bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetics of glucose transport by the perfused mid‐gut of the freshwater prawn Macrobrachium rosenberg ii.
Authors: Ahearn G A , Maginniss L A
Published: December 2014

1. Mucosal influx of [3H]glucose was examined in the mid‐gut of a freshwater prawn, Macrobrachium rosenbergii, using an in vitro perfusion technique. 2. [3H]glucose transfer across the apical cell membrane of the epithelium exhibited Michaelis‐Menten kinetics (Jmax.in = 0‐15 mumole glucose equiv/g. min, Kt = 0‐17 mM). Under Na‐free conditions, glucose influx was significantly reduced and a linear function of substrate concentration, indicative of either slow cellular diffusion (KD = 7‐6 X 10(3) mumole glucose equiv/g. min. mM) or a facilitated process with a low carrier affinity for the sugar. 3. Phlorizin was a potent competitive inhibitor of glucose influx (K1 = 3‐6 X10(‐3) mM), galactose and 3‐O‐methylglucose (3‐O‐MG) were weak inhibitors, and fructose had no evident effect on glucose uptake. Azide, but not iodoacetate (IAA), significantly depressed influx. 4. Absorbed [3H]glucose was rapidly metabolized by the mid‐gut. The majority of accumulated activity within the tissue was in the form of phosphorylated compounds and tritiated water (THO), while only 0‐3% was recovered as a free‐glucose. 5. Preliminary studies examining transmural [3‐H]glucose transport, however, demonstrated a significant net mucosal to serosal free‐glucose flux across the prawn mid‐gut which was Na‐dependent and IAA‐ and phlorizin‐sensitive. Two alternative interpretations of the data are advanced as possible mechanisms for transepithelial glucose transport: (1) group translocation, or (2) the operation of an energized, high affinity, baso‐lateral sugar transport carrier.
The response of Golgi tendon organs to single motor unit contractions.
Authors: Binder M D , Kroin J S , Moore G P , Stuart D G
Published: December 2014

1. Cross‐correlation analysis has been used to quantify the responses of cat soleus tendon organs to repetitive twitch contractions of: (a) different motor units within the muscle, (b) single motor units at different muscle lengths, and (c) single motor units when the pulse‐train pattern of stimulation delivered to the motor unit axon was altered. 2. Ib afferents were observed which responded to each of several hundred successive motor unit twitches with identical numbers of spikes and with relatively invariant latencies. 3. The present results show that tendon organs are sensitive to subtle alterations in motor unit twitch wave form and amplitude, and that this sensitivity is reflected in the precise timings of their afferent discharge. 4. Examination of these tendon organ responses indicates that the forces produced by single motor units couples to the receptor capsule are well above threshold. Calculations based on these results, and earlier soleus motor unit and muscle fibre data, suggest that the absolute force threshold for tendon organs may be as little as 4 mg, which is less than the estimated minimum twitch force generated by individual soleus muscle fibres. 5. Considering the number of tendon organs in a muscle, and the likelihood that every motor unit is connected with at least one receptor, the sensitivity of tendon organs ensures that every twitch of every motor unit will be reflected in the population of afferent signals projecting to the spinal cord.
Re‐innervation of fast and slow twitch muscle following nerve crush at birth.
Authors: McArdle J J , Sansone F M
Published: December 2014

1. The frequency of miniature end‐plate potentials (m.e.p.p.s) was significantly greater in the fast twitch extensor digitorum longus muscle (extensor) than in the slow twitch soleus, even though end‐plate surface area was greater for fibres in the latter muscle. 2. Crush of the sciatic nerve at birth did not prevent the appearance of this difference in m.e.p.p. frequency. However, the frequency of the potentials in the re‐innervated muscles was less than normal, even though the regenerated neuromuscular junction was qualitatively normal in morphology. 3. Though the re‐innevated muscles were differentiated with respect to twitch time course, the extensor muscle was more responsive than normal to the contracture‐inducing action of caffeine. 4. The Z line of the re‐innervated extensor muscle was similar to that of the normal soleus in thickness. 5. Resting potential, passive electrical properties and action potential generating mechanism of the sarcolemma were normal. 6. Since the re‐innervated muscles lacked muscle spindles, a role of sensory feed‐back in the function of the neuromuscular junction as well as the neutrotrophic regulation of muscle is discussed.
Changes in cardiac output and total peripheral resistance during the carotid sinus baroreceptor reflex in the pregnant rabbit.
Authors: Humphreys P W , Joels N
Published: December 2014

1. The reflex cardiovascular effects of changes in pressure within the isolated carotid sinus have been examined in sixteen anaesthetized pregnant rabbits. 2. Comparison of the mean results at sinus pressures of 40 and 200 mmHg showed that heart rate fell by 32.1 beats min‐1 and arterial pressure was reduced by 48.2 mmHg. Cardiac output, measured by thermal dilution, fell by 25.7 ml. min‐1.kg‐1 and total peripheral resistance was reduced by 0‐292 mmHg. ml.‐1 min. kg. 3. The corresponding changes previously reported in a group of seventeen non‐pregnant female rabbits were a similar fall in heart rate of 34.5 beats min‐1 but significantly greater reductions in arterial pressure of 69‐8 mmHg and in total peripheral resistance of 0‐432 mmHg. ml.‐1 min.kg. However, the fall in cardiac output of 12.6 ml.min‐1.kg‐1 was significantly smaller. 4. These observations show that the smaller blood pressure response of the pregnant rabbit to alterations in sinus pressure is due to a reduced change in total peripheral resistance.
The organization of the salivary gland microcirculation
Authors: Fraser P. A. , Smaje L. H.
Published: December 2014

1. The microvasculature of the rabbit submandibular salivary gland has been investigated employing in vivo microscopy, blood flow measurements, latex casts, microsphere injections and examination of fixed sections of the gland.

