Concentrations In Body Fluids Research Articles

Assessing Acid-Base Status: Physiologic Versus Physicochemical Approach

The physiologic approach has long been used in assessing acid-base status. This approach considers acids as hydrogen ion donors and bases as hydrogen ion acceptors and the acid-base status of the organism as reflecting the interaction of net hydrogen ion balance with body buffers. In the physiologic approach, the carbonic acid/bicarbonate buffer pair is used for assessing acid-base status and blood pH is determined by carbonic acid (ie, Paco2) and serum bicarbonate levels. More recently, the physicochemical approach was introduced, which has gained popularity, particularly among intensivists and anesthesiologists. This approach posits that the acid-base status of body fluids is determined by changes in the dissociation of water that are driven by the interplay of 3 independent variables: the sum of strong (fully dissociated) cation concentrations minus the sum of strong anion concentrations (strong ion difference); the total concentration of weak acids; and Paco2. These 3 independent variables mechanistically determine both hydrogen ion concentration and bicarbonate concentration of body fluids, which are considered as dependent variables. Our experience indicates that the average practitioner is familiar with only one of these approaches and knows very little, if any, about the other approach. In the present Acid-Base and Electrolyte Teaching Case, we attempt to bridge this knowledge gap by contrasting the physiologic and physicochemical approaches to assessing acid-base status. We first outline the essential features, advantages, and limitations of each of the 2 approaches and then apply each approach to the same patient presentation. We conclude with our view about the optimal approach.

Growth Hormone Concentrations in Different Body Fluids Before and After Moderate Exercise.

BackgroundGrowth hormone (GH) has many direct and indirect actions and roles including substrate regulation and priming of some cells of the immune system, and the expected aspects of growth and repair. Different concentrations in human body fluids reflect the exercise-induced growth hormone response (EIGR) after exercise. In populations such as elite athletes, the invasive nature of venous sampling is poorly accepted. Thus, this study examines possible viable alternatives such as urine and saliva samples and the GH concentration.MethodsA heterogeneous group of 11 males (age 26.0 ± 5.0 years; body mass 76.5 ± 9.3 kg; VO2peak 57.0 ± 6.0 mL kg−1 min−1) ran for 40 min on a treadmill at 5 % below their individually indentified lactate threshold pace. Samples of urine, saliva and blood were collected immediately pre- and post-test and at 30 and 60 min post-test.ResultsSalivary GH was correlated with serum pre- and post-exercise (p < 0.001); urinary GH was correlated with serum (p < 0.05). However, despite being significantly correlated, it is clear from the large differences in absolute concentration in the three media that the appearance of serum GH due to exercise is different from that of the appearance of salivary and urinary GH. This aspect of compartmental exchanges is very difficult to define and to investigate. Differences in any analyte concentration in different compartments are to be expected between different media, and hence the same medium should be used where the same ‘pattern of response’ can be tracked.ConclusionsThe results suggest that urinary and saliva sampling cannot substitute for venous sampling with respect to exercise-induced changes in GH concentration. The use of the analyses in these three areas may be appropriate for further investigation.

Hybrid materials for bone tissue engineering from biomimetic growth of hydroxiapatite on cellulose nanowhiskers

Cellulose nanowhiskers (CNWs) with different surface composition were used to generate the biomimetic growth hydroxyapatite (HAp). Hybrids materials primarily consist of CNWs with HAp content below 24%. CNWs were produced by different inorganic acid hydrolyses to generate cellulose particles with surface groups to induce HAp mineralization. In the present study, we evaluate the use of CNWs prepared from hydrochloric acid, sulfuric acid and phosphoric acid. HAp growth was obtained from the biomimetic method using a simulated body fluid concentration of 1.5M (SBF). The sulfonate and phosphonate groups on the CNW surface have a direct impact on the nucleation and growth of HAp. HAp/CNW were also compared with the physical mixture method using HAp nanoparticles prepared by chemical precipitation. The bioactivity and biocompatibility of the hybrid materials were assessed by cell viability studies using fibroblast cells (L929). The materials obtained from the biomimetic method have superior biocompatibility/bioactivity compared to the material synthesized by the wet chemical precipitation method with an incubation period of 24h.

Neurofilament Light: A Dynamic Cross-Disease Fluid Biomarker for Neurodegeneration

In the current issue of Neuron, Bacioglu, Maia, and colleagues show that neurofilament light concentrations inbody fluids reflect pathology and symptoms in mouse models of cerebral proteopathies and that these findings translate to human disease (Bacioglu etal., 2016).

