Search PubMed⌕ Search

Biomedical subjects

T Akita

Publications and source records attributed to T Akita.

At least 55 records · Page 3Linked to original sources
PubMed1994

Developmental changes in modulation of calcium currents of rabbit ventricular cells by phosphodiesterase inhibitors.

BACKGROUND: We have previously shown major differences in beta-adrenergic and muscarinic modulation of L-type calcium currents (ICa) in newborn and adult rabbit heart. However, little is known about developmental changes in modulation of ICa by phosphodiesterases (PDEs), which also regulate intracellular cAMP concentration by its hydrolysis. METHODS AND RESULTS: Enzymatically isolated adult and newborn (1- to 3-day-old) rabbit ventricular myocytes were used to study the effects of PDE inhibitors on ICa measured by the whole-cell patch-clamp method. 3-Isobutyl-1-methyl-xanthine (IBMX), a nonselective PDE inhibitor, increased ICa in a dose-dependent manner for both groups. The maximal effect of IBMX, expressed as percentage increase in ICa over control levels, was greater for newborn myocytes than for adult myocytes, but the effects of IBMX applied alone were observed only at concentrations > 10 mumol/L. The concomitant use of 0.1 mumol/L isoproterenol produced a significant potentiation of the IBMX effect on ICa, with a significant additive effect of IBMX in newborn myocytes even at 0.05 mumol/L IBMX. The concomitant use of a subthreshold concentration of IBMX (0.1 mumol/L) did not potentiate the dose dependence of adult ICa on isoproterenol but did markedly potentiate the dose dependence of newborn ICa on isoproterenol. The Emax and EC50 of isoproterenol in the presence of 0.1 mumol/L IBMX on newborn ICa were 235% and 8 nmol/L, respectively, whereas the Emax and EC50 of isoproterenol in the absence of IBMX on newborn ICa were 111% and 81 nmol/L, respectively. The addition of 50 mumol/L IBMX to 10 mumol/L isoproterenol markedly increased the newborn ICa density up to a level equivalent to that reached with 200 mumol/L cAMP in the pipette (14.9 +/- 1.2 versus 13.4 +/- 0.7 pA/pF). Our data suggest that the inhibition constant (Ki) of IBMX for inhibiting PDEs that participate in the regulation of ICa is much lower in newborn than in adult myocytes. Milrinone 1 mumol/L, a selective PDE III inhibitor, increased the 0.1 mumol/L isoproterenol-stimulated ICa of adult myocytes but had no significant additive effect for the 0.1 mumol/L isoproterenol-stimulated ICa of newborn myocytes. Rolipram 1 mumol/L, a selective PDE IV inhibitor, increased the 0.1 mumol/L isoproterenol-stimulated ICa for newborn myocytes but had no significant additive effect for the 0.1 mumol/L isoproterenol-stimulated ICa for adult myocytes. CONCLUSIONS: These results suggest that the most important PDE isozyme for regulation of ICa of rabbit myocytes changes from PDE IV to PDE III during the postnatal period.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Prediction of collapse with magnetic resonance imaging of avascular necrosis of the femoral head.

In order to predict the probability of collapse of a femoral head in which there is avascular necrosis, we used magnetic resonance imaging to evaluate sixty-six hips (fifty patients) in which avascular necrosis was in the early stages and in which collapse of the head was not yet visible. The hips were followed radiographically for an average of forty-nine months (range, sixteen to eighty-four months), and with magnetic resonance imaging for an average of forty-four months (range, twelve to seventy-three months). Twenty-one (32 per cent) of the femoral heads had collapsed by thirty-two months. Of the twenty-three femoral heads in which necrosis involved at least one-fourth of the diameter of the head and encompassed at least two-thirds of the major weight-bearing area, seventeen (74 per cent) had collapsed by thirty-two months.

Adult↗
PubMed1993

Deferoxamine reduces the reperfusion injury in isolated neonatal rabbit hearts after hypothermic preservation.

The protective action of deferoxamine, an iron chelator, against reperfusion injury following hypothermic preservation was investigated in the Langendorff-perfused hearts of neonatal rabbits. Left ventricular function and radical generation were used as parameters to evaluate functional and metabolic changes. The free radicals in coronary effluents were measured with an electron spin resonance spectroscope using a spin trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The hearts were preserved in cold St. Thomas solution at 4 degrees C for 6 h following cardiac arrest, then reperfused with oxygenated Krebs-Henseleit solution in a control. Deferoxamine (100 microM) was added to the perfusate just prior to reperfusion in group I, and 3 min after the start of reperfusion in group II. In the control group, the left ventricular developed pressure (LVDP) after 30-min reperfusion recovered up to 43.5 +/- 3.1% (mean +/- SD, n = 5) the preischemic value. Group I showed a significant improvement in LVDP recovery after 30-min reperfusion at 57.1 +/- 3.1% (P < 0.01 vs control), but group II did not (47.5 +/- 2.3%). When a burst of DMPO-OH signals was detected during the initial 5 min of reperfusion, the signal intensity in group I was significantly reduced to about 35-40% of the control value. Group II showed a similar intensity to the control group. Thus, we conclude that deferoxamine may exert a protective action against the dysfunction of neonatal mammalian hearts induced by preservation-reperfusion through an inhibition of iron-catalyzed radical formation.

