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Biomedical subjects

Y Amano

Publications and source records attributed to Y Amano.

At least 55 records · Page 3Linked to original sources
PubMed1998

Single-shot diffusion-weighted echo-planar imaging of normal and cirrhotic livers using a phased-array multicoil.

Single-shot spin-echo diffusion-weighted echo-planar imaging using a phased-array multicoil was performed to distinguish between normal and cirrhotic livers. Sets of 6 images with different b-values were acquired with breath-holding. Significant differences were observed between controls and cirrhosis cases in the signal ratios when the b-value was 383 s/mm2, and apparent diffusion coefficients.

Adult↗
PubMed1998

Osseointegration in implant-embedded mandible in rats fed calcium-deficient diet: a radiological study.

OBJECTIVE: The purpose of the present study was to investigate osseointegration using radiographs of titanium (Ti) implants into the osteoporotic mandible of rats. MATERIALS AND METHODS: Rats were divided into three groups: first group, which were fed a standard diet throughout (control group), second group which were fed a Ca-deficient diet for only 1 week before implantation (group A), and those which were fed the Ca-deficient diet before and after implantation (group B). On the 7th and 42nd days after implantation, bone changes in those rats were examined by microradiographs and autoradiographs. RESULTS: On the 7th day after implantation, calcification of newly formed bones was lower in groups A and B than in the control group, 45Ca uptake was seen in surrounding bones adjacent to the implant, as well as throughout the mandible. On the 42nd day after implantation, trabecular bone in group A showed radiopacity as seen in the control group. In the alveolar crest and peri-implanted bones in group B, thin bone formation with active 45Ca incorporation was found. CONCLUSIONS: It is suggested that irrespective of the calcium deficiency status in rats, trabecular bones around the implant are restored to a healthy state to some extent by resuming an intake of a necessary amount of dietary calcium. In continued calcium deficiency, osseointegration with the implant and alveolar bone was still observed as in the healthy rats suggesting calcium deficiency is not always a factor to regulate osseointegration of mandibular endosseous implants.

Alveolar Process↗
PubMed1998

28-day repeated oral toxicity study of a hypolipidemic agent, NK-104 in rats.

NK-104, an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, was administered orally to Wistar rats at a dose of 2, 10, 50 or 100 mg/kg for 28 days consecutively, and the toxicity of NK-104 and its recovery with 2 weeks cessation of drug treatment were examined. As major clinical signs, loose stool, diarrhea, crouching and emaciation were observed in both sexes at 50 or 100 mg/kg, and all females at 100 mg/kg died or became moribund due to severe emaciation before the completion of treatment. The suppression of body weight gain or decrease in body weight was observed in the female dose group at 50 mg/kg and both sexes at 100 mg/kg. Decreased food intake was observed in both sexes at 100 mg/kg. Moreover, an increase in cholinesterase (Ch.E) in the male dose groups at 50 and 100 mg/kg and an increase in glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) in the female dose group at 50 mg/kg were observed in blood chemistry testing. Macroscopic examination showed thickening of the forestomach mucosa in the groups of 10 mg/kg or more. Microscopic examination revealed hyperkeratosis and hypertrophy of the spinous layer associated with both cell infiltration of the mucosal propria and submucosal edema. In addition, skeletal muscle lesions including atrophy, vacuolation and focal necrosis were observed in the female dose groups at 50 and 100 mg/kg. The above-mentioned microscopic changes were not observed on cessation of drug treatment. The non-toxic dose level of NK-104 in the 28-day repeated oral toxicity study using rats was determined to be 2 mg/kg.

Administration, Oral↗
PubMed1998

Six-month repeated oral toxicity study of NK-104 in rats.

NK-104 is a novel potent inhibitor of the rate-limiting enzyme in cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, and has been shown to be a highly effective agent in lowering blood cholesterol. In the present study, NK-104 was orally administered to Wistar rats at a dose of 0.3, 1, 3 or 010 mg/kg for 6 months for examination of toxicity. Additional recovery groups of 8 rats each of both sexes receiving 0 and 10 mg/kg were maintained without treatment for 1 month in order to assess recovery. As a result, no toxicological changes were observed in general signs, body weight, food intake, ophthalmological examination, urinalysis, hematological and blood chemical examinations for organ weights. An autopsy revealed thickening of the forestomach mucosa in both sexes at a dose of 1 mg/kg or more. This change was microscopically recognized as hyperkeratosis and hypertrophy of the spinous layer associated with both cell infiltration of the mucosal propria and edema of sub-mucosa in the forestomach in both sexes at doses of 3 and 10 mg/kg. Forestomach changes were not observed in any cases after 1 month cessation of drug treatment. The non-toxic dose of NK-104 in the 6-month repeated oral toxicity study in rats is estimated to be 1 mg/kg/day.

