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L S Green

Publications and source records attributed to L S Green.

At least 37 records · Page 2Linked to original sources
PubMed1995

Estimating ECG distributions from small numbers of leads.

The utility of body surface potential mapping to improve interpretation of electrocardiographic information lies in the presentation of thoracic surface distributions to characterize underlying electrophysiology less ambiguously than that afforded by conventional electrocardiography. Localized cardiac disease or abnormal electrophysiology presents itself electrocardiographically on the body surface in a manner in which pattern plays an important role for identifying or characterizing these abnormalities. Thus, in myocardial infarction, transient myocardial ischemia, Wolff-Parkinson-White syndrome, or ventricular ectopy, observation of electrocardiographic potential patterns, their extrema, and their magnitudes permits localization and quantization of the abnormal activity. Conventional electrocardiography assesses pattern information incompletely and does not use information of distribution extrema locations or magnitudes. Thus, increases or decreases in the magnitudes of electrocardiographic features (ST-segment potential displacement, amplitude, or morphology of Q, R, S, or T waves) associated with changes in cardiac sources (ischemia, infarction, conduction abnormalities, etc.) as measured from fixed leads have a high likelihood of being misinterpreted if the distribution itself is changing. In this study, the authors demonstrate the utility of estimating distributions from small numbers of optimally selected leads, including conventional leads, to reduce uncertainty in the interpretation of electrocardiographic information. This issue is highly relevant when thresholds are used to detect significance of potential levels (exercise testing, detection of myocardial infarction, and continuous monitoring to assess ST-segment changes). Significance of this work lies in improved detection and characterization of abnormal electrophysiology using conventional or enhanced leadsets and methods to estimate thoracic potential distributions.

Angioplasty, Balloon, Coronary↗
PubMed1995

The Churg-Strauss syndrome. A case report with angiographically documented coronary involvement and a review of the literature.

The Churg-Strauss syndrome (CSS) is an unusual disease that presents as a systemic vasculitis and peripheral eosinophilia in a patient with chronic atopic disease. Although often not prominent on initial presentation, cardiac involvement is a major cause of morbidity and mortality in patients with CSS. We report a case of a young woman with CSS who had a myocardial infarction. Coronary arteriography was performed for recurrent chest pain and demonstrated diffuse vasculopathy consistent with vasculitis in CSS. We have also included a review of the literature on cardiac involvement in CSS.

Adult↗
PubMed1994

Inhibition of receptor binding by high-affinity RNA ligands to vascular endothelial growth factor.

The proliferation of new blood vessels (angiogenesis) is a process that accompanies many pathological conditions including rheumatoid arthritis and solid tumor growth. Among angiogenic cytokines that have been identified to date, vascular endothelial growth factor (VEGF) is one of the most potent. We used SELEX [systematic evolution of ligands by exponential enrichment; Tuerk, C., & Gold, L. (1990) Science 249, 505-510] to identify RNA ligands that bind to VEGF in a specific manner with affinities in the low nanomolar range. Ligands were selected from a starting pool of about 10(14) RNA molecules containing 30 randomized positions. Isolates from the affinity-enriched pool were grouped into six distinct families on the basis of primary and secondary structure similarities. Minimal sequence information required for high-affinity binding to VEGF is contained in 29-36-nucleotide motifs. Binding of truncated (minimal) high-affinity ligands to VEGF is competitive with that of other truncated ligands and heparin. Furthermore, truncated ligands from the six ligand families inhibit binding of [125I]VEGF to its cell-surface receptors. Oligonucleotide ligands described here represent an initial set of lead compounds in our ongoing effort toward the development of potent and specific VEGF antagonists.

Base Sequence↗
PubMed1994

Assessment of spatial and temporal characteristics of ventricular repolarization.

