What Do Aquaporin Knockout Studies Tell Us about Fluid Transport in Epithelia?

The investigation of near-isosmotic water transport in epithelia goes back over 100 years; however, debates over mechanism and pathway remain. Aquaporin (AQP) knockouts have been used by various research groups to test the hypothesis of an osmotic mechanism as well as to explore the paracellular versus transcellular pathway debate. Nonproportional reductions in the water permeability of a water-transporting epithelial cell (e.g., a reduction of around 80–90 %) compared to the reduction in overall water transport rate in the knockout animal (e.g., a reduction of 50–60 %) are commonly found. This nonproportionality has led to controversy over whether AQP knockout studies support or contradict the osmotic mechanism. Arguments raised for and against an interpretation supporting the osmotic mechanism typically have partially specified, implicit, or incorrect assumptions. We present a simple mathematical model of the osmotic mechanism with clear assumptions and, for models based on this mechanism, establish a baseline prediction of AQP knockout studies. We allow for deviations from isotonic/isosmotic conditions and utilize dimensional analysis to reduce the number of parameters that must be considered independently. This enables a single prediction curve to be used for multiple epithelial systems. We find that a simple, transcellular-only osmotic mechanism sufficiently predicts the results of knockout studies and find criticisms of this mechanism to be overstated. We note, however, that AQP knockout studies do not give sufficient information to definitively rule out an additional paracellular pathway.     

Temporal Structure in Cooperative Interactions: What Does the Timing of Exploitation Tell Us about Its Cost?

Exploitation in cooperative interactions both within and between species is widespread. Although it is assumed to be costly to be exploited, mechanisms to control exploitation are surprisingly rare, making the persistence of cooperation a fundamental paradox in evolutionary biology and ecology. Focusing on between-species cooperation (mutualism), we hypothesize that the temporal sequence in which exploitation occurs relative to cooperation affects its net costs and argue that this can help explain when and where control mechanisms are observed in nature. Our principal prediction is that when exploitation occurs late relative to cooperation, there should be little selection to limit its effects (analogous to “tolerated theft” in human cooperative groups). Although we focus on cases in which mutualists and exploiters are different individuals (of the same or different species), our inferences can readily be extended to cases in which individuals exhibit mixed cooperative-exploitative strategies. We demonstrate that temporal structure should be considered alongside spatial structure as an important process affecting the evolution of cooperation. We also provide testable predictions to guide future empirical research on interspecific as well as intraspecific cooperation.     

What the Erythrocytic Nuclear Alteration Frequencies Could Tell Us about Genotoxicity and Macrophage Iron Storage?

Erythrocytic nuclear alterations have been considered as an indicative of organism’s exposure to genotoxic agents. Due to their close relationship among their frequencies and DNA damages, they are considered excellent markers of exposure in eukaryotes. However, poor data has been found in literature concerning their genesis, differential occurrence and their life span. In this study, we use markers of cell viability; genotoxicity and cellular turn over in order to shed light to these events. Tilapia and their blood were exposed to cadmium in acute exposure and in vitro assays. They were analyzed using flow cytometry for oxidative stress and membrane disruption, optical microscopy for erythrocytic nuclear alteration, graphite furnace atomic absorption spectrometry for cadmium content in aquaria water, blood and cytochemical and analytical electron microscopy techniques for the hemocateretic aspects. The results showed a close relationship among the total nuclear alterations and cadmium content in the total blood and melanomacrophage centres area, mismatching reactive oxygen species and membrane damages. Moreover, nuclear alterations frequencies (vacuolated, condensed and blebbed) showed to be associated to cadmium exposure whereas others (lobed and bud) were associated to depuration period. Decrease on nuclear alterations frequencies was also associated with hemosiderin increase inside spleen and head kidney macrophages mainly during depurative processes. These data disclosure in temporal fashion the main processes that drive the nuclear alterations frequencies and their relationship with some cellular and systemic biomarkers.     

How Do Tsetse Recognise Their Hosts? The Role of Shape in the Responses of Tsetse (Glossina fuscipes and G. palpalis) to Artificial Hosts

