Effects of habitual moderate exercise on response processing and cognitive processing in older adults

We examined the effects of habitual moderate exercise on central information processing in older individuals using the reaction time (RT) and P3 component of event-related brain potentials (ERP). The present study was designed to assess cognitive function by comparing groups of 20 older individuals (69.20 +/- 1.3 years active group) who regularly engage in moderate physical activity with 20 subjects (66.90 +/- 1.1 years inactive group) who do comparatively little exercise. Subjects performed a somatosensory oddball task composed of pressing a button with their right foot as fast as possible following an electrical stimulus applied to the right index finger, and not responding to an electrical stimulus applied to the left index finger. Electroencephalogram (EEG) was recorded at the frontal (Fz), central (Cz), and parietal (Pz) sites according to the International 10-20 system referenced to linked earlobes. The RT was faster for the active group than for the inactive group, and the P3 amplitude of the active group was significantly larger than that of the inactive group. Moreover, the P3 amplitude for the active group was maximum at Pz and significantly larger than at Fz and Cz, but for the inactive group it was identical between Fz and Pz. The results suggest that habitual moderate exercise exerts positive influences in older adults not only on response processing, but also on cognitive processing.

Changes in arousal level by differential exercise intensity

OBJECTIVE

The purpose of the present study was to investigate the influence of exercise intensity on arousal level.

METHODS

Twelve subjects (22-33 years) performed a S1-S2 reaction time task consisting of warning stimulus (S1) and imperative stimulus (S2) in a control condition, and again after low, medium, and high intensity pedaling exercises. During this task, contingent negative variation (CNV) and spontaneous electroencephalogram before S1 were measured as indicators for arousal level.

RESULTS

CNV amplitude after high intensity pedaling exercise was significantly smaller than after medium pedaling exercise. Compared to the control condition, relative power value of alpha waves increased after the high intensity exercise.

CONCLUSIONS

These results suggested that arousal level was reduced after high intensity exercise and reached a state near optimal level after medium intensity exercise. The findings also suggested that changes in CNV amplitude by differences in exercise intensity followed an inverted-U shaped dose response curve.

SIGNIFICANCE

The present study supported the view that CNV amplitude and arousal level followed an inverted-U relationship. It is concluded that differences in exercise intensity influenced arousal level.

Resource allocation and somatosensory P300 amplitude during dual task: effects of tracking speed and predictability of tracking direction

OBJECTIVE

The amount of attentional resources allocated to a task is determined by the intrinsic demands, also denoted as task load or difficulty of the task. Effects of resource allocation on the somatosensory N140 and P300 were investigated in an inter-modal situation using a dual-task methodology.

METHODS

Under a dual-task condition, subjects concurrently performed a visuomotor tracking task and a somatosensory oddball task, while they performed just the oddball task under an oddball-only condition. In the tracking task, the subjects tracked the target line, which was presented on an oscilloscope and automatically moved, with the line which represented their own force generated by grip movement with the left hand. Tracking speed (experiment 1) and tracking predictability (experiment 2) were manipulated to vary task difficulty. N140, P300, and reaction time (RT) in the oddball task and tracking accuracy in the tracking task were measured.

RESULTS

The P300 and N140 amplitudes were reduced in the dual-task condition compared to those in the oddball-only condition. The fastest tracking speed produced lower tracking accuracy and later RT. However, the tracking speed did not affect the P300 or N140 amplitudes. In contrast, the P300 amplitude was smaller when the change in tracking direction was unpredictable than when it was predictable, without any differences in tracking accuracy or RT, N140.

CONCLUSIONS

The differences in behaviors among N140, P300, and RT following manipulation of task difficulty support the multiple-resource hypothesis, which defines functionally separate pools of resources.

SIGNIFICANCE

The present study may show that the P300 amplitude reflects modality-unspecific resource at more central level, and that the N140 amplitude involves perceptual resource.

Differential influences of exercise intensity on information processing in the central nervous system

The influence of exercise intensity on information processing in the central nervous system was investigated using P300 and no-go P300 event-related potentials. Twelve subjects (22-33 years) performed a go/no-go reaction time task in a control condition, and again after high-, medium-, and low-intensity pedaling exercises. Compared to the control condition, P300 amplitude decreased after high-intensity pedaling exercise and increased after medium-intensity pedaling exercise. There was no change after low-intensity pedaling exercise. These results suggested that the amount of attentional resources devoted to a given task decreased after high-intensity exercise and increased after medium-intensity exercise. The findings also suggest that changes in P300 amplitude are an inverted U-shaped behavior of differences in exercise intensity. In addition, no-go P300 amplitude showed the same changes as P300 amplitude at different exercise intensities. This indicates that differences in exercise intensity influenced not only the intensity of processing the requirement for a go response, but also processing of the need for a no-go response. It is concluded that differences in exercise intensity influenced information processing in the CNS.

