Immunocytochemical study of amelogenin deposition during the early odontogenesis of molars in alendronate-treated newborn rats.

Newborn rats were treated with sodium alendronate to study how enamel is formed and the effect of alendronate during early odontogenesis. Ultrastructural analysis combined with high-resolution immunocytochemistry for amelogenin was carried out. Twelve rats were subjected to daily SC injections of sodium alendronate (2.5 mg/kg/day) for 3 days on their dorsal region, whereas three rats were daily injected with saline solution as a control. Molar tooth germs from 3-day-old rats were fixed under microwave irradiation in 0.1% glutaraldehyde + 4% formaldehyde buffered at pH 7.2 with 0.1 M sodium cacodylate. The specimens were left undecalcified, postfixed with osmium tetroxide, dehydrated, and embedded in LR White resin. Ultrathin sections were incubated with a chicken anti-24-kDa rat amelogenin antibody, a secondary antibody, and finally with a protein A-gold complex. Large patches of amelogenin were present over the unmineralized mantle dentin and at early secretory ameloblasts. At more advanced stages, they were also detected at the enamel matrix, as well as in the mineralized dentin, at the periodontoblastic space of the dentinal tubules, and at the predentin. It is likely that the main effect of alendronate at early stages of odontogenesis is the increase of synthesis/secretion of amelogenin, promoting its deposition within the forming dentin and enamel.     

Modelling intraspecific resting egg shape variation in a freshwater fairy shrimp Tanymastix stagnalis (L., 1758) (Crustacea, Branchiopoda)

The shape of the resting eggs of a large branchiopod crustacean, the Anostraca Tanymastix stagnalis , is represented very accurately by analytical expressions. The occurrence of atypical shape of some T. stagnalis eggs may be viewed as a simple change of the analytical expression describing the usual egg shape. Their unusual shape may be explained by a higher embryo volume within an envelope of a given size. Biological implications are briefly discussed and hypothesized in an evolutionary point of view.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 55–60.     

Adult movements between populations in the specialist butterfly Proclossiana eunomia (Lepidoptera, Nymphalidae)

Abstract.

• 1 The structure of local populations of a monophagous butterfly, the bog fritillary Proclossiana eunomia, was studied in a complex of suitable habitat patches separated by spruce plantations or fertilized pasture.
• 2 An unexpected high level of adult movements between habitat patches was detected by a mark—release—recapture technique. Local populations were connected by adult movements across unsuitable habitats, leading to a meta-population structure.
• 3 This evidence of the metapopulation structure of a specialist butterfly challenges the supposed relationship between habitat specialization and closed, isolated populations.
• 4 Males and females of P.eunomia exhibited different spatial behaviours; females were more likely to emigrate and dispersed further than males. These differences in spatial behaviour are related to the mating system.

     

Isolation and characterization of tetranucleotide microsatellite markers in a mouth‐brooding haplochromine cichlid fish (Pseudocrenilabrus multicolor victoriae) from Uganda

Eight tetranucleotide microsatellite loci were isolated from the haplochromine cichlid fish, Pseudocrenilabrus multicolor victoriae, an important model species for studies in respiratory ecology, conservation, and evolution. We surveyed variation at these loci in 23 individuals from western Uganda, finding four to 19 alleles per locus and an average expected heterozygosity of 0.8575. These microsatellite loci will be used to examine gene flow and population structure in Ugandan P. m. victoriae.     

Global warming will affect the genetic diversity and uniqueness of Lycaena helle populations

The climate warming of the postglacial has strongly reduced the distribution of cold‐adapted species over most of Central Europe. Such taxa have therefore become extinct over most of the lowlands and shifted to higher altitudes where they have survived to the present day. The lycaenid butterfly Lycaena helle follows this pattern of former widespread distribution and later restriction to mountain areas such as the European middle mountains. We sampled 203 individuals from 10 populations representing six mountain ranges (Pyrenees, Jura, Massif Central, Morvan, Vosges and Ardennes) over the species' western distribution. Allozyme and microsatellite polymorphisms were analysed to study the genetic status of these highly fragmented populations. Both molecular marker systems revealed a strong genetic differentiation among the analysed populations, coinciding with the orographic structure and highly restricted gene flow among them. The large‐scale genetic differentiation is more pronounced in allozymes (F_CT: 0.326) than in microsatellites (R_CT: 0.113), but microsatellites show a higher resolution on the regional scale (R_SC: 0.082) compared with allozymes (F_SC: n.s.). For both analytical tools, we found private alleles occurring exclusively in a single mountain area. The highly fragmented and isolated occurrence of populations is supported by the distribution pattern of potentially suitable climate suggested by species distribution models. Model projections under two climate warming scenarios predict a decline of climatically suitable areas, which will result in the extinction of most of the populations showing unique genetic characteristics.     

