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Biomedical subjects

K Ashida

Publications and source records attributed to K Ashida.

At least 19 recordsLinked to original sources
PubMed1992

[A case of complete recanalization in the lower abdominal aorta by intraaortic infusion of a thrombolytic agent].

Intraarterial infusion of thrombolytic agent is useful in the treatment of obstructive arterial diseases in various vessels. However, few studies have shown that this treatment is useful for aortic occlusion. We report the case with complete recanalization in the lower abdominal aorta following intraaortic infusion of a thrombolytic agent. A 59-year-old man was admitted because of weakness and pain in the bilateral lower limbs at rest. Aortography showed complete occlusion of the abdominal aorta proximal to the inferior mesenteric artery. Both external arteries were supplied via rich collaterals. He was treated by intraaortic urokinase infusion of 2,100,000 units. Total recanalization in the abdominal aorta and both common iliac arteries was obtained. Intraaortic infusion of urokinase was shown to be effective treatment of occlusion in the abdominal aorta.

Aorta, Abdominal↗
PubMed1992

[Effect of chronic smoking on regional cerebral blood flow in asymptomatic individuals].

The chronic effects of cigarette smoking upon regional cerebral blood flow (rCBF) are unclear. The present study investigated the effects of smoking on rCBF assessed by intravenous 133Xe injection in 40 asymptomatic individuals. Analysis was performed using linear regression analysis and multiple regression analysis, creating a model of the rCBF as a function of cerebrovascular risk factor. The risk factors included smoking status, smoking index, age, gender, mean arterial blood pressure, total cholesterol, fasting blood glucose, hematocrit and STT change and left ventricular hypertrophy in electrocardiogram. The male-to-female ratio was higher in the smoking group (18/2) than that in the non-smoking group (2/18). Among the smokers, mean hematocrit was significantly higher than in the non-smokers (p < 0.01). There was no significant difference in rCBF and other variables between the two groups. Linear regression analysis revealed significantly negative correlations between smoking index and CBF in the whole brain (r = -0.33; p < 0.05), right hemisphere (r = -0.34; p < 0.05), right parietal cortex (r = -0.36; p < 0.05), right occipital cortex (r = -0.34; p < 0.05) and left parietal cortex (r = -0.33; p < 0.05). In other variables, age, male sex, hematocrit, left ventricular hypertrophy and STT change showed significantly negative correlations with rCBF. To reduce the effect of confounding variables in our assessment of the dose-related response, a multivariate regression analysis was carried out treating rCBF as a dependent variable and risk factors as independent variables. In the final model, age, hematocrit, male sex and presence of BCG changes remained as independent negative predictors for rCBF.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

[Cerebral blood flow distribution and reactivity during the symptom-free stages of transient ischemic attacks--a 99mTc-HMPAO SPECT study].

Even during the symptom-free stages, patients with transient ischemic attacks (TIA) often show cerebral blood flow (CBF) disturbances. For evaluating the factors which cause these abnormalities, we studied CBF and CBF reactivity to acetazolamide (Diamox) using a 99mTc-hexamethylpropyleneamine oxime (HMPAO) single photon emission computed tomography (SPECT). The results from CBF-SPECT were compared with X-ray computed tomography (CT), cerebral arteriogram, clinical characteristics of TIA and cerebrovascular risk factors. The overall sensitivity rates in detecting the lesion were 68% in CBF-SPECT and 9% in CT. The size of the hypoperfused area tended to be wide in patients who had intracranial, severe stenotic or multiple arterial lesions on the ipsilateral side. No such relations were found between CBF and other examinations. Brain hypoperfusion was located in the subcortical region in eight patients; two patients showed a small hypodense lesion on CT which corresponded to the hypoperfusion on SPECT, and three patients showed no arteriographic abnormality. Hypoperfusion in the cortex was seen in seven patients; all patients showed arteriographic abnormality, but no CT abnormality. The severity rating of the vascular stenosis and hypoperfusion, and the incidence of the intracranial lesions were higher in this group than the group with subcotical hypoperfusion. Seven patients showed fixed normoperfusion before and after diamox injection. Two patients with a subcortical small infarction showed fixed hypoperfusion even after diamox injection. Twelve patients showed focal hypoperfusion before diamox with a new filling-in after diamox. Only one patient showed resting hypoperfusion and decreased CBF reactivity to diamox.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗
PubMed1992

