Enhancing swine manure treatment: A full-scale techno-economic assessment of nitrogen recovery, pure oxygen aeration and effluent polishing

In regions with intensive livestock production, managing the environmental impact of manure is a critical challenge. This study, set in Flanders (Belgium), evaluates the effectiveness of integrating process intensification measures into the treatment of piggery manure to mitigate nitrogen (N) surplus issues. The research investigates the techno-economic benefits of implementing three key interventions: pure oxygen (PO) aeration, ammonia (NH3) stripping-scrubbing (SS) pretreatment, and tertiary treatment using constructed wetlands (CW), within the conventional nitrification-denitrification (NDN) process. Conducted at a full-scale pig manure treatment facility, our analysis employs steady-state mass balances for N and phosphorus (P) to assess the impact of these process intensification strategies. Findings indicate that the incorporation of advanced treatment steps significantly enhances the efficiency and cost-effectiveness of the manure management system. Specifically, the application of PO aeration is shown to reduce overall treatment costs by nearly 4%, while the addition of an NH3 SS unit further decreases expenses by 1-2%, depending on the counter acid utilized. Moreover, the implementation of a CW contributes an additional 4% in cost savings. Collectively, these measures offer substantial improvements in processing capacity, reduction of by-product disposal costs, and generation of additional revenue from high-quality fertilising products. The study highlights the potential of advanced treatment technologies to provide economically viable and environmentally sustainable solutions for manure management in livestock-dense regions, emphasizing the cumulative economic benefit of a holistic approach to process intensification (10%).

Dissolution rate and growth performance reveal struvite as a sustainable nutrient source to produce a diverse set of microbial protein

To provide for the globally increasing demand for proteinaceous food, microbial protein (MP) has the potential to become an alternative food or feed source. Phosphorus (P), on the other hand, is a critical raw material whose global reserves are declining. Growing MP on recovered phosphorus, for instance, struvite obtained from wastewater treatment, is a promising MP production route that could supply protein-rich products while handling P scarcity. The aim of this study was to explore struvite dissolution kinetics in different MP media and characterize MP production with struvite as sole P-source. Different operational parameters, including pH, temperature, contact surface area, and ion concentrations were tested, and struvite dissolution rates were observed between 0.32 and 4.7 g P/L/d and a solubility between 0.23 and 2.22 g P-based struvite/L. Growth rates and protein production of the microalgae Chlorella vulgaris and Limnospira sp. (previously known as Arthrospira sp.), and the purple non‑sulfur bacterium Rhodopseudomonas palustris on struvite were equal to or higher than growth on conventional potassium phosphate. For aerobic heterotrophic bacteria, two slow-growing communities showed decreased growth on struvite, while the growth was increased for a third fast-growing one. Furthermore, MP protein content on struvite was always comparable to the one obtained when grown on standard media. Together with the low content in metals and micropollutants, these results demonstrate that struvite can be directly applied as an effective nutrient source to produce fast-growing MP, without any previous dissolution step. Combining a high purity recovered product with an efficient way of producing protein results in a strong environmental win-win.

A bioreactor and nutrient balancing approach for the conversion of solid organic fertilizers to liquid nitrate-rich fertilizers: Mineralization and nitrification performance complemented with economic aspects

Due to the high water- and nutrient-use efficiency, hydroponic cultivation is increasingly vital in progressing to environment-friendly food production. To further alleviate the environmental impacts of synthetic fertilizer production, the use of recovered nutrients should be encouraged in horticulture and agriculture at large. Solid organic fertilizers can largely contribute to this, yet their physical and chemical nature impedes application in hydroponics. This study proposes a bioreactor for mineralization and nitrification followed by a supplementation step for limiting macronutrients to produce nitrate-based solutions from solid fertilizers, here based on a novel microbial fertilizer. Batch tests showed that aerobic conversions at 35 °C could realize a nitrate (NO₃^--N) production efficiency above 90% and a maximum rate of 59 mg N L^-1 d^-1. In the subsequent bioreactor test, nitrate production efficiencies were lower (44-51%), yet rates were higher (175-212 mg N L^-1 d^-1). Calcium and magnesium hydroxide were compared to control the bioreactor pH at 6.0 ± 0.2, while also providing macronutrients for plant production. A mass balance estimation to mimic the Hoagland nutrient solution showed that 92.7% of the NO₃^--N in the Ca(OH)₂ scenario could be organically sourced, while this was only 37.4% in the Mg(OH)₂ scenario. Besides, carbon dioxide (CO₂) generated in the bioreactor can be used for greenhouse carbon fertilization to save operational expenditure (OPEX). An estimation of the total OPEX showed that the production of a nutrient solution from solid organic fertilizers can be cost competitive compared to using commercially available liquid inorganic fertilizer solutions.

An integrated assessment of environmental, economic, social and technological parameters of source separated and conventional sanitation concepts: A contribution to sustainability analysis

Resource recovery and reuse from domestic wastewater has become an important subject for the current development of sanitation technologies and infrastructures. Different technologies are available and combined into sanitation concepts, with different performances. This study provides a methodological approach to evaluate the sustainability of these sanitation concepts with focus on resource recovery and reuse. St. Eustatius, a small tropical island in the Caribbean, was used as a case study for the evaluation. Three source separation-community-on-site and two combined sewerage island-scale concepts were selected and compared in terms of environmental (net energy use, nutrient recovery/reuse, BOD/COD, pathogens, and GHG emission, land use), economic (CAPEX and OPEX), social cultural (acceptance, required competences and education), and technological (flexibility/adaptability, reliability/continuity of service) indicators. The best performing concept, is the application of Upflow Anaerobic Sludge Bed (UASB) and Trickling Filter (TF) at island level for combined domestic wastewater treatment with subsequent reuse in agriculture. Its overall average normalised score across the four categories (i.e., average of average per category) is about 15% (0.85) higher than the values of the remaining systems and with a score of 0.73 (conventional activated sludge - centralised level), 0.77 (UASB-septic tank (ST)), 0.76 (UASB-TF - community level), and 0.75 (ST - household level). The higher score of the UASB-TF at community level is mainly due to much better performance in the environmental and economic categories. In conclusion, the case study provides a methodological approach that can support urban planning and decision-making in selecting more sustainable sanitation concepts, allowing resource recovery and reuse in small island context or in other contexts.

A systematic comparison of commercially produced struvite: Quantities, qualities and soil-maize phosphorus availability

Production of struvite (MgNH₄PO₄·6H₂O) from waste streams is increasingly implemented to recover phosphorus (P), which is listed as a critical raw material in the European Union (EU). To facilitate EU-wide trade of P-containing secondary raw materials such as struvite, the EU issued a revised fertilizer regulation in 2019. A comprehensive overview of the supply of struvite and its quality is presently missing. This study aimed: i) to determine the current EU struvite production volumes, ii) to evaluate all legislated physicochemical characteristics and pathogen content of European struvite against newly set regulatory limits, and iii) to compare not-regulated struvite characteristics. It is estimated that in 2020, between 990 and 1250 ton P are recovered as struvite in the EU. Struvite from 24 European production plants, accounting for 30% of the 80 struvite installations worldwide was sampled. Three samples failed the physicochemical legal limits; one had a P content of <7% and three exceeded the organic carbon content of 3% dry weight (DW). Mineralogical analysis revealed that six samples had a struvite content of 80-90% DW, and 13 samples a content of >90% DW. All samples showed a heavy metal content below the legal limits. Microbiological analyses indicated that struvite may exceed certain legal limits. Differences in morphology and particle size distribution were observed for struvite sourced from digestate (rod shaped; transparent; 82 mass% < 1 mm), dewatering liquor (spherical; opaque; 65 mass% 1-2 mm) and effluent from upflow anaerobic sludge blanket reactor processing potato wastewater (spherical; opaque; 51 mass% < 1 mm and 34 mass% > 2 mm). A uniform soil-plant P-availability pattern of 3.5-6.5 mg P/L soil/d over a 28 days sampling period was observed. No differences for plant biomass yield were observed. In conclusion, the results highlight the suitability of most struvite to enter the EU fertilizer market.

