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Biomedical subjects

F Michel

Publications and source records attributed to F Michel.

At least 127 records · Page 7Linked to original sources
PubMed1995

Progressive mediastinal widening after therapy for Hodgkin's disease.

A residual mass after treatment of Hodgkin's disease points to the diagnosis of fibrotic residue or of persistent disease. Radiological and radionuclide imaging, although helpful, cannot differentiate between both conditions with absolute certainty. Thus, residual masses are followed up: stable or regressive masses strengthen the hypothesis of fibrotic residue, while enlarging masses evoke relapsing disease. We report on a patient with an enlarging residual mass after completion of therapy, which proved to be a benign thymic hyperplasia after histological analysis. Previously reported similar observations are reviewed.

Adult↗
PubMed1995

Structure and activities of group II introns.

Group II introns are found in eubacteria and eubacterial-derived, organellar genomes. They have ribozymic activities, by which they direct and catalyze the splicing of the exons flanking them. This chapter reviews the secondary structure and known tertiary interactions of the ribozymic component of group II introns in relation to the problems of specifying splice sites and building a catalytic core. We pay special attention to the relationship between the transesterification and hydrolytic modes of initiating splicing and the stereospecificities of these reactions. A number of group II introns encode proteins of the reverse transcriptase family; the activity of these proteins enables the host introns to change genomic locations by mechanisms that are only beginning to be deciphered. Finally, we briefly discuss multipartite and post-transcriptionally edited group II introns, together with the intron microcosm of Euglena gracilis chloroplasts and the possible relationships between group II and spliceosome-catalyzed splicing processes.

Animals↗
PubMed1995

Gastrin-CCK-B type receptors on human T lymphoblastoid Jurkat cells.

The presence of specific receptors for gastrointestinal hormones on T cells and their involvement in the immune response are still matters of debate. We reported the effects of gastrin-cholecystokinin (CCK)-related peptides on J.RT3-T3.5 Jurkat cells. A single class of high-affinity binding sites (dissociation constant approximately 0.1 nM) for gastrin and CCK-8 was evident on these cells. These peptides dose-dependently induced a transient increase in intracellular Ca2+ concentration ([Ca2+]i), which was independent of extracellular Ca2-. L-365,260 was 150- to 300-fold more potent than L-364,718 to inhibit radiolabeled ligand binding or peptide-stimulated [Ca2+]i increase, confirming the gastrin-CCK-B nature of the receptor. Gastrin caused a rise in inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] level within 5 s of stimulation. Finally, gastrin increased interleukin (IL)-2 secretion in J.RT3-T3.5 cells. We conclude that 1) J.RT3-T3.5 cells possess "gastrin-CCK-B type" receptors coupled to phospholipase C activation, Ins(1,4,5)P3 formation, and Ca2+ release from intracellular Ca2+ pools, and 2) these receptors could be involved in the regulation of IL-2 production.

Calcium↗
PubMed1995

[Cervical spondylolysis in children. Apropos of 4 cases. Review of the literature].

PURPOSE OF THE STUDY: A clinical and radiological study of four cases of spondylolysis in children. Literature review shows the congenital origin of the disorder and how it is to be treated. MATERIAL AND METHODS: We report on four children with cervical spondylolysis. One of the children presented a two-level spondylolysis C5C6. One case was totally asymptomatic and was hazardly discovered. Standard radiographs were used for diagnosis. Conservative treatment was administered in all cases and all patients were immobilized for a few days. DISCUSSION: It has been clearly established that cervical spondylolysis is a congenital disorder often associated with other anomalies: spina bifida, dysplasia of the posterior articular processes. In the child, cervical spondylolysis is only discovered in fifty per cent of Post traumatic cases. The most frequent finding is at C6. A diagnosis can be made based on the radiographs and the CT scan. MRI will only be indicated in spondylolisthesis in order to analyze the disc statement and the degree of canal narrowing. When possible conservative treatment should be adopted. Arthrodesis is reserved for unstable and painful lesions. CONCLUSION: Cervical spondylolysis in the child is a rare congenital disorder. It must be distinguished from the congenital absence of a pedicle and from a pedicle or isthmic fracture. It is a lesion which is normally discovered once the patient has turned adult and is very well long term tolerated.

