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Biomedical subjects

K Nakai

Publications and source records attributed to K Nakai.

At least 199 records · Page 11Linked to original sources
PubMed1996

[FLAIR images of patients with head injuries].

FLAIR (fluid-attenuated inversion recovery) images are MR images obtained with an inversion recovery sequence, which has a long inversion time (TI) and a long echo time (TE). We examined 29 cases (49 graphics) of cerebral contusion, 11 cases (22 graphics) of diffuse axonal injury (DAI) and 11 cases (11 graphics) of traumatic subarachnoid hemorrhage (t-SAH) with FLAIR sequence consisting of a repetitive time (TR) of 6500 msec, TI of 1700 msec and TE of 110 msec, and these graphics were compared with T2-weighted images by spin-echo sequence (TR 2500 msec, TE 90 msec) and computed tomographic (CT) scans. Some lesions of DAI were demonstrated more clearly with FLAIR images than with conventional T2-weighted images. Although contusion could be detected with FLAIR images as well as with conventional T2-weighted images, lesions adjacent to cerebral sulci were better delineated with FLAIR images. Because the cerebrospinal fluid signals in cerebral sulci were low-intensity, FLAIR images were useful in detecting lesions of the cerebral cortex adjacent to cerebral sulci. Although it has been reported that detection of SAH is difficult with standard T1- and T2-weighted images, the presence of t-SAH could be confirmed with FLAIR images as seen in CT scans.

Adult↗
PubMed1996

Differential association of protein Ser/Thr phosphatase types 1 and 2A with the cytoskeleton upon platelet activation.

The association of protein Ser/Thr phosphatase type 1(PP1) and type 2A (PP2A) with the cytoskeleton (Triton X-100 insoluble residue) during human platelet activation was investigated. In unstimulated platelets, 40% of total PP1-like activity was present in the Triton-insoluble cytoskeleton, while only 10% of the total PP2A-like activity was present in this fraction. Stimulation with 1 U/ml thrombin produced a 1.8-fold increase in PP1-like activity and a 7-fold increase in PP2A-like activity, respectively, in the cytoskeletal fraction, under aggregating conditions. Immunoblot analysis revealed that thrombin treatment increased association of PP1 catalytic subunit isozymes (PP1 alpha, PP1 gamma, PP1 delta) and PP2A catalytic subunit with the cytoskeleton, with concomitant decrease of these enzymes in Triton-soluble fractions. The amounts of cytoskeleton-associated PP1 and PP2A depended on the dose of thrombin which could activate platelets. Agonist-induced redistribution of PP1 and PP2A into the cytoskeleton was inhibited by OP-41483 (a prostaglandin I2 analog). Interaction of PP2A with cytoskeletal proteins strongly correlates with aggregation, whereas the association of PP1 with cytoskeleton can be detected upon platelet activation, even in the absence of aggregation. Co-extraction of protein kinase C and myosin light chain kinase with the cytoskeleton eventually translocated to the cytoskeleton, but only during aggregation. These results suggest that differential translocation of PP1 and PP2A to the cytoskeleton is involved in platelet activation, and their association with cytoskeletal proteins may regulate phosphorylation levels together with protein kinases in platelets.

Cytoskeleton↗
PubMed1995

Up-regulation of protein serine/threonine phosphatase type 2C during 1 alpha,25-dihydroxyvitamin D3-induced monocytic differentiation of leukemic HL-60 cells.

Treatment with 20 nM 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) caused a progressive increase in the activity of Mg(2+)-dependent protein serine/threonine phosphatase type 2C (PP2C) in subcellular fractions of HL-60 cells, whereas PP2C activity was relatively constant throughout all-trans retinoic acid-induced (1 microM) granulocytic differentiation. The increase in PP2C activity appeared to parallel the 1,25(OH)2D3-induced phenotypic and functional changes in HL-60 cells. Immunoblot and Northern blot analysis indicated that the increase in PP2C activity corresponded to the increased expression of PP2C protein, which was preceded by an increase in the level of mRNA for PP2C beta. No mRNA for PP2C alpha was detected in resting or 1,25(OH)2D3-stimulated HL-60 cells. These results suggest that the increased expression of PP2C is related with the 1,25(OH)2D3-induced monocytic differentiation of HL-60 cells.

Calcitriol↗
PubMed1995

Translocation of protein phosphatase 1 catalytic subunits during 1,25-dihydroxyvitamin D3-induced monocytic differentiation of HL-60 cells.

