Decisions and prompts to screen for cervical, bowel, and breast cancer

OBJECTIVES

To investigate what makes Australians decide to screen and follow through for breast, cervical, and bowel cancer population screening programs.

METHODS

A convenience sample (N = 962) answered open-text questions about their decision to screen and what prompted them to act in an online survey. Open text responses were coded based on shared meaning using content analysis. Frequencies of each code were calculated.

RESULTS

For breast and cervical screening, decisions were commonly based on screening being routine (32.58%breast and 35.19%cervical) or receiving a reminder (20.53% breast 13.07% cervical), and similarly, common prompts were receiving a reminder (40.68% breast and 29.13% cervical), screening being routine (22.05% breast and 18.65% cervical). Participants reported deciding to screen for bowel cancer due to arrival of home screening test kit (40.50%) or the experience of loved one's cancer (13.57%) and were prompted by arrival of home test kit (23.58%), and convenience (15.72%).

CONCLUSIONS

Findings can inform the development of interventions targeting non-participants of cancer screening programs.

PRACTICE IMPLICATIONS

Messages to encourage breast and cervical cancer screening should frame screening as part of regular healthcare routine. Messages to encourage bowel cancer screening should encourage immediate use of the screening kit upon arrival.

Increasing the duration of an intervening distractor word can increase repetition blindness: Evidence for interitem competition in rapid visual sequences

In rapid serial visual presentation (RSVP), accurate report of a critical item (C2) declines when an earlier critical item (C1) is identical rather than unrelated. The most prominent theories of this phenomenon of repetition blindness (RB) concern the effects of processing C1 on later processing of C2. However, characteristics of distractor items between C1 and C2 strongly moderate RB, suggesting that items may compete for registration as separate events. We investigated interitem competition by manipulating the word frequency of distractors and C2s, and introducing novel manipulations of C1 and distractor duration. The frequency manipulations affected overall performance but not the size of RB; C2 reporting accuracy improved when distractors were of higher frequency and, contrary to typical results in lexical tasks, when C2s were of lower frequency. These results align with a competition model in which lower frequency words have an advantage. C1 duration had no significant effects on performance. A new finding was that increasing distractor duration had no main effect on performance but did increase the size of RB. The difficulty of registering a repeated C2 in memory under time pressure is exacerbated by the competitive effects of a temporally adjacent word of longer duration. The findings add to other evidence that interitem competition is important in RB and in processing of rapid visual sequences more generally. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Psychological distress and bowel cancer screening participation

OBJECTIVE

To better understand barriers to participation in mail-out bowel cancer screening programs, two survey studies tested the relationship between psychological distress and self-reported bowel cancer screening.

METHODS

First, a nationally representative sample of Australians N = 5421 completed measures of bowel cancer screening and psychological distress (using the Kessler Psychological Distress Scale; K10). Second, N = 479 completed a survey measuring participation in the National Bowel Cancer Screening Program (NBCSP) and psychological distress using the Depression, Anxiety and Stress Scale. In both studies, logistic regressions were conducted to test relationships between psychological distress and self-reported screening participation.

RESULTS

Study one found that psychological distress had a significant quadratic effect on having ever screened for bowel cancer, where screening rates were similar for those with low, moderate, or high levels of distress, but were lower for those with very high levels of distress. In study two, depression scores had a negative linear relationship with NBCSP participation (higher depression levels were associated with lower screening participation), and anxiety had a quadratic effect whereby NBCSP participation rates were higher with increasing levels of anxiety except in the severe category, where participation was significantly lower.

CONCLUSIONS

Findings indicate that psychological distress has a complex relationship with screening, and those with extreme levels of distress consistently show lower participation rates. Special efforts to encourage screening may be required for those experiencing extreme psychological distress and mental health disorders.

The role of need for control and self-reliance in gender and age differences in bowel cancer screening participation

OBJECTIVE

To examine the relationships between need for control and self-reliance and barriers to bowel cancer screening to better understand the reasons for lower bowel cancer screening adherence in males and younger individuals.

METHODS

Participants (n = 506) aged between 54 and 75 years old completed an online survey measuring demographic information, the four-factor Barriers to Home Bowel Cancer Screening Scale (BB-CanS) and a measure of Need for Control and Self-Reliance (NCSR). Model fit statistics were compared for seven path models testing the relationships between NCSR and BB-CanS factors and the moderating and mediating effects of age and gender.

RESULTS

Models where age and gender were included as moderators showed the best fit. When compared to females and those under 60 years of age, stronger positive associations between NCSR and BB-CanS factors were evident among males (β_avoidance  = 0.539, p < 0.001); β_disgust  = 0.558, p < 0.001; β_difficulty  = 0.489, p < 0.001; β_autonomy  = 0.619, p = 0.002) and those over 60 years of age (β_avoidance  = 0.400, p < 0.001); β_disgust  = 0.462, p < 0.001; β_difficulty  = 0.447, p < 0.001; β_autonomy  = 0.378, p < 0.001.

CONCLUSIONS

When encouraging males and people aged 60 years and over to participate in bowel cancer screening, public health messages may benefit from conveying preventative health behaviour and cancer screening participation as actions that reflect self-control and self-reliance.

Drug and alcohol practitioners' attitudes toward the use of standardized assessment

Despite their importance to evidence-based assessment, standardized assessments remain underutilized by mental health practitioners in practice. The underutilization has been attributed to a lack of appreciation of the importance of standardized assessments, lack of knowledge of standardized assessments, and practical barriers to implementation. This study sought to gather the first descriptive data on alcohol and other drug (AOD) practitioners' attitudes toward, and knowledge and self-reported use of, standardized assessments. Practical barriers to implementation in initial assessment and progress monitoring were also assessed. Ninety-nine Australian AOD practitioners recruited via newsletters of national representative bodies and practitioner networks completed an online survey. While practitioners' attitudes towards using standardized assessments for initial assessment and progress monitoring were generally positive and consistent with other populations of health practitioners, assessments remained underutilized in practice. Most AOD practitioners did not consider standardized assessments to be feasible to implement. The current findings highlight the importance of practical barriers, particularly organization-level barriers, in the underutilization of standardized assessments in AOD practice. Findings support an extension of dialogue surrounding evidence-based practice beyond treatment selection to include assessment practices at a more general level. The present study offers a starting point from which efforts to improve practitioner compliance with evidence-based best practices can be conceived, designed, and implemented.

A qualitative assessment of factors affecting nursing home caregiving staff experiences during the COVID-19 pandemic

Background

A large portion of COVID-19 cases and deaths in the United States have occurred in nursing homes; however, current literature including the frontline perspective of staff working in nursing homes is limited. The objective of this qualitative assessment was to better understand what individual and facility level factors may have contributed to the impact of COVID-19 on Certified Nursing Assistants (CNAs) and Environmental Services (EVS) staff working in nursing homes.

Methods

Based on a simple random sample from the National Healthcare Safety Network (NHSN), 7,520 facilities were emailed invitations requesting one CNA and/or one EVS staff member for participation in a voluntary focus group over Zoom. Facility characteristics were obtained via NHSN and publicly available sources; participant demographics were collected via SurveyMonkey during registration and polling during focus groups. Qualitative information was coded using NVIVO and Excel.

