Study of endocrine disruptor effects in AVP and OT mediated behavioral and reproductive processes in female rat models.

Environmental exposures may have endocrine disruptor (ED) effects, e.g., a role for halogenated hydrocarbon chlorobenzenes in increasing vasopressin (AVP), oxytocin (OT) secretion and, in association, anxiety and aggression in male rats has been shown. Our aim is to investigate whether 1,2,4-trichlorobenzenehexachlorobenzene= 1:1 (mClB) treatment of female rats also shows ED effects and reproductive biology differences, and whether AVP may have a mediator role in this? Female Wistar rats were treated (0.1; 1.0; 10.0 µg/bwkg/day) with mClB (by gastrictube) and then 30; 60; 90 days after treatment anxiety (open field test) and aggressive (resident intruder test) behaviors AVP, OT concentrations from blood plasma samples were detected by radioimmunoassay on 30; 60; 90 days. Treated female rats were mated with untreated males. Mating success, number of newborn and maternal aggression on the neonates were monitored. Results showed that AVP, OT levels; and anxiety, aggressive behaviors; and mothers' aggression towards their offspring increased significantly in relation to the duration and the dose of mClB treatment. But mating propensity and number of offspring decreased. Patterns of AVP, OT release and anxiety, aggression behaviors, and reproductive-related behaviors were correlated. Consistent with the literature, our studies confirmed the role of AVP and OT in different behavioral effects.

Long-term neurodevelopmental outcome of neonates born at term with perinatal haemorrhagic stroke: A population-based study.

AIM: To assess the long-term neurodevelopmental outcome of neonates born at term diagnosed with perinatal haemorrhagic stroke (PHS) and investigate the associations among brain territorial involvement, clinical risk factors, and neurodevelopmental outcomes. METHOD: We conducted a population-based study enrolling 55 neonates born at term with PHS confirmed by magnetic resonance imaging born between 2007 and 2017. Long-term neurodevelopmental outcome was assessed using the Bayley Scales of Infant Development, Second Edition, the Brunet-Lézine test, and the Stanford-Binet Intelligence Scales, Fifth Edition. RESULTS: Follow-up was available in 50 (91%) of the infants, at a median age of 60 months (interquartile range 35-88). Forty per cent of the infants developed according to population norms, and developmental disabilities were diagnosed less frequently among neonates with frontal lobe PHS. In a multivariable model, parietal lobe PHS increased the risk for cerebral palsy (odds ratio [OR] 6.7; 95% confidence interval [CI] 1.1-41.4) and cognitive impairment (OR: 23.6; 95% CI: 2.9-194.9), while the involvement of the thalamus and/or basal ganglia was associated with epilepsy (OR: 7.0; 95% CI: 1.3-37.7). Seizures on admission were associated with epilepsy (OR: 10.8; 95% CI: 1.8-64.3). Patients with PHS affecting multiple lobes had poor prognosis. INTERPRETATION: Parietal lobe haemorrhage, the involvement of the thalamus/basal ganglia, PHS affecting multiple lobes, and seizures were independent predictors of chronic neurodevelopmental sequelae, suggesting that the stroke territorial involvement and clinical risk factors influence the outcome of PHS.

The role of brain territorial involvement and infection/inflammation in the long-term outcome of neonates with arterial ischemic stroke: A population-based cohort study.

BACKGROUND: Neonatal arterial ischemic stroke (NAIS) carries the risk of significant long-term neurodevelopmental burden on survivors. AIMS: To assess the long-term neurodevelopmental outcome of term neonates diagnosed with NAIS and investigate the associations among brain territorial involvement on MRI, clinical risk factors and neurodevelopmental outcomes. STUDY DESIGN: Population-based cohort study. SUBJECTS: Seventy-nine term neonates with NAIS confirmed by MRI born between 2007 and 2017. OUTCOME MEASURES: Long-term neurodevelopmental outcome assessed using the Bayley Scales of Infant Development-II, the Brunet-Lézine test and the Binet Intelligence scales-V. RESULTS: Follow-up was available in 70 (89%) of the subjects enrolled, at a median age of 60 months [IQR: 35-84]. Normal neurodevelopmental outcome was found in 43% of the patients. In a multivariable model, infants with main MCA stroke had an increased risk for overall adverse outcome (OR: 9.1, 95% CI: 1.7-48.0) and a particularly high risk for cerebral palsy (OR: 55.9, 95% CI: 7.8-399.2). The involvement of the corticospinal tract without extensive stroke also increased the risk for cerebral palsy/fine motor impairment (OR: 13.5, 95% CI: 2.4-76.3). Multiple strokes were associated with epilepsy (OR: 9.5, 95% CI: 1.0-88.9) and behavioral problems (OR: 4.4, 95% CI: 1.1-17.5) and inflammation/infection was associated with cerebral palsy (OR: 9.8, 95% CI: 1.4-66.9), cognitive impairment (OR: 9.2, 95% CI: 1.8-47.8) and epilepsy (OR: 10.3, 95% CI: 1.6-67.9). CONCLUSIONS: Main MCA stroke, involvement of the corticospinal tract, multiple strokes and inflammation/infection were independent predictors of adverse outcome, suggesting that the interplay of stroke territorial involvement and clinical risk factors influence the outcome of NAIS.