Storage, fertilization and cost properties highlight the potential of dried microbial biomass as organic fertilizer

The transition to sustainable agriculture and horticulture is a societal challenge of global importance. Fertilization with a minimum impact on the environment can facilitate this. Organic fertilizers can play an important role, given their typical release pattern and production through resource recovery. Microbial fertilizers (MFs) constitute an emerging class of organic fertilizers and consist of dried microbial biomass, for instance produced on effluents from the food and beverage industry. In this study, three groups of organisms were tested as MFs: a high-rate consortium aerobic bacteria (CAB), the microalga Arthrospira platensis ('Spirulina') and a purple non-sulfur bacterium (PNSB) Rhodobacter sp. During storage as dry products, the MFs showed light hygroscopic activity, but the mineral and organic fractions remained stable over a storage period of 91 days. For biological tests, a reference organic fertilizer (ROF) was used as positive control, and a commercial organic growing medium (GM) as substrate. The mineralization patterns without and with plants were similar for all MFs and ROF, with more than 70% of the organic nitrogen mineralized in 77 days. In a first fertilization trial with parsley, all MFs showed equal performance compared to ROF, and the plant fresh weight was even higher with CAB fertilization. CAB was subsequently used in a follow-up trial with petunia and resulted in elevated plant height, comparable chlorophyll content and a higher amount of flowers compared to ROF. Finally, a cost estimation for packed GM with supplemented fertilizer indicated that CAB and a blend of CAB/PNSB (85%/15%) were most cost competitive, with an increase of 6% and 7% in cost compared to ROF. In conclusion, as bio-based fertilizers, MFs have the potential to contribute to sustainable plant nutrition, performing as good as a commercially available organic fertilizer, and to a circular economy.

Purple non-sulphur bacteria and plant production: benefits for fertilization, stress resistance and the environment

Purple non-sulphur bacteria (PNSB) are phototrophic microorganisms, which increasingly gain attention in plant production due to their ability to produce and accumulate high-value compounds that are beneficial for plant growth. Remarkable features of PNSB include the accumulation of polyphosphate, the production of pigments and vitamins and the production of plant growth-promoting substances (PGPSs). Scattered case studies on the application of PNSB for plant cultivation have been reported for decades, yet a comprehensive overview is lacking. This review highlights the potential of using PNSB in plant production, with emphasis on three key performance indicators (KPIs): fertilization, resistance to stress (biotic and abiotic) and environmental benefits. PNSB have the potential to enhance plant growth performance, increase the yield and quality of edible plant biomass, boost the resistance to environmental stresses, bioremediate heavy metals and mitigate greenhouse gas emissions. Here, the mechanisms responsible for these attributes are discussed. A distinction is made between the use of living and dead PNSB cells, where critical interpretation of existing literature revealed the better performance of living cells. Finally, this review presents research gaps that remain yet to be elucidated and proposes a roadmap for future research and implementation paving the way for a more sustainable crop production.

Dried aerobic heterotrophic bacteria from treatment of food and beverage effluents: Screening of correlations between operation parameters and microbial protein quality

Consortia of aerobic heterotrophic bacteria (AHB) have potential as sustainable microbial protein (MP) source in animal feed. A systematic screening of the nutritional value and safety of AHB biomass from full-scale activated sludge plants from 25 companies in the food sector was performed. The variable protein content (21-49%) was positively correlated with biomass-specific nitrogen loading rate and negatively with sludge retention time (SRT). Compared to the essential amino acid profile of soybean meal protein, AHB displayed an overall surplus of threonine and valine, and deficits in cysteine, histidine, lysine and phenylalanine. Histidine was positively correlated with bCOD/PO₄^3- in the influent and valine, isoleucine and threonine with SRT. Most AHB samples were safe apropos heavy metals, polycyclic aromatic hydrocarbons and antibiotics. Some pesticides exceeded regulatory limits, necessitating mitigation. This work highlighted that the food sector can provide high-quality MP, while retrofitting existing activated sludge plants towards high-rate processes can increase AHB quality and productivity.

Environmental impact of microbial protein from potato wastewater as feed ingredient: Comparative consequential life cycle assessment of three production systems and soybean meal

Livestock production is utilizing large amounts of protein-rich feed ingredients such as soybean meal. The proven negative environmental impacts of soybean meal production incentivize the search for alternative protein sources. One promising alternative is Microbial Protein (MP), i.e. dried microbial biomass. To date, only few life cycle assessments (LCAs) for MP have been carried out, none of which has used a consequential modelling approach nor has been investigating the production of MP on food and beverage wastewater. Therefore, the objective of this study is to evaluate the environmental impact of MP production on a food and beverage effluent as a substitute for soybean meal using a consequential modelling approach. Three different types of MP production were analysed, namely consortia containing Aerobic Heterotrophic Bacteria (AHB), Microalgae and AHB (MaB), and Purple Non-Sulfur Bacteria (PNSB). The production of MP was modelled for high-strength potato wastewater (COD = 10 kg/m3) at a flow rate of 1,000 m3/day. LCA results were compared against soybean meal production for the endpoint impact categories human health, ecosystems, and resources. Soybean meal showed up to 52% higher impact on human health and up to 87% higher impact on ecosystems than MP. However, energy-related aspects resulted in an 8-88% higher resource exploitation for MP. A comparison between the MP production systems showed that MaB performed best when considering ecosystems (between 13 and 14% better) and resource (between 71 and 80% better) impact categories, while AHB and PNSB had lower values for the impact category human health (8-12%). The sensitivity analysis suggests that the conclusions drawn are robust as in the majority of 1,000 Monte Carlo runs the initial results are confirmed. In conclusion, it is suggested that MP is an alternative protein source of comparatively low environmental impact that should play a role in the future protein transition, in particular when further process improvements can be implemented and more renewable or waste energy sources will be used.

Proof of concept of high-rate decentralized pre-composting of kitchen waste: Optimizing design and operationof a novel drum reactor

Each ton of organic household waste that is collected, transported and composted incurs costs (€75/ton gate fee). Reducing the mass and volume of kitchen waste (KW) at the point of collection can diminish transport requirements and associated costs, while also leading to an overall reduction in gate fees for final processing. To this end, the objective of this research was to deliver a proof of concept for the so-called "urban pre-composter"; a bioreactor for the decentralized, high-rate pre-treatment of KW, that aims at mass and volume reduction at the point of collection. Results show considerable reductions in mass (33%), volume (62%) and organic solids (32%) of real KW, while provision of structure material and separate collection of leachate was found to be unnecessary. The temperature profile, C/N ratio (12) and VS/TS ratio (0.69) indicated that a mature compost can be produced in 68  days (after pre-composting and main composting). An economic Monte Carlo simulation yielded that the urban pre-composter concept is not more expensive than the current approach, provided its cost per unit is €8,000-€14,500 over a 10-year period (OPEX and CAPEX, in 80% of the cases). The urban pre-composter is therefore a promising system for the efficient pre-treatment of organic household waste in an urban context.

Resource recovery from pig manure via an integrated approach: A technical and economic assessment for full-scale applications

Intensive livestock farming cannot be uncoupled from the massive production of manure, requiring adequate management to avoid environmental damage. The high carbon, nitrogen and phosphorus content of pig manure enables targeted resource recovery. Here, fifteen integrated scenarios for recovery of water, nutrients and energy are compared in terms of technical feasibility and economic viability. The recovery of refined nutrients with a higher market value and quality, i.e., (NH₄)₂SO₄ for N and struvite for P, coincided with higher net costs, compared to basic composting. The inclusion of anaerobic digestion promoted nutrient recovery efficiency, and enabled energy recovery through electricity production. Co-digestion of the manure with carbon-rich waste streams increased electricity production, but did not result in lower process costs. Overall, key drivers for the selection of the optimal manure treatment scenario will include the market demand for more refined (vs. separated or concentrated) products, and the need for renewable electricity production.

Capture-Ferment-Upgrade: A Three-Step Approach for the Valorization of Sewage Organics as Commodities

This critical review outlines a roadmap for the conversion of chemical oxygen demand (COD) contained in sewage to commodities based on three-steps: capture COD as sludge, ferment it to volatile fatty acids (VFA), and upgrade VFA to products. The article analyzes the state-of-the-art of this three-step approach and discusses the bottlenecks and challenges. The potential of this approach is illustrated for the European Union's 28 member states (EU-28) through Monte Carlo simulations. High-rate contact stabilization captures the highest amount of COD (66-86 g COD person equivalent^-1 day^-1 in 60% of the iterations). Combined with thermal hydrolysis, this would lead to a VFA-yield of 23-44 g COD person equivalent^-1 day^-1. Upgrading VFA generated by the EU-28 would allow, in 60% of the simulations, for a yearly production of 0.2-2.0 megatonnes of esters, 0.7-1.4 megatonnes of polyhydroxyalkanoates or 0.6-2.2 megatonnes of microbial protein substituting, respectively, 20-273%, 70-140% or 21-72% of their global counterparts (i.e., petrochemical-based esters, bioplastics or fishmeal). From these flows, we conclude that sewage has a strong potential as biorefinery feedstock, although research is needed to enhance capture, fermentation and upgrading efficiencies. These developments need to be supported by economic/environmental analyses and policies that incentivize a more sustainable management of our resources.