Results

Throughout April 2021, 23 focus groups including 110 participants from 84 facilities were conducted homogenous by participant role. Staffing problems were a recurring theme reported. Participants often cited the toll the pandemic took on their emotional well-being, describing increased stress, responsibilities, and time needed to complete their jobs. The lack of consistent and systematic guidance resulting in frequently changing infection prevention protocols was also reported across focus groups.

Conclusions

Addressing concerns of low wages and lack of financial incentives may have the potential to attract and retain employees to help alleviate nursing home staff shortages. Additionally, access to mental health resources could help nursing home staff cope with the emotional burden of the COVID-19 pandemic. These frontline staff members provided invaluable insight and should be included in improvement efforts to support nursing homes recovering from the impact of COVID-19 as well as future pandemic planning.

Chemical recovery and browning of Nova Scotia surface waters in response to declining acid deposition

Declining emissions of sulfur and nitrogen have curtailed acid deposition across large areas of North America and Europe. This has allowed many lakes to recover from acidification, with decreases in sulfate, increases in pH, and increases in alkalinity. But reduced acid deposition has not always coincided with chemical lake recovery. Surface waters in Nova Scotia did not exhibit clear evidence of recovery as recently as 2007, due in part to increasing organic acidity and slow replenishment of base cations. In an updated assessment with data collected as recently as 2019, we analyze water chemistry representing 81 lakes and rivers and two precipitation monitoring stations over up to 41 years. We find that Nova Scotia surface waters are now exhibiting signs of chemical recovery. We estimated the linear decrease in precipitation sulfate and nitrate yield at up to 0.31 and 0.18 kg ha^-1 year^-2, respectively, and the linear increase in precipitation pH at up to 0.014 year^-1. Sulfate decreased in 60 of 62 lakes and 14 of 17 rivers (-0.0051 to -0.23 mg L^-1 year^-1), while pH increased in 55 of 64 lakes and 11 of 17 rivers (0.0015-0.072 year^-1). Apparent colour increased in 54 of 62 lakes and 13 of 17 rivers (0.0026-3.9 Pt-Co year^-1). We identified increasing aluminum trends in 46 of 61 lakes, and we show using size-exclusion chromatography that binding to organic and iron-based colloids may help to explain these trends. To the extent that increases in apparent colour are explained by chromophoric dissolved organic matter (DOM), they imply greater binding capacity for metals in surface waters, and greater capacity for DOM to stabilize metal (oxyhydr)oxide colloids.

Infrared Fingerprint Engineering: A Molecular-Design Approach to Long-Wave Infrared Transparency with Polymeric Materials

Optical technologies in the long-wave infrared (LWIR) spectrum (7-14 μm) offer important advantages for high-resolution thermal imaging in near or complete darkness. The use of polymeric transmissive materials for IR imaging offers numerous cost and processing advantages but suffers from inferior optical properties in the LWIR spectrum. A major challenge in the design of LWIR-transparent organic materials is that nearly all organic molecules absorb in this spectral window which lies within the so-called IR-fingerprint region. We report on a new molecular-design approach to prepare high refractive index polymers with enhanced LWIR transparency. Computational methods were used to accelerate the design of novel molecules and polymers. Using this approach, we have prepared chalcogenide hybrid inorganic/organic polymers (CHIPs) with enhanced LWIR transparency and thermomechanical properties via inverse vulcanization of elemental sulfur with new organic co-monomers.

One Dimensional Photonic Crystals Using Ultrahigh Refractive Index Chalcogenide Hybrid Inorganic/Organic Polymers

We report on the fabrication of wholly polymeric one-dimensional (1-D) photonic crystals (i.e., Bragg reflectors, Bragg mirrors) via solution processing for use in the near (NIR) and the short wave (SWIR) infrared spectrum (1-2 μm) with very high reflectance (R ∼ 90-97%). Facile fabrication of these highly reflective films was enabled by direct access to solution processable, ultrahigh refractive index polymers, termed, Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs). The high refractive index (n) of CHIPs materials (n = 1.75-2.10) allowed for the production of narrow band IR Bragg reflectors with high refractive index contrast (Δn ∼ 0.5) when fabricated with low n polymers, such as cellulose acetate (n = 1.47). This is the highest refractive index contrast (Δn ∼ 0.5) demonstrated for an all-polymeric Bragg mirror which directly enabled high reflectivity from films with 22 layers or less. Facile access to modular, thin, highly reflective films from inexpensive CHIPs materials offers a new route to IR Bragg reflectors and other reflective coatings with potential applications for IR photonics, commercial sensing, and LIDAR applications.

Chalcogenide Hybrid Inorganic/Organic Polymers: Ultrahigh Refractive Index Polymers for Infrared Imaging

We report on the preparation of ultrahigh refractive index polymers via the inverse vulcanization of elemental sulfur, selenium, and 1,3-diisopropenylbenzene for use as novel transmissive materials for mid-infrared (IR) imaging applications. Poly(sulfur-random-selenium-random-(1,3-diisopropenylbenzene)) (poly(S-r-Se-r-DIB) terpolymer materials from this process exhibit the highest refractive index of any synthetic polymer (n > 2.0) and excellent IR transparency, which can be directly tuned by terpolymer composition. Sulfur or selenium containing (co)polymers prepared via inverse vulcanization can be described as Chalcogenide Hybrid Inorganic/Organic Polymers (CHIPs) and are polymeric analogues to wholly inorganic Chalcogenide Glasses (ChGs), which are commonly used as transmissive materials in mid-IR imaging. Finally, we demonstrate that CHIPs composed of (poly(S-r-Se-r-DIB) can be melt processed into windows that enabled high quality mid-IR thermal imaging of human subjects and highly resolved imaging of human vasculature.

High Refractive Index Copolymers with Improved Thermomechanical Properties via the Inverse Vulcanization of Sulfur and 1,3,5-Triisopropenylbenzene

The synthesis of a novel high sulfur content material possessing improved thermomechanical properties is reported via the inverse vulcanization of elemental sulfur (S₈) and 1,3,5-triisopropenylbenzene (TIB). A key feature of this system was the ability to afford highly cross-linked, thermosetting materials, where the use of TIB as a comonomer enabled facile control of the network structure and dramatically improved the glass transition temperature (relative to our earlier sulfur copolymers) of poly(sulfur-random-(1,3,5-triisopropenylbenzene)) (poly(S-r-TIB)) materials over a range from T = 68 to 130 °C. This approach allowed for the incorporation of a high content of sulfur-sulfur (S-S) units in the copolymer that enabled thermomechanical scission of these dynamic covalent bonds and thermal reprocessing of the material, which we confirmed via dynamic rheological characterization. Furthermore, the high sulfur content also imparted high refractive index (n > 1.75) and IR transparency to poly(S-r-TIB) copolymers, which offered a route to enhanced optical transmitting materials for IR thermal imaging applications with improved thermomechanical properties.

