bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of compensatory renal growth in rats
Authors: Dicker S. E.
Published: December 2014

1. Compensatory renal hypertrophy in unilaterally nephrectomized rats was measured by estimation of dry weight, protein content, RNA and DNA changes and rate of oxygen consumption. Inulin clearances (= GFR) and water and solute excretions were estimated in animals given by stomach tube either 5 ml. water or 5 ml. 0·6% NaCl solution/100 g body wt.

2. Kidneys removed when animals were unilaterally nephrectomized were homogenized in 0·25
M sucrose and fractions containing mitochondria or microsomes were obtained by centrifugation. Renal cortex and medulla were similarly treated.

3. Intraperitoneal injections of microsomes and/or supernatant fluid from a kidney homogenate or from the renal cortex usually inhibited compensatory growth of the contralateral kidney and prevented any increase of its protein content.

4. Injections of microsomes and/or supernatant fluid from the renal medulla had no significant effect on the rate of compensatory hypertrophy.

5. After
I.P. injection of microsomes and supernatant fluid from a homogenate from the renal cortex there was no rise of the RNA/DNA ratio in the contralateral kidney and the rate of oxygen uptake of its cortex decreased, while that of anaerobic glycolysis increased.

6. Injections of microsomes and supernatant fluid from kidney homogenate did not affect glomerular filtration rate which increased as in control unilaterally nephrectomized rats.

7. In unilaterally nephrectomized rats, injected with microsomes and supernatant fluid from a kidney homogenate, there was a decrease of osmolal clearance, in spite of the raised glomerular filtration rate. The decrease of osmolal clearance lasted for several days, and was most pronounced when the animals had been given by stomach tube 5 ml. 0·6% NaCl solution/100 g body wt.
A comparison of chemical and electrical synaptic transmission between single sensory cells and a motoneurone in the central nervous system of the leech
Authors: Nicholls J. G. , Purves D.
Published: December 2014

In leech ganglia, three sensory cells of different modality converge on a motoneurone, where they form chemical and electrical synapses. Each of these synapses behaves in a characteristic manner and the nature of the transmission mechanism has significant functional consequences for the operation of the reflexes. An analysis has been made of the effects of trains of impulses on synaptic transmission through these pathways, using frequencies that correspond to natural firing.

1. At the chemical synapse between the nociceptive sensory cell and the motoneurone, two opposing events occur: facilitation and depression. Thus, with trains of impulses, the synaptic potentials first increase in amplitude and then decrease. The two processes could be separated by altering the Mg and Ca content of the bathing fluid. In concentrations of Mg that reduced the amplitude of a single control chemical synaptic potential, pure facilitation occurred during a train. Depression predominated during brief trains in raised concentrations of Ca, although synaptic potentials were initially larger. These results suggest that changes in the amount of transmitter released by each presynaptic action potential can account for the changes observed in chemical synaptic transmission.

2. In contrast, electrical transmission between the sensory cell responding to touch and the same motoneurone did not show facilitation or depression. The electrical coupling potential in the motoneurone was relatively constant when the touch cell fired at high or low frequencies in normal Ringer fluid, high Mg, or high Ca fluid.

3. Further differences between chemical and electrical synapses were apparent when the preparation was cooled to 4° C. In the cold the latency of chemically evoked synaptic potentials in the motoneurone increased and their amplitude declined drastically with repetitive stimulation, while electrical coupling potentials were unaffected.

4. A brief hyperpolarization of the presynaptic cell by injected current produced a marked and prolonged increase in chemically evoked synaptic potentials, but did not influence electrical synaptic transmission.

5. The synapses of the sensory cell responding to pressure, which are both chemical and electrical, behaved as expected: the chemical synaptic potentials showed facilitation and depression while electrical transmission remained relatively constant.

6. These experiments emphasize the different functional consequences of electrical or chemical synapses in reflex pathways for the transmission of signals that arise as a result of natural sensory stimuli.
Effects of noradrenaline on potassium efflux, membrane potential and electrolyte levels in tissue slices prepared from guinea‐pig liver
Authors: Haylett D. G. , Jenkinson D. H.
Published: December 2014

1. Some effects of noradrenaline on potassium efflux, electrolyte levels, membrane potential and current distribution in guinea‐pig liver slices have been examined.

2. The slices (thickness ca. 300 μm) were prepared from the median lobe of the liver and incubated at 38° C in a mammalian Ringer fluid containing 2 m
M pyruvate. After an initial recovery period, the ionic composition of the tissue remained stable for several hours.

3. The steady‐state contents of sodium, potassium and chloride were 296, 266 and 272 m‐equiv/kg dry tissue respectively. The inulin space was 29 ml./100 g wet tissue.

4. Most if not all of the tissue potassium was exchangeable. The rate constant for 42K efflux was 0·019 min−1.

5. Noradrenaline (1 μ
M) markedly increased the efflux of 42K and within 2 min caused tissue potassium to fall by 8%. At the same time the sodium content rose.

6. Traverses of the slices with micro‐electrodes showed many negative‐going deflexions of 30–40 mV in amplitude. The evidence suggests that these correspond to the membrane potentials of the parenchymal cells.

7. Noradrenaline (1 μ
M) caused a reversible hyperpolarization of about 10 mV. The response became larger on replacing external chloride by isethionate or methylsulphate, but was little affected by a reduction in external potassium.

