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S R Simon

Publications and source records attributed to S R Simon.

At least 55 records · Page 3Linked to original sources
PubMed1993

Regulation of neutrophil elastase activity by elastin-derived peptide.

To understand the interaction between elastin and elastase, elastin from human aorta was incubated with human leukocyte elastase under conditions favoring proteolysis. Low molecular weight species were separated from the protein fraction by a small centrifuged gel filtration column. The only product of the elastin digest detected on acid polyacrylamide gel electrophoresis was a single band of slower cathodal mobility than human leukocyte elastase alone. This band cross-reacts with antibody to human elastase, indicating that the slow migrating band contains elastase. The putative human leukocyte elastase-elastin-derived peptide complex was treated with hydroxylamine to cleave any possible acyl-enzyme complexes and was then measured for amidolytic activity. Analysis of the amino acid composition of elastin-derived peptide indicates the presence of alanine, glycine, and richness in hydrophobic residues, suggesting that these residues are involved in elastase interaction(s). Incubation of the elastase-elastin-derived peptide with alpha 1-protease inhibitor causes dissociation of the complex and formation of an elastase-alpha 1-protease inhibitor complex. Our results suggest that, locally at the site of proteolysis, elastase activity may be regulated by elastin-derived peptide(s) during elastinolysis.

Amino Acid Sequence↗
PubMed1993

Kinetics of the inhibition of human leukocyte elastase by elafin, a 6-kilodalton elastase-specific inhibitor from human skin.

We have investigated the kinetics of inhibition of human leukocyte elastase by elafin, a small protein originally isolated from human skin. A single inhibitor molecule was found to bind to a single site on the protease, blocking the reactive serine at the enzyme's catalytic center. Association of the enzyme with the inhibitor proceeds via a single bimolecular process, with a second-order rate constant of 3.6 x 10(6) M-1 s-1 at pH 8.0 and 25 degrees C. Dissociation of the enzyme-inhibitor complex regenerates fully active enzyme with a first-order rate constant of 6.0 x 10(-4) s-1. The species of elafin which is released from the complex simultaneously with the enzyme was estimated to be at least 99.8% active, with association and dissociation kinetics identical to preparations of the inhibitor which had never been exposed to the enzyme. Ki, the equilibrium dissociation constant of the enzyme-inhibitor complex, decreases from 6.7 x 10(-9) to 2.0 x 10(-10) M as the pH is increased from 5.4 to 9.0. The effect of pH on the association rate constant reveals that the reaction rate is dependent on the concentration of the unprotonated form of a group with pKa of 6.8, which we have assigned to the histidine which forms part of the catalytic triad in the enzyme's active site. On the basis of these findings, we conclude that elafin is a potent, substrate-like, but fully reversible inhibitor of human leukocyte elastase.

Amino Acid Sequence↗
PubMed1993

Neuroendocrine carcinoma of the colon. Correct diagnosis is important.

Neuroendocrine carcinomas of the colon and rectum are unusual and have in the past been misrepresented as either carcinoid tumors or undifferentiated cancers. Colorectal neuroendocrine tumors comprise a clinicopathologic spectrum that ranges from indolent to highly aggressive. The case discussed illustrates the importance of the right diagnosis because it will affect treatment and may better predict the clinical course.

Adult↗
PubMed1993

Human alpha 1-proteinase inhibitor binds to extracellular matrix in vitro.

