• Inderjit Singh

      Articles written in Proceedings – Section B

    • The effect of hydrogen ions and tonic contraction on the viscosity of unstriated muscle

      Inderjit Singh

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      Plain muscle is capable of great changes in viscosity. The viscosity of plain muscle is about 100 to 1,000 times that of striated muscle and its movements correspondingly slower.

      The viscosity of plain muscle increases as a result of tonic contraction, but is decreased during active contraction.

      Hydrogen ions increase the viscosity; the optimum pH is 7·8, change on either side increasing the viscosity. The excitability is maximum at this pH.

      Substances that decrease the rate of relaxation, increase the viscosity; plain muscle is thus able to keep up tension without expenditure of energy. During active contraction, viscosity decreases to facilitate movement.

    • Isotonic extension of unstriated muscle

      Inderjit Singh

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      There are many variables involved in the extension of plain muscle. These are (1) tone, (2) viscosity, (3) extending force, (4) tonic contraction, (5) adaptation, (6) change of contraction with length, (7) change of viscosity with length, (8) change of viscosity with time, (9) stretch, (10) restoring force.

    • Surface and interior effects in unstriated muscle produced by various ions

      Inderjit Singh

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      Ions such as potassium, ammonium, hydrogen, to which the mu scleis permeable, neutralise the contractures produced by ions to which the muscle is comparatively less permeable, such as sodium chloride, adrenaline, acetylcholine. This suggests that excitation is caused by difference in concentrations of ions within and without the cells.

    • Reversal effects in unstriated muscle

      Inderjit Singh

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      Hydrogen ions may convert an excitatory effect into an inhibitory one.

      Calcium, sodium chloride and caffeine may produce reversal effects.

      Presence of tone alters an excitatory effect into an inhibitory one.

      Anions may convert an inhibitory effect into an excitatory one, and cations may produce an opposite effect.

      Reversal effects are also produced by adaptation, fatigue, inexci-tability and change of length.

    • Visco-elastic properties and contraction of unstriated muscle

      Inderjit Singh

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      The similarity of the effects of ions on the protoplasmic viscosity of simple organisms and that on unstriated muscle suggest that the latter consists of a viscous protoplasmic non-contractile element. The similarity of the reactions of isolated myosin strips and isolated muscle suggests that it contains a contractile element. This view is supported by (a) the differential action of drugs, (b) viscous elastic properties of plain muscle, and by its histological picture.

      Similarity of the responses of isolated muscle and isolated myosin suggests that plain muscle can contract without the use of oxygen.

    • The electrical resistance of unstriated muscle and other tissues and its relation to permeability and excitability

      Inderjit Singh Inderjit Singh

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      As shown by the effect of death, resistance of the muscle to alternating current of low frequency is a measure of the permeability of the cell.

      Permeability is high at low and high temperatures; frog muscle if heated beyond 35°C. and mammalian muscle beyond 40°C, is irreparably damaged, the resistance being permanently lowered.

      Cations such as potassium, calcium, ammonium, magnesium increase the resistance of the muscle in small concentrations.

      Anions such as Cl, Br, I, NO3, SCN, CN increase the resistance of the muscle in small concentrations.

      Drugs and narcotics such as adrenaline, caffeine, novocaine, chloral hydrate, ether, chloroform, ethyl alcohol, butyl alcohol, octyl alcohol increase the resistance in small and decrease it in large concentrations.

      Inhibition and narcosis are associated with increased resistance or decreased permeability. Increased excitability to ions without is associated with an opposite change. Excitability to electric current is increased with diminished permeability.

      For excitation an optimum permeability is necessary.

      The resistance of frog skin is higher than that of muscle.

    • Errata

      Inderjit Singh

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    • Adaptation or accommodation in unstriated muscle

      Inderjit Singh

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      There are two kinds of adaptation to alternating current. During one, the sensitivity to potassium decreases, and during the other, it increases. One is probably produced by calcium, and the other by ions outside.

      There are two kinds of adaptation to chemical stimulation; one is similar to the first kind of adaptation to A.C. and the second one is probably due to diffusion of ions into the muscle fibres. This kind of adaptation also occurs to A.C.

      Adaptation may be diminished by (a) leakage of the adaptation factor, (b) neutralisation of the same or (c) or inhibition of adaptation. This last appears to be responsible for tonic withdrawal contractions.

      Adaptation increases with length.

      Adaptation and fatigue are identical.

    • The effect of temperature and ions on the impedance of unstriated muscle and its relation to permeability and excitability

      Inderjit Singh Sunita Inderjit Singh

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    • Indirect stimulation of unstriated muscle - A preliminary communication

      B Narayana Inderjit Singh

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      The excitation produced by vagus stimulation has an inhibitory component.

      Tonus is antagonistic to vagus stimulation.

      The optimum temperature for vagus stimulation is 30° C.

      The optimum concentration of calcium is about 0·05-0·07 M CaCl, potassium about 0·06 M KCl and hydrogen ions, pH 7·8-7·4.

      The stimulation produced by vagus and acetylcholine does not belong to the potassium group. It resembles more that produced by alternating current.

