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J C Cook

Publications and source records attributed to J C Cook.

At least 37 records · Page 2Linked to original sources
PubMed1998

EAA receptors in the dorsomedial hypothalamic area mediate the cardiovascular response to activation of the amygdala.

The role of excitatory amino acid (EAA) receptors in the dorsomedial hypothalamus (DMH) in mediating the cardiovascular response to activation of the basolateral amygdala (BLA) was examined using conscious rats. Microinjection of the nonselective EAA receptor antagonist kynurenic acid (0.1-10 nmol) into the DMH blocked or reversed the increases in heart rate and arterial pressure resulting from injection of the GABAA receptor antagonists bicuculline methiodide (BMI; 100 pmol) and picrotoxin (100 pmol) into the BLA. Similar injections of kynurenic acid at sites lateral or dorsal to the DMH or injection of the inactive analog xanthurenic acid into the DMH were less effective in blocking the cardiovascular changes resulting from intra-amygdalar injection of BMI. Hypothalamic injection of the NMDA receptor antagonist 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (10 pmol) or the DL-alpha-amino-3-hydroxy-5-methylisoxazole-propionic acid receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2, 3-dioxo-benzo[f]quinoxaline-7-sulfonamide (50 pmol) at doses shown to be selective for their respective EAA receptor subtypes attenuated the cardiovascular changes associated with intra-amygdalar injection of BMI. Therefore, EAA receptors in the area of the DMH appear to be involved in mediating the cardiovascular changes resulting from activation of the amygdala.

Amygdala↗
PubMed1998

1,1,1-Trifluoro-2,2-dichloroethane (HCFC-123) and 1,1,1-trifluoro-2-bromo-2-chloroethane (halothane) cause similar biochemical effects in rats exposed by inhalation for five days.

1,1,1-Trifluoro-2,2-dichloroethane (HCFC-123) and 1,1,1-trifluoro-2-bromo-2 chloroethane (halothane) are gases with anesthetic properties. HCFC-123 is used as a refrigerant, fire extinquishing agent, and solvent, while halothane is a clinical anesthetic. Much information is available on chronic toxicity of HCFC-123 in animals, while the information available for halothane is from short-term animal exposures or chronic, low level human exposures. Thus, there is little biochemical information available on similar endpoints for these two chemicals, which share common metabolites. In the present study, male rats were exposed to 5000 ppm HCFC-123, 5000 ppm halothane, or room air for 6 hr per day for 5 consecutive days. Rats exposed to both test compounds gained little or no weight during the study. Liver weights were slightly decreased in the rats exposed to HCFC-123 and halothane compared to controls. The serum triglycerides were decreased to approximately 20% of control level in rats exposed to both HCFC-123 and halothane, and serum cholesterol was decreased to less than 80% of control by both compounds. Both test compounds increased hepatic beta-oxidation by approximately 3-fold over control, and HCFC-123 caused a significant increase in hepatic cytochrome P450 content, while the increase in cytochrome P450 was not statistically significant in the halothane-treated rats. The results indicate that HCFC-123 and halothane share not only common metabolic pathways, but also several common biological effects, specifically those associated with peroxisome proliferation. These data indicate that human experience with halothane may be useful in the risk assessment of HCFC-123.

Administration, Inhalation↗
PubMed1997

Interaction of GABA and excitatory amino acids in the basolateral amygdala: role in cardiovascular regulation.

Activation of the amygdala in rats produces cardiovascular changes that include increases in heart rate and arterial pressure as well as behavioral changes characteristic of emotional arousal. The objective of the present study was to examine the interaction of GABA and excitatory amino acid (EAA) receptors in the basolateral amygdala (BLA) in regulating cardiovascular function. Microinjection of the GABAA receptor antagonist bicuculline methiodide (BMI) or the E A A receptor agonists NMDA or AMPA into the same region of the BLA of conscious rats produced dose-related increases in heart rate and arterial pressure. Injection of the nonselective EAA receptor antagonist kynurenic acid into the BLA prevented or reversed the cardiovascular changes caused by local injection of BMI or the noncompetitive GABA antagonist picrotoxin. Conversely, local pretreatment with the glutamate reuptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid enhanced the effects of intra-amygdalar injection of BMI. The cardiovascular effects of BMI were also attenuated by injection of either the NMDA antagonist 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) or the AMPA receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2, 3-dioxo-benzo[f]quinoxaline-7-sulfonamide (NBQX). When these two EAA receptor antagonists were combined, their ability to suppress BMI-induced tachycardic and pressor responses was additive. These findings indicate that the cardiovascular effects caused by blockade of GABAergic inhibition in the BLA of the rat are dependent on activation of local NMDA and AMPA receptors.