alpha 1-Proteinase inhibitor (alpha 1-PI) is the major endogenous inhibitor of human leukocyte elastase (HLE). We have employed two different methods to quantitate the binding of alpha 1-PI to extracellular matrix (ECM), composed of 51% glycoproteins and proteoglycans, 37% types I and III collagen, and 12% elastin, derived from rat heart smooth muscle cells. alpha 1-PI is tightly bound to ECM via a saturable adsorption process; the bound protein fails to dissociate from the matrix after repeated washing. Binding of alpha 1-PI is unaffected by the prior removal of ECM glycoproteins with trypsin. Binding to ECM is not decreased in the presence of high salt but is decreased at low pH. A 40-fold excess of unlabeled alpha 1-PI displaces only 50% of [125I]alpha 1-PI prebound to ECM. A 30% decrease in the levels of alpha 1-PI bound to ECM is observed after DTT washes of ECM preincubated with alpha 1-PI or when alpha 1-PI is modified with iodoacetamide prior to incubation with ECM, implying that a fraction of bound alpha 1-PI is covalently linked to ECM via disulfide bond formation. Moreover, high molecular weight complexes between [125I]alpha 1-PI and ECM components can be visualized by SDS-PAGE under nonreducing conditions but disappear upon reduction. Approximately 50% of the total alpha 1-PI bound covalently or noncovalently to ECM retains the ability to inhibit HLE-mediated ECM proteolysis. alpha 1-PI-HLE complexes bound to ECM can be visualized by SDS-PAGE following the addition of HLE to ECM that was pretreated with [125I]alpha 1-PI. alpha 1-PI from normal plasma or serum also binds to ECM with retention of immunoreactivity and partial retention of inhibitory activity. However, ECM pretreated with alpha 1-PI-deficient serum retains no HLE-inhibitory activity.

Animals↗
PubMed1992

Role of disulfide exchange in alpha 1-protease inhibitor.

The major endogenous inhibitor of neutrophil elastase in the plasma, alpha 1-protease inhibitor (alpha 1-PI), has a single cysteine residue which has been shown to form mixed disulfides with a number of thiols in vitro. Under normal physiological conditions, the plasma concentrations of reduced and oxidized thiols are such that a major fraction of alpha 1-PI in the circulation in vivo is in the form of mixed disulfides [Laurell, C.-B. (1979) in The Chemistry and Physiology of Human Plasma Proteins (Bing, D. H., Ed.) pp 329-341, Pergamon, New York]. We show here that the mixed disulfide between glutathione or cysteine and alpha 1-PI (alpha 1-PI-SSG or alpha 1-PI-SScys) has an intrinsic fluorescence which distinguishes it from the reduced form of alpha 1-PI. By employing the fluorescence difference, we have measured the ratio of alpha 1-PI-SH to mixed disulfide alpha 1-PI in redox buffers of different ratios of reduced to oxidized glutathione (GSH to GSSG) or reduced to oxidized cysteine (cys to cysSScys) and have calculated an equilibrium constant and redox potential of 0.74 +/- 0.08 and 8 +/- 2 mV, respectively, for the alpha 1-PI-SH/alpha 1-PI-SSG couple and of 0.32 +/- 0.02 and 29 +/- 2 mV, respectively, for the alpha 1-PI-SH/alpha 1-PI-SScys couple. We are unable to detect any change in Trp fluorescence in the complex of alpha 1-PI and elastase when the preformed complex is added to the same GSH/GSSG or cys/cysSScys redox buffers.(ABSTRACT TRUNCATED AT 250 WORDS)

Amides↗
PubMed1992

Chemotherapy-induced myocardial infarction in a young man with Hodgkin's disease.

A 32-year-old male with stage IIIA nodular sclerosing Hodgkin's disease and no cardiac risk factors presented with chest pain after receiving chemotherapy consisting of multiple drugs, including vinca alkaloids. He completed an uncomplicated anterior wall myocardial infarction. Coronary angiography documented the absence of significant coronary artery disease. Exercise stress testing with gated scan confirmed loss of anterior wall motion and a decreased left ventricular ejection fraction. Vascular toxicity, including, rarely, myocardial infarction, has been reported following antineoplastic regimens containing vinca alkaloids. Hypercoagulable states, cardiac invasion by tumor, and coronary artery spasm are possible etiologies. Of these, coronary artery spasm appears most likely. Management should include discontinuation of the offending drug and supportive care.

Adult↗
PubMed1992

Intramedullary spinal cord metastases from epithelial ovarian carcinoma.

A patient with poorly differentiated serous cystadenocarcinoma of both ovaries who had undergone extensive medical treatment presented with nonspecific neurologic complaints. With the aid of magnetic resonance imaging, a metastatic lesion in the intramedullary area of the spinal cord was diagnosed. Rapidly instituted high-dose steroids and radiotherapy resulted in resolution of her symptoms. Intramedullary spinal cord metastasis is an unusual metastatic site. This is the first reported case of epithelial ovarian carcinoma metastatic to the intramedullary spinal cord.