The Sos1-Rac1 signaling. Possible involvement of a vacuolar H(+)-ATPase E subunit

We have purified and identified a 32-kDa protein interacting with the Dbl oncogene homology domain of mSos1(Sos-DH) from rat brains by glutathione S-transferase-Sos-DH affinity chromatography. Peptide sequencing revealed that the protein is identical to a positive regulatory E subunit (V-ATPase E) of a vacuolar H(+)-ATPase, which is responsible for acidification of endosome and alkalinization of intracellular pH. The interaction between V-ATPase E and Sos-DH was confirmed by yeast two-hybrid assay. A coimmunoprecipitation assay demonstrated that a V-ATPase E protein physiologically bound to mSos1, and the protein was colocalized with mSos1 in the cytoplasm, as determined by immunohistochemistry. mSos1 was found in the early endosome fraction together with V-ATPase E and Rac1, suggesting the functional involvement of mSos1/V-ATPase E complexes in the Rac1 activity at endosomes. Overexpression of V-ATPase E in COS cells enhanced the ability of mSos1 to promote the guanine nucleotide exchange activity for Rac1 and stimulated the kinase activity of Jun kinase, a downstream target of Rac1. Thus, the data indicate that V-ATPase E may participate in the regulation of the mSos1-dependent Rac1 signaling pathway involved in growth factor receptor-mediated cell growth control.

Early full donor myeloid chimerism after reduced-intensity stem cell transplantation using a combination of fludarabine and busulfan

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate lineage-specific chimerism reconstitution after reduced-intensity allogeneic stem cell transplantation (RIST) using a combination of fludarabine (30 mg/m2 for 6 days) and busulfan (4 mg/kg for 2 days).

DESIGN AND METHODS

We prospectively enrolled 8 consecutive patients with hematologic malignancies who were not candidates for conventional transplantation because of either high age or organ dysfunction. Host-donor chimerism was evaluated using polymerase chain reaction-based amplification of a polymorphic short tandem repeat region.

RESULTS

All of our patients achieved engraftment within a median of 11 days after transplantation. On day 30, full donor myeloid cell chimerism (>90%) was achieved in 7 patients whereas full donor T-cell chimerism was achieved in only one patient. Thus, in contrast to other reported results, full donor chimerism was achieved earlier in the myeloid lineage than the T-cell lineage. On day 60, however, T-cell chimerism caught up with myeloid chimerism. Two patients developed grade II-IV acute graft-versus-host disease (GVHD) before the detection of full donor T-cell chimerism.

INTERPRETATION AND CONCLUSIONS

Our findings suggest that the kinetics of lineage-specific chimerism depend on the agents used in the conditioning regimen, and may provide insight into the chimerism kinetics and pathogenesis of GVHD. Thus, the strategy for controlling immunosuppression after RIST should be modified according to the type of conditioning regimen applied.

Integrated approach of an artificial neural network and numerical analysis to multiple equivalent current dipole source localization

The authors have developed a PC-based multichannel electroencephalogram (EEG) measurement and analysis system. This system enables us (1) to simultaneously record a maximum of 64 channels of EEG data, (2) to measure three-dimensional positions of the recording electrodes, (3) to rapidly and precisely localize equivalent current dipoles (ECDs) responsible for the EEG data, and (4) to superimpose the localization results on magnetic resonance images. A new neural network and numerical analysis (NNN) approach to ECD localization is described which integrates a feedforward artificial neural network (ANN) and a numerical optimization (Powell's hybrid) method. It was shown that the ANN method has the advantages of high-speed localization and noise robustness, because in this approach: (1) ECD parameters are immediately initialized from the recorded EEG data by the ANN and (2) ECD parameters are accurately refined by the hybrid method. Our multiple ECD localization method was applied to sensory evoked potentials and event-related potentials using the present system.