Administration, Oral↗
PubMed1998

Using MR imaging to predict and evaluate the response of invasive cervical carcinoma to systemic chemotherapy.

OBJECTIVE: The goal of our study was to evaluate the accuracy of MR imaging in predicting the response of invasive cervical carcinoma to systemic neoadjuvant chemotherapy, to observe with MR imaging the difference in tumor response to chemotherapy between treatment cycles, and to correlate tumor size between MR imaging after chemotherapy and surgical specimen. SUBJECTS AND METHODS: Pelvic MR imaging was performed before and after chemotherapy in 41 patients with invasive cervical carcinoma. The difference in tumor reduction between the second course and the third or fourth course of treatment was statistically evaluated in 12 patients. MR images obtained after chemotherapy were compared with surgical specimens to determine residual tumor size in 10 patients. RESULTS: Tumor volume, complete replacement of cervical stroma with carcinoma, and uterine body involvement by tumor observed in the MR images before treatment were found to be significant factors in predicting tumor response. No difference in tumor reduction was found between the second course and the third or fourth course of chemotherapy. Estimates made on MR imaging of tumor size after chemotherapy were within 5 mm of the resected samples. CONCLUSION: Pelvic MR imaging proved useful in predicting and assessing the response of invasive cervical carcinoma to chemotherapy.

Adult↗
PubMed1998

Oxygen carrying capacity and oxygen supply rate of artificial oxygen carrier, Neo Red Cell (NRC).

Neo Red Cell (NRC), which is the liposome encapsulated hemolysate, has been developed as an artificial oxygen carrier. Oxygen carrying capacity and oxygen supply rate of NRC were estimated by continuous measurement of dissolved oxygen concentration in a spinner vessel. Oxygen carrying capacity of the medium was risen by adding NRC. The oxygen supply rate of the NRC medium containing hepatocytes was determined by the oxygen consumption rate of hepatocytes. The addition of NRC gave no effect on the oxygen transfer rate from gas phase to liquid phase (or kL a value) of the solution in the spinner vessel. The rate of oxygen absorption to NRC was limited by the oxygen transfer rate from gas phase to liquid phase in the spinner vessel. These results indicate that the oxygen supply from NRC may sustain the high-density culture of mammalian cells.

Air↗
PubMed1997

Magnetization transfer imaging of bone marrow with and without fat suppression.

RATIONALE AND OBJECTIVES: To assess magnetization transfer (MT) ratios of bone marrow at magnetic resonance (MR) imaging performed with and without fat suppression. MATERIALS AND METHODS: The authors performed MR imaging in 30 regions of normal bone marrow in 10 subjects by using four types of gradient-echo sequences: a combination of MT and fat-suppression techniques, only the fat-suppression technique, only the MT technique, and without MT or fat-suppression techniques. MT ratios of marrow obtained with and without the fat-suppression technique were quantitatively compared. RESULTS: The average MT ratio of marrow with fat suppression was significantly higher than that without fat suppression (P < .01). CONCLUSION: Because bone marrow includes both water and fat, the MT ratio of marrow was underestimated when MT imaging was performed without fat suppression. A fat-suppression technique should be used.

Adipose Tissue↗
PubMed1997

Effects of midazolam on pain sensations in the face.

OBJECTIVES: This study investigated the effects of midazolam, a sedative, on tactile and pain sensations on the skin of the chin. STUDY DESIGN: Thirty-seven volunteers were segregated into four groups; the first group was the control group; the second to fourth groups were administered 0.025 mg/kg, 0.05 mg/kg, and 0.075 mg/kg of midazolam, respectively, as a bolus injection. All volunteers reclined in a dental chair for the experiment. Tactile and pain sensations were determined over time after injection of midazolam, the former using von Fray thread, the latter using an esthesiometer. RESULTS: Thresholds of tactile sensitivity and of pain were statistically significantly different from control values at 10 minutes after injection of midazolam in the 0.05 mg/kg group and in the 0.075 mg/kg group. CONCLUSION: Although 0.025 mg/kg of midazolam produced sedation, at least 0.05 mg/kg of this agent was required to alter the thresholds for perception of tactile and painful stimulation.

