Arteriographically visualized extravasation in hypertensive intracerebral hemorrhage. Report of seven cases

Seven cases are reported in which extravasation of contrast medium from the lateral lenticulostriate artery was observed on cerebral angiography performed in the early stage of hypertensive intracerebral hemorrhage.

We advance the theory that continuous bleeding from the ruptured artery with mechanical destruction and displacement of cerebral tissue is the cause of massive hematoma formation, and discuss the possibility of surgical treatment of the acute stage of hypertensive intracerebral hemorrhage.

Bypass anomaly of the vertebral artery associated with cerebral aneurysm and arteriovenous malformation

✓ In a series of 1107 patients with cerebrovascular disease studied by four-vessel angiography, the authors have found 10 cases of a bypass anomaly of the vertebral artery. Six of the cases also had cerebral aneurysms, and two cerebral arteriovenous malformations. The authors discuss the possible origins for this relationship.

Influences of sodium and calcium on the recovery process from potassium contracture in the guinea-pig taenia coli

1. In the guinea-pig taenia coli, influences of Na and Ca ions on the recovery process from the K contracture were investigated. In the absence of Na ion (sucrose-Krebs solution), the K contracture did not recover when the external K (143 mM) was returned to the normal concentration (5.9 mM), although the membrane was repolarized to normal resting potential.2. After reducing the external K concentration to normal, the addition of Na rapidly terminated the contracture. About 5 mM-Na was enough to produce the relaxation, but the rate of relaxation was slower the lower the Na concentration.3. Lithium could substitute for Na in the relaxation, but Tris-hydroxymethyl aminomethane could not. The possibility of a chloride contribution was excluded.4. Ouabain (2 x 10(-6) g/ml.) and K removal reduced the rate of relaxation by Na ion only slightly. Lowering the temperature also had a small effect, having a Q(10) of about 1.4. Therefore, the Na-K pump may not be involved in this process, but a physical process seems responsible.5. The contracture in K-Krebs solution and in sucrose-Krebs solution was dependent on the external Ca concentration suggesting a high Ca permeability of the membrane. When sucrose was isosmotically replaced with Mn, Mg, La or Ca ions the relaxation was produced with a relatively fast speed in the absence of external Na ions.6. These results may be explained by assuming that external Na ions are involved in decreasing the Ca permeability of the membrane and in reducing the intracellular Ca concentration by Na-Ca exchange, energy for which is supplied by Na influx. In the relaxation by polyvalent cations, suppression of the Ca permeability is probably the main factor.

Noradrenaline action on nerve terminal in the rat diaphragm

1. The mechanism by which noradrenaline increases the release of transmitter from the nerve terminal was investigated in the rat diaphragm.2. Increase of the frequency of the miniature end-plate potential (m.e.p.p.) was exponential when plotted against the intensity of a constant current which depolarized the nerve terminal. Noradrenaline (5 x 10(-6) g/ml.) did not change the slope of the curve showing the relationship between the logarithm of the frequency of m.e.p.p.s and the depolarizing current (m.e.p.p.-current relationship), but simply shifted the curve along the axis of the current towards weaker intensities.3. End-plate potentials (e.p.p.s) were evoked by passing a brief depolarizing pulse to the nerve terminal in the presence of tetrodotoxin (1 x 10(-7) g/ml.). A sigmoidal relationship was obtained between the amplitude of e.p.p. and the intensity of the current pulse (e.p.p.-current intensity relationship). Noradrenaline (5 x 10(-6) g/ml.) shifted the e.p.p.-current intensity relationship along the axis of the current intensity to smaller values, without any change in the maximum amplitude of e.p.p.s.4. The frequency of m.e.p.p. was increased, as the [Ca](0) was raised from 0.01 to 7.5 mM. An increase in [Ca](0) beyond the normal concentration (2.5 mM) had no remarkable effect on the action of noradrenaline. However, when [Ca](0) was reduced, the action of noradrenaline became weaker.5. A kinetic model in which the transmitter release is modified by the binding of Ca with a specific site in the nerve terminal may explain the results. According to this model, noradrenaline did not change the dissociation constant of the reaction between Ca and the specific site (X), but increased the rate constant of the Ca complex (CaX) for releasing acetylcholine.6. The action of noradrenaline was potentiated when [Na](0) was reduced, and suppressed when [Mg](0) was increased. The results may be summarized: that noradrenaline augments the probability of release of transmitter quanta from the resting nerve terminals and that this action can be intensified by first raising the probability of release by some other means. Depolarization of the nerve terminals by current, increase of the external Ca concentration, decrease of Na and decrease of Mg are all effective in promoting the action of noradrenaline.

