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Biomedical subjects

E Greenberg

Publications and source records attributed to E Greenberg.

At least 55 records · Page 3Linked to original sources
PubMed1985

Prospective reimbursement for state-of-the-art medical practice: the case for invasive electrophysiologic evaluation.

This study is an examination of the economic consequences of invasive electrophysiologic (EP) evaluation for recurrent supraventricular tachycardia (SVT) and ventricular tachycardia (VT) on a tertiary health care facility during 1980 and 1981. The average cost of hospitalizations for EP evaluation was substantial (SVT, $6,990; VT, $13,897), as was the length of hospital stay (SVT, 12 +/- 8 days; VT, 24 +/- 8 days). The cost of a single EP procedure in the study period averaged $695 (range $200 to $1,206). During follow-up (1 to 3 years), there was substantial improvement in arrhythmia control on EP-based therapy in SVT and VT compared with prior empirical therapy. Cost:benefit analysis strongly favored EP-based therapy over empirical therapy (SVT, 6:1; VT, 18:1) in this follow-up period. Comparison with cost of noninvasive techniques for VT evaluation showed that EP evaluation had comparable cost. Current prospective reimbursement schedules have no DRG category for EP evaluation and do not fairly compensate hospitals for invasive or noninvasive arrhythmia studies. Invasive EP evaluation is both clinically effective and cost-effective in the management of patients with recurrent SVT and VT. Prospective reimbursement plans should include a specific DRG category for these studies.

Anti-Arrhythmia Agents↗
PubMed1985

Phase I study of elliptinium (2-N-methyl-9-hydroxyellipticinium).

Elliptinium (2-N-methyl-9-hydroxyellipticinium), a chemotherapeutic agent whose mechanism of action has not been completely elucidated, intercalates into DNA. In this Phase I clinical trial, the schedule of drug administration consisted of weekly intravenous infusions. Twenty-nine patients were evaluable for toxicity. The initial dose level was 40 mg/m2 and was escalated to 150 mg/m2 through six levels. The dose-limiting side effects were emesis, xerostomia, and azotemia. The lack of myelosuppression was the most striking feature. Objective responses (partial remission, minor response) were seen in one patient each with Hodgkin's disease, non-Hodgkin's lymphoma, breast cancer, and nasopharyngeal carcinoma. We recommend a Phase II evaluation of elliptinium at a dose of 100 mg/m2 on a weekly schedule.

Adolescent↗
PubMed1985

Value of a 24-hour image (four-phase bone scan) in assessing osteomyelitis in patients with peripheral vascular disease.

The delayed images of the four-phase 99mTc phosphonate bone scan are compared with the delayed images of the three-phase study in patients with diabetes mellitus and/or peripheral vascular disease and suspected osteomyelitis. Three-phase bone imaging includes an immediate postinjection radionuclide angiogram, a blood-pool image, and delayed static images to 7 hr. The four-phase study adds a 24-hr static image. The scan is positive for osteomyelitis if images show progressively increasing lesion to background activity ratios over time. The results of analyzing 21 three- and four-phase bone scans in 17 patients were correlated with clinical course, cultures, and/or x-rays, gallium scans, and CT scans. The accuracy of four-phase bone imaging for diagnosing osteomyelitis was 85%; for three phase, 80%. Sensitivity for four phase was 80%; specificity was 87%. Sensitivity for three phase was 100%; specificity was 73%. Since overall accuracy of the four-phase study is slightly better than three phase, in these patients with diabetes mellitus and/or peripheral vascular disease, the addition of a 24-hr image, creating a four-phase bone scan, is recommended.

Diabetic Angiopathies↗
PubMed1984

Management of recurrent ventricular tachycardia: economic impact of therapeutic alternatives.

