Time-dependent differential gene expression in lysophosphatidic acid-treated young and senescent human diploid fibroblasts

The gene expression profiles of lysophosphatidic acid (LPA)-treated young and senescent human diploid fibroblasts (HDFs) were examined using cDNA microarray analysis. The expression of some genes, including EGR 1/3 and MRRF, was controlled by LPA similarly in young and senescent cells, showing a typical time-dependent up-and-down expression profile. In contrast, some other genes, including DUSP6, CYR61, and F3, showed sustained upregulation in senescent HDFs later after LPA treatment. These genes might be involved in altered LPA responsiveness during the aging process.     

Changes in protein synthesis and breakdown rates and responsiveness to growth factors with ageing in human lung fibroblasts

The effects of insulin, epidermal growth factor, insulin-like growth factor-2 and fetal bovine serum on protein synthesis and protein breakdown have been measured in mid-passage and senescent cultures of human diploid lung fibroblasts. Each of the individual growth factors was a potent inhibitor of protein breakdown with no difference in either the maximum response or sensitivity evident between senescent cells and mid-passage cultures. Binding of 125I-labelled epidermal growth factor per mg of cell protein similarly showed no difference between senescent and confluent mid-passage fibroblasts, although sparse mid-passage cells bound more of the ligand. These results indicate normal binding and normal responsiveness to growth factors in senescent cultures. However, rates of protein synthesis are higher in confluent mid-passage cells and especially so in sparse mid-passage cells than in senescent cells of intermediate density. Furthermore, senescent cells differ from either growth state of mid-passage cells because protein synthesis in aged cells is much less responsive to any of the growth factors or to fetal bovine serum. It is suggested from these results that the reduced ability of serum or growth factors to initiate DNA synthesis or growth in ageing cells may be a consequence of an unresponsive protein synthesis pathway rather than a generalised defect in growth factor action.     

Mechanisms for the removal of senescent human erythrocytes from circulation: Specificity of the membrane-bound immunoglobulin G

Direct antiglobulin (Coombs') tests of erythrocyte (RBC) subpopulations confirmed the presence of membrane-bound immunoglobulin G (IgG) on old (density > 1.110) human RBCs but not on the young (density > 1.110) RBCs. After thermal elution of the bound IgG, this Coombs' reaction was negative, but incubation of thermally eluted IgG (He-IgG) with heat-treated RBCs indued a positive antiglobulin reaction was also obtained after incubation of heat-treated RBCs with anti-T antibody. Similar results were obtained when young RBCs treated with Vibrio cholerae neuraminidase (VCN) were incubated with anti-T or with IgG eluted by heat from old RBCs. Nevertheless, pre-absorption of heat-eluted IgG with T and/or Tn antigen, did not prevent it from binding to either heat-treated old or VCN-treated young RBCs as assessed by the antiglobulin consumption assay. Pre-treatment of either VCN-treated young or heat-treated old RBCs with anti-T and/or anti-Tn antibodies had no significant effect on the binding of radiolabeled He-IgG (eluted from old RBCs). The results indicate that even though desialylation of the erythrocyte membrane is required for binding of both anti-T/-Tn and He-IgG, the specificity and consequently the RBC binding sites for He-IgG and anti-T seem to be different.     

A correlation between aging and DNA repair in human epidermal cells

Ultraviolet-induced unscheduled DNA synthesis (i.e. repair synthesis) in human epidermal cells was measured as a function of age. Normal mammary skin specimens were obtained at surgery from 36 female patients, ranging in age from 17 to 77 years. The enzymatically isolated epidermal cells were analyzed for two parameters: (1) the number and percentage of cells carrying out repair synthesis, and (2) the rate of ultraviolet-induced unscheduled thymidine incorporation in individual cells. The results show that the percentage of epidermal cells capable of DNA excision repair synthesis does not decrease significantly with age, but that the rate of unscheduled DNA synthesis in individual cells decreases to a highly significant degree with advancing age.     

Identification of differentially expressed proteins in senescent human embryonic fibroblasts

Normal human fibroblasts undergo a limited number of divisions in culture, a process known as replicative senescence (RS). Although several senescence-specific genes have been identified, analysis at the level of protein expression can provide additional insights into the mechanisms that regulate RS. We have performed a proteomic comparison between young and replicative senescent human embryonic WI-38 fibroblasts and we have identified 13 proteins, which are differentially expressed in senescent cells. Some of the identified proteins are components of the cellular cytoskeleton, while others are implicated in key cellular functions including metabolism and energy production, Ca(2+) signalling, nucleo-cytoplasmic trafficking and telomerase activity regulation. In summary, our analysis contributes to the list of senescence-associated proteins by identifying new biomarkers and provides novel information on functional protein networks that are perturbed during replicative senescence of human fibroblast cultures.     