Measurement of dynamics and spatial characteristics of ventricular repolarization is of interest in assessing patients with ischemic heart disease, particularly in relation to the detection and characterization of ischemic events, identification of patients at risk of ventricular arrhythmias, or determination of the efficacy of drugs intended to alter repolarization. The QT interval (QTI) has been the index of choice for assessing repolarization abnormalities. It is a general measure of repolarization duration but lacks the power to assess the spatial aspects of repolarization and the ability to detect localized shortening in the setting of global prolongation. For direct cardiac surface measurement, QRST integrals and activation recovery intervals (ARIs) were used to assess repolarization and its disparity. The use of similar measurements from the body surface was proposed to provide better characterization of repolarization, its disparity, and its dynamics than is possible using the QTI. In one open-chest experiment using an intact canine heart and two experiments using isolated canine hearts suspended in a torso-shaped electrolytic tank, 64 epicardial electrograms and 192 torso surface electrocardiograms were measured simultaneously. Ventricular repolarization was globally altered by varying pacing cycle lengths or tank temperature. Atrial and ventricular pacing were used to assess sensitivity of repolarization indices to activation sequence. At the cardiac surface, (1) QTI tracks global repolarization changes but is affected by activation sequence and insensitive to localized shortening of repolarization; (2) distribution of QRST integrals reflects disparity of repolarization and is largely independent of activation sequence; and (3) ARI measures local repolarization duration and is only weakly affected by activation sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Resolution of pace mapping stimulus site separation using body surface potentials.

BACKGROUND: Several studies have related 12-lead ECG waveform during ventricular tachycardia to ECG waveform during ventricular pacing to identify ablation sites for therapy of ventricular tachycardia. QRS isopotential maps and QRS isointegral maps derived from body surface isopotential maps have also been correlated with left ventricular pacing sites with the same objective. The comparison process used is subjective and only semiquantitative. Improved accuracy of catheter placement may improve success rates of ablation therapy. METHODS AND RESULTS: This animal study was performed to determine the spatial resolution with which left ventricular pacing sites could be distinguished by body surface isopotential mapping. Potentials were recorded from 64 evenly spaced thoracic leads. Hexapolar or octapolar pacing catheters with 2-mm interelectrode spacing were placed percutaneously in the left ventricle in each of six dogs, and bipolar endocardial pacing was performed using each pair of adjacent electrodes. QRS isopotential maps of each pacing site for each catheter placement were cross-correlated by computer. Difference maps for each pair of pacing sites were calculated lead by lead and time instant by time instant, and root-mean-square voltage differences were calculated. Results indicated that correlation coefficients and root-mean-square error of voltage differences monotonically decrease and increase, respectively, with stimulus site separation. Both measures were significantly different (P < .05) for separations of 4 mm or more. CONCLUSIONS: A method of quantitative comparison of body surface potential maps can be used in normal hearts to localize ventricular pacing sites within a 4-mm range. The method may have utility in determining potential ablation sites for therapy of ventricular tachycardia or preexcitation syndromes.

Animals↗
PubMed1993

Bronchogenic cancer in patients under 40 years old. The experience of a Latin American country.

Lung cancer in young patients is increasing in frequency, as documented by data from the United States, Canada, Japan, and European countries. However, to date and to our knowledge, there have not been any reports from Latin America on this topic. The published reports show that lung cancer in young patients is associated with smoking habit and family history of lung cancer. Its clinical course seems to be more aggressive than in older patients and the histologic type is less often squamous type. We describe 48 patients, aged 40 years or younger, who were diagnosed as having lung cancer in the Instituto Nacional de Cancerología from 1980 to 1990. The patients were equally divided between men and women. Smoking was documented for only 46 percent of the cases. The histologic type most frequently diagnosed was adenocarcinoma (N = 26) followed by squamous cell carcinoma (N = 12). Almost all the cases (46 cases) were staged IV according to the TNM classification. A group of 33 patients older than 40 years (56 to 82 years) were used for comparison. The differences in sex ratio that were higher for men in the elder (m/f, 2.7:1) were family history for cancer in six patients elder; positive smoking habit in all the aged patients (100 percent) compared with only 43.7 percent in the younger group; histologic type (26 adenocarcinomas and 4 squamous in the younger compared with 14 and 12, respectively, in the elder).

Adult↗
PubMed1991

On-line coupling of supercritical fluid extraction with multidimensional microcolumn liquid chromatography/gas chromatography.

