Lack of Reproductive Toxicity in Adult Male Rats Exposed to Interferon-Alpha

Interferon-alpha (IFN-α), a type I IFN, is a protein with antiviral, antiproliferative, and immunoregulatory activities, widely used in the treatment of several types of cancers as well as hepatitis B and C. Decrease of libido and erectile dysfunction are commonly reported by male patients during treatment of chronic hepatitis C with IFN-α. However, IFN therapy-associated underlying factors attributed to sexual dysfunction are still not well defined. Currently, there are few studies investigating the effects of IFN on male reproductive system functions. Given that, the aim of the present investigation was to examine effects of subchronic exposure to IFN-α (5 × 10⁴ U/kg and 10 × 10⁴ U/kg, 30 d) on serum hormones, sperm parameters, fertility, and testicular and epididymal hystopathology and morphometry in adult male Wistar rats. None of the evaluated parameters was markedly altered by IFN-α. Thus, our results suggest that exposure to IFN-α, in this experimental design, did not adversely affect sperm quality and fertile capacity of male rats.     

Spatial Alternation Deficits Following Developmental Exposure to Aroclor 1254 and/or Methylmercury in Rats

doi:10.1093/toxsci/kfh290 Toxicological Sciences 82     

Enhanced Inflammatory Response to Acute Ozone Exposure in Rats during Pregnancy and Lactation

Experimental evidence from several studies suggests that pregnantanimals and women are more susceptible to oxidants than nonpregnantcontrols. In the study reported here, we sought to determinewhether pregnant rats are more sensitive than age-matched virginfemales to the inflammatory effects of ozone, a gaseous oxidantof considerable environmental significance. Rats at severalstages of pregnancy and lactation, as well as age-matched virginfemales, were exposed to 1 ppm ozone for 6 hr. Controls weresham-exposed to pure air for an identical period of time. Bronchoalveolarlavage was performed 24 hr after the beginning of exposure,and components of the lavage fluid considered to be indicatorsof inflammation were used to assess the severity of pulmonaryinflammation. The results of this experiment showed that significantlyenhanced sensitivity to ozone-induced pulmonary inflammationdevelops during pregnancy, is maintained during lactation, anddisappears following lactation. Implicit in this pattern ofdifferential sensitivity in rats is the possibility of a similarpattern of inflammatory response in analogous groups of humansas well as the potential for applicability to other oxidativepollutants.     

Biochemical and Morphological Studies in Testes of Rat Offspring of Mothers Exposed to Styrene during Lactation

Abstract: Methylazoxymethanol (MAM)-induced cerebral hypoplasia resulted in a significant increase in densities of norepinephrine uptake sites in cerebral cortex, suggsting that norepinephrinergic axon terminals were compressed in the smaller brain volumes. The density of β-adrenergic receptors in MAM-lesioned cerebral cortex was decreased probably due to down-regulation, while there were no changes in the proportions and affinities of agonist high-affinity sites and agonist low-affinity sites in the desensitized β-receptors.     

Mitochondrial Dysfunction Occurs before Transport or Tight Junction Deficits in Biliary Epithelial Cells Exposed to Bile from Methylenedianiline-Treated Rats

