Biomedical subjects

C C Franklin

Publications and source records attributed to C C Franklin.

27 records · Page 2Linked to original sources

PubMed1992

Induction of differentiation and c-jun expression in human leukemic cells by okadaic acid, an inhibitor of protein phosphatases.

Okadaic acid, a protein phosphatase inhibitor, is a strong tumor promoter which activates protein phosphorylation. Because another activator of protein phosphorylation, phorbol esters, stimulates hematopoietic differentiation, we sought to determine whether okadaic acid could also induce the differentiation of the human leukemic cell line U937. Differentiation was assessed by measuring changes in the following: mRNA levels, cell growth, morphology, cell surface markers, and the ability to induce superoxide. We found that okadaic acid treatment of U937 cells induces immediate increases in total cellular levels of both c-jun and c-fos mRNAs. Nuclear run-on experiments demonstrate that initial increases are secondary to increases in transcription, whereas latter changes may be secondary to mRNA stabilization. Like phorbol esters, okadaic acid treatment also activates AP-1 enhancer activity and induces the phosphorylation of c-Jun protein. Approximately 6-12 hours after treatment with okadaic acid, mRNA levels of c-myc, p34cdc2, and p58GTA, two cell cycle regulated protein kinases, decrease. Okadaic acid inhibits the growth of U937 cells, induces changes in nuclear morphology, stimulates increases in Mac-1 and Leu 11 surface antigens, and induces these cells to produce superoxide. These changes, taken together, suggest that U937 cells have been induced by okadaic acid to differentiate towards a more mature cell type.

Base Sequence↗

PubMed1991

Regulation of calcium-activated potassium efflux by neurotensin and other agents in HT-29 cells.

Neurotensin receptors have been shown previously to be coupled to polyphosphoinositide turnover and intracellular Ca2+ ([Ca2+]i) mobilization in HT-29 colonic epithelial cells (Bozou et al. Biochem. J. 264: 871, 1989; Turner et al. J. Pharmacol. Exp. Ther. 253: 1049, 1990). In this study, neurotensin was found to enhance dramatically the Ba2(+)- and tetraethylammonium chloride-sensitive K(+)-efflux rate (measured with 86Rb+) in the presence of ouabain and bumetanide, with basal efflux increasing 4.5 +/- 0.5-fold with 10 nM neurotensin. The K(+)-efflux rate, which was partially dependent on the extracellular Ca2+ concentration, was also increased by carbachol and ATP, two other [Ca2+]i-mobilizing agonists in HT-29 cells, as well as by the Ca2+ ionophores ionomycin and A23187, suggesting that the efflux was through Ca2(+)-activated K+ channels. Pretreatment of cells with neurotensin, carbachol, or ATP desensitized subsequent neurotensin-stimulated efflux by 82, 57, and 63%, respectively, confirming our previous results which indicated homologous and heterologous desensitization of the neurotensin receptor-signal transduction pathway. Pretreatment of cells with the protein kinase C activators phorbol 12-myristate 13-acetate (PMA) and mezerein did not affect [Ca2+]i mobilization or K+ efflux directly but desensitized neurotensin-stimulated efflux by greater than 80%. Pretreatment (2 h) with PMA also decreased K+ efflux in response to ionomycin by 59%, although ionomycin-induced [Ca2+]i mobilization was not inhibited. Downregulation of protein kinase C by overnight pretreatment with PMA resulted in recovery of ionomycin-stimulated efflux. These results suggest that agonist-stimulated Ca2(+)-activated K+ channels in HT-29 cells are regulated at multiple steps in the signal transduction pathway.

Adenocarcinoma↗

PubMed1990

Vasoactive intestinal peptide stimulates active K+ transport and Na(+)-K(+)-Cl- cotransport in HT-29 cells.

Regulation of active K+ influx and Na(+)-K(+)-Cl- cotransport activity in HT-29 cells by vasoactive intestinal peptide (VIP) was investigated. Both active K+ influx, defined as the ouabain-sensitive component, and Na(+)-K(+)-Cl- cotransport, defined as the ouabain-resistant bumetanide-sensitive component, of total K+ uptake were increased by VIP. VIP increased the maximum velocity (Vmax) values for both components with no change in apparent Michaelis constant (Km) values. Three lines of evidence support the role of adenosine 3',5'-cyclic monophosphate (cAMP) as a mediator of the VIP effects. 1) The rank order potencies of VIP and peptide histidineisoleucineamide (PHI) in binding and cAMP production (J. T. Turner, S. B. Jones, and D. B. Bylund, Peptides Fayetteville 7: 849, 1986) and K+ uptake were consistent; 2) alpha 2-adrenergic agonists inhibited both VIP-stimulated cAMP production (J. T. Turner, C. Ray-Prenger, and D. B. Bylund, Mol. Pharmacol. 28: 422, 1985) and K+ uptake; and 3) forskolin, but not dideoxyforskolin, mimicked the effects of VIP on K+ uptake. Because amiloride blocked the VIP-stimulated active K+ component, the VIP effects on active K+ influx may be secondary to a Na(+)-H+ antiporter-mediated increase in cellular Na+ content. Additional experiments indicated that pretreatment of cells with a protein kinase C activator, previously shown to decrease basal Na(+)-K(+)-Cl- cotransport activity and the apparent number of cotransporters in HT-29 cells (C. C. Franklin, J. T. Turner, and H. D. Kim, J. Biol. Chem. 264: 6667, 1989), did not change the magnitude of response of the remaining cotransporters after adenylate cyclase activation.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1990

Screening, diagnosis, and management of dyslipoproteinemia in children.

