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Query: UMLS:C0155339 (Brown)
 12,436 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The peroxidation of liposomes by a haem peroxidase and hydrogen peroxide in the presence of indole-3-acetic acid and derivatives was investigated. It was found that these compounds can accelerate the lipid peroxidation up to 65 fold and this is attributed to the formation of peroxyl radicals that may react with the lipids, possibly by hydrogen abstraction. The peroxyl radicals are formed by peroxidase-catalyzed oxidation of the enhancers to radical cations which undergo cleavage of the carbon-carbon bond on the side-chain to yield CO2 and carbon-centred radicals that rapidly add oxygen. In competition with decarboxylation, the radical cations deprotonate reversibly from the N1 position. Rates of decarboxylation, pka values and rate of reaction with the peroxidase compound I indicate consistent substituent effects which, however, can not be quantitatively related to the usual Hammett or Brown parameters. Assuming that the rate of decarboxylation of the radical cations taken is a measure of the electron density of the molecule (or radical), it is found that the efficiency of these compounds as enhancers of lipid peroxidation increases with increasing electron density, suggesting that, at least in the model system, the oxidation of the substrates is the limiting step in causing lipid peroxidation.
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PMID:Enhancement of lipid peroxidation by indole-3-acetic acid and derivatives: substituent effects. 758 24

The rates of reaction of seven indole-3-acetic acid derivatives with horseradish peroxidase compound 1 at pH 5 were measured by stopped flow, and the reduction potentials and pKa of their radical cations were determined by pulse radiolysis. Reasonable correlation of these properties with Hammett substituent parameters was found, but not with Brown-Okamoto (theta +) parameters. The rates of reaction with compound I correlate well with the reduction potentials under the same conditions, with rates of reaction that increase by ca. 2.5 orders of magnitude with a 100 mV decrease in the reduction potential. This relationship is in agreement with that previously estimated for the reaction of compound I with phenols and anilines, suggesting that the rate of reaction depends solely on the reduction potential of the substrate radical, even for compounds of dissimilar structure.
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PMID:Rates of reaction of indoleacetic acids with horseradish peroxidase compound I and their dependence on the redox potentials. 855 62

A mild to moderate branchial epitheliocystis infection was diagnosed in subyearling (11 months old, 250-300 g) white sturgeon (Acipenser transmontanus) from a private culture facility with a 4-8% mortality in the population. Infected branchial epithelial cells contained the coccoid to coccobacillary epitheliocystis organisms, which appeared as cytoplasmic inclusions composed of a fine, homogeneous, dense, basophilic, granular material. The infected cells were variably enlarged with spherical to oval profiles and were randomly distributed throughout the branchial epithelium. The cytoplasmic inclusions stained positive with Macchiavello stain but negative with Brown and Brenn, periodic acid-Schiff, and Gimenez stains. Expression of chlamydial antigen was demonstrated within the cytoplasmic inclusions using a standard peroxidase-antiperoxidase immunohistochemical technique. Three stages of coordinated intracellular development were recognized by electron microscopy. The reticulate bodies were oval to spherical and 0.4-0.8 x 0.5-1.4 microns but often exhibited a pleomorphic and convoluted appearance because of variable membrane invaginations and evaginations suggestive of uneven fission and budding. Separate host cells contained intermediate bodies that were spherical to oval and 0.2-0.4 x 0.3-0.6 microns although often observed in the process of apparent uneven division. The presence of a cap or plaque composed of hexagonally arrayed fibrillar surface projections was initially recognized in this stage. A homogeneous population of 0.3-0.4 microns oval elementary bodies were observed separately in individual host cells. This developmental stage had a single, dense, compact, eccentrically located cytoplasmic condensation that occurred opposite to the location of the cap of hexagonally arrayed fibrillar surface projections. Morphologic characteristics of the epitheliocystis organism in these white sturgeon were similar to those previously described in other teleosts and expands the species catalogue of epitheliocystis infection. Furthermore, the ultrastructural similarities to the chalmydiae and the immunohistochemical detection of chlamydial antigen provides further evidence that the epitheliocystis agent is related to members of the Chlamydiales. Although the infection was considered mild to moderate and could not be definitively attributed to the mortality in this population, the potential adverse impact of epitheliocystis infection on sturgeon culture should be considered especially in intensive fish culture operations.
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PMID:Epitheliocystis infection in cultured white sturgeon (Acipenser transmontanus): antigenic and ultrastructural similarities of the causative agent to the chlamydiae. 874 38

