The importance of clutch characteristics and learning for antiparasite adaptations in hosts of avian brood parasites

There is considerable variation in rejection rates of parasitic eggs among hosts of avian brood parasites. In this article, we develop a model that can be used to predict host egg rejection behavior in brood parasite-host systems in general, by considering both intra- and interclutch variation in host egg appearance; clutch characteristics that may be important in calculating the fitness of individuals adopting rejecter or acceptor strategies. In addition, we consider the importance of learning the appearance of own eggs during the first breeding attempt and host probability of survival between breeding seasons on evolution of rejection behavior. Based on this model we can predict at which level of parasitism fitness of rejecter individuals is higher than that of acceptor individuals and vice versa. The model analyses show that variation in egg appearance can be a key factor for the evolution of host defense against parasitism. In more detail, analyses show that we should expect to find a prolonged learning period only in hosts that have a high intraclutch variation in egg appearance, because such hosts may potentially experience high costs in terms of recognition errors. Furthermore, learning is in general more adaptive in parasite-host systems in which hosts do have some reproductive success even when parasitized, and when parasitism rates are moderate. By including variables that have not been considered in previous models, our model represents a useful tool in investigations of host rejection behavior in various host-parasite systems.     

Simultaneous determination of 6 beta-blockers, 3 calcium-channel antagonists, 4 angiotensin-II antagonists and 1 antiarrhythmic drug in post-mortem whole blood by automated solid phase extraction and liquid chromatography mass spectrometry. Method development and robustness testing by experimental design

A method for the simultaneous determination of the beta-blockers atenolol, sotalol, metoprolol, bisoprolol, propranolol and carvedilol, the calcium-channel antagonists diltiazem, amlodipine and verapamil, the angiotensin-II antagonists losartan, irbesartan, valsartan and telmisartan, and the antiarrhythmic drug flecainide, in whole blood samples from forensic autopsies was developed. Sample clean-up was achieved by precipitation and solid phase extraction (SPE) with a mixed-mode column. Quantification was performed by reversed phase high performance liquid chromatography with positive electrospray ionization mass spectrometric detection (HPLC-MS). The method has been developed and robustness tested by systematically searching for satisfactory conditions using experimental designs including factorial and response surface designs. With the exception of amlodipine, the concentration limit of quantification (cLOQ) covered low therapeutic concentration levels for all the compounds. Within assay precisions and accuracies (bias) were 3.4-21% RSD and from -24 to 21% for the concentration range 1.00-5.00 microM, respectively. Between assay precisions were 4.4-28% RSD for the concentration range from 0.1 to 5 microM and recoveries varied from 9 to 103%. The method is used for determination of cardiovascular drugs in post-mortem whole blood samples from forensic autopsy cases.     

Introduction of Mysis relicta (Mysida) reduces niche segregation between deep-water Arctic charr morphs

Hydrobiologia - Understanding the concordance between aquatic assemblages in ecological assessments and their responses to human-induced disturbances are fundamental steps toward achieving...     

Confirmation of House Crows Corvus splendens laying immaculate blue eggs

House Crows Corvus splendens lay eggs with bluish-green ground colour and black or brown blotches and only one egg morph was believed to exist. Here, we confirm the existence of an immaculate, spotless blue egg morph that is clearly different from the regular egg morph.     

The recombinant Azotobacter vinelandii mannuronan C-5-epimerase AlgE4 epimerizes alginate by a nonrandom attack mechanism

The Ca2+-dependent mannuronan C-5-epimerase AlgE4 is a representative of a family of Azotobacter vinelandii enzymes catalyzing the polymer level epimerization of beta-D-mannuronic acid (M) to alpha-L-guluronic acid (G) in the commercially important polysaccharide alginate. The reaction product of recombinantly produced AlgE4 is predominantly characterized by an alternating sequence distribution of the M and G residues (MG blocks). AlgE4 was purified after intracellular overexpression in Escherichia coli, and the activity was shown to be optimal at pH values between 6.5 and 7.0, in the presence of 1-3 mM Ca2+, and at temperatures near 37 degrees C. Sr2+ was found to substitute reasonably well for Ca2+ in activation, whereas Zn2+ strongly inhibited the activity. During epimerization of alginate, the fraction of GMG blocks increased linearly as a function of the total fraction of G residues and comparably much faster than that of MMG blocks. These experimental data could not be accounted for by a random attack mechanism, suggesting that the enzyme either slides along the alginate chain during catalysis or recognizes a pre-existing G residue as a preferred substrate in its consecutive attacks.     

Secondary structure of two regions in expansion segments ES3 and ES6 with the potential of forming a tertiary interaction in eukaryotic 40S ribosomal subunits

The 18S rRNA of the small eukaryotic ribosomal subunit contains several expansion segments. Electron microscopy data indicate that two of the largest expansion segments are juxtaposed in intact 40S subunits, and data from phylogenetic sequence comparisons indicate that these two expansion segments contain complementary sequences that could form a direct tertiary interaction on the ribosome. We have investigated the secondary structure of the two expansion segments in the region around the putative tertiary interaction. Ribosomes from yeast, wheat, and mouse-three organisms representing separate eukaryotic kingdoms-were isolated, and the structure of ES3 and part of the ES6 region were analyzed using the single-strand-specific chemical reagents CMCT and DMS and the double-strand-specific ribonuclease V1. The modification patterns were analyzed by primer extension and gel electrophoresis on an ABI 377 automated DNA sequencer. The investigated sequences were relatively exposed to chemical and enzymatic modification. This is in line with their indicated location on the surface at the solvent side of the subunit. The complementary ES3 and ES6 sequences were clearly inaccessible to single-strand modification, but available for cleavage by double-strand-specific RNase V1. The results are compatible with a direct helical interaction between bases in ES3 and ES6. Almost identical results were obtained with ribosomes from the three organisms investigated.     