Non-invasive screening for neuroendocrine tumors—Biogenic amines as neoplasm biomarkers and the potential improvement of “gold standards”

Early, noninvasive diagnosis of tumors is relevant, especially for rare, often asymptomatic, thus − hard to detect in curable stages of the disease – tumors, as neuroendocrine tumors (NET). To avoid or supplement the NET management via application of invasive biopsy or expensive imagining techniques, the biochemical evaluation of biomarkers from easy accessible body fluids could be the great, potential diagnostic or prognostic tool. Nevertheless, already existed biochemical diagnostic tools for NET must be improved. Biogenic amines’ (BA) determination in biological samples is significant for the description of the most NET, such as pheochromocytoma, neuroblastoma or carcinoid tumor. The bioanalytical approaches applied for the analysis of BA concentration in patient's body fluids still are required to be improved. It is caused by the low BA levels in real samples, their distinct physiochemical properties, light sensitiveness and easy degradation in the presence of oxygen, among others. Moreover, the interpretation of single analyte result is not clinically sufficient recently and more precise biomarkers or – more ideally – panels of several biomarkers are considered to be simultaneously measured and analyzed. Therefore, the NET-management “gold standards” can be routinely modified. Accordingly, presented review will focus on the recent status of BA analysis treated as the potential biomarker in terms of analytical method development applied for the real patients’ samples analysis. Furthermore, the main advantages of current dominance of panel of biomarkers analysis for the NET patients diagnosis, follow up and monitoring of the therapy, will be underlined.

The association of serum trans-nonachlor levels with atherosclerosis

ABSTRACTRecent epidemiological studies suggest a strong association between exposure to environmental contaminants, including organochlorine (OC) insecticides or their metabolites, and development of pathologies, such as atherosclerosis, in which oxidative stress plays a significant etiological role. Biomarkers of systemic oxidative stress have the potential to link production of reactive oxygen species (ROS), which are formed as a result of exposure to xenobiotic toxicants, and underlying pathophysiological states. Measurement of F2-isoprostane concentrations in body fluids is the most accurate and sensitive method currently available for assessing in vivo steady-state oxidative stress levels. In the current study, urinary concentrations of F2-isoprostanes and serum levels of persistent OC compounds p,p’-dichlorodiphenyldichloroethene (DDE), trans-nonachlor (a component of the technical chlordane mixture), and oxychlordane (a chlordane metabolite) were quantified in a cross-sectional study sample and the association of these factors with a clinical diagnosis of atherosclerosis determined. Urinary isoprostane levels were not associated with atherosclerosis or serum concentrations of OC compounds in this study sample. However, occurrence of atherosclerosis was found to be associated with serum trans-nonachlor levels. DDE and oxychlordane were not associated with atherosclerosis. This finding supports current evidence that exposure to environmental factors is a risk factor for atherosclerosis, in addition to other known risk factors.

Comparative study of inorganic elements determined in whole blood from Dmdmdx/J mice strain by EDXRF and NAA analytical techniques

Several diseases can be diagnosed observing the variation of specific elements concentration in body fluids. In this study the concentration of inorganic elements in blood samples of dystrophic (Dmdmdx/J) and C57BL/6J (control group) mice strain were determined. The results obtained from Energy Dispersive X-ray Fluorescence (EDXRF) were compared with Neutron Activation Analysis (NAA) technique. Both analytical techniques showed to be appropriate and complementary offering a new contribution for veterinary medicine as well as detailed knowledge of this pathology.

Comment on "Use of Carnosine for Oxidative Stress Reduction in Different Pathologies".

I congratulate Prokopieva et al. for their review “Use of Carnosine for Oxidative Stress Reduction in Different Pathologies” [1]. The authors overview properties and biological effects of the antioxidant carnosine (Cn). Data on the use of Cn in various conditions are discussed. Special attention is given to the use of carnosine in neurologic, mental diseases and alcoholism. I have read the paper with a great interest. However, a comment seems to be necessary to formulate a praxis-relevant and evidence-based conclusion.

