Activation of MAP kinase by insulin and vanadate in adipocytes from young and old rats

Vanadate has insulin-like effects in adipocytes without stimulating insulin receptor kinase activity. However, it activates IRS-1 associated PI 3-kinase, suggesting that it mimics insulin effects by stimulating signaling elements downstream of PI 3-kinase. Here we analysed the stimulation of MAPK by insulin and vanadate and observed that both elicit a rapid 3.5-4 fold activation which is abolished by wortmannin and PD98059. Simultaneous addition of insulin and vanadate does not result in an additive effect neither on MAPK nor in MEK. Whereas insulin action is transient, vanadate stimulation lasts up to 20 min. In insulin-resistant adipocytes from old rats, insulin stimulates poorly MAPK, whereas a normal activation is achieved with vanadate. We conclude that: (a) insulin and vanadate use a common signaling pathway from PI 3-kinase to MEK and MAPK; (b) vanadate but not insulin, elicits a sustained activation of both enzymes; (c) this pathway is functional in old rat adipocytes.

Tubular hydrogen-bonded networks sustained by water molecules

The design concept of functional solids relies on controlling the topology of crystal packing through exploitation of weak intermolecular forces. In the context of cyclic aggregates, the ability to anticipate the consequences of ring constituents and their stereochemistries on ring conformation is vitally important since even an apparently slight structural change effected on molecules can dramatically alter the crystal structure. We have found that solid-state structures formed by hydroxy acids with a general structure (+/-)-1 depend on steric interactions. Thus, with the exception of molecules 1b and 1e, compounds (+/-)-1a-(+/-)-1m, which possess bulky and conformationally rigid substituents, aggregate by forming tapes and sheets by alternating (+) and (-) subunits held together through carboxylic acid-to-alcohol hydrogen bonds. Homologue (+/-)-1n, with conformationally flexible substituents which allow conformational deformation, gives, by incorporation of molecules of water, an efficient hexagonal assembly which extends to the third dimension to form tubular H-bonding networks. Each puckered channel can be described as interconnected closely packed hexagons in chairlike conformations. The ethyl groups presented in (+/-)-1n gave the volume required to lock the inner hexagonal wall into a rigid structure. Attempts to obtain cyclic aggregates using small substituents, compounds (+/-)-1o-(+/-)-1q, failed. The observed supramolecular assemblies of the anhydrous compounds can be classified into one-dimensional strands and two-dimensional sheets, while three-dimensional networks are present only in the hydrated molecules (1b, 1e, and 1n). The crystal structure of the anhydrous (+/-)-1n compound confirms the important role played by water molecules in the formation of tubular structures.

Comparative binding energy (COMBINE) analysis of human neutrophil elastase inhibition by pyridone-containing trifluoromethylketones

The complexes of human neutrophil elastase with a series of 40 N3-substituted trifluoromethylketone-based pyridone inhibitors have been modelled. The series spans three orders of magnitude in inhibition constants despite the fact that it was originally developed in an attempt to improve the oral activity of a lead compound. Ligand-receptor interaction energies calculated using molecular mechanics did not correlate well with the experimental activities. A good correlation with activity was found, however, when a COMBINE analysis of the same data was carried out, which allowed a quantitative interpretation of the modelled complexes. The essence of this method is to partition the ligand-receptor interaction energies into individual residue-based van der Waals and electrostatic contributions, and to subject the resulting energy matrix to partial least squares analysis. Incorporation of two additional descriptors representing the electrostatic energy contributions to the partial desolvation of both the receptor and the ligands improved the QSAR model, as did the replacement of the distance-dependent electrostatic contributions with solvent-screened electrostatic interactions calculated by numerically solving the Poisson-Boltzmann equation. The model was validated both internally (cross-validation) and externally, using a set of twelve 6-phenyl-pyridopyrimidine analogs. The analysis reveals the subtle interplay of binding forces which occurs within the enzyme active site and provides objective information that can be interpreted in the light of the receptor structure. This information, gained from a series of real compounds, can be easily translated into 3D real or virtual database queries in the search for more active derivatives.

