Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 86
Filtrar
1.
Nutr Metab Cardiovasc Dis ; 25(7): 659-66, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26026207

RESUMO

BACKGROUND AND AIMS: Diabetes mellitus is associated with inflammatory endothelial activation and increased vascular leukocyte adhesion molecule expression, both playing a prominent role in the development of vascular complications. Centella asiatica (CA) and Lipoic Acid (LA) have shown anti-inflammatory and anti-oxidant properties in a variety of experimental models; however, their action on human umbilical vein endothelial cells (HUVECs), chronically exposed to hyperglycemia and pro-inflammatory environment during pregnancy, is still unknown. METHODS AND RESULTS: In HUVECs from umbilical cords of gestational diabetic (GD) or healthy (C) women, both CA and LA affected tumor necrosis factor-α (TNF-α)-induced inflammation, being associated with a significant decrease in vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) expression (western blot) and exposure (flow cytometry), as well as monocyte-HUVECs interaction (adhesion assay). Notably, this was associated with a significant reduction of an index of nitro-oxidative stress, such as the intracellular peroxynitrite levels (fluorescence detection by cytometric analysis), Mitogen-Activated Protein kinase (p44/42 MAPK) expression/phosphorylation levels and Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB p65) cytoplasm-nucleus translocation (flow cytometry). Overall our results indicate that both CA and LA used separately, and even better when combined, are effective to reduce the inflammatory response in TNF-α-treated HUVECs. Notably, this was more significant in GD than in C-HUVECs and also evident at baseline. CONCLUSION: In conclusion, our in vitro study demonstrates that both CA and LA, or a combination thereof, are able to mitigate the potentially dangerous effects on the endothelium of chronic exposure to hyperglycemia in vivo.


Assuntos
Antioxidantes/farmacologia , Adesão Celular/efeitos dos fármacos , Diabetes Gestacional/patologia , Células Endoteliais/efeitos dos fármacos , Células Endoteliais da Veia Umbilical Humana/efeitos dos fármacos , Monócitos/efeitos dos fármacos , Ácido Tióctico/farmacologia , Triterpenos/farmacologia , Adulto , Moléculas de Adesão Celular/biossíntese , Centella , Feminino , Humanos , Extratos Vegetais , Gravidez , Transdução de Sinais/efeitos dos fármacos , Fator de Necrose Tumoral alfa/farmacologia
2.
Biochim Biophys Acta ; 862(1): 65-71, 1986 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-3768369

RESUMO

Phenylhydrazine-induced oxidative damage in red cells results in increased binding of merocyanine 540, a fluorescence probe sensitive to changes in lipid packing. Fluorescence polarization studies with diphenylhexatriene did not reveal major changes in order parameters both in intact red cells and lysates treated with phenylhydrazine. These fluorescence studies indicate that major changes are observed in membrane lipids. Analytical studies of membrane phospholipids revealed a significant decrease in phosphatidylethanolamine. The results of the fluorescence and lipid studies, taken in association with our previously reported findings on spectrin and other cytoskeletal protein degradation in red cells exposed to phenylhydrazine, suggests that degradation of cytoskeleton membrane proteins is also responsible for changes in the lipid bilayer surface of the red cell membrane.


Assuntos
Membrana Eritrocítica/efeitos dos fármacos , Lipídeos de Membrana/análise , Fenil-Hidrazinas/farmacologia , Difenilexatrieno , Membrana Eritrocítica/análise , Fluorescência , Humanos , Técnicas In Vitro , Bicamadas Lipídicas/análise , Fosfolipídeos/análise , Pirimidinonas , Espectrina/análise
3.
Biochim Biophys Acta ; 979(1): 1-6, 1989 Feb 13.
Artigo em Inglês | MEDLINE | ID: mdl-2917160

