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Biomedical subjects

T Ebisu

Publications and source records attributed to T Ebisu.

32 records · Page 2Linked to original sources
PubMed1992

Purification and characterization of macrolide 2'-phosphotransferase type II from a strain of Escherichia coli highly resistant to macrolide antibiotics.

The resistance mechanism of Escherichia coli BM2506 to macrolides was found to be due to inactivation. Inactivated oleandomycin was identified as oleandomycin 2'-phosphate by thin-layer chromatography. A new type of macrolide-phosphorylating enzyme, macrolide 2'-phosphotransferase type II (MPH(2')II), was detected, purified 95-fold and its enzymological properties investigated. MPH(2')II was a constitutive intracellular enzyme which showed high levels of activity with both 14-member-ring and 16-member-ring macrolides. The optimum pH for the inactivation of oleandomycin was 8.2 and the optimum temperature of the reaction was 40 degrees C. Enzyme activity was lost by heat treatment at 60 degrees C for 1 min. The isoelectric point and M(r) of the enzyme were 5.3 and 48,000, respectively. Purine nucleotides, such as ITP, GTP and ATP, were effective as cofactors in the inactivation of macrolides. An inhibitory effect of iodine, EDTA, or divalent cations on MPH(2')II activity was observed.

Anti-Bacterial Agents↗
PubMed1991

[The application of in vivo diffusion weighted magnetic resonance imaging to intracranial disorders].

We have developed a magnetic resonance (MR) spin echo method to obtain diffusion weighted imaging using motion-probing gradient (MPG) pulses in one or three orthogonal directions before and after a 180 degree pulse. Phantom models containing water and acetone, normal volunteers and patients with brain tumors, brain edema and infarction were examined. Experimental models of brain edema including triethyltin intoxication and cold injuries were also examined in Wistar rats. MRI was performed at a 1.0-T clinical machine or a 4.7-T experimental machine using spin echo pulse sequences with or without additional MPGs on one or three orthogonal axes. The one direction method was useful to define diffusion anisotropy of myelinated axonal fibers in white matter. Faster diffusion was detected in the white matter parallel to the direction of MPGs. On the other hand, slower diffusion was detected perpendicular to the direction of MPGs because the myelin sheath restricted water diffusion. The three orthogonal gradients method was useful to demonstrate the difference in the diffusion coefficients in various diseases due to its larger total gradient strength. The clear distinction between the cytotoxic edema, which revealed slower diffusion, and the vasogenic edema, which revealed faster diffusion, was demonstrated in the experimental models using diffusion weighted image. In the clinical cases, faster diffusion was demonstrated in the brain tumor and perifocal vasogenic edema, which was in agreement with the results in the experimental models of rats. Brain tumors such as low grade astrocytoma with microcysts and perifocal vasogenic edema have very wide extracellular space.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Effects of atrial natriuretic peptide on brain oedema: the change of water, sodium, and potassium contents in the brain.

We examined the effect of atrial natriuretic peptide (ANP) administration on cerebral oedema in rats. Intravenous ANP infusion with total dose of 120 micrograms/kg and 100 micrograms/kg suppressed the elevation of water and Na contents in left middle cerebral artery (MCA) occluded and cold injured brain tissue, indicating that ANP has a suppressive effect on cerebral oedema. Similar ANP infusion at a low dose of 1 microgram/kg/h for 6 h also resulted in observation of the anti-oedematous effect in both models, with no observable occurrence of the known systemic effects of ANP on systolic blood pressure (SBP), heart rate (HR), hematocrit, or serum electrolyte ion (Na+, K+, Cl-) concentrations. The results thus suggest that the anti-oedematous effect of ANP is attributable to water and Na content control by ANP specific to the damaged tissue, possibly through inhibition of sodium transport. Taken together with a recent study in which it was shown that ANP might inhibit sodium transport in cerebral microvessel, our results suggest that ANP suppresses the development of brain oedema by inhibiting sodium transport and the coupled water influx.

Animals↗
PubMed1990

Effects of atrial natriuretic peptide on ischaemic brain oedema evaluated by the proton magnetic resonance method.

