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F W Booth

Publications and source records attributed to F W Booth.

At least 91 records · Page 5Linked to original sources
PubMed1989

Protein metabolism and beta-myosin heavy-chain mRNA in unweighted soleus muscle.

To investigate the relative influence of protein synthetic and degradative control mechanisms in vivo during skeletal muscle atrophy, we measured myofibril and total mixed protein synthesis rates in muscles of rats prevented from hindlimb weight-bearing for 5 h and 7 days. Protein synthesis rates were determined by infusing the animals with [3H]Leu for 5 h and measuring the specific activity of [3H]Leu in the aminoacyl-tRNA precursor and protein product fractions of the muscles. In the soleus muscle, myofibril protein synthesis rates decreased from a control value of 5.9 to 4.6%/day during 5 h of hindlimb unweighting and to 2.4%/day after 7 days of hindlimb unweighting. The relatively more phasic muscles (plantaris, medial gastrocnemius, quadriceps) showed a tendency for increased myofibril protein synthesis rates (117-127% of control) during the first 5 h followed by a decrease (46-62% of control) at 7 days of hindlimb unweighting. A predicted time course of soleus muscle myofibril protein degradation rate was obtained from a numerical model of the decrease in soleus myofibril protein synthesis rate as a first-order process [half-time (t1/2) = 0.3 day by least-squares fit] and the time course of soleus muscle myofibril protein previously observed with hindlimb unweighting (Thomason et al., J. Appl. Physiol. 63: 130-137, 1987). The degradation rate model makes specific, testable predictions for the mechanism of myofibril protein degradation during soleus muscle atrophy: 1) the first-order degradation rate constant does not obtain a fixed value over a 24-day period but is continuously changing throughout atrophy, and 2) the first-order degradation rate constant changes on a time scale slower than protein synthesis rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

VO2max limits.

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Adult↗
PubMed1989

Application of molecular biology in exercise physiology.

Past progress in exercise biochemical research has often depended on the use of knowledge and techniques which were originally reported from other disciplines. With the advent of newer methodologies in molecular biology, the purpose of this review has been to document the status of information gained from the application of molecular biological techniques to questions in exercise physiology. Furthermore, this review has speculated how new methods in molecular biology might be employed to answer classic questions in exercise physiology. A powerful revolution in science, that is, molecular biology, will provide new information about exercise mechanisms, which ideally will improve the training programs for elite athletes as well as continue to be associated with the public's interest in exercise training.

Exercise↗
PubMed1988

Effect of elective surgical procedures on tissue protein synthesis.

The purpose of the study was to examine whether an early decrease in protein synthesis rates occurred in any tissues after abdominal surgery in postprandial rats. Leucine-specific radioactivity in mixed protein and on tRNA was determined after continuous infusion of L-[3H]leucine. Synthesis rates of mixed protein were significantly decreased in the gastrocnemius muscle, but not in the jejunum, liver, or heart, of rats 1-2 hr after splenectomy and ovariectomy or after combining the groups that had various types of abdominal surgery. These results suggest that a very early decrease in the protein synthesis rate of the gastrocnemius muscle occurs after laparotomy.

Abdomen↗
PubMed1988

Alpha-actin and cytochrome c mRNAs in atrophied adult rat skeletal muscle.

Specific complementary DNA (cDNA) hybridization probes were used to estimate the levels of alpha-actin and cytochrome c mRNAs and also 18S rRNA in three models of skeletal muscle atrophy. After 7 days of hindlimb suspension, or immobilization, or denervation, protein content decreased 26-32% in all muscles studied except suspended fast-twitch muscle, which lost only half as much protein. alpha-Actin mRNA content decreased 51-66% and cytochrome c mRNA content decreased 42-61% in slow- and fast-twitch muscles in all three models of atrophy. However, total RNA content did not show similar directional changes; RNA content decreased 27-44% in suspended and immobilized muscle but was unchanged in denervated fast-twitch muscle. The results were interpreted to suggest that loss of weight-bearing function of skeletal muscle is a major factor affecting the levels of alpha-actin and cytochrome c mRNAs during muscle atrophy.

Actins↗
PubMed1988

Clenbuterol prevents or inhibits loss of specific mRNAs in atrophying rat skeletal muscle.