2. Two principal microcirculations were distinguished in the living gland, one supplying the acini and the other the intralobular ducts. Parasympathetic nerve stimulation (2, 5 or 10 sec−1) elicited different responses in each of the two microcirculations. Flow in the capillaries around the acini slowed initially before increasing. In contrast, flow in the intralobular duct capillaries increased soon after beginning stimulation.

3. In some experiments both whole gland flow and microvascular flow were monitored simultaneously. Whole gland flow increased at the same time as flow in the acinar capillaries was decreasing and as flow in the intralobular duct capillaries increased. Flow in acinar capillaries increased about 5 sec after glandular flow started to increase.

4. These observations could be explained if either the vascular beds of the acini and the intralobular ducts were arranged in parallel or if arteriovenous anastomoses were to shunt the acinar circulation. No such anastomoses were found in latex casts made of the gland vasculature, and microspheres injected into the artery supplying the gland were not found in the venous effluent.

5. The intraglandular distribution of microspheres was measured in histological sections of the injected glands to give an estimate of the distribution of blood flow between the duct and acinar microcirculations. At rest and during maintained stimulation about 55% of the blood flow passed through the intralobular duct microcirculations, whilst during this initial 15 sec of stimulation this proportion was increased to over 70%. This finding is consistent with a parallel arrangement of the two microcirculations.

6. The conclusions drawn from these observations are that the duct and acinar microcirculations are arranged in parallel, that there are differences in the way the vasodilatation is mediated in these circulations, and that arterio‐venous anastomoses play no significant role in this gland.
Voltage noise observed in rods of the turtle retina
Authors: Schwartz E. A.
Published: December 2014

1. Intracellular voltage was recorded from rods in isolated retinae of the snapping turtle, Chelydra serpentina. The voltage was observed during darkness or during uniform illumination of a large retinal area. During darkness the voltage fluctuated continuously about a mean level. The spontaneous fluctuation is termed ‘noise’. During illumination the amplitude of the noise was reduced.

2. The noise observed during darkness could also be reduced by injecting a hyperpolarizing current into the impaled rod. The noise could be increased by a depolarizing current. The component of the noise that could be altered by polarizing the rod is termed ‘voltage‐sensitive noise’.

3. When voltage‐sensitive noise was first minimized by a continuous hyperpolarizing current, bright light produced an additional decrease in the noise. The component of the noise that was eliminated by light, but not eliminated by the injection of current, is termed ‘light‐sensitive noise’.

4. The power density spectrum of voltage‐sensitive noise, Gv(f), could be described by an equation of the form [Formula: see text] τM was approximately 7 msec, which is in good agreement with an apparent membrane time constant of 5‐8 msec. The largest value of αv was 2·1 × 10−9 V2 sec.

5. The power density spectrum of light‐sensitive noise could be described by an equation of the form [Formula: see text] τL was approximately 200‐300 msec. The largest value of αL was 8·0 × 10−9 V2 sec.

6. The potential maintained during darkness could be altered by superfusing a retina with artificial media of different compositions. Depolarizing the rods by changing the extracellular calcium concentration from 1 to 5 m
M increased the voltage‐sensitive noise. A similar effect was observed after adding 2 m
M lanthanum.

7. In contrast, 5 m
M cobalt produced a small hyperpolarization and suppressed the voltage‐sensitive noise. Injecting a depolarizing current, after exposure to cobalt, re‐initiated the voltage‐sensitive noise. The ability to elicit voltage‐sensitive noise in the presence of cobalt indicates that it was not of synaptic origin.

8. The results are consistent with the noise present during dark being produced by two types of channel in the rod membrane. One is controlled by the phototransduction process; each individual channel of this type may be described as having a mean open time of 200‐300 msec and a conductance of approx. 6 × 10−13 Ω−1. The absorption of one photon closes approx. 100‐300 of these channels. The other type of channel is controlled by membrane potential; each individual channel of this type has a mean open time which is less than the membrane time constant of 8 msec.
A quantitative description of the pattern of breathing during steady‐state CO2 inhalation in man, with special emphasis on expiration
Authors: Cunningham D. J. C. , Gardner W. N.
Published: December 2014

1. Quantitative data on the pattern of breathing in normal men and women (Gardner, 1977) have been used to derive expressions that are based on known physiological mechanisms.

2. The relations between the applied chemical drive to breathing (expressed as ΔPA, CO2 in high O2) and the several components of the volume—time patterns described in the companion paper were examined. Neither mean tidal volume (V̄T), nor mean inspiratory nor mean expiratory times (T̄I, T̄E) were uniquely related to the chemical drive across the breakpoint, which could be demonstrated in two and suspected in the third of these plots.

3. Mean inspiratory flow (V̄T/T̄I) was linearly related to PA, CO2 over the whole range and, like minute ventilation (V̄), showed no breakpoint. The mean relation was V̄T/T̄I = 0·11 (PA, CO2 — 35·2). V̄T/T̄I was highly correlated with V̄; in individuals with healthy lungs and under relatively stable conditions of compliance and resistance it may be accepted as a wholly inspiratory alternative to V̄ as an index, on the efferent side, of the total prevailing chemical drive.

