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Biomedical subjects

R Tamura

Publications and source records attributed to R Tamura.

At least 109 records · Page 6Linked to original sources
PubMed1990

Dopamine and ACh involvement in plastic learning by hypothalamic neurons in rats.

Unit activity in the rat lateral hypothalamus (LHA) was recorded during discrimination learning of cue tone stimuli (CTS). CTS+ predicted reward (glucose or intracranial self-stimulation); CTS- predicted aversion (electric shock or tail pinch); and all behavior responses were by the same act, licking. Roles of the LHA dopaminergic and cholinergic systems in CTS learning were investigated by electrophoretic application of dopamine (DA) and acetylcholine (ACh), and their antagonists. The CTS+, the predicted reward and DA, all had similar effects (inhibition) on many LHA neurons; and these were all opposite to the effects (excitation) of CTS-, the predicted aversion, and ACh. Neural responses to CTS+ were blocked by spiperone, and responses to CTS- were blocked by atropine. Sensitivity of LHA neurons to DA was reduced by extinction of CTS+ learning for reward, and sensitivity to ACh was reduced by CTS- learning for aversion. The data suggest that afferent DA and ACh inputs to LHA neurons are essential for plastic CTS+ and CTS- learning.

Acetylcholine↗
PubMed1989

Characteristics of rat lateral hypothalamic neuron responses to smell and taste in emotional behavior.

Single unit activity in the lateral hypothalamus (LHA) of the rat was recorded while the animal learned to discriminate cue signals. Normally preferred potables (glucose, orange, or grape solution) or intracranial self-stimulation (ICSS) were used as rewards. Electric shock or tail pinch were used as aversive stimuli. The same behavior, licking, was the response required to either obtain the rewarding stimuli or avoid the aversive ones. For positive reinforcement a rat was rewarded with fluid or ICSS upon licking a spout presented in front of its mouth. In negative reinforcement experiments, an aversive stimulus, electric shock or tail pinch, was applied if the rat did not lick the spout. Solutions having smell only, taste only, or smell-plus-taste, were prepared from oranges or grape extract. Of 392 neurons analyzed, 256 responded differentially to rewarding and aversive stimuli, and 138 of these were tested with the 3 different solutions. Similar LHA neural responses occurred during actual drinking of the 3 kinds of solutions, as well as on recognition of the cue signal. Responses to smell only had shorter latency than responses to taste only. Neural activity in response to solutions that could be both smelled and tasted was the sum of activity in response to taste-only solutions plus that in response to smell-only solutions. Cue signal responses were rapidly acquired, usually within 2-5 trials, for both taste-only and smell-only solutions. The results indicate the integration of both taste and olfactory information by the same LHA neurons, and these neurons are involved in cue signal learning. Present results of LHA neuronal responses to taste and smell suggest that the intensity of gustation and olfaction may add together to enhance instinctive hedonic sensations. These neurons are involved in the formation of stimulus-reinforcement association in learning, and in elicitation of conditioned emotional responses.

Action Potentials↗
PubMed1989

Contribution of amygdalar and lateral hypothalamic neurons to visual information processing of food and nonfood in monkey.

Visual information processing was investigated in the inferotemporal cortical (ITCx)-amygdalar (AM)-lateral hypothalamic (LHA) axis which contributes to food-nonfood discrimination. Neuronal activity was recorded from monkey AM and LHA during discrimination of sensory stimuli including sight of food or nonfood. The task had four phases: control, visual, bar press, and ingestion. Of 710 AM neurons tested, 220 (31.0%) responded during visual phase: 48 to only visual stimulation, 13 (1.9%) to visual plus oral sensory stimulation, 142 (20.0%) to multimodal stimulation and 17 (2.4%) to one affectively significant item. Of 669 LHA neurons tested, 106 (15.8%) responded in the visual phase. Of 80 visual-related neurons tested systematically, 33 (41.2%) responded selectively to the sight of any object predicting the availability of reward, and 47 (58.8%) responded nondifferentially to both food and nonfood. Many of AM neuron responses were graded according to the degree of affective significance of sensory stimuli (sensory-affective association), but responses of LHA food responsive neurons did not depend on the kind of reward indicated by the sensory stimuli (stimulus-reinforcement association). Some AM and LHA food responses were modulated by extinction or reversal. Dynamic information processing in ITCx-AM-LHA axis was investigated by reversible deficits of bilateral ITCx or AM by cooling. ITCx cooling suppressed discrimination by vision responding AM neurons (8/17). AM cooling suppressed LHA responses to food (9/22). We suggest deep AM-LHA involvement in food-nonfood discrimination based on AM sensory-affective association and LHA stimulus-reinforcement association.

