bluuebunny/crossref_metadata_2025 huggingface dataset:
Origin and cross-century dynamics of an avian hybrid zone
Authors: Morales-Rozo Andrea , Tenorio Elkin A. , Carling Matthew D. , Cadena Carlos Daniel
Published: December 2014

Background

Characterizations of the dynamics of hybrid zones in space and time can give insights about traits and processes important in population divergence and speciation. We characterized a hybrid zone between tanagers in the genusRamphocelus(Aves, Thraupidae) located in southwestern Colombia. We tested whether this hybrid zone originated as a result of secondary contact or of primary differentiation, and described its dynamics across time using spatial analyses of molecular, morphological, and coloration data in combination with paleodistribution modeling.

Results

Models of potential historical distributions based on climatic data and genetic signatures of demographic expansion suggested that the hybrid zone likely originated following secondary contact between populations that expanded their ranges out of isolated areas in the Quaternary. Concordant patterns of variation in phenotypic characters across the hybrid zone and its narrow extent are suggestive of a tension zone, maintained by a balance between dispersal and selection against hybrids. Estimates of phenotypic cline parameters obtained using specimens collected over nearly a century revealed that, in recent decades, the zone appears to have moved to the east and to higher elevations, and has apparently become narrower. Genetic variation was not clearly structured along the hybrid zone, but comparisons between historical and contemporary specimens suggested that temporal changes in its genetic makeup may also have occurred.

Conclusions

Our data suggest that the hybrid zone likey resulted from secondary contact between populations. The observed changes in the hybrid zone may be a result of sexual selection, asymmetric gene flow, or environmental change.
Establishing the evolutionary compatibility of potential sources of colonizers for overfished stocks: a population genomics approach
Authors: Gonçalves da Silva Anders , Appleyard Sharon A. , Upston Judy
Published: December 2014

Identifying fish stock structure is fundamental to pinpoint stocks that might contribute colonizers to overfished stocks. However, a stock's potential to contribute to rebuilding hinges on demographic connectivity, a challenging parameter to measure. With genomics as a new tool, fisheries managers can detect signatures of natural selection and thus identify fishing areas likely to contribute evolutionarily compatible colonizers to an overfished area (i.e. colonizers that are not at a fitness disadvantage in the overfished area and able to reproduce at optimal rates). Identifying evolutionarily compatible stocks would help narrow the focus on establishing demographic connectivity where it matters. Here, we genotype 4723 SNPs in 616 orange roughy (Hoplostethus atlanticus) across five fishing areas off the Tasmanian coast in Australia. We ask whether these areas form a single genetic unit, and test for signatures of local adaptation. Results from amova, structure, discriminant analysis of principal components, bayesass and isolation by distance suggest that sampled locations are subjected to geneflow amounts that are above what is needed to establish ‘drift connectivity’. However, it remains unclear whether there is a single panmictic population or several highly connected populations. Most importantly, we did not find any evidence of local adaptation, suggesting that the examined orange roughy stocks are evolutionarily compatible. The data have helped test an assumption of the orange roughy management programme and to formulate hypotheses regarding stock demographic connectivity. Overall, our results demonstrate the potential of genomics to inform fisheries management, even when evidence for stock structure is sparse.
Caregiving across the lifespan: comparing caregiver burden, mental health, and quality of life
Authors: de Oliveira Gabriela Romano , Neto José Fittipaldi , de Camargo Sthephanie Marques , Lucchetti Alessandra Lamas Granero , Espinha Daniele Corcioli Mendes , Lucchetti Giancarlo
Published: December 2014

Background

Care can be considered a lifelong process, but caring for a child is different from caring for an older adult. The present study aims to compare the caregiving process from infancy through old age by evaluating differences in caregiver burden, mental health, and quality of life and to describe the factors that could impact these outcomes.

Methods

To compare different groups of caregivers, we included 300 caregivers recruited from admissions to a tertiary acute hospital: 100 caregivers of children, 100 caregivers of adults, and 100 caregivers of older adults. A self‐administered questionnaire was used that covered the following: sociodemographics, depression (Beck Depression Inventory), anxiety (Beck Anxiety Inventory), quality of life (Short Form Health Survey (SF‐36)), religiosity (Duke Religion Index) and caregiver burden (Zarit Caregiver Burden Interview).

Results

A comparison between groups was performed (through χ2 and anova), and a linear regression analysis was used to assess the related factors. We found that children's caregivers had more depressive symptoms (higher Beck Depression Inventory scores), better physical health (SF‐36: physical functioning and SF‐36: Physical Component Summary), and lower pain (SF‐36: bodily pain) than other caregivers. We found that caregivers of adults had better mental health (SF‐36: mental health and SF‐36: Mental Component Summary) than other caregivers and that caregivers of older adult had a higher caregiver burden (Zarit Caregiver Burden Interview scores) than other caregivers. After we controlled for baseline characteristics, only depressive symptoms and caregiver burden remained statistically significant.

Conclusion

In conclusion, there are important differences between caregiving across the lifespan. Caregiving for children was associated with more depressive symptoms, and caregiving for older adults was associated with higher caregiver burden. Further studies are needed to replicate these findings in other settings.
THE ELECTRICAL RESPONSE OF MUSCLE TO VOLUNTARY, REFLEX, AND ARTIFICIAL STIMULATION
Authors: Buchanan Florence
Published: December 2014

In the electrical response of human muscles to their normal stimulus a rhythm presents itself which for the flexores digitorum has no constant frequency but may vary during one and the same response between 50 and about 120 per second, but which for the masseters is more uniform and of a higher frequency (170 to 200 per second).

