Mycoplasma genitalium in the US (MyGeniUS): Surveillance Data From Sexual Health Clinics in 4 US Regions

BACKGROUND

Mycoplasma genitalium (MG) is on the CDC Watch List of Antimicrobial Resistance Threats, yet there is no systematic surveillance to monitor change.

METHODS

We initiated surveillance in sexual health clinics in 6 cities, selecting a quota sample of urogenital specimens tested for gonorrhea and/or chlamydia. We abstracted patient data from medical records and detected MG and macrolide-resistance mutations (MRMs) by nucleic acid amplification testing. We used Poisson regression to estimate adjusted prevalence ratios (aPRs) and 95% CIs, adjusting for sampling criteria (site, birth sex, symptom status).

RESULTS

From October-December 2020 we tested 1743 urogenital specimens: 57.0% from males, 46.1% from non-Hispanic Black persons, and 43.8% from symptomatic patients. MG prevalence was 16.6% (95% CI: 14.9-18.5%; site-specific range: 9.9-23.5%) and higher in St Louis (aPR: 1.9; 1.27-2.85), Greensboro (aPR: 1.8; 1.18-2.79), and Denver (aPR: 1.7; 1.12-2.44) than Seattle. Prevalence was highest in persons <18 years (30.4%) and declined 3% per each additional year of age (aPR: .97; .955-.982). MG was detected in 26.8%, 21.1%, 11.8%, and 15.4% of urethritis, vaginitis, cervicitis, and pelvic inflammatory disease (PID), respectively. It was present in 9% of asymptomatic males and 15.4% of asymptomatic females, and associated with male urethritis (aPR: 1.7; 1.22-2.50) and chlamydia (aPR: 1.7; 1.13-2.53). MRM prevalence was 59.1% (95% CI: 53.1-64.8%; site-specific range: 51.3-70.6%). MRMs were associated with vaginitis (aPR: 1.8; 1.14-2.85), cervicitis (aPR: 3.5; 1.69-7.30), and PID cervicitis (aPR: 1.8; 1.09-3.08).

CONCLUSIONS

MG infection is common in persons at high risk of sexually transmitted infections; testing symptomatic patients would facilitate appropriate therapy. Macrolide resistance is high and azithromycin should not be used without resistance testing.

Natural Clearance of Chlamydia trachomatis Infection Is Associated With Distinct Differences in Cervicovaginal Metabolites

BACKGROUND

Natural clearance of Chlamydia trachomatis in women occurs in the interval between screening and treatment. In vitro, interferon-γ (IFN-γ)-mediated tryptophan depletion results in C. trachomatis clearance, but whether this mechanism occurs in vivo remains unclear. We previously found that women who naturally cleared C. trachomatis had lower cervicovaginal levels of tryptophan and IFN-γ compared to women with persisting infection, suggesting IFN-γ-independent pathways may promote C. trachomatis clearance.

METHODS

Cervicovaginal lavages from 34 women who did (n = 17) or did not (n = 17) naturally clear C. trachomatis were subjected to untargeted high-performance liquid chromatography mass-spectrometry to identify metabolites and metabolic pathways associated with natural clearance.

RESULTS

In total, 375 positively charged metabolites and 149 negatively charged metabolites were annotated. Compared to women with persisting infection, C. trachomatis natural clearance was associated with increased levels of oligosaccharides trehalose, sucrose, melezitose, and maltotriose, and lower levels of indoline and various amino acids. Metabolites were associated with valine, leucine, and isoleucine biosynthesis pathways.

CONCLUSIONS

The cervicovaginal metabolome in women who did or did not naturally clear C. trachomatis is distinct. In women who cleared C. trachomatis, depletion of various amino acids, especially valine, leucine, and isoleucine, suggests that amino acids other than tryptophan impact C. trachomatis survival in vivo.

Sexual behavior shapes male genitourinary microbiome composition

The origin, composition, and significance of the distal male urethral microbiome are unclear, but vaginal microbiome dysbiosis is linked to new sex partners and several urogynecological syndromes. We characterized 110 urethral specimens from men without urethral symptoms, infections, or inflammation using shotgun metagenomics. Most urethral specimens contain characteristic lactic acid bacteria and Corynebacterium spp. In contrast, several bacteria associated with vaginal dysbiosis were present only in specimens from men who reported vaginal intercourse. Sexual behavior, but not other evaluated behavioral, demographic, or clinical variables, strongly associated with inter-specimen variance in urethral microbiome composition. Thus, the male urethra supports a simple core microbiome that is established independent of sexual exposures but can be re-shaped by vaginal sex. Overall, the results suggest that urogenital microbiology and sexual behavior are inexorably intertwined, and show that the male urethra harbors female urogenital pathobionts.

Evaluation of Clinical, Gram Stain, and Microbiological Cure Outcomes in Men Receiving Azithromycin for Acute Nongonococcal Urethritis: Discordant Cures Are Associated With Mycoplasma genitalium Infection

BACKGROUND

In men with nongonococcal urethritis (NGU), clinicians and patients rely on clinical cure to guide the need for additional testing/treatment and when to resume sex, respectively; however, discordant clinical and microbiological cure outcomes do occur. How accurately clinical cure reflects microbiological cure in specific sexually transmitted infections (STIs) is unclear.

METHODS

Men with NGU were tested for Neisseria gonorrhoeae, Chlamydia trachomatis (CT), Mycoplasma genitalium (MG), Trichomonas vaginalis, urethrotropic Neisseria meningitidis ST-11 clade strains, and Ureaplasma urealyticum (UU). Men received azithromycin 1 g and returned for a 1-month test-of-cure visit. In MG infections, we evaluated for the presence of macrolide resistance-mediating mutations (MRMs) and investigated alternate hypotheses for microbiological treatment failure using in situ shotgun metagenomic sequencing, phylogenetic analysis, multilocus sequence typing analyses, and quantitative PCR.

RESULTS

Of 280 men with NGU, 121 were included in this analysis. In the monoinfection group, 52 had CT, 16 had MG, 7 had UU, 10 had mixed infection, and 36 men had idiopathic NGU. Clinical cure rates were 85% for CT, 100% for UU, 50% for MG, and 67% for idiopathic NGU. Clinical cure accurately predicted microbiological cure for all STIs, except MG. Discordant results were significantly associated with MG-NGU and predominantly reflected microbiological failure in men with clinical cure. Mycoplasma genitalium MRMs, but not MG load or strain, were strongly associated with microbiological failure.

CONCLUSIONS

In azithromycin-treated NGU, clinical cure predicts microbiological cure for all STIs, except MG. Nongonococcal urethritis management should include MG testing and confirmation of microbiological cure in azithromycin-treated MG-NGU when MRM testing is unavailable.

