Zoospore Germination in Blastocladiella Emersonii

1972 ◽  
Vol 10 (2) ◽  
pp. 315-333
Author(s):  
D. R. SOLL ◽  
D. R. SONNEBORN
Keyword(s):  
Osmotic Shock ◽  
Cell Structure ◽  
Ion Selectivity ◽  
Choline Chloride ◽  
Exposure Period ◽  
Monovalent Cation ◽  
Continuous Exposure ◽  
Initial Exposure ◽  
Cell Conversion ◽  
High Concentrations

Zoospore germination in B. emersonii is accompanied by a series of abrupt, dramatic changes in cell structure. Membranes appear to be variously involved in many of these changes. Germination is subject to simple manipulations of the ionic environment: swimming zoospores can be maintained for long periods in the buffered CaCl2 solution into which they are initially released, whereas dilution into a solution containing KCl and MgCl2 in addition to CaCl2 results in rapid, semisynchronous germination of entire zoospore populations. The control of germination by ionic means has been characterized in the following ways: (a) Very brief (40 S to 2 min) exposure to GS, followed by replacement with buffered CaCl2 is as effective as continuous exposure in eliciting rapid germination of the entire zoospore population. (b) The effective component of GS is KCl: GS lacking KCl does not elicit rapid germination; conversely, buffered KCl alone is as effective as complete GS in eliciting germination. (c) Zoospore populations are sensitive to KCl concentration; as the KCl concentration is reduced, the proportion of cells which undergo rapid germination is also reduced. (d) At optimal concentration (5 x 10-2 M), the following salts are equally as effective as KCl in eliciting germination: KI, KBr, NaCl, CsCl, RbCl, and choline chloride. (e) At high concentrations (2.5-5 x 10-2 M), CaCl2 and MgCl2 elicit semi-synchronous conversion of zoospores to round cells, but only after sizeable delays (v. KCl). Conversion of round cells to germlings does not occur in MgCl2 and is enormously delayed in CaCl2; when formed, the germ tubes appear abnormal. (f) Monovalent cation salts of complex divalent anions (sulphate, tartrate, molybdate, tungstate) also exhibit decreased effectiveness (v. KCl) in eliciting germination. (g) The monovalent cation salts NH4Cl and LiCl, the divalent cation salt MnCl2, and the non-ionic compound sucrose are all ineffective in eliciting rapid germination. When in combination with an effective elicitor (KCl), LiCl totally blocks germination, MnCl2 and sucrose lead to significant delays in zoospore to round cell conversion, while NH4Cl has no effect on the population kinetics. (h) LiCl can block germination even when added after the completion of the otherwise sufficient early exposure period to GS (see (a) above). The blocking effect of LiCl can be almost completely reversed by replacement with KCl. On the basis of this characterization it is concluded that (1) rapid germination is not elicited simply by osmotic shock; rather, the cells are capable of responding to other (especially ionic) properties of their chemical environment; and (2) while brief exposure to KCl is sufficient to elicit germination, there are evidently other ion-sensitive steps occurring after the completion of this initial exposure period. Implications of the results in relation to the regular ion selectivity patterns found in other ion-dependent systems, the possible site(s) of action of the eliciting compounds, and the newly discovered ‘zoospore maintenance factor’ are discussed.

Toxic effects of inhaled DMMP on the kidneys of Fischer-344 rats

1987 ◽  
Vol 45 ◽  
pp. 880-881
Author(s):  
D.R. Mattie ◽  
C.J. Hixson
Keyword(s):  
Left Kidney ◽  
Inhalation Exposure ◽  
Electron Microscopic Examination ◽  
Exposure Period ◽  
Male Rats ◽  
Continuous Exposure ◽  
Fischer 344 Rats ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Fischer 344

