Proliferation Of Explants Research Articles

Accelerated fetal lung maturation by estrogen is associated with an epithelial-fibroblast interaction

The role of epithelial-mesenchymal interactions in the stimulation of lung development by estrogen is now investigated using organ cultures of lung from male and female fetal rats taken from Days 17 to 21 of gestation. Estradiol at 1 microgram/ml was found to reduce cell proliferation in explants taken during a rapid growth phase (Day 18) and to stimulate surfactant synthesis in both males and females only in Day 20 explants when cell division is much slower. At this time more epithelial cells from estrogen-treated explants contained lamellar bodies, which were also secreted to fill the air sacs. These cultures also showed a significant increase in the frequency of cell-to-cell contacts between epithelial cells and fibroblasts. Uptake of tritiated estradiol by explants increased from Day 18 onward, and by autoradiography, labeling was located predominantly over fibroblasts. Using pure cultures of fetal and adult cells, uptake of labeled estradiol was significantly higher in fibroblasts than in corresponding epithelial cells, and estradiol did not directly enhance palmitate incorporation into epithelial cells. The results suggest that the earlier maturation and increased surfactant synthesis in female fetal lung is related at least in part to enhanced binding of estrogen by the fibroblast with subsequent transfer of a maturation factor to the fetal epithelium.

Fibroblast growth factor (FGF) induces different responses in lens epithelial cells depending on its concentration.

We reported previously that epithelial cells in explants from neonatal rat lenses, when cultured in the presence of fibroblast growth factor (FGF), showed increased proliferation, cell migration and fibre differentiation; moreover, fibre differentiation in response to the basic form of FGF (bFGF) was virtually completely blocked by an anti-bFGF antibody. In the present study, we report a detailed analysis of the effects of bFGF on cells in the central region of lens epithelial explants. Proliferation in explants was assessed by measuring [3H]thymidine incorporation. Cell migration was measured by labelling cells in explants with fluorescein isothiocyanate (FITC)-dextran and monitoring them by UV fluorescence microscopy. Fibre differentiation in explants was assessed on the basis of beta-crystallin accumulation. This study showed that half maximal activities for the three responses, proliferation, migration and fibre differentiation, were achieved at different concentrations of bFGF, namely, 0.15, 3 and 40 ng ml-1, respectively. Thus, the response of lens epithelial cells to bFGF varied qualitatively, as well as quantitatively, as the concentration increased. Monitoring FITC-dextran injection cells for up to 5 days after exposure to bFGF allowed analysis of the interrelation between various responses to bFGF in individual cells. As expected some cells divided in response to FGF, mainly within the first three days. However, whether or not they divided, all labelled cells responded to FGF by migrating and elongating. Maximal migration occurred during the first day of culture and maximal elongation was achieved by day 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship Between Morphology and X-Ray Effects in Implants of Mouse Sarcoma 180 Irradiated with 5,000 and 60,000 Roentgens (in Air)

The experiment to be described in this paper deals with the morphology of implants of mouse sarcoma 180 previously irradiated with 5,000 r (in air), as compared with that of implants irradiated with 60,000 r (in air) and unirradiated controls, as they appeared during ten successive days following implantation into 100 per cent susceptible mice. This is an extension of previous investigations in which it was demonstrated (a) that a dose of 60,000 r, measured in air, was required to prevent the proliferation of explants of mouse sarcoma 180 in a culture medium in vitro (1); (b) that a dose of 5,000 r was sufficient to prevent implants from producing a detectable tumor in vivo in a strain in which control implants were 100 per cent successful (2); (c) that animals implanted with tumor fragments irradiated with 5,000 r became resistant to subsequent implants of the same type of tumor, while those animals implanted with tumor fragments irradiated with 60,000 r did not (3). Several authors (4–9) have investigated the reaction of an immune host to viable tumor implants, but there has apparently been no cytological study of tumor implants inducing resistance in 100 per cent susceptible hosts. Experimental Procedure The same strain of mice (C.F.X. strain from Carworth Farms) was used here as in the previous experiments (1–3), and the experimental procedure was similar. An eight-day-old tumor was removed from the host under aseptic precautions. In order to secure actively growing cells and to avoid necrosis, only portions from the periphery of the tumor were taken for implants. With a cataract knife, fragments were cut, ranging from 1 to 2 mg. in weight, from 1.2 to 1.5 mm. in length, and from 1.4 to 0.9 mm. in thickness. These fragments were divided into three portions. Each was placed on a No.1 coverslip, which had been previously attached to a square mica sheet, covered with a Maximow slide, and sealed with paraffin. To avoid evaporation, a fragment of moist filter paper was placed in the concavity of the Maximow slide. One portion of the tumor fragments was then irradiated with 5,000 r, measured in air without backscatter, and another with 60,000 r. The third portion, which was not irradiated, was used for a control. The physical factors were as follows: 200 kv., 20 ma., 0.5 mm. Cu + 1.0 mm. Al, half-value layer equivalent to 0.85 mm. Cu, focal tissuetarget distance 12.5 cm., with a dosage rate of 612 r per min. measured in air. Immediately after irradiation, the tumor fragments were implanted into animals by means of a trocar. The chosen site for implantation was about the middle of the abdomen, between the groin and the axilla. This site was found by Russell (4) to be the most suitable, for the graft is thus placed in clean fascial tissue below the cutis, avoiding the extensive adipose tissue which is present in the axillary and groin region in the mouse.