Granula motion and membrane spreading during activation of human platelets imaged by atomic force microscopy.

The redistribution of platelet constituents during activation is essential for their physiological function of maintaining hemostasis. We report here about real time investigations of the activation of native human platelets under physiological conditions from the initial formation of filopodia to the fully spread form by atomic force microscopy. We followed the trafficking of granules and their interaction with the plasma membrane within single cells. Our results show movement of certain granula towards the lamellipodia. Analysis of this rearrangement and the subsequent enlargement of the platelet surface reveals details of the membrane spreading process. Images of living cells are presented that show the distribution of cytoskeletal components and membrane-bound filaments at a resolution of better than 50 nm. The local minimum forces between the tip and the platelets were estimated to be smaller than 60 pN. A model for the elastic contributions of the glycocalix to the tip/membrane interaction was developed using the theory of grafted polymers.     

ADP-Ribosylation of Brain Neuronal Proteins Is Altered by In Vitro and In Vivo Exposure to Inorganic Mercury

Abstract: ADP-ribosylation is an essential process in the metabolism of brain neuronal proteins, including the regulation of assembly and disassembly of biological polymers. Here, we examine the effect of HgCl₂ exposure on the ADP-ribosylation of tubulin and actin, both cytoskeletal proteins also found in neurons, and B-50/43-kDa growth-associated protein (B-50/GAP-43), a neuronal tissue-specific phosphoprotein. In rats we demonstrate, with both in vitro and in vivo experiments, that HgCl₂ markedly inhibits the ADP-ribosylation of tubulin and actin. This is direct quantitative evidence that HgCl₂, a toxic xenobiotic, alters specific neurochemical reactions involved in maintaining brain neuron structure.     

Interfacial and micellar behavior of glucose lipid

Summary Glucose lipid of notable surfactant properties was produced by using hydrocarbon assimilating bacterium of the bacterial strain MM1. Its surface active properties were notable in spite of ,-hydrophilic and bulky molecule. The critical micelle concentration (cmc) was small (0.165 M); surface and interfacial tension for hexadecane at 0.1 % (pH 7.35) solution, 24.6 and 13.3 mN/m, respectively. The emulsifying action was excellent and comparable to those of rhamnolipids. The micelle has the outer radius. 28.5 Å and inner core, 6.7 Å on the basis of the concentric spherical shell model by means of the small angle X-ray solution scattering measurement.Dedicated to Professor Fritz Wagner on the occasion of his 65th birthday.     

A new approach for rhizosphere research by X-ray microanalysis of microliter soil solutions

Lolium perenne growing with high root density on a fine nylon mesh (Kuchenbuch and Jungk, 1982) caused the development of element gradients in the rhizosphere below the mesh. Micro-liter soil solutions from 2-mg soil samples were sprayed onto Formvar-coated grids and analyzed by X-ray microanalysis in a transmission electron microscope. The results were comparable to those obtained by flame photometry and atomic absorption spectrometry (AAS) of conventional soil solutions from 1 g soil. X-ray microanalysis of micro-soil solutions allows the application of different extraction procedures to even small amounts of soil usually available from rhizosphere experiments. Information about soil buffering characteristics in the rhizosphere can thus be obtained. Aluminum accumulation in the rhizosphere of small segments of single Picea abies fine roots grown in undisturbed natural forest soil could be detected with this technique.     

Characterization of serological properties of polyclonal antibodies produced against enzymes involved in the L-selective cleavage of hydantoin derivatives

Summary Polyclonal antibodies were produced against the highly purified enzymes L-hydantoinase, hydantoin-racemase and L-N-carbamoylamino acid amidohydrolase of Arthrobacter aurescens DSM 3747. In order to exploit these antibodies for basic research (molecular biology) or bioengineering (process development), the serological properties had to be characterized. Both, the hydantoinase- and carbamoylase-antibodies were observed to be monofunctional, whereas the hydantoin-racemase-antibody was found to be additionally specific against the L-hydantoinase. Monospecificity was realized after affinity chromatography. Investigations on serological crossreactions with several linear- and cyclic amidases (e.g. hydantoinases) as well as hydantoin-racemases are demonstrated in this paper.Deticated to Prof. Dr. Klaus Mosbach on the occation of his 60th birthday.     

Cloning,sequence analysis and expression of a cDNA encoding active phosphoenolpyruvate carboxylase of the C3 plant Solanum tuberosum

A cDNA coding for phosphoenolpyruvate carboxylase (PEPC) was isolated from a cDNA library from Solanum tuberosum and the sequence of the cDNA was determined. It was inserted into a bacterial expression vector and a PEPC^- Escherichia coli mutant could be complemented by the cDNA construct. A functional fusion protein could be synthesized in E. coli. The properties of this PEPC protein clearly resembled those of typical C3 plant enzymes.     

