bluuebunny/crossref_metadata_2025 huggingface dataset:
Autogenetic inhibition of motoneurones by impulses in group Ia muscle spindle afferents.
Authors: Fetz E E , Jankowska E , Johannisson T , Lipski J
Published: December 2014

1. Inhibitory post‐synaptic potentials evoked by adequate stimulation of group Ia muscle spindle afferents of homonymous and synergistic muscles and by selective electrical stimulation of tendon organ afferents were analysed in motoneurones of triceps surae and plantaris. 2. Selective activation of Ia afferents was verified to occur with brief stretches of triceps surae and plantaris 35 micrometer or less in amplitude with an initial muscle tension of 5 N; stretches of 30‐‐35 micrometer were estimated to activate 80‐‐90% of Ia afferents in these muscles. Under the same conditions the lowest thresholds for group Ib tendon organ afferents were about 40 micrometer. 3. Stretches less than or equal to 30 micrometer evoked i.p.s.p.s in 80% of triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s wef triceps surae and plantaris motoneurones; lowest thresholds for evoking i.p.s.p.s were 10 micrometer or less. However, such low thresholds for stretch‐evoked i.p.s.p.s, lower than the thresholds for activation of Ib afferents, were found mainly in spinalized, unanaesthetized (after decerebration) or lightly anaesthetized animals. The latencies of these i.p.s.p.s indicated disynaptic and trisynaptic coupling between Ia afferents and motoneurones. The i.p.s.p.s were evoked (i) from the homonymous and synergistic muscles stretched together, (ii) from the homonymous muscles alone and (iii) from the synergistic muscles alone. 4. Control experiments showed that i.p.s.p.s could be evoked by stretches sub‐threshold for discharging motoneurones, thus showing that those i.p.s.p.s were not mediated by Renshaw cells. The stretch‐evoked i.p.s.p.s disappeared after sectioning the nerves from the corresponding muscles, further excluding their mediation by afferents other than group Ia afferents from thf stretched muscle. 5. In order to selectively activate tendon organ afferents, thresholds for excitation of Ia afferents by electrical stimuli were increased to a level above the threshold for Ib afferents by prolonged muscle vibration (Coppin, Jack & MacLennan, 1970). I.p.s.p.s evoked by stimuli near threshold for Ib afferents appeared with latencies indicating disynaptic coupling. Later (trisynaptic) components of Ib i.p.s.p.s required somewhat stronger stimuli. 6. Amplitudes of Ia i.p.s.p.s evoked by muscle stretches activating about 80% of muscle spindle afferents were compared with amplitudes of Ib i.p.s.p.s due to less than 50% of tendon organ afferents of the same muscles. The Ia i.p.s.p.s were much smaller (16‐‐35%) than the Ib i.p.s.p.s. The amplitudes of such Ia and Ib i.p.s.p.s constituted about 10 and 25‐‐66%, respectively, of the maximal i.p.s.p.s evoked by electrical stimulation of all group I afferents. 7. We conclude that inhibition of motoneurones may be evoked from Ia muscle spindle afferents from homonymous and synergistic muscles as well as from Ib tendon organ afferents...
The effect on tension of non‐uniform distribution of length changes applied to frog muscle fibres.
Authors: Julian F J , Morgan D L
Published: December 2014

1. The stability of sarcomere lengths along single frog twitch fibres was examined, during lengthening and shortening, using a spot follower appparatus to monitor or control the length of a central segment. 2. During active shortening from sarcomere lengths beyond 2.2 micrometer the end sarcomeres shortened dramatically, while much of the fibre did not shorten at all. It is proposed that this is the cause of the tension failing to recover, after the shortening ceased, to the value of isometric tension at the shorter length. 3. During active lenghtening from sarcomere lengths beyond 2.2 micrometer, non‐uniformity of stretch was seen, with the middle stretching more than the ends. Some maintained extra tension after stretch above that appropriate to the longer length was found, as were consistent changes in internal movement, and in the shape of the tension record during relaxation. 4. Measurements of stiffness during and after a lengthening suggest that no increased activation is involved. Observation of internal movement during the raised tension after a lengthening contradicts theories involving ‘locked on’ bridges. 5. From these and other observations, an explanation for the extra tension in terms of non‐uniformity of sarcomeres is proposed. The explanation is in accord with that previously suggested for the creep phase of tension rise seen at these lengths.
Influence of the vagus nerve on release and action of secretin in dog.
Authors: Chey W Y , Kim M S , Lee K Y
Published: December 2014

1. The role of cholinergic nerve on plasma concentration of immunoreactive secretin and pancreatic bicarbonate secretion was investigated in conscious and anaesthetized dogs. 2. In conscious dogs with gastric and pancreatic fistulae, I.V. administration of 2‐deoxy‐D‐glucose (2‐DG) potentiated the pancreatic bicarbonate secretion stimulated by duodenal acidification. 3. In conscious dogs with same preparation, I.V. administration of atropine inhibited the pancreatic bicarbonate secretions stimulated by duodenal acidification or exogenous secretin. 4. Neither 2‐DG nor atropine had any effect on endogenous release of secretin. 5. In anaesthetized dogs, pancreatic bicarbonate secretion stimulated by duodenal acidification was decreased by bilateral cervical vagotomy. However, plasma secretion concentration achieved by duodenal acidification was not different from that of pre‐vagotomy state. 6. The data indicate that the changes of cholinergic tone do not affect release of endogenous secretin but alter the exocrine pancreatic bicarbonate secretion stimulated by secretin.
Cold acclimation in the secretory responses of the isolated exocrine pancreas of the rat
Authors: Habara Y. , Kanno T. , Saito A.
Published: December 2014

1. The secretory function of the isolated and perfused exocrine pancreas has been studied in the course of cold acclimation in rats that were fed at an ambient temperature of 1 °C in an artificial climatic room.

