bluuebunny/crossref_metadata_2025 huggingface dataset:
Myometrial activity in rats during the oestrous cycle and pseudopregnancy: interaction of oestradiol and progesterone.
Authors: Downing S J , Porter D G , Redstone C D
Published: December 2014

1. Oestradiol 17 beta inhibits the rat myometrium but the role of progesterone is uncertain. We have examined the interaction of the two steroids in the control of uterine activity in pseudopregnancy and the oestrous cycle. 2. Progesterone reversed the oestradiol‐induced inhibition of the myometrium in ovariectomized rats in vivo, but had little inhibitory effect of its own unless treatment was continued for several days. 3. The frequency and amplitude of intra‐uterine pressure cycles was unaffected by pseudopregnancy, but during the oestrous cycle frequency fell abruptly during late dioestrous and did not recover until early oestrus. 4. It is suggested that oestradiol is the major regulator of myometrial activity during the cycle and that progesterone interferes with the action of oestradiol, thereby paradoxically increasing uterine activity.
The interaction of potassium with the activation of anomalous rectification in frog muscle membrane.
Authors: Hestrin S
Published: December 2014

1. Inward rectification of frog muscle membrane was analysed with the Vaseline gap method. 2. Hyperpolarization, under voltage clamp, produced inward potassium currents, which had a component that activated with a time constant, tau K. 3. The activation time constant tau K of the inward potassium currents was voltage dependent. For a given external potassium concentration, the time constant was maximal for potentials near the potassium equilibrium potential, EK. 4. The potassium chord conductance gK, had a sigmoidal voltage dependency, increasing initially e‐fold per 11.6 mV of hyperpolarization. 5. When the internal potassium concentration was fixed, raising external potassium induced a shift of the tau K‐V and the gK‐V relations in the positive direction along the voltage axis. That shift was comparable to the change in EK. 6. No shift of the tau K‐V and the gK‐V relations was observed when the internal potassium was reduced from 150 to 50 mM. 7. Changes of internal sodium concentration between 5 and 100 mM did not significantly effect the magnitude of inward rectification.
The role of intrarenal pH in regulation of ammoniagenesis: [31P]NMR studies of the isolated perfused rat kidney.
Authors: Ackerman J J , Lowry M , Radda G K , Ross B D , Wong G G
Published: December 2014

1. [31P]NMR spectra were obtained from a functioning isolated perfused rat kidney with the aim of determining intrarenal pH in acute acidosis. 2. Signals from intracellular inorganic phosphate could be observed in the absence of phosphate in the perfusion medium. Under these conditions renal ATP and inorganic phosphate content fell by 30% but total adenine nucleotide and phosphorylation potential ATP/ADP x Pi were unchanged compared with kidneys perfused with phosphate‐containing medium. In addition, G.F.R., Na+ reabsorption and ammonia formation from glutamine remained normal. Ammonia production increased 93%, urine pH fell to 5.8 +/‐ 0.1 and kidney 2‐oxoglutarate content fell by 80% upon acidification of the perfusion medium from pH 7.4 to pH 6.9, findings identical with those obtained in controls (Ross & Tannen, 1979). 3. [31P]NMR spectra of the isolated perfused rat kidney showed a pattern of adenine nucleotides and a small concentration of phosphocreatine, Intra‐renal pH was measured from the resonance position of intracellular inorganic phosphate and in perfusions with pH 7.4 buffer was 7.19 +/‐ 0.10 (n = 11). 4. Acidification of the perfusion medium to pH 7.0 resulted in 0.3 pH unit fall in intrarenal pH. This fall in total intrarenal pH is insufficient to explain the fall in 2‐oxoglutarate concentration observed if the glutamate‐dehydrogenase‐equilibrium model is invoked. 5. The line‐width of the NMR signal is compatible either with heterogeneity of intra‐renal pH or the existence of a pH gradient between cytosol and mitochondria, or both.
The influence of innervation on differentiating tonic and twitch muscle fibres of the chicken
Authors: Gordon Tessa , Vrbová Gerta , Wilcock G.
Published: December 2014

1. The anterior (ALD) and posterior (PLD) latissimus dorsi muscles of adult chickens were denervated by section of their motor nerves. Four weeks later the contractile and membrane properties of these muscles were studied in vitro at room temperature.

2. Although the time course of the PLD muscle twitch was slightly prolonged, the qualitative difference in contractile characteristics of the slow ALD and the fast PLD muscles was maintained after denervation.

3. The difference in the passive membrane characteristics of the ALD and PLD muscle fibres was not lost after denervation, although the membrane resistance (Rm) and space constant (λ) of the denervated muscles fell. The membrane resistance, space (λ) and time (τm) constants of the ALD muscle remained significantly greater than for the PLD muscle fibres. The absolute values of τm in both muscles increased, implying that in the case of the ALD the membrane capacitance (Cm) was increased above normal after denervation. This is discussed in terms of the ultrastructural changes in this muscle after denervation.

4. The ALD muscle was cut into small pieces and replaced in the bed of the PLD muscle, which in turn was minced and placed into the bed of the ALD muscle. These muscles regenerated and became reinnervated by the PLD and ALD nerves respectively. They aligned themselves in the muscle bed and adopted the former shape of the muscle that they replaced. The passive cable properties of the regenerated ALD muscle fibres innervated by the PLD nerve resembled the control PLD fibres and the regenerated PLD fibres reinnervated by the ALD nerve resembled those of the control ALD. Regenerated ALD and PLD reinnervated by their own nerves had contractile and membrane properties similar to those of control muscles.

