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Biomedical subjects

D Lenoir

Publications and source records attributed to D Lenoir.

18 recordsLinked to original sources
PubMed1995

Developmental changes in intestinal glycosylation: nutrition-dependent multi-factor regulation of the fucosylation pathway at weaning time.

Developmental changes in the fucoglycoproteins of the intestinal brush-border membranes were determined by lectin affinoblotting after electrophoresis. Whereas only two alpha(1-6)-fucoglycoproteins were detected in brush-border membranes from suckling rats, a large number of N-fucoglycoproteins with alpha(1-2)- and/or alpha(1-6)-linked fucose residues were detected in rat membranes after weaning. Dietary manipulations at weaning time were used to investigate the effect of nutritional factors in the development of fucosylation in the small intestine of prolonged-nursed rats fed with milk (a high-fat, low-carbohydrate diet) compared to rats weaned normally with a standard high-carbohydrate diet. The fucose content of the mucosa glycoproteins was lower in 22-day-old prolonged-nursed rats than in 22-day-old rats weaned normally with the standard diet. The appearance of fucoglycoproteins in the brush-border membranes, which was delayed by prolonged nursing, was accompanied by a concomitant delay in the increase of intestinal fucosyl-transferase activity and in the decrease of GDP-fucose substrate breakdown. The developmental decrease in the activity of the inhibitory protein which regulates the fucosyl-transferase activity was also delayed by prolonged nursing. The intestinal fucosylation of brush-border membrane glycoproteins (which include many digestive enzymes) displayed ontogenic changes on which were superimposed dietary influences at the time of weaning. The complete maturation of the brush-border membrane glycoproteins, and particularly their terminal fucosylation, is a developmental event which thus seems to be strongly influenced by the manipulation of nutritional factors during the weaning period.

Animal Nutritional Physiological Phenomena↗
PubMed1994

Comparative effects of dietary corn, fish and Krill oils on intestinal glycosylation.

Antarctic Krill is considered as a valuable protein resource for animal and human nutrition. Due to the high content of long chain polyunsaturated fatty acids of the n-3 family, Krill consumption could be also interesting in cardiovascular diseases. In the search for the demonstration of the absence of toxicity of Krill, we studied the effect of Krill oil, as compared to fish and corn oil, on the rat intestinal fucosylation process at weaning, a very sensitive model of the influence of nutritional factors. Krill oil containing diets were very well tolerated as compared to other currently used oils and induced only slight modification in fucose and mannose proportions in intestinal glycoprotein sugars. These modifications were not reflected in the enzymatic activities involved in the fucosylation pathway. These results confirm the harmlessness of Krill derived products and their possible use in human nutrition.

Animals↗
PubMed1993

Indicator parameters for PCDD/F as a possible means to monitor emissions of toxicity equivalents from waste incinerators.

In the stack emissions from a hazardous waste incinerator we found highly significant correlations between 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalents (I-TE) and pentachlorobenzene (CI5Bz) and between I-TE and heptachlorobiphenyl (CI7B). We therefore propose to utilize these substances as indicator parameters from which I-TE values can be estimated. Since they are easier to analyze than PCDD/F the use of indicator parameters such as CI5Bz and CI7B offers the chance to monitor I-TE emissions which are limited to 0.1 ng/m3 in many European countries.

Air Pollutants↗
PubMed1992

Hormonal regulation of glycosylation process in rat small intestine: responsiveness of fucosyl-transferase activity to hydrocortisone during the suckling period, unresponsiveness after weaning.

The aim of this study was to examine the possible role of certain hormones (especially hydrocortisone) in the developmental variations of intestinal fucosyl-transferase activity in rats. Thyroxine and insulin, injected into suckling rats, did not induce significant modifications of the fucosyl-transferase activity, under the conditions used, whereas this enzyme activity was highly enhanced after administration of glucocorticoids (cortisone and hydrocortisone). Hydrocortisone administration to suckling rats induced a precocious and progressive activation of the fucosyl-transferase activity up to adult level as a function of the duration of treatment. The responsiveness of suckling rats to hydrocortisone, as shown by increased fucosyl-transferase activity, disappeared at the end of the third week (corresponding to the weaning time). These physiological periods of responsiveness and unresponsiveness to hydrocortisone could be related to the binding of the hormones to receptors since the antiglucocorticoid RU 38486 counteracted the effect of hydrocortisone in suckling rats but did not prevent the developmental rise of the fucosyl-transferase activity, when administered in the third week of life. These results suggest that the normal developmental rise of the fucosyl-transferase activity is independent of glucocorticoids.

Animals↗
PubMed1986

Brain-specific gene expression.

