Biomedical subjects

Makoto Araki

Publications and source records attributed to Makoto Araki.

14 recordsLinked to original sources

PubMed2007

[Transcriptional regulation of metabolic switching PDK4 gene under various physiological conditions].

Pyruvate dehydrogenase kinase 4 (PDK4) phosphorylates and inactivates the pyruvate dehydrogenase complex to respond to physiologic conditions. This response switches the energy source from glucose to fatty acids to maintain blood glucose levels. Transcription of the PDK4 gene is activated by fasting or by the administration of a peroxisome proliferator-activated receptor alpha (PPARalpha) ligand in a tissue-specific manner. However, the two mechanisms to induce PDK4 mRNA as well as the relationship between the two have not been studied in detail. In this study, we show that the two mechanisms are independent, at least in the mouse skeletal muscle, and that estrogen-related receptor alpha (ERRalpha) is directly involved in the PPARalpha-independent transcriptional activation of the PDK4 gene with peroxisome proliferator-activated receptor gamma co-activator 1alpha (PGC-1alpha) as a specific partner. The latter conclusion is based on the following evidence: 1) Deletion and point mutation analyses of the cloned mouse PDK4 gene promoter sequence identified an exact possible ERRalpha-binding motif as the PGC-1alpha responsive element. 2) The overexpression of ERRalpha by cotransfection enhanced, and the knocking down of it by specific shRNAs diminished, the PGC-1alpha-dependent activation. 3) Specific binding of ERRalpha to the identified PGC-1alpha-responsive sequence of the mouse PDK4 promoter was confirmed in the electrophoresis mobility shift assay using anti-ERRalpha antibodies. These results suggest that PGC-1alpha plays an essential role not only in regulating the amounts of energy creating enzymes, but also at the step of metabolic switching with unevenly distributed tissue transcription factors such as ERRalpha in the skeletal muscle, thus harmonizing tissue-specific functions and energy metabolism.

Animals↗

PubMed2006

Identification of ERRalpha as a specific partner of PGC-1alpha for the activation of PDK4 gene expression in muscle.

Pyruvate dehydrogenase kinase 4 (PDK4) is a key regulatory enzyme involved in switching the energy source from glucose to fatty acids in response to physiological conditions. Transcription of the PDK4 gene is activated by fasting or by the administration of a PPARalpha ligand in a tissue-specific manner. Here, we show that the two mechanisms are independent, and that ERRalpha is directly involved in PPARalpha-independent transcriptional activation of the PDK4 gene with PGC-1alpha as a specific partner. This conclusion is based on the following evidence. First, detailed mutation analyses of the cloned PDK4 gene promoter sequence identified a possible ERRalpha-binding motif as the PGC-1alpha responsive element. Second, overexpression of ERRalpha by cotransfection enhanced, and the knockout of it by shRNAs diminished, PGC-1alpha-dependent activation. Third, specific binding of ERRalpha to the identified PGC-1alpha responsive sequence was confirmed by the electrophoresis mobility shift assay. Finally, cell-type-specific responsiveness to PGC-1alpha was observed and this could be explained by differences in the expression levels of ERRalpha, however, ectopic expression of ERRalpha in poorly responsive cells did not restore PGC-1alpha responsiveness, indicating that ERRalpha is necessary, but not sufficient for the response.

Animals↗

PubMed2006

[Effect of collateral circulation on myocardial protection in patients with acute myocardial infarction: comparison of technetium-99m-tetrofosmin myocardial single photon emission computed tomography and coronary angiography].