The clinical and economic results of antiarrhythmic therapy selected on the basis of electrophysiologic (EP) studies in patients with recurrent ventricular tachycardia (VT) were examined and compared with previously administered empiric therapy. Twenty-nine patients with recurrent VT and organic heart disease, aged 39 to 78 years (mean 59 +/- 11) were evaluated. All patients had empiric therapy before EP studies and EP-based therapy after EP evaluation. Hospital records were analyzed from arrhythmia diagnosis 1 to 39 months (mean 7.5 +/- 10.4) before EP evaluation until completion of follow-up 1 to 20 months (mean 13.3 +/- 7.4) after EP studies. Clinical efficacy was assessed by comparing actual arrhythmic deaths or recurrences during EP-based therapy with predicted values on empiric therapy. Charges based on diagnosis-related groupings for empiric and EP-based therapy were compared. Charges for EP evaluation were included in the calculation for EP-based therapy. During empiric therapy, 1 to 7 unsuccessful drug trials (mean 3.7 +/- 1.6) were performed, with arrhythmia recurrences noted in all patients during a mean 7.5-month VT duration. Twenty-seven of 29 patients required 1 to 70 electrical terminations. There were 64 hospitalizations (mean 2.1 +/- 1.7) with a total length of hospital stay of 913 days (mean 31.0 +/- 19.9). EP evaluation required 90 EP procedures (mean 3.0 +/- 1.5) with a length of stay of 690 days (mean 23.8 +/- 12.0). During a follow-up period of 1 to 26.5 months (13.3 +/- 7.4) on EP-based therapy, 1 patient died suddenly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Biosynthesis of bacterial glycogen: characterization of adenosine diphosphate glucose synthetases from Enterobacter hafniae and Aeromonas hydrophila.

Enterobacter hafniae and Aeromonas hydrophila ADPglucose synthetases were purified approximately 39- and 61-fold, respectively, over the crude extract. Both enzymes were heat stable at 60 degrees C in the presence of inorganic phosphate. The molecular weights of both enzymes were approximately 200,000 which are similar to other enteric ADPglucose synthetases studied. Based on kinetic results obtained from the partially purified enzymes, the E. hafniae enzyme is activated twofold by phospho-enolpyruvate while the A. hydrophila enzyme is activated twofold by fructose 6-P and 1.5-fold by fructose 1,6 bis-phosphate. The E. hafniae enzyme activity is strongly inhibited by AMP and ADP and the inhibition can be partially reversed by P-enolpyruvate. ADP is the most effective inhibitor of the A. hydrophila enzyme and its inhibition can be partially overcome by the presence of the activators fructose 6-P and fructose 1,6-P2. These kinetic results show that the allosteric properties of the E. hafniae enzyme are distinctly different from the ADPglucose synthetases of those previously studied from bacteria of the genus Enterobacter. Although the A. hydrophila enzyme is activated by fructose 1,6-P2, its allosteric properties are quite different than those observed for ADPglucose synthetase of the Enterobacteriaceae.

Adenosine Diphosphate↗
PubMed1984

ADPglucose Pyrophosphorylase from the CAM Plants Hoya carnosa and Xerosicyos danguyi.

ADPglucose pyrophosphorylase from the Crassulacean acid metabolism plants Hoya carnosa and Xerosicyos danguyi were partially purified to study their regulatory and kinetic properties. The molecular weight of the native enzymes from both plants was determined to be about 209,000. The enzyme from both plants was found to be activated by glycerate 3-phosphate and inhibited by inorganic phosphate. The kinetic constants for the substrates and Mg(2+) are reported. The significance of the activation by glycerate 3-phosphate and inhibition by inorganic phosphate of ADPglucose synthesis catalyzed by the H. carnosa and X, danguyi enzymes is discussed. ADPglucose synthesized by the above enzymes was found to be the most effective donor of the glucosyl portion to alpha-glucan primer in the starch synthase reaction observed in CAM plants.

Journal Article↗
PubMed1983

Pyrophosphate may be involved in regulation of bacterial glycogen synthesis.

Inorganic pyrophosphate is a potent inhibitor of the enzyme that catalyzes synthesis of the glucosyl donor for Escherichia coli glycogen synthesis, ADP-glucose pyrophosphorylase. The Ki is determined to be 40 microM and the substrate ATP, the activator, fructose 1,6-P2 or the allosteric inhibitor, AMP do not greatly affect the inhibition. PPi exhibits mixed type inhibition with the other substrate, glucose 1-P. The potential regulation of glycogen synthesis by PPi is discussed.

