Isolation and characterization of microsatellite markers in Calomys musculinus (Muridae,Sigmodontinae, Phyllotini), the natural reservoir of Junin virus

Calomys musculinus, one of the most abundant rodent species in central Argentina, is the reservoir of Junin virus, the aetiological agent of Argentine hemorrhagic fever. We isolated six polymorphic microsatellite loci for microgeographical studies of population structure in this species. Amplification of these loci in 36 individuals from three natural populations revealed five to 14 alleles per locus and expected heterozygosities from 0.426 to 0.868. Cross‐species amplifications suggest that primers designed for these loci may be useful in other closely related species of the tribe Phyllotini, but not in species of other more distantly related tribes of the subfamily Sigmodontinae.     

Cytogenetic Follow-Up in a Case With a Primary Cutaneous Melanoma and Five Metastatic Lesions

Cytogenetic analyses conducted on several cases of melanoma have contributed to the identification of the chromosomal regions where the sequences responsible for malignant transformation and the evolution of this tumor are probably located. With regard to these problems, it is very important to have the possibility to analyze, through the use of cytogenetics, both the primary melanoma and the metastatic lesions from the same patient. We present a case in which the primary melanoma and five different metastases were studied by using cytogenetics. The primary tumor showed an inversion of chromosome 1 where the p36 region, often proposed in literature as the location of a melanoma susceptibility gene, was involved. Three cutaneous and one lymphonodal metastases presented the same nine clonal chromosomal aberrations. In particular, one is a further rearrangement of the marker present in the primary tumor; another is a deletion of the 9p21pter region in which the p16 gene is located. Our results can provide a contribution to the hypothesis of the location of a candidate gene for melanoma in the 1p36 region and can also underscore the role of the 9p21 region in the progression of melanoma.     

Simultaneous hydrolyses of esters and proteins at saturation levels

A direct titration method for the determination of proteolytic activity is discussed. This involves the potentiometric measurement of the volume of 0.08 N NaOH required to maintain a constant pH (8.0) during the time of the hydrolysis. It is a sensitive method which presents several advantages; viz., it measures simultaneously protease and esterase activity, it follows the hydrolysis very closely and from the first stages; the titration is continuous and on the same sample. This method determines a constant fraction of the groups titratable by formol titration. The ratio formol: direct titration is represented by a factor "f" which is presumed to be distinct for each protein-enzyme system. Kinetic studies, using this method, revealed that the rates of hydrolysis of mixtures casein-gelatin on one hand, casein-BAEE or gelatin-BAEE on the other, are always larger than those of the corresponding isolated substrates. In many cases the resulting rates are equal or nearly equal to the sum of the individual rates, even though the mentioned rates have been determined within the saturation zones for every substrate. The former observations are inconsistent with the theory of the formation of an intermediary enzyme-substrate compound, unless it is assumed that the enzyme has a specific active group for each substrate.     

Observation of some key stages of the embryonic development of Biomphalaria straminea (Dunker, 1848) (Molluska,Planorbidae)

Summary

Biomphalaria straminea is a freshwater snail and one of the intermediate hosts of the trematode parasite which causes schistosomiasis in Brazil. The main stages of embryonic development were analyzed with confocal laser scanning microscopy (CLSM), using the fluorescent probe DiOC and Nile Red as a vital stain in in vivo preparations. In fixed preparations nuclei were stained by the Feulgen reaction or the fluorescent DNA probe, Höechst 33342. Results obtained from the analysis of embryos at the stages of early cleavage, morula, blastula, gastrula, early trocophore and veliger showed that these stages are similar to those described for Biomphalaria glabrata and Biomphalaria tenagophila. CLSM optical sections of early trochophore showed important morphological structures such as the blastopore, stomodeum and shell gland; and in early veliger, internal organs such as the esophagus, stomach and male and female ducts were also clearly identified.     

