Reconstructed human epidermis for skin absorption testing: results of the German prevalidation study

Exposure to chemicals absorbed by the skin can threaten human health. In order to standardise the predictive testing of percutaneous absorption for regulatory purposes, the OECD adopted guideline 428, which describes methods for assessing absorption by using human and animal skin. In this study, a protocol based on the OECD principles was developed and prevalidated by using reconstructed human epidermis (RHE). The permeation of the OECD standard compounds, caffeine and testosterone, through commercially available RHE models was compared to that of human epidermis and animal skin. In comparison to human epidermis, the permeation of the chemicals was overestimated when using RHE. The following ranking of the permeation coefficients for testosterone was obtained: SkinEthic > EpiDerm, EPISKIN > human epidermis, bovine udder skin, pig skin. The ranking for caffeine was: SkinEthic, EPISKIN > bovine udder skin, EpiDerm, pig skin, human epidermis. The inter-laboratory and intra-laboratory reproducibility was good. Long and variable lag times, which are a matter of concern when using human and pig skin, did not occur with RHE. Due to the successful transfer of the protocol, it is now in the validation process.     

Dikaryotic fruiting body development in a single dikaryon of <Emphasis Type="Italic">Agrocybe aegerita</Emphasis> and the spectrum of monokaryotic fruiting types in its monokaryotic progeny

Using monokaryotic offspring from several dikaryotic parental strains, the phenomenon of monokaryotic fruiting has been previously analysed in the commercially cultivated high-quality edible mushroom Agrocybe aegerita, revealing a variety of monokaryotic fruiting types. Here, we report a single dikaryotic A. aegerita strain, A. aegerita AAE-3, and 40 monokaryons derived from it, which exhibit a wide spectrum of monokaryotic fruiting types, including a rare, previously unknown type. Advantageously, the selected parental strain A. aegerita AAE-3 completes its life cycle within three weeks by the formation of dikaryotic fruiting bodies of typical agaric morphology on malt extract agar plates. In order to morphologically compare normal dikaryotic fruiting to monokaryotic fruiting, histology was performed from all dikaryotic fruiting body development stages and all fruiting types of monokaryotic origin. No clamp connections or dikaryotic hyphae were observed within the plectenchyma of monokaryotic fruiting stages. Among the monokaryotic fruiting types of the A. aegerita AAE-3-derived monokaryons, we also characterised the rare ‘stipe type’ here described as ‘elongated initials type’ as no differentiation into a future cap and stipe was seen. The two mating-compatible monokaryotic strains representing the extremes of the fruiting type spectrum observed, A. aegerita AAE-3-13 (‘mycelium type’) and A. aegerita AAE-3-32 (‘abortive?+?true homokaryotic fruiting fruiter type, AHF?+?THF fruiter type’), were also found to readily produce oidia (arthrospores). In order to obtain a set of mating-compatible monokaryons covering the whole observed spectrum of monokaryotic fruiting, the two monokaryons A. aegerita AAE-3-40 (‘initials type’) and A. aegerita AAE-3-37 (‘elongated initials type’) have been selected for their mating compatibility with A. aegerita AAE-3-32 and A. aegerita AAE-3-13, respectively. Together with the parental dikaryotic strain A. aegerita AAE-3, this set of standard monokaryons could prove useful for studies exploring the factors regulating monokaryotic fruiting in comparison to dikaryotic mushroom formation.     

Sex-Specific Habitat Utilization and Differential Breeding Investments in Christmas Island Frigatebirds throughout the Breeding Cycle

In seabirds, equal bi-parental care is the rule, as it is considered crucial for raising chicks successfully because seabirds forage in an environment with unpredictable and highly variable food supply. Frigatebirds forage in poor tropical waters, yet males reduce and even stop parental care soon after chick brooding, leaving the female to provision the chick alone for an extended fledging period. Using bird-borne tracking devices, male and female Christmas Island Frigatebirds (Fregata andrewsi) were investigated during the brooding, late chick rearing and post-fledging period to examine whether sexes exhibit foraging strategies that may be linked to differential breeding investments. During brooding, males and females showed similar foraging behaviour under average marine productivity of oceanic waters close to the colony, but males shifted to more distant and more productive habitats when conditions deteriorated to continue with reduced chick provisioning. During the late chick rearing period, females progressively increased their foraging range to the more distant but productive marine areas that only males had visited during brooding. Birds spent the non-breeding period roosting in highly productive waters of the Sunda Shelf. The sex-specific utilisation of three different foraging habitats with different primary productivity (oceanic, coastal, and shelf areas) allowed for temporal and spatial segregation in the exploitation of favourable habitats which seems to enable each sex to optimise its foraging profitability. In addition, post-fledging foraging movements of females suggest a biennial breeding cycle, while limited information on males suggests the possibility of an annual breeding cycle.     

