Female Fischer-344 Research Articles

Ovarian Susceptibility to Benzo[a]Pyrene: Tissue Burden of Metabolites and DNA Adducts in F-344 Rats

Exposure to environmental toxicants has been implicated as one of the causative factors for infertility in mammals. The objective of this study was to determine the amount of ingested benzo[a]pyrene (BaP), an environmental toxicant that reaches the reproductive tissues (internal dose) subsequent to a single acute exposure. Toward this end, the concentrations of BaP reactive metabolites and BaP–DNA adducts were measured throughout the course of BaP's residence in the body. Ten-week-old female Fischer-344 rats weighing approximately 220 g were administered 5 mg BaP/kg body weight orally. 1, 7, 14, 2,1 and 28 d post BaP exposure, BaP parent compound and metabolites from plasma, ovaries, and liver tissues were extracted using liquid–liquid extraction. The extracts were analyzed by reverse-phase highperformance liquid chromatography (HPLC). DNA was isolated and analyzed for BaP-induced DNA adducts by 32P-postlabeling method. The BaP total metabolite concentrations in plasma, ovaries, and liver showed a gradual decrease from d 1 to 28 post BaP administration. The BaP–DNA adducts concentrations in ovaries and liver tissues from the treatment group demonstrated a trend similar to that observed for metabolites. Ovaries showed greater concentrations of DNA adducts compared to liver. However, with an increase in time post cessation of exposure, the adduct concentrations in liver tissue started declining rapidly, from d 1 to 28. For ovaries, the adduct concentrations demonstrated a significant decline from d 1 to 7 and a gradual fall thereafter. A concordance between BaP reactive metabolite levels and adduct concentrations indicates that the bioavailability of reactive metabolites determines the binding with DNA and consequently the formation and persistence of adducts in an acute exposure regimen.

Chronic inhalation exposures of Fischer 344 rats to 1,6-hexamethylene diisocyanate did not reveal a carcinogenic potential

The polyisocyanates of 1,6-hexamethylene diisocyanate (HDI) find widespread commercial use as components of paints and in the formulation of light-stable polyurethane coating materials. This 2-year study assessed the oncogenicity of the diisocyanate monomer HDI in male and female Fischer-344 rats exposed 6 h/day, 5 days/week to mean analytical air concentrations of 0, 0.005, 0.025, and 0.164 ppm HDI. During the in-life phase, transient eye irritation was observed in 0.164 ppm males, and a slight body weight decrease (5%) in the 0.164 ppm females during the second year of exposure. There were no exposure-related effects on mortality. Compound-related, non-neoplastic histopathologic changes were limited to the respiratory tract and changes were characterized by epithelial tissue reaction to the acute irritant properties of HDI vapor. For tissues of the nasal cavity, the major histopathologic findings were degeneration of the olfactory epithelium characterized by destruction of the epithelial architecture often with narrowing or atrophy and occasional focal erosion or ulceration. In addition, there was variable degeneration of the respiratory epithelium with hyperkeratosis of the epithelium, epithelial and mucus secretory cell hyperplasia, squamous metaplasia, chronic-active inflammation, and errosive or ulcerative changes. These tissue effects along with a statistically significant decrease in body weight of female rats demonstrated attainment of a maximum tolerated dose. There was no evidence of progression of these changes in the nasal epithelium to neoplasia nor evidence of any compound-related neoplastic lesions for any of the other tissues examined. Therefore, it is concluded that HDI did not show a carcinogenic potential in this study.

Early and late administration of MnTE-2-PyP 5+ in mitigation and treatment of radiation-induced lung damage

