Observations were made on the Ca-sensitivity of glycerinated muscle bundles from dog intestine. The results obtained were as follows:
1) The Ca-sensitivity of glycerinated muscle bundles depends on theduration of glycerol extraction. With long-term extraction, the muscle bundles lost a large part of the Ca-sensitivity of the ATP contractility.
2) When the bundles that had a typical Ca-sensitivity were treated with a low concentration of trypsin, their ATP-contractility became insensitive to varying concentrations of Ca ions.
3) On treatment with intestinal native tropomyosin, the Ca-sensitivity of the ATP-contractility of 2-year-glycerinated muscle bundles was restored, to a certain extent. With the same treatment, the Ca-sensitivity of trypsin-treated 2-year-glycerinated muscle bundle was restored to the same level as that of 2-year-glycerinated bundles.
From these results, it is concluded that the Ca-sensitivity of the ATP-contractility of intestinal glycerinated muscle is due to the native tropomyosin it contains.

View full abstract

1. The VR-EPSP of the spinal motoneuron of the toad was investigated by intracellular recording. Concerning the size, time course, and effect of membrane potential displacements, no essential difference was found between the VR-EPSP in the toad and that in the frog. A remarkable facilitatory effect of the DR-EPSP on the VR-EPSP was observed.
2. The effects of various pharmacological agents on the VR-EPSP were tested by topical application using a double- or triple-barrel microelectrode, or by application to the perfusion fluid through the vascular system.
3. The VR-EPSP was increased in size and the decaying phase was prolonged by topical application of physostigmine. Acetylcholine was effective in increasing the size of the VR-EPSP when applied topically or through the vascular system.
4. A transient depolarization, which may be called acetylcholine potential, was recorded intracellulary when acetylcholine was applied extracellularly by a brief outward current from the microelectrode filled with acetylcholine.
5. Curare was found to have no effect on the VR-EPSP, while nicotine and atropine were effective in depressing the VR-EPSP.
6. Cholinergic trasmission at the synapse between motor axon collaterals and motoneurons in the toad was demonstrated. It was, furthermore, pointed out that the present investigation did not exclude the possibility of electrical interaction between motoneurons.

View full abstract

In rabbits under light ether anesthesia, the midbrain and upper pons were explored with tetanic stimuli to alter cortically evoked rhythmic chewing and swallowing. The effects of various surgical sections of the brain stem upon these phenomena were also studied.
1. Stimulation in an extensive midbrain area produced a diminution of rhythmic chewing, and very often a complete arrest in the jaw-opened position, whereas that at two discretely localized areas produced an enhancement. Bilateral masseteric EMGs revealed a response comparable to the above, i. e., the activity decreased symmetrically during diminution, and accelerated during enhancement of rhythmic chewing. During the stimulation, elicitation of swallowing was consistently diminished without regard to changes occurring in rhythmic chewing.
2. Stimulation at the upper pons produced an arrest of rhythmic chewing, with the jaw closed. At the same time the masseteric EMG was tetanically activated ipsilaterally, while being quiescent contralaterally. Another area delimited within or near the preceding one was responsible for a conspicuously long-lasting bout of repetitive swallowing.
3. Longitudinal midline splits extending from the corpus callosum to the rostral border of the superior colliculi had no effect upon cortically evoked rhythmic chewing and swallowing or upon changes in those induced by brain stem stimulation. A short longitudinal cut at the superior colliculi largely eliminated the effect of enhancement, leaving that of diminution or arrest of cortically evoked rhythmic chewing. A similar split involving the lower midbrain and upper pons completely abolished cortically evoked rhythmic chewing. None of these midline splits, however, abolished swallowing, although it was reduced.
4. Transverse hemisection just rostral to the superior colliculus eliminated cortically evoked responses ipsilaterally, leaving them intact contralaterally, whereas midpontine hemisections did not alter the responses.
5. After complete decerebration at the supracollicular level the cortically evoked response was abolished but the irregular chewing and swallowing persisted with brain stemst imulation. Mid-pontine transection abolished such brain stem-elicited chewing and swallowing, leaving reflex swallowing intact.
6. On the basis of these findings the neural control of rhythmic chewing and swallowing is discussed in relation to the reticular activating and inhibiting systems, and its probable arrangement is tentatively proposed.

View full abstract

Two new treatments were attempted in the measurement of the pulmonary diffusing capacity in regard to the total lung capacity and the inspiration time. The alveolar gas volume was calculated by using the alveolar He concentration, which was measured originally in order to obtain the initial alveolar CO concentration. The inspiration time was corrected by use of a nomogram reported in a previous paper. As a result of measurements made in 18 normal subjects it was clarified that, when the alveolar gas volume was calculated through the above procedure, the effects of the error of He measurement on both the alveolar volume and the initial CO concentration counterbalanced each other and its effect on the D_L was somewhat reduced. On the other hand, the correction of inspiration time resulted in a 2-8% increase in the calculated D_L values.

