Abyssal hydrothermal springs-Cryptic incubators for brooding octopus.

Does warmth from hydrothermal springs play a vital role in the biology and ecology of abyssal animals? Deep off central California, thousands of octopus (Muusoctopus robustus) migrate through cold dark waters to hydrothermal springs near an extinct volcano to mate, nest, and die, forming the largest known aggregation of octopus on Earth. Warmth from the springs plays a key role by raising metabolic rates, speeding embryonic development, and presumably increasing reproductive success; we show that brood times for females are ~1.8 years, far faster than expected for abyssal octopods. Using a high-resolution subsea mapping system, we created landscape-scale maps and image mosaics that reveal 6000 octopus in a 2.5-ha area. Because octopuses die after reproducing, hydrothermal springs indirectly provide a food supplement to the local energy budget. Although localized deep-sea heat sources may be essential to octopuses and other warm-tolerant species, most of these unique and often cryptic habitats remain undiscovered and unexplored.

Phenology in the deep sea: seasonal and tidal feeding rhythms in a keystone octocoral.

Biological rhythms are widely known in terrestrial and marine systems, where the behaviour or function of organisms may be tuned to environmental variation over periods from minutes to seasons or longer. Although well characterized in coastal environments, phenology remains poorly understood in the deep sea. Here we characterized intra-annual dynamics of feeding activity for the deep-sea octocoral Paragorgia arborea. Hourly changes in polyp activity were quantified using a time-lapse camera deployed for a year on Sur Ridge (1230 m depth; Northeast Pacific). The relationship between feeding and environmental variables, including surface primary production, temperature, acoustic backscatter, current speed and direction, was evaluated. Feeding activity was highly seasonal, with a dormancy period identified between January and early April, reflecting seasonal changes in food availability as suggested by primary production and acoustic backscatter data. Moreover, feeding varied with tides, which likely affected food delivery through cyclic oscillation in current speed and direction. This study provides the first evidence of behavioural rhythms in a coral species at depth greater than 1 km. Information on the feeding biology of this cosmopolitan deep-sea octocoral will contribute to a better understanding of how future environmental change may affect deep-sea coral communities and the ecosystem services they provide.

Optimized design of windowed-sinc anti-aliasing filters for phase-preserving decimation of hydrophone data.

Passive acoustic monitoring generates large data sets for which decimation is beneficial to analysis and portability for data sharing. Among the goals for effective decimation are avoidance of aliasing in the passband, accurate and complete control of the attenuation profile, phase preservation, and high efficiency in processing. We present an approach to decimator design that addresses each of these goals, and we demonstrate its application to ocean audio recordings. Anti-aliasing is achieved by windowed-sinc filters that also preserve phase. Control of the passband attenuation profile is based on the specification of the maximum allowed attenuation at a certain percentage of the final output Nyquist frequency. The window type is selected to meet the stopband attenuation requirement. Efficiency is achieved through optimization of the anti-aliasing filters applied in each decimation stage, and through parallelization of processing. The best combination of the sinc function's cutoff frequency and the mainlobe bandwidth of the window function generates the shortest qualifying filter, optimizing the trade-off between filter performance and computational load. Parallelization is enabled by applying the overlap-add method to contiguous segments of audio data, consistent with the commonly used storage of contiguous audio data in files of limited duration. Beyond addressing common goals for effective decimation of audio data, the approach presented is deployable in open-source environments.

Evaluation of a Three-Dimensional Primary Human Hepatocyte Spheroid Model: Adoption and Industrialization for the Enhanced Detection of Drug-Induced Liver Injury.

