Interprofessional simulation-based team-training and self-efficacy in emergency medicine situations.

Teamwork quality has been shown to influence patient safety, and simulation-based team-training (SBTT) is an effective means to increase this quality. However, long-term effects are rarely studied. This study aims to investigate the long-term effects of interprofessional SBTT in emergency medicine in terms of global confidence, self-efficacy in interprofessional communication and in emergency medicine situations. Newly graduated doctors, nurses, auxiliary nurses, and medical and nursing students participated. Four emergency medicine scenarios focused on teamwork according to the A-B-C-D-E-strategy. All participants increased their global confidence from 5.3 (CI 4.9-5.8) before to 6.8 (CI 6.4-7.2; p < .0001) after SBTT. Confidence in interprofessional communication increased from 5.3 (CI 4.9-5.8) to 7.0 (CI 6.6-7.4; p < .0001). Students had the greatest gain. The self-efficacy following the A-B-C-D-E strategy increased from 4.9 (CI 4.4-5.3) to 6.6 (CI 6.2-7.0). Again, students had the steepest increase. Newly graduated doctors achieved a superior increase in global confidence as compared to nurses and auxiliary nurses (p < .0001). Their propensity to recommend SBTT to colleagues was 9.9 (CI 9.8-10.0). The positive effects were sustained over a six-month period, indicating that interprofessional SBTT had a positive impact on competence development, and a potential to contribute to increased team quality in emergency medicine care.

Dietary live yeast and increased water temperature influence the gut microbiota of rainbow trout.

AIMS: The objective was to determine the effects of dietary substitution of fishmeal (FM) with live yeast and increasing water temperature on the diversity and composition of gut microbiota in rainbow trout. METHODS AND RESULTS: Fish were fed either FM or yeast (Saccharomyces cerevisiae) and reared in water temperatures of either 11°C (cold) or 18°C (warm) for 6 weeks. Luminal content and mucosa were collected from the distal gut and the load, diversity and species abundance of yeast and bacteria were analysed using agar plating, MALDI-TOF and rRNA gene amplicon sequencing. Yeast in the gut of fish fed FM were represented by S. cerevisiae, Rhodotorula spp. and Debaryomyces hansenii, while fish fed yeast contained 4-5 log higher CFU per g of yeast that were entirely represented by S. cerevisiae. For gut bacteria, sequencing of 16S rRNA gene amplicons using Illumina MiSeq showed lower bacterial diversity and abundance of lactic acid bacteria, especially Lactobacillus, in fish reared in warm rather than cold water. Fish fed yeast had similar bacterial diversity and lower abundance of Leuconostocaceae and Photobacterium compared with fish fed FM. CONCLUSIONS: Feeding live yeast mainly increased yeast load in the gut, while increased water temperature significantly altered the gut microbiota of rainbow trout in terms of bacterial diversity and abundance. SIGNIFICANCE AND IMPACT OF THE STUDY: Live yeast can replace 40% of FM without disrupting bacteria communities in the gut of rainbow trout, while increased water temperature due to seasonal fluctuations and/or climate change may result in a gut dysbiosis that may jeopardize the health of farmed fish.

Community of practice and student interaction at an acute medical ward: An ethnographic study.

BACKGROUND: A deeper understanding is needed of the acute medical care setting as a learning environment for students. AIM: To explore workplace culture of an acute medical ward and students' interactions within this community. METHOD: An ethnographic design was applied. Medical and nurse students' interactions were observed and informal questioning performed. Field notes were transcribed and analysed qualitatively, inspired by Wengers' "Community of practice" theory. RESULTS: We identified four characteristics that regulated how students adapt and interact in the community of practice. Complex and stressful situations were stabilized by routines and carriers of culture. Variable composition and roles of community members were a part of the daily routine but did not seam obvious to students. Transitions through community boundaries were confusing especially for new students. Levels of importance and priority: Hierarchies and orders of priority were present as regulators of roles, routines and interactions, and of how staff approach different patient groups. CONCLUSION: The culture shaped a pattern for, and created prerequisites that challenged students' adaptation and created a space for learning. Students' task on arrival was to enter the semipermeable membrane of the community of practice and to understand and adapt to its culture, and try to become accepted.

Cytokine release assays: current practices and future directions.