RESUMO

The exposure of human erythrocytes to phenylhydrazine results in the degradation of both monomers of spectrin, a major cytoskeleton membrane protein. The degradative process, characterized by a loss of spectrin without the appearance of high-molecular-weight products, either under reducing conditions or not, is almost complete in 10 min when a 5% erythrocyte suspension is treated with 1 mM phenylhydrazine. Under these conditions, we found a loss of 62.3 and 48.5% for the alpha and beta monomer, respectively. A similar degradative extent was obtained when the membrane ghost plus cellular free extracts, were dialyzed, and the membrane ghost plus hemoglobin was exposed to 1 mM phenylhydrazine for 10 min. The presence of different proteinase inhibitors and effectors, such as EDTA, diethylenetriaminepentaacetic acid, EGTA, leupeptin, aprotinin, phenylmethylsulfonyl fluoride, pepstatin, Ca2+ and ATP plus Mg2+, in the membrane ghost plus cellular free extract system (undialyzed) did not affect the degree of the spectrin-degradative process induced by phenylhydrazine. In addition, a purified spectrin tetramer preparation exposed to 1 mM phenylhydrazine in the presence of hemoglobin was degraded to an extent comparable to that with intact cells. Our data suggest that the initial degradative step of spectrin induced by phenylhydrazine in intact erythrocytes may be ascribed more to a direct oxidative breakdown, probably involving main-chain cleavage and side-chain cleavage processes, than to an eventual proteolytic system.


Assuntos
Eritrócitos/efeitos dos fármacos , Fenil-Hidrazinas/toxicidade , Espectrina/metabolismo , Membrana Eritrocítica/efeitos dos fármacos , Radicais Livres , Humanos , Técnicas In Vitro , Oxirredução , Inibidores de Proteases/farmacologia
4.
Biochim Biophys Acta ; 990(2): 211-5, 1989 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-2917179

RESUMO

A new sulfur imino acid, 2H-1,4-thiazine-5,6-dihydro-3,5-dicarboxylic acid (lanthionine ketimine), has been detected in the bovine brain by means of fluorometric and HPLC procedures. The fluorometric assay is based on the fluorescent property of the copper-ketimine interaction product at pH 11.5. Other ketimines do not fluoresce in these conditions. The fluorophore exhibits an excitation maximum at 353 nm and an emission at 462 nm and is stable for at least 24 h. In the test conditions the fluorescence is proportional to the ketimine concentration from 1 to 200 microM. Detection of endogenous lanthionine ketimine has been performed after a simple enrichment procedure (brain deproteinization and extraction with diethyl ether) which minimizes degradative by-reactions of the unstable ketimine. The concentration of this new sulfur imino acid in the brain ranges from 0.5 to 1 nmol/g in three different samples. Identification and quantitations were confirmed by an HPLC procedure which takes advantage of the selective absorption at 380 nm of the phenylisothiocyanate-ketimine adduct. The identification of lanthionine ketimine in nervous tissues may have important metabolic and physiological implications.


Assuntos
Aminoácidos Sulfúricos/análise , Química Encefálica , Animais , Bovinos , Cromatografia Líquida de Alta Pressão , Fluorometria , Isotiocianatos , Tiocianatos
5.
Biochim Biophys Acta ; 1527(3): 149-55, 2001 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-11479031

RESUMO

Conversion of erythrocyte membrane protein 4.1b to 4.1a occurs through a non-enzymatic deamidation reaction in most mammalian erythrocytes, with an in vivo half-life of approximately 41 days, making the 4.1a/4.1b ratio a useful index of red cell age [Inaba and Maede, Biochim. Biophys. Acta 944 (1988) 256-264]. Normal human erythrocytes distribute into subpopulations of increasing cell density and cell age when centrifuged in polyarabinogalactan density gradients. We have observed that, when erythrocytes were stored at 4 degrees C under standard blood bank conditions, the deamidation was virtually undetectable, as cells maintained the 4.1a/4.1b ratio they displayed at the onset of storage. By measuring the 4.1a/4.1b values in subpopulations of cells of different density at various time points during storage, a modification of the normal 'cell age/cell density' relationship was observed, as erythrocytes were affected by changes in cell volume in an age-dependent manner. This may stem from a different impact of storage on the imbalance of monovalent cations, Na(+) and K(+), in young and old erythrocytes, related to their different complement of cation transporters.


