scholarly journals Graded and All-or-None Electrogenesis in Arthropod Muscle

1961 ◽  
Vol 44 (5) ◽  
pp. 997-1027 ◽  
Author(s):  
R. Werman ◽  
H. Grundfest
Keyword(s):  
Muscle Fibers ◽  
Relative Increase ◽  
Ion Flux ◽  
Alkali Earth ◽  
Low Concentrations ◽  
Na Inactivation ◽  
High Conductance ◽  
External K

Conversion of graded responsiveness of lobster muscle fibers to all-or-none activity by alkali-earth and tetraethylammonium (TEA) ions appears to be due to a combination of effects. The membrane is hyperpolarized, its resistance is increased, and its sensitivity to external K+ is diminished, all effects which indicate diminished K+ conductance. While the spikes are prolonged, the conductance is higher throughout the response than it is in the resting membrane. Repetitive activity becomes prominent. These effects indicate maintained high conductance for an ion which causes depolarization. This is normally Na+, since its presence in low concentrations potentiates the effects of Ba++, but the alkali-earth ions and TEA can also carry inward charge. Ba++, Sr++, and TEA appear to be more effective than is Ca++ in its normal role, which is probably to depress K+ conductance and Na inactivation. Thus, conversion of graded to all-or-none responsiveness appears to occur because of the relative increase of depolarizing inward ion flux and decrease of repolarizing outward flux.

scholarly journals MYOSITIS IN MICE FOLLOWING INTRAMUSCULAR INJECTION OF VIRUSES OF THE MOUSE ENCEPHALOMYELITIS GROUP AND OF CERTAIN OTHER NEUROTROPIC VIRUSES

1949 ◽  
Vol 89 (1) ◽  
pp. 69-92 ◽  
Author(s):  
Robert Rustigian ◽  
Alwin M. Pappenheimer
Keyword(s):  
Intramuscular Injection ◽  
Muscle Fibers ◽  
Lymphocytic Choriomeningitis ◽  
Equine Encephalitis Virus ◽  
Neurotropic Viruses ◽  
Low Concentrations ◽  
Encephalomyelitis Virus ◽  
Massive Necrosis ◽  
Muscle Lesions ◽  
Inflammatory Changes

A study has been made of the local effects following intramuscular injection of various neurotropic viruses. Early massive necrosis of muscle fibers accompanied by edema and acute inflammatory reaction is produced by Jungeblut's SK virus even in low concentrations. Similar but more slowly developing lesions follow the introduction of mouse encephalomyelitis GD-VII and FA strains. Strain 4727 (TO type) produces inflammatory changes with fibrosis in the intermuscular septa and necrosis of scattered individual fibers. The relatively avirulent FV strain (TO type) was not pathogenic for skeletal muscle. The Mitchell strain of lymphocytic choriomeningitis virus gives rise to a profuse lymphocytic and monocytic infiltration of the fat and connective tissue but does not cause necrosis of muscle fibers. No significant lesions resulted from intramuscular injection of the murine-adapted human poliomyelitis Lansing virus, the HF strain of herpes, a strain of Eastern equine encephalitis virus, or a still unidentified demyelinating mouse virus. Evidence is presented that the mouse encephalomyelitis virus GD-VII and Jungeblut's SK virus multiply locally in the injected limb. The GD-VII virus has been passed through four muscle to muscle passages and muscle lesions have been elicited at the same time. Specific and complete protection against myositis was obtained by anti-GD-VII and anti-SK rabbit sera.

