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Biomedical subjects

T Hayama

Publications and source records attributed to T Hayama.

At least 109 records · Page 6Linked to original sources
PubMed1982

Convergence of input from tongue and palate to the parabrachial nucleus neurons of rats.

Receptive fields (RFs) in the oral cavity were examined for 24 taste and 20 mechanoreceptive neurons in the parabrachial nucleus (PB) of anesthetized rats. All of the units studied had an RF on the ipsilateral half of the oral cavity. About half of the units in each category had at least two separate RFs. Most of the 'taste neurons', i.e. units receiving taste inputs, were activated by mechanical stimulation and some of them had a complex RF, e.g. separated into two parts, one on the tongue for taste and one on the palate for mechanical stimulation. The present findings show that the afferent inputs of two modalities from the tongue and palate converge on the PB neurons.

Animals↗
PubMed1982

Teratogenic activity of pyrimethamine in Göttingen minipig.

Pyrimethamine (PY) was mixed with mashed feed and given to the Göttingen miniature pig (G-mini) during gestional days 11-35. Major malformations such as cleft palate, club-foot and micrognathia were observed in 11 out of 16 newborns from 3 pregnant sows which received 3.6 mg/kg/day. Two sows of a high-dose group (7.2 mg/kg) showed severe anemia and low appetite during the experiment and did not give birth. No malformation was found in 22 newborns of low-dose groups (0.9 and 1.8 mg/kg). Among 130 offspring which died before weaning out of 505 from 47 farrows in a breeding farm, major teratoses such as cleft palate were found in 8 newborns.

Abnormalities, Drug-Induced↗
PubMed1982

Modulation of the immune responses against SRBC after oestriol treatment in mice.

Delayed-type hypersensitivity (DTH), primary direct and indirect PFC, memory antibody response and suppressor cell induction against sheep red blood cells (SRBC) have been examined in oestriol (E3) pretreated mice. The results showed that DTH and primary direct and indirect PFC responses were suppressed by E3 treatment. These suppressive effects could, however, be overcome when oestrogenized mice were given supra-optimal doses of SRBC for each response. On the other hand, the memory antibody response was markedly enhanced when E3 was given prior to the primary antigen stimulation. Induction of the suppressor cells for the antibody response seemed not to be affected by E3 treatment, but the characterization of the suppressor cells revealed that those obtained from E3 treated mice were surface immunoglobulin positive (sIg+) cells whereas those from control mice were not. These results were discussed in terms of the altered antigen distribution due to the activated phagocytic activity of the reticuloendothelial system (RES) after E3 treatment.

Animals↗
PubMed1981

Three compartment model for pyrimethamine disposition in the pig.

Plasma concentration and urine excretion of pyrimethamine (Py) after intravenous (i.v.) administration (10 mg/kg) were determined in four pigs, using NP-FID gas chromatography. A three-compartment model system adequately fitted the observed plasma data. Py may undergo an extensive extravascular distribution, because of the ratio of total volume of distribution to volume of the central compartment was extremely large (about 10). From the calculation of theoretical distribution, only 30% of the dose appears to remain in the central compartment 15 min after administration. Within 2 h of administration the proportion of drug within the two identified peripheral compartments exceeded the proportion remaining in the central compartment. Calculation of cumulative drug excretion showed that up to 90% of an administered dose is excreted within 24 h of administration, although only about 3% of the dose could be detected in urine in an unchanged form during the 24 h period.

Animals↗
PubMed1981

Serial endoscopic observation of swine gastroesophageal ulceration induced by injection of a histamine-oil-beeswax mixture.

The gastroesophageal (GE) area of swine was endoscopically observed before and after injection of a histamine-oil-beeswax mixture (5 mg of histamine/kg of body weight). The swine were anesthetized with halothane, and a rigid endoscope was inserted through a gastric cannula placed in the proximal greater curvature of the stomach. Observation was simple and the procedure lasted less than 10 minutes, without adverse reactions. In 4 swine with normal GE areas, hemorrhage was found at postmedication hour (PMH) 3 and ulcerative changes were seen at PMH 9 to 12. A more rapid pathologic change of the GE area was found in 2 animals with hyper- or parakeratotic changes before medication. Abnormalities were found up to PMH 9 in the GE area of 2 animals in which the stomach cannula was opened to allow the escape of gastric juice.

Animals↗
PubMed1980

Taste relay neurons in the solitary tract nucleus of rats.

Impulse discharges of 82 solitary tract nucleus neurons, in response to natural stimulation of the oral cavity, were recorded. Among these, 52 units responded to taste stimuli and 30 units to mechanical stimuli. When the caudal end of the parabrachial nucleus was stimulated ipsilaterally, 16 taste and 5 mechanoreceptive units were excited antidromically. Response types of rostrally projecting taste neurons were not different from those of the non-projecting ones, and both of them were similar to that of the chorda tympani.

Afferent Pathways↗
PubMed1979

Ultrastructure of the endoplasmic factor responsible for cytoplasmic streaming in Chara internodal cells.