To elucidate the roles of protein phosphatases type 1 (PP1) and type 2A (PP2A) in 1,25-dihydroxy-cholecalciferol [1,25(OH)2D3]-induced differentiation of HL-60 cells into monocytes, we examined the enzyme activity and the protein and gene expressions of PP1 and PP2A in these cells. Calyculin-A augmented the 1,25(OH)2D3-induced differentiation of the cells. Treatment of the cells with 1,25(OH)2D3 led to a decrease in PP1-like activity in the cytosol fraction, with a concomitant increase in the membrane and nuclear PP1-like activity, as determined when protein phosphatase activity was assayed using myosin light chain as substrate in the presence of 5 nM okadaic acid. Western blot analysis with antibodies specific for PP1 catalytic subunit isozymes (PP1 alpha, PP1 gamma, and PP1 delta) showed that all three PP1 isozymes were expressed but were differentially distributed in each cellular fraction. Subcellular redistribution of PP1-like activity during 1,25(OH)2D3-induced differentiation was mainly attributed to PP1 gamma and PP1 alpha proteins. In contrast, the localizations of PP1 delta and PP2A catalytic and regulatory subunits were not significantly affected by 1,25(OH)2D3 treatment. The gene expressions of PP1 alpha and PP1 gamma appeared to be constant during processes of monocytic differentiation. The correlation between phenotypic and functional changes of HL-60 cells on the one hand and subcellular redistribution of PP1-like activity on the other suggest that the translocations of PP1 alpha and PP1 gamma isozymes may contribute to the 1,25(OH)2D3-induced monocytic differentiation of HL-60 cells.

Calcitriol↗
PubMed1995

Mexiletine and lidocaine reduce post-ischemic functional and biochemical dysfunction of perfused hearts.

The present study was undertaken to determine whether class Ib antiarrhythmic agents, mexiletine and lidocaine, exert beneficial effects on ischemia/reperfusion-induced cardiac contractile dysfunction. Isolated rat hearts were subjected to 35-min global ischemia, followed by 60-min reperfusion and the functional and metabolic alterations were examined with and without mexiletine or lidocaine treatment. Ischemia/reperfusion resulted in a lack of recovery of contractile function, a sustained rise in left ventricular end-diastolic pressure and increased coronary perfusion pressure of the perfused heart during reperfusion. Contractile dysfunction was associated with increases in tissue Na+ and Ca2+ levels, decreases in K+ and Mg2+ levels, and release of creatine kinase and purine nucleosides and bases (ATP metabolites) from the heart. Treatment of the perfused heart with either 10-100 microM of either mexiletine or lidocaine during pre-ischemia resulted in an enhancement of post-ischemic contractile recovery, a suppression of changes in tissue Na+, K+, Ca2+ and Mg2+ contents and an attenuation of the release of creatine kinase and ATP metabolites in an almost concentration-dependent manner. Tissue sodium accumulation was observed at the end of ischemia, which was also attenuated by pretreatment with these agents. The prevention of Na+ overload and accompanying Ca2+ overload in cardiac cells may be the mechanism underlying the improvement of post-ischemic contractile function of perfused hearts by these agents.

Adenosine Triphosphate↗
PubMed1995

Unilateral spatial neglect due to a haemorrhagic contusion in the right frontal lobe.

We report two cases of unilateral spatial neglect associated with an isolated right frontal lobe lesion. Case 1 was a 59-year-old, right-handed man, who developed a left hemiplegia, disorientation, and frontal lobe neglect associated with a haemorrhagic contusion following a head injury. Case 2 was a 55-year-old, right-handed man, who also developed disorientation and frontal lobe neglect secondary to a haemorrhagic contusion following a head injury. 99mTc HM-PAO SPECT revealed an isolated reduction in the regional cerebral blood flow (CBF) around the haematoma in the frontal lobe; blood flow to remaining parts of the brain was normal. Damage to the right frontal lobes of these patients was confirmed as being the cause of the unilateral spatial neglect in accordance with the results of CBF studies.

Attention↗
PubMed1995

Myxoma of the mitral valve detected by echocardiography and magnetic resonance imaging.

Myxomas of the mitral valve diagnosed during life are exceedingly rare. We employed transthoracic and transoesophageal echocardiography and magnetic resonance imaging enhanced by gadolinium-diethylene-triamine-pentaacetic acid in a patient with palpitations. After these examinations clearly demonstrated a myxoma on the atrial side of the posterior mitral valve leaflet, urgent surgery was performed. When a small tumour of the mitral valve exists, these examinations are useful not only for detecting and characterizing the tumour, but also for deciding the optimal surgical management.