Molecularly Imprinted Polymer-carbon Nanotube based Cotinine Sensor

A cotinine sensor based on the dc resistance of a polymer composite films is presented. The composite film comprises a cotinine selective molecularly imprinted polymer and carbon nanotube particles. This polymer film is deposited over a gold interdigitated electrode array to measure its electrical resistance. The electrical resistance of the imprinted polymer changes upon its selective binding to the cotinine molecule. The electrical resistance increases with the increase in cotinine concentration, for the addition of 1000 ng/ml cotinine the resistance increases by ca. 190 kΩ. As a control experiment the response of un-imprinted polymer is also tested, which does not show any dependence on the cotinine concentration. Cotinine concentration in body fluid reflects the extent of tobacco smoking. This sensor has a potential to be used to detect active and passive smoking levels.

2H23 灰化ウシ骨担体材料の生体吸収性に及ぼす灰化温度の影響

Calcined bone is attractive as scaffold material for tissue-engineered bones in biocompatibility and low manufacturing cost. However, its bioabsorbability is still unknown. The objective of this study is to investigate the effects of calcination temperature on the bioabsorbability of calcined bone. Bovine compact bones were calcined at 600 ℃ or 900 ℃ for 22 hours and immersed in the simulated body fluid (Ringer lactate solution) at 37 ℃. The bioabsorbability of calcined bone were evaluated by measuring calcium concentration in the simulated body fluid during incubation time up to 3 days. As a result, either calcined bone at 600 ℃ or 900 ℃ decreased calcium concentrations in the fluid. This tendency was more remarkable in the samples at 600 ℃. The result suggests that calcined bone is osteoconductive rather than bioabsorbable.

Complexity of vitamin E metabolism.

Bioavailability of vitamin E is influenced by several factors, most are highlighted in this review. While gender, age and genetic constitution influence vitamin E bioavailability but cannot be modified, life-style and intake of vitamin E can be. Numerous factors must be taken into account however, i.e., when vitamin E is orally administrated, the food matrix may contain competing nutrients. The complex metabolic processes comprise intestinal absorption, vascular transport, hepatic sorting by intracellular binding proteins, such as the significant α-tocopherol-transfer protein, and hepatic metabolism. The coordinated changes involved in the hepatic metabolism of vitamin E provide an effective physiological pathway to protect tissues against the excessive accumulation of, in particular, non-α-tocopherol forms. Metabolism of vitamin E begins with one cycle of CYP4F2/CYP3A4-dependent ω-hydroxylation followed by five cycles of subsequent β-oxidation, and forms the water-soluble end-product carboxyethylhydroxychroman. All known hepatic metabolites can be conjugated and are excreted, depending on the length of their side-chain, either via urine or feces. The physiological handling of vitamin E underlies kinetics which vary between the different vitamin E forms. Here, saturation of the side-chain and also substitution of the chromanol ring system are important. Most of the metabolic reactions and processes that are involved with vitamin E are also shared by other fat soluble vitamins. Influencing interactions with other nutrients such as vitamin K or pharmaceuticals are also covered by this review. All these processes modulate the formation of vitamin E metabolites and their concentrations in tissues and body fluids. Differences in metabolism might be responsible for the discrepancies that have been observed in studies performed in vivo and in vitro using vitamin E as a supplement or nutrient. To evaluate individual vitamin E status, the analytical procedures used for detecting and quantifying vitamin E and its metabolites are crucial. The latest methods in analytics are presented.

Magnesium as a diagnostic marker of cancer

Magnesium plays a key role in many essential cellular processes. It is recognized that magnesium deficiency may lead to many disorders like cardiovascular disease, diabetes mellitus, hypertension, myocardial infarction or even cancer. Connection between magnesium concentration in body fluids and cancer occurrence still becomes unclear. Magnesium ions are crucial cofactors for enzymes involved DNA repairing. Thereby magnesium deficiency may result in genomic instability and consequently cause cancer. The aim of our study was to investigate if serum magnesium concentration may be useful biomarker for early detection of prostate and laryngeal cancer and also if serum Mg concentration may be marker of selection for CT of the lung, laryngeal examination, PSA levels or prostate biopsy. Independently we have investigated a prospective study where our aim was to investigate if the serum Mg concentration is a marker of increased breast cancer risk. We performed retrospective investigation in laryngeal cancer patients (n = 123) and prostate cancer groups (n = 166). Each group was compared with healthy controls group, which consists of equal to cases amount of controls. Controls and cases were matched by age, gender, negative supplementation status, negative status of hormonal contraceptives and smoking status. In the prospective study (sera collected before cancer diagnosis) Mg concentration was determined in BRCA (-) women and compared to controls. Mg serum levels ( 20800 µg/l) are associated with 2-fold higher occurrence of laryngeal cancers. Magnesium serum level is not a useful marker for selection of the patients for prostate cancer screening. Finally, magnesium concentration may be a marker for breast cancer risk in BRCA (-) patients but further investigation is needed.

