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Biomedical subjects

E Di Stasio

Publications and source records attributed to E Di Stasio.

18 recordsLinked to original sources
PubMed2001

Adult-onset familial laryngeal abductor paralysis, cerebellar ataxia, and pure motor neuropathy.

Two brothers presented with late-onset cerebellar ataxia and severe dysphonia. Brain MRI showed vermian and hemispheric cerebellar atrophy. Laringofiberscopy revealed laryngeal abductor paralysis in both patients. Neurophysiologic studies showed a pure motor neuropathy. The combined findings and the molecular analysis suggest a new familial disorder. Inheritance is most likely autosomal recessive, but X-linked transmission is also possible.

Aged↗
PubMed2001

Thermodynamics of Na+ binding to coagulation serine proteases.

The sodium binding to serine proteases triggers a conformational change in the proteins that enhances the catalytic activity of the enzymes. The interaction of the cation with the protein is mediated by the hydrogen-bonding network of water molecules that embed the Na+ site. We pointed out the crucial role of the insertion loop 186a-d and the I16-D194 ion pair in the stabilization of sodium binding pocket in thrombin. This paper contributes to better explain the molecular mechanism of sodium binding for different serine proteases leading to the identification of the structural changes necessary to engineer a functional Na+ site and regulate catalytic activity in serine proteases.

Blood Coagulation↗
PubMed2000

Characterization of the beta-dystroglycan-growth factor receptor 2 (Grb2) interaction.

The beta-dystroglycan/Grb2 interaction was investigated and a proline-rich region within beta-dystroglycan that binds Grb2-src homology 3 domains identified. We used surface plasmon resonance (SPR), fluorescence analysis, and solid-phase binding assay to measure the affinity constants between Grb2 and the beta-dystroglycan cytoplasmic tail. Analysis of the data obtained from SPR reveals a high-affinity interaction (K(D) approximately 240 nM) between Grb2 and the last 20 amino acids of the beta-dystroglycan carboxyl-terminus, which also contains a dystrophin-binding site. A similar K(D) value (K(D) approximately 280 nM) was obtained by solid-phase binding assay and in solution by fluorescence. Both Grb2-SH3 domains bind beta-dystroglycan but the N-terminal SH3 domain binds with an affinity approximately fourfold higher than that of the C-terminal SH3 domain. The Grb2-beta-dystroglycan interaction was inhibited by dystrophin in a range of concentration of 160-400 nM. These data suggest a highly regulated and dynamic dystrophin/dystroglycan complex formation and that this complex is involved in cell signaling.

Animals↗
PubMed2000

Structure-function analysis of hepatitis C virus envelope-CD81 binding.

Hepatitis C virus (HCV) is a major human pathogen causing chronic liver disease. We have recently found that the large extracellular loop (LEL) of human CD81 binds HCV. This finding prompted us to assess the structure-function features of HCV-CD81 interaction by using recombinant E2 protein and a recombinant soluble form of CD81 LEL. We have found that HCV-E2 binds CD81 LEL with a K(d) of 1.8 nM; CD81 can mediate attachment of E2 on hepatocytes; engagement of CD81 mediates internalization of only 30% of CD81 molecules even after 12 h; and the four cysteines of CD81 LEL form two disulfide bridges, the integrity of which is necessary for CD81-HCV interaction. Altogether our data suggest that neutralizing antibodies aimed at interfering with HCV binding to human cells should have an affinity higher than 10(-9) M, that HCV binding to hepatocytes may not entirely depend on CD81, that CD81 is an attachment receptor with poor capacity to mediate virus entry, and that reducing environments do not favor CD81-HCV interaction. These studies provide a better understanding of the CD81-HCV interaction and should thus help to elucidate the viral life cycle and to develop new strategies aimed at interfering with HCV binding to human cells.

Amino Acid Sequence↗
PubMed1999

Structural and functional analysis of the N-terminal extracellular region of beta-dystroglycan.

A protein fragment corresponding to the mouse beta-dystroglycan N-terminal extracellular region from position 654 to 750, beta-DG(654-750) was recombinantly expressed in BL21(DE3) Escherichia coli cells. Secondary structure prediction of the protein fragment reveals about 70% of random coil, as confirmed by circular dichroism analysis. Moreover, fluorescence analysis shows that the tryptophan residue in position 659 lays in a solvent-exposed fashion. These data suggest that the beta-DG(654-750) is likely to have a quite flexible structure and to be only partially folded. Interestingly, the protein still retains its biological function since using solid-phase assays we have detected binding of biotinylated beta-DG(654-750) both to native alpha-dystroglycan and to a recombinant fragment which spans the C-terminal region of alpha-dystroglycan.

Amino Acid Sequence↗
PubMed1998

Thermodynamics of inositol hexakisphosphate interaction with human oxyhemoglobin.