5. The results show that the fundamental differences, between slow and fast muscles once established, persist even when they are deprived of their innervation. The properties of developing muscle fibres however are determined by the motor nerves even in the adult animal.
β‐receptor numbers and thermodynamics in denervation supersensitivity
Authors: Bannister R. , Boylston A. W. , Davies I. B. , Mathias C. J. , Sever P. S. , Sudera D.
Published: December 2014

1. Denervation supersensitivity to adrenergic agonists occurs after degeneration of the sympathetic nervous system in the disease called multiple system atrophy (MSA) or the Shy Drager Syndrome.

2. Supersensitivity to the chronotropic effect of
i.v. isoprenaline on the heart was demonstrated in eight subjects with sympathetic nervous system degeneration and MSA.

3. There was an increased number of β‐receptors present in MSA as measured by [H3]dihydroalprenolol ([H3]DHA) binding to β‐receptors on lymphocytes isolated from venous blood taken from the MSA subjects compared with [H3]DHA binding to lymphocytes from seven normal subjects. There was no difference in the affinity of lymphocyte β‐receptors for [H3]DHA in MSA.

4. [H3]DHA binding to lymphocytes from MSA subjects was decreased at lower temperatures but was unaffected by lower temperatures in lymphocytes from normal subjects.

5. Equilibrium constants for [H3]DHA binding to normal and MSA lymphocytes were similar, indicating that the affinity of the β‐receptors was similar in both groups. The equilibrium constants were little affected by cooling from 37 to 4 °C suggesting that the heat of reaction (enthalpy) for [H3]DHA binding was low. The Gibbs free energy change on binding was negative and similar in quantity for both normal and MSA lymphocytes. There was a similar, large, increase in entropy on binding of [H3]DHA to both normal and MSA lymphocytes, showing that the binding reaction was entropy driven.

6. If lymphocyte β‐receptors reflect the status of cardiac β‐receptors, increased numbers of cardiac β‐receptors may contribute to the denervation supersensitivity to isoprenaline in MSA with sympathetic degeneration.
Extracellular potassium accumulation in the frog spinal cord induced by stimulation of the skin and ventrolateral columns
Authors: Czéh G. , Kr̆íz̆ N. , Syková Eva
Published: December 2014

1. Changes in extracellular K+ concentration (Δ[K]e), dorsal root potentials (DRPs) and single unit activity were studied in the frog spinal cord in response to stimulation of the skin of the hindlimb by touch, pressure, hot water (heat), single electrical pulses and to stimulation of the ventrolateral columns (LC).

2. Single electrical pulses, various types of adequate stimulation applied to the skin of the hind limb for 1‐2 s as well as single volleys of LC led to a Δ[K]e of up to 0.2 mmol.l−1. Stimuli which evoked larger Δ[K]e also produced larger DRPs in the same frog preparation.

3. The briefest heat stimuli, which lasted about 1‐2 s, led to more prolonged activity in dorsal horn interneurones than did a single volley or a single tactile stimulus and the Δ[K]e were longer and larger and had a slower rise time.

4. The ‘slow’ second component of dorsal root depolarization (presumably mediated by K+) was observed after electrical and heat stimulation of the skin on the hind limb corresponding to the time course of Δ[K]e.

5. The maximum Δ[K]e induced by nociceptive stimulation occurred in the grey matter of the dorsal horn at a depth of 300‐600 μm from the dorsal surface. The maximum response to single stimuli applied to the skin occurred at a depth of 400‐800 μm, while that evoked by LC stimulation in the ventral horn at a depth of 1000‐1400 μm.

6. Repetitive and more prolonged nociceptive stimulation (5‐20 s) produced a Δ[K]e of up to 1 mmol.l−1. The Δ[K]e in response to repetitive tactile stimulation does not exceed 0.2 mmol.l−1. Repetitive stimulation (100 Hz) of LC fibres led to an increase in [K]e of up to 9‐10 mmol.l−1 in the ventral horn; this level was similar to that achieved in the intermediate region by electrical repetitive stimulation of the skin (100 Hz). Tetanic stimulation of the ventral root led to a Δ[K]e of only about 0.05 mmol.l−1 at a depth of 500‐700 μm and no measurable Δ[K]e within the ventral horn.

7. Spontaneous Δ[K]e associated with spontaneous DRPs and VRPs were observed during the decay phase of Δ[K]e at various intervals from several seconds to one minute after nociceptive or electrical stimulation of the skin, suggesting the occurrence of a longlasting increase in excitability.

8. The depolarization of dorsal root fibres evoked by nociceptive stimulation, tetanic stimulation of the LC and single or tetanic stimulation of the skin was followed by a dorsal root hyperpolarization. Its size, as well as that of Δ[K]e, was dependent on the frequency and duration of stimulation and its time course correlated with the dissipation of Δ[K]e when stimulation was discontinued.