METABOLISM OF LEPTOSPIRES: II. THE ACTION OF 8-AZAGUANINE

1967 ◽  
Vol 13 (12) ◽  
pp. 1621-1629 ◽  
Author(s):  
Russell C. Johnson ◽  
Palmer Rogers
Keyword(s):  
Nucleic Acids ◽  
Ribonucleic Acid ◽  
Rna Synthesis ◽  
Inhibitory Effect ◽  
Relative Increase ◽  
Purine Biosynthesis ◽  
Low Concentrations

Both the pathogen Leptospira pomona and the saprophyte L. biflexa Patoc I can convert exogenous adenine, guanine, and 8-azaguanine to the corresponding nucleotide and incorporate them into nucleic acids. L. pomona is inhibited by low concentrations of 8-azaguanine (50 μg/ml) and this inhibition is associated with less than a 5% replacement of the ribonucleic acid (RNA) guanine residues by the analogue. Guanine possessed the highest activity for antagonizing the inhibitory effect of 8-azaguanine. The biosynthetic process of L. pomona most affected by the analogue was a relative increase in RNA synthesis. The analogue-resistant L. biflexa incorporated 1/10 as much 8-azaguanine as L. pomona. The higher rate of purine biosynthesis, in addition to the lesser amount of 8-azaguanine incorporated, may account for the analogue resistance of L. biflexa.

Spaceflight and growth effects on muscle fibers in the rhesus monkey

1992 ◽  
Vol 73 (2) ◽  
pp. S82-S89 ◽  
Author(s):  
S. C. Bodine-Fowler ◽  
R. R. Roy ◽  
W. Rudolph ◽  
N. Haque ◽  
I. B. Kozlovskaya ◽  
...  
Keyword(s):  
Muscle Fibers ◽  
Relative Increase ◽  
The Body ◽  
Medial Gastrocnemius ◽  
Biopsy Needle ◽  
Hindlimb Muscles ◽  
Fiber Size ◽  
The Mean ◽  
Metabolic Properties ◽  
Muscle Biopsies

Spaceflight causes considerable atrophy in hindlimb muscles of the rat. The purpose of this study was to investigate the effect of a 14-day spaceflight (COSMOS 2044) on selected morphological and metabolic properties of single muscle fibers in a nonhuman primate, Macaca mulatta. Biopsies were taken from the soleus (Sol), medial gastrocnemius (MG), and tibialis anterior (TA) muscles of two rhesus monkeys 107 days before flight and 24 h after return from flight. Muscle biopsies were taken from two independent sites in each muscle by use of a small (3-mm OD) Bergstrom biopsy needle. The biopsies weighed 8–14 mg and contained 100–200 fibers, of which an average of 40 fibers were acceptable for metabolic and size analyses. The 14-day spaceflight had little effect on fiber size in the Sol and MG muscles, whereas there appeared to be a slight decrease in size in the TA. In each of the flight animals, the mean fiber size in the postflight biopsies increased relative to preflight values. An increase in fiber size over the same period of time was also observed in four control monkeys that were the same age and approximately the same weight as the flight monkeys. The relative increase in size was related to the body weight of the monkey at the time of the pre- and postflight biopsies. The mean fiber succinate dehydrogenase activity appeared to decrease in the MG, whereas there was no apparent effect of spaceflight on the Sol and TA muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Modulation of Radula Opener Muscles in Aplysia

1999 ◽  
Vol 82 (3) ◽  
pp. 1339-1351 ◽  
Author(s):  
Colin G. Evans ◽  
Ferdinand S. Vilim ◽  
Orna Harish ◽  
Irving Kupfermann ◽  
Klaudiusz R. Weiss ◽  
...  
Keyword(s):  
Motor Neuron ◽  
Relaxation Rate ◽  
Muscle Relaxation ◽  
Muscle Fibers ◽  
Low Concentrations ◽  
Muscle Complex ◽  
Myogenic Activity ◽  
High Concentrations ◽  
Camp Levels ◽  
Rest Length

