PubMed Health⌕ Search

Biomedical subjects

C Lemaire

Publications and source records attributed to C Lemaire.

At least 91 records · Page 5Linked to original sources
PubMed1988

The chicken dystrophin cDNA: striking conservation of the C-terminal coding and 3' untranslated regions between man and chicken.

Dystrophin is a very large muscle protein (approximately 400 kd) the deficiency of which is responsible for Duchenne muscular dystrophy. Its function is unknown at present. In order to know whether different domains of the protein are differentially conserved during evolution, we have cloned and sequenced the chicken dystrophin cDNA. The protein coding sequence has almost the same size as in man. The N-terminal region that resembles the actin binding domain of alpha actinin, as well as the large spectrin like domain show 80% and 75% conservation respectively between chicken and man. In contrast, the C-terminal region shows 95% identity over 627 aa suggesting that it is an important region of interaction with other proteins. Comparison of the amino acid sequence of this C-terminal region to other protein sequences shows only marginally significant similarities. Finally we have found a striking conservation of three segments of the 3' untranslated sequence (85% homology over a total of 920 nt) between chicken and man. These also appear to be conserved in other mammals. This high conservation is not linked to open reading frames.

Amino Acid Sequence↗
PubMed1988

The center-tapped slotted tube autotransformer resonator: a coil for use with a high-resolution small animal imaging system.

A radiofrequency (rf) coil design based on a slotted tube resonator which allows high-resolution imaging of the rodent brain with excellent anatomic definition on a standard G.E. CSI II 2.0-T MR imaging unit with no modification of existing apparatus is described. The coil is easily constructed and permits very rapid tuning to different loading conditions, allowing a high sample throughput.

Animals↗
PubMed1988

Screening heterozygotes for 21-hydroxylase deficiency among hirsute women: lack of utility of the adrenocorticotropin hormone test.

Heterozygosity for 21-hydroxylase deficiency (21-OHD) was investigated in 174 adult hirsute women by using the sum of the incremental responses of serum 17 alpha-hydroxyprogesterone (17 alpha-OHP) and progesterone (P) (delta 17 alpha-OHP + P), 60 minutes after a 0.25 mg intravenous (IV) bolus of synthetic adrenocorticotropic hormone (ACTH). The distribution of 17 alpha-OHP + P in hirsute women was bimodal, allowing two subgroups to be distinguished. In one subgroup including 137 patients, the mode was similar to controls and all values were lower than 3 ng/ml. Thirty-seven (21%) patients constituted another subgroup with values higher than 3 ng/ml and could a priori have been considered as heterozygotes for 21-OHD. However, human leukocyte antigen genotyping provided no conclusive evidence that this subgroup included exclusively heterozygotes for the 21-OHD.

17-alpha-Hydroxyprogesterone↗
PubMed1988

Restoration of phototrophic growth in a mutant of Chlamydomonas reinhardtii in which the chloroplast atpB gene of the ATP synthase has a deletion: an example of mitochondria-dependent photosynthesis.

The Chlamydomonas reinhardtii mutant FUD50 has a deletion in the atpB gene of the chloroplast ATP synthase [Woessner, J. P., Masson, A., Harris, E. H., Bennoun, P., Gillham, N. W., and Boynton, J. E. (1984) Plant Mol. Biol. 3, 177-190]. We have isolated a suppressed strain (FUD50su) that can grow under phototrophic conditions, although it still showed no synthesis of the beta subunit of coupling factor 1. Thylakoid membranes of the FUD50su strain were similar to those of the original FUD50 strain, in that they both lacked all the subunits making up the chloroplast ATP synthase complex. We show that photosynthesis in FUD50su is sensitive to inhibitors such as antimycin, specific for mitochondrial electron transport. This observation indicates that photosynthesis in the FUD50su strain is achieved through an unusual interaction between mitochondria and chloroplast. Exportation of light-induced reduced compounds from the chloroplast to the mitochondria elicits ATP formation in the latter, and ATP is subsequently imported to the chloroplast. The activation of such an ATP shuttle coupled to an NADPH shuttle would thus provide the reducing power and the free energy needed for carbon assimilation in a chloroplast that lacks chloroplast ATP synthase.

Chlamydomonas↗
PubMed1988

Effects of a H2-He-O2 mixture on the HPNS up to 450 msw.

A H2-He-O2 mixture with 54 to 56% hydrogen was studied with 6 subjects (professional divers) during 2 dives to 450 m. The 38-h compression was the same as that used with other types of breathing mixtures (He-O2 and He-N2-O2). The results obtained during compression and during the stay at 450 m in H2-He-O2 show that the EEG changes (increase of theta activities in the anterior regions of the skull, decrease of alpha activities) are similar to those found with other respiratory mixtures. On the other hand, the other symptoms of high pressure neurologic syndrome (HPNS) were clearly improved for the same depths. Thus, neurologic symptoms (tremor, dysmetria, myoclonia, drowsiness) are nonexistent, and the performances during psychometric tests remain similar to those of the surface. Hydrogen, with its narcotic potency, suppresses some symptoms of HPNS and seems to open new perspectives for deep diving.

