A perifusion system was applied for the study on stimulus-enzyme secretion coupling in dispersed pancreatic acini. The system is highly simple, preserves the acini up to more than 3hr, and makes feasible clear-cut examination on the time course of enzyme secretion caused by secretagogues.
Caerulein (10^-9M) and carbamylcholine (10^-5M) caused a biphasic amylase secretory pattern consisting of an initial burst secretion and a sustained one. Caerulein induced a persistent amylase release even after cessation of the stimulation, while carbamylcholine-stimulated amylase release returned to basal levels. Atropine inhibited completely carbamylcholine-stimulated amylase release and the successive stimulation by caerulein evoked the amylase secretion with a decreased initial burst secretion. In calcium free medium, caerulein and carbamylcholine induced only a slight secretion, particularly in the sustained secretion phase and a gradual increase occurred with the addition of calcium.

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Overall gain of the O₂-ventilation feedback control system (G_O2) was determined in 9 male and one female healthy subjects. G_O2 progressively increased with decreasing end-tidal P_O2 (PET_O2). This value did not exceed the overall gain of the CO₂-ventilation feedback system (GC_O2) even at a PET_O2 level of 40mmHg, suggesting that hypoxic stimulation did not become predominant in the present experimental condition.
With addition of 250ml of external dead space, PET_O2 decrement (ΔPET_O2• actual) was experimentally observed. The ΔPET_O2•actual thus obtained was found to be in good agreement with the PET_O2 decrement deduced from G_O2•(ΔPET_O2•expected). This result was similar to that found in the PET_CO2 change previously seen in normoxia.

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1. Conduction velocity (CV) of an action potential recorded from a single muscle fiber of the frog was measured with a new method, unidimensional latency-topography, and electrical membrane constants were determined for the same muscle fiber. CV=1.96±0.27m/sec (n=52) at about 20°C. Temperature coefficient of CV: Q₁₀=2.0. Electrical membrane constants in the same muscle fibers (n=52): λ= 3.25±0.83mm, τ=33.4±14.3msec, C_m=6.09±2.13μF/cm², D=129.4±28.9μm (mean±S.D.).<br>2. The CV decreased linearly with increment of time constant, τ, and membrane capacity per unit area, C_m. The space constant, λ, and the fiber diameter of the muscle fiber, D, did not correlate with CV. It was concluded that the T-system, which contributes largely to membrane capacity, has a great influence on the CV.

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High resolution proton magnetic resonance spectra of intact frog muscle, obtained by the selective saturation of water signal with 15min accumulation, showed well-resolved signals from lactate, carnosine, and other compounds. This technique was used to monitor the changes in lactate content and in intracellular pH which was estimated from the chemical shift of carnosine in muscle. The intracellular pH was estimated to be 7.1 in fresh muscles. Under an anaerobic condition, resting muscle showed a gradual increase in lactate content with intracellular acidification. When the anaerobic muscle was electrically stimulated for 5sec, a transient acceleration of the lactate production and the intracellular acidification was observed. The intracellular buffer value was estimated to be 27mEq/(pH•kg muscle), based on the pH change due to the increase in lactate content.

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Effects of acute hypocapnia on respiratory timing (inspiratory and expiratory times (TI, TE)) and on inspiratory activities of the efferent superior laryngeal (Xsl), hypoglossal (XII), and phrenic (Phr) nerves were studied in artificially ventilated vagotomized, and anesthetized rats. Hyperventilation induced a decrease in respiratory frequency exclusively due to prolongation of TE and resulted in expiratory apnea. Inspiratory activities of three nerves decreased with reduction in CO₂ concentration of end-tidal gas (FET_CO2), and disappeared simultaneously at a threshold FET_CO2, for apnea. The decrease in the peak inspiratory activity by hypocapnia was larger in the XII than in the Phr or Xsl nerve (XII>Phr>Xsl). The results suggest that the CO₂ stimulus (mainly via a central chemosensor) plays an important role in the process of terminating expiration or of expiratory-inspiratory phase switching and that the responses of the XII or Xsl motoneurons to variation in CO₂ stimulus differ from that of the Phr motoneurons (or of the Phr driving medullary neurons). A possible functional significance of these observations is discussed.

