We have demonstrated previously that the Slit proteins, which are involved in axonal guidance and related developmental processes in nervous tissue, are ligands of the glycosylphosphatidylinositol-anchored heparan sulfate proteoglycan glypican-1 in brain (Liang, Y., Annan, R. S., Carr, S. A., Popp, S., Mevissen, M., Margolis, R. K., and Margolis, R. U. (1999) J. Biol. Chem. 274, 17885-17892). To characterize these interactions in more detail, recombinant human Slit-2 protein and the N-and C-terminal portions generated by in vivo proteolytic processing were used in an enzyme-linked immunosorbent assay to measure the binding of a glypican-Fc fusion protein. Saturable and reversible high affinity binding to the full-length protein and to the C-terminal portion that is released from the cell membrane was seen, with dissociation constants in the 80 -110 nM range, whereas only a relatively low level of binding to the larger N-terminal segment was detected. Co-transfection of 293 cells with Slit and glypican-1 cDNAs followed by immunoprecipitation demonstrated that these interactions also occur in vivo, and immunocytochemical studies showed colocalization in the embryonic and adult central nervous system. The binding affinity of the glypican core protein to Slit is an order of magnitude lower than that of the glycanated proteoglycan. Glypican binding to Slit was also decreased 80 -90% by heparin (2 g/ml), enzymatic removal of the heparan sulfate chains, and by chlorate inhibition of glypican sulfation. The differential effects of N-or O-desulfated heparin on glypican binding also indicate that O-sulfate groups on the heparan sulfate chains play a critical role in heparin interactions with Slit. Our data suggest that glypican binding to the releasable C-terminal portion of Slit may serve as a mechanism for regulating the biological activity of Slit and/or the proteoglycan.In previous studies we biochemically characterized a major heparan sulfate proteoglycan of nervous tissue (1, 2) that we later cloned and identified as the rat homologue of glypican-1 (3), the initial member of a family of glycosylphosphatidylinositol-anchored heparan sulfate proteoglycans that is currently composed of six vertebrate proteins. High levels of glypican-1 mRNA are present in brain and skeletal muscle, and in situ hybridization histochemistry demonstrated that glypican-1 mRNA is especially prominent in cerebellar granule cells, large motor neurons in the brain stem, and CA3 pyramidal cells of the hippocampus (4). These results and parallel immunocytochemical studies indicate that glypican-1 is predominantly a neuronal product in the late embryonic and postnatal rat nervous system. Based on genetic studies, it would appear that the glypicans play a significant role in cell growth and development. Dally, the Drosophila homologue of glypican-1, is required for the control of cell division in the developing visual system and for morphogenesis of other tissues (5), and the human homologue of glypican-3/OCI-5 (GPC3) is found to be mutated in pat...

In histological studies, it has frequently been demonstrated that ultraviolet (UV) exposure, in particular UVB, can induce significant thickening of the viable epidermis and/or stratum corneum. Since skin biopsy alters the original skin morphology and always requires an iatrogenic trauma, we aimed to introduce optical coherence tomography (OCT) in vivo for the investigation of changes of epidermal thickness (ET) following UVA1 and UVB irradiation. Twelve healthy subjects received daily 60 J/cm2 of UVA1 and 1.5 minimal erythema doses UVB on their upper back over 3 consecutive days. Twenty-four hours after the last irradiation, OCT assessments were performed on UV exposed and adjacent nonirradiated control sites. Data of ET as expressed by comparison of the averaged A-scans differed significantly between nonirradiated (94.2 +/- 15.7 microm), UVA1 (105.4 +/- 12.8 microm) and UVB (125.7 +/- 22.1 microm) exposed sites. In comparison to the nonirradiated sites, UVA1 exposed skin showed significant (P = 0.022) increase of ET of 11% and UVB exposed sites a significant (P < 0.001) increase of 25%. ET of UVA1 and UVB exposed skin sites differed significantly (P =0.005). Our results obtained from OCT in vivo measurements confirm data of previous histological studies indicating that not only erythemogenic doses of UVB, but also suberythemogenic doses of UVA1 may have a significant impact on ET. OCT appears to be a promising bioengineering technique for photobiological studies. However, further studies are needed to establish its measurement precision and validity, and to investigate in vivo spectral dependence on UV induced skin changes such as skin thickening.

Sunbed exposures seem to induce photoadaptation not only by skin pigmentation but also by epidermal thickening that is predominantly due to an increase in thickness of the horny layer. Moreover, our data indicate that UVA radiation has an influence on the cell size of the granular layer. CLSM is a promising tool for photobiological studies in vivo.

Diagnostic phototesting, including the determination of the minimal erythema dose (MED), is a useful procedure to detect abnormal sensitivity to UV radiation. We aimed to estimate the reference limits (RLs) of the MED in a reasonably large reference sample of white individuals. Skin phototypes and MED values for broadband UVB and for UVA were determined in 461 white subjects. When appropriate, the 95% reference intervals, including the 0.025 fractile and 0.975 fractile, were computed for the MED-UVB reference values (by means of parametric methods) and the MED-UVA reference values (by means of nonparametric methods). MED data were also converted to standard erythema doses (SEDs). As described elsewhere we observed a considerable overlap of MED values for all skin phototypes and confirmed that age and sex do not substantially influence the MED. The lower RLs observed for MED-UVB were 33 mJ cm(-2) (0.5 SEDs) and for MED-UVA 12.6 mJ cm(-2) (1.2 SEDs). The MED and SED findings from this investigation may serve as reference data for white individuals and give support to the clinician in differentiating between normal and pathologically abnormal photosensitivity. Although the MED data given here are limited to the phototest device used in the present study, the SED results establish comparability between our data and phototest results obtained from laboratories using different UV sources.