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Biomedical subjects

T Kamada

Publications and source records attributed to T Kamada.

At least 649 records · Page 36Linked to original sources
PubMed1988

A new accurate and non-invasive screening method for renovascular hypertension: the renal artery Doppler technique.

The clinical use of ultrasonic echo Doppler velocimetry as a screening test for renal artery stenosis was investigated in 11 control subjects and 20 hypertensive patients including 10 with renovascular disease. In these hypertensive patients, the accuracy of the diagnosis of renal artery stenosis using the echo Doppler method was compared with that of angiography. The accuracy of the radionuclide renography in the same subjects was also investigated and compared with that of the echo Doppler method. Seven patients with renovascular disease who required angioplasty were examined again after the operation. The duplex Doppler signals were detected through the muscle of the back (the translumbar approach). Diagnosis of renal artery stenosis was based on three objectively defined Doppler parameters, the acceleration index, the acceleration time, and the acceleration:time ratio. In comparison with angiography, the accuracy of the echo Doppler method evaluated by using these parameters was 95%; the sensitivity was 100% and the specificity was 93%. The accuracy of the ultrasonic study was superior to that of radionuclide renography (80%). The acceleration index of the affected side was significantly correlated with the percentage stenosis of the renal artery. The changes in renal arterial blood flow following the operation were detected well by the Doppler parameters. This non-invasive method is one of the most accurate screening tests available for renovascular hypertension and has also proved quite useful for follow-up examinations in the patients with angioplasty.

Blood Flow Velocity↗
PubMed1988

Albumin gene transcription is enhanced in liver of nephrotic rats.

The level of albumin mRNA and the transcription rate of the albumin gene were studied in the liver of control rats and rats with nephrosis induced by injection of the aminonucleoside of puromycin. Total RNA was extracted from liver by the guanidium thiocyanate method. The albumin mRNA level was measured by cDNA-RNA dot-blot hybridization, and the transcription rate of the albumin gene was measured by the "run-on" transcription assay using isolated nuclei. Urinary protein excretion in nephrotic rats was significantly higher than in control rats (258 +/- 132 vs. 12 +/- 2 mg/day), and the serum albumin concentration in nephrotic rats was significantly lower. There was no difference in body weight, liver weight, serum creatinine, or urea nitrogen between the two groups. Both the level of albumin mRNA and the transcription rate of the albumin gene in the nephrotic liver were about twice as high as those in the control liver. There was no difference in the level of beta-actin mRNA between the two groups. Northern blot analysis showed that both putative precursor RNA and the mature form of albumin mRNA were increased in nephrotic rats. We conclude that albumin synthesis is increased in the liver of nephrotic rats and a transcriptional process is responsible for this increase.

Actins↗
PubMed1988

Alpha 2-adrenoceptor activity exerts dual control of coronary blood flow in canine coronary artery.

To test the hypothesis that alpha 2-adrenoceptor activity exerts a dual control of coronary blood flow, i.e., vasoconstriction and augmentation of the vasodilatory effect of adenosine, four doses of adenosine were infused into left anterior descending coronary artery before and during alpha 2-adrenoceptor stimulation or attenuation in anesthetized open-chest dogs. During a moderate alpha 2-adrenoceptor attenuation (yohimbine or rauwolscine, ic), which did not alter coronary blood flow (CBF) at the base-line condition, the hyperemic response of CBF to infused adenosine was markedly reduced, whereas during the potent attenuation both base-line CBF and adenosine-induced hyperemic CBF were significantly increased. Inversely, the moderate alpha 2-stimulation (0.03 microgram.kg-1.min-1 norepinephrine with prazosin, ic, or 0.04 microgram.kg-1.min-1 clonidine ic, under propranolol pretreatment) augmented the adenosine-induced coronary vasodilation, but the potent alpha 2-stimulation (0.3 microgram.kg-1.min-1 norepinephrine with prazosin ic, or 0.3 microgram.kg-1.min-1 clonidine ic) reduced both base-line CBF hyperemic CBF. In contrast, alpha 2-adrenoceptor activity did not affect papaverine-induced coronary vasodilation. Moreover, the reactive hyperemic flow after a brief coronary occlusion was reduced significantly during the moderate alpha 2-adrenergic attenuation, but it was augmented during the potent one. These results indicate that the moderate activation of the alpha 2-adrenoceptor augments the hyperemic response of CBF to both exogenous and endogenous adenosine, whereas the potent alpha 2-activation may mask this vasodilatory effect through the coronary vasoconstrictive effect.

Adenosine↗
PubMed1988

Pharmacokinetic and pharmacodynamic interactions between furosemide and hydrochlorothiazide in nephrotic patients.