Measuring adaptive capacity of urban wastewater infrastructure - Change impact and change propagation

The ability of urban wastewater systems to adapt and transform as a response to change is an integral part of sustainable development. This requires technology and infrastructure that can be adapted to new operational challenges. In this study the adaptive capacity of urban wastewater systems is evaluated by assessing the interdependencies between system components. In interdependent and therefore tightly coupled systems, changes to one systems component will require alteration elsewhere in the system, therefore impairing the capacity of these systems to be changed. The aim of this paper is to develop a methodology to evaluate the adaptive capacity of urban wastewater systems by assessing how change drivers and innovation affect existing wastewater technology and infrastructure. The methodology comprises 7 steps and applies a change impact table and a design structure matrix that are completed by experts during workshops. Change impact tables quantify where change drivers, such as energy neutrality and resource recovery, require innovation in a system. The design structure matrix is a tool to quantify "emerging changes" that are a result of the innovation. The method is applied for the change driver of energy neutrality and shown for two innovations: a decentralised upflow anaerobic sludge blanket reactor followed by an anammox process and a conventional activated sludge treatment with enhanced chemical precipitation and high temperature-high pressure hydrolysis. The results show that the energy neutrality of wastewater systems can be address by either innovation in the decentralised or centralised treatment. The quantification of the emerging changes for both innovations indicates that the decentralised treatment is more disruptive, or in other words, the system needs to undergo more adaptation. It is concluded that the change impact and change propagation method can be used to characterise and quantify the technological or infrastructural transformations. In addition, it provides insight into the stakeholders affected by change.

Centralised, decentralised or hybrid sanitation systems? Economic evaluation under urban development uncertainty and phased expansion

Sanitation systems are built to be robust, that is, they are dimensioned to cope with population growth and other variability that occurs throughout their lifetime. It was recently shown that building sanitation systems in phases is more cost effective than one robust design. This phasing can take place by building small autonomous decentralised units that operate closer to the actual demand. Research has shown that variability and uncertainty in urban development does affect the cost effectiveness of this approach. Previous studies do not, however, consider the entire sanitation system from collection to treatment. The aim of this study is to assess the economic performance of three sanitation systems with different scales and systems characteristics under a variety of urban development pathways. Three systems are studied: (I) a centralised conventional activated sludge treatment, (II) a community on site source separation grey water and black water treatment and (III) a hybrid with grey water treatment at neighbourhood scale and black water treatment off site. A modelling approach is taken that combines a simulation of greenfield urban growth, a model of the wastewater collection and treatment infrastructure design properties and a model that translates design parameters into discounted asset lifetime costs. Monte Carlo simulations are used to evaluate the economic performance under uncertain development trends. Results show that the conventional system outperforms both of the other systems when total discounted lifetime costs are assessed, because it benefits from economies of scale. However, when population growth is lower than expected, the source-separated system is more cost effective, because of reduced idle capacity. The hybrid system is not competitive under any circumstance due to the costly double piping and treatment.

Assessment of nitrogen and phosphorus flows in agricultural and urban systems in a small island under limited data availability

Nitrogen (N) and phosphorus (P) are two essential macronutrients required in agricultural production. The major share of this production relies on chemical fertilizer that requires energy and relies on limited resources (P). Since these nutrients are lost to the environment, there is a need to shift from this linear urban metabolism to a circular metabolism in which N and P from domestic waste and wastewater are reused in agriculture. A first step to facilitate a transition to more circular urban N and P management is to understand the flows of these resources in a coupled urban-agricultural system. For the first time this paper presents a Substance Flow Analysis (SFA) approach for the assessment of the coupled agricultural and urban systems under limited data availability in a small island. The developed SFA approach is used to identify intervention points that can provide N and P stocks for agricultural production. The island of St. Eustatius, a small island in the Caribbean, was used as a case study. The model developed in this study consists of eight sub-systems: agricultural and natural lands, urban lands, crop production, animal production, market, household consumption, soakage pit and open-dump landfill. A total of 26 flows were identified and quantified for a period of one year (2013). The results showed that the agricultural system is a significant source for N and P loss because of erosion/run-off and leaching. Moreover, urban sanitation systems contribute to deterioration of the island's ecosystem through N and P losses from domestic waste and wastewater by leaching and atmospheric emission. Proposed interventions are the treatment of blackwater and greywater for the recovery of N and P. In conclusion, this study allows for identification of potential N and P losses and proposes mitigation measures to improve nutrient management in a small island context.

Adaptive capacity indicators to assess sustainability of urban water systems - Current application

Sustainability is commonly assessed along environmental, societal, economic and technological dimensions. A crucial aspect of sustainability is that inter-generational equality must be ensured. This requires that sustainability is attained in the here and now as well as into the future. Therefore, what is perceived as 'sustainable' changes as a function of societal opinion and technological and scientific progress. A concept that describes the ability of systems to change is adaptive capacity. Literature suggests that the ability of systems to adapt is an integral part of sustainable development. This paper demonstrates that indicators measuring adaptive capacity are underrepresented in current urban water sustainability studies. Furthermore, it is discussed under which sustainability dimensions adaptive capacity indicators are lacking and why. Of the >90 indicators analysed, only nine are adaptive capacity indicators, of which six are socio-cultural, two technological, one economical and none environmental. This infrequent use of adaptive capacity indicators in sustainability assessments led to the conclusion that the challenge of dynamic and uncertain urban water systems is, with the exception of the socio-cultural dimension, not yet sufficiently reflected in the application of urban water sustainability indicators. This raises concerns about the progress towards urban water systems that can transform as a response variation and change. Therefore, research should focus on developing methods and indicators that can define, evaluate and quantify adaptive capacity under the economic, environmental and technical dimension of sustainability. Furthermore, it should be evaluated whether sustainability frameworks that focus on the control processes of urban water systems are more suitable for measuring adaptive capacity, than the assessments along environmental, economic, socio-cultural and technological dimensions.

A new approach to nationwide sanitation planning for developing countries: Case study of Indonesia

Many developing countries struggle to provide wastewater and solid waste services. The backlog in access has been partly attributed to the absence of a functional sanitation planning framework. Various planning tools are available; however a comprehensive framework that directly links a government policy to nationwide planning is missing. Therefore, we propose a framework to facilitate the nationwide planning process for the implementation of wastewater and solid waste services. The framework requires inputs from government planners and experts in the formulation of starting points and targets. Based on a limited number of indicators (population density, urban functions) three outputs are generated. The first output is a visualization of the spatial distribution of wastewater and solid waste systems to support regional priority setting in planning and create awareness. Secondly, the total number of people served, budget requirements and distribution of systems is determined. Thirdly, the required budget is allocated to the responsible institution to assure effective implementation. The determined budgets are specified by their beneficiaries, distinguishing urban, rural, poor and non-poor households. The framework was applied for Indonesia and outputs were adopted in the National Development Plan. The required budget to reach the Indonesian government's 2019 target was determined to be 25 billion US$ over 5years. The contribution from the national budget required a more than fivefold increase compared to the current budget allocation in Indonesia, corresponding to an increase from 0.5 to 2.7 billion US$ per year. The budget for campaigning, advocacy and institutional strengthening to enable implementation was determined to be 10% of the total budget. The proposed framework is not only suitable for Indonesia, but could also be applied to any developing country that aims to increase access to wastewater and solid waste facilities.

Flexible design in water and wastewater engineering--definitions, literature and decision guide

Urban water and wastewater systems face uncertain developments including technological progress, climate change and urban development. To ensure the sustainability of these systems under dynamic conditions it has been proposed that technologies and infrastructure should be flexible, adaptive and robust. However, in literature it is often unclear what these technologies and infrastructure are. Furthermore, the terms flexible, adaptive and robust are often used interchangeably, despite important differences. In this paper we will i) define the terminology, ii) provide an overview of the status of flexible infrastructure design alternatives for water and wastewater networks and treatment, and iii) develop guidelines for the selection of flexible design alternatives. Results indicate that, with the exception of Net Present Valuation methods, there is little research available on the design and evaluation of technologies that can enable flexibility. Flexible design alternatives reviewed include robust design, phased design, modular design, modular/component platform design and design for remanufacturing. As developments in the water sector are driven by slow variables (climate change, urban development), rather than market forces, it is suggested that phased design or component platform designs are suitable for responding to change, while robust design is an option when operations face highly dynamic variability.