As a result of the CD28 superagonist biotherapeutic monoclonal antibody (TGN 1412) "cytokine storm" incident, cytokine release assays (CRA) have become hazard identification and prospective risk assessment tools for screening novel biotherapeutics directed against targets having a potential risk for eliciting adverse pro-inflammatory clinical infusion reactions. Different laboratories may have different strategies, assay formats, and approaches to the reporting, interpretation, and use of data for either decision making or risk assessment. Additionally, many independent contract research organizations (CROs), academic and government laboratories are involved in some aspect of CRA work. As a result, while some pharmaceutical companies are providing CRA data as part of the regulatory submissions when necessary, technical and regulatory practices are still evolving to provide data predictive of cytokine release in humans and that are relevant to safety. This manuscript provides an overview of different approaches employed by the pharmaceutical industry and CROs, for the use and application of CRA based upon a survey and post survey follow up conducted by ILSI-Health and Environmental Sciences Institute (HESI) Immunotoxicology Committee CRA Working Group. Also discussed is ongoing research in the academic sector, the regulatory environment, current limitations of the assays, and future directions and recommendations for cytokine release assays.

Comparison of manual and semi-automatic measuring techniques in MSCT scans of patients with lymphoma: a multicentre study.

OBJECTIVES: Multicentre evaluation of the precision of semi-automatic 2D/3D measurements in comparison to manual, linear measurements of lymph nodes regarding their inter-observer variability in multi-slice CT (MSCT) of patients with lymphoma. METHODS: MSCT data of 63 patients were interpreted before and after chemotherapy by one/two radiologists in five university hospitals. In 307 lymph nodes, short (SAD)/long (LAD) axis diameter and WHO area were determined manually and semi-automatically. Volume was solely calculated semi-automatically. To determine the precision of the individual parameters, a mean was calculated for every lymph node/parameter. Deviation of the measured parameters from this mean was evaluated separately. Statistical analysis entailed intraclass correlation coefficients (ICC) and Kruskal-Wallis tests. RESULTS: Median relative deviations of semi-automatic parameters were smaller than deviations of manually assessed parameters, e.g. semi-automatic SAD 5.3 vs. manual 6.5 %. Median variations among different study sites were smaller if the measurement was conducted semi-automatically, e. g. manual LAD 5.7/4.2 % vs. semi-automatic 3.4/3.4 %. Semi-automatic volumetry was superior to the other parameters (2.8 %). CONCLUSIONS: Semi-automatic determination of different lymph node parameters is (compared to manually assessed parameters) associated with a slightly greater precision and a marginally lower inter-observer variability. These results are with regard to the increasing mobility of patients among different medical centres and in relation to the quality management of multicentre trials of importance. KEY POINTS: • In a multicentre setting, semi-automatic measurements are more accurate than manual assessments. • Lymph node volumetry outperforms all other semi-automatically and manually performed measurements. • Use of semi-automatic lymph node analyses can reduce the inter-observer variability.

Prevention of type II endoleak using the AMPLATZER vascular plug before endovascular aneurysm repair.

OBJECTIVE: We evaluated the feasibility of visceral artery and lumbar artery (LA) embolization using AMPLATZER vascular plug (AVP) types 4 and 2 (AVP4, AVP2) prior to endovascular aneurysm repair (EVAR) to prevent the development of a type II endoleak. METHODS: Between January 2008 and April 2010, 45 arteries in 33 male patients were embolized with 44 AVP4 and one AVP2. Artery name and diameter; device number and size; and intervention, fluoroscopy, and deployment times for each procedure and each device were recorded. Computed tomography (CT) angiography was performed 2 days and 3, 6, 12, 18, 24, and 36 months after EVAR to confirm successful EVAR and embolotherapy, exclude endoleaks, and evaluate aneurysm shrinkage. RESULTS: AVP4 devices were implanted into the inferior mesenteric arteries in 33 cases, lumbar arteries in seven cases, and pelvic and renal arteries in two cases each. An AVP2 device was inserted into the gluteal artery in one case. The success rate was 100%, with total occlusion of all target vessels. No endoleaks were found in follow-up CT angiography. CONCLUSION: The use of AVP prior to EVAR is an efficient embolization technique that prevents the development of type II endoleaks.

[Examination of visual performance by adaptive optics]. / Untersuchung des Seheindrucks mittels adaptiver Optik.