Amygdala↗
PubMed1997

Development of a Tier I screening battery for detecting endocrine-active compounds (EACs).

One of the components of our research program is development of a mode-of-action screening battery to detect several different types of endocrine-active compounds (EACs). Our working hypothesis is that a comprehensive short-term in vivo/in vitro battery can be developed to identify endocrine toxicants using a collection of endpoints. The goals of this battery are that it be quick, cost effective, and predictive. The purpose of this battery is to identify potential EACs and to assess their potency in order to prioritize compounds for further study. Two in vivo screens (intact male and ovariectomized female rats) are being evaluated for their ability to detect several different types of endocrine activity. To validate this screen, 15 compounds with known endocrine activities are being used to evaluate a collection of different endpoints for their variability, stability over time, predictiveness, and dose dependency. These positive controls were chosen because they can modulate development, reproduction, or cancer. The advantage of an in vivo screen is that it utilizes a metabolically and physiologically intact system. The male in vivo battery will be used to assess several different types of endocrine activity, primarily by using a comprehensive hormonal battery. The female in vivo battery will be used to identify compounds which are either estrogenic/antiestrogenic or can alter the prolactin pathway. The in vitro portion of the screening battery consists of a yeast transactivation system (YTS). The YTS is being evaluated for its ability to identify compounds which are agonists or antagonists to the estrogen, androgen, or progesterone receptors. The expression of mammalian receptors in yeast allows for assessment of steroid-dependent transcriptional activators. The value of this system is that it can be used as a routine screen for compounds that interact with steroid receptors. Alterations in ligand binding to these receptors can be correlated with alterations in development via masculinization of females and/or feminization of males, decreases in reproductive success, or modulation of cancer incidence from in vivo tests. The in vivo and in vitro screens are designed to be run in parallel with built-in redundancy in order to reduce the probability of false-negative/ positive responses.

Animals↗
PubMed1997

Mechanisms for the pancreatic oncogenic effects of the peroxisome proliferator Wyeth-14,643.

