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Biomedical subjects

G Tedeschi

Publications and source records attributed to G Tedeschi.

At least 91 records · Page 5Linked to original sources
PubMed1995

Proton magnetic resonance spectroscopic imaging in childhood ataxia with diffuse central nervous system hypomyelination.

The spatial distribution of metabolite signal intensities can be measured within entire sections of the brain by proton magnetic resonance spectroscopic imaging (1H-MRSI). A group of six patients (4 unrelated girls and 2 brothers from 5 families) with childhood ataxia with diffuse CNS hypomyelination (CACH) underwent long-echo-time, single-slice 1H-MRSI. Relative to controls, there was a decrease in the signal intensity of N-acetylaspartate, choline, and creatine throughout the white matter in all six patients. We identified lactate signals in white matter in three of them with advanced disease. The degree of white matter involvement was not homogeneous over the entire patient group, but did correlate with clinical presentation. Deep and posterior white matter tended to be more involved. There were no 1H-MRSI abnormalities in the gray matter. 1H-MRSI findings suggest that this syndrome is secondary to a metabolic defect causing hypomyelination, axonal degeneration, and, in the most compromised cases, accumulation of lactate. This study shows that CACH is not limited to girls.

Aspartic Acid↗
PubMed1995

Supratentorial dermoid cysts. Presentation and management of five cases.

Five patients with supratentorial dermoid cysts who were surgically treated are presented. There were three males and two females, between the ages of 17 and 35 years (mean 26.6 years). The tumor location was frontobasal and/or temporobasal. The duration of illness before the diagnosis ranged from 1 to 14 months (mean 7.4 months). Clinical presentation included seizures, intracranial hypertension syndrome, aseptic meningitis, homonimous lateral hemianopsia, and memory defect. Preoperatively, all patients were investigated by computerized tomography (CT); in two cases, magnetic resonance (MR) imaging was also obtained. Tumor removal was performed by microsurgical procedures; it was total in 3 cases and subtotal in the remaining 2 cases. Histologically, all of the tumors exhibited the typical dermoid cyst pattern. There were no operative deaths. Two patients experienced postoperative language dysfunction and/or hemiparesis. No patient developed clinicoradiological evidence of tumor recurrence at 1 to 10 years (mean 5 years) following surgery. These results are discussed in light of the data previously reported by the literature.

Adolescent↗
PubMed1994

Amino-acid sequences of the alpha- and beta-subunits of hemerythrin from Lingula reevii.

The complete amino-acid sequences of the alpha- and beta-subunits of hemerythrin from the brachiopod Lingula reevii have been determined. These subunits are found in equal proportions in coelomic hemerythrocytes and form an octamer, presumably with an alpha 4 beta 4 composition. Both subunits were found to consist of 117 residues and to show 65% sequence identity to each other. Sequences of the alpha- and beta-subunits of L. reevii hemerythrin are closely related to their counterparts in hemerythrin from the related brachiopod, Lingula unguis, showing 95% and 87% sequence identities, respectively. Sequence alignments show that 25 residues in the lingulid hemerythrin subunits are identical to those found in other hemerythrins and myohemerythrins. These conserved residues include those known to provide iron ligands. However, these comparisons also indicate that the lingulid hemerythrin sequences are distinct from those of the sipunculid and annelid hemerythrins and myohemerythrins.

Amino Acid Sequence↗
PubMed1994

Properties of the flavoenzyme D-aspartate oxidase from Octopus vulgaris.

The properties of D-aspartate oxidase from Octopus vulgaris (EC 1.4.3.1) have been investigated. The protein is a monomer of M(r) 37,000 containing one mol flavin/mol protein. The enzyme as isolated exists at least in two forms, one containing FAD and the other, which is catalytically inactive, probably containing 6-OH-FAD, as inferred from the absorption spectrum of the enzyme. An additional form of the enzyme, as far as the nature of the coenzyme is concerned, has been detected in the purified enzyme and shown to derive from the form originally containing FAD. The modulation of the coenzyme reactivity exerted by Octopus D-aspartate oxidase, as studied by spectrophotometric techniques, conforms to the one expected for an enzyme belonging to the oxidase class of flavoproteins. Structural investigations show similarities in both the amino-acid composition and the N-terminal amino-acid sequence to bovine D-aspartate oxidase and porcine D-amino-acid oxidase. In summary, the general properties of the enzyme from Octopus vulgaris closely resemble those of the enzyme from beef kidney. Moreover, kinetic analyses suggest that two active-site residues with pKa of 7.1 and 9.1 are critical for catalysis, and that the ionization of such residues has different effects on the catalytic activity depending whether mono- or dicarboxylic D-amino acids are used as substrate.

