The influence of animals on phosphorus cycling in lake ecosystems

Aquatic animals directly influence the cycling of phosphorus in lakes through feeding and excretion. Traditionally, animals (zooplankton, benthic invertebrates and fish) have been assigned only minor roles in the process of freshwater phosphorus cycling. They were regarded as consumers without much regulating influence. Today there is growing evidence that animals, predators and herbivores, directly or indirectly can control biomass of primary producers and internal cycling of phosphorus.This paper summarizes different mechanisms of transformation and translocation of phosphorus via different groups of organisms.     

Interactions of acetylcholine receptor and acetylcholinesterase with lipid monolayers

The interaction of acetylcholine receptor and acetylcholinesterase with lipid monolayers was followed by measuring changes in surface pressure.When injected into the subphase of a lipid monolayer, the proteins caused increases in surface pressure from 5 to 10 dynes/cm, indicating a penetration of protein into the monolayer. At pH values below the isoelectric point of the proteins the incorporation was improved. The same was observed when Ca²⁺ (2 mM) was added.The presence of the enzyme in the mixed film could be demonstrated by using diiso[³H]propyl fluorophosphate-labelled acetylcholinesterase as well as by measuring enzyme activity. Acetylcholine receptor was shown to be present in the mixed film by using a complex made of the receptor and α-[³H]neurotoxin.     

Model-based optimization of viral capsid protein production in fed-batch culture of recombinant <Emphasis Type="Italic">Escherichia coli</Emphasis>

An optimized fed-batch cultivation process for the production of the polyoma virus capsid protein VP1 in recombinant Escherichia coli BL21 bacteria is presented. The optimization procedure maximizing the amount of desired protein is based on a mathematical model. The model distinguishes an initial cell growth phase from a protein production phase initiated by inducer injection. A new approach to model the target protein formation rate was elaborated, where product formation is primarily dependent on the specific biomass growth rate. Lower growth rates led to higher specific protein concentrations. The model was identified from a series of fed-batch experiments designed for parameter identification purposes and possesses good prediction quality. Then the model was used to determine optimal open-loop control profiles by manipulating the substrate feed rates in both phases as well as the induction time. Feed-rate optimization has been solved using Pontryagin's maximum principle. The solution was validated experimentally. A significant improvement of the process performance index was achieved.     

Nutrient composition,ruminal degradability and whole tract digestibility of whole crop maize silage from nine current varieties

Since maize silage is an important forage in cattle nutrition, it is important to know its nutritive value. Much effort is put into breeding maize, and several new varieties are introduced on the market every year. This requires periodical analyses of the nutritive value of current maize varieties for the formulation of cattle rations. The aim of this study was to examine the nutritive value of whole crop maize silage (WCMS) from nine maize varieties in 3 consecutive years. For the analysis of nutrient composition and ruminal degradability of organic matter (OM), crude protein (CP), neutral detergent fibre (aNDFom) and non-fibre carbohydrates (NFC), varieties were harvested at three harvest dates (50%, 55% and 60% dry matter content in ear). Due to capacity limitations, the digestibility of WCMS was tested only for the middle harvest date. The CP and acid detergent fibre (ADFom) content was affected (p < 0.05) while aNDFom and NFC content was not influenced by variety. With advancing maturity, CP, aNDFom and ADFom content declined while NFC content increased. Variety influenced effective ruminal degradability (ED) of nutrients, except for CP. The ED of all examined nutrients decreased as maturity advanced from first to third harvest date. Digestibility of OM, ADFom and NFC was significantly and digestibility of aNDFom was tendentially (p = 0.064) influenced by variety. Additionally, an effect of year and a harvest date × year interaction was found for almost all examined parameters. In conclusion, variety, harvest date and year influence the nutritive value of WCMS. A comparison with earlier studies shows that current varieties have a higher fibre digestibility and a slower-ripening stover compared to older varieties.     

Ultrastructure and Cytochemistry of Periostracum and Mantle Edge of Biomphalaria glabrata (Gastropoda,Basommatophora)

Abstract Three layers of different electron density can be distinguished in the periostracum. Periostracal units of up to 900 nm length are merged into the outer fibrous layer and binding of gold-labelled lectin-WGA indicates the presence of chitin because it is labile to chitinase treatment. The periostracum is formed by the epithelia of the groove and the belt at the mantle edge. The distal and basal epithelium of the groove consists mainly of type A cells with an extended Golgi apparatus and apical vesicles. The presence of peroxidase and phenol oxidase indicates a function in tanning of the periostracum. In the proximal epithelium of the groove, type B cells with protruding apices add more material for periostracum formation. Type C cells secrete single periostracal units which are formed within single vesicles or larger vacuoles. Type D cells secrete electron-dense vesicles which also contain WGA-positive material. The distal cells of the belt are characterized by predominating strands of the rER while subapical vacuoles, to some of which WGA binds, dominate in the cells of the central part. In the belt, phenol oxidase and peroxidase can be localized in cisternae of the rER and the Golgi apparatus. Numerous control incubations indicate that, indeed, two different enzymes are localized.     

Current perspectives in pulmonary surfactant — Inhibition, enhancement and evaluation

Pulmonary surfactant (PS) is a complicated mixture of approximately 90% lipids and 10% proteins. It plays an important role in maintaining normal respiratory mechanics by reducing alveolar surface tension to near-zero values. Supplementing exogenous surfactant to newborns suffering from respiratory distress syndrome (RDS), a leading cause of perinatal mortality, has completely altered neonatal care in industrialized countries. Surfactant therapy has also been applied to the acute respiratory distress syndrome (ARDS) but with only limited success. Biophysical studies suggest that surfactant inhibition is partially responsible for this unsatisfactory performance. This paper reviews the biophysical properties of functional and dysfunctional PS. The biophysical properties of PS are further limited to surface activity, i.e., properties related to highly dynamic and very low surface tensions. Three main perspectives are reviewed. (1) How does PS permit both rapid adsorption and the ability to reach very low surface tensions? (2) How is PS inactivated by different inhibitory substances and how can this inhibition be counteracted? A recent research focus of using water-soluble polymers as additives to enhance the surface activity of clinical PS and to overcome inhibition is extensively discussed. (3) Which in vivo, in situ, and in vitro methods are available for evaluating the surface activity of PS and what are their relative merits? A better understanding of the biophysical properties of functional and dysfunctional PS is important for the further development of surfactant therapy, especially for its potential application in ARDS.     

Detection of microsatellite instability during somatic embryogenesis of oak (Quercus robur L.)

Five microsatellite loci (QpZAG1/5, QpZAG9, QpZAG36, MSQ4, MSQ13) were used to test for genetic stability of three somatic embryogenic culture lines of Quercus robur L. and plantlets derived therefrom. DNA variation was detected among somatic embryos within all embryogenic lines, whereas no genetic instability was found among the regenerated plants. Two microsatellite loci revealed variation, and a locus-dependent instability was observed. The most polymorphic and useful microsatellite locus for detecting genetic variation was QpZAG9, with 28.5% of the investigated loci being variable.