Search PubMed⌕ Search

Biomedical subjects

S Niwa

Publications and source records attributed to S Niwa.

At least 109 records · Page 6Linked to original sources
PubMed1994

Rapid free radical reduction in the perfused rat liver.

The reduction of nitroxide free radicals was investigated in detail by Electron Paramagnetic Resonance (EPR) spectroscopy in perfused liver. The nitroxide free radical was rapidly reduced to the corresponding hydroxylamine more efficiently at the lower flow rate of 8 [ml/min], while at higher flow rates, the amount of reduced nitroxide showed a significant decrease. Oxidation of hydroxylamine using hydrogen peroxide provided dynamic information concerning the reduction of the free radical within the liver. In addition, liver homogenates were also investigated to determine the level of nitroxide uptake. The results suggested that a portion of the infused nitroxide was taken up by the liver and cleared from the circulation.

Animals↗
PubMed1994

[Effect of exercise in water on maternal blood circulation].

To elucidate the effects of exercise in water on the maternal circulation, twenty normal pregnancies were examined under the following three conditions; 1) on the land at rest, 2) during water immersion and 3) after the exercise in water. Their gestational ages were from 25 to 37 weeks (31 +/- 4 weeks, mean +/- S.D., n = 20). We examined the blood pressure, the urine volume throughout the examination, CBC and the levels of vasopressin, plasma renin activity and human atrial natriuretic peptide (hANP). The blood volume calculated from the Hb and Ht were significantly (p < 0.001) increased during the water immersion (105.8 +/- 2.5%), even after the exercise (101.6 +/- 2.9%). Vasopressin was decreased during the water immersion and increased after the exercise, but plasma renin activity was decreased in these two conditions. The hANP concentration was significantly (p < 0.001) increased after the exercise in water and correlated with the urine volume (ml/hour) during the examination. These results show that the decline in blood pressure and the increase in the urine volume during the maternal swimming were caused by the decreased plasma renin activity and the increased hANP concentration resulted from the blood volume expansion during the exercise in water.

Atrial Natriuretic Factor↗
PubMed1993

Nd and P300 in healthy volunteers.

We attempted to standardize values of the attention-related negative potential (Nd) and the P300 in 100 healthy volunteers (50 females, 50 males) who were given the task of making dichotic syllable discriminations requiring key-press responses. Ages ranged between 18 and 59 years. Nd was found to be maximum in the Fz region, P300 being maximum in the Pz region. The means and standard deviations of the Nd and P300 areas in their maximum regions were 554.1 +/- 307.8 microV.msec and 2148.5 +/- 1261.5 microV.msec, respectively. After being transformed into logarithmic values, the distribution patterns of the Nd and P300 areas followed a Gaussian distribution. When the lower limit of normal values was tentatively assigned to mean--2 SD using logarithmically transformed data for both Nd and P300, 94% of the subjects were found to display values above the lower normal limit for Nd, and 95% for P300. Neither Nd nor P300 areas correlated with age, while P300 latencies displayed a weak positive correlation with age. Females displayed relatively larger values than males for Nd and P300 areas and P300-peak amplitudes. Females and males showed nearly equal P300-peak latencies.

Acoustic Stimulation↗
PubMed1993

In-vitro evaluation of the cytocompatibility of wear particles generated by UHMWPE/zirconia friction.

Cytotoxicity of wear products generated by UHMWPE/yttria partially stabilized zirconia (YPSZ) friction and UHMWPE/surface-nitrided Ti-6Al-4V friction in pseudo-extracellular fluid (PECF) at 37 degrees C was evaluated. Though the amount of abraded UHMWPE against YPSZ was almost the same as that against nitrided Ti-6Al-4V, the wear products generated by UHMWPE/YPZ friction significantly inhibited cell growth while those by UHMWPE/nitrided Ti-6Al-4V friction showed no growth inhibition. Dissolved Zr and Y ions were at least 70 times less than the amount causing growth inhibition. The cytotoxicity was caused mainly by the particles less than 0.22 mum in size. Amorphous zirconium-containing particles (5-20 nm) found in the PECF, formed presumably by stress corrosion, would be a responsible factor for the cytotoxicity.

Biocompatible Materials↗
PubMed1993

Effects of TJ-960 on Sternberg's paradigm results in epileptic patients.

