Functional improvements in β-conglycinin by edible bioconjugation with carboxymethyl dextran

β-Conglycinin was conjugated with carboxymethyl dextran (CMD) by the Maillard reaction to improve its function. The β-conglycinin-CMD conjugate was purified by dialysis. Conjugation was confirmed by SDS-PAGE with CBB and PAS staining. Composition of the β-conglycinin-CMD was β-conglycinin:CMD = 1:2.7 (molar ratio) which was confirmed by BCA method and phenol sulfuric acid method. Solubility of β-conglycinin in the range of pH 2.0-7.0 was much improved by conjugation with CMD. Emulsifying property of β-conglycinin at pH 7 and in presence of salt was improved by conjugation with CMD. Immunogenicity of β-conglycinin was reduced by conjugation with CMD. Conjugation method performed in this study was considered to be valuable in that it can be used in food processing.

Inhibitors of calcineurin block expression of cyclins A and E induced by fibroblast growth factor in Swiss 3T3 fibroblasts

In Swiss 3T3 fibroblasts, growth factor-stimulated progression from G1 to S phase involves activation of the Ca2+/calmodulin-dependent serine/threonine-specific protein phosphatase 2B (calcineurin). Here we report that both cobalt and the calcium chelator EGTA, inhibitors of calcium uptake, as well as cyclosporin A and FK-506, specific inhibitors of calcineurin function, abolished fibroblast growth factor (FGF)-induced expression of cyclins A and E, but not cyclin D1. At 0.1 microM concentration cyclosporin A completely blocked FGF-induced expression of cyclins E and A and it inhibited FGF-stimulated DNA synthesis by 40%; full inhibition of DNA synthesis required 10 microM cyclosporin A. PD 98059, an inhibitor of mitogen-activated protein (MAP) kinase kinase, and hemicholinium-3, an inhibitor of FGF-induced MAP kinase activity, did not inhibit the stimulatory effect of FGF on the expression of cyclin E. On the other hand, the inhibitory effect of 0.1 microM cyclosporin A on FGF-stimulated DNA synthesis was additive with that of hemicholinium-3, suggesting that the two inhibitors acted by different mechanisms. The inhibitors of calcineurin and calcium uptake also completely blocked the stimulatory effects of lysophosphatidic acid on the expression of cyclins E and A, but not cyclin D1. The results suggest that FGF- or lysophosphatidic acid-induced transcription of cyclin A and cyclin E genes is mediated by calcineurin involving a MAP kinase-independent mechanism and that increased expression of cyclins A and E is required for the maximal stimulatory effects of these mitogens on DNA synthesis.

The choline kinase inhibitor hemicholinium-3 can inhibit mitogen-induced DNA synthesis independent of its effect on phosphocholine formation

In NIH 3T3 cells, phosphocholine (PCho) stimulates mitogenesis in synergism with insulin, ATP, and sphingosine-1-phosphate (S1P) via an extracellular target. Intracellular PCho also has been suggested to mediate the mitogenic effects of fibroblast growth factor (FGF) and several other growth factors based, in part, on the observed inhibition of growth factor-induced mitogenesis by the choline kinase inhibitor hemicholinium-3 (HC-3). Here we examined the specificity of HC-3 effects on mitogenesis in serum-starved NIH 3T3 and Swiss 3T3 cells. In both cell lines, FGF greatly enhanced DNA synthesis in a medium containing 28 microM choline, and it also stimulated the formation of -14C-PCho from both 50 microM and 5 mM [14C]choline. HC-3 (2 mM) inhibited basal or FGF-induced formation of [14C]PCho and [14C]phosphatidylcholine as well as the uptake of -14C-choline only at the 50 microM, but not the 5 mM, concentration of [14C]choline. In addition, HC-3 (1 mM) from three different sources (95-99.9% purity) inhibited FGF-stimulated DNA synthesis by 53-58% which was not reversed by 5 mM choline. The choline analogue dimethylethanolamine (1 mM) also inhibited FGF-stimulated formation of [14C]PCho from 50 microM -14C-choline, but it had no effect on FGF-induced DNA synthesis. Of the other growth regulators examined, synergistic stimulation of DNA synthesis by extracellular PCho and S1P or PCho and ATP via choline kinase-independent mechanisms was inhibited by 2 mM HC-3. However, HC-3 failed to inhibit the synergistic mitogenic effects of PCho and insulin or S1P and insulin. The results suggest that FGF-induced mitogenesis does not require PCho formation and that HC-3 can inhibit DNA synthesis independent of its inhibitory effects on choline metabolism.

