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1.
Indian J Pharmacol ; 54(5): 321-328, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36537400

RESUMO

OBJECTIVE: The rational use of medicines as per the World Health Organization (WHO) should be practiced globally. However, data regarding the completeness of the prescriptions and their rational use is lacking from developing countries like India. Thus, the aim of this study was to assess the prescribing patterns of drugs and completeness of prescriptions as per WHO core drug use and complementary indicators to provide real-life examples for the Indian Council of Medical Research (ICMR) online prescribing skill course for medical graduates. METHODS: Prescriptions of the patients, fulfilling inclusion criteria, attending Outpatient Departments of various specialties of tertiary care hospitals, were collected by thirteen ICMR Rational use of medicines centers located in tertiary care hospitals, throughout India. Prescriptions were evaluated for rational use of medicines according to the WHO guidelines and for appropriateness as per standard treatment guidelines using a common protocol approved by local Ethics committees. RESULTS: Among 4838 prescriptions, an average of about three drugs (3.34) was prescribed to the patients per prescription. Polypharmacy was noted in 83.05% of prescriptions. Generic drugs were prescribed in 47.58% of the prescriptions. Further, antimicrobials were prescribed in 17.63% of the prescriptions and only 4.98% of prescriptions were with injectables. During the prescription evaluation, 38.65% of the prescriptions were incomplete due to multiple omissions such as dose, duration, and formulation. CONCLUSION: Most of the parameters in the present study were out of the range of WHO-recommended prescribing indicators. Therefore, effective intervention program, like training, for the promotion of rational drug use practice was recommended to improve the prescribing pattern of drugs and the quality of prescriptions all over the country.


Assuntos
Pesquisa Biomédica , Farmacologia Clínica , Humanos , Prescrições de Medicamentos , Atenção Terciária à Saúde , Padrões de Prática Médica , Organização Mundial da Saúde
2.
PRiMER ; 3: 29, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-32537600

RESUMO

BACKGROUND AND OBJECTIVES: Racial bias in health care is increasingly recognized as a factor in health inequities, yet there is limited research regarding medical school education around race and racism and its impact on medical students. The purpose of this study was to understand attitudes of medical students on race and racism in health care and to study the impact of participation in a voluntary structured program on race and racism. METHODS: First-year medical students had the opportunity to participate in a series of discussions (10 hours total) on race and racism. A 10-question survey addressing comfort, knowledge, and the adequacy of education on race and racism was sent to all first-year medical students (n=61/180, response rate 34%), and was administered to series participants (n=23/25, response rate 92%) in a pre/post format. RESULTS: Participant and nonparticipant attitudes were similar at baseline, with the exception that participants were less likely to feel that the medical school curriculum provided adequate education on race and racism, and reported higher levels of knowledge around these issues. Following the discussion series, participants showed significant changes regarding knowledge and awareness, as well as comfort level discussing race and racism. CONCLUSIONS: Participants were more likely than nonparticipants to think that the curriculum should include more discussion on race and racism. Postparticipation analysis demonstrated significant increases in comfort level, knowledge, and awareness in discussion of race and racism.

4.
J Pediatr ; 187: 43-49.e1, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28526224

RESUMO

OBJECTIVE: To evaluate the difference in 10-year neurocognitive outcomes between extremely low gestational age newborns without bacteremia and those with suspected or confirmed late-onset bacteremia. STUDY DESIGN: Neurocognitive function was evaluated at 10 years of age in 889 children born at <28 weeks of gestation and followed from birth. Definite (culture-positive) late-onset bacteremia during postnatal weeks 2-4 was identified in 223 children, and 129 children had suspected bacteremia. RESULTS: Infants with the lowest gestational age and birth weight z-score had the highest prevalence of definite and suspected late-onset bacteremia. Compared with peers with no or suspected bacteremia, infants with definite bacteremia performed worse on tests of general cognitive ability, language, academic achievement, and executive function, even after adjustment for potential confounders. Adjustment for low IQ attenuated the associations between bacteremia and all dysfunctions at age 10 years. Children with suspected bacteremia did not differ appreciably from those with no evidence of bacteremia. The motor domain was unaffected. CONCLUSIONS: Extremely low gestational age newborns who had definite late bacteremia during postnatal weeks 2-4 are at heightened risk of neurocognitive limitations at age 10 years.


