bluuebunny/crossref_metadata_2025 huggingface dataset:
The surface area of sheep cardiac Purkinje fibres
Authors: Mobley Bert A. , Page Ernest
Published: December 2014

1. Measurements combining the techniques of point counting and line integration were performed on light and electron micrographs of Purkinje fibres from the sheep's heart. The measurements were aimed at determining membrane areas of importance for the cellular electrophysiology of this tissue.

2. The mean volume fractions of the cells occupied by various constituents were: myofibrils, 0·234; mitochondria, 0·103; and nuclei, 0·009. The mean volume fraction of the fibres occupied by the interspaces between the tightly packed cells was 0·0023.

3. The mean fractions of intercellular surface area occupied by junctional specializations were: nexus, 0·17; desmosome, 0·023; and fascia adherens, 0·014.

4. The mean surface to volume ratio of the Purkinje cells and fibres was 0·46 μ−1 which is 11·5 times the value of the surface to volume ratio of a long right circular cylinder 100 μ in diameter.

5. There are two reasons for the increment in the surface to volume ratio of the fibre (when compared to that of a long right circular cylinder 100 μ in diameter): the multicellular composition of the fibres and the extensive folding of the surface of the cells.

6. After correction for the intercellular nexal area the surface to volume ratio of a long cylindrical fibre 100 μ in diameter was 0·39 μ−1, or about 10 times the value for a long right circular cylinder 100 μ in diameter. The surface to volume ratio of the tissue interspaces in the same fibre was 170 μ−1.

7. It was concluded that the total sarcolemmal area in this tissue is great enough so that the specific membrane capacitance could be about 1 μF/cm2 and the specific membrane resistance 20,000 Ω cm2.
Activation heat, activation metabolism and tension‐related heat in frog semitendinosus muscles
Authors: Homsher E. , Mommaerts W. F. H. M. , Ricchiuti N. V. , Wallner A.
Published: December 2014

1. Frog semitendinosus muscles were stretched to various lengths beyond the rest length (l0) and their initial heat and isometric tension production were measured.

2. As the overlap between the thick and thin filaments is reduced, the initial twitch heat and tension decline in a linear manner. At a point at which the twitch tension approaches zero, the initial heat is 30% of that seen at l0. It is concluded that this heat is the activation heat and reflects the energetics of calcium release and reaccumulation. The initial heat at shorter sarcomere lengths appears to be the sum of the activation heat plus a heat production associated with the interaction of the thick and thin filaments.

3. A similar relationship between heat and tension production is seen in tetanic contractions.

4. The time course of activation heat production in a twitch can be resolved into two phases: a temperature insensitive (Q10 < 1·3) ‘fast’ phase (with a time constant of 45 msec) and a temperature sensitive (Q10 = 2·8) ‘slow’ phase (with a time constant of 330 msec at 0° C).

5. Measurements of the creatine phosphate (PC) hydrolysis by muscles contracting isometrically at various muscle lengths at and beyond l0, indicate an enthalpy change of −11·2 kcal/mole PC hydrolysed. The enthalpy change for the ATP hydrolysis by muscles stretched so that little or no tension was produced with stimulation was −9·9 kcal/mole ATP hydrolysed. It is concluded that the net activation heat is produced by the hydrolysis of PC or ATP.
Intracellular pH, H ion flux and H ion permeability coefficient in bullfrog toe muscle
Authors: Izutsu K. T.
Published: December 2014

1. The dimethyloxazolidinedione (DMO) technique was used to estimate intracellular pH (pHi) in bullfrog toe muscles incubated in vitro. The control value of pHi was 7·16 + ± 0·01 (
S.D.).

2. pHi was affected by changes in PCO2 and external bicarbonate ion concentration ([HCO3−]0). At a given PCO2, decreasing the external [HCO3−] was more effective in lowering pHi than increasing the external [HCO3−] was in increasing pHi.

3. On the assumption that the changes in pHi were due to hydrogen ion [H+) movements across the membrane, a H+ flux of 10−13 mole/cm2. sec was calculated. The corresponding H+ permeability coefficient was 10−3 cm/sec.

4. The variability of the tissue CO2 buffer value was examined.
Analysis of the membrane capacity in frog muscle
Authors: Hodgkin A. L. , Nakajima S.
Published: December 2014

1. The membrane capacity (Cf) was determined from the conduction velocity and the time constant of the foot of the action potential in frog's skeletal muscle.

2. In normal fibres Cf was 2·6 μF/cm2, and the value was almost constant over a range of diameter from 55 to 140 μ.

3. In fibres, in which the transverse tubular system was disconnected from the surface by the glycerol treatment, Cf was 0·9 μF/cm2 and was fairly constant over a range of diameter from 60 to 130 μ. The low frequency capacity in glycerol‐treated fibres was 1·9 μF/cm2.

4. These results as well as those obtained at low frequencies were consistent with the electrical model proposed by Adrian, Chandler & Hodgkin (1969).