Combined Modality Therapy↗
PubMed1992

Effects of gamma interferon on release of tumor necrosis factor alpha from lipopolysaccharide-tolerant human monocyte-derived macrophages.

After an initial stimulation of human monocyte-derived macrophages with bacterial lipopolysaccharide (LPS), which produces substantial release of tumor necrosis factor-alpha (TNF-alpha), a subsequent exposure to LPS results in about an order-of-magnitude reduction in the levels of TNF-alpha released. We have shown that macrophages which have been stimulated with LPS and then maintained in culture without LPS for as long as 2 weeks do not regain their original capacity to secrete TNF-alpha upon a second LPS challenge. After 2 to 4 days in adherent culture, monocyte-derived macrophages which were not pretreated with LPS also experience a measurable decline in their capacity to release TNF-alpha in response to an initial LPS stimulation. When compared with these previously nonstimulated cells, however, the levels of TNF-alpha released by LPS-pretreated cells in response to a second LPS challenge decline by over 90% after 8 to 9 days in culture. Unstimulated cells spontaneously release barely detectable levels of TNF-alpha. In contrast to the release of TNF-alpha, unstimulated cells release significant levels of prostaglandin E2 continuously over time, and these levels are variably increased by no more than a factor of two in response to a single LPS stimulation. Prostaglandin E2 levels released by LPS-pretreated cells in response to a second LPS stimulation are much closer to the levels released by unstimulated cells. We have also demonstrated that gamma interferon (IFN-gamma) enhances TNF-alpha release from LPS-stimulated macrophages but not from phorbol myristate acetate-stimulated cells. Addition of IFN-gamma to macrophages either during the initial stimulation or during a second stimulation with LPS enhances levels of TNF-alpha released after the second LPS challenge. The greatest enhancement is observed when IFN-gamma is added during both exposures to LPS, but addition of IFN-gamma during only the initial LPS stimulation still results in marked enhancement of TNF-alpha release in response to a second stimulation with LPS 24 h later. If an interval of 2 days of culture in medium alone separates the first and second 24-h LPS stimulations, IFN-gamma enhances TNF-alpha release only when it is included during the second LPS exposure, indicating that, unlike the persistence of endotoxin tolerance, enhancement of TNF-alpha release by IFN-gamma is transient.

Cells, Cultured↗
PubMed1992

Cough and ACE inhibitors.

To assess the prevalence of cough as a side effect of angiotensin-converting enzyme inhibitor antihypertensive therapy, we reviewed 300 consecutive patient charts from a private practice and 200 consecutive patient charts from a university-based referral center for hypertension. Incidence of definite angiotensin-converting enzyme inhibitor-induced cough in the private practice was 25% and in the university practice, 7%, with an additional 6% of university-practice patients reporting a possible angiotensin-converting enzyme-inhibitor induced cough. This incidence is considerably greater than listed in the Physicians' Desk Reference. Reasons for the variability in incidence as reported in the literature are explored. Clinicians must be aware of this potentially disturbing side effect of angiotensin-converting enzyme inhibitors to avoid expensive and unnecessary diagnostic evaluations.

Academic Medical Centers↗
PubMed1991

Parinaric acids as probes of binding domains in neutrophil elastase.

