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Biomedical subjects

D D Brown

Publications and source records attributed to D D Brown.

At least 91 records · Page 5Linked to original sources
PubMed1987

Self-adhesive monitor/defibrillation pads improve prehospital defibrillation success.

We compared self-adhesive, dual-function monitor/defibrillation electrode pads to standard chest monitoring leads and hand-held electrode paddles in the management of prehospital ventricular fibrillation in a single urban paramedic service. Shocks were delivered more quickly following paramedic arrival with self-adhesive pads than with hand-held paddles (1.6 vs 2.5 min; P less than .001). Ventricular fibrillation was terminated more frequently when shocks were delivered using the self-adhesive pads (55 of 58 patients, 95%) than when shocks were delivered using hand-held paddles (49 of 69 patients, 71%; P less than .005). Initial shocks delivered with self-adhesive pads were especially effective, converting 40 of 58 (69%) patients to an organized rhythm on the first or second shock; this was true of only 24 of 69 (35%) patients shocked with hand-held paddles (P less than .001). Patient survival to hospital admission improved when self-adhesive pads were used: 30 of the 58 (52%) patients shocked with self-adhesive pads achieved hospital admission, while only 21 of 69 patients (30%; P less than .025) survived to admission when hand-held paddles were used. In addition, electrical artifact that interfered with accurate rhythm interpretation was far more prevalent when standard monitoring electrodes were used, including artifact that resulted in inappropriate shock delivery (23% of patients monitored with standard electrodes vs 3% of patients monitored with self-adhesive pads; P less than .005). Self-adhesive monitor/defibrillation pads are superior to standard monitoring leads and hand-held electrode paddles in the management of prehospital ventricular fibrillation.

Adhesives↗
PubMed1987

Electrically evoked brainstem responses in cochlear implant recipients.

Electrical stimulation of the auditory nerve in the profoundly deaf population through implanted cochlear prostheses has increased the need for reliable electrophysiologic assessment tools. We have recorded electrically evoked brainstem responses (EABRs) in 21 subjects who have received a 3M/House cochlear implant. Recordings have been made, both intraoperatively and postoperatively, in the laboratory setting. The recording technique, methods of stimulus artifact suppression, and results of our measurements are described. Clinical applications of this technology are suggested.

Adolescent↗
PubMed1986

DNA replication in vitro erases a Xenopus 5S RNA gene transcription complex.

Replication of the Xenopus laevis 5S RNA gene in vitro is unimpeded by the presence of a complete transcription complex assembled on the internal control region of the gene. The transcription complex is disrupted by passage of the replication fork, specific transcription factors are displaced, and the daughter 5S RNA genes are inactivated. We have been unable to demonstrate that any "memory" of the preexisting transcription complex is transmitted to the daughter DNA duplexes following replication.

Animals↗
PubMed1986

The developmental expression of the gene for TFIIIA in Xenopus laevis.

The sequence of the trans-acting positive transcription factor TFIIIA has been deduced by sequencing cDNA and genomic DNA clones. Using DNA from a homozygous diploid animal we show that there is one gene for TFIIIA per haploid genome of X. laevis. Protein sequencing of proteolytic fragments of TFIIIA orients the protein in its interaction with the internal control region (ICR) of the 5S RNA gene. The protein lies along the DNA with its carboxyl terminus at the 5' end of the ICR and its amino terminus at the 3' end. The developmental pattern of TFIIIA and its mRNA during oogenesis and embryogenesis are consistent with the idea that the abundance of TFIIIA plays an essential role in the developmental change in 5S RNA gene expression. The change to almost exclusive somatic 5S RNA gene expression by gastrulation occurs using either the TFIIIA that was synthesized by oocyte and/or TFIIIA synthesized from maternal mRNA.

Amino Acid Sequence↗
PubMed1986

A bacteriophage RNA polymerase transcribes through a Xenopus 5S RNA gene transcription complex without disrupting it.