Drug-induced liver injury is a leading cause of compound attrition during both preclinical and clinical drug development, and early strategies are in place to tackle this recurring problem. Human-relevant in vitro models that are more predictive of hepatotoxicity hazard identification, and that could be employed earlier in the drug discovery process, would improve the quality of drug candidate selection and help reduce attrition. We present an evaluation of four human hepatocyte in vitro models of increasing culture complexity (i.e., two-dimensional (2D) HepG2 monolayers, hepatocyte sandwich cultures, three-dimensional (3D) hepatocyte spheroids, and precision-cut liver slices), using the same tool compounds, viability end points, and culture time points. Having established the improved prediction potential of the 3D hepatocyte spheroid model, we describe implementing this model into an industrial screening setting, where the challenge was matching the complexity of the culture system with the scale and throughput required. Following further qualification and miniaturization into a 384-well, high-throughput screening format, data was generated on 199 compounds. This clearly demonstrated the ability to capture a greater number of severe hepatotoxins versus the current routine 2D HepG2 monolayer assay while continuing to flag no false-positive compounds. The industrialization and miniaturization of the 3D hepatocyte spheroid complex in vitro model demonstrates a significant step toward reducing drug attrition and improving the quality and safety of drugs, while retaining the flexibility for future improvements, and has replaced the routine use of the 2D HepG2 monolayer assay at GlaxoSmithKline.

Human-relevant near-organ neuromodulation of the immune system via the splenic nerve.

Neuromodulation of immune function by stimulating the autonomic connections to the spleen has been demonstrated in rodent models. Consequently, neuroimmune modulation has been proposed as a new therapeutic strategy for the treatment of inflammatory conditions. However, demonstration of the translation of these immunomodulatory mechanisms in anatomically and physiologically relevant models is still lacking. Additionally, translational models are required to identify stimulation parameters that can be transferred to clinical applications of bioelectronic medicines. Here, we performed neuroanatomical and functional comparison of the mouse, rat, pig, and human splenic nerve using in vivo and ex vivo preparations. The pig was identified as a more suitable model of the human splenic innervation. Using functional electrophysiology, we developed a clinically relevant marker of splenic nerve engagement through stimulation-dependent reversible reduction in local blood flow. Translation of immunomodulatory mechanisms were then assessed using pig splenocytes and two models of acute inflammation in anesthetized pigs. The pig splenic nerve was shown to locally release noradrenaline upon stimulation, which was able to modulate cytokine production by pig splenocytes. Splenic nerve stimulation was found to promote cardiovascular protection as well as cytokine modulation in a high- and a low-dose lipopolysaccharide model, respectively. Importantly, splenic nerve-induced cytokine modulation was reproduced by stimulating the efferent trunk of the cervical vagus nerve. This work demonstrates that immune responses can be modulated by stimulation of spleen-targeted autonomic nerves in translational species and identifies splenic nerve stimulation parameters and biomarkers that are directly applicable to humans due to anatomical and electrophysiological similarities.

Morphologic, cytochemical, and ultrastructural features of gray eosinophils in nine cats.

BACKGROUND: Gray eosinophils, resembling those in sighthound dog breeds, have not previously been reported in cats. OBJECTIVES: We aimed to provide a morphologic, cytochemical, and ultrastructural description of gray eosinophils in cats. METHODS: Blood films examined as part of routine hematology profiles in cats from May 2015 to July 2018 were evaluated for the presence of gray eosinophils. When identified with modified Wright stain, cells were morphologically assessed and additionally stained with Diff-Quik, ALP, Luna, and Luxol fast blue stains and compared with feline controls. Two cases were prepared for transmission electron microscopy (TEM) and compared with a feline control. RESULTS: Gray eosinophils were identified in 9 of 2641 cats during the study period. Compared with typical feline eosinophils, these cells contained abundant round granules instead of the characteristic rod-shaped specific granules. These granules lacked the characteristic intense pink/red staining with Romanowsky stains and did not stain with ALP, Luna, or Luxol fast blue stains. On TEM, the classical electron-dense core of these granules was replaced by a core with fragmented or amorphous internal material. Typical eosinophils were not identified in any cat in which gray eosinophils were identified. CONCLUSIONS: The distinct morphologic, cytochemical, and ultrastructural changes in gray feline eosinophils might be associated with a reduction or lack of major basic protein (MBP) in specific granule cores. Similar to canine gray eosinophils, accurate recognition of these cells is essential to prevent their misclassification as toxic neutrophils.

