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Biomedical subjects

J Lefebvre

Publications and source records attributed to J Lefebvre.

At least 55 records · Page 3Linked to original sources
PubMed1994

Treatment of ambulatory hypertensives with nebivolol or hydrochlorothiazide alone and in combination. A randomized, double-blind, placebo-controlled, factorial-design trial.

This placebo-controlled multifactorial design trial assessed the antihypertensive efficacy of nebivolol, a novel cardioselective beta 1-blocker with vasodilating properties, and hydrochlorothiazide monotherapy and in combination. After a 4-week placebo period, 240 white patients with a mean daytime ambulatory blood pressure of > or = 90 mm Hg were randomized to receive either placebo, nebivolol (1, 5, or 10 mg), hydrochlorothiazide (12.5 or 25 mg), or one of the six possible combinations of nebivolol and hydrochlorothiazide for 12 weeks. A dose-related reduction in clinic and ambulatory blood pressure was demonstrated for each drug as monotherapy and for the two drugs in combination. Nebivolol, 5- and 10-mg doses, showed a larger effect than hydrochlorothiazide doses on clinic blood pressure and over the 24-h interval. Moreover, the combination doses had substantial antihypertensive effects that were sustained over the entire 24-h profile with a greater effect observed with the higher dose combinations. The reduction in ambulatory blood pressure was further substantiated by the reduction of blood pressure loads (% of BP > 140/90 mm Hg awake and > 120/80 mm Hg asleep) to as low as 11.5% with 10 mg of nebivolol combined with 25 mg of hydrochlorothiazide. Nebivolol and hydrochlorothiazide were well tolerated. We provided evidence that nebivolol, given as monotherapy or in combination with low dose of hydrochlorothiazide, is effective in reducing clinic and 24-h ambulatory blood pressure in patients with ambulatory hypertension. The results provided further evidence for the use of ambulatory blood pressure monitoring and factorial designs when investigating new antihypertensive agents.

Adolescent↗
PubMed1994

[11 beta-Hydroxysteroid dehydrogenase (11-beta-OHSD): physiology and lack of action in pathology].

The 11 beta OHSD is an ubiquitous enzyme which inactivates cortisol to cortisone by transforming the hydroxyl group at the 11-carbon to a keto group. Therefore, it confers to mineralocorticoid receptors their selectivity toward their ligand and may constitute an important mechanism of regulation tissue-specific of the access of ligand toward its receptors. More widely the 11 beta OHSD would modulate glucocorticoid activity to their own receptor. There is no possibility to measure directly this enzyme and its deficiency is indirectly evaluated by enhancement of the quotient (THF + alpha THF)/THE after analysis of urinary steroid metabolites. Such enzymatic deficits may be congenital and are observed in childhood where they give an apparent mineralocorticoid excess (AME) syndrome (type 1). Sometimes acquired and reversible, they are due to licorice intoxication, hypothyroidism, chronic alcoholism and may be involved in the genesis of some cases of hypertension.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1994

Association between cough and angiotensin converting enzyme inhibitors versus angiotensin II antagonists: the design of a prospective, controlled study.

BACKGROUND: A common adverse experience in hypertensive patients treated with angiotensin converting enzyme (ACE) inhibitors is a tickling dry cough. OBJECTIVES: The aim of the present study was to review clinical observations and mechanisms of cough associated with ACE inhibitors. In addition, since the AT1-type angiotensin II antagonists (represented by losartan, MK954, DuP753) are not expected to influence other systems (kinins, prostaglandins) affected by ACE inhibitors, we explored the hypothesis that antihypertensive therapy with these agents will not be associated with cough at a similar frequency or quality to that seen with ACE inhibitors. DESIGN AND METHODS: Patients with a history of an ACE inhibitor-associated dry cough confirmed by a second challenge with lisinopril were enrolled into an international, multicenter, randomly allocated, double-blind, parallel-group, controlled trial, to be treated with losartan, lisinopril or hydrochlorothiazide. The presence and severity of cough were assessed by a self-administered questionnaire and a visual analog scale, respectively. CONCLUSIONS: It is expected that the new class of antihypertensive agents, angiotensin II antagonists, will not be associated with the high incidence of dry cough associated with the use of ACE inhibitors. It appears that this cough is not related to alterations in the renin-angiotensin system but to kininase II effects.

Adult↗
PubMed1993

The specificity of the S1' subsite of cysteine proteases.

