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J Myers

Publications and source records attributed to J Myers.

320 records · Page 18Linked to original sources

Human pro alpha 1(I) collagen gene structure reveals evolutionary conservation of a pattern of introns and exons.

The collagens represent an interesting example of a structurally related but genetically distinct family of proteins. Type I, the most abundant of the vertebrate collagens, comprises two pro alpha 1(I) chains and one pro alpha 2(I) chain, each containing terminal propeptides and a central domain of 338 (Gly, X, Y) repeats. The structure of the chicken pro alpha 2(I) gene shows an intriguing relationship between exon organization and the arrangement of (Gly, X, Y) repeats (see ref. 2 for review). This has led to the suggestion that the collagens evolved from a common ancestral unit of 54 base pairs (bp). Here we present the structure of the entire human pro alpha 1(I) gene and compare this with the chicken pro alpha 2(I). The exon arrangement of the two genes is remarkably similar, although the human pro alpha 1(I) is more compact because of the shorter length of its introns. The data strongly support the notion that the type I genes have evolved from an ancestral multi-exon unit, and that once the gene was translated, a strong evolutionary pressure caused it to maintain this elaborate structure.

Amino Acid Sequence↗

Pitfalls in CT evaluation of chest wall invasion by lung cancer.

Computed tomography in a patient with a peripheral lung cancer in the right upper lobe revealed obliteration of the extrapleural fat and direct connection of the tumor with an intercostal soft tissue mass of similar density. The findings were suggestive of chest wall invasion by the cancer which was, however, proven to be false after en bloc resection of the tumor and the contiguous chest wall. Such a diagnostic pitfall could be avoided if special attention were paid to the asymmetry of the CT image at the level of upper thoracic outlet due to improper positioning of the patient.

Adenocarcinoma↗

Influence of intensive physical training on urinary nitrate elimination and plasma endothelin-1 levels in patients with congestive heart failure.

BACKGROUND: Congestive heart failure (CHF) is associated with increased peripheral vascular resistance. Exercise-induced shear stress may release endothelial relaxing factors, such as nitric oxide (NO), and inhibit the production of vasoconstrictors such as endothelin-1 (ET-1) thereby modulating vascular tone. We examined the effect of intensive training on ET-1 plasma concentrations and NO-metabolite elimination in patients with CHF after acute myocardial infarction. METHODS: Seventeen patients with CHF after a myocardial infarction were randomized to an exercise group (n = 9), who performed physical training for 8 weeks, or a control group (n = 8) who received usual care. A physical examination, pulmonary function test, and a maximum exercise test were performed, and 24-hour urinary nitrate elimination and ET-1 in plasma were determined before and at the end of the study period. RESULTS: Maximal oxygen uptake remained unchanged in controls (17.9 +/- 1.4 to 18.1 +/- 1.5 mL/(kg min) but increased in the exercise group (from 20.4 +/- 0.75 to 26.7 +/- 1.4 mL/(kg min). After 8 weeks the urinary nitrate elimination in controls was significantly decreased (1.25 +/- 0.20 to 1.03 +/- 0.22 mmol/24 hours; P < 0.001), while it was unchanged in the exercise group (1.26 +/- 0.23 to 1.39 +/- 0.28; P = 0.71). Plasma ET-1 levels did not change after 8 weeks (7.87 +/- 0.62 versus 7.57 +/- 0.75 and 7.13 +/- 0.6 versus 7.35 +/- 0.7 pg/mL for control and exercise groups, respectively). CONCLUSION: In patients with CHF after acute myocardial infarction nitrate elimination decreases over the subsequent 2 months. This trend was reversed by training. Because nitrate elimination mirrors endogenous NO production, these results suggest that training may positively influence endothelial vasodilator function.

Endothelin-1↗

A survey of exercise testing: methods, utilization, interpretation, and safety in the VAHCS.

BACKGROUND: Healthcare organizations are being graded in terms of their adherence to practice guidelines. The authors sought information on practice patterns of exercise testing within the Veterans Affairs Health Care System (VAHCS) to determine how well current practice patterns adhere to current guidelines. In addition, we sought to update past surveys to determine methods, indications, utilization of alternative diagnostic modalities, criteria for interpretation, safety, and physician supervision of exercise testing within the VAHCS. METHODS: Questionnaires were sent to 72 of the largest Veterans Affairs Medical Centers with cardiology divisions. The centers were queried regarding volume and type of exercise testing (standard, nuclear, and echocardiographic), indications, safety, protocols used, and criteria for interpretation. RESULTS: Seventy-one questionnaires were returned, comprising a total of 75,828 exercise tests performed within the last year. Virtually all indications for exercise testing fit the American Heart Association/American College of Cardiology (AHA/ACC) guidelines Class I criteria; 46% of patients were tested for the evaluation of chest pain; 14% were tested to evaluate patients at high risk for coronary artery disease; 10% were preoperative evaluations; and 8% were post-myocardial infarction evaluations. The most commonly used diagnostic test was the standard exercise electrocardiogram; a patient was five times more likely to undergo a standard exercise electrocardiogram or nuclear exercise test than an exercise or pharmacologic echocardiogram. The largest proportion of centers (49%) used 1.0-mm horizontal or downsloping ST depression as a criterion for an abnormal test, although 22% considered 1.5-mm upsloping ST depression to be abnormal, and 25% relied on a treadmill score. Seventy-eight percent of respondents used the treadmill, and of these, 82% used the Bruce or modified Bruce protocol. Four major cardiac events were reported (three myocardial infarctions, one sustained ventricular tachycardia) representing an event rate of 1.2/10,000. A physician was present during 73% of all standard exercise tests; 21% of respondents reported that a physician was required to be present "only for high-risk patients." CONCLUSION: Indications for exercise testing are in close agreement with the AHA/ACC guidelines; thus, the test continues to have an important role in diagnosis and prognosis among patients with or suspected of having coronary artery disease. The exercise test is an extremely safe procedure, with an event rate similar to other recent surveys. However, a great deal of variation exists in terms of criteria for abnormal results and whether physician presence is required during exercise testing.

