Ultrastructure of gravity-perceiving cells in plant roots

The root cap is the gravity-perceiving organ of plant roots. The central statenchyma consists of polarly organized statocytes which are characterized by sedimentable amyloplasts and by a striking distal endoplasmic reticulum (e.r. complex). During the normal downwards orientated growth of the root, the amyloplasts are sedimented onto the e.r. complex. Some observations indicate that the amyloplasts stress the e.r. complex by their sedimentation. The stress possibly influences the structural and functional state of the e.r. membranes. Therefore, graviperception is probably a function of differential stress on the e.r. complexes. The amyloplasts are partly or totally separated from the e.r. complex under experimental conditions such as deviations of the roots from the perpendicular between 30 and 180 degrees, rotation of the roots on the horizontal klinostat at 2 rev/min and at 55-120 rev/min, and placing the roots into an electric field at 2000-3000 V/cm. These are important facts for an understanding of the nature of graviperception. Spacelab experiments may help to verify the interpretation of results obtained in the experiments in simulated weightlessness.     

Circular dichroism of soybean leghemoglobin.

Circular dichroic (CD) spectra of soybean leghemoglobin, and some of its liganded derivatives were measured over the wavelength range of 650 to 200 nm. The heme-related circular dichroic bands in the visible, Soret and ultraviolet wavelength regions exhibit Cotton effects characteristic of each of the compounds examined. The positions of the dichroic bands vary with ligand substitutions and the oxidation state of the iron. All leghemoglobin derivatives, except the apoprotein, exhibit negative circular dichroic bands in the region of Soret absorption. In this region the optical activity of compounds with high-spin moments is greater than that of compounds with low or intermediate spin moments. The ellipticity of the heme band at about 260 nm is also altered by ligand binding and spin state. The dichroic spectra in the far-ultraviolet region indicated a high extent of alpha-helical structure (about 70%) in the native leghemoglobin and its liganded derivatives. The helicality of the apoprotein seems to diminish suggesting a decrease caused by the removal of the heme.     

Synthesis, molecular modeling studies and biological evaluation of fluorine substituted analogs of GW 501516

(±)-2-Fluoro-2-(2-methyl-4-(((4-methyl-2-(4-(trifluoromethyl)phenyl)thiazol-5-yl)methyl)thio)phenoxy)acetic acid (2a) has been prepared and subjected to biological testing against all three subtypes of the PPARs. This compound exhibited agonist effects with EC(50) values of 560 and 55 nM against PPARα and PPARδ, respectively, in a luciferase assay. Moreover, compound (±)-2a also exhibited potent ability to induce oleic acid oxidation in a human myotube cell assay with EC(50)=3.7 nM. Compound (±)-2a can be classified as a dual PPARα/δ agonist with a 10-fold higher potency against the PPARδ receptor than against the PPARα receptor. Molecular modeling studies revealed that both enantiomers of 2a bind to the PPARδ receptor with similar binding energies.     

Localization of stilbene synthase in Vitis vinifera L. during berry development

The localization of stilbene synthase (STS) (EC 2.3.1.95) in grape berry (Vitis vinifera L.) was investigated during fruit development. The berries were collected at 2, 4, 7, 11, and 15 weeks postflowering from the cultivar Nebbiolo during the 2005 and 2006 growing seasons. High-performance liquid chromatography analysis showed that berries accumulated cis- and trans-isomers of resveratrol mainly in the exocarp throughout fruit development. Immunodetection of STS protein was performed on berry extracts and sections with an antibody specifically developed against recombinant grape STS1. In agreement with resveratrol presence, STS was found in berry exocarp tissues during all stages of fruit development. The labeled epidermal cells were few and were randomly distributed, whereas nearly all the outer hypodermis cells were STS-positive. The STS signal decreased gradually from exocarp to mesocarp, where the protein was detected only occasionally. At the subcellular level, STS was found predominantly within vesicles (of varying size), along the plasma membrane and in the cell wall, suggesting protein secretion in the apoplast compartment. Despite the differences in fruit size and structure, the STS localization was the same before and after veraison, the relatively short developmental period during which the firm green berries begin to soften and change color. Nevertheless, the amount of protein detected in both exocarp and mesocarp decreased significantly in ripe berries, in agreement with the lower resveratrol content measured in the same tissues. The location of STS in exocarp cell wall is consistent with its role in synthesizing defense compounds and supports the hypothesis that a differential localization of phenylpropanoid biosynthetic machinery regulates the deposition of specific secondary products at different action sites within cells.     

