Biomedical subjects

G S Bailey

Publications and source records attributed to G S Bailey.

At least 91 records · Page 5Linked to original sources

PubMed1988

Comparative metabolism and DNA binding of aflatoxin B1, aflatoxin M1, aflatoxicol and aflatoxicol-M1 in hepatocytes from rainbow trout (Salmo gairdneri).

DNA binding and metabolism patterns of 3H-labeled aflatoxin B1 (AFB1) and its phase I metabolites, aflatoxicol (AFL), aflatoxin M1 (AFM1), and aflatoxicol-M1 (AFL-M1), were compared in freshly prepared rainbow trout (Salmo gairdneri) hepatocytes. Aflatoxins were incubated with hepatocytes for periods up to 1 h, cellular DNA was isolated and specific activities determined by scintillation counting and Burton analysis. Data for (pmol bound aflatoxin/micrograms DNA)/(mumol dose) versus time fit a linear function (P less than 0.002) passing nearly through the origin for each aflatoxin. DNA binding at 1 h relative to AFB1 was: AFL, 0.53 +/- 0.07; AFM1, 0.81 +/- 0.20 AFL-M1, 0.83 +/- 0.24. Statistical analysis indicated that binding of AFL, AFM1 and AFL-M1 were significantly less than that of AFB1. HPLC analysis of the cellular supernatants indicated that the major metabolites were AFL, AFB1, AFL-M1, and AFM1 from AFB1, AFL, AFM1 and AFL-M1 substrates, respectively. Small quantities of hydroxylated metabolites and glucuronides also were detected in some of the incubations. The time-course data suggested that initial formation of major metabolites was rapid and that, by 20-30 min, net changes in metabolite levels decreased or approached zero. Because the four compounds possess a 8,9-double bond, DNA binding could be due to activation of the parent substrates as well as of their phase I metabolites. Based on current mutagenicity data and limited carcinogenicity studies, AFM1 and AFL-M1 have binding levels which are higher than expected compared to AFB1 and AFL.

Aflatoxin B1↗

PubMed1987

Metabolism and DNA binding of aflatoxicol and aflatoxin B1 in vivo and in isolated hepatocytes from rainbow trout (Salmo gairdneri).

The purpose of this study was to compare the metabolism and DNA binding of aflatoxicol (AFL) with that of aflatoxin B1 (AFB1) in vivo and in isolated hepatocytes from Mt Shasta strain rainbow trout (Salmo gairdneri). Maximum total binding of [3H]AFL to liver DNA from trout exposed by intraperitoneal injection was 38-47% of that of [3H]AFB1 over a 1-7 day period. The average AFL/AFB1 DNA binding ratio in 1-h incubations with isolated hepatocytes was 0.67 +/- 0.36 (n = 13). In freshly isolated hepatocytes, substantial interconversion between AFB1 and AFL via reductase and dehydrogenase enzymes was observed. Total in vivo excretion of conjugates in bile over 4 days was greater for [3H]AFL substrate than for [3H]AFB1. To determine if AFL binding was due to direct activation or to prior metabolism to AFB1 followed by activation, AFL with a tritium atom on the carbon containing the cyclopentenol function [1-3H]AFL, was synthesized and incubated with hepatocytes. Binding of [1-3H]AFL was 3% that of [3H]AFB1 and represents only direct binding of the intact cyclopentenol epoxide molecule before transformation to AFB1 and consequent loss of 3H. H.p.l.c. analysis of DNA hydrolyzed after incubation with [1-3H]AFL resulted primarily in production of non-radioactive 8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B1 (AFB1-N7-guanine). A radioactive peak estimated to be 1% as abundant as the AFB1-N7-guanine was also observed. The overall binding of generally labeled [3H]AFL to trout liver DNA in vivo and in freshly prepared hepatocytes correlates well with available tumor incidence and mutagenicity data. Conclusions from these findings are that direct interaction of AFL-8,9-epoxide with DNA is of relatively minor quantitative importance in rainbow trout hepatocytes and that the major adduct results from conversion of AFL to AFB1 prior to epoxide formation.

