Biomedical subjects

A Zaliani

Publications and source records attributed to A Zaliani.

14 recordsLinked to original sources

PubMed2000

Solvation enthalpies as descriptors of structure--in vitro percutaneous permeation relationship of benzoxazinones regioisomers.

The aim of this work was to correlate the in vitro human skin permeability, expressed as the permeability coefficient (Kp), and some physicochemical parameters of a new series of benzoxazinones. The in vitro human skin permeability of 14 substances, including regioisomers with CH3, OH, OCH3, and Cl groups in different positions on the aromatic ring, was determined. The modified Franz diffusion cell method was used. The Kp values were in the range 0.14-8.24 cm/h, showing a strong dependence on the position and type of substituent. Physicochemical descriptors usually referred in literature, such as log P, molecular weight and volume (MV), hydrogen bond donor (Hd) and acceptor activity (Ha), and molecular refractivity were considered, with the addition of solvation enthalpy (delta deltaHsolv). Delta deltaHsolv is defined as the difference between formation enthalpies in water and octanol. The algorithm with the best correlation between Kp and physicochemical descriptors was calculated, taking into account the differences observed among the regioisomers. The algorithm obtained with delta deltaHsolv had a good correlation (r2 = 0.749, F = 16.43, P = 0.0005), comparable with the equation, proposed by Potts and Guy, based on MV, Hd and Ha (r2 = 0.830, F = 16.3, P = 0.0004).

Humans↗

PubMed2000

Global 3D-QSAR methods: MS-WHIM and autocorrelation.

The recently proposed MS-WHIM indices, a set of theoretical descriptors containing information about size, shape and electrostatic distribution of a molecule, have been further investigated. The main objectives of this work were: (i) to confirm the descriptive power of MS-WHIM in modelling specific biological interactions, (ii) to analyse the dependence of MS-WHIM on the type of atomic charges used for computing electrostatic potential and (iii) to compare the performances of MS-WHIM with those provided by other global 3D molecular descriptors. The spatial autocorrelation of atomic and molecular surface properties were selected for comparison purposes. WHIM-based and autocorrelation-based vectors were calculated for two molecular sets from the literature, namely a series of 18 HIV-1 reverse transcriptase inhibitors and a set of 36 sulphonamide endothelin inhibitors. PLS was adopted to derive statistical predictive models that were validated by means of cross-validation. The reported results confirmed that MS-WHIM indices are able to provide meaningful statistical correlations with biological activity. MS-WHIM descriptors are sensitive to the type of partial atomic charges applied and improved models were obtained using more accurate charges. Moreover for both the datasets, MS-WHIM results, in terms of fitting and predictive power of PLS models, were superior to those from autocorrelation. Finally, the strengths/weaknesses of global 3D-QSAR descriptors over local CoMFA-like methods, as well as the main differences between WHIM-based and autocorrelation-based vectors, are discussed.

Endothelins↗

PubMed1998

The interaction of myristylated peptides with the catalytic domain of protein kinase C revealed by their sequence palindromy and the identification of a myristyl binding site.

Using a model of the enzyme structure and the results from a series of free and myristylated peptides, we provide evidence that peptides corresponding to the pseudosubstrate sequence of protein kinase C bind to the enzyme substrate binding site in an essentially extended conformation. This and the nearly symmetrical location of positive charges around the substrate phosphoritable site allow the peptide to bind to the enzyme in either an N-to-C orientation or its C-to-N opposite orientation. The latter is favoured by a change in residue chirality or when the peptide bears a myristoyl chain at its N-terminus. A myristyl binding site was also identified in the enzyme structure and its location in a region proximal to the C-terminal residue of pseudosubstrate bound in the N-to-C direction suggested that C-myristylation of peptide substrates should be more effective than N-myristoylation in antagonizing the enzyme. A peptide (H-RFARKGALRQKN-CONH-Myr) which contains the myristyl chain covalently linked to the C-terminal residue of the pseudosubstrate was thus made and shown to be a potent inhibitor of the histone kinase reaction of protein kinase C and the phosphorylation of p47 in intact cells.