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Adrenergic transmissions were investigated by recording electrical and mechanical responses of the smooth muscle cells in the rabbit ear artery. Perivascular nerve stimulation generated an excitatory junction potential (e.j.p.) and a slow depolarization. The latter but not the former was suppressed by prazosin or phentolamine. Both the e.j.p. and slow depolarization were suppressed by tetrodotoxin (TTX) or guanethidine. Facilitation processes of e.j.p.s produced by repetitive stimulation of the nerves were not modified by prazosin, phentolamine, or yohimbine. Increasing the stimulus frequency increased the amplitude of e.j.p.s and slow depolarizations and, at high frequencies (>5Hz) generated a spike potential. Nicardipine (10^-7M) blocked the spike potential and reduced the e.j.p. amplitude, but did not affect the slow depolarization. Amplitude of muscle contractions produced by transmural nerve stimulation increased with increase in the stimulus frequency. The nerve-mediated contractions produced by high-frequency stimulation (10Hz) were reduced to 49% of the control value by prazosin (10^-6M), to 79% by nicardipine (10-⁷M), to 34% by prazosin (10^-6M) plus nicardipine (10^-7M), and to 1.2% by TTX (3×10^-7M). Exogenously applied noradrenaline depolarized the smooth muscle membrane and produced the muscle contraction. These effects of noradrenaline were antagonized by prazosin or phentolamine. Thus, in the rabbit ear artery, perivascular nerve stimulation produced three types of electrical responses, i.e., e.j.p., spike potential, and slow depolarization. The latter but not the former two was produced through activation of α₁-adrenoceptors. Nerve-mediated muscle contractions were the results of stimulation of α₁-adrenoceptors, generation of spike potentials, and of e.j.p.s.

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Using the abdominal ganglion cells of Aplysia, we analyzed the effects of various enzymes and chemical modification reagents on the acetylcholine (ACh)-induced responses of the excitatory (Na⁺-dependent) and inhibitory (Cl^--dependent) types. (1) Phospholipase A (2mg/ml) caused no appreciable effects on either type of response. (2) Phospholipase C (2mg/ml) markedly depressed both types of response. These suggested that the phosphoryl group of the phospholipid is an important site related to the binding of ACh, common to both types of ACh-receptors. (3) Carboxypeptidase A (10mg/ml) caused no observable effects on either type of response. (4) Carboxypeptidase B (10mg/ml) depressed the inhibitory type of response without affecting the excitatory one. (5) Pyridoxal-5′-phosphate (1mM) also depressed the inhibitory response without affecting the excitatory one. These findings (4, 5) suggested that the Cl^--channel in the inhibitory ACh-receptor complex includes a C-terminal lysine which may play an active role in the movement of Cl^- across the receptor membrane. (6) L-Leucine aminopeptidase (1mg/ml) depressed the excitatory response without altering the inhibitory one. (7) p-Nitrothiophenol (1mM) also depressed the excitatory response without affecting the inhibitory one. These findings (6, 7) suggested the presence of a certain N-terminal amino acid near a glutamate or aspartate residue within a molecular moiety of Na⁺-channel included in the excitatory ACh-receptor complex.

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The membrane of isolated frog skeletal muscle fibers with or without T-system is depolarized to about -30mV in a Ca-free solution containing 2mM EGTA. Under such a condition, the action potential can be produced by a cathodal pulse when the membrane is previously hyperpolarized to -70--100mV by a conditioning anodal current. The action potential consists of two different potential components, namely a spike potential and a following slow depolarizing response forming a plateau phase (plateau potential). The membrane conductance during the plateau potential is increased. Both spike and plateau potentials are abolished in the absence of NaCl. TTX blocks a spike potential without affecting a plateau potential, whereas Mn and D-600 act contrarily. The i-v relation shows an anomalous rectification in Na-free solution, suggesting that the K conductance during the plateau phase is decreased. It is suggested that spike and plateau potentials are produced by a movement of sodium ions through sodium and calcium channels of the membrane, respectively.

