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Biomedical subjects

E E Johnson

Publications and source records attributed to E E Johnson.

At least 19 recordsLinked to original sources
PubMed1998

The effect of inducing ventricular fibrillation with 50-Hz pacing versus T wave stimulation on the ability to defibrillate.

When testing an ICD, there are at least two techniques for inducing ventricular fibrillation: (1) high frequency (approximately equal to 50 Hz) pacing; and (2) a single T wave stimulus. It is generally assumed that these two methods yield similar results. This study directly tested this assumption. In six dogs, one defibrillation electrode was placed in the right ventricular (RV) apex and the second was placed cutaneously on the left thorax. All defibrillation and T wave stimuli were biphasic between these two electrodes. Pacing was monophasic from the tip of the RV catheter to the cutaneous patch. The voltage which defibrillates 50% of the time (DF50) was measured using a 10-step Bayesian up-down method. Observations for two DF50 measurements were randomly interleaved. For one DF50 measurement, fibrillation was induced with 99 pacing stimuli at a 20-ms pacing interval (50-Hz pacing). For the second DF50 measurement, fibrillation was induced with a single defibrillation shock of approximately 1/2 J delivered at a time corresponding to the peak of the T wave in the lead II electrogram (T wave stimuli). The average DF50 when measured after fibrillation induced with 50-Hz pacing was 379 +/- 54.6 V, as compared to 382 +/- 50.3 V when fibrillation was induced with T wave stimuli. The difference of 3 V was not statistically significant. If these results are confirmed in humans, it is reasonable to assume that the efficacy of a defibrillation shock is the same whether T wave stimuli or 50-Hz pacing are used to induce fibrillation.

Animals↗
PubMed1998

One-stage lengthening of femoral nonunion augmented with human bone morphogenetic protein.

Fifteen patients with posttraumatic shortened atrophic femoral nonunions were treated with one-stage lengthening. The alloimplant was composed of allogeneic antigen extracted autolyzed human bone perfused with partially purified human cortical bone morphogenetic protein associated with noncollagenous protein and used as graft. The composite was lyophilized and sterilized with ethylene oxide. All 15 nonunions were atrophic diaphyseal and were lengthened through intercalary segmental defects bridged with the human bone morphogenetic protein composite alloimplants stabilized to the medial femoral cortex through plate osteosynthesis and lag screw fixation. One lengthened proximal femur had fatigue failure of the plate and was treated successfully by exchange plating. The average increase in length was 2.8 cm (range, 1.5-5 cm) and an average percentage increase in length of 8% (range, 4%-132%) of the residual shortened femur. The human bone morphogenetic protein composite produced an immediate reactive bone formation in the host bone and progressive remodeling of the donor recipient interfaces. There were no infections, allergic reactions, clinical rejection of the human bone morphogenetic protein composite alloimplants, or evidence of malignant disease. One-stage femoral lengthening augmented with human bone morphogenetic protein composite graft bridged the intercalary defect, remodeled the atrophic host bone and restored bone continuity within 1 to 2 years. Human bone morphogenetic protein composite alloimplants are a substitute of autogeneic bone graft and offer an alternative to iliac crest bone without the associated morbidity.

Adult↗
PubMed1997

The aqueous pore through the translocon has a diameter of 40-60 A during cotranslational protein translocation at the ER membrane.

Eukaryotic secretory proteins are cotranslationally translocated through the endoplasmic reticulum (ER) membrane via aqueous pores that span the lipid bilayer. Fluorescent probes were incorporated into nascent secretory proteins using modified Lys-tRNAs, and the resulting nascent chains were sealed off from the cytosol in fully assembled translocation intermediates. Fluorescence quenching agents of different sizes were then introduced into the ER lumen in order to determine which were small enough to enter the pore and to quench the fluorescence of probes inside the ribosome and/or the pore. These accessibility studies showed that the aqueous pore in a functioning translocon is 40-60 A in diameter, making it the largest hole observed to date in a membrane that must maintain a permeability barrier.

4-Chloro-7-nitrobenzofurazan↗
PubMed1997

Internal atrial defibrillation in humans. Improved efficacy of biphasic waveforms and the importance of phase duration.

