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C Van Dijk

Publications and source records attributed to C Van Dijk.

15 recordsLinked to original sources
PubMed1997

Phylogenetic characterization of ineffective Frankia in Alnus glutinosa (L.) Gaertn. nodules from wetland soil inoculants.

Ineffective Frankia endophytes were retrieved from various wet soils by using Alnus glutinosa clones as trapping plants. No pure cultures could be isolated from these ineffective nodules. Therefore, the phylogenetic position of these endophytes was determined by sequence analysis of cloned PCR products of bacterial 16S rDNA, derived from nodules. The results showed that all nodule endophytes belong to a hitherto undescribed cluster of the Frankia phylogenetic tree. The position of these uncultured ineffective Frankia nodule endophytes is different from that of the ineffective Frankia isolates derived from A. glutinosa nodules, even when originating from the same geographical location. This suggests a bias in current isolation techniques.

Actinomycetales↗
PubMed1995

Electrochemical studies on nitrite reductase towards a biosensor.

A c-type hexaheme nitrite reductase (NiR) isolated from nitrate-grown cells of Desulfovibrio desulfuricans (Dd) ATCC 27774 catalyses the six-electron reduction of nitrite to ammonia. Previous electrochemical studies demonstrated that a simple electrocatalytic mechanism can be applied to this system (Moreno, C., Costa, C., Moura, I., LeGall, J., Liu, M. Y., Payne, W. J., Van Dijk, C. and Moura, J. J. G. (1992) Eur.J.Biochem. 212, 79-86). Its substrate specificity, availability and stability under ambient conditions makes this enzymatic system a promising candidate for use in a biosensor device. An electrochemical study of gel-immobilized Dd NiR on a glassy carbon electrode revealed both enzymatic activity and amperometric response to nitrite. In this study it was observed that the catalytic current density is a function of the nitrite concentration in solution and follows a characteristic Michaelis-Menten-type substrate dependence. Such a biosensor device (NiR-electrode) bears the option to be used for analytical determination of nitrite in complex media.

Biosensing Techniques↗
PubMed1992

Soman levels in kidney and urine following administration to rat, guinea pig, and marmoset.

Concentrations of C(+/-)P(+/-)-soman (1,2,2-trimethylpropyl methylphosphonofluoridate) in urine of anaesthetized, atropinized and artificially ventilated rats, guinea pigs and marmosets were determined 1-4 h after iv administration of 1-6 LD50 of the agent and in the kidneys 1 h after iv administration of 2-6 LD50 14C-C(+/-)P(+/-)-soman. The concentrations of the toxic C(+/-)P(-)-isomers in both urine and kidneys of the rat were at least two orders of magnitude higher than the corresponding levels in the two other species. Relatively high urine concentrations were also found for C(+/-)P(+/-)-soman-intoxicated (6 LD50) rats pretreated with the nontoxic soman analogue PDP (1,2,2-trimethyl dimethylphosphinate), which considerably decreases the persistence of C(+/-)P(-)-soman in rats, or the carboxylesterase inhibitor CBDP [2-(o-cresyl)-4H-1:3:2-benzodioxaphosphorin-2-oxide]. The lethal effect brought about by intravesical administration of C(+/-)P(+/-)-soman in rats showed that the agent can easily be reabsorbed from the bladder. It is concluded, that this reabsorption does probably not explain the previously observed persistence and "late toxicity" of C(+/-)P(+/-)-soman in rats, although the amount of renally excreted C(+/-)P(-)-soman (ca. 1% of the administered dose) should be sufficient for a toxicologically significant effect.

Administration, Intravesical↗
PubMed1987

Feed and water consumption and performance of male and female broilers fed salinomycin and maduramicin followed by a withdrawal ration.

A 3 x 2 factorial floor pen experiment was conducted to determine the effects of feeding salinomycin (60 ppm) or maduramicin (5 ppm) for 49 days followed by a 3-day withdrawal ration upon both male and female broiler chickens in a coccidia-free environment. Body weights, feed intake, and water consumption were recorded at 28, 49, and 52 days of age. Feed efficiency and overall mortalities were also measured. Inclusion of either ionophore into the ration had no effect on final body weight, but improved feed conversion (P less than .05). Birds fed maduramicin drank more than the nonmedicated birds (P less than .05), which in turn, drank more than the birds fed salinomycin (P less than .05).

