Human Reference Values Research Articles

A Pragmatic Framework for the Application of New Approach Methodologies in One Health Toxicological Risk Assessment.

Globally, industries and regulatory authorities are faced with an urgent need to assess the potential adverse effects of chemicals more efficiently by embracing new approach methodologies (NAMs). NAMs include cell and tissue methods (in vitro), structure-based/toxicokinetic models (in silico), methods that assess toxicant interactions with biological macromolecules (in chemico), and alternative models. Increasing knowledge on chemical toxicokinetics (what the body does with chemicals) and toxicodynamics (what the chemicals do with the body) obtained from in silico and in vitro systems continues to provide opportunities for modernizing chemical risk assessments. However, directly leveraging in vitro and in silico data for derivation of human health-based reference values has not received regulatory acceptance due to uncertainties in extrapolating NAM results to human populations, including metabolism, complex biological pathways, multiple exposures, interindividual susceptibility and vulnerable populations. The objective of this article is to provide a standardized pragmatic framework that applies integrated approaches with a focus on quantitative in vitro to in vivo extrapolation (QIVIVE) to extrapolate in vitro cellular exposures to human equivalent doses from which human reference values can be derived. The proposed framework intends to systematically account for the complexities in extrapolation and data interpretation to support sound human health safety decisions in diverse industrial sectors (food systems, cosmetics, industrial chemicals, pharmaceuticals etc.). Case studies of chemical entities, using new and existing data, are presented to demonstrate the utility of the proposed framework while highlighting potential sources of human population bias and uncertainty, and the importance of Good Method and Reporting Practices.

Indoor air chemistry: Terpene reaction products and airway effects.

Reactive chemistry is ubiquitous indoors with a wealth of complex oxidation reactions; some of these are initiated by both homogeneous and heterogeneous reaction of ozone with unsaturated organic compounds and subsequent the hydroxyl radical, either in the gas-phase or on reactive surfaces. One major focus has been the reaction of common and abundant terpene-based fragrances in indoor air emitted from many wood-based materials, a variety of consumer products, and citrus fruits and flowers. Inhalation of the terpenes themselves are generally not considered a health concern (both acute and long-term) due to their low indoor air concentrations; however, their gas- and surface reactions with ozone and the hydroxyl radical produce a host of products, both gaseous, i. a. formaldehyde, and ultrafine particles formed by condensation/nucleation processes. These reaction products may be of health concern. Human cell bioassays with key reaction products from ozone-initiated terpene reactions have shown some inflammatory reactions, but results are difficult to interpret for human exposure and risk assessment. Acute effects like sensory irritation in eyes and airways are unlikely or present at very low intensity in real life conditions based on rodent and human exposure studies and known thresholds for sensory irritation in eyes and airways and derived human reference values for airflow limitation and pulmonary irritation. Some fragrances and their ozone-initiated reaction products may possess anti-inflammatory properties. However, long-term effects of the reaction products as ultrafine particles are poorly explored. Material and product surfaces with high ozone deposition velocities may significantly impact the perceived air quality by altered emissions from both homogeneous and heterogeneous surface reactions.

Hemodynamic evaluation of anesthetized baboons and piglets by transpulmonary thermodilution: Normal values and interspecies differences with respect to xenotransplantation.

Transpulmonary thermodilution is well established as a tool for in-depth hemodynamic monitoring of critically ill patients during surgical procedures and intensive care. It permits easy assessment of graft function following cardiac transplantation and guides post-operative volume and catecholamine therapy. Since no pulmonary catheter is needed, transpulmonary thermodilution could be useful in experimental cardiac pig-to-baboon xenotransplantation. However, normal values for healthy animals have not yet been reported. Here, we present data from piglets and baboons before xenotransplantation experiments and highlight differences between the two species and human reference values. Transpulmonary thermodilution from baboons (body weight 10-34kg) and piglets (body weight 10-38kg) were analyzed. Measurements were taken in steady state after induction of general anesthesia before surgical procedures commenced. Cardiac index (CI), mean arterial pressure (MAP), systemic vascular resistance index (SVRI), parameters quantifying cardiac filling (global end-diastolic volume index, GEDI), and pulmonary edema (extravascular lung water, ELWI) were assessed. Preload, afterload, and contractility parameters clearly correlated with total body weight or body surface area. Baboons had lower CI values than weight-matched piglets (4.2±0.9l/min/m2 vs 5.3±1.0/min/m2 , P<.01). MAP and SVRI were higher in baboons than piglets (MAP: 99±22mmHg vs 62±11mmHg, P<.01; SVRI: 1823±581dyn*s/cm5 *m2 vs 827±204dyn*s/cm5 *m2 , P<.01). GEDI and ELWI did differ significantly between both species, but measurements were within similar ranges (GEDI: 523±103mL/m2 vs 433±78mL/m2 , P<.01; ELWI: 10±3mL/kg vs 11±2mL/kg, P<.01). Regarding adult human reference values, CI was similar to both baboons and piglets, but all other parameters were different. Parameters of preload, afterload, and contractility differ between baboons and piglets. In particular, baboons have a much higher afterload than piglets, which might be instrumental in causing perioperative xenograft dysfunction and post-operative myocardial hypertrophy after orthotopic pig-to-baboon cardiac xenotransplantation. Most transpulmonary thermodilution-derived parameters obtained from healthy piglets and baboons lie outside the reference ranges for humans, so human normal values should not be used to guide treatment in those animals. Our data provide reference values as a basis for developing algorithms for perioperative hemodynamic management in pig-to-baboon cardiac xenotransplantation.

