Uptake of Al across the plasma membrane of plant cells

Measurements of intracellular, cytosolic Al are plagued with technical difficulties. An accurate quantification of Al uptake into the cytosol relies on the effectiveness of the methods that desorb Al bound to the cell wall. However, published desorption methods are not completely effective in removing cell wall Al. Using giant algal cells of Chara corallina, where a physical separation of the cell wall and the cytosol can be achieved surgically, it was shown that up to 99.99% of the total cellular Al accumulates in the cell wall. Even when 95% of total Al present in intact cells was desorbed, still over 20 times more Al was left in the cell wall than in the cytosol. Therefore, without physical separation of the cell wall and the cytosol, minute amounts of cytosolic Al need to be measured in the considerably larger background of the cell wall Al. Consequently, up to several orders of magnitude lower uptake rates of Al were measured across the plasma membrane of intact Chara cells in comparison to currently available values on higher plant cells (Triticum aestivum, t Glycine max, Phaseolus vulgaris), where at least some of the cell wall Al was attributed to the intracellular, cytosolic Al. Uptake of Al across the plasma membrane of Chara cells occurs without a delay at a very low rate that is directly proportional to Al concentration in the uptake medium. Moreover, residual Al left in the cell wall after desorption can be taken up into the cytosol of Chara cells during subsequent growth in the artificial pond water. For measuring Al uptake into roots of higher plants, the Secondary Ion Mass Spectrometry is the best available technique because it appears to overestimate the cytosolic Al to the lower extent than any other currently used analytical method for determination of Al.     

Chlorsulfuron reduces rates of zinc uptake by wheat seedlings from solution culture

Wheat plants differing in zinc efficiency (Excalibur; Zn-efficient, Gatcher and Durati; Zn-inefficient) were grown in HEDTA chelate-buffered nutrient solution in controlled conditions and supplied with 0 or 40 g chlorsulfuron L^-1 . Zinc uptake rates of 12-d-old plants were measured over 80 or 90 minutes using⁶⁵ Zn added to nutrient solutions. Increasing the zinc concentration of the solution increased the rate of zinc uptake, while the percentage of zinc transported to shoots was decreased. Addition of chlorsulfuron to uptake solutions for 90 minutes did not influence rate of zinc uptake or transport of zinc to shoots. Pretreating plants with chlorsulfuron for 5 days decreased zinc uptake rates, but transport to shoots was proportionally increased. Three-day pretreatment with chlorsulfuron was the minimum required for significant differences in uptake and transport of zinc to occur. Plants exposed to chlorsulfuron for 3 days required a further 5 days of growth in chlorsulfuron-free solutions before uptake rates recovered to control plant rates. It is concluded that chlorsulfuron deleteriously but reversibly affects uptake of zinc across the plasma membrane after prolonged exposure.     

Determination of intracellular Ca2+ in cells of intact wheat roots: loading of acetoxymethyl ester of Fluo‐3 under low temperature

Loading of Ca²⁺-sensitive fluorescent probes into plant cells is an essential step to measuring activities of cytoplasmic free Ca²⁺ ions with a fluorescent imaging technique. A major barrier to the loading of the fluorescent probes into plant cells using the acetoxymethyl (AM) esters of the Ca²⁺-sensitive dyes is the presence of cell-wall associated esterases. These esterases hydrolyse the esterified form of the fluorescent probes, rendering the probes membrane-impermeable. A novel non-invasive loading protocol was described in this paper to load the Ca²⁺-sensitive fluorescent probe Fluo-3/AM ester into apical cells of intact wheat roots by incubating the roots in Fluo-3/AM ester solution at 4°C for 2 h followed by 2-h incubation in the dye-free solution at 20°C. The incubation at low temperature inhibited extracellular hydrolysis of Fluo-3/AM ester but had less effect on diffusion of membrane-permeable Fluo-3/AM ester across the plasma membrane, because hydrolysis of Fluo-3/AM ester by extracellular esterases is a chemical process (high Q₁₀), while diffusion of Fluo-3/AM across the plasma membrane is a physical process (low Q₁₀). The Fluo-3/AM ester, accumulated in the root cells during the low temperature incubation, was then cleaved by intracellular esterases during the incubation at 20°C, releasing the membrane-impermeable Ca²⁺-sensitive Fluo-3 in the cytoplasm. The root cells loaded with Fluo-3 showed strong intracellular fluorescence under confocal microscopy. The fluorescence from the root cells was sensitive to the Ca²⁺ ionophore and hydrogen peroxide, indicating that the intracellular fluorescence was due to intracellular Ca²⁺ ions.     

