Synthesis and pharmacological activity of the N-terminal dermorphin tetrapeptide analogs with CH2-NH peptide bond isosteres

The synthesis of pseudotetrapeptides H-Tyr-D-Ala-Phe-NH-(CH₂)₂-NH₂ (1a), H-Tyr-D-Ala-Phe-ψ(CH₂-NH)-Gly-NH₂ (2a), H-Tyr-D-Ala-ψ(CH₂-NH)-Phe-Gly-NH₂ (3a), and H-Tyr-ψ(CH₂-NH)-D-Ala-Phe-Gly-NH₂ (4a), representing the N-terminal tetrapeptide sequence of dermorphin, in which amide bonds are replaced by CH₂-NH bond, is described. N-acetyl-Tyr and desamino-Tyr pseudopeptide analogs (1-4b), (1-3c) are also described. The analogs were assayed in binding studies based on displacement of μ and δ-receptor selective radiolabels from rat brain membrane and in a bioassay using guinea pig ileum (GPI). Pseudopeptides in which the C-terminal (1a) or D-Ala-Phe (3a) amide bond are substituted, exhibit higher μ-affinities and μ-receptor selectivity than the corresponding Phe-Gly or Tyr-D-Ala analogs (2a, 4a). Acetyl-and desamino-Tyr pseudopeptide analogs (1-4b) and (1-3c) did not exhibit μ and δ-opioid receptor affinity at nM concentration. The relevance of the single peptide replacement and of its association to acetylation or amino group elimination of Tyr, is discussed on the basis of a receptor model for μ and δ opioids.     

Solution conformational analysis of sodium complexed [Gly6]. - and [Gly9]. -antamanide analogs

To investigate the conformational flexibility of metal-complexed cyclodecapeptides, we synthesized and studied two antamanide analogs, in which the phenylalanine residue in position 6 or 9 of the sequence was substituted by Gly. Previous conformational studies on antamanide suggested that these backbone regions are affected by conformational variation. The NMR conformational study showed a high degree of flexibility for the two analogs. With sodium ions, on the other hand, [Gly⁹]. -antamanide was able to form a fairly stable equimolar complex, whereas [Gly⁶]. -antamanide showed a conformational heterogeneity, with one prevailing conformer. For the [Gly⁹]. -antamanide analog, the whole NMR data, combined with extensive theoretical calculations, were consistent with the presence of 1) two (β-turns of type I, centered on Gly⁹-Phe¹⁰ and Ala⁴-Phe⁵, respectively; 2) a central cavity with a six-carbonyl oxygen cage, optimal for a Na⁺ hexacoordination; 3) strongly H-bonded amide protons for residues 1 and 6, both involved in the formation of the two type I β-turns, which, however, exhibited some fluctuations during the molecular dynamics simulations. For the [Gly⁶]. -antamanide-Na⁺ complex the prevailing conformer was consistent with a more open structure, with the partial solvent exposure of all the amide protons; that is, the Gly residue in position 6 increases the flexibility of this critical site more than does the Gly in position 9. These data in some way parallel the results of the cytotoxicity tests on B16-F10 transformed cells for the two analogs: [Gly⁹]. -antamanide is cytotoxic after 48 h exposure, whereas [Gly⁶]. -antamanide is almost inactive. On the contrary, both analogs are practically inactive in vivo against phalloidin.     

Reversal of chlorpromazine-induced avoidance depression by the N-methyl-d-aspartate antagonist,dizocilpine, in mice

Abstract— The non-competitive N-methyl-d -aspartate (NMDA) antagonist MK-801 (dizocilpine) was tested, alone or in combination with chlorpromazine, in mice previously trained in the shuttle-box. The lowest doses of dizocilpine (0·02 and 0·04 mg kg^?1) attenuated the disrupting action of the neuroleptic (1·5 mg kg^?1) on avoidance-performance, while avoidance depression induced by 1·5 and 2 mg kg^?1 chlorpromazine was completely or almost completely reversed by 0·08 mg kg^?1 NMDA antagonist. The highest dose (0·16 mg kg^?1) of dizocilpine did not ameliorate avoidance-performance of mice receiving 2 mg kg^?1 chlorpromazine, perhaps because of ataxic effects produced by the drug combination, at these doses. The results support suggestions for a potential use of NMDA antagonists in the treatment of extrapyramidal side-effects of neuroleptics.     

Opioid peptides Synthesis and binding properties of dermorphin related heptapeptides

C-Terminal amino acid residues of dermorphin (H-Tyr-D-Ala-Phe-Gly-Tyr-Pro-Ser-NH₂) were replaced by N^α-methyl- or D-amino acids in order to examine the effect on opioid activity. In binding studies based on displacement of μ, Δ, and κ opioid receptor selective radiolabels from guinea pig brain membranes, the 13 new analogues showed, like dermorphin, a negligible affinity for the κ binding site. The introduction of N^α-methyl- or D-amino acid residues at position 5, 6, or 7 of dermorphin, when matched with C-terminal amide function modifications, generally produced analogues with reversed μ/δ specificity.     

