PubMed Health⌕ Search

Biomedical subjects

C A Francis

Publications and source records attributed to C A Francis.

At least 19 recordsLinked to original sources
PubMed2003

Modelling faecal indicator concentrations in large rural catchments using land use and topographic data.

AIMS: To characterize and model spatial variations in faecal-indicator organism concentrations in watercourses draining a large rural catchment during the bathing season. METHODS AND RESULTS: Presumptive coliform (PC), presumptive Eschericia coli (PE) and presumptive enterococci (PEnt) concentrations were determined under base- and high-flow conditions at 24 monitoring points in the Rheidol/Ystwyth catchment, Wales. Relationships with land use and topographic variables within their 'subcatchments' were investigated. Geometric mean (GM) concentrations typically increase more than 10-fold at high flow. The proportion of improved pasture within subcatchments explains 81.6, 73.0 and 85.8%, respectively, of the variance in high-flow GM PC, PE and PEnt concentrations. Distributed modelling suggests that organisms derived from more distant parts of subcatchments may be lost through die-off and sedimentation along watercourses at base flow, although not at high flow. Reductions in concentrations are also evident downstream of reservoir impoundments. CONCLUSIONS: Large rural catchments may contribute substantially to faecal indicator loadings in coastal waters. Indicator concentrations can be modelled successfully using land use and topographic data. SIGNIFICANCE AND IMPACT OF THE STUDY: Development of a modelling approach that provides valuable insight into faecal indicator sources and the transport and survival of these organisms within large catchments.

Environmental Monitoring↗
PubMed2002

Petrographic and spectroscopic characterization of phosphate-stabilized mine tailings from Leadville, Colorado.

The use of soluble PO4(3-) and lime as a heavy metal chemical stabilization agent was evaluated for mine tailings from Leadville, Colorado. The tailings are from piles associated with the Wolftone and Maid of Erin mines; ore material that was originally mined around 1900, reprocessed in the 1940s, and now requires stabilization. The dominant minerals in the tailings are galena (PbS), cerrusite (PbCO3), pyromorphite (Pb5(PO4)3Cl), plumbojarosite (Pb0.5Fe3(SO4)2(OH)6), and chalcophanites ((Pb,Fe,Zn,Mn)Mn2O5 x 2H2O). The tailings were treated with soluble PO4(3-) and lime to convert soluble heavy metals (principally Pb, Zn, Cu, Cd) into insoluble metal phosphate precipitates. The treatment process caused bulk mineralogical transformations as well as the formation of a reaction rind around the particles dominated by Ca and P. Within the mineral grains, Fe-Pb phosphosulfates, Fe-Pb sulfates (plumbojarosite), and galena convert to Fe-Ca-Pb hydroxides. The Mn-Pb hydroxides and Mn-(+/-Fe)-Pb hydroxides (chalcophanites) undergo chemical alteration throughout the grains during treatment. Bulk and surface spectroscopies showed that the insoluble reaction products in the rind are tertiary metal phosphate (e.g. (Cu,Ca2)(PO4)2) and apatite (e.g. Pb5(PO4)3Cl) family minerals. pH-dependent leaching (pH 4,6,8) showed that the treatment was able to reduce equilibrium concentrations by factors of 3 to 150 for many metals; particularly Pb2+, Zn2+, Cd2+, and Cu2+. Geochemical thermodynamic equilibrium modeling showed that apatite family and tertiary metal phosphate phases act as controlling solids for the equilibrium concentrations of Ca2+, PO4(3-) Pb2+, Zn2+, Cd2+, and Cu2+ in the leachates during pH-dependent leaching. Both end members and ideal solid solutions were seen to be controlling solids.

Colorado↗
PubMed2001

Participating dentists' assessment of the pilot regional online videoconferencing in dentistry (PROVIDENT) project.

