A role for macrophage scavenger receptors in atherosclerosis and susceptibility to infection

Macrophage type-I and type-II class-A scavenger receptors (MSR-A) are implicated in the pathological deposition of cholesterol during atherogenesis as a result of receptor-mediated uptake of modified low-density lipoproteins (mLDL). MSR-A can bind an extraordinarily wide range of ligands, including bacterial pathogens, and also mediates cation-independent macrophage adhesion in vitro. Here we show that targeted disruption of the MSR-A gene in mice results in a reduction in the size of atherosclerotic lesions in an animal deficient in apolipoprotein E. Macrophages from MSR-A-deficient mice show a marked decrease in mLDL uptake in vitro, whereas mLDL clearance from plasma occurs at a normal rate, indicating that there may be alternative mechanisms for removing mLDL from the circulation. In addition, MSR-A-knockout mice show an increased susceptibility to infection with Listeria monocytogenes or herpes simplex virus type-1, indicating that MSR-A may play a part in host defence against pathogens.

Functional relevance of cross-modal plasticity in blind humans

Functional imaging studies of people who were blind from an early age have revealed that their primary visual cortex can be activated by Braille reading and other tactile discrimination tasks. Other studies have also shown that visual cortical areas can be activated by somatosensory input in blind subjects but not those with sight. The significance of this cross-modal plasticity is unclear, however, as it is not known whether the visual cortex can process somatosensory information in a functionally relevant way. To address this issue, we used transcranial magnetic stimulation to disrupt the function of different cortical areas in people who were blind from an early age as they identified Braille or embossed Roman letters. Transient stimulation of the occipital (visual) cortex induced errors in both tasks and distorted the tactile perceptions of blind subjects. In contrast, occipital stimulation had no effect on tactile performance in normal-sighted subjects, whereas similar stimulation is known to disrupt their visual performance. We conclude that blindness from an early age can cause the visual cortex to be recruited to a role in somatosensory processing. We propose that this cross-modal plasticity may account in part for the superior tactile perceptual abilities of blind subjects.

Ly-1 B cells: functionally distinct lymphocytes that secrete IgM autoantibodies

Studies presented here introduce another perspective on the mechanisms responsible for IgM autoantibody production. A unique subpopulation of B lymphocytes (Ly-1 B) that concomitantly expresses IgM, IgD, Ia, and Ly-1 membrane glycoproteins is present at higher frequencies in NZB and NZB-related mice. The Ly-1 B subpopulation in these autoimmune animals is responsible for the "spontaneous" IgM secretion demonstrated with cultured NZB spleen cells and contains the cells that secrete typical NZB IgM autoantibodies to single-stranded DNA and to thymocytes. In addition, the Ly-1 B population in normal mouse strains (and in NZB) contains virtually all of the spleen cells that secrete IgM autoantibodies reactive with bromelain-treated mouse erythrocytes. Since a different B-cell subpopulation (IgM+, IgD-, Ly-1) secretes most of the IgM antibodies produced in responses to exogenous antigens, we conclude that Ly-1 B cells constitute a functionally distinct B-cell population important in certain kinds of autoimmunity.

Complex HLA-DR and -DQ interactions confer risk of narcolepsy-cataplexy in three ethnic groups

Human narcolepsy-cataplexy, a sleep disorder associated with a centrally mediated hypocretin (orexin) deficiency, is tightly associated with HLA-DQB1*0602. Few studies have investigated the influence that additional HLA class II alleles have on susceptibility to this disease. In this work, 1,087 control subjects and 420 narcoleptic subjects with cataplexy, from three ethnic groups, were HLA typed, and the effects of HLA-DRB1, -DQA1, and -DQB1 were analyzed. As reported elsewhere, almost all narcoleptic subjects were positive for both HLA-DQA1*0102 and -DQB1*0602. A strong predisposing effect was observed in DQB1*0602 homozygotes, across all ethnic groups. Relative risks for narcolepsy were next calculated for heterozygous DQB1*0602/other HLA class II allelic combinations. Nine HLA class II alleles carried in trans with DQB1*0602 were found to influence disease predisposition. Significantly higher relative risks were observed for heterozygote combinations including DQB1*0301, DQA1*06, DRB1*04, DRB1*08, DRB1*11, and DRB1*12. Three alleles-DQB1*0601, DQB1*0501, and DQA1*01 (non-DQA1*0102)-were found to be protective. The genetic contribution of HLA-DQ to narcolepsy susceptibility was also estimated by use of lambda statistics. Results indicate that complex HLA-DR and -DQ interactions contribute to the genetic predisposition to human narcolepsy but that additional susceptibility loci are also most likely involved. Together with the recent hypocretin discoveries, these findings are consistent with an immunologically mediated destruction of hypocretin-containing cells in human narcolepsy-cataplexy.

