Formation and function of compression wood in gymnosperms

Westing, Arthur H. (Middlebury Coll., Vt.). 1965.Formation and function of compression wood in gymnosperms. Bot. Rev. 31: 381–480 A review with ca. 575 references. The world literature pertaining to the biology of compression wood (Rotholz; reaction wood) is evaluated critically. Compression wood is a geotropic reaction to an inertial force and is peculiar to the Coniferales, Ginkgoales, and Taxales. It is formed by the cambium (or cambial derivatives) of the lower side of inclined stems and branches, where it expandsin situ thereby tending to right the former and maintain (or restore) the inherent angle of the latter. Compression wood is stimulated to form by applications of indoleacetic acid, but under natural conditions is interpreted to result from an increased sensitization of cells on the lower side to an insignificantly changed level of endogenous auxin. A theoretical model of the perception (susception) mechanism is advanced. The mechanics of righting is discussed and the forces involved are estimated. Frequent reference is made to other geotropic phenomena of the higher plants, particularly to tension wood, the analogue of compression wood in the arborescent Dicotyledoneae. Much pertaining to the perception, formation, and function of compression wood remains to be elucidated     

LOCAL REDUCTION OF SPINDLE FIBER BIREFRINGENCE IN LIVING NEPHROTOMA SUTURALIS (LOEW) SPERMATOCYTES INDUCED BY ULTRAVIOLET MICROBEAM IRRADIATION

Irradiation of the mitotic spindle in living Nephrotoma suturalis (Loew) spermatocytes with an ultraviolet microbeam of controlled dose produced a localized area of reduced birefringence in the spindle fibers. The birefringence was reduced only at the site irradiated, and only on the spindle fibers irradiated. Areas of reduced birefringence, whether produced during metaphase or during anaphase, immediately began to move toward the pole in the direction of the chromosomal fiber, even though the associated chromosomes did not necessarily move poleward. Both the poleward and the chromosomal sides of the area of reduced birefringence on each chromosomal fiber moved poleward with about the same, constant, velocity. On the average, the areas of reduced birefringence moved poleward with about the same velocities as did the chromosomes during anaphase. The area of reduced birefringence was interpreted as a region in which most, though not necessarily all, of the previously oriented material was disoriented by the irradiation. The poleward movement of the areas of reduced birefringence indicates that the spindle fibers are not static, nonchangeable structures. The poleward movement possibly represents the manner in which the birefringent spindle fibers normally become organized. All the experiments reported were on primary spermatocytes which completed the second meiotic division subsequent to the experimentation. Since both the irradiated and the control cells completed the two meiotic divisions, the movement and irradiation effects studied in the first division were nondegenerative.     

MORPHOLOGICAL AND BIOCHEMICAL CORRELATES OF CEREBRAL MICROSOMES : I. Isolation and Chemical Characterization

Microsomal fractions, both homogeneous in appearance and functionally operative, were isolated from a homogenate of rat cerebral cortex by fractionation in water. The preparations thus obtained contain the membranous elements of the endoplasmic reticulum, synaptic vesicles, and ribosomes. Esterase, ATPase, and glutamine synthetase were found to be present and fully functional in the microsomal fractions isolated in water. The contamination of the water-isolated microsomal fractions by mitochondria and lysosomes was found to be considerably lower than in microsomal pellets isolated in sucrose. The contamination by nerve ending particles, as judged by electron microscopy and by the levels of soluble lactic dehydrogenase entrapped in the cytoplasm of the particles, was also low. Most of the contamination by mitochondria and nerve ending particles could be removed by treatment of the microsomal pellet with 150 mM NaCl. Resistant to elution by this treatment is the lysosomal contamination as well as microsomal esterase and ATPase. Glutamine synthetase, on the other hand, was almost totally solubilized. Microsomal preparations isolated in water are also shown to contain amounts of protein, RNA, phospholipid, and ganglioside comparable to those found in microsomal preparations isolated in sucrose.     

