Xenobiotic metabolizing enzymes in spawning English sole (Parophrys vetulus) exposed to organic-solvent extracts of marine sediments from contaminated and reference areas

Female English sole (Parophrys vetulus) within 1-2 days of spawning were exposed by i.m. injection to organic-solvent extracts of marine sediments at the following doses: Eagle Harbor (EHSE, contaminated site)--6.8 mg aromatic hydrocarbons (AHs)/kg body wt; Duwamish Waterway (DSE, contaminated site)--0.52 mg AHs and 0.040 mg chlorinated hydrocarbons (CHs)/kg body wt; Hood Canal (HCSE, reference site)--0.00090 mg AHs/kg body wt. Hepatic aryl hydrocarbon hydroxylase (AHH) activity, measured at spawning, was induced 10-, 23-and 2-fold by EHSE, DSE and HCSE, respectively, compared to sham and vehicle controls. Hepatic glutathione-S-transferase and epoxide hydrolase activities were not affected by any treatment. EHSE, but not DSE or HCSE, inhibited spawning (P less than 0.01) in 36% of the exposed fish and hepatic AHH activity in the non-spawning fish was significantly (P less than 0.05) higher than in the fish that did spawn. These results suggest a potential for reproductive toxicity in benthic fish after exposure to sediment-associated contaminants.     

Monocyte aryl hydrocarbon hydroxylase (AHH) activity mimics Kupffer cell and hepatocyte AHH activity in an animal model of liver disease.

We have previously reported that monocyte aryl hydrocarbon hydroxylase (AHH) activity is depressed in patients with liver disease and is decreased more in cirrhosis than in early stage liver disease. To determine if monocyte AHH activity reflects liver AHH activity, we studied an animal model of cirrhosis, i.e., yellow phosphorus induced cirrhosis in the pig. AHH activity was detectable in monocytes isolated from peripheral blood of normal pigs (0.32 +/- 0.13 nmol.mg-1 P.h-1, n = 11) and was comparable to the level of AHH activity in hepatic Kupffer cells isolated from wedge or needle biopsies of livers of normal pigs (0.38 +/- 0.21, n = 7). The AHH level in pig Kupffer cells was approximately 10% of the AHH level in hepatocytes and microsomes. To induce liver disease, pigs were administered yellow phosphorus (0.6 mg/kg) 5 days per week for 16 weeks. At 4 weeks of treatment, monocyte AHH activity was not different from control and liver histology was normal. Depression of monocyte AHH activity was evident at 8 weeks of treatment when liver fibrosis was seen histologically. At 12 weeks of treatment when histology revealed extensive liver fibrosis and collagen levels were elevated, the level of monocyte AHH activity was decreased 67% compared with controls. Similar changes were observed at 12 weeks in Kupffer cell AHH activity (86% decrease) and hepatocyte AHH activity (70% decrease) compared with controls. These results suggest that monocyte AHH activity reflects liver AHH activity and may be a good indicator of change in liver enzyme function in liver disease in the pig model of cirrhosis.     

Mirex induces ornithine decarboxylase in female rat liver

Ornithine decarboxylase, the rate-limiting enzyme in polyamine synthesis, was significantly induced in female rat liver following oral administration of the pesticide mirex. After dual oral exposure (120 mg/kg of mirex; 21 and 4 hr prior to sacrifice), ornithine decarboxylase activity in rat liver cytosol was 70-fold higher than control values. A single oral dose of mirex (180 mg/kg) induced hepatic ornithine decarboxylase activity 55-fold over controls. After a single oral dose of mirex the maximal induction of ODC activity occurred at 36 hr. Mirex is an unusually potent and long-lasting inducer of rat hepatic ornithine decarboxylase activity.     

Organ-selective induction of cytochrome P-450-dependent activities by indole-3-carbinol-derived products: influence on covalent binding of benzo[a]pyrene to hepatic and pulmonary DNA in the rat.

