bluuebunny/crossref_metadata_2025 huggingface dataset:
Mouse pancreatic acinar cells: the anion selectivity of the acetylcholine‐opened chloride pathway.
Authors: Petersen O H , Philpott H G
Published: December 2014

1. Anion replacement experiments were performed on superfused in vitro mouse pancreatic tissue and the effects on the electrical response of acinar cells to ACh investigated. 2. Electrical measurements were made with two micro‐electrodes inserted into electrically coupled cells. ACh was applied by microionophoresis. Potential recordings were taken before, during and after changeover from the control superfusion fluid, containing Cl‐, to one containing the substituted anion. 3. From the results obtained the tested anions were classified into three groups: I, Cl(‐)‐like anions: Br‐, I‐ and NO3‐, causing either no change or a negative displacement of the ACh null‐potential, compared to that measured in the control Cl(‐)‐containing solution, and only small changes in the resting and stimulated electrical properties of the acinar cell, II, ions less permeable than Cl‐: isethionate, acetate, sulphate and hippurate, showing a positive displacement of the ACh null‐potential and a similar or increased resting cell input resistance, and III, methylsulphate and benzenesulphonate, causing a negatively displaced ACh null‐potential but showing changes in the resting electrical properties of the acinar cells characteristic of anions in group II. 4. The ACh null‐potential sequence, in order of decreasing negativity, was NO3‐ greater than or equal to benzenesulphonate greater than or equal to I‐ greater than or equal to methylsulphate greater than Br‐ greater than or equal to Cl‐ greater than isethionate greater than acetate greater than or equal to sulphate greater than hippurate. 5. Experiments involving the use of bicarbonate demonstrated that it does not contribute significantly to the value of the ACh null‐potential. 6. The sequence of the anions in group I were compared to the Eisenman series I, suggesting that the ACh‐opened Cl‐ pathway comprises a large hydrated ion channel bearing a lining of weak positive charges. 7. A quantitative relationship was sought between the ACh null‐potential and extracellular Cl‐. It was found that a tenfold reduction in the extracellular concentration resulted in a 15 mV positive shift of the null‐potential.
Regional similarities and differences in thermoregulatory vaso‐ and sudomotor tone.
Authors: Bini G , Hagbarth K E , Hynninen P , Wallin B G
Published: December 2014

1. Skin nerve sympathetic activity was recorded simultaneously from the following pairs of nerves: left and right median, median and peroneal, left and right peroneal, posterior cutaneous antebrachial and superficial radial, posterior cutaneous antebrachial and median. The recordings were performed on healthy subjects exposed to different ambient temperatures. Electrodermal responses and pulse plethysmograms were recorded from the neural innervation zones. 2. Vasoconstriction impulse bursts recorded simultaneously from the median and peroneal nerves during exposure to a cold environment showed a striking similarity with respect to the timing and strength of individual bursts. A similar strong correlation was observed also among sudomotor bursts recorded simultaneously from the posterior cutaneous antebrachial and superficial radial nerve during exposure to a warm environment. 3. On some occasions, such as during exposure to a moderately warm environment or emotional stress, a temporal correlation was also observed between vasoconstrictor bursts recorded from the median and sudomotor bursts recorded simultaneously from the posterior cutaneous antebrachial nerve. 4. The double nerve recordings provided evidence that in the distal glabrous skin areas reflex thermoregulatory functions are mainly executed via vasoconstrictor fibres whereas sudomotor fibres are brought into action only at relatively high temperature. On the contrary, in the hairy skin on the dorsal side of forearm and hand reflex thermoregulation is to a large extent executed via sudomotor fibres.
Ionic currents in slow twitch skeletal muscle in the rat.
Authors: Duval A , Léoty C
Published: December 2014

1. The ionic currents in slow fibres isolated from rat soleus muscle have been studied under voltage‐clamp conditions with a double sucrose‐gap method and the results are compared to those obtained from fast fibres isolated from the iliacus muscle. 2. The mean value of the resting potential in slow fibres is ‐70 mV. a value 8 mV more positive that the mean resting potential of fast fibres (‐78 mV). 3. In slow muscle, a fast inward current which is blocked by tetrodotoxin and which depends on external sodium concentration is presumed to be carried by sodium ions. The characteristics of this current, which are time‐ and voltage‐dependent, are similar to those of the iliacus fibres. From a holding potential at ‐86 mV, this inward current is maximal (2.6 mA/cm2 +/‐ 0.3) at +49.1 mV +/‐ 1.5 (mean +/‐ S.E. of mean), reverses at +127.3 mV +/‐ 2.2 (mean +/‐ S.E. of mean), and its half inactivation occurs at +23.2 mV +/‐ 0.8 (mean +/‐ S.E. of mean). 4. The delayed outward current in slow fibres is unchanged by exposure to chloride free solution and has a time course very different from that found in fast fibres. This current reaches an initial peak in 5‐10 msec and a second peak or steady level after 40‐150 msec. The decay of the outward current is also very different, being ten times slower than that in fast fibres (1500‐3000 msec). 5. Analysis of the tail currents reveals the existence of two components of delayed current in slow fibres. The faster component reverses at a potential of 11.3 mV +/‐ 0.9 (mean +/‐ S.E. of mean) positive to the holding potential (equivalent to a membrane potential of about ‐75 mV), in contrast to a reversal potential of 35.4 mV +/‐ 2.5 (mean +/‐ S.E. of mean) positive to the holding potential for the slower component (equivalent to a membrane potential of about ‐51 mV. 6. In L‐glutamate solution the characteristics of the inward‐going rectification are the same in the two types of muscle.
Does activation of cyclic AMP dependent phosphorylation induced by beta‐adrenergic agent control the tone of vascular muscle?
Authors: Hirata M , Kuriyama H
Published: December 2014

