Improved solution for solitary waves in arteries

 Nonlinear waves are investigated numerically by a direct analysis of the field equations, thereby establishing the magnitude of the errors inherent in the commonly used reductive perturbation technique. The method is also applied beyond the long-wave approximation and a comparative assessment of the results obtained is presented. Received: 11 March 1998 / Revised version: 19 May 1998     

An enzyme-linked immunosorbent assay for the estimation of fungal biomass during solid-state fermentation

An enzyme-linked immunosorbent assay for sensitive, specific and quantitative estimation of fungal biomass during solid-state fermentation is described. Using this method, differential growth rates and colonization of the substrate can be studied. The assay has potential application for the efficient monitoring of solid-state fermentation involving specific fungus, for which available methods are not adequate. Received: 18 November 1997 / Received last revision: 8 June 1998 / Accepted: 14 June 1998     

Potential microbial risk factors related to soil amendments and irrigation water of potato crops

AIMS: This study assesses the potential microbial risk factors related to the use of soil amendments and irrigation water on potato crops, cultivated in one traditional and two intensive farms during two harvest seasons. METHODS AND RESULTS: The natural microbiota and potentially pathogenic micro-organisms were evaluated in the soil amendment, irrigation water, soil and produce. Uncomposted amendments and residual and creek water samples showed the highest microbial counts. The microbial load of potatoes harvested in spring was similar among the tested farms despite the diverse microbial levels of Listeria spp. and faecal coliforms in the potential risk sources. However, differences in total coliform load of potato were found between farms cultivated in the autumn. Immunochromatographic rapid tests and the BAM's reference method (Bacteriological Analytical Manual; AOAC International) were used to detect Escherichia coli O157:H7 from the potential risk sources and produce. Confirmation of the positive results by polymerase chain reaction procedures showed that the immunochromatographic assay was not reliable as it led to false-positive results. CONCLUSIONS: The potentially pathogenic micro-organisms of soil amendment, irrigation water and soil samples changed with the harvest seasons and the use of different agricultural practices. However, the microbial load of the produce was not always influenced by these risk sources. Improvements in environmental sample preparation are needed to avoid interferences in the use of immunochromatographic rapid tests. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential microbial risk sources of fresh produce should be regularly controlled using reliable detection methods to guarantee their microbial safety.     

PCR detection of Cryptosporidium parvum in environmental samples—a review of published protocols and current developments

Since 1991 more than 30 PCR protocols have been published, which show a potential to replace the current microscopic detection method for Cryptosporidium parvum in environmental samples and food. This review provides a synoptic comparison of these protocols with respect to the following features: isolation and purification of oocysts from tested matrices, elimination of free DNA, viability and infectivity assessment, release of nucleic acids, nucleic acid extraction, type of PCR (PCR, RT-PCR, internal-standard-PCR, in situ PCR, TaqMan-PCR), primary product detection, additional specificity control, secondary product detection, reported sensitivity, cross-reaction with other Cryptosporidium species, and target and sequence information such as amplicon length, primer sequences, multiple copy target, presence of strain-specific differences in the amplicon, GenBank accession numbers and gene function. The results demonstrate that problems like PCR inhibition, viability assessment, and the requirement of an extreme sensitivity have been solved. PCR assays would be most valuable to control presence-absence standards in defined matrix volumes, and the setup of such standards would very much contribute to a rapid introduction of this awaited technology into routine monitoring of environmental, water and food samples, and to a further standardization of the various protocols. It can be expected that satisfactory solutions for quantification will be found for a growing number of PCR-based assays. Systematic field evaluation and interlaboratory studies will complement our present knowledge of these methods in the near future. Received 5 May 1998/ Accepted in revised form 7 September 1998     

Current development of the human and environmental contamination in the Bryansk-Gomel Spot after the Chernobyl accident

Up to 1991, it was assumed that after the Chernobyl accident in 1986 the time development of radioactive contamination with regard to environment, foodstuff, and man would decrease due to migration processes in the soil, radioactive decay, and protective measures. This assumption was confirmed by all measurements in the first few years after the accident. Since 1991, however, a change in this development has been observed, as many measurements show stagnation or in some cases even an increase of foodstuff and human contamination. If normalised to an average local ground contamination, only a few groups of foodstuffs (e.g., potatoes) show a slight decrease in radioactivity. In this paper, the time development of radioactive contamination in the Bryansk-Gomel Spot on the basis of measurements since 1991 is presented. The consequences for long-term dose assessment are discussed. Received: 10 November 1998 / Accepted: 20 January 2000     

