Biomedical subjects

C Vial

Publications and source records attributed to C Vial.

At least 55 records · Page 3Linked to original sources

PubMed1999

CTG instability in myotonic dystrophy: molecular genetic analysis of families from south-eastern France with characteristics of intergenerational variation in CGT repeat numbers.

We report clinical, genetical and genealogical findings in 149 French families from the Rhône-Alpes area studied over a 5-year period. There was a significant excess of DM females compared to DM males with (CTG) repeat sizes between 1-2 kb. The mean maternal (CTG) repeat size was higher than paternal repeat size. Anticipation phenomenom was significantly higher after maternal than after paternal transmission. A significant correlation between parental (CTG) repeat size and intergenerational variation both in paternal and maternal transmissions was observed. The anticipation phenomenom was more important for sons than daughters particularly after maternal transmission. The mean (CTG) repeat size in mothers of CDM cases was about twice that of mothers of NCDM children. The risk of giving birth to a CDM child increased considerably when the number of maternal (CTG) repeats was over 300 (CTG). A significant excess of DM females was observed. They had on average 24% fewer children than male patients. Paternal transmission (63.6%) of DM occurred more frequently than maternal transmission (52.7%).

Female↗

PubMed1998

Evidence for kinetic intermediate states during the refolding of GdnHCl-denatured MM-creatine kinase. Characterization of a trapped monomeric species.

The kinetics of refolding of guanidinium chloride-denatured rabbit MM-creatine kinase was investigated. Recovery of enzymatic activity is biphasic, depending on the temperature but not on the protein or DTT concentration. Only 45% of the original, active dimeric form is recovered even after several hours of refolding. The reactivation yield is limited by the accumulation of a highly stable but nonproductive monomeric species. The ratio of "correct" to "incorrect" forms depends on the duration of exposure to the denaturant, which may be consistent with the existence of a heterogeneous population of unfolded states with regard to proline isomerization. The first fast reaction observed during renaturation results in the appearance of collapsed monomeric states, displaying features of a pre-molten globule state. These burst species are rapidly transformed into more structured monomers resembling a molten globule state possessing a partially folded C-terminal domain. A proportion of these latter transient intermediates (45%) associates into an active dimer, while the remainder (55%) is trapped by reshuffling in a monomeric dead-end product. Our results strongly indicate that (i) the dimeric state is a prerequisite for the expression of catalytic activity, (ii) the kinetic intermediates of refolding are very similar to those observed during equilibrium unfolding, and (iii) refolding of creatine kinase in these conditions is limited by the accumulation of inactive misfolded nondimerizable monomer.

Anilino Naphthalenesulfonates↗

PubMed1998

Increase of intracellular Ca2+ and relocation of E-cadherin during experimental decompaction of mouse embryos.

To determine the role of intracellular Ca2+ in compaction, the first morphogenetic event in embryogenesis, we analyzed preimplantation mouse embryos under several decompacting conditions, including depletion of extracellular Ca2+, blocking of Ca2+ channels, and inhibition of microfilaments, calmodulin, and intracellular Ca2+ release. Those treatments induced decompaction of mouse morulae and simultaneously induced changes in cytosolic free Ca2+ concentration and deregionalization of E-cadherin and fodrin. When morulae were allowed to recompact, the location of both proteins recovered. In contrast, actin did not change its cortical location with compaction nor with decompaction-recompaction. Calmodulin localized in areas opposite to cell-cell contacts in eight-cell stage embryos before and after compaction. Inhibition of calmodulin with trifluoperazine induced its delocalization while morulae decompacted. A nonspecific rise of intracellular free Ca2+ provoked by ionomycin did not affect the compacted shape. Moreover, the same decompacting treatments when applied to uncompacted embryos did not produce any change in intracellular Ca2+. Our results demonstrate that in preimplantation mouse embryos experimentally induced stage-specific changes of cell shape are accompanied by changes of intracellular free Ca2+ and redistribution of the cytoskeleton-related proteins E-cadherin, fodrin, and calmodulin. We conclude that intracellular Ca2+ specifically is involved in compaction and probably regulates the function and localization of cytoskeleton elements.

Animals↗

PubMed1998

Role of quaternary structure in muscle creatine kinase stability: tryptophan 210 is important for dimer cohesion.