1. The relaxing action of the beta‐adrenergic agent, isoprenaline, on the porcine coronary artery was investigated in relation to the cyclic AMP level, the endogenous binding of cyclic AMP to the regulatory unit of cyclic AMP dependent protein kinase or the phosphorylation as a result of activation of protein kinase of the muscle homogenate in Krebs solution and excess [K]o solution. These relations were also compared with those of the rat cardiac muscle, in which isoprenaline showed a positive inotropic action. 2. Excess [K]o decreased the cyclic AMP level in proportion to the amplitude of K‐induced contracture in the porcine coronary artery. Isoprenaline increased the cyclic AMP level in Krebs solution, while it had no effect in excess [K]o. 3. In the porcine coronary artery, the particulate fraction possessed only 5% of the total cyclic AMP dependent protein kinase, while in the rat cardiac muscle, the particulate fraction was 25% of the total protein kinase. 4. The cyclic AMP dependent protein kinase in the particulate fraction of the porcine coronary artery was already saturated with the endogenous cyclic AMP. However, the binding of cyclic AMP to the protein kinase in the particulate fraction in the cardiac muscle and in the cytosol fraction of both tissues were increased in accordance with the cyclic AMP level. In the coronary artery, the protein kinase in the cytosol fraction was bound to a greater extent with cyclic AMP than was measured in the rat cardiac muscle. 5. In the rat cardiac muscle, isoprenaline enhanced the phosphorylation, detected by autoradiography of SDS gel electrophoresis in individual fractions of phosphorylated protein, while little enhancement was observed in the porcine coronary artery. 6. These observations led to the conclusion that in the porcine coronary artery, beta‐adrenergic agent increases the levels of cyclic AMP but does not increase the phosphorylation. If the phosphorylation catalysed by cyclic AMP dependent protein kinase was utilized for Ca mobilization in the cell, the change in the cyclic AMP level would probably not have a causal relation to the muscle tone. This conclusion, however, may not be applicable in the case of the cardiac muscle.
Sodium channel permeation in squid axons. I: Reversal potential experiments.
Authors: Begenisich T B , Cahalan M D
Published: December 2014

1. Na channel reversal potentials were studied in perfused voltage clamped squid giant axons. The concentration dependence of ion selectivity was determined with both external and internal changes in Na and ammonium concentrations. 2. A tenfold change in the internal ammonium activity results in a 42 mV shift in the reversal potential, rather than the 56 mV shift expected from the Goldman, Hodgkin, Katz equation for a constant PNa/PNH4 ratio. However, changing [Na]o tenfold at constant internal [NH4] gives approximately the expected 56 mV shift. Therefore, the apparent channel selectivity depends upon the internal ammonium concentration but not the external Na concentration. 3. With ammonium outside and Na inside, the calculated permeability ratio is nearly constant, regardless of the permeant ion concentration. 4. Internal Cs ions can alter the Na/K permeability ratio. 5. The results are considered in terms of a three‐barrier, two‐site ionic permeation model.
Effects of pentagastrin on intestinal absorption and blood flow in the anaesthetized dog.
Authors: Mailman D
Published: December 2014

1. Pentagastrin (1, 10 micrograms/min) was infused I.V. into fed and fasted anaesthetized dogs and the intestinal absorption of NaCl and H2O and blood flow were determined. The influence of pentagastrin‐induced cardiovascular changes on absorption was investigated. 2. 22Na and 3H2O were used to determine the unidirectional Na and H2O fluxes from saline perfused through the ileal lumen and the clearances of 3H2O were used to calculate total and absorptive site blood flow. 3. Ileal absorption of Na and H2O was reduced by 10 micrograms/min pentagastrin due primarily to significant increases in the secretory flux of Na and decreases in the absorptive flux of H2O in both fed and fasted animals. 4. Neither total intestinal blood flow, arterial nor mesenteric vein pressure were changed by pentagastrin but absorptive site blood flow was decreased in fasted but not in fed dogs. 5. Pretreatment with atropine reduced the effects of pentagastrin but pretreatment with guanethidine potentiated the effects of pentagastrin. 6. Absorptive site blood flow was positively linearly correlated with the absorptive fluxes of both Na and H2O. The relationships between the secretory fluxes of Na and H2O and estimated capillary pressure were changed from a positive relationship in control periods to a less positive or negative relationship following pentagastrin. 7. It was concluded that pentagastrin reduces intestinal absorption through both a cardiovascular effect and an effect on the intestinal epithelium. Also, there is a strong autonomic component in the effects of pentagastrin on intestinal absorption.
Studies on the relationship between rat renal medullary cell volume and external anion concentration in hyperosmolal media.
Authors: Law R O
Published: December 2014

