BackgroundInvertebrate nervous systems are highly disparate between different taxa. This is reflected in the terminology used to describe them, which is very rich and often confusing. Even very general terms such as 'brain', 'nerve', and 'eye' have been used in various ways in the different animal groups, but no consensus on the exact meaning exists. This impedes our understanding of the architecture of the invertebrate nervous system in general and of evolutionary transformations of nervous system characters between different taxa.ResultsWe provide a glossary of invertebrate neuroanatomical terms with a precise and consistent terminology, taxon-independent and free of homology assumptions. This terminology is intended to form a basis for new morphological descriptions. A total of 47 terms are defined. Each entry consists of a definition, discouraged terms, and a background/comment section.ConclusionsThe use of our revised neuroanatomical terminology in any new descriptions of the anatomy of invertebrate nervous systems will improve the comparability of this organ system and its substructures between the various taxa, and finally even lead to better and more robust homology hypotheses.

The mRNA expression patterns of the androgen receptor and the androgen metabolizing enzymes 3beta-hydroxysteroid dehydrogenase/Delta(5-4)-isomerase, 17beta-hydroxysteroid dehydrogenase, 5alpha-reductase, and 3alpha-hydroxysteroid dehydrogenase were investigated in three different cell populations originating from human skin, SZ95 sebocytes, HaCaT keratinocytes, and MeWo melanoma cells, by means of reverse transcription polymerase chain reaction. Restriction analysis of cDNA fragments was performed to identify isozymes of 3beta-hydroxysteroid dehydrogenase/Delta(5-4)-isomerase and 3alpha-hydroxysteroid dehydrogenase. In addition, 3H-dihydroepiandrosterone and 3H-testosterone were used as substrates to determine the metabolic activity of these enzymes in SZ95 sebocytes, primary sebocyte cultures, and HaCaT keratinocytes. Furthermore, the effects of the selective 5alpha-reductase type 1 and 2 inhibitors, 4,7beta-dimethyl-4-aza-5alpha-cholestan-3-one and dihydrofinasteride, respectively, and of the 3beta-hydroxysteroid dehydrogenase/Delta(5-4)-isomerase inhibitor cyproterone acetate on androgen metabolism were investigated. Androgen receptor mRNA was detected in SZ95 sebocytes and HaCaT keratinocytes but not in MeWo melanoma cells, whereas 3beta-hydroxysteroid dehydrogenase/Delta(5-4)-isomerase isotype 1 mRNA and metabolic activity were only found in SZ95 sebocytes. The enzyme activity could be inhibited by cyproterone acetate. Type 2 17beta-hydroxysteroid dehydrogenase, type 1 5alpha-reductase, and 3alpha-hydroxysteroid dehydrogenase mRNA were expressed in all three cell populations tested, whereas type 3 17beta-hydroxysteroid dehydrogenase mRNA could only be detected in SZ95 sebocytes. The major metabolic steps of testosterone in SZ95 sebocytes, primary sebocyte cultures, and HaCaT keratinocytes were its conversion to androstenedione by 17beta-hydroxysteroid dehydrogenase and further to 5alpha-androstanedione by 5alpha-reductase. The type 1 5alpha-reductase selective inhibitor 4,7beta-dimethyl-4-aza-5alpha-cholestan-3-one, but not the type 2 selective inhibitor dihydrofinasteride, inhibited 5alpha-reductase at low concentrations in SZ95 sebocytes and HaCaT keratinocytes. 5alpha-androstanedione was degraded to androsterone by 3alpha-hydroxysteroid dehydrogenase, which exhibited a stronger activity in HaCaT keratinocytes than in SZ95 sebocytes and in primary sebocyte cultures. Lower levels of 5alpha-dihydrotestosterone and 5alpha-androstanediol were also detected in all cells tested. Our investigations show that specific enzyme expression and activity in cultured sebocytes and keratinocytes seem to allocate different duties to these cells in vitro. Sebocytes are able to synthesize testosterone from adrenal precursors and to inactivate it in order to maintain androgen homeostasis, whereas keratinocytes are responsible for androgen degradation.