2. A series of experiments was carried out in early autumn (autumn series). The sums of the outputs of protein, amylase, zymogen protease, lipase, and juice flow in samples collected for a total of 30 min during and after 5 min stimulation with different concentrations of cholecystokinin—pancreozymin (CCK—PZ; 5‐50 m‐u./ml.) were simultaneously measured in the autumn series of experiments, and they were plotted against the logarithmic scale of concentration of CCK—PZ to obtain a dose—response relation.

3. The sums of protein output, lipase output, and juice flow evoked by different concentrations of CCK—PZ in the group of rats fed at 1 °C for 3 weeks were almost identical to the corresponding value in the group fed at about 21 °C for 3 weeks.

4. The sum of output of zymogen protease in the former group was almost identical to the corresponding value in the latter group except that the sum induced by 20 m‐u. CCK—PZ/ml. was significantly larger in the former.

5. The sum of output of amylase induced by various concentrations of CCK—PZ in the former group was significantly smaller than the corresponding value in the latter group.

6. It was thus concluded that the CCK—PZ‐induced outputs of protein, lipase, and zymogen protease were little affected if any by 3 weeks of cold exposure, whereas the CCK—PZ‐induced amylase output was significantly suppressed.

7. Another similar series of experiments was performed in the summer of the same year. The results obtained suggest that the secretory function of exocrine pancreas is directly inhibited by prolonged cold exposure in summer but it is not in autumn.
Intracellular recording from neurones of the rat subfornical organ in vitro.
Authors: Buranarugsa P , Hubbard J I
Published: December 2014

1. Intracellular recordings from neurones in the subfornical organ in vitro showed that there were two classes of neurones. One class lay within 55 micron of the ventricular surface and was synaptically excited but not inhibited by stimulation of the body or columns of the fornix. These neurones could not be excited antidromically. The other class lay more deeply and was antidromically and synaptically excited and inhibited by stimulation of the body and columns of the fornix. 2. The neurones of the subfornical organ appeared to have the characteristics of neurosecretory neurones. Their action potentials were prolonged and their antidromic spike was easily broken down into components by repetitive stimulation. 3. The organization of the subfornical organ inferred from extracellular recording was confirmed by the results of intracellular recording.
Effects of some divalent cations on synaptic transmission in frog spinal neurones.
Authors: Alvarez‐Leefmans F J , De Santis A , Miledi R
Published: December 2014

1. Synaptic transmission between dorsal root afferents and motoneurones was studied in the isolated and hemisected spinal cord of frogs, using intracellular and extracellular recording techniques, and ionic substitutions of divalent cations in the bathing fluid. 2. Delayed components of excitatory post‐synaptic potentials (e.p.s.p.s) evoked in motoneurones by dorsal root supramaximal stimuli, as well as the Ca2+‐dependent slow after‐hyperpolarization which follows antidromic spikes, were reversibly blocked by superfusing the cords with ‘Ca2+‐free’ media containing Co2+ (4 mM) or Mg2+ (6‐10 mM). However, short latency e.p.s.p.s persisted in these media for more than 8 hr. 3. The minimum synaptic delay of the Co2+ and Mg2+, resistant e.p.s.p.s, measured from the peak negativity of the extracellularly recorded presynaptic spike to the onset of the e.p.s.p., was 0.3 msec at 10 +/‐ 1 degrees C. 4. The Co2+, Mg2+‐resistant e.p.s.p.s were graded, and could be elicited by stimulation of segmental or adjacent roots. Those evoked by each of two adjacent roots showed linear summation when the roots were stimulated simultaneously. 5. The Co2+, Mg2+‐resistant e.p.s.p.s decreased in amplitude at stimulating frequencies between 10 and 100 Hz, and with paired stimuli at intervals shorter than 20‐40 msec. These reductions in amplitude were paralleled by decreases in amplitude of the presynaptic population spike. 6. Solutions free of divalent ions, containing EGTA (2 mM) abolished the Co2+, Mg2+‐resistant e.p.s.p.s. They remained blocked for a variable time after returning to Ca2+‐free Ringer containing Mg2+ (8 mM). Their continued abolition at this stage is probably not due to changes in electrical properties of motoneuronal membranes. Eventually, the Mg2+‐resistant e.p.s.p.s started recovering in the Ca2+‐free Ringer containing Mg2+. The time of onset of this recovery depended on the duration of exposure to EGTA. 7. Sr2+ (2‐11 mM), although less effective than Ca2+, restored the composite e.p.s.p.s evoked by dorsal root supramaximal stimuli, as well as the Ca2+‐dependent slow after‐hyperpolarization of the motoneurone. The composite e.p.s.p.s could not be restored with Ba2+ (2‐10 mM). 8. The results suggest that the Co2+, Mg2+‐resistant e.p.s.p is generated by electrical coupling between some afferent fibres (probably primary afferents) and motoneurones. The after‐effects of EGTA treatments probably reflect uncoupling of electrotonic junctions. In contrast, the delayed components of the composite e.p.s.p.s are generated through chemical synapses whose divalent cation requirement is similar to that of the neuromuscular junction.
The responses of primary spindle afferents to fusimotor stimulation at constant and abruptly changing rates.
Authors: Hulliger M
Published: December 2014