Dynamic Covalent Polymers via Inverse Vulcanization of Elemental Sulfur for Healable Infrared Optical Materials

We report on dynamic covalent polymers derived from elemental sulfur that can be used as thermally healable optical polymers for mid-IR thermal imaging applications. By accessing dynamic S-S bonds in these sulfur copolymers, surface scratches and defects of free-standing films of poly(sulfur-random-1,3-diisopropenylbenzene) (poly(S-r-DIB) can be thermally healed, which enables damaged lenses and windows from these materials to be reprocessed to recover their IR imaging performance. Correlation of the mechanical properties of these sulfur copolymers with different curing methods provided insights to reprocess damaged samples of these materials. Mid-IR thermal imaging experiments with windows before and after healing of surface defects demonstrated successful application of these materials to create a new class of "scratch and heal" optical polymers. The use of dynamic covalent polymers as healable materials for IR applications offers a unique advantage over the current state of the art (e.g., germanium or chalcogenide glasses) due to both the dynamic character and useful optical properties of S-S bonds.

Inverse vulcanization of elemental sulfur with 1,4-diphenylbutadiyne for cathode materials in Li–S batteries

High sulfur content copolymers were prepared via inverse vulcanization of sulfur with 1,4-diphenylbutadiyne (DiPhDY) for use as the active cathode material in lithium–sulfur batteries.

A comparison between whites and blacks with severe multi-organ iron overload identified in 16,152 autopsies

BACKGROUND & AIMS

Little is known about differences in the prevalence of severe iron overload at death in whites and blacks. We evaluated data and samples from 16,152 autopsies (8484 whites, 7668 blacks) performed at a single university hospital.

METHODS

Cases of severe multi-organ iron overload were identified by review of autopsy protocols and Perls-stained tissue specimens, analysis of hepatocyte and Kupffer cell iron levels, and measurement of liver tissue iron concentrations.

RESULTS

We analyzed autopsy data from 10,345 adults (age > or =21 years), 1337 children (1-20 years), and 4470 infants (<1 year). Iron overload without reports of excessive exogenous iron was observed in 18 adults; the prevalence in whites and blacks was 0.0019 and 0.0015, respectively (P = .6494). Twenty-nine adults and 2 children had iron overload with reports of excessive exogenous iron. In adults, the prevalences of iron overload with reports of excessive exogenous iron in whites and blacks were 0.0040 and 0.0013, respectively (P = .0107). Among adults, the prevalence of cirrhosis was 6-fold greater in those with iron overload. In adults with severe iron overload, 67% without reports of excessive exogenous iron and 14% with reports of excessive exogenous iron died of hepatic failure or cardiomyopathy caused by siderosis. The overall prevalence of deaths caused by severe iron overload in whites and blacks was 0.0021 and 0.0009, respectively (P = .0842).

CONCLUSIONS

The prevalence of severe iron overload without reports of excessive exogenous iron did not differ significantly between whites and blacks. The prevalence of iron overload with reports of excessive exogenous iron was greater in whites. Hepatic failure and cardiomyopathy were common causes of death in severe iron overload cases.

A bioassessment approach for mid-continent great rivers: the Upper Mississippi, Missouri, and Ohio (USA)

The objectives of the Environmental Monitoring and Assessment Program for Great River Ecosystems (EMAP-GRE) are to (1) develop and demonstrate, in collaboration with states, an assessment program yielding spatially unbiased estimates of the condition of mid-continent great rivers; (2) evaluate environmental indicators for assessing great rivers; and (3) assess the current condition of selected great river resources. The purpose of this paper is to describe EMAP-GRE using examples based on data collected in 2004-2006 with emphasis on an approach to determining reference conditions. EMAP-GRE includes the Upper Mississippi River, the Missouri River, and the Ohio River. Indicators include biotic assemblages (fish, macroinvertebrates, plankton, algae), water chemistry, and aquatic and riparian physical habitat. Reference strata (river reaches for which a single reference expectation is appropriate) were determined by ordination of the fish assemblage and examination of spatial variation in environmental variables. Least disturbed condition of fish assemblages for reference strata was determined by empirical modeling in which we related fish assemblage metrics to a multimetric stressor gradient. We inferred least disturbed condition from the y-intercept, the predicted condition when stress was least. Thresholds for dividing the resource into management-relevant condition classes for biotic indicators were derived using predicted least disturbed condition to set the upper bound on the least disturbed condition class. Also discussed are the outputs of EMAP-GRE, including the assessment document, multimetric indices of condition, and unbiased data supporting state and tribal Clean Water Act reporting, adaptive management, and river restoration.

Effect of leaf position on levels of the chloroplast and cytosolic fructose bisphosphatase isozymes in the pea leaf nucleus

Immunocytolocalization experiments indicate that nuclear levels of the pea leaf cytosolic fructose bisphosphatase are higher in leaves located near the base of the plant and lower in expanded leaves at the apex. It seems possible that the cytosolic isozyme in the nucleus has a role in tissue aging. In contrast, there is no indication that leaf position or tissue age affects levels of the chloroplastic enzyme in the nucleus. The density of the chloroplast fructose bisphosphatase is higher in the nucleolus than in the nucleoplasm. Conversely, the density of the cytosolic isozyme is slightly higher in the nucleoplasm. Analysis of double immunolabeling experiments indicates that both isozymes are distributed nonrandomly with respect to DNA, and therefore colocalized with DNA, in the nucleus, and that the chloroplast isozyme is also distributed nonrandomly with respect to DNA in the chloroplast.

Both chloroplastic and cytosolic phosphofructoaldolase isozymes are present in the pea leaf nucleus

In higher plants, fructose bisphosphate aldolase (EC 4.1.2.13) occurs in chloroplast, cytosol, and nucleus. Immunocytolocalization experiments with isozyme-directed antibodies indicate that both chloroplastic and cytosolic aldolase isoforms are present in the pea (Pisum sativum L.) leaf nucleus.

Calcitonin gene-related peptide regulates gene transcription in primary afferent neurons

Although primary afferent neurons express receptors for calcitonin gene-related peptide (CGRP), understanding of the cellular effects of these receptors is limited. We determined that CGRP receptors regulate gene transcription in primary afferent neurons through a cyclic AMP (cAMP)-dependent pathway. CGRP increased cAMP in neonatal dorsal root ganglion (DRG) neurons in a concentration-dependent manner that was blocked by the receptor antagonist CGRP(8-37). The response to CGRP also occurred in adult DRG cells. In contrast, CGRP did not alter the concentration of free intracellular calcium in neonatal or adult DRG neurons. Immunohistochemical data showed that one downstream effect of the cAMP signaling pathway was phosphorylation of cAMP response element binding (CREB) protein, suggesting that CGRP regulates gene expression. This interpretation was supported by evidence that CGRP increased CRE-dependent gene transcription in neurons transiently transfected with a CRE-luciferase DNA reporter construct. The effect of CGRP on gene transcription was inhibited by H89, myristoylated-protein kinase A inhibitor(14-22)-amide and U0126, indicating that protein kinase A and mitogen-activated protein kinase/extracellular receptor kinase kinase are enzymes that mediate effects of CGRP on gene transcription. Therefore, CGRP receptors may regulate expression of proteins by primary afferent neurons during development and in response to tissue-damaging stimuli.

Both chloroplastic and cytosolic phosphoglycerate kinase isozymes are present in the pea leaf nucleus

Phosphoglycerate kinase (EC 2.7.2.3) occurs in chloroplasts, cytosol, and nuclei in higher plants. Immunocytolocalization experiments with isozyme-specific antibodies indicate that both the chloroplastic and the cytosolic forms of the enzyme are present in the pea (Pisum sativum L.) leaf nucleus.