A mutant of the dimeric rabbit muscle creatine kinase (MM-CK) in which tryptophan 210 was replaced has been studied to assess the role of this residue in dimer cohesion and the importance of the dimeric state for the native enzyme stability. Wild-type protein equilibrium unfolding induced by guanidine hydrochloride occurs through intermediate states with formation of a molten globule and a premolten globule. Unlike the wild-type enzyme, the mutant inactivates at lower denaturant concentration and the loss of enzymatic activity is accompanied by the dissociation of the dimer into two apparently compact monomers. However, the Stokes radius of the monomer increases with denaturant concentration as determined by size exclusion chromatography, indicating that, upon monomerization, the protein structure is destabilized. Binding of 8-anilinonaphthalene-1-sulfonate shows that the dissociated monomer exposes hydrophobic patches at its surface, suggesting that it could be a molten globule. At higher denaturant concentrations, both wild-type and mutant follow similar denaturation pathways with formation of a premolten globule around 1.5-M guanidine, indicating that tryptophan 210 does not contribute to a large extent to the monomer conformational stability, which may be ensured in the dimeric state through quaternary interactions.

Anilino Naphthalenesulfonates↗

PubMed1998

The P2Y1 receptor is necessary for adenosine 5'-diphosphate-induced platelet aggregation.

The human P2Y1 receptor heterologously expressed in Jurkat cells behaves as a specific adenosine 5'-diphosphate (ADP) receptor at which purified adenosine triphosphate (ATP) is an ineffective agonist, but competitively antagonizes the action of ADP. This receptor is thus a good candidate to be the elusive platelet P2T receptor for ADP. In the present work, we examined the effects on ADP-induced platelet responses of two selective and competitive P2Y1 antagonists, adenosine-2'-phosphate-5'-phosphate (A2P5P) and adenosine-3'-phosphate-5'-phosphate (A3P5P). Results were compared with those for the native P2Y1 receptor expressed on the B10 clone of rat brain capillary endothelial cells (BCEC) and for the cloned human P2Y1 receptor expressed on Jurkat cells. A2P5P and A3P5P inhibited ADP-induced platelet shape change and aggregation (pA2 = 5) and competitively antagonized calcium movements in response to ADP in fura-2-loaded platelets, B10 cells, and P2Y1-Jurkat cells. In contrast, these compounds had no effect on ADP-induced inhibition of adenylyl cyclase in platelets or B10 cells, whereas known antagonists of platelet activation by ADP such as Sp-ATPalphaS were effective. These identical signaling responses and pharmacologic properties suggest that platelets and BCEC share a common P2Y1 receptor involved in ADP-induced aggregation and vasodilation, respectively. This P2Y1 receptor coupled to the mobilization of intracellular calcium stores was found to be necessary to trigger ADP-induced platelet aggregation. The present results, together with data from the literature, also point to the existence of another as yet unidentified ADP receptor, coupled to adenylyl cyclase and responsible for completion of the aggregation response. Thus, the term, P2T, should no longer be used to designate a specific molecular entity.

Adenosine Diphosphate↗

PubMed1998

[Recurrent Miller Fisher syndrome and anti-GQ1b antibodies].

INTRODUCTION: Miller-Fisher syndrome is defined by the triad: ophthalmoplegia, ataxia and areflexia. This rare entity is generally regarded as a variant of the Guillain-Barré syndrome, although neurophysiological patterns differ. In the acute phase of the disease, sera of affected patients contain high titers of antiganglioside anti-GQ1b, which is a specific marker. Recurrences are exceptional. EXEGESE: We report the case of a man with three recurrences of Miller-Fisher syndrome within 16 years. Anti-GQ1b antibody titers were elevated during an episode, decreasing but not completely and vanishing 2 years later. Intravenous human immunoglobulin treatment probably accelerated improvement at the two last episodes. CONCLUSIONS: Some experimental and immunohistochemical data from the literature argue for a probable direct pathogenic role of antibodies against GQ1b ganglioside in this syndrome. This should be a rationale for the use of immunomodulating treatments.

Antibodies↗

PubMed1998

Brachial plexus injury during cardiac catheterisation in children. Report of two cases.

The arm is particularly vulnerable to neurological injury, due to the intimate anatomical relationship between the brachial plexus and the traction zones. Severe injuries of the brachial plexus can be caused by compression, traction or laceration. Fortunately, many deficits are superficial and permanent neurovascular deficits are rare. Nevertheless, it is important to identify the probable cause of the injury since the prognosis for recovery directly depends on the underlying nature of the neurological deficit. Two anaesthetised children who suffered brachial plexus injury during cardiac catheterisation are reported. The first, with Ebstein's anomaly and significant pulmonary valve stenosis, presented, after the procedure, with a right arm motor deficit with proximal predominance. The second patient, with tetralogy of Fallot and pulmonary atresia, presented difficulty in left arm abduction and external rotation on awakening. The risk factors for brachial plexus lesions during anaesthesia are discussed. These include improper positioning, anaesthetic agents, extreme variations of body mass index and anatomical anomalies. Prevention, evolution and treatment of the brachial plexus injury are also considered. With proper care by the cardio-radiologist and anaesthesiologist the frequency of this injury can be reduced.

