scholarly journals Calcium Binding and Tension Development in Detergent-Treated Muscle Fibers

1974 ◽  
Vol 63 (2) ◽  
pp. 168-186 ◽  
Author(s):  
M. Orentlicher ◽  
J. P. Reuben ◽  
H. Grundfest ◽  
P. W. Brandt
Keyword(s):  
Binding Sites ◽  
Calcium Binding ◽  
Time Course ◽  
Muscle Fibers ◽  
Contractile Proteins ◽  
Tension Development ◽  
Brij 58 ◽  
Ca Uptake ◽  
Before And After ◽  
Nonionic Detergent

The nonionic detergent Brij 58 eliminates irreversibly the capability of the sarcoplasmic reticulum (SR) of skinned crayfish muscle fibers to sequester Ca and to release it under appropriate stimulation. In contrast to deoxycholate (DOC) which causes an irreversible diminution of tension as well, Brij 58 does not affect the contractile proteins. Comparison of the time-course of tension development before and after Brij treatment demonstrates that Ca is accessible to the contractile proteins more rapidly after the SR is destroyed but, nevertheless, much more slowly than is predicted for free diffusion of Ca in the myoplasm. Slowing apparently results because of the presence of ca 1 mmol/kg fiber of myoplasmic Ca-binding sites that remain after Ca uptake of the SR is eliminated. A theoretical model is presented which allows for the effects of binding sites and of an unstirred layer in the vicinity of the fiber on Ca diffusion into the myoplasm.

Long-term facilitation alters transmitter releasing properties at the crayfish neuromuscular junction

1986 ◽  
Vol 55 (3) ◽  
pp. 484-498 ◽  
Author(s):  
J. M. Wojtowicz ◽  
H. L. Atwood
Keyword(s):  
Neuromuscular Junction ◽  
Synaptic Transmission ◽  
Time Course ◽  
Muscle Fibers ◽  
Low Frequencies ◽  
Before And After ◽  
Binomial Parameter ◽  
Small Muscle ◽  
Long Term Facilitation

Synaptic transmission at the neuromuscular junction of the excitatory axon supplying the crayfish opener muscle was examined before and after induction of long-term facilitation (LTF) by a 10-min period of stimulation at 20 Hz. Induction of LTF led to a period of enhanced synaptic transmission, which often persisted for many hours. The enhancement was entirely presynaptic in origin, since quantal unit size and time course were not altered, and quantal content of transmission (m) was increased. LTF was not associated with any persistent changes in action potential or presynaptic membrane potential recorded in the terminal region of the excitatory axon. The small muscle fibers of the walking-leg opener muscle were almost isopotential, and all quantal events could be recorded with an intracellular microelectrode. In addition, at low frequencies of stimulation, m was small. Thus it was possible to apply a binomial model of transmitter release to events recorded from individual muscle fibers and to calculate values for n (number of responding units involved in transmission) and p (probability of transmission for the population of responding units) before and after LTF. In the majority of preparations analyzed (6/10), amplitude histograms of evoked synaptic potentials could be described by a binomial distribution with a small n and moderately high p. LTF produced a significant increase in n, while p was slightly reduced. The results can be explained by a model in which the binomial parameter n represents the number of active synapses and parameter p the mean probability of release at a synapse. Provided that a pool of initially inactive synapses exists, one can postulate that LTF involves recruitment of synapses to the active state.

