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Results for “Proliferation”

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PubMed1976

Transient inhibition of cell proliferation in rat glioma monolayer cultures by cortisol.

The effect of 3 muM cortisol on cell proliferation in rat glioma (strain C6) monolayer cultures was investigated. Cell density measurements showed that cortisol-treated C6 cells continued to proliferate at maximum log phase rates for 1 to 2 days. Then cell proliferation ceased as growth in control cultures continued into stationary phase. A 2-day period of growth inhibition followed during which cell densities were 30 to 50% lower relative to controls. Growth resumed subsequently, and final cell densities were similar to those of controls. The presence of epicortisol (the biologically inactive isomer of cortisol) in the culture medium did not alter the rate of log phase growth relative to controls. During the initial period of continued growth after exposure to cortisol, the pH of the medium decreased at the same rate in control and treated cultures. During the growth-inhibitory period, erythrosin B dye was excluded equally well (greater than 94%) by control and treated cells, and no morphological differences were detected by phase contrast microscopy. When the culture medium was replaced daily, the control cells at elevated densities continued to proliferate at a reduced rate. In cortisol-treated cultures, the period of growth inhibition commenced 3 days after the cells were exposed initially to cortisol. A 2-day period of growth inhibition followed during which the pH of the 1-day-old media from both control and treated cultures decreased from 7.4 to 6.9. Growth resumed subsequently in the treated cultures to produce elevated cell densities similar to those of controls. These results demonstrate that cortisol at concentrations considered chemotherapeutic in vivo exerts a transient inhibitory effect on C6 glioma cell proliferation.

Cell Division↗

PubMed2026

Intestinal organoid screen reveals that Bacillus velezensis PGM541 promotes epithelial proliferation via its metabolite butyric acid.

BACKGROUND: Probiotics have been widely used for the regulation of intestinal health. Current screening methods for probiotics typically rely on animal or two-dimensional cell models. In this study, we employed intestinal organoids to identify a candidate probiotic strain. Furthermore, we investigated the potential mechanisms through which this strain and its active metabolites exert their effects, thereby evaluating the efficacy of this screening approach. RESULTS: Firstly, candidate probiotic strain PGM541 was identified from a porcine-derived Bacillus library by assessing organoid viability. Subsequently, to validate the organoid screening reliability, the potential mechanism of strain PGM541 on the intestinal epithelium was investigated; it was found to exhibit probiotic functions by regulating cell proliferation in both in vitro organoid and in vivo piglet models. Furthermore, organoid screening combined with metabolomic analysis identified butyric acid (BA) as the key bioactive metabolite responsible for driving epithelial proliferation. Whole-genome and transcriptomic analyses revealed the biosynthetic pathway of BA in strain PGM541. Importantly, BA receptor blockade experiments directly confirmed that BA enhances epithelial proliferation via interaction with the FFAR2 receptor, thereby validating its functional activity. Additionally, strain PGM541 exhibited protective effects against dextran sulfate sodium (DSS)-induced colitis, further validating the effectiveness of the intestinal organoid platform for probiotic screening. CONCLUSIONS: The probiotic strain PGM541, which was screened using intestinal organoids, promotes intestinal epithelial cell proliferation via its metabolite BA activating the FFAR2 receptor. These findings demonstrate that the intestinal organoid model serves as an effective platform for both preliminary probiotic screening and mechanistic investigation. Video Abstract.

Animals↗

PubMed2026

PDE4DIP-Derived MMG8 Supports Proliferation, Migration, and Tumor Growth in Hepatocellular Carcinoma Models.