OBJECTIVES: This study is aimed at investigating the effects of TJ-960 on cognitive function in epileptic patients. Sternberg's paradigm was used to examine the change in cognitive function, especially short-term memory, resulting from administration of TJ-960, along with the effects of the drug on seizures. SUBJECTS: The subjects of this investigation were 26 epileptic outpatients (14 males and 12 females; average age: 35 +/- 11 years old) of the Saitama Medical School Hospital, the Tokyo Medical and Dental University Hospital and the Tokyo University Hospital. The controls were 17 other epileptic outpatients (12 males and 5 females; average age: 40 +/- 12 years old) of the same hospitals. METHODS: The subjects were administered 7.5 g of TJ-960 per day for 8 weeks in addition to their previous medications. Immediately before the beginning of drug administration, and again after 8 weeks of administration, they were examined, using Sternberg's paradigm. The controls were examined at intervals of 8 weeks in the same manner as the subjects (i.e., no change in regimen). RESULTS: After 8 weeks of treatment with TJ-960, 8 of the subjects exhibited a greater than 25% decrease in the number of seizures. Seventeen cases showed no change, and one case showed exacerbation. The correct reaction times for Sternberg's paradigm in the group administered TJ-960 were 955 +/- 307 ms at the time of the first examination and 881 +/- 277 ms at the time of the second, and those of the control group were 845 +/- 288 ms for the first examination and 829 +/- 269 ms for the second. As these figures show, the correct reaction time was significantly shortened between the first and second examinations in the TJ-960 group. No change was exhibited in the sample reaction time between the first and second examination in either group. The difference in alpha wave power of the occipital region before and after the TJ-960 administration was significantly greater in the patients who showed improvement in Sternberg's paradigm as compared to the patients who remained unchanged in Sternberg's paradigm. In addition, the results for the theta wave power were opposite to those of alpha waves. As mentioned above, TJ-960 was presumed to have the effect of improving the cognitive function in epileptic patients.

Adult↗
PubMed1993

Synthesis of prolyl endopeptidase inhibitors and evaluation of their structure-activity relationships: in vitro inhibition of prolyl endopeptidase from canine brain.

By chemical modification of a known prolyl endopeptidase (PEP) inhibitor (N-[N-(4-phenylbutanoyl)-L-prolyl]pyrrolidine; SUAM-1221), several arylalkanoyl derivatives (V-1--27) were synthesized and tested for in vitro inhibitory activity towards PEP from canine brain. Among them, 4-(2-thienyl)butanoyl derivatives (V-24--27) showed more potent PEP-inhibitory activity than SUAM-1221. The structure-activity relationships of these compounds are discussed.

Amino Acid Sequence↗
PubMed1992

Development of a degradable composite for orthopaedic use: in vivo biomechanical and histological evaluation of two bioactive degradable composites based on the polyhydroxybutyrate polymer.

As a direct method for the evaluation of tissue bonding to two polyhydroxybutyrate (PHB) based composites, a mechanical push-out test was performed on implants in the femur of mature Japanese White rabbits. Three composites were tested. The first, a hydroxyapatite/PHB (HA/PHB) composite showed an increase in interfacial shear strength (ISS) up to 8 wk, after which the ISS decreased due to degradation of the implant. The second composite was an HA/glass/PHB (HGP) composite and this gave lower values for the ISS attributed to ion release from the glass causing a soft tissue reaction at the interface. The third composite was a carbon fibre reinforced polysulfone (CFRP) and this showed high interfacial shear strength values, which continued to increase with time. These conclusions were supported by contact microradiography (CMR) and histology which showed enhanced endosteal bone growth for the HA/PHB but for the HGP, no periosteal or endosteal activity was detected. Interposed soft tissue for the HGP composite was difficult to discern, histologically, but it was proposed that this was the reason for the low ISS values. It was concluded that the high ISS values for the carbon fibre control were due to surface morphology allowing deep ingrowth of soft tissue and this was confirmed by SEM.

Animals↗
PubMed1992

Distributions of the Nd and P300 in a normal sample.