Adult↗
PubMed1987

A 230kb cosmid walk in the Duchenne muscular dystrophy gene: detection of a conserved sequence and of a possible deletion prone region.

A 230 kb genomic region from the Duchenne muscular dystrophy gene has been cloned in a cosmid walk, using an improved vector and by screening the same unamplified library for all steps. The region cloned surrounds the translocation breakpoint characterized by Worton et al and Ray et al, and overlaps by 70 kb the Pert region cloned by Monaco et al. We have identified a region of strong sequence conservation in mammals and chicken, and comparison of the homologous sequences in chicken and man has indicated the presence of two putative protein coding exons. Comparison with the sequence recently published by Koenig et al shows that only one is present in the Duchenne cDNA, and this raises the question of the functional significance of the other conserved sequence. Single copy probes and whole cosmids generated during this work have been used to analyse the corresponding region in Duchenne patients. Of five independant patients shown to be deleted for a probe 30 kb in 3' of the translocation breakpoint, three have the 5' endpoint of the deletion within a region of less than 20 kb, 100 kb away from the probe used to ascertain the deletion. This might suggest the presence of a region where deletions occur preferentially.

Amino Acid Sequence↗
PubMed1987

A new route for the synthesis of [18F]fluoroaromatic substituted amino acids: no carrier added L-p-[18F]fluorophenylalanine.

L-p-[18F]fluorophenylalanine was designed as a potential marker for probing protein synthesis in the human brain by positron emission tomography. This radiotracer has been synthesized using nucleophilic displacement of the activated nitro group of p-nitrobenzaldehyde by NCA 18F- obtained from the 18O (p, n) reaction on enriched water. The L-form of the [18F]fluoroamino acid can be separated on an analytical scale chiral column. A typical production run of 22.2 GBq (600 mCi) of 18F obtained after a 10 microA.h bombardment of 18 MeV protons on 99.8% 18O-enriched water leads to a batch of 1.11 GBq (30 mCi) of NCA L-p-[18F]fluorophenylalanine after a total synthesis time of 120 min.

Chromatography, High Pressure Liquid↗
PubMed1987

Negative regulation contributes to tissue specificity of the immunoglobulin heavy-chain enhancer.

We have identified in and around the immunoglobulin heavy-chain enhancer two apparently distinct negative regulatory elements which repress immunoglobulin H enhancer, simian virus 40 enhancer, and heterologous promoter activity in fibroblasts but not in myeloma cells. We propose that in nonlymphoid cells, negative regulatory elements prevent activation of the immunoglobulin H enhancer by ubiquitous stimulatory trans-acting factors.

Animals↗
PubMed1986

Myocardial blood flow and glucose uptake after myocardial infarction.

Position emission tomography can picture the distribution of flow tracers as well as of metabolic substrates or analogs. Studies of the distribution of these tracers allow to infer information about regional myocardial clearance (flow X extraction) and substrate utilization. In a study of 32 patients after myocardial infarction, we have contrasted flow and substrate utilization to demonstrate ischemic but viable myocardium in the arterial territory of the infarct in a number of patients also specially after fibrinolytic reperfusion. Restoration of blood flow to the ischemic but viable myocardium through coronary bypass or dilatation improves flow from 56.3% to 84.2% of control and restores substrate utilization. In another group of 32 patients studied with the Strontium-82/Rubidium-82 generator, we have demonstrated perfusion changes both in the myocardial infarct area and at a distance. These changes predominate in patients with multiple vessel disease. Combined PET studies of flow and substrate utilization are new tools to study early intervention after myocardial infarction and to document the benefits of revascularization.

Aged↗
PubMed1984

High pressure nervous syndrome: psychometric and clinico-electrophysiological correlations.

The high pressure nervous syndrome (h.p.n.s.) was studied in man from clinical, electrophysiological and psychometric viewpoints during a variety of simulated dives to depths deeper than 300 m (between 300 and 610 m), which used different modes of compression and different gas mixtures (Heliox, Trimix). In particular we studied tremor, myoclonia, changes in electroencephalogram and psychometric performance. Three points stemmed from these results. Some h.p.n.s. signs are present whichever technique is used, while others depend on the technique, both in intensity and in quality; so there is a syndrome due to compression, whose effects diminish, and a pressure syndrome, which persists at depth. There are differences between the susceptibility of different individuals, not only concerning h.p.n.s. as a whole, but also each symptom and its evolution at a given constant depth. There are no close correlations between the different symptoms observed.

Animals↗
PubMed1984

Effects of addition of nitrogen during rapid compression of baboons.