BACKGROUND: The optimal waveform for internal atrial defibrillation (IAD) in humans is unknown. This study tested the effect of waveform duration and phase duration on the efficacy of biphasic waveforms for IAD. METHODS AND RESULTS: Electrodes were positioned in the right atrial appendage and coronary sinus in 13 patients. In part 1, the atrial defibrillation thresholds (ADFTs) for 5 monophasic waveforms (2, 4, 6, 10, and 20 ms) and 5 symmetrical biphasic waveforms (1/1, 2/2, 3/3, 5/5, and 10/10 ms) were compared in 6 patients. In part 2, the ADFTs for two asymmetrical biphasic waveforms (7.5/2.5 and 2.5/7.5 ms) were compared with those for a symmetrical biphasic waveform (5/5 ms) and a monophasic waveform (10 ms) in 7 patients. In part 1, biphasics with total durations of 4 to 20 ms had significantly lower ADFTs than monophasic waveforms of the same total duration. For a total duration of 2 ms, there was no significant difference in ADFTs between the biphasic and the monophasic waveforms. There was no difference between symmetrical biphasic waveforms of 4 to 20 ms. In part 2, the 7.5/2.5 ms asymmetrical biphasic had significantly lower ADFTs than the three other waveforms tested. Both the 7.5/2.5 ms asymmetrical and the 5/5 ms symmetrical biphasic waveform had significantly lower ADFTs than the 2.5/7.5 ms asymmetrical biphasic and the 10 ms monophasic waveforms. CONCLUSIONS: For IAD in humans, biphasic waveforms were more efficacious than monophasic waveforms. This improved efficacy is related to the total duration of the biphasic waveform and each individual phase duration of the biphasic waveform.

Adult↗
PubMed1997

The Lie/Bet Questionnaire for screening pathological gamblers.

A 2-item questionnaire was derived from 10 DSM-IV criteria for pathological gambling. Subjects were 362 men, 191 classified as pathological gamblers and 171 as nonproblem-gambling controls. The two items were significant in sensitivity and negative predictive value and significant in specificity and positive predictive value.

Adolescent↗
PubMed1997

Influence of health status and the timing of surgery on mortality in hip fracture patients.

The purpose of the study was to determine the relationship of preoperative health status and time to surgery to mortality and late functional outcome in hip fracture patients. The records of 168 consecutive patients who had operations for 171 intertrochanteric or femoral neck fractures were reviewed retrospectively. Preoperative health status was assessed by the American Society of Anesthetists (ASA) classification. Postoperative outcome was determined by mortality and ambulatory status. The follow-up period for survivors averaged 33 months. The overall mortality was 14% at 1 year, which rose to 26% at 2 years, and 33% at 3 years. The 3-year mortality was significantly less for ASA I and II patients (23%) than for ASA III, IV, and V patients (39%). There was also a significant difference in mortality between patients having surgery within 24 hours of admission (20%) and those having surgery beyond 24 hours of admission (50%). Even when only the healthy subgroup of ASA I and II patients were considered, the relative risk of death was 4.5 times greater if surgery occurred after 24 hours from admission. These data support the concept that hip fracture patients are not a homogeneous group with respect to mortality and that the ASA classification is a good predictor of mortality. Patients who had surgery within 24 hours of admission had a significantly lower mortality rate than did patients having surgery beyond 24 hours of admission, regardless of their preoperative ASA classification.

Adult↗
PubMed1996

Pectoralis major tendon avulsion in association with a proximal humerus fracture.

We report a very rare case of an avulsion of the pectoralis major tendon in association with a two-part proximal humerus fracture. Pectoralis major tendon avulsion was confirmed intraoperatively during open reduction and internal fixation of the humerus fracture. In retrospect, the preoperative radiographic finding of posterolateral and proximal displacement of the humeral shaft suggested an injury to the pectoralis major. Because others have reported that the best treatment of a pectoralis major tendon avulsion is surgical repair, we feel that it is important to suspect such an injury in a proximal humerus fracture when this anatomic displacement is present.

Adult↗
PubMed1996

Internal cardioversion in two patients with atrial fibrillation refractory to external cardioversion.

