Search PubMed⌕ Search

Biomedical subjects

M Sakamoto

Publications and source records attributed to M Sakamoto.

At least 613 records · Page 34Linked to original sources
PubMed1989

Functional properties of monkey caudate neurons. II. Visual and auditory responses.

1. Visual responses of caudate neurons were studied in monkeys trained to fixate on a small spot of light. A visual stimulus (another spot of light) was presented in various contexts of behavior using different behavioral paradigms. Visual receptive fields were usually large and centered on the contralateral hemifield. Among 217 neurons with visual responses, 184 were further classified into subtypes. 2. Visual responses in 64 neurons were not modulated by changing the paradigms (unconditional visual responses). In the other neurons, visual responses were dependent on the behavioral contexts in which the stimulus was presented. Three types of behavioral modulation were found. 3. A saccade-enhanced visual response (n = 37) was the one that was enhanced if the monkey made a saccade to the stimulus on its appearance. The enhancement was spatially selective: the response was depressed if the saccade was directed away from the stimulus. 4. Memory-contingent visual responses (n = 36) were present preferentially when the monkey remembered the location of the stimulus and a few seconds later made a saccade to the remembered location. Responses were greater when the location of the stimulus was randomized between trials. 5. Expectation-contingent visual responses (n = 46) were present preferentially when the stimulus came on while the monkey was not fixating another spot, and the stimulus was related directly to a reward. Unlike the other types, its receptive field included both contralateral and ipsilateral hemifields without a particular preference. 6. A small number of neurons (n = 16) showed a visual response that easily habituated. 7. Latencies of visual responses were usually between 100 and 200 ms. The latencies of the memory-contingent, expectation-contingent, and habituated visual responses tended to be longer than the others and tended to be more variable between trials. 8. Among auditory responsive neurons only a small proportion were related to the tasks. The response was greater to a contralateral sound. It was enhanced if the monkey used the sound as the cue for the future target location. 9. The results suggest that sensory responses of caudate neurons could be used to guide a subsequent sequence of learned behaviors by confirming predicted environmental states, renewing memory, or establishing a motor set.

Animals↗
PubMed1989

Functional properties of monkey caudate neurons. III. Activities related to expectation of target and reward.

1. The present paper reports complex neural activities in the monkey caudate nucleus that precede and anticipate visual stimuli and reward in learned visuomotor paradigms. These activities were revealed typically in the delayed saccade task in which memory and anticipation were required. We classified these activities according to their relationships to the task. 2. Activity related to expectation of a cue (n = 46) preceded the presentation of a spot of light (target cue) that signified the future location of saccade target. When the target cue was delayed, the activity was prolonged accordingly. The same spot of light was preceded by no activity if it acted as a distracting stimulus. 3. The sustained activity (n = 80) was a tonic discharge starting after the target cue as if holding the spatial information. 4. The activity related to expectation of target (n = 109) preceded the appearance of the target whose location was cued previously. It started with or after a saccade to the cued target location and ended with the appearance of the target. The activity was greater when the target was expected to appear in the contralateral visual field. 5. The activity related to expectation of reward (n = 57) preceded a task-specific reward. It started with the appearance of the final target and ended with the reward. In most cases, the activity was nonselective for how the monkey obtained the reward, i.e., by visual fixation only, by a saccade, or by a hand movement. The activity was dependent partly on visual fixation. 6. A few neurons showed tonic activity selectively before lever release and are thus considered to be related to the preparation of hand movements. 7. The activity related to breaking fixation (n = 33) occurred phasically if the monkey broke fixation, aborting the trial. 8. Activity related to reward (n = 104) was a phasic discharge that occurred before or after a reward of water was delivered. The activity was not simply related to a specific movement involved in the reward-obtaining behavior (eye, hand, or mouth movement). 9. Fixation-related activity (n = 72) was tonic activity continuing as long as the monkey attentively fixated a spot of light. It was dependent on reward expectancy in most cases. 10. The present results, together with those in the preceding papers, indicate that the activities of individual caudate neurons--sensory, motor, or cognitive--are dependent on specific contexts of learned behavior.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Hemangioendothelial sarcoma in brown adipose tissue of mouse induced by carcinogenic heterocyclic amine, Glu-P-1.