Adolescent↗

PubMed1998

[Resistance of human immunodeficiency virus (HIV) to zidovudine. Genotypic analysis in strains isolated from Chilean patients].

BACKGROUND: Resistance of HIV to AZT is the result of mutations in the pol gene that codifies the enzyme reverse transcriptase. AIM: To assess the resistance to antiretroviral drugs in Chilean patients infected with HIV. MATERIAL AND METHODS: The presence of mutations was searched in 22 patients infected with HIV. The emergence or persistence of these mutations was studied in sequential samples of 19 patients. The presence of the mutation that confers resistance to didanosine (DDI) was studied in those subjects exposed to the drug. Polymerase chain reaction techniques were used to analyze mutations in codons 41, 70 and 215 of the pol gene (resistance to AZT) and the mutation in codon 71 (resistance to DDI). RESULTS: On admission, none of the patients without previous exposure to AZT had drug resistance mutations. Seven of 12 patients (58.3%) that had received AZT had mutations in codon 215. In two, they were associated to a mutation in codon 41 and in two, a mutation in codon 70. After a mean follow up of 14 months, 13 of 15 patients (86%) that received AZT had viral strains genotypically resistant to the drug. In nine of these, the resistance was associated with disease progression. None of the 10 patients that received DDI had the mutation in codon 74 that confers resistance to the drug. However, in one of these patients, that never received AZT, a virus with a mutation in codon 215 was detected. CONCLUSIONS: A high percentage of patients that have received monotherapy with AZT have genotypic resistance to the drug. This resistance is associated with clinical and immunological derangement in 70% of these subjects.

Anti-HIV Agents↗

PubMed1997

Nucleotide binding sites in wild-type creatine kinase and in W227Y mutant probed by photochemical release of nucleotides and infrared difference spectroscopy.

Structural changes induced by nucleotide binding to the wild-type rabbit muscle creatine kinase (CK) and to its W227Y mutant were compared and probed by reaction-induced difference spectroscopy (RIDS). The reaction was induced by the photorelease of nucleotide from the caged nucleotides ADP[Et(PhNO2)] or ATP[Et(PhNO2)], producing the RIDS of CK. The concomitant addition of a saturated concentration of nucleotide and caged nucleotide modified the RIDS of CK, permitting structural changes caused by nucleotide binding in the wild-type creatine kinase to be identified. The W227Y mutant was inactive and its nucleotide binding site was partially impaired as shown by the disappearance or decrease of several nucleotide-sensitive bands in the RIDS of W227Y mutant. The magnitude of the decrease was not the same for each band, suggesting that distinct groups of W227Y mutant were affected differently during nucleotide binding. More precisely, the binding sites for gamma-phosphate and beta-phosphate of the nucleotide were not accessible in W227Y mutant as shown by the absence of the phosphate-sensitive 1666-1667-cm(-1) and 1625-cm(-1) bands in the RIDS of W227Y mutant. However the binding site of other parts of the nucleotide was partially accessible, since the 1638-1639-cm(-1) phosphate-insensitive band did not completely vanish in the RIDS of W227Y mutant. The RIDS of W227Y mutant with ADP[Et(PhNO2)] and creatine lacked the 1613-cm(-1) and 1581-cm(-1) bands, associated with vibrational modes of creatine, suggesting that coupling between the binding sites of the nucleotide and of creatine was altered in W227Y mutant. These results are in accordance with the earlier suggestions that residue W227 in CK is essential for preventing water molecules from penetrating into the active site and for orienting nucleotide in the binding site, by forming stacking interactions between its indole group and purine of the nucleotide and its indole group.

Adenosine Diphosphate↗

PubMed1997

Mitochondrial creatine kinase interaction with phospholipid vesicles.

The characteristics of the interaction of mitochondrial creatine kinase (mt-CK) with phospholipid vesicles are determined. The presence of negatively charged phospholipids is required to obtain a significant binding of mt-CK. The interaction seems to be largely of an electrostatic nature: it increases with increasing amounts of anionic phospholipid in liposomes and decreases when the ionic strength increases or when the pH of the medium is higher than the pI of mt-CK. We have compared the effects of various effectors used to solubilize mt-CK from the mitochondrial membrane on the binding of mt-CK to liposomes: the nucleotide substrates ATP and ADP have no influence, parahydroxymercuribenzoate, a negatively charged organomercurial compound, partially decreases mt-CK binding; and the anticancer agent adriamycin efficiently prevents mt-CK binding. As monitored by the increase in absorbance, mt-CK causes vesicle aggregation. A differential scanning calorimetry study, using dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol vesicles, shows that mt-CK produces a decrease in the enthalpy variation without any change in the position of the calorimetric peak maximum. This suggests a partial disorganization of the phospholipid bilayer upon interaction with mt-CK.

