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Biomedical subjects

T Akita

Publications and source records attributed to T Akita.

At least 37 records · Page 2Linked to original sources
PubMed2000

Production of betacyanins by a cell suspension culture of table beet (Beta vulgaris L.).

A cell suspension culture of table beet (Beta vulgaris L.) was established for efficient betacyanin production from violet callus induced from the hypocotyls of aseptic seedlings. This suspension culture produced large amounts of betacyanins. The betacyanin content increased with increasing cell growth during the log phase. Reducing the total nitrogen concentration (30 mM) and modifying the ratio of ammonium to nitrate (1:14) resulted in an increased betacyanin content. Supplementation of Fe2+ to the LS medium also promoted betacyanin production. The maximal betacyanin yield was achieved with a 2 mM Fe2+ concentration. Combining these conditions, we established a revised LS medium to improve betacyanin productivity (250 mg/l for a 14-day culture).

Carbocyanines↗
PubMed2000

Correlation between bone marrow edema and collapse of the femoral head in steroid-induced osteonecrosis.

OBJECTIVE: The purpose of this study was to clarify whether bone marrow edema is detectable on initial MR imaging of steroid-induced osteonecrosis of the femoral head. SUBJECTS AND METHODS: Forty-eight hips with osteonecrosis were examined consecutively with MR imaging and radiography. In a previously reported screening program, osteonecrosis was diagnosed on MR imaging when subchondral bands of abnormal signals were present. In the screening program, the MR images of 200 hips of 100 patients receiving high-dose steroid therapy were examined prospectively. Subchondral bands were detected in 48 hips at a mean of 14 weeks after the initiation of steroid therapy. RESULTS: On follow-up MR imaging of 47 hips (one hip excluded) bone marrow edema was initially observed in 13 hips after the onset of hip pain. MR imaging of the remaining 34 hips did not reveal bone marrow edema and the patients were all asymptomatic. MR imaging of 31 of the 34 hips continued to show subchondral bands and MR imaging of the other three hips indicated that the subchondral bands had disappeared. When bone marrow edema was detectable, abnormal findings on radiography were slight but 11 (85%) of the 13 hips progressed to advanced osteonecrosis. Bone marrow edema was highly correlated with the subsequent collapse of the femoral head (p<0.0001). CONCLUSION: Bone marrow edema was not present on initial MR imaging of osteonecrosis. Bone marrow edema should be considered a marker for potential progression to advanced osteonecrosis, and careful examinations for osteonecrosis are necessary when bone marrow edema is seen.

Adolescent↗
PubMed2000

[A case report of Binswanger type encephalopathy manifested after coronary artery bypass grafting].

A 68-year-old man showed signs of dementia after undergoing triple CABG with cardiopulmonary bypass. Brain CT revealed widespread atrophy and lucency in white matter without any sign of stroke. No critical stenosis in cervical vessels was found in duplex scanning. He kept politeness well, but had severe memory impairment. These findings were characteristic of Binswanger type encephalopathy which must have been latent preoperatively. This disease is caused by ischemic damage in brain stem and white matter due mainly to atherosclerotic micro cerebrovasculopathy, and highly related to hypertension. We have to be aware of intracranial cerebrovascular disease when assessing the risk of brain damage in candidates for CABG.

Aged↗
PubMed1999

Long-term use-dependent enhancement of impulse-induced exocytosis by adrenaline at frog motor nerve terminals.

Adrenaline (5-20 microM) use-dependently increased end-plate potentials (EPPs) in normal Ringer solution (containing d-tubocurarine to partially block acetylcholine receptors) and a low Ca2+, high Mg2+ solution for more than several hours and decreased the coefficient of variation of EPP amplitude in the latter solution in frog neuromuscular junctions. The amplitude and frequency of miniature EPPs and impulse-induced increases in intraterminal Ca2+ concentration were unaffected. Adrenaline thus causes sustained enhancement of impulse-induced exocytosis by acting at a mechanism of exocytosis downstream to Ca2+ entry.

