Biomedical subjects

M Giuliano

Publications and source records attributed to M Giuliano.

At least 37 records · Page 2Linked to original sources

PubMed1998

Induction of programmed cell death in human retinoblastoma Y79 cells by C2-ceramide.

C2-ceramide, a cell-permeable analogue of ceramide, induced significant, dose- and time-dependent death in human retinoblastoma Y79 cells. Dying cells strongly displayed the morphology of apoptosis as characterized by microscopic evidence of cell shrinkage, membrane blebbing, nuclear and chromatin condensation and degeneration of the nucleus into membrane-bound apoptotic bodies. Upon induction of apoptosis Y79 cells evidence early phosphatidylserine externalization, as shown by annexin V-FITC. Apoptosis was also assessed by monitoring changes in cell granularity by staining with the combined fluorescent dyes acridine orange and ethidium bromide. C2-ceramide induced these morphological changes without a concomitant production of oligonucleosomal fragments responsible for the DNA ladder and without changes in p53 protein level. Apoptosis was accompanied by accumulation of a modified Bcl-2 protein with a slower-mobility form, and by proteolytic cleavage of PARP. The effect seemed to be specific for C2-ceramide, as C2-dihydroceramide, or other amphiphilic lipid analogues, or products of ceramide hydrolysis were ineffective. The effect also depended on mRNA and protein synthesis as it was markedly inhibited by actinomycin D and cycloheximide. Sphingomyelinase and interleukin-1beta, which are known to activate the sphingomyelin turnover leading to ceramide generation, also induced apoptosis mimicking the effects of ceramide. These findings propose ceramide as an activator of the suicidal program in Y79 cells.

Apoptosis↗

PubMed1998

Bordetella parapertussis infection in children: epidemiology, clinical symptoms, and molecular characteristics of isolates.

The clinical trial conducted in Italy to evaluate the efficacy of acellular pertussis vaccines provided an opportunity to estimate the frequency of clinical infections with Bordetella parapertussis and to compare the clinical characteristics of children suffering from Bordetella pertussis illness with those of children with B. parapertussis illness. This study dealt with 76 B. parapertussis infections diagnosed from a population of 15,601 children participating in the follow-up of suspected cases of pertussis. An overall incidence of 2.1 cases of laboratory-confirmed parapertussis per 1,000 person-years was observed. Children affected by B. parapertussis infections showed a less severe clinical picture both in the duration of symptoms and in the percentage of patients affected, even when compared with vaccinated children with pertussis. To characterize the isolated strains, we performed assays for susceptibility to erythromycin and sulfamethoxazole-trimethoprim, and we examined the genomic DNAs by pulsed-field gel electrophoresis. The results showed a high degree of genetic stability among B. parapertussis strains regardless of time of collection and geographical distribution.

Bordetella↗

PubMed1998

Apoptotic effects of different drugs on cultured retinoblastoma Y79 cells.

This paper deals with the apoptotic effect exerted in human retinoblastoma Y79 cells by a number of compounds. A remarkable effect was observed after treatment with DNA-damaging agents, such as camptothecin, etoposide, cisplatin and carboplatin; camptothecin was found to be the most efficacious. Treatment with these compounds induced the appearance of morphological features of apoptosis in the cells together with the distinct fragmentation of DNA, as shown by agarose gel electrophoresis. These effects were also accompanied by a remarkable increase in the level of p53. Many other compounds, which are not DNA-damaging agents, induced the morphological features of apoptosis but none of them were capable of increasing the level of p53. Among these compounds, Taxol, suramin and sodium butyrate also stimulated the oligonucleosomal fragmentation of DNA, while C2-ceramide, a cell-permeable analogue of ceramide, and vitamin D3 were not effective in the induction of DNA laddering in Y79 cells. Apoptosis was dependent on macromolecular synthesis with all the compounds tested.

Amsacrine↗

PubMed1998

The apoptotic effects of cisplatin and carboplatin in retinoblastoma Y79 cells.

This study demonstrated that cisplatin and carboplatin stimulate apoptosis in human retinoblastoma Y79 cells, cisplatin being the most effective compound. The apoptotic effect appeared after 8 h and then increased in a time-dependent manner. Treatment with cisplatin and carboplatin also provoked an increase in the level of p53 and p21, and a lowering in Bcl-2. The prolonged exposure of Y79 cells to cisplatin induced resistance to cisplatin, carboplatin and etoposide. The basal level of p53 was in resistant cells higher than in untreated cells, while Bcl-2 was not modified. p53 and Bcl-2 levels did not change after treating of resistant cells with cisplatin, carboplatin or etoposide. However, camptothecin which is a powerful inducer of apoptosis in sensitive cells, triggered cell death even in resistant cells. Such an effect was not accompanied by any modification in p53 level while Bcl-2 was markedly reduced.

