Biomedical subjects

J Bergeron

Publications and source records attributed to J Bergeron.

At least 91 records · Page 5Linked to original sources

PubMed1997

The impact of a treatment process for substance users as a function of their degree of exposure to treatment.

The objective of this research is to evaluate the outcomes of a treatment for addicts. 248 subjects were tested before and 5 months after treatment with the Addiction Severity Index (ASI). Exposure to treatment was based on the number of clients' contact hours with a therapist. The sample was divided into three groups according to number of hours spent in treatment. The data were analyzed using MANOVA on the seven scales of the ASI for the three groups and the two time periods. Results showed that the severity of addiction problems decreased after treatment, and decreased more for subjects who underwent treatment for a longer period of time.

Adolescent↗

PubMed1996

Sequencing of Comamonas testosteroni strain B-356-biphenyl/chlorobiphenyl dioxygenase genes: evolutionary relationships among Gram-negative bacterial biphenyl dioxygenases.

In a previous work, all three components of Comamonas testosteroni B-356 biphenyl (BPH)/chlorobiphenyls (PCBs) dioxygenase (dox) have been purified and characterized. They include an iron-sulphur protein (ISPBPH) which is the terminal oxygenase composed of two subunits (encoded by bphA and bphE), a ferredoxin (FERBPH) encoded by bphF and a reductase (REDBPH) encoded by bphG. bphG Is not located in the neighbourhood of bphAEF in B-356. We are reporting the cloning of B-356-bphG and the sequencing of B-356-BPH dox genes. Comparative analysis of the genes provided genetic evidence showing that two BPH dox lineages have emerged in Gram-negative bacteria. The main features of the lineage that includes B-356 are the location of bphG outside the bph gene cluster and the structure of REDBPH which is very distinct from all other aryl dioxygenase-reductases.

Amino Acid Sequence↗

PubMed1996

Site-directed mutagenesis of the double-stranded RNA binding domain of bacterially-expressed sigma 3 reovirus protein.

The affinity of the reovirus sigma 3 protein for double-stranded RNA (dsRNA) is well established, and efforts have been made to identify the amino acids involved in this property. In the present study, we further examined the importance of two basic amino acids motifs, located in the carboxy-terminal third of the protein. Mutants, previously characterized in COS cells, were expressed in bacterial cells using the pET expression system. The capability of the different mutants to interact with dsRNA was then determined by the binding of radiolabeled dsRNA to proteins resolved by SDS-polyacrylamide gel electrophoresis and transferred to nitrocellulose filters. It appears that the most carboxy-terminal motif is absolutely required for the binding but the second motif also contributes to this property. However, only the carboxy-terminal motif is required for normal binding upon removal of the amino-terminal domain of the protein by proteolytic cleavage, a procedure previously shown to increase dsRNA-binding. The basic charges in both motifs are important, while breaking of their potential to adopt an alpha helical configuration does not affect binding efficiency. Furthermore, alanine substitution of a single basic amino acid in the carboxy-terminal motif can be sufficient to strongly reduce the binding of dsRNA to the protein. Altogether, these data suggest that basic amino acids of the sigma 3 carboxy-terminal motif are directly involved in dsRNA binding, while the other basic motif may contribute by preventing an inhibitory effect of the amino-terminal portion of the protein.

Animals↗

PubMed1996

Molecular cloning and functional analysis of a novel macrolide-resistance determinant, mefA, from Streptococcus pyogenes.

