Fine structure of IMR-90 cells in culture as examined by scanning and transmission electron microscopy

Apoptotic effects of ε-viniferin in combination with cis-platin in C6 cells

Glioblastoma (GBM) is one of the most common and lethal forms of primary brain tumors in human adults. Treatment options are limited, and in most cases ineffective. Natural products are sources of novel compounds endowed with therapeutic properties in many human diseases like cancer. ε-viniferin is a resveratrol dimer and well known for having antiproliferative and apoptotic effects on cancer cells. Cisplatin is a platinum containing anti-cancer drug. In this study, we aimed to investigate antiproliferative and apoptotic effects of using cis-platin and ε-viniferin alone or in combined treatment of C6 cells. Cell proliferation was detected by WST-1. Mitochondrial membrane potential changes in the cells (ΔΨm) were evaluated using cationic dye JC1. Apoptotic index which is a hallmark of late apoptosis was detected by using Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method and apoptotic alterations were observed by transmission electron microscope (TEM). Activation of caspase-8, -9, -3 in C6 cells at various incubation periods was measured by flow cytometer. Apoptotic index increased at highest level in only combined treatment cells (91.6%) after 48 h incubation. These results were supported by TEM images. Caspase-8 activation in C6 cells increased to a maximum (12.5%) after 6 h by using combined cis-platin/ε-viniferin treatment (13.25/95 μM). Caspase-9 was activated at 44.5% after combined treatment for 24 h. This rate is higher than using cis-platin (14.2%) or ε-viniferin (43.3%) alone. The combined 13.25 μM/cisplatin and 95 μM ε-viniferin treatment caused maximum caspase-3 activation in C6 cells (15.5%) at the end of the 72 h incubation. In conclusion, it was observed that caspase-8, -9, -3 activation which was determined in vitro, trigerred apoptotic mechanism in C6 cells by using low concentrations of combined cis-platin and ε-viniferin.

Towards novel anti-tumor strategies for hepatic cancer: ɛ-viniferin in combination with vincristine displays pharmacodynamic synergy at lower doses in HepG2 cells

Hepatocellular carcinoma is the fifth most common cancer and the third leading cause of cancer-related deaths worldwide. The efficacy of novel combination treatments are increasingly evaluated with use of integrative biology research and development (R&D) strategies and methodological triangulation. We investigated the anti-tumor effect of ɛ-viniferin alone, and the putative synergy of ɛ-viniferin with vincristine on the growth of HepG2 cells in vitro. Growth inhibition and apoptosis induction were determined by MTT assay and annexin V/propidium iodide (PI), respectively. Morphological changes and DNA fragmentation were investigated under electron microscopy and by agarose gel electrophoresis, respectively. The results collectively showed that treating cells with ɛ-viniferin and vincristine significantly inhibited cell viability at lower doses as compared to each agent applied alone. IC(50) values for ɛ-viniferin and vincristine were determined as 98.3 and 52.5 μM at 24 h, respectively. IC(50) value of ɛ-viniferin in combination with vincristine was 15.8+11.25 μM (mean/SD) at 24 h. The viability of cells treated with 17.9 μM vincristine alone for 24 h was 79.62%; it reduced to 26.53% when 25 μM ɛ-viniferin was added in combination with vincristine (p<0.05). We found that combination of drugs promoted the sensitivity of cells against to vincristine treatment. The effect of combined use was in support of a synergistic pharmacodynamic effect. Moreover, low doses of the combination regimen induced phosphatidyl re-localization, morphological changes, and DNA fragmentation, and therefore caused apoptotic death. This study thus suggests that low concentrations of ɛ-viniferin and vincristine can enhance the anti-tumor effects efficiently by inducing HepG2 cell apoptosis. Further studies in other model systems are warranted with a view to potential future applications in the clinic of such combination regimens and their putative mechanism of action in the observed synergy reported here.

