bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of sodium on calcium movements and catecholamine release in thin slices of bovine adrenal medulla.
Authors: Rink T J
Published: December 2014

1. 45Ca efflux and uptake, net Ca movements, and catecholamine secretion were studied in thin slices of bovine adrenal medulla. 2. There was a slow component of 45Ca wash‐out which is attributed to efflux to intracellular Ca. This efflux was strongly influenced by cations in the external solution, being reduced by 50% when Mg replaced Ca, and the residual efflux being reduced by 80% when choline replaced Na. 3. None of the substitutes tested, choline, K, Li, Tris or sucrose, could replace Na in maintaining 45Ca efflux into Ca‐free solution. The Na‐dependent Ca efflux showed sigmoidal activation by Na, indicating a requirement for the co‐operative action of two or more Na ions in the extrusion of each Ca. 4. In the presence of 3‐6 mM‐Ca, Na deprivation failed to reduce 45Ca efflux. When K, Li and choline replaced Na the rate constant of 45Ca efflux increased. 5. Ca‐dependent 45Ca efflux was studied by adding back Ca to Ca‐free solutions. Its activation by Ca was hyperbolic indicating that one external Ca is involved in the extrusion of each Ca, consistent with a Ca:Ca exchange process. The apparent affinity for Ca and the maximal efflux were different in the presence of different monovalent cations. 6. 45Ca uptake was increased when Li or choline replaced Na in a solution containing 3‐6 mM‐Ca. Net Ca uptake also increased, but to a much smaller extent, supporting the idea of a Ca:Ca exchange process. 7. Mg had little effect in activating or inhibiting 45Ca efflux. Co appeared to act as a weak agonist and weak inhibitor of Ca‐dependent 45Ca efflux. Ba strongly activated 45Ca efflux.8. Elevation of [Na]t, with ouabain treatment, did not appreciably affect Na‐dependent 45Ca efflux. This may indicate that while this Ca efflux is dependent on external Na, it is not dependent on the Na gradient. Elevation of [Na]i had rather little effect on 45Ca uptake. 9 Exposure of slices to Li or choline solutions evoked a Ca‐dependent increase in catecholamine output. This could be attributed to the observed increase in net Ca uptake in these conditions. Sucrose and Tris solutions produced Ca‐independent secretory responses with quite different time courses. These results emphasize the importance of the Na substitute used in determining the secretory effect of Na deprivation. 10. Elevation of [Na]i did not change basal catecholamine release, nor did it greatly affect the secretory response to Na deprivation. 11. Only some of the secretory effects of NA deprivation can be attributed to the influence of Na on Ca movements.
A dissociation between temperature regulation and fever in the rabbit.
Authors: Borsook D , Laburn H P , Rosendorff C , Willies G H , Woolf C J
Published: December 2014

1. The role of 5‐hydroxytryptamine (5‐HT) in temperature regulation and in fever in the rabbit has been investigated. 2. Intrahypothalamic microinjections of 5‐HT in the conscious rabbit alters body temperature in a dose‐dependent manner. 3. Low doses (5‐5nmol) of 5‐Ht and control saline injections produced a small, non‐significant increase in temperature, with a long latency. 4. Doses of 14 nmol 5‐HT produce a hyperthermia with a 45 min delay; while microinjections of 28 nmol result in a biphasic response; an initial short hypothermia is followed later by a hyperthermia. 5. Depleting the rabbit's brain of 5‐HT by pretreatment with p‐chlorophenylalanine (PCPA) fails to affect its body temperature at thermoneutral temperatures but significantly impairs the ability to thermoregulate against a cold stress. 6. PCPA pretreatment did not, however, impair the febrile response to bacterial pyrogen and prostaglandin E1. 7. These results reveal a dissociation between the effects of 5‐HT depletion on temperature regulation, and on fever. The site of action of 5‐HT in temperature regulation must be proximal to the fever input, but distal to the convengence of peripheral and hypothalamic temperature inputs.
Cone pigments in human deutan colour vision defects.
Authors: Alpern M , Wake T
Published: December 2014

1. The Nagel anomaloscope, neutral points and dichromatic matches to a spectral green light identified a population of seventy red‐green dichromats. 2. The anomaloscope settings allow the calculation of the relative action spectrum of the match at the wave‐length of the red (645 nm) and green (535 nm) primaries. The distribution of this ratio is bimodal; there are two clusters with a gap of about 0‐75 long units between. Among the thirty‐eight deuteranopes there are wide differences in anomaloscope matches; similar differences appear among the thirty‐two protanopes. 3. Retinal densitometry of the foveas of fifteen of the deuteranopes is compared and contrasted with measurements on trichromats. In the former, only one photolabile pigment is found in the red‐green region of the spectrum; normals always have two. The view of Rushton (1965a) that deuteranopes have erythrolabe but no measurable chlorolabe is confirmed for each member of this group. 4. Simple deuteranomalous show two red‐green cone pigments. The difference spectra of extreme deuteranomalous are very similar to those found in deuteranopia. 5. Individual differnce in kinetics (photosensitivity, time constant of regeneration) and in the density and lambdamax of the difference spectrum of erythrolabe in deuteranopia are appreciable; the reasons for these differences are not clear.
Detection of light‐induced changes of intracellular ionized calcium concentration in Limulus ventral photoreceptors using arsenazo III
Authors: Brown J. E. , Brown P. K. , Pinto L. H.
Published: December 2014

1. The metallochromic indicator dye, arsenazo III, was injected intracellularly into Limulus ventral photoreceptor cells to concentrations greater than 1 m
M.

