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Biomedical subjects

Mika Yamamoto

Publications and source records attributed to Mika Yamamoto.

At least 19 recordsLinked to original sources

Solid-phase synthesis of stereoregulated oligodeoxyribonucleoside phosphorothioates.

An efficient stereocontrolled synthesis of oligodeoxyribonucleoside phosphorothioates on a solid-support by an oxazaphospholidine method was achieved. A detailed investigation on the reagents and conditions for the solid-phase synthesis revealed that the use of the capping and sulfurizing reagents which are regularly used for the conventional synthesis of phosphorothioate DNA resulted in a sluggish removal of the chiral auxiliaries on the phosphorothioate internucleotidic linkages. After optimization of the capping and sulfurizing steps, the deprotection of the internucleotidic linkages were successfully conducted under the regular basic conditions, and P-stereoregulated phosphorothioate DNA oligomers were successfully obtained with excellent diastereopurity.

Oligodeoxyribonucleotides↗

Odontogenic orbital inflammation: clinical and CT findings--initial observations.

PURPOSE: To retrospectively review computed tomographic (CT) and clinical findings in patients with odontogenic orbital infection. MATERIALS AND METHODS: Approval from the institutional review board was obtained for chart and scan review, and informed consent was waived for this HIPAA-compliant study. Five patients, two male and three female (median age, 37 years; age range, 13-55 years), who had odontogenic orbital cellulitis underwent clinical evaluation, CT scanning, and treatment. CT findings, including periapical lucency suggesting abscess, sinus opacification, and the route of spread of infection, were analyzed in each patient. Imaging, clinical, and surgical findings, including the initial clinical diagnosis and the presence of a periapical abscess at surgery and at pathologic examination, were compared. RESULTS: Periapical lucency and sinus opacification were seen in all patients. The route of infection spread was through either the premalar soft tissues or the maxillary sinuses. The odontogenic origin of the orbital infection was not clinically suspected in any patients. Correct diagnosis was later made at CT in all patients. Four patients had periapical abscesses at pathologic analysis, and the fifth patient had apical periodontitis at clinical analysis and granuloma at pathologic analysis. Dental surgery was required in each of the five patients for resolution of infection; four patients underwent extraction of the infected tooth, and one patient underwent incision and drainage of a periapical abscess. CONCLUSION: Abnormal periapical lucency, widening of the periodontal ligament space, and the presence of a subperiosteal abscess suggested an odontogenic origin of orbital infection.

Adolescent↗

Parameters for diffusion weighted magnetic resonance imaging for temporomandibular joint.

The purpose of this study was to determine optimum diffusion parameters for diffusion weighted imaging (DWI) techniques, including echo planer imaging (EPI), single-shot fast spin echo (SSFSE), and steady-state free precession (SSFP) in Magnetic Resonance Imaging (MRI) of the Temporomandibular Joint (TMJ). A polyethylene tube with distilled water was individually positioned at the external acoustic meatus foramen in each of three volunteers with normal healthy TMJs. Images were obtained using three types of DWI at differing diffusion parameters, b-factors, and diffusion moment. Signal intensity and imaging ability for various anatomical structures, including the distilled water, were evaluated from each image. The details of the anatomical structures of the TMJ were unidentifiable in the images produced with EPI and SSFSE, but were identifiable on the SSFP images. A diffusion moment value from 100 mT/m(*)msec to 150 mT/m(*)msec for SSFP, in particular, restrained the signal intensity of the water, thereby protecting the comparably high image quality of the TMJ structure. In conclusion, only SSFP is capable of allowing interpretation of emerging pathologic conditions in the TMJ region, when used with a diffusion moment set at between from approximately 100 mT/m(*)msec to 150 mT/m(*)msec.

Diffusion Magnetic Resonance Imaging↗

Digital subtraction technique for evaluation of peri-implant bone change in digital dental imaging.

The purpose of this study was to investigate digital subtraction technique in digital dental imaging for implant performance, used to quantitatively evaluate bone change around dental implants. For longitudinal assessment of peri-implant bone change, we applied subtraction technique to digital peri-apical radiographs using a digital dental imaging system in two cases at the upper canine and premolar regions. In both cases, we found two peaks of bone change at the crestal region; we also quantitatively demonstrated a marked change over the first one-month period and approximately three-month period spanning the fourth month to the end of the sixth month following implantation. Digital peri-apical radiography accommodating the digital subtraction program should be re-acknowledged as a reliable modality for assessing amount of bone change at local implantation sites.