The brain of an adult rat expresses approximately 30,000 different brain-specific mRNAs. To investigate their encoded proteins, we have selected cDNA clones corresponding to mRNAs expressed exclusively in rat brain, determined their nucleotide sequences and generated antisera against synthetic peptides mimicking short regions of the deduced protein sequences. The clone plB236 encodes a protein that defines a widely distributed neuronal system and may be the precursor for a family of novel neuropeptides. A second clone, plB208, encodes rat brain proteolipid protein, the major protein component of central nervous system myelin. These studies have also identified an 82 nucleotide genetic element called an ID (identifier) sequence that may be involved in the regulation of transcription of brain-specific genes.

Amino Acid Sequence↗
PubMed1986

The brain-specific gene 1B236 is expressed postnatally in the developing rat brain.

The rat brain-specific polypeptide 1B236 was previously characterized by molecular cloning and nucleotide sequence determination of its mRNA. It has been shown to exist in rat brain in discrete neuronal circuits, primarily as a 100,000 Da glycoprotein. We now have determined the time course of expression of 1B236 mRNA and protein in rat brain during fetal and postnatal development, detecting 1B236 mRNA by RNA blotting and assaying 1B236 protein by electroblotting and radioimmunoassay with antibodies against synthetic peptides. By both indices, expression of the 1B236 gene products is found to be a relatively late event in neuronal development. 1B236 mRNA is first detectable in extracts of whole rat brain at Postnatal Day 5 (PD 5) and increases to a maximum concentration at PD 25. In extracts of dissected brain regions, 1B236 mRNA is first detectable at PD 5 in hindbrain and cerebellum, at PD 9 in midbrain/diencephalon, but not until PD 13 in telencephalon. The appearance of 1B236 protein follows a very similar time course to that of its mRNA in both whole brain and dissected brain regions, suggesting that the expression of the protein during development is regulated largely by transcription of its mRNA. The pattern of 1B236 expression was confirmed by immunocytochemical localization of 1B236 protein: Immunoreactive material can be detected first in spinal cord at PD 3-PD 5 and then appears in progressively more rostral brain regions in increasingly older animals. Several brain regions, however, that do not contain 1B236 immunoreactivity in the adult, such as optic nerve and somatic efferent cranial nerve nuclei, show transient expression of 1B236 during postnatal development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Nucleotide sequences of two mRNAs for rat brain myelin proteolipid protein.

The 3200 and 1600 nucleotide mRNAs encoding rat brain proteolipid protein (PLP), the major protein component of central nervous system myelin, are heterogeneous at their 5' ends, differ in their 3' polyadenylation sites, and are transcribed from a single gene. The mRNAs, which first appear postnatally, encode identical 277 amino acid proteins that are 99% identical to the bovine protein sequence. Thus, PLP has been highly conserved during mammalian evolution. A single amino-terminal methionine is removed post-translationally, indicating that PLP does not require a signal peptide sequence for insertion into the myelin membrane. Mouse and monkey utilize the 3200 but not the 1600 nucleotide mRNA, suggesting that there is no functional necessity for two sizes of rat PLP mRNAs.

Amino Acid Sequence↗
PubMed1984

Characterization and down-regulation of opiate receptors in aggregating fetal rat brain cells.

Aggregating brain cells prepared from embryonic rats bind radioactive opiates in a stereospecific manner. The drug selectivity, receptor content during culturing and down-regulation of these apparent opiate receptors were studied in aggregates prepared from the embryonic hindbrain or forebrain. The receptor content in hindbrain but not forebrain aggregates was increased up to 3-fold after 21 days in culture. Differences between the receptors of the two types of aggregates were also observed in the affinity of opiate alkaloids and D-Ala2,D-Leu5-enkephalin (DADL). The potent opiate alkaloid etorphine induced down-regulation of opiate receptors in aggregates prepared from either brain region whereas DADL was a potent down-regulator in the forebrain but not in the hindbrain aggregates and morphine had no effect in both tissues. The implications of these results concerning the control of various types of opiate receptors in the whole animal are discussed.

Animals↗
PubMed1983

Down-regulation of opiate receptors in serum-free cultures of aggregating fetal brain cells.

Brain cells from rat embryos that were cultured in serum-free medium form aggregates which possess stereospecific binding of radioactive opiates. The specificity of these opiate receptors and their regulation by opiate alkaloids and enkephalin was studied. D-ala2, D-leu5-enkephalin (DADL) induced down-regulation of opiate receptors in aggregates prepared from the forebrain but had no effect on hindbrain aggregates, whereas the potent alkaloid etorphine induced down-regulation of the receptors in both tissues. Interestingly, morphine did not induce down-regulation in both tissues. The significance of these findings and their relationship to the control of different types of opiate receptors are discussed.

