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Biomedical subjects

J G LeBlanc

Publications and source records attributed to J G LeBlanc.

At least 19 recordsLinked to original sources
PubMed2006

A thermostable alpha-galactosidase from Lactobacillus fermentum CRL722: genetic characterization and main properties.

Alpha-galactosidase (alpha-Gal) enzyme, which is encoded by the melA gene hydrolyzes alpha-1,6 galactoside linkages found in sugars, such as raffinose and stachyose. These alpha-galacto-oligosaccharides (alpha-GOS), which are found in large quantities in vegetables, such as soy, can cause gastrointestinal disorders in sensitive individuals because monogastric animals (including humans) do not posses alpha-Gal in the gut. The use of microbial alpha-Gal is a promising alternative to eliminate alpha-GOS in soy-derived products. Using degenerate primers, the melA gene from Lactobacillus (L.) fermentum CRL722 was identified. The complete genomic sequence of melA (2223 bp), and of the genes flanking melA, were obtained using a combination of polymerase chain reaction-based techniques, and showed strong similarities with the alpha-Gal gene of thermophilic microorganisms. The alpha-Gal gene from L. fermentum CRL722 was cloned and the protein purified from cell-free extracts of the native and recombinant strains using various techniques (ion exchange chromatography, salt precipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and ultra-filtration); Its main biochemical properties were determined. The enzyme was active at moderately high temperatures (55 degrees C) and stable at wide ranges of temperatures and pH. The thermostable alpha-Gal from L. fermentum CRL722 could thus be used for technological applications, such as the removal of alpha-GOS found in soy products. The complete melA gene could also be inserted in other micro-organisms, that can survive in the harsh conditions of the gut to degrade alpha-GOS in situ. Both strategies would improve the overall acceptability of soy-derived products by improving their nutritional value.

Enzyme Stability↗
PubMed2005

Ingestion of milk fermented by genetically modified Lactococcus lactis improves the riboflavin status of deficient rats.

Riboflavin deficiency is common in many parts of the world, particularly in developing countries. The use of riboflavin-producing strains in the production of dairy products such as fermented milks, yogurts, and cheeses is feasible and economically attractive because it would decrease the costs involved during conventional vitamin fortification and satisfy consumer demands for healthier foods. The present study was conducted to assess in a rat bioassay the response of administration of milk fermented by modified Lactococcus lactis on the riboflavin status of deficient rats. Rats were fed a riboflavin-deficient diet during 21 d after which this same diet was supplemented with milk fermented by Lactoccus lactis pNZGBAH, a strain that overproduces riboflavin during fermentation. The novel fermented product, with increased levels of riboflavin, was able to eliminate most physiological manifestations of ariboflavinosis, such as stunted growth, elevated erythrocyte glutathione reductase activation coefficient values and hepatomegaly, that were observed using a riboflavin depletion-repletion model, whereas a product fermented with a nonriboflavin-producing strain did not show similar results. A safety assessment of this modified strain was performed by feeding rodents with the modified strain daily for 4 wk. This strain caused no detectable secondary effects. These results pave the way for analyzing the effect of similar riboflavin-overproducing lactic acid bacteria in human trials. The regular consumption of products with increased levels of riboflavin could help prevent deficiencies of this essential vitamin.

Animals↗
PubMed2004

Effect of pH on Lactobacillus fermentum growth, raffinose removal, alpha-galactosidase activity and fermentation products.

In this study, the behaviour of Lactobacillus fermentum CRL 722 and CRL 251 were evaluated under different pH conditions (pH 6.0, 5.5, 5.0, 4.5) and without pH control. Growth was similar under all conditions assayed except at pH 4.5. These microorganisms were able to eliminate raffinose, a nondigestible alpha-oligosaccharide (NDO) found in soy products, showing a consumption rate of 0.25 g l(-1) h(-1) (pH 6.0-5.0). The removal of raffinose was due to the high alpha-galactosidase (alpha-gal) activities of these lactic acid bacteria, which was highest at pH 5.5 (5.0 U/ml). The yield of organic acids produced during raffinose consumption was also highest at this pH. The results of this study will allow selection of the optimum growth conditions of L. fermentum with elevated levels of alpha-gal to be used in the reduction of NDO in soy products when used as starter cultures.