BACKGROUND: The dependence of visual quality on higher order aberrations (HOA) is highly important for refractive surgery (LASIK) as well as for the correction by vision aids. The use of the adaptive optics (AO) enables the measurement and manipulation of conventional lower order aberrations (defocus, astigmatism) and for HOAs as well. In this work, an Adaptive Optics Visual Simulator is presented that enables one to correct wave-front deformations up to the sixth order of Zernike polynomials, as well as to induce specific aberrations. The subjects observe a TFT monitor, so that a subjective rating of the visual impression is possible, as well as objective measurements. METHODS: Possible applications of such an adaptive optics visual simulator are demonstrated by means of several studies in this survey paper. The main challenge was to investigate the influence of HOAs on the subjective visual impression. Thereby, the following questions have been examined among others: Does the correction of the HOAs lead to an improved visual impression? Are there ways to check the effect of HOAs, what are the effects of single HOAs on the subjective visual impression and what just-noticeable levels do they have? RESULTS: Three studies are presented investigating the impact of HOAs on visus, contrast sensitivity and on vision with glare as well as objective stimulus thresholds of selected HOAs. For example, by using a staircase-procedure it was possible to determine that the objective stimulus threshold for coma has a significantly lower value than the thresholds for astigmatism or trefoil. CONCLUSION: Adaptive optics enables the investigation of effects of HOAs on subjective and objective visual impression. In future, this may result in individualised corrections of refractive errors, which will improve the patient's quality of life.

Pre-filling of the extracorporeal circuit with autologous blood is safe, but not effective in optimizing biocompatibility in high-risk patients.

OBJECTIVES: Haemodilution resulting from crystalloid priming of the cardiopulmonary bypass circuit represents a major risk factor for blood transfusions in high-risk cardiac surgery patients. We designed this study to evaluate the effects of antegrade autologous priming (AAP) on reducing perioperative blood transfusion and markers of the inflammatory response in older patients (>75 years). METHODS: Seventy-two patients undergoing first-time coronary bypass and/or aortic valve replacement were prospectively randomised to a cardiopulmonary bypass (CPB) with or without AAP. AAP was performed by adding the patient's own blood to the prime solution (mean 280 ml). Perfusion and anaesthetic techniques were as usual. The haematocrit was maintained at a minimum of 21% during CPB. Patients were well matched for all preoperative variables, including established transfusion risk factors. The primary endpoint was the requirement of red cell transfusion. The surrogate endpoints were renal function, inflammatory response and ischaemic parameters. Blood samples were drawn pre- and intraoperatively and at intervals of 6 hours till POD 6. RESULTS: Current analysis shows no differences in patients receiving homologous packed red cell transfusions. Also, markers of the inflammatory response (IL6, IL8), renal function (cystatin C, creatinine) and myocardial ischaemia (troponin T, CK-MB) were comparable in both groups (p>0.05). Clinical outcomes were similar with respect to pulmonary, renal and hepatic function, length of ICU stay and hospital stay. CONCLUSION: These data suggest that antegrade autologous priming is a safe procedure, but an ineffective way for improving biocompatibility and reducing the need for blood transfusion in older patients.

Effect of nutritional status and sampling intensity on recovery after dorsal aorta cannulation in free-swimming Atlantic salmon (Salmo salar L.).

Recovery from implantation of a cannula in the dorsal aorta (DA) of Atlantic salmon (Salmo salar) was studied in relation to nutritional status and sampling intensity. The incentive for the study was the inconsistency between published reports and our own experience of recovery and longevity of fish exposed to this protocol. In two studies using starved fish, blood (0.3 ml) was sampled 0, 1 and 24 h after DA-cannulation, and thereafter at 48 and 72 h and thereafter once weekly for four weeks. In a third study using fed fish, four consecutive samples (0, 3, 6 and 12 h after a meal) were obtained twice a week over a four-week period. All fish displayed a sharp increase in pCO(2) and haematocrit (Hct) during surgery, followed by a marked raise in cortisol, glucose, sodium and potassium (1 h). pCO(2), pH and Hct approached baseline levels as early as the 1 h post-surgery sample, while this was not the case for cortisol and electrolytes before the 24 h post-surgery sample. Glucose did not display any significant changes post surgery. From then on, all variables displayed minor but non-significant (P > 0.05) changes indicating a steady state close to baseline values for unstressed fish. This pattern was independent of sampling procedure, i.e. repeated single or multiple samples and thus volume of blood removed. Nutritional status (fed vs. starved) did not affect post-surgical recovery pattern. Only K(+) and Hct displayed consistent and significant post-prandial patterns. We found marked differences between baseline level of cannulated fish and uncannulated control fish, in pH, K(+) and Hct indicating that cannulation may be the preferred method to obtain representative resting values in fish.