Amino Acid Sequence↗

PubMed1997

Mycobacterium tuberculosis chaperonin 10 stimulates bone resorption: a potential contributory factor in Pott's disease.

Pott's disease (spinal tuberculosis), a condition characterized by massive resorption of the spinal vertebrae, is one of the most striking pathologies resulting from local infection with Mycobacterium tuberculosis (Mt; Boachie-Adjei, O., and R.G. Squillante. 1996. Orthop. Clin. North Am. 27:95-103). The pathogenesis of Pott's disease is not established. Here we report for the first time that a protein, identified by a monoclonal antibody to be the Mt heat shock protein (Baird, P.N., L.M. Hall, and A.R.M. Coates. 1989. J. Gen. Microbiol. 135:931-939) chaperonin (cpn) 10, is responsible for the osteolytic activity of this bacterium. Recombinant Mt cpn10 is a potent stimulator of bone resorption in bone explant cultures and induces osteoclast recruitment, while inhibiting the proliferation of an osteoblast bone-forming cell line. Furthermore, we have found that synthetic peptides corresponding to sequences within the flexible loop and sequence 65-70 of Mt cpn10 may comprise a single conformational unit which encompasses its potent bone-resorbing activity. Our findings suggest that Mt cpn10 may be a valuable pharmacological target for the clinical therapy of vertebral tuberculosis and possibly other bone diseases.

Amino Acid Sequence↗

PubMed1997

A new rational hypothesis for the pharmacophore of the active metabolite of leflunomide, a potent immunosuppressive drug.

Leflunomide is one of the most promising disease-modifying antirheumatic drug now in clinical trials for the treatment of rheumatoid arthritis. Metabolic studies have indicated that leflunomide is rapidly processed in vivo to an active metabolite, A771726 (2). To identify the chemical characteristics necessary for the immunosuppressive activity of 2, configurational and conformational studies were carried out on the latter and its inactive analogues (ethyl 3-hydroxy-2-((4-(trifluoromethyl)phenyl)carbamoyl)but-2-enoate, 3a, and 3-hydroxy-2-nitro-N-(4-(trifluoromethyl)phenyl)but-2-enamide, 3b). These studies suggested that the pharmacophore responsible for the immunosuppressive activity of 2 is a beta-keto amide with the enolic hydroxy group cis to the amidic moiety. To verify this hypothesis, a new class of immunosuppressive agents was designed and synthesized. Their testing in vitro and in vivo identified compounds which were more potent than both leflunomide and 2 and above all confirmed our hypothesis as to the key structural and chemical determinants for the immunosuppressive properties of 2 and our compounds.

Aniline Compounds↗

PubMed1997

MS-WHIM, new 3D theoretical descriptors derived from molecular surface properties: a comparative 3D QSAR study in a series of steroids.

The recently proposed WHIM (Weighted Holistic Invariant Molecular) approach [Todeschini, R., Lasagni, M. and Marengo, E., J. Chemometrics, 8 (1994) 263] has been applied to molecular surfaces to derive new 3D theoretical descriptors, called MS-WHIM. To test their reliability, a 3D QSAR study has been performed on a series of steroids, comparing the MS-WHIM description to both the original WHIM indices and CoMFA fields. The analysis of the statistical models obtained shows that MS-WHIM descriptors provide meaningful quantitative structure-activity correlations. Thus, the results obtained agree well with those achieved using CoMFA fields. The concise number of indices, the ease of their calculation and their invariance to the coordinate system make MS-WHIM an attractive tool for 3D QSAR studies.

Computer Simulation↗

PubMed1996

Rational design of a new C-myristylamido peptide exerting potent and selective PKC inhibitory activity.