Axonal Glycoproteins with Immunoglobulin- and Fibronectin Type III-Related Domains in Vertebrates: Structural Features, Binding Activities, and Signal Transduction

Abstract: The L1- and F11-like axonal glycoproteins, implicated in neurite outgrowth and fasciculation, are members of the Ig superfamily comprising multiple fibronectin type III-like domains. Their Ig-like and fibronectin type III-related domains are likely to be composed of seven β-strands arranged in two opposing β-sheets of highly similar topology. Whereas the F11-like molecules lack a transmembrane sequence and are anchored in the plasma membrane by a glycosylphosphatidylinositol, the L1 -like molecules comprise cytoplasmic domains with highly conserved sequence motifs. Most of the latter proteins occur in different isoforms generated by alternative pre-mRNA splicing, which has not been documented for molecules of the F11 subgroup. L1 -like proteins undergo heterophils as well as homophilic interactions, whereas only the former mode of binding was observed for F11 -like proteins. Evidence is accumulating that these Ig superfamily molecules with fibronectin type III-like domains are interacting in a complex manner with each other and molecules of the extracellular matrix. Investigations assigning structure to function reveal that their individual extracellular domains serve distinct binding activities. Recent studies also suggest that L1 and NCAM are implicated in the transduction of transmembrane signals.     

A SIGNAL GLYCOPROTEIN WITH α-d-MANNOSYL RESIDUES IS INVOLVED IN THE WOUND-HEALING RESPONSE OF ANTITHAMNION SPARSUM (CERAMIALES,RHODOPHYTA)1

A variety of fluorescein isothiocyanate-labeled lectins specific for different sugar moieties were examined as probes for the wound-healing response in the filamentous red alga Antithamnion sparsum Tokida. Among them, only concanavalin A (ConA) and Lens culrinaris agglutinin (LCA), which have specificity to α-D-mannosyl residues, bound specifically to repair cells during the wound-healing process. When ConA or LCA was added at various time intervals after wounding, it first bound (3 h post-wounding) as a thin layer at the tips of the adjacent cells. Later (4–5 h post-wounding) labeling also appeared at the tips of the repair cells. Intense labeling at these sites continued throughout the healing process until repair cell fusion, at which time the lectin labeling was reduced to a narrow ring around the area of fusion. When added to plants prior to wounding and continually monitored, these same lectins acted as inhibitors to the wound-healing response. Other control lectins showed no inhibitory effects. A crude extract solution obtained from decapitated filaments stimulated the wound-healing response, and a lectin-binding component bound strongly to a protein-binding transfer membrane. These results suggest that the labeled compound is a glycoprotein that has α-D-mannosyl residues and is similar to the repair hormone rhodomorphin found in Griffithsia pacifica Kylin.     

An SAR sequence containing 395 bp DNA fragment mediates enhanced,gene-dosage-correlated expression of a chimaeric heat shock gene in transgenic tobacco plants

A 395 bp fragment located downstream from the soybean heat shock geneGmhsp 17.6-L exhibits several characteristics of scaffold attachment region (SAR) sequences. It contains matrix consensus elements, a topoisomerase II binding sequence and it associates with the isolated nuclear scaffold of soybeanin vitro. Chimaeric genes containing the SAR_L fragment either at one side (5 or 3) or at both sides of a heat shock promoter-regulated -glucuronidase reporter gene were constructed. A five-to nine-fold increase of heat-inducible -glucuronidase activity was observed in transgenic tobacco plants containing constructs with SAR_L fragments either at both sides or with at least one SAR_L copy located upstream from the reporter gene. The gene copy number is positively correlated with the level of heat-inducible reporter gene activity in these. plants but positional effects are not entirely eliminated. Thus, SAR sequences may potentially be used to increase gene expression, via as yet unknown mechanisms, and to reduce adverse effects on the expression of multiple gene copies in transgenic plants.     

ULTRASTRUCTURAL ASPECTS OF SEXUAL REPRODUCTION IN THE RED TIDE DINOFLAGELLATE GONYAULAX TAMARENSIS1

The marine dinoflagellate Gonyaulax tamarensis Lebour is best known for its propensity to form blooms known as red tides in coastal waters worldwide. This paper examines the sexual cycle of this organism using light and electron microscopy. Sexual reproduction begins with contact between thecate gametes which subsequently shed their thecae to fuse along their pellicular layers. Nuclear fusion occurs well after cytoplasmic fusion and is characterized by several distinctive features: a highly vesiculate nucleoplasm without microtubules; nucleoli and V-shaped chromosomes abut the nuclear envelope distal to the region of nuclear contact; and each chromosome possesses a longitudinal line, the central chromosomal axis. Fusion results in a planozygote with numerous cytoplasmic storage products and a slightly thickened layer beneath the pellicle. Subsequent loss of thecal plates and a thickening of the sub-pellicular layer results in a non-motile hypnozygote. A newly-formed hypnozygote possesses numerous minute papillae along its outer surface, formed by the up-folding of the accumulating wall layer. Maturation of the hypnozygote wall results in a smooth three-layered wall, the outermost layer of which is the pellicular layer. Hypnozygote germination produces a large quadriflagellate plan-omeiocyte with a single nucleus and thecal plates identical to vegetative cells. Two subsequent divisions, presumably meiotic, result in Jour cells morphologically identical to vegetative cells.