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At least 127 records · Page 7Linked to original sources
PubMed1976

Isolation of cells that retain differentiated functions in vitro: properties of clonally isolated type II alveolar pneymonocytes.

We have isolated byclonal culture techniques a diploid cell strain (L-2) from adult rat lung. These cells appear to retain differentiated functions that are present in type II alveolar epithelial cells of intact lung. The L-2 cells are diploid, epithelial cells, they contain osmiophilic lamellar bodies in their cytoplasm and they synthesize lecithin by the same de novo pathways as whole lung.

Animals↗
PubMed1992

Partial hydatidiform moles have impaired differentiated function (human chorionic gonadotropin and human placental lactogen secretion) in response to epidermal growth factor and 8-bromo-cyclic adenosine monophosphate.

OBJECTIVE: The null hypothesis is that partial hydatidiform moles have normal differentiated function (human chorionic gonadotropin and human placental lactogen secretion) in response to epidermal growth factor and 8-bromo-cyclic adenosine monophosphate. STUDY DESIGN: Two complete moles, 10 partial hydatidiform moles, and 19 normal first-trimester placentas in monolayer culture were exposed to 10 ng/ml epidermal growth factor, 1 mmol/L 8-bromo-cyclic adenosine monophosphate plus 1 mmol/L theophylline, or control. Human chorionic gonadotropin and human placental lactogen secretion was measured. Frequency of response to stimuli was compared by chi 2 analysis, and hormone secretion was compared by analysis of variance. RESULTS: Partial moles demonstrated reduced frequencies of response of human chorionic gonadotropin and human placental lactogen to epidermal growth factor (partial moles 2/8 and 2/8, respectively; normal placentas 16/19 and 7/18, respectively; p less than 0.025) and of human chorionic gonadotropin to 8-bromo-cyclic adenosine monophosphate (partial moles 3/5, normal placentas 13/16; p less than 0.005). CONCLUSION: Partial hydatidiform moles demonstrate impaired human chorionic gonadotropin and human placental lactogen secretory responsiveness to epidermal growth factor and cyclic nucleotides in comparison with normal first-trimester trophoblast.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

Replication initiator protein RepE of mini-F plasmid: functional differentiation between monomers (initiator) and dimers (autogenous repressor).

Replication of mini-F plasmid requires the plasmid-encoded RepE initiator protein and several host factors including DnaJ, DnaK, and GrpE, heat shock proteins of Escherichia coli. The RepE protein plays a crucial role in replication and exhibits two major functions: initiation of replication from the origin, ori2, and autogenous repression of repE transcription. One of the mini-F plasmid mutants that can replicate in the dnaJ-defective host produces an altered RepE (RepE54) with a markedly enhanced initiator activity but little or no repressor activity. RepE54 has been purified from cell extracts primarily in monomeric form, unlike the wild-type RepE that is recovered in dimeric form. Gel-retardation assays revealed that RepE54 monomers bind to ori2 (direct repeats) with a very high efficiency but hardly bind to the repE operator (inverted repeat), in accordance with the properties of RepE54 in vivo. Furthermore, the treatment of wild-type RepE dimers with protein denaturants enhanced their binding to ori2 but reduced binding to the operator: RepE dimers were partially converted to monomers, and the ori2 binding activity was uniquely associated with monomers. These results strongly suggest that RepE monomers represent an active form by binding to ori2 to initiate replication, whereas dimers act as an autogenous repressor by binding to the operator. We propose that RepE is structurally and functionally differentiated and that monomerization of RepE dimers, presumably mediated by heat shock protein(s), activates the initiator function and participates in regulation of mini-F DNA replication.

DNA Replication↗
PubMed1990

Primary culture of normal rat mammary epithelial cells within a basement membrane matrix. II. Functional differentiation under serum-free conditions.