Unmasking health determinants and health outcomes for urban First Nations using respondent-driven sampling

OBJECTIVE

Population-based health information on urban Aboriginal populations in Canada is limited due to challenges with the identification of Aboriginal persons in existing health data sets. The main objective of the Our Health Counts (OHC) project was to work in partnership with Aboriginal stakeholders to generate a culturally relevant, representative baseline health data set for three urban Aboriginal communities in Ontario, Canada.

DESIGN

Respondent-driven sampling (RDS).

SETTING

Hamilton, Ontario, Canada.

PARTICIPANTS

The OHC study, in partnership with the De dwa da dehs ney >s Aboriginal Health Access Centre (DAHC), recruited 554 First Nations adults living in Hamilton using RDS.

RESULTS

Among First Nations adults living in Hamilton, 78% earned less than $20 000 per year and 70% lived in the lowest income quartile neighbourhoods. Mobility and crowded living conditions were also highly prevalent. Common chronic diseases included arthritis, hypertension, diabetes and chronic obstructive pulmonary disease and rates of emergency room access were elevated.

CONCLUSIONS

RDS is an effective sampling method in urban Aboriginal contexts as it builds on existing social networks and successfully identified a population-based cohort. The findings illustrate striking disparities in health determinants and health outcomes between urban First Nations individuals and the general population which have important implications for health services delivery, programming and policy development.

Genetic dissection of scent metabolic profiles in diploid rose populations

The scent of flowers is a very important trait in ornamental roses in terms of both quantity and quality. In cut roses, scented varieties are a rare exception. Although metabolic profiling has identified more than 500 scent volatiles from rose flowers so far, nothing is known about the inheritance of scent in roses. Therefore, we analysed scent volatiles and molecular markers in diploid segregating populations. We resolved the patterns of inheritance of three volatiles (nerol, neryl acetate and geranyl acetate) into single Mendelian traits, and we mapped these as single or oligogenic traits in the rose genome. Three other volatiles (geraniol, beta-citronellol and 2-phenylethanol) displayed quantitative variation in the progeny, and we mapped a total of six QTLs influencing the amounts of these volatiles onto the rose marker map. Because we included known scent related genes and newly generated ESTs for scent volatiles as markers, we were able to link scent related QTLs with putative candidate genes. Our results serve as a starting point for both more detailed analyses of complex scent biosynthetic pathways and the development of markers for marker-assisted breeding of scented rose varieties.

The influence of supply and sewerage area characteristics on water and sewerage companies responses to the Water Framework Directive

Using the example of raw water quality this paper examines the relationship between different spatial characteristics (geographical and physical properties) of Water and Sewerage Companies (WaSCs) supply and sewage areas and response to the Water Framework Directive. Results were obtained from thematic analysis and content analysis of 14 interviews with WaSCs representatives. Principal component analysis and cluster analysis of 51 WaSCs business function characteristics was employed to derive groups of similar WaSCs. Results indicate that there is difference in how WaSCs approach raw water quality issues. It appears that small WaSCs with relatively large agricultural areas in their supply catchments are more likely to seek managerial solutions to raw water quality problems.

Effect of absorbable topical hemostatic agents on the relaxation time of blood: an in vitro study with implications for postoperative magnetic resonance imaging

OBJECT

Absorbable topical hemostatic agents are commonly used in neurosurgery. In this study the authors examine the longitudinal relaxation time (T1) of blood in contact with these agents over time, measured in vitro, to determine if their presence could affect the interpretation of postoperative magnetic resonance (MR) images.

METHODS

Coagulated and anticoagulated blood were used, both oxygenated and deoxygenated. The effects of a collagen-based agent (Collastat) and a cellulose-based agent (Surgicel) on the pH and T1 values of blood and on those of saline (used as a control) were investigated. The T1 was measured as a function of magnetic field strength and time by using a field-cycling relaxometer. This instrument measures 1/T1, the rate of T1, from which the T, value is computed. The T1 values of blood were compared with those of hemostat-induced blood clots and with those of both gray and white matter of the brain. Signal changes on T1-weighted MR images were predicted on the basis of altered T, values in vitro. Postoperative images were visually examined for the predicted changes. With the addition of Surgicel, blood had decreased pH and significantly shortened T1 at all fields, essentially within minutes, although it affected the T1 of saline only minimally. The effect of Surgicel increasingly shortened the T1 for 4 days in oxygenated blood. Collastat had no significant effect. The presence of some paramagnetic methemoglobin in Surgicel-induced clots was demonstrated using the relaxometer at a time when diamagnetic oxyhemoglobin would be present in naturally occurring blood clots. A bright signal that could mimic residual tumor on contrast-enhanced images was predicted and confirmed on postoperative T1-weighted MR images obtained in patients in whom Surgicel lined the tumor bed. It was not present in cases in which Surgicel was not used.

CONCLUSIONS

Surgicel alters the appearance of early postoperative MR images. To avoid misinterpretation, clinicians should be aware of this phenomenon.

The effect of standard care, ibuprofen, and music on pain relief and patient satisfaction in adults with musculoskeletal trauma

OBJECTIVE

The purposes of this study were to determine the most effective nursing intervention to decrease pain for patients with minor musculoskeletal trauma and moderate pain at triage and to examine patient satisfaction.

METHODS

Patients were assigned to 1 of 3 intervention groups: (1) standard care (ice, elevation, and immobilization); (2) standard care and ibuprofen; or (3) standard care and music distraction. Patients were monitored for pain ratings for 60 minutes. Patients who sustained minor musculoskeletal trauma within the past 24 hours and presented with pain ratings of 4 or greater were included. Two patient satisfaction questions were asked upon discharge from the emergency department.

RESULTS

Seventy-seven patients met the inclusion criteria. No differences in pain ratings between groups were demonstrated. A statistically significant reduction in pain for all patients occurred at 30 minutes (F = 16.18, P <.01) and was maintained at 60 minutes. However, 70% of patients continued to report pain ratings of 4 or greater (on a scale of 1 to 10) at 60 minutes. The reduction in pain was not found to be clinically significant.Eighty-four percent of patients stated that they were more satisfied with their overall care in the emergency department because of the immediate attention to pain relief they received at triage. No differences in satisfaction existed between treatment groups, although patients who reported higher pain ratings expressed statistically significant lower satisfaction with pain management scores (F = 9.375, P =.003).

CONCLUSION

None of the therapies-standard care (ice, elevation, immobilization), standard care with ibuprofen, or standard care with music distraction-provided clinically significant pain relief to patients who had minor musculoskeletal trauma (ie, sprains and fractures) and moderate pain at triage. Interestingly, satisfaction scores were sometimes positive, even when pain was not relieved.

Photometric method for the quantification of chlorophylls and their derivatives in complex mixtures: fitting with Gauss-peak spectra

Accurate quantification of pigments in mixtures is essential in all cases in which separation of pigments by chromatography is impracticable for one reason or another. An example is the analysis of in vivo formation of heavy metal-substituted chlorophylls in heavy metal-stressed plants. We describe here a novel, accurate UV/VIS spectrophotometric method for the quantification of individual chlorophyll derivatives in complex mixtures, which has the potential for universal applicability for mixtures difficult to separate. The method is based on the description of each pigment spectrum by a series of Gaussian peaks. A sample spectrum is then fitted by a linear combination of these "Gauss-peak spectra" including an automatic correction of wavelength inaccuracy and baseline instability of the spectrometer as well as a correction of the widening of absorbance peaks in more concentrated pigment solutions. The automatic correction of peak shifts can also partially correct shifts caused by processes like allomerization. In this paper, we present the Gauss-peak spectra for Mg-chlorophyll a, b, c, pheophytin a, b, c, Cu-chlorophyll a, b, c, and Zn-chlorophyll a in acetone; Mg-chlorophyll a, b, pheophytin a, b, Cu-chlorophyll a, b, allomerized Cu-chlorophyll a, b, and Zn-chlorophyll a, b in cyclohexane; Mg-chlorophyll a, b, pheophytin a, b, and Cu-chlorophyll a, b in diethyl ether.