Study of the Potential Endocrine-Disrupting Effects of Phenylurea Compounds on Neurohypophysis Cells In Vitro.

Homeostatic disruptor agents, and endocrine disruptor compounds (EDC) specifically, can originate from agricultural and industrial chemicals. If they modify the adaptation of living organisms as direct (e.g., by altering hormone regulation, membrane functions) and/or indirect (e.g., cell transformation mechanisms) factors, they are classified as EDC. We aimed to examine the potential endocrine-disrupting effects of phenylurea herbicides (phenuron, monuron, and diuron) on the oxytocin (OT) and arginine-vasopressin (AVP) release of neurohypophysis cell cultures (NH). In our experiments, monoamine-activated receptor functions of neurohypophyseal cells were used as a model. In vitro NH were prepared by enzymatic (trypsin, collagenase) and mechanical dissociation. In the experimental protocol, the basal levels of OT and AVP were determined as controls. Later, monoamine (epinephrine, norepinephrine, serotonin, histamine, and dopamine) activation (10-6 M, 30 min) and the effects of phenylurea (10-6 M, 60 min) alone and in combination (monoamines 10-6 M, 30 min + phenylureas 10-6 M, 60 min) with monoamine were studied. OT and AVP hormone contents in the supernatant media were measured by radioimmunoassay. The monoamine-activated receptor functions of neurohypophyseal cells were modified by the applied doses of phenuron, monuron, and diuron. It is concluded that the applied phenylurea herbicides are endocrine disruptor agents, at least in vitro for neurohypophysis function.

The Role of Uron and Chlorobenzene Derivatives, as Potential Endocrine Disrupting Compounds, in the Secretion of ACTH and PRL.

Uron herbicides polluting the environment represent a serious concern for environmental health and may be regarded as endocrine-disrupting compounds (EDCs), which influence the regulation of human homeostasis. We aimed to investigate the effect of EDC urons (phenuron: PU, monuron: MU, and diuron: DU) and chlorobenzenes on the basal release of the adrenocorticotropic hormone (ACTH), which is a part of the adenohypophysis-adrenocortical axis. Hormone secretion in the presence of EDC was studied in two cell types: normal adenohypophysis cells (AdH) and cells of prolactinomas (PRLOMA). PRLOMA was induced in female Wistar rats by subcutaneously injecting them with estrone acetate for 6 months. AdH and PRLOMA were separated from treated and untreated experimental animals, dissociated enzymatically and mechanically in order to create monolayer cell cultures, which served as an experimental in vitro model. We investigated the effects of ED agents separately and in combination on ACTH and prolactin (PRL) release through the hypophyseal-adrenal axis. Hormone determination was carried out by the luminescent immunoassay and the radioimmunoassay methods. Our results showed that (1) uron agents separately did not change ACTH and PRL release in AdH culture; (2) ACTH secretion in arginine vasopressin- (AVP-) activated AdH cells was significantly increased by EDC treatment; (3) ED agents increased the basal hormone release (ACTH, PRL) in PRLOMA cells; and (4) EDC exposure increased ACTH release in AVP-activated PRLOMA cells. We conclude that the herbicides PU, MU, and DU carry EDC effects and show human toxicity potential.

Effects of extremely low frequency electromagnetic fields on turkeys.

