Biomedical subjects

C G Chamberlain

Publications and source records attributed to C G Chamberlain.

26 records · Page 2Linked to original sources

PubMed1993

IGF-1 enhancement of FGF-induced lens fiber differentiation in rats of different ages.

PURPOSE: Previously, using lens epithelial explants from neonatal rats, we showed that both insulin and IGF-1 synergistically enhance the effectiveness of FGF as an inducer of fiber differentiation. The authors aimed to determine whether IGF-1 enhances FGF-induced fiber differentiation in lens epithelial cells at various ages and, in particular, whether it can counter a marked age-related decline in responsiveness to FGF noted previously. METHODS: The effects of IGF-1 and bFGF were assessed using lens epithelial explants from neonatal, weanling, and adult rats. Fiber differentiation (after 13 days' culture) was monitored by crystallin ELISAs of explant lysates and also by immunofluorescent localization of crystallins. RESULTS: IGF alone had minimal effects. For younger rats, FGF alone enhanced the accumulation of alpha-, beta- and gamma-crystallins throughout explants, the peripheral region being more responsive than the central region. For adult rats, only the peripheral region responded; small amounts of alpha- and beta-crystallins were detected, but gamma-crystallin was not. Combining IGF with FGF induced gamma-crystallin in explants from adult rats (peripheral region) and enhanced the accumulation of all crystallins more than additively at all ages, mainly in the central region (young rats) or only in the peripheral region (adults). Including IGF with FGF prevented an age-related decline in the beta/alpha-crystallin ratio but not in the gamma/beta-crystallin ratio. CONCLUSIONS: IGF-1 enhances the bFGF-induced fiber differentiation responses of lens epithelial cells in neonatal, weanling, and adult rats, partially restoring an age-related decline in the responsiveness of lens cells to FGF.

Aging↗

PubMed1992

Age of rats affects response of lens epithelial explants to fibroblast growth factor.

Fibroblast growth factor (FGF) is a potent inducer of fibre differentiation in lens epithelial explants from neonatal rats. Previously, using explants prepared from the central region of the lens epithelium, we showed an age-related loss of ability to accumulate fibre-specific crystallins in response to basic FGF. These studies have now been extended to include the peripheral region of the lens epithelium. Firstly we cultured explants from the central or peripheral regions of neonatal lenses with varying doses of FGF for 5 days, then determined how much fibre-specific beta-crystallin they had accumulated. The concentration of FGF required to induce a half-maximal response was lower for peripheral than for central cells (7 ng ml-1 compared with 36 ng ml-1). We then compared the ability of peripheral explants from 3-, 21-, 100- and 175-day-old rats to undergo fibre differentiation during culture with FGF for 13 days. In these studies alpha-, beta- and gamma-crystallins were localized in explants or quantified by ELISAs. There was an age-related decrease in responsiveness to FGF, as already observed for central explants; however, unlike central explants, peripheral explants from the oldest rats still retained the ability to respond to FGF by accumulating beta-crystallin. This suggests that FGF in the eye may play an important role in inducing lens epithelial cells at the lens equator to differentiate into fibres throughout life.

Aging↗

PubMed1991

The role of fibroblast growth factor in eye lens development.

In this review we have presented evidence that FGF plays an important role in inducing events in lens morphogenesis and growth. Our studies show that FGF stimulates lens epithelial cells in explants to proliferate, migrate, and differentiate into fibers at low, medium, and high concentrations, respectively. This has some important implications for understanding the behavior of lens cells in the eye. The fact that aFGF is detected in the equatorial region of the lens where cells are actively proliferating, possibly migrating, and differentiating into fibers suggests that these events may be under autocrine control in vivo, at least to some extent. Because FGF is also present in the ciliary and iridial region of retina and in the vitreous, paracrine control may also be involved. Cell proliferation, fiber differentiation, and (possibly) cell migration occur in characteristic spatial patterns that are related to distinct compartments of the lens. We suggest that cells in the germinative zone receive only a low level of FGF stimulation arising from the cells themselves and possibly also from the ciliary and iridial regions of the retina but, whatever the source, this is only sufficient to stimulate proliferation. Lens epithelial cells that migrate or are displaced into the transitional zone below the lens equator receive some FGF from these sources but in addition receive a strong stimulus from the high level of FGF in the vitreous; thus, fiber differentiation is induced. Cells at the junction between these two zones may receive an intermediate level of FGF stimulation, sufficient to induce cell migration. In essence, we are proposing that, in the eye, FGF acts as a lens morphogen in the sense that different levels of FGF stimulation elicit different lens cell responses. Hence its characteristic distribution in the eye establishes lens polarity and growth patterns. Since FGF has an inductive effect on lens cells from mature age animals, we also propose that this specific distribution of FGF in the eye is also important for maintenance of a normal lens throughout life. Finally the synergistic effects of insulin/IGF on the FGF-induced responses highlight the importance of considering the distribution of members of the insulin/IGF family of molecules in vivo. Mechanisms that control levels of both the FGF and insulin/IGF families of factors in the eye are probably of crucial importance in the formation and maintenance of a normal lens.