Assuntos
Bacteriemia/complicações , Deficiências do Desenvolvimento/epidemiologia , Doenças do Prematuro/epidemiologia , Criança , Deficiências do Desenvolvimento/etiologia , Função Executiva , Feminino , Humanos , Lactente , Lactente Extremamente Prematuro , Recém-Nascido , Doenças do Prematuro/etiologia , Masculino
5.
Blood ; 97(5): 1392-8, 2001 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-11222385

RESUMO

In 1997, a chimeric anti-CD20 monoclonal antibody (mAb) (Rituxan) was approved for the treatment of low-grade/follicular B-cell lymphoma. Rituxan has a long half-life and low immunogenicity, and it mediates effector function. Rituxan induces apoptosis in some tumor cell lines in vitro. Previous studies with mAbs that react with neoplastic B cells have demonstrated that homodimers of immunoglobulin G ([IgG](2)) often inhibit cell growth more effectively than their monomeric (IgG)(1) counterparts. In this study, the ability of IgG or F(ab')(2) homodimers vs monomers of Rituxan were compared for their ability to inhibit the growth of several different B-lymphoma cell lines in vitro. It was found that homodimers of Rituxan had superior antigrowth activity in vitro and that F(ab')(2) homodimers were the most active. Homodimers, but not monomers, of Rituxan induced both apoptosis and necrosis of several B-cell lymphoma lines in vitro; the inhibition of cell growth was not dependent upon the presence of Fc receptors or upon 10-fold or greater differences in the density of CD20 on the target cells. Rituxan homodimers, compared with monomers, also rendered drug-resistant CD20(+) B-lymphoma cells more sensitive to chemotherapeutic agents and synergized with an anti-CD22 immunotoxin in vitro.


Assuntos
Anticorpos Monoclonais/farmacologia , Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Apoptose/efeitos dos fármacos , Moléculas de Adesão Celular , Lectinas , Linfoma de Células B/tratamento farmacológico , Anticorpos Monoclonais/isolamento & purificação , Anticorpos Monoclonais/metabolismo , Anticorpos Monoclonais Murinos , Antígenos CD/imunologia , Antígenos de Diferenciação de Linfócitos B/imunologia , Divisão Celular/efeitos dos fármacos , Dimerização , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Humanos , Imunotoxinas/farmacologia , Linfoma de Células B/patologia , Receptores de Antígenos de Linfócitos B/imunologia , Receptores Fc/metabolismo , Ricina/farmacologia , Rituximab , Lectina 2 Semelhante a Ig de Ligação ao Ácido Siálico , Células Tumorais Cultivadas
6.
Biochemistry ; 39(38): 11808-17, 2000 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-10995249

RESUMO

Bromonitromethane is an inefficient suicide substrate for glucose oxidase (in contrast to the case of CH(3)CCl=NO(2)(-) and D-amino acid oxidase) because, in the enzyme-substrate encounter step, the required ionization states of enzyme (EH(0)(+), pK(a) approximately 3.5) and substrate (CHBr=NO(2)(-), pK(a) approximately 8.3) cannot be highly populated simultaneously. Because reprotonation of CHBr=NO(2)(-) is rapid at the pH value used for the assay of glucose oxidase, presentation of the enzyme with the preformed anion could not be exploited in this case. We circumvent this difficulty by allowing the enzyme to reductively dehalogenate CHBr(2)NO(2), thereby generating the desired protonically unstable suicide substrate in situ (E(r) + CHBr(2)NO(2) --> E(o) + CHBr=NO(2)(-) + HBr + H(+)). Irreversible inactivation of the enzyme, because of the formation of a dead-end N-5 formylflavin adduct, is more than 100-fold faster when CHBr=NO(2)(-) is generated in situ than when it is externally applied. The remaining competitive fates of CHBr=NO(2)(-) at the active site are protonation and release or oxidation to HCOBr (or HCONO(2)). Strong support for these conclusions comes from (1) the brisk evolution of CH(3)CBr=NO(2)(-) (which is too bulky to act further as an efficient suicide substrate) from the enzyme-catalyzed reductive debromination of CH(3)CBr(2)NO(2), (2) the 1:1 stoichiometry of enzyme inactivation, and (3) the identification of the modified flavin as 5-formyl-1, 5-dihydro-FAD.


