Search PubMed⌕ Search

Biomedical subjects

S H Johnson

Publications and source records attributed to S H Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Effects of flunarizine on neurological recovery and spinal cord blood flow in experimental spinal cord ischemia in rabbits.

BACKGROUND AND PURPOSE: The lipophilic calcium channel antagonist flunarizine has been demonstrated to be neuroprotective in several models of cerebral ischemia. Ischemic spinal cord injury may have a similar pathophysiology and hence may respond in a similar fashion. This study was designed to investigate the effects of pretreatment with flunarizine on systemic hemodynamics, spinal cord blood flow, and neurological recovery in a rabbit model of ischemic spinal cord injury. METHODS: New Zealand White rabbits were anesthetized with ketamine and xylazine and instrumented for systemic blood pressure monitoring and spinal cord blood flow measurements using the microsphere method. After pretreatment with flunarizine or vehicle, ischemic spinal cord injury was created selectively in the caudal regions of the spinal cord by cross-clamping the abdominal aorta for a period of 25 minutes. Spinal cord blood flow was measured before, during, and 15 minutes after cross-clamp removal. Animals were allowed to recover and were graded neurologically at 18 and 24 hours after ischemia. RESULTS: Flunarizine injection was associated with hypotension that was both transient and dose related. Animals pretreated with flunarizine 0.4 mg/kg had significantly improved neurological recovery scores at 18 hours after ischemia (P = .017) compared with vehicle controls. At 24 hours this effect was lessened (P = .095); however, 60% of flunarizine-treated animals retained their ability to hop, whereas all of the vehicle-treated animals were nonambulatory. CONCLUSIONS: Flunarizine has a protective effect on neurological recovery after experimental ischemic spinal cord injury. The therapeutic window is narrow, and dosing is limited by untoward hypotension. The mechanism of protection likely involves inhibition of pathological cytosolic calcium accumulation rather than a direct effect on vascular smooth muscle.

Animals↗
PubMed1993

Avoiding the "school paper style" rejection.

These style aspects are developed slightly differently by each journal or book publisher, so investigate how each is handled in your target publication. Through these steps and the advice of your editor, you can develop a professional style that communicates your professional ideas as the expert you are.

Education, Nursing↗
PubMed1993

Writing transition sentences.

Transition sentences help the reader move from point to point. They clarify a key point, so the reader can distinguish main points from specific details in an article or book. In this article, you will be able to practice writing transition sentences.

Linguistics↗
PubMed1992

Wayfinding on foot from information in retinal, not optical, flow.

People find their way through cluttered environments with ease and without injury. How do they do it? Two approaches to wayfinding are considered: Differential motion parallax (DMP) is a retinal motion invariant of near and far objects moving against fixation; the information in optical flow (IOF) is a radial pattern of vectors, relying on decomposition of retinal flow. Evidence is presented that DMP guides wayfinding during natural gait, accounting for errors as well as correct responses. Evidence against IOF is also presented, and a space-time aliasing artifact that can contaminate IOF displays is explored. Finally, DMP and IOF are separated, showing they can yield different results in different environments. Thus, it is concluded that (a) DMP and IOF are different, (b) DMP and not IOF is used for wayfinding, (c) moving observers do not usually decompose retinal flow, and (d) optical flow may be a mathematical fiction with no psychological reality.

Adult↗
PubMed1992

Getting your research published: adapting the thesis style.

Writing a research report is similar to the research experience; both are processes with many distinct steps. Break your research project into parts and write about key accomplishments as you complete each milestone in the project.

Academic Dissertations as Topic↗
PubMed1992

Strengthening your case study approach.

A well-written case study has an important place in nursing literature because it describes new problems and techniques in clinical practice and helps identify researchable clinical questions. Do not be deceived into thinking that the case study manuscript is easy to write, because it is not. But, with the application of a few guidelines, the case study can be fun to write, exciting to edit, and enjoyable to read.

Medical Records↗
PubMed1992

Fluorine-18-antimyosin monoclonal antibody fragments: preliminary investigations in a canine myocardial infarct model.

