Unraveling the toxicity of tire wear contamination in three freshwater species: From chemical mixture to nanoparticles

Tire wear particle (TWP) contamination is of growing concern as recent studies show the ubiquity and toxicity of this contaminant in various environmental compartments. The multidimensional aspect of TWPs makes it difficult to assess toxicity and predict impacts on ecosystems, as it combines a complex mixture of chemicals and can release micro- and nanoparticles when suspended in water. Our work aimed to shed light on the toxicity of the different components of TWP leachate, namely, the dissolved chemicals and the nanoparticle fractions, on three freshwater model species of different trophic levels: Chlorella vulgaris, Lemna minor, and Daphnia magna. Acute toxicity was observed for all three fractions in D. magna, and an additive effect was observed between the nanoparticles and dissolved chemicals. L. minor experienced phytotoxicity from the dissolved chemicals only with a decrease up to 50% in photosynthesis efficiency parameters. C. vulgaris showed minor signs of toxicity on apical endpoints in response to each of the fractions. Our study highlights that nanoparticles from TWP leachate that were mostly overlooked in several previous studies are as toxic as dissolved chemicals for the filter-feeder species D. magna, and we also show the toxicity to photosynthesis in aquatic plants.

Molecular and long-term behavioral consequences of neonatal opioid exposure and withdrawal in mice

Introduction

Infants exposed to opioids in utero are at high risk of exhibiting Neonatal Opioid Withdrawal Syndrome (NOWS), a combination of somatic withdrawal symptoms including high pitched crying, sleeplessness, irritability, gastrointestinal distress, and in the worst cases, seizures. The heterogeneity of in utero opioid exposure, particularly exposure to polypharmacy, makes it difficult to investigate the underlying molecular mechanisms that could inform early diagnosis and treatment of NOWS, and challenging to investigate consequences later in life.

Methods

To address these issues, we developed a mouse model of NOWS that includes gestational and post-natal morphine exposure that encompasses the developmental equivalent of all three human trimesters and assessed both behavior and transcriptome alterations.

Results

Opioid exposure throughout all three human equivalent trimesters delayed developmental milestones and produced acute withdrawal phenotypes in mice reminiscent of those observed in infants. We also uncovered different patterns of gene expression depending on the duration and timing of opioid exposure (3-trimesters, in utero only, or the last trimester equivalent only). Opioid exposure and subsequent withdrawal affected social behavior and sleep in adulthood in a sex-dependent manner but did not affect adult behaviors related to anxiety, depression, or opioid response.

Discussion

Despite marked withdrawal and delays in development, long-term deficits in behaviors typically associated with substance use disorders were modest. Remarkably, transcriptomic analysis revealed an enrichment for genes with altered expression in published datasets for Autism Spectrum Disorders, which correlate well with the deficits in social affiliation seen in our model. The number of differentially expressed genes between the NOWS and saline groups varied markedly based on exposure protocol and sex, but common pathways included synapse development, the GABAergic and myelin systems, and mitochondrial function.

Buprenorphine reduces somatic withdrawal in a mouse model of early-life morphine exposure

The rising prevalence of early-life opioid exposure has become a pressing public health issue in the U.S. Neonates exposed to opioids in utero are at risk of experiencing a constellation of postpartum withdrawal symptoms commonly referred to as neonatal opioid withdrawal syndrome (NOWS). Buprenorphine (BPN), a partial agonist at the mu-opioid receptor (MOR) and antagonist at the kappa-opioid receptor (KOR), is currently approved to treat opioid use disorder in adult populations. Recent research suggests that BPN may also be effective in reducing withdrawal symptoms in neonates who were exposed to opioids in utero. We sought to determine whether BPN attenuates somatic withdrawal in a mouse model of NOWS. Our findings indicate that the administration of morphine (10mg/kg, s.c.) from postnatal day (PND) 1-14 results in increased somatic symptoms upon naloxone-precipitated (1mg/kg, s.c.) withdrawal. Co-administration of BPN (0.3mg/kg, s.c.) from PND 12-14 attenuated symptoms in morphine-treated mice. On PND 15, 24h following naloxone-precipitated withdrawal, a subset of mice was examined for thermal sensitivity in the hot plate test. BPN treatment significantly increased response latency in morphine-exposed mice. Lastly, neonatal morphine exposure elevated mRNA expression of KOR, and reduced mRNA expression of corticotropin-releasing hormone (CRH) in the periaqueductal gray when measured on PND 14. Altogether, this data provides support for the therapeutic effects of acute low-dose buprenorphine treatment in a mouse model of neonatal opioid exposure and withdrawal.

