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Biomedical subjects

A Robert

Publications and source records attributed to A Robert.

At least 73 records · Page 4Linked to original sources
PubMed2000

Staphylococcal surface display and its applications.

Novel surface proteins can be introduced onto the bacterial cell surface by recombinant means. Here, we describe the development of such display systems for two food-grade bacteria, Staphylococcus carnosus and Staphylococcus xylosus, and present how such engineered bacteria can be used in different applications. A study will be described in which such staphylococci were employed as vaccine delivery vehicles to elicit protective antibody responses to respiratory syncytial virus (RSV). The use of surface-engineered staphylococci as novel microbial biocatalysts, as a new type of whole-cell diagnostic devices or for adsorption of metal ions with potential environmental or biosensor applications, will also be discussed.

Animals↗
PubMed2000

Long-term results of three randomized trials (58831, 58832, 58881) in childhood acute lymphoblastic leukemia: a CLCG-EORTC report. Children Leukemia Cooperative Group.

We present here the long-term results of three randomized clinical trials conducted on children with newly diagnosed acute lymphoblastic leukemia (ALL) between 1983 and 1998 by the Children Leukemia Cooperative Group (CLCG) from EORTC. In study 58831/32, the overall event-free survival (EFS) rates (+/- s.e.) at 6 and 10 years were 66% +/- 1.8% and 65% +/- 1.8%, respectively, and the risk of isolated central nervous system (CNS) relapse was 6% +/- 1% and 7% +/- 1%, respectively. In patients with a standard risk of relapse the omission of cyclophosphamide had no adverse effect on disease-free survival rates at 10 years (trial 58831). In medium- and high-risk patients the omission of radiotherapy did not increase the risk of CNS or systemic relapse (trial 58832). In study 58881 (1989-1998) the overall EFS rate at 8 years was 68.4% +/- 1.2% and the risk of isolated CNS relapse was 4.2%+/-0.5%. In this trial which adressed three randomized questions, the following results were obtained: the combination of cytarabine at high doses with methotrexate at high doses during interval therapy did not improve prognosis. The addition of 6-mercaptopurine iv during maintenance increased the risk of late relapse. E. coli asparaginase was more toxic and has a higher efficacy than Erwinia asparaginase. Leukocyte counts >100 x 10(9)/l, specific genetic abnormalities, a poor initial response to steroids or a high level of minimal residual disease at early time points were consistently associated with an adverse prognosis in the 58881 trial.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Direct comparison between endothelin-1, N-terminal proatrial natriuretic factor, and brain natriuretic peptide as prognostic markers of survival in congestive heart failure.

BACKGROUND: Endothelin-1 (ET-1) and cardiac natriuretic peptide plasma concentrations have prognostic significance in congestive heart failure (CHF). However, their respective prognostic values in this setting have never been directly compared. METHODS AND RESULTS: We studied the prognostic performances of ET-1, N-terminal proatrial natriuretic factor (N-proANF), and brain natriuretic peptide (BNP) to predict the long-term cardiac mortality in fully treated patients with CHF. Peripheral plasma concentrations of the 3 peptides were measured in 109 patients (left ventricular ejection fraction [LVEF] < 35%) in New York Heart Association (NYHA) functional classes II (n = 65) or III to IV (n = 44). The outcome of the patients was evaluated 3 years after the beginning of the study, and a Cox regression model was used to identify predictors of death. Plasma concentrations of the 3 peptides increased with the severity of heart failure. By univariate analysis, 6 parameters were significantly associated with death during follow-up: ET-1 level, NYHA classes III to IV, N-proANF level, BNP level, LVEF, and age (all P < .01). By multivariate analysis, only ET-1 level and, to a lesser extent, N-proANF level contributed significantly and independently to risk stratification (chi2 = 53.4 and 12.8; P < .0001 and P < .001, respectively). CONCLUSION: In a group of patients in whom the vast majority were administered angiotensin-converting enzyme inhibitor therapy, plasma ET-1 and N-proANF concentrations identify better than several clinical markers a very high-risk group, fairly amenable to heart transplantation or new therapies.

Aged↗
PubMed2000

From alpha-carbamoyl-alpha-cyanooxiranes to 3-halogenopyruvamides.

