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PubMed1985

Effects of altered Ca2+ and Mg2+ concentrations on proliferation and functional differentiation of the clonal insulin-producing cells RINm5F.

Effects of calcium and magnesium on proliferation and functional differentiation were investigated in the clonal insulin-producing rat cell line RINm5F. Variations of the extracellular concentrations of Ca2+ and Mg2+ had only minor effects on the cellular contents of these elements. Even when the medium was depleted of extracellular Ca2+ by the addition of EGTA, the Ca/Mg ratio corresponded to approximately 0.1. In a Mg2+-deficient medium a lowering of the extracellular calcium to 0.13 mM reduced the amount of insulin in the media but increased that in the cells. Irrespective of the concentration of Mg2+, depletion of Ca2+ was associated with low media levels of insulin and a reduced proliferation rate. In addition, the cells became smaller in size and showed an increased ability to exclude trypan blue. a rise of the magnesium concentration to 6.30 mM was accompanied by a decrease of the cellular content of insulin despite reduced amounts of hormone in the medium. This finding might be due to suppression of insulin biosynthesis, suggesting that the RINm5F cells have a markedly different metabolism and/or sensitivity to extracellular magnesium than non-tumorigenic beta-cells.

Adenoma, Islet Cell↗
PubMed1993

Alcohol dehydrogenases: gene multiplicity and differential functions of five classes of isozymes.

Mammalian alcohol dehydrogenases (ADHs) constitute an enzyme family of multiple forms (isozymes) which are differentially distributed throughout the body. Subunit types alpha, beta and gamma in dimeric combinations constitute the isozymes of human liver class I ADH, and are >94% homologous in structure. Human pi and chi subunits form homodimeric Class II and III ADH isozymes. pi-ADH is liver specific whereas chi-ADH is widely distributed throughout the body. A sixth human ADH subunit (designated mu or sigma), forming a new dimeric human stomach ADH, has been recently reported as Class IV ADH. Evidence for a seventh human ADH subunit has also been described, designated as Class V, the transcripts having been reported in the stomach and liver. All five classes of ADH represent isozymes which are homologous but exhibit at least 30% sequence differences in primary srtructure. Kinetic analyses of four of these classes of ADH indicated differential functions, serving either in the oxidative or reductive mode. Studies from various laboratories indicate the following respective functions: oxidation of aliphatic and aromatic alcohols-liver Class I and Class II, and stomach Class IV ADHs; reduction of peroxidic aldehydes-Classes I, II and IV; 'biogenic' alcohol oxidation-Classes I and II; and glutathione-dependent formaldehyde dehydrogenase-Class III.

Journal Article↗
PubMed1976

Cyclic nucleotides in the regulation of expression of differentiated functions in neuroblastoma cells.

Adenosine 3',5'-cyclic monophosphate (cAMP) may be one of the important factors in regulating the expression of many differentiated functions in neuroblastoma cells, but some of these functions can be induced by agents that do not increase the intracellular level of cAMP. An elevation of the intracellular level of guanosine 3',5'-cyclic monophosphate (cGMP) neither induced differentiation nor antagonized the effects of cAMP. Neuroblastoma cells increased the level of cAMP-binding proteins during differentiation, whereas glial cells and L-cells did not. This might have accounted in part for an increase in the intracellular level of cAMP even in the presence of high phosphodiesterase activity in neuroblastoma cells, since the protein-bound with the same proteins, but cAMP had about 10 times higher affinity than did cGMP. cAMP promoted the organization of microtubules and microfilaments necessary for the expression of differentiated phenotypes. The extension of neurites required the synthesis of new protein, but it did not need the synthesis of new RNA. cAMP induced differentiation in neuroblastoma cells by increasing the expression of some genetic information while suppressing the expression of others; e.g., the activities of neural enzymes increased, whereas the synthesis of histone and the phosphorylation of H1-histone markedly decreased in differentiated cells. A hypothesis was offered: An increase in cAMP phosphodiesterase activity as a result of mutation in the regulatory gene for phosphodiesterase in a single, or group of, dividing nerve cell(s) is the primary lesion that leads to malignancy. Based on the concept that selective cytocytoxic drugs should be used with agents that cause differentiation, a new therapeutic approach was suggested for the treatment of neuroblastoma. This involved administration of sodium butyrate followed by L-DOPA or prostaglandin E1 in the presence of cAMP phosphodiesterase inhibitor followed by the less immunosuppressive vincristine and 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide.