Bombesin and zinc enhance the synergistic mitogenic effects of insulin and phosphocholine by a MAP kinase-dependent mechanism in Swiss 3T3 cells

Simultaneous treatment of serum-starved (24 h) Swiss 3T3 cells with insulin (500 nM) and phosphocholine (PCho) (0.25-1 mM) resulted in synergistic stimulation of DNA synthesis via a mitogen activated protein (MAP) kinase-independent rapamycin-sensitive mechanism. Co-treatment of cells with bombesin (10 nM) or zinc (25 microM) enhanced the combined mitogenic effects of insulin and PCho 2-3-fold; however, in the presence of bombesin or zinc the combined effects of insulin and PCho were not inhibited by rapamycin. The potentiating effects of bombesin and zinc on insulin plus PCho-induced DNA synthesis were accompanied by large stimulation of p42 MAP kinase activity. The results indicate that in Swiss 3T3 cell cultures, synergistic stimulation of DNA synthesis by extracellular insulin and PCho via a p42 MAP kinase-dependent mechanism requires the presence of other growth regulatory agents, such as bombesin or zinc.

Calcineurin is essential for DNA synthesis in Swiss 3T3 fibroblasts

DNA synthesis was measured 16 h after stimulation of Swiss 3T3 fibroblasts in the resting phase with various growth factors (platelet-derived growth factor, fibroblast growth factor, lysophosphatidic acid and thrombin). When extracellular Ca2+ was chelated by EGTA, or when the influx of Ca2+ from outside to inside the cell was blocked by cobalt, DNA synthesis was completely inhibited. As there was no effect whatsoever on DNA synthesis when Ca2+ was chelated, or when the influx of Ca2+ was blocked up to the first 4 h after growth stimulation, it was concluded that, at an early stage, Ca2+ influx from outside to inside the cell is not related to the transition from the G1 to the S phase. A Ca2+/calmodulin-dependent protein kinase II inhibitor (KN-62) had no effect on DNA synthesis. However, cyclosporin A and FK-506, which are inhibitors of Ca2+/calmodulin-dependent protein phosphatase 2B (calcineurin), markedly inhibited DNA synthesis stimulated by all of the growth factors. These results indicate that calcineurin plays a role, not only in activation of T-cells of the immune system in the initial phase, but also in DNA synthesis in fibroblasts. It was concluded that Ca2+ influx from outside to inside the cell during the mid-to-late G1 phase, followed by calcineurin activation, is essential as a mechanism of growth signal transduction.

Compound D609 inhibits phorbol ester-stimulated phospholipase D activity and phospholipase C-mediated phosphatidylethanolamine hydrolysis

Tricyclodecan-9-yl-xanthogenate (compound D609) has recently been used in various cellular systems to specifically inhibit the activity of phosphatidylcholine (PtdCho)-directed phospholipase C (PLC). Here we show that in intact NIH 3T3 fibroblasts, concentrations of D609 (35 to 50 micrograms/ml) which have been used to inhibit PLC activity also significantly inhibit phorbol ester-induced phospholipase D-mediated hydrolysis of both PtdCho and phosphatidylethanolamine (PtdEtn). In addition, in isolated membranes compound D609 also inhibited PLC-mediated PtdEtn hydrolysis. The results indicate that compound D609 cannot be considered as a specific inhibitor of PtdCho-directed PLC activity.

