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J F Beaulieu

Publications and source records attributed to J F Beaulieu.

62 records · Page 4Linked to original sources
PubMed1985

Influences of dexamethasone on the maturation of fetal mouse intestinal mucosa in organ culture.

The effects of glucocorticoids on the maturation of the fetal small intestinal mucosa have been studied using duodenal explants resected at 17 days of gestation and cultured in a serum-free medium in the presence or absence of dexamethasone (30-300 ng/ml). Dexamethasone (a) increases specifically alkaline phosphatase, maltase, trehalase and sucrase activities and (b) allows an accumulation of goblet cells along the villi at a faster rate than that occurring in utero. These results indicate that glucocorticoids influence directly the differentiation of absorptive cells and goblet cells in the small intestine during the fetal period.

Alkaline Phosphatase↗
PubMed1985

Influence of epidermal growth factor on the maturation of the fetal mouse duodenum in organ culture.

The purpose of this work was to study the direct influence of epidermal growth factor (EGF) on the maturation of the fetal mouse duodenum in organ culture. Duodenal explants, resected at 17 days of gestation, were cultured during 48 h at 37 degrees C in Leibovitz L-15 serum-free medium alone or supplemented with EGF (100 ng/ml). Differentiation of absorptive cells was evaluated by measuring brush border hydrolytic activities. After 48 h of culture with and without EGF, villous architecture and the fine structural characteristics of the tissues are preserved. In control explants, the level of alkaline phosphatase, maltase, trehalase, and sucrase activities as well as the protein and DNA contents remain comparable to the values measured in 17-day explants at the beginning of the culture period, while lactase activity falls drastically. In explants cultured with EGF, the level of alkaline phosphatase, maltase, and trehalase activities and the protein contents significantly increase while sucrase activity and DNA contents are unchanged, and lactase activity remains under the onset level. From these results, it was concluded that EGF influences directly the maturation of some brush border enzymes in the duodenum during the fetal period.

Animals↗
PubMed1985

Permissive effect of glutamine on the differentiation of fetal mouse small intestine in organ culture.

The proximal third of the small intestine of 15-day-old mouse embryo can be cultured for 72 h at 37 degrees C. When Trowell-T8 medium is used, the integrity of the explants is maintained, but villi do not form and absorptive cells are poorly differentiated. However, when Leibovitz L-15 or RPMI-1640 medium is used, one can observe the formation of medium-sized villi, and absorptive cells in the explants are more differentiated. Since the chemical composition of T8 medium is quite different from that of the other two media, we decided to test the importance of two major differences, i.e., three amino acids and five vitamins, in order to find out which element(s) is necessary to permit the formation of intestinal villi. Subsequent testing demonstrated that the three amino acids are responsible for the effect on differentiation, and that glutamine is the only critical difference between T8 and the two other media. The results show that the addition of L-glutamine to T8 medium permits the formation of villi, the initiation of absorptive cell differentiation, an increase in DNA synthesis, and finally, an increase in the number of epithelial cells. These findings indicate that undifferentiated fetal mouse small intestine is able to express its phenotype in organ culture, even without any extrinsic regulatory influences, provided that L-glutamine is present at a sufficient level in the culture medium. The use of inhibitors indicated that L-glutamine may be essential as an energetic substrate and/or a precursor for glucosamine.

Animals↗
PubMed1984

Effect of dexamethasone on the fetal mouse small intestine in organ culture.

The formation of intestinal villi (organogenesis phase) may be studied in organ culture with a completely synthetic medium in 15-day fetal mouse duodenal explants. However, in these explants absorptive cells remained poorly differentiated with all the hormones studied except with epidermal growth factor. In order to elucidate the role of hormones and other factors on the maturation of absorptive cells (maturation phase) in the fetal rodent in organ culture, we have taken the explants after the organogenesis phase. We have studied different culture conditions and have found that 17-day mouse duodenal explants can be cultured during 48 hours with Leibovitz L-15 medium in a 95% O2-5% CO2 atmosphere provided that the explants are relatively large (5 X 2 mm). With this method, dexamethasone (Dx) has been shown to have a direct effect on the maturation of the fetal duodenal mucosa. The addition of Dx (300 ng/ml) to the completely synthetic medium 1) improves the morphology of the explants, 2) induces a significant increase in maltase activity in the tissues, and 3) reduces significantly the labeling index of the duodenal explants after 48 hours of culture. Direct action of Dx on the duodenal mucosa is shown for the first time in organ culture using a completely synthetic medium. This method will permit us to study the effects of other intrinsic and extrinsic factors on the regulation of enzymatic maturation in fetal small intestine.

