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Biomedical subjects

G Gagnon

Publications and source records attributed to G Gagnon.

At least 19 recordsLinked to original sources
PubMed2005

Platelet-rich plasmas: growth factor content and roles in wound healing.

UNLABELLED: Platelet-rich plasmas (PRPs) are used in a variety of clinical applications, based on the premise that higher growth factor content should promote better healing. In this study, we have determined the effects of calcium and thrombin on the release of EGF, TGF-alpha, IGF-1, Ang-2 and IL-1beta from PRPs, and assessed the mitogenic potential of PRP supernatants on osteoblast and endothelial cell division. ELISA assays indicate that (i) mean growth factor concentrations vary from traces (TGF-alpha) to 5.5 ng/mL (IGF-1), (ii) there are significant variations in growth factor concentrations between individuals, and (iii) calcium and thrombin regulate growth factor release, synthesis, and/or degradation in stereotyped patterns that are specific to each growth factor. PRP supernatants promote strong osteoblast and endothelial cell divisions, supporting the concept that PRPs may be beneficial in wound healing. ABBREVIATIONS: PRPs, platelet-rich plasmas; GFs, growth factors; EGF, epidermal growth factor; TGF-alpha, transforming growth factor-alpha; IGF-1, insulin-like growth factor-1; Ang-2, angiopoietin-2; IL-1beta, interleukin-1 beta; HUVECs, human umbilical vein endothelial cells; hFOB 1.19, human fetal osteoblasts; and FBS, fetal bovine serum.

Angiopoietin-2↗
PubMed2004

Effects of calcium and thrombin on growth factor release from platelet concentrates: kinetics and regulation of endothelial cell proliferation.

Platelet concentrates (PCs) constitute new biological mediators used in osseous reconstructive surgery. In this study, we assessed (i) the effects of various concentrations of calcium and thrombin on the kinetics of platelet-derived growth factor (PDGF-BB), transforming growth factor-beta1(TGF-beta 1), basic fibroblast growth factor (bFGF), and vascular endothelial growth factor (VEGF) release by PCs and (ii) the contribution of PC supernatants to endothelial cell proliferation. Our results indicate that high concentrations of calcium (Ca) and thrombin (Thr) trigger an immediate and significant increase in bFGF, TGF-beta 1 and PDGF-BB concentrations. Thereafter, PDGF-BB, VEGF and TGF-beta 1 levels remained generally constant over a 6-day period while a decrease in bFGF concentrations was noted after 24h. Lower Ca and Thr concentrations tended to reduce and delay growth factors release from PCs. Endothelial cell proliferation was greatly enhanced with PC supernatants (mean: 20-fold increase). This was especially evident when endothelial cells were treated with supernatants harvested early after PC treatment with high concentrations of Ca and Thr or later after PC treatment with low Ca and Thr concentrations. Additional research aiming to measure the effects of Ca and Thr on bone formation in vivo is needed.

Adaptation, Physiological↗
PubMed2001

Energy landscape view of fracture and avalanches in disordered materials.

Molecular simulations are carried out to probe how strain-induced changes in the energy landscape are related to fracture processes in disordered systems. The simulations address a two-dimensional system that consists of 9952 particles with a distribution of sizes, and the changes in the structure and properties with strain are determined with the system constrained to an energy minimum. As the system is strained, local minima of the energy landscape are found to flatten out and disappear, which causes discontinuous structural rearrangements. These structural rearrangements, which correspond to avalanche events, lead to void nucleation and crack growth in discrete steps.

Journal Article↗
PubMed1995

Regulation of ptsH and ptsI gene expression in Streptococcus salivarius ATCC 25975.

The transcriptional regulation of the Streptococcus salivarius ptsH and ptsI genes coding for the general energy-coupling proteins HPr and enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system were investigated. These genes form an operon with the gene order ptsH-ptsI. Three distinct mRNA species were detected: a 0.5 kb transcript specific for ptsH, and two long transcripts (2.2 and 2.4 kb) covering the whole pts operon. Transcription of all these mRNAs initiated at the same nucleotide located 9 bp downstream from a promoter located immediately upstream from the ptsH gene. The presence of a high-energy stem-loop structure (T0) located at the beginning of ptsI was responsible for the premature transcription termination generating the 0.5 kb ptsH-specific transcript. The long transcripts ended in the poly(U) region of two rho-independent-like terminators (T1 and T2) at the 3' end of ptsI. Studies with a 2-deoxyglucose-resistant spontaneous mutant of S. salivarius (L26) that produces an HPr-EI fusion protein suggest that the regulation of HPr and EI expression involves transcriptional as well as translational mechanisms.