2. The absorption spectrum (450‐750 nm) of the dye in single dark‐adapted cells was measured by a scanning microspectrophotometer. When a cell was light‐adapted, the absorption of the dye changed; the difference spectrum had two maxima at about 610 and 660 nm, a broad minimum at about 540 nm and an isosbestic point at about 585 nm.

3. When intracellular calcium concentration was raised in dark‐adapted cells previously injected with arsenazo III, the difference spectum had two maxima at about 610 and 660 nm, a broad minimum at about 530 nm and an isosbestic point at about 585 nm. The injection of Mg2+ into dark‐adapted cells previously injected with the dye induced a difference spectrum that had a single maximum at about 620 nm. Also, decreasing the intracellular pH of cells previously injected with the dye induced a difference spectrum that had a minimum at about 620 nm. The evidence suggests that there is a rise of intracellular ionized calcium when a Limulus ventral photoreceptor is light‐adapted.

4. The intracellular calcium concentration, [Ca2+]1, in light‐adapted photoreceptors was estimated to reach at least 10−4
M by compaing the light‐induced difference spectra measured in ventral photoreceptors with a standard curve determined in microcuvettes containing 2m
M arsenazo III in 400 m
M‐KCl, 1 m
M‐MgCl2 and 25 m
M MOPS at pH 7·0.

5. In cells injected to less than 3 m
M arsenazo III, light induced a transient decrease in optical transmission at 660 nm (T660). This decrease in T660 indicates that illumination of a ventral photoreceptor normally causes a transient increase of [Ca2+]1.

6. Arsenazo III was found to be sensitive, selective and rapid enough to measure light‐induced changes of intracellular ionized calcium in Limulus ventral photoreceptor cells.
Effects of cardiac aglycones on the sodium efflux in barnacle muscle fibres.
Authors: Bittar E E , Brown D J
Published: December 2014

1. External application of 10(‐4) M digitoxigenin caused an 80% fall in the Na efflux in barnacle muscle fibres. The observed inhibition was irreversible and could be produced by as little as 10(‐7) M digitoxigenin. 2. Internal application of 10(‐2) M digitoxigenin lowered the Na efflux by 46% but was without effect following addition of external ouabain or K removal. 3. External application of digitoxigenin (or ouabain) following internal application of the aglycone was without effect on the Na efflux. 4. The efflux of [3H]digitoxigenin was fairly rapid, whereas that of [3H]ouabain was slow. 5. Inhibition of the Na efflux by internal application of digitoxigenin is probably the result of an action of the aglycone on the external side of the membrane following its leakage from the fibre interior.
The effect of temperature on the potential difference and input resistance of rat seminiferous tubules
Authors: Gladwell R. T.
Published: December 2014

1. The p.d. of rat seminiferous tubules was 5·86 ± 0·15 mV, lumen negative, at 33° C and varied linearly with temperature between 24 and 37° C, exhibiting an apparent Q1025-35° C of 2·0 with a slope of 0·43 mV/° C. Exposing testes to a temperature of 37‐43° C resulted in an initial hyperpolarization followed by depolarization of the tubules. These changes were more rapid in testes exposed to 41‐43° C than in testes exposed to 37‐39° C.

2. The Rin of seminiferous tubules was 198 ± 7·8 kΩ at a testis temperature of 33° C. The Rin decreased when testes were maintained at 37 and 41° C, the rate of decrease being similar to the rate of depolarization.

3. Exposing testes to deep body temperature by unilateral surgical cryptorchidism caused a reduction of 30 and 64% in tubular p.d. and Rin respectively when measured 24 hr after surgery. Exposure to deep body temperature for up to 4 days did not cause any further change in either parameter.

4. There was no evidence that lanthanum penetrated through the Sertoli cell tight junctions after exposing testes to 41° C for up to 30 min.

5. The results indicate that the seminiferous tubule p.d. is maintained by a temperature‐sensitive, cellular mechanism. Exposing testes to deep body temperature or above depolarized the tubules and increased their permeability.
Oscillation of the human ankle joint in response to applied sinusoidal torque on the foot
Authors: Agarwal Gyan C. , Gottlieb Gerald L.
Published: December 2014

1. Low‐frequency (3‐30 Hz) oscillatory rotation of the ankle joint in plantarflexion—dorsiflexion was generated with a torque motor. Torque, rotation about the ankle and electromyograms (e.m.g.s) for the gastrocnemius—soleus and the anterior tibial muscles were recorded.

2. Fourier coefficients at each drive frequency were used to calculate the effective compliance (ratio of rotation and torque). The compliance has a sharp resonance when tonic, voluntary muscle activity is present.

3. The resonant frequency of compliance is between 3 and 8 Hz. The location of the resonant frequency and the magnitude of the compliance at resonance depend upon both the degree of tonic muscle activity and the amplitude of the driving torque. The resonant frequency increases with increasing tonic activity.

4. With tonic muscle activity, the compliance in the frequency range below resonance increases with increasing amplitudes of driving torque.

