Somatomedin C: Restoration in Vivo of Cycle Traverse in G
            <sub>0</sub>
            /G
            <sub>1</sub>
            Blocked Cells of Hypophysectomized Animals

Rothstein, H.; Wyk, Judson J. Van; Hayden, John H.; Gordon, Sheldon R.; Weinsieder, A.

doi:10.1126/science.7189293

Cited by 86 publications

(10 citation statements)

References 22 publications

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“…A molecule having Sm-C/IGF-I activity is both necessary and sufficient to cause DNA synthesis and mitosis in postmetamorphic frog lens epithelial cells (27). Whether this factor directly stimulates lens fiber differentiation in these animals is not known.…”

Section: Discussionmentioning

confidence: 99%

Lentropin, a protein that controls lens fiber formation, is related functionally and immunologically to the insulin-like growth factors.

Beebe¹,

Silver²,

Belcher³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

132

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Lentropin, a factor present in the vitreous humor of the eye, stimulates lens fiber differentiation from chicken embryo lens epithelial cells in vitro. Lentropin has been partially purified but has not been isolated in sufficient quantity or purity for direct comparison with other growth and differentiation factors. Previous studies have shown that insulin and fetal bovine serum share with lentropin the ability to stimulate lens fiber formation from cultured epithelial cells. In the present study, a number of hormones and growth factors were assayed for lentropin activity. Of those tested, the only substances that had this activity were the insulin-like growth factors (IGFs) somatomedin C (Sm-C/IGF-I) and multiplication-stimulating activity (MSA/IGF-ll). Sm-C/IGF-I was approximately 30 times more potent than insulin or MSA/IGF-ll in promoting fiber cell formation. A monoclonal antibody to human Sm-C/IGF-I inhibited purified Sm-C/IGF-I, fetal bovine serum, and chicken vitreous humor from stimulating fiber cell differentiation in vitro. This antibody has been shown not to crossreact with insulin and did not block insulinstimulated lens fiber formation. These findings indicate that lentropin is related to the IGFs and that these factors may play important roles in controlling cell differentiation, in addition to their better-known ability to stimulate cell division.The lens of the eye is composed of two populations of epithelial cells. The anterior surface of the lens is covered by a monolayer of cuboidal cells, which have several important transport functions, whereas the bulk of the lens is composed of elongated fiber cells, which are primarily responsible for the ability of the lens to transmit and refract light. Fiber cells do not normally divide once they are formed. During lens growth new fibers are continually derived from the mitotically active cells at the margin of the epithelium. Cells from the central region of the chicken embryo lens epithelium, which would not normally become fiber cells, will differentiate into fibers when placed in culture medium supplemented with fetal bovine serum (1, 2), insulin (3), or chicken vitreous humor (4). Fiber cell differentiation is characterized by extensive cellular and biochemical specialization, including cell elongation, specialization for the synthesis and accumulation of lens-specific cytoplasmic proteins (the crystallins), cessation of cell division, alteration of the lipid and protein composition of the plasma membrane, and the eventual degradation of nearly all intracellular, membrane-bound organelles, including the nucleus.Lentropin, the protein in vitreous humor that stimulates lens fiber differentiation, has been characterized and partially purified (4, 5) but has not been obtained in sufficient quantity or purity for structural comparison with other growth and differentiation factors. For this reason we assayed several growth factors and hormones for the ability to stimulate cell elongation in central epithelia dissected from the lenses of 6-day-o...

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Section: Discussionmentioning

confidence: 99%

Lentropin, a protein that controls lens fiber formation, is related functionally and immunologically to the insulin-like growth factors.

Beebe¹,

Silver²,

Belcher³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

132

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“…The previous position, that these animals required much higher doses to produce cataracts, was probably the result of the fact that in earlier studies animals were used which were captured in the wild, and no knowledge was, therefore, available as to their age. Also, mitosis in the frog lens is under strict pituitary control [Van Buskirk et al, 1975, Wainwrightet al, 1976Rothstein et al, 1980], and the endocrine system is, in turn, modulated by seasonal changes [Rosenbaum and Rothstein, 1972;Rothstein and Worgul, 1973]. Thus, the time of the year during which studies are conducted is an important consideration.…”

Section: Discussionmentioning

confidence: 99%

Radiation Cataractogenesis in the Amphibian Lens

Worgul¹,

Rothstein²,

Medvedovsky³

et al. 1982

Ophthalmic Res

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This report describes a reproducible and characteristic sequelae for radiation cataractogenesis in the amphibian. The development of lens opacification was investigated as a function of dose and time after X-irradiation of the eye of postmetamorphic bullfrogs. It was found that the development of radiation cataracts in frogs is both age and dose dependent. It was also determined that, far from being radiation resistant, frog lenses are sensitive to doses that are moderately cataractogenic for mammals.

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“…Hence, the state of mitotic arrest caused by pituitary ablation is reversed by injection of purified human somatomedin C [Rothstein et al, 1980b) multiplication stimulating activity (MSA) or insulin [Rothstein et al, 1980a], These materials also restore proliferation in organ-cultured lenses from hypophysectomized frogs, whereas the pre viously noted pituitary and thyroidal hormones are only active in vivo [Wainwright et al, 1978]. We demonstrate now that though X-ray cataracts do develop in intact frogs and rats, as well as hypophysectomized rats, such is not the case in hypophysectomized frogs.…”

mentioning

confidence: 99%

G₀/G₁Arrest of Cell Proliferation in the Ocular Lens Prevents Development of Radiation Cataract

Rothstein¹,

Worgul²,

Medvedovsky³

et al. 1982

Ophthalmic Res

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Somatomedin C: Restoration in Vivo of Cycle Traverse in G ₀ /G ₁ Blocked Cells of Hypophysectomized Animals

Cited by 86 publications

References 22 publications

Lentropin, a protein that controls lens fiber formation, is related functionally and immunologically to the insulin-like growth factors.

Lentropin, a protein that controls lens fiber formation, is related functionally and immunologically to the insulin-like growth factors.

Radiation Cataractogenesis in the Amphibian Lens

G₀/G₁Arrest of Cell Proliferation in the Ocular Lens Prevents Development of Radiation Cataract

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Somatomedin C: Restoration in Vivo of Cycle Traverse in G 0 /G 1 Blocked Cells of Hypophysectomized Animals

Cited by 86 publications

References 22 publications

Lentropin, a protein that controls lens fiber formation, is related functionally and immunologically to the insulin-like growth factors.

Lentropin, a protein that controls lens fiber formation, is related functionally and immunologically to the insulin-like growth factors.

Radiation Cataractogenesis in the Amphibian Lens

G0/G1Arrest of Cell Proliferation in the Ocular Lens Prevents Development of Radiation Cataract

Contact Info

Product

Resources

About

Somatomedin C: Restoration in Vivo of Cycle Traverse in G ₀ /G ₁ Blocked Cells of Hypophysectomized Animals

G₀/G₁Arrest of Cell Proliferation in the Ocular Lens Prevents Development of Radiation Cataract