bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of lung inflation on the control of respiratory frequency in the neonate
Authors: Boychuk Rodney B. , Rigatto Henrique , Seshia Mary M. K. 
Published: December 2014

1. We have measured the relationship between tidal volume (VT) and the duration of inspiration (Ti) and expiration (Te) for individual breaths (30 in each steady state).2. Ten pre‐term and ten term infants were studied during steady state while breathing 21% O2, then 21% O2 plus 2 and 4% CO2.3. In all infants, the average Ti at the various chemical drives was remarkably constant, and did not decrease as the tidal volume increased. However, at any given level of respiratory drive, there was a slightly positive correlation of VT with Ti and Te in 95% of the cases.4. In four pre‐term and two term infants, Te increased with increasing respiratory drive. In these infants, therefore, instantaneous respiratory frequency (1/(Ti + Te)) actually decreased as lung volume increased.5. We suggest that Ti is independent of VT within the range of volumes studied (up to 2 times the resting VT) and that changes in instantaneous respiratory frequency (1/(Ti + Te)) result from changes in Te.
Metabolism of the frog outer segments: a kinetic study
Authors: Bignetti E. , Cavaggioni A. 
Published: December 2014

1. The reaction of the high‐energy phosphate esters of the frog isolated rods, with the firefly lantern extract, has been studied by recording the luminescence in a stopped‐flow apparatus. The onset of the reaction was determined by the rapid mixing of the firefly lantern extract with the high‐energy phosphates released from the rods fragmented during the mixing.2. The time course of the reaction, i.e. of the luminescence, was not typical of adenosine‐5′‐triphosphate (ATP), indicating that the major part of the rod nucleotides is not ATP.3. The isolated rods were fragmented 1 sec‐2 min after a flash of light. As soon as 1 sec after illumination, a substantial decrease of the luminescent yield has been detected in a range of light bleaching from 0·007 to 20% of the rhodopsin, indicating an early reduction of the high‐energy phosphate esters.4. At longer times, flashes that bleached 7 or 20% of the rhodopsin induced a progressive decrease of the luminescent yield that was half completed in 6‐9 sec, and was nearly complete in 20 sec, whereas a more or less complete recovery was observed after flashes bleaching from 0·7 to 0·007% of the rhodopsin, indicating the presence of buffering mechanisms.5. Also, the time course of the reaction was modified in a complex way after stimulation of the rods, suggesting that other nucleotides beside ATP are hydrolysed.6. The light‐induced reduction of the high‐energy phosphates has been observed also in broken rods, in the presence of the calcium chelating agent EGTA, suggesting that calcium is not needed for this effect.7. Cyclic guanosine monophosphate (10−4
M) interfered with the photic effect.8. The rapid effect of light on the content of high‐energy phosphate esters suggests a physiological role in the mechanism of excitation.
Location of U.V.‐absorbing substance in isolated skeletal muscle fibres: the effect of stimulation (frog, snake)
Authors: Lännergren J. 
Published: December 2014

1. In an attempt to study the intracellular location of ATP in skeletal muscle the distribution of substances which absorb light at 260 nm wave‐length has been studied in isolated muscle fibres with the aid of a modified U.V.‐microscope.2. U.V.‐absorption in resting frog fibres was found to be higher in the I band than in the A band which confirms earlier findings. In stretched fibres (sarcomere length 2·9‐3·6 μm) an absorbing substance could be seen to be concentrated in a pair of narrow lines, centred at the Z‐line. The separation of the lines increased with increasing sarcomere length.3. Snake fibres, with sparse triads located at the A‐I junction, displayed an absorption pattern very similar to that of frog fibres. It is concluded that it is unlikely that the absorbing substance is associated with the sarcotubular system.4. The absorption pattern of frog fibres remained unchanged during a tetanus. No clear changes could be detected after a period of stimulation, neither after single twitches nor after repeated tetani.5. In further attempts to cause exhaustion, metabolically poisoned fibres were stimulated repetitively until they went into rigor. The absorption pattern was essentially unchanged also when rigor tension started to develop.6. The characteristic absorption pattern was observed also in glycerol‐extracted fibres. It was confirmed by spectrophotometry that glycerol‐extraction led to the disappearance of a large amount of a substance with the spectral characteristics of ATP.7. The higher U.V.‐absorption in the I band does not prove that the major part of the ATP in the fibre is concentrated here; the absorption could either be due to a minor fraction of the ATP or to RNA.
The membrane properties of the smooth muscle cells of the rabbit main pulmonary artery
Authors: Casteels R. , Kitamura K. , Kuriyama H. , Suzuki H. 
Published: December 2014

