Movement of Pulses of Labeled Auxin in Corn Coleoptiles

The transit of indole-3-acetic acid through 20-mm sections of corn coleoptiles can be separated from processes involved in the uptake of auxin by the section and the exit of auxin from the section. Aerobic sections are supplied with an exogenous source of (14)C IAA for a limited time, and after the source is removed, a pulse of (14)C IAA moves down at 12 to 15 mm/hour. After transfer to nitrogen, movement of the pulse at the aerobic rate persists for about 10 minutes; thereafter drops to only 1 to 2 mm/hour and remains at this level during the next 4 hours. Within 2 hours, 70% of the total (14)C in aerobic sections has moved 10 mm or more down the section from the position of the initial peak, whereas after the same time in nitrogen less than 10% of the total (14)C has moved as far.During the migration down the coleoptile, the peak of radioactivity becomes broader and less distinct. This dispersion is more rapid in aerobic than anaerobic sections, but appears to be nonpolar and to occur along the existing concentration gradients. Diffusion probably contributes to this dispersion.In both inhibited and uninhibited sections, the movement of the peak, in contrast to its dispersion, is A) polar (downward) and B) independent of existing concentration gradients. Thus transit within the section possesses the fundamental properties of the overall transport system. The reduced amount of transport in inhibited sections is more likely maintained by glycolysis than by a low level of aerobic respiration dependent on the residual oxygen in the tissue.     

Morphological variations of isolated liver mitochondria during spontaneous deterioration

Summary The effects of mitochondrial concentration, incubation temperature and composition of suspension medium on spontaneous swelling of rat liver mitochondria were investigated. The swelling was measured simultaneously by four different methods — optical density changes at 520 m, mitochondrial diameter measurements and differential counts made on phase contrast micrographs of fixed suspensions, and electron microscopical examination of the fine structural alterations.The findings indicate that, in isosmotic sucrose and KCl media, both mitochondrial concentration and incubation temperature influence the course of spontaneous swelling. It was also found that the ratio of Tris (hydroxymethyl) aminomethane to mitochondria concentration profoundly affects the morphological transformations.Correlation of the results obtained with the four methods shows that measurement of optical density changes alone is insufficient for full assessment of mitochondrial swelling and that this method therefore is best used in conjunction with electron microscopical studies.The authors wish to thank Mr. George O'Shea for valuable technical assistance.     

Adhesive apparatus in certain Indian hill stream fishes

The results of a detailed study on the adhesive apparatus of Indian hill stream cyprinid and sisorid fishes are presented. The structure of the mental suctorial disc in the genus Garra is described. Histological study of the mental region of Crossocheilus and Psilorhynchus has also been made and compared with the mental disc of Garra . The muscles of the disc which control its movements in bringing a partial vacuum during adhesion have been investigated. The complexity of the geniohyoideus muscles in Garra is interesting. Variations in the degree of development and histological modifications of the mental disc are exhibited by the fishes of the genus Garra .
A thoracic adhesive apparatus in the form of longitudinal or transverse ridges and grooves is present in the sisorids, Laguvia, Glyptothorax and Pseudecheneis except Gagata . A close study has revealed that the adhesive apparatus of the catfishes works mainly on the principle of friction. The variations in shape, size and location of the adhesive apparatus in various species are correlated to their respective habitats.
Structural variation in the adhesive apparatus of Pseudecheneis is maximum in comparison to that in Laguvia and Glyptothorax . It is discovered that the modifications are associated with the presence of multi-spinous layers, formation of caps by the basal or holdfast cells and with the transformation of loose areolar tissue into thick collagenous dermis. The presence of a pad of adipose tissue in the region of the adhesive apparatus has been reported and its physiological significance as a source of stored food suggested.
The anterior part of the protractor ischii muscle is modified to control the action of the adhesive apparatus. In Pseudecheneis , besides the m. protractor ischii, the ventral part of m. mesioventral is also associated with the adhesive apparatus.