A 3D model of the catalytic domain of PKC was built based on the X-ray structure of the homologous PKA enzyme. The two enzymes were found to have similar general architecture although differing for the number of negatively charged clusters and their location near the phosphorylation site. These differences were consistent with the charge requirements deduced from the consensus sequence of PKC and PKA substrates. A Myristyl Binding Site (MBS) was found in the PKC model between helix C and sheets 8 and 9. The identification of this MBS allowed the rationalization of the results obtained with N-myristoylated peptide inhibitors and, above all, the design of ITF1671 (H-RFARKGALRQKN-CONH-Myr), a new C-myristylamido peptide, which exerted one of the most potent inhibitory activity against PKC and PKM known to-date.

Animals↗

PubMed1995

Mycobacterium tuberculosis chaperonin 10 forms stable tetrameric and heptameric structures. Implications for its diverse biological activities.

The chaperonin activity of sequence-related chaperonin 10 proteins requires their aggregation into heptameric structures. We describe size-exclusion chromatography and ultracentrifugation studies that reveal that while Escherichia coli chaperonin 10 exists as a heptamer, the Mycobacterium tuberculosis chaperonin 10 is tetrameric in dilute solutions and in whole M. tuberculosis lysate. At high protein concentration and in the presence of saturating amounts of divalent ions, the protein is heptameric. Human chaperonin 10 is predominantly heptameric, although smaller oligomers were detected. These differences in structural assembly between species may explain differences in biological activity such as antigenicity. Using C-terminal and N-terminal fragments, sequence 1-25 was identified as indispensable for aggregation. CD spectroscopy studies revealed that (i) a minimum at 202-204 nm correlates with aggregation and characterizes not only the spectrum of the mycobacterial protein, but also those of E. coli and human chaperonin 10 proteins; (ii) the interactions between subunits are of the hydrophobic type; and (iii) the anti-parallel beta-pleated sheet is the main secondary structure element of subunits in both tetrameric and heptameric proteins.

Amino Acid Sequence↗

PubMed1995

Sequence and structural homologies between M. tuberculosis chaperonin 10 and the MHC class I/II peptide binding cleft.

The peptide corresponding to the C-terminal half of M.tuberculosis hsp10 was synthesised based on the prediction that it might represent an independent structural region of the protein. This hypothesis was confirmed by aggregation and CD studies using this peptide and longer sequences of the protein. The peptide shares about 40-50% sequence homology with alpha 2 and beta 1 chains of MHC class I and II antigens. This and the CD results which indicated that the peptide at acidic pHs folds into an anti-parallel beta-sheet were used to generate a 3D model which has the same "W" fold contained in the MHC peptide binding groove. These data suggest that the hypothesis of molecular mimicry proposed to be one of the mechanisms which triggers autoimmune diseases may be extended to hsp10 proteins. Furthermore the suggested evolutionary relationship between hsp's and MHC antigens may find support from these data.

Amino Acid Sequence↗

PubMed1989

[Type A behavior and cardiovascular reactivity. Preliminary findings].

In view of reports of a connection between ischaemic cardiopathies and "A" type behaviour, the response of certain cardiocirculatory parameters to given physical stimuli was investigated in a group of people doing high stress work. The data did in fact reveal a tendency to more pronounced cardiovascular reactivity in the A group, a difference that was statistically significant in the cold pressor and cold tests. The possible links between enhanced vasomotor response and increased risk of coronary heart disease are pointed out with emphasis on recent hypotheses about the possible pathogenic role of enhanced 5-OH-tryptamine release and particular alterations in the alpha/beta adrenergic receptor balance.

Adult↗

PubMed1988

[Vibration-induced angiopathy: significance of urinary beta-thromboglobulin increase after cold test].

Twenty subjects working with tools generating 100-400 Hz vibrations were submitted to volumetric pulse-plethysmography with cold Test (C.T.) and to the measurement of BTGU, a thromboxane urinary catabolite. After C.T. an increase of BTGU was observed, which attained statistical significance in the subgroup with the most evident plethysmographic modifications. The meaning of these findings is discussed, also in the light their apparent contrast with some literature data. The AA believe that the prostaglandin balance can actually play a role in the pathogenesis of C.T.-induces vasomotor changes, if the tools used generate a sufficiently high number of Hz and if the workers are still rather young. This last condition corresponds to a greater intactness of endothelia and thus to the ability to modulate the vasomotor response ("hunting reaction"). This would lead to the activation of more complex pathogenetic mechanism (also biohumoral ones) among which is thromboxane release.