Aflatoxin B1↗

PubMed1987

Abnormal regulation of renal kallikrein in experimental diabetes. Effects of insulin on prokallikrein synthesis and activation.

The effects of streptozotocin (STZ) diabetes and insulin on regulation of renal kallikrein were studied in the rat. 1 and 2 wk after STZ injection, diabetic rats had reduced renal levels and urinary excretion of active kallikrein. Tissue and urinary prokallikrein levels were unchanged, but the rate of renal prokallikrein synthesis relative to total protein synthesis was reduced 30-45% in diabetic rats. Treatment of diabetic rats with insulin prevented or reversed the fall in tissue level and excretion rate of active kallikrein and normalized prokallikrein synthesis rate. To further examine insulin's effects, nondiabetic rats were treated with escalating insulin doses to produce hyperinsulinemia. In these rats, renal active kallikrein increased. Although renal prokallikrein was not increased significantly by hyperinsulinemia, its synthesis was increased. As this was accompanied by proportionally increased total protein synthesis, relative kallikrein synthesis rate was not changed. Excretion of active kallikrein was unchanged, but prokallikrein excretion was markedly reduced. Therefore, increased tissue active kallikrein seen with hyperinsulinemia can be explained not only by increased synthesis but also by retention and increased activation of renal prokallikrein. These studies show that STZ diabetes produces an impairment in renal kallikrein synthesis and suggest that this disease state also impairs renal prokallikrein activation. The findings also suggest that insulin modulates renal kallikrein production, activation, and excretion.

Animals↗

PubMed1987

Enhancement of carcinogenesis by the natural anticarcinogen indole-3-carbinol.

Indole-3-carbinol (I3C), a natural constituent of cruciferous vegetables, is an inhibitor in several experimental animal models of carcinogenesis by polynuclear aromatic hydrocarbons or aflatoxin B1 (AFB1) when administered prior to or during carcinogen exposure. For assessment of the postinitiation effects of I3C, rainbow trout were exposed to dietary I3C in two different protocols--before and during AFB1 exposure or after AFB1 exposure only. Preinitiation exposure to I3C reduced AFB1-initiated hepatocellular carcinomas in trout as previously reported, but post-initiation I3C exposure strongly enhanced the tumor incidence above the positive AFB1 control. These results reveal the need for additional research to elucidate the overall effect of I3C on chemical carcinogenesis.

Aflatoxin B1↗

PubMed1986

A comparative study of prokallikreins and kallikreins from rat pancreatic tissue and juice.

Two zymogens, designated prokallikreins A and B, were isolated from homogenates of rat pancreatic tissue. The two forms of prokallikrein were found to be very similar in size and charge properties. They gave rise to very similar kallikreins on activation with exogenous trypsin. Differences in carbohydrate content of the two zymogens were probably responsible for differences seen in their behaviour on ion-exchange chromatography and immunoelectrophoresis. In contrast, only one form of prokallikrein was isolated from rat pancreatic juice. It showed almost identical behaviour on ion-exchange chromatography and identical mobility on electrophoresis to prokallikrein A. Thus it can be tentatively suggested that it is prokallikrein A which is secreted into the pancreatic juice and represents the physiologically important zymogen.

Animals↗

PubMed1986

Initial observations of a kallikrein-like enzyme associated with the plasma membranes of rat adipocytes.

Homogenates of rat adipocytes and plasma membranes thereof were shown by radioimmunoassay to contain immunoreactive glandular kallikrein. On the basis of the hydrolysis of D-Val-Leu-Arg-p-nitroanilide, the kallikrein-like enzyme associated with the plasma membranes was found not to be stimulated by prior incubation with melittin or phospholipase A2. However, pre-incubation of the membrane preparation with trypsin did increase the activity of the enzyme. Furthermore, activation could also be achieved by incubating the plasma membranes with insulin at a dose that stimulated glucose uptake into intact adipocytes. On the other hand, incubation with insulin at a dose that did not increase glucose uptake into rat adipocytes was ineffective in activating the kallikrein-like enzyme.

Adipose Tissue↗

PubMed1986

A study of glandular kallikrein in experimental diabetes.