Fermentation↗
PubMed2004

Reduction of alpha-galactooligosaccharides in soyamilk by Lactobacillus fermentum CRL 722: in vitro and in vivo evaluation of fermented soyamilk.

AIMS: Consumption of soya-derived products has been hampered by the presence of alpha-galactooligosaccharides (alpha-GOS) because mammals lack pancreatic alpha-galactosidase (alpha-Gal) which is necessary for their hydrolysis. These sugars thus reach the large intestine causing gastrointestinal disorders in sensitive individuals. The use of lactic acid bacteria (LAB) expressing alpha-Gal is a promising solution for the degradation of alpha-GOS in soyamilk. METHODS AND RESULTS: The capacity of the LAB Lactobacillus fermentum CRL 722 to properly degrade alpha-GOS was studied in vitro using controlled fermentation conditions and in vivo using a rat model. Lactobacillus fermentum CRL 722 was able to grow on commercial soyamilk and completely eliminated stachyose and raffinose during fermentation because of its high alpha-Gal activity. Rats fed soyamilk fermented by this LAB had smaller caecums compared with rats fed unfermented soyamilk. CONCLUSIONS: Soyamilk fermentation by Lact. fermentum CRL 722 results in the reduction of alpha-GOS concentrations in soyamilk, thus eliminating possible undesirable physiological effects normally associated with its consumption. SIGNIFICANCE AND IMPACT OF THE STUDY: Fermentation with Lact. fermentum CRL 722 could prevent gastrointestinal disorders in sensitive individuals normally associated with the consumption of soya-based products. This LAB could thus be used in the elaboration of novel fermented vegetable products which better suit the digestive capacities of consumers.

Animals↗
PubMed2002

Immunomodulating effects of peptidic fractions issued from milk fermented with Lactobacillus helveticus.

The effect of peptides released during the fermentation of milk on the humoral immune system and on fibrosarcoma growth was studied. Lactobacillus helveticus was able to release peptidic compounds during milk fermentation due to its high proteolytic activity, as was shown by the degree of proteolysis and size-exclusion HPLC elution profiles. Three fractions of these compounds were separated and fed to mice during different periods (2, 5, and 7 d). The humoral immune response was assessed by following the number of IgA-secreting cells, and the antitumor activity was monitored by studying the regression of subcutaneously implanted fibrosarcomas. Feeding during 2 and 7 d with the medium-sized fraction (Fraction II) significantly increased the IgA-producing cells in the intestines, whereas feeding with the large compound fraction (Fraction I) during 5 d and the small compound fraction (Fraction III) during all three feeding periods provided similar increases. A double dose of Fraction II showed the highest IgA-producing cell count. The increase by Fraction III was shown to be caused by the presence of L-Tryptophan. Fraction II significantly decreased the size of fibrosarcoma when previously fed during 7 d, and feeding with Fraction I during 5 d decreased significantly its size after 35 d of growth. Although the mechanisms by which lactic acid bacteria enhance the immune system are not clear, this study clearly shows that bioactive compounds released in fermented milks contribute to the immunoenhancing and antitumor properties of these products. The release of bioactive peptides by lactic acid bacteria can have important implications on the modulation of the cellular immune response.

Adjuvants, Immunologic↗
PubMed2000

Effects of propofol on cerebral oxygenation during cardiopulmonary bypass in children.

