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Biomedical subjects

D Alexander

Publications and source records attributed to D Alexander.

At least 55 records · Page 3Linked to original sources
PubMed1997

Ultrasonographic screening before hospital discharge for deep venous thrombosis after arthroplasty: the post-arthroplasty screening study. A randomized, controlled trial.

BACKGROUND: The clinical significance of asymptomatic deep venous thrombosis that develops after joint arthroplasty and the value of screening tests to detect thrombi are uncertain. OBJECTIVES: To determine 1) the rate of symptomatic deep venous thrombosis or pulmonary embolism occurring after hospitalization for joint arthroplasty and 2) the value of screening compression ultrasonography. DESIGN: Double-blind, randomized, controlled trial. SETTING: Tertiary care hospital. PATIENTS: 1024 patients undergoing elective total hip or knee arthroplasty who received warfarin prophylaxis. INTERVENTION: Patients were randomly assigned to undergo either bilateral compression ultrasonography or a sham procedure before hospital discharge. Patients with a diagnosis of asymptomatic deep venous thrombosis were treated after discharge with standard anticoagulant therapy; other patients had warfarin therapy discontinued at discharge. All patients were followed for 90 days. RESULTS: In the screening group, asymptomatic proximal deep venous thrombosis was detected in 13 of 518 patients (2.5%). Another 4 patients subsequently developed symptomatic proximal deep venous thrombosis, and 1 patient treated for asymptomatic deep venous thrombosis developed major bleeding, for a total outcome event rate of 1.0% (5 of 518 patients). In the placebo group, 3 patients developed symptomatic proximal deep venous thrombosis and 2 had nonfatal pulmonary embolism, for a total event rate of 1.0% (5 of 506 patients) (difference, 0 percentage points [95% CI, -1.2 to 1.2 percentage points]). CONCLUSIONS: In patients undergoing total hip or knee arthroplasty, the use of warfarin prophylaxis during hospitalization results in a very low rate of symptomatic deep venous thrombosis or pulmonary embolism after hospital discharge. The use of screening compression ultrasonography at hospital discharge does not seem to be justified in this setting.

Algorithms↗
PubMed1997

Zinc-bis-histidinate preserves cardiac function in a porcine model of cardioplegic arrest.

BACKGROUND: We examined the ability of zinc-bis-histidinate to preserve postarrest myocardial function when added to a standard crystalloid cardioplegic solution. METHODS: Domestic pigs (35 to 50 kg) on left-sided cardiopulmonary bypass were subjected to 90 minutes of regional ischemia followed by 60 minutes of hypothermic cardioplegic arrest induced by antegrade infusion of 20 mL/kg cold St. Thomas' #2 cardioplegic solution with or without 100 mumol/L of zinc-bis-histidinate and maintained by infusion of 10 mL/kg of the same every 20 minutes. During reperfusion function was assessed at 1 and 3 hours over increasing preloads using the right-sided bypass method. RESULTS: At roller pump flows up to 2,000 mL/min, stroke work index-end-diastolic pressure curves were significantly (p < 0.05) higher and shifted to the left in treated hearts. In a series of pigs, echocardiography was used to determine end-diastolic and end-systolic volumes. At roller pump flows up to 3,500 mL/min, end-systolic pressure-end-systolic volume curves were significantly higher and shifted to the left in treated hearts. Left ventricular ejection fraction, fractional shortening, stroke volume, and cardiac output were significantly (p < 0.05) higher in treated hearts. Electron microscopy revealed that mitochondria in tissue not at risk appeared more swollen in control hearts. CONCLUSIONS: The results of this study support the conclusion that zinc-bis-histidinate is effective as a myocardial preservative when added to a crystalloid cardioplegic solution.

Animals↗
PubMed1997

The emergence of repair strategies in infants and toddlers.

This article describes the emergence of repair behaviors in young children as a reflection of three significant developmental achievements: the emergence of communicative intentionality, the development of socioemotional perspective taking, and the acquisition of effective communicative means. Because research in the emergence of preverbal communicative repairs is limited, a cross-sectional study was conducted on the ontogeny of repair strategies using the normative samples from the Communication and Symbolic Behavior Scales (Wetherby & Prizant, 1993). Patterns of early repair behaviors of typically developing children, as well as those of small groups of children with hearing impairments and pervasive developmental disorders, are presented. Findings of this study suggest that the ability to repair communicative breakdowns develops at the same time as intentional communication and that gestures are integral to preconversational repairs. Assessment and intervention implications for clinical practice are discussed.