[Comparison of vulnerability between avian and mammalian inner ears--electrophysiological and morphological studies].

In order to assess the vulnerability of the inner ear, auditory function and morphology of the inner ear were compared between adult budgerigars and adult guinea pigs. Budgerigars have been considered to have an excellent auditory-vocal system. Two experimental conditions were produced in each species; one by acoustic hyperstimulation (1500 Hz, 120 dBSPL) for 96 hours, the other by administration of kanamycin (200 mg/kg) for 7 weeks. Measurement of auditory evoked potentials (AEP) and observation of hair cells by electron microscopy were performed both immediately and 14 days after exposure. In the acoustic hyperstimulation experiment, AEPs of budgerigars showed less damage and better recovery than those of guinea pigs, probably because of morphological differences between the two species in hair and supporting cells. Electron microscopic observation on the budgerigars showed that a small part of the hair cell area was damaged and that regeneration of hair cells had occurred in this area 14 days after exposure. Such observations in guinea pigs revealed that outer hair cells had been damaged and replaced by supporting cells 14 days after exposure. In the kanamycin administration experiment, AEPs showed the same degree of damage and recovery in both species. This suggests that blood supply and drug transport to the inner ear are almost the same although the structure of the inner ear differs markedly between the two species. Electron microscopic observation did not show an apparent regeneration of hair cells 14 days after administration in the budgerigars. Guinea pigs had a tendency to show progressive damage of both auditory function and inner ear morphology even after the cessation of administration. Regeneration of hair cells in the budgerigar differed under both experimental conditions, suggesting that there is a difference in the mode of auditory disturbance between acoustic hyperstimulation and administration of kanamycin. In conclusion, resistance to acoustic hyperstimulation is higher in the avian inner ear than in the mammalian inner ear, while resistance to administration of kanamycin does not differ significantly between the two species.

Acoustic Stimulation↗
PubMed1992

[Quantification of regional cerebral blood flow using 99mTc-HMPAO SPECT and intravenous 133Xe injection method].

We converted an absolute value of 133Xe-CBF (initial slope index, ISI) to the three dimensional CBF-SPECT using the intravenous 133Xe injection technique and 99mTc-HMPAO SPECT according to the microsphere model (method A), and the three compartment model described by Lassen et al. (method B): [formula: see text] [formula: see text] where f = flow in the region of interest (ROI), fr = flow in the reference region, C = count density of 99mTc-HMPAO SPECT in the ROI, Cr = count density of 99mTc-HMPAO SPECT in the reference region, and alpha = conversion to clearance ratio of HMPAO. We used alpha value of 1.5, and the whole cerebrum as a reference region. Four asymptomatic subjects and 15 patients with ischemic cerebrovascular disease were entered the study. In method A, excellent correlation was seen between ISI and SPECT-CBF in both of the cerebral hemisphere (r = 0.993; p < 0.001, n = 38) and the cerebellar hemisphere (r = 0.901; p < 0.001, n = 38). When back diffusion of HMPAO was corrected by method B, correlation coefficient of SPECT-CBF with ISI was equivalent to that in method A in the cerebrum (r = 0.978; p < 0.001, n = 38), while the correlation coefficient ih the cerebellum was lowered (r = 0.726; p < 0.001, n = 38) although high flow to low flow ratio was increased. Reproducibility of rCBF assessed 1 week apart from the first CBF-SPECT was highly reproducible in all of the brain regions; correlation coefficient ranged from 0.757 to 0.910 with a mean correlation coefficient of 0.834 (n = 11). The slope and intercept of the linear regression line between 2nd rCBF versus 1st CBF were 0.889 (range, 0.791-1.141) and 5.5 (range, -9.1-13.4), respectively. Regional CBF measured by method B was approximately 20% increase from that measured by method A. However, there was no significant difference in the reproducibility of rCBF between the two methods. Our results indicate that rCBF can be simply and noninvasively quantified using 99mTc-HMPAO SPECT and absolute unit of CBF measured by 133Xe injection technique. SPECT-CBF offers high resolution images and may be applicable for various cerebrovascular disorders in routine clinical use.