PURPOSE: Neurologic complications occur following cardiopulmonary bypass surgery. We conducted a randomized, controlled, single-blind study to determine the effect of propofol on the redox status of cytaa3, and to evaluate its potential for decreasing neurologic complications. METHODS AND MATERIALS: Twenty-four children (median age: 3.3 yr; median weight: 14.4 kg) scheduled for elective cardiopulmonary bypass surgery were assigned to either the experimental group (Group P, given sufficient propofol to eliminate brain electrical activity as measured on EEG (i.e. burst suppression)) or the control group (Group C, no propofol). Near infrared spectroscopy data were collected at one-second intervals throughout the surgical procedures. Pre- and postoperative neurologic examinations were completed by a physician blinded to the group to which the patient was assigned. Change in cytochrome aa3 data at 10-min intervals (10, 20, 30, 40 min) following start of bypass were compared between groups by repeated measures analysis of variance. RESULTS: The patterns of change in redox state of cytochrome were different between the two groups (P < 0.002). The pattern of change within Group P was similar to that in hypothermic patients in Group C. There were correlations between change in cytaa3 redox status and temperature in the control subjects. There were no gross neurologic complications in either group. CONCLUSIONS: Propofol appears to stabilize the energy supply/demand equilibrium of the brain during cardiopulmonary bypass surgery and thus theoretically could reduce the incidence or severity of neurologic complications.

Anesthetics, Intravenous↗
PubMed1998

Risks of repeat sternotomy in pediatric cardiac operations.

BACKGROUND: Repeat sternotomy has been associated with increased perioperative risks. METHODS: We reviewed 165 patients undergoing 192 repeat sternotomies between January 1985 and January 1997 (group 1) and a control group of 184 patients (group 2). The operations in group 1 were valve procedures in 94 patients, Fontan procedure in 46, ventricular septal defect closure in 10, pulmonary arterioplasty in 17, and others in 25; in group 2 ventricular or atrial septal defect closure in 120 patients, tetralogy of Fallot repair in 26, valve procedures in 16, bidirectional Glenn anastomosis in 7, repair of transposition of the great arteries in 7, pulmonary arterioplasty in 4, and others in 4. RESULTS: The hospital mortality was 2.6% in group 1 and 3.8% in group 2. Cardiac laceration occurred in 10 of 192 patients (5.2%), requiring emergent femorofemoral bypass in 6 patients. Two patients sustained an air embolism that was successfully treated with a hyperbaric chamber. Median total blood loss and requirements were not significantly different between the two groups. The length of stay in the intensive care unit and in the hospital were 4 days (range, 1 to 80 days) and 11 days (range, 1 to 135 days) in group 1, and 2 days (range, 1 to 87 days) and 7 days (range, 1 to 131 days) in group 2 (p < 0.02 and p < 0.002, respectively). The rate of complications was not significantly different in group 1 versus group 2. Overall survival was 97% (group 1) and 95% (group 2) at 120 months' follow-up (not significant). CONCLUSIONS: With careful surgical technique and judicious use of femorofemoral bypass, the risk of repeat sternotomy is minimized.

Adolescent↗
PubMed1998

Intermediate follow-up of right ventricular outflow tract reconstruction with allograft conduits.

BACKGROUND: Allograft conduits are among many varieties of material used for right ventricular outflow tract reconstruction. They invariably need to be replaced due to growth of the patient or conduit failure. METHODS: From June 1984 to June 1996, a total of 76 patients underwent reconstruction of the right ventricular outflow tract with an allograft conduit: 51 aortic and 25 pulmonary. The median age, weight and conduit size at surgery were 37 months (range, 0.2 to 228 months), 12.4 kg (range, 2.9 to 61.4 kg), and 17 mm (range, 8 to 26 mm), respectively. RESULTS: The hospital mortality was 5.3% (4 of 76 patients) and 2 patients died at 9 and 78 months follow-up. The median follow-up was 61 months (range, 2 to 132 months). Reoperation was necessary in 22 patients (28.9%) at a median interval of 50.5 months (range, 3 to 109 months) and the median conduit size was 21 mm (range, 12 to 23 months). There was no mortality. Freedom from reoperation at 64 months was 49.5% for conduits 15 mm and smaller, and 73.3% for conduits 16 mm and larger. Analysis by age shows freedom from reoperation at 64 months of 49.4% and 74.5% for patients younger than and older than 2 years, respectively. At 54 months there was no statistical difference in freedom from reoperation between pulmonary and aortic allografts. CONCLUSION: Right ventricular outflow tract reconstruction with allograft conduits results in a high reoperation rate at 4 years but provides significantly longer freedom from reoperation with conduits larger than 15 mm or in patients over 24 months of age.