Case Report: Candida dubliniensis as a Cause of Chronic Meningitis

Background: Candida dubliniensis is closely related to Candida albicans and rarely isolated in clinical specimens. C. dubliniensis is increasingly recognized as a pathogen in immunocompromised hosts. We present the third known case of Candida dubliniensis meningitis in a young immunocompetent host. Case Presentation: A 27-year-old female with a history of intravenous heroin use and chronic hepatitis C presented with a 10-month history of headaches and progressive bilateral vision loss. On physical examination, visual acuity was 20/20 in her right eye and grade II papilledema was noted. Examination of her left eye revealed complete loss of vision and grade IV papilledema. An MRI with and without contrast revealed increased leptomeningeal enhancement involving the posterior fossa and spinal cord. After multiple lumbar punctures, cerebrospinal fluid fungal cultures grew Candida dubliniensis. The patient was successfully treated with a combination of liposomal amphotericin and fluconazole for 6 weeks with complete resolution of her CNS symptoms, with the exception of irreversible vision loss. Conclusion: We report a case of chronic meningitis due to Candida dubliniensis in an immunocompetent woman with hepatitis C and a history of intravenous heroin use. Additional studies are needed to confirm risk factors for Candida dubliniensis colonization, which likely predisposes individuals to invasive candidiasis.

Aetiology and prevalence of mixed-infections and mono-infections in non-gonococcal urethritis in men: a case-control study

OBJECTIVES

Chlamydia trachomatis (CT) and Mycoplasma genitalium (MG) cause the majority of non-gonococcal urethritis (NGU). The role of Ureaplasma urealyticum (UU) in NGU is unclear. Prior case-control studies that examined the association of UU and NGU may have been confounded by mixed infections and less stringent criteria for controls. The objective of this case-control study was to determine the prevalence and aetiology of mixed infections in men and assess if UU monoinfection is associated with NGU.

METHODS

We identified 155 men with NGU and 103 controls. Behavioural and clinical information was obtained and men were tested for Neisseria gonorrhoeae and CT, MG, UU and Trichomonas vaginalis (TV). Men who were five-pathogen negative were classified as idiopathic urethritis (IU).

RESULTS

Twelve per cent of NGU cases in which a pathogen was identified had mixed infections, mostly UU coinfections with MG or CT; 27% had IU. In monoinfected NGU cases, 34% had CT, 17% had MG, 11% had UU and 2% had TV. In controls, pathogens were rarely identified, except for UU, which was present in 20%. Comparing cases and controls, NGU was associated with CT and MG monoinfections and mixed infections. UU monoinfection was not associated with NGU and was almost twice as prevalent in controls. Men in both the case and control groups who were younger and who reported no prior NGU diagnosis were more likely to have UU (OR 0.97 per year of age, 95% CI 0.94 to 0.998 and OR 6.3, 95% CI 1.4 to 28.5, respectively).

CONCLUSIONS

Mixed infections are common in men with NGU and most of these are UU coinfections with other pathogens that are well-established causes of NGU. UU monoinfections are not associated with NGU and are common in younger men and men who have never previously had NGU. Almost half of NGU cases are idiopathic.

Use of aspirin, other nonsteroidal anti-inflammatory drugs and acetaminophen and risk of endometrial cancer: the Epidemiology of Endometrial Cancer Consortium

BACKGROUND

Regular use of aspirin has been associated with a reduced risk of cancer at several sites but the data for endometrial cancer are conflicting. Evidence regarding use of other analgesics is limited.

PATIENTS AND METHODS

We pooled individual-level data from seven cohort and five case-control studies participating in the Epidemiology of Endometrial Cancer Consortium including 7120 women with endometrial cancer and 16 069 controls. For overall analyses, study-specific odds ratios (ORs) and 95% confidence intervals (CI) were estimated using logistic regression and combined using random-effects meta-analysis; for stratified analyses, we used mixed-effects logistic regression with study as a random effect.

RESULTS

At least weekly use of aspirin and non-aspirin nonsteroidal anti-inflammatory drugs (NSAIDs) was associated with an approximately 15% reduced risk of endometrial cancer among both overweight and obese women (OR = 0.86 [95% CI 0.76-0.98] and 0.86 [95% CI 0.76-0.97], respectively, for aspirin; 0.87 [95% CI 0.76-1.00] and 0.84 [0.74-0.96], respectively, for non-aspirin NSAIDs). There was no association among women of normal weight (body mass index < 25 kg/m2, Pheterogeneity = 0.04 for aspirin, Pheterogeneity = 0.003 for NSAIDs). Among overweight and obese women, the inverse association with aspirin was stronger for use 2-6 times/week (OR = 0.81, 95% CI 0.68-0.96) than for daily use (0.91, 0.80-1.03), possibly because a high proportion of daily users use low-dose formulations. There was no clear association with use of acetaminophen.

CONCLUSION

Our pooled analysis provides further evidence that use of standard-dose aspirin or other NSAIDs may reduce risk of endometrial cancer among overweight and obese women.

Stimulated peripheral blood mononuclear cells from chlamydia-infected women release predominantly Th1-polarizing cytokines

Chlamydia trachomatis infection (chlamydia) is the most prevalent sexually transmitted bacterial infection and causes significant reproductive morbidity in women. Little is known about how immunity to chlamydia develops in women, though animal models of chlamydia indicate that T-helper type 1 (Th1) responses are important for chlamydia clearance and protective immunity, whereas T-helper type 2 (Th2) responses are associated with persisting infection. In chlamydia-infected women, whether the predominant immune response is Th1- or Th2-polarizing remains controversial. To determine the cytokine profiles elicited by peripheral blood mononuclear cells (PBMCs) from chlamydia-infected women, we stimulated PBMCs with C. trachomatis elementary bodies and recombinant C. trachomatis Pgp3 and measured supernatant levels of select cytokines spanning Th1- and Th2-polarizing responses. We found that stimulated PBMCs from chlamydia-infected women secreted cytokines that indicate strong Th1-polarizing responses, especially interferon-gamma, whereas Th2-polarizing cytokines were expressed at significantly lower levels. In chlamydia-infected women, the predominant cytokine responses elicited on stimulation of PBMCs with C. trachomatis antigens were Th1-polarizing, with interferon-gamma as the predominant cytokine.

An Adaptive Chlamydia trachomatis-Specific IFN-γ-Producing CD4+ T Cell Response Is Associated With Protection Against Chlamydia Reinfection in Women

Background: Adaptive immune responses that mediate protection against Chlamydia trachomatis (CT) remain poorly defined in humans. Animal chlamydia models have demonstrated that CD4⁺ Th1 cytokine responses mediate protective immunity against reinfection. To better understand protective immunity to CT in humans, we investigated whether select CT-specific CD4⁺ Th1 and CD8⁺ T cell cytokine responses were associated with protection against CT reinfection in women. Methods: Peripheral blood mononuclear cells were collected from 135 CT-infected women at treatment and follow-up visits and stimulated with CT antigens. CD4⁺ and CD8⁺ T-cells expressing IFN-γ, TNF-α, and/or IL-2 were assessed using intracellular cytokine staining and cytokine responses were compared between visits and between women with vs. without CT reinfection at follow-up. Results: A CD4⁺TNF-α response was detected in the majority (77%) of study participants at the treatment visit, but a lower proportion had this response at follow-up (62%). CD4⁺ IFN-γ and CD4⁺ IL-2 responses occurred less frequently at the treatment visit (32 and 18%, respectively), but increased at follow-up (51 and 41%, respectively). CD8⁺ IFN-γ and CD8⁺ TNF-α responses were detected more often at follow-up (59% for both responses) compared to the treatment visit (30% for both responses). At follow-up, a CD4⁺IFN-γ response was detected more often in women without vs. with reinfection (60 vs. 33%, P = 0.005). Conclusions: Our findings suggest that a CT-specific CD4⁺ IFN-γ response is associated with protective immunity against CT reinfection and is thus an important component of adaptive immunity to CT in women.