Adult↗
PubMed1995

Effect of a new bombesin receptor antagonist, (E)-alkene bombesin isostere, on amylase release from rat pancreatic acini.

The short-chain pseudopeptide, [D-Phe6, Leu13 psi (CH2NH)Leu14]bombesin(6-14) (RDI), is reported to be a potent antagonist of bombesin, and development of this type of compound has greatly contributed to the investigation of biological actions of bombesin and its related peptides. We recently synthesized (E)-alkene bombesin isostere by replacing the peptide bond with an (E)-double bond: [D-Phe6, Leu13 psi [(E)CH = CH]Leu14] bombesin(6-14) (EABI). The present study examined the effect of EABI on amylase release from rat pancreatic acini. EABI showed no agonistic activity at concentrations up to 1 microM, and RBI showed slight agonistic activity at concentrations > 10 nM. EABI caused a dose-dependent inhibition of amylase release stimulated by 0.1 nM bombesin, with an IC50 of 6.7 +/- 1.7 nM, and induced almost-complete inhibition at 0.3 microM. RDI caused a dose-dependent inhibition of amylase release, with an IC50 of 68.7 +/- 16 nM. EABI caused a parallel and rightward shift of the entire dose-response curve of bombesin-stimulated amylase release, and the degree of the shift was dependent on the concentrations of EABI. EABI (100 nM) and RDI (100 nM) inhibited amylase releases stimulated by gastrin-releasing peptide (1 nM) and neuromedin-C (1 nM). In contrast, amylase release stimulated by cholecystokinin octapeptide (0.1 nM), carbachol (10 microM), vasoactive intestinal peptide (1 nM), and gastrin-17 (10 nM) was not inhibited by EABI and RDI. The results indicate that EABI is a potent and specific bombesin receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1995

Can the risk for acute cardiac events in acute coronary syndrome be indicated by platelet membrane activation marker P-selectin?

BACKGROUND: P-selectin, an adhesion molecule of the selectin family, is expressed on the surface of activated thrombocytes by thrombin. The aim of the present study was to assess the predictive value of P-selectin (estimated by flow cytometric assay) for acute cardiac events in acute coronary syndrome. METHODS: The study consisted of 48 patients with acute coronary syndrome and 30 healthy control subjects. After immediate fixation with 1% paraformaldehyde, 50 microliters of this aliquot was incubated with phycoerythrin-CD62-related antigen, and then measured by flow cytometry. The short-term clinical course of the patients was compared with their P-selectin values. RESULTS: The average P-selectin values in the 30 healthy volunteers was 0.11 +/- 0.20% (range, 0.0-0.5%). Significant differences were observed between acute cardiac events in patients with unstable angina and high P-selectin values and those with normal P-selectin values (chi 2 = 4.3; P < 0.05). Moreover, the angina patients who experienced acute cardiac events had significantly elevated P-selectin values (2.1 +/- 2.3%) compared with patients who did not experience acute cardiac events (0.3 +/- 0.4%, P < 0.05). The P-selectin values were elevated in seven out of 24 patients who suffered acute myocardial infarction. Seven of the 14 patients with acute coronary syndromes and high P-selectin values required urgent percutaneous transluminal coronary angioplasty (PTCA) and coronary artery bypass grafting (CABG), or both, otherwise they developed extension of the infarction. However, only five of the 34 patients with normal P-selectin values required urgent PTCA or CABG. Significant differences were observed in acute cardiac events between the high P-selectin and normal P-selectin groups (chi 2 = 4.8, P < 0.05). CONCLUSION: High P-selectin values indicate activation of platelets and the risk of acute cardiac events in patients with acute coronary syndrome.

Blood Platelets↗
PubMed1995

Transient cortical blindness following bypass graft angiography. A case report.

Transient cortical blindness, an uncommonly recognized complication of cerebral angiography, is an exceedingly rare event after cardiac catheterization and angiography. This report describes a sixty-two-year-old patient who had transient cortical blindness following bypass graft angiography. In this case, the authors showed that cortical blindness was associated with the breakage of the blood-brain barrier (BBB) and an increase in vascular permeability rather than with primary cerebral circulatory insufficiency. When the possibility exists that an excess volume of contrast medium may enter the cerebral circulation as in this case, that is, following a coronary artery bypass graft (CABG) using the internal mammary artery (IMA), precautionary measures may be necessary such as changing the type of contrast medium to be used or decreasing the volume injected. When cortical blindness occurs, it is a serious clinical problem whether transient or permanent. Therefore, the circumstances leading to this complication should be understood to determine suitable treatment and management.