Several streptococcal strains had an uncharacterized mechanism of macrolide resistance that differed from those that had been reported previously in the literature. This novel mechanism conveyed resistance to 14- and 15-membered macrolides, but not to 16-membered macrolides, lincosamides or analogues of streptogramin B. The gene encoding this phenotype was cloned by standard methods from total genomic digests of Streptococcus pyogenes 02C1064 as a 4.7 kb heterologous insert into the low-copy vector, pACYC177, and expressed in several Escherichia coli K-12 strains. The location of the macrolide-resistance determinant was established by functional analysis of deletion derivatives and sequencing. A search for homologues in the genetic databases confirmed that the gene is a novel one with homology to membrane-associated pump proteins. The macrolide-resistance coding sequence was subcloned into a pET23a vector and expressed from the inducible T7 promoter on the plasmid in E. coli BL21(DE3). Physiological studies of the cloned determinant, which has been named mefA for macrolide efflux, provide evidence for its mechanism of action in host bacteria. E.coli strains containing the cloned determinant maintain lower levels of intracellular erythromycin when this compound is added to the external medium than isogenic clones without mefA. Furthermore, intracellular accumulation of [14C]-erythromycin in the original S. pyogenes strain was always lower than that observed in erythromycin-sensitive strains. This is consistent with a hypothesis that the gene encodes a novel antiporter function which pumps erythromycin out of the cell. The gene appears to be widely distributed in S. pyogenes strains, as demonstrated by primer-specific synthesis using the polymerase chain reaction.

Bacterial Proteins↗

PubMed1996

Glycylcyclines bind to the high-affinity tetracycline ribosomal binding site and evade Tet(M)- and Tet(O)-mediated ribosomal protection.

N,N-dimethylglycylamido (DMG) derivatives of 6-demethyl-6-deoxytetracycline and doxycycline bind 5-fold more effectively than tetracycline to the tetracycline high-affinity binding site on the Escherichia coli 70S ribosome, which correlates with a 10-fold increase in potency for inhibition of E. coli cell-free translation. The potencies of DMG-doxycycline and DMG-6-demethyl-6-deoxytetracycline were unaffected by the ribosomal tetracycline resistance factors Tet(M) and Tet(O) in cell-free translation assays and whole-cell bioassays with a conditional Tet(M)-producing E. coli strain.

Anti-Bacterial Agents↗

PubMed1996

Characterization of active recombinant 2,3-dihydro-2,3-dihydroxybiphenyl dehydrogenase from Comamonas testosteroni B-356 and sequence of the encoding gene (bphB).

2,3-Dihydro-2,3-dihydroxybiphenyl-2,3-dehydrogenase (B2,3D) catalyzes the second step in the biphenyl degradation pathway. The nucleotide sequence of Comamonas testosteroni B-356 bphB, which encodes B2,3D, was determined. Structural analysis showed that the dehydrogenases involved in the bacterial degradation of aromatic compounds are related to each other and that their phylogenetic relationships are very similar to the relationships observed for dioxygenases that catalyze the initial reaction in the degradation pathway. The bphB sequence was used to produce recombinant active His-tagged B2,3D, which allowed us to describe for the first time some of the main features of a B2,3D. This enzyme requires NAD+, its optimal pH is 9.5, and its native M(r) was found to be 123,000, which makes it a tetramer. These characteristics are very similar to those reported for the related enzyme cis-toluene dihydrodiol dehydrogenase. The Km value and maximum rate of metabolism for 2,3-dihydro-2,3-dihydroxybiphenyl were 73 +/- 16 microM and 46 +/- 4 nmol min-1 microgram-1, respectively. Compared with the cis-toluene dihydrodiol dehydrogenase, B2,3D appeared to be more substrate specific since it was unable to attack cis-1,2-dihydroxy-cyclohexa-3,5-diene.

Amino Acid Sequence↗

PubMed1996

Genome organization of the Kresse strain of porcine parvovirus: identification of the allotropic determinant and comparison with those of NADL-2 and field isolates.