8. After slices had been bathed in potassium and chloride‐free solutions for several min, restoration of external potassium caused the membrane potential to increase by up to 10 mV. This hyperpolarization, but not that caused by noradrenaline, was abolished by ouabain.

9. Noradrenaline reduced the amplitude and quickened the time course of electrotonic potentials set up by current pulses from another microelectrode, suggesting that the membrane conductance had risen.

10. Although certain mechanisms based on electrogenic active transport processes with unusual properties have not been excluded, the present findings are more simply explained by supposing that noradrenaline increases the potassium permeability of the parenchymal cell membrane.
Renin responses to water restriction and rehydration
Authors: Blair‐West J. R. , Brook A. H. , Simpson Pamela A.
Published: December 2014

1. The effect of restricted water intake and rapid rehydration was studied in three conscious sheep with respect to plasma renin concentration (PRC), blood corticosteroid levels, plasma protein and electrolyte concentrations, and the renal and faecal excretion of sodium and potassium.

2. During water restriction the plasma concentrations of renin, protein and sodium rose while aldosterone levels were low or undetectable. Plasma potassium levels were unchanged. External sodium and potassium balance appeared to be unaffected.

3. During rehydration the sheep drank more than their estimated water deficit in 3–4 min with the following effects: PRC rose three‐ to fourfold during the ensuing 12 hr. Aldosterone levels too rose, while plasma protein, sodium and potassium concentrations fell. Urinary sodium excretion virtually ceased for 24 hr, and urine flow rate increased only little during this period.

4. If there was a single stimulus to renin release during water restriction and rehydration, it was not an alteration in vascular or extravascular volume, total body sodium, systemic
B.P. or plasma sodium concentration.

5. It is concluded that the rise in PRC in these experiments is compatible with the theory that altered sodium transport at the macula densa was the stimulus for renin release.
The vasomotor component of the carotid sinus baroreceptor reflex in the cat during stimulation of the hypothalamic defence area
Authors: Humphreys P. W. , Joels N.
Published: December 2014

1. The effect of moderate intensities of stimulation of the hypothalamic defence area on the baroreceptor reflex has been investigated in the cat by comparing the responses of arterial blood pressure and perfusion pressure of the isolated hind‐limb muscle bed perfused at constant volume inflow, when the isolated carotid sinus was subjected to a series of non‐pulsatile pressures with and without simultaneous hypothalamic stimulation.

2. In the absence of hypothalamic stimulation the characteristic sigmoid curves relating sinus pressure to blood pressure or muscle perfusion pressure were obtained.

3. With simultaneous stimulation of the hypothalamus a similar sigmoid relationship was found. There was no evidence of any reduction in the over‐all power or maximum sensitivity of the baroreceptor reflex.

4. However, in those cats which had been atropinized to abolish the cholinergically mediated muscle vasodilatation, the curves obtained during hypothalamic stimulation were displaced in such a manner as to suggest that, while baroreceptor modulation of vasoconstrictor tone continued during defence area stimulation, the blood pressure regulating mechanism had been ‘reset’ so that, within the physiological range of sinus pressures, any given level of sinus pressure was associated with a greater vasoconstrictor tone.

5. In non‐atropinized cats there was little displacement of the curves relating sinus pressure to blood pressure, while the curves relating sinus pressure to muscle perfusion pressure were displaced in the opposite direction so that over‐all muscle vascular resistance was less than normal at each level of sinus pressure.
Synaptic actions of peripheral nerve impulses upon Deiters neurones via the climbing fibre afferents
Authors: Allen G. I. , Sabah N. H. , Toyama K.
Published: December 2014

1. The cerebellar integration of sensory inputs to Deiters neurones was studied in cats under Nembutal anaesthesia.

2. Stimulation of peripheral nerves produced in the Deiters neurones a sequence of an initial excitatory post‐synaptic potential (e.p.s.p.) and a later inhibitory post‐synaptic potential (i.p.s.p.), or a relatively small e.p.s.p.

3. The Deiters neurones were classified as forelimb (FL)‐ or hind limb (HL)‐type cells according to the location of the most effective peripheral nerve. In the FL cells stimulation of the forelimb nerves produced the e.p.s.p.—i.p.s.p. sequence (dominant response), while stimulation of the hind limb nerves was ineffective or produced the small e.p.s.p. (non‐dominant response). In contrast, in the HL cells the non‐dominant response was evoked from the forelimb nerves, and the dominant response from the hind limb nerves.

4. The stimulus intensity—response relation indicates that Group I and II muscle afferents and low and high threshold cutaneous afferents contribute to the dominant and non‐dominant responses.

5. Antidromic identification of these Deiters neurones revealed that 90% of the HL cells and 85% of the FL cells project to the lumbo‐sacral and cervico‐thoracic segments of the spinal cord, respectively, while 10% of the HL cells and 15% of the FL cells innervate the cervico‐thoracic and lumbo‐sacral segments, respectively.

6. The mean latency of the e.p.s.p. evoked from the forelimb nerves was 14 msec in the FL cells and 13 msec in the HL cells, and the latency of the e.p.s.p. evoked from the hind limb nerves was 17 msec in the FL cells and 18 msec in the HL cells. The later i.p.s.p. regularly followed the onset of the e.p.s.p. with a delay of 3–5 msec.