An on-line multidimensional supercritical fluid extraction/microcolumn liquid chromatography/capillary gas chromatography system (SFE/LC/GC) has been developed and applied to the quantitative determination of trace levels (parts per billion) of chlorpyrifos insecticide in grass field samples. This system provides all the advantages of an on-line multidimensional system, including increased resolving power, high sensitivity, quantitation, precision, and automation potential. Off-line analysis of the grass extracts by GC with an electron capture detector yielded a complex chromatogram from which it was difficult to quantitate the chlorpyrifos, but analysis of the extract by LC/GC yielded a simple chromatogram from which chlorpyrifos could be quantitated. On-line SFE/LC/GC resulted in reduced sample preparation with the grass extract being deposited directly on the LC microcolumn via an impactor interface, followed by the LC/GC separation. The reproducibility of the on-line SFE/LC/GC procedure was studied and found to yield a relative standard deviation of 10.8% for the determination of chlorpyrifos insecticide in grass field samples at a concentration of 160 ng/g. Using this method, the entire analysis including extraction, clean-up, and gas chromatography required less than 0.1 mL of organic solvent.

Chlorpyrifos↗
PubMed1991

Protein-protein interactions with the acidic COOH terminus of the single-stranded DNA-binding protein of the bacteriophage T4.

The single-stranded DNA-binding protein of the bacteriophage T4 is encoded by gene 32. Monoclonal antibodies were raised against intact gene 32 protein (gp32). We mapped the epitopes recognized by 12 of these monoclonal antibodies; the epitopes are all within the COOH-terminal region of gp32. As shown by others, removal of the COOH terminus of gp32 abolishes the ability of the intact protein to bind to many T4 proteins involved in replication, recombination, repair, and late transcription. These results suggest that the COOH terminus of gp32 is a protein-binding domain. The COOH terminus is attached to a DNA-binding domain that includes a zinc finger. We propose a model in which the DNA-binding and protein-binding domains are used in T4 replication, recombination, repair, and late transcription. The COOH terminus of gp32 is very acidic and may form four negatively charged amphipathic alpha-helices, which could fold into a four-helix bundle when associated with other proteins. At least six of the monoclonal anti-gp32 antibodies bind to the COOH terminus of gp32 and to DNA. Similarities between the COOH terminus of gp32 and DNA are explored.

Antibodies, Monoclonal↗
PubMed1991

Ferredoxin and ferredoxin-NADP reductase from photosynthetic and nonphotosynthetic tissues of tomato.

Ferredoxin and ferredoxin-NADP+ oxidoreductase (FNR) were purified from leaves, roots, and red and green pericarp of tomato (Lycopersicon esculentum, cv VFNT and cv Momotaro). Four different ferredoxins were identified on the basis of N-terminal amino acid sequence and charge. Ferredoxins I and II were the most prevalent forms in leaves and green pericarp, and ferredoxin III was the most prevalent in roots. Red pericarp of the VFNT cv yielded variable amounts of ferredoxins II and III plus a unique form, ferredoxin IV. Red pericarp of the Momotaro cv contained ferredoxins I, II, and IV. This represents the first demonstration of ferredoxin in a chromoplast-containing tissue. There were no major differences among the tomato ferredoxins in absorption spectrum or cytochrome c reduction activity. Two forms of FNR were present in tomato as judged by anion exchange chromatography and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. FNR II had a lower apparent relative molecular weight, a slightly altered absorption spectrum, and a lower specific activity for cytochrome c reduction than FNR I. FNR II could be a partially degraded form of FNR I. The FNRs from the different tissues of tomato plants all showed diaphorase activity, with FNR II being more active than FNR I. The presence of ferredoxin and FNR in heterotrophic tissues of tomato is consistent with the existence of a nonphotosynthetic ferredoxin/FNR redox pathway to support the function of ferredoxin-dependent enzymes.

Amino Acid Sequence↗
PubMed1991

Nonparametric identification of discriminative information in body surface maps.