Indole-3-carbinol (I3C) is a dietary modulator of carcinogenesis that can reduce the level of carcinogen binding to DNA. I3C-derived products are potent inducers of certain cytochrome P-450(CYP)-dependent enzyme activities. To investigate whether the protective effects of I3C against carcinogen damage to DNA are associated with increased activities of CYP1A1 enzymes, we examined the relationship of I3C-mediated organ-specific CYP enzyme induction with total levels of benzo[a]pyrene (BP) binding to hepatic and pulmonary DNA of rats. Oral intubation (PO) of I3C (500 mumol/kg body wt.) in 10% DMSO in corn oil produced after 20 h, increases in ethoxyresorufin O-deethylase (EROD) activities (associated with CYP1A1 isozyme) of 700-fold, 245-fold and 36-fold in small intestine, lungs and liver, respectively, compared with activities in untreated controls. Hepatic aryl hydrocarbon hydroxylase (AHH) activity was increased 4-fold under these conditions. Pentoxyresorufin O-depentylase (PROD) activity (associated with CYP2B isoenzyme) was increased 6-fold in the liver but was unaffected in lung and small intestine. Intraperitoneal injection (IP) of I3C (500 mumol/kg body wt.) produced no significant change in EROD or PROD activities in lung, liver, or small intestine. PO administration of the acid reaction mixture (RXM) of I3C increased hepatic AHH activity (5-fold) and EROD activities in small intestine (650-fold), lung (100-fold) and liver (18-fold). IP administration of RXM (equivalent to 500 mumol I3C/kg body wt.) significantly increased only EROD activity in lung and liver, but did not affect EROD activity in small intestine, AHH activity in liver, or PROD activity in any of the organs examined. Twenty hours after inducer treatment, half of the rats were treated PO with 0.2 mumol [3H]BP in corn oil. Analysis of tissues 5 h after BP administration indicated that compared with untreated controls, administration of I3C and RXM by either route reduced by 30-50% the level of BP binding to hepatic DNA, an effect that was not correlated to CYP1A1 enzyme induction in any of the organs examined. However, PO administration of I3C and RXM produced a 50-70% decrease in carcinogen binding to pulmonary DNA, while IP administration of inducers had no effect on DNA binding in this organ. These results with the lung are consistent with an increased presystemic clearance of BP in the intestine and are discussed in terms of the role of induction of intestinal CYP1A1 activity in the decreased lymphatic and venous transport of unmetabolized BP to the lung.     

Liver and mammary arylhydrocarbon hydroxylase and epoxide hydratase in lactating rats fed polybrominated biphenyls

Female rats were fed polybrominated biphenyls (PBBs) (50 ppm) from day 8 of gestation through day 14 postpartum. Hepatic and mammary liver to body weight ratios, microsomal protein, arylhydrocarbon (benzo(a)pyrene) hydroxylase (AHH) activity and epoxide hydratase (EH) activities were measured. Exposure to PBBs significantly increased liver to body weight ratio, hepatic microsomal protein and hepatic AHH and EH activities. Mammary AHH activity was increased and EH activity was decreased after PBBs. These data demonstrate that AHH and EH are present in mammary tissue and can be altered by exposure to PBBs.     

Toxic and Carcinogenic Effects of Dimethylnitrosamine (Dmna) in the Blue Fox (Alopex Lagopus)

Single doses of DMNA from 8 to 15 mg/kg body weight (B.W.) were given in the feed, by stomach tube or by subcutaneous application to 37 foxes. The course and intensity of the disease was not influenced by the application route, but was directly related to the amount of DMNA given per kg body weight, and caused hemorrhagic centrolobular liver necrosis and acute vessel changes especially in the hepatic vein system. The possibility of liver regeneration after a single DMNA exposure depends on the degree of damage in the hepatic vein system. Some animals can recover from the acute disease caused by DMNA. But if the hepatic vessel changes are enough pronounced, progressive changes occur in the hepatic vein system eading to liver cirrhosis. The observation period of the foxes after a single exposure was from 13 to 380 days. LD50 should not be determined after a surviving time of 3 days but rather after 4 weeks. In our material LD50 was 10 mg DMNA/kg B.W. In an experiment over a longer period of time 18 foxes divided into 3 groups were given 2 weekly doses of DMNA in food. They were treated with daily estimated doses of 1.0, 0.2 and 0.1 mg DMNA/kg B.W., respectively. The foxes in Groups 1 and 2 developed ascites, jaundice and liver failure after intake of 45–70 mg DMNA/kg B.W. The foxes in Group 1 treated with 1 mg DMNA/kg B.W. showed centrolobular hemorrhagic liver necrosis and productive vessel changes in the hepatic vein system. The second group given 0.2 mg DMNA/kg B.W. developed hemorrhagic centrolobular necrosis which healed with fibrosis leading to cirrhosis and chronic occlusion in many of the hepatic veins. In addition noduli of chondroid lamellae and foci of hematopoietic tissue and early stages of hemagiomatous liver tumors were found in the liver. The group exposed with 0.1 mg DMNA/kg B.W./day did not develop hemorrhagic centrolobular liver necrosis, but thickening in the walls of the hepatic veins. After more than 3½ years of exposure multiple hemangiosarcomae were growing out from the changed vessel walls. In an experiment over a shorter time period with daily exposure of DMNA doses in the feed below 0.15 mg/kg B.W., all the foxes were completely healthy and only some showed beginning changes in the hepatic vein walls. Hematomae were often seen in foxes dying after a single DMNA dose. One fox treated with 0.1 mg DMNA/kg B.W. died of brain bleeding after 220 days of treatment. Chronic vessel changes were found in the heart and kidneys of the DMNA treated foxes. These results emphasize the fact that DMNA gives vessel changes of a more general nature.     