A serum-free primary culture system is described which allows normal rat mammary epithelial cells (RMECs) embedded within a reconstituted basement membrane to undergo extensive growth and functional differentiation as detected by synthesis and secretion of the milk products casein and lipid. RMECs isolated from mammary glands of immature virgin rats were seeded within an extracellular matrix preparation derived from the Engelbreth-Holm-Swarm sarcoma and cultured in a serum-free medium consisting of Dulbecco's modified Eagle's medium-F12 containing insulin, prolactin, progesterone, hydrocortisone, epidermal growth factor, bovine serum albumin, transferrin, and ascorbic acid. Casein synthesis and secretion were documented at the electron microscopic level as well as by an enzyme-linked immunosorbent assay (ELISA) assay using a polyclonal antibody against total rat caseins. Numerous secretory vesicles with casein micelles were noted near the apical surface of the RMECs, and secreted casein was observed in the lumen. These ultrastructural data were confirmed by the ELISA assay which showed that microgram amounts of casein per well were synthesized by the RMECs and that the amount of casein increased with time in culture. Using immunoblot analysis it was demonstrated that the full complement of casein proteins was synthesized. In addition to casein protein, beta-casein mRNA levels were shown to increase with time. Synthesized lipid was detected at both the light and electron microscopic levels. Phase contrast photomicrographs demonstrated extensive intracellular lipid accumulation within the ductal and lobuloalveolarlike colonies, and at the electron micrograph level, lipid droplets were predominantly localized near the apical surface of the RMECs. The lipid nature of these droplets was verified by oil red O staining. Results from this study demonstrate that RMECs from immature virgin rats proliferate extensively and rapidly develop the capacity to synthesize and secrete casein and lipid when grown within a reconstituted basement membrane under defined serum-free conditions. This unique system should thus serve as an excellent model in which the regulation of mammary development and gene expression can be investigated.

Animals↗
PubMed1998

Functional differentiation of multiple dopamine D1-like receptors by NNC 01-0012.

Although members of the multiple vertebrate/mammalian dopamine D1 receptor gene family can be selectively classified on the basis of their molecular/phylogenetic, structural, and tissue distribution profiles, no subtype-specific discriminating agents have yet been identified that can functionally differentiate these receptors. To define distinct pharmacological/functional attributes of multiple D1-like receptors, we analyzed the ligand binding profiles, affinity, and functional activity of 12 novel NNC compounds at mammalian/vertebrate D1/D1A and D5/D1B, as well as vertebrate D1C/D1D, dopamine receptors transiently expressed in COS-7 cells. Of all the compounds tested, only NNC 01-0012 displayed preferential selectivity for vertebrate D1C receptors, inhibiting [3H]SCH-23390 binding with an estimated affinity (approximately 0.6 nM) 20-fold higher than either mammalian/vertebrate D1/D1A or D5/D1B receptors or the D1D receptor. Functionally, NNC 01-0012 is a potent antagonist at D1C receptors, inhibiting to basal levels dopamine (10 microM)-stimulated adenylyl cyclase activity. In contrast, NNC 01-0012 (10 microM) exhibits weak antagonist activity at D1A receptors, inhibiting only 60% of maximal cyclic AMP production by dopamine, while acting as a partial agonist at vertebrate D1B and D1D receptors, stimulating adenylyl cyclase activity by approximately 33% relative to the full agonist dopamine (10 microM), an effect that was blocked by the selective D1 receptor antagonist NNC 22-0010. These data clearly suggest that the benzazepine NNC 01-0012, despite lacking the N-methyl residue in the R3 position, is a selective and potent D1C receptor antagonist. Moreover, the differential signal transduction properties exhibited by NNC 01-0012 at these receptor subtypes provide further evidence, at least in vertebrates, for the classification of the D1C receptor as a distinct D1 receptor subtype.

Animals↗
PubMed1998

Stimulative effect of high-level hypergravity on differentiated functions of osteoblast-like cells.

The exposure of freshly isolated osteoblasts and osteoblast-like cells to high-level hypergravity caused the inhibition of cell growth, elevation of cAMP content, and the stimulation of differentiated functions such as alkaline phosphatase activity, collagen synthesis, and osteocalcin synthesis. Blockage of elevation of cAMP by SQ22536, an inhibitor of adenylate cyclase, resulted in the inhibition of the hypergravity-stimulated alkaline phosphatase activity, indicating that cAMP is the intracellular mediator of this action of hypergravity. H89, an inhibitor of cAMP-dependent protein kinase (PKA), further inhibited the cell growth that was already inhibited by the hypergravity, and further stimulated the alkaline phosphatase activity that was already stimulated by hypergravity. If cAMP acts through the PKA system, H89 should have blocked the changes in cell function effected by the exposure to hypergravity. Therefore the elevated intracellular cAMP by the exposure of hypergravity caused the changes in cell function by a PKA-independent pathway.

Adenine↗
PubMed1992

The CD27- subset of peripheral blood memory CD4+ lymphocytes contains functionally differentiated T lymphocytes that develop by persistent antigenic stimulation in vivo.