T cell phenotypes in women with Chlamydia trachomatis infection and influence of treatment on phenotype distributions

T cell phenotypes involved in the immune response to Chlamydia trachomatis (CT) have not been fully elucidated in humans. We evaluated differences in T cell phenotypes between CT-infected women and CT-seronegative controls and investigated changes in T cell phenotype distributions after CT treatment and their association with reinfection. We found a higher expression of T cell activation markers (CD38⁺HLA-DR⁺), T helper type 1 (Th1)- and Th2-associated effector phenotypes (CXCR3⁺CCR5⁺ and CCR4⁺, respectively), and T cell homing marker (CCR7) for both CD4⁺ and CD8⁺ T cells in CT-infected women. At follow-up after treatment of infected women, there were a lower proportion of CD4⁺ and CD8⁺ T cells expressing these markers. These findings suggest a dynamic interplay of CD4⁺ and CD8⁺ T cells in CT infection, and once the infection is treated, these cell markers return to basal expression levels. In women without reinfection, a significantly higher proportion of CD8⁺ T cells co-expressing CXCR3 with CCR5 or CCR4 at follow-up was detected compared to women with reinfection, suggesting they might play some role in adaptive immunity. Our study elucidated changes in T cell phenotypes during CT infection and after treatment, broadening our understanding of adaptive immune mechanisms in human CT infections.

Immunoglobulin-Based Investigation of Spontaneous Resolution of Chlamydia trachomatis Infection

Chlamydia trachomatis elementary body enzyme-linked immunosorbent assay (ELISA) was used to investigate serum anti-CT immunoglobulin G1 (IgG1; long-lived response) and immunoglobulin G3 (IgG3; short-lived response indicating more recent infection) from treatment (enrollment) and 6-month follow-up visits in 77 women previously classified as having spontaneous resolution of chlamydia. Of these women, 71.4% were IgG1+IgG3+, consistent with more recent chlamydia resolution. 15.6% were IgG3- at both visits, suggesting absence of recent chlamydia. Using elementary body ELISA, we demonstrated approximately 1 in 6 women classified as having spontaneous resolution of chlamydia might have been exposed to C. trachomatis but not infected. Further, we classified their possible infection stage.

Lower Levels of Cervicovaginal Tryptophan Are Associated With Natural Clearance of Chlamydia in Women

Chlamydiatrachomatis (Ct) infection causes significant morbidity. In vitro studies demonstrate that Ct growth inhibition occurs by interferon-gamma (IFN-γ)-mediated depletion of intracellular tryptophan, and some Ct strains utilize extracellular indole to restore tryptophan levels. Whether tryptophan levels are associated with Ct infection clearance in humans remains unknown. We evaluated tryptophan, indole, and IFN-γ levels in cervicovaginal lavages from women with either naturally cleared or persisting Ct infection. Women who cleared infection had significantly lower tryptophan levels and trended toward lower IFN-γ levels compared to women with persisting infection. Due to its volatility, indole was not measurable in either group.

Determinants of survival and attempted resection in patients with non-metastatic pancreatic cancer: An Australian population-based study

BACKGROUND

There are indications that pancreatic cancer survival may differ according to sociodemographic factors, such as residential location. This may be due to differential access to curative resection. Understanding factors associated with the decision to offer a resection might enable strategies to increase the proportion of patients undergoing potentially curative surgery.

METHODS

Data were extracted from medical records and cancer registries for patients diagnosed with pancreatic cancer between July 2009 and June 2011, living in one of two Australian states. Among patients clinically staged with non-metastatic disease we examined factors associated with survival using Cox proportional hazards models. To investigate survival differences we examined determinants of: 1) attempted surgical resection overall; 2) whether patients with locally advanced disease were classified as having resectable disease; and 3) attempted resection among those considered resectable.

RESULTS

Data were collected for 786 eligible patients. Disease was considered locally advanced for 561 (71%) patients, 510 (65%) were classified as having potentially resectable disease and 365 (72%) of these had an attempted resection. Along with age, comorbidities and tumour stage, increasing remoteness of residence was associated with poorer survival. Remoteness of residence and review by a hepatobiliary surgeon were factors influencing the decision to offer surgery.

CONCLUSIONS

This study indicated disparity in survival dependent on patients' residential location and access to a specialist hepatobiliary surgeon. Accurate clinical staging is a critical element in assessing surgical resectability and it is therefore crucial that all patients have access to specialised clinical services.

Acute Cryptococcal Immune Reconstitution Inflammatory Syndrome in a Patient on Natalizumab

Presented is the first case of acute immune reconstitution inflammatory syndrome (IRIS)-associated cryptococcal meningoencephalitis in a patient on natalizumab for multiple sclerosis. The patient developed acute cerebral edema after initiation of amphotericin B. We propose several mechanisms that explain the acuity of IRIS in this specific patient population and suggest possible therapies.

Increasing thyroid cancer incidence in Queensland, Australia 1982-2008 - true increase or overdiagnosis?

BACKGROUND

Thyroid cancer incidence has been increasing worldwide. Some suggest greater ascertainment of indolent tumours is the only driver, but others suggest there has been a true increase. Increases in Australia appear to have been among the largest in the world, so we investigated incidence trends in the Australian state of Queensland to help understand reasons for the rise.

METHODS

Thyroid cancers diagnoses in Queensland 1982-2008 were ascertained from the Queensland Cancer Registry. We calculated age-standardized incidence rates (ASR) and used Poisson regression to estimate annual percentage change (APC) in thyroid cancer incidence by socio-demographic and tumour-related factors.

RESULTS

Thyroid cancer ASR in Queensland increased from 2·2 to 10·6/100 000 between 1982 and 2008 equating to an APC of 5·5% [95% confidence interval (CI) 4·7-6·4] in men and 6·1% (95% CI 5·5-6·6) in women. The rise was evident, and did not significantly differ, across socio-economic and remoteness-of-residence categories. The largest increase seen was in the papillary subtype in women (APC 7·9%, 95% CI 7·3-8·5). Incidence of localized and more advanced-stage cancers rose over time although the increase was greater for early-stage cancers.

CONCLUSION

There has been a marked increase in thyroid cancer incidence in Queensland. The increase is evident in men and women across all adult age groups, socio-economic strata and remoteness-of-residence categories as well as in localized and more advanced-stage cancers. Our results suggest 'overdiagnosis' may not entirely explain rising incidence. Contemporary aetiological data and individual-level information about diagnostic circumstances are required to further understand reasons for rising thyroid cancer incidence.

Identifying evaluation considerations for the recovery and restoration from the 2010 Gulf of Mexico oil spill: An initial appraisal of stakeholder concerns and values

Understanding what can be achieved and what should be avoided by environmental management decisions requires an understanding of values, or what is cared about in a decision. Decision analysis provides tools and processes for constructing objectives that transparently reflect the values being considered in environmental management decisions. The present study demonstrates parts of the initial decision analysis steps for identifying a decision context and constructing objectives for the recovery and long-term restoration of the Gulf of Mexico following the 2010 Deepwater Horizon oil spill. From a review of multiple reports, including those developed by policy makers and nongovernmental organizations, a preliminary structuring of concerns and considerations into objectives was derived to highlight features of importance in the recovery from the spill and long-term restoration. The fundamental objectives constructed for the long-term restoration context reflect broader concerns regarding well-being and quality of life. When developed through stakeholder engagement processes, clarifying objectives can potentially 1) lend insight into the values that can be affected, 2) meaningfully include stakeholders in the decision-making process, 3) enhance transparency and communication, and 4) develop high-impact management strategies reflecting broad public interests. This article is a US government work and is in the public domain in the United States of America.