Chronic production of reactive oxygen and nitrogen species is an underlying mechanism of irradiation (IR)-induced lung injury. The purpose of this study was to determine the optimum time of delivery of an antioxidant and redox-modulating Mn porphyrin, MnTE-2-PyP 5+, to mitigate and/or treat IR-induced lung damage. Female Fischer-344 rats were irradiated to their right hemithorax (28 Gy). Irradiated animals were treated with PBS or MnTE-2-PyP 5+ (6 mg /kg/24 h) delivered for 2 weeks by sc-implanted osmotic pumps (beginning after 2, 6, 12, 24, or 72 h or 8 weeks). Animals were sacrificed 10 weeks post-IR. Endpoints were body weight, breathing frequency, histopathology, and immunohistochemistry (8-OHdG, ED-1, TGF-β, HIF-1α, VEGF A). A significant radioprotective effect on functional injury, measured by breathing frequency, was observed for all animals treated with MnTE-2-PyP 5+. Treatment with MnTE-2-PyP 5+ starting 2, 6, and 12 h but not after 24 or 72 h resulted in a significant decrease in immunostaining for 8-OHdG, HIF-1α, TGF-β, and VEGF A. A significant decrease in HIF-1α, TGF-β, and VEGF A, as well as an overall reduction in lung damage (histopathology), was observed in animals beginning treatment at the time of fully developed lung injury (8 weeks post-IR). The catalytic manganese porphyrin antioxidant and modulator of redox-based signaling pathways MnTE-2-PyP 5+ mitigates radiation-induced lung injury when given within the first 12 h after IR. More importantly, this is the first study to demonstrate that MnTE-2-PyP 5+ can reverse overall lung damage when started at the time of established lung injury 8 weeks post-IR. The radioprotective effects are presumably mediated through its ability both to suppress oxidative stress and to decrease activation of key transcription factors and proangiogenic and profibrogenic cytokines.

Abstract C45: Preventive effect of Iressa in the hydroxybutyl(butyl) nitrosamine (OH-BBN) induced model of bladder cancer: Dose dependency, treatment timing, and alterations in biomarkers

Abstract The preventive efficacy of the EGFr inhibitor Iressa was examined on the induction by OH-BBN of urinary bladder cancers in female Fischer-344 rats. The OH-BBN induced model yields invasive bladder tumors with most having the histopathological appearance of transitional cell carcinomas (TCC). The resulting tumors show various protein changes; e.g., increased expression of survivin, GSTPi, and various S100 calcium binding proteins that are routinely observed in human bladder cancers. More recent array data have also implied many similarities. Recently we examined the effects of daily treatment of rats with Iressa (6 mg/kg BW/day, i.g.) beginning either 2 weeks after the last dose of OH-BBN (24 weeks of treatment) or at 12 weeks after the last dose of OH-BBN when microscopic TCCs already existed (14- weeks of treatment). Both regimens decreased the incidence of large palpable bladder cancers by 90%. This demonstrated that Iressa was highly effective even when administered late in tumor progression. In contrast, treatment with Iressa beginning 2 weeks after the last OH-BBN and followed for only 14 weeks caused a 60% decrease in the incidence of microscopic bladder cancers. Additional data examining various dose levels and the combination of suboptimal doses of Iressa with NSAIDs will be presented. In addition, we examined biomarker modulation in OH-BBN bladder cancers treated short term (5 days) with Iressa. When using a candidate marker approach, it was found that Iressa decreased levels of EGFrP as expected, but caused striking decreases in levels of phosphorylated AKT as well. A more generalized approach to modulation of biomarkers was also taken to examine altered expression of peptides in Iressa treated and control bladder tumors employing 2D gel analysis. When certain of the identified peptides were examined by pathway analysis, it was found that certain proteins associated with the VEGF pathway [ANP32A and HNPRL] were both decreased in Iressa treated tumors. Supported by NCI Contract HHSN261200433001C. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C45.

Functional Impact of Targeted Closed-Chest Transplantation of Bone Marrow Cells in Rats with Acute Myocardial Ischemia/Reperfusion Injury