On the basis of expression of the T cell differentiation antigen CD27, human peripheral blood CD4+ memory cells can be divided into two subsets, a large CD45RA-CD27+ (82%) and a small CD45RA-CD27- (18%) population. Analysis of the functional properties of these memory T cell subsets showed that proliferative responses to the recall antigen tetanus toxoid (TT), shortly after booster immunization, were mainly confined to the CD27- population. Also, in atopic individuals, proliferative responses to allergens for which these individuals are sensitized, were limited to the CD45RA-CD27- population. After stimulation with CD3 monoclonal antibody and phorbol ester, CD27+ cells produced vast amounts of interleukin (IL)-2 but minimal amounts of IL-4, whereas in marked contrast, CD27- T cells secreted low levels of IL-2 and high levels of IL-4. The capacity of the vast majority of these latter cells to produce IL-4 was found to be a stable feature since high IL-4 secreting T cell clones were generated from the CD27- subset. These findings suggest that upon renewed as well as chronic antigenic stimulation in vivo, memory T cells acquire the CD45RA-CD27- phenotype and that, as a consequence, in this subset functionally differentiated CD4+ T cells are compartmentalized. Our results predict that analysis of the small CD27- subset of memory cells, that makes up approximately 10% of the peripheral blood T cell population, will provide information on the specificity and function of responding CD4+ T cells at a given point in time in healthy and diseased individuals.

Antigens↗
PubMed1987

Placental lactogen production and functional differentiation of rat trophoblast cells in vitro.

Cells from the labyrinth region of the developing rat chorioallantoic placenta were able to differentiate in vitro into cells capable of producing placental lactogen. Progesterone selectively inhibited placental lactogen production by labyrinth cell cultures undergoing differentiation but had no apparent effect on lactogen production by mature trophoblast giant cells. The measurement of placental lactogen production is a useful method for monitoring the functional differentiation of rat trophoblast cells in vitro.

Animals↗
PubMed2003

Regional and developmental regulation of syntaphilin expression in the brain: a candidate molecular element of synaptic functional differentiation.

The conserved nature of the basic machinery underlying synaptic function makes it necessary to search for other factors--structural and molecular--that could account for the tremendous diversity found among synapses even within a single neuron. Syntaphilin is a presynaptic membrane protein previously described as a molecular clamp that controls free syntaxin-1A and dynamin-1 availability, and thereby regulates synaptic vesicle exocytosis and endocytosis at the nerve terminal. In this study, we report our finding that syntaphilin expression is developmentally regulated, and show that syntaphilin is expressed most prominently in the mature rat brain, in areas that have been previously characterized to undergo synaptic plastic change. We also find that syntaphilin undergoes divergent subcellular targeting to the mitochondrial outer membrane and the synaptic plasma membrane, giving rise to two neuronal subpopulations of the protein that are modified in their relative enrichment with synaptic maturation and with the formation of cell contacts. Finally, we demonstrate that syntaphilin expression is initiated with induction of neuronal differentiation in PC12 cells. Given its biochemical and functional properties, the spatially and temporally limited nature of syntaphilin expression provides evidence that syntaphilin could be a molecular element of synaptic functional differentiation.

Animals↗
PubMed1997

Functional differentiation of T cells in the intestine of T cell receptor transgenic mice.

The intestinal lamina propria (LP) is a major effector site of the mucosal immune system where antigen-specific and antigen-nonspecific factors shape the functional responses of CD4+ T helper cells. To study the functional differentiation of LP T helper cells we utilized DO11.10 T cell receptor (TCR) transgenic (Tg) mice that expressed a clonotypic TCR specific for a class II major histocompatibility complex-restricted peptide of chicken ovalbumin. The majority of cells expressing Tg TCR (Tg+) in peripheral lymphoid tissue expressed naive surface phenotypes whereas nearly all Tg+ T cells in the intestinal LP expressed an activated/ memory-like phenotype. Flow cytometric analysis of Tg+ T cell populations revealed that a small proportion of cells in peripheral lymphoid tissue but nearly all cells in the LP expressed dual (Tg plus non-Tg) TCRs. In Tg x recombinase-activating-gene-1-deficient (Tg x RAG-1(-/-)) mice, splenic and LP T cells expressed naive surface phenotypes and produced cytokines equivalent to naive splenic cells from Tg x RAG-1(+/+) mice. In contrast, Tg LP cells from Tg x RAG-1(+/+) mice produced 35-fold greater levels of interferon-gamma and 5-fold greater levels of interleukin 4 compared with naive splenic cells. These findings suggested that activation of Tg+ T cells through endogenous non-Tg TCR had promoted the localization and differentiation of memory-like effector T helper cells in the intestine.

