bluuebunny/crossref_metadata_2025 huggingface dataset:
THE MODE OF ACTION OF VASODILATOR AND VASO‐CONSTRICTOR NERVES
Authors: Bain W. A.
Published: December 2014

1. Experiments on the perfused tongue of the dog, which demonstrate directly that vasomotor nerves produce their effects by the peripheral liberation of chemical substances, are described.

2. It is shown that stimulation of the vasodilator nerves liberates a substance which can be transmitted humorally to an isolated strip of rabbit intestine and cause augmentation of the tone and/or contractions of this.

3. It is shown similarly that stimulation of the sympathetic supply to the blood‐vessels liberates a substance which diminishes the tone and/or contractions of an isolated strip of intestine.

4. An experiment is described in which the effects of spontaneous changes in vasomotor activity (Traube‐Hering effect) were humorally transmitted to the test tissue.

5. The effects described are only obtained when the perfusion fluid (Dale's solution) is uncontaminated with blood.

6. It is pointed out that the humoral transmission of the substances responsible for these effects is the method of demonstrating the existence of the neuromimetic substances, and that under normal circumstances such transmission is probably of little significance.
EFFECT UPON LACTATION OF OÖPHORECTOMY DURING PREGNANCY. (ALBINO RAT.)
Authors: Hain Annie M.
Published: December 2014

1. Removal of the ovaries at any stage of pregnancy in the rat may either prevent lactation or diminish it to almost negligible proportions. In one animal, however, normal lactation occurred after oophorectomy on the 17th day.

2. Injections of alkaline extract of anterior pituitary failed to promote lactation in rats obphorectomised during pregnancy.
THE DEVELOPMENT OF THE POLYMORPHONUCLEAR LEUCOCYTE IN THE BLOOD STREAM
Authors: Climenko David R. , Ponder Eric
Published: December 2014

1. The polymorphonuclear leucocytes kept under in vitro conditions do not show development from one class of the polynuclear count to another, as might be expected on theoretical grounds, nor can such development be observed under ordinary circumstances in ligated veins. The reason for this is that the slow forward development is masked by the appearance of cytolysed and degenerate forms, and also that the number of cells which are affected by the developmental process in a limited time is too few in normal blood.

2. If the number of young forms in the blood is increased by a stimulation of the bone marrow, development from Class I. to Class II. can be demonstrated in isolated veins.

A number of the in vitro experiments were carried out by Dr. George Saslow and Dr. Malvina Schweizer, whom we have to thank for kindly placing their results at our disposal.
THE LENGTH OF THE FIBRES OF THE CENTRIFUGAL MICTURITION PATH IN THE SPINAL CORD OF THE CAT
Authors: Barrington F. J. F.
Published: December 2014

The fibres of the centrifugal micturition path of the cat's spinal cord have, in most if not in all cases, at least one cell relay before reaching the cells of origin of the efferent fibres of the pelvic nerve.
ESTIMATION OF THE FERMENTABLE CARBOHYDRATES IN RABBIT LIVER. ISOLATION OF A REDUCING DEXTRIN
Authors: Purves C. B.
Published: December 2014

(1) A carbohydrate easily fermented by yeast, free from glucose and glycogen, was isolated as a slightly impure, amorphous powder in 0·07 per cent. yield from rabbit liver. The solubilities and general properties of the carbohydrate were those of a mixture of dextrins containing free, copper‐reducing groups. It gave no colour with iodine.

(2) The amorphous acetate of the above had a specific rotation of 127° in chloroform and a nitrogen content of 0·28 per cent. It contained no detectable amount of sulphur or phosphorus.

A Carnegie Teaching Fellowship enabled the author to carry out the work.
A NOTE ON THE MECHANISM OF IODOACETATE POISONING OF MUSCLE
Authors: Ghaffar Abdul
Published: December 2014

1. Isolated muscles of Rana esculenta were immersed in Ringer's solution containing sodium iodoacetate (N/1000), and the effect of the drug was followed in two ways: (i) the suppression of glycolytic activity, and (ii) the liberation of iodide (presumed to result from an interaction between iodoacetic acid and glutathione of muscle).

2. At 0° C. the glycolytic activity of muscle is reduced to ⅔ of normal in 2 hours, and is completely suppressed in 8 to 9 hours. But no iodide is liberated during the first two hours of immersion, and even at the end of 8 to 9 hours the amount produced is less than 10 per cent. of the maximum that the muscle is capable of liberating.

3. This maximum iodide liberation requires about 36 hours contact between iodoacetate and muscle at room temperature, and amounts to about 0·07 millimols per 100 grm. of muscle, irrespective of the amount and concentration of iodoacetate in the system, provided there. is an excess. This quantity is equivalent to 25 mg. of reduced glutathione per 100 grin. of muscle.

4. At 40° C. the inhibition of lactic acid production becomes apparent in about 10 minutes, and maximum poisoning effect is attained in 30 to 40 minutes. Liberation of iodide, on the other hand, begins in about 20 minutes, and the maximum production takes as much as 3 to 4 hours.

5. These results do not support the view that the suppression of glycolytic activity of muscle depends upon an interaction between iodoacetic acid and glutathione, although they do not rule out the possibility of the formation of an addition compound.

I am deeply indebted to Dr P. Eggleton for help and guidance generously given.