4. The description of the relation between T̄I and V̄T was essentially the same as that of Clark & Euler (1972): in range 1, T̄I = either 1·29 ‐ 0·07 V̄T or the constant 1·24 sec, and in range 2, T̄I = 0·65/(V̄T — 0·88) + 0·59.

5. Expiration was described by an equation based on the inverse linkage between T̄E and chemical drive and the direct link between both mean and breath‐by‐breath values of TI and TE: T̄E = pT̄I + q/(drive — r) in which p was 0·64 ± 0·09, q was 11·1 ± 2·64 sec. (torr CO2)−1 and r was ‐2·73 ± 1·09 torr CO2. All three parameters were necessary for an adequate description.

6. It is argued that the first term of the TE equation represents influences related to lung volume exerted through the vagus, and that the second represents the effects of over‐all chemical stimulation exerted through other pathways.
Effects of related sensory inputs on motor performances in man studied through changes in perceived heaviness
Authors: Gandevia S. C. , McCloskey D. I.
Published: December 2014

1. The perception of the heaviness of lifted objects was studied using a weight‐matching task when sensory inputs from parts related to the lifting task were altered.

2. A weight lifted by flexing the index finger feels heavier when the thumb is anaesthetized and lighter when the thumb is electrically stimulated. A weight lifted by flexing the distal joint of the thumb feels heavier when the sensory input from the skin and joint of the thumb is abolished by anaesthesia. It also feels heavier when the index (but not the little) finger is anaesthetized, and lighter when the index (but not the little) finger is electrically stimulated.

3. A weight lifted by extending the thumb feels lighter when the sensory input from the thumb is abolished.

4. The perceived heaviness of a weight lifted by flexing the thumb is increased during anaesthesia of the thumb when the flexor of the thumb is the prime mover but not when it is acting simply as a postural fixator to support the weight.

5. The sensation of the heaviness of lifted objects derives from the effort or centrally generated voluntary motor command employed in the lift. Our results indicate that the motor commands to either thumb or index finger flexors are facilitated by sensory inputs arising from a wide sensory field usually involved in co‐operative motor performances carried out by both muscle groups together.
Responses of atrial mechano‐receptors to pulsation of atrial volume
Authors: Baertschi Alex J. , Gann Donald S.
Published: December 2014

1. Firing patterns of single atrial fibres were monitored in order to study their sensitivity to rate of change of atrial volume and their dependence on receptor location in the atria.

2. To that effect, sinusoidal fluctuations of volume (±1 ml.; 60/min) were superimposed on the natural pulsations of the heart of spontaneously breathing anaesthetized cats.

3. Stimulus—response histograms revealed that maximal firing frequency of B‐impulses preceded maximal volume change by 10‐80° (average 48±7° (
S.E.), thirteen right and left atrial receptors) indicating that sensitivity to rate of change of atrial volume at least equalled volume sensitivity.

4. The rate sensitive component of B‐firing increased with respect to the volume sensitive component when atrial filling diminished and was larger for high threshold receptors than for low threshold receptors (P<0·001).

5. The A‐bursts were not affected by atrial pulsing in eight out of nine anatomically localized receptors; inspiration prolonged the A‐bursts of three receptors and advanced the timing of A‐bursts with respect to the a‐wave (10‐50 msec) of all nine receptors.

6. About half of all anatomically localized receptors were traced to the interatrial septum. These septal receptors differed from right and left atrial receptors as follows: (a) they were exclusively of the AB‐type (fired during atrial a‐ and v‐wave); (b) their B‐firing rates were significantly lower (P<0·05); (c) A‐firing patterns remained largely unaffected by respiration or by atrial pulsing; (d) they signalled volume changes of either atria; (e) no association of rate sensitivity with threshold was detected (P>0·95). The physiological role of septal receptors remains to be elucidated.

7. It was concluded that B‐fibres were sensitive to both change and rate of change of atrial volume; their role as sensors of venous return is suggested strongly. Results further suggested that A‐ and B‐firing are determined largely by the location of atrial stretch receptors.
Arterial chemoreceptors, ventilation and heart rate in man.
Authors: Drysdale D B , Petersen E S
Published: December 2014

1. Transient changes of heart rate (HR) and ventilation were recorded following step changes in alveolar gas composition in three healthy subjects. From a steady state of normo‐ or slightly hypercapnic hypoxia (PA,CO2 38‐46 torr, PA,O2 50‐60 torr) arterial chemoreceptor stimulation was transiently relieved by breathing a CO2‐free mixture for two breaths, either pur O2 (causing a fall in PA,CO2 and a rise in PA,O2; O2 test) or a low O2 mixture (causing a fall in PA,CO2 without any change in PA, O2; CO2 test). For both test types ventilation was either allowed to change freely ('free‐breathing' tests) or was consciously maintained at the pre‐test level by the subjects ('controlled‐breathing tests). The circulatory delay from the lungs to the ear was measured with a sensitive ear oximeter. 2. In all 'free‐breathing' tests ventilation decreased significantly after a mean latency of 5.2 sec; the average lung‐ear circulation time was 4.9 sec. HR increased slightly above pre‐test levels in eighty‐one of one hundred and four tests of all types, the changes being significant after a latency identical to that of the ventilatory changes. Except in the 'controlled‐breathing' CO2 tests this early tachycardia was followed by a decrease in HR within the following 5‐6 sec. 3.These findings indicate that the primary effect of withdrawal of arterial chemoreceptor stimulation in conscious man as in the anesthetized animal is tachycardia. The secondary development of bradycardia in 'free‐breathing' CO2 tests is probably due to the operation of a lung reflex sensing changes in ventilation. The absence of bradycardia in 'controlled‐breathing' CO2 tests and its presence in 'controlled‐breathing' O2 tests, finally, suggest that relief of systemic hypoxia causes a slowing of the heart not due to lung reflexes but to some other mechanism which operates with a latency nearly twice as long as the arterial chemoreflex.
The rabbit anococcygeus muscle and its response to field stimulation and to some drugs.
Authors: Creed K E , Gillespie J S , McCaffery H
Published: December 2014