Functional coupling and regional activation of human cortical motor areas during simple, internally paced and externally paced finger movements

We studied the activation and interaction of cortical motor regions during simple, internally paced and externally paced right-hand finger extensions in healthy volunteers. We recorded EEGs from 28 scalp electrodes and analysed task-related coherence, task-related power and movement-related cortical potentials. Task-related coherence reflects inter-regional functional coupling of oscillatory neuronal activity, task-related power reflects regional oscillatory activity of neuronal assemblies and movement-related cortical potentials reflect summated potentials of apical dendrites of pyramidal cells. A combination of these three analytical techniques allows comprehensive evaluation of different aspects of information processing in neuronal assemblies. For both externally and internally paced finger extensions, movement-related regional activation was predominant over the contralateral premotor and primary sensorimotor cortex, and functional coupling occurred between the primary sensorimotor cortex of both hemispheres and between the primary sensorimotor cortex and the mesial premotor areas, probably including the supplementary motor area. The main difference between the different types of movement pacing was enhanced functional coupling of central motor areas during internally paced finger extensions, particularly inter-hemispherically between the left and right primary sensorimotor cortexes and between the contralateral primary sensorimotor cortex and the mesial premotor areas. Internally paced finger extensions were also associated with additional regional (premovement) activation over the mesial premotor areas. The maximal task-related coherence differences between internally and externally paced finger extensions occurred in the frequency range of 20-22 Hz rather than in the range of maximal task-related power differences (9-11 Hz). This suggests that important aspects of information processing in the human motor system could be based on network-like oscillatory cortical activity and might be modulated on at least two levels, which to some extent can operate independently from each other: (i) regional activation (task-related power) and (ii) inter-regional functional coupling. We propose that internal pacing of movement poses higher demands on the motor system than external pacing, and that the motor system responds not only by increasing regional activation of the mesial premotor system, including the supplementary motor area, but also by enhancing information flow between lateral and mesial premotor and sensorimotor areas of both hemispheres, even if the movements are simple and unimanual.

Both primary motor cortex and supplementary motor area play an important role in complex finger movement

In order to clarify the roles played by the primary motor cortex and the supplementary motor area in the execution of complex sequential and simple repetitive finger movements, regional cerebral blood flow (rCBF) was measured with PET using 15O-labelled water in five normal subjects. The PET data of each individual subject co-registered to his own MRI, was analysed. Compared with the resting condition, the mean rCBF was markedly increased in the contralateral sensorimotor cortex (M1-S1) and moderately increased in the contralateral cingulate gyrus and putamen in both the simple and complex motor tasks. During the complex motor task, in addition to the above, the mean rCBF was markedly increased in the supplementary motor area and the contralateral premotor area, and moderately increased in the ipsilateral M1-S1 and cerebellum. In the supplementary motor area, there was a moderate rCBF increase also during the simple task. However, comparison of the mean rCBF increase against the resting condition between the two tasks revealed a greater increase during the complex task than in the other only in the supplementary motor area and the ipsilateral M1-S1. Thus, in agreement with our previous electrophysiological findings, not only the supplementary motor area but also the M1-S1 seems to play an important role in the execution of complex sequential finger movements.

