Biomedical subjects
D Pramer
Publications and source records attributed to D Pramer.
Role of N-Acetylgalactosamine-Specific Protein in Trapping of Nematodes by Arthrobotrys oligospora.
An N-acetylgalactosamine-specific protein was purified from mycelial homogenates of the nematode-trapping fungus Arthrobotrys oligospora by using affinity chromatography. The molecular weight of the protein was estimated at 22,000 by its comparative mobility on sodium dodecyl sulfate-polyacrylamide slab gels. Pretreatment of nematodes with the purified protein reduced entrapment, indicating a role for the sugar-binding protein in recognition and capture of prey by the fungus.
Collagenase production by nematode-trapping fungi.
A number of species of nematode-trapping fungi, which capture and digest nematodes having keratin and collagen in their cuticles, were tested for the ability to produce extracellular collagenase and keratinase. Collagenase, which is active on ichthyocol, earthworm collagen, and procollagen from chicken embryo fibroblasts, was found in the growth medium of all tested species; keratinase was not found. The enzyme from Arthrobotrys amerospora was concentrated by precipitation with (NH(4))(2)SO(4) and further purified by adsorption on collagen at 0 degrees C. The collagenase was active over a pH range of 2.5 to 10.0. It was not inactivated by dialysis against ethylenediaminetetraacetic acid for 48 h or by the sulfhydryl group inhibitors N-ethylmaleimide and p-chloromercuribenzoate. The production of collagenase may aid the fungus to penetrate the cuticle of its prey.
Influence of cadmium, zinc, and lead on growth, trap formation, and collagenase activity of nematode-trapping fungi.
Growth and morphogenesis of seven species of nematode-trapping fungi and the activity of a collagenase produced by Arthrobotrys amerospora were measured in the presence of various concentrations of divalent cadmium, zinc, or lead. In general, growth varied with species and was dependent on the metal present and the concentration at which it was tested. Cadmium was found to exhibit the greatest toxicity followed by zinc and lead, respectively. In most cases, inhibition of growth was directly correlated with a decreased capacity to form traps. However, in a few cases, trap formation was inhibited either more or less than was growth. The activity of the collagenase was less sensitive than was growth or trap formation to heavy-metal inhibition.
The effects of volatile compounds from nematodes on trap formation by a nematode-trapping fungus.
Although the presence of prey induced trap formation by nematode-trapping fungi, it is improbable that the activity was associated with volatile compounds of nematode origin.
Regulation of insect populations by protozoa and nematodes.
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Ultrastructure of nematode-trapping fungi.
Capture cells differ ultrastructurally from vegetative cells in the nematode-trapping fungi, Dactylella drechslerii, Monacrosporium rutgeriensis and Arthrobotrys dactyloides, which capture prey by means of adhesive knobs, adhesive hyphal networks, and constricting rings, respectively. Adhesive knobs and adhesive networks contain dense inclusions not found in hyphal tips or subapical regions of the vegetative hyphae, and rough- and smooth-surfaced membranes are abundant in these trap cells. The fine structure of constricting rings differs from that of adhesive traps, and it is altered by closure. In the open configuration, there are membrane-bound inclusions, labyrinthine networks, and electron-lucent regions between the protoplasts and cell wall, all localized on the luminal side of the ring cells. After closure, these features no longer are evident and the cytoplasm of trap cells stains less densely.
Herbicide transformation. I. Studies with whole cells of Fusarium solani.
A strain of Fusarium solani isolated from soil by enrichment techniques used propanil (3', 4'-dichloropropionanilide) as a sole source of organic carbon and energy for growth in pure culture. The primary product of the transformation of propanil by F. solani was isolated and identified as 3,4-dichloroaniline (DCA). This compound accumulated in the medium to a level (80 mug/ml) which stopped further herbicide utilization. Herbicide utilization by F. solani was influenced by various environmental and nutritional factors. It was more sensitive to acid than alkaline pH. Added glucose and yeast extract increased the rate of propanil decomposition, and the reduced aeration retarded growth of the fungus and herbicide utilization. The growth of F. solani on propionate was inhibited by added DCA.