A hybridoma producing monoclonal rat IgE antibodies of antidinitrophenyl (anti-DNP) specificity was generated by fusion of Sp2/0-Ag 14 (SP2) mouse myeloma cells and spleen cells from a DNP-Ascaris-sensitized Brown-Norway rat. Subsequently, the supernatant of the hybridoma (FE-3) was applied to an affinity column of DNP-bovine serum albumin-Sepharose 4B. The adsorbed protein fraction was pooled, concentrated, and further purified using Sephadex G-200. The molecular weight of the isolated protein was approximately 200,000 by SDS-PAGE, and the protein reacted with peroxidase (POD) mouse antirat myeloma IgE on Western blotting. Rabbit antibodies against DNP-specific rat IgE were also prepared by immunizing Japanese white rabbits with monoclonal DNP-specific rat IgE. These antibodies against DNP-specific rat IgE were applied to an affinity column of normal rat serum-Sepharose 4B and monoclonal DNP-specific rat IgG2b-Sepharose 4B to remove any other reactive substances apart from IgE contained in the serum proteins of the rat sensitized with DNP-Ascaris. On ELISA, it was found that the specificity of POD rabbit antibodies against DNP-specific rat IgE for monoclonal DNP-specific rat IgE was the same as that for rat myeloma IgE (IR 162). In addition, determinations of the monoclonal DNP-specific rat IgE revealed that the sensitivity of ELISA using POD-rabbit antibodies against DNP-specific rat IgE [POD-RA(DNP)RE] was higher than that using POD goat antibodies against rat myeloma IgE. Furthermore, an IgE capture ELISA employing the above-mentioned RA(DNP)RE was established for estimating the rat IgE antibodies to DNP-Ascaris suum. A good correlation was found between the antigen-specific IgE antibodies in the serum of Wistar rats estimated by this IgE capture ELISA and those estimated by passive cutaneous anaphylaxis.
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PMID:Production of a monoclonal dinitrophenyl-specific rat IgE and establishment of an IgE capture ELISA for estimating the concentration of rat IgE antibodies to dinitrophenyl-Ascaris suum. 876 5

Myeloperoxidase is the most abundant protein in neutrophils and catalyzes the production of hypochlorous acid. This potent oxidant plays a central role in microbial killing and inflammatory tissue damage. 4-Aminobenzoic acid hydrazide (ABAH) is a mechanism-based inhibitor of myeloperoxidase that is oxidized to radical intermediates that cause enzyme inactivation. We have investigated the mechanism by which benzoic acid hydrazides (BAH) are oxidized by myeloperoxidase, and we have determined the features that enable them to inactivate the enzyme. BAHs readily reduced compound I of myeloperoxidase. The rate constants for these reactions ranged from 1 to 3 x 10(6) M-1 s-1 (15 degrees C, pH 7.0) and were relatively insensitive to the substituents on the aromatic ring. Rate constants for reduction of compound II varied between 6.5 x 10(5) M-1 s-1 for ABAH and 1.3 x 10(3) M-1 s-1 for 4-nitrobenzoic acid hydrazide (15 degrees C, pH 7.0). Reduction of both compound I and compound II by BAHs adhered to the Hammett rule, and there were significant correlations with Brown-Okamoto substituent constants. This indicates that the rates of these reactions were simply determined by the ease of oxidation of the substrates and that the incipient free radical carried a positive charge. ABAH was oxidized by myeloperoxidase without added hydrogen peroxide because it underwent auto-oxidation. Although BAHs generally reacted rapidly with compound II, they should be poor peroxidase substrates because the free radicals formed during peroxidation converted myeloperoxidase to compound III. We found that the reduction of ferric myeloperoxidase by BAH radicals was strongly influenced by Hansch's hydrophobicity constants. BAHs containing more hydrophilic substituents were more effective at converting the enzyme to compound III. This implies that BAH radicals must hydrogen bond to residues in the distal heme pocket before they can reduce the ferric enzyme. Inactivation of myeloperoxidase by BAHs was related to how readily they were oxidized, but there was no correlation with their rate constants for reduction of compounds I or II. We propose that BAHs destroy the heme prosthetic groups of the enzyme by reducing a ferrous myeloperoxidase-hydrogen peroxide complex.
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PMID:Transient and steady-state kinetics of the oxidation of substituted benzoic acid hydrazides by myeloperoxidase. 1009 33

