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Biomedical subjects

M G Morgan

Publications and source records attributed to M G Morgan.

54 records · Page 3Linked to original sources
PubMed1991

Revascularization of infarcted vs. viable myocardium. Effects on symptoms, physical performance and global/regional left ventricular function.

Symptoms, physical performance and global vs. regional left ventricular (LV) function were reviewed in 25 patients with postinfarction anterior-apical akinesia and minor dyskinesia who subsequently underwent revascularization of all graftable stenotic vessels. The observed postoperative improvement in functional NYHA capacity and physical performance was not related to significant change in any systolic or diastolic variable of global LV function. 'Nonspecific postoperative septal hypokinesia' developed in most cases. The regional ejection fraction showed slight (nonsignificant) mean increase in the infarcted apex and low anterior wall supplied by the left anterior descending artery, but marked increase in the noninfarcted lateral wall supplied by the left circumflex branch. Hearts with grafted left circumflex artery showed on average lower preoperative and postoperative ejection fraction in the lateral wall than did hearts without such grafting, but the rise in regional ejection fraction was significant only after left circumflex grafting. The clinical response to coronary artery surgery is attributed mainly to functional improvement of non-infarcted myocardium. Revascularization of viable myocardium occurs directly via bypass grafts, but collateral vessels may also contribute.

Adult↗
PubMed1991

Revascularization of infarcted myocardium. Effect on myocardial perfusion assessed with quantified Tl-201 SPECT technique.

Myocardial perfusion was studied in 21 patients before and after revascularization of all graftable stenotic vessels following post-infarction anteroapical akinesia and minor dyskinesia. At preoperative and late postoperative evaluation, perfusion abnormalities in identified sectors were quantified with two methods, one (Q1) assessing the extent and the other (Q3) the severity of abnormal perfusion. The preoperative scores with both methods indicated permanent myocardial perfusion defects in all 21 patients and reversible defects, indicating myocardial ischemia, in 16 with Q1 and 14 with Q3. After bypass grafting there was overall reduction of myocardial perfusion defect and of abnormality scores: Notably, 13/21 patients (62%) had decreased permanent myocardial defect score, reflecting reactivation of 'hibernating myocardium'. The findings indicated that obstructed but graftable vessels supplying myocardium with loss of contractile function should be bypassed, since flow contribution to distant, viable myocardium is probable via preserved collateral circulation. This should be particularly relevant for the LAD, because of that artery's septal branches.

Adult↗
PubMed1990

Lay understanding of low-frequency electric and magnetic fields.

People do not start with a blank slate when they hear risk-communication messages. All such messages are processed through existing knowledge structures and understanding. Hence, to design effective and reliable risk-communication materials one must understand the state of people's knowledge--correct and incorrect--about an issue. We developed a simple "mental model" of what people minimally need to know to make informed decisions about field-related issues. Then we performed studies to explore how and to what extent respondents of various groups understood physical properties of 60-Hz electric and magnetic fields. Actual knowledge of respondents was then compared with the predicates of the model. Electrical engineering juniors and semi-technical employees of utilities displayed a good command of most of the concepts in the simple model, but little awareness of the limits to their knowledge. Lay respondents correctly knew only a few of the simplest elements of the model, but they displayed a much greater awareness of the limits to their knowledge. Both lay and semi-technical respondents were found to share several misconceptions. On average, they correctly rank-ordered some common field-exposure conditions by field strength, but they could not differentiate between electric and magnetic fields and could not differentiate among field strengths associated with different appliances. Most respondents dramatically underestimated the range of actual field strengths. Many respondents understood that field strength decreases with distance from a source, but they underestimated the rate of decrease. In contrast to X-rays and microwaves, which respondents appeared to think about in rather similar terms, 60-Hz fields were not thought of as being highly similar to any other agent, although the closest parallels were found with ultrasound. Changes in mood, thought, and behavior, and the existence of an "electrical aura," were all seen as plausible results of exposure to a 60-Hz field. Although lay respondents displayed a variety of incomplete and confusing ideas, most of these ideas probably do not pose significant obstacles to the learning of a correct, simple, mental model.

Communication Barriers↗
PubMed1990

Salmonella septic arthritis: a case report and review.

We describe a case of septic arthritis in a child with no apparent predisposing conditions. Salmonella virchow was isolated from her knee and faeces, both isolates being identical except for the latter's resistance to ampicillin. Evidence is presented for the acquisition of ampicillin resistance in vivo, including the demonstration of the R plasmid and its ready transferability to Escherichia coli. The recent literature on the subject is reviewed and the role of group CI salmonellae in invasive disease is examined.