Herbicide transformation. II. Studies with an acylamidase of Fusarium solani.
Replacement cultures liberated 3,4-dichloroaniline (DCA) from 3,4-dichloropropionanilide (propanil). The kinetics of the conversion suggest a requirement for de novo enzyme synthesis, but the system was not influenced by chloramphenicol or puromycin. Enzyme activity was detected when acetanilide (K(m) = 0.195 mm) was used to replace propanil as substrate. Fungal acylamidase (E.C. 3.5.1., an aryl acylamine amidohydrolase) was concentrated by salt precipitation and characterized. The Fusarium solani acylamidase exhibited an optimum at pH 7.5 to 9.0 and was inactivated in 10 min at 50 C. The enzyme was not sensitive to methyl-carbamate or organophosphate insecticides, but the herbicide, Ramrod (N-isopropyl-2-chloroacetanilide), acted as a competitive inhibitor of acetanilide hydrolysis (K(i) = 0.167 mm). Hydrolysis rates were decreased by various para substitutions of acetanilide. Chloro substitution in the acyl moiety of acetanilide also reduced the rate of hydrolysis. 3,4-Dichloroacetanilide was less susceptible to enzyme action than acetanilide, but 3,4-dichloropropionanilide was hydrolyzed much more rapidly than propionanilide. The fungal acylamidase was highly specific for N-acetylarylamines. It did not catalyze hydrolysis of formanilide, butyranilide, dicryl, Karsil, fenuron, monuron, or isopropyl-N-phenylcarbamate. It appears to differ from acylamidases that have been isolated from rice, rat liver, chick kidney, and Neurospora.
Amino acid transport by the filamentous fungus Arthrobotrys conoides.
Uptake of l-valine by germinated spores of Arthrobotrys conoides has all the characteristics of a system of transport that requires an expenditure of energy by the cells. It is dependent on temperature and has an energy of activation of 16,000 cal/mole. Uptake is optimal at pH 5 to 6. l-Valine accumulated against a concentration gradient and is not lost from the cells by leakage or exchange. The process requires energy supplied by the metabolic reactions that are inhibited by catalytic amounts of 2,4-dinitrophenol and azide. The kinetics of the system are consistent with a mechanism of transport that depends on a limited number of sites on the cell surface, and the Michaelis constant for the system is 1.5 x 10(-5) to 7.5 x 10(-5)m. Modification of the amino or carboxyl group abolishes l-valine uptake. The process is competitively inhibited by d-valine, glycine, and other neutral amino acids (K(i) = 1.5 x 10(-5) to 4.0 x 10(-5)m), indicating a lack of stereospecificity, and also indicating that aliphatic side chain is not required for binding with the carrier. The transport system has less affinity for acidic amino acids (glutamic and aspartic acids) than neutral amino acids, and a greater affinity for basic amino acids (histidine, lysine, and arginine). The range of affinity is in the order of 100, as measured in terms of K(i) values for various compounds. The data presented provide suggestive evidence that the uptake by A. conoides of all amino acids except proline is mediated by a single carrier system that possesses an overall negative charge.
Metabolism of valine by the filamentous fungus Arthrobotrys conoides.
Uptake of valine by Arthrobotrys conoides was an active process and was independent of its incorporation into cellular protein. Chemical fractionation of cells supplied with (14)C-l-valine for different time intervals revealed that the amino acid initially entered a pool of metabolic intermediates and was extractable with cold trichloroacetic acid. After a 4-min interval, some intracellular valine was incorporated into cell proteins, but most underwent metabolic transformation to a variety of products that included carboxylic acids and other amino acids. Carbon derived from valine was not localized in the lipid or nucleic acid fraction of cells, but some was completely oxidized and recovered as metabolic (14)CO(2). Autoradiograms of paper and thin-layer chromatograms of acid hydrolysates of cellular protein identified the following amino acids as having originated from valine: glutamate, aspartate, alanine, and leucine. Similar analysis of cold trichloroacetic acid extracts established that (14)C supplied as l-valine had been transformed also to alpha-ketoisovalerate, isobutyrate, propionate, succinate, malate, oxalacetate, pyruvate, and alpha-ketoglutarate. Pathways for transformation of the carbon skeleton of valine to various metabolic products are proposed.