Interactive effects of changes in UV radiation and climate on terrestrial ecosystems, biogeochemical cycles, and feedbacks to the climate system

Terrestrial organisms and ecosystems are being exposed to new and rapidly changing combinations of solar UV radiation and other environmental factors because of ongoing changes in stratospheric ozone and climate. In this Quadrennial Assessment, we examine the interactive effects of changes in stratospheric ozone, UV radiation and climate on terrestrial ecosystems and biogeochemical cycles in the context of the Montreal Protocol. We specifically assess effects on terrestrial organisms, agriculture and food supply, biodiversity, ecosystem services and feedbacks to the climate system. Emphasis is placed on the role of extreme climate events in altering the exposure to UV radiation of organisms and ecosystems and the potential effects on biodiversity. We also address the responses of plants to increased temporal variability in solar UV radiation, the interactive effects of UV radiation and other climate change factors (e.g. drought, temperature) on crops, and the role of UV radiation in driving the breakdown of organic matter from dead plant material (i.e. litter) and biocides (pesticides and herbicides). Our assessment indicates that UV radiation and climate interact in various ways to affect the structure and function of terrestrial ecosystems, and that by protecting the ozone layer, the Montreal Protocol continues to play a vital role in maintaining healthy, diverse ecosystems on land that sustain life on Earth. Furthermore, the Montreal Protocol and its Kigali Amendment are mitigating some of the negative environmental consequences of climate change by limiting the emissions of greenhouse gases and protecting the carbon sequestration potential of vegetation and the terrestrial carbon pool.

Naphthenic acid fraction compounds reduce the reproductive success of wood frogs (Rana sylvatica) by affecting offspring viability

Understanding the toxicity of organic compounds in oil sands process-affected water (OSPW) is necessary to inform the development of environmental guidelines related to wastewater management in Canada's oil sands region. In the present study, we investigated the effects of naphthenic acid fraction compounds (NAFCs), one of the most toxic components of OSPW, on mating behaviour, fertility, and offspring viability in the wood frog (Rana sylvatica). Wild adult wood frogs were exposed separately from the opposite sex to 0, 5, or 10 mg/L of OSPW-derived NAFCs for 24 h and then combined in outdoor lake water mesocosms containing the same NAFC concentrations (n = 2 males and 1 female per mesocosm, n = 3 mesocosms per treatment). Mating events were recorded for 48 h and egg masses were measured to determine adult fertility. NAFC exposure had no significant effect on mating behaviour (probability of amplexus and oviposition, amplexus and oviposition latency, total duration of amplexus and number of amplectic events) or fertility (fertilization success and clutch size). Tadpoles (50 individuals per mesocosm at hatching, and 15 individuals per mesocosm from 42 d post-hatch) were reared in the same mesocosms under chronic NAFC exposure until metamorphic climax (61-85 d after hatching). Offspring exposed to 10 mg/L NAFCs during development were less likely to survive and complete metamorphosis, grew at a reduced rate, and displayed more frequent morphological abnormalities. These abnormalities included limb anomalies at metamorphosis, described for the first time after NAFC exposure. The results of this study suggest that NAFCs reduce wood frog reproductive success through declines in offspring viability and therefore raise the concern that exposure to NAFCs during reproduction and development may affect the recruitment of native amphibian populations in the oil sands region.