The purpose of this study was to determine in a canine model whether selective myocardial infarct uptake of 18F-labeled antimyosin monoclonal antibody fragments could be achieved in a time frame compatible with the short half-life of this nuclide. Antimyosin monoclonal antibody fragments were labeled with 18F using a succinimidyl [18F]fluorobenzylamine ester acylation agent. Six dogs had myocardial infarction induced by coronary artery occlusion and were reperfused prior to the intravenous administration of 0.6-4.7 mCi of 18F-labeled F(ab')2 (two dogs) or Fab (four dogs). Analysis of tissues obtained 2-4 hr after antibody administration revealed infarct:normal myocardium uptake ratios as high as 14-21:1 for F(ab')2 and 9-12:1 for Fab. Even with Fab, however, prolonged 18F activity in the blood pool interfered with delineation of infarcts by PET imaging. In one dog, perfusion imaging with [13N]ammonia before antimyosin administration was performed, and regions of normal and ischemic myocardium were determined. With these regions of interest, infarct:normal myocardium uptake ratios calculated from the 18F-labeled Fab images increased from 1.5:1 at 1 hr to 4.0:1 at 5 hr. We conclude that 18F-labeled antimyosin fragments may be of value for hot-spot imaging of damaged myocardium with PET; however, blood-pool subtraction techniques will probably be required.

Animals↗
PubMed1992

Outlining: the key to an organized manuscript.

Faced by a blank sheet of paper and justifiable uncertainty about editorial review board approval, a nurse-author setting out to write an article should, before all, remember that ideas can be conveyed well in writing only if they are organized. The traditional "school-room" outlining methods may be replaced by one of the three approaches to manuscript organization that are described in this article. These approaches are tailored to the mental working habits of various categories of writers.

Humans↗
PubMed1991

Prediction of death and myocardial infarction by radionuclide angiocardiography in patients with suspected coronary artery disease.

The prognostic value of radionuclide angiocardiography was examined in patients with suspected coronary artery disease. Nine hundred and eight patients who underwent rest and exercise radionuclide angiocardiography without subsequent cardiac catheterization were followed for a median of 4.6 years. Fifty-two cardiovascular deaths and 28 nonfatal myocardial infarctions occurred during the follow-up period. Thirty-nine radionuclide angiocardiographic and clinical variables were analyzed in association with the end points of cardiovascular death, total cardiac events and death from all causes using the Cox proportional hazards model and Kaplan-Meier survival estimates. Univariable analysis identified the exercise ejection fraction as the best predictor of cardiovascular death (chi-square = 82), total cardiac events (chi-square = 84) and death from all causes (chi-square = 66). A small subset of patients (n = 45) with an exercise ejection fraction less than 0.35 were at high risk for future cardiac events, whereas most patients (n = 776) had an exercise ejection fraction greater than or equal to 0.50 and a low probability of a subsequent event. Three variables--the exercise ejection fraction, the exercise change in heart rate, and gender--contained independent prognostic information determined by multivariable analysis. The exercise ejection fraction was the strongest independent predictor (p less than 0.0001) for every end point. The measurement of ventricular function during exercise provides important independent prognostic information in patients with suspected coronary artery disease. Radionuclide angiocardiography successfully identifies patients requiring invasive assessment, and the low probability of cardiac events in patients with good exercise ventricular function obviates the need for interventional therapy.

Adult↗
PubMed1991

Safety and efficacy of sonicated albumin microspheres in perfusion and vein graft patency assessments.

This study was designed to identify a concentration of sonicated albumin microspheres that is safe, useful in determining graft patency, and provides an estimate of regional myocardial perfusion. The study included 8 patients between 50 and 72 years of age who were undergoing coronary artery bypass grafting. All patients were hemodynamically stable with left ventricular ejection fractions greater than or equal to 0.35. None had congestive heart failure or myocardial infarction within 4 months prior to the study. All had normal baseline neurologic and renal functions, and none had experienced allergic reactions to blood products or contrast dyes. A standard median sternotomy was performed for exposure of the heart at surgery, and saphenous veins were harvested and used for grafting. Intraoperative epicardial echocardiography (EE), always in the left ventricle short-axis at midpapillary level, was performed before and after grafting to determine regional myocardial wall motion. Sonicated albumin microspheres were prepared and injected into a single vein graft using an 18-gauge needle; 20 x 10(6), 100 x 10(6), and 200 x 10(6) microspheres were injected into the first graft sequentially. All other vein grafts were injected once with the dose that gave optimal contrast enhancement in the initial graft studied. In each patient, a minimum of 3 and maximum of 5 injections were performed, and graft perfusion was studied using EE. Graft flow, blood pressure, and electrocardiographic (ECG) measurements were continuously monitored, with a final EE performed after weaning the patient off cardiopulmonary bypass to assess wall motion. Preliminary results showed that no patient had adverse effects during or after the study and all remained hemodynamically stable.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Effects of internal mammary artery dissection on phrenic nerve perfusion and function.

