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Biomedical subjects

B Ellis

Publications and source records attributed to B Ellis.

At least 19 recordsLinked to original sources
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↗
PubMed1986

The separation of o-phthalaldehyde derivatives of amino acids by reversed-phase chromatography on octylsilica columns.

Amino acids were reacted with o-phthalaldehyde and 2-mercaptoethanol and were separated using a simple linear gradient from 10 to 65% methanol over 15 min on an octyl silica (C8) column by reversed-phase chromatography. The separation obtained was found to be sensitive to the pH, ionic strength, and tetrahydrofuran concentration of aqueous solvent A [THF: sodium acetate (45 mM), pH 5.7, (4:96)]. These effects were characterized and used to design a rapid (17 min) separation of the amino acids commonly found in acid hydrolysates of proteins. A more involved procedure was used to separate the more complex mixture of amino acids that are found in enzymatic hydrolysates of proteins or in physiological fluids. The simplicity of the methods allows their use on different chromatographic systems with little or no alteration.

Amino Acids↗
PubMed1979

Energy situation is precarious.

Given the uncertain future that lies ahead for meeting the nation's energy needs, many hospitals are assuming a posture of vigilance and preparedness. If they are not, they should be, experts say.

Conservation of Energy Resources↗
PubMed1979

AHA looks at nurse credentialing.

AHA's National Conference on Categories or Nursing Practice explores the weaknesses and strengths of the credentialing system and the ramifications of proposed changes.

Accreditation↗
PubMed1979

Speak up for children!

During 1979, the International Year of the Child, the United Nations General Assembly has asked its member nations to examine and improve their services for children.

Accident Prevention↗