Amino Acid Sequence↗
PubMed1994

IS1139 from Streptococcus salivarius: identification and characterization of an insertion sequence-like element related to mobile DNA elements from gram-negative bacteria.

An insertion sequence-like element, IS1139, was cloned and sequenced from Streptococcus salivarius ATCC 25975 chromosome. This insertion sequence-like element is 1168 bp long and is delimited by inverted repeats of 29 bp and by a duplicated sequence of 6 bp. This IS possesses an open reading frame that codes for a putative transposase of 339 amino acids which has, respectively, 94, 35, 33, and 30% amino-acid identity with the transposases of IS1161 from S. salivarius ATCC 25975, IS4351 from Bacteroides fragilis, IS30 from Escherichia coli, and IS1086 from Alcaligenes eutrophus. Sequence analysis revealed that these transposases may have evolved from a common ancestral gene. Southern hybridization of restriction endonuclease-digested genomic DNA from 21 strains of oral streptococci, using a probe specific to the transposase-encoding gene (tnpA), revealed that IS1139 is found in two strains of S. salivarius, ATCC 25975 and ATCC 13419, in eight and two copies, respectively.

Alcaligenes↗
PubMed1994

Positive selection for resistance to 2-deoxyglucose gives rise, in Streptococcus salivarius, to seven classes of pleiotropic mutants, including ptsH and ptsI missense mutants.

We have used the toxic non-metabolizable glucose/mannose analogue 2-deoxyglucose to isolate a comprehensive collection of mutants of the phosphoenolpyruvate:sugar phosphotransferase system from Streptococcus salivarius. To increase the range of possible mutations, we isolated spontaneous mutants on different media containing 2-deoxyglucose and various metabolizable sugars, either lactose, melibiose, galactose or fructose. We found that the frequency at which 2-deoxyglucose-resistant mutants were isolated varied according to the growth substrate. The highest frequency was obtained with the combination galactose and 2-deoxyglucose and was 15-fold higher than the rate observed with the mixture melibiose and 2-deoxyglucose, the combination that gave the lowest frequency. By combining results from: (i) Western blot analysis of IIIMan, a specific component of the phosphoenolpyruvate:mannose phosphotransferase system in S. salivarius; (ii) rocket immunoelectrophoresis of HPr and EI, the two general energy-coupling proteins of the phosphotransferase system; and (iii) from gene sequencing, mutants could be assigned to seven classes.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacterial Proteins↗
PubMed1994

Properties of a Streptococcus salivarius spontaneous mutant in which the methionine at position 48 in the protein HPr has been replaced by a valine.

HPr is a protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) that participates in the concomitant transport and phosphorylation of sugars in bacteria. In gram-positive bacteria, HPr is also reversibly phosphorylated at a seryl residue at position 46 (Ser-46) by a metabolite-activated ATP-dependent kinase and a Pi-dependent HPr(Ser-P) phosphatase. We report in this article the isolation of a spontaneous mutant (mutant A66) from a streptococcus (Streptococcus salivarius) in which the methionine at position 48 (Met-48) in the protein HPr has been replaced by a valine (Val). The mutation inhibited the phosphorylation of HPr on Ser-46 by the ATP-dependent kinase but did not prevent phosphorylation of HPr by enzyme I or the phosphorylation of enzyme II complexes by HPr(His-P). The results, however, suggested that replacement of Met-48 by Val decreased the affinity of enzyme I for HPr or the affinity of enzyme II proteins for HPr(His-P) or both. Characterization of mutant A66 demonstrated that it has pleiotropic properties, including the lack of IIILman, a specific protein of the mannose PTS; decreased levels of HPr; derepression of some cytoplasmic proteins; reduced growth on PTS as well as on non-PTS sugars; and aberrant growth in medium containing a mixture of sugars.

Bacterial Proteins↗
PubMed1994

Comparison between peak expiratory flow rates (PEFR) and FEV1 in the monitoring of asthmatic subjects at an outpatient clinic.