Blindness↗
PubMed1995

[The influence of pharyngoplasty on articulation].

UNLABELLED: Pharyngoplasty is a surgical technique for the treatment of obstructive sleep apnea and snoring. The most commonly employed pharyngoplasty technique is uvulopalatopharyngoplasty (UPPP). The anatomical structure of the pharynx is usually changed in this procedure, and a change in articulation may result, because the pharynx plays a important role in articulation. We, therefore, assessed the influence of pharyngoplasty on articulation in patients who underwent UPPP. Perceptual study: Twenty-five Japanese monosyllables uttered by 12 patients were tape-recorded pre-and postoperatively. The results of listening tests showed no significant changes in articulation scores for any syllables in the pre-and postoperative samples, and there were no nasalized articulations and no reduced intensity of consonants. Acoustical study: The first and second formant (F1, F2) of the five Japanese vowels pronounced by 20 patients were recorded pre-and postoperatively. In addition, intraindividual variation in the F1, F2 of the five Japanese vowels were measured in 4 normal subjects. The F1 and F2 of the vowel /e/ were slightly higher postoperatively. F2 of vowel /u/ was slightly lower postoperatively, and the F2 of vowel /o/ showed the same change. These changes in formants, however, fell within the range of intraindividual variation. RESULTS: There is no problem in the articulation of phonemes after UPPP, but the timbre of the voice may be influenced by the changes in formants.

Adult↗
PubMed1995

[Endovascular treatment of cerebral vasospasm with intra-arterial papaverine infusion].

Thirty-one cases of cerebral vasospasm following subarachnoid hemorrhage were treated with intraarterial papaverine infusion. Symptomatic cases were nineteen, and asymptomatic cases were twelve. Papaverine (120 mg/saline 50 ml, 30 min) was injected superselectively to vasospastic vessels through a microcatheter. The rate of symptomatically improved cases was 63% initially, but about two thirds of those cases had recurrence within a day. The 63% of symptomatic cases showed infarction in spite of papaverine infusion. Three cases of recurrent vasospasm after intra-arterial papaverine underwent PTA and showed good dilatation of vasospastic vessels. The complications of our intra-arterial papaverine were hypotension in two cases, convulsion in one case and transient disturbed consciousness in one case. We experienced no fatal complications. Overall outcome was ADL1 (19%), ADL2 (25%), ADL3 (44%), ADL4 (0%), ADL5 (6%), and death (6%). Since the effect of intra-arterial papaverine infusion is of short duration and weak, combination of PTA and papaverine may be necessary. It is recommended to use papaverine for vasospasm in distal arteries such as M2, A1, A2, and to carry out PTA for proximal arteries such as ICA and M1.

Adult↗
PubMed1995

[A penetrating injury of the extracranial vertebral artery: a case report].

Penetrating injury to the vertebral artery is a very rare accident and no case except ours has been reported to date in Japan. We reported a case of successful treatment of a penetrating injury by a nail to the left vertebral artery with the use of interventional radiologic procedure. A 27-year-old man was admitted to our hospital with a complaint of penetrating injury in his neck. Left vertebral angiography revealed that a nail had penetrated into the vertebral artery at the C6 level. Considering the possibility of thrombus formation around the metallic foreign body and the risk of uncontrollable bleeding, we performed embolization of the injured vertebral artery with Interlocking Detachable Coil.

Adult↗
PubMed1995

[The effect on higher cortical dysfunction of percutaneous transluminal angioplasty for internal carotid artery stenosis].

Seven patients with internal carotid artery (ICA) stenosis with higher cortical dysfunction due to hemodynamic ischemia were treated by percutaneous transluminal angioplasty (PTA). The patients ranged from 49 to 71 years of age, and included five males and two females. Neuropsychological tests were evaluated before and after PTA. Higher cortical dysfunction improved in all cases after PTA. It is concluded that PTA is effective to improve higher cortical dysfunction in patients who have ICA stenosis associated with hemodynamic compromise, if the ICA is satisfactorily dilated.

Aged↗
PubMed1995

Decreased expression of protein phosphatase type 2A in HL-60 variant (HL-60RAr) cells resistant to induction of cell differentiation by all-trans retinoic acid.