It is known that denervation or hindlimb suspension both decrease the content of rRNA, alpha-actin mRNA, and cytochrome c mRNA in adult rat skeletal muscle. In the present study, the provision of clenbuterol (an anabolic agent) to adult female rats during a 7-day period of denervation of the soleus and gastrocnemius muscles prevented entirely the loss of rRNA, alpha-actin mRNA, and cytochrome c mRNA that normally occurs in denervated muscle. Although clenbuterol inhibited most of the loss of alpha-actin mRNA that occurred in the soleus and gastrocnemius muscles after 7 days of hindlimb suspension, clenbuterol administration had less effect on preventing the loss of rRNA and cytochrome c mRNA in hindlimb suspended skeletal muscle. Clenbuterol had no effect on protein content in atrophied muscle resulting from denervation or suspension. These data suggest that clenbuterol can maintain the expression of certain RNAs in atrophying adult rat skeletal muscle.

Actins↗
PubMed1988

Skeletal muscle enlargement with weight-lifting exercise by rats.

A rat model of weight lifting that produces skeletal muscle enlargement utilizing regimens of resistance training similar to those employed in human training programs is described. The model consists of electrically stimulating the lower leg muscles to contract against a weighted pulley bar. Animals were subjected to training protocols employing low-frequency repetitions with high training loads within a training session. Initial maximum loads of between 200 and 800 g were progressively increased during the 16 wk of training. Work done at the end of the training period increased to an average value 66% higher than that performed at the start of training. The gastrocnemius wet weight and protein content increased (P less than 0.001) by 18 and 17%, respectively, in the stimulated loaded leg in all but one training protocol, a program in which rats were exercised more frequently. RNA content, but not concentration, was increased in the trained gastrocnemius muscle from each protocol, resulting in muscle enlargement. These data indicate that the basic model presented here provides a suitable vehicle for future studies into the biochemical events that may cause skeletal muscle enlargement during resistance training but, based on limited data, suggests that an increased frequency of training days may hinder muscle enlargement in this model.

Animals↗
PubMed1988

Perspectives on molecular and cellular exercise physiology.

A challenge to applied physiologists is to continue to apply new methods to their field. The purpose of this review is to speculate how recent advances in the fields of molecular and cell biology might be applied to exercise physiology to provide greater insights into the mechanisms underlying adaptations to a single bout of exercise and to repeated bouts of exercise (training). The review is organized to consider the actions occurring outside the cell, through the cellular membrane and cytoplasm to the nucleus. These topics are as follows: blood-borne signals, polypeptide growth factors, membrane receptors (insulin receptor, adrenergic receptors, acetylcholine receptors, phosphorylation of receptors, and mutant receptors), transduction through the plasmalemma (glucose transporters and G proteins), second messengers (phosphatidylinositol phosphates and calcium), cis sequences required for muscle-specific gene expression, transcriptional regulation by physiological signals, and gene expression. Exercise physiology is a challenging discipline that integrates molecules, cell-to-cell interaction, tissues, and the whole organism during the physiological stress of exercise by the live, unanesthetized animal.

Animals↗
PubMed1988

Sculpturing new muscle phenotypes.

Changes in the pattern of muscle activity are followed by new patterns of protein synthesis, both in the contractile elements and in the enzymes of energy metabolism. Although the signal transducers have not been identified, techniques of molecular biology have clearly shown that the adaptive responses are the regulated consequence of differential gene expression.

Adaptation, Physiological↗
PubMed1987

Cytochrome c protein-synthesis rates and mRNA contents during atrophy and recovery in skeletal muscle.

It is known that immobilization of the rat hindlimb by plaster casting leads to muscle atrophy and loss of muscle protein. In the present study, immobilization of the rat hindlimb for 6 h resulted in a significant 27% decrease in the absolute rate of cytochrome c synthesis in the red quadriceps muscle, without any change in the relative amount of cytochrome c mRNA. Cytochrome c mRNA in normal red quadriceps muscle was observed to be of four different lengths (1400, 1050, 650 and 580 bases). After 7 days of immobilization, the absolute rate of cytochrome c synthesis remained depressed and cytochrome c mRNA decreased by 40%; each of the cytochrome c mRNAs decreased, with a preferential disappearance of the 1050- and 1400-base lengths. Immobilization was ended on day 7, and the atrophied muscle was allowed to recover. At day 4 of recovery, the absolute rate of cytochrome c synthesis was 92% higher and the amount of cytochrome c mRNA had returned to control values. The abundances of the 1050- and 1400-base cytochrome c mRNAs had increased more than the shorter cytochrome c mRNAs, so that they were higher than control values. It appears that acute decreases in contractile activity of the red quadriceps muscle alter cytochrome c synthesis rates via translational or post-translational mechanisms, whereas chronic periods of modified contractile activity alter its synthesis rate via pre-translational mechanisms.

Animals↗
PubMed1987

Actin synthesis rate and mRNA level increase during early recovery of atrophied muscle.