Animals↗
PubMed1983

Insulin-like growth factor I (IGF I) stimulates DNA synthesis in fetal rat brain cell cultures.

Addition of insulin, IGF I or IGF II to serum-free cultures of fetal rat brain cells (gestation day 15/16) significantly stimulates DNA synthesis. The dose-response curves show that IGF I is more potent than insulin; half maximal stimulation of [3H]thymidine incorporation is obtained at about 0.4 nM IGF I and 14 nM insulin, respectively. Cultures initiated 2 days later (gestation day 17/18) showed a decreased responsiveness to both peptides. No additive effect was observed after combined addition of both peptides at near-maximal doses. Both peptides show a latency of action of about 12-18 h. In the presence of either IGF or insulin, neuronal as well as glial enzymes are increased, suggesting that neuronal and glial precursor cell division is influenced. IGF I and IGF II interact with a specific binding site for which insulin competes very weakly; however IGF I and IGF II bind with relatively high affinity to the insulin specific binding site. The present results support the hypothesis that both insulin and IGF stimulate mitotic activity by interacting with specific somatomedin receptors and suggest a physiological role of IGF in the developing brain.

Animals↗
PubMed1982

Nerve growth factor (NGF) stimulation of cholinergic telencephalic neurons in aggregating cell cultures.

The addition of nerve growth factor (2.5S NGF) to serum-free aggregating cell cultures of fetal rat telencephalon greatly stimulated the developmental increase in choline acetyltransferase activity. Two other neuronal enzymes, acetylcholinesterase and glutamic acid decarboxylase, showed only slightly increased activities after NGF treatment whereas the total protein content of the cultures and the activity of 2',3'- cyclic nucleotide phosphodiesterase remained unchanged. The stimulation of choline acetyltransferase was dependent on the NGF media concentrations, showing a 50% maximum effect (120% increase) at approximately 3 ng/ml (10-10 M 2.5S NGF). NGF treatments during different culture periods showed that the cholinergic neurons remained responsive for at least 19 days. The continued treatment was the most effective; however, an initial treatment for only 5 days still caused a significant stimulation of choline acetyltransferase on day 19. The observed stimulation appeared to be specific to NGF. Univalent antibody fragments (Fab) against 2.5S NGF completely abolished the NGF-dependent increase in choline acetyltransferase activity, whereas Fab fragments of control IgG were ineffective. Furthermore, angiotensin II, added in high amounts to the cultures, showed no stimulatory effect. The present results suggest that certain populations of rat brain neurons are responsive to nerve growth factor.

Acetylcholinesterase↗
PubMed1980

Triodothyronine enhancement of neuronal differentiation in aggregating fetal rat brain cells cultured in a chemically defined medium.

Triiodothyronine (30 nM) added to serum-free cultures of mechanically dissociated re-aggregating fetal (15-16 days gestation) rat brain cells greatly increased the enzymatic activity of choline acetyltransferase and acetylcholinesterase throughout the entire culture period (33 days), and markedly accelerated the developmental rise of glutamic acid decarboxylase specific activity. The enhancement of choline acetyltransferase and acetylcholinesterase specific activities in the presence of triiodothyronine was even more pronouned in cultures of telencephalic cells. If triiodothyronine treatment was restricted to the first 17 culture days, the level of choline acetyltransferase specific activity at day 33 was 84% of that in chronically treated cultures and 270% of that in cultures receiving triiodothyronine between days 17 and 33, indicating that relatively undifferentiated cells were more responsive to the hormone. Triiodothyronine had no apparent effect on the incorporation of [3H]thymidine at day 5 or on the total DNA content of cultures, suggesting that cellular differentiation, rather than proliferation was affected by the hormone. Our findings in vitro are in good agreement with many observations in vivo, suggesting that rotation-mediated aggregating cell cultures of fetal rat brain provide a useful model to study thyroid hormone action in the developing brain.

Acetylcholinesterase↗
PubMed1979

Growth and differentiation of aggregating fetal brain cells in a serum-free defined medium.

Aggregating cultures of mechanically dissociated fetal brain cells provide an excellent system for neurobiological studies of cellular growth and differentiation, but, in common with almost all culture systems, they have the disadvantage that crude serum is required in the medium. Although several cell lines have either been adapted to serum-free conditions or grown normally in serum-free media supplemented with hormones, trace elements and defined serum components, this approach has never been applied to differentiating primary cells of the central nervous system. We now describe the successful cultivation of aggregating fetal rat brain cells in a chemically defined, serum-free medium.

Animals↗