Several studies have examined the potential biological effects of electromagnetic fields (EMF) on birds; however, little attention has been paid to the extremely low frequency (ELF; 0-300 Hz; 0-50 µT) radiation found in an urbanized environment. For monitoring the effects of ELF EMF, we used a turkey (Meleagris gallopavo) model, because the nucleated erythrocytes of turkeys contain ß-adrenoceptors, and norepinephrine- (NE-) activated ß-adrenoceptors have an important role in physiological and behavioral processes. Our aims were the following: 1) to investigate the intracellular mechanisms; 2) to compare the intracellular mechanisms in the treated and control groups over time, considering inter-individual differences and intra-subject correlations; 3) and to study the reversible nature of the response. The turkeys in the treatment group were treated in vivo with ELF EMF (50 Hz; 10 µT) for 3 wk after a 1-wk-long adaptation period. The animals were not exposed to ELF EMF during the regeneration period (5 wk following the exposure). The NE-activated ß-adrenoceptor function was detected by measuring the amount of 3΄5΄-cyclic-adenosine-monophosphate (cAMP), and the biochemical enzyme parameters were defined. Repeated measurements of cAMP levels were analyzed using marginal models and a piecewise linear mixed model to compare treatment and control groups over time. According to our results, NE-activated ß-adrenoceptor function was decreased in the treated birds in a time-dependent manner, while there were no differences between toxicological parameters in the serum, compared to the normal ranges. The decreased NE-dependent ß-adrenoceptor function could be compensated by the homeostatic complex during the 5-wk regeneration period. Extended experimental periods and more sophisticated analysis methods may help prevent harmful environmental effects on birds; furthermore, these findings could affect public health and the economy.

A comparative assessment of two kynurenic acid analogs in the formalin model of trigeminal activation: a behavioral, immunohistochemical and pharmacokinetic study.

Kynurenic acid (KYNA) has well-established protective properties against glutamatergic neurotransmission, which plays an essential role in the activation and sensitization process during some primary headache disorders. The goal of this study was to compare the effects of two KYNA analogs, N-(2-N,N-dimethylaminoethyl)-4-oxo-1H-quinoline-2-carboxamide hydrochloride (KA-1) and N-(2-N-pyrrolidinylethyl)-4-oxo-1H-quinoline-2-carboxamide hydrochloride (KA-2), in the orofacial formalin test of trigeminal pain. Following pretreatment with KA-1 or KA-2, rats were injected with subcutaneous formalin solution in the right whisker pad. Thereafter, the rubbing activity and c-Fos immunoreactivity changes in the spinal trigeminal nucleus pars caudalis (TNC) were investigated. To obtain pharmacokinetic data, KA-1, KA-2 and KYNA concentrations were measured following KA-1 or KA-2 injection. Behavioral tests demonstrated that KA-2 induced larger amelioration of formalin-evoked alterations as compared with KA-1 and the assessment of c-Fos immunoreactivity in the TNC yielded similar results. Although KA-1 treatment resulted in approximately four times larger area under the curve values in the serum relative to KA-2, the latter resulted in a higher KYNA elevation than in the case of KA-1. With regard to TNC, the concentration of KA-1 was under the limit of detection, while that of KA-2 was quite small and there was no major difference in the approximately tenfold KYNA elevations. These findings indicate that the differences between the beneficial effects of KA-1 and KA-2 may be explained by the markedly higher peripheral KYNA levels following KA-2 pretreatment. Targeting the peripheral component of trigeminal pain processing would provide an option for drug design which might prove beneficial in headache conditions.

Diverse effects of Brilliant Blue G administration in models of trigeminal activation in the rat.

Activation of the trigeminal system plays an important role in the pathomechanism of headaches. A better understanding of trigeminal pain processing is expected to provide information helping to unravel the background of these diseases. ATP, a key modulator of nociceptive processing, acts on ligand-gated P2X receptors. Antagonists of the P2X7 receptors, such as Brilliant Blue G (BBG), have proved effective in several models of pain. We have investigated the effects of BBG after electrical stimulation of the trigeminal ganglion and in the orofacial formalin test in the rat. The right trigeminal ganglion of male rats was stimulated either with 5 Hz, 0.5 mA pulses for 5 min (mild procedure) or with 10 Hz, 0.5 mA pulses for 30 min (robust procedure), preceded by 50 mg/kg i.v. BBG. The animals were processed for c-Fos and calcitonin gene-related peptide (CGRP) immunohistochemistry. In the orofacial formalin test, 50 µL of 1.5 % formalin was injected into the right whisker pad of awake rats, following the pre-treatment with BBG. Behaviour was monitored for 45 min, and c-Fos and CGRP immunohistochemistry was performed. BBG attenuated the increase in c-Fos-positive cells in the caudal trigeminal nucleus (TNC) after robust stimulation, but not after mild stimulation. No alterations in CGRP levels were found with either methodology. BBG did not mitigate either the behaviour or the increase in c-Fos-positive cells in the TNC during the orofacial formalin test. These results indicate that P2X7 receptors may have a role in the modulation of nociception in the trigeminal system.

