The social and human relevance of in situ sediments

Dealing with in situ sediments is also dealing with our own identity. Our established confidence in scientific technical and economic progress and prosperity is undergoing a painful awakening. After all, sediments and pollution are a symbol of the destruction of our environment rather than an improvement of a quality of life. We are starting to see the wholeness of the issue. While in the past, manipulation of the environment left a few human concerns which were treated as residues of a view of progress, we are now faced with the fact that all environmental issues are human issues and that preoccupations with values, aspirations and interdependency need to be at center stage.Pollution issues become a disturbance of the perfect harmony between human beings and nature, and between different human groups. The restoration of the harmony requires a revision of paradigms, values and the interactivity of systems. Ultimately, the choices will be made on the basis of very many concerns. The rational and the irrational will combine to form a series of remedial measures that may not satisfy the traditional view of progress nor the newly acquired vision of a restorated environment. However, if communities are strengthened by the experience, if physical and social sciences as well as humanities find a new vision of their interdependency in the process, maybe the present state of high apathy, isolation and powerlessness will have been replaced with a better set of values with which to assess the problem and establish our common goal.If scientists, technocrats and decision-makers can come together in other places like this gathering, I believe that the momentum will lead to bringing together communities. Any such interaction inevitably creates its own dynamics so that interacting becomes the mechanism by which one experiences and through which one's choices are molded by each other's. The interactivity process does not guarantee any particular solution, it only leads to the point where humans are now the focus of the exercise.     

Development and characterization of continuous avian cell lines depleted of mitochondrial DNA

Summary Populations of quail and chicken cells were treated with ethidium bromide, an inhibitor of mitochondrial DNA replication. After long-term exposure to the drug, the cell populations were transferred to ethidium bromide (EtdBr)-free medium, and cloned. Clones HCF7 (quail) and DUS-3 (chicken) were propagated for more than a year, and then characterized. Analysis of total cellular DNA extracted from these cells revealed no characteristic mitochondrial DNA molecule by Southern blot hybridization of HindIII- or AvaI-digested total cellular DNA probed with cloned mitochondrial DNA fragments. Reconstruction experiments, where a small number of parental cells was mixed with HCF7 cells and DUS-3 cells before extraction of total cellular DNA, further strengthen the notion that the drug-treated cells are devoid of mitochondrial DNA molecules. The cell populations were found to proliferate at a moderately reduced growth rate as compared to their respective parents, to be auxotrophic for uridine, and to be stably resistant to the growth inhibitory effect of EtdBr and chloramphenicol. At the ultrastructural level, mitochondria were considerably enlarged and there was a severe reduction in the number of cristae within the organelles and loss of cristae orientation. Morphometric analysis revealed a fourfold increase of the mitochondrial profile area along with a twofold decrease of the numerical mitochondrial profiles. Analysis of biochemical parameters indicated that the cells grew with mitochondria devoid of a functional respiratory chain. The activity of the mitochondrial enzyme dihydroorotate dehydrogenase was decreased by 95% and presumably accounted for uridine auxotrophy. This work was supported by a grant from the Medical Research Council of Canada.     

Production of fumonisins by Fusarium moniliforme strains from various substrates and geographic areas.

Strains of Fusarium moniliforme from different geographic areas and from corn and other substrates were tested for the ability to produce fumonisins in culture. The test results indicate that the potential exists for production of fumonisins by such strains in agricultural commodities and other substrates in widespread geographic areas.     

Stainless steel mesh supports high density cell growth and production of recombinant Mullerian Inhibiting Substances

Summary Stainless steel mesh supported the high density growth of anchorage dependent CHO fibroblasts without the use of a special culture system. CHO cells, designated B-9, containing an amplified genomic construct of the human gene for Mullerian Inhibiting Substance (MIS), grew to a high confluent density on stainless steel meshwork while producing substantial amounts of human recombinant MIS over a long period of time. The mesh could be easily coated with various extracellular matrix proteins, such as Laminin, Fibronectin, Collagen or Matrigel, which permitted the testing of the effects of surface modifications on cell yield and recombinant protein production. Since the amount of medium per surface area required for optimal cell growth is lower than for some large volume cell culture methods, media costs can be reduced using mesh. In addition, no special cell culture equipment or complex manipulations are required. Thus, the use of meshwork for anchorage-dependent cells can increase the efficiency of growth and decrease the cost of recombinant protein production. This work is supported by NIH grant CA 17393 and American Cancer Society grant PDT 221A to P. K. D. and NIH grant EY 06535 to J. E. Editor's Statement This approach to large scale, high density cultivation of cells, one of several which are based on increasing surface area of the cultures, allows the production of large amounts of recombinant product within a research laboratory with modest bulk culture capability.     

Changes of the forest-savanna boundary in Brazilian Amazonia during the Holocene revealed by stable isotope ratios of soil organic carbon

The possibility of ecosystem boundary changes in northern Brazilian Amazonia during the Holocene period was investigated using soil organic carbon isotope ratios. Determination of past and present fluctuations of the forest-savanna boundary involved the measurement of natural ¹³C isotope abundance, expressed as ¹³C, in soil organic matter (SOM). SOM ¹³C analyses and radiocarbon dating of charcoal fragments were carried out on samples derived from soil profiles taken along transects perpendicular to the ecotonal boundary. SOM ¹³C values in the upper soil horizons appeared to be in equilibrium with the overlying vegetation types and did not point to a movement of the boundary during the last decades. However, ¹³C values obtained from deeper savanna and forest soil layers indicated that the vegetation type has changed in the past. In current savanna soil profiles, we observed the presence of mid-Holocene charcoals derived from forest species: fire frequency at that time was probably greater, and more extensive savanna may have resulted. Isotope data and the presence of these charcoals thus suggest that the forest-savanna boundary has shifted significantly in the recent Holocene period, forest being more extensive during the early Holocene than today. During the middle Holocene, the forest could have strongly regressed, and fires appeared, with a maximum development of the savanna vegetation. At the beginning of the late Holocene, the forest may have invaded a part of this savanna, and fires occurred again.     