Comparison of electroencephalographic dipoles of interictal spikes from prolonged scalp video-electroencephalography and magnetoencephalographic dipoles from short-term recording in children with extratemporal lobe epilepsy

We retrospectively compared electroencephalographic (EEG) dipoles of interictal spikes from prolonged video-EEG monitoring with magnetoencephalographic dipoles from short-term recording in four children with extratemporal lobe epilepsy. We analyzed both sets of dipoles using individual interictal spikes and single moving dipole modeling and evaluated the profiles of spike appearance, dipole position, and orientation in EEG and magnetoencephalography. We obtained more than 100 magnetoencephalographic spikes in two patients who manifested frequent interictal EEG spikes throughout both day and night but fewer than 40 magnetoencephalographic spikes in two patients who had interictal EEG spikes mainly during sleep. The dipole positions of EEG and magnetoencephalography were in close proximity and included in the surgical resection area. Most of the dipoles between EEG and magnetoencephalography were oriented perpendicularly. A combination of EEG dipole analysis from prolonged video-EEG monitoring and magnetoencephalographic dipole analysis provides complementary information for presurgical evaluation in children with intractable extratemporal lobe epilepsy.

Multiple dipole analysis of visual event-related potentials during oddball paradigm with silent counting

In order to cope with the non-uniqueness of multiple equivalent current dipole source (ECD) solutions, a priori knowledge about P300 generators of visual event-related potentials (ERPs) during an oddball paradigm with silent counting task was incorporated into the multiple ECD localization method. Four-ECD solutions for the target P300 were selected which had the left frontal ECD. The rest of the ECDs were localized to the inferior parietal lobule, the hippocampal formation and subcortical region. By comparing the present results with those on the visual ERPs with button-pressing task, the P300 dipoles common to both the tasks were located at the frontal cortices, the hippocampal formation and the thalamus, suggesting that these structures are the main P300 generators.

Dipole localization for identification of neuronal generators in independent neighboring interictal EEG spike foci

PURPOSE

We evaluated dipole localizations of independent neighboring interictal spike foci using scalp electroencephalogram (EEG) to identify neuronal generators of epileptic discharges.

METHODS

Three pediatric patients with extratemporal lobe epilepsy who had two independent neighboring interictal spike foci on scalp EEG were studied. Prolonged video EEG was digitally recorded from 19 scalp electrodes, whose positions were registered using a three-dimensional digitizer. Interictal spikes were visually selected based on negative phase reversals on bipolar montages. We analyzed the dipole position and moment of each spike using a single moving dipole and three-shell spherical head model. The dipoles were overlaid onto magnetic resonance (MR) images and divided into two groups based on two spike foci.

RESULTS

The dipoles of the two groups were oriented either tangentially or radially to the scalp in close proximity to each other. The dipoles oriented radially were located underneath the electrode with a negative peak; those oriented tangentially were between electrodes with a negative and positive peak. The positions of tangential dipoles were more concentrated than those of radial dipoles. The epileptogenic regions corresponded to the dipole localizations. Surgical excisions were performed based on the results of electrocorticography. After surgery, two patients were seizure free, and one had rare seizures (follow-up period, 13-31 months).

CONCLUSIONS

We showed that dipoles in close proximity but with different orientations projected two negative maxima on scalp EEG in three patients with extratemporal localization-related epilepsy. Equivalent current dipole analysis of individual interictal spikes can provide useful information about the epileptogenic zone in these patients.

A new adaptive temporal filter: application to photosensitive seizure patients

A new adaptive temporal filtering (ATF) technique was developed to prevent heath hazards due to flicker stimuli from televisions, videos or other displays. This ATF method could reduce frame-to-frame or field-to-field flicker stimuli at around 10-30 Hz which are particularly risky for photosensitive individuals. The present ATF efficacy with a computer simulation was studied in 11 photosensitive epilepsy patients. In order to control visual stimuli and induce photoparoxysmal response (PPR), we employed a problematic scene of the Pocket Monster incident containing 12 Hz red/blue flicker images lasting for 4 s. This image, shown with a 14-inch, television set 2 m in front of subjects, promptly elicited generalized PPR in all cases, while the filtered image did not induce any PPR. These results suggest that the present ATF method may be useful as a preventive measure of photosensitive seizures triggered by stimulative images from televisions or other displays.

