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Biomedical subjects

J Lemaire

Publications and source records attributed to J Lemaire.

At least 19 recordsLinked to original sources
PubMed1992

Optimal therapeutic level of heparin therapy in patients with venous thrombosis.

BACKGROUND: Audits of heparin sodium therapy suggest that heparin administration is fraught with difficulty. The literature indicates that the current clinical practice of intuitive ordering of heparin results in inadequate therapy because of fear of bleeding. The importance of exceeding the lower limit of the therapeutic range has been strongly supported by findings of prospective clinical trials. Firm evidence indicates that failure to exceed the lower limit is associated with unacceptably high rates of recurrent venous thromboembolism. By comparison, evidence supporting the risk of exceeding the upper limit of the therapeutic range is weak. OBJECTIVES: The purposes of this study were (1) to validate prospectively an approach designed to minimize the proportion of patients receiving subtherapeutic doses of heparin and (2) to determine the effectiveness and safety of decreasing the heparin dosage infused on the basis of activated partial thromboplastin time (APTT) prolongation reflecting both heparin and warfarin sodium effects. METHODS: We performed a randomized double-blind study evaluating a prescriptive approach to heparin administration in patients receiving heparin or heparin with warfarin. Thromboembolic and bleeding complications were objectively documented. RESULTS: Only 1% and 2% of patients had subtherapeutic heparin levels for 24 hours or more in the heparin and combined groups, respectively. Recurrent venous thromboembolism occurred infrequently in both groups (7%). Sixty-nine (69%) of 99 patients receiving combined therapy had supratherapeutic values, compared with 24 (24%) of 100 receiving heparin; bleeding complications occurred in 9% and 12%, respectively. CONCLUSIONS: Our findings demonstrate that no association exists between supratherapeutic APTT responses and bleeding, which is in direct contrast to the observed association between subtherapeutic APTT responses and recurrent venous thromboembolism.

Double-Blind Method↗
PubMed1991

[Development and evaluation of a laser catheter with tip fiberoptic for coronary angioplasty].

A fiber-optic tip catheter has been developed for treating coronary and peripheral atherosclerosis percutaneously. The catheter is coupled to an ionised Argon laser emitting at an optical power of 1 to 7 Watts. It is designed to follow a guide wire and to perform tissue ablation by a new concept combining the effects of central vaporisation and peripheral thermal remodelling of the obstructed artery. This mode of function should considerably reduce the risks of false route previously encountered with laser angioplasty. The optical and thermic properties of the catheter prototypes were determined by physical methods. These experiments showed that the temperature of the metallic component of the catheter tip did not exceed 30 degrees C at a continuous power of 6 laser Watts when the flush was functioning. It attained 400 degrees C in the absence of the flush. The performances of the catheter were then tested in a number of in vitro experiments. First of all, the catheter tip was placed perpendicularly to atheromatous cadaver aortae to study the effect of vaporisation with respect to the laser power. The threshold of vaporisation was 1 Watt (irradiance: 1100 Watts/cm2). The catheter was then introduced into plastic tubes obstructed by atheromatous plaques. This experiment demonstrated the mechanical solidity of the catheter and its flexibility in difficult operating conditions: diameter 2mm, 45 degrees angles, irregular calcified plaques. It also showed that the optimal safety-efficacy laser power was 3 laser Watts and that the exposure times varied with respect to the nature of the plaques tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1989

Cellular responses to "brucelline INRA" during the experimental brucellosis of the mouse.

"Brucelline INRA" is an aqueous extract of a rough strain of Brucella melitensis that is used to test cutaneous delayed hypersensitivity in man and animals. The cellular response of mice (either normal, or sensitized by a previous brucella infection) was investigated with local implanted "cell-traps" and by immunological testing in vitro. Brucelline markedly reduced the number of polymorphonuclear cells in the local infiltrate of sensitized animals during the early, nonspecific phase of the response. In vitro responses were dissociated; while brucelline depressed the incorporation of thymidine into lymphocytes, on controls as well as on sensitized animals, it induced an evident production of macrophage inhibitory factor. Since brucelline is a mixture of several molecular species, and antibodies to some of its components were present in sensitized animals, immunomodulation of these apparently paradoxical responses is probably the result of a combination of different mechanisms. These observations are discussed in the light of physiopathological features of the experimental brucellosis in mice.