Wortmannin has opposite effects on phorbol ester-induced DNA synthesis and phosphatidylcholine hydrolysis

The tumor promoter phorbol 12-myristate 13-acetate (PMA) and hormonal activators of protein kinase C (PKC) commonly stimulate phospholipase D (PLD)-mediated formation of phosphatidic acid from phosphatidylcholine (PtdCho) in fibroblasts and other cell types. On the basis that phosphatidic acid is a mitogen, PLD is often considered to have a major role in the regulation of cell growth by PKC activators. However, we found that in NIH 3T3 fibroblasts wortmannin, an inhibitor of phosphatidylinositol 3-kinase (PI3K), strongly inhibited DNA synthesis induced by 100 nM PMA, while it actually enhanced PMA-stimulated PtdCho hydrolysis. These results indicate that stimulation of PLD activity is either not required or not sufficient for the mitogenic action of PMA.

Synergistic potentiating effects of choline phosphate and ethanolamine on insulin-induced DNA synthesis in NIH 3T3 fibroblasts

In NIH 3T3 fibroblasts insulin is a much less potent mitogen than platelet-derived growth factor or fibroblast growth factor. Here we demonstrate that addition of choline phosphate (1 mM) or ethanolamine (1 mM) to these fibroblasts for a prolonged (16 h) period specifically and greatly enhanced, particularly when added in combination, the stimulatory effects of both insulin and insulin-like growth factor I on DNA synthesis. The results suggest that increased production of choline phosphate and ethanolamine, often observed in tumors and carcinogen-treated cells, may promote the mitogenic activity of insulin and insulin-like growth factor I.

Ethanol enhances the stimulatory effects of insulin and insulin-like growth factor-1 on DNA synthesis in NIH 3T3 fibroblasts

In practically all in vitro experimental systems examined so far, including embryonal fibroblasts, ethanol was shown to inhibit cell growth. Here we report that in NIH 3T3 fibroblasts, (patho)physiologically relevant concentrations (50-100 mM) of ethanol significantly (2- to 2.8-fold) enhanced the stimulatory effects of both insulin and insulin-like growth factor-1 on DNA synthesis. Ethanol had no major effects on the mitogenic effects of platelet-derived growth factor, fibroblast growth factor and lyso-phosphatidic acid. These data suggest that ethanol is not a universal inhibitor of cell growth.

Wortmannin inhibits carcinogen-stimulated phosphorylation of ethanolamine and choline

We have previously reported that in C3H/10T1/2 fibroblasts the environmental carcinogen 7,12-dimethyl-benz[a]anthracene (DMBA) stimulated phosphorylation of ethanolamine (Etn). Here we show that in these fibroblasts DMBA also stimulates phosphorylation of choline (Cho). Wortmannin (50-200 nM), an established inhibitor of phosphatidylinositol-3-kinase (PI3K), significantly inhibited DMBA-induced phosphorylation of both Etn and Cho. Wortmannin also inhibited the effect of insulin, a major activator of PI3K, on DNA synthesis. However, insulin had no effect on the phosphorylation of Etn and Cho. These data suggest that a carcinogen-induced kinase phosphorylates both Etn and Cho, and that the inhibitory effect of wortmannin on Etn/Cho kinase activity may be unrelated to its inhibitory effect on PI3K activity.

Vitamin K3 preferentially inhibits stimulation of phospholipase D-mediated hydrolysis of phosphatidylethanolamine by protein kinase C activators in NIH 3T3 fibroblasts

Vitamin K3 (menadione), a synthetic vitamin K congener, inhibits the growth of tumor cells. Here, we examined possible effects of vitamin K3 on phospholipase D (PLD) activity, an enzyme which produces growth regulatory substances. In NIH 3T3 fibroblasts, vitamin K3 (50-100 microM) alone had no effect on PLD-catalyzed formation of phosphatidylethanol, a marker of PLD activity, but it slightly (10-21%) inhibited the stimulatory effect of phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC). Of the two major substrates of PLD, phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn), vitamin K3 (10-100 microM) preferentially inhibited PtdEtn hydrolysis when stimulated by PMA or platelet-derived growth factor, the latter being a hormonal activator of PKC. Vitamin K3 had no inhibitory effect on sphingosine- or staurosporine-induced hydrolysis of PtdEtn or PtdCho. Inhibition of PMA-induced PtdEtn hydrolysis by vitamin K3 was effectively reduced by both cysteine (1 mM) and reduced glutathione (1 mM) and was mimicked by the superoxide-generating xanthine/xanthine oxidase system. The results show that vitamin K3 preferentially inhibits the effects of PKC activators on PLD-mediated hydrolysis of PtdEtn by a mechanism which may involve oxidation of thiols in a critically important regulatory component.

