Immunofluorescence studies on the effect of cyclic adenosine 3′,5′-monophosphate in tissue culture preparations of the cervicovaginal anlage from neonatal mice

Summary The authors have studied the production of antigenic material, specific for the cervicovaginal epithelium, in organ cultures of the cervicovaginal region from neonatal mice. In control cultures the antigenic material appeared at a time corresponding to the normal appearance under in vivo conditions. When cyclic adenosine 3, 5-monophosphate (dibutyryl derivate) was added to the medium, a strong increase of the fluorescent material was seen.This investigations was supported by grants from the Norwegian Research Council and the Norwegian Cancer Society (Landsforeningen mot Kreft).     

Ultrastructure of four types of striated muscle fibers in the atlantic hagfish (Myxine glutinosa,L.)

Summary Four types of striated muscle fibers with distinctive ultrastructure were defined in the Atlantic hagfish (Myxine glutinosa, L.): white, intermediate, and red fibers of m. parietalis, and red fibers of m. craniovelaris.White fibers are thick, contain very few mitochondria and fat vacuoles, and possess distinct and separate myofibrils with thin Z-disks and distinct M-lines. Intermediate fibers are thinner, possess largely similar myofibrils that often are even better separated due to a higher content of fat vacuoles and especially mitochondria and glycogen granules. Red fibers of m. parietalis contain large amounts of mitochondria, fat vacuoles, and glycogen granules. Their myofibrils possess M-lines, and although branching more, the myofibrils of red fibers conform with a Fibrillenstruktur pattern like those of white and intermediate fibers. Red fibers of m. craniovelaris are very thin, possess many smaller fat vacuoles, and large amounts of mitochondria and glycogen granules. The myofibrils are significantly thinner than in m. parietalis fibers, run as quite independent well separated units, possess thicker Z-disks, and lack M-lines. Large amounts of myosatellite cells are associated with these red fibers.Triads are located near A/I-junctions in all four fiber types and occur irregularly, the density of triads being different in the various fiber types.We are indebted to Dr. Finn Walvig, Biological Station, University of Oslo, Drøbak, for supply of hagfishes, and we also wish to thank Dr. Jan K. S. Jansen, Institute of Physiology, University of Oslo, for valuable suggestions during this study.     

Dense-core vesicles in motor nerve terminals

Summary Motor nerve terminals on white and intermediate muscle fibers of the Atlantic hagfish (Myxine glutinosa, L.) contain translucent synpatic vesicles and about 1–2% dense-core vesicles. Terminals on red muscle fibers contain up to 40% dense-core vesicles with diameter 800–1100 Å. Examinations for formaldehyde-induced fluorescence indicate yellow fluorescence (5-HT ?) apparently corresponding with terminal axons on red muscle fibers in craniovelar muscles. Possibly red muscle fibers of Myxine receive monoaminergic innervation.The author is indebted to Dr. Finn Walvig, Biological station, University of Oslo, Drøbak, for supply of hagfishes.     

Investigating Cross‐Sectoral Synergies through Integrated Aquaculture,Fisheries, and Agriculture Phosphorus Assessments: A Case Study of Norway

Future phosphorus (P) scarcity and eutrophication risks demonstrate the need for systems‐wide P assessments. Despite the projected drastic increase in world‐wide fish production, P studies have yet to include the aquaculture and fisheries sectors, thus eliminating the possibility of assessing their relative importance and identifying opportunities for recycling. Using Norway as a case, this study presents the results of a current‐status integrated fisheries, aquaculture, and agriculture P flow analysis and identifies current sectoral linkages as well as potential cross‐sectoral synergies where P use can be optimized. A scenario was developed to shed light on how the projected 2050 fivefold Norwegian aquaculture growth will likely affect P demand and secondary P resources. The results indicate that, contrary to most other countries where agriculture dominates, in Norway, aquaculture and agriculture drive P consumption and losses at similar levels and secondary P recycling, both intra‐ and cross‐sectorally, is far from optimized. The scenario results suggest that the projected aquaculture growth will make the Norwegian aquaculture sector approximately 4 times as P intensive as compared to agriculture, in terms of both imported P and losses. This will create not only future environmental challenges, but also opportunities for cross‐sectoral P recycling that could help alleviate the mineral P demands of agriculture. Near‐term policy measures should focus on utilizing domestic fish scrap for animal husbandry and/or fish feed production. Long‐term efforts should focus on improving technology and environmental systems analysis methods to enable P recovery from aquaculture production and manure distribution in animal husbandry.     

Leaf litter diversity alters microbial activity,microbial abundances,and nutrient cycling in a subtropical forest ecosystem

Human activities affect both tree species composition and diversity in forested ecosystems. This in turn alters the species diversity of plant litter and litter quality, which may have cascading effects on soil microbial communities and their functions for decomposition and nutrient cycling. We tested microbial responses to litter species diversity in a leaf litter decomposition experiment including monocultures, 2-, and 4-species mixtures in the subtropical climate zone of southeastern China. Soil microbial community composition was assessed by lipid analysis, and microbial functions were measured using extracellular enzyme activity and gross rates of nitrogen mineralization. We observed a positive relationship between litter species diversity and abundances of mycorrhizal fungi and actinomycetes. Alternatively, enzyme activities involved in carbon and phosphorus acquisition, and enzyme indices of relative carbon limitation, were higher only in the 4-species mixtures. This suggests that the minimum basal substrate level for enzyme production was reached, or that limitation was higher, at the highest diversity level only. Responses to litter diversity also changed over time, where phosphatase responses to litter diversity were strongest early in decomposition and the indices of carbon limitation relative to other nutrients showed stronger responses later in decomposition. Enzyme activities were related to lipid biomarker data and the mass of litter remaining at the third time point, but relationships between enzyme activity and the mass of litter remaining were not consistent across other time points. We conclude that litter species richness will likely only reduce microbial functions at key intervals of diversity loss while microbial growth is more sensitive to incremental diversity loss, with no clear relationships between them or to ecosystem functions. The observed litter diversity effects on soil microbial biomass and enzyme activity indicate interactions of aboveground and belowground communities, and together with environmental conditions they are important for maintaining ecosystem functions.     

