Nutrient ratios, differential retention, and the effect on nutrient limitation in a deep oligotrophic lake

Nutrient ratios have been related to nutrient limitation of algal growth in lakes. Retention of nutrients in lakes, by sedimentation and by denitrification, reduces the nutrient concentrations in the water column, thereby enhancing nutrient limitation. Differential retention of nitrogen and phosphorus alters their ratios in lakes and thereby contributes to determine whether nitrogen or phosphorus limits algal growth. We examined the relationships between differential nutrient retention, nutrient ratios, and nutrient limitation in Lake Brunner, a deep oligotrophic lake. The observed retention of nitrogen (20%) and phosphorus (47%) agreed with predictions by empirical equations from literature. As a result of differential retention with a much larger proportion of phosphorus retained than that of nitrogen, the nitrogen:phosphorus ratio was higher in the lake (69) than in the inflows (46). While the mean ratio in the inflows suggested no or only moderate phosphorus limitation, the lake appeared to be severely phosphorus limited. Combining empirical equations from literature that predict nitrogen and phosphorus retention suggests that the nitrogen:phosphorus ratio is enhanced by greater retention of phosphorus compared to nitrogen only in deep lakes with relatively short residence times, such as Lake Brunner. In contrast, in most lakes differential retention is expected to result in lower nitrogen:phosphorus ratios.     

Evidence for Geomagnetic Imprinting as a Homing Mechanism in Pacific Salmon

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Highlights? Sockeye salmon use geomagnetic imprinting as a homing mechanism ? The homing route of salmon is predicted by magnetic field drift (secular variation)     

Morphological variation in the deep ocean-dwelling coccolithophore Florisphaera profunda (Haptophyta)

Detailed analysis of the morphology of Florisphaera profunda from plankton samples collected at three sites in the Atlantic and Pacific Oceans reveals wide variation in this deep ocean-dwelling coccolithophore. In addition to the two varieties described previously, we found a third distinctive form, Florisphaera profunda var. rhinocera var. nov. All three varieties occur at each of the sampling sites. The analysis of monthly samples from different levels in the lower photic zone (LPZ) (100–200?m) at the Hawaii Ocean Time series station suggests that the varieties have similar distributions, which are correlated to primary productivity and the availability of light. The analysis of coccolith and coccosphere size in F. profunda reveals the existence of several size modes in Florisphaera profunda var. profunda and F. profunda var. elongata. The biological significance of these modes, or morphotypes is not known. However, their co-occurrence in single samples from different oceanic areas suggests that they are not ecophenotypes. In the light of recent molecular genetic analyses of intraspecific groups within commonly occurring coccolithophores, the varieties and size morphotypes of F. profunda are of significant interest for the study of marine phytoplankton biodiversity. Coccolithophores inhabiting the LPZ may be adapted to the low light, high nutrient conditions of this layer and hold great potential as a means to reconstruct past oceanographic conditions such as the position of the nutricline. However, coccolithophore biodiversity in the LPZ is poorly documented and the number of species may be much higher than previously thought.     

Exploring the implications of recreational disturbance on an endangered butterfly using a novel modelling approach

Site and wildlife managers globally are under increasing pressure to implement management strategies that address the negative implications of outdoor recreational activities on wildlife. For many rare and isolated species any anthropogenic activities that cause disturbance could potentially be detrimental to existing populations. Understanding how non-consumptive recreation can influence a species may therefore be critical to its preservation. We developed a novel approach to specifically address this need. Using a combination of field surveys and simulation modelling exercises, we (1) explored the responses of endangered Karner blue butterflies (Lycaeides melissa samuelis) to recreation, (2) assessed whether such responses influenced oviposition rate and/or host plant choice and (3) tested alternative management strategies that could alleviate the negative impacts of recreation. Our field surveys confirmed that Karner blues were sensitive to recreational disturbance. Butterflies flushed at similar speeds and distances from recreationists (2.2 m at 0.17 m/s), as they would from natural threats, such as predators (2.2 m at 0.19 m/s). Incorporating female response parameters into a simulation model revealed that regular disturbance could reduce egg laying potential and significantly restrict host plant choice, which in turn, could impact the butterfly’s population dynamics. However, we established that it was possible to effectively offset the implications of recreational disturbance using our simulation modelling approach. For example, extending Karner blue breeding habitat from trails and other public rights of way has the potential to alleviate such disturbance. Our study demonstrates that the potential impact of recreation on species of conservation concern should not be overlooked.     

MicroRNA-146a Is Upregulated by and Negatively Regulates TLR2 Signaling

TLR signaling is a crucial component of the innate immune response to infection. MicroRNAs (miRNAs) have been shown to be upregulated during TLR signaling. Specifically, microRNA-146a (miR-146a) plays a key role in endotoxin tolerance by downregulating interleukin-1 receptor-associated kinase 1 (IRAK-1). The aim of this study was to assess the role of miR-146a in the TLR2 signaling and development of bacterial lipoprotein (BLP) self-tolerance and cross-tolerance to bacteria. Expression of miR-146a increased in a dose- and time-dependent manner in BLP-stimulated human THP-1 promonocytic cells. In BLP-tolerised cells miR-146a was even further upregulated in response to BLP re-stimulation (p<0.001). Re-stimulation of BLP-tolerised cells with heat-killed gram-negative Salmonella typhimurium (S. typhimurium), but not gram-positive Staphylococcus aureus (S. aureus), led to significant overexpression of miR-146a (p<0.05). Transfection of naive cells with a miR-146a mimic substantially suppressed TNF-α production (p<0.05). Furthermore, overexpression of miR-146a resulted in strong reduction in IRAK-1 and phosphorylated IκBα expression in naive and S. typhimurium-stimulated THP-1 cells. Collectively, miR-146a is upregulated in response to BLP and bacterial stimulation in both naive and BLP-tolerised cells. Overexpression of miR-146a induces a state analogous to tolerance in BLP-stimulated cells and therefore may represent a future target for exogenous modulation of tolerance during microbial infection and sepsis.     