A 26-year-old man underwent an electrophysiological study for evaluation of a history of congenital heart disease, presyncope, and wide complex tachycardia. During the study the patient developed sustained atrial fibrillation with a rapid ventricular response. A 17-year-old man with a history of sick sinus syndrome developed sustained atrial fibrillation. Both patients failed four attempts at external cardioversion with a maximum delivered energy of 360 J. Low energy cardioversion was successful in both patients using biphasic waveforms and internal transvenous defibrillation electrodes. Internal cardioversion using a transvenous electrode system can be successful in patients with atrial fibrillation refractory to external cardioversion.

Adolescent↗
PubMed1995

Total knee replacement including a modular distal femoral component in elderly patients with acute fracture or nonunion.

Distal femoral fracture or nonunion in elderly patients with osteopenic bone and coexisting gonarthrosis poses a difficult treatment challenge. Open reduction and internal fixation with or without the use of bone cement may not provide sufficient stabilization, requires a prolonged period of weightbearing restrictions, and does not address preexisting knee arthrosis. We report five patients, three with distal femoral nonunion, two with acute distal femoral fracture, and all with concomitant gonarthrosis treated with total knee replacement including a modular distal femoral component [distal femoral replacement (DFR)]. In this group of patients, modular DFR provided immediate pain relief and allowed early weightbearing and aggressive rehabilitation. We recommend this treatment modality in selected osteopenic elderly patients with difficult distal femoral reconstructive problems and coexisting gonarthrosis.

Aged↗
PubMed1995

Predicting patterns of epicardial potentials during ventricular fibrillation.

Ventricular fibrillation (VF) is a fatal cardiac arrhythmia, characterized by uncoordinated propagation of activation wavefronts in the ventricular myocardium. Short-term predictions of epicardial potential fields during VF in pigs were attempted using linear techniques, and prediction accuracy was measured at various stages during sustained episodes. VF was induced in five pigs via premature electrical stimulation. Unipolar electrograms were recorded from an epicardial array of 506 electrodes in a 22 x 23 array with 1-mm spacing. Optimal spatial basis functions (modes) and time-varying weighting coefficients were found using the Karhunen-Loeve decomposition. Linear autoregressive (AR) models incorporating the dynamics of only a few spatial modes led to predicted patterns that were qualitatively similar to observed patterns. Predictions were made 0.256 s into the future, based on 0.768 s of past data, over an area of approximately 5 cm2 on the ventricular epicardium. The mean squared error of predictions varied from as much as 1.23 to as little as 0.14, normalized to the variance of the actual data. Inconsistency in long-term forcasts is partly due to the limitations of linear AR models. Changes in predictability, however, were consistent. Predictability varied inversely with spatial complexity, as measured by the mean squared error of a five-mode approximation. Predictability also increased significantly during the first minute of VF.

Algorithms↗
PubMed1995

Characterization of the deoxycytidine kinase promoter in human lymphoblast cell lines.

Deoxycytidine kinase (dCK) phosphorylates 2'-deoxycytidine, as well as the purine deoxyribonucleosides and a number of nucleoside analogues that are important in the chemotherapy of leukemias. The enzyme is highly expressed in the thymus relative to other tissues and may play an important role in the T cell depletion associated with adenosine deaminase and purine nucleoside phosphorylase deficiencies. To characterize the dCK promoter region and to determine whether it mediates higher levels of gene expression in T lymphoblasts, we have analyzed a 700-bp genomic fragment encompassing 548 bp of 5' flanking region for functional activity and for transcription factor binding using T and B lymphoblast cell lines and nuclear extracts. The regions of the promoter that were defined as important to its function include a 5' GC box, and E box, a 3' GC box, and an E2F site. The transcription factor Sp1 binds to both GC boxes, activating at the 5' site but repressing at the 3' site. MLTF/USF activates transcription through the E box, whereas E2F activates through the E2F site, but binds weakly to this site in vitro and does not appear to mediate cell cycle-specific expression of dCK in vivo. No significant differences in promoter activity or transcription factor binding were observed between Jurkat T and Raji B lymphoblasts. The promoter of the dCK gene is thus regulated by a number of ubiquitously expressed transcription factors. DCK expression in cultured lymphoblast cell lines is not solely a function of the T or B lineage derivation.

B-Lymphocytes↗
PubMed1995

Improving mental fitness reports of candidates for police officer and fire fighter.

