Biomedical subjects

T Iwamoto

Publications and source records attributed to T Iwamoto.

At least 163 records · Page 9Linked to original sources

PubMed1998

[Atrophy and magnetization transfer ratio of the corpus callosum in patients with Alzheimer's disease].

We compared atrophy and magnetization transfer ratio (MTR) in the corpus callosum in patients with Alzheimer's disease and age-matched normal subjects. Fifteen patients with Alzheimer's disease and fourteen normal subjects received MRI. The corpus callosum was divided into three parts (anterior, middle, and posterior portions) on midsagittal slice, and their areas on T2-weighted reversed images and MTR on magnetization transfer contrast images in each portion were measured. The area and MTR decreased significantly in the posterior portion in patients with Alzheimer's disease. In the anterior portion, MTR decreased significantly, but although the area showed no significant change. In the middle portion, the area and MTR showed no significant change. MTR and the area was correlated in each portion in patients with Alzheimer's disease. The score of Hasegawa dementia scale-revised (HDS-R) and the area of the middle, posterior and total of corpus callosum were significantly related. The score of HDS-R and MTR in the anterior portion of corpus callosum were significantly related. The present study revealed decreases in MTR in the anterior portion of the corpus callosum of patients with Alzheimer's disease although the area showed no significant change, and this change suggests the increase in free water and/or the decrease in bound water in tissues, probably due to demyelination and axonal degeneration.

Aged↗

PubMed1998

[A case of primary malignant lymphoma of the bladder].

The patient was a 34-year-old male. He visited a community hospital complaining of macroscopic hematuria and pollakiuria. Cystoscopic examination demonstrated a bladder tumor. Transurethral resection of the bladder tumor (TUR-Bt) was performed. Histological examination disclosed malignant lymphoma (non-Hodgkin's lymphoma, mixed type). The tumor was classified into the B cell type by the immunohistological staining with surface antigens. He was referred to St. Marianna University, School of Medicine for chemotherapy. Pelvic computed tomography (CT) after admission demonstrated a tumor with a wide pedicle located in the vesicle triangle extending to the posterolateral wall of the bladder. No abnormalities were found in other organs. After establishment of the diagnosis of primary bladder malignant lymphoma, 6 courses of chemotherapy (adriamycin, vincristine, cyclophosphamide, prednisolone, etoposide, methotrexate) were performed. The tumor disappeared completely on imaging studies after chemotherapy. Biopsy of the bladder disclosed no abnormal tissues. No evidence of recurrence or metastasis was found 5 years after chemotherapy.

Adult↗

PubMed1998

[Magnetization transfer imaging of periventricular white matter lesions in patients with multi-infarct dementia].

Using magnetization transfer (MT) imaging, we studied the underlying pathological conditions of periventricular hyperintense (PVH) white matter changes seen on T2-weighted MR images of patients with multi-infarct dementia. Twenty-two patients with multiple lacunar infarcts and PVH lesions, including 11 with dementia (diagnosed as multi-infarct dementia) and 11 without dementia, and 10 control subjects (with multiple lacunes, but no PVH lesion) were studied using the MT technique. MT ratios (MTRs) were calculated for PVH lesions (normal-appearing frontal white matter in controls) and the genu of the corpus callosum. Signal intensities on T2-weighted images in PVH lesions of patients were significantly higher than those in normal-appearing white matter of controls, while there were no significant differences in signal intensity in the genu of the corpus callosum among the dementia, non-dementia and control groups. However, MTRs in patients with PVH lesions were significantly lower than those in controls, and MTRs in demented patients were significantly lower than those in non-demented patients. Moreover, MTRs in the genu of the corpus callosum of demented patients were significantly lower than in those in non-demented patients and controls. MTRs in PVH lesions and the genu of the corpus callosum significantly correlated with Hasegawa's dementia scale score. These results suggest that there is some difference in histopathologic changes of PVH lesions between demented and non-demented patients and that the pathological substrate in the corpus callosum may play a role in inducing cognitive decline. Studies with MT imaging may allow the characterization of different pathological conditions that cannot be visualized by conventional MRI.

Aged↗

PubMed1997

Calmodulin-binding autoinhibitory domain controls "pH-sensing" in the Na+/H+ exchanger NHE1 through sequence-specific interaction.

