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Biomedical subjects

L Michaud

Publications and source records attributed to L Michaud.

At least 91 records · Page 5Linked to original sources
PubMed1996

Percutaneous endoscopic gastrostomy in children: influence on gastroesophageal reflux.

OBJECTIVE: Few data exist in the literature about the relationship between percutaneous endoscopic gastrostomy (PEG) and gastroesophageal reflux (GER) in children, and the data that do exist are contradictory. The aim of the present study was to evaluate the effect of PEG on GER. METHODS: Twenty children underwent PEG for enteral nutrition. They were 55 +/- 55 months old and weighed 13 +/- 10 kg. A pH study was performed before and after PEG without treatment when GER status was unknown (n = 10) or under treatment (n = 10) if previous GER was demonstrated. In these cases, the pH study was performed under the same treatment before and after PEG. RESULTS: Six pH studies had abnormal results before PEG. After PEG, the GER of these 6 children significantly improved after the treatment was intensified (n = 50 or spontaneously normalized (n = 1). Results of 13 pH studies that were previously normal remained normal. Only one child with a normal reflux index before PEG had GER after it. For the 20 children, the mean reflux index did not change significantly after PEG (5.5% vs 5.6%). CONCLUSION: Contrary to surgical gastrostomy, PEG does not worsen GER. Therefore, GER is not a contraindication to PEG.

Adolescent↗
PubMed1995

Biological and molecular differentiation between coronaviruses associated with neonatal calf diarrhoea and winter dysentery in adult cattle.

Cytopathic coronaviruses were isolated in HRT-18 cells from bloody faecal samples collected from cows in Québec dairy herds with classical winter dysentery (WD). The formation of polykaryons in the infected cell cultures was found to be dependent on the presence of trypsin in the medium. Virus identification was confirmed by indirect immunofluorescence and indirect protein A-gold immunoelectron microscopy using rabbit hyperimmune serum, as well as monoclonal antibodies directed against the spike (S) and hemagglutinin-esterase (HE) glycoproteins of the prototype Mebus strain of bovine coronavirus (BCV-Meb). Four WD isolates differed from BCV-Meb by their ability to agglutinate rat erythrocytes at 4 and 37 degrees C, their higher receptor destroying enzyme activity, but lower acetylesterase activity. The WD isolates were serologically indistinguishable from the reference BCV-Meb strain by virus neutralization and Western immunoblotting, but could be differentiated by hemagglutination-inhibition. Sequence analysis of the PCR-amplified HE gene of a plaque-purified WD isolate (BCQ-2590) revealed sufficient number of nucleotide and amino acid substitutions which may explain this antigenic variability.

Animals↗
PubMed1995

Comparison of bovine coronavirus isolates associated with neonatal calf diarrhoea and winter dysentery in adult dairy cattle in Québec.

Cytopathic coronaviruses were isolated in HRT-18 cells from bloody faecal samples collected from cows in Québec dairy herds having experienced typical outbreaks of winter dysentery (WD). The formation of polykaryons in the infected cell cultures was found to be dependent on the presence of trypsin in the medium. The WD isolates differed from the prototype Mebus strain of bovine enteropathogenic coronavirus (BCV.Meb) in respect to haemagglutination inhibition (HI), haemagglutination patterns at 4 degrees C and 37 degrees C, and receptor destroying enzyme activity with rat erythrocytes. Other field strains of BCV associated with outbreaks of neonatal calf diarrhoea (NCD) also differed from the BCV.Meb strain by demonstrating differences in HI. In all cases, no differences were detected by virus neutralization and Western immunoblotting. Analysis and comparison of the nucleotide and deduced amino acid sequences of the PCR-amplified haemagglutinin esterase (HE) genes of one representative WD strain (BCQ.2590) and two highly cytopathic NCD strains (BCQ.3 and BCQ.571) revealed high degrees of similarities (nt and aa sequence homologies > 98%) with the BCV.Meb strain. The putative esterase active site FGDS was conserved among these four BCV strains, indicating that this domain is probably not a determinant for BCV virulence. Six amino acid substitutions occurred between the HE glycoproteins of BCV.Meb and BCQ.2590 strains; two proline substitutions occurred respectively in the signal peptide (at aa 5) and near the sequences of the putative esterase domain (at aa 53).