OBJECTIVE: To assess the educational effectiveness of delivering continuing professional education (CPE) from dental schools to small groups of dentists at distant sites via videoconferenced links using relatively inexpensive equipment and ISDN2 links. DESIGN: 41 videoconferences between the four campuses of London Dental Schools and postgraduate centres in South East England were assessed using a pre-piloted questionnaire which contained open and specific questions. The questionnaire was given to all participants at the end of each videoconference. Answers to the specific questions were graded using the Likert scale. RESULTS: 40 of the 41 videoconferences were completed satisfactorily and were attended by 257 participants, all of whom completed questionnaires. However, no individual question was answered by all the participants. Of the responses 90% were positive on the topics of appropriateness of the teaching material for delivery by videoconference and of its educational level. 90% of responses also indicated a wish to attend further videoconferences and satisfaction at avoiding the need to travel to London for similar educational activity. 87% rated the lecturers as good or excellent in their use of the medium. 85% of responses indicated that the question and answer sessions within the videoconferences were useful and 82% that the visual aids enhanced the sessions. The technical aspects of the videoconferences were rated positively but to a lesser extent than the educational aspects with 69% of positive responses for visibility of visual aids, 54% for sound quality and 76% for the lecturers use of the technology. The technical aspects of the videoconferences improved during the pilot study. In response to the open questions, participants stated that they found the most useful aspects of the videoconferences were not having to travel, access to first rate lecturers, the discussions and the opportunity to interact with experts. CONCLUSIONS: The participants in this pilot study were positive about the use of videoconferencing to deliver educational material from dental schools to small groups. Once the technology has improved, this medium has the potential to provide CPE for dentists at work or at home in response to their specific needs.

Education, Dental, Continuing↗
PubMed2001

A simple modified membrane filtration medium for the enumeration of aerobic spore-bearing bacilli in water.

Aerobic spore-bearing bacilli have been proposed as a surrogate indicator for the removal of Cryptosporidium by drinking water treatment processes. Pasteurisation of samples followed by culture on non-selective media is the method of choice. Using white membranes for filtration of water samples makes colony counting difficult. Vital dyes such as neutral red or trypan blue can help when added to the growth medium but these dyes tend to colour the membrane and reduce the contrast between the colonies and the background. The incorporation of bromothymol blue at a concentration of 0.005% (w/v) into nutrient agar facilitated colony counting without inhibiting colony formation compared with unsupplemented nutrient agar. Statistical analysis of the data (ANOVA) confirms this observation. The modified technique was found to be satisfactory with spore suspensions of Bacillus globigii and B. cereus as well as with samples of surface water, settled water and drinking water.

Animals↗
PubMed2001

A study of videoconferencing for postgraduate continuing education in dentistry in the UK--the teachers' view.

Videoconferencing is an established method for providing medical education over long distances. Our aims were to assess the feasibility of videoconferencing in dental postgraduate education, to evaluate its practicability, teacher satisfaction and evaluate equipment. Twenty-seven teachers from the 4 London Dental Schools provided 41 postgraduate dental education sessions on a range of topics to regional postgraduate centres and dental practices as part of the Thames Health Region's programme. Videoconferencing was carried out using a relatively inexpensive personal computer system link using ISDN2 telephone lines and Z350 protocol. Presenter views and assessment were obtained by questionnaire, interview and videotape. Teachers felt that minimal additional preparation time was required for videoconferencing and 21/27 preferred it to in-person teaching, most noting the saving in travel time. Only 3 of the teachers were dissatisfied with their ability to communicate, 4 were equivocal and 20 were either pleased or very pleased. The teachers largely enjoyed the experience and performed well in the new medium. However, sound quality proved inadequate in 5/41 links and most sessions included some periods of suboptimal sound. Only 4 teachers were satisfied with their ability to perform question and answer interaction with the audience. We conclude that experienced teachers adapt readily to videoconferencing and learn to communicate effectively very quickly. Teachers were positive about the medium despite its shortcomings and improvements in sound quality would allow a rapid expansion of postgraduate dental education by videoconference.

Attitude of Health Personnel↗
PubMed2001

Levels of pre-kallikrein in resting and stimulated human parotid and submandibular saliva.