Aging↗

PubMed1991

The effects of insulin and basic fibroblast growth factor on fibre differentiation in rat lens epithelial explants.

We have shown that fibroblast growth factors (FGFs) induce epithelial cells throughout lens explants to progressively divide, migrate and differentiate into fibres as the concentration of FGF is increased. We now report the effects of insulin and insulin-like growth factor-1 on rat lens epithelial explants, alone or in combination with the basic form of FGF. Fibre cell-specific beta- and gamma-crystallins were localised in explants by immunofluorescence or determined by ELISAs. For insulin, high doses induced limited beta-crystallin accumulation, much less than for FGF and mostly restricted to the explant periphery. When insulin was included with a low concentration of FGF, fibre differentiation was substantially enhanced. Both beta- and gamma-crystallin accumulation were affected synergistically, the effect being greater for gamma- than for beta-crystallin, and epithelial cells in both the central and peripheral region of the explant participated in the synergistic response. Insulin-like growth factor-1 at a concentration of 50 ng/ml mimicked the effects of insulin.

Animals↗

PubMed1990

Growth factors in the eye.

In this review we report the distribution and functional significance of growth factors in the eye. Representatives of the major growth factor families are found in the eye: fibroblast growth factor, insulin and insulin-like growth factor, transforming growth factor-beta, platelet-derived growth factor, nerve growth factor, epidermal growth factor and colony-stimulating factor. There are numerous examples of their actions on ocular tissues in vitro and in some cases in vivo. The findings presented clearly illustrate that a growth factor can elicit different responses depending on the context of its action; the cell type involved, the concentration of the growth factor and the presence or absence of other growth factors can all influence the cellular response both quantitatively and qualitatively. The results of these studies in the eye are of general significance to our understanding of the role of growth factors in biological processes.

Animals↗

PubMed1989

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)

Animals↗

PubMed1989

Induction of lens fibre differentiation by acidic and basic fibroblast growth factor (FGF).

Explants of epithelial cells from newborn rat lenses undergo changes characteristic of fibre differentiation when cultured with neural retina or retina-conditioned medium. Here we show that similar changes occur when acidic and basic fibroblast growth factor (FGF) are used instead of retina-conditioned medium. When cultured without FGF, epithelial explants contained negligible amounts of beta-crystallin, a lens protein found only in fibre cells. However, at saturating concentrations of FGF, about 20 micrograms beta-crystallin was produced per explant in 5 days. The response was dose-dependent, half maximal response requiring 55 and 290 ng/ml of basic and acidic FGF, respectively. FGF also stimulated cell proliferation and cell migration. All three responses to basic FGF were blocked by an antibody specific for basic FGF. The concentration of FGF required to produce a maximal response was lower for cell proliferation and migration than for beta-crystallin accumulation. The results suggest a possible role for FGF in the control of events in lens development.

Animals↗

PubMed1987

Evidence that fibroblast growth factor promotes lens fibre differentiation.

Lens epithelial cells from newborn rats undergo changes characteristic of fibre differentiation when cultured with rat neural retina or with a soluble mitogenic factor present in calf retina-conditioned medium. Mitogens have been isolated from retina in other laboratories, but have not previously been shown to promote fibre differentiation in mammalian lens. We prepared eye-derived growth factors I and II and alpha- and beta-retina-derived growth factors from bovine retinas. These factors all promoted lens fibre differentiation in our culture system, as assessed by morphological changes and the appearance of fibre cell-specific crystallins. There is now strong evidence that these retina-derived factors are identical to the acidic and basic forms of fibroblast growth factor (FGF), which is present in a variety of tissues. We found that acidic and basic FGF from rat brain also promoted lens fibre differentiation, suggesting that FGF is the factor from the retina responsible for inducing lens fibre differentiation.

Animals↗