Mesial motor areas in self-initiated versus externally triggered movements examined with fMRI: effect of movement type and rate

The human frontomesial cortex reportedly contains at least four cortical areas that are involved in motor control: the anterior supplementary motor area (pre-SMA), the posterior SMA (SMA proper, or SMA), and, in the anterior cingulate cortex, the rostral cingulate zone (RCZ) and the caudal cingulate zone (CCZ). We used functional magnetic resonance imaging (fMRI) to examine the role of each of these mesial motor areas in self-initiated and visually triggered movements. Healthy subjects performed self-initiated movements of the right fingers (self-initiated task, SI). Each movement elicited a visual signal that was recorded. The recorded sequence of visual signals was played back, and the subjects moved the right fingers in response to each signal (visually triggered task, VT). There were two types of movements: repetitive (FIXED) or sequential (SEQUENCE), performed at two different rates: SLOW or FAST. The four regions of interest (pre-SMA, SMA, RCZ, CCZ) were traced on a high-resolution MRI of each subject's brain. Descriptive analysis, consisting of individual assessment of significant activation, revealed a bilateral activation in the four mesial structures for all movement conditions, but SI movements were more efficient than VT movements. The more complex and more rapid the movements, the smaller the difference in activation efficiency between the SI and the VT tasks, which indicated an additional processing role of the mesial motor areas involving both the type and rate of movements. Quantitative analysis was performed on the spatial extent of the area activated and the percentage of change in signal amplitude. In the pre-SMA, activation was more extensive for SI than for VT movements, and for fast than for slow movements; the extent of activation was larger in the ipsilateral pre-SMA. In the SMA, the difference was not significant in the extent and magnitude of activation between SI and VT movements, but activation was more extensive for sequential than for fixed movements. In the RCZ and CCZ, both the extent and magnitude of activation were larger for SI than for VT movements. In the CCZ, both indices of activation were also larger for sequential than for fixed movements, and for fast than for slow movements. These data suggest functional specificities of the frontomesial motor areas with respect not only to the mode of movement initiation (self-initiated or externally triggered) but also to the movement type and rate.

Tissue engineering of complex tooth structures on biodegradable polymer scaffolds

Tooth loss due to periodontal disease, dental caries, trauma, or a variety of genetic disorders continues to affect most adults adversely at some time in their lives. A biological tooth substitute that could replace lost teeth would provide a vital alternative to currently available clinical treatments. To pursue this goal, we dissociated porcine third molar tooth buds into single-cell suspensions and seeded them onto biodegradable polymers. After growing in rat hosts for 20 to 30 weeks, recognizable tooth structures formed that contained dentin, odontoblasts, a well-defined pulp chamber, putative Hertwig's root sheath epithelia, putative cementoblasts, and a morphologically correct enamel organ containing fully formed enamel. Our results demonstrate the first successful generation of tooth crowns from dissociated tooth tissues that contain both dentin and enamel, and suggest the presence of epithelial and mesenchymal dental stem cells in porcine third molar tissues.

Mutagenicities of smoke condensates and the charred surface of fish and meat

Smoke condensates obtained from broiling fish showed mutagenic activity for Salmonella typhimurium TA100 and TA98. Metabolic activation was required to induce mutagenic activity of smoke condensates of some species of fish. The smoke condensate obtained during charcoal broiling of beefsteak was far less mutagenic than that of fish, with or without metabolic activation. Extracts of the charred surface of broiled fish and meat also contained mutagenic substances. These extracts needed metabolic activation to exhibit mutagenicities on TA98. The mutagenic activity of the smoke condensate obtained from one sardine weighing 100 g was equivalent to that of 132 micrograms benzo(a)pyrene and that of the charred surface of the sardine was equivalent to 358 micrograms benzo(a)pyrene. One piece of beefsteak weighing 190 g, contained mutagenic activity equivalent to that of 855 micrograns benzo(a)pyrene.

The functional neuroanatomy of simple and complex sequential finger movements: a PET study

The brain regions activated by simple repetitive and sequential finger movements of different length were localized by measuring regional cerebral blood flow (rCBF) with PET. The experimental design consisted of finger movements cued by auditory pacing at 0.5 Hz. In all conditions of different sequence length the contralateral primary sensorimotor and premotor cortex, supplementary motor area and ipsilateral cerebellar cortex were activated. These areas showed a large increase in activation from rest to simple repetitive movement, and a further increase with the shortest sequence, suggesting an executive role in running sequences. The ipsilateral premotor area (Brodmann area 6), bilateral posterior parietal areas (Brodmann area 7) and precuneus showed an increase in rCBF related only to the length of the sequences, without any change from rest to simple repetitive movement. These areas are more selectively related to sequence performance. This finding is consistent with the hypothesis that these areas function in the storage of motor sequences in spatial working memory. Our results suggest that sequential finger movements recruit discrete sets of brain areas with different functions.