Salivary tissue kallikrein is stored in an active form in human salivary glands. Pre-kallikrein has been demonstrated in mixed saliva, but it is not clear if the various salivary glands contribute equally. This study set out to determine if pre-kallikrein is present in human parotid and submandibular salivas at rest, whether levels change during stimulation, and to compare the pattern of pre-kallikrein and kallikrein secretion with that of total protein. Resting and citric acid-stimulated parotid and submandibular, and gum-stimulated parotid saliva samples were collected from 6 healthy subjects. Salivary flows were determined gravimetrically. Total protein concentration and kallikrein enzymic activity were assayed using standard techniques. Pre-kallikrein was assayed following trypsinisation of duplicate samples. Pre-kallikrein was present in parotid and submandibular ductal saliva. Proportions of pre-kallikrein and active kallikrein were similar in salivas secreted at rest and during stimulation, and both outputs mirrored protein output in both major glands. Gum-stimulated parotid saliva showed lower activity than resting, and no differences were seen between resting and stimulated submandibular samples.

Adult↗
PubMed2001

Enzymatic manganese(II) oxidation by a marine alpha-proteobacterium.

A yellow-pigmented marine bacterium, designated strain SD-21, was isolated from surface sediments of San Diego Bay, San Diego, Calif., based on its ability to oxidize soluble Mn(II) to insoluble Mn(III, IV) oxides. 16S rRNA analysis revealed that this organism was most closely related to members of the genus Erythrobacter, aerobic anoxygenic phototrophic bacteria within the alpha-4 subgroup of the Proteobacteria (alpha-4 Proteobacteria). SD-21, however, has a number of distinguishing phenotypic features relative to Erythrobacter species, including the ability to oxidize Mn(II). During the logarithmic phase of growth, this organism produces Mn(II)-oxidizing factors of approximately 250 and 150 kDa that are heat labile and inhibited by both azide and o-phenanthroline, suggesting the involvement of a metalloenzyme. Although the expression of the Mn(II) oxidase was not dependent on the presence of Mn(II), higher overall growth yields were reached in cultures incubated with Mn(II) in the culture medium. In addition, the rate of Mn(II) oxidation appeared to be slower in cultures grown in the light. This is the first report of Mn(II) oxidation within the alpha-4 Proteobacteria as well as the first Mn(II)-oxidizing proteins identified in a marine gram-negative bacterium.

Alphaproteobacteria↗
PubMed2001

cumA multicopper oxidase genes from diverse Mn(II)-oxidizing and non-Mn(II)-oxidizing Pseudomonas strains.

A multicopper oxidase gene, cumA, required for Mn(II) oxidation was recently identified in Pseudomonas putida strain GB-1. In the present study, degenerate primers based on the putative copper-binding regions of the cumA gene product were used to PCR amplify cumA gene sequences from a variety of Pseudomonas strains, including both Mn(II)-oxidizing and non-Mn(II)-oxidizing strains. The presence of highly conserved cumA gene sequences in several apparently non-Mn(II)-oxidizing Pseudomonas strains suggests that this gene may not be expressed, may not be sufficient alone to confer the ability to oxidize Mn(II), or may have an alternative function in these organisms. Phylogenetic analysis of both CumA and 16S rRNA sequences revealed similar topologies between the respective trees, including the presence of several distinct phylogenetic clusters. Overall, our results indicate that both the cumA gene and the capacity to oxidize Mn(II) occur in phylogenetically diverse Pseudomonas strains.

Amino Acid Sequence↗
PubMed2000

Anticoagulant proteins in childhood venous and arterial thrombosis: a review.