Antineoplastic Agents↗

PubMed1998

Induction of apoptosis in human retinoblastoma cells by topoisomerase inhibitors.

PURPOSE: To examine the apoptotic effect induced in human retinoblastoma Y79 cells by camptothecin, etoposide, and amsacrine, to examine the effect of these drugs on the expression of many apoptosis-related modulators, and to test the antiapoptotic effect exerted by insulin-like growth factor-I (IGF-I). METHODS: Morphologic features of apoptosis were demonstrated using acridine orange- ethidium bromide staining and electron microscopy. DNA fragmentation was determined by means of an in situ cell detection procedure (TdT-dUTP terminal nick-end labeling [TUNEL]) or by electrophoresis on agarose gels and was quantified by enzyme-linked immunosorbent assay. The expression of apoptosis-related modulators was studied by western blot analysis. The processing of latent p53 was examined by means of pulse- chase analysis. RESULTS: Camptothecin, etoposide, and amsacrine induced apoptosis in Y79 cells in a dose-dependent manner; camptothecin was the most efficacious compound. The effect, which was dependent on macromolecular synthesis, appeared after a lag of 8 hours and increased for as long as 24 hours. It was lower in cells treated with IGF-I, a potent mitogenic factor. Camptothecin and etoposide increased the p53 level after 4 hours of treatment, before the onset of apoptosis. This effect seemed to be a consequence of the conversion of latent p53 to one that is transcriptionally active. The drugs also induced an increase in p53-related proteins, such as p21, Bax, and IGF binding protein-3 (IGF-BP3), and caused a significant reduction of the Bcl-2 level. The latter effect was less evident in cells pretreated with IGF-I. CONCLUSIONS: Topoisomerase inhibitors induce apoptosis in Y79 cells. This event is accompanied by a decrease in the expression of Bcl-2, a death antagonist, and an increase in that of Bax, a death agonist. A probable consequence of these modifications is the activation of ICE-like activity with degradation of poly-(adenosine diphosphate [ADP] ribose)-polymerase. Insulin-like growth factor-I exerts an antiapoptotic action in Y79 cells, and this function is most likely reduced by the overexpression of IGF-BP3 that is induced by drug treatment.

Amsacrine↗

PubMed1998

Human malignant mesothelioma of the pleura: new perspectives for diagnosis and therapy.

The ability to immortalize human mesothelioma cells in vitro with simian virus (SV) 40 and the fact that SV40 induces mesotheliomas in hamsters prompted us to look for SV40 deoxyribonucleic acid (DNA) sequences in human mesotheliomas. In a previous study, we found that over half (29/48) of human malignant pleural mesotheliomas contained SV40-like sequences whereas only a few (3/47) control samples contained the same detectable sequences. The SV40 genome encodes the 90 KD nuclear large T-antigen (Tag) and the 17 KD small-t antigen (tag), responsible for SV40's transforming and oncogenic properties. These antigens block tumour suppressor gene products, such as p53. We considered the possibility of reverting this effect by adding exogenous wild-type p53 and thus restoring normal cell functions. For this purpose, we developed a recombinant adenovirus carrying complementary DNA (cDNA) for wild type p53 (AdCMV.p53) and infected mesothelioma cell lines with this virus. Inhibition of proliferation, halting of the cell cycle and massive apoptosis was observed in all mesothelioma cell lines tested. In addition, proliferation of human mesothelioma tumours into nude mice was inhibited by in vivo adenovirus-mediated p53 transgene expression. We also report preliminary evidence of expression, by immunoreactivity, of the extracellular matrix protein tenascin in human malignant pleural mesotheliomas. It was interesting to find predominant tenascin positivity at the tumour's invasive edge and in areas of tumour vascularization. This preliminary report suggests that adenovirus-mediated p53 hyperexpression counteracts transforming properties of the large T-antigen and suggests that gene therapy may be useful in treating human malignant mesothelioma.

Animals↗

PubMed1998

Increased cyclin E level in retinoblastoma cells during programmed cell death.