Dynamic cortical involvement in implicit and explicit motor sequence learning. A PET study

We examined the dynamic involvement of different brain regions in implicit and explicit motor sequence learning using PET. In a serial reaction time task, subjects pressed each of four buttons with a different finger of the right hand in response to a visually presented number. Test sessions consisted of 10 cycles of the same 10-item sequence. The effects of explicit and implicit learning were assessed separately using a different behavioural parameter for each type of learning: correct recall of the test sequence for explicit learning and improvement of reaction time before the successful recall of any component of the test sequence for implicit learning. Regional cerebral blood flow was measured repeatedly during the task, and a parametric analysis was performed to identify brain regions in which activity was significantly correlated with subjects' performances: i.e. with correct recall of the test sequence or with reaction time. Explicit learning, shown as a positive correlation with the correct recall of the sequence, was associated with increased activity in the posterior parietal cortex, precuneus and premotor cortex bilaterally, also in the supplementary motor area (SMA) predominantly in the left anterior part, left thalamus, and right dorsolateral prefrontal cortex. In contrast, the reaction time showed a different pattern of correlation during different learning phases. During the implicit learning phase, when the subjects were not aware of the sequence, improvement of the reaction time was associated with increased activity in the contralateral primary sensorimotor cortex (SM1). During the explicit learning phase, the reaction time was significantly correlated with activity in a part of the frontoparietal network. During the post-learning phase, when the subjects achieved all components of the sequence explicitly, the reaction time was correlated with the activity in the ipsilateral SM1 and posterior part of the SMA. These results show that different sets of cortical regions are dynamically involved in implicit and explicit motor sequence learning.

Critical period for cross-modal plasticity in blind humans: a functional MRI study

The primary visual cortex (V1) in congenitally blind humans has been shown to be involved in tactile discrimination tasks, indicating that there is a shift in function of this area of cortex, but the age dependency of the reorganization is not fully known. To investigate the reorganized network, we measured the change of regional cerebral blood flow using 3.0 Tesla functional MRI during passive tactile tasks performed by 15 blind and 8 sighted subjects. There was increased activity in the postcentral gyrus to posterior parietal cortex and decreased activity in the secondary somatosensory area in blind compared with sighted subjects during a tactile discrimination task. This suggests that there is a greater demand for shape discrimination processing in blind subjects. Blind subjects, irrespective of the age at onset of blindness, exhibited higher activity in the visual association cortex than did sighted subjects. V1 was activated in blind subjects who lost their sight before 16 years of age, whereas it was suppressed in blind subjects who lost their sight after 16 years of age during a tactile discrimination task. This suggests that the first 16 years of life represent a critical period for a functional shift of V1 from processing visual stimuli to processing tactile stimuli. Because of the age-dependency, V1 is unlikely to be the "entry node" of the cortex for the redirection of tactile signals into visual cortices after blinding. Instead, the visual association cortex may mediate the circuitry by which V1 is activated during tactile stimulation.

Concomitant loss of dynorphin, NARP, and orexin in narcolepsy

BACKGROUND

Narcolepsy with cataplexy is associated with a loss of orexin/hypocretin. It is speculated that an autoimmune process kills the orexin-producing neurons, but these cells may survive yet fail to produce orexin.

OBJECTIVE

To examine whether other markers of the orexin neurons are lost in narcolepsy with cataplexy.

METHODS

We used immunohistochemistry and in situ hybridization to examine the expression of orexin, neuronal activity-regulated pentraxin (NARP), and prodynorphin in hypothalami from five control and two narcoleptic individuals.

RESULTS

In the control hypothalami, at least 80% of the orexin-producing neurons also contained prodynorphin mRNA and NARP. In the patients with narcolepsy, the number of cells producing these markers was reduced to about 5 to 10% of normal.

CONCLUSIONS

Narcolepsy with cataplexy is likely caused by a loss of the orexin-producing neurons. In addition, loss of dynorphin and neuronal activity-regulated pentraxin may contribute to the symptoms of narcolepsy.