Effect of prostigmine on the time course of the end-plate potential in the rat diaphragm

1. End-plate potentials (e.p.p.s) were evoked by applying brief depolarizing pulses to motor nerve endings in a phrenic nerve-diaphragm preparation paralysed by tetrodotoxin (TTX). Without prostigmine, the time to decay from the summit of the e.p.p. to half amplitude (the half-decay time) was roughly constant (2-4 msec) when the amplitude was increased by increasing stimulus intensity or duration.2. In the presence of prostigmine (5 x 10(-7)-2 x 10(-5) g/ml.), the falling phase of the e.p.p. was different in time course depending on the amplitude. The half-decay time had, very roughly, an exponential dependence on amplitude. The relationship was not affected by increasing the TTX or the prostigmine concentration, but D-tubocurarine (10(-6) g/ml.) made the relationship less steep.3. Hyperpolarizing current pulses, applied after the depolarizing current pulse which produced the e.p.p., had no effect on the time course of the e.p.p. No facilitating effect of repetitive stimulation was observed without prostigmine up to a frequency of 40 c/s, but there was a strong effect of repetitive stimulation in increasing the amplitude and duration of the e.p.p. in the presence of prostigmine. During stimulation, the endplate was continuously depolarized by 10-20 mV, and its recovery was very slow, the half-decay time being about 3 sec.4. The half-decay time of the acetylcholine potentials produced by iontophoretically applied acetylcholine was almost independent of the amplitude, with or without prostigmine, although it increased the amplitude of the potential and prolonged the falling phase.5. Possible mechanisms for the alteration of the falling phase of the e.p.p. were discussed. It is speculated that, in the presence of prostigmine, a process which is involved in a conductance increase of the post-synaptic membrane, after acetylcholine has combined with the receptor molecules, is the main factor determining the falling phase of the e.p.p.

Effects of removing the external potassium on the smooth muscle of guinea-pig taenia coli

1. Removal of the external K ions depolarized the membrane of the guinea-pig taenia coli by about 5 mV, and increased the frequency of the spontaneous spike activity. After about 20 min in K-free solution, the frequency gradually decreased and spontaneous activity stopped after about 60 min.2. Readmission of K produced a transient hyperpolarization by 10-15 mV for 10-20 min, and lowered the excitability. The membrane resistance decreased during the hyperpolarization. When the external K concentration was returned to normal before the spontaneous activity had disappeared in K-free solution, there was a complete suppression of the spontaneous electrical and mechanical activities, accompanied by hyperpolarization of the membrane. The duration of this suppression of electrical and mechanical activities depended on the exposure time to K-free solution, the recovery being delayed by longer exposure.3. The effects of removing external K were essentially the same in the presence of tetrodotoxin (10(-7) g/ml.), of atropine (10(-6) g/ml.), and also in low Cl (2-7 mM).4. The effects of ouabain (10(-6) g/ml.) were similar to those of zero K but appeared more slowly. After treatment with ouabain, the membrane was hyperpolarized by removing the external K and there was no hyperpolarization nor suppression of the mechanical activity on readmission of external K.5. Rb substitution for K produced little effect and addition of 5.9 mM-Rb after K-removal produced a typical suppression of activity as the readmission of K. When K was replaced with an equimolar concentration of Cs, the effects were similar to those produced by K-free solution.6. The pattern of the response to a change in the external K concentration was different below 23 degrees C. The spontaneous activity was suppressed by removal of K, and increased by returning the external K.7. It is concluded that, in the taenia, the membrane potential can be modified by an electrogenic pump, the activity of which is inhibited by removing K, by ouabain, and by lowering the temperature to about 23 degrees C. During the recovery from the exposure to K-free solution or to ouabain, the pump activity is potentiated, causing hyperpolarization of the membrane by 10-20 mV. Rb can, Cs cannot, replace K in activating the pump at the same concentration as K.