This rhythm is to be regarded as of peripheral origin, because it is of the same order and subject to the same sort of variation as is a rhythm which experiments on frogs have proved to be of such origin.

As the corresponding rhythm may be produced in the response of frogs' muscle to various kinds of artificial stimuli which are not discontinuous, the rhythm obtaining in the electrical response of human muscle to the will has as yet given us no information as to whether the natural stimulus is rhythmical. Such information can only be gained by further experiments upon animals (not only upon cold‐blooded, but on warm‐blooded ones), in which it is possible to simplify and control the conditions to a greater extent than is possible in man.
LOCALISATION OF THE MOTOR AREA IN THE SHEEP
Authors: Simpson Sutherland , King J. Luella
Published: December 2014

1. In the sheep the cortical motor area is located in the superior frontal convolution. It extends antero‐posteriorly from a line about 2 mm. in front of the cruciate sulcus behind, almost to the frontal pole of the hemisphere, and latero‐mesially from the coronal sulcus over the dorso‐mesial border about 1 mm. on to the mesial aspect of the hemisphere.

2. It can be subdivided into four portions which are, from behind forwards, centres for movements of (a) hind limb, (b) fore limb, (c) head and eyes, and (d) face, mouth, and tongue.

3. Of these the centre for the fore limb is the most easily excitable, that for the face, mouth, and tongue the least.

4. In many individuals motor responses are not obtainable from one or more of these areas. The results of extirpation show that in the sheep these cortical centres are probably unimportant.

5. The best results were obtained under local anæsthesia with the animal in the conscious state.

6. No evidence of pain or other unpleasant sensation could be elicited from stimulation of any of the cortical surface which was exposed.
ON THE MOVEMENTS OF THE ISOLATED SMALL INTESTINE AND THE ACTION OF VARIOUS DRUGS AND EXTRACTS UPON THEM
Authors: Young Alexander Waugh
Published: December 2014

Alkali and Acid.—Sodium bicarbonate in concentration of ·01 per cent. to ·04 per cent. increases the tone of the intestine without altering the pendulum movements; with higher concentration the movements are inhibited. Hydrochloric acid inhibits both the tone and the movements of the intestine; the inhibition is seen with ·0005 per cent. HCL.

Carbon Dioxide.—CO2 has an inhibitory action on both the tone and the movements of the intestine. If the action of CO2 is prolonged the intestine is permanently injured and eventually killed.

Hyoscyamine and Hyoscine.—Hyoscyamine has a stimulating action; it can initiate the movements when they are absent. The pendulum movements are increased in size and made more regular, the tonus oscillations being partially or completely abolished. Stimulation is seen with ·001 per cent. of concentration. The action of hyoscine is similar to that of hyoscyamine, but it is weaker; ·02 per cent. being the weakest concentration having a distinct action. Both drugs inhibit the stimulation produced by pilocarpine.

Cocaine.—Cocaine has a stimulating action in strength from ·001 per cent. to ·01 per cent.; with higher concentration no stimulation is seen, but a marked regularising effect then appears; with ·2 per cent. a paralysing of the intestine comes on. Inhibition to the action of pilocarpine does not occur.

Choline and Neurine.—Choline produces a marked rise of tone in the isolated intestine; this occurs with concentration of 1 in 50,000; with high concentration the pendulum movements are obliterated. Atropine inhibits the action. There is also a mutual antagonism between the actions of choline and adrenaline. Neurine in its action·resembles choline, but it is more powerful; 1 in 100,000 produces an effect.

Pituitary Extract.—Watery extract of the posterior lobe on the isolated intestine of the cat has the effect of raising the tone and causing the development of large tonus oscillations. The action occurs only with high concentrations; thus two glands per 100 c.c. of Ringer's solution is the weakest extract to give definite results. Alcoholic extract has no action.

Suprarenal Extract.—Hemisine causes inhibition of the movements and lowering of the tone of the intestine; 1 in 10,000,000 produces a small but distinct effect.

Other Extracts.—Extracts of spleen, thyroid, thymus, pancreas, liver, kidney, and brain give no definite results.

Gastro‐Intestinal Contents.—Stomach contents inhibit the movements by their acidity alone. The contents of the small intestine have often a marked stimulating effect apart from, but to a considerable degree influenced by, their reaction. Extract of digesting gastric mucous membrane and of mucous membrane of small intestine, and also secretine, have when neutralised no definite action. Pancreatic secretion increases the tone. Indol inhibits the movements and lowers the tone. Bile has a similar action.
THE EFFECTS OF INSULIN INJECTION UPON THE BODY AND ORGANS OF THE WHITE RAT
Authors: Herring P. T.
Published: December 2014

The hypodermic administration to young white rats of a daily dose of insulin insufficient to produce convulsions has no effect upon the rate of growth of the body in either the male or the female.

The injection of insulin has little effect, if any, upon the weights of the thyroids, pituitary body, and suprarenals. The thyroids of the rats injected with insulin, however, present histological changes which are interpreted as suggestive of a decreased activity of these glands.

The islets of Langerhans of the pancreas are increased in size and stain more deeply with eosin in the rats injected with insulin. No definite distinction between the α and β cells of the islets is recorded, although this was looked for, but the granular content of most of the cells of the islets is increased.

The thymus, spleen, heart, kidneys, liver, testes, and ovaries show no alterations.

The experiments indicate that the continued use of insulin does not upset the general balance maintained by the endocrine glands.