5. Analysis in terms of the model and of Peachey's (1965) data on tubular dimensions led to the following quantitative conclusions. The capacities of the surface membrane (CS) and of the tubular wall (CW) are both about 1 μF/cm2. The conductances of the surface membrane (GS) and tubular wall (GW) are ca. 0·11 and 0·03 mmho/cm2, respectively. The conductivity of the luminal fluid in the tubules is ca. 6 mmho/cm.
Modifications of dorsal horn cell activities in the spinal cord, after intra‐arterial injection of bradykinin
Authors: Besson J. M. , Conseiller C. , Hamann K.‐F. , Maillard Marie‐Claude
Published: December 2014

1. A method is described to study the modification in the activity of the lamina IV and V cells of the dorsal horn under the intra‐arterial administration of bradykinin into the hind limb of the spinal cat.

2. The modifications induced by intra‐arterial injection of bradykinin preferentially affected the lamina V cells (77% of the units) and produced few changes in the lamina IV cells (16% of the units showed variations).

3. 52% of the lamina V cells were activated; the mean increase in the firing rate was 700%. The mean latency of the effect was 20 sec and the mean duration was 47 sec. However, there was large variance in the excitatory effect across cells. On the other hand, for the same cell, the observed effects were perfectly reproducible and injections of physiological fluid induced no response.

4. 25% of the lamina V cells were inhibited. Generally, the activity of the cell was reduced to 13% of its initial value; in some cases, a total suppression of activity was observed. The mean latency of the inhibitory effect was 12 sec and its duration 28 sec. All these units had a very wide inhibitory field (activated by stimulations of low intensity) which asymmetrically surrounds the excitatory field.

5. This study confirms the role played by the lamina V cells in the transmission of nociceptive messages. The existence of inhibitory phenomena is in favour of the gate control theory described by Melzack & Wall (1965) without deciding the pre‐ or post‐synaptic nature of these mechanisms.
The effects of vasopressin on the diuretic response to left atrial distension
Authors: Ledsome J. R. , Mason J. M.
Published: December 2014

1. The diuretic response to left atrial distension was studied during infusion of saline or during infusion of vasopressin at four different dose rates.

2. During infusion of saline left atrial distension caused an increase in free water clearance and an increase in osmolal clearance.

3. During infusion of vasopressin at a rate of 0·025 m‐u./kg.min and 0·1 m‐u./kg.min there was no statistically significant increase in free water clearance during left atrial distension but there were variations in free water clearance in individual experiments.

4. During infusion of vasopressin in doses of 0·4 m‐u./kg.min and 1·0 m‐u./kg.min changes in free water clearance were dependent upon changes in osmolal clearance indicating that these doses of vasopressin provided a maximum antidiuretic effect.

5. Infusion of vasopressin had no effect on the increase in osmolal clearance which occurred in response to left atrial distension.

6. The results allow the view that a part of the diuretic response to left atrial distension could depend upon a decrease in the concentration of antidiuretic hormone in the circulating blood.
Active secretion of thyroxine into bile: the role of tissue thyroxine‐binding sites
Authors: Hillier A. P.
Published: December 2014

1. An investigation has been made into factors regulating the secretion of thyroid hormones into bile. The preparation employed was the isolated rat liver perfused with a modified Tyrode solution.

2. Tracer amounts of radioactive thyroxine were injected into the Tyrode solution just before its entry into the liver. This allowed the thyroxine‐binding sites in the tissue to capture most of the injected hormone. It was found that this tissue‐bound hormone was then gradually secreted into the bile and that the process could be resolved into two components. There was a steady, continuous secretion of hormone, which maintained a fairly constant bile:liver ratio in thyroxine concentration of about 2·3. There was also, superimposed upon this, an extra transient secretion of thyroxine occurring just after the injection. This transient effect was abolished by injecting the hormone at 22° C and it was probably due to the sudden flood of free thyroxine into the tissue during the 15 sec injection period.

3. Very similar results were obtained with tri‐iodothyronine except that the secretion process maintained a higher bile:liver ratio of about 3·7.

4. The secretion mechanism was extremely sensitive to changes in temperature and it was able to generate very high concentrations of free thyroxine in the bile. It was concluded that the over‐all process was probably an active one.

5. The presence of 30% bovine serum in the perfusion fluid did not reduce the bile:liver thyroxine ratio even though it caused a massive fall in the amount of thyroxine in the tissue.

6. These results show that the rate of thyroxine secretion into bile is determined by the total amount of thyroxine trapped in the tissue. It is not directly related to the concentration of free thyroxine in the perfusing medium.

7. It is suggested that the secretion mechanism works from a small intracellular pool of free thyroxine which is in rapid exchange with the large pool of tissue‐bound hormone, and that thyroxine exchange between this small intracellular pool and the free thyroxine pool in the plasma is relatively slow.
Autoregulation of thyroxine secretion into bile
Authors: Hillier A. P.
Published: December 2014

1. An investigation has been made into the effect on thyroxine secretion into bile of suddenly raising the thyroxine concentration in the liver.

2. Isolated rat livers, perfused with Tyrode solution, were injected with trace amounts of radioactive thyroxine. This injected hormone was captured by the binding sites in the tissue and then gradually secreted into the bile. A second injection of 100 μg stable (non‐radioactive) thyroxine caused an enormous increase in the secretion rate. At its peak, the concentration of thyroxine in the bile was about 24 × its concentration in the liver (this was 10 × higher than the concentration ratio at tracer thyroxine levels). The effect extended well into the physiological range and injections of only 0·1 μg stable thyroxine caused a transient doubling of the secretion rate. Tri‐iodothyronine also accelerated thyroxine secretion but it was 30 × less potent than thyroxine.

