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Biomedical subjects

R Shaw

Publications and source records attributed to R Shaw.

At least 91 records · Page 5Linked to original sources
PubMed1994

Truly silent ischemia and the relationship of chest pain and ST segment changes to the amount of ischemic myocardium: evaluation by supine bicycle stress echocardiography.

OBJECTIVES: The objectives of this study were 1) to determine the relationship between the amount of exercise-induced ischemic myocardium and the presence or absence of chest pain and ST segment depression, and 2) to define the incidence and characteristics of "truly silent ischemia," that is, ischemia that is not manifested by symptoms or electrocardiographic (ECG) findings. BACKGROUND: There are no prior data relating ischemia to chest pain and ST depression. Thallium-201 imaging studies have evaluated perfusion but not ischemia. In contrast, supine bicycle stress echocardiography demonstrates exercise-induced ischemic dysfunction. METHODS: Supine bicycle stress echocardiography and arteriography were performed in 130 patients and the severity and geographic extent of ischemic myocardium were compared in three groups. On exercise, Group I patients had both chest pain and ST segment depression (symptomatic ischemia), Group II patients ST depression without chest pain (asymptomatic ischemia) and Group III patients had neither chest pain nor ST depression (truly silent ischemia). RESULTS: There were no differences among groups in arteriographic characteristics. The incidence of "truly silent ischemia" was 43%. The number of abnormally contracting ischemic segments, average score per segment and sum of scores were virtually identical in Groups I and II and significantly greater than in Group III for the patients (p < 0.01 to < 0.0001), for the vessels as a group (p < 0.01 to < 0.0001) and for the left anterior descending (p < 0.01 to < 0.0001) and right (p < 0.05) coronary arteries. By multivariate analysis, positive findings on the stress ECG was the single most significant variable in relation to the amount of ischemia (p < 0.001); exercise chest pain had no significant relationship. CONCLUSIONS: Exercise-induced ST segment depression is the single most significant variable in relation to the amount of ischemic myocardium; exercise-induced chest pain is not related to the amount of ischemia. Patients with "truly silent ischemia" constitute almost 50% of patients with coronary artery disease and have less ischemia than do patients with ECG indications of ischemia, with or without chest pain.

Coronary Angiography↗
PubMed1994

Should we stitch the subcutaneous fat layer following saphenous vein excision for coronary revascularization?

We report a prospective trial to establish whether a subcutaneous fat stitch reduces the incidence of haematoma formation, infection and wound dehiscence following saphenous vein excision for coronary revascularization. Two groups of patients undergoing coronary revascularization were studied. In the first group of 100 patients the saphenous vein was harvested from both legs. Legs were randomized to have either a fat stitch or no fat stitch during wound closure. By using both legs of each patient we eliminated the effect of general factors on wound healing, thus the patients acted as their own controls. In the second group of 200 patients, the saphenous vein was harvested from the thigh, and patients randomly allocated to either a fat stitch or no fat stitch during wound closure. The wounds were examined daily for 7 days, and again after 6 weeks at the follow-up. There was no difference in the rate of wound complication in the fat stitch groups (9%) compared with the no fat stitch groups (8%), however, the fat stitch groups required more surgical intervention for skin edge necrosis. It appears that closure of the subcutaneous fat following saphenectomy is unnecessary, and may be detrimental to skin healing.

Adipose Tissue↗
PubMed1994

Proton and charge circulation through substrate symports in Saccharomyces cerevisiae: non-classical behaviour of the cytosine symport.