Aquaporins Mediate Silicon Transport in Humans.

In animals, silicon is an abundant and differentially distributed trace element that is believed to play important biological functions. One would thus expect silicon concentrations in body fluids to be regulated by silicon transporters at the surface of many cell types. Curiously, however, and even though they exist in plants and algae, no such transporters have been identified to date in vertebrates. Here, we show for the first time that the human aquaglyceroporins, i.e., AQP3, AQP7, AQP9 and AQP10 can act as silicon transporters in both Xenopus laevis oocytes and HEK-293 cells. In particular, heterologously expressed AQP7, AQP9 and AQP10 are all able to induce robust, saturable, phloretin-sensitive silicon transport activity in the range that was observed for low silicon rice 1 (lsi1), a silicon transporter in plant. Furthermore, we show that the aquaglyceroporins appear as relevant silicon permeation pathways in both mice and humans based on 1) the kinetics of substrate transport, 2) their presence in tissues where silicon is presumed to play key roles and 3) their transcriptional responses to changes in dietary silicon. Taken together, our data provide new evidence that silicon is a potentially important biological element in animals and that its body distribution is regulated. They should open up original areas of investigations aimed at deciphering the true physiological role of silicon in vertebrates.

An empirical method to determine inadequacy of dietary water

ObjectivesThe physiological regulation of total body water and fluid concentrations is complex and dynamic. The human daily water requirement varies because of differences in body size, dietary solute load, exercise, and activities. Although chronically concentrated urine increases the risk of renal diseases, an empirical method to determine inadequate daily water consumption has not been described for any demographic group; instead, statistical analyses are applied to estimate nutritional guidelines (i.e., adequate intake). This investigation describes a novel empirical method to determine the 24-h total fluid intake (TFI; TFI = water + beverages + moisture in food) and 24-h urine volume, which correspond to inadequate 24-h water intake (defined as urine osmolality of 800 mOsm/kg; U800). MethodsHealthy young women (mean ± standard deviation; age, 20 ± 2 y, mass, 60.8 ± 11.7 kg; n = 28) were observed for 7 consecutive days. A 24-h urine sample was analyzed for volume and osmolality. Diet records were analyzed to determine 24-h TFI. ResultsFor these 28 healthy young women, the U800 corresponded to a TFI ≥2.4 L/d (≥39 mL/kg/d) and a urine volume ≥1.3 L/d. ConclusionsThe U800 method could be employed to empirically determine 24-h TFI and 24-h urine volumes that correspond to inadequate water intake in diverse demographic groups, residents of specific geographic regions, and individuals who consume specialized diets or experience large daily water turnover. Because laboratory expertise and instrumentation are required, this technique provides greatest value in research and clinical settings.

Dependence of ion concentration in simulated body fluid on apatite precipitation on titania surface

Titanium and its alloys are used as biomaterials, because of their high biocompatibility. Apatite precipitates on a titania surface in vivo, and living bone and titanium alloy are coupled through the thin apatite layer. The initial precipitation behavior of apatite on titania in simulated body fluid (SBF) solutions was evaluated and the effect of inorganic ions in the SBF was investigated. Measurement using the SPR phenomenon was used to evaluate the initial apatite precipitation. An SBF containing approximately equal ion concentrations to those in blood plasma was added to a titania surface and the SPR profile was obtained, from which the initial apatite precipitation rate was found to be 1.14nm/h. Furthermore, the relationship between the inorganic concentration and the precipitation rate was determined for SBFs with different Na+ and Ca2+ concentrations. Apatite precipitation did not occur in the SBF with a low Na+ concentration, whereas the initial apatite precipitation rate in the SBF that did not contain Ca2+ was 0.32nm/h. According to these results, Ca2+ has little effect on the initial apatite precipitation. In the initial reaction of apatite precipitation, sodium titanate is formed by the absorption of Na+. Next, calcium titanate precipitates upon the substitution of Na+ with Ca2+. Finally, Na+, phosphate ions and hydroxyl ions are attracted to the surface and apatite is formed. Thus, the rate-limiting factor in the initial nucleation of apatite is the Na+ concentration.