Effects of Ca removal on the smooth muscle of the guinea-pig taenia coli

1. The effects of removing the external Ca ions on the spontaneous and evoked activity of the smooth muscle of the guinea-pig taenia coli were investigated with the double sucrose-gap method.2. In Ca-free Locke solution the membrane was depolarized, the membrane resistance became low, the spike amplitude became small and the mechanical response decreased. In most preparations the electrical and mechanical activity was abolished within 10 min, but in some preparations the electrical activity continued for more than 30 min.3. In Ca-free solution containing 0.1 mM-EGTA, the membrane was depolarized and the electrical and mechanical activity was abolished within 5 min in every preparation. When NaCl was replaced with sucrose, the effects of Ca removal on the spike activity and contraction appeared very slowly and the membrane potential and membrane resistance remained unchanged.4. When Ca was replaced with Mg (2 mM) the spike was blocked within 1 min without depolarization or reduction of the membrane resistance. In Na-deficient (sucrose) solution, the presence of Mg accelerated the disappearance of the spike caused by Ca removal.5. In Ca-free solution containing 0.5 mM-Mg, a spike-like activity was observed without accompanying mechanical response. This activity was blocked by increasing the Mg concentration above 2 mM. It was Na-dependent, since it was abolished by removing Na from the external solution, but it was not influenced by tetrodotoxin (2 x 10(-6) g/ml.).6. It was concluded that calcium has at least two functions, one as current carrier for the action potential and another as controller of the Na permeability of the membrane. It was also suggested that the Ca which is bound at the membrane may be utilized as a source of Ca ions to carry the current for the action potential.

The effects of papaverine on the electrical and mechanical activity of the guinea-pig taenia coli

1. Effects of papaverine (5 x 10(-6)-5 x 10(-5)M) were studied on the spontaneous and evoked electrical and mechanical activity of the guinea-pig taenia coli. In normal Locke solution, papaverine slowed and finally stopped the spontaneous spike discharge, usually with a small hyperpolarization of a few mV.2. Papaverine did not change the membrane resistance in normal Locke solution. It abolished the repetitive firing of spikes during the depolarization in response to a current pulse, but a single spike of normal amplitude could always be evoked.3. The mechanical response elicited by a single spike was reduced by papaverine in normal Locke solution. During the maintained depolarization produced by a long current pulse the tonic component of the contraction was more reduced than the phasic component related to the initial spike activity.4. The effects of papaverine were essentially the same as in normal Locke solution when NaCl was replaced with LiCl, or in excess K (24 mM), except that the membrane resistance was increased by papaverine in the presence of excess K.5. Excess Ca (6 mM) antagonized the effect of papaverine on the mechanical response, but not on the electrical response. When the muscle was depolarized in Ca-free solution, papaverine caused repolarization of the membrane and electrical activity reappeared. This effect was similar to that of Mg (4 mM).6. The mechanism by which papaverine suppresses the spontaneous spike activity is discussed and is compared with that of isoprenaline, from which it appears to differ. The observations indicate that papaverine, like Mg, may bind with a site at the membrane with which Ca normally binds, thereby modifying the electrical and mechanical activity controlled by Ca.

Electrical activity of vertebrate photoreceptors

It has been known since the time of Schultze (1866) that in the vertebrate retina there are two types of photoreceptors, rods and cones, and that they serve different visual functions; rods for scotopic vision, and cones for photopic. The terminology originates from the shape of the outer segments in which the photosensitive pigment molecules are contained. The cone outer segments are conic and taper towards the tips, while the rod outer segments are typically cylindrical. Fig. 1 is a schematic diagram from Brown, Gibbons & Wald (1963) of the ultrastructure of the rod and cone outer segments of the mudpuppy, Necturus, as studied by electron microscopy. Both appear to be made up of a pile of transverse paired membranes. In cones these arise by infolding of the plasma membrane, and in rods they have probably arisen in a similar way, but each pair of membranes is sealed around the edge so as to form a closed double-membrane disc (Sjöstrand, 1961). Because of the universal lamellation within the rod and cone outer segments, it looks as if there were no appreciable intracellular space, but yet Toyoda, Nosaki & Tomita (1969), and Toyoda et al. (1970) were successful in intracellular recording from the outer segments of single rods of the nocturnal gecko and frog.

The action potential in the smooth muscle of the guinea pig taenia coli and ureter studied by the double sucrose-gap method

The configuration of the electrotonic potential and the action potential observed by the double sucrose-gap method was similar to that observed with a microelectrode inserted into a cell in the center pool between the gaps. In the taenia and the ureter, the evoked spike was larger in low Na or in Na-free (sucrose substitute) solution than in normal solution. However, the plateau component in the ureter was suppressed in the absence of Na. In Ca-free solution containing Mg (3-5 mM) and Na (137 mM), the membrane potential and membrane resistance were normal, but no spike could be elicited in both the taenia and ureter. Replacement of Ca with Sr did not affect the spike in the taenia, nor the spike component of the ureter but prolonged the plateau component. The prolonged plateau disappeared on removal of Na, while repetitive spikes could still be evoked. It was concluded that the spike activity in the taenia and in the ureter of the guinea pig is due to Ca entry, that the plateau component in the ureter is due to an increase in the Na conductance of the membrane, and that both mechanisms, for the spike and for the plateau, are separately controlled by Ca bound in the membrane.