Can an herbivore affect where a top predator kills its prey by modifying woody vegetation structure?

In large mammal communities, little is known about modification of interspecific interactions through habitat structure changes. We assessed the effects of African elephants (Loxodonta africana) on features of woody habitat structure that can affect predator–prey interactions. We then explored how this can influence where African lions (Panthera leo) kill their prey. Indeed, lions are stalk-and-ambush predators and habitat structure and concealment opportunities are assumed to influence their hunting success. During 2 years, in Hwange National Park, Zimbabwe, kill sites (n = 167) of GPS-collared lions were characterized (visibility distance for large mammals, distance to a potential ambush site and presence of elephant impacts). We compared characteristics of lion kill sites with characteristics of random sites (1) at a large scale (i.e. in areas intensively used by lions, n = 418) and (2) at the microhabitat scale (i.e. in the direct surrounding available habitat, < 150 m, n = 167). Elephant-impacted sites had a slightly higher visibility and a longer distance to a potential ambush site than non-impacted sites, but these relationships were characterized by a high variability. At large scale, kill sites were characterized by higher levels of elephant impacts compared to random sites. At microhabitat scale, compared to the direct nearby available habitat, kill sites were characterized by a reduced distance to a potential ambush site. We suggest a conceptual framework whereby the relative importance of habitat features and prey abundance could change upon the scale considered.     

Prevalence of methotrexate intolerance in rheumatoid arthritis and psoriatic arthritis

Introduction

The aim of this study was to determine the prevalence of gastrointestinal and behavioural symptoms occurring before (anticipatory/associative) and after methotrexate (MTX) administration, termed MTX intolerance, in rheumatoid (RA) and psoriatic arthritis (PsA).

Methods

Methotrexate Intolerance Severity Score (MISS), previously validated in juvenile idiopathic arthritis patients, was used to determine MTX intolerance prevalence in 291 RA/PsA patients. The MISS consisted of four domains: abdominal pain, nausea, vomiting and behavioural symptoms, occurring upon, prior to (anticipatory) and when thinking of MTX (associative). MTX intolerance was defined as ≥6 on the MISS with ≥1 point on anticipatory and/or associative and/or behavioural items.

Results

A total of 123 patients (42.3%) experienced at least one gastrointestinal adverse effect. The prevalence of MTX intolerance was 11%. MTX intolerance prevalence was higher in patients on parenteral (20.6%) than on oral MTX (6.2%) (p < 0.001).

Conclusion

Besides well-known gastrointestinal symptoms after MTX, RA and PsA patients experienced these symptoms also before MTX intake. RA and PsA patients on MTX should be closely monitored with the MISS for early detection of MTX intolerance, in order to intervene timely and avoid discontinuation of an effective treatment.     

Social Structure of Lions (Panthera leo) Is Affected by Management in Pendjari Biosphere Reserve,Benin

Lion populations have undergone a severe decline in West Africa. As baseline for conservation management, we assessed the group structure of lions in the Pendjari Biosphere Reserve in Benin. This reserve, composed of one National Park and two Hunting Zones, is part of the WAP transboundary complex of protected areas. Overall mean group size was 2.6±1.7 individuals (n = 296), it was significantly higher in the National Park (2.7±1.7, n = 168) than in the Hunting Zones (2.2±1.5, n = 128). Overall adult sex ratio was even, but significantly biased towards females (0.67) in the National Park and towards males (1.67) in the Hunting Zones. Our results suggest that the Pendjari lion population is affected by perturbations, such as trophy hunting.     

TWEAK and Fn14 expression in the pathogenesis of joint inflammation and bone erosion in rheumatoid arthritis

Introduction

TNF-like weak inducer of apoptosis (TWEAK) has been proposed as a mediator of inflammation and bone erosion in rheumatoid arthritis (RA). This study aimed to investigate TWEAK and TWEAK receptor (Fn14) expression in synovial tissue from patients with active and inactive rheumatoid arthritis (RA), osteoarthritis (OA) and normal controls and assess soluble (s)TWEAK levels in the synovial fluids from patients with active RA and OA. Effects of sTWEAK on osteoclasts and osteoblasts were investigated in vitro.

Methods

TWEAK and Fn14 expression were detected in synovial tissues by immunohistochemistry (IHC). Selected tissues were dual labelled with antibodies specific for TWEAK and lineage-selective cell surface markers CD68, Tryptase G, CD22 and CD38. TWEAK mRNA expression was examined in human peripheral blood mononuclear cells (PBMC) sorted on the basis of their expression of CD22. sTWEAK was detected in synovial fluid from OA and RA patients by ELISA. The effect of sTWEAK on PBMC and RAW 264.7 osteoclastogenesis was examined. The effect of sTWEAK on cell surface receptor activator of NF Kappa B Ligand (RANKL) expression by human osteoblasts was determined by flow cytometry.