Animals↗
PubMed1993

Genetic polymorphism of the sixth component of complement (C6) in the pig.

Using agarose gel isoelectric focusing and immunoblotting with rabbit anti-rabbit C6, a genetic polymorphism has been found in the sixth component of complement (C6) in six breeds of pigs. The C6 locus was highly polymorphic. Family data indicated that pig C6 phenotypes were inherited by means of five codomonant alleles named C6A, C6B, C6C, C6D and C6E at a single autosomal locus. C6 deficiency in two of 241 individuals tested was found, which suggested the presence of a null allele in pig populations. Marked breed differences among the gene frequencies and heterozygosities at C6 locus were observed.

Animals↗
PubMed1993

Protective effects of diltiazem and ryanodine against ischemia-reperfusion injury in neonatal rabbit hearts.

The effects of diltiazem, a sarcolemmal Ca2+ channel blocker, and ryanodine, an inhibitor of sarcoplasmic reticulum function, were investigated in isolated newborn rabbit hearts (2 to 5 days old) subjected to ischemia and reperfusion. After cardioplegic arrest with St. Thomas' Hospital solution, global ischemia was induced at 37 degrees C (normothermia) for 45 minutes or at 20 degrees C (hypothermia) for 180 minutes. The hearts were then reperfused at 37 degrees C for 30 minutes. Diltiazem or ryanodine, at concentrations that have minimal to moderately negative inotropic effects under nonischemic conditions, was added to the cardioplegic solution. After normothermic ischemia, reperfusion of untreated hearts resulted in recovery of left ventricular developed pressure to 52.9% +/- 2.5% of the preischemic level. In hearts treated with diltiazem, recovery of left ventricular developed pressure was significantly improved (84.2% +/- 2.9% at 3 x 10(-8) mol/L; p < 0.01). Comparable improvement was achieved with ryanodine (90.5% +/- 4.1% at 10(-9) mol/L; p < 0.01). Creatine kinase leakage and structural derangement of mitochondria were also reduced by both agents. With hypothermic ischemia, left ventricular developed pressure recovered in untreated hearts to 72.7% +/- 3.3% of preischemic values. Treatment with diltiazem improved the recovery of left ventricular developed pressure to 96.9% +/- 3.5% at 3 x 10(-8) mol/L and reduced creatine kinase leakage and mitochondrial damage. Ryanodine also improved the recovery of left ventricular developed pressure and attenuated ultrastructural damage. These findings suggest that Ca2+ handling by the sarcoplasmic reticulum, like transsarcolemmal Ca2+ influx, plays an important role in the pathogenesis of myocardial ischemia-reperfusion injury in the neonatal heart despite the morphologic and functional immaturity of the sarcoplasmic reticulum in the neonate.

Animals↗
PubMed1993

[Safe and accurate coronary artery bypass grafting: combined use with single aortic clamp and retrograde coronary perfusion].

Neurological injury following myocardial revascularization may result from embolization of atheromatous debris from clamping the diseased aorta. The hazards of manipulating and clamping the aorta has been reported in some literatures. The proximal anastomoses with partial occluding clamp is conventional technique, but it may cause neurological injury, aortic tear or traumatic laceration. We developed a technique for coronary bypass grafting with single aortic cross clamp and combined antegrade/retrograde infusion of cardioplegia. Our method allows accurate performance of the proximal anastomosis without partial clamping and adequate protection of myocardium.

Aorta↗
PubMed1992

Deferoxamine, an iron chelator, reduces myocardial injury and free radical generation in isolated neonatal rabbit hearts subjected to global ischaemia-reperfusion.