3. In contrast, the secretion of tri‐iodothyronine into bile was only very slightly affected by injections of stable thyroxine or tri‐iodothyronine, the maximum response being a 20–30% increase in the secretion rate.

4. This autoregulating mechanism would help to stabilize the concentration of thyroxine in the tissues but not the concentration of tri‐iodothyronine.
An electrophysiological analysis of the synthesis of acetylcholine in preganglionic nerve terminals
Authors: Bennett M. R. , McLachlan Elspeth M.
Published: December 2014

1. An electrophysiological analysis has been made of the synthesis of acetylcholine (ACh) in the preganglionic nerve terminals of the isolated superior cervical ganglion of the guinea‐pig. The mean amplitude of excitatory post‐synaptic potentials recorded intracellularly was taken as a measure of the ACh output per impulse from the terminals of a preganglionic axon.

2. Prolonged repetitive stimulation of the cervical sympathetic trunk at 10 and 20 Hz led to a decline in ACh output over the first 5‐15 min and then a maintained output for periods of up to an hour. The mean level of maintained output was 0·4 of the peak initial output.

3. The maintained level of output was shown to be equal to the rate of synthesis of new transmitter and was not dependent on the addition of choline (3 × 10−5
M) to the fluid in the organ bath.

4. The ACh output per minute was shown to be directly proportional to the frequency of stimulation.

5. A model has been proposed of the storage and synthesis of ACh in preganglionic nerve terminals during prolonged stimulation, in which choline from the hydrolysis of released ACh is the main source of substrate for synthesis of new transmitter, and the rate at which synthesis proceeds is controlled by the rate at which transmitter is released.
Intestinal absorption rate of L‐methionine in man and the effect of glucose in the perfusing fluid
Authors: Cook G. C.
Published: December 2014

1. Using a double‐lumen tube perfusion system the rates of absorption of
L‐methionine and glucose from a 30 cm segment of the jejunum were estimated in eight relatively normal Zambian African subjects. The effect of each substrate on the absorption of the other has also been investigated. The solutions perfused were given at 12·0 ml. min−1, and contained (A) 100 m‐mole l.−1
L‐methionine, (B) 100 m‐mole l.−1
L‐methionine and 150 m‐mole l.−1 glucose and (C) 150 m‐mole l.−1 glucose.

2. The presence of glucose in the perfusing fluid did not significantly alter the mean absorption rate of methionine; in six subjects, the rate of methionine absorption from solution B was less than from solution A, but in two there was a marked difference in the opposite direction. This may indicate an individual difference in the effect of glucose on
L‐methionine absorption in man. The presence of methionine in the perfusing fluid did not significantly alter the mean absorption rate of glucose.

3. Five subjects had a transitory psychiatric disturbance after the investigation. The cause of this is not clear, but was probably caused by the absorption of a break‐down product of methionine from the large intestine.
Reflex discharge patterns of cardiac vagal efferent fibres
Authors: Kunze Diana Lee
Published: December 2014

1. Unit activity was recorded from single and few fibre preparations in a cardiac branch of the right vagus nerve of the cat.

2. Increases in blood pressure mediated solely by the right carotid sinus nerve produced bradycardia when all other nerves to the heart had been cut. Myelinated fibres in the cardiac branch of the right vagus nerve were reflexly activated by the same procedure.

3. The fibres were silent when blood pressure was below 140–150 mm Hg. As the pressure began to rise, they discharged phasically with the cardiac cycle. At pressures greater than 180 mm Hg, the discharge was continuous attaining maximum rates of 40/sec.

4. Stimulation of carotid body chemoreceptors also reflexly excited these fibres, as did stimulation of baroreceptors in both the left carotid sinus and aortic arch. Afferent fibres in the left vagus discharging in response to changes in blood pressure reflexly excited the cardiac efferent fibres. Increases in phrenic motoneurone discharge coincided with inhibition of these fibres. Electrical stimulation of the glossopharyngeal nerve also produced inhibition.
The effect of denervation on the mechanical and electrical responses of fast and slow mammalian twitch muscle
Authors: Lewis D. M.
Published: December 2014

1. The soleus (slow twitch), flexors digitorum and hallucis longus muscles (fast twitch) of the cat were denervated. Isometric contractions and electrical responses were examined 2–160 days after the operation.

2. In the first week the time course of the twitch and the ratio of tetanus tension to twitch tension were normal in both muscles. The maximum rate of rise of tension in the tetanus was reduced in fast muscles.

3. In the second week all the twitches showed a normal contraction phase but relaxations were interrupted by a repetitive after‐contraction. This became less marked after longer periods of denervation.

4. During the third and subsequent weeks, the contraction and relaxation phases of the twitches in all muscles became slower than normal. These changes were greater in fast muscles which, nevertheless, remained quite distinct from soleus. The ratio of tetanus tension to twitch tension fell below normal. It is suggested that these changes are brought about by more complete activation of the contractile proteins in a twitch. In flexor hallucis longus the rate of rise of tension in isometric tetani was found to be further reduced. No change was found in soleus.

5. In extracellular and intracellular records the initial response was a single action potential. An after‐discharge occurred in a proportion of fibres during the relaxation phase of the twitch.

