PubMed Health⌕ Search

Biomedical subjects

B Ellis

Publications and source records attributed to B Ellis.

At least 73 records · Page 4Linked to original sources
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↗
PubMed1985

Purification of a uridine-specific acid nuclease from chicken liver by fast protein liquid chromatography.

A rapid purification procedure for a novel uridine-specific nuclease from chicken liver based on the Pharmacia fast protein liquid chromatography (FPLC) system is presented. The purification was achieved by applying crude extract to a Mono S cation-exchange column equilibrated with 10 mM potassium phosphate buffer (pH 6.0). The enzyme was eluted in 20 min with a potassium chloride gradient at a flow-rate of 2 ml/min. The enzyme was then chromatographed on a Superose 12 size-exclusion column in less than 1 h at a flow-rate of 0.5 ml/min (Kav = 0.77). The enzyme was re-chromatographed on a second Mono S column to concentrate the protein. The uridine-specific nuclease hydrolyzed poly(U) and Escherichia coli 5S RNA. Poly(A) was hydrolyzed by the nuclease less efficiently (about 10% of the poly(U) activity). No hydrolysis was detected with poly(C), poly(G), poly(dT) or poly(dA) as substrate. The speed with which each purification step could be carried out facilitated the determination of optimal chromatographic conditions. We found that the resolution of the Mono S and Superose 12 columns was superior to that of conventional ion exchangers and size-exclusion columns respectively.

Animals↗
PubMed1985

The fracture topography of acrylic dentures broken in service.

The fracture surfaces of full dentures that failed in service, and others broken under controlled conditions, have been examined using scanning electron microscopy. The results allow the direction of crack propagation to be deduced and indicate that brittle impact is the predominant mode of fracture. Improvements in the strength of the denture tooth/denture base bond may be the most effective means of achieving an increase in the strength of full dentures.

Acrylic Resins↗
PubMed1985

Choristoma of the breast.

A well-circumscribed breast mass composed of well-organized breast parenchymal elements, dense fibrous tissue, mature hyaline cartilage, fat, and smooth muscle is described, and the pertinent literature is reviewed. This lesion is considered to be a choristoma.

Adult↗
PubMed1984

The use of standardized neonatal mortality ratios to assess the quality of perinatal care in Colorado.

Neonatal mortality in Colorado in the 3-year period 1977-1979 has been analyzed by means of standardized neonatal mortality ratios derived from birth weight-specific mortality for every obstetric facility. The standardized neonatal mortality ratios adjusted for the percentage of neonatal deaths due to untreatable disorders are presented as one possible method for comparing the neonatal outcome in obstetric populations of dissimilar risk. We have suggested that facilities with adjusted standardized neonatal mortality ratios significantly above 1 are those that might benefit from an in-depth review of perinatal services.

Birth Weight↗
PubMed1981

Physicians pivotal to successful cost containment efforts.

Medical staffs are involved in a variety of activities to lower health care costs in their institutions and communities. The various mechanisms for medical staff participation in and accountability for cost-effective management of hospital resources are explored in the following report on the National Symposium on the Role of the Medical Staff in Controlling Costs.

Cost Control↗