The purpose of this study was to correlate actin synthesis rate and alpha-actin mRNA level in the gastrocnemius-plantaris muscles of limbs during their recovery from 7 days of immobilization in 200- to 280-g female rats. The fractional synthesis rate of actin in control muscle was 1%/day. Actin synthesis rate was 33% of control level at the 7th day of hindlimb immobilization, returned to control value at the 2nd recovery day, and was three times higher than control on the 4th day of recovery. The alpha-actin mRNA was 53% of control at the 7th day of immobilization, and its increase during the 1st 2 recovery days paralleled the increase in actin synthesis rate; this suggests that pretranslational mechanisms caused the initial increase in actin synthesis. Further increases in actin synthesis from the 2nd to the 4th day appear to be under translational control, since actin synthesis was 300% of control on the 4th recovery day and alpha-actin mRNA was only 128% of control.

Actins↗
PubMed1987

Physiologic and biochemical effects of immobilization on muscle.

Muscle strength rapidly declines during limb immobilization because of a decrease in muscle size and a decrease in tension per unit of muscle cross-sectional area. Muscle fatigability also increases rapidly after limb immobilization. Muscles within limbs fixed by plaster casts have lower levels of resting glycogen and adenosine triphosphate (ATP), a more rapid depletion of muscle glycogen and ATP during work, a greater increase in lactate during work, and a decreased capacity to oxidize fatty acids during work. The greatest loss of absolute muscle mass occurs at the beginning of muscle wasting with subsequent loss of muscle being exponential. A significant decrease in the rate of protein synthesis in muscles is observable at the sixth hour of limb immobilization, which most likely initiates the net loss of muscle protein. A change in the amount of either translational or elongational factor is most likely responsible for the early decrease in this rate of protein synthesis.

Adenosine Triphosphate↗
PubMed1985

Control of adaptations in protein levels in response to exercise.

The nature of the contractile stimuli to which a skeletal muscle is subjected determines which proteins will increase in skeletal muscle. Rates of muscle protein synthesis decrease during an exercise bout for durations of less than 30 min. Synthesis has been reported to increase, remain unchanged, or decrease during exercise bouts lasting from 30 min to 7 h. Protein synthesis rates apparently increase when exercise exceeds 7 h. After short bouts of exercise, protein synthesis rates in muscles appear to decrease in the first hour after exercise, but in the second hour after exercise increase to levels greater than normal. We hypothesize that decreases in ATP and pH levels in muscle during contractile activity may dampen a calcium-mediated stimulation of translation of RNA. That the content of alpha-actin mRNA in muscles of immobilized limbs is unchanged when actin synthesis initially decreases suggests that a decrease in the translation of alpha-actin mRNA is the facilitating step in the decrease in actin synthesis. Rates of muscle protein degradation decrease during exercise if exercise duration is less than 12 h, but increase when exercise is continuous for a day. After intense exercise, rates of protein degradation in skeletal muscle may be increased. An increased ratio of NAD(P)H:NAD(P) in muscle during short-term exercise may decrease degradation. Increased lysosomal enzyme activity in muscle occurs during the postexercise period.

Adenosine Triphosphate↗
PubMed1984

Levels of blood-bourne factors and cytosol glucocorticoid receptors during the initiation of muscle atrophy in rodent hindlimbs.

When only 1 hindlimb of the adult mouse was immobilized for 13 h, the immobilization-induced failure of insulin to stimulate 2-deoxyglucose uptake was observed in the immobilized soleus muscle. 2-deoxyglucose uptake was unchanged in the contralateral, nonimmobilized muscle. In the rat, protein synthesis rates decreased in the one immobilized limb as compared to rates measured in the contralateral nonimmobilized limb of the same animal. The synthesis rates in the contralateral nonimmobilized limb of a rat with one immobilized limb were not significantly different from rates of muscle protein synthesis observed in rats with no hindlimb immobilization. Specific binding of 3H-dexamethasone, as determined by exchange assay in the gastrocnemius muscle cytosol, increased after 7 days of immobilization, but not after only 6 h of immobilization. Changes in the level of blood-bourne factors or in cytosolic glucocorticoid levels do not by themselves initiate muscle atrophy in immobilized rodent limbs.

Animals↗
PubMed1984

Muscle atrophy by limb immobilization is not caused by insulin resistance.

Hindlimbs of adult female rats were immobilized for 1 day. The hindquarter was then perfused either without or with 200 microunits of insulin/ml perfusate. The percentage increase in muscle protein synthesis rates by the inclusion of insulin in the perfusate was similar between control and hindlimb immobilized groups. Thus, the previously reported inability of insulin to stimulate any increase in glucose metabolism in skeletal muscle after 1 day of immobilization ( Seider , Nicholson and Booth 1982) does not also extend to an inability of insulin to stimulate an increase in protein synthesis in muscles of immobilized limbs.

Animals↗