bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model of thyroxine metabolism based on the effects on environmental temperature
Authors: Harland W. A. , Orr J. S. 
Published: December 2014

1. Evidence is presented that, in rats, the whole body and plasma half‐lives of [131I]thyroxine are different.2. It is shown that the whole body half‐life can be influenced by environmental temperature: plasma half‐life is influenced to a much lesser extent.3. It is demonstrated that, in the rabbit, free labelled thyroxine and plasma bound labelled thyroxine leave the plasma at different rates when administered by intravenous injection.4. It is deduced from the above and other evidence that the currently accepted view of thyroxine distribution and metabolism is invalid and a model compatible with the evidence is presented and discussed.5. The essential feature of the model is that protein binding in plasma or in various tissues, once it has occurred, may be regarded as being irreversible and that no significant interchange takes place.6. Indices of thyroxine metabolism are derived. These enable thyroxine content and turnover of the whole body or of individual organs to be measured.
Distribution and kinetics of CoEDTA in smooth muscle, and its use as an extracellular marker
Authors: Brading Alison F. , Jones A. W. 
Published: December 2014

1. [60Co]EDTA has been evaluated as an extracellular marker in guinea‐pig taenia coli and rabbit myometrium.2. The complex was found to be stable, non‐toxic, convenient to use and had the advantage of being readily measured without interfering with the analysis of water and electrolyte contents.3. In both smooth muscles [60Co]EDTA distributed rapidly into a volume equivalent to that available to [14C]sorbitol and slightly greater than that available to inulin.4. The optimum concentrations of carrier required to effectively saturate any adsorption sites were 0·1 m
M‐CoEDTA for taenia coli and 1·0 m
M for myometrium.5. [60Co]EDTA was distributed into a volume equivalent to the total water content of rabbit tendon, indicating that it was not excluded from connective tissue water.6. About 5% of the [60Co]EDTA taken up by smooth muscle in 15 minutes exhibited slow efflux kinetics. This property was also exhibited by [14C]sorbitol and has been reported for other extracellular markers.7. The efflux of 95% of [60Co]EDTA followed bulk diffusion kinetics for both taenia coli and myometrium.8. The simultaneous efflux of 24Na indicated that 1‐2% exchanged slowly while 98‐99% of the 24Na exchange could be described by bulk diffusion kinetics, similar to [60Co]EDTA. About 15% of this 24Na was contained outside of the [60Co]EDTA space.9. More detailed studies involving the analysis of simultaneous efflux of [60Co]EDTA and 24Na may help to locate and characterize the properties of the excess rapidly exchanging sodium (12‐15 m‐equiv/kg. wet wt.) in smooth muscle.
Metabolism, sperm and fluid production of the isolated perfused testis of the sheep and goat
Authors: Linzell J. L. , Setchell B. P. 
Published: December 2014

1. A total of nineteen ram and three goat testes have been perfused in isolation at 34–35° C for 3½‐9 hr with heparinized blood and an added 5‐HT antagonist (bromolysergic acid diethylamide) and their function compared with that of the normal ram testes in vivo.2. The metabolism of the perfused testes and the testes in vivo was similar but blood flow through the perfused testes was two to three times normal.3. Vasoconstriction was produced by adrenaline and noradrenaline (10–20 μg
I.A.) and by electrical stimulation of nerves in the spermatic cord or of the lumbar sympathetic chain; these responses were abolished or reduced by phenoxybenzamine.4. Flow of fluid from the rete testis continued only if ischaemia was reduced to a minimum and glucose concentration in the blood perfusing the testis was kept above about 25 mg/100 ml.; the fluid secreted during perfusion was of normal composition.5. The perfused testis showed no evidence of autoregulation and the flow of fluid was not affected by changes in perfusion pressure.6. When the temperature of three testes was raised to 40° C for 2 hr, metabolism increased but blood flow was unaltered; the flow of fluid and the concentration of spermatozoa decreased during heating.7. The testes perfused at normal scrotal temperatures (34–35° C) were histologically normal but some abnormalities were observed in the heated testes.
The longitudinal tissue impedance of the smooth muscle of guinea‐pig taenia coli
Authors: Tomita T. 
Published: December 2014

