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PubMed2000

Kenneth Mellanby Review Award. Bioaccumulation of persistent organic chemicals: mechanisms and models.

A review is presented of bioaccumulation of organic substances in organisms, especially fish, including the incentives for developing a tiered predictive approach for addressing the large number of chemicals of commerce. From a review of the existing estimation methods it is suggested that the simplest Tier 1 approach is an empirical correlation for bioconcentration factor as a function of the octanol-water partition coefficient. For more detailed Tier 2 evaluation, the bioaccumulation factor is best predicted using a mechanistic mass balance model applied to the organism at steady state in which relevant uptake and loss processes are quantified. The equivalence of rate constant and fugacity models is demonstrated and methods of obtaining parameter values are discussed. Such a model reveals the relative significance of gill ventilation, food uptake, egestion, and metabolism. The most detailed Tier 3 evaluation should involve prediction of the potential for biomagnification in a food chain involving both fish and air-breathing animals. Research needs are discussed with a view to understanding the mechanisms more fully and developing more accurate quantitative descriptions or models of bioaccumulation phenomena.

Journal Article↗
PubMed1998

Age patterns of smoking initiation among Kuwait university male students.

The present study is a detailed evaluation of age at smoking initiation among university male students in Kuwait based on a random sample of 664 students selected from all students during 1993. The Acturial Life Table analysis revealed that almost one tenth of the students initiated cigarette smoking between ages 16 and 17 with the rate of initiation increasing rapidly thereafter and reaching 30% by age 20 and almost 50% by the time they celebrate their 24th birthday. The most important environmental risk factor positively associated for smoking initiation was observed to be the history of smoking among siblings with a relative risk of 1.4. Compared to students of medicine and engineering, the students of other faculties revealed a higher risk in smoking initiation with an RR = 1.77 for sciences and commerce and 1.61 for other faculties (arts, law, education and Islamic studies). The analysis revealed a rising generation trend in cigarette smoking. There is a need for reduction of this trend among young adults in Kuwait and throughout other countries in the region.

Adolescent↗
PubMed2001

A review of structure-based biodegradation estimation methods.

Biodegradation, being the principal abatement process in the environment, is the most important parameter influencing the toxicity, persistence, and ultimate fate in aquatic and terrestrial ecosystems. Biodegradation of an organic chemical in natural systems may be classified as primary (alteration of molecular integrity), ultimate (complete mineralization; i.e. conversion to inorganic compounds and/or normal metabolic processes), or acceptable (toxicity ameliorated). Most of the biodegradation correlations presented in the literature focus on the characterization of primary or ultimate, aerobic degradation. The US Environmental Protection Agency (USEPA) is charged with determining the risks associated with the thousands of chemicals employed in commerce, an effort that is being facilitated through much research aimed at reliable structure-activity relationships (SAR) to predict biodegradation of chemicals in natural systems. To this end, models are needed to understand the mechanisms of biodegradation, to classify chemicals according to relative biodegradability, and to develop reliable biodegradation estimation methods for new chemicals. Frequently, published correlations associating molecular structure to biodegradation will attempt to quantify the degradability of a limited set of homologous chemicals. These correlations have been dubbed quantitative structure biodegradability relationships (QSBRs). More scarce and valuable to researchers are those models that predict the biodegradability of compounds possessing a wide variety of chemical structures. The latter may use any of several techniques and molecular descriptors to correlate biodegradability: QSBRs, pattern recognition, discriminant analysis, and principle component analysis (PCA), to name several. Generally, models either predict the propensity of a chemical to biodegrade using Boolean-type logic (i.e. whether a chemical will "readily biodegrade" or not), or else they quantify the degree of biodegradation by providing information such as rate constants. Such quantitative predictions of biodegradability come in a diversity of parameters, including half-lives, various biodegradation rates and rates constants, theoretical oxygen demand (ThOD), biological oxygen demand (BOD), and others. In this paper, after describing the advantages and disadvantages of the various biodegradation estimation methods found in the literature, the best models are compared to conclude which provide the greatest utility for determining the biodegradability of chemicals with widely varying structures. The group contribution technique presented by Boethling et al. [Environmen. Sci. Technol. 28 (1994) 459] appears to be the most advantageous for use in broad screening for tendency to biodegrade. The model is simple to use, calculating a probability of biodegrading ranging from 0 (none) to 1 (certain), and has proven to be accurate for a wide range of chemical structures, as established by the large, high-quality data set (BIODEG evaluated biodegradation database, Syracuse Research Corporation, Merrill Lane, Syracuse, NY 13210) used to develop this correlation. The authors, therefore, recommend the method of Boethling et al. [Environ. Sci. Technol. 28 (1994) 459] for the initial screening of chemicals to aid in determining whether additional information is necessary to establish relative biodegradability. For readers with applications requiring more quantitative results, such as biodegradation rate constants, enough model details are presented in this paper to allow the reader to pick a suitable correlation, although the reader is cautioned to consult the original, primary reference for the complete method description, equations, and limitations.