Thrombotic disease is less frequent in children than in adults, but may result in severe morbidity and mortality. The coagulation system is balanced to provide rapid activation to stop bleeding and appropriate inhibition to prevent unwanted clot extension. It is regulated by fibrinolysis and by three major anticoagulant pathways: the protein C, antithrombin, and tissue factor pathway inhibitor systems. Acquired or inherited abnormalities of coagulation proteins or hemostatic regulatory mechanisms, particularly when combined with dehydration or the presence of indwelling catheters, may pose a high risk for thrombosis. Thrombosis in a child warrants investigation of potential underlying prothrombotic conditions. These include acquired antiphospholipid antibodies or the lupus anticoagulant as well as abnormalities of the inherited anticoagulant factors including protein C, protein S, antithrombin, and Factor V Leiden. Other abnormalities may result in heightened levels of otherwise normal coagulation proteins such as hyperprothrombinemia due to the prothrombin 20210 mutation. A large survey of children with thrombosis indicated that Factor V Leiden, protein C deficiency, and increased lipoprotein(a) were found most commonly. The most severe predisposition occurs with homozygous protein S or protein C deficiency with resultant purpura fulminans in the newborn. The risk of thrombosis in children with heterozygous deficiencies of anticoagulant proteins is not well defined, although it is clear that combined heterozygotes or a combination of an inherited and an acquired defect heightens the risk for thrombosis. Treatment of thrombosis primarily involves a rapidly acting anticoagulant such as heparin or low-molecular-weight heparin to prevent extension, and long-term anticoagulation with warfarin may be instituted to prevent recurrence. Fibrinolytic therapy is infrequently used because of the risk of serious bleeding complications and is reserved for selected cases of arterial thrombosis to initiate rapid reperfusion of ischemic tissue or used in those patients with a large venous thrombosis and pulmonary emboli causing hemodynamic compromise.

Anticoagulants↗
PubMed2000

Precipitation of specific proteins by freeze-thawing of human saliva.

Frozen saliva samples demonstrate a variable amount of precipitate on thawing depending on the type of secretion [submandibular-sublingual (SML) greater than parotid]. This precipitate has been resuspended using EDTA or removed by centrifugation by some workers and others do not mention it. Yet others collect the salivas into EDTA or centrifuge them before freezing. To determine the adsorption of proteins to hydroxyapatite, prior treatment with EDTA would be disadvantageous. The aim here was to determine if the protein pattern in parotid and SML saliva as demonstrated by sodium dodecyl sulphate gel electrophoresis is affected by the formation of precipitates. Portions of parotid and SML saliva were thawed and treated in the following ways: (a) mixed vigorously with a vortex mixer; (b) centrifuged to remove the precipitate; (c) mixed with EDTA (1 and 5 mmol final concentration for parotid and SML samples, respectively) to resuspend the precipitate. The samples were loaded on to gradient (5-20%) SDS gels and, following electrophoresis, the gels were stained with Coomassie brilliant blue R-250. The protein patterns obtained for (a) and (c) were the same. The centrifuged samples demonstrated loss of a specific band of less than 14 kDa, although this was less obvious in the parotid samples. The SML samples also showed a reduction in other lower molecular-weight proteins. This study demonstrates that precipitates in thawed frozen salivas contain specific proteins and that these samples require careful handling to avoid any alteration in the overall protein composition.

Chemical Precipitation↗
PubMed2000

Race-related differences among patients with left ventricular dysfunction: observations from a biracial angiographic cohort. Harlem-Bassett LP(A) Investigators.

BACKGROUND: This study was designed to describe race-related differences in left ventricular function among a consecutive series of patients undergoing cardiac catheterization and to identify racial differences in coexistent medical and social conditions that are associated with the development of heart failure (HF). METHODS AND RESULTS: This was a prospective cohort study conducted at 2 university-affiliated teaching hospitals. We used the database of the Harlem-Bassett Lp(a) Study. We included all black (N = 143) or white (N = 313) patients from the main study database for whom complete survey, laboratory, coronary angiographic, and ventriculographic data were available. "Left ventricular dysfunction" was arbitrarily defined as an ejection fraction < or =0.40 or prior pharmacologic treatment for HF. We found that blacks were younger, had a higher proportion of women, and had fewer years of formal education than their white counterparts. Coronary artery disease was less common among blacks, although this group had a higher prevalence of hypertension, diabetes, cigarette smoking, illicit drug use, and alcohol consumption. Black patients had a higher prevalence of previous treatment for HF, larger left ventricular volumes, and lower ejection fractions than white patients. Blacks with left ventricular dysfunction were more likely to have had a previous myocardial infarction or a history of hypertension compared with those without left ventricular dysfunction. CONCLUSIONS: Regarding left ventricular dysfunction and HF, we conclude that blacks seem to have a much higher burden of disease than whites. Our observations support prior evidence that hypertension is linked to race-related differences in the epidemiology of HF. The interaction between race and access to quality care for HF remains an important area for future investigation.