1. The absolute value of the tissue impedance of the guinea‐pig taenia coli was measured in the longitudinal direction in air at 36° C. The relation between the tissue impedance and the separation of the recording electrodes indicated that the tissue has cable‐like properties. The frequency dependence of the impedance, observed at various distances from the current supplying electrode, showed that the tissue has a capacity component in the longitudinal direction.2. The tissue impedance in the longitudinal direction was also measured while the tissue was suspended in a narrow tube at 25–28° C. The tissue impedance was calculated on the basis of the difference between the total impedance in Krebs solution and that in Krebs solution containing half the normal Na concentration, knowing the specific resistance of both solutions.3. The impedance per unit volume of the tissue was 370 Ω cm at 10 c/s and 190 Ω cm at 10 kc/s; at these frequencies the impedance was nearly independent of current frequency. The difference between the impedances (370 — 190 = 180 Ω cm) was taken to be the impedance of the junctions between cells. The possibility of slightly lower values for the actual tissue impedance was discussed. The capacity located at or near the junction was calculated to be 1–3 μF/cm, the time constant of the junctional membrane being about 0·5 msec.4. Ca ions (0–12·5 m
M) and adrenaline (2 × 10−7 g/ml.) had no measurable effect on the longitudinal impedance within 10–15 min. In hyperosmotic solution of twice osmolarity (by adding sucrose), the tissue impedance was increased by about 50%. When the tissue was immersed in sucrose solution containing no ions, the impedance gradually increased up to nearly 10 times in the course of 1 hr.
Transcellular transport of isosmotic volumes by the rabbit gall‐bladder in vitro
Authors: Frederiksen O. , Leyssac Paul P. 
Published: December 2014

1. Fluid transport rate and oxygen consumption (QO2) were studied in rabbit gall‐bladder preparations in vitro exposed on both sides to identical Ringer solutions with NaCl concentrations (and osmolarities) varying from 70 to 140 m‐equiv Na+/l.).2. The time sequence of acute effects on transport rate resulting from sudden changes in the NaCl concentration of the bathing solutions indicated that, (a) as a primary effect, fluid volume transfer rate remained unaffected whereas Na transport rate changed abruptly in direct proportion to the Na concentration of the bathing media; (b) a secondary, delayed and partly reversible depression of fluid transfer rate following elevation of the NaCl concentration was observed only when the rate of transport was relatively high initially.3. A fixed, and highly significant, linear relationship between changes in transport‐linked oxygen consumption (ΔQO2) and measured net fluid volume transport (ΔTvol) was found independent of the NaCl concentration of the bathing media, dQO2/dTvol being 0·22 ± 11% and 0·25 ± 8% in bladders incubated in solutions containing 140 and 70 m‐equiv Na+/l. respectively.4. Oxygen consumption per equiv of Na+ (calculated) transported varied in inverse proportion to the Na concentration of the bathing media, dQO2/dTNa being 0·0016 ± 11% and 0·0036 ± 8% in ‘140 R’ and ‘70 R’ solutions, respectively.5. Removal of K from the bathing solutions was followed by a gradual and partly reversible depression of fluid transport rate to a minimum level (about 100 × 10−4 μl H2O. min−1.mg−1) independent of the initial transport rate.6. It is concluded that the range of absorption rates of isosmotic fluid from the gall‐bladder lumen represents a range of energy requiring capacities for transfer of fluid volume units; the data suggest that the intracellular (cytoplasmic) ion composition, depending on the presence of external K, as well as hormonal action may influence the capacity of the transcellular fluid transport mechanism.7. A model (a ‘mechanical volume pump’) for transcellular transfer of fluid volume units, allowing for flexible specificity with regard to the actively transported solutes, and requiring the presence of Na+ and Cl−, is proposed.
The effect of vagotomy, vagal cooling and efferent vagal stimulation on breathing and lung mechanics of rabbits
Authors: Karczewski W. , Widdicombe J. G. 
Published: December 2014