    • Excitation in unstriated muscle

      Inderjit Singh

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      Excitatory phenomena in unstriated muscle can be explained if it is assumed that the muscle consists of two zones, outer and inner, and excitation be due to difference in concentration of ions in these two zones. Moderate increase in permeability would diminish the excitability to alternating current and increase that to potassium; great increase would dimmish the excitability to both. An increase in the permeability of the outer membrane by physiological action, injury, asphyxia would cause excitation or inhibition. Spontaneous contractions are caused by increase in permeability, not great enough to cause continuous tension. Substances to which the muscle is moderately permeable, such as sodium and barium, produce continuous tension as they are unable to enter the inner zone. Substances to which the muscle is more permeable such as ammonium or potassium produce only a temporary contraction.

    • The swelling of unstriated muscle produced by certain ions and its relation to permeability, excitability, absorption and secretion

      Inderjit Singh

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      Mytilus muscle gains base when immersed in solutions of cations in the order Li< Na< NH4 < K; Ca < Sr < Ba. The physiological activity varies not in the order of the swelling produced by ions, but the gain in base. This gain of base appears to be determined by permeability. As the exciting and inhibitory power of ions varies in the same order, it is therefore concluded that excitation or inhibition depends upon a common factor, such as the permeability of the membrane. It is suggested that the mechanism of absorption and secretion by cells depends upon its colloidal reactions.

    • The effect of Ammonium on the potassium content of unstriated muscle and its relation to the contraction produced on withdrawal of chemical substances from around the muscle

      S K Gokhale Inderjit Singh

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      In frog stomach muscle, ammonium enters the cells and replaces potassium; this is associated with the ammonium withdrawal contraction having the properties of the A.C. contraction.

      In dog muscle there is no significant difference between the potassium contents of muscles soaked in normal saline, and in ammonium-rich saline respectively; with this is probably associated the absence in dog muscle of the ammonium withdrawal contraction having the properties of the A.C. contraction.

      Ammonium causes greater replacement of potassium than the tetra-ammonium salts; with this is probably associated the fact that the latter do not produce a contraction on withdrawal, similar to that of ammonium in frog muscle. Withdrawal of the latter salt produces a tonic contraction similar to that produced by withdrawal of ammonium in dog muscle.

      There is greater loss of potassium produced by ammonium in alkaline than in acid solutions; but there is greater loss of potassium in a potassium-free saline in acid solutions. As the ammonium withdrawl contraction in frog muscle is more marked in acid than in alkaline solutions, it suggests that the contraction is due to the outward passage of the ammonium ion.

      Slow relaxation of a contraction produced by a chemical substance may be due to tonic contraction on withdrawal of the substance or to persistence of the previous contraction, probably due to increase in viscosity of the muscle.

    • Reversal of the effect of acetylcholine on the frog heart with normal vagus action; tetanisation of the frog heart; Graded responses in the frog heart; the effect of electrolyte free-medium

      Inderjit Singh Kumar Bhanu Sehra Sunita Inderjit Singh

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      Frogs were encountered, the stomachs and hearts of which were refractory to the action of acetylcholine, even after eserine. In the hearts, the beats were augmented by acetylcholine, but diminished by vagus stimulation. They could be tetanised, and the responses with electrical stimulation were graded. The aurides and ventricles beat rhythmically but independently in the absence of electrolytes.

    • The mode of action of potassium on unstriated muscle

      Inderjit Singh

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      The action of potassium, calcium and sodium suggest that they exist in the combined and free form in the unstriated muscle, they respectively determine the excitatory, inhibitory and tonic and viscous states in the muscle.

      One of the actions of potassium is due to its difference in concentration on the two sides of the muscle membrane. This is shown by the fact that the optimum concentration of potassium in the saline for excitability depends upon its concentration inside the fibres. For maximum excitability there is an optimum ratio of potassium on two sides of the muscle membrane.

      The second action of potassium is probably on the cell membrane as it is antagonised by calcium.

      A third action of potassium is probably on the muscle colloid as it affects the viscosity of the muscle.

    • The mode of action of drugs on unstriated muscle and the nature of inhibition

      Inderjit Singh

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      Both adrenaline and acetylcholine produce contraction of unstriated muscle in the electrolyte-free medium, suggesting that their action is due to mobilisation of ions within the fibres.

      They also produce contractions or inhibitions resembling those produced by ions outside the fibres; this suggests that they may also act by sensitising the muscle to ions outside.

      Acetylcholine produces two kinds of contractions in the unstriated muscle.

      Inhibition is really an excitatory process, masked by adaptation.

      Adrenaline inhibition is antagonised by potassium, ammonium, electric current, hydrogen ions, and increase in osmotic pressure; it is potentiated by calcium, hydrogen ions, and also by electric current. Adrenaline thus produces two kinds of inhibitions.

      Eserine acts by means other than combining with choline-esterase.

      Ephedrine potentiates adrenaline also by a process of summation.

      Drugs produce a contraction, which is a class by itself.

      The optimum temperature for adrenaline inhibition is 30°

    • The relation of permeability to adaptation in unstriated muscle

      Inderjit Singh

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      A hydrostatic model is described to explain adaptation in unstriated muscle.

    • Comparative physiology of unstriated cardiac, and striated muscles

      Inderjit Singh

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      Unstriated, cardiac and striated muscles show differential action of substances on the excitability to electrical stimulation and potassium.