Quantification of clinically applicable stimulation parameters for precision near-organ neuromodulation of human splenic nerves.

Neuromodulation is a new therapeutic pathway to treat inflammatory conditions by modulating the electrical signalling pattern of the autonomic connections to the spleen. However, targeting this sub-division of the nervous system presents specific challenges in translating nerve stimulation parameters. Firstly, autonomic nerves are typically embedded non-uniformly among visceral and connective tissues with complex interfacing requirements. Secondly, these nerves contain axons with populations of varying phenotypes leading to complexities for axon engagement and activation. Thirdly, clinical translational of methodologies attained using preclinical animal models are limited due to heterogeneity of the intra- and inter-species comparative anatomy and physiology. Here we demonstrate how this can be accomplished by the use of in silico modelling of target anatomy, and validation of these estimations through ex vivo human tissue electrophysiology studies. Neuroelectrical models are developed to address the challenges in translation of parameters, which provides strong input criteria for device design and dose selection prior to a first-in-human trial.

Sponge Behavior and the Chemical Basis of Responses: A Post-Genomic View.

Sponges perceive and respond to a range of stimuli. How they do this is still difficult to pin down despite now having transcriptomes and genomes of an array of species. Here we evaluate the current understanding of sponge behavior and present new observations on sponge activity in situ. We also explore biosynthesis pathways available to sponges from data in genomes/transcriptomes of sponges and other non-bilaterians with a focus on exploring the role of chemical signaling pathways mediating sponge behavior and how such chemical signal pathways may have evolved. Sponge larvae respond to light but opsins are not used, nor is there a common photoreceptor molecule or mechanism used across sponge groups. Other cues are gravity and chemicals. In situ recordings of behavior show that both shallow and deep-water sponges move a lot over minutes and hours, and correlation of behavior with temperature, pressure, oxygen, and water movement suggests that at least one sponge responds to changes in atmospheric pressure. The sensors for these cues as far as we know are individual cells and, except in the case of electrical signaling in Hexactinellida, these most likely act as independent effectors, generating a whole-body reaction by the global reach of the stimulus to all parts of the animal. We found no evidence for use of conventional neurotransmitters such as serotonin and dopamine. Intriguingly, some chemicals synthesized by symbiont microbes could mean other more complex signaling occurs, but how that interplay might happen is not understood. Our review suggests chemical signaling pathways found in sponges do not reflect loss of a more complex set.

Proteomic analysis of filaggrin deficiency identifies molecular signatures characteristic of atopic eczema.

BACKGROUND: Atopic eczema (AE) is characterized by skin barrier and immune dysfunction. Null mutations in filaggrin (FLG), a key epidermal barrier protein, strongly predispose to AE; however, the precise role of FLG deficiency in AE pathogenesis remains incompletely understood. OBJECTIVES: We sought to identify global proteomic changes downstream of FLG deficiency in human epidermal living skin-equivalent (LSE) models and validate findings in skin of patients with AE. METHODS: Differentially expressed proteins from paired control (nontargeting control short hairpin RNA [shNT]) and FLG knockdown (FLG knockdown short hairpin RNA [shFLG]) LSEs were identified by means of proteomic analysis (liquid chromatography-mass spectrometry) and Ingenuity Pathway Analysis. Expression of key targets was validated in independent LSE samples (quantitative RT-PCR and Western blotting) and in normal and AE skin biopsy specimens (immunofluorescence). RESULTS: Proteomic analysis identified 17 (P ≤ .05) differentially expressed proteins after FLG knockdown, including kallikrein-7 (KLK7; 2.2-fold), cyclophilin A (PPIA; 0.9-fold), and cofilin-1 (CFL1, 1.3-fold). Differential protein expression was confirmed in shNT/shFLG LSEs; however, only KLK7 was transcriptionally dysregulated. Molecular pathways overrepresented after FLG knockdown included inflammation, protease activity, cell structure, and stress. Furthermore, KLK7 (1.8-fold) and PPIA (0.65-fold) proteins were differentially expressed in lesional biopsy specimens from patients with AE relative to normal skin. CONCLUSIONS: For the first time, we show that loss of FLG in the absence of inflammation is sufficient to alter the expression level of proteins relevant to the pathogenesis of AE. These include proteins regulating inflammatory, proteolytic, and cytoskeletal functions. We identify PPIA as a novel protein with levels that are decreased in clinically active AE skin and show that the characteristic upregulation of KLK7 expression in patients with AE occurs downstream of FLG loss. Importantly, we highlight disconnect between the epidermal proteome and transcriptome, emphasizing the utility of global proteomic studies.