The Kresse strain of porcine parvovirus (PPV) was cloned into pUC19, and independent infectious clones were sequenced. The PPV Kresse and NADL-2 strains, which have different pathogenicities, shared an identical genomic organization and a high degree of sequence identity. Partial genomes (1.5 or 1.6 kb) of 15 field isolates were also amplified by PCR in regions with significant sequence differences between the laboratory strains. Five amino acid differences were consistently present within the VP1/VP2 coding region of the Kresse strain and virulent field isolates. A number of inconsistent point mutations were also found throughout the genomes of field isolates. In addition, among those with the vaccine amino acid profile, all but one isolate (IAF-3) contained a 127-bp noncoding direct repeat downstream of the capsid protein gene. The one exception was also the only vaccine-type PPV obtained from a mummified fetus. In order to identify genetic elements responsible for the distinct tropism (and possibly the pathology) of the Kresse strain, in vitro cell systems which differentiated the virulent from the vaccinal strains were established. Subsequently, chimeric infectious clones of the Kresse and NADL-2 strains were used to identify the allotropic determinant located in the VP1/VP2 region. The transfer of the BglII fragment of the Kresse genome, containing three amino acid differences, into the NADL-2 background, or the opposite construct, caused the phenotype of the target genome to revert to that of the parent strain of the BglII fragment. Prediction of the localization of amino acid differences on the basis of canine parvovirus capsid structure indicates that each is located on or near the outer surface of the virion. In particular, the position of one mutation (S-436-->P) maps by analogy to the threefold spike, the most accessible region of the capsid.

Amino Acid Sequence↗

PubMed1996

Preventing diabetic foot disease: lessons from the Medicare therapeutic shoe demonstration.

OBJECTIVES: Every year about 38,000 elderly people with diabetes have a lower extremity amputation. Therapeutic shoes are prescribed by clinicians specializing in foot care to prevent foot ulcerations and amputations among at-risk patients with diabetes. Medicare ran a 3-year demonstration of a therapeutic-shoe benefit for beneficiaries with diabetes. Medicare added the benefit nationwide in May 1993. METHODS: This paper describes the benefit and its implementation in the demonstration based on demonstration records, a patient survey, and discussions with clinicians and shoe suppliers before and during the demonstration. RESULTS: During the demonstration, far fewer beneficiaries applied for the therapeutic shoes than were eligible for them. The paper discusses reasons for the low beneficiary application rate and the associated low participation rate among physicians treating patients with diabetes. CONCLUSIONS: The benefit is unlikely to be used any more in the national program than in the demonstration unless physicians are educated in the role therapeutic shoes can play in diabetic foot disease, they prescribe the shoes for their patients, and they increase their patients' awareness of the shoes' value.

Centers for Medicare and Medicaid Services, U.S.↗

PubMed1996

Human papillomavirus DNA in invasive cervical carcinomas and its association with patient survival: a nested case-control study.

This study sought to examine the association between the presence of human papillomavirus (HPV) DNA in invasive cervical cancer and prognosis. A case-control study was undertaken nested in a cohort of 208 patients with invasive cervical carcinoma in Montreal. All 40 deceased patients formed the case groups. A control group of equal size was selected by matching to each case (1:1) a patient of the same age and year of admission who had survived her disease. HPV DNA was detected by the use of a PCR protocol. The odds ratio (OR) for cervical cancer death was computed by logistic regression. Detection of HPV, particularly of types 16 and 18, was negatively correlated with disease stage and histological grade. The OR for death was 0.27 [95% confidence interval (CI), 0.1-0.8] for those whose tumors were positive for HPV DNA versus those in whom HPV DNA was not detected. After adjusting for the confounding effects of stage and grade, the prognostic effect was somewhat reduced, with an OR of 0.34 (CI, 0.1-1.1), which was no longer significant. The magnitude of the HPV-survival association was not altered when the analyses were restricted to carcinomas of stages I and II. Regardless of the mechanism for the prognostic role, detection of HPV DNA in primary tumors may play an important adjunct role in assessing prognosis of patients with invasive cervical cancer.

Adult↗

PubMed1996

Human endometrial cells cultured in a type I collagen gel.

