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Biomedical subjects

B Ellis

Publications and source records attributed to B Ellis.

At least 55 records · Page 3Linked to original sources
PubMed1994

Mechanism of electrical enhancement of efficacy of antibiotics in killing biofilm bacteria.

The bioelectric effect, in which electric fields are used to enhance the efficacy of biocides and antibiotics in killing biofilm bacteria, has been shown to reduce the very high concentrations of these antibacterial agents needed to kill biofilm bacteria to levels very close to those needed to kill planktonic (floating) bacteria of the same species. In this report, we show that biofilm bacteria are readily killed by an antibiotic on all areas of the active electrodes and on the surfaces of conductive elements that lie within the electric field but do not themselves function as electrodes. Considerations of electrode geometry indicate that very low (< 100 microA/cm2) current densities may be effective in this electrical enhancement of antibiotic efficacy against biofilm bacteria, and flow experiments indicate that this bioelectric effect does not appear to depend entirely on the possible local electrochemical generation of antibacterial molecules or ions. These data are expected to facilitate the use of the bioelectric effect in the prevention and treatment of device-related bacterial infections that are caused by bacteria that grow in biofilms and thereby frustrate antibiotic chemotherapy.

Anti-Bacterial Agents↗
PubMed1994

Testing antimicrobial susceptibilities of adherent bacteria by a method that incorporates guidelines of the National Committee for Clinical Laboratory Standards.

Membrane filters (0.22-microns pore size) were colonized with 10(4) CFU of logarithmic-phase bacteria per filter under laminar flow conditions in a Modified Robbins Device. Colonized filters were then placed upon agar dilution plates for MIC determinations. Subsequently, filters were transferred to control plates and incubated to obtain MBCs.

Bacterial Adhesion↗
PubMed1994

Physicians' perspectives of HMOs and marketing: implications and recommendations.

The authors compare physicians in HMOs and those not in HMOs in order to determine how HMOs have affected their practices. Physicians in HMOs see more patients per day, but receive less income per patient than physicians not in HMOs; however, both groups of physicians agree that HMOs have not changed marketing practices. In fact, both groups report uncertainty as to the best way to market their practice, and in their understanding of marketing. The physicians do agree that patient referrals are the most important means of patient acquisition; however, both groups report a surprisingly low use of patient questionnaires. Implications and recommendations for HMOs, physicians, and health care marketing researchers are discussed.

Attitude of Health Personnel↗
PubMed1993

Purification and characterization of sinapine synthase from seeds of Brassica napus.

1-O-Sinapoylglucose:choline sinapoyltransferase ("sinapine synthase") has been purified from immature seeds of Brassica napus by sequential hydroxylapatite absorption, ion-exchange chromatography, and gel filtration. The purified enzyme has an apparent molecular weight of 65 kDa on gel filtration and a subunit structure on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 28 kDa. Sinapine synthase has Km values in the high micromolar range for both substrates (1-O-sinapoylglucose and choline chloride) but these values are sensitive to the concentration of the second substrate. The enzyme displays a marked substrate specificity for 1-O-sinapoylglucose among other related glucose esters. No requirements for thiol protectants or divalent cations were found, but sinapine synthase activity is inhibited by Cu2+ and Hg2+ ions. Partial amino acid sequence data have been obtained from a tryptic digest of the 28-kDa polypeptide.

Acyltransferases↗
PubMed1993

Changing competition in health care marketing: a method for analysis and strategic planning.

As the cost and importance of healthcare continue to increase, competition in the medical industry is taking new forms and becoming more intense. The driving trends behind this competition are analyzed in the framework of Porter's Five Forces of Competition Model. The authors then discuss how the widely accepted strategies of cost, differentiation, focus, and domestication can be utilized to counter the implications of these trends and how to capitalize on opportunities in medical practice in the 1990's.

Consumer Behavior↗
PubMed1992

Cellular variability in the development of tight junctions after activation of protein kinase C.