6. The intracellularly recorded action potential was smaller and had a longer duration than that of normal muscle. Refractory period increased. Conduction velocity decreased. These changes were greater in fast muscle and differences between fast and slow twitch muscle were less marked than in normal muscle. Fibrillation potentials occurred at the same rate in fast and slow muscle.

7. The mechanisms of the mechanical changes are discussed and the possible relevance to the question of motor nerve influence on muscle is indicated.
Potentiation and depression of synaptic transmission in the olfactory cortex of the guinea‐pig
Authors: Richards C. D.
Published: December 2014

1. The extracellular field potentials of the olfactory cortex evoked by stimulation of the lateral olfactory tract (l.o.t.) were studied in in vitro preparations from the olfactory cortex. The field potentials comprised an initial diphasic wave — the l.o.t. compound action potential — followed by a negative wave of about 10 msec duration which in turn was followed by a low amplitude positive wave of long duration (100 msec or more). In this paper, the size of the negative field potential (extracellularly recorded EPSP) has been studied during and after periods of repetitive stimulation of the l.o.t.

2. If two identical volleys were delivered to the l.o.t. the second evoked EPSP was not the same size as the conditioning EPSP. At brief conditioning intervals (up to 10 msec) the second (test) EPSP was smaller than the control. For conditioning intervals between 10 and 200 msec, the test EPSP was potentiated over the control. For long conditioning intervals (300 msec up to 5 sec) the test EPSP was again slightly smaller than the control EPSP. After a brief conditioning train, the depression of a test EPSP (elicited 300 msec or more after the conditioning train) was more pronounced and lasted longer. These changes of test EPSP size were attributed to the presence of two opposing processes: an initial potentiation superimposed on a more prolonged but less pronounced depression.

3. During prolonged repetitive stimulation the final steady amplitude of an EPSP varied with the frequency of stimulation. At low frequencies (0·5–2/sec) the steady EPSP amplitude was 90–95% of the initial control amplitude. At moderate frequencies (5–20/sec) the steady EPSP amplitude was greater than the initial control. At high frequencies (above 20/sec) the steady amplitude of the EPSPs declined with increasing frequency of stimulation. Potentiation of EPSPs was observed early in a train of impulses when the stimulation frequency was 5–70/sec.

4. After a large number of stimuli at frequencies from 20 to 100/sec the amplitude of individual, infrequently evoked, EPSPs passed through a phase of depression that lasted about 30 sec. This depression was followed by a phase of potentiation (post‐tetanic potentiation). The amplitude and duration of post‐tetanic potentiation appeared to depend on the characteristics of the conditioning train.

5. The discussion compares the results obtained with those obtained for other mammalian synapses. It is suggested that the transmitter in the presynaptic terminals could be in three parts, (a) immediately available transmitter (b) conditionally available transmitter requiring a single nerve impulse for its availability and (c) main depot transmitter which replenishes the other two stores. Potentiation and depression of evoked EPSPs were interpreted in terms of changes in the amount of transmitter released by the test volley. According to this analysis, a fixed proportion (about 10%) of the immediately available transmitter is released by each nerve impulse.
The importance of timing on the respiratory effects of intermittent carotid sinus nerve stimulation
Authors: Eldridge Frederic L.
Published: December 2014

1. The respiratory response, measured directly as tidal volume or indirectly by using integrated peak phrenic activity, to intermittent electrical stimulation of the carotid sinus nerve was determined in anaesthetized cats.

2. Stimulation at rates of 20–25 Hz for 0·5 sec had a rapid effect, increasing inspiratory airflow and phrenic discharge, but only if applied during inspiration. An increase in tidal volume or peak level of integrated phrenic discharge occurred only if the stimulus was exhibited during the second half of inspiration. Continuous stimulation had no greater effect on size or frequency of breathing than did intermittent inspiratory stimuli alone. Stimulation during expiration had no effect on the form or magnitude of subsequent breaths.

3. Stimuli in expiration led to a prolongation of expiration. Stimuli in late inspiration caused a prolongation of both inspiration and expiration. Because of these effects, the respiratory rate could be changed by stimulation; in some instances entrainment of respiration by the intermittent carotid sinus nerve stimuli occurred.

4. The findings are attributable to modulation of incoming carotid sinus nerve information by the central respiratory neurones, which use primarily that which arrives during inspiration. They show a possible mechanism by which oscillating signals may have a different effect than their mean level would indicate.
The passage of calcium and strontium across the gut of the anaesthetized goat
Authors: Gibbons R. A. , Sansom B. F. , Sellwood R.
Published: December 2014

1. The translocation of calcium and strontium across the intestine of the anaesthetized goat has been studied. It has been found to be unaffected by ouabain, by the absence of sodium, by a severely hypertonic environment and by heparin and chondroitin sulphate. Thus it is unlikely that, in the intact goat, the trans‐mucosal sodium and calcium transport systems are interrelated.

2. The effect of sodium alginate both on the rate of absorption and the calcium/strontium discrimination ratio has been confirmed.

3. The movement of calcium ion in both directions across the intestinal mucosa has been studied and evidence for the active transport of calcium adduced.
Efflux of potassium from the isolated frog retina: a study of the photic effect
Authors: Cavaggioni A. , Sorbi R. T. , Turini S.
Published: December 2014

1. Illumination of the isolated frog retina reduces the efflux of 42K (and 86Rb).

2. Perfusion with a solution containing glutamate ions does not abolish the effect, although the electroretinogram is modified and the b‐wave absent in this condition.

