Microbiological leaching of sulfide minerals with different percolation regimes

Summary The microbiological leaching of Fe, Al, Zn, Cu, Ni and Co from sulfide ore material was evaluated with four percolation regimes involving trickle and flood leaching. Continuous circulation of the leach solution associated with flood leaching resulted in the highest rates of leaching of Ni (44% recovery), Zn (25%), Co (18%), and Cu (8%) over a period of about half a year. Iron and aluminum recoveries remained low because of their precipitation. Bacterial counts increased from 3.2×10⁶ to 4.8×10⁷ iron-oxidizers and from 6.6×10⁶ to 1.8×10⁷ glucose-oxidizers per ml leach solution. Microscopic counts reached a maximum of 4.9×10⁸ cells per ml. Neither microscopic nor viable counts reflected the time course and the progress of the leaching. However, both the microscopic and viable counts were highest with the continuous flooding technique which also yielded the fastest rates of metal solubilization.     

B-L antigens (Class II) of the chicken major histocompatibility complex control T-B cell interaction

The detailed study of the genetic control of T-B cell interactions in the chicken has been hampered by the lack of defined major histocompatibility complex (MHC) recombinant chicken lines. In the present study we have used some recently described MHC recombinant chicken lines separating regions encoding antigens that are homologous to class I and class II antigens of mammals in adoptive bursa cell transfer experiments, in which bursa cells from newly hatched chicks were transplanted into cyclophosphamide (Cy)-treated chicks. Subsequent immunizations of the recipients with a thymus-dependent antigen (SRBC) and a thymus-independent antigen (Brucella abortus) showed that the generation of germinal centers in the spleen and the production of antibodies to SRBC required identity between donor and recipient class II antigens (B-L antigens), whereas response to Brucella antigen did not require identity at any of the known MHC loci of the chicken. The results thus reveal that also in the chicken class II (B-L) region genes encode cell-surface glycoproteins that serve as restriction elements in T-B cell cooperation.This work has been presented in part at the Ninth International Congress of the Transplantation Society (Vainio et al. 1983a).     

Development and fate of Eutreptiella gymnastica bloom in nutrient-enriched enclosures in the coastal Baltic Sea

Response of the phytoplankton community to bottom-up (nutrients,organic carbon source) and top-down (fish) manipulations, bothsingly and together, were studied daily during a 3 week periodin July 1993 by using eight 50 m³ mesocosms in the coastal northernBaltic Sea. Nutrient additions (once per week) invoked a seriesof blooms of Eutreptiella gymnastica Throndsen (Euglenophyceae)(up to 13 x 10³ cells ml^–1) which formed the major part(60–90%) of the total autotrophic biomass. After rapiddepletion of nutrients (2–3 days) from the surface layer(0–6 m) downwards migration and a subsequent peak of E.gymnasticain the lower part of the water columns (6–12 m) followed.Settled material collected from the bottom of the enclosurescontained a considerable amount of E.gymnastica cells and restingcysts. Nevertheless, sinking loss rates of E.gymnastica wereestimated to be less than 1% day^–1 of the suspended cellnumbers. The fate of E.gymnastica blooms was estimated to begrazing through mesozooplankton. However, provided the nutrientsare plentiful in the water column, the growth potential of E.gymnasticaappears to exceed the ambient grazing pressure. If the nutrientsbecome depleted, it seems to be effectively controlled by mesozooplanktongrazing, which is probably limiting the likelihood of massiveE.gymnastica blooms in the coastal Baltic Sea. Our study suggeststhat E.gymnastica appears to be a fast-growing fugitive (bloom)species with flexible behavioural (vertical migration) and lifehistory (cyst formation) adaptations which is able to exertdominant role and direct trophic relations similar to otherbloom species adapted for decaying turbulence and high nutrientenvironments.     

Optical and EPR spectroscopy studies on haem arginate, a new compound used for treatment of porphyria

A protohaem compound, used for treatment of porphyrias, has been studied to elucidate its state of aggregation. EPR and absorption spectroscopy measurements reveal that 38.3 mM protohaem, dissolved in 40% 1,2-propanediol/10% ethanol/water solution, also containing 153 mM arginine, is partly EPR silent. It exists as high molecular weight aggregates and probably also as mu-oxo-dimers. Dilution in the aqueous alcohol solution dissolves the aggregates first to oligomers and dimers, and finally to monomers (Kdiss = 24 X 10(-6)M). When haem is diluted in 0.9% sodium chloride, a fully monomeric state is not reached even at 1 microM concentration. At 3.5 microM concentration, that used for infusion in patients, the haem is still totally aggregated.     

