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Biomedical subjects

Y Pouliot

Publications and source records attributed to Y Pouliot.

13 recordsLinked to original sources
PubMed2004

Effect of temperature and pore size on the fractionation of fresh and reconstituted buttermilk by microfiltration.

The objective of this research was to evaluate the effect of temperature (7, 25, and 50 degrees C) and pore size (0.1, 0.8, and 1.4 micro m) on the separation of proteins and lipids (neutral lipids and phospholipids) during microfiltration (MF) of fresh or reconstituted buttermilk. Buttermilk was subjected to MF using a pilot-scale unit mounted with ceramic membranes. The MF runs were carried out in a uniform transmembrane pressure (UTP) mode. Changes in processing temperature had no significant impact on protein transmission, whereas increasing temperature reduced both lipid and phospholipid transmission. A maximum concentration factor (CF) for lipids was reached at 25 degrees C, as protein CF remained essentially unaffected by temperature. The use of the smaller pore size (0.1 microm) resulted in low lipid (10%) and protein (approximately 20%) transmission. Larger pore sizes (0.8 and 1.4 microm) resulted in higher levels of protein, lipid, and phospholipid transmission (>50%), but gave high permeation fluxes. Transmission of both proteins and lipids was markedly different when using fresh buttermilk as opposed to reconstituted buttermilk. This study showed that MF temperature, pore size, and buttermilk type influence fractionation but that MF alone cannot achieve optimal separation of lipids and proteins for the production of novel ingredients from buttermilk.

Chemical Fractionation↗
PubMed2001

Improved storage stability of model infant formula by whey peptides fractions.

The purpose of this study was to evaluate the shelf-life stability (6 months) of model infant formula with whey protein hydrolysates or peptidic fractions as carrageenan replacers. Whey protein hydrolysates were prepared with trypsin and followed by ultrafiltration of the hydrolyzed mixture, and peptidic fractions were isolated from the ultrafiltered tryptic hydrolysate by anion- or cation-exchange chromatography. The stability of the model infant formula was evaluated using a stratification method based on fat content differences between the top and bottom strata of the samples. With protein hydrolysate-based formulations, the creaming rate of the fat in the product was slightly higher than in the standard formulation (with carrageenan), which is indicative of lower storage stability. The addition of cationic fractions to model infant formula also resulted in lower product stability, whereas the fat creaming rate was retarded in anionic fraction based formulations. The physicochemical characteristics of certain peptides combined with the reported high emulsifying properties of peptidic sequences found within these fractions may account for their ability to act as carrageenan replacers.

Animals↗
PubMed2001

DIAN: a novel algorithm for genome ontological classification.

Faced with the determination of many completely sequenced genomes, computational biology is now faced with the challenge of interpreting the significance of these data sets. A multiplicity of data-related problems impedes this goal: Biological annotations associated with raw data are often not normalized, and the data themselves are often poorly interrelated and their interpretation unclear. All of these problems make interpretation of genomic databases increasingly difficult. With the current explosion of sequences now available from the human genome as well as from model organisms, the importance of sorting this vast amount of conceptually unstructured source data into a limited universe of genes, proteins, functions, structures, and pathways has become a bottleneck for the field. To address this problem, we have developed a method of interrelating data sources by applying a novel method of associating biological objects to ontologies. We have developed an intelligent knowledge-based algorithm, to support biological knowledge mapping, and, in particular, to facilitate the interpretation of genomic data. In this respect, the method makes it possible to inventory genomes by collapsing multiple types of annotations and normalizing them to various ontologies. By relying on a conceptual view of the genome, researchers can now easily navigate the human genome in a biologically intuitive, scientifically accurate manner.

Algorithms↗
PubMed1994

Developmental regulation of M-cadherin in the terminal differentiation of skeletal myoblasts.

Cadherins form a large family of membrane glycoproteins which mediate homophilic calcium-dependent cell adhesion. They are thought to mediate the initial calcium-dependent cell adhesion which precedes the plasma membrane fusion of skeletal myoblasts. Two cadherin subtypes are known to be expressed in mammalian skeletal myoblasts: muscle cadherin (M-cadherin) and neural cadherin (N-cadherin). In the present study we demonstrate that 1) the expression of M- and N-cadherin is differentially regulated during myoblast differentiation in vitro, 2) the expression of M-cadherin but not N-cadherin is inhibited by 5-bromo-2'-deoxyuridine (BUdR), an agent which selectively inhibits skeletal myoblast differentiation, and 3) fusion and differentiation-competent rat L6 myoblasts do not express detectable levels of N-cadherin mRNA. In vivo, M-cadherin mRNA was detectable exclusively in skeletal muscle. M-cadherin mRNA levels peaked during the secondary myogenic wave in rat hindlimb muscle, becoming barely detectable in 1-week-old and adult rats. These observations indicate that M-cadherin is unique in two ways: It is the first cadherin to be included in the family of skeletal muscle-specific genes, and it shows peak levels of expression in developing skeletal muscle tissue. Taken together, these results suggest that M-cadherin plays an important role in skeletal myogenesis.