1. The effects of bilateral cervical vagotomy, of bilateral vagal cooling and of efferent vagal stimulation were studied on rabbits anaesthetized with pentobarbitone sodium. Total lung conductance, lung compliance, breathing frequency, tidal volume, end‐tidal CO2%, systemic arterial and right atrial blood pressures and heart rate were measured. Some of the rabbits were first paralysed and artificially ventilated.2. The changes in lung conductance were consistent with the presence of a tonic efferent vagal discharge in bronchoconstrictor fibres, reflexly damped down by a tonic afferent vagal discharge dilator to the airways, probably the Hering—Breuer inflation reflex.3. Neither vagotomy nor efferent vagal stimulation significantly influenced lung compliance, right atrial pressure or end‐tidal CO2%; vagal cooling lowered end‐tidal CO2% in spontaneously breathing rabbits, but did not affect the other variables.4. Efferent vagal stimulation in the rabbit decreased lung conductance with no significant change in lung compliance.5. In the rabbit, vagal efferent activity affects primarily the larger (resistance) air passages with little action on the distal (compliance‐influencing) airways.
The role of the vagus nerves in the respiratory and circulatory responses to intravenous histamine and phenyl diguanide in rabbits
Authors: Karczewski W. , Widdicombe J. G. 
Published: December 2014

1. The responses of rabbits, anaesthetized with pentobarbitone sodium, to intravenous injections of histamine and phenyl diguanide have been studied. Total lung conductance, lung compliance, breathing frequency, tidal volume, end‐tidal CO2%, systemic arterial and right atrial blood pressures and heart rate were measured. Some of the rabbits were first paralysed and artificially ventilated.2. The role of vagal afferent nerves was determined by observing the responses before and after bilateral vagotomy, and before and during cooling the vagus nerves to 8–10° C; such cooling selectively blocks some vagal afferent pathways.3. Histamine decreased conductance (bronchoconstriction), in spontaneously breathing and in paralysed, artificially ventilated animals, and caused rapid shallow breathing. The responses were considerably reduced or abolished by vagal cooling and vagotomy and are thought to be mainly vagal reflexes due to stimulation by histamine of irritant receptors in the lungs.4. Phenyl diguanide also decreased conductance, in spontaneously breathing and in paralysed, artificially ventilated animals, and caused rapid shallow breathing. Vagotomy abolished the respiratory changes and considerably reduced the bronchoconstriction. Vagal cooling caused an equal reduction of the bronchoconstriction but an increase in minute volume persisted. This respiratory response to phenyl diguanide which persists during vagal cooling is thought to be due to stimulation of deflation receptors in the lungs; it was associated with vagal reflex hypotension and bradycardia.5. Both histamine and phenyl diguanide decreased lung compliance when vagal conduction was unimpaired. The effects were largely secondary to changes in the pattern of breathing, although histamine also had a weak direct action on lung tissue leading to a fall in compliance.6. Both histamine and phenyl diguanide decreased end‐tidal CO2% and increased right atrial pressure by direct (non‐vagal) actions on lung tissues. Histamine also caused a non‐vagal hypertension.
Wave‐length discrimination at the foveal chromatic threshold
Authors: Wilson M. E. 
Published: December 2014

1. Wave‐length discrimination has been measured at the chromatic threshold to test the assumption that when a monochromatic stimulus is reduced to its chromatic threshold, the activity of a single cone mechanism may be isolated.2. It has been shown that, at the chromatic threshold, all wave‐lengths between 559 and at least 665 mμ are significantly confused. Similar ranges of confusion extend from 457 to 570 mμ and from 485 to at least 419 mμ.3. These results have been shown to be consistent with previous measures of the spectral sensitivities of the cone pigments. They support the view that the hue of a monochromatic stimulus at its chromatic threshold may be dependent on light absorbed by only one cone pigment.
Membrane current and intracellular sodium changes in a snail neurone during extrusion of injected sodium
Authors: Thomas R. C. 
Published: December 2014