Evaluation of docking functions for protein-ligand docking

Docking functions are believed to be the essential component of docking algorithms. Both physically and statistically based functions have been proposed, but there is no consensus about their relative performances. Here, we propose an evaluation approach based on exhaustive enumeration of all possible docking solutions obtained with a discretized description of a rigid docking process. We apply the approach to study both molecular mechanics and statistical potentials. It is found that the statistical potential evaluated is less effective than the AMBER molecular mechanics function to provide an accurate description of the docking process when the exact experimental coordinates are used. However, when coordinates of crystal structures obtained with analogous ligands are used, similar performances are obtained in both cases. Possible reasons for the successes and failures of both docking schemes have been uncovered using linear discriminant analysis, on the basis of a set of physicochemical descriptors capturing the main physical effects at play during protein-ligand docking. In both types of potentials steric effects appear critical to obtain a successful docking. Our results also indicate that neglecting desolvation effects and the explicit treatment of hydrogen bonds are the main source of the failures observed with the molecular mechanics potential. On the other hand, detailed consideration of steric interactions, with a careful treatment of dispersive forces, seems to be needed when using statistical potentials derived from a structural database. The possibility of filtering combinatorial libraries in order to maximize the probability of correct docking is discussed.

Solution structure and dynamics of the functional domain of Paracoccus denitrificans cytochrome c(552) in both redox states

A soluble and fully functional 10.5 kDa fragment of the 18.2 kDa membrane-bound cytochrome c(552) from Paracoccus denitrificans has been heterologously expressed and (13)C/(15)N-labeled to study the structural features of this protein in both redox states. Well-resolved solution structures of both the reduced and oxidized states have been determined using high-resolution heteronuclear NMR. The overall protein topology consists of two long terminal helices and three shorter helices surrounding the heme moiety. No significant redox-induced structural differences have been observed. (15)N relaxation rates and heteronuclear NOE values were determined at 500 and 600 MHz. Several residues located around the heme moiety display increased backbone mobility in both oxidation states, while helices I, III, and V as well as the two concatenated beta-turns between Leu30 and Arg36 apparently form a less flexible domain within the protein structure. Major redox-state-dependent differences of the internal backbone mobility on the picosecond-nanosecond time scale were not evident. Hydrogen exchange experiments demonstrated that the slow-exchanging amide proton resonances mainly belong to the helices and beta-turns, corresponding to the regions with high order parameters in the dynamics data. Despite this correlation, the backbone amide protons of the oxidized cytochrome c(552) exchange considerably faster with the solvent compared to the reduced protein. Using both differential scanning calorimetry as well as temperature-dependent NMR spectroscopy, a significant difference in the thermostabilities of the two redox states has been observed, with transition temperatures of 349.9 K (76.8 degrees C) for reduced and 307.5 K (34.4 degrees C) for oxidized cytochrome c(552). These results suggest a clearly distinct backbone stability between the two oxidation states.

Cyano-bridged bimetallic assemblies from hexacyanometalate, [M(CN)6](3-) (M = Mn(III) and Fe(III)), and [M(N4-macrocycle)]2+ (M=Fe(III), Ni(II) and Zn(II)) building blocks. Syntheses, multidimensional structures, and magnetic properties

