Genetic activity of allyl chloride

Allyl chloride (3-chloroprene) is mutagenic for Salmonella typhimurium and it induces gene conversions in Saccharomyces cereuisiae. It also displays DNA-modifying activity for E. coli. This is in contrast to a recent study which reported its lack of genetic activity for Salmonella typhimurium.     

Intracellular chloride activity in cultured mesangial cells.

Glomerular mesangial cells require Cl ions for the development of a variety of metabolic and functional properties. In the present study the electrochemical distribution for Cl- was examined in cultured rat mesangial cells with Cl(-)-sensitive intracellular microelectrodes. It was determined that the intracellular Cl activity exceeded the levels predicted for a passively distributed ion. This was further substantiated by exposing mesangial cells to 10(-5) M bumetanide which drove intracellular Cl to a value close to electrochemical equilibrium. We conclude that Cl accumulates in mesangial cells, against its electrochemical gradient, through a transport pathway that is highly sensitive to bumetanide.     

Genetic activity of niridazole in yeast.

Niridazole, one of several drugs presently known to be of value in the treatment of human schistosomiasis, was tested for its activity in inducing mitotic recombination in yeast. It was found that niridazole is genetically active when the treatment of yeast cells is performed in a rich medium (YPG-medium) under growing conditions, but not when treatment is carried out in a non-nutrient suspension (phosphate buffer). The data suggest that niridazole might be converted to an active compound by yeast metabolism. The results of the experiments with niridazole in the non-nutrient medium were compared with those of AF-2 and SQ18, 506, two agents which have been shown to be genetically active in the present assay system.     

Inhibition of nitrogenase activity by ammonium chloride in Azotobacter vinelandii.

In Azotobacter vinelandii cells, the short-term inhibition of nitrogenase activity by NH4Cl was found to depend on several factors. The first factor is the dissolved oxygen concentration during the assay of nitrogenase. When cells are incubated with low concentrations of oxygen, nitrogenase activity is low and ammonia inhibits strongly. With more oxygen, nitrogenase activity increases. Cells incubated with an optimum amount of oxygen have maximum nitrogenase activity, and the extent of inhibition by ammonia is small. With higher amounts of oxygen, the nitrogenase activity of the cells is decreased and strongly inhibited by ammonia. The second factor found to be important for the inhibition of nitrogenase activity by NH4Cl was the pH of the medium. At a low pH, NH4+ inhibits more strongly than at a higher pH. The third factor that influenced the extent of ammonia inhibition was the respiration rate of the cells. When cells are grown with excess oxygen, the respiration rate of the cells is high and inhibition of nitrogenase activity by ammonia is small. Cells grown under oxygen-limited conditions have a low respiration rate and NH4Cl inhibition of nitrogenase activity is strong. Our results explain the contradictory reports described in the literature for the NH4Cl inhibition of nitrogenase in A. vinelandii.     

Regulation of nitrogenase activity by ammonium chloride in Azospirillum spp.

Ammonium chloride (greater than or equal to 0.05 mM) effectively and reversibly inhibited the nitrogenase activity of Azospirillum brasilense, Azospirillum lipoferum and Azospirillum amazonense. The glutamine synthetase inhibitor L-methionine-DL- sulfoximine abolished this "switch-off" in A. lipoferum and A. brasilense, but not in A. amazonense. Azaserine, an inhibitor of glutamate synthase, inhibited nitrogenase activity itself. This provides further evidence for glutamine as a metabolite of regulatory importance in the NH4+ switch-off phenomenon. In A. brasilense and A. lipoferum, a transition period before the complete inhibition of nitrogenase activity after the addition of 1 mM ammonium chloride was observed. The in vitro nitrogenase activity also was decreased after treatment with ammonium. During sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a second dinitrogenase reductase (Fe protein) subunit appeared, which migrated in coincidence with the modified subunit of the inactive Fe protein of the nitrogenase of Rhodospirillum rubrum. After the addition of ammonium 32P was incorporated into this subunit of the Fe protein of A. brasilense. In A. amazonense, the inhibition of nitrogenase activity by ammonium was only partial, and no transition period could be observed. The in vitro nitrogenase activity of ammonium-treated cells was not decreased, and no evidence for a modified Fe protein subunit was found. Nitrogenase extracts of A. amazonense were active and had an Fe protein that migrated as a close double band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.     

Effect of lithium chloride on ornithine decarboxylase activity in rat adrenal.