Animals↗
PubMed1999

Transforming growth factor beta1 helps maintain differentiated functions in mitogen-treated primary rat hepatocyte cultures.

Mechanisms that control function and repair of the injured liver remain unclear. We hypothesized that after liver injury, elevated blood TGF-beta1 levels may reflect an adaptive response to help maintain differentiated functions in surviving hepatocytes affected by excessive amounts of HGF. We thus studied the effect of HGF, EGF, TGF-beta1, HGF + TGF-beta1, or EGF + TGF-beta1 on the expression of liver-enriched transcription factors and genes which remain under their regulatory activity. The peak [3H]thymidine uptake induced by 20 ng/ml of either HGF or EGF was seen after 72 h; however, DNA binding of C/EBP and HNF1 decreased already after 6 h (electrophoretic mobility shift assay). Addition of TGF-beta1 antagonized these effects. Also at the mRNA level, TGF-beta1 counteracted at one point or another the decrease in C/EBPalpha, C/EBPbeta, HNF1beta, and HNF4 expression; HNF1alpha and COUP-TF showed similar responses and, additionally, were downregulated by TGF-beta1 at 24 h (Northern blot). Albumin and apolipoprotein B mRNA levels were decreased after 24-h treatment with HGF, whereas addition of TGF-beta1 increased their levels. The same pattern was found with EGF, but not until 48 h. PEPCK mRNA was dramatically lowered with either EGF or HGF, and TGF-beta1 did not counteract these effects. Id-1 was expressed only in cultures treated for 24 and 48 h with both the mitogen (EGF, HGF) and TGF-beta1 and in those treated for 48 h with TGF-beta1 alone.

Animals↗
PubMed2006

Calmodulin is a critical regulator of osteoclastic differentiation, function, and survival.

Increased osteoclastic resorption and subsequent bone loss are common features of many debilitating diseases including osteoporosis, bone metastases, Paget's disease, and rheumatoid arthritis. While rapid progress has been made in elucidating the signaling pathways directing osteoclast differentiation and function, a comprehensive picture is far from complete. Here, we explore the role of the Ca(2+)-activated regulator calmodulin in osteoclastic differentiation, functional bone resorption, and apoptosis. During active bone resorption, calmodulin expression is increased, and calmodulin concentrates at the ruffled border, the organelle utilized for acid transport and bone dissolution. Pharmacologic inhibitors of calmodulin, several of which are already used clinically as anti-cancer and anti-psychotic agents, inhibit osteoclastic acid transport, suggesting their potential as bone-sparing drugs. Recent studies also implicate calmodulin in osteoclast apoptosis through a mechanism involving its direct interaction with the death receptor Fas. During osteoclastogenesis, RANKL-induction stimulates a rise in intracellular Ca2+, which in turn activates calmodulin and its downstream effectors. In particular, the Ca(2+)/calmodulin-dependent phosphatase calcineurin and its targets, the NFAT family of transcription factors, have been posited as the master regulators of osteoclastogenesis. However, recent in vivo and in vitro studies demonstrate that another Ca(2+)/calmodulin-regulated effector protein, CaMKII, is also involved. CaMKII(+/-) mutant mice have reduced osteoclast numbers, and CaMKII antagonists inhibit osteoclastogenesis in vitro. Furthermore, CaMKII is known to activate AP-1 transcription factors, which are also required for RANKL-induced osteoclast gene transcription, and recent findings suggest that CaMKII can down-regulate gp130, a cytokine receptor involved in bone remodeling and implicated in numerous osteo-articular diseases.

Animals↗
PubMed1992

Transient mosaic patterns of morphological and functional differentiation in the Caco-2 cell line.

To gain further insight on the mosaic expression of specific functional intestinal markers (such as sucrase-isomaltase) in postconfluent Caco-2 cells, a human colon cancer cell line unique in its property to differentiate in vitro into a mature enterocyte-like cell type, a comparative study was undertaken to examine the morphological and functional differentiation of Caco-2 cells at various culture stages. The observations clearly indicate that Caco-2 cells can exist only in three different states in culture: homogeneously undifferentiated (at subconfluence), heterogeneously polarized and differentiated (between 0 and 20 days after confluence), and homogeneously polarized and differentiated (after 30 days). Indeed, in the intermediate state, a strong discrepancy is found among adjacent differentiating cells throughout the monolayer relative to sucrase-isomaltase expression as well as to cell morphology and brush border organization. Back-scattered electron imaging analysis showed a lack of correlation between these parameters at the cellular level. These observations indicate that morphological and functional differentiations of Caco-2 cells progress concomitantly according to a transient mosaic pattern, thus providing evidence that these two processes are not coupled.

