This study examined the effect of resistance training on exercise-induced contrast shift in magnetic resonance (MR) images. It was hypothesized that a given load could be lifted after training with less muscle showing contrast shift, thereby suggesting less muscle was used to perform the exercise. Nine males trained the left quadriceps femoris (QF) muscle 2 days/wk for 9 wk using 3-6 sets of 12 knee extensions each day. The right QF served as a "control." Exercise-induced contrast shifts in MR images evoked by each of three bouts of exercise (5 sets of 10 knee extensions with a load equal to 50, 75, and 100% of the maximum pretraining load that could be lifted for 5 sets of 10 repetitions) were quantified pre- and posttraining. MR image contrast shift was quantified by determining QF cross-sectional area (CSA) showing increased spin-spin relaxation time. One repetition maximum increased 14% in the left trained QF and 7% in the right untrained QF. Left QF CSA increased 5%, with no change in right QF CSA. Left QF CSA showing contrast shift was less after each bout of the exercise test posttraining. This was also true, to a lesser extent, for the right QF at the higher two loads. The results suggest that short-term resistance training reduces MR image contrast shift evoked by a given effort, thereby reflecting the use of less muscle to lift the load. Because this response was evident in both trained and contralateral untrained muscle, neural factors are suggested to be responsible.(ABSTRACT TRUNCATED AT 250 WORDS)

Plant roots grow in the direction of increasing soil moisture, but studies of hydrotropism have always been difficult to interpret because of the effect of gravity. In this study it was found that roots of the mutant pea ;Ageotropum' are neither gravitropic nor phototropic, but do respond tropically to a moisture gradient, making them an ideal subject for the study of hydrotropism. When the root caps were removed, elongation was not affected but hydrotropism was blocked, suggesting that the site of sensory perception resides in the root cap.

1984. Thigmomorphogenesis; Ethylene evolution and its role m the changes observed in mechanically perturbed bean plants. -Physiol. Plant 62: 289-296. 'Mechanical perturbations, in the form of either rubbing or wounding, cause ethylene evolution from bean internodes {Phaseolus vulgaris L. cv. Cherokee Wax). This evolution begins 45 to 60 min after perturbation or wounding and peaks about 2 h later. Maxima! thigmomorphogenesis oceurs if internodes are perturbed when they are 10 mm or less in length. Maximal ethylene evolution, however, occurs in longer internodes. When one internode is perturbed, ethylene evolution is not observed from other internodes even though they respond thigmomorphogenetically by exhibiting decreased elongation. Ethylene evolution is apparently a result of increased 1-amino-eyclopropane-l-carboxyiie acid (ACC) production after perturbation. Inhibitors of ACC and ethylene synthesis block increased radial growth but not reduced elongation. Ethylene may therefore be only one of several factors eausing thigmomorphogenesis .

A protein identifiable as calmodulin has been isolated from oat (Avena sativa, var Garry) tissues. This protein is relatively heat stable, binds to hydrophobic gels, and phenothiazines in a calcium-dependent fashion, and binds to antibody to rat testes calmodulin. Based on its migration on sodium dodecyl sulfate-polyacrylamide gels, ultraviolet absorption spectrum, and amino acid composition, oat calmodulin is essentially identical to calmodulin isolated from other higher plants. Radioimmunoassays indicate that calmodulin is associated with isolated oat protoplasts, mitochondria, etioplasts, and nuclei and also appears to be a component of oat cell wall fractions.Much evidence has accumulated recently to support the hypothesis that Ca 2 plays a major role in mediating the adaptations of plants to certain environmental changes (12,22). As in animals, at least some Ca2-imediated responses in plants are controlled by Ca2-binding regulatory proteins. Among these, the most studied and best characterized is calmodulin (1).We have published reports suggesting a possible role for calmodulin in mediating phytochrome and gravitropic responses in Avena saliva (oats) (2, 21). As part of our ongoing research on this question, we have isolated and characterized calmodulin from oats and have estimated its content, both in intact tissue and in isolated subcellular fractions, by radioimmunoassay. Here we report the results of these experiments.MATERIALS AND METHODS Plant Material. Except where indicated, the starting material for all extractions was taken from the coleoptiles and primary leaves of 3-to 4-d-old dark-grown oat (A vena sativa, var. Garry) seedlings, harvested 5 to 7.5 mm above the seed. The oats were grown on water-saturated vermiculite at 27C.Calmodulin Isolation. Two extraction methods were employed.'Supported by grants from the National Aeronautics and Space Administration (NSG 7480), The National Science Foundation (PCM 81-03429), and The Robert A. Welch Foundation (F 858) to S. J. R.