We observed fibers immunoreactive (IR) to serotonin (5-HT), the myomodulins (MMs), and FMRFamide on the I7-I10 complex in the marine mollusk Aplysia californica. The I7–I10 muscle complex, which produces radula opening, is innervated primarily by one motor neuron, B48. B48 is MM-IR and synthesizes authentic MMA. When B48 is stimulated in a physiological manner, cAMP levels are increased in opener muscles. cAMP increases also are seen when the MMs are applied to opener muscles but are not seen with application of the B48 primary neurotransmitter acetylcholine (ACh). Possible physiological sources of 5-HT and FMRFamide are discussed. When modulators are applied to resting opener muscles, changes in membrane potential are observed. Specifically, 5-HT, MMB, and low concentrations of MMA all depolarize muscle fibers. This depolarization is generally not sufficient to elicit myogenic activity in the absence of neural activity under “rest” conditions. However, if opener muscles are stretched beyond rest length, stretch- and modulator-induced depolarizations can summate and elicit contractions. This only occurs, however, if “depolarizing” modulators are applied alone. Thus other modulators (i.e., FMRFamide and high concentrations of MMA) hyperpolarize opener muscle fibers and can prevent depolarizing modulators from eliciting myogenic activity. All modulators tested affected parameters of motor neuron-elicited contractions of opener muscles. MMB and 5-HT increased contraction size over the range of concentrations tested, whereas MMA potentiated contractions when it was applied at lower concentrations but decreased contraction size at higher concentrations. FMRFamide decreased contraction size at all concentrations and did not affect relaxation rate. Additionally, the MMs and 5-HT increased muscle relaxation rate, decreased contraction latency, and decreased the rate at which tension was developed during motor neuron-elicited muscle contractions. Thus these modulators dramatically affect the ability of opener muscles to follow activity in the opener motor neuron B48. The possible physiological significance of these findings is discussed.

scholarly journals The Ionic Mechanisms of Hyperpolarizing Responses in Lobster Muscle Fibers

1961 ◽  
Vol 45 (2) ◽  
pp. 243-265 ◽  
Author(s):  
J. P. Reuben ◽  
R. Werman ◽  
H. Grundfest
Keyword(s):  
Membrane Permeability ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Oscillatory Behavior ◽  
Current Leads ◽  
Oscillatory Characteristic ◽  
Ionic Mechanisms ◽  
External K

Lobster muscle fibers develop hyperpolarizing responses when subjected to sufficiently strong hyperpolarizing currents. In contrast to axons of frog, toad, and squid, the muscle fibers produce their responses without the need for prior depolarization in high external K+. Responses begin at a threshold polarization (50 to 70 mv), the potential reaching 150 to 200 mv hyperpolarization while the current remains constant. The increased polarization develops at first slowly, then becomes rapid. It usually subsides from its peak spontaneously, falling temporarily to a potential less hyperpolarized than at threshold for the response. As long as current is applied there can be oscillatory behavior with sequential rise and subsidence of the polarization, repeating a number of times. Withdrawal of current leads to rapid return of the potential to the resting level and a small, brief depolarization. Associated with the latter, but of longer duration, is an increased conductance whose magnitude and duration increase with the antecedent current. Hyperpolarizing responses of lobster muscle fibers are due to increased membrane resistance caused by hyperpolarizing K inactivation. The oscillatory characteristic of the response is due to a delayed superimposed and prolonged increase in membrane permeability, probably for Na+ and for either K+ or Cl-. The hyperpolarizing responses of other tissues also appear to result from hyperpolarizing K inactivation, on which is superimposed an increased conductance for some other ion or ions.

scholarly journals RELAXATION IN EXTRACTED MUSCLE FIBERS

1954 ◽  
Vol 38 (2) ◽  
pp. 149-159 ◽  
Author(s):  
Emil Bozler
Keyword(s):  
Critical Level ◽  
Critical Concentration ◽  
Muscle Fibers ◽  
Complexing Agent ◽  
Tetraacetic Acid ◽  
Relaxation Factor ◽  
Low Concentrations ◽  
High Concentrations ◽  
Relaxing Effect ◽  
Subsequent Addition

