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Biomedical subjects

S F Takagi

Publications and source records attributed to S F Takagi.

31 records · Page 2Linked to original sources
PubMed1978

Activation and inhibition of olfactory bulb neurones by anterior commissure volleys in the rabbit.

1. In the rabbit olfactory bulb, analysis has been carried out on intracellular potentials recorded from mitral cells and neurones in the granule cell layer (g.c.l. cells) in addition to the extracellular field potentials in the olfactory bulb elicited by anterior commissure (a.c.) stimulation. 2. Most mitral cell recordings showed i.p.s.p.s with latency of 7-11 msec following a.c. stimulation. These i.p.s.p.s were similar to those evoked by lateral olfactory tract (l.o.t.) stimulation in their sensitivity to internally applied current and showed asymmetrical reversal during application of the hyperpolarizing current. 3. Volleys in the a.c. elicited e.p.s.p.s in type 1 g.c.l. cells whose characteristics were in agreement with those of inhibitory interneurones inferred from the analyses of mitral cell i.p.s.p.s. It has been suggested that these type 1 g.c.l. cells may be the common inhibitory interneurones (presumably granule cells) mediating both a.c.-evoked and l.o.t.-evoked i.p.s.p.s in mitral cells. 4. Conditioning a.c. stimulation depressed the test l.o.t.-evoked i.p.s.p.s in mitral cells and test l.o.t.-evoked e.p.s.p.s in type 1 g.c.l. cells. These observations are in good agreement with the hypothesis that l.o.t.-evoked i.p.s.p.s are mainly mediated by the dendrodendritic reciprocal synapses between mitral cell dendrites and peripheral processes of granule cells. 5. The results are discussed in relation to the inhibitory mechanisms controlling mitral cell activity in the olfactory bulb.

Animals↗
PubMed1978

Water response of the frog olfactory epithelium as observed from the olfactory bulb.

The water response elicited by application of distilled water on the olfactory epithelium was recorded extracellularly from single olfactory bulb neurones. Characteristics of the water response in the frog olfactory epithelium were examined in comparison with those of the water response in the gustatory and palatal organs. 1. Effects of various electrolyte solutions on the generation of the water response were studied by dripping distilled water on the olfactory epithelium after adaptation to each of these electrolyte solutions. Number of the olfactory bulb cells responding to distilled water increased with increasing the charge of the adapting cations and also with decreasing the size of the cations with a few exceptions. 2. Magnitude of the 'water response' increased with decreasing concentration of salt in the solution which was dripped after adaptation to the isotonic solution of the same salt. 3. The water response was effectively depressed by an electrolyte solution but not by a non-electrolyte solution. An electrolyte also depressed effectively the water response which was produced after adaptation to an organic salt solution. 4. The water response was blocked by treatment of the olfactory epithelium with the uranyl ions which had high affinity for phospholipids. A tentative hypothesis on the generating mechanism of the water response in the frog olfactory epithelium is presented on the basis of the present experimental results and the water responses of the gustatory and palatal organs so far reported.

Action Potentials↗
PubMed1978

Effects of gustatory stimulants upon the olfactory epithelium of the bullfrog and the carp.

Effects of various gustatory stimulants upon the olfactory spithelia were examined in the olfactory bulb of the bullfrog and the carp. 1. The olfactory epithelia of the two animals responded to the salty, bitter- and acid-tasting substances, but not to the sweet ones. 2. The olfactory epithelium of the bullfrog responded immediately to sodium solutions of high concentrations (the "initial response"), but the response to those of low concentrations showed long latency (the "delayed response"). In the carp, the "initial response" was found, while the "delayed response" was not in most cases. A "negative" delayed response was found only infrequently. 3. Responses only to high alkali or acid solutions were found in the two animals. 4. When 0.05 M NaCl was added to HCl solutions, an enhancing effect was found in the bullfrog, while a reducing effect occurred in the carp. On the contrary, when 0.05 M NaCl was added to NaOH solutions, an enhancing effect occurred in the carp, while no consistent result was founding the bullfrog. 5. Many amino acids were effective stimuli in the bullfrog, but only betaine and 1-aspartic acid were found effective in the carp. 6. Changes in temperatures beyond 35 degrees C or under 10 degrees C elicited responses. Mechanical stimuli were effective in the carp, but not in the bullfrog. 7. The "water response" was found in the bullfrog, but not in the carp. 8. Sensitivities of the olfactory epithelia of the two animals were compared and discussed.