Effects of a Neonicotinoid Insecticide and Population Density on Behavior and Development of Wood Frogs (Rana sylvatica)

Amphibians have been facing global declines over the last decades from direct and indirect effects of anthropogenic activities. A contributor to declines is waterway contamination from agricultural runoffs of pesticides such as neonicotinoids. Beyond direct and indirect effects of the pesticide, few studies have investigated the possible interactions between neonicotinoids and natural environmental stressors across larval development, which could alter the strength and direction of observed neonicotinoid effects. The present study used a fully crossed design to investigate how a concentration of imidacloprid (a neonicotinoid; 10 µg/L) measured in surface waters interacted with low and high population densities (0.33 and 1 tadpole/L, respectively), an important environmental stressor, to influence behavior and development across metamorphosis in wood frogs (Rana sylvatica), known to breed in agricultural landscapes. Behaviors were measured in the absence and presence of predation cues using open-field tests at three distinct developmental stages, up to the metamorph stage. We found that imidacloprid did not interact with population density or independently affect behaviors in the absence of predation cues. However, individuals raised at high density compared with low density were more active at an early developmental stage but less active at metamorphic climax. Furthermore, both density and imidacloprid independently decreased the natural freezing response of tadpoles to predation cues. Finally, we found that distance traveled in the open-field test was weakly repeatable between aquatic stages but not repeatable across metamorphosis, a pattern that was not affected by treatments. The present study provides novel insights on the ecotoxicology of imidacloprid in the presence of a natural stressor, highlighting the importance of including behavioral assays and natural stressors in studies of amphibian ecotoxicology. Environ Toxicol Chem 2022;41:2968-2980. © 2022 SETAC.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2021

The Environmental Effects Assessment Panel of the Montreal Protocol under the United Nations Environment Programme evaluates effects on the environment and human health that arise from changes in the stratospheric ozone layer and concomitant variations in ultraviolet (UV) radiation at the Earth’s surface. The current update is based on scientific advances that have accumulated since our last assessment (Photochem and Photobiol Sci 20(1):1–67, 2021). We also discuss how climate change affects stratospheric ozone depletion and ultraviolet radiation, and how stratospheric ozone depletion affects climate change. The resulting interlinking effects of stratospheric ozone depletion, UV radiation, and climate change are assessed in terms of air quality, carbon sinks, ecosystems, human health, and natural and synthetic materials. We further highlight potential impacts on the biosphere from extreme climate events that are occurring with increasing frequency as a consequence of climate change. These and other interactive effects are examined with respect to the benefits that the Montreal Protocol and its Amendments are providing to life on Earth by controlling the production of various substances that contribute to both stratospheric ozone depletion and climate change.

Daily physical activity and sleep in veterans: the role of insomnia severity

Physical activity (PA) is suggested as an easily accessible adjunctive lifestyle intervention for insomnia. It is not clear if PA is equally beneficial across different levels of insomnia severity. The current study examined the relationship between daily PA (steps) and sleep (duration, efficiency, and quality) across the spectrum of insomnia severity. Multilevel models estimated day-to-night relationships between PA and sleep, and if insomnia severity moderated these relationships. Days with greater PA were associated with nights with longer sleep duration. This was moderated by insomnia severity; PA was associated with longer sleep that night in participants with mild insomnia and associated with less sleep in those with severe insomnia. PA was not associated with sleep efficiency or quality. PA is potentially an easily accessible and impactful intervention to promote sleep duration in participants who are experiencing less severe sleep disturbance. More complex, resource-intensive interventions may be needed as insomnia severity increases.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

This assessment by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) provides the latest scientific update since our most recent comprehensive assessment (Photochemical and Photobiological Sciences, 2019, 18, 595-828). The interactive effects between the stratospheric ozone layer, solar ultraviolet (UV) radiation, and climate change are presented within the framework of the Montreal Protocol and the United Nations Sustainable Development Goals. We address how these global environmental changes affect the atmosphere and air quality; human health; terrestrial and aquatic ecosystems; biogeochemical cycles; and materials used in outdoor construction, solar energy technologies, and fabrics. In many cases, there is a growing influence from changes in seasonality and extreme events due to climate change. Additionally, we assess the transmission and environmental effects of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is responsible for the COVID-19 pandemic, in the context of linkages with solar UV radiation and the Montreal Protocol.

