Effects of high peak power microwaves on the retina of the rhesus monkey

We studied the retinal effects of 1.25 GHz high peak power microwaves in Rhesus monkeys. Preexposure fundus photographs, retinal angiograms, and electroretinograms (ERG) were obtained to screen for normal ocular structure and function and, after exposure, as endpoints of the study. Histopathology of the retina was an additional endpoint. Seventeen monkeys were randomly assigned to receive sham exposure or pulsed microwave exposures. Microwaves were delivered anteriorly to the face at 0, 4.3, 8.4, or 20.2 W/kg spatially and temporally averaged retinal specific absorption rates (R-SAR). The pulse characteristics were 1.04 MW ( approximately 1.30 MW/kg temporal peak R-SAR), 5.59 micros pulse length at 0, 0.59, 1. 18, and 2.79 Hz pulse repetition rates. Exposure was 4 h per day and 3 days per week for 3 weeks, for a total of nine exposures. The preexposure and postexposure fundus pictures and angiograms were all within normal limits. The response of cone photoreceptors to light flash was enhanced in monkeys exposed at 8.4 or 20.2 W/kg R-SAR, but not in monkeys exposed at 4.3 W/kg R-SAR. Scotopic (rod) response, maximum (combined cone and rod) response, and Naka-Rushton R(max) and log K of scotopic b-waves were all within normal range. Retinal histopathology revealed the presence of enhanced glycogen storage in photoreceptors among sham (2/5), 8.4 W/kg (3/3), and 20.2 W/kg (2/5) exposed monkeys, while enhanced glycogen storage was not observed in the 4.3 W/kg (0/4) exposed group. Supranormal cone photoreceptor b-wave was R-SAR dependent and may be an early indicator of mild injury. However no evidence of degenerative changes and ERG depression was seen. We concluded that retinal injury is very unlikely at 4 W/kg. Functional changes that occur at higher R-SAR are probably reversible since we saw no evidence of histopathologic correlation with ERG changes. Bioelectromagnetics 21:439-454, 2000. Published 2000 Wiley-Liss, Inc.     

Patterns of Gene Duplication in Lepidopteran Pheromone Binding Proteins

We have isolated and characterized cDNAs representing two distinct pheromone binding proteins (PBPs) from the gypsy moth, Lymantria dispar. We use the L. dispar protein sequences, along with other published lepidopteran PBPs, to investigate the evolutionary relationships among genes within the PBP multigene family. Our analyses suggest that the presence of two distinct PBPs in genera representing separate moth superfamilies is the result of relatively recent, independent, gene duplication events rather than a single, ancient, duplication. We discuss this result with respect to the biochemical diversification of moth PBPs. Received: 19 March 1997 / Accepted: 11 July 1997     

Towards a Model of Contemporary Parenting: The Parenting Behaviours and Dimensions Questionnaire

The assessment of parenting has been problematic due to theoretical disagreement, concerns over generalisability, and problems with the psychometric properties of current parenting measures. The aim of this study was to develop a comprehensive, psychometrically sound self-report parenting measure for use with parents of preadolescent children, and to use this empirical scale development process to identify the core dimensions of contemporary parenting behaviour. Following item generation and parent review, 846 parents completed an online survey comprising 116 parenting items. Exploratory and confirmatory factor analyses supported a six factor parenting model, comprising Emotional Warmth, Punitive Discipline, Anxious Intrusiveness, Autonomy Support, Permissive Discipline and Democratic Discipline. This measure will allow for the comprehensive and consistent assessment of parenting in future research and practice.     

Factors Associated with Clinical Research Recruitment in a Pediatric Academic Medical Center—A Web-Based Survey

Background

One of the most difficult aspects of conducting clinical research is the ability to successfully recruit participants. Pediatric clinical research presents unique recruitment challenges that relate to the need for parental consent on behalf of a minor, child assent, and school attendance. Yet, this has been less well studied. We conducted a survey of investigators performing human subjects research in a single large academic pediatric hospital to better understand characteristics of studies with successful recruitment.

Methods

We conducted a web-based survey from September 2011 to December 2011 of all principal investigators with an Institutional Review Board approved human subjects protocol at Boston Children’s Hospital, a pediatric Academic Medical Center. The survey captured various characteristics of the protocols including study design, staffing, resources, and investigator experience and training as well as respondents’ perceived barriers and facilitators to recruitment. We used chi square tests and Mantel-Haenszel test for linear trend to examine the relationship between selected predictor variables and the binary outcome of successful vs. unsuccessful recruitment and multivariable logistic regression analyses to examine the simultaneous influence of potential predictors on each outcome.