Assuntos
Dioxigenases , Precursores Enzimáticos/química , Flavina-Adenina Dinucleotídeo/análogos & derivados , Glucose Oxidase/antagonistas & inibidores , Glucose Oxidase/química , Metano/análogos & derivados , Metano/química , Nitroparafinas/química , Prótons , Ânions , Aspergillus niger/enzimologia , Sítios de Ligação , Bromo/química , Inibidores Enzimáticos/química , Flavina-Adenina Dinucleotídeo/química , Glucose/química , Cinética , Oxigenases/química , Relação Estrutura-Atividade , Especificidade por Substrato
7.
Viral Immunol ; 13(1): 125-35, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-10733174

RESUMO

Lung surfactant protein A (SP-A) has a central role in host defense mediated by the interaction of surface carbohydrates of inhaled pathogens with the lectin domains of SP-A. Respiratory syncytial virus (RSV), the most important viral pathogen of neonates and infants, encodes a highly glycosylated attachment protein, G. Binding studies were performed with G-protein from RSV (human, A2 strain) and human SP-A. The effect of SP-A on the interaction between RSV and host cells was determined by two methods: an infectivity study with monolayers of Hep-2C cells and by interleukin-8 (IL-8) release from buffy coat (BC) cells. SP-A binds to RSV G-protein in a concentration-dependent manner that is inhibitable by both ethylenediamine tetraacetic acid (EDTA) and mannan, indicating that binding is through the carbohydrate recognition domain of the SP-A and a carbohydrate moiety of the G-protein. The level of RSV infection of Hep-2C cells increases with increasing concentrations of SP-A. The amount of IL-8 released by BC cells in the presence of RSV is increased with SP-A concentrations of 2.9 microg/mL or greater. Our results show that SP-A enhances the attachment of RSV and subsequent entry into host cells. The effect of SP-A on viral uptake by epithelial cells and macrophage may determine both innate and adaptive immune responses to RSV.


Assuntos
Proteína HN , Proteolipídeos/metabolismo , Surfactantes Pulmonares/metabolismo , Vírus Sinciciais Respiratórios/patogenicidade , Proteínas Virais/metabolismo , Líquido da Lavagem Broncoalveolar/química , Humanos , Interleucina-8/metabolismo , Leucócitos , Mananas/farmacologia , Proteolipídeos/isolamento & purificação , Proteína A Associada a Surfactante Pulmonar , Proteínas Associadas a Surfactantes Pulmonares , Surfactantes Pulmonares/isolamento & purificação , Vírus Sinciciais Respiratórios/metabolismo , Células Tumorais Cultivadas , Proteínas do Envelope Viral , Virulência
8.
Am J Emerg Med ; 17(7): 695-6, 1999 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-10597093

RESUMO

Anaphylaxis, a multisystem allergic reaction, represents a true medical emergency. Anaphylaxis is characterized by a combination of the following: urticaria, angioedema, distributive shock, and respiratory failure. Most often, the patient is rapidly treated with prompt resolution of the anaphylaxis in either the out-of-hospital or emergency department (ED) setting. Infrequently, recurrent, or multiphasic, anaphylaxis is encountered, involving a reappearance of allergic phenomena after complete resolution of the original reaction. Recurrence may involve nuisance-level issues such as urticaria; alternatively, multiphasic reactions may be characterized by cardiovascular collapse and/or respiratory compromise. Initially aggressive pharmacological therapy followed by prolonged observation in either the ED or the in-hospital setting is strongly recommended to monitor for potential recurrence.