Spondyloarthritis in sub-Saharan Africa.

Spondyloarthritis (SpA) is generally uncommon in sub-Saharan Africa, in part because of the rarity of HLA-B27 in this region. However, the relationship between HLA-B27 and SpA, particularly ankylosing spondylitis (AS), is complex. Despite the HLA-B 27:05 risk allele occurring in some West African populations, associated AS is not seen. In fact, most patients with AS are HLA-B27-negative, although there is emerging evidence that another class I HLA molecule, HLA-B 14:03, is associated with AS in black Africans. The Assessment of SpondyloArthritis International Society criteria for detecting early axial disease are of limited value in sub-Saharan Africa, because of both the rarity of HLA-B27 and very limited access to magnetic resonance imaging. Reactive arthritis (ReA), psoriatic arthritis, and undifferentiated SpA are seen mainly in the context of HIV infection, although the exact effect of the virus in the pathogenesis of arthritis is unclear. In Zambia, ReA is associated with the HLA-B*57:03 allele, which is paradoxically also associated with slow progression of HIV infection. HIV-associated ReA has a more protracted and aggressive course than standard ReA. Enthesitis-related arthritis is more common in children infected with HIV by vertical mother-to child transmission. Use of TNF inhibitors for axial disease is problematic, mainly because of cost, but also because of potential safety problems, especially reactivation of tuberculosis.

Progress made towards enhancement of rheumatology education and practice in Zambia: review of an ILAR-supported project.

The burden of non-communicable diseases such as musculoskeletal diseases in the developing world is often overshadowed by the more prevalent infectious diseases. Generally, there is gross underestimation of the burden of rheumatologic disease in the backdrop of scanty or indeed non-existent rheumatology services in these countries. Local studies conducted in the last two decades in Zambia have documented the increasing burden of rheumatologic conditions in the country. There are unfortunately negligible rheumatology services in the country both at tertiary or primary health-care facility levels. There is thus an urgent need to build capacity for these services so as to improve the care and management of rheumatic conditions. Here, we review progress made by an International League of Associations for Rheumatology (ILAR)-supported project that has run for the past 2 years (2012-2013) with the objective of enhancing paediatric and adult rheumatology education and practice so as to stimulate positive change in practice and related care services in Zambia. During this short time of the project, substantial progress has been made in the areas of paediatric and adult rheumatology services enhancement at the University Teaching Hospital, Lusaka: streamlining of referrals and follow-ups of rheumatology patients, laying foundations for short- and long-term medical education in rheumatology and raising public awareness of rheumatic diseases. The progress made by this grant underscores the suitability of the ILAR mission statement "think global, act local" demonstrating that even with minimum resources and networking, improvement of rheumatology care in developing countries is attainable.

Clinical patterns of juvenile idiopathic arthritis in Zambia.

