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M T Huang

Publications and source records attributed to M T Huang.

At least 109 records · Page 6Linked to original sources
PubMed1991

Inhibitory effect of curcumin and some related dietary compounds on tumor promotion and arachidonic acid metabolism in mouse skin.

Topical application of curcumin, the major yellow pigment in turmeric and curry, has a potent inhibitory effect on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion in mouse skin. The structurally related compounds chlorogenic acid, caffeic acid and ferulic acid are less potent inhibitors. Curcumin is a potent inhibitor of TPA-induced ornithine decarboxylase activity and inflammation in mouse skin whereas chlorogenic acid, caffeic acid and ferulic acid are only weakly active or inactive. Curcumin is a potent inhibitor of arachidonic acid-induced inflammation in vivo in mouse skin, and this compound is also a potent inhibitor of epidermal lipoxygenase and cyclooxygenase activity in vitro. Although chlorogenic acid is only weakly active as an inhibitor of epidermal lipoxygenase activity and TPA-induced ear inflammation, it is more active than caffeic acid and ferulic acid. The inhibitory effects of curcumin, chlorogenic acid, caffeic acid and ferulic acid on TPA-induced tumor promotion in mouse skin parallel their inhibitory effects on TPA-induced epidermal inflammation and epidermal lipoxygenase and cyclooxygenase activities. Examination of the structural features of curcumin required for its biological activity indicate that free hydroxyl groups on the benzene rings are not required for inhibition of TPA-induced ornithine decarboxylase activity and inflammation in mouse skin.

Arachidonic Acid↗
PubMed1991

Cerebral blood flow and metabolic rate in the conscious, freely moving rat: the effects of hypercapnia, and acute ethanol administration.

We propose a simple method that can be used to measure cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2), and cerebral glucose consumption (CMRglu) in the conscious, freely moving rat. The method is based on the classical Kety-Schmidt approach, and uses a chronic cannula in the confluens sinuum. We tested the method by investigating the response of CBF, CMRO2, and CMRglu to hypercapnia and used the approach to investigate the effects of acute alcohol administration. Severe hypercapnia (PaCO2 approximately 80 mmHg) increased the CBF by a factor of 3.5, decreased the CMRO2 by 30%, and had no significant effect on the CMRglu. Under normocapnic conditions moderate blood alcohol levels (100-200 mg%) caused no significant effects on CBF, CMRO2, or CMRglu, but high blood alcohol levels (250-400 mg%) decreased all three parameters by approximately 25%. Under hypercapnic conditions high blood alcohol levels had no effect on CBF, CMRO2, and CMRglu.

Alcoholic Intoxication↗
PubMed1991

Simple validation for the hepatic venous cannula implanted chronically in conscious rats.

A method for the detection of vena caval contamination in blood taken from hepatic venous cannulas in conscious rats was described. The procedures included 1) bolus injection of tritiated water (50 microCi) through a cannula into the abdominal inferior vena cava and 2) continuous blood sampling (less than 0.2 ml) from the hepatic venous cannula for 2 min into a 180-cm piece of Tygon tubing, starting concurrently with tracer injection. The washout of tritium was determined from samples in 15-cm sections of Tygon tubing. Because circulation from the inferior vena cava to the hepatic vein is interceded by the systemic circulation, the washout of tritium from a valid hepatic venous cannula should resemble the pattern determined elsewhere in the systemic circulation. In the current study, the reference systemic washout was determined in the superior vena cava of a group of rats similarly injected with tritiated water in the inferior vena cava. The maximum of tritium washout derived from a valid hepatic venous cannula should fall in the range encompassed by one standard deviation of the mean of the maximum of the reference (1,400 to 1,930 cpm/sample). The maximum of the washout pattern derived from the invalid cannula, which lay adjacent to the site of injection, was expected to exceed this range. On the basis of these criteria, hepatic blood flow (HBF) was determined by sulfbromophthalein (BSP) extraction in groups of rats with valid and invalid cannulas. HBF in rats with valid hepatic venous cannulas was 2.58 +/- 0.15 in the conscious state and 2.76 +/- 0.26 ml.min-1.g wet wt-1 in the ketamine-anesthetized state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

In vivo portal-hepatic venous gradients of glycogenic precursors and incorporation of D-[3-3H]glucose into liver glycogen in the awake rat.