Results

Among the 349 eligible investigators, 52% responded to the survey, and 181 with valid data were included in the analyses. Two-thirds of the 87 protocols closed to enrollment reached 80% or more of their target enrollment, whereas, only one-third of the 94 protocols actively recruiting were meeting 80% of their target. Recruitment method appeared to be the only significant and independent factor associated with achieving 80% or more of target enrollment in closed to enrollment protocols. Closed to enrollment protocols that used recruitment in person were 4.55 times (95% CI 1.30 to 15.93; p = 0.02) more likely to achieve 80% or more of their target enrollment when compared to those that used other recruitment methods. Other potentially modifiable factors such as number of study visits, study duration and investigator experience were suggestive of being meaningfully related to recruitment.

Conclusion

Recruiting in person may promote reaching an acceptable target enrollment in pediatric as well as adult clinical research. Future research is needed on larger and more diverse samples to gain a better understanding of how the characteristics and qualifications of the individuals who conduct recruitment influence participant enrollment as well as how best to approach patient and families for their participation.     

Dose Response of MARV/Angola Infection in Cynomolgus Macaques following IM or Aerosol Exposure

Marburg virus infection in humans causes a hemorrhagic disease with a high case fatality rate. Countermeasure development requires the use of well-characterized animal models that mimic human disease. To further characterize the cynomolgus macaque model of MARV/Angola, two independent dose response studies were performed using the intramuscular or aerosol routes of exposure. All animals succumbed at the lowest target dose; therefore, a dose effect could not be determined. For intramuscular-exposed animals, 100 PFU was the first target dose that was not significantly different than higher target doses in terms of time to disposition, clinical pathology, and histopathology. Although a significant difference was not observed between aerosol-exposed animals in the 10 PFU and 100 PFU target dose groups, 100 PFU was determined to be the lowest target dose that could be consistently obtained and accurately titrated in aerosol studies.     

Prior hydration of Brassica tournefortii seeds reduces the stimulatory effect of karrikinolide on germination and increases seed sensitivity to abscisic acid

Background and Aims

The smoke-derived compound karrikinolide (KAR₁) shows significant potential as a trigger for the synchronous germination of seeds in a variety of plant-management contexts, from weed seeds in paddocks, to native seeds when restoring degraded lands. Understanding how KAR₁ interacts with seed physiology is a necessary precursor to the development of the compound as an efficient and effective management tool. This study tested the ability of KAR₁ to stimulate germination of seeds of the global agronomic weed Brassica tournefortii, at different hydration states, to gain insight into how the timing of KAR₁ applications in the field should be managed relative to rain events.

Methods

Seeds of B. tournefortii were brought to five different hydration states [equilibrated at 15 % relative humidity (RH), 47 % RH, 96 % RH, fully imbibed, or re-dried to 15 % RH following maximum imbibition] then exposed to 1 nm or 1 µm KAR₁ for one of five durations (3 min, 1 h, 24 h, 14 d or no exposure).

Key Results

Dry seeds with no history of imbibition were the most sensitive to KAR₁; sensitivity was lower in seeds that were fully imbibed or fully imbibed then re-dried. In addition, reduced sensitivity to KAR₁ was associated with an increased sensitivity to exogenously applied abscisic acid (ABA).

Conclusions

Seed water content and history of imbibition were found to significantly influence whether seeds germinate in response to KAR₁. To optimize the germination response of seeds, KAR₁ should be applied to dry seeds, when sensitivity to ABA is minimized.     

A new type of specialized morphophysiological dormancy and seed storage behaviour in Hydatellaceae, an early-divergent angiosperm family

Background and Aims

Recent phylogenetic analysis has placed the aquatic family Hydatellaceae as an early-divergent angiosperm. Understanding seed dormancy, germination and desiccation tolerance of Hydatellaceae will facilitate ex situ conservation and advance hypotheses regarding angiosperm evolution.

Methods

Seed germination experiments were completed on three species of south-west Australian Hydatellaceae, Trithuria austinensis, T. bibracteata and T. submersa, to test the effects of temperature, light, germination stimulant and storage. Seeds were sectioned to examine embryo growth during germination in T. austinensis and T. submersa.

