IGF-I Immunoreactivity Research Articles

Interactions between Bcl-2 and the IGF system control apoptosis in the developing mouse brain

The IGF system and the pro-survival Bcl-2 proteins protect cells from apoptosis and play a key role in brain development. In order to examine a possible relationship between these two potent anti-apoptotic systems, we utilised two transgenic mice models overexpressing either Bcl-2 or IGF-I proteins in olfactory bulb (OB) or cerebellar neurons, respectively. We have demonstrated that while the organization of the defined layers of the OB from the bcl-2 transgenic and wildtype mice cultured in serum free medium (SF) was similarly poor, the mitral cell layer from the transgenic mice was expanded and their neurons were well preserved. Addition of IGF-I improved the definition of the layers normally present within the OB, in both wildtype and bcl-2 transgenic mice, and restored wildtype mitral cell layer structure and neuronal survival similar to that in bcl-2 mice, whose mitral cell survival was not further enhanced by IGF-I. Immunoreactivity for IGF-I and IGFBP-2 was markedly increased in these Bcl-2-expressing mitral cells compared to wildtype mice. In newborn IGF-I transgenic mice, cerebellar Purkinje cells overexpressing IGF-I showed markedly increased immunoreactivity for Bcl-2 and IGFBP-2. These studies indicate that in the developing brain IGF-I modulates expression of its major binding protein IGFBP-2, as well as the Bcl-2 protein. In addition apoptosis caused by culturing OBs in SF medium, is inhibited by expression of Bcl-2 in the mitral neurons and is associated with enhanced expression of the IGF system, including IGF-I and IGFBP-2. The later may thus play a role in IGF targeting. This complex interaction between the two potent anti-apoptotic systems is likely to provide a robust system of cell protection during brain development and repair.

Ontogeny of the Insulin-like Growth Factor System (IGF-I, IGF-II, and IGF-1R) in Gilthead Seabream (Sparus aurata): Expression and Cellular Localization

There is evidence for the presence of an insulin-like growth factor (IGF) system during fish development. The pattern of gene expression of IGF-I, IGF-II, and their cognate receptors during early development of gilthead seabream (Sparus aurata) was studied by reverse transcription-polymerase chain reaction (RT-PCR). Transcripts for IGF-I, IGF-II, and IGF-1R were detected throughout development in unfertilized eggs, embryos, and larvae, suggesting that these mRNAs are products of both the maternal and the embryonic genomes. Analysis of IGF-1R mRNA in various adult tissues using RT-PCR revealed expression in all tissues studied, with the highest levels in gill cartilage, skin, kidney, heart, pyloric caeca, and brain. The distribution of the two types of IGF-1R and IGF-I in gilthead seabream larvae was studied by immunohistochemistry and found to be tissue-specific and age-dependent. IGF-I and its receptors are widely distributed and appear in various tissues of seabream larvae. IGF-I immunoreactivity was highest in skeletal muscle and pancreas. The general distribution of the two types of IGF receptors in larval tissues appeared similar except for the muscle and the corpus cerebelli, in which IGF-1R was detected only by SpIR6 antisera. Both IGF-I and IGF-II may thus play a role during early development of teleosts, as in other vertebrates.

Insulin-like growth factor-I and -II in the ovary of a bony fish, Oreochromis mossambicus, the tilapia: in situ hybridisation, immunohistochemical localisation, Northern blot and cDNA sequences