Role of Tachykinin 1 and 4 Gene-Derived Neuropeptides and the Neurokinin 1 Receptor in Adjuvant-Induced Chronic Arthritis of the Mouse

Objective

Substance P, encoded by the Tac1 gene, is involved in neurogenic inflammation and hyperalgesia via neurokinin 1 (NK1) receptor activation. Its non-neuronal counterpart, hemokinin-1, which is derived from the Tac4 gene, is also a potent NK1 agonist. Although hemokinin-1 has been described as a tachykinin of distinct origin and function compared to SP, its role in inflammatory and pain processes has not yet been elucidated in such detail. In this study, we analysed the involvement of tachykinins derived from the Tac1 and Tac4 genes, as well as the NK1 receptor in chronic arthritis of the mouse.

Methods

Complete Freund’s Adjuvant was injected intraplantarly and into the tail of Tac1^−/−, Tac4^−/−, Tacr1^−/− (NK1 receptor deficient) and Tac1^−/−/Tac4^−/− mice. Paw volume was measured by plethysmometry and mechanosensitivity using dynamic plantar aesthesiometry over a time period of 21 days. Semiquantitative histopathological scoring and ELISA measurement of IL-1β concentrations of the tibiotarsal joints were performed.

Results

Mechanical hyperalgesia was significantly reduced from day 11 in Tac4^−/− and Tacr1^−/− animals, while paw swelling was not altered in any strain. Inflammatory histopathological alterations (synovial swelling, leukocyte infiltration, cartilage destruction, bone damage) and IL-1β concentration in the joint homogenates were significantly smaller in Tac4^−/− and Tac1^−/−/Tac4^−/− mice.

Conclusions

Hemokinin-1, but not substance P increases inflammation and hyperalgesia in the late phase of adjuvant-induced arthritis. While NK1 receptors mediate its antihyperalgesic actions, the involvement of another receptor in histopathological changes and IL-1β production is suggested.     

Aerobic exercise alone results in clinically significant weight loss for men and women: Midwest exercise trial 2

Exercise is recommended by public health agencies for weight management; however, the role of exercise is generally considered secondary to energy restriction. Few studies exist that have verified completion of exercise, measured the energy expenditure of exercise, and prescribed exercise with equivalent energy expenditure across individuals and genders.

Objective:

The objective of this study was to evaluate aerobic exercise, without energy restriction, on weight loss in sedentary overweight and obese men and women.

Design and Methods:

This investigation was a randomized, controlled, efficacy trial in 141 overweight and obese participants (body mass index, 31.0 ± 4.6 kg/m²; age 22.6 ± 3.9 years). Participants were randomized (2:2:1 ratio) to exercise at either 400 kcal/session or 600 kcal/session or to a nonexercise control. Exercise was supervised, 5 days/week, for 10 months. All participants were instructed to maintain usual ad libitum diets. Because of the efficacy design, completion of ≥90% of exercise sessions was an a priori definition of per protocol, and these participants were included in the analysis.

Results:

Weight loss from baseline to 10 months for the 400 and 600 kcal/session groups was 3.9 ± 4.9 kg (4.3%) and 5.2 ± 5.6 kg (5.7%), respectively, compared with weight gain for controls of 0.5 ± 3.5 kg (0.5%) (P < 0.05). Differences for weight loss from baseline to 10 months between the exercise groups and differences between men and women within groups were not statistically significant.

Conclusions:

Supervised exercise, with equivalent energy expenditure, results in clinically significant weight loss with no significant difference between men and women.     

HSP60/10 chaperonin systems are inhibited by a variety of approved drugs,natural products,and known bioactive molecules

All living organisms contain a unique class of molecular chaperones called 60?kDa heat shock proteins (HSP60 – also known as GroEL in bacteria). While some organisms contain more than one HSP60 or GroEL isoform, at least one isoform has always proven to be essential. Because of this, we have been investigating targeting HSP60 and GroEL chaperonin systems as an antibiotic strategy. Our initial studies focused on applying this antibiotic strategy for treating African sleeping sickness (caused by Trypanosoma brucei parasites) and drug-resistant bacterial infections (in particular Methicillin-resistant Staphylococcus aureus – MRSA). Intriguingly, during our studies we found that three known antibiotics – suramin, closantel, and rafoxanide – were potent inhibitors of bacterial GroEL and human HSP60 chaperonin systems. These findings prompted us to explore what other approved drugs, natural products, and known bioactive molecules might also inhibit HSP60 and GroEL chaperonin systems. Initial high-throughput screening of 3680 approved drugs, natural products, and known bioactives identified 161 hit inhibitors of the Escherichia coli GroEL chaperonin system (4.3% hit rate). From a purchased subset of 60 hits, 29 compounds (48%) re-confirmed as selective GroEL inhibitors in our assays, all of which were nearly equipotent against human HSP60. These findings illuminate the notion that targeting chaperonin systems might be a more common occurrence than we previously appreciated. Future studies are needed to determine if the in vivo modes of action of these approved drugs, natural products, and known bioactive molecules are related to GroEL and HSP60 inhibition.