Key Results

Some embryo growth and cell division in T. austinensis and T. submersa occurred prior to the emergence of an undifferentiated embryo from the seed coat (‘germination’). Embryo differentiation occurred later, following further growth and a 3- to 4-fold increase in the number of cells. The time taken to achieve 50 % of maximum germination for seeds on water agar was 50, 35 and 37 d for T. austinensis, T bibracteata and T. submersa, respectively.

Conclusions

Seeds of Hydatellaceae have a new kind of specialized morphophysiological dormancy in which neither root nor shoot differentiates until after the embryo emerges from the seed coat. Seed biology is discussed in relation to early angiosperm evolution, together with ex situ conservation of this phylogenetically significant group.     

Interaction of Mycobacterium ulcerans with Mosquito Species: Implications for Transmission and Trophic Relationships

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a severe necrotizing skin disease that causes significant morbidity in Africa and Australia. Person-to-person transmission of Buruli ulcer is rare. Throughout Africa and Australia infection is associated with residence near slow-moving or stagnant water bodies. Although M. ulcerans DNA has been detected in over 30 taxa of invertebrates, fish, water filtrate, and plant materials and one environmental isolate cultured from a water strider (Gerridae), the invertebrate taxa identified are not adapted to feed on humans, and the mode of transmission for Buruli ulcer remains an enigma. Recent epidemiological reports from Australia describing the presence of M. ulcerans DNA in adult mosquitoes have led to the hypothesis that mosquitoes play an important role in the transmission of M. ulcerans. In this study we have investigated the potential of mosquitoes to serve as biological or mechanical vectors or as environmental reservoirs for M. ulcerans. Here we show that Aedes aegypti, A. albopictus, Ochlerotatus triseriatus, and Culex restuans larvae readily ingest wild-type M. ulcerans, isogenic toxin-negative mutants, and Mycobacterium marinum isolates and remain infected throughout larval development. However, the infections are not carried over into the pupae or adult mosquitoes, suggesting an unlikely role for mosquitoes as biological vectors. By following M. ulcerans through a food chain consisting of primary (mosquito larvae), secondary (predatory mosquito larva from Toxorhynchites rutilus septentrionalis), and tertiary (Belostoma species) consumers, we have shown that M. ulcerans can be productively maintained in an aquatic food web.Infection with Mycobacterium ulcerans, the causative agent of Buruli ulcer (BU) disease, is associated with residence near stagnant and slow-moving water bodies in areas in which the disease is endemic (5, 36, 40, 45, 50). A plasmid-encoded macrolide toxin, mycolactone, is the primary virulence determinant of M. ulcerans (8, 41). Biting aquatic insects, such as several taxa in the Belostomatidae and Naucoridae families (Hemiptera), have been suggested as possible vectors of M. ulcerans in several laboratory experiments (16, 19, 20, 24, 31, 32); however, there is little empirical evidence from field studies to support the contention that these biting insects vector M. ulcerans to humans (2). In Melbourne, Australia, recent epidemiological evidence suggests that mosquitoes may serve as vectors in the transmission of BU disease (10, 11, 12, 34, 35). In this study, 957 pools consisting of over 11,000 mosquitoes of four different species were collected and tested by quantitative PCR (qPCR) for the presence of M. ulcerans DNA, and positive results were obtained from 48 of 957 pools tested (10). Of the 48 positive pools, 13 were positive for PCR directed against two insertion sequences (IS2404 and IS2606) as well as against sequence based on the ketoreductase domain of the mycolactone toxin genes. Because all of these target sequences are present multiple times in the genome, it was difficult to assign genome equivalents to these results. However, data from laboratory experiments suggested that 10 to 100 M. ulcerans isolates per mosquito were present in the positive pools. Epidemiological work also suggested a seasonal relationship between Buruli ulcer and mosquito-vectored diseases in Australia (12). These studies are extremely provocative and raise a number of questions for further work. What is the prevalence of M. ulcerans in other invertebrate taxa in the same environment? What is the infection rate in equal numbers of mosquitoes collected from areas in which the disease is not endemic? Is it possible to obtain physical evidence for the presence of M. ulcerans through microscopy or culture of mosquitoes in areas in which the disease is endemic, and, finally, what can we learn from laboratory studies concerning the interaction between mosquitoes and M. ulcerans?The recent work from Australia suggesting that M. ulcerans is spread by mosquitoes is particularly significant because adult mosquitoes are the most important group of insects in the spread of human disease. They may serve as biological vectors that provide a major environment for pathogen replication, as in malaria or yellow fever, or as mechanical vectors that carry organisms between hosts without serving as a site of replication (1, 4, 7, 9, 