Time course of vasodilation at the onset of repetitive skeletal muscle contractions

2007 ◽  
Vol 292 (1) ◽  
pp. R505-R515 ◽  
Author(s):  
Marika L. Armstrong ◽  
Ashok K. Dua ◽  
Coral L. Murrant
Keyword(s):  
Skeletal Muscle ◽  
Time Course ◽  
Vascular Reactivity ◽  
Muscle Fibers ◽  
Similar Response ◽  
Stimulation Parameter ◽  
Vasodilatory Response ◽  
Train Duration ◽  
Before And After ◽  
Parameter Dependent

To characterize the vasodilatory response in the transition from a single skeletal contraction to a series of contractions, we measured the response of hamster cremaster muscle arterioles associated with four to five skeletal muscle fibers stimulated to contract for one, two, three, or four contractions (250-ms train duration) at 4-s intervals [15 contractions per minute (CPM)] for up to 12 s, at stimulus frequencies of 4, 10, 20, 30, 40, 60, and 80 Hz. To investigate the contribution of contraction frequency, we stimulated muscle fiber bundles at 30 or 60 CPM for 12 s at stimulus frequencies of 4, 20, and 60 Hz. Arteriolar diameters at the site of overlap with the stimulated muscle fibers were measured before and after each contraction. At 15 CPM at 4, 20, and 60 Hz, we observed a peak change in diameter following the first contraction of 1.1 ± 0.1, 1.6 ± 0.2, and 2.1 ± 0.2 μm that almost doubled in response to the second contraction (2.0 ± 0.1, 3.0 ± 0.1, and 3.8 ± 0.1 μm, respectively), but there was no further dilation following the third or fourth contraction. A similar response occurred at all stimulus and contraction frequencies tested. At 30 and 60 CPM at 60 Hz, the plateau after two contractions was followed by a further increase in diameter to a second plateau at 7–8 s. Therefore, the vasodilatory response in the transition from single to multiple contractions had components that were stimulation parameter dependent and independent and showed a plateauing behavior indicative of rapid changes in either the nature and/or concentration of vasodilators released or changes in vascular reactivity.

High-affinity calcium binding sites in luminal and basolateral renal membranes

1985 ◽  
Vol 248 (4) ◽  
pp. F472-F481
Author(s):  
Z. Talor ◽  
G. Richison ◽  
J. A. Arruda
Keyword(s):  
Binding Sites ◽  
Calcium Binding ◽  
Divalent Cations ◽  
Ruthenium Red ◽  
Affinity Constant ◽  
Affinity Binding ◽  
High Affinity Binding ◽  
High Affinity ◽  
Ca Uptake ◽  
Number Of Binding Sites

We evaluated Ca binding by highly purified luminal (L) and basolateral (BL) tubular membranes prepared from beef kidney. Ca binding was measured by using 45Ca and a rapid-filtration technique. After Ca uptake reached equilibrium, the vesicles were lysed and the amount of 45Ca retained in the membranes was considered the bound Ca. Ca binding in both membranes accounted for approx. 80% of total Ca uptake. Analysis of binding data by Scatchard plot revealed the presence of two distinct types of binding sites in both L and BL membranes. The high-affinity binding sites showed a similar affinity constant of 10(-5)M for both L and BL membranes, but the maximum number of binding sites was 0.75 and 1.6 nmol/mg protein, respectively. In contrast, the low-affinity binding sites were similar regarding affinity constant and maximum number of binding sites in the two membranes. In L and BL membranes, high-affinity binding sites were selective for Ca, as high concentrations of divalent cations were required to inhibit Ca binding. In both membranes Ca binding was inhibited by ruthenium red, LaCl3, and detergents, and it was stimulated by calmodulin inhibitors (trifluoperazine, calmidazolium), ionophore A-23187, and ATP. These results demonstrate that L and BL membranes possess high-affinity binding sites with different capacities but similar characteristics as regards affinity constant and stimulation and inhibition of binding. The data further demonstrate that most of Ca uptake by these membranes represents binding.

