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Biomedical subjects

T Asakura

Publications and source records attributed to T Asakura.

At least 235 records · Page 13Linked to original sources
PubMed1991

Absorption and metabolism of pyridoxamine in mice. I. Pyridoxal as the only form of transport in blood.

[3H]Pyridoxamine was orally administered to mice in physiological amounts, and the distribution of isotope between the six recognized forms of vitamin B6 and pyridoxic acid was determined at different times in the intestine, liver, blood, and brain. After 7 min about 50% of the radioactivity in pyridoxamine had been absorbed by the intestine and transported to the blood and other organs. Labeled pyridoxal phosphate was found in the intestine and liver. Labeled pyridoxamine could not be detected in the peripheral blood, but substantial amounts of labeled pyridoxal and pyridoxal phosphate were found in the blood. However, when a large amount (40-140 nmol) was given, a significant amount of labeled pyridoxamine was found in the blood, together with labeled pyridoxal and pyridoxal phosphate. These results suggest that the intestine and/or liver play a major role in completely converting physiological amounts of pyridoxamine to circulating pyridoxal, which is then taken up and phosphorylated by other organs.

Absorption↗
PubMed1991

Measurement of blood flow velocity in retinal vessels utilizing laser speckle phenomenon.

The laser speckle phenomenon was applied to the measurement of the blood flow velocity in glass capillary tubes and human retinal vessels. The instrument consists of a fundus camera, a He-Ne laser, a photomultiplier, a photon-counting unit, a digital correlator, and a microcomputer system. The scattered laser beam from the retina was detected by the photomultiplier and these signals were processed by the photon-counting unit. The digital correlator and the microcomputer calculated the autocorrelation function of these processed signals. The power of the laser beam was 18 mW/cm2, which was sufficiently below the minimum level considered hazardous to the retina. This technique did not require fine optical alignment and the measurement could be done in 1.05 seconds. A linear relationship between the blood flow velocities in glass capillary tubes and the reciprocal of the correlation time was proved, and the pulsatile flow of a human retinal artery was demonstrated. The reproducibility of the method was 12.4 +/- 6.5% in arteries (Mean +/- SD, n = 4) and 12.4 +/- 5.1% in veins (Mean +/- SD, n = 16). The mean blood flow rate in retinal vessels obtained in this experiment agreed with the values of previous studies. This technique utilizing the laser speckle phenomenon is useful in clinical application to measure the retinal blood flow velocity.

Adult↗
PubMed1991

[Spinal artery aneurysm associated with dural AVM of the posterior fossa].

The incidence of an aneurysm of the spinal artery is extremely rare. Only several cases have been documented previously. Herewith, the authors present a patient with a ruptured aneurysm of the anterior spinal artery associated with dural AVM of the posterior fossa. A 51-year-old male had a sudden onset of occipital headache and left shoulder pain. Lumbar puncture revealed bloody CSF. Angiography showed a saccular aneurysm, filling from the anterior spinal artery and dural AVM of the posterior fossa. Aneurysmal neck clipping and cauterization for nidus of dural AVM was performed successfully through suboccipital craniectomy with laminectomy of C1 and C2. The authors reviewed the literature and discussed the features of the aneurysm of a spinal artery.

Aneurysm↗
PubMed1991

[Clinical application of total body retrograde perfusion to aortic dissection operation].

Open distal anastomosis technique proposed by Cooley facilitates operative management of aortic dissection. Usually this procedure is performed under circulatory arrest, therefore, prolonged management is hazardous to cerebral and visceral organ systems. We have utilized profound hypothermia with total body retrograde perfusion: 1) myocardial protection through coronary sinus, 2) cerebral perfusion through superior vena cava with pretreatment of cerebral protective drugs, 3) abdominal visceral perfusion through inferior vena cava). We have obtained good results with this method in consecutive four patients with aortic dissection.

Adolescent↗
PubMed1991

[A report of a transsphenoidal operation during pregnancy for a pituitary adenoma].

A 29-year old female, in her second pregnancy, complained of headache, nausea, vomiting and left blurred vision. In spite of improvement of these symptoms in the second postpartum, she complained of recurrent symptoms in her third pregnancy. CT and MRI showed a pituitary adenoma with hematoma. It was totally removed using the transsphenoidal approach during pregnancy at 8 months. The histological examination revealed that the tumor was an acidophilic adenoma with a hemorrhagic change. A healthy baby was born at the full term after the operation. Our transsphenoidal operation during pregnancy was only the second such attempt reported in our collected literature. The management of the pituitary tumor during pregnancy is discussed.

Adenoma↗
PubMed1991

Morphology of sickle cells produced in solutions of varying osmolarities.

