Confidence images for MR spectroscopic imaging

Automated spectral analysis and estimation of signal amplitudes from magnetic resonance data generally constitutes a difficult nonlinear optimization problem. Obtaining a measure of the degree of confidence that one has in the estimated parameters is as important as the estimates themselves. This is particularly important if clinical diagnoses are to be based on estimated metabolite levels, as in applications of MR Spectroscopic Imaging for human studies. In this report, a standard method of obtaining confidence intervals for nonlinear estimation is applied to simulated data and short-TE clinical proton spectroscopic imaging data sets of human brain. So-called "confidence images" are generated to serve as visual indicators of how much trust should be placed in interpretation of spatial variations seen in images derived from fitted metabolite parameter estimates. This method is introduced in a Bayesian framework to enable comparison with similar techniques using Cramer-Rao bounds and the residuals of fitted results.

Assessment of a polyester-covered nitinol stent in the canine aorta and iliac arteries

PURPOSE

To evaluate the patency and healing characteristics of a woven polyester fabric-covered stent in the canine model.

METHODS

Twenty-four self-expanding covered stents were placed in the infrarenal aorta and bilateral common iliac arteries of eight dogs and evaluated at 1 (n = 2), 3 (n = 2), and 6 (n = 4) months. Stent assessment was done using angiography prior to euthanasia, and light and scanning electron microscopy.

RESULTS

Angiographically, just prior to euthanasia, 8 of 8 aortic and 14 of 16 iliac endovascular covered stents were patent. Histologically, the stented regions showed complete endothelialization 6 months after graft implantation. A neointima had formed inside the stented vessel regions resulting in complete encasement of the fabric-covered stent by 3 months after graft implantation. Medial compression with smooth muscle cell atrophy was present in all stented regions. Explanted stent wires, examined by scanning electron microscopy, showed pitting but no cracks or breakage.

CONCLUSION

The covered stent demonstrated predictable healing and is effective in preventing stenosis in vessels 10.0 mm or greater in diameter but does not completely preclude stenosis in vessels 6.0 mm or less in diameter.

Thyroid cancer: patients' experiences of receiving iodine-131 therapy

PURPOSE/OBJECTIVES

To enhance understanding of the experiences and educational needs of patients receiving iodine-131 (131I) therapy for the treatment of thyroid cancer.

DESIGN

Qualitative design using interpretive description.

SETTING

A 24-bed oncology/acute-care medical unit in a large tertiary hospital in western Canada.

SAMPLE

5 men and 22 women (18-80 years of age) who have received 131I therapy in the past two years.

METHODS

Unstructured focus group and telephone interviews and field notes. Interviews were tape-recorded, transcribed verbatim, and subjected to thematic analysis.

FINDINGS

Researchers elicited four major themes from the analysis: (a) recognizing the totality of the cancer experience, (b) being isolated, (c) recognizing the totality of the treatment experience, and (d) understanding barriers to treatment.

CONCLUSIONS

Healthcare providers require a better understanding of thyroid disease and the treatment and side effects of 131I therapy. Furthermore, educational programs are required to adequately prepare nurses and patients for future care.

IMPLICATIONS FOR NURSING PRACTICE

A need exists to improve the care and education provided to patients receiving 131I therapy. In particular, recognition of the totality of the cancer experience and the need for both staff and patient education were illustrated. If nurses are to provide comprehensive cancer care, both psychosocial and physical needs must be addressed and fulfilling these needs requires a collaborative approach among patients, nurses, and other healthcare professionals.

Common and rare ABCA1 variants affecting plasma HDL cholesterol

Mutations in ABCA1, a member of the ATP-binding cassette family, have been shown to underlie Tangier disease (TD) and familial hypoalphalipoproteinemia (FHA), which are genetic disorders that are characterized by depressed concentrations of plasma high density lipoprotein (HDL) cholesterol. An important question is whether common variants within the coding sequence of ABCA1 can affect plasma HDL cholesterol in the general population. To address this issue, we developed a screening strategy to find common ABCA1 variants. This strategy involved long-range amplification of genomic DNA by using coding sequences only, followed by deep sequencing into the introns. This method helped us to characterize a new set of amplification primers, which permitted amplification of virtually all of the coding sequence of ABCA1 and its intron-exon boundaries with a single DNA amplification program. With these new sequencing primers, we found 3 novel ABCA1 mutations: a frameshift mutation (4570insA, A1484S-->X1492), a missense mutation (A986D) in a TD family, and a missense mutation (R170C) in aboriginal subjects with FHA. We also used these sequencing primers to characterize 4 novel common amino acid variants in ABCA1, in addition to 5 novel common silent variants. We tested for association of the ABCA1 I/M823 variant with plasma HDL cholesterol in Canadian Inuit and found that M823/M823 homozygotes had significantly higher plasma HDL cholesterol compared with subjects with the other genotypes. The results provide proof of principle of the effectiveness of this approach to identify both rare and common ABCA1 genomic variants and also suggest that common amino acid variation in ABCA1 is a determinant of plasma HDL cholesterol in the general population.

