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Biomedical subjects

H Okazaki

Publications and source records attributed to H Okazaki.

At least 469 records · Page 26Linked to original sources
PubMedDate not supplied

Hepatic parenchymal enhancement in the cirrhotic liver: evaluation by triple-phase dynamic MRI.

BACKGROUND: To evaluate the changes of liver parenchymal enhancement in the cirrhotic liver by means of triple-phase dynamic magnetic resonance (MR) imaging. METHODS: Triple-phase multisection dynamic MR imaging was performed in 32 patients with liver cirrhosis. The control group consisted of 19 patients without liver cirrhosis. After precontrast images were obtained, arterial phase images were acquired 20 s after the start of intravenous bolus administration of 0.10 mmol/kg of gadopentetate dimeglumine. Portal and delayed phase images were then acquired 1 and 3 min, respectively, after the injection of contrast material. On each phase image, the signal-to-noise ratio (S/N) from the liver parenchyma was measured by operator-defined regions of interest (ROIs). The contrast-enhanced ratio (CER) on each phase was then obtained according to the following formula: [S/N(arterial or portal or delayed phase image) - S/N(precontrast image)] / S/N(precontrast image). The portal perfusion index (PPI) also was obtained according to the following formula: [S/N(portal phase image - S/N(arterial phase image)] / S/N(arterial phase image). The results were expressed as mean +/- SD. RESULTS: The CERs of arterial, portal, and delayed phase images in patients with and without liver cirrhosis were 0.256 +/- 0.211, 0.640 +/- 0.384, and 0.554 +/- 0.318 and 0.132 +/- 0.094, 0.404 +/- 0.204, and 0.324 +/- 0.144, respectively. The CERs were highest in the portal phase and lowest in the arterial phase in patients with and without liver cirrhosis. The CER of the cirrhotic liver was significantly higher than that of the normal liver in every phase (p < 0.05). PPIs with and without liver cirrhosis were 2.90 +/- 4.03 and 3.86 +/- 3.89, respectively. The PPI with liver cirrhosis was significantly lower than that without liver cirrhosis (p < 0.05). CONCLUSION: The enhancement of cirrhotic liver parenchyma is greater than that of the normal liver parenchyma at every phase of triple-phase dynamic MR imaging.

Adult↗
PubMedDate not supplied

Evaluation of the fracture site mechanical properties in vivo by monitoring the motion of a dynamic pin clamp during simulated walking.

OBJECTIVE: To monitor pin clamp motion using a displacement sensor over time during weight bearing and to investigate whether this method could contribute to quantitative assessment of the mechanical properties of fracture healing. METHODS: Patients with a shaft fracture of the tibia were monitored, all of whom were in the stage of dynamization. The hifixator equipped with a ball bearing mechanism was used as a dynamic external fixator. The displacement was recorded versus time during stamping with weight bearing of the patients. The displacement curve had an oscillatory component synchronized with touch down and lift up of the foot, a time-dependent component expressed by shifting of the baseline, and an irreversible component during a non-weight bearing period after stamping. The three components were analyzed with a simple Voigt model. RESULTS: In all patients, both the amplitude of the oscillatory component and the time-dependent component expressed as retardation time decreased as fracture healing proceeded, and by the time of fixator removal the irreversible component had disappeared. CONCLUSIONS: The monitoring method could quantitatively evaluate viscoelastoplasticity of the healing fracture site. RELEVANCE: Until now, there has been few method for assessing the viscoelastic property of the healing fracture site in vivo. Although the method described here involves some assumptions and approximations, it was able to quantitatively assess the viscoelasticity of the healing fracture site.

Adult↗
PubMedDate not supplied

Binding of a non-beta-lactam antibiotic to penicillin-binding proteins.