The expenses of this research were defrayed from a grant from the Moray Endowment Fund.
EFFECT OF SNAKE VENOMS ON GLYCOLYSIS AND FERMENTATION IN CELL‐FREE EXTRACTS
Authors: Chain E.
Published: December 2014

A number of dried snake venoms contain a substance which inhibits completely glycolysis in a cell‐free muscle extract and fermentation in a yeast maceration juice when added to these solutions in concentrations of 0·2 to 2 mg. per c.c. The inhibiting substance of some venoms is not affected by heating the solutions for 10 minutes at 100° C.; in some venoms it is destroyed by this procedure.
A FACTOR INHIBITING THE GROWTH OF MESENCHYME
Authors: Medawar P. B.
Published: December 2014

1. The work of Heaton on a factor present in malt extracts which inhibits the growth of connective tissue is confirmed.

2. The action of the factor on explants of heart, spleen, buffy coat, periosteum, perichondrium, Jensen Rat Sarcoma, etc., indicates that it extends to all mesenchyme derivatives.

3. It is shown to be a constituent of normal diet; and its dietic status is discussed.

4. A survey of its manner of action on explanted tissues is reported, and a method of assay described.

5. The factor is shown to have no demonstrable direct effect on the growth of epithelia.

6. The meaning to be attached to the term “growth‐inhibition” is discussed.

The author wishes to thank Professor H. W. Florey, Mr. J. Z. Young, and Dr. H. M. Carleton for their interest in this work and for their advice. He also wishes to thank the Christopher Welch Trust for the supply of certain apparatus.
ON THE MECHANISM OF THE URETERO‐VESICAL SPHINCTER
Authors: Stewart J. Cuming
Published: December 2014

In these experiments on dogs, method used gave readings of bladder pressure, ureteric pressure and ureteric flow.

A bladder pressure of 25 cm. of water caused a cessation of ureteric flow.

With bladder pressures up to 60 cm. of water no demonstrable ureteric reflux was obtained.

Stimulation of the ipsilateral pelvic nerve caused a cessation of ureteric flow irrespective of whether or not the intravesical pressure was raised.

Stimulation of the hypogastric nerves and the lumbar sympathetic chains and section of these various nerves had no effect on ureteric flow.

In the “ringed” ureter experiments, where the distal end of the ureter and surrounding bladder wall was isolated from the rest of the bladder except by mucous membrane, the results were the same as for the intact bladder.

The evidence presented above suggests that the flow of fluid from ureter to bladder is controlled by a sphincter possessing its own intrinsic nervous mechanism.
THE THYROID NERVE IN THE DOG AND ITS FUNCTION
Authors: Ross W. Donald , Moorhouse V. H. K.
Published: December 2014

The thyroid nerve described by Nonidez in puppies and canine fœtuses has been found in adult dogs.

It is usually made up of nerve fibres derived from the superior cervical ganglion of the sympathetic and from the superior laryngeal branch of the vagus. The vagus fibres may arise from the ganglion nodosum or the vago‐sympathetic trunk, and occasionally from the external laryngeal nerve.

The thyroid nerve terminates in branches which enter the thyroid with the branches of the superior thyroid artery.

Stimulation of the thyroid nerve consistently slows the flow of blood through the gland. Acceleration of the blood‐flow has been obtained by stimulating the ipsilateral vagus and, in one instance, fibres from the external laryngeal nerve.

These results, indicating that the thyroid has a constant constrictor and some dilator innervation, suggest an indirect nervous control of the output of thyroid hormone into the blood‐stream.

Histological changes in the thyroid, after electrical stimulation of the thyroid nerve for some hours, could not be demonstrated. Section of the nerve, allowing time for degeneration, produced no demonstrable histological change.
RELATION BETWEEN THE “VILLIKININE” AND THE ABSORPTION OF GLUCOSE FROM THE INTESTINE
Authors: Kokas E. v. , Ludány G. v.
Published: December 2014

1. Villikinine is not activated by glucose.

2. Dilute HCI introduced into the duodenum increases sugar absorption by 12·7–30·8 per cent. An intraduodenal injection is without effect on the absorption of sugar in the colon. This increase therefore takes place only in the small intestine. The increased absorption is due to increased motility of the villi.

3. This hormonal regulation of absorption was confirmed by cross‐circulation experiments.

4. Extracts containing villikinine introduced into the intestine increase the automatism of the villi and, hence, the absorption of sugar.

5. Glucose absorption caused by the activity of the villi is estimated as approximately 20 per cent. of the entire absorption.
A RETICULOCYTOGENIC AGENT FOR GUINEA‐PIGS PRESENT IN CERTAIN GASTRO‐INTESTINAL SECRETIONS
Authors: Goodfriend J. , Chain E. , Florey H. W.
Published: December 2014

1. A reticulocytogenic agent for reactive guinea‐pigs (selected according to a modified Jacobson technique) is found in the pyloric, duodenal and ileal secretions of the pig, in the pyloric and duodenal secretions of the cat and in the duodenal secretions of the rabbit and goat, but not in the fundic secretions of either pig or cat.

2. The sites of the production of the agent, therefore, correspond to those sections of the gastro‐intestinal mucosa which have been found by Meulengracht and his co‐workers to yield therapeutic agents active in pernicious anæmia.

3. From the duodenal secretion of the goat and pig a substance has been prepared which is reticulocytogenic for guinea‐pigs in very small amounts when injected subcutaneously.

4. The active agent is thermolabile. It is soluble in acetone and in alcohol. It is partly precipitated by mineral acids, the precipitation being more complete in the presence of salts. It is precipitated by phosphotungstic acid, lead acetate and tannic acid. It is dialysable through cellophane and collodion membranes. The molecular weight is therefore probably less than 4000. It is not destroyed by pepsin or trypsin.

