New details on the morphology of fossil onagraceous pollen grains

Fossil onagraceous pollen grains from two Upper Miocene localities in E. Austria were investigated by LM and EM. Exine structure and sculpture as well as viscin threads suggest affinities with the extant genusCircea.     

Dominant expression of an amino-acid uptake deficiency in carrot somatic fusion hybrids

Somatic hybrids were selected previously by their ability to grow in medium containing normally inhibitory levels of the two amino acid analogs aminoethylcysteine (AEC) and 5-methyltryptophan (5MT) following fusion of protoplasts from a cell strain resistant to AEC with protoplasts resistant to 5MT. The hybrid nature of the selected clones was shown by several criteria including the presence of another resistance, azetidine-2-carboxylate (A2C), carried by one of the parental strains which was not selected for in the initial hybrid selection scheme. The characterization presented here shows that the AEC resistance in the parental strain, as well as the two somatic hybrids, was due to decreased AEC uptake. Also the 5MT resistance in the hybrids, as in the parent was caused by a feedback altered form of the tryptophan biosynthetic control enzyme, anthranilate synthase which leads to increases in free tryptophan. The A2C resistance was caused by the accumulation of free proline by a mechanism which has not been studied. These studies confirm that AEC resistance caused by decreased uptake can be expressed dominantly in protoplast fusion hybrids.Abbreviations A2C Azetidine-2-carboxylate - AEC Aminoethylcysteine - 5MT 5-methyltryptophan     

Metabolism of some carcinogenic aromatic amines in four species of marine sponges

Postmitochondrial fractions from marine sponges Geodia cydonium, Tethya aurantium, Verongia aerophoba and Pellina semitubulosa activate precarcinogenic aromatic amine 2-aminoanthracene, but not precarcinogenic polycyclic aromatic hydrocarbon benzo(a)pyrene, to Salmonella typhimurium TA 98 mutagens. All four sponge species lack a benzo(a)pyrene monooxygenase activity, but possesses the enzyme activity whose characteristics (selective activation of aromatic amines, NADPH-dependency, pH optimum at 8.4) are similar to FAD-containing monooxygenase. Tethya postmitochondrial fraction possesses an UDP-glucuronyl transferase activity which catalyzes the conjugation of a considerable part of metabolized 2-acetylamino [9-14C]fluorene to water soluble glucuronides. The possible ecological significance of exuded aromatic amine metabolites as well as the significance of the presence of the selective potential for the activation of aromatic amines to mutagens among sponges for our understanding of the fate and effects of carcinogens in the marine environment are discussed.     

Occurrence of Mycoplasma-like Organisms in Parenchyma Cells of Cuscuta odorata (Ruiz et Pav.)

In shoots of the dodder Cuscuta odorata mycoplasma-like organisms (MLO) were observed to occur in nearly all mature sieve elements. Their frequency within the sieve elements varied from a few organisms to high concentrations. In addition, MLO, were found in other cell types. By identifying these cells and investigating the location in the vascular tissue three different types of cells infected with MLO could be distinguished: (1) phloem parenchyma cells, (2) parenchyma cells separating the five vascular bundles of C. odorata and (3) cells in the outer region of the vascular system next to the cells looking like an endodermis. Within the cells of the types 2 and 3, MLO occurred in large numbers and at different morphological structures., Therefore, we assume that the MLO multiply in these cells.     

Lipopeptides of the N-terminus of Escherichia coli lipoprotein: synthesis, mitogenicity and properties in monolayer experiments

The N-terminal part of the lipoprotein from the outer membrane of Escherichia coli, tripalmitoyl-S-glyceryl-L-Cys-Ser and analogs with longer sequences, are polyclonal activators for B-lymphocytes. Triple-chain lipopeptides also constitute efficient low-molecular-weight carrier/adjuvant systems, which can be linked to antigens to yield immunogens for antibody production without further additives. This is the first report of monolayer experiments with chemically well defined, synthetic lipopeptide mitogens with the composition of the N-terminus of an important bacterial membrane protein. Various derivatives of the lipoprotein N-terminus were synthesized. These lipopeptides differed in the length of the peptide moiety, the number of fatty acid residues, and protective groups. In order to obtain the surface areas for the lipopeptides in isotherms and hysteresis isotherms, monolayer experiments with a computer-controlled film balance were performed. To get some information about the interaction of these compounds with typical membrane lipids mixed monolayers were formed from triple-chain lipopeptides with dipalmitoylphosphatidylcholine and cholesterol. A comparison of the mitogenic response of the compounds was made in an in vitro system with B-lymphocytes from Balb/c mice.     