Transesophageal Echocardiography in Swine: Establishment of a Baseline

The porcine model is a commonly used animal model in cardiovascular research. Along with new innovative operative techniques, choice of the optimal imaging technique is crucial. Transesophageal echocardiography (TEE) is a reliable imaging tool is highly important in a large number of experimental evaluations. But so far, TEE data for swine are limited, and few standard values have been established for the porcine model. The experience and baseline results for TEE in 45 swine are presented in this study. A full TEE examination was conducted in 45 German landrace or German large white swine, with an average body weight of 49 ± 3 kg, before experimental off-pump mitral valved stent implantation. Additionally hemodynamic measurements were evaluated. The valve implantation procedure was guided solely by real-time 3-D TEE. Baseline values of standard echocardiographic parameters are provided and, where appropriate, compared with human reference values. TEE proved to be an adequate imaging technique in this experimental porcine animal model. The baseline TEE and hemodynamic parameters established for the widely used porcine model can serve as a reference in future studies.

Tympanometric measurements in conscious sheep - a diagnostic tool for pre-clinical middle ear implant studies

Objective: To investigate and establish the use of tympanometry in conscious sheep to provide a means of objective assessment of tympanic membrane integrity, middle ear ventilation and functioning of the Eustachian tube (ET). Design: After conditioning the sheep for four weeks, tympanometric measurements at 226 Hz were carried out weekly for 13 weeks. Before measurements, the external ear canal had been cleaned. Resultant curves were classified according to human reference values. Study Sample: Tests were performed on 12 female blackface sheep. Results: After cleaning of the external ear canal under otoscopic control, tympanic membranes were intact with no evidence of acute or chronic middle ear inflammation, middle ear effusion or retraction. Cleaning ensured valid, objective and reproducible measurements. As the majority of normal tympanograms were notched without the appearance of any malformation, an additional tympanogram type (AN) was introduced. The notched appearance can most likely be explained by the anatomy of the middle ear of the sheep and the test frequency that was used. Conclusion: The current study demonstrated how tympanometry can be used to evaluate treatment modalities for middle ear and ET function in conscious sheep. This provided a large animal model for further human research in otology.

A mechanistic study of limonene oxidation products and pathways following cleaning activities

Indoor air pollution has caused increasing concern since the 1970s, when the advent of stricter energy efficiency measures lead to increased reports of building related symptoms. Cleaning activities have been linked to adverse health effects indoors, although it is unclear which of the components of cleaning products cause these reported health effects. This paper uses a detailed chemical model for indoor air chemistry, to identify the species formed at the highest concentrations following use of a limonene-based cleaning product. The explicit nature of the chemical mechanism also permits the key pathways to their formation to be identified. The results show that the key species in terms of gas-phase concentration are multi-functional carbonyl species including limonaldehyde, 4-acetyl-1-methyl-1-cyclohexene and other dicarbonyl species. The particle-phase was dominated by peroxide species. The predicted gas-phase concentrations for three limonene-oxidation products were compared to recently published human reference values, but found not to be high enough to cause concern for typical indoor conditions, or under high indoor ozone conditions. However, cleaning products contain a range of terpenes other than limonene, which could also produce some of the secondary products identified here, as well as more common species such as formaldehyde, glyoxal and hydrogen peroxide. A mechanistic pathway analysis shows that the secondary products formed through limonene oxidation indoors depend critically on the competition between ozone and hydroxyl radicals, such that indoor pollutant concentrations and composition could vary widely in different locations for a nominally similar residence and indoor activities. Future studies should focus on aiming to measure multi-functional carbonyl species indoors to help validate models, whilst human reference values are needed for many more relevant species indoors.