Adenosine Diphosphate Glucose↗
PubMed1983

Biosynthesis of bacterial glycogen: activator specificity of the ADPglucose pyrophosphorylase of Rhodopseudomonads.

The adenosine diphosphate glucose pyrophosphorylases from Rhodopseudomonas acidophila, Rhodopseudomonas blastica, Rhodopseudomonas globiformis, and Rhodopseudomonas viridis were purified to the extent that their regulatory properties could be studied. With the exception of the R. viridis enzyme, all the enzymes could be activated by pyruvate or its analog, oxamate. The most effective activator for all the enzymes was fructose 6-P. However, the R. globiformis and R. viridis ADP glucose pyrophosphorylases can also be activated by fructose 1,6-P2. Thus a new activator specificity class was observed for the R. viridis enzyme while the R. acidophila and R. blastica enzymes exhibited the same activator specificity previously observed for Rhodopseudomonas capsulata ADPglucose pyrophosphorylase. The R. globiformis enzyme, activated by fructose 6-P, fructose 1,6-P2, and by pyruvate had a similar activator specificity previously seen for the Rhodopseudomonas sphaeroides and Rhodopseudomonas gelatinosa enzymes. For some enzymes, the presence of activator increased the apparent affinity for the substrates and MgCl2. The activator also modulated the sensitivity of the R. viridis and R. acidophila enzymes to Pi inhibition and the R. blastica enzyme to AMP inhibition. ADPglucose is the glucosyl donor for glycogen synthesis in these bacteria. Thus, regulation of glycogen synthesis in these microorganisms is probably regulated by the ratio of the activator concentration to inhibitor concentration.

Bacterial Proteins↗
PubMed1981

Biosynthesis of bacterial glycogen: activator specificity of the adenosine diphosphate glucose pyrophosphorylases from the genus Rhodospirillum.

The adenosine diphosphate (ADP) glucose pyrophosphorylases from Rhodospirillum fulvum, Rhodospirillum molischianum, and Rhodospirillum tenue were partially purified, and their kinetic properties were studied. The enzyme from the three organisms was found to be activated by pyruvate and thus was similar to the Rhodospirillum rubrum enzyme that had been previously studied (C. E. Furlong, and J. Preiss, J. Biol. Chem. 244:2539-2548, 1979). The enzymes from R. fulvum, R. molischianum, and R. tenue were also activated by oxamate, an analog of pyruvate. Other alpha-keto acids, alpha-ketobutyrate and hydroxypyruvate, activated to a smaller extent. The presence of pyruvate increased the apparent affinity for adenosine 5'-triphosphate and MgCl2 for all three enzymes. The R. molischianum enzyme has very little sensitivity to inhibition by adenosine 5'-monophosphate, ADP, or inorganic phosphate. However, R. tenue ADPglucose pyrophosphorylase is very sensitive to inhibition by adenosine 5'-monophosphate, and the R. fulvum enzyme is inhibited by ADP. Increasing pyruvate concentration reversed the inhibition caused by adenosine 5'-monophosphate or ADP. Since ADPglucose is the glycosyl donor for synthesis of glycogen, it is possible that in vivo glycogen synthesis is regulated by the concentration of pyruvate and, in the case of R. fulvum and R. tenue, by the ratio of pyruvate concentration to inhibitor concentration.

Adenosine Diphosphate Glucose↗
PubMed1980

Regulatory properties of the ADPglucose pyrophosphorylase from Rhodopseudomonas sphaeroides and from Rhodopseudomonas gelatinosa.

The ADPglucose pyrophosphorylases from Rhodopseudomonas sphaeroides and Rhodopseudomonas gelatinosa are activated by fructose-6-phosphate, pyruvate and fructose-1,6 biophosphate-P2. The effects of the activators are to increase significantly the Vmax of ADPglucose synthesis and to lower the S0.5 values (concentration of substrates giving 50% maximal velocity) for ATP and MgCl2. The R. sphaeroides enzyme is inhibited by Pi while the R. gelatinosa enzyme is inhibited by AMP as well as by Pi. The interaction between inhibitor and activator is complex. At very low concentrations of activator the enzyme is more sensitized to inhibition. However, at higher concentrations of activator there is a decrease in the sensitivity of the enzyme towards inhibition. The findings are discussed with respect to glycogen synthesis in these microorganisms and may be related to findings that indicate that Rhodopseudomonads have the ability to degrade sugars via the Entner-Duodoroff or Embden-Meyerhoff pathways.