Male Wistar fed rats were chronically cannulated and fed ground chow for 2 h for 6 days. On the 7th post-operative day, blood was simultaneously drawn from the portal and hepatic veins over a 2-h feeding period. The position of the hepatic vein cannula was verified using a tritiated water washout technique. In separate experiments, 200 microCi of [3-3H]glucose was added to the food in order to determine the relative contribution of D-glucose and 3-C precursors to newly synthesized glycogen. The 22-h fasting plasma portal vein concentrations of D-glucose, L-lactate, and L-alanine were 4.8 +/- 0.03, 0.81 +/- 0.06, and 0.20 +/- 0.03 mM, respectively (n = 5). The fasting hepatic vein plasma concentrations were 5.1 +/- 0.2, 0.70 +/- 0.15 and 0.19 +/- 0.03 mM, respectively. The portal-hepatic vein gradients after 22 h were -0.24, +0.16, and +0.01 mM for D-glucose, L-lactate, and L-alanine, respectively. At 20 min after beginning the meal, the respective gradients were +2.2, +0.53, and +0.44 mM, indicating hepatic uptake of all glycogen precursors. Of the total carbon from the three major precursors entering the liver as C-6, D-glucose contributed 82%, while alanine and lactate contributed 18% at 20 min. As portal vein D-glucose and L-alanine levels exceeded 6.65 +/- 0.69 and 0.32 +/- 0.07 mM, respectively, the portal-hepatic venous gradient became positive and increased linearly with portal concentrations. The glycogen concentration in the liver increased from a 22-h fast value of 5 mumol of glucosyl units/g wet weight to 101 +/- 7 mumol/g 2 h after the meal. The mean specific activity of portal vein plasma of [3-3H]glucose was 11,490 +/- 1,180 dpm/mumol (+/- S.E.) and that in the glycogen isolated from liver was 8,175 +/- 785 dpm/mumol of glycosyl units 2 h after the meal. The specific activity of liver [3H]glycogen relative to glucose after the meal was 0.73 +/- 0.08. It was concluded that a minimum of 73% of the newly synthesized glycogen was formed from the uptake and direct phosphorylation of portal blood D-glucose by the liver without prior conversion of glucose to 3-C units.

Alanine↗
PubMed1990

Identification of epidermal cell subpopulations with increased ornithine decarboxylase activity following treatment of murine epidermis with 12-O-tetradecanoylphorbol-13-acetate.

Ornithine decarboxylase (ODC), the initial enzyme in the polyamine biosynthetic pathway, has been used as a marker for the hyperplasia that occurs following exposure of mouse epidermis to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Using flow cytometry in combination with polyclonal antibodies to ODC, we examined the levels of ODC-associated immunoreactive protein present within mouse epidermal cells at 4 and 24 h after a single topical application of TPA, as well as following chronic exposure to TPA and in papillomas. Basal levels of ODC-specific antibody binding were detectable in acetone-treated CD-1 mouse epidermis and were increased 3-fold at 4 h after TPA treatment. The amount of ODC antibody binding detected after exposure to 17 nmol TPA twice weekly for 3 weeks was similar to that detected within cells isolated from papillomas and was 2.5-fold higher than in cells isolated at 4 h after a single topical treatment of mice with TPA. These observations support the hypothesis that specific subpopulations of keratinocytes constitutively express high levels of ODC following chronic exposure to TPA. The novel method for ODC detection described in these studies provides a means to identify, isolate, and further characterize epidermal cells that may give rise to papillomas and carcinomas.

Animals↗
PubMed1990

Intervening sequences increase efficiency of RNA 3' processing and accumulation of cytoplasmic RNA.

