Risk of Infection with Leishmania spp. in the Canine Population in the Netherlands

The dog is the main reservoir of Leishmania infantum, the causative agent of visceral leishmaniasis (VL) in humans in Southern Europe. In order to identify the risk of dogs from a Leishmania non-endemic area traveling to a Leishmania -endemic area becoming infected and the risk of transmitting infection to humans in non-endemic areas an investigation was performed, in which the results of a questionnaire were combined with the results of a serologic survey.     

Amino-acid Sequence of Thermolysin

The following three articles describe how chemical and X-ray analyses have been combined to elucidate the structure of thermolysin. This first article describes the determination of the amino-acid sequence of this metalloendopeptidase.     

The Obvious Aspects of Ecological Underprivilege in Ankarana, Northern Madagascar

On the basis of research conducted in the Ankarana region of northern Madagascar, I discuss the speculating that Malagasy participants in the local sapphire trade do about foreign ecotourists who come to this region. Although some have been promoting international ecotourism in the region as a viable means to a sustainable future for local people and ecosystems, others, including many of the observers discussed here, see the rise of the ecotourist trade and the increasing presence of its clients in Ankarana as signs of foreigners' long-standing interests in Malagasy resources. I argue that to understand the perspectives of these critical observers, it is necessary to appreciate what they take to be obvious about ecotourism and the conservation projects with which they are commonly associated.     

THE INFLUENCE OF BAT DETECTOR BRAND ON THE QUANTITATIVE ESTIMATION OF BAT ACTIVITY

ABSTRACT

Bat detectors are commonly used to monitor bat behaviour. Earlier research has suggested that there may be systematic differences in the response of different detectors to bat calls. Such differences would have important implications for the comparability of quantitative surveys conducted with bat detectors. The present study examines variability within and between brands of bat detector in accuracy of tuning, directionality and sensitivity to different types of bat echolocation call in bat detectors from three manufacturers. The consistency of results from a field survey incorporating the three brands in a standardised methodology are also examined. Significant differences were found within and between brands in directionality and sensitivity which would lead to bias in bat surveys. The implications of these findings for bat surveys are discussed, as are the design features of importance for species identification.     

Variation in heat shock proteins within tropical and desert species of poeciliid fishes

The 70-kilodalton heat shock protein (hsp70) family of molecular chaperones, which contains both stress-inducible and normally abundant constitutive members, is highly conserved across distantly related taxa. Analysis of this protein family in individuals from an outbred population of tropical topminnows, Poeciliopsis gracilis, showed that while constitutive hsp70 family members showed no variation in protein isoforms, inducibly synthesized hsp70 was polymorphic. Several species of Poeciliopsis adapted to desert environments exhibited lower levels of inducible hsp70 polymorphism than the tropical species, but constitutive forms were identical to those in P. gracilis, as they were in the confamilial species Gambusia affinis. These differences suggest that inducible and constitutive members of this family are under different evolutionary constraints and may indicate differences in their function within the cell. Also, northern desert species of Poeciliopsis synthesize a subset of the inducible hsp70 isoforms seen in tropical species. This distribution supports the theory that ancestral tropical fish migrated northward and colonized desert streams; the subsequent decrease in variation of inducible hsp70 may have been due to genetic drift or a consequence of adaptation to the desert environment. Higher levels of variability were found when the 30- kilodalton heat shock protein (hsp30) family was analyzed within different strains of two desert species of Poeciliopsis and also in wild-caught individuals of Gambusia affinis. In both cases the distribution of hsp30 isoform diversity was similar to that seen previously with allozyme polymorphisms.      

Viruses infecting winter oilseed rape (Brassica napus ssp. oleifera)

Turnip mosaic virus (TuMV) and cauliflower mosaic virus (CaMV) have been found infecting field crops of winter oilseed rape (Brassica napus ssp. oleifera) in South Warwickshire. Other viruses found include broccoli necrotic yellows virus (BNYV) and a member of the beet western yellows virus group. Systemic leaf symptoms caused by TuMV varied within and between cultivars; the three predominant reaction types were classified as necrotic, mosaic and immune. Some recently introduced cultivars of oilseed rape were more severely affected by TuMV infection than older cultivars. Reactions to CaMV were less varied and immunity was not found. The seed yield from TuMV and CaMV-infected plants was less than that of healthy control plants. This effect was due to infected plants producing either fewer seeds, smaller seeds or both. Germination of seeds from infected plants was unaffected if sown soon after harvest. After storage for one year the germination of seed from a virus infected plant was significantly less than that of seed from a virus-free plant. All commercial cultivars tested were experimentally susceptible to turnip yellow mosaic virus (TYMV) and some American strains of cucumber mosaic virus (CMV).     

Proton density and apoplastic domains within soybean nodules in relation to the oxygen diffusion barrier

A spin-echo pulse sequence was used to obtain ¹H nuclear magnetic resonance microimages of soybean nodules, with resolution to 40 mm and 3D presentation. At an acquisition time (TR) of c. 270 ms and a short echo time (TE) of 8.3 ms, a high proton intensity was detected in infected tissue and vascular strands, relative to the cortex. A longer TE of 15.5 ms was associated with a relatively low proton intensity in infected tissue. Thus protons in infected tissue were characterized by a short T₂. Following detopping of the plant, or treatment of the root system with Ar:O₂, proton intensity (TE 5.9, TR 120 ms) decreased exponentially in a zone corresponding to the inner cortex-outer infected region. This result is interpreted as being caused by a loss of water mobility (i.e. increase in viscosity) or a filling of intercellular air spaces with fluid (i.e. loss of air-water interfaces). The membrane impermeant tracer lucifer yellow was observed to infiltrate from the rhizosphere through the nodule cortex into the infected region in intact nodules of detopped and Ar:O₂-treated, but not control, plants. This result is consistent with the filling of air spaces with fluid following the imposed treatments, allowing infiltration of aqueous tracers. Variation in intercellular air space volume within the inner cortex has been suggested as a mechanism to allow a variable rate of diffusion of O₂ into soybean nodules.     

Purine and Pyrimidine Synthesis by the Avian Malaria Parasite,Plasmodium lophurae*

SYNOPSIS. Purine and pyrimidine biosynthesis in the avian malaria parasite Plasmodium lophurae and its host cell, the duck erythrocyte, were investigated in vitro. Pyrimidine synthesis, as measured by the incorporation of C¹⁴-NaHCO₃ into cytosine, uracil and thymine was slight in uninfected duck erythrocytes, whereas infected erythrocytes and erythrocyte-free parasites had high rates of incorporation of NaHCO₃ into these bases. In addition, orotidine-5′-monophosphate pyrophosphorylase and thymidylate synthetase, 2 enzymes of the pyrimidine biosynthetic pathway, were found in cell-free extracts of the plasmodia. Purine synthesis was measured by determining the extent of incorporation of C¹⁴-Na-formate into adenine and guanine. Uninfected and infected erythrocytes had similar rates of Na-formate incroporation into adenine. whereas free parasites incorporated little of this compound into adenine, or guanine. On the other hand, the incorporation of Na-formate into guanine was 54% higher in infected erythrocytes than in uninfected erythrocytes. It is suggested that P. lophurae synthesizes purines to a limited extent, and derives most of its purines from the host erythrocyte. The greater incorporation of Na-formate into guanine by infected cells, and its low incorporation into free parasites may be accounted for by parasite conversion of host cell adenine (in the form of ATP) into guanine. Pyrimidine biosynthesis in infected cells can be accounted for by de novo synthesis by the parasite itself.