We are greatly indebted to Professor Wayne, Dr. Wilkinson, Dr. Ungley and Dr. H. J. Gardner for their kindness in performing the clinical tests referred to in the text. Mr. J. H. D. Kent has had the care of the animals from which he collected the secretions. Without his assistance the work would have been impossible.
ANTAGONISM OF EVIPAN BY PICROTOXIN, CORAMINE, AND CARDIAZOL
Authors: Das S. C.
Published: December 2014

1. The production of a steady state of respiratory depression by continuous intravenous infusion of sodium evipan into rabbits affords a convenient method for measuring the efficiency of analeptic drugs and for comparing their relative activities.

2. Picrotoxin causes an increase in the depth of respiratory movements as well as in the rate, whereas coramine and cardiazol improve the rate of respiration rather than the depth.

3. 0·3 mg. of picrotoxin causes the same increase in amplitude of respiratory stimulation as does 10 mg. of coramine or of cardiazol. Picrotoxin takes about 3‐5 minutes to develop its maximum effect, whilst the action of coramine or of cardiazol reaches its maximum very quickly.

4. When the respiratory depression is severe, coramine often fails to produce a stimulant effect and may even augment the depression. Picrotoxin still produces a stimulant effect in such cases.

5. Picrotoxin is detoxicated at the rate of 1/70 of the amount present per minute, whereas the rate of destruction of coramine is about 1/10 and of cardiazol 1/16 of the amount present per minute.

6. Continuous intravenous infusion of picrotoxin simultaneously with continuous infusion of evipan permits the balancing of evipan and picrotoxin, and it is possible to work up to doses of both drugs, either of which alone would be fatal. There is a linear relation between the doses of evipan and the log. of the doses of picrotoxin which balance each other.

7. Continuous infusion of coramine superimposed on the continuous infusion of evipan at first shows an increase in the respiratory activity, but after some time there is a gradual fall and the final depression may be greater than that produced by evipan alone. This suggests the formation of an intermediary product during coramine metabolism, which has a depressant action and is more stable than coramine.

I gratefully acknowledge my indebtedness to Professor A. J. Clark for his advice and help throughout the course of my work.

The expenses of this research were defrayed by a grant from the Moray Fund of Edinburgh University.
THE INFLUENCE OF LYSOLECITHIN AND OF INCUBATION ON THE SHAPE, SIZE, AND FRAGILITY OF ERYTHROCYTES
Authors: Gillespie W. A.
Published: December 2014

1. Lysolecithin added in suitable doses to blood does not increase the red cell fragility in hypotonic saline, although the cells become spherical. The fragility of washed cells is slightly diminished by lysolecithin. The spherical cells produced by lysolecithin are essentially different from the spherocytes of congenital hæmolytic anæmia.

2. After intravenous injection of lysolecithin into a rabbit, the fragility of the red cells remains raised for a much longer period than the spherical shape of the cells can be observed.

3. The effects of incubation of whole blood, and of plasma alone, on the morphology, volume, and fragility of the erythrocytes are contrasted.

4. The importance of the inhibiting action of plasma constituents on lysolecithin hæmolysis is stressed.

5. The bearing of these experiments on some of the problems of hæmolytic anæmia is discussed.
NITROGEN METABOLISM AFTER BURNING
Authors: Clark E. J. , Peters R. A. , Rossiter R. J.
Published: December 2014

Blood and urinary changes in nitrogen compounds in animals after burning at 70°, 75°, and 80°C. for 30 seconds have been compared with anæsthetised controls.

1. Blood Changes.—Within an hour after burning there commenced an increase in blood urea in both rats and rabbits, present in the latter four days later. There was also a fall in the total plasma protein and a persistent fall in the plasma albumin. Though falling slightly at first, the globulin levels rose; this caused a progressive fall in the albumin/globulin ratio.

2. Urinary Changes.—In rats upon constant diet the following changes occurred with increasing severity of the burn, namely:

(a) An initial rise in weight (due to water retention), followed by a fall in weight.

(b) Creatinuria.

(c) Increased urea elimination; except for early nitrogen retention in the more severe cases for 1 to 2 days. The latter was also a constant feature of rats dying from burns and indicates some form of kidney disturbance.

No constant changes took place in ammonia excretion or in creatinine output, though the latter fell for 1 to 2 days in the more severe burns.

3. The early changes may be explained by the decreased blood volume (shock). The later changes, which are important clinically, indicate a protein mobilisation.

4. As practical measures suggested by the above, carbohydrates should be given during the period of shock, and high protein diets later.
RADIOGRAPHIC STUDIES OF THE EFFECTS OF MEPACRINE ON THE GASTRO‐INTESTINAL TRACT OF THE RAT
Authors: Army Malaria Research Unit  , The Nuffield Institute for Medical Research
Published: December 2014

1. A technique has been developed with which the effect of drugs on the gastro‐intestinal tract may be studied in the intact unanæsthetised animal. The technique consists in giving rats bismuth meals and observing their rate of passage radiographically.

2. The effects of mepacrine on the rat's gut are: hypertonicity and disturbed peristalsis in the stomach; pylorospasm, increased gastric secretion; delay in gastric emptying; increased accumulation of gas in the stomach and the cæcum; and slight delay in the rate of passage of the bismuth meal through the small intestine.

3. The severity of the effect on the stomach may be measured by determining the length of time taken for the stomach to empty.

4. The effect of various doses of mepacrine dihydrochloride given before the barium meal has been determined, and this information will serve as a basis for comparative studies with other salts of this drug and with other methods of administration.
EXPERIMENTAL OBSERVATIONS ON THE STRUCTURE OF THE BONE MARROW
Authors: Nizet A.
Published: December 2014

By means of an original technique it is shown that no ripe erythrocytes are stored in the bone marrow. All the red cells achieve their ripening in the circulating blood.
“AVIDITY” OF ANTI‐A AGGLUTINATING SERA
Authors: Barnes D. W. H. , Loutit J. F.
Published: December 2014

“Avidity” of anti‐A blood‐grouping sera was measured by

(a) the unagglutinated red cell count,

(b) the time of agglutination,

with A1 and A2 red cells.