There is accumulating evidence that insulin-like growth factor (IGF)-I and IGF-II are present in the mammalian ovary but comparable studies on bony fish remain scarce. Thus, the present study aims to analyse several parameters of the IGFs in the ovary of a bony fish, the tilapia, ( Oreochromis mossambicus). Molecular biological and morphological techniques were applied. The IGF-I and IGF-II cDNA sequences established from the ovary indicate that the same molecules are present in ovary and liver. Northern blot analysis revealed four IGF-I mRNA transcripts (6.0, 3.9, 1.9, 0.5 kb) and three IGF-II mRNA transcripts (5.0, 4.0, 2.0 kb) in ovary and liver. The amounts of IGF-I and IGF-II mRNA in the ovary were considerably high when compared to those in liver (IGF-I: 80.7%; IGF-II: 63.7%). The expression of IGF-I mRNA and IGF-II mRNA in the ovary were studied by in situ hybridisation and the peptides located by immunohistochemistry. The expression of IGF-I varied between the different developmental stages. Both IGF-I mRNA and IGF-I immunoreactivity were present in small oocytes. Moderate IGF-I expression and immunoreactivity occurred in granulosa cells of follicles at the lipid stage. A high IGF-I expression was observed in the granulosa and theca cells surrounding oocytes at the yolk globule stages and mature oocytes but neither IGF-I mRNA nor IGF-I immunoreactivity occurred in oocytes of the later stages. Thus, the IGF-I production seems to change from the young oocyte to the surrounding follicle cells at the later stages. In contrast, IGF-II mRNA and IGF-II-immunoreactivity occurred only in granulosa cells of the late follicle stages. The results suggest that both IGF-I and IGF-II are involved in the maturation of bony fish oocytes and in follicle development in a paracrine/autocrine manner. IGF-I and IGF-II may exert their effects at different stages of development. Furthermore, the intraovarian IGF-I and IGF-II systems seem to have a long phylogenetic history indicating the importance of the IGFs in reproductive biology.

Regulation of Gonadal and Somatotropic Axis by Chronic Intraventricular Infusion of Insulin-Like Growth Factor 1 Antibody at the Initiation of Puberty in Male Rats

There has been increasing experimental evidence to suggest that insulin-like growth factor 1 (IGF-I) may be one of the essential regulators in the reproductive system of the rat. IGF-I is synthesized in the hypothalamus and IGF-I immunoreactivity increases during puberty. Consequently we hypothesized that centrally located IGF-I might contribute to the initiation of puberty. Centrally located IGF-I was immunoneutralized to assess this hypothesis. Male Wistar rats, 28 days old, were infused intracerebroventricularly with specific purified IgGs from rabbit IGF-I antiserum (IGF-I-Ab). The intracerebroventricular administration of IGF-I-Ab resulted in a reduction in testicular weight and consequently in delayed pubertal development. There was also a reduction in serum testosterone, pituitary immunoreactive (IR) luteinizing hormone (LH) and serum IR follicle-stimulating hormone (FSH). The accumulation of βLH mRNA was not modified, whereas βFSH mRNA was increased. An increment in the serum growth hormone (GH) levels was also observed. There were no significant alterations in hypothalamic IR growth hormone releasing factor content, although IR somatostatin (SRIH) content was increased by IGF-I-Ab. The body weight gain remained unaltered. As a whole, our study suggests that centrally located IGF-I influences pubertal development, production and release of gonadotropins and supports the finding that endogenous centrally located IGF-I plays a role at the initiation of puberty in the male rat. It also gives support to the physiological role of centrally located IGF-I in the release of GH mediated by hypothalamic SRIH at the initiation of puberty.

Possible interactions between gonadotrophs and somatotrophs in the pituitary of tilapia: apparent roles for insulin-like growth factor I and estradiol.

The unique organization of the teleost pituitary, in which cells are grouped according to their characteristic hormone, makes this a suitable model for studying pituitary paracrine interactions. In a number of fish, including tilapia, there are variations in the circulating levels of the gonadotropins and GH, which are elevated during the reproductive season, suggesting interactions between the reproductive and growth axes. The aim of this study was to investigate paracrine interactions between the gonadotrophs and somatotrophs in the tilapia pituitary. Initially, dispersed pituitary cells were separated on a density gradient in which the gonadotrophs were found in the least dense fractions, and the somatotrophs were concentrated in the densest fraction. After 4 days in culture, cells in the least dense fractions showed characteristic cytoplasmic extensions not seen in the somatotrophs, which appeared small and failed to form aggregates; somatotrophs were found, however, attached to other non-GH cells. Staining of the nuclei with 4,6-diaminidino-2-phenyl-dihydrochloride revealed that the isolated somatotrophs had undergone nuclear condensation and fragmentation typical of apoptosis. Addition of either estradiol or human recombinant insulin-like growth factor I (IGF-I; 10 nM) to the somatotroph cultures increased the number of cell aggregates and reduced the number of condensed or fragmented nuclei. Immunocytochemical studies on pituitary sections revealed IGF-I immunoreactivity in regions of the proximal pars distalis that stain with gonadotropin IIbeta antisera and also in regions of the rostral pars distalis characteristic of corticotrophs; immunoreactive IGF-I was never seen in the region of the somatotrophs. Incubation of cells from the different fractions with testosterone (10 nM; 24 h) revealed that cells of the least dense fractions, which were rich in gonadotrophs, possessed aromatizing ability, which was absent in the somatotroph-enriched fraction. These results suggest that estradiol and IGF-I, both generated from cells other than the somatotrophs, may exert antiapoptotic effects and thus possibly control the size of this population of cells.