Chemiluminescent detection of tear glucose on paper microfluidic devices

WHO Global Info Base declared that the number of people with diabetes in 2008 was 347 million that was doubled from 153 million in 1980. With rising obesity in global, concern has risen about prevalence of diabetes. Global estimates of mortality from diabetes will be dramatically increased in 2030. In fact, diabetes is one of important causes of mortality from cardiovascular and kidney diseases. Regarding vision power, severe ophthalmic complication such as cataract or retinopathy could be drawn from diabetes. These complications could lead to lose sight permanently. Therefore, early diagnosis and ongoing management is essential to ensure a healthy life for patients and avoid other diseases, such as blood circulation problems, kidney failure, heart disease, vision disease due to diabetes. The current methods of diabetes management rely on monitoring the glucose levels in the blood. The patients need to collect the blood drops at least four times a day and thousands times a year in invasive way to determine the glucose levels. In addition, There has been many reports of warning the invasive glucose sensor caused blood-related infections. Also, frequent invasive glucose measurements could result in the inadequate glycemic concentration as well as increased risk of hypoglycemia. Therefore, the development of glucose monitoring system with easy to use, convenient, cheap, and also non-invasive method is essential to self-monitor the glucose level and improve the quality of life of patients who require frequent glucose measurements. Approach for measuring the glucose concentration in body fluids, including alternative to urine, saliva and tears have tremendous potential for non-invasive diagnosis and management of diabetes. In comparison with other fluids, tear fluids are more easily accessible than blood and other interstitial fluids and have the benefits with consistent supply. The tear fluid is less sensitive in dilution than urine fluid. Previous studies applied a microfluidic technology to paper and measured glucose concentration in a non-invasive method using tears. Noh et al. quantified the colorimetric changes in glucose concentration using Photoshop’s grayscale program to unify the color changes in the limited sunlight when taking indoor illuminance. However, it is not easy to generalize the illuminance applicable to all situations. In the power usage statistics of 200 countries surveyed by the US Central Intelligence Agency (CIA) showed that in more than 100 countries around the world more than 1000 kW/year was consumed. On the other hand, where the 30 countries less than 0.1 kW/year was consumed. Turning on the 30 W bulb about 9 h per day for one year costs a power of about 100 kW. In 30 countries out of 200 countries, minimum power consumption is impossible. To those situated in such harsh conditions, it is difficult to measure the glycemic concentration using conventional paper based glucose sensors. Also, there are possibilities of the worst power outage by a sudden increase in power consumption even in the power supply sufficient country. For special situations such as in war training or in war, glucose measurements by conventional methods that require constant power supply are not easy. The purpose of this study was to investigate the chemiluminescent measurement of tear glucose and to attain quantitative tendencies of tear glucose without the need to be replaced by the specific gray-scale technique and no particular brightness conditions in order to be applied to all countries including the specific situations. This study sought to quantify the glucose concentration by using light-emitting reaction of luminol followed by the glucose oxidation. This study was to present the possibility of clinical application to measure glucose non-invasively with tears.

Colorimetric nanoplasmonic assay to determine purity and titrate extracellular vesicles.

Extracellular Vesicles (EVs) - cell secreted vesicles that carry rich molecular information of the parental cell and constitute an important mode of intercellular communication - are becoming a primary topic in translational medicine. EVs (that comprise exosomes and microvesicles/microparticles) have a size ranging from 40 nm to 1 μm and share several physicochemical proprieties, including size, density, surface charge, and light interaction, with other nano-objects present in body fluids, such as single and aggregated proteins. This makes separation, titration, and characterization of EVs challenging and time-consuming. Here we present a cost-effective and fast colorimetric assay for probing by eye protein contaminants and determine the concentration of EV preparations, which exploits the synergy between colloidal gold nanoplasmonics, nanoparticle-protein corona, and nanoparticle-membrane interaction. The assay hits a limit of detection of protein contaminants of 5 ng/μL and has a dynamic range of EV concentration ranging from 35 fM to 35 pM, which matches the typical range of EV concentration in body fluids. This work provides the first example of the exploitation of the nanoparticle-protein corona in analytical chemistry.

Pharmacokinetics and distribution of voriconazole in body fluids of dogs after repeated oral dosing.