Adenylyl Cyclases↗
PubMed1988

Isolation and characterization of guinea-pig tracheal smooth muscle cells that retain differentiated function in long-term subculture.

A simple 30-min enzyme digestion procedure has been used to release guinea-pig tracheal smooth muscle cells that retain differentiated function in long-term subculture. Primary cell cultures initially consist of numerous epithelial colonies and 70-1000 morphologically differentiated smooth muscle cells per 600 mg (wet weight) tracheal tissue depending on the age of the animal. Both cell types proliferate to form a confluent monolayer within 5-17 days. Pure subcultures of tracheal smooth muscle cells are obtained by limited trypsin digestion of the primary culture. Eighty percent of these subcultured smooth muscle cells retain the ability to contract in response to histamine (10(-6) M) and to form reaggregates even after 20 or more passages. Examination of these cells by electron microscopy reveals both biosynthetic and contractile components of smooth muscle. Analysis of this dual phenotype may provide valuable information about the regulation of tracheal smooth muscle cell growth and differentiation.

Animals↗
PubMed1987

Loss of expression of a differentiated function gene, steroid 17 alpha-hydroxylase, as adrenocortical cells senescence in culture.

Senescence in cultured adrenocortical cells involves changes in expression of differentiated functions as well as changes in responses to mitogenic stimulation. Steroid 17 alpha-hydroxylase (steroid 17 alpha-monooxygenase, EC 1.14.99.9) is an adrenal-specific enzyme, the expression of which is dependent on the presence of stimulators of cyclic AMP production, such as cholera toxin. Dot-blot hybridization of RNA from bovine adrenocortical cells that had been incubated with cholera toxin showed a marked decline in 17 alpha-hydroxylase mRNA levels as a function of population doubling level, closely paralleling the decline in induction of 17 alpha-hydroxylase enzyme activity. The lower levels of 17 alpha-hydroxylase induction did not result from a requirement for a longer time period for induction or from a specific defect in response to cholera toxin and were not caused by a general failure of enzyme induction in response to cyclic AMP. The decreased growth rate in older cells results from a general decline in response to several growth factors. However, the decline in 17 alpha-hydroxylase induction did not result from a loss of response of the cells to mitogens, since quiescent cells at a low population doubling level showed stimulation of 17 alpha-hydroxylase mRNA by cholera toxin to levels similar to those in nonquiescent cultures and added mitogens either had no effect on 17 alpha-hydroxylase mRNA levels or decreased them. There was, however, a specific posttranscriptional effect of insulin on 17 alpha-hydroxylase. The loss of 17 alpha-hydroxylase induction is unlikely to result from overgrowth of a minority cell type lacking the ability to induce 17 alpha-hydroxylase, because adrenocortical cell clones that had high levels of 17 alpha-hydroxylase induction gave rise to cells with lower levels of induction on subcloning. Thus, loss of 17 alpha-hydroxylase activity in adrenocortical cellular senescence results from a primary failure of accumulation of 17 alpha-hydroxylase mRNA after incubation with the inducing agent.

Adrenal Cortex↗
PubMed2000

Role of winged helix transcription factor (WIN) in the regulation of Sertoli cell differentiated functions: WIN acts as an early event gene for follicle-stimulating hormone.