doi:10.1093/toxsci/kfi061 Toxicological Sciences 84     

Spatial Learning and Memory in HIV-1 Transgenic Rats

HIV-1 infection of the central nervous system impairs neural, cognitive, and behavioral functioning in patients despite antiretroviral therapy. However, studying mechanisms underlying HIV-1-related neurological and cognitive dysfunction has been limited without an adequate animal model. A novel, noninfectious HIV-1 transgenic (HIV-1Tg) rat model was recently created that expresses an HIV-1 provirus with a deletion of functional gag and pol genes. This HIV-1Tg rat reportedly develops clinical manifestations of human HIV disease and thus appears to mimic the persistent infection that results from the presence of HIV viral proteins in the host. We evaluated the HIV-1Tg rat model using the Morris water maze, a popular paradigm for testing learning and memory deficits in rodents. Because of congenital cataracts in HIV-1Tg rats, however, the traditional use of visual navigational cues in this paradigm were precluded. We first designed a modified Morris water maze and demonstrated that neurologically intact rats can effectively learn the water maze in the absence of visual cues and in the presence of non-visual navigation cues. We then tested HIV-1Tg rats in this modified Morris water maze. These HIV-1Tg rats showed a deficit in learning how to swim to the location of the hidden platform but did not show a deficit in their memory of the general location of the hidden platform. These results suggest that the noninfectious HIV-1Tg rat can be a valid model for the behavioral studies of HIV-related neurological dysfunction. A poster was presented at the 36th meeting of the Society for Neuroscience, October 14–16, 2006, Atlanta, GA (Program No. 752.12/AA24).     

Lack of Effect of 3,3′4,4′,5-Pentachlorobiphenyl (PCB 126) Throughout Gestation and Lactation on Multiple Fixed Interval–Fixed Ratio and DRL Performance in Rats

There is evidence that polychlorinated biphenyl (PCB) congeners have differential effects on endpoints of neurotoxicity depending on their chemical structure: specifically, that ortho-substituted congeners are neurotoxic while coplanar (dioxin-like) congeners are relatively inactive in producing neurotoxic effects. This study extends research on the effects of developmental exposure to the coplanar congener 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) in Long–Evans rats. Dams were dosed with 0, 0.25, or 1 μg/kg/day Monday to Friday beginning 5 weeks before and continuing through gestation and lactation. The first 2-week breeding period produced 10, 7, and 13 litters in the three dose groups, respectively, used in behavioral assessment. Breeding females from the control and low-dose group that did not conceive were rebred after 76 days of dosing, producing 6 and 6 litters used in behavioral testing. One female and male from each litter were tested on a multiple fixed interval–fixed ratio schedule of reinforcement beginning at about 200 days of age, followed immediately by performance on a DRL schedule. There were no compelling indications of a treatment-related effect on either schedule. These same rats failed to exhibit PCB-induced impairment on a spatial delayed alternation task performed prior to the current experiments. This regimen of PCB exposure produced reduced weight gain between birth and weaning in Cohort 1, and decreased thyroxine levels and changes in hematology and serum biochemistry parameters in both cohorts. These data provide further evidence for absence of behavioral toxicity as a result of gestational and lactational exposure to a dioxin-like PCB congener. Published by Elsevier Science Inc.     

Developmental Toxicity NOAEL and Postnatal Recovery in Rats Fed Boric Acid during Gestation

Boric acid (BA), an essential plant micronutrient, occurs naturallyin fruits, vegetables, and other foods. It is widely used inthe manufacture of glass, ceramics, and other products. In aprior study, gestational exposure to BA was associated withdevelopmental toxicity in the rat, including fetal growth retardationand altered skeletal morphology. In order to establish the developmentaltoxicity no-observed-adverse-effect level (NOAEL) in the rat,BA (0, 0.025, 0.05, 0.075, 0.1, or 0.2% in feed) was administeredto timed-mated rats (60/group) from gestational day (gd) 0 togd 20. Approximately half the dams were terminated on gd 20,and the remaining dams delivered their litters. Pup growth andviability were monitored until postnatal day (pnd) 21. Damssacrificed on gd 20 (pnd 21) ingested average doses of 0(0),19(19), 36(37), 55(56), 76(74), or 143(145) mg BA/kg/day. Maternalclinical signs, body weight, and food and water intake weremeasured at regular intervals during gestation and lactation.At termination, maternal liver and right kidney were weighed,and live fetuses (gd 20) and pups (pnd 21) were weighed, sexed,and examined for morphological anomalies (external, visceral,skeletal). Maternal effects were limited to increased relativekidney weight at 0.2% BA. Viability of the offspring was unaffected.On gd 20, fetal body weight was 94 and 88% of controls at 0.1and 0.2% BA, but recovery was complete at birth ({small tilde}gd22). The incidence of short rib XIII was increased on gd 20at >0.1% BA, but only at 0.2% on pnd 21. The incidence ofwaxy rib was increased on gd 20 at >0.1% BA, but the reversibilityof this effect was confirmed on pnd 21. A slight decrease inextra lumbar ribs was observed at 0.2% BA on gd 20, and extralumbar ribs were not found in any pups on pnd 21. Thus, thedevelopmental toxicity NOAEL in the rat was 0.075% BA (55 mg/kg/day)on gd 20 and 0.1% BA (74 mg/kg/day) on pnd 21.     