Seborrhoea and acne are exclusively human diseases and sebaceous gland differentiation is species specific. Therefore, fundamental research on human sebaceous cell function and control requires human in vitro models. The human sebocyte culture model, introduced in 1989, has been used in several studies to elucidate sebaceous gland activity and its regulation at the cellular level. Cultured human sebocytes have been shown to preserve important sebocytic characteristics, although they undergo an incomplete terminal differentiation in vitro. In vitro synthesis of free fatty acids without bacterial involvement and marked interleukin 1α expression at the mRNA and protein levels with no further induction by lipopolysaccharides lead to the assumption that human sebocytes may initiate acne lesions by an intrinsic mechanism. Androgens affected sebocyte activity in vitro in a manner dependent on the localization of the sebaceous glands. In vitro stimulation of sebocyte proliferation by androgens could be completely abolished by spironolactone. Cultured sebocytes strongly expressed type 1 5α-reductase and metabolized testosterone to androstenedione, 5α-androstanedione, 5α-dihydrotestosterone, androsterone and 5α-androstanediol, whereas the levels of 5α-reductase activity were probably not feedback regulated. 4,7β-Dimethyl-4-aza-5αcholestan-3-one, a type 1 5α-reductase inhibitor, induced an early, marked down-regulation of 5α-reductase activity in human sebocytes in vitro, while hydrofinasteride, a type 2 inhibitor, required 10³-fold higher concentrations to induce similar effects. Stimulation of sebocyte proliferation by insulin, thyroid-stimulating hormone and hydrocortisone indicates that the hormonal control of the sebaceous gland could be a complex mechanism. Retinoids inhibited sebocyte proliferation in a dose-dependent manner and down-regulated lipid synthesis and sebocyte differentiation in vitro. Isotretinoin was the most potent compound. On the other hand, vitamin A was found essential for sebocyte activity and differentiation in vitro and could be partially substituted by synthetic retinoids. The inhibitory effect of isotretinoin on sebocyte proliferation was barely affected by the presence of vitamin A. The low persistent isotretinoin levels or, more likely, the considerably elevated tretinoin concentrations detected in human sebocytes after treatment with isotretinoin in vitro may be responsible for the inhibitory effect of this compound on sebocyte activity.

The new peptide hormone insulin-like peptide 3 (INSL3) is a member of the insulin-relaxin family, yet, unlike insulin, it signals through a new G-protein coupled receptor, LGR8, distantly related to the receptors for LH and FSH. INSL3 is produced in large amounts by the Leydig cells of the testis in both fetal and adult mammals. Using a combination of mRNA analysis by RT-PCR, immunohistochemistry, ligand-binding, and/or bioactivity assays, the distribution of LGR8 expression was assessed in testicular tissues and cells and in the epididymis. There was consistent agreement that LGR8 was expressed in meiotic and particularly postmeiotic germ cells and in Leydig cells, though not in Sertoli or peritubular cells. Leydig cells appear to express only a low level of the LGR8 gene product; other transcripts may be present, representing nonfunctional products. Messenger RNA analysis suggested that LGR8 transcripts in germ cells represented mostly full-length forms. LGR8 mRNA was also expressed in the epididymis, though no function can yet be ascribed to this expression. Therefore, the INSL3/LGR8 system represents a further paracrine hormone-receptor system in the testis, which conveys information about Leydig cell status to germ cells, and possibly as part of an autocrine feedback loop.

BackgroundMollusca is an extremely diverse animal phylum that includes the aculiferans (worm-like aplacophorans and eight-shelled polyplacophorans) and their sister group, the conchiferans, comprising monoplacophorans, bivalves (clams, mussels), gastropods (snails, slugs), scaphopods (tusk shells) and cephalopods (squids, octopuses). Studies on mollusks have revealed an overall number of 11 Hox genes in seven out of eight molluscan “class”-level taxa, but expression data of key developmental regulators such as homeotic genes are only available for three gastropod and two cephalopod species. These show that Hox genes are involved in the formation of specific features including shell, foot, funnel or tentacles and not in antero-posterior body plan patterning as in most other bilaterian animals. The role of Hox genes in non-conchiferan (i.e., aculiferan) mollusks remains entirely unknown.ResultsHere we present the first data on the expression of seven Hox genes in apolyplacophoran mollusk, Acanthochitona crinita. In A. crinita the Hox genes Acr-Hox1-5, Hox7 and Post2 are expressed in a co-linear pattern along the antero-posterior axis, but not in molluscan-specific features such as the shell or the foot. The expression pattern is restricted to the post-trochal region and the transcripts are present in ecto-, endo- and mesodermal cell layers. Contrary to the situation in gastropods and cephalopods, we did neither find Hox gene expression in distinct neural subsets of A. crinita, nor in its developing shell plates.ConclusionsOur analysis and comparison with other lophotrochozoans indicate that the basal role of Hox genes is in antero-posterior axis patterning in mollusks, similar to the vast majority of bilaterian animals, and that this role has been conserved in polyplacophorans, while co-option into patterning of evolutionary novelties emerged either at the base of Conchifera or independently in gastropods and cephalopods. These morphological innovations most likely contributed to the evolutionary success of its representatives, as exemplified by, e.g., the wide ecological range and species richness of gastropods.