Peak expiratory flow rate (PEFR) monitoring is often used alone in evaluating bronchial caliber and the response to a bronchodilator in the assessment of asthmatic subjects. A 15% change in airway caliber has been proposed as the criteria for modifying treatment. Our aim was to determine if changes in PEFR from one visit to the next can adequately evaluate changes in airway caliber as assessed by FEV1, which is considered the gold standard, and to identify the characteristics of subjects whose evaluations were inadequate. This was a retrospective study of 197 asthmatic subjects seen regularly at an outpatient clinic for whom FEV1 and PEFR assessments, prebronchodilator and postbronchodilator, were available for two visits. There was a high correlation between PEFR and FEV1 (in absolute value or percent predicted) (r = 0.83 and r = 0.75). However, 24 of 56 (43%) of those who had a change in FEV1 of 15% or more between two visits (mean change [%] +/- SD, range [best-lowest/best] = 20.9 +/- 5.1%, 15 to 36%) showed changes in PEFR of less than 15% (6.7 +/- 6.5%, 8.0 to 13.9%). On the other hand, 14 of 42 (33%) subjects with changes in FEV1 of less than 15% (9.8 +/- 3.2%, 1.1 to 13.8%) had changes in PEFR of 15% or more (22.2 +/- 10.9%, 16 to 35%). This discrepancy was not related to differences in baseline FEV1, control status, or the relationship between changes in FEV1 and PEFR in response to a bronchodilator. In conclusion, assessment of airway caliber through PEFR monitoring may not be valid in some asthmatic subjects and can often lead to underestimation or overestimation of changes in FEV1. None of the explanations considered made it possible to identify these subjects.

Adolescent↗
PubMed1993

Phosphotransferase system of Streptococcus salivarius: characterization of the ptsH gene and its product.

The Streptococcus salivarius ptsH gene encoding histidine-containing phosphocarrier protein (HPr) of the phosphotransferase system (PTS) has been cloned, sequenced, and found to be part of a ptsH, ptsI operon. Upstream from ptsH, putative -35 and -10 boxes and a Shine-Dalgarno sequence highly similar to the Escherichia coli consensus regulatory elements were identified. A second promoter, located in the ptsH coding sequence was also observed and is sufficient for the expression of the S. salivarius ptsI gene, encoding enzyme I of the PTS in E. coli [Gagnon et al., Gene 121 (1992) 71-78]. The amino acid sequence of S. salivarius HPr, inferred from the ptsH sequence, shared identity varying between 37 and 76% with known HPr from other bacteria. Moreover, the S. salivarius HPr shared 78% identity with an HPr-like protein of Aspergillus fumigatus, a eukaroytic mold that does not possess a functional PTS. Expression analysis of S. salivarius HPr in E. coli demonstrated that (i) S. salivarius ptsH is expressed in E. coli under the control of its own promoter, (ii) S. salivarius HPr synthesized by E. coli is completely processed by methionine aminopeptidase, and (iii) S. salivarius HPr is phosphorylated in vivo by E. coli enzyme I. It was also observed that, in E. coli, the copy number of pUC18 bearing S. salivarius ptsH was reduced more than 25-fold, as compared to pUC18 without an insertion.

Amino Acid Sequence↗
PubMed1992

Cloning, sequencing and expression in Escherichia coli of the ptsI gene encoding enzyme I of the phosphoenolpyruvate:sugar phosphotransferase transport system from Streptococcus salivarius.

We present the cloning and sequencing of the ptsI gene, encoding enzyme I (EI) of the phosphoenolpyruvate (PEP): sugar phosphotransferase (PTS) transport system from Streptococcus salivarius. The ptsI gene corresponds to an open reading frame of 1731 nucleotides, which translates into a putative 577-amino acid (aa) protein with a M(r) of 62,948 and a pI of 4.49. The EI was produced in Escherichia coli under the control of its own promoter located immediately upstream of ptsI, a situation never previously reported for any other gene coding for an EI. The deduced aa sequence of the S. salivarius EI shows a high degree of similarity with the E. coli EI and the EI moiety of the multiphosphoryl transfer protein from Rhodobacter capsulatus. The S. salivarius EI also shares a highly conserved aa cluster with a non-PTS protein, the maize pyruvate:orthophosphate dikinase. The conserved cluster is located in a domain which is hypothesized to be the PEP-binding site.