Effects of chronic and subtoxic chlorobenzenes on adrenocorticotrophic hormone release.

Many environmental chemicals and pesticides have been found to alter neuroendocrine communication in exposed biological objects. The environmental loads have primary and secondary effects that can alter the homeostatic regulation potential. Since it is difficult to avoid human exposition, a potentially important area of research to develop in vivo and in vitro experimental models. In this context, the primary aim of this study was to demonstrate the effects of chlorobenzenes on adrenocorticotrophic hormone (ACTH) release. In our experimental study, male Wistar rats were exposed to 0.1, 1.0 and 10 µg/b.w. (body weight)kg of 1,2,4- trichlorobenzene and hexachlorobenzene (ClB) mix via gastric tube for 30, 60 or 90 days. At the endpoints of the experiment blood samples were taken and animals were decapitated. Primary, monolayer adenohypophysis cell cultures were prepared by enzymatic and mechanical digestion. The ACTH hormone content in serum and supernatant media was measured by immuno-chemiluminescence assay. The Mg(2+)-dependent ATPase activity was determined by modified method of Martin and Dotty. Significant differences were detected in the hormone release between the control and treated groups. The hormone release was enhanced characteristically in exposed groups depending upon the dose and duration of exposure. The Mg(2+)-ATPase activity enhanced after chronic and subtoxic ClB exposition. Light microscopy revealed that the adenohypophysis seemed to be more abundant. Results indicate that Wistar rats exposed to subtoxic ClB have direct and indirect effects on hypothalamus-hypophysis-adrenal axis.

The use of regression methods for the investigation of trends in suicide rates in Hungary between 1963 and 2011.

PURPOSE: Suicide rates in Hungary have been analyzed from different aspects in recent decades. However, only descriptive rates have been reported. The aim of our epidemiological study was to characterize the pattern of annual rates of suicide in Hungary during the period 1963-2011 by applying advanced statistical methods. METHODS: Annual suicide rates per 100,000 population (>6 years) for gender, age group and suicide method were determined from published frequency tables and reference population data obtained from the Hungarian Central Statistical Office. Trends and relative risks of suicide were investigated using negative binomial regression models overall and in stratified analyses (by gender, age group and suicide method). Joinpoint regression analyses were additionally applied to characterize trends and to find turning points during the period 1963-2011. RESULTS: Overall, 178,323 suicides (50,265 females and 128,058 males) were committed in Hungary during the investigated period. The risk of suicide was higher among males than females overall, in all age groups and for most suicide methods. The annual suicide rate exhibited a significant peak in 1982 and remained basically constant after 2006. Different segmented patterns were observed for the suicide rates in the various age groups. CONCLUSIONS: Suicide rates revealed segmented linear pattern. This is the first detailed trend analysis with risk estimates obtained via joinpoint and negative binomial regression methods simultaneously for age-specific suicide frequencies in Hungary.

Association between the ABCG2 C421A polymorphism and Alzheimer's disease.

ATP binding cassette subfamily G member 2 (ABCG2) is involved in amyloid-ß transport and was found to be significantly up-regulated in Alzheimer's disease (AD) brain. A functional polymorphism of the ABCG2 gene (C421A; rs2231142) was genotyped in a sample of 299 Hungarian late-onset AD patients and 259 elderly, non-demented controls to investigate for the first time its association with AD, either alone or in combination with apolipoprotein E (APOE) ɛ2/ɛ3/ɛ4 polymorphism. A significantly increased susceptibility to AD (OR=1.741, 95% CI: 1.075-2.819, p=0.024) associated with ABCG2 C/C genotype was found when compared with the variant allele containing genotypes (CA and AA) as the reference category. Logistic regression analysis revealed a significant interaction effect between the ABCG2 C/C genotype and APOE ɛ4 allele on AD risk (p=0.003). It seems that the potential modest risk effect of the ABCG2 C/C genotype on AD risk is more pronounced in combination with the APOE ɛ4 allele. Further independent replications of our findings are required.

