Comparison of microridges in juvenile and adult sunfish,Lepomis gibbosus

Microridges are F-actin-based surface protrusions of the superficial layer cells of fish epidermis. Microridge patterns progress in complexity during fish embryogenesis, often transitioning from abundant surface microvilli to the classical fingerprint arrangement. This progression suggests pattern changes may also occur during later stages of fish development. Fluorescent labelling of F-actin and morphometric analysis were therefore used to assess changes in epidermal microridge patterns in juvenile and adult sunfish (Lepomis gibbosus). The microridge patterns found in adult pumpkinseed were similar to that described for many fishes, consisting of whorls or complex multi-branched ridges. The microridge patterns of the scales from three different-sized groups of juvenile pumpkinseed were distinctly different from that of adult, however, and were present mainly as unbranched concentric or nearly concentric rings in the two larger juvenile groups. In the smallest juveniles, microridges were often apparent as fragmented ridges with abundant actin puncta. Larger juveniles sometimes displayed mixed patterns, with some microridges similar to that of both adult and juvenile patterns. The results show a transition from simple microridge patterns in juvenile pumpkinseeds to distinctly different, diverse and more complex patterns in adults. The different pattern types may reflect particular microridge functions relevant to fish size and age.     

Predictivity of an in vitro model for acute and chronic skin irritation (SkinEthic) applied to the testing of topical vehicles

An in vitro human reconstructed epidermis model (SkinEthic) used for screening acute and chronic skin irritation potential was validated against in vivo data from skin tolerability studies. The irritation potential of sodium lauryl sulfate (SLS), calcipotriol and trans-retinoic acid was investigated. The in vitro epidermis-like model consists of cultures of keratinocytes from human foreskin on a polycarbonate filter. The modulation of cell viability, the release and gene expression of proinflammatory cytokines, interleukins 1α and 8, and morphological changes were evaluated during 3 days as endpoints representative for an inflammatory reaction. The cumulative irritation potential of the topical products was evaluated in a human clinical study by visual scoring and biophysical measurement of inflammatory skin reaction after repeated 24 h applications over 3 weeks under Finn chamber patches. All topical products that were nonirritating in the human study were noncytotoxic and did not induce cytokine expression in the in vitro acute model (day 1 exposure). All irritating controls exhibited specific cell viability and cytokine patterns, which were predictive of the in vivo human data. The ranking of mild to moderate skin irritation potential was based on the lack of cytotoxicity and the presence of cytokine patterns including gene expression specific for each irritant, using the chronic in vitro model (up to 3 days exposure). The human reconstructed epidermis model SkinEthic was shown to be a reliable preclinical tool predicting the irritation potential of topical products. Moreover, it is a useful model in a two-step tiered strategy for screening acute and chronic irritation potential for the selection of vehicles for new topical drugs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Dynamic stem cell selection safeguards the genomic integrity of the epidermis

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Purification and immunohistochemical localization of the auxin binding site i protein from maize coleoptiles

An auxin binding protein fraction prepared by means of affinity chromatography on 2-OH-3,5-diiodobenzoic acid-Sepharose and gel filtration was used as antigen. The obtained rabbit antisera contained antibodies against the auxin, binding protein (ABP) and several contaminating proteins (nonABP). The nonABP could be separated on an appropriate affinity matrix omitting the TIBA analogue. After their immobilization on Sepharose antibodies directed towards contaminating, the proteins were isolated and immobilized, too. This IgGanti nonABP-Sepharose retains almost all contaminating proteins present in the specific eluates of the auxin affinity matrix. In a final affinity chromatography step on IgG-Sepharose a highly purified ABP could be eluted. This ABP was immobilized on Sepharose for the separation of monospecific antibodies against ABP (IgGanti abp). Using these antibodies the ABP could be localized within the outer epidermal cells of the coleoptile by immunofluorescence microscopy. From the inhibition of auxin induced elongation of coleoptile tissue by IgGanti abp it is concluded that the ABP is localized at the plasmalemma of the epidermal cells and that the ABP is involved in auxin action as a true hormone receptor. Presented at the International Symposium “Plant Growth Regulators” held on June 18–22, 1984 at Liblice, Czechoslovakia.     

