Combination acetaminophen and doxapram potentiated hepatotoxicity in mouse primary cultured hepatocytes

Doxapram-induced potentiation of acetaminophen-induced reductions in cell viability and apoptosis was examined in mouse primary cultured hepatocytes. Loss of viability following exposure of acetaminophen and/or doxapram in cultured hepatocytes was assessed by monitoring [3H]-thymidine incorporation and mitochondrial activity, and apoptosis of hepatocytes was determined by nuclear microscopic observation and from detection of a ladder-like DNA fragmentation pattern in agarose gel electrophoresis. The combination of acetaminophen (5 mM) and doxapram (10, 20, 50 or 100 microM) potentiated the reduction in cell viability and increased lipid peroxide levels of hepatocytes. Hepatocytes exposed for 24 h to acetaminophen (5 mM) plus doxapram (100 microM) showed atrophy of nuclei including chromatin condensation and a ladder-like DNA fragmentation pattern characteristic of apoptosis. Antioxidant (N-acetylcysteine), iron-chelator (deferoxamine), intracellular calcium ion chelator (quin 2-AM), endonuclease inhibitor (aurintricarboxylic acid) and poly (ADP-ribose) polymerase inhibitor (3-aminobenzamide) all improved the viability of cells and eliminated the ladder-like DNA fragmentation in cells exposed to acetaminophen plus doxapram. In conclusion, the combination acetaminophen and doxapram potentiated the reduction in cell viability and apoptosis in mouse primary cultured hepatocytes. We suggest that careful observation for hepatotoxicity is recommended when acetaminophen and doxapram are prescribed simultaneously.

Exposure to hydrogen peroxide induces cell death via apoptosis in primary cultured mouse hepatocytes

To investigate whether direct oxidant damage induces hepatotoxicity via an apoptotic cell suicide pathway, we exposed primary cultured mouse hepatocytes to pro-oxidant hydrogen peroxide. We demonstrate that brief exposure to a concentration of hydrogen peroxide (3 mM) can induce hepatocyte cell death via apoptosis as shown by toxicity assays, specific DNA staining, and the appearance of DNA laddering on agarose gels. When hepatocytes were treated with N-acetylcysteine 15 min prior to hydrogen peroxide exposure, the cells were found to be protected from cytotoxicity and apoptosis. These results suggest that direct oxidative injury serves as a general trigger for apoptosis in the liver, and that other apoptotic stimuli, such as exposure to acetaminophen, also involve oxidative injury. Hydrogen peroxidase-induced apoptosis may serve as a valuable model for further studies of apoptosis in the liver.

Tandem repeat structure of rhamnose-binding lectin from catfish (Silurus asotus) eggs

The primary structure of catfish (Silurus asotus) egg lectin (SAL) was determined. SAL cDNA contained 1448-bp nucleotides and 308 amino acid residues, deduced from open reading frame. The SAL mature protein composed of 285-amino acid residues was followed by a predicted signal sequence having 23 residues. The mRNA of SAL was found to be expressed in eggs, but not in liver. SAL is composed of three tandem repeat domain structures divided into exactly 95 amino acid residues each, and all cysteine positions of each domain were completely conserved. Sequence homologies between the three domains, termed D1 (1-95), D2 (96-190) and D3 (191-285), were as follows; D1-D2, 28%; D2-D3, 33%; D1-D3, 43%. Two conserved peptide motifs, -(AN)YGR(TD)S(T)XCS(TGR)P- and -DPCX(G)T(Y)KY(L)-, appear to exist at the N- and C-terminal regions of each domain, respectively. The kinetic parameters of SAL obtained by measuring surface plasmon resonance were as follows: K(a) (M(-1)) for neohesperidosyl-BSA, 7. 1 x 10(6); for melibiosyl-BSA, 4.9 x 10(6); and for lactosyl-BSA, 5. 2 x 10(5). These results show that RBLs including SAL comprise a family of alpha-galactosyl binding lectins having characteristic tandem repeat domain structures.

