Viola hirta (Violaceae) and its relatives in Norway

Viola hirta is widespread in most of Europe but rare in Norway, occurring in four isolated enclaves around the Oslo Fjord. Allozymic and morphological patterns of variation were studied in 320 individuals of Viola hirta (2n = 20) and its relatives V. collina (2n = 20), V. odorata (2n = 20), and V. suavis (2n = 40) from 22 Norwegian populations. Ongoing introgression from both V. collina and V. odorata , as hypothesised by several authors, was not supported by our data. All hybrids proved to be primary ones and, apparently, introgression is rare. However, allozyme markers suggested that V. hirta may have been affected by ancient introgression from V. collina and possibly also from the East European V. ambigua (2n = 40) during its evolutionary history. Geographical differentiation, presumably relatively recent and post-glacial, was evident in V. hirta. Variation occurred also between and within V. odorata populations, most likely a consequence of independent introductions by man. No variation was observed in V. collina or in V suavis. A key to the Norwegian species of subsection Viola and their primary hybrids based on morphological characters is provided in Flora Nordica note No. 26.     

Eryngium maritimum, biology of a plant at its northernmost localities

The prospects for persistence of Eryngium maritimum in its northern distribution area was evaluated by studying historical data, matrix modelling, dispersal, seed germination and molecular variation. Historical data revealed a fragmented distribution of small populations with decrease in both population numbers and size during the last 150 years. Fruits of E. maritimum were found to have a relative low floating ability, making the prospects of long distance water dispersal more limited than would be expected from the world distribution of the species. Germination was found to be low (< 25 %). Elasticity matrices showed that survival of reproductive plants were more important than reproduction. High juvenile mortality and low germination activity emphasised the importance of rapid growth and survival. The population insurance against natural catastrophes and environmental stochasticity is suggested to be in a "root bank" of established individuals that are able to tolerate disturbances due to clonal reproduction and regrowth from root fragments. Isozyme electrophoresis revealed low molecular variation on a large geographical scale. The chromosome number is 2n = 16. A high degree of fixed heterozygosity suggests that the species is tetraploid with basic chromosome, number x = 4. The persistence prospects of E. maritimum in its northernmost distribution area are considered low considering the small population sizes, the low dispersal ability and low germination.     

Balanced expression of single subunits in a multisubunit protein, achieved by cell fusion of individual transfectants.

To establish stable cell lines that produce recombinant multisubunit proteins, it is usually necessary to cotransfect cells with several independent gene constructs. Here, we show that a stepwise fusion of individually transfected cells, results in a fused cell-line that secretes a complete multisubunit protein. Functional expression of recombinant multisubunit proteins may require a defined expression ratio between each protein subunit. The cell-fusion technology described allows a predefined expression level of each subunit. Using SIgA as a model protein we demonstrate that the majority of the fused cells inherit the molar expression ratio of the parental transfected cells. These results indicate that simplified screening of clones expressing the expected subunit ratios may be possible using the cell-fusion technology. This technology may therefore be an alternative to generic transfection methods for the establishment of cells that produce multiprotein complexes such as antibodies, receptors, ion channels and other multisubunit proteins.     

Complement-mediated lysis of cultured osteosarcoma cell lines using chimeric mouse/human TP-1 IgG1 and IgG3 antibodies

Osteosarcoma is the commonest malignant tumour of the bones. The presence of micrometastases at the time of primary diagnosis is associated with poor prognosis. Despite developments in surgery and aggressive chemotherapy, about 50% of the patients still succumb to the disease. Thus, there is a need to develop alternative treatment modalities. One such strategy is to use antibodies with improved effector functions. The two monoclonal antibodies, TP-1 and TP-3, recognize a tumour-associated antigen on human osteosarcoma cells. In the present study, we describe the cloning of the TP-1 variable genes, and the production of complete chimeric mouse/human monoclonal antibodies. Constructs containing the constant genes from human IgG1, IgG3 or a mutant IgG3 with a shortened hinge region, called m15, were expressed in the mouse myeloma cell line, NS0. The m15 mutant has been shown to be very potent in triggering complement-mediated lysis. Our goal was to investigate whether this mutant could overcome the complement protection on human osteosarcoma cells, which is generally present on all human cells. We found that the target cells expressed several membrane-bound complement inhibitors, and that masking of these inhibitors rendered the cells sensitive to lysis. The m15 mutant exhibited greater lytic activity than both IgG3 and IgG1, although it could not cause extensive killing of the target cells alone. Received: 21 January 1999 / Accepted: 3 June 1999     

Prescribed burning of northern heathlands: <Emphasis Type="Italic">Calluna</Emphasis> <Emphasis Type="Italic">vulgaris</Emphasis> germination cues and seed-bank dynamics

The European coastal heathlands are important habitats for international conservation. Today, these low-intensity farming systems are threatened by the cessation of traditional management regimes, such as grazing and prescribed burning. In natural systems, the effects of fire on germination responses are often explained by adaptation to fire over extended periods of time. However, Northern heathlands are semi-natural systems with only a limited fire history. We investigated whether and how the keystone species in this system, Calluna vulgaris, responded to prescribed burning, based on previous findings where Calluna germinable seed-bank densities showed a pronounced peak right after fire. Our main findings were (i) an ecophysiological response to smoke; (ii) a potential explanation for this pattern, revealed by a seed-bank experiment where we managed to re-create the germination pattern experimentally by using an aqueous plant-derived smoke solution; and (iii) a history of anthropogenic use of fire and the development of heathlands in the region documented through palaeoecological investigations.     