With each serum agglutination time was always shortest with the lowest dilution. The lowest unagglutinated cell count was with A2 cell usually in the lowest serum dilution, but with A1 cells was variable.

Agglutination time and agglutinating strength are therefore probably determined by different factors in serum.

Immune rabbit sera approximated to the ideal anti‐A blood‐grouping sera rather than natural or immune human sera.

We should like to thank Dr. W. T. J. Morgan of the Lister Institute for his help and for liberal supplies of immnlune rabbit sera.
THE LOCATION OF CHOLINESTERASE IN THE CENTRAL NERVOUS SYSTEM
Authors: Burgen A. S. V. , Chipman L. M.
Published: December 2014

1. The oil/water distribution coefficients of a number of cholin‐esterase inhibitors have been obtained.

2. The inhibition of cholinesterase in the brain of dogs has been measured after injection of TEPP and 3‐diisopropylphosphato‐N‐methyl pyridinium methyl sulphate (PPS) both systemically and intracranially.

3. PPS is almost insoluble in lipoid and produces no physiological effects on the central nervous system.

4. Less than lethal doses of PPS produced only 16 per cent inhibition of cholinesterase in grey and white matter.

5. Cholinesterase in a sympathetic ganglion is freely inhibited by PPS.

6. The way in which anticholinesterase drugs produce their central effects is discussed.

7. It is probable that cholinesterase is located at different sites in neuromuscular, sympathetic, and central synapses.
Muscarinic enhancement of the voltage‐dependent calcium current in an identified snail neuron.
Authors: Gerschenfeld H M , Paupardin‐Tritsch D , Yakel J L
Published: December 2014

1. In the F1 neuron of the snail Helix aspersa bathed in a Ba2+ and 4‐aminopyridine‐containing saline, carbamylcholine (CCh) enhanced the inward current carried by Ba2+ through the voltage‐dependent Ca2+ channels. 2. This effect of CCh on the F1 neuron was not affected by the nicotinic antagonists (+)‐tubocurarine and hexamethonium, but it was mimicked by oxotremorine and blocked by both atropine and pirenzepine. 3. The intracellular injection of GTP gamma S (guanosine 5'‐O‐(3‐ thiotriphosphate] into the F1 neuron caused both a decrease in Ca2+ current and a blockade of the CCh‐induced enhancement of the Ca2+ current. 4. Neither cyclic AMP, cyclic GMP nor arachidonic acid mimicked the effect of CCh on the Ca2+ current in the F1 neuron. In contrast, the intracellular injection of EGTA blocked the CCh‐induced enhancement of the Ca2+ current thus suggesting that cytosolic Ca2+ is involved in the CCh‐induced response. 5. We then investigated the possible role of inositol 1,4,5‐trisphosphate (InsP3) and Ca(2+)‐dependent protein kinases in the CCh‐induced enhancement of the Ca2+ current. The intracellular injection of InsP3 in the F1 neuron elicited no consistent change in the Ca2+ current. Diacylglycerol analogues (OAG and DOG) decreased the Ca2+ current amplitude, i.e. an effect opposite to that produced by CCh. This effect of the diacylglycerol analogues resulted from the activation of protein kinase C (PKC) since it was blocked by staurosporine. In addition, staurosporine did not affect the CCh‐induced increase in Ca2+ current. 6. The intracellular injection of either Ca(2+)‐calmodulin‐dependent protein kinase II (Ca(2+)‐CaM‐PK) or a peptide inhibitor of this enzyme into the F1 neuron affected neither the Ca2+ current nor its enhancement by CCh. 7. We conclude that the CCh‐induced enhancement of the Ca2+ current in the snail F1 neuron involves the activation via muscarinic receptors of an intracellular transduction mechanism in which cytosolic Ca2+ plays a key role. However, InsP3, protein kinase C and Ca(2+)‐CaM‐PK do not appear to be directly involved in this CCh‐induced response.
Regulation by synapsin I and Ca(2+)‐calmodulin‐dependent protein kinase II of the transmitter release in squid giant synapse.
Authors: Llinás R , Gruner J A , Sugimori M , McGuinness T L , Greengard P
Published: December 2014

1. Presynaptic or simultaneous pre‐ and postsynaptic voltage‐clamp protocols were implemented in the squid giant synapse in order to determine the magnitude and time course of the presynaptic calcium current (ICa) and its relation to transmitter release before and after presynaptic injection of proteins. These included several forms of synapsin I, calcium‐calmodulin‐dependent protein kinase II (CaM kinase II) and avidin. 2. The quantities and location of these proteins were monitored by fluorescence video‐enhanced microscopy during the electrophysiological measurements. 3. Presynaptic injection of dephosphorylated synapsin I inhibited synaptic transmission with a time course consistent with diffusion of the protein through the terminal and action at the active release zone. A mathematical model relating the diffusion of synapsin I into the terminal with transmitter release was developed to aid in the interpretation of these results. 4. Synapsin I inhibition of transmitter release was reversible. 5. The action of synapsin I was highly specific, as phosphorylation of the tail region only or head and tail regions prevented synapsin I from inhibiting release. 6. Injections of heat‐treated synapsin I or of avidin, a protein with a size and isoelectric point similar to those of synapsin I, had no effect on transmitter release. 7. CaM kinase II injected presynaptically was found to facilitate transmitter release. This facilitation, which could be as large as 700% of the control response, was related to the level of penetration of the enzyme along the length of the preterminal A mathematical model of this facilitation indicates a reasonable fit between the distribution of CaM kinase II within the terminal and the degree of facilitation. 8. The overall shape of the postsynaptic response was not modified by either synapsin I or CaM kinase II injection. 9. The data suggest that, in addition to releasing transmitter, calcium also penetrates the presynaptic cytosol and activates CaM kinase II. When activated, CaM kinase II phosphorylates synapsin I, which reduces its binding to vesicles and/or cytoskeletal structures, enabling more vesicles to be released during a presynaptic depolarization. The amplitude of the postsynaptic response will then be both directly and indirectly regulated by depolarization induced Ca2+ influx. This model provides a molecular mechanism for synaptic potentiation.
Acute electrophysiological responses of bradykinin‐stimulated human fibroblasts.
Authors: Estacion M
Published: December 2014

