Biomedical subjects

A Favre

Publications and source records attributed to A Favre.

At least 91 records · Page 5Linked to original sources

PubMed1991

Conformation and structural fluctuations of a 218 nucleotides long rRNA fragment: 4-thiouridine as an intrinsic photolabelling probe.

The structure in solution of an RNA fragment (218 nucleotides long) containing part of E. coli 16S rRNA domain 2 has been studied using the intrinsic photoaffinity probe 4-thiouridine (s4U). In vitro transcription with T7 polymerase, in the presence of s4U triphosphate yielded complete RNA molecules. An affinity electrophoresis system based on Phenylmercuric substituted polyacrylamide (APM) gels allows separation of the RNA chains as a function of their s4U content. Distribution of s4U within chains follows a binomial law indicating that (i) substitution is close to random, (ii) efficiency of s4U incorporation is 0.22 times that of U. The monothiolated RNA fraction isolated from APM gel was irradiated at 366 nm under native conditions and the intramolecularly crosslinked molecules, (34%), were separated on denaturing polyacrylamide gel according to loop size. The positions of the two partners of bridges were identified by mean of reverse transcription and RNA sequencing. 17 of the 41 possible s4U positions lead to detectable bridges. These crosslinks formed efficiently at the border of bihelical regions or when structural mobility is allowed. The pattern of crosslinks is in agreement with the previously proposed secondary structure but indicates that it is much more flexible than expected.

Base Sequence↗

PubMed1991

A novel integrin involved in thymocyte-thymic epithelial cell interactions.

Thymocytes differentiate in the thymic microenvironment into immunocompetent T cell through the interaction with a variety of accessory cells, including thymic epithelial cells (TEC). TEC plays an important role in the selection process presenting self antigens in association with major histocompatibility complex (MHC) molecules to the maturing T cells. The T cell receptor recognizes the self antigen-MHC complex, but other surface molecules help stabilize this interaction. Thus, the CD2/LFA-3 and LFA-1/intercellular adhesion molecule 1 pairs have been shown to participate in the binding between lymphoid cells and TEC. Here we describe an integrin of the very late activation antigen subfamily composed by the known beta 1 chain and by a novel alpha chain. This adhesion molecule is expressed on the surface of medullary TEC and is involved in the adhesion between TEC and thymocytes, but not peripheral blood T lymphocytes.

Antibodies, Monoclonal↗

PubMed1991

Sites of contact of mRNA with 16S rRNA and 23S rRNA in the Escherichia coli ribosome.

The locations of close encounter between ribosomal RNA (rRNA) and messenger RNA (mRNA) were determined by photochemical cross-linking experiments that employ an artificial mRNA, 51 nucleotides long, containing 14 U residues that were randomly substituted by 1-4 4-thiouridine (s4U) residues. The mRNA was bound to 70S ribosomes or 30S subunits and then was irradiated at 366 nm to activate cross-linking between the s4U residues and rRNA. Cross-linking occurred to both 16S rRNA and 23S RNA. The rRNA was then analyzed by a series of reverse transcriptase experiments to determine the locations of cross-linking. Twelve sites in the 16S rRNA and two sites in the 23S rRNA have been detected. In the 16S rRNA, two of the sites (U1381, C1395) are in the middle part of the secondary structure close to position C1400, and the remaining sites (G413, U421, G424; A532; G693; U723; A845; G1131/C1132; G1300; G1338) are distributed between six regions that are peripheral in the secondary structure. In the 23S rRNA, one site (U1065) is located in the GTPase center close to A1067, the site of thiostrepton-resistance methylation in domain II, and the other site (U887) is located a short distance away also in domain II. The distribution of these rRNA sites in the ribosome specifies an mRNA track that is consistent with other information. In addition, some of the contact points represent new constraints for the three-dimensional folding of the rRNA.

Base Sequence↗

PubMed1991

Morphological features of cloned lymphocytes expressing gamma/delta T cell receptors.