Assuntos
Anafilaxia/tratamento farmacológico , Anafilaxia/etiologia , Aviação , Tratamento de Emergência/métodos , Óleos de Plantas/efeitos adversos , Viagem , Adulto , Anafilaxia/diagnóstico , Anafilaxia/fisiopatologia , Feminino , Humanos , Óleo de Amendoim , Recidiva , Autoadministração
9.
Eur J Immunol ; 29(11): 3478-84, 1999 11.
Artigo em Inglês | MEDLINE | ID: mdl-10556802

RESUMO

The pulmonary collectin, lung surfactant protein D (SP-D), plays a role in host defense mediated by the interaction of surface carbohydrates of inhaled pathogens with the lectin domains of SP-D. Respiratory syncytial virus (RSV), the most important viral pathogen of neonates and infants, encodes a highly glycosylated attachment protein, G. Binding studies were performed with G protein from RSV (human, A2 strain) and both native and recombinant human SP-D. The effect of recombinant trimeric SP-D lectin domains (rSP-D) on the interaction between RSV and host cells was determined by two methods: an infectivity study with monolayers of Hep-2C cells and in vivo infections in BALB/c mice. These studies show that full-length and recombinant SP-D bind to RSV G protein in a concentration-dependent manner. Both EDTA and mannan inhibited binding of full-length SP-D. These results indicate that binding occurs via the carbohydrate recognition domain of the SP-D. The recombinant SP-D inhibited RSV infectivity in cell culture in a dose-dependent manner, giving 100% inhibition of replication. Intranasal administration of recombinant SP-D to RSV-infected mice inhibited replication of the virus in the lungs, reducing levels of lung virus by 80%. These results suggest that SP-D plays a major role in clearing RSV from the lungs.


Assuntos
Metabolismo dos Carboidratos , Glicoproteínas/metabolismo , Proteína HN , Surfactantes Pulmonares/metabolismo , Vírus Sincicial Respiratório Humano/metabolismo , Animais , Sítios de Ligação , Glicoproteínas/farmacologia , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Proteína D Associada a Surfactante Pulmonar , Surfactantes Pulmonares/farmacologia , Proteínas Recombinantes de Fusão/metabolismo , Proteínas Recombinantes de Fusão/farmacologia , Vírus Sincicial Respiratório Humano/fisiologia , Células Tumorais Cultivadas , Proteínas do Envelope Viral , Proteínas Virais/metabolismo , Replicação Viral
11.
Am J Respir Cell Mol Biol ; 19(1): 38-54, 1998 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9651179

RESUMO

We recently described a murine model of atopic asthma in which a marked, extensive hyperplasia of airway goblet cells is induced by repeated challenge of ovalbumin (OA)-sensitized mice with intratracheally administered allergen (Am. J. Respir. Cell Mol. Biol. 1996;14:425-438). We report here the time course of the duration of this feature and of its spontaneous resolution in the absence of further allergen exposure. Induction of severe neutrophilic inflammation in the airways by repeated intratracheal administration of lipopolysaccharide failed to induce goblet cell hyperplasia (GCH) to as great a degree as that induced by allergen, suggesting that nonallergic inflammation is a relatively poor inducer of this phenotype change in mice. When a "subclinical" infection of the lungs with the human A2 strain of respiratory syncytial virus was superimposed on the model of atopic asthma, recruitment of monocytes and lymphocytes to the airways was enhanced and a discharge of goblet cell mucin contents was observed. This may partly explain the respiratory difficulty that typifies virally induced exacerbations of asthma in humans. Daily systemic treatment of sensitized mice with dexamethasone during the period of allergen challenge produced a dose-related suppression of developing GCH, while similar treatment during the period following the establishment of extensive hyperplasia induced an accelerated resolution toward a normal epithelial phenotype. These results confirm and extend the relevance of this model as a representation of the human disease.


Assuntos
Asma/patologia , Dexametasona/uso terapêutico , Pulmão/patologia , Infecções por Vírus Respiratório Sincicial/complicações , Infecções Respiratórias/complicações , Alérgenos , Animais , Anti-Inflamatórios/uso terapêutico , Asma/complicações , Asma/tratamento farmacológico , Líquido da Lavagem Broncoalveolar/citologia , Eosinófilos , Células Epiteliais/patologia , Hiperplasia , Contagem de Leucócitos , Lipopolissacarídeos/farmacologia , Linfócitos , Macrófagos , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Neutrófilos , Ovalbumina/imunologia
13.
Vaccine ; 13(10): 915-22, 1995 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-7483764