7. The dominant and non‐dominant responses in both types of cells exhibited the following three characteristic features: (i) a strong depression after conditioning stimulation of the inferior olive, (ii) an increase of the inferior olivary excitability during the responses, and (iii) a striking frequency depression with stimulation at relatively low frequency (5–10/sec).

8. Consequently it was concluded that all of the responses were produced through the climbing fibres originating from the inferior olive, the i.p.s.p.s due to inhibition from Purkyně cells activated by the climbing fibres and the e.p.s.p.s due to excitation from the collaterals of the climbing fibres.
Potential‐dependent membrane current during the active transport of ions in snail neurones
Authors: Kostyuk P. G. , Krishtal O. A. , Pidoplichko V. I.
Published: December 2014

1. The membrane current caused by the iontophoretic injection of sodium into giant neurones of the snail Helix pomatia was investigated under a long lasting voltage clamp. The inhibition of this current by ouabain (10−4 M) and by cooling to + 7° C confirmed its link with the active transport of ions. Therefore this current is called the pump current.

2. Over the range of membrane potential −40 to −100 mV the changes in the steady current—voltage curves caused by the pump current development were investigated. The pump current was found to be potential‐dependent. It decreased with increasing hyperpolarization of the neurone.

3. With large hyperpolarizations the current—voltage curves obtained before the sodium injection and after eliciting the pump current coincided with each other. An increase in the membrane conductance was observed over the range of membrane potential corresponding to the pump current display.

4. The applied sodium injections did not cause any marked changes in the passive permeability of the membrane. This fact made it possible to measure the charge transferred across the membrane during operation of the pump current. Unlike previous data, the ratio of this value to the charge used to inject sodium into the neurone appeared to be a variable.

5. When the preparation was cooled to + 11° C, and also during the first few minutes after the application of a potassium‐free solution, both the pump current and the membrane potential at which it disappeared could increase.

6. The pump current measurements during a number of transitions from one fixed level of the membrane potential to another showed that the current did not depend upon the potential at which it developed before each transition.

7. The data presented allow the suggestion that the potential dependence of the pump current is determined by the changes in the rate of active transport of potassium, while the rate of active transport of sodium remains constant.
Mechanisms of ion transport across the choroid plexus
Authors: Wright Ernest M.
Published: December 2014

1. Mechanisms of ion transport across the choroidal epithelium were investigated using an in vitro preparation of the frog choroid plexus.

2. Sodium was actively transported across the plexus from the vascular to the ventricular surface by an ouabain sensitive electrically silent pump. As in other epithelial membranes the rate of sodium transport was stimulated by the presence of bicarbonate ions in the Ringer solutions. Chloride and bicarbonate ions accompany the net flux of sodium across this tissue.

3. Some experiments suggest that potassium is actively transported from the ventricular to the serosal surface, and that the rate of transport is a function of the extracellular potassium concentration.

4. No evidence was obtained to suggest that calcium is actively transported across this tissue in either direction.

5. Diamox, ethoxyzolamide, pitocin, pitressin, hydrocortisone, amiloride, spironolactone and anoxia all failed to influence sodium transport.

6. The sequence of passive ion permeation across the plexus was PRb ∼ PK > PCs ∼ PNa ∼ PCl ∼ PHCO3 > PLi as deduced from diffusion potential measurements. At least for Na, K and Cl there was a good correlation between the permeability coefficients derived from unidirectional flux measurements and from electrical parameters. This indicates that exchange diffusion is unimportant as a mechanism for passive ion transport.

7. The instantaneous current—voltage curves were linear in both symmetrical and asymmetrical salt solutions and the choroid plexus conductance was found to be directly proportional to the external salt concentration. These and other lines of evidence suggest that the major route of passive ion permeation across this epithelium is via the tight junction route and not through the cell interior.

8. These results are discussed in relation to the in vivo studies of c.s.f. secretion and the mechanisms of active and passive ion transport across other epithelial membranes such as the gall‐bladder, intestine and renal proximal tubule.
The efflux of magnesium from single crustacean muscle fibres
Authors: Ashley C. C. , Ellory J. C.
Published: December 2014

1. In the large single muscle fibres from the barnacle Balanus nubilus, the total fibre Mg concentration was estimated as 15·1 m‐mole/kg wet wt., of which about 3–3·5 m‐mole/kg wet wt. was extracellular. The diffusible Mg, measured by internal sampling, was 11·5 m‐mole/kg wet wt., of which at least half may be complexed to larger diffusible molecules. The free ionized Mg level was estimated as < 5 m‐mole/kg wet wt.

2. The loss of [28Mg]MgCl2 from both Maia and Balanus muscle fibres following axial micro‐injection approximated to first‐order kinetics. The maximum rate constant for the loss was 1·51 ± 0·20 (
S.E.) × 10−5 sec−1 for Balanus (sixty‐seven fibres) and 1·06 ± 0·46 (
S.E.) × 10−5 sec−1 for Maia (seven fibres) at 20–25° C.

3. The calculated Mg efflux was in the range 6–12 p‐mole/cm2.sec based on this rate constant, assuming isotopic equilibration internally and that the surface area of the fibres approximated to that of a simple cylinder. If account was taken of the area of the cleft system the efflux was reduced by about fifteen times.