This work was done under a grant from the Medical Research Council.
HIGHER NERVOUS ACTIVITY IN THE THYROIDECTOMISED SHEEP AND GOAT
Authors: Liddell Howard S.
Published: December 2014

The attempt was made to test the effect of thyroidectomy on the intelligence of the sheep and goat, and for this purpose the well‐known maze or labyrinth method was employed. Significant differences in maze behaviour between the thyroidectomised animals and their twin controls were noted, but it was found impossible to interpret these differences by using the concepts of animal psychology. Regarding the problem physiologically, however, it was possible to frame a hypothesis to harmonise the facts, viz. the weakening in the cretin animal, of the inhibitory processes of the cerebral cortex. A criticism of the maze or labyrinth method from a physiological viewpoint is given.

The expenses of this investigation were in part defrayed by grants from the Heckscher Research Foundation and the Sage Research Fund of Cornell University.
THE EFFECTS ON BLOOD‐PRESSURE OF SECTION OF THE SPLANCHNIC NERVES
Authors: Kremer M. , Wright Samson
Published: December 2014

1. The effects on blood‐pressure of section of both splanchnic nerves have been studied in the cat under urethane, chloralose, ether, and amytal anæsthesia. In animals with the cardio‐aortic and sinus nerves (“buffer” nerves) intact, a comparatively small fall of pressure results, commonly 0 to 15 per cent., and occasionally 25 per cent. This is the ease in spite of evident vasodilatation in the splanchnic area. Analysis shows that compensatory vasoconstriction probably occurs in other parts of the body, including the skeletal muscles. Evidence is given that the vasoconstrictor control of the vessels of skeletal muscle is of greater functional significance than is usually accepted.

2. When the buffer nerves are inactivated the extent of the fall is greater and exceeds on an average 50 per cent. It has been shown that this is not the result of the higher initial blood‐pressure, and indicates (in agreement with
Izquierdo and
Koch) that the buffer nerves help to protect the circulation against a fall (as against a rise) of blood‐pressure.

3. The fall of pressure is also diminished by the integrity of one pair of buffer nerves, and to a less extent by one intact sinus nerve. One intact cardio‐aortic nerve alone is comparatively ineffective.

4. In the decerebrate preparation, even with the buffer nerves intact, splanchnic section produces an extensive fall of pressure.

5. The cardio‐aortic nerves still display inhibitory tone after splanchnic section, even in the flayed animal, as shown by division of the vagi causing a rise of pressure even after atropine.

6. The rise of pressure resulting from occlusion of the carotids is diminished as a result of splanchnic section, even if the level of blood‐pressure is unchanged.

7. Contrary to
Moissejef, traction on the carotids lowers the pressure in an animal with vagi and splanchnics both divided.

The expenses of this research were partially defrayed out of a Government grant through the Royal Society.
THE SERUM CALCIUM AND MAGNESIUM LEVEL IN THE OVARIAN CYCLE OF THE LAYING HEN
Authors: Charles Enid , Hogben Lancelot
Published: December 2014

1. The calcium content of the serum of sexually immature White Leghorn pullets is about 11·4 mg. per 100 c.c. A maximum variation of ± 1·5 mg. was recorded.

2. The calcium content of the serum of laying hens during the interval between oviposition and the next ovulation is about 17 mg. The maximum variation recorded was ± 2·5 mg.

3. When an egg is present in the oviduct the calcium content of the serum was found to vary between 10·5 and 28·5 mg.

4. It is suggested that the functionally active ovary maintains the blood calcium at a higher level than that of the sexually immature bird, and that the presence of an egg in the oviduct is accompanied by the mobilisation of calcium in the tissue during shell secretion, producing a transitory rise in blood calcium.

5. Some evidence for a transitory rise in the magnesium content of the serum during shell secretion was also obtained.

The expenses of this research were defrayed by a grant from the Sex Hormones Committee of the Medical Research Council.
THE PHYSIOLOGY OF PREGNANCY IN THE RAT: FURTHER DATA ON THE PASSAGE OF HORMONES VIA THE PLACENTA AND THE MOTHER'S MILK
Authors: Hain A. M.
Published: December 2014

1. The effect of the ante‐natal administration of œstrone on the morphological development of the female fœtus (rat) was further examined: the minimum amount of œstrone capable of modifying fœtal morphology was ascertained, and the earliest day at which the effect could be induced. Large amounts of œstrone did not cause further abnormalities or affect the male in a similar manner.

2. Experiments with preparations of various ductless glands failed to demonstrate that the action of œstrone was an indirect one.

3. Other compounds related to œstrone in chemical structure were examined: the di‐hydroxy derivative of androsterone (male hormone) was found to affect the morphology of the female fœtus in the same way as œstrone.

4. The benzoate of œstrone has a similar action on the fœtus; the effective amounts of the two forms are compared. The suckling female also is capable of modification when the benzoate is injected into the lactating mother.

5. The urogenital region of the female rat is capable of modification by the direct injection of œstrone on the day of birth.

6. The subsequent reproductive history of litters which came under the influence of œstrone in the early stages of development is examined.

7. The significance of a similar action on the fœtus by both male and female hormones is discussed.

8. The results obtained with the benzoate of œstrone suggest that the concentration reached by the hormone is of more importance in determining the effect on the fœtus than the duration of its activity; they indicate that the effect is brought about by the hormone in its physiologically active form.
ACTION OF PROSTIGMINE AND ACETYLCHOLINE ON RESPIRATION
Authors: Schweitzer Alfred , Wright Samson
Published: December 2014

1. The effects of intravenously injected prostigmine and acetylcholine on the respiration of cats under chloralose anæsthesia and of decerebrate cats were examined.