1. The volumes of cells in slices of rat renal outer medulla have been examined following incubation or 25 min in hyperosmolal media (650 and 950 m‐osmole/kg H2O) containing independently variable concentrations of Cl (70‐325 mM) and HCO3 (10‐60 mM) (gas phase 95% O2/5% CO2). 2. For any given level of external Cl concentration cell volumes were reduced by increasing the external HCO3 concentration. These reductions were accompanied by net loss of cellular K and Cl. In confirmation of earlier findings, cell volumes were also reduced by increasing external Cl concentration. 3. Experiments in which the HCO3 concentration and pH of the incubation media were independently varied by the use of N‐2‐hydroxyethylpiperazine‐N'‐2‐ethanesulphonic acid (HEPES)/100% O2 showed that it is the HCO3 anion per se which influences cell volume. 4. The anion exchange inhibitor 4‐acetamido‐4'‐isothiocyanatostilbene‐2,2'‐disulphonic acid (SITS, disodium salt, 1 mM) abolished the dependence of cell volume upon HCO3 but not upon Cl. 5. Acetazolamide (1 mM) influenced (reduced) cell volumes only in the presence of low (10 mM) HCO3. 6. CNS (25 mM) also markedly reduced cell volumes in media containing 10mM‐HCO3 and, to a lesser extent, 25 mM‐HCO3. It was without effect on cell volume when external HCO3 was 60 mM. 7. The presence of CNS was associated with the significant cellular net accumulation of Cl in media in which either Cl or HCO3 concentration (or both) was low (70 or 130 mM and 19 mM respectively). 8. The outer medullary [35S]CNS space at 25 min, determined for slices incubated in a representative selection of the various media employed in this study, exceeded the [14C]inulin space by 1.77 microliters/10 mg wet weight.
Adrenal medullary responses to stimulation of the splanchnic nerve in the conscious calf.
Authors: Edwards A V , Furness P N , Helle K B
Published: December 2014

1. Right adrenal medullary and various cardiovascular responses to stimulation of the peripheral end of the right splanchnic nerve have been investigated in conscious calves, 2‐‐5 weeks after birth. 2. The output of both adrenaline and noradrenaline was linearly related to stimulus frequency over the range 2.0‐‐10.0 Hz, 2 1/2 min after stimulation was initiated. Peak outputs of both amines were obtained in response to stimulation at 15.0 Hz. 3. The output of adrenaline invariably exceeded that of noradrenaline, roughly in the proportion 3:2. At all frequencies tested between 7.0 and 40.0 Hz this difference was statistically significant (P less than 0.1). 4. Continuous stimulation at either 4.0 or 10.0 Hz produced a small but significant rise in the output of dopamine‐beta‐monooxygenase (DBH) activity from the right adrenal gland. Mean maximal outputs were obtained after 10 min; the levels were closely similar at both 4.0 and 10.0 Hz and could not be related to stimulus frequency or to the output of either adrenaline or noradrenaline. 5. The results are discussed in relation to perfusion studies in vitro and experiments in anaesthetized animals. It is concluded that the levels of DBH in adrenal effluent plasma is an unreliable index of catecholamine exocytosis in the conscious calf.
The uptake and release of [3H]glycine in the goldfish retina.
Authors: Chin C A , Lam D M
Published: December 2014

1. In the goldfish retina, uptake of exogenous [3H]glycine follows Michaelis‐‐Menten kinetics with increasing concentrations of glycine. This uptake can be explained kinetically by the presence of two independent affinity systems: a ‘high‐affinity’ mechanism with an apparent Km(H) of 8.1 microM and a Vmax(H) of 9.12 p‐moles/min. mg protein, and a ‘low‐affinity’ mechanism with an apparent Km(L) of 0.63 mM and a Vmax(L) of 430 p‐mole/min . mg protein. 2. The high‐affinity mechanism, and probably also the low‐affinity mechanism, is temperature‐ and Na+‐dependent. 3. The low‐affinity mechanism for glycine uptake is not affected by 5 mM‐isoleucine, methionine and valine in the medium. However, it is inhibited more than 90% by 5 mM‐alanine, proline and serine in the medium. This result indicates that the low‐affinity transport for glycine may go through system A of the neutral amino acid transport system which is present in most tissues to transport glycine and certain neutral amino acids for metabolic purposes. 4. The high‐affinity mechanism for glycine uptake is, however, not affected by the presence of up to 100‐fold excess of all amino acids examined. 5. Autoradiographic studies show that at least one type of amacrine cell and one type of probable interplexiform cell take up [3H]glycine both in the presence and absence of 5 mM‐alanaine, proline and serine, indicating that these neurones possess the high‐affinity mechanism for glycine uptake. 6. [3H]Glycine accumulated in the retina can be released by increasing the external K+ concentration. This release is probably Ca2+‐dependent since it is blocked by 10 mM‐Co2+ in the medium. Additionally, autoradiographic studies show that [3H]glycine taken up by the glycine‐accumulating neurones can also be released by Ca2+‐dependent, K+‐depolarization of the retina.
Voltage‐clamp investigations of membrane currents underlying pace‐maker activity in rabbit sino‐atrial node.
Authors: Brown H , Difrancesco D
Published: December 2014

1. Small preparations of spontaneously beating rabbit sino‐atrial node have been investigated using the two micro‐electrode voltage‐clamp technique. 2. Hyperpolarizing clamp pulses given from holding potentials of about ‐45 mV reveal a time‐dependent change of a membrane current, if, which is shown to overlap the pace‐maker range (‐65 mV to ‐45 mV) for these preparations. 3. The changes in if are shown to be quite distinct from the de‐activation of the time‐dependent outward current, iK. 4. The time‐dependent changes of the if system increase during adrenaline application and therefore contribute to the chronotropic action of adrenaline on the heart. 5. Evidence for a link between slow inward current (iSi) and time‐dependent outward current (iK) in rabbit sino‐atrial node is presented and assessed.
Different pathways for lysine transport across neonatal pig intestine.
Authors: Burton K A , James P S , Smith M W , Young J D
Published: December 2014