Cellular distribution and ontogeny of insulin-like growth factors (IGFs) and IGF binding protein messenger RNAs and peptides in developing rat pancreas.

To determine the role of insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) in the development of the pancreas, and specifically of the islets of Langerhans, we have examined the cellular distribution and developmental changes in the expression of IGFs and IGFBPs in the pancreas of the fetal and neonatal rat between 19.5 days of gestation and postnatal day 28. This represents a period of substantial growth and restructuring of the beta cell component in islets of this species. IGF-I, IGF-II, and IGFBPs-1 to -6 mRNAs were localized by in situ hybridization, and peptides by immunohistochemistry, in histological sections. IGF-II mRNA was highly expressed in islet cells and some ductal epithelial cells in late fetal and early neonatal life, but was barely detectable by postnatal day 28. IGF-II peptide showed a similar distribution. IGF-I mRNA was barely detected in the fetus or neonate and was localized predominantly in the ductal and acinar tissues after postnatal day 7. IGF-I immunoreactivity was associated with some islet cells in the fetus and neonate, suggesting an endocrine rather than a paracrine source. We performed co-localization studies to assess whether the distribution of IGFs within the pancreas might be due to a sequestration by locally produced IGFBPs. The presence of mRNAs for both IGFBPs-1 and -2 was minimal in the pancreas prior to postnatal day 7, although subsequently IGFBP-1 mRNA was seen in islet cells, while IGFBP-2 mRNA was localized in both islets and acinar tissues. In contrast, both IGFBPs-1 and -2 immunoreactivities were identified in islets from late fetal life, suggesting a circulatory source for these IGFBPs during early pancreatic development. IGFBPs-3 to -5 mRNAs and immunoreactivities were identified within islet cells throughout fetal and neonatal life, with IGFBPs-3 and -5 being mainly associated with the alpha cell-rich islet mantle. The results show a compartmentalization of IGFs within pancreatic tissue, reflecting both paracrine and endocrine sources. The localization and action of IGFs in pancreas likely involves sequestration and distribution by endogenous as well as circulating IGFBPs.

Immunohistochemical evidence for the presence, localization and partial coexistence of insulin, insulin-like growth factor I and relaxin in the protochordate Ciona intestinalis.

The occurrence and coexistence of peptides of the insulin-like growth factor (IGF)/insulin superfamily were investigated in the ovary and gastro-intestinal tract of the protochordate Ciona intestinalis. Antisera specific for mammalian IGF-I, insulin and relaxin were used in a double-immunofluorescence method on paraffin sections and with an immunogold technique on consecutive semi-thin sections. IGF-I and relaxin immunoreactions but no insulin immunoreactions occurred in the ovary and were confined to medium-sized and mature follicle cells. Two subpopulations of reacting follicular cells were present: those containing only IGF-I immunoreactivity (5%) and those containing IGF-I and relaxin immunoreactivities (95%). In the gastro-intestinal tract, IGF-I and insulin immunoreactions coexisted, whereas no relaxin immunoreactions were obtained. Gel chromatography and radioimmunoassay in Ciona ovary revealed IGF-I immunoreactivity in two peaks with apparent molecular masses of approximately 16 kDa and 3 kDa. The present results indicate that (1) the same IGF-I-related peptide probably occurs in gastro-intestinal tract and ovary, (2) three different members of the insulin/IGF family of peptides are probably present in protochordates, (3) different types of coexistence of these peptides seem to exist in protochordates, i.e. an IGF-I-related peptide and an insulin-related peptide in the digestive tract and, as shown previously, in central nervous system, and the IGF-I-related peptide and relaxin in the ovary, (4) an IGF-I-related peptide and relaxin may be involved in oocyte maturation in the protochordate ovary.