The crystal structures of the first stable alpha-diol from the alpha-halogenopyruvamide series, 3-chloro-2, 2-dihydroxy-3-phenylpropanamide, C(9)H(10)ClNO(3), and three products [3-(4-chlorophenyl)-2-cyano-2,3-epoxypropanamide, C(10)H(7)ClN(2)O(2), 3-bromo-2-cyano-2-hydroxy-3-p-tolylpropanamide, C(11)H(11)BrN(2)O(2), 3-bromo-2-oxo-3-p-tolylpropanamide, C(10)H(10)BrNO(2)] obtained during the systematic synthesis of alpha-halogenopyruvamides are reported. The crystal structures are dominated by hydrogen bonds involving an amide group. The stability of the geminal diol could be ascribed to hydrogen bonds which involve both hydroxyl groups.

Crystallography, X-Ray↗
PubMed2000

In vitro and in vivo potentiation of artemisinin and synthetic endoperoxide antimalarial drugs by metalloporphyrins.

The in vitro potentiation of artemisinin by synthetic manganese porphyrin complexes has been recently reported (F. Benoit-Vical, A. Robert, and B. Meunier, Antimicrob. Agents Chemother. 43:2555-2558, 1999). Since the activity of artemisinin and synthetic antimalarial endoperoxides is related to their interaction with heme (S. R. Meshnick, A. Thomas, A. Ranz, C. M. Xu, and H. Z. Pan, Mol. Biochem. Parasitol. 49:181-190, 1991), an improvement of their efficiency may be expected in the presence of a synthetic metalloporphyrin having the same activating role as endogenous heme. With the aim to boost the activity of antimalarial endoperoxide drugs, we were thus led to evaluate the in vitro and in vivo potentiation of natural and synthetic drugs of this family by a nontoxic and cheap metalloporphyrin. The potentiation of artemisinin, beta-artemether, and arteflene (Ro 42-1611) by synthetic heme models is reported. In vitro studies on the chloroquine-resistant Plasmodium falciparum FcB1-Columbia strain indicate a synergistic effect of the manganese complex of meso-tetrakis(4-sulfonatophenylporphyrin) (Mn-TPPS) on the activity of artemisinin or beta-artemether, whereas this heme model has no influence on the activity of arteflene. A significant synergistic effect on rodent malaria was also observed in vivo between artemisinin and Mn-TPPS using Plasmodium vinckei petteri strain.

Animals↗
PubMed2000

CD4(+) T-cell-mediated antiviral protection of the upper respiratory tract in BALB/c mice following parenteral immunization with a recombinant respiratory syncytial virus G protein fragment.

We analyzed the protective mechanisms induced against respiratory syncytial virus subgroup A (RSV-A) infection in the lower and upper respiratory tracts (LRT and URT) of BALB/c mice after intraperitoneal immunization with a recombinant fusion protein incorporating residues 130 to 230 of RSV-A G protein (BBG2Na). Mother-to-offspring antibody (Ab) transfer and adoptive transfer of BBG2Na-primed B cells into SCID mice demonstrated that Abs are important for LRT protection but have no effect on URT infection. In contrast, RSV-A clearance in the URT was achieved in a dose-dependent fashion after adoptive transfer of BBG2Na-primed T cells, while it was abolished in BBG2Na-immunized mice upon in vivo depletion of CD4(+), but not CD8(+), T cells. Furthermore, the conserved RSV-A G protein cysteines and residues 193 and 194, overlapping the recently identified T helper cell epitope on the G protein (P. W. Tebbey et al., J. Exp. Med. 188:1967-1972, 1998), were found to be essential for URT but not LRT protection. Taken together, these results demonstrate for the first time that CD4(+) T cells induced upon parenteral immunization with an RSV G protein fragment play a critical role in URT protection of normal mice against RSV infection.

Adoptive Transfer↗
PubMed2000

Comparison of myocardial contrast echocardiography with NC100100 and (99m)Tc sestamibi SPECT for detection of resting myocardial perfusion abnormalities in patients with previous myocardial infarction.