Palpalis-group tsetse, particularly the subspecies of Glossina palpalis and G. fuscipes, are the most important transmitters of human African trypanomiasis (HAT), transmitting >95% of cases. Traps and insecticide-treated targets are used to control tsetse but more cost-effective baits might be developed through a better understanding of the fly's host-seeking behaviour. Electrocuting grids were used to assess the numbers of G. palpalis palpalis and G. fuscipes quanzensis attracted to and landing on square or oblong targets of black cloth varying in size from 0.01 m(2) to 1.0 m(2). For both species, increasing the size of a square target from 0.01 m(2) (dimensions=0.1 × 0.1 m) to 1.0 m(2) (1.0 × 1.0 m) increased the catch ~4x however the numbers of tsetse killed per unit area of target declined with target size suggesting that the most cost efficient targets are not the largest. For G. f. quanzensis, horizontal oblongs, (1 m wide × 0.5 m high) caught ~1.8x more tsetse than vertical ones (0.5 m wide × 1.0 m high) but the opposite applied for G. p. palpalis. Shape preference was consistent over the range of target sizes. For G. p. palpalis square targets caught as many tsetse as the oblong; while the evidence is less strong the same appears to apply to G. f. quanzensis. The results suggest that targets used to control G. p. palpalis and G. f. quanzensis should be square, and that the most cost-effective designs, as judged by the numbers of tsetse caught per area of target, are likely to be in the region of 0.25 × 0.25 m(2). The preference of G. p. palpalis for vertical oblongs is unique amongst tsetse species, and it is suggested that this response might be related to its anthropophagic behaviour and hence importance as a vector of HAT.     

Physiological Trade-Offs Along a Fast-Slow Lifestyle Continuum in Fishes: What Do They Tell Us about Resistance and Resilience to Hypoxia?

It has recently been suggested that general rules of change in ecological communities might be found through the development of functional relationships between species traits and performance. The physiological, behavioural and life-history traits of fishes are often organised along a fast-slow lifestyle continuum (FSLC). With respect to resistance (capacity for population to resist change) and resilience (capacity for population to recover from change) to environmental hypoxia, the literature suggests that traits enhancing resilience may come at the expense of traits promoting resistance to hypoxia; a trade-off may exist. Here I test whether three fishes occupying different positions along the FSLC trade-off resistance and resilience to environmental hypoxia. Static respirometry experiments were used to determine resistance, as measured by critical oxygen tension (P_crit), and capacity for (RC) and magnitude of metabolic reduction (RM). Swimming respirometry experiments were used to determine aspects of resilience: critical (U_crit) and optimal swimming speed (U_opt), and optimal cost of transport (COT_opt). Results pertaining to metabolic reduction suggest a resistance gradient across species described by the inequality Melanotaenia fluviatilis (fast lifestyle) < Hypseleotris sp. (intermediate lifestyle) < Mogurnda adspersa (slow lifestyle). The U_crit and COT_opt data suggest a resilience gradient described by the reverse inequality, and so the experiments generally indicate that three fishes occupying different positions on the FSLC trade-off resistance and resilience to hypoxia. However, the scope of inferences that can be drawn from an individual study is narrow, and so steps towards general, trait-based rules of fish community change along environmental gradients are discussed.     

What Can Surrogate Tissues Tell Us about the Oxidative Stress Status of the Prostate? A Hypothesis-Generating In-Vivo Study

Background

Prostatic oxidative stress (OS) is androgen-regulated and a key event in the development of prostate cancer (PC). Thus, reducing prostatic OS is an attractive target for PC prevention strategies. We sought to determine if the individual''s prostatic OS status can be determined by examining the OS in surrogate androgen regulated tissues from the same host.

Methodology/Principal Findings

Adult male rats were divided equally into three groups: (A−) underwent bilateral orchiectomy, (A+) received continuous testosterone supplementation or (C) were eugonadal. Serum testosterone, 8-hydroxy-2-deoxyguanosine (8-OHdG) and anti-oxidative capacity (AOC) were determined after 72 hrs and the prostate, salivary glands and the hair follicles'' Dermal Papillary Cells (DPC) from each animal were harvested, embedded into tissue microarray and examined for the expression of 8-OHdG by immuno-staining. Multi-variate regression was used to analyze inter-individual differences in OS staining within each androgen group and if there was a correlation between serum testosterone, 8-OHdG or AOC and Prostatic OS in tissues of same host.At the group level, 8-OHdG staining intensity directly correlated with serum testosterone levels in all three target tissues (p>0.01, Mann-Whitney Test). Although different levels of prostatic OS were noted between rats with similar serum testosterone levels and similar systemic OS measurements (p<0.01), there were no intra-individual differences between the OS status of the prostate and DPC (p<0.05).

Conclusions/Significance

The level of prostatic OS is correlated with the OS of hair follicles and salivary glands, but not systemic OS. Moreover, systemic AOC negatively correlates with both prostatic and hair follicle OS. This suggests that hair follicle and salivary gland OS can serve as surrogate markers for the efficiency of OS reduction. This has tremendous potential for the rational evaluation of patient response to prevention strategies.     

