Genesis of microspore-derived triploid petunias

Summary A total of 61 microspore-derived plants of Petunia parodii were grown to maturity revealing a predominent population of triploids, 80.3%. Cytological investigations, together with the evidence from microfluorimetry, suggest that the origin of these triploids was due to the fusion of interphase nuclei in two different pathways. In the majority of embryogenic microspores, a vegetative nucleus of 1C DNA content fused with an endo-reduplicated 2C DNA generative nucleus at the binucleate stage and produced true triploid embryoids and plantlets (A pathway). Where this fusion failed, both the vegetative and the generative nuclei divided separately and in the multinucleate microspore two or more daughter nuclei fused to form a mixoploid embryoid. Such mixoploid embryoids produced a mixed population of plants with various ploidy levels as well as ploidy polymorphism within an individual. Since the triploids are morphologically superior with a faster growth rate than their diploids and related tetraploids, a predominent population of triploid plants was obtained from such mixoploid embryoids (B pathway). By low temperature treatment of the anther-donor buds, the embryogenic response of microspores was enhanced up to 5-fold.     

Effects of microtubule-inhibitors on nuclear migration and rhizoid differentiation in germinating fern spores (Onoclea sensibilis)

Summary Germinating spores of the sensitive fern,Onoclea sensibilis L., undergo premitotic nuclear migration before a highly asymmetric cell division partitions each spore into a large protonemal cell and a small rhizoid initial. Nuclear movement and subsequent rhizoid formation were inhibited by the microtubule (MT) inhibitors, colchicine, isopropyl-N-3-chlorophenyl carbamate (CIPC) and griseofulvin. Colchicine prevented polar nuclear movement and cell division so that spores developed into enlarged, uninucleate single cells. CIPC and griseofulvin prevented nuclear migration, but not cell division, so that spores divided into daughter cells of approximately equal size. In colchicine-treated spores, MT were not observed at any time during germination. CIPC prevented MT formation at a time coincident with nuclear movement in the control and caused a disorientation of the spindle MT. Both colchicine and CIPC appeared to act at a time prior to the onset of normal nuclear movement. The effects of colchicine were reversible but those of CIPC were not. Cytochalasin b had no effect upon nuclear movement or rhizoid differentiation. These results suggests that MT mediate nuclear movement and that a highly asymmetric cell division is essential for rhizoid differentiation.     

The changes of nuclear position and distribution of circumferentially aligned cortical microtubules during the progression of cell cycle inAdiantum protonemata

The intracellular positions of the nucleus and of cortical, circumferentially aligned microtubules (CCAM) in filamentous, single-celled protonemata ofAdiantum capillus-veneris were determined throughout the cell cycle in the dark. When apical growth continued at G₁ phase, the nucleus migrated keeping a constant distance from the tip. When the apical growth stopped at late S or G₂ phase, the nucleus stopped moving forward and then slightly moved backward to the site of cytokinesis. The CCAM were found only in the dome of protonemal tip when growing under continuous red light; they increased in number after dark incubation for 12 hr and then decreased after 20th hr in the dark. The CCAM were usually observed in the region between the nucleus and the tip at 28 hr in the dark. They were located around the nuclear region at pre-prophase and prophase, but then totally disappeared at metaphase and thereafter.     

A hepatic membrane-associated factor stimulates nuclear DNA synthesis in cultured fibroblastic cells

Nuclear DNA replication in cultured mouse fibroblasts is stimulated by isolated hepatic plasma membranes in a time- and concentration-dependent manner. The plasmalemmal activity is susceptible to trypsin treatment, and to treatment with protein modifying agents, N-ethylmaleimide, N-bromosuccinimide, and 2-hydroxy-5-nitro-benzylbromide.     

The fluidity of the nuclear envelope lipid does not affect the rate of nucleocytoplasmic RNA transport in mammalian liver

The effects of in vitro and in vivo modifications of nuclear envelope lipid on DNA leakage and on ATP-stimulated RNA release from isolated rat liver nuclei were investigated. The modifications included corn-oil feeding of the animals to alter the fatty acid composition of the lipids, phospholipase treatment of the isolated nuclei, and extraction of the total lipid with Triton X-100. Significant changes in lipid composition and approximate order parameter values of the spin-label 5-doxylstearate resulted, but there was no significant effect on RNA transport rate. It was concluded that the nuclear envelope lipid does not play any important part in nucleocytoplasmic RNA transport in mammalian liver.     

A new variant of Autographa californica nuclear polyhedrosis virus

A variant of the baculovirus, Autographa californica nuclear polyhedrosis virus, has been isolated in Idaho during an epizootic disease in a field population of A. californica. Genotypic characterization indicates that the virus is distinct from variants previously characterized. Analysis of five clones, derived by plaque purification in cell culture, indicates relative homogeneity of the original virus isolate. Further exploration of the factors involved in natural genetic variability of baculoviruses is appropriate.     

Nuclear inclusions in the nerve cells of the sphenopalatine ganglion of the dog

Summary Large numbers of nuclear inclusions have been found in the nerve cells of the sphenopalatine ganglia of six healthy adult dogs. Their morphological characteristics are similar to those previously described elsewhere. The presence of simple and granular bodies in normal cells seems to support the hypothesis that these nuclear structures might be considered as normal nuclear organelles related to cellular metabolic activity.     

The structure of two alanine containing ferrichromes: Sequence determination by proton magnetic resonance

Summary Metal coordination confers an extraordinary structural stability to the ferrichromes which, independent of their variable amino acid composition, results in a basically unperturbed conformation for all the homologous peptides in the series. The proton magnetic resonance (pmr) characteristics for Al³⁺ analogues (alumichromes) reflect this conformational isomorphism in usual solvents so that single site substitutions are clearly recognized in the pmr spectra. Thus, the substitution of glycine byl-alanine orl-serine introduce new resonances characteristic of the sidechains and alter the pattern of the amide NH pmr region in that doublets substitute for glycyl triplets at the same site. Since for glycine- andl-serine-containing alumichromes the resonances have already been identified, it is possible to unequivocally establish the primary structure of the twol-alanyl homologues ferrichrome C ( ) and sake colorant A ( ) on the basis of the comparative pmr spectra of their Al³⁺ analogues, namely, alumichrome C and alumisake. The resonance assignment, and hence the site occupancy, is substantiated by the temperature coefficients of the NH chemical shifts, rates of¹H-²H exchange and homonuclear proton spin decoupling experiments centered on the NH spectral region. Occupancy of site 1 by a glycine residue is observed for all known ferrichromes, which serves to conserve a hairpin turn. This method of obtaining sequence information should prove of general use for other systems of homologous polypeptides, provided their conformations are not affected by the residue substitutions.     

Microfilament bundles in antheridial nuclei of Achlya ambisexualis E 87

This is the first report of intranuclear microfilaments within gametangial nuclei of oömycetous fungi. Longitudinal sections of four to six microfilaments were frequently observed in meiotic antheridial nuclei of Achlya ambisexualis. Each microfilament measured approximately 7–10 nm in diameter. Spindle tubules (25 nm in diameter) were also observed within some of the nuclei possessing microfilaments.