Effects of uridine triphosphate on skinned skeletal muscle fibers of the rat

1995 ◽  
Vol 73 (10) ◽  
pp. 1451-1457 ◽  
Author(s):  
G. Suarez-Kurtz ◽  
C. G. Ponte ◽  
M.-P. Catinot ◽  
Y. Mounier ◽  
R. Vianna-Jorge
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Muscle Fibers ◽  
Ruthenium Red ◽  
Uridine Triphosphate ◽  
Skinned Muscle ◽  
Brij 58 ◽  
Longus Muscle ◽  
Nonionic Detergent ◽  
Skinned Muscle Fiber ◽  
Sarcoplasmic Reticulum Calcium

Chemically skinned muscle fibers from rat extensor digitorum longus muscle were used to study the effects of uridine triphosphate (UTP) on Ca2+ uptake and release by the sarcoplasmic reticulum (SR) and on Ca2+-activated tensions. Total replacement (2.5 mM) of adenosine triphosphate (ATP) with UTP (i) increased submaximal Ca2+-induced tension (pCa 6.2–5.8) but diminished Po, the maximum tension elicited by pCa 4.2, by ca. 15%; (ii) markedly reduced Ca2+ uptake by the SR (evaluated by caffeine-elicited tension); and (iii) induced tension in Ca2+-loaded fibers. The UTP-induced tension averaged 55% of Po and its rates of development and decay were considerably slower than those of caffeine-evoked tension. The UTP-induced tension (i) depended on the Ca2+-loading conditions; (ii) was reversibiy blocked by brief (15 s) exposures of Ca2+-loaded fibers to 5 mM EGTA or by pretreatment with caffeine; (iii) was abolished by functional disruption of the SR with the nonionic detergent Brij-58; and (iv) persisted after blockade of the SR Ca2+ release channels with ruthenium red. Exposure of Ca2+-loaded fibers to UTP depressed the tension elicited subsequently by caffeine, and enhanced the rate of depletion of caffeine-sensitive Ca2+ stores during soaking in relaxing solutions containing 5 mM EGTA. The UTP-induced tension is attributed to increased release of Ca2+ from the SR, via a ruthenium red insensitive pathway(s), combined with reduced Ca2+ uptake by the SR and increased Ca2+ affinity of the contractile proteins.Key words: skinned muscle fiber, UTP-induced tension, tension–pCa relationship, sarcoplasmic reticulum, calcium transport.

Preliminary Evaluation of a Weibull Function for Fitting Slow-Component Eye Velocity over the Time Course of Caloric-Induced Nystagmus

1989 ◽  
Vol 32 (3) ◽  
pp. 681-687 ◽  
Author(s):  
C. Formby ◽  
B. Albritton ◽  
I. M. Rivera
Keyword(s):  
Time Course ◽  
Slow Component ◽  
Weibull Function ◽  
Preliminary Evaluation ◽  
Mathematical Function ◽  
Before And After ◽  
Best Fitting ◽  
Eye Velocity ◽  
Fitting Parameters ◽  
Weibull Equation

We describe preliminary attempts to fit a mathematical function to the slow-component eye velocity (SCV) over the time course of caloric-induced nystagmus. Initially, we consider a Weibull equation with three parameters. These parameters are estimated by a least-squares procedure to fit digitized SCV data. We present examples of SCV data and fitted curves to show how adjustments in the parameters of the model affect the fitted curve. The best fitting parameters are presented for curves fit to 120 warm caloric responses. The fitting parameters and the efficacy of the fitted curves are compared before and after the SCV data were smoothed to reduce response variability. We also consider a more flexible four-parameter Weibull equation that, for 98% of the smoothed caloric responses, yields fits that describe the data more precisely than a line through the mean. Finally, we consider advantages and problems in fitting the Weibull function to caloric data.

scholarly journals Measuring phenotypic flexibility by transcriptome time‐course analyses during challenge tests before and after energy restriction

2019 ◽  
Vol 33 (9) ◽  
pp. 10280-10290 ◽  
Author(s):  
Inge P. G. Bussel ◽  
Parastoo Fazelzadeh ◽  
Gary S. Frost ◽  
Milena Rundle ◽  
Lydia A. Afman
Keyword(s):  
Time Course ◽  
Energy Restriction ◽  
Phenotypic Flexibility ◽  
Before And After ◽  
Challenge Tests
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