The protective action of deferoxamine, an iron chelator, against functional and metabolic deteriorations of ventricular muscle, induced by ischaemia-reperfusion, was investigated in Langendorff-perfused hearts of neonatal rabbits in comparison with superoxide dismutase (SOD) plus catalase. The perfused hearts were subjected to normothermic (37 degrees C) global ischaemia for 45 min following cardiac arrest with St Thomas cardioplegic solution and then reperfused with oxygenated Krebs-Henseleit solution. In control hearts, the recovery of the left ventricular developed pressure (LVDP) after 30 min reperfusion was 50.7 +/- 3.1% (mean +/- SE, n = 5) of the pre-ischaemic value. The LVDP recovery was significantly improved in the hearts treated with deferoxamine at 10-100 microM (89.4 +/- 1.4% at 30 microM, P < 0.01 vs. control). The improvement in LVDP was less prominent when treated with 30 x 10(4) U/l SOD plus 30 x 10(4) U/l catalase (67.9 +/- 2.0%, P < 0.01 vs. deferoxamine at 30 microM). CPK leakage into the coronary effluent during the initial 5 min of reperfusion was reduced to around half of the control value with 30 microM deferoxamine (P < 0.05 vs. control), while unaffected by the addition of SOD plus catalase. Free radicals in the coronary effluent were measured with electron spin resonance spectroscopy in separate experiments by using a spin-trapping agent, 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). A burst of DMPO-OH signal was detected during the initial minutes of reperfusion. The intensity of DMPO-OH signal was significantly reduced by 30 microM deferoxamine to about one-third of control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Protective action of iron-chelating agents (catechol, mimosine, deferoxamine, and kojic acid) against ischemia-reperfusion injury of isolated neonatal rabbit hearts.

Iron is suggested to play an important role in free radical generation during ischemia reperfusion. In the present study, the protective action of 4 iron-chelating agents, with different iron affinities, against reperfusion injury was examined in Langendorff-perfused hearts of neonatal rabbits. The chelators and their iron-binding constants (log Km) were as follows: catechol (43), mimosine (36), deferoxamine (31) and kojic acid (27). Following cardiac arrest, the hearts were subjected to global ischemia for 45 min at 37 degrees C, and then reperfused with modified Krebs-Henseleit solution for 30 min. In control, the left ventricular developed pressures (LVDP) after 30 min reperfusion recovered to 50.5 %/- 3.0% (mean +/- SEM; n = 5) of the preischemic level. In the hearts treated with catechol (30 microM), mimosine (30 microM) or deferoxamine (30 microM), the LVDP recovery was significantly improved up to 84.9 +/- 1.3, 88.2 +/- 2.9 or 87.4 +/- 1.5%, respectively (p < 0.01 vs. control). Creatine phosphokinase (CPK) leakage during the initial 5 min of reperfusion was significantly decreased to about half of control in the hearts treated with catechol, mimosine, or deferoxamine. However, the treatment with kojic acid (30 microM) showed no improvement in the LVDP recovery and CPK leakage. Free radical generation was measured with an electron spin resonance using a spin-trapping agent, 5,5-dimethyl-pyrroline-N-oxide (DMPO). The treatment with catechol, mimosine, or deferoxamine reduced the maximum intensity of DMPO-OH signal to about one third of control. However, the maximum intensity in the hearts treated with kojic acid showed a similar level to control.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[A case of completely unroofed coronary sinus with persistent left superior vena cava].

A 34-year-old female presented with exertional dyspnea. Investigation by echocardiography and cardiac catheterization showed completely unroofed coronary sinus with persistent left superior vena cava (PLSVC) (coronary sinus atrial septal defect, absence of the coronary sinus, and PLSVC-left atrium connection) combined with tricuspid valve regurgitation. Angiocardiography made by injection into the PLSVC demonstrated that the PLSVC was connected to the hemiazygos vein before it drained into the left atrium and the left innominate vein was absent. Although jugular vein pressure rose up to 18 mmHg when the PLSVC was temporarily occluded, it remained unchanged. Therefore, simple ligation of the PLSVC was selected for therapy. Patch closure of the atrial septal defect, tricuspid valve repair, and ligation of the PLSVC was performed successfully.

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

[Myocardial revascularization using bilateral internal mammary arteries for total occlusion of LMCA in an adult case: sequelae of Kawasaki's disease in childhood].

A 43-year-old female patient suffering from effort angina underwent coronary artery bypass grafting. Coronary arteriogram demonstrated complete occlusion of the left main, proximal circumflex (Cx), and proximal left anterior descending coronary arteries (LAD) and a nonocclusive fusiform calcified aneurysm of the proximal right coronary artery (RCA). The left coronary artery system opacified via collateral vessels from the RCA. No other abnormalities were found in the entire aorta and its major branches. Myocardial revascularization was performed using the right IMA to bypass to the Cx and the left IMA to bypass to the LAD successfully. Prior to the operation, she had neither coronary risk factors nor inflammatory signs, though she had experienced fever of unknown origin lasting about a week when she was 11 years old. Accordingly we supposed that such coronary arterial lesions might have arisen from Kawasaki's disease in her childhood.