Several peroxisome proliferators have been shown to produce pancreatic acinar cell hyperplasia/adenocarcinomas in 2-year bioassays with rats: ammonium perfluorooctanoate (C8), clofibrate, methylclofenapate, HCFC-123, and Wyeth-14,643 (WY). We have used in vitro (C8, WY) and in vivo (WY) approaches to examine several possible mechanisms of pancreatic tumorigenesis by peroxisome proliferating compounds. These mechanisms include cholecystokinin receptor agonism (CCK(A)), trypsin inhibition, alterations in gut fat content, cholestasis, and altered bile flow/composition. All of these mechanisms enhance pancreatic growth either by binding to the CCK(A) receptor or by increasing plasma CCK levels. In vitro experiments using a receptor competition binding assay demonstrated that WY and C8 do not bind directly to the CCK(A) receptor. In a continuous spectrophotometric assay, WY and C8 also failed to inhibit trypsin, a common mechanism for increasing plasma CCK levels. These in vitro results suggested that WY was not acting via the two most common mechanisms for modulation of pancreas growth. Two types of in vivo experiments were conducted. The subchronic study (2-month duration) was designed primarily to detect early changes in pancreatic growth such as those mediated by compounds that inhibit trypsin or act as CCK(A) receptor agonists. The chronic study (6 months) was designed primarily to evaluate whether the pancreatic lesions were secondary to hepatic changes such as cholestasis and/or altered bile flow/composition. In the in vivo experiments, male Crl:CDBR rats were fed diets containing 0 or 100 ppm WY. In the subchronic study WY-treated rats had a twofold increase in mean relative liver weights, an eightfold increase in hepatic peroxisomal proliferation, and a fourfold increase in hepatocyte cell proliferation after 1 week which remained elevated throughout the 2 months of treatment. In contrast, no pancreatic weight effects, increases in plasma CCK, or acinar cell proliferation was seen through 2 months in the WY group when compared to the control group. Fecal fat concentrations were also measured at 2 months and demonstrated no difference between control and WY-treated animals. The absence of any early pancreas changes in the subchronic study is consistent with the in vitro data which demonstrated that WY is not a CCK(A) agonist or a trypsin inhibitor. The chronic study demonstrated increases in pancreatic weights at 3 months (6% above control) and 6 months (17% above control), as well as increased CCK plasma levels in the WY-treated group. Liver effects in the chronic study paralleled those of the subchronic time points. Clinical pathology endpoints including increased serum concentrations of bile acids, alkaline phosphatase, and bilirubin were indicative of cholestasis in the chronic WY-treated group. The cholestasis may be responsible for the downward trend in total bile acid output, both of which may contribute to the modest increases in plasma CCK levels. These results indicate that chronic exposure to WY causes liver alterations such as cholestasis, which may increase plasma concentrations of CCK. Hence, WY may induce pancreatic acinar cell adenomas/adenocarcinomas via a mild but sustained increase in CCK levels secondary to hepatic cholestasis.

Adenoma↗
PubMed1997

Evidence that A8947 enhances pancreas growth via a trypsin inhibitor mechanism.

A8947 is a member of the sulfonyl urea class of compounds and is the active ingredient in a commercial broad leaf herbicide. This compound has been shown to produce pancreatic hypertrophy in rats, mice, and dogs. The objectives of this study were to investigate the mechanism(s) for the A8947 induction of pancreatic acinar cell hypertrophy and proliferation and to evaluate whether these pancreatic changes are reversible. A8947 was fed to male Crl:CD BR rats for up to 28 days (0, 300, 10,000, 30,000 ppm) or 56 days (0, 30,000 ppm). Rats were terminated on Test Days 7, 14, and 28 to assess the time course and dose response for the A8947-induced pancreatic changes, while rats terminated on Test Day 56 were used to assesss the reversibility of the pancreas effects at 30,000 ppm A8947. A8947 produced significant increases in pancreatic weight and acinar cell proliferation and diffuse acinar cell hypertrophy in 7 days at 10,000 and 30,000 ppm dose levels. By Day 14, absolute pancreas weights in the 10,000 and 30,000 ppm groups were maximally increased and remained at these levels throughout the study. In contrast, acinar cell proliferation in the 30,000 ppm group was still elevated at Test Day 14, but attenuated relative to the 7-day response, and returned to control levels by Test Day 28. No effects were observed at 300 ppm after a 28-day exposure period, while complete reversibility of A8947-induced pancreatic effects was demonstrated at 30,000 ppm following a 1-month recovery period (Test Day 56). Cholecystokinin (CCK) levels were increased by A8947 and closely followed the time course for pancreatic changes. MK-329, a specific CCKA receptor antagonist, completely ablated the ability of 30,000 ppm A8947 to increase pancreas weight following 7 days of exposure. A8947 did not bind the CCKA receptor in a receptor competition assay, negating any potential agonist mechanism. A8947 did, however, inhibit trypsin in vitro, suggesting a mechanism of action similar to that of raw soy protein, in which trypsin inhibition in vivo results in increased CCK levels followed by pancreatic acinar cell hypertrophy and proliferation.

Animals↗
PubMed1997

Human papillomavirus type 11 (HPV-11) neutralizing antibodies in the serum and genital mucosal secretions of African green monkeys immunized with HPV-11 virus-like particles expressed in yeast.