Amino Acid Oxidoreductases↗
PubMed1994

Central action of cinnarizine and flunarizine: a saccadic eye movement study.

The mechanism of action of flunarizine (FZ) and cinnarizine (CZ) on the CNS is not fully understood. Computer analysis of saccadic eye movements (SEM) provides a sensitive and objective method for evaluating drug effect on the function of specific brain structures. This study aimed to assess the effect of a single oral dose of FZ (20 mg) and CZ (150 mg) on CNS function by means of computer analysis of SEM. Ten healthy volunteers were studied according to a double-blind, cross-over, placebo-controlled design. Peak saccadic velocity (PSV), which is related to the function of a specific group of burst neurons located in the brain stem, was significantly reduced by FZ. No significant effect of FZ on saccade accuracy (SA) and saccade latency (SL) was found. CZ did not produce significant effects on SEM, but a trend to decrease PSV. The possibility that a FZ central effect may be related to a stabilizing action on burst activity of neurons is discussed.

Administration, Oral↗
PubMed1993

Structural features responsible for kinetic thermal stability of a carboxypeptidase from the archaebacterium Sulfolobus solfataricus.

Investigations were performed on the structural features responsible for kinetic thermal stability of a thermostable carboxypeptidase from the thermoacidophilic archaebacterium Sulfolobus solfataricus which had been purified previously and identified as a zinc metalloprotease [Colombo, D'Auria, Fusi, Zecca, Raia and Tortora (1992) Eur. J. Biochem. 206, 349-357]. Removal of Zn2+ by dialysis led to reversible activity loss, which was promptly restored by addition of 80 microM ZnCl2 to the assay mixture. For the first-order irreversible thermal inactivation the metal-depleted enzyme showed an activation energy value of 205.6 kJ.mol-1, which is considerably lower than that of the holoenzyme (494.4 kJ.mol-1). The values of activation free energies, enthalpies and entropies also dropped with metal removal. Thermal inactivation of the apoenzyme was very quick at 80 degrees C, whereas the holoenzyme was stable at the same temperature. These findings suggest a major stabilizing role for the bivalent cation. Chaotropic salts strongly destabilized the holoenzyme, showing that hydrophobic interactions are involved in maintaining the native conformation of the enzyme. However, the inactivation rate was also increased by sodium sulphate, acetate and chloride, which are not chaotropes, indicating that one or more salt bridges concur in stabilizing the active enzyme. Furthermore, at the extremes of the pH-stability curve, NaCl did not affect the inactivation rate, confirming the stabilizing role of intramolecular ionic bonds, as a pH-dependent decrease in stability is likely to occur from breaking of salt bridges involved in maintaining the native conformation of the protein.

Acetates↗
PubMed1993

Ribonucleases from the extreme thermophilic archaebacterium S. solfataricus.

A purification procedure consisting of DEAE-Sephacel chromatography, heparin-Sepharose CL-6B chromatography and Mono-S chromatography led to the isolation of three proteins endowed with RNase activity from the thermoacidophilic archaebacterium Sulfolobus solfataricus. They were referred to as p1, p2 and p3, according to their elution order from the Mono-S column. Complete amino acid sequence of p2 and partial sequence of p3 displayed high sequence similarity to the 7-kDa DNA-binding proteins previously isolated in Sulfolobus strains [Choli, T., Wittman-Liebold, B. & Reinhardt, R. (1988) J. Biol. Chem. 263, 7087-7093]. The molecular mass of p2, calculated from sequence data, was 7.02 kDa, which compares fairly well with the value of 7.4 kDa determined by SDS/PAGE. Gel filtration of the molecule under native conditions displayed, however, a largely prevailing form with an assessed molecular mass of 13.0 kDa, which points to a dimeric structure. Kinetic characterization of protein p2 showed a broad pH optimum in the range 6.7-7.6 using yeast RNA as substrate; also, it was shown that activity was unaffected by EDTA, Mg2+ and phosphate. The enzyme did not accept as substrate any homopolyribonucleotide, which points to a rather narrow substrate specificity. This was also confirmed by incubating p2 with tRNA(fMet)Met (fMet, N-formylmethionine) from Escherichia coli: the hydrolysis products were thus identified as 3'-phosphooligonucleotides.

Amino Acid Sequence↗
PubMed1993

Intranasal versus intravenous neostigmine in myasthenia gravis: assessment by computer analysis of saccadic eye movements.