5. The e.m.g., when evoked by the rhythmic stretch, lags the start of stretching by between 50 and 70 msec.

6. When tonic muscle activity is present, the resonant frequency of the stretch reflex is between 5 and 6·5 Hz.

7. Following the start of driven oscillation at frequencies near resonance, slowly increasing amplitudes of angular rotation (to a limit) are observed.

8. Distortion (from the sinusoidal wave shape) of angular rotation is frequently observed with drive frequencies between 8 and 12 Hz during which there sometimes occur spontaneous recurrences of oscillation at the drive frequency. For the angular rotation, a significant portion of the power may be in subharmonic frequency components of the drive frequency when that frequency is between 8 and 12 Hz.

9. Self‐sustaining oscillation (clonus) near the resonant frequency of the compliance is sometimes observed after the modulation signal to the motor is turned off. This is most often seen when the gastrocnemius—soleus muscles are fatigued. Clonus may be evoked by driven oscillation at any frequency.

10. The hypothesis that physiological tremor, which occurs between 8 and 12 Hz, is a consequence of stretch reflex servo properties seems to be at odds with the observations of resonance in the compliance and of self‐generated clonus both occurring in the 5‐8 Hz region.
Hyperpolarizing effects of dopamine on chemoreceptor nerve endings from cat and rabbit carotid bodies in vitro
Authors: Sampson S. R. , Vidruk E. H.
Published: December 2014

1. The effects of dopamine on DC potential changes recorded from the carotid sinus nerve were studied in vitro using carotid bodies and associated sinus nerves removed from anaesthetized cats and rabbits.

2. The carotid body was placed in one compartment of a superfusion chamber and was superfused with buffered salt solution. The carotid sinus nerve was led into an adjoining compartment, containing lightweight mineral oil, for recording DC potential changes with chlorided silver electrodes.

3. Dopamine injected into the superfusing solution in amounts of 50‐250 μg caused hyperpolarization of the DC potential. This effect occurred repeatedly in each preparation, the maximum number of tests in any one preparation being twenty‐seven.

4. In the same preparations, acetylcholine (50‐100 μg) and NaCN (10‐20 μg) caused depolarizations of the DC potential, effects that have been described by others.

5. The hyperpolarizing effects of dopamine were reduced or abolished by the α‐adrenergic antagonists, dihydroergotamine (10‐100 μg/ml.) and phenoxybenzamine (5 μg/ml.) and the dopamine antagonist droperidol (10‐25 μg/ml.).

6. The results indicate that the inhibitory effects of dopamine on the frequency of carotid body chemosensory discharges in cats and rabbits are due to hyperpolarization of chemoreceptor afferent nerve endings and not necessarily to local vascular effects in the carotid body.
Voltage jump analysis of procaine action at frog end‐plate
Authors: Adams P. R.
Published: December 2014

1. In the absence of procaine the end‐plate conductance evoked by suberyldicholine increases exponentially to a new level following a step hyperpolarization. In the presence of procaine the suberyldicholine‐evoked conductance first rapidly decreases and then slowly increases following a hyperpolarizing step. The fast relaxation has a time constant of ∼ 1 msec, and the slow relaxation a time constant of 10‐150 msec.

2. The existence and sign of these two relaxations is predicted by a sequential model in which procaine enters and blocks open but not closed end‐plate channels. The concentration dependence of the fast and slow relaxation time constants agrees well with the predictions of this model, and allows the apparent dissociation constant for binding of procaine within the open channel to be estimated at about 20 μ
M at ‐80 mV membrane potential.

3. This apparent binding constant is voltage sensitive. It decreases e‐fold for 50 mV hyperpolarization, suggesting that the procaine binding site is electrically half way through the channel.

4. Procaine concentrations comparable to the dissociation constant for binding to open channels strongly depress the equilibrium current evoked by low suberyldicholine concentrations. This finding is not in accord with the sequential model.

5. A cyclic model in which procaine binds to both closed and open channels explains well the equilibrium observations. The affinity of procaine for closed channels is similar to its affinity for open channels, and is also increased by hyperpolarization. This model also fits well the kinetic observations, if it is assumed that blocked channels open and close much more slowly than unblocked channels.

6. The concentration dependence of the relaxation amplitudes disagrees with the predictions of the sequential model, but agrees well with the predictions of the cyclic model.

7. No other model appears to explain the various observations as economically as the cyclic channel blocking model. If the model is correct the ‘gate’ controlling the end‐plate channel must be in the inner half of the membrane.
Nerve‐induced and spontaneous redistribution of acetylcholine receptors on cultured muscle cells.
Authors: Anderson M J , Cohen M W
Published: December 2014

1. Theree‐day‐old cultures of myotomal muscle, obtained from embryos of Xenopus laevis, were stained with fluorescent conjugates of alpha‐bungarotoxin and maintained in native toxin in order to ensure that ACh receptors subsequently inserted into the sarcolemma would not be stained. Neural tube cells were then added to the cultures. 2. When cultures were exmained 1‐3 days later fluorescent stain was found to be associated with sites of nerve‐muscle contact. In some cases the stain along the path of contact extended for greater distances than the patches of stain seen on non‐contacted muscle cells. 3. The development of new areas of fluorescent stain at sites of nerve‐muscle contact was confirmed by making successive observations on the same muscle cells over a period of a day. 4. Similar experiments on muscle cells not contacted by nerve revealed the formation of new receptor patches, usually in areas of cell growth. 5. The majority of fluorescent pathes on non‐contacted muscle cells did not undergo changes in size or shape over the course of 1‐2 days. However some examples of enlargement, shrinkage and disappearance were observed. 6. On the basis of these findings it is concluded that ACh receptors aggregate within the sarcolemma, spontaneously as well as in response to innervation. In the latter case extrajunctional receptors accumulate at the site of nerve contact thereby contributing to the development of high receptor density in the subneural muscle membrane. This process of receptors redistribution occurs in the absence of synaptic or contractile activity. 7. Possible mechanisms involved in the redistribution of ACh receptors are discussed in relation to those which appear to modulate ligand‐induced changes in the distribution of lectin and immunoglobulin receptors.
Caffeine and the contractility of single muscle fibres from the barnacle Balanus nubilus
Authors: Ashley C. C. , Ellory J. C. , Griffiths P. J.
Published: December 2014