We examined the response of 8 patients with nephrotic syndrome (creatinine clearance 70.4 +/- 16.0 ml/min) to oral furosemide (F; 40 mg) in the absence (control) and in the presence of oral hydrochlorothiazide (HCT; 100 mg). In the 24-hour period after oral F, HCT was shown to increase urine volume and urinary sodium and chloride excretion. Increment was most significant during the 12- to 24-hour period. Enhancement of the diuresis with HCT was associated neither with a significant increase in the area under the curve of plasma F concentration nor an increase in urinary F excretion. Urinary excretion of glucuronidated F, one of the main metabolites of F, however, was decreased with HCT. In summary, HCT significantly enhanced the response to F in nephrotic patients.

Drug Interactions↗
PubMed1988

Value and limitations of Doppler echocardiography in the quantification of stenotic mitral valve area: comparison of the pressure half-time and the continuity equation methods.

Two Doppler methods, the pressure half-time method proposed by Hatle and the method based on the equation of continuity, were used to estimate stenotic mitral valve area noninvasively, and the accuracy of these methods was examined in patients with and without associated aortic regurgitation. Mitral valve area determined at catheterization by the Gorlin formula was used as a standard of reference. The study population consisted of 41 patients with mitral stenosis, and 20 of the 41 patients had associated aortic regurgitation. According to the equation of continuity, mitral valve area was determined as a product of aortic or pulmonic annular cross-sectional area and the ratio of time velocity integral of aortic or pulmonic flow to that of the mitral stenotic jet. Mitral valve area was determined by the pressure half-time method as 220/pressure half-time, the time from the peak transmitral velocity to one-half the square root of the peak velocity on the continuous-wave Doppler-determined transmitral flow velocity pattern. The pressure half-time method tended to overestimate catheterization measurements, and the correlation coefficient for this relation was .69 (SEE = 0.44 cm2). The correlation coefficient improved to .90 when the patients with associated aortic regurgitation were excluded. Mitral valve areas determined by the continuity equation method correlated well with catheterization measurements at a correlation coefficient of .91 (SEE = 0.24 cm2), irrespective of the presence of aortic regurgitation. The ratio of the time-velocity integral or aortic or pulmonic flow to the time-velocity integral of mitral stenotic jet also correlated well with mitral valve area determined by catheterization at a correlation coefficient of .84 (SEE = 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The role of intracoronary thrombus in unstable angina: angiographic assessment and thrombolytic therapy during ongoing anginal attacks.

Intracoronary thrombus is regarded as a potentially important factor in the etiology of unstable angina, but the incidence of intracoronary thrombus in unstable angina has not been clearly defined. To determine the occurrence of intracoronary thrombus during ongoing angina pectoris, coronary angiography was performed during spontaneous ischemic attacks in 37 patients with prolonged rest angina. All patients exhibited significant (greater than 50%) stenoses of at least one major coronary artery. Of the 37 patients, 21 (57%) had intracoronary thrombus in major coronary arteries, whereas 14 (38%) had fixed narrowings without evidence of intracoronary thrombus and two exhibited coronary spasm. ST segment elevation was observed in 16 of 21 patients with thrombus and in all of the patients with coronary spasm, but all the patients with organic stable obstruction showed ST segment depression. Twenty of the 21 patients with thrombus improved after thrombolytic therapy with intracoronary injection of urokinase; obstructed arteries were reopened, or narrowings were attenuated, with relief of ischemic symptoms. In patients with fixed obstructions, the rate-pressure product during active symptoms was significantly higher than during an asymptomatic period, indicating that a transient increase in myocardial oxygen demand may contribute to the ischemic attack in these patients. A high incidence (71%) of recurrent symptoms was observed in patients with intracoronary thrombus even after successful thrombolysis, in contrast to a much lower incidence (36%) in those without intracoronary thrombus. Myocardial infarction within 4 weeks after catheterization was observed more frequently in patients with intracoronary thrombus (24%) than in those without thrombus (7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗
PubMed1988

Vascular response to carbon dioxide in areas with and without diaschisis in patients with small, deep hemispheric infarction.

The reactivity of cerebral blood vessels to changes in PaCO2 in areas of the cerebral cortex with or without diaschisis was investigated in 13 patients in a subacute or chronic stage after a small capsular infarct. A focal area of hypoperfusion (area of diaschisis) was detected in the ipsilateral sensorimotor cortex in each patient. Hyperventilation caused a significant reduction of regional cerebral blood flow in the area without diaschisis and only a tendency for regional cerebral blood flow to decrease in the area with diaschisis; CO2 inhalation induced a slight increase in regional cerebral blood flow in the area without diaschisis and a significant increase in regional cerebral blood flow in the area with diaschisis. Regional cerebral blood flow reactivity to hypocapnia was significantly less in the area with diaschisis than in the area without, whereas the hypercapnic response was more marked in the area with diaschisis than in the area without. Our results suggest that in the area with diaschisis, the arterioles may be abnormally vasoconstricted at rest such that they cannot constrict further in response to hypocapnia but can dilate more during hypercapnia than in the area without diaschisis. This excessive resting vasoconstriction may result from decreased tissue elaboration of CO2 due to local decrease of metabolic function.

Adult↗
PubMed1988

Immunohistochemical demonstration of beta-adrenoreceptor in the rat brain--with reference to the central control of blood pressure.