2. Prostigmine inhibits respiration of cats under chloralose anæsthesia; the depression of breathing may be either preceded or followed by periods of respiratory stimulation. The inhibitory effect of prostigmine is partially annulled by atropine, and enhanced by section of the vagi and denervation of the carotid sinus nerves.

3. The stimulatory phenomena preceding or subsequent to the inhibition are more marked in decerebrate preparations. The initial stimulation is usually abolished by elimination of the vaso‐sensory nerves.

4. The inhibition of breathing and the secondary stimulation are partly due to an action on the respiratory and spinal centres.

5. Eserine inhibits respiration; it is less potent in this respect than prostigmine.

6. Acetylcholine produces a “triple response” consisting of initial stimulation, subsequent inhibition, and secondary stimulation. Injection of an anticholinesterase may result in (1) a simple potentiation of the effects of previously injected acetylcholine, (2) a marked enhancement of the inhibitory phase of the acetylcholine action, (3) a marked potentiation of the initial stimulation; this last effect disappears after the elimination of the vaso‐sensory nerves.

7. After elimination of the vaso‐sensory nerves, acetylcholine mainly inhibits respiration; secondary stimulation was sometimes observed.

8. Analysis of the results shows that acetylcholine stimulates the chemo‐receptor zones in the carotid sinus and the aortic arch. The inhibitory effects on breathing are partially due to an action of acetylcholine on the respiratory centre and the spinal cord.
MECHANISM OF ŒSTRUS INHIBITION IN THE MOUSE DURING PREGNANCY
Authors: Robson J. M.
Published: December 2014

1. A method for the quantitative estimation of vaginal smears is described.

2. The vaginal changes following the administration of various doses of cœstradiol to pregnant mice have been quantitatively studied and compared with the vaginal effects produced by the administration of similar doses of œstradiol to spayed mice under the influence of progesterone or testosterone propionate.

3. The results suggest that in the pregnant mouse a concentration of progesterone is present similar to that produced by the daily administration of 1·5 mg. of the luteal hormone. There is evidence that a certain quantity of this hormone is produced outside the ovary.

The expenses of this investigation have been defrayed by a grant from the Medical Research Council.
OBSERVATIONS ON DYE EXCRETION THROUGH SYNOVIAL MEMBRANE AFTER LUMBOSACRAL SYMPATHECTOMY AND CIRCULATORY OBSTRUCTION
Authors: Cheng Kwok ‐ Kew
Published: December 2014

1. The claim made by Engel [1941] that lumbosacral sympathectomy gives a reduction in dye excretion into the knee‐joint despite increased muscle temperature and presumably increased blood‐flow is not confirmed.

2. Technical factors responsible for discrepant results are discussed. Engel's assumption that muscle temperature measures local circulation, other things being equal, is criticised.

3. Only severe vascular obstruction in the limb influences dye excretion in the knee‐joint, probably because of decreased capillary pressure.
Effects of external and internal K+ ions on magnesium block of inwardly rectifying K+ channels in guinea‐pig heart cells.
Authors: Matsuda H
Published: December 2014

1. Block of the inwardly rectifying K+ channel by intracellular Mg2+ was studied in guinea‐pig ventricular cells at varying external or internal K+ concentrations. Sucrose or glucose was mainly used as a substitute for K+. 2. The current‐voltage (I‐V) relation for the single channel, in the absence of internal Mg2+, was almost linear in 30 mM‐external K+ and 150 mM‐internal K+ (30 mM [K+]o) and in 45 mM‐internal K+ and 150 mM‐external K+ (45 mM [K+]i) as well as in 150 mM‐external and internal K+ (the control condition). The channel conductance was 31.7 +/‐ 1.7 pS (mean +/‐ S.D., n = 36) in the control, 23.1 +/‐ 1.2 pS (n = 8) in 30 mM [K+]o and 29.7 +/‐ 1.3 pS (n = 16) in 45 mM [K+]i, respectively. 3. Mg2+ on the cytoplasmic side blocked the outward currents without affecting the inward currents. Outward mean open‐channel currents were measured at different Mg2+ concentrations (0‐100 microM) and voltages. The current‐voltage relation rectified inwardly in the presence of internal Mg2+ in a voltage‐ and concentration‐dependent manner. 4. Outward mean open‐channel currents were normalized to that measured in the absence of Mg2+. The normalized current‐voltage relation in 45 mM [K+]i was almost superimposable on that obtained in the control at the same Mg2+ concentration, while that in 30 mM [K+]o was shifted in the negative direction by some 30 mV. 5. The normalized current‐Mg2+ concentration curve was fitted by a one‐to‐one binding curve at each K+ condition and voltage. In a semilogarithmic plot of dissociation constant versus membrane potential, data points for 45 mM [K+]i were located on the same line as the control, whereas data points for 30 mM [K+]o were shifted in the negative direction by about 30 mV. The dissociation constant at 0 mV is 37 microM in the control and 45 mM [K+]i and 8.8 microM in 30 mM [K+]o. The voltage dependence of dissociation constants gives a value for the fractional electrical distance of the Mg2+ binding site of 0.57. 6. Subconductance levels with one‐third and two‐thirds of the unitary amplitude were seen with low internal Mg2+ at 45 mM [K+]i or 30 mM [K+]o as well as in the control condition. Blocking and unblocking rates were calculated on the assumption that the channel is composed of three identical conducting units and each unit is blocked by Mg2+ independently.(ABSTRACT TRUNCATED AT 400 WORDS)
Flux of Ca2+ across the sarcoplasmic reticulum of guinea‐pig cardiac cells during excitation‐contraction coupling.
Authors: Sipido K R , Wier W G
Published: December 2014