Adult↗
PubMed1992

[Relationship between extent of brain hypoperfused area and functional outcome in patients with a small subcortical infarction: evaluation with X-ray CT, 123I-IMP cerebral perfusion SPECT and cerebral angiography].

We performed 123I-IMP single photon emission computed tomography (SPECT) in 43 patients who had a small infarction (less than 2 cm) in subcortical area and who were less than 1 month after onset of stroke. Hypoperfused area of brain was qualitatively assessed and was compared with functional outcome at 6-month after the stroke and the cerebral angiogram. Functional outcome was poorer in patients who had wider hypoperfused area in brain (chi 2 = 29.3; p less than 0.001). The extent of brain hypoperfused area showed a positive correlation with the degree of stenosis in the extracranial and/or intracranial arteries (r = 0.61; p less than 0.01). In patients who had no angiographic abnormality, the extent and the location of the hypoperfused area were equivalent to that of the low density area in CT. Thus 123I-IMP SPECT in patients with a small infarction may discriminate lacunar infarction from embolic or hemodynamic infarction, which was caused by vascular lesions of major cerebral arteries, in subcortical area. Our study suggests that functional outcome is better in lacunar infarction than embolic or hemodynamic infarction in subcortical area.

Aged↗
PubMed1992

Cerebral blood flow imaging with technetium-99m-HMPAO SPECT in a patient with chronic subdural hematoma: relationship with neuropsychological test.

We report the relationship between cerebral blood flow (CBF) and neuropsychologic tests in a patient with a chronic subdural hematoma suffering from severe dementia and left hemiparesis. Regional CBF was quantified using 99mTc-HMPAO SPECT and 133Xe-CBF. CBF-SPECT could detect the hematoma which was isodense by CT scan and the neuropsychological test improved remarkably with the increase in CBF after surgery. We conclude that if there is a strong clinical suspicion of subdural hematoma and CT scan is not diagnostic then CBF-SPECT may be valuable in localizing the hematoma and monitoring the effect of operation.

Aged↗
PubMed1991

[Cerebral blood flow velocity measurements by transcranial Doppler during postural changes and walking in idiopathic orthostatic hypotension].

Transcranial Doppler (TCD) was utilized to estimate the cerebral blood flow velocity during postural changes or walking in two patients with idiopathic orthostatic hypotension (IOH). The probe of TCD was attached tightly to the temporal skull with a headband to measure the flow velocity of middle cerebral artery (MCA). The patients' postures were altered passively by a tilting table or actively by standing up or walking with their own feet. The TCD study clearly demonstrated a complete loss of autoregulation in Case 2 and an incomplete impairment of autoregulation in Case 1. In both patients, the blood pressure dropped markedly at a standing position, and MCA flow velocity decreased accordingly resulting in manifestation of dizziness. In Case 1, the blood pressure was elevated during walking, and MCA flow velocity increased leading to the improvement of ischemic symptoms. In Case 2, the TCD study was repeated after administration of fluorohydrocortisone, a mineralocorticoid agent, which ameliorated clinical symptoms. The results, however, indicated no improvement of autoregulatory response. The amelioration of symptoms was attributable to the elevation of blood pressure levels. Our study indicates the capability of TCD to estimate cerebral blood flow alteration during postural changes or walking. The TCD appears to be useful for evaluating the autoregulatory response and effectiveness of therapy in patients with orthostatism, like IOH.