Dimethylmethylphosphonate (DMMP) is a simple organophosphate used industrially as a flame retardant and to lower viscosity in polyester and epoxy resins. The military considered the use of DMMP as a nerve gas simulant. Since military use of DMMP involved exposure by inhalation, there was a need for a subchronic inhalation exposure to DMMP to fully investigate its toxic potential.Male Fischer-344 rats were exposed to 25 ppm or 250 ppm DMMP vapor on a continuous basis for 90 days. An equal number of control rats were sham-exposed. Following the 90-day continuous exposure period, 15 male rats were sacrificed from each group. Two rats from each group had the left kidney perfused for electron microscopic examination. The kidneys were perfused from a height of 150 cm water with 1% glutaraldehyde in Sorensen's 0.1M phosphate buffer pH 7.2. An additional kidney was taken from a rat in each group and fixed by immersion in 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer pH 7.4. A portion of the 9 kidneys collected for electron microscopy were processed into Epon 812. Thin sections, stained with uranyl acetate and lead citrate, were examined with a JEOL 100B Transmission Electron Microscope. Microvilli height was measured on photographs of the cells of proximal tubules. This data, along with morphologic features of the cells, allows the proximal convoluted tubules (PCT) to be identified as being S1, S2, or S3 segment PCT.

The Effect of High Concentrations of Ethylene on Seed Germination of Douglas Fir (Pseudotsugamenziesii (Mirb.) Franco)

1975 ◽  
Vol 5 (3) ◽  
pp. 419-423 ◽  
Author(s):  
Carey Borno ◽  
Iain E. P. Taylor
Keyword(s):  
Seed Germination ◽  
Germination Rate ◽  
Inhibitory Effect ◽  
Germination Percentage ◽  
Douglas Fir ◽  
Control Treatment ◽  
Continuous Exposure ◽  
Short Term ◽  
Short Term Exposure ◽  
High Concentrations

Stratified, imbibed Douglas fir (Pseudotsugamenziesii (Mirb.) Franco) seeds were exposed to 100% ethylene for times between 0 and 366 h. Germination rate and germination percentage were increased by treatments up to 48 h. The 12-h treatment gave largest stimulation; 30% enhancement of final germination percentage over control. Treatment for 96 h caused increased germination rate for the first 5 days but reduced the germination percentage. Germinants were subject to continuous exposure to atmospheres containing 0.1 – 200 000 ppm ethylene in air, but it did not stimulate growth, and the gas was inhibitory above 100 ppm. Although some effects of high concentrations of ethylene may have been due to the lowering of oxygen supplies, this alone was insufficient to account for the full inhibitory effect. The mechanism of stimulation by short-term exposure to ethylene is discussed.

Intracellular distribution of lead in Tetrahymena during continuous exposure to the metal

1979 ◽  
Vol 39 (1) ◽  
pp. 383-396
Author(s):  
J.R. Nilsson
Keyword(s):  
Cell Growth ◽  
Growth Medium ◽  
Food Vacuole ◽  
Continuous Exposure ◽  
Organic Growth ◽  
Food Vacuoles ◽  
Entire Cell ◽  
Membrane Bound ◽  
Lag Period ◽  
High Concentrations

Lead acetate (0.1–0.2%) forms a precipitate with the organic growth medium. The Tetrahymena cells ingest this lead-containing precipitate and cell growth is resumed after a variable lag period. Ingested lead is observed as electron-dense material in food vacuoles. Soon after exposure, cytoplasmic lead (preserved with certain fixation only) is revealed as electron-dense particles in cilia and in a halo around digestive vacuoles. Later the lead particles pervade the entire cell but after the lag period they are confined to membrane-bound spaces. In dilute growth medium, high concentrations of lead inhibit food-vacuole formation and cell growth. Under these conditions lead is deposited in alveoli of the pellicle and is also found in autophagic vacuoles and other membrane-limited structures. The study has revealed that lead enters Tetrahymena through the membrane of digestive vacuoles and through the cell surface. The change in distribution of lead during the lag period indicates that a mechanism is activated for removal of lead into membrane-bound spaces. The final storage of lead seems to be in lysosomes.

scholarly journals 2',3'-Dideoxyadenosine is selectively toxic for TdT-positive cells