The effect of atrial natriuretic peptide (ANP) on cerebral oedema in rats was examined by magnetic resonance (MR). After occlusion of the left middle cerebral artery (MCA) to induce cerebral ischaemia, rats received continuous infusion of ANP for 24 h at a total dose of 120 micrograms/kg or 150 micrograms/kg. Proton relaxation times (T1 and T2) of excised oedematous tissue were measured in vitro and the area of the oedematous region was determined in vivo by the use of magnetic resonance imaging (MRI). The administration of ANP was found to decrease the lengthening of both T1 and T2 in the oedematous tissues and shown by MRI to decrease the area of the oedematous region, compared with group receiving saline. The topographic observations in vivo suggest that ANP suppress the development of the oedematous region.

Animals↗
PubMed1990

Neurenteric cysts with meningomyelocele or meningocele. Split notochord syndrome.

Two rare cases of neurenteric cysts with meningomyelocele and meningocele were treated. The mechanism of the development of these anomalies is discussed. It is considered that the terminal, dorsal part of the enteric fistula, which is produced between the endoderm and the ectoderm through a partially duplicated notochord in the development of the embryo, remains after obliteration of the fistula and, consequently, that the mucosa of the enteric remnant is inverted and projects through the skin of the back.

Abnormalities, Multiple↗
PubMed1990

Impairment of CO2 reactivity in severe head injury patients: an investigation using thermal diffusion method.

For measurement of the cerebral blood flow (CBF) the thermal diffusion method is quite convenient and allows the chronological measurement of CBF and CO2 reactivity of cerebral vessels. We investigated the CO2 reactivity of fifteen head injury patients. The results showed that in head injury cases, the disturbance of the CO2 reactivity correlates well to poor outcome. Using thermal diffusion method, investigations of CO2 reactivity are useful for further understanding of the physiological state of head injury patients.

Adult↗
PubMed1990

Positron emission tomographic studies on cerebral hemodynamics in patients with cerebral contusion.

Positron emission tomography is currently one of the most useful methods for measurements of cerebral hemodynamics and oxygen metabolism, because it facilitates accurate analysis of the local cerebral circulation in three-dimensional quantitative images. In this study, we performed positron emission tomography studies to measure cerebral circulation in a total of 11 patients who sustained head injuries with contusion. Several parameters were measured including regional cerebral blood flow, regional cerebral blood volume, permeability, and regional cerebral metabolic rate for oxygen. Data from brains both with and without contusion were analyzed for chronological changes, in the subacute stage from the 8th to 29th day and in the chronic stage until 360 days after the injury and compared with similar data in a group of normal subjects. It was concluded that in the subacute stage, regional cerebral blood flow decreased (26 +/- 7 and 39 +/- 10 ml/100 g/min) and regional cerebral blood volume increased (5.6 +/- 1.8 and 5.4 +/- 0.9 ml/100 g) both in areas of cerebral contusion and in areas remote from cerebral contusion and that permeability increased in areas of contusion but not in remote brain areas. In the chronic stage, these parameters showed a tendency for recovery.

Adolescent↗
PubMed1989

Magnetic resonance imaging of brain contusion.

In this study we investigated the time course of brain contusions using magnetic resonance imaging and compared the findings with those of a computed tomography scan. The lesions, which were demonstrated as homogeneous density areas on the computed tomography scan were demonstrated as different intensity areas in the magnetic resonance image. The intensity of the images varied according to the time at which the images were obtained. The findings indicated changes in the nature of the contusions including hematoma hemoglobin, perifocal edema extension, and so on. In conclusion, magnetic resonance imaging is important in the follow-up of chronological change as well as in original diagnosis of brain contusions.

Adolescent↗
PubMed1989

Purification and characterization of macrolide 2'-phosphotransferase from a strain of Escherichia coli that is highly resistant to erythromycin.

Macrolide 2'-phosphotransferase [MPH(2')] was purified 90-fold from an erythromycin-resistant strain of Escherichia coli, and its enzymatic properties were investigated. MPH(2') is an inducible intracellular enzyme which showed high levels of activity with 14-member-ring macrolides and extremely low levels with 16-member-ring macrolides. The optimum pH for inactivation of oleandomycin was 8.2, and the optimum temperature of the reaction was 40 degrees C. Enzyme activity was lost by heat treatment at 50 degrees C for 1 min. The isoelectric point and molecular weight of the enzyme were 5.3 and 34,000, respectively. Purine nucleotides, such as GTP, ITP, and ATP, were effective as cofactors in the inactivation of macrolides. Iodine, EDTA, or divalent cations inhibited MPH(2') activity.