Antidromic stimulation of the stump of the VIIIth nerve was combined with microelectrode recording in the spiral ganglion of the guinea pig cochlea in an attempt to identify a sub-population of neurons with long-latency antidromic action potentials that might correspond to the thin unmyelinated afferent neurons emanating from the outer hair cells. The techniques used were similar but not identical to those employed in an earlier study by Brown (1994). By far the largest population of cells contacted had short antidromic latencies (0.58+/-0.12 ms, 76 units) and also responded to acoustic stimulation. These were assumed to be type I afferents emanating from inner hair cells. Eight cells had antidromic latencies larger than 1 ms, all but one of which had a zero spontaneous rate. All eight of these longer-latency cells were unresponsive to acoustic stimulation despite the fact that short-latency neurons in the same cochleas showed robust responses to sound before and after they were contacted. Four of these longer-latency cells had their antidromic thresholds accurately measured and two had significantly higher thresholds to electrical stimulation (0.1 ms duration) than type I cells in the same animal while two had similar electrical thresholds. Attempts to trace the eight long-latency neurons to the outer hair cells using intracellular injection of horseradish peroxidase were unsuccessful. On the basis of present evidence, we cannot conclude definitively that the long-latency neurons found in the spiral ganglion belong to the outer hair cell afferent population.
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PMID:The continuing search for outer hair cell afferents in the guinea pig spiral ganglion. 1051 34

The distribution of cortical efferent connections to the vestibular nuclei was quantitatively analyzed by means of retrograde axonal transport of horseradish peroxidase, wheat germ agglutinin-horseradish peroxidase, and Fast Blue in rats. The tracer substances were injected into the spinal vestibular nucleus (SpVe), the caudal part of the medial vestibular nucleus (MVe), and nucleus X of Brown Norwegian rats. Projections to the vestibular nuclei were revealed bilaterally, but predominantly contralaterally from five cortical areas: (1) the parietotemporal region (PT) which occupied the caudal two-thirds of the secondary somatosensory area and spread over the caudal part of the primary somatosensory area and the visceral cortex; (2) the anterior forelimb (AF) overlapping the anterior part of the forelimb area and the transitional zone; (3) the anterior hindlimb (AH) overlapping the anterior part of the hindlimb area and the transitional zone; (4) the lateral forelimb (LF) centered in the intercalated zone lateral to the forelimb area; and (5) the ventrotemporal region (VT) located at the ventral part of the temporal cortex. In addition to these cortical fields, the frontal cortex was found to project directly to the vestibular nuclei. These corticofugal projections were verified in experiments in which biocytin was injected into the rat PT. Anterogradely labelled fibers were traced predominantly contralaterally to the SpVe, caudal part of the MVe, and nucleus X. It is suggested that the rat corticofugal projections to the caudal vestibular nuclei modify vestibular reflexes to assist in coordinating eye, head and body movements during locomotion.
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PMID:Corticofugal connections between the cerebral cortex and the vestibular nuclei in the rat. 1075 8

