Manabu Watanabe

Detection of nitric oxide production in lipopolysaccharide-treated rats by ESR using carbon monoxide hemoglobin

Release of nitric oxide (NO), from macrophages activated with E. coli lipopolysaccharide (LPS) and endothelial cells, has been proposed using chemiluminescence and spectrophotometry. However these methods can not distinguish NO from NO2-. The present study was aimed to prove in vivo production of NO, by ESR using CO-hemoglobin (HbCO) as a trapping agent of NO in the peritoneal cavity of rats treated with LPS. We detected a broad signal in the recovered HbCO solution. Inositol hexaphosphate induced a three-line hyperfine structure, characteristic of NO-hemoglobin (HbNO). In the arterial blood, ESR signal of HbNO with faint hyperfine structure was detected. NG-Monomethyl-L-arginine inhibited the formation of HbNO. HbNO was not detected in the peritoneal cavity of the LPS-untreated rat given i.p. both NO2- and HbCO. HbNO was, therefore, derived from NO, not from NO2-. These results show that free NO is produced in vivo by the stimulation of LPS.

Association of Plasma Homocysteine Concentration With Atherosclerotic Carotid Plaques and Lacunar Infarction

Background and Purpose— Higher plasma total homocysteine (tHcy) levels have been associated with carotid atherosclerosis and cerebral infarction in whites. However, data regarding such associations are limited for Asians. This study examined associations between tHcy levels and severity of carotid atherosclerosis in Japanese subjects. Additionally, because lacunar infarction is the most prevalent type of ischemic stroke in Japan, we also investigated its associations with tHcy levels. Methods— The subjects were 152 Japanese patients (age, 66.2±11.0 years) at our hospital. Using ultrasound, we evaluated severity of carotid atherosclerosis by plaque score, which is defined by the sum of all plaque (intima-media thickness ≥1.1 mm) height in bilateral carotid arteries. In 112 of 152 patients, the existence of lacunar infarction was evaluated on brain MRI scans. Results— A moderate linear association was found between tHcy levels and plaque score (r =0.48, P <0.0001). Moreover, tHcy level was associated with plaque score (&bgr;=0.26, P <0.001) independently of traditional atherosclerotic risk factors. In logistic regression analyses, each 1-&mgr;mol/L-higher tHcy level was associated with a 1.37-fold-higher [95% confidence interval (CI), 1.19 to 1.58] likelihood for lacunar infarction, increasing the likelihood by 1.22-fold (95% CI, 1.04 to 1.43) independently of traditional atherosclerotic risk factors. Conclusions— Higher tHcy levels appear to have associations with increased severity of carotid atherosclerotic plaques and prevalent lacunar infarction in the Japanese. Larger prospective studies are necessary to establish whether higher tHcy levels serve as a harbinger for insidious carotid and cerebrovascular diseases.

Intravital Microreflectometry of Individual Pial Vessels and Capillary Region of Rat

A microscopic reflectance spectrophotometer was constructed to obtain the spectra of single pial vessels and of a region containing only capillaries (capillary region). The difference in the oxygen saturation (So2) of hemoglobin between the regional arteriole and venule [R(A – V)] and that between the regional arteriole or capillaries [R(A – C)] were calculated. The reduction of cytochrome aa3 was also estimated in the capillary region. This method was applied to the brain surface of spontaneously breathing rats subjected to hypoxic and anemic hypoxia. On decreasing the inhaled O2 from 100 to 15%, elevation of R(A – V) and R(A – C) with slight arteriolar dilatation (though statistically not significant) was observed. Below 10% O2 (especially at 4 and 3% O2), the R(A – V) and R(A – C) decreased in spite of significant arteriolar dilatation with progressive reduction of cytochrome aa3, indicating suppression of oxygen transport to mitochondria. In the case of hemodilution down to 37% hematocrit (Ht), elevation of R(A – V) and R(A – C) occurred with a slight tendency toward arteriolar dilatation. Below 32% Ht, the R(A – V) decreased but the R(A – C) remained steady, while reduction of cytochrome aa3 progressed. Altogether, the So2 in the capillary region decreased and the reduction of cytochrome aa3 progressed with the decline of arteriolar O2 supply in both hypoxic and anemic hypoxia.

Synergistic stimulation of nitric oxide hemoglobin production in rats by recombinant interleukin 1 and tumor necrosis factor

Nitric oxide (NO) is formed from arginine in Escherichia coli lipopolysaccharide (LPS) treated rat; however, none of specific cytokine inducing NO generation is yet determined. We studied the effect of interleukin 1 (IL-1) and tumor necrosis factor (TNF) on NO production in rats by detecting NO-hemoglobin in their blood, using electron spin resonance. Either IL-1 or TNF alone stimulated NO-hemoglobin formation. Combined administration of IL-1 and TNF markedly enhanced NO-hemoglobin generation, demonstrating the synergistic character of both stimuli on NO production. Further, LPS and TNF in combination were more potent stimulator of NO-hemoglobin production in rats than each alone.

Imaging of distal internal carotid artery by ultrasonography with a 3.5-MHz convex probe.