It has been shown previously that immunization of animals with recombinant virus-like particles (VLPs) consisting of the viral capsid proteins L1 or L1 plus L2 protected animals against experimental viral challenge. However, none of these experimental models addresses the issue of whether systemic immunization with VLPs elicits a neutralizing antibody response in the genital mucosa. Such a response may be necessary to protect the uterine cervix against infection with genital human papillomavirus (HPV) types. African green monkeys systemically immunized with HPV-11 VLPs expressed in Saccharomyces cerevisiae and formulated on aluminum adjuvant elicited high-titered HPV-11 VLP-specific serum antibody responses. Sera from these immunized monkeys neutralized HPV-11 in the athymic mouse xenograft system. Significant levels of HPV-11-neutralizing antibodies also were observed in cervicovaginal secretions. These findings suggest that protection against HPV infection of the uterine cervix may be possible through systemic immunization with HPV VLPs.

Animals↗
PubMed1996

Effect of the peroxisome proliferator, ammonium perfluorooctanoate (C8), on hepatic aromatase activity in adult male Crl:CD BR (CD) rats.

The incidence of Leydig cell adenomas increases in CD rats fed for 2 years with the hepatic peroxisome proliferator, ammonium perfluorooctanoate (C8). Treatment with C8 increased the serum concentration of estradiol in 2-week gavage studies, and feeding studies at various time points up to 2 years, and was also accompanied by increases in liver weight and hepatic beta-oxidation activity. Since peroxisome proliferators induce both hepatic beta-oxidation and specific cytochrome P450 enzymes, C8 may also induce aromatase (cytochrome P450-19A1), the cytochrome P450 monooxygenase which converts androgens to estrogens. This hypothesis was investigated in the present study. Adult male CD rats were dosed daily by gavage for 14 days with 0, 0.2, 2, 20, or 40 mg C8/kg body wt. An additional group, the pair-fed control, was fed at a rate matched to the daily consumption by the 40 mg C8/kg group. Treatment with C8 produced a dose dependent decrease in body weight, and increases in absolute and relative liver weights, and in the protein yield of hepatic microsomes. These C8-induced changes were associated with a 2-fold increase in the serum concentration of estradiol and up to a 16-fold increase in total hepatic aromatase activity. A significant linear correlation was established between serum estradiol and total hepatic aromatase activity. The absolute weights and the aromatase activity of the testes were not affected by C8. Hepatic peroxisomal beta-oxidation activity and the microsomal concentration of total cytochrome P450 were also increased by C8. A comparison of estimated EC50 values suggested that these parameters may be less sensitive to induction by C8 than hepatic aromatase activity. Co-incubation of control liver microsomes with C8 in the aromatase assay for 2 hr dose dependently reduced the apparent aromatase activity. This inhibition of aromatase in vitro but increase in vivo was further investigated using cultured rat hepatocytes. Decreases in aromatase activity were found after up to 42 hr of treatment with C8, but the enzyme activity was increased almost 2-fold after 66 hr. The results of this study suggest that the increased serum concentration of estradiol produced by C8 in rats is at least partly due to a direct effect on the liver to increase synthesis of estradiol through induction of aromatase cytochrome P450 in the endoplasmic reticulum.

Animals↗
PubMed1996

Chiropractic treatment of chronic 'whiplash' injuries.

Forty-three per cent of patients will suffer long-term symptoms following 'whiplash' injury, for which no conventional treatment has proven to be effective. A retrospective study was undertaken to determine the effects of chiropractic in a group of 28 patients who had been referred with chronic 'whiplash' syndrome. The severity of patients' symptoms was assessed before and after treatment using the Gargan and Bannister (1990) classification. Twenty-six (93 per cent) patients improved following chiropractic treatment (U = 34, P < 0.001). The encouraging results from this retrospective study merit the instigation of a prospective randomized controlled trial to compare conventional with chiropractic treatment in chronic 'whiplash' injury.

Adult↗
PubMed1996

An in vivo battery for identifying endocrine modulators that are estrogenic or dopamine regulators.