Camptothecin (an inhibitor of topoisomerase I) and etoposide and amsacrine (inhibitors of topoisomerase II) both capable of triggering programmed cell death in Y79 cells, induced a remarkable dose-dependent increase in the level of cyclin E in these cells. Camptothecin was found to be the most effective compound. The effect was not observed when the cells were treated with other inducers of programmed cell death (C2-ceramide, sodium butyrate, interleukin-1beta and tumor necrosis factor), all of which do not damage DNA. The effect, which was completely prevented by inhibitors of macromolecular synthesis, occurred after a lag phase (12 hrs.) and increased concurrently with the rise in programmed cell death (PCD), reaching a maximum after 36 hrs. of incubation, when a large percentage of cells (95%) showed clear PCD signals. We suggest that cyclin E takes part in the final stage of programmed cell death which is induced by topoisomerase inhibitors in Y79 cells.

Amsacrine↗

PubMed1997

Cell-mediated and antibody responses to Bordetella pertussis antigens in children vaccinated with acellular or whole-cell pertussis vaccines. The Progetto Pertosse-CMI Working Group.

OBJECTIVE: To examine induction and persistence of cell-mediated immunity (CMI) and antibody responses to Bordetella pertussis antigens in infants receiving antipertussis vaccines. DESIGN AND SETTING: A randomized, blinded study of 142 children receiving acellular pertussis vaccines combined with diphtheria-tetanus toxoids (DTaP) (DTaP manufactured by SmithKline Beecham [DTaP-SB], Rixensart, Belgium, and DTaP manufactured by Chiron Biocin [DTaP-CB], Siena, Italy), or a whole-cell pertussis vaccine (DTwP) (Connaught Laboratories Inc, Swiftwater, Pa), or a diphtheria-tetanus (DT) (Chiron Biocine) only vaccine. Three doses of each vaccine were given at 2, 4, and 6 months of age, and CMI and antibody responses were evaluated before and at 1 and 14 months after vaccination. METHODS AND MAIN OUTCOME MEASURES: Cell-mediated immunity was assessed by proliferation of peripheral blood mononuclear cells stimulated in vitro by B pertussis antigens (pertussis toxin, filamentous hemagglutinin, and pertactin). Antibody titers against pertussis toxin, filamentous hemagglutinin, and pertactin were determined by a standardized enzyme-linked immunosorbent assay. RESULTS: A CMI-positive response to at least 1 B pertussis antigen at 1 or both postvaccination assays was detected in 46%, 55%, and 83% of DTwP, DTaP-SB, and DTaP-CB vaccine recipients, respectively. Frequency of CMI response to individual antigens ranged from less than 4.9% against pertussis toxin in DTwP recipients to 52% against pertactin in DTaP-CB recipients. The postvaccination responses measured at 14 months equalled, or had increased frequency or intensity, that of the 1-month postvaccination responses. Elevated antibody titers against the 3 antigens were present in all DTaP recipients 1 month after vaccination and were higher in CMI-positive children than in CMI-negative children. They fell, however, to low, if not negligible, levels 14 months after vaccination. CONCLUSIONS: Acellular pertussis vaccines were better inducers of CMI response than the whole-cell vaccine, particularly against pertussis toxin. Once acquired, CMI persisted, in contrast with the rapid antibody decline. Thus, CMI responses could be a useful adjunct to serology in the evaluation of pertussis vaccine immunogenicity and a better correlate of long-term immunity to B pertussis than antibody titers.

Bordetella pertussis↗

PubMed1997

Extracellular adenosine 5' triphosphate involvement in the death of LAK-engaged human tumor cells via P2X-receptor activation.

This study reports that extracellular ATP is a critical factor involved in LAK cell-mediated cytotoxicity. Human colon carcinoma LoVo cells were resistant to LAK cells as well as to ATP, while their multidrug resistant (MDR-1+) derivative, LoVo-Dx cells, were sensitive to both LAK and ATP. LoVo-Dx cells, became resistant to LAK cells and ATP after 48 h pretreatment with Phorbol 12-Myristate-13-Acetate (PMA), while 48 h pretreatment with verapamil in parallel sensitized LoVo cells to LAK cells and to ATP as well. The sensitivity to ATP and LAK cells was not related to the expression of extracellular ecto-ATPase activity on cell targets membranes. Conversely, apyrase, an enzyme with powerful ecto-ATPase activity, abolished the LAK- and ATP-mediated cytotoxicity. Furthermore, ADP-beta-S, an antagonist of ATP, abolished both LAK and ATP-mediated cell killing. Purine binding sites have been detected by radioreceptor assays with ADP-beta[35S] on the cell surface of ATP and LAK-sensitive LoVo-Dx cells. By contrast, no nucleotide receptor was found on the ATP and LAK-resistant cells. Such a putative cytotoxic purinoreceptor has been categorized as P2x purinergic receptor by a panel of synthetic nucleotides. These results demonstrate that extracellular ATP is needed for an efficient LAK cell-mediated killing of tumor cells. We propose that ATP acts as a natural amplifier of physical, or immune cytotoxic damages since it may be released in large amounts from target cells injured by several cytotoxic mediators secreted by LAK effectors.