The calmodulin (CaM)-binding domain reduces the affinity of the Na+/H+ exchanger NHE1 for intracellular H+ by exerting an autoinhibitory function in quiescent cells. We replaced this domain (aa 637-656) with homologous segments from other NHE isoforms (NHE2 and 4) or functionally similar regions from other sources (Na+/Ca2+ exchanger, CaM-dependent protein kinase II, plasma membrane Ca2+-pump, or CaM-binding peptide Trp3). The NHE-1-, NHE2-, and NHE4-segments bound CaM with Kds of 16, 130, and 27 nM, respectively. These chimeric molecules were expressed in the exchanger-deficient cell PS120. NHE1 with incorporated NHE2-segment was activated in response to Ca2+-mobilizing agents ionomycin and thrombin resulting in an alkaline shift of the intracellular pH (pHi)-dependence of 22Na+ uptake, as was the case with the intact rat NHE2. In contrast, incorporation of the NHE4-segment or other CaM-binding segments induced a constitutive alkaline shift of pHi-dependence with concomitant abolishment of Ca2+-dependent activation, indicating that these segments could not function as an autoinhibitory domain in NHE1. Detailed analyses revealed that Leu639, Lys651 and Tyr652, conserved in the NHE1- and NHE2-segments, but not in the NHE4-segment, are important for the autoinhibition. Furthermore, 125I-labeled CaM-binding peptide from NHE1 was efficiently crosslinked to the NHE1 protein, suggesting that the inhibitory domain physically interacts with part(s) of the molecule. Together, these findings support the notion that the reduction of H+ affinity in Na+/H+ exchange occurs through a mechanism involving a highly sequence-specific interaction of the inhibitory domain with its putative acceptor in NHE1.

Amino Acid Sequence↗

PubMed1997

Effect of radiotherapy on anorectal function in patients with cervical cancer.

PURPOSE: The acute and long-term effects of pelvic radiation on defecation were studied. METHOD: Anorectal function was assessed based on manometry and subjective symptoms in 31 patients with cervical cancer treated by radiotherapy alone. Sixteen of 31 patients were examined periodically before, during, and after radiotherapy (early group). Fifteen others were examined more than six months after completion of radiotherapy (late group). RESULTS: One-third of patients in both groups had symptoms, mainly diarrhea and increased stool frequency. Patients in the late group also suffered from disturbed gas-stool discrimination, urgency, a sense of residual stool, and soiling. Anal canal resting pressure was significantly higher after radiotherapy (47 +/- 15.5 mmHg) than before radiotherapy (36.3 +/- 12.5 mmHg; P < 0.05). The maximum tolerable volume decreased with radiation, from 163.3 +/- 45 before to 119.2 +/- 41.4 ml during, 112.7 +/- 36.6 ml immediately after, and 94.6 +/- 34.4 ml in the late group (P < 0.01). Rectal compliance also decreased over time and was lower in the early group (before, 5.7 +/- 1.3 ml/mmHg; P < 0.01; during, 4.6 +/- 2.2 ml/mmHg, P < 0.01; after, 3.7 +/- 1.4 ml/mmHg; P < 0.05) than the late group (2.1 +/- 1.5 ml/mmHg) and lower before than after in the early group (P < 0.01). Although rectal pressure initiating continuous desire to defecate did not change, the maximum tolerable pressure was significantly higher in the late group (81 +/- 19.5 mmHg) than during (59 +/- 16.8 mmHg) or after (59.9 +/- 16.9 mmHg) radiotherapy in the early group (P < 0.05). CONCLUSION: Radiation reduces the capacity of the rectal reservoir, even in asymptomatic patients. These changes develop during radiotherapy and progress over time.

Aged↗

PubMed1997

Whole-cell currents from the cloned canine cardiac Na+/Ca2+ exchanger NCX1 overexpressed in a fibroblast cell CCL39.