View full abstract

The diffusing capacity and cardiac output were measured in 18 normal subjects and in 5 patients with pulmonary silicosis. These values were found to be in a close correlation with each other, suggesting that the overall reaction rate of CO with the red cell including diffusion and chemical reaction is almost identical among normal subjects. Thus, assuming that the overall reaction rate is constant, a simple method of estimating the contact time was tested. The overall rate was determined by referring to both the data on reaction rate obtained by FUKUI and KAKIUCHI and the data on D_LCO obtained by KRUHOFFER and FORSTER et al. The contact time obtained was 1.9sec, on an average, in normal subjects and the mean capillary blood volume was 134ml.
In patients with silicosis the diffusing capacity was markedly reduced in parallel with the cardiac output, so that the calculated contact times were distributed within a range similar to those of normal subjects. The capillary blood volume showed a significant decrease, suggesting that the diffusion impairment may have been caused by the reduction of the capillary blood volume.

View full abstract

The effects of tetrodotoxin on the electrical components slow potential and spikes have been studied in the crab cardiac ganglion cell.
1. The slow potential was periodically produced, and it initiated a short high-frequency train of spikes in the axon.
2. The spikes were abolished selectively by tetrodotoxin at extremely low concentrations, but the slow potential remained, indicating that the slow potential and the spikes are produced by different mechanisms.
3. Four large cells in the anterior part of the ganglionic trunk produced slow potentials synchronously, which did not result only from the electrotonic spread of the slow potential in a single cell.

View full abstract

The physiological mechanism of auditory temporal masking was studied by single-unit analysis in the cat's cochlear nucleus and inferior colliculus. Forward masking was found at the levels of both the cochlear nucleus and the inferior colliculus; the mechanism can be explained by the phenomena of postexcitatory inhibit on and synaptic inhibition. Backward masking may involve central processes because it was not demonstrable in the cochlear nucleus. At the midbrain collicular region, it was found that there were three modes that could explain backward masking.

View full abstract

The rates of synthesis and release of growth hormone (GH), prolactin, and whole protein of the rat anterior pituitary were determined using an in vitro method.
1. Thyroidectomy caused a marked decrease in both synthesis and release of GH. Decreased synthesis was restored by a single injection of T₃ (20μg/100g body weight) within 12hr. Decreased GH release was also increased gradually by T₃ injection. The percentage release of GH was increased by thyroidectomy and the increase was depressed by T₃ injection.
2. Prolactin synthesis was increased by thyroidectomy, and the increased synthesis was suppressed as early as 3 hr after T₃ injection. Prolactin release was not affected by thyroidectomy. The percentage release decreased significantly after thyroidectomy.
3. Whole protein synthesis was increased by thyroidectomy and the increase was suppressed by T₃ injection. The whole protein release and the percentage release were not influenced by thyroidectomy and decreased significantly within 3 hr after T₃ injection.
4. Added in vitro, T₃ had no effect on synthesis of whole pituitary protein, but whole protein release was clearly suppressed at concentrations as low as 10^-7m.
These results indicated that thyroid hormone stimulated GH synthetic processes and depressed GH release processes. Prolactin synthetic processes were depressed by thyroid hormone. The mechanisms of the thyroid hormone action and the physiological significance of the facts observed are discussed.

View full abstract

Microphonic potentials were recorded from the sacculus of goldfish with glass pipette electrodes to study the effects on the potentials of changes in the ionic composition of endo-and perilymph and of administered ouabain. Ions and drugs were applied with perfusion techniques and special attention was paid to the difference in effects between endo-and perilymphatic applications. The results obtained were as follows:
1. No marked changes were found in the amplitude of microphonic potentials when the endolymph was replaced either with 120mm NaCl or with KCl.
2. Microphonic potentials were reduced in size when the perilymphatic K⁺ concentration was raised, and this reduction was reversible when the solution returned to normal. The amplitude of microphonic potentials was linearly related to the logarithm of perilymphatic K⁺ concentrations in a range between 25 and 120mM.
3. A marked reduction in the amplitude of microphonic potentials was produced when over 5×10^-6g/ml of ouabain was applied to the perilymphatic space. An endolymphatic application of ouabain produced no effects even at much higher concentrations. This finding suggests the presence of an active extrusion mechanism of Na⁺ across the membrane at the basal part of hair cells. Functional differentiation between the membrane at the hair-bearing surface and at the basal part of hair cells and the functional significance of a high K⁺ concentration of the endolymph were discussed.

View full abstract

The effects of streptomycin and kanamycin on the goldfish's saccular microphonic potentials were examined following their local application with a perfusion technique. The results obtained were compared with those of other drugs.
Streptomycin and kanamycin suppressed microphonics only when they were administered intraluminally to the sacculus but showed almost no effect when administered extraluminally.
Metabolic inhibitors (cyanide, azide, DNP), quinine, and procaine also suppressed microphonics, but, unlike streptomycin and kanamycin, there was no difference in their effects if administered to the luminal side or to the extraluminal side. Namely, cyanide and azide at 5×10^-4g/ml, DNP at 5×10^-3g/ml, quinine at 1×10^-4g/ml and procaine over 2×10^-3g/ml suppressed microphonic potentials through either route of administration. Tetrodotoxin and salicylates showed no effect on microphonics.
The site and the possible mechanism of action of streptomycin and kanamycin on hair cells were discussed by comparing their effects with those of other drugs.

View full abstract