Background and Purpose— Conventionally, carotid ultrasonography has been performed with a 7.5-MHz linear probe to evaluate the extracranial internal carotid artery (ICA). However, usually only the carotid bulb or proximal portion of the ICA can be evaluated. We attempted to evaluate the distal extracranial ICA with a 3.5-MHz convex probe. Methods— The subjects were 17 consecutive patients with ICAs free of occlusive disease and 3 other patients with distal extracranial ICA stenosis. Using a 7.5-MHz linear probe and a 3.5-MHz convex probe, we performed long-axis B-mode imaging of the ICAs to evaluate the distance between the distal limit of visualized ICA and the bifurcation of the common carotid artery. Results— The distal limit of the ICA, visualized with a 7.5- or a 3.5-MHz probe, was 31±11 or 57±8 mm distal to the common carotid artery bifurcation, respectively. In the 3 patients with distal extracranial ICA stenosis, the lesion could be successfully diagnosed with only the 3.5-MHz probe. Conclusions— This form of carotid imaging is feasible and may be potentially useful in the evaluation of carotid disease.

Transient Patchy Boundary Zone Hyperemia Following TIA Episode with Deep Hemispheric Ischemia: Serial HMPAO SPECT Study

Sirs: It is unquestionably important to know the sequential changes in regional cerebral blood flow (CBF) in patients suffering ischemic brain attack for predicting whether an episode would be reversible. The clinical prognostic value of early postischemic hyperperfusion (EPIH), occasionally detected as a hallmark of recanalization in the acute phase of ischemic stroke, has attracted much attention but still remains controversial [1–3]. Investigating temporal changes in regional cerebral blood flow (CBF) in the patients with transient ischemic attacks (TIAs) may afford a key insight, although there have as yet been only few reports [4] of EPIH early after an TIA episode. This is because of the short duration of neurological deficits and the limited availability of CBF measurement modalities such as single photon emission computed tomography (SPECT). Here, we report a case of prolonged TIA due to cardioembolism with unique patchy boundary zone hyperemia detected in serial CBF studies by 99mTc-labeled hexamethylpropyleneamine oxime (HMPAO) SPECT. A 75-year-old right-handed man suddenly presented with aphasia and progressive weakness of the right side of his body. Sick sinus syndrome and paroxysmal atrial fibrillation had been diagnosed at the age of 70 years. Informed consent to participate in the study was obtained from his family. Neurologically a right-sided hemiplegia, a right-sided sensory disturbance, conjugate deviation to the left, and global aphasia were observed, and his score on the Scandinavian Stroke Scale (SSS) at admission was only 2 points. In the first 1.5 h after onset 99mTcHMPAO neuro-SPECT showed severe and widespread hypoperfusion over the left middle cerebral artery (MCA) territories (Fig. 1, top row). At that time hemiparesis and sensory aphasia were still present (SSS 11 points). Just after the first SPECT the patient showed a dramatic improvement, without thrombolytic or antiplatelet therapy. Finally, 3.0 h after onset he had no neurological deficit or symptom (SSS was maximal 58 points). 99mTc-HMPAO SPECT scintigraphy was performed 20 min after intravenous injection of 740 MBq 99mTc-HMPAO on a dualheaded dedicated 99mTc-HMPAO neuro-SPECT detector utilizing FanBeam collimators. The transaxial slices were reconstructed by filtered backprojection with a Butterworth filter. Each reconstructed slice was corrected for tissue absorption by Chang’s method. SPECT performed 24 h after onset showed patchy hyperperfusion over the boundary areas of the left MCA territories (Fig. 1, middle row), and severely hypoperfused areas observed during TIA had completely disappeared. MRI 33 h after onset showed no definite abnormalities of the left hemisphere on T1weighted and T2-weighted images (Fig. 2). By 48 h after onset regional hyperperfused areas had returned to almost normal (Fig. 1, bottom row). Symmetrical mirror regions of interLETTER TO THE EDITORS

Impacts of Interface Energies and Transformation Strain from BCC to FCC on Massive-like δ-γ Transformation in Steel

Interface energies of δ/γ, γ/γ, δ/δ, L/δ, and L/γ interfaces, at first, as a function of misorientation were evaluated with an aid of atomistic simulations with embedded atom method. Then, under geometric constraints where grains or interfaces compete each other to minimize overall free energy, effective interface energies for those interfaces were quantified. It is found that neither the minimum nor effective δ/γ interface energies, 0.41 or 0.56 J/m2, respectively, is significantly higher than those of other interfaces including liquid/solid interfaces, but the δ/γ interface energy is significantly high for the small entropy change upon δ-γ massive-like transformation, resulting in significantly higher undercooling required for γ nucleation in the δ phase matrix than in solidification. Detachment of δ-phase dendrite tips away from γ-phase dendrite trunks can be explained only from a viewpoint of interface energy if small misorientationis introduced at the δ/γ interface from the perfect lattice matching between BCC and FCC crystal structures. Examining the BCC-to-FCC transformation strain on the γ nucleation in the massive-like transformation, the γ nucleation is prohibited 170 K or more undercooling is achieved unless any relaxation mechanism for the transformation strain is taken into account.