A series of dives was carried out to depths of 600 and 800 m seawater (msw) using baboons (Papio papio). Experiments were designed to study the effects of compression and the use of a He-N2-O2 gas mixture on high-pressure nervous syndrome (HPNS). When N2 was added to the He-O2 mixture at the beginning of a linear compression (200 msw/h), the symptoms associated with HPNS were still seen; in addition, the electroencephalogram (EEG) changes were more severe than those seen without N2. By use of an identical mixture, a 2-h exponential compression to 600 msw produced less severe signs of HPNS than the nonexponential profile. By use of a 2-h exponential compression to 600 msw and with addition of N2 at the end of compression, the HPNS that had been started under the He-O2 mixture decreased. Progressive addition of N2 during compression reduced the behavioral signs of HPNS without further EEG changes. These results show that the action of N2 is more complex than can be explained by a simple narcotic pressure antagonism and that the HPNS differed according to the gas mixture used.

Animals↗
PubMed1983

Estimation of human susceptibility to the high-pressure nervous syndrome.

Twenty-four professional divers were put through a series of electroencephalographic (EEG) and psychometric tests at the surface and at 180 m after a fast compression (15 min) in an attempt to determine their susceptibility to high-pressure nervous syndrome (HPNS). The subjects were classified according to the EEG changes between the surface and 180 m: group 0, less than 10% increase in theta-band activity in the anterior region of the scalp; group 1, between 10 and 100% increase in theta-activity; group 2, theta-activity increase above 100%. Eight subjects were selected to make a dive to 450 m to verify the quality of our classification (3 from group 0, 3 from group 1, 2 from group 2). The results showed that, for the psychometric tests, the large individual variability between the surface and 180 m does not allow us to prejudge the behavior of each subject at 450 m, but the classification established from absolute values is stable from the surface to 450 m. For the EEG activities, intensity of the modifications at 450 m can be predicted at group level by a 180-m dive, performed with fast compression and similar breathing mixtures.

Disease Susceptibility↗
PubMed1982

Binding and exchange of nucleotides on the chloroplast coupling factor CF1. The role of magnesium.

On the soluble part of the coupling factor (CF1), extracted from spinach chloroplasts, three nucleotide-binding sites are identified. Three ADP are bound per CF1 when the enzyme is incubated with ADP either with or without Mg2+. Two ADP and one ATP are bound per CF1 when the enzyme is incubated with a limiting concentration of ATP, in the presence of Mg2+. At high ATP concentration, in the presence of Mg2+, one free ATP exchanges with one bound ADP and two ATP and one ADP remain bound per CF1. When Mg2+ is omitted from the incubation medium of ATP and CF1, only two ADP and around 0.5 ATP are bound per CF1. The three nucleotide binding sites of CF1 fall into two different and independent categories according to the ability of the bound nucleotides to be exchanged with free nucleotides. On one site the bound ADP is difficult to exchange. On the other two sites, the bound nucleotides. ADP or ATP, are readily exchangable. We propose that the two exchangeable sites form the catalytic part of the enzyme where ATP is hydrolyzed. When ATP concentration is high enough, in the presence of Mg2+, one ATP displaces one bound ADP and allows the ATP hydrolysis to proceed. We propose too that the site where ADP is difficult to exchange may represent the 'tight' ADP-binding site, different from the catalytic ones, which becomes exchangeable on the CF1 in vivo when the thylakoid membranes are energized by light, as stressed by Bickel-Sandkötter and Strotman [(1976) FEBS Lett. 65, 102-106].

Adenosine Diphosphate↗
PubMed1978

Quantifying fatigue in working divers.

Thirty professional divers involved in training, bounce dives, working saturations, and deep experimental saturations were observed over a 1-month period. The subjects themselves performed simple twice-daily measurements of oral temperature, heart rate, breathhold time, handgrip strength, length and quality of sleep, and a subjective estimation of fatigue. The data were analysed with respect to the type of work done by the diver, separating diving from nondiving days. The results showed that subjective estimation of fatigue corresponded to the increment of evening oral temperature and heart rate over morning values. Both inspiratory and expiratory breathhold times decreased from morning to evening in those situations deemed most tiring by the divers. Sleep was generally of average duration and quality; however, diving during the daytime was associated with a decreased amount of sleep in the 24-h period including the following night. Sleep was also of poorer quality during periods of saturation diving. In addition to such group variations, individual divers showed significant performance changes on the various tests, demonstrating the value of this approach to the practical question of deciding when a man is too tired to dive safely. Extension of this method can, we hope, aid in the definition of safe working rotations for professional divers.

Adult↗
PubMed1977

Heart rate and core temperature as indicators of heat stress during deep underwater activity.

In hyperbaric environments, comfortable ambient temperatures are necessarily higher than normal room temperature, and high levels of humidity are also common. These conditions are stressful and even hazardous for an exercising diver. We monitored the heart rates and core temperatures of divers participating in deep experimental dives to pressures up to 300 msw. Accelerated heart rates (100 to 180 beats/min) and elevated core temperatures (+0.4 to 0.9 degrees C) were registered. The increase in heart rate can be explained by the rise in core temperature. Formulas are presented for the relationships between heart rate and duration of activity, between core temperature and duration of activity, and between heart rate and core temperature. These formulas allow the estimation of core temperature from the diver's pulse, and serve to prevent excessive heat stress which could lead to an accident.

Body Temperature↗