A yeast strain lacking cytosine deaminase activity and over-expressing the cytosine proton symport has been used to study three aspects of symport function. (1) The proton flow during cytosine uptake after depletion of cellular ATP implies that the distribution of cytosine eventually approaches equilibrium with the proton gradient, one proton being absorbed with each molecule of cytosine. After correction for the presence of a minor leak pathway for cytosine, the cytosine distribution during energy metabolism was used to assay the magnitude of delta microH. Values of about 280 mV at pH 5 were obtained in this way. (2) Certain other substrates of the cytosine symport (hypoxanthine and especially fluorocytosine) cause the uptake of more than one equivalent of protons, but nevertheless accumulate to the same extent as cytosine. This phenomenon appears to be distinct from that of proton slip and is termed pseudochannelling. (3) The recycling of symported protons through the proton pump is an ill-defined process in plants and fungi. It usually occurs only after a distinct time lag during which the change in bulk intracellular pH may be relatively small. We have found conditions where there is no apparent time lag before protons entering yeast with glycine or histidine are recycled. This behaviour is discussed in relation to the possible voltage characteristics of the proton pump, its putative regulation by delta microH and the metabolic consequences of ATP hydrolysis being accelerated.

Adenosine Triphosphate↗
PubMed1994

[The parameters of image quality of a novel ultra high resolution film-screen system].

A film/screen system is described where the light emission of the intensifying screen is in the UV, which is more efficiently absorbed by the film, and hence print-through is virtually eliminated. In addition, because of significantly higher UV absorption within the screen, MTF is superior to conventional systems based on visible light. Thus the overall UV film/screen system has imaging efficiency and quality, as measured by the Detective Quantum Efficiency (DQE) and the Noise Equivalent Quantum Efficiency (NEQ), with superior characteristics to those of conventional systems. These imaging characteristics of the novel systems are described here and are compared with those of some conventional systems.

Humans↗
PubMed1993

Recombinant bovine heart mitochondrial F1-ATPase inhibitor protein: overproduction in Escherichia coli, purification, and structural studies.

A synthetic gene coding for the inhibitor protein of bovine heart mitochondrial F1 adenosine triphosphatase was designed and cloned in Escherichia coli. Recombinant F1-ATPase inhibitor protein was overproduced in E. coli and secreted to the periplasmic space. Biologically active recombinant F1-ATPase inhibitor protein was recovered from the bacterial cells by osmotic shock and was purified to near homogeneity in a single cation-exchange chromatography step. The recombinant inhibitor protein was shown to inhibit bovine mitochondrial F1-ATPase in a pH-dependent manner, as well as Saccharomyces cerevisiae mitochondrial F1-ATPase. Thorough analysis of the amino acid sequence revealed a potential coiled-coil structure for the C-terminal portion of the protein. Experimental evidence obtained by circular dichroism analyses supports this prediction and suggests F1I to be a highly stable, mainly alpha-helical protein which displays C-terminal alpha-helical coiled-coil intermolecular interaction.

Amino Acid Sequence↗
PubMed1993

Prevalence of asthma symptoms among adolescents in the Wellington region, by area and ethnicity.

AIMS: To compare the self-reported prevalence of asthma symptoms, among 12 to 15 year olds in three districts in the greater Wellington region, and to compare prevalence among three ethnic groups--Maori, Pacific Island and others. METHODS: Third form students from 13 secondary schools in the Wellington region, were surveyed using a video questionnaire and a standardised written questionnaire, during July 1991. RESULTS: Using the video questionnaire, the prevalence of wheeze during the previous 12 months was similar in Wellington city (32%), Lower Hutt (38%), and Porirua (37%); the corresponding findings using the written questionnaire were 28%, 27% and 30% respectively. The reported prevalence was also similar among Maori (38% using the video and 29% using the written questionnaire) and other children (36% and 30% respectively), but lower among Pacific Island children (31% and 20% respectively). The prevalence and frequency of severe attack of wheezing was similar in all three districts and all three ethnic groups. CONCLUSIONS: These findings contradict previous speculations of possible differences in asthma prevalence or severity within the greater Wellington region. They are consistent with other evidence that there are at most minor differences in asthma prevalence between Maori and nonMaori children in New Zealand; however, asthma prevalence may be lower among Pacific Island children. Thus ethnic differences in asthma morbidity and mortality are not likely to be due to differences in prevalence, but more likely relate to differences in access to and delivery of asthma care.