The effects of lithium chloride on ornithine decarboxylase (ODC) activity were compared in the adrenal and kidney of control (saline treated) and prolactin-treated rats. ODC activity was decreased in kidney of both groups of animals, the magnitude of the effect of lithium in the hormone-treated group varying with the time of administering the lithium relative to prolactin. The response in the adrenal was quite different. Following treatment with LiCl, there was a gradual increase in ODC activity from a low of 10-35 pmol CO2 x 30 min-1.mg protein-1 in control animals to values 20- to 30-fold greater at 5 h. In rats treated simultaneously with LiCl and prolactin, ODC activity was greater at 5 h than that observed in animals receiving either compound alone, indicating that their effects were additive. When LiCl was given 4 h after prolactin, i.e., 1 h before sacrifice, ODC activity decreased to a very low level at 5 h, as in other tissues. The increase in ODC activity in the adrenal following LiCl is of the same magnitude as the changes observed in tissues stimulated to undergo alterations in proliferation, differentiation, or metabolic or membrane activity by hormones and other external stimuli.     

Genotoxic activity of methyl mercury chloride and dimethyl mercury in human lymphocytes.

The genotoxicity of methyl mercury chloride (MMC, 0-25 x 10(-6) M) and dimethyl mercury (DMM, 0-434 x 10(-6) M) was evaluated by chromosome metaphase analysis in human lymphocytes treated in vitro for 24 h. Structural (CA) and numerical (AN) chromosomal aberrations were scored for the assessment of induced genotoxic effects, while the variation in mitotic index (MI) was considered a monitor for induced cellular toxicity. MMC induced CA and AN in a dose-related manner at doses exceeding 0.6 x 10(-6) M, and the proportion of cells with CA was constantly and significantly higher than that of cells with AN. DMM was able to induce both effects as well, although to a lesser extent than MMC, CA and AN being induced at doses exceeding 43.4 x 10(-6) M and 1.73 x 10(-6) M, respectively. MMC was 6-fold more effective in inducing CA than DMM at equivalent toxic doses. On the other hand, no significant difference was observed between the two compounds in inducing AN. Therefore MMC was much more clastogenic than DMM, whereas mitotic spindle disturbances appeared to be almost equally induced by both compounds.     

Plant nucleases. IV. Genetic control of ribonuclease activity in corn endosperm

Ribonuclease activity in the endosperms of 14 corn (Zea mays L.) inbreds ranged from 285 to 1305 units/g fresh weight 50 days after pollination. Activity is low in the inbred M14 and high in the inbred WF9. Hybrid endosperms contain intermediate levels of ribonuclease, and segregation occurs in the F₂ generation. The ribonuclease contents of the opaque-2 versions of nine inbred lines ranged from 1288 to 5110 units/g. The floury-2 mutation apparently does not affect ribonuclease content. Two or more genes may be involved in the control of ribonuclease content of developing endosperms.Cooperative investigations of the Plant Science Research Division, Agricultural Research Service, U.S. Department of Agriculture, and the Illinois Agricultural Experiment Station, Urbana, Illinois.     

The effect of calcium chloride on the activity and inhibition of bacterial collagenase.

The enzymatic behavior and inhibition patterns of collagenase of Clostridium histolyticum in the presence of 0.5 M and 3.4 mM CaCl2 have been examined viscosimetrically. The more concentrated salt was found to enhance the rate of digestion of calfskin collagen when either measured viscosimetrically or colorimetrically by trinitrobenzenesulfonate. However, the rate of digestion of calfskin gelatin is unaffected by 0.5 M CaCl2 as determined colorimetrically. Calcium chloride also proved to have a marked effect on the inhibitory behavior of a series of imidazole compounds. Histidine (10mM) is about three-fold more effective as an inhibitor in 0.5 M CaCl2 than in 3.4 mM CaCl2, whereas a reverse effect is true for histamine, Imidazolylpropionate (10mM) was only weakly inhibitory (16%) in 0.5 M CaCl2 and not at all in 3.4 mM CaCl2. Inhibition by 10 mM imidazole was not detectable. These observations may be useful in the design of inhibitors for tissue collagenases which share a number of common characteristics with the bacterial enzyme.     

Genetic analysis and overexpression of lipolytic activity in Bacillus subtilis.

The previously cloned Bacillus subtilis lipase gene (lip) was mapped on the chromosome and used in the construction of a B. subtilis derivative totally devoid of any lip sequence. Homologous overexpression was performed in this strain by subcloning the lip open reading frame on a multicopy plasmid under the control of a strong gram-positive promoter. A 100-fold overproducing strain was obtained, which should facilitate purification of the secreted protein. Furthermore, the delta lip strain BCL1050 constitutes an ideal host for the cloning of heterologous lipase genes.     

