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C M Boyd

Publications and source records attributed to C M Boyd.

At least 19 recordsLinked to original sources
PubMed2003

Transinhibition and voltage-gating in a fungal nitrate transporter.

We have applied enzyme kinetic analysis to electrophysiological steady-state data of Zhou et al. (Zhou, J.J., Trueman, L.J., Boorer, K.J., Theodoulou, F.L., Forde, B.G., Miller, A.J. 2000. A high-affinity fungal nitrate carrier with two transport mechanisms. J. Biol. Chem. 275:39894-9) and to new current-voltage-time records from Xenopus oocytes with functionally expressed NrtA (crnA) 2H+-NO3- symporter from Emericella (Aspergillus) nidulans. Zhou et al. stressed two Michaelis-Menten (MM) mechanisms to mediate the observed nitrate-induced currents, I(NO3-). We show that a single straightforward reaction cycle describes the data well, pointing out that during exposure to external substrate, S = (2H+ + NO3-)o, the product concentration inside, [P] = [H+]i(2) x [NO3-]i, may rise substantially near the plasma membrane, violating the condition [P] << [S] for MM kinetics. Here, [P] and its changes during experimentation are treated explicitly. K(1/2) approximately 20 microM for I(NO3-) at pHo from Zhou et al. is confirmed. According to our analysis, NrtA operates between about 0.2 and 0.6 of the electrical distance in the membrane (outside 0, inside 1). In absence of thermodynamic gradients, the predominant orientation of the binding site(s) is probably inwards. The activity of the enzyme is sensitive to the transmembrane voltage, V, with an apparent gating charge of +1.0 +/- 0.5 for inactivation, and transition probabilities of 0.3-1.3 s(-1) at V = 0. This gating mode impedes loss of cellular NO3- during depolarization.

Animals↗
PubMed2000

Three types of membrane excitations in the marine diatom Coscinodiscus wailesii.

Three types of electrical excitation have been investigated in the marine diatom Coscinodiscus wailesii. I: Depolarization-triggered, transient Cl(-) conductance, G(Cl)(t), followed by a transient, voltage-gated K(+) conductance, G(K), with an active state a and two inactive states i(1) and i(2) in series (a-i(1)-i(2)). II: Similar G(Cl)(t) as in Type-I but triggered by hyperpolarization; a subsequent increase of G(K) in this type is indicated but not analyzed in detail. III: Hyperpolarization-induced transient of a voltage-gated activity of an electrogenic pump (i(2)-a-i(2)), followed by G(Cl)(t) as in Type-II excitations. Type-III with pump gating is novel as such. G(Cl)(t) in all types seems to reflect the mechanism of InsP(-)(3) and Ca(2+)-mediated G(Cl)(t) in the action potential in Chara (Biskup et al., 1999). The nonlinear current-voltage-time relationships of Type-I and Type-III excitations have been recorded under voltage-clamp using single saw-tooth command voltages (voltage range: -200 to +50 mV, typical slope: +/-1 Vs(-1)). Fits of the corresponding models to the experimental data provided numerical values of the model parameters. The statistical significance of these solutions is investigated. We suggest that the original function of electrical excitability of biological membranes is related to osmoregulation which has persisted through evolution in plants, whereas the familiar and osmotically neutral action potentials in animals have evolved later towards the novel function of rapid transmission of information over long distances.

Action Potentials↗
PubMed2000

The forehead flap for nasal reconstruction.