We have combined several endpoints into a single 5-day in vivo screening procedure to identify estrogenic compounds and dopaminergic modulators, both of which play important roles in enhancing mammary tumorigenesis in rodents. The endpoints evaluated as markers of estrogenicity included increases in uterine fluid and vaginal cornification incidence, serum prolactin levels, uterine weight, uterine epithelial cell height, uterine stromal cell proliferation, and uterine progesterone receptor (PR) number and decreases in uterine estrogen receptor (ER) number. The endpoints evaluated for changes in dopamine regulation included increases in prolactin and decreases in growth hormone levels. The estrogen agonist estradiol (E2) and estriol (E3), the mixed estrogen agonist/ antagonist tamoxifen (TAM), the full antiestrogen ICI-182, 780 (ICI),and the dopamine modulators haloperidol (HAL) and reserpine (RES) were tested using a three-time/day (8-hr intervals) intraperitoneal dosing regimen in sexually mature ovariectomized female Crl:CD BR rats. All compounds were evaluated over a range of concentrations. This in vivo battery was used to evaluate the effects of different classes of endocrine modulators on the selected endpoints. For example, the estrogen receptor agonists E2 and E3 display a unique profile based on changes in the uterotrophic endpoints (estrus conversion, uterine fluid imbibition, increases in uterine weight, and uterine endometrial cell proliferation) where full and partial agonists can be distinguished by the magnitude of these responses. Both the estrogen receptor antagonist ICI and the dopamine modulators HAL and RES lack these uterotrophic responses. Dopamine modulators can be distinguished from estrogen receptor agonists by the profile of increased prolactin levels with no uterotrophic changes. Estrogen receptor antagonists can be distinguished from agonists by comparing their effects on ER, PR, and uterotrophic responses. For instance, the full estrogen receptor antagonist ICI decreased ER (to almost 0) and PR levels, but has no uterotrophic effects, while TAM decreases ER (to almost 0) and increases PR with uterotrophic effects. The most useful endpoints for distinguishing estrogen agonists and dopamine modulators were uterine fluid imbibition, uterine weight, uterine stromal cell proliferation, and serum prolactin levels. In order to distinguish an estrogen agonist from an antagonist, other endpoints, such as receptor levels, are necessary. The advantage of an in vivo screen is that it utilizes a metabolically and physiologically defined system which is especially important with highly integrative system such as the endocrine system. This battery can be used as a screening tool to identify potential endocrine modulators as well as to identify mode of action following adverse findings in toxicology studies. Last, additional endpoints may be added to identify other classes of endocrine modulators.

Animals↗
PubMed1995

Sequence determination of human papillomavirus type 6a and assembly of virus-like particles in Saccharomyces cerevisiae.

Human papillomavirus 6a (HPV6a), the most abundant HPV6 subtype, was detected in a vulvar condyloma acuminatum. The complete genome of HPV6a was cloned, and its DNA sequence was shown to be over 97% identical to the HPV6b sequence. Of the eight open reading frames (ORFs) of HPV6a, only the imputed amino acid sequence of the major capsid protein L1 was identical to the corresponding HPV6b sequence; all other HPV6a ORFs showed amino acid changes compared to the HPV6b ORFs. The HPV6a L1 or the L1 + L2 ORFs were expressed in the yeast Saccharomyces cerevisiae. Self-assembly of the L1 capsid protein into virus-like particles (VLPs) was demonstrated both in the L1 as well as L1 + L2 coexpressing yeast strains. Copurification of the L1 and L2 proteins showed complex formation of the L1 and L2 proteins in the yeast-derived VLPs of coexpressing strains.

Adult↗
PubMed1995

Phosphorylation of ubiquitin-activating enzyme in cultured cells.