The role of Apodemus mice and Microtus voles in the diet of the Tengmalm’s owl in Central Europe

Based on a long-term dataset (1999–2010), we investigated how the availability of main prey affects the breeding density and food ecology of the Tengmalm’s owl (Aegolius funereus) in the Czech Republic. In particular, we assessed the role of Microtus voles and Apodemus mice in the diet, based on the main predictions of the optimal diet theory that the diet composition depends on the availability of the main prey. We found that (i) the Tengmalm’s owl exhibited no numerical response to the availability of Microtus voles and Apodemus mice in the field; (ii) the availability of Apodemus mice in the field positively affected their proportion in the diet (26 %), and despite a high proportion of Microtus voles in the owls’ diet (47 %), no relationship was found between their availability in the field and proportion in the diet; (iii) the proportion of Apodemus mice was negatively correlated to the proportion of Microtus voles, Sorex shrews and birds in the diet, but no similar relationship was detected for Microtus voles; (iv) the reproductive output of Tengmalm’s owls was positively correlated to the proportion of Apodemus mice in the diet, as well as to Apodemus mice and Microtus vole availability in the field; and (v) diet diversity and diet overlap were not significantly affected by the abundance of Apodemus mice and Microtus voles. Therefore, the validity of these main optimal diet theory predictions was not confirmed, especially for Microtus vole prey, due to an opportunistic choice between Apodemus mice and Microtus voles. We suggest that the reproductive output of nocturnal raptors in Central Europe may be less dependent on Microtus vole supply than that of their northern counterparts.     

What determines the impact of alien birds and mammals in Europe?

An often-cited reason for studying the process of invasion by alien species is that the understanding sought can be used to mitigate the impacts of the invaders. Here, we present an analysis of the correlates of local impacts of established alien bird and mammal species in Europe, using a recently described metric to quantify impact. Large-bodied, habitat generalist bird and mammal species that are widespread in their native range, have the greatest impacts in their alien European ranges, supporting our hypothesis that surrogates for the breadth and the amount of resources a species uses are good indicators of its impact. However, not all surrogates are equally suitable. Impacts are generally greater for mammal species giving birth to larger litters, but in contrast are greater for bird species laying smaller clutches. There is no effect of diet breadth on impacts in birds or mammals. On average, mammals have higher impacts than birds. However, the relationships between impact and several traits show common slopes for birds and mammals, and relationships between impact and body mass and latitude do not differ between birds and mammals. These results may help to anticipate which species would have large impacts if introduced, and so direct efforts to prevent such introductions.     

What can metazoan parasites reveal about the taxonomy of Scomber japonicus Houttuyn in the coast of South America and Madeira Islands?

The metazoan parasites of four populations of the chub mackerel Scomber japonicus were analysed from two localities in the Atlantic Ocean (Madeira Islands, Portugal, and Rio de Janeiro, Brazil) and two localities in the Pacific Ocean (Callao, Peru, and Antofagasta, Chile), collected during 2002 and 2003. A total of 373 fish specimens were studied and 34 metazoan parasite species were obtained. Parasites identified from the populations of chub mackerel studied could be separated into three categories: parasites with a wide distribution, present in the Pacific and Atlantic, parasites proper of the Pacific Ocean and parasites proper of the Atlantic Ocean. The analyses of some highly specific parasites of the genus Scomber ( i.e. monogeneans of the genus Kuhnia and didymozoid digeneans) strongly suggest the need for a revision of the taxonomic status of chub mackerels from the Atlantic and Pacific coast of America. The results demonstrated the usefulness of parasites as adequate tools to clarify the taxonomic status of their hosts.     

Listening In on the Past: What Can Otolith δ18O Values Really Tell Us about the Environmental History of Fishes?

Oxygen isotope ratios from fish otoliths are used to discriminate marine stocks and reconstruct past climate, assuming that variations in otolith δ¹⁸O values closely reflect differences in temperature history of fish when accounting for salinity induced variability in water δ¹⁸O. To investigate this, we exploited the environmental and migratory data gathered from a decade using archival tags to study the behaviour of adult plaice (Pleuronectes platessa L.) in the North Sea. Based on the tag-derived monthly distributions of the fish and corresponding temperature and salinity estimates modelled across three consecutive years, we first predicted annual otolith δ¹⁸O values for three geographically discrete offshore sub-stocks, using three alternative plausible scenarios for otolith growth. Comparison of predicted vs. measured annual δ¹⁸O values demonstrated >96% correct prediction of sub-stock membership, irrespective of the otolith growth scenario. Pronounced inter-stock differences in δ¹⁸O values, notably in summer, provide a robust marker for reconstructing broad-scale plaice distribution in the North Sea. However, although largely congruent, measured and predicted annual δ¹⁸O values of did not fully match. Small, but consistent, offsets were also observed between individual high-resolution otolith δ¹⁸O values measured during tag recording time and corresponding δ¹⁸O predictions using concomitant tag-recorded temperatures and location-specific salinity estimates. The nature of the shifts differed among sub-stocks, suggesting specific vital effects linked to variation in physiological response to temperature. Therefore, although otolith δ¹⁸O in free-ranging fish largely reflects environmental temperature and salinity, we counsel prudence when interpreting otolith δ¹⁸O data for stock discrimination or temperature reconstruction until the mechanisms underpinning otolith δ¹⁸O signature acquisition, and associated variation, are clarified.     