1. In single striated muscle fibres from the barnacle Balanus nubilus tension development following axial injection of caffeine (50 m
M in 150 m
M‐KCl, pH 7·1) was used as an index of releasable Ca. It was shown that fibres incubated in 0 Ca (Na replaced) salines for up to 400 min gave ca. 15% of the control tension response. Inclusion of 1 m
M‐La in the 0 Ca (Na) saline significantly reversed this decline.

2. Estimates of the total fibre calcium assayed under the same experimental conditions indicated a 67% loss of fibre Ca in 0 Ca, and only a 37% loss in La‐0 Ca media. No correction was made for the loss of calcium from the extracellular space.

3. Experiments with 45Ca indicated that the efflux of calcium from this preparation was inhibited by 1 m
M‐La externally and that this effect was still significant even in the presence of 0 Ca (Na) salines. The caffeine‐stimulated efflux of Ca was also reduced by ca. 70% in the presence of 1 m
M La saline externally.

4. The influx and efflux of 14C caffeine were shown to be rapid, and apparently passive. The diffusion coefficient for caffeine following intracellular injection was 2·4 ± 0·2 × 10−6 cm2 sec−1 at 18‐22° C.

5. There was no significant loss of 140La over a period of 2 hr following axial micro‐injection into the fibres.

6. In 140La uptake experiments there was a progressive increase in the La space over 10·5 hr, in contrast to the results with [3H]inulin, whose uptake saturated in ca. 1·5 hr. The probability of surface binding and the precipitation of La salts in the extensive extracellular space was suggested as an explanation.

7. It is concluded that internal Ca within the sarcoplasmic reticulum, and not cleft or extracellular Ca is the most significant source for these caffeine‐induced contractions. Fluxes across the surface membrane can however alter the internal Ca stores over longer periods of time.
Membrane properties and conduction velocity in sensory neurones following central or peripheral axotomy
Authors: Czéh G. , Kudo N. , Kuno M.
Published: December 2014

1. The properties of dorsal root ganglion cells in the lumbosacral segments were examined with intracellular electrodes about 3 weeks after section of the central (dorsal roots) or peripheral processes in the cat.

2. Chronic section of the peripheral nerve in the hind limb resulted in a reduction in conduction velocity of both the central and peripheral processes of sensory neurones.

3. Sensory neurones arising from the triceps surae and plantaris muscles were subject to ‘disuse’ conditions for about 3 weeks by section of the ventral roots combined with severance of the Achilles tendon. Under such conditions, the central and peripheral conduction velocities of these sensory neurones tended to decrease, but the decrease was significantly less than that following peripheral nerve section.

4. Chronic section of the dorsal roots produced no significant changes in conduction velocity of the central processes of muscle sensory neurones but caused a significant increase in the peripheral conduction velocity.

5. The only electrophysiological property of dorsal root ganglion cells which altered following axotomy was the time‐dependent membrane rectification in response to hyperpolarizing current pulses. The rectification characteristics were modified by chronic section of the peripheral nerve but not by chronic section of the dorsal root.

6. It is concluded that injuries in nerve fibres per se do not necessarily result in a decrease of their conduction velocity and that a decrease in their conduction velocity is associated with changes in the properties of the cell bodies.

7. It is suggested that a decrease in conduction velocity following nerve section may require the participation of changes in the neurone cell body.
Short circuit current and total conductance measurements on rat ileum
Authors: Emílio M. Graça , De Jesus C. Henriques
Published: December 2014

1. Short circuit current and total conductance measurements were made on preparations of rat terminal ileum, using either the intact tissue or the isolated epithelium.

2. The effects of
D‐glucose, 3‐O‐methyl‐
D‐glucose, and 3‐deoxy‐3‐fluor‐
D‐glucose, added in suitable concentrations to the external bathing medium, were studied.

3. An increase in both short circuit current and total conductance was detected when these sugars were used. It was possible to determine a linear relationship between the two variables and to study the kinetics of the interaction of glucose and 3‐O‐methyl‐
D‐glucose with the sodium sugar carrier by using increasing concentrations of these substances.

4. The increases in short circuit current and total conductance were also verified in isolated epithelium.

5. Phlorizin, or the withdrawal of glucose, reversed the increase in short circuit current, but the total conductance remained unchanged.

6. Increasing concentrations of 2‐deoxy‐
D‐glucose added to the mucosal bathing medium caused a decrease in short circuit current without changing the total conductance, either in preparations of intact ileum or in isolated epithelium.