The effects of left internal mammary artery (LIMA) dissection and distal division on phrenic nerve perfusion and function were examined in an adult swine model. Phrenic nerve perfusion was determined by left atrial injection of radioactively labeled microspheres. Phrenic nerve function was determined by measuring nerve and diaphragm potentials evoked by bilateral phrenic nerve stimulation. In the first group of animals (n = 9), the LIMA was dissected with ligation of all its branches. Left phrenic nerve perfusion and function decreased after LIMA dissection in every animal studied, whereas only minimal changes were observed on the right. Sixty minutes after LIMA dissection, left phrenic nerve mean perfusion decreased 71%. Left phrenic nerve and left diaphragm mean action potential amplitudes decreased 54% and 80%, respectively. In the second group of animals (n = 4), the LIMA dissection was performed without division of the pericardiacophrenic artery, a small proximal branch of the internal mammary artery that supplies the phrenic nerve. Sixty minutes after LIMA dissection, left phrenic nerve perfusion had decreased by 21% from control values, with a corresponding decrease in left phrenic nerve and diaphragm mean action potential amplitudes of 19% and 23%, respectively. These results indicate that LIMA dissection with division of all its branches in this model is associated with a significant impairment in left phrenic nerve perfusion and function and suggests a causal relationship. These results may also explain the apparent increased phrenic nerve cold sensitivity and increased incidence of phrenic nerve dysfunction associated with LIMA grafting.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1991

Neodymium:YAG laser damage to UV-absorbing poly(methyl methacrylate) and UV-absorbing MMA-HEMA-EGDMA polymer intraocular lens materials.

MemoryLenses and UV-poly(methyl methacrylate) intraocular lenses, which served as controls, were individually exposed to twenty 5 mJ shots of the Nd:YAG laser focused onto the posterior surface while placed in a sterile holder containing 5 ml of saline. The MemoryLens is a new foldable intraocular lens (IOL) manufactured from a polymer consisting of methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and ethylene glycol dimethyacrylate (EGDMA) with a UV absorber. Damage to the lenses was assessed by scanning electron microscopy. Cytotoxicity tests designed to detect potentially toxic substances released during laser damage were conducted with the saline solution by incubating it with mouse fibroblasts. Additional tests of the saline solution were conducted by high performance liquid chromatography and spectrophotometry. Damage induced by the Nd:YAG laser to the UV-poly(methyl methacrylate) IOLs was similar to that reported by other authors. Damage to the MemoryLens appeared less severe and showed no radial stress cracking. Cytotoxicity tests were negative for both types of IOLs. High performance liquid chromatography tests were negative for residual monomers (MMA, HEMA, EGDMA) and spectrophotometry did not reveal residual UV absorber.

Animals↗
PubMed1991

Exercise radionuclide angiocardiography predicts cardiac death in patients with coronary artery disease.

The purpose of this investigation was to document the relative importance of three clinical and three radionuclide variables for prediction of cardiac death in a consecutive group of patients evaluated for coronary artery disease. During a 6 1/2-year period, beginning in January 1978, 2,042 consecutive patients underwent radionuclide angiocardiography, with a clinical diagnosis of coronary artery disease, at Duke University Medical Center. A subgroup of 318 patients who underwent surgical myocardial revascularization near the time of initial study were excluded from later analysis. Clinical follow-up information was complete in a group of 1,663 patients who did not undergo interventional therapy. The 141 cardiac deaths in these 1,663 patients were the study end point. Cox proportional hazards models analyzed the prognostic information contained in three clinical variables (pain type, age, and sex) and three radionuclide angiocardiogram variables (exercise ejection fraction, resting end-diastolic volume, and change in heart rate with exercise). One-variable models confirmed the prognostic importance of each of these six variables. A multivariable model in which all six variables were used showed clinical variables to contain only 5% and the radionuclide variables 95% of the prognostic information. The exercise ejection fraction was the single most important variable, which alone contained 85% of the total information in the model. Curves relating probability of no cardiac death to the exercise ejection fraction identified a value of 0.50 as an inflection point. Patients with exercise ejection fractions below 0.50 demonstrate a probability of cardiac death that increases as the ejection fraction decreases.(ABSTRACT TRUNCATED AT 250 WORDS)

Angina Pectoris↗