Aggregate formation and degradation of overexpressed wild-type and mutant urate oxidase proteins. Quality control of organelle-destined proteins by the endoplasmic reticulum

To analyze the cellular response caused by the overexpression of proteins in subcellular compartments, we constructed four expression clones encoding wild-type peroxisomal urate oxidase (UO), truncated UO lacking the peroxisomal targeting signal (UOdC), and chimeric UOs with a mitochondrial targeting signal (MTS) at the N-terminus of UOdC (MUOdC) or UO (MUO). After transfection, we examined COS-1 and HEK293 cells by immunofluorescence and immunoelectron microscopy, transmission electron microscopy, and pulse-chase experiments. The overexpressed UO and UOdC formed large electron-dense aggregates with no limiting membrane in both the cytoplasm and the nucleus. The UO aggregates exhibited the crystalloid structure quite similar to that of rat liver peroxisomal cores, whereas the UOdC aggregates formed a loose mass consisting of small dense substructures. The overexpressed MUOdC and MUO, on the other hand, formed other types of aggregates which were distributed in the cytoplasm. They consisted of tubular and circular membrane structures, which were morphologically confirmed to be derived from the endoplasmic reticulum (ER). No immunolabeling signals for MUOdC and MUO were present free in the cytoplasm and most of them were associated with membrane structures, suggesting that overexpressed UO containing the MTS attached to the ER membranes soon after synthesis and segregated from the cytosolic compartment. All the UO aggregates were stained for ubiquitin antigen. Pulse-chase experiments in combination with proteasome inhibitors suggested that proteasomes did not contribute to the degradation of these products.

Multiple equivalent current dipole source localization of visual event-related potentials during oddball paradigm with motor response

Event-related potentials (ERPs) during a visual oddball paradigm with button-pressing responses were recorded in 12 right-handed subjects from 32 scalp electrodes. The single equivalent current dipole (ECD) of the target C1 (weak occipito-parietal negativity from 30-80 ms) was consistently located at the primary visual cortex. From the 4-ECD localization of the target P1/N1 (temporally coincident frontal positivity and occipito-temporal negativity), it was suggested that this complex reflected activities from distributed sources along both dorsal occipito-parietal and ventral occipito-temporal areas. The stable multiple ECD solutions for the target P3b were chosen as those including the left primary motor and/or sensorimotor dipole and satisfying goodness-of-fit (GOF) of more than 98% and confidence limit (CL) of less than 1 mm. The obtained frontal dipoles were discussed in terms of visual working memory and sustained attention in reference to the previous PET, fMRI and MEG studies. The distributed multiple ECDs may suggest that P3 should be interpreted as being the embodiment of the cortico-limbic-thalamic network which involves Halgren and Marinkovic's emotional and behavioral model and Mesulam's attentional circuit.

Systematic approach to dipole localization of interictal EEG spikes in children with extratemporal lobe epilepsies

OBJECTIVES

To assess the reliability of dipole localization based on residual variances (RV), using equivalent current dipole analysis of interictal EEG spikes in children with extratemporal lobe epilepsy.

METHODS

Four pediatric patients with extratemporal lobe epilepsy were studied. Digital EEG was recorded from 19 scalp electrodes. Computer programs for spike detection and clustering analysis were used to select spikes. Dipoles were calculated 5 times for each spike using different initial guesses by the moving dipole model. Standard deviation (SD) of the dipole positions was calculated at each time point in the 5 trials.

RESULTS

We analyzed the dipoles at 1097 time points from 4 patients. Among 106 time points with RV < 2%, the SD was < 1 mm in 78 (74%), while in those with SD > 1 mm the dipole positions varied between 2.8 and 52.6 mm. Of dipoles with RV < 1%, 26 of 27 (96%) had an SD < 1 mm; the one dipole with SD > 1 mm varied within 2.5 mm. The dipole localizations with RV < 2% corresponded to the epileptogenic zones identified on intracranial invasive video EEG and intraoperative ECoG.

CONCLUSIONS

The systematic approach of equivalent current dipole analysis using spike detection, clustering analysis, and an RV < 2% as a standard is useful for identifying extratemporal epileptic regions.