Biodegradation, Environmental↗
PubMed2000

Attenuation mechanisms of N-nitrosodimethylamine at an operating intercept and treat groundwater remediation system.

The North Boundary Containment System (NBCS), an intercept-and-treat system, was established at Rocky Mountain Arsenal (RMA), Commerce City, CO, to remove low-level organic contaminants from a groundwater plume exiting RMA to the north and northwest. N-nitrosodimethylamine (NDMA) was detected in groundwater collected from the dewatering and recharge zones of the NBCS system. Concern over the fate of NDMA, in terms of potentially exiting the boundaries of the arsenal, prompted an investigation to evaluate potential attenuation mechanisms for NDMA within the alluvial aquifer system and within the NBCS itself. Groundwater, soil, and granular activated carbon (GAC) samples were taken from key locations in the NBCS system. Soil and GAC samples were assayed for sorption kinetics and for adsorption and desorption properties using 14C-labeled NDMA. NDMA biodegradation experiments were conducted by following 14CO(2) evolution from 14C-labeled NDMA in soils and GAC samples under aerobic and anaerobic conditions. The sorptive capacity of the site soils for NDMA was insignificant. Furthermore, the adsorption of the NDMA by the soil was almost completely reversible. Evaluation of the degradation potential of the native microbial consortia indicated a high level of NDMA mineralization when measured using bench-scale microcosms. The native consortia had capability to mineralize the NDMA under both aerobic and anaerobic incubations, indicating facultative characteristics. Testing of the local groundwater chemistry revealed that the area of the aquifer of interest was microaerobic and neutral in pH. These conditions were optimal for NDMA removal. While sorption was insignificant, degradation was a significant attenuation mechanism, which may be the reason that no NDMA has migrated off-site. This gives rise to the potential of a long-term sink for attenuating NDMA within the recharge zone of the treatment system.

Adsorption↗
PubMed2000

Historical perspectives and current global challenges of Trichinella and trichinellosis.

Trichinella spiralis and related species of Trichinella have had a long history of causing human disease, and as a foodborne pathogen have had a major impact on international commerce of pork and other meat animal species which are known to transmit the parasite. Our knowledge of Trichinella has increased substantially over the past few years particularly in the areas of phylogeny, host diversity, epidemiology and control. In this paper, we provide a brief overview of our understanding of Trichinella from its discovery to present time. Past and current challenges of the control of Trichinella and trichinellosis are summarized. As editors of this special issue of Veterinary Parasitology, we introduce a series of invited review articles prepared by experts from around the world, summarizing recent knowledge in Trichinella and trichinellosis.

Animals↗
PubMed1998

Emerging infectious diseases and travel medicine.

International movement of individuals, populations, and products is one of the major factors associated with the emergence and reemergence of infectious diseases as the pace of global travel and commerce increases rapidly. Travel can be associated with disease emergence because (1) the disease arises in an area of heavy tourism, (2) tourists may be at heightened risk because of their activities, or (3) because they can act as vectors to transport the agent to new areas. Examples of recently recognized diseases with relationship to travel include HIV, Legionnaire's disease, cyclosporiasis, Vibrio cholerae O139 Bengal, hantavirus, and variant Creutzfeldt-Jacob disease. Reemerging diseases include dengue fever, malaria, cholera, schistosomiasis, leptospirosis, and viral hemorrhagic fevers. In addition, tuberculosis, drug-resistant shigellosis, and cholera have been major concerns in refugee and migrant populations. Because of the unique role of travel in emerging infections, efforts are underway to address this factor by agencies such as the CDC, WHO, the International Society of Travel Medicine, and the travel industry.