Reactions between [M(N(4)-macrocycle)](2+) (M = Zn(II) and Ni(II); macrocycle ligands are either CTH = d,l-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane or cyclam = 1,4, 8, 11-tetrazaazaciclotetradecane) and [M(CN)(6)](3-) (M = Fe(III) and Mn(III)) give rise to cyano-bridged assemblies with 1D linear chain and 2D honeycomblike structures. The magnetic measurements on the 1D linear chain complex [Fe(cyclam)][Fe(CN)(6)].6H(2)O 1 points out its metamagnetic behavior, where the ferromagnetic interaction operates within the chain and the antiferromagnetic one between chains. The Neel temperature, T(N), is 5.5 K and the critical field at 2 K is 1 T. The unexpected ferromagnetic intrachain interaction can be rationalized on the basis of the axially elongated octahedral geometry of the low spin Fe(III) ion of the [Fe(cyclam)](3+) unit. The isostructural substitution of [Fe(CN)(6)](3-) by [Mn(CN)(6)](3-) in the previously reported complex [Ni(cyclam)](3)[Fe(CN)(6)](2).12H(2)O 2 leads to [Ni(cyclam)](3)[Mn(CN)(6)](2).16 H(2)O 3, which exhibits a corrugated 2D honeycomblike structure and a metamagnetic behavior with T(N) = 16 K and a critical field of 1 T. In the ferromagnetic phase (H > 1 T) this compound shows a very important coercitive field of 2900 G at 2 K. Compound [Ni(CTH)](3)[Fe(CN)(6)](2).13H(2)O 4, C(60)H(116)Fe(2)N(24)Ni(3)O(13), monoclinic, A 2/n, a = 20.462(7), b = 16.292(4), c = 27.262(7) A, beta = 101.29(4) degrees, Z = 4, also has a corrugated 2D honeycomblike structure and a ferromagnetic intralayer interaction, but, in contrast to 2 and 3, does not exhibit any magnetic ordering. This fact is likely due to the increase of the interlayer separation in this compound. ([Zn(cyclam)Fe(CN)(6)Zn(cyclam)] [Zn(cyclam)Fe(CN)(6)].22H(2)O.EtOH) 5, C(44)H(122)Fe(2)N(24)O(23)Zn(3), monoclinic, A 2/n, a = 14.5474(11), b = 37.056(2), c = 14.7173(13) A, beta = 93.94(1) degrees, Z = 4, presents an unique structure made of anionic linear chains containing alternating [Zn(cyclam)](2+) and [Fe(CN)(6)](3)(-) units and cationic trinuclear units [Zn(cyclam)Fe(CN)(6)Zn(cyclam)](+). Their magnetic properties agree well with those expected for two [Fe(CN)(6)](3-) units with spin-orbit coupling effect of the low spin iron(III) ions.

Adesmia aegiceras: antimicrobial activity and chemical study

The antimicrobial activity of the ethanolic extract of Adesmia aegiceras was studied by the agar-well diffusion method. Antibacterial activity against Micrococcus luteus and eight pathogenic bacterial strains as well as antifungal activity against Candida albicans, was detected. Bacterial and fungal strains exhibited similar concentration-response curves (EC50 and Rmax values) and similar MIC. The MBC/MIC was about 8. These data would indicate the potential usefulness of the A. aegiceras extract as a microbiostatic, antiseptic or disinfectant agent. Furthermore, chemical study of the bioactive alcoholic extract was performed, which revealed quercetin, isorhamnetin-3-rutinoside, isovitexin, pinitol and chlorogenic acid as its main components.

Improved activity and stability of lysozyme at the water/CH2Cl2 interface: enzyme unfolding and aggregation and its prevention by polyols

Protein inactivation and aggregation at the water/CH2Cl2 interface is one of the most detrimental events hindering the encapsulation of structurally unperturbed proteins into poly(lactide-co-glycolide) (PLG) microspheres for their clinical application as sustained release dosage forms. We have investigated the inactivation and aggregation of the model protein hen egg-white lysozyme at this interface and devised methods to prevent both events. When lysozyme was exposed to a large water/CH2Cl2 interface achieved by homogenization, lysozyme aggregation occurred. Fourier-transform infrared (FTIR) spectroscopic data demonstrated that the aggregates formed contained intermolecular beta-sheets. The aggregates were of a noncovalent nature because they slowly dissolved in D2O and the IR spectral bands typical for the intermolecular beta-sheets disappeared at approximately 1617 and 1690 cm(-1). The observed loss in specific enzyme activity of soluble lysozyme was caused by the irreversible formation of an unfolded lysozyme species, which was found to be monomeric, and was able to leave the water/CH2Cl2 interface and accumulate in the aqueous phase. Polyols were, in a concentration dependent fashion, efficient in ameliorating lysozyme unfolding and aggregation. However, prevention of lysozyme aggregation and activity loss in the various samples were unrelated. Thus, polyols must work by more than one mechanism preventing the two events. For the first time, an excipient effect on the conformational stability of lysozyme has been excluded from contributing to the prevention of lysozyme unfolding and aggregation.

