Fixed wavelength fluorescence (FF) of bile as a monitoring tool for polyaromatic hydrocarbon exposure in fish: an evaluation of compound specificity, inner filter effect and signal interpretation

Fixed wavelength fluorescence (FF) of bile has been evaluated as a monitoring tool for the screening of polyaromatic hydrocarbon (PAH) contamination in fish. The methodology was studied through laboratory and field experiments with Atlantic cod (Gadus morhua L.) and flounder (Platichthys flesus L.) exposed to various forms of PAH contamination. The present study demonstrates the ability of FF screening to discriminate between 2-, 4- and 5-ring PAH metabolites by using the wavelength pairs 290/335 nm, 341/383 nm and 380/430 nm, respectively. In general, the degree of fluorescence interference between these metabolite groups appears to be low. Dose- and time-response patterns of the FF signals were shown to give a good reflection of the PAH exposure. Further, the necessity of an appropriate dilution of bile samples prior to fluorescence measurements is demonstrated by a study of inner filter effect. Normally a dilution of 1000-2000-fold is necessary. Individual differences in the bile density, e.g. measured as the concentration of the bile pigment biliverdin, have to be allowed for when applying the FF method. However, it is shown that normalizing the FF signals to biliverdin concentrations on an individual basis added extra error to the data set. The simple, rapid and cost-effective FF method is found to be well suited for screening fish for PAH contamination.     

Viscosity of concentrated solutions and of human erythrocyte cytoplasm determined from NMR measurement of molecular correlation times. The dependence of viscosity on cell volume

Metabolically active human erythrocytes were incubated with [alpha-13C]glycine which led to the specific enrichment of intracellular glutathione. The cells were then studied using 13C-NMR in which the longitudinal relaxation times (T1) and nuclear Overhauser enhancements of the free glycine and glutathione were measured. The T1 values of labelled glycine were also determined in various-concentration solutions of bovine serum albumin and glycerol and also of the natural abundance 13C of glycerol in glycerol solutions. From the T1 estimates the rotational correlation time (tau r) was calculated using a formula based on a model of an isotropic spherical rotor or that of a symmetrical ellipsoidal rotor; for glycine the differences in estimates of tau r obtained using the two models were not significant. From the correlation times and by use of the Stokes-Einstein equations viscosity and translational diffusion coefficients were calculated; thus comment can be made on the likelihood of diffusion control of certain enzyme-catalysed reactions in the erythrocyte. Bulk viscosities of the erythrocyte cytoplasm and the above-mentioned solutions were measured using Ostwald capillary viscometry. Large differences existed between the latter viscosity estimates and those based upon NMR-T1 measurements. We derived an equation from the theory of the viscosity of concentrated solutions which contains two phenomenological interaction parameters, a 'shape' factor and a 'volume' factor; it was fitted to data relating to the concentration dependence of viscosity measured by both methods. We showed, by using the equation and interaction-parameter estimates for a particular probe molecule in a particular solution, that it was possible to correlate NMR viscosity and bulk viscosity; in other words, given an estimate of the bulk viscosity, it was possible to calculate the NMR 'micro' viscosity or vice versa. However, the values of the interaction parameters depend upon the relative sizes of the probe and solute molecules and must be separately determined for each probe-solute-solvent system. Under various conditions of extracellular osmotic pressure, erythrocytes change volume and thus the viscosity of the intracellular milieu is altered. The volume changes resulted in changes in the T1 of [alpha-13C]glycine. Conversely, we showed that alterations in T1, when appropriately calibrated, could be used for monitoring changes in volume of metabolically active cells.     

The Ethnography of Landscape: GIS and Remote Sensing in the Study of Forest Change in West African Guinea Savanna

In this paper we explore the application of Amazonian forest change models to the Guinea savanna environment of western Africa. In particular, we examine recent research documenting the growth of peri-village forest islands in the area of Kissidougou, Guinea, which purports to challenge the pervasive view of Guinea savanna deforestation brought about by human activity. As a more systematic approach to the analysis of human/environmental interactions, we propose an "ethnography of landscape," in which the findings of detailed, local ethnographic and ecological case studies are combined with remotely sensed information on what the wider region looks like as it changes over time. In pursuing this research, we employ aerial photography and Geographic Information Systems (GIS) techniques to examine our study area of Kilimi in northwestern Sierra Leone. We show that a Kissidougou-type model of peri-village forest island growth is not applicable to this region, where other environmental change processes are underway. In future work, we propose to employ Landsat satellite image archives to examine, monitor, and compare processes of ecological change throughout the Guinea savanna. [deforestation, ecological anthropology, remote sensing, Sierra Leone, West Africa]     