BACKGROUND: Juvenile idiopathic arthritis (JIA) is a heterogeneous group of disorders with different disease manifestations among various populations. There are few reports of JIA among indigenous Africans especially sub-Saharan Africa. We present herein the clinical patterns of JIA encountered at a tertiary hospital in Lusaka, Zambia. METHOD: Hospital records of patients with a diagnosis of chronic arthritis with onset at the age of 16 years or less presenting to University Teaching Hospital, Lusaka, Zambia for the periods 1994-98 and 2006-2010 were retrospectively reviewed and reclassified as Juvenile Idiopathic Arthritis (JIA) based on the International League of Associations for Rheumatology (ILA R) JIA diagnostic criteria. RESULTS: In total, 126 patients with chronic arthritis of onset at age 16 years or less were evaluated over these periods at the hospital. Of these, 85 could further be analyzed by ILAR JIA criteria but 7 (8.24%) were HIV seropositive and were assessed separately. The average age at disease onset among the 78 JIA patients was 8.70 years (range: 1-15 years) with average age at first visit to hospital being 11.3 years (range: 2 to 25 years) and with a female to male ratio of 1.2:1. Polyarticular rheumatoid factor negative JIA, at 34.62%, was the most frequent type of chronic arthritis encountered. Oligoarthritis was found in 32.05% while 11.54% and 14.10% were polyarticular rheumatoid factor positive and systemic JIA, respectively. Enthesitis-related arthritis was found in 6.41% and only 1.28% were determined to have psoriatic arthritis among this population. CONCLUSION: JIA is predominantly a polyarticular rheumatoid factor negative disease in Zambia. Late presentation is an issue with major implications for educational input and resource acquisition. There is need to elucidate the genetics and environmental factors of JIA in this region.

Hyalinization of the pyloric stomach in CD-1 mice following oral (dietary) administration of the corticosteroid agonists mometasone furoate, budesonide, and flunisolide.

The purpose of this study was to compare the toxicity of three marketed corticosteroid receptor agonists (mometasone furoate, budesonide, or flunisolide) to the stomach of female CD-1 mice following oral administration via the diet for up to 52 weeks, with a 16-week recovery period (budesonide and flunisolide). A range of tissues was examined by light microscopy, accompanied by clinical pathology measurements to assess anticipated corticosteroid effects as a surrogate marker of systemic drug exposure. Microscopic changes seen in the stomach with each corticosteroid included pyloric hyalinization. This previously unreported finding was investigated using histochemical and immunohistochemical techniques and was found to consist of hyalinized collagen, in association with increased immunohistochemical signal for transglutaminase-2 and osteopontin. The significance of the osteopontin finding is unclear; however, the ability of transglutaminase-2 to facilitate the formation of degradation resistant protein bonds implies this protein may be involved in the pathogenesis of this change. Furthermore, published evidence that transglutaminase-2 may be induced by a corticosteroid agonist raises the possibility that pyloric stomach hyalinization may be a class effect of corticosteroids via the action of this enzyme.

Time course characterization of serum cardiac troponins, heart fatty acid-binding protein, and morphologic findings with isoproterenol-induced myocardial injury in the rat.

We investigated the kinetics of circulating biomarker elevation, specifically correlated with morphology in acute myocardial injury. Male Hanover Wistar rats underwent biomarker and morphologic cardiac evaluation at 0.5 to seventy-two hours after a single subcutaneous isoproterenol administration (100 or 4000 microg/kg). Dose-dependent elevations of serum cardiac troponins I and T (cTnI, cTnT), and heart fatty acid-binding protein (H-FABP) occurred from 0.5 hour, peaked at two to three hours, and declined to baseline by twelve hours (H-FABP) or forty-eight to seventy-two hours (Serum cTns). They were more sensitive in detecting cardiomyocyte damage than other serum biomarkers. The Access 2 platform, an automated chemiluminescence analyzer (Beckman Coulter), showed the greatest cTnI fold-changes and low range sensitivity. Myocardial injury was detected morphologically from 0.5 hour, correlating well with loss of cTnI immunoreactivity and serum biomarker elevation at early time points. Ultrastructurally, there was no evidence of cardiomyocyte death at 0.5 hour. After three hours, a clear temporal disconnect occurred: lesion scores increased with declining cTnI, cTnT, and H-FABP values. Serum cTns are sensitive and specific markers for detecting acute/active cardiomyocyte injury in this rat model. Heart fatty acid-binding protein is a good early marker but is less sensitive and nonspecific. Release of these biomarkers begins early in myocardial injury, prior to necrosis. Assessment of cTn merits increased consideration for routine screening of acute/ongoing cardiomyocyte injury in rat toxicity studies.