Occurrence of both growth hormone- and prolactin-immunoreactive material in the cells of human somatotropic pituitary adenomas containing Mammotropic elements

Summary With the use of immunoperoxidase staining, both growth hormone- and prolactin-immunoreactivity were demonstrated in the cells of 6 pituitary adenomas removed because of frank or suspected acromegaly. By double immunostaining of individual sections or comparison of adjacent immunostained sections, partial to almost complete identity of the cell populations containing growth hormone and prolactin was found in 5 of the tumors.     

Recombinant interleukin-1 alpha inhibits the growth of rat mesangial cells in culture.

We have investigated the effect of interleukin-1 (IL-1) on the growth of mesangial cells isolated from rat kidney. Recombinant IL-1 alpha inhibited 3H-thymidine uptake by mesangial cells in a dose-dependent manner in the presence of either 0.5% or 5% fetal bovine serum (FBS). In the presence of high concentration of FBS (10%), the effect of IL-1 was not prominent. The inhibitory effect of IL-1 on the growth of mesangial cells was also confirmed by a change in cell numbers and measurements of protein synthesis with 3H-leucine. IL-1-induced inhibition of mesangial cell growth was not affected by indomethacin. IL-1 showed no effects on intracellular Ca2+ levels in mesangial cells. These observations indicate that IL-1 inhibits the growth of mesangial cells, and thus may play a protective role for mesangial cells from abnormal proliferation in some pathophysiological states.     

Selective immortalization of mammary epithelial cells by microinjection of SV40 DNA into human milk cells

Immortalization of mammary epithelial cells has been obtained by microinjection of SV40 DNA into epithelial cells from primary cultures of rabbit mammary glands. A modification of this technique, allowing selective immortalization of a specific cell type of mammary epithelial cells from human milk by microinjection of SV40 DNA, is described. It includes the selection of luminal epithelial cells from human milk cells after identification of these cells by antibodies directed against specific markers such as intermediate filaments and membrane antigens, and finally, the introduction of SV40 DNA into cell nuclei which will selectively immortalize this restricted cell population. This procedure can be used to derive permanent cell lines with a defined phenotype when only a few cells are available within a heterogeneous cell population.     

人原生殖细胞的分离与培养

目的:探讨人原生殖细胞(PGC)的分离取材时机与体外培养方法,为人类胚胎生殖细胞(EG)的建系研究奠定基础。方法:取不同孕龄的人胚,分离人PGC,在不同培养体系中,观察其增殖与分化情况。结果:孕8、9周较孕7周人胚用酶机械法分离PGC后,原代克隆形成率高,以小鼠胚胎成纤维细胞或STO细胞作为饲养层,并且在培养液中加入hLIF、hbFGF\,hSCF,能较好地维持人PGC的增殖并保持未分化。结论:孕8、9周龄人胚为分离PGC的适宜材料,酶机械法分离PGC简单有效,饲养层细胞与生长因子为人PGC细胞体外培养所必需。     

人胚胎成纤维细胞对人胚胎干细胞生长的作用

目的：比较人和小鼠胚胎成纤维细胞对人胚胎干细胞生长的作用,为胚胎干细胞定向诱导各系统细胞应用于临床,消除异种蛋白污染打下基础。方法：分别采用人胚胎成纤维细胞和小鼠胚胎成纤维细胞为饲养层细胞,支持人受精卵的培养,观察其增殖和分化情况。结果：人和小鼠胚胎成纤维细胞分别加入白血病抑制因子（hLIF）均能很好支持人胚胎干细胞生长增殖,并保持未分化状态。结论：完全可以使用人胚胎成纤维细胞支持人胚胎干细胞增殖,消除异种蛋白污染的可能性,为胚胎干细胞定向诱导分化发育应用于临床打下坚实基础。     

Telomere length and telomerase activity: effect of ageing on human NK cells

Telomeres are repeats of TTAGGG sequences located at the end of eukaryotic chromosomes. They are essential for stabilisation and protection of chromosomal ends and for the regulation of cell replicative capacity. Due to the end-replication defect of DNA polymerase, telomeres shorten progressively with each cell division and telomere length may be an indicator of the replicative history of a cell. Compensatory mechanisms for the telomere loss have been identified. The most widely studied one is mediated by telomerase a ribonuclear protein-enzyme complex that synthesise telomeric repeats. In this study we have investigated whether NK cells, derived from a group of old healthy subjects, underwent the modifications of telomere length and telomerase activity observed in other sub-populations of lymphocytes with advancing age. We demonstrated that: (a) telomere shortening occurred and telomerase activity decreased in human NK cells with ageing; (b) the rate of telomere loss was different under and over 80 years of age; (c) similarly to telomere shortening, the modification of telomerase activity was particularly evident in octogenarians; (d) subjects with the most evident modifications of telomeres and telomerase were the oldest and those with increased NK cell numbers.     