Kinetics and inductive potency of 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (H7CDD) in rats

The kinetic properties and the inductive potency of 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (H7CDD) were studied in Wistar rats following subcutaneous (s.c.) injections. For assessing the dose-response, rats were treated with a single dose of 3. 10 or 30 microg H7CDD/kg body wt. Tissue concentrations and enzyme induction were measured 1, 2, and 3 weeks after treatment, and in the 30 microg/kg group additionally after 6, 20 and 57 weeks. Tissue concentrations increased dose-dependently from 3 to 30 microg/kg. Concentrations in liver were always higher than in adipose tissue, the concentration ratio: liver/adipose tissue varied between 32 and 67. The activity of (ethoxyresorufin O-deethylase) (EROD) in liver microsomes was clearly induced by H7CDD, reaching maximal induction three weeks after treatment. (3-fold at 3 microg/kg, 5-fold at 10 microg/kg and nearly 30-fold at 30 microg/kg). For assessing the time dependency, tissue levels and hepatic enzyme induction were monitored over a period of 57 weeks after a single s.c.-injection of 30 microg H7CDD/kg body wt. Hepatic concentrations of the congener remained rather constant from the 2nd to the 20th week after treatment (280 ng/g and 319 ng/g, respectively). In contrast, concentrations in adipose tissue and thymus increased 2-fold during this period, and 20 weeks after injection reached a maximum of 11 ng/g and 3 ng/g, respectively. Thereafter, the concentrations decreased and tissue levels of 91 ng/g (liver), 3 ng/g (adipose tissue) and 2 ng/g (thymus) were detected 57 weeks after treatment. The elimination half-life (t 1/2) calculated from our data was 140 days in liver and 130 days in adipose tissue. The reasonable explanation for the increase in tissue concentrations of H7CDD up to 20 weeks after treatment is the slow release of this congener from the subcutaneous injection site. Induction of hepatic EROD activity always closely followed changes in the hepatic concentrations of H7CDD, reaching a maximum 3 weeks after treatment and remaining at this level until the 20th week. Correlation analysis of hepatic H7CDD concentrations versus the extent of EROD induction indicated a linear relationship in a double-logarithmic plot. When compared with TCDD, the hepatic monooxygenase-inducing potency of H7CDD within the low dose range was found in the rat to be 170 to 440-times lower than that of TCDD. Measurement of 14C-caffeine demethylation, using a 14CO2 breath test, revealed a similar time course in vivo when compared with the microsomal EROD activity ex vivo.     

Benzo[a]pyrene-DNA-adducts and monooxygenase activities in mice treated with benzo[a]pyrene, cigarette smoke or cigarette smoke condensate