3. Perfusion with a solution with only 2·36 m
M sodium abolishes the effect of light on the efflux of potassium (and rubidium).

4. The amplitude of the photic effect, measured in the first 2 min of illumination, is in linear proportion with the logarithm of the concentration of extracellular sodium ions.

5. A steady rate of absorption of a few quanta per rod and per second yields a just detectable effect on the efflux of potassium (and rubidium).

6. Strong illuminations followed by darkness reduce the efflux of rubidium for a period of time roughly comparable to the time of dark adaptation.

7. The interpretation is proposed that the photoreceptor cells (and possibly other retinal cells too) cause the effect, and that the retention of potassium induced by light is secondary to the hyperpolarization of their membrane.
The effect of muscle length and rate of fusimotor stimulation on the frequency of discharge in primary endings from muscle spindles in the cat
Authors: Lewis D. M. , Proske U.
Published: December 2014

1. Responses from the primary endings of muscle spindles in the soleus muscle of the cat were recorded during repetitive fusimotor stimulation at a number of different muscle lengths.

2. An increase in the rate of stimulation increased the size of both the peak and the plateau of the responses to stimulation of both static and dynamic fusimotor fibres.

3. Responses, with the exception of the peak frequency of the discharge during dynamic fusimotor stimulation, increased in size on raising the muscle length up to maximum body length. The peak of the dynamic response reached its highest value at intermediate lengths.

4. The effect of increasing stimulation rate and muscle length was to reduce both the latency and time to peak of fusimotor responses. The change in latency with muscle length was particularly dramatic at low stimulus rates.

5. In an attempt to compare fusimotor responses with the behaviour of extrafusal muscle fibres, a model is proposed which consists of a mixture of extrafusal tension and rate of change of tension. This model could simulate the static fusimotor responses reported here.
Synaptic actions of single interneurones mediating reciprocal Ia inhibition of motoneurones
Authors: Jankowska Elżbieta , Roberts W. J.
Published: December 2014

1. The investigation was aimed at defining the function of the interneurones which, according to indirect evidence, mediate the reciprocal Ia inhibition of motoneurones (Hultborn, Jankowska & Lindstrom, 1971 b) by studying their direct synaptic actions. These actions were tested by recording post‐synaptic potentials in motoneurones following spike activity of single interneurones activated by iontophoretic application of glutamate. The interneurones were found to produce unitary monosynaptic IPSPs in those motoneurones in which disynaptic IPSPs are evoked by the group Ia afferents which monosynaptically excite the interneurones.

2. Unitary IPSPs were found in more than 80% of the motoneurones impaled in the immediate vicinity of the axonal branches of the investigated Q interneurones in the PBSt motor nucleus. It is estimated that each interneurone might inhibit about every fifth PBSt motoneurone. The amplitudes of the unitary IPSPs ranged between 8 and 220 μV and were 10–200 times smaller than the maximal Ia IPSPs evoked in the same motoneurones.

3. The synaptic delay in the generation of unitary IPSPs was measured in relation to the spike potentials recorded from the terminal branches of interneurones in the immediate vicinity of the impaled motoneurones. The synaptic delays ranged between 0·28 and 0·42 msec.

4. From chloride reversal tests and an analysis of the time course of the unitary IPSPs it was concluded that the terminals of the investigated interneurones make synaptic contact predominantly on the soma and/or on the proximal parts of the dendrites of the motoneurones, their distribution being, however, not quite uniform.
Calcium uptake and force development by skinned muscle fibres in EGTA buffered solutions
Authors: Ford L. E. , Podolsky R. J.
Published: December 2014

1. The uptake of 45Ca and the development of force by segments of skinned muscle fibres were measured in Ca solutions buffered with EGTA. When the Ca ion concentration in these solutions was above the contraction threshold, Ca was accumulated by the sarcoplasmic reticulum during the delay phase before force developed. The uptake rate increased, and the length of the delay decreased, when the concentration of the calcium buffer was increased.

2. The maximum accumulation of Ca was 2–3 m
M. Force developed, ending the delay phase, when the calcium uptake approached this maximum level.

3. The pattern of force development suggested that this process was often accompanied by a sudden release of accumulated Ca.

4. The relation between the kinetics of 45Ca uptake and the interaction of calcium with EGTA and the sarcoplasmic reticulum is discussed. The data indicate that at the low concentrations necessary for relaxation the sarcoplasmic reticulum takes up Ca fast enough to account for the rate at which force falls when intact muscle fibres relax.
The isolation of a renally active substance from arterial blood
Authors: Lockett Mary F. , Retallack R. W.
Published: December 2014

1. A substance (Art. HS) which resembles the 18‐monoacetate of
D‐aldosterone (18 MA) in its biological actions is found in arterial blood of cats and sheep: Art. HS is assayed in terms of antidiuretic activity equivalent to synthetic 18 MA.

2. In cats under chloralose anaesthesia, dialysis of arterial blood (2–3 ml./min) in a small external circuit (8–15 ml.) without disturbance of heart rate, blood pressure or respiration, predicts a physiological concentration of Art. HS equivalent to 31·5–51·9 ng 18 MA/100 ml. Efficiency of dialysis assumed in this calculation is 100%.