Members of the winged helix transcription factor family are known to regulate epithelial cell differentiation by regulating cell-specific gene expression. rWIN is a newly discovered member of the winged helix family shown to be present in the adult rat testis. In the testis the human homolog of rWIN, HFH-11, was localized to the germ cells (i.e. spermatocytes and spermatids) undergoing spermatogenesis. In the present study we show that rWIN is also expressed in testicular Sertoli cells. Sertoli cells are the epithelial component of the seminiferous tubule and provide both the cytoarchitectural support and the microenvironment for developing germ cells. The presence of rWIN in Sertoli cells was confirmed by Northern blot and RT-PCR analysis. The rWIN transcript size in the Sertoli cells was different from the germ cell transcript that is probably due to alternative splicing or modifications of the 3'-untranslated region. At least two spliced variants of rWIN were observed in the Sertoli cells corresponding to the deletion of an exon in the DNA-binding region. Long term stimulation of cultured Sertoli cells with the gonadotropin FSH down-regulated rWIN expression. In contrast, short-term stimulation (2 h) transiently up-regulated rWIN expression. The FSH-induced transient stimulation of rWIN precedes expression of the transferrin gene that is a marker of Sertoli cell differentiation. FSH-induced transferrin promoter activity was inhibited when cultured Sertoli cells were treated with an antisense oligonucleotide to rWIN. Interestingly, the constitutive overexpression of the DNA-binding domain of rWIN also down-regulated transferrin promoter activity. Analysis of the transferrin promoter with various deletion mutations suggested that rWIN acts at an upstream gene of the transferrin promoter. The results indicate that a transient up-regulation of rWIN in part mediates the ability of FSH to activate the transferrin promoter, which can be inhibited with a rWIN antisense oligonucleotide or constitutive expression of the rWIN DNA-binding domain. The current study demonstrates that rWIN acts as an early event gene for FSH actions on Sertoli cells and that rWIN appears to have a role in the regulation of Sertoli cell differentiated functions.

Animals↗
PubMed1989

Primary rabbit kidney proximal tubule cell cultures maintain differentiated functions when cultured in a hormonally defined serum-free medium.

A primary rabbit kidney epithelial cell culture system has been developed which retains differentiated functions of the renal proximal tubule. In addition, the cells have a distinctive metabolism and spectrum of hormone responses. The primary cells were observed to retain in vitro a Na+-dependent sugar transport system (distinctive of the proximal segment of the nephron) and a Na+-dependent phosphate transport system. Both of these transport processes are localized on the apical membrane of proximal tubule cells in vivo. In addition, probenicid-sensitive p-aminohippurate (PAH) uptake was observed in basolateral membranes of the primary tubule cells, and the PAH uptake by these vesicles occurred at a rate that was very similar to that observed with membranes derived from the original tissue. Several other characteristics of the primary cells were examined, including hormone-sensitive cyclic AMP production and phosphoenolpyruvate carboxykinase (PEPCK) activity. Like the cells in vivo, the primary proximal tubule cells were observed to produce significant cyclic AMP in response to parathyroid hormone, but not in response to arginine vasopressin or salmon calcitonin. Significant PEPCK activity was observed in the particulate fraction derived from a homogenate of primary rabbit kidney proximal tubule cells.

Animals↗
PubMed1994

Modification of the expression of adenosine 3',5'-cyclic monophosphate-induced differentiated functions in neuroblastoma cells by beta-carotene and D-alpha-tocopheryl succinate.

