Thomas P O'brien

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1. The polychromatic staining of plant cell walls by toluidine blue O is described and illustrated. 2. The effects of various common fixatives and the effects of the pH of the staining solution are evaluated. 3. Simple and rapid procedures are described for preparing stained temporary mounts of fresh material, or permanent mounts of embedded and sectioned(More)
Developing aleurone cells can first be distinguished 10 days after anthesis beneath the degenerating nucellus as somewhat cuboidal cells with extremely thin walls and large nuclei. Ribosomes are very abundant but little endoplasmic reticulum (ER) is apparent. By 14 days the cell walls are intensely autofluorescent, possibly due to the presence of a ferulic(More)
A n earl ier p a p e r (S r i v a ~ it a v ,a a n d O 'B 9 i e ~ 1966, P a r t I) ,described ~h,e ,s,tr:uct:ur:e o.f ,the .eamib,ial ~i~nit'iais in .the w'inter 'and ,s~uananer an~nth.s. T~he presen t :paper ,de,s,eri'bes the eh,ar~g,es in ~the ,cell :pr~f,o,pl,a,st which ~ e e o m p a n y ,differentiation .of t~he ,seieo,ndary iphlo, ean e~em,en:t,s.(More)
The distribution of pit fields and plasmodesmata in the mestome-sheath cells of a wheat leaf has been determined by study of sections and partial macerates. Each bundle is approximately symmetrical about the sagittal plane and most plasmodesmata occur in the mestome sheath where its cells abut the metaphloem. Plasmodesmata are absent adjacent to xylem(More)
Early cellularization of the free-nuclear endosperm and subsequent differentation of the aleurone cells in the ventral region of the developing wheatgrain (Triticumaestivum L. cv. Heron) were examined using both light and electron microscopy. In ovules harvested 1 d after anthesis, irregular wall ingroths typical of transfer cells protrude into the(More)
Cell wall formation during the transition from free-nuclear to cellular endosperm of wheat (Triticum aestivum L. cv. Heron) was investigated using correlated light and electron microscopy. Partitioning of the multinucleate syncytium that lines the inner periphery of the embryo sac is initiated 1–2 days after anthesis. Wall ingrowths, at first recognizable(More)
The overall morphology of the developing wheat embryo in relation to its neighbouring tissues is described. The embryo is “isolated” early in development, but appears to be a powerful sink for nutrients. It is supplied initially by hydrolysis of the nucellar parenchyma and later by hydrolysis of neighbouring endosperm cells, which are completely digested.(More)
Extensive structure-activity relationship studies utilizing a beta-MSH-derived cyclic nonapeptide, Ac-Tyr-Arg-[Cys-Glu-His-D-Phe-Arg-Trp-Cys]-NH(2) (3), led to identification of a series of novel MC-4R selective disulfide-constrained hexapeptide analogs including Ac-[hCys-His-D-Phe-Arg-Trp-Cys]-NH(2) (12). The structural modifications associated with(More)
The structure and distribution of cell organelles were observed in the gametophytes of Adiantum capillus-veneris L. undergoing the first cell division induced by white-light irradiation. Under continuous red light, the nucleus is spindle-shaped, encased in a sheath of chloroplasts, and located some distance back from the tip. The apical pole of the nucleus(More)
The giant cells of the petiolar hairs of Heracleum mantegazzianum contain cytoplasmic fibres that are readily visible with phase contrast or interference contrast optics. These fibres are associated with saltatory particle movement and protoplasmic streaming in this cell and are believed to be the living image of similar fibres reported in electron(More)