Parkinson's disease revisited

Parkinson's disease (PD) is a neurodegenerative disorder that affects an estimated 1 million persons in the United States each year. Although PD has been studied for almost 50 years, several shortcomings in management still exist. Symptom management, addressing movement disorders, psychological aspects, sexual dysfunction, and gastrointestinal concerns may all affect the person with PD.

Dynamic cerebral autoregulation in sick newborn infants

The sick newborn infant is vulnerable to brain injury and impaired cerebral autoregulation is thought to contribute to this. Coherent averaging is a method of measuring the dynamic cerebral autoregulatory response that is particularly suitable for neonates. We used this method in combination with a measure of the gradient of the cerebral blood flow velocity (CBFV) response following transient blood pressure (BP) peaks to study dynamic autoregulation in infants undergoing intensive care. Term and preterm infants at high risk of neurologic injury were compared with a control group of infants, also undergoing intensive care. Simultaneous video-EEG, CBFV (using transcranial Doppler), and arterial blood pressure measurements were obtained intermittently during a study period of at least 2 h. Cerebral autoregulatory response curves were constructed for high risk and control groups. Intact cerebral autoregulation produces a characteristic response consisting of a brief period when CBFV follows arterial blood pressure but quickly returns to baseline value. An impaired autoregulatory response shows CBFV mirroring the arterial blood pressure curve closely. Thirteen high-risk infants, who also had seizures (10 term and 3 preterm) and 12 control infants (6 term and 6 preterm) were studied. Autoregulation was absent in high-risk term and preterm infants. It was also absent in preterm control infants. Term, neurologically healthy infants undergoing intensive care have an intact autoregulatory response. The constant passive response seen in high-risk infants may reflect the severity of the underlying neurologic disease.

Department of Veterans Affairs Cooperative Studies Program genetic linkage study of schizophrenia: ascertainment methods and sample description

To help clarify the genetics of schizophrenia, the Department of Veterans Affairs Cooperative Studies Program has completed data collection for a genetic linkage study of schizophrenia. This article describes the methodological details of the data collection. Subsequent articles will describe the results of our genome scan, which is now in progress. The data collection protocol included the Diagnostic Interview for Genetic Studies, the Family Interview for Genetic Studies, a review of medical records, and the collection of blood for transformation into lymphoblast cell lines. Among relatives of schizophrenic probands, we assessed auditory attention and verbal memory with neuropsychological tests. Among the 166 families ascertained for the study, 143 had a single affected sib-pair, 17 had three affected siblings, one had five affected siblings and five had two sets of affected siblings. There was a total of 216 affected sib-pairs in these families. Using the n-1 rule, these families contain 188 independent affected sib-pairs.

Generalising to theory: the use of a multiple case study design to investigate needs assessment and quality of care in community nursing

This paper outlines the detail of the case study method used in a project commissioned by the English National Board for Nursing, Midwifery and Health Visiting (ENB) to investigate the changing educational needs of community nurses with regard to needs assessment and quality of care in the context of the NHS and Community Care Act, 1990. It explains the methodological procedures and analytic processes which led to integration of data across the whole study, focusing on the role of a prior theoretical framework in case study design. Recently qualified practitioners (health visitors and district nurses) were observed during a regular shift (N=134 visits), concentrating on their practice of assessing needs, and on liaison and collaboration within teams and across sectors. They were interviewed after the observation period (N=33 practitioners), to determine the extent of formality they attached to each assessment, and elicit information about aspects which may be embedded in everyday practice as well as those recorded for explicit requirements.The preliminary analysis resulted in the modification of a model for assessing service quality, and identified various points where a 'policy-practice gap' might arise between policies and practice in both the health service and education. The practicalities of operationalising a multiple case study design into research are highlighted, and the mechanism for 'generalising to theory' illustrated.