OBJECTIVE: The role of beta-carotene and vitamin E in modifying the effect of cell differentiating agent has not been studied. This study has investigated the effects of beta-carotene and d-alpha-tocopheryl succinate (alpha-TS) on adenosine 3',5'-cyclic monophosphate (cAMP) induced differentiated functions in murine neuroblastoma cells (NBP2) in culture. METHODS: Prostaglandin E1 (PGE1), a stimulator of adenylate cyclase, and 4-(3-butoxy-4-methoxy-benzyl)-2-imidazolidinone (R020-1724), an inhibitor of cyclic nucleotide phosphodiesterase, were used to induce differentiation in NB cells. RESULTS: Both beta-carotene and alpha-TS markedly enhanced the level of morphologic differentiation (neurite formation) induced by both PGE1 and R020-1724. However, beta-carotene and alpha-TS by themselves were ineffective. These vitamins increased tyrosine hydroxylase (TH) activity. However, beta-carotene did not significantly affect PGE1- and R020-1724-stimulated rise in TH activity. alpha-TS at a higher concentration inhibited PGE1- and R020-1724-stimulated increase in TH activity. None of the above treatments affected basal choline acetyltransferase (ChAT) activity. beta-carotene and alpha-TS caused a transient increase in cAMP level, and they also enhanced the effect of PGE1 and R020-1724 on cAMP level in a transient manner. CONCLUSION: These results suggest that beta-carotene and alpha-TS modify the effects of cAMP stimulating agents on differentiation of NB cells in culture.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗
PubMed1987

The role of thyroid hormone as a biological amplifier of the actions of follicle-stimulating hormone in the functional differentiation of cultured porcine granulosa cells.

To characterize thyroid hormone action on the ovary, the direct effects of T4 or T3 were investigated in vitro using a monolayer culture system of porcine granulosa cells. Monolayer cultures were maintained for 6 days in 4% serum-supplemented medium in the absence or presence of porcine FSH (20 ng/ml), with or without graded doses of T4 or T3. Combined treatment with FSH and T4 (10(-7) M) induced morphological alternation resembling epithelioid cells, while FSH alone or T4 alone failed to bring about the epithelioid morphology. Concomitant treatment with FSH and T4 (10(-7) M) markedly increased FSH-stimulated induction of [125I]iodo-human CG binding to cultured granulosa cells obtained from small follicles. The combined treatment with FSH and T4 (10(-7) M) also resulted in a significant increase in progesterone and estrogen secretion by the cultured cells relative to treatment with FSH alone. Increases in progesterone, 17 beta-estradiol, and estrone secretion caused by the combined treatment with FSH and T4 (10(-7) M) were further augmented in response to the addition of exogenously provided substrate pregnenolone, testosterone, and androstenedione, respectively. Furthermore, aromatase activity assessed by the release of [3H]water from [1 beta-3H, 4-14C]androstenedione was significantly higher in cells treated concomitantly with FSH and T4 (10(-7) M) than that in cells treated with FSH alone. All the stimulatory effects of T4 (10(-7) M) on the morphological and functional differentiation of cultured granulosa cells were also found in combined treatment with FSH and T3 (10(-9) M). Either treatment with higher or lower concentrations of T4 or T3 gave attenuated effects, and T4 or T3 alone without FSH was incapable of exhibiting these stimulatory effects. These findings suggest that thyroid hormones synergize with FSH to exert direct stimulatory effects on granulosa cell functions, including morphological differentiation, LH/human CG receptor formation and steroidogenic enzyme (3 beta-hydroxysteroid dehydrogenase and aromatase) induction. Hence, decreases in ovarian functions during the states of hypo- or hyperthyroidism may account for diminished responsiveness of the granulosa cells to FSH.

Animals↗
PubMed1993

Reduction of structured population models to threshold-type delay equations and functional differential equations: a case study.

It is shown by way of a simple example that certain structured population models lead naturally to differential delay equations of the threshold type and that these equations can be transformed in a natural way to functional differential equations. The model examined can be viewed as a model of competition between adults and juveniles of a single population. The results indicate the possibility that this competition leads to instability.

Age Factors↗
PubMed2006

Broca's area and the ventral premotor cortex in language: functional differentiation and specificity.