Adsorption↗

PubMed1997

ADP-binding and ATP-binding sites in native and proteinase-K-digested creatine kinase, probed by reaction-induced difference infrared spectroscopy.

Conformational changes induced by nucleotide binding to native creatine kinase (CK) from rabbit muscle and to proteinase-K-digested (nicked) CK, were investigated by infrared spectroscopy. Photochemical release of ATP from ATP[Et(PhNO2)] in the presence of creatine and native CK produced reaction-induced difference infrared spectra (RIDS) of CK related to structural changes of the enzyme that paralleled the reversible phosphoryl transfer from ATP to creatine. Similarly the photochemical release of ADP from ADP[Et(PhNO2)] in the presence of phosphocreatine and native CK allowed us to follow the backward reaction and its corresponding RIDS. Infrared spectra of native CK indicated that carboxylate groups of Asp or Glu, and some carbonyl groups of the peptide backbone are involved in the enzymatic reaction. Native and proteinase nicked CK have similar Stokes' radii, tryptophan fluorescence, fluorescence fraction accessible to iodide, and far-ultraviolet CD spectra, indicating that native and modified enzymes have the same quaternary structures. However, infrared data showed that the binding site of the gamma-phosphate group of the nucleotide was affected in nicked CK compared with that of the native CK. Furthermore, the infrared absorptions associated with ionized carboxylate groups of Asp or Glu amino acid residues were different in nicked CK and in native CK.

Adenosine Diphosphate↗

PubMed1997

High salt concentrations induce dissociation of dimeric rabbit muscle creatine kinase. Physico-chemical characterization of the monomeric species.

Incubation of dimeric MM-creatine kinase (MM-CK) with high NaCl or LiCl concentrations results in dissociation of the subunits and complete enzyme inactivation. In NaCl, this process, which depends on protein concentration, may be described according to a two-state model where the dimer can be reversibly converted into compact folded monomers (D <--> 2M). At LiCl concentrations higher than 2-2.5 M, MM-CK is recovered in two monomeric states: an inactive compact species (M) and a more expanded form (EF), which represents 15-20% of the population. Thus, in LiCl, a three-state model (D <--> 2M --> 2EF) more adequately accounts for our experimental results. The monomeric species (M) obtained in NaCl and LiCl exhibits some properties of the molten globule state described in guanidine hydrochloride. Indeed, this form is compact and devoid of any enzymatic activity; it maintains a high degree of secondary structure and binds 8-anilino-1-naphthalenesulfonate. The formation of this intermediate induces the exposure of a second tryptophan (among the four present) which is located at the monomer-monomer interface in the native structure. In LiCl, the monomeric species (M) is irreversibly converted into a less compact form (EF) which seems to have lost a large part of its secondary structure.

Animals↗

PubMed1997

Denaturation by guanidinium chloride of dimeric MM-creatine kinase and its proteinase K-nicked form: evidence for a multiple-step process.

Cytosolic MM-creatine kinase is a homodimeric protein. Each monomer can be cleaved by proteinase K at an exposed surface loop, into two fragments K1 and K2, which remain associated. The nicked protein is thus a heterotetrameric protein, named (K1K2)2, made up of two heterodimers K1K2 linked together by their K1 subunit. In non-denaturing conditions, the cleaved protein does not present any measurable difference compared with uncleaved MM-creatine kinase, except for the loss of enzymatic activity. Comparative equilibrium denaturation of the two oligomeric proteins by guanidinium chloride indicates a multistep process with formation of either compact monomer or compact K1K2 dimer, a molten globule and a pre-molten globule state. In the case of the nicked-enzyme, the molten globule is composed of the two peptides K1 and K2, whereas in the pre-molten globule the interactions between K1 and K2 are too weak to maintain their cohesion. At low guanidinium chloride concentration, the proteinase K-nicked protein exhibits a higher accessibility of one of its tryptophan accompanied by a small decrease in its molar ellipticity suggesting a secondary structure loosening of the K1 peptide. Our results suggest that K1 and K2 are not strictly autonomous unfolding units and thus cannot be considered as independent domains.

Animals↗

PubMed1997

The P2Y1 receptor is an ADP receptor antagonized by ATP and expressed in platelets and megakaryoblastic cells.