A method for efficient calculation of diffusion and reactions of lipophilic compounds in complex cell geometry

A general description of effects of toxic compounds in mammalian cells is facing several problems. Firstly, most toxic compounds are hydrophobic and partition phenomena strongly influence their behaviour. Secondly, cells display considerable heterogeneity regarding the presence, activity and distribution of enzymes participating in the metabolism of foreign compounds i.e. bioactivation/biotransformation. Thirdly, cellular architecture varies greatly. Taken together, complexity at several levels has to be addressed to arrive at efficient in silico modelling based on physicochemical properties, metabolic preferences and cell characteristics. In order to understand the cellular behaviour of toxic foreign compounds we have developed a mathematical model that addresses these issues. In order to make the system numerically treatable, methods motivated by homogenization techniques have been applied. These tools reduce the complexity of mathematical models of cell dynamics considerably thus allowing to solve efficiently the partial differential equations in the model numerically on a personal computer. Compared to a compartment model with well-stirred compartments, our model affords a more realistic representation. Numerical results concerning metabolism and chemical solvolysis of a polycyclic aromatic hydrocarbon carcinogen show good agreement with results from measurements in V79 cell culture. The model can easily be extended and refined to include more reactants, and/or more complex reaction chains, enzyme distribution etc, and is therefore suitable for modelling cellular metabolism involving membrane partitioning also at higher levels of complexity.

Cultured murine dermal fibroblast-like cells from senescence-accelerated mice as in vitro models for higher oxidative stress due to mitochondrial alterations

The senescence-accelerated mouse is a model for senescence acceleration, a higher oxidative stress status, and age-associated disorders. We studied whether fibroblasts cultured from accelerated senescence-prone SAMP11 mice could be used as in vitro models for oxidative stress in senescence. Dichlorofluorescein and hydroethidine assays demonstrated that cells from SAMP11 mice produced more reactive oxygen species than did cells from accelerated senescence-resistant SAMR1 mice. These differences were not due to the defective induction of antioxidants. Double labeling with hydroethidine and MitoTracker Green revealed that most of the reactive oxygen species were generated within the mitochondria. Nonyl acridine orange and JC-1 assays showed an increase in the mass of the mitochondria, especially those with low membrane potential, in SAMP11 cells. Ultrastructurally, mitochondria with degenerative morphology were increased in SAMP11 cells with longer culture periods. These results suggest that cells from SAMP11 mice are useful models for spontaneous higher oxidative stress in vitro due to dysfunctional mitochondria.

The concept of telomeric non-reciprocal recombination (TENOR) applied to human fibroblasts grown in serial cultures: concordance with genealogical data

Since the discovery of the limited life span of human fibroblasts some 50 years ago, many genealogical studies have been undertaken to describe growth kinetics of fibroblasts in serial cultures by their individual division behavior. It is now accepted that proliferation capacities of human fibroblasts strongly depend on their telomere lengths and integrity. Telomeres shorten with each replication round, and there is a direct correlation between cell division capacity and telomere lengths; that is, the consumption of disposable telomeric DNA repeats during cell divisions progresses until critically short telomeres determining the replicative senescence of the cells are present. Recently, we have suggested that telomeres in fibroblasts can also become elongated during DNA replication by telomeric non-reciprocal recombination (TENOR). Here we discuss genealogical data collected over the last decades as well as more recent findings on the telomere-driven replicative senescence process, and we summarize both to give an integrated picture.

Garbage catastrophe theory of aging: imperfect removal of oxidative damage?

Increasing evidence suggests an important role of oxidant-induced damage in the progress of senescent changes, providing support for the free radical theory of aging proposed by Harman in 1956. However, considering that biological organisms continuously renew their structures, it is not clear why oxidative damage should accumulate with age. No strong evidence has been provided in favor of the concept of aging as an accumulation of synthetic errors (e.g. Orgel's 'error-catastrophe' theory and the somatic mutation theory). Rather, we believe that the process of aging may derive from imperfect clearance of oxidatively damaged, relatively indigestible material, the accumulation of which further hinders cellular catabolic and anabolic functions. From this perspective, it might be predicted that: (i) suppression of oxidative damage would enhance longevity; (ii) accumulation of incompletely digested material (e.g. lipofuscin pigment) would interfere with cellular functions and increase probability of death; (iii) rejuvenation during reproduction is mainly provided by dilution of undigested material associated with intensive growth of the developing organism; and (iv) age-related damage starts to accumulate substantially when development is complete, and mainly affects postmitotic, cells and extracellular matrix, not proliferating cells. There is abundant support for all these predictions.