4. The diffusion coefficient for injected 28Mg was estimated as 2–3 × 10−6 cm2 sec−1, about half the value in free solution. Injections of 2
M‐MgCl2 or 200 m
M‐EDTA subsequent to the injection of the isotope caused about a 30% reduction in the tracer efflux.

5. External application of salines containing 100 m
M‐Ca or Mg caused a rapid but reversible inhibition of the magnesium efflux. Similar effects were observed with salines containing 32 m
M‐Co or Mn chlorides or 1–2 m
M‐La or Gd chlorides. Polyarginine (200 μg/ml.) had no effect.

6. The Mg efflux had a Q10 of 3–4 over the temperature range of about 5–20° C. It was irreversibly inhibited by the sulphydryl reagent NEM (1 m
M), but PCMBS (0·2–2 m
M) had no effect. Contractile agents (5 m
M caffeine or 200 m
M‐K salines) and a variety of inhibitors of ion movement or active transport had no appreciable effect on the Mg efflux. Lowering the pH of the saline from 7 to 5 produced a 70% reduction in the efflux which was reversible over short periods of application.

7. Replacement of external Na, but not Ca or Mg, with Li, choline or sucrose caused a rapid and partially reversible reduction of the Mg efflux, but increasing the internal Na by micro‐injection in zero Na salines had no consistent effect. It is suggested that the extrusion of Mg from these muscle cells is largely dependent upon the inward movement of Na.
Calcium dependence of ciliary activity in the oviduct of the salamander Necturus
Authors: Eckert Roger , Murakami Akira
Published: December 2014

1. Ciliary activity in the oviduct of the mud puppy Necturus maculosus was monitored by a photometric technique in normal, decalcified, and Triton X‐extracted preparations to investigate the regulatory role of calcium ions.

2. The frequency of ciliary beating in the isolated tissue ranged from 0 to 12 beats/sec. The frequency in any one group of cells underwent large cyclical variations with periods of 2 min or more.

3. Frequency of beating reached a maximum and remained at a plateau upon addition of 1 m
M caffeine. Beating temporarily ceased upon removal of the caffeine.

4. Ionophoretic injection of calcium ions into an active cell bathed in Ringer solution produced an increased rate of beating. In cells rendered quiescent by prior decalcification with EGTA, injected calcium rapidly restored ciliary activity.

5. Epithelia extracted in Triton X‐100 were inactive until reactivated by addition of ATP and magnesium ions. The frequency of beating increased between 0·1 and 4·0 m
M ATP in 1 m
M magnesium, and between 0·2 and 2·5 m
M magnesium in 1 m
M ATP.

6. The frequency of beating in the ATP‐reactivated, Triton‐extracted tissue was independent of the calcium ion concentration.

7. Cells inactivated by decalcification were reactivated by injection of ATP or by extracellular ATP levels as low as 3 × 10−8
M.

8. It is concluded that the frequency of beating depends directly on the concentration of the available energy source, presumably ATP, and that an indirect dependence of beating frequency on calcium concentration in the living tissue results from rate‐limiting effects of intracellular calcium on metabolic steps in pathways leading to ATP synthesis.
Factors forming the edge of a receptive field: the presence of relatively ineffective afferent terminals
Authors: Merrill E. G. , Wall P. D.
Published: December 2014

A specialized type of spinal cord cell has its cell body in lamina IV and has a small low threshold cutaneous receptive field which is remarkable for its abrupt edge. No signs could be found of a subliminal fringe to this field since its size remains fixed during wide excursions of the cell's excitability. Reversible blocking of peripheral nerves and dorsal roots showed that the afferents responsible for exciting these cells following natural stimuli, run in a restricted area of peripheral nerve and dorsal root. When the fibres necessary to sustain the natural stimulus receptive field were blocked, it was shown that other large myelinated fibres in neighbouring roots were still capable of firing the cell monosynaptically following electrical stimulation of the root or periphery although no natural stimuli were able to change the cell's excitability. It is necessary to divide the afferent synapses on such cells into a class which is highly effective in firing the cell on natural stimulation and a second class which has no effect yet detected following natural stimuli but which can fire the cell monosynaptically if synchronously activated by electrical stimulation. Suggestions are made for possible presynaptic and post‐synaptic mechanisms which might divide the effect of arriving impulses into two such classes.
Vascular responses and noradrenaline overflows in the isolated blood‐perfused cat spleen: some effects of cocaine, normetanephrine and α‐blocking agents
Authors: Cripps Heather , Dearnaley D. P.
Published: December 2014

1. Vascular responses and noradrenaline overflows have been studied in the isolated blood‐perfused cat spleen in response to electrical stimulation of the splenic nerve with trains of 200 supramaximal pulses at a frequency of 10 Hz given at 10 min intervals.

2. In the absence of blocking agents the spleen gave well‐defined responses and a mean maximum overflow of 436 ± 96 pg noradrenaline per stimulus (n = 4) at the third train of stimuli.

3. Cocaine (2 × 10−5
M) increased the response nearly threefold and raised the overflow to 840 ± 131 pg/stim (n = 4). At later stimulations the responses remained stable, but the overflows rose progressively to 1076 ± 51 pg/stim after five trains of stimuli.

4. Normetanephrine (10−4
M) had no significant effect on response, but elevated the overflow to a mean maximum of 868 ± 169 pg/stim (n = 4).