Aged↗
PubMed1991

[Effect of white matter lesions on cerebral blood flow in asymptomatic individuals: assessment by MRI and 133Xe-CBF method].

In 32 patients with asymptomatic white matter lesions (WMLs), we evaluated the age-related changes in the number of white matter lesions, cerebral blood flow (CBF), cerebrovascular resistance (CVR) and mean arterial blood pressure (MABP). CBF was measured with the intravenous 133Xe injection method. The number of WMLs in whole brain was measured by the magnetic resonance imaging. CBF decreased with advancing age (r = 0.529; p less than 0.01), while the number of WMLs (r = 0.39; p less than 0.05), CVR (r = 0.464; p less than 0.01) and MABP (r = 0.229; ns) increased with advancing age. There was a significantly negative correlation (r = -0.499; p less than 0.01) between CBF and the number of WMLs. While, CVR showed a positive correlation with the number of WMLs (r = 0.468; p less than 0.01). Multivariate regression analysis with stepwise forward selection method indicated that the number of WMLs and age were independent and negative predictors for CBF, while other factors did not. CBF decreased with a concomitant rise in CVR. On the basis of the results listed above, we assumed that ischemic damage of the white matter and/or functional suppression of distant loci due to the primary tissue damage are the best explanation for CBF reduction in asymptomatic individuals with WMLs. High resolution CBF imaging as well as evaluation of structural alterations in cerebrovascular vessels should be required to further define the mechanisms.

Adult↗
PubMed1990

Platelet production, clearance and distribution in patients with idiopathic thrombocytopenic purpura.

Platelet destruction mechanism was thought to play a primary role in autoimmune thrombocytopenia (ITP). There is, however, some evidence that anti-platelet antibodies in ITP impair megakaryocytopoiesis. Using autologous In-111 platelets, we tried to elucidate this point. We measured platelet survival, platelet turnover, platelet sequestration sites, and platelet production (turnover) to the clearance (sum of liver and spleen platelet uptake) ratio in 8 normal subjects and 12 patients with ITP whose platelet counts ranged from 9 x 10(9) to 40 x 10(9)/L. The sum of platelet uptake in the liver and spleen showed a significant inverse correlation with platelet survival. Platelet survival, platelet production to clearance ratio correlated significantly with the platelet count. No significant correlation was found between platelet turnover and platelet counts. The distribution of platelet turnover showed considerable individual variation; 8 of 12 patients showed platelet turnovers which were lower than the normal value, but the others were within the normal range. We concluded that although the platelet destruction mechanism in the reticuloendothelial system shows a primary role in thrombocytopenia, the impaired rate of effective thrombopoiesis may also contribute to the severity of ITP.

Adult↗
PubMed1990

[Functional alterations of human platelets following 111In labeling with different ligands and incubation media].

We studied the effects of various 111In-water soluble chelates and incubation media on labeling efficiency of platelets and in vitro platelet aggregability. High labeling efficiency of platelets in ACD-saline was achieved with 111In-oxine sulfate, 111In-tropolone and 111In-MPO (2-mercaptopyridine-N-oxide). In the condition with 4.8 x 10(6)/mm3 platelets in ACD-plasma, 111In-oxine-sulfate had low labeling efficiency and inconsistent labeling, while 111In-tropolone and 111In-MPO had high labeling efficiency. In vitro platelet aggregability (ADP 2 microM) was reduced when platelets were labeled in the absence of plasma. However, there was no significant difference in platelet aggregability among 111In-platelets labeled by three different chelates. In conclusion, to maintain aggregation activity of the platelets with relatively high labeling efficiency, the best result was obtained by using MPO or tropolone chelate in plasma at 4.8 x 10(6)/microliters platelet concentration.