Leucocyte profiles and H/L ratios in chicks of Red-tailed Tropicbirds reflect the ontogeny of the immune system

Immune defence is fundamentally important for the survival prospects of young animals. While innate immunity offers initial protection from a variety of pathogens, acquired immunity responds more specifically to pathogens, but is considered to be more costly and to respond slower. Moreover, the acquired immunity is not yet fully developed in neonatal chicks. Little is known about the ontogeny of the immune system of wild birds. Long-lived seabirds, with their slow chick development, are good models to investigate how young birds invest in both arms of their immune system. We determined leucocyte profiles and heterophil to lymphocyte (H/L) ratios of Red-tailed Tropicbirds (Phaeton rubricauda westralis) on Christmas Island, Indian Ocean. Young chicks (N?=?10) had significantly higher H/L ratios than older chicks (N?=?19), while adults (N?=?47) showed intermediate values and did not differ from either chick age class. High H/L ratios in young chicks were caused by high initial numbers of heterophils per 10,000 erythrocytes that declined with age. In contrast, the number of lymphocytes per 10,000 erythrocytes was similar for young and older chicks. These data suggest that young chicks invested heavily in innate immunity to protect themselves from pathogens, while investment into acquired immunity became more important in older chicks with a functional acquired immune response. Body condition did not have a significant influence on any leucocyte parameter.     

Transcriptional response of mushrooms to artificial sun exposure

Climate change causes increased tree mortality leading to canopy loss and thus sun‐exposed forest floors. Sun exposure creates extreme temperatures and radiation, with potentially more drastic effects on forest organisms than the current increase in mean temperature. Such conditions might potentially negatively affect the maturation of mushrooms of forest fungi. A failure of reaching maturation would mean no sexual spore release and, thus, entail a loss of genetic diversity. However, we currently have a limited understanding of the quality and quantity of mushroom‐specific molecular responses caused by sun exposure. Thus, to understand the short‐term responses toward enhanced sun exposure, we exposed mushrooms of the wood‐inhabiting forest species Lentinula edodes, while still attached to their mycelium and substrate, to artificial solar light (ca. 30°C and 100,000 lux) for 5, 30, and 60 min. We found significant differentially expressed genes at 30 and 60 min. Eukaryotic Orthologous Groups (KOG) class enrichment pointed to defense mechanisms. The 20 most significant differentially expressed genes showed the expression of heat‐shock proteins, an important family of proteins under heat stress. Although preliminary, our results suggest mushroom‐specific molecular responses to tolerate enhanced sun exposure as expected under climate change. Whether mushroom‐specific molecular responses are able to maintain fungal fitness under opening forest canopies remains to be tested.     

Differential Interaction of the Two Related Fungal Species Candida albicans and Candida dubliniensis with Human Neutrophils

Candida albicans, the most common facultative human pathogenic fungus is of major medical importance, whereas the closely related species Candida dubliniensis is less virulent and rarely causes life-threatening, systemic infections. Little is known, however, about the reasons for this difference in pathogenicity, and especially on the interactions of C. dubliniensis with the human immune system. Because innate immunity and, in particular, neutrophil granulocytes play a major role in host antifungal defense, we studied the responses of human neutrophils to clinical isolates of both C. albicans and C. dubliniensis. C. dubliniensis was found to support neutrophil migration and fungal cell uptake to a greater extent in comparison with C. albicans, whereas inducing less neutrophil damage and extracellular trap formation. The production of antimicrobial reactive oxygen species, myeloperoxidase, and lactoferrin, as well as the inflammatory chemokine IL-8 by neutrophils was increased when stimulated with C. dubliniensis as compared with C. albicans. However, most of the analyzed macrophage-derived inflammatory and regulatory cytokines and chemokines, such as IL-1α, IL-1β, IL-1ra, TNF-α, IL-10, G-CSF, and GM-CSF, were less induced by C. dubliniensis. Similarly, the amounts of the antifungal immunity-related IL-17A produced by PBMCs was significantly lower when challenged with C. dubliniensis than with C. albicans. These data indicate that C. dubliniensis triggers stronger early neutrophil responses than C. albicans, thus providing insight into the differential virulence of these two closely related fungal species, and suggest that this is, in part, due to their differential capacity to form hyphae.     

Stimulation of de novo glutathione synthesis by nitrofurantoin for enhanced resilience of hepatocytes

Cell Biology and Toxicology - Toxicity is not only a function of damage mechanisms, but is also determined by cellular resilience factors. Glutathione has been reported as essential element to...