Intramyocardial transplantation of bone marrow-derived stem cells is a potential therapeutic option after myocardial infarction (MI). Intramyocardial administration is invasive but allows efficient and targeted stem cell delivery. Aims of this study were validation of minimal-invasive, echo-guided closed-chest cell transplantation (CTx) of mononuclear (MNC) or mesenchymal stem cells (MSC) and quantification of systolic left ventricular function and assessment of contractile reserve with high-resolution reconstructive 3D-echocardiography (r3D-echo) 3 weeks after CTx. Female Fischer344 rats received syngeneic male MNC, MSC, or medium after myocardial ischemia and reperfusion via echo-guided percutaneous injection (open-chest for control). Left ventricular systolic function was measured and dysfunctional myocardium was quantified with r3D-echo. For investigation of contractile reserve and myocardial viability r3D-echo was additionally conducted during low-dose dobutamine 3 weeks after CTx. Cell persistence after echo-guided CTx was quantified via real-time PCR; scar size was measured histologically. Echo-guided percutaneous CTx was feasible in all animals (n = 30) without periprocedural complications. After 3 weeks, 1.4 +/- 1.1% of transplanted MNC and 1.9 +/- 1.2% of MSC were detected. These numbers were comparable to those after open-chest intramyocardial injection of MNC (0.8 +/- 1.1%; n = 8, p = 0.3). In r3D-echo no functional benefit was associated with CTx after MI and reperfusion. All groups (MNC, MSC, and controls) revealed a significant decrease of dysfunctional myocardium and similar contractile reserve during inotropic stimulation.In conclusion, percutaneous echo-guided closed-chest CTx promises to be an effective and safe approach for CTx in small-animal research. However, intramyocardial CTx of MNC or MSC had no influence on systolic function and contractile reserve after reperfused MI.

Ischemic Preconditioning Augments Survival of Stem Cells via miR-210 Expression by Targeting Caspase-8-associated Protein 2

MicroRNAs (miRs) participate in most cellular functions by posttranscriptional regulation of gene expression albeit with little information regarding their role in ischemic preconditioning (IP) of stem cells. We report that IP of bone marrow-derived mesenchymal stem cells (MSCs) with two cycles of 30-min ischemia/reoxygenation (I/R) supported their survival under subsequent longer exposure to anoxia and following engraftment in the infarcted heart. IP significantly reduced apoptosis in MSCs through activation of Akt (Ser(473)) and ERK1/2 (Thr(202)/Tyr(204)) and nuclear translocation of hypoxia-inducible factor-1alpha (HIF-1alpha). We observed concomitant induction of miR-210 in the preconditioned MSCs ((PC)MSCs). Inhibition of HIF-1alpha or of miR-210 abrogated the cytoprotective effects of preconditioning. Extrapolation of these data to in vivo studies in a rat model of acute myocardial infarction predominantly improved stem cell survival after engraftment with a role for miR-210. Notably, multiple I/R cycles more effectively regulated the miR-210 and hence promoted MSC survival compared with single-cycle hypoxia of an equal duration. Real time PCR array for rat apoptotic genes, computational target gene analyses, and luciferase reporter assay identified FLICE-associated huge protein (FLASH)/caspase-8-associated protein-2 (Casp8ap2) in (PC)MSCs as the target gene of miR-210. Induction of FLASH/CASP8AP2 in miR-210 knocked-down (PC)MSCs resulted in increased cell apoptosis. Taken together, these data demonstrated that cytoprotection afforded by IP was regulated by miR-210 induction via FLASH/Casp8ap2 suppression. These results highlighted that IP by multiple short episodes of I/R is a novel strategy to promote stem cell survival.

Estrogen replacement restores flow-induced vasodilation in coronary arterioles of aged and ovariectomized rats

The risk for cardiovascular disease (CVD) increases with advancing age; however, the age at which CVD risk increases significantly is delayed by more than a decade in women compared with men. This cardioprotection, which women experience until menopause, is presumably due to the presence of ovarian hormones, in particular, estrogen. The purpose of this study was to determine how age and ovarian hormones affect flow-induced vasodilation in the coronary resistance vasculature. Coronary arterioles were isolated from young (6 mo), middle-aged (14 mo), and old (24 mo) intact, ovariectomized (OVX), and ovariectomized + estrogen replaced (OVE) female Fischer-344 rats to assess flow-induced vasodilation. Advancing age impaired flow-induced dilation of coronary arterioles (young: 50 +/- 4 vs. old: 34 +/- 6; % relaxation). Ovariectomy reduced flow-induced dilation in arterioles from young females, and estrogen replacement restored vasodilation to flow. In aged females, flow-induced vasodilation of arterioles was unaltered by OVX; however, estrogen replacement improved flow-induced dilation by approximately 160%. The contribution of nitric oxide (NO) to flow-induced dilation, assessed by nitric oxide synthase (NOS) inhibition with N(G)-nitro-l-arginine methyl ester (l-NAME), declined with age. l-NAME did not alter flow-induced vasodilation in arterioles from OVX rats, regardless of age. In contrast, l-NAME reduced flow-induced vasodilation of arterioles from estrogen-replaced rats at all ages. These findings indicate that the age-induced decline of flow-induced, NO-mediated dilation in coronary arterioles of female rats is related, in part, to a loss of ovarian estrogen, and estrogen supplementation can improve flow-induced dilation, even at an advanced age.