The specificity of the S1' subsite of the cysteine proteases cathepsin B, L, S and papain has been investigated using a series of intramolecularly quenched fluorogenic substrates (Dansyl-Phe-Arg-AA-Trp-Ala) where the P1' amino acid (AA) has been varied. Taken individually, each enzyme displays a relatively broad S1' subsite specificity and this subsite cannot be considered as a primary site of specificity. Notable differences do exist however between the various proteases. Cathepsin B prefers large hydrophobic residues in the P1' position of a substrate while cathepsin L has an opposite trend, favoring amino acids with small (Ala, Ser) or long but non-branched (Asn, Gln, Lys) side chains. Cathepsin S and papain display a somewhat broader S1' subsite specificity.

Amino Acid Sequence↗
PubMed1993

[Prevalence of cervical Chlamydia trachomatis infection in a female population seeking contraception counseling].

OBJECTIVES: To determine the prevalence and risk indicators of cervical infection due to Chlamydia trachomatis among female patients consulting for contraception and to evaluate an enzyme immunoassay for the detection of C. trachomatis in this setting. DESIGN: Prevalence study. Endocervical specimens were analysed by means of culture and enzyme immunoassay. C. trachomatis infection was diagnosed through culture. SETTING: A hospital family planning clinic in Trois-Rivières, Que. SUBJECTS: All 533 female patients who consulted for contraception between November 1986 and March 1988. Results of culture were available for 495 patients. MAIN OUTCOME MEASURE: Demographic, epidemiologic and clinical information was collected by means of a standard questionnaire and a gynecologic examination. MAIN RESULTS: The prevalence rate of chlamydial infection was 9% (45/495). Enzyme immunoassay detected 37 (82%) of the infections. The mean age of the patients was 19.8 years, and 98% of the infections were diagnosed in those aged 25 years or less. The variables significantly associated with C. trachomatis infection were having more than one sexual partner in the preceding year (odds ratio [OR] 2.9; 95% confidence limits [CL] 1.7 and 5.0) and having more than one partner in the preceding 3 months (OR 2.3; 95% CL 1.2 and 4.3). These two indicators would have detected 58% and 22% of the infections respectively. CONCLUSIONS: Screening for C. trachomatis infection by means of enzyme immunoassay should be proposed to all female patients aged 25 years or less consulting for contraception in our clinic. Such screening may prove to be an effective preventive measure in other similar clinical settings.

Adolescent↗
PubMed1993

Differential scanning calorimetric studies of the effects of ions and pH on ribulose 1,5-bisphosphate carboxylase/oxygenase.

Lucerne rubisco (ribulose 1,5 bisphosphate carboxylase/oxygenase, EC 4.1.1.39) was purified by ammonium sulfate fractionation and gel chromatography. Differential scanning calorimetry (d.s.c.) was used to study the effects of pH in the range 3.5 to 11.4, and the effects, at pH 7.5, of various salts at ionic strength lower than 0.3 (NaH2PO4, (NH4)2SO4, Na2SO4, NaCl, MgCl2, CaCl2) on the thermal denaturation of the protein. Van't Hoff and calorimetric enthalpies, and the change in heat capacity between the native and denatured states were calculated from the experimental data. The effects of salts on the thermal denaturation seem to follow the Hofmeister series. In some cases, the thermal denaturation may be interpreted as a two-step transition of the polypeptide chains. Moreover, comparison of the results with literature data suggests that the thermal denaturation parameters depend on the botanical origin of rubisco and are affected by the conditions of its purification.

Calorimetry, Differential Scanning↗
PubMed1993

Plasma insulin-like growth factor-1 (IGF-1) concentrations in human breast cancer.

Insulin-like growth factor-1 (IGF-1) is capable of stimulating breast cancer cell growth in vitro and the presence of IGF-1 receptors has been demonstrated in primary breast cancers. We determined plasma IGF-1 in a primary breast cancer population and in a control population. Radioimmunoassays were performed either directly on plasma, IGF-1 (NE), or after an acid-ethanol extraction of the plasma, IGF-1 (E). We demonstrated an inverse correlation between age and IGF-1: for this reason, only results obtained in females of the same age range (> 35 years) were compared. Median concentrations of IGF-1 were significantly higher in primary breast cancers [IGF-1 (E) = 152 ng/ml, IGF-1 (NE) = 26 ng/ml, n = 44] than in controls [IGF-1 (E) = 115 ng/ml, IGF-1 (NE) = 20 ng/ml, n = 92]. To our knowledge such a growth factor increase has never been described in breast cancer. We conclude that IGF-1 could be an important factor involved in the development of breast cancer and that treatment reducing IGF-1 levels could be beneficial for patients.

