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Biomedical subjects

S D Roberts

Publications and source records attributed to S D Roberts.

At least 19 recordsLinked to original sources
PubMed2000

Ventricular arrhythmias.

Sudden cardiac death remains a leading cause of death in the United States. It is usually due to ventricular arrhythmia, either ventricular tachycardia or ventricular fibrillation. The probability of life threatening ventricular arrhythmia correlates closely with underlying structural heart disease. In any patient presenting with a ventricular arrhythmia, a careful search for underlying causes is required, and treatment should be considered primarily if it will prolong survival. Treatment of patients without underlying heart disease who are experiencing ventricular ectopy, and/or nonsustained ventricular tachycardia, consists of reassurance and education. If symptoms are severe, a beta-blocker is an appropriate choice for drug treatment. Patients with ventricular arrhythmia and structural heart disease are generally best managed in conjunction with a cardiologist.

Adolescent↗
PubMed1999

How to resolve stool retention in a child. Underwear soiling is not a behavior problem.

Many parents do not realize their child has stool retention when they bring him or her for an office visit. Some complaints that may be a tip-off and should prompt questioning about stool frequency and underwear soiling are vague abdominal pain, urinary incontinence, and stools so large they plug the toilet. A rectal examination is usually adequate to confirm the diagnosis. Management begins with educating parents that leaking of liquid stool around impaction and onto underwear is completely involuntary, so the child should never be scolded or embarrassed. Stool retention may begin because of unpleasant or unavailable toilet facilities, constipation, or painful elimination and often becomes self-perpetuating. Impaction must be removed immediately; magnesium citrate solution is usually effective. To allow the rectum to return to its normal size, which can take an extended time, stool must be kept soft and movable with administration of mineral oil and appropriate dietary choices (eg, fruit, juice, fiber). Recurrence is common, so ongoing measures and follow-up are important.

Cathartics↗
PubMed1992

The effect of age and acetylator phenotype on the pharmacokinetics of sulfasalazine in patients with rheumatoid arthritis.

The pharmacokinetic disposition of sulfasalazine and its metabolites was studied in 8 young and 12 elderly patients with active rheumatoid arthritis. Equal numbers of slow and fast acetylators were included in each age group. Patients received enteric-coated sulfasalazine 2g daily for 21 days; specimens of serum and urine were collected for 96 h after administration on days 1 and 21. The elimination half-life of sulfasalazine was greater in the elderly patients. Many disposition parameters of sulfapyridine differed in slow and fast acetylators; of greatest significance were the increased values of steady-state serum concentration in the slow acetylators. There was no effect of age on any sulfapyridine disposition parameters. Values for the steady-state serum concentrations of N-acetyl-5-acetylsalicylic acid were greater in elderly than in young patients. The metabolism of sulfapyridine was markedly affected by acetylator phenotype and this was reflected in the composition of sulfapyridine-related material in the urine. Thus, age is a determinant of the steady-state concentrations of salicylate moieties but acetylator phenotype plays a greater role in determining the serum concentration of sulfapyridine, which has greater therapeutic implications in rheumatology.

Acetylation↗
PubMed1991

Immunoglobulin isotype composition of circulating and intra-articular immune complexes in patients with inflammatory joint disease.

The immunoglobulin (Ig) heavy chain isotype composition of intra-articular and circulating immune complexes (ICs) were determined by a Raji cell flow cytometric assay in paired serum and synovial fluid samples from 15 patients with rheumatoid arthritis (RA) and 15 patients with other articular diseases (osteoarthritis, ankylosing spondylitis, gout, psoriatic arthritis, Reiter's disease). ICs were most prevalent in synovial fluid samples of patients with RA but were infrequently detected in serum and synovial fluid samples from the non-RA patients. ICs in patients with RA were heterogeneous both in the prevalence of Ig subclasses identified and in the distribution of the respective Ig isotypes within the complexes. Furthermore, differences were observed in the Ig isotype composition of ICs in paired serum and synovial fluid samples indicating that circulating ICs may not always arise simply by spill-over from articular sites. The possible mechanisms for IC formation in RA are discussed with reference to four patients who displayed features of extra-articular disease.

Adult↗
PubMed1989

Quantifying uncertainty in medical decisions.

Effective handling of uncertainty is one of the central problems in medical decision making. The sources and effects of uncertainty in medical decision making are examined and some new quantitative approaches for solving the associated problems are outlined. To handle uncertainty in the branching probabilities and node utilities for probability trees representing alternative treatment strategies, a public domain software package that can be used for the construction, analysis and comparison of probability trees with random parameters was developed. To facilitate specification of the random variables that arise in medical decision making problems, public domain software packages for both data-driven and subjective estimation of probability densities from the Johnson translation system of distributions have also been developed. For the analysis of complex problems that cannot be adequately represented by probability trees or by simple stochastic processes such as Markov chains, network simulation approaches that are oriented toward the sequence of activities seen by individual patients in the course of treatment are described.

