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Biomedical subjects

L J White

Publications and source records attributed to L J White.

At least 55 records · Page 3Linked to original sources
PubMed1995

Refractive changes at extreme altitude after radial keratotomy.

PURPOSE: We studied the effects of altitude on four corneas that had undergone radial keratotomy and four normal corneas exposed to increasing elevation during a high-altitude excursion. METHODS: We measured visual acuity, cycloplegic refraction, keratometry, and intraocular pressure at sea level and after 24-hour exposure to 12,000 and 17,000 ft. RESULTS: We observed a significant increase in spherical equivalence (hyperopic shift) in radial keratotomy eyes exposed to altitude as compared to controls (P < .0001). The average change in spherical equivalent cycloplegic refraction from sea level to 12,000 ft was 1.03 +/- 0.16 diopters and from sea level to 17,000 ft was 1.94 +/- 0.26 diopters. We also observed a significant decrease in keratometry values at altitude as compared with control corneas (P < .0001). The average change in keratometry from sea level to 12,000 ft was 0.59 +/- 0.19 diopter and from sea level to 17,000 ft was 1.75 +/- 0.27 diopters. CONCLUSIONS: Although the specific origin of these changes is open to question, we hypothesize that hypoxic corneal expansion in the area of the radial keratotomy incisions may lead to central corneal flattening and a hyperopic shift in refractive error. The cornea that has undergone radial keratotomy appears to adjust constantly to changing environmental oxygen concentration, producing a new refractive error over a period of 24 hours or more. Additional study is required to identify with certainty the specific origin of the hyperopic shift at high altitude.

Adult↗
PubMed1995

Specific proteolytic cleavage of recombinant Norwalk virus capsid protein.

Norwalk virus (NV) causes epidemic outbreaks of acute nonbacterial gastroenteritis in humans. The NV capsid is made up of a single protein, and expression of the capsid protein in baculovirus recombinants results in spontaneous assembly of the protein into virus-like particles (X. Jiang, M. Wang, D. Y. Graham, and M. K. Estes, J. Virol. 66:6527-6532, 1992). We have investigated whether the NV capsid protein undergoes a specific proteolytic cleavage. Recombinant NV (rNV) particles were digested with trypsin to determine if a specific cleavage occurred. A predominant band with a molecular weight of approximately 32,000 (32K protein) was observed when trypsin-treated rNV was electrophoresed on sodium dodecyl sulfate-polyacrylamide gels. Determination of the N-terminal sequence of this band showed that a trypsin-specific cleavage occurred at amino acid residue 227. Early studies identified two proteins with molecular weights of 59,000 and 30,000 (59K and 30K proteins) in the stool of NV-infected volunteers that were reactive with postinfection antiserum. (H. B. Greenberg, J. R. Valdesuso, A. R. Kalica, R. G. Wyatt, V. J. McAuliffe, A. Z. Kapikian, and R. M. Chanock, J. Virol. 37:994-999, 1981). We hypothesized that the 32K rNV cleavage product might be analogous to the 30K soluble protein detected in stools of NV-infected volunteers. Immunoprecipitation of soluble protein from these stool extracts with a rabbit polyclonal antiserum made against rNV, and Western blot detection with a mouse polyclonal antiserum made against rNV, revealed a single band with an apparent molecular weight of 30,000 that migrated similarly to the trypsin cleavage product observed in vitro. The N terminus of this band was identical to that of the 32K cleavage product of rNV capsid protein. These data show that the 30K protein in stool is produced by specific cleavage of the NV capsid protein in vivo. Trypsin cleavage of isolated soluble rNV 58K capsid protein and of assembled particles showed that only soluble 58K capsid protein is susceptible to cleavage. The presence of a large amount of soluble capsid protein may influence the immune response to or pathogenicity of NV infections.

Amino Acid Sequence↗
PubMed1993

The clinical efficacy assessment program of the American College of Physicians.