NC100150 Injection, a preparation of optimized iron oxide nanoparticles for positive-contrast MR angiography

A preparation of monocrystalline iron oxide nanoparticles with an oxidized starch coating, currently in clinical trials (NC100150 Injection; CLARISCAN), was characterized by magnetization measurements, relaxometry, and photon correlation spectroscopy. By combining the results with a measure of iron content, one can obtain the size and magnetic attributes of the iron cores, including the relevant correlation times for outer sphere relaxation (tau(SO) and tau(D)), and information about the interaction of the organic coating with both core and solvent. The results are 6.43 nm for the iron oxide core diameter, a magnetic moment of 4.38x10(-17) erg/G, and a water-penetrable coating region of oxidized oligomeric starch fragments and entrained water molecules. The latter extends the hydrodynamic diameter to 11.9 nm and lowers the average diffusivity of solvent about 64% (which increases tau(D) accordingly). The nanoparticles show little size-polydispersity, evidenced by the lowest value of r(2)/r(1) at 20 MHz reported to date, an asset for magnetic resonance angiography.

'NC100150', a preparation of iron oxide nanoparticles ideal for positive-contrast MR angiography

A laboratory-scale synthesis of NC100150 (iron oxide particles with an oxidized starch coating) was characterized by magnetization measurements (vibrating sample magnetometry, VSM), relaxometry (1/T1 NMRD profiles and 1/T2 at 10 and 20 MHz), and dynamic light scattering (photon correlation spectroscopy, PCS). The results were related to give a self-consistent physical description of the particles: a water-impenetrable part making up 12% of the total particle volume, 82% of this volume consisting of an iron oxide core and the remaining 18% consisting of an oxidized starch rind; and, a water-penetrable part making up 88% of the total particle volume, consisting of oxidized starch polymers and entrained water molecules. Relating the magnetization to the relaxometry results required that the oxidized starch coating slows the diffusivity of solvent water molecules in the vicinity of the iron oxide cores. The effect of the organic coating on water diffusivity, not previously considered in the application of relaxation theory to iron oxide nanoparticles, is supported by the much greater (factor of about 2) diameter obtained from the dynamic light scattering measurements in comparison to that obtained from the magnetization measurements. The present work shows that three physical techniques--VSM, relaxometry, and PCS--are needed for properly assessing iron oxide nanoparticles for use as contrast agents for magnetic resonance angiography (MRA). It is also shown that NC100150 has a narrow range of diameters and the smallest value of r2/r1 reported to date, an asset for MRA.

NMRD assessment of Gd-DTPA-bis(methoxyethylamide), (Gd-DTPA-BMEA), a nonionic MRI agent

RATIONALE AND OBJECTIVES

Gd-DTPA-BMEA, a nonionic bis(methoxyethylamide) derivative of Gd-DTPA, is the active ingredient of OptiMARK, now awaiting FDA approval. In this study, we compare the relaxivities of Gd-DTPA-BMEA (OptiMARK) with those of the commercially available DTPA-based agents Gd-DTPA2- (Magnevist) and Gd-DTPA-BMA (Omniscan) at different field strengths (1/T1 nuclear magnetic relaxation dispersion (NMRD) profiles). In addition, we study how changes in structural attributes of small paramagnetic chelate complexes of Gd3+ ions influence 1/T1 NMRD profiles.

METHODS

1/T1 NMRD profiles of Gd-DTPA-BMEA (OptiMARK) were measured at 5 degrees and 35 degrees C and a set of values for the parameters that describe relaxation by Gd(3+)-proton magnetic dipolar interactions was obtained. The rotational (tau R) and the diffusional (tau D) correlation times for Gd-DTPA-BMA were adjusted for the 15% greater molecular weight of Gd-DTPA-BMEA. tau M (the resident lifetime of Gd(3+)-bound water) was obtained from available 17O NMR relaxation data. For tau S0 and tau V (the low-field relaxation time of the Gd3+ moment and its correlation time), Gd-DTPA-BMA values were taken as initial values and tau S0 refined as needed.

RESULTS

Although, at 35 degrees C, tau M is comparable for the two neutral agents and an order of magnitude longer than that for Gd-DTPA2-, the 1/T1 NMRD profiles of Gd-DTPA-BMEA are indistinguishable from those of Gd-DTPA2- and Gd-DTPA-BMA. A 40% increase in the value of tau S0 from Gd-DTPA2- is required for agreement of data and theory for Gd-DTPA-BMEA.

CONCLUSIONS

Based on their 1/T1 NMRD profiles, the efficacy of the three agents should be identical in typical clinical MRI applications. The data can be fit reliably to theory, and differences in the fit parameters (and structure) have no effect on the three profiles at 35 degrees C. The relatively long values of tau M for the two neutral agents would only be of importance at low temperatures.

NMRD investigation of DyDTPA- and GdDTPA-labeled starch particles. Selection of a suitable suspension medium and influence of the starch matrix on relaxivity

RATIONALE AND OBJECTIVES

The primary aim was to investigate the influence of the starch matrix on the T1 relaxivities of starch particles labeled with gadolinium and dysprosium diethylenetriamine pentaacetic acid (GdDTPA-SP and DyDTPA-SP). Achieving this required the selection of a medium that was suitable for suspending the particles and that had field-independent T1 relaxation rates, thereby eliminating errors in relaxivity determinations resulting from a field-dependent background.

METHODS

GdDTPA-SP with low and high gadolinium content, DyDTPA-SP, and empty DTPA-SP were suspended in an aqueous medium containing 5% (w/w) of a polyethylene glycol-based block copolymer. 1/T1 NMRD profiles were obtained in the temperature range of 5 degrees to 35 degrees C.

RESULTS

Using the block copolymer, particles did not settle, and samples could be prepared at a low temperature to avoid particle degradation, the intrinsic T1 relaxation rate of the suspension medium was field-independent and identical to that of water from 25 degrees to 35 degrees C. The T1 relaxivities of DyDTPA-SP were higher than those of dysprosium diethylenetriamine pentaacetate-bis(methylamide) (DyDTPA-BMA) and decreased with increasing magnetic field strength. The T1 relaxivity of GdDTPA-SP was higher than that of GdDTPA at all fields, and decreased with decreasing temperature and increasing gadolinium content.

CONCLUSIONS

The GdDTPA-SP results showed that the particulate starch matrix served a dual role, with opposing influences on relaxivity. It provided a means for increasing the rotational correlation time (tau R), which resulted in higher relaxivities. However, it also retarded radial diffusion of water molecules within the particle interior, which significantly counteracted the enhancing effect of tau R. For DyDTPA-SP, the starch matrix provided an additional diamagnetic contribution, resulting in relaxivities higher than those of DyDTPA-BMA. The block copolymer was suitable as a suspension medium for DyDTPA-SP and GdDTPA-SP and should also be applicable for other particulates.

[Cervical factor in sterility: treatment with intravaginal estriol]

BACKGROUND

The aim of our study was to evaluate the efficacy and tolerability of vaginal estriol in treating the isolated cervical factor.

METHODS

Three different groups of patients were selected at random on the basis of the administered therapy (estriol, ethinyl-estradiol, bromhexine associated with gonadotropins). The patients (thirty in all) came to the Autonomous Sterility Department of the Niguarda Ca' Granda Hospital in Milan during the November 1994-January 1996 period. The following parameters were evaluated: cervical score according to Insler, cervical pH; in vivo penetration test (PCT) at third and sixth cycle of treatment; evaluation of the hormonal profile during the ovulatory period of estriol, estradiol, LH and progesterone at the third and sixth cycles of treatment; any possible pregnancy.

RESULTS

On the whole, 23 patients out of 30 (76.6%) had a positive in vivo penetration test. Particularly, a more favourable result was observed in the group to which vaginal estriol was administered as it presented, at treatment end, a positive PCT in 90% of cases. Moreover, always in the latter group, a greater percentage of pregnancies (40%) was observed.

CONCLUSIONS

The obtained results have demonstrated that the drug we have studied can be recommended as a valid therapy for the treatment of the isolated cervical factor of sterility.

Secretory and nonsecretory pituitary adenomas are distinguishable by 1/T1 magnetic relaxation rates at very low magnetic fields in vitro

RATIONALE AND OBJECTIVES

The authors investigated whether hormonally active and inactive pituitary adenomas can be discriminated in vitro by magnetic resonance (MR) imaging-related data.

METHODS

1/T1 nuclear magnetic relaxation dispersion profiles were measured for 39 fresh surgical specimens of secreting and nonsecreting adenomas, classified using clinical criteria or preoperative serum hormone levels. Nonsecreting adenomas were subdivided into hormone-producing and nonhormone-producing by immunostains. At five fields (0.00024 to 1.2 tesla [T]), mean 1/T1 was analyzed for statistically significant differences among these three tumor categories.