Blood ◽  
1988 ◽  
Vol 71 (6) ◽  
pp. 1601-1608
Author(s):  
Z Spigelman ◽  
R Duff ◽  
GP Beardsley ◽  
S Broder ◽  
D Cooney ◽  
...  
Keyword(s):  
Cell Death ◽  
Cell Lines ◽  
Ex Vivo ◽  
Exposure Period ◽  
Lymphocytic Leukemia ◽  
Leukemic Cells ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Parental Line ◽  
Continuous Exposure ◽  
Hiv Replication

The 2′,3′-dideoxynucleosides (ddNs) are currently undergoing clinical evaluation as antiretroviral agents in HIV-infected individuals. When phosphorylated, the ddNs (ddNTPs) function as chain-terminating substrate analogues with reverse transcriptase, thereby inhibiting HIV replication. These nucleoside analogues can also inhibit, by chain- terminating additions, the primitive lymphoid DNA polymerase, terminal deoxynucleotidyl transferase (TdT). To determine the effect of possible intracellular chain-terminating additions of ddNMPs by TdT, we exposed a series of TdT-positive and TdT-negative cell lines to 2′,3′- dideoxyadenosine (ddA), a representative ddN. At ddA concentrations 25- fold higher than required for inhibition of HIV replication, progressive dose-related cytotoxicity was observed in the TdT-positive cell lines. This was accentuated by the adenosine deaminase inhibitor Coformycin (CF), presumably by enhancing the intracellular generation of ddATP from ddA. A central role of TdT in mediating the ddA/CF cytotoxicity was suggested by studies in a pre-B-cell line rendered TdT positive by infection with a TdT cDNA-containing retroviral vector. After a 48-hour continuous exposure period to 250 mumol/L ddA and 30 mumol/L CF, 30% cell death was observed in the TdT-negative parental line, whereas 90% cell death was observed in the TdT-positive daughter line. Exposure of fresh TdT-positive leukemic cells to ddA/CF for 72 hours ex vivo resulted in cytotoxicity (six cases of acute lymphocytic leukemia [ALL]) while not affecting TdT-negative acute leukemic cells (six cases). We conclude that ddA/CF selectively damages TdT-positive cells, presumably by chain-terminating additions of ddAMP, and that this may have therapeutic relevance in TdT-positive malignant disease.

scholarly journals Effects of neuraminidase on the regulation of erythropoiesis

Blood ◽  
1984 ◽  
Vol 63 (4) ◽  
pp. 784-788 ◽  
Author(s):  
VF LaRussa ◽  
F Sieber ◽  
LL Sensenbrenner ◽  
SJ Sharkis
Keyword(s):  
Bone Marrow ◽  
Colony Formation ◽  
Bone Marrow Cells ◽  
Marrow Cell ◽  
Colony Growth ◽  
Mouse Bone Marrow ◽  
Continuous Exposure ◽  
Low Concentrations ◽  
High Concentrations ◽  
Marrow Cells

Abstract In this article, we present evidence that sialic acid-containing surface components play a role in the regulation of erythropoiesis. A 1- hr exposure of mouse bone marrow cells to high concentrations of neuraminidase reduced erythroid colony formation. Coculture of 10(6) untreated thymocytes with neuraminidase-treated bone marrow cells restored erythroid colony growth. Neuraminidase-treated thymocytes retained their ability to suppress erythroid colony formation by untreated marrow cells, but lost their ability to enhance erythroid colony formation. Continuous exposure to low concentrations of neuraminidase enhanced erythroid bone marrow cell colony growth in response to a suboptimal dose of erythropoietin.