Adenosine Diphosphate↗

PubMed1997

Differentiation of Y79 cells induced by prolonged exposure to insulin.

Y79 human retinoblastoma cells are known to contain receptors for both insulin and insulin-like growth factors (IGFs), to produce these cytokines and release them in the culture medium. Previously we have demonstrated that IGFs and insulin stimulate Y79 cell proliferation through the involvement of type I IGF receptor and Insulin Receptor Substrate 1 (IRS-1). This paper studies the effect of prolonged exposure to insulin on Y79 cells. Cells grown for 10 days in the presence of insulin were reseeded and incubated once more with insulin. In the reseeded cells proliferation lowered and morphological changes appeared. After 10 days of reseeding, cells stopped proliferating and showed long ramifying neurite processes and varicosities consistent with neuronal differentiation. Morphological differentiation was accompanied by a marked increase in the content of total protein and in that of tubulin, the major protein constituent of microtubules, a marked increase in the content of specialized protein markers of dopaminergic and cholinergic differentiation (dopamine beta-hydroxylase and choline acetyltransferase activities, respectively); a contemporaneous decrease in the content of glial fibrillary acidic protein (GFAP), a specific marker of glial cells, was also observed. Our results demonstrate that prolonged exposure to insulin induces Y79 cells to differentiate into a neuronal-like phenotype. At this moment it is not possible to establish the mechanism by which insulin induces this differentiative effect.

Biomarkers↗

PubMed1997

Molecular characterization of two Bordetella bronchiseptica strains isolated from children with coughs.

During a surveillance program associated with the Italian clinical trial for the evaluation of new acellular pertussis vaccines, two bacterial isolates were obtained in cultures of samples from immunocompetent infants who had episodes of cough. Both clinical isolates were identified as Bordetella bronchiseptica by biochemical criteria, although both strains agglutinated with antisera specific for Bordetella parapertussis, suggesting that the strains exhibited some characteristics of both B. bronchiseptica and B. parapertussis. Both children from whom these strains were isolated exhibited an increase in serum antibody titer to pertussis toxin (PT), a protein that is produced by Bordetella pertussis but that is not thought to be produced by B. bronchiseptica. We therefore examined whether the clinical isolates were capable of producing PT. Neither strain produced PT under laboratory conditions, although both strains appeared to contain a portion of the ptx region that encodes the structural subunits of PT. In order to determine whether the ptx genes may encode functional proteins, we inserted an active promoter directly upstream of the ptx region of one of these strains. Biologically active PT was produced, suggesting that this strain contains the genetic information necessary to encode an active PT molecule. Sequence analysis of the ptx promoter region of both strains indicated that, while they shared homology with the B. bronchiseptica ATCC 4617 sequence, they contained certain sequence motifs that are characteristic of B. parapertussis and certain motifs that are characteristic of B. pertussis. Taken together, these findings suggest that variant strains of B. bronchiseptica exist and might be capable of causing significant illness in humans.

Acute Disease↗

PubMed1997

Differences by antigen in seroconversion: sensitivity, specificity and bias in the serological confirmation of pertussis.

Vaccine efficacy of the most efficacious acellular pertussis vaccines in the three recent placebo-controlled clinical trials, when estimated using the primary clinical case criterion, does not change substantially with the inclusion of serological confirmation in addition to culture confirmation. In the Italy trial, because of relatively high anti-PT antibody levels at the time of the acute-phase specimen in episodes of 21 or more days of paroxysmal cough, significant increases in antibody to PT are less likely to be seen in the acellular vaccine groups when evaluating children with bacterial isolation. However, the effect of this decreased sensitivity appears to be compensated by significant antibody increases in the FHA assay. When projecting a maximally sensitive criterion for serological assessment using the observed decreases in IgG antibody to PT over time following primary vaccination stratified by vaccine group, and comparing the expected antibody level with the observed level in the convalescent-phase specimen, the effect on estimated vaccine efficacy is minimal.