1. A method has been developed for calculating the flux of Ca2+ across the sarcoplasmic reticulum (SR) during excitation‐contraction coupling in mammalian heart cells. FSR will symbolize the net rate of movement of Ca2+, per litre of accessible cytoplasm, into or out of the sarcoplasmic reticulum. FSR has the units MS‐1. 2. A theory of the cytoplasmic [Ca2+]i transient in mammalian heart cells is presented in which the [Ca2+]i transient results from the various cellular processes that tend to increase or decrease cytoplasmic [Ca2+]i. According to the theory, FSR can be calculated if all cellular processes that contribute to the [Ca2+]i transient (other than Ca2+ fluxes across the SR) are either eliminated or are known quantitatively. 3. To obtain the measurements required to apply this theory, [Ca2+]i transients and membrane currents were recorded in guinea‐pig single ventricular myocytes subjected to whole‐cell voltage clamp and internal perfusion. [Ca2+]i transients were recorded through the use of the Ca2+ indicator, Fura‐2 (pentapotassium salt). 4. Ca2+ fluxes through the sodium‐calcium exchanger were eliminated in all experiments, by perfusing the cells, internally and externally with Na(+)‐free solutions. Ca2+ flux through the sarcolemmal L‐type Ca2+ channel was measured as the verapamil‐sensitive current. Influx of Ca2+ through all other voltage‐dependent pathways was found to be negligible for the calculation of FSR over the time course of a single [Ca2+]i transient. 5. In the combined absence of Ca2+ current, Na(+)‐Ca2+ exchange and fluxes across the SR (10 mM‐caffeine), the net rate of removal of Ca2+ from the cytoplasm, which includes presumed contributions from sarcolemmal Ca(2+)‐ATPase and mitochondrial Ca2+ transport, was found to be a negligible quantity in the calculation of FSR, over the time course of a single [Ca2+]i transient. 6. Calculation of FSR requires that the Ca(2+)‐binding capacity of cytoplasm be known. [Ca2+]i transients recorded during measurable total Ca2+ influx into the cytoplasm (verapamil‐sensitive current in the absence of fluxes across the SR) were compared with theoretical Ca2+ transients computed on the assumption that the entering Ca2+ could bind only to intracellular ligands (values for ligands taken from literature) and to Fura‐2 (30 microM). The slope of the regression line relating calculated total change in [Ca2+]i to the measured total Ca2+ influx was 0.99, not different from the perfect theoretical slope of 1.0 (correlation coefficient, 0.81; standard deviation of slope, 0.14; n = 7).4+ the SR and FSR had a similar time course to that on depolarization. 10. The unidirectional efflux of Ca2+ from the SR, symbolized FSR, rel was calculated utilizing assumed characteristics of the Ca2+ pump of the SR. The value of FSR, rel was not affected by repolarization from voltage‐clamp pulses greater than 150 ms in duration.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of neuropeptides, ruthenium red and neuraminidase on chemoreflexes mediated by afferents in the dog epicardium.
Authors: Staszewska‐Woolley J , Woolley G
Published: December 2014

1. Experiments were performed on anaesthetized, open‐chest dogs to determine reflex effects on blood pressure and heart rate produced by stimulation of neural afferents of the left ventricular epicardium by local application of capsaicin, bradykinin, nicotine and the neuropeptides substance P (SP), neurokinin A (NKA), neurokinin B (NKB) and calcitonin gene‐related peptide (CGRP). 2. Studies also included assessing whether reflexogenic actions of capsaicin, bradykinin and nicotine are influenced by epicardial treatment with either neuropeptides, Ruthenium Red or neuraminidase. 3. Epicardial application of either capsaicin (0.1‐10 micrograms) or bradykinin (0.1‐1 micrograms), consistently resulted in dose‐related increases in blood pressure and heart rate, whereas reflex bradycardia and hypotensive effects were initiated by the application of nicotine (30‐50 micrograms). 4. SP, NKA, NKB and CGRP caused marked hypotensive effects and tachycardia when injected intravenously (1 microgram), but failed to produce any cardiovascular response when applied to the epicardium of the left ventricle (0.1‐1 microgram). Treatment of the heart surface with these neuropeptides (0.05‐0.5 micrograms min‐1) was also without any effect on the magnitude of reflex responses evoked by epicardial application of either capsaicin, bradykinin or nicotine. 5. Superfusion of the ventricular epicardium with Ruthenium Red (10‐30 microM), a cationic dye known to have sialic acid as a molecular target, antagonized the reflexogenic effects of capsaicin but not those of bradykinin or nicotine. The reflex effects of capsaicin, but not those of bradykinin, were also sensitive to inhibition by epicardial treatment with neuraminidase, an enzyme which cleaves sialic acid residues from glycosides and sialoglycoproteins. 6. We conclude that neuropeptides which may be released from the peripheral endings of some cardiac sensory neurons neither directly activate nor sensitize spinal sympathetic and vagal afferents in the dog heart to the reflexogenic action of bradykinin, nicotine or capsaicin. 7. We further suggest that activation of the cardiac sympathetic chemoreflex by capsaicin involves its interaction with calcium‐binding sialic acid moieties present on the surface of axons and/or terminals of chemosensitive sympathetic afferents distributed in the dog ventricular epicardium.
Electrophysiological effects of calcitonin gene‐related peptide in bull‐frog and guinea‐pig atrial myocytes.
Authors: Ono K , Giles W R
Published: December 2014

