Biomedical subjects
Publications and source records attributed to E Yoshikawa.
Aryne reagents, unlike alkynes, undergo insertion by allyl palladium complexes. The verification of the conversion described here is shown using Equation (1) as an example. The reaction proceeds in a few hours in refluxing acetonitrile to give the phenanthrene derivative in up to 71 % yield.
To investigate changes in the relation between presynaptic and postsynaptic dopaminergic functions in vivo in both nigrostriatal and mesocortical systems in Parkinson's disease (PD), 10 drug-naive early PD patients were studied twice using positron emission tomography with [11C]CFT (dopamine transporter probe) followed by [11C]SCH 23390 (D1 receptor probe). Regional binding potentials (k3/k4) of [11C]CFT and [11C]SCH 23390 in the striatum (nigrostriatal system) and the orbitofrontal cortex (mesocortical system) were estimated by compartment analyses. Levels of [11C]CFT k3/k4 in the two projection areas were shown to be significantly lower in PD, whereas [11C]SCH 23390 levels remained unchanged. Regression analysis showed that estimates of CFT k3/k4 were positively correlated with those of SCH 23390 k3/k4 in the striatum in normal control, whereas the two binding estimates were less positively correlated in the caudate and inversely correlated in the putamen in PD. No significant correlation was observed in the orbitofrontal cortex in both groups. These results indicated that dopamine transporters and D1 receptors change in parallel in the normal striatal synapses, but the association becomes asymmetrical because of reduction in presynaptic and relative elevation in postsynaptic markers in PD. Alterations in synaptic parallel regulation in the nigrostriatal system might reflect early pathophysiology in the parkinsonian brain.
Human cortical areas activated in relation to vergence eye movements were determined using positron emission tomography. Binocular disparity-driven visual stimuli were presented using a head-mounted display. Eye movements were monitored continuously by an infrared limbus tracker. A combination of a bar and a cross was used as the target. In the vergence task, subjects were instructed to follow an approaching bar, while ignoring a stationary cross. Activation in relation to vergence eye movement was discriminated from activation in relation to motion vision by using the ignore-bar task as the control. In the ignore-bar task, subjects were instructed to fixate on a stationary cross, while ignoring an approaching bar. The fixation task was used as the basic control for both the vergence and the ignore-bar tasks. Areas of activation in relation to vergence eye movements were found in the bilateral temporooccipital junction, the left inferior parietal lobule, and the right fusiform gyrus by comparing regional cerebral flow between the vergence and ignore-bar tasks and by the conjunctive analyses of vergence-vs-ignore comparison with vergence-vs-fixation comparison.
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The regulatory mechanism of bipedal standing in humans remains to be elucidated. We investigated neural substrates for maintaining standing postures in humans using PET with our mobile gantry PET system. Normal volunteers were instructed to adopt several postures: supine with eyes open toward a target; standing with feet together and eyes open or eyes closed; and standing on one foot or with two feet in a tandem relationship with eyes open toward the target. Compared with the supine posture, standing with feet together activated the cerebellar anterior lobe and the right visual cortex (Brodmann area 18/19), and standing on one foot increased cerebral blood flow in the cerebellar anterior vermis and the posterior lobe lateral cortex ipsilateral to the weight-bearing side. Standing in tandem was accompanied by activation within the visual association cortex, the anterior and posterior vermis as well as within the midbrain. Standing with eyes closed activated the prefrontal cortex (Brodmann area 8/9). Our findings confirmed that the cerebellar vermis efferent system plays an important role in maintenance of standing posture and suggested that the visual association cortex may subserve regulating postural equilibrium while standing.