Transmission of hapten-specific tolerance to an unrelated carrier

The principle of linked recognition is well defined in response and suppression. Yet, to our knowledge, it is not explored in the context of tolerance. To investigate, whether the status of tolerance toward a hapten (TNP) can be transferred to a subsequently introduced carrier, animals which were tolerized by a subimmunogenic dose of hapten (TNP) coupled to syngeneic monoclonal anti-TNP IgG, with the rationale of combining the phenomena of low zone tolerance and syngeneic IgG-induced suppression, were challenged with TNP-horse red blood cells (HRBC). Conjugates of high density (40 mM) TNP-syngeneic IgG (TNP40-IgG) were immunogenic and after challenge with TNP-HRBC, animals responded to TNP and to HRBC. Yet, spleen cells (SC) of mice injected with TNP2.5-IgG and challenged with TNP-HRBC were tolerant against TNP as well as the carrier. Limiting dilution (LD) analysis revealed that subimmunogenic doses of TNP coupled to IgG resulted in diminished activation of help, failure to activate contrasuppressor T cells (TCS), and significantly augmented activation of suppressor T cells (TS). On the other hand, after challenge with TNP-HRBC, activation/expansion of carrier-specific helper (TH), suppressor, and contrasuppressor T cells were not affected by previous immunization with subimmunogenic or immunogenic doses of TNP-IgG conjugates, but HRBC-specific TCS could not interact with TNP-specific TS. Hence, to initiate tolerance it was necessary (and sufficient) that an activated and expanded TS population was not counterregulated by TCS. In this situation, an established status of dominance of suppression for the epitope TNP could not be disrupted by an immunogene carrying a multitude of new epitopes; i.e., tolerization by subimmunogenic doses of the individual epitope TNP resulted in unresponsiveness against any immunogen carrying this epitope.     

Thermal phase behaviour and structure of hydrated mixtures between dipalmitoyl- and dihexadecylphosphatidylcholine

Mixtures of 1,2-dipalmitoyl- and 1,2-O-dihexadecyl-sn-glycero-3-phosphocholine (DPPC and DHPC) in dispersion with excess water were studied by differential scanning calorimetry (DSC) and X-ray diffraction techniques. The transition parameters of the main gel-to-liquid crystalline transition show a monotonous dependence on the composition, indicating ideal miscibility of the two lipids, in keeping with the closely similar structures of the pure, hydrated lipids in the P beta' and L alpha states. The pre-transition shows a depression to a minimum temperature of 23 degrees C occurring around equimolar mixtures. Below the pre-transition temperatures, the L beta' gel phase of DPPC maintains bimolecular structure up to DHPC admixtures of 50 mol%, with adaptations in hydrocarbon chain packing and multilayer periodicity. On the side of DHPC, the interdigitated gel structure shows full solubility for DPPC up to equimolarity without major structural changes. The crystalline Lc-phase of DPPC exhibits immiscibility with DHPC, demonstrated by the fact that the subtransition is abolished already at less than 15 mol% DHPC. DHPC, below its subtransition, can accommodate up to 50 mol% DPPC within an interdigitated layer structure with unperturbed, crystalline hydrocarbon chain packing.     

The effects of experimental hypo- and hyperthyroidism on blood viscosity and other blood parameters in the rat

Three groups of male Sprague Dawley rats received methimazole without or with Na-thyroxine in drinking water (3 and 0.33 mg T4/l, respectively) to induce characteristic alterations of their thyroid status (hypothyroid, hyperthyroid, euthyroid). A fourth group served as an untreated control without any additive to the drinking water. With respect to the different thyroid status, the following changes in the blood parameters were found: increasing plasma-T3-levels caused a reduction in plasma viscosity, in total plasma protein and in alpha 1-globulin, but an increase in hematocrit, whole blood viscosity, the number of erythrocytes and leukocytes, alpha 2-globulin and beta-globulin. It was concluded that the increase in the plasma viscosity in the hypothyroid status is mainly due to an alteration of the plasma protein pattern, and that the increase in whole blood viscosity in the hyperthyroid rat is a consequence of increased hematocrit.