Adolescent↗
PubMed1993

Digital supine bicycle stress echocardiography: a new technique for evaluating coronary artery disease.

OBJECTIVES: The objective of this study was to determine the accuracy of digital supine bicycle stress echocardiography, a new technique for evaluating coronary artery disease during peak exercise. BACKGROUND: Prior stress echocardiographic techniques have not utilized peak exercise imaging to determine the extent and location of coronary artery disease. METHODS: Two-hundred twenty-two patients were studied: 180 underwent both supine bicycle stress echocardiography and coronary arteriography; 42 had a < 5% likelihood of disease. Forty-three patients had normal coronary arteries, 55 had single-vessel, 42 had double-vessel and 40 had triple-vessel coronary artery disease. RESULTS: Supine bicycle stress echocardiography was 93% sensitive, 86% specific and 92% accurate for identifying patients with coronary artery disease irrespective of prior myocardial infarction or achievement of > or = 85% maximal predicted heart rate. The "normalcy" rate in the low probability group was 100%. Supine bicycle stress echocardiography was 87% sensitive, 89% specific and 88% accurate for specific vessel identification. The sensitivity was greatest for the left anterior descending compared with the right coronary artery and the left circumflex coronary artery (95% vs. 81% vs. 78%, p < 0.01) and for vessels in patients with double- and triple-vessel compared with single-vessel disease (90% vs. 89% vs. 78%, p < 0.05). The procedure was significantly more sensitive for detection of vessels with 90% to 100% compared with 50% to 70% diameter stenosis (91% vs. 81%, p < 0.05) and was 88% correct in the prediction of multivessel disease. CONCLUSIONS: Supine bicycle stress echocardiography is a highly accurate tool for evaluating coronary artery disease, identifying both the patient with coronary artery disease and the location and extent of disease.

Adult↗
PubMed1993

Usefulness of supine bicycle stress echocardiography for detection of restenosis after percutaneous transluminal coronary angioplasty.

The role of supine bicycle stress echocardiography (SBSE) for detecting restenosis after percutaneous transluminal coronary angioplasty (PTCA) was evaluated in 80 patients: 41 (51%) with single and 39 (49%) with multivessel PTCA (total 129 dilated vessels). Total revascularization was performed in 54 (68%) and partial revascularization in 26 (32%) patients. Restenosis was angiographically demonstrated in 60 patients (75%) and in 72 vessels (56%) 6.1 +/- 2.9 months after PTCA. The results for detecting restenosis were: (1) SBSE versus exercise electrocardiographic sensitivity, 87 versus 55% (p < 0.001); (2) specificity, 95 versus 79%; and (3) accuracy, 89 versus 61% (p < 0.001). SBSE was 83% sensitive, 95% specific and 88% accurate for restenosis detection in specific vessels with comparable results for single versus multivessel PTCA and total versus partial revascularization. Sensitivity, specificity and accuracy were: 91, 93 and 91% for the left anterior descending coronary artery; 77, 94 and 85% for the right coronary artery; and 76, 96 and 88% for the left circumflex coronary artery. Ninety-four percent of the nondilated diseased vessels were correctly identified. It is concluded that SBSE is an excellent tool for identifying restenosis after PTCA.

Aged↗
PubMed1993

Gene fusions with human carbonic anhydrase II for efficient expression and rapid single-step recovery of recombinant proteins: expression of the Escherichia coli F1-ATPase epsilon subunit.

A new expression vector was constructed which allows the overproduction in Escherichia coli of tripartite proteins consisting of human carbonic anhydrase isozyme II (hCAII), a peptide linker containing an enterokinase cleavage site, and a target protein of interest. Carbonic anhydrase is soluble and stable in E. coli and serves as a highly specific purification tag in the recovery of the fusion protein by a single affinity chromatography step. The enterokinase cleavage site was engineered into the construct to allow accurate and efficient release of the target protein. To demonstrate the practical value of this vector, the E. coli F1-ATPase epsilon subunit was expressed as a fusion with hCAII. After a single purification step, biologically active recombinant E. coli F1-ATPase epsilon subunit was recovered following proteolytic removal of the hCAII moiety.