Animals↗
PubMed1986

Selective release of inner core proteins from intestinal microvillus membrane by lithium diiodosalicylate.

Lithium diiodosalicylate (LIS) was used to selectively solubilize proteins from purified intestinal brush border membrane vesicles. Incubation of the vesicles with increasing concentrations of LIS resulted in the progressive release of proteins with total disruption of the membranes being obtained at 200 mM. Maximum selectivity was observed at 20-30 mM LIS which preferentially released actin and other non-glycosylated proteins while all the glycoproteins remained associated with the membrane. Electron micrographs showed that, after LIS treatment, brush border vesicles are partially disrupted and have lost their inner core of microfilaments. Sucrase, trehalase, leucylnaphthylamide hydrolase, gamma-glutamyl transpeptidase and alkaline phosphatase all retained more than 70% of their activities and remained associated with the membrane fraction after LIS solubilization (30 mM). The results indicate that lithium diiodosalicylate treatment provides an efficient method for the separation of cytoskeletal proteins from intrinsic membrane glycoproteins and should be very useful for the purification of microvilli proteins and for the study of membrane-protein interactions.

Animals↗
PubMed1984

Fundic vagotomy by waveguide CO2 laser: experimental study of a new technique in dogs.

Anterior lesser curve seromyotomy with posterior truncal vagotomy is an alternative operation to the highly selective vagotomy. After preoperative gastric function testing, four dogs underwent an anterior lesser curve seromyotomy with posterior truncal vagotomy. However, a new prototype hand-held laser was used to perform the seromyotomy. This laser delivers 20 W and is small, light, and highly maneuverable. Results of the operation indicate that this laser was easy to use and yielded a very effective seromyotomy without complications. Peroperatively, the laser performed simultaneous section and hemostasis. Postoperatively, no significant acid production could be stimulated with either histamine, pentagastrin, or insulin. This operation yields good control of acid production and is faster and easier than the highly selective vagotomy. The hand-held waveguide CO2 laser may further facilitate the ease of this procedure.

Animals↗
PubMed1983

[Adapto-electroretinographic study of regeneration of the visual pigments in the fauve de Bourgogne and albino rabbit after photobleaching with monochromatic light].

Kinetics of rod pigment regeneration were studied in vivo in Fauve de Bourgogne and Albino rabbits by adapto-electroretinography (AERG). Electroretinography in the rabbit using polychromatic flashes affords the means to dissociate the response of the cones (a-wave, b1-wave: photopic function), from that of the rods (b2-wave scotopic function). After photobeachting, electroretinograms were recorded at two minutes' intervals during dark adaptation of one hour duration. Variations of b2/b1 with time of dark adaptation provide an adapto-electroretinogram giving relative measurements of rod pigment concentration at various stages of regeneration. In the present study, photobleaching was provoked by monochromatic light (at 405, 436 and 546 nm) actinometrically controlled. Studies were conducted in two Fauve de Bourgogne and two Albino rabbits. The effect of four doses, varying from 4.10(17) photon.cm-2 to 1.10(19) photon.cm-2, was measured at each wavelength on the AERG in the four rabbits. First order kinetics for rod pigment regeneration were observed, mainly at 546 nm and at high dose levels: overall regeneration rate is apparently controlled by the isomerization step. For Fauve de Bourgogne and Albino rabbits, the regeneration rate depends on the bleaching wavelength and on the dose. At high dose levels and for long wavelengths, delayed recoveries are observed in the Fauve de Bourgogne animals. However, durations of delays are shorter with monochromatic light experiments than with polychromatic light bleaching, at the same dose. Differences of ocular media transmission may be responsible for a faster regeneration process at shorter than at longer wavelengths.

Adaptation, Physiological↗
PubMed1982

Mechanism of neomycin stimulation of D-glucose uptake in rabbit intestinal brush border membrane.

