Sensitive detection of malaria infection by third harmonic generation imaging

Malaria remains a major health concern worldwide, with 350-500 million cases reported annually in endemic countries. In this study, we report a novel and highly sensitive optical-based detection of malaria-infected blood cells by third harmonic generation (THG) imaging of hemozoin pigment that is naturally deposited by the parasite during its lifecycle. The THG signal from the hemozoin was greater than we have observed in any cell type with signal/noise ratios that reach 1000:1. This method allows a rapid and robust detection of early stage infections of blood cells. The immense nonlinear response of the intrinsic parasitic by-product pigments suggests that automated optical detection by THG could be used for sensitive and rapid screening of parasite infection in blood samples.     

Predicted warming and browning affect timing and magnitude of plankton phenological events in lakes: a mesocosm study

1. Aquatic ecosystems in Northern Europe are expected to face increases in temperature and water colour (TB) in future. While effects of these factors have been studied separately, it is unknown whether and how a combination of them might affect phenological events and trophic interactions. 2. In a mesocosm study, we combined both factors to create conditions expected to arise during the coming century. We focused on quantifying effects on timing and magnitude of plankton spring phenological events and identifying possible mismatches between resources (phytoplankton) and consumers (zooplankton). 3. We found that the increases in TB had important effects on timing and abundance of different plankton groups. While increased temperature led to an earlier peak in phytoplankton and zooplankton and a change in the relative timing of different zooplankton groups, increased water colour reduced chlorophyll‐a concentrations. 4. Increased TB together benefitted cladocerans and calanoid copepods and led to stronger top‐down control of algae by zooplankton. There was no sign of a mismatch between primary producers and grazers as reported from other studies. 5. Our results point towards an earlier onset of plankton spring growth in shallow lakes in future with a stronger top‐down control of phytoplankton by zooplankton grazers.     

31P-NMR observation of free ADP during fatiguing, repetitive contractions of murine skeletal muscle lacking AK1

Metabolic control within skeletal muscle is designed to limit ADP accumulation even during conditions where ATP demand is out of balance with ATP synthesis. This is accomplished by the reactions of adenylate kinase (AK; ADP+ADP AMP+ATP) and AMP deaminase (AMP+H₂O NH₃+IMP), which limit ADP accumulation under these conditions. The purpose of this study was to determine whether AK deficiency (AK^–/–) would result in sufficient ADP accumulation to be visible using ³¹P-NMRS during the high energy demands of frequent in situ tetanic contractions. To do this we examined the high-energy phosphates of the gastrocnemius muscle in the knockout mouse with AK1^–/– and wild-type (WT) control muscle over the course of 64 rapid (2/s) isometric tetanic contractions. Near-complete depletion of phosphocreatine was apparent after 16 contractions in both groups. By 40 contractions, ADP was clearly visible in AK1^–/– muscle. This transient concentration of the NMR visible free ADP was estimated to be 1.7 mM, and represents the first time free ADP has been directly measured in contracting skeletal muscle. Such an increase in free ADP is severalfold greater than previously thought to occur. This large accumulation of free ADP also represents a significant reduction in energy available from ATP, and has implications on cellular processes that depend on a high yield of energy from ATP such as calcium sequestration. Remarkably, the AK1^–/– and WT muscles exhibited similar fatigue profiles. Our findings suggest that skeletal muscle is surprisingly tolerant to a large increase in ADP and by extension, a decline in energy from ATP. muscle energetics; muscle relaxation; magnetic resonance spectroscopy     

Effect of extrusion under controlled temperature and moisture conditions on ileal apparent amino acid and starch digestibility in peas determined with young broilers