1. Acute responses to bradykinin in human dermal fibroblasts were studied at 20‐24 degrees C using both the patch‐clamp technique to monitor ion currents and Fura‐2 fluorescence to monitor [Ca2+]i. 2. During subconfluent culture, human dermal fibroblasts can express a diversity of ion channels as described in the preceding paper. 3. When GTP (1 mM) was included in the pipette solution, two additional ion channel populations were transiently augmented in response to bradykinin stimulation. 4. The first is a component of outwardly rectifying current which reached maximal induction within 10‐15 s after bradykinin addition (1 microM) and then decayed back to near baseline over 60 s. 5. Ion substitution experiments combined with tail current analysis indicate that the outward current is carried predominantly by K+. 6. Video imaging of single‐cell Fura‐2 fluorescence from both intact cells and patch‐clamped cells showed temporal correlation of the K+ current modulation and the Ca2+ transients in response to bradykinin stimulation. 7. The calcium ionophore, ionomycin, caused both an increase in intracellular calcium and the augmentation of the outward K+ current. The amount of additional K+ current was correlated with [Ca2+]i levels and could be elicited even without the presence of GTP in the pipette. 8. Apamin, a blocker of Ca(2+)‐activated K+ channels, inhibited (at 1 microM) the ionomycin‐induced modulation of K+ current. 9. In addition, an inward current was transiently induced in response to bradykinin. This current was strictly dependent on the presence of GTP in the pipette solution. This current showed little voltage dependence, as evidenced by a linear current vs. voltage relation, and a reversal potential near but measurably more positive than 0 mV. 10. This current could be decoupled from the Ca2+ transient and be irreversibly induced by including GTP gamma S (100 microM) in the pipette solution. 11. Ion substitution experiments show that this is a non‐specific cation channel. This current prefers monovalents but exhibits a small permeability to divalents. 12. GTP gamma S‐induced single channels from isolated outside‐out patches showed similar ion selectivity and voltage dependence. These channels are 32 pS in size with an estimated reversal potential of 17 mV.(ABSTRACT TRUNCATED AT 400 WORDS)
Excitation by irritant chemical substances of sensory afferent units in the cat's cornea.
Authors: Belmonte C , Gallar J , Pozo M A , Rebollo I
Published: December 2014

1. Single‐unit electrical activity was recorded from thin myelinated sensory nerve fibres innervating the cornea of deeply anaesthetized cats. 2. Based on their responses to mechanical (calibrated von Frey hairs), chemical (10 mM‐acetic acid and/or 616 mM‐NaCl) and thermal (ice‐cold or heat up to 51 degrees C) stimuli, corneal A delta fibres were classified as polymodal nociceptors (63%), high‐threshold mechanoceptors (22%) and mechano‐heat nociceptors (15%). Thin myelinated fibres responding only to cold were found in the limbus of the eye. 3. Application of 10 mM‐acetic acid on the corneal surface for 30 s evoked in polymodal fibres a brisk discharge of impulses often followed by a low‐frequency impulse activity. NaCl (616 mM) produced a more gradual and sustained firing response. 4. The responses of polymodal fibres to acid were proportional to extracellular pH values (pH range: 4.5‐6.0). After sensitization to repeated heating, most mechano‐heat units developed a sensitivity to acidic stimulation. 5. Topical 0.33 mM‐capsaicin excited polymodal nociceptors of the cornea; 5 min after capsaicin about 15% of these fibres were inactivated to all subsequent stimuli. In the rest of the fibres, chemical and thermal sensitivity disappeared after 0.33‐3.3 mM‐capsaicin, but mechanosensitivity was preserved. 6. Corneal mechanoceptors and limbal cold receptors were not affected by capsaicin (up to 33 mM). 7. These experiments demonstrate that the cornea of the cat is innervated by polymodal as well as mechanoceptive A delta nociceptors. In polymodal nociceptive fibres, mechanical and chemical sensitivities appear to be subserved by separate transduction mechanisms.
Monovalent cation conductance in the ryanodine receptor‐channel of sheep cardiac muscle sarcoplasmic reticulum.
Authors: Lindsay A R , Manning S D , Williams A J
Published: December 2014

