Population- and ecosystem-level effects of predation on microbial-feeding nematodes

We studied the role of nematode predation in the functioning of detrital food webs assembled in microcosms. The microcosms contained defaunated humus and litter materials, a diverse microbial community with bacteria, fungi and protozoa, and a birch (Betula pendula) seedling infected with mycorrhizal fungi. Different levels of top-down control upon microbivorous nematodes were set up by assembling food webs either without predators, or in combinations with a specialist and a non-specialist predatory mite (Mesostigmata). The nematode community was composed of either (1) three species of bacterivorous, or (2) three species of fungivorous nematodes or (3) both groups together. After two growing periods for the birch (38 weeks), the microcosms were destructively sampled for animal and microbial biomasses, concentration of mineral N in the soil, plant biomass and plant N concentration. The specialist predator reduced biomasses of both bacterial- and fungal-feeding nematodes by more than 50%, whereas the non-specialist predator weakly increased the biomass of fungivorous nematodes. Thus, under high predation pressure, the biomass of microbivores changed as predicted by trophic dynamic models assuming strong top-down control and uniformly behaving trophic levels. Despite this, microbial biomass was unaffected by the predators. However, microbial respiration increased slightly in the presence of predators. Assuming that microbial respiration correlates with microbial productivity, the increase in microbial respiration indicates a cascading productivity regulation. The composition of the microbivore community had only a minor effect on the outcome of the top-down control on microbes. The >50% reduction in nematode biomass and respiration coincided with <16% increase in microbial respiration and did not affect microbial biomass. Presence of the specialist predator slightly reduced soil NH⁺ ₄ concentration in communities with fungivore nematodes but plant growth and N uptake remained unchanged. Thus, the structure of the community only weakly controlled nutrient mineralisation. Received: 18 May 1998 / Accepted: 3 May 1999     

Matrix metalloproteinase 2 (gelatinase A) is related to migration of keratinocytes.

The role of matrix metalloproteinases (MMPs) in cell migration was studied by measuring cell growth, migration, and production of MMP-2 and -9 in oral mucosal and skin keratinocytes cultured in the presence of synthetic MMP inhibitors. MMP-2 was the major gelatinolytic MMP produced by these cells while MMP-9 was produced at a low basal level. Inhibitor effects on MMP-9 production were therefore studied in keratinocytes stimulated by tumor necrosis factor alpha (TNFalpha). Tetracycline analogues at concentrations that inhibited the production of MMP-2 but not MMP-9 were able to drastically inhibit migration of both mucosal and skin keratinocytes. Tetracycline analogues also inhibited keratinocyte growth, an effect not found for the other inhibitors tested. Heterocyclic carbonate-derived compounds (LWs) that inhibited MMP-9 but not MMP-2 production had no effect on cell migration. Batimastat, a potent MMP inhibitor, did not have any effect on MMP production or cell growth but did inhibit keratinocyte migration. Tumor growth factor beta (TGFbeta) increased keratinocyte migration as well as both cell-associated and secreted MMP-2 production in wounded cell cultures. The secreted enzyme was partially converted into an active form. In this model batimastat totally blocked TGFbeta-promoted keratinocyte migration. Immunostaining of keratinocytes advancing into the wound revealed that MMP-2 was localized in extracellular matrix contactlike structures against the endogenously produced laminin-5-rich matrix. MMP-9 was localized diffusely along the cell membranes. Using in situ hybridization we observed that in chronically inflamed human gingiva MMP-2 is expressed in epithelium extending into subepithelial connective tissue. These results suggest that MMP-2 plays a specific role in epithelial migration, possibly by detaching the advancing cells from the pericellular matrix or by activating other MMPs.     

Recurrent adenylation domain replacement in the microcystin synthetase gene cluster

Background  

Microcystins are small cyclic heptapeptide toxins produced by a range of distantly related cyanobacteria. Microcystins are synthesized on large NRPS-PKS enzyme complexes. Many structural variants of microcystins are produced simulatenously. A recombination event between the first module of mcyB (mcyB1) and mcyC in the microcystin synthetase gene cluster is linked to the simultaneous production of microcystin variants in strains of the genus Microcystis.     