7. The meaning of these variations in the electrical parameters of the preparations is discussed.
Slow mechanism for sodium permeability inactivation in myelinated nerve fibre of Xenopus laevis.
Authors: Brismar T
Published: December 2014

1. Single myelinated nerve fibres were isolated and the nodal currents were recorded under potential clamp conditions. The effect of membrane potential on the Na permeability (PNa) mechanism was analysed. 2. The available PNa increased slowly during negative polarization of the membrane. The time course of this change was about 10(3) times slower than the time course of the mechanism for the usual PNa inactivation (h‐system). The slow PNa changes could be distinguished from changes in h because of the difference in rate. 3. The slow PNa variation was independent of the state of the h‐system and was largely due to a slow inactivation system, which empirically could be described as separate from the other permeability variables. 4. In the steady state the slow inactivation appeared almost absent at a holding potential of ‐120 mV, whereas it was 30% complete at the resting potential (‐70 mV) and 80% complete at a holding potential of ‐20 mV. 5. Changes in the slow inactivation system showed an approximately exponential time course. At 10‐12 degrees C the time constant was about 3 sec with U = ‐70 mV, 7 sec with U = ‐100 mV and 1‐5 sec with U = ‐127 mV. 6. High Ca shifted the steady state slow inactivation curve in the positive direction along the potential axis.
Nasal field loss in kittens reared with convergent squint: neurophysiological and morphological studies of the lateral geniculate nucleus
Authors: Ikeda Hisako , Plant G. T. , Tremain K. E.
Published: December 2014

1. Recordings of single cells were made in layers A and A1 of the lateral geniculate nucleus of kittens raised with convergent squint in one eye, and morphological studies of cells representing the different parts of the visual fields in these layers were also made from histological sections.

2. For the normal eye, cells receiving inputs from the nasal and temporal visual fields were evenly represented up to the periphery, whereas for the squinting eye, no cells which permitted quantitative studies of receptive field properties could be found in the periphery of the nasal field.

3. The loss of nasal field, represented by the loss of functional cells in the LGN layer A1 fed by the squinting eye, depended on the severity of the squint. The greater the angle of convergent squint, the greater the loss of nasal field represented by the loss of functional cells.

4. The cells fed by the squinting eye's temporal visual field retained their brisk function, although minor modifications in the receptive field organisation were apparent.

5. The mean perikaryal size was smaller and the cell‐density higher for cells in layers fed by the squinting eye. As found for the functional loss of cells, the shrinkage of perikaryal size and the increase of cell‐density was smallest in the zones fed by the temporal visual field, and greatest in the zones fed by the peripheral nasal visual field.

6. The functional and morphological changes in the cells in the LGN, which receive inputs from the nasal field of the squinting eye, are attributed to part of the temporal retina being hidden behind the bridge of the nose. It is proposed that this is a consequence of disuse atrophy, due to lack of stimulation during the sensitive period of development.
A comparison of the energy balance in two successive isometric tetani of frog muscle
Authors: Curtin Nancy A. , Woledge Roger C.
Published: December 2014

1. Measurements were made of the energy produced as heat and work (h + w) and the chemical changes which occurred between the beginning and end of each of two periods of stimulation. The muscles contracted tetanically under isometric conditions. Each period of stimulation (tetanus) lasted 5 sec and there was an interval of 3 sec between them. The tension developed in the second tetanus was 91% of that in the first.

2. The observed (h + w) was greater in each tetanus than the quantity expected from the measured chemical changes. This excess was 230 ± 43 mJ/g dry wt. (mean ±
S.E. of mean) in the first tetanus, but only 89 ± 46 mJ/g in the second tetanus (mean ±
S.E. of mean). The result for the first tetanus agrees with previous findings.

3. The observed (h + w) was divided into two parts, labile and stable, which were defined by Aubert (1956). This division was made on the basis of the time course of the (h + w) production, without reference to the chemical changes. The labile part of the (h + w) has an exponentially declining rate, and the stable part has a constant rate.

4. The observed (h + w) was less in the second tetanus than in the first. This was due largely to the decrease in the labile part in the second tetanus; it was only ca. 0·35 of that in the first tetanus. However, the stable part remained relatively constant, 0·83 of that in the first tetanus. Aubert & Maréchal (1963) and Aubert (1968) have reported similar results.

5. Having divided the (h + w) into the stable and labile parts, we found that the stable part could be accounted for by the chemical change, but the labile part could not. Thus, for both tetani, the stable part of the energy is about equal to the explained energy, and the labile part is about equal to the unexplained energy. The possible interpretations of these equalities are discussed.
Collecting duct flow rate as a determinant of equilibration between urine and renal papilla in the rat in the presence of a maximal antidiuretic hormone concentration
Authors: Lote C. J. , Snape B. M.
Published: December 2014

1. Antidiuretic hormone (ADH) was infused into normal male rats at a rate of 60 μu./min. 100 g body wt., to maintain an effectively constant maximal circulating level. Four groups of rats were used; they were water‐loaded by receiving together with the ADH,
I.V. infusions of hypotonic dextrose (2·5 g/100 ml.) at different rates (1·0, 4·5, 9·0 and 12 ml./hr, respectively), over an infusion period of 4 hr.

2. Urine flow rate increased in all groups, the rate and extent of the increase being related to the volume rate of infusion. The differences in urine flow rates between the four groups were due almost entirely to increases in free water clearance, with no consistent differences in osmolal clearance between the groups. At the end of the 4 hr infusion period, osmolal clearances were closely similar in the four groups.

