Occurrence of unidentified bodies that resemble “plastid initials” in poplar cells after breaking of dormancy in midwinter

Summary Electron-microscopic studies of plastids in cortical cells of poplar (Populus euramericana cv. gelrica) were carried out to examine whether any structural changes were initiated after breaking of dormancy in midwinter under non-growing conditions. After the breaking of dormancy, ultrastructural changes became evident and the profiles of plastids became heterogeneous. Organelles resembling the plastid initials proposed by Mühlenthaler and Frey-Wyssling in 1965 were frequently observed concomitant with changes in the plastid envelope. The formation of plastid initials appeared to be initiated by the formation of septa in pre-existing plastids. After this stage, narrow connections appeared between the initials and the parent plastids. Approximately 50 days after the breaking of dormancy in late March, further heterogeneity in the profiles of plastids was observed. At this stage, young plastids (plastids without starch granules) were frequently observed and the formation of plastid initials was hardly ever observed. These observations suggest that the plastid initials may be present for only a limited period in the cortical cells of the poplar and may be the precursors of the proplastids. Similar ultrastructural profiles were found in cortical cells of mulberry and in leaf buds of apple trees, suggesting that such changes in the ultrastructure of plastids are a general feature of perennials.     

The signal distinguishing between targeting of outer membrane β-barrel protein to plastids and mitochondria in plants

The proteome of the outer membrane of mitochondria and chloroplasts consists of membrane proteins anchored by α-helical or β-sheet elements. While proteins with α-helical transmembrane domains are present in all cellular membranes, proteins with β-barrel structure are specific for these two membranes. The organellar β-barrel proteins are encoded in the nuclear genome and thus, have to be targeted to the outer organellar membrane where they are recognized by surface exposed translocation complexes. In the last years, the signals that ensure proper targeting of these proteins have been investigated as essential base for an understanding of the regulation of cellular protein distribution. However, the organellar β-barrel proteins are unique as most of them do not contain a typical targeting information in form of an N-terminal cleavable targeting signal. Recently, it was discovered that targeting and surface recognition of mitochondrial β-barrel proteins in yeast, humans and plants depends on the hydrophobicity of the last β-hairpin of the β-barrel. However, we demonstrate that the hydrophobicity is not sufficient for the discrimination of targeting to chloroplasts or mitochondria. By domain swapping between mitochondrial and chloroplast targeted β-barrel proteins atVDAC1 and psOEP24 we demonstrate that the presence of a hydrophilic amino acid at the C-terminus of the penultimate β-strand is required for mitochondrial targeting. A mutation of the chloroplast β-barrel protein psOEP24 which mimics such profile is efficiently targeted to mitochondria. Thus, we present the properties of the signal for mitochondrial targeting of β-barrel proteins in plants.     

“Transfer cells” Plant cells with wall ingrowths,specialized in relation to short distance transport of solutes—Their occurrence,structure, and development

Summary Plant cells possessing ingrowths of wall material, and hence having protoplasts with unusually high surface-to-volume ratios, may be found in a wide variety of anatomical situations and in most of the major taxa of multicellular plants. They are termed here transfer cells. Their function relates to any of four categories of trans membrane flux: 1. Absorption of solutes from the external environment (e.g. epidermis of submerged leaves), 2. Secretion of solutes to the external environment (e.g. nectaries and other glands), 3. Absorption of solutes from an internal, extracytoplasmic compartment (e.g. vascular parenchyma, haustorial-type connections, embryo sacs and embryos), 4. Secretion of solutes into an internal extracytoplasmic compartment (e.g. tapetum of anther, pericycle of root nodule). An overall assessment of their occurrence, structure, development and role in the plant is presented taking account of published information and new observations.The wall ingrowths form just as intensive transport starts; they become best developed on those faces of the cell presumed to be most active in solute transport and their form, frequency and final degree of development are within limits characteristic of the plant species and of the location of its transfer cells. Numerous mitochondria and a conspicuous endoplasmic reticulum usually accompany this wall specialization, and the relevance of these features to the exchange of solutes across the plasma membrane is discussed.Transfer cells are apparently restricted to situations where adverse surface area—volume relationships exist between donor and receptor compartments of the transport pathway and/or where the transported solutes are accompanied by a minimal flow of solvent. This suggests that selection pressures of a physiological nature may have shaped evolution of the transfer cell, its wall-membrane apparatus emerging as a module which may serve in any of several forms of intensive, short distance transport.     

The occurrence of “wasting disease” of Zostera in Ireland in the 1930's

There is only one publication quoted in connection with “wasting disease” of Zostera marina L. in Ireland. This was examined and it was concluded that in fact, it did not describe “wasting disease”, but merely the normal seasonal changes of Zostera. However, another report which has not been quoted before did give an account of the disease in County Down. Evidence that the disease occurred in County Mayo is presented for the first time.     