Actuarial Analysis↗
PubMed1998

Pediatric cardiac surgery in the 1990s.

Future developments in the repair of these complex anomalies will rely heavily on a complete understanding of present results, which can be achieved only with attention to detail and rigorous standards. Results must be continually updated and management changes carefully planned and then critically examined for significant differences. Thus, the day-to-day care of patients with congenital heart disease must withstand careful scrutiny, both for consistency and for end results.

Angioplasty, Balloon↗
PubMed1997

Effect of glutamate-aspartate reperfusion on postischemic neonatal myocardium.

OBJECTIVE: We postulated that L-glutamate- and L-aspartate-enriched perfusate would improve functional recovery of postischemic neonatal rabbit hearts. METHODS: Isolated working neonatal rabbit hearts were perfused with Krebs-Henseleit buffer and then subjected to 1 hour of hypothermic cardioplegic arrest with St. Thomas' Hospital solution. Hearts were then reperfused with L-glutamate- and L-aspartate-enriched (20 mmol/L) Krebs-Henseleit buffer (AA-enriched Krebs-Henseleit buffer). Hearts reperfused with Krebs-Henseleit buffer alone acted as controls (experiment A). Another group of hearts underwent a similar protocol but were reperfused with the AA-enriched Krebs-Henseleit buffer with correction of the sodium content (experiment B). RESULTS: Hearts reperfused with AA-enriched Krebs-Henseleit buffer showed a significant decrease in aortic flow at both 15 (p = 0.04) and 30 (p = 0.025) minutes compared with controls. Arrhythmias were frequent. Sodium content of the AA-enriched Krebs-Henseleit buffer was 174 +/- 0.5 mmol/L. In experiment B, hearts reperfused with the AA-enriched Krebs-Henseleit buffer with correction of the sodium content exhibited no difference in aortic flow and cardiac output at either 15 or 30 minutes (p = 0.95 and 0.5 and 0.48 and 0.78, respectively) compared with controls. No arrhythmias were observed. The sodium content of the AA-enriched Krebs-Henseleit buffer was 146 +/- 0.7 mmol/L. CONCLUSIONS: A beneficial effect on functional recovery of neonatal hearts reperfused with AA-enriched Krebs-Henseleit buffer was not demonstrated.

Animals↗
PubMed1997

Peritoneal dialysis in children after cardiopulmonary bypass.

OBJECTIVE: We reviewed 5 years' experience with peritoneal dialysis in children with acute renal failure after cardiac operations. We hypothesized that peritoneal dialysis is safe and effective in children with low-output cardiac failure after cardiac operations. RESULTS: Mortality in these patients with renal failure (n = 32) was 46.9%. Fluid removed by peritoneal dialysis was 48 +/- 28 ml/kg per 24 hours. Most complications of peritoneal dialysis were minor, hyperglycemia being the most frequent (53.1%). Peritoneal infection was suspected in 25%. Bowel perforation developed in two patients. None of the complications required early termination of dialysis. Hemodynamics and pulmonary function improved continuously during the study period. CONCLUSION: The early institution of peritoneal dialysis in acute renal failure and low cardiac output after cardiac operations not only removes fluid, thus easing fluid restriction, but may also improve cardiopulmonary function.

Acute Kidney Injury↗
PubMed1995

Influence of bidirectional superior cavopulmonary anastomosis on pulmonary arterial growth.