Adult↗
PubMed1997

Oral sustained-release cisplatin preparation for rats and mice.

A new oral sustained-release solid-dispersion preparation of cisplatin (cis-diamminedichloroplatinum(II): cisplatin) has been developed for administration to small experimental animals such as mice. This preparation was obtained by formulating cisplatin with the water-insoluble polymer ethylcellulose and with stearic acid in different ratios. In-vitro dissolution studies showed that cisplatin release characteristics were zero-order for the formulation cisplatin-ethylcellulose-stearic acid (1:10:5) and levels equilibrated 7 h after the start of the experiment. The availability of cisplatin from this preparation was evaluated both in rats and mice. The cisplatin preparation (20 mg kg-1) was administered orally to rats and the resulting curve of serum cisplatin levels against time was compared with that obtained after intravenous infusion (20 mg kg-1) to rats. By comparing the areas under serum concentration-time curves (AUCs), the bioavailability of cisplatin was estimated to be 31%. The mean residence time (MRT) of cisplatin solid dispersion was 6.13 +/- 0.43 h, whereas the MRT of cisplatin administered by intravenous infusion was 3.89 +/- 0.05 h. Serum cisplatin levels were maintained above 0.3 mg mL-1 (believed from our clinical studies to be the minimum effective concentration) for 24 h. The curve of serum cisplatin level against time suggested that cisplatin was released from the solid dispersion preparation in a sustained-release fashion. Similar levels were also maintained in mice for 24 h. The MRT of the cisplatin preparation was 10-16 h in mice, which is longer than that obtained after oral administration of the physical mixture. The serum free-cisplatin concentration was determined to be 0.10 mg mL-1 in mice serum in which the total cisplatin concentration was 0.30 mg mL-1. The free fraction of cisplatin in mice serum was the same as that in human patient serum. Pathological examination showed that this new sustained-release oral cisplatin preparation did not have any side effects on the gastrointestinal tract. These results suggest usefulness of this new solid-dispersion preparation for oral cisplatin therapy in lung cancer patients.

Administration, Oral↗
PubMed1997

Helicobacter pylori infection accelerates gene expression of glicentin in the gastric mucosa. Its association with intestinal metaplasia of the stomach.

BACKGROUND: Glicentin is an intestinal polypeptide hormone which seems to promote intestinal metaplasia (IM) in the gastric mucosa. The aim of this study was to clarify whether Helicobacter pylori infection accelerates glicentin gene expression. METHOD: Glicentin mRNA was investigated by reverse-transcription polymerase chain reaction using gastric biopsies from 47 patients examined endoscopically and denying IM. RESULTS: IM was observed in 18 (38.3%) cases histologically, but not in the other 29 (62.7%). Glicentin mRNA was significantly correlated with histological IM (P < 0.01) and was positively correlated with H. pylori infection (P < 0.05). CONCLUSION: Our results indicate that H. pylori infection is associated with the induction of glicentin in the gastric mucosa, thus supporting the hypothesis that H. pylori infection accelerates IM of the stomach.

Adult↗
PubMed1997

Bartonellosis in Ecuador: serosurvey and current status of cutaneous verrucous disease.

Human bartonellosis is a classically biphasic disease caused by infection with the alpha-2 Proteobacteria Bartonella bacilliformis, which is phylogenetically related to the etiologic agents of cat scratch disease, bacillary angiomatosis, and trench fever. In Ecuador, typical bartonellosis has remained endemic for the past century in highland provinces near the Peruvian border. During the past six years, public health officials have noted an increasing number of atypical cases in which monophasic verrucous cutaneous disease is the only clinical manifestation. Epidemiologic, immunologic, histopathologic, and molecular biological studies have confirmed the presence of sporadic, atypical bartonellosis in residents of the lowland province of Manabi, where archeologic evidence exists of bartonellosis in pre-Colombian times. Between 1987 and 1995, 11 cases of cutaneous bartonellosis were investigated and serologic studies were done on 224 persons from five villages, two lowland and three highland. In the lowland village of Pajan in the province of Manabi, there was a 21% seropositivity proportion in contacts of index cases. These combined data suggest that bartonellosis is significantly under-reported due to the existence of mild clinical disease, possibly associated with less virulent bacterial strains, which are now disseminating or re-emerging in previously disease-free areas.

Antibodies, Bacterial↗
PubMed1997

Normal contrast enhancement of extraocular muscles: fat-suppressed MR findings.

