SHELF-LIFE ESTIMATION OF APPLE-BABY FOOD

The aim of the present work was to study the evolution of the color of an apple‐baby food and to estimate its sensory shelf life. Samples of apple‐baby food stored at 25C were analyzed using trained assessors and a consumer panel. A zero‐order reaction kinetics was found for the evolution of sensory color with storage time. Color was highly correlated with consumers' rejection percentage and overall acceptability, which indicates that consumers consider this attribute when deciding to accept or reject this product and in assigning their acceptability scores. Using this correlation, the sensory cutoff point for color, corresponding to a 25% consumer rejection, was calculated. Sensory shelf life was estimated using consumer data. Sensory shelf life estimated by survival analysis was in agreement with that calculated considering an acceptability limit of 6.0 in a 9‐point hedonic scale.     

Inhibition of Aspartate Aminotransferase by Glycation In Vitro Under Various Conditions

Incubation of 50 mM d -glucose with aspartate aminotransferase (AST, EC 2.6.1.1) preparations (purified pig heart enzyme or a rat liver 20,000 × g supernatant) at 25°C had no effect on enzyme activity. 50 mM d -fructose or d -ribose gradually inhibited pig heart AST under the same conditions to zero activity after 14 days. 50 mM dl -glyceraldehyde decreased enzyme activity to zero after 6 days of incubation. The inhibition of pig heart AST by 50 mM d -fructose or d -ribose was marked even at a temperature of 4°C but it was less pronounced than at 25°C. There was no effect of 0.5 mM 2-oxoglutarate on AST activity during incubation, while the presence of 25 mM l -aspartate decreased it rapidly. 0.5 mM 2-oxoglutarate partly prevented inhibition of AST by d -ribose or d -fructose, while an analogous experiment with 25 mM aspartate resulted in a rapid decline similar to that in the absence of sugars.     

Low-volume application by mist-blower compared with conventional compression sprayer treatment of houses with residual pyrethroid to control the malaria vector Anopheles albimanus in Mexico

Abstract. Village-scale trials were carried out in southern Mexico to compare the efficacy of indoor-spraying of the pyrethroid insecticide lambda-cyhalothrin applied either as low-volume (LV) aqueous emulsion or as wettable-powder (WP) aqueous suspension for residual control of the principal coastal malaria vector Anopheles albimanus. Three indoor spray rounds were conducted at 3-month intervals using back-pack mist-blowers to apply lambda-cyhalothrin 12.5 mg a.i./m² by LV, whereas the WP was applied by conventional compression sprayer at a mean rate of 26.5 mg a.i./m².
Both treatments caused mosquito mortality indoors and outdoors (collected inside house curtains) as a result of contact with treated surfaces before and after feeding, but had no significant impact on overall population density of An. albimanus resting indoors or assessed by human bait collections. Contact bioassays showed that WP and LV treatments with lambda-cyhalothrin were effective for 12–20 weeks (>75% mortality) without causing excito-repellency.
Compared to the WP treatment (8 houses/man/day), LV treatment (25 houses/man/day) was more than 3 times quicker per house, potentially saving 68% of labour costs. This is offset, however, by the much lower unit price of a compression sprayer (e.g. Hudson 'X-pert' at US120) than a mist-blower (e.g. 'Super Jolly' at US350), and higher running costs for LV applications. It was calculated, therefore, that LV becomes more economical than WP after 18.8 treatments/100 houses/10 men at equivalent rates of application, or after 7.6 spray rounds with half-rate LV applications.     

Histocompatibility Gene Organization and Mixed Lymphocyte Reaction

TRANSFORMATION of allogenic lymphocytes in mixed cultures depends chiefly on an incompatibility between the lymphocyte donors at the major histocompatibility locus in man (HL-A), mouse (H-2) and rat (H-l)¹. Although the mouse H-2 locus can be divided into several regions each of which controls one or more antigenic specificities² and two or more subloci control HL-A antigens in man³, it is not known whether all parts of the major histocompatibility locus are equally important in eliciting transformation in mixed lymphocyte cultures. We now show that capacity to elicit lymphocyte transformation is different for different parts of the mouse H-2 locus.     