Very high blood glucose concentrations were seen in rats one day after injection with alloxan or streptozotocin. Those levels fell (compared to day one, p less than 0.005) by the third day after injection and subsequently rose again during the ensuing days. In contrast, no significant differences between treated and control rats in concentrations of submandibular kallikrein were recorded until the tenth day after the initial injection. At that time the submandibular kallikrein concentrations in the alloxanized and streptozotocinized rats were less (p less than 0.01) than those of the untreated rats. A further fall (compared to day ten, p less than 0.005) took place over the next four days. Thus submandibular kallikrein would not seem to have been involved in the early stages of the experimental diabetes. In agreement with that conclusion were the results of a related series of experiments in which exogenous porcine pancreatic kallikrein was administered to alloxanized rats. The kallikrein did not bring about a reduction in the high blood glucose levels.

Animals↗

PubMed1986

Studies of the effects of insulin, bradykinin, and captopril on blood glucose levels of alloxan-diabetic rats.

Infusion of bradykinin (1 microgram/min) or saline vehicle for 30 minutes into alloxan-diabetic rats produced no change in the very high levels of blood glucose. Furthermore, intravenous injection of captopril (3 mg/Kg body weight) into the diabetic rats did not result in a significant change of glucose concentrations over a period of 60 minutes. However, infusion of bradykinin 15 minutes after intravenous injection of captopril resulted in a marked decrease of glucose levels (p less than 0.01, compared to pretreatment) by 20 minutes after the start of the infusion. Thus, the captopril potentiated the effect of the kinin, possibly by inhibition of kininase II. Using a spectrophotometric assay with Bz-Gly-Gly-Gly as substrate insulin was shown to be an inhibitor of kininase II purified from hog lungs with an I50 of 1.6 X 10(-5)M compared to captopril with I50 of 2.2 X 10(-9)M. Furthermore, it was found that in vivo infusion of as little as 50 mU insulin over a period of 30 minutes, a dose that by itself was ineffective, potentiated the glucose-lowering activity of a bradykinin infusion in alloxanized rats. Interestingly, the infusion of insulin 15 minutes after injection of captopril, at doses of each compound which alone were inactive, did produce a significant fall (p less than 0.005) in glucose concentrations. Overall, the results show that captopril, insulin and bradykinin can interact to promote a reduction in blood glucose of alloxan-diabetic rats.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1986

Mechanisms of anti-carcinogenesis by indole-3-carbinol: effect on the distribution and metabolism of aflatoxin B1 in rainbow trout.

Indole-3-carbinol (I3C), a component of cruciferous vegetables, was previously shown to inhibit aflatoxin B1 (AFB1) carcinogenesis in trout. The purpose of this study was to examine the effect of I3C on AFB1 metabolism and hepatic DNA adduct formation in vivo and in vitro. When fed at 0.2%, I3C produced a 70% reduction in average in vivo hepatic DNA binding of injected AFB1 over a 21-day period when compared to controls. A 24-h distribution study of injected tritiated AFB1 in I3C fish showed less total radioactivity in the blood and liver at all times examined, compared to controls. These reductions were due primarily to reduced levels of AFB1 bound to red blood cell DNA, reduced plasma levels of the primary metabolite aflatoxicol (AFL), and decreased levels of AFB1 and polar metabolites present in the liver of I3C fish. In contrast to blood, total radioactivity was significantly elevated in the bile of I3C fish resulting from a 7-fold increase in aflatoxicol-M1 glucuronide levels over controls. No difference was observed in concentration of AFL glucuronide, the primary conjugate present in control fish. There was no difference in total radioactivity remaining in the carcass of I3C or control fish. AFB1 metabolism in freshly isolated hepatocytes from I3C fish showed 20% less DNA binding in a 1-h assay, with a 2-fold increase in aflatoxin M1 production. Addition of I3C to control hepatocytes at levels of 1, 10 or 100 microM had no effect on AFB1 DNA binding. These findings indicate that I3C inhibition of AFB1 hepatocarcinogenesis in trout involves substantial changes in the pharmacokinetics of carcinogen distribution, metabolism and elimination, leading to significantly reduced initial hepatic-nuclear DNA damage in vivo.