Enhanced resolution of microscopic objects by image inversion interferometry.

We demonstrate in experiment that the resolution of a conventional light microscope can be enhanced by 26% with the help of an image inverting interferometer. In order to prove this statement, we measured the point spread function of the system as well as the resolution of two-point objects. Additionally, the contrast transmission function of the interferometric setup was measured and compared to the results gained with a conventional wide-field microscope. Using the interferometric system, the spatial frequencies near the cutoff-frequency were far better transmitted than by the conventional microscope. Finally, we demonstrate the improved resolution with the help of images of two-dimensional structures.

Changes in arterial oxygen tension and physiological status in resting, unrestrained Arctic charr Salvelinus alpinus (L.) exposed to mild hypoxia and hyperoxia.

In arctic charr Salvelinus alpinus, arterial blood partial pressures of oxygen (PaO2) and carbon dioxide increased with increasing water oxygen tension (PwO2), while the water to arterial PO2 difference (PwO2-PaO2) did not change in relation to PwO2.

Lack of arterial PO2 downregulation in Atlantic salmon (Salmo salar L.) during long-term normoxia and hyperoxia.

Regulation of arterial partial pressure of O2 (PaO2) in Atlantic salmon (Salmo salar) was investigated during resting conditions in normoxic and hyperoxic water. Dorsal aorta cannulated adult Atlantic salmon (1.2-1.6 kg, n=8) were exposed to 2 week sequential periods of normoxia [16.7±1.1 kPa (mean±SD)] and hyperoxia (34.1±4.9 kPa) in individual tanks containing seawater (33.7±0.2 ppt) at stable temperature conditions (8.7±0.7°C) and a light regime of L:D=12:12. Tank design and sampling procedures were optimized to provide suitable shelter and current for the fish, and to allow repeated, undisturbed sampling of blood from free-swimming fish. Fish were sampled regularly through the experimental period. PwO2, PaO2, blood ion composition (Na+, K+, Cl-), acid-base status (pH, PCO2, HCO3-), haematocrit and glucose were measured. The most frequently observed PaO2 values were in the range of 60-80% of PwO2, both during normoxia and hyperoxia, and PaO2 values were significantly lower during normoxia than during hyperoxia. Blood pH, PCO2 and HCO3- were significantly elevated during hyperoxia, while, Na+, Cl- and Hct were significantly lower. K+ and glucose showed no significant differences. This study demonstrates a lack PaO2 regulation in Atlantic salmon to low partial pressures, in contrast to previous reports for many aquatic gill breathing animals. Both during normoxia and hyperoxia, PaO2 reflects PwO2, and alterations in external PO2 consequently result in proportional arterial PO2 changes. Physiological adaptation to hyperoxia, as illustrated by changes in several blood parameters, does not include down-regulation of PaO2 in Atlantic salmon. The lack of PaO2 regulation may make Atlantic salmon vulnerable to the oxidative stress caused by increased free radical formation in hyperoxic conditions.

Levosimendan in patients with acute myocardial ischaemia undergoing emergency surgical revascularization.

BACKGROUND AND OBJECTIVE: Levosimendan is a calcium-sensitizing drug that enhances myocardial contractility without increasing intracellular calcium. By activating adenosine triphosphate-dependent potassium channels it exerts cardioprotective and vasodilatory effects. METHODS: A retrospective matched pair analysis was performed in 52 patients undergoing emergency coronary artery bypass grafting for acute myocardial ischaemia with or without cardiogenic shock. A total of 27 patients received levosimendan (bolus 6 microg kg(-1); continuous infusion 0.2 microg kg(-1) min(-1)) in addition to catecholamines, while 25 patients were treated with catecholamines only. RESULTS: Predicted mortality by logistic EuroSCORE was 42% (14-90%) in the levosimendan group and 38% (9-90%) in the control group (median, range). Cardiogenic shock was diagnosed in 52% of the patients in both groups. Compared to the control group, levosimendan-treated patients had fewer intra-aortic balloon pumps inserted (33% vs. 76%, P 0.05) and need for dialysis (11% levosimendan; 32% control, P > 0.05) did not reach statistical significance. Length of hospital stay did not differ (14 +/- 18 days, levosimendan; 13 +/- 19 days, control; P > 0.05) between the two groups. CONCLUSION: In this retrospective matched pair analysis of 52 patients undergoing emergency coronary artery bypass grafting for acute ischaemia, levosimendan reduced morbidity. The reduced morbidity did not translate into reductions in mortality or length of stay. A larger, prospective randomized trial is warranted to confirm the potentially beneficial effects of levosimendan in patients with acute ischaemia.