Mechanistic simulation models of nutrient uptake: A review

Mechanistic models of nutrient uptake consider diffusion and mass flow acting simultaneously to supply nutrients to the sorbing root surface. Plant parameters that determine nutrient uptake include those describing changes in root geometry and size due to root growth and others describing kinetics of the nutrient uptake process. Mechanistic models generally assume that nutrient uptake occurs evenly along the roots that are uniformly distributed in homogeneous and isotropic soil having no temporal and spatial gradients in volumetric moisture content. Uptake of immobile nutrients (like P and K) is mainly determined by the soil-supply parameters and is well predicted by the simulation models. In contrast, uptake of mobile nutrients (e.g. Ca and Mg) that usually accumulate at the root surface is determined mainly by the plant-uptake parameters; prediction of uptake of those nutrients is subject to a much wider error due to uncertainties of applying kinetic parameters measured on hydroponically-grown plants to soil-grown plants. Comparison of model-predicted and experimentally-observed uptake values should be done by calculating the mean squares of deviates instead of performing regression analysis, especially if data that encompass a relatively wide range in root length are considered. Complementary-ion effects occurring at the soil-root interface raise the need for developing a multi-nutrient uptake model that will simultaneously calculate uptake of several essential nutrients taking into account interactions among them.     

Cushing's syndrome in childhood

A patient with Cushing''s syndrome whose clinical manifestations began at approximately 9 years of age was followed for a period of four years. Initial laboratory studies revealed urinary 170HCS and 17 KS levels which were elevated for her age, with a normal diurnal variation of plasma cortisol and normal suppression of urinary 170HCS by 1.5 mg. of dexamethasone daily. It was not until four years after the onset of the disease that laboratory studies unequivocally supported the diagnosis of Cushing''s syndrome resulting in definitive therapy. Clinical features consisted primarily of cessation of growth, obesity, and hirsutism, with no evidence of protein depletion. It is suggested that the clinical and laboratory features of Cushing''s syndrome in childhood may present differences from those found in the adult. Failure to recognize these differences may result in delay in therapy with subsequent persisting stigmata of the disorder.     

Die Assimilation von n-Alkanen durch ein marines Bakterium

Zusammenfassung Unter den cellulären Fettsäuren von Stamm H überwiegen die mit 15–18 Kohlenstoffatomen. Ungeradzahlige Fettsäuren treten nur nach Wachstum auf Propionat und ungeradzahligen n-Alkanen auf. Die Kohlenstoffketten der Fettsäuren werden überwiegend de novo synthetisiert, können aber auch unverkürzt vom Substrat übernommen werden. Ungesättigte Fettsäuren werden auf dem anaeroben Wege durch Kettenverlängerung aus kurzkettigen ungesättigten Vorstufen gebildet oder durch direkte Dehydrierung der korrespondierenden Säure.

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The assimilation of n-alkanes by a marine bacterium

Summary Among the cellular fatty acids of Strain H those with 15–18 Carbonatoms are dominating. Odd-numbered fatty acids only occur after growth on propionate and odd-numbered n-alkanes. The carbon chains of the fatty acids are synthesized mostly de novo, but can also be taken unshorted from the substrate. Unsaturated fatty acids are synthesized from short-chained unsaturated precursors via the anaerobic pathway or by dehydrating directly the corresponding saturated fatty acid.