1. Undirectional fluxes of lysine, presented free and in the form of a dipeptide, have been measured in vitro using the small intestines of pigs taken during the first 2 weeks of post‐natal life. 2. The concentration dependence of free lysine transfer to the serosal surface of new‐born pig intestine (Jms) can be described as the sum of a saturable (Km 0.2 mM; Jm 3 n‐ mole cm‐2 in‐1) and a non‐saturable (1.0 n‐mole cm‐2 min‐1 mM‐1) component. 3. The dipeptide isoleucyl‐lysine was hydrolysed completely during transfer to the serosal surface of intestines taken at all stages of development. The concentration dependence of peptide‐derived lysine transfer can be described as if it took place through a single saturable process (Km 5 mM; Jm 27 n‐mole cm‐2 min‐1). 4. The mucosa to serosa transfer of free lysine fell to a half and that of peptide‐derived lysine fell to a quarter, during the first 8 days of post‐natal life. The decline in peptide‐derived lysine transport correlated with changes in peptide hydrolase activity, measured in homogenates of intestinal mucosa using isoleucyl‐lysine as substrate. 5. The new‐born pig intestine transported lysine derived from isoleucyl‐lysine twice as quickly as from lysyl‐isoleucine. Lysine and isoleucine did not inhibit the transfer of isoleucine and lysine derived from isoleucyl‐lysine. The transport of lysine, but not isoleucine, from isoleucyl‐lysine took place more quickly than from equimolar solutions of the free amino acids. 6. It is suggested from these results that lysine and isoleucyl‐lysine use different pathways when crossing the intestinal mucosa. Attempts are made to assess the probable contributions made by these pathways to the total absorption of lysine taking place during neonatal development.
Electrophysiological analysis of colchicine‐induced supersensitivity in the rat vas deferens.
Authors: Goto K
Published: December 2014

1. The supersensitivity in smooth muscle of the rat vas deferens induced by local application of colchicine to the hypogastric plexus was investigated electrophysiologically. 2. Spontaneous junction potentials could be detected in nearly all of the impaled cells, but they occurred with lesser frequency and smaller amplitude in the colchicine‐treated rat vas deferens than in the control tissue. However, this clearly demonstrated that, although attenuated, neuromuscular transmission still persisted after colchicine treatment. 3. The mean resting potential of smooth muscle cells of the colchicine‐treated vas deferens (58.2 +/‐ 0.3 mV, n ‐ 146) was not significantly different from that of the cells of the contralateral control tissue (58.1 +/‐ 0.2 mV, n = 130). 4. The threshold potential for action potentials induced by either nerve stimulation or extracellular current application was more negative by approximately 10 mV in the colchicine‐treated vas deferens in comparison with the control tissue. 5. Externally applied current pulses of long duration failed to produce electrotonic potentials in any smooth muscle cell of normally innervated rat vas deferens which was located more than 0.5 mm from the partition electrode. In the colchicine‐treated tissue, however, electrotonic potentials in the smooth muscle cell could be detected for a distance up to 2.5 mm from the partition electrode. The space constant in the colchicine‐treated tissue was determined to be 0.79 +/‐ 0.02 mm (n = 10). 6. It is concluded that (i) the magnitude of depolarization from resting to threshold potentials in the colchicine‐treated vas deferens was significantly smaller than that in the contralateral control tissue and (ii) that the current spread in a longitudinal direction was improved following colchicine treatment.
Bile acid metabolism in fetal sheep; perinatal changes in the bile acid pool.
Authors: Hardy K J , Hoffman N E , Mihaly G , Sewell R B , Smallwood R A
Published: December 2014

1. A chronic fetal bile fistula model was developed in sheep which allowed observations on fetal bile for periods of up to 10 days. A comparison of fetal, lamb and adult bile acids was made in bile fistula animals. 2. Bile was analysed by thin layer chromatography, gas liquid chromatography, and high pressure liquid chromatography. Fetal bile contained a much greater proportion of chenodeoxycholic acid (42.0 +/‐ 1. S.E. of mean 3.0% of total bile acids by high pressure liquid chromatography) than lamb bile (8.1 +/‐ 1.9%) or adult bile (5.4 +/‐ 0.6%). The corresponding figures for cholic acid were fetal: 45.8 +/‐ 2.9%, lamb: 89.1 +/‐ 2.9%, and adult: 75.2 +/‐ 2.6%. Deoxycholic acid, a secondary bile acid, was present in fetal bile (12.2 +/‐ 4.9%). In the lamb, deoxycholic acid comprised only 2.8 +/‐ 1.1% of total bile acids, compared with 19.3 +/‐ 2.9% in adult sheep. Taurine conjugates predominated in sheep bile, but this predominance was least marked in lamb bile. 3. The fetal bile acid pool (101 +/‐ 13 mu mole/kg) was significantly smaller than the neonatal pool (214 +/‐ 26 mu mole/kg, P < 0.01). This increase in pool size, together with the increased proportion of cholic acid, suggests a rapid rise in cholic acid synthesis soon after birth. 4. Bile acid synthetic rates were estimated from bile acid secretion rates at the nadir of the washout curves. The values obtained were 0.71 +/‐ 0.18 mu mole/kg.hour (adult), 0.47 +/‐ 0.16 mu mole/kg.hour (lamb), and 0.35 +/‐ 0.08 mu mole.hour (fetus). 5. In the fetus and in pregnant adult sheep, the normal increase in bile acid synthesis in response to depletion of the bile acid pool was much less marked. 6. In the fetus, biliary secretion of cholesterol and phospholipid ran parallel with bile acid secretion. Bile lipid composition was similar to that in the adult. 7. Fetal bile water production was higher, relative to bile acid secretion, than lamb or adult bile water secretion.
Comparative study of the smooth muscle layers of the rabbit duodenum.
Authors: Cheung D W , Daniel E E
Published: December 2014