1. Sodium was injected into an identified snail neurone by passing current between two intracellular micro‐electrodes, the membrane potential being recorded with a third micro‐electrode.2. The injection of about 25 p‐equiv Na, but not the injection of similar quantities of K or Li, caused a hyperpolarization of up to 20 mV. This response to Na injection was blocked by application of ouabain or removal of external K, indicating that it was due to the stimulation of an electrogenic pump.3. To measure the current produced by the sodium pump the output of a feed‐back amplifier was fed into the cell via a fourth intracellular micro‐electrode so as to keep the average membrane potential constant. The pump current, measured in this way, rose at a constant rate during, and declined exponentially after, an injection of Na, the decline having an average time constant of 4·4 min. The total charge transferred by the pump was between a third and a quarter of the charge passed to inject sodium.4. An intracellular Na‐sensitive glass micro‐electrode was used to follow changes in the concentration of intracellular Na ions. The results showed that both the pump current and the rate of Na extrusion were proportional to the concentration of intracellular Na ions above the normal level.5. It was concluded that about two thirds of the Na extruded was coupled to the active transport of other ions, probably to the uptake of K, the uncoupled third producing the electrogenic effect.
The influence of activity on some contractile characteristics of mammalian fast and slow muscles
Authors: Salmons S. , Vrbová Gerta 
Published: December 2014

1. The time course of contraction and relaxation in the isometric twitch of a rabbit soleus muscle becomes more rapid following tenotomy and spinal cord section. This increase in speed could be prevented by long‐term electrical stimulation at frequencies of 5 or 10/sec. It was not prevented by stimulation at frequencies of 20 or 40/sec.2. Long‐term electrical stimulation of fast rabbit and cat muscles at a frequency of 10/sec had a slowing effect on the time course of contraction and relaxation.3. It is concluded that the almost continuous low frequency discharge of motoneurones innervating postural muscles plays an important part in establishing and maintaining the slow time course of contraction of these muscles. The characteristically different speeds of contraction of fast and slow striated muscles can in this way be related to the different patterns of impulse activity which they normally receive.
Contractile repriming in snake twitch muscle fibres
Authors: Heistracher P. , Hunt C. C. 
Published: December 2014

1. Contractile repriming has been studied in voltage‐clamped snake twitch muscle fibres. Maintained depolarization causes a contractile response which inactivates after a few seconds. Repolarization of the fibre can restore its ability to contract to a subsequent depolarization. This restoration, or repriming, depends on the magnitude and the duration of the repolarization. At −100 mV the minimal period of repolarization which restores contractile response is 0·38 sec. The time for recovery to half maximal tension is about 0·68 sec, and restoration is complete at about 4 sec.2. Repolarization to smaller levels of membrane potential results in a slower rate of repriming. For example, at −60 mV the mean minimal time for repriming was 2·89 sec, and nearly 17 sec of repolarization was required for full restoration of contractile response.3. The rate of repriming was not influenced by lowering the external sodium concentration.4. Repriming could be produced by repetitive, brief pulses of repolarization.5. The restoration of contractile response and of outward inactivating current showed similar time courses.
The effects of changes in haematocrit on the intrarenal distribution of blood flow in the dog's kidney
Authors: Nashat F. S. , Scholefield F. R. , Tappin J. W. , Wilcox C. S. 
Published: December 2014

1. The effect of changes in the haematocrit of blood perfusing the kidney on its intrarenal distribution was studied in dogs.2. Two types of preparations were employed. (i) In the isolated perfused kidney evidence is presented that flow in the autoregulating preparation represents predominantly cortical flow while flow in the ‘low flow non‐autoregulating’ kidney reflects medullary flow. (ii) In the intact kidney renal blood flow rate and its intrarenal distribution was studied by the injection of 133Xe into the renal artery and measuring its clearance from the kidney by an external counter.3. In both types of preparation cortical flow was found to be independent of changes in P.C.V. but medullary flow varied inversely with haematocrit.4. A change in the haematocrit of the perfusing blood leads to alteration of its viscosity. It was argued that an increase in viscosity must lead to a reduction in the resistance of the cortical afferent arterioles but that medullary afferent arterioles were not able to respond in this manner.5. These findings demonstrate that changes in total body haematocrit cause a redistribution of blood flow between renal cortex and medulla.
Frequencygrams of rabbit spindle primary endings elicited by stimulation of fusi‐motor fibres
Authors: Emonet-Dénand Françoise , Laporte Y. 
Published: December 2014