Serotonin transporter and serotonin receptor 2A gene polymorphisms in Alzheimer's disease.

Genetic variants of the serotonergic neurotransmitter system are potential contributing factors in the pathological processes underlying Alzheimer's disease (AD). We examined polymorphisms of the serotonin transporter (SLC6A4) and serotonin receptor 2A (HTR2A) genes for possible association with AD, and therefore genotyped 5-HTTLPR, STin2-VNTR and HTR2A T102C polymorphisms in 252 Hungarian AD patients and 234 ethnically matched control individuals. We did not detect statistically significant differences in genotype distribution comparing the AD and the control group when the polymorphisms were investigated separately. Logistic regression analyses, however, revealed an interaction effect between 5-HTTLPR and HTR2A T102C (p=0.019), but not between 5-HTTLPR and STin2-VNTR (p=0.494) or STin2-VNTR and HTR2A T102C (p=0.310) polymorphisms. Our study suggests no individual influence of the investigated polymorphisms but a potential combined effect of the 5-HTTLPR L/L and HTR2A T102C C/C genotypes on AD risk. However, the results need to be treated with considerable caution, and further analyses in larger samples are required.

Association between a variant of the sigma-1 receptor gene and Alzheimer's disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder with complex etiology and strong genetic predisposition. A number of investigations support the possible involvement of sigma non-opioid intracellular receptor 1 (SIGMAR1) in the pathophysiology of AD. We aimed to investigate the association between SIGMAR1 polymorphisms and late-onset AD, therefore we genotyped rs1799729 (GC-241-240TT) and rs1800866 (Q2P) in 322 Hungarian late-onset AD patients and 250 ethnically matched, elderly control individuals. The investigated polymorphisms were in nearly complete linkage disequilibrium resulting in the GC-Q and TT-P predominant haplotypes that were subjected to the statistical analyses. Our data demonstrates an association between the SIGMAR1 TT-P variant and the risk for developing AD (p=0.019), and a potential modest interaction effect (p=0.058) of the co-presence of the TT-P haplotype with apolipoprotein E4 allele on the risk for AD. Based on this mild significance, we could not fully support the hypothesis that TT-P haplotype in interaction with APOE E4 allele confers risk for developing AD.

Proteoglycan-induced arthritis and recombinant human proteoglycan aggrecan G1 domain-induced arthritis in BALB/c mice resembling two subtypes of rheumatoid arthritis.

OBJECTIVE: To develop a simplified and relatively inexpensive version of cartilage proteoglycan-induced arthritis (PGIA), an autoimmunity model of rheumatoid arthritis (RA), and to evaluate the extent to which this new model replicates the disease parameters of PGIA and RA. METHODS: Recombinant human G1 domain of human cartilage PG containing "arthritogenic" T cell epitopes was generated in a mammalian expression system and used for immunization of BALB/c mice. The development and progression of arthritis in recombinant human PG G1-immunized mice (designated recombinant human PG G1-induced arthritis [GIA]) was monitored, and disease parameters were compared with those in the parent PGIA model. RESULTS: GIA strongly resembled PGIA, although the clinical symptoms and immune responses in mice with GIA were more uniform than in those with PGIA. Mice with GIA showed evidence of stronger Th1 and Th17 polarization than those with PGIA, and anti-mouse PG autoantibodies were produced in different isotype ratios in the 2 models. Rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies were detected in both models; however, serum levels of IgG-RF and anti-CCP antibodies were different in GIA and PGIA, and both parameters correlated better with disease severity in GIA than in PGIA. CONCLUSION: GIA is a novel model of seropositive RA that exhibits all of the characteristics of PGIA. Although the clinical phenotypes are similar, GIA and PGIA are characterized by different autoantibody profiles, and the 2 models may represent 2 subtypes of seropositive RA, in which more than 1 type of autoantibody can be used to monitor disease severity and response to treatment.

Development of proteoglycan-induced arthritis depends on T cell-supported autoantibody production, but does not involve significant influx of T cells into the joints.