Comparison of peri-prosthetic bone density in cemented and uncemented total knee arthroplasty.

The aim of our study was to assess the effect of knee replacement with or without bone cement on periprosthetic bone density. Periprosthetic bone density in two comparable groups (30 each) of cemented and uncemented knee replacements was measured with DEXA scanner. Bone loss was more in the area posterior to the anterior femoral flange in the cemented subgroup, nearing statistical significance (p = 0.059). In both groups, the reported bone density at a median of four years postoperatively was reduced at several periprosthetic sites. However, the method of fixation could not be clearly demonstrated to influence the bone loss differentially. This brings into question the use of the more expensive cementless implants. Reduction in bone density in both groups at several periprosthetic sites remains a concern. Whether or not this can be addressed with medical intervention like post arthroplasty bisphosphonate treatment needs further consideration.

Soft tissue rheumatic lesions and HIV infection in Zambians.

OBJECTIVE: To explore the relationship between human immunodeficiency virus (HIV) infection and soft tissue rheumatic lesions in HIV-positive black Zambians. METHODS: We performed a prospective study of all patients over 18 years of age attending a rheumatic clinic in a teaching hospital. All patients underwent routine blood tests, and radiographs were performed when indicated. HIV status was determined by ELISA, and clinical staging was determined by World Health Organization criteria. Patients with isolated sacroiliac pain, enthesitis, or a soft tissue lesion were selected for analysis. For HIV-positive patients, only those in clinical stage 1 (asymptomatic or persistent generalized lymphadenopathy) were selected. RESULTS: Our study cohort comprised 120 patients (41 men, 79 women, age 23-70 yrs). Diagnosis and number (% HIV positive) were distributed as follows: sacroiliitis, 14 (100%); heel pain, 14 (100%); costochondritis, 3 (100%); polyenthesitis (> or = 4 sites), 20 (100%); carpal tunnel syndrome, 8 (63%); rotator cuff syndrome, 18 (30%); tendinitis, 8 (25%); sciatica/cervical spondylosis, 12 (16%); sacroiliac strain, 7 (0%); and de Quervain's tenosynovitis, 16 (0%). HIV seroprevalence was 54% overall, 74% in those under 45 years of age, and 17% in those over 45 years of age. Population prevalence of HIV in Lusaka is about 30% in the 30-40-year age range. Mean erythrocyte sedimentation rate (ESR) in 65 patients positive for HIV was 80 mm/h and in 55 patients negative for HIV, 18 mm/h. Within each subgroup the mean ESR was significantly higher in HIV-positive patients. CONCLUSION: A young age and a raised ESR are both good indications of HIV infection in Zambian patients with soft tissue lesions. Enthesitis is a distinct HIV-related phenomenon, either an early form or a forme fruste of HIV-related spondyloarthropathy.

Human immunodeficiency virus related reactive arthritis in Zambia.