The human P2Y1 purinoceptor has been expressed in Jurkat cells and the effects of HPLC purified nucleotides on calcium movements were measured. The most potent agonist was 2-methylthio-ADP followed by ADP. ATP, Sp-ATPalphaS and beta,gamma-methylene-ATP were competitive antagonists. Suramin and PPADS inhibited the effects of ADP. This pharmacological profile is the same as that of the so-called P2T purinoceptor responsible for platelet aggregation, which has not yet been identified. Using PCR we found the P2Y1 receptor to be present in blood platelets and megakaryoblastic cell lines. These data suggest that the P2Y1 receptor may be the elusive P2T receptor.

Adenosine Diphosphate↗

PubMed1997

Proteinase K processing of rabbit muscle creatine kinase.

Proteinase K cleaves selectively both cytosolic and mitochondrial isoforms of creatine kinase leading to the appearance of two fragments, a large N-terminal one (K1) and a small C-terminal peptide (K2) which remain associated together. The loss of enzymatic activity correlates with the extent of monomer cleavage. N-terminal sequencing of the K2 fragments from rabbit cytosolic and pig mitochondrial creatine kinase shows that these peptides begin with A328 and A324, respectively. Electrospray ionization mass spectrometry demonstrates that K2 peptide is composed of 53 residues (A328-K380). However, the C-terminal end of the K1 fragment is not A327 as expected, but D325. Thus, the amino acids residues T326 and A327 have been eliminated by the protease.

Amino Acid Sequence↗

PubMed1997

Involvement of a tyrosine residue in the ADP binding site of creatine kinase. A second-derivative UV-spectroscopy study.

Second-derivative spectroscopy was used to determine the percentage of tyrosine residues that are exposed to solvent in rabbit MM-creatine kinase. Six residues, among the ten present per monomer, are solvent-exposed. The presence of creatine in the incubation medium does not modify this value. However, this number is decreased by one when the enzyme is incubated with saturating concentrations of MgADP. A dissociation constant for MgADP can be estimated and the obtained value (0.085 mM) is comparable to the Km for this substrate. Thus, a tyrosine residue is located near the MgADP binding site or is masked during protein conformational change induced by adenyl nucleotide binding.

Adenosine Diphosphate↗

PubMed1997

Molecular and clinical correlations in spinocerebellar ataxia 2: a study of 32 families.

Spinocerebellar ataxia 2 (SCA2) is caused by the expansion of an unstable CAG repeat encoding a polyglutamine tract. One hundred and eighty four index patients with autosomal dominant cerebellar ataxia type I were screened for this mutation. We found expansion in 109 patients from 30 families of different geographical origins (15%) and in two isolated cases with no known family histories (2%). The SCA2 chromosomes contained from 34 to 57 repeats and consisted of a pure stretch of CAG, whereas all tested normal chromosomes (14-31 repeats), except one with 14 repeats, were interrupted by 1-3 repeats of CAA. As in other diseases caused by unstable mutations, a strong negative correlation was observed between the age at onset and the size of the CAG repeat (r = -0.81). The frequency of several clinical signs such as myoclonus, dystonia and myokymia increased with the number of CAG repeats whereas the frequency of others was related to disease duration. The CAG repeat was highly unstable during transmission with variations ranging from -8 to +12, and a mean increase of +2.2, but there was no significant difference according to the parental sex. This instability was confirmed by the high degree of gonadal mosaicism observed in sperm DNA of one patient.

Adolescent↗

PubMed1997

Microvascular decompression for the treatment of hemifacial spasm. Retrospective study of a consecutive series of 75 operated patients--electrophysiologic and anatomical surgical analysis.

The authors report the results of a series of 75 patients operated on for hemifacial spasm by the same surgeon between October 1981 and January 1997. Microsurgical vascular decompression was performed through a retromastoid approach in contralateral position. The conflicting vessel was identified as the posterior inferior cerebellar artery in 41.3% of the cases, the anterior inferior artery in 38.6%, and the vertebrobasilar complex in 18.7%. Follow-up varied from 1 month to 13 years (with a mean duration of 5 years and 2 months). The outcome was excellent (total improvement) in 57 cases, good (> 75% improvement) in 11 cases, fair (< 75%) in 4 cases and poor in 3 cases. Neurological complications included deafness or hearing loss in 3 cases (2 occurred in the absence of intraoperative monitoring and the other during the first part of the series) and facial paralysis in 1 case. Brainstem auditory evoked potential (BAEP) intraoperative monitoring should be performed to avoid postoperative auditory complications; a marked auditory loss was observed in only 1.6% of the 60 patients of our series who underwent BAEP intraoperative monitoring.

Adult↗