ALBERT

Notes: In Spain, consumption of organic products has not kept pace with production. Up till now, foreign markets have been a natural destination for excess supply. However, world trade liberalization might cause important commercial problems to Spanish producers that could be partially solved by enlarging the domestic market. The goal of this paper is to assess the opportunity for such enlargement focusing on two main aspects: consumers’ and retailers’ attitudes and willingness to pay for organic products. Concerns about health, natural diets or environmental issues could stimulate consumption, while retailing dynamism and competition to gain new market segments might favour distribution. Both aspects are investigated through two surveys addressed to consumers and retailers in two Spanish towns. The results confirm that only a small proportion of consumers and distributors show attitudes that might favour demand expansion. The most sensitized segments are willing to pay more for organic products, but this premium is still very far from the prevailing gap between conventional and organic food products.

Notes: 1 It is generally recognized that the vasodilator hydralazine produces hypotension accompanied by baroreflex-mediated tachycardia. In some experimental conditions, however, the accompanying heart rate change is bradycardia, a paradoxical response which has not been satisfactorily explained. The present study examined the possibility of hydralazine-induced bradycardia being mediated by vagal or sympathetic afferents activated by changes in left ventricular pressure. 2 Systolic blood pressure and heart rate responses to hydralazine were recorded in conscious normotensive intact rats by a tail cuff method and compared with responses in animals subjected to previous sino-aortic deafferentation (SAD) to remove the influence of the arterial baroreflex. Responses were also obtained after blockade of myocardial afferent vagal C-fibres with urethane, of efferent vagal impulses to the heart with methylatropine, of positive inotropic effects of hydralazine with atenolol, and of prostanoid sensitization of myocardial nerve fibres with indomethacin. 3 Hydralazine produced hypotension and tachycardia in intact rats, and hypotension and bradycardia in SAD animals. In intact rats, this pattern was not affected by any of the pretreatments, while in SAD rats, all pretreatments reversed the bradycardia to hydralazine. 4 The present results indicate that suppression of the arterial baroreflex by SAD propitiates the appearance of a bradycardiac response to hydralazine. This reaction probably results from activation of a vagal cardiodepressant reflex originating in the heart, as suggested by its blockade by drugs acting at various sites along the reflex arch.

Notes: The ability of a parasite to transmit from one fish to another is important in the dissemination of disease. Groups of 25 naive rainbow trout (RBT), Oncorhynchus mykiss (Walbaum), were exposed to Loma salmonae by feeding on the viscera (gills, hearts and spleens) from L. salmonae-infected donor RBT (DRBT) or by cohabitation with infected DRBT. Exposure occurred 3, 7, 11 and 15 weeks after the DRBT were infected. All naive RBT were examined 7 weeks post-exposure (PE) to the DRBT. Naive RBT, exposed to DRBT at week 3 PE, by feeding on viscera or by cohabitation, failed to develop visible branchial xenomas. Cohabiting naive RBT with DRBT, at week 7 PE and week 11 PE, resulted in the development of branchial xenomas. Xenomas failed to develop in naive RBT exposed via cohabitation to week 15 PE DRBT. Naive RBT, exposed by feeding on the viscera of DRBT at week 7 PE, week 11 PE and week 15 PE, developed branchial xenomas. The transmission potential of viscera from L. salmonae-infected DRBT at week 15 and week 20 PE was also examined. Naive RBT, fed with viscera free of visible branchial xenomas, from DRBT at week 15 PE and week 20 PE, developed branchial xenomas by week 7 PE. A polymerase chain reaction (PCR) was used to detect L. salmonae DNA from the water and sediments of a tank of L. salmonae-infected RBT at week 7 PE. The method and timing of exposure of naive fish to L. salmonae-infected fish are important in disease transmission and may be useful in predicting and preventing disease outbreaks in aquaculture.

Notes: The shrub Cistus ladanifer (gum cistus, rock rose) is a key component of the Maquis in the Mediterranean forests of southern Spain and Portugal. Between 1996 and 1998, and coinciding with exceptionally high rainfall rates, a disease characterized by foliar wilting and death of branches, leading to death of the whole plant, affected C. ladanifer in the Mediterranean oak and pine forests in Andalucía (southern Spain). Field surveys carried out in 15 forest areas showed that diseased branches were associated with the presence of strips of necrotic bark. Botryosphaeria dothidea was consistently obtained from the necrotic tissues. Growth of isolates on potato dextrose agar was very rapid at high temperatures, with a growth rate of 25 mm day−1 at the optimum temperature (about 28°C). Germination rate of conidia increased with temperature, with the optimum temperature being over 35°C. Pathogenicity tests were conducted on cut branches, 3-year-old seedlings and mature plants in the field. In every situation, disease symptoms were reproduced in the inoculated branches and Koch’s postulates were fulfilled. The results demonstrate the behaviour of B. dothidea as a primary pathogen of C. ladanifer. The present work constitutes the first description of fungal canker of C. ladanifer caused by B. dothidea, being the first report of a disease affecting this shrub species.

Notes: Oilseed rape mosaic (ORMV) and tobacco mild green mosaic (TMGMV) tobamoviruses interfered with each other when infecting the same host, and interference was host-dependent. In tobacco cross-protection was obtained in two ways: the protecting virus prevented the accumulation of the challenging virus, even in the inoculated leaf; in Arabidopsis, protection was obtained only when the protecting virus was TMGMV. The protecting mechanism in Arabidopsis appeared to differ from that operating in tobacco. Although ORMV could be detected in the inoculated leaf, TMGMV prevented systemic infection by ORMV. Thus the host appears to play an important role in this type of cross-protection.