CONTEXT: Reconstruction of extensive nasal defects often represents a significant challenge owing to several unique qualities of the nose, such as complex topography, mobile free margins, and multiple nasal subunits. Furthermore, loss of internal nasal lining and/or structural skeletal support may be present following removal of extensive skin cancers. OBJECTIVE: To describe our experience with the use of forehead flap reconstruction for extensive nasal defects. DESIGN: Retrospective case series. SETTING: Academic health care hospital system. PATIENTS/INTERVENTION: One hundred forty-seven patients with extensive nasal defects repaired with a forehead flap. MAIN OUTCOME MEASURES: The functional and aesthetic results were assessed. The characteristics of defects repaired with the forehead flap and the need for lining and/or cartilage were examined. RESULTS: The forehead flap was used to repair 147 nasal defects after Mohs excision of nonmelanoma skin cancer. Full-thickness skin was lost in all cases, structural skeletal support in 68 cases (46%), and internal mucosal lining in 45 cases (31%). Our experience and surgical technique using the forehead flap are described. CONCLUSIONS: The forehead flap represents one of the best methods for repair of extensive nasal defects. Near-normal functional and cosmetic results can be achieved.

Adult↗
PubMed1999

Electrophysiology of the marine diatom Coscinodiscus wailesii IV: types of non-linear current-voltage-time relationships recorded with single saw-tooth voltage-clamp experiments.

Electrophysiological states of the marine diatom Coscinodiscus wailesii are known to change spontaneously in the temporal range of seconds. In order to assess the genuine current-voltage-time relationships of individual states in less than a second, voltage-clamp experiments have been carried out using single sweeps of saw-tooth shaped command voltages. This method is introduced with model calculations. Plotting the results in current-voltage coordinates provides convenient access to several electrophysiological entities, such as absence of drift (smoothly closed IV loops), membrane capacitance (by I jump at sign reversal of dV/dt), and ohmic conductances (in linear regions of the current-voltage relationship), as well as equilibrium voltage (internal intersection of capacitance-corrected, 8-shaped tracings) and coarse gating kinetics (rise or fall of capacitance-corrected I at sign reversal of dV/dt) of a voltage-sensitive ion conductance. From electrophysiological measurements with double-barreled glass-microelectrodes on C. wailesii, several distinct types of current-voltage loops are presented. Most of the data, including recordings from electrical excitation, can be interpreted as temporal relaxations of voltage-sensitive conductances for K(+) and Cl(-). A more detailed analysis of the effect of tetraethylammonium (TEA(+)) shows that 10 and 20 mM TEA(+) inhibit the K(+) conductance in C. wailesii only by up to about 20% but predominantly via a K(+) outward rectifier.

Diatoms↗
PubMed1999

Species and genotypic diversities and similarities of pathogenic yeasts colonizing women.

We examined the patterns of strain relatedness among pathogenic yeasts from within and among groups of women to determine whether there were significant associations between genotype and host condition or body site. A total of 80 yeast strains were isolated, identified, and genotyped from 49 female volunteers, who were placed in three groups: (i) 19 women with AIDS, (ii) 11 pregnant women without human immunodeficiency virus (HIV) infection, and (iii) 19 women who were neither pregnant nor infected with HIV. Seven yeast species were recovered, including 59 isolates of Candida albicans, 9 isolates of Candida parapsilosis, 5 isolates of Candida krusei, 3 isolates of Candida glabrata, 2 isolates of Saccharomyces cerevisiae, and 1 isolate each of Candida tropicalis and Candida lusitaniae. Seventy unique genotypes were identified by PCR fingerprinting with the M13 core sequence and by random amplified polymorphic DNA analysis. Of the nine shared genotypes, isolates from three different hosts were of one genotype and pairs of strains from different body sites of the same host shared each of the other eight genotypes. Genetic similarities among groups of strains were calculated and compared. We found no significant difference in the patterns of relatedness of strains from the three body sites (oral cavity, vagina, and rectum), regardless of host conditions. The yeast microflora of all three host groups had similar species and genotypic diversities. Furthermore, a single host can be colonized with multiple species or multiple genotypes of the same species at the same or different body sites, indicating dynamic processes of yeast colonization on women.

AIDS-Related Opportunistic Infections↗
PubMed1998

Personal performance profiles: a useful adjunct to quality assurance in cervical cytology.