Sustainable watersheds: integrating ecosystem services and public health

Sustainable management of aquatic ecosystems is a worldwide priority; the integrity of these systems depends, in turn, on the integrity of the watersheds (catchments) in which they are embedded. In this article, we present the concepts, background, and scientific foundations for assessing, both nationally and at finer scales, the relationships between ecosystem services, human health, and socioeconomic values in the context of water quality, water quantity, landscapes, the condition of watersheds, and the connectivity of waters, from headwaters to estuaries and the coastal ocean. These assessments will be a foundation for what we have termed "watershed epidemiology," through which the connections between ecosystems and human health can be explored over broad spatial and temporal scales. Understanding and communicating these relationships should lead to greater awareness of the roles watersheds play in human well-being, and hence to better management and stewardship of water resources. The U.S. Environmental Protection Agency is developing the research, models, and planning tools to support operational national assessments of watershed sustainability, building upon ongoing assessments of aquatic resources in streams, rivers, lakes, wetlands and estuaries.

Effects of nitrogen inputs on freshwater wetland ecosystem services - a Bayesian network analysis

Increased nitrogen (N) inputs to freshwater wetlands potentially affect the interaction between nitrous oxide (N2O) emissions and outflow water quality. The purpose of this study is to evaluate the influence of N inputs on N removal, as well as the interaction between N2O emissions and outflow water quality, using a Bayesian Belief Network (BBN). The BBN was developed by linking wetland classification, biogeochemical processes, and environmental factors. Empirical data for 34 freshwater wetlands were gathered from a comprehensive review of published peer-reviewed and gray literature. The BBN was implemented using 30 wetlands (88% of the case file) and evaluated using a single test file containing 4 wetlands (12% of the case file). The BBN implies it is not average annual total N load entering the wetland, but the N removal efficiency that influences the interactions between N2O emissions and outflow water quality. Even though the network has a very low error rate indicating a high predictive accuracy, additional testing and larger training and testing datasets would increase confidence in the model's ability to provide robust predictions and to reduce the uncertainty resulting from an incomplete dataset and knowledge gaps regarding the interactions between N2O emissions and outflow water quality.

Breast-feeding and risk of epithelial ovarian cancer

PURPOSE

Evidence suggests that breast-feeding may decrease the risk of epithelial ovarian cancer but it is not clear whether there is a relationship with duration of breast-feeding, patterns of breast-feeding, or particular histological subtypes of ovarian cancer. We sought to investigate these issues in detail.

METHODS

Data from participants in a population-based study of ovarian cancer in western Washington State, USA (2002-2007) who had had at least one birth (881 cases and 1,345 controls) were used to assess relations between patterns of breast-feeding and ovarian cancer. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Women who ever breast-fed had a 22 % reduction in risk of ovarian cancer compared with those who never breast-fed (OR = 0.78, 95% CI 0.64-0.96) and risk reduction appeared greater with longer durations of feeding per child breast-fed (OR = 0.56, 95% CI 0.32-0.98 for 18 months average duration breast-feeding versus none). Introduction of supplementary feeds did not substantially alter these effects. The overall risk reduction appeared greatest for the endometrioid and clear cell subtypes (OR per month of average breast-feeding per child breast-fed = 0.944, 95% CI 0.903-0.987).

CONCLUSIONS

Among women who have had the opportunity to breast-feed, ever breast-feeding and increasing durations of episodes of breast-feeding for each breast-fed child are associated with a decrease in the risk of ovarian cancer independent of numbers of births, which may be strongest for the endometrioid subtype.

Ecosystem services altered by human changes in the nitrogen cycle: a new perspective for US decision making

Human alteration of the nitrogen (N) cycle has produced benefits for health and well-being, but excess N has altered many ecosystems and degraded air and water quality. US regulations mandate protection of the environment in terms that directly connect to ecosystem services. Here, we review the science quantifying effects of N on key ecosystem services, and compare the costs of N-related impacts or mitigation using the metric of cost per unit of N. Damage costs to the provision of clean air, reflected by impaired human respiratory health, are well characterized and fairly high (e.g. costs of ozone and particulate damages of $28 per kg NO(x)-N). Damage to services associated with productivity, biodiversity, recreation and clean water are less certain and although generally lower, these costs are quite variable (<$2.2-56 per kg N). In the current Chesapeake Bay restoration effort, for example, the collection of available damage costs clearly exceeds the projected abatement costs to reduce N loads to the Bay ($8-15 per kg N). Explicit consideration and accounting of effects on multiple ecosystem services provides decision-makers an integrated view of N sources, damages and abatement costs to address the significant challenges associated with reducing N pollution.

Antibodies directed against merozoite surface protein-6 are induced by natural exposure to Plasmodium falciparum in a low transmission environment

Malaria caused by Plasmodium falciparum is a major cause of global infant mortality, and there is currently no licensed vaccine that provides protection against infection or disease. Several P. falciparum vaccine targets have undergone early testing, but many more candidates remain with little data to support their development. Plasmodium falciparum Merozoite Surface Protein 6 (PfMSP6) is a candidate of particular interest because it is a member of the PfMSP3 multi-gene family, raising the possibility that vaccine-induced immune responses could cross-react across multiple family members. However, few immunoepidemiological studies of PfMSP6 have been carried out to measure domain-specific anti-PfMSP6 responses. This study investigated anti-PfMSP6 responses in P. falciparum-infected individuals from the Peruvian Amazon, using two different PfMSP6 N-terminal allele antigens and a single C-terminal domain antigen, and compared the responses with both PfMSP6 genotyping data and anti-PfMSP3 response data that had been previously generated for the same samples. Anti-PfMSP6 responses were detected despite the low transmission setting, but were less frequent and of considerably lower intensity than anti-PfMSP3 responses. There was a positive correlation between anti-PfMSP3 and PfMSP6 responses, suggesting that the possibility that PfMSP3 family antigens could induce cross-reactive responses requires further detailed investigation.

Limited variation in vaccine candidate Plasmodium falciparum Merozoite Surface Protein-6 over multiple transmission seasons

BACKGROUND

Plasmodium falciparum Merozoite Surface Protein-6 (PfMSP6) is a component of the complex proteinacious coat that surrounds P. falciparum merozoites. This location, and the presence of anti-PfMSP6 antibodies in P. falciparum-exposed individuals, makes PfMSP6 a potential blood stage vaccine target. However, genetic diversity has proven to be a major hurdle for vaccines targeting other blood stage P. falciparum antigens, and few endemic field studies assessing PfMSP6 gene diversity have been conducted. This study follows PfMSP6 diversity in the Peruvian Amazon from 2003 to 2006 and is the first longitudinal assessment of PfMSP6 sequence dynamics.