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In order to examine the possibility that cyclic-GMP is an internal transmitter in the process of phototransduction, cyclic-GMP was iontophoretically injected into a gecko photoreceptor from one barrel of a double-barrelled microelectrode with the other barrel monitoring membrane potential and conductance changes. Cyclic-GMP induced a prolonged depolarization accompanied by a marked increase in membrane conductance. In the sodium-free bathing solution (substituted by choline), injection of cyclic-GMP did not cause any depolarization. The cells, which showed the cyclic-GMP-induced depolarization, produced no significant potential changes with injection of 5′-GMP or cyclic-AMP, indicating that the depolarization was cyclic-GMP-specific. The results suggest that cyclic-GMP is involved in the phototransduction process in the gecko photoreceptors. However, uncertainty still remained as to whether the cyclic-GMP level directly correlates with the photoreceptor membrane potential.

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The purpose of the study was to determine whether activation of cardiac receptors and arterial baroreceptors by myocardial ischemia could elicit reflex alteration of the effective refractory period (ERP) of nonischemic ventricular myocardium in cats. Changes in ERP of nonischemic area of the right ventricle and mean arterial pressure (MAP) were measured during transient left anterior descending (LAD) coronary artery occlusion in anesthetized cats. LAD coronary occlusion for 90sec caused a small but significant shortening of ERP (maximal change=2.5±2.3msec) associated with a decrease in MAP. Vagotomy significantly augmented the shortening of ERP to -3.4±1.6msec and attenuated the decrease in MAP. After selective cardiac sympathectomy, the reflex response in refractoriness was virtually abolished. In cats with sinoaortic denervation with intact sympathetic nerves, marked attenuation was observed in the reflex change in refractoriness, although the decrease in MAP was significantly greater. These results indicate that: (1) autonomic reflexes activated during acute myocardial ischemia shorten the refractory period of nonischemic ventricular myocardium;(2) the reflex response is predominantly mediated by enhancement of cardiac sympathetic nerve activity resulting from the reduced baroreceptor activity due to concurrent hypotension.

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The mechanism of kaliuresis induced by massive antibiotic administration was studied using α-sulfobenzyl penicillin (SBPC). In experimental group (n=8), urinary electrolytes excretion were compared between following the infusion of 10g SBPC in 200ml water at a constant rate and following the infusion of 48mmol of NaCl (equal to that contained in 10g SBPC) in 200ml water. For the control group, 96mmol NaCl in 400ml water was infused (n=5). In the experimental group, urinary Na (UNaV) and urinary K excretion (UKV) increased relative to the control period. In the control group, UKV was not increased although UNaV was increased (p<0.05). UKV following SBPC infusion was correlated with UNaV (p<0.05) and urinary SBPC excretion (p<0.05). The ratio of urinary anion gap to urinary cation [1-{urinary Cl concentration/(urinary Na concentration+ urinary K concentration)}] was significantly increased following SBPC infusion (p<0.005) but not in the control group. This increase in anion gap is possibly due to urinary SBPC, which will be ionized over 90% as nonreabsorbable anion in maximally acidic urine. We conclude that the kaliuresis induced by massive SBPC administration in man is probably caused by the nonreabsorbable anion effect of SBPC itself.

