On the basis of the marked expression of VDR and the VD metabolizing enzymes in human testis, ejaculatory tract and mature spermatozoa, we suggest that VD is important for spermatogenesis and maturation of human spermatozoa.

No abstract

The use of live prey is still necessary for a large number of raised ¢sh species. Small sized rotifers are usually used as live preys during the ¢rst days of feeding in small mouth ¢sh. An alternative to this is the use of copepods as prey for ¢rst feeding. In this study, the sizes, weight and biochemical contents of two copepods and one rotifer species raised on similar algal food conditions were compared. Rotifers contained a higher proportion of essential amino acids in the free amino acid (FAA) fraction (43%) than copepods (30^32%). However, rotifers had lower levels of important fatty acids like DHA (7% compared with 23^32% in copepods) and their DHA/EPA ratio was lower than that in copepods (0.54 compared with 1.35^1.63 in copepods). The FAA pattern of the preys tended to be species-speci¢c and its implications from an aquaculture point of view is discussed. In contrast, the-protein bound amino acids tended to be very conservative among the studied organisms. The second part of the work is focused on 'the price' of hatching in Acartia tonsa eggs before or after cold storage at 3 1C. The fatty acid contents in A. tonsa tended to decrease with the storage time. It also decreased with hatching of the nauplii, but its proportion compared with the dry weight remained constant.The table also presents the DHA/EPA ratio and the (EPA1DHA)/total FA ratio and, ¢nally, the proportion of essential amino acids in the free amino acid pool for the di¡erent live feed organisms. DW, dry weight; DHA, docosahexaenoic acid; EPA, eicosabentaenoic acid.Aquaculture Research, 2006, 37, 756^772 Biochemical and technical observations larviculture G Drillet et al.

Viral infection of bacteria causes release of dissolved organic matter (DOM), which is available for bacterial uptake. In aquatic environments, this virus-mediated transformation of living cells into dissolved and colloidal organic matter may be a quantitatively important process in the pelagic recycling of carbon and nutrients, but little is known about the amount, composition, or bioavailability of viral lysates. By using a model system of a marine bacterium (Cellulophaga sp.) and a virus specific to this bacterium, the present study provides a first quantification of the input of dissolved free and combined amino acids (DFAA and DCAA) and bacterial cell wall compounds following viral lysis. The DCAA constituted 51–86% of the total virus-mediated organic carbon release of 1087–1825 μg C l−1 (estimated biomass of the lysed bacteria), whereas DFAA and glucosamine each accounted for 2–3% of total lysate-C. The viral particles themselves constituted 4–6% of the released organic carbon, and altogether, the applied analyses thus identified 53–92% of the released lysates. Approximately 12% of the identified compounds were derived from bacterial cell wall peptidoglycan, including various D-isomers of DFAA and DCAA, glucosamine and diaminopimelic acid (DAPA). Although a portion of this cell wall material may have entered the pool of refractory material, a significant fraction of some peptidoglycan-derived components, e.g. 83% of the released D-DFAA, were removed from the dissolved phase during the last part of the incubations, suggesting that part of the cell wall material were utilized by the developing virus-resistant Cellulophaga population. Therefore, we suggest that virus-mediated DOM is a source of a variety of organic compounds, which contribute significantly to the pool of rapidly recycling material in the ocean.

Riverine inputs of nitrogen is an important factor that controls productivity of coastal marine waters. Dissolved organic nitrogen (DON) comprises most of the N in boreal rivers. During spring floods, DON flux may exceed the baseflow flux by several orders of magnitude. However, little is known about the biological availability of spring flood DON and, thus, its potential effect on coastal productivity.We have investigated the dynamics of DON bioavailability and chemical composition during a spring flood in two streams in northern Sweden. Potential bioavailability was determined by employing bacterial regrowth bioassays with brackish medium and a coastal bacterial inoculum. In addition, concentrations of urea and amino acids and the proportion of D-isomers in total dissolved amino acids were analyzed because a high proportion of D-isomers is suggested to indicate old and refractory organic material.During the flood, potential DON bioavailability increased from 19-28% at baseflow to 55-45% during peak flow in the two streams, while DON concentration remained relatively constant. At the end of the flood, bioavailability returned to the baseflow values. Potential DON bioavailability was positively correlated with the concentration of dissolved combined amino acids and the proportion of L-enantiomers of amino acids. However, only 5-18% of DON was identified as urea and free and combined amino acids, suggesting that bacteria also utilized other DON compounds. Our results imply that a major portion of the annual export of labile nitrogen occurred during a few weeks of spring flood.