The effect of varying osmolarities (0.6% to 1.5% NaCl solutions, 213 to 492 mOsm/kg H2O) on the morphology of deoxygenated sickle cells was studied quantitatively with a computer-assisted image analysis system. Discocyte-rich, less dense fractions of sickle cells (density less than or equal to 1.11) were suspended in buffered NaCl solutions (pH 7.4) of various osmolarities, deoxygenated at room temperature for up to 5 hours, and stained by Wright's solution. Microscopic images were analyzed by circular shape factor (CSF = 4 pi x [area]/[perimeter]2) and elliptical shape factor (ESF = [short axis]/[long axis]). Since these two parameters yield different values for elongated cells and for cells of other shapes, such as maple-leaf- or star-shaped cells, the morphologic changes of sickle cells can be analyzed numerically. We found that both the rate and the degree of deformation depended highly on the osmotic pressure of the media in which the cells were suspended. In hypertonic solution, most sickle cells assumed a maple-leaf shape. The deformation occurred quickly, but the degree of deformation (circular shape factor and elliptical shape factor) was lower than that found in isotonic and slightly hypotonic solutions. Although elongated cells were formed in hypotonic and isotonic solutions, deformation was slower in these solutions than in hypertonic solutions. These results indicate that the shape and the degree of deformation of deoxygenated sickle cells are highly dependent on the osmolarity of the suspending medium and that the rate of deformation is inversely related to osmolarity. The relationship between morphology of deoxygenated sickle cells and osmotic pressure of the suspending media is discussed.

Buffers↗
PubMed1991

[Direct surgical management of aneurysms in the cavernous sinus: a report of 5 cases].

Five patients with aneurysms in the cavernous sinus were treated by direct surgical approach. Two small aneurysms were located in the C3 segment, one small aneurysm was on the primitive trigeminal artery (PTA), and the last two aneurysms were giant ones. The three small aneurysms were discovered incidentally by angiography and the two giant aneurysms presented oculomotor palsy. After ordinary fronto-temporal craniotomy, the two C3 aneurysms were treated through an intradural approach, and the PTA aneurysm and the two giant aneurysms were treated through combined epi- and subdural approach. The three small aneurysms were clipped and the two giant aneurysms were trapped with the reconstruction of ICA by saphenous veins. In all cases the aneurysms were excluded postoperatively, but in one giant-aneurysm case (Case 5) the bypass was occluded postoperatively, but the patient had no permanent neurological deficit. The four patients developed third nerve palsy and one developed fourth nerve palsy which resolved within 3 to 6 months. In one C3-aneurysm case (case i) the patient had loss of vision due to much packing in the medial side of the ICA. All patients were discharged and returned to their usual life. Three cases (case 2, 4, 6) are presented here and the problems of direct surgical management of aneurysms in the cavernous sinus are discussed with the related literature.

Adult↗
PubMed1991

[The significance of internal thoracic artery-left anterior descending coronary artery bypass grafting in postoperative angiographic studies--with reference to indication of ITA and factors of string sign].

Internal thoracic artery (ITA) graft for myocardial revascularization has shown superior long-term patency. However, several reports pointed out that the flow capacity of ITA was questionable and the string sign of ITA graft was sometimes observed in the findings of postoperative angiography when the stenosis of the coronary artery was of a lesser degree. We studied pre- and postoperative angiographic findings of 101 patients who underwent ITA grafting to the left anterior descending coronary artery. Postoperative angiography showed that the blood flow from the ITA graft ran through the site of anastomosis only towards the distal end when preoperative stenosis of the native left anterior descending coronary was less than 75%. ITA flow ran bidirectionally (retrogradely and antegradely) when stenosis was within 75 to 90%. Many cases with stenosis of greater than 90% showed the progression of the native lesion, that is, total obstruction of the left anterior descending coronary artery. It becomes clear by statistical study that the postoperative progression of native proximal lesion of the left anterior descending coronary artery correlates neither with the morphological state of the coronary artery nor sites of lesions, but the severity of stenosis. A conclusion has been drawn from angiographic study, that the blood flow from the ITA graft run into two directions; towards the distal and the lesion of the left anterior descending coronary artery, if the free flow through ITA was about 60 ml/min and at the same time, preoperative stenosis of coronary artery was 75% or more.

Adult↗
PubMed1991

In vitro modeling of the magnetic resonance appearance of cerebral hemorrhage.

In vitro studies provide a framework for understanding the biophysical mechanisms in the evolution of the magnetic resonance (MR) appearance of cerebral hematomas. Varying concentrations of oxyhemoglobin, deoxyhemoglobin and methemoglobin in saline or in concentrated bovine serum albumin solutions were imaged at 1.5 T, allowing assessment of the relative relaxation effects of heme oxidation state, oxygenation, and protein concentration. The findings demonstrate the importance of susceptibility effects arising from local field heterogeneity in producing T2 shortening upon varying hemoglobin concentration for intracellular deoxyhemoglobin and methemoglobin. Correlation between the clinically observed MR appearance of acute and subacute hematomas with these in vitro models is presented.

Brain↗
PubMed1990

Characterization of two types of fetal hemoglobin: alpha 2G gamma 2 and alpha 2A gamma 2.