In our laboratory, which processes approximately 40,000 smears annually, the reporting patterns of each individual primary screener have been continuously monitored over a 6-year period. The detection rates for minor abnormalities (borderline/mild dyskaryosis) and major abnormalities (moderate dyskaryosis and worse) are published quarterly in the laboratory. Individual continuous monitoring rapidly identifies screeners with low detection rates. It is a useful adjunct to existing methods of quality assurance; rescreening can be more appropriately directed to smears reported by screeners with low detection rates. It also identifies training needs and may be used to assess the value of update courses for each screener. It is a faster method of identifying poor performance than rapid review of all smears. The reporting rate of inadequate smears is also calculated and published on a quarterly basis. This promotes a degree of uniformity within the laboratory in the rate at which smears are reported as inadequate, and also reduces the inadequate rate.

Employee Performance Appraisal↗
PubMed1998

External loops at the C terminus of Erwinia chrysanthemi pectate lyase C are required for species-specific secretion through the out type II pathway.

The type II secretion system (main terminal branch of the general secretion pathway) is used by diverse gram-negative bacteria to secrete extracellular proteins. Proteins secreted by this pathway are synthesized with an N-terminal signal peptide which is removed upon translocation across the inner membrane, but the signals which target the mature proteins for secretion across the outer membrane are unknown. The plant pathogens Erwinia chrysanthemi and Erwinia carotovora secrete several isozymes of pectate lyase (Pel) by the out-encoded type II pathway. However, these two bacteria cannot secrete Pels encoded by heterologously expressed pel genes from the other species, suggesting the existence of species-specific secretion signals within these proteins. The functional cluster of E. chrysanthemi out genes carried on cosmid pCPP2006 enables Escherichia coli to secrete E. chrysanthemi, but not E. carotovora, Pels. We exploited the high sequence similarity between E. chrysanthemi PelC and E. carotovora Pel1 to construct 15 hybrid proteins in which different regions of PelC were replaced with homologous sequences from Pell. The differential secretion of these hybrid proteins by E. coli(pCPP2006) revealed M118 to D175 and V215 to C329 as regions required for species-specific secretion of PelC. We propose that the primary targeting signal is contained within the external loops formed by G274 to C329 but is dependent on residues in M118 to D170 and V215 to G274 for proper positioning.

Amino Acid Sequence↗
PubMed1997

Impaired vocal cord mobility in the setting of acute suppurative thyroiditis.

BACKGROUND: Acute suppurative thyroiditis is an increasingly rare entity, accounting for less than 0.1% of thyroid surgery. This is the first report in the literature of acute thyroiditis causing a unilateral reversible vocal cord paralysis. METHODS: A 41-year-old woman was initially seen with a unilateral vocal cord paralysis resulting from acute suppurative thyroiditis. RESULTS: The vocal cord paralysis resolved following surgical drainage of the thyroid abscess and treatment with intravenous antibiotics. CONCLUSIONS: We present this case to emphasize the need for a complete and thorough head and neck exam including preoperative documentation of vocal cord mobility.

Acute Disease↗
PubMed1996

Differential effect of site-directed mutations in pelC on pectate lyase activity, plant tissue maceration, and elicitor activity.

Oligonucleotide site-directed mutations were introduced into the pelC gene of Erwinia chrysanthemi EC16 that directed single or double amino acid changes affecting disulfide linkages, calcium binding, catalysis, and protein folding. Subsequent characterization of the purified PelC mutant proteins demonstrated that pectinolytic function involves amino acids located near the calcium binding site rather than those surrounding an invariant vWiDH sequence. Wild-type PelC and the tested mutant proteins generally macerated plant tissue in proportion to their specific pectinolytic activity in vitro. However, some mutants gave higher maceration activity in plant tissue and elicited greater production of the phytoalexin, glyceollin, in soybean cotyledons than predicted by their in vitro pectinolytic activity. Most notable in this regard were three different mutations at lysine 172 with greatly reduced pectinolytic activity but as much elicitor activity as the wild-type protein. PelE macerated plant tissue 10 times more efficiently than PelC, as observed previously, but surprisingly showed equal activity in the elicitor assay. The results indicate that factors other than pectinolytic activity per se are involved in plant tissue maceration and elicitor activity.