Assuntos
Cátions Monovalentes/análise , Envelhecimento Eritrocítico , Eritrócitos/química , Bancos de Sangue , Separação Celular , Tamanho Celular , Membrana Eritrocítica/química , Eritrócitos/classificação , Humanos , Lactatos/análise , Proteínas de Membrana/análise , Fatores de Tempo , Preservação de Tecido
6.
Biochim Biophys Acta ; 1146(2): 229-35, 1993 Mar 14.
Artigo em Inglês | MEDLINE | ID: mdl-8383998

RESUMO

EPR and fluorescence probes were used in this study to define the effects of L-carnitine and its short-chain esters, acetyl-L-carnitine and propionyl-L-carnitine, on the natural fluidity gradient and molecular packing of phospholipid headgroups of erythrocyte membrane in intact cells. Purified erythrocyte suspensions, labeled with different stearic acid derivatives containing a stable doxyl radical ring at the C-5, C-7, C-12 and C-16, were incubated with 0.5-5 mM L-carnitine and its esters for 60 min at 37 degrees C and washed twice with an isosmotic buffer. A decrease in the order parameter, calculated from the EPR spectra of the 5-doxylstearic acid derivative, was observed at all the concentrations of propionyl-L-carnitine and the extent of the decrease was dose and temperature dependent. An increase of the chain length between the doxyl ring and the carboxylic group of the spin label, resulted in a much lower efficacy of propionyl-L-carnitine in decreasing the order parameter. Acetyl-L-carnitine also showed a significant effect of decreasing the molecular order but only at the lower temperatures of red cells labeled with 5-doxyl and treated with the highest concentration of the drug. L-Carnitine did not modify the molecular dynamics at all the temperatures and concentrations used in this study. L-Carnitine and its short-chain derivatives did not alter significantly membrane fluidity of deeper regions of the erythrocyte membrane, measured by means of the excimer/monomer fluorescence intensity ratio of pyrene incorporated into the membrane of intact erythrocytes. However, these compounds were all capable of loosening the molecular packing of the polar head of erythrocyte membrane phospholipids evaluated by the membrane binding fluorescence properties of merocyanine-540. The binding of the fluorescent probe decreased in the order propionyl-L-carnitine > acetyl-L-carnitine > L-carnitine. Our findings suggest that this category of compounds affect the molecular dynamics of a membrane bilayer region close to the glycerol backbone of phospholipids, which might be relevant for the expression of membrane functions.


Assuntos
Acetilcarnitina/farmacologia , Carnitina/análogos & derivados , Carnitina/farmacologia , Membrana Eritrocítica/efeitos dos fármacos , Difenilexatrieno , Espectroscopia de Ressonância de Spin Eletrônica , Membrana Eritrocítica/química , Ésteres/farmacologia , Humanos , Fluidez de Membrana/efeitos dos fármacos , Proteínas de Membrana/química , Palmitoilcarnitina/farmacologia , Pirimidinonas , Marcadores de Spin
7.
Biochim Biophys Acta ; 970(2): 113-21, 1988 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-3382695

RESUMO

Experiments were performed to investigate the effects of 60 min severe global ischemia followed by 30 min reperfusion on the antioxidant enzymatic system in the isolated perfused rat heart. Ischemia induced a significant increase of cytoplasmic and mitochondrial selenium-dependent glutathione peroxidase (EC 1.11.1.9) activity. In reperfused hearts, only the mitochondrial form showed a further significant increase. Glutathione reductase (EC 1.6.4.2) was increased in ischemic hearts, whilst the reperfused hearts showed a decrease towards the level found in aerobic hearts. Mitochondrial superoxide dismutase (EC 1.15.1.1) activity was depressed in ischemic as well as in reperfused hearts, though the cytoplasmic form was unmodified. Catalase (EC 1.11.1.6), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and glutathione transferase (EC 2.5.1.18) activities were unchanged throughout the experiment. Ischemia and reperfusion induced a significant fall in tissue-reduced glutathione content concomitant with an increase of its oxidized form. We have also studied the mitochondrial inner membrane proteins for both molecular weight, with Coomassie blue, and thiol status, with monobromobimane stain, using a sodium dodecyl sulfate polyacrylamide gel electrophoresis technique. Neither ischemia nor reperfusion effected any relevant modification of the molecular weight of the mitochondrial inner-membrane proteins either in the presence or absence of a reducing agent. However, two of these proteins with an apparent molecular weight of 52,0000 and 12,000 showed a decrease in the monobromobimane stain, probably due to the oxidation of their thiol groups.