5. Cocaine (2 × 10−5
M) and normetanephrine (10−4
M) given together increased the response by a factor of 6·5 and raised the overflow to 1258 ± 247 pg/stim (n = 4).

6. Hydergine (approx. 10−5
M) almost completely abolished the response and raised the overflow to 859 ± 173 pg/stim (n = 4).

7. Cocaine (2 × 10−5
M), normetanephrine (10−4
M) and hydergine (approx. 10−5
M) given in combination abolished the response and raised the overflow to 4089 ± 1148 pg/stim (n = 4).

8. Phenoxybenzamine (10−4
M) abolished the response and elevated the overflow to 4215 ± 738 pg/stim (n = 4).

9. These results are interpreted in terms of selective and combined block of ‘uptake I’, ‘uptake II’ and α‐adrenergic receptors. Facilitation of transmitter release by α‐blocking drugs, and the possible existence of an uptake process associated with the α‐receptors are discussed.
Mobility and transport of magnesium in squid giant axons
Authors: Baker P. F. , Crawford A. C.
Published: December 2014

1. The Mg content of axons obtained from Loligo forbesi averaged 6·4 ± 0·8 m‐mole/kg axoplasm.

2. A small patch of radioactive 28Mg injected into an axon broadened considerably. A similar patch of 45Ca showed hardly any broadening. The self‐diffusion coefficient of Mg in axoplasm is about 2 × 10−6 cm2/sec which is at least twenty times greater than that of Ca.

3. Under the influence of an applied electric field Mg migrated towards the cathode. Its mobility was about half of that of Mg in free solution. This suggests that the concentration of ionized Mg in squid axoplasm is between 2 and 3 m‐mole/kg axoplasm. The mobility of Mg was not changed by poisoning the axon fully.

4. Mg influx and Mg efflux were roughly the same and equal to about 1 p‐mole/cm2 sec. Mg efflux was reduced by poisoning with cyanide and by replacement of external Na by choline. Removal of external K or Ca had little effect and removal of external Mg tended to increase the efflux.

5. The dependence of Mg efflux on Na seems not to be secondary to changes in Ca because it persists in the absence of external Ca and in axons pre‐injected with EGTA. The form of the dependence on Na ions approximates to a simple rectangular hyperbola.

6. Replacement of external Na by Li or choline increased Mg influx. Mg influx was unaffected by cyanide.

7. Mg efflux was reduced to an average of 15% by poisoning with cyanide or DNP. The efflux could be recovered by injection of ATP. Inhibition persisted in axons pre‐injected with EGTA, showing that it is not secondary to a rise in Cai.

8. During nervous activity there is an extra entry of Mg. For axons immersed in sea water this extra Mg entry per impulse is roughly the same as the extra Ca entry per impulse.
The influence of external caesium ions on potassium efflux in frog skeletal muscle
Authors: Beauge L. A. , Medici A. , Sjodin R. A.
Published: December 2014

1. At a concentration of 2·5 m
M in the external solution, Cs ions reduced K efflux in muscles incubated in Na media. This effect was demonstrated in the presence or absence of 2·5 m
M‐K and in the presence or absence of 10−4
M ouabain.

2. In Ringer solution in which NaCl was replaced by an osmotic equivalent of MgCl2, external Cs ions increased K efflux if the solution was K‐free and decreased K efflux if the solution contained 2·5 m
M‐K.

3. External Cs ions reduced the inward rate of leakage of Na ions into muscle cells by about 25% when the medium was K‐free and contained 10−5
M ouabain.

4. The effects of 2·5 m
M‐K ions and 2·5 m
M‐Cs ions on the muscle fibre membrane potential were about the same. The influence of Cs ions on K efflux cannot be explained by changes in the resting membrane potential.

5. The results suggest that a large part of the K efflux from muscle cells is mediated by a K:K exchange mechanism that is inhibited by external Cs ions.

6. The results also suggest that a smaller part of the K efflux is due to K:Na exchange that is also inhibited by external Cs ions.

7. In the absence of either external K or Na ions for internal K to exchange with, Cs ions promote a small amount of K exchange, perhaps via both mechanisms.
Lateral inhibition in human colour mechanisms
Authors: Kelly D. H.
Published: December 2014

1. The spatial properties of human colour mechanisms were explored by measuring contrast thresholds for sine‐wave gratings, under conditions of intense chromatic adaptation, from 0·25 to 12 cycles/degree.

2. With adapting colours that tend to isolate the red‐, green‐, and blue‐sensitive spatial responses, all three results differ markedly from each other and from the neutral grating sensitivity. The green mechanism is much more sensitive than the others, the blue, much less.

In all cases, the contrast sensitivity decreases at low spatial frequencies, which is typically the result of lateral inhibition. This low‐frequency inhibition effect is greatest for the unadapted case; it diminishes significantly but does not vanish when the red or green mechanism is isolated.

4. These results imply that there is spatial inhibition both between and within the red and green mechanisms. Chromatic adaptation can eliminate the former but not the latter.
Maturation of glomerular blood flow distribution in the new‐born dog
Authors: Kleinman Leonard I. , Reuter John H.
Published: December 2014

1. Glomerular blood flow distribution was studied in seventy‐eight new‐born mongrel dogs aged 1–40 days by measuring the distribution of radioactive labelled microspheres within the kidney.