Neurobehavioral effects of neonatal opioid exposure in mice: Influence of the OPRM1 SNP

Opioid use among pregnant women is a growing public health concern in the United States. Infants exposed to opioids in utero are at risk of exhibiting neonatal opioid withdrawal syndrome (NOWS). The biological mechanisms underlying short and long-term consequences of in utero opioid exposure and NOWS are unknown. A potential genetic factor is a single-nucleotide polymorphism (SNP) in the mu-opioid receptor gene (OPRM1 A118G). Opioid exposed infants with the G-allele spend less time in hospitals after birth. To determine whether this SNP modulates the neurobehavioral effects of neonatal opioid exposure and withdrawal, we used mice possessing the equivalent Oprm1 SNP (A112G). Pups were treated chronically with saline or morphine from postnatal days (PNDs) 1 to 14, a developmental period equivalent to the third trimester of a human pregnancy and a sensitive period for opioid exposure in rodents. Morphine treatment produced significant developmental delays regardless of genotype and increased total ultrasonic vocalizations in males during spontaneous withdrawal. Animals were aged and tested for anxiety and drug response during adolescence and adulthood, respectively. AA morphine-treated animals showed reduced activity in the marble burying task compared with saline controls; however, this effect was absent in AG and GG animals. As adults, AA males exposed to morphine from PNDs 1 to 14 exhibited enhanced development of locomotor sensitization to morphine, whereas females showed reduced locomotor sensitization. These data suggest the involvement of the Oprm1 SNP for certain outcomes of neonatal opioid exposure and highlight the importance of considering sex and genetic variability for the prognosis of NOWS.

Environmental effects of stratospheric ozone depletion, UV radiation and interactions with climate change: UNEP Environmental Effects Assessment Panel, update 2019

This assessment, by the United Nations Environment Programme (UNEP) Environmental Effects Assessment Panel (EEAP), one of three Panels informing the Parties to the Montreal Protocol, provides an update, since our previous extensive assessment (Photochem. Photobiol. Sci., 2019, 18, 595-828), of recent findings of current and projected interactive environmental effects of ultraviolet (UV) radiation, stratospheric ozone, and climate change. These effects include those on human health, air quality, terrestrial and aquatic ecosystems, biogeochemical cycles, and materials used in construction and other services. The present update evaluates further evidence of the consequences of human activity on climate change that are altering the exposure of organisms and ecosystems to UV radiation. This in turn reveals the interactive effects of many climate change factors with UV radiation that have implications for the atmosphere, feedbacks, contaminant fate and transport, organismal responses, and many outdoor materials including plastics, wood, and fabrics. The universal ratification of the Montreal Protocol, signed by 197 countries, has led to the regulation and phase-out of chemicals that deplete the stratospheric ozone layer. Although this treaty has had unprecedented success in protecting the ozone layer, and hence all life on Earth from damaging UV radiation, it is also making a substantial contribution to reducing climate warming because many of the chemicals under this treaty are greenhouse gases.

Buprenorphine prevents stress-induced blunting of nucleus accumbens dopamine response and approach behavior to food reward in mice

Alterations to the mesolimbic dopamine (DA) system are thought to underlie dysfunctional reward processing in stress-related psychiatric disorders. Using in vivio microdialysis in awake freely moving mice, we assessed the effects of stress on the motivational and neurochemical correlates underlying conditioned approach behavior for palatable food in the non-deprived mouse. Mice trained to approach and consume food in a familiar environment exhibited a 30% increase in nucleus accumbens shell (AcbSh) extracellular dopamine levels coincident with approach towards and consumption of the food reward. This effect was not observed in mice that were presented with the food in an unfamiliar environment or were exposed for the first time and were region specific. The addition of an acute environmental stressor (bright light and novel scent) during food exposure decreased DA release and delayed approach to the food. The disruptive impact of acute novelty stress on DA levels and approach behavior was reversed in animals pretreated with buprenorphine, an opioid drug with antidepressant-like and anxiolytic effects. Together, these data indicate that exposure to mild stress reduces incentive drive to approach palatable food via alterations in AcbSh dopamine responsiveness to food reward. Moreover, they implicate the brain opioid system as a potential pharmacological target for counteracting behavioral and neurochemical elements associated with stress.