Synthetic Tyr-phospho and non-hydrolyzable phosphonopeptides as PTKs and TC-PTP inhibitors*

Tyrosine-specific protein kinases and phosphatases are important signal transducing enzymes in normal cellular growth and differentiation and have been implicated in the etiology of a number of human neoplastic processes. In order to develop agents which inhibit the function of these two classes of enzymes by interfering with the binding of their substrates, we synthesized analogs derived from the peptide EDNEYTA. This sequence reproduces the main autophosphorylation site of Src tyrosine kinases. In this work we report the synthesis, by classical solution methods, of the phosphotyrosyl peptide ED-NEYpTA as well as of three analogs in which the phosphotyrosine is replaced by a phosphinotyrosine and by two unnatural, non-hydrolyzable amino acids 4-phosphonomethyl-l -phenylalanine and 4-phosphono-l -phenylalanine. The Src peptide and its derivatives were tested as inhibitors of three non-receptor tyrosine kinases (Lyn, belonging to the Src family, CSK and PTK-IIB) and a non-receptor protein tyrosine phosphatase obtained from human T-cell (TC-PTP). The biomimetic analogues, which do not significantly affect the activity of CSK, PTK-IIB and TC-PTP, act:is efficient inhibitors on Lyn, influencing both the exogenous phosphorylation and, especially, its autophosphorylation. In particular, the Pphe derivative may provide a basis for the design of a class of inhibitors specific for Lyn and possibly Src tyrosine kinases, capable of being used in vivo and in vitro conditions. © Munksgaard 1995.     

Concurrence Between the Maxillary Midline and Bisector to the Interpupillary Line

Purpose:  Symmetry is one of the factors that contributes to facial harmony, and in oral rehabilitation it determines the success of esthetic treatment. Therefore, the aim of the present study was to analyze the axial symmetry between the bipupillar midline and maxillary central incisors midline of 102 dental students (both genders) distributed across five Brazilian dental schools.
Materials and Methods:  Students with no teeth missing and who had never been subjected to any dental treatment were selected. Photographs were taken with a Dental Eye III camera with a 100-mm macro objective and ratio of 1 : 10 from natural size, recorded on an Ektachrome ASA/ISO 100 film. The images were developed and applied to Microsoft Office Power Point 2007 software. The results were analyzed by analysis of variance and Student's t -test (α = 0.05).
Results:  There was no significant correlation between bipupillar midline and the maxillary dental midline, irrespective of gender.
Conclusion:  No significant coincidence was observed between the interpupillary and dental midline. However, the interpupillar distance and its relationship with other anatomic structures may be used as a reference in treatment, but measurements must be assessed individually.  

CLINICAL SIGNIFICANCE

Anatomic measurements and facial proportions can be helpful during the planning of esthetic oral rehabilitation.     

Effect of Steroid Eluting Versus Conventional Electrodes on Propafenone Induced Rise in Chronic Ventricular Pacing Threshold

The aim of this study was to evaluate chronic ventricular pacing threshold increase after oral propafenone therapy. Eighty-three patients affected by advanced atrioventricular hJock and sick sinus syndrome were studied at least 3 months after pacemaker implantation, before and after oral propafenone therapy (450–900 mg/day based on body weight). The patients were subdivided into three groups according to the type of unipolar electrode that was implanted: group I (41 patients)Medtronic CapSure 4003, group II(30 patients)Medtronic Target Tip 4011, and group III (12 patients)Osypka Vy screw-in lead. In all cases a Medtronic unipolar pacemaker was implanted: 30 Minix, 23 Activitrax, 14 Elite, 12 Legend, and 4 Pasys. Propafenone biood level was measured in 75 patients 3–5 hours after propafenone administration. The pacing autothreshoid was measured at 0.8 V, 1.6 V, and 2.5 V by reducing puise width. At the three different outputs before and after propafenone, threshold increments were significantly lower in group I in comparison with group II and group III (propafenone ranging from < 0.001 to < 0.05). No significant difference was found in pacing impedance or in propafenone plasma concentration in the three groups. Strength-duration curves were drawn for each group at baseline and after propafenone administration. Before propafenone, in group I, the knee was markedly shifted to the left and downward as compared to the classic curve, so that the steep part was predominant; in group II and group III this shift was progressively less evident. After propafenone we found the curve shifted to the right with the flat part progressively more evident in group II and group III as compared to group I. We conclude that steroid eiuting leads cause less threshold increase than conventionol and screw-in ones after oral propafenone, thus leading to safer chronic pacing. Chronic pacing at 2.5-V amplitude and 0.6-msec width was feasible in 97% of group I patients and in 80% of group II patients, but not in group III due to an insufficient safety margin. propafenone, pacing threshold     

Synthetic peptides including acidic clusters as substrates of yeast casein kinase-2

The synthesis is reported of a series of glutamyl peptide analogs of the model substrate H-Ser-Glu-Glu-Glu-Glu-Glu-OH of casein kinase-2 (CK-2). A convenient HPLC method for the separation of slightly different acidic peptides is also reported. The site specificity of yeast casein kinase-2 (Y-CK2) is examined with the aid of synthesized peptide substrates.