Long-Term Marginal Zinc Supply Is Not Detrimental to the Skeleton of Aged Female Rats

In this experiment, we investigated the long-term effects of a marginal zinc (Zn) supply on bone metabolism in aged rats. Nine-mo-old female Fischer-344 rats were divided into 8 weight-matched groups of 8 rats each. All rats were adapted for 1 mo to restrictive feeding (7.5 g/d) of a purified diet containing 8 g/kg sodium phytate and 64 mg/kg Zn. Control rats were pair-fed throughout the experiment. During the 1-mo depletion phase, controls received the Zn-replete diet with 64 mg/kg Zn, whereas Zn-deficient rats were fed the same diet with 2.2 mg/kg Zn. The depletion phase was followed by a 3-mo marginal phase in which the rats fed the diet with 2.2 mg/kg Zn received an additional daily Zn supplement of 75 μg Zn/rat by gavage. In the following 2-mo repletion phase, a marginal group was switched to the Zn-replete diet, while the other groups were maintained on marginal Zn supply or on the Zn-replete diet. Zn depletion and marginal Zn reduced serum and bone Zn and serum alkaline phosphatase activity. Zn repletion normalized serum Zn. However, apart from subtle changes in bone mineralization density distribution, Zn deficiency was not associated with detrimental effects on bone mineral density, turnover, architecture, or biomechanics relative to control rats at any time point. Our data suggest that Zn does not play an essential role in bone metabolism in aged rats and cast doubt on the hypthosis that Zn deficiency is a risk factor for osteoporosis.

Antitumor effects of photodynamic tumor cell lysates on rat epithelial ovarian cancer in vivo

To study the antitumor effects of photodynamic therapy (PDT) treated by ovarian cancer cell lysates in rat epithelial ovarian cancer in vivo. Female Fischer344 rats of 6 - 8 weeks were allocated to four groups (n = 8 each): PDT group (inoculated intraperitoneal with PDT tumor cell lysates), freeze/thaw group (inoculated intraperitonealy with freeze-thaw tumor cell lysates), normal saline group (inoculated intraperitoneal with normal saline) and control group. Rat epithelial ovarian cancer NuTu19 cells were injected into all rats by intraperitoneal at day 7, while injected with normal saline in control group. The number of tumor specific interferon-gamma (IFN-gamma) secreting splenocytes was quantified by enzyme linked immunospot (ELISPOT) assay, the cytotoxic T lymphocyte (CTL) activity of splenocytes was measured by lactate dehydrogenase (LDH) analysis and tumor growth and the survival time of rats were also observed. Stimulated by PDT tumor cell lysates, the number of tumor specific IFN-gamma secreting splenocytes in PDT group, freeze/thaw group, normal saline group and control group were 448.8 +/- 34.2, 211.2 +/- 47.9, 43.3 +/- 11.1, 16.1 +/- 2.4 respectively, which were significant differences among of them (P < 0.05). Stimulated by freeze/thaw tumor cell lysates, the number of tumor specific IFN-gamma secreting splenocytes in four groups were 151.7 +/- 22.6, 188.7 +/- 53.0, 18.2 +/- 12.2, 8.8 +/- 7.7 respectively, which were not significant differences among of them (P > 0.05). Cytotoxicity of splenocytes of PDT group increased significantly than that in other three groups (P < 0.05). Except rats in control group were all alive until the experiment ended, the mean survival time of other rats were 234 d in PDT group, 171 d in freeze/thaw group and 168 d in normal saline group, which in PDT group was significantly higher than those in freeze/thaw group and normal saline group (P < 0.05). Rats treated by PDT tumor cell lysates could produce antitumor effects in vivo, which shown that induce tumor-specific immune response and prolong the life span.