A conventional patch-clamp technique was used to record the whole-cell current from the cloned canine cardiac Na+/Ca2+ exchanger NCX1 overexpressed in a fibroblast cell. Ca2+ was extracellularly applied to the Na+-loaded cell to activate the outward current by operating the reverse mode of NCX1. No measurable outward current was ever elicited from the nontransfected cell. Na+/Ca2+ exchange blocker 5 mM Ni2+ or 3 microM KB-R7943 that was applied extracellularly abolished the outward current. With 140 mM external Li+ (replacing Na+), the outward current was transient during the Ca2+ application. In contrast, with 140 mM external Na+, the outward current was maintained without any inactivation during the Ca2+ application. I-V relations predicted from the whole-cell clamp protocols used were obtained both before and during the Ca2+ application. The exchanger whole-cell currents are thus successfully detectable from NCX1 which is overexpressed in this stable transfectant system.

Animals↗

PubMed1997

Effects of ethyl-all-cis-5,8,11,14,17-icosapentaenoate (EPA-E), pravastatin and their combination on serum lipids and intimal thickening of cuff-sheathed carotid artery in rabbits.

The anti-arteriosclerotic effects of ethyl all-cis-5, 8, 11, 14, 17-icosapentaenoate (EPA-E), pravastatin and their combination in cuff-treated rabbits were investigated. EPA-E at 600 mg/kg, pravastatin at 50 mg/kg or their combination was orally administered once daily for 5 weeks, and each of the animals was sheathed with a cuff on the carotid artery 2 weeks after the beginning of drug administration. EPA-E, pravastatin and their combination significantly reduced serum total cholesterol compared to the control group. EPA-E also potently reduced serum triglyceride, while pravastatin only slightly reduced it. The combination of these two agents had the most potent effect on the level of serum triglyceride. Serum phospholipids were also reduced by these treatments in a similar fashion. At the end of treatment, diffuse intimal thickening was observed in the cuff-covered region in all animals in the control group, and the intima/media area ratio in this group was 0.293 +/- 0.038. Treatment with EPA-E alone tended to prevent the intimal thickening, and the intima/media area ratio was 0.209 +/- 0.058 (p = 0.094). This ratio was 0.287 +/- 0.048 (p = 0.902) when pravastatin was administered alone, indicating that it had no significant effect on intimal thickening. The ratio was 0.175 +/- 0.041 (p = 0.042) when both EPA-E and pravastatin were administered, indicating that this combination had a significant inhibitory effect on intimal thickening in the cuff-sheathed region. These findings suggest that combined treatment with EPA-E and pravastatin is more effective than respective monotherapies in lowering serum lipids and/or preventing an intimal thickening as events of atherogenesis.

Animals↗

PubMed1997

Bioactivity of sol-gel derived organically modified silicates: part i: in vitro examination.

Bioactivity was investigated for several organically modified silicates (Ormosils) prepared through sol-gel processes. Ca(II)-free samples were biocompatible only, but Ca(II)containing samples were bioactive and deposited apatite during immersion in a simulated body fluid. The ease of silanol (Si-OH) group formation on the ormosils was considered a predominant factor controlling the bioactivity, while the effect of dissolved Ca(II) ions to increase the degree of supersaturation in the simulated body fluid is secondary.

Journal Article↗

PubMed1997

Change in colonic motility after extrinsic autonomic denervation in dogs.

Changes in colonic motility were compared in dogs undergoing autonomic denervation of the paraaortic and presacral (group A), paraaortic (group B), or mesocolonic region (group C), and sham operation (group D). Five bipolar recording electrodes were placed into the seromuscular layer of the colon and rectum. The numbers of continuous electrical response activity and contractile electrical complex after an intragastric olive oil injection were smaller in group A than in the other groups (P < 0.05) from three weeks through six months after denervation. This difference was significant even in the proximal colon. These data suggest that the pelvic plexus may play an important role in colonic motility including the proximal colon. The damage to the plexus did not recover for at least six months after denevation. Pelvic plexus injury may thus be one of possible explanations for the prolonged change in bowel habit after anterior resection of the rectum.

Animals↗

PubMed1997

Effects of brain temperature on calmodulin and microtubule-associated protein 2 immunoreactivity in the gerbil hippocampus following transient forebrain ischemia.