OBJECTIVE: To elaborate in vitro conditions that enable epithelial and stromal cells of human endometrium to grow within a gel of collagen. STUDY DESIGN: Primary cultures of epithelial cells derived from human endometrial biopsies were dissociated and mixed with a collagen solution, and the gel was allowed to form at physiologic pH. Control cultures were grown in plastic dishes. DNA replication was assessed by 3H-thymidine incorporation, morphology by histology and cell characterization by monoclonal antibodies to cytokeratins. RESULTS: Cells grown on plastic dishes exhibited a typical monolayer arrangement, and replication was increased 1.6-fold by the addition of stromal cell-conditioned medium (50% vol/vol). After a two- to three-week period of culture within the collagen gel in the presence of either stromal cells or stromal cell-conditioned medium, epithelial cells formed circular arrangements of cuboidal to columnar cells with open lumina resembling glands. These glandlike structures were cytokeratin positive as assessed by immunohistochemistry, thereby confirming their epithelial nature. CONCLUSION: The development of differentiated epithelial structures in a three-dimensional gel provides a promising method of studying various biochemical and cellular interactions of eutopic and ectopic endometrium.

Biopsy↗

PubMed1995

Apolipoprotein A-I conformation in reconstituted discoidal lipoproteins varying in phospholipid and cholesterol content.

The effects of the size and cholesterol content on the conformation of apolipoprotein A-I (apoA-I) have been studied in reconstituted discoidal lipoproteins containing two apoA-I per particle (Lp2A-I). The immunoreactivity of a series of 13 epitopes distributed along the apoA-I sequence has been evaluated in Lp2A-I with a phospholipid/apoA-I molar ratio ranging from 31 to 156 and in Lp2A-I with constant phospholipids but varying in cholesterol content from 0 to 22 molecules. The results are compatible with a three domain structure in apoA-I in which the central domain is located between residues 99 and 143 and postulated to be a hinged domain that responds differentially to changes in phospholipid and cholesterol contents. Increasing the phospholipid content results in significant changes of epitope immunoreactivity throughout the N-terminal and central domains of apoA-I with fewer modifications in the C-terminal domain. In contrast, increasing Lp2A-I of two central epitopes, A11 (residues 99-132) and 5F6 (residues 118-148), and an extreme N-terminal epitope, 4H1 (residues 2-8). Interestingly, the effects of increasing cholesterol or phospholipids on these epitopes are opposite. This suggests a specific effect of cholesterol on the central domain tertiary structure between residues 99 and 143. Competition binding assays among pairs of antibodies binding to apoA-I on Lp2A-I are best explained by invoking inter- as well as intramolecular competitions. The specificity of the intermolecular competitions suggests an N to C termini arrangement of the two apoA-I molecules around the disc. Increasing the phospholipid content of Lp2A-I mainly increases the competitions between 3G10 and antibodies binding to most adjacent epitopes. Simultaneously as Lp2A-I enlarges, several of these antibodies also enhance the binding of 3G10. This has been interpreted as evidence of a structural rearrangement of apoA-I as a result of the size increase where the alpha-helix (residues 99-121) that contains the 3G10 epitope is increasingly interacting with lipids resulting in the enhanced expression of this epitope. The increasing interactions of apoA-I helices with lipids in the enlarging disc are compatible with previous reports of a greater apoA-I stability in the large discs. By contrast, cholesterol has limited but specific effects on antibody competitions and decreases the interaction of the N-terminal domain with the domain containing 3G10, either by direct cholesterol protein interaction or by modification of the lipid phase packing.

Antibodies, Monoclonal↗

PubMed1995

Allogeneic-syngeneic cultured epithelia. A successful therapeutic option for skin regeneration.

Organ transplantation has progressed rapidly during the last decades. Furthermore, tissue engineering has and will continue to enlarge the scope of organ grafting. Thus, severe skin wounds, as observed in large burn trauma patients, can now be permanently treated with cultured autologous epithelial sheets. However, the time required for autologous cell growth is a major limitation. We propose to alleviate this pitfall through a novel chimeric (allogeneic-syngeneic) epithelial cell culture technique. These chimeric epidermal grafts implanted in an animal model have been shown to allow the reappearance of a histologically normal epidermal coverage similar to simultaneously performed isografts. The regenerated epidermis contained only syngeneic keratinocytes. Thus, allogeneic cells were eliminated passively. This new culture technology could find multiple applications, notably in various skin disease therapies.