      The response to nervous stimulation and acetylcholine may be similarly or oppositely affected.

      Muscle shows adaptation to temperature.

      Tonus may be shown by three kinds of muscle; one kind of tone in unstriated muscle is similar to the contracture of striated muscle.

      In all the three kinds of muscle, twitch is antagonistic to contracture; a synergistic contracture also occurs.

      In some instances, there is a gradation in the properties of unstriated, cardiac and striated muscles.

      Adaptation to electric current is more rapid in unstriated than in striated muscle.

      Many drugs and ions act similarly on the three kinds of muscle.

      Many agencies affect excitation and inhibition similarly.

      The properties ofMytilus muscle and the motor end plate of striated muscle are in many respects similar.

    • Erratum

      Inderjit Singh

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    • The effect of some metals, vitamins, anÆsthetics, and other substances on unstriated muscle

      Inderjit Singh Sunita Inderjit Singh

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    • Tonus in unstriated muscle

      Inderjit Singh Inderjit Singh

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      No single explanation of tonus in unstriated muscle can suffice as there are two kinds of tonic contractions, one with and the other without oxygen usage. The former is akin to ordinary contraction and the latter to some structural change in muscle. It is suggested that in tonic contractions without oxygen usage, myosin forms a stable compound with some ions in the muscle fibres, while in twitch such a compound is unstable. The two factors which combine with myosin to form the contractible compounds of tonic and twitch contractions respectively are mutually exclusive in their combination with myosin; this explains many tonic and twitch phenomena in unstriated muscle.

    • Errata

      Inderjit Singh Sunita Inderjit Singh M C Muthana

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    • (I) The interaction between ions drugs and electrical stimulation as indicated by the contraction of avian unstriated muscle. (II) active elongation of unstriated muscle

      Inderjit Singh Sunita Inderjit Singh M C Muthana

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      The responses of avian plain muscle in general resemble those of mammalian plain muscle.

      Eserine has little or no potentiating effect on the action of acetylcholine.

      In sodium deficient solutions, the gut elongates activity when stimulated with alternating current.

      In a muscle inexcitable to nervous stimulation, alternating current produces its usual effects.

    • The mode of action of nerves on unstriated muscle

      Inderjit Singh Sunita Inderjit Singh

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      The nature of response of frog’s stomach muscle to nervous stimulation is described. The contraction is similar to that produced by acetylcholine and potassium, and is not of the same type as that produced by alternating current, suggesting that acetylcholine is liberated during nervous stimulation of frog’s stomach. Excitation by nervous stimulation appears to involve the potassium ion.

      Nervous stimulation also produces a contraction similar to that produced by alternating current, thus suggesting that electrical transmission precedes chemical. It is suggested that chemical transmission imparts tome properties to the effects of electrical transmission.

      On nervous stimulation, circular fibres of the stomach give the second kind of contraction, and longitudinal the first kind or tonic contraction. It is probable that the function of the longitudinal fibres is to maintain a tonic pressure on its contents and prevent the sagging of the stomach, and that of the circular fibres is to mix the contents by rhythmic contractions, as well as to exert a tonic pressure.

    • The effect of the interaction between ions, drugs and electrical stimulation, as indicated by the contraction of human unstriated muscle

      A K M Khan Inderjit Singh

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      Human unstriated muscle differs from unstriated muscle of lower animals in the following respects:

      The optimum temperature for excitability is higher, 37°.

      Many substances affect the tone as well as the excitability to alternating current and potassium similarly. It is suggested that this is due to decrease of adaptation, as an increase produces inhibition.

    • The action of direct current on unstriated muscle

      Inderjit Singh Sunita Inderjit Singh

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      The properties of the contraction produced by break of a constant current are similar to those of the alternating current off-contracture; the make contraction resembles that produced by alternating current.

      The muscle responds to break of a constant current when it may be inexcitable to all other forms of stimulation; it may respond when all the sodium chloride of the saline is replaced with chlorides of lithium, ammonium, potassium, calcium, magnesium and strontium or in acid solutions (pH 5).

      Magnesium and adrenaline abolish the break contraction.

      The response differs with polarity of the direct current; this suggests that the permeability of the membranes is different in the two directions. Stimulation by alternating current is probably due, therefore, to rectification.

      The make and the break contractions bear a reciprocal relation to each other.

      With polar stimulation, the results are very complicated; contraction or inhibition may occur at the anode or the cathode on make or break of the current.

    • The effect of asphyxia on the mechanical response of the frog’s unstriated muscle and its relation to tonus

      Inderjit Singh Sunita Inderjit Singh

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      Asphyxia at first increases the response of frog’s unstriated muscle; this is followed by diminution and then paralysis. These effects are also produced by cyanide. This increase in excitability is not abolished by iodoacetic acid.

      Asphyxiai arrest is relieved by glucose, potassium and the other substances that produce tonic contraction.

      In the presence of oxygen the muscle becomes hyperirritable in acid solutions and so possesses different aerobic metabolic mechanisms in alkaline and acid solutions respectively.

      In acid solutions, pH 6, sodium lactate, acetate and propionate improve the response to alternating current.

      Asphyxia does not produce rapid arrest of movement in muscle poisoned with iodoacetic acid.