The interaction of inositol hexakisphosphate (IHP) with oxygenated human adult hemoglobin (Hb) was investigated at 25 degreesC. The affinity of IHP for oxygenated Hb is strongly pH-dependent, and potentiometric measurements of proton uptake and release upon IHP addition have shown that over the range between pH 8.0 and pH 6.0 in oxygenated Hb there are three groups of residues that change their pKa values after IHP addition, likely because of their interaction with negative charges of the heterotropic effector. On the basis of previous calculations on the electrostatic properties of human Hb (Matthew, J. B., Hanania, G. I. H., and Gurd, F. R. N. (1979) Biochemistry 18, 1919-1928; Lee, A. W.-m., Karplus, M., Poyart, C., and Bursaux, E. (1988) Biochemistry 27, 1285-1301), two of these groups might be Val1beta and His143beta, which are located in the beta1beta2 dyad axis, where they have been also proposed to interact with 2,3-diphosphoglycerate, whereas the third group does not appear easily identifiable. Calorimetric measurements of the heat associated with IHP binding at different pH values over the same range indicate that IHP binding is mostly enthalpy-driven at pH < 7 and mostly entropy-driven at pH > 7.

Adult↗
PubMed1998

Cl- regulates the structure of the fibrin clot.

The differences between coarse and fine fibrin clots first reported by Ferry have been interpreted in terms of nonspecific ionic strength effects for nearly 50 years and have fostered the notion that fibrin polymerization is largely controlled by electrostatic forces. Here we report spectroscopic and electron microscopy studies carried out in the presence of different salts that demonstrate that this long-held interpretation needs to be modified. In fact, the differences are due entirely to the specific binding of Cl- to fibrin fibers and not to generic ionic strength or electrostatic effects. Binding of Cl- opposes the lateral aggregation of protofibrils and results in thinner fibers that are also more curved than those grown in the presence of inert anions such as F-. The effect of Cl- is pH dependent and increases at pH > 8.0, whereas fibers grown in the presence of F- remain thick over the entire pH range from 6.5 to 9.0. From the pH dependence of the Cl- effect it is suggested that the anion exerts its role by increasing the pKa of a basic group ionizing around pH 9.2. The important role of Cl- in structuring the fibrin clot also clarifies the role played by the release of fibrinopeptide B, which leads to slightly thicker fibers in the presence of Cl- but actually reduces the size of the fibers in the presence of F-. This effect becomes more evident at high, close to physiological concentrations of fibrinogen. We conclude that Cl- is a basic physiological modulator of fibrin polymerization and acts to prevent the growth of thicker, stiffer, and straighter fibers by increasing the pKa of a basic group. This discovery opens new possibilities for the design of molecules that can specifically modify the clot structure by targeting the structural domains responsible for Cl- binding to fibrin.

Binding Sites↗
PubMed1998

Long-term outcome of migraine therapy: predictive value of the frontotemporal nitroglycerin test.

We evaluated whether type of response to the migraine-induction test with a nitroglycerin ointment applied to the frontotemporal head region could predict the efficacy of antimigraine therapy. Forty-two patients with migraine without aura underwent the test before and 2 months after antimigraine therapy. Two and 4 months after treatment withdrawal, most subjects with a negative response to the post-treatment test maintained treatment benefit, whereas benefit was lost in patients with an early onset migraine response.

Adult↗
PubMed1997

Dynamic light scattering study of fine semiflexible fibrin networks.

Fine fibrin networks have been investigated using the dynamic light scattering (DLS) technique. At the shortest delay times, t, the dynamic structure factor s(q,t) is found to depend on time according to an exponential function and, at intermediate delay times (up to 1 ms), to a stretched exponential. At longer times (t > 1 ms), a progressively increasing deviation from the stretched exponential behaviour has been observed. These results are in agreement with the theoretical predictions of a recently forwarded model for semiflexible polymers in semidilute solutions [K. Kroy and E. Frey, Physical Review E 55 (1996) p. 3092.], despite the fact that fibrin networks are made up of crosslinked branched polymers. The model, moreover, allows the calculation from the initial decay rate gamma q(0) of the average diameter of the fibrin fibres, a. The value of a = 30 +/- 2 nm, at fibrinogen concentration c(f) = 1676 nM and ionic strength 0.5, fits well into the data reported in electron microscopy studies. A concentration dependence of the average diameter of the fibrin fibres has been observed which saturates at the highest concentrations. The diameter of fibrin fibres is an important component in determining the physical properties of the fibrin networks, since the radial growth of fibrin fibres is limited by twisting during protofibrils aggregation. Our results indicate the importance of taking into account intrinsic semiflexibility in studying the physical properties of 'real' polymers and emphasize the high sensitivity of the DLS technique to investigate biological polymers also at the lowest concentrations where the systems are very fragile.

