RESUMO
CGI 17341 (2-ethyl-5-nitro-2,3-dihydro[2-1b]imidazo-oxazole) is a novel orally active representative of the 5-nitroimidazole series of antimicrobial agents. At concentrations ranging from 0.1 to 0.3 micrograms/ml, CGI 17341 inhibited the drug-susceptible and multi-drug-resistant strains of Mycobacterium tuberculosis. CGI 17341 had no cross-resistance with isoniazid, rifampin, streptomycin, or ethambutol. While the in vitro activity of CGI 17341 against M. tuberculosis was comparable to those of isoniazid and rifampin, it was superior to those of streptomycin, ciprofloxacin or norfloxacin, and oxazolidinone DuP 721. The MIC of CGI 17341 was not affected when the pH of the medium was decreased from 6.8 to 5.6, while four- to sixfold increases in the MICs of ciprofloxacin and isoniazid were observed. In mice infected with M. tuberculosis, the 50% effective dose for CGI 17341 was 7.7 mg/kg of body weight (95% confidence limits, 3.5 and 10.27) when administered on days 11 and 12 postinfection. CGI 17341 gave a dose-dependent (r = 0.995) and significant increase in the survival time. Our data indicate that the 5-nitroimidazole CGI 17341 is a promising and novel antituberculosis compound with potent in vitro and in vivo activities. Further investigations on this compound are warranted.
Assuntos
Antituberculosos/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , Nitroimidazóis/farmacologia , Oxazóis/farmacologia , Animais , Antituberculosos/uso terapêutico , Bacteroides fragilis/efeitos dos fármacos , Meios de Cultura , Resistência Microbiana a Medicamentos , Feminino , Concentração de Íons de Hidrogênio , Camundongos , Testes de Sensibilidade Microbiana , Nitroimidazóis/uso terapêutico , Oxazóis/uso terapêutico , Tuberculose Pulmonar/tratamento farmacológico , Tuberculose Pulmonar/microbiologiaRESUMO
DL-S-n-(3-(4-acetyl)-2-oxo-5-oxazolidynyl methyl) acetamide (DuP-721) is an orally active representative of the oxazolidinone series of antimicrobials. At concentrations ranging from 1.5 to 4 micrograms/ml, DuP-721 inhibited equally the strains of Mycobacterium tuberculosis susceptible and resistant to conventional antituberculosis drugs. DuP-721 inhibited M. gordonae and M. fortuitum at 3.9 micrograms/ml, M. kansasii at 1.95, and M. scrofulaceum at 15.6 micrograms/ml. It was not active against M. avium and M. intracellulare at concentrations of 250 micrograms/ml. The inhibition of the metabolism of M. tuberculosis as indicated by the liquid scintillation radiometric method was 56% at fourfold the minimum inhibitory concentration (MIC) of DuP-721 that compared well to that of the fourfold MIC concentrations of rifampicin and isoniazid. The in vitro activity of DuP-721 was not affected by reducing the pH from 6.8 to 5.5. In mice infected with M. tuberculosis, the 50% effective dose (ED50) for DuP-721 was 13.2 mg/kg when administered daily beginning 4 hr postinfection for 17 days. The ED50 was 71.8 mg/kg when DuP-721 was administered only on days 11 and 12 postinfection. A 100% survival rate was obtained at 50 and 160 mg/kg when DuP-721 was administered daily for 17 days, and only on days 11 and 12 after the infection, respectively. The increase in the survival time by DuP-721 at 100 mg/kg (eightfold the ED50 dose) when administered daily for 17 days beginning 4 hr after infection was inferior to that by eightfold the ED50 dose of rifampicin and isoniazid administered on days 11 and 12 postinfection.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Antituberculosos/farmacologia , Mycobacterium tuberculosis/efeitos dos fármacos , Micobactérias não Tuberculosas/efeitos dos fármacos , Oxazóis/farmacologia , Tuberculose/tratamento farmacológico , Animais , Antituberculosos/uso terapêutico , Relação Dose-Resposta a Droga , Resistência Microbiana a Medicamentos , Feminino , Concentração de Íons de Hidrogênio , Camundongos , Mycobacterium avium/efeitos dos fármacos , Complexo Mycobacterium avium/efeitos dos fármacos , Mycobacterium scrofulaceum/efeitos dos fármacos , Oxazóis/uso terapêutico , OxazolidinonasRESUMO
In 1979 the first abnormal human insulin was discovered. With the minute samples from the patient a Phe leads to Leu replacement could be established in either position B24 or B25. For the unequivocal localization of the substitution both the Leu analogues had to be prepared by semisynthesis. While another laboratory did this with the sequence of porcine insulin, here we are dealing with the true analogues of human insulin. In the present paper the structural consequences of the substitutions are investigated. Human insulin obtained by total synthesis served as a reference. Its CD spectral properties are herewith documented. According to the substantial deviations of the CD spectrum of [Leu B24]insulin, the introduction of the new side-chain forces conformational changes to occur not only in its immediate surrounding but also in the peptide chain. The failure to give the typical CD spectral response to variations of protein and zinc concentration indicates that the ability to form quaternary structure is impaired. Though dimerization was confirmed by gel chromatography to be largely reduced, it is concluded that, in addition, interactions normally responsible for the increase in tyrosine-CD with association are weakened. [Leu B25]insulin, on the other hand, does exhibit all CD spectral effects characteristic of the native hormone, though quantitatively somewhat reduced. The CD spectroscopic results are in full agreement with the computergraphic analysis of the sterical consequences of the substitutions. For B24-leucine an acceptable packing without movements of the mainchain and/or B15-leucine and without affecting dimerization is impossible, whereas B25-leucine can be accommodated without causing bad contacts either in the monomer or in the dimer. The structural results do not explain why [Leu B25]-insulin should have a lower biological activity than the B24 analogue, 2.1 +/- 0.3% versus 20.9 +/- 2.8%, in the fat cell test. They suggest, however, an important but not critical stereospecific role for the B25-phenylalanine in binding.