Macrophytes are highly sensitive to the herbicide diquat dibromide in test systems of varying complexity

The herbicide diquat dibromide is used in North America to manage nuisance macrophytes. However, its effect on native macrophytes is less clear and it could cause indirect effects on other aquatic biota. This study determined the sensitivity of both native and non-native macrophytes grown in test systems with varying complexity to diquat dibromide applied directly to water following label directions. In an outdoor mesocosm experiment and single species greenhouse concentration-response tests, Elodea canadensis Michx., Myriophyllum spicatum L., Ceratophyllum demersum L. and Hydrocharis morsus-ranae L. were exposed to a range of diquat dibromide concentrations (4.7 - 1153 µg/L), corresponding to 0.4 - 100% of the recommended label rate of the formulated product. The mesocosm experiment contained all four plant taxa in the same system along with caged amphipods (Hyalella azteca Saus.), tadpoles (Lithobates pipiens Schreber), phytoplankton and periphyton; however, this study focuses on the macrophytes only. In both test systems, severe direct effects of diquat dibromide on macrophytes were detected, with almost 100% mortality of all macrophytes in both test systems at 74 µg/L. The most sensitive species in the single species tests, E. canadensis, showed almost 100% mortality at concentrations below the HPLC-based method detection limit of 5 µg/L. Effects occurred very rapidly and showed no difference in severity between native and non-native macrophytes or complexity of test systems. These results suggest that diquat dibromide could be applied at a considerably lower label rate, depending on the characteristics of the waterbody, while still achieving effective control of nuisance macrophytes.

Knee-high compression socks minimize head-up tilt-induced cerebral and cardiovascular responses following dynamic exercise

In healthy individuals during a non-exercised state, knee-high compression socks (CS) may reduce the magnitude of lower limb venous pooling during orthostasis but are not effective at minimizing the incidence of pre-syncopal symptoms. However, exaggerated reductions in cerebral blood flow velocity (CBV) and cardiac stroke volume (SV) occur during passive head-up tilt (HUT) testing following dynamic exercise. It is unknown if CS can minimize post-exercise HUT-induced decrements in CBV and SV in this population. To test the hypothesis that CS will attenuate the reductions in SV and CBV during 60° HUT following 60 minutes of moderate-intensity (60% VO₂ peak) cycling exercise. Ten healthy volunteers (22.6 ± 2.1 years, 24.1 ± 2.5 kg/m² ) completed pre- and post-exercise 15-minute HUT tests during randomized CS and Control (no CS) conditions. Changes in blood pressure (finger plethysmography), SV (Modelflow® method), and CBV (Transcranial Doppler) were measured during HUT and preceding supine rest periods. Pre-exercise HUT-induced similar (all, P > .47) reductions in SV (Control; -23.1 ± 11.5%, CS; -20.5 ± 10.9%) and CBV (Control; -18.1 ± 6.3%, CS; -15.3 ± 9.0%). However, larger post-exercise decreases in SV and CBV during HUT were observed in the Control versus CS condition. Specifically, CS attenuated the drop in SV (Control: -32.9 ± 5.6%, CS: -24.3 ± 11.6%; P = .01) and CBV (Control: -25.1 ± 5.8%, CS: -17.6 ± 7.8%; P = .02) during the post-exercise HUT test. These results indicate that CS attenuated HUT-induced reductions in SV and CBV following moderate-intensity cycling exercise and suggest that CS may be an effective countermeasure to reduce the incidence of post-exercise syncope in vulnerable populations.