Ultrastructure of dermal fibroblasts during development and aging: relationship to in vitro senescence of dermal fibroblasts

One approach to understanding the relationship between in vitro cellular senescence and in vivo aging is to define the development and aging of cells in vivo and then to compare these in vivo properties with the in vitro behavior of the same cells. The Syrian hamster is being used as an experimental aging model to investigate the intrinsic developmental program of dermal fibroblasts in vivo (proliferation, extracellular matrix (ECM) production, quiescence, and reactivation during wound repair) in order to determine whether the in vivo differentiation program and mature function of these cells is related to their in vitro proliferation and senescence pattern. The ultrastructure of dermal fibroblasts from midfetal development through old age is described, and a working hypothesis of the development and aging of dermal fibroblasts is proposed as a framework for further evaluation of the relationship between in vitro proliferative capacity of dermal fibroblasts and in vivo developmental and age-related changes in the dermis.

Mitochondrial antigenic structure and enzyme activity in ageing human diploid fibroblasts

It has been proposed that cellular ageing may be caused by loss of mitochondrial function due to the action of free radicals. To investigate this hypothesis, antigenic structures of the mitochondrial inner membrane/matrix and of the outer mitochondrial membrane of human diploid fibroblasts were monitored by immunoblotting at four stages during cellular lifespan in vitro. At the same time, specific activities of the enzymes oligomycin-sensitive ATPase (O-S ATPase), malate dehydrogenase (MDH) and glutamate dehydrogenase (GDH) were assayed to assess the functional capacity of cellular oxidative phosphorylation and of the tricarboxylic acid cycle. No changes were found with ageing in inner mitochondrial membrane-associated matrix components, or in the activities of O-S ATPase and MDH. However GDH activity increased significantly with ageing in vitro, possibly indicating greater amino acid utilization for energy production in older cells. There was loss of an outer mitochondrial membrane antigen, of approximate molecular weight 60 kilodaltons (kDa), in the oldest cells tested, which may influence outer membrane transport capacity late in the cellular lifespan. Overall, the results fail to provide support for the hypothesis that ageing primarily results from free radical-induced impairment of mitochondrial function.

The ultrastructure of fiber cells in primate lenses: a model for studying membrane senescence

We have compared the surface morphology of the youngest (cortical) fiber cells with that of the most senescent (nuclear) fiber cells in monkey and baboon crystalline lenses by stereo scanning electron microscopy (SEM) and thick-section stereo transmission electron microscopy (TEM). Both the broad and the narrow faces of the most senescent fiber cells featured distinctive, polygonal areas (domains) of furrowed cell membrane. The domains ranged in size from 2.42 to 8.78 microns2. Stereopair SEM and TEM micrographs demonstrated precisely oriented microvilli measuring approximately 0.14 micron in diameter and ranging in length from 1.27 to 4.65 microns overlying each ridge in the domains. Formation of microvilli on senescent cells has been noted in other types of aging cells but they are imprecisely arranged and their function is unknown. Since every fiber cell remains in a fixed location (relative to other fiber cells) throughout life, the lens provides a unique model to study structure-function relationships of senescent microvilli in situ. The discovery of an age-related elaboration of numerous microvilli on senescent fiber cells of noncataractous lenses invalidates the currently accepted theory that close, parallel apposition of the broad faces of lens fiber cells is necessary for the lens to be transparent.

Changes in negative surface charge of human diploid fibroblasts, TIG-1, during in vitro aging

The electrophoretic mobility of human diploid fibroblasts, TIG-1, was studied at different passages. The net negative surface charge of the cells decreased from -1.658 +/- 0.108 micron/s/V/cm at an early passage (15 population doublings, PD) to -1.173 +/- 0.116 at the final passage (67 PD) in 1/15 M phosphate buffer supplemented with 5.4% glucose. The decrease was slow at 15-45 PD, but was rapid at 45-67 PD. The net negative surface charge of small cells in the late passage populations was not different from that of larger cells in this population, and was significantly lower than that of small cells in the middle passage populations. The distribution of the mobilities of cells in each passage was independent of the size of the individual cells, and the mean value was distinct for the passage number. The viability of the cells was retained during the assay of electrophoretic mobility under these conditions. These results indicate that the net negative surface charge of human diploid fibroblasts represents a cell surface maker for in vitro cellular age in the population.