To obtain objective criteria for assessing the attentional and cognitive functioning of psychiatric populations, we attempted to standardize values of two components in Event-Related Potentials (ERPs), namely the attention-related negative potential (Nd) and the P300, in normal populations. The study consisted of 100 healthy volunteers (50 females, 50 males) who were given the task of making dichotic syllable discriminations requiring key-press responses. Their ages ranged between 18 and 59 years (mean +/- S.D., 32.3 +/- 11.3 years). Nd was found to be maximum in the Fz region, P300 being maximum in the Pz region. The means and standard deviations of Nd and P300 areas in their maximum regions were 554.1 +/- 307.8 microV ms and 2148.5 +/- 1248.5 microV ms, respectively. The transformation plot for symmetry indicated the suitable power of transformation to be 1/2 for both Nd and P300 distributions. After being transformed into square-root values, the distribution patterns of Nd and P300 areas were examined. When the lower limit of normal values was tentatively assigned to mean -2 S.D. using square-root transformed data for both Nd and P300, 97% of the subjects were found to display values above the lower normal limit for Nd, and 98% for the P300. Neither, Nd nor P300 areas correlated with age, while P300 latencies displayed a weak positive correlation with age. Females displayed relatively larger values than males for Nd and P300 areas and P300-peak amplitudes. However, the differences between females and males were not statistically significant. Females and males showed nearly equal P300-peak latencies.

Adolescent↗
PubMed1992

Schizophrenia research in Japan: editor's introduction.

The aim and circumstances of the special theme on "Schizophrenia Research in Japan" are described. The six articles included in the issue cover the history, epidemiology, psychophysiology, animal as well as human models, and neurochemistry of schizophrenia.

Animals↗
PubMed1992

The history of schizophrenia research in Japan.

When schizophrenia research began in Japan in the late 19th century, it mainly followed the German school. Since World War II, however, Japanese research has been more influenced by the developments in American psychiatry. The research in Japan has included studies in epidemiology, histopathology, cerebral metabolism, animal models using amphetamine, postmortem brain chemistry, psychophysiology, psychopathology, and protective intervention from relapses. Principal domains of current studies are subjective phenomena in psychopathology and biological correlates of cerebral dysfunctioning in schizophrenia.

Amphetamine↗
PubMed1992

Information dysregulation and event-related potentials in schizophrenia.

Clinical experiences indicate that schizophrenic cognitive disturbances may be partly due to the unsuccessful construction of their cognitive context. In this article, two experiments are introduced in which schizophrenic deficits in utilization of information for construction of effective cognitive context were examined through measurements of event-related potentials, particularly P300s. In a 3-tone discrimination task, schizophrenic subjects failed to elicit P300s to frequent nontarget tones that were as important as standard tones for performing the required task. In the second task, consisting of detecting two consecutive identical tones, unlike healthy controls, schizophrenic subjects failed to display P300s to nontarget tones at target position. These results are discussed in relation to ineffective context construction of schizophrenic subjects. Moreover, a single-trial analysis of relationships between P300s and reaction times in the 3-tone discrimination task disclosed a loose coupling between the stimulus set and response set in patients.

Adult↗
PubMed1992

Temporal lobe CO2 vasoreactivity in patients with complex partial seizures.

The topography of CO2 vasoreactivity during hyperventilation in 8 patients with complex partial seizure (CPS) was visualized using the regional cerebral blood flow (rCBF) as measured by H(2)15O-PET (positron emission tomography) and compared with that of 10 normal volunteers. In the normal volunteers, the vascular response to CO2 (VrCO2 = delta CBF%/delta PaCO2) in the temporal lobe was 2.46 +/- 0.56 (%/mmHg). In the patients with CPS, VrCO2 in the temporal lobe of the affected side was 2.08 +/- 0.40 (%/mmHg), while VrCO2 on the contralateral side was 2.30 +/- 0.46 (%/mmHg). There was a significant difference in VrCO2 between the affected side of the temporal lobes and the temporal lobes of the normal volunteers. Furthermore, there was a tendency for VrCO2 to be lower in the affected than in the contralateral side of the temporal lobe in patients with CPS. As CO2 is the main regulator of CBF, this impaired vasoreactivity may reflect the brain dysfunction in the seizure focus and adjacent areas.

Adolescent↗
PubMed1992

Shortening of N1 and P3 latencies in event-related potentials observed coincidentally with clinical improvement during nootropic medication in a demented patient: specific effect of nicergoline.

Event-related potentials, measured eight times in a patient in the early stages of dementia, demonstrated that clinical symptoms, especially loss of motivation, improved coincidentally with a shortening of reaction time, N1 latency, and P3 latency during nicergoline medication among three nootropics prescribed. Such a longitudinal study design was considered to be useful for quantifying and objectively comparing effects of various nootropics noninvasively.

Aged↗
PubMed1991

Diagnostic reliability and significance of irregular beta patterns.