The authors provide an extensive and comprehensive review of dyslipoproteinemia in children. An effective program for CVD reduction in this population will include an accessible screening program to identify high-risk children, high-quality measurements of TC and LP-C, careful follow-up of screening results with multiple measurement to classify risk status and diagnose primary dyslipidemia, a key role for family and education, and consistent and long-term follow-up for diet and drug adherence, efficacy, and safety.

Adolescent↗

PubMed1989

Regulation of Na+/K+/Cl- cotransport and [3H]bumetanide binding site density by phorbol esters in HT29 cells.

The involvement of protein kinase C in the regulation of Na+/K+/Cl- cotransport was investigated in cultured HT29 human colonic adenocarcinoma cells. We have demonstrated previously the presence of a Na+/K+/Cl- cotransport pathway in HT29 cells (Kim, H.D., Tsai, Y-S., Franklin, C.C., and Turner, J.T. (1989) Biochim. Biophys. Acta 946, 397-404). Treatment of cells with the phorbol esters phorbol 12-myristate 13-acetate (PMA) and phorbol 12,13-dibutyrate (PDBu) caused an increase in membrane-associated protein kinase C activity that was accompanied by a concomitant decrease in cytosolic protein kinase C activity. PMA also produced a rapid transient increase in cotransport to 137% of control values by 5 min followed by a progressive decrease to 19% of control values by 2 h. To determine the underlying mechanism for the reduction in Na+/K+/Cl- cotransport, changes in cotransporter number and/or affinity were determined in radioligand binding studies using [3H]bumetanide. PMA and PDBu produced essentially identical time- and dose-dependent decreases in specific [3H]bumetanide binding that were similar to the observed decreases in cotransport. Analysis of saturation and competition binding data indicated that the decrease in binding was due to a lowered Bmax with no change in affinity. Both the decrease in binding and the changes in cotransport elicited by PMA were prevented by the protein kinase inhibitor H7. These findings suggest that phorbol esters cause a decrease in the number of cotransporters in HT29 cells, resulting in a reduction in Na+/K+/Cl- cotransport activity.

Binding, Competitive↗

PubMed1988

Characterization of Na+/K+/Cl- cotransport in cultured HT29 human colonic adenocarcinoma cells.

A Na+/K+/Cl- cotransport pathway has been examined in the HT29 human colonic adenocarcinoma cell line using 86Rb as the K congener. Ouabain-resistant bumetanide-sensitive (OR-BS) K+ influx in attached HT29 cells was 17.9 +/- 0.9 nmol/min per mg protein at 25 degrees C. The identity of this pathway as a Na+/K+/Cl- cotransporter has been deduced from the following findings: (a) OR-BS K+ influx ceased if the external Cl- (Cl-o) was replaced by NO3- or the external Na+ (Na+o) by choline; (b) neither OR-BS 24Na+ nor 36Cl- influx was detectable in the absence of external K+ (K+o); and (c) concomitant measurements of 86Rb+, 22Na+, and 36Cl- influx indicated that the stoichiometry of the cotransport system approached a ratio of 1N+:1K+:2Cl-. In addition, OR-BS K+ influx was exquisitely sensitive to cellular ATP levels. Depletion of the normal ATP content of 35-40 nmol/mg protein to 10-15 nmol/mg protein, a concentration at which the ouabain-sensitive K+ influx was unaffected, completely abolished K+ cotransport. OR-BS K+ influx was slightly reduced by the divalent cations Ca2+, Ba2+, Mg2+ and Mn2+. Although changes in cell volume, whether shrinking or swelling, did not influence OR-BS K+ influx, ouabain-sensitive K+ influx was activated by cell swelling. As in T84 cells, we found that the OR-BS K+ influx in HT29 cells was stimulated by exogenous cyclic AMP analogues and by augmented cyclic AMP content in response to vasoactive intestinal peptide, forskolin, norepinephrine and forskolin or prostaglandin E1.

Adenocarcinoma↗

PubMed1988

Insulin regulation of glucose metabolism in HT29 colonic adenocarcinoma cells: activation of glycolysis without augmentation of glucose transport.