METHODS

Parasite DNA was extracted from 506 distinct P. falciparum infections spanning the transmission seasons from 2003 to 2006 as part of the Malaria Immunology and Genetics in the Amazon (MIGIA) cohort study near Iquitos, Peru. PfMSP6 was amplified from each sample using a nested PCR protocol, genotyped for allele class by agarose gel electrophoresis, and sequenced to detect diversity. Allele frequencies were analysed using JMP v.8.0.1.0 and correlated with clinical and epidemiological data collected as part of the MIGIA project.

RESULTS

Both PfMSP6 allele classes, K1-like and 3D7-like, were detected at the study site, confirming that both are globally distributed. Allele frequencies varied significantly between transmission seasons, with 3D7-class alleles dominating and K1-class alleles nearly disappearing in 2005 and 2006. There was a significant association between allele class and village location (p-value = 0.0008), but no statistically significant association between allele class and age, sex, or symptom status. No intra-allele class sequence diversity was detected.

CONCLUSIONS

Both PfMSP6 allele classes are globally distributed, and this study shows that allele frequencies can fluctuate significantly between communities separated by only a few kilometres, and over time in the same community. By contrast, PfMSP6 was highly stable at the sequence level, with no SNPs detected in the 506 samples analysed. This limited diversity supports further investigation of PfMSP6 as a blood stage vaccine candidate, with the clear caveat that any such vaccine must either contain both alleles or generate cross-protective responses that react against both allele classes. Detailed immunoepidemiology studies are needed to establish the viability of these approaches before PfMSP6 advances further down the vaccine development pipeline.

Effects of nutrient pre-exposure on atrazine toxicity to Vallisneria americana Michx. (wild celery)

Accelerated eutrophication is common to many freshwater and marine environments and often co-occurs with the presence of anthropogenic chemicals. However, the toxic effects of common chemical stressors such as herbicides in the presence of elevated nutrients are not well understood for most aquatic flora, particularly vascular species. To provide insight, field-collected Vallisneria americana Michx. (wild celery) were sequentially exposed to three nutrient concentrations for 3 months and then to nominal 11 and 110 microg L(-1) atrazine for 96 h. Nutrient concentrations (combined NH(4)(+), NO(2)(-), NO(3)(-), PO(4)(-)) were based on ambient concentrations in the St. Johns River (FL) and ranged from 0.013 to 0.668 mg L(-1). Nutrient pretreatment potentiated the toxicity of atrazine as determined by chlorophyll fluorescence activity. Electron transport rates (ETR) were significantly less (48-59%) for plants pretreated with low and ambient nutrient levels in the presence of an average of 107.5-128.1 microg L(-1) atrazine. Significant ETR reductions were also observed for plants exposed to an average of 11.4 microg L(-1) atrazine after exposure to nutrients three times the ambient concentration in the St. Johns River. The results indicate the importance of considering the presence of nutrients in chemical hazard assessments, particularly for phytotoxicants and nontarget vascular plants.

Accounting for natural resources and environmental sustainability: linking ecosystem services to human well-being

One of society's greatest challenges is to sustain natural resources while promoting economic growth and quality of life. In the face of this challenge, society must measure the effectiveness of programs established to safeguard the environment. The impetus for demonstrating positive results from government-sponsored research and regulation in the United States comes from Congress (General Accountability Office; GAO) and the Executive Branch (Office of Management and Budget; OMB). The message is: regulatory and research programs must demonstrate outcomes that justify their costs. Although the concept is simple, it is a complex problem to demonstrate that environmental research, policies, and regulations cause measurable changes in environmental quality. Even where changes in environmental quality can be tracked reliably, the connections between government actions and environmental outcomes seldom are direct or straightforward. In this article, we describe emerging efforts (with emphasis on the role of the U.S. Environmental Protection Agency; EPA) to frame and measure environmental outcomes in terms of ecosystem services and values-societally and ecologically meaningful metrics for gauging how well we manage environmental resources. As examples of accounting for outcomes and values, we present a novel, low-cost method for determining relative values of multiple ecosystem services, and describe emerging research on indicators of human well-being.

Genetic diversity of the malaria vaccine candidate Plasmodium falciparum merozoite surface protein-3 in a hypoendemic transmission environment

The N-terminal domain of Plasmodium falciparum merozoite surface protein-3 (PfMSP3) has been excluded from malaria vaccine development largely because of genetic diversity concerns. However, no study to date has followed N-terminal diversity over time. This study describes PfMSP3 variation in a hypoendemic longitudinal cohort in the Peruvian Amazon over the 2003-2006 transmission seasons. Polymerase chain reaction was used to amplify the N-terminal domain in 630 distinct P. falciparum infections, which were allele-typed by size and also screened for sequence variation using a new high-throughput technique, denaturing high performance liquid chromatography. PfMSP3 allele frequencies fluctuated significantly over the 4-year period, but sequence variation was very limited, with only 10 mutations being identified of 630 infections screened. The sequence of the PfMSP3 N-terminal domain is relatively stable over time in this setting, and further studies of its status as a vaccine candidate are therefore warranted.

Transient association of Ku with nuclear substrates characterized using fluorescence photobleaching

The autoantigen Ku, composed of subunits Ku70 and Ku86, is necessary for repair of DNA double-strand breaks by nonhomologous end joining. Similarly, Ku participates in repair of DNA double-strand breaks that occur during V(D)J recombination, and it is therefore required for the development of B and T lymphocytes. Although previous studies have identified the DNA-binding activities of Ku, little is known concerning its dynamics, such as the mobility of Ku in the nucleus and its rate of association with substrates. To address this question, fluorescence photobleaching experiments were performed using HeLa cells and B cells expressing a green fluorescent protein (GFP) fusion construct of either Ku70 or Ku86. The results show that Ku moves rapidly throughout the nucleus even following irradiation of the cells. However, the rate of diffusion of Ku was approximately 100-fold slower than that predicted from its size. Association of Ku-GFP with a filamentous nuclear structure was also evident, and nuclear extraction experiments suggest that this represents nuclear matrix. A central domain of Ku70 containing its DNA-binding and heterodimerization regions and its nuclear localization signal shows that this alone is sufficient for the observed mobility of Ku70-GFP and its association with nuclear matrix. These data suggest the mobility of Ku is characterized by a transient, high flux association with nuclear substrates that includes both DNA and the nuclear matrix and may represent a mechanism for repair of double-strand breaks using the nuclear matrix as a scaffold.

Use of single-strand conformation polymorphism analysis to examine the variability of the rpoS sequence in environmental isolates of Salmonellae

The natural environment places its resident microflora under stress, which may often result in adaptation by the microflora in order to increase the probability of survival. One such mechanism that has been postulated involves rpoS, which encodes a sigma factor that is known to enhance survival upon exposure to stress. The present work aimed to examine the genetic variability of rpoS in a selection of Salmonella enterica subspecies environmental isolates with an automated single-strand conformation polymorphism analysis technique. The results indicated that sequence variation does occur and that these changes are mainly located in two areas: at the center and near the end of the coding region. The variability was generally at the single-base level, although one strain (S. arizonae) did demonstrate significant differences in nucleotide sequence.