Aflatoxin B1↗

PubMed1986

Mechanisms of anti-carcinogenesis: the distribution and metabolism of aflatoxin B1 in rainbow trout fed aroclor 1254.

Polychlorinated biphenyls (PCBs) have previously been shown to be inhibitors of carcinogenesis in trout. The mechanism of this inhibition was investigated by studying the effects of PCBs on aflatoxin B1 (AFB1) distribution, metabolism and DNA adduct formation, both in vivo and in vitro. A 24 h distribution study of injected tritiated AFB1 showed more radioactivity in blood, liver and bile in fish fed PCBs, but less in residual carcass. The metabolites of AFB1 found in vivo in blood plasma and liver homogenates were shifted by PCB pretreatment towards greater production of the polar metabolite aflatoxin M1 (AFM1) and glucuronide conjugates. The major metabolite in bile of PCB fish was the glucuronide of aflatoxicol M1 (AFL-M1), which was enhanced 15-fold over controls. Levels of aflatoxicol (AFL) glucuronide, the major conjugate in controls, were unaltered by PCBs. The pattern of AFB1 metabolism in isolated hepatocytes from PCB-prefed fish was consistent with in vivo metabolism. AFB1--DNA adduct formation in a 1 h assay was similar in hepatocytes from PCB-fed and control fish. However, the total rate of AFB1 metabolism was significantly elevated in hepatocytes from PCB-fed fish such that the degree of AFB1--DNA adduct formed per unit AFB1 metabolized was 42% lower than control. Similarly, adduct formation in vivo during the first 24 h post-AFB1 injection in PCB fish was not significantly different from controls. However, over a longer 21 day period, adduct levels in PCB fish were only 48-69% of controls (P less than 0.005, analysis of variance), once peak adduct formation was reached. Thus, initial rates of adduct formation may be misleading in the absence of further information on rates of carcinogen metabolism in vitro and/or pharmacokinetics of peak adduct formation in vivo. These results indicate that PCB inhibition of AFB1 carcinogenesis in trout involves dramatic initial changes in carcinogen distribution, metabolism and elimination which, over time, results in a net reduction of DNA adduct formation.

Aflatoxin B1↗

PubMed1985

Urinary and renal tissue kallikrein in the streptozocin-diabetic rat.

The renal kallikrein-kinin system is thought to participate in blood pressure regulation and displays abnormalities in human hypertension, as well as in many animal models of hypertension. Urinary excretion and tissue levels of renal kallikrein were measured in streptozocin (STZ)-diabetic rats in relation to blood pressure, glycemia, and insulin treatment. In study 1, STZ-diabetic rats with marked hyperglycemia showed reduced kallikrein-like esterase excretion, compared with control rats, when first measured after 7 days of diabetes (9.9 +/- 2.5 versus 17.5 +/- 2.4 EU/24 h, P less than 0.05). This difference increased with time and, after 210 days, urinary esterase excretion in diabetic and control rats was 6.7 +/- 2.1 and 39.0 +/- 6.0 EU/24 h, respectively (P less than 0.001). Urine kallikrein, measured by radioimmunoassay, was similarly reduced in diabetic rats (40.4 +/- 8.0 versus 88.0 +/- 6.5 micrograms/24 h, at 30 days, P less than 0.001). At 120 days, systolic blood pressures were elevated in diabetic rats (P less than 0.05), and at 180 days over 60% of the diabetic rats had pressures above the highest pressures of control rats. In study 2, STZ-diabetic rats were treated with insulin for 2 wk (2 U NPH at 0800 h, or 2 U NPH at 0800 and 1600 h). In the single-dose group, with hyperglycemia similar to that of diabetic rats in study 1, kallikrein excretion was reduced as early as day 2, compared with nondiabetic rats (56.0 +/- 6.1 versus 109 +/- 9.4 micrograms/24 h, respectively, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Hepatocarcinogenicity of benzo[a]pyrene to rainbow trout by dietary exposure and intraperitoneal injection.