The effect of differences in G gamma and A gamma fractions of fetal hemoglobin (HbF) on the kinetics of polymerization of HbS-HbF mixtures was studied. We also examined their effect on oxygen affinity, surface hydrophobicity, mechanical stability, and solubility of HbF. Differences in G gamma:A gamma ratio did not affect the polymerization of mixtures of HbF and HbS, suggesting that the inhibitory effect of HbF on the polymerization of HbS is independent of the G gamma:A gamma ratio of HbF and is totally dependent on the fraction of HbF in the mixture. The oxygen equilibrium curve of HbF was not affected by differences in the ratios of G gamma and A gamma in HbF. In contrast, surface hydrophobicity, mechanical stability, and solubility of HbF were affected by differences in the G gamma:A gamma ratio. The higher the G gamma:A gamma ratio, the smaller the elution volume on a TSK Gel SW hydrophobic column in high phosphate buffer. The mechanical stability of HbF was also dependent on the ratio of G gamma:A gamma; stability was greater at higher fractions of A gamma. Differences in the G gamma:A gamma ratio also affected solubility of HbF: HbF containing the higher fraction of G gamma was the more soluble. These data indicate that although alanine at the 136th position of the gamma chains has a stronger surface hydrophobicity than does glycine, this difference does not affect either the polymerization of HbS or the oxygen affinity of HbF.

Alanine↗
PubMed1990

Human sickle hemoglobin in transgenic mice.

DNA molecules that contain the human alpha- and beta s-globin genes inserted downstream of erythroid-specific, deoxyribonuclease I super-hypersensitive sites were coinjected into fertilized mouse eggs and a transgenic mouse line was established that synthesizes human sickle hemoglobin (Hb S). These animals were bred to beta-thalassemic mice to reduce endogenous mouse globin levels. When erythrocytes from these mice were deoxygenated, greater than 90 percent of the cells displayed the same characteristic sickled shapes as erythrocytes from humans with sickle cell disease. Compared to controls the mice have decreased hematocrits, elevated reticulocyte counts, lower hemoglobin concentrations, and splenomegaly, which are all indications of the anemia associated with human sickle cell disease.

Anemia, Sickle Cell↗
PubMed1990

Magnetic resonance study of brain oedema induced by cold injury--changes in relaxation times before and after the administration of glycerol.

Experiments were carried out to determine the ability of magnetic resonance systems to assess change in relaxation times following the induction of experimental brain oedema and subsequent administration of hypertonic glycerol. Nine small mongrel dogs were used for these experiments. Twenty-four hours after producing a cold lesion, magnetic resonance (MR) studies were performed and physiological data were measured. Thirty min after beginning the administration of glycerol, serum osmotic pressure was raised 88 mOsm/l. After administering glycerol a small reduction in long spin echo images was observed in the periventricular high intensity area. The T1 and T2 values appeared to be decreased from 30 min after glycerol administration. This decrease continued until the period of observation ended. Statistically significant changes in the T2 values, especially in the white matter of the opposite side, were seen. The changes in T1 were generally not statistically significant. We conclude that the changes in water content of the oedematous brain following the administration of glycerol can be detected by magnetic resonance systems, that these changes become appreciable 30 min after administration of glycerol and continue at least two more hours, and that the changes in T2 were larger than those in T1.

Animals↗
PubMed1990

Magnetic resonance studies in human brain oedema following administration of hyperosmotic agents. Special references to relaxation times and proton MRS.

Changes of proton relaxation times (T1 and T2) and proton Magnetic Resonance Spectroscopy (MRS) were studied in patients with brain oedema following administration of hyperosmotic agents. Relaxation times of oedema tended to decrease following infusion of hyperosmotic agents. In most patients examined, changes of relaxation times tended to achieve their lowest value at 30-60 minutes after infusion. However, the changes of relaxation times were not uniform. In some patients, relaxation times continued to decrease for more than 2 hours, while in other patients relaxation times which had earlier decreased subsequently had increased at 2 hours. The peak of water components, obtained by SIDAC (Spectroscopic Imaging by Dephasing Amplitude Changing) method was observed to change as did relaxation times. Changes of relaxation times and the peak of water components, obtained by SIDAC (Spectroscopic Imaging by Dephasing Amplitude Changing) method was observed to change as did relaxation times. Changes of relaxation times and the peak of water component may vary depending upon factors including the kinds of lesions causing oedema, phase of oedema (acute or chronic), etc. Proton relaxation times and the peak of water component obtained by proton MRS were useful in evaluating the changes of oedematous area.

Body Water↗
PubMed1990

Early detection of cerebral infarction by 31P spectroscopic imaging.

Recent advances in magnetic resonance spectroscopy permit noninvasive study of brain metabolism in vivo, 31P spectroscopic imaging being the method for evaluation of localized phosphorous metabolism. Experimentally, an ischemic-hypoxic brain insult is characterized by depletion of high energy metabolites. These changes are seen immediately after an ischemic insult. We had the opportunity of carrying out 31P spectroscopic imaging of hyperacute cerebral infarction, while MRI and CT were negative. Cerebral infarction of the middle cerebral artery territory was suggested by 31P spectroscopic imaging, which was closely consistent with a later-developing region of low density on CT. In cerebral infarction, early detection of the lesion is a useful pointer to the patient's prognosis, making 31P spectroscopic imaging a potential tool.

Aged↗