      In a muscle poisoned with iodoacetic acid, then exhausted by frequent stimulation in asphyixia, and then revived by oxygen, sodium lactate and sodium butyrate improve the response. Glucose, glycine, sodium acetate and propionate have no effect.

      In asphyxia, tone at first decreases and then increases; this asphyxiai contraction is identical with tone that does not use oxygen.

    • Neuromuscular transmission in frog’s unstriated muscle

      Inderjit Singh Sunita Inderjit Singh

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      The neuromuscular junction in frog’s unstriated muscle is more susceptible than the muscle to fatigue, toxic action of substances and oxygen lack.

      Calcium and potassium are necessary for neuromuscular transmission.

      Spontaneous contractions and those produced by electric current are myogenic.

    • Tonus and inhibition in unstriated muscle

      Inderjit Singh

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    • The action of ions and drugs on the effects of asphyxia on the mechanical response of unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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      There is a glycolytic system in unstriated muscle for acid solutions, as shown by the effect of glucose in improving the response both aerobically and anaerobically.

      The glycolytic system for acid solutions is antagonistic to that for alkaline solutions.

      Both the ærobic and anaerobic mechanisms for tone and twitch respectively are different both in acid as well as in alkaline solutions.

      Potassium postpones or hastens asphyxiai arrest.

      Calcium also has similar action.

      Tone producing substances act similarly to potassium.

      Riboflavine improves the response aerobically as well as anaerobically. Thiamine, ascorbic acid and nicotinic acid have no such action.

      Sudden increase of osmotic pressure of the saline relieves asphyxiai arrest.

      Glucose has inhibitory effect also in the presence of oxygen.

      Fatty acids, such as acetic, propionic and butyric also improve the response in the presence of oxygen.

      Inexcitability is of two kinds: one due to changes in the excitatory process, and other due to exhaustion of energy supplies.

    • Reactions of fatigued unstriated muscle and their relation to those of cardiac muscle

      Sunita Inderjit Singh Inderjit Singh

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    • The effect of asphyxia on the response of unstriated muscle to ions and drugs

      Inderjit Singh Sunita Inderjit Singh

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      Asphyxia at first increases the responses to potassium and acetyl-choline, then depresses them.

      The decline of excitability is affected by the nature of tone.

      The resistance to asphyxia of various responses varies in the following order: Nervous stimulation < electrical stimulation < acetylcholine < potassium.

      Tone-producing substances depress the response of asphyxiated frog’s unstriated muscle, if the latter is stimulated about once in 10–15 minutes. In mammalian muscle the result is opposite.

      Glucose has at first an inhibitory and then a stimulatory action on the response of unstriated muscle to potassium; if the metabolism is increased by raising the temperature, then, the effect becomes stimulatory the outset.

      Iodoacetic acid increases the response to potassium after a preliminary depressant effect.

      pH 6 increases the response to acetylcholine and potassium after a preliminary depressant effect.

    • The interrelation between the various metabolic mechamisms in unstriated muscle

      Inderjit Singh Sunita Inderjit Singh

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      One kind of asphyxial increase in excitability is inhibited by glucose and increased by iodoacetic acid and acid solutions.

      The second kind of asphyxial increase in excitability is increased by glucose and inhibited by iodoacetic acid and acid solutions.

      The mechanism, which produces the glycolytic asphyxial increase in excitability is antagonistic to the non-glycolytic one.

      Glucose is utilised anaerobically in two ways; one of these is the same as that in which it is utilised ærobically, and the other is antagonistic.

      Tone producing substances depress the response of asphyxiated muscle to alternating current if the latter is stimulated about once in 10–15 minutes.

      There are two anaerobic mechanisms in acid solutions; one is antagonistic to and the other same as aerobic one,

      During asphyxial increase in excitability, inhibition may be turned into contraction.

    • A separate contractile mechanism for tonus in unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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      At 20° C., dog’s stomach muscle shows the first asphyxiai contraction, but not the second.

      At 20° C., glucose loses its inhibitory action, but that of oxygen is increased; at higher temperature, the reverse happens.

      At 20° C., iodoacetic acid and cyanide also do not produce contraction.

      If the second asphyxiai contraction is prevented mechanically or if developed, is abolished mechanically, then the power to contract on asphyxiation is permanently lost. Twitch contractions can be produced, but not tonic contractions. This suggests a separate contractile mechanism for tonic contraction (alactic tone).

    • The action of various substances on the contractile mechanism of unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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    • Active elongation of unstriated muscle during inhibition, accommodation and relaxation

      Sunita Inderjit Singh Inderjit Singh

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      Dog’s stomach muscle and the human appendix relax actively after being stimulated.

      Dog’s stomach muscle relaxes actively during inhibition and accommodation.

      Relaxation is of two kinds, active and passive.

      Active relaxation is diminished by asphyxia, cyanide and partially restored by glucose.

      Active relaxation is diminished by iodoacetic acid.

      Active relaxation is diminished by substances that produce tonic contraction, such as potassium, ammonium, lithium, sodium, barium, hydrogen, ions, calcium, strontium, magnesium, bromide, nitrate, iodide, thiocyanate, acetylcholine, pilocarpine, nicotine, eserine, adrenaline.

      Methyl and ethyl alcohols diminish active elongation in small and increase in large concentrations.