1. Ethylenediamine tetraacetic acid (EDTA) in low concentrations imitates all the known effects of the relaxation factor ("Marsh factor"). In extracted muscle fibers which have contracted in a solution containing adenosinetriphosphate (ATP), the addition of EBTA causes relaxation, the subsequent addition of CaCl2, contraction. 2. In fibers which have been briefly immersed in 5 MM EDTA, ATP causes rapid relaxation if Mg is also present. These fibers have essentially the same properties as briefly extracted fibers. Brief immersion into a solution containing CaCl2 restores at once the original condition. It is concluded that EDTA produces its action by firmly combining with bound Ca, thereby inactivating it. 3. In relaxed muscle fibers not only Ca, but also lowering the concentration of Mg below a critical level, causes contraction. In such fibers Mg in the lowest effective concentrations increases contraction, but the effect reverses above a certain concentration. 4. At 0° Mg in the presence of ATP has a relaxing effect without the relaxation factor. 5. The results indicate that Mg has two distinct effects in the presence of ATP. It causes contraction at low concentrations, but above a critical concentration its relaxing action prevails. The last of these effects is blocked by bound Ca. If the latter is inactivated by EDTA, Mg in sufficiently high concentrations causes relaxation. The action of the relaxation factor can similarly be explained by assuming that it acts as a complexing agent which inactivates bound Ca. 6. Previous evidence that the relaxed state depends on the formation of an enzymatically inactive ATP-protein complex was confirmed. It was found that PP in low concentrations strongly increases the relaxing effect of ATP in briefly extracted fibers.

scholarly journals Potassium blocks barium permeation through a calcium-activated potassium channel.

1988 ◽  
Vol 92 (5) ◽  
pp. 549-567 ◽  
Author(s):  
J Neyton ◽  
C Miller
Keyword(s):  
Skeletal Muscle ◽  
Lipid Bilayers ◽  
Dissociation Rate ◽  
Planar Lipid Bilayers ◽  
Rat Skeletal Muscle ◽  
K Channels ◽  
Calcium Activated Potassium Channel ◽  
Micromolar Range ◽  
High Conductance ◽  
External K

Single high-conductance Ca2+-activated K+ channels from rat skeletal muscle were inserted into planar lipid bilayers, and discrete blocking by the Ba2+ ion was studied. Specifically, the ability of external K+ to reduce the Ba2+ dissociation rate was investigated. In the presence of 150 mM internal K+, 1-5 microM internal Ba2+, and 150 mM external Na+, Ba2+ dissociation is rapid (5 s-1) in external solutions that are kept rigorously K+ free. The addition of external K+ in the low millimolar range reduces the Ba2+ off-rate 20-fold. Other permeant ions, such as Tl+, Rb+, and NH4+ show a similar effect. The half-inhibition constants rise in the order: Tl+ (0.08 mM) less than Rb+ (0.1 mM) less than K+ (0.3 mM) less than Cs+ (0.5 mM) less than NH4+ (3 mM). When external Na+ is replaced by 150 mM N-methyl glucamine, the Ba2+ off-rate is even higher, 20 s-1. External K+ and other permeant ions reduce this rate by approximately 100-fold in the micromolar range of concentrations. Na+ also reduces the Ba2+ off-rate, but at much higher concentrations. The half-inhibition concentrations rise in the order: Rb+ (4 microM) less than K+ (19 microM) much less than Na+ (27 mM) less than Li+ (greater than 50 mM). The results require that the conduction pore of this channel contains at least three sites that may all be occupied simultaneously by conducting ions.

scholarly journals THE EFFECT OF POLYPHOSPHATES AND MAGNESIUM ON THE MECHANICAL PROPERTIES OF EXTRACTED MUSCLE FIBERS

1956 ◽  
Vol 39 (5) ◽  
pp. 789-800 ◽  
Author(s):  
Emil Bozler
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Modulus Of Elasticity ◽  
Muscle Fibers ◽  
Configurational Entropy ◽  
Partial Removal ◽  
Relaxation Factor ◽  
Low Concentrations ◽  
Strong Contraction ◽  
Plastic Extension

Loading of extracted muscle fibers causes a small, sudden lengthening, followed by a slower, plastic extension, which is reversed only by active contraction. Polyphosphates in the presence of Mg strongly accelerate plastic extension, but elastic changes in length remain the same as during rigor. The modulus of elasticity on the average is about 6.2 x 107 dynes per cm.2 This value is about 40 times larger than that of rubber, if compared on a water-free basis. Extension of muscle, therefore, is almost entirely due to plastic deformation. Mg is essential for the softening action of adenosinetriphosphate (ATP) and can produce partial relaxation in the absence of a relaxation factor. After partial removal of bound Mg, ATP causes strong contraction, but only slight softening. The same condition is produced by very low concentrations of ATP in the presence of phosphocreatine. These observations show that during contraction passive mechanical properties may remain essentially like those during rigor. The constancy of elastic extensibility distinguishes contraction produced by ATP from contraction induced by non-specific agents in various fibrous structures and caused by an increase in configurational entropy.

