Search PubMed⌕ Search

Biomedical subjects

B Michel

Publications and source records attributed to B Michel.

At least 73 records · Page 4Linked to original sources
PubMed1995

Prediction of iron deficiency in chronic inflammatory rheumatic disease anaemia.

We prospectively studied 45 anaemic patients (37 women, 8 men) with chronic inflammatory rheumatic diseases. The combination of serum ferritin and CRP (as well as ESR) in its predictive capacity for bone marrow iron stores was examined. The relationship between other iron-related measurements (transferrin, transferrin saturation, soluble transferrin receptor, erythrocyte porphyrins and percentage of hypochromic/microcytic erythrocytes) and bone marrow iron stores was also investigated. Stainable bone marrow iron was taken as the most suitable standard to separate iron-deficient from iron-replete patients. 14 patients (31%) were lacking bone marrow iron. Regression analysis showed a good correlation between ferritin and bone marrow iron (adjusted R2 = 0.721, P < 0.0001). The combination of ferritin and CRP (ESR) did not improve the predictive power for bone marrow iron (adjusted R2 = 0.715) in this cohort of patients with low systemic inflammatory activity. With respect to the bone marrow iron content the best predictive cut-off value of ferritin was 30 micrograms/l (86% sensitivity, 90% specificity). The other iron-related parameters both individually and when combined were less powerful in predicting bone marrow iron than ferritin alone. Only zinc bound erythrocyte protoporphyrin in combination with ferritin slightly improved prediction (adjusted R2 = 0.731). A cut-off point of 11% hypochromic erythrocytes reached a high specificity (90%), but was less sensitive (77%).

Adult↗
PubMed1995

Transcription-induced deletions in Escherichia coli plasmids.

Characterization of functions that render DNA susceptible to rearrangement is important for a better understanding of genome instability. In a previous work, we showed that sequences located downstream of a strong promoter are particularly prone to deletion. In this paper, the parameters that influence transcription-induced deletions were studied. pBR322 derivatives carrying the M13 (+) replication origin and a PTac-dependent transcription region were used. Deletion formation was analysed in the presence of the replication protein of M13, which introduces a nick at the phage replication origin, and in a rep- strain to avoid M13-driven replication. Our study showed that: (i) 4 h after induction of transcription, a few per cent of the plasmids have experienced a deletion; (ii) these deletions result in joining of the M13 replication origin to a nucleotide located in or downstream of the transcribed region; (iii) deletion formation strongly depends on the orientation of transcription, on promoter strength and transcript length, but is independent of translation; (iv) formation of transcription-induced supercoiling domains does not induce deletion formation. We propose that deletions in the transcribed region result from collisions between converging replication and transcription machineries.

Base Sequence↗
PubMed1995

Lethality of rep recB and rep recC double mutants of Escherichia coli.

A rep mutation in combination with a recB or a recC mutation renders Escherichia coli non-viable. This conclusion is based on the following lines of evidence: (i) double mutants cannot be constructed by P1 transduction; (ii) induction of the lambda Gam protein, which inactivates most of the RecBCD activities, is lethal in rep mutants; (iii) rep recBts recCts mutants are not viable at high temperature. The resons for a requirement for the RecBCD enzyme in rep strains were investigated. Initiation of chromosome replication, elongation and chromosomal segregation do not seem impaired in the rep recBtsrecCts mutant at the non-permissive temperature. The viability of other rep derivatives was tested. rep recA recD triple mutants are not viable, whereas rep recD and rep recA double mutants are. Inactivation of both exoV activity and recBC-dependent homologous recombination is therefore responsible for the non-viability of rep recBC strains. However, sbcA and sbcB mutations, which render recBC mutants recombination proficient, do not restore viability of rep recBC mutants, indicating that recombination via the RecF or the RecE pathways cannot functionally replace RecBCD-mediated recombination. The specific requirement for RecBCD suggests the occurrence of double-strand DNA breaks in rep strains. Additional arguments in favour of the presence of DNA lesions in rep mutants are as follows: (i) expression of SOS repair functions delays lethality of rep derivatives after inactivation of RecBCD; (ii) sensitivity of rep strains to ultraviolet light is increased by partial inactivation of RecBCD. A model for the recovery of cells from double-strand breaks in rep mutants is discussed.

Bacterial Proteins↗
PubMed1995

[A case of transient amnesia caused by cerebral thrombophlebitis: contribution of neuroimaging to physiopathogenesis of transient amnesia].