Hot water extract of bark of Nikko maple (Acer nikoense) induces apoptosis in leukemia cells

In screening for antitumor constituents in traditional crude drugs, we used three cultured cell lines: mouse leukemia P388 cells, doxorubicin-resistant P388 cells and leczyme (catalytic lectin)-resistant P388 cells. The hot water extract (HWE) of the bark of Nikko maple (Acer nikoense) showed concentration-dependent inhibitory effects on the growth of these three cell lines. DNA fragmentation and morphological changes, accompanied by condensed and fragmented nuclei, were observed in the leukemia cell lines cultured with HWE of the bark of Nikko maple. Treatment with this HWE increased the expression of sialylated glycoconjugates on the apoptotic cells. These results suggest that HWE induces cell death via apoptosis in vitro.

Potentiation of acetaminophen hepatotoxicity and mortality by doxapram in mice

Whether a single dose of doxapram (DOP) can modulate the acute toxicity and the hepatotoxicity induced by acetaminophen (AA) was examined. Pretreatment with DOP (40 mg/kg, i.p.) 30 min prior to the administration of AA dose-dependently potentiated the lethality of AA in both native mice and mice fasted for 18 h, and the potentiating activity was greater in fasted mice than in native mice. The hepatotoxicity of AA was assessed by plasma transaminases activity (glutamyl oxaloacetic transaminase, GOT; glutamyl pyruvic transaminase, GPT) and the amount of plasma lipid peroxides at 6, 12, 18, 24, 36 and 48h after the administration of AA and histopathological examination of liver sections at 24 h after the administration of AA. DOP (40 mg/kg, i.p.) did not increase the plasma transaminase activity or the lipid peroxides level significantly, whereas AA administration to DOP-treated animals produced earlier maximal elevation of transaminase and lipid peroxide values compared to AA alone. These findings indicate that mortality and hepatotoxicity of AA is potentiated by DOP in mice.

Thalidomide promotes the release of tumor necrosis factor-alpha (TNF-alpha) and lethality by lipopolysaccharide in mice

We investigated the in vivo effects of thalidomide on the production of tumor necrosis factor-alpha (TNF-alpha). An in vivo systemic release of TNF-alpha occurred after the injection of lipopolysaccharide (LPS) in male ddY mice, and the TNF-alpha serum levels reached 652.2 +/- 75.7 pg/ml 90 min after the injection of LPS (0.3 mg/kg, i. p.). When thalidomide (1, 3, or 6 mg/kg) was administered intraperitoneally 3 h before the injection of LPS (0.3 mg/kg, i. p.), thalidomide markedly enhanced LPS-induced TNF-alpha release in a dose-dependent manner. The TNF-alpha serum levels at 90 min were 640 +/- 58.6, 1985 +/- 132.6, and 2795 +/- 203.5 pg/ml, respectively, compared to 628.6 +/- 64.4 pg/ml in mice treated with LPS-alone. Pretreatment with a single injection of thalidomide (1, 3, or 6 mg/kg, i. p.) dose-dependently increased the subsequent mortality caused by a challenge with LPS (15 mg/kg, i. p.), a dose that caused death in 10% of the control mice. We conclude that thalidomide enhances in vivo TNF-alpha secretion and the lethality of LPS in mice.

Cepharanthine inhibits proliferation of cancer cells by inducing apoptosis

Cepharanthine, a biscoclaurine alkaloid extracted from Stephania cepharantha Hayata was examined for a possible apoptosis-inducing effect in murine P388 doxorubicin-sensitive (P388/S) and -resistant (P388/DOX) cells. A significant increase in LDH release from cells was observed after P388/S and P388/DOX cells had been exposed to cepharanthine for 24 h. Cepharanthine (10 micrograms/ml) markedly induced apoptosis in resistant cells after 6 h and 24 h. By the means of agarose electrophoresis the DNA ladder was detected in cell lines treated with cepharanthine for 24 h. Cepharanthine (1-10 micrograms/ml) also induced the production of reactive oxygen species in P388/DOX cells, while no such cepharanthine-induced increase in reactive oxygen species was observed in P388/S cells. Flow cytometry analysis showed a high level of Fas-antigen expression in P388/DOX cells treated with cepharanthine. Furthermore, we found that the inhibitition of DNA and protein synthesis caused by cepharanthine (10 micrograms/ml) was more significant in resistant cells than in sensitive cells. Cepharanthine had no effect on the GSH content of P388/S and P388/DOX cells. Our experimental results suggest that cepharanthin can induce apoptosis both in P388/S and P388/DOX cells, especially in the latter. Apoptosis induced by cepharanthine may be implicated in the production of reactive oxygen species and Fas-antigen expression in tumor cells.