Child Language↗
PubMed1997

The study of natural disasters, 1977-1997: some reflection on a changing field of knowledge.

As part of a series of papers to mark the 21st year of publication of Disasters, it is opportune to consider some of the changes that have occurred in the field it has covered so diligently for the last two decades. The paper begins with a brief review of the major natural disasters during this period and assesses their impact. It then considers the problem of how to define two key concepts: natural disaster and vulnerability, which remains an open question. The latter is one of the key determinants of the former. Next comes a review of what has occurred in the disasters field since the journal began publication, including some notes on the rise in vulnerability, the information technology revolution and the dilemmas of hazard mitigation. The following two sections assess, respectively, what hoped-for developments did not occur during the period studied and what assets were lost in the name of progress. For example, on the theoretical front, academic over-specialisation has predominated, while on the practical side there has been insufficient transfer of technology to where it is needed. The paper concludes that analyses of disaster need to become more sophisticated and multi-disciplinary and must take account of several forms of context within which developments take place.

Disaster Planning↗
PubMed1997

Drug resistant organisms and their implications for the outpatient dialysis setting.

Ever since antibiotics have been used to combat infection, resistance to them has also developed. The elderly and immunosuppressed populations found in today's dialysis facility comprise a group at risk for acquiring infection caused by drug resistant organisms. By utilizing antibiotics prudently and developing infection control strategies based on the disease/organism epidemiology, mode of transmission and individualized needs of the patient as well as the care setting, the proliferation of drug resistant organisms may be curtailed.

Ambulatory Care Facilities↗
PubMed1996

Characterization of mutations induced by 300 and 320 nm UV radiation in a rat fibroblast cell line.

The cytotoxic and mutagenic activities of monochromatic ultraviolet light (UV) at four wavelengths (254, 290, 300 and 320 nm) were determined using a rat fibroblast cell line CREF stably infected with a retroviral vector carrying the neo and HSV-tk markers. In this system, mutations can be positively detected as acyclovir-resistant colonies. Although the action spectra for these activities closely fit some of the previously reported spectra for photochemical DNA modifications, erythema, cell killing and mouse skin carcinogenesis, they diverge at 320 nm from the absorption spectrum for DNA and the action spectrum for bacterial inactivation and mutagenesis. Structural comparison of the HSV-tk mutants detected after irradiation with 300 and 320 nm UV revealed (1) CC dimers and C oligomers as predominant targets at both wavelengths; (2) increased incidence of relatively large deletions at 300 nm; and (3) greatly increased frequency of tandem double mutations at both wavelengths and of clustered multiple mutations at 320 nm. These results suggest the involvement of distinct mechanisms specifically operating, or becoming evident, in UV-mediated mutagenesis at these different wavelengths in mammalian cells.

Acyclovir↗
PubMed1996

The health effects of earthquakes in the mid-1990s.

This paper gives an overview of the global pattern of casualties in earthquakes which occurred during the 30-month period from 1 September 1993 to 29 February 1996. It also describes some of the behavioural and logistical regularities associated with mortality and morbidity in these events. Of 83 earthquakes studied, there were casualties in 49. Lethal earthquakes occurred in rapid succession in Indonesia, China, Colombia and Iran. In the events studied, a disproportionate number of deaths and injuries occurred during the first six hours of the day and in earthquakes with magnitudes between 6.5 and 7.4. Ratios of death to injury varied markedly (though with some averages close to 1:3), as did the nature and causes of mortality and morbidity and the proportion of serious to slight injuries. As expected on the basis of previous knowledge, few problems were caused by post-earthquake illness and disease. Also, as expected, building collapse was the principal source of casualties: tsunamis, landslides, debris flows and bridge collapses were the main secondary causes. In addition, new findings are presented on the temporal sequence of casualty estimates after seismic disaster. In synthesis, though mortality in earthquakes may have been low in relation to long-term averages, the interval of time studied was probably typical of other periods in which seismic catastrophes were relatively limited in scope.

Building Codes↗
PubMed1995

In situ isolation of mRNA from individual plant cells: creation of cell-specific cDNA libraries.