Ampicillin Resistance↗
PubMed1990

Haemophilus influenzae and H. parainfluenzae as urinary pathogens.

Two cases are described, one of Haemophilus influenzae urinary infection in a female with no past history of urinary tract infection (UTI) and the other of Haemophilus parainfluenzae infection in a male with a renal calculus. Haemophilus spp. are rare urinary pathogens and these cases are even more unusual because H. influenzae UTI has almost always previously been found in either children or adult males, while H. parainfluenzae UTI has only been reported once before.

Aged↗
PubMed1989

Methicillin-resistant Staphylococcus aureus: a ten-year survey in a Dublin hospital.

We undertook a retrospective, longitudinal survey to monitor the changing incidence, phage types and patterns of antibiotic resistance of methicillin-resistant Staphylococcus aureus (MRSA) in St Laurence's Hospital (SLH), Dublin over the last 10 years. Following a peak in 1979, the incidence of MRSA has gradually decreased to around 17% of S. aureus isolates in 1986, almost identical to its incidence 10 years before. However, the spectrum of antibiotic resistance among these organisms remains broad and this seems to be at least partially related to antibiotic usage. Many strains could not be phage typed and others were typable only by the additional phage 90. This has severely limited the usefulness of phage typing in the tracing of sources of outbreaks. Thus, there is a need for a more specific method of typing as well as a rational antibiotic policy, to successfully monitor and curtail the hospital spread of MRSA.

Anti-Bacterial Agents↗
PubMed1988

Measurements of housing density along transmission lines.

One of the fundamental inputs to models of population exposure to the power-frequency fields of high-voltage transmission lines is the density of population about the lines. We examined aerial photographs of over 1,700 km of transmission corridor to characterize the density of nearby housing units. The data show that the density of houses within 200 m of transmission lines 1) is typically smaller than the average density of houses in the local utility's service area, 2) tends to increase with distance from the line, and 3) is inversely correlated with line voltage.

Electromagnetic Fields↗
PubMed1988

Urethral and prostatic colonization and infection in patients undergoing prostatectomy.

We conducted a prospective trial to identify organisms colonizing the urethra and prostate and their role in the aetiology of infection after prostatectomy. Twenty-five patients were studied of whom six developed postoperative infection. The causative organisms were previously recovered from the urethra but not the prostate. There was a high rate of urethral colonization by streptococci (14/25) and a low incidence of prostatic colonization. We describe a novel method of sampling the prostate.

Bacteriological Techniques↗
PubMed1985

Powerline frequency electric and magnetic fields: a pilot study of risk perception.

The perception of the potential risk arising from human exposure to 50/60 Hz electric and magnetic fields was studied with a quasi-random sample of 116 well-educated, opinion leaders using the risk perception framework previously developed by Slovic, Fischhoff, and Lichtenstein. These individuals rated exposure to fields from transmission lines and electric blankets on a variety of scales that have been found useful in characterizing people's risk attitudes and perceptions. These judgments allowed us to conjecture about the likely desire for regulation of these potential hazards and the likely response to a publicized problem (e.g., an accident or ominous research finding) involving these two sources of exposure. Various forms of detailed information about 50/60 Hz fields were supplied to respondents. The provision of information produced modest, but statistically significant, changes in perceptions in the direction of greater concern about the risks. In response to questions of public policy, participants desired modest regulatory control of field exposure from transmission lines and little or no control of field exposure from appliances like electric blankets.

Electric Injuries↗
PubMedDate not supplied

Left atrial size in patients with atrial fibrillation: an echocardiographic study.

Left atrial dimensions were recorded echocardiographically in 50 patients with atrial fibrillation. Fibrillatory wave amplitude (f wave) was measured in lead V1 of standard electrocardiograms for all patients. Left atrial dimensions (LAD), LAD compared to body surface area (LAD/M2) and the ratio of LAD to aortic root diameter (LAD/AR) were calculated. There was no significant correlation between f wave size and LAD (p = 0.6480), between f wave size and LAD/M2 (p = .6721), or between f wave size and LAD/AR (p = .1157), nor was there any association between LAD and the etiology of the heart disease. F wave size did correlate (p = .0073) with the age of the patient, the older the individual, the more likely was he to have fine atrial fibrillation (peak to trough f wave less than 0.5 mm).

Action Potentials↗