Two expression vectors were constructed that differ only in the presence (+) or absence (-) of an intervening sequence (IVS) in their 5'-untranslated leaders. Transient transfection into four mammalian cell lines resulted in higher levels of the indicator protein (CAT) from the IVS(+) vector (6 to 50-fold). Cytoplasmic RNA concentrations in 293s and HeLa cell lines corresponded directly to resultant protein levels; measurements in 293s cells of transcription initiation and elongation, steady-state total nuclear RNA, and cytoplasmic RNA stability, were equivalent for the two vectors. Surprisingly, the amount of poly(A)+ nuclear RNA was greater from the IVS(+) vector. Since this difference matches the ratio seen with polyadenylated cytoplasmic RNA, our results imply that splicing is coupled to a polyadenylation/transport pathway.

Animals↗
PubMed1990

Flow cytometric detection of ornithine decarboxylase activity in epidermal cell subpopulations.

Using flow cytometry in combination with membrane permeabilization techniques to enhance binding of antibodies with immunoreactive protein within the cytoplasm, we have developed a method to examine the ornithine decarboxylase (ODC) activity present within subpopulations of epidermal cells following acute and chronic exposure to the phorbol ester tumor promoter 12-0-tetradecanoylphorbol-13-acetate (TPA). The method described has the sensitivity to detect basal levels of ODC as well as increases in ODC at early time points following treatment with TPA and has the additional advantage of allowing subpopulation identification and characterization.

Animals↗
PubMed1990

The simian virus 40 small-t intron, present in many common expression vectors, leads to aberrant splicing.

Polymerase chain reaction analysis was used to identify aberrant splicing of the simian virus 40 small-t intron present in pRSVcat. We examined factors governing the selection and relative use of aberrant 5' splice sites derived from the chloramphenicol acetyltransferase-coding region. Our results indicated that transcripts from virtually any cDNA positioned upstream of the small-t intron could contain alternative 5' splice sites and therefore be subject to deletions within the protein-coding region.

Animals↗
PubMed1989

Deuterium isotope effects on ethanol oxidation in perfused rat liver and in rats and rabbits in vivo: application to determine the contribution of various pathways.

The kinetic deuterium isotope effect, D(V/K), on ethanol oxidation was measured by the radiometric, competitive method using 14C-labelled ethanol containing deuterium in the (1-R) position. Acetate was isolated and used for the determination. Experiments were performed on rats either anaesthetized and laparotomized, or provided with indwelling catheters in a. carotis, v. cava and v. portae. Experiments were also made on perfused liver from rats pretreated with acetone, or a mixture of acetone and phenobarbital. Finally, intact non-anaesthetized rabbits were used. The apparent isotope effect in all in vivo experiments decreased rapidly in the presence of acetaldehyde as a consequence of the reversibility of the ADH reaction. In the case of rabbits and catheterized rats this problem was tackled by taking blood samples in quick succession, thus permitting extrapolation of the apparent isotope effect to the time of injection of the labelled ethanol. In anaesthetized rats injection of the ADH inhibitor isobutyramide was used to reduce the concentration of acetaldehyde and thereby the rate of decline of the apparent isotope effect. At high doses of isobutyramide the isotope effect was constant with time at about 1.9 suggesting the presence of non-ADH activity. In all three kinds of in vivo experiments the isotope effect ranged from 2.66 to 2.93. In the case of anaesthetized rats the mean value was 2.89 +/- 0.05 (S.D.). This figure is significantly different from that of rat liver ADH, P less than 0.001. As the figures for the initial isotope effects are minimum values the contribution of non-ADH ethanol oxidizing systems is likely to be small, probably less than 10 percent.

Acetaldehyde↗
PubMed1988

Inhibitory effect of curcumin, chlorogenic acid, caffeic acid, and ferulic acid on tumor promotion in mouse skin by 12-O-tetradecanoylphorbol-13-acetate.