Cell surface oligosaccharide modulation during differentiation. II. Membrane mobility of oligosaccharide lectin conjugates

The quantitative, population doubling level (PDL) dependent changes in cell surface oligosaccharides on IMR-90 cells, were investigated from the perspective of membrane mobility of the lectin-oligosaccharide conjugates. Concanavalin-A (CON-A), wheat germ agglutinin (WGA), Ricinus communis agglutinin (RCA-120), and Dolichos biflorus agglutinin (DBA) were all observed to cluster, cap, and endocytose in cultured human diploid fibroblasts (IMR-90). Quantitative photometry at 37 degrees C over defined periods of time indicated that as the IMR-90s approached cellular senescence a specific lectin-dependent inability to either endocytose or process the capped complex occurred. The development of a biotin/avidin/enzyme amplification assay permitted the assignment of the accumulating signal to the internal compartment. Kinetic data indicate that there are at least three separate (and separable) mechanisms for the PDL related changes in lectin binding. Data for the CON-A complex indicates that at least two classes of functional complexes are present. Regression analysis of the kinetic data for the RCA-120 complex indicates a similar membrane clearance for the IMR-90s at all population doubling levels (PDL), suggesting that the quantitative differences observed earlier were due to simple quantitative reductions in the RCA complexing molecules. Data for WGA mobility on the membrane indicates that they are both changes in the number and mobility status of the complexes. These results indicate that the quantitative changes in lectin binding observed previously as IMR-90 cells approach senescence are correlated with alterations in membrane mobility patterns of the lectin oligosaccharide conjugates.

Effects of morphine on rat kidney glomerular podocytes: a scanning electron microscopic study

Degenerative kidney changes are associated with heroin use in human addicts, but it is not known whether these changes result from exposure to the opioid or from contaminants in street heroin. In the present study, 4-6-month-old rats each received 1 subcutaneous pellet containing 75 mg of morphine or placebo, followed 3 days later by implantation of 2 additional morphine or placebo pellets. Seven days after implantation of the first pellet, the rats were killed by aldehyde perfusion. The right kidney was excised, and coronal slices were prepared for scanning electron microscopy. Micrographs were taken at 5000X and were scored on the presence of short or long microprojections (a score of '1' indicating few and a score of '4' indicating many). Morphine significantly altered the frequencies of scores for long microprojections, suggesting that morphine treatment increased the number of microprojections on glomerular podocytes. No changes in filtration slits, pedicels, or blebbing (foval enlargements) were noted. The data support the view that kidney degeneration associated with opioid abuse reflects effects of opioids per se, and they are consistent with microprojection changes as a function of altered intracellular cyclic AMP levels.

Oxidative damage to DNA and replicative lifespan in cultured adrenocortical cells