The goal of this project was to determine the pharmacokinetics of voriconazole and its concentration in cerebrospinal fluid (CSF), aqueous humor, and synovial fluid in five healthy dogs following once daily oral dose of 6 mg/kg for 2 weeks. Body fluid and plasma drug concentrations were determined by high-performance liquid chromatography (HPLC). Mild to moderate gastrointestinal adverse effects were seen. The mean AUC0-24 : minimum inhibitory concentration (MIC) ratio was 15.23 for a chosen MIC of 1 μg/mL, which is lower than the recommended target of 20-25 and also lower than previously reported in dogs, perhaps reflecting induction of metabolizing enzymes by multiple dosing. Voriconazole concentrations in the CSF, aqueous humor, and synovial fluid were only 13-30% the concurrent plasma concentration, which is lower than previously reported in other species. Results of this study suggest that twice daily, administration may be necessary to maintain therapeutic plasma concentrations in dogs but further studies are warranted.

Influence of Machine-Derived Smoke Yields on Biomarker of Exposure (BOE) Levels in Cigarette Smokers*

AbstractIndividual uptake of tobacco smoke constituents by smoking is highly variable in cigarette smokers and cannot be predicted by smoking behaviour variables and machine-derived smoke yields. It is well established that uptake of smoke constituents is best described by a series of bio-markers of exposure (BOEs) such as metabolites of nico-tine, tobacco-specific nitrosamines (TSNAs), polycyclic aromatic hydrocarbons (PAHs), aromatic amines, benzene, 1,3-butadiene, acrolein, hydrogen cyanide, 2,5-dimethyl-furan and other smoke constituents.The purpose of this review is to investigate the relationship between BOE levels and machine-derived smoking yields on the basis of published data. The influence of other smoking behaviour variables, in particular the number of cigarettes smoked per day (CPD) and smoking topography (puffing and inhalation patterns) is also considered, pro-vided suitable data are available.Twenty eight (28) published studies, which report data on machine-derived smoke yields and biomarker concentrations in body fluids of smokers of these products were identified. In total, 33 different BOEs were applied in these studies. Important properties of the BOEs used in the further evaluation were described and discussed. In almost all studies selected, data for CPD were reported. In only a few studies, puffing and inhalation profiles have been determined so that no systematic evaluation of the association between smoking topography and BOE levels was possible. In the studies evaluated, no statistically significant association between daily cigarette consumption (CPD) and smoke yields was observed. This clearly indicates that low machine-derived yields were not com-pensated by increasing the daily cigarette consumption. As expected, positive and statistically significant relationships were found between CPD and BOE levels for most of the biomarkers investigated.Bi- and multivariate linear regressions were calculated for the relationships between BOE levels (dependent variable) and machine-derived yields as well as CPD (independent variables). Whenever possible, results from various studies were combined (this was only possible, when identical biomarkers and yield types were available). Aggregation of the results from all studies independent of BOE and yield type used is feasible on the basis of relative BOE and yield levels. The multivariate linear regression models obtained reveal that both CPD and machine-derived yields are significant predictors of the measured BOE levels. The models predict that, on average, a 50% reduction in CPD or yield are accompanied by a 33 or 15% reduction, respectively, in smoke uptake, as measured by various BOEs. Taken together, the evaluated data from the literature show that lower machine-derived yields lead to a reduced uptake of smoke constituents. The reduction is statistically significant, but substantially lower than the decrease in machine-derived yields. [Beitr. Tabakforsch. Int. 26 (2014) 138-175]

Quantitative assessment of prion infectivity in tissues and body fluids by real-time quaking-induced conversion.

Prions are amyloid-forming proteins that cause transmissible spongiform encephalopathies through a process involving the templated conversion of the normal cellular prion protein (PrP(C)) to a pathogenic misfolded conformation. Templated conversion has been modelled in several in vitro assays, including serial protein misfolding amplification, amyloid seeding and real-time quaking-induced conversion (RT-QuIC). As RT-QuIC measures formation of amyloid fibrils in real-time, it can be used to estimate the rate of seeded conversion. Here, we used samples from deer infected with chronic wasting disease (CWD) in RT-QuIC to show that serial dilution of prion seed was linearly related to the rate of amyloid formation over a range of 10(-3) to 10(-8) µg. We then used an amyloid formation rate standard curve derived from a bioassayed reference sample (CWD+ brain homogenate) to estimate the prion seed concentration and infectivity in tissues, body fluids and excreta. Using these methods, we estimated that urine and saliva from CWD-infected deer both contained 1-5 LD50 per 10 ml. Thus, over the 1-2 year course of an infection, a substantial environmental reservoir of CWD prion contamination accumulates.