3. Art. HS is almost evenly distributed throughout the plasma and formed elements of blood.

4. Concentrations of Art. HS found during severe arterial haemorrhage are equivalent to 188 ± 6·7 and 151 ± 9·2 ng 18 MA/100 ml. in cats and sheep respectively.

5. Art. HS has been isolated from 27·6 l. sheep arterial blood by ethyl acetate: chloroform 1:1 extraction, defatting by partitioning between methanol and petroleum ether and purifying by seven‐stage thin layer chromatography on MN Kieselgel UV254. Final yield was equivalent in activity to 21·6 μg 18 MA. Synthetic 18 MA was used as RF marker. Spots of 2 μg 18 MA are visible on MN Kieselgel UV under U.V. Art. HS activity equivalent to 21·6 μg 18 MA cannot be seen.

6. Art. HS was not detectable in IVC blood of cats under chloralose anaesthesia during haemorrhage. The threshold for detection was the equivalent of 15–20 ng 18 MA/100 ml.

7. Art. HS resembles a substance liberated by the heart (Lockett & Retallack, 1970a, b, 1971) in chromatographic properties, biological properties and stability in aqueous solution. Art. HS is very much more stable in aqueous solution than 18 MA.
The release of prostaglandins and progestin into the utero‐ovarian venous blood of guinea‐pigs during the oestrous cycle and following oestrogen treatment
Authors: Blatchley F. R. , Donovan B. T. , Horton E. W. , Poyser N. L.
Published: December 2014

1. Blood was collected from the utero‐ovarian vein of guinea‐pigs on days 3, 9, 10, 11, 12, 13, 14 and 15 of the oestrous cycle, and from animals injected with oestrogen over days 4–6 and used on day 7. The content of prostaglandin F2α and E2 was determined by bio‐assay and gas chromatography‐mass spectrometry, and of progestin by competitive protein binding assay.

2. The concentration of prostaglandin F2α on day 3 was 14·1 ng/ml.; it fell below detectable limits on day 7, but after day 11 the concentration rose to between 15·7–17·2 ng/ml. A value of 60·7 ng/ml. was recorded on day 15.

3. The release of prostaglandin F2α was increased in animals pre‐treated with oestrogen but was below threshold levels in similarly treated hysterectomized females.

4. Prostaglandin E2 was not detectable in blood collected on days 3, 9, 10, 11 and 12. From a threshold value of 1·1 ng/ml. on day 13, the concentration rose to 5·4 ng/ml. on day 14 and to 54·9 ng/ml. on day 15.

5. The progestin concentration rose from 66 ng/ml. on day 3 to values of 80–180 ng/ml. between days 9–14. It fell to 45 ng/ml. between days 14 and 15.

6. This work establishes that prostaglandin F2α is released into the utero‐ovarian venous blood, and that its concentration fluctuates in the course of the oestrous cycle and can be related to changes in luteal function.
Effect of acid‐base alterations on hepatic lactate utilization
Authors: Goldstein Philip J. , Simmons Daniel H. , Tashkin Donald P.
Published: December 2014

1. The effect of acid‐base changes on hepatic lactate utilization was investigated in anaesthetized, mechanically ventilated dogs.

2. Portal vein flow and hepatic artery flow were measured with electromagnetic flowmeters, lactate concentration of portal vein, arterial and mixed hepatic venous blood was determined by an enzymatic technique, and hepatic lactate uptake was calculated using the Fick principle.

3. Respiratory alkalosis (Δ pH 0·25 ± 0·02) in four dogs resulted in a significant fall in total hepatic blood flow (−22 ± 4%) and a significant rise in both arterial lactate concentration (2·18 ± 0·32 m‐mole/l.) and hepatic lactate utilization (3·9 ± 1·2 μmole/min.kg).

4. 0·6
M‐Tris buffer infusion (Δ pH 0·21 ± 0·02) in four dogs produced no significant changes in liver blood flow, arterial lactate concentration or hepatic lactate uptake.

5. Respiratory acidosis (Δ pH −0·20 ± 0·03) in six dogs and metabolic acidosis (Δ pH −0·20 ± 0·02) in four dogs produced no significant changes in liver blood flow, decreases in arterial lactate concentration of 0·38 ± 0·09 m‐mole/l. (P < 0·05) and 0·13 ± 0·13 m‐mole/l., respectively, and no significant changes in hepatic lactate uptake.

6. A significant correlation (r = 0·63; P < 0·01) was found between hepatic lactate utilization and arterial lactate concentration during the hyperlactataemia associated with respiratory alkalosis.

7. Hyperlactataemia induced in four dogs by infusion of buffered sodium lactate (Δ pH 0·05 ± 0·01;% Δ liver blood flow 29 ± 7%) was also significantly correlated with hepatic lactate utilization (r = 0·70; P < 0·01) and the slope of the regression was similar to that during respiratory alkalosis.

8. These data suggest that the hyperlactataemia of alkalosis is not due to impaired hepatic utilization of lactate and that the principal determinant of hepatic lactate uptake during alkalosis or lactate infusion is blood lactate concentration, rather than liver blood flow or acid‐base status.
Absence of compensatory renal hypertrophy in baboons
Authors: Dicker S. E. , Morris Christine A.
Published: December 2014

1. The weights of kidneys of fifteen adolescent and forty‐six adult male baboons were estimated. In contrast with what has been described in other mammals, in the majority of baboons (thirty‐nine out of fifty‐seven) the left kidney was heavier than the right.