The extent and differences in mitotic activity of the root tip ofVicia faba L.

Mitotic activity does not stop for different meristematic cells of the root apex at the same distance from the initials. The differences are connected with the functional heterogeneity of the apical meristem of the root. The arrangement of vascular bundles,i.e. the alternation of independent xylem and phloem groups, is of major importance. In broad bean roots, the protophloem sieve elements stop dividing first. The centre of the stelei. e. late metaxylem elements stop dividing next. Division in the stele gradually ceases centrifugally, while it ceases centripetally in the peripheral part of the root. The cylindrical region with prolonged cell division includes internal layers of the cortex including endodermis, pericycle and adjoining cells of the stele. Proximally apical meristem is reduced to isolated strands of cells adjacent to the protoxylem poles. Pericycle cells stop dividing last at a distance of approx. 9–10 mm from the initials. The number of the division cycles is limited and is specific for individual cell types. Epidermal and cortical cells divide in broad bean roots transversely approximately seven times, cells of late metaxylem approximately five times. Root apical meristem is an asynchronous cell population with a different duration of the mitotic cycle. We determined local variations in the duration of the mitotic cycle in the apical meristem of broad bean root by means of colchicine-induced polyploidy. The cells of the quiescent centre had the longest mitotic cycle after colchicine treatment. The region of the proper root adjacent to the quiescent centre was mixoploid (2n and 4n). Isolated cells with a long cycle occurred also in the cortex and in the central cylinder. Cells with a division cycle of 18h were found in the root cap, in the epidermis, in the cortex and in the central cylinder. Relatively numerous cells with the shortest division cycle, approx. 12 h, occurred farther of the quiescent centre in the epidermis, in the cortex, in the pericycle, and in adjacent layers of the stele through-out the entire meristematic region. The results derived from the analysis of the apical meristem are discussed in connection with the ontogenesis of different types of cells taking part in the primary structure of the root.     

Inorganic self-organisation in precambrian cherts

Silica biomorphs are inorganic self-organized precipitates resulting from a crystal aggregation process controlled by a metal silicate membrane. They display morphological and symmetric properties of living organisms and form under physico-chemical conditions similar to some geochemical conditions suggested for the chemical precipitation of Precambrian chert precursors. In consequence, these inorganic precipitates are proposed as an alternative interpretation to be considered when trying to decipher the biogenicity of putative Precambrian microbiotas.     

Species-specific phytoplankton responses to nutrients and zooplankton manipulations in enclosure experiments

1. In situ enclosure experiments were performed in the mesotrophic Bermejales reservoir to evaluate the algal response to changes in the nutrient supply and in the zooplankton size structure and density in a 2 × 2 factorial design. The experiments were conducted during the spring bloom of nanoplanktonic diatoms in 1989. 2. Nutrient enrichment promoted a great increase of phytoplankton biomass indicating a strong nutrient limitation on phytoplankton growth. Total phytoplankton biomass was significantly lower in the Daphina-added enclosures at a given nutrient level and strong direct an indirect effect of zooplankton on phytoplankton community structure and nutrient availability were observed. 3. Most of the nanoplanktonic species were effectively grazed but species with protective coverings and large size colonies were favoured by grazers and small chlorococcales were unaffected probably because of their compensatory high growth rates. The decrease in total biomass imposed by grazers is attributable mainly to the decrease of Cyclotella ocellata, the most abundant species. This taxon suffers two net effects of zooplankton: direct grazing and the indirect decrease of Si availability caused by the growth of C. ocellata which was promoted by P excretion by zooplankton. Indirect effects of grazers on Si availability should, therefore, be taken into account in explaining phytoplankton succession and community structure. 4. In this experiment grazers affected considerably the nanoplanktonic community in Bermejales reservoir. The extent which they were affected, however, depended not only on the algal size as a determinant of edibility but also greatly on the specific nutrient requirements and taxonomic features of the algal species.     

