Guluronic acid content as a factor affecting turbidity removal potential of alginate

Alginates are natural polymers composed of mannuronic and guluronic acid residues. They are currently extracted from brown algae; however, alginate can also be synthesized by some species of Azotobacter and Pseudomonas. Alginates with different proportion of mannuronic and guluronic acids are known to have different characteristics and form gels at different extents in the presence of calcium ions. The aim of this work was to investigate the usefulness of alginate as a non-toxic coagulant used in purification of drinking water. This study utilized alginates from Azotobacter vinelandii having different guluronic acid levels. These were obtained partly by changing the cultivation parameters, partly by epimerizing a purified alginate sample in vitro using the A. vinelandii mannuronan C-5 epimerase AlgE1. The different alginates were then used for coagulation together with calcium. The results showed that turbidity removal capability was dependent on the content of guluronic acid residues. For the best performing samples, the turbidity decreased from 10 NTU to 1 NTU by the use of only 2 mg/L of alginate and 1.5 mM of calcium chloride.

     

Cardiac defects in chromosomally abnormal human embryos of 10–14 weeks' gestation

Cardiac defects were studied in five chromosomally abnormal embryos of 10–14 weeks' gestation by free-hand microdissection of hearts measuring 2·5–6 mm in diameter. The type of cardiac malformation alone or in association with other anomalies helped to confirm the chromosome diagnosis established prenatally by chorionic villus sampling or after spontaneous abortion. It was suggestive of a chromosomal disorder in one case in which cytogenetic investigation had failed.     

Prenatal morphology in meckel's syndrome (with special reference to polycystic kidneys and double encephalocele)

Prenatal morphology of Meckel's syndrome was studied in five fetuses of different gestational age, that had been aborted because ultrasonography and elevated amniotic AFP-levels indicated neural tube defect. Histologically, the enlarged polycystic kidneys were completely alike with respect to the type of involvement and differed only in the severity of changes. They could be identified as type III cystic kidneys according to the classification of Potter. Proliferation of hepatic bile ducts and slight cystic dilatation of pancreatic ducts is already evident in the youngest fetus. Additional cyst formation in the epididymis was found in one of the cases. Occipital encephalocele, located within an apical occipital bone defect was always associated with a second mostly occult encephalocele protruding through a separate defect of the basal occipital squame and of the first and second vertebral arch. It is assumed that double encephalocele represents a constant finding in Meckel's syndrome, indicating a specific pattern within the disturbance of neural tube closure.     

Development of an immuno-immobilized androgen receptor assay (IRA) and its application for the characterization of the receptor binding affinity of different pesticides

Pesticides are synthetic chemicals used not only for improving food and feed production but also for the protection of materials and of human health and well-being. Some of these substances are suspected for adverse effects attributable to an interaction with the endocrine system of vertebrates by mimicking or inhibiting endogenous hormones. One of the biological targets important in this relation is the androgen receptor (AR). To be able to screen environmental samples for the presence of compounds which might interfere with androgen action, we aimed to develop a receptor assay based on recombinant human AR (rhAR). We herein describe an rhAR assay in which the receptor is immobilized in microtiter plates via a specific antibody. The assay can be used for high throughput screening of chemicals spread into the environment. 29 of the most recommended pesticides of the Federal Country Hessen, Germany, were tested for their ability to displace [3H]-DHT bound to the rhAR. This evaluation included the major part of the most common herbicides, insecticides and fungicides and covered three potential groups of endocrine disrupting chemicals. For 28 of the substances evaluated, the relative binding affinity to the rhAR was below 0.1% when compared to dihydrotestosterone (DHT) (100%), only fentinacetate exhibited an affinity of 1.42%. An exchange assay indicated that the binding inhibition was reversible. In consequence, fentinacetate seems to be a hormonally active substance which may be present in vegetables or fish, but also on clothing. We conclude that further investigations on this compound and its metabolites are necessary.     