Affect↗
PubMed1987

Central sites involved in lateral hypothalamus conditioned neural responses to acoustic cues in the rat.

1. Unit activity in the lateral hypothalamus (LHA) of the rat was recorded during discrimination learning of cue-tone stimuli (CTS) predicting glucose (CTS1+) or intracranial self-stimulation (ICSS) (CTS2+) as positive reinforcement or electric shock (CTS1-) or tail pinch (CTS2-) as negative reinforcement. The same action, licking, was used as the behavioral response to all stimuli. Procaine hydrochloride, a local anesthetic, was microinjected into the ventral tegmental area (VTA) and the amygdala (AM). LHA neuron responses and licking were analyzed to investigate the afferent input pathway(s) responsible for LHA neural responses to conditioning CTSs in positive reinforcement and to identify the central site involved in CTS learning. Although the animals were restrained, there was no respiratory, cardiac rate, or blood pressure evidence of stress. The headholder was specially designed in our laboratory to avoid pain or discomfort to the animal. The subjects would often, after the first few sessions, voluntarily enter into position in the apparatus, presumably to obtain the reward available during the experiments. 2. In positive reinforcement, a rat was rewarded by 5 microliters of glucose or ICSS when it licked a spout. The rat licked for glucose after CTS1+ or for ICSS after CTS2+. In negative reinforcement, an aversive stimulus, either electric shock or tail pinch, was applied if the rat did not lick the spout. The electric shock and tail pinch were maintained weak enough to produce an avoidance ratio less than 20-30%, averaged in all trials. The rat licked to avoid electric shock after CTS1- or tail pinch after CTS2-. 3. Of 271 LHA neurons analyzed, 202 (74.5%) responded to either or both rewarding and aversive stimuli. The number of neurons that responded to only rewarding stimuli was relatively large (105/271), and the number that responded similarly to both rewarding and aversive stimuli was small (29/271). The effects of both glucose and ICSS, and the effects of both electric shock and tail pinch, were usually similar in neurons analyzed for both rewarding and aversive stimulation. Of 271 neurons, 173 responded differentially to rewarding and aversive stimuli. 4. Neural and behavioral responses were recorded before, during, and after local anesthesia of the VTA in 15 rats and of the AM in 14 rats. Injections of 0.3-0.8 microliters of 5% procaine hydrochloride or 0.9% saline were made at a rate of 0.3 microliters/min through guide cannulae chronically implanted in the VTA and AM, ipsilateral to the recording and ICSS sites in 29 rats that self-stimulated.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1987

Free fatty acids in gallstones in mice fed a diet containing cholic acid.

In mice, combined addition of 1% cholesterol and 0.5% cholic acid to a diet induced cholesterol gallstones within 40 days as a result of the supersaturation of cholesterol in the bile, as has been reported. The major component of the gallstone was cholesterol, which was measured by HPLC. In this study, however, single addition of 1% cholic acid to a diet, which did not decrease cholesterol solubilizing capacity in bile, contributed to gallstone formation in mice within 50 days. The gallstones thus formed contained a large amount of palmitic acid. In the hepatic bile of this animal, palmitic acid was also detected; however, no solid material was observed by light and polarized-light microscopes. Free fatty acids such as palmitic acid seem to be dissolved in a complex micelle composed of bile acids and lecithin. This probably causes gallstone formation by reducing cholesterol solubilizing capacity in bile.

Animals↗
PubMed1986

Ultrasonic assessment of fetal response to second-trimester amniocentesis.