Coronary Disease↗

The effect of sodium intake on blood pressure related to the age of the patients.

1. Sodium intake was varied in 182 normotensive volunteers. 2. systolic blood pressure rose by 3.3 (s.e.m. = 0.9) mmHg supine, 2.8 (s.e.m. = 0.7) mmHg erect. 3. Diastolic blood pressure rose by 2.7 (s.e.m. = 0.8) mmHg supine, 2.6 (s.e.m. = 0.8) mmHg erect. 4. In people over 50 y the rise was 12.4/8.1 mmHg (supine) and 9.1/7.1 mmHg (erect). 5. Blood pressure rose as sodium intake increased. Most of the rise was in the older patients but about 25% of younger patients were sensitive to sodium.

Adolescent↗

Effects of exercise training on abnormal ventilatory responses to exercise in patients with chronic heart failure.

Patients with chronic heart failure frequently report shortness of breath during daily activities as their primary symptom. In recent years, many efforts have been made by researchers to explain the mechanisms that underlie the characteristic heightened ventilatory response to activity in patients with chronic heart failure. The degree to which the ventilatory response to exercise is heightened parallels the severity of the disease, and measuring the ventilatory gas exchange response to exercise can help quantify the patient's response to therapy. Prior to the 1990s, patients with chronic heart failure were generally discouraged from participating in programs of exercise training. However, in the last decade, studies have demonstrated that exercise training is quite safe for these patients, and a multitude of benefits have been reported. Among the benefits of training are improvements in the abnormal ventilatory response to exercise. Although many mechanisms could potentially explain this response, it appears most likely that this improvement after training is due to a reduction in lactate accumulation and an attenuation of the heightened muscle receptor reflex response that occurs in chronic heart failure. This article reviews the mechanisms of dyspnea in chronic heart failure, along with recent studies assessing the effects of training on abnormal ventilatory responses to exercise in these patients. (c)2000 by CHF, Inc.

Journal Article↗

Polymerase chain reaction assays for the detection of cytomegalovirus in organ and bone marrow transplant recipients.

Cytomegalovirus (CMV) infection is ubiquitous and results in a wide spectrum of clinical manifestations ranging from asymptomatic infection to severe life threatening disease. Infection in normal children and adults usually causes no symptoms but in the immunocompromised host, CMV may result in severe opportunistic infections with high morbidity and mortality. Historically, virus detection was dependent on culture of the virus or on a centrifugation culture system referred to as a shell vial assay. The shell vial assay frequently lacked sensitivity and was unable to detect infection in its early phase. Also, as with culture assays, the results were affected by antiviral therapy. The CMV antigenemia assay was developed to provide more rapid results and has gained wide usage. This assay is limited to detection of the virus in white blood cells and is more sensitive than culture or the shell vial assay. Application of the polymerase chain reaction (PCR) to these problems has resulted in the development of assays for CMV which are more sensitive than previously available methods. This method employs liquid hybridization with 32P labeled probes and gel retardation analysis for detection of amplified DNA specific for each virus. A comparison of the detection of CMV by an antigenemia assay or the PCR method in the leukocytes of renal transplant patients revealed that the PCR assay detects cytomegalovirus earlier and more consistently than the antigenemia assay. Finally, the application of a fluorescent dye detection system and image analysis of the acrylamide gel with a laser scanner provides additional sensitivity to the detection of cytomegalovirus, as well as avoiding the use of radioactivity, making the assay more adaptable to the clinical laboratory.

Bone Marrow Transplantation↗

Comparison of the 20-MHz ultrasound probe with ultrasound biomicroscopy in glaucoma.

The 20-MHz ultrasound probe was compared with ultrasound biomicroscopy to determine its usefulness in imaging various glaucomatous conditions. Ten patients with glaucoma underwent anterior segment imaging with both the 20-MHz probe, which attaches to the I3 B-scan (Innovative Imaging Inc., Sacramento, CA), and the Ultrasonic BioMicroscope (UBM; Paradigm Medical Industries, Salt Lake City, UT). All pathology was easily demonstrable using the 20-MHz probe, in one case showing a retinal detachment not seen with the UBM. However, anterior findings such as fluid in the suprachoroidal space and sclerostomy sites in postoperative trabeculectomy cases were more difficult to view with the 20-MHz probe. The use of coupling enhanced the quality of the latter images. The 20-MHz ultrasound probe may be a viable aid in diagnosis and follow-up of certain glaucomatous conditions, and the use of a coupling device enhances its images.

Anterior Eye Segment↗

Association and dissociation of a protease and its inhibitor on the surface of lung squamous cell carcinoma cells.

Squamous cell carcinoma cells possess a cell surface protease, referred to as guanidinobenzoatase (GB). GB is a plasminogen-activator-like enzyme which can be located by the fluorescent probe 9-amino acridine in frozen sections. Fluorescence microscopy has been used to study the inhibition of this GB, the displacement of inhibitor from GB, the displacement of GB from the cell surface receptor and the preparation of both active GB and inhibitor, obtained from these frozen sections of tumour tissue.

Carboxylic Ester Hydrolases↗