A secondary effect of transformation in Rhizobium leguminosarum transgenic for Bacillus thuringiensis subspecies tenebrionisδ-endotoxin (cryIIIA) genes

 By introducing Bacillus thuringiensis subspecies tenebrionisδ-endotoxin genes (cryIIIA) into Rhizobium leguminosarum we have produced strains for the biological control of Sitona larvae. Comparisons between a transgenic and the parent strain show that transformation has induced changes not associated with the intended function of the transgene. Although growth rates in laboratory cultures are similar for both strains, the ability to compete for nodule occupancy is greater in the transgenic than in the non-transformed parent strain. This result demonstrates the importance of studying ecological and agronomic characters of transgenic micro-organisms that could have a bearing on the safety and success of their release into the environment, even if they are not thought to be connected with the transgenes introduced. Received: 20 April 1997 / Accepted: 2 June 1997     

AFLP analysis of variation in pecan somatic embryos

Before somatic embryogenesis can be applied, the genetic fidelity of cultures needs to be determined. Problematic of tissue-cultured woody species is the extensive evaluation time needed for assessments. The development of methods whereby plants could be rapidly screened for potential tissue culture-derived genetic changes would be very valuable. We evaluated the applicability of AFLP (amplified fragment length polymorphism) analysis for the assessment of genetic variability in somatic embryos of pecan [Carya illinoinensis (Wangenh.) C. Koch] and made comparisons between and within embryogenic culture lines. AFLP readily detected differences between culture lines, with 368 polymorphic loci identified. Individual culture lines generally produced somatic embryos with similar overall banding patterns. Embryos derived from the same culture line generally grouped together in a phenogram generated by UPGMA (unweighted pair-group method, arithmetic average) analysis. However, a few somatic embryos exhibited higher levels of polymorphism and failed to group with others regenerated from the same line. The relation between the detected within-line differences and their contribution to phenotypic variation is yet to be determined. Received: 9 September 1998 / Revision received: 12 November 1998 / Accepted: 8 December 1998     

Degradation of lignite (low-rank coal) by ligninolytic basidiomycetes and their manganese peroxidase system

Ligninolytic basidiomycetes (wood and leaf-litter-decaying fungi) have the ability to degrade low-rank coal (lignite). Extracellular manganese peroxidase is the crucial enzyme in the depolymerization process of both coal-derived humic substances and native coal. The depolymerization of coal by Mn peroxidase is catalysed via chelated Mn(III) acting as a diffusible mediator with a high redox potential and can be enhanced in the presence of additional mediating agents (e.g. glutathione). The depolymerization process results in the formation of a complex mixture of lower-molecular-mass fulvic-acid-like compounds. Experiments using a synthetic ¹⁴C-labeled humic acid demonstrated that the Mn peroxidase-catalyzed depolymerization of humic substances was accompanied by a substantial release of carbon dioxide (17%–50% of the initially added radioactivity was released as ¹⁴CO₂). Mn peroxidase was found to be a highly stable enzyme that remained active for several weeks under reaction conditions in a liquid reaction mixture and even persisted in sterile and native soil from an opencast mining area for some days. Received: 31 July 1998 / Received revision: 29 September 1998 / Accepted: 2 October 1998     

The Relevance of the Distribution of Micro-organisms Within Batches of Food to the Control of Microbiological Hazards from Foods

The distribution of micro-organisms within batches of food is identified as log-normal and this distribution has practical implications in the control of microbial hazards in foods. These implications are explained as effects upon counting procedures, changes in levels through processes, detection of low levels of micro-organisms, the use of indicator groups, presence/absence tests, consumer safety calculations, and sample unit size analysed.     