9. It is suggested that the extracellular K+ accumulation could, under physiological conditions, contribute to the modulation of spinal cord transmission, acting both pre‐and post‐synaptically. Low levels of increased [K]e were associated with facilitation of impulse transmission while higher increases could result in its inhibition.
Healing‐over in rat crystalline lens.
Authors: Bernardini G , Peracchia C , Venosa R A
Published: December 2014

1. 42K efflux has been studied in normal and injured rat crystalline lenses to test their ability to heal over. Following injury, a sizeable, but transient, increase in fractional loss of 42K takes place. 2. The lens healing‐over is Ca‐dependent and cannot be accounted for by membrane resealing. This is excluded by the fact that Procion Yellow gains access to damaged fibres even 2 hr after injury (when the healing‐over is completed). 3. The occlusion of the junctional channels is the basic mechanism of healing‐over. This is supported by the observation that Procion Yellow does not diffuse from damaged to intact fibres and by the Ca dependency of the phenomenon.
The effect of vagotomy on sodium reabsorption and renin release in anaesthetized dogs subjected to 60 degrees head‐up tilt.
Authors: DiBona G F , Johns E J , Osborn J L
Published: December 2014

1. Anaesthetized dogs were subjected to two 15 min periods of 60 degrees head‐up tilt. Renal perfusion pressure was regulated to minimize changes during tilting. 2. In both intact and vagotomized animals there was a fall in systemic arterial pressure and a rise in heart rate. In both intact and vagotomized animals glomerular filtration rate fell slightly during the first tilt but remained unchanged in the second tilt period. Renal blood flow was unchanged throughout. 3. Both absolute and fractional excretions of sodium were reduced in intact animals subjected to the two consecutive periods of tilt. Following vagotomy these responses were as large as those observed in intact animals. 4. Tilting caused an increase in renin secretion from the kidney in both tilting periods to which the intact animals were subjected. In the vagotomized animals the increase in renin secretion was as large as that observed in intact animals. 5. The results of the present study show that, under the experimental conditions used, vagal afferent activity had no measurable effect on the decreases in sodium excretion or increases in renin secretion mediated by the renal nerves during short periods of 60 degrees head‐up tilt.
Orthodromic production of non‐cholinergic slow depolarizing response in the superior cervical ganglion of the rabbit
Authors: Ashe J. H. , Libet B.
Published: December 2014

1. A late slow depolarization in the rabbit superior cervical ganglion, recorded extracellularly as ‘late late negative’ (l.l.n.) response, can be elicited by suitably repetitive stimulation of cervical sympathetic nerve. The l.l.n. response is not blocked by strong nicotinic, muscarinic or adrenergic antagonists; it appears with latencies in seconds, rise times in minutes, durations of up to 20 min or more, and extracellular amplitudes that can exceed 1 mV when recorded in an air‐gap chamber.

2. The l.l.n. component is a graded post‐synaptic response that decreases with a length constant similar to those of the known p.s.p.s (fast e.p.s.p., slow i.p.s.p., and slow e.p.s.p.). This and its other characteristics indicate that the l.l.n. response is neuronally generated and represents a non‐cholinergic late slow depolarization. The term ‘slow slow e.p.s.p.’ is suggested for this response, to replace both ‘slow depolarization’ and ‘late slow e.p.s.p.’.

3. The amplitudes, evaluated relative to the compound action potentials, and the durations of l.l.n. responses recorded from intact neurones of rabbit superior cervical ganglion were considerably greater and more consistently producible than the non‐cholinergic slow depolarizations recorded by others from impaled neurones of guinea‐pig inferior mesenteric ganglion.

4. The l.l.n. response does not exhibit the special sensitivity to sodium azide previously found for the muscarinic ‘late negative’ or slow e.p.s.p. response.

5. The total number of orthodromic volleys is the chief determinant of the amplitude and duration of the l.l.n. response. Increases in pulse frequency, with no change in pulse number, exert only a minor influence on amplitude and duration of the l.l.n. response but can markedly decrease latency and rise time.

6. Even very low pulse frequencies (e.g. 1/sec) are almost as effective as higher frequencies if a sufficiently large number of stimulus pulses is applied.

7. The features of orthodromic production of the l.l.n., slow slow e.p.s.p. response, as well as the amplitudes and durations of this depolarization, indicate that this non‐cholinergic post‐synaptic response could, like the muscarinic slow e.p.s.p., play a significant role in mediating physiological activities of sympathetic ganglia.
Daily water and electrolyte balance in chronically hyperprolactinaemic rats.
Authors: Kaufman S , Mackay B J , Scott J Z
Published: December 2014

1. Chronic hyperprolactinaemia was induced in eight male rats by implantation of anterior pituitary glands from inbred female rats. The ten control rats underwent sham operations. 2. The spontaneous 24 hr water intake of hyperprolactinaemic rats was greater than that of the controls. Intake was increased only at night. 3. The increased water intake was independent of food intake and was not secondary to increased salt intake. 4. When prolactin secretion was inhibited with bromocriptine, there was a parallel fall in water intake and plasma prolactin levels in the experimental animals to the levels observed in the controls. 5. Urine volume was greater and urine osmolality lower in the hyperprolactinaemic rats than in the controls during both day and night. 6. In the evening, plasma osmolality was lower in the hyperprolactinaemic animals than in the controls. No such difference was observed in the morning. 7. Blood volume was greater in the hyperprolactinaemic rats than in the controls, but the haematocrits were the same. 8. These findings indicate prolactin may have a primary dipsogenic activity.
Post‐tetanic potentiation and facilitation of synaptic potentials evoked in cat spinal motoneurones.
Authors: Hirst G D , Redman S J , Wong K
Published: December 2014