Cytosolic glyceraldehyde-3-P dehydrogenase and the B subunit of the chloroplast enzyme are present in the pea leaf nucleus

Immunolocalization experiments indicate that both the subunit B of the NADP-linked chloroplastic glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13) and the NAD-linked cytosolic enzyme (EC 1.2.1.12) are present in the pea ( Pisum sativum L.) leaf nucleus. Subunit A of the NADP-linked enzyme appears to be restricted to the chloroplast.

Rats can discriminate illuminance, but not magnetic fields, as a stimulus for learning a two-choice discrimination

In each of the two experiments, nine rats were trained for 64 trials (eight trials per day) to determine if they could acquire a two-choice discrimination based on a specified discriminative stimulus (S(D)). In one experiment, the S(D) was a change in ambient illumination, while in the second experiment the S(D) was a change in the combination of sinusoidal 60 Hz and static magnetic field (MF) and any cues attendant to energizing the coils that produced the MF exposure. The rats that had a change in illuminance as the S(D) learned the two-choice task easily, P <.001, whereas the rats having a change in MFs as the S(D) did not.

Regulation of progesterone and prostaglandin F2alpha production in the CL

After the luteinizing hormone (LH) surge, the cells that remain from the ovulated follicle undergo a process of differentiation termed luteinization. Two key features of the cells after luteinization are the capacity for tremendous production of progesterone [10(16) molecules of progesterone per (min/(g of CL))] and the capacity to undergo regression or death of the cells at the appropriate time. There are two steroidogenic cell types, the small and large luteal cells that are regulated by different mechanisms. In small luteal cells, production of progesterone is stimulated by LH through the protein kinase A (PKA) pathway. The large luteal cells of ruminants produce large quantities of progesterone that is independent of LH stimulation. Although luteotrophins clearly regulate luteal function, much of luteal progesterone production in some species appears to be constitutive, consistent with the autonomous aspects of the large luteal cell. The key regulated step in luteal progesterone production appears to be regulation of transport of cholesterol to the inner mitochondrial membrane apparently mediated by the steroidogenic acute regulatory protein (StAR). In addition, our recent research indicates that PKA is tonically active in large luteal cells and this may be responsible for the high, relatively autonomous nature of luteal progesterone production. Regression of the corpus luteum (CL) in many species is initiated by prostaglandin (PG) F2alpha secreted from the uterus. Luteal cells also have the capacity for production of PGF2alpha. Luteal PGF2alpha production can be regulated by a variety of substances including inhibition by progesterone and stimulation by cytokines. We have also characterized a positive feedback pathway in ruminant and porcine CL in which small amounts of uterine PGF(2alpha) stimulate intraluteal production of PGF2alpha due to induction of the cycloxygenase-2 (Cox-2) enzyme in large luteal cells. This positive feedback pathway is only present in CL that has acquired the capacity for luteal regression ( approximately day 7 in cow, approximately day 13 in pig). Regulation by protein kinase C (PKC) of transcriptional factors interacting with an E-box in the 5' flanking region of the Cox-2 gene is the critical regulatory element involved in this positive feedback pathway. Thus, luteinization in some species appears to change specific gene transcription such that progesterone production becomes relatively independent of acute luteotrophic regulation and intraluteal PGF2alpha synthesis is induced by the second messenger pathways that are activated by PGF2alpha.

Chloroplast glyceraldehyde-3-phosphate dehydrogenase contains a single disulfide bond located in the C-terminal extension to the B subunit

Mass mapping analysis based on cyanylation and CN-induced cleavage indicates that the two cysteine residues in the C-terminal extension of the B subunit of the light-activated pea leaf chloroplast glyceraldehyde-3-phosphate dehydrogenase form a disulfide bond. No evidence was found for a disulfide bond in the A subunit, nor was there any indication of a second disulfide bond in the B subunit. The availability of the structure of the extended glyceraldehyde-3-phosphate dehydrogenase from the archaeon Sulfolobus solfataricus allows modeling of the B subunit. As modeled, the two cysteine residues in the extension are positioned to form an interdomain disulfide cross-link.

Prostaglandin F(2alpha) receptor in the corpus luteum: recent information on the gene, messenger ribonucleic acid, and protein

The prostaglandin (PG) F(2alpha) receptor (FPr) in the corpus luteum is essential for maintaining normal reproductive cyclicity in many species. Activation of this seven-transmembrane spanning receptor at the end of the cycle leads to a decrease in progesterone and the demise of the corpus luteum (luteolysis). Recently, the gene structure of the FPr in three mammalian species has been elucidated; however, promoter regulation of the gene is still poorly understood. The FPr mRNA is extremely low in steroidogenic follicular cells (theca or granulosa) but is expressed at high levels in the corpus luteum, particularly in the large luteal cells. Treatment with PGF(2alpha) decreased FPr mRNA expression in luteal cells in most species that have been studied. Key amino acids have been suggested to be critical for binding of FPr to PGF(2alpha) based on three-dimensional modeling and comparisons with other G-protein-coupled receptors. Moieties of the PGF(2alpha) molecule that are essential for binding or specificity of binding to the FPr have been identified by radioreceptor binding studies. In this article, recent information is reviewed on the structure of the FPr gene, regulation of luteal FPr mRNA, and receptor/ligand interaction requirements for the FPr protein.

Large granular lymphocytic (LGL) leukemia in rats exposed to intermittent 60 Hz magnetic fields

An animal model for large granular lymphocytic (LGL) leukemia in male Fischer 344 rats was utilized to determine whether magnetic field exposure can be shown to influence the progression of leukemia. We previously reported that exposure to continuous 60 Hz, 1 mT magnetic fields did not significantly alter the clinical progression of LGL leukemia in young male rats following injection of spleen cells from donor leukemic rats. Results presented here extend those studies with the following objectives: (a) to replicate the previous study of continuous 60 Hz magnetic field exposures, but using fewer LGL cells in the inoculum, and (b) to determine if intermittent 60 Hz magnetic fields can alter the clinical progression of leukemia. Rats were randomly assigned to four treatment groups (18/group) as follows: (1) 1 mT (10 G) continuous field, (2) 1 mT intermittent field (off/on at 3 min intervals), (3) ambient controls ( < 0.1 microT), and (4) positive control (5 Gy whole body irradiation from cobalt-60 four days prior to initiation of exposure). All rats were injected intraperitoneally with 2.2 x 10(6) fresh, viable LGL leukemic spleen cells at the beginning of the study. The fields were activated for 20 h per day, 7 days per week, and all exposure conditions were superimposed over the natural ambient magnetic field. The rats were weighed and palpated for splenomegaly weekly. Splenomegaly developed 9-11 weeks after transplantation of the leukemia cells. Hematological evaluations were performed at 6, 8, 10, 12, 14, and 16 weeks of exposure. Peripheral blood hemoglobin concentration, red blood cells, and packed cell volume declined, and total white blood cells and LGL cells increased dramatically in all treatment groups after onset of leukemia. Although the positive control group showed different body weight curves and developed signs of leukemia earlier than other groups, differences were not detected between exposure groups and ambient controls. Furthermore, there were no overall effects of magnetic fields on splenomegaly or survival in exposed animals. In addition, no significant and/or consistent differences were detected in hematological parameters between the magnetic field exposed and the ambient control groups.