Relationship between ectoenzymatic activity and availability of organic substrates (Ross Sea, Antarctica): an experimental approach

Organic matter consumption and decomposition were studied in four experimental systems, having collected different organic substrates in the Ross Sea in December 1994. For the experimental approach selected, processes normally acting on a mixed pool of substances could be separated and the main features of each phenomenon could be focused on. Through the strict relationship between each experimental system and natural conditions shown by organic matter assessment, ectoenzymatic activity trends and their relation with Antarctic water substrates could be described. Through ice melting the water column becomes rich in large pools of substrates, as well as enzyme-producing micro-organisms, capable of quick development. The quantitative predominance of leucine-aminopeptidase throughout the year is well known, but its relative importance seems to decrease when, owing to production events, the environment is enriched with autotrophic- and heterotrophic-derived substances, leading to glycolytic enzymes expression. Thus, ectoenzymatic activity is supposed to be one of the factors responsible for organic matter variations, showing quantitative and qualitative changes depending on substrate availability. Received: 26 September 1997 / Accepted: 17 May 1998     

Identification of quantitative trait loci influencing annual height- and diameter-increment growth in loblolly pine (Pinus taeda L.)

 Quantitative trait loci (QTLs) for annual height- and diameter-increment growth were estimated in each of two three-generation loblolly pine pedigrees. Annual height-increment was measured in three consecutive years in the BASE pedigree and in four consecutive years in the QTL pedigree. Annual diameter-increment was measured only in the QTL pedigree for two consecutive years. An interval mapping-approach was used to estimate the number of QTLs, the magnitude of QTL effects, and their position on genetic linkage maps. Thirteen different height-increment and eight different diameter-increment QTLs were detected, suggesting that the these traits are, at least in part, controlled by a few genes of large effect. Little evidence was found for the expression of individual QTLs in multiple years or in multiple genetic backgrounds. These results were discussed in terms of the power of the experiment and their consequences for marker-assisted breeding. Received: 12 July 1998/Accepted: 5 August 1998     

Assessing the Environmental-Hazard Potential for Life Cycle Assessment,Eco-Efficiency and SEEbalance (8 pp)

Intention, Goal, Scope, Background BASF has developed the eco-efficiency analysis tool to address not only strategic issues but also issues posed by the marketplace, politics and research. The goal was to develop a tool for supporting decision-making processes, which is useful for many of applications in the Chemical and other industries. A part of the eco-efficiency analysis involves the evaluation of the toxicity and the eco-toxicity potential. Objectives Many life cycle analyses do not include an assessment of the toxicity potential nor the eco-toxicity potential. However, in order to arrive at a comprehensive assessment of products and processes, it is often the eco-toxicity potential, which constitutes an important factor with regard to the evaluation of sustainability. The cradle-to-grave approach is also important for this calculation and will be done based on a database that will be discussed also in this paper. Methods The method used for the determination of the eco-toxicity potential follows the basic rules of the European Union Risk Ranking System (EURAM). The other criteria of the ecological fingerprint are combined with the economical results in the eco-efficiency portfolio. Results and Discussion The results of the studies are shown in a simple diagram, the eco-efficiency portfolio. Therefore ecological data are summarized in a special manner as described previously. It has been shown that the weighting factors, which are used in our method, have a negligible impact on the results. In most cases, the input data have the dominant impact on the results of the study. The eco-toxicity assessment will be a part of the ecological calculation. Because of the cradle-to-grave approach, substances of the whole life cycle can be identified that might have a toxic impact to the environment. The results can be used for optimization of the process. Conclusions The new calculation model allows the assessment of eco-toxicological substances in an appropriate and easy way. In most of the cases the data from a European safety data sheet are sufficient for the calculation. The normalized data can be incorporated very easily in the ecological fingerprint and in the drawing of the eco-efficiency portfolio. Recommendations and Outlook LCA in combination with the evaluation of the eco-toxicity potential will for reasons of optimizing for least impact become more important in certain cases. Especially in those systems where water emissions are likely, the use of the evaluation system in the eco-efficiency analysis is recommended. This new methodology allows the calculation of eco-toxicity potentials in a short time with a small set of input information. The analytical eco-efficiency tool helps in implementing more sustainable processes and products in the future.     

