Identification and localization of talin in chick retinal pigment epithelial cells

Retinal pigmented epithelial cells are adherent at their basal surface to Bruch's membrane and at their apical surface to the neural retina. We examined the expression and distribution of two proteins that are found in regions of cell-matrix interaction, talin and integrin. Talin is a 235-kDa cytoplasmic protein that has been localized to regions of cell-substrate adhesion. It binds to both integrin, a transmembrane glycoprotein complex, and to vinculin, a cytoskeletal protein. In the present study, we produced a polyclonal antibody to chicken gizzard talin. Using this antibody we showed by western blot analysis that talin is expressed by RPE cells and is found in the triton-soluble fraction. Talin was shown to co-localize with integrin and vinculin in the basal region of chick RPE cells isolated from 18-day-old chick embryos. Neither talin nor integrin was found in the apical processes or in the zonula adherens. Antibodies to vinculin showed staining both in the apical and basal regions of the RPE cells. The localization of integrin, talin and vinculin along the basal membrane suggests that this complex is important in the attachment of the RPE cells to the basement membrane. The distribution of integrin and talin was examined in primary cultures of RPE cells grown on permeable filters. In these cells, a polarized distribution of integrin and talin was not observed. This may suggest that the neural retina may be important for maintaining the differentiated state of the RPE cells.     

Effects of continuous darkness on ERG correlates of disc shedding in rabbit retina.

The electroretinogram (ERG) was recorded in the dark from photo-entrained albino rabbits, using a constant-intensity, 500-nm, 50- or 100-msec stimulus at 1-min intervals. Under these conditions, the b-wave of the ERG was previously shown to decrease in amplitude at the time of the morning rod photoreceptor disc shedding event. We have extended our observations to rabbits housed in continuous darkness. The present data show that in constant darkness the change in retinal sensitivity continues to occur, but with a period slightly less than 24 hr. Unilateral dark adaptation, achieved by eyepatching, alters the timing of the event only in the retina of the occluded eye. Thus, the change in retinal sensitivity shares the characteristics of endogenous rhythmicity and intraocular control that have been demonstrated by histologic methods for mammalian rod disc shedding. We also report elongation of rod outer segments in some regions of the albino rabbit retina after continuous darkness.     

Macrophage colony-stimulating factor gene transfer into tumor cells induces macrophage infiltration but not tumor suppression

In order to analyze the effect of a high local concentration of macrophage colony-stimulating factor (M-CSF; CSF-1) on tumor growth, the plasmacytoma cell line J558L was transfected with the human M-CSF gene and injected into syngeneic BALB/c mice. In contrast to the parental tumors, M-CSF transfectants were heavily infiltrated by macrophages as evidenced by immunohistochemistry with antibodies to Mac-1 and Mac-3 and by isolation of the macrophages from the tumor. Nevertheless, tumor growth was only slightly affected by M-CSF and M-CSF-producing cells grew as tumor in all cases. The growth retardation of M-CSF-producing cells varied depending on the experiment and seemed to be due to an indirect effect because the growth rate of the cells in vitro had not changed upon gene transfer. Attempts to activate the tumor-infiltrating macrophages for tumor suppression by systemic application of interferon-γ and/or lipopolysaccharide were not successful. Altogether, our results suggest that M-CSF is a potent chemoattractant for macrophages in vivo but alone is not sufficient to activate these macrophages for tumoricidal activity.     

Genetic polymorphisms and cerebrospinal fluid levels of tissue inhibitor of metalloproteinases 1 in sporadic Alzheimer's disease

Tissue inhibitor of metalloproteinases 1 (TIMP-1) inhibits several proteinases including a disintegrin and metalloproteinase 10 (ADAM10), a major alpha-secretase that cleaves the beta-amyloid precursor protein within its amyloidogenic Abeta domain. The gene encoding TIMP-1 (TIMP 1) maps to the short arm of the X chromosome, in a region previously suggested as conferring genetic susceptibility for Alzheimer's disease (AD). To determine whether genetic variability of TIMP 1 contributes to the pathogenesis of AD, we analysed one single nucleotide polymorphism within TIMP 1 and one single nucleotide polymorphism in the 5'-untranslated region of TIMP 1 in patients with AD and control subjects from two independent and ethnically different populations. We did not observe any association between TIMP 1 genotypes and the diagnosis of AD in men or women. We also measured TIMP-1 protein levels in the cerebrospinal fluid of patients with AD, healthy control subjects, and patients with other neurological disorders. TIMP-1 levels were similar in all groups. In addition, no significant differences were observed after stratification for TIMP 1 genotypes. Our data show that neither genetic variability nor protein levels of TIMP-1 are associated with AD.     

Gene transfer of the interleukin (IL)-2 receptor β chain into an IL-7-dependent pre-B cell line permits IL-2-driven proliferation: Tyrosine phosphorylation of Shc is induced by IL-2 but not IL-7

Expression of the interleukin (IL)-2 receptor β chain in the IL-7-dependent pre-B cell line I × N/2B permitted growth in presence of either IL-2 or IL-7, allowing for a direct comparison of intracellular signaling events. Protein tyrosine phosphorylation was essential for IL-2- and IL-7-induced signal transduction since the tyrosine kinase inhibitor herbimycin A blocked proliferation in response to both factors. Western blot analysis of tyrosine-phosphorylated proteins revealed that both IL-2 and IL-7 stimulation led to enhanced phosphorylation of proteins of 170-, 145, 115- and 99-kDa, as well as induction of phosphorylation of a 96-kDa protein. However, a 55- and a 155-kDa protein were only phosphorylated after IL-2 stimulation. The 55-kDa protein specifically phosphorylated by IL-2 could be identified as p52^shc which has recently been shown to be critically involved in Ras activation. Shc tyrosine phosphorylation as a result of IL-2 stimulation was consistently found in CTLL-2 cells and human T lymphoblasts. Taken together our results indicate that the IL-2- and IL-7-stimulated intracellular pathways are partially different and that Shc is a target of IL2-, but not IL-7-, stimulated tyrosine phosphorylation.