2-Amino-6-methyldipyrido[1,2-a:3',2'-d]limidazole, a potent bacterial mutagen from glutamic acid pyrolysate, when given to male CDF1 mice at a concentration of 0.05% in the diet induced blood vessel tumors characterized histopathologically. These hemangioendothelial sarcomas showed positive alkaline phosphatase activity histochemically and Weibel-Palade bodies ultrastructurally. Neoplasms were predilective for brown adipose tissue and foci of atypical cells, not peliosis-like lesions, appear to be an early stage in tumor development.

Adipose Tissue↗
PubMed1989

[Lipid peroxidation induced by methylmercury in rats].

The ability of methylmercury (MMC) to induce lipid peroxidation was tested in rats. One group of 5 rats (MMC group) took a diet to which 10 ppm of methylmercury was added while another group of 5 rats was fed a diet containing no MMC as a control. During the experimental period of 14 weeks (98 days) on these diets, body weight gain and amount of food consumption were checked individually for each two-day interval. Samples of expired air and blood were obtained every two weeks and analysed for ethane and pentane production and for plasma fatty acid composition, respectively. Results obtained were as follows: 1. During the first half of the 14-week experimental period, there was no significant difference in the amount of food consumption between the MMC group and the control group. However, a significantly smaller amount of food consumption was found in the MMC group as compared to the control group during the latter half of the experiment. The amount of food consumption was directly reflected in the body weight gain throughout the experimental period. 2. The amount of expired ethane was generally higher in the MMC group than in the control group throughout the experimental period. During the last 2 weeks of the experimental period, the difference in the amount of expired ethane between the two groups was statistically significant. 3. The amount of expired pentane was also higher in the MMC group than in the control group during all the weeks of the experimental period.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Induction of lipid peroxidation and change of fatty acid composition in rats fed methylmercury].

Four groups of rats, with 5 animals in each, were fed a diet to which 1, 2, 4 or 8 ppm of methylmercury (MeHg) were added while another group of 5 rats was fed a diet containing no MeHg as a control. Moreover, each rat was daily supplied the same volume of these diets. During the experimental period of 40 days, body weights of the rats were daily checked individually. On day 40, expired air of the rats was collected to analyse for ethane and pentane production, and then the rats were sacrificed to obtain the liver, kidneys, brain and plasma. Thio-barbituric acid (TBA)-reactants in the selective organs and plasma were measured to investigate the effects of MeHg on lipid peroxidation. Further, gas-chromatographic analyses of fatty acids were carried out on the samples of the selective organs and plasma to examine the effects of MeHg on lipid metabolism. Results obtained were as follows: 1. The fifth day after the experiment started, the growth rates of the groups fed a diet containing MeHg (the MeHg groups) were higher than those of the control group. Moreover, the growth rates tended to increase with increases of MeHg concentrations in food from days 25 to 32 of the experimental period. Furthermore, the weights of the kidneys increased with increases in MeHg concentrations in food. 2. The amounts of expired ethane and pentane did not increase proportionally with increases in MeHg concentrations in food but those of expired ethane and pentane were higher in the MeHg groups than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Matrix collagen of devitalized bone is resistant to osteoclastic bone resorption.

The resorption of devitalized bone by isolated osteoclasts in culture was studied by scanning electron microscopy. Osteoclasts attached to the bone and resorbed mineral but left most of matrix collagen undigested in the resorption pits. Postculture-treatment of bone substrate with collagenase completely removed the matrix collagen in the resorption pits, whereas trypsin did not. The results suggest that native matrix collagen is resistant to osteoclastic attack in this in vitro model using devitalized bone.

Animals↗
PubMed1989

Structure-activity relationship studies on 4''-O-acyltylosin derivatives: significance of their 23-O-mycinosyl and 4''-O-acyl moieties in antimicrobial activity against macrolide-resistant microbes.

Essential roles for both the 23-O-mycinosyl and 4''-O-acyl moieties of 4''-O-acyltylosin derivatives in the expression of antimicrobial activity against multiple macrolide-resistant strains of Staphylococci and mycoplasmas were demonstrated by in vitro comparison of the MICs of erythromycin, josamycin, tylosin and its 3- and 4''-O-acyl derivatives, demycinosyltylosin (DMT) and its 3- and 4''-O-acyl derivatives and 23-modified 3-O-acetyl-4''-O-isovaleryl-DMT derivatives.