Assuntos
Antioxidantes , Doença das Coronárias/enzimologia , Glutationa Peroxidase/metabolismo , Proteínas de Membrana/metabolismo , Mitocôndrias Cardíacas/enzimologia , Miocárdio/enzimologia , Perfusão , Animais , Eletroforese em Gel de Poliacrilamida , Radicais Livres , Glutationa/análogos & derivados , Glutationa/metabolismo , Dissulfeto de Glutationa , Membranas Intracelulares/enzimologia , Membranas Intracelulares/metabolismo , Masculino , Mitocôndrias Cardíacas/metabolismo , Miocárdio/metabolismo , Ratos , Ratos Endogâmicos
8.
Biochim Biophys Acta ; 999(2): 203-7, 1989 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-2597709

RESUMO

An investigation of the tryptophan emission properties of glutathione transferase from human placenta was conducted in order to characterize the environments of the two aromatic residues. The low-temperature phosphorescence spectra and temperature dependence of the phosphorescence quantum yield of the tryptophan residues revealed a difference in the chemical nature and dynamical structure of the surrounding protein matrix. Thus, one tryptophan residue seems to be deeply embedded within the polypeptide in a rigid weakly polar environment, characteristic of a beta-type secondary structure. The other is located in a more polar site, probably near the surface, in a rather flexible region of the macromolecule. At high temperature, the heterogeneity in the triplet lifetime of the internal residue attests to the presence of multiple conformers which are not in rapid equilibrium in the phosphorescence time scale. The anisotropy of the phosphorescence emission of glutathione transferase indicates that no energy transfer occurs between the two residues, and measurement of the rotational correlation time yields an hydrodynamic volume which is in good agreement with the molecular weight reported in the literature for the dimer.


Assuntos
Glutationa Transferase , Placenta/enzimologia , Triptofano , Feminino , Congelamento , Humanos , Medições Luminescentes , Gravidez , Conformação Proteica , Espectrometria de Fluorescência , Termodinâmica
9.
Curr Opin Chem Biol ; 1(4): 467-74, 1997 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9667888

RESUMO

In the past year progress in the study of cationic species has been made, particularly in our understanding of the factors which control the selective recognition of biologically important cations such as ammonium, alkali and alkaline earth metal ions, and of metal ions used in biomedicine such as lanthanides and iron(III). Based on this knowledge, several new hosts with improved transport, photophysical and biological properties have been designed.


Assuntos
Cátions , Modelos Químicos , Conformação Molecular , Sideróforos/química , Sítios de Ligação , Bioquímica/métodos , Metais , Metais Terras Raras , Modelos Moleculares , Proteínas/química , Receptores de Superfície Celular/química , Sideróforos/metabolismo
10.
Int J Artif Organs ; 28(2): 177-87, 2005 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-15770606

RESUMO

AIM: Commercial glucose peritoneal dialysis solutions expose the peritoneum to hyperosmolar glucose containing variable amounts of non-enzymic breakdown products of glucose. These solutions are toxic for the peritoneum. The aim of the present study is to compare in vitro and in vivo characteristics of a new dialysis solution containing carnitine, a naturally occurring compound, as substitute of glucose. MATERIAL AND METHODS: We compared in vitro and in the rabbit a new peritoneal dialysis solution containing carnitine, with two standard bicarbonate glucose peritoneal dialysis solutions and a solution containing icodextrin. RESULTS: In vitro and in vivo the solution containing carnitine seems to be more biocompatible than standard glucose solutions and those containing icodextrin. CONCLUSIONS: In our study the peritoneal dialysis solution containing carnitine seems to prevent the mesothelial changes observed with solutions containing glucose. Since carnitine has been extensively studied and seems to be well tolerated by hemodialysis patients, even at high doses for long periods, clinical trials in humans may be planned in the near future.


Assuntos
Carnitina/análise , Soluções para Diálise/química , Glucose/análise , Peritônio/efeitos dos fármacos , Peritônio/patologia , Animais , Células Cultivadas , Soluções para Diálise/efeitos adversos , Dinoprostona/metabolismo , Células Epiteliais/efeitos dos fármacos , Células Epiteliais/metabolismo , Células Epiteliais/ultraestrutura , Humanos , Técnicas In Vitro , L-Lactato Desidrogenase/metabolismo , Diálise Peritoneal , Fosfatidilcolinas/metabolismo , Fosfolipídeos/metabolismo , Coelhos , Esclerose
11.
Free Radic Biol Med ; 9(6): 511-3, 1990.
Artigo em Inglês | MEDLINE | ID: mdl-2079231