Human neutrophil elastase has an extended hydrophobic substrate binding site which serves as a target for a number of hydrophobic inhibitors. We show here that the parinaric acids, fluorescent-conjugated tetraenoic fatty acids of plant origin, are inhibitors of neutrophil elastase. cis-Parinaric acid (cis-PA) interacts with the enzyme in two inhibitory modes. The high affinity interaction (Ki = 55 +/- 6 nM) results in partial noncompetitive inhibition of amidolytic activity, with 82% residual activity. A lower affinity interaction with cis-PA (Ki = 4 +/- 1 microM) results in competitive inhibition. trans-PA also acts as a high affinity partial noncompetitive inhibitor of elastase with a Ki equal to that for cis-PA but has no low affinity competitive inhibitory action. The endogenous fluorescence from the 3 tryptophan residues in elastase is partially quenched on binding cis- or trans-PA. Dependence of quenching of tryptophan fluorescence on PA concentration is consistent with binding to a single site with an apparent Kd of 26 +/- 3 nM, which may be equivalent to the high affinity partial noncompetitive inhibitory binding mode. Analysis of quenching according to the modified Forster theory of energy transfer developed by Snyder and Freire (Snyder, B., and Freire, E. (1982) Biophys. J. 40, 137-148) leads to an estimate of apparent closest indole-PA distance of 13 +/- 3 A. Fluorescence of either cis- or trans-PA is apparently unperturbed upon binding in the high affinity mode to elastase, but at micromolar cis-PA concentrations, binding to elastase results in a blue shift and 20% increase in intensity of PA emission, suggesting that the lower affinity competitive inhibitory binding mode of binding to elastase provides a hydrophobic environment for cis-PA.

Amino Acid Sequence↗
PubMed1991

Inhibition of human leucocyte elastase by ursolic acid. Evidence for a binding site for pentacyclic triterpenes.

Several pentacyclic triterpenoid metabolites of plant origin are inhibitors of hydrolysis of both synthetic peptide substrates and elastin by human leucocyte elastase (HLE). Ursolic acid, the most potent of these compounds, has an inhibition constant of 4-6 microM for hydrolysis of peptide substrates in phosphate-buffered saline. With tripeptide and tetrapeptide substrates, the inhibition is purely competitive, whereas with a shorter dipeptide substrate the inhibition is non-competitive, suggesting that ursolic acid interacts with subsite S3 of the extended substrate-binding domain in HLE, but not with subsites S1 and S2. The carboxy group at position 28 in the pentacyclic-ring system of the triterpenes contributes to binding to HLE, since replacement of this group with a hydroxy group, as in uvaol, the alcohol analogue of ursolic acid, reduces the potency of inhibition. The inhibitory potency of ursolic acid is also reduced by addition of 1 M-NaCl, further supporting a postulated electrostatic interaction between the negative charge on the triterpene and a positively charged residue on the enzyme, which we assign to the side chain of Arg-217, located in the vicinity of subsites S4 and S5 in HLE. These observations are consistent with a binding site for ursolic acid which extends from S3 towards S4 and S5 on the enzyme. Other triterpenes, including oleanolic acid, erythrodiol, hederagenin and 18 beta-glycyrrhetic acid, can also interact with this binding site. On the basis of these results we conclude that the extended substrate-binding domain of HLE can accommodate a variety of hydrophobic ligands, including not only such molecules as fatty acids [Ashe & Zimmerman (1977) Biochem. Biophys. Res. Commun. 75, 194-199; Cook & Ternai (1988) Biol. Chem. Hoppe-Seyler 369, 629-637], but also polycyclic molecules such as the pentacyclic triterpenoids.

Amino Acid Sequence↗
PubMed1991

Complete response of carcinosarcoma of the ovary to therapy with doxorubicin, ifosfamide, and dacarbazine.

Although carcinosarcoma occurs in various locations throughout the body, it rarely originates in the ovary. Chemotherapy has been minimally beneficial. This case describes a patient with carcinosarcoma of the ovary who responded minimally to chemotherapy used for epithelial carcinomas but had a complete response after receiving chemotherapy used for sarcomas. The patient relapsed within 1 year after receiving cisplatin therapy. She was treated with mesna, ifosfamide, Adriamycin, and dacarbazine (MAID) chemotherapy and after one cycle of chemotherapy she had no evidence of tumor. She has received six cycles of chemotherapy without evidence of progression 13+ months since beginning MAID therapy. MAID chemotherapy may be useful in the treatment of carcinosarcoma of the ovary.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Tumor necrosis factor release from lipopolysaccharide-stimulated human monocytes: lipopolysaccharide tolerance in vitro.