OBJECTIVE: To characterize the clinical, radiological, and diagnostic features of reactive arthritis (ReA) in indigenous Black Zambians with human immunodeficiency virus (HIV) infection. METHODS: Consecutive patients attending an arthritis clinic over a 5-year period were studied prospectively. Those who satisfied diagnostic criteria for ReA were analyzed. RESULTS: In total, 170 patients satisfied the ESSG criteria for ReA; 71 (45 men, 26 women) had one or more extraarticular manifestations; 30% had enteroreactive and 14% uroreactive disease. Only 59% of patients had the diagnostic features of ReA at presentation. The initial diagnosis was undifferentiated spondyloarthropathy (uSpa) in 20%, other ReA in 14%, and "arthritis alone" in 7%. Of 65 (42 men, 23 women) patients tested, 94% were HIV-positive (91% men, 100% women). In those with HIV, the arthritis was predominantly polyarticular, lower limb-predominant, and progressive; 58% of 33 with persistent disease had erosions of foot and/or hand joints (average disease duration, 24.4 mo); 6 of 10 showed early radiological spine or sacroiliac joint changes (average duration 47.7 mo). Anterior uveitis occurred in 33% of patients, while keratoderma blenorrhagicum and stomatitis occurred in 14.3% and 9.5%, respectively, of patients with enteroreactive ReA. Uroreactive ReA was more common in women. There were no significant differences in the clinical, diagnostic, or radiographic features between men and women or between those with or without a known preceding trigger. CONCLUSION: HIV associated ReA in Black Zambians frequently follows an accelerated course with a strong tendency to relapse, develop early erosions and joint deformity, and become chronic. The clinical, diagnostic, and radiographic features are indistinguishable from those described in the conventional (HLA-B27 related) disease, although our HIV-positive patients have a high overall frequency of uveitis, keratoderma, and onycholysis.

Tryptophan-NAD+ pathway metabolites as putative biomarkers and predictors of peroxisome proliferation.

The present study was designed to provide further information about the relevance of raised urinary levels of N-methylnicotinamide (NMN), and/or its metabolites N-methyl-4-pyridone-3-carboxamide (4PY) and N-methyl-2-pyridone-3-carboxamide (2PY), to peroxisome proliferation by dosing rats with known peroxisome proliferator-activated receptor alpha (PPARalpha) ligands [fenofibrate, diethylhexylphthalate (DEHP) and long-chain fatty acids (LCFA)] and other compounds believed to modulate lipid metabolism via PPARalpha-independent mechanisms (simvastatin, hydrazine and chlorpromazine). Urinary NMN was correlated with standard markers of peroxisome proliferation and serum lipid parameters with the aim of establishing whether urinary NMN could be used as a biomarker for peroxisome proliferation in the rat. Data from this study were also used to validate a previously constructed multivariate statistical model of peroxisome proliferation (PP) in the rat. The predictive model, based on 1H nuclear magnetic resonance (NMR) spectroscopy of urine, uses spectral patterns of NMN, 4PY and other endogenous metabolites to predict hepatocellular peroxisome count. Each treatment induced pharmacological (serum lipid) effects characteristic of their class, but only fenofibrate, DEHP and simvastatin increased peroxisome number and raised urinary NMN, 2PY and 4PY, with simvastatin having only a transient effect on the latter. These compounds also reduced mRNA expression for aminocarboxymuconate-semialdehyde decarboxylase (ACMSDase, EC 4.1.1.45), the enzyme believed to be involved in modulating the flux of tryptophan through this pathway, with decreasing order of potency, fenofibrate (-10.39-fold) >DEHP (-3.09-fold) >simvastatin (-1.84-fold). Of the other treatments, only LCFA influenced mRNA expression of ACMSDase (-3.62-fold reduction) and quinolinate phosphoribosyltransferase (QAPRTase, EC 2.4.2.19) (-2.42-fold) without any change in urinary NMN excretion. Although there were no correlations between urinary NMN concentration and serum lipid parameters, NMN did correlate with peroxisome count (r2=0.63) and acyl-CoA oxidase activity (r2=0.61). These correlations were biased by the large response to fenofibrate compared to the other treatments; nevertheless the data do indicate a relationship between the tryptophan-NAD+ pathway and PPARalpha-dependent pathways, making this metabolite a potentially useful biomarker to detect PP. In order to strengthen the observed link between the metabolites associated with the tryptophan-NAD+ pathway and more accurately predict PP, other urinary metabolites were included in a predictive statistical model. This statistical model was found to predict the observed PP in 26/27 instances using a pre-determined threshold of 2-fold mean control peroxisome count. The model also predicted a time-dependent increase in peroxisome count for the fenofibrate group, which is important when considering the use of such modelling to predict the onset and progression of PP prior to its observation in samples taken at autopsy.