Health and income inequalities in Europe: What is the role of circumstances?

Equality of opportunity theories distinguish between inequalities due to individual effort and those due to external circumstances. Recent research has shown that half of the variability in income of World population was determined by country of birth and income distribution. Since health and income are generally strictly related, the aim of this paper is to estimate how much variability in income and health is determined by external circumstances. We use data from the Survey of Health, Ageing and Retirement (SHARE) and the English Longitudinal Survey on Ageing (ELSA), two comparable multidisciplinary surveys that provide micro-level data on health and financial resources among the elderly for a large number of European countries. Our baseline estimation shows that about 20% of the variability in income is explained by current country-specific circumstances, while health outcomes range from 12% using BMI to 19% using self-rated health. By including early-life circumstances, the explained variability increases almost 20 percentage points for income and for self-rated health but less for other health outcomes. Finally, by controlling for endogeneity issues linked with effort, our estimates indicate that circumstances better explain variability in health outcomes. Results are robust to some tests, and the implications of these findings are discussed.     

What Do District Health Managers in Ghana Use Their Working Time for? A Case Study of Three Districts

Background

Ineffective district health management potentially impacts on health system performance and service delivery. However, little is known about district health managing practices and time allocation in resource-constrained health systems. Therefore, a time use study was conducted in order to understand current time use practices of district health managers in Ghana.

Methods

All 21 district health managers working in three districts of the Eastern Region were included in the study and followed for a period of three months. Daily retrospective interviews about their time use were conducted, covering 1182 person-days of observation. Total time use of the sample population was assessed as well as time use stratified by managerial position. Differences of time use over time were also evaluated.

Results

District health managers used most of their working time for data management (16.6%), attending workshops (12.3%), financial management (8.7%), training of staff (7.1%), drug and supply management (5.0%), and travelling (9.6%). The study found significant variations of time use across the managerial cadres as well as high weekly variations of time use impulsed mainly by a national vertical program.

Conclusions

District health managers in Ghana use substantial amounts of their working time in only few activities and vertical programs greatly influence their time use. Our findings suggest that efficiency gains are possible for district health managers. However, these are unlikely to be achieved without improvements within the general health system, as inefficiencies seem to be largely caused by external factors.     

The Islands in the South China Sea: How Does Their Presence Limit the Extent of the High Seas and the Area and the Maritime Zones of the Mainland Coasts?

A number of small islands (the Paracel Islands, Pratas Island, the Spratly Islands, and Scarborough Reef) may have a considerable influence on the extent of maritime zones in the South China Sea. The maritime zones of these islands can limit the extent of the high seas and the Area in the South China Sea and the extent of the maritime zones of the mainland coasts. To assess the impact of the islands, it is necessary to establish whether they can generate the full suite of maritime zones. Under international law, some islands do not have an entitlement to an exclusive economic zone and continental shelf. Where islands can generate these maritime zones, a second issue arises, namely, how to delimit these zones with those of the mainland coasts bordering the South China Sea.     

What can the Samoan "Fa'afafine" teach us about the Western concept of gender identity disorder in childhood?

This article examines whether gender identity disorder in childhood (GIDC) constitutes a mental disorder as outlined by the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV-TR). Data were collected in Samoa, a culture that is characterized by a high degree of social tolerance towards feminine males who are known locally as fa'afafine. The study location was chosen because, unlike Western locales, it afforded the opportunity to examine whether gender-atypical behavior, gender-atypical identity, and sex-atypical identity, in and of themselves, cause distress in sex/gender variant individuals, while simultaneously controlling for the confounding effects of extreme societal intolerance towards such individuals. Because of our focus on the DSM-IV-TR's diagnosis of GIDC, we were specifically interested in ascertaining whether adult fa'afafine recalled a strong and persistent cross-gender identification in childhood, a sense of inappropriateness in the male-typical gender role, a discomfort with their sex, or distress associated with any of the above. In addition, we sought to determine whether parental encouragement or discouragement of cross-gender behaviors influence feelings of distress in relation to the behaviors in question. Based on the cross-cultural information presented here, we conclude that the diagnostic category of GIDC should not occur in its current form in future editions of the DSM, as there is no compelling evidence that cross-gender behaviors or identities, in and of themselves, cause distress in the individual.