BACKGROUND: PDE4DIP encodes a scaffold protein that has been implicated in compartmentalized signaling and cytoskeletal organization, but the role of its myomegalin variant 8 (MMG8) isoform in hepatocellular carcinoma (HCC) remains unclear. To address this gap, we examined PDE4DIP expression in public HCC datasets and investigated the functional role of MMG8 in HCC models. METHODS: PDE4DIP expression was analyzed in The Cancer Genome Atlas Liver Hepatocellular Carcinoma (TCGA-LIHC) cohort and two Gene Expression Omnibus (GEO) cohorts (GSE14520, GSE36376). MMG8 function was assessed in Huh7 cells using siRNA-mediated knockdown and in Hepa1-6 cells using lentiviral Clustered Regularly Interspaced Short Palindromic Repeats - CRISPR-associated protein 9 (CRISPR-Cas9)-mediated knockout. Cell proliferation in MMG8-KD Huh7 cells and MMG8-KO Hepa1-6 cells was assessed using Cell Counting Kit-8 (CCK-8) assays, while Huh7 cell migration was evaluated using Transwell assays. Tumor growth was assessed using a murine subcutaneous tumor model. Immunohistochemical staining for Ki67 and cleaved caspase-3 was employed to assess tumor cell proliferation and apoptosis-associated changes, respectively. Gene set enrichment analysis was performed in TCGA-LIHC tumors stratified based on PDE4DIP expression. RESULTS: PDE4DIP expression differed between tumor and non-tumor tissues across HCC cohorts, although the directionality of this difference was not uniform. MMG8 knockdown in Huh7 cells reduced proliferation and migratory activity. A single-cell-derived MMG8-KO Hepa1-6 clone exhibited reduced proliferation in vitro and formed smaller tumors in vivo, with lower Ki67 positivity but no significant difference in cleaved caspase-3 positivity between groups. In tumors from the TCGA-LIHC cohort, PDE4DIP expression was associated with distinct transcriptional programs. Specifically, PDE4DIP-high tumors presented with positive normalized enrichment score (NES) values for several metabolic pathways, whereas adhesion/extracellular matrix (ECM), cell cycle/proliferation, and translation/ribosome-related pathways exhibited negative NES values. CONCLUSIONS: These findings support a functional contribution of MMG8 to proliferative, migratory, and tumor-growth phenotypes in the tested HCC models. Bulk gene-level PDE4DIP expression in human tumors was associated with context-dependent transcriptional states and should not be interpreted as a direct surrogate for MMG8 function.

Liver Neoplasms↗

PubMed2026

PDZ-binding kinase promotes ovarian cancer cell proliferation and invasion via CCNB1 regulation.

BACKGROUND: Ovarian cancer is one of the most lethal gynecological malignancies, characterized by late diagnosis, frequent recurrence, and high mortality. PDZ-binding kinase (PBK), a serine/threonine kinase of the mitogen-activated protein kinase kinase (MAPKK) family, has been implicated in the tumorigenesis of multiple cancers, yet its role in ovarian cancer remains incompletely characterized. This study aimed to investigate the effect of PBK on the proliferation and invasion of ovarian cancer cells. METHODS: The expression of PBK and cyclin B1 (CCNB1) in normal ovarian tissues and ovarian cancer tissues was analyzed using online databases including Gene Expression Profiling Interactive Analysis 2 (GEPIA2), Clinical Proteomic Tumor Analysis Consortium (CPTAC), and Kaplan-Meier Plotter. Clinical tissue specimens were collected to detect the expression of PBK and CCNB1 by immunohistochemistry. Quantitative real-time polymerase chain reaction (PCR) was performed to detect PBK messenger RNA (mRNA) expression levels in clinical specimens and cell lines. Western blot was used to detect PBK protein expression in ovarian cancer cell lines. ES2 and A2780 cells with higher PBK expression were selected to construct PBK knockdown cell lines using lentiviral interference vectors. Cell Counting Kit-8 (CCK-8) assay, colony formation assay, and 5-ethynyl-2'-deoxyuridine (EdU) assay were performed to explore the effect of PBK knockdown on cell proliferation. Transwell assay was used to investigate the effect on cell invasion. The Cancer Genome Atlas (TCGA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were utilized to analyze PBK-related pathways and predict CCNB1 as the gene most closely related to PBK. RESULTS: PBK was significantly overexpressed in ovarian cancer tissues and cell lines compared with normal controls, and high PBK expression was associated with poor overall survival (OS) and progression-free survival (PFS). Knockdown of PBK expression inhibited the proliferation, colony formation, and invasion of ovarian cancer cells. Bioinformatics analysis revealed that CCNB1 was significantly overexpressed in ovarian cancer and high CCNB1 expression was associated with poor OS. CCNB1 was also significantly highly expressed in ovarian cancer tissues as validated by immunohistochemistry and was associated with lymph node metastasis. PBK and CCNB1 expression showed a significant positive correlation in TCGA ovarian cancer datasets. Knockdown of PBK inhibited CCNB1 expression in ovarian cancer cells. CONCLUSIONS: PBK promotes ovarian cancer cell proliferation and invasion. PBK knockdown leads to CCNB1 downregulation. These findings suggest that CCNB1 contributes to PBK-mediated oncogenic effects and identify the PBK-CCNB1 axis as a potential therapeutic target for ovarian cancer treatment.