Apoptotic cell death induced by physarumin (hemagglutinin from myxomycete, Physarum polycephalum)

Physarumin, a carbohydrate-binding protein (hemagglutinin or lectin), was isolated from the plasmodium of Physarum polycephalum. Physarumin agglutinated not only several species of erythrocytes but also tumor cells such as AH109A ascites hepatoma cells, sarcoma 180 ascites cells and mouse leukemia P388 cell lines. Physarumin had tumor cell growth-inhibitory activity, and induced the apoptosis of P388 cell lines. Physarumin-induced apoptosis required binding to a 68 kDa counter-receptor on the P388 cell surface. Since the agglutinating and antiproliferative activities of physarumin were inhibited by asialofetuin and thyroglobulin, respectively, it is suggested that physarumin reacts with the galactose moiety of carbohydrate chains of physarumin receptor.

Potentiation of pirarubicin activity in multidrug resistant cells by rifampicin

The effect of the anti-tuberculosis drug rifampicin on pirarubicin activity was investigated in multidrug-resistant cells overexpressing P-glycoprotein. Rifampicin increased the sensitivity of pirarubicin to anthracycline-resistant mouse leukemic P388 cells and significantly enhanced the cytotoxicity and intracellular accumulation of pirarubicin in resistant cells, but had no effect in parent cells. By contrast, two other rifamycins, rifamycin B and SV, had no effect on pirarubicin accumulation in resistant cells. Rifampicin also enhanced pirarubicin-induced apoptosis and G2/M blockade on the cell cycle in resistant cells. These results show that rifampicin enhances the cytotoxic action of pirarubicin in resistant cells, at least partly via the inhibition of cellular pirarubicin efflux.

Reversal of multidrug resistance by tacrolimus hydrate

Tacrolimus hydrate, a potent immunosuppressant produced by Streptomyces tsukubaensis, was examined for its effect on epirubicin activity in multidrug-resistant P388 leukemia (P388/R) cells overexpressing P-glycoprotein and the parent (P388/S) cells. In the absence of modulator, the 50% inhibitory concentration for epirubicin after 48-h incubation, determined using a microculture tetrazolium assay, was 0.8 microgram/ml in P388/R cells and 0.009 microgram/ml in P388/S cells. P388/R cells demonstrated a 90-fold reduction in sensitivity to epirubicin. Tacrolimus hydrate (1 and 10 microM) markedly enhanced epirubicin cytotoxicity by 4.2- and 26.7-fold for P388/R cells. A significant increase in LDH release from cells by tacrolimus hydrate was also observed in P388/R cells treated with epirubicin. Tacrolimus hydrate had a marked effect on epirubicin-induced G2/M blockade in the resistant cells. Both tacrolimus hydrate and cyclosporin A dramatically increased the accumulation of epirubicin by the resistant cells, while these compounds had no effect on epirubicin accumulation in the parent cells. Thus, tacrolimus hydrate is able to down-modulate P-glycoprotein-associated resistance through inhibition of P-glycoprotein function, suggesting that the drug may be a candidate for killing drug-resistant tumor cells.

The enhancing effect of tumour necrosis factor-alpha on oxidative stress in endotoxemia