We designated EEGs with marked and irregular beta waves in basic patterns as "irregular beta patterns" on the basis that these patterns are related with particular symptoms such as dysphoria, irritability and autonomic symptoms and they implicate choice of therapeutic agents. Because of good response to antiepileptic agents in patients with "irregular beta patterns" along with EEG characteristics, we hypothesized that the prevalence of "irregular beta patterns" is higher in epileptics than in other psychiatric patients. In the present study, we tested this hypothesis, investigating actual frequencies of these patterns among different diagnostic categories for all patients whose EEG were recorded in all the first-visit patients to the Outpatient Clinic, Department of Neuropsychiatry of the Tokyo University Hospital during one year period of 1986. Before starting this investigation, we checked the interrater reliability for these patterns. Therefore, two studies are reported here. In Study 1, five raters judged 98 EEG recordings blindly (43 epileptics and 55 healthy subjects). As a result, the generalized Kappa of 0.473 was obtained, indicating our agreement level was moderate or fair. This result lends support to our contention that irregular beta patterns are reliably judged. In Study 2, we judged the EEG recordings (137 schizophrenics, 62 affective disorders, 43 epileptics and 55 healthy controls) and calculated the prevalence rate of "irregular beta patterns" among the diagnostic categories. The results show that the prevalence rates of "irregular beta patterns" among psychiatric disorders and normal controls were 13% (18/137) in schizophrenics, 11% (7/62) in affective disorders, 14% (6/43) in epileptics and 4% (2/55) in healthy controls. These rates did not differ significantly among the three disorders. Thus, our hypothesis was not supported. The clinical significance of these patterns is discussed.

Adult↗
PubMed1991

[Magnetoencephalographic studies on spike foci using a 37-channel biomagnetometer system].

We report the results of a clinical trial of Magnetoencephalography (MEG) on spike foci in patients with epilepsy, which was performed from December 1990 to June 1991 at The University of Tokyo Hospital. Fifty patients with focal epilepsy; 26 primary epilepsy, 24 secondary epilepsy (7 brain tumor, 4 arteriovenous malformation, 4 encephalitis, 3 porencephaly, 2 arachnoid cyst, 1 brain abscess, 1 hemimegaloencephaly, 1 Lance-Adams syndrome, 1 hygroma), and ten normal subjects were enrolled in this study. MEG data were recorded using a 37-channel biomagnetometer system SMI-1001 (BTi Magnes, Biomagnetic Technologies, Inc., San Diego). A simultaneous 19-channel EEG recording with linked-ear reference was also obtained. The overall study was completed safely and none of the normal subjects showed abnormal paroxysmal MEG activity. Two patients showed interictal EEG spikes which would not have been noticed without first noting the presence of corresponding prominent MEG spikes. On the whole, the MEG signal seemed to have a wider frequency bandwidth than EEG. In most cases, the source localization predicted by MEG corresponded well with the EEG findings. The relative accuracy of MEG spike source localization was estimated to be within a cubic centimeter from the cases which showed tightly clustered localization of individual spikes. High-pass filtering reduced interference by superimposed slow wave activity, thereby improving the localization of spike sources. These results demonstrate that 37-channel biomagnetometer system could be a useful tool for analyzing epileptic spike sources.

Adolescent↗
PubMed1990

Percutaneous fiberoptic spinal laser endoscopy.

For percutaneous observation of lesions near the spinal cord and percutaneous spinal laser surgery under the visual field, we studied a method and approach to the spinal cord and intraspinal surgical procedures with laser using a newly developed, small-diameter laser endoscope. The subarachnoid and epidural spaces of a goat were punctured using a 17-gauge epidural needle, and the endoscope (diameter 0.7 mm) was inserted through the needle. The spinal cord and surrounding tissue were observed. Next, an endoscope (diameter 1.5 mm) was inserted into the subarachnoid space, and the quality of the picture and manageability of the endoscope were examined. The Xe:Cl excimer laser was irradiated to a nerve root through a 0.4 mm optical fiber for laser transmission through this endoscope. The spinal cord, nerve roots, and arachnoid were clearly observed through this endoscope. The pulsation of the artery accompanying a root was seen clearly, and the quality of the picture of the endoscope was thought to be sufficient for diagnosis. The nerve root was cut within 30 seconds by excimer laser, and the possibility of laser surgery was demonstrated. Although it was shown that this endoscope could be a useful diagnostic and therapeutic tool, improvement in the manageability of the tip of the endoscope was considered to be important for a clinically usable endoscope.

Animals↗