Communicable Disease Control↗
PubMed2000

International Conference on Harmonization--critical discussion of the biotech 'Specifications' document.

Since 1990, the International Conference on Harmonization (ICH) has served as the primary medium for the development of consistent, harmonized and scientifically based international standards that keep abreast of the complexity of rapidly evolving technologies, and health, safety and commerce issues. Of the 45 guidance documents generated to date, influencing the conduct of drug development at various points during its continuum, six are dedicated to biotechnology. 'Specifications', the last in the series, was completed in 1999. It is fully complimentary to the other five guidance documents in the ICH biotechnology compendium. The process of establishing product specifications (principles and applications) is functionally couched within the multifaceted strategy of ensuring quality and consistency, and is proving to be a fundamental resource in crafting future harmonized documents such as the Common Technical Document.

Biotechnology↗
PubMed2002

Computer applications in the search for unrelated stem cell donors.

The majority of patients which are eligible for a blood stem cell transplantation from an allogeneic donor do not have a suitable related donor so that an efficient unrelated donor search is a prerequisite for this treatment. Currently, there are over 7 million volunteer donors in the files of 50 registries in the world and in most countries the majority of transplants are performed from a foreign donor. Evidently, computer and communication technology must play a crucial role in the complex donor search process on the national and international level. This article describes the structural elements of the donor search process and discusses major systematic and technical issues to be addressed in the development and evolution of the supporting telematic systems. The theoretical considerations are complemented by a concise overview over the current state of the art which is given by describing the scope, relevance, interconnection and technical background of three major national and international computer appliances: The German Marrow Donor Information System (GERMIS) and the European Marrow Donor Information System (EMDIS) are interoperable business-to-business e-commerce systems and Bone Marrow Donors World Wide (BMDW) is the basic international donor information desk on the web.

Bone Marrow Transplantation↗
PubMed1998

MoldaNet: a network distributed molecular graphics and modelling program that integrates secure signed applet and Java 3D technologies.

MoldaNet is a molecular graphics and modelling program that integrates several new Java technologies, including authentication as a Secure Signed Applet, and implementation of Java 3D classes to enable access to hardware graphics acceleration. It is the first example of a novel class of Internet-based distributed computational chemistry tool designed to eliminate the need for user pre-installation of software on their client computer other than a standard Internet browser. The creation of a properly authenticated tool using a signed digital X.509 certificate permits the user to employ MoldaNet to read and write the files to a local file store; actions that are normally disallowed in Java applets. The modularity of the Java language also allows straightforward inclusion of Java3D and Chemical Markup Language classes in MoldaNet to permit the user to filter their model into 3D model descriptors such as VRML97 or CML for saving on local disk. The implications for both distance-based training environments and chemical commerce are noted.

Computer Graphics↗
PubMed2000

Contracting opportunities: interpreting post-asylum geographies of mental health care in Auckland, New Zealand.

In New Zealand, the process of deinstitutionalization is continuing to unfold as a specific manifestation of welfare state restructuring rather than as a discrete process within the health care sector. In this paper we consider the geography of mental health care in Auckland, New Zealand's only metropolitan city. Here, a highly fluid and competitive housing market has profoundly (re)shaped the opportunities for community care. We report on findings from a survey of representatives of the key agencies providing mental health care in central Auckland. We argue that the re-placing of mental health care into the community has often involved the separation of residential and treatment issues, to the detriment of the communities, institutions and (especially) individuals involved. We trace this fragmentation back to the primacy of the ideology of restructuring over the philosophy of deinstitutionalization. We build our argument around a discussion of the Mental Health (Compulsory Assessment and Treatment) Act 1992 and the apparent subordination of the Act to the emerging of a 'contract state' and broader legislation, such as the Resource Management Act 1991, the Privacy Act 1992 and the Commerce Act 1986, which underpins the re-regulation of New Zealand society.

Community Mental Health Services↗
PubMed2001

Fourier transform infrared and Raman spectral analysis of trans-1,4-polyisoprene.