Importance of mixotrophic bacterivory can be predicted by light and loss rates

Recent observational studies form oligotrophic waters provide ample evidence that mixotrophic flagellates often account for the bulk of bacterivory. However, we lack a general framework that allows a mechanistic understanding of success of mixotrophs in the competition with heterotrophic bacterivores. This is especially needed for integrating mixotrophy in models of the microbial loop. Based on general tradeoffs linked to the combined resource use in mixotrophs (generalist versus specialist), we propose a concept where mixotrophs are favored by conditions of high light – low losses, corresponding to the situation found in the surface waters of oligotrophic oceans. Under such conditions, they can achieve positive net growth at very low resource levels, allowing simultaneous competition with specialized protists. Conversely, heterotrophic bacterivores and photoautotrophs should be especially favored in more productive and low‐light conditions. We show experimentally that the combined effect of light and loss rates (dilution) predicts the success of mixotrophic bacterivorous flagellates. Moreover, our results suggest that total bacterivory, contrary as seen in the traditional microbial loop concept, has a more intricate coupling to light.     

Herbivore and pathogen effects on tree growth are additive,but mediated by tree diversity and plant traits

Herbivores and fungal pathogens are key drivers of plant community composition and functioning. The effects of herbivores and pathogens are mediated by the diversity and functional characteristics of their host plants. However, the combined effects of herbivory and pathogen damage, and their consequences for plant performance, have not yet been addressed in the context of biodiversity–ecosystem functioning research. We analyzed the relationships between herbivory, fungal pathogen damage and their effects on tree growth in a large‐scale forest‐biodiversity experiment. Moreover, we tested whether variation in leaf trait and climatic niche characteristics among tree species influenced these relationships. We found significant positive effects of herbivory on pathogen damage, and vice versa. These effects were attenuated by tree species richness—because herbivory increased and pathogen damage decreased with increasing richness—and were most pronounced for species with soft leaves and narrow climatic niches. However, herbivory and pathogens had contrasting, independent effects on tree growth, with pathogens decreasing and herbivory increasing growth. The positive herbivory effects indicate that trees might be able to (over‐)compensate for local damage at the level of the whole tree. Nevertheless, we found a dependence of these effects on richness, leaf traits and climatic niche characteristics of the tree species. This could mean that the ability for compensation is influenced by both biodiversity loss and tree species identity—including effects of larger‐scale climatic adaptations that have been rarely considered in this context. Our results suggest that herbivory and pathogens have additive but contrasting effects on tree growth. Considering effects of both herbivory and pathogens may thus help to better understand the net effects of damage on tree performance in communities differing in diversity. Moreover, our study shows how species richness and species characteristics (leaf traits and climatic niches) can modify tree growth responses to leaf damage under real‐world conditions.     

Presence and Characterization of a Mosaic Genomic Island Which Distinguishes Sorbitol-Fermenting Enterohemorrhagic Escherichia coli O157:H? from E. coli O157:H7

A mosaic genomic island comprising Shigella resistance locus (SRL) sequences flanked by segments of Escherichia coli O157:H7 strain EDL933 O islands 43, 81, and 82 was identified in sorbitol-fermenting (SF) enterohemorrhagic Escherichia coli (EHEC) O157:H⁻ strain 493/89. This mosaic island is absent from strain EDL933. PCR targeting the SRL-related sequence is a useful tool to distinguish SF EHEC O157:H⁻ from EHEC O157:H7.     

CD8alpha and CD8beta in Atlantic halibut, Hippoglossus hippoglossus: cloning, characterization and gene expression during viral and bacterial infection

CD8 is expressed on cytotoxic T-cells where it functions as a co-receptor for the TCR by binding to MHC class I proteins that present peptides on the cell surface. In this study we describe the cloning and sequencing of full length cDNAs encoding CD8alpha and CD8beta from Atlantic halibut (Hippoglossus hippoglossus L.) and subsequent isolation and characterization of the CD8alpha and CD8beta genes. The predicted halibut CD8alpha and CD8beta proteins are similar to those of mammals and other fish. Real time RT-PCR revealed that the highest levels of CD8 mRNA were found in the thymus, while some expression was also seen in the spleen, the gills, and the anterior and posterior kidney. In situ hybridization confirmed that the halibut thymus contained numerous CD8alpha and CD8beta expressing cells, while the anterior kidney had no CD8alpha positive cells but only a few CD8beta expressing cells. Only moderate changes in CD8 mRNA expression in other organs during either nodavirus or Vibrio anguillarum infection were observed. Both CD8alpha and CD8beta were significantly (P<0.05) down-regulated in spleen at 48h compared to their levels at 12h post-infection with nodavirus and V. anguillarum.