Antibodies, Bacterial↗

PubMed1997

Bordetella parapertussis infections.

The rate of isolation of Bordetella parapertussis among children with cough during the follow-up of different clinical efficacy studies has been evaluated. In the Italian trial, a comparison of clinical characteristics between B. pertussis and B. parapertussis infections showed lower frequencies and shorter duration of typical symptoms of whooping cough such as paroxysmal coughing, whooping, and vomiting in the group of children affected with B. parapertussis infections. In about 70% of B. parapertussis infections, there was a two-fold increase of IgA or IgG anti-FHA from acute- and convalescent-phase serum specimens. The analysis of the distribution of B. parapertussis cases in children fully immunized with each pertussis vaccine suggested that vaccination is irrelevant in preventing B. parapertussis infection.

Adhesins, Bacterial↗

PubMed1997

Antibody kinetics and long-term sero-prevalence in the Italian clinical trial of acellular pertussis vaccines.

In the Italian Pertussis Vaccine Trial, data were collected to evaluate the persistence of anti-pertussis antibodies. A sub-cohort of 1275 children was followed for this purpose until a mean age of 21 months. An additional evaluation included pooled cross-sectional analysis of serum specimens collected for analysis of cough illnesses. Antibodies to PT, FHA and PRN were measured by ELISA using a standardized technique. With both acellular vaccines in the study (the Chiron Biocine three-component and SmithKline Beecham three-component vaccines) there was a fast and steep decrease of mean geometric titres for PT, FHA and PRN in the months immediately following vaccination. Titres were close to the detection limit 15 months after the end of primary immunization. The immunogenicity of the whole-cell study vaccine (produced by Connaught Laboratories, Inc. Swiftwater, USA) was poor as determined one month after the third dose and no antibody was detected in nearly all children 15 months after the end of vaccination.

Adhesins, Bacterial↗

PubMed1996

SV40-like sequences in human bone tumors.

Simian virus 40 (SV40) is a monkey virus that induces ependymomas, choroid plexus tumors, mesotheliomas, osteosarcomas, sarcomas and true histiocytic lymphomas when injected in hamsters. Recently, approximately 60% of human ependymomas, choroid plexus tumors and mesotheliomas were reported to contain and express SV40-like sequences (N. Engl. J. Med., 1992, 36, 988-993; Oncogene, 1994, 9, 1781-1790). In this study the presence of SV40-like sequences was investigated in additional types of human tumors. Initially, 200 tumor and normal tissue DNA samples were analysed by polymerase chain reaction (PCR) with primers that amplify a 574 base pair region of SV40 large T antigen (Tag), which includes the Rb-pocket binding domain and the intron of Tag. PCR amplification and Southern blot hybridization with a probe specific for SV40 Tag revealed that 18/200 samples contained SV40-like sequences and, unexpectedly, 11/18 were from patients with osteosarcomas. Additional DNA samples from bone tumors were then analysed. In 40/126 osteosarcomas, and 14/34 other bone-related tumors, Tag sequences could be amplified. Sequence analysis of the DNA amplified from seven different tumors confirmed that the amplified sequences corresponded to SV40 Tag, with some demonstrating deletions in the intron region but not in the Rb-pocket binding domain. The extent of SV40 genome sequences present in the DNA samples was further analysed in two osteosarcomas. PCR amplification, Southern blot hybridization, and sequence analysis revealed that these samples also contained sequences for the carboxy-terminal domain of Tag, the viral regulatory region, and the VP1 capsid protein. These results indicate that SV40-like sequences are present in human bone tumors.

Base Sequence↗

PubMed1996

Role of insulin-like growth factors in autocrine growth of human retinoblastoma Y79 cells.

