Tatsurou Kaminaga

Effects of carbon dioxide on preoptic thermosensitive neurons in vitro

Effects of carbon dioxide (CO2) on the firing rates of preoptic thermosensitive neurons were examined in rat brain slice preparations. The perfusing medium was saturated with gas mixtures consisting of 90% O2 and one of various concentrations (5%, 6.3%, 7.5%, and 10%) of CO2 balanced with N2. The medium containing 5% CO2 was used as control. Most preoptic neurons were inhibited during application of a high CO2 medium. An excitatory effect of CO2 on a small number of neurons was also significant, although this was weak and transient compared to the inhibitory effect. Thermosensitivities of the neurons did not correlate with their CO2 sensitivities. The influence of CO2 tended to be more evident at higher temperatures. We conclude that the direct effect of CO2 on PO thermosensitive neurons as well as on thermally insensitive neurons is mainly inhibitory.

Myocardial damage in patients with dilated cardiomyopathy : CT evaluation

Objective The purpose of this study was to evaluate myocardial damage in patients with dilated cardiomyopathy (DCM) by ultrafast CT (UFCT) and estimate the improvement of DCM. Materials and Methods Seventeen patients with DCM were examined with UFCT, cardiac catheterization, left ventriculography (LVG) with manometry, and thallium myocardial scintigraphy (SCINTI). The findings of each examination were compared with each other. Especially, UFCT findings were compared with LV function. Results Late enhancement, focal wall thinning, and fatty component were detected by UFCT as focal abnormal findings. Left ventricular segments with these findings on UFCT correlated well with asynergy on LVG (p < 0.01) and perfusion defects on SCINTI (p < 0.05). Patients with these findings on UFCT showed significantly lower LV ejection fractions (p < 0.05), higher LV end-diastolic pressure (p < 0.05), and a higher incidence of ventricular tachycardia (p < 0.05). Conclusion The focal myocardial abnormalities in DCM patients were well depicted with UFCT. Ultrafast CT was useful in estimating the severity of DCM and classifying the DCM patients.

Thermally induced salivary secretion in anesthetized rats

Effect of thermal stimulation on salivary secretion was examined in urethane anesthetized (i.p., 1.0 g/kg) rats. First, rectal temperature (Tre) was maintained at various levels by warming the whole trunk with a heating blanket. Copious salivary secretion occurred whenTre reached a threshold value above 40°C, which is considerably higher than the threshold for tail vasodilation. Local warming of the scrotum, face, or hypothalamus also elicited salivary secretion, but only ifTre was in a limited range just below the threshold temperature at whichTre alone would induce salivary secretion. The higher theTre within that limited range, the lower the temperature of the site locally warmed at which salivary secretion began. Changes in temperature of the abdomen, not including the scrotum, modulated the salivary secretion elicited by scrotal warming. Hypothalamic and scrotal temperatures interacted with each other to affect salivary secretion. Temperature signals from both core and periphery thus appear to be integrated in bringing about salivary secretion. Thermally induced salivary secretion may function as a basis for saliva spreading behavior observed in rats in a hot environment.

Sequential MR signal change of the thrombus in the false lumen of thrombosed aortic dissection

The evolution of thrombus in the false lumen was investigated in 14 patients with thrombosed aortic dissection, by reviewing the findings acquired at a total of 21 magnetic resonance imaging (MRI) examinations performed between 2 and 146 days after the onset. On electrocardiographic gated 1.5-Tesla MRI, T1-(TR/TE = 860 +/- 190 ms/17-40 ms) and T2-(TR/TE = 1620 +/- 240 ms/70-80 ms) weighted spin echo and gradient echo images were obtained, and the signal intensity of the thrombus on these images was evaluated independently by two observers. The density of the thrombus was also evaluated using computed tomography (CT) images obtained at a total of 54 examinations. On both T1- and T2-weighted images, the thrombus showed signal iso- or hypointensity compared to that of skeletal muscle during the first several days after the onset and, thereafter, showed signal intensity similar to that of fat tissue. It is suggested that the low signal intensity of the thrombus observed during the initial period after the onset was caused by the presence of deoxyhemoglobin and the high intensity observed thereafter was caused by methemoglobin. Focal discrepancy of the signal intensities within two parts of the lumen on spin echo images was observed in 7 patients, and a low-intensity layer on the surface of the thrombus inside the false lumen was observed on gradient echo images in 5 of these 7 patients. This characteristic MR signal change of the thrombus in the false lumen of thrombosed aortic dissection provides useful information concerning the age of the thrombus and in the differential diagnosis of the thrombus from a mural thrombus of aortic aneurysm.