1. Excitatory post‐synaptic potentials (e.p.s.p.s) were evoked in spinal alpha‐motoneurones of the cat by impulses in single group Ia nerve fibres. 2. The average peak amplitude of some of these e.p.s.p.s was increased by a conditioning tetanus. The maximum increase observed was 54% of the control amplitude. 3. The average peak amplitude of some e.p.s.p.s was increased by a single conditioning stimulus which preceded the test stimulus by 1 or 2 msec. The maximum increase observed was 28% of the control amplitude. 4. The ability of e.p.s.p.s to potentiate following a tetanus was correlated with their ability to be facilitated by a single conditioning stimulus. 5. If an e.p.s.p. could be facilitated prior to a tetanus, the amount of facilitation was reduced after the tetanus, with all facilitation being abolished when post‐tetanic potentiation was maximal. 6. The fluctuations of an e.p.s.p. were analysed before and after a tetanus. The peak amplitudes that an e.p.s.p. fluctuated between while potentiated did not gradually diminish as the effect of the tetanus disappeared. Post‐tetanic potentiation, when it occurred, was accompanied by a decrease in the probability of occurrence of components with smaller peak amplitudes and an increase in the probability of occurrence of components with larger peak amplitudes. 7. These results are consistent with the suggestion that the magnitude of the synaptic potential generated at a single bouton does not vary from trial to trial (Jack, Redman & Wong, 1981a). Nor does the amplitude of this potential vary following a single conditioning stimulus or a tetanus. Post‐tetanic potentiation and facilitation result from a decrease in the probability of failure to release transmitter following the conditioning stimuli.
Chemical modification of sodium channel surface charges in frog skeletal muscle by trinitrobenzene sulphonic acid.
Authors: Cahalan M D , Pappone P A
Published: December 2014

1. We have investigated the effects of externally applied trinitrobenzene sulphonic acid (TNBS) on sodium currents of voltage‐clamped frog skeletal muscle fibres. TNBS is a membrane‐impermeant reagent which reacts specifically with amino groups under physiological conditions. 2. TNBS shifts the voltage dependence of steady‐state sodium current inactivation (h infinity) by approximately 18 mV to more hyperpolarized potentials when measured at pH 9. This effect of TNBS is irreversible, suggesting that the reagent permanently modifies some membrane component(s). 3. Time constants for the development of and recovery from inactivation of sodium current are similarly shifted to more hyperpolarized potentials by TNBS treatment. External TNBS did not affect the completeness of sodium current inactivation during depolarizing pulses. 4. The activation of sodium current is less affected by TNBS than is inactivation. The voltage dependence of peak sodium current activation was shifted by only approximately 4 mV by TNBS treatment at pH 9. The kinetics of sodium current activation during depolarization were little affected by TNBS. 5. The TNBS‐induced shift in h infinity and sodium current activation are independent of pH when measured at pHs between 7.4 and 11. 6. The results are consistent with the hypothesis that TNBS increases the negative surface charge of the membrane by reacting with membrane amino groups having a high pK.
Do identical activity patterns in fast and slow motor axons exert the same influence on the twitch time of cat skeletal muscle?
Authors: Goldring J. M. , Kuno M. , Núñez R. , Weakly J. N.
Published: December 2014

1. The fast‐twitch flexor digitorum (the lateral head; equivalent to the flexor hallucis longus) and slow‐twitch soleus muscles of the cat were denervated, and the two nerves immediately reunited to one or the other muscle. Contraction times of the dually reinnervated muscle were examined 9 weeks post‐operatively in response to separate stimulation of its own and the foreign nerve. Over a 5 week period before the terminal experiment, a variety of artificial activity patterns was imposed on the two nerves.

2. Following the dual‐union operation, the flexor digitorum muscle was preferentially reinnervated by its own nerve. In contrast, the soleus muscle showed no evidence of preferential reinnervation.

3. When neural activity was not artificially modified, the dually reinnervated flexor digitorum or soleus muscle showed faster contractions in response to stimulation of the flexor digitorum nerve than to stimulation of the soleus nerve.

4. Following a 5 week period in which neural activity was virtually eliminated by cord transection or in which the two nerves were stimulated at the same frequency, the contraction times of the dually reinnervated soleus muscle were the same in response to stimulation of either nerve.

5. In contrast, under the experimental conditions described above (cord transection or nerve stimulation), the dually reinnervated flexor digitorum muscle showed a significantly faster contraction in response to stimulation of its own nerve than to stimulation of the soleus nerve.

6. It is concluded that, when neural activity is absent or identical in pattern, motoneurones normally innervating the fast‐ or slow‐twitch muscles exert the same influence on contraction times of the soleus muscle.

7. The dependence of contraction times of the dually reinnervated flexor digitorum muscle upon the type of the innervating motoneurone may be explained either by selective reinnervation of a particular group of muscle fibres or by different trophic substances emanating from the motoneurones.
The effect of theophylline on intestinal bicarbonate transport measured by pH stat in Amphiuma.
Authors: Imon M A , White J F
Published: December 2014

1. The influence of theophylline on the mucosa to serosa and serosa to mucosa fluxes of HCO3‐ were measured by the pH stat technique in isolated segments of proximal small intestine from Amphiuma maintained under short‐circuited conditions. The mucosal or serosal fluid was exposed to media containing 25 mM‐HCO3‐ (pH 7.4) while the pH of unbuffered media in the opposite compartment was maintained by addition of acid. 2. Theophylline significantly increased the secretory flux of HCO3‐ and significantly reduced the absorptive flux when measured in Cl‐ ‐free (SO4(2‐)) media. 3. In normal media theophylline did not alter the secretory flux but significantly lowered the absorptive flux of HCO3‐. 4. Acetazolamide (0.1 mM) inhibited the theophylline‐stimulated secretory flux of HCO3‐ and reduced the effect of theophylline on the absorptive flux. 5. In normal intestine there was an inequality between the secretory or absorptive HCO3‐ flux and the short‐circuit current (Isc) consistent with the presence of Cl‐ absorption. After addition of theophylline the Isc was more nearly equal to the net secretory or absorptive HCO3‐ flux. 6. Exogenous cyclic AMP had effects identical with theophylline. 7. The results provide strong evidence that elevation of cyclic AMP stimulates net HCO3‐ secretion in urodele small intestine and provide indirect evidence that Cl‐ absorption is simultaneously reduced.
The summation of left and right lung volume information in the control of breathing in dogs
Authors: Cross Brenda A. , Guz A. , Jones P. W.
Published: December 2014

1. Reflex respiratory responses to unilateral and bilateral changes of lung volume have been studied in anaesthetized paralysed, open‐chest dogs.