Metolachlor and Alachlor Effects on Membrane Permeability and Lipid Synthesis

Weed Science ◽  
1982 ◽  
Vol 30 (4) ◽  
pp. 399-404 ◽  
Author(s):  
Jill M. Mellis ◽  
Parthan Pillai ◽  
Donald E. Davis ◽  
Bryan Truelove
Keyword(s):  
Zea Mays ◽  
Glycine Max ◽  
Choline Chloride ◽  
Lipid Synthesis ◽  
Significant Loss ◽  
Phospholipid Synthesis ◽  
Root Tips ◽  
Naphthalic Anhydride ◽  
Cotton Root ◽  
High Concentrations

Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] at 1 × 10−5and 1 × 10−4M increased the leakage of previously absorbed,32P-labeled orthophosphate from the roots of onion (Allium cepaL.), a susceptible species, by 14 and 41 times the control values, respectively. A significant amount of32P leaked from the roots of the moderately susceptible species, cotton (Gossypium hirsutumL. ‘DPL 61′) and cucumber (Cucumis sativusL. ‘Ashley′), whereas no significant loss of32P occurred from two tolerant species, soybean [Glycine max(L.) Merr. ‘Bragg′] and corn (Zea maysL. ‘Pioneer 3369A′). At either 1 × 10−7or 1 × 10−6M, 1,8-naphthalic anhydride (NA) prevented32P leakage from onion roots in the presence of 1 × 10−5M metolachlor. High concentrations of NA [0.1% (w/v) suspensions], however, promoted32P leakage and did not protect onion roots from the leakage induced by high concentrations (1 × 10−4M) of metolachlor. Neither metolachlor nor alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], at 1 × 10−4M, inhibited the uptake of acetate-2-14C or malonic acid-2-14C into excised cotton root tips or the incorporation of the precursors into lipids. Similarly, neither herbicide inhibited phospholipid synthesis by cotton root tips. Incorporation of14C-choline chloride into phosphatidylcholine was not significantly inhibited by metolachlor.

scholarly journals Effect of Added Sugar on the Consumption of A Lipid-Based Nutrient Supplement Among 7–24-Month-Old Children

Nutrients ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 3069
Author(s):  
Harriet Okronipa ◽  
Amado D. Quezada-Sánchez ◽  
Susan L. Johnson ◽  
Cloe Rawlinson ◽  
Selene Pacheco-Miranda ◽  
...  
Keyword(s):  
Exposure Period ◽  
Primary Objective ◽  
Health Centers ◽  
Double Burden ◽  
Added Sugar ◽  
Initial Exposure ◽  
Nutrient Supplements ◽  
Before And After ◽  
Study Population ◽  
Food Mixture

Small-quantity lipid-based nutrient supplements (SQ-LNS) could help prevent malnutrition. Our primary objective was to examine the acceptability and consumption of sweetened and unsweetened versions of SQ-LNS before and after 14-days of repeated exposure. A total of 78 mother-infant dyads recruited from health centers in Morelos, Mexico, were randomized to two groups of SQ-LNS (sweetened, LNS-S; unsweetened, LNS-U). During the study, infants were fed SQ-LNS (20 g) mixed with 30 g of complementary food of the caregiver’s choice. The amount of supplement-food mixture consumed was measured before, during and after a 14-day home exposure period. We defined acceptability as consumption of at least 50% of the offered food mixture. At initial exposure, LNS-U consumption was on average 44.0% (95% CI: 31.4, 58.5) and LNS-S 34.8% (25.3, 44.0); at final exposure, LNS-U and LNS-S consumption were 38.5% (27.8, 54.0) and 31.5% (21.6, 43.0). The average change in consumption did not differ between the groups (2.2 p.p. (−17.2, 24.4)). We conclude that the acceptability of sweetened and unsweetened SQ-LNS was low in this study population. Since consumption did not differ between supplement versions, we encourage the use of the unsweetened version given the potential effects that added sugar may have on weight gain especially in regions facing the double burden of malnutrition.

scholarly journals Isolation and Characterization of NaCl-Sensitive Mutants of Caulobacter crescentus