Anti-Bacterial Agents↗
PubMed1989

[Clinical studies of subcapsular orchiectomy with an intracapsular testicular prosthesis--improving the quality of life in patients with prostatic cancer].

Twenty-five patients termed the method group, having a carcinoma of the prostate, underwent a subcapsular orchiectomy, followed by the placement of an intracapsular prosthesis for anti-androgen treatment. In tandem, a control group of 16 patients, having a carcinoma of the prostate underwent, a total orchiectomy. Further, a histological study of a testicular capsula was performed on an autopsy specimen, but almost no seminiferous residue was detected. Postoperatively, serum testosterone levels decreased to less than 10% of their Preoperative levels, and remained at this level for 30 months. Similar results were obtained in both the method group and the control group postoperative questionnaires showed that the method group experienced less mental and physical stress than did the control group. In a society composed largely of elderly people, this type of operation can be very beneficial to those suffering from prostate carcinoma in maintaining the quality of their lives.

Aged↗
PubMed1989

[Methylguanidine synthesis by active oxygen generated by stimulated human neutrophils].

In previous papers, we have reported that methylguanidine (MG), a known uremic toxin, was synthesized from creatinine (Cr) by active oxygen generated not only by chemical reagents but also by isolated rat hepatocytes. In this paper, we studied whether or not active oxygen generated by stimulated human neutrophils produces MG from Cr. MG was measured after incubating 2 x 10(6) human neutrophils for 2 h in 1 ml of Hanks' balanced salt solution (pH 7.4) containing 100 mg/dl Cr at 37 degrees C after the addition of phorbol myristate acetate (PMA). MG was measured by high pressure liquid chromatography followed by reaction with 9, 10-phenanthrenequinone. MG was synthesized by the stimulated neutrophils and not by the unstimulated ones. MG synthesis reached a plateau (1.11 +/- 0.03 nmol/120 min/2 x 10(6) cells) at a concentration of 0.125 microM PMA and reached a maximum value (1.95 +/- 0.03 nmol/120 min/2 x 10(6) cells) at a concentration of 100 mg/dl Cr. MG synthesis increased depending on the concentration of neutrophils between 1 and 8 x 10(6)/ml and increased depending on the duration of incubation up to 4 h. MG synthesis was strongly inhibited by superoxide dismutase, by the scavengers of hypochloride (taurine and methionine) and by sodium azide. Catalase and the scavenger of the hydroxyl radical (dimethyl sulfoxide) inhibited MG synthesis less effectively. The effects of the scavengers of active oxygen suggest the participation of active oxygen in MG synthesis from Cr in this system. Among the active oxygen species, superoxide anion and hypochloride play an important role in this system.(ABSTRACT TRUNCATED AT 250 WORDS)

Cells, Cultured↗
PubMed1989

[PTCA and coronary artery bypass operation prior to subsequent surgery of gastric cancer in patients with coronary artery disease].

Two patients with coronary artery disease required operation for gastric cancer. In one patient with single vessel disease, 37 days later after successful PTCA, gastric resection for early gastric cancer was performed without any cardiac complication. The other patient with severe three vessel disease initially underwent coronary artery bypass operation, and 13 days later gastric resection for advanced cancer was performed. This patient developed supraventricular arrhythmia as a sole complication which was easily controlled by medical treatment. In both cases, fentanyl was used as an anesthetic agent and nitroglycerin was continuously administered intravenously during the perioperative period. ECG, central venous pressure, and direct arterial pressure were also carefully monitored. We feel that noncardiac operation such as gastric resection can be performed without major cardiac complications even shortly after coronary artery bypass operation.

Aged↗
PubMed1989

Diethylcarbamazine: inhibitory effect on acetylcholinesterase of Dirofilaria immitis and Brugia pahangi.