Looking on the bright side: females prefer coloration indicative of male size and condition in the sexually dichromatic spadefoot toad, <Emphasis Type="Italic">Scaphiopus couchii</Emphasis>

Females across many taxa commonly use multiple or complex traits to choose mates. However, the functional significance of multiple or complex signals remains controversial and largely unknown. Different elements of multiple or complex signals may convey independent pieces of information about different aspects of a prospective mate (the “multiple messages” hypothesis). Alternatively, multiple or complex signals could provide redundant information about the same aspect of a prospective mate (the “redundant” or “back-up” signal hypothesis). We investigated these alternatives using spadefoot toads, Scaphiopus couchii. Spadefoot toads primarily use calls to attract their mates, but males also exhibit sexually dimorphic coloration. We investigated whether male coloration is indicative of male size, condition, or infection status by a socially transmitted monogenean flatworm. We found that male coloration and dorsal patterning predicts male size and condition but not infection status. Moreover, when we presented females with a choice between a bright male model and a dark male model, we found that females preferred the bright model. Because aspects of males’ calls are also associated with male size and condition, we conclude that coloration is a potentially redundant indicator of male phenotype. We suggest that coloration could enhance mate choice in conjunction with male calling behavior by providing females with a long distance cue that could enable them to identify prospective mates in a noisy chorus environment where the discrimination of individual calls is often difficult. Generally, such redundant signals may facilitate mate choice by enhancing the quality and accuracy of information females receive regarding prospective mates.     

A comparison of European and North American atmospheric deposition networks: polycyclic aromatic hydrocarbons and lindane

A comparison between the sampling and analytical methods used by Canadian (IADN) and German (OSPAR) regional monitoring networks for persistent organic pollutants was conducted from September 2002 to October 2003 at a rural site in Ontario, Canada. Polycyclic aromatic hydrocarbons (PAHs) and the currently-used pesticide lindane were measured in precipitation and ambient air samples. Overall the two networks sampling and analytical methods agreed well in their results of deposition (wet and dry particulate). Lindane concentrations between the two networks agreed well in the air samples while too few precipitation samples could be compared to conclude on agreement. The lindane seasonal profile with a peak in spring-early summer was consistent with previous results pointing to the continued use of this pesticide in 2002-2003 in Canada. Annual lindane wet depositions were comparable between the two network methodologies. PAHs concentrations in precipitation and in gas phase agreed well while there was a discrepancy for particulate PAHs in air. This study confirmed that the use of data from the two regional POPs monitoring networks for hemispherical modelling studies is warranted.     

Vortex formation and foraging in polyphenic spadefoot toad tadpoles

Animal aggregations are widespread in nature and can exhibit complex emergent properties not found at an individual level. We investigate one such example here, collective vortex formation by congeneric spadefoot toad tadpoles: Spea bombifrons and Spea multiplicata. Tadpoles of these species develop into either an omnivorous or a carnivorous (cannibalistic) morph depending on diet. Previous studies show that S. multiplicata are more likely to develop into omnivores and feed on suspended organic matter in the water body. The omnivorous morph is frequently social, forming aggregates that move and forage together and form vortices in which they adopt a distinctive slowly rotating circular formation. This behaviour has been speculated to act as a means to agitate the substratum in ponds and thus could be a collective foraging strategy. Here we perform a quantitative investigation of the behaviour of tadpoles within aggregates. We found that only S. multiplicata groups exhibited vortex formation, suggesting that social interactions differ between species. The probability of collectively forming a vortex, in response to introduced food particles, increased for higher tadpole densities and when tadpoles were hungry. Individuals inside a vortex moved faster and exhibited higher (by approximately 27%) tailbeat frequencies than those outside the vortex, thus incurring a personal energetic cost. The resulting environmental modification, however, suggests that vortex behaviour may be an adaptation to actively create and exploit a resource patch within the environment.