Oxidative damage to DNA in cultured bovine adrenocortical cells was investigated by exposing cells to a sublethal concentration (10 microM) of cumene hydroperoxide under conditions previously shown to be deficient in the biological antioxidants selenium and alpha-tocopherol (vitamin E). DNA prepared from cells incubated for 4 h with 10 microM cumene hydroperoxide had a greater fraction showing resistance to S1 nuclease after denaturation and reassociation to a log C0t of -3. Cross-linking by cumene hydroperoxide was abolished in cells that had been grown in the presence of 20 nM selenite or 1 microM alpha-tocopherol for 96 h prior to peroxide addition, whereas such cells remained susceptible to cross-linking by nitrogen mustard. Extensive strand breaks in DNA from peroxide-treated cells as assessed by alkaline sucrose gradient centrifugation were greatly reduced in cells grown in selenite or alpha-tocopherol. Despite the evidence of damage to DNA, cumene hydroperoxide was not detectably mutagenic, in contrast to 5 microM methylnitronitrosoguanidine (MNNG), when assessed as the incidence of resistance to 25 microM ouabain. We confirmed that cumene hydroperoxide at greater than 10 microM lowers cloning efficiency and that this is largely prevented by selenite or alpha-tocopherol. Additionally, selenite or alpha-tocopherol produced increased clonogenicity in cells not incubated with peroxide. To examine effects of the biological antioxidants on replicative lifespan, cells were grown continuously in fetal bovine serum (FBS), fibroblast growth factor (FGF), and selenite or alpha-tocopherol. Selenium increased replicative lifespan by 10-20% and alpha-tocopherol by 22-30%. Levels of DNA cross-links and strand breaks did not differ under any circumstances between early (second) passage and late (30th) passage cells. The experiments on replicative potential were all performed in the presence of FGF. When FGF was omitted from the culture medium, replicative lifespan was reduced by 85%. We conclude that types of damage to DNA resulting from peroxide exposure are not present in cells under standard culture conditions at early or late stages of the lifespan. Other work has noted a relationship between clonogenicity and replicative lifespan; thus, the increase in cloning efficiency seen with selenium and alpha-tocopherol may cause the observed slight increase in replicative lifespan. Oxidative damage does not appear to be a major determinant of cellular senescence in adrenocortical cells.

Hydrocortisone is associated with cell surface blebbing in cultures of human embryonic lung fibroblasts

Treatment with hydrocortisone (HC) is associated with increased cell surface blebbing of proliferatively active WI-38 and IMR-90 fibroblasts at low and high population doubling levels within the first 24 h after seeding. Time course studies show a marked decrease in blebbing after 2 days. In contrast, very old cells near the end of the population life span (greater than 96% life span completed) show blebbing which is independent of HC treatment. Since the time of increased HC-associated blebbing in cycling cell populations coincides with the time during which HC-treated cells condition the medium with a growth-stimulating (autocrine) factor, it is possible that blebbing may represent extrusion of this factor from the cells at these times.

Filopodia number increases with age and quiescence in populations of normal WI-38 cells, and is correlated with drug-induced changes in proliferation in both normal and transformed populations

Filopodia in log and stationary phase populations of human fetal lung fibroblasts (WI-38) at low and high population doubling levels (PDLs) and of SV40 transformed WI-38 cells (VA13A), were observed and counted under different conditions of in vitro growth by scanning electron microscopy. Cells from old non-vigorously growing WI-38 populations (those at a high PDL) had more filopodia than younger populations (those at a lower PDL) at all times after seeding, and for any given population stationary phase cells (those entering, or in, quiescence), had more than log phase cells. Hydrocortisone (HC, 14 microM), which stimulates proliferation and increases life span of WI-38 cells, was associated with a marked decrease in filopodia. Conversely, retinoic acid (RA, 10 microM), which inhibits growth and decreases life span of WI-38 cells, was associated with an increase in filopodia. Since old cell populations have lower saturation densities than young, it is suggested that cell contact signaling growth cessation in these populations may be mediated by filopodia. The HC-associated decrease in filopodia may thus be possibly interpreted as a decrease in filopodia-mediated "density dependent inhibition," and the increase in filopodia with RA as a possible increase in this "inhibition." Both HC and RA inhibit growth and are associated with an increase in filopodia in VA13A cultures.

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.

The effects of in vitro ageing on the exopeptidases of human diploid fibroblasts

Six exopeptidases present in human diploid fibroblasts were identified by separation on polyacrylamide gel electrophoresis and their activity profiles against 17 dipeptides, two tripeptides and L-leucine-p-nitroanilide determined. No differences in relative activity or in the electrophoretic patterns of any of the six exopeptidases were detected with ageing. Aminoacylarylamidase activity assayed spectrophotometrically showed significantly increased activity in the middle age-group cells as opposed to the enzyme isolated from young and old cells. Heat-inactivation studies using the same substrate suggested the possibility of an increased proportion of heat-labile enzyme in the old cells but interpretation of the data was difficult because of the complex nature of the inactivation curves obtained. Overall, the results tended to refute the hypothesis that age-related changes in the free amino acid pool of human diploid fibroblasts were associated with significant alterations in the activities of cellular exopeptidases.