Bacterial complementation as a means to test enzyme–ligand interactions

A bacterial complementation assay has been developed for the rapid screening of a large number of compounds to identify those that inhibit an enzyme target for structure-based inhibitor design. The target enzyme is the hypoxanthine phosphoribosyltransferase (HPRT). This enzyme has been proposed as a potential target for inhibitors that may be developed into drugs for the treatment of diseases caused by several parasites. The screening assay utilizes genetically deficient bacteria complemented by active, recombinant enzyme grown in selective medium in microtiter plates. By comparing absorbance measurements of bacteria grown in the presence and absence of test compounds, the effect of the compounds on bacterial growth can be rapidly assayed. IC₅₀ values for inhibition of bacterial growth are a reflection of the ability of the compounds to bind and/or inhibit the recombinant enzyme. We have tested this bacterial complementation screening assay using recombinant HPRT from the parasites Plasmodium falciparum and Trypanosoma cruzi, as well as the human enzyme. The results of these studies demonstrate that a screening assay using bacterial complement selection can be used to identify compounds that target enzymes and can become an important part of structure-based drug design efforts. Received: 4 December 1997 / Received revision: 17 March 1998 / Accepted: 26 March 1998     

Risk Assessment and Safety Evaluation Using Probabilistic Fault Tree Analysis

Risk assessment is an essential prelude to the development of accident prevention strategies in any chemical or petrochemical industry. Many techniques and methodologies such as HAZOP, failure mode effect analysis, fault tree analysis, preliminary hazard analysis, quantitative risk assessment and probabilistic safety analysis are available to conduct qualitative, quantitative, and probabilistic risk assessment. However, these methodologies are limited by: extensive data requirements, the length of study, results are not directly interpretable for decision making, simulation is often difficult, and they are applicable only at the operation or late design stage. Khan et al. (2001a) recently proposed a detailed methodology for risk assessment and safety evaluation. This methodology is simple, yet it is effective in safety and design-related decision making, and it has been applied successfully to many case studies. It is named SCAP, where S stands for safety, C and A stand for credible accident respectively, and P stands for probabilistic fault tree analysis. This paper recapitulates the SCAP methodology and demonstrates its application to a petrochemical plant.     

How to evaluate the environmental safety of microbial plant protection products: A proposal

Plant protection products with active micro-organisms are allegedly less hazardous to the environment and wildlife than synthetic chemical pesticides. Nevertheless, they need a proper pre-marketing environmental safety evaluation because of their potential toxicity and pathogenicity. Scientific and technical guidance on such a safety evaluation for regulatory purposes is scarce. Therefore, a risk decision tree is proposed to provide such guidance and to discern the acceptable from the unacceptable environmental risks. The decision tree is based on the risk criteria of the European Union. It takes integrally into account the characterisation, identification and efficacy and also emission, exposure, environmental effects and, finally, the environmental risk assessment. Case by case expert judgement remains necessary in view of limited knowledge of microbial ecology, limited experience with regulatory test protocols and taxonomic difficulties in relation to the indigenousness of active micro-organisms. The decision tree offers regulatory guidance on the environmental safety evaluation of microbial plant protection products.     

Alteration of the LIS1 gene in Japanese patients with isolated lissencephaly sequence or Miller-Dieker syndrome

LIS1 is a genetic entity that is responsible for lissencephaly. Previously we have reported isolated lissencephaly sequence(ILS) in a Japanese patient carrying a balanced chromosomal translocation that disrupted the LIS1 gene. We examined mutations of LIS1 in 12 additional Japanese patients, 8 of them with ILS and 4 with Miller-Dieker syndrome (MDS). Fluorescence in situ hybridization (FISH) analysis disclosed deletions of part of the LIS1 gene or of the chromosomal region surrounding it in three of the ILS cases and in three of the MDS cases. In one of the remaining five ILS cases, SSCP analysis and subsequent sequence analysis identified a 1-bp deletion in exon IV, which can be expected to result in premature termination of the gene product. Our results indicate that in Japan, as elsewhere, abnormality of the LIS1 gene is a common cause of MDS/ILS. Received: 20 April 1998 / Accepted: 28 July 1998     

Identification of the High-Virulence Clone of Group B Streptococci in Mexican Isolates by Growth Characteristics at 40°C