We have analyzed the morphological characteristics of human T lymphocytes bearing CD3-associated T cell receptor (TcR) gamma and delta chains. BB3 and delta-TCS1 monoclonal antibodies (mAb) were used to identify two distinct, nonoverlapping populations of TcR gamma/delta + cells which express the products of V delta 2 and V delta 1 gene segments, respectively. In the peripheral blood, most V delta 1+ (delta TCS-1+) lymphocytes express the non-disulfide-linked form of receptor whereas V delta 2+ (BB3+) cells express the disulfide-linked form. The majority of cloned TcR gamma/delta + cells exhibit a growth pattern different from that of conventional TcR alpha/beta + cells as they adhere promptly to surfaces and undergo morphological changes which can be summarized as follows: cells spread on the surface, form a distinct uropod and, in the final phase of adherence, emit long filopodia ending with adhesion plaques. Immunofluorescence studies of TcR gamma/delta + clones demonstrated the presence of submembraneous actin microfilaments and actin-binding protein confirming that these cells are capable of active motility which is related to the propensity of TcR gamma/delta + cells to home to epithelia. Scanning electron microscope analyses of effector/target cell conjugates showed that in TcR gamma/delta + cells the region of the uropodia next to the cell body is responsible for the binding to tumor target cells. Interestingly, immunofluorescence analyses revealed that LFA-1 molecules are predominantly distributed in the uropodium whereas they are virtually absent in the cell bodies. These morphological characteristics of TcR gamma/delta + cells may pertain to defensive mechanisms the mucosal level.

Actinin↗

PubMed1990

In vivo incorporation of the intrinsic photolabel 4-thiouridine into Escherichia coli RNAs.

The in vivo incorporation of the photoactivable uridine analogue 4-thiouridine into the RNAs of an Escherichia coli K12 pyrD strain has been optimised. s4Urd uptake in RNAs appears to be strikingly dependent upon the age of the preculture, i.e. the number of generations the cells have undergone immediately before dilution in the thiolation medium. Conditions have been set up where efficient RNA thiolation occurs in cells growing exponentially at 50 to 70% the rate of the control. The substitution level s4U/U is maximal after growth for 9 to 10 generations in the thiolation medium and reaches 17 +/- 3% in tRNA and bulk RNA. Most of ribosomal derived ribonucleoproteins, 65 +/- 5%, sediment as 70S ribosomes (s4U/U = 7 +/- 2%) on a high Mg2+ sucrose gradient. The thiolated RNAs were characterized by their migration on a thiol-specific affinity electrophoretic gel.

Escherichia coli↗

PubMed1990

Near-ultraviolet illumination inhibits the liquid holding recovery in Escherichia coli B.

Liquid holding recovery (LHR) consists of an increase in the survival of UV-irradiated cells when they are held under non-nutrient conditions before plating. In this study we investigated in E. coli B cells the effect of the growth inhibition induced by near UV (365 nm) illumination (growth delay, GD) before irradiation with UV-254 nm on the amplitude of LHR and the induction of an SOS function (filamentation) during the liquid holding period. Our results demonstrated that pre-illumination with near-UV inhibits LHR and the induction of filamentation when the cells are incubated in nutrient medium. Moreover, this inhibition is due to GD, an effect caused by a photoproduct in the E. coli t-RNA, the 8-13 link.

Cell Division↗

PubMed1990

Quantum yields of triplet and O2(1 delta g) formation of 4-thiouridine in water and acetonitrile.

The quantum yield of triplet formation, phi T, and that of the photosensitized formation of singlet molecular oxygen, phi delta, were determined for a rare nucleoside, 4-thiouridine (4t-Urd), in water and in acetonitrile, using singlet molecular oxygen phosphorescence, laser-induced optoacoustics and time-resolved thermal lensing. These yields, phi T and phi delta, the latter in aerated solutions, were found to be, respectively, in water: 0.67 +/- 0.17 and 0.18 +/- 0.04 and in acetonitrile: 0.61 +/- 0.15 and 0.50 +/- 0.20. The fraction of the 4t-Urd triplet molecules quenched by oxygen leading to singlet molecular oxygen, S delta, was calculated to be between 0.7 and unity in both solvents, this value being indicative of a pi pi*character for the lowest triplet state of 4t-Urd.