Phorbol 12-myristate 13-acetate (PMA) decreases the tight junction conductance (TJC) during the reorganization of LLC-PK1A monolayers, but has the opposite effect in LLC-PK1B4, MDCK, and MDCK4 cells. Because no protein synthesis was required for the effects of PMA on the TJC of LLC-PK1A monolayers, we conclude that the regulation of the tight junction by protein kinase C (PKC) is a posttranslational event. In LLC-PK1A monolayers with existing tight junctions, PMA produced an initial increase in the TJC that reverted later to control values despite the continuous presence of PMA and cycloheximide. The inhibitory effect of PMA on the other cell lines was not revertible. A downregulation of total PKC activity and phorbol ester receptors was only observed during the reorganization of LLC-PK1A monolayers. PMA further increases this downregulation. This indicates that the peculiar response to PMA observed in LLC-PK1A monolayers is the result of two concurrent events: 1) the early activation of the enzyme just before the reorganization of the tight junctions begin, and 2) its late downregulation induced after prolonged exposure to phorbol esters. We conclude that PKC regulates the development of the occluding junctions, but through different mechanisms dependent on the characteristics of the cells.

Animals↗
PubMed1991

Biofilm and scleral buckle-associated infections. A mechanism for persistence.

Scleral buckle infections tend to be persistent as well as resistant to antimicrobial treatment. Often, scleral buckle infections require removal of the buckling elements for resolution. To determine if bacteria are able to persist on scleral buckles by elaborating a glycocalyx matrix or biofilm that offers protection against host defenses and antimicrobial treatment, the authors cultured 28 scleral buckle elements removed for infection and extrusion. Bacteria were isolated from 18 elements (64%). The most frequently isolated bacteria were Staphylococcus epidermidis and other coagulase-negative staphylococci (8), Staphylococcus aureus (3), corynebacteria (3), Mycobacterium chelonei (3), and Proteus mirabilis (3). Eleven (65%) of 17 buckles evaluated with scanning electron microscopy demonstrated the presence of bacteria encased in biofilm. Biofilm was demonstrated on the surfaces and ends of solid silicon elements. In the silicon sponges, biofilm also extended into the matrix of the sponges. The authors believe that bacterial production of biofilm offers an explanation for the persistence of scleral buckle infections and their ability to withstand antimicrobial treatment.

Adult↗
PubMed1991

Idiotypic characterisation of monoclonal antibodies with restricted epitope specificity for retinal S-antigen.

This paper describes the idiotypic specificities of eight murine monoclonal antibodies directed to three independent epitopes on retinal S-antigen. The antigenic sites recognised by these monoclonal antibodies have previously been localised to a small region near the C-terminal of bovine S-antigen. Xenogeneic, site-related anti-idiotypes prepared against each of the monoclonal antibodies recognised common idiotypes only amongst those monoclonal antibodies which reacted with the same epitope on S-antigen. Two of the three idiotypes were detected in the sera of BALB/c mice but not in two strains of rat immunised with xenogeneic S-antigen and none could be detected in the sera of patients with anti-photoreceptor autoantibodies. Our results demonstrate that the idiotypes of murine monoclonal antibodies to retinal S-antigen exhibit restricted epitope specificity but are species-restricted and imply that the S-antigen lacks a dominant antigenic epitope.

Antibodies, Monoclonal↗
PubMed1990

Fluoride penetration into dentine abutments in vitro.

The diffusion of fluoride ions from various concentrations of sodium fluoride solution into the dentine of decoronated human canine teeth, prepared as for reception of overdentures, was studied in vitro. The decoronated preparations were immersed for 7 days in 2.0, 1.5, 1.0, 0.5 and 0.05% solutions of neutral-pH sodium fluoride and then fluoride penetration into the prepared transverse face of the dentine was assessed by electron microprobe. Only with high concentrations of fluoride (2.0%) was there significant penetration. In peritubular dentine, fluoride penetration could be measured to a depth of 400 microns, but in intertubular dentine penetration did not take place beyond 100 microns. These findings call into question the efficacy of patient-administered caries prophylaxis with low-concentration fluoride treatments in overdenture cases.