Vestibulo-Ocular Disturbances in Rats Exposed to Organic Solvents

Abstract: The influence of different kinds of industrial solvents on the vestibular function of rats has been studied by recording nystagmus, induced by accelerated rotation. The effect was related to the blood levels of the solvents. One group of solvents, including halogenated saturated hydrocarbons like dichloromethane, caused depression of the vestibulo-oculomotor reflex (VOR). Another group, including benzene compounds like xylene, toluene, styrene and cumene and halogenated unsaturated hydrocarbons like trichloroethylene caused an excitation of the VOR. The most striking chemical similarity between the different solvents in the last group is the occurence of double-bonds. If the animals were exposed simultaneously to solvents from both groups the excitatory effect prevailed and was even potentiated. It is suggested that solvents cause depression or excitation of the VOR by interaction with central pathways in the reticular formation and the cerebellum.     

The Effects of Puerariae Flos on Stress-induced Deficits of Learning and Memory in Ovariectomized Female Rats

Puerariae flos (PF) is a traditional oriental medicinal plant and has clinically been prescribed for a long time. The purpose of the present study was to examine the effect of PF on repeated stress-induced alterations of learning and memory on a Morris water maze (MWM) test in ovariectomized (OVX) female rats. The changes in the reactivity of the cholinergic system were assessed by measuring the immunoreactive neurons of choline acetyltransferase (ChAT) in the hippocampus after behavioral testing. The female rats were randomly divided into four groups: the nonoperated and nonstressed group (normal), the sham-operated and stressed group (control), the ovariectomized and stressed group (OS), and the ovariectomized, stressed and PF treated group (OSF). Rats were exposed to immobilization stress (IMO) for 14 d (2 h/d), and PF (400 mg/kg, p.o.) was administered 30 min before IMO stress. Results showed that treatments with PF caused significant reversals of the stress-induced deficits in learning and memory on a spatial memory task, and also increased the ChAT immunoreactivities. In conclusion, administration of PF improved spatial learning and memory in OVX rats, and PF may be useful for the treatment of postmenopausal-related dementia.     

Milk Transfer and Neonatal Uptake of Coplanar Polychlorinated Biphenyl (PCB) Congeners in Mice

Abstract: The selective accumulation of 3,3′,4,4′-tetrachlorobiphenyl metabolites in late gestational foetal blood and soft tissues in mice as a result of administration of different coplanar polychlorinated biphenyl (PCB) congeners, is reported elsewhere. The situation in the nursing neonate after maternal exposure to the same congeners is now studied: The ¹⁴C-labelled congeners 3,V,4,4′-telrachlorobiphenyl (IUPAC number CB-77), 3 ,3′,4,4′,5-pentachlorobipheny] (IUPAC number CB-126), 3 ,3′,4,4′,5,5′-hexachlorobiphenyl (IUPAC number CB-169) (all three non-ortho congeners) and 2,3,3′,4,4′-pentachlorobiphenyl (IUPAC number CB-105) (mano-ortho congener) were injected intravenously in lactating mice at day 11 post partum. One day and four days later, milk and neonatal/maternal tissues and plasma radioactivity was monitored by liquid scintillation counting (dose: 2.0 μmol (20-50 μCi)/kg body weight). In milk, CB-126, -169 and -105 showed higher levels (1450-2520 pmol/ml; one day after administration) than did CB-77 (580 pmol/ml), and in neonates, the relative whole-body levels of radioactivity (CB-169 and -105 highest) were related to the levels seen in milk (probably the consequences of their metabolic persistence). The comparably high ¹⁴C-concentration found in neonatal liver (about 15,000 pmol/kg) after CB-126 administration and in plasma (880 pmol/ml) after CB-77 administration could be explained by binding to specific proteins. In general, neonatal mice had two to seven times higher plasma levels than those of their mothers. These results indicate that CB-126, -169 and -105 are transferred via milk to neonates in considerable quantity and are deposited mainly in neonatal liver, whereas CB-77 is transferred in a comparably lower amount and accumulated in neonatal plasma. The lower ^l4C-levels in the NMRI mothers and offspring (about half of C57BL values in maternal and neonatal plasma), could possibly be explained by a differentiated metabolism of CB-77 in these two strains.     