Spatial association of Aspidosperma quebracho‐blanco juveniles with shrubs and conspecific adults in the Arid Chaco,Argentina

Abstract The survival of Aspidosperma quebracho‐blanco juveniles in the Arid Chaco is facilitated under the canopy of nurse plants. The possible effects of nurse plants were studied at intra‐ and interspecific levels by analysing the spatial distribution of juveniles and adults of A. quebracho‐blanco, of the main shrubs Larrea divaricata and Mimozyganthus carinatus, and of the group of deciduous and evergreen shrub species, and their pair associations. Data were analysed using the SADIE (Spatial Analysis by Distance Indices) software. A. quebracho‐blanco seedling abundance followed the distribution pattern of the main shade‐providing species: an aggregated spatial distribution pattern in most of the categories studied. The seedling bank of A. quebracho‐blanco also showed an aggregated pattern and was spatially associated with shrubs and adults of its own species. The intensity of the association depended on the functional types: deciduous Fabaceae, deciduous non‐Fabaceae, evergreen and conspecific adults, each of which provides a different canopy structure and therefore different amounts of shade. The spatial association was significant with the evergreen group, and less significant with the deciduous Fabaceae group. There was no positive association with deciduous non‐Fabaceae, or with gaps (open sky). The differences generated by canopy cover may influence the nurse effect, as observed in the intensity of association of A. quebracho‐blanco with shrubs and conspecific adults.     

Protection of livestock against bluetongue virus vector Culicoides imicola using insecticide‐treated netting in open areas

The protection of livestock against Culicoides species (Diptera: Ceratopogonidae) using physical barriers or chemically treated barriers is difficult owing to the small size of these biting midges and animal welfare concerns associated with the reduction of air flow. Culicoides imicola Kieffer is the main bluetongue virus vector in the Mediterranean basin, including the southern Iberian peninsula, where livestock is mainly housed in open pens or sheds which offer no physical protection against C. imicola. In this study we assessed the efficacy of surrounding yearling ewe pens with a canvas barrier or a cypermethrin‐treated canvas barrier in reducing the entry of Culicoides spp. and C. imicola. Analyses were based on comparisons of Culicoides catches in traps in pens with and without barriers, and in traps located outside pens. Although there was no clear reduction in the abundance of Culicoides other than C. imicola in pens with either barrier, the C. imicola presence was markedly reduced by the insecticide‐treated barrier compared with the untreated barrier; the latter did not reduce the abundance of this species in pens. Estimates of the protection conferred against C. imicola by the treated barrier differed depending on whether catch comparisons were based on outside traps or on traps located inside no‐barrier pens. The results suggest that the use of insecticide‐treated barriers may reduce contact between livestock and C. imicola in open areas or sheds. More research is necessary to assess the degree of protection as a function of barrier height, C. imicola abundance, and the size of the area to be protected.     

SOURNESS–SWEETNESS INTERACTIONS IN DIFFERENT MEDIA: WHITE WINE,ETHANOL AND WATER*

The aim of this work was to study the sourness–sweetness interactions in water, white wine and alcoholic environment to interpret sweet/sour perception in low concentrations within the range normally encountered in white wine. Nine trained assessors rated sweetness and sourness intensity in mixtures of fructose (11.1, 25.0 and 38.9 mM) and tartaric acid (pH 3.0, 3.4 and 3.8) in water and wine (experiment 1) or ethanol solutions at 2.0, 4.0 and 12.0% v/v (experiment 2). The range of quantitative responses was larger for sourness than for sweetness in the three media. The global sourness intensity perception in wine mixtures was significantly lower than in water and ethanol mixtures, indicating the effect of other wine components. The suppressive effect of tartaric acid on fructose sweetness was stronger than the suppressive effect of fructose on tartaric acid sourness.     

Enhancement of root hydraulic conductivity by methyl jasmonate and the role of calcium and abscisic acid in this process

The role of jasmonic acid in the induction of stomatal closure is well known. However, its role in regulating root hydraulic conductivity (L) has not yet been explored. The objectives of the present research were to evaluate how JA regulates L and how calcium and abscisic acid (ABA) could be involved in such regulation. We found that exogenous methyl jasmonate (MeJA) increased L of Phaseolus vulgaris, Solanum lycopersicum and Arabidopsis thaliana roots. Tomato plants defective in JA biosynthesis had lower values of L than wild‐type plants, and that L was restored by addition of MeJA. The increase of L by MeJA was accompanied by an increase of the phosphorylation state of the aquaporin PIP2. We observed that MeJA addition increased the concentration of cytosolic calcium and that calcium channel blockers inhibited the rise of L caused by MeJA. Treatment with fluoridone, an inhibitor of ABA biosynthesis, partially inhibited the increase of L caused by MeJA, and tomato plants defective in ABA biosynthesis increased their L after application of MeJA. It is concluded that JA enhances L and that this enhancement is linked to calcium and ABA dependent and independent signalling pathways.