1. The response of the rabbit anococcygeus muscle to field stimulation of its intramural nerves and to some drugs has been examined and compared with results previously obtained in the rat and the cat. 2. The rabbit muscle possesses an adrenergic innervation as demonstrated histologically by the Falck and Hillarp fluorescence technique. This innervation is sparser than in the rat or cat. 3. In vitro the muscle usually shows little tone but if suitably stretched will develop a maintained contraction. The response to field stimulation depends on the level of tone. When this is low purely motor responses are obtained. In the presence of tone the response depends on its level and the frequency of stimulation; low frequencies are purely inhibitory, with increasing frequency the response becomes biphasic and high frequencies produce a purely motor response. The higher the tone the more prominent the inhibitory components. Guanethidine 10(‐5)M abolishes the motor component. 4. The muscle is caused to contract by noradrenaline, acting through alpha receptors, by hista,ome actomg through H1 receptors and by 5‐hydroxy‐tryptamine. Part of the effect of the latter appears to be due to the release of noradrenaline. 5. The muscle is caused to relax by acetylcholine acting through muscarinic receptors, by isoprenaline through beta receptors, by histamine in the presence of mepyramine through H2 receptors and by ATP and bradykinin. 6. The significance of these findings for the motor and inhibitory innervation of the muscle is discussed.
The effects of external cations and ouabain on the intracellular sodium activity of sheep heart Purkinje fibres
Authors: Ellis David
Published: December 2014

1. The intracellular Na activity of sheep heart Purkinje fibres has been measured using recessed‐tip Na+‐sensitive glass micro‐electrodes.

2. The internal Na activity was 7·2 ± 2·0 m
M (mean ±
S.D., n = 32) at the normal external Na concentration, [Na]o, in these experiments of 140 m
M (equivalent to an external Na activity of 105 m
M). The equilibrium potential for Na across the fibre membrane was therefore approximately + 70 mV.

3. When the [K]o was altered the internal Na activity changed, reaching a new level within about 20 min. Increasing the [K]o from 4 to 25 m
M decreased the internal Na by approximately 30%, while decreasing the [K]o from 4 to 1 m
M increased internal Na by 20%.

4. The removal of external K produced an easily reversible increase in the internal Na with an initial rate equivalent to a concentration change of 0·24 ± 0·07 m‐mole/min (mean ±
S.D., n = 8).

5. Ouabain produced increases in the internal Na activity that were only very slowly reversible. The threshold concentration for producing an increase was approximately 10−7
M.

6. When [Na]o was reduced the internal Na activity fell rapidly with a single exponential time course (time constant 3·3 ± 0·8 min, mean ±
S.D., n = 16) to a new, relatively stable level. The recovery of internal Na on return to the normal [Na]o did not have a simple time course. It was normally complete within 10‐30 min.

7. The relationship of the stabilized level of the internal Na activity to the [Na]o was approximately linear over the range 140‐14 m
M‐[Na]o. When [Na]o was reduced from 140 to 14 m
M the internal Na activity fell by 72 ± 5% (mean ±
S.D., n = 21).

8. When the [Na]o was reduced, the decrease in the internal Na activity was partially inhibited by Mn or by removal external Ca.

9. When the [Ca]o was altered over the range 0·2‐16 m
M the internal Na activity was reduced by approximately 50% for a tenfold increase in the [Ca]o.

10. The relationship between internal Na and contractility is discussed.
Compensatory renal hypertrophy in hypophysectomized rats
Authors: Dicker S. E. , Greenbaum A. L. , Morris Christine A.
Published: December 2014

1. After hypophysectomy, both body and kidney weights fall, but at different rates. The rate at which the kidney decreases in weight is faster than that of the whole body.

2. Seven days after unilateral nephrectomy, the dry weight of the remaining kidney of hypophysectomized rats, with the exception of rats which had been hypophysectomized for 2 days only, was always heavier than the kidney of control hypophysectomized rats of similar body weight.

3. The difference between the dry weight of kidneys of unilaterally nephrectomized hypophysectomized and control hypophysectomized rats increased from 15% in early hypophysectomized (9 days) to about 35% in late hypophysectomized animals (23 days).

4. The implantation of renal cortical cells from 2 day hypophysectomized rats into unilaterally nephrectomized control litter‐mates inhibited compensatory renal hypertrophy in the latter. When a similar operation was made using kidney cells from animals which had been hypophysectomized for 23 days, there was no significant inhibition of compensatory renal hypertrophy.

5. The renal contents of adenosine‐3′,5′‐monophosphate (cyclic AMP) and of guanosine‐3′,5′‐monophosphate (cyclic GMP) in rats hypophysectomized for 2 days were of the same order as those in normal rats, but were markedly lower in rats hypophysectomized for 23 days.