Increased intracellular calcium and cytoskeletal damage play a crucial role in neuronal death following injury such as cerebral ischemia. The effect of brain temperature on early intracellular calcium increase and neuronal cytoskeletal damage following cerebral ischemia has not been rigorously investigated. In the current communication we evaluated calmodulin (CaM) and microtubule-associated protein 2 (MAP2) in the same brain section using a double labeling immunohistochemical technique, and obtained evidence that the brain temperature has a significant effect on the early calcium increase and cytoskeletal damage as well as the delayed neuronal death occurring in CA1 sector of the gerbil hippocampus after transient forebrain ischemia. In the normothermia (36.7 degrees C) group, CaM and MAP2 immunoreactivity were markedly decreased within 48 h after ischemia and thereafter dramatic neuronal death (grade 3) was seen in the CA1 sector at 7 days. Mild hypothermia (33.3 degrees C) significantly protected against all these changes, whereas cytoskeletal damage and delayed neuronal death were aggravated by mild hyperthermia (39.7 degrees C). We conclude that mild hypothermia protects the brain against transient forebrain ischemia by reducing early cytoskeletal damage and subsequent neuronal death.

Animals↗

PubMed1997

Synthetic mutants of Clostridium pasteurianum ferredoxin: open iron sites and testing carboxylate coordination.

The entire polypeptide chains for two new Clostridium pasteurianum ferredoxin (Fd) mutants were prepared with the following site-specific substitutions: Cys11Asp and Cys11 alpha-aminobutyric acid (Cys11 alpha-Aba), the latter being a non-naturally occurring amino acid. Standard t-Boc procedures were used for the synthesis and the peptides. The two apoproteins were reconstituted to the 2[4Fe-4S] holoprotein and their spectroscopic, redox and thermal properties were compared with those of native C.pasteurianum Fds. The fully reconstituted Cys11Asp and Cys11 alpha-Aba mutants were initially found to have both clusters intact, i.e. they were 2[4Fe-4S] ferredoxins. The unconventional ligands of Asp and alpha-Aba led to holo-Fds that were not very stable and easily released an iron to form the [3Fe-4S] cluster, presumably through oxidation. The Cys11 alpha-Aba mutant was somewhat more thermally stable than Cys11Asp. In contrast, while both mutants were less stable than the native protein upon exposure to oxygen, the Cys11 alpha-Aba mutant was less stable than Cys11Asp. The Cys11Gly mutant was also prepared, but all attempts, despite repeated and varied experimental conditions, at reconstitution to the Cys11Gly holo 2[4Fe-4S] Fd were unsuccessful, probably because a Gly-Gly sequence is known to break structure. This work, when compared with molecular biological site-specific mutagenesis, shows some of the advantages of chemical/in vitro reconstitution: certain mutants which cannot be detected as holoproteins by site-specific mutagenesis can be formed after all in vitro. Nonetheless, it seems apparent that altering any of the Cys coordination sites of the Fd clusters results in fundamentally more unstable ferredoxins.

Clostridium↗

PubMed1997

Differences in refractory-period response of canine subendocardium and subepicardium to bunazosin, an alpha1-adrenoceptor antagonist, and propranolol during myocardial ischemia.

Our objective was to investigate the effects of alpha1- or beta-adrenoceptor blockers on endocardial and epicardial refractory-period changes during myocardial ischemia in alpha-chloralose-anesthetized dogs. The first and second diagonal branches of the left anterior descending coronary artery were ligated. The refractory period was determined by an S1-S2 extrastimulus method. Dogs were treated with the alpha1-blocker bunazosin (0.1-0.2 mg/kg, i.v.; n = 16), the beta-blocker propranolol (0.2 mg/kg, i.v.; n = 15), or saline (n = 11). Dogs that developed ventricular tachycardia/fibrillation (VT/VF) during the experiment were excluded from the statistical assessment in refractory periods. In all groups, coronary ligation produced a significant shortening of the refractory period of ischemic epicardial tissue (p < 0.05) but only minimal shortening of ischemic endocardial refractory periods, resulting in an increased difference in repolarization time between the endo- and epicardial sites. Treatment with bunazosin ameliorated this ischemia-related shortening of refractory periods at both the endo- and epicardial sites, with a greater effect seen epicardially (p < 0.05), resulting in values similar to those in the nonischemic tissue. Treatment with propranolol prolonged refractory periods more in the epicardial (p < 0.01) than in endocardial sites, exacerbating the disparity in the refractory period between the endo- and epicardial sites (p < 0.05). Propranolol also prolonged the refractory period of nonischemic tissue (p < 0.05 and p < 0.01 in endo- and epicardial sites, respectively), resulting in a significant difference between the ischemic and normal myocardium at the endocardial site (p < 0.05). Results suggest that the alpha1-blocker bunazosin reduces the refractory-period disparity between the ischemic and normal myocardium without increasing the disparity between the endo- and epicardial surfaces, whereas propranolol produces a greater disparity.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1997