1. Intracellular electrodes were used to compare the electrical activity of smooth muscle cells from the longitudinal and circular layers of the rabbit duodenum and their responses to stimulation of the intramural nerves. 2. The longitudinal muscle cells had an average membrane potential of 52 mV when measured between slow waves. Spontaneous action potentials were superimposed on every slow wave. 3. The circular muscle cells had a higher membrane potential of 64 mV although the amplitude of the slow waves was similar to that of the longitudinal muscle cells. Spontaneous action potentials were rarely observed in the circular muscle cells. 4. Lowering the temperature from 36 to 30 degrees C caused a reduction in the membrane potential of the longitudinal muscle cells but not in the circular muscle cells. However, the amplitude of the slow waves of the two layers was reduced to a similar extent. 5. Electrical stimulation produced advances of the slow wave cycles if the stimuli were applied between slow waves. The responses of the cells from the two layers were identical. 6. Under normal conditions, electrotonic coupling was observed only in cells of the muscle layer whose long axis was aligned along the direction of the applied current. 7. In the longitudinal muscle, cholinergic responses blocked by atropine were observed. Inhibitory potentials were the predominant response in the circular muscle. 8. Excitatory responses were recorded in 9% of the circular muscle cells. "Off' excitation following termination of a train of repetitive stimulation pulses was also observed. 9. The differences in membrane potentials, spontaneous spiking activities, neural responses, and the failure to demonstrate good electrotonic coupling between the muscle layers suggest that there was poor electrotonic interaction between the muscle layers. The amplitude of the slow waves of the two layers was nevertheless similar. Thus the validity of the hypothesis that slow waves were transmitted passively from the longitudinal layer into the circular layer through electrotonic coupling must be questioned.
Reaction of synapses on motoneurones to section and restoration of peripheral sensory connexions in the cat.
Authors: Goldring J M , Kuno M , Núñez R , Snider W D
Published: December 2014

1. Monosynaptic excitatory post‐synaptic potentials (e.p.s.p.s.) were recorded from triceps surae motoneurones of the cat 2‐8 months after section of the medial gastrocnemius nerve whose regeneration into the muscle was prevented. In other animals, the cut nerve was reunited to the muscle with a post‐denervation delay varying from 2 to 6 months, and the e.p.s.p.s were recorded 2 months later. The e.p.s.p.s were evoked by stimulation of the medial gastrocnemius nerve central to the site of the section or reunion. 2. The mean amplitudes of the e.p.s.p.s decreased with time after nerve section, virtually disappearing by the eighth post‐operative month. The decrement of the e.p.s.p. amplitude occurred more quickly in soleus motoneurones than in medial or lateral gastrocnemius motoneurones. 3. The e.p.s.p.s evoked in medial or lateral gastrocnemius motoneurones from the cut medial gastrocnemius nerve returned to normal levels 2 months after reunion of the cut nerve even following a post‐denervation delay of 6 months. However, in soleus motoneurones the e.p.s.p. recovery was incomplete. 4. The degree of functional motor reinnervation of the medial gastrocnemius muscle depended upon the post‐denervation delay preceding the reunion operation. With a delay of 6 months before the reunion, the muscle showed no or only weak contractions in response to nerve stimulation. 5. Axotomized medial gastrocnemius motoneurones showed a significant decrease in conduction velocity and significant increase in the amplitude of overshoot of action potentials. The changes persisted even when the cut nerve was reunited to the muscle 2‐6 months after denervation. 6. When the cut medial gastrocnemius nerve was reunited to the muscle 4 months after denervation, most of the sensory fibres, tested 2 months later, failed to respond to muscle stretch. 7. It is concluded that recovery of monosynaptic e.p.s.p.s following reconnexion of the cut nerve with its muscle does not require recovery of muscle activity, full restoration of sensory activity or the recovery of normal motoneurone properties. 8. It is also suggested that the degree to which central synaptic efficacy declines and recovers following section and regeneration of a peripheral nerve depends partly upon the type of motoneurone (fast phasic or slow tonic) with which the sensory fibres form synaptic connexions.
Electrical responses and photopigments of twin cones in the retina of the walleye.
Authors: Burkhardt D A , Hassin G , Levine J S , MacNichol E F
Published: December 2014

1. The properties of twin and single cones in the retina of the walleye (Stizostedion vitreum vitreum) were studied by intracellular recording, dye injection and microspectrophotometry. 2. Twin cones generate hyperpolarizing responses to central illumination, can receive depolarizing influences (feed‐back) from the receptive field surround, and show no detectable dye coupling when injected with Procion yellow. In seventeen of eighteen dye‐injected cones, fluorescence was intense in the inner segment and undetectable or weak in the cone pedicle. 3. Both members of the twin cone contain the same photopigment in their outer segments. It absorbs maximally at about 605 nm. 4. A 533 nm green‐sensitive photopigment was found in single cones. No blue‐sensitive cones have been found. 5. With the exception of a modest discrepancy in the violet, the absorptance spectrum of the 605 nm photopigment of twin cones agrees closely with the action spectrum measured by intracellular recording. 6. The spectral properties established by the twin cone's photopigment are not detectably altered by the hyperpolarizing influences arising from nearby cones or by the depolarizing influences arising from the receptive field surround. 7. The twin cones of the walleye retina are thus "identical twins', both photochemically and physiologically, and seem designed to function as long‐wave, spectrally univariant receptor units for colour vision. 8. The available evidence suggests that identical twin cones differ functionally from double cones and non‐identical twin cones. 9. Although they outnumber single cones by about three to one in adults, identifiable twin cones were rarely observed in the cone population of retinas examined 3‐5 days after birth. If walleye twin cones develop by fusion of single cones this process apparently occurs only for cones containing the 605 nm photopigment.
The effect of lithium on electrolyte transport by the in situ choroid plexus of the cat.
Authors: Reed D J , Yen M H
Published: December 2014