38). Larval mosquitoes are common in habitats associated with BU disease, most notably lentic or standing water habitats, and feed by filtering particles in the water using labral head fans (21). Members of some genera (i.e., Anopheles) aggregate at the air-water interface in microlayers near plant stems and algal mats (27, 28, 46), where they feed on microorganisms such as bacteria and algae (47). Because of their collecting-filtering feeding mode, there is potential for larvae to consume M. ulcerans and concentrate mycobacteria through their feeding activities (22, 23).In Ghana, the occurrence of M. ulcerans among invertebrate communities in lentic habitats has been documented from regions in Ga West and Ga East Districts in which the disease is endemic as well as those in which it is not endemic (2, 49) but not in geographically distinct areas in which the disease is not endemic such as the Volta region (49). M. ulcerans has been identified in a suite of environmental samples such as filtered water, biofilms, and algae as well as among a broad spectrum of invertebrate taxa, including both larval and adult mosquitoes (2, 11, 17, 49). However, the replication and trophic movement of M. ulcerans within these environmental samples and invertebrate communities have not been experimentally investigated. Conceptual models have been proposed that assume that the primary consumers of M. ulcerans (e.g., mosquito larvae, cladocerans, and chironomid larvae) may feed on bacteria and algae in biofilms, filter suspended matter from the water column, and then initiate the passage of M. ulcerans through an aquatic food web (2, 22, 31). This model predicts the movement of M. ulcerans through secondary and tertiary consumers and implies a complex trophic relationship in the ecology of M. ulcerans as well as an important role of aquatic invertebrates in the disease ecology of M. ulcerans.In the studies reported here, we have explored the role of mosquitoes as biological or mechanical vectors of M. ulcerans, as well as the potential of mosquito larvae to play a central role in the movement of M. ulcerans through an aquatic food web. In order to investigate the ability of mosquito larvae to ingest and maintain M. ulcerans within their digestive tract as well as to persist throughout the mosquito development cycle, we took advantage of the fact that mosquito larvae naturally feed upon bacteria. Results presented here show that strains of M. ulcerans from Africa and Australia, as well as Mycobacterium marinum, were maintained at high levels in the larval mosquito gut for 6 days. However, neither M. ulcerans nor M. marinum was detected in adult mosquitoes that were infected in the larval stage. These results suggest that mosquitoes are unlikely to serve as biological vectors of M. ulcerans.We further developed a model for following the passage of M. ulcerans through a series of consumers to determine whether M. ulcerans could be passed up a trophic chain from primary to tertiary consumers. In this model, we conducted similar experiments using four species of nonpredatory mosquito larvae, Aedes aegypti (Linnaeus), Aedes albopictus (Skuse), Ochlerotatus triseriatus (Theobald), and Culex restuans (Theobald), as primary consumers. These larvae were infected with isogenic wild-type (WT) and toxin-negative isolates of M. ulcerans and of M. marinum, the closest relative to M. ulcerans (13, 14, 51). We have shown that M. ulcerans in mosquito larvae survive passage through secondary and tertiary consumers, thus providing the first laboratory evidence that M. ulcerans has the potential to move between and be maintained within different species in an aquatic food web.     

Recovery of plant species composition and ecosystem function after cessation of grazing in a Mediterranean grassland

Short- and long-term changes in species composition, plant biomass production, and litter decomposition after cessation of grazing were examined in a Mediterranean grassland with high dominance of annual species and strong seasonality in biomass production. Short-term changes were assessed during three consecutive years in plots previously exposed to different grazing pressures and compared to plots in long-term (30–40 years) exclosures. Short-term cessation of grazing led in the short-term to an increase in relative biomass of annual crucifers and tall annual and perennial grasses, while biomass of annual legumes, annual thistles and short annual grasses decreased. Consequently, similarity increased between vegetation recently excluded from grazing and vegetation in long-term protected plots. Our research showed that in systems with high dominance of grasses and annual species, the rapid changes in plant species composition that occur after grazing cessation were associated with a fast recovery of the potential for biomass production to levels found in long-term protected plots, while litter decomposition rate did not change even after long-term cessation of grazing. Moreover, previous history of grazing did not affect plant litter decomposition, despite higher litter quality in grazed treatments. This study provides new insights about the processes involved in the diverse responses of ecosystem functions resulting from shifts in species composition associated with grazing cessation and land use change in Mediterranean grasslands.