RESULTS

Mean 1/T1 was significantly higher (P < 0.02) for hormone-secreting than for nonsecreting adenomas at fields below 0.24 T; no significant difference existed at typical MR imaging fields (0.5 to 1.5 T). Mean 1/T1 for hormone-producing and nonhormone-producing, nonsecreting adenomas were not significantly different at any field.

CONCLUSIONS

Because 1/T1 at low fields is related to 1/T2 at imaging fields, it may be possible to detect hormone secretion of pituitary adenomas noninvasively by MR imaging.

Relaxation of solvent protons by solute Gd3+-chelates revisited

The magnetic field dependence (NMRD profile) of 1/T1 of solvent protons in an aqueous solution of Gd(DTPA)2- was remeasured at 5, 15, 25, 30, and 35 degrees C. The data were reanalyzed with the usual low-field theory, using recently published values for tauM, the residence lifetime of the single inner-coordinated waters of solute Gd(DTPA)2-. (These tauM values are significantly longer than earlier estimates). Values were obtained for three dynamic parameters: tauR, the rotational relaxation time of solute ions, and tauSo and tauV, the low-field relaxation time of the Gd3+ magnetic moment and the related correlation time. These Gd(DTPA)2- values, together with recent results for tauM for Gd(DTPA-BMA)--a nonionic structural analog of Gd(DTPA)2- with an unusually long tauM--were used to calculate NMRD profiles at 5 and 35 degrees C. These profiles agree very well with new data given here for a solution of Gd(DTPA-BMA). This reaffirms the importance of knowing the temperature-dependent values of tauM a priori in order to obtain unambiguous quantitative theoretical analyses of NMRD profiles of chelates of known structure. Additionally, the theory of inner sphere relaxation is extended to high fields, at which the magnetic energy of a solute moment is greater than its thermal energy.

Calcification can shorten T2, but not T1, at magnetic resonance imaging fields. Results of a relaxometry study of calcified human meningiomas

RATIONALE AND OBJECTIVES

Water content and water-proton relaxation rates are reported for fresh, histologically characterized, surgical specimens of calcified human intracranial meningiomas and compared with results for noncalcified meningiomas from an earlier study and with calcium hydroxyapatite (CaHA) suspensions to elucidate the influence of calcification on magnetic resonance imaging (MRI) signal intensity of calcified meningiomas.

METHODS

The magnetic field dependence of 1/T1 of water protons (nuclear magnetic relaxation dispersion profile) and dry weights are reported for 38 calcified nonhemorrhagic and 3 hemorrhagic specimens of known histologic subtype, a subset of the 67 specimens measured earlier. Calcification was considered mild or heavy when the dry weight was within or above the range for noncalcified meningiomas. Preliminary 1/T1 profiles for pure CaHA and a single high-field 1/T2 value also are reported.

RESULTS

The ranges of dry weights and of low-field 1/T1 values were twice as large for calcified as for noncalcified meningiomas. No correlation was found between low-field 1/T1 and either histologic subtype or dry weight. Mild calcification produced the highest low-field 1/T1 values; the most heavily calcified tumor had slightly increased low-field 1/T1. Calcium hydroxyapatite increases low-field 1/T1 significantly but not high-field 1/T1; high-field 1/T2 is large. For calcified hemorrhagic meningiomas, increases in both low-field and high-field 1/T1 were seen.

CONCLUSION

For mild calcification, MRI signal voids result from an increased high-field 1/T2; for heavier calcification, reduced proton density (from excluded water) becomes of increasing importance. Cellular CaHA appears to brighten the signal in T1-weighted MRI in the presence of hemorrhage.

Correlation of relaxometry and histopathology: the transplantable human glioblastoma SF295 grown in athymic nude mice

Human glioblastomas of the brain are characterized by a wide range of proton relaxation rates in vitro (1/T1 and 1/T2) and heterogeneous appearance in magnetic resonance imaging. It was previously found that their 1/T1 values vary widely at magnetic field strengths much below imaging fields, even at the same water content. In the present study, we measure 1/T1 at different magnetic field strengths (NMRD profile) for a specific transplantable, human glioblastoma (SF295), grown subcutaneously in athymic nude mice, to search for histologic characteristics that might correlate with the variability of 1/T1 at low fields (1/T1L). Using a field-cycling relaxometer, NMRD profiles were obtained for 32 fresh, histologically characterized, tumor specimens, 7 to 24 days post implantation of cryopreserved SF295 fragments. Tumor volume, dry weight, and pH of specimens were determined, the extent of hemorrhage and necrosis rated, and specimen location within the tumor recorded. A statistically significant increase in the average 1/T1 was found with increasing level of necrosis at 0.0024 T and below, possibly reflecting progressive protein aggregation in samples with up to 40% necrosis. This correlation was not significant at imaging fields. Although pH was increased in central necrosis, neither pH, dry weight, sample location, nor fresh hemorrhage could explain the changes in 1/T1L. The variability of 1/T1L among SF295 samples is much reduced compared to that of fresh surgical specimens of human glioblastomas of the brain. The heterogeneous appearance of glioblastomas in MRI may have a histologic correlate which reflects molecular changes involved with induction of cell death and necrosis. Further investigations may identify the factors responsible for affecting 1/T1L (hypoxia, radiation, chemotherapy).

Relaxometry of noncalcified human meningiomas. Correlation with histology and solids content

RATIONALE AND OBJECTIVES

Resected meningiomas were examined by relaxometry and light microscopy to evaluate the potential of magnetic resonance imaging (MRI) for identifying histologic subtypes and for discriminating among benign, radiation therapy-induced, and malignant meningiomas.

METHODS

The magnetic field dependence of 1/T1 of water protons (nuclear magnetic relaxation dispersion [NMRD] profile) and the water content (dry weight) were measured for 67 specimens, and the data were compared with histology. Only noncalcified, nonhemorrhagic meningiomas are reported.

RESULTS

No correlations were found between NMRD profiles, dry weight, and any histologic subtype, in contrast to an analogous study of astrocytomas. Rather, meningiomas have a broader variability of dry weight and 1/T1 than related parenchyma but a much narrower range than all grades of astrocytomas. The mean value of 1/T1, at all fields, is slightly higher in meningiomas--and the mean water content about the same--as adult cortical gray matter.

CONCLUSION

Meningiomas are frequently isointense with cortex, and histologic subtypes cannot be differentiated at any magnetic field strength by MRI using only T1- or proton density-weighted MRI.

Variation of the magnetic relaxation rate 1/T1 of water protons with magnetic field strength (NMRD profile) of untreated, non-calcified, human astrocytomas: correlation with histology and solids content

The magnetic relaxation rate 1/T1 of tissue water protons was measured over a wide range of magnetic field strengths (NMRD profile) for 92 fresh surgical specimens of astrocytomas to search for correlations of 1/T1 with tumor histology, as determined by light microscopy, and to assess the diagnostic potential of NMRD profiles for grading astrocytomas. A third goal was to elucidate the molecular determinants of 1/T1. Each specimen was histologically graded and inspected for evidence of mineral deposits (Ca, Fe); its dry weight was determined and expressed in % of original wet weight. To minimize variability not directly related to tumor grade, this initial report is limited to NMRD profiles of 47 non-calcified, non-hemorrhagic, untreated astrocytomas. For these, the mean value of 1/T1 at very low magnetic field strengths was found to increase with increasing grade of malignancy; no clear correlation could be demonstrated at high fields where most imaging is done. The spread of 1/T1 for different grades of malignancy is large, however, and the overlap significant, even at the lowest field, so that astrocytomas can not be graded by NMRD profiles alone. Average 1/T1 and average dry weight increase with grade of malignancy; but the variability of 1/T1 among specimens of the same dry weight is large, indicating that at least one other cellular parameter, not variable in normal tissue, influences 1/T1 strongly. We hypothesize that this parameter reflects changes at the molecular level in size distribution, mobility, or intermolecular interaction of cytoplasmic proteins. Which specific changes are induced by malignant transformation in astrocytomas remains to be investigated.