Adolescent↗
PubMed1995

[Substituted methoxyphenol with antioxidative activity: correlation between physicochemical and biological results].

Guaiacol moiety has been found in antiinflammatory compounds present in traditional african or chinese medicine. As the activity of these products could be due to reactions with the reactive oxygen species (ROS) or enzymes involved in the inflammatory reaction, a comparative study has been done between biological and physico-chemical investigations. Antioxidant properties of six guaiacol derivatives were measured in vitro by the inhibition of cyclooxygenase activities in human platelets and of the release of ROS by human polymorphonuclear leucocytes (PMNs). PMNs were stimulated by the bacterial peptide N-fMetLeuPhe (FMLP) and the protein kinase C activator phorbol myristate acetate (PMA) using luminol as chemiluminescent probe. Electron Spin Resonance (ESR) and the technique of spin-trapping with 5,5-dimethyl-pyrroline-N-oxide (DMPO) have been used to quantify hydroxyl and superoxide scavenging activities. Hydroxyl radicals were generated by the Fenton's reaction (Fe2+/H2O2) and the superoxide anion by the acetaldehyde/xanthine oxydase system (AC/XOD). The PMNs tests revealed that curcumin and methyl ferulate appeared as the most active compounds. Platelet cycloxygenase activity was inhibited by curcumin and cyclovalone. ESR studies showed a better ROS scavenging activity for vanillin, methyl ferulate and curcumin. Whatever test we used, curcumin and methylferulate appeared as the most interesting antioxidative compounds.

Antioxidants↗
PubMed1994

Involvement of a GNRA tetraloop in long-range RNA tertiary interactions.

Terminal loops with a GNRA consensus sequence are widespread in RNA. It has been suggested that these loops act as "anchors" during tertiary folding, by interacting in a sequence-specific way with helices at distant locations along the molecule. We now show that a GUGA loop changes state upon disruption of the tertiary architecture of a self-splicing group I intron. Successful replacement of the postulated loop-helix contact by classical base-pairing points to binding of the loop into the shallow (minor) groove of the helix, as also indicated by partial restoration of ribozyme stability upon a specific double nucleotide substitution.

Bacteriophage T4↗
PubMed1994

Automatic identification of group I intron cores in genomic DNA sequences.

Automatic identification of the ribozyme core of group I catalytic introns in genomic sequences is shown to be feasible in spite of the scarcity of strictly conserved features in the sequence and secondary structure of group I introns. An algorithm is described that successfully identified 132 out of the 143 currently reported group I cores with a false positive rate of only 10(-6) per nucleotide. The recognition process consists in generating and rating large sets of potential local solutions which are gradually combined into more complex structures until an entire core (six to seven pairings, six connecting segments, three terminal loops) has been assembled. The extent to which successful recognition may be prevented by sequencing errors is assessed. Also discussed are (1) possible relationships between scores allocated by the program and ability to self-splice in vitro and (2) the potential for objectively assessing the degree of relatedness to group I of structures claimed to resemble group I introns.

Algorithms↗
PubMed1994

Tectal plate gliomas. Part III: Apparent lack of auditory consequences of unilateral inferior collicular lesion due to localized glioma surgery.

The authors present one of their cases operated on for intrinsic tectal plate glioma. The complete resection of the right inferior colliculus (I.C.) had no apparent auditory consequences. The pre- and post-operative tonal and vocal auditory tests were normal. The brain-stem auditory evoked potentials (BAEPs) and middle latency potentials (MLPs) were recorded pre-, post- and intraoperatively. At the end of surgery all waves were present with a marked delay of wave V and a slight delay of the Pa component. The dichotic test showed a significant right ear extinction but admittedly much less important than expected. The role of inferior colliculus (I.C.) in hearing is discussed.

Astrocytoma↗
PubMed1994

Sibling resemblance in two manual laterality tasks.