6. In contrast to what had been observed in normal rats, in hypophysectomized (2 or 23 days) rats, unilateral nephrectomy did not affect significantly the levels of cyclic nucleotides in the remaining kidney.

7. Cross‐circulating anephric normal rats with 2 day hypophysectomized animals resulted in an increase of cyclic GMP content in their kidneys. The cross‐circulation between anephric normal rats and 23 days hypophysectomized rats had no effect on the level of renal cyclic GMP of the latter.

8. When rats hypophysectomized for either 2 or 23 days and which had been nephrectomized were cross‐circulated with normal rats, there were no changes in the content of cyclic GMP in the kidneys of the latter.
Relationship between intrapulmonary airway diameter and smooth muscle tone in excised lungs.
Authors: Clay T P , Hughes J M , Jones H A
Published: December 2014

1. Intrapulmonary bronchi in excised dog lungs were outlined with tantalum dust and stereoscopic radiographs taken during deflation and inflation of the lung after rinsing with solutions of saline, histamine, isoprenaline or EDTA. Dimensions of airways were calculated from measurements of the stereoscopic X‐ray images. 2. After treatment with EDTA to minimize bronchial smooth muscle activity, airway diameters increased at all transpulmonary pressures (Ptp) and lung volumes relative to their diameter after treatment with histamine; airway hysteresis in relation to Ptp decreased. 3. At low lung volumes, the per cent increase from histamine to EDTA for airways of different sizes was the same (24‐30%) but at high volumes (30 cm H2O distending pressure) the dilatation induced by EDTA was 30% for airways less than 3.0 mm diameter and 13% for those greater than 5.0 mm diameter. 4. Even at high lung volumes, intrapulmonary airways are free to constrict or dilate in spite of the stiffness of the supporting parenchyma.
Action of brown widow spider venom and botulinum toxin on the frog neuromuscular junction examined with the freeze‐fracture technique.
Authors: Pumplin D W , Reese T S
Published: December 2014

1. Structural changes which normally accompany transmitter release at frog neuromuscular junctions are visualized with the freeze‐fracture technique. The effects of brown widow spider venom and botulinum toxin were evaluated in terms of their ability to block or produce these structural changes. Changes produced by these neuropoisons were correlated with their known effects on neurotransmitter release. 3. Fusion of synaptic vesicles with the presynaptic plasmalemma, normally evoked by electrical stimulation, was abolished at neuromuscular junctions from frogs treated with botulinum toxin. 3. The concentration of large intramembranous particles in the presynaptic plasmalemma, an indication of the excess of synaptic vesicle fusion over recovery of synaptic vesicle membrane, was increased by treatment with brown widow spider venom, even in the presence of botulinum toxin. 4. When external calcium was present, sites of vesicle fusion induced by brown widow spider venom, as well as by electrical stimulation, were located mainly in the active zone. In the absence of external calcium, many plasmalemmal deformations, also though to be sites of vesicle fusion, were more evenly dispersed over the presynaptic surface of nerve terminals. 5. Botulinum toxin decreased the number of vesicle fusion sites in the active zone induced by spider venom in the presence of external calcium but had little effect on the number of fusion sites induced by spider venom in the absence of external calcium. 6. Nerve terminals soaked in a sodium‐free Ringer solution were partially depleted of vesicles. Addition of spider venom to this Ringer did not cause additional depletion of vesicles. 7. Formation of cation‐permeable channels in the presynaptic membrane could account for these effects of spider venom on the frog neuromuscular junction. Botulinum toxin blocks vesicle fusion by some means which is not yet understood.
Diencephalic efflux of calcium ions in the monkey during exercise, thermal stress and feeding
Authors: Gisolfi C. V. , Mora F. , Myers R. D.
Published: December 2014

1. The diencephalon of the unanaesthetized macaque monkey was radio‐labelled with calcium by a microinjection of 6‐8 μC 45Ca2+ into the third cerebral ventricle through a permanently implanted cannula. Successive 5 min push—pull perfusions of the mid‐line hypothalamic region with an artificial
C.S.F. were carried out at a rate of 28 μl./min every 20 min. A washout curve of declining 45Ca2+ radioactivity was thus generated.

2. When the monkey exercised strenuously on a special ‘rowing machine’ to obtain highly palatable banana pellets, its body temperature rose sharply. As the monkey exercised, during a sequence of push—pull perfusions, the concurrent efflux of 45Ca2+ ions increased markedly in the corresponding samples of diencephalic perfusate. This enhanced activity of calcium ions continued throughout a 30 min work period and persisted as long as the monkey's temperature was elevated in the interval immediately following exercise.

3. Exposure of the monkey's trunk, between neck and thigh to cold air of 5 °C likewise augmented the amount of 45Ca2+ ions in the diencephalic push—pull perfusates; however, a similar exposure to air warmed to 35 °C failed to alter the pattern of 45Ca2+ efflux from the animal's diencephalon. If a fasted monkey consumed only the banana pellets but was not exercised, the level of 45Ca2+ in the perfusate also increased transiently, just at the onset of feeding.