Cuspid↗
PubMed1989

The rheology of silicone rubber impression materials.

A selection of silicone rubber impression materials were studied for their rheological properties prior to and following mixing. The techniques used were a cone and plate viscometer and a capillary viscometer. All the impression materials were found to show pseudoplastic behaviour which is readily described by a power law function. For the mixed materials the onset of molecular entanglement, whilst theoretically establishing the absolute end of the working time, gave a gross overestimate of the clinical working time. The capillary viscometer is more useful than the cone and plate viscometer in providing information on the clinical working time.

Chemical Phenomena↗
PubMed1988

Mild asymptomatic primary hyperparathyroidism is not a risk factor for vertebral fractures.

STUDY OBJECTIVE: To determine the prevalence of vertebral fractures in patients with mild asymptomatic primary hyperparathyroidism and to ascertain whether this prevalence is increased in comparison with the rate in a retrospective control group previously studied at the same institution or with current estimates of the risk for vertebral fractures in subjects of similar age. DESIGN: Prospectively collected data were retrospectively analyzed and compared with data from a historical control group at the same institution and with published data. SETTING: The outpatient department of a bone and mineral metabolism clinic. PATIENTS: A consecutive series of patients with mild asymptomatic primary hyperparathyroidism diagnosed between 1 January 1976 and 31 December 1985. Criteria for inclusion in the study were the absence of symptoms due to hyperparathyroidism, no current kidney stone disease, no radiographic evidence of osteitis fibrosa, a serum calcium level of less than 3.00 mmol/L, a serum creatinine level of less than 133 mumol/L, and a forearm bone density value not more than 2.5 standard deviations below the age-, sex-, and race-adjusted normal value. INTERVENTIONS: A conservative nonintervention study. MEASUREMENTS AND MAIN RESULTS: The prevalence of vertebral fractures in 174 patients (mean age, 62 years) with mild asymptomatic primary hyperparathyroidism was 1.7%; in a subset of white women, the prevalence was 2.8%. These rates were not higher than those expected, by comparison with the rate in a retrospective control group or with the risk for vertebral fractures in subjects of similar age, and may even be lower. CONCLUSIONS: The risk for vertebral fractures is not increased in patients with mild asymptomatic primary hyperparathyroidism and is not a reason to recommend surgical intervention in asymptomatic patients. The increased rates of vertebral fractures that occurred in other series are probably due to the use of inappropriate controls and the influence of referral or selection bias, the inclusion of patients with severer disease, and the effect of geographic differences in vitamin D nutrition on the expression of disease. Possible differences between lateral spine and lateral chest radiographs for determining vertebral body shape need further study.

Aged↗
PubMed1988

Upper extremity exercise training in chronic obstructive pulmonary disease.

Many patients with chronic obstructive pulmonary disease (COPD) report greater limitation for activities involving the upper extremities than the lower extremities. Exercise training has generally emphasized lower-extremity exercise. We designed and evaluated two simple, practical, and widely applicable upper-extremity training programs in 45 patients with COPD participating concurrently in a comprehensive, multidisciplinary pulmonary rehabilitation program. Patients were randomly assigned to one of the following three groups: (1) gravity-resistance (GR) upper-extremity training; (2) modified proprioceptive neuromuscular facilitation (PNF) upper-extremity training; or (3) no upper-extremity training (control). Patients were evaluated before and after at least six weeks of uninterrupted training. Twenty-eight patients completed the study. Compared to controls, both GR and PNF patients demonstrated improved performance on tests specific to the training performed (upper-extremity performance test, maximal level and endurance on isokinetic arm cycle). There were no significant changes on isotonic arm cycle, ventilatory muscle endurance, or simulated activities of daily-living tests. Ratings of perceived breathlessness and fatigue decreased significantly in all groups for several tests. We conclude that specific upper-extremity training may be beneficial in the rehabilitation of patients with COPD and warrants further investigation.

Activities of Daily Living↗