In vivo production of nitric oxide in rats after administration of hydroxyurea

The metabolism of nitrovasodilators such as glyceryl trinitrate and nitroprusside provides the active moiety of these drugs (that is, nitric oxide). This process is not limited to the known nitrovasodilators, but also occurs with nitroaromatic antimicrobials. Here we report that the administration of hydroxyurea, an antitumor drug, to rats at pharmacological doses formed detectable nitrosyl hemoglobin, which increased with dose. At higher doses, nitrosyl hemoprotein complexes could also be detected in liver tissue. [15N]hydroxyurea was synthesized and compared with [14N]hydroxyurea. These observations verified that nitric oxide detected as nitrosyl hemoglobin or nitrosyl hemoprotein complexes in rats was the result of the metabolism of hydroxyurea. The time course and dose-dependence of nitric oxide generation were also investigated. Hydroxyurea's antineoplastic activity is caused by its direct action on ribonucleotide reductase, the rate-limiting enzyme in DNA synthesis. Because nitric oxide also inhibits ribonucleotide reductase, this metabolite may supplement this action of hydroxyurea. In addition, the known ability of hydroxyurea to ease the pain of sickle cell anemia patients may be the result of vasodilation by the drug-derived nitric oxide.

Detection of free radical metabolite formation using in vivo EPR spectroscopy: evidence of rat hemoglobin thiyl radical formation following administration of phenylhydrazine

The spin-trapping technique in conjunction with a low-frequency electron paramagnetic (or spin) resonance (EPR or ESR) spectrometer was used to detect the hemoglobin thiyl free radical in living rats using a whole body resonator. The hemoglobin thiyl free radical was formed following the intragastric administration of phenylhydrazine at the LD50 dose of 188 mg/kg. The hemoglobin thiyl free radical was then trapped by preinjected 5,5-dimethyl-1-pyrroline N-oxide (DMPO), which formed the DMPO/hemoglobin thiyl-free radical adduct in the blood. The time course of the in vivo formation and disappearance of the spin adduct was followed. The DMPO/hemoglobin thiyl free radical was detected in blood samples using 9.5 GHz (X-band) and 1.1 GHz (L-band) EPR at room temperature and 77 K. Pretreatment of rats with ascorbate and diethylmaleate (DEM) decreased the signal intensity of the DMPO/hemoglobin thiyl free radical spin adduct. The incubation of ascorbate or DEM at 37 degrees C with rat blood containing preformed DMPO/hemoglobin thiyl radical adduct showed that there was no effect of DEM on the free radical concentration, while ascorbate reduced the radical adduct. This study provided direct evidence of the formation of the DMPO/hemoglobin thiyl free radical in vivo and enabled us to study this formation in living animals free of any artifacts that can occur when using ex vivo methods.

Tumor necrosis factor-alpha and nitric oxide production in endotoxin-primed rats administered carbon tetrachloride

Tumor necrosis factor-alpha (TNF alpha) is elevated in the sera of rats administered non-lethal doses of carbon tetrachloride (CCl4) followed by endotoxin. Elevated TNF alpha levels are correlated with the increased release of hepatic enzymes indicating hepatic damage. Under these conditions, nitric oxide (NO) was also produced in the liver as evidenced by the formation of nitrosyl complexes which were measured by electron paramagnetic resonance (EPR) spectroscopy. Decreased nitrosyl complex formation occurred in livers following treatment with either an inhibitor or macrophage activation (gadolinium trichloride; GdCl3), an inhibitor of cytokine responses (dexamethasone) or a NO synthase inhibitor (NG-monomethyl-L-arginine; 1-NMA), GdCl3 or dexamethasone treatment decreased, while 1-NMA treatment increased, TNF alpha serum level. Taken together, these data suggest that TNF alpha and NO are induced following CCl4 and LPS exposure and may be important regulators in the hepatotoxicity of this liver injury model.

Targets of nitric oxide in a mouse model of liver inflammation by Corynebacterium parvum

Treatment of mice with Corynebacterium parvum induces chronic inflammation. This treatment followed by an injection of lipopolysaccharide (LPS) produces hepatic necrosis and death. We examined liver tissue by using electron paramagnetic resonance (EPR) spectroscopy and found that, in addition to the previously reported nonheme nitrosyl complexes, heme nitrosyl complexes were also formed. Hemoglobin nitrosyl complexes measured in the whole blood of mice treated with C. parvum were not increased after additional LPS treatment. However, this treatment significantly increased the heme nitrosyl complexes in the liver, whereas the nonheme nitrosyl complex concentration was unaffected. EPR signals from whole blood and liver tissues from mice treated with C. parvum and C. parvum + LPS were inhibited by prolonged treatment with NG-monomethyl-L-arginine (L-NMA). Nitric oxide (.NO) is known to bind to cytochrome P450 heme, and we consistently found a suppression of EPR signals attributable to ferric low-spin cytochrome P450/P420 peaks in the livers of mice treated with C. parvum and C. parvum + LPS. By performing analyses of EPR spectra obtained from hepatocytes exposed to .NO, we were able to unambiguously identify EPR signals attributable to cytochrome P420 and nonheme nitrosyl complexes in the livers of both treatments. Deconvolution of the composite in vivo EPR spectra indicated that hemoglobin nitrosyl complexes contributed weakly in the C. parvum livers, but threefold more in the C. parvum + LPS livers, suggesting that hemorrhage may have occurred. Experiments with L-NMA treatment revealed that this additional .NO production did not correlate with hepatic necrosis and onset of death. Immunoprecipitation of liver cytosols from C. parvum- and (C. parvum + LPS)-treated mice using an antibody against mouse inducible nitric oxide synthase showed that this enzyme was indeed present in the cytosolic fractions and was absent in those from control livers. Our novel detection of cytochrome P420 nitrosyl complex in vivo may be linked to any role of hepatic P450's functions during liver inflammation.

The metabolism of 17 beta-estradiol by lactoperoxidase: a possible source of oxidative stress in breast cancer

Electron spin resonance (ESR) spectroscopy and oxygen consumption measurements using a Clark-type oxygen electrode have been used to study the metabolism of the estrogen 17 beta-estradiol by lactoperoxidase. Evidence for a one-electron oxidation of estradiol to its reactive phenoxyl radical intermediate is presented. The phenoxyl radical metabolite abstracts hydrogen from reduced glutathione generating the glutathione thiyl radical, which is spin trapped by 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and subsequently detected by ESR spectroscopy. In the absence of DMPO, molecular oxygen is consumed by a sequence of reactions initiated by the glutathione thiyl radical. Similarly, the estradiol phenoxyl radical abstracts hydrogen from reduced beta-nicotinamide-adenine dinucleotide (NADH) to generate the NAD. radical. The NAD. radical is not spin trapped by DMPO, but instead reduces molecular oxygen to the superoxide radical, which is then spin-trapped by DMPO. The superoxide generated may either spontaneously dismutate to form hydrogen peroxide or react with another NADH to form NAD., thus propagating a chain reaction leading to oxygen consumption and hydrogen peroxide accumulation. Ascorbate inhibits oxygen consumption when estradiol is metabolized in the presence of either glutathione or NADH by reducing radical intermediates back to their parent molecules and forming the relatively stable ascorbate radical. These results demonstrate that the futile metabolism of micromolar quantities of estradiol catalyzes the oxidation of much greater concentrations of biochemical reducing cofactors, such as glutathione and NADH, with hydrogen peroxide produced as a consequence. The accumulation of intracellular hydrogen peroxide could explain the hydroxyl radical-induced DNA base lesions recently reported for female breast cancer tissue.