Intranasal (i.n.) neostigmine has been developed to obtain a quicker onset of action and a more adaptable dosage regimen than oral neostigmine. The effect of this neostigmine formulation in myasthenia gravis (MG) was studied by means of computer analysis of saccadic eye movements (SEMs). Six MG patients were selected on the basis of a positive effect of Tensilon on hypometria of the first saccade. The effect of the i.v. formulation (0.5 mg) was compared to 1, 2, 3, and 4 puffs of i.n. neostigmine (one puff = 4.6 mg). The drug effect on SEMs was monitored at intervals up to 2 h. Administration of i.v. neostigmine produced a marked effect immediately after the injection and the benefit lasted over 1 h. Following administration of i.n. neostigmine a marked effect was found for two, three, and four puffs. The drug effect was evident within 3 min, peaked at 18-33 min, and lasted over 2 h. Our data indicate the efficacy of the new formulation of neostigmine in MG as measured by means of quantitative analysis of SEMs.

Administration, Intranasal↗
PubMed1993

Pineal cysts: an incidental MRI finding?

The incidence of pineal cysts (PC) in "standard" MRI was reviewed. Seven cases of PC were found from 400 consecutive MRI examinations. PC did not produce clinically relevant symptoms in any of the patients. Our data, as well as those emerging from a critical review of the literature, suggest that PC are often asymptomatic and represent an incidental MRI finding.

Adolescent↗
PubMed1993

MR signal enhancement in cervical spondylotic myelopathy. Correlation with surgical results in 35 cases.

In a review of Magnetic Resonance (MR) imaging findings of 35 cervical spondylotic myelopathy patients, a localized increased signal intensity was observed within the most compressed segment of the cervical cord on T2 and proton density weighted images. Size and duration of cervical cord constriction seemed to be the predisposing factors in producing such an abnormality. All patients underwent surgery. Postoperatively the high MR signal intensity disappeared in 3 (8.6%) cases, decreased in other 20 (57.1%) cases, and did not change in the remaining 12 (34.3%) cases. Thus reversible (edema, transient ischemia) and/or irreversible (malacia, gliosis) histological changes seemed to be represented in MR signal enhancement.

Adult↗
PubMed1993

Cord diameters and their significance in prognostication and decisions about management of cervical spondylotic myelopathy.

The cases of 35 cervical spondylotic myelopathy patients exhibiting areas of high signal intensity within the cervical cord on T2 and proton density weighted MR images were reviewed. In each case, the ratio of the anteroposterior diameter to the transverse diameter (anteroposterior compression ratio or APCR) at the most compressed segment of the cervical cord was measured on axial MR images and compared with the patient's neurological status. The patients with APCR of 40% or more had a better neurological condition than those with APCR of 38% or less. At the same time, the neurological condition was worse in the patients with APCR of 10% or less than in those with APCR of 15% or more. All patients underwent surgery. The preoperative APCR was compared with the outcomes. The patients with preoperative APCR of 15% or more improved after the operation, but the degree of recovery varied considerably from case to case. The patients with preoperative APCR of 10% or less remained unchanged postoperatively.

Adult↗
PubMed1993

[Subarachnoid hemorrhage of unknown etiology: management, prognosis, and predictive factors].

Thirty-nine consecutive patients with subarachnoid hemorrhage (SAH) of unknown etiology were studied retrospectively. A significant relationship between arterial hypertension, blood on CT and angiographic spasm was found. The use of nimodipine was associated with a reduction of vasospasm. Antifibrinolytic agents did not increase the risk of ischemic complications. The prognosis was generally favorable.

Cerebral Angiography↗
PubMed1992

Myohemerythrin from the sipunculid, Phascolopsis gouldii: purification, properties and amino acid sequence.

Two previously unknown isoforms, labelled iso I and iso II, of the oxygen-carrying protein, myohemerythrin, have been isolated from carcasses of the sipunculid worm, Phascolopsis gouldii. The two isoforms have non-identical N-terminal amino acid sequences and slightly different absorption spectra in the met form. Far-ultraviolet circular dichroism shows that iso I contains approximately 69% alpha-helix. The complete amino acid sequence for iso I was obtained. The molecular weight calculated from this amino acid sequence and including the active site Fe-O-Fe unit, is 13,829. All of the physical and chemical properties of iso I noted above, including the amino acid sequence, are very similar to those of T. zostericola myohemerythrin. Except for the amino acid sequence, these properties are also very similar to that of a subunit in hemerythrin, the octameric analog found in hemerythrocytes. Only 58 of the 113 residues in P. gouldii hemerythrin are conserved in iso I. Sequence comparisons were used to help identify residues responsible for maintaining the common tertiary and diiron site structures in hemerythrin and myohemerythrin. The seven iron ligand residues previously identified in crystal structures of hemerythrin and myohemerythrin are conserved in iso I. However, none of the ten residue pairs previously identified as engaging in direct salt-bridge or hydrogen bond interactions between subunits in the hemerythrin octamer are conserved in iso I.