Adenosine Diphosphate Glucose↗
PubMed1980

Characterization of the spinach leaf phosphorylases.

The chloroplastic and the cytoplasmic phosphorylases were purified and their kinetic properties characterized. The cytoplasmic enzyme was purified to homogeneity via affinity chromatography on a glycogen-Sepharose column. Subunit molecular weight studies indicated a value of 92,000, whereas a native molecular weight value of 194,000 was obtained by sucrose density gradient centrifugation. The chloroplast enzyme's native molecular weight was determined to be 203,800. The cytoplasmic enzyme shows the same V(max) for maltopentaose, glycogen, amylopectin, amylose, and debranched amylopectin but is only slightly active toward maltotetraose. The K(m) for phosphate at pH 7.0 is 0.9 millimolar and for glucose-1-phosphate, 0.64 millimolar. The K(m) values for phosphorolysis of amylopectin, amylose, glycogen, and debranched amylopectin are 26, 165, 64, and 98 micrograms per milliliter, respectively. In contrast, the relative V(max) values for the chloroplast enzyme at pH 7.0 are debranched amylopectin, 100, amylopectin, 63.7, amylose, 53, glycogen, 42, and maltopentaose, 41. K(m) values for the above high molecular weight polymers are, respectively, 82, 168, 122 micrograms per milliliter, and 1.2 milligrams per milliliter. The K(m) value for inorganic phosphate is 1.2 millimolar. The chloroplastic phosphorylase appears to have a lower apparent affinity for glycogen than the cytoplasmic enzyme. The results are discussed with respect to previous findings of multiple phosphorylase forms found in plant tissues and to possible regulatory mechanisms for controlling phosphorylase activity.

Journal Article↗
PubMed1979

Subcellular localization of the starch degradative and biosynthetic enzymes of spinach leaves.

The subcellular localization of the starch biosynthetic and degradative enzymes of spinach leaves was carried out by measuring the distribution of the enzymes in a crude chloroplast pellet and soluble protein fraction, and by the separation on sucrose density gradients of intact organelles, chloroplasts, peroxisomes, and mitochondria of a protoplast lysate. ADP-Glucose pyrophosphorylase, starch synthase, and starch-branching enzymes are quantitatively associated with the chloroplasts. The starch degradative enzymes amylase, R-enzyme (debranching activity), phosphorylase, and D-enzyme (transglycosylase) are observed both in the chloroplast and soluble protein fractions, the bulk of the degradative enzyme activities reside in the latter fraction. Chromatography of a chloroplast extract on diethylaminoethyl-cellulose resolves the R- and D-enzymes from amylase and phosphorylase activities although the two latter enzyme activities coeluted. The digestion pattern of amylase with amylopectin as a substrate indicates an endolytic activity but displays properties unlike the typical alpha-amylase as isolated from endosperm tissue.

Journal Article↗
PubMed1977

Inkblot content and interpersonal distance.

Four Ht content scales were related to a projective and a live measure of interpersonal distance. Based on previour research, negative correlations between human and barrier content and interpersonal distance were predicted, with positive correlations predicted between anxiety and hostility content and distance behavior. All four content scales were found to relate significantly to projective distance, but only anxiety and hostility correlated significantly with distance behavior. The content scales also were combined in regression equations to predict interpersonal distance. The projective measure of interpersonal distance correlated signifiantly with the live measure of distance. The results were interpreted as support for the construct validity of the inkblot scales.

Anxiety↗
PubMed1976

Biosynthesis of bacterial glycogen. Purification and properties of the Escherichia coli B ADPglucose:1,4-alpha-D-glucan 4-alpha-glucosyltransferase.