4. We conclude that a local change in calcium transport, binding or other cellular activity of the cation within the diencephalon could play an important role in the central mechanism underlying the set‐point rise in a primate's temperature which accompanies vigorous exercise. Further, the results support the idea that this cation functions in the diencephalic control of metabolic heat production as well as in the overall processes of energy metabolism, particularly in relation to feeding.
The effect of 2,3‐diphosphoglycerate on the oxygen dissociation curve of human haemoglobin.
Authors: Goodford P J , Norrington F E , Paterson R A , Wootton R
Published: December 2014

1. Oxygen dissociation curves for concentrated human haemoglobin solutions (1.6 mmol dm‐3 in haem) have been measured by mixing known quantities of oxy‐ and deoxyhaemoglobin solutions and measuring the resulting partial pressure of oxygen with an oxygen electrode. 2. Observations in the presence of 2,3‐diphosphoglycerate support previous conclusions derived from experiments at low haemoglobin concentrations, the validity of which has been questioned. 3. The two affinity state model of Monod, Wyman & Changeux (1965) does not fully describe the actions of 2,3‐diphosphoglycerate and a model in which this allosteric effector not only binds preferentially to the T state but also lowers the oxygen affinity of this state gives an improved fit to the data.
Cell replacement and changing transport function in the neonatal pig colon.
Authors: Jarvis L G , Morgan G , Smith M W , Wooding F B
Published: December 2014

1. Measurements of intracellular methionine concentration in pig colon, following in vitro incubation in methionine containine medium, have been carried out during the first 10 days of post‐natal life. 2. The new‐born pig colon concentrates methionine within its mucosa. Autoradiography of 3H‐labelled phenylalanine shows it to be accumulated to greatest extent in cells located in the surface epithelium. 3. The ability of the colonic mucosa to concentrate methionine disappears during the first few days of post‐natal life. 4. Radioactive thymidine, injected at birth, shows cell mitosis to be confined to the lower third of each colonic crypt. Labelled cells later migrate out of the crypts on to the surface epithelium. The cell replacement time is 105 h. 5. The time course for the fall in the ability of the pig colon to actively accumulate methionine corresponds to that predicted if cells synthesized from birth were unable to transport this amino acid. 6. The ability of the new‐born pig colon to transport amino acids, though transient, may be physiologically important. The nature of the signal which changes the physiological function of cells synthesized post‐natally remains to be determined.
Comparison of chloride concentration and osmolality in proximal tubular fluid, peritubular capillary plasma and systemic plasma in the rat.
Authors: Atherton J C
Published: December 2014

1. Chloride concentration and osmolalities were compared in consecutively collected samples of proximal tubular fluid, peritubular capillary plasma and systemic plasma. 2. Mean chloride concentrations (m‐mole/l) were 141.3+/‐2.6 in tubular fluid, 114.8+/‐1.7 in peritubular capillary plasma and 119.4+/‐1.8 in systemic plasma. 3. Mean osmolalities (m‐osmole/kg H2O) were 297+/‐2.2 in tubular fluid, 293+/‐2.4 in peritubular capillary plasma and 299+/‐1.8 in systemic plasma. 4. These differences are discussed in relation to the anatomical and functional organization of the peritubular capillaries and renal tubules.
Octanol reduces end‐plate channel lifetime
Authors: Gage Peter W. , McBurney Robert N. , Van Helden Dirk
Published: December 2014

1. Post‐synaptic effects of n‐octanol at concentrations of 0·1‐1 m
M were examined in toad sartorius muscles by use of extracellular and voltage‐clamp techniques.

2. Octanol depressed the amplitude and duration of miniature end‐plate currents and hence depressed neuromuscular transmission.

3. The decay of miniature end‐plate currents remained exponential in octanol solutions even when the time constant of decay (τD) was decreased by 80‐90%.

4. The lifetime of end‐plate channels, obtained by analysis of acetylcholine noise, was also decreased by octanol. The average lifetime measured from noise spectra agreed reasonably well with the time constant of decay of miniature end‐plate currents, both in control solution and in octanol solutions.

5. Octanol caused a reduction in the conductance of end‐plate channels. Single channel conductance was on average about 25 pS in control solution and 20 pS in octanol.

6. In most cells the normal voltage sensitivity of the decay of miniature end‐plate currents was retained in octanol solutions. The lifetime of end‐plate channels measured from acetylcholine noise also remained voltage‐sensitive in octanol solutions. In some experiments in which channel lifetime was exceptionally reduced the voltage sensitivity was less than normal.

7. In octanol solutions, τD was still very sensitive to temperature changes in most cells although in some the temperature sensitivity of τD was clearly reduced. Changes in τD with temperature could generally be fitted by the Arrhenius equation suggesting that a single step reaction controlled the decay of currents both in control and in octanol solutions. In some cells in which τD became less than 0·3 ms, the relationship between τD and temperature became inconsistent with the Arrhenius equation.

8. As the decay of end‐plate currents in octanol solutions remains exponential, and the voltage and temperature sensitivity can be unchanged even when τD is significantly reduced, it seems likely that octanol decreases τD by increasing the rate of the reaction which normally controls the lifetime of end‐plate channels.
Aldosterone effects on renal metabolism.
Authors: Snart R S , Taylor E
Published: December 2014