The idea is put forward that Broca's area (BA 44/45) and the left ventral premotor cortex (BA 6) together with the frontal operculum support different functions during language processing. While BA 44/45 is seen to be increasingly activated whenever the internal re-construction of a hierarchical structure from a sequential input is necessary, BA 6 is involved in the processing of local structural dependencies. This functional differentiation is discussed in the context of the neurocytoarchitectonical differentiation between agranular structure characterizing BA 6 and a dysgranular cortical structure characterizing BA 44/45. This differentiation is exemplified in the domain of language, but is possibly applicable to non-language domains.

Comprehension↗
PubMed2001

Effect of the beta(3)-adrenergic agonist Cl316,243 on functional differentiation of white and brown adipocytes in primary cell culture.

We investigated the effect of the specific beta(3)-adrenergic receptor agonist CL 316,243 (CL) on proliferation and functional differentiation of the Siberian hamster (Phodopus sungorus) white and brown preadipocytes in primary cell culture. Proliferation of both white and brown preadipocytes was stimulated by a general beta-adrenergic agonist (isoproterenol) but not by CL. Lipolysis of differentiated white and brown adipocytes was stimulated similarly by CL with maximum effect at 10 nM. Thermogenic properties of cells were assessed by immunodetection of UCP-1, the brown adipocyte specific uncoupling protein, and measurement of cytochrome c oxidase (COx) activity as an index of mitochondrial capacity. UCP-1 content was largely increased by CL in BAT but not in WAT cultures. Basal UCP-2 mRNA levels were similar in WAT and BAT cultures and increased by both CL and isoproterenol. COx activity of BAT cultures was twice as high as that of WAT cultures but in neither cell culture system could it be increased by beta-adrenergic stimulation. We suggest (i) that white and brown preadipocyte proliferation is increased in vitro via beta1 or beta(2), but not beta(3)-adrenergic pathways, (ii) that white and brown preadipocytes represent different cell types, and (iii) that in vitro beta-adrenergic stimulation it is not sufficient to induce complete thermogenic adaptation of brown adipocytes.

Adipocytes↗
PubMed2004

Functional differentiation of endosomes in Arabidopsis cells.

Endocytosis plays an important role in plant physiology, but how endocytic organelles are organized remains unknown. We present the evidence that endosomes are functionally differentiated in Arabidopsis cells. Two types of Rab5-related GTPases are localized on distinct population of endosomes in a partially overlapping manner. Ara7 and Rha1 are on an early type of endosomes with AtVamp727, where recycling of plasma membrane proteins occurs. In contrast, the plant-unique Rab5, Ara6, resides on distinct endosomes with the prevacuolar SNAREs. Partially overlapping localization of Ara6 and Ara7/Rha1 with reciprocal gradients suggests maturation of endosomes from one to the other.

Arabidopsis↗
PubMed1991

Structural heterogeneity and functional differentiation: a rationale for glycosylation analysis of recombinant therapeutics.

Many secreted and membrane-bound proteins exhibit microheterogeneity, even after purification to 'homogeneity'. Posttranslational processing and modification, including glycosylation, often accounts for the observed heterogeneity. While microheterogeneity is traditionally viewed as a biochemical nuisance of little or no functional significance, the increasing weight of recent evidence suggests quite a different perspective: that structural heterogeneity, including microheterogeneity, can impart functional differentiation within the population and thus represents a sophisticated mechanism of biological control and functional diversification. Because of a presumed connection between functional attributes and clinical characteristics, this perspective is the fundamental rationale for the analysis of the glycosylation of proteins employed as therapeutic agents.

Amino Acid Sequence↗
PubMed1998

Functional differentiation in the hippocampus.