Pharmacokinetics and disposition of recombinant human osteoprotegerin (rhOPG) after intravenous administration in female fischer rats

Osteoprotegerin (OPG) is a secreted member of the tumour necrosis factor receptor (TNFR) family that leads to the suppression of the differentiation, activation and survival of osteoclasts. The objective was to investigate the in vivo pharmacokinetics and tissue distribution of full-length recombinant human OPG (rhOPG) as well as its clearance mechanism using 125I-labelled protein (125I-rhOPG) after intravenous administration to female Fischer rats.2. 125I-rhOPG was rapidly and predominantly distributed to the liver after dosing (3 mg kg−1). Immunohistochemical analysis indicated that rhOPG was located in the sinusoids of the liver.The hepatic uptake of 125I-rhOPG (0.01 mg kg−1) was partly regulated under a saturable process. Pre-dosing of some sulfated glycans (20 mg kg−1), especially dextran sulfate, heparin and fucoidan, markedly inhibited the hepatic uptake of 125I-rhOPG. The clearance of 125I-rhOPG was markedly reduced by the conjugation of dextran sulfate.The results suggested that the hepatic clearance of 125I-rhOPG was mainly mediated by the interaction with glycosaminoglycans.

Effect of cranberry juice concentrate on chemically-induced urinary bladder cancers

The chemopreventive efficacy of cranberry juice concentrate in an experimental model of urinary bladder cancer was evaluated using female Fischer-344 rats. The animals received N-butyl-N-(4-hydroxybutyl)-nitrosamine (OH-BBN) for a period of eight weeks. Cranberry juice concentrate was administered at doses of 1.0 or 0.5 ml/rat/day beginning one week after the final OH-BBN treatment and continuing until the end of the study. The urinary bladders of all the rats were weighed and examined grossly for lesions, and all masses were submitted for pathological evaluation. A dose-dependent preventive effect of cranberry treatment was observed, with a reduced number of urinary bladder cancers (38%) in the 1.0 ml/rat/day group versus the control group. The cranberry extract neither affected body weight gain nor caused other signs of toxicity. For the metabolic studies, serum and urine were collected at 4 and 12 h after the administration of the cranberry juice concentrate and were analyzed by LC-MS/MS. Quercetin and its methylated derivative were detected in the urine samples. However, no quercetin was detected in the serum samples, indicating its poor bioavailability. These data suggest that components of cranberries may be effective in preventing urinary bladder carcinogenesis.

Stable therapeutic effects of mesenchymal stem cell-based multiple gene delivery for cardiac repair

We have previously shown that transplantation of mesenchymal stem cells (MSCs) co-overexpressing angiopoietin-1 (Ang-1) and Akt prevented cell apoptosis, enhanced angiogenesis, and improved left ventricular heart function. The present study was designed to determine the persistence of therapeutic benefits on longer term basis. Acute myocardial infarction model was developed in 30 young female Fischer-344 rats by permanent ligation of the left anterior descending coronary artery. The animals were grouped (n = 10) to receive 70 microL Dulbecco's modified Eagle's medium (DMEM) without cells (DMEM group 1) or containing 3 x 10(6) non-transduced male MSCs (MSC group 2) or transduced MSCs co-overexpressing Ang-1 and Akt (MAA group 3). The injections were carried out intramyocardially in the free wall of left ventricle at multiple sites. Three months after cell transplantation, real-time polymerase chain reaction for the rat sry gene, confocal imaging, and immunohistochemical studies revealed the extensive survival and myogenic differentiation of the PKH67-labelled cell graft. Blood vessel density was significantly higher in the MAA group (P < 0.05) at 3 months compared with the other groups. Blood vessel maturation index as determined by double-fluorescent immunostaining for vWFactor VIII and smooth muscle actin showed that most of the newly formed vessels matured to develop a smooth muscle covering in MAA group. Sonographic assessment of heart function showed that heart function deteriorated in the DMEM group, whereas the functional benefits were stable over a period of 3 months following transplantation of transfected cells. Engraftment of genetically modified MSCs co-overexpressing Ang-1 and Akt produced long-term histological and functional benefits in an infarcted heart.

