Diabetes-induced suppression of IGF-1 and its receptor mRNA levels in rat superior cervical ganglia.

Insulin-like growth factor-I (IGF-I) is implicated in the development, survival and maintenance of function of sympathetic and sensory neurons. These neurons are affected at an early stage during the course of diabetes. Reverse transcriptase polymerase chain reaction (RT-PCR) based assay revealed that rat superior cervical ganglia (SCG) express mRNA transcripts for IGF-I and its receptor.

Scleral matrix metalloproteinases, serine proteinase activity and hydrational capacity are increased in myopia induced by retinal image degradation.

In the avian model of myopia, retinal image degradation quickly leads to ocular enlargement. We now give evidence that regionally specific changes in ocular size are correlated with both biomechanical indices of scleral remodeling, e.g.

Developmental changes in serum insulin-like growth factor-I and insulin-like growth factor binding proteins in the turkey embryo.

The ontogeny of insulin-like growth factor-I (IGF-I) and ontogeny as well as the molecular nature of the insulin-like growth factor binding proteins (IGFBP) as they relate to embryogenesis and posthatch growth in the turkey have not been reported. In this study, serum samples were harvested from turkey embryos incubated under shell-less and shelled conditions from Day 12 to 28 of incubation. Samples from 3, 6, and 8 wk posthatch were also evaluated.

Differential temporal and spatial expression of insulin-like growth factor binding protein-2 in developing chick ocular tissues.

Purpose: To determine the developmental expression and localization of mRNA for insulin-like growth factor binding protein-2 (IGFBP-2), a major binding protein of IGF-I and IGF-II, in ocular tissues of the embryonic and early posthatched chick.

Methods: In situ hybridization and northern blot analysis were used to analyze the cellular origin and relative expression of IGFBP-2 mRNA in ocular tissues.

Results: Wholemount in situ hybridization reveals that, as early as 3.

Cloning and characterization of a chick embryo cDNA and gene for IGF-binding protein-2.

We have isolated and characterized a cDNA for IGF-binding protein-2 (IGFBP-2) and its gene from the chick embryo. Using primers from a conserved region of the mammalian IGFBP-2 sequence, a cDNA clone (1.6 kb) was isolated from an embryonic day-18 chick retina cDNA library.

Truncation of IGF-I yields two mitogens for retinal Müller glial cells.

In the CNS only a truncated form of insulin-like growth factor-I (IGF-I) is detected. Although truncated IGF-I (t-IGF-I) retains mitogenicity, growth promoting activities have not been detected for the tripeptide that is cleaved from IGF-I during truncation. Here, we asked whether the tripeptide is itself a growth factor.

Vitreous and aqueous humors contain a latent proteinase activity that abolishes IGF binding to specific IGF binding proteins.

Several distinct insulin-like growth factor binding proteins (IGFBPs) are present in tissues and fluids of the developing and adult eye. However, the mechanism(s) involved in the regulation of ocular IGFBP levels is unknown. We have now identified an endogenous factor in vitreous and aqueous humors that, when activated by sodium dodecyl sulfate (SDS), abolishes the capacity of specific low molecular weight IGFBPs (i.

Identification and partial characterization of a proteinase specific for insulin-like growth factor binding protein-3 in aqueous and vitreous humors.

The IGFs (-I and -II) are normally found in serum and other extracellular fluids complexed to specific binding proteins (IGFBPs). While several IGFBPs have been identified in vitreous and aqueous humors, the major serum carrier of IGF, IGFBP-3, is notably absent from these fluids. To determine if this paucity could be due to an IGFBP-3 proteinase (IGFBP-3ase), samples of bovine vitreous or aqueous humor were mixed with serum and incubated at 37 degrees C for 4 h followed by western ligand blotting.

Characterization and novel activation of 72-kDa metalloproteinase in retinal interphotoreceptor matrix and Y-79 cell culture medium.