RESUMO

Specific proliferative T-cell responses were induced in the lymph node cells (LNC) of mice immunised with a sucrose density gradient purified preparation of respiratory syncytial (RS) virus or an immunoaffinity purified preparation of the F glycoprotein. Inhibition studies and flow cytometric analysis showed that the responding cell population were CD4+ T cells. The cytokines produced by virus-specific and F-specific cells were assessed using the CTLL cell line. Peak quantities of cytokine were consistently detected in the supernatants of stimulated cultures 24 h prior to maximum proliferation. The proportion of IL-2 released was determined by blocking IL-2 activity with an anti-IL-2 monoclonal antibody. In cultures of RS virus primed LNC challenged with whole virus there was a switch of cytokine production from 70% IL-2 at day 3 to 80% IL-4 by 6 days of culture. In contrast, LNC cultures from mice immunised with F protein secreted 75-100% IL-2 throughout the culture period. These data suggest that after 6 days of challenge with viral antigen, the RS virus-primed LNC response consists of T helper cells which are predominantly of the Th2 subset, secreting IL-4, whilst F protein-primed LNC secrete large quantities of IL-2 and can therefore be classified as predominantly of the Th1 subset.


Assuntos
Vírus Sinciciais Respiratórios/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Proteínas Virais de Fusão/imunologia , Animais , Anticorpos Monoclonais/farmacologia , Ligação Competitiva , Citometria de Fluxo , Interleucina-2/metabolismo , Interleucina-4/metabolismo , Linfonodos/imunologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos BALB C , Vírus Sinciciais Respiratórios/química , Proteínas Virais de Fusão/farmacologia
14.
CMAJ ; 151(3): 273, 1994 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-8039079
15.
J Biol Chem ; 262(30): 14428-34, 1987 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-3667582

RESUMO

On the fifth day following inoculation into an unstirred liquid surface culture, Penicillium atrovenetum abruptly, and reproducibly, secretes large quantities (2 g/liter) of the toxic antibiotic 3-nitropropionate into the medium. Concomitantly and with the same time course, crude extracts of the fungus acquire the ability to catalyze the oxidation of 3-nitropropionate by O2. We purified this activity some 300-fold to homogeneity and find it to be a soluble, dimeric (Mr = 73,000) flavoprotein oxidase having FMN as prosthetic group with lambda max = 363 and 433 nm. The preferred substrates are propionate-3-nitronate (3-NP-2) and O2 while the reaction products are malonate semialdehyde, NO2-, NO3-, O2-., and H2O2. Of 13 nitronates tested only butyrate-4-nitronate is more than 2% as reactive as 3-NP-2. 3-NP-2 (0.1 mM) rapidly reduces E-FMN anaerobically to E-FMNH., the flavin semiquinone (t1/2 less than 5 s), but reduces E-FMNH. to the fully reduced enzyme (E-FMNH2) very slowly (t1/2 approximately 900 s). The steady state turnover number with 0.1 mM 3-NP-2 and infinite O2 is 350 s-1. Therefore, the enzyme must oscillate almost exclusively between E-FMN and E-FMNH. during aerobic turnover. (Formula: see text). The complicated and non-integral reaction stoichiometry provides further support for this free radical mechanism. Each mole of 3-NP-. generated enzymatically initiates the nonenzymatic autoxidation of at least 2.2 mol of 3-NP-2 through a free radical chain reaction. An appropriate name for the newly characterized enzyme is propionate-3-nitronate oxidase.


Assuntos
Oxirredutases/isolamento & purificação , Oxigênio/metabolismo , Propionatos/metabolismo , Mononucleotídeo de Flavina/análise , Flavoproteínas/isolamento & purificação , Radicais Livres , Peróxido de Hidrogênio/metabolismo , Cinética , Nitrocompostos , Oxirredução , Oxirredutases/análise , Penicillium/enzimologia
16.
J Biol Chem ; 262(19): 9154-9, 1987 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-3110155