      Active elongation is diminished by hypo- and hypertonic solutions.

      The optimum pH for active elongation is 8.

      The optimum temperature for active elongation is 30° C.

      Substances that depress the vitality of the muscle cause contraction by antagonising active elongation.

    • The mechanism of tonus in unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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      Frog ’s and dog ’s stomach show the predominance of alactic tone in the pyloric regeion and lactic tone in the cardiac region.

      The tone in the pyloric region has the properties of the asphyxial contraction.

      The tension due to tonic contraction of the pyloric muscle can be destroyed without affecting the twitch contraction suggesting that these two are mediated by different contractile mechanisms.

      Stretching of muscle antagonises elongation produced by distilled water and other substances.

      The muscle from the pyloric and cardiac regions behave differently in distilled water. The former contracts and the latter relaxes. These reactions are produced both in living as well as dead muscles, so it is concluded that unstriated muscle contains two kinds of contractile proteins for lactic and alactic tones respectively.

      Stretching increases the tendency to contraction and decreases that to inhibition. Asphyxia also produces similar effects.

      When increased demand is made on unstriated muscle with normal oxygen supply or normal demand with diminished oxygen supply, it puts into action a contractile mechanism which does not require energy.

    • Further observations on the effect of some substances on the contractile mechanism of unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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    • Errata

      Sunita Inderjit Singh Inderjit Singh K S Venkataramani

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    • A comparative study of the contractile mechanism of unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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      A comparative study of the contractile mechanism of frog’s, dog’s andMytilus muscles has been made.

      Sodium and potassium chlorides have identical action on the three kinds of muscles. Barium chloride and sodium cyanide cause contraction of the contractile mechanism of unstriated muscle ofMytilus and elongation of frog’s and dog’s muscle.

      Contraction of the contractile mechanism of unstriated muscle are of two kinds. One kind is relaxed by swelling of the muscle and the other kind not. Relation of this finding to the tonus mechanism is discussed.

      Action of ammonium, calcium, strontium, magnesium, bromide, nitrate, iodide and thiocyanate is described. Potassium, magnesium relax the contractile mechanism.

      The excitatory and the contractile mechanism of unstriated muscle have been dissociated by destroying the former by high voltages (110–880 volts A.C.) and by methyl alcohol. Action of substances on the contractile mechanism has then been studied.

      If normal tone of the muscle is destroyed, then the asphyxiai contraction does not occur, proving the identity of the two.

    • Active relaxation of unstriated muscle produced by adrenaline

      Sunita Inderjit Singh Inderjit Singh

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    • Lactic acid production in unstriated muscle and its relation to tonus and inhibition

      U R Bharadwaj Inderjit Singh

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    • Stimulation of unstriated muscle by change of temperature and other effects of temperature

      Sunita Inderjit Singh Inderjit Singh

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    • The mode of action of adrenaline on unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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    • Recovery of excitability from inhibition in unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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      Substances that cause excitation, hasten recovery from electrical inhibition. As inhibition is identical with accommodation, these experiments support the view, that accommodation to excitation is due to the liberation of inhibitory substances, and accommodation to inhibition, due to liberation of excitatory substances.

    • Early tension relaxation during contraction of unstriated muscle

      Inderjit Singh

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      Unstriated muscle relaxes a little prior to contraction, and the contraction curve dips below the starting level before it returns to normal; the former relaxation has been termed as LR and the latter, AR. Properties of LR, AR and adrenaline inhibition have been studied.

      LR, AR and adrenaline inhibition require an optimum length for their production.

      The optimum temperature for LR, AR and adrenaline inhibition is about 25° C.; higher temperature cause inactivation.

      Previous activity decreases LR, AR and adrenaline inhibition.

      Iodoacetic acid decreases LR, AR and adrenaline inhibition.

      Sodium cyanide abolishes the peak tension, but increases inhibition,

      LR, AR and adrenaline inhibition decrease in the absence of calcium ions; excess of calcium at first increases and then decreases these relaxations.

      Increase in hydrogen-ion concentration from pH 8 to 6, decreases LR, AR and adrenaline inhibition.

      Potassium at first increases and then decreases LR, AR and adrenaline inhibition.

      Nitrate at first increases and then decreases LR, AR and adrenaline inhibition.

      It is concluded that LR and AR are identical with inhibition and are produced by relaxation of muscle fibres.

    • Role of actomyosin in contraction of unstriated muscle

      Inderjit Singh Sunita Inderjit Singh

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      Experiments have been performed on dying muscles. In such muscles, the excitatory system is destroyed and the substances act directly upon the contractile mechanism. The excitatory system was also rendered inoperative by chloroform.

      In such muscles 0·1–0·3M KC1 produces contraction, and higher concentrations (0·4 to2 M) produce passive relaxation. This suggests that contraction is due to association and relaxation to dissociation of actomyosin.

      Urea and thiourea produce active relaxation. As urea is also known to produce dissociation of actomyosin, these experiments suggest that the dissociation of actomyosin is of two kinds, one producing active and the other passive relaxation.

      Many salts which produce dissociation of actomyosin produce relaxation.

      Distilled water causes active relaxation.

      The effect of potassium chloride has been tested on livingMytilus muscle in normal physiological condition. These experiments also suggest that contraction is due to association and relaxation to dissociation of actomyosin.