INTRODUCTION: Inflammatory joint destruction in rheumatoid arthritis (RA) may be triggered by autoantibodies, the production of which is supported by autoreactive T cells. Studies on RA and animal models of the disease suggest that T cells recruited in the joints can locally initiate or propagate arthritis. Herein, we investigated the role of joint-homing versus lymphoid organ-homing T cells in the development of proteoglycan-induced arthritis (PGIA), an autoimmune model of RA. METHODS: To identify T cells migrating to the joints before and during development of autoimmune arthritis, we transferred fluorescence-labeled T cells, along with antigen-presenting cells, from BALB/c mice with PGIA to naïve syngeneic severe combined immunodeficient (SCID) mice. We then monitored the recruitment of donor T cells in the ankle joints and joint-draining lymph nodes of the recipients using in vivo two-photon microscopy and ex vivo detection methods. To limit T-cell access to the joints, we selectively depleted T cells in the blood circulation by treatment with FTY720, an inhibitor of lymphocyte egress from lymphoid organs. Reduction of T cell presence in both lymphoid organs and blood was achieved by injection of donor cells from which T cells were removed prior to transfer. T and B cells were quantitated by flow cytometry, and antigen (PG)-specific responses were assessed by cell proliferation and serum antibody assays. RESULTS: Despite development of adoptively transferred arthritis in the recipient SCID mice, we found very few donor T cells in their joints after cell transfer. Treatment of recipient mice with FTY720 left the T-cell pool in the lymphoid organs intact, but reduced T cells in both peripheral blood and joints. However, FTY720 treatment failed to inhibit PGIA development. In contrast, arthritis was not seen in recipient mice after transfer of T cell-depleted cells from arthritic donors, and serum autoantibodies to PG were not detected in this group of mice. CONCLUSIONS: Our results suggest that antigen-specific T cells, which home to lymphoid organs and provide help to B cells for systemic autoantibody production, play a greater role in the development and progression of autoimmune arthritis than the small population of T cells that migrate to the joints.

BALB/c mice genetically susceptible to proteoglycan-induced arthritis and spondylitis show colony-dependent differences in disease penetrance.

INTRODUCTION: The major histocompatibility complex (H-2d) and non-major histocompatibility complex genetic backgrounds make the BALB/c strain highly susceptible to inflammatory arthritis and spondylitis. Although different BALB/c colonies develop proteoglycan-induced arthritis and proteoglycan-induced spondylitis in response to immunization with human cartilage proteoglycan, they show significant differences in disease penetrance despite being maintained by the same vendor at either the same or a different location. METHODS: BALB/c female mice (24 to 26 weeks old after 4 weeks of acclimatization) were immunized with a suboptimal dose of cartilage proteoglycan to explore even minute differences among 11 subcolonies purchased from five different vendors. In vitro-measured T-cell responses, and serum cytokines and (auto)antibodies were correlated with arthritis (and spondylitis) phenotypic scores. cDNA microarrays were also performed using spleen cells of naïve and immunized BALB/cJ and BALB/cByJ mice (both colonies from The Jackson Laboratory, Bar Harbor, ME, USA), which represent the two major BALB/c sublines. RESULTS: The 11 BALB/c colonies could be separated into high (n = 3), average (n = 6), and low (n = 2) responder groups based upon their arthritis scores. While the clinical phenotypes showed significant differences, only a few immune parameters correlated with clinical or histopathological abnormalities, and seemingly none of them affected differences found in altered clinical phenotypes (onset time, severity or incidence of arthritis, or severity and progression of spondylitis). Affymetrix assay (Affymetrix, Santa Clara, CA, USA) explored 77 differentially expressed genes (at a significant level, P < 0.05) between The Jackson Laboratory's BALB/cJ (original) and BALB/cByJ (transferred from the National Institutes of Health, Bethesda, MD, USA). Fourteen of the 77 differentially expressed genes had unknown function; 24 of 77 genes showed over twofold differences, and only 8 genes were induced by immunization, some in both colonies. CONCLUSIONS: Using different subcolonies of the BALB/c strain, we can detect significant differences in arthritis phenotypes, single-nucleotide polymorphisms (SNPs), and a large number of differentially expressed genes, even in non-immunized animals. A number of the known genes (and SNPs) are associated with immune responses and/or arthritis in this genetically arthritis-prone murine strain, and a number of genes of as-yet-unknown function may affect or modify clinical phenotypes of arthritis and/or spondylitis.