No abstract

No abstract

Female Syrian hamsters have been subjected to continual centrifugation for a period of 4 weeks at four or five times the earth's gravity. Animals were 5 weeks of age at the onset of exposures. Although an increased gravitational field curtails body growth, certain organs were found to show an increase in their relative mass when compared to control littermates. The heart, diaphragm, gastrocnemius muscle, lungs, kidney, and head showed a relative increase in mass, and the femur bones of centrifuged hamsters showed a relative increase in length.

No abstract

One of the factors believed to influence growth of organisms is gravity. Experimental investigation of how development is altered by changing gravity has been quite limited. Matthews( 1 ) reports that rats, which developed in a centrifugal field 3 times that of the earth's gravitational field, were smaller than normal rats. The purpose of this paper is to report that the growth of fly larvae was retarded by simulating an increased gravitational field.Materials and methods. Kewly hatched larvae of the common fruit fly (Drosophila melanogaster, wild type, red eye), cultured upon a banana-agar medium,t were subjected to continual centrifugation so as to produce the effect of increased gravity. They remained in a given centrifugal field throughout the experiment. The media was centrifuged under experimental conditions for 24 hours previous to the experiment and excess water, squeezed from the media during this process, was drained off. Control and experimental animals were placed on similar preparations.Sizes of the larvae were recorded by means of contact photographs (Fig. 1). Volumes --Light source 0 f LOOD cut from ton of ~ lidped plastic~-r -. Cellophone stretched Over mouth of tube %-L * I centrifuge tube .Aubber bond s , , 'Larvae in woter or fixative 'Photogrophic plote FIG. 1. Arrangement of materials used to record size of larvae by contact photographs. * This work was supported in part by The Central Scientific Fund, College of Medicine, State University of Iowa. t n i s medium is described in Turtox Service Leaflet No. 15, 'General Biological Supply House, Chicago, Ill.(v) were calculated by assuming the shape to be that of an ellipsoid of revolution so that the following equation would apply:where w is the width and 1 is the length. Growth constants (k's) were calculated by dividing the change in the natural logarithm of v by the time required for such a change.These changes were based upon 2 measurements of v, one made when the experiment began and the second, a day later. Approximately 20 test and 20 control animals were studied in each experiment. When no later records of size were desired, the animals were killed and fixed in a solution of formalinacetic-alcohol. If experiments were continued, the larvae were photographed alive in water each day, placed on a fresh preparation of media, and returned to the centrifuge. Centrifugation of test preparations was carried out with a Servel, angle centrifuge (Type XL) in an incubator at 31.5 t 0.3OC. Control preparations were placed in the same incubator. Field was varied in one of two ways: the rate of revolution could be controlled or the radius of revolution could be decreased by packing cotton in the bottom of the tube holders. In this paper, the field is expressed in g's, with one g equal to the Earth's gravitational field of 980 cm/s&.Results. The growth rate was reduced by centrifugation ( Fig. 2 and 3 ) . In 3 different experiments, using 1630 g, 2250 g, and 3100 g, where the larvae were permitted to develop for several days, size leveled off before th...