Suppression of sustained ventricular tachyarrhythmias: a comparison of d,l-sotalol with no antiarrhythmic drug treatment

CONTEXT: Antenatal corticosteroids for fetal maturation have been underused, despite evidence for their benefits in cases of preterm birth. OBJECTIVE: To evaluate dissemination strategies aimed at increasing appropriate use of this therapy. DESIGN AND SETTING: Twenty-seven tertiary care institutions were randomly assigned to either usual dissemination of practice recommendations (n = 14) or usual dissemination plus an active, focused dissemination effort (n = 13). SUBJECTS: Obstetricians and their preterm delivery cases at participating hospitals. INTERVENTION: Recommendations by a National Institutes of Health (NIH) Consensus Conference held in late February-early March 1994 were disseminated in early May 1994. Usual dissemination was publication of the recommendations and endorsement by the American College of Obstetricians and Gynecologists. Active dissemination was a year-long educational effort led by an influential physician and a nurse coordinator at each facility, consisting of grand rounds, a chart reminder system, group discussion of case scenarios, monitoring, and feedback. MAIN OUTCOME MEASURE: Use or nonuse of antenatal corticosteroids was abstracted from medical records of eligible women delivering at the participating hospitals in the 12 months immediately prior to release of the NIH recommendations (average number of records abstracted, 130) and in the 12 months following their release (average number of records abstracted, 122). RESULTS: Active dissemination significantly increased the odds of corticosteroid use after the conference. Use increased from 33.0% of eligible patients receiving corticosteroids to 57.6%, or by 75% over baseline, in usual dissemination hospitals. Use increased from 32.9% to 68.3%, oran 108% increase, in active dissemination hospitals. Gestational age and maternal diagnosis affected use of the therapy in complex ways. CONCLUSION: An active, focused dissemination effort increased the effectiveness of usual dissemination methods when combined with key principles to change physician practices.     

Spinal arteriovenous malformations

Spinal cord arteriovenous malformations encompass a variety of distinct lesions with aberrant connections between the arterial and venous circulation. Symptomatology and clinical presentation of such lesions are directly related to their location and particular pathophysiology. In the authors' surgical experience, 90% of patients have had the same or improved neurologic function and long-term follow-up.     

Urokinase-type plasminogen activator receptor reversibly dissociates from complement receptor type 3 (alpha M beta 2' CD11b/CD18) during neutrophil polarization

Previous studies have shown that the leukocyte integrin CR3 (CD11b/CD18) is physically associated with the urokinase-type plasminogen activator receptor (uPAR;CD87), a glycosyl-phosphatidylinositol (GPI)-linked protein, in resting neutrophil membranes. We now show that uPAR-to-CR3 interactions are reversible, correlating with cell shape. Neutrophils were first labeled with fluorescein conjugates of anti-CR3 F(ab')2 fragments followed by capping using a second-step F(ab')2 directed against murine F(ab')2s. Cells were then probed using rhodamine-conjugated anti-uPAR F(ab')2s. Although uPAR co-caps with CR3 on resting cells, uPAR was found to dissociate or uncap coincident with spontaneous cell polarization for migration. CR3 caps transformed into uropods while uPAR accumulated at lamellipodia of polarized cells. Capping was unnecessary for the observed distribution of CR3 and uPAR since the anti-CR3 and anti-uPAR F(ab')2s traffic to the uropod and lamellipodium, respectively, during polarization of uncapped cells. These receptors reassociate when cells return to a spherical morphology. In contrast to uPAR, Fc gamma RIIIB did not dissociate from CR3 caps during cell polarization. Resonance energy transfer (RET) microscopy was used to image the spatial distribution of RET and to follow the kinetics of association and dissociation. Initial levels of RET dramatically fell during cell polarization, but did not change on cells fixed with paraformaldehyde. Receptor reassociation was a biphasic process with initial reassociation about the perimeter of a cap, followed by a plateau and a slower rise in RET within a cap. We suggest that cells regulate receptor-receptor associations depending upon their physiologic activities.     