2. The two lungs were separately ventilated by two phrenic‐driven respirators via a specially designed double‐lumen tube. Respiratory motor output was measured from the phrenic motoneurone activity recorded from the C5 root. Expiratory lung volumes were set by the use of expiratory threshold loads (e.t.l.s).

3. The reflex changes of expiratory time (te) were used to study the summation of left and right expiratory lung volume information. Changes in the peak amplitude of the phrenic ‘integral’ (Phr) and inspiratory time (ti) were used to assess summation of left and right tidal volume information.

4. Summation in the reflex responses to bilateral lung volume changes was estimated by comparing the measured responses to these manoeuvres with the sum of the component unilaterally evoked responses. If simple addition were present, response (measured)/response (predicted) would equal 1.0 Mutual facilitation would give a value higher than this; mutual inhibition, a lower value.

5. The responses of te to changes of e.t.l. on the right side were always greater than for changes confined to the left, and in each animal the response of te to bilateral changes of e.t.l. were greater than for either of the unilaterally evoked responses. In six out of eight animals this was shown to be due to simple addition of the responses evoked from the two lungs individually. In the remaining two animals, slight mutual inhibition was seen.

6. The tidal volume VT was changed in one or both lungs. During the bilateral VT changes, the volumes were changed simultaneously, either in the same direction (‘same’ VT changes) or in one direction in one lung and in the opposite direction in the other (‘opposite’ VT changes).

7. In the bilateral ‘same’ VT changes, mutual facilitation was seen in the response of Phr; Phr (measured)/Phr (predicted) = 1.60 ± 0.42 (
s.d.), n = 8. There was only slight facilitation in the response of ti; ti (measured)/ti (predicted) = 1.18 ± 0.17, n = 8.

8. With the bilateral ‘opposite’ VT changes, responses of ti and Phr were markedly and significantly reduced compared to those for the bilateral ‘same’ VT changes. During these manoeuvres significant mutual inhibition was seen in the response of ti, and the predicted responses of Phr in general could not be correlated with the measured response.

9. The responses of the phrenic ‘integrals’ were the same in both right and left phrenic nerves.

10. Unilateral vagotomy abolished both the responses of Phr and ti to ipsilateral VT changes in the range ± 100% of control VT, and also the response of te to ipsilateral expiratory volume changes.
The influence of starvation on intestinal cholecystokinin‐like activity and pancreatic growth
Authors: Brand S. J. , Morgan R. G. H.
Published: December 2014

1. This study examines the influence of starvation on intestinal CCK content and pancreatic growth. Intestinal CCK content was determined by measuring the CCK‐like activity using an in vitro gall‐bladder bio‐assay. Starvation for up to 72 hr causes a parallel fall in intestinal CCK content and pancreatic DNA synthesis. Since there was no significant decrease in liver DNA synthesis, the effect of starvation was probably not simply a consequence of malnutrition. Furthermore there was little effect of starvation on pancreatic protein and DNA content, suggesting that pancreatic cell turnover is particularly sensitive to changes in dietary stimulation.

2. With refeeding after starvation CCK‐like activity in intestinal extracts gradually increased, approaching non‐fasting levels 72 hr after refeeding. Pancreatic DNA synthesis also returned to non‐fasting levels after feeding but this rose faster than the intestinal CCK content.

3. Pentagastrin treatment prevented the atrophy of both the pancreas and the gastrointestinal tract with starvation without influencing the fall in intestinal CCK‐like activity. This suggests that the control of CCK‐containing cells is different from that of the surrounding intestinal parenchyma.

4. The effect of starvation was also studied in antrectomized rats. Antrectomy alone did not reduce pancreatic DNA synthesis although DNA synthesis of the small intestine was significantly reduced. When antrectomized rats were starved pancreatic DNA synthesis fell to the same degree as was found in unoperated animals. The pancreatic atrophy was also accompanied by a drop in intestinal CCK content. Starvation of antrectomized rats, however, did not further depress the already greatly reduced plasma gastrin concentration.
Lacrimal gland electrolyte and water secretion in the rabbit: localization and role of (Na+ + K+)‐activated ATPase.
Authors: Dartt D A , Møller M , Poulsen J H
Published: December 2014