We report a case of transient global amnesia (TGA), in a right-handed woman, which was due to a cerebral venous thrombosis. In our knowledge it is the first case reported. MRI and SPECT revealed the existence of a dysfunction in the right internal temporal region. Such a localization leads us to discuss the specialisation of each hippocampus.

Amnesia, Retrograde↗
PubMed1994

Naturally occurring active N-domain of human angiotensin I-converting enzyme.

Angiotensin I-converting enzyme (ACE, kininase II) is a single-chain protein containing two active site domains (named N- and C-domains according to position in the chain). ACE is bound to plasma membranes by its C-terminal hydrophobic transmembrane anchor. Ileal fluid, rich in ACE activity, obtained from patients after surgical colectomy was used as the source. Column chromatography, including modified affinity chromatography on lisinopril-Sepharose, yielded homogeneous ACE after only a 45-fold purification. N-terminal sequencing of ileal ACE and partial sequencing of CNBr fragments revealed the presence of an intact N terminus but only a single N-domain active site, ending between residues 443 and 559. Thus, ileal-fluid ACE is a unique enzyme differing from the widely distributed two-domain somatic enzyme or the single C-domain testicular (germinal) ACE. The molecular mass of ileal ACE is 108 kDa and when deglycosylated, the molecular mass is 68 kDa, indicating extensive glycosylation (37% by weight). In agreement with the results reported with recombinant variants of ACE, the ileal enzyme is less Cl(-)-dependent than somatic ACE; release of the C-terminal dipeptide from a peptide substrate was optimal in only 10 mM Cl-. In addition to hydrolyzing at the C-terminal end of peptides, ileal ACE efficiently cleaved the protected N-terminal tripeptide from the luteinizing hormone-releasing hormone and its congener 6-31 times faster, depending on the Cl- concentration, than the C-domain in recombinant testicular ACE. Thus we have isolated an active human ACE consisting of a single N-domain. We suggest that there is a bridge section of about 100 amino acids between the active N- and C-domains of somatic ACE where it may be proteolytically cleaved to liberate the active N-domain. These findings have potential relevance and importance in the therapeutic application of ACE inhibitors.

Amino Acid Sequence↗
PubMed1994

[Diagnosis and course assessment of collagenoses and vasculitides].

The different forms of vasculitis and connective tissue disorders are multisystem diseases which must be distinguished from a variety of infectious illnesses, neoplastic and degenerative diseases. The diagnosis, established by clinical, radiographic, laboratory and histologic investigation, influences treatment and thereby the outcome of the disease. A diagnostic approach to the patient with possible vasculitis and/or connective tissue disease is described.

Clinical Laboratory Techniques↗
PubMed1994

Copy-choice illegitimate DNA recombination revisited.

Nearly precise excision of a transposon related to Tn10 from an Escherichia coli plasmid was used as a model to study illegitimate DNA recombination between short direct repeats. The excision was stimulated 100-1000 times by induction of plasmid single-stranded DNA synthesis and did not involve transfer of DNA from the parental to the progeny molecule. We conclude that it occurred by copy-choice DNA recombination, and propose that other events of recombination between short direct repeats might be a result of the same process.

Base Sequence↗
PubMed1994

Effects of dietary protein and uninephrectomy on renal angiotensin converting enzyme activity in the rat.

This study examines the effects of dietary protein and of uninephrectomy on angiotensin converting enzyme (ACE) in the normotensive rat, with particular regard to the kidney. Male Wistar Kyoto rats were fed isocaloric diets containing 5, 16 or 50% protein for three weeks. Other groups of rats were subjected to either left unilateral nephrectomy or sham operations, and the rats were killed eight days after surgery. ACE activity was measured in the kidney medulla, cortex, proximal tubule brush border membrane and in the plasma, heart and lung. Renal cortex and brush border ACE activity increased in parallel with protein intake, whereas plasma and lung ACE activity decreased; heart and kidney medulla ACE activity did not vary significantly. Uninephrectomy also led to a high increase in brush border ACE activity in the contralateral kidney, with no effect in the renal medulla or in the other tissues. The increase in ACE activity in the brush border membrane corresponded to a similar increase in the maximum number of binding sites of 3H-ramiprilat. This suggested that the increase in ACE activity corresponded to an increase in ACE concentration. The increase in renal tubular ACE activity could result in higher angiotensin II levels, and could consequently play a role in the modification of sodium reabsorption and cellular growth which occurs in the proximal tubule in these experimental models.