Alveolar Bone Loss↗

Improvement of regional cerebral blood flow after oral intake of branched-chain amino acids in patients with cirrhosis.

AIM: To evaluate the effect of oral intake of branched-chain amino acids (BCAA) on brain perfusion in patients with liver cirrhosis. METHODS: Single photon emission computed tomography scans were performed in 43 patients with cirrhosis and in 15 age-matched healthy subjects. Twenty-nine out of forty-three patients were randomly treated with either BCAA granules or placebo, and single photon emission computed tomography was performed before and after the treatment. We measured the regional cerebral blood flow values using a three-dimensional stereotaxic region of interest template. RESULTS: Cirrhotic patients had regions of significant hypoperfusion in the bilateral central (right P=0.039, P<0.05; left P=0.006 P<0.01), parietal (right P=0.018, P<0.05; left P=0.009, P<0.01), angular (right P=0.039, P<0.05; left P 0.008, P<0.01), and left pericallosal segments (P=0.038 P<0.05) as compared with healthy subjects. A significant increase in cerebral perfusion was observed 70 min after the oral intake of BCAA in the angular (right P=0.012, P<0.05; left P=0.049, P<0.05), temporal (right P=0.012, P<0.05; left P=0.038, P<0.05), pericallosal segments (right P=0.025, P<0.05; left P=0.049, P<0.05) and left precentral (P=0.044, P<0.05), parietal (P=0.040, P<0.05) and thalamus (P=0.033, P<0.05). No significant change in perfusion was observed in the placebo group. CONCLUSION: Administration of BCAA rapidly improves cerebral perfusion.

Administration, Oral↗

Evaluation of cingulate gyrus blood flow in patients with liver cirrhosis.

Although neuropsychological tests are commonly applied to detect minimal hepatic encephalopathy (HE) in patients with liver cirrhosis (LC), they provide no information about the cerebral regions involved. Recently, it has been reported that some populations of alcoholic cirrhotics, with mild HE, have reduced cerebral metabolic rate for glucose in bifrontal cortices and in the anterior cingulate gyrus. We evaluated the degree of reduction in blood flow at the anterior cingulate gyrus and the frontal lobes in cirrhotic patients who underwent single photon emission computed tomography (SPECT). Data were obtained from 47 cirrhotic patients and 47 subjects without LC. Three radiologists unaware of the results of laboratory tests visually evaluated the transaxial, coronal, and sagittal views of SPECT. The area and the degree of blood flow reduction in the anterior cingulate gyrus and frontal lobes were scored. Reduced blood flow in the anterior cingulate gyrus was observed in most LC patients. In patients without overt HE, poor performance in neuropsychological tests was correlated with reduced cerebral blood flow in the anterior cingulate gyrus. Blood flow in the anterior cingulate gyrus as measured by SPECT may be a simple and good indicator of cerebral functional changes in patients with LC.

Aged↗

Efficacy of long-term dietary restriction of total calories, fat, iron, and protein in patients with chronic hepatitis C virus.

OBJECTIVES: A diet restrictive in total calories, fat, iron, and protein intake reduces serum alanine aminotransferase levels in patients with long-term hepatitis C virus infection. However, whether long-term dietary therapy causes adverse effects such as malnutrition and anemia due to a shortage of energy intake is not clear. We evaluated the balance of energy intake and changes in physical and hematologic indices of nutrition after a long-term dietary therapy. METHODS: Twenty-two patients with long-term hepatitis C virus infection that did not respond to or who were able or unwilling to take interferon therapy were enrolled in this study. Our prescriptions included 7 mg/d or less of iron, 30 kcal. kg(-1). d(-1) of energy, 1.1 to 1.2 g. kg(-1). d(-1) of protein, and a fat energy fraction of 20%. Patients were followed for 24 mo. RESULTS: Mean body fat percentage was 24.6% at entry and was significantly reduced after the diet prescription. Mean serum ferritin decreased significantly from 376 ng/mL at entry to 141 ng/mL after 24 mo. Mean serum alanine aminotransferase levels decreased significantly from 66 to 49 IU/L. Mean levels of hemoglobin, serum albumin, and cholinesterase did not change significantly during the follow-up period. CONCLUSIONS: These results suggest that restriction of energy, fat, iron, and protein intakes is safely tolerated, so its long-term use should be recommended to patients with long-term infection with hepatitis C virus.