RESUMO

Reflectance spectroscopy was utilized to monitor the oxidation states of myoglobin (Mb) in isolated, buffer-perfused rat hearts. Hearts were subjected to 30 min global, no-flow ischemia, followed by reperfusion under anoxic conditions. The addition of Na2S to the buffer at reperfusion permitted the detection of ferryl myoglobin (MbIV) as its sulfmyoglobin derivative. The accumulation of MbIV was prevented by addition of ascorbic acid (1 mM), ergothioneine (2 mM), or desferal (1 mM) to the buffer prior to ischemia. Ascorbate and other agents have been previously shown to serve as one-electron reductants of MbIV. We propose that during the early phases of ischemia, deoxymyoglobin is oxidized to MbIV by residual H2O2. It also seems reasonable that the peroxidative activity of Mb(IV), during oxygenated reperfusion, might lead to cellular damage if this hypervalent form of Mb is not reduced.


Assuntos
Doença das Coronárias/metabolismo , Mioglobina/análogos & derivados , Mioglobina/metabolismo , Animais , Ácido Ascórbico/farmacologia , Radicais Livres , Peróxido de Hidrogênio/farmacologia , Oxirredução , Ratos , Espectrofotometria
12.
Free Radic Biol Med ; 13(4): 449-54, 1992 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-1398221

RESUMO

The reactivity of the endogenous antioxidants ascorbate, ergothioneine, and urate toward the high oxidation state of sperm whale myoglobin, ferrylmyoglobin-formed upon oxidation of metmyoglobin by H2O2--was evaluated by optical spectroscopy and SDS-PAGE analysis. Depending on whether these antioxidants were present in the reaction mixture before or after the addition of H2O2 to a metmyoglobin suspension, two different effects were observed: (a) In the former instances, ascorbate, ergothioneine, and urate reduced efficiently the oxoferryl moiety in ferrylmyoglobin to metmyoglobin and prevented dimer formation, a process which requires intermolecular cross-link involving specific tyrosyl residues. In addition, all the reducing compounds inhibited--albeit with different efficiencies--dityorosine-dependent fluorescence build up produced via dimerization of photogenerated tyrosyl radicals. (b) In the latter instances, the antioxidants reduced the preformed sperm whale ferrylmyoglobin to a modified metmyoglobin, the spectral profile of which was characterized by a blue shift of the typical 633 nm absorbance of native metmyoglobin. In addition, under these experimental conditions, the antioxidants did not affect dimer formation, thus indicating the irreversible character of the process. The dimeric form of sperm whale myoglobin--separated from the monomeric form by gel electrophoresis of a solution in which ergothioneine was added to preformed ferrylmyoglobin--revealed optical spectral properties in the visible region identical to that of the modified myoglobin. This suggests that the dimeric form of the hemoprotein is redox active, inasmuch as the oxoferryl complex can be reduced to its ferric form. These results are discussed in terms of the potential reactivity of these endogenous antioxidants toward the reducible loci of ferrylmyoglobin, the oxoferryl moiety, and the apoprotein radical.


Assuntos
Ácido Ascórbico/metabolismo , Ergotioneína/metabolismo , Metamioglobina/metabolismo , Ácido Úrico/metabolismo , Baleias , Animais , Eletroforese em Gel de Poliacrilamida , Peróxido de Hidrogênio/metabolismo , Substâncias Macromoleculares , Oxirredução , Espectrofotometria
13.
J Thromb Haemost ; 2(8): 1275-81, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15304031