The experience of the American College of Physicians (ACP) in evaluating the clinical literature and publishing clinical guidelines spans more than a decade. The ACP uses an evidence-based method for the development of clinical practice guidelines for diagnostic technologies and treatments. The approach of the Clinical Efficacy Assessment Program (CEAP) involves collation, methodologic review, and analysis of the clinical literature. The process focuses on the safety, contraindications, efficacy, limitations, and cost of diagnostic technologies or treatments. To ensure a balanced perspective of the evidence, methodologic and content experts cooperate to prepare a summary paper. Strengths of this evidence-based approach include: (1) focus on the needs of practicing internists; (2) identification of all pertinent clinical literature; (3) integration of expert opinion when literature is inadequate; (4) recommendations based on high-quality scientific evidence; (5) preparation of conservative guidelines when evidence is lacking; and (6) reevaluation of past guidelines as new evidence becomes available. Limitations of the process include: (1) access only to published research; (2) use of criteria for scientific quality that are not standardized across projects; (3) published recommendations based on small numbers of high-quality research products; (4) compromise with expert opinion when evidence is limited; and (5) ad hoc management of conflict between experts when scientific evidence is sparse. The process produces credible recommendations that may improve physician knowledge and acceptance of practice guidelines.

Clinical Medicine↗
PubMed1993

Pharmaceutical representatives and emergency medicine residents: a national survey.

STUDY OBJECTIVES: To determine the extent and diversity of involvement of pharmaceutical representatives in emergency medicine residency programs and to assess chief residents' beliefs and attitudes concerning this activity. DESIGN AND PARTICIPANTS: A multi-item survey with cover letter was mailed to the chief resident at each of the 87 Accreditation Council on Graduate Medical Education-approved emergency medicine residency programs in the United States at the time of study conception. MEASUREMENTS AND MAIN RESULTS: Eighty-three percent (72 of 87) of the questionnaires were returned. Ninety-three percent (66 of 71) of responders reported the involvement of pharmaceutical representatives in their emergency medicine residency. The most frequent activities (90%, 63 of 70) were to distribute small gifts (pens, notepads) and to provide meals during department functions such as journal clubs (80%, 56 of 70). Only 32 of 70 responding chief residents (46%) were aware of any established guidelines in their institution or residency program concerning relationships with pharmaceutical representatives, and 14 respondents (20%) believed that accepting gifts from pharmaceutical companies could affect their own prescribing habits. A few stated that pharmaceutical representative-sponsored educational functions were inappropriate. CONCLUSION: The interaction of pharmaceutical representatives with emergency medicine residents and residencies is widespread. More than 50% of the institutions supporting emergency medicine residency programs have no formal guidelines with regard to the interaction of their residents with pharmaceutical representatives or their guidelines are not known to the person most responsible for approval and arrangement of the pharmaceutical representative interaction--the emergency medicine chief resident. While most chief residents believed that accepting small gifts was reasonable, they also believed that accepting gifts valued at $100 or more and pharmaceutical representative sponsorship of trips was inappropriate.

Drug Industry↗
PubMed1993

Oral agents in the management of urticaria: patient perception of effectiveness and level of satisfaction with treatment.

OBJECTIVE: Orally administered diphenhydramine, famotidine, and cromolyn sodium were compared for their abilities to alleviate symptoms of acute urticaria. DESIGN AND SETTING: This was a prospective, randomized, blind study, implemented in the emergency departments (EDs) of two teaching hospitals, each with an annual average of 40,000 ED patient visits. Patient perception of the effectiveness of treatment was assessed using a visual analog scale. PATIENTS: 33 adult patients presenting to the EDs were entered into the study over a one-year period. Of these, 8 were lost to follow-up and 5 were noncompliant with medications and not included in data analysis. Twenty adult patients, aged 19-78 years, completed the five-day study: 7 received diphenhydramine, 6 received famotidine, and 7 received cromolyn sodium. RESULTS: Patients receiving diphenhydramine reported the greatest satisfaction with treatment: 86 percent (6/7) indicated they would use the medication again. Fifty percent (3/6) in the famotidine group and 43 percent (3/7) in the cromolyn sodium group rated the treatment as worth using again. Patients receiving famotidine reported the greatest occurrence of adverse effects (50 percent, 3/6); the lowest incidence of such effects was seen in the cromolyn sodium group (14 percent, 1/7). Patients receiving diphenhydramine reported adverse effects at a rate of 43 percent (3/7). CONCLUSIONS: Our results suggest that patients receiving diphenhydramine are more satisfied with their treatment than are patients receiving famotidine or cromolyn sodium.