To evaluate the molecular basis for susceptibility of the cell differentiation induced by all-trans retinoic acid (ATRA), we examined biochemical activities and expression of protein phosphatases type 1 (PP1) and type 2A (PP2A) from HL-60 cells that are susceptible to differentiation induced by ATRA and HL-60RAr cells, HL-60 variant cells that are resistant to such induction. One nM of calyculin-A (CAL-A) achieved the enhancement of granulocytic differentiation in ATRA-treated HL-60 (1 microM) cells. ATRA exerted no differential action in HL-60RAr cells, but when used in combination with CAL-A, the differential activity was partly resumed at functional and phenotypic levels without change in morphology. The phosphatase activity in the cytosol from HL-60RAr cells was 50% of that from parental HL-60 cells, but the enzyme activities in either membrane or nuclear fractions showed similar values. The decreased phosphatase activity in the cytosol of HL-60RAr cells was mainly due to the decreased expression of the PP2A catalytic subunit. This low level of PP2A protein was reflected at a relative deficiency in expression of the PP2A beta gene in HL-60RAr cells. The exposure to 1 microM ATRA resulted in downregulation of PP2A catalytic subunit protein in HL-60 cells, but ATRA did not affect PP2A expression in HL60RAr cells. Both cell lines expressed the proteins of each PP1 catalytic subunit isozyme (i.e., PP1 alpha, PP1 gamma, and PP1 delta) at comparable levels. ATRA treatment had no effect on the levels of PP1 isozymes. Our results show a correlation between the extent of PP2A expression and the response of HL-60 and HL-60RAr cells to the differentiative effects of ATRA.

Blotting, Northern↗
PubMed1995

[Detection of CD62P (GMP-140) on peripheral blood platelet membrane in various heart diseases].

The protein CD62P expressed on platelet surface membrane was measured by flow cytometry to evaluate its clinical significance. Whole blood contained 0.32% citrate from 64 patients with heart disease and 30 healthy adults were fixed with 0.1% paraformaldehyde. To 50 microliters of the fixed blood, 10 microliters of CD62 PE (Becton Dickinson) was added. After standing for 20 minutes at room temperature, the samples were washed and suspended in 1ml of PBS. Platelets were analyzed with Spectrum III (Ortho) flow cytometer. In healthy control, the percentage of platelets positive for anti-CD62P was 0.16 +/- 0.20 (mean +/- SD)%. Abnormal levels of CD62P were observed in 5 patients with unstable angina, 6 patients with acute myocardial infarction, 1 patient with old myocardial infarction, and 2 patients with mitral stenosis. These results show that activated platelets may play some roles in pathogenesis of heart disease though it is not fully clear yet.

Biomarkers↗
PubMed1995

Concentration of soluble vascular cell adhesion molecule-1 (VCAM-1) correlated with expression of VCAM-1 mRNA in the human atherosclerotic aorta.

BACKGROUND: Adherence of circulating monocytes and lymphocytes to arterial endothelium is detectable early in experimental and human atherosclerotic plaque formation. The purpose of the present study was to assess vascular cell adhesion molecule-1 (VCAM-1) mRNA expression and the properties of soluble VCAM-1 in patients with atherosclerotic aortic disease. METHODS: Thirteen patients with aortic disease (mean age 64 years) and 40 healthy volunteers (mean age 32 years) were included in the study. We investigated the expression of VCAM-1 mRNA in eight human aortic specimens obtained during surgery. Of these, two showed no evidence of atherosclerotic plaque formation [aortic dissection (n = 1) and annuloaortic ectasia (n = 1)], whereas six had demonstrable complex atherosclerotic formation [abdominal aneurysm (n = 5) and aortic dissection (n = 1)]. The RNase protection assay was performed using an alpha 32P-labeled 121 base pair VCAM-1 cRNA probe. We also measured concentrations of the soluble VCAM-1 using two-site enzyme immunoassays in 40 healthy volunteers and in 13 patients with abdominal and thoracic aortic aneurysms. RESULTS: In human samples, VCAM-1 mRNA expression was found to be higher in the six patients with complex atherosclerotic formation [optical density (OD), 0.71 +/- 0.14] than in the two patients with no evidence of atherosclerotic plaque formation (OD, 0.53 and 0.49). The concentration of serum soluble VCAM-1 was higher (850 +/- 298 ng/ml) in patients with aortic or thoracic disease than in the healthy volunteers (494 +/- 94 ng/ml). In addition, there was a relationship between VCAM-1 mRNA expression and the concentration of soluble VCAM-1 (y = 2088x-554, r2 = 0.73). CONCLUSION: VCAM-1 expression is higher in the human aorta in patients with atheromatous changes. Furthermore, concentrations of soluble VCAM-1 may provide important information about endothelial activation or in-vivo damage.

Adult↗