Amino Acid Sequence↗
PubMed1992

The primary structure of the flavoprotein D-aspartate oxidase from beef kidney.

The complete primary structure of the peroxisomal flavoenzyme D-aspartate oxidase from beef kidney has been determined by analyses of the peptides obtained through fragmentation of the carboxymethylated protein with trypsin, CNBr, heptafluorobutyric acid/CNBr and Staphylococcus aureus V8 protease. The protein consists of a single polypeptide of 338 residues, accounting for a M(r) of 37,305 for the apoprotein. A form of the enzyme lacking Lys-338 and therefore ending with Pro-337 has been detected. The N-terminal residue is blocked. Seven cysteines and no disulfide bridges are present. Residue 228 can be either Ile or Val. Thus, D-aspartate oxidase presents two types of heterogeneity in the polypeptide chain in addition to the one already described concerning the possible content of FAD or 6-hydroxyflavin adenine dinucleotide. Comparison of the primary structure of D-aspartate oxidase with other known sequences reveals that D-aspartate oxidase is homologous with D-amino acid oxidase (another flavo-oxidase) and does not present significant sequence similarities with any other protein, including flavoenzymes.

Amino Acid Oxidoreductases↗
PubMed1992

Purification, inhibitory properties and amino acid sequence of a new serine proteinase inhibitor from white mustard (Sinapis alba L.) seed.

A new serine proteinase inhibitor, mustard trypsin inhibitor 2 (MTI-2), has been isolated from white mustard (Sinapis alba L.) seed by affinity chromatography and reverse phase HPLC. The protein inhibits the catalytic activity of bovine beta-trypsin and bovine alpha-chymotrypsin, with dissociation constants (Kd) of 1.6 x 10(-10) M and 5.0 x 10(-7) M, respectively, at pH 8.0 and 21 degrees C, the stoichiometry of both proteinase-inhibitor complexes being 1:1. The amino acid sequence of MTI-2, which was determined following S-pyridylethylation, is comprised of 63 residues, corresponding to a molecular weight of about 7 kDa, and shows only extremely limited homology to other serine proteinase inhibitors.

Amino Acid Sequence↗
PubMed1992

Chemical modification of functional arginyl residues in beef kidney D-aspartate oxidase.

Chemical modification of beef kidney D-aspartate oxidase by phenylglyoxal is a biphasic process involving the transient formation of an enzymatic species with a decreased activity versus dicarboxylic substrates, an increased activity versus D-proline and a new activity versus other monocarboxylic D-amino acids which is absent in the native protein. Prolonged incubation with the modifier causes complete inactivation of the enzyme. The presence of the competitive inhibitor L-tartrate in the incubation mixture prevents enzyme inactivation. Kinetic and structural data suggest that complete loss of activity is paralleled by modification of eight arginine residues, of which two are critical for the specificity and the activity of the enzyme. We propose that the two essential arginine residues are located in the substrate binding site of D-aspartate oxidase.

Amino Acid Oxidoreductases↗
PubMed1991

Structural and functional characteristics of polypeptide subunits of the bovine heart ubiquinol--cytochrome-c reductase complex.

Structural and functional characteristics of subunits of bovine heart cytochrome-c reductase have been investigated by controlled digestion of soluble and membrane-reconstituted purified bc1 complex and direct amino acid sequencing of native and digested protein subunits. The results obtained show that the N-terminal segments of core protein II and the 14-kDa protein extend at the periphery of the complex, protruding into the inner matrix space. The Fe-S protein, located at the outer C-periphery of the complex, is shown to be anchored to other subunits of the complex by the amphipathic N-terminal region. Proteolytic cleavage of 7-11 residues from the N-terminal segment of the 14-kDa protein is apparently associated with decoupling of redox-linked proton pumping. Partial digestion of core protein II, the 6.4-kDa protein, and the C-terminal region of the 9.2-kDa protein, is without effect on the redox and proton-motive activity of the complex.

Amino Acid Sequence↗