Animals↗
PubMed1986

The dopaminergic innervation of the ventral striatum in the rat: a light- and electron-microscopical study with antibodies against dopamine.

Dopamine (DA) in the dorsal and ventral striatum is associated with different aspects of locomotor activity control. The ventral striatum may form an interface between the limbic system and the extrapyramidal motor system. The distribution of dopaminergic fibers in this interface position was studied in detail with a method applying antibodies against DA. Furthermore, the ultrastructural morphology of the DA fibers was examined by means of immuno-electron microscopy. The results show that DA immunoreactivity is distributed over the ventral striatum in a highly compartmentalized fashion. In the dorsal striatum few compartments were found. The DA fibers in the ventral striatum establish mainly symmetric synaptic contacts, preferably with dendritic shafts and spines. The results are discussed in relation to previous data concerning the light and electron-microscopic identification of catecholaminergic fibers in the ventral and dorsal striatum.

Animals↗
PubMed1985

A study of one of the iron-sulphur clusters in oxidized hydrogenase from Megasphaera elsdenii by magnetic-circular-dichroism spectroscopy.

The m.c.d. spectrum of the oxidized state of hydrogenase from Megasphaera elsdenii has been measured at liquid-helium temperatures. This oxidation state of the enzyme displays a characteristic rhombic e.p.r. signal with g-values of 2.101, 2.052 and 2.005 assigned previously to a [4Fe-4S]3+ cluster as in oxidized HiPIP (high-potential iron-sulphur protein) [Van Dijk, Grande, Mayhew & Veeger (1980) Eur. J. Biochem. 107, 251-261]. The low-temperature m.c.d. spectrum shows no features attributable to an oxidized four-iron cluster of the HiPIP type, but does reveal broad, positive peaks at 460 and 730 nm, which magnetize in a manner untypical of a spin S = 1/2 cluster with g-values close to 2. The m.c.d. spectrum is most closely similar to that of dye-oxidized P-clusters known in the enzyme nitrogenase. It is therefore proposed that the rhombic e.p.r. spectrum at a g-value close to 2 arises from an m.c.d.-silent radical species that may be related chemically to the cysteine persulphide species, RS-S., recently found in the hexacyanoferrate-oxidized seven-iron ferredoxin of Azotobacter vinelandii [Morgan, Stephens, Devlin, Stout, Melis & Burgess (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 1931-1935].

Circular Dichroism↗
PubMed1985

Effects of coccidiostats and dietary protein on performance and water consumption in broiler chickens.

Two, 7-week floor pen experiments were conducted consecutively with male broilers and then female broilers to determine the effects of feeding salinomycin (60 ppm), monensin (99 ppm), or lasalocid (125 ppm) at the following three levels of dietary protein: 1) that which meets National Research Council specifications (NRC, 1977), 2) that level deficient in sulfur amino acids (SAA), or 3) that deficient in protein. Group body weights, feed intake, and water consumption were noted at 28 and 49 days of age with feed efficiency and overall mortalities determined. Reducing SAA resulted in depressed (P less than .05) body weights at 7 weeks in both experiments, whereas deficient protein reduced (P less than .05) growth, feed efficiency, and water consumption. Generally, inclusion of coccidiostats in the diet did not significantly hinder growth or feed efficiency. Feeding of coccidiostats in combination with the low protein diet did not produce additional anorexigenic effects. Although a significant lasalocid SAA-sparing effect was not observed, diet X coccidiostat interactions (P less than .05) were apparent and attributable to an apparent "protein-sparing" effect upon body weight gain when salinomycin was fed in combination with the low protein diet. Lasalocid increased water consumption (P less than .05) relative to monensin in the female broilers.

Amino Acids, Sulfur↗
PubMed1985

Structural and stereochemical specificity of mouse monoclonal antibodies to the organophosphorous cholinesterase inhibitor soman.