Amino Acid Sequence↗
PubMed1993

Emergency department satisfaction: what matters most?

STUDY OBJECTIVE: To determine the relative importance of variables correlated with patient satisfaction with emergency department care and service. DESIGN: Retrospective telephone survey targeting all patients who visited the Panorama City Kaiser Permanente ED from April 4 to April 17, 1991. Patients were contacted within one week of their discharge from the ED or hospital. PARTICIPANTS: Two hundred fifty-eight ED patients completed telephone surveys. Fifty-one percent of the respondents were male, and the mean age was 53 years. The majority of the respondents were white (70%); the most common service received was medical (82%). MEASUREMENTS AND RESULTS: Of the 14 variables that were found to be correlated with overall ED satisfaction, a multiple regression analysis revealed that the five most important variables were patient satisfaction with the amount of time it took before being cared for in the ED; patients' ratings of how caring the nurses were, how organized the ED staff was, and how caring the physicians were; and patient satisfaction with the amount of information the nurses gave them about what was happening to them. CONCLUSION: The total time patients spend in the ED and patients' perceptions of their wait time for an ED bed are not as important to patient satisfaction as is receiving prompt and caring service. The above service variables are key areas that may be targeted to improve ED services.

Adolescent↗
PubMed1992

Fluorocytosine causes uncoupled dissipation of the proton gradient and behaves as an imperfect substrate of the yeast cytosine permease.

At pH 5-6 ATP-depleted washed cell preparations of strain NC233-10b[pII4-9], in which the cytosine permease was overexpressed, absorbed cytosine, hypoxanthine or fluorocytosine stoichiometrically with, respectively, about 1, 1.4 and 5 proton equivalents. The cellular pH fell proportionately. The membrane depolarization caused by each compound was assayed in the presence of glucose with a voltage-sensitive dye and increased in the same order. Fluorocytosine significantly lowered the growth yield that a 'petite' strain of the yeast formed at limiting glucose concentrations. At pH 5.6 with extracellular [K+] below 1 mM, each of the three substrates was accumulated about 200-fold from a dilute solution at the expense of the proton gradient. This concentration ratio corresponds to a solute gradient (delta mu(s)) of 13 kJ mol-1. Raising [K+]o systematically lowered the substrate accumulation ratio and delta muH. The mean ratio delta mu(s)/delta muH was 0.82 for all three substrates. It was concluded that whereas the behaviour of cytosine approximated to that expected for a symport of unit proton stoichiometry, the absorption of protons with fluorocytosine and, to a lesser extent, hypoxanthine, was only partly conserved as useful work. A possible mechanism of this novel phenomenon is outlined.

Adenosine Triphosphate↗
PubMed1992

The effects of stopper drying on moisture levels of Haemophilus influenzae conjugate vaccine.

The discovery and development of increasingly potent biological and pharmaceutical products have resulted in very small amounts of the active ingredient in final product formulations. Pediatric vaccines with sub-milliliter dose sizes pose unique problems for final formulation and lyophilization, especially when stabilizers used are present in small amounts or are hygroscopic. Lyophilized Haemophilus b Conjugate Vaccine (Meningococcal Protein Conjugate) (PedvaxHIB) has a plug weight of about 3 mg in its final formulation. Microgram amounts of water absorbed by the lyophilized plug can cause drastic changes in the moisture content of the product. In a small percentage of the final containers absorption of moisture by the vaccine may cause aesthetic defects (plug collapse) over time, or at elevated temperatures. This paper describes drying methods developed to control residual moisture levels in stoppers used as final container closures. Results on the moisture stability of the product capped with dried and non-dried stoppers are presented.