The effects of topically applied curcumin, chlorogenic acid, caffeic acid, and ferulic acid on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced epidermal ornithine decarboxylase activity, epidermal DNA synthesis, and the promotion of skin tumors were evaluated in female CD-1 mice. Topical application of 0.5, 1, 3, or 10 mumol of curcumin inhibited by 31, 46, 84, or 98%, respectively, the induction of epidermal ornithine decarboxylase activity by 5 nmol of TPA. In an additional study, the topical application of 10 mumol of curcumin, chlorogenic acid, caffeic acid, or ferulic acid inhibited by 91, 25, 42, or 46%, respectively, the induction of ornithine decarboxylase activity by 5 nmol of TPA. The topical application of 10 mumol of curcumin together with 2 or 5 nmol of TPA inhibited the TPA-dependent stimulation of the incorporation of [3H]-thymidine into epidermal DNA by 49 or 29%, respectively, whereas lower doses of curcumin had little or no effect. Chlorogenic acid, caffeic acid, and ferulic acid were less effective than curcumin as inhibitors of the TPA-dependent stimulation of DNA synthesis. Topical application of 1, 3, or 10 mumol of curcumin together with 5 nmol of TPA twice weekly for 20 weeks to mice previously initiated with 7,12-dimethylbenz[a]anthracene inhibited the number of TPA-induced tumors per mouse by 39, 77, or 98%, respectively. Similar treatment of mice with 10 mumol of chlorogenic acid, caffeic acid, or ferulic acid together with 5 nmol of TPA inhibited the number of TPA-induced tumors per mouse by 60, 28, or 35%, respectively, and higher doses of the phenolic acids caused a more pronounced inhibition of tumor promotion. The possibility that curcumin could inhibit the action of arachidonic acid was evaluated by studying the effect of curcumin on arachidonic acid-induced edema of mouse ears. The topical application of 3 or 10 mumol of curcumin 30 min before the application of 1 mumol of arachidonic acid inhibited arachidonic acid-induced edema by 33 or 80%, respectively.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Comparison of the effect of sn-1,2-didecanoylglycerol and 12-O-tetradecanoylphorbol-13-acetate on cutaneous morphology, inflammation and tumor promotion in CD-1 mice.

Since sn-1,2-didecanoylglycerol mimics 12-O-tetradecanoylphorbol-13-acetate (TPA) by inducing ornithine decarboxylase activity and stimulating DNA synthesis in mouse epidermis [Smart, R.C., Huang, M.-T. and Conney, A.H. Carcinogenesis, 7, 1865 (1986)], we have investigated morphological changes induced by TPA and sn-1,2-didecanoylglycerol in the epidermis and we have also examined sn-1,2-didecanoylglycerol as a possible complete tumor promoter. It was determined that topical application of 2.5 or 10 mumol of sn-1,2-didecanoylglycerol induced epidermal ornithine decarboxylase activity to about the same extent as the application of 1 or 2 nmol of TPA respectively. Therefore, these doses of TPA and sn-1,2-didecanoylglycerol were used in most of our studies. Single or multiple application (2 X/week for 4 weeks) of 1, 2 or 5 nmol of TPA to the skin of CD-1 mice produced a dose-dependent increase in the number of epidermal non-cornified cell layers, epidermal thickness, leukocyte infiltration and intracellular edema. In contrast, neither single nor multiple application (2 X/week for 4 weeks) of 2.5 or 10 mumol sn-1,2-didecanoylglycerol produced any of these responses. However, when 5 mumol sn-1,2-didecanoylglycerol was applied topically twice a day (10 mumol/day) for 5 days there was a significant increase in the number of epidermal non-cornified cell layers and epidermal thickness. The effects of TPA and sn-1,2-didecanoylglycerol were compared using the mouse ear inflammation model. Application of TPA caused edema, but sn-1,2-didecanoylglycerol had little or no effect. sn-1,2-Didecanoylglycerol was then evaluated as a complete tumor promoter utilizing the mouse skin two-stage model. CD-1 mice were initiated with 200 nmol 7,12-dimethylbenz[a]anthracene and then treated with 1 nmol TPA or 2.5 mumol sn-1,2-didecanoylglycerol twice a week for 28 weeks. A 28 weeks, 28% of the mice treated with TPA had developed tumors, while none of the mice treated with 2.5 mumol sn-1,2-didecanoylglycerol developed tumors. The data indicate that topical application of 2.5 mumol sn-1,2-didecanoylglycerol induced ornithine decarboxylase activity to the same extent as a tumor-promoting dose of 1 nmol TPA, but it did not cause morphological changes in the epidermis when applied once or when applied twice a week for 4 weeks and did not function as a complete tumor promoter when applied twice a week for 28 weeks.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Role of the direct and indirect pathways for glycogen synthesis in rat liver in the postprandial state.