IGF-I, bFGF AND TGF-?? IMMUNOREACTIVITIES AFTER ECCENTRIC CONTRACTION-INDUCED MUSCLE INJURY IN VIVO

584 Many in vitro studies have suggested that local growth factors play important roles for skeletal muscle regeneration. It has not been clearly shown that when and where these growth factors express in muscle tissue during regeneration process after exercise-induced muscle injury. This study immunohistochemically examined the time course of changes in insulin-like growth factor (IGF-I), basic fibroblast growth factor (bFGF), and transforming growth factor beta (TGF-β) immunoreactivities after eccentric contraction-induced muscle injury in vivo. Immunoreactivities of the growth factors in the tibialis anterior (TA) muscle of adult female Wistar rats (6-8 months) were compared between the right and left limb on 6 successive days(3-4 rats /group, n=20) after eccentric contractions. The right TA was subjected to a bout of 50 eccentric contractions elicited by electrical stimulation, and the left TA was served as a noncontraction control. The IGF-I immunoreactivity started to increase at 1 day after contractions and the most pronounced increase was observed at 4 days within the cytosol and the mononuclear cells of the extra cellular space of damaged fibers. The level gradually decreased to the control level thereafter. The bFGF level only elevated at 4-5 days particularly at the mononuclear cells in the extra cellular space. The level of TGF-β slightly increased at 1 day, and markedly increased at 3 days around the mononuclear cells, then gradually decreased by 4-6 days. It is concluded that the level and the time course of changes in immunoreactivities were different among IGF-I, bFGF, and TGF-β during regeneration after eccentric contraction-induced muscle injury. The mononuclear cells around the damaged fibers were intensely stained for all of the growth factors.

Insulin-like growth factor I in the teleost Oreochromis mossambicus, the tilapia: gene sequence, tissue expression, and cellular localization.

Using reverse transcription-PCR and molecular cloning, the complementary DNA sequence encoding preproinsulin-like growth factor I (IGF-I) of a teleost, the tilapia (Oreochromis mossambicus) was established from liver. At the amino acid level, tilapia IGF-I shows all residues necessary for the maintenance of tertiary structure and shares about 80% identity with IGF-I from other teleosts. The B and A domains of tilapia IGF-I show more than 90% homology to those of other teleosts and 86-93% to those of human. However, in contrast to salmonids, the C domain of tilapia is truncated. Reverse transcription-PCR analysis followed by Southern blotting with an internal probe specific for tilapia IGF-I indicated a transcript in liver, pancreas, gut, kidney, head kidney, gill, ovary, testis, eye, and brain. In correlation, parenchymal cells were identified as likely local production sites by the use of immunohistochemistry. IGF-I immunoreactivity was confined to D cells in pancreatic islets, gastroentero-endocrine cells, cells of renal proximal tubules, interrenal cells of the head kidney, gill chondrocytes, chloride cells of the gill epithelium, granulosa cells in the ovary, spermatocytes and Sertoli cells in testis, and neurons in retina and brain. The local production of IGF-I in multiple organs of the tilapia indicates paracrine/autocrine actions of IGF-I involved in organ-specific functions. The results further demonstrate that the primary structure of IGF-I, especially in the B and A domains, is highly conserved during phylogeny.

Characterization of Insulin‐Like Growth Factor‐I and Its Receptor and Binding Proteins in Transected Nerves and Cultured Schwann Cells

The insulin-like growth factors (IGFs) are trophic factors whose growth-promoting actions are mediated via the IGF-I receptor and modulated by six IGF binding proteins (IGFBPs). In this study, we observed increased transcripts of both IGF-I and IGF-I receptor after rat sciatic nerve transection. Schwann cells (SCs) were the main source of IGF-I and IGFBP-5 immunoreactivity until 7 days after nerve transection, when invading macrophages in the distal nerve stumps were strongly IGF-I positive. In vitro, IGF-I promoted SC mitogenesis. Northern analysis revealed that SCs expressed IGF-I receptor and IGFBP-5. IGF-I treatment increased the intensity of IGFBP-5 without affecting gene expression. Des(1-3)IGF-I, an IGF-I analogue with low affinity for IGFBP, had no such effect. Incubation of recombinant human IGFBP-5 with SC conditioned media revealed IGF-I protection of IGFBP-5 from proteolysis, implying the presence of an IGFBP-5 protease in SC conditioned media. Collectively, these data support the concept that, in response to nerve injury, invading macrophages produce IGF-I and SC express the IGF-I receptor, to facilitate regeneration. This regenerative process may be augmented further by the ability of SC to secrete IGFBPs, which in turn may increase local IGF-I bioavailability.