Human peripheral blood monocytes secrete tumor necrosis factor (TNF) in response to stimulation with bacterial lipopolysaccharide (LPS). We have shown that isolated human monocytes pretreated with LPS for 24 h secrete lower levels of TNF on a second stimulation with LPS than monocytes that have been stimulated with a single dose of LPS either immediately after isolation or 24 h after isolation. The levels of TNF released by monocytes after the second stimulation with LPS are proportional to the LPS concentration over a range from 1 ng/mL to 10 micrograms/mL. Increasing concentrations of LPS used during the first 24-h stimulation induce greater suppression of TNF release after a second stimulation with LPS. After an initial stimulus of 10 micrograms/mL LPS, a second stimulation of monocytes even with 10 micrograms/mL LPS will result in TNF secretion similar to that of unstimulated cells. This in vitro tolerance apparently can be overcome by stimulating previously activated cells with phorbol myristate acetate. We have also shown that neither prostaglandin E2 nor dexamethasone added during the initial stimulation with LPS had an effect on the subsequent reduction in TNF release on a second stimulation of monocytes with LPS.

Acetyltransferases↗
PubMed1991

Interaction of neutrophil elastase with hydrophobic polyanionic chelators.

The polyanionic calcium chelators, ethylenediamine-tetraacetic acid (EDTA), ethylene-bis-(oxyethylenenitrilo)-tetraacetic acid (EGTA), [bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA), 1-[2-amino-5-(6-carboxyindol-2-yl) phenoxyl]-2-(2'-amino-5'-methylphenoxy)ethane-N,N,N1, N1-tetraacetic acid (INDO-1), 1-[2-(5-carboxyoxazol-2yl)-6-phenoxyl]-2-(2'-amino-5'- methylphenoxy)ethane-N,N,N',N'-tetraacetic acid (FURA-2), and 2-([2-bis-(carboxymethyl)-amino-5-methylphenoxy]-methyl(-6-methyl-8- bis-(bis-(carboxymethyl)-aminoquinoline (QUIN-2), are all inhibitors of amidolytic activity of human neutrophil elastase (HNE). With MeOSuc-Ala-Ala-Pro-Val-pNA as substrate, these chelators all display mixed partial competitive and partial noncompetitive inhibition, but with the smaller substrate, pGlu-Pro-Val-pNA, only the noncompetitive component persists. The most effective inhibitor is FURA-2, with an apparent Ki of 0.5-0.7 mM. QUIN-2 is somewhat less effective, with a Ki of 2 mM, while EDTA is much less effective, with a Ki of 7 mM. In general, the more hydrophobic chelators are the best inhibitors, although INDO-1, which is about the same size as FURA-2, is surprisingly ineffective as an inhibitor. The chelators no longer function as effective inhibitors if their carboxyl groups are blocked by esterification with acetoxymethyl groups or by complexation with calcium ions, indicating that their binding to HNE is mediated in part through electrostatic interactions with a center of positive charge on the protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1991

Biomechanical gait analysis in obese men.

The purpose of this study was to identify and compare the kinematic components of the walking gait of obese men to those of nonobese men. Self-paced walking trials of 12 obese volunteers, ranging in age from 30 to 47 years and in obesity from 70% to 99% above ideal body weight, were recorded via cinematography. The following findings were recorded: (1) obese persons (1.09m/sec) walk significantly (p less than .001) slower than nonobese subjects (1.64m/sec); (2) obese persons take significantly (p less than .001) shorter strides (1.25m vs 1.67m) and exhibit step widths (.16m) twice those of nonobese persons (.08m); (3) mean hip abduction angles of the obese are significantly (p less than .001) different at some events of the walking cycle from the hip angles of nonobese persons; (4) mean hip and knee flexion angles are not significantly different for obese and nonobese subjects; and (5) obese individuals demonstrate a walking gait pattern with significantly greater (p less than .001) mean magnitude of ankle dorsiflexion and lesser (p less than .001) mean magnitude of ankle plantar flexion than nonobese subjects throughout the walking cycle. It is concluded that obese individuals display a walking gait that follows a normal pattern but some of the temporal and angular components of their gait are different from those of nonobese persons mainly because of the excessive adipose tissue inside their thighs.

Adult↗