Tacrolimus (FK 506) induced thrombotic thrombocytopenic purpura after ABO mismatched second liver transplantation: salvage with plasmapheresis and prostacyclin

We report the course of thrombotic thrombocytopenic purpura (TTP) in a patient receiving tacrolimus (FK506) immunosuppression for an ABO mismatched second liver graft. A Chinese woman with fulminant hepatitis-B reactivation failed a living-related orthotopic liver transplantation (OLT) due to portal vein thrombosis. An ABO mismatched cadaveric OLT (group A to O) was performed, with peri-operative plasmapheresis to reduce anti-A hemagglutinin titers. On day 30, she developed fever, hemolysis, thrombocytopenia and neurologic dulling. Prominent microangiopathic features in peripheral blood film, and characteristic brain lesions on magnetic resonance imaging confirmed TTP. She responded initially to intensive plasmapheresis with cryosupernatant replacement, and withdrawal of FK506. An attempted reintroduction of FK506 for threatened rejection led to TTP exacerbation. This was controlled with prolonged plasmapheresis and a ten-day infusion of prostacyclin. Immunosuppression was changed to mycophenolate mofetil. By day 53, the peripheral film and lactate dehydrogenase level had returned to baseline and plasmapheresis was stopped.

Sentinel node biopsy and internal mammary lymphatic mapping in breast cancer

BACKGROUND

Currently outer quadrant breast tumors are not felt to have significant drainage to the internal mammary nodal chain. We evaluated the incidence of internal mammary sentinel nodes (IMSN) found with lymphoscintigraphy for all breast quadrants.

METHODS

Eighty women were prospectively studied by technitium-sulfur colloid injection, nuclear medicine imaging, and intraoperative gamma probe identification of sentinel nodes. IMSN detected were surgically removed.

RESULTS

Ten of 80 ( 12%) patients had IMSN identified in addition to axillary sentinel nodes (AXSN). Four tumors were located medially, 6 (60%) were in the outer quadrants. Metastatic disease was present in 3 of 10 women. Patients with positive IMSN also had positive AXSN.

CONCLUSIONS

Patients undergoing lymphatic mapping for the management of breast cancer should have radiolabelled tracer and gamma probe sentinel node identification regardless of tumor location in the breast.

Proton NMR chemical shifts and coupling constants for brain metabolites

Proton NMR chemical shift and J-coupling values are presented for 35 metabolites that can be detected by in vivo or in vitro NMR studies of mammalian brain. Measurements were obtained using high-field NMR spectra of metabolites in solution, under conditions typical for normal physiological temperature and pH. This information is presented with an accuracy that is suitable for computer simulation of metabolite spectra to be used as basis functions of a parametric spectral analysis procedure. This procedure is verified by the analysis of a rat brain extract spectrum, using the measured spectral parameters. In addition, the metabolite structures and example spectra are presented, and clinical applications and MR spectroscopic measurements of these metabolites are reviewed.

Proton NMR chemical shifts and coupling constants for brain metabolites

Proton NMR chemical shift and J-coupling values are presented for 35 metabolites that can be detected by in vivo or in vitro NMR studies of mammalian brain. Measurements were obtained using high-field NMR spectra of metabolites in solution, under conditions typical for normal physiological temperature and pH. This information is presented with an accuracy that is suitable for computer simulation of metabolite spectra to be used as basis functions of a parametric spectral analysis procedure. This procedure is verified by the analysis of a rat brain extract spectrum, using the measured spectral parameters. In addition, the metabolite structures and example spectra are presented, and clinical applications and MR spectroscopic measurements of these metabolites are reviewed.