Nuclear magnetic relaxation dispersion profiles of aqueous solutions of a series of Gd(NOTA) analogs

Nuclear magnetic relaxation dispersion (NMRD) profiles and ESR linewidths have been measured for a series of neutral Gd(3+)-triazamacrocyclic complexes and compared with previous data for the simplest member of the macrocyclic triaza series, Gd(NOTA), and for the widely studied linear triaza complex, Gd(DTPA)2-. Water proton relaxivities and their temperature dependence were found to vary widely with the size of the triaza macrocycle and the identity of the side-chain chelating groups. The number of rapidly exchanging water molecules directly coordinated to the Gd3+ ion (q) was found to vary from 2 to 4 for eight of the ten complexes examined and a linear relationship between the 50-MHz relaxivity value and integral values of q is presented for this series of complexes. tau s values derived from ESR linewidths for some of the complexes are in reasonable agreement with those derived from their NMRD profiles; however, those complexes which either tended to form aggregates in solution or gave evidence for multiple averaged solution structures showed broad, near Lorentzian linewidths which were clearly not dominated by the electron spin relaxation time (tau s).

Intermolecular protein interactions in solutions of calf lens alpha-crystallin. Results from 1/T1 nuclear magnetic relaxation dispersion profiles

From analyses of the magnetic field dependence of 1/T1 (NMRD profiles) of water protons in solutions of calf lens alpha-crystallin at several concentrations, we find two regimes of solute behavior in both cortical and nuclear preparations. Below approximately 15% vol/vol protein concentration, the solute molecules appear as compact globular proteins of approximately 1,350 (cortical) and approximately 1,700 (nuclear) kD. At higher concentrations, the effective solute particle size increases, reversibly, as evidenced by the appearance of spectra-like 14N peaks in the NMRD profiles and a change in the field and temperature dependence of 1/T1. At these higher concentrations, the profiles are very similar to those of calf gamma II-crystallin, a crystallin that undergoes an analogous transition near approximately 15% protein (Koenig, S. H., C.F. Beaulieu, R. D. Brown III, and M. Spiller, 1990. Biophys. J. 57:461-469). By comparison with recent analyses of NMRD results for solutions of immobilized proteins as models for the transition from protein solutions to tissue (Koenig, S. H., and R. D. Brown III. 1991. Prog. NMR Spectr. 22:487-567), we argue that alpha-crystallin solute behaves as aggregates approximately greater than 50,000 kD as protein concentration is progressively increased above 15%. Finally, the concentration dependence of the NMRD profiles of alpha- and gamma II-crystallin can readily explain recent osmotic pressure data, in particular the intersection of the respective pressure curves at approximately 23% vol/vol (Vérétout, F., and A. Tardieu. 1989. Eur. Biophys. J. 17:61-68).

Permeability of liposomal membranes to water: results from the magnetic field dependence of T1 of solvent protons in suspensions of vesicles with entrapped paramagnetic ions

The diffusive permeability to water molecules, Pd, of lipid vesicles with entrapped paramagnetic solute ions can be determined rapidly from analysis of the magnetic field dependence (nuclear magnetic relaxation dispersion, or NMRD profile) of T1 of exterior solvent water protons. Such data yield tau, the mean lifetime of solvent molecules inside the vesicles, from tau = (fT1Para) - T1Ves, where f is the volume fraction of entrapped water, T1Para is the observed T1 corrected for buffer background, and T1Ves is the relaxation time of water protons in the entrapped solution. For small spherical unilamellar vesicles of inner radius R, Pd = R/3 tau, f can be obtained accurately from knowledge of both the concentration of Gd(DTPA)2- in the solution in which the vesicles were formed and the average concentration of ions in the final sample. At low temperatures, in the limit of slow exchange, T1Para becomes independent of field and tau = fT1Para; the observation of a field-independent profile is a control that confirms that no paramagnetic material is external to the vesicles. We have measured T1Para, using a field-cycling relaxometer, for suspensions of POPC (1-palmitoyl-2-oleoyl-lecithin) vesicles with 100-500 mM entrapped Gd(DTPA)2- and membrane concentrations of cholesterol ranging from 0 to 40 mol %. These profiles, which span the field range 0.01-50 MHz proton Larmor frequency, were taken at 5, 15, 25, and 35 degrees C. Concentrations of Gd(DTPA)2- were determined independently by both ICP analyses and NMRD methods. Values for Pd for vesicles with 100 mM Gd(DTPA)2- and outer diameters 100 nm +/- 20%, as determined by quasielastic light scattering, are 63, 47, 24, 16, and 8.7 x 10(-4) cm s-1, at 25 degrees C, for cholesterol concentrations of 0, 10, 20, 30, and 40%, respectively. The corresponding activation enthalpies are 14, 14, 14, 17, and 17 kcal/M. Comparison with 2H NMR studies of deuterated POPC vesicles with no cholesterol at 20 degrees C, and with 10% at 40 degrees C, which yielded the same order parameter for the palmitoyl acyl chains, gives no indication of a correlation between order parameter and permeability.

Relaxometry of brain: why white matter appears bright in MRI

The remarkable success of magnetic resonance imaging of adult brain relates to the unusually large ratio of the longitudinal relaxation rates 1/T1 of white and gray matter, approximately 2:1 at physiological temperature and traditional imaging fields. Several investigators have conjectured that myelin is the source of the greater 1/T1 of white matter without, however, suggesting details of the molecular mechanisms responsible. From measurements of the magnetic field dependence of 1/T1 (NMRD profiles) of adult and neonatal gray and white matter at 5 and 35 degrees C, we find a thermally activated contribution to the NMRD profile of adult white matter that is not present in the profiles of either adult gray or neonatal gray and white matter. We attribute this contribution to myelin and develop a quantitative model that accounts for the unique relaxation behavior of myelinated white matter. We find that myelin water, 15% of the total, has a relatively short T1 that arises from an unexpectedly large interaction with myelin lipid; when cast in terms of an interaction over the entire myelin bilipid-water interface, it is sevenfold greater than the analogous protein-water interfacial interaction. Its magnitude remains to be accounted for, but cholesterol, known to alter the relaxation rates of lipid protons, may play an important role. The contribution of myelin to 1/T1 at physiological temperatures is attributed to thermally activated transmembrane diffusion of water and, hence, more rapid mixing of axonal and the rapidly relaxing myelin water molecules.

Oligomerization and conformation change in solutions of calf lens gamma II-crystallin. Results from 1/T1 nuclear magnetic relaxation dispersion profiles

From analyses of the magnetic field dependence of 1/T1 (nuclear magnetic relaxation dispersion [NMRD] profiles) of water protons in solutions of highly purified calf lens gamma II-crystallin, we find that monomers form oligomers at relatively low concentrations, which increase in size with increasing concentration and decreasing temperature. At approximately 16% by volume and -4 degrees C, the mean oligomeric molecular weight is approximately 120-fold greater than the monomeric value of 20 kD. Below this concentration, there is no indication of any substantive change in conformation of the monomeric subunits. At higher concentrations, the tertiary structure of the monomer appears to reconfigure rather abruptly, but reversibly, as evidenced by the appearance of spectra-like 14N peaks in the NMRD profiles. The magnitudes of these peaks, known to arise from cross-relaxation of water protons through access to amide (NH) moieties of the protein backbone, indicate that the high concentration conformation is not compact, but open and extended in a manner that allows enhanced interaction with solvent. The data are analogous to those found for homogenates of calf and chicken lens (Beaulieu, C. F., J. I. Clark, R. D. Brown III, M. Spiller, and S. H. Koenig. 1988. Magn. Reson. Med. 8:47-57; Beaulieu, C. F., R. D. Brown III, J. I. Clark, M. Spiller, and S. H. Koenig. 1989. Magn. Reson. Med. 10:62-72). This unusually large dependence of oligomeric size and conformation on concentration in the physiological range is suggested as the mechanism by which osmotic equilibrium is maintained, at minimal metabolic expense, in the presence of large gradients of protein concentration in the lens in vivo (cf Vérétout and Tardieu, 1989. Eur. Biophys. J. 17:61-68). Finally, the results of the NMRD data provide a ready explanation of the low temperature phase transition, and "cold-cataract" separation of phases, observed in gamma II-crystallin solutions; we suggest that the phases that separate are the two major conformers detected by NMRD.