Synchronous fluorescence spectrophotometry (SFS), developed to study benzo[a]pyrene-7,8-diol-9,10-epoxide(BPDE)-DNA, was used to measure the in vivo formation of DNA-adducts in genetically responsive C57BL/6 (B6) and non-responsive DBA/2 (D2) mice. Treatment with cigarette smoke by inhalation for 3-16 days, or i.p. injection of cigarette smoke condensate or neutral fraction did not lead to detectable levels of BPDE-DNA-adducts in either lungs or liver, although aryl hydrocarbon hydroxylase (AHH) activity, an indicator of benzo[a]pyrene (BP) metabolism, was clearly induced in lungs of B6 mouse. A dose-dependent amount of BPDE-DNA-adducts in lung and somewhat less in liver was found after i.p. injection with BP (20-80 mg/kg). Mice treated with vehicle or 4 mg/kg of BP were negative for adducts by SFS. In B6 mice AHH was induced both in lungs and livers while there was no AHH induction in D2 mice although the levels of BPDE-DNA-adducts were somewhat higher than in B6 mice. Thus, no clear correlation seems to exist between AHH activity and the formation of BPDE-DNA-adducts. Also, according to our results SFS can be used to quantitate adduct-formation in in vivo animal studies.     

Protection to glycolysis by a combination of 5-hydroxy-L-tryptophan and 2-aminoethylisothiuronium bromide hydrobromide in lethally irradiated rats.

Rate of glycolysis in vivo at different time intervals following 8 Gy [LD100(30)] whole body gamma radiation (WBGR) was evaluated by estimating liver glycogen, blood sugar, serum lactic dehydrogenase (LDH) and blood lactic acid concentration in adult male Sprague Dawley rats. Within 1 hr of radiation exposure, a significant fall in liver glycogen was observed in rats fed food and water ad libitum. The glycogen content increased after 24 hr and had returned to control level on 7th day after radiation exposure. Blood sugar, serum LDH and blood lactate levels increased significantly as compared to non irradiated controls. Pretreatment with 5-hydroxy-L-tryptophan (5-HTP; 100 mg/kg) + 2-aminoethylisothiuronium bromide hydrobromide (AET; 20 mg/kg) ip 30 min before 8 Gy WBGR, modified these values and restored them to normal level on 7th day post-irradiation.     

右美托咪定预防全麻下后路减压椎间植骨融合术后寒战的临床研究

目的:观察右美托咪定对全麻下后路减压椎间植骨融合术(PLIF)后寒战的预防效果。方法:选择行全身麻醉的PLIF手术患者80例,并将其随机分为高剂量右美托咪定组(HD组)、中剂量右美托咪定组(MD组)、低剂量右美托咪定组(LD组)和对照组(C组),每组20例患者。HD组、MD组及LD组在麻醉诱导后分别以0.8、0.5及0.2μg/kg/h静脉泵注右美托咪定至手术结束前40 min;C组泵注生理盐水。监测并记录患者麻醉前的基础体温值及BIS值,送入恢复室即刻、20 min、40 min、60 min的Ramsay镇静评分值、体温值;记录各组手术时长、拔管时间、术中输液量及失血量以及心动过缓、恶心、呕吐等不良反应的发生情况和苏醒期各组寒战程度分级及发生情况。结果:各组患者手术结束时的体温均较基础体温明显降低(P0.05)。入恢复室后,HD组同一时段的Ramsay镇静评分显著高于其他三组(P0.01)。HD组的拔管时间明显延长(P0.01)。与C组比较,MD组及HD组术后心动过缓、口干的发生率明显升高(P0.05),而恶心、呕吐及呛咳的发生率明显降低(P0.05)。在恢复室观察期间,MD组及HD组寒战的发生率较C组明显降低(P0.01);MD组寒战发生率也明显低于LD组(P0.05)。结论:0.5μg/kg/h持续泵注右美托咪定可以有效预防全麻下PLIF手术术后寒战的发生。     

Effect of chronic cysteamine treatment on mouse liver aryl hydrocarbon hydroxylase activity

Patients receive chronic cysteamine in the management of nephropathic cystinosis. In a previous report our results indicated that acute cysteamine treatment inhibited cytochrome P-450. Cysteamine (85 mg/kg i.p.) was administered daily to female Swiss mice for 1.5 and 8.5 months. Cysteamine treatment (8.5 months) did not affect hepatic microsomal aryl hydrocarbon hydroxylase (AHH) activity compared with controls. A small decrease in liver AHH activity was seen after 1.5 months of treatment with cysteamine. Liver histology, body weight, liver and spleen weights, and serum aminotransferase activity after chronic and subchronic treatment did not differ from controls. Chronic in vivo cysteamine treatment, unlike acute in vitro treatment did not decrease AHH activity. Incubation of isolated murine hepatocytes with cysteamine significantly inhibited AHH activity compared with controls. The inhibition occurred in a concentration-related manner, with 65% inhibition at 8.8 mM (1 mg/mL) (equivalent to the predicted plasma concentration using the maximally tolerable human dose), and 100% inhibition at 44 mM (5 mg/mL). The concentrations used in vitro were not cytotoxic. This suggests that chronic cysteamine treatment may not result in drug interactions and that in vitro results are not always good indicators of in vivo effects.     

