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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mechanical work, ATP, ADP, PC, free creatine and lactate concentrations were determined on IAA poisoned frog sartorii tetanically stimulated in humidified N2 at 10 degrees C in isotonic conditions (0.25 or 0.45 Po). Tetanus duration was 0.35 s, number of tetani was varied from 0 (rest) to 25 (exhaustion). The mechanical work performed per mole ATP + PC split (W*P) amounted on the average to 16.7 kJ/mol. It was observed, however, that W*P increased from about 13 to about 24 kJ/mol with decreasing ATP concentration from about 2 (resting value) to about 1 mumol/g and that this decrease in ATP was associated with a decrease of the shortening (and relaxation) speed of the muscle to about 30% of the values observed on the first tetanus. It is concluded that the thermodynamic efficiency of muscle contraction, calculated from the ratio of WP* (measured) to the thermodynamic affinity (free energy change) of ATP hydrolysis (estimated) increases from about 0.3 to about 0.5 with decreasing ATP concentration and shortening speed.
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PMID:Efficiency of work performance and contraction velocity in isotonic tetani of frog sartorius. 319 67

Mouse hybrid cell clones secreting antigonadotropin releasing hormone monoclonal antibody were developed by fusion of SP2/O-Ag 1.4 myeloma cells with splenocytes of mouse immunized with gonadotropin releasing hormone (GnRH) tagged to tetanus toxoid. The product of hybrid cell clones obtained as ascites fluid from mouse peritoneal cavity had a titre of 10(6) (30-40% binding of 125I-GnRH) in radioimmunoassay. The antibody was IgG2a and Kappa. The association constant (Ka) of the product of hybrid cell clone P(8)16(62) for binding with GnRH was 1.2 X 10(9) L/mole. The monoclonal antibody (P(8)16(62)) was highly specific for the native GnRH and devoid of reactivity with thyroid releasing hormone as tested in competitive radioimmunoassay. The recognition for GnRH agonists by monoclonal was 387-fold less with D-Ser (But)6 des Gly10 GnRH ethylamide and 608-fold less with Bz1-His6 GnRH. Monoclonal anti-GnRH antibody was competent to neutralize the in vivo bioactivity of the hormone as evident by the block of estrus cycle and termination of pregnancy in mice. Termination of pregnancy in animals receiving anti-GnRH monoclonal could be prevented by administration of progesterone.
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PMID:Characteristics and bioefficacy of monoclonal antigonadotropin releasing hormone antibody. 388 52

1. Changes in the concentrations of ATP, ADP, AMP, IMP, creatine and phosphorylcreatine (PC) have been measured in frog sartorius muscles after different periods of isometric stimulation at 20 degrees C. The heat production was measured in parallel experiments with a thermopile of the Hill-Downing type.2. Muscles were either in O(2) and unpoisoned or in N(2) and poisoned with iodoacetic acid to prevent aerobic and glycolytic recovery processes.3. Poisoning did not appear to alter the heat production of these muscles and had little effect on the tension for up to 8 sec tetanus.4. The break-down of high-energy phosphates ( approximately P) during contraction was faster in the poisoned muscles. Normal muscles were thus able to resynthesize high energy phosphates during the contraction. The resynthesis began at its maximum rate; part of it was probably due to glycolytic activity.5. During the first 2 sec of contraction (poisoned muscles), the only net reaction was an hydrolysis of PC, with an apparent enthalpy change of -8.3 kcal/mole. During longer contractions, the PC hydrolysis was accompanied by a net ATP hydrolysis and appearance of AMP and IMP.6. For the first 2 sec of contraction in the poisoned muscles, the observed heat agreed with that expected from the observed chemical changes multiplied by their molar enthalpy changes. After 2 sec, the observed heat was greater than that expected. At 12 sec this excess was about 74 mcal/g. Possible explanations for this discrepancy are discussed.
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PMID:Energy balance in frog sartorius muscle during an isometric tetanus at 20 degrees C. 475 78

In an isometric tetanus in frog's sartorius muscle tension approaches the plateau exponentially with rate constant alpha. alpha a depends on sarcomere length, s, and temperature, T, according to the Arrhenius equation See PDF for Equation for temperatures between 1 and 20 degrees C and for sarcomere lengths 2.0-2.8 microm. The energy of activation, E, does not vary significantly with s; E = 13.9 +/- 2.4 kcal/mole. A(s) decreases monotonically with s; A(2.1 microm) is about three times greater than A(2.8 microm). Late in relaxation active tension approaches zero exponentially with rate constant r. r decreases exponentially with increasing duration of tetanus, D, from r(0) in a twitch to r(infinity) for large D. The rate constant for decrease of r with D increases with s and with T. r(0) and r(infinity) obey the Arrhenius equation and decrease with increasing s.
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PMID:Transient phases of the isometric tetanus in Frog's striated muscle. 556 60

1. Heat production, tension development and phosphorylcreatine (PC) splitting have been measured simultaneously during isometric contractions of iodoacetate-poisoned frogs' sartorii at 0 degrees C. The muscles were stimulated to produce a series of 30 twitches or a 10 sec tetanus or a 30 sec tetanus.2. Of the several possible methods of calculating PC breakdown the best appears to be the one based on the assumption that PC/(total creatine) was originally the same in the two muscles of a pair.3. The difficulty of expressing PC break-down, heat production etc. in terms of the muscle's size is demonstrated.4. Several artifacts are discussed, including the heat produced by the stimulus and the possible role of reactions other than PC splitting.5. Even when these have been substantially eliminated there remains the rather intractable statistical problem of establishing a functional relationship between heat produced and PC split when both of these variables contain errors, so that ordinary regression analysis is misleading. It is shown that this problem can be dealt with satisfactorily by introducing other instrumental variables that can be determined experimentally.6. The final conclusion is that the in vivo enthalpy of hydrolysis of PC is about 10.6 kcal/mole, and is the same in twitches and in tetani.
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PMID:The relation between heat produced and phosphorylcreatine split during isometric contraction of frog's muscle. 603 12