A possible role of immunoglobulin E in patients with hyperthyroid Graves' disease

To investigate the possible participation of immunoglobulin E (IgE) in the autoimmune process of Graves' disease, incidence of elevation of serum IgE level, TSH receptor antibody (TRAb), and thyroid status were studied in 66 patients with hyperthyroid Graves' disease, 54 patients with Hashimoto's thyroiditis, 19 patients with bronchial asthma, and 15 patients with pollen allergy. In hyperthyroid Graves' patients, elevation of serum IgE levels (> or = 170 U/mL) was found in 19 of 66 patients (29%), 11 of whom had hereditary and/or allergic conditions. Elevations of serum IgE levels were found in 63% of patients with bronchial asthma and in 40% of patients with pollen allergy. Mean values of serum IgE were the same in patients with hyperthyroid Graves' disease and with bronchial asthma. During methimazole treatment TRAb decreased without fluctuation of IgE levels in both groups. The decrease in TRAb was significantly greater in patients with normal IgE than in patients with IgE elevation. After prednisone administration, reduction in TRAb was greater in patients with normal IgE than that in patients with IgE elevation. High incidence of IgE elevation in hyperthyroid Graves' disease and slower reduction in TRAb in association with IgE elevation suggest a difference in the autoimmune processes in Graves' disease with and without elevation of IgE.

Degradation of overexpressed wild-type and mutant uricase proteins in cultured cells

Wild-type and mutated urate oxidase (UO) proteins were overexpressed in Cos-1 and HEK293 cells and were analyzed by Western blotting and several morphological methods. By immunoelectron microscopy, wild-type UO formed large aggregates in the cytoplasm and nucleoplasm and exhibited a crystalloid structure. Mutated UO (UOdC), from which 28 amino acids, including peroxisomal targeting signal at the C-terminus, were deleted, formed dispersed aggregates in the cytoplasm and nucleus. Chimeric UO (MUOdC), which was made by addition of the mitochondrial targeting signal of serine:pyruvate/glyoxylate aminotransferase to the N-terminus of UOdC, attached to ER to form a complicated MUOdC-ER complex. These three structures were immunostained for ubiquitin- and p32-subunits of proteasomes. Western blotting showed strong signal for UO and UOdC but very weak signal for MUOdC. The results suggest that overexpressed UO and UOdC accumulate in the cells because their synthesis rate is higher than the degradation rate, whereas MUOdC forming a complex with ER is degraded very rapidly. The ubiquitin-proteasome pathway may be involved in the degradation of these proteins.

Clinical significance of a sensitive assay for thyroid-stimulating antibodies in Graves' disease using polyethylene glycol at high concentrations and porcine thyroid cells

The Inui and Ochi group recently reported that cAMP production by porcine thyroid cells (PTC) was augmented more by polyethylene glycol (PEG) 22.5% precipitated fractions from almost all Graves' sera than those of PEG 12.5%. In the present study, thyroid stimulating immunoglobulin (TSI) activity was determined with PTC and prepared crude Ig fractions precipitated by two different concentrations of PEG (final concentrations 13.5% and 22.5%) from sera obtained from 117 Graves' patients. The activity of TSI determined by the PEG 13.5% assay and activity determined by the PEG 22.5% assay were designated as thyroid-stimulating antibody (TSAb) and sTSAb, respectively. At first we studied 55 TSAb-positive patients with untreated hyperthyroid Graves' disease and classified them according to the TSAb activity-below 500% (group 1) and above 500% (group 2). The positive stimulatory effect, arbitrarily defined as the ratio of sTSAb to TSAb, being more than 1.2, was observed in 85% of patients, and group 1 had a significantly (P<0.025) greater stimulatory effect (34/35, 97.1%) than group 2 (13/20, 65%). Subsequently, in 29 TSAb-negative patients, sTSAb was measured and detected in 26 (89.7%). Finally, sTSAb, TSAb and TBII were compared between patients presenting with recurrent Graves' disease and those with silent thyroiditis after withdrawal of antithyroid drug treatment for Graves' disease. sTSAb was detected in all 14 relapsed patients, but none of the 9 patients with silent thyroiditis had detectable sTSAb. In contrast, TSAb and TBII activities were found in only 7 (50.0%) of the 14 relapsed cases. The present paper demonstrated that the assay with a higher PEG concentration was found to be sensitive, specific and useful for the diagnosis and follow-up of Graves' disease after drug withdrawal, although the underlying mechanism remains unclear.