Isolation by flow sorting of cytokinetic and morphological heterogeneity in late-passage cultures of human diploid fibroblasts (IMR-90)

Considerable structural, metabolic, and proliferative heterogeneity develops in populations of cultured diploid cells which have reached advanced levels of population doubling. Isolation of noncycling cells from late-passage cultures would permit more definitive investigation of the structure and behavior of individual senescent cells. In this paper, we report the viable sorting of late-passage cultures of human diploid fibroblasts (IMR-90) into two subpopulations of cells with different proliferative potentials. Sorting is based on cellular light-scattering properties and autofluorescence. Structural and behavioral features of the subpopulation exhibiting increased forward-angle light scatter are more characteristic of senescent cells than the subpopulation sorted by decreased forward-angle light scatter.

Ageing of hamster embryo fibroblasts as the result of both differentiation and stochastic mechanisms

Fibroblasts from hamster embryos were serially cultivated in vitro and their evolution followed from a morphological, physiological and biochemical point of view. After an exponential growth for about 20 passages, cells entered the ageing phase which ended up after 29-34 passages. From our observations, it seems that the arrest of growth results from two different phenomena: first, the typically fibroblastic cells may undergo a stochastic ageing process; second, some of these cells evolve into a terminal differentiation process, characterized by a different non-fibroblastic phenotype.

Age-related ultrastructural changes in human embryonic lung fibroblasts

Scanning and transmission electron microscopy were used to examine human embryonic lung fibroblasts at different population doubling levels. Scanning electron microscopy of cells at population doubling levels 26, 45 and 59 did not reveal a significant change in cell size with increasing age. However, transmission electron microscopy of cells at population doubling levels 19 and 45 showed an increase in nuclear lobes, a decrease in the number of ribosomes associated with rough endoplasmic reticulum, and changes to the internal structure of mitochondria on increasing population doubling level. No other previously reported age-related changes were found.

The effects of in vitro ageing on the composition of the intracellular free amino acid pool of human diploid fibroblasts

The composition of the free amino acid pool of the human diploid fibroblast cell line, BCL-D1, was analysed by automated ion-exchange chromatography throughout the life-span of the culture. Significant age-related changes, independent of growth effects, were found with six essential amino acids: a decrease in tyrosine, phenylalanine, leucine, isoleucine and valine, and an increase in methionine. The nature of the changes were suggestive of a decline in the operation of the L-system of amino acid transport with in vitro age. However, it is also possible that age-related changes in the proportions of tRNA iso-acceptors and/or the availability and accuracy of tRNA synthetases were involved.

Energy metabolism in cultured human fibroblasts during aging in vitro

To explore the relationship between energy metabolism and the limited replicative life span of cultured human fibroblasts, we studied several bioenergetic parameters in normal fibroblasts at early passage (young cells) and at late passage (old cells) and early passage cells from a subject with the Hutchinson-Gilford (progeria) syndrome. Old cells consumed more glucose and produced more lactate during growth, but O2 consumption, both basal and following maximum uncoupling of oxidative phosphorylation by SF-6847, was the same as in young cells. Progeria cells produced the most lactate but did not consume more glucose, while their basal and uncoupled O2 consumption was similar to that of young and old cells during both log and confluent states. Consumption of glutamine, a source of both oxidative energy and lactate, was approximately the same in all three cell types as was 14CO2 production from 2- 14C-pyruvate and 5- 14C-glutamate. ATP and ADP concentrations were similar in all cell types with a rise in the ATP/ADP ratio during growth from log to confluent state. Thus, old and progeria cells, in contrast to young cells, produce more lactate during growth consistent with a rise in energy demand and/or inefficiency of oxidative phosphorylation. Although limitations in total energy output do not appear to be causal to the loss of replicative capacity in normal cells after serial passage, they could play a role in the curtailed replicative capacity of progeria cells.