Effect of injected vitamin A and level of dietary vitamin E on alpha-tocopherol status in gestating swine

A 2 x 2 trial was conducted to determine the effects of injected vitamin A and dietary level of vitamin E on blood serum and tissue concentrations of alpha-tocopherol during early gestation of gilts. Thirty-two crossbred gilts were fed a corn soybean meal basal diet supplemented with DL-alpha tocopheryl acetate to provide either 25 or 500 IU of vitamin E/kg of diet. Gilts were fed daily 1.9 kg/gilt beginning 7 days before breeding until day 25 of gestation. Sixteen gilts were injected (i.m.) with 350,000 IU of retinol palmitate 7 days before breeding, at the time of breeding (d0), and 7 days after breeding. Blood samples were collected on day -7, 0, 7, and 24, and all gilts were slaughtered on day 25 of gestation. Supplemental vitamin E at 500 IU/kg of diet increased alpha-tocopherol concentrations (P < 0.01) in blood serum in all tissues examined, including reproductive and embryonic, except fat. Vitamin A injections had no effect (P > 0.10) on blood serum alpha-tocopherol concentrations except on day 7 when a small increase (P < 0.06) was noted. Vitamin A injections had no effect (P > 0.10) on tissue alpha-tocopherol concentrations. Increasing dietary level of vitamin E increased blood serum and tissue alpha-tocopherol concentrations, and vitamin A injections had little or no effect on these concentrations during the early gestation of gilts.

Actions of prostaglandin F2alpha and prolactin on intercellular adhesion molecule-1 expression and monocyte/macrophage accumulation in the rat corpus luteum

Expression of intercellular adhesion molecule-1 (ICAM-1) and the accumulation of monocytes/macrophages are inflammatory events that occur during PRL (PRL)-induced regression of the rat corpus luteum. Here we have compared the ability of prostaglandin F2alpha (PGF) and PRL to induce, in rat corpora lutea, inflammatory events thought to perpetuate luteal regression. Immature rats were ovulated with eCG-hCG and then hypophysectomized (Day 0), which resulted in a single cohort of persistent, functional corpora lutea. On Days 9-11, the rats received twice daily injections of saline, PGF (Lutalyse, 250 microg/injection), or PRL (312 microg/injection) to induce luteal regression. Surprisingly, luteal weight and plasma progestin concentrations (progesterone and 20alpha-dihydroprogesterone) did not differ between PGF-treated rats and controls; whereas both luteal weight and plasma progestins declined significantly in PRL-treated rats. Furthermore, corpora lutea of PGF-treated rats and controls contained relatively minimal ICAM-1 staining and few monocytes/macrophages. In contrast, but as expected, corpora lutea of PRL-treated rats stained intensely for ICAM-1 and contained numerous monocytes/macrophages. In an additional experiment, there was no indication that luteal prostaglandin F2alpha receptor mRNA diminished as a result of hypophysectomy. These findings suggest that prolactin, not PGF, induces the inflammatory events that accompany regression of the rat corpus luteum.

A novel DNA-binding protein associated with DNA polymerase-alpha in pea stimulates polymerase activity on infrequently primed templates

A 42 kDa DNA-binding protein is associated with DNA polymerase-alpha-primase in pea (Pisum sativum). In a previous publication it was shown that the protein has strong preference for ds-ss junctions in DNA, including the cohesive termini generated by restriction endonucleases. In this paper it is shown that when the DNA-binding protein is added back to polymerase-primase, the protein stimulates the activity of the polymerase. The stimulation is particularly marked when M13 DNA, primed with a single sequencing primer or primed with oligoribonucleotides by the polymerase's associated primase activity, is used as a template. The stimulation of polymerase activity is not caused by an increase in processivity. These data lead to the suggestion that the 42 kDa DNA-binding protein is a primer-recognition protein.

Oxidation-reduction properties of two engineered redox-sensitive mutant Escherichia coli malate dehydrogenases

Redox potentials for two inactivating intrasubunit disulfides that link helix-5 and helix-9 in mutant Escherichia coli malate dehydrogenases have been determined. The Em is -285 mV when cysteines are at positions 121 and 305 and -295 mV when the cysteines are at positions 122 and 305. Oxidation to the disulfide affects kcat but not Km values. In the single V121C and N122C mutants, the Cys in helix-5 affects the Km for oxalacetate. The pH optimum in the direction of malate formation is affected by the redox state of the enzyme. Clearly, a disulfide bond can and does form between Cys residues substituted into positions 121 or 122 in the nucleotide binding domain and 305 in the carbon substrate binding domain of this NAD-dependent malate dehydrogenase. Apparently, crosslinking the domains interferes with catalysis.

Persistence and distribution of azinphos-methyl following application to littoral enclosure mesocosms

The organophosphorus insecticide azinphos-methyl was applied once to the surface of 12 of 18 littoral enclosure mesocosms (5x10 m) constructed in a 2-ha pond near Duluth, Minnesota. Water, sediment, macrophytes, and adult fathead minnows were analyzed for residue to determine the persistence, distribution, and mass balance of azinphos-methyl. Nominal treatment concentrations were 0, 0.2, 1, 4, and 20 microg/liter active ingredient. The maximum residue concentration in the water was measured 1h after treatment. The half-life in the water column ranged from 1.2 to 2 days and 95% of the residue dissipated in 5.4 to 10.2 days. Measurable residues were found in the sediment, macrophytes, and fish. Maximum residues in these media were measured at 4, 1, and 0.12 days. respectively. The water and sediment were the most important sorptive compartments for azinphos-methyl residue. The macrophytes and fish were of minor importance, containing only trace amounts of the mass applied.

Effects of 50- or 60-hertz, 100 microT magnetic field exposure in the DMBA mammary cancer model in Sprague-Dawley rats: possible explanations for different results from two laboratories

In line with the possible relationship between electric power and breast cancer risk and the underlying melatonin hypothesis, 50-Hz magnetic field (MF) exposure at microtesla flux densities for either 13 or 27 weeks significantly increased the development and growth of mammary tumors in a series of experiments from Löscher's group in Germany. Löscher's group used the 7,12-dimethylbenz[a]anthracene (DMBA) model of breast cancer in Sprague-Dawley rats. The finding could not be replicated when a similar experimental protocol was used in a study conducted by Battelle in the United States. In the present paper, investigators from the two groups discuss differences between their studies that might explain the apparent discrepancies between the results. These differences include the use of different substrains of Sprague-Dawley rats (the U.S. rats were more susceptible to DMBA than the European rats), different sources for diet and DMBA, differences in environmental conditions, and differences in MF exposure metrics. Furthermore, the effects of MF exposure reported by Löscher's group, albeit significant, were weak. We also discuss the general problem of replicating such weak effects.

