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Biomedical subjects

P Lefebvre

Publications and source records attributed to P Lefebvre.

At least 145 records · Page 8Linked to original sources
PubMed1991

Influence of the bicarbonate pool and on the occurrence of 13CO2 in exhaled air.

In 13CO2 breath tests, based on 13C:12C ratio measurements, the appearance of 13C in exhaled CO2 was monitored after the administration of a 13C-labelled compound. Independently of the substrate used, the existence of a bicarbonate pool into which the CO2 produced enters before being exhaled, imposes a delay on the appearance of changes in the 13C:12C ratio. To estimate the nature and magnitude of this delay, we applied a two-compartment model to describe the kinetics of the body bicarbonate pool and we evaluated the 13C:12C ratio of CO2 entering that pool from the measured 13C:12C ratio in the exhaled CO2 after an oral intake of "naturally labelled" 13C-glucose. Our results demonstrated that discrepancies between total and exogenous glucose oxidation in relation to the peak occurrence time, as well as the absolute quantities, could be adequately explained by the interference of the bicarbonate stores.

Bicarbonates↗
PubMed1991

Two regions of the mouse mammary tumor virus long terminal repeat regulate the activity of its promoter in mammary cell lines.

In vivo expression of the mouse mammary tumor virus (MMTV) is restricted to a few organs, with the highest rate of transcription found in the mammary gland. Using a series of mammary and nonmammary murine cell lines, we have identified two regulatory elements, located upstream of the hormone responsive element, that specifically regulate the MMTV promoter. The first element displays an enhancerlike activity and is coincident with the binding of a nuclear factor (designated MP4; position -1078 to -1052 in the long terminal repeat) whose presence is apparently restricted to mammary cell lines. The second regulatory region mediates a repressive activity and is mapped to the long terminal repeat segment from -415 to -483. This repression is specific for a particular subtype of mammary cells (RAC cells) able to grow under two differentiation states (A. Sonnenberg, H. Daams, J. Calafat, and J. Hilgers, Cancer Res. 46:5913-5922, 1986). The MMTV promoter in mammary cell lines thus appears to be modulated by two cis-acting elements that are likely to be involved in tissue-specific expression in vivo.

Animals↗
PubMed1991

[Families with and without children: poverty or affluence? Evidence for Canada and Quebec from 1971 to 1987].

"This study compares the economic well-being of families with and without children and looks into their place in the size distribution of income, in Canada and Quebec from 1971 to 1987. The evidence presented in the paper suggests that having children reduces the chances of affluence and increases the risk of poverty. Viewed from the perspective of the low levels of fertility in Canada and in Quebec, the evidence casts some doubts on the consistency of recent changes, by the two levels of government, in the fiscal and transfer policies concerning families with children." (SUMMARY IN ENG)

Adolescent↗
PubMed1991

[Degeneration of scars. Apropos of 14 cases].

The authors report 14 cases of scar carcinomas, arising in different types of scars, over a 5-year period. The histological type of tumour was squamous cell carcinoma. The different sites of occurrence, from those of spontaneous skin neoplasms reflect their different pathogenesis. The diagnosis must be made early, before lymph node involvement, which is the most significant prognostic factor. Treatment should be first prophylactic to ensure good quality healing. Once the tumour has appeared, only aggressive wide excision provides a hope of cure.

Adult↗
PubMed1991

[Failure and problems: apropos of a cranioplasty].

The authors report a case of post-traumatic cranioplasty associated with various complications. They stress the difficulties in managing this type of reconstruction when a vast cerebral defect is associated with ventriculo-peritoneal by-pass.

Craniocerebral Trauma↗
PubMed1991

[Does the Leveen valve still have a place in the treatment of refractory ascites? An evaluation of 107 cases].

One hundred and seven patients have been treated by the peritoneovenous shunt (PVS) : 54 patients from 1979 to 1984 (P1) and 53 patients from 1985 to 1990 (P2). The mean age was 58 years (25-79 years) and 73 % of the patients had a cirrhosis of alcoholic origin. The mortalities at two weeks and one month were 22 % and 26 % for P1 and 6 % and 11 % for P2. The risk of operation was related to the importance of hepatic and kidney insufficiency and to the importance of hyponatremia. Long term outcome depended on the causal illness. At short term, the morbidity can be reduced and the PVS should be indicated earlier in the progression of the illness.

Adult↗
PubMed1991

[Opsoclonus associated with multisystemic sarcoidosis].

A 32 year old patient with unexplained cough developed an opsoclonus-ataxic-myoclonic syndrome. Chest X-ray film were normal at this onset but became pathologic, and the diagnosis of multisystemic sarcoidosis was made. The possibility of sarcoidosis being the cause of the opsoclonus is discussed.

Adult↗
PubMed1991

Pharmacokinetics of oral all-trans retinoic acid in patients with acute promyelocytic leukemia.