Adult↗
PubMed1993

Differential binding of acapsulate and encapsulated strains of Cryptococcus neoformans to human neutrophils.

Investigations into mechanisms of binding of encapsulated and acapsulate strains of Cryptococcus neoformans by human neutrophils were performed, using a monolayer assay. The two strains bound to neutrophils by different mechanisms although both had an absolute requirement for opsonization with complement components in normal human serum for binding to occur. Neutrophil binding of encapsulated yeasts required conformational changes in actin yet did not appear to lead to phagocytosis of the organism. A maximum of 12 acapsulate cells bound per neutrophil compared with only four encapsulated yeasts. Cytochalasin D treatment reduced the maximum numbers able to bind per neutrophil by 50%. The encapsulated cryptococci appeared to compete with each other for binding to neutrophils whereas the acapsulate yeast cells bound to neutrophils in an approximately Poisson distribution, suggesting independent binding. Binding of acapsulate cryptococci did not require actin filaments and appeared to trigger phagocytosis. Thus, the capsule of C. neoformans appeared to inhibit binding and internalization by neutrophils.

Actins↗
PubMed1992

Effect of signal frequency and masker level on the frequency regions responsible for the overshoot effect.

Two experiments investigated the relative influence of components close to and remote from the signal frequency (fs) on the overshoot effect. Overshoot was defined as the difference in threshold between a signal presented 4 ms after, and that for one presented 300 ms after, the onset of a 350-ms masker. Experiment 1 measured the overshoot effect using both wideband and narrow-band maskers (centered on fs), at two signal frequencies and three masker levels. Experiment 2 used a masker consisting of a "middle band" (MB, centered on fs) and two flanking bands (FBs, which, when combined with the MB, produced a flat wideband spectrum). The masker was continuous except for a 300-ms interval just prior to the signal, during which either all three bands, the MB alone, or the FBs alone were turned off. The results of both experiments showed that the overshoot effect was usually determined by off-frequency components. However, the on-frequency components played a substantial role when signal-to-noise ratios (SNRs) at threshold were unusually high, such as at fs = 6500 Hz and intermediate masker levels. It is suggested that two different mechanisms contribute to the overshoot effect: an off-frequency mechanism which operates at all fs and masker levels, and an on-frequency mechanism which contributes to the overshoot effect only at high-threshold SNRs.

Attention↗
PubMed1990

Integrating practice guidelines with financial incentives.

Practice guidelines, in whatever form, hold significant implications for the delivery and the financing of health care. Hence, great care must be taken in developing them. They must be scientifically sound and thus defensible. They must incorporate clinical perspectives and consider patients' preferences. They must cover appropriate as well as inappropriate services. They must foster creation and adoption of a rational payment system. What guidelines, in their best form, can do is enable physicians, faced with an overwhelming array of often conflicting information, to reduce some of the uncertainty they must cope with and to practice the most clinically effective medicine. For physicians to do so requires valid information from a credible source, most often in conjunction with appropriate financial incentives.

Clinical Protocols↗
PubMed1979

Say it audiovisually to physicians, patients, and the public.

The Department of Pathology at the Medical College of Wisconsin has, in addition to the medical school's central TV facility, its own closed circuit TV equipment. Here, the authors recall the initial reaction of laboratory personnel to the system, and they explain the many ways in which the equipment has been used since its installation.

Audiovisual Aids↗
PubMed1976

Coproduction of Regan isoenzyme and carcinoembryonic antigen in HCT-8 cells.

The presence of the Regan isoenzyme of alkaline phosphatase was demonstrated in the carcinoembryonic antigen-producing human cell line HCT-8 Biochemical, histochemical, immunologic, and electrophoretic methods were used as criteria for the identification and characterization of this isoenzyme.

Carcinoembryonic Antigen↗