2. The microsphere technique was found to be a valid indicator of glomerular blood flow distribution for the new‐born dog since (a) the spheres were completely extracted by the kidney, (b) more than 95% of the spheres were trapped in glomerular capillaries, (c) the spheres were evenly distributed within any specific region of the kidney and, (d) the spheres did not interfere with renal haemodynamics.

3. Plasma flow per gram tissue to inner cortical glomeruli, relative to that to outer cortical glomeruli, the IC/OC flow ratio, was high at birth, decreased over the first 2 weeks of life and remained relatively constant thereafter. Plasma flow per gram tissue to the outer cortex increased over the whole 40 day period while that to the inner cortex decreased slightly and then increased after 2 weeks.

4. The IC/OC flow ratio decreased in a curvilinear fashion as blood pressure rose with maturation. Acute increases or decreases in blood pressure in any animal produced decreases or increases, respectively, in the IC/OC flow ratio.

5. There was no correlation between the IC/OC flow ratio and renal extraction of p‐amino‐hippurate (E
PAH).

6. There was histological evidence that glomerular differentiation persists for 2 weeks during the post‐natal period in the dog. This continuing post‐natal glomerulogenesis takes place only in the outer cortex.

7. These results are consistent with the hypothesis that an important factor in renal maturation is a redistribution of blood flow within the kidney. As the animal matures a greater fraction of the total glomerular blood flow goes to outer cortical glomeruli. This is due partly to the continuing glomerular differentiation taking place in the outer cortical region and partly to the increasing arterial blood pressure occurring with maturation.
Left ventricular inotropic and peripheral vasomotor responses from independent changes in pressure in the carotid sinuses and cerebral arteries in anaesthetized dogs
Authors: Hainsworth R. , Karim F.
Published: December 2014

1. The pressure perfusing the isolated carotid sinuses and the pressure perfusing the cerebral circulation were changed independently, and the resulting inotropic responses in the left ventricle and peripheral vasomotor responses were determined.

2. Inotropic responses were assessed by measuring changes in the maximum rate of change of left ventricular pressure (dP/dt max) with heart rate and mean aortic pressure held constant. Vascular resistance changes were usually assessed by perfusing the descending thoracic aorta at constant flow and measuring changes in perfusion pressure.

3. Decreases in carotid sinus pressure over the baroreceptor sensitivity range resulted in a 45% increase in dP/dt max and a 59% increase in vascular resistance.

4. Unless arterial oxygen tension was abnormally low, lowering cerebral perfusion pressure to 50 mm Hg resulted in little or no inotropic and vasomotor responses. In the presence of hypoxaemia (Pa,O2 < 60 mm Hg), lowering cerebral perfusion pressure to below about 80 mm Hg resulted in marked responses.

5. These experiments suggest that, unless arterial oxygen tension is abnormally low, the carotid sinus reflex and not cerebral hypotension is important in the control of the inotropic state of the heart and of vasomotor activity. With hypoxaemia, responses from cerebral hypotension may also be important.
Metabolic and ionic requirements for the intra‐axonal transport of noradrenaline in the cat hypogastric nerve
Authors: Kirpekar S. M. , Prat J. C. , Wakade A. R.
Published: December 2014

1. Metabolic and ionic requirements for the intra‐axonal transport of noradrenaline were investigated in the cat hypogastric nerve in vitro using a histochemical fluorescence procedure.

2. Specific noradrenaline fluorescence appeared at the proximal region after crushing the nerve at a distance of about 1·5 cm distal to the inferior mesenteric ganglion within 30 min, and the intensity of fluorescence increased with the perfusion time.

3. Prior removal of the ganglion from the rest of the hypogastric nerve, or denervation of the ganglion, had no effect on the appearance of the specific fluorescence.

4. Iodoacetic acid (5 × 10−4 M), glucose deprivation, dinitrophenol (DNP, 5 × 10−4 M) and anoxia, singly, did not affect the accumulation of noradrenaline, but combined treatment with glucose deprivation and anoxia, or glucose deprivation and dinitrophenol, very markedly interfered with noradrenaline accumulation.

5. If the temperature of the perfusion fluid was reduced to 15° C, the fluorescence was not seen at the region of occlusion.

6. Removal of sodium from Krebs solution markedly inhibited the axoplasmic transport of noradrenaline.

7. Treatment with ouabain (10−4 M) or tetracaine (2 × 10−4 M) did not affect the appearance of specific fluorescence after occlusion.

8. Our findings suggest that transport of noradrenaline storage particles within the hypogastric nerve is dependent on metabolic energy derived from either glycolysis or oxidative phosphorylation. This active process also has an absolute requirement for extracellular sodium ions.
The reflex effects of intralaryngeal carbon dioxide on the pattern of breathing
Authors: Boushey H. A. , Richardson P. S.
Published: December 2014

1. The reflex effects on the pattern of breathing and total lung resistance of introducing 30, 10 and 5% CO2 in air into the larynx have been studied in anaesthetized and decerebrate cats breathing through a tracheostomy tube.

2. Flowing 30% CO2 into the larynx caused a two‐phased response. First, respiratory frequency and tidal volume decreased, with a consequent fall in minute ventilation. After two to ten breaths, frequency remained slow, but tidal volume increased beyond the control level, so that minute ventilation was restored to control levels.