Immunohistochemical Localization of Insulin-like Growth Factor I and II in the Endocrine Pancreas of Birds, Reptiles, and Amphibia

Immunoreactive insulin-like growth factors I and II (IGF-I, IGF-II) were sought in the endocrine pancreas of representative birds, reptiles, and amphibia using antisera specific for mammalian IGF-I and IGF-II and the classical islet hormones insulin (INS), glucagon (GLUC), somatostatin (SOM), and pancreatic polypeptide (PP) in double immunofluorescence. Both IGF-I and IGF-II immunoreactivities were present in the endocrine pancreas of all species. IGF-II immunoreactivity was exclusively found in INS-immunoreactive (-IR) cells, indicating evolutionary conservation of the islet IGF-II system. In contrast, IGF-I immunoreactivity was distributed differently among the species and never occurred in INS-IR cells. In the anuran Xenopus laevis, IGF-I immunoreactivity was present in islet cells showing coexistence of GLUC and PP immunoreactivities. In reptiles, the lizards ( Lacerta viridis, Scincus officinalis) exhibited IGF-I immunoreactivity in PP-IR and SOM-IR cells and the snakes ( Psamophis leniolatum, Coluber ravergieri) in SOM-IR and GLUC-IR cells. In birds, IGF-I immunoreactivity was located either in SOM-IR cells only ( Gallus g. domesticus, Streptopelia roseogrisea) or in PP-IR and SOM-IR cells ( Coturnix c. japonica). Thus, the distribution patterns of islet IGF-I immunoreactivities in birds, reptiles, and amphibia are equivalent to those in mammals and most bony fish. They differ, however, from those found in cartilaginous fish, cyclostomes, and protochordates, where a total or partial coexistence of IGF-I and INS immunoreactivities has been obtained. Therefore, the divergence of IGF-I and INS seems to have occurred early in vertebrate phylogeny. Furthermore, the existence of IGF-I immunoreactivity likely is common in the islets of all vertebrates. Finally, no phylogenetic trend to concentrate IGF-I immunoreactivity in a particular islet cell type is apparent.

Regional variation of insulin-like growth factor-I gene expression in mature rat bone and cartilage

Regulation of long bone growth by growth hormone and other endocrine factors is mediated by the local synthesis of IGF-I in the growth plate. Recent evidence suggests that different regions of the growth plate exhibit variable growth rates. To investigate whether IGF-I gene expression in the growth plate differs in relation to growth, we examined the distribution of IGF-I mRNA and peptide using in situ hybridization and immunohistochemistry, respectively, in the tibiae of 18-week-old rats ( n = 6). Osteoblasts were identified by osteocalcin immunoreactivity, and osteoclasts by tartrateresistant acid phosphatase (TRAP) histochemistry. The abundance of IGF-I mRNA in growth plate chondrocytes was quantified by counting the autoradiographic signal associated with each cell. IGF-I mRNA was identified in chondrocytes of both the proliferative and hypertrophic zones of the growth plate. Cells in the marginal regions of both zones contained significantly more IGF-I mRNA than those in the central region ( p < 0.05). In addition, IGF-I mRNA levels were greater in the periphery of the growth plate on the medial side of the tibia ( p < 0.05) in which there was more active growth than the lateral side. IGF-I immunoreactivity was present predominantly in the hypertrophic zone chondrocytes and no regional differences in its distribution were observed. IGF-I mRNA and peptide were also identified in periosteal fibroblasts, notably at sites of muscle attachment to bone, and in osteoblasts at active sites of bone remodelling in the periosteal, endocortical, and endosteal bone envelopes. In the TRAP-positive osteoclasts, IGF-I immunoreactivity, but not IGF-I mRNA, was detected. In addition, both IGF-I mRNA and peptide were identified in the hemopoietic cells of the metaphyseal bone marrow, whereas only IGF-I immunoreactivity was detectable in the diaphysis. We conclude that, in the tibiae of mature rats: (i) IGF-I gene expression in the growth plate is related to its growth and/or synthetic activity; and (ii) the presence of IGF-I in osteoblasts and osteoclasts suggests its involvement in active bone growth and remodeling.