Chloroazobenzenes: studies on syntheses.
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Chloroazobenzenes: IR and UV characteristics.
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Pesticide transformations: production of chloroazobenzenes from chloroanilines.
Aniline and 11 different chloroanilines were added to soil. No azo compound was formed from aniline, but all monochloro-and some dichloroanilines were transformed to their corresponding dichloro-and tetrachloroazobenzenes. Other dichloroanilines and the trichloroanilines were stable in soil. Peroxidase catalyzed the formation of azo compounds by some chloroanilines. Correspondence in the range of substrates used and products formed in the two systems suggests a peroxidatic mechanism for the synthesis of azo compounds residues in soil.
Purification and properties of peroxidase from Nitrosomonas europaea.
Peroxidase from the obligate chemosynthetic bacterium Nitrosomonas europaea was purified 1,500-fold, and its properties were examined. The enzyme had a molecular weight of 53,000 and exhibited characteristic absorption maxima at 410, 524, and 558 mmu. The optimal pH and temperature were 7.5 and 44 C, respectively. The peroxidase reaction had an energy of activation of 5,850 cal/mole and required a primary substrate (H(2)O(2)) concentration of 7 x 10(-6)m to proceed at half maximal velocity (K(m)). Reduced cytochrome, c,p-phenylenediamine and pyrogallol acted as hydrogen donors to the purified peroxidase-H(2)O(2) complex. Conditions most suitable for the chemical oxidation of ammonium by H(2)O(2) were determined. The reaction was rapid and produced nitrite but no nitrate. Hydroxylamine was not detected as an intermediate, but it could substitute for ammonium in the system. Neither the rate nor the extent of these reactions was influenced by purified peroxidase, and no evidence was obtained to support a conclusion that the enzyme performs a vital role in the transformation of ammonium to nitrite by N. europaea.
Pesticide transformation to aniline and azo compounds in soil.
The herbicide 3',4'-dichloropropionanilide decomposes in soil to carbon dioxide and 3,4-dichloroaniline. and two molecules of the latter compound are condensed to form 3,3',4,4'-tetrachloroazobenzene. Soil microorganisms are involved in both transformations.
Stability and effects of some pesticides in soil.
The influence of 29 pesticides on CO(2) production and nitrification by soil microorganisms was determined. A few compounds were stable but without significant effect in soil (chlorinated hydrocarbons), some persisted and depressed respiration and nitrification (carbamates, cyclodienes, phenylureas, thiolcarbamates), and others displayed toxicity but were transformed by soil microorganisms (amides, anilides, organophosphates, phenylcarbamates, triazines). Some compounds of the last type induced an initial increase and subsequent decrease in CO(2) production by soil. No simple explanation of this effect is possible, but the results of studies of model systems having established activities suggest that in soil any one or a combination of the following mechanisms is responsible for the observed complex relation of CO(2) production to time: (i) a pesticide acts to uncouple oxidative phosphorylation in a manner analogous to 2,4-dinitrophenol; (ii) a pesticide lacking antimicrobial action is oxidized in part and transformed to a stable and toxic product; (iii) a pesticide that is selectively toxic inhibits CO(2) production by sensitive microorganisms but is subject to oxidation without detoxification by other members of the microbial population that are resistant to its initial action. Pesticide concentrations greatly in excess of those recommended for agricultural and home use were required to produce an effect, and supplementary organic matter (glucose) tended to reduce pesticide toxicity and increase the microbial degradation of pesticides in soil.
Symposium on nonpharmaceutical uses of antibiotics. Introduction.
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