Ubiquitin-activating enzyme, E1, is the first enzyme in the pathway leading to formation of ubiquitin-protein conjugates. E1 exists as two isoforms in human cells which are separable by electrophoresis. These isoforms migrate with apparent molecular sizes of 110 kDa and 117 kDa in SDS/polyacrylamide gels. Immunoprecipitation of E1 from lysates of HeLa cells metabolically labeled with [32P]phosphate indicated the presence of a phosphorylated form of E1 which migrates at 117 kDa. Phospho amino acid analysis identified serine as the phosphorylated residue in E1. Phosphorylated E1 was also detected in normal and transformed cells from another human cell line. Phosphatase-catalyzed dephosphorylation of E1 in vitro did not eliminate the 117-kDa E1 isoform detected by Coomassie staining after SDS/polyacrylamide gel electrophoresis, thereby demonstrating that phosphorylation is not the sole structural feature differentiating the isoforms of E1. These observations suggest new hypotheses concerning mechanisms of metabolic regulation of the ubiquitin conjugation pathway.

Cells, Cultured↗
PubMed1995

Subchronic toxicity study in rats with 1-methyl-3-propylimidazole-2-thione (PTI): effects on the thyroid.

A 90-day gavage study was performed to evaluate the subchronic toxicity of 1-methyl-3-propylimidazole-2-thione (PTI) when administered to Crl:CD BR rats. PTI is a chemical catalyst and is structurally similar to the thioureas, which are known to adversely affect the thyroid. Therefore, this study was designed to investigate the effects of PTI on the thyroid. Male and female rats were dosed with 0, 5, 10, 25, or 75 mgPTI/kg/day for 13 weeks. Clinical pathology examinations and pathology examination were performed and the following were measured periodically: serum T3, T4, and TSH, hepatic UDP-glucuronyltransferase activity, and cell proliferation of the thyroid and liver. Under the conditions of this study, the overall no-observed-adverse-effect level (NOAEL) for the subchronic effects of PTI in male and female rats was 10 mg PTI/kg/day. The NOAEL was based on the effects on the thyroid gland in male and female rats dosed with 25 and 75 mg PTI/kg/day, as well as the hepatic centrilobular fatty change, increased severity of chronic progressive nephropathy, fatty change in the adrenal medulla, and the substantial reduction in body weight and body weight gain. The primary target organs were the thyroid and liver. Alterations in thyroid hormones (T3, T4, and TSH) occurred predominantly at 25 and 75 mg/kg/day. Toxicologically significant alterations in T3, T4, and TSH levels, cell proliferation, and UDP-glucuronyltransferase activity occurred in rats dosed with 25 and 75 mg/kg/day, which correlated with organ weight and histopathological effects. Additionally, the effect of PTI on thyroid peroxidase activity, a key step in thyroid hormone synthesis, was evaluated in vitro using microswine thyroid microsomes. PTI was shown to inhibit thyroid peroxidase, with an IC50 of 0.02 M. These data suggest that PTI enhances the excretion of T4 via induction of glucuronyltransferase and inhibits thyroid hormone synthesis via a direct affect on thyroid peroxidase. Both of these effects contribute to the disruption of the hypothalamic-pituitary-thyroid axis and result in sustained elevation of TSH and the corresponding thyroid hypertrophy and hyperplasia.

Animals↗
PubMed1995

Effects of ammonium perfluorooctanoate on Leydig cell function: in vitro, in vivo, and ex vivo studies.

Ammonium perfluorooctanoate (C8) produced a dose-dependent increase in Leydig cell adenomas in Crl:CD BR (CD) rats fed 0, 30, or 300 ppm for 2 years. Administration of C8 to adult male CD rats, by gavage for 14 days, produced decreased serum and testicular interstitial fluid testosterone levels and increased serum estradiol levels. The C8-mediated decrease in the serum testosterone levels appeared to be due to a lesion at the level of the testis. These endocrine changes may play a role in the C8 induction of Leydig cell tumors. In the present work, C8 was examined for its ability to (1) directly affect Leydig cells in vitro using isolated Leydig cells from untreated rats and ex vivo using Leydig cells isolated from C8-treated rats, (2) affect testicular interstitial fluid hormone levels, and (3) induce aromatase activity. These studies were conducted to investigate the hypothesis that C8 produces an increase in estradiol by inducing cytochrome P450 XIX (aromatase), which converts testosterone to estradiol, and that the elevated estradiol levels ultimately produce Leydig cell hyperplasia and adenoma formation by acting as a mitogen or enhancing growth factor secretion. In the in vivo and ex vivo studies, adult male CD rats were gavaged with either 0 or 25 mg/kg/day C8 for 14 days. In addition to the ad libitum control, a second control group was pair-fed to the 25 mg/kg/day C8 group. In the in vitro and ex vivo studies, Leydig cells were isolated from testes of adult males by collagenase digestion followed by enrichment over Percoll gradients. A dose-dependent decrease in testosterone levels was observed in hCG-stimulated Leydig cells treated in vitro with C8 for 5 hr (IC50 approximately 200 microM). In contrast, ex vivo studies demonstrated an increase in testosterone production in hCG-stimulated Leydig cells from C8-treated rats when compared to Leydig cells isolated from either the ad libitum or pair-fed control rats. The in vitro data demonstrate that C8 directly inhibits testosterone release from Leydig cells, while the ex vivo data demonstrate that this inhibition is reversible.(ABSTRACT TRUNCATED AT 400 WORDS)