PDZ-binding kinase (PBK)↗

PubMed1976

Proliferation of blood vessels and stroma in brain tumours. An enzyme-histochemical study.

Proliferation of the vascular endothelium occurring in brain tumours is accompanied by a proliferation of histiocytes in the peripheral part of the vessel wall. These histiocytes infiltrate the tumour tissue in a very regular pattern. Enzyme-histochemically, there are marked differences between the activities of alkaline phosphatase, 5-nucleotidase, and ATPase in the normal and proliferating blood vessels. The whole process encompasses reactive changes evoked by the destroyed perivascular sheath of astroglial foot processes and the subsequent oedema in the tumour and the surrounding parenchyma. There are often tumour areas where diminished vascular permeability is established by proliferation of perivascular connective tissue. Here the oedema has completely disappeared. A clearcut influx of monocytes from the blood into the vessel wall is seen only in the vicinity of necrotic foci; the number of histiocytes is increased and their turnover is observed in swollen macrophages. In the rest of the tumour influx of monocytes and activity of macrophages are inconspicious.

Adenosine Triphosphatases↗

PubMed1977

Autoradiographic demonstration of proliferating cells in cerebrospinal fluid.

The proliferative activity of cells, isolated from 82 human CSF specimens, was examined by 3H-thymidine autoradiography. High labelling indices (LI) were found in acute viral meningitis (up to 8 per cent) and radiculitis (up to 6 per cent). CSF cell proliferation was also shown in the subacute stages of viral diseases and in other inflammatory processes (LI ranging from 0.5 per cent to 3 per cent). Most of the cells labelled from these CSF specimens were large lymphocytes, "lymphoid cells" and plasmacytes. Their presence in CSF is presumed to indicate an immune reaction. By the demonstration of a proliferative activity of these cells, aseptic inflammatory processes can be differentiated from "unspecific" pleocytosis. Because of a correlation between the LI of CSF cells and the stages of some inflammations, this method is suggested for an assessment of pregression or remission of chronic processes, e.g. "chronic meningitis" and multiple sclerosis. It can also be used in experimental research: the same type of mononuclear cells was labelled after having been cultured for 23 hours prior to the incubation with 3H-thymidine. Proliferating tumor cells as well as proliferating non-neoplastic mononuclear cells were demonstrated in CSF from various neoplastic diseases. In the clinical diagnosis of these processes, the method is of limited value. It proved very useful, however, for an assessment of the therapeutic effects of intrathecal cytostatic therapy. CSF specimens from non-inflammatory and non-neoplastic diseases regularly contained very few proliferating cells (LI: less than 0.1).

Autoradiography↗

PubMed1978

Reversal by aminoguanidine of the inhibition of proliferation of human fibroblasts by spermidine and spermine.

The inhibitory effect of the polyamines, spermidine and spermine, on the proliferation of human fibroblasts in culture was found to be reversed by the addition of aminoguanidine (AM), a specific and highly effective inhibitor of diamine oxidase (DAO) present in fetal calf serum (FCS). Aminoguanidine itself in concentration as high as 10(-3) M exhibited no effect upon cell proliferation nor did putrescine at similar concentrations. However, at higher concentrations of putrescine, cell proliferation was inhibited and this inhibition was unaffected by the addition of mM concentrations of AM. These studies support earlier hypotheses on the mechanisms of the toxic effects of polyamines on cell proliferation and establish further that the diamine oxidase-catalyzed metabolism of spermine and spermidine is necessary for their toxic effects in cell culture.