The enhancing effect of tumour necrosis factor-alpha (TNF-alpha) on oxidative stress with or without a sublethal dose of endotoxin was examined. The mortality of mice treated with recombinant human TNF-alpha (1 x 10(4) units/mouse, intravenously) and endotoxin (0.01-1 mg/kg, intraperitoneally) was dependent on the dose of endotoxin. The liver lipid peroxide level, superoxide anion generation and serum lactate dehydrogenase activity, especially serum lactate dehydrogenase-5 isozyme leakage, in mice 2-4 hr after administration of recombinant human TNF to endotoxin-pretreated mice (0.5 mg/kg, intraperitoneally) were markedly higher than in those without endotoxin, whereas the administration of recombinant human TNF significantly decreased the non-protein sulfhydryl level, superoxide dismutase and glutathione peroxide activities in the liver of endotoxin-injected mice compared with those in mice treated with recombinant human TNF or endotoxin alone. Furthermore, findings clearly demonstrated that J774A.1 cells stimulated with recombinant human TNF (1 x 10(4) units/ml) can effectively produce nitric oxide in the presence of endotoxin, and the production was dependent on the dose of endotoxin (0.01-10 micrograms/ml). The level of lipid peroxide in mice 4 hr after administration of recombinant human TNF and lead acetate (50 mg/kg, intravenously) was markedly higher than that in the mice treated with recombinant human TNF alone. By contrast, injection of polymyxin-B (20 mg/kg, intraperitoneally, an anti-endotoxin drug) markedly decreased the lipid peroxide level in the liver of the mice treated with recombinant human TNF and lead acetate. These findings suggest that the oxidative stress caused by TNF occurs as a enhancing effect of endotoxin or by bacterial translocation from the intestinal gut under reduction of reticuloendothelial system function in various disease states, and that the effect of TNF may cause a marked increase of toxicity of oxidative stress by endotoxin.

Effects of antitumor activity and protection of shock symptoms by a traditional Chinese medicine (sho-saiko-to) in recombinant human tumor necrosis factor administered mice

The effects of a traditional Chinese medicine Sho-saiko-to (Kampo prescription) were investigated on the various metabolic disorders and antitumor activity of recombinant human tumor necrosis factor (rhTNF) administered to mice. The glycogen level in liver of rhTNF (5 x 10(4) units/mouse, i.v.)-injected mice was markedly lower at 4 h post-intoxication than that in the control, whereas the administration of rhTNF to Sho-saiko-to (500 mg/kg/d, p.o.)-pretreated mice resulted in a greater level of glycogen than that in rhTNF alone-treated mice. In mice pretreated with Sho-saiko-to, the level of fibrinogen 4 h after rhTNF injection markedly increased as compared to that in mice treated with rhTNF alone. We also estimated the NO2 in murine macrophage cell line J774A.1 using mice serum after administration of Sho-saiko-to. Our results clearly demonstrated that J774A.1 cells stimulated with endotoxin (1 micrograms/ml) and rhTNF (1 x 10(4) units/ml) can effectively produce nitric oxide (NO), and ascertained the suppressive effect of Sho-saiko-to (500 mg/kg/d, p.o)-pretreated serum on NO generation by endotoxin/TNF-activated J774A.1 cells. When the cells were incubated with endotoxin/TNF and Sho-saiko-to pretreated serum (10-100 microliters), the NO level was significantly lower than that in control serum incubated with endotoxin/TNF alone. The effect of Sho-saiko-to (1 and 10 micrograms/ml) on in vitro cytotoxicity by rhTNF in Meth-A Sarcoma cells was observed to be in a dose dependent fashion. In addition, there was a remarkable enhancement of antitumor activity of rhTNF by Sho-saiko-to pretreatment in mice. These findings suggest that the Kampo prescription Sho-saiko-to may protect mice from severe shock syndrome by rhTNF, and that it may enhance rhTNF-induced activity.

[Studies on reversing effect of multidrug resistance by dipyridamole. I. modulation of epirubicin-induced effects on cell proliferation and cell cycle by dipyridamole]

Dipyridamole, a nucleoside membrane transport inhibitor, enhanced the cytotoxicity of epirubicin for mouse leukemia P388 cells by a factor of 1.8-fold and that for 30-fold doxorubicin-resistant sublines of P388 cells (P388/DOX) by a factor of 6.5-fold. This interaction was shown to be truly synergistic by DNA histogram and median effect analysis. The dipyridamole enhancement of the cytotoxicity of epirubioin was a dose-dependent effect; it was greatest when cells were exposed to dipyridamole before treatment with epirubicin. In cell cycle experiments, 1-5 microM dipyridamole increased the accumulation of G2 + M phase produced by the treatment with 0.5-1 microM epirubicin. Dipyridamole, however, did not appear to alter the patterns of DNA histogram in sensitive cells. These results suggest that the increase of the accumulation of G2 + M phase in resistant cells is an important factor for the interaction between epirubicin and dipyridamole.