Subacute inhalation of cigarette smoke by pregnant and lactating rodents: AHH changes in perinatal tissues

To study the transplacental acquisition of tobacco smoke products and the effects on fetal tissue enzymes, pregnant rats, guinea pigs, and hamsters were exposed to freshly generated cigarette smoke via a nose-only inhalation system on a daily basis through the latter one-third (guinea pigs) or latter half (rats, hamsters) of the gestational period. Following euthanasia on the day of parturition, microsomal aryl hydrocarbon hydroxylase (AHH) activities were determined in the lungs, livers, and kidneys of both dams and fetuses. The possible acquisition of tobacco smoke products via the milk was studied by exposing lactating dams to cigarette smoke daily for either 4 or 14 days (rats), 4 or 7 days (guinea pigs), or 10 days (hamsters), with analysis of tissues from the euthanized pups for AHH. Pups were also exposed directly (nose only) to cigarette smoke. In the treated pregnant and lactating rat, maternal pulmonary, hepatic, and renal AHH was significantly increased but only fetal lung and the liver of 14-day-old pups showed a marked induction of AHH activity. In the pregnant and lactating guinea pig, only the pulmonary and renal AHH activities were increased following exposure, whereas in the fetuses and nursing pups, none of the tissue AHH activities was significantly altered by exposure. In the pregnant and lactating hamster, only the pulmonary AHH was increased following exposure to cigarette smoke, whereas the activity in fetal and pup tissues remained unchanged from the levels observed in control animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro and in vivo inhibition of pulmonary cytochrome P450 activities by piperine, a major ingredient of piper species

In vitro and in vivo modulation of drug metabolizing enzymes by piperine was investigated in microsomes of rats and guinea pigs. In vitro piperine caused concentration related inhibition (50% at 100 microM) of arylhydrocarbon hydroxylase (AHH) and 7-ethoxycourmarin deethylase (7ECDE) activities, which were comparable in control and 3-methylcholanthrene (3MC) treated rats. In guinea pig microsomes however, piperine caused strong inhibition at lower concentrations (35% at 10 microM) and relatively much lesser inhibition with further increase in piperine concentrations. A Dixon plot of the kinetic data of both AHH and 7ECDE indicated noncompetitive inhibition with a Ki of approx. 100 microM. In vivo, piperine given at a dose of 25 mg/kg body wt to rats caused a maximal inhibition at 1 hr of both the enzymes, while only AHH returned to normal value within 4 hr. Similarly, upon daily treatment of piperine (15 mg/kg body wt) to rats for 7 days, 7ECDE was consistently inhibited, while AHH showed faster recovery. Piperine thus appeared to cause differential inhibition of two forms of cytochrome P450 and thus would accordingly affect the steady-state level of those drugs metabolized by these pulmonary forms of cytochromes P450.     

Effects of interleukin 11 (IL-11) on early post-implantation development of the rat

The development of embryos, trophoblast and decidua of IL-11-treated rats were examined in vivo, while ectoplacental cones (EPC) were studied in vitro. Female Wistar rats were injected daily with buffer (C), 1 mg/kg IL-11 (HD) daily or 30 microgram/kg (LD) IL-11 twice a week. On day 9 of pregnancy, embryonic tissue volume was reduced in IL-11-treated animals, but EPC volume was elevated, compared to controls. Mitotic indices were reduced in embryos (P<0.05 for LD, P<0.001 for HD) and in EPCs of both groups. Pycnotic indices were elevated in LD (NS) and HD (P<0.05) embryos, but decreased in EPCs of the LD group (P<0.01). Morphological abnormalities were observed in decidua, embryo and trophoblast. In HD, EPC attachment was impaired after 1 day culture but proliferation was stimulated after 5 days. Defective decidualization in IL-11 treated rats may therefore result in abnormal development of embryo and trophoblast.     