Two tests of manual performance were adapted for French children: a dot-filling test and a tapping test. Sibling resemblance was assessed in a sample of 46 pairs of sibs. The power of intra-class correlation was estimated by a procedure of Approximate Randomization Tests. In both tests sibling resemblance was significant for overall level of motor skill (i.e. when the two hands were considered separately). Sibling resemblance was significant for degree of laterality in the dot-filling test (the closest task to writing) but not in the tapping test. The usefulness of including degree of laterality measures, in future genetic research is discussed.

Adolescent↗
PubMed1994

Impairment of grasping movements following a bilateral posterior parietal lesion.

The observation of a patient (A.T.) with a bilateral posterior parietal lesion of vascular origin is reported. A.T. presented a bilateral (more marked on the right) deficit in grasping simple objects (neutral cylindrical dowels) without deficit in reaching toward the location of these objects. The major symptom was an exaggerated anticipatory opening of the fingers with poor correlation with object size, resulting in awkward grasps. It was present both when the hand was visible to the subject and when it was not. This deficit was much less marked if the neutral objects were replaced by usual objects of the same sizes. Finally, in tasks where she had to indicate with her fingers the size of visual objects presented as virtual images through a mirror, or the size of imagined usual objects, A.T. performed normally. These results are discussed within the framework of a dual representation of objects. Only the "pragmatic" representation for steering object-oriented actions would be impaired in this patient as a result of posterior parietal damage. By contrast the semantic representation for object identification would be intact.

Adult↗
PubMed1994

Effects of hyposmotic shock on taurine transport in isolated trout hepatocytes.

Isolated trout hepatocytes exposed to hypotonic medium undergo a regulatory volume decrease (RVD) that occurs via two separate routes, K(+)-Cl- cotransport and amino acid release, the ion efflux accounting for 70% of the total osmolyte loss. Taurine, glutamine and glutamic acid are the most important and represent 73% of the total amino acid content (53 mmol (l cell water)-1). The osmolarity-sensitive release of amino acids was studied using [3H]taurine. Kinetic studies indicated two components for taurine influx: a linear Na(+)-independent transport and a saturable Na(+)-dependent system with a Michaelis-Menten constant (Km) of 122 microM and a maximum velocity (Vmax) of 31.2 pmol (mg protein)-1 min-1. This second way of uptake was also chloride dependent and indicated an apparent coupling ratio Na+:Cl-:taurine of 2:1:1. The latter component and the taurine efflux were stimulated during RVD, leading to intracellular amino acid loss. Taurine efflux activation during volume recovery was transient and also dependent on the presence of both Na+ and Cl- in the extracellular medium. Furthermore, taurine release and RVD were slowed down when Ca2+ was omitted from the medium. These results suggested two distinct and complementary mechanisms for volume regulation in trout hepatocytes during hypotonic conditions.

Amino Acids↗
PubMed1994

CD5+ chronic B-cell leukemia with features intermediate to chronic lymphocytic leukemia and hairy cell leukemia.

Chronic lymphocytic leukemia (CLL) and hairy cell leukemia (HCL) are differentiated B-cell leukemias with well-described clinical, morphologic, and immunologic characteristics. We encountered two patients with indolent chronic B-cell leukemia showing overlapping features of these malignancies. The patients had progressive splenomegaly, minimal lymphadenopathy, and abnormal lymphoid cells with abundant cytoplasm and villi, which were strongly positive for surface antigens CD22 and CD11c, features associated with HCL. However, blood counts showed lymphocytosis without neutropenia and monocytopenia, and the bone marrow biopsies demonstrated tightly aggregated nodules of lymphocytes. In addition, the lymphoid cells were dual positive for CD19 and CD5, displaying weak-to-moderately positive monoclonal surface immunoglobulin, findings strongly suggestive of CLL. One patient failed to respond to therapy with chlorambucil and prednisone. The second patient showed a partial response to treatment with 2-chlorodeoxyadenosine. We compare our patients with similar variants of differentiated B-cell leukemias reported in the literature, including disorders described as hairy cell variant (HCL-V) or splenic lymphoma with villous lymphocytes (SLVL).