Analysis of bovine interphotoreceptor matrix and conditioned medium from human Y-79 retinoblastoma cells by gelatin SDS-PAGE zymography reveals abundant activity of a 72-kDa M(r) gelatinase. The 72-kDa gelatinase from either source is inhibited by EDTA but not aprotinin or NEM, indicating that it is a metalloproteinase (MMP). The 72-kDa MMP is converted to a 62-kDa species with APMA treatment after gelatin sepharose affinity purification, typical of previously described gelatinase MMP-2.

Vitreal insulin-like growth factor binding proteins (IGFBPs) are increased in human and animal diabetics.

Although patients with diabetic retinopathy have been reported to have elevated vitreal IGF-I levels, it is not known whether diabetes also affects the levels of vitreal IGF binding proteins (IGFBPs) which control IGF's bioavailability. To address this issue, vitreal IGFBP levels were assayed in human diabetics, rats with streptozotocin-induced diabetes and galactose-fed dogs with diabetic-like retinopathy. Using 125I-IGF-II ligand blots, it was found that human diabetics have a 4-fold increase in vitreal IGFBP levels.

Distribution of IGF-I and -II, IGF binding proteins (IGFBPs) and IGFBP mRNA in ocular fluids and tissues: potential sites of synthesis of IGFBPs in aqueous and vitreous.

Levels of insulin-like growth factor-I and II (IGF-I and IGF-II) in bovine aqueous humor are twice those found in the vitreous (aqueal IGF-I = 0.62 nM, vitreal IGF-I = 0.30 nM; aqueal IGF-II = 0.

Local synthesis and developmental regulation of avian vitreal insulin-like growth factor-binding proteins: a model for independent regulation in extravascular and vascular compartments.

The expression and regulation of insulin-like growth factor-binding proteins (IGFBPs) in developing avian vitreous humor and serum were compared. Vitreal IGF-I-binding activity was highest on embryonic day 6 [E-6; bound/free ratio (B/F), 0.22 +/- 0.

Monkey retinal pigment epithelial cells in vitro synthesize, secrete, and degrade insulin-like growth factor binding proteins.

Cultured monkey retinal pigment epithelial (RPE) cells rapidly secrete large amounts of insulin-like growth factor binding proteins (IGF-BPs). IGF-II tracer binding activity in conditioned media is two to three times greater than that of IGF-I. Under reducing SDS-PAGE conditions, 125I-IGF affinity-crosslinked binding protein (BP) is visualized as a broad band between 36 +/- 2.

Evidence for an insulin-like growth factor autocrine-paracrine system in the retinal photoreceptor-pigment epithelial cell complex.

The interphotoreceptor matrix (IPM), lying between retinal photoreceptor and pigment epithelial (RPE) cells, contains insulin-like growth factor I (IGF-I) immunoreactivity that co-elutes with authentic human IGF-I in HPLC analyses. Cultured human RPE cells synthesize and release IGF-I, raising the possibility that the RPE serves as a source of IPM IGF-I in vivo. Photoreceptor rod outer segments and cultured monkey RPE cells express specific IGF-I receptors with alpha-subunits of 120 and 138 kDa, respectively.

Insulin and IGF-I binding in developing chick neural retina and pigment epithelium: a characterization of binding and structural differences.

We have characterized insulin and insulin-like growth factor I (IGF-I) binding sites in developing chick retina and pigment epithelium (10- and 14-day embryonic, and 2-week post-hatched). For comparison, binding sites in brain and liver were also examined. Both the retina and pigment epithelium (PE) contain separate, specific, high affinity binding sites for insulin and IGF-I.

Insulin and IGF-1 binding in chick sclera.

The sclera of embryonic (days 10 and 14) and young adult (2-week posthatching chicks) contains distinct binding sites for insulin and for insulin-like growth factor-1 (IGF-1). Since there is a nearly 50% decrease in insulin and IGF-1 binding between embryonic day 10 and the 2nd week posthatching, it is clear that these sites are developmentally regulated. The affinity of each binding site for its ligand is stable across development.

IGF-I receptors in the bovine neural retina: structure, kinase activity and comparison with retinal insulin receptors.