3. Flowing 5 or 10% CO2 into the larynx caused slowing of breathing with small and inconsistent changes in tidal volume. Minute ventilation was significantly diminished.

4. Off effects, on re‐introducing air into the larynx, after 2 and 10 min of CO2 exposure, suggested that the reflex response diminishes with increased duration of exposure to CO2.

5. None of the concentrations of intralaryngeal CO2 changed total lung resistance or compliance.

6. CO2 mixtures in the larynx generally caused no change in blood pressure or pulse rate of the cats.

7. The reflex effects of intralaryngeal CO2 were abolished by denervating the larynx.

8. Hypoxic mixtures introduced into the larynx did not change breathing.
Neuromuscular transmission in a mammalian preparation in the absence of blocking drugs and the effect of D‐tubocurarine
Authors: Hubbard J. I. , Wilson D. F.
Published: December 2014

1. Neuromuscular transmission in the presence and absence of
D‐tubocurarine was examined in cut muscle preparations of the rat diaphragm using intracellular recording techniques. The method of localizing the end‐plates is described and evidence is presented indicating that end‐plate potential (e.p.p.) recordings were made close to the end‐plate region and that reliable estimates of the quantum content of e.p.p.s could be made.

2. During repetitive nerve stimulation at rates between 2 and 10 Hz, e.p.p. amplitudes declined in response to the first 6–8 stimuli to reach a plateau level which was maintained for 1500 stimuli. At higher rates of stimulation some 500–700 stimuli were needed before a plateau level of amplitude was reached. It was demonstrated that these amplitude changes reflected similar changes in the quantal release of ACh.

3. Tubocurarine in a concentration of 4 × 10−8 g/ml. had no effect on quantal release but did reduce quantal size. In the presence of tubocurarine, 8 × 10−8 g/ml., small reductions in the quantum content of the first e.p.p. in response to a train of stimuli and the maintained quantal release were observed. In the presence of tubocurarine 4 × 10−7 g/ml., the quantum content of the first e.p.p. and the maintained release were further reduced, to the level previously described for curarized preparations. At this concentration a significant effect of tubocurarine upon the presynaptic measurements could be detected (t test). Studies on single junctions revealed that the post‐ and presynaptic effects of tubocurarine developed with different time courses.

4. Neuromuscular preparations in vivo have been reported to be much more resistant to maintatined stimulation than curarized neuromuscular preparations in vitro. It is suggested that this disparity is explained by the presynaptic action of tubocurarine.

5. From the quantal release rates of the present investigation and reports of ACh release/stimulus/end‐plate in previous investigations it can be calculated that a quantum of ACh contains between 12,000 and 21,000 molecules.
The specific effect of potassium on transmitter release by motor nerve terminals and its inhibition by calcium
Authors: Cooke J. D. , Quastel D. M. J.
Published: December 2014

1. There exist two distinct effects of potassium on the transmitter release system, one which develops rapidly and another which becomes maximal much more slowly. The fast effect is inhibited by raised Ca2+, which does not inhibit transmitter release evoked by depolarizing pulses. Thus the fast effect is not secondary to nerve terminal depolarization.

2. The fast effect of K+ was found to consist in an increase in the slope of the linear relation between log m.e.p.p. frequency and nerve terminal depolarization. This effect is complete within a few seconds, is inhibited by raised Ca2+, and is not produced by prolonged focal or electrotonic depolarization, which instead tends to reduce the slope of log m.e.p.p. frequency vs. depolarization.

3. A slope change effect like that of K+ was not found with ouabain or ethanol, nor did these agents depress the slope change effect of K+. The specific action of K+ was not exerted on release evoked in the absence of Ca2+ by ethanol, chloral hydrate, or raised osmotic pressure.

4. It is suggested that the specific action of K+ is to increase the lability of nerve terminal Ca permeability with respect to depolarization of the nerve terminal membrane, while the slow effect of K+ simply reflects nerve terminal depolarization, slow to become maximal because of diffusion barriers limiting access of raised K+ to the Ranvier nodes of motor axons.
Effect of sodium and sodium‐substitutes on the active ion transport and on the membrane potential of smooth muscle cells
Authors: Casteels R. , Droogmans G. , Hendrickx H.
Published: December 2014

1. The changes of the ion content and of the membrane potential of taenia coli cells have been studied during prolonged exposure to Na‐deficient solutions containing either Li or choline.

2. A K‐free solution containing either 71 m
M‐Na‐71 m
M‐Li or 71 m
M‐Na‐71 m
M choline causes a slower loss of cellular K than a 142 m
M‐Na solution. In both these Na‐deficient solutions the membrane hyperpolarizes to about −100 mV for periods up to 6 hr. This hyperpolarization is partially abolished by 2 × 10−5
M ouabain.

3. Replacing all extracellular Na by Li and maintaining 5.9 m
M‐K causes a fast loss of all Na and a progressive replacement of K by Li. These changes of the intracellular ion content are accompanied by a depolarization of the cells, suggesting that intracellular Li cannot substitute for Na in activating the ion pump.

4. Exposing K‐depleted cells to a K‐free 71 m
M‐Na‐71 m
M‐Li solution results in a ouabain sensitive transport of Na and Li against their electro‐chemical gradient.