1. Single fusimotor fibres to de‐efferented soleus of the cat were stimulated to investigate the size and time course of the responses elicited in single primary spindle afferents. The muscle was kept at constant length close to the physiological maximum. Constant and alternating rates of fusimotor stimulation were used: (a) repetitive stimulation at constant rate (maintained stimulation); (b) modulated stimulation with the rate of activation alternating between two constant levels at repeat frequencies between 0.09 and 2 Hz (rectangular stimulation). The responses were averaged and displayed as post‐stimulus time (pst) histograms (a) or as cycle histograms (b). 2. During static fusimotor stimulation the pst histograms could be clearly modulated over a range of rates of stimulation. However, histogram modulation was not a prerequisite of static action since with different fibres the degree of modulation could range from deeply modulated to completely non‐modulated to completely non‐modulated. 3. Dynamic fusimotor stimulation was almost always accompanied by non‐modulated pst histograms. 4. Primary spindle afferents responded to rectangular stimulation of either kind of fusimotor fibre with an approximately rectangular modulation of the rate of discharge. At the repeat frequencies studied the size of the responses was appreciably larger with static than with dynamic activation. It was assessed as ‘fusimotor rate‐sensitivity during alternating stimulation’ by the response/stimulus ratio which is defined as change in firing/change in alternating rate of stimulation, in impulses/stimuli. The mean values of rate‐sensitivity were 1.35 impulses/stimuli (statics) and 0.29 (dynamics), with a static/dynamic ratio of 4.7. 5. The afferents’ ‘fusimotor rate‐sensitivity during steady stimulation’ (change in firing/change in maintained rate of stimulation( was also determined. The mean values were 0.78 (static) and 0.37 (dynamics), with a static/dynamic ratio of 2.1. 6. The time course of the responses to rectangular stimulation was of the same order of magnitude for static and dynamic fibres. It was assessed by fitting a single exponential to the rising and falling phase of cycle histograms. The mean values of the time constants for static fibres were 58 msec (rising phase) and 59 msec (falling phase), and for dynamic fibres 34 msec (rising phase) and 49 msec (falling phase). The differences were statistically non‐significant. 7. The significance of the modulation in pst histograms and the mechanisms and functional implications of the differences in rate‐sensitivity are discussed. It is concluded that at constant muscle length static and dynamic fusimotor fibres differ significantly by the size rather than the speed of their action on primary spindle afferents.
Effects of dark adaptation on spatial and temporal properties of receptive fields in cat lateral geniculate nucleus.
Authors: Kaplan E , Marcus S , So Y T
Published: December 2014

1. We studied the effect of dark adaptation on the spatial organization of receptive fields of single cells in the lateral geniculate nucleus l.g.n. of the cat. 2. Contrary to previous reports, we found that in many l.g.n. cells the ability of the receptive field surround to suppress the response of the centre was diminished following dark adaptation. 3. The degree of reduction of the surround antagonistic strength varied from cell to cell, and was independent of the various classifications of visual neurones (X/Y, ON/OFF, layer, A/layer, A1 and central/peripheral). 4. Most cells also showed an increase in the apparent size of the excitatory centre upon dark adaptation. On the average, the width of the most effective bar stimulus located at the centre of the receptive field increased more than twofold. 5. We also studied the effect of dark adaptation on the temporal properties of l.g.n. receptive fields. In many cells dark adaptation changed the temporal modulation transfer function: it flattened the amplitude function, and changed the phase relationship between the centre response and the surround response. 6. Retinal ganglion cells showed qualitatively similar behaviour to that of l.g.n. neurones. 7. Our data do not support the notion that retinal ganglion cell centres converge on l.g.n. cells to form their surround mechanism.
Evidence supporting a role for endogenous vasopressin in natural suppression of fever in the sheep.
Authors: Cooper K E , Kasting N W , Lederis K , Veale W L
Published: December 2014

1. The antipyretic effect of arginine vasopressin (AVP) introduced into the brain by push‐pull perfusion was investigated in the sheep. 2. Control perfusions with sucrose solutions had no effect on fevers induced by a bacterial endotoxin. Sucrose solutions containing AVP (4.0 microgram/ml.) perfused at 40 microliter./min had significant antipyretic activity, reducing the two peaks of the fever but had no effect on resting body temperature. 3. Loci in which AVP induced antipyresis were limited to the septal region about 2‐3 mm anterior to the anterior commissure. 4. The amounts of AVP in perfusates from the septal region correlated negatively with changes in body temperature. 5. AVP administered I.V. did not lower fever. 6. AVP plasma levels correlated negatively with fever magnitude following premature birth induced by dexamethasone.
Characteristics of saxitoxin binding to the sodium channel of sarcolemma isolated from rat skeletal muscle.
Authors: Barchi R L , Weigele J B
Published: December 2014