Immunohistochemical aspects of insulin-like growth factors I and II in the bovine corpus luteum.

The cellular distribution of insulin-like growth factors I and II (IGF-I and -II) was examined in bovine corpora lutea at different stages of the luteal phase using specific antibodies and the avidin-biotin immunoperoxidase technique. At the cellular level, intense immunostaining for IGF-I was exclusively observed in large and small luteal cells and in a limited number of endothelial cells. Positive IGF-I immunoreactivity in luteal cells was thereby distributed in a distinct topographical, lobule-specific manner. Immunoreactivity in central areas of luteal lobules was most abundant in large luteal cells, whereas in peripheral zones significantly (P < 0.05) more small luteal cells exhibited IGF-I immunoreactivity. This distribution pattern was evident from day 4 of the cycle onwards and occurred at all the stages investigated. The percentage of positive small (SLC) and large (LLC) luteal cells revealed by semiquantitative analysis depended on the stage of the cycle as follows: days 4-7: 34% LLC versus 21.3% SLC in central areas and 25.1% LLC versus 32.7% SLC in peripheral zones; days 8-12: 42.9% LLC versus 19.9% SLC in central areas and 23.5% LLC versus 35.2% SLC in peripheral zones; days 13-16: 47.7% LLC versus 19.4% SLC in central areas and 19.2% LLC versus 41.4% SLC in peripheral zones. In contrast to IGF-I, no expression of IGF-II immunoreactivity was seen in large or small luteal cells. Positive immunoreactivity was restricted to the perivascular fibroblasts of large blood vessels and to the pericytes of capillaries.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of the genes encoding the insulin-like growth factors (IGF-I and II), the IGF and insulin receptors, and IGF-binding proteins-1-6 and the localization of their gene products in normal and polycystic ovary syndrome ovaries.

To discern the potential role of the insulin-like growth factors (IGFs) in polycystic ovary syndrome (PCOS), we examined the expression of the genes encoding the IGFs, IGF receptors (IGFr), insulin receptor (Ir), and IGF-binding proteins (IGFBPs-1-6) as well as the localization of the gene products in specific cellular compartments of normal and PCOS human ovaries. Messenger ribonucleic acid (mRNA) was localized by in situ hybridization with specific 35S-labeled human antisense RNA probes, and protein was detected by immunohistochemistry using specific antisera. Thecal cells, but not granulosa cells (GC), of small antral follicles (3-6 mm) from PCOS ovaries expressed both IGF-I and IGF-II transcripts. Abundant IGF-Ir mRNA was found only in GC, IGF-IIr mRNA was found in both granulosa and thecal cells, and Ir mRNA was detected in all cell types, including granulosa, thecal, and stromal cells. Localization of the gene products revealed no IGF-I immunoreactivity; however, immunostaining for each of the other gene products was colocalized with its corresponding mRNA. The cellular distribution of mRNA and protein in PCOS follicles was indistinguishable from that observed in small antral follicles from normal ovaries. In dominant follicles, however, IGF-I mRNA was no longer detectable, but abundant IGF-II mRNA was expressed exclusively in GC. Although IGF-Ir mRNA was expressed in GC, IGF-IIr mRNA was found in both granulosa and thecal cells. In follicles taken from PCOS ovaries, no IGFBP-1 mRNA was detected, IGFBP-2 mRNA was abundant in both granulosa and thecal cells, moderate IGFBP-3 mRNA was found only in thecal cells, IGFBP-4 and -5 mRNAs were present in all cellular compartments, and IGFBP-6 mRNA was not detected. Localization of the gene products by immunostaining revealed that each protein colocalized with its corresponding mRNA. The cellular distribution of IGFBP mRNA and protein in PCOS follicles was also indistinguishable from that in small antral follicles of normal ovaries, but remarkable differences were found in dominant follicles, where abundant IGFBP-1 mRNA was seen exclusively in GC, IGFBP-2 mRNA in thecal cells, and IGFBP-3 mRNA in both granulosa and thecal cells. Moderate expression of the IGFBP-4 and IGFBP-5 genes was seen in all cell types, including stromal cells, but no IGFBP-6 mRNA was detected. Again, each of the gene products colocalized with its corresponding mRNA. We conclude the following.(ABSTRACT TRUNCATED AT 400 WORDS)

Insulin-like and fibroblast growth factors in spinal cords, nerve roots and skeletal muscle of human controls and patients with amyotrophic lateral sclerosis.