Nitric oxide production during endotoxic shock in carbon tetrachloride-treated rats

Earlier studies showed that hepatotoxicant-treated experimental animals were more susceptible than controls to the lethal effects of bacterial endotoxin. The exact mechanisms of this effect were not understood. In this paper we showed that nitric oxide (.NO) was produced in whole blood and in liver tissues of rats that had been treated with a nonlethal dose of CCl4 (1.3 g/kg) followed by a low dose of lipopolysaccharide (LPS) (100 micrograms/kg). EPR spectroscopy was used in this study to detect nitrosyl-protein complexes. Hemoglobin-nitrosyl complexes were detected in both whole blood and liver. By performing analyses of EPR spectra obtained from hepatocytes exposed to .NO, we were able to identify EPR signals attributable to nitrosyl-cytochrome P420 in rat liver. We found that nitrosyl complex formation in red blood cells and liver was inhibited by treatment with NG-mono-methyl-L-arginine, suggesting enzymatic biosynthesis of .NO. A small but significant inhibition of nitrosyl complex formation by gadolinium trichloride pretreatment was found in the liver, suggesting that Kupffer cells were also involved in .NO biosynthesis, because this treatment decreased Kupffer cells. There was a synergistic effect of CCl4 and LPS on the serum levels of the hepatic enzymes aspartate aminotransferase, alanine amino-transferase, lactate dehydrogenase, and sorbitol dehydrogenase, which are indices of parenchymal cell damage. NG-Mono-methyl-L-arginine treatment increased these hepatic enzyme activities, suggesting a protective role for .NO. EPR resonances at g approximately 2.48, 2.29, and 1.91, due to low-spin cytochromes P450/P420 (FE3+), were decreased in the livers of LPS-induced rats that had been previously treated with CCl4, indicating cytochrome P450/P420 destruction or at least a change in the valence state of the cytochrome P450/P420 heme groups to Fe2+ in the presence of .NO. Because nitrosyl-cytochrome P450 is not stable, the concomitant detection of nitrosyl-cytochrome P420 (Fe2+) could account, at least in part, for the decrease of the ferric low-spin heme groups. Our novel observations of hepatic nitrosyl species suggest that .NO plays an important role during hepatic injury caused by CCl4 in hosts exposed to endotoxin.

Role of metallothionein in zinc(II) and chromium(III) mediated tolerance to carbon tetrachloride hepatotoxicity: evidence against a trichloromethyl radical-scavenging mechanism

The .CCl3 radical generated during the metabolism of CCl4 is readily spin trapped in vivo and in vitro by phenyl N-tert-butylnitrone (PBN) to form the stable PBN/.CCl3 radical adduct, which can then be extracted into organic solvents and detected by ESR spectroscopy. We have used this technique to examine the proposed protective roles of Zn(II), Cr(III), and metallothionein (MT) against carbon tetrachloride toxicity in vivo. Hepatic MT, which is induced by Zn(II), has been proposed to protect against CCl4-induced cellular damage by scavenging the free radical metabolites formed. CCl4-induced hepatotoxicity was significantly suppressed in male Sprague-Dawley rats pretreated with a single dose of 5 mg/kg Zn(II) or Cr(III) according to standard serum assays for liver-specific enzymes, and hepatic MT was elevated after pretreatment with either Zn(II) or Cr(III). In vitro, no difference was detected in either the amount of CCl4-derived free radical metabolites formed or the rate at which they were formed by microsomes from rats pretreated 24 h in advance with 5 mg/kg Zn(II) or Cr(III). Extraction of rat liver with 2:1 chloroform/methanol 1 h after the administration of a 0.8 mL/kg intraperitoneal or intragastric dose of CCl4 also revealed no difference in the amount of trichloromethyl radical spin trapped in vivo following pretreatment with either Zn(II) or Cr(III). These results suggest that pretreatment with either Zn(II) or Cr(III) does not affect CCl4 metabolism nor does the MT significantly scavenge the trichloromethyl free radical metabolite.

Electron spin resonance evidence for free radical generation in copper-treated vitamin E- and selenium-deficient rats: in vivo spin-trapping investigation

The ESR spin-trapping technique has been used to investigate free radical generation in copper-challenged rats deficient in vitamin E and/or selenium. Radical adduct excreted in the bile was detected only from copper-challenged rats deficient in both vitamin E and selenium. The phenyl-N-t-butylnitrone radical adduct has hyperfine coupling constants of aN = 15.36 G and a beta H = 2.50 G and arises from the trapping of a radical formed from an endogenous molecular species. The induction of this radical species in vivo may be important in the increased toxicity of copper in rats deficient in both vitamin E and selenium. These findings support the proposal that dietary selenium and vitamin E can protect against lipid peroxidation and copper toxicity. The results obtained suggest that the presence of only one of these nutrients in the diet is enough to prevent the formation of this radical adduct at ESR-detectable levels, and they provide the most direct ESR evidence yet obtained for the involvement of in vivo lipid peroxidation in the toxicity of copper.

Nitric oxide formation during light-induced decomposition of phenyl N-tert-butylnitrone

Phenyl N-tert-butylnitrone (PBN) is a spin trap commonly employed in free radical research. PBN has been shown to have adverse and beneficial effects on various biological systems. We report here evidence that photolysis (or even ambient light) decomposes PBN to nitric oxide in aqueous solutions. Non-heme and heme proteins have been employed to form nitrosyl complexes, which were detected using EPR spectroscopy. Concomitantly, nitrite formation was detected after light-induced decomposition of PBN. In addition, we found that tert-nitrosobutane and decomposed PBN caused an activation of guanylate cyclase. We propose a mechanism where PBN is decomposed by light to tert-nitrosobutane. The latter compound is, in turn, decomposed to nitric oxide. This study suggests the possibility that PBN or PBN radical adducts may be sources of nitric oxide in biological environments. When using PBN as a spin trap in biological samples, not only is the trapping of reactive free radicals operative, but nitric oxide produced from PBN decomposition may play an important role in altering biological functions.

Electron spin resonance spin-trapping investigation into the effects of paraquat and desferrioxamine on hydroxyl radical generation during acute iron poisoning

We have previously described a secondary radical-trapping technique for the detection of in vivo hydroxyl radical generation during acute iron overload. With this technique, the hydroxyl radical (.OH) reacts with dimethylsulfoxide to form the methyl radical (.CH3), which is then detected by ESR spectroscopy as its adduct with the spin trap phenyl-N-tert-butylnitrone in the bile of treated animals. In this study, we report both the individual and combined effects of the futile-cycling agent paraquat (PQ2+) and the iron-chelating agent desferrioxamine (DFO) on iron-dependent .OH generation. Interactions between iron and the partially reduced oxygen species superoxide and hydrogen peroxide, which are generated during the metabolism of PQ2+, might be expected to stimulate .OH generation to a level above that seen in the presence of the metal ion alone. Although PQ2+ was often found to promote further .OH generation when administered to animals also given iron, the large variation observed between individual animals in response to the reagent meant that the effect was not statistically significant (p < 0.05). DFO was found to abolish iron-dependent .OH generation, both in the presence and in the absence of PQ2+. This is believed to result from the chelation of iron by DFO, to form an essentially redox-inert iron(III) complex that is unable to catalyze .OH radical formation. In addition, it was found that the iron(II) complex of DFO can reduce PQ2+ to its radical cation in vitro, indicating, therefore, that the chelation of iron by DFO may not necessarily prevent its participation in free radical reactions.