1. The ryanodine receptor protein of sheep cardiac muscle sarcoplasmic reticulum membranes functions as a ligand‐regulated ion channel following solubilization with the zwitterionic detergent CHAPS (3‐[(3‐cholamidopropyl)‐dimethylammonio]‐1‐ propane sulphonate); purification by density gradient centrifugation, reconstitution into proteo‐liposomes and incorporation into planar phospholipid bilayers. 2. In the absence of divalent cations, measurable conductance is observed with the group 1a cations and with some larger organic cations. In symmetric 210 mM solutions the following conductance sequence was determined: K+ greater than Rb+ = NH4+ greater than Na+ = Cs+ greater than Li+ much greater than Tris+. 3. Other organic cations, e.g. TEA+, do not produce measurable current under these conditions. 4. Single‐channel conductance saturates with increasing ionic activities of K+, Na+ and Li+. Saturation curves are described by Michaelis‐Menten kinetic schemes with the following values of maximal conductance and apparent dissociation constant: K+ 900 pS, 19.9 mM; Na+ 516 pS, 17.8 mM; Li+ 248 pS, 9.1 mM. 5. The channel displays only minor differences in permeability amongst the group 1a cations. Relative permeability, monitored under bi‐ionic conditions, yields the following sequence: Na+, 1.15 greater than K+, 1.00 = Li+, 0.99 greater than Rb+, 0.87 greater than Cs+, 0.61. Under similar conditions the permeability ratio of NH4+ to K+ was found to be 1.32 and that for Tris+ to K+ was 0.22. 6. The K+ conductance is reduced by low concentrations of the impermeant cation TEA+. Block appears as a smooth reduction in single‐channel current amplitude and the degree of block is dependent upon applied voltage. These observations are consistent with a single‐site blocking scheme in which TEA+ has access to a site within the voltage drop of the channel from only the cytosolic face of the channel protein and interacts with a site located approximately 90% of the electrical distance across the channel. The zero‐voltage dissociation constant for TEA+ block is 50 mM. 7. Single‐channel conductance measurements in mixtures of K(+)‐Na+ and K(+)‐Li+ reveal no anomalous behaviour as the mole fraction of the ions is varied. 8. With monovalent cations as permeant species, the sheep cardiac sarcoplasmic reticulum ryanodine receptor protein functions as a poorly selective, ligand‐regulated channel. Under the conditions described here the channel functions as a single‐ion pore. It is proposed that discrimination is largely dependent upon the strength of interaction of the permeant ion with a binding site in the conduction pathway.
Endocrine responses to intra‐aortic infusions of acetylcholine in conscious calves.
Authors: Jones C T , Edwards A V , Bloom S R
Published: December 2014

1. Adrenal responses to intra‐aortic infusions of acetylcholine (4.5 nmol min‐1 kg‐1 for 10 min) have been investigated in conscious, functionally hypophysectomized, 3‐ to 6‐week‐old calves, in the presence and absence of exogenous ACTH (2 ng min‐1 kg‐1, I.V.). 2. Acetylcholine produced a substantial fall in adrenal vascular resistance, which was significantly reduced in the presence of exogenous ACTH, while producing minimal changes in aortic blood pressure and heart rate. 3. There was also a significant rise in right adrenal cortisol output which was sufficient to produce a measurable rise in plasma cortisol concentration. The effect could be accounted for by the increase in adrenal ACTH presentation. It was abolished by pre‐treatment with atropine (0.2 mg kg‐1). A small but significant rise in aldosterone output during acetylcholine infusions was also abolished in the presence of ACTH. 4. Both adrenaline and noradrenaline were released during intra‐aortic acetylcholine infusions and these responses were substantially reduced, but not abolished, by pre‐treatment with atropine. 5. Acetylcholine also stimulated the release of corticotrophin‐releasing factor (CRF) and [Met5]enkephalins from the gland. The output of CRF was enhanced and that of free [Met5]enkephalin was significantly reduced in the presence of exogenous ACTH. All these responses were largely, but not completely, suppressed by atropine. 6. Acetylcholine also promoted the release of the pancreatic hormones glucagon, insulin and pancreatic polypeptide (PP). The amounts of pancreatic glucagon and insulin that were released were highly dependent on the concentration of glucose in the circulating plasma and all these responses were abolished by atropine. 7. It is concluded that acetylcholine is capable of stimulating the release of a wide variety of agonists from the adrenal gland when infused intra‐aortically at a dose of 4.5 nmol min‐1 kg‐1. The increase in cortisol output appears to be secondary to an increase in blood flow whereas the adrenal medullary responses are not, and appear to be due largely, but not entirely, to activation of muscarinic receptors.
Effects of protein kinase inhibitors on canine Purkinje fibre pacemaker depolarization and the pacemaker current i(f).
Authors: Chang F , Cohen I S , DiFrancesco D , Rosen M R , Tromba C
Published: December 2014

1. The effects of the protein kinase inhibitors H‐7 and H‐8 were investigated on diastolic depolarization of the action potential with microelectrodes and on the pacemaker current if with the two‐microelectrode voltage clamp in canine cardiac Purkinje fibres. 2. Both 200 microM‐H‐7 and 100 microM‐H‐8 had no significant effect on the slope of diastolic depolarization but eliminated the actions of isoprenaline (1 microM). 3. We examined the actions of H‐7 and H‐8 on if in the presence and absence of isoprenaline. H‐7 (200 microM) shifted the pacemaker current if in the negative direction on the voltage axis, whereas 100 microM‐H‐8 had no significant effect by itself. Both 200 microM‐H‐7 and 100 microM‐H‐8 can reverse or prevent the actions of isoprenaline (1‐5 microM) on if. 4. We applied activators of the cyclic AMP cascade down‐stream to the beta‐receptor, to further evaluate where H‐7 and H‐8 might be exerting their effects. When exposing Purkinje fibres to an adenylyl cyclase activator (forskolin, 10‐50 microM), a phosphodiesterase inhibitor (IBMX, 100 microM) and a permeable cyclic AMP analogue (8‐chlorophenylthio‐cyclic AMP, 200 microM‐1 mM), the amplitude of if was increased. H‐7 and H‐8 at 100‐200 microM eliminated each of these actions. 5. These results suggest that a phosphorylation process is involved in the modulation of the pacemaker current, if, in Purkinje fibres. The different actions of H‐7 and H‐8 on basal if suggest the hypothesis that other protein kinases, possibly protein kinase C, might also be involved in regulating basal phosphorylation of if in Purkinje fibres.
Pain evoked by polymodal stimulation of hand veins in humans.
Authors: Arndt J O , Klement W
Published: December 2014

