bluuebunny/crossref_metadata_2025_split huggingface dataset:
Urine concentration during solute diuresis in potassium‐depleted rabbits. Evidence for a defect in tubular sodium transport
Authors: Barraclough M. A. , Guignard J-P. , Jones N. F. 
Published: December 2014

1. The relationship between osmolal clearance (Cosm) and the reabsorption of solute‐free water by the kidney (TH2Oc) was examined during 10% mannitol and 2·3% saline diuresis in normal and potassium‐depleted rabbits.2. In normal rabbits at osmolal clearances close to 3·0 ml./min, TH2Oc during mannitol diuresis was 0·87 ± 0·06 ml./min and during saline diuresis 1·19 ± 0·07 ml./min. The mean difference in TH2Oc of 0·32 ± 0·05 ml./min was highly significant (P < 0·001).3. In one group of potassium‐depleted rabbits with a reduction in maximal urinary concentration, TH2Oc during both mannitol and saline diureses was reduced significantly below normal and the increment in TH2Oc normally seen during saline diuresis was abolished.4. In a second group of potassium‐depleted rabbits maximal urinary concentration (1253 ± 88 m‐osmole/kg H2O) was not significantly different from that in normal rabbits (1272 ± 116 m‐osmole/kg H2O). In these animals, TH2Oc at osmolal clearances close to 3·0 ml./min was not significantly different during mannitol diuresis (0·83 ± 0·07 ml./min) from that in normal animals, whereas it was reduced significantly during saline diuresis (0·89 ± 0·07 ml./min, P < 0·001) and the difference in TH2Oc normally seen between mannitol and saline diuresis was abolished.5. The inability to increase TH2Oc during saline diuresis above that achieved during mannitol appears to be the earliest manifestation of the concentrating defect associated with potassium depletion. It probably results from an impairment of sodium transport by the ascending limb of the loop of Henle. This is supported by the fact that potassium‐depleted rabbits excreted a greater percentage of the filtered load of sodium than did normal controls.
Inward spread of activation in vertebrate muscle fibres
Authors: González‐Serratos H. 
Published: December 2014

1. A method for detecting the activation of individual myofibrils or groups of myofibrils within an isolated muscle fibre is described. It consists in making all the myofibrils wavy by setting the fibre in gelatine and compressing it longitudinally; active shortening of myofibrils can then be recognized by the straightening out of the waves.2. The time course of this straightening during a twitch was found by high‐speed ciné micrography.3. There is a delay of activation between the superficial and central myofibrils, from which the velocity of inward spread of activation can be found.4. This velocity has a Q10 of 2, and is about 7 cm/sec at 20° C. The mechanism of the inward spread of activation is discussed.5. On relaxation the waves reappear, showing that there is a spontaneous elongation of the myofibrils.
Effects of removing the external potassium on the smooth muscle of guinea‐pig taenia coli
Authors: Tomita T. , Yamamoto T. 
Published: December 2014

1. Removal of the external K ions depolarized the membrane of the guinea‐pig taenia coli by about 5 mV, and increased the frequency of the spontaneous spike activity. After about 20 min in K‐free solution, the frequency gradually decreased and spontaneous activity stopped after about 60 min.2. Readmission of K produced a transient hyperpolarization by 10–15 mV for 10–20 min, and lowered the excitability. The membrane resistance decreased during the hyperpolarization. When the external K concentration was returned to normal before the spontaneous activity had disappeared in K‐free solution, there was a complete suppression of the spontaneous electrical and mechanical activities, accompanied by hyperpolarization of the membrane. The duration of this suppression of electrical and mechanical activities depended on the exposure time to K‐free solution, the recovery being delayed by longer exposure.3. The effects of removing external K were essentially the same in the presence of tetrodotoxin (10−7 g/ml.), of atropine (10−6 g/ml.), and also in low Cl (2–7 m
M).4. The effects of ouabain (10−6 g/ml.) were similar to those of zero K but appeared more slowly. After treatment with ouabain, the membrane was hyperpolarized by removing the external K and there was no hyperpolarization nor suppression of the mechanical activity on readmission of external K.5. Rb substitution for K produced little effect and addition of 5·9 m
M‐Rb after K‐removal produced a typical suppression of activity as the readmission of K. When K was replaced with an equimolar concentration of Cs, the effects were similar to those produced by K‐free solution.6. The pattern of the response to a change in the external K concentration was different below 23° C. The spontaneous activity was suppressed by removal of K, and increased by returning the external K.7. It is concluded that, in the taenia, the membrane potential can be modified by an electrogenic pump, the activity of which is inhibited by removing K, by ouabain, and by lowering the temperature to about 23° C. During the recovery from the exposure to K‐free solution or to ouabain, the pump activity is potentiated, causing hyperpolarization of the membrane by 10–20 mV. Rb can, Cs cannot, replace K in activating the pump at the same concentration as K.
The frequency dependent character of the membrane capacity in cardiac Purkyně fibres
Authors: Carmeliet E. , Willems J. 
Published: December 2014