1. Electrophysiological effects of calcitonin gene‐related peptide (CGRP) on action potentials and corresponding transmembrane currents in single myocytes from bull‐frog and guinea‐pig atria were studied using a whole‐cell voltage‐clamp method. 2. CGRP at relatively low concentrations increased the height of the action potential plateau in a dose‐dependent manner in both bull‐frog and guinea‐pig myocytes. In addition, in bull‐frog cells CGRP accelerated the early phase of repolarization, thus shortening the overall duration of the action potential. In contrast, in guinea‐pig myocytes CGRP prolonged the action potential duration at all concentrations that were studied. 3. Voltage‐clamp measurements demonstrated that CGRP increased transmembrane calcium current (ICa) in guinea‐pig myocytes without a significant change in its voltage dependence. The ED50 value for this effect on ICa was 1.28 +/‐ 0.55 X 10(‐8) M (n = 4). The time course of the inactivation of ICa was not affected by CGRP. 4. CGRP increased the delayed rectifier K+ current (IK) at relatively low concentrations in bull‐frog atria, whereas relatively high concentrations were needed to increase IK in guinea‐pig myocytes. This effect was observed even after complete inhibition of ICa. 5. CGRP had no significant effect on the inwardly rectifying background K+ current, IK1, even at very high concentrations. 6. Comparison of the time course of ICa augmentation in bull‐frog and guinea‐pig myocytes revealed an important difference in the effect of CGRP in these two types of cells. CGRP at maximal concentrations increased ICa transiently in bull‐frog myocytes, whereas this response was sustained in guinea‐pig myocytes. Isoprenaline (Iso) induced sustained increase in ICa in both species. When ICa was fully activated by Iso, CGRP at high concentrations strongly inhibited ICa in the bull‐frog, whereas it had little effect on ICa in guinea‐pig myocytes. 7. Intracellular application of GTP gamma S (guanosine 5'‐O‐(3‐thiotriphosphate) 10(‐4) M) greatly potentiated the CGRP effect on ICa; in contrast, GDP beta S (guanosine 5'‐O‐(2‐thiodiphosphate), 2 x 10(‐3) M) partially inhibited the CGRP‐induced augmentation of ICa. Taken together, these results indicate that the stimulation of ICa by CGRP is mediated by a GTP‐binding protein. 8. The observed dose‐dependent changes in ICa and IK in bull‐frog and guinea‐pig myocytes can explain the different patterns of CGRP‐induced changes in action potential shape in these two myocyte preparations.
The cytosolic calcium transient modulates the action potential of rat ventricular myocytes.
Authors: duBell W H , Boyett M R , Spurgeon H A , Talo A , Stern M D , Lakatta E G
Published: December 2014

1. The modulation of the action potential by the cytosolic Ca2+ (Cai2+) transient was studied in single isolated rat ventricular myocytes loaded with the acetoxymethyl ester form of the Ca(2+)‐sensitive fluorescent dye Indo‐1. Stimulation following rest and exposure to ryanodine were used to change the amount of Ca2+ released from the sarcoplasmic reticulum and thus the size of the Cai2+ transient. The Cai2+ transient was measured as the change, upon stimulation, in the ratio of Indo‐1 fluorescence at 410 nm to that at 490 nm (410/490) and action potentials or membrane currents were recorded using patch‐type microelectrodes. 2. When stimulation was initiated following rest, the magnitude of the Cai2+ transient decreased in a beat‐dependent manner until a steady state was reached. The negative staircase in the Cai2+ transient was accompanied by a similar beat‐dependent decrease in the duration of the action potential, manifested primarily as a gradual loss of the action potential plateau (approximately ‐45 mV). A slow terminal phase of repolarization of a few millivolts in amplitude was found to parallel the terminal decay of the Cai2+ transient. 3. The terminal portion of phase‐plane loops of membrane potential (Vm) vs. Indo‐1 ratio from all of the beats of a stimulus train followed a common linear trajectory even though the individual beats differed markedly in the duration and amplitude of the action potential and Cai2+ transient. 4. When the stimulation dependence of the Cai2+ transient was titrated away with submaximal exposure to ryanodine, the stimulation‐dependent changes in the action potential plateau and terminal phase of repolarization were also eliminated. The same effect was noted in cells which, fortuitously, did not show a staircase in the Cai2+ transient following a period of rest. 5. When action potentials were triggered immediately following spontaneous release of Ca2+ from the sarcoplasmic reticulum, which results in a small depolarization at the resting potential, phase‐plane loops (Vm vs. Indo‐1 ratio) of the spontaneous events followed the same linear trajectory as the terminal phase of repolarization in the loops of the stimulated beats. 6. Following repolarization from brief voltage clamp pulses (to minimize time and voltage‐dependent currents associated with depolarization), an inward current was observed that rose and fell in phase with the Cai2+ transient. This current was present at ‐70 mV, near the resting potential, and at ‐40 mV, a potential relevant to the plateau of the action potential.(ABSTRACT TRUNCATED AT 400 WORDS)
Influence of pressure alterations on tone and vasomotion of isolated mesenteric small arteries of the rat.
Authors: VanBavel E , Giezeman M J , Mooij T , Spaan J A
Published: December 2014