Anti-Bacterial Agents↗
PubMed1989

Nonacute subdural hematoma: fundamental interpretation of MR images based on biochemical and in vitro MR analysis.

Few reports have described the nature of the appearance of nonacute subdural hematoma on magnetic resonance (MR) images. The authors analyzed MR images in 39 cases of nonacute subdural hematoma and subdural effusion by measuring in vitro proton relaxation times and the biochemical variables of hematoma fluids. T1 became proportionally shorter than T2 with an increase in hematocrit but the direct cause of the variation in T1 and T2 was the amount of methemoglobin. The free iron content, not the bound iron content, was another main cause for shortened T1 and T2. Paradoxical findings in the correlation between the total protein or albumin concentration and relaxation times were noted. It is possible that as the protein level in the supernatant increased, more free iron was bound to the protein, decreasing the influence of the free iron on the relaxation times.

Adult↗
PubMed1988

The investigation of experimental brain tumours using 31P-MRS and 1H-MRI.

In vivo 31P-magnetic resonance spectra (MRS) were obtained by the surface coil method from rat glioma, human glioblastoma, and human neuroblastoma inoculated subcutaneously in CD Fisher rats and hamsters, and the effects of chemotherapy, photoradiation therapy, and radiofrequency hyperthermia as well as 60Co-irradiation were evaluated by sequentially observing spectral changes. In the 31P-spectra of tumour tissue, the nucleoside triphosphate (NTP), phosphomonoesters (PME) peaks were high and the phosphocreatine peak was low compared to those of normal brain. When the antitumour agents were given and were effective, NTP peaks decreased, and inorganic phosphate increased remarkably within several hours after the treatment. 1H-magnetic resonance imaging (MRI) were also obtained in some cases. Necrotic regions was detected by the 1H-MRI as image changes which appeared later than those detected by MRS. It proved practical to monitor the effect of therapy by employing either 31P-MRS or 1H-MRI. However, the image changes which demonstrated the effect of the therapy used closely resembled those changes which occurred with the onset of necrosis in tumour tissue during tumour growth. Several problems for future application of these techniques to human brain tumours are also mentioned.

Animals↗
PubMed1988

Pathophysiological investigation of experimental cerebral ischaemia using in vivo 31P-NMR spectroscopy and 1H-MRI.

The cerebral energy metabolism and brain oedema were investigated in three experimental cerebral ischaemia models using 31P-NMR spectroscopy (MRS) and 1H-NMR imaging (MRI) in the same subject animal. These measurements were performed also in experimental brain oedema models and the findings were compared with each other. 31P-MRS showed an ischaemic pattern in all of the cerebral ischaemia models, that is, ATP and PCr peaks decreased, and the Pi peak increased and shifted to a higher resonant frequency. However, 31P-MRS did not show any remarkable change in the brain oedema models. On the other hand, 1H-MRI clearly demonstrated brain oedema in the brain oedema model. In the cerebral ischaemia models, 1H-MRI findings differed depending upon the type of model, namely the most marked brain oedema was detected in the unilateral middle cerebral arterial occlusion model and no marked change was detected in the temporary four vessel occlusion model. It was thought that this difference depended on the severity of the ischaemic insult. Accordingly, the fundamental pathophysiological problem of cerebral ischaemia was the energy metabolism disturbance with the brain oedema being associated with this disturbance but occurring secondarily. However, in the brain oedema model the main pathological change was the increase in tissue water.

Animals↗
PubMedDate not supplied

Discrimination between different types of white matter edema with diffusion-weighted MR imaging.

Brain edema can be classified into three categories: vasogenic, cytotoxic, and interstitial. The mechanism of edema is thought to be different in each type. The authors studied the movement of water molecules in each type of white matter edema in a rat model by using diffusion-weighted magnetic resonance imaging. Conventional T2-weighted imaging did not allow distinction between the three types of white matter edema; the three types of edema were, however, distinguished by using diffusion-weighted imaging. The apparent diffusion coefficient (ADC) of water was different in each type of edema. Water molecules in cytotoxic edema induced by triethyl-tin intoxication showed a smaller and less anisotropic ADC than in normal white matter. In contrast, water in vasogenic edema induced by cold injury had a larger and more anisotropic ADC than in normal white matter. Water in interstitial edema due to kaolin-induced hydrocephalus had an anisotropic and very large ADC.

Animals↗