Augmentation of epirubicin cytotoxicity by cycloheximide

The effect of cycloheximide (CH) on the cytotoxic activity of the anthracycline antibiotic epirubicin (EPI) was examined in cell cultures of murine leukemia doxorubicin (DOX)-sensitive P388 and -resistant P388 cells. The addition of CH (0.002 mu g/ml) to the growth medium markedly enhanced the EPI-induced cytotoxic effect in sensitive cells as well as that observed in resistant cells. CH, however, did not affect the intracellular content of EPI. The inhibition of DNA synthesis in leukemia cells was remarkable with the combination of EPI and CH compared with each drug alone. These results suggest that the combination of EPI and CH appears to be useful in killing mouse leukemia cells.

Inhibition of doxorubicin-induced cell death in vitro and in vivo by cycloheximide

We studied the effects of the protein synthesis inhibitor, cycloheximide (CH), on cell killing by doxorubicin (DOX) in vitro and in vivo. At the concentration of CH used (1 microgram/ml) the cytotoxicity of DOX was reduced in cultured P388 leukemia cells. An analysis of the DNA histogram obtained by flow cytometry showed that DOX exerts its growth-inhibitory effect by blocking the cell cycle at the G2/M phase in P388 cells. Treatment with CH diminished this blocking effect. When CH was added to the growth medium before DOX exposure, no change in intracellular DOX accumulation was observed. Treatment with CH (15 mg/kg) significantly diminished the lethality of DOX (20 mg/kg) in mice and it also reduced the antitumor activity of mice with P388 leukemia. Thus, CH inhibited cell death induced by DOX in vitro and in vivo. These results suggest that CH has an antagonistic effect on the pharmacological actions of DOX in cells and mice. The cytoprotective effect of CH may be due to protein synthesis inhibition.

Effect of glutathione depletion by buthionine sulfoximine on doxorubicin toxicity in mice

The role of the glutathione (GSH) system in vivo or in drug resistance has received much attention, since GSH is a major component of the cellular detoxification system. We Studied the effect of GSH depletion by buthionine sulfoximine (BSO), a potent inhibitor of gamma-glutamylcysteine synthetase, on doxorubicin (DOX) toxicity in mice. The administration of BSO (30 mM in drinking water for 5 days) significantly decreased the tissue GSH. The GSH depletion in various tissues by BSO was associated with a decrease in the detoxification of DOX in mice. A single dose of 20 mg/kg of DOX significantly reduced body weight and rectal temperature in mice 3 days after injection. The combination with BSO and cepharanthine (biscoclaurine alkaloid), a P-glycoprotein (P-gp) inhibitor, significantly potentiated decrease in body and hypothermia induced by DOX. The study demonstrates that BSO markedly increases the toxicological effect of DOX with the alterations in GSH of tissues and Suggests that the intracellular accumulation of DOX is not a factor.

Depressive effect of a traditional Chinese medicine (sho-saiko-to) on endotoxin-induced nitric oxide formation in activated murine macrophage J774A.1 cells

The present study investigated whether or not Sho-saiko-to (crude powder extract, TJ-9) can suppress nitric oxide (NO) generation by endotoxin-activated J774A.1 cells in order to study the preventive mechanism of Sho-saiko-to against endotoxemia. In this experiment, we estimated the NO2- in the murine macrophage cell line J774A.1 using the Griess method. Our results clearly demonstrated that J774A.1 cells stimulated with endotoxin (0.01-10 micrograms/ml) can effectively produce NO, and the production was dependent on the dose of endotoxin. On the other hand, we investigated the suppressive effect of TJ-9 (10-100 micrograms/ml) on NO generation by endotoxin (0.1 microgram/ml)-activated J774A.1 cells. The NO level when the cells were incubated with endotoxin and TJ-9 (10-20 micrograms/ml) was slightly lower than that in cells treated with endotoxin alone. In contrast, treatment with TJ-9 (50-100 micrograms/ml) significantly inhibited endotoxin-activated NO generation in J774A.1 cells, whereas the treatment with TJ-9 (10-100 micrograms/ml) alone was ineffective in inducing NO formation and in inhibiting cell viability in the J774A.1 cells. These findings suggest that a Kampo presciption of Sho-saiko-to shows a suppressive effect on NO generation in macrophages stimulated with endotoxin, and that it may be useful in improving endotoxin-shock symptoms.