Adult↗
PubMed1990

Solution synthesis of human peptide YY (hPYY).

Human peptide YY (hPYY) was synthesized in a conventional manner by assembling six peptide fragments followed by deprotection with 1 M trimethylsilyl trifluoromethanesulfonate (TMSOTf)-thioanisole in trifluoroacetic acid (TFA). After purification by gel-filtration on Sephadex G-25, followed by reversed-phase high-performance liquid chromatography, a highly purified sample of synthetic hPYY was obtained. When administered in dogs, synthetic hPYY was as active as synthetic porcine PYY in terms of the effects on systemic arterial blood pressure, and splanchnic blood flow.

Amino Acid Sequence↗
PubMed1990

[Studies on anti-allergic agent. I. 1,2,3-trisubstituted-2-propen-1-one derivatives, 3,4-disubstituted-4-oxo-2-butenoic acids and the related compounds].

A new series of 1,2,3-trisubstituted-2-propen-1-one derivatives (9a-v, 10a-j, 13a-c, 14a-j) and 3,4-disubstituted-4-oxo-2-butenoic acids (6a-i, 7a-n) with azole compounds were synthesized. Inhibitory activities against rat passive cutaneous anaphylaxis (PCA) reaction and histamine release from rat mast cells were tested. The ester derivatives (7a-n, 14a-j) exhibited a more potent inhibitory activity against histamine release compared with alkylamine (9a-v), beta-hydroxyethoxy (10a-j) and carboxylic acid (6a-i, 13a-c) derivatives, but somewhat weaker in their anti-PCA activity. Structure-activity relationships were discussed.

Animals↗
PubMed1990

Acetabular cover in congenital dislocation of the hip.

The exact measurement of femoral head cover is essential for an assessment of reduction of congenital dislocation of the hip. We have compared standard anteroposterior radiographs with computerised tomograms and thereby classified the shape of the acetabular roof into four types. We found that the CE angle of Wiberg is a more reliable measure of head cover when the lateral point of bony condensation of the roof is chosen as the reference point rather than the edge of the bone, where these two points do not overlap. We conclude that head cover can be more accurately determined in younger children with dysplastic hips by our 'refined' CE angle, than by the original method of Wiberg.

Acetabulum↗
PubMed1990

[Two cases of HTLV-I associated myelopathy (HAM) after cardiac operation].

Sixty-one and 51-year-old males had progressive walk disturbance after cardiac operations at the intervals of 1 and 2 years. They had received blood transfusion at their operations. Physical examination revealed spastic paraparesis, sensory disturbance of the lower and rectobladder disorder. High titers of anti-Human T-lymphotrophic Virus type-I (HTLV-I) antibody were found in sera and CNF in both cases. They were diagnosed as HTLV-I associated myelopathy (HAM). Because they lived in Aichi Prefecture where the virus is non-epidemic, they were possibly infected through the blood transfusion at their operations. For prevention of HAM, the anti-HTLV-I antibody of all donor blood should be checked before transfusion.

Heart Valve Prosthesis↗
PubMed1990

[A case of concomitant repair of aortic regurgitation due to congenital aortic quadricuspid valve and coronary artery occlusive disease].

A case of rare congenital anomaly of quadricuspid aortic valve and coexisting coronary artery occlusive disease of a 60-year-old female was presented. She was admitted to our hospital for heart murmur and angina pectoris. The echocardiography and aortography showed quadricuspid aortic valve and aortic valve regurgitation. The coronary arteriography revealed the presence of triple vessels disease. Successful aortic valve replacement and Coronary bypass grafting were performed simultaneously.

Aortic Valve↗
PubMed1990

[Mediastinal infection after open cardiac surgery].

Mediastinal infection is a rare but life-threatening complication after open cardiac surgery. Of 852 patients undergoing cardiac operations performed with a median sternotomy between January of 1981 and August of 1989, 19 patients (2.2%) developed deep sternal infections with mediastinitis, and 6 of them (31.6%) died. Tissue cultures were obtained from all but three patients, and staphylococcus aureus was the most frequent infecting organism associated with high mortality rates (3/8). 18 patients were managed with debridement and irrigation as the primary treatment, but 4 of them developed infective endocarditis during the course of irrigation treatment and then died. After 1987, 6 patients, who didn't gain wound closure with irrigation alone, were treated with reconstructive techniques, one with pectoral muscle flap closure, another with rectus myocutaneous flap mobilization, and the remainder with omental transfer respectively. All of them achieved eradication of infection as well as wound closure. Then we have advocated early debridement and mobilization of viable tissues such as omentum into the mediastinum.

Adult↗