Group B streptococci (GBS) colonizing the vagina and rectum of pregnant women cause invasive disease of the offspring in a small number of cases. The immune status of the host and differences in virulence among strains appear to be the main determinants for neonatal infection. A high-virulence clone (HVC) was proposed to cause much of the morbidity and mortality when a collection of GBS isolates was examined by multilocus enzyme electrophoresis. HVC isolates could be further distinguished by their inability to grow at 40°C. This characteristic was used in the present study to examine a collection of 57 GBS isolates from Mexico City for the HVC. Three serotype III invasive strains were classified in the HVC. The other eleven invasive strains and all carrier isolates had growth curves unaffected at 40°C. These results demonstrate the presence of the HVC in Mexico. Such a low prevalence could explain in part the low rate of GBS invasive neonatal disease in Mexico. Received: 21 May 1998 / Accepted: 14 September 1998     

Safety Evaluation of Transgenic Tilapia with Accelerated Growth

Recent advances in modern marine biotechnology have permitted the generation of new strains of economically important fish species through the transfer of growth hormone genes. These transgenic fish strains show improved growth performance and therefore constitute a better alternative for aquaculture programs. Recently, we have obtained a transgenic tilapia line with accelerated growth. However, before introducing this line into Cuban aquaculture, environmental and food safety assessment was required by national authorities. Experiments were performed to evaluate the behavior of transgenic tilapia in comparison to wild tilapia as a way to assess the environmental impact of introducing transgenic tilapia into Cuban aquaculture. Studies were also conducted to evaluate, according to the principle of substantial equivalence, the safety of consuming transgenic tilapia as food. Behavior studies showed that transgenic tilapia had a lower feeding motivation and dominance status than controls. Food safety assessment indicated that tilapia growth hormone has no biological activity when administered to nonhuman primates. Furthermore, no effects were detected in human healthy volunteers after the consumption of transgenic tilapia. These results showed, at least under the conditions found in Cuba, no environmental implications for the introduction of this transgenic tilapia line and the safety in the consumption of tiGH-transgenic tilapia as an alternative feeding source for humans. These results support the culture and consumption of these transgenic tilapia. Received: March 9, 1998; accepted June 25, 1998.     

Wide applicability of a flow cytometric assay to measure absolute membrane potentials on the millivolt scale

To prove the general applicability of a recently published flow cytometric method to determine the membrane potentials of cells on the absolute (mV) scale, the validity of the premises involved were analyzed individually. Experimental evidence was given for bis-oxonol, the applied membrane potential indicator being a Nernstian dye. The results of special measurements proved that extracellular dye concentrations were not affected by cellular dye uptake under the applied experimental conditions and that the dye content of the suspending medium did not contribute directly to the measured cellular fluorescence. A direct, membrane-potential-independent contribution of the extracellular dye to cellular fluorescence was also found to be negligible, as membrane potential values of the same type of cells evaluated from measurements in the presence of different extracellular oxonol concentrations were very close to each other. The transmembrane potential of B lymphoid JY cells was measured by the method as a function of cell density in the tissue culture. Cells isolated during the log phase of growth displayed a –40±4 mV membrane potential. At a high density of the culture (plateau phase), a significant increase of the membrane potential to –61±3 mV was observed and a medium value of –47±3.5 mV was measured at an intermediate density of the cells. Our observation indicates that nonadherent cells can also be hyperpolarized when optimal growth conditions are terminated. Received: 14 April 1998 / Revised version: 22 June 1998 / Accepted: 16 July 1998     

Degradation of dioxin-like compounds by microorganisms

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF; PCDD/F, dioxins) have not been commercially produced in bulk amounts, as were polychlorinated biphenyls and other haloaromatic organics. Within the past two decades a lot␣of information has accumulated on the biodegradation of PCDD/F and other dioxin-like compounds because of their toxicity and because of significant environmental concern about many congeners of this class of chemicals. PCDD/F are subjected to reductive dehalogenations leading to less halogenated congeners, which can be attacked efficiently by fungal and bacterial oxidases and dioxygenases. In several cases these compounds can be utilized as carbon and energy sources. Pathways for their enzymatic degradation and the organisation of the corresponding degradative genes have been elucidated. Consequently, biotechnological applications will exploit the degradative potential of such microorganisms for bioremediation of contaminated sites. Received: 29 August 1997 / Received revision: 6 January 1998 / Accepted: 8 January 1998