Voluntary Climate Change Mitigation Actions of Young Adults: A Classification of Mitigators through Latent Class Analysis

Encouraging individuals to take action is important for the overall success of climate change mitigation. Campaigns promoting climate change mitigation could address particular groups of the population on the basis of what kind of mitigation actions the group is already taking. To increase the knowledge of such groups performing similar mitigation actions we conducted a population-based cross-sectional study in Finland. The study population comprised 1623 young adults who returned a self-administered questionnaire (response rate 64%). Our aims were to identify groups of people engaged in similar climate change mitigation actions and to study the gender differences in the grouping. We also determined if socio-demographic characteristics can predict group membership. We performed latent class analysis using 14 mitigation actions as manifest variables. Three classes were identified among men: the Inactive (26%), the Semi-active (63%) and the Active (11%) and two classes among women: the Semi-active (72%) and the Active (28%). The Active among both genders were likely to have mitigated climate change through several actions, such as recycling, using environmentally friendly products, preferring public transport, and conserving energy. The Semi-Active had most probably recycled and preferred public transport because of climate change. The Inactive, a class identified among men only, had very probably done nothing to mitigate climate change. Among males, being single or divorced predicted little involvement in climate change mitigation. Among females, those without tertiary degree and those with annual income €≥16801 were less involved in climate change mitigation. Our results illustrate to what extent young adults are engaged in climate change mitigation, which factors predict little involvement in mitigation and give insight to which segments of the public could be the audiences of targeted mitigation campaigns.     

Genetic structure and gene flow in an endangered perennial grass, <Emphasis Type="Italic">Arctophila fulva</Emphasis> var. <Emphasis Type="Italic">pendulina</Emphasis>

Arctophila fulva var. pendulina is a rare endemic perennial grass confined to seashore and riverbank meadows around the Bothnian Bay, the northernmost part of the Baltic Sea. The number of A. fulva populations has decreased during the last few decades in Finland and Sweden, and nowadays there are only eight populations left in the drainage area of the Bothnian Bay. We investigated the distribution of genetic variation within and between six subpopulations in the largest remaining population at Liminka Bay, Finland, using amplified fragment length polymorphism (AFLP) markers. Relatively high amounts of variation were found in the subpopulations, the mean Nei’s expected heterozygosity being typical (0.267) for an outcrossing species. Despite the fact that no seedlings or viable seeds of A. fulva have been found in the previous field studies, the observed high genotypic diversity suggested that sexual reproduction has played an important role at some time during the history of the studied A. fulva population. Analysis of population structure revealed a low level of genotypic differentiation (Φ_ST=0.046) between subpopulations, and also significant sub-structuring within subpopulations. Isolation-by-distance between subpopulations was present on scales larger than 1 km. The overall pattern of genetic variation within and between subpopulations suggest that the population has characters of both stepping-stone and metapopulation models. Because our results suggested that subpopulations are more or less ephemeral, the conservation and management effort in this species should be targeted to conservation of the required habitat of the species instead of extant subpopulations.     

Disassembly of structurally modified viral nanoparticles: characterization by fluorescence correlation spectroscopy

Analysis of the breakdown products of engineered viral particles can give useful information on the particle structure. We used various methods to breakdown both a recombinant enveloped virus and virus-like particles (VLPs) from two non-enveloped viruses and analysed the resulting subunits by fluorescence correlation spectroscopy (FCS). Analysis of the enveloped baculovirus, Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), displaying the green fluorescent protein (GFP) fused to its envelope protein gp64 was performed in the presence and absence of 5 mM SDS and 25 mM DTT. Without treatment, the viral particle showed a diffusion time of 3.3 ms. In the presence of SDS, fluorescent subunits with diffusion times of 0.2 ms were observed. Additional treatment with DTT caused a drop in the diffusion time to 0.1 ms. Changes in the amplitude of the autocorrelation function suggested a 3-fold increase in fluorescent particle number when viral particles were treated with SDS, and a further 1.5-fold increase with additional treatment with DTT. Thus, the data showed that an average of 4.5 molecules of gp64-GFP was incorporated in the membrane of the modified baculovirus. Further, this suggests that each fluorescent gp64 trimer carries on average 1.5 fluorescent units. Similar experiments were carried out with two non-enveloped fluorescent virus-like particles (fVLPs) that displayed enhanced green fluorescent protein (EGFP). These, fVLPs of canine and human B19 parvoviruses were treated with 6 M urea and 5 mM SDS, respectively. Correspondingly, the original hydrodynamic radii of 17 and 14 nm were reduced to 9 and 5 nm after treatment. Here, the change in the amplitude of the autocorrelation curve suggested a 10-fold increase in particle number when viral particles of CPV were treated with 6 M urea at 50 degrees C for 10 min. For EGFP-B19, there was a decrease in the amplitude, accompanied by a 9-fold increase in the number of fluorescent units with SDS treatment. The results showed that approximately 10 and 9 fluorescent units were associated with the corresponding CPV and B19 VLPs. In summary, we were able to estimate the number of fluorescent subunits in a baculovirus containing a GFP-fusion with its gp64 envelope protein and in two different parvo-VLPs containing EGFP-fused with their VP2 capsid proteins.     

