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Biomedical subjects

M F Morales

Publications and source records attributed to M F Morales.

71 records · Page 4Linked to original sources
PubMed1972

Creatine and the control of myosin synthesis in differentiating skeletal muscle.

These experiments provide evidence that creatine, an end product of contraction unique to muscle, is involved in the control of muscle-protein synthesis. Skeletal muscle cells formed both in vitro and in vivo synthesize myosin heavy chain faster when supplied creatine in vitro. The response is apparent within four hours after addition of creatine to the culture medium, and is dependent on concentration over a range of 10-100 muM creatine. The effect seems to be selective for cell-specific proteins(s), since the rate of total protein synthesis is unaffected.

Animals↗
PubMed1972

Individual states in the cycle of muscle contraction.

By using appropriate analogs of ATP, isometrically-held glycerol-extracted psoas fibers from rabbits are forced successively into states corresponding to molecular species in the contractile cycle. In each state measurements are made of P[unk], a fluorescence polarization parameter thought to relate to attitude of S-1 moieties of the myosin molecules. Also, the value of P[unk] is measured during active tension development. It is suggested that this value is a time-average of the P[unk] as S-1 moieties move through the various states of the cycle. Proposals are made concerning the sequence of states in the cycle.

Actins↗
PubMed1972

Polarization of tryptophan fluorescence from single striated muscle fibers. A molecular probe of contractile state.

Instrumentation has been developed to detect rapidly the polarization of tryptophan fluorescence from single muscle fibers in rigor, relaxation, and contraction. The polarization parameter (P( perpendicular)) obtained by exiciting the muscle tryptophans with light polarized perpendicular to the long axis of the muscle fiber had a magnitude P( perpendicular) (relaxation) > P( perpendicular) (contraction) > P( perpendicular) (rigor) for the three types of muscle fibers examined (glycerinated rabbit psoas, glycerinated dorsal longitudinal flight muscle of Lethocerus americanus, and live semitendinosus of Rana pipiens). P( perpendicular) from single psoas fibers in rigor was found to increase as the sarcomere length increased but in relaxed fibers P( perpendicular) was independent of sarcomere length. After rigor, pyrophosphate produced little or no change in P( perpendicular), but following an adenosine triphosphate (ATP)-containing solution, pyrophosphate produced a value of P( perpendicular) that fell between the contraction and relaxation values. Sinusoidal or square wave oscillations of the muscle of amplitude 0.5-2.0% of the sarcomere length and frequency 1, 2, or 5 Hz were applied in rigor when the myosin cross-bridges are considered to be firmly attached to the thin filaments. No significant changes in P( perpendicular) were observed in either rigor or relaxation. The preceding results together with our present knowledge of tryptophan distribution in the contractile proteins has led us to the conclusion that the parameter P( perpendicular) is a probe of the contractile state of myosin which is probably sensitive to the orientation of the myosin S1 subfragment.

Adenosine Triphosphate↗