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Masashi Sakamoto

Publications and source records attributed to Masashi Sakamoto.

4 recordsLinked to original sources

Goal-directed, serial and synchronous activation of neurons in the primate striatum.

To study roles of cortico-basal ganglia loops in action planning, we examined interactions between the activities of simultaneously recorded neurons in the striatum of monkeys performing sequence motor tasks by cross-correlation analysis. Serial activation occurred between projection neurons in a motor sequence-dependent manner, and was in the direction of a neuron encoding an early event in the sequence to a neuron encoding the same event or later, but closer event to the reward. Synchronous activation occurred between pairs of interneurons. The serial activation seems to originate through the cortico-basal ganglia loops, because projection neurons are inhibitory. We propose that the task-dependent serial and synchronous activation of striate neurons may be a neural substrate for goal-directed planning through the basal ganglia.

Animals↗

Endoscopic color Doppler ultrasonographic evaluation of recurrent esophagogastric varices following endoscopic injection sclerotherapy.

BACKGROUND: Endoscopic injection sclerotherapy (EIS) for treatment of esophagogastric varices is well established in Japan. However, varices may still recur unpredictably following EIS. We studied this problem using endoscopic color Doppler ultrasonography (ECDUS) and specifically examined esophagogastric blood flows. METHODS: Prophylactic EIS was performed by intravariceal injection of 5% ethanolamine oleate (EO) in 49 patients with esophageal varices secondary to liver cirrhosis. No patient had documented hepatocellular carcinoma (HCC) before EIS, and patients who developed HCC during follow-up were excluded. We performed ECDUS before EIS, and 2 weeks and 2 years later. The esophagogastric intra- and extramural venous blood flows, including flow in the azygos vein, were compared between these observations. Gastric intramural blood flow and changes in extramural gastric blood flow, including the azygos vein flow, were scored. Dynamic computer tomography (CT), ultrasonography (US), and color Doppler-ultrasonography (CDUS) were also performed before EIS and 1 month following the procedure. Thereafter, patients underwent CT and US examinations every 6 months for 2 years to detect any development of porto-systemic shunts or HCC. RESULTS: The average number of EIS procedure per patient was 3.1+/-0.8 (mean+/-SD), and the total amount of sclerosant injected was approximately 33.5+/-6.5 ml. The overall recurrence rate over the 2-year follow-up was 36.7%. The gastric intra- and extramural blood flows did not differ between those patients with or without major shunts before EIS. In patients with recurrent variceal formation, the gastric intramural blood flow score following EIS (2.1+/-0.5) was significantly higher than that in patients without recurrence (0.8+/-0.6) (P<0.01). In addition, gastric extramural blood flow score following EIS (0.8+/-0.6) was significantly lower in patients with recurrence than that in those without recurrence (1.7+/-0.5) (P<0.01). The same differences held after exclusion of patients with major shunts. The gastric intramural blood flow score in patients with recurrent variceal formation (2.1+/-0.4) was significantly higher than that in patients without recurrence score (P<0.01). Moreover, gastric extramural blood flow score in patients with recurrent variceal formation (1.0+/-0.7) was significantly lower than in patients without recurrence (1.6+/-0.5) (P<0.01). CONCLUSIONS: Two characteristics were observed in patients with recurrent cases of esophageal varices 2 weeks following EIS. The first was the maintenance of gastric intramural blood flow. The second was the absence of dilation of the gastric extramural blood vessels. These observations may enable us to predict the recurrence of esophagogastric varices using ECDUS within 2 weeks following EIS.

Journal Article↗

Coaggregation among nonflocculating bacteria isolated from activated sludge.

Thirty-two strains of nonflocculating bacteria isolated from sewage-activated sludge were tested by a spectrophotometric assay for their ability to coaggregate with one other in two-membered systems. Among these strains, eight showed significant (74 to 99%) coaggregation with Acinetobacter johnsonii S35 while only four strains coaggregated, to a lesser extent (43 to 65%), with Acinetobacter junii S33. The extent and pattern of coaggregation as well as the aggregate size showed good correlation with cellular characteristics of the coaggregating partners. These strains were identified by sequencing of full-length 16S rRNA genes. A. johnsonii S35 could coaggregate with strains of several genera, such as Oligotropha carboxidovorans, Microbacterium esteraromaticum, and Xanthomonas spp. The role of Acinetobacter isolates as bridging organisms in multigeneric coaggregates is indicated. This investigation revealed the role of much-neglected nonflocculating bacteria in floc formation in activated sludge.

Acinetobacter↗

Coaggregation between Acinetobacter johnsonii S35 and Microbacterium esteraromaticum strains isolated from sewage activated sludge.

The extent and nature of intergeneric coaggregations among non-flocculating sludge bacteria were studied through examination of the coaggregation abilities of Acinetobacter johnsonii S35 with two other strains of non-flocculating sludge bacteria (Microbacterium esteraromaticum S38 and M. esteraromaticum S51). At first, the effect of electrolyte concentration as well as the addition of EDTA and proteases on coaggregation were studied. Changes in electrolyte concentration had little effect on the aggregation index (A.I.). However, the A.I. was reduced by 35-45% (addition of 2 mM EDTA) and 15-58% (addition of 0.2 mg/ml Actinase E) within 1 h depending upon the bacterial pair involved. Furthermore, the effect of pretreating either A. johnsonii S35 or its partners with Actinase E and periodate, respectively, was studied. The results indicate that these coaggregations involve a protein on the partner's surface that may interact with carbohydrate or a carbohydrate-containing moiety on the surface of A. johnsonii S35.

Journal Article↗