OBJECTIVE: To determine whether myocardial contrast echocardiography (MCE) following intravenous injection of perfluorocarbon microbubbles permits identification of resting myocardial perfusion abnormalities in patients who have had a previous myocardial infarction. PATIENTS AND INTERVENTIONS: 22 patients (mean (SD) age 66 (11) years) underwent MCE after intravenous injection of NC100100, a novel perfluorocarbon containing contrast agent, and resting (99m)Tc sestamibi single photon emission computed tomography (SPECT). With both methods, myocardial perfusion was graded semiquantitatively as 1 = normal, 0.5 = mild defect, and 0 = severe defect. RESULTS: Among the 203 normally contracting segments, 151 (74%) were normally perfused by SPECT and 145 (71%) by MCE. With SPECT, abnormal tracer uptake was mainly found among normally contracting segments from the inferior wall. By contrast, with MCE poor myocardial opacification was noted essentially among the normally contracting segments from the anterior and lateral walls. Of the 142 dysfunctional segments, 87 (61%) showed perfusion defects by SPECT, and 94 (66%) by MCE. With both methods, perfusion abnormalities were seen more frequently among akinetic than hypokinetic segments. MCE correctly identified 81/139 segments that exhibited a perfusion defect by SPECT (58%), and 135/206 segments that were normally perfused by SPECT (66%). Exclusion of segments with attenuation artefacts (defined as abnormal myocardial opacification or sestamibi uptake but normal contraction) by either MCE or SPECT improved both the sensitivity (76%) and the specificity (83%) of the detection of SPECT perfusion defects by MCE. CONCLUSIONS: The data suggest that MCE allows identification of myocardial perfusion abnormalities in patients who have had a previous myocardial infarction, provided that regional wall motion is simultaneously taken into account.

Aged↗
PubMed2000

Development of glutamatergic synaptic activity in cultured spinal neurons.

The development of glutamatergic synapses involves a sequence of events that are still not well understood. We have studied the time course of the development of glutamatergic synapses in cultured spinal neurons by characterizing spontaneous synaptic currents recorded from cells maintained in vitro for different times. At short times in culture (2 days in vitro; DIV2), spontaneous synaptic activity consisted almost solely of N-methyl-D-aspartate (NMDA) receptor (NMDAR) openings. In contrast, older neurons (DIV5 to DIV8) displayed clear alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR)-mediated synaptic currents, while the NMDAR-mediated activity remained small. Between 8 and 14 days in vitro there was a large increase in the density of synaptically activated NMDARs, although there was no significant increase in the density of the NMDAR-mediated current activated by exogenous glutamate. The results indicate that there is a switch in NMDAR targeting from somatic to synaptic regions during the course of the second in vitro week. Finally, our results support the conclusion that the spontaneous synaptic activity displayed in culture depends on ongoing NMDAR-mediated activity, even when the expression of synaptic NMDARs is low.

2-Amino-5-phosphonovalerate↗
PubMed2000

Localized childhood Hodgkin's disease: response-adapted chemotherapy with etoposide, bleomycin, vinblastine, and prednisone before low-dose radiation therapy-results of the French Society of Pediatric Oncology Study MDH90.

PURPOSE: The French Society of Pediatric Oncology MDH82 study demonstrated the effectiveness of 20 Gy irradiation of involved fields after doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) or mechlorethamine, vincristine, procarbazine, and prednisone/ABVD chemotherapy in children with localized Hodgkin's disease (HD). The response to primary chemotherapy was the only predictor of survival. To reduce long-term treatment complications without compromising efficacy, the MDH90 study was based on a new chemotherapy regimen devoid of both alkylating agents and anthracycline, followed by 20 Gy of radiotherapy (RT) for good responders. PATIENTS AND METHODS: From January 1990 to July 1996, 202 children were enrolled from 30 institutions. Good responders to four cycles of vinblastine, bleomycin, etoposide (VP16), and prednisone (VBVP) were given 20 Gy of RT and no further therapy. Poor responders were given vincristine, procarbazine, prednisone, and doxorubicin. After a second evaluation, good responders were given 20 Gy of RT, and poor responders were given 40 Gy of RT. RESULTS: One hundred seventy-one patients (85%) were good responders to VBVP, 27 (15%) were poor responders, and four did not respond. With a median follow-up of 74 months (range, 25 to 117 months), the 5-year overall survival rate (mean +/- SD) is 97.5% +/- 2.1%, and the event-free survival rate (mean +/- SD) is 91.1% +/- 1.8%. Significant predictors of worse event-free survival in multivariate analysis were hemoglobin < 10.5 g/L, "b" biologic class, and nodular sclerosis. CONCLUSION: These results suggest that most children with clinical stage I and II HD can be treated with chemotherapy devoid of alkylating agents and anthracycline, followed by low-dose RT.

Adolescent↗
PubMed1999

Engineering of a Staphylococcus carnosus surface display system by substitution or deletion of a Staphylococcus hyicus lipase propeptide.