Alkaline Phosphatase↗
PubMed1994

When replication forks stop.

DNA synthesis is an accurate and very processive phenomenon, yet chromosome replication does not proceed at a constant rate and progression of the replication fork can be impeded. Several structural and functional features of the template can modulate the rate of progress of the replication fork. These include DNA secondary structures, DNA damage and occupied protein-binding sites. In addition, prokaryotes contain sites where replication is specifically arrested. DNA regions at which the replication machinery is blocked or transiently slowed could be particularly susceptible to genome rearrangements. Illegitimate recombination, a ubiquitous phenomenon which may have dramatic consequences, occurs by a variety of mechanisms. The observation that some rearrangements might be facilitated by a pause in replication could provide a clue in elucidating these processes. In support of this, some homologous and illegitimate recombination events have already been correlated with replication pauses or arrest sites.

Chromosomes↗
PubMed1994

Effects of triiodothyronine and dexamethasone on plasma and tissue angiotensin converting enzyme in the rat.

In order to identify tissue specific regulation of angiotensin converting enzyme (ACE), the effects of dexamethasone (0.04 mg sc per day for 7 days) and triiodothyronine (T3) (0.5 mg/kg sc per day for 10 days) on ACE activity were investigated in different tissues in male Wistar rats. ACE activity was measured by fluorimetry in the plasma, heart, lung and kidney. In the kidney, ACE activity was measured in the medulla, cortex and brush border of proximal tubular cells and 3H-ramiprilat binding was used to characterise the changes in brush border ACE activity. Dexamethasone elicited a significant increase in lung ACE activity and a significant decrease in plasma ACE activity, but did not alter enzyme activity in the other tissues studied. T3 produced a significant decrease in lung ACE activity and an increase in ACE activity in the plasma and heart. In the kidney, ACE activity was not modified in the medulla whereas in the cortex and brush border ACE activity was doubled. This increase in ACE activity corresponded to a similar increase in the maximum number of binding sites of 3H-ramiprilat, suggesting that the increase in activity corresponded to an increase in the ACE level. The increased heart and kidney ACE activity in response to T3 may contribute to the cardiovascular effects of thyroid hormones through increased local angiotensin II generation. These results show that under dexamethasone or T3, ACE activity can vary from one tissue to another, suggesting that the ACE regulatory mechanism acts differently in each tissue.

Animals↗
PubMed1994

Flanking sequences affect replication arrest at the Escherichia coli terminator TerB in vivo.

We have analyzed the effect of flanking sequences on Tus-induced replication arrest. pBR322 plasmid derivatives which carry the Escherichia coli replication terminator TerB at different locations were used. Efficiency of the replication arrest was estimated from the plasmid copy number and transformation frequency of tus+ cells. We found that flanking sequences do affect replication arrest efficiency, a weak arrest being correlated with the presence of an AT-rich region which is replicated just before TerB. Some sequences located after the replication terminator can also affect replication termination. We propose that the AT-rich regions might impair binding of the Tus protein to the TerB sequence or facilitate helicase-induced unwinding of DNA and Tus displacement from the TerB site.

Bacterial Proteins↗
PubMed1994

Plasma renin activity and changes in tissue angiotensin converting enzyme.

OBJECTIVES: Recent evidence suggests that tissue generation of angiotensins I and II depends on the level of the plasma components of the renin-angiotensin system and on tissue-specific processes. The present study was undertaken to clarify the possible relationship between plasma renin activity (PRA) and tissue angiotensin converting enzyme (ACE) activity in the heart, lung, kidney cortex and kidney medulla of Wistar-Kyoto rats. In the kidney cortex particular attention was focused on renal brush-border ACE. METHODS: Different experimental models known to have opposite effects on PRA were used: changes in salt intake, deoxycorticosterone acetate (DOCA) with or without salt supplements, and the Goldblatt two-kidney, one clip (2-K,1C) model. Two weeks after the start of the experiments the rats were killed, and PRA, and plasma and tissue ACE activity, were measured. RESULTS: At the end of the study the blood pressure in the treated rats was not significantly different from control. As expected, the PRA were highest in the 2-K,1C and depleted-salt groups and lowest in the DOCA, DOCA-salt and high-salt groups. ACE responses were different in different types of tissue, with no relationship between PRA and plasma or tissue ACE activity. For example, DOCA treatment led to increased ACE activity in the heart and the kidney only if the rats were maintained on a high salt intake. DOCA or salt alone failed to have this effect. In the 2-K,1C model the unclipped kidneys did not show any significant variation in ACE activity, but the clipped kidneys exhibited increased ACE activity compared with sham-operated rats. This increase, coupled with increased renal renin secretion, could play a role in the acceleration of local angiotensin II formation, and could thus initiate and sustain the development of hypertension in this model. CONCLUSION: The present results show that variations in ACE activity were organ-specific and were not linked either to hypertension or to changes in PRA.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1993

Mechanisms of illegitimate recombination.