Interrelations between plasma homocysteine and intracellular S-adenosylhomocysteine

S-Adenosylhomocysteine, a potent intracellular methylation inhibitor, is suggested as a potential mediator for hyperhomocysteinemia-related vascular changes. We investigated the effect of acute and chronic hyperhomocysteinemia on intracellular S-adenosylhomocysteine and S-adenosylmethionine in rats and humans. Elevated plasma homocysteine in rats infused with homocysteine produced an increase in S-adenosylhomocysteine (P < 0.001) but not S-adenosylmethionine levels (P > 0.05) in various rat tissues. However intraerythrocyte S-adenosylhomocysteine and S-adenosylmethionine levels were not changed in homocysteine-infused rats and human subjects with experimentally acute hyperhomocysteinemia by methionine loading test. In contrast, erythrocyte S-adenosylhomocysteine levels were significantly higher in chronic renal failure patients, who had chronically elevated plasma homocysteine levels, than in either vascular disease patients or healthy controls (P < 0.05). In conclusion, acute hyperhomocysteinemia can increase intracellular S-adenosylhomocysteine levels in tissues actively involved in homocysteine metabolism. The findings are relevant to homocysteine-related endothelial dysfunction since S-adenosylhomocysteine modulates endothelial cell apoptosis.

Assessment of a polyester-covered nitinol stent in an atherosclerotic swine model

PURPOSE

To evaluate the short-term patency and healing characteristics of the Cragg EndoPro covered stent in an atherosclerotic model as one of the Food and Drug Administration requirements before possible approval of the device for human use in the United States.

MATERIALS AND METHODS

Seventeen self-expanding stent-grafts were placed in the aorta and right and left iliac arteries of six Yucatan microswine exposed to a regimen of accelerated atherosclerosis. The stent-grafts were constructed from nitinol wire formed into a tubular zigzag configuration. The stent frame was covered by a thin woven polyester fabric tube, with medium permeability, available in multiple diameters and lengths. The animals were killed at 24 hours, 3 months, and 6 months. Assessment was done by angiography and histology.

RESULTS

All stents were patent immediately after deployment. Two stents were occluded at follow-up, indicating an 88% patency rate. Minor lumen narrowing was found at the follow-up intervals. Histologic examination revealed a mixture of mature and immature endothelial cells lining both the native and stented regions in all vessels examined. The new endoluminal surface was composed primarily of fibrocollagen and elastic fibers and smooth muscle cells. Intimal thickness was inversely correlated to medial thickness. Medial compression with atrophy was observed routinely with rare necrosis. Complete tissue ingrowth was seen by 3 months. The degree of vascular inflammation increased over time, as well as the foreign body giant cell reaction to the polyester fabric.

CONCLUSION

The patency rate does not appear to be better than that with angioplasty or noncovered stent placement in the studied time frame. The progressive vascular inflammatory changes noted should be further investigated in longer-term animal trials to ensure its safety in humans because this device is meant to be permanent.

Cervical pathology in West Virginia adolescents

Cytologic screening is an important diagnostic tool used to detect precancerous and cancerous lesions of the cervix. We studied the prevalence of cervical abnormalities, based on Pap smear results, in patients at the Outpatient Adolescent Clinic at West Virginia University. We found a high incidence of overall intraepithelial cell pathology (24%) in this group with 2.4% high grade and 9.9% low-grade lesions. These findings show that major cervical pathology is present in this age group. Furthermore, repeat smears at intervals of < one year were performed on 317 patients. Of these repeat smears, 7% changed from normal to abnormal in this period. Sexually active adolescent females should have Pap smears at least annually to detect abnormalities that may otherwise not be detected until they are more advanced and difficult to manage. Higher risk adolescents may need semiannual screening.

Skeletal muscle contractile and noncontractile components in young and older women and men

To examine the influences of age, gender, and habitual physical activity level on human skeletal muscle composition, we developed a relatively simple magnetic resonance imaging method for the quantitation of leg anterior compartment contractile and noncontractile content. We studied 23 young (11 women and 12 men, 26-44 yr old) and 21 older (10 women and 11 men, 65-83 yr old) healthy adults. Analysis was by two-factor (age, gender) ANOVA. Physical activity, quantitated by three-dimensional accelerometer worn about the waist for 1 wk, was not different between groups. Men had larger contractile and noncontractile cross-sectional areas (cm(2)) than women, with no gender effect on percent noncontractile area. Young subjects had larger contractile areas and smaller absolute (cm(2)) and relative (percent total) noncontractile areas than older subjects. There was a significant linear relationship between physical activity and percent noncontractile area in older (r = -0.68, P = 0.002) but not young subjects. These data demonstrate a more than twofold increase in the noncontractile content of locomotor muscles in older adults and provide novel support for physical activity as a modulator of this age-related change in muscle composition.