1. The upstroke of the action potential was used as a signal of variable frequency in order to measure the apparent membrane capacity of cardiac Purkyně fibres.2. The upstroke in Na‐Tyrode can be regarded as a high frequency signal. Action potentials in Na‐free, Sr‐Tyrode are characterized by a very small rate of depolarization (5 V/sec) and conduction velocity (15 cm/sec) and were used as a low frequency signal.3. On changing from Na‐ to Sr‐Tyrode the apparent membrane capacity increased by a factor of 3·77 and approached the value estimated by the square‐current technique.4. Cable properties (space and time constants, internal core and membrane resistance) were found to be constant when changing from Na‐ to Sr‐Tyrode.5. The significance of the frequency dependent character of the membrane capacity is discussed in relation to propagation and form of the action potential.
Control of water content of non‐metabolizing kidney slices by sodium chloride and polyethylene glycol (Peg 6000)
Authors: Robinson J. R. 
Published: December 2014

1. Cortical slices from kidneys of adult rats were equilibrated for 24 and 48 hr in the refrigerator in solutions containing 5 m
M‐K, 2·5 m
M‐Ca and Mg,
M/15 phosphate buffer (pH 7·4), 5 m
M cyanide and iodoacetate with 5, 6, 7 and 8% polyethylene glycol (PEG 6000) and 77, 154, 308, 462 and 770 m
M‐NaCl.2. There were no consistent differences in water content between slices after 24 and after 48 hr.3. Slices contained more water when either the concentration of NaCl or that of PEG was reduced. The increase in water content induced by lowering the concentration of either was prevented by a higher concentration of the other.4. Water content was held constant at 3·25 kg.kg−1 dry PEG‐free tissue despite a fall in [NaCl] from 770 to 77 m
M (more than 1200 m‐osmole.kg−1) by increasing PEG from 5·1 to 7·7% corresponding to an increase of the order of 15 m‐osmole.kg−1.5. It is suggested that PEG 6000 was so much more effective than NaCl, osmole for osmole, because PEG 6000 acted as a non‐penetrating solute, whereas NaCl penetrated the slices and reduced the ‘Donnan excess’ component of the intracellular colloid osmotic pressure so that this could be balanced by a smaller concentration of PEG.
Factors affecting the quantitative response of human eccrine sweat glands to intradermal injections of acetylcholine and methacholine
Authors: Foster K. G. 
Published: December 2014

1. Using a ventilated capsule in conjunction with an infra‐red water vapour analyser, and an indwelling intradermal needle, quantitative studies were made relating the magnitude of the sweat responses to the doses of acetylcholine or methacholine.2. Acetylcholine dose—response curves were constructed, and from these curves the threshold dose was defined. The threshold was similar in all subjects (10−3 ±
S.E. 10−4 μg/0·1 ml.).3. Factors affecting the acetylcholine dose—response curves were studied. Optimum conditions for stimulation in all subjects occurred using a capsule of 0·63 cm diameter, injection volume of 0·1 ml. and a solution temperature of 37° C. When the skin temperature was 36° C the maximal acetylcholine response was then the same as the maximal thermal response.4. No change in the acetylcholine dose—response curves occurred with repeated determinations at the same site on the same occasion.5. The dose—response relationship for methacholine was similar to that for acetylcholine. The methacholine response was, however, more prolonged and so the volumes secreted were greater.
Influence of variations in hydration and in solute excretion on the effects of lysine‐vasopressin infusion on urinary and renal tissue composition in the conscious rat
Authors: Atherton J. C. , Evans Jeanne A. , Green R. , Thomas S. 
Published: December 2014