Isolation and characterization of a water-stress-inducible cDNA clone from Solanum chacoense

A rich source of valuable genes are wild species. Solanum chacoense Bitter with its extreme resistance to viruses, insects and drought, is a good example.In the present study, a stress gene, designated DS2, has been isolated from S. chacoense. We have shown that the expression of the gene is organ-specific being detected in leaf, stem and stolon, but not in root, tuber or flower. Treatment of detached leaves with abscisic acid (ABA), salicylic acid or methyl jasmonate resulted in only very moderate accumulation of DS2 mRNA. Thus, DS2 represents a very rare type of the water-stress-inducible genes whose signalling pathway is not primarily related to ABA.Based on DNA sequence analysis, DS2 encodes a putative protein starting with 20 amino acids homologous to the ABA- and water-stress-inducible, ripening-related (ASR) proteins of tomato continued by an insert of 155 amino acids structurally similar to certain LEAs (late embryogenesis-abundant proteins) and ending in 88 amino acids homologous again to the ASR sequences and to an unpublished partial cDNA fragment isolated from the root of rice. The N-terminal region of the DS2 protein is hydrophilic with ten 13-mer amino acid motifs and random coil structure. In contrast, the C-terminus predicts an -helix and possesses a bipartite nuclear targeting sequence motif. These data suggest that the function of the DS2 may be the protection of the nuclear DNA from desiccation.     

Natural products and enzymes from plant cell cultures

Plants represent an unlimited source of natural products. Many of the recently detected phytochemicals exhibit remarkable bioactivities, ranging from anticancer activity, phosphodiesterase inhibition to cytotoxicity against HIV-infected cells. Cultivated plant cells produce at their unorganized, dedifferentiated stage secondary metabolites, but in very different amounts in so far as new compounds are concerned. In fact, more than 140 novel natural products are presently known from plant cell cultures, which also include new metabolites formed by biotransformation. The biotransformation capacity of suspended cells is described and recent high yielding transformations, like the formation of arbutin by hydroquinone-transformation withRauwolfia cells are discussed. As an example of alkaloid production by cell suspensions, the pattern of monoterpenoid indole alkaloids of the Indian medicinal plantRauwolfia serpentina Benth. is described and the so far 30 identified compounds are divided into eight groups which are biosynthetically closely related. Some of the key biosynthetic reactions leading to theRauwolfia alkaloids are discussed and an overview of the enzymes involved in the formation of the alkaloid ajmaline and proteins catalyzing side reactions of the ajmaline pathway are given.     

Diisopropylfluorophosphate-binding proteins in the outer membrane of Fusobacterium nucleatum: strain variations

Six strains of Fusobacterium nucleatum were tested for their ability to react with [3H]diisopropylfluorophosphate (DFP), a serine protease inhibitor. Several cytoplasmic proteins were labelled but the strongest labelling was regularly observed in a few outer membrane proteins. The number and the molecular mass of the proteins detected varied according to the strain tested. A 61 kDa protein was labelled in all strains tested, including the two type strains ATCC 10953 and ATCC 25586. A 65 kDa protein was particularly strongly labelled in strains Fev1 and F6.     

EXPERIMENTALLY INDUCED CHANGES IN THE BASE COMPOSITION OF THE RIBONUCLEIC ACIDS OF ISOLATED NERVE CELLS AND THEIR OLIGODENDROGLIAL CELLS

The effect of tricyano-amino-propene, a dimer of malononitrile, on the base composition of the RNA in isolated Deiters' nerve cells and their oligodendroglial cells has been studied using a microelectrophoretic method. Tri-a-p in a dose of 20 mg/kg has the effect of increasing the RNA and protein content per nerve cell by 25 per cent and decreasing the glia RNA by 45 per cent. The RNA base composition of the nerve cells from the control animals differs from that of their glial cells. The guanine of the nerve cell is significantly higher than that of the glia, but the content of cytosine is higher in the glia than in the RNA of nerve cell. The cytosine of nerve cells decreased significantly after tri-a-p administration. In the glial cells the cytosine showed a 20 per cent increase, and the guanine a 25 per cent decrease. Tri-a-p sharpened the difference in RNA composition already existing between the control nerve cells and their glial cells by almost 300 per cent for the guanine and by 400 per cent for the cytosine. The chemical and functional relationship between the nerve cell and its oligodendroglial cells is discussed.