Surface display of recombinant proteins on bacteria and phages has become an important topic in bioscience. A system for the display of heterologous proteins on the surface of Staphylococcus carnosus employs the secretion signal and propeptide from a Staphylococcus hyicus lipase for translocation and since the propeptide is of considerable size (207 amino acids) and not processed in S. carnosus, we have investigated the possibility to delete or substitute the propeptide for smaller protein domains, to thereby improve the surface display system. A set of new vectors was constructed and the surface expression of model proteins was investigated by various methods, including fluorescence-activated cell sorting. The results suggest that the propeptide region indeed can be deleted when proteins which are easily secretable are displayed. In contrast, the propeptide seems to be advantageous for translocation of inefficiently secreted proteins. Moreover, our study also presents a rational strategy for how to monitor the engineering efforts for the optimization of a surface display system.

Base Sequence↗
PubMed1999

Prevalence of herds with young sows seropositive to pseudorabies (Aujeszky's disease) in northern Belgium.

In Belgium, pseudorabies in swine has been the subject of a mandatory eradication programme since 1993. From December 1995 to February 1996, a survey was conducted in the five provinces of northern Belgium to estimate the provincial pseudorabies virus (PRV) herd seroprevalence. Seven hundred and twenty randomly selected herds were included in this survey. To detect recently infected animals, only young sows were sampled. The results show that 44% of these herds had an important number of PRV-seropositive young sows. The highest herd seroprevalence was observed in West Flanders (68%), followed by Antwerp (60%), East Flanders (43%), Limburg (18%), and Flemish Brabant (8%). Assuming a diagnostic test sensitivity and specificity of 95% and 99%, respectively, and a true PRV within-herd prevalence of 43%, the overall true PRV herd prevalence was estimated to be 35%. A logistic multiple-regression revealed that the presence of finishing pigs was associated with a two-fold increase in odds of a herd being seropositive (odds ratio (OR)=2.07, 95% confidence interval (CI) = 1.31-3.26); a breeding herd size > or =70 sows was associated with a four-fold increase in odds of a herd being seropositive (OR = 4.09, 95% CI = 2.18-7.67); a pig density in the municipality of >455 pigs/km2 was associated with a 10-fold increase in odds of a herd being seropositive (OR = 9.68, 95% CI = 5.17-18.12). No association was detected between the PRV herd seroprevalence and purchase policy of breeding pigs (purchased gilts, or use of homebred gilts only).

Animal Husbandry↗
PubMed1999

A surface-displayed cholera toxin B peptide improves antibody responses using food-grade staphylococci for mucosal subunit vaccine delivery.

The possibility of improving the antibody responses to a model streptococcal antigen, administered by intranasal immunization as surface-displayed on the food-grade bacterium Staphylococcus carnosus, by co-exposure of a peptide (CTBp) comprising amino acids 50-75 of the cholera toxin B subunit, was investigated. It was found that the introduction of the CTBp into the chimeric surface proteins, containing a serum albumin binding protein (ABP) from streptococcal protein G as model antigen, significantly increased serum IgG responses upon intranasal immunization. Similarly, elicited local IgA responses were also found to be improved. Furthermore, it was demonstrated that live delivery of the staphylococci was required to obtain this effect, since UV-irradiated or heat-killed bacteria exposing the same chimeric surface proteins did not show increased anti-ABP IgG responses.

Adjuvants, Immunologic↗
PubMed1999

Prognostic value of myocardial ischemia and viability in patients with chronic left ventricular ischemic dysfunction.

BACKGROUND: Previous studies showed that thallium scintigraphy and dobutamine echocardiography were accurate, noninvasive ways of predicting contractile recovery after revascularization in patients with left ventricular (LV) dysfunction. However, the prognostic impact of such methods remains uncertain. METHODS AND RESULTS: We prospectively studied 137 consecutive patients with coronary disease and LV dysfunction who underwent exercise-redistribution-reinjection thallium scintigraphy and dobutamine echocardiography to identify myocardial ischemia and viability. A total of 94 patients subsequently underwent revascularization, and 43 underwent medical treatment. The primary endpoint was cardiac mortality, and mean follow-up was 33+/-10 months. Twenty-four patients died of cardiac causes. By Cox's regression analysis, long-term survival was related to the extent of coronary disease, the presence of diabetes, type of treatment, the presence of ischemic myocardium as determined by thallium scintigraphy, and the presence of viable myocardium as determined by both tests. Three-year survival was greater in patients with ischemic myocardium (as determined by thallium scintigraphy) or viable myocardium (as determined by both tests) who underwent revascularization than in the other groups (P=0.018 with thallium; P<0.001 with dobutamine). Subgroup analyses indicated that among patients with 1- or 2-vessel disease, only those with ischemic or viable myocardium improved survival after revascularization, whereas in patients with 3-vessel or left main diseases, revascularization always improved survival, albeit more in the presence of ischemic or viable myocardium. CONCLUSIONS: Among the parameters commonly available in patients with LV ischemic dysfunction, the presence of ischemic myocardium (as determined by thallium scintigraphy) and that of viable myocardium (as determined by dobutamine echocardiography) are independent predictors of subsequent mortality. These observations may be useful in the preoperative selection of patients for revascularization.

