Previously, we reported that the countercurrent urine concentration mechanism in birds appears to operate by recycling of a single solute (NaCl), in which the thick ascending limb of looped nephrons provides an energy source. To determine the importance of the medullary collecting duct (MCD) in the countercurrent multiplier system, we examined in isolated and perfused MCDs from Japanese quail, Coturnix coturnix, the osmotic and/or diffusional water permeability and whether arginine vasotocin (AVT) regulates water permeability. We noted that dark cells that possess electron-dense cytoplasm and numerous mitochondria and light mucus-secreting cells exist in the cortical collecting duct (CD), whereas only mucus-secreting cells are present in the MCDs. The volume flux (Jv) in the MCDs from intact birds and that from the water-deprived birds were nearly zero; after exposure to a hyperosmotic bath and AVT (2 x 10(-5) M), the Jv was significantly higher in water-deprived birds. The diffusional water permeability (Pdw) was moderately high in MCDs bathed in an isosmotic bath in which the Pdw was increased slightly by AVT (10(-5) M, bath) and more markedly (10(-5) M) by forskolin (Fsk), whereas 1,9-dideoxy Fsk (an inactive analogue) showed no effect. Furthermore, the basal adenosine 3',5'-cyclic monophosphate (cAMP) levels were higher in the medulla than in the cortex and were stimulated only slightly by AVT (10(-5) M) and markedly by Fsk (10(-4) M) in both the cortex and medulla. These results in the C. coturnix CD indicate the following. 1) Two types of cells are present; whereas dark cells resemble mammalian intercalated cells morphologically, it is not certain whether mucus-secreting cells are equivalent to principal cells. 2) AVT increases Pdw via a cAMP mechanism; the relatively high basal Pdw and minor effect of AVT on Jv and Pdw suggest, however, that diffusional water movement across the MCD may occur without significant direct control by AVT.

Previous studies on murine T cell IgD-R have shown that these receptors recognize N-glycans of murine IgD, and not of other Ig isotypes. We have now studied the specificity of IgD-R on human T cells. Human IgD digested with proteinase K to fragments of X 5 kDa inhibit the ability of T cells to form rosettes with IgD-coated ox erythrocytes. The same amount of digested IgG does not. We tested all the human Ig isotypes: IgG1,-2,-3,-4, IgA2, IgE and IgM fail to inhibit significantly at 20 ? g/assay. However, IgA1 is as effective as IgD itself, showing approximately 60 % and 80 % inhibition at 5 ? g and 10 ? g/assay. Human IgA1 and IgD both contain Gal-1 1 3-GalNac-rich O-linked glycans, and on this basis are both bound to ricin and jacalin. The O-linked glycans may therefore also represent the common moiety binding to IgD-R. Disaccharides Gal-1 1 3-GalNac, and Gal-1 1 4-Glc at 10 ? g/assay blocked IgD rosetting while Gal-1 1 6-Glc did not. We conclude that the human IgD-R is a lectin, differing from the murine IgD-R in that it has both IgA1 and IgD as ligands.

Background: Sex or gender disparity in skin cancer has been documented for a long time at the population level. UV radiation (UVR) is a common environmental risk for all three major types of skin cancer: cutaneous melanoma (CM), basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC). The underlying mechanism for sex disparity has been largely attributed to sex-differentiated behaviour patterns related to UVR. Non-UVR factors such as intrinsic physiological differences have been suggested but remain understudied. Aims, Materials and Methods: This review summarizes and compares the known sex differences in three skin cancer types with regard to body site distribution and age influence. Results: We found a similar age-dependent sex difference pattern in CM and BCC. Specifically, CM and BCC tend to show higher incidence in young women and old men, with a switching age around menopause. The switching age suggests involvement of sex hormones, which has shown controversial influence on skin cancers at epidemiological level. Literatures regarding sex hormone receptors for oestrogen, androgen and progesterone are summarized for potential explanations at molecular level. Discussion: Overall, more and more evidence suggests non-UVR factors such as sex hormones play critical roles in skin cancer (especially CM and BCC), yet solid population and molecular evidence are required. Incidences of skin cancer are increasing which suggests limited effect for the current UVR-avoidance prevention methods. Conclusion: Fully understanding the causes of sex disparities in incidence is necessary for developing a comprehensive prevention strategy. V. Collier and M. Musicante have contributed equally to this work.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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