1. Myogenic responses may account for control of organ blood flow. The study of these responses without interference from the organ requires an isolation technique for vessels which contribute significantly to flow resistance. This study reports on experiments on isolated small mesenteric arteries. 2. Distal rat mesenteric arcade arteries and first‐order branches (diameter range 145‐365 microns, mean 293 microns) were manually dissected and cannulated using a double‐barrelled micro‐cannula. Luminal cross‐sectional area of these vessels was continuously monitored by means of a fluorescence technique. 3. Nine out of eighteen vessels developed basal tone at 80 mmHg distending pressure, resulting in a 45.2 +/‐ 5.1% (mean +/‐ S.E.M) decrease of cross‐sectional area. Tone was induced in the other vessels by 0.3‐1 microM‐noradrenaline, resulting in a 59.5 +/‐ 7.1% decrease in cross‐sectional area. 4. In vessels with either spontaneous or induced tone, stepwise changes of pressure resulted in passive effects, followed by myogenic responses. 5. Steady‐state pressure‐cross‐sectional area relations of vessels with basal tone showed a significant negative slope (‐0.5% mmHg‐1), while pressure‐cross‐sectional area relations of vessels with induced tone were essentially flat between 40 and 120 mmHg. 6. Five vessels with basal tone and eight vessels with induced tone developed vasomotion at 80 mmHg. Frequencies of spontaneous and induced vasomotion were 14 (range 4‐31) and 21 (9‐25) cycles min‐1 respectively. Amplitudes were 5 (1‐10) and 8 (3‐17)% of the passive cross‐sectional area. In both groups, frequency was positively, and amplitude negatively correlated with pressure. 7. These data show that myogenic responses are induced by wall stress, rather than by distension of the vascular wall. Basal tone is not a prerequisite for the appearance of myogenic responses.
Nociceptive inputs into rostral ventrolateral medulla‐spinal vasomotor neurones in rats.
Authors: Sun M K , Spyer K M
Published: December 2014

1. In anaesthetized rats recordings were made from thirty‐eight neurones in the rostral ventrolateral medulla (RVL) with spinal‐projecting axons. Their responses to mechanical, thermal and/or electrical stimulation were examined as were the accompanying changes in arterial pressure. 2. Mechanical, thermal and electrical stimulation of either hindpaw at a strength that can be regarded as noxious produced a consistent rise in arterial pressure. RVL‐spinal‐projecting ‘vasomotor’ neurones were excited by the noxious mechanical and thermal (52 degrees C) stimulation at a latency that was shorter than that of the evoked pressor response. 3. Percutaneous electrical stimulation of either hindlimb extremity resulted in an early peak of excitation (fourteen out of fourteen), an early trough of inhibition (twelve out fourteen), and a later peak of excitation (two out of fourteen). This response pattern to stimulation of either limb was independent of which limb was activated, but contralateral hindpaw stimulation elicited excitation at a shorter latency. The differences in latency of responses to stimulating two locations along the tail suggested that the early excitation and inhibition of RVL‐spinal ‘vasomotor’ neurones were evoked by activation of peripheral fibres with a mean conduction velocity in the A delta range. 4. Short‐latency excitatory and inhibitory responses in RVL‐spinal ‘vasomotor’ neurones were observed also when single‐pulse stimuli were delivered within the lateral part of the spinal cord. 5. Ionophoretic application of bicuculline, a GABAA receptor antagonist, blocked the evoked inhibition of these neurones on electrical stimulation of the hindpaw without attenuating the excitatory input from the same stimulus. 6. These results indicate that RVL‐spinal ‘vasomotor’ neurones receive an input from cutaneous nociceptive afferents. This suggests that these neurones mediate, at least partly, the cardiovascular responses related to nociceptor stimulation.
Forces and powers of slow and fast skeletal muscles in mice during repeated contractions.
Authors: Brooks S V , Faulkner J A
Published: December 2014

1. The normalized force or power developed during each of a series of repeated contractions was averaged over the entire cycle of activity and rest to provide a measure of performance referred to as sustained force or sustained power. We tested the hypotheses that compared with slow soleus muscles, fast extensor digitorum longus (EDL) muscles would attain lower maximum values of sustained force, but higher maximum values of sustained power. 2. During repeated contractions at a stimulation frequency of 150 Hz, forces and powers of soleus and EDL muscles of mice were determined in situ at 35 degrees C. The train rate of repeated contractions was incremented every 5 min to increase duty cycle until a maximum value for sustained force or power was reached. 3. In one set of repeated contractions, each contraction was preceded by a quick stretch and thereafter muscle length was held constant. The stretch minimized active shortening of muscle fibres. Sustained force was calculated from force at constant length. The maximum sustained force developed by soleus muscles of 4.58 +/‐ 0.31 N cm‐2 (mean +/‐ S.E.M.) occurred at a duty cycle of 0.48. Compared with soleus muscles, EDL muscles attained a lower (P less than 0.05) maximum value of 1.38 +/‐ 0.15 N cm‐2 at a 0.35 duty cycle. 4. During isovelocity shortening contractions, the maximum value for sustained power developed by soleus muscles of 7.4 +/‐ 0.5 W kg‐1 occurred at a duty cycle of 0.18. Compared with soleus muscles, EDL muscles achieved a significantly greater maximum value of 9.1 +/‐ 0.4 W kg‐1 at a 0.21 duty cycle.
The effects of opiates on the respiratory activity of thoracic motoneurones in the anaesthetized and decerebrate rabbit.
Authors: Howard R S , Sears T A
Published: December 2014