The Escherichia coli B glycogen synthase has been purified to apparent homogeneity with the use of a 4-aminobutyl-Sepharose column. Two fractions of the enzyme were obtained: glycogen synthase I with a specific activity of 380 mumol mg-1 and devoid of branching enzyme activity and glycogen synthase II having a specific activity of 505 mumol mg-1 and containing branching enzyme activity which was 0.1% of the activity observed for the glycogen synthase. Only one protein band was found in disc gel electrophoresis for each glycogen synthase fraction and they were coincident with glycogen synthase activity. One major protein band and one very faint protein band which hardly moved into the gel were observed in sodium dodecyl sulfate gel electrophoresis of the glycogen synthase fractions. The subunit molecular weight of the major protein band in sodium dodecyl sulfate gel electrophoresis of both glycogen synthase fractions was determined to be 49 000 +/- 2 000. The molecular weights of the native enzymes were determined by sucrose density gradient ultracentrifugation. Glycogen synthase I had a molecular weight of 93 000 while glycogen synthase II had a molecular weight of 200 000. On standing at 4 degrees C or at -85 degrees C both enzymes transform into species having molecular weights of 98 000, 135 000, and 185 000. Thus active forms of the E. coli B glycogen synthase can exist as dimers, trimers, and tetramers of the subunit. The enzyme was shown to catalyze transfer of glucose from ADPglucose to maltose and to higher oligosaccharides of the maltodextrin series but not to glucose. 1,5-Gluconolactone was shown to be a potent inhibitor of the glycogen synthase reaction. The glycogen synthase reaction was shown to be reversible. Formation of labeled ADPglucose occurred from either [14C]ADP or [14C]glycogen. The ratio of ADP to ADPglucose at equilibrium at 37 degrees C was determined and was found to vary threefold in the pH range of 5.27-6.82. From these data the ratio of ADP2- to ADPglucose at equilibrium was determined to be 45.8 +/- 4.5. Assuming that deltaF degrees of the hydrolysis of the alpha-1,4-glucosidic linkage is -4.0 kcal the deltaF degrees of hydrolysis of the glucosidic linkage in ADPglucose is -6.3 kcal.

Amylases↗
PubMed1976

Kinetic properties of Serratia marcescens adenosine 5'-diphosphate glucose pyrophosphorylase.

The regulatory properties of partially purified adenosine 5'-diphosphate-(ADP) glucose pyrophosphorylase from two Serratia marcescens strains (ATCC 274 and ATCC 15365) have been studied. Slight or negligible activation by fructose-P2, pyridoxal-phosphate, or reduced nicotinamide adenine dinucleotide phosphate (NADPH) was observed. These compounds were previously shown to be potent activators of the ADPglucose pyrophosphorylases from the enterics, Salmonella typhimurium, Enterobacter aerogenes, Enterobacter cloacae, Citrobacter freundii, Escherichia aurescens, Shigella dysenteriae, and Escherichia coli. Phosphoenolpyruvate stimulated the rate of ADPglucose synthesis catalyzed by Serratia ADPglucose pyrophosphorylase about 1.5- to 2-fold but did not affect the S0.5 values (concentration of substrate required for 50% maximal stimulation) of the substrates, alpha-glucose-1-phosphate, and adenosine 5'-triphosphate. Adenosine 5'-monophosphate (AMP), a potent inhibitor of the enteric ADPglucose pyrophosphorylase, is an effective inhibitor of the S. marcescens enzyme. ADP also inhibits but is not as effective as AMP. Activators of the enteric enzyme counteract the inhibition caused by AMP. This is in contrast to what is observed for the S. marcescens enzyme. Neither phosphoenolpyruvate, fructose-diphosphate, pyridoxal-phosphate, NADPH, 3-phosphoglycerate, fructose-6-phosphate, nor pyruvate effect the inhibition caused by AMP. The properties of the S. marcescens HY strain and Serratia liquefaciens ADPglucose pyrophosphorylase were found to be similar to the above two S. marcescens enzymes with respect to activation and inhibition. These observations provide another example where the properties of an enzyme found in the genus Serratia have been found to be different from the properties of the same enzyme present in the enteric genera Escherichia, Salmonella, Shigella, Citrobacter, and Enterobacter.

1,4-alpha-Glucan Branching Enzyme↗