Brown precipitates were obtained by polymerization of low molecular weight lignin fragments contained in a model effluent. Polymerization reactions were initiated by potato-polyphenoloxidase (PPO) or horseradish peroxidase/H(2)O(2) system (HRP/H(2)O(2)). The insolubilization processes occurred after a molecular weight increase of the lignin, as shown by gel permeation chromatography (GPC). The effect of reaction time, pH and amount of soluble lignin per unit of enzyme activity on the molecular weight distribution was evaluated for PPO-initiated reactions. For HRP-initiated system the amount of H(2)O(2) per unit of enzyme activity was also evaluated. Chemical characterization of the macromolecules obtained under optimized conditions and the soluble lignin fragments present in the effluent suggests that the polymerization reactions occur by oxidative cleavage of alpha-beta unsaturated bonds of the soluble lignin fragments. Methoxyl group analysis showed that p-hydroxycoumaryl units were preferentially oxidized by PPO. In contrast, HRP oxidized preferentially guaiacyl and siringyl units giving more condensed polymers.
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PMID:Molecular weight distribution and structural characteristics of polymers obtained from acid soluble lignin treated by oxidative enzymes. 1124 Jan 84

We examined the role of primary afferent neurons in the somatosensory cortical "reactivation" that occurs after a localized cervical dorsal root lesion (Darian-Smith and Brown [2000] Nat. Neurosci. 3:476-481). After section of the dorsal rootlets that enervate the macaque's thumb and index finger (segments C6-C8), the cortical representation of these digits was initially silenced but then re-emerged for these same digits over 2-4 postlesion months. Cortical reactivation was accompanied by the emergence of physiologically detectable input from these same digits within dorsal rootlets bordering the lesion site. We investigated whether central axonal sprouting of primary afferents spared by the rhizotomy could mediate this cortical reactivation. The cortical representation of the hand was mapped electrophysiologically 15-25 weeks after the dorsal rootlet section to define this reactivation. Cholera toxin subunit B conjugated to horseradish peroxidase was then injected into the thumb and index finger pads bilaterally to label the central terminals of any neurons that innervated these digits. Primary afferent terminal proliferation was assessed in the spinal dorsal horn and cuneate nucleus at 7 days and 15-25 postlesion weeks. Labeled terminal bouton distributions were reconstructed and the "lesion" and control sides compared within each monkey. Distributions were significantly larger on the side of the lesion in the dorsal horn and cuneate nucleus at 15-25 weeks after the dorsal rootlet section, than those mapped only 7 days postlesion. Our results provide direct evidence for localized sprouting of spared (uninjured) primary afferent terminals in the dorsal horn and cuneate nucleus after a restricted dorsal root injury.
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PMID:Primary afferent terminal sprouting after a cervical dorsal rootlet section in the macaque monkey. 1475 Jan 57

The congeners Gyrodactylus salaris and G. derjavini are specific ectoparasites of Atlantic salmon Salmo salar and brown trout S. trutta, respectively. To elucidate the involvement of lectin-carbohydrate interactions in this host specificity, carbohydrates on the tegument of the two species and the corresponding lectin activity of their hosts have been studied. Carbohydrate composition on the tegument differed significantly between the two gyrodactylids. Three of four commercially available peroxidase-labelled lectins with primary affinity towards D-mannoside, D-GalNAc and L-fucose bound more strongly to G. derjavini than to G. salaris. Lectins with an affinity towards D-mannoside and D-GalNAc bound significantly stronger to the cephalic lobes on G. derjavini compared to the tegument and sheaths of the hamuli. One brown trout strain and three different salmon strains were tested for lectin activity in skin and plasma. Two Baltic salmon strains and one strain from the Atlantic region were included. Brown trout differed significantly from the salmon strains when skin samples were tested for D-GalNAc activity. Lectins binding to other carbohydrates showed trends for similar host differences. The implications of carbohydrate-lectin interactions for host specificity in gyrodactylids are discussed.
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PMID:Carbohydrate localization on Gyrodactylus salaris and G. derjavini and corresponding carbohydrate binding capacity of their hosts Salmo salar and S. trutta. 1583 Nov 12


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