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Zweiter Auszug aus einer Dissertation der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Hamburg, 1969.     

Human minimal androgen insensitivity with normal dihydrotestosterone-binding capacity in cultured genital skin fibroblasts: evidence for an androgen-selective qualitative abnormality of the receptor

We have studied a kindred in which two parts of siblings, maternal first cousins, have a form of "minimal" androgen insensitivity that permits morphogenesis of unambiguous male external genitalia, but interferes with normal virilization at puberty. All four had gynecomastia that required reductive surgery. Apart from this common phenotype, they varied considerably in the temporal and regional aspects of their subvirilization and appreciably in their androgenic responsiveness to pharmacological doses of testosterone. The cultured genital skin fibroblasts from one set of siblings have an androgen-receptor activity with the following properties: (1) a normal maximum-binding capacity (Bmax) with 5 alpha-dihydrotestosterone (DHT), or the synthetic androgen, methyltrienolone (MT; R1881) as ligand; (2) a higher than normal apparent equilibrium dissociation constant (Kd) for DHT (0.77 nM) but not for MT; and (3) an elevated dissociation rate (k) of DHT-receptor (0.013 min-1, 37 degrees C), but not MT-receptor, complexes within intact cells. In addition, prolonged incubation with MT, but not DHT, augments the specific androgen-binding activity of the mutant cells as much as that of the controls. Normal cells yield lower values of apparent Kd for DHT (0.1-0.3 nM) after 2- than after 0.5-hr incubation (0.3-1.8 nM), and 1-hr values are intermediate. This occurs despite concurrent catabolic consumption of DHT from the medium and is considered to reflect transformation of initial, low-affinity DHT-receptor complexes to subsequent, higher-affinity states by a process that depends on time and initial ligand concentration. The mutant complexes described here can readily attain the highest state of affinity with MT, but have an impeded, variably expressed ability to do so with DHT. These findings suggest that a structural mutation at the X-linked locus that encodes the androgen-receptor protein is responsible for its androgen-selective dysfunction. Synthetic, nonhepatotoxic androgens, with corrective effects in vitro comparable to those of MT, may be therapeutically useful for these subjects.     

The Mechanical transmission and some properties of a virus disease of cow-parsnip,Heracleum sphondylium L

The described virus of cow-parsnip,Heracleum sphondylium L., was found in three ruderal localities of Greater Praha. The symptoms are manifested by decolorations which consist of bright yellow areas spreading from the centre of the leaf blade along the main veins. These symptoms appear severely in May. Under higher temperatures and in a chronic stage of infection the symptoms are more or less masked. The disease is mechanically transmissible to parsley, coriander, parsnip, dill, sowbane,Chenopodium quinoa and C.giganteum. The author failed to transmit the disease to celery, carrot, caraway and to 27 species of differential host plants, he failed in the transmission of the virus by the dodder,Cuscuta campestris YUNCK., too. Thermal inactivation point of the virus lies between 51° and 55° C. Infectivity of extracted sap was lost after 2 days at room temperature.     

Erdheim-Chester disease and concomitant tuberculosis successfully treated with chemotherapy and long-term steroids

Erdheim-Chester disease (ECD) is a rare histiocytosis usually affecting the skeletal system, but visceral organs and central nervous system involvement are common as well. Probability exists that immunomodulatory therapies and disorders can play a role in clinical course of the disease. Because of rarity of the disorder, it is hard to classify it and standardize the treatment options, but, according to published material and our experience, cytotoxic chemotherapy and long-term steroids have therapeutic benefit. Although this approach can probably be accepted as standard of care management, novel therapeutic modalities should be explored, and pathogenesis and disorder classification should be cleared out as well. The case of ECD affecting skeletal system and lungs and concomitant laryngeal tuberculosis successfully treated with chemotherapy and long-term steroid therapy is presented.