From climate change predictions to actions – conserving vulnerable animal groups in hotspots at a regional scale

Current climate change is a major threat to biodiversity. Species unable to adapt or move will face local or global extinction and this is more likely to happen to species with narrow climatic and habitat requirements and limited dispersal abilities, such as amphibians and reptiles. Biodiversity losses are likely to be greatest in global biodiversity hotspots where climate change is fast, such as the Iberian Peninsula. Here we assess the impact of climate change on 37 endemic and nearly endemic herptiles of the Iberian Peninsula by predicting species distributions for three different times into the future (2020, 2050 and 2080) using an ensemble of bioclimatic models and different combinations of species dispersal ability, emission levels and global circulation models. Our results show that species with Atlantic affinities that occur mainly in the North‐western Iberian Peninsula have severely reduced future distributions. Up to 13 species may lose their entire potential distribution by 2080. Furthermore, our analysis indicates that the most critical period for the majority of these species will be the next decade. While there is considerable variability between the scenarios, we believe that our results provide a robust relative evaluation of climate change impacts among different species. Future evaluation of the vulnerability of individual species to climate change should account for their adaptive capacity to climate change, including factors such as physiological climate tolerance, geographical range size, local abundance, life cycle, behavioural and phenological adaptability, evolutionary potential and dispersal ability.     

Sentinel systems on the razor's edge: effects of warming on Arctic geothermal stream ecosystems

The Earth is experiencing historically unprecedented rates of warming, with surface temperatures projected to increase by 3–5 °C globally, and up to 7.5 °C in high latitudes, within the next century. Knowledge of how this will affect biological systems is still largely restricted to the lower levels of organization (e.g. species range shifts), rather than at the community, food web or ecosystem level, where responses cannot be predicted from studying single species in isolation. Further, many correlational studies are confounded with time and/or space, whereas experiments have been mostly confined to laboratory microcosms that cannot capture the true complexity of natural ecosystems. We used a ‘natural experiment’ in an attempt to circumvent these shortcomings, by characterizing community structure and trophic interactions in 15 geothermal Icelandic streams ranging in temperature from 5 °C to 45 °C. Even modest temperature increases had dramatic effects across multiple levels of organization, from changes in the mean body size of the top predators, to unimodal responses of species populations, turnover in community composition, and lengthening of food chains. Our results reveal that the rates of warming predicted for the next century have serious implications for the structure and functioning of these fragile ‘sentinel’ ecosystems across multiple levels of organization.     

Two closely linked tomato HKT coding genes are positional candidates for the major tomato QTL involved in Na+/K+ homeostasis

The location of major quantitative trait loci (QTL) contributing to stem and leaf [Na⁺] and [K⁺] was previously reported in chromosome 7 using two connected populations of recombinant inbred lines (RILs) of tomato. HKT1;1 and HKT1;2, two tomato Na⁺‐selective class I‐HKT transporters, were found to be closely linked, where the maximum logarithm of odds (LOD) score for these QTLs located. When a chromosome 7 linkage map based on 278 single‐nucleotide polymorphisms (SNPs) was used, the maximum LOD score position was only 35 kb from HKT1;1 and HKT1;2. Their expression patterns and phenotypic effects were further investigated in two near‐isogenic lines (NILs): 157‐14 (double homozygote for the cheesmaniae alleles) and 157‐17 (double homozygote for the lycopersicum alleles). The expression pattern for the HKT1;1 and HKT1;2 alleles was complex, possibly because of differences in their promoter sequences. High salinity had very little effect on root dry and fresh weight and consequently on the plant dry weight of NIL 157‐14 in comparison with 157‐17. A significant difference between NILs was also found for [K⁺] and the [Na⁺]/[K⁺] ratio in leaf and stem but not for [Na⁺] arising a disagreement with the corresponding RIL population. Their association with leaf [Na⁺] and salt tolerance in tomato is also discussed.