Accumulation of pollutants in fish

The amount of radioactivity which derived from 14C-labeled pollutants was determined in liver, kidney, intestine, blood, muscle and gills of carp, exposed for 6, 24 and 72 hr to high external concentrations of urea, methanol, atrazine and PCP. The results allowed one to calculate roughly the uptake rate for these compounds. It was low for urea (0.055 micrograms/g per hr), higher for methanol (0.12) and atrazine (0.16) and highest for PCP (1.5). The bioaccumulation factors (BFs) were determined for the different substances and organs. They correlated with the hydrophilic-lipophilic nature of the chemicals. The more lipophilic the substances the more accumulation occurred in the liver. PCP accumulated the most. BF was 300-400 in most tissues except muscle where it was quite low. The BF was 3-4 for atrazine in liver, kidney and intestine, but just 1 in blood, muscle and gills. There is some evidence that the BF for methanol equals 1 in liver, kidney, gills and intestine. It is less than 1 in blood and muscle. Urea was equally distributed in all organs and in the external medium.     

Novel stabilization of phenylalanine ammonia-lyase catalyst during bioconversion of trans-cinnamic acid to l-phenylalanine

Summary Production of l-phenylalanine from trans-cinnamic acid using isolate SPA10 cells was reduced to 26% of that observed initially when cells were reacted a second time with fresh substrate mixture. The stability (reuseability) of Phenylalanine Ammonia-Lyase (PAL) containing cells was significantly influenced by both the trans-cinnamate concentration and initial reaction pH. Using 2% t-cinnamate, l-phenylalanine production was 7-fold greater after 3 successive runs at pH 9.0 than at the optimum of pH 10.2. Cells reacted in the presence of 5% t-cinnamate were relatively unstable. Permeabilising agents, such as toluene and xylene, stimulated l-phenylalanine production but also enhanced instability of the catalyst. Several effectors were shown to stimulate the initial rate of the PAL bioconversion, but only sorbitol, alginate, glutaraldehyde, polyethylene glycol and glycerol conferred any significant degree of stability. Sparging of cultures and bioreactors with various gases revealed that oxygen enhanced PAL inactivation, CO₂ had little effect and nitrogen conferred remarkable stability on PAL activity for several weeks in culture medium. The presence of chloride ions (from HCl) and aeration of substrate mixtures resulted in poor reuseability of catalyst. A combination of H₂SO₄ substitution for HCl and N₂-sparging resulted in excellent initial conversions and good catalyst stability at 26°C but less at 30°C. The inclusion of 1.5 M sorbitol in reaction mixtures maintained PAL stability over several successive incubations.     

Formation and activity of covalent conjugates of poliovirus and ligands binding to cell surface structures

Disulfide-linked conjugates of poliovirus with streptavidin or concanavalin A were formed and the binding of the conjugates to mouse L cells that lack natural poliovirus receptors was studied. The conjugate with streptavidin was specifically bound to biotinylated L cells, but not to unmodified L cells. The conjugate with conA was bound to L cells in the absence of, but not in the presence of alpha-methyl mannoside. Incubation of L cells with bound conjugates did not produce virus, although the conjugates were highly infectious in HeLa cells, containing natural poliovirus receptors. This suggests that the artificially bound virus was unable to penetrate the L cells and start replication. The possibility that binding of the virus to the natural receptor is required for efficient infection is discussed.     

Differential localization of leu-enkephalin and hyperglycemic hormone in axon terminals of the sinus gland of the crabsCarcinus maenas,eriocheir sinensis,andUca pugilator

Summary Leu-enkephalin containing secretory granules were demonstrated in axon terminals of immunogoldlabeled electron-microscopic sections of the sinus gland of three brachyuran crustaceans. These granules have a diameter of 120+-15 nm and differ in electron density from those located in adjacent terminals containing hyperglycemic or molt-inhibiting hormone. These neurohormones do not show co-localization with leu-enkephalin. The cross-reactivity of leu-enkephalin antiserum with met-enkephalin is less than 1%. The sinus glands of the three species examined show no immunoreactivity for FMRF-amide. A modulatory activity of endogenous enkephalin by paracrine mechanisms is suggested.     

