Nematode Biomass Spectra at Two Abyssal Sites in the NE Atlantic with a Contrasting Food Supply

Abundance and biomass sizes spectra of nematodes have been investigated at two contrasting abyssal sites in the NE Atlantic. The northern site is situated on the Porcupine Abyssal Plain where there is evidence for a high, seasonal input of organic matter derived from the overlying water column. The southern site is the oligotrophic station of the French EUMELI programme off Mauritania and is characterized by low primary productivity in the overlying water column and consequently by a lower organic input to the deep-sea floor. Low nematode density and total biomass in the surficial centimetre of the sediment at the EUMELI site (89 ind/10 cm², 8.52 μg wwt/10 cm²), in contrast to the PAP site (254 ind/10 cm², 54.16 μg wwt/10 cm²), supports a presumed lower food supply to this area. Similary, mean individual nematode body weight is significantly smaller at the oligotrophic EUMELI site (0.0241 μg dwt) compared to the PAP site (0.0511 μg dwt), which supports the hypothesis that mean nematode body size is correlated with food availability. However, differences are much less obvious when comparing geometric mean biomasses and median individual body sizes. The abundance size spectra for the two localities diverge appreciably only in the upper quartile. The differences in mean individual body weights are caused by the relatively greater abundance of larger nematodes at the more eutrophic PAP site.     

Degradation of dibenzothiophene by Pseudomonas putida

The microbial degradation of dibenzothiophene (DBT) and other organosulphur compounds such as thiophene-2-carboxylate (T2C) is of interest for the potential desulphurization of coal. The feasibility of degradation of DBT and T2C by Pseudomonas putida and other bacteria was analysed. Pseudomonas putida oxidized sulphur from DBT in the presence of yeast extract, but it did not when DBT was the sole source of carbon.     

Partial reversible inactivation of enzymes due to binding to the human erythrocyte membrane

Summary Hypotonic human erythrocyte ghosts, devoid of the original glyceraldehyde-3-phosphate dehydrogenase content of the red cell, bind added glyceraldehyde-3-phosphate dehydrogenases, isolated from human erythrocytes, rabbit and pig muscle, as well as rabbit muscle aldolase. There are only slight differences in the affinities towards the various glyceraldehyde-3-phosphate dehydrogenases. On the other hand, glyceraldehyde-3-phosphate dehydrogenases are bound much stronger than aldolase; in an equimolar mixture the former can prevent the binding of the latter, or replace previously bound aldolase at the membrane surface. Binding is always accompanied by the partial inactivation of enzymes, which can be reverted by desorption. Unwashed ghosts rich in hemoglobin seem to have a more pronounced inactivating effect on bound glyceraldehyde-3-phosphate dehydrogenase. In isotonic media ghosts, whether white or unwashed, reseal and do not interact with the enzymes.     

Osmotic homeostasis and radiosensitivity of NKLy lymphosarcoma cells]

In experiments with cells of ascites NKLy lymphoma differing in ploidy and position in the cell cycle, a study was made of the radiosensitivity, osmotic homeostasis peculiarities and thermoradiation changes in potassium content. It was shown that the resistance of osmotic homeostasis of NKLy cells to thermoradiation correlated with their radioresistance and was maximally displayed in cells at the stage of DNA synthesis.     

Recolonisation of meiofauna after catastrophic iceberg scouring in shallow Antarctic sediments

A series of 10 samples from sediment in and adjacent to a shallow coastal iceberg scour at Signy Island, Antarctica, were taken by hand coring from 17 December 1993 until 23 August 1994. Scouring by the iceberg led to more than a 95% decrease in meiofaunal abundance and to a certain degree of reduction in diversity. Nematodes were always the most dominant group of meiofauna. The return of major meiofauna groups to control levels was accomplished in 30 days, although a decrease in abundance on the 50th day made interpretation difficult. The pioneering meiofaunal colonisers were copepods and ostracods, followed by nematodes. Microlaimus sp.1 was dominant among the nematodes throughout the whole period. Epistratum feeders and non-selective deposit feeders were highly dominant over selective deposit feeders and predators/omnivores. The Maturity Index, a measure for stress within nematode communities, was relatively low at all times and in controls, which indicates that r-strategists prevail in this community. In spite of the catastrophic destruction, nematode community structure was not affected by the iceberg impact, and there was no evidence of succession during recovery. This suggests that the nematode community in the shallow subtidal coast at Signy Island is well adapted to ice disturbance.     

Effect of irradiation on the cellular sensitivity of separate NKLy tumor subpopulations to the membrane-toxic action of natural killers

A study was made of sensitivity of NKLy tumor fractions, differing in the proliferative activity, position in the cell cycle, and ploidy, to membrane-toxic action of natural killer cells from mouse spleen. The membrane toxicity index for cells of three out of five fractions under study was shown to decrease after exposure to 4 Gy radiation. It is concluded that there is no correlation between NKLy cell sensitivity to membrane-toxic effect of natural killer cells and their radiosensitivity as well as their ability to repair potentially lethal damages.     

Demographic analysis of a dominant shrub (Cytisus scoparius): Prospects for encroachment control

Shrub encroachment in pastoral areas subsequent to land-use changes has become a major problem for biodiversity and pastoral resource conservation. Controlling encroachment by grazing is the most promising prospect at this time, but the impact of small domestic ruminants on the population dynamics of dominant shrubby species is still poorly understood. To control the rapid densification of dominant shrub populations means that we have to focus on the early stages of shrub colonisation. In this paper, we present a modelling approach that includes deterministic matrix modelling to understand demography strategy at the very beginning of shrub population growth and to identify potential targeted life stages for control. We collected demographic data over a period of 5 years on the European dominant shrub, Cytisus scoparius (Scotch broom; Fabaceae), which is often part of the heathlands that establish themselves on former permanent grasslands in Europe. Our results reveal a very high variation in flowering frequency between years and a large contribution of the seed bank to the total number of seedlings that emerge each year. Modelling shows that population growth is very vigorous and is not stopped by repeated “bad years” for seed production. Sensitivity analyses indicate that early life stage survival (seedling, juvenile) has the greatest impact on population growth. These results make it possible to identify juveniles as one of the best targets for control since they combine a high degree of sensitivity in terms of population demography, good palatability for domestic herbivores and easy accessibility within a management schedule.