The effects of insulin on glucose transport and metabolism were examined in cultured HT29 human colonic adenocarcinoma cells. The presence of glucose transporters was verified by D-glucose displaceable [3H]cytochalasin B binding. The Kd and Bmax values from cytochalasin B binding studies were 190 +/- 30 nM and 8.4 +/- 1.4 pmol/mg protein, respectively. Glucose transport determined with 3-O-methylglucose showed saturable kinetics with a Km of 5.8 +/- 0.4 mM and a Vmax of 0.047 +/- 0.003 mumol/mg protein per min at 25 degrees C. Moreover, in HT29 cells, two classes of insulin binding sites were detected in radioligand binding experiments. Although insulin failed to stimulate glucose transport, it was found to activate glycolysis in HT29 cells. Glucose consumption increased from 0.33 +/- 0.03 mumol/mg protein per h to 0.49 +/- 0.05 mumol/mg protein per h and lactate production was augmented from 0.67 +/- 0.04 mumol/mg protein per h to 0.87 +/- 0.06 mumol/mg protein per h in response to 10(-7) to 10(-5) M insulin. Insulin also enhanced mannose metabolism. Apart from these two hexoses, HT29 cells exhibited a surprisingly narrow substrate specificity. With the possible exception of glyceraldehyde, little lactate was produced from alternative substrates, including adenosine, inosine, ribose, deoxyribose, dihydroxyacetone, galactose and fructose either with or without insulin. Despite its limited utilization by the glycolytic pathway, adenosine was readily salvaged for de novo synthesis of adenine nucleotides. These findings suggest that insulin directly influences substrate utilization through the glycolytic pathway in HT29 cells without activating the glucose transport pathway.

3-O-Methylglucose↗

PubMed1987

Activation of phospholipase C in platelets by platelet activating factor and thrombin causes hydrolysis of a common pool of phosphatidylinositol 4,5-bisphosphate.

Despite their physicochemical and mechanistic differences platelet activating factor (or acetylglycerylether phosphorylcholine; AGEPC) and thrombin, both platelet stimulatory agents, induce phosphoinositide turnover in platelets. We therefore investigated the stimulation of the phosphoinositide phosphodiesterase by these agents and questioned whether they evoked hydrolysis of the same or different pools of phosphoinositides. [3H]Inositol-labelled rabbit platelets were challenged with thrombin and/or AGEPC under a variety of protocols, and the phospholipase C mediated production of radioactive inositol monophosphate (IP); inositol bisphosphate (IP2) and inositol trisphosphate (IP3) was used as the parameter. AGEPC (1 X 10(-9) M) caused a transient maximum (5 to 6-fold) increase in [3H]IP3 at 5 s followed by a decrease. Thrombin (2 U/ml) elicited an increase in [3H]IP3 at a much slower rate than AGEPC; 2 fold at 5 s, 5 fold at 30 s and a maximum 6 to 8-fold at 2-5 min. Compared to AGEPC, thrombin stimulated generation of [3H]IP2 and [3H]IP were severalfold higher. When thrombin and AGEPC were added together to platelets there was no evidence for an additive increase in inositol polyphosphate levels except at earlier time points where increases were submaximal. When AGEPC was added at various time intervals after thrombin pretreatment, no additional increases in [3H]IP3 were observed over that maximally seen with thrombin or AGEPC alone. In another set of experiments, submaximal increases (about 1/4 and 1/2 of maximum) in [3H]IP3 were achieved by using selected concentrations of thrombin (0.1 U and 0.3 U, respectively) and then AGEPC (1 X 10(-9) M) was added for 5 s. Once again the increase in [3H]IP3 was close to the maximal level seen with thrombin or AGEPC individually. It is concluded that thrombin and AGEPC differentially activated phosphoinositide phosphodiesterase (phospholipase C) in rabbit platelets and that the stimulation of the phospholipase C by these two stimuli causes IP3 production via hydrolysis of a common pool of phosphatidylinositol 4,5-bisphosphate.

Animals↗

PubMedDate not supplied

Gastrointestinal adenovirus: an important cause of morbidity in patients with necrotizing enterocolitis and gastrointestinal surgery.

Adenoviruses have recently been recognized as etiologic agents of enteric disease in hospitalized infants and young children. Patients who have undergone surgical procedures related to the complications of neonatal necrotizing enterocolitis constitute a population of infants who are often hospitalized for extended periods of time. We studied the incidence of enteric adenovirus infections in infants with necrotizing enterocolitis who had undergone intestinal surgery resulting in colostomies or ileostomies. These studies revealed that 31.7% of the hospital admissions in such patients were complicated by symptomatic infection with enteric adenoviruses. The rate of adenovirus infection in this population was significantly higher than the rate of such infections encountered in infants undergoing ostomy procedures for other conditions and in age-matched hospitalized infants without prior gastrointestinal surgery. The infections with enteric adenovirus were generally accompanied by an increase in intestinal output which was temporally associated with the excretion of adenovirus in the intestinal fluid. In addition infections with enteric adenoviruses in the infants with necrotizing enterocolitis and ostomies were associated with a marked increase in length of hospitalization as compared to uninfected infants with similar underlying gastrointestinal pathology. Epidemiologic analysis revealed that many of the cases of enteric adenovirus infection in the study population occurred during seasons in which enteric adenovirus infections were prevalent in the hospital population. These studies demonstrate that enteric adenovirus infections are major causes of morbidity in hospitalized patients who have of morbidity in hospitalized patients who have undergone ileostomy or colostomy procedures for necrotizing enterocolitis and that the prevention of enteric adenovirus infections might result in a significant improvement in the hospital care of infants with these conditions.

Adenoviridae Infections↗