Adult↗
PubMed2000

Dissimilatory metal reduction by the facultative anaerobe Pantoea agglomerans SP1.

Anaerobic enrichments with acetate as the electron donor and Fe(III) as the terminal electron acceptor were obtained from sediments of Salt Pond, a coastal marine basin near Woods Hole, Mass. A pure culture of a facultatively anaerobic Fe(III) reducer was isolated, and 16S rRNA analysis demonstrated that this organism was most closely related to Pantoea (formerly Enterobacter) agglomerans, a member of the family Enterobacteriaceae within the gamma subdivision of the Proteobacteria. This organism, designated strain SP1, can grow by coupling the oxidation of acetate or H(2) to the reduction of a variety of electron acceptors, including Fe(III), Mn(IV), Cr(VI), and the humic substance analog 2,6-anthraquinone disulfonate, but not sulfate. To our knowledge, this is the first mesophilic facultative anaerobe reported to couple acetate oxidation to dissimilatory metal reduction.

Acetates↗
PubMed1999

Marine Bacillus spores as catalysts for oxidative precipitation and sorption of metals.

The oxidation of soluble manganese(II) to insoluble Mn(III,IV) oxide precipitates plays an important role in the environment. These Mn oxides are known to oxidize numerous organic and inorganic compounds, scavenge a variety of other metals on their highly charged surfaces, and serve as electron acceptors for anaerobic respiration. Although the oxidation of Mn(II) in most environments is believed to be bacterially-mediated, the underlying mechanisms of catalysis are not well understood. In recent years, however, the application of molecular biological approaches has provided new insights into these mechanisms. Genes involved in Mn oxidation were first identified in our model organism, the marine Bacillus sp. strain SG-1, and subsequently have been identified in two other phylogenetically distinct organisms, Leptothrix discophora and Pseudomonas putida. In all three cases, enzymes related to multicopper oxidases appear to be involved, suggesting that copper may play a universal role in Mn(II) oxidation. In addition to catalyzing an environmentally important process, organisms capable of Mn(II) oxidation are potential candidates for the removal, detoxification, and recovery of metals from the environment. The Mn(II)-oxidizing spores of the marine Bacillus sp. strain SG-1 show particular promise, due to their inherent physically tough nature and unique capacity to bind and oxidatively precipitate metals without having to sustain growth.

Bacillus↗
PubMed1991

Alleviation of acute heat stress by food withdrawal or darkness.

1. Growing 33-d-old broiler fowl were exposed to air temperatures of 35 to 40 degrees C for a period of 4 h each day for 5 d. 2. The birds were fed on diets providing widely differing proportions and intakes of energy as protein, carbohydrate and fat. 3. Three lighting and feeding treatments were superimposed on the 4-h heat stress period. The treatments were: LF (control) lights and food throughout, NL (no light) extinguished throughout the hot period, NF (no food) food withdrawn 2 h before the hot period and replaced immediately after it. 4. Diet had no significant effect on rate of increase of rectal temperature (TR) during heat stress. 5. The NL and NF treatments significantly reduced the rate of increase of TR and the TR attained after 4 h of heat exposure.

Animals↗
PubMed1989

The response of Langerhans cells to palatal cover plates in the rat.

It is not known whether the long-term use of prosthetic or orthodontic appliances, which may be associated with fungal infections, affects Langerhans cells (LC) in the underlying mucosa. The number and distribution of LC was studied in rat palatal epithelium over a 7-day period after insertion of cover plates. Smears of cultures taken before and at the end of the experiment were examined for fungi. LC were identified in cryostat sections using an immuno-alkaline phosphatase technique to demonstrate cell surface Ia (Class II Major Histocompatibility Complex antigens). Occluding the palate predisposed to food trapping and microbial growth. Fungi were recovered from the plates of two animals but not from control or experimental animals before fitting the plates. No differences in LC numbers were found on days 1 and 3 after insertion of the plates, but a significant increase was observed on day 7. It is not known whether this change represents a true increase in LC number or an increase in Ia expression, but it is likely to be the response to an alteration in the number and/or nature of antigens penetrating the mucosa because of microbial growth and food retention.

Animals↗