5. The K‐uptake by K‐depleted cells from a solution containing 0.59 m
M‐K is increased by reducing [Na]o to half of its normal value. This finding indicates that external Na inhibits the active Na‐K exchange.

6. In Na‐enriched tissues half of the Na efflux is due to a ouabain insensitive Na‐exchange diffusion. If Li is used as a Na substitute, the Na‐Li exchange compensates for the diminution of the Na‐exchange diffusion unless ouabain is added.
Spontaneous activity in isolated bovine mesenteric lymphatics
Authors: Mawhinney H. J. D. , Roddie I. C.
Published: December 2014

1. Longitudinal tension was measured in isolated segments (approximately 20 mm in length and 2 mm in diameter) of bovine mesenteric lymphatic vessels.

2. Seventeen out of thirty‐nine vessels showed regular spontaneous rhythmic contractions, the most common frequency being about 2/min.

3. The strength of each contraction was related to the duration of the preceding pause, a longer pause being associated with a stronger contraction.

4. Noradrenaline increased the frequency and decreased the amplitude of the contractions. This effect was abolished by α‐receptor blockade with phentolamine.

5. Isoprenaline slowed the frequency of the contractions. This effect was abolished by β‐receptor blockade with propranolol.

6. Acetylcholine had little effect on the rate of spontaneous contractions.
Prostaglandin E2 and gastric acid secretion in man
Authors: Bennett A. , Stamford I. F. , Unger W. G.
Published: December 2014

1. Extracts of human stomach homogenized in Krebs solution had more PGE2‐like activity than tissue homogenized in acid/ethanol or in the presence of indomethacin, indicating that the tissue can synthesize PGE2.

2. The distribution and synthesis of PGE2‐like substance in human stomach was determined by extracting frozen sections cut parallel to the mucosal surface. Peak levels usually occurred at a depth of 0–600 μm in the mucosa.

3. Small amounts of a PGE2‐like substance were present in basal gastric juice, and its concentration was usually even lower in secretion stimulated by pentagastrin or histamine.

4. Submaximal acid secretion produced by I.V. infusion of pentagastrin generally fell slightly when indomethacin was administered rectally to inhibit PG synthesis.

5. These experiments, together with the findings that orally administered PGE compounds do not inhibit human gastric acid secretion, seem to argue against a possible inhibitory role for PGE2 in gastric acid secretion in man.

6. If this is so, it would follow that gastric bleeding caused by aspirin‐like drugs is not due to increased acid secretion. A hypothesis is presented that tissue damage following vasoconstriction and ischaemia, due to inhibition of PG synthesis in blood vessels, contributes to the bleeding.
Metabolic aspects of the synthesis and intra‐axonal transport of noradrenaline storage vesicles
Authors: Banks P. , Mayor D. , Mraz P.
Published: December 2014

1. Constricted cat hypogastric nerve/inferior mesenteric ganglion preparations have been maintained for 24 hr in vitro, in either test‐tubes or a two compartment box, and used to study the roles of energy metabolism, protein synthesis and calcium ions in the synthesis and transport of noradrenaline storage vesicles in sympathetic neurones.

2. When preparations were incubated so that the nerve trunks but not the ganglia were made anoxic, dense‐cored vesicles lost their store of noradrenaline and did not accumulate above the ligature. This was accompanied by profound ultrastructural damage to the nerves.

3. When in contact with the ligated nerve trunks, sodium fluoride inhibited the intra‐axonal movement of dense‐cord vesicles but did not deplete them of their stored noradrenaline. When sodium fluoride and pyruvate were present in the medium bathing the nerve trunks the movement of noradrenaline storage vesicles was unaffected.

4. Whilst a reduction of the calcium ion concentration in the incubation medium and the inhibition of protein synthesis by cycloheximide prevented the synthesis of dense‐cored vesicles in the neuronal perikaryon they had no effect on the movement of preformed dense‐cored vesicles along non‐myelinated axons.
Blood pressure effects obtained by drugs applied to the ventral surface of the brain stem
Authors: Guertzenstein P. G.
Published: December 2014

1. In cats anaesthetized with pentobarbitone sodium the effect on arterial blood pressure was examined of substances applied bilaterally to the exposed ventral surface of the brain stem by means of Perspex rings placed lateral to the pyramids and caudal to the trapezoid bodies. Routinely, atropine methyl nitrate, which does not pass the blood—brain barrier, was injected I.V.

2. The cholinomimetic substances carbachol and physostigmine, and the amino acids glycine and GABA, caused a fall in arterial blood pressure.

3. Atropine produced a small but definite rise in arterial blood pressure, antagonized the depressor effects of the cholinomimetic substances, but not those of the amino acids.

4. Strychnine, leptazol and tubocurarine, caused a rise in arterial blood pressure.

5. The depressor and pressor effects are due to changes in vasomotor tone. They are central effects brought about by penetration of the substances into the brain tissue from the ventral surface of the brain stem. They are not due to their absorption into the blood stream.

6. The depressor effects of the cholinomimetic substances may imitate the action of cholinergic neurones, and those of the amino acids that of central inhibitory neurones ending on cells near the ventral surface of the brain stem and exerting an inhibitory influence on vasomotor tone. The pressor effects of strychnine and tubocurarine may in part result from ‘disinhibition’, i.e. from an antagonistic action produced by these drugs on the amino acids released from the central inhibitory neurones.