Animals↗

PubMed1995

Sequence of the bphD gene encoding 2-hydroxy-6-oxo-(phenyl/chlorophenyl)hexa-2,4-dienoic acid (HOP/cPDA) hydrolase involved in the biphenyl/polychlorinated biphenyl degradation pathway in Comamonas testosteroni: evidence suggesting involvement of Ser112 in catalytic activity.

The nucleotide sequence of bphD, encoding 2-hydroxy-6-oxo-(phenyl/chlorophenyl)hexa-2,4-dienoic acid hydrolase involved in the biphenyl/polychlorinated biphenyl degradation pathway of Comamonas testosteroni strain B-356, was determined. Comparison of the deduced amino-acid sequence with published sequences led to the identification of a 'lipase box', containing a consensus pentapeptide sequence GlyXaaSerXaaGly. This suggested that the mechanism of action of this enzyme may involve an Asp-Ser-His catalytic triad similar to that of classical lipases and serine hydrolases. Further biochemical and genetic evidence for the active-site involvement of Ser112 was obtained by showing that a semipurified enzyme was inhibited by PMSF, a classic inhibitor of serine hydrolases, and by site-directed Ser112-->Ala mutagenesis.

Amino Acid Sequence↗

PubMed1995

Role of apolipoprotein A-I in cholesterol transfer between lipoproteins. Evidence for involvement of specific apoA-I domains.

A series of monoclonal antibodies against epitopes spanning different domains of apoA-I have been tested for their effects on unesterified cholesterol transfer between low density lipoprotein (LDL) and well-defined homogenous lipoproteins reconstituted with phosphatidylcholine, cholesterol, and apoA-I (LpA-I). Antibodies 2G11 (reacting between residues 25 and 110), A05 (residues 25-82), A03 (residues 135-140), A44 and r5G9 (residues 149-186), and 4A12 (residues 173-205) significantly inhibit cholesterol transfer from LDL to Lp2A-I while they enhance transfer in the opposite direction, thus causing an increased net transfer to LDL. Most of these monoclonal antibodies (mAbs) also enhance phospholipid transfer to LDL but in a lesser and variable proportion relative to cholesterol. Their epitopes are mainly contained within domains that are predicted to be amphipathic alpha-helices. In contrast, mAbs 4H1 (residues 2-8), 3G10 (residues 96-121), and 5F6 (residues 116-141) have little or no effect on either cholesterol or phospholipid transfer, and the epitopes for these three mAbs have been shown in earlier studies to be structurally and functionally related. Their immunoreactivity responds similarly to variation in lipoprotein cholesterol content, and the antibodies binding to these sites compete with one another and have similar effects on the cholesterol esterification reaction. Thus, the current results are compatible with the hypothesis that they form an integrated domain with a common function in cholesterol metabolism, possibly as part of a hinge domain. Most mAbs were found to increase significantly the alpha-helicity of apoA-I in the Lp2A-I immunecomplexes, suggesting that they may increase the stability of the lipid-bound apoA-I. However, not unexpectedly, there is no correlation between the effects of mAbs on alpha-helicity and their effects on cholesterol or phospholipid transfer since each mAb has a discrete effect on these transfers. These studies demonstrate the specificity of LpA-I particles in cholesterol transport and document the existence of apoA-I domains with different functions in cholesterol transport.

Antibodies, Monoclonal↗

PubMed1995

Cloning, sequencing and expression of the S1 gene of avian reovirus.