Local temperatures inferred from plant communities suggest strong spatial buffering of climate warming across Northern Europe

Recent studies from mountainous areas of small spatial extent (<2500 km²) suggest that fine‐grained thermal variability over tens or hundreds of metres exceeds much of the climate warming expected for the coming decades. Such variability in temperature provides buffering to mitigate climate‐change impacts. Is this local spatial buffering restricted to topographically complex terrains? To answer this, we here study fine‐grained thermal variability across a 2500‐km wide latitudinal gradient in Northern Europe encompassing a large array of topographic complexities. We first combined plant community data, Ellenberg temperature indicator values, locally measured temperatures (LmT) and globally interpolated temperatures (GiT) in a modelling framework to infer biologically relevant temperature conditions from plant assemblages within <1000‐m² units (community‐inferred temperatures: CiT). We then assessed: (1) CiT range (thermal variability) within 1‐km² units; (2) the relationship between CiT range and topographically and geographically derived predictors at 1‐km resolution; and (3) whether spatial turnover in CiT is greater than spatial turnover in GiT within 100‐km² units. Ellenberg temperature indicator values in combination with plant assemblages explained 46–72% of variation in LmT and 92–96% of variation in GiT during the growing season (June, July, August). Growing‐season CiT range within 1‐km² units peaked at 60–65°N and increased with terrain roughness, averaging 1.97 °C (SD = 0.84 °C) and 2.68 °C (SD = 1.26 °C) within the flattest and roughest units respectively. Complex interactions between topography‐related variables and latitude explained 35% of variation in growing‐season CiT range when accounting for sampling effort and residual spatial autocorrelation. Spatial turnover in growing‐season CiT within 100‐km² units was, on average, 1.8 times greater (0.32 °C km^?1) than spatial turnover in growing‐season GiT (0.18 °C km^?1). We conclude that thermal variability within 1‐km² units strongly increases local spatial buffering of future climate warming across Northern Europe, even in the flattest terrains.     

The Pox in the North American Backyard: Volepox Virus Pathogenesis in California Mice (Peromyscus californicus)

Volepox virus (VPXV) was first isolated in 1985 from a hind foot scab of an otherwise healthy California vole (Microtus californicus). Subsequent surveys in San Mateo County, CA, revealed serological evidence suggesting that VPXV is endemic to this area, and a second viral isolate from a Pinyon mouse (Peromyscus truei) was collected in 1988. Since then, few studies have been conducted regarding the ecology, pathology, and pathogenicity of VPXV, and its prevalence and role as a potential zoonotic agent remain unknown. To increase our understanding of VPXV disease progression, we challenged 24 California mice (Peromyscus californicus) intranasally with 1.6×10(3) PFU of purified VPXV. By day five post infection (pi) we observed decreased activity level, conjunctivitis, ruffled hair, skin lesions, facial edema, and crusty noses. A mortality rate of 54% was noted by day eight pi. In addition, internal organ necrosis and hemorrhages were observed during necropsy of deceased or euthanized animals. Viral loads in tissues (brain, gonad, kidney, liver, lung, spleen, submandibular lymph node, and adrenal gland), bodily secretions (saliva, and tears), and excretions (urine, and/or feces) were evaluated and compared using real time-PCR and tissue culture. Viral loads measured as high as 2×10(9) PFU/mL in some organs. Our results suggest that VPXV can cause extreme morbidity and mortality within rodent populations sympatric with the known VPXV reservoirs.     

Vanillic acid metabolism by selected soft-rot,brown-rot,and white-rot fungi

Metabolism of vanillic acid, a product of lignin degradation, has been studied in selected representatives of soft-rot, brown-rot and white-rot fungi. All of the brown-and white-rot species examined decarboxylated vanillate to methoxyhydroquinone oxidatively. Mycelium extracts of all these fungi, except Pleurotus ostreatus contained high levels of an NAD(P)H-dependent vanillate hydroxylase. P. ostreatus also released ¹⁴CO₂ from ¹⁴COOH-vanillate but by a different mechanism possibly involving phenoloxidases. Most of these fungi also contained a dioxygenase which catalysed the intra-diol cleavage of hydroxyquinol (1,2,4-trihydroxybenzene) to form maleylacetate. No 3-O-demethylase activity was detected, and data indicate that in some of the fungi examined cleavage of the aromatic ring occurs without prior removal of the methoxyl group. None of the soft-rot fungi tested contained vanillate hydroxylase or hydroxyquinol 1,2-dioxygenase, but very low levels of protocatechuate 3,4-dioxygenase were detected in mycelium extracts. Vanillate catabolism among members of this group occurs via a different route which may involve ring demethylation although no 3-O-demethylase activity was detected in this study. The enzyme NAD(P)H-quinone oxidoreductase was demonstrated to exist in all the studied groups of fungi.