Administration, Oral↗
PubMed1995

Vaccination with yeast-expressed cottontail rabbit papillomavirus (CRPV) virus-like particles protects rabbits from CRPV-induced papilloma formation.

Papillomaviruses infect epithelia of the skin and mucous membranes and cause benign or malignant tumours in animals and in humans. The viruses are highly species-specific, and cell culture systems for propagating human papillomaviruses (HPVs) do not exist. However, there are several animal papillomavirus models. In the cottontail rabbit papillomavirus (CRPV) system, we demonstrated that recombinant CRPV virus-like particles (VLPs) consisting of the capsid proteins L1 or L1+L2 can be produced in the yeast Saccharomyces cerevisiae. Three immunizations with L1 VLPs formulated on aluminum adjuvant at 1-100 micrograms dose-1 efficiently protected rabbits from challenge with CRPV. Sera of immunized rabbits were shown to contain high-titered serum antibodies to CRPV L1 VLPs and to neutralize CRPV in vitro. Our results suggest that recombinant yeast-derived VLPs could be the basis for a candidate HPV vaccine.

Animals↗
PubMed1995

Effects of superoxide on nitric oxide-dependent N-nitrosation reactions.

Recent studies have demonstrated that nitric oxide (NO) in the presence of superoxide (O2-) may mediate mutagenesis via the N-nitrosation of DNA bases followed by nitrosative deamination to yield their hydroxylated derivatives. We have found that phorbol myristate acetate (PMA)-activated extravasated rat neutrophils (PMNs) will N-nitrosate 2,3-diaminonaphthalene (DAN) to yield its highly fluorescent nitrosation product 2,3-naphthotriazole (triazole) via the L-arginine dependent formation of NO. Addition of SOD enhanced triazole formation suggesting that O2- production may inhibit the N-nitrosating activity and thus the mutagenic activity of inflammatory PMNs. The objective of this study was to assess the role of superoxide as a modulator of NO-dependent N-nitrosation reactions using PMA-activated PMNs as well as a chemically defined-system that generates both NO and superoxide. We found that PMA-activation of PMNs reduced found that PMA-activation of PMNs reduced the amount of N-nitrosation of DAN by approximately 64% when compared to non-stimulated cells (450 vs. 1250 nM). Addition of SOD but not inactivated SOD or catalase to PMA-activated PMNs enhanced the formation of triazole by approximately 4-fold (1950 nM). In addition, we found that the NO-releasing spermine/NO adduct (Sp/NO; 50 microM) which produces approximately 1.0 nmol NO/min generated approximately 8000 nM of triazole whereas the combination of Sp/NO and a superoxide generator (hypoxanthine/xanthine oxidase) that produces approximately 1.0 nmol O2-/min reduced triazole formation by 90% (790 nM). Addition of SOD but not catalase restored the N-nitrosating activity. We conclude that equimolar fluxes of superoxide react rapidly with NO to generate products that have only limited ability to N-nitrosate aromatic amino compounds and thus may have limited ability to promote mutagenesis via the nitrosative deamination of DNA bases.

2-Naphthylamine↗