1. The characteristics of saxitoxin (STX) binding to the mammalian Na channel have been studied in purified sarcolemma isolated from rat skeletal muscle. 2. STX binds specifically to isolated sarcolemma with a Kd of 1.43 x 10(‐9) M and Bmax of 7‐8 p‐mole STX bound/mg membrane protein at 0 degrees C in the presence of 140 mM‐NaCl. In rat muscle homogenate under the same conditions the corresponding values are Kd = 1.53 x 10(‐9) M and Bmax = 0.15‐0.20 p‐mole/mg protein (18‐20 p‐mole/g wet wt.). Membrane purification produced a fortyfold increase in STX binding site concentration per milligram protein. Calculated binding site density in isolated sarcolemma was about 30 sites/micron 2 of membrane surface. 3. Denervation (10‐14 days) results in a 43% reduction in the density of high‐affinity STX binding sites in purified sarcolemma, but the Kd for this class of sites is not changed. 4. In sarcolemma, the apparent Kd for STX binding is dependent on temperature pH and ionic strength. The Q10 for Kd between 0 and 40 degrees C is 1.3. Protonation of a group having a pK of 6.0 markedly raises Kd without affecting Bmax. Apparent Kd increases eightfold when ionic strength is raised from 20 to 600 mM. 5. Dissociation and association rate constants for STX binding are temperature dependent with Q10 of 2.6 and 1.9 respectively between 0 and 20 degrees C. 6. STX binding is competitively inhibited by monovalent and divalent cations under conditions of constant total ionic strength. An affinity sequence of Tl+ greater than Li+ greater than Na+ greater than K+ greater than Rb+ greater than Cs+ is seen for the monovalent cation‐binding site. 7. The STX binding site is relatively stable to heat and to enzymic degradation. A specific modifier of carboxyl residues inactivates subsequent STX binding. This process can be prevented by the presence of STX during the reaction. 8. Characteristics of the STX binding site in isolated sarcolemma are compared to those reported for other isolated excitable membranes and for studies of whole muscle and muscle homogenate. Sarcolemma provides a potential source of enriched Na channels for further purification efforts in a mammalian system.
The fate of exogenous arachidonic acid in guinea‐pig isolated lung.
Authors: Al‐Ubaidi F , Bakhle Y S
Published: December 2014

1. The fate of [14C]arachidonic acid perfused through the pulmonary circulation was studied in guinea‐pig lungs perfused with Krebs solution. 2. Radioactivity in the lung effluent fell rapidly and by 10 min about 20% of the infused radioactivity had emerged. 3. Most (70%) of the effluent radioactivity was associated with products of cyclo‐oxygenase activity, whereas in the lung tissue most of the retained radioactivity was present as phospholipid. 4. Radioactivity in phospholipid was distributed equally between three groups: phosphatidyl choline, phosphatidyl ethanolamine and the other phosphatides. 5. Addition of albumin to the Krebs solution perfusing the lung increased the proportion of effluent radioactivity to 50%, decreased the cyclo‐oxygenase products but increased the label in phospholipid in lung. 6. Indomethacin, frusemide, bromcresol green and diethylcarbamazine all decreased biological activation of arachidonic acid. 7. Indomethacin, bromcresol green and diethylcarbamazine also decreased effluent radioactivity and cyclo‐oxygenase products with minimal effects on the distribution of radioactivity in lung lipid. 8. It appears that the major metabolic pathway for exogenous arachidonic acid perfused through the pulmonary circulation was incorporation into phospholipid. Metabolism via cyclo‐oxygenase only involved about 15% of the total substrate infused.
A kinetic study of the interactions between amino acids and monosaccharides at the intestinal brush‐border membrane.
Authors: Alvarado F , Robinson J W
Published: December 2014

1. The influx of amino acids into guinea‐pig intestinal rings in vitro is inhibited by monosaccharides, and that of monosaccharides by amino acids. Two hypotheses have been proposed to account for these heterologous interactions. According to the first, the cis hypothesis, there is an allosteric interaction between substrates binding to separate but related sites at the outer face of the brush‐border membrane matrix. In contrast, the trans hypothesis envisages the interaction to result from a partial dissipation of the electrochemical sodium gradient due to the cotransport of each substrate with sodium ions. 2. In an attempt to distinguish between the merits of the two hypotheses, we examined the kinetics of the inhibition of phenylalanine influx by two sugars of widely different affinities, galactose and beta‐methylglucoside. Since beta‐methylglucoside carries more sodium into the cell than galactose, the trans hypothesis would predict it to be the stronger inhibitor, but in fact the opposite result is found. 3. Equations were developed to describe the inhibitions in accordance with the cis hypothesis. The satisfactory agreement between experimental observations and theoretical predictions provides support for the applicability of the model. Further implications of the polyfunctional carrier model are discussed.
Properties of single fibre excitatory post‐synaptic potentials in triceps surae motoneurones.
Authors: Munson J B , Sypert G W
Published: December 2014

1. E.p.s.p.s and terminal potentials (t.p.s) produced by the action of single medial gastrocnemius Ia afferent fibres were examined with intracellular microelectrodes in cat triceps surae motoneurones. 2. Simple terminal potentials (t.p.s) appeared as positive‐negative diphasic waves with a single positive peak. Shape indices of excitatory post‐synaptic potentials (e.p.s.p.s) recorded in conjunction with simple t.p.s indicate that these e.p.s.p.s were generated at an electrotonically confined compartment on the motoneurone somadendritic membrane. 3. Compound t.p.s. were similar ones, except that they had two or more positive peaks. Shape indices of e.p.s.p.s recorded in conjunction with compound t.p.s indicate that these e.p.s.p.s were generated at two or more electrotonically separate compartments. 4. E.p.s.p. latency and post‐synaptic electrotonic delay were determined for a group of single fibre e.p.s.p.s with simple t.p.s. The shortest recorded latency was 0.26 msec. By subtracting estimated electrotonic delay, the shortest synaptic delay obtained for a medial gastrocnemius Ia single fibre e.p.s.p. was 0.17 msec. 5. The finding of a significant synaptic delay supports the hypothesis that the Ia‐motoneurone synapse is a chemically mediated synapse.
Changes in rodent muscle fibre types during post‐natal growth, undernutrition and exercise.
Authors: Goldspink G , Ward P S
Published: December 2014