Polyisoprene is the most widely used polymer in industry and commerce. Fourier transform infrared (FTIR) and Raman spectra of trans-1,4-polyisoprene have been recorded in the range of 4000-400 and 4000-100 cm(-1), respectively. In the present investigation, detailed assignments of the observed fundamental bands of trans-1,4-polyisoprene has been analysed in terms of peak positions and relative intensities. With the hope of providing more and effective information on the fundamental vibrations, a normal co-ordinate analysis has been performed on trans-1,4polyisoprene, by assuming Cs symmetry. The simple general valance force field (SGVFF) method has been employed in normal co-ordinate analysis and to calculate the potential energy distribution (PED) for each fundamental vibration. The PED contribution corresponding to each of the observed frequencies shows the reliability and accuracy of the spectral analysis. The validity of the SGVFF method as a practical tool for complete analysis of vibrational spectra, even for a polymer of this complexity, is confirmed in the present work.

Hemiterpenes↗
PubMed2000

Architecture for networked electronic patient record systems.

There have been two major approaches to the development of networked electronic patient record (EPR) architecture. One uses object-oriented methodologies for constructing the model, which include the GEHR project, Synapses, HL7 RIM and so on. The second approach uses document-oriented methodologies, as applied in examples of HL7 PRA. It is practically beneficial to take the advantages of both approaches and to add solution technologies for network security such as PKI. In recognition of the similarity with electronic commerce, a certificate authority as a trusted third party will be organised for establishing networked EPR system. This paper describes a Japanese functional model that has been developed, and proposes a document-object-oriented architecture, which is-compared with other existing models.

Computer Communication Networks↗
PubMed2000

Trophic-dynamic considerations in relating species diversity to ecosystem resilience.

Complexity in the networks of interactions among and between the living and abiotic components forming ecosystems confounds the ability of ecologists to predict the economic consequences of perturbations such as species deletions in nature. Such uncertainty hampers prudent decision making about where and when to invest most intensively in species conservation programmes. Demystifying ecosystem responses to biodiversity alterations may be best achieved through the study of the interactions allowing biotic communities to compensate internally for population changes in terms of contributing to ecosystem function, or their intrinsic functional redundancy. Because individual organisms are the biologically discrete working components of ecosystems and because environmental changes are perceived at the scale of the individual, a mechanistic understanding of functional redundancy will hinge upon understanding how individuals' behaviours influence population dynamics in the complex community setting. Here, I use analytical and graphical modelling to construct a conceptual framework for predicting the conditions under which varying degrees of interspecific functional redundancy can be found in dynamic ecosystems. The framework is founded on principles related to food web successional theory, which provides some evolutionary insights for mechanistically linking functional roles of discrete, interacting organisms with the dynamics of ecosystems because energy is the currency both for ecological fitness and for food web commerce. Net productivity is considered the most contextually relevant ecosystem process variable because of its socioeconomic significance and because it ultimately subsumes all biological processes and interactions. Redundancy relative to productivity is suggested to manifest most directly as compensatory niche shifts among adaptive foragers in exploitation ecosystems, facilitating coexistence and enhancing ecosystem recovery after disturbances which alter species' relative abundances, such as extinctions. The framework further explicates how resource scarcity and environmental stochasticity may constitute 'ecosystem legacies' influencing the emergence of redundancy by shaping the background conditions for foraging behaviour evolution and, consequently, the prevalence of compensatory interactions. Because it generates experimentally testable predictions for a priori hypothesis testing about when and where varying degrees of functional redundancy are likely to be found in food webs, the framework may be useful for advancing toward the reliable knowledge of biodiversity and ecosystem function relations necessary for prudent prioritization of conservation programmes. The theory presented here introduces explanation of how increasing diversity can have a negative influence on ecosystem sustainability by altering the environment for biotic interactions and thereby changing functional compensability among biota--under particular conditions.

Animals↗
PubMed1995

Taenia ovis recombinant vaccine--'quo vadit'.