A nonparametric method, based on the Kolmogorov-Smirnov (K-S) test was used to detect significant differences between classes of body surface maps (BSPM's). By systematic application of the method throughout the cardiac cycle, discriminative spatio-temporal information can be identified. In a second method, a Sebestyen linear transformation (SLT) was derived to give estimates of pairwise, linear separability of clinical classes. The utility of the method was illustrated by the pairwise comparison of 40 normal subjects (NOR), 40 patients with anterior myocardial infarction (AMI), and 40 with inferior myocardial infarction (IMI). The application examples demonstrated that: a) diagnostic information in low potential amplitude regions may surpass that in high amplitude regions, b) probability distributions of characteristic features showed small overlap in NOR versus AMI and NOR versus IMI dichotomies although they were not linearly separable, and c) the single best separating potential sample in the K-S sense for NOR versus AMI or NOR versus IMI dichotomies recovered 88 and 73% of the SLT performance, respectively.

Electrocardiography↗
PubMed1991

Detection and localization of prolonged epicardial electrograms with 64-lead body surface signal-averaged electrocardiography.

BACKGROUND: Prolonged, fractionated ventricular electrograms often are detectable after myocardial infarction and are a marker for an arrhythmia-prone state. QRS late potentials detected on the body surface with signal-averaged electrocardiography (SAECG) are thought to arise from the diseased tissue that generates prolonged ventricular electrograms and as such are also a marker for arrhythmias. A limitation of the current SAECG technique is that recordings are obtained from only three bipolar lead pairs. Because late potentials probably arise from multiple small sources in the heart, more extensive sampling of the body surface may contribute additional information to the SAECG: The present study investigates the additional sensitivity of SAECG using 64 body surface leads in detecting prolonged epicardial electrograms and examines its use in determining the epicardial location of prolonged electrograms. METHODS AND RESULTS: Dogs were studied before and 5-10 days after either lateral left ventricular (n = 13) or right ventricular (n = 8) myocardial infarction. Greater prolongation of signal-averaged QRS duration was detected with 64-lead SAECG (postinfarction QRS duration, 100.3 +/- 16.3 msec) than with three-lead SAECG (postinfarction QRS duration, 89.4 +/- 10.1, p = 0.0005). Nineteen of the 21 dogs (90%) had prolonged epicardial electrograms detected over the infarct. The correlation between epicardial electrogram duration and signal-averaged QRS duration calculated from individual leads was much better for 64-lead SAECG (r = 0.88, p less than 0.0001) than for three-lead SAECG (r = 0.53, p = 0.01), and the difference was most marked in cases with longer electrogram durations (more than 100 msec). Local late potential maxima on the thorax after lateral left ventricular infarction were located to the left and inferior compared with those after right ventricular infarction (p = 0.006). CONCLUSIONS: SAECG with more extensive recording from the body surface using 64 leads detects greater QRS prolongation than three-lead SAECG, and the longer QRS durations detected correspond to the duration of prolonged epicardial electrograms. Body surface location of late potentials corresponds to the epicardial location of the prolonged electrograms. This application of body surface mapping techniques to SAECG may permit more sensitive detection of arrhythmia-prone states and may aid in identifying arrhythmia sources.

Animals↗
PubMed1991

Epicardial potential mapping. Effects of conducting media on isopotential and isochrone distributions.

BACKGROUND: Epicardial excitation sequences, recovery sequences, and potential distributions are recorded from patients during surgery and from animals in the research laboratory for a variety of purposes. During such recordings, a portion of the cardiac surface is exposed to air, and the remainder of the epicardial surface variably is in contact with conductive tissue. No systematic studies document the degree to which these different conditions affect measured excitation times, potential distributions, and/or the configuration of epicardial electrograms. METHODS AND RESULTS: Epicardial potential distribution was recorded from five isolated, perfused hearts using a 64-unipolar-lead sock. Data were recorded first with the heart suspended in air and then with the heart immersed in a heated tank filled sequentially to full and half-full levels with conductive Tyrode's solution and then NaCl-sucrose solution. These solutions had resistivity less than and more than that of blood, respectively, and air was assumed to have infinite resistivity. Epicardial potentials were recorded from two hearts before removal from the chest, both with and without a latex sheet insulating the heart from the pericardial cradle. Amplitude of recorded potentials from both intact and isolated hearts was markedly higher when the heart was surrounded by an insulating medium, but locations of positive and negative regions were less affected by surrounding medium. Isochrone activation maps calculated using the minimum derivative of the QRS (intrinsic deflection) were not affected by the conductivity of media surrounding the heart. CONCLUSIONS: The present study provides evidence that isochrone maps recorded at surgery are not distorted by exposure of the cardiac surface to insulating air. Results suggest that epicardial isochrones recorded during cardiac surgery could be used in patients to assess the accuracy of "inverse" procedures that noninvasively compute epicardial electrograms and isochrones from body surface potentials.