The effect of vitamin-mineral supplementation on the intelligence of American schoolchildren: a randomized, double-blind placebo-controlled trial

CONTEXT

Many medical, nutrition, and education professionals have long suspected that poor diet impairs the academic performance of Western schoolchildren; academic performance often improves after improved diet. However, others have suggested that such academic gains may be due to psychologic effects rather than nutrition. To resolve this issue, two independent research teams conducted randomized trials in which children were given placebos or low-dose vitamin-mineral tablets designed to raise nutrient intake to the equivalent of a well-balanced diet. Both teams reported significantly greater gains in nonverbal intelligence among the supplemented groups. The findings were important because of the apparent inadequacy of diet they revealed and the magnitude of the potential for increased intelligence. However, none of the ten subsequent replications, or the two original trials, were without limitations leaving this issue in controversy.

OBJECTIVES

To determine if schoolchildren who consume low-dose vitamin-mineral tablets will have a significantly larger increase in nonverbal intelligence than children who consume placebos in a study that overcomes the primary criticisms directed at the previous 12 controlled trials.

DESIGN

A double-blind, placebo-controlled trial using stratified randomization within each teacher's class based on preintervention nonverbal intelligence.

SETTINGS AND SUBJECTS

Two "working class," primarily Hispanic, elementary schools in Phoenix, Arizona, participated in the study. Slightly more than half the teachers in each school distributed the tablets daily to 245 schoolchildren aged 6 to 12 years.

INTERVENTION

Daily vitamin-mineral supplementation at 50% of the U.S. daily recommended allowance (RDA) for 3 months versus placebo.

OUTCOME MEASURES

Post-test nonverbal IQ, as measured by the Wechsler Intelligence Scale for Children-Revised (WISC-R), while controlling for pretest nonverbal IQ as a covariate. FOUR MAIN RESULTS: First, a significant difference of 2.5 IQ points (95% CI: 1.85-3.15) was found between 125 children given active tablets and 120 children given placebo tablets (p = 0.038). Second, this finding is consistent with the mean 3.2 IQ point net gain found in the 12 similar but less rigorous studies. Third, a significantly higher proportion of children in the active group gained 15 or more IQ points when compared to the placebo group (p < 0.01). Fourth, although 81 matched pairs produced no difference at all in nonverbal IQ gain, the modest 2.5 IQ point net gain for the entire sample can be explained by the remaining 24 children who took active tablets, and had a 16 point higher net gain in IQ than the remaining 19 placebo controls.

CONCLUSIONS

This study confirms that vitamin-mineral supplementation modestly raised the nonverbal intelligence of some groups of Western schoolchildren by 2 to 3 points but not that of most Western schoolchildren, presumably because the majority were already adequately nourished. This study also confirms that vitamin-mineral supplementation markedly raises the non-verbal intelligence of a minority of Western schoolchildren, presumably because they were too poorly nourished before supplementation for optimal brain function. Because nonverbal intelligence is closely associated with academic performance, it follows that schools with children who consume substandard diets should find it difficult to produce academic performance equal to those schools with children who consume diets that come closer to providing the nutrients suggested in the U.S. RDA. The parents of schoolchildren whose academic performance is substandard would be well advised to seek a nutritionally oriented physician for assessment of their children's nutritional status as a possible etiology.

Popular cinema and lesbian interpretive strategies

In its examination of the relationship between popular film and lesbian viewing practices, this study attempts to more fully elucidate current ideas around audience engagement and forms of cultural reception. Drawing on 15 in-depth interviews conducted in Western Canada in 1996, the results clearly demonstrate the existence of active lesbian viewers, whose interpretations of popular film are intimately informed by lesbian-specific life experiences and cultural competencies. Although the social conditions which create the need for resistant viewing are themselves oppressive, subversion of mainstream film holds out some possibility of empowerment for lesbian viewers.