Adipose Tissue↗

Multiple protein-protein interactions by RNA polymerase I-associated factor PAF49 and role of PAF49 in rRNA transcription.

We previously demonstrated the critical role of RNA polymerase I (Pol I)-associated factor PAF53 in mammalian rRNA transcription. Here, we report the isolation and characterization of another Pol I-associated factor, PAF49. Mouse PAF49 shows striking homology to the human nucleolar protein ASE-1, so that they are considered orthologues. PAF49 and PAF53 were copurified with a subpopulation of Pol I during purification from cell extracts. Physical association of PAF49 with Pol I was confirmed by a coimmunoprecipitation assay. PAF49 was shown to interact with PAF53 through its N-terminal segment. This region of PAF49 also served as the target for TAF(I)48, the 48-kDa subunit of selectivity factor SL1. Concomitant with this interaction, the other components of SL1 also coimmunoprecipitated with PAF49. Specific transcription from the mouse rRNA promoter in vitro was severely impaired by anti-PAF49 antibody, which was overcome by addition of recombinant PAF49 protein. Moreover, overexpression of a deletion mutant of PAF49 significantly reduced pre-rRNA synthesis in vivo. Immunolocalization analysis revealed that PAF49 accumulated in the nucleolus of growing cells but dispersed to nucleoplasm in growth-arrested cells. These results strongly suggest that PAF49/ASE-1 plays an important role in rRNA transcription.

Amino Acid Sequence↗

Differences in temporomandibular joint pain and age distribution between marrow edema and osteonecrosis in the mandibular condyle.

This study investigated the differences of age distribution and temporomandibular joint (TMJ) pain between marrow edema and osteonecrosis in the mandibular condyle. Subjects consisted of 35 TMJs in 35 patients with abnormal bone marrow on MR images who were selected from a consecutive series of 527 patients with TMJ disorders. Proton density and T2-weighted MR images taken in the oblique sagittal and coronal planes were used to diagnose condylar marrow abnormalities and divide them into either edema or osteonecrosis. The differences in TMJ pain and age distribution for these two abnormalities were assessed with the one-sided Wilcoxon rank sum test with 0.05 alpha level. The degree of pain was higher in joints with marrow edema than in joints with osteonecrosis (p = 0.033). The mean age was higher in joints with osteonecrosis (p < 0.001). Our results suggest that there is more severe pain in TMJs with marrow edema of the mandibular condyle than in those with osteonecrosis. Since the patients with marrow edema have lower age, it also appears that marrow edema may be a precursor condition for osteonecrosis of the TMJ.

Adolescent↗

Significance of the level of monocyte chemoattractant protein-1 in human atherosclerosis.

BACKGROUND: Monocyte chemoattractant protein-1 (MCP-1), a potent chemoattractant for monocytes, plays an important role in the earliest events of atherogenesis. However, direct evidence of the effects of MCP-1 on atherosclerosis in chronic hemodialysis (HD) patients has not been reported. METHODS AND RESULTS: The serum MCP-1 concentrations and the intimal - medial thickness (IMT) in the carotid arteries were measured in 42 non-diabetic chronic HD patients and 20 age-matched controls. The expression of MCP-1 was examined immunohistochemically in radial arterial tissues obtained from the HD patients. IMT and the serum concentration of MCP-1 in the HD patients were both significantly greater than in controls. Multiple regression analysis revealed that the serum concentration of MCP-1 was an independent factor influencing IMT. Tissue immunostaining showed that MCP-1 is expressed in both endothelial and smooth muscle cells and that its level of expression correlates with the serum concentration of MCP-1. CONCLUSIONS: An increase in MCP-1 may be an important factor in the progression of atherosclerosis in non-diabetic HD patients.

Adult↗

Temporomandibular joint: MR imaging.

Diagnostic imaging of TMJ has improved remarkably in the last 20 years. Various abnormalities related patient symptoms. Further studies using the latest imaging techniques will allow a better understanding of the sources of joint pain and the discrepancy between imaging findings and patient symptoms. For clinical practice, appropriate clinical examinations are needed to determine exactly which imaging findings are significant.

Humans↗

Usefulness of proton density and T2-weighted vs. T1-weighted MRI in diagnoses of TMJ disk status.