OBJECTIVES: Evaluation of myocardial blood flow from collateral vessels into the infarct area has been estimated by coronary angiography. In patients with acute myocardial infarction with Thrombolysis in Myocardial Infarction (TIMI) 0 flow, myocardial tracer uptake on single photon emission computed tomography (SPECT) images can predict the collateral blood flow in the infarct area if technetium (Tc)-99m-tetrofosmin was administered before recanalization. The present study investigated whether collateral blood flow evaluated by myocardial scintigraphy is a good predictor of myocardial salvage in patients with acute myocardial infarction. METHODS: The study group consisted of 30 patients (mean age 65 +/- 14 years, 23 males, 7 females) with first acute myocardial infarction and coronary angiography evidence of total occlusion (TIMI 0) within 12 hr after the onset. All patients had one vessel disease related to infarction and TIMI 3 flow after percutaneous coronary intervention (PCI). Tc-99m-tetrofosmin was injected intravenously before the PCI. The regional severity score index (RSSI) was obtained from SPECT using the 17 segment method with the four-point scoring system. Myocardial viability was evaluated by the RSSI obtained from thallium-glucose-insulin infusion SPECT after 1 week and regional wall motion score index obtained from echocardiography during the chronic phase. RESULTS: The patients were divided into two groups according to the angiographic collateral finding. There were no differences in RSSI on thallium-glucose-insulin SPECT and regional wall motion score between the good collateral group (n = 8) and poor collateral group (n = 22). Myocardial Tc-99m-tetrofosmin RSSI was similar in these groups. On the other hand, the patients were divided according to Tc-99m-tetrofosmin scintigraphic evaluation before PCI. RSSI on thallium-glucose-insulin SPECT was significantly greater (0.7 +/- 0.5 vs 1.5 +/- 0.4, p < 0.01) and regional wall motion score was significantly less (1.46 +/- 0.50 vs 2.08 +/- 0.78, p < 0.05) in the lower Tc-99m-tetrofosmin RSSI (< 1.9) group (n = 22) compared with the higher RSSI (> or = 1.9) group (n = 8). In addition, a significant correlation was obtained between Tc-99 m-tetrofosmin RSSI and regional wall motion score index (r = 0.53, p < 0.01). CONCLUSIONS: The collateral flow evaluated by scintigraphy was significantly correlated with myocardial viability.

Aged↗

PubMed2005

Decrease in excitability of LG following habituation of the crayfish escape reaction.

Crayfish escapes from threatening stimuli to the abdomen by tailflipping upwards and forwards. This lateral giant (LG)-mediated escape reaction habituates readily upon repetitive sensory stimulation. Using an isolated abdominal nerve cord preparation, we have analyzed the change in LG activity by applying additional sensory stimulation after different periods following habituation to characterize the retention of LG habituation. Results show that the LG mediated response habituates more quickly, but the retention time is shorter, as repetitive sensory stimulation is applied at progressively shorter inter-stimulus time intervals. The spike response of LG recovers quickly, within several minutes after habituation, but they fail to spike when an additional stimulus is applied after specific long periods following habituation. The critical period of the delay for this decrease in excitability of LG is dependent on the inter-stimulus time interval of the initial repetitive stimulus. As the inter-stimulus interval became longer, the delay needed for decrease in excitability became shorter. Furthermore, the local injection of 10(-6) mol l-1 octopamine into the neuropil just following habituation promotes the achievement of decrease in excitability. No effects were observed when 10(-6) mol l-1 serotonin and tyramine were injected. These results suggested octopamine promotes decrease in excitability of LG following habituation.

Animals↗

PubMed2005

Cyclic AMP mediates serotonin-induced synaptic enhancement of lateral giant interneuron of the crayfish.

The lateral giant (LG)-mediated escape behavior of the crayfish habituates readily on repetitive sensory stimulation. Recent studies suggested that the biogenic amines serotonin and octopamine modulate the time course of recovery and/or re-depression of the LG response after habituation. However, little is known of how serotonin and octopamine effect LG habituation and what second-messenger cascades they may activate. To investigate the effect of biogenic amines on LG habituation, serotonin and octopamine were superfused before presenting repetitive sensory stimulation. Serotonin and octopamine increased the number of stimuli needed to habituate the LG response. Their effects were mimicked by mixed application of a cAMP analogue [8-(4-chlorophenylthio)-cAMP (CPT-cAMP)] and a phosphodiesterase inhibitor [3-isobutyl-1-methylxanthine (IBMX)] but not by a cGMP analogue (8-bromoguanosine 3',5'-cyclic monophosphate). Perfusion of the adenylate cyclase inhibitor (SQ22536) abolished the effect of serotonin but not that of octopamine. To investigate the site of action of each biogenic amines in the neural circuit meditating LG escape, the effect of drugs on directly and indirectly elicited postsynaptic potentials in LG was investigated. Serotonin, octopamine, and a mixture of CPT-cAMP and IBMX increased both the direct and indirect synaptic inputs. Simultaneous application of SQ22536 abolished the effect of serotonin on both inputs but did not block the effect of octopamine. Direct injection of the cAMP analogue (Sp-isomer of adenosine-3',5'-cyclic monophosphorothioate) into LG increased both the direct and indirect inputs to LG. These results indicate that serotonin mediates an increase in cAMP levels in LG, but octopamine acts independently of cAMP and cGMP.

