Five different indices concerning the granularity of renal juxtaglomerular apparatus in the spontaneously hypertensive rat of OKAMOTO and AOKI were determined. HARTROFT'S juxtaglomerular cell granulation index and OKAMOTO'S index were decreased definitely in the hypertensive rats. Index of granularity decreased markedly, while index of hypertrophy and hyperplasia became only slightly smaller. Juxtaglomerular cell count was normal. These findings indicate that the decreased granularity is due mainly to the decrease in granularity of each juxtaglomerular apparatus, and that the numbers of juxtaglomerular cells per apparatus or of juxtaglomerular apparatus per kidney do not differ markedly in the spontaneously hypertensive rats. The results also are in accord with the fact that the activity of the renin-angiotensin system is de-creased in such hypertensive rats.

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Enzyme histochemical studies were performed on the hyhothalamus of spontaneously hypertensive rats (OKAMOTO and AOKI) in the pre-hypertensive stage (40 to 60 days after birth). Each positive finding in spontaneously hypertensive rats was obtained by comparing it to the reaction of normotensive Wistar strain rats with almost the same survival duration. On the other hand, in order to clarify the meaning of the findings thus obtained in spontaneously hypertensive rats, the hypothalamus of normotensive Wistar strain adult rats subjected to various endocrine interferences were similarly examined histochemically and compared with the reaction of the control adult rats. 1) As far as the normal distribution of enzyme activities in the hypothalamus is concerned, acid phosphatase activity was clearly demonstrated in the cytoplasma of nerve cells in contrast with glial substances. Most prominent staining was found in nerve cells of Nucl. paraventricularis and Nucl. supraopticus. Nucl. perifornicalis and Nucl. mamillaris prelateralis were stained relatively deeply. Most of the others were stained moderately. By diphosphopyridine nucleotide diaphorase activity determination, all hypothalamic nuclei showed more or less the activity in the perikaryon of nerve cells. Monoamine oxidase activity was mainly detected diffusely in neuropils and hardly demonstrated in the perikaryon. 2) By enzyme histochemical studies on the hypothalamus of spontaneously hypertensive rats in the pre-hypertensive stage, increase of acid phophatase activity was observed in Nucl. preopticus pars lateralis, Nucl. supraopticus, Nucl. ventromedialis pars anterior, medialis, centralis et lateralis, Nucl. dorsomedialis, Nucl. perifornicalis, Area lateralis hypothalami pars tuberalis, Nucl. arcuatus pars tuberalis et mamillaris, Nucl. posterior hypothalami, Nucl. mamillaris prelateralis, Nucl. supramamillaris and Nucl. mamillaris medialis. Increase of diphosphopyridine nucleotide diaphorase activity was detected in Nucl. premamillaris dorsalis, Nucl. premamillaris ventralis and decrease of the activity was noted in Nucl. arcuatus pars mamillaris and Nucl. mamillaris lateralis. Enhancement of monoamine oxidase activity was observed in Nucl. arcuatus pars tuberalis, Nucl. ventromedialis pars medialis, centralis et lateralis and the activity was reduced in Nucl. suprachiasmaticus and Nucl. mamillaris prelateralis.

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Characteristics of the action potential and stimulus conduction in the A-V nodal region were studied electrophysiologically, especially in connection with the histological findings by means of ultramicroelectrode technique. The intracellular records in each case of normal sinus rhythm and A-V conduction disturbance were obtained. And situation of the tip of the microelectrode was ascertained by using immigration of cobalt ion. The specific muscle fibers were recognized in the vicinity of the A-V node. The action potentials of those fibers represented an inter-mediate type between the nodal type and the ordinary atrial muscle type. When the recording microelectrode was moved from the upper part of the node to the His' bundle, the shape of the action potential changed from the typical nodal type to the His' type, and the onset of the activation was gradually delayed. Disturbances of the A-V conduction were made using the effects of acetylcholine. And incomplete A-V block, complete A-V dissociation, and A-V dissociation with nodal or ventricular capture were observed and the boundary of characteristic changes of the action potential in all cases was found at the atrial margin of the A-V node which is netlike in structure.