Pharmacologically Preconditioned Skeletal Myoblasts Are Resistant to Oxidative Stress and Promote Angiomyogenesis via Release of Paracrine Factors in the Infarcted Heart

Strategies to enhance skeletal myoblast (SkM) survival after transplantation in the ischemic heart have achieved little success. We posit that preconditioned (PC) SkMs show improved survival and promote repair of the infarcted myocardium via paracrine signaling after transplantation. SkMs from male Fischer-344 rats (rSkMs) were PC for 30 minutes with 200 micromol/L diazoxide. Treatment of PC rSkMs with 100 micromol/L H(2)O(2) for 2 hours resulted in significantly reduced cell injury, as shown by lactate dehydrogenase-release assay, and prevented apoptosis, as demonstrated by cytochrome c translocation, TUNEL, annexin V staining, and preservation of mitochondrial membrane potential. PC rSkMs expressed elevated phospho-Akt (1.85-fold), basic fibroblast growth factor (1.44-fold), hepatocyte growth factor (2.26-fold), and cyclooxygenase-2 (1.33-fold) as compared with non-PC rSkMs. For in vivo studies, female Fischer-344 rats after permanent coronary artery ligation were grouped (n=12/group) to receive 80 microL of basal medium without rSkMs (group 1) or containing 1.5 x 10(6) non-PC (group 2) or PC (group 3) rSkMs. Real-time PCR for sry gene 4 days after transplantation (n=4/group) showed 1.93-fold higher survival of rSkMs in group 3 as compared with group 2. Four weeks later, echocardiography revealed improved indices of left ventricular function, including ejection fraction and fractional shortening in group 3 (P<0.02) as compared with groups 1 and 2. Blood vessel count per surface area (at x400 magnification) was highest in scar and periscar areas in group 3 as compared with the other groups (P<0.05). We conclude that activation of signaling pathways of preconditioning in SkMs promoted their survival by release of paracrine factors to promote angiomyogenesis in the infarcted heart. Transplantation of PC SkMs for heart cell therapy is an innovative approach in the clinical perspective.

Endothelial‐dependent and –independent vasodilation in cerebral resistance arteries: Effects of age and estrogen Status

At menopause, women undergo an increase in risk for cardiovascular disease. Estrogen is known to play a role in modulating vascular function and providing protective cardiovascular effects. However, it is not known whether the protective cardiovascular effects of estrogen change with age. Therefore, the purpose of this study was to determine effects of age and estrogen status on endothelial-dependent and –independent vasodilation in cerebral resistance arteries. Posterior communicating arteries (PCoA) were isolated from young (6 mo), middle aged (14 mo), and old (24 mo) in control (CON) and ovariectomized (OVEX) female Fischer-344 rats, and flow-, acetylcholine (ACh-), and DEA-NONOate–induced vasodilation were assessed. Flow-induced vasodilation (FID) of the PCoA was preserved with age in intact female rats (6 mo: 73.9 ± 5.4 % vs. 24 mo: 82.4 ± 7.1%), but OVEX rats exhibited a lower FID in contrast to intact female rats (Ovex: 68.0 ± 4.1 % vs. CON: 79.8 ± 3.6%). Endothelium-dependent dilation to ACh declined with age (6 mo: 51.3 ± 4.5%; 14 mo: 40.0 ± 5.9%; 24 mo: 33.2 ± 4.9%); however, ACh-induced dilation increased in OVEX young rats (Ovex: 57.4 ± 6.9% vs. CON: 45.2 ± 5.9%). No age effect was present in DEA-NONOate treated vessels. These data suggest both age and circulating ovarian hormones are determinants of vascular reactivity in cerebral resistance arteries and influence the risk for cerebral vascular disease. Funded by NIH grant HL077224.

Thromboxane induced‐vasoconstriction in coronary resistance arteries: Effects of age and ovarian hormone status

Both age and ovarian hormones are known to influence coronary vascular function; however, little is known of the influence of ovarian hormones on coronary vascular reactivity in aged females. Therefore, the purpose of this study was to examine the effects of age and ovarian hormones on vasoconstrictor responses to U46619, a thromboxane A2 agonist. Coronary resistance arteries were isolated from the Left Anterior Descending (LAD) and Septal Artery distributions (SA) from young (6 mo), and old (24 mo) control (CON) and ovariectomized (OVEX) female Fischer-344 rats. In intact female rats, U46619-induced constriction was preserved with age in both LAD (6 mo: 31.6 ± 5.7 %; 24 mo: 32.7 ± 7.5%) and SA (6 mo: 27.6 ± 5.7 %; 24 mo: 20.0 ± 6.1%) regions. Ovariectomy increased U46619-induced constriction in resistance arteries from the LAD and SA regions in old but not young rats. Furthermore, the magnitude of the increase in constriction that occurred following ovariectomy in old rats was greater in LAD (OVEX: 75.0 ± 6.1% vs. 32.7%) resistance arteries as compared to SA (OVEX: 35.1 ± 6.6% vs. 20.0 ± 6.1%) resistance arteries. These data indicate that modulation of arteriolar function by ovarian hormones is heterogeneous in the coronary circulation and increases with advancing age. Funded by NIH grant HL077224.

