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J ARONSON

Publications and source records attributed to J ARONSON.

11 recordsLinked to original sources
PubMed1963

OVERLAP OF THE BIREFRINGENT COMPONENT OF ADJACENT A REGIONS DURING THE INDUCED SHORTENING OF FIBRILS TEASED FROM DROSOPHILA MUSCLE.

Fibrils from the indirect flight muscle of Drosophila melanogaster which have been teased into a solution containing 0.1 M KCl, 2 mM EDTA, 4 mM MgCl(2), and 2.5 mM ATP at pH 7.0 can be made to shorten to 10 per cent of their initial length by reducing the level of ATP at a pH of about 8 or by briefly treating the fibrils with trypsin before lowering the level of ATP. Fibrils shortened in either of these ways, when dehydrated and immersed in nitrobenzene, display a strong positively birefringent band at the level of the Z band. In the trypsin-treated fibrils the width of this Z band increases as the fibril shortens. The data obtained are in agreement with the view that the positively birefringent Z band results from the interdigitation of A filaments in adjacent sarcomeres. With shortening to about 35 per cent of the initial length, the cytological pattern suggests that the A filaments of alternate as well as of adjacent A regions interdigitate.

Adenosine Triphosphate↗
PubMed1963

OBSERVATIONS ON THE VARIATIONS IN SIZE OF THE A REGION OF ARTHROPOD MUSCLE.

The muscles of three different arthropods, a mite, a fly, and an ostracod, show variations in the length of the A region within a given individual. There is no indication that the observed differences in A band length are related to the functional state of the muscle since little, if any, decrease in the length of the A bands was noted when sarcomeres shortened. The length of the A region was determined by polarized light microscopy and in the case of the mite and the ostracod this measurement was made on intact muscles. It is concluded that the size of the A filaments in an individual can vary in a manner unrelated to immediate functional changes. The I filaments may vary in size, but this could not be clearly demonstrated.

Animals↗
PubMed1962

The elongation of myofibrils from the indirect flight muscle of Drosophila.

Myofibrils which lengthen by several per cent in the presence of ATP and magnesium ions were prepared by teasing indirect flight muscle of Drosophila in solutions containing ethylenediaminetetraacetate. A study was made of the hydrogen ion, magnesium ion, ATP, and potassium chloride concentrations with which this effect could be observed. The lack of elongation with pyrophosphate and several nucleoside triphosphates suggests that the lengthening is ATP specific. A relaxing factor system comparable to that described for rabbit muscle was not demonstrable, as elongated fibrils did not shorten with calcium ions, carnosine, or digitonin.

Animals↗
PubMed1961

Sarcomere size in developing muscles of a tarsonemid mite.

The embryo of a tarsonemid mite was found to be suitable for in vivo observations of muscle development by polarization microscopy. The four dorsal muscles of the metapodosoma each contain three sarcomeres, the anterior two of which can be seen clearly. These sarcomeres can be identified and followed during much of their development. Sarcomeres are about 2.5 micra long when first detected and increase in length until they are about 10 micra long. The change in length is associated with a slow, approximately constant rate of increase in the length of the A region, and an initially slow then much more rapid increase in the length of the I band. Preceding the period when the I band elongates rapidly there is an increase in the diameter of the muscle fibers and an increase in the retardation of the A band. A, I, Z, and H bands are visible during most of these changes. The change in A band length has been interpreted in terms of the growth of the A filaments which have been observed by electron microscopy in muscles of other animals. It is suggested that the exceptionally long sarcomeres in this mite result from the early fixing of the number of sarcomeres in a given muscle fiber.

Animals↗