Aging↗
PubMed1992

Phylogenetic analysis of the cadherin superfamily.

Cadherins are a multigene family of proteins which mediate homophilic calcium-dependent cell adhesion and are thought to play an important role in morphogenesis by mediating specific intercellular adhesion. Different lines of experimental evidence have recently indicated that the site responsible for mediating adhesive interactions is localized to the first extracellular domain of cadherin. Based upon an analysis of the sequence of this domain, I show that cadherins can be classified into three groups with distinct structural features. Furthermore, using this sequence information a phylogenetic tree relating the known cadherins was assembled. This is the first such tree to be published for the cadherins. One cadherin subtype, neural cadherin (N-cadherin), shows very little sequence divergence between species, whereas all other cadherin subtypes show more substantial divergence, suggesting that selective pressure upon this domain may be greater for N-cadherin than for other cadherins. Phylogenetic analysis also suggests that the gene duplications which established the main branches leading to the different cadherin subtypes occurred very early in their history. These duplications set the stage for the diversified superfamily we now observe.

Amino Acid Sequence↗
PubMed1990

Identification of a conserved region common to cadherins and influenza strain A hemagglutinins.

Cadherins are a family of integral membrane glycoproteins that mediate homophilic, calcium-dependent cell adhesion in vertebrate species. The primary structures of six members of the cadherin family have recently been determined. The extracellular portion of these proteins is composed of five domains, the first of which is the most highly conserved among cadherins. Previous searches of protein sequence databases have revealed little or no sequence homology between cadherins and other proteins. Here we report that the first extracellular domain of cadherins exhibits substantial sequence homology with the amino termini of influenza strain A hemagglutinins. These regions of sequence homology have been shown to be functionally important in both cadherins and hemagglutinins. Our observations suggest that a functional domain of cadherins is conserved among other proteins.

Amino Acid Sequence↗
PubMed1990

Identification of a cadherin cell adhesion recognition sequence.

The molecular mechanisms by which the cadherins interact with one another to promote cell adhesion have not been elucidated. In particular, the amino acid sequences of the cadherin cell adhesion recognition sites have not been determined. Here we demonstrate that synthetic peptides containing the sequence HAV, which is common to all of the cadherins, inhibit two processes (compaction of eight-cell-stage mouse embryos and rat neurite outgrowth on astrocytes) that are known to be mediated by cadherins. The data suggest that the tripeptide HAV is a component of a cadherin cell adhesion recognition sequence.

Amino Acid Sequence↗
PubMed1990

Developmental regulation of a cadherin during the differentiation of skeletal myoblasts.

Cadherins are a family of integral membrane glycoproteins which mediate calcium-dependent intercellular adhesion in vertebrate species. Here we present evidence that fusion-competent rat L6 myoblasts express a cadherin (Mr 127 kDa). The levels of this cadherin were found to be developmentally regulated. Maximal levels were expressed prior to fusion. The increase in cadherin levels observed during differentiation was prevented by the differentiation inhibitor, 5-bromo-2'-deoxyuridine. L6 myoblasts grown in the presence of anti-cadherin antibodies exhibited an altered morphology in comparison to control cultures, coupled with decreased myoblast fusion. These data indicate that the developmental regulation of cadherin is part of the program of terminal differentiation of skeletal myoblasts, and that cadherins are involved in the process of myoblast fusion.

Animals↗
PubMed1990

Efficient recognition of immunoglobulin domains from amino acid sequences using a neural network.

A neural network was trained using back propagation to recognize immunoglobulin domains from amino acid sequences. The program was designed to identify proteins exhibiting such domains with minimal rates of false positives and false negatives. The National Biomedical Research Foundation NEW protein sequences database was scanned to evaluate the performance of the program in recognizing mouse immunoglobulin sequences. The program correctly recognized 55 out of 56 mouse immunoglobulin sequences, corresponding to a recognition efficiency of 98.2% with an overall false positive rate of 7.3%. These data demonstrate that neural network-based search programs are well suited to search for sequences characterized by only a few well-conserved subsequences.