Amino Acid Sequence↗
PubMed1990

A 24-month clinical study of the incidence and progression of dental caries in relation to consumption of chewing gum containing xylitol in school preventive programs.

The effect of chewing gum containing xylitol on the incidence and progression of dental caries was tested in a sample of 274 children, aged eight and nine years, of low socio-economic status and high caries rate. They were divided into two experimental groups (15% and 65% xylitol chewing gum distributed three times a day at school) and one control group (without chewing gum). The three groups were exposed to the same basic preventive program. Children who chewed gum had a significantly lower net progression of decay (progressions-reversals) over a 24-month period than did the controls. Results for the two groups chewing gum were similar. Chewing xylitol gum had a beneficial effect on the caries process for all types of tooth surfaces, and especially for bucco-lingual surfaces. The two experimental groups had a DMF(S) increment of 2.24 surfaces, compared with 6.06 surfaces for the control group. For this indicator, there was no difference between the two experimental groups. Results for the plaque index were in agreement with those of the DMF(S) increment and the net progression of decay.

Analysis of Variance↗
PubMed1990

Elderly dental care. Needs and costs in three different resident settings.

Although the real dental treatment needs of the elderly has been established, the costs for these needs has not been determined. This report compares dental services and costs required for older adults living in three different resident settings. Dental needs and costs have been evaluated from a sample of 305 aged persons living in nursing homes (N = 156), low-cost housing facilities (N = 79) or dependent on home care services (N = 70). This study indicates that the homebound or institutionalized elderly population presents with poor dental and periodontal conditions, a high rate of edentulousness, and inadequate dentures. Dental needs are essentially characterized by the repair or replacement of prosthesis, the screening and treatment of mucosal lesions of prosthetic origin, and scaling/curettage of remaining teeth. The average rehabilitative dental costs was Can. $720 and there was no difference between the three types of residence. Important differences in cost, however, were observed between the dentate and edentulous population. The F-test (P less than .05) and chi-square were used to analyze differences in dental treatment needs and costs between different residences. Maintenance care corresponds to Can. $80/year/person.

Aged↗
PubMed1989

Association of granulocytosis with poor prognosis in patients with acute myelogenous leukemia and translocation of chromosomes 8 and 21.

Forty-three patients with acute myelogenous leukemia (AML) and a translocation 8;21 were reviewed. The patients' median age was 30 years, and 62% were men. Twenty-three patients (53%) had loss of a sex chromosome and ten (23%) had other chromosomal abnormalities in addition to the 8;21 translocation. Complete remission (CR) with induction chemotherapy was achieved in 40 patients (93%). The median CR duration was 18 months (range, 1 to 137+ months). Median survival time was 17 months (range, 0.5 to 138+ months) with a 3-year survival rate of 31%. Twenty-three patients (53%) relapsed between 1 and 58 months after entering remission with reinduction therapy resulting in 8 CRs (35%). Thirteen characteristics were examined for an effect on survival. The most striking finding was a significant association between elevated absolute granulocyte count and poor survival (P = .002). WBC count greater than 10,000/microL was also associated with shorter survival (P = .05). Patient age, albumin level, and platelet count showed trends for survival association. Although patients with AML and t(8;21) are regarded as a favorable group with respect to survival, we found a subset of patients who do very poorly. Intensive or more investigational approaches in first remission should be considered for these patients.

Adolescent↗
PubMed1988

Lamin B shares a number of distinct epitopes with lamins A and C and with intermediate filament proteins.

Four monoclonal antibodies raised against rat liver nuclear lamins and an anti-intermediate filament antibody [Pruss, R. M., Mirsky, R., & Raff, M. C. (1981) Cell (Cambridge, Mass.) 27, 419-428] have been used to identify epitopes shared by lamin B with lamins A and C, and with intermediate filament proteins. The antibodies defined two major antigenic regions on the three lamins which were both homologous with mouse epidermal keratins as well as hamster vimentin and desmin. Three distinguishable epitopes shared by lamin B with lamins A and C were identified by competition studies between pairs of antibodies and by reaction against N-chlorosuccinimide and cyanogen bromide cleavage fragments. These results support the hypothesis that lamin B, despite important biochemical differences with lamins A and C, shares with them some of the structural characteristics typical of intermediate filament proteins.

Animals↗