Animals↗
PubMed1984

Comparative study of some intestinal brush border membrane enzymes during perinatal development of the mouse.

Intestinal brush border membrane (bbm) fractions have been isolated from fetal and neonatal mice. The existence of discordant developmental patterns of intestinal enzymatic activity derived from total homogenate and bbm fraction was confirmed. It originates chiefly from two phenomena: (a) variations in the state of purity of brush border fractions, and (b) loss of brush border membrane enzyme activities in supernatant that increases with age. The phenomenon of solubility for glucoamylase and alkaline phosphatase is already present two days before birth.

Aging↗
PubMed1981

The effect of epidermal growth factor (EGF) on the differentiation of the rough endoplasmic reticulum in fetal mouse small intestine in organ culture.

The differentiation of the rough endoplasmic reticulum (RER) of mouse duodenal absorptive cells located at the tip of the villi at 17 days of gestation was compared to that of absorptive cells in duodenal explants of 15-day-old mouse fetuses cultured for 72 hr 1) with Trowell T8 medium (without insulin) alone or supplemented 2) with epidermal growth factor (EGF; 100 ng/ml) or 3) with 25% bovine amniotic fluid (BAF). Glucose-6-phosphatase activity (G6Pase) was localized cytochemically to ensure a better identification of the RER. The intersections of a double lattice falling over and outside the RER were counted and the percentage of intersections over the RER was estimated. With this method, the extent of the RER is not statistically different when the absorptive cells in utero are compared to those of explants cultured with EGF. However, the extent of the RER in the absorptive cells cultured with Trowell T8 medium alone or supplemented with BAF is 50% lower than in the former two groups. It is concluded that EGF promotes the maturation of duodenal absorptive cells in organ culture.

Animals↗
PubMedDate not supplied

Silica exposure induces cytotoxicity and proliferative activity of type II pneumocytes.

The contribution of the type II pneumocyte to the pathogenesis of silicosis is largely unknown. Prominent features of silicosis are hyperplasia and hypertrophy of type II epithelial cells, often accompanied by phospholipid accumulation in the lung. The biologic regulation of these events is poorly understood. This study addresses the question of a direct effect of silica on type II pneumocytes, since direct contact of the inhaled silica dust can occur in vivo. Type II cells were isolated from fetal rat lungs and their epithelial specificity was verified. Experiments were performed on 2nd passage monolayers in 2% serum. Repair, replication, and growth activity was evaluated by the incorporation of [3H]thymidine. Cytotoxicity was measured by quantitating the release of [14C]adenine and expressed as a cytotoxicity index (CI). Type II cell proliferation and cytotoxicity were evaluated for the mineral dusts silica (SiO2), aluminum-treated silica (SiO2AlK), and titanium (TiO2). Of these mineral dusts, only low concentrations of silica increased type II cell [3H]thymidine incorporation (silica 2.5 micrograms/mL: 52% above control, P less than .05; silica 20 micrograms/mL: 57% above control, P less than .02). In addition, silica increased the cell number significantly, although to a lesser degree. Exposure of the type II epithelial cells to silica dust for 24 h resulted in dose-dependent cytotoxicity (silica 10 micrograms/mL, CI = 9.1%, P less than .0002; 250 micrograms/mL, CI = 45.1%, P less than .0001). SiO2Al completely suppressed these proliferation and cytotoxicity effects, which were then similar to those of the inert dust, TiO2. These data suggest that direct exposure and contact of the type II pneumocytes to low-dose silica dust initiated repair, replication, and growth activity, while exposure to higher silica concentrations resulted in marked cytotoxicity. Both the repair, replication, and growth and the cytotoxic responses of the type II epithelial cells to silica exposure are related to the surface properties of silica.

Animals↗