Several years have elapsed since the publication by Johnson et al. (1989) of the cloning of a recombinant antigen from the cestode parasite Taenia ovis which stimulated high levels of protective immunity in sheep. A great deal of subsequent research and development was necessary to bring the fledgling vaccine to the point of being a registered commercial product. The results of these subsequent studies are dealt with briefly in this paper, including the results of field trials. The T. ovis vaccine was registered by the New Zealand Animal Remedies Board in February 1994. Where then is the commercial product? This paper gives a background to market problems which have emerged through the politics (and realities) of the NZ T. ovis control campaign. It serves as notice that the best science dedicated to producing vaccines or products for parasitic, or other, diseases often faces significant hurdles in the real world of commerce and politics.

Animals↗
PubMed2001

U.S. Chemical program: purpose, challenges, and evolution.

This article explores long-term issues and problems that have seriously undermined the U.S. Chemical Testing Program established by the Environmental Protection Agency (EPA) under the Toxic Substances Control Act. This program is meant to gather information needed to protect human health and the environment from damaging exposure to toxic chemicals. Despite seemingly broad and impressive authority under the statute, there are a number of inherent difficulties, as well as substantial political constraints, that impede comprehensive oversight of chemicals in U.S. commerce. The article discusses several approaches that EPA has adopted to overcome statutory and political limitations and increase chemical testing information. The most recent and promising of these efforts has involved international negotiations to harmonize testing approaches with OECD nations and to cooperate on an agenda that will better share the testing burden on an international level.

Journal Article↗
PubMedDate not supplied

2D-3D migration of large chemical inventories with conformational multiplication. Application of the genetic algorithm.

Mathematical chemistry has afforded a variety of research areas with important tools to understand and predict the behavior of chemicals without having to consider the complexities of three-dimensional conformations of molecules. Predictive toxicology, an area of increasing importance to toxicity assessments critical to molecular design and risk management, must be based on more explicit descriptions of structure, however. Minimum energy conformations are often used for convenience due, in part, to the difficulty of computing a representative population of conformers in all but rigid structures. Such simplifying assumptions fail to reveal the variance of the stereoelectronic nature of molecules as well as the misclassification of chemicals which initiate receptor-based toxicity pathways. Because these errors impact both the success in discovering new lead and the identification of possible hazards, it is important that mathematical chemistry develop additional tools for conformational analysis. This paper presents a new system for automated 2D-3D migration of chemicals in large databases with conformer multiplication. The main advantages of this system are its straightforward performance, reasonable execution time, simplicity and applicability to building large 3D chemical inventories. The module for conformer multiplication within the 2D-3D migration system is based on a new formulation of the genetic algorithm for computing populations of possible conformers. The performance of the automated 2D-3D migration system in building a centralized 3D database for all chemicals in commerce worldwide is discussed. The applicability of the 3D database in assessing the impact of molecular flexibility on identifying active conformers in QSAR analysis and assessing similarity between chemicals is illustrated.

Algorithms↗
PubMed2000

Coverage of Indian leather patents in chemical abstracts

Patent information is increasingly becoming important in the current context of international trade and commerce. The printed version of Chemical Abstracts still continues to be used heavily, and it was evaluated as the source of information on Indian patents using leather patents as a case study. The results of the study are given.

Journal Article↗
PubMed2006

Screening level risk assessment model for chemical fate and effects in the environment.

A screening level risk assessment model is developed and described to assess and prioritize chemicals by estimating environmental fate and transport, bioaccumulation, and exposure to humans and wildlife for a unit emission rate. The most sensitive risk endpoint is identified and a critical emission rate is then calculated as a result of that endpoint being reached. Finally, this estimated critical emission rate is compared with the estimated actual emission rate as a risk assessment factor. This "back-tracking" process avoids the use of highly uncertain emission rate data as model input. The application of the model is demonstrated in detail for three diverse chemicals and in less detail for a group of 70 chemicals drawn from the Canadian Domestic Substances List. The simple Level II and the more complex Level III fate calculations are used to "bin" substances into categories of similar probable risk. The essential role of the model is to synthesize information on chemical and environmental properties within a consistent mass balance framework to yield an overall estimate of screening level risk with respect to the defined endpoint. The approach may be useful to identify and prioritize those chemicals of commerce that are of greatest potential concern and require more comprehensive modeling and monitoring evaluations in actual regional environments and food webs.

Animals↗