Animals↗
PubMed1999

A linkage map of 243 DNA markers in an intercross of Göttingen miniature and Meishan pigs.

A resource family of pigs has been constructed by using a boar of Göttingen miniature pig and two sows of Meishan pig as parents. In the construction of the family, two F1 males and 18 F1 females were intercrossed to generate 143 F2 offspring. The members of the family were genotyped using 243 genetic markers including 26 markers developed in our laboratory in order to generate a linkage map of markers for use in detecting quantitative trait loci (QTLs) in the family. The markers consisted of 237 microsatellites, five PRE-1 markers, and one RFLP marker. The linkage map was revealed to cover all 18 autosomes and the X chromosome; and the total length of the sex-averaged linkage map was calculated to be 2561.9 CM. Four out of the 26 markers developed in our laboratory exended the current linkage map at the termini of chromosomes 1p, 5p, 11p, and Xq. The linkage maps of all the chromosomes except for chromosome 1 were found to be longer in females than in males. Concerning chromosome 1, the length of the linkage map showed no difference between females and males, which was attributed to low recombination rates between markers localized in the centromeric region in females. The average ratio of female-to-male recombination was calculated to be 1.55.

Animals↗
PubMed1999

Transcatheter coil embolization of large-size patent ductus arteriosus in adult patients: usefulness and problems.

Transcatheter coil embolization of the patent ductus arteriosus (PDA) has been frequently used in children, especially for small lesions. It was attempted in 3 adults using Cook detachable coils. For 2 of the patients, relatively old age and heart failure were the reasons for choosing coil embolization of the PDA. In the remaining patient, who had Wolff-Parkinson-White syndrome, coil embolization was performed after radiofrequency catheter ablation of Kent's bundle. Their respective minimal PDA diameters were 5.0 mm, 4.5 mm and 4.0 mm measured by transesophageal echocardiography. Two coils were placed in 2 patients and 1 coil in the remaining patient. After the procedures, the size of the left ventricle decreased and heart failure was improved in 2 patients, although all 3 patients had a residual shunt, which caused hemolytic anemia in 2 patients. Repeat coil-embolization procedures resulted in complete occlusion and the hemolysis disappeared in these patients. In adult patients who have heart failure due to large PDA, coil embolization with detachable coils, even if residual shunt persists, is useful for improvement of the heart failure. In cases of hemolysis related to residual shunt, a second coil-embolization procedure can improve it completely.

Adult↗
PubMed1998

A Ca2+-induced Ca2+ release mechanism involved in asynchronous exocytosis at frog motor nerve terminals.

The extent to which Ca2+-induced Ca2+ release (CICR) affects transmitter release is unknown. Continuous nerve stimulation (20-50 Hz) caused slow transient increases in miniature end-plate potential (MEPP) frequency (MEPP-hump) and intracellular free Ca2+ ([Ca2+]i) in presynaptic terminals (Ca2+-hump) in frog skeletal muscles over a period of minutes in a low Ca2+, high Mg2+ solution. Mn2+ quenched Indo-1 and Fura-2 fluorescence, thus indicating that stimulation was accompanied by opening of voltage-dependent Ca2+ channels. MEPP-hump depended on extracellular Ca2+ (0.05-0.2 mM) and stimulation frequency. Both the Ca2+- and MEPP-humps were blocked by 8-(N, N-diethylamino)octyl3,4,5-trimethoxybenzoate hydrochloride (TMB-8), ryanodine, and thapsigargin, but enhanced by CN-. Thus, Ca2+-hump is generated by the activation of CICR via ryanodine receptors by Ca2+ entry, producing MEPP-hump. A short interruption of tetanus (<1 min) during MEPP-hump quickly reduced MEPP frequency to a level attained under the effect of TMB-8 or thapsigargin, while resuming tetanus swiftly raised MEPP frequency to the previous or higher level. Thus, the steady/equilibrium condition balancing CICR and Ca2+ clearance occurs in nerve terminals with slow changes toward a greater activation of CICR (priming) during the rising phase of MEPP-hump and toward a smaller activation during the decay phase. A short pause applied after the end of MEPP- or Ca2+-hump affected little MEPP frequency or [Ca2+]i, but caused a quick increase (faster than MEPP- or Ca2+-hump) after the pause, whose magnitude increased with an increase in pause duration (<1 min), suggesting that Ca2+ entry-dependent inactivation, but not depriming process, explains the decay of the humps. The depriming process was seen by giving a much longer pause (>1 min). Thus, ryanodine receptors in frog motor nerve terminals are endowed with Ca2+ entry-dependent slow priming and fast inactivation mechanisms, as well as Ca2+ entry-dependent activation, and involved in asynchronous exocytosis. Physiological significance of CICR in presynaptic terminals was discussed.