Adult↗

PubMedDate not supplied

[Angiopathy caused by vibrating tools: cold test and prostaglandin balance].

A study was made on a group of workers occupationally exposed to tools producing medium-to-low frequency vibrations, and on a comparable control group. The subjects underwent a plethysmographic examination with the cold test, which revealed a greater number of sphygmic alterations in the exposed group; at the same time spontaneous platelet aggregation, blood levels of 6-K-PGF-1 alpha and TXB2 and urinary levels of BTGU were determined in basal conditions and after the cold test. Except for the slight, and not statistically significant, increase in TXB2, the results did not reveal any alterations in the constituents of the prostaglandin balance after the cold test. This therefore indicates that biohumoral changes of this type were not involved in producing cold-induced vasomotor alterations in the group under study. However, further investigations are recommended which will take account of the age and working history of the subjects, and particularly of the physical characteristics of the vibrations produced by the tools used, especially the Hz number.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

[Cardiocirculatory findings in a group of workers exposed to nitro derivatives. A pathogenetic hypothesis of withdrawal hazard].

After briefly recalling the professional pathology characteristics of workers exposed to nitro derivatives and the perplexities surrounding the actual pathogenetic mechanism of the "Withdrawal hazard", the AA report the results of an investigation carried out among the workers of a dynamite producing plant. In the study, the NG and EGDN environmental levels were checked and the workers were submitted to ECG tracings, ECG D according to Holter, and monitoring of postural pressure changes both during exposure to the substances and during time-outs. The results obtained showed that the concentrations found in the plant were practically within the recommended TLV values, with no pathological modifications of the parameters examined. The AA put forward a pathogenetic hypothesis based on these findings and analyzing epidemiologic data on coronary sudden death as well as the mechanisms regarded as responsible for the disorders described in the literature in professionally exposed subjects. According to such hypothesis, the "Withdrawal hazard" (if any) would not be due to the cessation of the vasodilation effect of the nitro derivatives but would be a "rebound" phenomenon following the NG - and EGDN - inhalation induced stimulation to the production of endothelial prostaglandins, and of EDRF in particular, in exposed workers. The withdrawal of nitro derivatives inhalation would thus eliminate a vascular and coronary protection mechanism in the case of pathogenetic noxae at cardiovascular level. Such an interpretation would at last account for the time elapsing between cessation of work and occurrence of the disorders, which would not be justified by the cessation of the mere vasodilating action, since this wears out within a few hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular Diseases↗

PubMedDate not supplied

[An ergonomic analysis of 5 technics for moving patients]].

Nursing personnel and physical therapists refer to the lifting and moving of patients as the most important determinant of occupationally related low-back pain. This study was conducted in 12 nurses and 12 patients, to compare three methods of transferring patients from bed to wheelchair; (I) manual lifting, (II) an assistive device-a walking belt (with both one- and two-person transfers) and (III) a mechanical hoist. After completion of a given transfer, nurses were asked to rate the physical stress and how secure they felt the method was. Patients were asked to rate how secure and comfortable they felt. We also recorded the time required to make each transfer. The walking belt two persons had the most favourable ratings (the least stressful and most secure and comfortable), however transfers with this method took longer than those with the manual methods (although less than transfers with the hoist). Both nurses and patients rated one-person manual lifting as most stressful and least secure. Two-person transfer methods were preferred to the corresponding one-person methods. The hoist was the least suitable transfer method in view of the corresponding one-person methods. The hoist was the least suitable transfer method in view of the considerable physical stresses to the nurses, perceived lack of safety, discomfort for the patients and time involved.

Adult↗