Amino Acid Sequence↗
PubMed1994

Paternal isodisomy for chromosome 5 in a child with spinal muscular atrophy.

Paternal isodisomy for chromosome 5 was detected in a 2-year-old boy with type III spinal muscular atrophy (SMA), an autosomal recessive degenerative disorder of alpha motor neurons, known to map to 5q11.2-13.3. Examination of 17 short-sequence repeat polymorphisms spanning 5p15.1-15.3 to 5q33.3-qter produced no evidence of maternally inherited alleles. Cytogenetic analysis revealed a normal male karyotype, and FISH with probes closely flanking the SMA locus confirmed the presence of two copies of chromosome 5. No developmental abnormalities, other than those attributable to classical childhood-onset SMA, were present. While the absence of a maternally derived chromosome 5 could have produced the symptoms of SMA through the mechanisms of genomic imprinting, the lack of more global developmental abnormalities would be unusual. Paternal transmission of two copies of a defective gene at the SMA locus seems to be the most likely cause of disease, but proof of this will have to await the identification of the SMA gene. While uniparental isodisomy is a rare event, it must be considered as a possible mechanism involved in SMA when conducting prenatal testing and counseling for this disorder.

Alleles↗
PubMed1993

Characterization of monoclonal antibodies to bovine enteric coronavirus and antigenic variability among Quebec isolates.

Twenty monoclonal antibodies (MAbs) were prepared against the Mebus strain of bovine enteric coronavirus, 14 of them reacting with the peplomeric S (gp 100) glycoprotein. Competition binding assays allowed the definition of at least 4 distinct antigenic domains for the S glycoprotein, designated as A, B, C, and D; epitopes associated to neutralizing activity being located in sites A, B, and C. One MAb directed to the hemagglutinin HE (gp 140/gp 65) glycoprotein inhibited the hemagglutinating activity of the virus, but had no neutralizing activity. Comparison of Quebec enteropathogenic BCV isolates using polyclonal antiserum and MAbs directed to the S glycoprotein confirmed their close antigenic relationship, but also revealed the occurrence of at least three distinct antigenic subgroups. Antigenic domain D was highly conserved among BCV isolates, as well as non-neutralizing epitopes assigned to antigenic domains A and C. The Minnesota strain of turkey enteric coronavirus could be distinguished from BCV isolates by MAbs directed to epitopes of antigenic domain C, whereas human coronavirus HCV-OC 43 could be distinguished by MAbs directed to epitopes of antigenic domain A. The porcine hemagglutinating encephalomyelitis virus could be distinguished from the other hemagglutinating coronaviruses by neutralizing epitopes located on antigenic domains A, B, and C.

Animals↗
PubMed1993

[Cow's milk proteins intolerance disclosed by ulcero-necrotizing enterocolitis in a full-term infant].

BACKGROUND: Necrotizing enterocolitis associated with milk protein intolerance is rare. CASE REPORT: A girl, born at term, weighing 3,150 g, was fed several different formulas because of persistent vomiting and diarrhea; some of these formulas contained cow's milk proteins. At 5 weeks of age, the patient developed acute abdominal distension and obstructive manifestations. Laparotomy showed intestinal distension and perforation of the distal small bowel, requiring resection with temporary ileostomy. Histological examination of the resected segment of the small bowel showed extensive necrosis of the mucosa and submucosa with involvement of the muscular layers. The patient was given parenteral nutrition for 3 weeks then refed with human milk. Cow's milk was introduced at the age of 2 1/2 months; this was immediately followed by vomiting and an anaphylactic reaction, with increased ileostomy fluid volume and blood and sugars in stools. A jejunal biopsy performed 3 weeks later showed moderate villous atrophy with a dense infiltrate of eosinophils below the epithelium. The RAST test was positive to beta-lactoglobulin and negative to casein and lactalbumin. The patient tolerated cow milk by the age of 18 months. CONCLUSIONS: Cow's milk protein tolerance should be evaluated when necrotizing enterocolitis occurs in the absence of classical risk factors.

Animals↗
PubMed1992

Electrophoretic transfer of DNA from gels to filters by using a homemade apparatus.