On the basis of 18 years of experience on the Medical Review Panel of the New Jersey Department of Personnel, the author points out some shortcomings commonly observed in psychological/psychiatric evaluative reports on mental fitness of police officer and fire fighter candidates. Each shortcoming is noted under one of two headings, i.e., routine information or inferences.

Fires↗
PubMed1995

Radiographic analysis of tibial fracture malalignment following intramedullary nailing.

Intramedullary nailing of the tibia was performed on 145 tibiae (137 patients) for fracture or nonunion from 1985 to 1992. There were 133 cases available for radiographic analysis of postoperative tibial alignment. Of the 133 nailings, 16 (12%) were malaligned (12 acute fractures and 4 nonunion-malunions). Malalignment was defined as 5 degrees angulatory deformity in any plane. Malalignment was seen in 58% of proximal third fractures, 7% of middle third fractures, and 8% of distal third fractures. Of the malaligned fractures, 83% were either segmental or comminuted. Thirteen percent of the reamed tibiae were malaligned as compared with 9% of the unreamed tibiae. There was no relationship between nail insertion site and degree of angulation. The medial entrance angle averaged 9.5 degrees and contributed to a valgus deformity in 4 proximal third tibial fractures. The average anterior bow deformity of 5 proximal third fractures was 7 degrees (range, 5 degrees-12 degrees). Careful attention to operative technique and entrance angle, particularly with proximal third or comminuted fractures, is recommended to prevent angular deformity and malunion after tibial nailing. Proximal third tibial fractures may require a neutral or slightly lateral entrance angle to ensure a more anatomic reduction and centromedullary nail orientation to offset the tendency for valgus angulation.

Adolescent↗
PubMed1994

The use of the unreamed nail in tibial fractures with concomitant preoperative or intraoperative elevated compartment pressure or compartment syndrome.

Twelve patients with tibial shaft fractures and evidence of compartment syndrome or with documented elevated compartment pressures were treated with an unreamed locked intramedullary nail and a single-incision lateral four-compartment fasciotomy. There were six closed fractures and three grade I and three grade II open fractures. Ten fractures have achieved a solid union without shortening or significant angulation at an average follow-up of 8.1 months (range 4-26). Two patients were lost to follow-up. There were two delayed unions and one nonunion, all of which healed after additional treatment. Average time to tibial union was 5.8 months (range 2-24), with six fractures healing in < or = 4 months. One patient whose treatment was delayed > 12 h after his injury has a persistent neurologic deficit with a claw toe deformity. There were no superficial or deep infections. All patients obtained an excellent range of motion of the knee and ankle. Unreamed nailing of diaphyseal tibial fractures with an associated compartment syndrome provides optimal internal fixation while allowing excellent access for soft tissue care. We believe that the unreamed tibial nail, when combined with a single-incision, lateral, four-compartment fasciotomy, offers substantial advantage in the treatment of this injury, permitting optimal treatment of a difficult fracture and soft tissue injury.

Adult↗
PubMed1994

Acute lengthening of shortened lower extremities after malunion or non-union of a fracture.

Forty-nine skeletally mature patients who had either a non-union or a malunion of a fracture of the tibia or the femur had correction of the deformity and acute axial lengthening of the fractured bone. Distraction was provided by the short AO/ASIF fracture distractor applied directly to the site of the osteotomy or non-union. At an average of sixty-three months (range, twenty-six to 105 months), the average increase in the tibial and femoral length was 1.7 and 3.2 centimeters, respectively. There were no compartment syndromes or ischemia secondary to any of the procedures. One patient had a transient sensory-nerve loss. Fatigue fractures were seen in two tibial plates, two femoral plates, and one femoral intramedullary nail used for osteosynthesis. A non-union developed after four other femoral intramedullary nailing procedures. One infection developed after lengthening of a tibia. Restoration of normal length by acute lengthening and internal fixation was achieved in twenty-seven patients. One patient had overlengthening of one centimeter. Fifteen patients had residual shortening of approximately one centimeter, three had shortening of more than one to 2.5 centimeters, and three patients had more than 2.5 centimeters of shortening. The patients in this series had acute restoration of limb length after traumatic shortening with a low prevalence of complications of neurovascular compromise. Three of the thirty tibial lengthenings and seven of the nineteen femoral lengthenings had to be followed by at least one additional procedure to obtain union.

Adult↗