TETRAETHYLAMMONIUM-INDUCED CONTRACTIONS OF FROG'S SKELETAL MUSCLE: II. EFFECTS ON INTRAMUSCULAR NERVE ENDINGS

1967 ◽  
Vol 45 (5) ◽  
pp. 833-844 ◽  
Author(s):  
G. Beaulieu ◽  
G. B. Frank ◽  
F. Inoue
Keyword(s):  
Motor Nerve ◽  
Muscle Fibers ◽  
Electrical Stimulus ◽  
Nerve Fibers ◽  
Ventral Root ◽  
Nerve Endings ◽  
Glass Capillary ◽  
Action Potential Firing ◽  
Low Concentrations ◽  
Potential Firing

By recording simultaneously from muscle fibers and from the ventral root supplying the muscle, it was found that low concentrations of tetraethylammonium (TEA) caused the muscle fibers to fire without antidromic impulses being conducted to the ventral root. Exposing the muscles to higher TEA concentrations induced action potential firing in both the muscle and the ventral root. d-Tubocurarine prevented the muscle fiber activity but did not modify the ventral root firing. The application of a single supramaximal electrical stimulus to the sciatic nerve resulted in an afterdischarge of the muscle fibers either alone or simultaneous with an afterdischarge of fibers in the ventral root. By recording from fine intramuscular motor nerve fibers with extracellular glass capillary microelectrodes while simultaneously recording from the ventral root, it was demonstrated that TEA could cause these fine intramuscular motor nerve fibers to fire without the activity being conducted antidromically to the ventral root. A consideration of the patterns of TEA-induced electrical activity and afterdischarging led to the suggestion that TEA causes these effects by displacing calcium from binding sites on the motor nerve endings, making the latter hyperexcitable and unstable and thereby causing afterdischarging and 'spontaneous' activity.

scholarly journals Discrete Ba2+ block as a probe of ion occupancy and pore structure in the high-conductance Ca2+ -activated K+ channel.

1988 ◽  
Vol 92 (5) ◽  
pp. 569-586 ◽  
Author(s):  
J Neyton ◽  
C Miller
Keyword(s):  
External Solution ◽  
K Channel ◽  
Enhancement Effect ◽  
Single Channels ◽  
Internal Solution ◽  
Conduction Pathway ◽  
Lock In Effect ◽  
Lock In ◽  
High Conductance ◽  
External K

In this study, high-conductance Ca2+-activated K+ channels from rat skeletal muscle were incorporated into planar phospholipid bilayers, and discrete blockade of single channels by Ba2+ was studied. With 150 mM K+ held constant in the internal solution, increasing external K+ over the range 100-1,000 mM raises the rate of Ba2+ dissociation. This "enhancement effect," which operates at K+ concentrations 3-4 orders of magnitude higher than those required for the "lockin" effect described previously, depends on applied voltage, saturates with K+ concentration, and is not observed with Na+. The voltage dependence of the Ba2+ off-rate varies with external K+ in a way suggesting that K+, entering the channel from the external side, forces Ba2+ dissociation to the internal solution. With K+ held fixed in the external solution, the Ba2+ off-rate decreases as internal K+ is raised over the range 0-50 mM. This "lock-in" effect is similar to that seen on the external side (Neyton and Miller, 1988), except that the internal lock-in site is of lower affinity and shows only a fivefold preference for K+ over Na+. All the results taken together argue strongly that this channel's conduction pathway contains four sites of very high affinity for K+, all of which may be simultaneously occupied under normal conducting conditions. According to this view, the mutual destabilization resulting from this high ionic occupancy leads to the unusually high conductance of this K+-specific channel.

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