The development of in vitro and in vivo anti-tumor cytotoxicity in noncytotoxic,MOPC-315-tumor-bearer,spleen cells “educated” in vitro with MOPC-315 tumor cells

Summary Spleen cells from mice bearing various sizes of MOPC-315 plasmacytoma tumors were not cytotoxic in the ⁵¹Cr release assay or the local adoptive transfer assay. These noncytotoxic spleen cells became cytotoxic, however, upon in vitro cocultivation with MOPC-315 tumor cells. The maximal level of in vitro anti-tumor cytotoxicity (⁵¹Cr release) with in vitro educated tumor-bearer spleen cells was obtained on the fifth day of the cocultivation and was equal to or lower than the level of cytotoxicity seen with in vitro educated normal spleen cells. On the other hand, the level of in vivo anti-tumor cytotoxicity (Winn assay) achieved with tumor-bearer spleen cells educated in vitro was at least equal to, but usually greater than the level of anti-tumor cytotoxicity obtained with normal spleen cells educated in vitro. Thus, in vitro education can generate anti-tumor cytotoxicity in autochthonous lymphoid cells from tumor-bearing hosts. Such educated histocompatible cells should be useful for immunotherapy regimens that might be applicable to man.     

Division and DNA distribution in ribosome-deficient plastids of the barley mutant “albostrians”

The ribsome-deficient plastids of the albino leaves of the barley mutant albostrians divide at about the same rate as normal plastids and contain similar levels of plastids DNA to the normal plastids. Double-ring structures were observed around the neck of constricting dumbbell-shaped, ribosome-deficient plastids in the basal intercalary meristem of albino leaves. In the distal region of albino leaves the ribosome-deficient plastids contain a rudimentary thylakoid system often closely associated with DNA nucleoids. It is suggested that nuclear coded proteins synthesized within the cytoplasm are responsible for the formation of the double-ring structures and the rudimentary thylakoids of albino plastids.     

Bioactive chemicals and biological—biochemical activities and their functions in rhizospheres of wetland plants

Wetland soils provide anoxia-tolerant plants with access to ample light, water, and nutrients. Intense competition, involving chemical strategies, ensues among the plants. The roots of wetland plants are prime targets for root-eating pests, and the wetland rhizosphere is an ideal environment for many other organisms and communities because it provides water, oxygen, organic food, and physical protection. Consequently, the rhizosphere of wetland plants is densely populated by many specialized organisms, which considerably influence its biogeochemical functioning. The roots protect themselves against pests and control their rhizosphere organisms by bioactive chemicals, which often also have medicinal properties. Anaerobic metabolites, alkaloids, phenolics, terpenoids, and steroids are bioactive chemicals abundant in roots and rhizospheres in wetlands. Bioactivities include allelopathy, growth regulation, extraorganismal enzymatic activities, metal manipulation by phytosiderophores and phytochelatines, various pest-control effects, and poisoning. Complex biological-biochemical interactions among roots, rhizosphere organisms, and the rhizosphere solution determine the overall biogeochemical processes in the wetland rhizosphere and in the vegetated wetlands. To comprehend how wetlands really function, it is necessary to understand these interactions. Such understanding requires further research.     

Histochemical investigation of β-glucuronidase in culture cells and regenerated plants of Scutellaria baicalensis Georgi

 Strong activity of β-glucuronidase first appeared in the epidermal and glandular hair cells of leaf primordia regenerated from callus of Scutellaria baicalensis Georgi. Leaf primordia matured rapidly in culture to form shoots within 1 month in which both the mesophyll cells and the glandular hairs were deeply stained. Leaves predominantly accumulated β-glucuronidase in both glandular hair cells and mesophyll cells. β-Glucronidase activity in leaves was higher in the summer and decreased in the winter. The stem section collected in the summer had a different β-glucuronidase distribution pattern from that of the root in that in the former strong activity appeared in the periderm cells and collenchyma cells which was decreasingly dispersed into the phloem layer cells. In the winter, β-glucronidase activity decreased compared to that in summer. It can be argued that the distribution of β-glucuronidase in this plant is closely linked with the defense against pathogens: it is a starting key enzyme which may act together with the flavonoids, which play an important role as a proton donor for the detoxification metabolism of H₂O₂. Received: 1 December 1998 / Revision received: 10 March 1999 / Accepted: 14 June 1999     

Transient expression of β-glucuronidase in plastids of various plant cells and tissues delivered by a pneumatic particle gun