Quantitative morphological analysis of proliferating and nonproliferating subpopulations of IMR-90 fibroblasts during aging in vitro

Early-, mid- and late-passage cultures (population doubling levels 12, 35, and 51, respectively) of IMR-90 fibroblasts were exposed to 3H-thymidine for 48 h prior to fixation in situ for morphometric analysis in order to determine quantitatively what ultrastructural changes accompany the loss of proliferative capacity during aging in vitro. Analysis of autoradiographs, both at the light and electron microscopic levels, with an image analyzer followed by ANOVA statistical scrutiny demonstrated that a significant increase in relative cell area, an indicator of cell size, was characteristic of cells unable to incorporate 3H-TdR at both mid- and late-passage, but not at early-passage levels. Nuclear size also increased significantly with progressive passage level but was not related to proliferative capacity. No significant difference in the area fraction of nucleoli per unit area of nucleus or of mitochondria, Golgi, or lysosomes was seen in either subpopulation at any passage level. Dilated cisternae of rough endoplasmic reticulum in early-passage cells were seen if cells were harvested with trypsin and fixed either before or after centrifugation, but were not seen in labeled or unlabeled cells from any passage level when cultures were fixed in situ. We conclude that a significant increase in cell size is the only significant morphological change associated with the loss of proliferative capacity of IRM-90 fibroblasts. Furthermore, our data indicate that there is no accumulation of secondary lysosomes in human diploid fibroblasts during aging in vitro; we therefore cannot support any hypothesis of aging or proliferative decline that is based mechanistically upon this phenomenon.

The role of limited cell replicative capacity in pathological age change. A review

Physiological functions are carried out by differentiated cells, with finite lifespans, which age and need to be replaced. In young individuals, tissue functions are sustained at optimal levels because cellular dysfunction and cell loss are balanced by the emergence of newly differentiated cells as stem cells and their partially differentiated descendants replicate. However, with the passage of time the mitotic rates of these cells diminish. Eventually, replications occur too infrequently to offset the loss. It is at this point that the tissue begins to show structural changes and declining function which, as they become pervasive, are identified as "ageing". In this paper the theory is set forth that: (1) Diminishing mitotic activity in older tissues results from limited stem cell replicative capacity. (2) All stem cells, regardless of tissue, exhibit similar replicative patterns over time, progressing from the actively proliferating to the nonproliferating state. However, stem cells in different kinds of tissue have different rates of replicative decline, with the result that some tissues show age earlier than others. (3) The combination of two cellular properties--differentiated cell ageing and limited stem cell replicative capacity--is sufficient to establish the framework in which other pathological changes characteristic of aged people and animals take place.

Changes in nuclear shape and mitochondrial structure do not accompany the loss of division potential in human fibroblasts in vitro

Previous studies on ultrastructural changes that occur in cultured human fibroblasts during their in vitro life-span indicate that "senescent" cells characteristically possess structurally altered mitochondria, highly lobed nuclei, and an abundance of secondary lysosomes when compared to early passage cells. In the present study, we demonstrate that improper preparative methods can induce altered mitochondrial morphology in preparations of both IMR-90 and HF730A fibroblasts, regardless of passage level. We also show that nuclei of both living and fixed IMR-90 fibroblasts are ovoid in shape, not lobulate, in well-spread cells, regardless of either the passage level or the proliferative capacity of the cell. Fibroblasts contain lobulated nuclei only when they have not spread completely on the culture substrate. Lobulations can be induced at any passage level by collagenase/trypsin or trypsin/EDTA treatment prior to fixation, but not by cytochalasin B treatment or by cold temperatures. We conclude that any treatment that affects cytoskeleton-membrane-culture substrate interactions will induce this aberrant nuclear morphology, but that this is not indicative of "senescence" and does not relate to proliferative decline.