We investigated changes in the kinetics in the binding of the dopamine transporter probe 2-beta-carbomethoxy-3beta-(4-[11C]fluorophenyl)tropane (beta-CFT) in living brain by compartmental analysis, using positron emission tomography in unmedicated patients with Parkinson's disease (PD) (Hoehn and Yahr stages I-II). With dynamic positron emission tomographic data from 90-minute acquisitions and metabolite-corrected arterial input functions, binding potentials (k3/k4) were calculated by using estimated rate constants (K1 - k4). In this analysis, the magnitude of the distribution volume (K1/k2) measured in the cerebellum, in which specific binding is negligible, was used as a constrained value for fitting in binding regions. Statistics showed that k3/k4 values in the striatum, the orbitofrontal cortex, and the amygdala were significantly lower in PD patients than in normal controls, whereas there were no differences in K1/k2 ratios and structural volumes between the groups. Correlation analysis showed that the putaminal and orbitofrontal binding levels were correlated positively with motor and mentation scores, respectively, of the Unified Parkinson's Disease Rating Scale. These results indicated that not only the striatal but also the orbitofrontal and amygdalar presynaptic dopaminergic functions were altered in early PD. The reductions in these mesocortical/mesolimbic functions might contribute to the mental and behavioral impairment observed in PD.
A beta microprobe was successfully applied to monitor arterial input function for quantification of regional cerebral blood flow (rCBF) in the monkey brain with (15)O-water and positron emission tomography (PET). The sensitivity of the probe was approximately 0.83 to 1.67 cps/kBq/ml depending on the studies. A preliminary study was performed to find a suitable use and to evaluate the performance of the system and data analysis procedure. The results showed that dispersion correction of measured input function was unnecessary if microprobes were connected directly to the arterial catheter. Then multiple CBF measurements were done in three monkeys under anesthesia. Identical regions of interest were placed with the aid of magnetic resonance imaging (MRI) of each monkey and rCBF values were estimated. Estimated rCBFs were reproducible for several measurements. The mean CBF value for a pentobarbital anesthetized monkey was 46.0 ml/min/100 g (PaCO2 = 46.3 mmHg). This shows that the use of the beta microprobe for quantification of rCBF with PET was validated. The lack of a need for dispersion correction of observed input function is an advantage with the beta microprobe system because the probes are small enough to be placed near the arterial sampling site.
The antibiotic susceptibilities of 43 strains of Escherichia coli O157:H7 identified in the summer of 1996 in Japan were investigated. Growth of 90% of O157 strains was inhibited at a concentration of < or = 0.5 micro/ml by several agents including fosfomycin with glucose-6-phosphate.
OBJECTIVE: To evaluate the relevance of hypometabolism in the hippocampal head to the pathophysiology of memory impairment. BACKGROUND: Neurofunctional imaging studies with an image reslicing technique provided by using software suggest that dysfunction of the amygdalohippocampal system causes memory impairment. However, metabolic and morphologic profiles of the whole hippocampal formation have not been evaluated in detail. METHODS: By tilting the gantry of a high-resolution PET scanner in a plane parallel to the hippocampal longitudinal axis determined beforehand by MRI, we performed quantitative measurement of glucose metabolism in the subdivisions of the hippocampal formation (head, body, tail) in 10 patients of normal intelligence with pure amnesia, in eight patients with AD, and in eight normal subjects. RESULTS: Although the volumes of the amygdala and hippocampal formation in pure amnesics were not different significantly from those of normal subjects, glucose metabolism in the head of the hippocampus was significantly lower in pure amnesics. In patients with AD, marked hypometabolism was found extending to the amygdala, the hippocampal head, and the parietotemporal cortex, along with amygdalohippocampal atrophy. CONCLUSION: Hippocampal head dysfunction plays an important role in memory impairment in amnesic patients. Further metabolic impairment over the amygdalohippocampal system and the surrounding association cortex reflects the pathophysiology of AD.
Among recent clinical isolates in Japan, strain CU264 was discovered which formed unusual colonies. This strain was identified as Rahnella aquatilis which is usually found in water. The antibiotic susceptibilities against tetracycline, carbenicillin, chloramphenicol, streptomycin, kanamycin, gentamicin, sulphonamide, neomycin, fosfomycin, rifampicin, norfloxacin and nalidixic acid, were investigated. The result demonstrated that the strain was highly resistant to fosfomycin only. It was further shown that this resistance was transmissible with low frequency to Serratia marcescens whereas it was not transmissible to Escherichia coli.
