Postembryonic brain development in the monarch butterfly,Danaus plexippus plexippus L.

Development Genes and Evolution -     

Phytochrome in etiolated annual rye

Summary During a seven-fold increase in length the content of the coleoptile in photoreversible phytochrome increased four-fold and that of the primary leaf nine-fold. The phytochrome content, during growth, expressed on a fresh- or dry-weight basis did not vary greatly for either organ. Phytochrome per mg dry weight (OD⁷³⁰/mg=0.5) was nearly the same in the leaf as in the coleoptile. Coleoptiles studied had a constant DNA content of 4.1 g per organ. DNA content of the leaf increased with age. Phytochrome per DNA was much higher in the coleoptile than in the primary leaf and increased with growth in each of these organs. Thus, there was not a constant amount of phytochrome per cell in either tissue with increasing age and there was not the same amount of phytochrome per cell in the coleoptile as in the primary leaf at any age.This work was supported in part by U.S. Atomic Energy Commission Contract No. AT (30-I)2373.     

Micromorphology of Cryptococcus neoformans

Fine details of the internal and external morphology of Cryptococcus neoformans as seen in ultrathin sections are described and illustrated with electron micrographs. The capsule characteristic of this species contained microfibrils (30 to 40 A in diameter) that appeared to radiate from the cell wall and to coil and intertwine in various directions. These thin, uniformly structured, electron-dense filaments are believed to represent complex polysaccharide molecules. The internal morphology of C. neoformans was in many ways similar to that of yeasts studied by other authors. The cell was uninucleate with a single nucleolus. The nuclear envelope, a pair of unit membranes interrupted by pores, was typical of that found in eucaryotic organisms. Smooth endoplasmic reticulum, mitochondria, vacuoles, storage granules, and ribosomes were consistent features of the cytoplasm. In addition, C. neoformans presented membranous organelles derived from the plasma membrane and comparable to bacterial mesosomes and mitochondria of an annulate type.     

Spectrophotometric Measurements of Phytochrome in vivo and Their Correlation with Photomorphogenic Responses of Phaseolus

Direct in vivo measurements of phytochrome have been made in Phaseolus vulgaris by 2-filter difference spectrophotometry (Ratiospect). All measurements were made at 730 versus 800 nm and it is assumed that the Δ (ΔOD) is directly proportional to the PFR concentration of phytochrome present. Dose response curves were determined for both physiological and spectrophotometric responses for red induction and far-red photoinactivation. For induction, saturation occurs at 100 mj/cm² and for inactivation at 30 mj/cm². The rate of hook opening and the physiological response measured 20 hours after induction are both shown to be directly proportional to the initial amount of PFR present spectrophotometrically. The sensitivity of the tissue correlates well with the absolute amount of phytochrome present, the inner portion of the hook having the maximum concentration of 0.042 Δ (ΔOD)/g fresh weight. If the total reversible phytochrome concentration is reduced by exposure to red light and allowing PFR to decay out of the system the remaining sensitivity of the tissue is shown to be directly correlated with the amount of PR remaining in the tissue. PFR disappears rapidly in the dark at 25°, and is not detectable after 6 hours. There is no indication that PFR reverts in the system to PR. At 4°, PFR does not disappear measurably up to 1 hour and is nearly totally reversible to PR.