To test the usefulness of immunotherapy in organophosphate poisoning, two mouse monoclonal antibodies were prepared to the chemical warfare agent soman. The antibodies bound reversibly to soman and afforded considerable protection to acetylcholinesterase in vitro. However, they were only marginally effective in preventing the consequences of soman poisoning in mice (these data have been published elsewhere). Since potential for immunotherapeutic usefulness resides in antibody affinity and specificity, we conducted experiments to define these parameters to enable us to maximize them in the production of later antibodies. Interaction of the antibodies (CC1 and BE2) in affinity-purified form with a series of soman analogs in a competitive inhibition enzyme immunoassay was used to assess the contribution to binding affinity of each functional group on the soman molecule. Neither antibody interacted with the -P = S analog of soman or methylphosphonic acid. A decrease in the number of methyl groups on the pinacolyl side chain reduced or eliminated binding with both antibodies while increasing the size of this group had a mixed result. The major metabolite of soman, its basic hydrolysis product, interacted weakly with BE2 and failed to interact with CC1. Alkyl ester group substitution at the fluorine position increased antibody binding up to the symmetrical dipinacolyl analog. Stereochemical specificity was determined by measuring the apparent decrease in the rate of inhibition of cholinesterases (acetylcholine acetylhydrolase, EC 3.1.1.7, or acylcholine acylhydrolase, EC 3.1.1.8) by pure soman stereoisomers in the presence of increasing concentrations of each antibody. CC1 demonstrated specificity that varied as C(+)P(+) less than C(-)P(+) less than C(-)P(-) less than C(+)P(-). Although affinities were much lower, BE2 also showed a preference for the more toxic P(-) isomers.

Acetylcholinesterase↗
PubMed1984

Proteinuria in intact and splenectomized dogs after running and swimming.

The occurrence of post-exercise proteinuria was investigated in intact and splenectomized dogs after treadmill running and swimming and compared to control experiments. Albumin and lysozyme were measured by radial diffusion. Urinary protein was analyzed by SDS-polyacrylamide gel electrophoresis. Swimming in the splenectomized dogs increased the albumin excretion in the first 30 min after exercise from 0.03 to 0.22 mg X min-1 and the lysozyme excretion in the same period from 0.11 to 0.75 micrograms X min-1. Swimming in intact dogs caused smaller increase in the lysozyme and albumin excretions during the exercise period itself as well as in the albumin excretion in the first 30 min after exercise. Running had no effect on urinary albumin or lysozyme but increased the low molecular weight protein fraction in the splenectomized dogs. Plasma lactate concentrations were higher during swimming in the splenectomized dogs than in the intact dogs. Possible mechanisms of post-exercise proteinuria are discussed.

Animals↗
PubMed1983

Electron paramagnetic resonance and other properties of hydrogenases isolated from Desulfovibrio vulgaris (strain Hildenborough) and Megasphaera elsdenii.

The hydrogenases of Desulfovibrio vulgaris and Megasphaera elsdenii are compared with respect to some of their physical properties. In addition to Fe the only metal ions that are present in significant amounts are Ni and Cu. From cluster extrusion experiments it follows that the D. vulgaris enzyme contains three 4 Fe-4S clusters, while M. elsdenii hydrogenase only releases part of its Fe-S clusters. The resting D. vulgaris enzyme shows only a small 3 Fe-xS type of EPR signal (maximum 5% electron equivalent). This amount can be increased to approximately 25% by treatment with ferricyanide, with a concomitant large decrease in activity. The M. elsdenii enzyme shows in its oxidized state a normal Hipip (high-potential iron-sulphur protein) type of EPR spectrum. After a reduction/oxidation cycle the D. vulgaris enzyme also shows a weak Hipip type of EPR spectrum. In the reduced state both enzymes show complex spectra. By integration of those spectra it is shown that 1.5 electron equivalents are present. The complex spectra do not arise from nuclear hyperfine interactions but are partially due to electron spin interactions. It is proposed that the spectrum of reduced D. vulgaris hydrogenase consists of a sum of three different ferredoxin-like spectra.

Binding Sites↗
PubMed1982

A pulse-radiolysis study of cytochrome c3. Kinetics of the reduction of cytochrome c3 by methyl viologen radicals and the characterisation of the redox properties of cytochrome c3 from Desulfovibrio vulgaris (Hildenborough).