Action Potentials↗
PubMed1998

[A case of submitral left ventricular pseudoaneurysm following mitral valve replacement for infective endocarditis].

A 25-year-old female presented with high fever and dyspnea. She was diagnosed as infective endocarditis, severe mitral regurgitation, grade II A-V block and acute left heart failure We performed emergency mitral valve replacement. At operation, mitral ring abscess was found which was extended to submitral left ventricular wall. The abscess was excised and the defect of mitral annulus was repaired with Xenomedica patch. Left ventriography at 30 days after the operation showed a submitral left ventricular pseudoaneurysm (size: 30 x 26 x 33 mm) without evidence of infection. Further examinations showed that the aneurysm extended to the annulus of tricuspid valve through interatrial septum. About 1 year after the operation, she had paroxysmal atrial fibrillation due to right atrial overloading. We decided to perform reoperation. At reoperation, the ostium of the aneurysm was closed with a Xenomedica patch after taking off the prosthetic valve. It was very difficult to close the ostium because we could not see the submitral ventricular wall directly. Although postoperative course was good, she had complete A-V block necessitating permanent pacemaker.

Adult↗
PubMed1997

Anticoagulant therapy during successful pregnancy and delivery in a Kawasaki disease patient with coronary aneurysm--a case report.

Thirty-one-year-old woman with Kawasaki disease wanted a child. She had a large coronary aneurysm on the left main coronary artery and complete obstruction of the right coronary artery, but there was no sign of ischemia. Heparin anticoagulant therapy was begun 8 weeks after the onset of pregnancy. The activated partial thromboplastin time (APTT) was successfully maintained at 1.5 to 2.0 times normal value during pregnancy and puerperium. There were no thromboembolic complications during pregnancy or after an uneventful cesarean delivery. The neonate was healthy.

Adult↗
PubMed1997

Osteonecrosis of the femoral head: a prospective study with MRI.

We performed a prospective study using MRI to evaluate early necrosis of the femoral head in 48 patients receiving high-dose corticosteroids for the treatment of various autoimmune-related disorders. The mean interval from the initiation of corticosteroid therapy to the first MRI examination was 2 months (0.5 to 6). MRI was repeated, and the mean period of follow-up was 31 months (24 to 69). Abnormalities were found on MRI in 31 hips (32%). The initial changes showed well-demarcated, band-like zones which were seen at a mean of 3.6 months after initiation of treatment with steroids. In 14 of these hips (45%) there was a spontaneous reduction in the size of the lesions about one year after treatment had started, but there was no further change in size with a longer follow-up.

Adolescent↗
PubMed1996

Adenosine and carbachol are not equivalent in their effects on L-type calcium current in rabbit ventricular cells.