The hippocampus is critically involved in certain kinds of memory. During memory formation, it may operate as an integrated unit, or isolated parts may be responsible for different functions. Recent evidence suggests that the hippocampus is functionally differentiated along its dorsoventral (septotemporal) axis. The cortical and subcortical connections of the dorsal and ventral hippocampus are different, with information derived from the sensory cortices entering mainly in the dorsal two-thirds or three-quarters of the dentate gyrus. Rats can acquire a spatial navigation task if small tissue blocks are spared within this region, but equally large blocks at the ventral end are not capable of supporting spatial learning. In primates, the posterior hippocampus (corresponding to the dorsal hippocampus of rodents) appears to be more important than anterior areas for encoding of spatial memory and certain forms of nonspatial memory. The ventral (or anterior) hippocampal formation is to some extent disconnected from the rest of the structure both in terms of intrahippocampal and extrahippocampal connections and may be performing functions that are qualitatively different from, and independent of, those of the dorsal hippocampal formation.

Animals↗
PubMed2001

TSH-induced differentiated functions correlate with enhancement of phosphotyrosine phosphatase activity in thyroid cells. Effect of phorbol 12-myristate 13-acetate.

TSH-treated pig thyroid cells reorganize into follicle-like structures and exhibit differentiated functions. TSH also induces a phosphotyrosine phosphatase (PTPase) activity evaluated by phosphorylated substrate hydrolysis. Incubation of thyrocytes with various concentrations of 8-bromo-cyclic AMP or forskolin induces an increase of PTPase activity in a dose-dependent manner. During the culture period, adenylyl cyclase sensitivity, protein binding iodine and PTPase activity progressively increase from the first to the fourth day of the culture. Chronic treatment with phorbol 12-myristate 13-acetate (PMA) significantly inhibits PTPase activity during the first 24 h following PMA addition. GF 109203X, a specific inhibitor of protein kinase C, abolishes the inhibitory effect of PMA. Electrophoresis of membrane extracts allowed us to demonstrate a phosphatase activity at 111 kDa (p111). Vanadate inhibits this activity, indicating that p111 is a PTPase. This p111 is significantly reduced in PMA-treated cells. These data suggest that PTPase activity evidenced at 111 kDa is correlated with a differentiated state of primary cultured pig thyroid cells induced by TSH.

Adenylyl Cyclases↗
PubMed1989

Cellular senescence involves stochastic processes causing loss of expression of differentiated function genes: visualization by in situ hybridization for steroid 17 alpha-hydroxylase in bovine adrenocortical cells.

When grown for long periods in culture, bovine adrenocortical cells lose the expression of a differentiated function gene, steroid 17 alpha-hydroxylase. Previously, we documented a decline in 17 alpha-hydroxylase mRNA with increasing culture passage level after induction with cyclic AMP (P. J. Hornsby et al., 1987, Proc. Natl. Acad. Sci. USA 84, 1580). We used in situ hybridization to investigate the loss of expression of this gene during cellular senescence at an individual cell level. In primary cultures, cells were uniformly positive for hybridization with cDNA for 17 alpha-hydroxylase after cyclic AMP induction. After two passages, cultures comprised a mixture of hybridizing and nonhybridizing cells. Cells appeared either to hybridize at a level comparable to that in primary cultures or to be nonhybridizing. When in situ hybridization was combined with immunofluorescence, cells positive for immunofluorescence were also positive for hybridization. Senescing mass cultures showed decreasing numbers of positive cells, and after 30 passages cultures comprised entirely nonhybridizing cells. Thus, the previously observed decline in overall 17 alpha-hydroxylase mRNA levels results from a decline in the fraction of expressing cells in the culture, and the rate of loss of expressing cells is in agreement with the rate of loss of total 17 alpha-hydroxylase mRNA. Primary clones, even when isolated at an early stage of clonal expansion, had mixtures of subclones of hybridizing and nonhybridizing cells. On recloning, hybridizing subclones usually produced uniformly nonhybridizing sub-subclones. Some subclones within primary clones had a morphology associated with replicative senescence (flattened cells with sparse intercellular contacts), yet had high numbers of hybridizing cells. We conclude that, in both mass and clonal populations, cells initially expressing 17 alpha-hydroxylase rapidly give rise to clones of nonexpressing cells. Such cells are continually derived by a stochastic process from cells originally expressing the gene.

Adrenal Cortex↗