Animals↗
PubMed1978

Ionic stimulation of the olfactory epithelium in the bullfrog and the carp.

The stimulating effects of mono- and divalent cations and anions were studied in the olfactory epithelia of the bullfrog and the carp. The rhythmic waves induced by these ions were recorded in the olfactory bulb. 1. Many mono- and divalent cations and anions showed stimulating actions in the bullfrog and the carp. 2. Microelectrode studies disclosed that the olfactory receptor cells respond to different ions differently. 3. When many ions were applied with various concentrations, responses appeared with long latencies while the concentration was very low (the "delayed responses"). The responses nearly disappeared at the intermediate concentrations, but then responses with short latencies appeared at the higher concentrations (the "initial responses"). Thus, many ions showed dual responses in the bullfrog, although some exceptional cases were found (choline+, Tl+, La3+, Cd2+). 4. Cd2+ and other heavy metal ions showed depressive actions upon the responses induced by other ions in the olfactory epithelium. 5. Tetrodotoxin of even 10 (-5) g/ml was found ineffective in depressing the rhythmic waves induced by ions. 6. Chemoreceptive activities of the olfactory epithelia of the bullfrog and the carp were compared with the activities of the gustatory receptors. They were also compared with the other chemoreceptors of the fish, namely the palatal organ, external chemoreceptors over the snout region and the lateral-line organ. Chemical senses of the fish were discussed.

Animals↗
PubMed1978

Stimulation of the olfactory epithelium with odorants in gaseous and aqueous phases.

The olfactory epithelia of the bullfrog and the carp were stimulated with various odorants in the gaseous and/or aqueous phases. Some ionic solutions were also applied. 1. By recording the induced waves in the olfactory bulb, it was shown that the bullfrog responds to odorants in the two phases, but the carp can respond only to odorants in the aqueous phase. 2. Comparison of the stimulative effects of the same odorants in the two phases were made in the bullfrog. Although various response patterns to gaseous and aqueous stimuli of single cells in the olfactory bulb were found in most cases, a difference in the application methods of vapors and solutions made such comparison difficult. 3. The same single cells in the olfactory bulb usually responded to various odorous vapors and solutions as well as to ions in different patterns. When the responses to the vapors and solutions of the same odorants of different concentrations were compared, different patterns were also found.

Acetates↗
PubMed1975

An olfactory projection area in orbitofrontal cortex of the monkey.

An olfactory projection area was studied in monkeys anesthetized with Nembutal. 1. Evoked potentials were recorded when the olfactory bulb (OB) was electrically stimulated in the lateroposterior portion of the orbitofrontal cortex (LPOF). However, those potentials disappeared when the anterior pyriform cortex (AP) (probably together with the medial portion of the amygdala (MA)) was aspirated or electrically destroyed. 2. In nearly the entire hypothalamic region, evoked potentials were recorded by the same stimulation of the OB. When the hypothalamic region was stimulated, evoked potentials were recorded in the LPOF. 3. The evoked potentials in the LPOF due to the OB stimulation never disappeared even when the thalamus was extensively aspirated or destroyed electrically, but they did disappear when the anterolateral and dorsoposterior portions of the hypothalamus were absorbed or electrocoagulated. 4. Evoked potentials in the mediodorsal nucleus (MD) of the thalamus were recorded when the OB was stimulated. When this nucleus was stimulated, evoked potentials were observed in the broad extent of the orbitofrontal cortex anterior to the LPOF, but never in the LPOF itself. 5. Monkeys were conditioned to discriminate two odors. When the LPOF was removed, such ability strikingly decreased; but when other areas in the prefrontal cortex were removed, the ability decreased only slightly. 6. It was concluded that there exists an olfactory pathway from the OB to the LPOF through the AP (and probably the MA) and the hypothalamus, but none through the thalamus, and that the LPOF plays an important role in the discrimination of odors. 7. It was proved that the entorhinal cortex (ER) is neither located as an intermediate olfactory area nor is it situated as a higher area than the LPOF in the newly found olfactory pathway stated above. It may be a link between the high olfactory area and the limbic system.