Insulin-like growth factors (IGF-I and IGF-II) and fibroblast growth factors [acidic FGF (aFGF) and basic FGF (bFGF)] are trophic for motor neurones in vitro and (in laboratory animals) in vivo. An immunohistochemical investigation was performed on the distribution of these factors in the neuromuscular system of control patients and patients with amyotrophic lateral sclerosis (ALS). Comparisons were made with rat tissue. IGF-I immunoreactivity (IGF-I-IR) was seen in motor neurone cell bodies and axons, astroglia and Schwann cells, and in muscle fibres. IGF-II-IR was weak in all these cells. aFGF-IR was present in motor neurone cell bodies and axons, oligodendroglia and muscle fibres, but was not demonstrable in Schwann cells. bFGF-IR was present in motor neurone cell bodies and axons, and in astroglia, but was not seen in Schwann cells or muscle fibres. The distribution of the IGFs and FGFs in material from motor neurone disease (MND) and controls was similar. A role for any of these factors in the etiology of MND is, therefore, unlikely. IGF-I-IR and aFGF-IR were stronger in type II than in type I muscle fibres and were increased in denervated fibres. Species differences were found for IGF-I and bFGF. The function of these factors is apparently not entirely similar in humans and rats.

Insulin-like and fibroblast growth factors in spinal cords, nerve roots and skeletal muscle of human controls and patients with amyotrophic lateral sclerosis

Insulin-like growth factors (IGF-I and IGF-II) and fibroblast growth factors [acidic FGF (aFGF) and basic FGF (bFGF)] are trophic for motor neurones in vitro and (in laboratory animals) in vivo. An immunohistochemical investigation was performed on the distribution of these factors in the neuromuscular system of control patients and patients with amyotrophic lateral sclerosis (ALS). Comparisons were made with rat tissue. IGF-I immunoreactivity (IGF-I-IR) was seen in motor neurone cell bodies and axons, astroglia and Schwann cells, and in muscle fibres. IGF-II-IR was weak in all these cells. aFGF-IR was present in motor neurone cell bodies and axons, oligodendroglia and muscle fibres, but was not demonstrable in Schwann cells. bFGF-IR was present in motor neurone cell bodies and axons, and in astroglia, but was not seen in Schwann cells or muscle fibres. The distribution of the IGFs and FGFs in material from motor neurone disease (MND) and controls was similar. A role for any of these factors in the etiology of MND is, therefore, unlikely. IGF-I-IR and aFGF-IR were stronger in type II than in type I muscle fibres and were increased in denervated fibres. Species differences were found for IGF-I and bFGF. The function of these factors is apparently not entirely similar in humans and rats.

Increase in insulin-like growth factor I in hypertrophying smooth muscle

The present study focuses on the role of the insulin-like growth factor (IGF) system in the development of smooth muscle hypertrophy. Hypertrophy was initiated by partial ligation of portal vein or urethra in female Sprague-Dawley rats weighing approximately 220 g. Levels of mRNA were analyzed by solution hybridization. Seven days after ligation, the wet weight of the portal vein was increased about threefold and the concentration of IGF-I mRNA was increased fourfold. The bladder wet weight was increased twofold 3 days after ligation and fourfold 10 days after ligation. IGF-I mRNA in the bladder was elevated 3-fold after 3 days and 2.5-fold after 10 days, whereas IGF binding protein 2 mRNA was increased approximately 2-fold after 3 days and 5-fold after 10 days. IGF-I receptor mRNA in the hypertrophying bladder remained unchanged. Increased levels of IGF-I were demonstrated with immunohistochemistry in both hypertrophying portal vein and urinary bladder. The results show a specific increase in IGF-I mRNA as well as an increased IGF-I immunoreactivity during hypertrophy of smooth muscle, which suggests that the local IGF-system may play a role in smooth muscle hypertrophy.