1. Efferent discharges were recorded from inspiratory and expiratory intercostal nerve filaments (T2‐T10) in artificially ventilated, anaesthetized or decerebrate rabbits with or without vagotomy. 2. Hypocapnic apnoea was used to study the fractional end‐tidal CO2 (FET,CO2)‐dependent tonic discharges of the expiratory motoneurones, the FET,CO2 threshold for rhythm generation and the FET,CO2 response curve of both inspiratory and expiratory burst activity. 3. Incremental doses of morphine (e.g. 1 mg kg‐1 I.V.) produced slowing of the respiratory rhythm due to prolongation of the expiratory duration and an elevation of the FET,CO2 threshold for rhythm generation. Eventually apnoea supervened with associated tonic firing of the expiratory motoneurones. At the elevated levels of FET,CO2 bursts of inspiratory activity, with concomitant phasic inhibition of the tonic expiratory activity, could occur either spontaneously or following sensory stimulation. The peak integrated activities of these bursts were closely similar to the values obtained for corresponding levels of FET,CO2 before the administration of morphine. 4. Tonic expiratory activity responded to increased levels of FET,CO2, as it had during hypocapnic apnoea prior to morphine, by an increased discharge frequency of single units or recruitment of new units. 5. All of these effects of morphine were immediately reversed by naloxone (100 micrograms kg‐1). 6. Naloxone (greater than 100 micrograms kg‐1), without pre‐treatment with morphine, led to an increase in respiratory frequency due to a shortening of the expiratory duration and a dose‐dependent reduction in the FET,CO2 threshold for rhythm generation. There was little alteration either in the inspiratory response to FET,CO2 during rhythm or in the FET,CO2 response of the expiratory output whether expressed as tonic activity during hypocapnic apnoea or phasic activity following the onset of rhythm. 7. Thus opiates act upon the mechanisms of rhythm generation without depressing the FET,CO2 drive as expressed either as phasic or tonic activation of the motoneurones.
The effect of chronic exercise on the pituitary‐adrenocortical response in conscious rats.
Authors: Watanabe T , Morimoto A , Sakata Y , Wada M , Murakami N
Published: December 2014

1. This study was designed to investigate the effect of chronic exercise on exercise‐induced changes in plasma concentrations of adrenocorticotrophic hormone (ACTH) and corticosterone in rats. Corticotrophin releasing factor (CRF) and ACTH were injected I.V. in order to assess the responsiveness of the pituitary and adrenal glands after chronic exercise. 2. The concentrations of ACTH and corticosterone in the plasma increased significantly after acute exercise in both the control and the exercised groups but both responses were significantly smaller in the exercised group. 3. The ACTH response to I.V. CRF was also significantly smaller in the exercised rats. However, both groups of animals showed similar increases in plasma corticosterone levels after the administration of exogenous ACTH. 4. The ACTH response to CRF attenuated by repeated administration of CRF. 5. These results suggest that attenuated ACTH and corticosterone responses to acute exercise after chronic exercise result from reduced responsiveness of the pituitary gland to CRF.
Bombesin excites a subpopulation of 5‐hydroxytryptamine‐sensitive neurones in the rat dorsal raphe nucleus in vitro.
Authors: Pinnock R D , Woodruff G N
Published: December 2014

1. The effects on dorsal raphe neurones of the peptides bombesin, gastrin‐releasing peptide and neuromedin B were studied using intracellular recording techniques from slices of rat brain maintained in vitro. The peptides were added to the solutions perfusing the slices. 2. The peptides bombesin, gastrin‐releasing peptide and neuromedin B depolarized neurones in the dorsal raphe nucleus. The same neurones were depolarized by phenylephrine and hyperpolarized by 5‐hydroxytryptamine (5‐HT) but were insensitive to sulphated cholecystokinin octapeptide (CCK). 3. The responses to the peptides were not blocked by CCKA, CCKB and alpha 1‐adrenoreceptor antagonists. 4. The response to the peptides persisted in the presence of tetrodotoxin (TTX) and low‐calcium, high‐magnesium‐containing artificial cerebrospinal fluid (ACSF). 5. Under voltage clamp conditions the peptides caused a decrease in membrane conductance accompanied by an inward current. The reversal potential for the event was the same as that for 5‐HT. 6. The results of the present study demonstrate that bombesin and the structurally related peptides gastrin‐releasing peptide (GRP) and neuromedin B depolarized a subpopulation of raphe 5‐HT neurones by acting on a postsynaptically located receptor linked to potassium channels.
Strychnine‐sensitive glycine responses of neonatal rat hippocampal neurones.
Authors: Ito S , Cherubini E
Published: December 2014

1. Intracellular recordings employing current and voltage clamp techniques were used to study the effects of glycine on rat CA3 hippocampal neurones during the first 3 weeks of postnatal (P) life. 2. Glycine (0.3‐1 mM) depolarized neurones from rats less than 4 days old (P4). Neurones from older neonates (P5‐P7) were hyperpolarized by glycine, whereas adult neurones were unaffected. 3. Both depolarizing and hyperpolarizing responses were associated with large conductance increases; they reversed polarity at a potential which changed with the extracellular chloride concentration. The responses persisted in tetrodotoxin (1 microM) or in a solution with a much reduced calcium concentration. 4. Strychnine (1 microM) but not bicuculline (10‐50 microM) antagonized the effects of glycine. The action of strychnine was apparently competitive with a dissociation constant of 350 nM. 5. In voltage clamp experiments, glycine elicited a non‐desensitizing outward current at ‐60 mV. When a maximal concentration of glycine was applied at the same time as gamma‐aminobutyric acid (GABA), the conductance increase induced by the two agonists was additive, suggesting the activation of different populations of channels. 6. Concentrations of glycine lower than 100 microM did not affect membrane potential. However, at 30‐50 microM glycine increased the frequency of spontaneous GABA‐mediated synaptic responses; this action was not blocked by strychnine. 7. It is concluded that during the first 2 weeks of life glycine acts at strychnine‐sensitive receptors to open chloride channels.