Self-consistent Karplus parametrization of 3J couplings depending on the polypeptide side-chain torsion chi1

Recently proposed self-consistent 3J coupling analysis (Schmidt, J. M.; Blümel, M.; Löhr, F.; Rüterjans, H. J. Biomol. NMR 1999, 14, 1-12) has been carried out to calibrate Karplus parameters constituting the empirical dependence of 3J coupling constants on the chi1 dihedral angle in amino acid side chains. The procedure involves simultaneous least-squares optimization of six sets of three Karplus coefficients related to all six 3J coupling types accessible in 15N,13C-labeled proteins. A simple concept of fundamental and incremental component couplings is proposed to account for substituent effects, eventually yielding amino acid topology-specific Karplus parameters. The method is exemplified with recombinant Desulfovibrio vulgaris flavodoxin (147 amino acids, 16 kDa) with reference to a total of 749 experimental 3JHalpha,Hbeta, 3JN',Hbeta, 3JC',Hbeta, 3JHalpha,Cgamma, 3JN',Cgamma, and 3JC',Cgamma coupling constants. Unlike other parametrizations, the present method does not make reference to X-ray coordinates, so that the Karplus coefficients obtained are not influenced by differences between solution and crystal states. Cross validation using X-ray torsion angles demonstrates the improvement relative to previous parametrizations. The Karplus coefficients derived are applicable to other proteins, too. Parameter refinement also yields a series of chi1 torsion angles, providing valuable constraints for protein structure determination, as well as optional parameters of local angular mobility in the contexts of Gaussian random fluctuation or a three-site jump model. The procedure permits automatic stereospecific assignments of Hbeta and Cgamma chemical shifts. The majority of the flavodoxin side-chain conformations agrees with high-resolution X-ray structures of the protein. Marked deviations between NMR and X-ray datasets are attributed to different rotameric states due to crystal-packing effects and to conformational equilibria between multiple chi1 rotamers.

Inhibition of melanogenesis in response to oxidative stress: transient downregulation of melanocyte differentiation markers and possible involvement of microphthalmia transcription factor

H2O2 and other reactive oxygen species are key regulators of many intracellular pathways. Within mammalian skin, H2O2 is formed as a byproduct of melanin synthesis, and following u.v. irradiation. We therefore analyzed its effects on melanin synthesis. The activity of the rate-limiting melanogenic enzyme, tyrosinase, decreased in H2O2-treated mouse and human melanoma cells. This inhibition was concentration- and time-dependent in the B16 melanoma model. Maximal inhibition (50-75%) occurred 8-16 hours after a 20 minute exposure to 0.5 mM H2O2. B16 cells withstand this treatment adequately, as shown by a small effect on glutathione levels and a rapid recovery of basal lipid peroxidation levels. Enzyme activities also recovered, beginning to increase 16-20 hours after the treatment. Inhibition of enzyme activities reflected decreased protein levels. mRNAs for tyrosinase, tyrosinase-related protein 1, dopachrome tautomerase, silver protein and melanocortin 1 receptor also decreased after H2O2 treatment, and recovered at different rates. Downregulation of melanocyte differentiation markers mRNAs was preceded by a decrease in microphthalmia transcription factor (Mitf) gene expression, which was quantitatively similar to the decrease achieved using 12-O-tetradecanoylphorbol-13-acetate. Recovery of basal Mitf mRNA levels was also observed clearly before that of tyrosinase. Therefore, oxidative stress may lead to hypopigmentation by mechanisms that include a microphthalmia-dependent downregulation of the melanogenic enzymes.