Biosynthesis of mercapturic acids from allyl alcohol, allyl esters and acrolein

1. 3-Hydroxypropylmercapturic acid, i.e. N-acetyl-S-(3-hydroxypropyl)-l-cysteine, was isolated, as its dicyclohexylammonium salt, from the urine of rats after the subcutaneous injection of each of the following compounds: allyl alcohol, allyl formate, allyl propionate, allyl nitrate, acrolein and S-(3-hydroxypropyl)-l-cysteine. 2. Allylmercapturic acid, i.e. N-acetyl-S-allyl-l-cysteine, was isolated from the urine of rats after the subcutaneous injection of each of the following compounds: triallyl phosphate, sodium allyl sulphate and allyl nitrate. The sulphoxide of allylmercapturic acid was detected in the urine excreted by these rats. 3. 3-Hydroxypropylmercapturic acid was identified by g.l.c. as a metabolite of allyl acetate, allyl stearate, allyl benzoate, diallyl phthalate, allyl nitrite, triallyl phosphate and sodium allyl sulphate. 4. S-(3-Hydroxypropyl)-l-cysteine was detected in the bile of a rat dosed with allyl acetate.     

Intracellular chloride activity of leech neurones and glial cells in physiological,low chloride saline

Leech blood apparently contains considerably less chloride than generally used in physiological experi ments. Instead of 85–130 mM Cl^– used in experimental salines, leech blood contains around 40 mM Cl^– and up to 45 mM organic anions, in particular malate. We have reinvestigated the distribution of Cl^– across the cell membrane of identified glial cells and neurones in the central nervous system of the leech Hirudo medicinalis L., using double-barrelled Cl^–- and pH-selective micro electrodes, in a conventional leech saline, and in a saline with a low Cl^– concentration (40 mM), containing 40 mM malate. The interference of anions other than Cl^–to the response of the ion-selective microelectrodes was estimated in Cl^–-free salines (Cl^– replaced by malate and/or gluconate). The results show that the absolute intracellu lar Cl^– activities (aCl_i) in glial cells and neurones, but not the electrochemical gradients of Cl^– across the glial and the neuronal cell membranes, are altered in the low Cl^–, malate-based saline. In Retzius neurones, aCl_i is lower than expected from electrochemical equilibrium, while in pressure neurones and in neuropil glial cells, aCl_i is distributed close to its equilibrium in both salines, re spectively. The steady-state intracellular pH values in the glial cells and Retzius neurones are little affected (0.1 pH units) in the low Cl^–, malate-based saline.     

Heterotropic effects of chloride on the ligation microstates of hemoglobin at constant water activity.

Dimer-tetramer assembly reactions of the 10 CN-met ligation microstates of hemoglobin (Hb) were analyzed as a function of NaCl concentration while maintaining constant water activity by the addition of compensating sucrose. The assembly free energy for fully ligated cyanomet Hb and for fully oxygenated Hb becomes less favorable by 1.8 kcal when [NaCl] is increased from 0.08 to 0.7 M, whereas that of unligated Hb is practically insensitive to changes in [NaCl]. Values of 1.6 and 0.3 mol chloride release were found for the assembly of fully ligated and deoxy Hb, respectively; i.e., a net release of 1.3 mol chloride is coupled to the ligation of tetramers for both oxygen and cyanomet ligation. The ligation-linked salt component at constant water activity was evaluated to be 1.0 mol for the full oxygenation of the Hb tetramer in agreement with the overall value previously reported. When the detailed salt linkages accompanying all 16 stepwise cyanomet ligation reactions were experimentally resolved, only two "chloride" effects were found. The first chloride effect correlates with the ligation steps, which create tertiary constraint, and the second effect is coupled to the six switchpoints of quaternary T-->R transition. The distribution of these chloride effects agrees closely with predictions of the "symmetry rule mechanism." The total chloride release for CN-met ligation is in good agreement with that for oxygenation. Free energy contributions to assembly and cooperativity arising from the osmotic effects of chloride were found to be small for all ligation species.     

Intratracheal injection of nickel chloride and copper-zinc superoxide dismutase activity in lung of rats.

Superoxide radical (O2-) is a free radical that may be involved in various toxic processes. Cu--Zn superoxide dismutase catalyses the dismutation of the superoxide free radical and protects cells from oxidative damage, and it has been used clinically. The concentration of Ni2+ and Cu--Zn superoxide dismutase activity were measured in lungs of rats at time intervals of 5, 12, 19, 26, 33, and 40 days following an intratracheal injection of 127 nmol of NiCl2. Nickel chloride increased nickel content and resulted in a significant increase of Cu--Zn superoxide dismutase activity in lungs. This elevation of Cu--Zn superoxide dismutase activity was highest on the 12th day (approximately threefold) and is at levels comparable to controls rats on day 40 onwards. Since Cu--Zn superoxide dismutase activity was increased in lung throughout our experimental period without corresponding increases of Cu2+ and Zn2+, we speculate that the elevation of Cu--Zn superoxide dismutase activity might be due to an increased half-life of the enzyme, induced by nickel.