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C R Lovell

Publications and source records attributed to C R Lovell.

At least 37 records · Page 2Linked to original sources
PubMed2000

Molecular analysis of diazotroph diversity in the rhizosphere of the smooth cordgrass, Spartina alterniflora.

N(2) fixation by diazotrophic bacteria associated with the roots of the smooth cordgrass, Spartina alterniflora, is an important source of new nitrogen in many salt marsh ecosystems. However, the diversity and phylogenetic affiliations of these rhizosphere diazotrophs are unknown. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified nifH sequence segments was used in previous studies to examine the stability and dynamics of the Spartina rhizosphere diazotroph assemblages in the North Inlet salt marsh, near Georgetown, S.C. In this study, plugs were taken from gel bands from representative DGGE gels, the nifH amplimers were recovered and cloned, and their sequences were determined. A total of 59 sequences were recovered, and the amino acid sequences predicted from them were aligned with sequences from known and unknown diazotrophs in order to determine the types of organisms present in the Spartina rhizosphere. We recovered numerous sequences from diazotrophs in the gamma subdivision of the division Proteobacteria (gamma-Proteobacteria) and from various anaerobic diazotrophs. Diazotrophs in the alpha-Proteobacteria were poorly represented. None of the Spartina rhizosphere DGGE band sequences were identical to any known or previously recovered environmental nifH sequences. The Spartina rhizosphere diazotroph assemblage is very diverse and apparently consists mainly of unknown organisms.

Bacteria, Anaerobic↗
PubMed1999

Latex allergy in an orthognathic patient and implications for clinical management.

A 19-year-old girl with mild asthma had had 16 months of orthodontic treatment as part of the joint orthodontic/orthognathic approach to her 9.5 mm overjet. At the time of banding her second molars she developed latex protein allergy as a reaction to the operator's non-sterile powdered latex gloves. She also gave a history of allergy to other substances as well as of eczema. The patient was confirmed as allergic to latex protein by radioallergosorbent test (RAST) for IgE, requiring precautions be taken during further orthodontic procedures as well as during the subsequent orthognathic surgery for the underlying Class II skeletal pattern.

Adult↗
PubMed1998

Physiological diversity of the rhizosphere diazotroph assemblages of selected salt marsh grasses.

Rhizosphere diazotroph assemblages of salt marsh grasses are thought to be influenced by host plant species and by a number of porewater geochemical parameters. Several geochemical variables can adversely affect plant productivity and spatial distributions, resulting in strong zonation of plant species and growth forms. This geochemically induced stress may also influence the species compositions and distributions of rhizosphere diazotroph assemblages, but little is currently known about these organisms. The diversity and key physiological features of culturable, O2-tolerant rhizosphere diazotrophs associated with the tall and short growth forms of Spartina alterniflora and with Juncus roemerianus were examined. A total of 339 gram-negative strains were isolated by a root stab culture approach and morphologically and physiologically characterized by using API and BIOLOG tests. Eighty-six distinct groups composed of physiologically similar strains were identified. Of these groups, 72% were shown to be capable of N2 fixation through molecular analyses, and a representative strain was chosen from each diazotroph group for further characterization. Cluster and principal-components analysis of BIOLOG data allowed the designation of physiologically distinct strain groupings. Most of these groups were dominated by strains that were not identifiable to species on the basis of API or BIOLOG testing. Representatives of several families including the Enterobacteriaceae, Vibrionaceae, Azotobacteraceae, Spirillaceae, Pseudomonadaceae, and Rhizobiaceae were recovered, as well as strains with no clear taxonomic affiliations. This study identifies numerous potentially important physiological groups of the salt marsh diazotroph assemblage.

Bacteria↗
PubMed1997

Notomastus lobatus chloroperoxidase and Amphitrite ornata dehaloperoxidase both contain histidine as their proximal heme iron ligand.

