomys system under laboratory conditions, probably the same is likely to occur in natural conditions. In support to this hypothesis there are also the facts that human mansonic schistosomiasis has a very low prevalence in Sumidouro and endemicity among the rodents has not changed even after repeated treatments of the local patients. Based on our experiments, we conclude that N. squamipes has become a natural host of S. mansoni and possibly may participate in keeping the cycle of schistosomiasis transmission at Pamparrao Valley.  (+info)

Nectomys squamipes (Rodentia: Cricetidae) as an experimental model for Schistosomiasis mansoni. (78/710)

Twenty specimens of Nectomys squamipes born in captivity, were infected with 500 cercariae by the transcutaneous route. Coprologic examinations were carried out from the 5th to 23rd week after infection. On the 7th, 8th, 12th, 16th, and 23rd weeks the animals were sacrificed and perfused. The oogram was performed in segments of the small intestine (proximal, medial and distal portions) and the large intestine. The average pre-patent period was of 42 days. The average number of eggs varied from 350 on the 6th week, to 800 on the 13th. From the 14th week on, the average number of eggs eliminated was lower than 50 per gram of feces. The recovery of worms kept steady on the 7th, 8th and 12th week (16.85%; 15.45% and 11.95%), decreasing to 7.70% on the 16th week and 8.45% on the 23rd week. The proportion of male/female worms was about the same on the first two weeks, but from the 12th week on, the proportion was: 1.4/1 on the 12th week; 2.5/1 on the 16th week and 1.8/1 on the 23rd week. These observations suggest that N. squamipes may be used as an experimental model for schistosomiasis mansoni, to which it develops resistance mechanism, useful for immunity studies.  (+info)

Holochilus brasiliensis and Nectomys squamipes (Rodentia-Cricetidae) natural hosts of Schistosoma mansoni. (79/710)

After several Brazilian researchers, the author examines the capacity of two species of rodents Cricetidae, Holochilus brasiliensis and Nectomys squamipes, to maintain the biological cycle of Schistosoma mansoni in the field and to be parasite reservoir: (a) the role they are able to play in human endemy; (b) the methods necessary to characterize the population of Schistosoma mansoni related either to man, either to rodents, either to both.  (+info)

Lysine residues form an integral component of a novel NH2-terminal membrane targeting motif for myristylated pp60v-src. (80/710)

Association of pp60v-src with the plasma membrane is fundamental to generation of the transformed phenotype. Although myristylation of pp60v-src is required for interaction with a membrane-bound receptor, the importance of NH2-terminal amino acids in receptor binding has not yet been uncoupled from their role in signaling myristylation. Using chimeric src proteins, peptides identical or related to the NH2 terminus of src, and site-directed mutagenesis, we demonstrate that NH2-terminal lysines in conjunction with myristate are essential for membrane localization. Subsequent to NH2-terminal interaction with the "src receptor," internal regions of the src protein also participate in membrane binding. This novel NH2-terminal motif and internal contact mechanism may direct other members of the src family of tyrosine kinases to their membrane receptors.  (+info)