Amine Oxidase (Copper-Containing)↗

PubMed1979

A simple reliable system for studying antigen-specific murine T cell proliferation.

Antigen-specific T cell proliferation can be readily elicited from the popliteal lymph node cells of mice which have received immunizations of antigen in the hind footpads. The advantages of our system over other published methods are (i) simplicity in method and materials, (ii) much improved reproducibility, (iii) negligible concomitant B cell proliferation, (iv) large degrees of antigen specific proliferation with very low background, and (v) complete dependence of the response on accessory cells or macrophages. These results were brought about by proper immunization procedures for mice and judicious choice of culture conditions. Our data show that the system is very suitable for the study of macrophage-T cell interaction in the induction of T cell proliferation as well as the genetic basis of responsiveness or non-responsiveness to protein and polypeptide antigens.

Animals↗

PubMed1978

Cyclic AMP in relation to proliferation of the epidermal cell: a new view.

Four agents known to increase the level of cellular cAMP by different means (cholera toxin, dibutyryl cAMP, methyl isobutyl xanthine and isoproterenol) increase the growth of colonies of cultured human epidermal cells and of keratinocytes derived from other stratified squamous epithelia. This effect is due to an increase in the overall rate of cell proliferation in the colonies. When added to cultures under hitherto optimum conditions for epidermal cell growth [in the presence of supporting 3T3 cells and epidermal growth factor (EGF)], most of the agents exert an effect of considerable magnitude, the toxin being the most potent. Since the toxin exerts an effect in the absence of supporting 3T3 cells, it must be able to act directly on the keratinocytes. It can also act in the absence of ECF and of medium conditioned by 3T3 cells, although proliferation is greatest when supporting 3T3 cells and EGF are present. The increased proliferation in the presence of the toxin is associated with an increased proportion of small cells known to include the multiplying fraction. The use of toxin makes the cultivation of keratinocytes from epidermis and other stratified squamous epithelia much easier and prolong the culture life of the cells. Whether cell proliferation in the intact epidermis is regulated through agents affecting cAMP (in a direction opposite to that suggested by much of the earlier literature) remains to be elucidated, but the existence of such a mechanism in cultured cells suggests that it may function in the intact epithelium.

1-Methyl-3-isobutylxanthine↗

PubMed1977

Regulation of B-lymphocyte clonal proliferation by stimulatory and inhibitory macrophage-derived factors.

A functional subpopulation of murine B lymphocytes proliferate in semisolid agar culture in the presence of 2-mercaptoethanol to form colonies. The effects of diffusible macrophage-derived factors on this focal proliferation was investigated using a two-layer culture system which prevented macrophage-lymphocyte contact and permitted B-cell activation to be critically assessed under conditions of extremely low cell densities. Adherent peritoneal macrophages incorporated within underlayers of spleen or lymph node cell cultures potentiated both the number and size of developing B-cell colonies. These effects were most striking when low numbers of spleen or lymph node cells, or macrophage- depleted lymphoid cell suspensions were used. Thus, macrophage-depleted lymph node ceils gave rise to virtually no colonies, but colony-forming ability was restored by the presence of an optimal number of macrophages. When the number of macrophages exceeded that required for optimal stimulation, colony formation was suppressed; an effect which was largely prevented by indomethacin, an inhibitor of prostaglandin synthesis. Under these conditions, stimulation and inhibition of B-cell activation by macrophages could be dissociated, indicating that each signal is selectively controlled by individual molecules elaborated by the macrophage. With an appropriate number of macrophages required for B-cell activation, and sufficient indomethacin to inhibit the accumulation of macrophage-derived prostaglandin, B-lymphocyte clonal proliferation was a linear function of the number of B cells placed in culture. In the absence of macrophages, B-cell colony formation was potentiated by both lipopolysaccharide and intact sheep erythrocytes through a mechanism different from that of the macrophage-derived stimulatory factor. In addition to their direct stimulatory effect on B-cell proliferation, lipopolysaccharide and sheep erythrocytes were each capable of modulating the production and/or release of B-cell stimulatory and inhibitory factors by the macrophage. Parallel studies of conventional mitogen- stimulated lymphocyte cultures did not show a requirement for macrophages and confirm that the semisolid assay is uniquely suited to studies on the regulatory role of the macrophage in B-cell activation.