1. To explore the function of the sensory innervation of veins in humans we used a psychophysical approach to study painful and non‐painful sensations by applying polymodal stimuli (electrical, stretch, cold/heat and osmotic) inside vascularly isolated hand vein segments before and after blockade of either venous or cutaneous afferents. 2. All modes of stimulation elicited pain, which showed only slight adaptation during 10 min of maintained stimulation. Pain increased monotonically with stimulus intensity between threshold and the maximally tolerable pain. 3. The exponents of the power functions of the pain magnitude‐stimulus strength relations for five stimulus modes ranged between 2.5 and 3.3 but did not significantly differ from one another (P = 0.3). 4. Pain evoked by all stimuli was reported to be of similar quality, i.e. sharp, aching and unpleasant; it was accompanied by non‐painful sensations (skin movements on stretching, warm and cold sensation with intravenous thermal stimulation) unless the skin above the stimulated vein segment was numbed with benzocaine ointment. 5. Pain could no longer be evoked in the presence of 0.4‐0.8% procaine within the stimulated vein segment. 6. These observations are consistent with the view that veins are invested with polymodal nociceptors only, which in all likelihood are connected with thinly myelinated afferents of the A delta group. 7. The vascularly isolated vein segment may open a new avenue for pain research in humans.
A functional microcircuit for cat visual cortex.
Authors: Douglas R J , Martin K A
Published: December 2014

1. We have studied in vivo the intracellular responses of neurones in cat visual cortex to electrical pulse stimulation of the cortical afferents and have developed a microcircuit that simulates much of the experimental data. 2. Inhibition and excitation are not separable events, because individual neurones are embedded in microcircuits that contribute strong population effects. Synchronous electrical activation of the cortex inevitably set in motion a sequence of excitation and inhibition in every neurone we recorded. The temporal form of this response depends on the cortical layer in which the neurone is located. Superficial layer (layers 2+3) pyramidal neurones show a more marked polysynaptic excitatory phase than the pyramids of the deep layers (layers 5+6). 3. Excitatory effects on pyramidal neurones, particularly the superficial layer pyramids, are in general not due to monosynaptic input from thalamus, but polysynaptic input from cortical pyramids. Since the thalamic input is transient it does not provide the major, sustained excitation arriving at any cortical neurone. Instead the intracortical excitatory connections provide the major component of the excitation. 4. The polysynaptic excitatory response would be sustained well after the stimulus, were it not for the suppressive effect of intracortical inhibition induced by the pulse stimulation. 5. Intracellular recording combined with ionophoresis of gamma‐aminobutyric acid (GABA) agonists and antagonists showed that intracortical inhibition is mediated by GABAA and GABAB receptors. The GABAA component occurs in the early phase of the impulse response. It is reflected in the strong hyperpolarization that follows the excitatory response and lasts about 50 ms. The GABAB component occurs in the late phase of the response, and is reflected in a sustained hyperpolarization that lasts some 200‐300 ms. Both components are seen in all cortical pyramidal neurones. However, the GABAA component appears more powerful in deep layer pyramids than superficial layer pyramids. 6. The microcircuit simulates with good fidelity the above data from experiments in vivo and provides a novel explantation for the apparent lack of significant inhibition during visual stimulation. The basic circuit may be common to all cortical areas studied and thus the microcircuit may be a ‘canonical’ microcircuit for neocortex.
Neurones in commissural nucleus tractus solitarii required for full expression of the pulmonary C fibre reflex in rat.
Authors: Bonham A C , Joad J P
Published: December 2014

1. The pulmonary C fibre reflex, triggered by activating pulmonary C fibre endings in the lung, consists of rapid shallow breathing (which may be preceded by apnoea), bradycardia, and hypotension. The purpose of this work was to identify proximal synapses in this reflex. From pilot data, we hypothesized that neurones in a discrete region of the commissural nucleus in the nucleus tractus solitarii (NTS) are required for full expression of the pulmonary C fibre reflex. Studies were carried out in urethane‐anaesthetized, unilaterally vagotomized, spontaneously breathing rats, in which diaphragm electromyogram, arterial pressure, and blood gases were measured. Phenyldiguanide (PDG) was injected in the right atrium to elicit the pulmonary C fibre reflex. Unilateral NTS injections were made through multibarrelled pipettes containing DL‐homocysteic acid (DLH) to mimic the reflex, cobalt chloride to reversibly impair the reflex, and/or dye to mark the injection sites. 2. PDG (5‐16 micrograms kg‐1) injected in the right atrium of twenty‐six rats produced the classic pulmonary C fibre reflex: a vagally mediated, rapid onset of rapid shallow breathing, bradycardia and hypotension. 3. Injection of DLH (3‐12 nl of 20 mM for a total of 60‐240 pmol) in the dorsomedial aspect of the commissural nucleus of the NTS in thirty rats mimicked the pulmonary C fibre reflex, producing rapid shallow breathing, hypotension, and a slight bradycardia. 4. Interruption of neuronal transmission by injecting cobalt chloride (15‐30 nl of 100 mM) in the site where DLH produced rapid shallow breathing, reversibly impaired the rapid shallow breathing and bradycardia produced by right atrial injections of PDG in fifteen rats. The commissural region where DLH produced rapid shallow breathing and cobalt impaired the pulmonary C fibre reflex extended from 720‐1100 microns caudal to the obex, 30‐200 microns lateral to mid‐line, and 200‐600 microns ventral to the dorsal surface of the brain stem within the NTS. 5. Taken together, the results suggest that neurones within a discrete region in the dorsomedial commissural nucleus in caudal NTS are required for full expression of the pulmonary C fibre reflex.
Changes produced by increased hydrostatic pressure in isometric contractions of rat fast muscle.
Authors: Ranatunga K W , Geeves M A
Published: December 2014