RESUMO

Platelet activation is associated with exposure of the aminophospholipid phosphatidylserine (PS) to the outer hemi-leaflet of the plasma membrane bilayer, which seems to be involved in the coagulation process. Because platelet activation may occur in patients suffering from chronic uremia, which is frequently associated with a thrombophilic tendency, we studied whether uremic platelets show an increased propensity to expose PS on the outer membrane leaflet and whether this process is linked with important functional and molecular changes. Flow cytometric percentage of annexin V-positive platelets, a measure of PS externalization, was significantly elevated (P < 0.001) in uremic patients when compared to normal controls under both unstimulated and agonist-stimulated conditions. Uremic platelet procoagulant activity, as measured by thrombin generation, was more than twice as high (4.13 +/- 0.3 micro mL(-1)) as that found in normal controls (1.86 +/- 0.2 micro mL(-1)). Two independent assays showed that the enzymatic activity of caspase-3, a protease involved in the loss of membrane PS asymmetry, was significantly greater in the platelets of uremic subjects than in those of healthy controls. PS exposure in agonist-stimulated platelets was markedly reduced by inhibition of caspase-3 activity but was not affected by inhibition of calpain activity. These results support the view that the thrombophilic susceptibility of uremic patients may be partly ascribed to increased PS exposure to the outer membrane leaflet of platelets. This process seems to be causally linked to an increase in caspase-3 activity, particularly during platelet activation.


Assuntos
Plaquetas/metabolismo , Caspases/metabolismo , Fosfatidilserinas/metabolismo , Uremia/sangue , Idoso , Anexina A5/biossíntese , Estudos de Casos e Controles , Caspase 3 , Inibidores de Caspase , Separação Celular , Doença Crônica , Coagulantes/metabolismo , Dipeptídeos/farmacologia , Ativação Enzimática , Feminino , Citometria de Fluxo , Humanos , Masculino , Pessoa de Meia-Idade , Oligopeptídeos/farmacologia , Fosfatidilserinas/química , Ativação Plaquetária , Diálise Renal , Trombina/biossíntese , Fatores de Tempo
14.
J Med Chem ; 44(15): 2383-6, 2001 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-11448219

RESUMO

A series of carnitine related compounds of general formula XCH(2)CHZRCH(2)Y were evaluated as CPT I inhibitors in intact rat liver (L-CPT I) and heart mitochondria (M-CPT I). Derivative 27 (ZR = -HNSO(2)R, R = C(12), X = trimethylammonium, Y = carboxylate, (R) form) showed the highest activity (IC(50) = 0.7 microM) along with a good selectivity (M-CPT I/L-CPTI IC(50) ratio = 4.86). Diabetic db/db mice treated orally with 27 showed a significant reduction of serum glucose levels.


Assuntos
Carnitina O-Palmitoiltransferase/antagonistas & inibidores , Carnitina/análogos & derivados , Carnitina/síntese química , Inibidores Enzimáticos/síntese química , Hipoglicemiantes/síntese química , Ácido 3-Hidroxibutírico/sangue , Animais , Carnitina/química , Carnitina/farmacologia , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacologia , Hipoglicemiantes/química , Hipoglicemiantes/farmacologia , Técnicas In Vitro , Mitocôndrias Cardíacas/efeitos dos fármacos , Mitocôndrias Cardíacas/metabolismo , Mitocôndrias Hepáticas/efeitos dos fármacos , Mitocôndrias Hepáticas/metabolismo , Ratos , Ratos Sprague-Dawley , Estereoisomerismo , Relação Estrutura-Atividade
15.
Am J Kidney Dis ; 37(4): 807-14, 2001 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11273881

RESUMO

Cell surface-exposed phosphatidylserine (PS) represents a signal for macrophage recognition and cell phagocytosis. This study examines PS exposure and susceptibility to erythrocyte phagocytosis in patients with chronic uremia in an attempt to assess the possible pathogenic mechanism behind cell removal in a condition associated with shortened erythrocyte life. Both PS-expressing erythrocytes and erythrophagocytosis (human monocyte-derived macrophages ingesting one or more erythrocytes) were significantly increased in uremic patients compared with healthy controls. Phagocytosed uremic erythrocytes appeared intact, suggesting they were identified before lysis through some surface change recognized by the macrophages. The degree of phagocytosis was markedly greater for PS-positive than PS-negative fluorescence-activated cell sorter (FACS)-sorted uremic erythrocytes. A significant correlation (r = 0.655) was found between the percentage of PS-expressing red blood cells (RBCs) and the percentage of phagocytosing macrophages in uremic patients. Reconstitution experiments showed the ability of uremic plasma to promote both PS exposure and erythrophagocytosis, the latter without direct interaction with the macrophage population. Phagocytosis of uremic erythrocytes was strongly inhibited when the macrophages were preincubated with glycerophosphorylserine (GPS), a structural derivative of PS, but this was not the case with the equivalent derivative of phosphatidylethanolamine, glycerophosphorylethanolamine. This inhibition appeared to be specific because GPS failed to inhibit the phagocytosis of opsonized uremic erythrocytes that occurs through an Fc receptor-mediated pathway. These findings suggest that a PS-recognition mechanism may promote the susceptibility of uremic RBCs to phagocytosis and thus be involved in the shortened erythrocyte life span of uremia.