Insulin-like growth factor (IGF) I and II and IGF binding protein (IGFBP) 1, 2 and 3 in serum from patients with Cushing's syndrome

In the present study of twenty-two patients with Cushing's syndrome, serum insulin-like growth factor (IGF)-I concentrations were normal to high with an increased mean IGF-I concentration, 40% above that of healthy subjects of the same age (p&lt;0.001). Serum IGF-II concentrations were normal. The morning serum IGF binding protein (IGFBP)-l concentrations were within the range of healthy controls. IGFBP-1 was inversely correlated to the IGF-I concentration (p&lt;0.001) and to the 24 h urinary cortisol excretion (p &lt;0.005) with a combined R squared value of 0.58. In contrast to IGFBP-l, serum IGFBP-2 and IGFBP-3 concentrations were elevated by 1.89±1.78 sd and 0.92±0.78 sd (mean±2 sd), respectively. Although increased, the serum IGFBP-2 concentration was inversely correlated to the IGF-I concentration (r= −0.67, p&lt;0.001). Immunoreactive IGFBP-3 was increased in proportion to IGF-I and the molar ratio [IGFBP-3]: [IGF-I]±[IGF-II] was close to unity (1.04±0.14), as that of healthy subjects. In serum from patients with Cushing's syndrome, with increased immunoreactive IGFBP-3, there was a corresponding increase in intact glycosylated 40–43 kDa IGFBP-3 as determined by Western ligand blotting. Neutral size chromatography of serum from patients with Cushing's syndrome showed that IGF-I and IGFBP-3 immunoreactivity were predominantly found at the elution volume of the ternary 1 50 kDa IGF-I/IGFBP-3/acid labile subunit complex and a similar pattern was displayed by normal serum. We conclude that the catabolism and impairment of growth in patients with Cushing's syndrome cannot be attributed to the suppression of the GH-endocrine IGF-I axis. Furthermore, our findings suggest that the previously reported increased IGF inhibitory activity, of low molecular weight, in Cushing's serum could not be attributed to IGFBP-3, IGFBP-3 fragments or IGFBP-1. The possible role of IGFBP-2 or other IGFBPs in blocking the effects of IGFs has to be further evaluated.

Insulin-like growth factor immunoreactivity increases in muscle after acute eccentric contractions

The purpose of the study was to note whether insulin-like growth factor (IGF) immunoreactivity increased after eccentric contractions. IGF immunoreactivity in the rat tibialis anterior muscle was measured on 5 successive days (4-5 rats/group, n = 28) after an acute bout of 192 eccentric contractions elicited by electrical stimulation. The muscle tissue sections were immunocytochemically processed with rabbit anti-human IGF-I serum. Immunoreactivity was analyzed with videomicroscopy and computer-aided image processing. Four days after eccentric contractions, IGF immunoreactivity was significantly higher than control [0.081 +/- 0.073 (SD) absorbance at 480 nm vs. 0.026 +/- 0.018; P < 0.05]. The increases in IGF-I immunoreactivity were mostly within the muscle fibers. These results suggest that an acute bout of eccentric exercise increases IGF-I immunoreactivity in rat type II muscle 4 days postexercise.

Expression of insulin-like growth factors and their receptors in human meningiomas.

Meningiomas have previously been shown to highly express the gene for insulin-like growth factor-II (IGF-II), and receptors for IGF-I have been demonstrated by binding studies in membranes prepared for meningiomas. The co-expression of insulin and the insulin-like growth factors with their corresponding receptors in meningiomas has not been explored. Immunofluorescence microscopy was carried out on twelve meningotheliomatous meningiomas using antibodies directed against insulin, IGF-I, IGF-II, insulin receptor and IGF-I receptor. In addition, these results were contrasted with similar studies using antibodies against desmoplakin and basic fibroblast growth factor. Although insulin immunoreactivity was detected in only one tumor, IGF-I and IGF-II immunoreactivity was present in six and eight of the tumors, respectively. In addition, the IGF-I receptor was expressed in four of the tumors while the insulin receptor was expressed in 10 out of 12 meningiomas. The pattern of distribution of IGF-II and the insulin receptor was especially regional. The insulin-like growth factors and their receptors are expressed in meningiomas in a pattern of distribution suggestive of a paracrine mechanism.