Clinical progression of transplanted large granular lymphocytic leukemia in Fischer 344 rats exposed to 60 Hz magnetic fields

The purpose of this study was to determine if 60 Hz magnetic fields can alter the clinical progression of leukemia in an animal model. Large granular lymphocytic (LGL) leukemia cells from spleens of leukemic rats were transplanted into young male Fischer 344 rats, producing signs of leukemia in approximately 2-3 months. The animals were randomly assigned to 4 treatment groups (108/group) as follows: 1) 10 G (1.0 mT) linearly polarized 60 Hz magnetic fields, 2) sham exposed [null energized unit with residual 20 mG (2 microT) fields], 3) ambient controls [<1 mG (0.1 [microT)], and 4) positive controls (a single 5 Gy whole body exposure to 60Co 4 days prior to initiation of exposure). All rats were injected intraperitoneally (ip) with 2.2 x 10(7) LGL leukemic cells at the initiation of exposure or sham exposure. The magnetic fields were activated for 20 h/day, 7 days/week, allowing time for animal care. The experimental fields were in addition to natural ambient magnetic fields. Eighteen rats from each treatment group were bled, killed, and evaluated at 5, 6, 7, 8, 9, and 11 weeks of exposure. Peripheral blood hematological endpoints, changes in spleen growth, and LGL cell infiltration into the spleen and liver were measured to evaluate the leukemia progression. No significant or consistent differences were detected between the magnetic field exposed groups and the ambient control group, although the clinical progress of leukemia was enhanced in the positive control animals. These data indicate that exposure to sinusoidal, linearly polarized 60 Hz, 10 G magnetic fields did not significantly alter the clinical progression of LGL leukemia. Furthermore, the data are in general agreement with previous results of a companion repeated-bleeding study in which animals were exposed for 18 weeks.

Effects of 60 Hz magnetic field exposure on the pineal and hypothalamic-pituitary-gonadal axis in the Siberian hamster (Phodopus sungorus)

Experiments using the dwarf Siberian hamster Phodopus sungorus were carried out to determine possible neuroendocrine consequences of one-time and repeated exposures to 60 Hz magnetic fields (MF). Animals were maintained in either a short-light (SL, 8 h light:16 h dark) or long-light (LL, 16 h light:8 h dark) photoperiod. Acute (one-time, 15 min) exposure of male SL animals to a linearly polarized, horizontally oriented, 60 Hz MF (0.1 mT) gave rise to a statistically significant (P < .005) reduction in pineal melatonin content as determined 3 and 5 h after onset of darkness. In LL animals, acute exposure to 0.10 mT resulted in a significant decrease in pineal melatonin as measured 4 h after onset of darkness, whereas acute exposure to 50 microT showed no effect compared with sham exposure. In SL animals, an increase in norepinephrine was observed in the medial basal hypothalamus (including the suprachiasmatic nucleus) after acute exposure (P < .01). Daily MF exposure of SL animals to a combination of steady-state and on/off 60 Hz magnetic fields (intermittent exposure) at 0.1 mT for 1 h per day for 16 days was associated with a reduction in melatonin concentrations at 4 h after onset of darkness and an increase in blood prolactin concentrations (P < .05). Exposure of SL animals to a steady state 60 Hz MF for 3 h/day for 42 days resulted in a statistically significant reduction in body weight (ANOVA: P > .05), compared with sham-exposed SL animals. At 42 days, however, no significant changes in overnight melatonin or prolactin levels were detected. In both repeated exposure experiments, gonadal weights were lowest in the MF-exposed groups. This difference was statistically significant (P < .05) after 42 days of exposure. These data indicate that both one-time and repeated exposure to a 0.1 mT, 60 Hz MF can give rise to neuroendocrine responses in Phodopus.

Hemochromatosis heterozygotes may constitute a radiation-sensitive subpopulation

A primary mechanism of radiation-induced DNA damage is by generation of free radicals. Chronically increased oxidative stress from elevated levels of iron in the body may increase radiation sensitivity by decreasing cellular oxygen radical scavenging capability. Hemochromatosis heterozygotes have elevated body iron. Low-level radiation sensitization by iron may be particularly pertinent for risk of breast cancer. Since 10% of the population appears to be heterozygous for the hemochromatosis gene, a radiosensitizing effect would have pervasive implications.

Phosphorylated cAMP response element binding protein increases in neurokinin-1 receptor-immunoreactive neurons in rat spinal cord in response to formalin-induced nociception

The rat neurokinin-1 (NK1) receptor gene contains a cyclic adenosine monophosphate (cAMP) response element, and gene transcription may be activated upon binding of phosphorylated cAMP response element binding protein (pCREB). If pCREB contributes to increased expression of NK1 receptors, pCREB should increase in neurons that express NK1 receptors under conditions that increase NK1 receptor mRNA. Evidence for this relationship was found following injection of formalin into one hindpaw of rats. Immunohistochemistry was employed to visualize NK1 receptors and pCREB in spinal cord sections. Formalin injection produced an increase in pCREB-immunofluorescence within NK1 receptor-immunoreactive neurons from segments L4 and L5. No change occurred in pCREB-immunofluorescence within NK1 receptor-immunoreactive neurons from segment T11. These data support the hypothesis that transcription factor pCREB contributes to increased expression of spinal NK1 receptors during persistent pain.

Nocturnal 6-hydroxymelatonin sulfate excretion in female workers exposed to magnetic fields

The objective of this study was to determine whether daytime occupational exposure to extremely low frequency magnetic fields (MFs) suppresses nocturnal melatonin production. Sixty female volunteers were recruited. Thirty-nine worked in a garment factory, and 21 office workers served as a reference group. Exposure assessment was based on the type of sewing machine used and MF measurements around each type of machine. Eye-level MF flux density was used to classify the operators to higher (>1 microT) and lower (0.3-1 microT) exposure categories. A third group of factory workers had diverse MF exposures from other sources. The reference group had average exposure of about 0.15 microT. Urine samples were collected on Friday and Monday for three consecutive weeks. Melatonin production was assessed as urinary 6-hydroxymelatonin sulfate (6-OHMS) excretion. The ratio of Friday morning/Monday morning 6-OHMS was used to test the hypothesis that melatonin production is suppressed after 4 days of occupational MF exposure with significant recovery during the weekend. Possible chronic suppression of melatonin production was evaluated by studying exposure-related differences in the Friday values by multivariate regression analysis. The Monday/Friday ratios were close to 1.0, suggesting that there is no increase in melatonin production over the weekend. The average 6-OHMS excretion on Friday was lower among the factory workers than in the reference group, but no monotonous dose-response was observed. Multivariate regression analysis identified MF exposure, smoking, and age as significant explanatory variables associated with decreased 6-OHMS excretion.

Effect of constant light on DMBA mammary tumorigenesis in rats

A study of light, and mammary tumorigenesis was conducted in rats. One-hundred female Sprague-Dawley rats were divided by weight into two groups. One group was exposed to constant light (LL) from 26 days of age, and the second group was exposed to 8 h light and 16 h dark per day (LD). Both groups received an 8 mg dose of a chemical carcinogen, dimethylben-zanthracene (DMBA) at 52 days of age. At 13 weeks post-DMBA, there were significantly fewer mammary tumors in the LL group compared with the LD group. Constant light was clearly demonstrated to have a profound effect on mammary tissue development. Although virgin, the majority of the LL rats (29/50) had gross evidence of lactation at 141 days of age. None of the LD rats (0/50) showed evidence of milk production. These results suggest that constant light not only substantially accelerated mammary gland development, but pushed development of the tissue past the stage normally observed in virgin animals (to the lactation stage).