Traumatic aneurysm of the temporal artery: a report of five cases.

Five cases of traumatic aneurysm of the superficial temporal artery are reported. Four patients clearly stated that they had sustained traumatic injuries within 3 months prior to the appearance of the pulsating aneurysms; in the remaining case, more than two years had passed before the appearance of the nodule, and it was without pulsation. Color Doppler echography was very useful for observing the circulation in these aneurysms. Histologically, these cases were pseudoaneurysms composed of small vessels with internal elastic lamina and adjacent connective tissue proliferation, suggesting a break in the arterial wall.

Adolescent↗

PubMed1997

Diagnostic magnetic resonance-urography in an infant girl with an ectopic ureter associated with a poorly functioning segment of a duplicated collecting system.

We report on a case of an ectopic ureter associated with a duplicated collecting system in a 6-month-old girl. Results of conventional imaging and endoscopic studies, including intravenous pyelography, ultrasonography of the kidneys, cystoscopy, vaginoscopy, and vaginogram, were unremarkable. An ectopic ureter, extending from a poorly functioning upper pole of the ipsilateral duplicated kidney to its vaginal opening, was visible on the magnetic resonance-urogram. The imaging time was not extensive, and the need for patient sedation was minimal. Respiratory motion and intestinal gas did not interfere with the quality of the images. Magnetic resonance-urography may possibly be used as a primary diagnostic method for this anomaly when it is not detected by standard imaging techniques, or as a noninvasive substitute for some interventional studies in infants.

Female↗

PubMed1997

A synthetic peptide derived from glycine-gated Cl- channel induces transepithelial Cl- and fluid secretion.

M2GlyR is a synthetic 23-amino acid peptide that mimics the second membrane-spanning region of the alpha-subunit of the postsynaptic glycine receptor. This peptide has been shown to form an anion-selective channel in phospholipid bilayers. We have investigated the possibility that the peptide may incorporate into the apical membrane of secretory epithelia and induce the secretion of Cl- and water. We improved the solubility of this peptide by adding four lysine residues to the carboxy terminus, C-K4-M2GlyR, and assayed its channel-forming activity using a subculture of Madin-Darby canine kidney (MDCK) cells. The addition of 100 microM C-K4-M2GlyR to the apical surface of MDCK monolayers significantly increased short-circuit current (Ise), hyperpolarized transepithelial potential difference, and induced fluid secretion. The increase in Ise was inhibited by 100 microM bumetanide and by Cl- channel inhibitors. The effectiveness of the channel blockers followed the sequence niflumic acid > or = 5-nitro-2-(3-phenylpropylamino)benzoate > diphenylamine-2-carboxylate (DPC) > glibenclamide. The effect of the peptide was not inhibited by 4.4'-diisothiocyanostilbene-2-2'-disulfonic acid. Removing Cl from the bathing solutions also inhibited the effect of the peptide. The Cl- efflux pathway induced by C-K4-M2GlyR differs from the native pathway activated by the adenosine 3',5'-cyclic monophosphate (cAMP) agonist, forskolin. First, intracellular cAMP levels were unaffected. Second, the concentration of DPC required to inhibit the effect of the peptide was much lower than that needed to block the forskolin response (100 microM vs. 3 mM). These results support the hypothesis that the synthetic peptide C-K4-M2GlyR can from Cl -selective channels in the apical membrane of secretory epithelial cells and can induce sustained transepithelial secretion of Cl- and fluid.

Amino Acid Sequence↗

PubMed1997

Increased water diffusion in cerebral white matter in Alzheimer's disease.