1. Manometric studies of the sodium dependent oxygen consumption in rat kidney slices have failed to reveal any significant effect of aldosterone treatment, adrenalectomy or sodium diet on sodium diet on sodium metabolism. 2. However, ammonia release from kidney slices was significantly reduced following adrenalectomy and this decrease was influenced by aldosterone treatment. 3. The dose‐response characteristic obtained for this aldosterone‐stimulated ammonia release has been determined. 4. The effect of a high Na+ diet on the ammonia release has been studied. An initial decrease after 2 days may be associated with decreased endogenous aldosterone secretion. However, aldosterone (2.5 microgram/100 g body weight)injections into these high Na+ treated animals fails to restore the normal ammonia release. 5. The effects of aldosterone (2.5 microgram/100 g body weight), dexamethasone (2.5 microgram/100 g body weight) and corticosterone (2.5 microgram/100 g body weight) injections, in adrenalectomized rats, on ammonia release and tissue tyrosine aminotransferase activities have been compared.
Increase in efflux of inorganic phosphate during electrical activity in small non‐myelinated nerve fibres.
Authors: Ritchie J M , Straub R W
Published: December 2014

1. The movements of labelled phosphate were measured in garfish olfactory and in rabbit vagus nerves at rest and during activity. 2. In garfish olfactory nerve kept in solutions with 120 mM‐sodium and 0.2 mM‐phosphate the fractional loss of 32P was 9.82 X 10(‐4) min‐1. Lowering the sodium concentration of the washing fluid decreased the efflux; lowering the phosphate produced a transient increase with subsequent return towards the efflux in 0.2 mM‐phosphate. 3. Stimulation at 0.50 sec produced an extra fractional loss of 12 X 10(‐6) impulse‐1. At 1/sec the effect was larger; at 5/sec it was about the same as at 0.5/sec. 4. After stimulation the effect of activity disappeared exponentially with a time constant of 4.4 min. 5. Lowering the sodium decreased the extra efflux with stimulation, whereas changing the phosphate concentration did not much affect the extra efflux. 6. In rabbit vagus nerve kept in 154 mM‐sodium and 0.2 M‐phosphate the fractional loss of 32P was 4.91 X 10(‐4) min‐1. Lowering the sodium or the phosphate decreased the resting efflux. 7. Stimulation of the vagus nerve at 15/sec produced an extra fractional loss of 0.87 X 10(‐6) impulse‐1. 8. The extra efflux with stimulation seems to result predominantly from an increase in intracellular inorganic phosphate resulting from increased break‐down of ATP after activity.
Calcium‐dependent repolarization in Paramecium
Authors: Brehm Paul , Dunlap Kathleen , Eckert Roger
Published: December 2014

1. Intracellular injection, recording and current‐passing methods were used to investigate the role of intracellular Ca in the modulation of electrical behaviour in the ciliate Paramecium caudatum.

2. Injection of EGTA converted graded regenerative responses ascribed to Ca inward current to all‐or‐none action potentials. The EGTA injection also caused a discontinuity in the steady state I—V relations to outward current, but had little effect on hyperpolarizing current—voltage responses.

3. The overshoot of the all‐or‐none spike produced by the EGTA‐injected cell followed an approximate 29 mV increase for a tenfold increase in external Ca concentration and was independent of changes in external K and Na concentrations.

4. The EGTA‐induced all‐or‐none action potential tended to produce plateaus that could last up to 20 sec. During the plateau the membrane slowly repolarized to a critical potential, upon which repolarization occurred precipitously.

5. Injection of 10−6
M‐free Ca2+ as a Ca‐EGTA buffer hyperpolarized the membrane and decreased the potential shifts to inward current pulses. These responses are consistent with an increase in K conductance.

6. During EGTA plateaus reversed beating of the cilia indicated a rise in intracellular Ca, and thus an inability of the EGTA to complex the Ca as rapidly as it entered the cilia. Reversal of the motile apparatus thus appears to be activated at lower concentrations of intracellular Ca than are required to activate the inferred Ca‐dependent K system.

7. In uninjected cells removal of the cilia, which results in a loss of the voltage‐activated Ca channels (Dunlap, 1977), or addition of extracellular Ba both tended to linearize the steady state I—V relations.

8. Injections of Cs and TEA tended to linearize the steady state I—V relations, but did not result in either a conversion to an all‐or‐none spike or a discontinuity in the depolarizing steady‐state I—V relations.

9. It is concluded that in Paramecium a Ca‐activated K conductance short‐circuits the inward current of the regenerative Ca response, preventing all‐or‐none behaviour. The occurrence of plateau spikes following EGTA injection indicates that the Ca conductance inactivates very slowly in face of a maintained depolarization. Such slow Ca‐inactivation is consistent with the slow relaxation of Ca‐dependent ciliary reversal that occurs during maintained depolarization.

10. The possibility is discussed that injection of EGTA may also enhance the Ca conductance.
Uptake of [14C]urea by the in vivo choroid plexus—cerebrospinal fluid—brain system: identification of sites of molecular sieving
Authors: Johanson Conrad E. , Woodbury Dixon M.
Published: December 2014

1. The time course of the uptake of [14C]urea by the lateral ventricular choroid plexus of the adult rat in vivo was analysed to delineate further the permeability characteristics of the epithelial membrane of this secretory tissue.

2. Eight hours after
I.P. injection, [14C]urea attained a steady‐state distribution in 78% of the tissue water of lateral ventricular choroid plexus; similarly, approximately 8 hr was required for radiourea to reach a steady‐state concentration in both the cerebral cortex and cerebrospinal fluid (c.s.f.).

3. Results obtained for compartment analysis were used to calculate the concentration of [14C]urea in the epithelium of the lateral ventricular plexus during the approach to and at steady‐state distribution. Even after 1 hr of distribution, the [14C]urea concentration in choroid cell water was less than 15% of that in plasma water.