Computer Simulation↗
PubMed1988

Reduction of monocyte 5'nucleotidase activity by gamma-interferon in multiple sclerosis and autoimmune diseases.

Ecto-5'nucleotidase (5'NT) activity in the plasma membrane of peripheral blood monocytes from patients with multiple sclerosis (MS), rheumatoid arthritis (RA), myasthenia gravis (MG), motor neuron disease (MND), and from normal control subjects of similar age was determined by radioisotopic assay. The activity in unstimulated monocytes cultured for 24 and 48 hours was found to be higher than normal in 56% of patients with active relapsing MS, 29% of patients with RA, and 7% of patients in the MG/MND group. While the enzyme activity was reduced after cultivation of the cells with recombinant interferon-gamma (gamma-IFN) in all of the groups studied, the percentage reduction was significantly greater in monocytes from patients with active relapsing MS who were in relapse at the time of sampling (p = 0.03). HLA-DR expression was monitored using immunofluorescence staining with monoclonal antibody and showed that similar numbers of monocytes in all patient and control groups expressed this antigen. Thus, while high monocyte 5'NT activity was found principally in patients with active relapsing MS and in some patients with RA, the monocytes from patients with MS were, in addition, exquisitely sensitive to stimulation with gamma-IFN.

5'-Nucleotidase↗
PubMed1988

Sunbed-induced melanoma in a rheumatoid patient.

The development in a rheumatoid patient of a cutaneous malignant melanoma following repeated exposure to UV-A Radiation from a sunbed for its supposed therapeutic effect, is described. A causal-effect relationship is proposed and the potential risks to other arthritic patients and in particular those with pigmented skin lesions, is highlighted.

Arthritis, Rheumatoid↗
PubMed1988

Cost-effective management of patients following myocardial infarction: the impact of ischemia on alternative approaches.

Following uncomplicated myocardial infarction patients are at varying risk for cardiovascular morbidity and mortality. In order to identify and treat high risk patients, various management approaches can be employed. We performed a decision analysis to examine the cost-effectiveness of seven alternative strategies under the assumption that prognosis is affected by both the location of anatomic obstruction and the degree of myocardial ischemia. Strategies included combinations of angiography and two theoretical diagnostic tests capable of detecting ischemia with different degrees of accuracy. The strategy associated with the lowest overall six month mortality initiated testing with the diagnostic test most sensitive for ischemia, slightly better than proceeding initially to angiography. Initial use of a test sensitive for ischemia was also considerably more cost-effective than proceeding directly to angiography. Future analyses evaluating the role of diagnostic tests in coronary artery disease should incorporate the dimension of ischemia.

Coronary Disease↗
PubMed1988

Detection of circulating immune complexes by Raji cell assay: comparison of flow cytometric and radiometric methods.

Several flow cytometric methods for the measurement of circulating immune complexes (CIC) have recently become available. We report a Raji cell flow cytometric assay (FCMA) that uses aggregated human globulin (AHG) as primary calibrator. Technical advantages of the Raji cell flow cytometric assay are discussed, and its clinical usefulness is evaluated in a method comparison study with the widely used Raji cell immunoradiometric assay. FCMA is more precise and has greater analytic sensitivity for AHG. Diagnostic sensitivity by the flow cytometric method is superior in systemic lupus erythematosus (SLE), rheumatoid arthritis, and vasculitis patients: however, diagnostic specificity is similar for both assays, but the reference interval of FCMA is narrower. Significant correlations were found between CIC levels obtained with both methods in SLE, rheumatoid arthritis, and vasculitis patients and in longitudinal studies of two patients with cerebral SLE. The Raji cell FCMA is recommended for measurement of CIC levels to clinical laboratories with access to a flow cytometer.

Antigen-Antibody Complex↗
PubMed1987

Viral antibody titers. Comparison in patients with multiple sclerosis and rheumatoid arthritis.

Higher titers of antibodies to measles virus envelope antigens, hemolysin and hemagglutinin, Epstein-Barr virus (EBV) capsid antigen and nuclear antigen, and rubella virus hemagglutinin were demonstrated in serum samples of patients with multiple sclerosis and rheumatoid arthritis than in age- and sex-matched control subjects. A significant correlation was observed between antibodies to measles and rubella viruses both in patients with multiple sclerosis and rheumatoid arthritis, but such a correlation was not observed between antibodies to EBV and measles or rubella viruses. Whether elevated levels of antibodies to EBV are due to reactivation of the virus, or elevated levels of antibodies to all the enveloped viruses result from cross-reactions between viruses and host tissue, or perhaps reflect defects in immunoregulation, needs further investigation.

Adult↗