Transvaginal, ultrasound-guided biopsy of the corpus luteum in cattle

An ultrasound-guided transvaginal technique for corpus luteum biopsy was developed and tested in cattle. The biopsy needle set consisted of an inner needle (o.d. 1 mm) with a 20-mm long specimen notch, an outer cannula (o.d. 1.2 mm) with a cutting edge, and an automated spring-loaded handle with trigger. The biopsy needle set was inserted into the channel guide of the handle of a convex-array transvaginal ultrasound probe. The transducer was positioned in the vaginal fornix, and the ovary was manipulated transrectally against the vaginal wall and transducer face. During monitoring on the ultrasound screen, the inner needle was pushed through the vaginal wall into the corpus luteum, and the cutting cannula was fired, cutting and trapping luteal tissue in the specimen notch. Three luteal biopsies at each of Hours 0 and 4 were taken 10 d after ovulation in 6 heifers; 6 other heifers served as controls. A biopsy core was obtained in 36 of 39 attempts (92%). The tissue specimens seemed normal based on gross evaluation. The effect of biopsy on luteal function was assessed by daily ultrasound monitoring of luteal area, by assay of progesterone concentrations in blood samples obtained daily, and by the length of the interval from biopsy to ovulation. No significant differences were found for post-biopsy function for any of the 3 end points. The results indicated repeated transvaginal, ultrasound-guided biopsy of the corpus luteum in cattle is a practical procedure and may be useful for experimental and diagnostic purposes.

Effect of 13 week magnetic field exposures on DMBA-initiated mammary gland carcinomas in female Sprague-Dawley rats

Several studies suggest that exposure to 50 Hz magnetic fields may promote chemically induced breast cancer in rats. Groups of 100 female Sprague-Dawley rats were initiated with four weekly 5 mg gavage doses of 7,12-dimethylbenz[a]anthracene (DMBA) starting at 50 days of age. After the first weekly DMBA administration, exposure to ambient fields (sham exposed), 50 Hz magnetic fields at either 1 or 5 G field intensity or 60 Hz fields at 1 G for 18.5 h/day, 7 days/week was initiated. Exposure continued for 13 weeks. A vehicle control group without DMBA was included. In a second study, using lower doses of DMBA, groups of 100 female Sprague-Dawley rats were initiated with four weekly doses of 2 mg of DMBA starting at 50 days of age followed, after the first weekly DMBA administration, by exposure to ambient fields (sham exposed) or 50 Hz magnetic fields at either 1 or 5 G field intensity for 18.5 h/day, 7 days/week for 13 weeks. Rats were weighed and palpated weekly for the presence of tumors. There was no effect of magnetic field exposure on body weight gains or on the time of appearance of mammary tumors in either study. At the end of 13 weeks, the animals were killed and the mammary tumors counted and measured. Mammary gland masses found grossly were examined histologically. In the first 13 week study, the mammary gland carcinoma incidences were 92, 86, 96 and 96% for the DMBA controls, 1 G, 50 Hz, 5 G, 50 Hz and 1 G, 60 Hz groups, respectively. The total numbers of carcinomas were 691, 528 (P < 0. 05, decrease), 561 and 692 for the DMBA controls, 1 G, 50 Hz, 5 G, 50 Hz and 1 G, 60 Hz groups, respectively. In study 2, the mammary gland carcinoma incidences were 43, 48 and 38% for the DMBA controls, 1 G, 50 Hz and 5 G, 50 Hz groups, respectively. The total numbers of carcinomas were 102, 90 and 79 for the DMBA controls, 1 G, 50 Hz and 5 G, 50 Hz groups, respectively. There was no effect of magnetic field exposure on tumor size either by in-life palpation or by measurement at necropsy in either study. There was no evidence that 50 or 60 Hz magnetic fields promoted breast cancer in these studies in female rats. These studies do not support the hypothesis that magnetic field exposure promotes breast cancer in this DMBA rat model.

Pea chloroplast glyceraldehyde-3-phosphate dehydrogenase has uracil glycosylase activity

Pea (Pisum sativum) chloroplastic glyceraldehyde-3-P dehydrogenase (EC 1.2.1.13) was tested for uracil DNA glycosylase activity. It was found that both the chloroplast and the recombinant subunit B dehydrogenases remove uracil from poly(dA[3H]dU). The glycosylase activity of the recombinant subunit B enzyme and that of a truncated form corresponding in length to subunit A were associated with the dehydrogenase activity in gel-filtration experiments. Both activities of the chloroplast enzyme were inhibited by antisera raised against recombinant subunit B, and both activities of the recombinant subunit B enzyme were inhibited by antisera raised against pea chloroplast glyceraldehyde-3-P dehydrogenase. Antisera raised against Escherichia coli uracil glycosylase did not affect the glycosylase activity of the recombinant subunit B enzyme. The glycosylase pH activity profile of the chloroplast dehydrogenase was unique. It is distinct from the dehydrogenase pH activity profile and from the pH activity profiles of other plant glycosylases. The glycosylase activity, but not the dehydrogenase activity, of the recombinant subunit B enzyme was inhibited by uracil. Pyridine nucleotides stimulated the glycosylase activity. To our knowledge this is the first example of a nonhuman glyceraldehyde-3-P dehydrogenase, and of an NADP-dependent glyceraldehyde-3-P dehydrogenase, that exhibits uracil glycosylase activity.

Prostaglandin moieties that determine receptor binding specificity in the bovine corpus luteum

This study provided a pharmacological evaluation of prostaglandin binding to bovine luteal plasma membrane. It was found that [3H]PGF2 alpha' [3H]PGE2' [3H]PGE1 and [3H]PGD2 all bound with high affinity to luteal plasma membrane but had different specificities. Binding of [3H]PGF2 alpha and [3H]PGD2 was inhibited by non-radioactive PGF2 alpha (IC50 values of 21 and 9 nmol l-1, respectively), PGD2 (35 and 21 nmol l-1), and PGE2 (223 and 81 nmol l-1), but not by PGE1 (> 10,000 and 5616 nmol l-1). In contrast, [3H]PGE1 was inhibited by non-radioactive PGE1 (14 nmol l-1) and PGE2 (7 nmol l-1), but minimally by PGD2 (2316 nmol l-1) and PGF2 alpha (595 nmol l-1). Binding of [3H]PGE2 was inhibited by all four prostaglandins, but slopes of the dissociation curves indicated two binding sites. Binding of [3H]PGE1 was inhibited, resulting in low IC50 values, by pharmacological agonists that are specific for EP3 receptor and possibly EP2 receptor. High affinity binding of [3H]PGF2 alpha required a C15 hydroxyl group and a C1 carboxylic acid that are present on all physiological prostaglandins. Specificity of binding for the FP receptor depended on the C9 hydroxyl group and the C5/C6 double bond. Alteration of the C11 position had little effect on affinity for the FP receptor. In conclusion, there is a luteal EP receptor with high affinity for PGE1' PGE2' agonists of EP3 receptors, and some agonists of EP2 receptors. The luteal FP receptor binds PGF2 alpha' PGD2 (high affinity), and PGE2 (moderate affinity) but not PGE1 due to affinity determination by the C9 and C5/C6 moieties, but not the C11 moiety.

