Nanoparticle Induced Cell Magneto-Rotation: Monitoring Morphology, Stress and Drug Sensitivity of a Suspended Single Cancer Cell

Single cell analysis has allowed critical discoveries in drug testing, immunobiology and stem cell research. In addition, a change from two to three dimensional growth conditions radically affects cell behavior. This already resulted in new observations on gene expression and communication networks and in better predictions of cell responses to their environment. However, it is still difficult to study the size and shape of single cells that are freely suspended, where morphological changes are highly significant. Described here is a new method for quantitative real time monitoring of cell size and morphology, on single live suspended cancer cells, unconfined in three dimensions. The precision is comparable to that of the best optical microscopes, but, in contrast, there is no need for confining the cell to the imaging plane. The here first introduced cell magnetorotation (CM) method is made possible by nanoparticle induced cell magnetization. By using a rotating magnetic field, the magnetically labeled cell is actively rotated, and the rotational period is measured in real-time. A change in morphology induces a change in the rotational period of the suspended cell (e.g. when the cell gets bigger it rotates slower). The ability to monitor, in real time, cell swelling or death, at the single cell level, is demonstrated. This method could thus be used for multiplexed real time single cell morphology analysis, with implications for drug testing, drug discovery, genomics and three-dimensional culturing

Low doses of caffeine reduce heart rate during submaximal cycle ergometry

<p>Abstract</p> <p>Background</p> <p>The purpose of this study was to examine the cardiovascular effects of two low-levels of caffeine ingestion in non habitual caffeine users at various submaximal and maximal exercise intensities.</p> <p>Methods</p> <p>Nine male subjects (19–25 yr; 83.3 ± 3.1 kg; 184 ± 2 cm), underwent three testing sessions administered in a randomized and double-blind fashion. During each session, subjects were provided 4 oz of water and a gelatin capsule containing a placebo, 1.5 mg/kg caffeine, or 3.0 mg/kg caffeine. After thirty minutes of rest, a warm-up (30 Watts for 2 min) the pedal rate of 60 rpm was maintained at a steady-state output of 60 watts for five minutes; increased to 120 watts for five minutes and to 180 watts for five minutes. After a 2 min rest the workload was 180 watts for one minute and increased by 30 watts every minute until exhaustion. Heart rate (HR) was measured during the last 15-seconds of each minute of submaximal exercise. Systolic blood pressure (BP) was measured at rest and during each of the three sub-maximal steady state power outputs. Minute ventilation (V_E), Tidal volume (V_T), Breathing frequency (Bf), Rating of perceived exertion (RPE), Respiratory exchange ratio (RER), and Oxygen consumption (VO₂) were measured at rest and during each minute of exercise.</p> <p>Results</p> <p>Caffeine at 1.5 and 3.0 mg/kg body weight significantly lowered (p < 0.05) HR during all three submaximal exercise intensities compared to placebo (range – 4 to 7 bpm lower) but not at rest or maximal exercise. BP was significantly higher (p < 0.05) at rest and after the 3 mg/kg caffeine vs placebo (116 ± 13 vs 123 ± 10 mm Hg). Neither dose of caffeine had any effect on BP during submaximal exercise. Caffeine had no effect on V_E, V_T, VO₂, RPE, maximal power output or time to exhaustion.</p> <p>Conclusion</p> <p>In non habitual caffeine users it appears that consuming a caffeine pill (1.5 & 3.0 mg/kg) at a dose comparable to 1–3 cups of coffee lowers heart rate during submaximal exercise but not at near maximal and maximal exercise. In addition, this caffeine dose also only appears to affect systolic blood pressure at rest but not during cycling exercise.</p

Spatial Patterns in Herbivory on a Coral Reef Are Influenced by Structural Complexity but Not by Algal Traits