THE ASSOCIATION OF ACETYLCHOLINESTERASE AND MEMBRANE IN SUBCELLULAR FRACTIONS OF THE ELECTRIC TISSUE OF ELECTROPHORUS

Subcellular fractions of the electric tissue of the main organ of the eel Electrophorus electricus were prepared in sucrose media by differential centrifugation and differential discontinuous gradient centrifugation. The distributions of acetylcholinesterase, cytochrome oxidase, DNA, and protein were determined. The appearance of the fractions was determined by phase contrast microscopy and by electron microscopy. A fraction prepared by differectial centrifugation at 30,000 g for 20 minutes in 0.89 M sucrose contained 63 per cent of the total acetylcholinesterase activity at 4 times the specific activity of that of the tissue homogenate. A subfraction prepared by centrifugation in a discontinuous density gradient showed a peak of total and relative specific acetylcholinesterase activity of 35 per cent and 1.9, respectively. The average over-all purification was 7 times. The acetylcholinesterase peak was below the cytochrome oxidase peak and above the DNA peak in the density gradient. The presence of acetylcholinesterase in the fractions was correlated with the presence of large fragments of the cell membrane; however, the presence of other tissue components was noted. The acetylcholinesterase associated with membrane was found to be activated by incubation with sodium deoxycholate. The possible use of the peak fraction containing membranes rich in acetylcholinesterase for the investigation of other components of the acetylcholine system and of other properties of the membrane is discussed.     

Die Ausdrucksbewegungen der Sichelente,Anas falcata L.

Zusammenfassung Die Ausdrucksbewegungen der Sichelente,Anas (Eunetta) falcata Georgi, werden beschrieben, soweit möglich vorläufig analysiert und mit denen nächstverwandter Arten, vor allem denen vonAnas (Nettium) crecca crecca L.,Anas (Chaulelasmus) strepera L. undAnas (Mareca) penelope L. verglichen. Dieser Vergleich ergibt, genau wie der morphologischer Merkmale des Gefieders und der Knochentrommel, eine systematische Stellung vonfalcata genau zwischen den drei genannten Arten, näher den beiden erstgenannten als der dritten. Die Verteilung der Merkmal-Gemeinsamkeiten einerseits mitcrecca, andererseits mitstrepera, läßt den Schluß zu, daß die drei Arten divergent aus einer gemeinsamen Ahnenform entstanden seien. Keine gemeinsamen Merkmale, die bei anderen Arten fehlen, verbinden die drei genannten Formen zu einer Gruppe.Beim Gesellschaftsspiel der Sichelerpel sind, im Gegensatz zu dem aller anderen bisher daraufhin untersuchten Schwimmentenarten, alle beteiligten Bewegungsweisen, einschließlich des einleitenden Schüttelns, zur Ente hin orientiert, die hier, wie beicrecca undstrepera, am Spiel der Erpel sehr regen Anteil nimmt. Dagegen fehlen solche Bewegungen, die durch Ritualisierung aus Angriffsverhalten entstanden sind, beim Gesellschaftsspiel völlig, spielen aber eine große Rolle, analog dem Triumphgeschrei der Gänse und Tadorninen, beim Zusammenhalt der bereits verpaarten Tiere.     

Egg Membrane Lytic Activity of Sperm Extract and its Significance in Relation to Sperm Entry in Hydroides hexagonus (Annelida)

Previous electron microscope studies indicated that the individual spermatozoön of Hydroides hexagonus forms a hole in the vitelline membrane by means of lysis. Other observations established that the hole is real, being visible in living material during sperm entry. During the present investigation sea water extracts from frozen-thawed sperm were tested for lytic effect on the membrane. In normal living eggs the membrane appears as a single thick envelope, but in electron micrographs of sections it is seen to consist of a narrow outer border layer, a wide principal or middle layer, and a narrow inner border layer. After immersion in sperm extract the outer border layer elevates but does not dissolve, the middle layer liquefies and disappears, and the inner border layer seems not to change. This is interpreted as lysis of the middle layer. The extract exerted the same effect on fertilized and unfertilized eggs. In electron micrographs the sections treated with extract greatly resemble that part of the membrane which has been penetrated by the individual spermatozoön. It is concluded that the individual spermatozoön, too, exerts a lytic effect. Together, the present and two earlier studies are considered clearly to demonstrate that in Hydroides the individual spermatozoön does indeed make an entry hole in the egg membrane by applying lytic material to that part of the membrane in its own vicinity.