Right-sided BSCA provides for satisfactory pulmonary arterial growth in infants and children with complex congenital heart defects, and it could enhance the growth of a small right pulmonary artery. The growth of the left pulmonary artery, particularly in younger patients, needs close attention to confirm the safe role of BSCA in long-term palliation.

Anastomosis, Surgical↗
PubMed1995

Influence of competitive pulmonary blood flow on the bidirectional superior cavopulmonary shunt. A multi-institutional study.

BACKGROUND: It is common practice to interrupt all alternative sources of pulmonary blood flow ("competitive flow") at the time of a bidirectional superior cavopulmonary anastomosis (BCPA), although the merits of this have not been systematically studied. METHODS AND RESULTS: We reviewed the early and medium-term clinical and hemodynamic findings in 108 consecutive patients 3 weeks to 25 years old (median, 1.9 years) undergoing BCPA at one of three institutions. Preoperatively, pulmonary blood flow was dependent on antegrade ventricular flow (n = 50), systemic-to-pulmonary shunts (n = 33), or mixed sources (n = 25). Postoperatively, competitive sources of pulmonary blood flow were left patent in 43 of 108 patients (40%). There were four early (3.7%) and four late deaths, none related to persistence of competitive flow. After BCPA, patients with competitive flow had significantly higher systemic oxygen saturations at 1 hour (85% versus 79%), 24 hours (84% versus 78%), and at hospital discharge (84% versus 78%) and required a shorter period of artificial ventilation (median, 9 versus 24 hours) and intensive care (median, 2 versus 4 days). Oxygen saturations at late follow-up (median, 2.8 years; range, 1 to 7) did not differ (83% versus 82%). No patient developed pulmonary arteriovenous malformations. CONCLUSIONS: Competitive flow is well tolerated in the short and medium term after BCPA, and early postoperative systemic oxygen saturations are improved. The long-term influence of competitive flow on pulmonary arterial growth, arteriovenous malformation development, and ventricular function warrants investigation.

Adolescent↗
PubMed1995

Pulmonary artery banding is not contraindicated in double inlet left ventricle with transposition and aortic arch obstruction.

It has been widely stated that pulmonary artery banding (PAB) is contraindicated in the setting of double inlet left ventricle with transposition of the great vessels (DILV/TGA), especially if aortic arch obstruction is present. We postulated that the poor results for this condition reflect the tendency to leave the band in place long-term without early recognition and relief of subaortic stenosis (SAS). Short-term PAB with early relief of SAS remains an attractive option compared to a neonatal "Norwood" strategy. We reviewed our results applying this approach to 18 consecutive infants presenting since 1980 with DILV/TGA and an obstructive anomaly of the aortic arch (coarctation 16, interruption or atresia 2). Four of the infants (22%) were considered to have important SAS at presentation. One underwent neonatal aortopulmonary connection and died. The remaining 17 patients underwent arch repair with PAB (median age 1.4 weeks; range 2 days-22 weeks) with one early death. The 16 survivors have been followed for 5.6 +/- 3.7 years. All but one ultimately developed SAS. Relief of SAS was performed in 15 patients (median age 8 months) using a proximal aortopulmonary anastomosis. There were two early deaths, and one late death. Thirteen of the 18 patients (72%) are alive and well, and 12 have achieved Fontan repair or bidirectional superior cavopulmonary anastomosis (BCPA) with persistent relief of SAS. Most patients with DILV/TGA and aortic arch obstruction will tolerate temporary PAB with adequate protection of the pulmonary vascular bed. Our current approach (in the absence of severe SAS at presentation) is PAB at the time of arch repair, followed by careful surveillance for, and early relief of, SAS combined with BCPA in infancy.

Anastomosis, Surgical↗
PubMed1994

Systolic and diastolic function in tricuspid valve atresia before the Fontan operation.

