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Biomedical subjects

R J Lewis

Publications and source records attributed to R J Lewis.

323 records · Page 18Linked to original sources
PubMed1970

Warfarin metabolism in man: identification of metabolites in urine.

After administration of the coumarin anticoagulant racemic warfarin to normal humans, seven fluorescent compounds were chromatographically separated from extracts of their urine. Four of these were identified using mass spectrometry, thin-layer chromatography, and ultraviolet absorption spectroscopy. One metabolic pathway, reduction of the acetonyl side chain of warfarin, resulted in the formation of a second asymmetric carbon atom, and two diastereoisomer alcohols were identified. These warfarin alcohols are structurally similar to pharmacologically active coumarin derivatives. They have not been reported in animal studies. In addition, 6- and 7-hydroxywarfarin were identified. These are the first studies to document the metabolic fate of warfarin in the normal human.

Alcohols↗
PubMedDate not supplied

Statistical concepts and methods for the reader of clinical studies in emergency medicine.

An understanding of statistical concepts and methods is essential for the clinician who wishes to interpret the results of clinical studies. In this article the concepts of descriptive statistics, classical hypothesis testing, P values, a priori information, and Type I and Type II errors are discussed with examples to illustrate their application to the interpretation of clinical trials. In addition, descriptions of Student's t test, the chi-squared test, Fisher's exact test, the rank sum test, and sequential methods are given.

Bias↗
PubMedDate not supplied

Ashman's phenomenon--a source of nonsustained wide-complex tachycardia: case report and discussion.

The refractory period of the right bundle branch is increased when the R-R interval between the prior two conducted impulses is long. Thus, an impulse that arrives soon after the second of two impulses separated by a long R-R interval may be aberrantly conducted with a right bundle branch block morphology on electrocardiogram. This aberrant conduction is termed "Ashman's phenomenon" and is often responsible for isolated wide QRS complexes in the presence of underlying atrial fibrillation. This process may also produce runs of wide QRS complexes that must be distinguished from nonsustained ventricular tachycardia. A case of such multibeat Ashman's phenomena is presented, and the characteristics used to identify this phenomenon are discussed. A brief review of several recent studies on the differentiation of sustained ventricular tachycardia from supraventricular tachycardia with aberrancy in the setting of a regular underlying rhythm is given as well.

Atrial Fibrillation↗
PubMedDate not supplied

Can perforated appendicitis Be diagnosed preoperatively based on admission factors?

The optimal initial treatment for selected patients with perforated appendicitis may be nonoperative. For this reason it is important to be able to diagnose perforated appendicitis preoperatively. The purpose of this study was to determine the accuracy of diagnosing perforated appendicitis using only admission factors. The study population was comprised of 366 adult patients who underwent appendectomy for presumed appendicitis during 1997. Admission factors associated with perforated appendicitis were determined using univariate and multivariate analyses. These variables were then used to formulate a rule for the diagnosis of perforated appendicitis. Sensitivity and specificity were calculated for this rule. The admission factors analyzed were sex, race, age, days of pain, temperature, heart rate, symptoms, physical examination findings, and laboratory findings. Multivariate regression analysis revealed days of pain, temperature, and localized tenderness outside the right lower quadrant to be significant (P <0.05). Using two or more days of pain, a temperature of >/=101 F (38.3 C), or localized tenderness outside the right lower quadrant as criteria to indicate perforation, we achieved a sensitivity of 86% and a specificity of 58% for distinguishing perforated from nonperforated appendicitis. We concluded that (1) perforated appendicitis cannot reliably be distinguished from nonperforated appendicitis based on admission factors, and (2) two or more days of pain, localized tenderness outside the right lower quadrant, and a temperature of >/=101 F (38.3 C) define a group of patients with appendicitis who have a high incidence of perforation.

Adolescent↗
PubMedDate not supplied

Characteristics of participants and nonparticipants in worksite health promotion.

PURPOSE: To identify demographic characteristics associated with worksite health promotion participation and to determine whether employees with high-risk health-related behaviors, as measured by a health risk appraisal, were participating in programs designed to address these behaviors. DESIGN: Descriptive. SETTING: A petrochemical research and development company where employees were offered a health risk appraisal questionnaire, a series of on-site wellness programs, and an on-site fitness center. SUBJECTS: All employees (n = 2290) working continuously from May 1, 1990, through February 28, 1992. MEASURES: Demographic and behavioral risk characteristics of participants and nonparticipants. RESULTS: Participation was 37% (health risk appraisal), 64% (all wellness programs), and 10% (fitness center), with women participating at higher rates than men in all programs. Most programs attracted 10% to 40% of the employees at risk for the particular behavior addressed by the program, although lower penetration (7% to 9%) was observed for the on-site fitness center and blood pressure education programs. With the exception of wellness programs for weight, smoking, and blood pressure, employees at lower behavioral risk tended to be more likely to participate than employees at high risk. CONCLUSIONS: Efforts to increase participation by all company employees, especially among those with high-risk behaviors, would benefit all health promotion programs, particularly the on-site fitness center.

Adult↗
PubMedDate not supplied

Ciguatera in Australia. Occurrence, clinical features, pathophysiology and management.

Ciguatera is a type of food poisoning that results from eating certain tropical fish which have become toxic. It is common in Australia: 175 outbreaks, which involved 527 people, were reported in Queensland between 1965 and 1984. It seems restricted to certain areas around the Australian coastline. Most reports have involved the narrow-barred Spanish mackerel, Scomberomorus commersoni, most of which were caught in southern Queensland waters. Up to 2100 cases may have occurred in north Queensland between 1965 and 1984, which were not recorded by the writers. The symptoms of ciguatera in Australia are similar to those reported elsewhere in the South Pacific. Ciguatoxin acts by increasing the permeability of excitable membranes to sodium ions. This type of membrane is found throughout the body in nerve tissue as well as in heart and skeletal muscle. The treatment of ciguatera remains symptomatic and supportive only. Major advances in treatment for ciguatera and detection of ciguatoxin await the means of producing additional ciguatoxin.

Animals↗
PubMedDate not supplied

Osteochondroma of the cervical spine. Case report.

Only 1 well-documented case of osteochondroma in the posterior elements of the cervical spine has been previously reported. Although unusual, osteochondroma should be considered in the differential diagnosis of benign appearing tumors in the cervical spine.

Cervical Vertebrae↗
PubMedDate not supplied

Drugs from the peptide venoms of marine cone shells.

Australian cone shell venoms are being investigated as an exciting new source of bioactive peptides as part of a new collaborative project between the 3D Centre and AMRAD. Initial studies have already revealed a number of new and novel acting peptides amongst the hundred or so small, heavily constrained peptides present in the venom of each cone shell. The aim of the project is to develop peptidomimetic drugs based on a selection of these native peptides.

Amino Acid Sequence↗
PubMedDate not supplied

Does VATS favor seeding of carcinoma of the lung more than a conventional operation?

Seeding of carcinoma has always been of concern to surgeons. Recent reports have focused on possible implantation of tumor in the small wounds of minimally invasive procedures, i.e. VATS. A patient is presented who had a conventional open lobectomy for carcinoma and later developed tumor in the traditional thoracotomy wound. Although seeding or tumor implantation is accepted by thoracic surgeons, the exact mechanism of tumor implantation has never been scientifically explained or documented. Possibly, a rare and necessary pattern of genetic mutations could be responsible for this infrequent but serious problem.

Adenocarcinoma↗