Aged↗
PubMed1994

[Resistance to chemotherapy: current progress].

Chemotherapy has become a very important part of the therapy for several cancers. Complete remission, and sometime cure, can be achieved with this treatment modality. However, when relapse occur, a second remission is seldom obtained. This failure is believed to be linked, at least in part, to the development of drug resistant tumor cells. Our understanding of the mechanisms underlying this resistance, especially regarding the multidrug resistance (MDR) phenomenon, has improved over the recent years. New strategies are being developed to circumvent drug resistance and come now to clinical trials.

Cross Reactions↗
PubMed1994

Multiple group II self-splicing introns in mobile DNA from Escherichia coli.

By PCR (polymerase chain reaction) amplification and cloning, we have identified four group II self-splicing introns encoding proteins related to reverse transcriptases in natural Escherichia coli isolates belonging to the ECOR collection. One intron, IntD, interrupts a DNA sequence virtually identical to that of the previously described IS3411 Insertion Sequence. A second intron, IntC, is located within an open reading frame that is closely related to a reading frame in the T-DNA of Agrobacterium tumefaciens. Finally, introns IntA and IntB are inserted at two distinct sites in one of the Rhs elements of E. coli. A comparison of their open reading frames shows that the two Rhs introns are more closely related to each other than to any other known group II intron: this suggests that transposition of group II introns may occur preferentially in cis, along the same piece of DNA.

DNA Transposable Elements↗
PubMed1994

[Uncommon cardiac manifestations disclosing pheochromocytoma. Apropos of 3 cases].

The diagnosis of pheochromocytoma is usually considered in the presence of permanent hypertension with exacerbations. However, pheochromocytoma may be responsible for a varied range of adrenergic symptomatology and hemodynamic equilibrium may be threatened by the spontaneous or induced massive release of pressor amines. Three cases form the basis of a description of unusual situations: acute pulmonary edema, acute circulatory failure and myocardial infarction with normal coronary vessels. The divercity and severity of these clinical situations are such that the possibility should always be suspected when confronted by any cardiomyopathy without obvious etiology, in particular in a hypertensive patient. The only treatment remains ablation of the tumour and diagnosis as an emergency is based, apart from history, on ultrasonography and/or abdominal CT scan and assay of urinary catecholamine derivative levels, which can be obtained within a few hours.

Adrenal Gland Neoplasms↗
PubMed1993

Monitoring of the cooperative unfolding of the sunY group I intron of bacteriophage T4. The active form of the sunY ribozyme is stabilized by multiple interactions with 3' terminal intron components.

We have studied the mechanism by which the 3' terminal domain of the sunY intron of bacteriophage T4 activates the group I ribozyme core of this intron, from which it is separated by some 800 nucleotides. As shown by monitoring either UV absorbance or self-splicing reaction kinetics as a function of temperature, intron transcripts undergo highly cooperative unfolding/inactivation upon heating: the two methods yield similar estimates of the thermodynamic parameters associated with this process. Such cooperativity makes it possible in turn to assess the energetic contribution of specific interactions to the overall structure, by comparing the sensitivity to heat inactivation of molecules carrying various nucleotide substitutions. By combining this approach with chemical modification, we have probed several proven or putative interactions between the core and 3' terminal domain of the intron and conclude that the role of the 3' terminal domain is to stabilize the active form of the ribozyme. Interestingly, the P9.0 interaction, which brings 3' terminal nucleotides next to the core site that binds the guanosine cofactor of the self-splicing reaction, is now shown to be composed in fact of two distinct pairings. An isolated base-pair (P9.0a), involving a residue located only six nucleotides upstream of the 3' splice site, participates in the stabilization of the ribozyme and appears to persist during the second stage of self-splicing (exon ligation). In contrast, formation of the previously demonstrated P9.0b pairing, which involves the two penultimate intron nucleotides, contributes no additional stability and results in no detectable rearrangement of the core structure. Implications for the concept of a static ribozyme are discussed in the light of a slightly revised three-dimensional model of the sunY intron.

Bacteriophage T4↗