Using anti-beta 2-adrenoreceptor antibody, we examined immunohistochemically the localization of adrenoreceptor in the rat central nervous system at both lightmicroscopic and electronmicroscopic level. In the areas which are known to be involved in the control of blood pressure, such as the hypothalamus, the nucleus of the solitary tract and the locus coeruleus, there were a number of adrenoreceptor-like immunoreactive (ADR-IR) structures. They were mainly associated with cellular surface of the neuron. However, those localized within the cytoplasm or the nerve fiber were also observed. Immunoelectron microscopic analysis revealed that the ADR-IR structures were associated with post-synaptic density and cytoplasmic organella (endoplasmic reticulum, vesicle). Ultrastructural feature of the ADR-IR fiber was characterized by the synaptic vesicles with immunoreaction products. In addition, we detected that the running pattern of the ADR-IR fibers was often quite similar to that of tyrosine hydroxylase-immunoreactive (i.e. catecholaminergic) fibers. These findings suggest the presence of the presynaptic autoreceptor. In the present study, we have clearly demonstrated the cellular and subcellular localization of adrenoreceptors in the areas related to blood pressure control immunocytochemically. These results suggest the immunocytochemical method should be quite useful for further investigation of the CNS control of blood pressure.

Animals↗
PubMed1988

Albumin prevents erythrocyte crenation in patients undergoing extracorporeal circulation.

Free fatty acid-induced massive erythrocyte crenation has been reported in patients undergoing extracorporeal circulation (EC), suggesting that the crenated cells impair microcirculatory flow and tissue oxygenation during and after the operation. Effect of albumin administration on erythrocyte crenation was examined in 18 patients undergoing coronary bypass operation: 9 patients were given 25 g and another 9 patients were given 50 g of human albumin as a part of the priming solution. Erythrocyte crenation was almost completely prevented in the patients given 50 g albumin. Crenated erythrocytes during EC were 3.6 +/- 2.3% (mean +/- SD) of all erythrocytes and 2.8 +/- 3.7% after EC. This was significantly lower than in patients without albumin administration (63.4 +/- 34.0% during EC and 28.6 +/- 33.3% after EC, n = 20). But the effect was less striking in the patients given 25 g albumin, 32.4 +/- 39.1% during and 28.3 +/- 40.8% after EC. Maintaining an adequate level of plasma albumin is important in preventing erythrocyte crenation during EC, improving microcirculatory flow in patients undergoing open heart surgery.

Aged↗
PubMed1988

The evaluation of glucagon infusion algorithms for a counterregulatory system in artificial endocrine pancreas.

As counterregulatory system of artificial endocrine pancreas, glucagon infusion algorithm has been developed and its usefulness has been examined in pancreatectomized dogs and a pancreatectomized diabetic patient. Glucagon infusion rate (G1nIR(t)) was determined depending on proportional plus derivative action to blood glucose concentration (BG(t] with the time delay (tau) to start infusion as follows. G1nIR(t) = Gp(BGp- BG(t-tau)) + Gd(-dBG(t-tau)) + Gc where BGp is the projected value of blood glucose concentration, Gp, and Gd are the coefficients and Gc is the constant for basal glucagon supplement. Glucagon infusions based only on proportional action (Gp/Gd/Gc/tau) = (0.2/0/0.4/10 or 0.4/0/0.4/10) failed in simulating the pattern of blood glucose or glucagon response seen in normal dogs. Glucagon infusion based on proportional plus derivative action (Gp/Gd/Gc/tau = 0.2/0.4/0.4/10) successfully mimicked the pattern of blood glucose concentration and plasma glucagon profile seen in normal dogs. This glucagon infusion algorithm has been applied to control insulin-induced hypoglycemia in a pancreatectomized patient with the same infusion parameters. Hypoglycemia was recovered to normoglycemia in 80 min and the plasma glucagon patterns showed no significant difference from those in healthy volunteers. These data indicate that glucagon infusion algorithm thus developed is effective to render hypoglycemia to normoglycemia and mimic plasma glucagon response seen in normal subjects.

Algorithms↗
PubMed1988

Fail-safe systems for the wearable artificial endocrine pancreas.

For the long-term clinical use of the wearable artificial endocrine pancreas, a fail-safe system is an essential mechanism. Several hardware alarm systems have been incorporated for battery-down, and short-run of the pumps. Software alarm systems for overflow or underflow of the AD converter, empty bags, hypoglycemia, hyperglycemia, abnormal values of parameters, and excessive insulin infusion have also been built into the system. The software noise filter was effective in eliminating superimposed artificial noises and the noises induced by muscle exercise. Sudden changes in sensor output during glycemic control of diabetics due to short circuit, or disconnection of the sensor lead, were detected as overflow or underflow of the AD converter. A gradual change in the sensor output was heralded by the hyper- or hypoglycemia alarm sound. These data indicated that the fail-safe system built into the wearable artificial endocrine pancreas is useful for the long-term glycemic control of diabetics.

Blood Glucose↗