3. Papillary and medullary tissue solute concentrations were progressively reduced at the higher rates of infusion. The changes were due to small increases in the water content, together with a profound decrease in urea concentration and a smaller decrease in sodium concentration. However, papillary osmolality was consistently higher than urine osmolality at the three highest rates of dextrose infusion.

4. As urine flow rate increased, there was a progressive reduction in the degree of osmotic equilibration between the final urine and the papillary tip. For urea, however, the degree of equilibration remained high.

5. It is concluded that, in the rat, the rate of flow per se, along the collecting duct, is an important determinant of final urine concentration; even if there is an osmotic driving force for water re‐absorption in the renal medulla, and the collecting duct walls are permeable to water, osmotic equilibration is restricted by tubular flow rate.
An analysis of the actions of prostaglandin E1 on membrane currents and contraction in uterine smooth muscle (rat)
Authors: Grosset Alain , Mironneau Jean
Published: December 2014

1. The effects of prostaglandin E1 have been studied on the transmembrane potentials, ionic currents, and contractions in isolated myometrial strips from pregnant rats by means of a double sucrose gap apparatus.

2. At low concentrations (10−8 g/ml.), prostaglandin E1 reduced the duration (though not the amplitude) of the action potential, but significantly increased the contraction. The inward current was unchanged, as well as the phasic component of the contraction. However, the tonic contraction, recorded when the transmembrane calcium influx was blocked selectively with D 600, was stimulated significantly, and the outward current secondarily increased.

3. At maximally effective doses (10−6 g/ml.), the electrical response to prostaglandin E1 consisted of a slight depolarization, while a large contracture developed. The depolarization and contracture were unaffected by the removal of external calcium. The inward current was reduced by prostaglandin E1 and the reversal potential was shifted towards less positive values of voltage, indicating a decrease in the driving force and consequently, an increase in the internal calcium concentration.

4. Dibutyryl‐c‐AMP (5 × 10−4
M) produced a marked relaxation of the resting tension and a slight hyperpolarization of the uterine membrane. Under these conditions, a triggered action potential was able to evoke a larger contractile response. However, prostaglandin E1 is known to increase tissue c‐AMP, so that its contractile effect cannot be mediated by c‐AMP.

5. It is suggested that prostaglandin E1 acts essentially by increasing the intracellular calcium concentration. This might result from the translocation of membrane‐bound calcium from surface microvesicles or sarcoplasmic reticulum. The increase in internal calcium concentration could, in turn, lead to an increase in the outward current intensity.
Physiological properties of dissociated muscle fibres obtained from innervated and denervated adult rat muscle.
Authors: Bekoff A , Betz W J
Published: December 2014

1. Adult rat flexor digitorum brevis muscles were dissociated by treatment with collagenase and trituration. Several hundred isolated fibres were obtained from each muscle. 2. Most isolated fibres appeared to be intact as judged by some morphological and physiological criteria, although resting membrane potentials were about ‐60 mV, which is somewhat lower than normal. 3. A small percentage of the muscle fibres were branched. 4. Acetylcholine sensitivity was measured iontophoretically. The sensitivity fell abruptly outside the margin of the end‐plate. Extrajunctional sensitivty was detected on all fibres, and declined smoothly away from the end‐plate to an undetectable level over a distance of about 200 micron. On a few fibres, ACh sensitivity was mapped circumferentially from the end‐plate. It appeared to decline with distance in a manner similar to the longitudinal sensitivity gradient. 5. Fibres dissociated from muscles denervated a week earlier were sensitive to ACh everywhere on their surfaces.
Movement of strontium ions into mast cells and its relationship to the secretory response
Authors: Foreman J. C. , Hallett M. B. , Mongar J. L.
Published: December 2014

1. Non‐stimulated mast cells take up 89Sr and 45Ca. There is a rapid phase of uptake of both labels which is complete in 1 min and the 89Sr uptake is similar in magnitude to the 45Ca uptake. A further slower phase of uptake occurs in the period from 1 to 30 min of incubation. The magnitude of this slower phase is about 6 times greater for 89Sr than for 45Ca.

2. Non‐stimulated and antigen‐stimulated mast cells accumulate Sr which can be measured by atomic absorption spectroscopy. There is a direct relationship between Sr accumulation and histamine secretion which is independent of whether or not the cells are stimulated. 10% histamine secretion is associated with Sr accumulation of 0.25 f‐mole/cell.

3. The time course of 89Sr uptake is similar to the time course of histamine secretion in non‐stimulated cells.

4. The uptake of 89Sr is linearly related to the external Sr concentration in the range 0.5‐16 m‐mole/l. for both stimulated and non‐stimulated cells.

5. Ca, 10‐1000 μmole/l. inhibits 89Sr uptake in non‐stimulated cells.

6. Inhibition of glycolysis and oxidative phosphorylation prevents spontaneous histamine secretion in the presence of Sr without blocking the accumulation of Sr by the cells.

7. Dibutyryl cyclic AMP, 10 m‐mole/l. produces only 18% inhibition of 89Sr uptake whereas histamine secretion is inhibited by 45% by the same concentration. The antigen‐stimulated Sr uptake on the other hand can be completely inhibited by dibutyryl cyclic AMP, 10 m‐mole/l.