Buffers↗
PubMed1995

The frontotemporal region plays a role in the genesis of migraine without aura.

We have compared the migraine-inducing effect of nitroglycerin ointment applied to the frontotemporal region of the head, which is innervated by the ophthalmic and maxillary divisions of the trigeminal nerve, with that of nitroglycerin applied to the chin (innervated by the mandibular division), the posterolateral region of the neck (innervated by the second and third cervical roots), the lateral surface of the proximal third of the forearm (innervated by the sixth cervical root), and the medial surface of the upper-arm region (second dorsal root). One hundred patients suffering from migraine without aura were randomly divided into five equal groups. Each group received an application of 5 mg nitroglycerin in 2% ointment on a preselected body area for 2 hours. Frontotemporal nitroglycerin induced a significantly greater number of early onset migraine attacks with respect to the arm and forearm regions. In all cases, nitroglycerin applied to the frontotemporal region resulted in subsequent migraine, whereas there was a significant number of negative trials with nitroglycerin applied to the neck, arm, and forearm vs the frontotemporal area. It, therefore, appears that the trigeminal nerve endings in the affected frontotemporal region are particularly sensitive to the migraine-inducing effect of the nitrate. This suggests a peripheral neurogenic hypothesis of migraine genesis.

Adolescent↗
PubMed1990

[Possible mechanisms of the action of drugs for hemicrania].

Different classes of drugs are used in the pharmacological treatment of headache, both during migraine crisis and migraine prophylaxis. How these drugs exert their therapeutical effect in migraine is not clearly understood. Hypothetical mechanisms of action are discussed by the Authors in regard to the different pathogenetical events relevant to migraine. It is proposed that different pathological events can be modified by one drug and, conversely, one mechanism of action may be common to different drugs.

Humans↗
PubMed1986

The effect of bromocriptine on plasma catecholamine concentrations in normal volunteers.

The effect of the ergot derivative bromocriptine (5 mg orally) on blood pressure and plasma catecholamine concentrations was explored in normal volunteers. A significant decrease of plasma noradrenaline was found, while dopamine and adrenaline concentrations did not change significantly. Systolic and diastolic blood pressures were significantly lowered at 150 min after administration. The hypotensive effect of bromocriptine seems to be mediated by a lowered release of noradrenaline from sympathetic nerve endings. It may be hypothesized that the drug stimulates presynaptic dopamine receptors located on postganglionic sympathetic nerves, thus inhibiting noradrenaline discharge.

Adult↗
PubMed1983

Timed-release dihydroergotamine in the prophylaxis of mixed headache. A study versus amitriptyline.

A pharmacological trial has been carried out on 41 out-patients suffering from mixed headache. The prophylactic effect of a timed-release dihydroergotamine formulation was tested versus amitriptyline. Patients reported daily, on appropriate cards, the hours of headache and the degree of pain during the month before therapy and on the following two months of treatment. Whereas amitriptyline was found to be more effective than dihydroergotamine in reducing headache intensity, timed-release dihydroergotamine was found significantly more effective than amitriptyline in reducing attacks of "migraine" type.

Adolescent↗
PubMed1980

[Lithium therapy in Horton's neuralgia: preliminary results].

Prophylactic use of Lithium salts in patient suffering from cluster headaches has been evaluated looking at the mean number of headache attacks in one critical period and the mean weekly duration of the period itself. These two elements have been compared to those observed on other drugs treatments. Plasma Lithium monitoring has been performed weekly during the trial. Authors discuss the results reported and the hypothetic basis of them.

Cluster Headache↗
PubMedDate not supplied

The antimigraine effect of ergotamine: a role for alpha-adrenergic blockade?

The hypothesis that alpha-adrenergic receptor blockade accounts for the ability of ergotamine to stop migraine attacks was tested, in migraine patients, in an experimental migraine model based on nitroderivative- induced attacks. In a preliminary single blind, placebo controlled study, thymoxamine, a prevalently post-synaptic alpha adrenergic receptor antagonist, was able to abort migraine attack in 9 out of 10 patients, as opposed to 2 out of 10 by placebo (p < 0.005 Fisher's exact test). In a subsequent randomized, crossover, placebo controlled double blind study, the ability of a selective alpha-1 adrenergic receptor agonist, methoxamine, to block ergotamine antimigraine effect was studied. In 26 patients migraine was induced in two separate tests and then ergotamine was administered once after methoxamine pretreatment and once after placebo; methoxamine was significantly more effective than placebo in blocking antimigraine effect of ergotamine (p = 0.0055 Fisher's exact test). These results support the hypothesis that ergotamine alpha-1 adrenolytic properties may account for its antimigraine effect suggesting that this action takes place outside the blood-brain barrier, since methoxamine can cross it very poorly. Ergotamine target structure could be the trigeminal innervation of the extracranial and/or dural vessels.

Adolescent↗