2. The medulla/cortex ratio was of the order of 1·8. The maximum urinary concentration, after 36 hr of food and water deprivation, averaged 1050 ± 80 m‐osmole/kg H2O.

3. Unilateral nephrectomy was performed in twelve baboons with body weight ranging from 5 to 14 kg. In six animals, the left kidney was removed and the right kidney in the others.

4. In two baboons, the left kidney was transplanted to the left iliac artery and vein, the ureters being left intact. After a few weeks, the right kidney was taken out, and the animals were kept under observation, one for a further 3 months and the other for a further 4 months.

5. In none of the animals, whether after simple unilateral nephrectomy or after unilateral nephrectomy following transplant of one kidney, did the renoprival kidney show any significant enlargement.

6. After unilateral nephrectomy, the health of the animals remained excellent, all the baboons increasing in body weight. The ability to concentrate urine by the renoprival kidney was not impaired.

7. In contrast with what has been described in mice and rats, in unilaterally nephrectomized baboons no significant changes in the concentration of either RNA or DNA in renal cortex and medulla of the contralateral kidney were observed.

8. After unilateral nephrectomy in baboons, there was a marked increase of oxygen uptake in slices from the cortex, but not from the medulla. In contrast with what had been observed in rats where the enhanced rate of oxygen uptake returned to pre‐operative values, in baboons no decrease was observed, the rate of oxygen uptake remaining high during the whole period of observation.

9. In the limit of time of observation (maximum 4 months) there was no evidence that unilateral nephrectomy resulted in compensatory hypertrophy of the contralateral kidney.
The effect of low temperature on the excitation‐contraction coupling phenomena of frog single muscle fibres
Authors: Caputo Carlo
Published: December 2014

1. Potassium contractures are affected by low temperature: the maximum contracture tension is diminished by about 15% at 3° C, while the response time course is greatly prolonged.

2. The contractile threshold for potassium contractures is lowered by about 10 mV at 3° C.

3. The fibre's membrane is depolarized by approximately the same amount when exposed to solutions with increased potassium concentrations at 20 or 3° C.

4. The repriming process, that is, the process by which the fibres recover their contractile ability following a potassium contracture, proceeds about six times slower at 3° C. This effect is not due to failure of the fibres to repolarize in the cold when transferred from a high potassium to a low potassium medium.

5. At low temperature repolarization occurs, even though it is somewhat slower. Following the solution change, from 190 m
M potassium to a low potassium solution, the initial rate of repolarization is 8·5 mV/sec at 20° C, and 3·4 mV/sec at 3° C. This effect is not sufficient to account for the delay in the repriming process.

6. After a potassium contracture, recovery of the fibre's twitching ability at 3° C is also delayed. At a time when twitches have not yet been recovered, membrane potentials of −90 mV and almost normal action potentials can be recorded.
Post‐stimulus hyperpolarization and slow potassium conductance increase in Aplysia giant neurone
Authors: Brodwick M. S. , Junge D.
Published: December 2014

1. Intracellular records from Aplysia giant (R2) cell somata showed long lasting 4–10 mV hyperpolarizations after passage of outward current through a second intracellular electrode.

2. An increase in membrane slope conductance occurred simultaneously with the post‐stimulus hyperpolarization (PSH).

3. Both the PSH and conductance‐increase varied strongly with stimulus amplitude and duration.

4. Both the PSH and the conductance increase occurred in Ca‐free medium containing tetrodotoxin, when action‐potential production was completely blocked.

5. The PSH persisted in the presence of ouabain or DNP, with cooling, with removal of external K+, and in media where all the Na+ was replaced with Li+, suggesting that it was not due to the activity of an electrogenic pump.

6. A reversal potential for the PSH was demonstrated by application of maintained inward current following the end of an outward‐directed stimulus.

7. The PSH reversal potential varied with [K]o, but not with [Cl]o or [Na]o, suggesting that the PSH was mainly due to an increase in K conductance.

8. The PSH and the conductance increase were reduced strongly when all the Na+ was replaced with Tris, and only slightly when Na+ was replaced with sucrose.
Potassium activated phosphatase from human red blood cells. The effects of p‐nitrophenylphosphate on cation fluxes
Authors: Garrahan P. J. , Rega A. F.
Published: December 2014

1. When red cells are incubated in solutions containing p‐nitrophenyl‐phosphate (p‐NPP), intracellular p‐NPP quickly builds up reaching with a half‐time of 3 min a concentration in cell water equal to one fourth the external concentration, which under the conditions used is the expected value for a divalent anion in Gibbs—Donnan equilibrium. Hence p‐NPP added to the incubation media in red cells has quick access to the active centre of the membrane phosphatase which is located at the inner surface of the cell membrane.

2. When p‐NPP is added to the incubation media of ATP‐free red cells or reconstituted ghosts, no ouabain‐sensitive cation movements are detectable, suggesting that hydrolysis of p‐NPP by the active transport system is unable to energize active ion translocation.

