Accuracies in Po-210 determination for lead-210 dating

Various laboratory techniques have been utilized worldwide for measuring lead-210 in sub-recent deposits through its grand-daughter product polonium-210. Isotope dilution alpha spectrometry proved a suitable tool for absolute determination of lead-210 for the dating of aquatic deposits. Moreover, isotope dilution alpha spectrometry along with speciation experiments can be used to resolve depositional anomalies arising from supported lead-210/Ra-226 disequilibrium levels and unsupported lead-210 mobile fractions. Isotope dilution alpha spectrometry of sub-recent sediment and peat deposits has been critically evaluated for more than ten years. Our results show that type, size and composition of deposits analyzed as well as radiochemical procedures used, together with alpha counting techniques, are important factors influencing lead-210 determinations and tailing corrections using its granddaughter product polonium-210. Optimization of these parameters is of prime importance to achieve economic and accurate analyses, especially at low lead-210 concentrations and small sample sizes.     

Ethylene and IAA interactions in the inhibition of photoperiodic flower induction of <Emphasis Type="Italic">Pharbitis nil</Emphasis>

It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis.     

Letter: Crystallization and preliminary x-ray investigation of bovine erythrocyte carbonic anhydrase

The major form of bovine erythrocyte carbonic anhydrase has been prepared by a new method in which the conventional chloroform-ethanol treatment is replaced by chromatography on DEAE-Sephadex. Single crystals, suitable for high resolution X-ray diffraction studies, have been obtained from enzyme prepared by this method. The space group is P6₁22. The unit cell contains 12 enzyme molecules and has the dimensions $\text{a = b = 68}\text{A}\text{?}$, $\text{c = 244}\text{A}\text{?}$.     

Synthesis of phosphorylated 3,4-branched trisaccharides corresponding to LPS inner core structures of Neisseria meningitidis and Haemophilus influenzae

2-(N-Benzyloxycarbonyl)aminoethyl 7-O-acetyl-6-O-allyl-2-O-benzoyl-4-O-benzyl-3-O-chloroacetyl-l-glycero-α-d-manno-heptopyranosyl-(1→3)-[2,3,4,6-tetra-O-benzoyl-β-d-glucopyranosyl-(1→4)]-6,7-di-O-acetyl-2-O-benzyl-l-glycero-α-d-manno-heptopyranoside, a spacer-equipped protected derivative of the common 3,4-branched diheptoside trisaccharide structure of the lipopolysaccharide core of Neisseria meningitidis and Haemophilus influenzae has been synthesized. The protecting group pattern installed allows regioselective introduction of phosphoethanolamine residues in the 3- and 6-position of the second heptose unit in accordance with native structures. From this intermediate the 3-and 6-monophosphoethanolamine as well as the non-phosphorylated deprotected trisaccharides have been synthesized to be used in evaluation of antibody binding specificity and in investigation of the substrate specificity of glycosyl transferases involved in the biosynthesis of LPS core structures.     

Nonlinear dynamics of the blood flow studied by Lyapunov exponents

In order to gain an insight into the dynamics of the cardiovascular system throughout which the blood circulates, the signals measured from peripheral blood flow in humans were analyzed by calculating the Lyapunov exponents. Over a wide range of algorithm parameters, paired values of both the global and the local Lyapunov exponents were obtained, and at least one exponent equaled zero within the calculation error. This may be an indication of the deterministic nature and finite number of degrees of freedom of the cardiovascular system governing the blood-flow dynamics on a time scale of minutes. A difference was observed in the Lyapunov dimension of controls and athletes.     

Detection of nodularin in European flounder (Platichthys flesus) in the west coast of Sweden: Evidence of nodularin mediated oxidative stress

The brackish, bloom-forming cyanobacterium Nodularia spumigena produces a peptide called nodularin, which may induce liver damage in fish. In the summer of 2007, nodularin was detected in liver tissue of European flounder caught in Swedish waters of Öresund, within the upper salinity limit for N. spumigena. Nodularin concentrations ranging between 22 and 557 μg kg⁻¹ liver (d.w.) were detected in fish liver. Nodularin was not detected in blue mussels (Mytilus edulis). Although N. spumigena blooms can occur in the area, the cyanobacteria were only present in very small amounts in 2007. Results suggested that nodularin accumulated in flounder livers during the summer of 2006, when vast N. spumigena blooms were observed in Öresund, and persisted over several months. Nodularin has previously been shown to induce oxidative stress in mice, crustaceans and mollusks but work on the potential negative effects of nodularin on fish is still scarce. To examine the dynamics of nodularin induced oxidative stress in liver tissue of flounder, the differential responses of the antioxidant enzymes glutathione-S-transferase catalase (CAT) and the formation of malondialdehyde (MDA) were monitored during 14 days in flounder exposed to an intraperitoneal injection of nodularin (0, 2, 10 and 50 μg nodularin kg⁻¹ body weight). The activities of GST and CAT in the liver decreased significantly in the 50 μg nodularin kg⁻¹ exposure after 7 days, but were restored to control levels after an additional 10 days of recovery. The results suggested that nodularin induced oxidative stress in terms of decreased GST and CAT activity, which can result in increased vulnerability of the cell to reactive oxygen species (ROS). No significant changes could be found in MDA levels between the treatments. Thus, the antioxidant defense system presumably managed to prevent oxygen mediated toxicity as seen by the unchanged levels of MDA. Alteration of the enzymatic defense system may increase energetic costs, thus reducing fish growth and survival. The present study also suggests that oxidative stress biomarkers can be used in fish to detect early responses to nodularin.     

Microsatellites in the Sand Lizard (Lacerta agilis): Description, Variation, Inheritance, and Applicability

We developed microsatellite markers for the sand lizard (Lacerta agilis) to enable investigations of the genetic variability within and among populations with a heterogeneous spatial distribution in Sweden. The populations, which could not be characterized by variation in allozymes or mitochondrial DNA, had a substantial level of variability in microsatellite loci. However, the variability in Swedish populations was limited compared to a large, outbred Hungarian population. In the sand lizard, the number of (GT/CA) _n repeats was approximately three times higher than that for (CT/GA) _n. The number of repeats and the frequency of microsatellites were within the range reported for other species. Three of nine microsatellite loci showed alleles that could not be amplified, which is in agreement with recent reports describing microsatellite “null alleles” as a common occurrence. We discuss the caution which this calls for when calculating paternity probabilities and when estimating between-population allelic differentiation. A potential problem with different mutation rates for alleles within the same locus is discussed.