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Mechanism of the metabolic disturbance as the cause of the experimental hypertension was further studied in this report. Using the heart and skeletal muscle of toad, the author demonstrated that dinitrophenol and monoiodoacetate induce the accumulation of Na ion in the muscle cells. Here neurogenic factor of hypertension was also examined and discussed.

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Thus far, we have reported electrocardiographic patterns of several congenital heart diseases in relation to operative findings, and discussed about some points of differential diagnosis.

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1. 微小電極とstrain gaugeを用いて, 家兎の心房大静脈標本および近心部大静脈条片標本の興奮と収縮について研究し, これを心房筋のそれらと比較検討した. 2. 心房大静脈条片標本および自動性を有する上大静脈条片標本から, 細胞内活動電位と, これに同期した攣縮張力を同時に記録することができる. しかし自動性を欠く下大静脈からは, 細胞内活動電位も攣縮張力も記録することができない. 3. 心房大静脈標本において, 同一心周期で最も早く収縮するのは上大静脈の起始部であり, 右心房収縮に20~30msce先行する. これは, 同部の弁作用としての生理的意義を示唆する. 4. 上大静脈には, 心筋同様に階段現象やvulnerable periodが認められるが, 他方, 平滑筋の混在を思わせる加重を伴った不完全強縮現象をみる場合がある. 5. 刺激頻度と収縮張力の関係, 刺激休止期間とrest potentiationの関係を上大静脈と心房について比較すると, 両者の間には有意の差が認められる. 6. 上大静脈にepinephrine, norepinephrine, isoproterenolを作用させると, 攣縮張力はすべて著名に増強する. しかし活動電位の接続は前2者ではやや延長するのに, 後者では短縮する. 7. propranolo(β-blocker)を上大静脈に作用させると, 活動電位の立ち上がりにsiurrやnotchを生じ, 次第に高さが小となり, 収縮張力も漸減し, ついには伝導が杜絶する. 心房においても同様の変化が認められる. 8. propranololで前処置した上大静脈にepinephrine, norepinephrine, isoproterenolを作用させても攣縮張力は増大しないが, 静止張力については, 前2者では著名に増大し, 後者では不変である. しかし, tolazoline(α-blocker)で前処置した場合には静止張力は増大しない. 下大静脈と心房では, propranololで前処置を施しても, 静止張力は常に不変である. これらの事実は, 上大静脈中に交感神経性α-受容体の興奮で持続的収縮を営む平滑筋と, β-受容体の興奮で攣縮張力を増強する心筋様横紋筋が混在することを示唆する. 9. 比較的高濃度のacetylcholineを上大静脈に作用させると, 心房筋と同様に静止電位がやや増大し, 再分極が著名に促進, 攣縮張力は著減するが, 数分後にatropineを加えると, 逆に持続の長い活動電位を伴った異常に大きな収縮をきたす. これは, acetylcholineが大静脈の組織を刺激してcatecholamineを遊離させるためと推測される. 10. 強心配糖体oubainを心房に作用させると, ほとんどの例(90%)で収縮張力が増強するが, 上大静脈では40%について増強するにすぎない. 一方, 上大静脈, 心房とも活動電位には有意の変化が認められない. 11. 家兎の近心部大静脈は, 少くとも 機能的には心筋と血管平滑筋の両方の性質, またはその中間的性質を有し, この部には大別して律動的収縮と持続的収縮の2つが存在する. 前者は心筋様横紋筋に由来し, 心房収縮時に生じる大静脈への血液逆流を阻止するように働き, 後者は血管平滑筋に由来し, 還流静脈血量の調節にその生理的意義を有するものと考えられる.

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