Two novel heme-containing peroxidases, one able to incorporate halogens into aromatic substrates and the other able to remove them, have recently been isolated from marine sources and initially characterized by Chen et al. [(1991) J. Biol. Chem. 266, 23909-23915; (1996) J. Biol. Chem. 271, 4609-4612]. The haloperoxidase Notomastus lobatus chloroperoxidase (NCPO) is unusual in requiring a flavoprotein component for peroxidase activity. The dehaloperoxidase (DHP), isolated from Amphitrite ornata, is the only heme-containing peroxide-dependent dehalogenase known to be capable of removing halogens including fluorine. Both enzymes are also quite atypical in that the molecular weights of their heme-containing subunits are less than 16,000, approximately one-half to one-fifth the size of typical heme-containing peroxidases. Interestingly, we have also found that both enzymes are isolated in their oxyferrous states even though all protein purification was done in the absence of any reductant. In the present study, we have examined these two enzymes with magnetic circular dichroism and UV-visible absorption spectroscopy in order to determine the identity of their proximal heme iron ligand. Four derivatives of each enzyme, cyanoferric, deoxyferrous, oxyferrous, and (carbonmonoxy)ferrous, have been examined and spectroscopically compared to parallel derivatives of myoglobin, a well-studied histidine-ligated heme protein. The spectra observed for each derivative of the two new enzymes are very similar to each other and, in turn, to the spectra of the same derivatives of myoglobin. We conclude that both new heme enzymes contain histidine as their proximal heme iron ligand. This makes NCPO the first histidine-ligated heme-containing peroxidase capable of chlorinating halogen acceptor substrates using chloride as the halogen donor. Further, the novel reactivity of DHP is not the result of an unusual proximal ligand. The present results with NCPO and DHP challenge the current dogma of how heme-containing peroxidases function: one chlorinates substrates without having a thiolate proximal ligand, and the other both oxygenates and dehalogenates haloaromatics and yet has a histidine proximal ligand like numerous other peroxidases that are not capable of such a combined reactivity.

Animals↗
PubMed1996

Crystallization and initial spectroscopic characterization of the heme-containing dehaloperoxidase from the marine polychaete Amphitrite ornata.

The heme-containing dehaloperoxidase from Amphitrite ornata was crystallized from an unbuffered solution containing 30% PEG 8000 and 200 mM ammonium sulfate by the hanging-drop vapor-diffusion method. Dark-red bipyramidal crystals are orthorhombic in space group P2(1)2(1)2(1) with unit-cell dimensions a = 68.5, b = 68.4 and c = 61.1 A. The asymmetric unit contains two subunits related by a non-crystallographic twofold axis. The crystals scatter beyond 2 A resolution. The native data have been collected and one single-site mercury derivative has been found. SIRAS phasing was used to determine the positions of the heme Fe atoms and structure determination is in progress. A preliminary spectroscopic investigation indicates that the heme is protoporphyrin IX and its coordination sphere resembles that of a typical heme peroxidase, i.e. histidine ligated. Detailed spectroscopic and electrochemical studies are now under way.

Journal Article↗
PubMed1996

An unusual dehalogenating peroxidase from the marine terebellid polychaete Amphitrite ornata.

The terebellid polychaete Amphitrite ornata produces no detectable volatile halogenated secondary metabolites, but frequently inhabits coastal marine sediments heavily contaminated with anthropogenic or biogenic haloaromatic compounds. This animal contains high levels of two very unusual enzymes, dehalogenating peroxidases. We have purified and partially characterized one of these dehaloperoxidases, DHP I. DHP I is a heme enzyme (Mr = 30,790) composed of two identical subunits (Mr = 15,529) and is very rich in the amino acids aspartic acid (+ asparagine) and glutamic acid (+ glutamine). The enzyme converts trihalogenated phenols, such as 2,4,6-tribromophenol, into dihalogenated quinones. The optimum pH for this reaction is 5.0. DHP I is also active against di- and monohalogenated phenols and will oxidize bromo-, chloro-, and fluorophenols. We have identified similar dehaloperoxidase activities in other infaunal polychaetes, including halometabolite-producing species.

Amino Acids↗
PubMed1996

VCAM-1 expression on endothelium in lesions from cutaneous lupus erythematosus is increased compared with systemic and localized scleroderma.