Untersuchungen über die Mycorrhizen von Allium- und Solanum-Arten

Ohne Zusammenfassung     

Phylogenetic position of Gluconobacter species as a coherent cluster separated from all Acetobacter species on the basis of 16S ribosomal RNA sequences

Abstract The 16S rRNA sequences from the Gluconobacter species G. asaii G. cerinus and G. frateurii were determined and compared with homologous sequences from published databases and sequences of G. oxydans and Acetobacter species previously described [Sievers M., Ludwig W. and Teuber M. (1994) System. Appl. Microbiol. 17, 189–196]. The Gluconobacter species have unique 16S rRNA sequences and exhibit sequence similarity values of 97.4 to 99.1%, corresponding to 36 to 14 base differences. The phylogenetic tree inferring methods (distance matrix, maximum parsimony and maximum likelihood) show that the species of Gluconobacter form a coherent, closely related cluster. Based on the distance matrix method including Rhodopila globiformis as an outgroup reference organism, Gluconobacter is well separated from Acetobacter .     

Pleiotrophin Gene Therapy for Peripheral Ischemia: Evaluation of Full-Length and Truncated Gene Variants

Pleiotrophin (PTN) is a growth factor with both pro-angiogenic and limited pro-tumorigenic activity. We evaluated the potential for PTN to be used for safe angiogenic gene therapy using the full length gene and a truncated gene variant lacking the domain implicated in tumorigenesis. Mouse myoblasts were transduced to express full length or truncated PTN (PTN or T-PTN), along with a LacZ reporter gene, and injected into mouse limb muscle and myocardium. In cultured myoblasts, PTN was expressed and secreted via the Golgi apparatus, but T-PTN was not properly secreted. Nonetheless, no evidence of uncontrolled growth was observed in cells expressing either form of PTN. PTN gene delivery to myocardium, and non-ischemic skeletal muscle, did not result in a detectable change in vascularity or function. In ischemic hindlimb at 14 days post-implantation, intramuscular injection with PTN-expressing myoblasts led to a significant increase in skin perfusion and muscle arteriole density. We conclude that (1) delivery of the full length PTN gene to muscle can be accomplished without tumorigenesis, (2) the truncated PTN gene may be difficult to use in a gene therapy context due to inefficient secretion, (3) PTN gene delivery leads to functional benefit in the mouse acute ischemic hindlimb model.     

A comparison of the palaeolimnology of Peipsi and Võrtsjärv: connected shallow lakes in north-eastern Europe for the twentieth century, especially in relation to eutrophication progression and water-level fluctuations

We applied a multi-proxy palaeolimnological approach to provide insights into the natural variability and human-mediated trends of two interconnected temperate large shallow lakes, Peipsi and Võrtsjärv, during the twentieth century. The history of the lakes was assessed on the basis of age-related changes in the sediment main constituents (water, organic matter and carbonate), sub-fossil pigments, diatom assemblages and organic matter dissolved in pore water. The temporal changes in the palaeodata indicate an increase of the in-lake biological production in both lakes from about the 1960s, suggesting enhanced nutrient inputs. In subsequent decades, the gradual increase of autochthonous organic matter becomes more obvious, indicating progressive eutrophication of the lakes. Palaeolimnological indicators from the sediment record of Lake Peipsi indicate a slight recession of the lake’s eutrophication in the 1990s but not for Lake Võrtsjärv. The results of the study also suggest that after the lakes became eutrophied, the climatically induced water-level fluctuations ceased to be the main driver determining the abundance of phytoplankton. Responses of the lakes to human-induced impacts are better recorded in the sediments of Lake Peipsi than in those of Lake Võrtsjärv, which is shallower of the two and where the wave-induced resuspension of deposits markedly smooths or erases the signals of environmental changes. The results of the investigation expand the knowledge on how large shallow lakes respond to human-mediated and natural perturbations, including those in the lake catchment areas and the capability of the lakes to store the chronology and sequence of these changes.