In vitro embryo survival and early viability of larvae in relation to male sexual ornaments and parasite resistance in roach, Rutilus rutilus L

According to the 'good genes' hypothesis, sexual ornaments provide an indication of the 'quality' of the bearer. In roach, Rutilus rutilus, breeding tubercles (BTs) may signal resistance against the digenean parasite, Rhipidocotyle campanula. Life history theory predicts that there should be a trade-off between parasite resistance and other life history traits. In roach, this could imply a trade-off between parasite resistance in mature fish and some larval feature. We studied embryo survival and the early viability of larvae of male roach in relation to expression of BTs and parasite resistance in maternal half-sibling families. Highly ornamented males had higher resistance against R. campanula than less ornamented males, but the BTs were not related to either embryo survival or larval viability. However, sires having higher resistance to R. campanula had lower larval viability. These results suggest that BTs of male roach do not indicate 'quality' in terms of early survival or viability, but rather in terms of adult parasite resistance.     

Localization of heat shock proteins in clinical Actinobacillus actinomycetemcomitans strains and their effects on epithelial cell proliferation

Actinobacillus actinomycetemcomitans is an important pathogen in periodontitis. In the present study we localized the GroEL- and DnaK-like heat shock proteins (Hsp) in subcellular fractions of 12 A. actinomycetemcomitans strains of various clinical origin and compared their effects on periodontal epithelial cell proliferation and viability. In all strains, GroEL-like protein was found in the membrane, cytoplasm, and periplasm, whereas DnaK-like protein was present in the cytoplasm and periplasm. No correlation was observed between the Hsp expression and the serotype or origin of A. actinomycetemcomitans strains. The bacterial membrane fractions that expressed the GroEL-like protein moderately or strongly induced epithelial cell proliferation more strongly than strains that expressed the protein weakly. The results suggest that GroEL-like Hsp may play a role in the virulence of A. actinomycetemcomitans by increasing epithelial proliferation.     

The alpha 5 chain of type IV collagen is the target of IgG autoantibodies in a novel autoimmune disease with subepidermal blisters and renal insufficiency

We describe a novel autoimmune disease characterized by severe subepidermal bullous eruptions and renal insufficiency with IgG autoantibodies directed against the NC1 domain of the alpha5(IV) collagen chain. In vivo deposits of IgG and C3 were found along the dermal-epidermal junction of skin lesions. The identity of the target antigen was determined by immunochemical analyses of candidate antigens using the patients' autoantibodies. The patients' IgG autoantibodies reacted with a 185-kDa polypeptide that was distinguished from the known autoantigens of the extracellular matrix including type XVII collagen, type VII collagen, or the alpha3, beta3, and gamma2 chains of laminin 5. Preincubation of the serum with recombinant alpha5(IV)NC1 domain of type IV collagen abolished immunoreactivity with the 185-kDa antigen. The serum reacted specifically with the alpha5(IV)NC1, among the six NC1 domains of type IV collagen, by Western blot and enzyme-linked immunosorbent assay analyses. The patients' autoantibodies reacted with normal skin and renal glomerulus but not with skin and glomerulus of a patient with Alport syndrome in which the basement membranes are devoid of the alpha5(IV) collagen chain. This study provided for the first time unambiguous evidence for the alpha5(IV) collagen chain as the target antigen in a novel autoimmune disease characterized by skin and renal involvement.