Lack of Trigeminal Nerve Toxicity in Rats Exposed to Trichloroethylene Vapor for 13 Weeks

Male and female Fischer-344 rats were exposed to 1,1,2-trichloroethylene (TCE) at 250, 800, or 2500 ppm for 6 h/day, 5 days/week, for 13 weeks. Weekly body weights and daily clinical observations were recorded and a functional observational battery (FOB) was performed monthly. Postexposure neurotoxicological evaluations included an electrodiagnostic evaluation of auditory function, the trigeminal nerve, and a comprehensive neuropathological examination. After 8 weeks of exposure, female, but not male, rats exposed to 2500 ppm were slightly more reactive to handling than the controls but not after 13 weeks of exposure. After 13 weeks, female rats exposed to 2500 ppm TCE were slightly more active during the 1-min observation period than the controls. There were no treatment-related differences in grip performance, landing foot splay, or on the trigeminal nerve-evoked potential at any dose. At 2500 ppm TCE, mild frequency-specific hearing deficits were observed, including elevated tone-pip auditory brainstem response thresholds. Focal loss of hair cells in the upper basal turn of the cochlea was observed in 2500 ppm-exposed rats. Except for the cochleas of 2500 ppm-exposed rats, no treatment-related lesions were noted during the neuro-histopathologic examination. The no-observable-adverse-effect level for this study was 800 ppm based on ototoxicity at 2500 ppm.

Transient Improvement in Cognitive Function and Synaptic Plasticity in Rats Following Cancer Chemotherapy

Cancer chemotherapy has been associated with cognitive impairment. Several issues complicate such findings including the patients' health, use of multiple chemotherapeutic agents, and proper assessment of cognition. To control these factors, we conducted cognitive studies in female rats receiving cyclophosphamide or 5-fluorouracil (5FU). Young (7 months) female Fischer-344 rats received five injections of cyclophosphamide (100 mg/kg), 5FU (150 mg/kg), or saline i.p. every 4 weeks for a total of 18 weeks. Aged (18 months) female Fischer-344 rats were treated with cyclophosphamide (80 mg/kg i.p.) for 16 weeks. After 8 to 10 weeks of recovery, rats were tested in two maze learning tasks, the Morris water maze and the Stone 14-unit T-maze. Neuronal synaptic function was assessed by examining long-term potentiation (LTP) in hippocampal slices obtained from young cyclophosphamide-treated rats. Despite the toxic effects induced by chemotherapy, cyclophosphamide- and 5FU-treated rats showed significantly better maze performance compared with controls. Following 29 to 42 weeks of recovery from chemotherapy, no significant effects were observed on maze performance. In aged rats, cyclophosphamide treatment for 14 weeks also produced toxicity, but no impairment in Stone maze learning after 16 weeks of recovery. When assessed during cyclophosphamide treatment, evidence of impaired LTP emerged; however, with 8 weeks of recovery following five cyclophosphamide treatments, we observed enhanced LTP. Despite toxicity accompanying chemotherapy, no evidence of impaired cognitive performance emerged after recovery. Indeed, following 7 to 9 weeks of recovery, we noted evidence of improved learning and LTP.