1. The rate of acetylcholine (ACh)‐induced fluid secretion was measured from the main secretory duct of rabbit lacrimal glands perfused in vivo with Krebs Henseleit bicarbonate solutions. 2. Perfusion with ouabain (10(‐5) M) decreased the rate of lacrimal gland fluid secretion to 23% of the control value. 3. Perfusion with furosemide (10(‐4) and 10(‐3) M), which has been shown to inhibit the coupled transport of Na+ and Cl‐, reversibly decreased the rate of secretion to 43 and 33% of the control value respectively. 4. (Na+ + K+)‐activated ATPase was localized in slices of rabbit lacrimal gland using autoradiography with [3H]ouabain. 5. A high density of [3H]ouabain binding sites was present on ductal cells, whereas a very low density was found on acinar cells. For both types of cells the [3H]ouabain binding sites were located on the basolateral plasma membranes. 6. It is concluded that ACh‐induced secretion of electrolytes and water is dependent upon (Na+ + K+)‐activated ATPase. In addition, coupled transport of Na+ and Cl‐ appears to be involved in secretion. 7. Basolateral location of the (Na+ + K+)‐activated ATPase implies that it plays an indirect role in electrolyte and water secretion. A possible role may be to energize a secondary active transport of Cl‐ that is mediated by a NaCl cotransport system.
Human intestinal potential difference: recording method and biophysical implications.
Authors: Gustke R F , McCormick P , Ruppin H , Soergel K H , Whalen G E , Wood C M
Published: December 2014

1. The transmural electrical potential difference (PD) of the intact human small intestine was recorded with close attention to electrical symmetry, shielding from electro‐magnetic waves and correction for junction potentials. 2. The PD is ‐12 mV (mucosa‐negative) in the fasting jejunum and ileum and does not change during perfusion with isotonic NaCl. 3. Absorption of Na and Cl appears to be non‐electrogenic and the ‘resting’ PD is probably generated by active anion secretion of fasting intestinal contents. 4. Diffusion potentials during isotonic D‐mannitol perfusion indicated higher cation selectivity in the ileum than in the jejunum. 5. The calculated contribution of a free‐solution path to total paracellular permeability is 55% in the jejunum but only 15% in the ileum. 6. No ‘streaming’ potential was detected during osmotic water flow, suggesting that the cation‐selectivity of the channels is temporarily inactivated during dilatation of the lateral intercellular space.
Factors that determine the excitability of parasympathetic reflexes to the cat bladder
Authors: McMahon S. B. , Morrison J. F. B.
Published: December 2014

1. Spino‐bulbo‐spinal reflex responses could be recorded from the vesical branches of the pelvic nerve following electrical stimulation of afferents in the vesical or colonic branches of the pelvic nerves, the hypogastric or pudendal nerves. The latencies of responses from these different sources were similar.

2. Short latency responses could be recorded from the vesical branches of the pelvic nerve on electrical stimulation of descending pathways in the spinal cord and ipsilateral to and just below a hemitransection at the second cervical segment.

3. These responses were facilitated by increases in intravesical pressure, maximal facilitation occurring at about 30 mmHg. Conversely, increases in intracolonic pressure inhibited these parasympathetic evoked responses, the maximum effect being seen with intracolonic pressures of 40‐50 mmHg.

4. These results suggest that the spino‐bulbo‐spinal responses that are recorded from the vesical parasympathetic efferents can be elicited from nerves innervating viscera other than the bladder, and also somatic structures. The effects of these spino‐bulbo‐spinal pathways on vesical parasympathetic efferents are dependent on antagonistic influences of intravesical and intracolonic pressure.

5. The pathways that mediate the changes in excitability in these reflexes appear to act at least in part at the termination of the bulbo‐spinal limb of the reflex, and involve afferents in the pelvic nerves but not the hypogastric or lumbar colonic nerves.

6. It is proposed that the neurones that mediate this ‘gating’ action on the excitability of pelvic nerve reflexes are located in the sacral cord, and form a proportion of the population of interneurones described by McMahon & Morrison (1982b). In addition it is proposed that the neurones which mediate the ascending limb of the spino‐bulbo‐spinal reflexes are the long ascending neurones described by McMahon & Morrison (1982a).
Exocrine pancreatic function following proximal small bowel resection in rats.
Authors: Gelinas M D , Morin C L , Morisset J
Published: December 2014

1. In order to assess if proximal enterectomy induces changes in the function of the exocrine pancreas, the exocrine pancreas was studied 1 week, 4 weeks, and 6 months after 50 or 75% proximal small bowel resection. 2. One week after 50 and 75% proximal small bowel resections, basal pancreatic bicarbonate outputs, studied by means of an external pancreatic fistula in conscious rats, were increased significantly over control values by 43 and 78% respectively. Four weeks after a 75% resection, the bicarbonate output was still significantly higher in resected animals than in sham operated animals. 3. The increase of volume and bicarbonate of the basal pancreatic secretion coincided with a 4‐fold increase in plasma secretin concentration 1 week after resection. Both increased pancreatic secretion and plasma secretin concentration were transient. 4. The pancreatic hypersecretion was specifically reversed to control values with an I.P. injection of jejunoileal mucosa homogenate. 5. Serum gastrin and somatostatin values in intestinal mucosa and pancreas were not changed 1 and 4 weeks after enterectomy compared with sham operated animals. 6. The weight of the pancreas and its content of DNA were unaltered by resection. Amylase and chymotrypsinogen per gram pancreatic tissue and per microgram DNA were reduced 4 weeks following resections as compared with sham operated rats. After 6 months, chymotrypsinogen appeared further reduced in resected animals. 7. It is concluded that extensive proximal enterectomy in rats produced early, transient and marked increases in basal pancreatic water and bicarbonate secretion and in plasma secretin due to the loss of jejunoileal inhibitor(s), and a selective decrease in certain enzymes in pancreatic tissue.
Histograms of the unitary evoked potential of the mouse diaphragm show multiple peaks
Authors: Kriebel M. E. , Llados F. , Matteson D. R.
Published: December 2014

1. Two classes of miniature end‐plate potentials (m.e.p.p.s) were recorded from diaphragm neuromuscular junctions. Amplitude histograms of both classes had multiple peaks that were integral multiples of the smallest peak (s‐m.e.p.p.s). The smaller m.e.p.p.s formed the first three or four peaks of histograms and the number of m.e.p.p.s (skew‐m.e.p.p.s) in each peak decreased, forming an over‐all skewed distribution. The larger m.e.p.p.s (bell‐m.e.p.p.s) formed a more‐or‐less bell‐shaped distribution. The distribution of m.e.p.p.s varied from mainly skew‐ to mainly bell‐m.e.p.p.s. In young adult mice the number of subunits composing the classical m.e.p.p.s varied between ten and fifteen at room temperature; at higher temperatures the range was from three to ten subunits.