Assuntos
Envelhecimento Eritrocítico/fisiologia , Eritrócitos/química , Macrófagos/fisiologia , Fagocitose/fisiologia , Fosfatidilcolinas/análise , Uremia/sangue , Anemia/sangue , Anemia/etiologia , Anemia/fisiopatologia , Comunicação Celular/fisiologia , Quimiotaxia/fisiologia , Doença Crônica , Membrana Eritrocítica/química , Membrana Eritrocítica/fisiologia , Eritrócitos/fisiologia , Feminino , Citometria de Fluxo , Glicerilfosforilcolina/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Fosfatidilcolinas/fisiologia , Diálise Renal , Uremia/fisiopatologia , Uremia/terapia
16.
Biochem Pharmacol ; 34(24): 4283-9, 1985 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-4074388

RESUMO

The effects of phenylhydrazine on intact red cells and on red cell ghost membrane proteins were studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In intact red cells 1 mM phenylhydrazine induced a marked decrease in intensity of the alpha- and beta-bands of spectrin without the formation of high molecular weight materials. Phenylhydrazine was also responsible for cross-linking of hemoglobin, which is apparent by the appearance of two new broad bands on the gel. Membrane glycoproteins were unaffected. Electrophoretic patterns of cytoskeletal proteins from phenylhydrazine-treated red cells obtained on two-dimensional SDS-polyacrylamide gels and stained with Coomassie blue or fluorescently labeled with monobromobimane indicated the presence of a new band between bands 4.2 and 5 at 60-65 kilodaltons (K). An immunoelectrophoretic blotting procedure utilizing polyclonal IgG antibodies for alpha- and beta-spectrin of the red cell cytoskeletal proteins revealed that the band observed at 60-65 K in the two-dimensional SDS-PAGE studies reacted with the antibodies. The presence or absence of glucose in the incubation medium and modification of oxyhemoglobin to met- or carboxyhemoglobin in the red cells did not protect the phenylhydrazine-mediated degradation of the major cytoskeletal proteins. Metal chelators and antioxidants had no effect on membrane protein changes. Ghost red cell proteins did not undergo changes at 1 mM phenylhydrazine in the presence or absence of hemoglobin, although at 5 mM phenylhydrazine the appearance of a faint high molecular weight band was observed. These results indicate that spectrin degradation without significant polymerization can be induced by phenylhydrazine.


Assuntos
Eritrócitos/metabolismo , Fenil-Hidrazinas/farmacologia , Espectrina/sangue , Antioxidantes/farmacologia , Quelantes/farmacologia , Relação Dose-Resposta a Droga , Eletroforese em Gel de Poliacrilamida , Eritrócitos/análise , Eritrócitos/efeitos dos fármacos , Hemoglobinas/análise , Humanos , Técnicas In Vitro , Proteínas de Membrana/análise
17.
Chemistry ; 6(1): 73-80, 2000 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-10747390

RESUMO

A number of calix[6]arenes bearing ureas at the upper rim positions of alternate rings 1, 3 and 5 were prepared and studied in detail by NMR spectroscopy and gel permeation chromatography. N-Unsubstituted ureas were shown to dimerize through a cyclic array of hydrogen bonds to give cylindrical cavities capable of encapsulating small molecules such as dichloromethane, benzene and fluorobenzene. Slow equilibria between dimer and monomer were observed in [D6]DMSO-CDCl3 mixtures. By contrast, N-substituted ureas are monomeric. All urea monomers with bulky O-substituents display a solvent-dependent, slow equilibrium between C3v and Cs cone conformations.