Adenosine is one of the most important inhibitory modulators of heart function, producing negative inotropic, chronotropic and dromotropic effects and is also a major regulator of coronary circulation. The decrease in contractility by adenosine is mediated through inhibition of adenylyl cyclase by Gi-proteins coupled to adenosine receptors. However, little is known about the developmental differences in the effect of adenosine on cardiac cells. We have now shown that there is a striking developmental difference in the inhibitory effect of adenosine on isoproterenol-stimulated ICa between adult and newborn rabbit ventricular cells. Adenosine had no significant inhibitory effect on 0.1 muM isoproterenol-stimulated ICa in adult cells, while it completely blocked the 10 muM isoproterenol-stimulated ICa in newborn cells with an inhibitory potency similar to carbachol in newborn cells. Similarly, adenosine did not decrease the isoproterenol-stimulated cAMP levels in adult cells while it inhibited isoproterenol-stimulated cAMP levels significantly and equipotently to carbachol in newborn. However, for forskolin-stimulated ICa and cAMP levels in newborn cells, adenosine had a much lower inhibitory potency than carbachol. In adult cells, forskolin-stimulated ICa and cAMP levels were not affected by adenosine. We showed previously that the Gia3 isoform of inhibitory G protein was present in newborn cell membranes, but not detectable in adult cell membranes. We have now used a synthetic decapeptide corresponding to the C-terminal sequence of Gia3 in the patch pipette and have shown a selective partial block of the inhibitory action of adenosine for isoproterenol-stimulated ICa, suggesting that the inhibitory action of adenosine on ICa is mediated primarily through the Gia3 pathway.

Adenosine↗
PubMed1996

Protective effects of dimethyl amiloride against postischemic myocardial dysfunction in rabbit hearts: phosphorus 31-nuclear magnetic resonance measurements of intracellular pH and cellular energy.

The effects of 5-(N,N-dimethyl)amiloride, a potent and specific Na(+)-H+ exchange inhibitor, were investigated in isolated perfused rabbit hearts subjected to ischemia and reperfusion. Phosphorus 31-nuclear magnetic resonance spectroscopy was used to monitor intracellular pH, creatine phosphate, beta-adenosine triphosphate, and inorganic phosphate. After cardioplegic arrest with St. Thomas' Hospital solution, normothermic (37 degrees C) global ischemia was induced for 45 minutes, and the hearts were reperfused for 50 minutes. Dimethyl amiloride at 10 mumol/L, which has minimal inotropic and chronotropic effects on the nonischemic heart, was added to the cardioplegic solution. Treatment with dimethyl amiloride reduced the elevation of left ventricular end-diastolic pressure during and after the ischemia and improved the postischemic recovery of developed pressure from 76% +/- 3.2% at 30 minutes of reperfusion in control hearts (n = 6) up to 99% +/- 1.9% in hearts treated with dimethyl amiloride (n = 8). Dimethyl amiloride did not affect the decline in intracellular pH during ischemia for up to 30 minutes but enhanced the intracellular acidosis thereafter. The intracellular pH at the end of ischemia was 6.21 +/- 0.05 in control hearts compared with 5.24 +/- 0.17 in hearts treated with dimethyl amiloride (p < 0.05). During reperfusion, intracellular pH of hearts treated with dimethyl amiloride was less than control for 5 minutes, but subsequent recovery of intracellular pH was similar to control. Treatment with dimethyl amiloride did not affect creatine phosphate breakdown, inorganic phosphate accumulation, and beta-adenosine triphosphate depletion during 45 minutes of ischemia. The creatine phosphate resynthesis and inorganic phosphate reduction during reperfusion were also unaffected. These findings suggest that Na(+)-H+ exchange plays an important role not only during reperfusion but also during ischemia for the development of postischemic cardiac dysfunction most likely by inducing primary Na+ and secondary Ca2+ overload. Specific Na(+)-H+ exchange inhibitors like dimethyl amiloride would have a potential therapeutic profile in cardiac surgery, especially if added before ischemia.

Acidosis↗
PubMed1996

Ludloff's medial approach for open reduction of congenital dislocation of the hip. A 20-year follow-up.