1. Using histochemical staining methods for myosin ATPase oxidative and glycolytic enzymes, three major types of muscle fibre could be identified in the skeletal muscle of hamsters and mice. 2. Muscle fibre counts showed that the proportions of the different fibres were not entirely stable with age. In the hamster biceps brachii which is predominantly composed of ATPase‐high fibres there was a decrease in the number of ATPase‐low fibres. In the soleus muscle which is predominantly composed of ATPase‐low fibres there was a decrease in ATPase‐high fibres with age. 3. Although there was a change in the proportions of fibre types there was no change in the total number of fibres within the muscles with age. It is suggested that some reinnervation may take place during growth and that this is why the less dedominant fibre type decreases. 4. The response of the different fibre types to partial starvation was studied. The ATPase‐high fibres showed the greatest decrease in size. Of these, the ATPase‐high glycolytic type responded more than the ATPase‐high oxidative type. The effects of the under‐nutrition on the different fibre types were found to be completely reversible. Starvation did not affect the total number of fibres or the numbers of any fibre type. 5. The response of the different types to high intensity exercise (weight lifting) was studied. This type of exercise resulted in hypertrophy of all three major fibre types. However, the extent of the response varied according to the fibre type and the exact nature of the exercise. In most cases the ATPase‐high fibres underwent hypertrophy more readily than the ATPase‐low fibres. Where distinction was made between the two types of ATPase‐high fibres, the ATPase‐high glycolytic were found to hypertrophy more than the ATPase‐high oxidative fibres. The effects of post exercise recovery (return to relative inactivity) were also studied and the changes in size of the fibres were found to be completely reversible.
Thyroid hormones and the energetics of active sodium‐potassium transport in mammalian skeletal muscles.
Authors: Biron R , Burger A , Chinet A , Clausen T , Dubois‐Ferrière R
Published: December 2014

1. The steady‐state heat production rate (E) of soleus muscles obtained from adult mice in various thyroid states was measured in a perfused microcalorimeter. The ouabain‐suppressible fractions of E and 42K influx were compared and the energetic efficiency of active Na‐K transport assessed. 2. Hypothyroidism with plasma thyroxine concentrations below 1 microgram/100 ml. was induced by pretreatment with 131I or perchlorate. In soleus muscles isolated from treated animals, mean E values were 25.1 +/‐ 0.7 and 24.2 +/‐ 0.5 mcal.g wet wt.‐1.min‐1 for the 131I and the perchlorate series respectively, i.e. about 30% lower than the control level (36.3 +/‐ 1.5 mcal.g wet wt.‐1.min‐1). Following triiodothyronine treatment, E was increased by about 45%. 3. In muscles from hypothyroid (131I and perchlorate series), euthyroid and hyperthyroid mice ouabain (10(‐3) M) induced a rapid decrease in E of 1.6 +/‐ 0.1 and 1.4 +/‐ 0.1, 2.5 +/‐ 0.2, and 4.3 +/‐ 0.6 mcal.g wet wt.‐1.min‐1 respectively, i.e. between 6 and 8% of E. 4. In muscles obtained from hypothyroid, euthyroid and hyperthyroid mice, the ouabain‐suppressible component of 42K influx was 0.17 +/‐ 0.04, 0.31 +/‐ 0.02 and 0.45 +/‐ 0.02 micromole. g wet wt.‐1.min‐1 respectively. Whereas the total number of ouabain binding sites varied appreciably with the thyroid status, the Na‐K contents of soleus or diaphragm muscles showed no significant changes. 5. Notwithstanding the parallelism between the changes in basal E and ouabain‐sensitive components of E and K influx with the thyroid status, it is concluded that active NA‐K transport cannot be considered a primary effector of thyroid thermogenesis in intact mammalian skeletal muscle. The direct contribution of active NA‐K transport to this thermogenesis was indeed small compared with the over‐all cellular energy dissipation. 6. The minimum over‐all energetic efficiency of the transport process in the intact muscles (30‐‐35%) was not dependent on the thyroid status.
Localization of synaptic input on dendrites of a lamprey spinal cord neurone from physiological measurements of membrane properties.
Authors: Christensen B N , Teubl W P
Published: December 2014

1. Composite excitatory post‐synaptic potentials (e.p.s.p.s) resulting from electrotonic and chemical synaptic junctions were recorded from eighteen interneurones following stimulation of the I2 burster axon in the isolated lamprey spinal cord. 2. In each cell, the half‐width of the electrotonic e.p.s.p. was measured and used, together with the cable parameters estimated for the same neurone, to locate the position of synaptic contact made by the I2 axon on the dendrites of the interneurone. The synaptic location ranged from 0.05 to 1.35 space constants with a mean of 0.46. 3. The synaptic potential was simulated using the Rall model of the neurone. When compared with the experimentally recorded e.p.s.p. with the same half‐width, the rise‐time of the simulated synaptic potential was found to be faster. By changing the value of synaptic distance and/or synaptic current duration the half‐width, rise‐time, and decay of the simulated synaptic potential fit closely the experimental e.p.s.p. The range of synaptic distance estimated from the simulation decreased considerably (0.2‐‐0.7 space constants; mean 0.52). 4. Direct comparison of synaptic location estimated from histological tracings of dendritic trees from these same cells injected with horseradish peroxidase compared favourably with synaptic location estimated from the simulations. 5. These results support the hypothesis that functionally similar presynaptic axons make synaptic connexions at the same electrotonic distance from the soma on functionally similar post‐synaptic cells. This occurs in the face of large variations in physical distance for these same synaptic contacts.
Permeability of the fenestrated capillaries in the cat submandibular gland to lipid‐insoluble molecules.
Authors: Mann G E , Smaje L H , Yudilevich D L
Published: December 2014