The influence of benzo[a]pyrene [(BP) CAS: 50-32-8] on the induction of certain enzymes within the hepatic mixed-function oxidase (MFO) system and its potential carcinogenicity were examined in rainbow trout (Salmo gairdneri). Nine-week feeding trials were performed with 500 and 1,000 ppm BP to determine trout tolerance to BP. Levels of MFO enzymes, including ethoxyresorufin-O-deethylase (EROD), ethoxycoumarin-O-deethylase (ECOD), benzo[a]pyrene monooxygenase (BPMO), and cytochrome P450 were measured during this time. An 18-month feeding trial of a 1,000-ppm BP dose was initiated in duplicate groups of 100 fingerling rainbow trout. Samples of trout were killed at 6, 12, and 18 months for gross and histologic examination of the internal organs for neoplasms. A group of fifty 10-month-old rainbow trout were given 12 monthly ip injections of 1 mg BP in 0.4 ml propylene glycol (PG), and comparable controls were given PG injections only. The trout were held for an additional 6 months, killed at age 28 months, and examined as in the dietary study. Mean MFO enzyme levels of EROD, ECOD, BPMO, and cytochrome P450 were significantly (P less than .001) elevated, showing dose- and time-response relationships when compared to MFO enzyme levels in control fish. Twelve months after BP exposure was initiated, 15% of the BP-fed fish had histologically confirmed neoplasms of the liver. After 18 months the incidence increased to 25%. No evidence of neoplasia was observed in control fish. BP injected ip resulted in a 50% incidence of hepatocellular neoplasms and in a fibrosarcoma of the liver and papillary adenomas of the swim bladder in 1 fish. These results indicate that BP is a potent inducer of selected hepatic MFO enzymes and establish, for the first time, the hepatocarcinogenicity of BP in an aquatic species.

Adenocarcinoma↗

PubMed1984

A time-course study of submandibular kallikrein, blood glucose and insulin of alloxan-diabetic and streptozotocin-diabetic rats.

A time-course study was carried out of the levels of submandibular kallikrein, serum insulin and blood glucose of rats rendered diabetic by alloxan or streptozotocin. The permanent hyperglycemia seen one day after treatment and the subsequent relative changes in the levels of blood glucose recorded over the following nine days were in agreement with previous observations. A significant reduction in the concentration of submandibular kallikrein did not become apparent until ten days following the injection of alloxan or streptozotocin. Thus the enzyme would not appear to have played either a causal or a preventative role in the production of the hyperglycemic state. Furthermore, in disagreement with previous speculation, the submandibular gland had not compensated for the deficiency of insulin with an increase in production of kallikrein. The fall in the level of serum insulin had preceded the decrease in submandibular kallikrein. However, administration of exogenous insulin over a period of three days did not bring about an increase in the concentration of submandibular kallikrein of the diabetic rats. Thus insulin would not seem to be involved in controlling the level of kallikrein in the submandibular gland.

Alloxan↗

PubMed1984

A quantitative study of the levels of glandular kallikrein in normal and diabetic rats.

The concentrations of kallikrein, as measured by specific radioimmunoassay, in pancreatic tissue of normal, alloxan-, and streptozotocin-diabetic rats were found to be essentially the same. In contrast, the levels of kallikrein in the submandibular glands of the diabetic rats were significantly less than that of the normal rats. However, there were no such differences in the levels of acid phosphatase or alpha-amylase. Thus, the experimentally induced diabetic state would seem to involve a specific reduction in submandibular kallikrein.

Acid Phosphatase↗

PubMed1984

The hepatocarcinogenicity of diethylnitrosamine to rainbow trout and its enhancement by Aroclors 1242 and 1254.

Rainbow trout (Salmo gairdneri) were fed diets containing 100 ppm Aroclor 1242 (AC42) or Aroclor 1254 (AC54) in combination with 1100 ppm diethylnitrosamine (DEN) for one year. The incidence of hepatocarcinomas was determined and compared with the incidence in trout fed 1100 ppm DEN alone. The two Aroclors dramatically enhanced tumor incidence from 10.2% in the positive controls (DEN alone) to 40.2% for AC42 and 21.6% for AC54. This is in contrast to previous results obtained when AC54 was fed concomitantly with aflatoxin B1 (AFB1), where a substantial inhibition of carcinogenesis was observed. The alteration of chemical carcinogenesis in trout by PCB, therefore, depends upon the carcinogen involved and is not a generalized effect.