Identification of a putative binding site for [2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-ribofuranosyl]-3'-spiro-5''-(4''-amino-1'',2''-oxathiole-2'',2''-dioxide)thymine (TSAO) derivatives at the p51-p66 interface of HIV-1 reverse transcriptase

A binding site for TSAO-m(3)T at the interface between the p66 and p51 subunits of HIV-1 reverse transcriptase (RT) and distinct from that of "classical" HIV-1 non-nucleoside inhibitors is proposed. The feasibility of the binding mode was assessed by carrying out nanosecond molecular dynamics simulations for the complexes of TSAO-m(3)T with reduced models of both the wild-type enzyme and a more sensitive R172A mutant. The molecular model is in agreement with a previous proposal, with known structure-activity and mutagenesis data for this unique class of inhibitors, and also with recent biochemical evidence indicating that TSAO analogues can affect enzyme dimerization. The relative importance of residues involved in dimer formation and TSAO-RT complex stabilization was assessed by a combination of surface area accessibility, molecular mechanics, and continuum electrostatics calculations. A structure-based modification introduced into the lead compound yielded a new derivative with improved antiviral activity.

[Tridimensional theory of personality: applications to substance abuse disorders]

INTRODUCTION

We have assessed the weight that Cloninger' dimensions play in the substance abuse disorder. Also, we have analysed the hypothetical self-independence of these dimensions and if there is some correlation between those and some demographic variables.

METHODOLOGY

20 drug abstinents and 20 controls, all males, fulfilled the Tridimensional Personality Questionnaire.

RESULTS

All the values on the Novelty Seeking (NS) subclass and the overall NS scale were higher in the abstinent group. The most meaningful differences were found on the excitable and extravagant subclass and the total NS scale. There was also a significant though smaller difference on the disorderly subclass. Only the Harm Avoidance (HA) subclass fatigability was significantly higher in the abstinent group. The value of persistence substantially low in the abstinent subjects was the most significant difference between groups when the Reward Dependence (RD) scale was considered. The correlation analysis demonstrated that the three dimensions were mutually independent in the controls. However, in the abstinent group NS correlated positively with HA and negatively with persistence. Any correlation was found between the dimensions and the demographic variables in both groups.

CONCLUSION

A high sensation seeking behaviour and a low persistence seems to be the most prominent characteristic of our abstinent subjects. Both tendencies could explain in part their high substance seeking tendency and possibly the high rate of relapse found in similar populations. Finally, the Cloninger's hypothesis about the mutually independence of the dimensions seems to be fulfilled only in the control group.

[Aeromonas spp bacteremia: study of 12 cases and review of the literature]

Twelve cases of Aeromonas spp. bacteremia are here reviewed in adult patients occurred at our institution during a 6-year period. Three cases corresponded to patients with hematological disease and four had a solid neoplasm. The source of infection in seven patients was extra-nosocomial; infections in the five remaining patients were considered to be acquired in the hospital. In seven patients, potential portals of entry were found. The usual clinical presentation was febrile syndrome in all cases and only in two patients did the clinical picture evolve to fulminant septic shock. Speciation of microorganisms was determined in only four cases: 2 A. hydrophilia, 1 A. caviae, and 1 A. veronii. Most isolates were susceptible to aminoglycosides, cotrimozazol, phosphomycin, and quinolonos, and resistant to ampicillin. Three patients (25%) died as a result of the infection. Aeromonas spp. bacteremia represented 0.12% of blood cultures in our hospital and occurs in immunosuppressed patients although it may be reported in previously healthy individuals.

Vertical HIV-1 transmission: prophylaxis and paediatric follow-up

OBJECTIVES

To study the effectiveness of anti-HIV therapy for vertical HIV-1 transmission based on the PACTG protocol 076, modified and adapted to Venezuela.