It has been shown that patients with acute promyelocytic leukemia (AML3 subtype) treated with all-trans retinoic acid (all-trans RA), 45 mg/m2/day, achieve complete remission through differentiation of the leukemic clone to mature myeloid cells, which die spontaneously. The pharmacokinetics of all-trans RA given by mouth were studied in 15 AML3 patients. Blood samples were drawn for 24 h following a single oral dose of 45 mg/m2 and assayed for all-trans RA and 13-cis retinoic acid (13-cis RA) plasma concentrations by specific high-performance liquid chromatography. In one patient all-trans RA and 13-cis RA levels were below the detection limits at all times. In the other patients, the time to peak concentration of all-trans RA was between 60 and 210 min (median 90 min) after ingestion, with maximum concentrations between 0.03 and 2.5 micrograms/ml (median 0.4 micrograms/ml). These concentrations were within the in vitro differentiating concentration range of all-trans RA for these patients' cells. In nine patients, enterohepatic cycling was suggested by the presence on the concentration versus time curve of a secondary peak that occurred at meal times. The apparent plasma elimination half-life was between 16.8 and 77.4 min (median 30 min). Detectable plasma levels of 13-cis RA in 12 patients indicated in vivo isomerization of all-trans RA. Despite the high inter-individual variability of all-trans RA pharmacokinetics in these patients, high blast cell counts and failure to respond to differentiation treatment tended to be associated with low all-trans RA Cmax values and high clearance estimates.

Administration, Oral↗
PubMed1991

[Biological parameters of the efficiency of retinoic acid in acute leukemia].

We have previously shown that all-trans retinoic acid therapy is an alternative therapy for acute promyelocytic leukemia (AML3) via differentiation of the leukemic cells. The t(15;17) translocation is specifically found in this leukemia. We and others have shown that through this translocation the RAR alpha gene is rearranged and its expression altered in AML3 cells. The gene is truncated and fused to a novel gene (PLM). This results in a fusion protein whose transactivating properties may be implicated in the leukemogenesis of this disease. Retinoic acid cytoplasmic binding proteins (CRABP and CRBP) are not detected by PAGE chromatography in normal or malignant hematopoietic cells. During all-trans RA therapy, a) all-trans RA plasma concentrations are within in vitro differentiating concentration (med. 0.4 microgram/ml); b) increased expression of the normal remaining RAR alpha allele is rapidly observed and may explain the paradoxical induction of RA differentiation in these cells; c) CRABPII is induced in the bone marrow cells of AML3 patients and remains detectable 1 month after withdrawal of RA. AML3 in relapse after RA therapy is always less sensitive to RA in vitro and in vivo. Our data suggest that modification of the metabolisation pathways of RA may be one of parameters linked to this resistance. It appears that the efficacy of all-trans RA is the resultant of multiple parameters (RA concentration, ratio of PML/RAR alpha transcripts to normal RAR alpha, CRABP) which need to be defined to efficiently monitor all-trans RA therapy in APL.

Drug Administration Schedule↗
PubMed1991

[Carcinoma inside of an amygdaloid cyst. Apropos of a case].

The authors report one case of tonsillar cyst with area of dysplasia in the epithelium, in situ carcinoma, and invasive carcinoma which are peculiar to branchiogenic carcinoma. A tonsillarectomy made ten month after the operation contradict this diagnosis. The criteria for making the diagnosis of branchiogenic carcinoma are discussed so as the clinical sensibility of this cysts. Present imagery is not able to assert the primarity of such lesion. Removing of the tonsil would be made systematically.

Aged↗
PubMed1990

Non-enzymatic glycation reduces heparin cofactor II anti-thrombin activity.

The effects of non-enzymatic glycation on heparin cofactor II activity, at glucose concentrations which might be expected in physiological or diabetic conditions have been evaluated in this study. Radiolabelled glucose incorporation was associated with a loss of heparin cofactor anti-thrombin activity. The heparin cofactor heparin and dermatan sulfate-dependent inhibition of thrombin was significantly reduced, showing a remarkable decrease of the maximum second order rate constant. This study shows that heparin cofactor can be glycated at glucose concentrations found in the blood, and that this phenomenon produces a loss of heparin cofactor-antithrombin activity. These data suggest, furthermore, a possible link between heparin cofactor glycation and the pathogenesis of thrombosis in diabetes mellitus.

Antithrombins↗
PubMed1990

The role of hyperglycaemia-induced alterations of antithrombin III and factor X activation in the thrombin hyperactivity of diabetes mellitus.

Factor X concentration and factor X activation, antithrombin III anti-Xa activity and plasma concentration, and fibrinopeptide A were measured in 20 diabetic patients and 20 normal subjects. Although factor X activation (81.3 +/- 2.2 vs 97.3 +/- 2.1%, p less than 0.01; mean +/- SE) and antithrombin III activity (76.5 +/- 2.2 vs 96.3 +/- 1.8%, p less than 0.01) were reduced in the diabetic patients, fibrinopeptide A concentration was increased (3.7 +/- 0.4 vs 1.7 +/- 0.2 ng ml-1, p less than 0.01). The ratio of factor X activation to antithrombin III anti-factor Xa activity was increased in the diabetic patients (1.10 +/- 0.01 vs 1.01 +/- 0.02, p less than 0.01). Induced hyperglycaemia was able to mimic all these abnormalities, without changing factor X or antithrombin III concentration. The results suggest that in vivo hyperglycaemia produces a decrease of factor X activation, but at the same time increases fibrinopeptide A formation due to a greater decrease of antithrombin III anti-Xa activity.

Adult↗