Reproductive Toxicity and Tissue Concentrations of Low Doses of 2,3,7,8-Tetrachlorodibenzo-p-Dioxin in Male Offspring Rats Exposed Throughout Pregnancy and Lactation

The effects of low doses of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the reproductive system of male offspring rats were examined. The dams were treated subcutaneously 2 weeks prior to mating and throughout mating, pregnancy, and lactation. They received an initial loading dose of 25, 60, or 300 ng TCDD/kg body wt, followed by a weekly maintenance dose of 5, 12, or 60 ng TCCD/kg body wt (TCDD 25/5, TCDD 60/12, and TCDD 300/60). Three dams per group were killed on Gestation Day 21 and the fetuses were removed. The concentration of TCDD in the maternal liver and fat was measured. After birth, developmental landmarks in male rats were monitored. At weaning, the concentration of TCDD in the offspring liver and testis was determined. Effects on male reproduction were studied on Postnatal Days (PND) 70 and 170. At weaning, the concentration of TCDD in the offspring liver was 0.24, 0.39, and 1.78 ng/g in the TCDD 25/5, TCDD 60/12, and TCDD 300/60 groups, respectively. In the testes, the concentration of TCDD was 0.25 ng/g in the TCDD 25/5 and TCDD 60/12 groups and 0.28 ng/g in the TCDD 300/60 group. The number of sperm per cauda epididymis was reduced in TCDD groups at puberty and at adulthood. Daily sperm production was permanently decreased as was the sperm transit rate in the TCDD-exposed male rats, thus increasing the time required by the sperm to pass through the cauda epididymis. Moreover, the male rats of the TCDD groups showed an increased number of abnormal sperm when investigated at adulthood. Similarly, mounting and intromission latencies were significantly increased in the TCDD 25/5 and TCDD 300/60 groups. In the highest dose group, serum testosterone concentration was decreased at adulthood. Likewise, in this dose group permanent changes including pyknotic nuclei and the occurrence of cell debris in the lumen were revealed. The lowest adverse effect level and the no observed effect level can be estimated to be substantially lower than the estimated daily dose of the lowest dose which is 0.8 ng/kg body wt/day. Sperm parameters were more susceptible than the other end points investigated. However, the question as to whether such doses exposed throughout gestation and lactation induce subtle changes in humans remains to be determined.     

低剂量精氨酸血管加压素提高大鼠空间学习与记忆能力研究

目的 探讨多次外周给予低剂量精氨酸血管加压素（AVP）对大鼠空间学习和记忆能力的影响。方法分别将不同剂量(0.5,1.0 μg•kg 1) AVP或0.9%氯化钠溶液0.12 mL（对照组）于每次训练前30 min经皮下注入Wistar大鼠体内,采用Morris水迷宫检测对大鼠学习和记忆能力的影响及其量 效关系。结果皮下注射0.5和1.0 μg•kg 1AVP组大鼠在4 d训练中,隐匿平台试验中潜伏期和潜伏距离与对照组比较差异无显著性。空间搜索实验显示,0.5和1.0 μg•kg 1AVP组大鼠在原平台象限游泳时间百分比和距离百分比均明显高于对照组,各组大鼠寻找平台的动机和视敏度差异无显著性。结论训练前经外周多次注射低剂量AVP可提高大鼠长期记忆能力。     