RESUMO

We identify the cyanogenic substrate for horseradish peroxidase (HRP) as a conjugated enamine and explore this unusual reaction using alpha-aminocinnamate (RH) as follows. 1) HRP catalyzes the oxidation of RH by O2 (and its peroxidation by H2O2 to form R-R) to produce, simultaneously, CN- and benzaldehyde cyanohydrin. 2) RH is transient and must be generated in situ. The properties of the cyanogenic reaction of HRP are independent of the method of preparation of RH (whether this be condensation of NH3 with phenylpyruvate, enzymatic hydrolysis of glycyldehydrophenylalanine, or oxidation of L-phenylalanine by L-amino acid oxidase). 3) The oxidation of RH is a free radical chain reaction initiated by HRP Compounds I and II (I (or II) + RH----R. + II (or HRP], propagated by RO2. (R. + O2----RO2., RO2. + RH----R. + RO2H), and terminated by recombination reactions such as 2R.----R2 and RO2.----R' + HO2. followed by R. + HO2.----RH + O2. KMnO4 and K3Fe(CN)6 can substitute for HRP. 4) The proximal precursor of CN- and cyanohydrin is postulated to be RO2H (phi-CH(-O2H)-CCO2-(= NH]. These results explain why cyanide is generated from the synergistic action of HRP and L-amino acid oxidase on aromatic L-amino acids and O2 and suggest that the requirement for a beta-aryl substituent on the enamine originates in the reaction of RH with HRP, or of R with O2, rather than the imine/enamine tautomerization of the L-amino acid oxidase product.


Assuntos
Aminas/metabolismo , Peroxidase do Rábano Silvestre/metabolismo , Peroxidases/metabolismo , Benzaldeídos/metabolismo , Dipeptídeos/metabolismo , Consumo de Oxigênio , Fenilalanina/análogos & derivados , Fenilalanina/metabolismo
17.
J Biol Chem ; 262(20): 9608-14, 1987 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-3597427

RESUMO

We find ethanenitronate (formula; see text) to be a H2O2- (and peracetic acid-) dependent suicide substrate for bovine liver catalase (E) which converts E to Em, a modified form of the enzyme. The catalytic and suicide pathways are related to E, Em, Compound I, and Compound II according to the following scheme. (formula; see text) The catalytic cycle generates free radical products (EN.) which then participate in an O2-dependent chain reaction. Within experimental error the exclusive target for inactivation by EN- is Compound II. This partitions in the ratio (k4 = 1.2 M-1 s-1)/(k3 = 1.6 M-1 s-1) to generate Em and E, respectively. The species Em acquires 1 eq of 14C/ferriheme from [1-14C]ethanenitronate which is firmly (presumably covalently) affixed to the protein moiety. According to the standard H2O2 assay, Em is 7% as active catalytically as E. We regard inactivation as resulting from that fraction of EN. in the E...EN. complex which fails to diffuse from the complex because it is trapped by reaction with a neighboring amino acid residue to generate Em irreversibly. (formula; see text) This mechanism is identical to that deduced previously for suicide inactivation of horseradish peroxidase by alkane nitronates (Porter, D. J. T., and Bright, H. J. (1983) J. Biol. Chem. 258, 9913-9924) with the exception that EN. is trapped in that case by a methine carbon at the edge of the ferriheme rather than by the apoenzyme. The labeled residue in the catalase apoenzyme probably resides at or near the site of reduction of Compound II.


Assuntos
Catalase/metabolismo , Nitrocompostos/metabolismo , Animais , Catalase/antagonistas & inibidores , Bovinos , Ditiotreitol/farmacologia , Cinética , Fígado/enzimologia , Nitrocompostos/farmacologia , Espectrofotometria
18.
J Biol Chem ; 262(14): 6552-63, 1987 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-3106357