1. The changes in urinary and renal tissue composition induced by continuous, intravenous infusion of lysine‐vasopressin (60 μ‐u./min. 100 g body wt. until steady‐state conditions prevailed) in normally hydrated, hydropaenic, saline‐loaded (0·9%, w/v) and mannitol‐loaded (15%, w/v) rats were determined and compared with those induced in water‐loaded rats.2. Previous reports that the urinary responses to antidiuretic hormones vary both with hydration status and with concurrent solute excretion rate were confirmed.3. The data show that variations in urinary responses were accompanied by differences in the papillary responses to lysine‐vasopressin.4. The results are discussed in terms of the effects of hydration and concurrent solute excretion on factors influencing (a) medullary accumulation of water and solute, (b) osmotic water reabsorption and (c) osmotic equilibration across the collecting duct; and of the effects of lysine‐vasopressin on these factors.5. It is concluded that the effects of hydration and solute excretion on the antidiuretic responses to lysine‐vasopressin may be interpreted by differences in (a) the medullary composition prevailing at the start and (b) any further changes in medullary composition that can be induced under the experimental circumstances.
Chromatic sensitivity and spatial organization of cat visual cortical cells: cone‐rod interaction
Authors: Hammond P. 
Published: December 2014

1. Colour sensitivity and spatial organization were determined for the dominant‐eye receptive fields of thirty‐eight simple or complex cells in cat primary visual vortex. Receptive fields were all from the cortical area associated with central vision. Each cell was investigated with threshold or suprathreshold monochromatic stimuli, under scotopic, low and high mesopic adaptation.2. The Purkinje shift, well defined for all units, was consistent with dual input from each of only two receptor mechanisms, viz. 556 nm cones and 500 nm rods. With change of adaptation level there was a systematic change in the peak sensitivity of spectral response curves to suprathreshold monochromatic stimuli, equated for quantum flux but of different wave‐length. Equally with change of adaptation, the relative shift in threshold between wave‐lengths selective for cone or rod activation was in close agreement with the change predicted from the Dartnall nomogram curves for visual pigments 556 and 507 respectively.3. For ganglion cells with concentric fields rod input derives from a spatially larger area than cone input. Rod field centre and rod field surround are substantially larger than the corresponding centre and surround for cones (Andrews & Hammond, 1970b). For cortical cells a conclusive comparable change could only be demonstrated for one simple unit. Its receptive field consisted of a horizontal excitatory stripe with asymmetric inhibitory flanks. When light‐adapted the weaker, upper flank was functionally undetectable, indicative of purely rod input to this sideband, and the preference for upward movement was enhanced.4. No difference in receptive field configuration, or in spatial extent of input mediated by cones or by rods, was detected for any other unit. The discrepancy between retinal and cortical findings is discussed. It is inferred that cortical fields are compounded essentially by convergent input from geniculate cell field‐centres.
Pressure waves and gradients in the canine thoracic duct
Authors: Browse N. L. , Lord R. S. A. , Taylor Alexis 
Published: December 2014

1. Pressures have been measured in the thoracic duct of anaesthetized and conscious dogs to ascertain the mean pressures, the nature of the pressure waves and the pressure gradients along the duct and between it and the great veins.2. The average mean pressure in the thoracic duct of ten anaesthetized dogs was 1·4 mm Hg. The pressure waves were secondary to respiration and the pulsations of the aorta. No waves were transmitted from the great veins.3. Pressures in conscious dogs varied from day to day, sometimes being positive, sometimes negative. They were increased by panting and by drinking.4. The pressure gradients along the duct were small, no more than 0·5–2·0 mm Hg along its whole length.5. No evidence was found of spontaneous contractions of the duct.
The glycogenolytic response to stimulation of the splanchnic nerves in adrenalectomized calves, sheep, dogs, cats and pigs
Authors: Edwards A. V. 
Published: December 2014