    • Factors other than active relaxation responsible for the lengthening of unloaded unstriated muscle

      U R Bharadwaj Inderjit Singh

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      Substances that depress metabolism suppress relaxation of unloaded muscle and increase that of loaded muscle.

      It is therefore concluded that relaxation in unstriated muscle is of two kinds, one active and the other passive.

      Substances that increase metabolism may diminish the mechanical response, by simultaneously increasing active relaxation, while the muscle is contracting.

    • A comparison of the contractile systems of striated and unstriated muscles

      Inderjit Singh B B Sharma

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      The effect of various substances on the contractile mechanism of frog’s sartorius and rectus has been studied by using the dying muscle.

      It has been found that the effect of various substances on the frog’s striated muscle resembles that onMytilus unstriated muscle and not that on frog’s unstriated muscle.

      The common feature of frog’s striated muscle andMytilus muscle is, that active relaxation is absent in these muscles.

    • The effect of ions on the contractile mechanism of unstriated muscle and its relation to tonus

      Sunita Inderjit Singh Inderjit Singh

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      A new technique is described to determine the action of substances on the contractile mechanism of unstriated muscle. It consists in killing the muscle by heating it to 50° C. for a few minutes.

      The results obtained on heat killed muscle are more or less similar to those on dying muscle with minor differences.

      Active relaxation occurs if the muscle is heated to 50–60° C. As heat denatures the proteins, it appears that the process of relaxation of muscle is similar to that of denaturation of proteins. Most substances that denature proteins, cause unstriated muscle to relax actively. These experiments therefore throw light both on the process of relaxation and on that of denaturation of proteins.

      Urea, sodium cyanide, distilled water, formamide, acetamide, acids and alkalies cause active relaxation of heat killed muscle.

      Potassium chloride has similar action on heat killed muscle as on dying muscle. It causes two or three kinds of contraction. One of these is antagonised by calcium, and probably corresponds to superprecipitation of actomyosin. The other contractions are probably due to some other proteins.

      The effect of sodium chloride resembles that of potassium chloride.

      Possible mechanisms of tonus are discussed.

    • The intimate nature of muscular contraction

      Sunita Inderjit Singh Inderjit Singh

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    • The relation between the excitatory and the contractile mechanisms of muscle

      Sunita Inderjit Singh Inderjit Singh

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    • Responses of the contractile mechanism of unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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      1. The properties of the contractile mechanism of unstriated muscle have been studied by recording the contraction of heat killed muscle, produced by raising its temperature to 70° C.

      2. The effects of heat show that the contractile mechanism of unstriated muscle consists of two components; in one the relaxation is active and in the other passive. The latter again consists of two parts one of which is activated by heat.

      3. The thermal contraction of heat killed unstriated muscle resembles the phasic response of living muscle.

      4. The thermal response of heat killed unstriated muscle shows staircase and fatigue effects. It increases with initial length up to a certain point, so that there is an optimum length of muscle for its production. These phenomena in living muscle are therefore properties of the contractile mechanism.

      5. Starling’s law of the heart is also shown by thermal contraction of dead muscle.

    • Further observations on the relation between denaturation of proteins and relaxation of unstriated muscle

      Sunita Inderjit Singh Inderjit Singh

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      1. Small concentrations of methyl, ethyl, propyl and butyl alcohols cause active relaxation of the contractile mechanism of unstriated muscle; larger concentrations produce contraction.

      2. Copper sulphate, mercuric chloride, carbolic acid and formalin have similar effects.

      3. The above substances are known to produce denaturation of proteins in small concentrations and coagulation in higher concentrations; it therefore appears that active relaxation is akin to denaturation and contraction to coagulation of proteins.

    • Active relaxation of unstriated muscle produced by proteolytic enzymes and the mode of action of these enzymes

      Sunita Inderjit Singh Inderjit Singh

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    • The action of sodium and potassium on blood vessels and its relation to hypertension

      Sunita Inderjit Singh Inderjit Singh

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      1. The reaction of blood vessels to sodium and potassium ions have been studied: (a) by perfusing the hind limbs of the dog with isotonic solutions of sodium and potassium chlorides; (b) by direct microscopic observation of the blood vessels in the mesentery of the guinea pig and dog; (c) by studying the reaction of rings from dog’s aorta.

      2. The effect of the above ions on the contractile mechanism of the smooth muscle of the arterioles was studied by the dying muscle technique and by prior heating to 50°C.

      3. Sodium has a contractile and potassium, a relaxing effect on the contractile mechanism of the smooth muscle of the arterioles. This explains the role of sodium in essential hypertension.

    • The action of cholesterol on unstriated muscle and blood vessels and its relation to hypertension

      Sunita Inderjit Singh Inderjit Singh

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      1. The action of cholesterol on the excitatory and the contractile mechanisms of unstriated muscle has been described.

      2. Cholesterol causes contraction of dog’s and frog’s stomach muscle by action on the excitatory system. It changes the nature of tone, so that the muscle is unable to relax.

      3. Cholesterol increases the tone of the blood vessels of dog’s hind limbs.

      4. Cholesterol causes contraction of the contractile mechanism of unstriated muscle; this contraction is dependent upon the ionic balance.