Background: Patterns of herbivory can alter the spatial structure of ecosystems, with important consequences for ecosystem functions and biodiversity. While the factors that drive spatial patterns in herbivory in terrestrial systems are well established, comparatively less is known about what influences the distribution of herbivory in coral reefs. Methodology and Principal Findings: We quantified spatial patterns of macroalgal consumption in a cross-section of Ningaloo Reef (Western Australia). We used a combination of descriptive and experimental approaches to assess the influence of multiple macroalgal traits and structural complexity in establishing the observed spatial patterns in macroalgal herbivory, and to identify potential feedback mechanisms between herbivory and macroalgal nutritional quality. Spatial patterns in macroalgal consumption were best explained by differences in structural complexity among habitats. The biomass of herbivorous fish, and rates of herbivory were always greater in the structurally-complex coral-dominated outer reef and reef flat habitats, which were also characterised by high biomass of herbivorous fish, low cover and biomass of macroalgae and the presence of unpalatable algae species. Macroalgal consumption decreased to undetectable levels within 75 m of structurally-complex reef habitat, and algae were most abundant in the structurally-simple lagoon habitats, which were also characterised by the presence of the most palatable algae species. In contrast to terrestrial ecosystems, herbivory patterns were not influenced by the distribution, productivity or nutritional quality of resources (macroalgae), and we found no evidence of a positive feedback between macroalgal consumption and the nitrogen content of algae. Significance: This study highlights the importance of seascape-scale patterns in structural complexity in determining spatial patterns of macroalgal consumption by fish. Given the importance of herbivory in maintaining the ability of coral reefs to reorganise and retain ecosystem functions following disturbance, structural complexity emerges as a critical feature that is essential for the healthy functioning of these ecosystems

Responses of savanna lawn and bunch grasses to water limitation

<p>The grass layer of African savannas consists of two main vegetation types: grazing lawns, dominated by short, mostly clonally reproducing grasses, and bunch grasslands, dominated by tall bunch grasses. This patchy distribution of vegetation types is mostly created by large herbivores, which selectively feed on the more nutritious lawn grass species. Besides grazing, herbivores trample the soil, thereby causing soil compaction, with possible consequences for water infiltration. This raises two questions: (i) is water more limiting in grazing lawns than in bunch grasslands and (ii) are lawn grasses more drought tolerant than bunch grasses? To study these questions, we compared drought conditions in both lawn and bunch grasslands in a South African savanna. Additionally, in a climate room, we compared the performance of three lawn and three bunch grass species under a control and a water limitation treatment. Thirdly, we investigated whether there are differences between lawn and bunch grasses in traits related to drought tolerance. Our results show that despite large differences in water availability in the field, lawn and bunch grasses did not differ in their growth response to drought. Drought reduced growth of both growth forms equally. However, we found strong intrinsic trait differences between growth forms, with lawn grasses having higher specific root length and relative growth rate and bunch grasses having a higher root:shoot ratio. These results suggest that after drought-induced plant death, lawn grasses might be more capable of recolonizing patches of bare soil.</p>

Global environmental controls of diversity in large herbivores

Large mammalian herbivores occupy half of the earth's land surface and are important both ecologically and economically, but their diversity is threatened by human activities. We investigated how the diversity of large herbivores changes across gradients of global precipitation and soil fertility. Here we show that more plant-available moisture reduces the nutrient content of plants but increases productivity, whereas more plant-available nutrients increase both of these factors. Because larger herbivore species tolerate lower plant nutrient content but require greater plant abundance, the highest potential herbivore diversity should occur in locations with intermediate moisture and high nutrients. These areas are dry enough to yield high quality plants and support smaller herbivores, but productive enough to support larger herbivores. These predictions fit with observed patterns of body size and diversity for large mammalian herbivores in North America, Africa and Australia, and yield a global map of regions with potentially high herbivore diversity. Thus, gradients of precipitation, temperature and soil fertility might explain the global distribution of large herbivore diversity and help to identify crucial areas for conservation and restoration.

Determinants of woody cover in African savannas

Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties 1-3. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover1,2,4,5, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than ~650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered 'stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of ~650 mm, savannas are 'unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation 6 may considerably affect their distribution and dynamics