1. The effects of stimulation of the peripheral ends of one or both splanchnic nerves have been investigated in calves, sheep, dogs, cats and pigs after removal of both adrenal glands.2. Stimulation of both splanchnic nerves produced comparable hyperglycaemic and glycogenolytic effects in sheep, dogs and cats; the mean liver glycogen concentration was reduced by between 7·0 and 10·5 mg/g, five min after stimulation was discontinued, at which time the mean plasma glucose concentration had risen by between 126 and 137 mg/100 ml.3. In five 3‐5 week‐old calves which were tested under identical conditions the mean liver glycogen concentration was reduced by 13·3 ± 1·9 mg/g and the plasma glucose concentration raised by 216 ± 1·9 mg/100 ml., 5 min after stimulation was terminated.4. In pigs, stimulation of both splanchnic nerves invariably produced a rise in the plasma glucose concentration, even when the concentration of glycogen in the liver was less than 5 mg/g before stimulation. The response was, nevertheless, considerably smaller in these animals than in any of the other species investigated.5. Splanchnic nerve stimulation also caused a rise in mean aortic blood pressure and blood haematocrit during the period of stimulation; changes of approximately the same order of magnitude were encountered in all five species.6. Dogs were found to resemble calves in that the hyperglycaemic response to stimulation of a single splanchnic nerve did not differ significantly from that obtained when both were stimulated simultaneously; furthermore, either nerve was found to be equally effective.7. In cats the change in plasma glucose concentration in response to stimulation of a single splanchnic nerve was always less than that which occurred in response to bilateral stimulation although comparable changes in blood haematocrit occurred in both groups of animals.8. It is concluded that stimulation of the splanchnic nerves causes break‐down of glycogen in the livers of various unrelated species of adult animals but that the magnitude of the hyperglycaemic response in the young calf provides further evidence of the importance of the sympathetic system in the control of metabolism in the young animal.
Presynaptic depolarization of myelinated afferent fibres evoked by stimulation of cutaneous C fibres
Authors: Jänig W. , Zimmermann M. 
Published: December 2014

1. The origin of the dorsal root potential observed following a volley in cutaneous unmyelinated or C fibres (C‐DRP) has been investigated by several assays.2. Measurements of the spatial decrement of the C‐DRP along the dorsal roots indicate that mainly the thick myelinated primary afferent fibres contribute to this C‐DRP.3. The spatial configuration of the intraspinal potential field during the course of the C‐DRP is similar to that of the field correlated to the A‐DRP, i.e. the DRP evoked by a volley in the A fibres of the same cutaneous nerve. It is concluded therefrom that both A‐ and C‐DRPs signal presynaptic depolarizations of afferent fibres in the same regions of the dorsal horn.4. Intrafibre recordings reveal that C input produces primary afferent depolarization (C‐PAD) mainly in cutaneous and articular afferents, but not in muscle Group Ia afferents.5. These findings and direct measurements of the interactions between A‐ and C‐DRPs indicate that the pathways involved in A‐ and C‐PAD exhibit convergence.6. C‐DRPs were also recorded from contralateral rootlets.7. Some functional aspects of the PAD produced by an afferent volley in C fibres are discussed.
Effects of changing the ionic environment on passive and active membrane properties of pregnant rat uterus
Authors: Abe Y. 
Published: December 2014

1. In pregnant rat myometrium electrotonic potentials, produced by externally applied current, were recorded intracellularly.2. The space constant, λ, was 1·8 mm, the time constant, τm, 120 msec. The values obtained on the 7th day and on the 20th day of pregnancy were the same.3. The magnitude of the electrotonic potential and the time constant of the membrane were increased in the absence of potassium from the external solution and decreased by excess potassium.4. The magnitude of the electrotonic potential and the time constant of the membrane were increased by the replacement of chloride with C6H5SO3μ or SO42‐, and decreased with NO3μ or Iμ replacement.5. When the sodium chloride was replaced with sucrose (16·7 m
M sodium remaining in the buffers) the spontaneous spikes deteriorated and activity stopped within 30 min. However, for periods up to 4 hr, a spike of larger amplitude and faster rate of rise than in normal solution could be evoked when a depolarizing current was applied.6. When the external calcium concentration was raised (5 and 10 m
M) the amplitude and the rate of rise of the evoked spike were increased. They were decreased by reducing calcium. In zero calcium spontaneous activity stopped within 15 min.7. The effects of calcium deficiency were much less marked and slower in onset when, simultaneously, the sodium concentration was reduced to 16·7 m
M.8. When calcium was replaced with strontium (2·5 m
M), the membrane was depolarized and the duration of the spontaneous and evoked action potential was prolonged, mainly due to a slowed rate of repolarization. When the concentration of strontium was raised to 7·5 or 12·5 m
M the membrane was hyperpolarized, the duration of the action potential became short and the amplitude of the spike was increased.9. Addition of barium or the replacement of calcium with barium caused depolarization and oscillatory membrane activity. However, a spike could be evoked by applying conditioning hyperpolarization.10. Manganese abolished the spontaneous and evoked spike. Tetrodotoxin had no effect.11. The results show that rat uterus has cable‐like properties. The action potential may be due to calcium entry, while sodium, by influencing the membrane potential in competition with calcium, may be involved in the spontaneous spike generation and the spread of excitation.
Oxytocin and ADH secretion in relation to electrical activity in antidromically identified supraoptic and paraventricular units
Authors: Dyball R. E. J. 
Published: December 2014