Cerebral processes related to visuomotor imagery and generation of simple finger movements studied with positron emission tomography

Positron emission tomography was used to compare the functional anatomy of visual imagination and generation of movement. Subjects were asked to generate visual images of their finger movement in response to a preparatory signal. Four conditions were tested: in two, no actual movement was required; in the other two, a second signal prompted the subjects to execute the imagined movement. Which movement to imagine was either specified by the preparatory stimulus or freely selected by the subjects. Compared with a rest condition, tasks involving only imagination activated several cortical regions (inferoparietal cortex, presupplementary motor area, anterior cingulate cortex, premotor cortex, dorsolateral prefrontal cortex) contralateral to the imagined movement. Tasks involving both imagination and movement additionally increased activity in the ipsilateral cerebellum, thalamus, contralateral anteroparietal, and motor cortex and decreased activity in the inferior frontal cortex. These results support the hypothesis that distinct functional systems are involved in visuomotor imagination and generation of simple finger movements: associative parietofrontal areas are primarily related to visuomotor imagination, with inferior frontal cortex likely engaged in active motor suppression, and primary motor structures contribute mainly to movement execution.

A phylogenetically conserved stem-loop structure at the 5' border of the internal ribosome entry site of hepatitis C virus is required for cap-independent viral translation

Hepatitis C virus (HCV) initiates translation of its polyprotein under the control of an internal ribosome entry site (IRES) that comprises most of the 341-nucleotide (nt) 5' nontranslated RNA (5'NTR). A comparative analysis of related flaviviral sequences suggested that an RNA segment for which secondary structure was previously ill defined (domain II, nt 44 to 118) forms a conserved stem-loop that is located at the 5' border of the HCV IRES and thus may function in viral translation. This prediction was tested by a mutational analysis of putative helical structures that examined the impact of both covariant and noncovariant nucleotide substitutions on IRES activity in vivo and in vitro. Results of these experiments provide support for predicted base pair interactions between nt 44 to 52 and 111 to 118 and between nt 65 to 70 and 97 to 102 of the HCV 5'NTR. Substitutions at either nt 45 and 46 or nt 116 and 117 resulted in reciprocal changes in V1 nuclease cleavage patterns within the opposing strand of the putative helix, consistent with the predicted base pair interactions. IRES activity was highly dependent on maintenance of the stem-loop II structure but relatively tolerant of covariant nucleotide substitutions within predicted helical segments. Sequence alignments suggested that the deduced domain II structure is conserved within the IRESs of pestiviruses as well as the novel flavivirus GB virus B. Despite marked differences in primary nucleotide sequence within conserved helical segments, the sequences of the intervening single-stranded loop segments are highly conserved in these different viruses. This suggests that these segments of the viral RNA may interact with elements of the host translational machinery that are broadly conserved among different mammalian species.

Mechanisms underlying gait disturbance in Parkinson's disease: a single photon emission computed tomography study

Single photon emission computed tomography was used to evaluate regional cerebral blood flow changes during gait on a treadmill in 10 patients with Parkinson's disease and 10 age-matched controls. The subjects were injected with [99mTc]hexamethyl-propyleneamine oxime twice: while walking on the treadmill, which moved at a steady speed, and while lying on a bed with their eyes open. On the treadmill, all subjects walked at the same speed with their preferred stride length. The patients showed typical hypokinetic gait with higher cadence and smaller stride length than the controls. In the controls, a gait-induced increase in brain activity was observed in the medial and lateral premotor areas, primary sensorimotor areas, anterior cingulate contex, superior parietal cortex, visual cortex, dorsal brainstem, basal ganglia and cerebellum. The Parkinson's disease patients revealed relative underactivation in the left medial frontal area, right precuneus and left cerebellar hemisphere, whereas they showed relative overactivity in the left temporal cortex, right insula, left cingulate cortex and cerebellar vermis. This is the first experimental study showing that the dorsal brainstem, which corresponds to the brainstem locomotor region in experimental animals, is active during human bipedal gait. The reduced brain activity in the medial frontal motor areas is a basic abnormality in motor performance in Parkinson's disease. The underactivity in the left cerebellar hemisphere, in contrast to the overactivity in the vermis, could be associated with a loss of lateral gravity shift in parkinsonian gait.