The cutaneous lesions in systemic sclerosis (SSc) and lupus erythematosus (LE) are pathologically distinct and may display separate cell adhesion receptors. We have scored lesional skin for the presence of cell adhesion molecules that may influence inflammatory and fibrotic processes in five patients with LE, six patients with diffuse scleroderma and four patients with morphoea. The immunohistological distribution, and the number and intensity of cells staining, were recorded for VCAM-1, ICAM-1, E-selectin, alpha 2 to alpha 6 and beta 2 integrins and HLA-DR. VCAM-1 staining intensity was increased on endothelium from lesions in LE compared with SSc (P = 0.05). Low-level VCAM-1 and E-selectin expression was present on endothelium from uninvolved skin including that from patients with morphoea. HLA-DR expression was increased on infiltrating mononuclear cells (P < 0.05) and keratinocytes in LE (P < 0.05) and the number of fibroblasts staining for ICAM-1 was increased in lesions from patients with SSc, although this did not reach statistical significance. Overall, with respect to endothelial adhesion events, our findings support an important role for VCAM-1 in sustaining chronic inflammation in cutaneous LE.

Adult↗
PubMed1994

Psoriatic arthritis: outcome of disease subsets and relationship of joint disease to nail and skin disease.

Subgroups of PsA have been described but their relationship to the mode of onset of arthritis, to DIP joint disease and to nail and skin disease remains controversial. Therefore, the pattern of disease was documented in 100 patients with PsA in whom the mode of onset was known. The patients were divided into six subgroups: monoarthritis; DIP joint disease only; oligoarthritis; polyarthritis; spondyloarthropathy and arthritis mutilans. Sixty-four patients changed pattern. Nail disease (67% of total) was more common in patients with DIP joint disease (27% of total) and was significantly associated with adjacent DIP joint disease. Skin and nail disease severity did not correlate with joint severity, joint activity or functional status, nor differ between subgroups. Therefore, the mode of onset does not predict outcome in the majority. The topographic association of nail disease and involvement of the adjacent DIP joints suggests a common local inflammatory mechanism.

Adolescent↗
PubMed1994

Subungual keratoacanthoma--a report of four cases and review of the literature.

Subungual keratoacanthoma is a rare benign neoplasm which most commonly occurs in middle-aged Caucasians. It usually presents as a painful, rapidly growing lesion of the terminal phalanx. Radiography consistently demonstrates a well-defined cup-shaped erosion of the underlying bone. Clinically, subungual keratoacanthoma must be distinguished from subungual squamous carcinoma. We report four further cases and discuss the literature.

Adult↗
PubMed1993

Crystallization and preliminary crystallographic data for formyltetrahydrofolate synthetase from Clostridium thermoaceticum.

Formyltetrahydrofolate synthetase from Clostridium thermoaceticum has been crystallized using the hanging-drop method from ammonium sulphate and PEG solutions. Crystals are trigonal, the space group is R32, a = 163 A, c = 259 A. A 4.2 A resolution data set has been collected. Analysis of the data using the self-rotation function shows that tetramers have approximate 222 symmetry and are positioned on a crystallographic 2-fold axis.

Clostridium↗
PubMed1993

Chemotaxis of azospirillum species to aromatic compounds.

Chemotaxis of Azospirillum lipoferum Sp 59b and Azospirillum brasilense Sp 7 and Sp CD to malate and to the aromatic substrates benzoate, protocatechuate, 4-hydroxybenzoate, and catechol was assayed by the capillary method and direct cell counts. A. lipoferum required induction by growth on 4-hydroxybenzoate for positive chemotaxis to this compound. Chemotaxis of Azospirillum spp. to all other substrates did not require induction. Maximum chemotactic responses for most aromatic compounds occurred at concentrations of 1 to 10 mM for A. lipoferum and 100 muM to 1 mM for A. brasilense. Threshold levels of these chemoattractants ranged from nanomolar to micromolar, with A. brasilense Sp CD showing the lowest threshold levels for the substrates tested. Benzoate was the strongest chemoattractant tested, with threshold concentrations in the nanomolar to picomolar range for all strains. Azospirillum spp. clearly have more sensitive chemosensory mechanisms for certain aromatic substrates than previously reported in some other soil bacteria. This sensitivity allows Azospirillum spp. to detect and respond to aromatic substrates at concentrations relevant to the soil and rhizosphere environments. The ability to detect such low concentrations of aromatic compounds in soils may confer advantages in survival and colonization of the rhizosphere by Azospirillum species.

Journal Article↗