Acetonitriles↗

PubMed1989

[Evaluation of the readaptation of patients with triple coronary vessel disease unfit for by-pass surgery].

The objective of this study is to evaluate the effects of rehabilitation in 46 consecutive patients with triple vessel coronary disease, and unfit for by-pass surgery: there were 45 men and 1 woman (mean age = 58 years), admitted during the 3rd week of a myocardial infarction (N = 31) or following unstable angina (N = 15). The stroke volume (SV) is normal in 50 p. cent of the patients, but 15 p. cent presented as SV less than 0.30. 3 patients were unable to start their rehabilitation because of unstable angina (N = 2), or severe pulmonary edema (N = 1). Following 4 weeks of rehabilitation, comparison of the stress tests pre- and post-rehabilitation, reveals improved functional capacities (maximum level reached 103.6 +/- 27 vs 126.4 +/- 31; p less than 0.001, and an improvement of the ischemic threshold (82 +/- 32 vs 92 +/- 31; p less than 0.05). During the long-term follow-up (32.5 months), 4 patients died from cardiac complications (8.7%) and one from extra-cardiac reasons. Among the 41 alive patients, 58.6 p. cent were asymptomatic, 39 p. cent presented cardiac complications, one had a GI malignancy. The rate of return to work among the active population is 68.5 p. cent within a mean time of 1.7 months after rehabilitation. Overall, this study demonstrates the possibility of cardiac rehabilitation under medical supervision in patients with severe triple vessel coronary disease. The improvement of the functional abilities under stress conditions is obvious, enabling the patient to regain confidence in him/herself and improve his/her comfort.

Adult↗

PubMed1989

New RNA-protein crosslinks in domains 1 and 2 of E. coli 30S ribosomal subunits obtained by means of an intrinsic photoaffinity probe.

Functionally active 70S ribosomes containing 4-thiouridine (s4U) in place of uridine were prepared by a formerly described in vivo substitution method. Proteins were crosslinked to RNA by 366 nm photoactivation of s4U. We observe the systematic and characteristic formation of 30S dimers; they were eliminated for analysis of RNA-protein crosslinks. M13 probes containing rDNA inserts complementary to domains 1 and 2 of 16S RNA from the 5'end up to nucleotide 868 were used to select contiguous or overlapping RNA sections. The proteins covalently crosslinked to each RNA section were identified as S3, S4, S5, S7, S9, S18, S20 and S21. Several crosslinks are compatible with previously published sites for proteins S5, S18, S20 and S21; others for proteins S3, S4, S7, S9, S18 correspond necessarily to new sites.

Cell Line↗

PubMed1989

Induction of sfiA SOS function by peroxides using three different E. coli strains.

Five peroxides and two related compounds were tested for genotoxicity by the SOS Chromotest using 3 different E. coli strains (PQ37, PM21, GC4798). All tested hydroperoxides (hydrogen peroxide, tert-butylhydroperoxide, cumene hydroperoxide) were clearly positive in all strains. From a comparison of results obtained from the different strains it can be concluded that neither DNA lesions leading to the induction of excision repair nor covalent binding of radicals to DNA is responsible for the induction of sfiA-SOS function by hydroperoxides. Among the remaining compounds tested, only dibenzoylperoxide gave a clearly positive result in strain PQ37 whereas di-tert-butylperoxide and azobisisobutyronitrile showed only borderline activity. When using strains PM21 and GC4798, none of the latter compounds was positive. Paraquat was inactive in all strains.

DNA↗

PubMed1989

Induction of SOS repair by monofunctional methanesulphonates in various Escherichia coli strains. Structure-activity relationships in comparison with mutagenicity in Salmonella typhimurium.