1. Permeability‐surface area products for the fenestrated capillaries in the perfused cat submandibular gland have been measured for graded lipid‐insoluble molecules using the single‐passage, multiple‐tracer dilution technique. 2. The permeability‐surface area for [57Co]cyanocobalamin (mol. wt. 1353) increased as the perfusion flow was increased, but reached a constant value of 4.11 +/‐ 0.25 ml.min‐1.g‐1 (mean +/‐ S.E., n = 9) at flows above 8 ml. min‐1.g‐1. For [125I]insulin (approximate mol. wt. 6000) it was 1.80 +/‐ 0.13 ml.min‐1.g‐1 (mean +/‐ S.E., n = 9) and apparently diffusion‐limited at all the high flow rates studied. A similar permeability‐surface area product was measured for [14C]inulin (mol. wt. 5500): 1.76 +/‐ 0.10 (mean +/‐ S.E., n = 4). 3. Permeability‐surface area values for cyanocobalamin and insulin in the salivary gland are respectively about 20 and 200 times larger than the estimates reported for the continuous capillaries of cardiac and skeletal muscle. 4. The permeability‐surface area (PS) ratio [57Co]cyanocobalamin/[125I]insulin (2.33 +/‐ 0.15, mean +/‐ S.E., n = 9) was significantly greater than the apparent ratio of their free diffusion coefficients (1.76), suggesting restricted diffusion of insulin relative to cyanocobalamin across the capillary endothelium. 5. Permeability‐surface area products for the smaller molecular weight tracers (22Na, 86Rb and 51Cr‐EDTA (mol. wt. 357)) increased continuously with perfusion rate, indicating flow‐limited solute exchange. The PS ratio of Rb/EDTA was close to unity whereas the corresponding free diffusion ratio is 3.85. 6. The high permeability‐surface area values measured were thought to be associated with the fenestrae which appeared to act as high concentrations of ‘small pores’ rather than as ‘large pores'.
The trophic influence of tetrodotoxin‐inactive nerves on normal and reinnervated rat skeletal muscles.
Authors: Bray J J , Hubbard J I , Mills R G
Published: December 2014

1. Nerve impulses in the rat sciatic nerve were blocked for long periods by tetrodotoxin (TTX) released from capillary implants. The TTX capillaries did not block axonal transport, nor did they cause any sign of nerve degeneration. 2. A comparison of the effects of TTX paralysis and denervation was made on both extensor digitorium longus (e.d.l.) and soleus muscles over 21 days, a time when the products of nerve degeneration were unlikely to contribute to the changes associated with denervation. The resting membrane potential of TTX‐paralysed muscles was significantly different (P less than 0.005) from that of the denervated muscles at all periods and at 21 days the decrease that can be attributed to inactivity was 61% (e.d.l.) and 49% (soleus) of that which follows denervation. This disparity was even more pronounced for the ACh receptor density where the increase in receptors due to inactivity was only 34% (e.d.l.) and 21% (soleus) of that due to denervation. 3. A similar comparison was made on muscles which had been reinnervated by TTX‐inactive nerves. These muscles were found to have a significantly higher resting membrane potential and lower ACh receptor density than the denervated muscles (P less than 0.05). 4. The experiments on reinnervated muscles preclude the possibility that nerve degeneration products are solely responsible for the difference between the TTX‐paralysed and denervated muscles and suggest that the difference can be attributed to the trophic influence of the nerve. 5. An observed increase in the m.e.p.p. frequency of the TTX‐paralysed muscles indicated that nerve action potentials play a role in regulating the spontaneous release from nerve terminals.
Evidence supporting the indirect depolarization of primary afferent terminals in the frog by excitatory amino acids
Authors: Evans R. H.
Published: December 2014

1. Isolated hemisected spinal cords of the frog have been used to investigate the way excitant amino acids depolarize primary afferent fibres and terminals.

2. GABA and excitant amino acids caused depolarization in dorsal roots. But dorsal roots sectioned at the point of exit from the spinal cord responded only to GABA.

3. Prolonged application of kainate or
N‐methyl‐
D‐aspartate to hemicords caused a depolarization of dorsal roots in association with an increased extra‐cellular [K+]. The two effects decayed with similar time courses. The depolarization recorded from ventral roots was maintained in the presence of the excitants.

4. Field potentials, elicited by electrical stimulation of ventral roots and recorded in the ventral horn of Mg blocked preparations, were abolished by prolonged treatment with kainate. Corresponding dorsal horn field potentials elicited by electrical stimulation of dorsal roots were resistant to the presence of kainate.

5. Excitability of motoneurones or afferent terminals was measured from the amplitude of action potentials evoked by submaximal cathodal stimulation of ventral or dorsal horns and recorded in ventral or dorsal roots respectively. Prolonged application of kainate to Mg blocked preparations abolished the excitability of motoneurones within 5 min, but the excitability of primary afferent terminals was increased and maintained for several hours.