2003 ◽  
Vol 69 (6) ◽  
pp. 3029-3035 ◽  
Author(s):  
Luiz Fernando G. Zuleta ◽  
Val�ria C. S. Italiani ◽  
Marilis V. Marques
Keyword(s):  
Caulobacter Crescentus ◽  
Osmotic Shock ◽  
Promoter Regions ◽  
Isolation And Characterization ◽  
Lipopolysaccharide Biosynthesis ◽  
Severe Reduction ◽  
Mutant Strains ◽  
High Concentrations ◽  
Severe Growth

ABSTRACT An attempt to characterize Caulobacter crescentus genes important for the response to high concentrations of NaCl was initiated by the isolation of mutants defective in survival in the presence of 85 mM NaCl. A transposon Tn5 library was screened, and five strains which contained different genes disrupted by the transposon were isolated. Three of the mutants had the Tn5 in genes involved in lipopolysaccharide biosynthesis, one had the Tn5 in the nhaA gene, which encodes a Na+/H+ antiporter, and one had the Tn5 in the ppiD gene, which encodes a peptidyl-prolyl cis-trans isomerase. All the mutant strains showed severe growth arrest in the presence of 85 mM NaCl, but only the nhaA mutant showed decreased viability under these conditions. All the mutants except the nhaA mutant showed a slightly reduced viability in the presence of 40 mM KCl, but all the strains showed a more severe reduction in viability in the presence of 150 mM sucrose, suggesting that they are defective in responding to osmotic shock. The promoter regions of each disrupted gene were cloned in lacZ reporter vectors, and the pattern of expression in response to NaCl and sucrose was determined; this showed that both agents induced ppiD and nhaA gene expression but did not induce the other genes. Furthermore, the ppiD gene was not induced by heat shock, indicating that it does not belong to the σ32 regulon, as opposed to what was observed for its Escherichia coli homolog.

The γ-subunit of Na-K-ATPase is incorporated into plasma membranes of mouse IMCD3 cells in response to hypertonicity

2005 ◽  
Vol 288 (4) ◽  
pp. F650-F657 ◽  
Author(s):  
Kaarina Pihakaski-Maunsbach ◽  
Shigeki Tokonabe ◽  
Henrik Vorum ◽  
Christopher J. Rivard ◽  
Juan M. Capasso ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Time Course ◽  
Plasma Membranes ◽  
Cultured Cells ◽  
Osmotic Shock ◽  
Collecting Duct ◽  
Choline Chloride ◽  
Basolateral Membrane ◽  
Γ Subunit ◽  
Subunit Expression

Hypertonicity mediated by chloride upregulates the expression of the γ-subunit of Na-K-ATPase in cultured cells derived from the murine inner medullary collecting duct (IMCD3; Capasso JM, Rivard CJ, Enomoto LM, and Berl T. Proc Natl Acad Sci USA 100: 6428–6433, 2003). The purpose of this study was to examine the cellular locations and the time course of γ-subunit expression after long-term adaptation and acute hypertonic challenges induced with different salts. Cells were analyzed by confocal immunofluorescence and immunoelectron microscopy with antibodies against the COOH terminus of the Na-K-ATPase γ-subunit or the γb splice variant. Cells grown in 300 mosmol/kgH2O showed no immunoreactivity for the γ-subunit, whereas cells adapted to 600 or 900 mosmol/kgH2O demonstrated distinct reactivity located at the plasma membrane of all cells. IMCD3 cell cultures acutely challenged to 550 mosmol/kgH2O with sodium chloride or choline chloride showed incorporation of γ into plasma membrane 12 h after osmotic challenge and distinct membrane staining in ∼40% of the cells 48 h after osmotic shock. In contrast, challenging the IMCD3 cells to 550 mosmol/kgH2O by addition of sodium acetate did not result in expression of the γ-subunit in the membranes of surviving cells after 48 h. The present results demonstrate that the Na-K-ATPase γ-subunit becomes incorporated into the basolateral membrane of IMCD3 cells after both acute hyperosmotic challenge and hyperosmotic adaptation. We conclude that the γ-subunit has an important role in the function of Na-K-ATPase to sustain the cellular cation balance over the plasma membrane in a hypertonic environment.

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