Chloroplast expression plasmids pTRBCL-GUS (tobaccorbcL promoter-gusA-tobaccorbcL terminator) and pHHU3004 (spinach ‘x gene’ promoter-gusA-spinachrbcL terminator) and a control nuclear expression plasmid pBI221 (CaMV 35S promoter-gusA-NOS terminator) were introduced separately into cultured cells and tissues of tobacco andArabidopsis thaliana, as well as into cultured cells of the lower land plants liverwort and hornwort by a pneumatic particle gun. The pTRBCL-GUS and pHHU3004 plasmids produced many blue spots in the BY-2 cells and the roots ofArabidopsis thaliana, but not in any of the green cells or tissues. The results suggest that the pTRBCL-GUS and pHHU3004 plasmids are expressed more in proplastids and amyloplasts than in chloroplasts. GUS activities of the BY-2 cells bombarded with pTRBCL-GUS and pHHU3004 were insensitive to α-amanitin treatment (10 and 50 μg/ml), while that of the cells with pBI221 greatly decreased by the same treatment. Hence, it is likely that the pTRBCL-GUS and pHHU3004 plasmids were substantially expressed in the proplastids.     

The occurrence and properties of histone H1° in quiescent rabbit tissue

• 1.1. The issue of the existence and the properties of histone H1° in quiescent rabbit tissues was approached by electrophoretic, Chromatographic and immunochemical techniques.
• 2.2. The results demonstrated that the rabbit tissues did contain a typical histone H1°, its properties being comparable to those of H1° from all other sources studied thus far.

     

Acid phosphatase and peroxidase in ‘resting’ acinar cells of the major salivary glands of cats and their possible movement into secretory granules

Synopsis After fixation by perarterial perfusion using an aldehyde mixture, salivary tissues were prepared for ultrastructural cytochemistry of acid phosphatase or peroxidase. Great variations in the distributions of the reaction products occurred, often within the same cell. Acid phosphatase staining occurred not only in lysosomes and sometimes in a GERL system, but a diffuse cytoplasmic component was also found in submandibular central acinar cells and to a lesser extent in parotid acini and variable staining occurred in the secretory granules of these cells. Peroxidase was variably associated with rough endoplasmic reticulum in submandibular demilunar cells, parotid acini, and more strongly in some sublingual cells. The secretory granules of the latter were darkly stained, but in parotid granules there was varibale staining and least staining occurred in the granules of submandibular demilunes.These results are thought to indicate that not all enzymes present in secretory granules have reached there by an elective secretory process. Sometimes they appear to have entered the granules haphazardly, possibly having been enzymes associated with intracellular cisternal channels for transport or metabolism of other secretory substances and ultimately to have passed into the cisternal channels by chance or as part of a natural removal of redundant material.     

The role of pleiotrophin and β-catenin in fetal lung development

Mammalian lung development is a complex biological process, which is temporally and spatially regulated by growth factors, hormones, and extracellular matrix proteins. Abnormal changes of these molecules often lead to impaired lung development, and thus pulmonary diseases. Epithelial-mesenchymal interactions are crucial for fetal lung development. This paper reviews two interconnected pathways, pleiotrophin and Wnt/β-catenin, which are involved in fibroblast and epithelial cell communication during fetal lung development.     

The purification of cellulase and exo-laminaranase and their role in the formation ofPythium sp. “protoplasts”

A cellulase and a laminaranase have been purified from a Streptomyces lytic enzyme complex. Lipase and protease were separated from glucanases. A combination of the purified glucanases produced protoplasts fromPythium sp. PRL 2142. Lipase was shown to act as an adjuvant in this process.National Research Council of Canada Postdoctorate Fellow 1965–67.     

The mechanism of cytogenetic genotoxicity of exogenous glutathione in V-79 cells in vitro—implication of hydrogen peroxide and general traits of oxidative chromosome damage

The mechanism of cytogenetic genotoxicity (clastogenicity, induction, cell cycle delay) of 10^–3 M glutathione in V79-E cells, as described by Thust and Bach (1985), was studied in detail by using different treatment conditions. It was found that I-cystine is the essential cofactor in the incubation system. Catalase, but not superoxide dismutase, abolished the genotoxic effect, and the iron chelator desferoxamine, as well as the hydroxyl radical scavenger mannitol, diminished the activity. It is suggested that glutathione, in combination with V79-E cells and cystine, forms a hydrogen peroxide-generating system which provokes the adverse effects. Glutathione as well as I-cysteine and 2-mercaptopropionylglycine, which were checked for comparison, show a paradoxic genotoxicity, i.e., at 10^–2 M the effects return almost to the level of controls. Concentration dependence and other criteria of cytogenetic genotoxicity observed with glutathione show obvious similarities to those of other oxidatively acting agents and reveal striking differences to the cytogenetic effects of typical genotoxins.Abbreviations BUdR 5-bromodeoxyuridine - EMEM Eagle's minimum essential medium - GSH glutathione - MPG 2-mercaptopropionylglycine - SCE sister chromatid exchange - SOD superoxide dismutase - TPA 12-0-tetradecanoylphorbol-13-acetate