The objective of the experimental programme was to examine the influence of extrusion of peas under controlled temperature and moisture conditions on coefficient of ileal apparent digestibility (CIAD) of amino acids and to examine the changes to starch structure (crystallisation) and subsequent effects on CIAD of starch in young broilers. Experiment 1 used one pea cultivar (2.94 mg trypsin inhibitor units (TIU)/g DM) processed under two extrusion temperatures (exit temperatures of 70 and 140 °C) and two moisture levels (0 and 1.96l water added/h) giving a 2 × 2 factorial design (with a 5th treatment being the raw pea sample). All pea samples were added at a rate of 500 g/kg into a purified diet where peas were the only source of protein/amino acids. Processing generally led to a reduction in CIAD of amino acids but CIAD of starch for Raw, Treatments 1 and 3 (added water) was lower than that for Treatments 2 and 4 (no water) with data of 0.730, 0.808 and 0.759 vs. 0.852 and 0.834, respectively. Experiment 2 evaluated two near-isogenic lines of peas (HA5 and HB5) processed under the same conditions as for Experiment 1. Extrusion at 70 °C/addition of water had no significant effect on trypsin inhibitor activity but the inhibitor was eliminated at 140 °C with or without addition of water (P<0.001). Pea line HA5 generally had higher CIAD than HB5 (P<0.05 for cystine, lysine, leucine, histidine, alanine; P<0.01 for threonine). There were significant temperature × water addition interactions for CIAD (P<0.001 for all amino acids except methionine; P=0.006). For example, data for lysine were 0.760, 0.828, 0.860 and 0.759, respectively for 140 °C/no water, 140 °C/1.96 l/h, 70 °C/no water and 70 °C/1.96 l/h. CIAD for starch improved following processing, attributed to the loss of crsytallinity. The data indicate that peas are sensitive to high processing temperatures which are associated with a reduction in nutritive value, in terms of amino acid digestibility, for young poultry. In contrast, the results reinforce the adverse effect of crystallinity on starch digestibility and show that extrusion in the absence of water improves the digestibility of raw starches due to granular disorganisation (as evidenced by X-ray diffraction patterns) and changes in crystallinity.     

Behavior of free-ranging common dolphins (Delphinus sp.) in the Hauraki Gulf, New Zealand

Here we present the first data describing the behavior of common dolphins ( Delphinus sp.) in the Hauraki Gulf, New Zealand. Activity budgets are used to assess the effects of diel, season, depth, sea surface temperature, group size, and composition on dolphin behavior. Additionally, the presence/absence of Bryde's whale ( Balaenoptera brydei ) and Australasian gannet ( Morus serrator ) is examined in relation to dolphin behavior. Behavioral data were collected from 686 independent dolphin groups during boat-based surveys conducted between February 2002 and January 2005. Foraging (46.7%) and social (7.2%) were the most and least frequently observed behaviors, respectively. Travel (28.9%), mill (9.5%), and rest (7.7%) accounted for the remainder of the activity budget. Behavior varied seasonally, with the highest proportion of foraging and resting groups observed during the spring and autumn, respectively. Behavior also varied with water depth, with foraging animals observed in the deepest and resting groups recorded in the shallowest regions of the Hauraki Gulf. A correlation between group size and behavior was evident, although behavior did not vary with the composition of dolphin groups. Resting, milling, and socializing animals were more frequently observed in smaller group sizes. Foraging behavior was prevalent in both small and large group sizes, suggesting foraging plasticity exists within this population. Behavior differed between single- and multispecies groups, with foraging more frequent in multispecies groups. Resting, milling, or socializing was rarely observed in the presence of any associated species, indicating the primary mechanism for association is likely prey related.     

Quantum dot fluorescence characterizes the nanoscale organization of T cell receptors for antigen

Changes in the clustering of surface receptors modulate cell responses to ligands. Hence, global measures of receptor clustering can be useful for characterizing cell states. Using T cell receptor for antigen as an example, we show that k-space image correlation spectroscopy of quantum dots blinking detects T cell receptor clusters on a scale of tens of nanometers and reports changes in clustering after T cell activation. Our results offer a general approach to the global analysis of lateral organization and receptor clustering in single cells, and can thus be applied when the cell type of interest is rare.     

A large cost of female mate sampling in pronghorn

We measured the energy cost of mate sampling by female pronghorn (Antilocapra americana), a species for which there are no apparent direct benefits of mate choice and for which the sampling tactic most closely resembles best-of-n or comparative Bayes. We used Global Positioning System collars to record the position of individuals at 10-min intervals during the 2 weeks preceding estrus in females that actively sampled and in females that did not sample. The difference in the 2-week energy costs of these two classes of females was 8,200 (+/-2,300) kJ, or roughly one-half of the energy cost of a single day. This value, expressed as the fraction of total yearly energy expenditure, is 59 times the value reported for a lekking bird. Our finding calls into question the common assumption in models of mate search that the cost of search is negligible as well as the common assumption that the cost of sampling must be small when there are only indirect benefits of female choice.