8. The uptakes of 89Sr and Sr by unstimulated mast cells after 60 min incubation are dependent on extracellular H ion concentration. Both uptakes increase with increasing pH over the range pH 7‐8.5.
Cerebral circulatory and metabolic effects of 5‐hydroxytryptamine in anesthetized baboons.
Authors: Harper M A , MacKenzie E T
Published: December 2014

1. The cerebral circulatory effects of the intracarotid administration of 5‐hydroxytryptamine were examined in anaesthetized baboons. Cerebral blood flow was measured by the intracarotid 133Xe technique, cerebral O2 consumption and glucose uptake were measured as indices of brain metabolism and electrocortical activity was continuously monitored. 2. Despite a marked reduction in the calibre of the internal carotid artery (assessed angiographically), the intracarotid infusion of 5‐hydroxytryptamine 0‐1 microgram/kg. min did not effect any significant changes in cerebral blood flow, O2 consumption or glucose uptake. 3. Following transient osmotic disruption of the blood‐brain barrier with the intracarotid infusion of hypertonic urea, the same dose of 5‐hydroxytryptamine effected a marked reduction in cerebral blood flow from 51 +/‐ 2 to 36 +/‐ 2 ml./100 g. min (mean +/‐ S.E.; P less than 0‐01). Both indices of cerebral metabolism were reduced significantly and the e.e.g. showed a more pronounced suppression‐burst pattern. 4. We postulate that the cerebral circulatory responses to 5‐hydroxytryptamine are dependent upon the integrity of the blood‐brain barrier and the predominant effect of the intravascular administration of 5‐hydroxytryptamine is on cortical activity or metabolism, rather than on cerebrovascular smooth muscle.
Membrane currents underlying activity in frog sinus venosus
Authors: Brown Hilary F. , Giles Wayne , Noble Susan J.
Published: December 2014

1. The spontaneous electrical activity of small strips of muscle from the sinus venosus region of the heart of Rana catesbeiana was investigated using the double sucrose gap technique. The voltage clamp was used to record the ionic currents underlying the pace‐maker depolarization and the action potential.

2. The records of spontaneous electrical activity are very similar to those obtained from the sinus venosus using micro‐electrodes. Moreover, the pace‐maker activity is almost completely insensitive to tetrodotoxin (TTX) at 2·0 × 10−6 g/ml., which suggests that the pace‐maker responses can be classified as primary, as opposed to follower pacing.

3. In response to short rectangular depolarizing voltage clamp pulses, only one inward current is activated. This current is almost completely insensitive to TTX but can be blocked by manganese ions. It appears, therefore, to be equivalent to the slow inward (Ca2+/Na+) current, Isi, of other cardiac tissues. The threshold for Isi is near to the maximum diastolic potential, indicating that it must be activated during the pace‐maker depolarization.

4. Interruption of the normal pace‐maker depolarization by rapid activation of the voltage clamp circuit reveals the time‐dependent decay of outward current. This current reverses between ‐75 and ‐90 mV and, therefore, is probably carried mainly by potassium ions.

5. Outward current decay is not a simple exponential, and Hodgkin—Huxley analysis suggests that two distinct components of outward current may be present. One of these is activated in the potential range of the pace‐maker depolarization and the other at more positive potentials. Both outward currents reach full, steady‐state activation at about zero mV, i.e. within the ‘plateau’ range of the sinus action potential.

6. These results are compared with other recently published voltage clamp data from the rabbit sino—atrial node.

7. A hypothesis for the generation of pace‐maker activity is presented which involves (i) decay of outward current and (ii) activation of the slow inward current, Isi.
Effect of cold exposure on mammary circulation oxygen consumption and milk secretion in the goat.
Authors: Thompson G E , Thomson E M
Published: December 2014

1. Measurements of milk secretion, mammary oxygen consumption and blood flow, cardiac output and blood pressure have been made in lactating goats exposed to a thermoneutral environment and to two levels of cold stress which were sufficient to raise total body oxygen consumption by an average of 18 and 46% above that in a thermoneutral environment. 2. Mammary blood flow and oxygen consumption were not appreciably affected by the milder cold stress but fell to 63 and 70%, respectively, of their thermoneutral value in the moderately cold environment. Resistance to blood flow through the udder was increased by this level of cold stress and the gland took a smaller fraction of an increased cardiac output. 3. Both levels of cold exposure caused a reduction in milk secretion, to 80 and 40% of its thermoneutral value in the mild and moderate cold respectively. The amount of milk secreted per unit volume of blood flowing through the gland decreased as the severity of the cold stress increased. 4. Voluntary food intake was not affected by the change in environmental temperature but the intake of water was reduced to 55% of the thermoneutral value during mild cold exposure and to 40% of the thermoneutral value during the moderate cold stress. 5. It is concluded that a reduction in blood flow to the mammary gland could be one of several possible mechanisms underlying the depression of milk secretion during cold exposure.
Sodium entry in rat diaphragm induced by depolarizing drugs
Authors: Creese R. , Franklin G. I. , Mitchell L. D.
Published: December 2014

1. An increased uptake of labelled sodium was found in the end‐plate region of rat diaphragm following brief exposure to solution containing 24Na plus carbachol (100 μ
M), with a wash in inactive saline. Tetrodotoxin (0·1 μ
M) was also present. Comparable results were obtained with decamethonium and suberyldicholine.