Assuntos
Variação Genética , Insulina/genética , Leucina , Mutação , Fenilalanina , Dicroísmo Circular , Humanos , Substâncias Macromoleculares , Modelos Moleculares , Conformação Proteica , Espectrofotometria UltravioletaRESUMO
We synthesized seventeen analogues of human insulin, applying the principle of stepwise, selective formation of the disulphide bonds. Most of these analogues only differ from human insulin in the replacement of a single amino acid in positions 2, 5, 6, 7, 8 and 11 of the A chain and 5, 7, 13 and 16 of the B-chain. The influence of these modifications on the physicochemical properties of the analogues is discussed. Eight analogues could be crystallized. All the analogues produce the same biological effects as insulin, but differ markedly in their potency. In isolated fat cells in vitro, [HisA8]insulin showed a relative potency of 2.46 in stimulating glucose oxidation (human insulin = 1), whereas [D-CysA6,A11]insulin had a potency of only 0.00027. Very low potency was observed when IleA2 or the half-cystines A6, A7, A11 or B7 were modified. Replacement of the invariant GlnA5 by alanine only reduced potency slightly. All the analogues are full agonists. The effects of the analogues on glucose oxidation and lipolysis are correlated, supporting the view that they are mediated by a common receptor on the fat-cell membrane. Hypoglycaemic potencies in the rat were similar to potencies in vitro. As expected, no correlation was demonstrable between antiserum binding--measured in the radioimmunoassay--and biological activity. Several results of this investigation are difficult to reconcile with the current view regarding the structure-activity relationship of insulin which appears to require further refinement.
Assuntos
Insulina/análogos & derivados , Tecido Adiposo/efeitos dos fármacos , Tecido Adiposo/metabolismo , Sequência de Aminoácidos , Animais , Bioensaio , Cristalização , Glucose/metabolismo , Humanos , Insulina/síntese química , Insulina/farmacologia , Substâncias Macromoleculares , Conformação Proteica , RatosAssuntos
Cistina/metabolismo , Dissulfetos/biossíntese , Insulina/biossíntese , Tecido Adiposo/metabolismo , Aminoácidos , Animais , Sítios de Ligação , Fenômenos Químicos , Química , Cromatografia em Gel , Cromatografia em Camada Fina , Distribuição Contracorrente , Feminino , Humanos , Hipoglicemia/metabolismo , Focalização Isoelétrica , Isomerismo , Masculino , Camundongos , Ratos , Convulsões/metabolismoRESUMO
The influence of positions 11 and 24 on hypocalcaemic potency and duration of action was examined. These positions are respectively occupied by threonine and glutamine in HCT, but by the basic amino acids lysine and arginine in SCT. Replacement of threonine by lysine trebled the hypocalcaemic potency of HCT and slightly prolonged its duration of action. Substitution of arginine for glutamine reduced the activity to about one tenth. The simultaneous introduction of both basic amino acids yielded an analogue intermediate in activity between those obtained by the single substitutions. The analogue [Bmp1, Va18, Lys11, Arg24]-HCT displayed the same effects as [Lys11]-HCT.