Effect of sulphate on photosynthesis in greenhouse–grown tomato plants

Sulphate accumulates in the rhizosphere of plants grown in hydroponic systems. To avoid such sulphate accumulation and promote the use of environmentally sound hydroponic systems, we examined the effects of four sulphate concentrations (0.1, 5,2, 10.4 and 20.8 m M ) on photosynthesis, ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco, EC 4.1.1.39) activities and related physiological processes in greenhouse–grown tomato plants ( Lycopersicon esculentum Mill. cv. Trust). The lowest sulphate concentration (0.1 m M ) significantly decreased photosynthetic capacity (P_c) and Rubisco activities on a leaf area basis. This result was supported by our data for dry matter per plant, which was low for plants in the 0.1 m M treatment. The photosynthesis-related variables such as leaf conductance, chlorophyll and soluble protein were lowest for the 0.1 m M treatment. Both total Rubisco activity and the activated ratio were reduced with this treatment. However, Rubisco activities expressed per g of protein or per g of chlorophyll were not significantly affected. These results suggest that sulphur deficiency depressed P_c– by reducing the amount of both Rubisco and chlorophyll and by causing an inactivation of Rubisco. The ratio of organic sulphur vs organic nitrogen (S/N) in plants of the 0.1 m M treatment was far below the normal values. This low S/N ratio might be accountable for the negative effect of low sulphate on P_c and plant growth. P_c and dry matter were not affected until sulphate concentration in the nutrient solution reached a high level of 20.8 m M .     

Inhibition of adenylate cyclase by adenosine analogues in preparations of broken and intact human platelets. Evidence for the unidirectional control of platelet function by cyclic AMP.

Whereas adenosine itself exerted independent stimulatory and inhibitory effects on the adenylate cyclase activity of a platelet particulate fraction at low and high concentrations respectively, 2-substituted and N6-monosubstituted adenosines had stimulatory but greatly decreased inhibitory effects. Deoxyadenosines, on the other hand, had enhanced inhibitory but no stimulatory effects. The most potent inhibitors found were, in order of increasing activity, 9-(tetrahydro-2-furyl)adenine (SQ 22536), 2',5'-dideoxyadenosine and 2'-deoxyadenosine 3'-monophosphate. Kinetic studies on prostaglandin E1-activated adenylate cyclase showed that the inhibition caused by either 2',5'-dideoxyadenosine or compound SQ 22536 was non-competitive with MgATP and that the former compound, at least, showed negative co-operativity; 50% inhibition was observed with 4 micron-2',5'-dideoxyadenosine or 13 micron-SQ 22536. These two compounds also inhibited both the basal and prostaglandin E1-activated adenylate cyclase activities of intact platelets, when these were measured as the increases in cyclic [3H]AMP in platelets that had been labelled with [3H]adenine and were then incubated briefly with papaverine or papaverine and prostaglandin E1. Both compounds, but particularly 2',5'-dideoxyadenosine, markedly decreased the inhibition by prostaglandin E1 of platelet aggregation induced by ADP or [arginine]vasopressin as well as the associated increases in platelet cyclic AMP, so providing further evidence that the effects of prostaglandin E1 on platelet aggregation are mediated by cyclic AMP. 2'-Deoxyadenosine 3'-monophosphate did not affect the inhibition of aggregation by prostaglandin E1, suggesting that the site of action of deoxyadenosine derivatives on adenylate cyclase is intracellular. Neither 2',5'-dideoxyadenosine nor compound SQ 22536 alone induced platelet aggregation. Moreover, neither compound potentiated platelet aggregation or the platelet release reaction when suboptimal concentrations of ADP, [arginine]vasopressin, collagen or arachidonate were added to heparinized or citrated platelet-rich plasma in the absence of prostaglandin E1. These results show that cyclic AMP plays no significant role in the responses of platelets to aggregating agents in the absence of compounds that increase the platelet cyclic AMP concentration above the resting value.     

Host-Pathogen Interactions : XX. BIOLOGICAL VARIATION IN THE PROTECTION OF SOYBEANS FROM INFECTION BY PHYTOPHTHORA MEGASPERMA F. SP. GLYCINEA

Phytophthora megasperma f.sp. glycinea, which causes soybean (Glycine max) root and stem rot, exists as several races which differ in their ability to infect a range of soybean cultivars. A glycoprotein-rich fraction (Fraction I) isolated from fungal culture fluid protects soybean seedlings from infection with compatible races. In an early study (13), seedlings were protected only by Fraction I purified from incompatible races. In 1979, seedlings were better protected by Fraction I isolated from incompatible races than by Fraction I isolated from compatible races. In 1980, seedlings were protected equally well by Fraction I from incompatible and compatible races. Materials similar in composition to Fraction I did not protect seedlings from infection. No cause could be identified for the apparent change, during the 3-year period, in the race specificity of the protection assay. Variability in the bioassay prohibited further purification or characterization of Fraction I components that protect seedlings from infection.