Relaxometry of lens homogenates. II. Temperature dependence and comparison with other proteins

We have extended our earlier work (C.F. Beaulieu, J.I. Clark, R.D. Brown III, M. Spiller, and S.H. Koenig, Magn. Reson. Med. 8, 45 (1988] on the magnetic field dependence of 1/T1 (NMRD profiles) of calf lens nuclear homogenates, at 25 degrees C, to 5 degrees C, and to other protein systems as well. These include concentrated solutions of myoglobin and bovine serum albumin, both globular proteins, the first compact and roughly spherical, the other extended, flexible, and with weak internal bonding; chicken lens homogenate, for which the dominant crystallins (lens proteins) are approximately 70% alpha-helical compared with calf crystallins, which are essentially all beta-sheet; and hen egg white, both native and heat-denatured. Our earlier conjectures regarding a reversible change in protein organization of the calf lens crystallins as a function of solute protein concentration is given added support. Our findings suggest that cytoplasmic homogenate can be characterized as a heterogeneous and polymorphic solution of crystallins. At high concentrations the NH moieties of the protein backbone become accessible to solvent with water (not NH proton) exchange rates greater than 10(4) s-1. This conclusion is based on two aspects of the observed NMRD profiles. At low crystallin concentration, the profiles of calf and chicken lens homogenates are similar in form to those of myoglobin and native hen egg white, a form that has been studied previously for a range of diamagnetic globular proteins and has been demonstrated to arise from the rotational thermal motion of the solute molecules. At high crystallin concentrations, the NMRD profiles of the lens homogenates develop a monotonic background (high rates at low fields), much like that of the heat-denatured egg-white sample and those of most tissues. In addition, there is a set of peaks in the central part of the profiles of the concentrated crystallins, seen also in the denatured egg white and some tissues but not in the myoglobin sample, which is known to arise from cross-relaxation interactions between the water protons and (through the intermediary of the NH proton) the 14N quadrupolar levels. The magnitude of these peaks, which is larger by an order of magnitude for native calf lens homogenates than for any tissue, requires that the majority of the NH moieties be accessible to water. Finally, going to 5 degrees C for the native calf lens homogenate takes the sample below the temperature of reversible phase separation, and it becomes opaque.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of polyaza macrocyclic methylene phosphonate chelates of Gd3+ ions as MRI contrast agents

Gd(DTPA)2- (diethylenetriaminepentaacetic acid) and the polyaza macrocyclic Gd(DOTA)- (1,4,7,10-tetraazacyclododecane-N,N',N'',N''') are paradigms of general purpose paramagnetic complexes useful for enhancing contrast in magnetic resonance imaging (MRI). It is of both fundamental and practical interest to determine how one might modify the chemical structure of these chelate complexes to improve their utility for MRI in specific circumstances. In the present work, we investigated polyaza methylene phosphonate complexes of Gd3+ ions to compare their NMRD profiles with those of their carboxylate analogs and with Gd(DTPA)2-. We find that the number q of exchangeable water molecules coordinated directly to the Gd3+ ions tends to be smaller in the phosphonates, in principle reducing their utility in MRI. However, these phosphonates have a tendency to oligomerize, and the resulting decrease in rotational mobility of the paramagnetic oligomers increases their relaxivity at higher fields, offsetting the effect of decreases in q. In particular, Gd(DOTRP)3- (1,5,9-triazacyclododecane-N,N',N'',-tris(methylenephosphonic++ + acid] would be an increasingly effective contrast agent above approximately 10 MHz if the oligomerization was stable in vivo (and the Gd3+ ions were sufficiently well bound). At lower fields, the relaxivity of these small chelate complexes is dominated by tau S0, the relaxation time of the spin moments of the paramagnetic ions. We find this to be favorably long for complexes of Gd3+ with the macrocyclic phosphonate ligands, as was found earlier by us for Gd(DOTA)-. This situation, ostensibly related to the relatively high symmetry and rigidity of the macrocyclic complexes, can increase the low-field relaxivity of the phosphonates almost a factor of 2 beyond that of Gd(DTPA)2-.

Longitudinal proton relaxation rates in rabbit tissues after intravenous injection of free and chelated Mn2+

The factors that determine the field-dependent increase in 1/T1 of tissue water protons were investigated for MnCl2 and Mn2+ (PDTA) (1,3-propylenediamine-N,N',N'',N'''-tetraacetic acid) introduced intravenously into rabbits. Mn2+ was used in preference to other paramagnetic ions in part because of the distinct NMRD profiles (magnetic field dependence of 1/T1) of free Mn2+ ions, their small chelate complexes, and their macromolecular conjugates, and in part because the relatively low toxicity of Mn2+ is favorable for animal studies. Tissue content of Mn2+ was determined in all samples by inductively coupled plasma analyses the state of Mn2+ in excised tissues was determined from the form of the 1/T1 NMRD profile of water protons; and distribution of contrast agent within tissue and access of water on a T1 time scale were determined by double-exponential analyses of proton relaxation behavior in intact doped tissue, as well as by the change of single-exponential relaxation rates and proton signal intensity upon gentle disruption of the tissue. MnCl2 is found in all tissues, except fat and skeletal muscle, but liver is most avid at low dose, and Mn2+ accumulates in spleen after high doses. Chelation targets Mn2+ to liver and kidney, saturating the liver chemically at relatively low dose. We suggest that pronounced increase in tissue relaxivity results from irrotationally bound Mn2+, ostensibly associated with the polar head groups of cell membranes. Compartmentalization of contrast agent and restricted diffusion of tissue water influences the maximum relaxation rates attainable, so that there is an optimal dose of these contrast agents which is rather low.

Duodenal duplication in the adult: its relationship with pancreatitis

Seven cases of duodenal duplication in the adult are reported. The ultrasound and computed tomographic findings are analyzed. The relationship between duodenal duplication and pancreatitis is discussed.

Number of inner-sphere water molecules in Gd3+ and Eu3+ complexes of DTPA-amide and -ester conjugates

The inner-sphere water coordination number for Eu3+ and Gd3+ complexed with five DTPA analogs, in which one or two terminal carboxylate groups are functionalized as propyl amides or propyl esters, have been studied using phosphorescence lifetime and nuclear magnetic relaxation dispersion (NMRD) measurements. Both methods show that the water coordination number does not increase above that observed for the analogous DTPA complexes. The phosphorescence lifetime results indicate that all five Eu3+ complexes have one inner-sphere water molecule at 25 degrees C. The NMRD profiles for three of the Gd3+ complexes at 25 degrees C are also consistent with one inner-sphere water molecule, whereas two complexes have profiles consistent only with a mixture of complexes, 50% containing a single water molecule and 50% with none. Lowering the temperature alters the population of these species such that all five Gd3+ complexes have significantly less bound water on average at 5 degrees C. These results explain the anomalous temperature dependencies of the NMRD curves reported previously for the Gd(DTPA)-protein conjugates. We suggest that the Gd(DTPA)-conjugate systems have a fluxional coordination sphere whereby the amount of inner-sphere coordinated water varies from near zero at 5 degrees C to a high of two near 37 degrees C.

Relaxometry of calf lens homogenates, including cross-relaxation by crystallin NH groups

We studied the magnetic field dependence of the longitudinal relaxation rates of water protons (1/T1 nuclear magnetic relaxation dispersion (NMRD) profiles) in transparent homogenates of calf lens. The samples included nuclear homogenates with total (heterogeneous) crystallin contents between 34% (v/v) (native) and 14% (diluted) as well as cortical homogenate, 21% (native) and 34% (concentrated). The NMRD profiles had two components: a monotonic dispersive component (analogous to that of both globular protein solutions and diamagnetic tissue) and "14N quadrupolar peaks." 14N peaks have never been reported for protein solutions, only for tissues and dehydrated proteins. These peaks occur between 0.5 and 5 MHz proton Larmor frequency and arise from interactions of solvent water protons with NH moieties of proteins. The 14N peaks in lens cytoplasm are very large and may correlate with the crystallin structure and interactions required to maintain short-range order and lens transparency. The monotonic and 14N quadrupolar components were largest in concentrated samples, but with different concentration dependencies. The dispersive components of samples above approximately 19% protein concentration had a fixed functional form, the amplitude of which varied with protein volume fraction, f, by the multiplicative factor f/(1 - f), suggesting spatial organization and dynamics of the solute proteins that are relatively independent of water content. In contrast, at concentrations less than 19%, the NMRD profiles are concentration dependent, indicating a dependence of the orientational relaxation time of the proteins on protein-protein interactions seen previously in other globular proteins at these concentrations. The 14N peaks are not resolved below approximately 19% protein and increase linearly with incremental volume fraction at protein concentrations above 19%. In addition, the 14N peaks in nuclear homogenates are 50-100% larger than those of cortical homogenates at the same concentrations. Partial substitution of solvent D2O for H2O decreases the peak heights, indicating that an exchangeable proton mediates the interaction between solvent protons and protein 14N nuclei.