18.
Chemistry ; 6(12): 2135-44, 2000 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-10926218

RESUMO

Conformationally rigidified tetraCMPO derivatives have been prepared from calix[4]arene bis(crown ether) 4a in which adjacent oxygens are bridged at the narrow rim by two diethylene glycol links. Acylation of the tetraamine 4c with the CMPO-active ester 5b gave the tetraphosphine oxide 6a, while the tetraphosphinate 6b and the tetraphosphonate 6c were obtained by Arbuzov reaction of tetrabromoacetamido derivative 7 with PhP(OEt)2 or P(OEt)3. The extraction ability of these CMPO derivatives was checked for selected lanthanides and actinides and compared with the analogous compounds 1b, 10b and 10d derived from calix[4]arene tetrapentyl ether. All rigidified bis(crown ether) ligands are more effective extractants than their pentyl ether counterparts and require only 1/10 of the concentration (cL= 10 4M) to obtain the same distribution coefficients, while with CMPO itself a 2,000-fold concentration is necessary. This could be a consequence of a better preorganisation of the ligating functions owing to the rigidity which on the other hand did not change the observed selectivity for americium (DAm/DEu=9-19) and for light lanthanides over heavy ones. NMR relaxivity titration curves show that the complex of Gd3+ with ligand 6a is highly oligomerised in anhydrous acetonitrile over a large range of ligand:metal concentration ratios. Nuclear magnetic relaxation dispersion (NMRD) profiles also showed that large oligomers were formed, and their mean tumbling times were deduced from the Solomon-Bloembergen-Morgan equations. The NMR spectra of dia- and paramagnetic lanthanide complexes with 6a agreed with the presence of two conformers with an elongated calix[4]arene skeleton in which the distances between opposite methylene groups are different. Contrary to what was observed with ligand 2a, the addition of nitrate ions does not labilize the metal complexes, presumably because of the rigidification effect of the ether bridges. Single-crystal X-ray structures were obtained for the active ester 5b and for diphenylphosphorylacetic acid 5a.

19.
J Org Chem ; 65(26): 9085-91, 2000 Dec 29.
Artigo em Inglês | MEDLINE | ID: mdl-11149855

RESUMO

The synthesis of new hosts specifically designed for the recognition of amides, characterized by two binding regions: a rigid calix[4]arene cavity and a sidearm, inserted at its rim, able to form strong hydrogen bonds, is described. The binding abilities of the new receptors toward amides of general structure R(1)CONR(2)R(3) have been investigated in CDCl(3) solution by (1)H NMR spectroscopy. When the additional binding site is the N-phenylureido group spaced by a methylene unit from the apolar cavity, binding constants up to 756 M(-)(1) were measured. Neither the two separate potential binding sites, nor the model host, where the calix[4]arene skeleton is flexible show detectable binding ability toward the series of guests examined. The rigidity of the calix[4]arene apolar cavity is the key control element in determining the efficiency of these molecular recognition processes. The presence of NH groups in the guest controls the efficiency and selectivity of binding.

20.
Life Sci ; 69(15): 1733-8, 2001 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-11665835

RESUMO

Pivalic acid is used as a prodrug to increase gut absorption of a variety of different antibiotics. Pivalic acid is also known to induce a number of metabolic aberrations which may be in part explained by concurrent mild carnitine depletion. Rat pups (5 days old) born to mothers treated throughout their pregnancy and lactation period with sodium pivalate, showed an increase in liver and muscle triglycerides and elevated plasma ketone bodies, compared to controls. A reduction of free carnitine content in liver, muscle and plasma was also observed in the pivalate treated group. In a second study, pups were treated with either pivalate for 24 days (females), or pivalate for 120 days (males). Both groups were fed standard diets. In both groups (male and female), the pivalate treatment showed a statistically significant hyperinsulinaemia and an increase of body mass compared with that of age- and sex-matched control groups. In addition, after a glucose loading, significantly higher levels of insulin in the pivalate-treated group (male) with respect to controls were observed. In conclusion, our data suggest that maternal pivalate treatment may predispose adult offspring to developing insulin-resistance and obesity.


Assuntos
Hiperinsulinismo/etiologia , Insulina/sangue , Obesidade/etiologia , Ácidos Pentanoicos/farmacologia , Ácido 3-Hidroxibutírico/metabolismo , Animais , Animais Recém-Nascidos , Glicemia/metabolismo , Carnitina/metabolismo , Feminino , Hiperinsulinismo/metabolismo , Resistência à Insulina , Lactação , Masculino , Troca Materno-Fetal , Obesidade/metabolismo , Gravidez , Pró-Fármacos/farmacologia , Ratos , Triglicerídeos/metabolismo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA