Chlorophylle und Carotinoide der Chaetophorineae (Chlorophyceae; Ulotrichales)

In air-supplied inorganic liquid cultures, the highly differentiated green alga Fritschiella tuberosa forms only branched filaments with long slender cells. In nitrogen-deficient medium and with ageing of the cultures these cells become much shorter in length by subsequent formation of transverse walls. The chloroplasts of the slender cells contain the typical pigments of green algae. Together with the morphogenetic change to “short cells” secondary carotenoids are synthesized and stored in lipid droplets. Besides traces of lutein, violaxanthin and neoxanthin and reduced amounts of β-carotene, the following pigments have been demonstrated: Esters of astaxanthin (main pigment) and adonixanthin, canthaxanthin, echinenone and a Keto-α-carotinoid, which presumably is identical with α-doradexanthin, (3,3′-Dihydroxy-4-keto-α-Carotene) a pigment not known in plants until now. In nitrogen deficient cultures the chlorophylls are totally decomposed, the total-lipids increase by about 500%. By supplying nitrogen-deficient cultures with nitrogen and subsequent illumination regreening of the cells starts already 16 hrs later.     

Post-embedding localization of glycoconjugates by means of lectins on thin sections of tissues embedded in LR white

Summary A simple post-embedding technique for the electron microscopical detection of lectin-binding sites using thin sections of tissues embedded in the resin LR White is described. With this technique, no prior etching of the sections is necessary. The cellular fine structure is well preserved and permits close correlation of the labelling to distinct cellular compartments. After mild aldehyde fixation (4% formaldehyde and 0.5% glutaraldehyde for 30 min), enterocyte brush border, vesicles and lysosomes as well as goblet cell Golgi apparatus and mucin are intensely stained after 30–60 min.The hydrophilia and penetrability of LR White is shown by the formation of oxidized diaminobenzidine reaction product arising from horseradish peroxidase-conjugated lectins. The precipitate not only covers the surface of the sections but is also formed within the resin, as is revealed on cross-sections through thin and semithin sections. The addition of 0.2m solutions of the appropriate inhibitory sugars prevented staining, which indicates a specific binding. Examples are given of the binding of gold-, ferritin- and peroxidase-conjugated lectins for the purpose of detecting glycoconjugates in various intracellular compartments.     

Cyanogenic compounds as protecting agents for organisms

Biochemical and physiological arguments and several plant-predator relationships described in the literature are presented in which cyanogenesis plays a role as a protecting process. HCN arising from the cleavage of cyanogenics is regarded to be the most important agent, but also the cyanogenic itself, carbonyls and -cyanoalanine, which are products of degradation processes of cyanogenics, may possess protecting properties. Some examples show that these substances are also utilized by arthropods. This presents the opportunity to look at a coevolutionary system combined of snails, plants, moths and moth-parasites in which cyanogenesis obviously plays an interesting role.Lecture presented during the Tagung der Deutschen Botanischen Gesellschaft, Vienna, September 1984.     

Electron microprobe analysis of frog skin epithelium: Evidence for a syncytial sodium transport compartment

Summary For elucidation of the functional organization of frog skin epithelium with regard to transepithelial Na transport, electrolyte concentrations in individual epithelial cells were determined by electron microprobe analysis. The measurements were performed on 1-m thick freeze-dried cryosections by an energy-dispersive X-ray detecting system. Quantification of the electrolyte concentrations was achieved by comparing the X-ray intensities obtained in the cells with those of an internal albumin standard.The granular, spiny, and germinal cells, which constitute the various layers of the epithelium, showed an identical behavior of their Na and K concentrations under all experimental conditions. In the control, both sides of the skin bathed in frog Ringer's solution, the mean cellular concentrations (in mmole/kg wet wt) were 9 for Na and 118 for K. Almost no change in the cellular Na occurred when the inside bathing solution was replaced by a Na-free isotonic Ringer's solution, whereas replacing the outside solution by distilled water resulted in a decrease of Na to almost zero in all layers. Inhibition of the transepithelial Na transport by ouabain (10^–4 m) produced an increase in Na to 109 and a decrease in K to 16. The effect of ouabain on the cellular Na and K concentrations was completely cancelled when the Na influx from the outside was prevented, either by removing Na or adding amiloride (10^–4 m). When, after the action of ouabain, Na was removed from the outside bathing solution, the Na and K concentration in all layers returned to control values. The latter effect could be abolished by amiloride.The other cell types of the epithelium showed under some experimental conditions a different behavior. In the cornified cells and the light cells, which occurred occasionally in the stratum granulosum, the electrolyte concentrations approximated those of the outer bathing meium under all experimental conditions. In the mitochondria-rich cells, the Na influx after ouabain could not be, prevented by adding amiloride. In the gland cells, only a small change in the Na and K concentrations could be detected after ouabain.The results of the present study are consistent with a two-barrier concept of transepithelial Na transport. The Na transport compartment comprises all living epithelial layers. Therefore, with the exception of some epithelial cell types, the frog skin epithelium can be regarded as a functional syncytium for Na.     