Animals↗
PubMed1989

A region of a cyanobacterial genome required for sulfate transport.

Using the cysA locus of Salmonella typhimurium as a heterologous probe, we have cloned a region of the Anacystis nidulans R2 (Synechococcus PCC 7942) genome involved in sulfate assimilation. The 8.3-kilobase-pair region encodes at least five transcripts that cannot be detected unless the cells are deprived of sulfur. One of the genes in this region has been sequenced, and the protein that it encodes is homologous to a polypeptide component of other permease systems of Escherichia coli and Salmonella. Insertional inactivation of the putative sulfate permease gene, designated cysA, as well as of other genes within this region, results in cysteine auxotrophy, reduced sulfate uptake, and altered expression of soluble and cytoplasmic-membrane polypeptides associated with sulfur starvation.

Amino Acid Sequence↗
PubMed1989

Instrumentation and practice standards for electrocardiographic monitoring in special care units. A report for health professionals by a Task Force of the Council on Clinical Cardiology, American Heart Association.

The proposed recommendations for continuous electrocardiographic monitoring systems represent goals for future development. Description of a technique in the report does not constitute an endorsement of its clinical use. Lead systems for ECG monitoring must adequately sense the cardiac electrical field and the leads should be standardized. Future monitors should be capable of simultaneously displaying and analyzing multiple leads. Recommendations for electrode placement and position of patient are made. Important parameters in each category of standards for instrumentation published in 1983 in the American National Standard for Cardiac Monitors, Heart Rate Meters, and Alarms are listed. Selected procedures proposed by the Association for the Advancement of Medical Instrumentation to inform users of minimally acceptable accuracy of computerized systems in a standardized manner are presented. Emphasis is placed on the importance of nursing and medical staff capabilities. Personnel qualifications and training as well as systems to assure and maintain quality of immediate ECG diagnosis are highlighted.

Allied Health Personnel↗
PubMed1989

Sources of variability in normal body surface potential maps.

Within-group variability of body surface potential maps was assessed on data from 685 carefully validated normal subjects (348 men and 337 women). Sources of within-group variability were evaluated by subgrouping maps by patient sex, age, height, and weight. Contribution of reproducibility error to total variance was assessed in a separate group of 52 normal subjects in whom multiple maps were recorded. Total variance was significantly lower in women than in men. Total variance tended to decrease with age, and the greatest decrease occurred in men during the 3rd decade. The ratio of total variance to mean signal energy showed a slow decrease with age for each group. Results suggest that the dominant source of within-group variability arises from variability of cardiac electric sources while the influence of volume conductor variability is significantly less. Variability due to measurement reproducibility was approximately half of the total variance.

Adult↗
PubMed1988

Changes in sulfate transport characteristics and protein composition of Anacystis nidulans R2 during sulfur deprivation.

Sulfur-starved cells of Anacystis nidulans have an increased capacity to take up sulfate. The apparent Vmax for sulfate uptake increased at least 10-fold after 24 h of sulfur deprivation, whereas the K1/2 remained unchanged at approximately 1.35 microM. The initial rate of sulfate uptake increased between 2 and 6 h after transfer of the cells to sulfur-free medium, in concert with elevated levels of three cytoplasmic membrane polypeptides with molecular masses of 43, 42, and 36 kilodaltons (kDa). The amounts of these polypeptides did not increase in response to nitrogen or phosphorus deprivation. A fourth cytoplasmic membrane polypeptide of 17 kDa did not appear until 24 h after transfer to sulfur-deficient medium. In the total soluble fraction, three polypeptides with masses of 36.5, 33.5, and 28.5 kDa increased dramatically in response to sulfur deprivation, but not in response to nitrogen or phosphorus deprivation. The specificity and abundance of these polypeptides indicate that they could play an important role in the response of A. nidulans to sulfur deprivation.

Biological Transport↗