Protection against cisplatin lethality and renal toxicity by chlorpromazine in mice

The effect of chlorpromazine on acute lethal toxicity and nephrotoxicity induced by cisplatin was studied in mice. Chlorpromazine (i.p.) given 1 h before cisplatin greatly reduced lethal and renal toxicities of cisplatin, while chlorpromazine did not reduce the antitumor activity of cisplatin against sarcoma 180 in ddY mice or El-4 leukemia in C57BL/6J mice.

Structure of the 5' upstream region and the regulation of the rpoS gene of Escherichia coli

The nucleotide sequence of the 5' upstream region of the Escherichia coli rpoS gene was determined and analyzed. At least four promoters responsible for rpoS transcription were identified, and designated P1, P2, P3 and P4, P1 being furthest from the upstream. Using lacZ fusion genes, the P2 promoter was found to be the strongest of the four. All of these promoters are regulated similarly, and their activity is enhanced 2 to 3-fold in stationary phase. P1 and P2 transcription start sites were determined by primer extension analyses. The P2 promoter region shows similarity to the consensus sigma 70-type promoter sequence, and was recognized by both E sigma 70 and E sigma 38 holoenzymes in vitro. The mRNA transcribed from the most distal promoter, P1, appears to include another open reading frame (orf-281), indicating that the two open reading frames comprise an operon. The rpoS gene product (sigma 38) was rapidly degraded after addition of chloramphenicol to cultures in the exponential, but not the stationary phase. This strongly suggests that posttranslational regulation is involved in the control of rpoS expression.

Drug interaction effects on antitumour drugs (XV): Disulfiram as protective agent against cyclophosphamide-induced urotoxicity without compromising antitumour activity in mice

The prevention of cyclophosphamide-induced urotoxicity by disulfiram was studied in mice. A single dose of cyclophosphamide (100-400 mg/kg, intraperitoneally) produced a significant dose-dependent increase in urinary bladder weight within 48 hr of treatment. Disulfiram prevented cyclophosphamide-induced bladder damage in a dose-dependent manner in mice when orally administered simultaneously with antitumour agents, but failed to diminish the acute toxicity, leukocytotoxicity and immunotoxicity of cyclophosphamide. The protective effect of disulfiram on the bladder was critically dependent on administration timing. Oral administration of disulfiram between 60 min. before and 60 min. after the injection of cyclophosphamide was found to be effective. The optimum time was simultaneous administration of both drugs. Diethyldithiocarbamate and carbon disulfide, metabolites of disulfiram, prevented cyclophosphamide-induced bladder damage when administered simultaneously with cyclophosphamide 1 to, 3 or 5 hr afterwards. Disulfiram slightly potentiated the antitumour activity of cyclophosphamide against Sarcoma 180 or EL-4 leukaemia in vivo when administered simultaneously with cyclophosphamide. In contrast, diethyldithiocarbamate or carbon disulfide did not interfere with cyclophosphamide antitumour activity when administered 3 hr after cyclophosphamide. From these preliminary studies, disulfiram appears to be a likely candidate for protection against cyclophosphamide-induced urotoxicity without compromising the therapeutic utility of the alkylating agent.