Status of mitochondria in living human fibroblasts during growth and senescence in vitro: use of the laser dye rhodamine 123

Rhodamine 123, a fluorescent laser dye that is selectively taken up into mitochondria of living cells, was used to examine mitochondrial morphology in early-passage (young), late-passage (old), and progeric human fibroblasts. Mitochondria were readily visualized in all cell types during growth (mid-log) and confluent stages. In all cell strains at confluence, mitochondria became shorter, more randomly aligned, and developed a higher proportion of bead-like forms. Treatment of cells for six days with Tevenel, a chloramphenicol analog that inhibits mitochondrial protein synthesis, brought about a marked depletion of mitochondria and a diffuse background fluorescence. Cyanide produced a rapid release of preloaded mitochondrial fluorescence followed by detachment and killing of cells. Colcemid caused a random coiling and fragmentation of mitochondria particularly in the confluent stage. No gross differences were discernible in mitochondria of the three cell strains in mid-log and confluent states or after these treatments. Butanol-extractable fluorescence after loading with rhodamine 123 was lower in all cell strains in confluent compared to mid-log stages. At confluence all three cell strains had similar rhodamine contents at zero-time and after washout up to 24 h. At the mid-log stage, young cells contained more rhodamine initially and lost it more rapidly than old or progeria cells, in that order. The data indicate no gross derangement in the morphology or number of mitochondria in old and progeria fibroblasts but there is a reduction of protonmotive force evident in these cells at the mid-log stage that may be growth limiting.

Effects of hypophysectomy on age-related changes in the rat kidney glomerulus: observations by scanning and transmission electron microscopy

The kidney glomeruli of 9-month-old intact, 23-month-old intact, and 23-month-old hypophysectomized female rats were examined by scanning and transmission electron microscopy. With increasing age, the glomeruli increased in diameter and more podocyte microvilli were found. Hypophysectomy (4 months before sacrifice) reduced these values to levels approaching values seen in the 9-month intact controls. Transmission electron microscopy revealed that increased numbers of podocytes and endothelial cells had cytoplasmic dense bodies with advancing age. Granular cytoplasmic material, seen in podocytes, did not alter in frequency with age. Hypophysectomy reduced the number of cells containing the dense bodies as well as the number of podocytes containing granular material. Basal laminar thickness, while increasing with age, was unaffected by hypophysectomy. The results show that hypophysectomy can return some structural age-related changes to values seen in younger subjects. The effects are similar in some respects to the effects of dietary restriction.

Fine structural alterations in the aging rat pineal gland

The pineal glands of 1 mo to 28 mo old male and female rats were examined by electron microscopy. With increasing age the following observations were made: (1) the capsule thickness increases; (2) there is an increase in collagen infiltration; (3) increased amounts of granular deposits are seen between cells; (4) there is a greater variability in the number of light pinealocytes; (5) pinealocytes with nuclear invaginations and pinealocytes with nuclear inclusions increase in number; (6) more cytoplasmic dense bodies are seen in pinealocytes and gliocytes; (7) the maximum diameter of pinealocyte lipid droplets tends to increase; (8) no definite change is observed in granular endoplasmic reticulum; (9) occasional cells are found to contain reticulated mitochondria, and a few cell processes have an appearance similar to neuroaxonal dystrophy. Besides illustrating age-rated changes, the present study proves the existence of pinealocyte nuclear inclusions, suggests the possibility of pineal concretions in the rat, and morphometrically or semi-morphometrically analyzes several structural features not previously quantified.

Effects of age and dietary restriction on the kidney glomeruli of mice: observations by scanning electron microscopy

A study was undertaken to examine, by scanning electron microscopy (SEM), the kidney glomeruli of control mice 1 mo, 10 mo, and 24 mo of age, as well as dietarily restricted mice 10 mo and 24 mo of age. One month old female C57BL/6J mice were offered one of the following: 1) a control diet containing 24% protein fed ad lib; 2) the control diet fed on alternate days (intermittently fed); or 3) a diet containing 4% protein fed ad lib. Animals were sacrificed, by aldehyde perfusion at 1 mo, 10 mo, and 24 mo of age. The kidneys were sliced and prepared for SEM. There was a significant age-related increase in glomerular diameter and amount of microvilli on the podocyte surface (microvillus index). Although the diameters of the podocytes increased approximately 20% with age, these differences were not statistically significant. Feeding a 4% protein diet resulted in smaller diameters of glomeruli and podocytes as well as smaller microvilli indices as compared to those of control animals. Although similar differences were observed in the kidneys of intermittently fed animals, only the microvillus index was statistically significant. Therefore, dietary manipulations, which have been shown to increase life span, result in marked morphological differences when compared to control animals.