A taxonomy of needs assessment, elicited from a multiple case study of community nursing education and practice

The role and expectations of community nurses in carrying out needs assessments changed when an internal quasi-market was introduced to the British health service under the National Health Service (NHS) & Community Care Act 1990. This paper reports on a study commissioned by the English National Board for Nursing, Midwifery and Health Visiting (ENB) to investigate the changing educational needs of community nurses with regard to needs assessment in the context of this legislation. A multiple case study design was utilized and four cases identified, incorporating the geographical variation in England. Recently qualified practitioners (health visitors and district nurses) were observed during a regular shift (n=134 visits), concentrating on their practice of assessing needs, and on liaison and collaboration within teams and across sectors. Participants were interviewed after the observation period (n=33 practitioners), to determine the extent of formality they attached to each assessment, and to elicit information about aspects which may be embedded in everyday practice. Single and multiple case analyses across the four cases used an iterative process of pattern-matching, replication logic and explanation building. The preliminary analysis yielded a descriptive 'taxonomy' which could serve as a basis for classifying the variants of needs assessment and help to clarify the whole phenomenon. When applied further to the data, this revealed the complex interactions between the different ideals (relating to policy, nursing and ascribed worth), the various types (purpose, formality/specificity and complexity) and timing (in relation to client, service and practice issues) within needs assessment.

Computer model for cryosurgery of the prostate

The objective of this study was to devise an interactive tool to assist in cryoablation therapy through computer modeling, simulation, and visualization. CryoSim, a software package, accepts a set of acquired and processed three-dimensional ultrasound images, then models heat diffusion (formation of the iceball) based on numerical approximation of the heat equation and knowledge of the thermal properties of the underlying tissues. Results of cryoexperiments were found to be significantly similar to those generated by CryoSim. Therefore, CryoSim provides a viable technique for predicting the outcome of cryosurgery, and establishes a platform for future automation of cryosurgery.

Inhibition of IMP-1 metallo-beta-lactamase and sensitization of IMP-1-producing bacteria by thioester derivatives

IMP-1 metallo-beta-lactamase is a transferable carbapenem-hydrolyzing enzyme found in some clinical isolates of Pseudomonas aeruginosa, Serratia marcescens and Klebsiella pneumoniae. Bacteria that express IMP-1 show significantly reduced sensitivity to carbapenems and other beta-lactam antibiotics. A series of thioester derivatives has been shown to competitively inhibit purified IMP-1. As substrates for IMP-1, the thioesters yielded thiol hydrolysis products which themselves were reversible competitive inhibitors. The thioesters also increased sensitivity to the carbapenem L-742,728 in an IMP-1-producing laboratory stain of Escherichia coli, but will need further modification to improve their activity in less permeable organisms such as Pseudomonas and Serratia. Nonetheless, the thioester IMP-1 inhibitors offer an encouraging start to overcoming metallo-beta-lactamase-mediated resistance in bacteria.

Spectral simulations incorporating gradient coherence selection

Computer-aided methods can considerably simplify the use of the product operator formalism for theoretical analysis of NMR phenomena, which otherwise becomes unwieldy for anything but simple spin systems and pulse sequences. In this report, two previously available programming approaches using symbolic algebra (J. Shriver, Concepts Magn. Reson. 4, 1-33, 1992) and numerical simulation using object-oriented programming (S. A. Smith, T. O. Levante, B. H. Meier, and R. R. Ernst, J. Magn. Reson. A 106, 75-105, 1994) have been extended to include the use of gradient operators for simulation of spatially localized NMR spectroscopy and gradient coherence selection. These methods are demonstrated using an analysis of the response of an AX(3) spin system to the STEAM pulse sequence and verified with experimental measurements on lactate.

Mobile elements carrying ermF and tetQ genes in gram-positive and gram-negative bacteria

Bacteroides spp. conjugative transposon Tn5030 is 150 kb which includes a 43 kb characterized region containing a number of defined genes and an open reading frame (ORF). The 43 kb region is organized with the ORF1 immediately upstream from the ermF gene, coding for an rRNA methylase, then an unknown 20 kb region downstream followed by the tetQ gene (coding for a ribosomal protection protein) then the rteA and rteB genes. The role of ORF1 is unclear; rteA is a putative sensor and rteB a regulator. Thirty-seven (62%) of 60 isolates, representing one gram-positive anaerobic and 13 gram-negative anaerobic species, co-transferred the ermFand tetQ genes to an unrelated Enterococcus faecalis recipient. We used the polymerase chain reaction to show the linkage between ORF1, ermF, tetQ, rteA and rteB. Our data suggest that the ORF1 gene product may participate in the transfer of the ermF gene with or without the ORF1-rteB region and has homology to bacterial transposases. Isolates that co-transferred the ermF and tetQ genes carried and transferred the rteB gene, suggesting that the rteB gene product may be important in transfer of the 43 kb ORF1-rteB region to E. faecalis. The rteB gene product is not required when ermF is transferred independently of tetQ.