链脲佐菌素诱导C57小鼠1型糖尿病模型的研究

目的:通过小剂量多次腹腔注射链脲佐菌素(STZ)诱导建立与人类1型糖尿病相似的C57小鼠糖尿病模型,研究建模剂量和成模率。方法:将32只C57小鼠随机分为正常对照组(A)和实验组(B)。实验组(B)可分为低、中、高剂量组(50 mg/kg、70mg/kg、90 mg/kg)(n=8)。两组都喂普通饲料1周后,B组连续5天腹腔注射不同剂量STZ,测定注射前、注射后1周、2周、3周、4周、5周的空腹血糖和体重,观察小鼠饮食、饮水和排尿情况。STZ注射第3周进行口服糖耐量实验(OGTT)。结果:给药前A、B组体重和血糖无显著差异,给药1周后,B组饮水量和进食量明显增加,体重减轻。C57小鼠用药2周后,中剂量组达到建模标准,成模率75%。各剂量组均出现了糖耐量异常。结论:诱导建立C57小鼠1型糖尿病模型方法是连续5日腹腔注注射STZ,适宜剂量为70 mg/kg。     

Induction of hepatic drug metabolizing enzymes by DL-methionine in rats

A single intraperitoneal injection of DL-methionine (500 mg/kg body wt.) to adult male Wistar rats was shown to significantly induce all the components of the hepatic microsomal mixed function oxidase system such as NADPH cytochrome C reductase activity, cytochromes P-450 and b₅, as well as activities of drug metabolizing enzymes such as aminopyrine demethylase and uridine 5′ -diphosphate-glucuronosyltransferase. Combined administration of nicotinamide (250 mg/kg body wt.) and DL-methionine (500 mg/kg body wt.) was shown to bring about an additional increase (25-30%) in the activities of these enzymes as compared to their induction on independent administration of the two endobiotics. In rats bearing Yoshida sarcoma (ascites) tumour as well as in normal rats injected with serum from tumour bearing animals, the decreased activities of hepatic mixed function oxidases could be restored to their normal levels by administration of DL-methionine (500 mg/kg body wt.) to these rats. Whereas actinomycin D (1 mg/kg body wt.) had no effect on the increased incorporation of [¹⁴C] labelled leucine into microsomal proteins following administration of nicotinamide, the enhanced incorporation of the label following DL-methionine administration was completely inhibited by the same dose of actinomycin D. Administration of cycloheximide (0·5 mg/kg body wt.) to rats could completely inhibit the increased incorporation of [¹⁴C] leucine into hepatic microsomal proteins following independent administration of nicotinamide and DL-methionine. Similar inhibitory pattern with actinomycin D and cycloheximide was also demonstrated in case of induction of NADPH cytochromeC reductase activity by both these endobiotics.     

PCB impairs smoltification and seawater performance in anadromous Arctic charr (Salvelinus alpinus)

The impacts of polychlorinated biphenyl (PCB) exposure on smoltification and subsequent seawater performance were investigated in hatchery-reared, anadromous Arctic charr (Salvelinus alpinus). The fish were subjected to a 2-month summer seawater residence, after which they were orally dosed with 0 (Control, C), 1 (Low Dose, LD) or 100 mg Aroclor 1254 kg(-1) body mass (High Dose, HD) in November. They were then held in fresh water, without being fed (to mimic their natural overwintering in freshwater), until they had smolted in June the next year. The smolts were then transferred to seawater and fed to mimic their summer feeding residence in seawater, followed by a period without food in freshwater from August until maturation in October. Compared with C and LD charr, the HD charr had either a transient or a permanent reduction in plasma growth hormone, insulin-like growth factor-1, and thyroxin and triiodothyronine titers during the period of smoltification. These hormonal alterations in the HD charr corresponded with impaired hyposmoregulatory ability in May and June, as well as reduced growth rate and survival after transference to seawater. Consequently, fewer fish in the HD group matured in October compared to the other two treatments. The HD fish had a liver PCB concentration ranging between 14 and 42 mg kg(-1) wet mass, whereas there were similar, and very low, liver PCB concentrations in LD and C fish throughout the smolting period. Our findings suggest that PCB might compromise mechanisms important for fitness in a fish species living in an extreme environment.     