1. Electrical recordings were made from antidromically identified supraoptic and paraventricular units during intracarotid injections of hypertonic and isotonic sodium chloride solutions in rats.2. The blood concentrations of vasopressin and oxytocin were estimated by bio‐assay before and at different intervals after similar injections.3. Although a significant change in the action potential activity of the supraoptic nucleus was associated with hormone release, the results were not entirely consistent with a simple relationship between action potential activity and hormone secretion. Firstly, although some units were excited by the stimulus a substantial number were inhibited. Secondly, the blood concentration of the hormones, particularly ADH, remained elevated for longer than might have been expected if additional hormone had ceased to be secreted as soon as firing rates had returned to control values.4. There were substantial differences between the initial blood concentrations of vasopressin and oxytocin but the firing rates of units in the supraoptic and paraventricular nuclei appeared to be the same.5. Although significantly less paraventricular than supraoptic units were affected by hypertonic injections the blood concentration of oxytocin was increased by a factor of 8 whereas that of vasopressin was increased by a factor of 2·7.
Variations in mucosal water and sodium transfer associated with the rat oestrous cycle
Authors: Crocker Ann D. 
Published: December 2014

1. Mucosal water and sodium transfer were measured in everted sacs of rat jejunum.2. Mucosal water transfer was higher at pro‐oestrus and oestrus than at metoestrus and dioestrus.3. Injection of 10 μg aldosterone
I.P. 28 hr before the experiment produced a stimulation of mucosal water and sodium transfer in sacs prepared from rats at dioestrus but not in sacs from rats at oestrus.4. A significant increase in mucosal water and sodium transfer was observed when sacs from dioestrous rats were incubated with angiotensin at a concentration of 10−9 g/ml. No effect was obtained in sacs from oestrous rats.5. Treatment of adrenalectomized‐ovariectomized rats with oestradiol caused a stimulation of mucosal water transfer 28 hr after injection.6. It is suggested that the actions of ovarian steroids on water and electrolyte metabolism might be due to increased activity of both the adrenal cortex and the renin‐angiotensin system.
The effect on drinking of peptide precursors and of shorter chain peptide fragments of angiotensin II injected into the rat's diencephalon
Authors: Fitzsimons J. T. 
Published: December 2014

1. Recently it has been shown that injection of angiotensin II into the anterior diencephalon causes the rat to drink water. In the present experiments the dipsogenic action of a number of other substances including substances related to angiotensin was tested.2. Injection of 0·001 Goldblatt u. renin into the angiotensin‐sensitive region causes the water‐replete rat to drink. Drinking is slower in onset and continues for longer than after injection of angiotensin II.3. Synthetic tetradecapeptide renin substrate and angiotensin I were as effective as angiotensin II at causing water‐replete rats to drink.4. β‐aspartic acid1‐valine5‐angiotensin II was also fully effective; but the
D‐arginine substituted octapeptide was much less effective.5. The (2–8) heptapeptide retained about 50% of the dipsogenic activity of the octapeptide, whereas the absence of phenylalanine at the other end of the peptide chain in the (1–7) heptapeptide results in an inactive compound.6. The (3–8) hexapeptide and the (4–8) pentapeptide, both of which have phenylalanine at the end of the chain, and the (1–4) and (5–8) tetrapeptide fragments of angiotensin II showed only a slight action on intake of water.7. Kallikrein, bradykinin, adenosine‐3′5‐cyclic phosphate, vasopressin and oxytocin caused no drinking when injected into the angiotensin‐sensitive region.8. It is concluded that the requirements for the dipsogenic activity of angiotensin are the same as those for its other biological actions with the qualification that the precursor peptides are also active, presumably because they give rise to angiotensin II locally.