Conditions are described for programming with active transcription complexes essentially all the Xenopus 5S RNA genes added to an extract of Xenopus oocyte nuclei. We call this rate enhancement. Transcription by SP6 RNA polymerase of either strand of a Xenopus 5S RNA gene is unimpeded by the presence of a complete transcription complex associated with the internal control region of the gene. Furthermore, the transcription complex remains stably associated with the 5S RNA gene following multiple transits by the prokaryotic polymerase.

Animals↗
PubMed1986

Refibrillation managed by EMT-Ds: incidence and outcome without paramedic back-up.

Some patients converted from ventricular fibrillation to organized rhythms by defibrillation-trained ambulance technicians (EMT-Ds) will refibrillate before hospital arrival. The authors analyzed 271 cases of ventricular fibrillation managed by EMT-Ds working without paramedic back-up. Of 111 patients initially converted to organized rhythms, 19 (17%) refibrillated, 11 (58%) of whom were reconverted to perfusing rhythms, including nine of 11 (82%) who had spontaneous pulses prior to refibrillation. Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not (53% versus 76%, P = NS), although discharge rates were virtually identical (37% and 35%, respectively). Scene-to-hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome. Defibrillation-trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back-up is not available.

Allied Health Personnel↗
PubMed1986

Efficacy of an automated external defibrillator in the management of out-of-hospital cardiac arrest: validation of the diagnostic algorithm and initial clinical experience in a rural environment.

Automatic external defibrillators (AEDs) may have advantages over manual defibrillation in managing prehospital cardiac arrest, particularly in rural communities. We conducted a two-part evaluation of a commercially available AED. We first established the diagnostic accuracy of the AED's rhythm recognition algorithm by challenging it with 205 cardiac arrest rhythms previously recorded from actual patients in the field. The AED demonstrated 100% specificity and 92% sensitivity for ventricular fibrillation (VF) in this nonclinical setting. We then compared the clinical efficacy of AEDs in 18 small communities (study group) with that of manual defibrillation in 18 additional communities (control group) of similar size. Ambulance technicians using manual defibrillators correctly diagnosed VF more frequently than the AEDs (98% vs 83%; p less than .025). Specificity for VF was similar in the two groups (100% for AEDs vs 94% for technicians; p greater than .10). AEDs were able to deliver shocks more quickly than was possible with the manual defibrillators (1.56 vs 2.77 min; p less than .001). The ability of the AEDs to terminate VF was excellent, converting VF in 28 of 29 (97%) patients to some other rhythm compared with only 37 of 53 (70%) patients in the control group (p less than .01). Hospital admission and discharge rates were similar for the two groups. Ten of the 35 (29%) patients managed with AEDs achieved admission and six (17%) were ultimately discharged. In the control group 17 of 53 (33%) patients with VF were admitted and seven (13%) were discharged (p less than .75). AEDs are an effective alternative to manual defibrillation in small communities.

Diagnosis, Computer-Assisted↗
PubMed1986

Special considerations for defibrillation performed by emergency medical technicians in small communities.

Defibrillation by minimally trained ambulance technicians can significantly improve survival after out-of-hospital cardiac arrest in communities of all sizes. However, special consideration must be given to the development of such services in small communities, chiefly because of problems associated with the low volume of true emergency calls. Communities considering implementing programs by which defibrillation is performed by the emergency medical technician (EMT-D) must first evaluate their ambulance response times and, if inadequate, alter their system of ambulance response. After implementation of such a program, a permanent, formal skill maintenance program must be established. Defibrillation protocols must allow for the fact that many patients will refibrillate after successful conversion, yet no advanced care beyond the defibrillator will generally be available. Finally, every community instituting an EMT-D program must maintain a system of monitoring EMT performance and patient outcome that documents acceptable survival-to-discharge rates as well as the safety of the program. For smaller communities a regional or statewide evaluation system may be preferable to individual community programs.

Allied Health Personnel↗
PubMed1985

Formation and stability of the 5 S RNA transcription complex.