1-Methyl-3-isobutylxanthine↗

PubMed2005

Behavioral and electrophysiological experiments suggest that the antennular outer flagellum is the site of pheromone reception in the male helmet crab Telmessus cheiragonus.

Sexually competent females of Telmessus cheiragonus (helmet crab) release two pheromones that elicit grasping and copulation behaviors in males (Kamio et al., 2000, 2002, 2003). Our study aimed to use behavioral and electrophysiological techniques to identify the site of reception of these sex pheromones. In behavioral experiments, either the inner or the outer flagella of the antennules were ablated bilaterally from male crabs, and responses of male crabs to female odor were examined. When the inner flagella were surgically ablated, the sexual response (i.e., grasping and copulation behavior) of male crabs was not significantly changed relative to control animals that had their second antennae ablated. In contrast, the sexual response was significantly reduced when the outer flagella of the antennules were ablated, suggesting that the outer flagellum is the receptor organ that detects the sex pheromones. In electrophysiological experiments, urine, which in females contains the pheromone that elicits grasping behavior by males but does not contain the pheromone eliciting copulation, whose release site is not known, was tested. Female and male urine as well as shrimp extract evoked phasic responses of chemosensory afferents innervating aesthetasc sensilla on the outer flagellum of male crabs. The response of the afferents had significantly higher magnitude and lower threshold when female urine was applied. Thus, behavioral and electrophysiological observations suggest that in male helmet crabs, the outer flagellum of the antennule is the chemosensory organ that detects female sex pheromone.

Animals↗

PubMed2004

Distribution of glutamatergic immunoreactive neurons in the terminal abdominal ganglion of the crayfish.

Using an antiserum directed against glutamate, we have analyzed the distribution of glutamate-like immunoreactive neurons in the terminal abdominal ganglion of the crayfish Procambarus clarkii. Approximately 160 central neurons (157 +/- 8; mean +/- SEM, n = 8) showed positive glutamate-like immunoreactivity, which represents approximately 25% of the total number of neurons in the terminal ganglion. Using a combination of intracellular staining with the marker Lucifer yellow and immunocytochemical staining has shown that most excitatory motor neurons are glutamatergic and that glutamate acts as an excitatory transmitter at peripheral neuromuscular junctions. Seven of 10 identified spiking local interneurons and only 2 of 19 identified ascending interneurons, showed positive immunoreactivity. Our observation that inhibitory spiking interneurons were immunopositive, whereas excitatory ascending interneurons were immunonegative, indicates that glutamate is likely to act as an inhibitory neurotransmitter within the central nervous system. Local pressure injection of L-glutamate into the neuropil of the ganglion caused a hyperpolarization of the membrane potentials of many interneurons. gamma-Aminobutyric acid (GABA)ergic posterolateral nonspiking interneurons and the bilateral nonspiking interneuron LDS showed no glutamate-like immunoreactivity, whereas non-GABAergic anterolateral III nonspiking interneurons showed glutamate-like immunoreactivity. Thus, not only GABA but also glutamate are used in parallel as inhibitory neurotransmitters at central synapses.

Abdomen↗

PubMed2004

Nitric oxide modulates local reflexes of the tailfan of the crayfish.

Electrical stimulation of sensory neurons that innervate receptors on the tailfan of crayfish evokes a reflex response of motor neurons that produce movements of the blades of the tailfan, the uropods. We analyzed the modulatory effects of nitric oxide (NO) on the spike frequency of the reflex response. Bath application of L-arginine and SNAP, which elevate endogenous and exogenous NO levels, increased the frequency of the evoked response, whereas the application of L-NAME and PTIO, which reduce NO levels, decreased the frequency of the response. To determine through what pathway and target NO exerted these effects we bath applied ODQ, an inhibitor of soluble guanylyl cyclase (sGC), which decreased the frequency of response, and 8-br-cGMP, which increased the spike frequency of response. To provide further evidence that NO acts via sGC, we elevated NO levels with L-arginine while simultaneously inhibiting sGC with ODQ. This application reduced the response to control levels, indicating that NO in the terminal ganglion of crayfish acts via sGC to modulate cGMP levels, which in turn regulate the responses of the uropod motor neurons.