The pathway for hepatic glycogen synthesis in the postprandial state was studied in meal-fed rats chronically cannulated in the portal vein. Plasma glucose concentration in the portal vein was found to be 4.50 +/- 1.01 mM (mean +/- SE; n = 3) before a meal and 11.54 +/- 0.70 mM (mean +/- SE; n = 4) after a meal in rats meal-fed a diet consisting of 100% commercial rat chow for 7 d. The hepatic-portal difference of plasma glucose concentration showed that liver released glucose in the fasted state and either extracted or released glucose after feeding depending on plasma glucose concentration in the portal vein. The concentration of portal vein glucose at which liver changes from glucose releasing to glucose uptake was 8 mM, the Km of glucokinase [E.C. 2.7.1.12]. The rate of glycogen synthesis in liver during meal-feeding was found to be approximately 1 mumol glucosyl U/g wet wt/min in rats meal-fed a 50% glucose supplemented chow diet. The relative importance of the direct vs. indirect pathway for the replenishment of hepatic glycogen was determined by the incorporation of [3-3H,U-14C]glucose into liver glycogen. Labeled glucose was injected into the portal vein at the end of meal-feeding. The ratio of 3H/14C in the glucosyl units of glycogen was found to be 83-92% of the ratio in liver free glucose six minutes after the injection, indicating that the majority of exogenous glucose incorporated into glycogen did not go through glycolysis. The percent contribution of the direct versus indirect pathway was quantitated from the difference in the relative specific activity (RSA) of [3H] and [14C]-glycogen in rats infused with [3-3H,U-14C]glucose. No significant difference was found between the RSA of [3H]glycogen and [14C]glycogen, indicating further that the pathway for glycogen synthesis in liver from exogenous glucose is from the direct pathway. Our results do not support the thesis that the majority of liver glycogen is synthesized from glucose-6-phosphate derived from gluconeogenesis. Reasons for the discrepancy between current findings and other reports supporting the indirect pathway for glycogen synthesis in the liver are discussed.

Animals↗
PubMed1987

Inhibition of 12-O-tetradecanoylphorbol-13-acetate induction of ornithine decarboxylase activity, DNA synthesis, and tumor promotion in mouse skin by ascorbic acid and ascorbyl palmitate.

The effects of topically applied 12-O-tetradecanoylphorbol-13-acetate (TPA) on the level of ascorbic acid in the epidermis and the effects of topically applied ascorbic acid, ascorbyl palmitate (a synthetic lipophilic derivative of ascorbic acid), palmitic acid and sorbitan monopalmitate on TPA-induced epidermal ornithine decarboxylase activity, epidermal DNA synthesis, and the promotion of skin tumors were evaluated in female CD-1 mice. Topical application of 5 or 16 nmol of TPA resulted in a 45-50% decrease in the amount of ascorbic acid per mg protein in mouse epidermis at 5 h after TPA application. Large topical doses of ascorbic acid inhibited TPA-induced tumor promotion in mouse epidermis, but smaller doses were inactive. The topical application of relatively small doses of ascorbyl palmitate had a marked inhibitory effect on TPA-induced ornithine decarboxylase activity, DNA synthesis, and tumor promotion in mouse epidermis. Ascorbic acid, palmitic acid, and sorbitan monopalmitate were less effective than ascorbyl palmitate as inhibitors of tumor promotion. The topical application of 4 mumol of ascorbyl palmitate inhibited by 60-76% the induction of epidermal ornithine decarboxylase activity and DNA synthesis that occurred after a single topical application of 2 nmol of TPA whereas similar doses of ascorbic acid had no inhibitory effect. The topical application of 4 mumol of ascorbyl palmitate together with 5 nmol of TPA twice weekly for 20 weeks to previously initiated mice inhibited by 91% the number of tumors per mouse.

Administration, Topical↗
PubMed1986

Disposition of the naturally occurring antimutagenic plant phenol, ellagic acid, and its synthetic derivatives, 3-O-decylellagic acid and 3,3'-di-O-methylellagic acid in mice.