In the search for new beta-lactam antibiotics of natural origin, the discoveries of cephamycins and sulfazecins (monobactams) were important turning points in that they accelerated many screening efforts aimed at other new compounds. In our target-directed screening for beta-lactam antibiotics using beta-lactam hypersensitive mutants, we have examined Gram-negative bacteria isolated from natural habitats and have recently reported several types of beta-lactam antibiotics such as cephabacins and formadicins. Here we report a novel antibiotic, lactivicin, found using this system. Although lactivicin has various biological activities commonly observed in beta-lactam antibiotics, it does not possess a beta-lactam ring in its molecule, but has the unique structure of a dicyclic dipeptide.

Anti-Bacterial Agents↗
PubMedDate not supplied

Angioscopy in transluminal balloon and laser angioplasty in the management of chronic hemodialysis fistulae.

In chronic hemodialysis patients, there is the major problem of occlusion in the arteriovenous fistulae. To investigate this problem, the authors have developed angioscopy for examination and detection of occlusion developing to allow early use of transluminal balloon angioplasty (PTA) or laser angioplasty and prevent occlusions. The authors have examined 27 patients using a 2.7 mm diameter Olympus flexible angioscope and 9F sheath, following-up with a 4 mm balloon catheter (BARD) or SLT Nd-YAG laser. PTA was performed for 25 cases, with 19 demonstrating after one session patency lasting 9 months to date. Three cases revealed restenosis and have each received three PTA sessions. Laser angioplasty was performed in one case of 15 cm chronic occlusion, with subsequent PTA successfully enabling hemodialysis. Angioscopically, the authors were able to observe the various rest-forms within the shunt and detected the mural thrombus attached to the punctured pore. Both circumferential and valvular stenoses were observed. Initially after laser angioplasty, rough irregularity and a mural thrombus in the vessel was observed, but 2 months later, the vessel lumen had become smooth, probably due to intimal growth. Thrombus is acute stenosed cases were clearly observed. Angioplasty enabled new observations in the A-V fistulae, which allows investigation of the mechanism of stenosis or occlusion and enables an extended use of the hemodialysis blood access.

Angioplasty, Balloon↗
PubMedDate not supplied

Dynamic MR follow-up of small hepatocellular carcinoma after percutaneous ethanol injection therapy.

For patients with small hepatocellular carcinomas (HCCs) treated by percutaneous ethanol injection (PEI) therapy, dynamic MRI has been performed to evaluate the therapeutic efficacy at our institute. In this pictorial essay, we illustrate the various dynamic MR findings of HCCs after PEI therapy, including complete necrosis, partial necrosis, local recurrence, and pathologic conditions such as arterioportal shunt and contractive changes of hepatic parenchyma. We also present the limitation of dynamic MRI in the evaluation of therapeutic effectiveness of PEI therapy.

Aged↗
PubMedDate not supplied

Lumbar motoneurons of man: I) number and diameter histogram of alpha and gamma axons of ventral root.

The numbers of large and intermediate diameter myelinated fibers of 17 ventral lumbar (L3, L4 and L5) spinal roots (vsr) of man (ages 17-81 years) have been evaluated using the improved methods of histologic processing and morphometry now available, semi-automatic methods of measurement and programmed calculation and plotting. A population of small diameter myelinated fibers as found in thoracic (T11) vsr, which are presumed to be preganglionic sympathetic fibers, were essentially absent from L3, L4 and L5 roots. On the average, there were 5716 (70%) large diameter fibers and 2625 (30%) intermediate diameter fibers in the L3 ventral spinal root. Comparable figures for L4 vsr were 4900 (70%) and 2152 30%) and for L5 vsr were 5043 (75%) and 1559 (25%). On the assumption that these lumbar roots contain few if any small diameter myelinated pre-ganglionic sympathetic axons, the large diameter fibers correspond to alpha motoneuron axons and the small diameter fibers to gamma motoneuron axons. With age, a decrease in the number of myelinated fibers was estimated to be 350 fibers per decade (approximately 5% per decade).

Adolescent↗