1. The effects of lithium on electrolyte transport were studied by using the cat choroid plexus isolated in a chamber in situ. 2. Lithium infused intravenously to produce plasma lithium concentrations up to 5 m‐equiv/l. caused an increase in plasma magnesium with no effect on the concentration of magnesium in the chamber fluid. 3. When 22NaCl was infused intravenously the chamber fluid/plasma ratio of 22Na was nearly 1 in the first 30 min sample and at the steady state it was significantly greater than 1. 4. When lithium chloride (1.5 m‐equiv/l.) or potassium chloride (6.6 m‐equiv/l.) was added to the chamber at the start of a collection period with plasma 22Na in the steady state, the 22Na content of the chamber fluid promptly increased 118 and 68%, respectively, above the control value with no increase in secretory rate. 5. The addition of ouabain to the chamber fluid, in addition to the lithium chloride or potassium chloride, tended to stimulate or have no significant effect on 22Na uptake at a concentration of 10(‐5) M and to reduce it as well as the secretory rate at 10(‐3) M. 6. The date are compatible with there being two functionally separate sodium transport systems in the choroid plexus. One transports sodium accompanied by an anion and water to provide the fluid secreted into the chamber (c.s.f.) and the other operates primarily to regulate the potassium concentration of the c.s.f. by pumping potassium out in exchange for sodium. 7. Lithium can be transported by both systems to a limited extent and the presence of lithium in the c.s.f. stimulates the sodium‐potassium regulating pump.
The influence of the infusion of noradrenaline on plasma cortisol levels in man.
Authors: Few J D , Gawel M J , Imms F J , Tiptaft E M
Published: December 2014

1. Noradrenaline was infused into normal resting male subjects for consecutive 20 min periods at 3, 7.5 and 15 microgram min‐1. At the end of the 1 hr of noradrenaline infusion, total catecholamine levels were in the range 4‐6 microgram l.‐1, comparable with those observed in severe exercise. 2. At all rates of infusion there were marked elevations of arterial blood pressure leading to reflex reductions of heart rate. Blood flow in the foot was reduced but blood flow in the calf was unaffected. Following the infusion, blood pressure rapidly returned to normal but the heart rate was raised by some 15 beat min‐1 higher than the preinfusion control for at least 90 min. 3. Plasma cortisol tended to decrease slightly during the noradrenaline infusion but in twelve out of seventeen experiments it began to rise 30‐75 min after termination of the infusion, reaching values 5‐15 microgram 100 ml.‐1 higher than those at the end of the noradrenaline infusion. Simultaneous rises in plasma aldosterone level were observed in those experiments in which it was measured. 4. Because of the long delay in the onset of hypercortisolaemia it is suggested that this is initiated not by the noradrenaline levels per se but by some physiological readjustments to the rapid fall in plasma noradrenaline level when the infusion was discontinued. The nature of these changes was not determined. 5. It is concluded that the elevated levels of plasma noradrenaline observed during exercise are not responsible for the synchronous increases in cortisol secretion.
Ouabain‐sensitive thallium fluxes in smooth muscle of rabbit uterus.
Authors: Johns A
Published: December 2014

1. Rabbit myometrium accumulates Tl in a time‐dependent fashion and the majority of the uptake of Tl is ouabain‐sensitive. 2. In normal chloride‐containing media, the uptake of Tl, though ouabain‐sensitive, is less than in chloride‐free media and this difference is due to a greater ouabain‐insensitive uptake. 3. The ouabain‐insensitive uptake in normal chloride‐containing media is reduced by furosemide and furosemide also reduces total uptake in this solution. In chloride‐free media, however, furosemide is without effect on total or ouabain‐sensitive uptake. 4. In chloride‐free media, the uptake of Tl against Tl concentration is sigmoidal, suggesting that more than one Tl ion is being transported at a time. 5. Tl was capable of substituting for K in electrogenic Na pumping; it was approximately twice as effective as K and the inhibitory effect of Tl was blocked by ouabain. 6. Tl efflux can be explained by a simple two‐compartment model in both normal and chloride‐free solutions. 7. The uptake of Tl was inhibited by alkali cations with the order of potency being Tl+ > K+ > Rb+ > Cs+ at 10 mM and Tl+ > K4 = Rb+ > Cs+ at 5 mM ion concentrations. 8. It is concluded that Tl enters the smooth muscle of rabbit uterus by diffusion, active ouabain‐sensitive transport and active chloride‐ and furosemide‐sensitive transport.
Relationship of arterial pressure and heart rate in fetal, new‐born and adult sheep.
Authors: Dawes G S , Johnston B M , Walker D W
Published: December 2014