Bacterial Outer Membrane Proteins↗
PubMed1992

Bremsstrahlung imaging using the gamma camera: factors affecting attenuation.

Quantitative imaging of bremsstrahlung from pure beta emitters is proposed as a means for in vivo management of antibody therapy. The method involves the use of high-energy collimation, an empirically selected broad photon energy window to enhance detector sensitivity, and a Wiener restoration filter to compensate for system blur. The measured and filtered data were obtained for an idealized scattering medium and isolated spherical sources. An effective linear attenuation coefficient of about 0.13 cm-1 was determined from the raw image data of 32P. A coefficient of 0.14 cm-1 was determined after the images were restored using the Wiener filter. The measured attenuation was not significantly dependent on the size of the region of interest or the size of the source. Its variation was within the experimental error of measurement (+/- 5%). The measured sensitivity (6 x 10(-6) cps/Bq) was sufficient for imaging therapy doses of 32P or 90Y.

Filtration↗
PubMed1991

Characterization of a cDNA encoding a protein involved in formation of the skeleton during development of the sea urchin Lytechinus pictus.

In order to investigate the role of proteins in the formation of mineralized tissues during development, we have isolated a cDNA that encodes a protein that is a component of the organic matrix of the skeletal spicule of the sea urchin, Lytechinus pictus. The expression of the RNA encoding this protein is regulated over development and is localized to the descendents of the micromere lineage. Comparison of the sequence of this cDNA to homologous cDNAs from other species of urchin reveal that the protein is basic and contains three conserved structural motifs: a signal peptide, a proline-rich region, and an unusual region composed of a series of direct repeats. Studies on the protein encoded by this cDNA confirm the predicted reading frame deduced from the nucleotide sequence and show that the protein is secreted and not glycosylated. Comparison of the amino acid sequence to databases reveal that the repeat domain is similar to proteins that form a unique beta-spiral supersecondary structure.

Amino Acid Sequence↗
PubMed1991

Screening for enteropathogenic Escherichia coli in infants with diarrhea by the fluorescent-actin staining test.

The attaching effacing (AE) adherence property is now recognized as an important virulence characteristic of enteropathogenic Escherichia coli (EPEC). The fluorescent-actin staining (FAS) test (S. Knutton, T. Baldwin, P. H. Williams, and A. S. McNeish, Infect. Immun. 57:1290-1298, 1989), which is diagnostic for the AE lesions produced by EPEC (and Vero cytotoxin-producing E. coli), has provided an additional tool with which to investigate this important class of enteric pathogens. In this study, we screened for the AE adherence property in two groups of E. coli isolated from infants with diarrhea by using the FAS test and compared the results with those from O:H serotyping, localized adhesion to HEp-2 cells (LA), and the EPEC adherence factor (EAF) probe. Only 16 of 41 (39%) E. coli strains previously diagnosed as EPEC by O antigen serogrouping were FAS test positive, and of these only 12 belonged to recognized EPEC O:H serotypes; 9 strains which did belong to EPEC O:H serotypes were FAS test negative. Of a second group of 297 untyped E. coli, 7 (2.3%) were FAS test positive, and of these only 2 belonged to EPEC serogroups; 5 belonged to serogroups not regarded as EPEC serogroups or were nontypeable. Of the 23 FAS-test-positive strains identified, 10 were EAF probe positive and showed good LA; 13 were EAF probe negative and showed a quantitatively distinctly poor LA. EAF-positive and EAF-negative strains, however, showed equally good adhesion to human small intestinal mucosa. None of the FAS-test-positive E. coli hybridized with probes for Vero toxins 1 or 2. We conclude that the FAS test is diagnostic not only for classical EPEC and Vero cytotoxin-producing E. coli but also for EPEC strains which are not currently being diagnosed because they belong to serotypes not generally regarded as EPEC serotypes.

Actins↗