The effect of ellagic acid and some of its more lipophilic derivatives on the mutagenicity of (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenz[a]pyrene was examined in Salmonella typhimurium TA100. Ellagic acid, 3,3'-di-O-methylellagic acid, 4,4'-di-O-methylellagic acid and 3-O-decylellagic acid were found to have approximately equal antimutagenic activity. The tissue distribution and elimination of ellagic acid, 3,3'-di-O-methylellagic acid and 3-O-decylellagic acid were examined in CD-1 mice. Little or no ellagic acid (less than 1 nmol/g) was found in blood, lung or liver after the oral administration by gavage of 300 mumol of ellagic acid per kg body weight of after feeding 1% of ellagic acid in the diet for 1 week. Following the i.p. administration of 120 mumol/kg of ellagic acid, the blood and lung levels of ellagic acid were 15-20 nmol/g at 30 min after the dose, and the concentrations of ellagic acid decreased to 1-3 nmol/g at 6-8 h after the dose. A portion of the administered i.p. dose precipitated in the abdominal cavity. After i.v. administration, ellagic acid was eliminated very rapidly from blood, lung and liver, and approximately 70% of the administered dose was recovered in the urine and feces as free ellagic acid and its conjugates. At 2 h after an i.v. injection of 60 mumol/kg of ellagic acid, 46% of the dose was recovered in the urine as ellagic acid and its conjugates. Of this amount, about half was excreted as free ellagic acid and half was excreted as conjugates. An additional 25% of the dose was recovered in the feces (mostly as free ellagic acid) after 7 h. The disposition of 3,3'-di-O-methylellagic acid or 3-O-decylellagic acid after i.v. administration (32 mumol/kg) was examined and compared to the disposition of the same i.v. dose of ellagic acid. The concentrations of ellagic acid, 3,3'-di-O-methylellagic acid and 3-O-decylellagic acid decreased rapidly in the blood, liver and lung, but the concentrations of 3-O-decylellagic acid in the lung throughout the experimental period (2-360 min) was on average 20- to 40-fold higher than the corresponding average concentrations of ellagic acid or 3,3'-di-O-methylellagic acid.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1986

Effect of ellagic acid and 3-O-decylellagic acid on the formation of benzo[a]pyrene-derived DNA adducts in vivo and on the tumorigenicity of 3-methylcholanthrene in mice.

The effect of ellagic acid and its more lipophilic derivative, 3-O-decylellagic acid, on the amount of DNA-bound adducts in the epidermis or lung of CD-1 mice treated with [3H]benzo-[a]pyrene ([3H]B[a]P) was evaluated using several different treatment protocols. The i.v. administration of 50 mumol/kg of ellagic acid or 3-O-decylellagic acid either together with or 5 min before a 0.2 mumol/kg i.v. dose of [3H]B[a]P did not inhibit the formation of pulmonary DNA-bound adducts. Feeding mice a diet that contained 1% ellagic acid for 10 days or the i.p. administration of 120 mumol/kg of ellagic acid 30 min before the i.v. administration of 0.2 mumol/kg of [3H]B[a]P did not inhibit the formation of DNA-bound adducts in the lung. The application of 2,500 nmol of ellagic acid or 3-O-decylellagic acid to mouse skin 5 min before the application of 2, 10 or 50 nmol of [3H]B[a]P had little or no effect on the covalent binding of [3H]B[a]P metabolites to epidermal DNA. Feeding mice a diet containing 1% ellagic acid for 10 days did not inhibit the formation of epidermal DNA-bound adducts after a topical dose of 2 nmol of [3H]B[a]P. Similarly, the topical application of 2,500 nmol of ellagic acid at 2 h, 1 h and 5 min before and at 10 min after the application of 2 nmol of [3H]B[a]P did not inhibit the formation of DNA-bound adducts, but the same dosing regimen of 3-O-decylellagic acid (total dose of 10,000 nmol) resulted in a modest inhibition in the formation of DNA-bound adducts. The topical application of 1,500 nmol of ellagic acid 1 h before the application of 1,500 nmol of 3-methylcholanthrene (3-MC) to CD-1 or BALB/c mice twice weekly did not inhibit the development of skin tumors. Our results indicate that ellagic acid and 3-O-decylellagic acid are not effective in inhibiting [3H]B[a]P DNA adduct formation in mouse skin and lung and that ellagic acid does not inhibit 3-MC-induced skin tumorigenesis in BALB/c or CD-1 mice.