Cell Differentiation↗
PubMed2000

[Versatility of differentiated functions of cultured joint chondrocytes. Eventual usefulness in treatment].

The chondrocyte is the unique cell type in articular cartilage. It is responsible for the extracellular matrix production which permits the cartilaginous tissue to compensate the skeletal pressures during movements. The regulation of the different extracellular matrix components (type II collagen and aggrecan) depends on the differentiated state of the chondrocyte. However, in vivo, such as during aging and osteoarthritis, as well as in vitro, in monolayer culture, chondrocytes lose their morphological and biochemical characteristics. This phenomenon has been particularly studied in culture. As soon as at passage 1, there is a gradual shift from the synthesis of type II collagen to type I and III collagens and from the synthesis of large aggregating proteoglycans (aggrecan) to low molecular weight proteoglycans. However, it has been shown that dedifferentiated chondrocytes can reexpress phenotypic markers of the articular chondrocyte. These conditions include tridimensional culture in gels of agarose, collagen and alginate. This can be also obtained after treatment of chondrocytes in monolayer by dihydrocytochalasin B or staurosporine. Although the mechanisms involved in restoration of the differentiated phenotype have not been elucidated yet, it has been shown that the synthesis of specific proteoglycans and type II collagen can be related to a modification of actin architecture. The restoration of the differentiated functions using tridimensional culture of chondrocytes has been used to perform autologous chondrocyte implantation in chondral defects. In the future, the grafts could be improved using chondrocytes treated with stimulating growth factors and synthetically derived matrices.

Cell Differentiation↗
PubMed2004

Synthesis and self-association, absorption, and fluorescence properties of differentially functionalized hexakis(p-substituted-phenylethynyl)benzenes.

The dual Sonogashira coupling reactions of 1,3,5-tribromo-2,4,6-triiodobenzene with p-X-phenylacetylene followed by another p-Y-phenylacetylene (X, Y = OSiMe(2)Bu-t or CO(2)Et) produced a series of differentially functionalized hexakis(p-substituted-phenylethynyl)benzenes with D(3)(h)() symmetry (3h: 1,3,5-X-2,4,6-Y) and C(2)(v)() symmetry (3g,i: 1,2,3,5-X-4,6-Y; 3f,j: 1-X-2,3,4,5,6-Y). In a similar manner, 1,3,5-tris(p-X-phenylethynyl)-2,4,6-tris(p-Y-phenylethynyl)benzenes and 1,2,3,5-tetrakis(p-X-phenylethynyl)-4,6-bis(p-Y-phenylethynyl)benzenes (3l: X = OSiMe(2)Bu-t, Y = NO(2); 3m,n: X = N(n-octyl)(2), Y = NO(2); 3o,p: X = N(n-octyl)(2), Y = CH(OCH(2)CH(2)O); 3q,r: X = N(n-octyl)(2), Y = CHO; 3s,t: X = N(n-octyl)(2), Y = CH=C(CN)(2)) were prepared. Compounds 3 with electron-withdrawing groups self-aggregated by a pi-pi stacking interaction and solvophobic effect. In the absorption and fluorescence spectra of 3, lambda(max)(abs) and lambda(max)(em) showed red shifts as the donor-acceptor dipole at the end functional groups of the para position was increased. In the absorption spectra, lambda(max)(abs) showed red shifts upon increasing the number of combination of electron-donating and -withdrawing groups on the diagonal line in a molecule, whereas lambda(max)(em) in the fluorescence spectra exhibited red shifts upon decreasing the molecular symmetry.

Journal Article↗
PubMed1982

Functional differentiation of the medullary collecting tubule: influence of vasopressin.