Adult↗
PubMed1990

[Platelet production, clearance and distribution in patients with idiopathic thrombocytopenic purpura].

We have studied 8 normal subjects, and 12 patients with idiopathic thrombocytopenic purpura whose platelet counts ranged from 9 x 10(9)/L to 40 x 10(9)/L. Autologous platelets labeled with 111Intropolone were used for evaluation of mean platelet survival, platelet turnover, platelet sequestration sites, and platelet production (turnover) to clearance (sum of platelet uptake in the liver and the spleen) ratio. Platelet survival correlated directly with platelet counts. There was no significant correlation between the platelet sequestration pattern and platelet count, survival, or turnover. Sum of platelet uptake in the liver and the spleen showed a significant inverse correlation with platelet survival. No significant correlation was found between platelet turnover and platelet count. There was a significant correlation between the platelet production to clearance index when all subjects were analyzed. The distribution of platelet turnover showed considerable individual variation; eight of twelve patients showed platelet turnover less than mean minus 2SD of the control value, but others showed normal range. We conclude that although platelet destruction mechanism in RES shows a primary role of thrombocytopenia, impaired rate of effective thrombopoiesis may also contribute to disease severity in ITP.

Adult↗
PubMed1986

Mechanism of action of a polypeptide neurotoxin from the coral Goniopora on sodium channels in mouse neuroblastoma cells.

Goniopora toxin (GPT), a polypeptide toxin of 9700 Da isolated from coral, markedly slows inactivation of sodium currents recorded under voltage clamp in mouse neuroblastoma cells. The voltage dependence of sodium channel activation is shifted to more negative membrane potentials by 9.8 +/- 2.1 mV, and the voltage dependence of channel inactivation is shifted to more positive membrane potential by 6.0 +/- 2.5 mV. These actions of GPT are voltage dependent with an e-fold increase in K0.5 for toxin action for each 48.3-mV depolarization between -80 and +40 mV. GPT requires Na+ or another alkali metal cation in the extracellular medium for its effect on sodium channels. The relative effectiveness of the different cations tested is Na+ greater than K+ greater than Rb+ greater than Li+ greater than Cs+ much greater than choline+. Like other polypeptide neurotoxins that slow inactivation of sodium channels, GPT enhances persistent activation of sodium channels by veratridine. However, GPT does not block the binding of 125I-labeled Leiurus scorpion toxin to neurotoxin receptor site 3 on sodium channels at concentrations which effectively slow channel inactivation. Therefore, our results define a new site on the sodium channel at which specific effects on inactivation can occur.

Action Potentials↗
PubMed1985

Effects of goniopora toxin on bullfrog atrial muscle are frequency-dependent.

When goniopora toxin (GPT), a marine toxin isolated from coral, was applied to the bullfrog atrial muscle, the duration of action potential (APD) was prolonged, and a positive inotropic effect was produced. Such effects of GPT were influenced by stimulus frequency. At lower frequencies of 0.1 Hz, GPT (10 to 100 nmol/l) produced a moderate prolongation of APD and positive inotropic effect. At higher frequencies (1.0 Hz), however, the effects of GPT on both APD and contraction were suppressed. In contrast, APD and duration of contraction were prolonged with long intervals of stimulation (1-3 min), in the presence of GPT. The rested-state contraction was also markedly increased and prolonged by GPT. When the membrane potential was conditioned by voltage clamp pulses, the prolonged action potential in GPT-treated muscle was shortened in proportion to the increase in conditioning depolarization. However, the shortening effect of conditioning depolarization was attenuated by lengthening the resting period after the conditioning depolarization. These results, in conjunction with our previous results, suggest that the frequency-dependent effects of GPT on APD and contraction reflect time- and and membrane potential-dependent changes of the toxin-modified sodium channels.

Action Potentials↗