2. End‐plate potentials (e.p.p.s) were reduced with cobalt ions (ca. 4 m
m) until most nerve impulses failed to release transmitter. The amplitudes of ‘unitary evoked potentials’ were of the bell‐m.e.p.p. class and histograms show integral multiple peaks that correspond to the peaks in histograms of the bell‐m.e.p.p.s.

3. The peaks in both m.e.p.p. and unitary e.p.p. histograms remained in the same position throughout the recording period and became more distinct as the sample size increased.

4. The variance of the s‐m.e.p.p. was estimated from the noise and measurement error and the variance of all peaks in the histograms. Most variance of the first peak (s‐m.e.p.p.) was due to noise and measurement error.

5. The integral peaks in the m.e.p.p. and ‘unitary evoked potential’ histograms are predicted with a probability density model based on the estimated variance of the s‐m.e.p.p. and the assumption that larger potentials are composed of subunits the size of s‐m.e.p.p.s. The data and model support the hypothesis that m.e.p.p.s and unitary potentials are composed of subunits.
Development of post‐tetanic potentiation at identified inhibitory and excitatory synapses in Aplysia
Authors: Ohmori Harunori
Published: December 2014

1. The development of post‐tetanic potentiation (p.t.p.) was studied at three identified synapses in the abdominal ganglion of Aplysia californica. They are (1) the excitatory synapse made onto R15 by an axon in the right connective (RC1—R15), (2) the inhibitory synapse made by L10 onto one of its follower cells in the rostral quadrant of the left abdominal ganglion (L10—LUQC), and (3) the excitatory synapse made by L10 onto RB cells (L10—RB). Animals examined ranged from stage 11 juveniles weighing 2 mg to stage 13 adults weighing 300 g.

2. Despite a marked decrease of the input resistance (34‐fold) and a marked increase in the capacitance of the cells of the LUQC, the amplitude of i.p.s.p. measured at 50 mV more negative than its reversal potential decreases only 4‐fold, between juvenile animals (25‐65 mg) and adult animals (100 g). This suggests a marked increase in the synaptic current. A similar discrepancy in the extent of decrease between the input resistance and e.p.s.p. amplitude was found in the RC1—R15 synapse during development.

3. The amount of p.t.p., after tetanization at 5 Hz for 30 sec, increased with development. At the excitatory RC1—R15 synapse, p.t.p. (defined as the percent of the maximal post‐tetanus p.s.p. over the control p.s.p.) increased from 135±11% (mean±
s.d., n = 7) to 334±72% (n = 10). At the inhibitory L10—LUQC synapse, p.t.p. increased from 99±11% (n = 6) to 276±58% (n = 7).

4. At both types of synapses, the time course of p.t.p. decay was measured by fitting a single exponential function, showing no systematic developmental change in the time constant of p.t.p. decay from the time p.t.p. was first measured onwards. The time constant was 129±52 sec (n = 39) for RC1—R15, and 45±7 sec (n = 20) for L10—LUQC.

5. Divergent connexions made by the same presynaptic neurone L10 on the inhibitory follower cells (L10—LUQC) and on the excitatory cells (L10—RB) showed the same amount of potentiation in the same animal after an L10 tetanus. Convergent connexions onto the RB cells from the axon in the right connective and from L10 produced completely independent potentiation. These results provide an independent support for the well established finding that p.t.p. results exclusively from presynaptic changes.

6. At each of these several synapses which show robust p.t.p. in adult animals, p.t.p. appears as a late step in their development. There is thus a discrete and considerable interval of time between the establishment of functional connexions and the emergence of synaptic plasticity in these excitatory and inhibitory synapses in Aplysia.
Desensitization at the frog neuromuscular junction: a biphasic process
Authors: Feltz Anne , Trautmann Alain
Published: December 2014

1. The desensitization of the cholinergic receptor has been investigated at the frog neuromuscular junction. The agonist was either perfused or applied by ionophoresis.

2. In all situations, desensitization develops in two phases: a fast one, experimentally in the second range but likely to be briefer, and a slower one, which extends over tens of seconds.

3. When the presence of the agonist is prolonged, desensitization approaches a steady state, estimated through the amplitude of a test response. In steady‐state conditions, this amplitude depends upon the desensitizing agonist concentration. The dose—response curve for desensitization induced by carbachol (CCh) indicates that half of the receptors can be desensitized at room temperature in the presence of 2·3 μ
m‐CCh. The shape of the curve suggests that one desensitized receptor can bind two CCh molecules.

4. The recovery from desensitization, estimated with a repetitive test pulse, displays two exponential phases. The time constant of the fast phase is 11‐12 sec, and 4‐5 min for the slow phase, regardless of the concentration or the nature of the agonist (acetylcholine or carbachol).