The Ras/Raf signaling pathway is required for progression of mouse embryos through the two-cell stage.

We have used microinjection of antisense oligonucleotides, monoclonal antibody, and the dominant negative Ras N-17 mutant to interfere with Ras expression and function in mouse oocytes and early embryos. Microinjection of either ras antisense oligonucleotides or anti-Ras monoclonal antibody Y13-259 did not affect normal progression of oocytes through meiosis and arrest at metaphase II. However, microinjection of fertilized eggs with constructs expressing Ras N-17 inhibited subsequent development through the two-cell stage. The inhibitory effect of Ras N-17 was overcome by simultaneous injection of a plasmid expressing an active raf oncogene, indicating that it resulted from interference with the Ras/Raf signaling pathway. In contrast to the inhibition of two-cell embryo development resulting from microinjection of pronuclear stage eggs, microinjection of late two-cell embryos with Ras N-17 expression constructs did not affect subsequent cleavages and development to morulae and blastocysts. It thus appears that the Ras/Raf signaling pathway, presumably activated by autocrine growth factor stimulation, is specifically required at the two-cell stage, which is the time of transition between maternal and embryonic gene expression in mouse embryos.

c-mos expression in mouse oocytes is controlled by initiator-related sequences immediately downstream of the transcription initiation site.

We have employed transient expression assays to analyze the sequences that direct c-mos transcription in mouse oocytes. Plasmids containing the chloramphenicol acetyltransferase (CAT) gene fused to either a 2.4-kb or a 731-bp fragment from the 5'-flanking region of c-mos produced similar levels of CAT activity when injected into nuclei of growing oocytes. BAL 31 deletions revealed that sequences up to 20 bp upstream of the major transcription start site could be removed without any significant loss of CAT activity. Promoter activity only decreased when these deletions closely approached the transcription start site, which was mapped at 53 nucleotides upstream of the first ATG in the c-mos open reading frame. On the other hand, deletion of sequences within 20 nucleotides downstream of the transcription initiation site resulted in a 10-fold reduction in CAT expression. A similar decrease in promoter activity was observed as a result of point mutations in these 5' untranslated sequences. Thus, sequences immediately downstream of the transcription start site, including a consensus sequence (PyPyCAPyPyPyPyPy) present in the initiator elements of several genes, appear to regulate c-mos expression in mouse oocytes. Reverse transcription-polymerase chain reaction analysis of RNA from injected oocytes showed that this regulation is manifest at the transcriptional level. Expression of c-mos in mouse oocytes thus appears to be directed by a simple promoter consisting only of sequences immediately surrounding the transcription start site, including an initiator element in the untranslated leader.

[Combination of radiological and nuclear medical imaging in animals: an overview about today's possibilities]. / Kombinierte radiologische und nuklearmedizinische Bildgebung in Tierexperimenten: Ein Uberblick über die aktuellen Möglichkeiten.

Molecular imaging of small animals has made considerable progress in the last years. Various research fields are interested in imaging small animals due to the lower numbers of animals per experiment. This has advantages with respect to financial, ethical and research aspects. Non-invasive imaging allows examination of one animal several times during the same experiment. This makes it possible to follow a pathological process in the same animal over time. However, the radiological methods used such as magnetic resonance imaging or computed tomography as well as the nuclear medicine methods such as single photon emission computed tomography or positron emission tomography suffer from disadvantages. Molecular aspects are limited in the radiological methods while anatomical localization is difficult in nuclear medicine. The fusion of these methods leads to additional information. This review shows today's possibilities with their advantages as well as disadvantages.

Medical students' opportunities to participate and learn from activities at an internal medicine ward: an ethnographic study.