Algorithms↗
PubMed1989

Experiments on the heat-induced salt balance changes in cow's milk.

The heat-induced changes in salt balance between the colloidal phase of milk and its serum were studied using an ultrafiltration technique. Milk permeate was isolated at the heating temperature by means of a hollow fibre ultrafiltration cartridge coupled with a stainless steel heat exchanger unit. The milk samples initially at 4 degrees C were heated to 20, 40, 60, 80 or 90 degrees C. Ca, P, Mg and citrate contents of the permeates were determined. The decreases in Ca and P were proportional to the increase in temperature. Smaller losses in Mg and citrate were observed. An initial sharp decrease in concentration occurred within the first seconds of holding time and was followed by a slower and smaller decrease. The possible occurrence of a two-stage mechanism for the heat-induced salt precipitation is discussed. The precipitation of dicalcium phosphate is believed to occur together with some tricalcium citrate precipitation.

Animals↗
PubMed1989

Dystrophin is expressed in mdx skeletal muscle fibers after normal myoblast implantation.

In mdx mice, the dystrophin gene of the X chromosome is defective and, as a result, immunoreactive dystrophin is undetectable in all muscle fibers of all animals of this highly inbred strain. This study showed that implantation of suspensions of clonal cultures of normal human myoblasts into different regions of quadriceps muscles of 6-to-10-day-old mdx mice or 60-day-old mdx mice (whose muscles have been crushed 4 days before implantation) results in the appearance of scattered fiber segments containing microscopically demonstrable immunoreactive dystrophin. In the animals that received the normal myoblast implantation in the prenecrotic stage of the disease (6 to 10 days of age), the dystrophin-positive fiber segments (demonstrated at ages 35, 45, and 60 days) escaped necrosis. This was determined by the absence of the characteristic chains of central nuclei, a reliable marker of prior necrosis in mdx muscle fibers. By heavy labeling of the nuclear DNA of the transplantable human myoblasts with H3-thymidine during culturing, and by sequential performance of an immunocytochemical staining for dystrophin and autoradiography on the same sections, some dystrophin-positive fiber segments were shown to contain radiolabeled myonuclei. It was concluded that nondystrophic myoblasts fused with host muscle fibers to form mosaic muscle fibers in which the normal dystrophin gene of the implanted myoblasts was expressed. This approach may be employed for the mitigation of the deleterious consequences of a gene defect in recessively inherited human muscle diseases such as Duchenne dystrophy.

Animals↗
PubMed1988

Expression of immunoreactive major histocompatibility complex products in human skeletal muscles.

Immunoreactive class 1 and class 2 major histocompatibility complex gene products (MHCP) and beta 2 microglobulin (beta 2 MG) were demonstrated by microscopic immunocytochemistry in cryostat sections of skeletal muscle biopsies of 67 patients with various neuromuscular diseases. Diagnoses included normal muscle, chronic partial denervation, Duchenne dystrophy, polymyositis, dermatomyositis, inclusion body myositis, and miscellaneous neuromuscular diseases. Normal mature muscle fibers did not express MHCP, but blood vessels showed both class 1 and 2 MHCP and beta 2 MG. Regenerating muscle fibers showed consistent sarcolemmal class 1 MHCP expression irrespective of the disease. In polymyositis, the majority of extrafusal muscle fibers of most patients showed strong sarcolemmal class 1 MHCP expression. In dermatomyositis, muscle fibers situated either in perifascicular or in randomly clustered distribution revealed strong class 1 MHCP reactivity. In inclusion body myositis, scattered small clusters of muscle fibers were positive for class 1 MHCP. In polymyositis and inclusion body myositis, particularly strong class 1 MHCP expression was invariably seen in nonnecrotic muscle fibers partially invaded by lymphocytes whose cytotoxic effects are believed to be class 1 MHCP restricted. Factors or agents that trigger class 1 MHCP expression are presumed also to sensitize lymphocytes to muscle fibers in these diseases, but their identity remains obscure at this time. In dermatomyositis, the expression of MHCP in perifascicular muscle fibers and in areas of capillary loss may represent the triggering of MHCP expression by a nonspecific cellular stress reaction, in this case probably low-grade ischemia.

Adult↗