Human reference values for acute airway effects of five common ozone-initiated terpene reaction products in indoor air

Ozone-initiated monoterpene reaction products have been hypothesized to cause eye and airway complaints in office environments and some have been proposed to cause skin irritation and sensitization. The respiratory effects of 60min exposures to five common oxidation products from abundant terpenoids (e.g. limonene), used as solvent and fragrance in common household products or present in skin lipids (e.g. squalene), were studied in a head out mouse bioassay. This allowed determination of acute upper airway (sensory) irritation, airflow limitation in the conducting airways, and pulmonary irritation in the alveolar region. Derived human reference values (RFs) for sensory irritation were 1.3, 0.16 and 0.3ppm, respectively, for 4-acetyl-1-methylcyclohexene (4-AMCH), 3-isopropenyl-6-oxo-heptanal (IPOH), and 6-methyl-5-heptene-2-one (6-MHO). Derived RFs for airflow limitation were 0.8, 0.45, 0.03, and 0.5ppm, respectively, for dihydrocarvone (DHC), 4-AMCH, 4-oxo-pentanal (4-OPA), and 6-MHO. Pulmonary irritation was unobserved as a critical effect. The RFs indicate that the oxidation products would not contribute substantially to sensory irritation in eyes and upper airways in office environments. Reported concentrations in offices of 6-MHO and 4-OPA would not result in airflow limitation. However, based upon the RFs for IPOH and 4-OPA, precautionary actions should be considered that disfavor their formation in excess.

Ovine Blood

Ovine animal models are widely used to conduct preclinical studies, e.g., to evaluate cardiovascular prostheses intended to be applied in man. However, although analyzed in many of those studies, information about ovine blood reference values is scanty. The aim of this study is to establish a reference list of ovine blood parameters relevant for blood coagulation. A cohort of 47 mature ewes was evaluated. Parameters comprised the following: cells and cellular components-platelet, red, and white cell counts (including subsets), hemoglobin (Hb), hematocrit (HCT), mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV), and MCH concentration (MCHC); global tests of coagulation-prothrombin time (Quick's time) and activated partial thromboplastin time (aPTT); and parameters relevant for blood coagulation-fibrinogen, antithrombin (AT), and von Willebrand Factor. After explorative data analysis, a list of ovine reference values was established. Interestingly, a comparison with human reference values revealed some interspecies differences between sheep and man, i.e., much higher ovine ranges for some cell counts (neutrophils, lymphocytes, basophils, eosinophils, and platelets) but lower values for some other parameters (Hb, HCT, MCV, MCH, AT, and Quick's test). We established a reference list of ovine blood count and blood coagulation parameters. Because of some peculiarities of the ovine blood, this list may have implications for the interpretation of experimental data.

Reference values of biochemical and hematological parameters for Guizhou minipigs

The pig is not only an economically important livestock animal but is also a valuable model animal for biomedical research and xenotransplantation. Reference values for clinical biochemical and hematological parameters are required for accurate data interpretation while using a pig model. In this study, whole blood samples were collected from 54 healthy Chinese Guizhou minipigs. We analyzed routine biochemical and hematological parameters and special coagulation parameters, including thrombelastography and coagulation factor activities, and have presented the baseline values of these parameters. These data provide valuable information for investigators using minipigs as animal models in biomedical studies and useful physiological data for veterinarians and livestock producers. We also compared all the results for the minipigs with the corresponding data from healthy humans. The bilirubin, uric acid and cholesterol levels of minipigs were significantly lower than those of humans (14%, 0.086% and 48% of human levels, respectively), whereas the serum enzyme levels were much higher than those in humans (e.g. the hydroxybutyrate dehydrogenase and creatine kinase levels of the minipigs were 19- and 8.4-fold higher than the human reference values). The red blood cell counts, platelet counts and white blood cell counts of the minipigs were significantly higher than those of the humans. The coagulation activities of factor VII and factor X were higher in minipigs than in humans. The significant differences observed between minipigs and humans for many of these parameters suggest substantial interspecies disparities in organs and tissues. These differences merit greater attention in biomedical research involving minipigs, particularly in the area of pig-to-human transplantation.

Haemostatic parameters in the camel (Camelus Dromedarius) comparison with humans

Haemostatic measurements were undertaken in 46 camels (Camelus dromedarius) and the results were compared to human reference values. The effects of sex, age and pregnancy on camel haemostatic parameters were studied. There was significant shortening of the prothrombin time and activated partial thromboplastin time and marked elevation of factor VIII clotting activity (FVIII:C), FVII and FIX in camels as compared to humans. On the other hand, FX, fibrinogen and packed cell volume levels were lower in camels than humans. These results indicate a more active state of the coagulation system in camels as compared to humans and this might be a physiological adaption that protects this animal from excessive blood or fluid loss under the conditions of drought and transhumance.

Analysis of Hematologic Findings in Healthy and Sick Adult Chimpanzees (Pan troglodytes)

In order to assess the validity of interspecies extrapolation of hematological information, reference values obtained on 63 captive adult chimpanzees were compared with normal values for man. The discriminative power of both chimpanzee and human reference values was tested by the ability of each to identify abnormalities in the blood in 15 sick chimpanzees. The results indicated that human criteria could be applied to most chimpanzee red cell values but species differences were found in erythrocyte sedimentation rates and neutrophil counts.