6. These observations support the hypothesis that primary afferent terminals in the frog do not have receptors for excitatory amino acids and that depolarization of terminals induced by excitatory amino acids is mediated through release of K from other cells within the dorsal horn.
Inhibition of transmitter release in bullfrog sympathetic ganglia induced by gamma‐aminobutyric acid.
Authors: Kato E , Kuba K
Published: December 2014

1. Effects of gamma‐aminobutyric acid (GABA) on the nicotinic synapses in bullfrog sympathetic ganglia were studied. 2. When GABA (100 microM‐‐1 mM) was applied to the ganglion, the post‐synaptic membrane depolarized slightly and transiently with a slight decrease in the membrane resistance. 3. GABA (5 microM‐‐1 mM) decreased the amplitude of the fast excitatory post‐synaptic potentials (fast e.p.s.p.) and its quantal content without a significant change in the quantal size, and these effects were seen even after the subsidence of the membrane depolarization. Picrotoxin (10 microM) did not antagonize the GABA action. 4. The sensitivity of the subsynaptic membrane to ACh was unaffected by GABA. On the other hand, the synaptic current underlying the fast e.p.s.p. was significantly depressed in the presence of GABA. 5. Neither the frequency nor the amplitude of the miniature e.p.s.p.s which occurred spontaneously were altered by GABA, in either normal or high K+ solutions. 6. The depressant action of GABA on the fast e.p.s.p. was not changed in a high K+ solution, while it was markedly decreased in a Cl‐ ‐deficient solution. 7. A small, but significant reduction in the amplitude of the presynaptic terminal spike recorded with a focal extracellular electrode was observed under the effect of GABA. 8. It was concluded that GABA inhibits synaptic transmission of bullfrog sympathetic ganglion mainly by decreasing the evoked release of transmitter and only partly by post‐synpatic action. Possible mechanisms of the presynaptic action of GABA were discussed.
Enkephalin inhibits the release and action of secretin on pancreatic secretion in the dog.
Authors: Chey W Y , Coy D H , Konturek S J , Schally A V , Tasler J
Published: December 2014

1. Pancreatic bicarbonate and protein secretion as well as immuno‐reactive plasma secretin concentration in response to a meal, duodenal acidification and exogenous secretin or octapeptide of cholecystokinin (OP‐CCK) have been measured following administration of methionine‐enkephalin in chronic pancreatic fistula dogs. 2. Methionine‐enkephalin inhibited pancreatic responses to both exogenous hormones (secretin and OP‐CCK) and to endogenous hormones released from the gut by food or duodenal acidification. 3. Naloxone, a potent opiate receptor antagonist, partly prevents this methionine‐enkephalin‐induced inhibition of pancreatic secretion suggesting that this effect might be mediated by opiate receptors. 4. The inhibitory effect of methionine‐enkephalin on pancreatic response to endogenous stimulants was more pronounced than that to exogenous hormones and was accompanied by a significant reduction in plasma immuno‐reactive secretin concentration. 5. This study indicates that methionine‐enkephalin inhibits pancreatic secretion, at least in part, by suppressing the release of the intestinal hormones stimulating the exocrine pancreas.
Interaction of impulse activities originating from individual Golgi tendon organs innervated by branches of a single axon.
Authors: Fukami Y
Published: December 2014

1. Both physiological and morphological studies revealed that cat tail muscles contain at least one pair of Golgi tendon organs innervated by branches of a single axon. 2. Fifteen pairs of such organs were subjected to physiological studies. It was found that, depending on the experimental conditions, two modes of interaction, ‘resetting’ and ‘impulse mixing’ may occur between impulse activities originating from individual tendon organs. 3. When a single action potential was elicited from one of a pair of Golgi tendon organs during an interimpulse interval of a train of impulse discharge originating from the partner organ, the subsequent impulses in the train were delayed ('resetting'). Similarly, if both organs were stimulated individually by a mechanical pulse to elicit a train of discharge, then during stimulation of both, only the response of one responding with higher frequency discharge was seen in the parent axon, the impulse activity of the partner organ being completely suppressed during this period. 4. Using the conditioning‐test technique it was demonstrated that the initiation of an action potential in one of a pair of Golgi tendon organs caused a significant decrease in excitability of the partner organ to mechanical stimulation. 5. Mixing of impulse discharges originating from individual Golgi tendon organs was shown to occur during stimulation of both by suprathreshold short mechanical pulses. 6. The functional implication of the above results has been discussed.
Gastrin cell proliferation after chronic stimulation: effect of vagal denervation or gastric surgery in the rat.
Authors: Alumets J , El Munshid H A , Håkanson R , Hedenbro J , Liedberg G , Oscarson J , Rehfeld J F , Sundler F , Vallgren S
Published: December 2014

