The nervous system regulates host immunity in complex ways. Vertebrate olfactory sensory neurons (OSNs) are located in direct contact with pathogens; however, OSNs' ability to detect danger and initiate immune responses is unclear. We report that nasal delivery of rhabdoviruses induces apoptosis in crypt OSNs via the interaction of the OSN TrkA receptor with the viral glycoprotein in teleost fish. This signal results in electrical activation of neurons and very rapid proinflammatory responses in the olfactory organ (OO), but dampened inflammation in the olfactory bulb (OB). CD8α + cells infiltrate the OO within minutes of nasal viral delivery, and TrkA blocking, but not caspase-3 blocking, abrogates this response. Infiltrating CD8α + cells were TCRαβ T cells with a nonconventional phenotype that originated from the microvasculature surrounding the OB and not the periphery. Nasal delivery of viral glycoprotein (G protein) recapitulated the immune responses observed with the whole virus, and antibody blocking of viral G protein abrogated these responses. Ablation of crypt neurons in zebrafish resulted in increased susceptibility to rhabdoviruses. These results indicate a function for OSNs as a first layer of pathogen detection in vertebrates and as orchestrators of nasal-CNS antiviral immune responses. neuroimmunology | olfactory sensory neurons | teleost | viral immunity | TrkA

No abstract

(+)- and (-)-petromyroxol [(+)-1 and (-)-1, respectively], two novel tetrahydrofuran (THF)-diol fatty acid enantiomers, were isolated from water conditioned with larval sea lamprey. We herein describe their isolation and subsequent resolution using chiral chromatography. The absolute configuration of each enantiomer was determined by a combination of Mosher ester analysis and comparison with related natural and synthetic products. Electro-olfactogram (EOG) assays indicated that (+)-petromyroxol (1) possesses potent olfactory activity for sea lamprey.

No abstract

To investigate the effect of stocking density on growth and sex ratio in European eel, four constant density conditions were tested during the transition from the glass to the elver stage for 90 days (Period 1). The test conditions combined the weight of fish per unit surface or volume (surface density or volume density) resulting in four experimental groups: low surface density (0.5 kg/m(2)) and low volume density (5 kg/m(3)) (group S(0.5)V(5)); low surface density (0.5 kg/m(2)) and high volume density (10 kg/m(3)) (group S(0.5)V(10)); high surface density (2 kg/m(2)) and low volume density (5 kg/m(3)) (group S(2)V(5)); and high surface density (2 kg/m(2)) and high volume density (10 Kg/m(3)) (group S(2)V(10)). Subsequently, fish from the S(0.5)V(5), S(2)V(5), and S(2)V(10) groups were transferred to low density conditions (0.1-0.4 kg/m(2) or 0.1-0.3 kg/m(3)) for another 21 months (630 days; Period 2). After Period 1, fish maintained at high surface density, regardless of the volume density, showed higher standard growth rates (SGRs) and RNA/DNA ratio in muscle than those cultured at low surface density. The percentage of mortality was similar in three of the groups (34.2%-41.8%), but not in the S(2)V(10) group (83.3%). At the end of Period 2, most fish (about 95%) exhibited fully differentiated gonads, but different sex ratios were observed in each group. Thus, the S(2)V(5) group showed a higher proportion of females (36.1%) and a lower proportion of males (56.8%) than the S(0.5)V(5) group (11.4% and 72.5%, respectively), while all survivor fish from the S(2)V(10) group developed into females. The gonadosomatic index and SGR were higher in females than in males. These results suggest that glass eels maintained at high surface density during the first months of growth tend to develop into females. The data also indicate that growth and sex ratio are linked processes during eel development, with growth seeming to be sex dependant rather than being influenced by the density conditions in which glass eels are maintained.

No abstract

Two experiments were carried out in which male and female tench Tinca tinca were placed in individual containers and tritiated steroids then added to the water. Water samples were collected over the next 6 or 7 h and the fish then sacrificed, bled and the gall bladder removed. Radioactivity was counted in all the samples. Over the course of the exposure period in the first experiment (7 h), radioactivity of 11-ketotestosterone (11-KT) in the water was depleted by 11%, 17,20b-dihydroxypregn-4-en-3-one (17,20ß-P) and 17,20a-dihydroxypregn-4-en-3-one (17,20a-P) by 28%, testosterone (T) by 56% and androstenedione (AD) by 68%. HPLC analysis of water samples at 3 h indicated that none of the steroids was extensively metabolized during the experiment. Females had a faster rate of uptake of AD than males. In the second experiment (6 h), radioactivity of cortisol in the water was depleted by 5%, 11-KT by 7%, 17-hydroxypregnen-4-ene (17-P) by 17%, 17b-oestradiol (E 2 ) by 35%, T by 37% and AD by 44%.In both experiments, the amounts of radioactivity that were recovered from the gall bladder and plasma were positively correlated with the rate of disappearance of radioactivity from the water. The ability of the steroids to bind to sex steroid binding protein (SBP) of tench plasma was tested by incubating plasma with radioactive steroids and then separating bound and free with ice cold dextran-coated charcoal. When plasma at a final dilution of 1 : 60 (v/v) was incubated with 5 nM of each steroid, the percentage of radiolabel bound to SBP was: T 48% AD 44%, E 2 30%, 17-P 17%, 11-KT 13Á2%, 17,20a-P 10Á3%, 17,20b-P 4Á5% and cortisol 0%. Saturation analysis established dissociation constants (K d ; mean AE S.E.) of 3Á4 AE 0Á4, 2Á2 AE 0Á2, 4Á0 AE 0Á3. 9Á0 AE 2Á8 and 51Á8 nM and binding capacities (B max ) of 201 AE 29, 201 AE 33, 165 AE 3, 187 AE 15 and 13Á4 nM for T, AD, E 2 ,17-P and 17,20b-P respectively. The ability of steroids to displace tritiated T and AD from SBP was in the rank order AD > T > E 2 > 17,20aP ¼ 17,20b-P ¼ 11-KT ¼ 17-P > cortisol. Thus, the ability of tench plasma to bind certain steroids showed a relatively strong correlation with the ability of the fish to take up these steroids from water. Modelling of data for AD and 17,20b-P helped to show why and how plasma binding had a strong influence on the rate of uptake (and hence release) of the steroids. # 2005 Crown copyright

The present study assessed the olfactory potency of conspecific bile fluid and skin mucus in the European eel Anguilla anguilla by the electro‐olfactogram. Immature males showed high olfactory sensitivity to conspecific bile, giving large amplitude responses in a concentration‐dependent manner with estimated thresholds of detection of <1:107 (n= 6). Mucus also proved to contain highly potent odorants with thresholds of detection of c. 1:106 (n= 6). Crude solid‐phase extraction of bile fluid (C‐18 and C‐2/ENV+ cartridges) showed that the majority of olfactory activity in bile fluid was contained in the eluate of C‐18 cartridges (n= 6). There were quantitative differences, however, between the sexes; female bile fluid had a higher proportion of activity in this fraction. Similar solid‐phase extraction of mucus showed that it contains a higher proportion of odorants in the C‐18 filtrate than bile fluid. Mucus from mature eels, however, had a higher proportion of olfactory activity in the eluate than immature fish (n= 6). Cross‐adaptation experiments suggest that there are qualitative differences in the odorants contained in bile and mucus depending on both the sex and state of sexual maturation of the donor (n= 6). These results are consistent with a role for chemical communication in the reproduction of the European eel and suggest that both bile and mucus are potential sources of the odorants involved.