Structural requirements for initiation of translation by internal ribosome entry within genome-length hepatitis C virus RNA

Cap-independent translation of hepatitis C virus (HCV) RNA is mediated by an internal ribosomal entry segment (IRES) located within the 5' nontranslated RNA (5'NTR), but previous studies provide conflicting views of the viral sequences which are required for translation initiation. These discrepancies could have resulted from the inclusion of less than full-length 5'NTR in constructs studied for translation or destabilization of RNA secondary structure due to fusion of the 5'NTR to heterologous reporter sequences. In an effort to resolve this confusion, we constructed a series of mutations within the 5'NTR of a nearly full-length 9.5-kb HCV cDNA clone and examined the impact of these mutations on HCV translation in vitro in rabbit reticulocyte lysates and in transfected Huh-T7 cells. The inclusion of the entire open reading frame in HCV transcripts did not lead to an increase in IRES-directed translation of the capsid and E1 proteins, suggesting that the nonstructural proteins of HCV do not include a translational transactivator. However, in reticulocyte lysates programmed with full-length transcripts, there were multiple aberrent translation initiation sites resembling those identified in some picornaviruses. The deletion of nucleotides (nt) 28-69 of the 5'NTR (stem-loop IIa) sharply reduced capsid translation both in vitro and in vivo. A small deletion mutation involving nt 328-334, immediately upstream of the initiator AUG at nt 342, also resulted in a nearly complete inhibition of translation, as did the deletion of multiple intervening structural elements. An in-frame 12-nt insertion placed within the capsid-coding region 9 nt downstream of the initiator AUG strongly inhibited translation both in vitro and in vivo, while multiple silent mutations within the first 42 nt of the open reading frame also reduced translation in reticulocyte lysates. Thus, domains II and III of the 5'NTR are both essential to activity of the IRES, while conservation of sequence downstream of the initiator AUG is required for optimal IRES-directed translation.

Expression of glucocorticoid receptor beta in lymphocytes of patients with glucocorticoid-resistant ulcerative colitis

BACKGROUND & AIMS

Recently, the glucocorticoid receptor beta (hGRbeta) was suggested to play a role as a dominant negative regulator for determining glucocorticoid response. The aim of this study was to clarify whether reverse-transcription polymerase chain reaction (RT-PCR) analysis of hGRbeta messenger RNA (mRNA) can predict the response to glucocorticoids in patients with ulcerative colitis.

METHODS

Total RNA obtained from peripheral blood mononuclear cells (PBMCs) of 23 patients with ulcerative colitis and 20 healthy volunteers was reverse transcribed; the resulting complementary DNA was amplified using specific primers for hGRalpha and hGRbeta. Protein expression of hGR in PBMCs was confirmed by immunoprecipitation-Western blot analysis.

RESULTS

The expression of hGRalpha mRNA (477 base pairs) was detected in all patients and all healthy volunteers. In contrast, a hGRbeta mRNA (366 base pairs) was detected in 1 (9.1%) of 11 glucocorticoid-sensitive patients, 10 (83.3%) of 12 glucocorticoid-resistant patients, and 2 (10%) of 20 healthy volunteers. The positive rate of hGRbeta mRNA in the resistant group was significantly higher than that in the sensitive group (P = 0.0019). The hGRbeta band could be detected by immunoprecipitation-Western blotting in hGRbeta mRNA-positive patients.

CONCLUSIONS

The results show that the expression of hGRbeta mRNA in PBMCs examined by RT-PCR may serve as a novel predictor of glucocorticoid response in ulcerative colitis.

A PET study of sequential finger movements of varying length in patients with Parkinson's disease

To study the difficulty that patients with Parkinson's disease have in performing long sequential movements, we used H2(15)O PET to assess the regional cerebral blood flow (rCBF) associated with the performance of simple repetitive movements, well-learned sequential finger movements of varying length and self-selected movements. Sequential finger movements in the Parkinson's disease patients were associated with an activation pattern similar to that found in normal subjects, but Parkinson's disease patients showed relative overactivity in the precuneus, premotor and parietal cortices. Increasing the complexity of movements resulted in increased rCBF in the premotor and parietal cortices of normal subjects; the Parkinson's disease patients showed greater increases in these same regions and had additional significant increases in the anterior supplementary motor area (SMA)/cingulate. Performance of self-selected movements induced significant activation of the anterior SMA/cingulate in normal subjects but not in Parkinson's disease patients. We conclude that in Parkinson's disease patients more cortical areas are recruited to perform sequential finger movements; this may be the result of increasing corticocortical activity to compensate for striatal dysfunction.