The aim of this study was to test the hypothesis that proton density and T2-weighted magnetic resonance (MR) images are more useful than T1-weighted MR images in the diagnoses of disk displacement, disk reduction, and disk shape. The subject group consisted of 92 patients referred for bilateral MRI imaging because of diagnosed signs of temporomandibular disorders (TMD). In the experimental group (52 patients), both T2-weighted and proton density images were made. In the control group (40 patients), only T1-weighted images were taken. The images were evaluated by two oral radiologists relative to their usefulness as a diagnostic aid and rated as either good or fair in each diagnostic category. The percentages of ratings that were good were higher (p < 0.01) for T2-weighted and proton density images than for T1-weighted images in all three types of diagnoses (Fisher's Exact test). In conclusion, T2-weighted and proton density-weighted images were found to be more useful than T1-weighted images in the diagnoses of disk status.

Adolescent↗

Improvement of regional cerebral blood flow after treatment with branched-chain amino acid solutions in patients with cirrhosis.

OBJECTIVE: The administration of solutions rich in branched-chain amino acids leads to mental recovery from acute hepatic encephalopathy in patients with liver cirrhosis. However, the mechanism of action of branched-chain amino acids remains unclear. The purpose of this study was to evaluate the effect of intravenous infusion of branched-chain amino acids on brain perfusion in patients with liver cirrhosis. METHODS: Single photon emission computed tomography scans were performed in 14 patients with liver cirrhosis before and after the administration of branched-chain amino acids in a single-day split-dose protocol. The per cent change in regional brain perfusion was calculated in high frontal, parietal, temporal, occipital lobes and cerebellum. Thereafter, statistical parametric mapping was performed to identify brain regions with abnormal cerebral perfusion. RESULTS: Intravenous infusion of solutions enriched with branched-chain amino acids induced a 13-20% increase in regional cerebral blood flow. Cirrhotic patients had regions of significant hypoperfusion, as determined by statistical parametric mapping, in the left superior parietal and posterior cingulate as compared to the control group. This hypoperfusion of parietal and cingulate regions was not detected after treatment with solutions of branched-chain amino acids. CONCLUSIONS: The results of the present study suggest that administration of solutions enriched with branched-chain amino acids improves cerebral perfusion in patients with cirrhosis.

Aged↗

Carvedilol decreases elevated oxidative stress in human failing myocardium.

BACKGROUND: Oxidative stress has been implicated in the pathogenesis of heart failure. However, direct evidence of oxidative stress generation in the human failing myocardium has not been obtained. Furthermore, the effect of carvedilol, a vasodilating beta-blocker with antioxidant activity, on oxidative stress in human failing hearts has not been assessed. This study was therefore designed to determine whether levels of lipid peroxides are elevated in myocardia of patients with dilated cardiomyopathy (DCM) and whether carvedilol reduces the lipid peroxidation level. Methods and Results- Endomyocardial biopsy samples obtained from 23 patients with DCM and 13 control subjects with normal cardiac function were studied immunohistochemically for the expression of 4-hydroxy-2-nonenal (HNE)-modified protein, which is a major lipid peroxidation product. Expression of HNE-modified protein was found in all myocardial biopsy samples from patients with DCM. Expression was distinct in the cytosol of cardiac myocytes. Myocardial HNE-modified protein levels in patients with DCM were significantly increased compared with the levels in control subjects (P<0.0001). Endomyocardial biopsy samples from 11 patients with DCM were examined before and after treatment (mean, 9+/-4 months) with carvedilol (5 to 30 mg/d; mean dosage, 22+/-8 mg/d). After treatment with carvedilol, myocardial HNE-modified protein levels decreased by 40% (P<0.005) along with amelioration of heart failure. CONCLUSIONS: Oxidative stress is elevated in myocardia of patients with heart failure. Administration of carvedilol resulted in a decrease in the oxidative stress level together with amelioration of cardiac function.

Adrenergic beta-Antagonists↗

Common abnormalities in temporomandibular joint imaging.

Magnetic resonance imaging has evolved as a prime diagnostic method for soft-tissue abnormalities of the temporomandibular joint. The most common temporomandibular joint abnormalities are internal derangement and osteoarthritis, but there are many other reasons for pain and dysfunction that are often overlooked. The purpose of this paper is to illustrate several of these more unusual and less well-recognized causes for temporomandibular joint pain and dysfunction. For example, internal derangement is often seen in asymptomatic individuals. Another purpose is to illustrate the difference in magnetic resonance imaging of asymptomatic and symptomatic internal derangement.

Body Fluids↗