Positron emission tomography (PET) was used to measure changes in the regional cerebral blood flow (rCBF) of rhesus monkeys performing visual discrimination tasks. In comparison with both position and brightness discrimination tasks, the color discrimination task activated the posterior inferior temporal cortex and a ventromedial occipital region, which is located along the anterior one-third of the calcarine sulcus. In contrast, the position task activated the middle temporal area and intraparietal cortex as compared with the color task. These results confirm the segregation of visual pathways and delineate the visual areas involved in color vision. This approach might bridge the gap between invasive studies in animals and functional imaging studies in humans.
This study was designed to evaluate the ability of cementum-impregnated gelatine membranes (CGM) to stimulate regeneration of periodontal ligament following surgery. Three monkeys with no periodontal disease were used. Following flap elevation, recession type defects were created on the buccal side of maxillary lateral incisors and second premolars, and roots were subsequently planed. Experimental sites received CGM at approximately 2-3 mm below the cementoenamel junction while control sites received gelatine membrane (GM) free of cementum. Wounds were allowed to heal for 3 weeks, during which time daily plaque control measures were maintained. Tissues prepared from sacrificed animals revealed that experimental specimens exhibited formation of new cementum, new bone, and periodontal ligament. Control specimens exhibited connective tissue adhesion without either new cementum or significant new bone formation. Histometric analysis showed that the average vertical growth of cementum (NC) and bone (NB) at experimental sites were 3.48 +/- 0.29 and 0.64 +/- 0.43 mm, respectively. At the control sites the corresponding results were NC = 0.09 +/- 0.03 and NB = 0.06 +/- 0.28. It was concluded that placement of CGM resulted in significantly greater postsurgical cementum and bone formation than that of GM alone.
The purpose of this study was to investigate the initial healing response of surgically flapped periodontal tissues in the presence of gelatine membrane compounded with particles of cementum. Four monkeys with no periodontal disease were used in this experiment. Full thickness flaps were raised and recession type defects were created on the buccal side of the maxillary lateral incisors and second premolars. Exposed root surfaces were thoroughly curetted, and composite cementum-impregnated membranes placed directly onto planed root surfaces. Flaps were then sutured back to the original position. Animals were sacrificed at 2, 4, 7 and 10 post-surgical days, and block specimens including the tooth, gingiva and bone were subsequently processed for light and electron microscopy. The resultant analysis revealed that gelatine membranes were partially resorbed at 2 days post-surgery and completely resorbed by 10 postoperative days. In the early stages of gelatine resorption, most liberated cementum particles accumulated on planed dentin surface but some became demineralized within the surgical wound. Cementoblast-like cells with well-developed rough endoplasmic reticulum appeared on the root surface 7 days following surgery. Newly synthesized collagen fibrils aligned parallel to the root surface were seen at 10 post-surgical days. The results suggest that the newly developed composite membrane enhances the formation of new periodontal attachment.
A system for the measurement of brain activity in conscious monkeys by positron emission tomography (PET) was established in the present study. The signal/noise ratio was maximal around 40 s for data acquisition in the PET scan with 15O-labeled water. When the monkey was stimulated by vibration and subtraction images of the data sets from regional cerebral blood flow (rCBF) changes in paired stimulation and control were superimposed on magnetic resonance images obtained from the same specimens, a somatotopic map corresponding to the sites stimulated was clearly demonstrated. Visual stimulation with a photic stimulator activated the corresponding regions of the primary visual cortex. Comparison of the activated sites and extents under the conscious state with those under anesthesia assured that the study is controllable; there was little unpredictable activation due to unlimited subject movement or to psychological effects.
A case of fatal hematemesis due to an aberrant right subclavian artery-esophageal fistula is presented. The patient was a 9-year-old male child with complex congenital heart disease and developed the fistula by prolonged tracheal and nasogastric intubation after Fontan type operation. To avoid this unusual but serious complication, aberrant subclavian artery should be treated surgically before repair of complex cardiac anomaly.
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Pretreatment for 3 days with oral ofloxacin or norfloxacin had no significant effect on the disposition of a single i.v. dose the theophylline in healthy volunteers.
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