3. When p‐NPP concentration in the incubation media of ATP‐containing cells is progressively raised, both ouabain‐sensitive Na loss and ouabain‐sensitive Rb uptake tend to zero along rectangular hyperbolae. For both movements inhibition is half‐maximal at 77 m
M external p‐NPP (i.e. 19 m
M internal p‐NPP).

4. p‐NPP inhibits with equal effectiveness the Na:K and the Na:Na exchanges catalysed by the Na pump.

5. The inhibitory effect of p‐NPP cannot be attributed to the products of its hydrolysis, is inversely related to the intracellular ATP concentration and seems to be exerted at the inner surface of the cell membrane with an apparent affinity similar to that of the membrane phosphatase. These facts suggest that inhibition is mediated by the combination of p‐NPP with the active centre of the membrane phosphatase.

6. Apart from affecting the ouabain‐sensitive cation movements, p‐NPP increases the ouabain‐resistant uptake and loss of both Na and Rb. This effect is about 4 times larger for Rb than for Na, and its kinetic analysis suggests that it is due to an increase in the passive permeability of the cell membrane.

7. The increase in passive cation permeability upon addition of p‐NPP cannot be attributed to the products of its hydrolysis. It seems to be due to the combination of p‐NPP with a site which, like the active centre of the ouabain‐resistant membrane phosphatase, faces the inner surface of the cell membrane, is unaffected by ATP and is half saturated by about 15 m
M‐p NPP.
Thermoregulatory effects of intraventricular injection of noradrenaline in the mouse and the influence of ambient temperature
Authors: Handley Sheila L. , Spencer P. S. J.
Published: December 2014

1. At an ambient temperature of 20° C, intraventricular injection of noradrenaline in the mouse resulted in hypothermia accompanied by a fall in metabolic rate and by cutaneous vasodilatation. Subcutaneous injection of noradrenaline resulted in hyperthermia with raised metabolic rate and cutaneous vasodilatation.

2. The hypothermia and fall in oxygen consumption rate following intraventricular noradrenaline were prevented by pre‐treatment with subcutaneous propranolol, while the cutaneous vasodilatation was un‐affected. However, the effects of subcutaneously injected noradrenaline were completely abolished by subcutaneous propranolol. Intraventricular propranolol did not modify the hypothermic effect of intraventricular noradrenaline.

3. The direction of the effect on body temperature of intraventricular noradrenaline was dependent upon ambient temperature; hypothermia occurring at low (15° C) and hyperthermia at high (36° C) ambient temperatures. However, when the possibility of any peripheral action of noradrenaline escaping into the systemic circulation was prevented by prior subcutaneous injection of propranolol, significant hypothermia could be detected at temperatures as high as 32° C.

4. The possibility that the effects of intraventricular noradrenaline could be due to complete abolition of central temperature regulation was further excluded by the occurrence of thermal salivation in all animals during experiments performed at 36° C.

5. It is suggested that, in the mouse, the hypothermic actions of intraventricular noradrenaline are due to a central effect, while its hyperthermic effects at high ambient temperature are due to escape of noradrenaline into the peripheral circulation. The hypothermia could be the result of selective activation of central heat loss mechanisms.

6. Intraventricular noradrenaline was without effect on brain plasma‐space although exposure to 100% oxygen caused a detectable fall.
Preliminary observations on the mechanical and electrical activity of the rat ureter
Authors: Tindall A. R.
Published: December 2014

1. The electrical and mechanical activity have been recorded from the rat ureter in situ.

2. The frequency of peristaltic contractions is usually about 25/min, and each peristalsis is preceded by electrical activity which normally travels from the renal end of the ureter towards the vesicular end. The electrical and mechanical activities are closely correlated.

3. The velocity of propagation of the electrical activity is about 20 mm/sec.

4. The normal electromyogram probably arises in the first 5 mm of the renal end of the ureter, and retrograde activity may arise from a similar region at the vesicular end of the ureter.

5. A close arterial injection technique shows that the proximal end of the ureter behaves as if it possessed α‐receptors; the distal end behaves as if it had β‐receptors. This conclusion is discussed.
The actions of dibutyryl cyclic adenosine 3′,5′‐monophosphate and methyl xanthines on pancreatic exocrine secretion
Authors: Case R. M. , Scratcherd T.
Published: December 2014

1. The effects of dibutyryl cyclic adenosine 3′,5′‐monophosphate (dibutyryl cyclic AMP) and theophylline have been tested in the stimulated and unstimulated perfused cat pancreas.

2. Dibutyryl cyclic AMP (1·0 m
M) elicited the secretion of water and electrolytes, but not of enzymes, from this preparation. The composition of this secretion was the same as that secreted in response to secretin. This response could be slightly potentiated by theophylline.

3. Theophylline, theobromine and caffeine all markedly potentiated submaximal secretin stimulation, the relative effectiveness of these methyl xanthines being the same as that observed in the inhibition of pure phosphodiesterase prepared from beef heart.

4. At high concentration, theophylline had two effects: it was capable of initiating electrolyte and water secretion alone (whilst having only a very small stimulatory effect on enzyme secretion); it also had an inhibitory effect on secretion stimulated maximally by secretin.

5. Thus it was easy to mimic the action of secretin, but not pancreozymin, using dibutyryl cyclic AMP and theophylline. This suggests that the action of secretin, but not that of pancreozymin, may be mediated through cyclic AMP. Further evidence is, however, needed before these conclusions can be made with confidence.