Ethylene and IAA interactions in the inhibition of photoperiodic flower induction of <Emphasis Type="Italic">Pharbitis nil</Emphasis>

It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis.     

Fickean and Non-Fickean Water Desorption During Vacuum Drying of <Emphasis Type="Italic">L. bulgaricus</Emphasis>

The recovery of Lactobacillus bulgaricus was studied in correlation to the kinetics of cell drying. When bacteria were dehydrated at 30 °C, either in the presence or the absence of sucrose, the drying kinetics corresponds to a Fickean diffusion in correspondence with a short lag time. In contrast, when the bacteria were dehydrated at 70 °C in the absence of sugar, the kinetics corresponds to an anomalous diffusion, and the lag time is four to five times higher than that at 30 °C. However, when drying at 70 °C was carried out in the presence of sucrose, drying kinetics turned into a Fickean process parallel to a substantial decrease in the lag time. The pattern of water desorption was correlated with the critical water activity. When the drying kinetics corresponds to a Fickean diffusion, the lag time started to increase at 0.7 water activity, but when the cells were dried at 70 °C, the damage started at 0.5 water activity. This observation indicates that the drying rate affects the pattern of water desorption, and it can change the value of critical water activity. These results put into relevance that the cell recovery is due to the drying history and that the recovery increase produced by sucrose can be related to the maintenance of kinetic barriers for water desorption.     

Neural inhibition sharpens auditory spatial selectivity of bat inferior collicular neurons

This study examines the role of neural inhibition in auditory spatial selectivity of inferior collicular neurons of the big brown bat, Eptesicus fuscus, using a two-tone inhibition paradigm. Two-tone inhibition decreases auditory spatial response areas but increases the slopes of directional sensitivity curves of inferior collicular neurons. Inferior collicular neurons have either directionally-selective or hemifield directional sensitivity curves. A directionally-selective curve always has a peak which is at least 50% larger than the minimum. A hemifield directional sensitivity curve rises from an ipsilateral angle by more than 50% and either reaches a plateau or declines by less than 50% over a range of contralateral angles. Two-tone inhibition does not change directionally-selective curves but changes most hemifield directional sensitivity curves into directionally-selective curves. Auditory spatial selectivity determined both with and without two-tone inhibition increases with increasing best-excitatory frequency. Sharpening of auditory spatial selectivity by two-tone inhibition is larger for neurons with smaller differences between excitatory and inhibitory best frequencies. The effect of two-tone inhibition on auditory spatial selectivity increases with increasing inhibitory tone intensity but decreases with increasing intertone interval. The implications of these findings in bat echolocation are discussed. Accepted: 18 January 2000     

Structural characterization and dynamics of globotetraosylceramide in vascular endothelial cells under TNF-α stimulation

In several vascular inflammatory reactions (i.e. immunity and thrombosis) inflammatory mediators lead to the activation of vascular endothelial cells (EC). To date, a number of functional molecules induced on the surface of activated-EC have been identified. We report here that Globotetraosylceramide (Gb4), a glycosphingolipid expressed in EC, is a novel inducible molecule on EC activated by TNF-α. The cell surface expression of Gb4 is increased in a time-dependent manner under TNF-α stimulation, which shows distinct expression kinetics of major proteins induced by TNF-α on EC. MALDI-TOF-MS analysis revealed that the enhanced Gb4 predominantly contains C24:0 fatty acid in the ceramide moiety. Isolated caveolae/lipid raft-enriched detergent insoluble membrane domains in activated-EC predominantly contain this molecular species of Gb4. Gb4 containing C16:0 fatty acid in the ceramide moiety, which is known to constitute the major species of Gb4 in plasma, is also found as a major molecular species in EC. These observations indicate that Gb4, especially with very long fatty acid, is enhanced in EC during its inflammatory reaction, and suggest the potential utility of Gb4 as a biomarker for monitoring inflammation status of EC involving its related diseases.     

Multimeric bivalent immunogens from recombinant tetanus toxin H<Subscript>C</Subscript> fragment,synthetic hexasaccharides,and a glycopeptide adjuvant

Using recombinant tetanus toxin H_C fragment (rTT-H_C) as carrier, we prepared multimeric bivalent immunogens featuring the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Ogawa, in combination with either the synthetic hexasaccharide fragment of O-PS of Vibrio cholerae O:1, serotype Inaba, or a synthetic disaccharide tetrapeptide peptidoglycan fragment as adjuvant. The conjugation reaction was effected by squaric acid chemistry and monitored in virtually real time by SELDI-TOF MS. In this way, we could prepare well-defined immunogens with predictable carbohydrate–carrier ratio, whose molecular mass and the amount of each saccharide attached could be independently determined. The ability to prepare such neoglycoconjugates opens unprecedented possibilities for preparation of conjugate vaccines for bacterial diseases from synthetic carbohydrates.     

Superoxide dismutase is upregulated in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> following protoporphyrin-mediated photodynamic inactivation and does not directly influence the response to photodynamic treatment

Background  

Staphylococcus aureus, a major human pathogen causes a wide range of disease syndromes. The most dangerous are methicillin-resistant S. aureus (MRSA) strains, resistant not only to all β-lactam antibiotics but also to other antimicrobials. An alarming increase in antibiotic resistance spreading among pathogenic bacteria inclines to search for alternative therapeutic options, for which resistance can not be developed easily. Among others, photodynamic inactivation (PDI) of S. aureus is a promising option. Photodynamic inactivation is based on a concept that a non toxic chemical, called a photosensitizer upon excitation with light of an appropriate wavelength is activated. As a consequence singlet oxygen and other reactive oxygen species (e.g. superoxide anion) are produced, which are responsible for the cytotoxic effect towards bacterial cells. As strain-dependence in photodynamic inactivation of S. aureus was observed, determination of the molecular marker(s) underlying the mechanism of the bacterial response to PDI treatment would be of great clinical importance. We examined the role of superoxide dismutases (Sod) in photodynamic inactivation of S. aureus as enzymes responsible for oxidative stress resistance.     

SuperSAGE analysis of the <Emphasis Type="Italic">Nicotiana attenuata</Emphasis> transcriptome after fatty acid-amino acid elicitation (FAC): identification of early mediators of insect responses

Background  

Plants trigger and tailor defense responses after perception of the oral secretions (OS) of attacking specialist lepidopteran larvae. Fatty acid-amino acid conjugates (FACs) in the OS of the Manduca sexta larvae are necessary and sufficient to elicit the herbivory-specific responses in Nicotiana attenuata, an annual wild tobacco species. How FACs are perceived and activate signal transduction mechanisms is unknown.