Experimental climate effect on seasonal variability of polyphenol/phenoloxidase interplay along a narrow fen–bog ecological gradient in Sphagnum fallax

Extracellular phenoloxidase enzymes play an important role in the stability of soil carbon storage by contributing to the cycling of complex recalcitrant phenolic compounds. Climate warming could affect peatland functioning through an alteration of polyphenol/phenoloxidase interplay, which could lead them to becoming weaker sinks of carbon. Here, we assessed the seasonal variability of total phenolics and phenoloxidases subjected to 2–3 °C increase in air temperature using open‐top chambers. The measurements were performed along a narrow fen–bog ecological gradient over one growing season. Climate warming had a weak effect on phenoloxidases, but reduced phenolics in both fen and bog areas. Multivariate analyses revealed a split between the areas and also showed that climate warming exacerbated the seasonal variability of polyphenols, culminating in a destabilization of the carbon cycle. A negative relationship between polyphenols and phenoloxidases was recorded in controls and climate treatments suggesting an inhibitory effect of phenolics on phenoloxidases. Any significant decrease of phenolics through repeatedly elevated temperature would greatly impact the ecosystem functioning and carbon cycle through an alteration of the interaction of polyphenols with microbial communities and the production of extracellular enzymes. Our climate treatments did not have the same impact along the fen–bog gradient and suggested that not all the peatland habitats would respond similarly to climate forcing.     

Acclimation of isoprene emission and photosynthesis to growth temperature in hybrid aspen: resolving structural and physiological controls

Acclimation of foliage to growth temperature involves both structural and physiological modifications, but the relative importance of these two mechanisms of acclimation is poorly known, especially for isoprene emission responses. We grew hybrid aspen (Populus tremula x P. tremuloides) under control (day/night temperature of 25/20 °C) and high temperature conditions (35/27 °C) to gain insight into the structural and physiological acclimation controls. Growth at high temperature resulted in larger and thinner leaves with smaller and more densely packed chloroplasts and with lower leaf dry mass per area (M_A). High growth temperature also led to lower photosynthetic and respiration rates, isoprene emission rate and leaf pigment content and isoprene substrate dimethylallyl diphosphate pool size per unit area, but to greater stomatal conductance. However, all physiological characteristics were similar when expressed per unit dry mass, indicating that the area‐based differences were primarily driven by M_A. Acclimation to high temperature further increased heat stability of photosynthesis and increased activation energies for isoprene emission and isoprene synthase rate constant. This study demonstrates that temperature acclimation of photosynthetic and isoprene emission characteristics per unit leaf area were primarily driven by structural modifications, and we argue that future studies investigating acclimation to growth temperature must consider structural modifications.     

Odontoblasts: the cells forming and maintaining dentine

Odontoblasts are tall columnar cells located at the periphery of the dental pulp. They derive from ectomesenchymal cells originated by migration of neural crest cells during the early craniofacial development. Odontoblasts form the dentine, a collagen-based mineralized tissue, through secretion of its collagenous and noncollagenous organic matrix components and by control the mineralization process. A conspicuous cell process arises from the cell body of odontoblasts and penetrates into the mineralized dentine. After dentinogenesis, odontoblasts deposit new layers of dentine throughout life and might also form a type of reactionary/reparative dentine in response to dental caries and other external factors may affect teeth.     

The effects of O2 on net photosynthesis at low temperature (5°C)

Abstract. It has been shown that atmospheric O₂ can either depress or stimulate the rate of apparent photosynthesis of white mustard depending on the environmental conditions: CO₂ concentration, light intensity and temperature. Stimulation by O₂ was observed only under high photon fluence rate and at high CO₂ concentrations. The critical CO₂ concentration below which O₂ was inhibiting and above which it was stimulating was dependent on the temperature of the assay: for plants grown at 12°C the critical CO₂ concentration was 13.35 mmol at 5° C and 21.92 mmol at 10° C. Stimulation by O₂ depended also on the growth temperature: for measurements at 26.31 mmol m^?3 CO₂, O₂ was stimulating at temperatures less than 12°C for plants grown at 12°C and less than 19°C for plants grown at 27°C. The efficiency of the O₂-dependent stimulation of net photosynthesis was maximum at 9.21 mol m^?3 O₂ at 26.31 mmol m^?3 CO₂. Oxygen-stimulation of net photosynthesis was detected in Nicotiana tabacum L. var Samsun, Lycopersicum esculentum L. and Chenopodium album L. At 5°C and under high photon fluence rate, O₂ increased the carboxylation capacity of the photosynthetic apparatus of mustard and decreased its affinity for CO₂. The O₂ inhibition of the net CO₂ uptake observed at low CO₂ concentrations was the result of a decrease in the affinity for carbon dioxide. The nature of the mechanism which causes the stimulation of photosynthesis is discussed.