OBJECTIVES: To optimise medical students' early clerkship is a complex task since it is conducted in a context primarily organised to take care of patients. Previous studies have explored medical students' perceptions of facilitation and hindrance of learning. However, the opportunities for medical student to learn within the culture of acute medicine care have not been fully investigated. This study aimed to explore how medical students approach, interact and socialise in an acute internal medicine ward context, and how spaces for learning are created and used in such a culture. DESIGN AND SETTING: Ethnographic observations were performed of medical students' interactions and learning during early clerkship at an acute internal medicine care ward. Field notes were taken, transcribed and analysed qualitatively. Data analysis was guided by Wenger's theory of communities of practice. PARTICIPANTS: 21 medical students and 30 supervisors participated. RESULTS: Two themes were identified: Nervousness and curiosity-students acted nervously and stressed, especially when they could not answer questions. Over time curiosity could evolve. Unexplored opportunities to support students in developing competence to judge and approach more complex patient-related problems were identified. Invited and involved-students were exposed to a huge variation of opportunities to learn, and to interact and to be involved. Short placements seemed to disrupt the learning process. If and how students became involved also depended on supervisors' activities and students' initiatives. CONCLUSIONS: This study shed light on how an acute internal medicine ward culture can facilitate medical students' possibilities to participate and learn. Medical students' learning situations were characterised by questions and answers rather than challenging dialogues related to the complexity of presented patient cases. Further, students experienced continuous transfers between learning situations where the potential to be involved differed in a wide variety of ways.

Development and validation of an instrument to assess patients' appraisal, emotions and action tendencies preceding care-seeking in acute myocardial infarction: The PA-AMI questionnaire.

BACKGROUND: Reducing patient delay for patients afflicted by an acute myocardial infarction is a task of great complexity, which might be alleviated if more factors that influence this delay could be identified. Although a number of self-reported instruments associated with patient delay exist, none of these taps the content of the appraisal process related to patients' subjective emotions. AIM: The aim of this study was to develop and validate a questionnaire aimed at assessing patients' appraisal, emotions and action tendencies when afflicted by an acute myocardial infarction. METHODS: An item pool was generated based on themes conceptualized in a recent qualitative study of acute myocardial infarction patients' thoughts, feelings and actions preceding the decision to seek medical care. The 'Think-Aloud Protocol' and test-retest analysis at item level were performed. The modified item pool was administered to 96 patients when treated for acute myocardial infarction. Explorative factor analysis and principal component analysis with the non-linear iterative partial least squares algorithm were performed to examine the underlying factor structure of the items. RESULTS: The findings indicated three core dimensions corresponding to three subscales, namely, 'symptom appraisal'; 'perceived inability to act'; 'autonomy preservation'. The results demonstrated acceptable measures of reliability and validity Conclusions: The PA-AMI questionnaire demonstrated satisfactory psychometric properties. Assessment of the included core dimensions may contribute to greater understanding of the appraisal processes for patients afflicted by an acute myocardial infarction.

Multivalent Fcγ-receptor engagement by a hexameric Fc-fusion protein triggers Fcγ-receptor internalisation and modulation of Fcγ-receptor functions.

Engagement of Fcγ-receptors triggers a range of downstream signalling events resulting in a diverse array of immune functions. As a result, blockade of Fc-mediated function is an important strategy for the control of several autoimmune and inflammatory conditions. We have generated a hexameric-Fc fusion protein (hexameric-Fc) and tested the consequences of multi-valent Fcγ-receptor engagement in in vitro and in vivo systems. In vitro engagement of hexameric-Fc with FcγRs showed complex binding interactions that altered with receptor density and triggered the internalisation and degradation of Fcγ-receptors. This caused a disruption of Fc-binding and phagocytosis. In vivo, in a mouse ITP model we observed a short half-life of hexameric-Fc but were nevertheless able to observe inhibition of platelet phagocytosis several days after hexameric-Fc dosing. In cynomolgus monkeys, we again observed a short half-life, but were able to demonstrate effective FcγR blockade. These findings demonstrate the ability of multi-valent Fc-based therapeutics to interfere with FcγR function and a potential mechanism through which they could have a sustained effect; the internalisation and degradation of FcγRs.

Detection of reverse transcriptase activity in human cells.

Samples of three nonmalignant and seven leukemic human cells were examined for DNA polymerase activity that could be identified as RNA tumor virus reverse transcriptase. Experiments on virus-infected model animal cells provided the basis for cell fractionation procedures, and reconstituted systems of known virus, added to human cells, established a threshold of virus detection by enzyme assay at 1 to 10 particles/cell. DNA polymerase activity with some properties similar to a reverse transcriptase was detected in some of the human leukemic cells. However, parallel analyses of nonmalignant cells showed sufficient similarities to raise serious questions about the specificity of the criteria. Reverse transcriptase activity has been reported to be present in white blood cells from a proportion of cases of leukemia; however, it is concluded from the present study that the usual enzymatic criteria using synthetic template primers, which were used in most of the studies reported, are not sufficient to identify a DNA polymerase activity as viral reverse transcriptase.