1. Baroreflex activity was assessed in nine fetal, four new‐born and six adult sheep, using the relationship between heart period and arterial pressure. Arterial pressure was raised either by inflating a balloon in the dorsal aorta, by rapid intravenous injection of phenylephrine or methoxamine, or by slow intravenous infusion of methoxamine. 2. In the fetus the three methods gave different estimates of baroreflex sensitivity (balloon, 1.3 +/‐ 0.7 mmHg; injections, 5.4 +/‐ 0.5 msec mmHg; infusions, 7.2 +/‐ 0.9 msec/mmHg) whereas they were comparable in the new‐born and adult. 3. Estimates of baroreflex sensitivity were significantly lower in the fetus and new‐born than in the adult whichever method was used. 4. In the fetus there were variable changes of heart period when arterial pressure was raised by inflation of the balloon. The responses to injection of phenylephrine or methoxamine were also variable. 5. This variability was not associated with changes in electrocortical activity, the presence or absence of breathing movements or limb movements, or changes of blood gases. 6. In the fetus the heart period frequently did not change unless the arterial pressure was raised by approximately 15 mmHg (to 61 mmHg), suggesting that the threshold for baroreflex activity is above the normal range of arterial pressure before birth.
Nerve‐mediated descending inhibition in the proximal colon of the rabbit.
Authors: Julé Y
Published: December 2014

1. Descending inhibition in the rabbit proximal colon, evoked by distension, was studied in vivo by recording extracellularly electrical activity from pressure electrodes placed on the serosa. 2. Distention produced, blow the level of the balloon, a brief hyperpolarization of smooth muscle fibres which could be recorded up to 20 cm from the point of distension. 3. This hyperpolarization like that produced by vagal stimulation (inhibitory junction potentials) persisted in the presence of sympathetic blocking agents and atropine, and was produced by non‐adrenergic non‐cholinergic intramural neurones. 4. In the presence of vagally evoked excitatory junction potentials (e.j.p.s), distension produced a transient inhibition of e.j.p.s, in addition to the hyperpolarization of smooth muscle. 5. The inhibition of these e.j.p.s persisted in the presence of sympathetic blocking agents, but in contrast to the hyperpolarization of smooth muscle produced by distension alone, was modulated by drugs interfering with 5‐HT synthesis, re‐uptake and activity. 6. The results indicate that descending inhibition in the rabbit proximal colon was produced by two distinct neuronal non‐adrenergic inhibitory mechanisms exerted simultaneously on the smooth muscle and on the cholinergic excitatory pathways which innervate it.
The role of sodium ions in pancreatic fluid secretion in the rabbit.
Authors: Bonting S L , De Pont J J , Jansen J W
Published: December 2014

1. NaCl in the bathing medium of the isolated rabbit pancreas has been gradually replaced by isotonic amounts of either sucrose, choline chloride or KCl. 2. The replacement of NaCl always leads to a reduction in pancreatic flow. This reduction is largest with sucrose as replacing agent and smallest with KCl. 3. The Na+ concentration in the secreted fluid decreases only slightly when NaCl is replaced by sucrose. In the experiments with choline chloride, the Na+ concentration in the secreted fluid decreases slightly when less than 60 mM‐NaCl has been replaced, but decreases markedly after more extensive NaCl replacement. Upon replacement of NaCl by KCl, the Na+ concentration in the secreted fluid is always equal to that in the bathing medium. 4. The K+ concentration in the secreted fluid increases by 8 mM upon replacing NaCl by either sucrose or choline chloride. Upon replacement by KCl the K+ concentration in the secreted fluid is always approximately equal to that in the bathing medium. 5. There is a linear relationship between the ratio of the K+ concentrations in the secreted fluid and the bathing medium and the ratio of the Na+ concentrations in these fluids. 6. Replacement of NaCl in the bathing medium does not lead to a change in the transepithelial potential. 7. The secreted fluid is always isotonic with that of the bathing medium; in the case of an extensive replacement of NaCl by either sucrose or choline chloride isotonicity is maintained by a higher cation concentration and an increased appearance of the replacing agents in the secreted fluid. 8. These studies confirm previous findings that extracellular Na+ is essential for pancreatic fluid secretion. 9. They also indicate that the monovalent cations reach the secreted fluid through a paracellular pathway. 10. These findings are incorporated in a model for the electrolyte movements involved in the pancreatic fluid secretion by ductular as well as by acinar cells.
The effect of adrenaline and noradrenaline on coronary vascular reserve in the dog.
Authors: Creates M S , Grayson J
Published: December 2014

1. Experiments were performed on dogs, anaesthetized with pentobarbitone sodium to measure the oxygen utilization of anterior ventricular wall. The anterior interventricular vein was used for venous blood collection and flow measurement. 2. Oxygen contents of arterial blood and coronary vein were measured. 3. Intravenous (femoral vein) adrenaline infusions raised arterial blood pressure and caused an initial fall in oxygen extraction from control values of 67‐45%. Noradrenaline caused an initial fall from 67 to 51%. With both, the oxygen extraction began to rise during the infusion and continued, reaching maximum levels, (mean ‐82%) 10 min after start of infusion. The range of maximum values for oxygen extraction ratio after noradrenaline was 76‐95%. 4. An inverse linear relation was established between blood pressure and oxygen extraction; whereas a direct linear relationship was established between coronary venous blood flow and mean arterial pressure. 5. When a change in blood pressure was prevented, the oxygen extraction ratio rose. 6. In all experiments, whether extraction rose or fell, the oxygen consumption rose. 7. It is suggested that oxygen extraction is a controlled variable and, with coronary blood flow, contributes quantitatively to coronary vascular reserve. 8. The tension‐time index was not directly related to oxygen consumption in these experiments. Oxygen consumption rose in response to catecholamines by about the same amount even when mean arterial blood pressure was controlled. It is suggested that cardiac adjustments to altered afterload may also involve alterations in mechanical efficiency.
A method for studying oxygen diffusion barrier in erythrocytes: effects of haemoglobin content and membrane cholesterol.
Authors: Kon K , Maeda N , Sekiya M , Shiga T , Suda T
Published: December 2014