Aged↗
PubMed1999

Changes in occipital cortex activity in early blind humans using a sensory substitution device.

The purpose of this study was to investigate the neural networks involved when using an ultrasonic echolocation device, which is a substitution prosthesis for blindness through audition. Using positron emission tomography with fluorodeoxyglucose, regional brain glucose metabolism was measured in the occipital cortex of early blind subjects and blindfolded controls who were trained to use this prosthesis. All subjects were studied under two different activation conditions: (i) during an auditory control task, (ii) using the ultrasonic echolocation device in a spatial distance and direction evaluation task. Results showed that the abnormally high metabolism already observed in early blind occipital cortex at rest [C. Veraart, A.G. De Volder, M.C. Wanet-Defalque, A. Bol, C. Michel, A.M. Goffinet, Glucose utilization in human visual cortex is, respectively elevated and decreased in early versus late blindness, Brain Res. 510 (1990) 115-121.] was also present during the control task and showed a trend to further increase during the use of the ultrasonic echolocation device. This specific difference in occipital cortex activity between the two tasks was not observed in control subjects. The metabolic recruitment of the occipital cortex in early blind subjects using a substitution prosthesis could reflect a concurrent stimulation of functional cross-modal sensory connections. Given the unfamiliarity of the task, it could be interpreted as a prolonged plasticity in the occipital cortex early deprived of visual afferences.

Acoustic Stimulation↗
PubMed1999

Surface display of functional fibronectin-binding domains on Staphylococcus carnosus.

The surface expression in Staphylococcus carnosus of three different fibronectin binding domains (FNBDs), derived from fibronectin binding proteins of Streptococcus dysgalactiae and Staphylococcus aureus, has been investigated. Surface localization of the chimeric proteins containing the FNBDs was demonstrated. All three surface-displayed FNBDs were demonstrated to bind fibronectin in whole-cell enzyme-linked binding assays. Furthermore, for one of the constructs, intranasal immunizations with the recombinant bacteria resulted in improved antibody responses to a model immunogen present within the chimeric surface proteins. The implications of the results for the design of live bacterial vaccine delivery systems are discussed.

Adhesins, Bacterial↗
PubMed1999

Relation of exercise capacity to left ventricular systolic function and diastolic filling in idiopathic or ischemic dilated cardiomyopathy.

Although exercise intolerance is a cardinal symptom of patients with dilated cardiomyopathy (DC) and heart failure, the factors that limit exercise capacity in these patients remain a matter of debate. To assess the contribution of left ventricular (LV) diastolic filling to the variable exercise capacity of patients with DC, we studied 47 patients (60 +/- 12 years) with DC in stable mild-to-moderate heart failure with a mean LV ejection fraction of 28%. Exercise capacity was measured as total body peak oxygen consumption (VO2) during symptom-limited bicycle (10 W/min) and treadmill (modified Bruce protocol) exercise. LV systolic function and diastolic filling were assessed at rest before each exercise by M-mode, Doppler echocardiography, and radionuclide ventriculography. As expected, treadmill exercise always yielded higher peak VO2 than bicycle exercise (21 +/- 6 vs 18 +/- 5 ml/kg/min, range 12 to 35 and 7 to 30 ml/kg/min, respectively, p <0.001). Both of these VO2 measurements were highly reproducible (R = 0.98). With univariate analysis, close correlations were found between peak VO2 (with either exercise modalities) and Doppler indexes of LV diastolic filling, as well as with the radionuclide LV ejection fraction. Stepwise multiple regression analysis identified 3 nonexercise variables as independent correlates of peak VO2, of which the most powerful was the E/A ratio (multiple r2 = 0.38, p <0.0001), followed by peak A velocity (r2 = 0.54, p <0.0001) and mitral regurgitation grade (r2 = 0.58, p = 0.024). In conclusion, our data indicate that in patients with DC, peak VO2 is better correlated to diastolic filling rather than systolic LV function.

Adult↗