RESUMO

The CO2 adducts resulting from N-, O-, and S-carboxylation of suitable precursors are close analogues of carboxylate substrates in which -NH-CO2-, -O-CO2-, or -S-CO2- replaces -CH2-CO2- in the physiological substrate, -NOH-CO-2 replaces -CHOH-CO-2 and O-CO2- replaces -O-PO3H- R-XH + CO2 in equilibrium with R-X-CO2- + H+ X(-XH = -NH2, -NHOH, -OH or -SH). We find that aconitase catalyzes the CO2-dependent dehydration of N-hydroxy-DL-aspartate and erythro-beta-hydroxyl-L-aspartate with respective kcat values 62 and 90% of kcat for citrate and Km values of 3.6 and 3.2 mM, respectively. The CO2 adducts (carbamates) of the precursors would be structural and stereo analogues of the physiological substrate isocitrate. Detailed kinetic analyses of the behavior of intermediates and products show that aconitase catalyzes the formation of the enzyme-bound CO2 adducts from enzyme-bound precursors and CO2 and directs them, as well as the preformed CO2 adducts, into alpha,beta water elimination reactions formally identical to the isocitrate/cis-aconitate reaction. Six other enzymes of carbohydrate metabolism (succinate thiokinase and isocitrate, glucose-6-phosphate, succinate semialdehyde, glutamate, and malate dehydrogenase) utilize CO2 adducts as reactive substrate analogues. At least one of these (glucose-6-phosphate dehydrogenase) catalyzes the formation of the enzyme-bound CO2 adduct (presumed to be D-glucose 6-carbonate in this case) from enzyme-bound precursor (D-glucose) and CO2 in the manner of aconitase. The case of malate dehydrogenase is unique because the reactive malate analogue, -O2C-O-CHOH-CO-2, arises from nucleophilic attack of HCO-3 on the carbonyl of glyoxylate, rather than electrophilic attack of CO2 on the hydrated carbonyl of glyoxylate.


Assuntos
Aconitato Hidratase/metabolismo , Metabolismo dos Carboidratos , Dióxido de Carbono , Ácidos Carboxílicos , Enzimas/metabolismo , Animais , Cinética , Miocárdio/enzimologia , Relação Estrutura-Atividade , Especificidade por Substrato , Suínos
19.
J Enzyme Inhib ; 1(3): 215-22, 1987.
Artigo em Inglês | MEDLINE | ID: mdl-3508912

RESUMO

3-Nitro-1-propanamine is a close structural analog of the neuro-transmitter GABA. The nitro compound is a good substrate for the GABA aminotransferase from porcine brain. However, it inactivates the GABA aminotransferase from GABA-grown Pseudomonas fluorescens in a slowly reversible reaction. Both enzymes are inactivated by the homolog 4-nitro-1-butanamine.


Assuntos
4-Aminobutirato Transaminase/antagonistas & inibidores , Encéfalo/enzimologia , Propilaminas/farmacologia , Animais , Cinética , Suínos
20.
J Biol Chem ; 260(7): 4069-74, 1985 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-3980468

RESUMO

The nitric oxide (N = O) free radical exhibits potent cytocidal, mutagenic and vasodilatory properties. We have examined the hypothesis that the hydroxynitrosamino functionality (see sequence in text), which occurs naturally in antineoplastic and antihypertensive agents, will directly generate N = O following peroxidatic 1-electron oxidation. Cupferron (see sequence in text) is indeed an excellent (k greater than 10(7) m-1 s-1) substrate for horseradish peroxidase. The products are N = O and nitrosobenzene (phi - N = O) which are generated and consumed as follows. First, cupferron is oxidized by the classical peroxidatic mechanism to form an unstable nitroxide free radical (see sequence in text) which then forms N = O and phi - N = O spontaneously (see sequence in text). The N = O then reacts with phi - N = O to reform cupferron (see sequence in text) or with the enzyme to generate the characteristic peroxidase--N = O chromophore. Simultaneously, in a competitive reaction with O2, the N = O is converted to NO-2 (4N = O + O2 + 2H2O------------4NO-2 + 4H+). The reactivity of hydroxynitrosamino compounds with horseradish peroxidase is in the order cupferron greater than hydroxynitrosaminomethane greater than alanosine. These model reactions, involving direct oxidation of the hydroxynitrosamino moiety, comprise a novel pathway for the biological production of N = O.


Assuntos
Hidroxilaminas/metabolismo , Óxido Nítrico/metabolismo , Nitrosaminas/metabolismo , Fenômenos Químicos , Química , Peroxidase do Rábano Silvestre/metabolismo , Peróxido de Hidrogênio/metabolismo , Concentração de Íons de Hidrogênio , Matemática , Compostos Nitrosos/metabolismo , Consumo de Oxigênio
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