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The effects of β-endorphin and vasoactive intestinal peptide (VIP) on the body shaking response to ice water immersion were observed in anesthetized rats. Intraventricular injection of β-endorphin markedly inhibited body shaking, but γ- and α-endorphin and methionine-enkephalin showed only slight or little effect. VIP also suppressed the body shaking. The inhibitory effect of β-endorphin and VIP was blocked by naloxone. When small doses of β-endorphin and VIP which could not affect the shaking behavior by themselves were administered simultaneously, significant suppression occurred, indicating potentiation of the effect of β-endorphin by VIP.

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Effects of noradrenaline on the portal and aortic plasma pancreatic hormone concentrations were studied in the cold- and heat-acclimated rats in order to know possible roles of these hormones in temperature acclimation. Noradrenaline (NA) infusion (2μg/min, i.v., 30min) effected greater elevation of colonic temperature (T_c) in the cold-acclimated rats (CA) than in the warm controls (WC), and did not influence T_c in the heat-acclimated rats (HA) under hexobarbital anesthesia. Portal and aortic glucagon levels increased in the NA-infused CA and HA, but no changes were observed in the NA-infused WC. NA-infusion did not affect the portal and aortic insulin levels in WC and CA, but increased aortic insulin level in HA. Aortic glycerol and free fatty acid (FFA) levels increased in all NA-infused groups. Portal and jugular vein FFA levels increased in NA-infused WC, but did not in NA-infused CA and HA. Neither NA infusion, nor glucagon was related to the elevation of T_c in HA. These results suggest that temperature acclimation modifies a glucagon-releasing action of NA and the NA-released glucagon could cooperate with NA to enhance nonshivering thermogenesis in the cold.

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Properties of Ca-dependent outward current were studied in bullfrog atrial muscle using double sucrose-gap techniques. Decreasing [Ca]_o inhibited the instantaneous outward current (I_k1) and inward background current (I_b), and the reverse was noted with increases in [Ca]_o. When gk₁ was blocked with 0.3mM Ba, there were no such effects. In the presence of Ba and TTX (1.5×10^-6M), 3mM Co abolished the slow inward current (I_si) and depressed the delayed outward current (I_out). The depression was confined to the voltage range of activation of I_si. Similar results were obtained by replacement of [Ca]_o with Co in concentration of equal surface charge effects. Contrarily, isoproterenol (10^-7M) increased the I_si and I_out at the same voltage range. The activation of I_out became More rapid in the presence of isoproterenol but slowed with Co. In the presence of Ba, TTX, and Co, Ca-free EGTA (-0.3mM) Ringer further depressed the I_out, eliminating any remaining tension response. The depression, however, was more extensive, the stronger the depolarization. The activation of I_out was Markedly retarded and amplitude of the fully activated I_out diminished, yet the deactivation became More rapid. Thus, the Ca-sensitive outward current was classified into 1) Ca-linked I_k1 2) I_si-dependent I_out, and 3) I_si-independent but [Ca]_o-related I_out.

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Microperfusion experiments with Na⁺-free and/or K⁺-free solutions revealed that the generation of Cl^--dependent lumen-positive transtubular potentials of the early distal tubule of Triturus kidney was absolutely dependent on the presence of both Na⁺ and K⁺ in the lumen. Increases in luminal Na⁺ or K⁺ concentration increased the luminal positivity in a saturable manner, and the half saturation concentration was found to be about 1mM for both cations. The results strongly suggest that Cl^- is cotransported with Na⁺ and K⁺ across the luminal membrane.

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A balloon was introduced into the isolated rabbit left ventricle with intraventricular volume being controlled by a feedback amplifier. Pressure-volume and stiffness-pressure relations were determined as intraventricular volume was changed. These ventricular relations were explained according to the theory of wall muscle mechanics.

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Intracellular Cl^- activity (aⁱ_Cl) and transmembrane potential (ΔΨ_m) of canine submandibular gland cells were measured in vitro by using Cl^- sensitive liquid membrane microelectrodes. Under the conditions of superfusion with a control solution, average Cl^- activity of the resting cells was slightly higher than those predicted from Nernstian equilibrium.

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