Medullary collecting tubules of rabbits were dissected from the outer zone at different stages of ontogenetic evolution and perfused in vitro. The hydraulic conductivity coefficient (Lp) was measured in the presence of either hypotonic perfusate and isotonic bath or isotonic perfusate and hypertonic bath. Basal Lp (cm s-1 atm-1 10(-7) was 85 +/- 34 (N = 17) during early functional differentiation of the outer medullary collecting tubule (e-OMCT), 36 +/- 6 (N = 8) in the intermediate state (i-OMCT), and 10 +/- 7 (N = 11) in the final, mature state of function (m-OMCT). Addition of supramaximal concentrations of arginine-vasopressin (AVP) to the bath increased Lp in i-OMCT (250 +/- 36) and m-OMCT (327 +/- 63) but did not activate the osmotic hydraulic conductance in e-OMCT (105 +/- 27). In 11 studies, OMCT were analyzed using isotonic solutions as the perfusate and bath medium. The spontaneous transtubular voltage (PD) was lumen positive, 1.71 +/- 0.3 in e-OMCT, lumen negative 2.43 +/- 0.3 in i-OMCT, and 6.1 +/- 0.4 in m-OMCT. AVP had no effect on PD in e- and i-OMCT but increased the PD significantly (P less than 0.025) to 9.2 +/- 0.6 in m-OMCT. The results indicate that both hydraulic conductivity coefficient and transtubular voltage in the medullary collecting tubule are dependent upon epithelial ontogeny and, particularly, display differential responses to the antidiuretic hormone. The data suggest that the differentiation of water and ion transport in the medullary collecting tubule may contribute to the increasing efficacy of the medullary countercurrent system.

Aging↗
PubMed1981

Morphological and functional differentiation of Kirsten murine sarcoma virus-transformed rat adrenocortical cell lines.

This study was undertaken to examine relationships of the phenotype of malignant cells to target cell properties and to events early in the transformation process. Eighteen transformed lines were obtained by Kirsten murine sarcoma virus infection of cells from adrenal glands of rats ages 4 to 30 weeks, at first or second passages in culture. They were grown either as fibroblastic adrenocortical stem cells or as more differentiated epithelial cells, depending on culture conditions. Of 14 lines examined for their capacity to synthesize corticosteroids, 11 converted [14C]pregnenolone to progesterone, and one converted to deoxycorticosterone. In vivo, seven lines produced tumors resembling pleomorphic carcinomas, six lines grew as sarcomas, four grew as mixed tumors, and one line produced anaplastic tumors. Distinguishing features in culture of the carcinoma-producing lines were early onset and rapid progression of morphological transformation, a noncohesive epithelial cell form in some lines, lack of extracellular matrix, and, possibly, and origin in older animals. In contrast, sarcoma-producing cells were fibroblastic and cohesive, produced extracellular matrix, and transformed morphologically after longer and less well-defined periods in culture. The variation in histopathology was unrelated to the differentiation of the target cells and to the capacity of the transformed cells to synthesize corticosteroids. The results show that adrenocortical cells, transformed by Kirsten murine sarcoma virus after short-term culture, usually retain some functional differentiation and sometimes resemble human adrenocortical carcinomas histologically. The susceptibility of adrenocortical cells to Kirsten murine sarcoma virus raises the possibility that mesodermally derived epithelia in general may be target tissues for C-type sarcoma viruses.

Adrenal Cortex↗
PubMed1979

Stimulation of differentiated functions in human melanoma cells by tumor-promoting agents and dimethyl sulfoxide.

Treatment of cultured human HO melanoma cells with the mouse skin tumor promoter phorbol-12-myristate-13-acetate (PMA) at 5 x 10(-10) to 5 x 10(-7) M resulted in a dose-related inhibition of growth and a stimulation of differentiated functions. These included melanin synthesis and formation of dendrite-like structures. Higher doses of phorbol dibutyrate, a less potent tumor promoter, were required to produce an effect comparable to that of PMA for dendrite induction. Phorbol and two other phorbol esters, which lack tumor-promoting activity, were either inactive or elicited a poor response. In addition to morphological changes, treatment with PMA altered glucosamine incorporation into membrane gangliosides. After PMA treatment, glucosamine incorporation increased 8- to 10-fold in the GM3 ganglioside and decreased 2-fold in the GM1 ganglioside, as compared to phorbol or untreated control. Inhibition of cell growth and stimulation of melanin synthesis were also observed after treatment of the HO cells with dimethyl sulfoxide. Unlike the tumor-promoting agents, dimethyl sulfoxide did not induce the formation of dendrite-like structures in the cells. These findings indicate that HO melanoma cells can be stimulated into terminally differentiated cells after treatment with tumor-promoting agents such as phorbol diesters.

Cell Differentiation↗