Reversal of Stress-Induced Social Interaction Deficits by Buprenorphine

BACKGROUND

Patients with post-traumatic stress disorder frequently report persistent problems with social interactions, emerging after a traumatic experience. Chronic social defeat stress is a widely used rodent model of stress that produces robust and sustained social avoidance behavior. The avoidance of other rodents can be reversed by 28 days of treatment with selective serotonin reuptake inhibitors, the only pharmaceutical class approved by the U.S. Food and Drug Administration for treating post-traumatic stress disorder. In this study, the sensitivity of social interaction deficits evoked by 10 days of chronic social defeat stress to prospective treatments for post-traumatic stress disorder was examined.

METHODS

The effects of acute and repeated treatment with a low dose of buprenorphine (0.25 mg/kg/d) on social interaction deficits in male C57BL/6 mice by chronic social defeat stress were studied. Another cohort of mice was used to determine the effects of the selective serotonin reuptake inhibitor fluoxetine (10 mg/kg/d), the NMDA antagonist ketamine (10 mg/kg/d), and the selective kappa opioid receptor antagonist CERC-501 (1 mg/kg/d). Changes in mRNA expression of Oprm1 and Oprk1 were assessed in a separate cohort.

RESULTS

Buprenorphine significantly reversed social interaction deficits produced by chronic social defeat stress following 7 days of administration, but not after acute injection. Treatment with fluoxetine for 7 days, but not 24 hours, also reinstated social interaction behavior in mice that were susceptible to chronic social defeat. In contrast, CERC-501 and ketamine failed to reverse social avoidance. Gene expression analysis found: (1) Oprm1 mRNA expression was reduced in the hippocampus and increased in the frontal cortex of susceptible mice and (2) Oprk1 mRNA expression was reduced in the amygdala and increased in the frontal cortex of susceptible mice compared to non-stressed controls and stress-resilient mice.

CONCLUSIONS

Short-term treatment with buprenorphine and fluoxetine normalized social interaction after chronic social defeat stress. In concert with the changes in opioid receptor expression produced by chronic social defeat stress, we speculate that buprenorphine's efficacy in this model of post-traumatic stress disorder may be associated with the ability of this compound to engage multiple opioid receptors.

Sensitivity of the early-life stages of freshwater mollusks to neonicotinoid and butenolide insecticides

Neonicotinoid insecticides can be transported from agricultural fields, where they are used as foliar sprays or seed treatments, to surface waters by surface or sub-surface runoff. Few studies have investigated the toxicity of neonicotinoid or the related butenolide insecticides to freshwater mollusk species. The current study examined the effect of neonicotinoid and butenolide exposures to the early-life stages of the ramshorn snail, Planorbella pilsbryi, and the wavy-rayed lampmussel, Lampsilis fasciola. Juvenile P. pilsbryi were exposed to imidacloprid, clothianidin, or thiamethoxam for 7 or 28 d and mortality, growth, and biomass production were measured. The viability of larval (glochidia) L. fasciola was monitored during a 48 h exposure to six neonicotinoids (imidacloprid, thiamethoxam, clothianidin, acetamiprid, thiacloprid, or dinotefuran), or a butenolide (flupyradifurone). The 7-d LC50s of P. pilsbryi for imidacloprid, clothianidin, and thiamethoxam were ≥4000 μg/L and the 28-d LC50s were ≥182 μg/L. Growth and biomass production were considerably more sensitive endpoints than mortality with EC50s ranging from 33.2 to 122.0 μg/L. The 48-h LC50s for the viability of glochidia were ≥456 μg/L for all seven insecticides tested. Our data indicate that neonicotinoid and butenolide insecticides pose less of a hazard with respect to mortality of the two species of mollusk compared to the potential hazard to other non-target aquatic insects.

Toxoplasma gondii major surface antigen (SAG1): in vitro analysis of host cell binding

Previous studies have indicated that SAG1, the major surface molecule of the protozoan parasite Toxoplasma gondii, is an important attachment ligand for the host cell. However, the research data that supports this claim comes largely from studies investigating tachyzoite binding, and not SAG1 binding per se. In this study we successfully developed an in vitro attachment assay to directly evaluate the mechanism of SAG1-host cell binding. Competition experiments were then performed using SAG1 that had been pre-treated with the neoglycoprotein BSA-glucosamide or with antibody. Soluble BSA-glucosamide blocked SAG1 attachment to MDBK cells in a dose-dependent manner, implying that SAGI binding is mediated, in part, via attachment to host cell surface glucosamine. Interestingly, pre-incubation of SAG1 in polyclonal sera from chronically infected mice failed to block binding. This challenges the assumption that anti-SAG1 antibodies block parasite attachment through the masking of SAG1 host cell binding domains. Taken together, this evidence presents new strategies for understanding SAG1-mediated attachment.