Animals↗

PubMed1975

Connective tissue cells, cell proliferation and synthesis of extracellular matrix-a review.

The ubiquitous connective tissues contain a wide range of cells including fibroblasts, osteoblasts and chondroblasts. Recently it has been demonstrated that another principal cell of the connective tissue is the smooth muscle cell in several organ systems. These have been shown to be responsible for the synthesis of the connective tissue matrix components of the uterine myometrium and of the arterial system, including collagen, both elastic fibre proteins and glycosaminoglycan. Microtubule inhibitors such as colchicine and vinblastine, and iron chelators such as alpha,alpha -dipyridyl have been used to study their morphologic and chemical effects on collagen synthesis and secretion. Colchicine produces an increase in large Golgi-associated vacuoles, which sometimes contain material reminiscent of aggregates of collagen macromolecules. Vinblastine produces alterations in the endoplasmic reticulum cisternae similar to alterations seen in ascorbic acid deficiency, and alpha,alpha-dipyridyl increases the frequency of regions in cells, interpretable as potential sites of communication of rough endoplasmic reticulum cisternae with the cell surface. Ferritin conjugated anti-procallagen sera were used to localize procollagen in cells and demonstrated procollagen not only in the cisternae of rough endoplasmic reticulum but in all of the elements of the Golgi complex as well. The studies reported in this review have shown that in cell culture arterial smooth muscle will produce not only the microfibrillar protein of the elastic fibre but soluble and/or insoluble elastin as well. Recent studies on serum factors responsible for the proliferation of connective tissue cells have demonstrated that at least one of the principal factors responsible for fibroblast and/or smooth muscle cell proliferation in culture is derived from thrombocytes. Medium containing serum derived from cell-free plasma lacks most of this proliferative effect which can be reinstated when platelets are present during recalcification to form serum. This effect is due to the platelet release reaction as shown by combining supernatant factors derived from platelets exposed to purified thrombin to cell-free, plasma derived serum. Studies with macrophages have also suggested that phagocytic macrophages release factor(s) into a cell culture medium that may also participate in stimulating fibroblasts to proliferate in vitro. The means by which these factors stimulate fibroblast proliferation and connective tissue synthesis remains to be elucidated.

Animals↗

PubMed1979

Proliferating ovarian "epithelial" tumours: a clinico-pathological analysis of 144 cases.

In a 25-year period, 144 patients with proliferating epithelial ovarian tumours were treated at the King George V Memorial Hospital. These tumours were classified according to the World Health Organisation (WHO) Histological Classification of Ovarian Tumours and subsequently divided into 4 grades of proliferation, again on histological criteria. The tumours were staged at laparotomy in accord with the recommendations of the International Federation of Gynecology and Obstetrics (FIGO). Follow-up data, analysed by a life-table method, were correlated against histological type of tumour, histological grade of proliferation, clinical/laparotomy stage, and mode of surgical therapy. Stage 1 proliferating tumours may be treated by surgery alone, including unilateral salpingo-oophorectomy in selected cases. Stage 2 and Stage 3 tumours should be treated similarly to invasive ovarian carcinomas of the same stage, despite their overall favourable prognosis.

Castration↗

PubMed1975

[Pathogenesis of aleutian mink disease. VII. Chronic hepatitis with bile duct proliferation].

Aleutian disease is a chronic persistent viral infection of mink characterized by hypergammaglobulinema, generalized plasmacytosis, sclerosing glomerulonephritis, polyarteritis, and plasma cell hepatitis with bile duct proliferation. The development of hepatic lesions was studied both light- and electron-microscopically in mink experimentally infected with Aleutian disease virus. Fifteen normal and 99 mink experimentally infected with Aleutian disease virus were used. Experimental mink were killed in intervals from 3 weeks to 23 months after infection, and liver sections were processed for both light- and electron-microscopic studies. Experimentally infected mink developed portal and intralobular lymphocytic and plasmacytic infiltrates in the liver 3 weeks after infection. Four to five weeks after infection there was evidence of early bile duct proliferation that began as an outgrowth of the portal bile ducts. Three to five months after infection a marked bile duct proliferation was present in some of the portal triads and adjacent liver lobules; but there was no tendency of these lesions to progress into biliary cirrhosis. Ultrastructural characteristics of proliferating bile duct cells were marked deformation, formation of multiple cell layers, reduction in the number of microvilli and desmosomes, and infiltration of the epithelial cells by lymphoid cells and plasmacytes. The hepatic lesions either develop by direct virus stimulation or by the deposition of virus-antibody complexes.

