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Biomedical subjects

D Alexander

Publications and source records attributed to D Alexander.

At least 37 records · Page 2Linked to original sources
PubMed1999

Acute myocarditis following Tityus trinitatis envenoming: morphological and pathophysiological characteristics.

The clinicopathological features of four cases of scorpion envenoming by Tityus trinitatis are presented. The cardiac histopathology is recorded in the two fatal cases. The pathology of the acute myocarditis was a mixed picture of a toxic myocarditis and coagulative myocytolysis. These cardiac lesions are also seen in catecholamine induced cardiotoxicity and lend support to the theory that an adrenergic surge follows scorpion envenoming. A brief review of scorpion envenoming syndrome is undertaken in the light of these findings.

Acute Disease↗
PubMed1999

Limits in reliability of glycoprotein G-based type-specific serologic assays for herpes simplex virus types 1 and 2.

Type-specific serologic assays for herpes simplex virus (HSV) types 1 and 2 based on glycoprotein G-1 (gG-1) (HSV-1) and gG-2 (HSV-2) discriminate between antibodies against HSV-1 and HSV-2. We previously developed a Western blot assay using gG-1 and gG-2 expressed in baculovirus, performed extensive validation studies, and determined that it was both sensitive and specific for type-specific detection of HSV antibody. Here we report that, among a cohort of Thai military recruits, the serostatus of some individuals changed from positive to negative over time (6.6% among those ever positive for HSV-1, and 14.9% among those ever positive for HSV-2). We tested a subset of these specimens in three other gG-based assays: an enzyme-linked immunosorbent assay, an immunoblot strip assay, and a Western blot assay. Positive-to-negative shifts occurred in every assay; the frequency of the shifts ranged from 6. 1% to 21.2% of the specimen sets tested. There was only limited agreement among the assays concerning which individuals lost reactivity. This inaccuracy, exhibited by all of the assay protocols, was not predicted by validation studies employing specimens from cross-sectional studies and was most pronounced in HSV-2 testing. This argues for the inclusion of serial blood specimens in serologic assay validation procedures.

Adult↗
PubMed1998

Influence of chronic hypoxia on the contributions of non-inactivating and delayed rectifier K currents to the resting potential and tone of rat pulmonary artery smooth muscle.

Exposing rats to chronic hypoxia increased the 4-aminopyridine (4-AP) sensitivity of pulmonary arteries. 1 mM 4-AP caused smooth muscle cell depolarization and contraction in arteries from hypoxic rats, but had little effect in age-matched controls. Chronic hypoxia downregulated delayed rectifier K+ current (IK(V)), which was nearly 50% blocked by 1 mM 4-AP, and non-inactivating K+ current (IK(N)), which was little affected by 1 mM 4-AP. The results suggest that IK(N) determines resting potential in control rats and that its downregulation following hypoxia leads to depolarization, which activates IK(V) and increases its contribution to resting potential. The hypoxia-induced increase in 4-AP sensitivity thus reflects a switch in the major K+ current determining resting potential, from IK(N) to IK(V). This has important implications for the actions and specificity of pulmonary vasodilator drugs.

4-Aminopyridine↗
PubMed1998

Association between human immunodeficiency virus and herpes simplex virus type 2 seropositivity among male factory workers in Zimbabwe.

To determine the seroprevalence of herpes simplex virus type 2 (HSV-2), to identify correlates of infection, and to describe the correlation with human immunodeficiency virus (HIV) seropositivity, 224 HIV-negative and 191 HIV-positive male factory workers in Zimbabwe were screened for HSV-2-specific antibodies. HSV-2 seroprevalence was 35.7% among HIV-negative subjects and 82.7% among HIV-positive subjects. The weighted estimate of HSV-2 seroprevalence in this population is 44.6%. The correlation between HIV and HSV-2 remained significant after controlling for multiple sex partners, paying for sex, and history of sexually transmitted disease (adjusted odds ratio, 8.0; 95% confidence interval, 4.8-13.1). If the association between HSV-2 and HIV is causal, then the high seroprevalence of HIV and HSV-2 suggests that suppressive HSV-2 treatment should be considered as a strategy to reduce HIV transmission in this population. HSV-2 seroconversion may be a suitable surrogate end point to evaluate HIV prevention interventions.

Adolescent↗
PubMed1998

National and international veterinary reference laboratories for infectious diseases.

Reference laboratories play an increasingly important role in the harmonisation of laboratory diagnostic tests and the standardisation of veterinary vaccines. This is particularly important in building confidence between international trading partners. The authors review aspects of the organisation, designation and support of reference laboratories for infectious diseases of animals and discuss the principal activities which such laboratories would normally perform. These activities include advice and consultancy, publications and communication, training, research, disease surveillance, maintenance of culture collections, evaluation of reference methods, preparation of reference materials and organisation of inter-laboratory comparisons.

Animals↗
PubMed1998

Accuracy of screening compression ultrasonography and clinical examination for the diagnosis of deep vein thrombosis after total hip or knee arthroplasty.

OBJECTIVE: To determine whether compression ultrasonography or clinical examination should be considered as screening tests for the diagnosis of deep vein thrombosis (DVT) after total hip or knee arthroplasty in patients receiving warfarin prophylaxis postoperatively. DESIGN: A prospective cohort study. SETTING: A single tertiary care orthopedic centre. PATIENTS: One hundred and eleven patients who underwent elective total hip or knee arthroplasty were enrolled. Postoperatively the warfarin dose was adjusted daily to maintain the international normalized ratio between 1.8 and 2.5. Eighty-six patients successfully completed the study protocol. INTERVENTION: Before they were discharged from hospital, patients were assessed for DVT by clinical examination, bilateral compression ultrasonography of the proximal venous system and bilateral contrast venography. RESULTS: DVT was found in 29 patients (34%; 95% confidence interval [CI] 24% to 45%), and 6 patients (7%; 95% CI 3% to 15%) had proximal DVT. DVT developed in 18 (40%) of 45 patients who underwent total knee arthroplasty and in 11 (27%) of 41 patients who underwent total hip arthroplasty. The sensitivity of compression ultrasonography for the diagnosis of proximal DVT was 83% (95% CI 36% to 99%) and the specificity was 98% (95% CI 91% to 99%). The positive predictive value of compression ultrasonography was 71%. In contrast, clinical examination for DVT had a sensitivity of 11% (95% CI 2% to 28%) and a positive predictive value of 25%. CONCLUSIONS: DVT is a common complication after total hip or knee arthroplasty. Compression ultrasonography appears to be a relatively accurate noninvasive test for diagnosing postoperative proximal DVT. In contrast, clinical examination is a very insensitive test. Whether routine use of screening compression ultrasonography will reduce the morbidity of venous thromboembolism after joint arthroplasty requires confirmation in a prospective trial involving long-term follow-up of patients.

Aged↗
PubMed1997

Mixed paramyxovirus infection of wild and domestic birds in Israel.

Five cases of dual isolations of different serotypes of avian paramyxoviruses (APMV) from domestic and wild birds are described: one case of mixed infection by APMV-1 and APMV-4 and four cases of infection by APMV-1 and APMV-2 serotypes. The double infection was proven by consecutive isolations of two viruses from allantoic fluid samples derived from single swabs after their respective treatment by antisera against each suspected virus. The finding of double APMV infection in poultry farms appears to be important for epizootiology and pathogenesis of APMV-caused diseases.

Animals↗
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↗