Effects of Tall Fescue Endophyte Type and Dopamine Receptor D2 Genotype on Cow-Calf Performance during Late Gestation and Early Lactation

Grazing endophyte-infected, toxic tall fescue reduces cow/calf production; therefore, this study examines alternate strategies such as use of novel endophyte fescue varieties during late gestation and early lactation or genetic selection of resistant cows. Pregnant cows (n = 75) were randomly assigned to fescue endophyte type: 1) endophyte-infected ergot alkaloid producing tall fescue (E+) or 2) novel endophyte-infected, non-toxic tall fescue (NOV) within maternal (A|A, n = 38 and G|G, n = 37) DRD2 genotype to examine changes in cow/calf performance and milk production during late gestation and early lactation. Grazing E+ fescue pastures during late gestation reduced cow body weight gain but did not alter calf birth weight compared to NOV. Milk production and calf ADG during the first 30 day of lactation were lower for E+ than NOV. The calving rate was reduced, but not calving interval for E+ cows. The adjusted 205-day weight of calves was lower in those grazing E+ with their dams compared to NOV. There were no interactions between DRD2 genotype and fescue endophyte type indicating that genotype was not associated with response to E+ fescue in this study. Overall, grazing NOV tall fescue pastures rather than E+ during critical stages of production improved cow gain during late gestation, calving rate, early milk production and calf growth.     

Age-Induced Spatial Memory Deficits in Rats Are Correlated with Specific Brain Region Alterations in Microglial Morphology and Gene Expression

Effect of age and ladostigil treatment (1 mg/kg/day), given for 6 months to 16 month old rats, was investigated on microglial morphology in brain regions associated with control of spatial learning. This was assessed in the Morris water maze (MWM). Microglial morphology was assessed with diaminobenzidine and fluorescent staining with Iba1 and CD11b in these brain regions. Aging did not change the number of microglia in the parietal cortex (PC) or hippocampal CA1 region (CA1-HC), but decreased microglial process tips in the CA1-HC, increased the area fraction stained by CD11b and number of bulbs on processes in PC and CA1-HC and thickness of microglial processes in corpus callosum (CC) and fornix (Fx). Performance in MWM (distance swam to escape platform) was negatively correlated with number of bulbs in PC and thickness of process in CC, and positively correlated with number of process tips in CA1-HC. Aging increased expression of MHC class II genes and others associated with motility and membrane adhesion in the PC and hippocampus, but Adora2a (Adenosine A2a receptor), only in hippocampus. Age-related increase in the number of bulbs and expression of inflammatory genes was prevented by ladostigil in PC. In the CA1-HC, ladostigil increased the number of process tips and prevented the increase in expression of Adora2a and genes regulating ion channels. Ladostigil also decreased thickening of the processes in CC and Fx. The data show brain region-specific relations induced by age in spatial learning, microglial morphology and associated genes and their response to ladostigil treatment.

Graphical Abstract

     

Effect of Beta-Asarone on Impairment of Spatial Working Memory and Apoptosis in the Hippocampus of Rats Exposed to Chronic Corticosterone Administration

β-asarone (BAS) is an active component of Acori graminei rhizoma, a traditional medicine used clinically in treating dementia and chronic stress in Korea. However, the cognitive effects of BAS and its mechanism of action have remained elusive. The purpose of this study was to examine whether BAS improved spatial cognitive impairment induced in rats following chronic corticosterone (CORT) administration. CORT administration (40 mg/kg, i.p., 21 days) resulted in cognitive impairment in the avoidance conditioning test (AAT) and the Morris water maze (MWM) test that was reversed by BAS (200 mg/kg, i.p). Additionally, as assessed by immunohistochemistry and RT-PCR analysis, the administration of BAS significantly alleviated memory-associated decreases in the expression levels of brain-derived neurotrophic factor (BDNF) and cAMP-response element-binding protein (CREB) proteins and mRNAs in the hippocampus. Also, BAS administration significantly restored the expression of Bax and Bcl-2 mRNAs in the hippocampus. Thus, BAS may be an effective therapeutic for learning and memory disturbances, and its neuroprotective effect was mediated, in part, by normalizing the CORT response, resulting in regulation of BDNF and CREB functions and anti-apoptosis in rats.     