1. Muscle fibre bundles isolated from the extensor digitorum longus (a fast muscle) of the rat were exposed to different hydrostatic pressures (range 0.1‐10 MPa), in order to determine the pressure dependence of their isometric contractions. 2. The pressure dependent changes in the contractions were reversible and linearly related to pressure. 3. The peak tension, the time to peak and the time to half‐relaxation of a twitch contraction increased with pressure; the mean (+/‐ S.E.M.) percentage increases were 5.9 +/‐ 0.5% MPa‐1, 2.7 +/‐ 0.2% MPa‐1 and 2.7 +/‐ 0.4% MPa‐1, respectively. 4. In a fused tetanus, the tension was typically depressed at high pressure (0.9 +/‐ 0.16% MPa‐1); the half‐time of tension rise was decreased (2.1 +/‐ 0.2% MPa‐1) and the half‐time of exponential relaxation was increased (2.4 +/‐ 0.3% MPa‐1).
Effect of voltage and cyclic AMP on frequency of slow‐wave‐type action potentials in canine colon smooth muscle.
Authors: Huizinga J D , Farraway L , Den Hertog A
Published: December 2014

1. A non‐L‐type calcium conductance is involved in the generation of the initial part of the slow‐wave‐type action potential in colonic smooth muscle. The present study addresses the question whether this conductance is voltage or metabolically activated. 2. Current‐induced hyperpolarization increased frequency and amplitude of slow waves measured in Krebs solution. 3. The upstroke potential was ‘isolated’ from the slow wave by superfusion with ‘glucamine‐nitrendipine’ Krebs solution (NaCl was replaced by glucamine, nitrendipine was added). 4. Hyperpolarization up to ‐100 mV did not affect the upstroke potential frequency and increased its amplitude. Only hyperpolarization further than ‐100 mV decreased the frequency less than or equal to 20%, and reduced the amplitude less than or equal to 20%. 5. Depolarization did not affect the upstroke potential frequency. 6. Forskolin, but not 1,9‐dideoxyforskolin dramatically decreased the upstroke potential frequency, without affecting other parameters including the resting membrane potential. 7. The effect of forskolin was mimicked by dibutyryl cyclic AMP, 8‐bromo‐cyclic AMP and 3‐isobutyl‐1‐methylxanthine (IBMX), but not extracellular cyclic AMP. 8. The upstroke potential could not be evoked by depolarizing pulses after inhibition of activity by forskolin. 9. The effect of forskolin could be reversed by the calcium ionophore A23187. 10. In summary, voltage changes up to ‐40 mV and down to ‐100 mV do not, but changes in intracellular cyclic AMP do affect the frequency of the upstroke potential. 11. It is likely that intracellular metabolic activity, which may include cyclic AMP but not a voltage change, activates the conductance responsible for the generation of the upstroke potential.
Effects of putative modulators of relaxation microinjected into intact amphibian smooth muscle cells.
Authors: Fay F S , Granger W C , Shelvin H H , Taylor S R
Published: December 2014

1. Single smooth muscle cells were isolated intact from the stomach of the toad Bufo marinus. The relaxation of cells following cessation of electrical stimulation was compared with those relaxed by pressure microinjection of either metal ion chelators or cyclic nucleotides. 2. Injection of either a Ca2+ chelator or 3',5'‐cyclic AMP slowed or halted shortening and promoted re‐extension of a cell or collapse of membrane evaginations (blebs) in a manner similar to that following cessation of electrical stimulation. Collapse of blebs occurred first and was then followed smoothly by the next stage with cells re‐extending at maximum rates in one of three ranges at 22 degrees C. These rates, in order of increasing speed, were 0.005, 0.009 and 0.03 cell lengths s‐1 after electrical stimulation, 3',5'‐cyclic AMP and EDTA injection, respectively. On the other hand, shortening began at a maximum rate of about 0.1 cell lengths s‐1 unless a Ca2+ chelator or 3',5'‐cyclic AMP was injected about 30 s or less before electrical stimulation. Injection of these agents reduced the speed of shortening by about half. 3. Injection of a liquid per se (e.g. 140 mM‐KCl) neither altered action potentials nor duplicated the changes produced by the aforementioned relaxing agents. Large, sustained injections of substances that were not relaxing agents (e.g. dilute KCl) ruptured the membrane without producing any bleb collapse or re‐extension of a contracted cell. Blebs not only collapsed rapidly when a relaxing agent was injected but bleb collapse was a much more sensitive indication of relaxation than cell re‐extension; small injections of relaxing agents could clearly collapse blebs with no associated measurable change in cell length. This supports the idea previously inferred from fixed or permeabilized cells, that filaments in smooth muscle are organized to produce force over short distances at points along the cell membrane, in addition to shortening along the long axis. 4. Physiological relaxation of smooth muscle can evidently be mimicked by 3',5'‐cyclic AMP elevation. Restoring forces may develop during shortening of isolated smooth muscle cells in elements of their cytoskeleton, surface membrane, or contractile filaments. However, these putative forces may not be able to produce physiological re‐extension in the absence of a rise in cyclic AMP and/or a fall in [Ca2+].