Illegitimate recombination, which is one of the major causes of genome rearrangements, can occur in a number of ways. These might involve enzymes which cut and join DNA or enzymes which replicate DNA, as illustrated by two examples: (i) formation of deletions at the replication origin (ori) of an Escherichia coli bacteriophage, M13; and (ii) excision of E. coli transposon Tn10. It is proposed that a common theme to various ways by which illegitimate recombination can occur might be the capacity to create ends in the DNA molecule and to make the ends meet.

Bacteriophage M13↗
PubMed1993

Effects of one-hour and one-week treatment with ramipril on plasma and renal brush border angiotensin converting enzyme in the rat.

Prolonged treatment with an angiotensin converting enzyme inhibitor produces an induction of plasma angiotensin converting enzyme. Induction of angiotensin converting enzyme in tissues during prolonged treatment with an angiotensin converting enzyme inhibitor is less well documented. We compared the effects of 1 h and 1 week treatment with ramipril (0.1, 0.3, 1 mg/kg) on angiotensin converting enzyme activity in the plasma, renal cortex and renal brush border membrane of Wistar rats. As an increase in activity could be masked by the inhibition due to the presence of ramiprilat which is the active form of ramipril, we eliminated the ramiprilat present in renal cortex homogenates with EGTA during brush border preparation. The 1-h treatment with ramipril induced a dose-dependent inhibition of plasma and renal cortex angiotensin converting enzyme activity. The 1-week treatment with ramipril produced an increase in plasma angiotensin converting enzyme activity, whereas renal cortex angiotensin converting enzyme activity decreased. The decrease in angiotensin converting enzyme activity persisted in the brush border membrane after elimination of residual ramiprilat with EGTA. Our results show that prolonged ramipril treatment produces opposite responses in plasma and renal cortex angiotensin converting enzyme activity, suggesting that plasma and epithelial angiotensin converting enzymes are subject to specific local regulatory factors.

Animals↗
PubMed1993

[Diffuse idiopathic skeletal hyperostosis (DISH) and pseudo-coxarthritis following long-term etretinate therapy].

A 51-year old patient with congenital basal cell naevus syndrome was treated with etretinate (50-100 mg/daily) over a period of 5 years (cumulative dose 110 g). Clinically he developed a stiff back with pronounced disability of both hips. Radiologically, axial involvement of the spine with severe diffuse idiopathic skeletal hyperostosis especially of the lumbar spine, and ossifications of both hips were documented. Rheumatological implications of long-term therapy with etretinate are discussed.

Basal Cell Nevus Syndrome↗
PubMed1993

Angiotensin converting enzyme variability in hypertensive and normotensive rats.

Recent data have revealed biological and genetic variability in normotensive Wistar-Kyoto rats, which are considered to be the most appropriate control strain for spontaneously hypertensive rats. To investigate the possibility that angiotensin converting enzyme activity could be affected by this variability, we measured plasma and tissue (lung, heart, renal cortex, renal medulla, and adrenal gland) angiotensin converting enzyme activity in spontaneously hypertensive rats and normotensive Wistar-Kyoto rats from three commercial suppliers in France: Iffa-Credo, Janvier, and Charles River Laboratories. Angiotensin converting enzyme activity was measured in vitro with a fluorometric assay using carbobenzoxy-Phe-His-Leu as substrate. Angiotensin converting enzyme activity in both rat strains varied considerably from one supplier to another, and therefore, comparisons of spontaneously hypertensive rats and Wistar-Kyoto rats from the different suppliers produced conflicting results. For Wistar-Kyoto rats, angiotensin converting enzyme activity in the plasma, heart, kidney, and adrenal glands was highest in rats from Iffa-Credo and lowest in rats from Charles River. For spontaneously hypertensive rats, angiotensin converting enzyme activity in the plasma and tissues was highest in rats from Janvier, whereas no difference could be observed between rats from Iffa-Credo and Charles River. These data confirm the problem of how to interpret and compare studies that use spontaneously hypertensive and Wistar-Kyoto rat strains.

Adrenal Glands↗