Systolic and diastolic function were assessed at preoperative cardiac catheterization in 6 patients with classic tricuspid atresia and were compared with those in control subjects. All patients had systemic-to-pulmonary shunts. Left ventricular end-systolic and end-diastolic volumes and masses were significantly larger in the patient group; stroke volume and the ratio of volume to mass were also higher, but not significantly. Mean end-diastolic, peak systolic and end-systolic pressures were similar. Mean stress at end-systole and peak systole were significantly higher in the patient group. Operant chamber stiffness tended to be lower than normal, but was not statistically significant, and myocardial stiffness was normal for the patient group also. Indexes of systolic function were compared. The rate-corrected mean velocity of fiber shortening in the patient group was lower and its relation with stress at end-systole was variable with 4 abnormal patients. The ratio of stress at end-systole/end-systolic volume was significantly lower in patients. The duration of hospital stay did not correlate with end-diastolic volume or any parameter. Thus, this study found abnormalities of load-dependent and independent indexes of systolic function with normal diastolic function in young preoperative patients with tricuspid atresia.

Cardiac Catheterization↗
PubMed1993

Giant hydatid lung cysts in the Canadian northwest: outcome of conservative treatment in three children.

Hydatid lung disease due to Echinococcus granulosus in the Canadian northwest and Alaska is often asymptomatic and usually benign. We reviewed the course and outcome of three children with giant hydatid lung cyst seen over a 2-year period. All were North American Indian children aged 9 to 12 years who presented with cough, fever, and chest pain. One had a rash. There was a history of exposure to domestic dogs who had been fed moose entrails in each case. Chest x-rays showed solitary lung cysts with air-fluid levels, from 6 cm to 12 cm in diameter. Aspiration of each cyst demonstrated Echinococcus hooklets and protoscolices. Serology was unhelpful, being negative in two cases. Transient pneumonitis and pneumothorax were seen as complications of needle aspiration. Two cysts gradually resolved over the following 6 months. One child returned after 9 months with a lung abscess due to superimposed infection of the cyst remnant with Haemophilus influenzae, and eventually required lobectomy. The existence of an endemic benign variant of E granulosus in Canada is not widely known, and it is important to distinguish it from the more aggressive pastoral form of the disease seen in immigrants from sheep-rearing countries. The native Canadian disease usually resolves spontaneously, does not cause anaphylaxis, and does not implant daughter cysts if spilled. Surgical treatment should be avoided except for complications such as secondary bacterial infection.

Animals↗
PubMed1993

Antiplatelet therapy in children with left-sided mechanical prostheses.

Valve replacement in children has always been associated with a high mortality, outgrowth of the prosthetic valve and difficulty in managing anticoagulation. Between January 1985 and April 1991, 20 patients (14 males and 6 females) underwent replacement of a left-sided cardiac valve. The median age at diagnosis was 21.6 months (1 to 120 months) and the median age at surgery was 85 months (11 to 213 months). Six patients were under 4 years of age. The site of valve replacement was aortic in 11 patients and left atrioventricular (AV) valve in 9 patients. The indications for aortic valve replacement were stenosis (6) and incompetence (5). The left AV valve was replaced in three patients following repair of AV septal defect, in one patient with corrected transposition of the great arteries (LTGA), in one patient with severe dysplasia and insufficiency, and in four patients for congenital mitral stenosis. A Bjork-Shiley prosthesis was used in three mitral and one aortic position, all the other patients receiving a St. Jude prosthesis: six mitral and ten aortic. All patients were anticoagulated (warfarin) for 3 months post implantation and then switched to a regimen of aspirin and persantine. There was no early or late death. Median follow-up was 12.3 months (4 to 72 months). Total follow-up was 59 patient-years or 708 months. There was one incident of thromboembolism (1.7%/patient-year) and four instances of bleeding (6.8%/patient-year). There was no valve thrombosis. Our regime of early warfarin followed by long-term antiplatelet therapy has been associated with a low incidence of thromboembolism and no valve thrombosis.

Adolescent↗