Unscheduled DNA synthesis in various types of cells of the mouse brain in vivo

Summary Very low incorporation of ³H-thymidine (TdR) into neurons and non-proliferating glial and endothelial cells in various brain areas of the adult mouse after ³H-TdR injection and subsequent X-irradiation of the head with 45 Gy has been demonstrated autoradiographically after exposure times of 250 days. In accordance with biochemical studies this incorporation of ³H-TdR represents DNA repair synthesis or UDS (unscheduled DNA synthesis). However, ³H-TdR incorporation into nuclear DNA of non-proliferating cells in the brain was not only found in X-irradiated but also in sham-irradiated mice. This suggests that spontaneous UDS also occurs. Up to now spontaneous UDS has been shown only in HeLa cells in vitro. Nearly all the various types of brain cells tested exhibited UDS after X-irradiation as well as spontaneous UDS. After correcting the mean grain numbers per nucleus not only for background but also for -self-absorption, substantial differences became apparent in the extent of UDS between the individual types of cells. After X-irradiation, UDS was highest in Purkinje cells and hippocampal granular cells but comparable UDS was also found in endothelial cells, regardless of the different brain areas studied. The extent of spontaneous UDS is also quite different in the various cell types, being highest in neurons of different sites and considerably lower in endothelial and glial cells.     

Restriction enzyme analysis of mitochondrial DNA in aging human cells

Human diploid fibroblasts show a limited lifespan in vitro. To investigate the integrity of mitochondrial DNA (mtDNA) in aging fibroblasts, whole cell DNA samples from the human cell line IMR-90 have been prepared at 36, 22, and 3 population doublings (PD) from the end of the lifespan (63 PD). These DNA samples were then digested separately with 19 different restriction endonucleases, and the resulting fragments were separated by agarose gel electrophoresis and transferred to nitrocellulose filters. Fragment sizes were revealed by hybridization to 32P-labelled mouse mtDNA and autoradiography, and were compared with computer maps of fragments generated from the known sequence of human mtDNA. These 19 enzymes recognize a total of 297 recognition sites comprising 1315 nucleotide base pairs (bp), approximately 8% of the human mtDNA (16 569 bp). Control experiments reveal that a minor component representing as little as 5% of the total mtDNA can be detected. No changes were seen in the restriction fragment pattern with fibroblast cell age. It is concluded that there are no large deletions, insertions, or rearrangements in human mtDNA, and no single base changes in the detectable regions. This suggests efficient maintenance of mtDNA molecules and/or elimination of damaged mtDNA during fibroblast cell lifespan.     

A serum-free [3H]thymidine incorporation assay for the detection of transforming growth factors

Summary A rapid mitogenic assay suitable for the detection of transforming growth factors in the extracts of tissues or cells or in the medium conditioned by tumor cells in vitro is described. The method utilizes a nontumorigenic mouse embryo cell line (AKR-2B cells) maintained in serum-free conditions. Three classes of growth factors can be distinguished using this assay.     

造血生长因子促进RV介导LacZ-NeoR基因在人骨髓造血细胞中转染的机制

目的：本文探索了不同组合的造血生长因子ＳＣＦ、ＩＬ３及ＩＬ６对逆转录病毒（ＲＶ）介导的ＬａｃＺ－ＮｅｏＲ双标志基因转染人骨髓造血细胞转染效率、表达水平的影响及其相关机理。方法：采用ＲＶ转染人骨髓非粘附造血细胞（ＮＡＢＭＣ）及经ＳＣＦ、ＩＬ３及ＩＬ６不同组合预激４８ｈ后的ＮＡＢＭＣ。经荧光素二－β－Ｄ－半乳糖呋喃苷脂（ＦＤＧ）标记的半乳糖苷酶、Ｇ４１８ＲＣＦＵ－ＧＭ及ＰＣＲ／Ｓｏｕｒｔｈｅｒｎ－ｂｌｏｔ检测ＮｅｏＲ和ＬａｃＺ基因的表达。结果：早期造血生长因子（ＨＧＦｓ）的预激明显改善了ＲＶ介导的ＬａｃＺ－ＮｅｏＲ基因在人骨髓造血细胞中的转染效率与表达水平,ＳＣＦ＋ＩＬ３＋ＩＬ６＞ＳＣＦ＋ＩＬ３＞ＩＬ３＋ＩＬ６＞ＳＣＦ＋ＩＬ６。氚标记脱氧胸苷（３Ｈ－ＴｄＲ）自杀及５－溴脱氧尿苷－碘化丙啶（ＢｒｄＵ－ＰＩ）双标流式细胞仪（ＦＣＭ）检测显示,ＨＧＦｓ预激后人骨髓造血细胞及ＣＦＵ－ＧＭ的Ｓ期比例显著提高。结论：ＳＣＦ＋ＩＬ３＋ＩＬ６的联合预激可显著改善ＲＶ介导的外源基因在人骨髓造血细胞中的转染效率与表达水平,这可能与ＨＧＦｓ预激后明显提高人骨髓造血细胞及ＣＦＵ－ＧＭ的Ｓ期比例密切相关     