Decreased Fetal Weights in Rats Exposed to Sidestream Cigarette Smoke

Pregnant Sprague-Dawley rats were exposed to sidestream Cigarettesmoke (SS) for 6 hr a day, at a concentration of 1 mg/m³ ofrespirable total suspended particulate material (TSP) on Days3, 6–10, and 13–17 of pregnancy. Controls were keptin an identical chamber without smoke exposure. The animalswere killed on Day 20 of gestation. No differences were foundin maternal body weight gain or average daily food consumptionbetween the smoke-exposed and control groups. The numbers offetuses and of implantation sites per litter were comparableamong the groups. None of the pups showed any gross malformationsand no difference was found between controls and SS-exposedpups when examined for reduced skeletal ossifications. However,there was a small but significant reduction in mean pup weight.We conclude that intermittent exposure of rats to sidestreamcigarette smoke at concentrations severalfold greater than thoseencountered in smokey public indoor environments causes intrauterinegrowth retardation.     

老年大鼠空间参考学习和记忆能力改变的研究

目的 观察老年大鼠学习记忆功能的改变并探讨其意义。方法 采用水迷宫试验进行训练试验和探索试验，检测空间参考学习和记忆能力。对老年组及青年组大鼠分别进行学习记忆及行为观察。结果 与青年组大鼠比较，老年组大鼠的水迷宫逃避潜伏期显著延长（P〈0．01），在平台95％中心区域占总路径的百分数明显降低（P〈0．05），第1次穿越平台所在位置的时间明显延长（P〈0．05）；可见平台实验中，老年组大鼠较青年组大鼠水迷宫逃避潜伏时明显延长（P〈0．05）。结论 老年大鼠空间参考学习和记忆能力明显减退，记忆维持能力降低。     

Detection of Aldehydes in Bronchoalveolar Lavage of Rats Exposed to Ozone

We report the detection of hexanal, heptanal, and nonanal inthe bronchoalveolar lavage (BAL) of rats exposed to 0.5 to 10ppm ozone with or without simultaneous 5% CO₂. These three aldehydesprimarily result from the Criegee ozonation of specific mono-or polyunsaturated fatty acids that are present in significantamounts in the rat lung; e.g., palmitoleic acid gives heptanal,oleic gives nonanal, and linoleic and arachidonic can give hexanal.Hexanal also is produced in the ozone-initiated autoxidationof any n-6 polyunsaturated fatty acid, and thus is a measureof generalized oxidative stress. (Monounsaturated fatty acidsdo not undergo appreciable autoxidation.) This detection andquantitation of aldehydes directly demonstrates for the firsttime that unsaturated fatty acids undergo Criegee ozonationin the lung when ozone is inhaled. Exposure to ozone alone producedsmaller apparent yields of the three aldehydes than did exposureto ozone plus 5% CO₂. Hexanal, heptanal, and nonanal can bedetected in BAL of rats 5 hr after the end of the ozone exposure,but after more than 5 hr only hexanal can be found, probablyfrom ozone-induced autoxidation of n-6 PUFA that continues afterozone exposure. The measured amounts of aldehydes are low, andthat, coupled with inherent biovariability, suggests that aldehydesmay not be useful as quantitative dosimeters. However, theycan be useful biomarkers, since some of these aldehydes (e.g.,nonanal) are produced in ozone-specific pathways and aldehydesare the most easily detected among the lipid ozonation products(LOP). Furthermore, our identification of these aldehydes byBAL, coupled with our recognition that ozone itself cannot penetratefar enough into the lung to cause many of the effects associatedwith the inhalation of ozone, suggests that these aldehydes,as well as other types of LOP (such as hydroxyhydroperoxidesand Criegee ozonides), may act as signal transduction molecules,activating lipases and causing the release of inflammatory moleculesby a variety of pathways not yet entirely elucidated.