Twenty-three patients undergoing second-trimester amniocentesis were ultrasonically monitored for 30 minutes before and 30 minutes after the amniocentesis. Fetal movements were recorded as movements of limbs, trunk, or combined limb-trunk movements. Fetal heart rates were determined at ten-minute intervals before and after the amniocentesis. No significant increase in total fetal movements, limb movements, trunk movements, or heart rate were found. A significant increase in combined fetal movements was observed. The authors conclude that amniocentesis in the second trimester elicits a change in fetal movement pattern.

Adult↗
PubMed1985

Endometriosis after tubal ligation.

Twenty-three (27.3%) of 84 patients discharged with the diagnosis of endometriosis had undergone tubal ligation 1-15 years (mean, 5) before this diagnosis was made. Twenty (87%) of the 23 underwent laparotomy because of symptoms consistent with endometriosis. Forty-four percent had stage I disease; 52%, stage II; and 4%, stage III. Endometriosis was the only pathologic finding in 19 women (82.6%). This study demonstrated that endometriosis is not a chance finding in women who have undergone tubal sterilization.

Adult↗
PubMed1985

Effect of organic and inorganic mercury compounds on the growth of incisor and tibia in rats.

The pharmacological effects of methyl mercury chloride (MMC) and mercuric chloride (HgCl2) (2-16 mg/Kg per day subcutaneously, for 6 d) upon the growth were studied in the incisors and proximal tibiae of immature rats histologically. Lead acetate was used as a time marker. 1. Mercury compounds slightly affected the body weight gains of the rats but apparently inhibited the longitudinal growth of proximal tibia and the effect increased with higher dosages. 2. Mercury compounds definitely inhibited not only the longitudinal growth (incisor growth) but also the appositional growth (dentin formation) of incisal dentin. 3. The inhibitory effect on the growth was ranked as follows: bone growth greater than dentin formation greater than incisor growth. 4. The actions of MMC on the growth of incisors and proximal tibiae appeared gradually and the response was biphasic; stimulatory and then inhibitory. The inhibitory effect appeared even after the injection was discontinued and appeared more extremely than during the injections. 5. In HgCl2 groups the inhibitory effect on the growth appeared rapidly. The effect increased with higher dosages and became stronger as the injections were repeated. However, this effect was weakened promptly after the injection was discontinued. 6. The repeated injections of mercury compounds hardly affected the level of serum calcium but disturbed the calcification of incisal dentin. From the above-mentioned results a possible mechanism was discussed. It is suggestive that MMC acts directly upon a cell and is transported into it. Once MMC was introduced into a cell it is slowly demethylated to inorganic Hg and acts as the demethylated mercury. When accumulated mercury is slight in volume, it stimulates and then inhibits the cell function with increasing mercury. However HgCl2 binds directly with an effector cell membrane in loose fashion. This may cause the ready reversibility of the effect.

Animals↗
PubMed1984

Immunolocalization of the 33 kD protein in the microvilli of rabbit small-intestinal epithelial cells.

Rabbit small-intestinal microvilli isolated by a Ca2+ precipitation method contain a 33 kD protein, which has not been observed in microvilli isolated in the presence of Ca2+-chelators. The intracellular localization of this protein in rabbit intestinal epithelial cells was studied by immunofluorescence and immunoperoxidase microscopy, and was compared with that of aminopeptidase M, a well-known microvillus membrane-bound enzyme. The results obtained show that the 33 kD protein is located in the inside of the microvillus, but not in the terminal web of the epithelial cell. The protein may also be located on the basolateral surface of the cell.

Aminopeptidases↗
PubMed1983

Investigation of actin in Tetrahymena cells. A comparison with skeletal muscle actin by a devised two-dimensional gel electrophoresis method.

Total protein constituents of Tetrahymena thermophila strain B1868 III were studied by two-dimensional agarose-polyacrylamide gel electrophoresis to detect actin among the constituents. In the attempts to prepare a whole-cell extract of Tetrahymena, it was found that protease activity in the extract was so high that high molecular components were quickly digested with the endogenous protease into small peptides unless the homogenization and heat-treatment in a sodium dodecylsulfate solution were performed within 5 s. It was eventually found that employment of 8 M guanidine hydrochloride (HCl) in the homogenization of cells perfectly prevented the degradation of protein components, even through a long preparation procedure. A devised two-dimensional agarose-polyacrylamide gel electrophoresis of the guanidine HCl extract gave a 'protein map' on which most proteins were located in their respective positions, including proteins with more than 200,000 mol. wt. Addition of rabbit skeletal muscle actin on the protein map revealed that no protein with isoelectric point and molecular weight identical with those of the actin was contained in the whole Tetrahymena extract, suggesting that Tetrahymena actin may have characteristics far different from those of skeletal muscle actin.