Live analysis of free centrosomes in normal and aphidicolin-treated Drosophila embryos

In a number of embryonic systems, centrosomes that have lost their association with the nuclear envelope and spindle maintain their ability to duplicate and induce astral microtubules. To identify additional activities of free centrosomes, we monitored astral microtubule dynamics by injecting living syncytial Drosophila embryos with fluorescently labeled tubulin. Our recordings follow multiple rounds of free centrosome duplication and separation during the cortical division. The rate and distance of free sister centrosome separation corresponds well with the initial phase of associated centrosome separation. However, the later phase of separation observed for centrosomes associated with a spindle (anaphase B) does not occur. Free centrosome separation regularly occurs on a plane parallel to the plasma membrane. While previous work demonstrated that centrosomes influence cytoskeletal dynamics, this observation suggests that the cortical cytoskeleton regulates the orientation of centrosome separation. Although free centrosomes do not form spindles, they display relatively normal cell cycle-dependent modulations of their astral microtubules. In addition, free centrosome duplication, separation, and modulation of microtubule dynamics often occur in synchrony with neighboring associated centrosomes. These observations suggest that free centrosomes respond normally to local nuclear division signals. Disruption of the cortical nuclear divisions with aphidicolin supports this conclusion; large numbers of abnormal nuclei recede into the interior while their centrosomes remain on the cortex. Following individual free centrosomes through multiple focal planes for 45 min after the injection of aphidicolin reveals that they do not undergo normal modulation of their astral dynamics nor do they undergo multiple rounds of duplication and separation. We conclude that in the absence of normally dividing cortical nuclei many centrosome activities are disrupted and centrosome duplication is extensively delayed. This indicates the presence of a feedback mechanism that creates a dependency relationship between the cortical nuclear cycles and the centrosome cycles.     

Mapping a conserved conformational epitope from the M protein of group A streptococci

The carboxyl terminus of the M protein of group A streptococci (GAS) is highly conserved and contains epitopes that have been shown to induce opsonic antibodies and protection against GAS infection. This region of the protein can also stimulate T cells, which can react in vitro with heart antigens. Since different segments of the carboxyl terminus may be involved in immunity to GAS and in the pathogenesis of autoimmune disease (rheumatic heart disease), it is important to precisely define critical epitopes. However, the M protein is known to be a coiled coil, and a critical immunodominant antibody-binding epitope within this region (peptide 145, a 20-mer with the sequence LRRDLDASREAKK-QVEKALE) is shown here to be conformational. Thus, small synthetic overlapping peptides of 8-12 amino acids in length that span peptide 145 (p145) were unable to capture antibodies present in p145-immune mouse sera or in endemic human sera, even though antibodies raised to these small peptides coupled to diphtheria toxoid could bind the smaller peptides and, in some cases, p145. A series of mutated peptides in which every residue of p145 was sequentially altered also failed to identify critical residues for antibody binding. We thus devised a strategy to produce chimeric peptides in which small peptides copying the M protein sequence were displayed within a larger 28-mer peptide derived from the sequence of the GCN4 leucine zipper DNA binding protein of yeast. A 12-amino-acid window of the p145 sequence was inserted into the GCN4 peptide in such a way as to preserve any potential helical structure. The window was moved along one residue at a time to give a series of peptides representing p145. Circular dichroism demonstrated that these larger chimeric peptides and p145, but not a shorter 12-mer peptide, displayed alpha-helical potential in 50% trifluoroethanol. Certain chimeric peptides efficiently captured antibodies specific for p145 and thus enabled us to map the minimal antibody-binding sequence. RRDLDASREAKK, referred to as J(1)2. The chimeric peptide containing this sequence, referred to as J2, was able to inhibit opsonization of GAS by human antisera containing anti-peptide 145 antibodies. The T-cell response from p145-immunized responder B10.BR mice to J2 and J(I)2 was much lower than the response to p145 and mapped to a different peptide.