Chronic stimulation of the antral gastrin cells by elevated antral pH was achieved by fundectomy, antrum exclusion, fundectomy plus antrum exclusion, antrocolic transposition, and vagal denervation plus pyloroplasty. For comparison we studied also the effects of pyloroplasty alone and of portacaval shunting. All operations that elevated the antral pH resulted in high gastrin concentrations in serum. Particularly high concentrations were observed in fundectomized rats. Vagal denervation of fundectomized or antrum excluded rats reduced the serum gastrin concentration slightly compared with the corresponding innervated animals. Portacaval shunting reduced the gastrin concentration in serum. The antral gastrin concentration was raised or unchanged following fundectomy and vagal denervation, and reduced following antrum exclusion, antrum exclusion plus vagotomy, fundectomy plus antrum exclusion, fundectomy plus vagotomy, antrocolic transposition and portacaval shunt. The gastrin cell density in the antral mucosa was raised following fundectomy, vagotomy, and fundectomy plus vagotomy, unchanged following fundectomy plus antrum exclusion and antrocolic transposition, and reduced following antrum exclusion and portacaval shunting. Ultrastructurally the gastrin (G) cells in the excluded antrum and in the antrum of fundectomized rats showed signs of secretory activity in that the granule volume density or the number of granules per unit cytoplasm was lowered. In the fundectomized rats moreover, the endoplasmic reticulum of the G cells was increased, the Golgi area enlarged and the proportion and volume density of electron dense granules greatly increased. The granule profile diameter was not affected by either antrum exclusion or fundectomy. The results on the excluded antrum indicate that elevated antral pH per se is not sufficient to produce gastrin cell proliferation. In the fundectomized rats, where the hyperlasia of antral gastrin cells was considerable, there is the added stimulus of ingested food. In fundectomized plus antrum excluded rats this stimulus is eliminated and no proliferation ensues. The passage of intestinal material, as in the rats subjected to antrocolic transposition, did not elicit gastrin cell proliferation which seems to suggest that the character of the luminal material is important. We propose therefore that gastrin cell proliferation is due to the combined stimulation of high antral pH and passage of food. Vagal innervation is not required.
The adequacy of stretch receptors in the cat knee joint for signalling joint angle throughout a full range of movement.
Authors: Ferrell W R
Published: December 2014

1. The present experiments were performed to resolve the discrepancy between the experiments of Boyd & Roberts (1953) in which receptors active at intermediate angles (mid range units) were frequently encountered, and the experiments of Burgess & Clark (1969) where mid range units were rarely encountered. 2. The discharge of knee joint afferents in the cat posterior articular nerve was recorded from both the dorsal roots and from the intact joint nerve. 3. No receptors were isolated which exhibited intermediate adaptation rates (similar to the "phasic" receptors described by Burgess & Clark, 1969). 4. The proportion of mid range units isolated in the present experiments (17.8%) was substantially larger than in the experiments of Burgess & Clark (4.8%). 5. Direct recordings from the posterior articular nerves of a series of cats revealed that there were always receptors tonically active at all intermediate positions. 6. Afferents from the popliteus muscle did not make a major contribution to the population of mid range units in the posterior articular nerve as removal of the popliteus muscle did not significantly alter the mean number of mid range units in the joint nerves of a series of nine cats. 7. Succinylcholine (SCh) in low doses (0.05‐0.1 mg/kg) was found not to be specific for spindle afferents as these doses of SCh could elevate the resting discharge of mid range units of true articular origin. 8. It is concluded that slowly adapting joint receptors can adequately signal joint angle throughout the full normal range of movement and hence could make an important contribution to position sense.
Protan‐like spectral sensitivity of foveal Y ganglion cells of the retina of macaque monkeys.
Authors: de Monasterio F M , Schein S J
Published: December 2014

1. The spectral sensitivity of two varieties of macaque Y ganglion cells with a centre‐surround organization, type III (non‐colour opponent) and type IV (broad‐band colour opponent), was examined with test stimuli of different size, shape and wave‐length. 2. The spectral sensitivity of type III cells to large stimuli decreased at the long wave‐lengths with decreasing retinal eccentricity; this change was due to a lower sensitivity of green‐sensitive than of red‐sensitive cone input to the surround of foveal cells, which resulted in stronger surround antagonism at the long than at the short wave‐lengths leading to a rudimentary form of colour opponency. 3. The spectral properties of foveal type III cells were intermediate between those of perifoveal type III cells, whose surrounds receive a rather similar input from both cone types, and of the predominantly foveal type IV cells, whose surrounds appeared to lack input from green‐sensitive cones. 4. The results indicate that both cell types represent varieties within a continuum of a single macaque Y‐cell system which has a reduced long‐wave‐length sensitivity in the foveal region. The fact that a similar reduction of long‐wave‐length sensitivity can be observed in (foveal) macaque photopic luminosity functions measured with different techniques by different authors suggest that both types of Y cell have an important role in the processing of luminance information.
The effect of buffer composition and deoxygenation on the concentration of ionized magnesium inside human red blood cells.
Authors: Flatman P W
Published: December 2014

1. A method is described in which the concentration of ionized magnesium can be measured in intact red cells. The method uses an equilibrium dialysis technique originally developed by Ferreira & Lew (1976) and Flatman & Lew (1977) where the magnesium permeability of the red cell membrane is increased with the ionophore A23187. 2. The concentration of ionized magnesium in the oxygenated cells was found to be 0.39 mM and was not greatly affected by changes in the composition of the medium. 3. The concentration of ionized magnesium in deoxygenated cells showed more dependence on the composition of the medium. Values of 0.54 and 0.62 mM were found in cells incubated in Tris‐ and HCO3‐ buffered media respectively. The difference probably reflects increased competition between chloride and 2,3‐diphosphoglycerate for common binding sites on haemoglobin in Tris‐buffered cells. 3. Only a small increase of 0.16‐0.22 mM was found in the concentration of ionized magnesium when the cells were deoxygenated. These changes are smaller than had been anticipated from estimates of the binding of ATP and 2,3‐diphosphoglycerate to oxy‐ and deoxyhaemoglobin (Bunn, Ransil & Chao, 1971; Berger, Jänig, Gerber, Ruckpaul & Rapoport, 1973; Gerber, Berger, Jänig & Rapoport, 1973) and are unlikely to alter greatly the operation of magnesium‐dependent metabolic or transport systems.