1. The membrane potential of the smooth muscle cells of the rabbit main pulmonary artery amounts to ‐57 mV, the length constant of the tissue is 1·48 mm and the time constant of the membrane 182 msec. On the basis of the electrical properties of its membrane, this smooth muscle tissue is classified as a single‐unit type. During outward current pulses, the membrane shows marked rectification and action potentials can never be generated.2. Tetraethylammonium (10 m
M) and procaine (5 m
M) depolarize the membrane and increase the membrane resistance. By studying the effect of both substances on the 42K efflux, it could be concluded that they reduce the K‐permeability of the membrane. They also suppress the rectification of the membrane and increase the length constant of the membrane. In the presence of TEA and procaine, a graded response of the membrane can be induced by outward current pulses, but overshoot potentials never occur.3. Noradrenaline, in concentrations between 2 × 10−8 and 10−7
M, evokes contraction without depolarizing the membrane. When the concentration is increased above 2 × 10−7
M, noradrenaline depolarizes the membrane and reduces the membrane resistance. A study of the effect of noradrenaline on the K, Cl and Na fluxes has revealed that it increases the permeability of the membrane for these three ions.4. The tissue concentrations of Na and K are 80 and 38 m‐mole/kg wet wt., respectively. The amount of Cl in the cellular compartment was measured by an extrapolation procedure and found to be 13 m‐mole/kg wet wt. The extracellular space measured with [14C]sorbitol is 550 ml./kg wet wt. and the dry wt./wet wt. ratio 19%. The calculated equilibrium potentials for K, Na and Cl (EK, ENa and ECl) are ‐83, +59 and ‐26 mV, respectively. In efflux experiments under steady‐state conditions, the following rate constants have been calculated: 0·092 min−1 for Na, 0·029 min−1 for Cl and 0·0054 min−1 for K. The calculated value for the ratio PNa/PK was 0·22 and for PCl/PK 0·63.5. K‐free solution and 2 × 10−6
M ouabain depolarize the cells by about 8 mV. After exposure of the cells to K‐free solution, they hyperpolarize on readmission of K, suggesting that part of the membrane potential could be due to electrogenic transport of ions.6. A decrease of external Ca depolarizes the cells and increases the membrane resistance. Na‐deficiency hyperpolarizes these smooth muscle cells but this procedure does not prevent the depolarization induced by Ca deficiency.
Characterization of the responses of oxytocin‐ and vasopressin‐secreting neurones in the supraoptic nucleus to osmotic stimulation
Authors: Brimble M. J. , Dyball R. E. J. 
Published: December 2014

1. Extracellular action potentials were recorded from forty antidromically identified single units in the supraoptic nucleus of lactating, urethane‐anaesthetized female rats. The activity was monitored both during reflex milk ejection and during an increase of 10‐15 m‐osmole/kg in plasma osmotic pressure induced by intraperitoneal injection of 1 ml. of 1.5
M‐NaCl solution.2. About half (eighteen) the cells showed a burst of activity before reflex milk ejection and were dubbed oxytocin cells. Oxytocin cells responded to a hypertonic injection with a smooth sustained threefold increase in firing rate.3. The remainder (twenty‐two) showed no burst of activity before reflex milk ejection and were dubbed vasopressin cells. Vasopressin cells doubled their firing rate as plasma osmotic pressure increased. Neither cell type increased its firing rate after injections of isotonic NaCl.4. A phasic firing pattern was rarely seen in slow firing vasopressin cells (< 2 spikes/sec) but was seen in almost all vasopressin cells (twelve out of fourteen) firing between 3 and 8 spikes/sec. Above 8 spikes/sec, some vasopressin cells fired continuously. Phasic firing was only once encountered in an oxytocin cell.5. The firing rate of both oxytocin and vasopressin cells decreased when plasma osmotic pressure was reduced 10‐15 m‐osmole/kg by an intragastric water load of 10 ml.6. Hypothalamic cells lying just outside the supraoptic nucleus did not show a consistent response to injection of hypertonic NaCl.7. Clearly, both oxytocin and vasopressin cells are osmoresponsive, but phasic firing is characteristic of stimulated vasopressin cells. Thus, osmotic activation allows discrimination between oxytocin‐ and vasopressin‐secreting neurones.
An in vitro system for studying insulin release: effects of glucose and glucose‐6‐phosphate
Authors: Davis Brian , Lazarus Norman R. 
Published: December 2014

1. Investigation of the ionic requirements of the in vitro insulin release system, which consists of cod islet plasma membrane and rabbit islet granules incubated at pH 6.5, showed that the presence of Ca2+ was obligatory for the system to operate.2. Glucose‐initiated insulin release was as effective in the presence of β‐γ‐methylene ATP, as it was in the presence of ATP. This analogue of ATP is a substrate neither for adenylate cyclase nor for any known animal membrane proteases. The effect of ATP on glucose mediated release is allosteric.3. Glucose (16 m
M)‐initiated insulin release was slower than that induced by glucose‐6‐phosphate (4 m
M); 150 and 120 sec, respectively.4. The lag found with glucose‐mediated insulin release was dependent upon glucose concentration. The lower the glucose concentration, the longer the lag. With 1 m
M glucose the lag extended to 30 min.5. Once insulin release was initiated, the rate and amount of insulin release was independent of the glucose concentration.6. Pre‐incubation of membranes with Ca2+, glucose and ATP prior to the addition of granules, abolished the extended lag that had been obtained with 1 m
M glucose. Events in the plasma membrane are the major contributor to the generation of the extended lag.7. The glucose analogue 5′thio‐
D‐glucose, although not able to release insulin, was shown to compete with glucose for the glucoreceptor. By increasing the ratio of analogue to glucose the lag time increased. Thus, the lag time is dependent upon the ‘effective’ external glucose concentration.8. The max. amount of insulin released by 4 ng of membrane in the presence of glucose (16 m
M) was 300 ng. The fact that membranes became refractory to glucose after this max. amount of insulin was released showed that recycling of release sites was not taking place in vitro and that granule: granule interactions were not occurring.9. The 120 sec lag before glucose‐6‐phosphate‐initiated release was independent of glucose‐6‐phosphate concentration. The rate of insulin release with glucose‐6‐phosphate was concentration dependent.10. Glucose‐6‐phosphate did not cause further insulin release from a membrane that had released the max. amount of insulin it was capable of in the presence of glucose. The addition of tolbutamide (10 m
M) to such a membrane did cause insulin release. This suggests that glucose and glucose‐6‐phosphate share a final common pathway.11. Adrenaline and somatostatin did not inhibit glucose‐mediated insulin release.
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.