Analysis of Variance↗

PubMed2004

Effects of nitric oxide on proprioceptive signaling.

We have analysed the effects of the neuromodulator nitric oxide (NO) on proprioceptive information processing by ascending intersegmental interneurons that form part of the local circuits within the terminal abdominal ganglion of the crayfish. NO modulates the synaptic inputs to ascending interneurons, enhancing the amplitude of class I interneurons and reducing the amplitude of class II interneurons. Repetitive proprioceptive stimulation leads to rapid depression in a specific set of identified interneurons but not in others. Bath application of a nitric oxide scavenger, PTIO, causes a significant decrease in the rate of depression of the interneurons showing a rapid depression, independent of interneuron class, but has no effect on the dynamic responses of the interneurons that show little initial depression. These results indicate that NO exerts multiple effects at the very first stage of synaptic integration in local circuits.

Animals↗

PubMed2004

Monitoring of dnaK gene expression in Porphyromonas gingivalis by oxygen stress using DNA microarray.

Porphyromonas gingivalis, a Gram-negative anaerobe associated with adult periodontitis, expresses numerous potential virulence factors. dnaK, a member of the heat shock protein family, functions as a molecular chaperone and plays a role in microbial pathogenicity. However, little is known regarding its gene expression caused by oxygen stress in P. gingivalis. In the present study, a custom-made DNA microarray was designed and used to monitor dnaK gene expression in P. gingivalis caused by oxygen stress. The results demonstrated that dnaK mRNA was up-regulated in a short time, and the DNA microarray results were confirmed by real-time polymerase chain reaction analysis. These findings suggest that oxygen stress stimulates gene expression of dnaK and may have a relationship to the aerotolerance activity of this organism as well as its expression of pathogenesis.

Adenosine Triphosphatases↗

PubMed2003

Assessment of clinical features in transient left ventricular apical ballooning.

OBJECTIVES: We sought to assess the clinical features of transient left ventricular (LV) apical ballooning. BACKGROUND: Although several cases regarding transient LV apical ballooning have been reported, the etiology remains unknown. METHODS: We investigated 17 patients (14 women, median age 74 years old with a range of 54 to 91 years old) who fulfilled the following criteria: 1) transient LV apical ballooning; 2) ST-T segment change in several leads in electrocardiogram; and 3) no history of old myocardial infarction, valvular heart disease, subarachnoid hemorrhage, or pheochromocytoma. RESULTS: Emotional and physical stress were observed in 16 patients (94%). Technetium-99m tetrofosmin tomographic imaging revealed decreased uptake at the apex of the left ventricle in 11 patients (85%) that later returned to uniform. No significant stenosis or angiographical slow flow in epicardial coronary arteries was observed (n = 9). Provocative focal vasospasm was induced in only one patient (14%) (n = 7). Moreover, no significant abnormality in the coronary microcirculation was detected by Doppler guidewire (n = 3) or contrast echocardiography (n = 1). No patients showed a rise in viral antibody titers. Biopsy specimens revealed interstitial fibrosis in six patients (100%) and slight cell infiltration in three others (50%) (n = 6). CONCLUSIONS: These findings suggested that neither abnormalities in the coronary circulation nor acute myocarditis was related to the etiology. Although neurogenic stunned myocardium induced by emotional or physical stress was suggested as the etiology, further investigations are necessary.

Aged↗

PubMed2003

[Usefulness of technetium-99m tetrofosmin single-photon emission computed tomography for short-term risk stratification in patients with acute chest pain in the emergency room].