Translocation of histone proteins across lipid bilayers and Mycoplasma membranes

We show that the three core histones H2A, H3 and H4 can transverse lipid bilayers of large unilamellar vesicles (LUVs) and multilamellar vesicles (MLVs). In contrast, the histone H2B, although able to bind to the liposomes, fails to penetrate the unilamellar and the multilamellar vesicles. Translocation across the lipid bilayer was determined using biotin-labeled histones and an ELISA-based system. Following incubation with the liposomes, external membrane-bound biotin molecules were neutralized by the addition of avidin. Penetrating biotin-histone conjugates were exposed by Triton treatment of the neutralized liposomes. The intraliposomal biotin-histone conjugates, in contrast to those attached only to the external surface, were attached to the detergent lysed lipid molecules. Thus, biotinylated histone molecules that were exposed only following detergent treatment of the liposomes were considered to be located at the inner leaflet of the lipid bilayers. The penetrating histone molecules failed to mediate translocation of BSA molecules covalently attached to them. Translocation of the core histones, including H2B, was also observed across mycoplasma cell membranes. The extent of this translocation was inversely related to the degree of membrane cholesterol. The addition of cholesterol also reduced the extent of histone penetration into the MLVs. Although able to bind biotinylated histones, human erythrocytes, erythrocyte ghosts and Escherichia coli cells were impermeable to them. Based on the present and previous data histones appear to be characterized by the same features that characterize cell penetrating peptides and proteins (CPPs).     

Studien über Dedifferenzierung bei der Seeanemone Aiptasia carnea Andr

Ohne ZusammenfassungZeichenerklärung zu den Abbildungen C Kutikula - D Deckschicht - Dj junge Drüsenzellen - Ec Ektoderm - En Entoderm - Gz Ganglienzellen - Kd Körnerdrüsenzellen - M Mesogloea - Mf Mesenterialfilament - Mu Muskelfasern - Nf Nervenfaserschicht - Nz Nesselzellen - P Phagozyten - Se Septum - St Stützzellen - Sy symbiontische Algen - Sz Schleimzellen - Tf Tonofibrillen     

Characterization of a high-affinity monoclonal antibody specific for CD44v6 as candidate for immunotherapy of squamous cell carcinomas

 Variant isoforms of CD44, a family of cell-surface glycoproteins generated by alternative splicing and post-translational modifications, are expressed in a variety of human tumors and play important roles in tumor progression and metastasis formation. The murine monoclonal IgG1 antibody VFF18, specific for an epitope encoded by human CD44 variant exon 6, binds with high affinity to the recombinant protein (K _d = 1.7×10^–10 M) as well as to tumor cell lines in vitro, and is suitable for immunohistochemical analysis of human tumors. Screening of more than 500 tumor samples of different histogenesis showed that VFF18 most strongly and uniformly reacts with squamous cell carcinomas (SCC). Detailed analysis of 185 SCC (head and neck, lung, skin) confirmed reactivity of the antibody with 99% of the samples, with intense and homogeneous staining of the tumor cells in the majority of cases, whereas reactivity of VFF18 with normal tissues is limited to certain epithelia and activated lymphocytes. When radiolabelled VFF18 was administered to nude mice bearing human epidermoid carcinoma (A-431) xenograft, fast and selective tumor uptake of the radioimmunoconjugate with a maximum of 18% of the injected dose per gram of tissue was observed. Taken together, these data suggest that mAb VFF18 is a promising targeting vehicle for radioimmunotherapy of squamous cell carcinomas in humans. Received: 9 September 1996 / Accepted: 25 September 1996