Animals↗
PubMed1986

sn-1,2-Diacylglycerols mimic the effects of 12-O-tetradecanoylphorbol-13-acetate in vivo by inducing biochemical changes associated with tumor promotion in mouse epidermis.

12-O-Tetradecanoylphorbol-13 acetate (TPA) or various acylglycerols were applied topically to CD-1 mice, and biochemical changes associated with tumor promotion in the epidermis were examined. The topical application of 5 mumol of sn-1,2-didecanoylglycerol caused a 40-fold increase in ornithine decarboxylase activity which was similar to that found after the topical application of 2 nmol of TPA. The time course for the induction of ornithine decarboxylase activity by TPA and the time course for its induction by sn-1,2-didecanoylglycerol were similar; both compounds produced rapid increases in ornithine decarboxylase activity with peak induction occurring 4-6 h after application of the inducing chemical. sn-1,2-Dioctanoylglycerol and sn-1-oleoyl-2-acetylglycerol also increased ornithine decarboxylase activity in mouse epidermis, but sn-1,2-dioleoylglycerol, 1,3-didecanoylglycerol and rac-1-monodecanoylglycerol were inactive at the dose tested. trans-Retinoic acid, a potent inhibitor of tumor promotion, markedly inhibited the epidermal induction of ornithine decarboxylase activity that resulted from the topical administration of sn-1,2-didecanoylglycerol or TPA. The effects of TPA and the acylglycerols on epidermal DNA synthesis in vivo were determined by measuring the incorporation of [3H]thymidine into epidermal DNA. The application of sn-1,2-didecanoylglycerol or TPA to mouse skin stimulated epidermal DNA synthesis. The maximum increase occurred 18 h after administration of the inducing chemical, and the increase in DNA synthesis was proportional to the dose of sn-1,2-didecanoylglycerol. Although sn-1,2-didecanoylglycerol, sn-1,2-dioctanoylglycerol and sn-1,2-dioleoylglycerol stimulated epidermal DNA synthesis, sn-1-oleoyl-2-acetylglycerol, 1,3-didecanoylglycerol and rac-1-monodecanoylglycerol had little or no effect. The increase in epidermal DNA synthesis induced by sn-1,2-didecanoylglycerol or TPA was inhibited by the simultaneous application of fluocinolone acetonide, a potent inhibitor of tumor promotion. The results indicate that several sn-1,2-diacylglycerols mimic TPA in vivo with respect to their effects on certain biochemical parameters associated with tumor promotion in mouse skin.

Animals↗
PubMed1986

A physical map of the viral genome for infectious pancreatic necrosis virus Sp: analysis of cell-free translation products derived from viral cDNA clones.

The two segments of double-stranded RNA from infectious pancreatic necrosis virus Sp were cloned into the plasmid vector pUC8. Two sets of overlapping clones were identified by restriction enzyme and Southern blot analyses. Each of these sets was shown by Northern blot analysis to be exclusively related to either segment A or B of the genomic RNA. The entire lengths of the cloned segments were estimated to be 2.9 and 2.6 kilobases, respectively. Sequences from the two segments of viral cDNA were subcloned into the bacteriophage T7 RNA polymerase vectors pT71 and pT72. The activity of the single-stranded RNAs transcribed from these subclones in a rabbit reticulocyte lysate translation system provided information on the polarity of and the protein products coded for by each subclone. The four proteins encoded by the genome of infectious pancreatic necrosis virus were identified among the translation products of the individual cloned segments by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. By constructing plasmids containing deletions in the sequences from either the 5' or 3' end of segment A, we were able to construct a physical map for the larger segment of double-stranded RNA. The proteins derived from these plasmids indicated that the linear gene order for viral proteins encoded in segment A is beta, gamma 2, and gamma 1.

Animals↗