The retina contains specific high-affinity receptors for insulin-like growth factor-I (IGF-I). Although IGF-I binding was observed in photoreceptor outer segments, the level of this binding was only 10% of that found in whole retina or mixed preparations of rod outer (ROS) and inner (RIS) segments. The higher IGF-I binding activity in RIS and non-photoreceptor regions of the retina suggests these sites as candidates for putative IGF-I action.

Insulin-related materials in the nervous system of vertebrates and non-vertebrates: possible extrapancreatic production.

Studies from multiple laboratories with a range of methods raised the possibility that insulin production occurs naturally at extrapancreatic sites. Part A covers the presence of insulin-related materials in organisms that do not have an endocrine pancreas, including unicellular prokaryotes and eukaryotes as well as multicellular non-vertebrate animals (insects et al.) and plants.

Anomalous insulin-binding activity in the bovine neural retina: a possible mechanism for regulation of receptor binding specificity.

Crude membrane from the bovine neural retina contains one IGF-I and two insulin binding sites. Although both insulin binding sites have a high affinity for insulin (IC50 = 0.1 and 7.

Retinal insulin receptors: localization using a polyclonal anti-insulin receptor antibody.

Although retinal insulin receptors have recently been described biochemically, the location of these receptors within the retina is unknown. The study presented here used a polyclonal anti-insulin receptor antibody (B10), immunofluorescence and immunoelectron microscopy to determine the location of insulin receptors in bovine, monkey and human retina. It was found that antibody immunofluorescence formed discrete bands localized predominantly to photoreceptor and neuronal cell bodies.

Insulin-induced drinking: an analysis of the involvement of renal angiotensin II and insulin-induced changes in plasma volume.

Male Long-Evans rats were used to investigate the potential hydrational mechanisms underlying insulin-induced drinking (IID). Plasma volume effects of insulin were assessed using both hematocrit and dye dilution procedures. Evidence is presented indicating that insulin produces a long-lasting and dose-dependent reduction in plasma volume.

Retinal insulin receptors. 2. Characterization and insulin-induced tyrosine kinase activity in bovine retinal rod outer segments.

Bovine retinal rod outer segments (ROS) possess specific, high-affinity receptors for insulin. These receptors exhibit an insulin-stimulatable tyrosine-specific activity that is capable of phosphorylating the receptor's own beta-subunit and exogenous substrate. ROS insulin receptors exhibit heterogeneity in the apparent molecular weight of the receptor's alpha-subunit.

Retinal insulin receptors. 1. Structural heterogeneity and functional characterization.

Neural cells of the bovine retina contain specific, high-affinity receptors for insulin. When solubilized and wheat-germ purified, these receptors exhibit a kinase activity that is capable of phosphorylating the receptor's beta-subunit (autophosphorylation) and a tyrosine-containing exogenous substrate, poly (Glu, Tyr) 4:1. Studies of the structure of retinal insulin receptors revealed the existence of two insulin receptor subpopulations.

Insulin receptors in the peripheral nervous system: a structural and functional analysis.

Although the brain is known to contain specific insulin receptors, there is no information on whether these receptors are also present in the peripheral nervous system (PNS). The present studies sought to provide this information by characterizing insulin binding in bovine autonomic (superior cervical) and sensory (trigeminal) ganglia. It was found that both ganglia contain specific, high-affinity receptors for insulin.

Rostral hypothalamic microinfusions of 5,7 dihydroxytryptamine produce anatomically and neurochemically selective depletions of hippocampal serotonin and increase the influence of estrogen and food deprivation on locomotor activity.

Ovariectomized Long-Evans rats received bilateral rostral hypothalamic infusions of 5,7-dihydroxytryptamine (5,7-DHT). Neurochemical determination of catecholamines (CA) and indoleamines in the hippocampus, hypothalamus and mesencephalon revealed that 5,7-DHT infusions had no effect on CA content in these areas nor in mesencephalic serotonin or 5-hydroxyindoleacetic acid (5-HIAA). However, the neurotoxin produced significant decreases in hippocampal serotonin and 5-HIAA.