Dickeya chrysanthemi↗
PubMed1996

The immunology of thyroid cancer.

This article reviews the immunologic aspects of thyroid cancer, including thyroid-specific effector elements on thyroid cancer, and discusses the potential antigens, unique molecular markers, and transcription factors that could serve as targets for immunotherapy. The potential role of this type of treatment for thyroid cancer is examined also.

Antigens, Neoplasm↗
PubMed1995

Clinical utility of In-111 leukocyte imaging in Crohn's disease.

Thirty six patients with Crohn's disease were studied with In-111 leukocyte imaging. There was a correlation of the presence of activity on early (4 hour) imaging (r = 0.516, P < 0.001) and on delayed 18-24 hour) imaging (r = 0.457, P < 0.003). In the total group of 36 patients, the results of imaging were useful in the immediate management of 13 patients (36.1%). These included four patients (11.1%) who refused to undergo colonoscopic examination and nine patients (25%), six of whom had previous intestinal resection.

Adult↗
PubMed1993

Characterization of the Pseudomonas aeruginosa alginate lyase gene (algL): cloning, sequencing, and expression in Escherichia coli.

Mucoid strains of Pseudomonas aeruginosa produce a viscous exopolysaccharide called alginate and also express alginate lyase activity which can degrade this polymer. By transposon mutagenesis and gene replacement techniques, the algL gene encoding a P. aeruginosa alginate lyase enzyme was found to reside between algG and algA within the alginate biosynthetic gene cluster at 35 min on the P. aeruginosa chromosome. DNA sequencing data for algL predicted a protein product of ca. 41 kDa, including a 27-amino-acid signal sequence, which would be consistent with its possible localization in the periplasmic space. Expression of the algL gene in Escherichia coli cells resulted in the expression of alginate lyase activity and the appearance of a new protein of ca. 39 kDa detected on sodium dodecyl sulfate-polyacrylamide gels. In mucoid P. aeruginosa strains, expression of algL was regulated by AlgB, which also controls expression of other genes within the alginate gene cluster. Since alginate lyase activity is associated with the ability to produce and secrete alginate polymers, alginate lyase may play a role in alginate production.

Amino Acid Sequence↗
PubMed1990

Osteoporosis: diagnosis by plain chest film versus dual photon bone densitometry.

Readers of chest radiographs often comment on the presence of osteoporosis. We have hypothesized that diagnoses of osteoporosis from chest films are not reliable even when made by experienced radiologists. To test this hypothesis, we had nine radiologists estimate the degree of bone density seen on 45 lateral chest films. We compared their estimates of bone density to the results of dual photon bone densitometry of the lumbar spine. We found that there was little ability to accurately diagnose osteoporosis by chest film since the group of nine readers achieved accuracies ranging from 0.59 to 0.64. Therefore, we feel it is unjustified to comment upon the presence or absence of osteoporosis on the basis of chest films.

Absorptiometry, Photon↗
PubMed1990

A rapid method for standardization of the gated radionuclide left ventricular ejection fraction.

Radionuclide ventriculography has become the standard method for serially evaluating left ventricular ejection fraction (EF). The "gold standard" for evaluating EF is the contrast ventriculogram, which uses mathematical models to arrive at the volumes used to calculate EF. These models are subject to possible error. This paper reports the standardization of volume measurements of a digital angiographic camera system using a series of cardiac phantoms and the correlation of measurement of the EF of a series of patients whose EF was determined by digital angiography and radionuclide ventriculography.

Aged↗