Relatively low-dose cyclophosphamide is likely to induce apoptotic cell death in rat thymus through Fas/Fas ligand pathway.

Cyclophosphamide (CPA) is widely used as an efficiently antineoplastic drug, but also causes immunosuppression as its adverse-side effect. To understand the effect of low- or relative low-dose CPA on the immune system, apoptotic cell death in rat thymus, either exposed to different doses of CPA (0, 2, 7, 20 and 70 mg/kg) for 12 h or exposed to 70 mg/kg for different times (4-48 h), was investigated by DNA fragmentation (DNA ladder) detection and in situ morphological examination using hematoxylin and eosin (H and E) staining. Immunohistochemical staining for Fas protein expression in the thymus of rats exposed to CPA was performed. Results showed that exposure of rats to CPA 0-70 mg/kg for 12 h did not cause significant decrease in the ratio of thymus weight to body weight. However, the ratio of thymus weight to body weight was decreased significantly at 48 h after exposure to 70 mg/kg CPA. Exposure to 20 and 70 mg/kg CPA for 12 h caused a visible DNA ladder in gel electrophoresis. DNA ladder formation was increased progressively in the groups from 8 h to optimal magnitude at 12-24 h and then disappeared at 48 h after 70 mg/kg CPA. This pattern was confirmed by a quantitative evaluation of the apoptotic cells using H and E staining. Expression of Fas protein was enhanced in the thymus of rats exposed to 70 mg/kg CPA for 4-8 h as compared to control rats. These results are different from previous studies on high dose CPA and the induction of the apoptotic cell death in thymus by low or relative low doses of CPA might be a result of Fas/Fas-ligand interactions.     

Aryl hydrocarbon hydroxylase activity in F-344 rats subchronically exposed to benzo(a)pyrene and fluoranthene through diet

In order to investigate the relationship between aryl hydrocarbon hydroxylase (AHH) activity and exposure to benzo[a]pyrene [B(a)p] and fluoranthene (FLA), AHH activities in liver tissues of male and female F-344 rats were determined. Based on a range-finding study, doses of 0, 5, 50, and 100 mg/kg B(a)p or 0, 150, 750, and 1500 mg/kg FLA were administered in the animal diet over a 90-day period. After dosing, animals were sacrificed, liver tissues were removed, and microsomes were isolated. AHH activities were determined by reverse-phase HPLC coupled with fluorescence detection using 3-hydroxy B(a)p, and trans-2,3-dihydroxy-1,10-epoxy-1,2,3,10b tetrahydrofluoranthene as the standards. A dose-dependent increase in enzyme activity was observed with increased B(a)p or FLA exposure in both males and females. Our results also demonstrate that B(a)p-exposed females possess a higher AHH activity than males, but there is no significant sex difference with regard to enzyme activity in the case of FLA at higher doses. Overall, our findings suggest that long-term exposure to the parent compound results in elevated levels of AHH activity, which may contribute to the formation of toxic reactive metabolites and subsequent symptoms in target organs.     

Melatonin effects on food intake and activity rhythms in two fish species with different activity patterns: Diurnal (goldfish) and nocturnal (tench)

Melatonin has several known physiological functions, the main one being synchronization of daily and seasonal rhythms. In addition, melatonin has been reported to influence food intake and behavioral rhythms with varying results depending on the species. The aim of this research was to evaluate the effects of intraperitoneal melatonin injection on food intake and locomotor activity in two different fish species: goldfish (diurnal) and tench (nocturnal), under different light regimes: constant light (LL) conditions or LD 12:12, with melatonin administration at mid-light (ML), mid-dark (MD), and after a 1-h light pulse at MD. In addition to these acute tests, in the case of goldfish we also investigated the effects of daily melatonin administration for 1 week. Our results indicated that acute melatonin administration significantly decreased goldfish food intake (16-52% inhibition, depending on the light regime) and locomotor activity (55-100%), with the chronic treatment inducing a similar total food intake inhibition that persisted for 7 days. In tench, a nocturnal fish species, acute melatonin administration at MD and ML reduced food intake (37% and 29%, respectively), while locomotor activity was not affected at MD and slightly increased at ML. Taken together, these results indicated that melatonin reduced food intake in both species, while its effects on locomotor activity depended on the time of administration (light or dark phase) and the activity patterns of the species.