A comparative study of the leaves of Cat hay a argyrophylla Chun & Kuang and three species of Keteleeria Carrière

Details of the cuticular, epidermal and anatomical features of the leaves of Cathaya argyrophylla Chun & Kuang, are described and compared with those of three species of Keteleeria (K. davidiana (Bertrand) Beissner, K. fortunei (Murray) Carriere, and K. chien-peii Flous). The study supports the creation of Cathaya Chun & Kuang as a new genus of the Pinaceae.     

Role of keratinocyte‐derived factors involved in regulating the proliferation and differentiation of mammalian epidermal melanocytes

Melanocytes characterized by the activities of tyrosinase, tyrosinase‐related protein (TRP)‐1 and TRP‐2 as well as by melanosomes and dendrites are located mainly in the epidermis, dermis and hair bulb of the mammalian skin. Melanocytes differentiate from melanoblasts, undifferentiated precursors, derived from embryonic neural crest cells. Because hair bulb melanocytes are derived from epidermal melanoblasts and melanocytes, the mechanism of the regulation of the proliferation and differentiation of epidermal melanocytes should be clarified. The regulation by the tissue environment, especially by keratinocytes is indispensable in addition to the regulation by genetic factors in melanocytes. Recent advances in the techniques of tissue culture and biochemistry have enabled us to clarify factors derived from keratinocytes. Alpha‐melanocyte‐stimulating hormone, adrenocorticotrophic hormone, basic fibroblast growth factor, nerve growth factor, endothelins, granulocyte‐macrophage colony‐stimulating factor, steel factor, leukemia inhibitory factor and hepatocyte growth factor have been suggested to be the keratinocyte‐derived factors and to regulate the proliferation and/or differentiation of mammalian epidermal melanocytes. Numerous factors may be produced in and released from keratinocytes and be involved in regulating the proliferation and differentiation of mammalian epidermal melanocytes through receptor‐mediated signaling pathways.     

A microhistological survey on the trees of a relict subtropical laurel forest from the Macaronesian Islands as a base for assessing vertebrate plant diet

A microhistological collection and its respective key on the leaves and fleshy fruits produced by the mostly endemic trees that integrate the relict laurel forest in the Macaronesian Islands are presented. Epidermal tissues from the adaxial and abaxial surfaces of leaves and fruits of 23 species were extracted by scraping and prepared on individual microscope slides. An optical microscope with a camera lucida fixed at magnifications of ×400 was used to analyse and to draw the morphological traits of epidermal tissues to the same scale. Furthermore, quantitative data for those congeneric species were also obtained by using an image analysis program system. The results indicate that this microhistological method permits the differentiation of practically all species of trees present in the Macaronesian laurel forest. Furthermore, most species belonging to the same taxa (genus or family) show a general common pattern in the morphology of the different epidermal traits. Lastly, despite the effort that constitutes the preparation of plant microhistological collections of a determined ecosystem, it is of basic importance because it makes possible the performance of feeding ecological studies of several herbivorous and frugivorous vertebrate species. These results provide crucial information that elucidates the functioning of the food web and energetic flux dynamics of the Macaronesian laurel forest ecosystem.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 409–426.     

Divergent roles of HDAC1 and HDAC2 in the regulation of epidermal development and tumorigenesis

The histone deacetylases HDAC1 and HDAC2 remove acetyl moieties from lysine residues of histones and other proteins and are important regulators of gene expression. By deleting different combinations of Hdac1 and Hdac2 alleles in the epidermis, we reveal a dosage‐dependent effect of HDAC1/HDAC2 activity on epidermal proliferation and differentiation. Conditional ablation of either HDAC1 or HDAC2 in the epidermis leads to no obvious phenotype due to compensation by the upregulated paralogue. Strikingly, deletion of a single Hdac2 allele in HDAC1 knockout mice results in severe epidermal defects, including alopecia, hyperkeratosis, hyperproliferation and spontaneous tumour formation. These mice display impaired Sin3A co‐repressor complex function, increased levels of c‐Myc protein, p53 expression and apoptosis in hair follicles (HFs) and misregulation of HF bulge stem cells. Surprisingly, ablation of HDAC1 but not HDAC2 in a skin tumour model leads to accelerated tumour development. Our data reveal a crucial function of HDAC1/HDAC2 in the control of lineage specificity and a novel role of HDAC1 as a tumour suppressor in the epidermis.