Magnetic resonance imaging of pericardial malignant mesothelioma

Magnetic resonance imaging of pericardial malignant mesothelioma in two patients is reported. Magnetic resonance imaging clearly depicted the tumor location and expansion, and was useful in delineating the anatomic extent of pericardial malignant mesothelioma.

Detection of intramyocardial fatty components in patients with cardiac disease by ultrafast X-ray CT

To investigate intramyocardial fatty components as regards their distribution, frequency by disorder and cause, 331 patients with cardiac disease were examined with ultrafast X-ray CT (UFCT). The patient group consisted of 139 cases of myocardial infarction and angina, 27 cases of Kawasaki disease, 28 cases of hypertrophic cardiomyopathy (HCM), 22 cases of dilated cardiomyopathy (DCM), 3 cases of arrhythmogenic right ventricular dysplasia (ARVD), 40 cases of valvular disease, 33 cases of left ventricular hypertrophy due to hypertension, 17 cases of arrhthmia, 10 cases of cardiac sarcoidosis, 6 cases of myocarditis and 6 cases of congenital anomaly. Intramyocardial fatty components were detected in 15 patients (5 myocardial infarction, 2 Kawasaki disease, 3 HCM, 4 DCM, 1 ARVD). In patients with myocardial infarction, Kawasaki disease of DCM, the segments with fatty components agreed well with the segments with asynergy in left ventriculography and/or the segments with perfusion defects in thallium myocardial scintigraphy. The frequency of intramyocardial fatty components in each disease was initially determined as follows: 6% in myocardial infarction, 7% in Kawasaki disease, 11% in HCM and 18% in DCM. Ischaemic myocardial damage can induce intramyocardial fatty components in patients with myocardial infarction, Kawasaki disease or DCM.

Visualization of posture-dependent cerebral blood flow in a patient with Takayasu's disease by means of 99mTc-HMPAO brain single photon emission tomography.

A case of Takayasus disease in a 22-year-old woman who complained of severe fainting attacks is presented. Bilateral obstruction of the cervical arteries was confirmed by digital subtraction angiography. Preoperative technetium-99m hexamethylpropylene amine oxime brain SPET in the sitting position showed bilateral hypoactivity in the temporoparietal areas. Subtraction brain SPET showed slightly increased activity in the lying position. The patient has had no fainting attacks since bypass surgery. Postoperative 99mTc-HMPAO brain SPET in the sitting position showed normal activity except in the right temporoparietal area. This area was filled in the lying position. 99mTc-HMPAO brain SPET is the only technique that can visualize the cerebral blood flow in any position, this capability deriving on the fact that the distribution of 99mTc-HMPAO in the brain is fixed in the first 2–3 min following injection. The use of both sitting and lying 99mTc-HMPAO brain SPET is very useful for detecting an abnormality (i.e. an inhomogeneous response due to the fall in perfusion pressure) that could not be seen if the cerebral blood flow were to be assessed only in the lying position.

Clinical application of spontaneous red blood cell labeling with Tc-99m sodium pertechnetate.

Red blood cells (RBC) may be labeled with Tc-99m after Tc-99m sodium pertechnetate is injected in the presence of a reducing agent, such as stannous chloride. Thus, spontaneous RBC labeling with Tc-99m is expected to be seen in patients with a high plasma concentration of tin. Spontaneous RBC labeling with Tc-99m was obtained in a 73-year-old woman who was clinically diagnosed with tin intoxication and proved to have a high concentration of plasma tin. The RBC labeling rate was calculated as 96% with blood sampling. Spontaneous RBC labeling with Tc-99m is a very simple method for proving a high plasma tin concentration and is adaptable to clinical diagnosis.