Anti-acetylcholinesterase activity of diethylcarbamazine (DEC) was studied. Acethylcholinesterase (AchE) of adult worms of Dirofilaria immitis, those of the 4th-stage larvae, early 5th-stage larvae and adults worms of Brugia pahangi, and that of hamster brain tissue were all inhibited by DEC. Michaelis constant (Km) of D. immitis and B. pahangi adult worm AchE were 1.47 x 10(-4) and 1.81 x 10(-4) M respectively. DEC was a competitive inhibitor of the filarial AchE. Inhibition constant (Ki) for AchE of D. immitis and B. pahangi adult worms were 2.56 x 10(-4) and 6.39 x 10(-4) M, respectively. DEC is a less potent anticholinesterase inhibitor, because Ki of DEC is 10(4) times higher than that of eserine, a potent anti-cholinesterase agent.

Acetylcholinesterase↗
PubMed1989

[A case of acute airway obstruction with sharp sawdust particles, successfully treated by extracorporeal lung assist].

A 17 year-old male accidentally fell into a loading shute filled with sharp particles of sawdust. He aspirated a large amount of sawdust and suffered from acute airway obstruction accompanied by barotrauma, probably due to severe cough and tissue damage from the needle sharp sawdust particles. Ordinary mechanical ventilation was not enough to keep normal gas exchange. To sustain life, a venovenous extracorporeal lung assist, ECLA, with two Kolobow membrane lungs was performed. Under ECLA, the sawdust particles were removed from the airway one by one with a bronchofiber scope taking almost 10 hours. Then the left lung lavage was performed with normal saline to remove finer sawdust. The patient survived these procedures and was weaned from ECLA after 36 hrs. His recovery was uneventful.

Adult↗
PubMed1989

[Muscle carnitine deficiency associated with myalgia and rhabdomyolysis following exercise].

A case of 16-year-old female with myalgia and myoglobinuria following prolonged exercise was reported. Neurological examination revealed mild weakness of proximal muscle in the lower extremities. Serum CK, LDH, myoglobin were significantly increased during the attacks. On biopsy, the muscle fibers contained myriad lipid-filled vacuoles, in predominantly type 1 fibers. Electron microscope examinations revealed numerous lipid droplets adjacent to mitochondria and glycogen particles. Carnitine level in the patient's muscle was markedly reduced (under 5% of control), but the serum carnitine concentration was normal. The muscle carnitine palmityl transferase level was not depressed. A forearm ischemic test resulted in normal lactate production. On exercise tolerance test by a bicycle ergometer, mild exercise (15-30 watts for 15 minutes) induced myalgia and marked elevation in serum CK, lactate and pyruvate, while severe exercise showed no increase in serum CK level. The findings suggest that the energy production system in the skeletal muscle was impaired. However, the enzyme activities of NADH oxidation in mitochondria and the anaerobic glycolysis pathway were within normal limits. During fasting (36 hours), there was a normal production of ketone bodies, suggesting that hepatic metabolism of lipids was normal. She showed good response to L-carnitine therapy.

Adolescent↗
PubMed1989

[Effects of open-heart surgery on renal function].

Effects of open-heart surgery on renal function were studied in 38 patients who had uneventful postoperative course with no sign of acute renal failure. Of these, 19 underwent aorto-coronary bypass grafting (Group 1) and 19 underwent valve replacement (Group 2). During cardiopulmonary bypass (CPB), renal plasma flow (RPF) and glomerular filtration rate (GFR) significantly decreased in both groups as compared to the preoperative values. The decreased GFR remained significantly low on the day of operation in both groups and returned to the preoperative level on the 1st postoperative day (POD) in group 1 and on the 3rd POD in group 2. On the other hand, plasma antidiuretic hormone (ADH) level markedly increased during CPB and remained significantly higher than the preoperative level through the 1st POD. Despite the decreased GFR and increased ADH, however, urinary flow markedly increased during CPB in both groups and remained at significantly higher level than the preoperative values through the 3rd POD in group 1 and through the 5th POD in group 2. Fractional excretion of sodium significantly increased during CPB in both groups and remained high through the 1st POD in group 1 and through the 3rd POD in group 2. These data demonstrate that the renal function of urine concentration is disturbed in the early phase following open-heart surgery even in the patients who have uneventful postoperative course.

Adult↗