5 S ribosomal RNA in Xenopus has been shown to be transcribed in vitro from 5 S RNA genes that remain stably associated with required transcription factors through multiple rounds of transcription (Bogenhagen, D. F., Wormington, W. M., and Brown, D. D. (1982) Cell 28, 413-421). We have studied the formation and stability of these "transcription complexes" by using cloned 5 S RNA genes immobilized on cellulose as templates for the assembly of complexes in crude extracts. RNA polymerase III is the least tightly bound component required for transcription of 5 S RNA genes. All other factors remain bound in 1 M NaCl, even though transcription complexes do not form at salt concentrations as low as 0.25 M. RNA polymerase III dissociates from transcription complexes as a result of RNA synthesis and is capable of reassociating with complexes to support additional rounds of transcription. A 5 S-specific positive transcription factor (factor A) and two crude phosphocellulose column fractions (B and C) are also required for 5 S RNA synthesis in vitro (Engelke, D. R., Ng, S.-Y., Shastry, B. S., and Roeder, R. G. (1980) Cell 19, 717-728; Segall, J., Matsui, T., and Roeder, R. G. (1980) J. Biol. Chem. 255, 11986-11991; Shastry, B. S., Ng, S.-Y., and Roeder, R. G. (1982) J. Biol. Chem. 257, 12979-12986). Fraction B stably interacts with 5 S RNA genes to form a stable, active complex only after the template has first been incubated with factor A and fraction C. In contrast, either factor A or fraction C can stably associate with 5 S RNA genes in the absence of other factors. The activities of fractions B and C are removed from solution as a result of transcription complex formation, suggesting the factors in these fractions act stoichiometrically. The rate-limiting step in complex formation is carried out by fraction B, which accounts for the lag in transcription activity observed in crude extracts.

Animals↗
PubMed1985

A positive transcription factor controls the differential expression of two 5S RNA genes.

Somatic 5S RNA genes are transcribed preferentially over oocyte 5S RNA genes by 25- to greater than 200-fold when mixtures of cloned genes are injected into cleaving Xenopus embryos. This preference is an order of magnitude greater than that observed in cell-free extracts. Mutations that decrease the binding of the 5S RNA gene-specific transcription factor TFIIIA to the 5S RNA genes' internal control regions are exaggerated when assayed by embryo injection compared to in vitro transcription. Injection of TFIIIA into cleaving embryos greatly increases endogenous oocyte 5S RNA synthesis at midblastula even when DNA replication is inhibited. Much, but not all, of the preference for somatic over oocyte 5S RNA gene transcription in somatic cells can thus be attributed to the concentration of TFIIIA and to differences in binding constants of TFIIIA to the internal control regions of the two types of genes.

Animals↗
PubMed1985

A comparison of four empathy instruments in simulated patient-medical student interactions.

Prior investigations of empathy in medicine have used several available instruments for assessment, including a scale developed by Hornblow, Hogan's empathy scale, the Carkhuff-Truax empathic understanding scale, and the Barrett-Lennard relationship inventory. The purpose of the study reported in this article was to investigate the intercorrelations of the scores on these four instruments when used in a medical student-simulated patient interaction. The results showed that measures of empathy based on observed behavior of the students were highly intercorrelated but that empathy self-assessed by the students themselves as having that trait did not correlate significantly with any of the behavior-based measures. No significant effect on these findings was attributable to the timing of the instrument administration, to the students' interpersonal skills training or experience in taking histories and performing physical examinations, or to the sex of the students and the observers.

Clinical Competence↗
PubMed1985

The effectiveness of continuing medical education in changing the behavior of physicians caring for patients with acute myocardial infarction. A controlled randomized trial.

A randomized controlled trial was done to assess the ability of continuing medical education to change physicians' knowledge and behavior in the care of patients with acute myocardial infarction. Patient care practices on eight objectives were audited 6 months before and after physicians completed a 2-hour educational program. Sixty-three physicians from eight randomly selected communities constituted the experimental group and 40 physicians from four similar communities served as controls. The average score for desired care practices over all objectives increased from 48.5% to 60% (p less than 0.001). Three objectives showed significantly greater gains for physicians in the experimental group. The generalizability of these effects was also studied in two additional educational contexts: a multitopic and a unitopic university-based continuing medical education program. Similar significant changes in behavior resulted in both contexts. Significant overall increases in knowledge occurred and persisted for all groups. Continuing medical education can effect changes in physicians' knowledge and care practices that can persist for at least 6 months.

Cardiology↗