Ultrasonic imaging of the temporomandibular joint: a clinical trial for diagnosis of internal derangement

Kinematic imaging of the temporomandibular joint (TMJ) was applied for diagnosis of TMJ disorders using an ultrasonic diagnostic imaging system. Patients with a normal TMJ (male, 24 y 1 mon) and a symptomatic TMJ (female, 20 y 2 mon) were selected for imaging. The transducer must be placed in a specific location in order to propagate ultrasound through soft tissue because it is difficult for ultrasound to penetrate bone such as the condyle and the eminence. Therefore the ultrasonic images were not taken in sagittal cross-section, as is the case with magnetic resonance images. The ultrasonic diagnostic imaging system showed a transverse cross-section and no hard tissue images. It was difficult to become accustomed to these images, thus making it difficult to find differences between the normal TMJ and the symptomatic TMJ on the basis of static ultrasonic images alone. However a difference between the kinematic images of the normal and symptomatic TMJ was observed during jaw opening. Irregularity in the striated pattern of the soft tissue surrounding the condyle was observed in the image of the symptomatic TMJ. In order to make a precise diagnosis using ultrasonic imaging, it may be useful to understand the kinematics of the soft tissue surrounding the TMJ during jaw opening and closing.

Physiological and psychological evaluation for visual display colour readability: a visual evoked potential study and a subjective evaluation study

This study was conducted, by subjective and objective evaluation, to clarify the complex relationships among VDT (visual display terminal) display colour readability and the related physical and physiological factors. Readability was defined as participants being able to read sentences easily on a VDT screen irrespective of their meanings. In the subjective evaluation, paired comparison tests and a colour impression test using the semantic differential (SD) method with factor analysis were carried out for 30 colour stimuli with different dominant wavelengths and stimulus purity values. The former test yielded identification of the most readable stimulus purity, which was in the range of 0.2 to 0.55 for any dominant wavelength. From the latter test, a 'conspicuousness factor' and a 'comfort factor' were extracted for evaluating readability. In the objective evaluation, three kinds of dominant wavelengths and three levels of stimulus purity were used. This evaluation showed that P100 peak latencies of colour-VEPs (visual evoked potentials) evoked by the subjectively optimal stimulus purity colours fully displayed on the screen were significantly shorter than those evoked by any other stimulus purity colours. Moreover, VEP P100 peak latencies evoked by the text colours that had the most readable stimulus purities were also shorter than those evoked by any other stimulus purity colours. Consequently, it was concluded that the optimum VDT display colour was that which had the most readable stimulus purity for each dominant wavelength, and that colour-VEP peak latency could serve as an indicator for quantification of VDT display colour readability.

Two novel missense mutations in the ATP-binding domain of the adrenoleukodystrophy gene: immunoblotting and immunocytological study of two patients

Two novel missense mutations, 1939G to A (R518Q) and 2017A to G (Q544R) were identified in Japanese patients with adrenoleukodystrophy (ALD). They are located in exon 6, which encodes part of the putative adenosine triphosphate binding domain of ALD protein. The ALD protein carrying the R518Q mutation was undetectable in fibroblasts, by immunoblot and immunofluorescence analysis, while the Q544R mutation had no apparent effect on the stability and localization of the ALD protein, but is expected to affect its function.

Inhibition of peroxisome proliferator signaling pathways by thyroid hormone receptor. Competitive binding to the response element

Peroxisome proliferators (e.g. clofibric acid) and thyroid hormone play an important role in the metabolism of lipids. These effectors display their action through their own nuclear receptors, peroxisome proliferator-activated receptor (PPAR) and thyroid hormone receptor (TR). PPAR and TR are ligand-dependent, DNA binding, trans-acting transcriptional factors belonging to the erbA-related nuclear receptor superfamily. The present study focused on the convergence of the effectors on the peroxisome proliferator response element (PPRE). Transcriptional activation induced by PPAR through a PPRE was significantly suppressed by cotransfection of TR in transient transfection assays. The inhibition, however, was not affected by adding 3,5,3'-triiodo-L-thyronine (T3). Furthermore, the inhibition was not observed in cells cotransfected with retinoic acid receptor or vitamin D3 receptor. The inhibitory action by TR was lost by introducing a mutation in the DNA binding domain of TR, indicating that competition for DNA binding is involved in the molecular basis of this functional interaction. Gel shift assays revealed that TRs, expressed in insect cells, specifically bound to the 32P-labeled PPRE as heterodimers with the retinoid X receptor (RXR). Both PPAR and TR bind to PPRE, although only PPAR mediates transcriptional activation via PPRE. TR.RXR heterodimers are potential competitors with PPAR.RXR for binding to PPREs. It is concluded that PPAR-mediated gene expression is negatively controlled by TR at the level of PPAR binding to PPRE. We report here the novel action of thyroid hormone receptor in controlling gene expression through PPREs.