1. Pulse-radiolysis experiments were performed in the presence of methyl viologen and cytochrome c3. After the pulse, methyl viologen radicals are formed and the kinetics of these radicals with cytochrome c3 are studied, The reaction between cytochrome c3 and methyl viologen radicals (MV+) is diffusion controlled. The ionic strength dependence and the pH-dependence of this reaction were studied. From the ionic strength dependence (at pH 7.8) we found that the net charge of the fully oxidized cytochrome c3 molecule was Z = + 4.7 +/- 0.7. 2. After the pulse an equilibrium is reached for the reaction of MV+ with cytochrome c3. From this equilibrium an apparent midpoint potential can be obtained. The apparent midpoint potential of this multihaem molecule was found to depend on the degree of reduction, alpha. With the help of the Nernst equation an empirical equation is obtained to describe this dependence of the midpoint potential: E0 = - 0.250 - 0.088 alpha (in V). 3. An estimation is made of the energy of interaction between the haems due to electrostatic interactions (delta epsilon less than 32 mV) and due to ionic strength effects (- 12 mV less than delta epsilon less than 26 mV). The results suggest that the redox properties of the individual haems in the cytochrome c3 molecule are dependent on the degree of reduction of the other haems in the molecule. 4. The reaction of cytochrome c3 with MV+ or with ethanol radicals (EtOH) has been compared with the reactions of horse-heart cytochrome c and of metmyoglobin with the same radicals. The reaction of MV+ or EtOH with horse-heart cytochrome c is found to be diffusion controlled; the reactions with metmyoglobin on the other hand are most probably controlled by an activation energy.

Animals↗
PubMed1979

Purification and properties of hydrogenase from Megasphaera elsdenii.

A hydrogenase has been purified to homogeneity from the soluble fraction of the rumen bacterium Megasphaera elsdenii, the overall purification is 200 times with a yield of 14%. The pure enzyme consists of a single polypeptide chain with Mr approximately 50 000 which contains 12 atoms of non-haem iron and 12 atoms of acid-labile sulphide. The enzyme is rapidly inactivated by O2 and it is therefore purified under nitrogen and in the presence of sodium dithionite. The optical spectrum of the enzyme, after removal of the dithionite with air, shows a peak at 275 nm (epsilon 275 nm = 143 mM-1 cm-1) and a shoulder between 350 nm and 400 nm (epsilon 400 nm = 46 mM-1 cm-1). The enzyme catalyses hydrogen production from sodium dithionite at a low rate. The rate is greatly enhanced by addition of the electron donors flavodoxin, ferredoxin and methyl viologen. The kinetic data with these three electron donors suggest co-operativity, but no indication of self-association of the enzyme was obtained. Sodium chloride enhances the rate of hydrogen production with methyl viologen semiquinone and changes the kinetic behaviour of the enzyme with this electron donor, but causes inhibition of the reactions mediated by ferredoxin and flavodoxin. Two kinetic models were developed which are consistent with the kinetic data of the three electron donors tested. The apparent co-operativity for the hydrogen production can be fitted with the mathematical form of those models. The identical kinetic behaviour of the hydrogenase with the one-electron donors flavodoxin and methyl viologen semiquinone monomer and the two-electron donor ferredoxin indicates that the hydrogenase accepts two electrons in two separate, independent steps and further indicates that the two (4Fe-4S) clusters of the donor ferredoxin are independent. The interpretation of the kinetic data with methyl viologen semiquinone is complicated by the fact that the semiquinone dimerises, and that the formation of the dimer is enhanced by salt. Taking into account the association of this donor, the activity of the enzyme with methyl viologen semiquinone can be described by the sum of the activities of the enzyme with methyl viologen monomer and methyl viologen dimer. The enzyme catalyses the oxidation of hydrogen gas with methyl and benzyl viologen as electron acceptors to their semiquinone forms; both electron acceptors show Michaelis-Menten kinetics. The hydrogen oxidation activity with both electron acceptors is stimulated by addition of sodium chloride. The kinetic data of the oxidation of hydrogen with the two-electron acceptors used are consistent with the porposed models, if it is assumed that the pathway followed is compulsory. At this moment no choice can be made between the models proposed.

Computers↗
PubMedDate not supplied

Field trials of an immunization procedure against hemorrhagic enteritis of turkeys.

The efficacy of oral vaccination for hemorrhagic enteritis of turkeys was assessed by comparing flocks raised on the same premises, under the same management, with and without vaccination. The immunizing virus, a strain of marble spleen disease virus of pheasants, was administered via the drinking water. Vaccinated and unvaccinated turkeys differed significantly in feed conversion rates and spleen weights after challenge.

Administration, Oral↗