We reviewed 33 patients (35 hips) after open reduction of congenital dislocation of the hip using Ludloff's medial approach. The mean age at the time of operation was 14 months (5 to 29) and at the time of final follow-up 20.1 years (15 to 24) giving a mean duration of follow-up of 19.4 years (14 to 23). We evaluated the radiological results by the Severin classification and the extent of avascular necrosis using the criteria of Kalamchi. At the latest review 16 hips (45.7%) were in Severin groups I or II (acceptable results) and 19 (54.3%) in Severin groups III, IV or V (unacceptable results). There was evidence of avascular necrosis in 15 hips (42.9%). The radiological results began to become worse at about the age of ten years when type-II avascular changes presented. We conclude that Ludloff's medial approach for open reduction is unsatisfactory for the treatment of congenital dislocation since about half of our patients required additional operations.

Child, Preschool↗
PubMed1995

Developmental changes in modulation of contractility of rabbit hearts.

We recently described postnatal developmental differences of beta-adrenergic- and G-protein-mediated modulation of L-type calcium currents (ICa) in newborn and adult rabbit heart. To extend the results obtained by ICa experiments, we studied developmental changes in modulation of contractility induced by isoproterenol (ISO), forskolin (FOR) and isobutyl-methylxanthine (IBMX), all of which work through the cyclic AMP-dependent pathway. Left ventricular developed pressure (LVDP) and its first derivative (dP/dt) were measured with an intraventricular fluid-filled balloon in isolated adult and newborn (ages 1-3 days) rabbit hearts under Langendorff perfusion. ISO increased LVDP and +/- dP/dtmax dose dependently, with much greater positive inotropic effect on adult than on newborn heart. Concomitant use of a subthreshold concentration of IBMX (0.1 microM), a nonselective phosphodiesterase inhibitor (PDEI), did not significantly potentiate the dose-dependent inotropic effect of ISO in adult heart, but did markedly potentiate such effect in newborn heart. ISO 10 microM and FOR 10 microM had comparable inotropic effects on adult heart, whereas 10 microM ISO had a much weaker inotropic effect than 10 microM FOR on newborn heart. However, the increase in LVDP and +dP/dtmax and the percentage increase in these values induced by 10 microM FOR in newborn heart was still significantly lower than that in adult heart. Newborn heart has less effective signal transduction from beta-adrenergic stimulation (ISO) to increased contractility than does adult heart. Although newborn heart responds more to direct stimulation of adenylyl cyclase activity (FOR) than to beta-adrenergic stimulation, it still has less overall contractile reserve than adult heart. PDE isozymes of newborn heart are much more sensitive to IBMX than are those of adult heart, producing a significant potentiation of ISO effect by low doses of IBMX in newborn, but not adult, heart.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Postnatal changes in the G-proteins, cyclic nucleotides and adenylyl cyclase activity in rabbit heart cells.

We have studied the postnatal changes in the levels of isoforms of stimulatory (Gs) and inhibitory (Gi) G-proteins, cAMP and cGMP in washed particulate membranes (WPM) from whole ventricles as well as from isolated ventricular myocytes and have also measured adenylyl cyclase (AC) activity in WPM prepared from isolated myocytes of adult (AD) and newborn (NB) rabbit heart. Immunoblot analysis for the levels of Gi alpha 1, G alpha 2, Gi alpha 3 and Gs alpha subunits showed that Gi alpha 2 and Gi alpha 3 were higher in WPM from whole ventricles of NB compared to AD. This ratio was much higher in WPM from isolated ventricular myocytes since Gi alpha 2 and Gi alpha 3 were either absent or present in extremely low immunodetectable levels in WPM from AD ventricular myocytes. Gi alpha 1 levels were not different for AD compared to NB WPM, whether prepared from whole ventricle or from isolated myocytes. Two forms of Gs alpha, a small form (Gs alpha-S) and a large form (Gs alpha-L), were immunodetected at 43 and 48 kDa, respectively. The Gs alpha-S form was higher in AD WPM and the Gs alpha-L form was higher in NB WPM while the total Gs alpha(L+S) was not different. The Gs alpha results for WPM from isolated myocytes were not different from the results for WPM from whole ventricles. Basal levels of cAMP were 80% higher in NB compared to AD whole ventricles and were 200% higher in NB compared to AD isolated myocytes. Levels of cGMP were 4-5 fold higher in NB than in AD myocytes and ventricular tissue. Basal AC activity was higher in NB than in AD WPM from isolated myocytes and was enhanced by Gpp(NH)p pretreatment in AD but not in NB WPM. The isoproterenol-induced increase in AC activity was higher in AD compared to NB WPM and was completely abolished by Gpp(NH)p pretreatment in NB but not in AD WPM. Forskolin caused a greater increase in AC activity in NB than in AD WPM. The post-natal decrease in the levels of Gi alpha 2 and Gi alpha 3, particularly in isolated ventricular myocytes, may help to explain the smaller effects of isoproterenol and greater muscarinic influence on ICa, as we previously showed, and the smaller effect of isoproterenol on AC activity in NB compared to AD WPM.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenylyl Cyclases↗
PubMed1994