We investigated the changes in water diffusion in the cerebral white matter in 19 patients with Alzheimer's disease (AD), including 11 without and 8 with periventricular hyperintensity (PVH) lesions, using diffusion-weighted magnetic resonance imaging (MRI). The apparent diffusion coefficients in the anterior and posterior white matter were significantly higher in the 19 AD patients than in the 10 age-matched controls. The apparent diffusion coefficients were higher in patients with PVH than in those without. The anisotropic ratios, defined as diffusion restricted perpendicular to the direction of the nerve fibers, were significantly higher in AD patients, even in those without PVH, than in the controls. Our results suggest that mild myelin loss occurs in AD patients even in the apparently normal white matter. A definite loss of myelin and axons, including incomplete infarction, occurs in the white matter, as seen on T2-weighted images as PVH. Studies with diffusion-weighted MRI may allow the characterization of different pathological processes and enable the demonstration of underlying white matter lesions in AD that cannot be visualized by conventional MRI.

Aged↗

PubMed1997

Angiotensin-converting enzyme gene polymorphism adds risk for the severity of coronary atherosclerosis in smokers.

To investigate the relation between the angiotensin-converting enzyme (ACE) gene polymorphism and acute coronary syndromes with respect to environmental factors, we analyzed the association of genotype with the coronary angiographic findings of patients with acute myocardial infarction or unstable angina pectoris, and we examined the linkage of each genotype with established risk factors for coronary artery disease. We determined the ACE genotype in 152 Japanese patients with acute coronary syndromes and 399 healthy individuals. The genotype distributions were not different between the two groups (P=.74, chi2 test). In the former group, coronary angiograms were evaluated by criteria based on the number of diseased vessels, the number of stenotic lesions (> or = 50%), and the relative abnormal arterial portion (extent index). Although the number of stenotic lesions was higher in patients with the DD genotype than in those with the ID or II genotype (P=.006), there were no differences in the number of diseased vessels or the extent index. When only smokers were analyzed, the number of diseased vessels (P=.032), number of stenotic lesions (P=.003), and extent index (P=.019) were all higher in patients with the DD genotype than in those with the ID or II genotype. In contrast, these differences in the respective parameters did not exist in nonsmokers. The results indicate smoking-associated effects of the ACE genotype on the severity of coronary atherosclerosis.

Coronary Artery Disease↗

PubMed1997

[Aging and ultrasonographic findings of carotid atherosclerosis].

To establish the prevalence of carotid atherosclerosis and its relation to aging in Japanese population, 270 participants in voluntary health screening at our hospital were studied with 7.5 MHz B-mode ultrasonography and accelerated plethysmography (APG), and their levels of serum lipids were measured. The subjects consisted of 84 people in the fifth decade of life, 89 in the sixth decade, 67 in the seventh decade, and 30 in the eighth decade. Carotid lesions were deemed to be present when occlusion, atheromatous plaque, or both were found. Atheromatous plaque was defined as a thickened intima-media complex of 2.1 mm or more. Plaques were divided into two types based on morphometric criteria, and into three types based on echogenic criteria. Thickness of the intimamedia complex (IMT) was measured at two randomly chosen points along the common carotid artery. APG was obtained by double-differentiation of finger-plethysmograph record, and the APG index was calculated as (-b+c+d)/a, where the letters are the distances from the baseline to the peaks of each wave (a, b, c, and d waves) on the APG waveform. Carotid lesions were seen in 5% of subjects in the fifth decade of life, 7% of subjects in the sixth decade, 24% of those in the seventh decade, and 27% of those in the eighth decade. All the lesions were plaques, and neither plaque type nor size differed between young-adult and elderly subjects. Multiple regression analysis revealed that the thickness of the intima-media complex correlated significantly with age, but not with carotid lesions, sex, body weight, serum lipid levels, hemoglobin A1 level, or uric acid level. The APG index also decreased significantly with age, but no correlation was seen with carotid lesions or with the thickness of the intima-media complex. These findings indicate that people aged 60 or over could be at risk for plaque formation in the carotid arteries and their carotid arteries should be examined carefully even in the absence of risk factors for vascular disease. These findings also suggest that both increased thickness of the intima-media complex and a low APG index arise via pathophysiologic mechanisms different from those that lead to atheromatous plaque.

Adult↗