Aleutian Mink Disease↗

PubMed2025

Baculovirus enhances arginine uptake and induces mitochondrial autophagy to promote viral proliferation.

As obligatory intracellular parasites, viruses must rely on metabolic reprogramming of host cells to meet their replication needs. Baculovirus is an important biopesticide and a vector for the preparation of biological products. In addition, one of its representative species, Bombyx mori nucleopolyhedrovirus (BmNPV-Baculoviridae), also causes huge losses to the insect industry. In our previous study, amino acid metabolism has been found to play a crucial role in the BmNPV infection process. However, the mechanisms by which BmNPV reprograms host amino acid metabolism remains unclear. In fact, current insights in the importance of amino acid metabolism are limited to the impact of glutamine on viral infection. Therefore, unraveling the mechanism of amino acid metabolism reprogramming induced by baculovirus would advance this field of research to a great extent. In this study, targeted metabolomics revealed that the preferred amino acids of BmNPV budded virus (BV) include arginine, lysine, proline, isoleucine, histidine and others. In addition, most of the viral amino acids were found to be increased in the hemolymph of BmNPV infected silkworms at the later stage of infection, especially arginine, valine, phenylalanine and others. Furthermore, the importance of arginine for BmNPV proliferation was validated. Next, we confirmed that the expression of the arginine transporter Slc7a6 was strongly induced by BmNPV infection and that Slc7a6 could promote arginine uptake to support BmNPV proliferation in host cells. Moreover, using Slc7a6 knockout cells which eliminate extracellular arginine uptake, we confirmed that BmNPV could induce mitochondrial autophagy, thereby supplementing intracellular arginine and providing necessary amino acids for BmNPV proliferation. Overall, these findings support a model in which baculovirus (BmNPV) enhances the uptake of exogenous amino acids by inducing the expression of amino acid transporters and activating autophagy of organelles to maintain intracellular amino acid levels, thereby facilitating virus proliferation.

Animals↗

PubMed1975

An ultrastructural-cytochemical study on the proliferation of smooth endoplasmic reticulum induced by chlorobiphenyls (PCB) in the guinea pig liver cells.

The ultrastructural changes in the liver cells of guinea pigs induced by the oral administration of PCB were studied by electron microscopy; also electron-microscopic cytochemistry for glucose-6-phosphatase (G-6-Pase) activity was applied. Proliferation of smooth endoplasmic reticulum (sER) was the most prominent change observed in the liver cells, which remained as long as 90 days after the final administration. G-6-Pase activity was ultracytochemically demonstrated not only in the rough and smooth endoplasmic reticulum and the nuclear envelope in the liver cells of normal controls, but also in the proliferated sER in the liver cells of PCB-treated animals. The present investigation revealed that PCB stored in the animal body induced the proliferation of sER in the liver cells for a long time after the cessation of the treatment, and that sER in the liver cells, normally existing or proliferated, always showed positive activity of G-6-Pase.

Animals↗

PubMed1976

Circulating factors controlling cell proliferation.