Seventeen monofunctional alkylmethanesulphonates of widely varying structures were investigated in the SOS Chromotest using the Escherichia coli strains PM21, PQ37 and GC4798. As a measure of the SOS-inducing activity, the beta-galactosidase enzyme units (Up/mumol) were determined. Strains PM21 and PQ37 gave similar results in spite of the presence of different genetic markers. In general, the SN1 type secondary compounds (O-alkylation) induced higher SOS repair than the SN2 type primary compounds (N-alkylation). However, methylmethanesulphonate exerted the highest SOS induction of all tested strains, presumably due to its extremely high SN2 reactivity. In general, strain GC4798, which lacks 3-alkyladenine-DNA glycosylases I and II, was more sensitive towards monofunctional alkylating compounds and in particular towards the SN2 type compounds. A good correlation was found between the SOS repair response in the E. coli strains PM21 and PQ37 and the mutagenicity in Salmonella typhimurium TA100. There was, however, little correspondence when comparing the two measures used for the SOS-inducing activity in this work, the SOSIP (SOS-inducing potency) and the specific beta-galactosidase activity (Up/mumol). This effect was explained by the different toxicity corrections used for the calculation of the two measures. Whereas for the SOSIP value the single constitutive enzyme alkaline phosphatase is used, for the Up/mumol the absorbance at 600 nm, which indicates the growth delay (overall toxicity), is utilized. The influence of the toxicity corrections is discussed in more detail.

Alkylating Agents↗

PubMed1989

Identification of filaggrin in Hassall's corpuscle by histochemical and immunohistochemical methods.

The Hassall's corpuscles of man and other mammals have been deeply stained by a histochemical method that demonstrates bound histidine. We have employed a polyclonal anti-filaggrin antibody on thymus sections to verify whether this positivity was due to filaggrin and profilaggrin, its polymeric precursor, like in the skin. The immunohistochemical reaction has confirmed the presence of filaggrin in human Hassall's corpuscles as well as in other species. Different patterns have been obtained for corpuscles at different developmental stages.

Animals↗

PubMed1989

Immunohistochemical investigations of the human palatine tonsil from surgical specimens using polyclonal and monoclonal antikeratin antibodies.

The keratinization process of tonsillary epithelium in patients with different age, who underwent surgery because of chronic inflammatory processes, has been studied by employing low (40 KD), medium (52-56-58 KD), high (56-64 and 68 KD) as well as broad spectrum antikeratin antibodies. The findings thus obtained outline the various keratin patterns of the tonsil in the outer covering and, even more, in the crypt labyrinth wall. These findings have been compared with those obtained by histochemical reactions for acid phosphatase and non-specific esterase activities (Favrz et al. 1986 II). In crypt epithelium keratinization, 56-64 KD keratins are involved in cells where also high enzymic activities are taking place, namely 1. in those elements delimiting the lumen as well as in those belonging to the reticulum mesh which are nearest to it and host lymphoid elements active in immunity reactions; 2. in elements at the bottom of small and large crypts, where excavation continues into the lymphoid tissue and interfollicular spaces. 68 KD keratin, although present in lower amounts, is synthesized almost everywhere, but only irregularly. It marks surface epithelium surrounding some dermal papillae, some meshes of the crypt reticulum, the "gallery" bottom as well as elements of interfollicular proliferation developing in the lymphoid tissue like arborescence. The path of congested blood vessels in the crypt wall towards the surface is marked by keratinized epitheliocytes. 56-64 KD keratin is present in the most superficial elements and is generally accompanied by the wall growing thinner, its blistering and breaking. The most frequent pathologic alterations of the epithelium (like cellular hypertrophy) involve variations in cytoplasm keratin pattern, in still un-flattened polyhedral elements of the intermediate layers.

Adolescent↗

PubMed1989

Fast neutron boost for the treatment of grade IV astrocytomas.

A previous study, on grade IV astrocytomas, compared a combination of photons and fast neutron boost to photons only, both treatments being delivered following a concentrated irradiation schedule. A slight improvement in survival was observed after neutron boost for non operated patients, but not for operated patients. Since death was always related to local recurrence and since no complication occurred after neutron boost, the neutron dose was increased from 6 to 7 Gy in January 1985. No improvement in survival was observed for patients treated with neutron boost after complete resection. After subtotal resection, the group that was treated with the higher neutron boost (7 Gy) showed a significant benefit in survival at twelve months. When patients had only a biopsy before irradiation, there was a benefit in survival after neutron boost, but no additional benefit was gained when the size of the neutron boost was increased from 6 to 7 Gy.