Stroke and glide of wing-propelled divers: deep diving seabirds adjust surge frequency to buoyancy change with depth

In order to increase locomotor efficiency, breath-holding divers are expected to adjust their forward thrusts in relation to changes of buoyancy with depth. Wing propulsion during deep diving by Brünnich's guillemots (Uria lomvia) was measured in the wild by high-speed (32 Hz) sampling of surge (tail-to-head) and heave (ventral-to-dorsal) accelerations with bird-borne data loggers. At the start of descent, the birds produced frequent surges (3.2 Hz) during both the upstroke and the downstroke against buoyancy to attain a mean speed of 1.2-1.8 m s(-1) that was close to the expected optimal swim speed. As they descended deeper, the birds decreased the frequency of surges to 2.4 Hz, relaying only on the downstroke. During their ascent, they stopped stroking at 18 m depth, after which the swim speed increased to 2.3 m s(-1), possibly because of increasing buoyancy as air volumes expanded. This smooth change of surge frequency was achieved while maintaining a constant stroke duration (0.4-0.5 s), presumably allowing efficient muscle contraction.     

Percutaneous cryoablation of colorectal liver metastases: potentiated by two consecutive freeze-thaw cycles

Cryoablation may be beneficial for selected patients with liver tumours. Two freeze-thaw cycles at the same location have been recommended during treatment as this potentiate the effect of ablation in experimental studies. However, single freeze ablations are used by some as double freeze procedures are time-consuming and have been associated with increased risk of complications. Estimation of ice-ball volume is difficult using regularly used monitoring techniques. Magnetic resonance imaging, however, allows excellent and multiplanar visualisation of the frozen region during ablation. We comment on the effect of double freeze cycles in regard to ice-ball volume as estimated from magnetic resonance imaging during percutaneous cryoablation of colorectal liver metastases. The ice-ball volume at the end of the second freeze cycle was median 42% larger than the volume at the end of the first freeze. Double freeze cycles may thus facilitate tumour destruction.     

Cardiovascular and neuroendocrine responses to left lateral position in non-obese young males

Previous results from our laboratory indicate that the heart is distended by the left lateral position (LAT) compared to horizontal supine (SUP). We therefore tested the hypothesis that cardiac output is increased by LAT and that mean arterial pressure is maintained unchanged or even decreased through peripheral vasodilatation induced by cardiopulmonary low-pressure receptor stimulation. Twelve non-obese young males were investigated. The location of the mid-aorta between the aortic valves was used as the hydrostatic reference point for the arterial pressure measurements. It was determined by magnetic resonance (n=6) to be 7.0 +/- 0.2 cm below the sternum in SUP (1/3 of anteroposterior chest diameter below the sternum) and 2.5 +/- 0.2 cm below the midsternal level in LAT. Brachial mean (auscultation) and finger mean arterial pressures (infrared photoplethysmography), cardiac output (foreign gas rebreathing), heart rate, and plasma concentrations (n=6) of vasoactive hormones were unchanged by LAT. In conclusion, cardiac output, mean arterial pressures, and vasoactive hormone releases were unaffected by 30 min of LAT. Furthermore, the hydrostatic reference points for arterial pressure measurements is located one third of the antero-posterior chest diameter below the sternum in SUP and 2.5 cm below the midsternal level in LAT in non-obese young males.     

Effects of sodium intake on cardiovascular variables in humans during posture changes and ambulatory conditions

The hypothesis was tested that cardiac output (CO) and stroke volume (SV) are increased by a moderate physiological elevation in sodium intake with a more pronounced effect in the ambulatory upright seated than supine position. Fourteen healthy males were investigated during ambulatory and controlled laboratory conditions at the end of two consecutive 5-day periods with sodium intakes of 70 (low) and 250 (high) mmol/24 h or vice versa, respectively. Comparing high and low sodium intake, plasma volume and plasma protein concentrations were 9 and 8% higher in the seated and the supine position, respectively. When seated during laboratory conditions, CO was 5.3 +/- 0.2 l/min on the high sodium intake vs. 4.8 +/- 0.2 l/min on the low (P < 0.05), and SV was 81 +/- 3 vs. 68 +/- 3 ml (P < 0.05). In the supine position, SV was 107 +/- 3 ml on the high vs. 99 +/- 3 ml (P < 0.05) on the low sodium intake, while CO remained unchanged. The difference in CO and SV induced by the change in sodium intake was significantly higher in the seated than in the supine position (P < 0.05). During upright ambulatory conditions, CO was 5.9 +/- 0.2 l/min during the high and 5.2 +/- 0.2 l/min during the low sodium intake (P < 0.05), and SV was 84 +/- 3 and 69 +/- 3 ml (P < 0.05), respectively. Mean arterial pressure was unchanged by the variations in sodium intake. In conclusion, increments in sodium intake within the normal physiological range increase CO and SV and more so in the seated vs. the supine position. These changes are readily detectable during upright, ambulatory conditions. The results indicate that the higher SV and CO could constitute an arterial baroreflex stimulus for the augmented renal sodium excretion.