The control of bud dormancy in potato tubers

Potato (Solanum tuberosum L.) tuber buds normally remain dormant through the growing season until several weeks after harvest. In the cultivar Majestic, this innate dormancy persisted for 9 to 12 weeks in storage at 10° C, but only 3 to 4 weeks when the tubers were stored at 2° C. At certain stages, supplying cytokinins to tubers with innately dormant buds induced sprout growth within 2 d. The growth rate was comparable to that of buds whose innate dormancy had been lost naturally. Cytokinin-treatment did not accelerate the rates of cell division and cell expansion in buds whose innate dormancy had already broken naturally. Gibberellic acid did not induce sprout growth in buds with innate dormancy. We conclude that cytokinins may well be the primary factor in the switch from innate dormancy to the non-dormant state in potato tuber buds, but probably do not control the subsequent sprout growth.Abbreviations tio ⁶ade 6-(4-hydroxy-3-methylbut-trans-2-enyl amino)purine, zeatin - tio⁶ado 6-(4-hydroxy-3-methylbut-trans-2-enyl amino)-9--D-ribofuranosyl purine, zeatin riboside     

The control of bud dormancy in potato tubers. Measurement of the seasonal pattern of changing concentrations of zeatin-cytokinins

A radioimmunoassay, combined with high-performance liquid chromatography, has been used to analyse the zeatin-type cytokinins of potato (Solanum tuberosum L. cv. Majestic) tubers and tuber buds throughout growth and storage. During tuber growth, zeatin riboside was the predominant cytokinin detected in all tissues. Immediately after harvest, the total cytokinin concentration fell dramatically in the storage tissue, largely as a consequence of the disappearance of zeatin riboside. During storage, levels of cytokinins in the storage tissue remained relatively constant, but increased in the tuber buds. In the buds of tubers stored at 2°C there was a 20-to 50-fold increase in total cytokinin over six weeks, coinciding with the natural break of innate dormancy. At 10°C the rise in the level of bud cytokinins was slower, correlating with the longer duration of innate dormancy. Injecting unlabelled cytokinins into tubers in amounts known to induce sprouting gave rise to increases in cytokinin concentrations in the buds of the same order as the increase associated with the natural break of dormancy. Metabolism of injected cytokinins was greater in non-dormant than in dormant tubers. The roles of cytokinin concentration and the sensitivity of the buds to cytokinin in the control of dormancy are discussed.Abbreviations CK cytokinin - FW fresh weight - HPLC high-performance liquid chromatography - RIA radioimmunoassay - tio⁶ade 6-(4-hydroxy-3-methylbut-trans-2-enylamino)-purine=zeatin - tio⁶adeglc⁹ 6-(4-hydroxy-3-methylbut-trans-2-enylamino)-9--D-glucopyranosyl purine=zeatin-9-glucoside - tio⁶ado 6-(4-hydroxy-3-methylbut-trans-2-enylamino)-9--D-ribofuranosyl purine=zeatin riboside - tio⁶ado-[³H]-diol a radioactive derivative of zeatin riboside, synthesised by periodate-oxidation followed by [³H]NaBH₄-reduction - tio⁶AMP 6-(4-hydroxy-3-methylbut-trans-2-enylamino)-9--D-5-phosphoribofuranosyl purine=zeatin riboside 5-monophosphate - t(ioglc⁴)⁶ade 6-(4-O--D-glucopyranosyl-3-methylbut-trans-2-enylamino)-purine=zeatin-O-glucoside     

Incorporation of ion channels from bovine rod outer segments into planar lipid bilayers.

Membranes vesicles, prepared from bovine rod outer segments were fused with planar lipid bilayers. Two different ion channels were identified by recording currents from single channels. Both types of channels were selective for sodium rather than potassium and were impermeable to chloride ions. Unit conductances were 20 and 120 pS, respectively, in 150 mM sodium chloride. The channel with the larger unit conductance was sensitive to the transmembrane potential. This channel rapidly activated within less than 10 ms after a voltage jump to a more negative membrane potential and then inactivated after several seconds. The duration of the active period and the properties of the channel depended on the amplitude of the voltage jump. The channel of smaller unit conductance did not show any voltage-dependent activation or inactivation. Both types of channels were insensitive to light in the planar bilayer system. Channels incorporated into planar bilayers on a Teflon sandwich septum or on the tip of a glass micropipette gave similar results.     

Breakdown of phosphatidylinositol in soybean callus

We have investigated the breakdown of membrane-bound phosphatidylinositol (PI) in homogenates of soybean (Glycine max) callus. The breakdown of PI was stimulated by the detergent deoxycholate. At pH 7.0 and 1·gl^-1 of deoxycholate the loss of PI was rapid and extensive: more than 80% was broken down within 10 min. The breakdown of PI was also stimulated by millimolar concentrations of Ca²⁺. The products of breakdown of added PI (purified from soybean callus) in this system were identified from their chromatographic mobilities as 1,2-diacylglycerol, myo-inositol 1-phosphate and myo-inositol 1:2-cyclic monophosphate.Abbreviations DOC deoxycholate - EDTA ethylenedi-aminetetraacetic acid,-acetate - Pi Inorganic phosphate - PI phosphatidylinositol - PS phosphatidylserine - TLC thinlayer chromatography