Animals↗
PubMed1975

Discrimination of odors in olfactory bulb, pyriform-amygdaloid areas, and orbitofrontal cortex of the monkey.

In the orbitofrontal olfactory area (LPOF) which was delineated in a previous paper, the capacity for odor discrimination was studied and compared with that in the anterior pyriform cortex (AP), the medial portion of the amygdala (MA), and the olfactory bulb (OB). Unanesthetized monkeys were used and eight odors were applied. 1. In the OB, 12.5% of the cells responded to only one odor, and the cells which responded to five odors were most numerous (25%). The total of the cells which responded to two, three, and four odors was 52%, which was less than the total of the cells responding to three, four, and five odors (67.5%). A small number oc cells responded to all eight odors (2.5%). The responses were classified as an increase (+type), a decrease (-type), or no change (no-type) in the rate of spike discharge. 2. In the AP and MA, no difference in the response patterns was found. The cells which responded to only one odor were 12.3% of the total, and the cells which responded to three different kinds of odors were most numerous (34.3%). The total of the cells responding to two, three, and four odors was 80%, much more than that in the OB. In addition, no cell responded to all eight odors. Concerning the response types, an increase followed by a decrease, or vice versa, in the rate of spike discharges (mixed-type) was observed which did not appear in the OB. Thus, an advance was found in the processing of olfactory information when compared with the OB. 3. A most striking finding in the LPOF was that 50% of the cells responded to only one odor. The cells which responded to two, three, and four odors decreased in this order, and no cell responded to more than five odors. These cells never responded to light or sound. 4. Using three very similar odors and five very different odors, it was apparent that the ability to discriminate odors of the same category is far more advanced in the LPOF than in the lower olfactory areas; and, in contrast, the lower olfactory areas also play a significant role in the discrimination of odors which belong to different categories. 5. It was concluded that the capacity for odor discrimination definitely improves along the olfactory nervous system from the lower to the higher areas. It is highly probable that a fine and sepcific discrimination of odors is performed in the LPOF.

Amygdala↗
PubMed1974

Secretion and electrogenesis of the supporting cell in the olfactory epithelium.

1. Electrophysiological study disclosed that chloroform and some other odours generate long-lasting positive potentials in the olfactory epithelium of the bullfrog, while electron microscopical study showed that they elicit vigorous protrusion of the distal cytoplasmic portion of the supporting cell containing the secretory granules.2. The secretory process of the supporting cell is as follows: The first detectable indication is the protrusion of the apical portion of the supporting cell (Pls. 3 and 4); the protruded part detaches from its maternal supporting cell (Pl. 7 B), floats as a droplet in the mucus (Pl. 5), and finally the secretory granules inside the droplet disintegrate into the mucus (Pls. 6 and 7 A).3. The secretion was not elicited by the odours which elicit the negative potentials.4. In Cl(-)-free Ringer solution, neither the positive potential nor the protrusion and secretion occurred.5. When 1-2 mM-Ba(2+) in Ringer solution was dripped on the epithelium, both the positive potential and the protrusion and secretion resulted. Subsequent application of chloroform vapour only advanced further disintegration of the secretory granules, but it elicited neither a new protrusion of the granules nor the positive potential.6. In the olfactory epithelium in which the olfactory cells had degenerated but the supporting cells survived, both the positive potential and the protrusion and secretion occurred, but the negative potential did not.7. It is concluded that Cl(-) entry which mainly generates the longlasting positive potential triggers the secretion of the supporting cell.