5. The factor which most strikingly affects the relative amplitudes of the fast and slow phases of recovery is the duration of the (desensitizing) agonist application. Desensitizations lasting a few seconds are followed by a ‘fast’ recovery, whereas the slow phase of recovery is prominent when the agonist has been applied for more than 2 min.

6. The fast and slow phases of desensitization onset and offset are not due to independent causes but are coupled: in given conditions, the onset can be essentially fast, and the recovery slow.

7. All our findings can fit in a cyclic scheme of desensitization, derived from the one of Katz & Thesleff (1957) with two modifications: whether activatable or desensitized, one receptor molecule would have two agonist binding sites; moreover, the desensitized receptor would exist in two distinct and interconverting conformations: D1, giving rise to the fast phases of onset and offset, and D2, responsible for the existence of the slow components of desensitization.
Excitatory post‐synaptic potentials from single muscle spindle afferents in external intercostal motoneurones of the cat.
Authors: Kirkwood P A , Sears T A
Published: December 2014

1. The discharges of muscle spindle afferents from the external intercostal muscles of anaesthetized, paralysed cats were recorded from dorsal roots in continuity. The dynamic responses, regularities of firing and conduction velocities of the afferents were measured and used to characterize the afferents as primary‐like or secondary‐like. 2. The synchronization of afferent discharges was investigated by the construction of cross‐correlation histograms from the simultaneously recorded discharges of pairs of afferents. The discharges of primary‐like afferents with high dynamic responses were found to be synchronized within a few msec. The cardiac pulse was a strong contributary factor in this synchronization. 3. Intracellular recordings were made from external intercostal motoneurones, and spike‐triggered averaging was used to reveal unitary e.p.s.p.s evoked by muscle spindle afferents which were from the same spinal cord segment. Dorsal roots other than the rootlet containing the afferent were cut to prevent the synchronization of afferent discharges from affecting the averaged e.p.s.p.s. 4. For primary‐like afferents the mean amplitude of the e.p.s.p.s was 171 microV and the mean connectivity (the proportion of motoneurones connected by one afferent) was between 42 and 48%. 5. The amplitudes and shapes of the e.p.s.p.s varied with the respiratory phase, usually being larger in inspiration than in expiration and sometimes also having a longer time course. In particular some e.p.s.p.s showed that components, only represent in inspiration, which were interpreted as indicating polysynaptic connexions gated by the respiratory cycle. 6. The results are discussed in comparison with the connexions of individual muscle spindle afferents from other muscles, with particular reference to the conduction velocities of the afferents.
The brain‐stem projections of pulmonary stretch afferent neurones in cats and rabbits.
Authors: Donoghue S , Garcia M , Jordan D , Spyer K M
Published: December 2014

1. Micro‐electrode recordings were made from slowly adapting pulmonary stretch afferents within the nodose ganglia of cats and rabbits. Recordings sites were distributed throughout the ganglia. 2. The projections of these afferents to the medulla oblongata were studied by antidromic stimulation. ‘Point’ and ‘Field’ type depth‐‐threshold curves were interpreted as corresponding to stimulation of the main afferent axons and its branches, respectively. Increases in antidromic latency in conjunction with ‘field’ contours was additional evidence in support of this interpretation. 3. In cats, most (six out of seven) afferents had extensive branches, and probably also terminations, within the medial subnucleus of the ipsilateral nucleus tractus solitarius (n.t.s.). Two of these, plus one other afferent, also had projections to the lateral and ventrolateral subnuclei. 4. In rabbits the projections of such afferents were similar, i.e. mainly to the medial subnucleus of the n.t.s. (eight out of eleven) but also extending into the nucleus alaris, and occasionally to lateral and ventrolateral subnuclei (two out of eleven) or to both regions (one out of eleven). 5. Branching of single afferents was seen to occur over up to 3 mm of the rostro‐caudal extent of the intermediate region of the n.t.s. The significance of the observations is discussed.
Fluctuation analysis of neutral amino acid responses in cultured mouse spinal neurones.
Authors: Barker J L , McBurney R N , MacDonald J F
Published: December 2014

1. Intracellular recordings using the voltage‐clamp technique were made at room temperature (24 +/‐ 1.5 degrees C) from mouse spinal and sensory neurones growing in dissociated cell culture. 2. Membrane current responses could be elicited by ionophoresis of the neutral amino acids, gamma‐aminobutyric acid (GABA), beta‐alanine (BALA) and glycine to the cell body and processes of these neurones. 3. All membrane current responses were associated with increases in current fluctuations. Most of the analysis presented here was applied to responses generated at the cell body. 4. Many of the fluctuations in membrane current occurring during the responses could be interpreted as reflecting the kinetic behaviour of a single population of two‐state Cl‐ ion‐channels. 5. The properties of channels estimated during the desensitized phase of an amino acid‐induced current response were not significantly different from those estimated during the peak of the response. 6. The properties of the amino acid‐activated channels were relatively constant over the ‐40 to ‐90 mV range of membrane potential. 7. There was considerable variation in the estimated average conductance, gamma, and duration, tau, of the elementary events evoked by the neutral amino acids on spinal cord neurones. The properties of the elementary channel events activated by one of the amino acids were significantly different from those activated on the same neurones by either of the other amino acids. 8. In sensory neurones the average gamma and tau values for GABA‐activated ion‐channels were also determined and these values fell within the range of those for channels activated by GABA in spinal neurones. 9. The results indicate that different naturally occurring neutral amino acids activate channels with unique properties in cultured mouse spinal neurones. The relative charge transfer associated with these channels averages 1.00:0.74:0.32; GABA:glycine:beta‐alanine.