OBJECTIVES: High-risk patients with acute coronary syndrome are difficult to distinguish from low-risk patients with chest pain in the emergency room. Technetium-99m (99mTc) tetrofosmin single-photon emission computed tomography (SPECT) was investigated to exclude high-risk patients with chest pain in the emergency room. METHODS: 99mTc-tetrofosmin SPECT was evaluated using a four-point scoring system in 228 patients (144 men, 84 women, mean age 68 +/- 12 years) with chest pain. Negative was defined as the myocardial segments with a defect score (DS) of < 2. The patients were divided into two groups; the negative group with DS < 2 (n = 78) and the positive group with DS > or = 2 (n = 150). Cardiac events (cardiac death, acute myocardial infarction and refractory angina) were evaluated within 30 days of onset. ST-segment elevation or depression > or = 0.1 mV was defined as positive in electrocardiography. The results of SPECT were compared with those of electrocardiography, transthoracic echocardiography and serum cardiac markers (troponin T and creatine kinase-MB) in 95 patients. RESULTS: The negative group had very few cardiac events (three patients with refractory angina) (3.8%). The negative predictive value of cardiac events evaluated by electrocardiography was calculated as 83.1%, whereas the negative predictive value by SPECT was 96.2% (p < 0.01). In addition, the negative predictive value of acute myocardial infarction by SPECT was 100%. The negative predictive values of cardiac events evaluated by SPECT, electrocardiography, transthoracic echocardiography and serum cardiac markers were 95.8%, 81.5% (vs 99mTc-tetrofosmin; NS), 84.9% (NS) and 60.4% (p < 0.05), respectively. CONCLUSIONS: 99mTc-tetrofosmin SPECT is a useful method to exclude high-risk patients among patients with chest pain in the emergency room.

Aged↗

PubMed2002

Basic fibroblast growth factor protects cardiac myocytes from iNOS-mediated apoptosis.

Basic fibroblast growth factor (bFGF) is an important angiogenic factor produced by hearts subjected to ischemia. However, the direct effects of bFGF on myocardial cells are unknown. Primary cultured cardiac myocytes from neonatal rats were stimulated with lipopolysaccharide (LPS), a potent inducer of inducible nitric oxide synthase (iNOS), in the presence or the absence of bFGF. LPS induced the expression of iNOS in cardiac myocytes, demonstrated at both mRNA and protein levels. We showed that LPS activated the apoptotic pathway, evidenced by TUNEL staining, DNA ladder formation, and morphologic features. LPS-induced apoptosis was blocked by the administration of L-NAME, an inhibitor of NOS. This indicates that LPS induces apoptosis via an iNOS-dependent pathway. Administration of bFGF completely inhibited myocardial cell apoptosis induced by hydrogen peroxide or acidic medium as well as LPS. To determine signaling pathways for this inhibitory effect, we utilized PD098059, an MEK-1-specific inhibitor. PD098059 blocked bFGF-induced activation of ERK (extracellularly responsive kinase)-1/2 and neutralized the apoptotic inhibitory effect of bFGF. These findings demonstrate that LPS induces myocardial cell apoptosis in an iNOS-dependent manner. The results also suggest that bFGF is a protective factor against myocardial cell apoptosis and that this protection requires the MEK-1-ERK pathway.

Animals↗

PubMedDate not supplied

Noninvasive assessment of coronary microvascular dysfunction using Tc-99m tetrofosmin SPECT in patients with acute myocardial infarction.

BACKGROUND: We investigated whether technetium 99m tetrofosmin (TF) single photon emission computed tomography (SPECT) could predict coronary microvascular dysfunction in patients with acute myocardial infarction. METHODS AND RESULTS: We obtained the regional severity score index (TF-RSSI) using TF SPECT immediately after percutaneous coronary intervention in 25 patients with acute myocardial infarction. Using a Doppler guidewire, we evaluated the deceleration time of diastolic flow velocity (DDT) after percutaneous coronary intervention, and DDT of 600 milliseconds or less was suggested to be an indicator of coronary microvascular dysfunction. Moreover, the chronic regional wall motion score index (RWMSI) was obtained from echocardiography during the chronic phase. There was a good correlation between TF-RSSI and DDT (r = -0.68, P < .01). The optimal cutoff value of TF-RSSI to predict DDT of 600 milliseconds or less was defined as 1.9 or greater (sensitivity, 1.00; specificity, 0.71). The group with poor scintigraphic coronary microvascular function (TF-RSSI > or =1.9, n = 7) demonstrated a significantly shorter DDT (P = .0003), a lower frequency of early systolic retrograde flow (P = .0038), and greater chronic RWMSI (P = .0015) than the group with good scintigraphic coronary microvascular function (TF-RSSI <1.9, n = 15). CONCLUSIONS: Analysis of TF SPECT immediately after percutaneous coronary intervention in patients with acute myocardial infarction is a useful noninvasive method for evaluating coronary microvascular dysfunction.

Adult↗