In this study, we have demonstrated that human retinoblastoma Y79 cells produce insulin-like growth factors (IGFs) type I and type II and release them into the medium. We have also ascertained, by means of competitive studies and cross-linking procedure, that Y79 cells contain the type-I IGF receptor (IGF-IR). Furthermore, surface-bound IGF-I is internalised by the receptor, then degraded to amino acids. Insulin, IGF-I and IGF-II caused down-regulation of IGF-IR; the effect is concentration and time dependent. Scatchard analysis demonstrated that incubation with insulin markedly decreased the binding capacity measured for IGF-I while the apparent Kd value calculated for IGF-I binding was not significantly modified. IGF-I, IGF-II and insulin induced tyrosine phosphorylation of IGF-IR. Tyrosine phosphorylation of this receptor with, however, a less strong signal, was detectable even in cells cultured in serum-free medium without the addition of any exogenous growth factor. Similar results have been found concerning the tyrosine phosphorylation of insulin receptor substrate-1 (IRS 1). Tyrosine phosphorylation of both IGF-IR and IRS 1, either under basal conditions or after stimulation with growth factors, was strongly inhibited when alpha-IR3, a monoclonal antibody to IGF-IR, was added to the culture. IGF-I was capable of inducing Y79 cell proliferation and its effect was entirely inhibited by the addition of alpha-IR3. This antibody also markedly reduced the proliferation of Y79 cells cultured in serum-free medium not supplemented with stimulatory factors. Our results indicate that IGF-I and IGF-IR mediate an autocrine growth mechanism in Y79 cells.

Binding, Competitive↗

PubMed1996

A controlled trial of two acellular vaccines and one whole-cell vaccine against pertussis. Progetto Pertosse Working Group.

BACKGROUND: Concern about both safety and efficacy has made the use of whole-cell pertussis vaccines controversial. In some European countries, including Italy, the rate of vaccination against pertussis is low. METHODS: We conducted a double-blind trial in Italy in which infants were randomly assigned to vaccination at two, four, and six months of age with an acellular pertussis vaccine together with diphtheria and tetanus toxoids (DTP); a DTP vaccine containing whole-cell pertussis (manufactured by Connaught Laboratories); or diphtheria and tetanus toxoids without pertussis (DT). The acellular DTP vaccine was either one containing filamentous hemagglutinin, pertactin, and pertussis toxin inactivated with formalin and glutaraldehyde (SmithKline Beecham) or one with filamentous hemagglutinin, pertactin, and genetically detoxified pertussis toxin (Chiron Biocine). Pertussis was defined as 21 days or more of paroxysmal cough, with infection confirmed by culture or serologic testing. RESULTS: The efficacy of each vaccine, given in three doses, against pertussis was determined for 14,751 children over an average of 17 months, with cases included in the analysis if cough began 30 days or more after the completion of immunization. For both of the acellular DTP vaccines, the efficacy was 84 percent (95 percent confidence intervals, 76 to 89 percent for Biocine DTP and 76 to 90 percent for SmithKline DTP), whereas the efficacy of the whole-cell DTP vaccine was only 36 percent (95 percent confidence interval, 14 to 52 percent). The antibody responses were greater to the acellular vaccines than to the whole-cell vaccine. Local and systemic adverse events were significantly more frequent after the administration of the whole-cell vaccine. For the acellular vaccines, the frequency of adverse events was similar to that in the control (DT) group. CONCLUSIONS: The two acellular DTP vaccines we studied were safe, immunogenic, and efficacious against pertussis, whereas the efficacy of the whole-cell DTP vaccine was unexpectedly low.

Antibodies, Bacterial↗

PubMed1996

Insulin-like growth factors in chick embryo retina during development.

Evidence exists supporting an important role for insulin-like growth factors (IGFs) during fetal growth. In the present report we performed studies to define whether developing chick retina contains IGFs and whether IGFs play a role in the growth of this tissue. We have shown that both IGF-I and IGF-II are present in chick embryo retina throughout development (7th-18th day). The highest values, when expressed as ng/g of tissue, were found in the youngest retinas studied (7th-9th day) and at 16th-18th day of development. During whole development the content of IGF-II was about two to three times higher than that ascertained for IGF-I. The tissue also contains cell-surface binding for IGFs. However, the developmental pattern of IGF-I binding was quite different from that found for IGFs, showing the highest values during the second week of development. Competitive studies showed that this receptor has a high affinity for IGF-I, a lower affinity for IGF-II, and a very much lower affinity for insulin. Also anti-IGF-I receptor antibody (alpha IR3) inhibited 125I-labeled IGF-I binding to the receptor. Such results indicate the presence of type I IGF receptor in chick embryo retina. Affinity labeling experiments have confirmed this hypothesis. We have also shown that cultured retinal explants contain, synthesize and release into the medium appreciable amounts of IGFs. Both exogenous IGF-I and IGF-II added to the culture medium stimulated DNA synthesis of retinal explants. Evidence that the retinas produce IGFs and possess IGF-IR together with the growth-promoting effect of IGFs suggests that these factors play an important role as regulators of retinal growth.

Animals↗