Actins↗
PubMed1982

A 33,000-dalton protein of the microvilli isolated from rabbit small-intestinal epithelial cells. Purification and some properties.

Actin and four major associated proteins have been identified in the microvillus cytoskeleton from chicken intestinal brush borders isolated in the presence of Ca2+-chelating agents. We have isolated microvilli from rabbit small intestine in the presence of Ca2+ and found by sodium dodecyl sulfate-gel electrophoresis that a protein of 33,000 daltons exists in a molar ratio to actin of 1:3 within the isolated microvillus. The protein could be extracted from acetone powder of microvilli in the absence, but not in the presence, of Ca2+. Thus, for its purification the acetone powder was extracted twice with buffer containing Ca2+ and then with buffer containing a Ca2+-chelator. The 33,000-dalton protein was purified from the last extract by Sephadex G-100 gel filtration and DEAE-cellulose column chromatography. The purified protein was a water-soluble monomeric protein with a molecular weight of 33,000. Antisera against the purified protein raised in guinea pigs reacted with the antigen but not with actin or tropomyosin purified from rabbit skeletal muscle. Freezing-thawing resulted in aggregation of the purified protein, and the aggregates showed filamentous and sheet-like structures. These results suggests that the 33,000-dalton protein is a major component of the microvillus cytoskeleton.

Actins↗
PubMed1977

Immunochemical studies on the subunits of rabbit-intestinal sucrase-isomaltase complex.

Purified sucrase-isomaltase complex sucrose alpha-glucohydrolase, EC 3.2.1.48 - dextrin 6-alpha-glycanohydrolase, EC 3.2.1.10) solubilized by papain from rabbit intestine was dissociated by citraconylation into its subunits, sucrase and isomaltase, which were then isolated in a form active immunologically as well as enzymatically by affinity chromatography on Sephadex G-200 and gel-filtration on Bio-gel P-300. Antibodies against the purified complex inhibited isomaltase but not sucrase and formed precipitation lines, crossing each other, with isolated sucrase and isomaltase, showing that the two enzymes differ in antigenicity from each other. By absorbing the antibodies with isolated sucrase and isomaltase, antibodies specific for isomaltase and sucrase, respectively, were obtained. Like the original antibodies, both of the specific antibodies quantitatively agglutinated microvillous vesicles. Sucrase was inhibited by neither of the antibodies. In contrast, isomaltase was greatly inhibited by the isomaltase-specific antibodies, but not by the sucrase-specific ones.

Agglutination↗
PubMed1977

A newly devised cutting probe for endoscopic sphincterotomy of the ampulla of vater.

A new diathermy cutting probe for endoscopic sphincterotomy has been devised. This consisted of a standard Teflon catheter with a diathermy wire and a metal-marked long tip. Using an Olympus duodenoscope and this cutting probe, endoscopic sphincterotomy has been successfully performed in 38 out of 40 patients with common bile duct stones without any serious complications. Advantages and clinical results of this instrument are presented.

Ampulla of Vater↗
PubMed1977

An experimental study on endoscopic papillotomy in monkeys.

Endoscopic papillotomy would appear to have distinct advantages in non-operative treatment of common bile duct stones. To investigate the effects of this procedure on the papilla and adjacent organs, diathermy papillotomy was performed at laparotomy in three monkeys. White-cell count and levels of liver function parameters temporarily increased during the follow-up period of twelve months, suggesting that diathermy papillotomy might have brought about some pathological changes in the hepatobiliary system of monkeys, whereas no definite evidence of cholestasis or pancreatitis were noticed, and an excellent condition of papillotomy orifice and adjacent ogans was revealed at autopsy about 1 year after diathermy papillotomy.

Ampulla of Vater↗