Acetates↗
PubMed1969

Further studies on the roles of sodium and potassium in the generation of the electro-olfactogram. Effects of mono- , di- , and trivalent cations.

In the negative EOG-generating process a cation which can substitute for Na(+) was sought among the monovalent ions, Li(+), Rb(+), Cs(+), NH(4) (+), and TEA(+), the divalent ions, Mg(++), Ca(++), Sr(++), Ba(++), Zn(++), Cd(++), Mn(++), Co(++), and Ni(++), and the trivalent ions, Al(+++) and Fe(+++). In Ringer solutions in which Na(+) was replaced by one of these cations the negative EOG's decreased in amplitude and could not maintain the original amplitudes. In K(+)-Ringer solution in which Na(+) was replaced by K(+), the negative EOG's reversed their polarity. Recovery of these reversed potentials was examined in modified Ringer solutions in which Na(+) was replaced by one of the above cations. Complete recovery was found only in the normal Ringer solution. Thus, it was clarified that Na(+) plays an irreplaceable role in the generation of the negative EOG's. The sieve hypothesis which was valid for the positive EOG-generating membrane or IPSP was not found applicable in any form to the negative EOG-generating membrane. The reversal of the negative EOG's found in K(+)- , Rb(+)- , and Ba(++)-Ringer solutions was attributed to the exit of the internal K(+). It is, however, not known whether or not Cl(-) permeability increases in these Na(+)-free solutions and contributes to the generation of the reversed EOG's.

Acetates↗
PubMed1968

The role of sodium and potassium ions in the generation of the electro-olfactogram.

In order to clarify whether or not the electronegative olfactory mucosal potentials (EOG) are generator potentials, the effects of changed ionic enviroment were studied. The EOG decreased in amplitude and in some cases nearly or completely disappeared, when Na(+) in the bathing Ringer solution was replaced by sucrose, Li(+), choline(+), tetraethylammonium(+) (TEA), or hydrazine. In the K(+)-free Ringer solution, the negative EOG's initially increased and then decreased in amplitude. In Ringer's solution with increased K(+), the negative EOG's increased in amplitude. When K(+) was increased in exchange for Na(+) in Ringer's solution, the negative EOG's decreased, disappeared, and then reversed their polarity (Fig. 6). Next, when the K(+) was replaced by equimolar sucrose, Li(+), choline(+), TEA(+), hydrazine, or Na(+), the reversed potentials recovered completely only in Na(+)-Ringer's solution, but never in the other solutions. Thus, the essential role of Na(+) and K(+) in the negative EOG's was demonstrated. Ba(++) was found to depress selectively the electropositive EOG, but it hardly decreased and never increased the negative EOG. Hence, it is concluded that Ba(++) interferes only with Cl(-) influx, and that the negative EOG's are elicited by an increase in permeability of the olfactory receptive membrane to Na(+) and K(+), but not to Cl(-). From the ionic mechanism it is inferred that the negative EOG's are in most cases composites of generator and positive potentials.

Animals↗
PubMed1966

Anion permeability of the olfactory receptive membrane.

The ionic mechanism of the electropositive olfactory receptor potential was studied in the bullfrog and the swamp frog. The positive receptor potential strikingly decreased in amplitude in chloride-free solution. When the olfactory epithelium was immersed in high-KCl-Ringer's solution and then in Cl-free, high-K solution, the polarity of the positive potential could be reversed. This is supposed to be due to the exit of the increased internal chloride ion. From the above two experiments it is concluded that the positive olfactory receptor potential depends primarily upon the influx of the chloride ion through the olfactory receptive membrane. Some contribution by potassium and possibly other ions may occur. The ability of other anions to substitute for chloride was examined. It was found that only Br-, F-, and HCO2- could penetrate the olfactory receptive membrane. The sieve hypothesis in the inhibitory post-synaptic membrane (Coombs, Eccles, and Fatt, 1955) is not applicable to the olfactory receptive membrane on the basis of the size of hydrated ions, but it may be applicable on the basis of the sizes of naked ions.

Animals↗