Brain Neoplasms↗

PubMed1988

tRNAPhe and tRNAPro are the near-ultraviolet molecular targets triggering the growth delay effect.

The illumination of Escherichia coli cells with UVA light, 320 nm less than or equal to lambda less than or equal to 380 nm, triggers a transient growth and division delay. The built-in 4-thiouridine chromophore which absorbs light at 340 nm leads to the quantitative 8-13 crosslinking of a number of tRNA species corresponding to 50% of the bulk tRNA molecules. Determination of the tRNA acylation level by the various aminoacids shows that only the tRNA species acylated by Phe and Pro are strikingly affected in vivo. Both acylation levels decrease to less than 10% of their initial value during the illumination period, remain stable all along the growth lag and increase concomitantly with cell mass when growth resumes. Hence tRNA(Phe) and tRNA(Pro) are the UVA light molecular targets triggering growth delay and related effects of biological significance such as cell volume reduction, photoprotection and protection against UV mutagenesis (antiphotomutagenesis).

Acylation↗

PubMed1988

Evidence for tertiary structure in natural single stranded RNAs in solution.

Binding isotherms (20 degrees C) of ethidium bromide to a number of tRNA species at various ionic strengths indicate that i) the number ni of intercalation sites is high 7 to 11 per molecule, in the low salt form III, but small, 2 to 1, at high Mg2+ or Na+ when form I predominates. ii) modification of tRNA at strategic positions for 3D folding prevents full expression of intercalation restriction iii) maximal restriction is obtained at salt concentrations higher than needed for full conversion to form I. It is inferred that restriction, which is not observed with bihelical RNA (or DNA), requires the native tRNA 3D structure but also some physical coupling between the region of 3D folding and bihelical arms. Ribosomal RNAs, some viral RNAs, mRNA from sheep mammary gland as well as the random copolymers Poly UG, Poly AUG, Poly AUCG all exhibit intercalation restriction. Hence 3D folding of the polyribonucleotide chains appears to be a feature common to single-stranded RNAs when free in solution under physiological conditions.

DNA↗

PubMed1988

Induction of the SOS function sfiA in E. coli by systems which generate triplet ketones.

Generation of triplet ketones, either chemically through thermal decomposition of 3-hydroxymethyl-3,4,4-trimethyl-1,2-dioxetane and 3-[N-(pyridino)carbamoyl]methyl-3,4,4-trimethyl-1,2-dioxetane++ + or enzymatically via the aerobic oxidation of isobutyraldehyde trimethylsilyl enol ether catalyzed by horse-radish peroxidase, triggers the SOS function sfiA in E. coli. Although the observed effects are relatively weak and the triplet ketone scavenger tryptophan was ineffective in this system, our results provide evidence for the involvement of triplet ketones in this type of DNA damage. Possible mechanisms are discussed.

Antioxidants↗

PubMed1987

Pulmonary acinus: geometry and morphometry of the peripheral airway system in rat and rabbit.

The geometry and morphometry of intraacinar airways in rat and rabbit lungs were studied from silicone rubber casts. Acini, defined as the complex of alveolated airways distal to the "terminal" bronchiole, were trimmed off the bronchial tree. In both species, the acinar volume followed a log-normal distribution over a range in size of one order of magnitude. At an inflation level of 60% total lung capacity, their mean volume was 1.86 mm3 in the rat and 3.46 mm3 in the rabbit. On a representative sample of acini of different volumes, the branching pattern was characterized as irregular dichotomy, and the segment length and inner and outer diameters were measured. The average acinus had a mean of six generations in the rat and seven in the rabbit. Both showed a decrease in segment length and inner diameter with each generation. The mean longitudinal pathway length--that is, the distance from the initial acinar segment to the terminal sacs--was found to depend on the cube root of the acinar volume in both species. It was calculated at 1.46 and 1.95 mm for rat and rabbit, respectively.

Animals↗