In order to study the effect of the antibiotic neomycin on the intestinal epithelium, D-glucose was used as a probe molecule and its transport into rabbit brush border membrane vesicles was measured by a rapid filtration method. Treatment of the epithelium with neomycin sulfate prior to the preparation of the brush border membrane enhanced the D-glucose uptake, whereas neutral N-acetylated neomycin did not. This action of neomycin was related to its polycationic character and not to its bactericidal action. No significant difference could be demonstrated between the protein content or disaccharidase-specific activities of the brush border fractions from treated or non-treated intestines. Electrophoretic protein patterns of SDS-solubilized membrane were not significantly different after neomycin treatment. To gain more information on the mechanism involved in the stimulation of D-glucose transport, experiments were conducted on phosphatidyl glycerol artificial membranes and the results compared with those obtained with brush border membrane. At a concentration of 10(-7) M, neomycin decreased the nonactin-induced K+ conductance by a factor of approx. 100. The membrane conductance was linearly dependent on the neomycin concentration and the conductance in 10(-2) M KCl was 10 times that in 10(-3) M KCl. The valence of neomycin was estimated, from the slope of these curves, to be between 6 and 4. In contrast, acetylated neomycin had no effect on the nonactin-induced K+ membrane conductance. Therefore, the effect of neomycin on artificial membrane is related to its 4 to 6 positive charges. It is proposed that the stimulation of sugar transport in brush border membrane is related to screening of the membrane negative charges by the positively-charged neomycin. Accumulation of anions at the membrane surface then occurs and their diffusion into the intravesicular space would increase the transmembrane potential which, in turn, stimulates the entry of D-glucose.

Animals↗
PubMed1982

[Photobleaching quantum yields of visual pigments in the "fauve de Bourgogne" and "albino" rabbit (author's transl)].

Photobleaching quantum yields of visual pigments extracted from retinas of the "fauve de bourgogne" and "albino" rabbit were measured in monochromatic light. For the "fauve de Bourgogne" rabbit, the photobleaching quantum yield was to be 0.65 at different excitation wavelengths (546, 491.6 and 436 nm); at shorter wavelengths, this quantum yield was lower ie. 0.36 at 405 nm. This wavelength effect has been observed on visual pigments extracted from bees retina. In contrast, in the "albino" rabbit, the photobleaching quantum yield was constant and equal to 0.31 whatever the excitation wavelength between 546 and 405 mn.

Animals↗
PubMed1979

[Photochemistry of visual pigments (author's transl)].

Recent studies of the photochemistry of visual pigments are reported. Results obtained on rhodopsine and model compounds, by means of techniques based upon continous or pulsed excitation are compared. The mechanique of the primary photochemical step of the bleaching of rhodopsine is discussed. The process is occuring on a time scale of picosecond and a new concept of proton transfer followed by a conformation charge is opposed to the classical cis-trans photo isomerisation of the retinal moiety. The origin of the electrical response of the photoreceptor cells is still controversial.

Animals↗
PubMed1978

Labeling of a glucose binding protein in the rabbit intestinal brush border membrane.

Using a double labeling method based on the method of Thomas (Thomas, L. 1973). Isolation of N-ethylmaleimide-labeled phloridzin-sensitive D-glucose binding protein of brush border membrane from rat kidney cortex. Biochim. Biophys. Acta, 291, 454--464), with radioactive N-ethylmaleimide ([3H]NEM and [14C]NEM) in the presence and absence of D-glucose, a protein band which is periodic acid--Schiff staining insensitive and which has a relative mobility (Rm) of 0.55 (corresponding to a molecular weight of 51 000 daltons) as determined by sodium dodecyl sulfate (SDS) electrophoresis was labeled preferentially. When radioactive p-hydroxymercuriphenylsulfonate ([203Hg]PCMBS) is used in the presence and absence of D-glucose, as described by Smith et al. (Smith, M. W., Ferguson, D. R., and Burton, K. A. 1975. Glucose- and phloridzin-protected thiol groups in pig intestinal brush border membranes. Biochem. J. 147, 617--619.), a protein band which has a relative mobility of 0.62 and a corresponding molecular weight of 42 000 daltons was labeled. Control experiments have shown that increasing concentrations of nonradioactive NEM (0.1--5.0 mM) do not substantially modify the electrophoretic pattern of SDS-solubilized brush border membrane. Nonradioactive PCMBS (0.1--10 mM), on the other hand, modifies the electrophoretic pattern and especially causes a change in relative mobility of the 0.55 protein band which migrates after 1 mM PCMBS treatment with a Rm of 0.62. The effect of 1 mM PCMBS can be reversed by adding L-cysteine or dithiothreitol. Actin extracted from rabbit muscle migrates with the same Rm as the 0.55 protein band in our electrophoretic conditions.

Actins↗