Dechlorination and spectral changes associated with bacterial degradation of 2-(2-methyl-4-chlorophenoxy)propionic acid

Summary The bacterial degradation of mecoprop (2-(2-methyl-4-chlorophenoxy)propionic acid) was studied using a mixed culture under aerobic conditions. The release of chlorine from mecoprop indicated incomplete degradation (75%), which did not proceed to completion upon extended incubation. The UV absorbance initially increased and this was associated with spectral distortion of the shoulder and trough regions and a slight shift in the maximum wavelength of absorption. GC-MS analysis indicated that 4-chloro-2-methylphenol was an intermediate in the degradative pathway of mecoprop. The GC-MS data also suggested the formation of other phenolic compounds with repositioned chloro-and methylgroups.     

Midday stomatal closure in Mediterranean type sclerophylls under simulated habitat conditions in an environmental chamber

Summary Shrubs of the Mediterranean sclerophyllous species Arbutus unedo and Quercus ilex were studied under simulated habitat conditions in an environmental chamber. Temperature, humidity, and light intensity were altered stepwise to simulate diurnal changes in conditions similar to those measured in an evergreen macchia in Sobreda, Portugal. Leaves were enclosed in cuvettes which reproduced the growth chamber climate and which allowed measurement of gas exchange. Increasing atmospheric stress in the form of higher temperature and lower humidity on successive days gradually results in midday depression of transpiration rate and net photosynthesis rate of leaves due to midday stomatal closure.Dedicated with the greatest appreciation to a scientist, Prof. Dr. M. Evenari, who has stimulated ecological work all over the world and to a publisher, Dr. F.K. Springer, who has promoted communication among scientists and distributed results of their experimentation worldwide     

Distribution of a major surface-associated glycoprotein,fibronectin, in cultures of adherent cells

Fibronectin was present in media and cell layers of cultures of adherent cells from human skin, kidney, lung, chest wall, liver, and heart. Cell-surface fibronectin, visualized by immunofluorescence, was in dense fibrillar (cultures from lung), discrete fibrillar (e.g., cultures from skin), or punctate (some cultures from kidney) structures. The subunit sizes of cell-surface fibronectin and fibronectin soluble in medium appeared identical in sodium dodecyl sulfate-polyacrylamide gels. To explain the polymorphism of cell-surface fibronectin, there must be chemical differences among the fibronectins synthesized by different cell strains or factors in the cell layer which influence fibronectin binding and aggregation.     

The Influence of Hydrogen Bonding on Sphingomyelin/Colipid Interactions in Bilayer Membranes

The phospholipid acyl chain composition and order, the hydrogen bonding, and properties of the phospholipid headgroup all influence cholesterol/phospholipid interactions in hydrated bilayers. In this study, we examined the influence of hydrogen bonding on sphingomyelin (SM) colipid interactions in fluid uni- and multilamellar vesicles. We have compared the properties of oleoyl or palmitoyl SM with comparable dihydro-SMs, because the hydrogen bonding properties of SM and dihydro-SM differ. The association of cholestatrienol, a fluorescent cholesterol analog, with oleoyl sphingomyelin (OSM) was significantly stronger than its association with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, in bilayers with equal acyl chain order. The association of cholestatrienol with dihydro-OSM, which lacks a trans double bond in the sphingoid base, was even stronger than the association with OSM, suggesting an important role for hydrogen bonding in stabilizing sterol/SM interactions. Furthermore, with saturated SM in the presence of 15 mol % cholesterol, cholesterol association with fluid dihydro-palmitoyl SM bilayers was stronger than seen with palmitoyl SM under similar conditions. The different hydrogen bonding properties in OSM and dihydro-OSM bilayers also influenced the segregation of palmitoyl ceramide and dipalmitoylglycerol into an ordered phase. The ordered, palmitoyl ceramide-rich phase started to form above 2 mol % in the dihydro-OSM bilayers but only above 6 mol % in the OSM bilayers. The lateral segregation of dipalmitoylglycerol was also much more pronounced in dihydro-OSM bilayers than in OSM bilayers. The results show that hydrogen bonding is important for sterol/SM and ceramide/SM interactions, as well as for the lateral segregation of a diglyceride. A possible molecular explanation for the different hydrogen bonding in SM and dihydro-SM bilayers is presented and discussed.