METHODS

Between March 1997 and March 2000, 74 HIV-1-infected women (15-42 years old) with 77 singleton pregnancies were evaluated. Zidovudine (ZDV) 500 mg/day (average 8 weeks) was begun after Western blot confirmatory tests, independent of CD4+ count or viral load. ZDV was administered as follows: 47 patients (61 per cent) received prenatal, perinatal and postnatal therapy; 13 (17 per cent) received prenatal and postnatal therapy; two (3 per cent) received prenatal and perinatal therapy; one patient received perinatal and postnatal therapy; seven (9 per cent) received only postnatal therapy. Seven HIV-1 infected women received no treatment. Thirty-two newborns were obtained by C-section (45.7 per cent), while 38 were delivered vaginally (54.2 per cent). Due to advanced maternal illness, seven HIV-1-infected women received ZDV+3TC, two women received ZDV+ddI and one woman received ZDV+3TC+ Ritonavir. Breastfeeding was avoided in all cases.

RESULTS

Outcomes showed 65 term newborns and five preterm newborns; three abortions; one fetal loss and one preterm death. Two maternal/fetal deaths were secondary to complications related to AIDS at 27 and 29 weeks, respectively. Twenty-one children over 18 months old were considered uninfected. Thirty-five infants below 15 months of age were considered with the status of indeterminate HIV-1 infection (PO). Three infants fewer than 5 months of age with multiple risk factors were considered infected (P2). Two infants were asymptomatic and HIV positive at 12 months of age (P1). Eight children were lost to follow-up.

CONCLUSIONS

Independent of maternal status and delivery type, confirmed vertical transmission of HIV-1-infected women who received ZDV is 4.25 per cent. Prenatal care with a multidisciplinary team is necessary for good obstetric and newborn outcomes.

A chloroform extract obtained from a decoction of Ficus carica leaves improves the cholesterolaemic status of rats with streptozotocin-induced diabetes

The antidiabetic effects of Ficus carica leaf extracts have been reported previously. From the aqueous decoction of fig leaves, after treatment with HCI, centrifuging, treatment with sodium hydroxide (NaOH) and extraction with chloroform (CHCl3), the administration of the organic phase rats with streptozotocin-induced diabetes led to a decline in the levels of total cholesterol and an decrease in the total cholesterol/HDL cholesterol ratio (with respect to the control group), together with a reduction of the hyperglycaemia.

[Acquired oculomotor paralysis in the adolescent]

INTRODUCTION

Acquired oculomotor palsy in juvenile age are most commonly due to head trauma, tumors, migraine, vasculopathies and demyelinating diseases.

CLINICAL CASES

We document three cases of paroxysmal oculomotor nerve palsy in childhood, illustrating the main clinical symptoms, neurological examination, MR images, diagnosis, treatment and evolution. Final diagnosis were: multiple sclerosis, pineoblastoma, and craniopharyngioma.

CONCLUSIONS

Sudden oculomotor nerve palsy occurring in youth in the absence of head trauma, viral infection or migraine access, firmly suggests a serious intracranial disease, and neuroimage studies should be quickly obtained to have an early diagnosis.

[Infection of ascending aortic graft: treatment with surgical cleaning, graft preservation and transposition of muscle flaps. Report of two cases]

Mediastinitis with graft infection is a serious complication of ascending aorta replacement. We report two cases of graft infection, treated with surgical cleaning, graft preservation and transposition of muscle flaps. A 62 years old male was admitted 34 days after an ascending aortic grafting due to a sternal dehiscence and mediastinitis. Antimicrobial treatment was started and a surgical cleaning performed, leaving an open sternotomy. Three days later, the thoracic cavity was closed with a rectus abdominis muscle flap. After 23 months of follow up, the patient is well and without evidence of infection. A 74 years old male was subjected to an aortic valve and ascending aorta replacement and a myocardial revascularization. In the postoperative period, the patient developed septic signs, and a purulent drainage. A CAT scan showed a liquid collection surrounding the aortic graft. On tW Sixteenth postoperative day, a surgical cleaning was performed and the thorax was closed with the pectoralis major muscle. After 10 months of follow up, the patient is in Good condition and without evidence of infection.