The S1 genome segment of avian reovirus strain S1133 was cloned and completely sequenced. The sequence comprised 1636 bp with three distinct open reading frames (ORFs), suggesting the gene was polycistronic in nature. The three ORFs from 5' to 3' were predicted to encode polypeptides of 9.8, 3.8 and 34.9 kDa, respectively. Of the three ORFs, only the third possessed the AUG initiation codon in an optimum context for translation. The third ORF-encoded protein, 326 amino acids in length, was expressed in Escherichia coli and used as antigen in immunoblots. The protein was concluded to be sigma 3 on the basis of its recognition by a chicken anti-reovirus antiserum and due to the fact that a mouse antiserum raised against it recognized specifically the viral sigma 3 polypeptide. Sequence comparison of the avian reovirus S1 gene with its mammalian counterpart did not show any significant similarity between the two. However, amino acid sequence analysis and the predicted existence of a heptapeptide repeat pattern, as well as the relatively high frequency of alpha-helix structures in the amino terminal portion of sigma 3 suggests that this protein is structurally, and probably functionally, related to mammalian reovirus sigma 1 protein.

ATP-Binding Cassette Transporters↗

PubMed1995

Why do so few HMOs offer Medicare risk plans in rural areas?

Only 17 of the 38 health maintenance organizations (HMOs) that have Medicare risk contracts and offer coverage to commercial clients in rural counties include the rural counties in their Medicare plan service areas. Rural counties in which HMOs offer Medicare coverage have higher average adjusted average per capita costs (AAPCCs), larger populations, and more physicians per capita than rural counties excluded by risk plans. Interviewed plans cite low and erratic AAPCCs, scarcity of potential enrollees, lack of negotiating power with physicians, and adverse selection as drawbacks in rural areas. Proposed changes to the payment methodology would probably lead HMOs to increase their Medicare offerings in urban fringe areas, but not in isolated rural areas.

Actuarial Analysis↗

PubMed1994

Protein tyrosine kinases transcribed in a murine thymic medullary epithelial cell line.

Medullary epithelial cells of the thymus can be activated by contact with thymocytes. We identified a number of protein tyrosine kinases (PTKs) that could be responsible for the tyrosine phosphorylation observed in a murine thymic medullary epithelial cell line (E-5) following complex formation with thymocytes. Degenerate oligodeoxyribonucleotides (oligos) derived from the amino acid (aa) sequence motifs of PTK catalytic domains were used as oligo primers for PCR amplification to determine the PTK genes which are normally transcribed in the E-5 cell line. Amplicons were cloned, sequenced and the deduced aa sequences were compared to known PTK sequences. Among the 13 distinct PTK catalytic domains identified in E-5 cells, two were novel: they were encoded by eteck, a member of the eph sub-family of PTKs, and thy, a member of the src sub-family of PTKs.

Amino Acid Sequence↗

PubMed1994

A new rapid immunoinhibition pancreatic amylase assay: diagnostic value for pancreatitis.

A new rapid immunoinhibition pancreatic amylase assay was compared to total amylase and lipase in an unbiased sample of 1005 emergency department patients with suspicion of pancreatitis, of which 55 had a final diagnosis of pancreatitis. Imprecision of the assays for both amylases (less than 2.5%) were better than for lipase (less than 6.1%). Correlation (R2) of pancreatic amylase with total amylase was 0.991 but only 0.789 with lipase. Using Receiver Operator Characteristics analysis, the best diagnostic cutoff point for all three enzymes was near the upper limit of the reference interval. With pancreatic amylase, sensitivity, specificity, and predictive values for positive and negative results are, respectively, 85.5, 92.5, 39.8, and 99.1%; we found similar values for lipase but poorer values (78.2, 92.0, 36.1, and 98.7%) for total amylase. Tests combination did not improve the diagnostic performance significantly. In the diagnosis of pancreatitis, pancreatic amylase (p = 0.037) and lipase (p = 0.049) had better diagnostic performance than total amylase. The correct diagnosis of pancreatitis could be achieved in 47 instead of 43 patients with either pancreatic amylase or lipase as opposed to total amylase among 1005 patients in this study. We conclude that pancreatic amylase and lipase are incrementally better diagnostic tools than total amylase for the diagnosis of pancreatitis.

Acute Disease↗