Adult↗
PubMed1993

Comparison of quinapril and atenolol as single drugs or in combination with hydrochlorothiazide in moderate to severe hypertensives, using automated ambulatory monitoring.

1. Forty patients with moderate to severe hypertension and daytime ambulatory diastolic blood pressure > or = 90 mm Hg were randomized double-blind to once-daily treatment with either quinapril up to 20 mg (n = 20) or atenolol up to 100 mg (n = 20) as single drugs or in combination with hydrochlorothiazide 25 mg over a period of 12 weeks. 2. Conventional and ambulatory blood pressure, heart rate, side effects and metabolic changes were compared at the end of the run-in period on placebo, after 4 weeks on monotherapy and at the end of the 12-week period of active treatment. 3. Quinapril and atenolol reduced conventional blood pressure equally with substantial additional effect seen on combination therapy. The two regimens induced a significant decrease in ambulatory BP. However, the atenolol treated ambulatory hypertensive group experienced significantly greater decreases in diastolic blood pressure during 24 h, awake and sleep periods than did the quinapril group. 4. Adverse reactions were mild with both drugs except for severe Raynaud phenomenon in one patient in the atenolol group. Triglyceride levels were significantly increased with atenolol alone and in combination with hydrochlorothiazide. 5. Thus, within the limits of the dose ranges tested, quinapril and atenolol as single drugs or in combination with hydrochlorothiazide reduce significantly conventional and ambulatory blood pressure in moderate to severe hypertensives, but atenolol is more effective in reducing ambulatory diastolic blood pressure.

Adolescent↗
PubMed1993

Spatial distribution of viable cells immobilized in agar membranes.

The biocatalytic structures obtained by immobilizing microorganisms in planar gel slabs have been studied and modeled to better understand the dynamics of systems controlled by diffusion-reaction-growth couplings. The theoretical results give two kinds of information: the time evolution of the extra-membrane system due to the intra-membrane reactions which can easily be compared to experiments, and the intra-membrane behaviour which is mainly characterized by the concentration profiles. The steady state cell concentration profile is one of the most important elements of a system's behaviour. In addition to photographs taken at different depths in the membrane, we have developed an original, simple and reproducible technique for the experimental determination of the intra-membrane cell concentration profiles. The technique uses a home-made microtome to obtain gel slices, in which the cell concentration is determined using visible spectroscopy. By using this technique, we have shown a good agreement between the theoretical predictions and the experimental profiles, which validates the modeling.

Agar↗
PubMed1992

The sequence of the gene encoding elongation factor Tu from Chlamydia trachomatis compared with those of other organisms.

Nucleotide (nt) sequences encoding the elongation factor Tu (EF-Tu), tRNA(Thr) and tRNA(Trp) from Chlamydia trachomatis have been determined. The environment of the EF-Tu-encoding gene (tuf), between two tRNA gene sequences, suggests that it is part of a tufB locus. The nt sequence and the deduced amino acid (aa) sequence were aligned with comparable sequences from other organisms and the resulting data bases were used to infer phylogenies. Phylogenetic trees based on aa sequences and nt sequences are similar, but not completely congruent with rRNA gene-based phylogenies. Both the nt and aa sequence trees concur on the early divergence of Thermotoga and Chlamydia from the bacterial root. The aa alignment highlights the presence of four unique Cys residues in the chlamydial sequence which are found at strictly conserved positions in other sequences. Further peculiarities of the chlamydial and eubacterial sequences have been mapped to the X-ray crystallographic structure of the protein.

Amino Acid Sequence↗
PubMed1992

Synthesis of a homologous series of ketomethylene arginyl pseudodipeptides and application to low molecular weight hirudin-like thrombin inhibitors.