A method for isolating and cloning mRNA populations from individual cells in living, intact plant tissues is described. The contents of individual cells were aspirated into micropipette tips filled with RNA extraction buffer. The mRNA from these cells was purified by binding to oligo(dT)-linked magnetic beads and amplified on the beads using reverse transcription and PCR. The cell-specific nature of the isolated mRNA was verified by creating cDNA libraries from individual tomato leaf epidermal and guard cell mRNA preparations. In testing the reproducibility of the method, we discovered an inherent limitation of PCR amplification from small amounts of any complex template. This phenomenon, which we have termed the "Monte Carlo" effect, is created by small and random differences in amplification efficiency between individual templates in an amplifying cDNA population. The Monte Carlo effect is dependent upon template concentration: the lower the abundance of any template, the less likely its true abundance will be reflected in the amplified library. Quantitative assessment of the Monte Carlo effect revealed that only rare mRNAs (< or = 0.04% of polyadenylylated mRNA) exhibited significant variation in amplification at the single-cell level. The cDNA cloning approach we describe should be useful for a broad range of cell-specific biological applications.

Base Sequence↗
PubMed1995

Antigenic heterogeneity of avian paramyxoviruses of serotype 2 ("Yucaipa-like") isolated from domestic and wild birds in Israel.

Thirty-three viruses of PMV-2 serotype isolated in Israel from domestic and wild birds during epizooty of a respiratory disease in 1979-1981 were studied comprehensively in comparison with a set of reference PMV-2 viruses using cross reaction hemagglutination inhibition tests, elution-hemagglutination pattern and pattern of migration of viral proteins in polyacrylamide gel electrophoresis. The results demonstrated considerable heterogeneity amongst the local isolates by the above three criteria which were not correlated with each other. There was no significant correlation between the differences found and chronology of isolation of the viruses. The results indicated that there may have been simultaneous co-circulation of different PMV-2 strains in the local avian reservoir at the beginning of the epizootic rather than temporal accumulation of variants as a result of antigenic drift of an "ancestor" virus which caused the initial infection.

Animals↗
PubMed1995

Strike-through contamination in saturated sterile dressings: a clinical analysis.

This multisite study examined the risk of strike-through contamination of 4" x 4" gauze sponges using a shortcut method of saturating sterile sponges directly on their wrappers. Sterile gauze sponges were saturated directly on their wrappers on hospital over-bed tables of postoperative general surgical patients. Cultures were taken at 0.5, 1, 3, and 5 minutes after saturation to ascertain whether strike-through contamination occurred. Saturated sponges showed significant microorganism growth when compared to expected zero microorganisms at all sampling times following saturation. Although microorganisms identified in strike-through contamination were not microbiologically or pathogenically threatening, the basic principle of asepsis was violated. There was no significant difference in strike-through contamination between sponges saturated on coated wrappers and sponges saturated on uncoated wrappers. Clinicians should be aware that coated wrappers do not provide a moisture-proof barrier against strike-through contamination. The findings suggest the shortcut method should not be used for saturating sponges.

Asepsis↗
PubMed1995

Ventilatory muscle strength and endurance in myasthenia gravis.

Patients with generalized myasthenia gravis (MG) often have associated ventilatory muscle involvement. It is not known whether patients with isolated ocular muscle involvement have identifiable involvement of their ventilatory muscles. Most studies have assessed muscle involvement by measuring muscle strength; however, we hypothesized that measures of ventilatory muscle endurance may be more sensitive tests of ventilatory muscle involvement in myasthenia gravis. We studied 17 patients with myasthenia gravis (four with ocular involvement alone and 13 with varying degrees of generalized myasthenia gravis). Spirometry, ventilatory muscle strength (maximum inspiratory and expiratory pressures (MIP and MEP)) and endurance (2 min incremental threshold loading test) were measured before and 20 min after i.m. neostigmine. We compared the results with those of 10 normal controls. We found no difference between patients with isolated ocular involvement and controls. Ocular myasthenia gravis patients did not improve after neostigmine. The patients with generalized myasthenia gravis had reduced baseline ventilatory muscle strength (MIP 67 cmH2O (70% of predicted), MEP 86 cmH2O (50% of pred) and endurance (mean maximal load achieved = 246 g, mean pressure at highest load (P) = 19.4 cmH2O) compared with controls. After neostigmine, there was a significant increase in MIP in patients with generalized myasthenia gravis and a trend towards an increased MEP. As a group, the patients with generalized myasthenia gravis did not demonstrate a change in their ventilatory muscle endurance after neostigmine; however, there was considerable interpatient variability in response. We conclude that patients with isolated ocular MG have normal ventilatory muscle strength when tested conventionally.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