Previous investigators have proposed that cytoplasmic streaming in Chara internodal cells results from the interaction between an endoplasmic factor and fibrils composed of microfilaments in the stationary cortex. Using the internal perfusion technique, we confirmed the observation that organelles which had been attached to the fibrils by decreasing the internal concentration of ATP moved along the fibrils after ATP was introduced. Thin-sectioned specimens revealed that endoplasmic organelles of various shapes were linked to microfilament bundles in the absence of ATP. Linkage was effected by regularly arranged electron-dense materials with a spacing of 100 -- 130 nm at definite regions on each organelle. The organelles in question were studied in negatively stained preparations of endoplasm. The organelles had some common features. (1) They were all membrane-limited.(2) Their sizes and configurations varied largely. (3) One or more protuberances were present on them. (4) The protuberances were usually rod- or horn-like. (5) Small globular bodies 20--30 nm in diameter were found in ordered array with the same spacing as those in thin sections at the surface of the protuberances. (6) Many fine filaments were always attached to the surface of the protuberances. These fine filaments differed from F-actin in diameter (less than 4 nm) and inability to react with heavy meromyosin from rabbit skeletal muscle. The role of such components of the organelles in cytoplasmic streaming is discussed. A paracrystalline array of microfilaments with a transverse periodicity of about 38 nm is presented, together with its optical diffraction pattern.

Adenosine Triphosphate↗
PubMed1978

Site of emetic action of oral copper sulfate in dogs. (I) Thresholds of various portions of gastrointestinal tract to locally applied copper sulfate.

Emetic thresholds to copper sulfate administered into the Pavlov pouch, Forrest pouch, Thiry fistulas of the jejunum and ileum, and duodenal, jejunal and ileal catheters were measured in dogs to conjecture the site of emetic action of copper sulfate. The oral emetic threshold had been measured preoperatively. In the stomach, the pyloric antrum had a high sensitivity, while the corpus had a low sensitivity to the topically applied copper sulfate. In the intestine, the sensitivity was high in the duodenum, whereas a low sensitivity was noted in the jejunum. Almost no sensitivity was observed in the ileum. Thus it would appear that the site of the emetic action of copper sulfate was the pyloric antrum and/or duodenum.

Administration, Oral↗
PubMed1978

Site of emetic action of oral copper sulfate in dogs. (II) Importance of lower duodenum.

Sensitivities of the stomach and duodenum to oral copper sulfate emesis were compared in dogs. 1) Dogs equipped with a stainless stell cannula in the middle of the duodenum were challenged to the oral threshold emetic dose of copper sulfate administered by a gastric tube. When the cannulas were opened, the oral thresholds were not effective to elicit vomiting in the most cases (1/13). Fairly rapid and high rate recoveries of copper through the open cannula were noted. With the closed cannulas, the thresholds were highly effective (16/16). 2)In the dogs with a cannula at the upper part of the jejunum, the oral threshold doses were always effective whether the canula was opened (9/9) or closed (11/11). Recovery rates of copper from the cannula were usually poor. 3) The oral thresholds administered into the proximal end or the middle of the duodenum through a PVC tubing were equally effective. 4) Although copper sulfate might irritate the stomach and upper duodenum to evoke vomiting, these results suggested a higher sensitivity of the lower duodenum.

Administration, Oral↗
PubMed1976

Antigen inhibition on antibody forming cells at the level of effector cell.

In this study a possibility was examined that the specific antigen might inhibit antibody forming cells in order to know whether a non-T-cell-dependent mechanism of self-tolerance is present or not. If an autoantigen inhibits autoantibody forming cells, this inhibition may be one of the non-T-cell-dependent mechanisms of self-tolerance. Spleen cells from mice which were immunized with sheep red blood cells (SRBC) were incubated with SRBC and after an hour incubation erythrocytes added were removed. After 4 and 8 hr incubation, the plaques against SRBC were assayed by the plaque method. 1) After 8 hr incubation, SRBC reduced the plaque count to about 60% of the control aliquot incubating spleen cells with C3H mouse red blood cells. 2) This inhibition required 1% SRBC suspension, but despite increase in its concentration to more than 1% the degree of the inhibition remained constant. 3) This inhibition seemed to require neither T cells, macrophages nor the cells which display the cytotoxic activity in the antibody dependent cell-mediated cytotoxicity.

Animals↗
PubMed1976

The endogenous secretin in chicken: minor physiological role in exocrine pancreatic secretion.

The action of secretin (SN) on the exocrine pancreas in the chicken was studied in comparison with the rat and dog. Hydrochloric acid (0.1 N), pepton (5%) and olive oil were introduced into the small intestine of conscious chickens with chronic pancreatic fistula and caused the volume and protein output to increase slightly in about two-thirds of the chickens tested. The percent increase of the volume output in anesthetized chickens by HCl instillation was only one-tenth of that in the rat. Acid extracts of the intestinal mucosa (80 mg) from chickens when given intravenously to rats caused the volume of secretion from the rat pancreas to increase about twofold, whereas the extracts from the dogs' and rats' intestine increased the volume output 5.9 and 5.5 times respectively. The increase of pancreatic secretion in chickens by intravenous injection of commercial SN was about one-third of that in the rat. The present studies indicate that SN or a SN-like hormone may be present in the chicken, but it plays only a minor physiological role.

Animals↗