The design of low molecular weight thrombin inhibitors IIa-d (hirutonins) that bind concurrently with the enzyme's catalytic site and auxiliary "anion-binding exosite" for fibrinogen recognition is reported. A practical synthesis of the required homologous ketomethylene arginyl dipeptide inserts [Arg psi CO(CH2)nCO] (n = 1-4) corresponding to the P1-P1' scissile position of hirutonins is described. The substitution of the scissile amide function by a ketomethylene group is compatible with the enzyme active site and conferred complete plasma proteolytic stability. This modification also enhanced enzyme affinity up to 20-fold with hirutonin-4 (IIb, n = 4) displaying highest affinity (Ki = 140 +/- 20 pM). Hirutonins 1-4 exhibited potent inhibition of plasma prothrombin time (PT) and activated partial thromboplastin time (aPTT). The inhibition was biphasic and showed good correlation with the corresponding Ki. Hirutonin-2 inhibited thrombin-mediated platelet aggregation and exhibited a strong antithrombotic effect comparable to r-hirudin in an in vivo rat arteriovenous shunt model (ED15 = 1.20 mg/kg for hirutonin-2 and 1.14 mg/kg for r-hirudin). Lower molecular weight inhibitors were obtained by substituting the six native amino acid residues (Q-S-H-N-D-G), connecting the active site and the auxiliary exosite binding elements with a variable number of interening omega-aminopentenoyl units. In addition, the exosite component was reduced to seven amino acid residues (D-F-E-P-I-P-L). Incorporation of these modifications into the bifunctional format resulted in nanomolar thrombin inhibitory peptides (IIIa-c). The resulting inhibitors were studied by molecular modeling with alpha-thrombin, and the bimolecular interactions served to explain the retention of high enzyme affinity.

Amino Acid Sequence↗
PubMed1992

Comparative effects of a new cardioselective beta-blocker nebivolol and nifedipine sustained-release on 24-hour ambulatory blood pressure and plasma lipoproteins.

This double-blind, parallel-group study compared the effects of nebivolol, a novel cardioselective beta-blocker, with those of nifedipine sustained-release on 24-hour ambulatory blood pressure and plasma lipoprotein levels. After a washout period of 8 weeks, 51 patients with mild to moderate essential hypertension were randomized to double-blind treatment with either nebivolol 5 mg once a day (n = 26) or nifedipine sustained-release 20 mg bid (n = 25) over a period of 12 weeks. Both treatments produced similar and significant (P = .0001) reduction in office blood pressure as well as in 24-hour, work, awake, and sleep ambulatory blood pressure. The clinical response (diastolic blood pressure less than 90 mmHg or decreased by greater than or equal to 10 mmHg) rate was 69% for nebivolol and 59% for nifedipine, respectively. Moreover, the nebivolol and nifedipine treatment-induced decreases in mean 24-hour ambulatory blood pressure were similar to the decreases in clinic blood pressure. Furthermore, the percentages of "blood pressure loads" (awake greater than 140/90 mmHg and asleep greater than 120/80 mmHg) were lowered significantly (P = .0001), from 60% to 29% with nebivolol and from 60% to 39% with nifedipine. Mean ambulatory heart rate was reduced (P = .0001) from 79 +/- 7 to 68 +/- 7 beats/minute during nebivolol therapy and from 80 +/- 9 to 79 +/- 7 (not significant) with nifedipine. Total plasma cholesterol and low-density lipoprotein levels decreased significantly (P less than .05) by 5 and 8%, respectively, after nebivolol treatment, and each decreased by 3% after nifedipine treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Basic fibroblast growth factor (bFGF): mitogenic activity and binding sites in human breast cancer.

We investigated binding characteristics of basic fibroblast growth factor (bFGF) on membranes prepared from 4 human breast cancer cell lines and 38 primary BC biopsies. Competitive binding experiments were performed and analyzed using the "Ligand" program. Furthermore bFGF mitogenic activity was measured by [3H]thymidine incorporation into DNA from breast cancer cell lines. The presence of high-affinity binding sites was demonstrated in each cell type (MCF-7: Kd = 0.60 nM; T-47D: Kd = 0.55 nM; BT-20: Kd = 0.77 nM; MDA-MB-231: Kd = 0.34 nM). The presence of these high-affinity binding sites was confirmed with saturation experiments. A second class of low-affinity binding sites was detected in the 2 hormone-independent cells (BT-20: Kd = 2.9 nM; MDA-MB-231: Kd = 2.7 nM). bFGF stimulated the proliferation of MCF-7, T-47D, BT-20 but not MDA-MB-231 cell lines. With competition experiments, binding sites were detectable in 36/38 breast cancers; high-affinity binding sites (Kd less than 1 nM) were present in 19/36 cases and low-affinity binding sites (Kd greater than 2 nM) were present in 29/36 cases (the two classes of binding sites were present in 12 breast cancers). No relation between bFGF binding sites and node involvement, histologic type or grading of the tumor was evidenced. There were negative correlations (Spearman test) between total bFGF binding sites and estradiol receptor (P = 0.05) or progesterone receptor (P = 0.009). The demonstration of (1) bFGF specific binding sites in breast cancer membranes, and (2) bFGF growth stimulation of some breast cancer cell lines indicates that this factor may be involved directly in the growth of some breast cancers.

Adult↗