Fatty acid radical formation in rats administered oxidized fatty acids: in vivo spin trapping investigation

We report in vivo evidence for fatty acid-derived free radical metabolite formation in bile of rats dosed with spin traps and oxidized polyunsaturated fatty acids (PUFA). When rats were dosed with the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) and oxidized PUFA, the DMPO thiyl radical adduct was formed due to a reaction between oxidized PUFA and/or its metabolites with biliary glutathione. In vitro experiments were performed to determine the conditions necessary for the elimination of radical adduct formation by ex vivo reactions. Fatty acid-derived radical adducts of alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) were detected in vivo in bile samples collected into a mixture of iodoacetamide, desferrioxamine, and glutathione peroxidase. Upon the administration of oxidized 13C-algal fatty acids and 4-POBN, the EPR spectrum of the radical adducts present in the bile exhibited hyperfine couplings due to 13C. Our data demonstrate that the carbon-centered radical adducts observed in in vivo experiments are unequivocally derived from oxidized PUFA. This in vivo evidence for PUFA-derived free radical formation supports the proposal that processes involving free radicals may be the molecular basis for the previously described cytotoxicity of dietary oxidized PUFA.

Sustained and selective block of IPSPs in brain slices from rats made epileptic by intrahippocampal tetanus toxin

A small dose of tetanus toxin (2-5 ng; 10 mouse LD50) injected into the rat hippocampus produces a chronic epileptic syndrome in which epileptic discharges recur intermittently for 6-8 weeks. Hippocampal slices prepared during this period and maintained in vitro generate both evoked and spontaneous epileptic discharges. The present study used slices prepared 8-18 days after injection of tetanus toxin or vehicle solution into both hippocampi to test whether or not synaptic inhibition was selectively impaired in this experimental epilepsy. Intracellular recordings were made from CA3 pyramidal layer neurones within the tetanus toxin focus, which was identified by field potential recordings of synchronous bursts evoked by afferent stimulation. The intrinsic properties of these neurones did not differ from comparable cells in control-injected rats. All cells generated excitatory postsynaptic potentials (EPSPs) following stimulation of stratum radiatum in CA3. In control slices EPSPs were followed by a 'fast' inhibitory postsynaptic potential (IPSP), peaking at 25-30 ms, with a mean amplitude (+/- SEM) of -6.7 mV (+/- 0.66). In the epileptic slices these were absent, and the EPSP prolonged so that the potential at 30 ms was a depolarisation of +6.6 mV (+/- 2.75). The slow IPSP at 120 ms dropped to -0.27 mV (+/- 0.18) from -3.97 mV (+/- 1.43) (11 cells in each group). The loss of IPSPs cannot be attributed to a shift in reversal potentials in the toxin-injected group because no IPSPs were unmasked by current injection (n = 11). IPSPs also occurred spontaneously in the neurones in control slices, with a mean amplitude of -1.30 mV. Their frequency decreased by a factor of 13 in cells from the chronic focus induced by tetanus toxin (P less than 0.0001, analysis of variance), but their amplitude did not change significantly (mean of -1.22 mV). Spontaneous EPSPs were significantly more frequent and slightly smaller in the toxin-injected group (mean amplitudes 1.35 and 1.13 mV respectively). Together these studies support the hypothesis that the chronically recurring seizures induced by low doses of tetanus toxin can be attributed to a substantial, persistent and selective reduction of inhibitory neurotransmission in the hippocampus.

In vivo thiyl free radical formation from hemoglobin following administration of hydroperoxides

Although free radical formation due to the reaction between red blood cells and organic hydroperoxides in vitro has been well documented, the analogous in vivo ESR spectroscopic evidence for free radical formation has yet to be reported. We successfully employed ESR to detect the formation of the 5,5-dimethyl-1-pyrroline-N-oxide (DMPO)/hemoglobin thiyl free radical adduct in the blood of rats dosed with DMPO and tert-butyl hydroperoxide, cumene hydroperoxide, ethyl hydrogen peroxide, 2-butanone hydroperoxide, 15(S)-hydroperoxy-5,8,11,13-eicosatetraenoic acid, or hydrogen peroxide. We found that pretreating the rats with either buthionine sulfoximine or diethylmaleate prior to dosing with tert-butyl hydroperoxide decreased the concentration of nonprotein thiols within the red blood cells and significantly enhanced the DMPO/hemoglobin thiyl radical adduct concentration. Finally, we found that pretreating rats with the glutathione reductase inhibitor 1,3-bis(2-chloroethyl)-1-nitrosourea prior to dosing with tert-butyl hydroperoxide enhanced the DMPO/hemoglobin thiyl radical adduct concentration and induced the greatest decrease in nonprotein thiol concentration within the red blood cells.

In vivo rat hemoglobin thiyl free radical formation following administration of phenylhydrazine and hydrazine-based drugs

We have employed the ESR spin trapping technique in vivo to detect the formation of the 5,5-dimethyl-1-pyrroline N-oxide (DMPO)/hemoglobin thiyl free radical adduct in the blood of rats following administration of hydrazine-based drugs. The drugs examined were isoniazid, iproniazid, phenelzine, and hydralazine. In addition, phenylhydrazine and acetylhydrazine were also studied in a like manner. Of the four drugs, only phenelzine and iproniazid were able to induce the formation of the DMPO/hemoglobin thiyl free radical adduct in vivo, whereas only phenelzine and hydralazine were able to form this adduct in vitro. We were able to decrease the in vivo iproniazid-induced adduct formation by pretreating the rats with bis-para-nitrophenylphosphate, an arylamidase inhibitor. Our results support the idea that iproniazid is hydrolyzed in the liver to a more reactive metabolite, most likely isopropylhydrazine, which is subsequently released into the blood stream. In addition to the drug studies, experiments were performed to provide additional evidence that the radical adduct we detected was indeed of a hemoglobin thiyl free radical. Studies employing alpha-phenyl-N-t-butylnitrone (PBN) as the spin trap in place of DMPO also showed the formation of the PBN/hemoglobin thiyl free radical adduct.

In vivo rat hemoglobin thiyl free radical formation following phenylhydrazine administration

The reaction of oxyhemoglobin with phenylhydrazine has received considerable attention for many decades. The basis for this interest stems from the ability of phenylhydrazine and hydrazine-based drugs to induce hemolytic anemia. Considerable evidence obtained from in vitro ESR experiments implicates free radicals in the events leading to red blood cell hemolysis. However, until this report, no corroborating ESR evidence for in vivo free radical formation has been presented. We have successfully employed ESR to detect the formation of a radical adduct in the blood of rats which received an intragastric dose of phenylhydrazine followed by an intraperitoneal injection of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO). An immobilized radical adduct was detected by ESR when phenylhydrazine was administered in a dosage comparable to that prescribed for currently employed hydrazine-based drugs. We were also able to detect this immobilized DMPO adduct when hydrazine was employed in place of phenylhydrazine in the rat studies. The results of a series of experiments led us to ascribe this DMPO radical adduct to the trapping of a hemoglobin-derived thiyl free radical.