Reversible synchronization of cultured rodent and human diploid fibroblast cells in G2 phase

This paper describes a three-step procedure for induction of reversible cell synchrony in the G₂ phase of the cell cycle of Chinese hamster ovary (line CHO) cells and non-transformed, human skin fibroblast (HSF) cells. The CHO cells are presynchronized in early S phase by isoleucine deficiency and hydroxyurea blockades. The culture is transferred to medium supplemented with the DNA topoisomerase II inhibitor, Hoechst 33342 for 12 hours after which 95% of the cells are arrested in G₂ phase. When G₂ synchronized cells are transferred to Hoechst-free, complete medium, they divide as a highly synchronous cohort within 3 hours. The HSF cells are initially cultured in low serum to arrest them in G₀ and then transferred to complete medium containing aphidicolin to arrest them in early S phase. The culture is then transferred to aphidicolin-free, complete medium with Hoechst 33342 (0.1 g/ml) for 10 hours after which up to 85% of the cells arrest in G₂ phase. Synchronous cell division occurs 3.5 hours after transfer of cells to complete, drug-free medium. The synchrony techniques are useful for studying G₂/M biochemical events in mammalian cells.Abbreviations -MEM minimum essential medium alpha medium - BCS bovine calf serum - DMSO dimethyl sulfoxide - EDTA ethylenediaminetetraacetic acid - FCM flow cytometry - PBS phosphate buffered saline - Top II DNA topoisomerase II     

Growth factors and cytokines in paragangliomas and pheochromocytomas,with special reference to sustentacular cells

The aim of this study was to localize various growth factors and cytokines in paragangliomas and pheochromocytomas in order to understand their possible autocrine or paracrine functions, and to compare sustentacular cells of the adrenal medulla with pituitary stellate cells. Thirteen resected tumors, 11 paragangliomas and 2 pheochromocytomas of the adrenal medulla, were studied. In addition, five surgically removed nontumorous adrenals and five nontumorous pituitaries were studied. Varying numbers of sustentacular cells were immunopositive for S-100 protein and in most instances for glial fibrillary acidic protein. Insulin-like growth factor-1 (IGF-1), tumor necrosis factor-α (TNF-α), and interleukin-6 were localized to both cell types in all cases, whereas epidermal growth factor (EGF) immunopositivity was noted in only three. In all tumors, leukemia inhibitory factor (LIF) was restricted to chief cells and EGF receptor to sustentacular cells. Nontumorous chief cells and sustentacular cells of adrenal medulla exhibited immunoreactivities similar to those of paragangliomas and pheochromocytomas. Secretory adenohypophysial cells displayed various immunoreactivities for all growth factors, receptors, and cytokines studied. Pituitary stellate cells were immunopositive for EGF, EGF receptor, IGF-1, LIF, and TNF-α. In conclusion, paragangliomas and pheochromocytomas are immunoreactive for a wide spectrum of growth factors and cytokines. Immunocytochemistry demonstrated similarities between sustentacular cells and stellate cells of the pituitary in addition to their similar morphology. The significance of these observations regarding paracrine activities of chief and sustentacular cells remains to be determined.     

Cytoplasmic DNA synthesis by cord blood cells of premature and full-term infants

Summary Cord blood cells from 8 full-term and 12 premature infants as well as blood leukocytes from 10 adults were incubated with³H-thymidine and were subsequently exposed to autoradiographic emulsion for prolonged periods of 45 and 90 days. Cytoplasmic label — which we interpreted as evidence of mitochondrial DNA synthesis — was found in 1.7 per cent of lymphoid cells from adult blood, in 2.9 per cent and 4.5 per cent of lymphoid cells from full-term and premature infants, respectively. Statistical analysis of the data shows that the number of labelled cells is significantly larger in the blood of premature infants than in adults (p<0.01).On leave from the Department of Pediatrics, University of Göttingen, West-Germany, under the auspices of the Committee for Scientific Co-operation between German Institutions and the Weizmann Institute