Dipolid human fibroblast-rich tissues contain a macromolecule with a molecular weight between 30,000 and 50,000 daltons which will inhibit the proliferation of fibroblasts in the G1 phase of the cell cycle (i.e., inhibit both 3H-thymidine uptake as well as the normal increase in cell number). The inhibitor is destroyed by trypsin but not by ribonuclease or deoxyribonuclease, and it is thermolabile. It has an acid IEP. It is not cytotoxic, and its inhibitory activity appears to be completely reversible. This fibroblast endogenous inhibitor does not interfere with the proliferation of DNA synthesis by human lymphocytes, bronchial carcinoma cells, or HeLa cells. The activity does not appear to be species specific. Therefore, we suggest that it is quite possible that the control of fibroblast proliferation resides in a fibroblast chalone. Diploid human fibroblasts, in contrast to chicken or mouse fibroblasts or heteroploid fibroblasts in general, stringently require serum for their proliferation. All of this mitogenic activity of calf serum can be concentrated in a molecular weight range around 100,000 daltons by ultrafiltration. All of the mitogenic activity within this molecular weight class can be concentrated at a pH of 5.2 via isoelectric focusing, and all of the activity at this isoelectric point can be concentrated in one peak on preparative polyacrylamide gel electrophoresis. This latter material is homogeneous at three different pH's in analytical gel electrophoresis as well as in SDS electrophoresis. This purified serum mitogen for diploid human fibroblasts in vitro also works in vivo and represents as much as 0.5% of calf serum protein, albeit there is much less of this protein in adult cow or horse. It is composed of two equal subunits weighing about 60,000 daltons each and contains about 2 moles of sialic acid, one S-S bond, and 6 moles of hexose per subunit. There is a reciprocal relationship between the biological activity of fibroblast inhibitor and serum mitogen, but there is no apparent direct interaction between these two proteins. Addition of pure serum mitogen to diploid human fibroblasts in vitro results in the release of commensurable chalone activity into the medium and a reciprocal loss of mitogen from the medium. Therefore, we propose that serum contains a single macromolecule which competes with endogenous chalone on the surface of diploid human fibroblasts and that this functions as an anti-chalone for the fibroblast.

Cells, Cultured↗

PubMed1977

Chalone-like inhibition of Ehrlich ascites cell proliferation in vitro by an ultrafiltrate obtained from the ascitic fluid.

An aqueous ultrafiltrate (10 000-50 000 dalton) prepared from the cell-free ascitic fluid of mice bearing Ehrlich ascites tumour (EAT) in the plateau phase of growth (12-16 days after transplantation) was investigated with regard to its inhibitory effects on the proliferation of EAT cells in a 24-hr suspension culture. The following results were obtained: (1) The in vitro proliferation of cells obtained from the plateau phase of in vivo growth was reversibly inhibited. (2) The dose-response curves show a plateau with a maximum inhibition of about 50%, which suggests that not all cells can be affected. (3) Young cells (4-6 days after transplantation) were not inhibited. (4) Preincubation of plateau phase cells in the culture medium before treatment abolishes the inhibitory effect of the ultrafiltrate. This effect of preincubation is dependent on time and serum concentration. It provides the possibility to differentiate between true "chalone-like" and cytotoxic effects. (5) the inhibitory properties of the ultrafiltrate are destroyed by heating or trypsin treatment. (6) Extracts prepared in the same way from ascitic fluid of mice bearing lymphocytic leukemia L1210 do not inhibit the proliferation of EAT cells. Corresponding extracts from ascitic fluid of mice bearing myelocytic leukemia YM were found to be inhibitory; however, the inhibitory effect was also found on preincubated cells and is therefore considered to be due to an unspecific cytotoxicity. In conclusion, evidence was obtained for a factor from the ascitic fluid of mice bearing EAT, which prevents EAT cells from entering the proliferating state.

Animals↗

PubMed1978

Calcium requirements for the proliferation of cells infected with a temperature-sensitive mutant of Rous sarcoma virus.

Between 32 degrees and 39 degrees, uninfected normal rat kidney (NRK) cells proliferated minimally, or not at all, in medium containing 0 to 0.01 mM extracellular free calcium. Transformation of NRK cells by wild-type avian sarcoma virus B77 enabled them to proliferate equally rapidly at all temperatures in high (1.25 mM)- or low (0.001 mM-calcium medium. Transformation by the temperature-sensitive LA-23 mutant of Rous sarcoma virus also enabled NRK cells to proliferate in low (0.001 mM)-calcium medium at 32 degrees or 37 degrees. However, the LA-23 NRK cells could not proliferate in low (0.001 mM)-calcium medium at a nonpermissive temperature such as 39 degrees, which prevents expression of other aspects of the transformed phenotype.

Avian Sarcoma Viruses↗