1. In order to study the kinetics os the oxygen egress from human red cells in the 50 sec‐20 min time range, an apparatus for measuring the oxygen dissociation process was constructed, combining a spectrophotometer with an oxygen electrode of quick response. 2. Starting from air‐saturated haemolysate or red cell suspensions, the velocity of oxygen dissociation from oxyhaemoglobin (Vdiss) and of oxygen disappearance in the medium (Vobs) after addition of bakers' yeast (consuming the dissolved oxygen at the velocity of Vconsump) were recorded. A parameter (r) was defined as the ratio of two velocities, Vegress (the velocity of oxygen egress into the medium) and Vdiss, r identical to Vegress/Vdiss = (Vconsump ‐Vobs)/Vdiss. Vcomsump could be calculated by the Michaelis‐Menten equation as follows, Vconsump = Vmax [O2]/(Km + [O2]), where Vmax was the maximal velocity of oxygen consumption of bakers' yeast. 3. The r value was always 1.0 for the haemolysate, but it was less than 1.0 for the normal red cells. Further, the oxygen dissociation curve of red cells obtained at higher Vmax was distorted, due to the non‐equilibration between intra‐ and extracellular oxygen concentrations. 4. The r value was (i) independent of the amounts of the allosteric effectors (2,3‐diphosphoglycerate and H+) but (ii) dependent on the haemoglobin contents and (iii) dependent on the amounts of the membrane cholesterol. Therefore, the r value reflected only the process of the oxygen diffusion but not the "chemical reaction' rate. The "barrier' of the oxygen diffusion decreased at lower haemoglobin contents, but increased at higher cholesterol contents in the membrane.
Two components of electrical dark noise in toad retinal rod outer segments.
Authors: Baylor D A , Matthews G , Yau K W
Published: December 2014

1. Physiological noise in the visual transduction mechanism was studied by recording membrane current from single rod outer segments in pieces of isolated toad retina. 2. The inward current in darkness showed spontaneous fluctuations which disappeared during the response to bright light. 3. The dark noise consisted of two components, a continuous fluctuation of rms amplitude about 0.2 pA and occasional discrete events about 1 pA in size. 4. Intervals between discrete events followed the exponential distribution expected of a Poisson process with a mean rate of about one event per 50 sec (20 degrees C). 5. The amplitude and power spectrum of the discrete events resembled those of single photon effects in the same rod, suggesting that discrete events may arise from spontaneous activation of single rhodopsin molecules. 6. The temperature dependence of the mean frequency of occurrence of discrete events gave an activation energy of 22 kcal mole‐1, probably characteristic of thermal isomerization of rhodopsin. 7. The variance of the continuous component of the dark noise rose linearly with the length of the outer segment drawn into the suction electrode, indicating that this component is generated in the outer segment. 8. The power spectrum of a rod's continuous noise was usually fitted by the square of a Lorentzian with the same time constant as that of the four first‐order delays in the cell's single photon response. The shot effects composing the continuous component thus appear to be shaped by two of four sequential processes in transduction. 9. The variance and spectrum of the continuous noise are interpreted to reflect shot effects about 1/400 the size of a single photon effect occurring at a frequency of 6 x 10(3) sec‐1. 10. The rod's flash sensitivity was halved by a steady light to giving about 8 photoisomerizations sec‐1. The much lower mean rate of discrete events indicates that Io in increment sensitivity experiments on individual receptors is not set by thermal activation of rhodopsin. 11. Values of sensitivity and time‐to‐peak flash response collected from many cells in darkness were correlated by the same power law relation obtaining in the presence of backgrounds. The correlation observed would be explained if a single variable controlled both the gain and time scale of several stages of the transduction mechanism in background light and in darkness.
Voltage‐dependent potentiation of the slow inward current in frog atrium.
Authors: Noble S , Shimoni Y
Published: December 2014

1. Slow inward currents, isi, were measured using a double sucrose‐gap voltage‐clamp technique during experiments involving different depolarization protocols. 2. Following short rest periods, repetitive stimulation gave rise to slow inward currents which changed progressively in a voltage‐dependent manner. Small voltage depolarizations gave rise to initial small decreases in current (negative ‘staircase'). The current usually then showed a secondary increase but still remained, in most cases, below the control amplitude. Larger depolarizations produced increasingly larger and more rapidly rising positive current ‘staircases'. 3. The amount of increase in current magnitude during repetitive depolarization was more strongly dependent on the size of the voltage step than on the amplitude of the initial current. 4. Twin‐pulse experiments having a fixed interval between pulses (usually 1.0 sec), showed that ‘test’ pulses produced more slow inward current than preceding ‘conditioning’ depolarizations. The augmentation was larger following conditioning pulses of longer duration. Current augmentation was larger during ‘staircase’ obtained with longer pulses. 5. Following constant duration ‘conditioning’ depolarizations, varying the interpulse interval showed that the slow inward current flowing during the ‘test’ pulse could be augmented following intervals of as long as 6‐8 sec. 6. Small pre‐pulses also augmented the slow inward currents obtained in response to ‘tet’ pulses. 7. Experiments in calcium‐free solutions (with EGTA) showed qualitatively similar ‘staircase’ effects and current augmentation following preceding depolarizations. 8. Experiments in which sodium was replaced by lithium gave rise to larger slow inward currents. The ‘staircase’ for such currents developed in a similar manner to that seen under control conditions. 9. It is concluded that slow inward current augmentation is produced by membrane depolarization in a fashion which is at least partially independent of calcium or sodium ion influx.