Inhibition of cell proliferation by Rana catesbeiana and Rana japonica lectins belonging to the ribonuclease superfamily

Two frog egg lectins [Rana catesbeiana lectin (SBL-C) and Rana japonica lectin] preferentially agglutinate a large variety of human and animal tumor cells but not blood cells, lymphocytes, or fibroblasts. These lectins belong to the superfamily of pyrimidine base-specific RNases. The two lectins bound to a heparin-Sepharose column and were eluted from the column by an increase of NaCl molarity. Both their tumor cell-agglutinating activity and RNase activity were inhibited by heparin, and also by polyamines, such as spermine. Both lectins inhibited P388 leukemia cell proliferation. The inhibitory activity of SBL-C was blocked by addition of heparin. SBL-C inhibited protein synthesis by P388 cells, but RNase A did not. No lectin-induced antiproliferative effect was observed after sialidase treatment of cells. The antiproliferative activity of SBL-C was also inhibited by ammonium chloride treatment. These results suggest that internalization of the lectins by lectin receptor (sialoglycoconjugate)-mediated endocytosis is followed by cell death due to inhibition of protein synthesis. Administration of SBL-C i.p. delayed time to death in mice receiving i.p. transplants of Sarcoma 180 and Mep II cells.

[Partial purification and properties of deoxyribonucleases from eggs and liver of Xenopus laevis. Comparison with deoxyribonuclease II from bovine spleen]

Deoxyribonucleases from eggs and the liver of Xenopus laevis were partially purified by DEAE-cellulose and heparin-Sepharose affinity column chromatographies. The fractions having egg and liver DNase activities were eluted on high performance liquid chromatography through TSK gel G3000SW at the molecular weights of 41.5 and 45 kDa, respectively. The frog DNases hydrolyzed a native DNA over a heat-denatured DNA, and also formed double-strand cuts not only in linear lambda-DNA but also in closed circular pBR322DNA. The pH optimum of the DNases was 4.5-5.0 in 50 mM acetate buffer. These enzyme activities were abolished by treatment at 80 degrees C for 5 min and pH 2, 3 or 12 for 1 h. The enzymes act in such a manner as deoxyribonuclease II (from bovine spleen)-type nuclease with respect to substrate specificity, optimum pH and cation dependence.

Drug interaction effects on antitumor drugs. XIII. Amelioration of cisplatin lethality and renal toxicity by chlorpromazine in mice

We investigated the possibility that chlorpromazine (CPZ), an antiemetic frequently used to control nausea and vomiting in cancer patients receiving chemotherapy, might modify the progression of the renal toxicity and lethality of cisplatin (CDDP). In mice the preadministration of CPZ (i.p.) 1 h prior to CDDP (i.p.) injection efficiently reduced not only the lethal toxicity, but also the renal (indicated by increased blood urea nitrogen values) and intestinal toxicity (indicated by the incidence of diarrhea) which are usually observed in mice treated with CDDP alone. To further study the apparent protective activity of CPZ against CDDP nephrotoxicity we chose rats a species more commonly used as a model for nephrotoxicity. In F344 rats, CPZ ameliorated CDDP-induced increases in blood urea nitrogen (BUN), urine glucose, protein and lactate dehydrogenase (LDH). The preadministration of CPZ had no observed effect on the antitumor activity of CDDP in mice inoculated i.p. with Sarcoma 180, EL-4 lymphoma, or P-388 leukemia cells. The present study suggest that CPZ may be of therapeutic benefit when used with CDDP. This study also provides a rational basis for the selection of antiemetic therapy.

Stationary phase-specific expression of the fic gene in Escherichia coli K-12 is controlled by the rpoS gene product (sigma 38)

The fic gene, near pabA located at 75 min of the Escherichia coli chromosome, was previously identified as the regulatory factor of cell division. In this paper we have examined how fic gene expression is controlled during the growth cycle using a fic-lacZ protein fusion plasmid (pFL1). Its expression was induced at stationary phase while it was nearly abolished in rpoSmutants. Using a RNase protection assay, fic transcript at stationary phase was detected in rpoS+ strains, but not in the rpoS mutants. Furthermore, primer extension analysis indicated that the fic transcript controlled by RpoS initiates at a G located 185 bp upstream from ATG of the fic coding region. Compared with the sigma 70 recognition sequence, the -10 region of fic promoter resembled the Pribnow box, but no homologous sequence was observed at the -35 region. These results were consistent with the characteristic sequence profile of fic promoter recognized specifically by RpoS in vitro, which is the only example of the type III promoter so far detected in vitro and in vivo.