Results

TWEAK and Fn14 expression were significantly higher in synovial tissue from all patient groups compared to the synovial tissue from control subjects (P < 0.05). TWEAK was significantly higher in active compared with inactive RA tissues (P < 0.05). TWEAK expression co-localised with a subset of CD38⁺ plasma cells and with CD22⁺ B-lymphocytes in RA tissues. Abundant TWEAK mRNA expression was detected in normal human CD22⁺ B cells. Higher levels of sTWEAK were observed in synovial fluids isolated from active RA compared with OA patients. sTWEAK did not stimulate osteoclast formation directly from PBMC, however, sTWEAK induced the surface expression of RANKL by human immature, STRO-1⁺ osteoblasts.

Conclusions

The expression of TWEAK by CD22⁺ B cells and CD38⁺ plasma cells in RA synovium represents a novel potential pathogenic pathway. High levels of sTWEAK in active RA synovial fluid and of TWEAK and Fn14 in active RA tissue, together with the effect of TWEAK to induce osteoblastic RANKL expression, is consistent with TWEAK/Fn14 signalling being important in the pathogenesis of inflammation and bone erosion in RA.     

Cancer as a dynamical phase transition

Background

We review and extend the work of Rosen and Casti who discuss category theory with regards to systems biology and manufacturing systems, respectively.

Results

We describe anticipatory systems, or long-range feed-forward chemical reaction chains, and compare them to open-loop manufacturing processes. We then close the loop by discussing metabolism-repair systems and describe the rationality of the self-referential equation f = f (f). This relationship is derived from some boundary conditions that, in molecular systems biology, can be stated as the cardinality of the following molecular sets must be about equal: metabolome, genome, proteome. We show that this conjecture is not likely correct so the problem of self-referential mappings for describing the boundary between living and nonliving systems remains an open question. We calculate a lower and upper bound for the number of edges in the molecular interaction network (the interactome) for two cellular organisms and for two manufacturomes for CMOS integrated circuit manufacturing.

Conclusions

We show that the relevant mapping relations may not be Abelian, and that these problems cannot yet be resolved because the interactomes and manufacturomes are incomplete.     

A quantitative cytochemical method for measuring carbonic anhydrase activity

Synopsis Components of a histochemical method for demonstrating carbonic anhydrase activity have been investigated quantitatively. It was found that it is not necessary to use free-floating sections provided the reaction is done in a reaction medium of controlled depth. This permits the use of normal cryostat sections on glass slides, so making this technique applicable to the cytochemical bioassay of gastrin. The better control of the pH of the reaction, and changes in the concentration of phosphate and of cobalt, have resulted in a quantitatively reproducible reaction in the parietal cells of guinea-pig fundus. The reaction product is measured by microdensitometry. The specificity of the carbonic anhydrase reaction has been tested by the response elicited by gastrin acting on the parietal cellsin vitro and by the use of acetazolamide.     

Getting to the core: Internal body temperatures help reveal the ecological function and thermal implications of the lions’ mane

It has been proposed that there is a thermal cost of the mane to male lions, potentially leading to increased body surface temperatures (T_s), increased sperm abnormalities, and to lower food intake during hot summer months. To test whether a mane imposes thermal costs on males, we measured core body temperature (T_b) continuously for approximately 1 year in 18 free‐living lions. There was no difference in the 24‐hr maximum T_b of males (n = 12) and females (n = 6), and males had a 24‐hr mean T_b that was 0.2 ± 0.1°C lower than females after correcting for seasonal effects. Although feeding on a particular day increased 24‐hr mean and 24‐hr maximum T_b, this phenomenon was true of both male and female lions, and females had higher 24‐hr mean and 24‐hr maximum T_b than males, on both days when lions did not feed, and on days when lions did feed. Twenty‐four‐hour T_b was not influenced by mane length or color, and 24‐hr mean T_b was negatively correlated with mane length. These data contradict the suggestion that there exists a thermal cost to male lions in possessing a long dark mane, but do not preclude the possibility that males compensate for a mane with increased heat loss. The increased insulation caused by a mane does not necessarily have to impair heat loss by males, which in hot environments is primarily through respiratory evaporative cooling, nor does in necessarily lead to increased heat gain, as lions are nocturnal and seek shade during the day. The mane may even act as a heat shield by increasing insulation. However, dominant male lions frequent water points more than twice as often as females, raising the possibility that male lions are increasing water uptake to facilitate increased evaporative cooling. The question of whether male lions with manes compensate for a thermal cost to the mane remains unresolved, but male lions with access to water do not have higher T_b than females or males with smaller manes.