Cellular insulin-like growth factor binding protein-3 (IGFBP-3) mRNA and IGFBP-3 levels in conditioned medium were consistently higher in cultures of late passage normal (old) fibroblasts and prematurely senescent fibroblasts derived from Werner syndrome (WS) during quiescence induced by serum depletion and during the renewed growth ensuing after serum repletion, compared to cultures of early passage normal (young) fibroblasts. Molar ratios of IGFBP-3/IGF-II were always higher in senescent cultures and maintained a hierarchy of old > WS > young human diploid fibroblasts. Transfection into fibroblasts of the normal full-length IGFBP-3 cDNA in an expression vector resulted in a significant reduction in colony formation compared to cells transfected with an empty expression vector (no cDNA) or with IGFBP-3 cDNA altered by a 273 base pair (bp) deletion. Addition to old and young cultures of recombinant human IGFBP-3 and IGF-I at 1:1 or 5:1 molar ratios inhibited IGF-I-mediated DNA synthesis by approximately 70-80%. These data indicate that IGFBP-3 may play an important role in the quiescent and senescent growth arrest of HDF.

Aging↗

PubMedDate not supplied

Identification of gene sequences overexpressed in senescent and Werner syndrome human fibroblasts.

The phenotype of replicative senescence is a dominant trait in human diploid fibroblasts (HDF). Therefore, we have sought to identify overexpressed and/or newly expressed causal genes by constructing and screening a subtracted cDNA library derived from polyA+RNA of prematurely senescent Werner syndrome (WS) HDF. We have identified 15 cDNA clones that are overexpressed in senescent and WS HDF. Among them are six known sequences coding for: acid sphingomyelinase, fibronectin, SPARC, nm23-metastasis suppressor protein, and two translation factors, eIF-2 beta and EF-1 alpha. Among the 10 unknown clones are: S1-5, which encodes a secreted protein containing EGF-like domains and paradoxically stimulates DNA synthesis of young HDF in an autocrine and paracrine manner, S1-3, which encodes a protein containing "zinc finger" domains, suggesting nucleic acid binding properties; S1-15, which shows sequence similarities to human alpha 2-chimerin; and S2-6, which represents a new member of the LIM family of proteins. The other five clones do not have any significant homology to known sequences. Steady-state mRNA levels of all gene sequences thus far studied are elevated in both WS and senescent normal HDF when compared to young HDF, which suggests that senescent and WS HDF enter a final common pathway where multiple gene overexpression may generate diverse antiproliferative mechanisms and pathogenic sequelae.

Adult↗

PubMedDate not supplied

Expression of senescence-induced protein WS3-10 in vivo and in vitro.

In our efforts to characterize cellular senescence we have shown that the mRNA encoding WS3-10 protein is overexpressed in senescent human diploid fibroblasts (HDF) when compared with their younger counterparts, and that forced expression of the WS3-10 cDNA in young HDF results in suppression of calcium-dependent membrane currents, presumably due in part to the presence of a calcium binding domain within the WS3-10 protein. We have now expressed this protein in E. coli and have obtained affinity purified antibodies. Western blot analysis utilizing these antibodies showed that WS3-10 protein is also overexpressed in senescent HDF when compared to young HDF, and in normal fetal lung HDF when compared to SV40-transformed fetal lung HDF. HeLa cells do not express WS3-10 protein. In addition, we looked for WS3-10-related species in a variety of rat tissues. Analysis of WS3-10 immunologically related proteins in rat tissue extracts revealed two WS3-10 homologs, sized 22 kDa and 20 kDa. The latter presumably result from proteolytic removal of the C-terminal end of the 22 kDa polypeptide. The ratio between these polypeptides varies in a tissue-specific manner. Two proteins immunologically related to WS3-10 with sizes of 39 kDa and 91 kDa were present in rat spleen and skeletal muscle, respectively.

Actins↗

PubMedDate not supplied

Effects of labetalol on plasma renin, aldosterone, and catecholamines in hypertensive patients.

We studied the effects of labetalol, an alpha- and beta-adrenoceptor antagonist, on maximum exercise heart rate and on plasma renin, aldosterone, noradrenaline, and adrenaline levels at rest and during exercise in hypertensive patients. The dose of labetalol was doubled weekly from 0.3 to 2.4 g per day. The maximum exercise heart rate fell significantly during labetalol treatment, and there was a significant correlation between exercise tachycardia and the dosage of labetalol. Plasma renin activity and aldosterone concentration at rest decreased during treatment with labetalol. The exercise-induced increase in plasma renin activity was reduced by labetalol. Labetalol did not cause any significant changes in plasma noradrenaline and adrenaline at rest or during exercise.

Adult↗