Electroblotting is a rapid and high-efficiency method of transferring DNA from gels to the variety of membranes available, in very short time frames when compared with capillary-blotting techniques and with much less preparation required. A simple apparatus made of two food savers, one dialysis membrane, one sponge, and two removable electrodes was used to transfer DNA molecules up to 21 kb, from agarose gels to nitrocellulose filters, in less than 30 min. A recombinant pAT153 plasmid carrying the human cytomegalovirus BamH I-P fragment (7.2 kb) was rapidly identified by hybridization, using our simplified transfer procedure.

Blotting, Southern↗
PubMed1991

Inactivation mechanism of tetrameric beta-galactosidase by gamma-rays involves both fragmentation and temperature-dependent denaturation of protomers.

The radiation inactivation method is widely used to estimate the molecular size of membrane-bound enzymes, receptors, and transport systems in situ. The method is based on the principle that exposure of frozen solutions or lyophilized protein preparations to increasing doses of ionizing radiations results in a first-order decay of biological activity proportional to radiation inactivation size of the protein. This parameter is believed to reflect the "functional unit" of the protein defined as the minimal assembly of structure (protomers) required for expression of a given biological activity. We tested the functional unit as a concept to interpret radiation inactivation data of proteins with Escherichia coli beta-galactosidase, where the protomers are active only when associated in a tetramer. Gamma-Irradiation of beta-galactosidase at both -78 and 38 degrees C followed by quantitation of the residual unfragmented promoter band by SDS-polyacrylamide gel electrophoresis yielded the protomer size, indicating that only one protomer is fragmented by each radiation hit. By following the enzyme activity as a function of dose it was found that only the protomer that has been directly hit and fragmented at -78 degrees C was effectively inactivated. In contrast, at 38 degrees C, it was the whole tetramer that was inactivated. beta-Galactosidase cannot have two different functional units depending on temperature. The inactivation of the whole beta-galactosidase tetramer at 38 degrees C is in fact related to protomer fragmentation but also to the production of stable denatured protomers (detected by gel-filtration HPLC and differential UV spectroscopy) due to energy transfer from fragmented protomers toward unhit protomers.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme Activation↗
PubMed1990

Human neuraminidase is a 60 kDa-processing product of prosaposin.

Human neuraminidase was purified from placenta as part of a large molecular weight complex with lysosomal beta-galactosidase and carboxypeptidase. Passage of this purified complex through a sialic acid-affinity column (fetuin-agarose) retained a minor 60 kDa protein which was eluted with 100 mM N-acetylneuraminic acid. This 60 kDa protein is recognized in Western blots of the purified complex by an anti-prosaposin antibody which at the same time was able to inhibit neuraminidase activity in the preparation. Furthermore, probing of cultured skin fibroblasts of patients affected with neuraminidase deficiency using the antiprosaposin antibody revealed an abnormal 57 kDa protein. These results indicate that the 60 kDa protein is derived from prosaposin and has the characteristics of a neuraminidase.

Antibodies↗
PubMed1990

Deficient lysosomal carboxypeptidase activity in galactosialidosis.

In the lysosome, the glycosidases neuraminidase (EC 3.2.1.18) and beta-galactosidase (EC 3.2.1.23) are associated to a 52 kDa "protective protein" to form a large multi-enzymatic complex. Deficient synthesis or inactivation of this protective protein causes galactosialidosis, a lysosomal storage disorder in man in which both neuraminidase and beta-galactosidase activities are deficient. Since the protective protein possesses extensive sequence homology with carboxypeptidase Y (carb Y) and the KEX 1 gene product from yeast, we have used the artificial substrate N-CBZ-Phe-Leu to detect and characterize the peptidase activity of the lysosomal carboxypeptidase (carb L). Using both a purified preparation of the lysosomal multi-enzymatic complex and cultured skin fibroblasts of patients affected with galactosialidosis, we demonstrate that the 52 kDa protective protein is responsible for carb L activity. The fibroblasts of three patients affected with late infantile and juvenile galactosialidosis were found to be deficient in carb L activity (1.4% of normal mean value).

Carbohydrate Metabolism, Inborn Errors↗