Role of cadherin internalization in hydrogen peroxide-mediated endothelial permeability

Exposure of endothelial monolayers to hydrogen peroxide results in increased solute permeability in a time- and dose-dependent fashion. This effect is prevented by either staurosporine, an inhibitor of PKC, or by Gö6976, an inhibitor of "classical" PKC isoforms. Immunohistochemistry of peroxide-treated monolayers illustrates a loss of cadherin staining at cell junctions and gap formation predominantly at tri-cellular junctions. Both staurosporine and Gö6976 prevented peroxide-induced gap formation. Peroxide also stimulated internalization of cadherins as measured by the trypsin protection assay, which was not blocked by staurosporine or Gö6976. These data suggest that peroxide causes: 1) a time- and dose-dependent increase in permeability and dose-dependent increase in gap formation, both of which are PKC dependent; and 2) promotes PKC-independent cadherin internalization. These data indicate that cadherin internalization may be part of the mechanism through which oxidants regulate solute permeability.

Participatory health development in rural Nepal: clarifying the process of community empowerment

Community-based participatory development empowers villagers to develop community cohesion and confidence, increase their ability to identify, analyze, and priorize their own needs, and organize the resources to meet these needs. An important first step in the process involves establishing a cohesive and functional community group. The authors believe that this is best accomplished through villagers' critical examination of their experiences with development including their understanding of reasons for success or failure, and the gradual emergence of a model of working together that acknowledges and builds on participation and collective expertise. This approach to development is demonstrating encouraging results in a rural area of western Nepal in a university affiliated Canadian/Nepali Health Development Project. This paper describes two mini-projects to illustrate the evolution of group formation through reflection, analysis, and action, and identifies outcomes that could serve as indicators of community empowerment. The paper also presents a generic model of empowerment, and offers lessons learned by the project through the application of the empowerment process to sustainable health development.

Measurements of the Engagement of Cyanide-Resistant Respiration in the Crassulacean Acid Metabolism Plant Kalanchoë daigremontiana with the Use of On-Line Oxygen Isotope Discrimination

Discrimination against (18)O during dark respiration in tissues of Kalanchoë daigremontiana, Medicago sativa, and Glycine max was measured using an on-line system that enabled direct measurements of the oxygen fractionation of samples in a gas-phase leaf disk electrode unit. Discrimination factors for cytochrome pathway respiration were 18.6 to 19.8%(o) for all tissues. However, discrimination in cyanide-resistant respiration was significantly higher in green tissues (30.4-31.2%(o)) compared with nongreen tissues (25.3-25.9%(o)). Using these discrimination factors, the partitioning of electron transport to these pathways was calculated from measurements of discrimination in the absence of inhibitors. Changes in flux through the alternative pathway were measured during the light and dark phases of Crassulacean acid metabolism in leaf disks of K. daigremontiana. The flux of electrons through the alternative pathway was higher during deacidification than during the other phases of Crassulacean acid metabolism. The increase in alternative pathway electron flux accounted for all of the increased respiration in the light phase. Despite this increase, simultaneous measurements of malate concentration and respiratory flux confirm that only a small proportion of the total malate decarboxylation occurs in the mitochondria.