PURPOSE: To evaluate contrast enhancement of normal extraocular muscles in the orbit. METHODS: Noncontrast and contrast-enhanced T1-weighted images of the orbit were acquired using a fat-suppression MR technique in eight patients with no orbital disease. Contrast enhancement of 64 extraocular muscles was evaluated and compared with that of 16 temporal muscles. RESULTS: Compared with temporal muscles, all extraocular muscles markedly enhanced after administration of contrast material. CONCLUSIONS: Because normal extraocular muscles enhanced markedly with contrast material, more attention should be paid to these muscles when using contrast-enhanced, fat-suppressed T1-weighted MR imaging to evaluate pathologic conditions.

Adipose Tissue↗
PubMed1997

[Proton MR spectroscopy of hyperplastic hematopoietic marrow in aplastic anemia].

The purpose of this study was to compare the findings of magnetic resonance (MR) spectroscopy of hyperplastic hematopoietic marrow with those of normal bone marrow. Twenty-four samples of normal marrow from eight control subjects and 19 samples of hyperplastic marrow in aplastic anemia were examined with a 1.5T MR unit. The former showed low intensity on opposed-phase T1-weighted images, while the latter showed high intensity on both fast STIR and opposed-phase T1-weighted images. MR spectroscopy quantitatively confirmed that the water: fat ratio was increased and the transverse relaxation time of water was changed in hyperplastic bone marrow, compared with normal bone marrow. In summary, MR imaging is able to detect hematopoietic regions among a wide range of bone marrow of aplastic anemia, while MR spectroscopy allowed us to quantitatively analyze the cell population of hyperplastic hematopoietic marrow in aplastic anemia.

Adolescent↗
PubMed1997

[Assessment of cerebral circulation using echo planar imaging--basic analysis in quantitating the mean transit time, cerebral blood flow, and cerebral blood volume].

The mean transit time (MTT), cerebral blood flow (CBF) and cerebral blood volume (CBV) using echo planar imaging (EPI) in 22 aged volunteers were measured based on moment analysis and gamma variate method. The first peak of signal intensity curve (p delta R2.) and the area under the curve after the first peak (AUC) were calculated according to the height over area method, as a convenient quantification. Then, MTT, CBF, and CBV were compared with AUC/p delta R2, p delta R2, and AUC, respectively. There was a good correlation between each other parameter (r = 0.67 - 0.92, every p < 0.001). The slow upward slope and the low peak height, however, caused a larger error between each other parameter.

Blood Flow Velocity↗
PubMed1997

[Assessment of regional microcirculatory changes by EPI perfusion studies in patients with multiple lacunar infarction].

The aim of this report is to assess regional cerebral microcirculatory changes by EPI perfusion study in patients with multiple lacunar infarction(MLI). Especially, we focused on the parameter(rCBV, MTT, rCBF) changes in the white matter and on the relationship between these changes in the gray and white matter. Twenty MLI patients(mean age 72 +/- 15 years) and 10 age-similar normal controls (mean age 65 +/- 12 years) were examined. As a result, the MLI patients demonstrated an insignificant rCBF reduction due to the rCBV elevation in the gray matter and a moderate rCBF reduction with less rCBV elevation in the white matter. These results show a difference in the vascular reserve between the gray and white matter, and insufficiency of the vascular reserve in MLI's white matter.

Aged↗
PubMed1996

Synthesis and structure-activity relationships of 2-substituted D-tryptophan-containing peptidic endothelin receptor antagonists: importance of the C-2 substituent of the D-tryptophan residue for endothelin A and B receptor subtype selectivity.

Continuing studies on modifications of potent cyclic pentapeptide endothelin (ET) receptor antagonists, represented by BQ-123, and potent linear tripeptide derivative ET receptor antagonists, represented by BQ-788, are described herein. The introduction of D-tryptophan analogues with C-2 substituents in these peptidic ET antagonists resulted in potent ET receptor antagonists with various ETA/ETB subtype selectivity. Combined ETA/ETB receptor antagonists were found in both cyclic pentapeptide and linear tripeptide series with 2-halo- and 2-methyl-D-tryptophans. In contrast, compounds with 2-cyano-D-tryptophan were ETB receptor-selective antagonists. The C-2 substituent of the D-tryptophanyl residue appeared to be very important for the discrimination of ETA/ETB subtype selectivity of the antagonists. The potent ET receptor antagonists with various ETA/ETB subtype selectivity synthesized in this study may be useful tools for elucidating the physiological and pathophysiological roles of ET and ET receptors.

Animals↗