Administration, Oral↗

PubMed1984

Glucuronides in bile of rainbow trout (Salmo gairdneri) injected with [3H]aflatoxin B1 and the effects of dietary beta-naphthoflavone.

Rainbow trout Salmo gairdneri were fed a diet containing the mixed-function oxidase system inducer, beta-naphthoflavone or were fed a control diet. For the two respective diets, as much as 50 and 12% of an i.p.-injected dose of [3H]aflatoxin B1 was recovered in the bile. The major product in the bile of beta-naphthoflavone-fed trout was an aflatoxicol-M1 glucuronide, whereas the major product in the control bile was an aflatoxicol glucuronide.

Aflatoxin B1↗

PubMed1984

Effect of dose on the inhibition of carcinogenesis/mutagenesis by Aroclor 1254 in rainbow trout fed aflatoxin B1.

Prior studies have shown that Aroclor 1254 (PCB) differentially alters the incidence of aflatoxin B1 (AFB1) induced hepatocellular carcinomas in trout, depending upon the time of PCB administration relative to AFB1 exposure (Shelton et al., 1983). When fed simultaneously with AFB1, PCB inhibits carcinoma incidence. We investigated the effect of AFB1 and PCB dose on this inhibition. Duplicate tanks of 100 rainbow trout were fed AFB1 at concentrations of 1, 4, or 8 ppb, either with or without the addition of 50 ppm PCB. Other groups were fed 4 ppb AFB1 + 5 ppm PCB, 50 ppm PCB alone, or control diet alone. After 9 and 12 mo, 40 and 60 fish per tank, respectively, were sampled to determine the incidence of liver tumors. The results show a parallel inhibition of the AFB1-tumor dose-response curve by the presence of 50 ppm PCB. Fish fed 4 ppb AFB1 + 5 ppm PCB showed slight inhibition in response when compared with 4ppb AFB1 alone. Also, livers from fish fed 50 ppm PCB were used to prepare S20 for use in the Salmonella mutagenesis assay. These livers were less efficient in converting AFB1 to a mutagen, when compared to control S20. The AFB1-mutagenesis dose-response curve was again shifted parallel to the right of the curve generated using control S20. These results suggest that the inhibitory action is at least partly at the level of carcinogen activation. The finding of parallel, as opposed to proportional, inhibition with varying carcinogen exposure for certain classes of inhibitors may have important implications for inhibition of environmental carcinogenesis at low levels of carcinogen exposure.

Aflatoxin B1↗

PubMed1984

Comparative activation of aflatoxin B1 to mutagens by isolated hepatocytes from rainbow trout (Salmo gairdneri) and coho salmon (Oncorhynchus kisutch).

Isolated hepatocytes from rainbow trout readily activated aflatoxin B1 (AFB1) to mutagens detectable by S. typhimurium TA 98. Characterization studies demonstrated that activation efficiency was essentially linear with respect to hepatocyte concentration (5 X 10(5)-2 X 10(7) cell/ml) and AFB1 dose (0-10 micrograms/ml). This system was employed to assess possible differences in AFB1 activation in hepatocytes from rainbow trout and coho salmon, two species which have been shown in in vivo studies to differ widely in sensitivity to AFB1 carcinogenesis. Activation efficiency was approximately three times greater in trout hepatocytes compared with salmon hepatocytes. This difference was more marked when S20 liver fractions from the two species were used. Analysis of unbound [3H]AFB1 metabolites performed on supernatants of hepatocyte incubations revealed that under the normal conditions of assay, addition of bacteria does not perturb the various pathways of AFB1 metabolism within hepatocytes. These results support other studies which suggest that the greater sensitivity of trout to AFB1 carcinogenicity resides largely in increased initial DNA damage, compared with coho salmon.

Aflatoxins↗