Effect of 26 week magnetic field exposures in a DMBA initiation-promotion mammary gland model in Sprague-Dawley rats

Several studies have suggested that exposure to 50 Hz magnetic fields promote chemically induced breast cancer in rats. Groups of 100 female Sprague-Dawley rats were initiated with a single 10 mg gavage dose of 7,12-dimethylbenz[a]anthracene (DMBA) at 50 days of age followed by exposure to ambient fields (sham exposed), 50 Hz magnetic fields at either 1 or 5 Gauss (G) field intensity or 60 Hz fields at 1 G for 18.5 h/day, 7 days/week for 26 weeks. A vehicle control group without DMBA was included. Rats were palpated weekly for the presence of tumors. There was no effect of magnetic field exposure on body weight gains or the time of appearance of mammary tumors. At the end of 26 weeks, the animals were killed and the mammary tumors counted and measured. Mammary gland masses found grossly were examined histologically. The mammary gland carcinoma incidence was 96, 90, 95 and 85% (P < 0.05, decrease) for the DMBA controls, 1 G 50 Hz, 5 G 50 Hz and 1 G 60 Hz groups, respectively. The total numbers of carcinomas were 649, 494 (P < 0.05, decrease), 547 and 433 (P < 0.05, decrease) for the DMBA controls, 1 G 50 Hz, 5 G 50 Hz and 1 G 60 Hz groups, respectively. The number of fibroadenomas varied from 276 to 319, with the lowest number in the 1 G 60 Hz exposure group. Measurement of the tumors revealed no difference in tumor size between groups. In this breast cancer initiation-promotion study in female Sprague-Dawley rats, there was no evidence that 50 or 60 Hz magnetic fields promoted breast cancer under the conditions of this assay. This study does not support the hypothesis that magnetic field exposure can promote breast cancer in this rat model.

Lack of effect of a 60 Hz magnetic field on biomarkers of tumor promotion in the skin of SENCAR mice

It has been proposed that extremely low frequency magnetic fields may enhance tumorigenesis through a co-promotional mechanism. This hypothesis has been further tested using the two-stage model of mouse skin carcinogenesis, i.e. 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced promotion of skin carcinogenesis in mice initiated by a single subcarcinogenic dose of 7,12-dimethylbenz[a]anthracene. Experimentation utilized three different doses of TPA within its dose-response range (0.85, 1.70 or 3.40 nmol) and examined the following early biomarkers of tumor promotion after 1, 2 and 5 weeks of promotion: increases in epidermal thickness and the labeling index of epidermal cells, induction of epidermal ornithine decarboxylase activity and down-regulation of epidermal protein kinase C activity. Mice exposed to a 60 Hz magnetic field having a flux density of 2 mT for 6 h/day for 5 days/week were compared with mice exposed to an ambient magnetic field. Within the sensitivity limits of the biomarker methodology and the exposure parameters employed, no consistent, statistically significant effects indicative of promotion or co-promotion by the magnetic field were demonstrated.

Regulation of prostaglandin F2 alpha and E receptor mRNA by prostaglandin F 2 alpha in ovine corpora lutea

Prostaglandins regulate many physiological functions, including reproduction, by binding to specific plasma membrane receptors. In this study we evaluated the regulation of PGF2 alpha (FP) and PGE (EP3 subtype) receptors in ovine corpora lutea. In the first study, tissue distribution of FP and EP3 receptors was evaluated in 13 ovine tissues. FP receptor mRNA was present in 100-fold higher concentration in corpora lutea than in other tissues. Similarly, [3H]PGF2 alpha binding was much greater in luteal plasma membranes than in membranes from other tissues. In contrast, EP3 receptor mRNA was more uniformly distributed, with high concentrations in adrenal medulla, inner myometrium, kidney medulla and heart. The distribution of [3H]PGE1 binding was generally similar to EP3 mRNA, with the exception that ovarian stroma, endometrium and outer myometrium had high [3H]PGE1 binding but low concentrations of EP3 receptor mRNA. The second study evaluated the action of PGF2 alpha on luteal mRNA encoding FP and EP3 receptors. Ewes had PGF2 alpha or saline infused into the ovarian artery and corpora lutea were removed at 0, 1, 4, 12 and 24 h. FP receptor mRNA decreased by 50% at 12 and 24 h after infusion with PGF2 alpha, whereas EP3 mRNA was unchanged. Treatment of large luteal cells with PGF2 alpha, phorbol didecanoate (protein kinase C activator), or ionomycin (calcium ionophore) decreased FP receptor mRNA after 24 h (P < 0.05). Glyceraldehyde 3-phosphate dehydrogenase mRNA was not changed by any treatment. These results show that EP3 receptors are expressed in many tissues and expression is not regulated by PGF2 alpha. In contrast, FP receptors are primarily expressed in corpora lutea and expression is inhibited by PGF2 alpha.

Lack of a co-promoting effect of a 60 Hz magnetic field on skin tumorigenesis in SENCAR mice

It has been proposed that extremely low frequency (ELF) magnetic fields may enhance tumorigenesis through a co-promotional mechanism. This hypothesis has been further tested using the two-stage model of mouse skin carcinogenesis, i.e. 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced promotion of skin tumors in mice initiated by a single subcarcinogenic dose of 7,12-dimethylbenz[a]anthracene. Experimentation described herein utilized the SENCAR mouse and examined the effect of a magnetic field on skin tumor promotion induced by three different doses of TPA within its dose-response range, i.e. 0.85, 1.70 or 3.40 nmol, administered twice per week. SENCAR mice (56/treatment group) were exposed to a 60 Hz magnetic field having a flux density of 2 mT for 6 h/day for 5 days/week and compared with mice exposed to the ambient magnetic field. Tumor incidence and multiplicity were monitored weekly for 23 weeks of TPA promotion. Statistical evaluation of the effects of the magnetic field on tumor incidence and multiplicity did not reveal any statistically significant effects; thus, within the sensitivity limits imposed by the animal model and the exposure parameters employed, no promotional or co-promotional effect of a 2 mT magnetic field on skin tumor development in SENCAR mice could be demonstrated.

Inhibition of antagonist and agonist binding to the human brain muscarinic receptor by arachidonic acid

Arachidonic acid (AA) inhibits the binding of [3H]quinclidinyl benzilate ([3H]QNB) to the human brain muscarinic cholinergic receptor (mAChR). AA inhibits at lower concentrations in the absence of glutathione (I50 = 15 microM) than in the presence of glutathione (I50 = 42 microM). Inhibition of mAChR binding shows specificity for AA and is reduced with loss of one or more double bonds or with either a decrease or increase in the length of the fatty acid chain. Metabolism of AA by the lipoxygenase, epoxygenase, or fatty acid cyclooxygenase pathways is not required for the inhibitory activity of AA on mAChR binding. Inhibition of [3H]QNB binding by AA is reversible. While decreasing Bmax, AA increased the apparent KD for [3H]QNB and for the more polar antagonist [3H]NMS. In addition, AA inhibits binding of the agonist [3H]oxotremorine-M (I50 = 60 microM) and is the first mediator of mAChR action to be shown to reversibly inhibit mAChR binding. The feedback inhibition of the mAChR by AA may serve a homeostatic function similar to the reuptake and hydrolysis of acetylcholine following cholinergic nerve transmission.