      5. It is concluded that cholesterol may be active in later stages of hypertension, in increasing tonus of arterioles, and producing irreversibility.

    • The action of calcium on blood vessels and its relation to hypertension

      Sunita Inderjit Singh Inderjit Singh

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      1. The action of calcium on the contractile mechanism of the unstriated muscle of the arterioles has been studied by prolonged immersion of dog’s hind limbs in solutions of calcium chloride and recording the rate of flow before and after immersion for 24 hours.

      2. Isotonic solutions of calcium chloride produce a strong irreversible contraction of the arterioles. This is due to the action of calcium on the contractile mechanism.

      3. The possible role of calcium in hypertension has been discussed.

    • The antagonism between active and passive relaxation of muscle

      Sunita Inderjit Singh Inderjit Singh

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    • The action of lead on unstriated muscle and blood vessels and its relation to hypertension

      Sunita Inderjit Singh Inderjit Singh

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      1. The action of lead on the excitatory and contractile mechanism of smooth muscle is described. The latter has been determined by testing the effect of lead on dying and heat killed muscles.

      2. Lead causes contraction of smooth muscle and arterioles by direct action on the contractile mechanism. This action may be of significance in producing contraction of smooth muscle in the body and in producing hypertension.

    • Muscular contraction and relaxation

      Sunita Inderjit Singh Inderjit Singh

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    • Mechanical and electrical responses of unstriated muscle in sodium-free solutions

      Inderjit Singh Jagdish Bhatt

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      1. If frog’s stomach muscle is immersed in hypotonic sucrose solution, it maintains its excitability for about 24 hours, after a preliminary depression. The responses in the sucrose solutions may be several times bigger than in saline.

      2. The spontaneous contractions of the muscle in sucrose solution are accompanied by action potentials.

      3. When the muscle is contracting strongly in the sucrose solution, the sodium content (of the muscle) is negligible thus showing that sodium is not necessary for the production of mechanical and electrical changes.

      4. When the muscle has acclimatised to sucrose, sodium has a depressant action, showing that the mechanical and electrical responses of the muscle are not due to any retention of sodium in the interspaces between the fibres.

      5. The muscle also responds as in sucrose solution, if all the sodium of the saline is replaced with ammonium, potassium, calcium, strontium and magnesium. This suggests that the membrane of this tissue is comparatively resistant and hence this muscle can be deprived of sodium, and still maintain its excitability.

    • Ionic changes in unstriated muscle immersed in sodium-free solutions

      Inderjit Singh A K Acharya

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      1. Frog’s stomach muscle responds when immersed in hypotonic sucrose solution. The more thoroughly, sodium is eliminated from the external medium, the better it responds.

      2. After the muscle has acclimatised to sucrose solution, re-immersion in solution of sodium chloride, or sodium chloride containing a little calcium or potassium abolishes the spontaneous contractions.

      3. The sodium and potassium concentration in the muscle after immersion in sucrose for 4 hours becomes 0·0018 m.Eq. and 0·03 m.Eq. respectively per ml. of water in the muscle.

      4. The mechanical response of the muscle in sucrose solution varies as the intracellular potassium.

      5. These experiments suggest that intracellular potassium, and not extracellular sodium, that is mainly responsible for excitability of the muscle.

    • Excitation, inhibition, contraction, action potentials and conduction in unstriated muscle in the absence of any electrolyte in the external medium

      Inderjit Singh A K Acharya

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    • ElectricalVersus chemical theory of neuromuscular transmission

      Inderjit Singh A K Acharya

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      1. Unstriated muscle shows two kinds of responses; one kind is produced by electric current and the other by chemicals such as potassium or acetylcholine.

      2. Certain reagents affect these two kind of responses differentially.

      3. In dog’s stomach muscle, the responses produced by electric current are inhibited by tone-producing substances such as bromide, nitrate, iodide, thiocyanate. The responses to chemical stimulation are potentiated. The response to nervous stimulation are inhibited. It is concluded, therefore, the response produced by nervous stimulation is produced by electric current, and that can only be the action potential.

      4. Excess of calcium potentiates the response to nervous stimulation, acetylcholine and potassium, but inhibits that to electric current. So it is concluded that the response due to nervous stimulation is also due to liberation of a chemical substance, presumably acetylcholine.

      5. Neuromuscular transmission in unstriated muscle is therefore electro-chemical, produced both by the action potential of nerve and liberation of a chemical substance. The former produces the initial response, and the latter sustains it, and imparts to it, tonic properties.

    • Absence of response to adenosinetriphosphate in a glycerinated unstriated muscle

      Inderjit Singh

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      1. Glycerinated frog’s stomach muscle fromRana tigrina does not respond to ATP with contraction. As this muscle responds physiologically like other muscles, this throws doubt on the accepted role of ATP in muscular contraction.

      2. In a few glycerinated muscles ATP has produced active relaxation. As the number of positive results is small, they are of doubtful value. But theoretically such a possibility exists as increased metabolism definitely occurs during relaxation.

    • Absence of secretion of acetylcholine on stimulation of nerves in an unstriated muscle

      Inderjit Singh Shakuntala Sharma O P Bhatnagar

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      1. Frog’s stomach muscle when immersed in eserinised Ringer’s solution for 2 hours shows no leakage of acetylcholine, whether extended or unextended.