Sympathetic neuroaxonal dystrophy in the aged rat pineal gland

Dysfunction of circadian melatonin production by the pineal gland in aged humans and rats is thought to reflect the functional loss of its sympathetic innervation. Our ultrastructural neuropathologic studies of the sympathetic innervation of the pineal gland of aged (24 months old) Fischer-344 and Sprague–Dawley rats showed loss of nerve terminals as well as the development of neuroaxonal dystrophy (NAD), an ultrastructurally distinctive distal axonopathy, far in excess of that in young control rats. Immunolocalization of tyrosine hydroxylase confirmed the age-related loss of normal noradrenergic innervation and development of NAD. NAD was more frequent in aged female rats compared to males and was particularly severe in aged female Sprague–Dawley rats compared to Fischer-344 rats. Pineal NGF content was significantly increased or unchanged in female and male aged Fischer-344 rats, respectively, compared to young controls. The rat pineal is a sensitive experimental model for the quantitative ultrastructural examination of age-related neuropathological changes in nerve terminals of postganglionic noradrenergic sympathetic axons, changes which may reflect similar changes in the diffusely distributed sympathetic innervation of other targeted endorgans.

Respiratory tract toxicity of inhaled hydrogen sulfide in Fischer-344 rats, Sprague–Dawley rats, and B 6C 3F 1 mice following subchronic (90-day) exposure

The goal of this study was to characterize the toxicity of hydrogen sulfide (H 2S), including nasal and pulmonary effects, in adult male and female Fischer-344 and Sprague–Dawley rats and B 6C 3F 1 mice. Animals underwent whole-body exposure to 0, 10, 30, or 80 ppm H 2S for 6 h/day for at least 90 days. Exposure to 80 ppm H 2S was associated with reduced feed consumption during either the first exposure week (rats) or throughout the 90-day exposure (mice). Male Fischer-344 rats, female Sprague–Dawley rats, and female B 6C 3F 1 mice exposed to 80 ppm H 2S had depressed terminal body weights when compared with air-exposed controls. Subchronic H 2S inhalation did not result in toxicologically relevant alterations in hematological indices, serum chemistries, or gross pathology. Histologic evaluation of the nose showed an exposure-related increased incidence of olfactory neuronal loss (ONL) and rhinitis. ONL occurred following exposure to ≥30 ppm H 2S in both sexes of all experimental groups, with one exception, male Sprague–Dawley rats demonstrated ONL following exposure to 80 ppm H 2S only. A 100% incidence of rhinitis was found in the male and female B6C3F1 mice exposed to 80 ppm H 2S. In the lung, exposure to H 2S was associated with bronchiolar epithelial hypertrophy and hyperplasia in male and female Sprague–Dawley rats following exposure to ≥30 ppm H 2S and in male Fischer-344 rats exposed to 80 ppm H 2S. Our results confirm that the rodent nose, and less so the lung, are highly sensitive to H 2S-induced toxicity, with 10 ppm representing the NOAEL for ONL following subchronic inhalation.

Proton and hyperpolarized helium magnetic resonance imaging of radiation-induced lung injury in rats*1

<h2>Abstract</h2><h3>Purpose</h3> To assess the usefulness of hyperpolarized helium (³He) MRI, including apparent diffusion coefficient measurements, in the detection and evaluation of radiation-induced lung injury in rats. <h3>Methods and materials</h3> Female Fischer-344 rats were treated to the right lung with fractionated dose of 40 Gy (5 × 8 Gy) using 4-MV photons. Conventional proton (¹H) and hyperpolarized (³He) MRI were used to image the lungs 3–6 months after radiation treatment. Apparent diffusion coefficient (ADC) maps of hyperpolarized ³He in the lungs were calculated using a nonlinear, least-squares fitting routine on a pixel-by-pixel basis. After imaging, lungs were processed for histologic assessment of damage. <h3>Results</h3> The effect of radiation was time dependent with progressive right lung damage ranging from mild to moderate at 3 months to severe fibrosis with structural deformation at 6 months after radiation. There was a significant decrease in the apparent diffusion coefficient of hyperpolarized ³He gas in radiation-treated lungs. Areas of decreased ADC in the lungs correlated with fibrosis shown by histology. <h3>Conclusion</h3> This is the first study to show that hyperpolarized ³He MRI can detect radiation-induced lung injury noninvasively. Reduced hyperpolarized ³He ADC values postradiation likely reflect reduced alveolar volumes associated with fibrosis of the interstitium. Future studies at earlier time points may determine whether this noninvasive imaging technique can detect lung damage before clinical symptoms. Development of this new approach of magnetic resonance lung imaging in the rat model of radiation-induced lung injury will increase the ability to develop appropriate algorithms and more accurate models of the normal tissue complication probability.