Redox regulation of MAPK pathways and cardiac hypertrophy in adult rat cardiac myocyte

OBJECTIVES

We analyzed the regulatory function of reactive oxygen species (ROS) on the hypertrophic signaling in adult rat cardiac myocytes:

BACKGROUND

The ROS regulate mitogenic signal transduction in various cell types. In neonatal rat cardiac myocyte, antioxidants have been shown to inhibit cardiac hypertrophy, and ROS are suggested to modulate the hypertrophic signaling. However, the conclusion may not reflect the situation of mature heart, because of the different natures between neonatal and adult cardiac myocytes.

METHODS

Cultured adult rat cardiac myocytes were stimulated with endothelin-1 (ET-1) or phenylephrine (PE), and intracellular ROS levels, the activities of mitogen-activated protein kinases (MAPKs; ERK, p38, and JNK), and 3H-phenylalanine incorporation were examined. We also examined the effects of antioxidant pretreatment of myocytes on MAPK activities and cardiac hypertrophy to analyze the modulatory function of redox state on MAPK-mediated hypertrophic signaling.

RESULTS

The ROS levels in ET-1- or PE-stimulated myocytes were maximally increased at 5 min after stimulation. The origin of ROS appears to be from NADH/NADPH oxidase, because the increase in ROS was suppressed by pretreatment of myocytes with NADH/NADPH oxidase inhibitor diphenyleneiodonium. Extracellular signal-regulated kinase (ERK) activity was increased by the stimulation of ET-1 or PE. In contrast, p38 and c-Jun-N-terminal protein kinase (JNK) activities did not change after these stimulations. Antioxidant treatment of myocytes suppressed the increase in ROS and blocked ERK activation and the subsequent cardiac hypertrophy induced by these stimuli.

CONCLUSIONS

These data demonstrate that ROS mediate signal transduction of cardiac hypertrophy induced by ET-1 or PE in adult rat cardiac myocytes.

Integrative visuomotor behavior is associated with interregionally coherent oscillations in the human brain

Coherent electrical brain activity has been demonstrated to be associated with perceptual events in mammals. It is unclear whether or not it is also a mechanism instrumental in the performance of sensorimotor tasks requiring the continuous processing of information between primarily executive and receptive brain areas. In particular it is unknown whether or not interregional coherent activity detectable in electroencephalographic (EEG) recordings on the scalp reflects interareal functional cooperativity in humans. We studied patterns of changes in EEG-coherence associated with a visuomotor force-tracking task in seven subjects. Interregional coherence of EEG signals recorded from scalp regions overlying the visual and the motor cortex increased in comparison to a resting condition when subjects tracked a visual target by producing an isometric force with their right index finger. Coherence between visual and motor cortex decreased when the subjects produced a similar motor output in the presence of a visual distractor and was unchanged in a purely visual and purely motor task. Increases and decreases of coherence were best differentiated in the low beta frequency range (13-21 Hz). This observation suggests a special functional significance of low frequency oscillations in information processing in large-scale networks. These findings substantiate the view that coherent brain activity underlies integrative sensorimotor behavior.

Enhanced lateral premotor activity during paradoxical gait in Parkinson's disease

Parkinson's disease (PD) patients often show marked improvement of hypokinetic gait when exposed to special stimuli. To investigate physiological mechanisms underlying this "paradoxical gait" induced by visual cues in PD patients, we examined regional cerebral blood flow changes during gait on a treadmill guided by two different visual cues, the lines oriented transversely to the direction of walk (TL) and the lines parallel to it (PL). Ten PD patients and 10 age-matched controls received injections of 99mTc-hexamethylpropyleneamine oxime twice, once during each walking condition. Brain perfusion images were obtained by single-photon emission computed tomography. When affected by TL, PD patients showed marked improvement of gait parameters, mainly reduction of cadence. In regional cerebral blood flow analysis, when TL was compared with PL, both groups had common activation in the posterior parietal cortex and cerebellar hemispheres. Especially in the right lateral premotor cortex, PD patients showed enhanced activation induced by TL to a significantly greater degree than the controls. The present study indicates that the network dedicated to visuomotor control, particularly the lateral premotor cortex, plays an important role in the development of the paradoxical gait induced by special visual stimuli in PD patients.