      2. Electrical stimulation of the muscle or its nerves does not release any acetylcholine.

      3. Depolarisation with strong solutions of potassium chloride does not liberate acetylcholine.

      4. Immersion in strong solutions of calcium chloride does not liberate acetylcholine.

      5. Heating to 50–60° C., or treatment with ether liberates acetylcholine; the muscle also relaxes actively if heated. Adrenaline or noradrenaline is also liberated by heating.

      6. As heating to 50–60° C. causes active relaxation as well as liberation of acetylcholine, it is suggested that acetylcholine is in some way connected with contractility by direct action on the contractile mechanism.

      7. The above results were obtained in autumn, but in winter acetylecholine was liberated.

    • Some evidence against the chemical theory of neuromuscular transmission

      Inderjit Singh Shakuntala Sharma O P Bhatnagar

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      1. Some frog’s stomach muscles and dog’s stomach muscle continuously release acetylcholine.

      2. Stimulation of vagus nerve increases the release of acetylcholine.

      3. After the nerve has fatigued, direct electrical stimulation releases acetylcholine; this direct stimulus is far more potent than nervous stimulation, showing that the release of acetylcholine can occur independently of nervous stimulation.

      4. In dog’s stomach muscle, the release of acetylcholine continues undiminished after the nerves have fatigued. It occurs whether the nerves are further stimulated or not. This suggests that the acetylcholine released during nervous stimulation originates from the muscle. These experiments therefore throw doubt on the chemical theory of neuromuscular transmission.

    • Source of acetylcholine in the Frog’s heart on stimulation of the vagus nerve

      Inderjit Singh Singh O P Bhatnagar

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      1. The vagus nerves of the frog’s heart were stimulated in 26 experiments. In 11 experiments, there was no detectable release of acetylcholine; in 15 there was release in variable amounts.

      2. Direct electrical stimulation caused release of acetylcholine in all the 26 experiments, in amounts greater than that released by nervous stimulation after the fatigue of the vagus nerves, and also in those experiments in which the stimulation of the vagus nerves did not show any detectable release of acetylcholine. It is concluded, therefore, that the acetylcholine liberated on stimulation of the vagus nerves comes from the heart muscle cells and not the nerve endings.

    • The source of acetylcholine in the frog’s heart on direct electrical stimulation

      Inderjit Singh Sunita Inderjit Singh O P Bhatnagar

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      1. In frog’s heart, on electrical stimulation, more acetylcholine per g./wt. is liberated from the lower half of the ventricle which is free from ganglion cells, than from the rest of the heart which contains ganglion cells. This suggests that acetylcholine mainly originates from the muscle cells.

      2. The acetylcholine per g./wt. content of the ganglion free portion of the ventricle is greater than the rest of the heart which contains ganglia. This shows that acetylcholine is also contained in muscle cells besides nerve cells.

    • Source of adrenaline and noradrenaline in the frog’s heart on stimulation of the sympathetic nerves

      Inderjit Singh Sunita Inderjit Singh C L Malhotra K Prasad

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      1. Frog’s heart (Rana tigrina) contains more noradrenaline than adrenaline.

      2. Spontaneously beating frog’s heart releases adrenaline and noradrenaline.

      3. Stimulation of the sympathetic nerves releases adrenaline as well as noradrenaline.

      4. After fatigue of the sympathetic nerves by maximal stimulation for one hour, direct electrical stimulation releases adrenaline and noradrenaline in amounts greater than can be released by nervous stimulation. These hormones therefore can originate from muscle cells.

    • Contraction of unstriated muscle without fission of adenosinetriphosphate or creatine phosphate

      Inderjit Singh T Janardana Sarma

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      1. The fission of ATP and phosphocreatine in frog’s stomach muscle has been studied.

      2. In winter, there is no decrease in the concentration of ATP or phosphocreatine due to contraction induced by potassium chloride.

      3. In summer, when the muscle is more active and shows frequent spontaneous contractions, there is breakdown of phosphocreatine, but if these muscles are cooled to 0°C.; then there is no change in phosphocreatine content.

      4. These experiments suggest that ATP is not the primary substance that supplies energy for contraction in unstriated muscle.

    • Life without breathing oxygen

      Inderjit Singh Amarjit Singh Kunwarjit Singh

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      1. Oxygen has been injected intravenously into dogs during hypothermia.

      2. There was no significant difference between the amount of oxygen that could be injected at 37° C. and at 27–28°C. But at the latter temperature, owing to reduction in metabolism, about 40–70% of the oxygen requirements of the animal could be met by intravenous oxygen.

      3. At 24–25°C., slightly greater quantity of oxygen could be injected than at 27–28°C., but owing to greater reduction in metabolism, the entire oxygen requirement of the animal could be met by the intravenous route.

    • Release of 5-hydroxytryptamine on stimulation of nerves to frog’s stomach

      Inderjit Singh Sunita Inderjit Singh C L Malhotra O P Bhatnagar

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    • Life without breathing oxygen—II

      Inderjit Singh Amarjit Singh Kunwarjit Singh

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      If the body temperature of dogs is reduced to 25–27°C., it is possible to give all the oxygen required by the animal by the intravenous route so that they need not breathe oxygen from outside.

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