Assuntos
Calcitonina/análogos & derivados , Cálcio/sangue , Sequência de Aminoácidos , Animais , Sítios de Ligação , Calcitonina/farmacologia , Relação Dose-Resposta a Droga , Ratos , Relação Estrutura-AtividadeRESUMO
Relative activities of a series of corticotrophin analogues have been measured by means of five different bioassays using the rat. Similarities in the relative potencies of various ACTH analogues determined using lipolysis or steroidogenesis in vivo and for the lipolytic and steroidogenic responses of fat pads and adrenal slices in vitro emerged and support the concept of a close structural relationship between the ACTH receptors in adipose and adrenal tissues in the rat. Potencies based on the steroidogenic response of isolated adrenal cells, adrenal slices or in-vivo experiments differed markedly from each other. Inactivation of peptides did not occur in the isolated cell assay, so it is likely that this assay estimates potency at the receptor level. A number of arguments suggest that the difference between the isolated cell assay and the other steroidogenic assays lies solely in the effects of peptide inactivation in the latter, and this allows the relative metabolic stabilities for the peptide analogues in these assays to be calculated. In this way it can be shown that: (1) Replacement of L-Ser by D-Ser in amino acid position 1 markedly increases the metabolic stability of the peptide and has only a slight effect on receptor properties. (2) Shortening at the NH2-terminus reduces the activity of peptides at the receptor level by several orders of magnitude, but increases their relative metabolic stability. (3) Introduction of amide groups at the CO2H-terminus markedly increases receptor potency of (1-16), (1-17) and (1-18) ACTH without affecting their metabolic stability in vivo. However, amidation of the CO2H-terminus does have a large effect on metabolic stability in the adrenal slice assay. (4) Replacement of Arg by Lys in positions 17 and 18 of (1-18) ACTH increases potency at the receptor level (adrenal cells) but has little effect on metabolic stability. The comparison of potencies obtained in the various assays, therefore, throws light on the significance of each assay. In addition, the effects of structural modification of analogues can be separately evaluated with respect to the metabolic stability of a peptide and its potency at the receptor level.
Assuntos
Glândulas Suprarrenais/efeitos dos fármacos , Hormônio Adrenocorticotrópico/análogos & derivados , Cosintropina/análogos & derivados , Cosintropina/farmacologia , Corticosteroides/sangue , Animais , Bioensaio/métodos , Ácidos Graxos não Esterificados/sangue , Técnicas In Vitro , Masculino , Ratos , Relação Estrutura-AtividadeRESUMO
Assays of 8 synthetic analogues of human calcitonin in rats showed that their hypocalcaemic activity was drastically reduced by deletion of the C-terminal amide group, chain-shortening or opening of the disulphide ring, but unaffected or enhanced by modification of the N-terminal amino group.
Assuntos
Calcitonina/análogos & derivados , Animais , Calcitonina/farmacologia , Cálcio/sangue , Humanos , Fragmentos de Peptídeos/farmacologia , Ratos , Relação Estrutura-Atividade , Fatores de TempoRESUMO
The replacement of the three aromatic amino acids in positions 12, 16 and 19 of human calcitonin (HCT) by leucine residues, which occupy the corresponding positions, in ultimobranchial, e.g. salmon and eel, calcitonins, increased the hypocalcaemic potency of the peptide, as determined by bioassay on the rat, about 10-fold. The individual substitutions were not all equally augmentative: leucine (12) enhanced the activity of HCT about 4--5 times, but leucine (16) and (19) afforded no increase at all. Combination of leucine (12) with a deamino cysteine at the N-terminus yielded an analogue 10 times more potent than HCT. Another analogue containing valine in position 8 in place of methionine as well as the three leucine substituents in position 12, 16 and 19 proved more active than the tri-leucine analogue, but the additional introduction of tyrosine (22) nearly doubled the hypocalcaemic potency of the latter. The duration of the hypocalcaemic effects of the substituted peptides closely followed the changes in potency.
Assuntos
Calcitonina/análogos & derivados , Cálcio/sangue , Sequência de Aminoácidos , Animais , Calcitonina/farmacologia , Depressão Química , Relação Dose-Resposta a Droga , Humanos , Leucina/farmacologia , Ratos , Relação Estrutura-Atividade , Fatores de TempoRESUMO
The calcitonin analogues [Val8] -HCT and [Tyr22] -HCT, each with a single modification, and [Val8, Tyr22] -HCT and [Bmp1, Val8] -HCT, with two replaced amino acids were compared with synthetic human calcitonin (HCT) in respect of their hypocalcemic effects in the rat. The introduction of either valine in place of methionine in position 8 or of tyrosine for phenylalanine in position 22 of the HCT molecule yielded analogues 4 to 5 times as potent and nearly twice as long-acting as HCT. The doubly substituted peptide [Val8, Tyr22] -HCT displayed properties closely similar to those of [Val8] -HCT and [Tyr22] -HCT. The analgoue [Bmp1, Val8] -HCT, with a deaminated cysteine residue at the N-terminus, was about 6 times more potent than HCT and slightly longer-acting than [Val8] -HCT.