Notes: Twenty isolates of Phytophthora infestans from potato and twenty-two from tomato, collected in Uganda and Kenya in 1995, were compared for dilocus allozyme genotype, mitochondrial DNA (mtDNA) haplotype, mating type and restriction fragment length polymorphism (RFLP) fingerprint using probe RG57. Based on RFLP fingerprint and mtDNA haplotype, all isolates were classified in the US−1 clonal lineage. Nonetheless, isolates from potato differed from isolates from tomato in several characteristics. Isolates from potato had the 86/100 glucose-6-phosphate isomerase (Gpi) genotype, while those from tomato were 100/100, which represents a variant of US−1 that had been identified previously as US−1.7. Furthermore, while pure cultures of the pathogen were acquired from infected potato leaflets by first growing the isolates on potato tuber slices, this approach failed with infected tomato tissue because the isolates grew poorly on this medium. Tomato isolates were eventually purified using a selective medium. Six isolates from each host were compared for the diameter of lesions they produced on three tomato and three potato cultivars in one or two detached-leaf assays (four isolates from the first test were repeated in the second). On potato leaflets, isolates from potato caused larger lesions than isolates from tomato. On tomato leaflets, isolates from that host caused larger lesions than did isolates from potato, but the difference was significant in only one test. The interaction between source of inoculum (potato or tomato) and inoculated host (potato or tomato) was significant in both tests. Isolates from tomato were highly biotrophic on tomato leaflets, producing little or no necrosis during the seven days following infection, even though abundant sporulation could be seen. In contrast, isolates from potato sporulated less abundantly on tomato leaflets and produced darkly pigmented lesions that were most visible on the adaxial side of the leaflets. Nonetheless, all isolates infected and sporulated on both hosts, indicating that host adaptation is not determined by an ability to cause disease but rather by quantitative differences in pathogenic fitness. Assessment of Gpi banding patterns, mtDNA haplotype and RFLP fingerprint of 39 isolates from potato collected in Uganda and Kenya in 1997 indicated that the population had not changed on this host. The population of P. infestans from Kenya and Uganda provides an interesting model for the study of quantitative host adaptation.

Notes: This study provides new constraints on fast cooling and exhumation rates of high-pressure metamorphic rocks in young active mountain belts. Ion microprobe (SHRIMP) U–Pb analysis of zircon in a pyroxenite layer of the Cerro del Almirez ultramafic rocks (Nevado-Filábride Complex, southern Spain) gave an age of 15.0 ± 0.6 Myr (95% c.l.). Mineral inclusions demonstrate that zircon formed close to the high-pressure peak. Combined with previous fission track data, the 15 Myr age suggests high cooling (˜ 80 °C Myr−1) and exhumation (˜1.2 cm yr−1) rates for the unit. The new results indicate that both the Nevado-Filábride Complex and the overlying Alpujárride Complex, with somewhat higher ages and exhumation rates, underwent similar metamorphic evolutions at different times. This implies that the Alpujárride rocks were exhumed when the Nevado-Filábride was subducting and that the same tectonic scenario propagated from one portion of the Betic Cordilleras to another.

Notes: The analysis of the not well understood composition of the stalk, a key ribosomal structure, in eukaryotes having multiple 12 kDa P1/P2 acidic protein components has been approached using these proteins tagged with a histidine tail at the C-terminus. Tagged Saccharomyces cerevisiae ribosomes, which contain two P1 proteins (P1α and P1β) and two P2 proteins (P2α and P2β), were fractionated by affinity chromatography and their stalk composition was determined. Different yeast strains expressing one or two tagged proteins and containing either a complete or a defective stalk were used. No indication of protein dimers was found in the tested strains. The results are only compatible with a stalk structure containing a single copy of each one of the four 12 kDa proteins per ribosome. Ribosomes having an incomplete stalk are found in wild-type cells. When one of the four proteins is missing, the ribosomes do not carry the three remaining proteins simultaneously, containing only two of them distributed in pairs made of one P1 and one P2. Ribosomes can carry two, one or no acidic protein pairs. The P1α/P2β and P1β/P2α pairs are preferentially found in the ribosome, but they are not essential either for stalk assembly or function.

Notes: Proteins with bacterial immunoglobulin-like (Big) domains, such as the Yersinia pseudotuberculosis invasin and Escherichia coli intimin, are surface-expressed proteins that mediate host mammalian cell invasion or attachment. Here, we report the identification and characterization of a new family of Big domain proteins, referred to as Lig (leptospiral Ig-like) proteins, in pathogenic Leptospira. Screening of L. interrogans and L. kirschneri expression libraries with sera from leptospirosis patients identified 13 lambda phage clones that encode tandem repeats of the 90 amino acid Big domain. Two lig genes, designated ligA and ligB, and one pseudogene, ligC, were identified. The ligA and ligB genes encode amino-terminal lipoprotein signal peptides followed by 10 or 11 Big domain repeats and, in the case of ligB, a unique carboxy-terminal non-repeat domain. The organization of ligC is similar to that of ligB but contains mutations that disrupt the reading frame. The lig sequences are present in pathogenic but not saprophytic Leptospira species. LigA and LigB are expressed by a variety of virulent leptospiral strains. Loss of Lig protein and RNA transcript expression is correlated with the observed loss of virulence during culture attenuation of pathogenic strains. High-pressure freeze substitution followed by immunocytochemical electron microscopy confirmed that the Lig proteins were localized to the bacterial surface. Immunoblot studies with patient sera found that the Lig proteins are a major antigen recognized during the acute host infection. These observations demonstrate that the Lig proteins are a newly identified surface protein of pathogenic Leptospira, which by analogy to other bacterial immunoglobulin superfamily virulence factors, may play a role in host cell attachment and invasion during leptospiral pathogenesis.