The functioning of cytochrome b in the electron transport to fumarate in Propionibacterium freudenreichii and Propionibacterium pentosaceum

Fumarase-free electron particles from Propionibacterium freudenreichii and P. pentosaceum were prepared by discontinuous sucrose gradient centrifugation, and the influence of 2-n-heptyl-4-hydroxy-quinoline-N-oxide (HQNO) and ultraviolet irradiation on the reduction of menaquinone and cytochrome b with l-lactate or glycerol-3-phosphate and the reoxidation by fumarate was studied. In the presence of HQNO the steady state reduction level of menaquinone during fumarate reduction was increased whereas the steady state reduction level of cytochrome b was decreased as compared with the reduction levels measured in the absence of HQNO. The steady state reduction level of menaquinone during electron transport to fumarate was not influenced by ultraviolet irradiation and the steady state reduction level of cytochrome b was decreased at increasing irradiation times. The data indicate that cytochrome b is involved in the electron transport to fumarate.Abbreviations HQNO 2-n-heptyl-4-hydroxyquinoline-N-oxide - NQNO 2-n-nonyl-4-hydroxyquinoline-N-oxide Visiting Professor at the Biological Laboratory     

A split-pot experiment with sorghum to test a root water uptake partitioning model

Correct modeling of root water uptake partitioning over depth is an important issue in hydrological and crop growth models. Recently a physically based model to describe root water uptake was developed at single root scale and upscaled to the root system scale considering a homogeneous distribution of roots per soil layer. Root water uptake partitioning is calculated over soil layers or compartments as a function of respective soil hydraulic conditions, specifically the soil matric flux potential, root characteristics and a root system efficiency factor to compensate for within-layer root system heterogeneities. The performance of this model was tested in an experiment performed in two-compartment split-pot lysimeters with sorghum plants. The compartments were submitted to different irrigation cycles resulting in contrasting water contents over time. The root system efficiency factor was determined to be about 0.05. Release of water from roots to soil was predicted and observed on several occasions during the experiment; however, model predictions suggested root water release to occur more often and at a higher rate than observed. This may be due to not considering internal root system resistances, thus overestimating the ease with which roots can act as conductors of water. Excluding these erroneous predictions from the dataset, statistical indices show model performance to be of good quality.     

Complete profiling of some eicosanoids using glass capillary gas chromatography with flame ionization detection: application to biological samples

The improvement of glass capillary preparation technology has allowed the development of high-resolution and very low-bleeding gas chromatographic columns. Using an all-glass injector and a flame ionization detector, it was possible to get a complete resolution of some of the principal stable oxygenated metabolites of arachidonic acid (cyclized and aliphatic, i.e., eicosanoids). Due to the low bleeding of the column, detector limits exceed those obtained with previously prepared columns. Total profiling studies have been obtained with small amounts of activated washed platelets after only an ether extraction, allowing for the first time a complete, simultaneous survey of cycloxygenase and lipoxygenase pathways. The application has been extended with success to other cell types.     

Vegetativ vermehrbare Birnenunterlagen

Theoretical and Applied Genetics -     

Monoclonal anti-mouse macrophage antibodies recognize the globular portions of C1q, a subcomponent of the first component of complement

One of seven monoclonal antibodies generated against mouse macrophages (M phi) was found to recognize isolated heterologous C1q. This antibody was shown to be cytotoxic and to react in a strain-independent way with mouse M phi derived from bone marrow cells as well as with M phi from the peritoneal cavity; it did not react, however, with mouse granulocytes, thymocytes, or T and B lymphocytes. The hemolytic activity of fluid phase C1q was inhibited to 50% at a 2 X 10(-4) dilution of hybridoma supernatant, whereas a 100-fold higher concentration was required to inhibit C1q bound to immune complexes ( EAC1q ) to the same extent. It was demonstrated that this antibody recognizes the isolated globular, Fc-binding portions of the C1q molecule and reacts with the A and B chains. Because M phi have been shown to synthesize C1q, the Fc-recognizing subcomponent of the first component of complement, evidence was provided that endogeneous C1q can serve as an Fc receptor on M phi during secretion. This fact was demonstrated by a dose-dependent inhibition of Fc-receptor activity for EIgG by the F(ab')2 fragment of this monoclonal antibody. These experiments further support the concept that C1q produced by M phi functions on the surface as an Fc-recognizing molecule before it is released and incorporated into the macromolecular complex of serum C1.     

Selecting high-dimensional mixed graphical models using minimal AIC or BIC forests

Background  

Chow and Liu showed that the maximum likelihood tree for multivariate discrete distributions may be found using a maximum weight spanning tree algorithm, for example Kruskal's algorithm. The efficiency of the algorithm makes it tractable for high-dimensional problems.