Phorbol ester selectively stimulates the phospholipase D-mediated hydrolysis of phosphatidylethanolamine in multidrug-resistant MCF-7 human breast carcinoma cells

The phospholipase D (PLD)-mediated synthesis of phosphatidylethanol (PtdEtOH) and the hydrolysis of phosphatidylethanolamine (PtdEtn) and phosphatidylcholine (PtdCho) were examined in drug-sensitive and multidrug-resistant lines of MCF-7 human breast carcinoma cells. In drug-sensitive (MCF-7/WT) cells, the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) failed to enhance either the synthesis of PtdEtOH or the hydrolysis of either phospholipid. In the drug-resistant (MCF-7/MDR) cells, 100 nM PMA greatly enhanced both the synthesis of PtdEtOH (approximately 21-fold) and the hydrolysis of PtdEtn (approximately 29-fold), but had no effect on the hydrolysis of PtdCho. The PLD activators sphingosine and H2O2 were found to elicit only a slight (1.28-1.4-fold) stimulatory effect on PtdCho hydrolysis in both the MCF-7/WT and MCF-7/MDR cell types, and had only a small effect on PtdEtn hydrolysis in the MCF-7/WT cells as well. However, these agents significantly (approximately 2.6-3.5-fold) stimulated PtdEtn hydrolysis in the MCF-7/MDR cells. These data indicate that MCF-7/MDR cells contain a PtdEtn-specific PLD activity which can be selectively stimulated by PMA, sphingosine and H2O2.

Suppression of cytoplasmic Ca2+ response and protein secretion by oxidizing agents

The influence of the oxidizing agents (H2O2, KO2 and Vitamin K) on the action of vasopressin to guinea pig hepatocytes was investigated from the view-point of cytoplasmic Ca2+ concentration and protein secretion. 10 nmol/l vasopressin brought about increase in prothrombin secretion along with increase in the cytoplasmic Ca2+ concentration compared to the non-stimulation level. The pretreatment of the cells with 1 mumol/l of the oxidizing agents, however, led to suppression of Ca2+ elevation and inhibited the vasopressin-induced prothrombin secretion completely, while no leak if lactic dehydrogenase (LDH), Na+ and K+ were detected. The same results of the inhibition in fibrinogen and albumin secretion were observed. These results suggested a possibility that the oxidizing agents such as the peroxides act on some site of cellular signal transduction system in cell membrane to reduce the cytoplasmic Ca2+ level and to suppress the vasopressin-induced secretion.

The effect of oxidizing agents on cell division and shape

Certain oxidizing agents such as vitaminK(VK) and lipid peroxides were found to suppress an increase in cytoplasmic Ca2+ concentration by growth factors, and inhibit on cell proliferation. These oxidizing agents induced a marked change in cell shape. In a detailed analysis of each phase in the cell cycle, the inhibition of an increase in cytoplasmic Ca2+ and cell division occurred only when the agents were added at G0/G1 phase. The addition to S or M phase cells did not influence in cytoplasmic Ca2+ and cell division. These experimental results suggest that these oxidizing agents may inhibit the transfer of stimulation signals from growth factors by acting on cell membrane sites and suppress subsequent DNA replication and mitotic division.

[Effect of active oxygen on cytoplasmic Ca2+ sequestration mechanism]

Effects of the active oxygen on the extrusion mechanism of once-increased cytoplasmic Ca2+, which causes various physiological phenomena, were investigated using different kinds of culture cells. First we found that, in response to stimulation with vitamin K (VK), various culture cells showed a decrease in cytoplasmic Ca2+ concentration. On the presumption that this phenomenon might be related to the oxidizing action of VK, we performed the same experiments using oxidizing agents such as H2O2 or KO2. They also showed a decrease in cytoplasmic Ca2+ concentration. Furthermore, they suppressed the increase of cytoplasmic Ca2+ by vasopressin. It would be inferred from these results that the active oxygen may act upon some site of the cellular signal transduction system of cell membrane to lower the cytoplasmic Ca2+ level.