1. Frequencygrams of rabbit spindle primary endings elicited by stimulation of single fusimotor axons were obtained by the method described by Bessou, Laporte & Pagès (1968a) which gives indirect information on the contraction of intrafusal muscle fibres.2. Repetitive stimulation of the majority of static axons (twenty out of twenty‐five axons studied) gave frequencygrams showing discrete large peaks corresponding to each stimulus, even for rates of stimulation as high as 300‐500/sec.3. Large responses to single stimuli were elicited by thirteen of these axons. The responses consisted of a fast‐rising phase lasting 5‐10 msec and declining phase lasting 30–50 msec.4. Repetitive stimulation of some static axons (five out of twenty‐five) gave frequencygrams displaying a smooth contour with no sign of individual responses to single stimuli and with a slow rising and declining phase.5. Both kinds of ‘static’ frequencygrams may be obtained from the same spindle.6. Repetitive stimulation of dynamic axons gave frequencygrams of small amplitude with a slow rising and declining phase and no sign of individual responses, even at low rates of stimulation.7. Although rabbit spindles lack nuclear chain muscle fibres (Barker & Hunt, 1964), rabbit's frequencygrams were essentially similar to those of cat spindles. The functional implications of this similarity are discussed.
Acetylcholine and related enzymes in the neural lobe and anterior hypothalamus of the rabbit
Authors: Lederis K. , Livingston A. 
Published: December 2014

1. Acetylcholine (ACh), cholinesterases and choline acetyltransferase (choline acetylase) were estimated in the neural lobe and hypothalamus of the adult male rabbit. Acetylcholine was also estimated in the neural lobes and hypothalami of some other mammals.2. Acetylcholine‐like activity was measured by bio‐assay using the leech dorsal muscle preparation.3. Characterization experiments indicated that about 90% of the activity measured was due to acetylcholine.4. Mean acetylcholine content in the neural lobe of the rabbit, after extraction with perchloric acid, was 4·38 ± 0·98 μg/g fresh tissue, and 4·87 ± 1·53 μg/g in the hypothalamus.5. Acetylcholine was also found to be present, in comparable concentrations, in the neural lobe of man and in the neural lobes and hypothalami of ox, rat and hedgehog.6. Acetylcholinesterase, present in the neural lobe and hypothalamus of the rabbit, hydrolysed 1·74 ± 0·11 μ‐moles of substrate/min/g and 3·78 ± 0·60 μ‐moles substrate/min/g fresh tissue respectively.7. The concentration of butyrylcholinesterase was about one tenth that of acetylcholinesterase in both tissues.8. Choline acetyltransferase present in the neural lobe and in the hypothalamus synthesized 87 ± 22 μg ACh/hr/g fresh tissue and 378 ± 149 μg respectively.
Electrical activity in the supraoptic and paraventricular nuclei associated with neurohypophysial hormone release
Authors: Dyball R. E. J. , Koizumi Kiyomi 
Published: December 2014

1. Unit recordings were made from the hypothalamus in anaesthetized male rats using steel or glass micro‐electrodes.2. Stimuli which are known to release vasopressin and oxytocin (electrical stimulation of the central end of the severed right vagus nerve and intracarotid injection of CaCl2 solution) also excite units in the supraoptic and paraventricular nuclei. In addition, these units are excited by intracarotid injections of carbachol, acetylcholine and NaCl (5%) which are less effective stimuli for vasopressin release.3. These stimuli also excite units from which potentials can be evoked by stimulation of the pituitary stalk and which are likely to be neurosecretory neurones. Neurosecretory neurones can conduct electrical impulses like other less specialized nerve cells. Estimations of conduction velocity range between 0·4 and 1·3 m/sec.4. The proportion of units in the supraoptic and paraventricular nuclei which are excited and the degree of excitation corresponds approximately to the amount of vasopressin released by the stimuli. In addition, excitation of the supraoptic nucleus seems to be more directly associated with vasopressin release and excitation of the paraventricular nucleus with oxytocin release.