Regulation of glutamate dehydrogenase activity in relation to carbon limitation and protein catabolism in carrot cell suspension cultures

Glutamate dehydrogenase (GDH) specific activity and function have been studied in cell suspension cultures of carrot (Daucus carota L. cv Chantenay) in response to carbon and nitrogen supply in the culture medium. The specific activity of GDH was derepressed in sucrose-starved cells concomitant with protein catabolism, ammonium excretion, and the accumulation of metabolically active amino acids. The addition of sucrose led to a rapid decrease in GDH specific activity, an uptake of ammonium from the medium, and a decrease in amino acid levels. The extent of GDH derepression was correlated positively with cellular glutamate concentration. These findings strengthen the view that the function of GDH is the catabolism of glutamate, which under conditions of carbon stress provides carbon skeletons for tricarboxylic acid cycle activity.

The role of glutamate dehydrogenase in plant nitrogen metabolism

In vivo nuclear magnetic resonance spectroscopy, in vitro gas chromatography-mass spectrometry, and automated (15)N/(13)C mass spectrometry have been used to demonstrate that glutamate dehydrogenase is active in the oxidation of glutamate, but not in the reductive amination of 2-oxogiutarate. In cell suspension cultures of carrot (Daucus carota L. cv Chantenay), primary assimilation of ammonium occurs via the glutamate synthase pathway. Glutamate dehydrogenase is derepressed in carbonlimited cells and in such cells the function of glutamate dehydrogenase appears to be the oxidation of glutamate, thus ensuring sufficient carbon skeletons for effective functioning of the tricarboxylic acid cycle. This catabolic role for glutamate dehydrogenase implies an important regulatory function in carbon and nitrogen metabolism.

The relative influence of the community and the health system on work performance: a case study of community health workers in Colombia

A central component of the primary health care approach in developing countries has been the development and utilization of community-based health workers (CHWs) within the national health system. While the use of these front line workers has the potential to positively influence health behavior and health status in rural communities, there continues to be challenges to effective implementation of CHW programs. Reports of high turnover rates, absenteeism, poor quality of work, and low morale among CHWs have often been associated with weak organizational and managerial capacity of government health systems. However, no systematic research has examined the contribution of work-related factors to CHW job performance. The research reported in this paper examines the relative influence of reward and feedback factors associated with the community compared to those associated with the health system on the performance of CHWs. The data are drawn from a broader study of health promoters (CHWs) conducted in two departments (provinces) in Colombia in 1986. The research was based on a theoretical model of worker performance that focuses on job related sources of rewards and feedback. A survey research design was employed to obtain information from a random sample of rural health promoters (N = 179) and their auxiliary nurse supervisors about CHW performance and contributing factors. The findings indicate that feedback and rewards from the community have a greater influence on work performance (defined as degree of perceived goal attainment on job tasks) than do those stemming from the health system.(ABSTRACT TRUNCATED AT 250 WORDS)

Primary health care experiences in the developing world: lessons for Canada?

Primary health care, as practised in many developing countries, is a set of guidelines for designing health strategies that are both appropriate to the health needs of the population and to cultural and socio-economic contexts. Four aspects of primary health care experience in developing countries may be relevant to Canadian health care: the integration of health and development, participation of the community in problem identification and program planning, the role of the community-based worker, and the use of health information. Canadian physicians may draw on this experience to address present challenges in our health system: providing health services to marginal groups, viewing health in a broader perspective, the escalating costs of health services, and increasing community involvement in planning health services.

Late endocrine effects of L-dopa, 5-HTP, and 6-OH-dopa administered to neonatal rats

Neonatal rats were injected with L-dopa, 5-hydroxytryptophan (5-HTP) or 6-hydroxy-dopa (6-OH-dopa) and allowed to mature. Eye opening, vaginal opening, endocrine organ weights and pituitary hormone concentration in the serum were measured. Treatment with either the dopamine (DA) precursor or the serotonin (5-HT) precursor caused an acceleration in eye opening, a significant decrease in serum TSH (males) an elevation of serum prolactin (Prl; males), and a lowering of serum growth hormone (females). After chemical sympathectomy (6-OH-dopa) vaginal opening was delayed, thyroid weights were increased and serum TSH decreased (males). It is concluded that during the critical neonatal period overloading either of 2 of the principal monaminergic systems results in similar and persistent alterations in pituitary function. Chemical sympathectomy produced a different pattern of abnormalities.