Formation of lambda transducing phage in vitro: involvement of DNA gyrase

We found that transducing phages carrying the gal or bio regions of the Escherichia coli genome were formed during in vitro packaging of endogenous lambda DNA. Structural analysis of the transducing phage genomes indicated that they were formed by abnormal excision of lambda prophage. Formation of transducing phages was stimulated by oxolinic acid, an inhibitor of DNA gyrase, implying that DNA gyrase participates in the abnormal excision of lambda prophage. When pBR322 DNA was added to the reaction mixture, transducing phages into which pBR322 had been inserted were produced at a high frequency. This reaction was also stimulated by oxolinic acid. Sequence analyses revealed that pBR322 is inserted into the sites of abnormal excision of the prophage. These results show that transducing phages can be formed by DNA gyrase-dependent illegitimate recombination in an in vitro system and that secondary recombination takes place frequently at the site where the first recombination occurs.

Calmodulin antagonists inhibit the phagocytic activity of cultured Kupffer cells

The mechanism of phagocytosis by Kupffer cells is still unknown. In this study we found that trifluoperazine, chlorpromazine, and W-7, drugs which bind to Ca2+-calmodulin and inhibit its interaction with other proteins, inhibit phagocytosis by cultured Kupffer cells using polystyrene beads, time-lapse VTR systems, and fluorescent staining techniques. Inhibitory effects of these drugs on phagocytosis suggests that the Ca2+-calmodulin system may be involved in this complex cellular function and the integrity of the cytoskeletal system of Kupffer cells is essential to this phenomenon.

Bile canalicular contraction in the isolated hepatocyte doublet is related to an increase in cytosolic free calcium ion concentration

Dynamic contractions of bile canaliculi have been observed in cultured doublet hepatocytes by means of time-lapse cinephotomicrography, and this contractile movement plays an important role in bile secretion. Although details of the mechanism are still unknown, the Ca2+-calmodulin system is believed to play a main role in this mechanism. In this study we measured the intracellular Ca2+ concentration of individual doublet hepatocytes using the Ca2+ indicator "fura 2" and microscopic fluorometry. We also observed the effects of A23187, norepinephrine and epinephrine on bile canalicular contraction and intracellular Ca2+ concentration. After loading 1 mumol/l fura 2 in doublet cells, we added A23187, epinephrine or norepinephrine and then measured the Ca2+ concentration in a given small area in the cytoplasm of individual doublet cell. A23187, norepinephrine and epinephrine caused a prompt increase of the intracellular Ca2+ concentration and also caused bile canalicular contraction. The present study indicates that the sudden increase of intracellular Ca2+ concentration causes bile canalicular contraction through the Ca2+-calmodulin system.

Microscopic fluorometric analysis of Na-fluorescein transport in the smallest secretory unit (couplet hepatocytes) and the effects of cytochalasin B

The uptake and secretion of sodium fluorescein by couplet hepatocytes was examined in primary culture. When sodium fluorescein was added at an early stage of primary couplet hepatocytes culture, this resulted in a rapid uptake of the dye and its subsequent accumulation in bile canaliculi. From microscopic fluorometry observations, cytochalasin B pretreatment of the couplet hepatocytes caused much more rapid uptake and secretion of the dye in bile canaliculi. The present study indicates that the cholestatic agent cytochalasin B causes choleresis at the bile canalicular level of cultured couplet hepatocytes and also indicates that a defect in canalicular secretion plays no role in the cytochalasin B-induced impairment of bile flow.

Guillain-Barré syndrome associated with acute hepatitis A

A case of Guillain-Barré syndrome in a 49-year-old male is described. The syndrome presented as tetraplegia with sensory impairment and the pre-icteric phase of acute hepatitis A. Both viral hepatitis and neurologic disturbances improved, although neurologic changes lasted for 3 months after the onset. HA IgM antibody in cerebrospinal fluid was first manifest with onset of neurologic symptoms. On the basis of this finding and some reports in the literature it seems possible that the Guillain-Barré syndrome may be related to the immunopathogenetic mechanism of hepatitis A virus infection.