2. With carbachol (100 μ
M) the influx of labelled sodium at the end‐plate region was increased by a factor of at least three as compared with that at the end of the fibres.

3. After entry the labelled sodium spread along the fibres with an apparent diffusion coefficient which was half that expected in the external solution.

4. The dose—response curve for the effect of carbachol gave a half‐maximal value of 72 μ
M.

5. In muscles depolarized by potassium methyl sulphate the effect of carbachol on the entry of sodium was reduced although demonstrable.

6. The entry of labelled sodium at the end‐plate was maintained during prolonged exposure to carbachol (100 μ
M) or decamethonium (100 μ
M).

7. The rate of entry of 24Na obtained with carbachol, after corrections for the wash, was estimated as 1·5 × 103 ions channel−1 sec−1, measured over a period of 15 sec.

8. Labelled decamethonium and labelled carbachol also accumulated at the end‐plate region. After extrapolation to allow for the effects of the wash the entry of decamethonium when expressed as a clearance (pl. mg−1 sec−1) was comparable to that of sodium, as expected if decamethonium and sodium enter through the same channels.
The effects of manganese ions on the contraction of the frog's heart
Authors: Chapman R. A. , Ellis D.
Published: December 2014

1. The effects of Mn2+ in particular but also of Ni2+, Co2+, Cd2+, verapamil and D600 on the contraction of isolated frog atrial trabeculae have been investigated. Contraction was initiated either by electrical stimulation, or by raising the [K]o or by lowering the [Na]o.

2. Mn ions like Ca ions cause a hyperpolarization of the cell membrane and a rise in the threshold for the action potential and twitch. Mn ions, particularly at low concentrations, reduce the overshoot of the ventricular action potential.

3. Mn ions reduce the strength of the regularly evoked heart beats. Prolonged exposure, in beating hearts, results in a rise in resting tension and often a small recovery of the heart beat.

4. In normal Ringer solution and in Ringer free of Na ions, the addition of Mn causes the tension—depolarization curve to be displaced by an amount equivalent to an 18 mV hyperpolarization of the membrane potential for a tenfold increase in the divalent cation concentration.

5. Mn, Co, Ni and Cd ions all cause a marked reduction in the tension generated by exclusion of Na ions from the bathing fluid. In the presence of these divalent cations the contracture divides into an initial phasic and a later tonic contraction. This inhibition is reversed by raising the [Ca]o, while the tension developed during the initial phasic contraction varies with the [Ca]o/[Mn]o quotient.

6. A similar tonic contracture is initiated after exposure to Na‐free fluid containing a high [Mn]o by the addition of a small concentration of Na, Li, hydrazinium or hydroxylammonium ions.

7. The organic ‘Ca antagonists’ verapamil and D600 have little effect on the contracture induced by lowering [Na]o even after prolonged exposure at relatively high concentrations but they do inhibit the twitch contraction and the K contractures.

8. The effects of Mn on the Na‐withdrawal contracture of frog heart can be interpreted in terms of an exclusively extracellular effect where Mn ions resemble Na ions in their action, and both antagonize the movement of Ca across the cell membrane.

9. The experimental evidence suggests that the K contracture in frog heart is initiated by a mechanism which is, in some ways different to that underlying the Na‐withdrawal contracture, and may involve two different sources of activator Ca.

10. The several different effects of Mn on the frog heart probably reflects the ability of this cation to interfere with many processes involving Ca, and that there are a number of such processes involved in the results described in this work. The effects of Mn are more complex than might be generally supposed.
The variability of muscle nerve sympathetic activity in resting recumbent man
Authors: Sundlöf Göran , Wallin B. Gunnar
Published: December 2014

1. Pulse synchronous bursts of multi‐unit sympathetic activity was recorded from median or peroneal muscle nerve fascicles in fourteen subjects resting in the recumbent position. The neural activity was quantitated in terms of burst incidence, i.e. the number of bursts in the mean voltage neurogram/100 heart beats, during successive rest periods of 2‐4 min.

2. For each individual the burst incidence was fairly constant between different rest periods but the mean burst incidence varied widely between individuals, the range being from less than 10 to more than 90 bursts/100 heart beats.

3. Simultaneous double nerve recordings were made on one subject from median and peroneal nerves and on eight subjects from the two peroneal nerves. There was always close similarity between the two records in such experiments regardless of which muscles the nerve fascicles innervated. When analysed separately the difference in burst incidence between the two sides ranged from 0·7 to 5·1 bursts/100 heart beats. The findings suggest that sympathetic neurones destined to skeletal muscles are subjected to a homogenous central drive and that contributions to the activity from ganglionic or segmental sources are of lesser importance.

4. On seven subjects repeated recordings at rest were made with intervals of 3 weeks—21 months between recordings. In each subject mean burst incidences were similar in all recordings (range of differences 0·5‐11·2 bursts/100 heart beats) suggesting an individually constant level of sympathetic activity in muscle nerves.

5. For each individual the variability of burst amplitudes in the mean voltage neurogram was described by burst amplitude spectra. Most subjects had a relatively larger proportion of small than high amplitude bursts, but there was a tendency for more even amplitude distributions in subjects with high burst incidence. The finding may be an indication of interindividual differences in the average number of impulses/burst.

6. It is concluded that the multi‐unit recording technique can be used for comparisons of the level of muscle nerve ‘sympathetic tone’ between different subjects.