4. Although the concentration of radiourea in choroid cell water continually increased after 3 hr, it remained in equilibrium with the concentration of [14C]urea in c.s.f. water. At the steady state (i.e., 8 hr), the distribution of [14C]urea between the water of plasma and that of the choroidal epithelium was considerably away from equilibrium (i.e., by 25‐30%).

5. An analysis of the concentration gradients for [14C]urea across both the apical (c.s.f.‐facing) and basolateral (plasma‐facing) membranes of the epithelium of the lateral ventricular plexus suggests that the movement of urea is hindered to a greater extent by the basolateral membrane than by the apical membrane.

6. Only a single half‐time component (1·3 hr) can be resolved from analysis of the curve describing the time course of uptake of radiourea by the choroid epithelial cell compartment.

7. The concentration gradient data suggest that urea penetrates from blood to c.s.f. via the choroid plexus by a transcellular pathway; however, it is not possible to rule out a paracellular pathway for urea movement.

8. At the steady state, radiourea distributes into 88% of the water of cerebral cortex. This observation, together with the finding of a steady‐state concentration gradient for [14C]urea from cortical tissue to c.s.f., constitutes evidence that urea movement is hindered at the blood‐brain barrier as well as at the blood—c.s.f. barrier.
Afterhyperpolarization mechanism in the dorsal spinocerebellar tract cells of the cat.
Authors: Gustafsson B , Linström S , Takata M
Published: December 2014

1. The longlasting afterhyperpolarization (a.h.p.) following single or short trains of spikes in dorsal spinocerebellar tract (DSCT) neurons of the cat has been studied with intracellular recording techniques. 2. The a.h.p. amplitude was found to be potential dependent, increasing with depolarization and decreasing with hyperpolarization of the membrane. With large membrane hyperpolarization, the a.h.p. could be reversed in direction, the estimated reversal level being around 30 mV more negative than the threshold potential for spike initiation. The a.h.p. amplitude was also little affected by Cl‐ ions injected into the cell. 3. The a.h.p. was associated with an increase in the membrane conductance, as measured with short current pulses. The major part of the conductance change was related to the a.h.p. itself and not secondary to the hyperpolarization, i.e. to an anomalous rectification. A conductance change was also found when the membrane potential was polarized close to the a.h.p. reversal level. There was a clear correlation between the a.h.p. amplitude and the measured conductance changes. 4. It is concluded that the a.h.p. in DSCT neurones, as in spinal motoneurones, is caused primarily by an increase in membrane conductance to potassium ions. 5. The time course of the conductance change underlying the a.h.p. was calculated from the a.h.p. voltage and a mathematical expression describing this time course is given. The properties of the a.h.p. in DSCT cells are compared with those in spinal motoneurones and the functional significance of the differences is discussed briefly.
Autonomic thermoregulation after intermittent cooling of the spinal cord and cold exposure in the rat.
Authors: Banet M , Hensel H , Pothmann B
Published: December 2014

1. O2 consumption, rectal and several skin temperatures were studied, at various ambient temperatures, in unanaesthetized rats that had been thermally stressed for an average of 290 h either by prolonged and intermittent cooling of the spinal cord or by prolonged and intermittent exposure to an ambient temperature which induced the same increase in O2 consumption as did the thermal stimulation of the spinal cord. 2. At all the test ambient temperatures, both groups of thermally stressed animals maintained a metabolic level higher than that of the controls. In the animals previously exposed to cold the extent by which the metabolic rate was greater than that of the control animals was independent of ambient temperature; in those previously subjected to cooling of the spinal cord, however, it increased as the ambient temperature was lowered. Rectal and average skin temperatures were essentially unaffected by the treatments. 3. It is concluded that prolonged and intermittent cooling of the spinal cord increases the gain of the temperature control system, whereas prolonged and intermittent cold exposure has no effect on it, and that these forms of thermal stimulation are therefore not equivalent.
Effect of amiloride on the renal response to saline expansion in new‐born dogs.
Authors: Banks R O , Kleinman L I
Published: December 2014

1. The renal effects of amiloride were studied in twenty‐six new‐born and nine adult dogs, with and without saline expansion. 2. Without saline expansion, amiloride inhibited more sodium reabsorption (normalized to GFR) in puppies than in adults (5.95 vs. 2.18 muequiv/ml. GFR, P less than 0.01). Amiloride inhibited sodium reabsorption more in saline expanded than in nonexpanded puppies (9.39 vs. 5.95 muequiv/ml. GFR, P less than 0.01) but there was no difference between expanded and non‐expanded adults. 3. Saline expansion by itself increased fractional sodium excretion (CNa/GFR) more in the adult than in the puppy (0.071 vs. 0.019, P less than 0.01). During amiloride inhibition, saline expansion increased CNa/GFR to 0.045 in the puppy (compared to 0.019 in the nonamiloride inhibited puppy) but saline expansion increased CNa/GFR to the same degree in the amiloride as in the non‐amiloride inhibited adult. 4. In all puppies amiloride inhibited more sodium reabsorption than potassium secretion and there was poor correlation between the degree of inhibition of sodium reabsorption and potassium secretion for both the puppy (r = 0.14) and the adult (r = 0.05). 5. Assuming that amiloride acts by inhibiting sodium reabsorption and potassium secretion in the late distal and cortical collecting tubules, these results support the conclusion that in these regions of the nephron of the new‐born dog (a) a greater fraction of the filtered sodium is reabsorbed than in the adult and (b) increased fractional sodium reabsorption is responsible, in part, for the attenuated natriuretic response to saline expansion.