Developmental changes in the actions of phosphatase inhibitors on calcium current of rabbit heart cells.

We used whole-cell voltage clamp to compare the modulation of calcium current density (ICa, picoampere per picofarad) of freshly isolated, adult and newborn rabbit heart in response to intracellular application of microcystin and okadaic acid, both of which block phosphatase activity of phosphatase type 1 and 2A. Newborn cells showed a much larger response to the intracellular application of either microcystin or okadaic acid than did adult cells. In newborn cells, the application of microcystin produced an increase in ICa which appeared to maximize ICa, as shown by the rise in ICa to levels which could be reached by application of 10 microM forskolin or by the intracellular application of 200 microM 3',5'-cyclic adenosine monophosphate (cAMP). In adult cells, the maximal response to microcystin was considerably less than that obtainable with forskolin or cAMP. After achieving a maximal response with microcystin, the addition of forskolin increased ICa further in adult cells but elicited no additional response in newborn cells. The treatment of cells with 0.1 microM isoproterenol, a concentration approximately equal to that required for a half-maximal response, strongly potentiated the effect of microcystin in newborn cells, but not in adult cells. We propose that newborn rabbit heart cells compared with adult rabbit heart cells have a greater level of protein phosphatase activity (perhaps combined with a somewhat greater kinase activity), a greater proportion of the protein phosphatase activity in the form of protein phosphatase type 1 (which is inhibited by isoproterenol) and a greater dependence on the inhibition of protein phosphatase as a mechanism of action of isoproterenol, compared with the increase in kinase activity on calcium channels.

Animals↗
PubMed1994

Production of chimeric pigs and the analysis of chimerism using mitochondrial deoxyribonucleic acid as a cell marker.

Two injection methods were examined for making chimeras between Chinese pigs (Meishan) and European pigs (Landrace or Landrace x Large White). Furthermore, mitochondrial DNA (mtDNA) polymorphism was detected as a cell marker for the analysis of chimerism. In the first experiment, blastomeres were transplanted into embryos at the 4-16-cell stage. Of 41 transplanted embryos transferred into 3 females, 12 were single-colored, but no overt chimeras were obtained. Judging from coat color and mtDNA in white blood cells, 2 piglets in 2 litters were derived from injected blastomeres, and 10 piglets in 3 litters were derived from recipient blastomeres. In the second experiment, inner cell mass cells of Day 6 Landrace embryos were injected into blastocoels of Day 6 Meishan embryos. Of 35 injected embryos transferred into 3 females, 2 overt chimeras of each sex were obtained in a single litter. In the overt male chimera, mtDNA clearly showed chimerism in spleen, pancreas, brain, kidney, lung, liver, heart, testis, and small intestine. The overt female chimera showed chimerism not only in blood but also in germ line according to a progeny test. No chimerism was detected in any of the 21 single-colored piglets in the second experiment.

Animals↗