A New Technology for Applanation Free Corneal Trephination: The Picosecond Infrared Laser (PIRL)

The impact of using a Femtosecond laser on final functional results of penetrating keratoplasty is low. The corneal incisions presented here result from laser ablations with ultrafast desorption by impulsive vibrational excitation (DIVE). The results of the current study are based on the first proof-of-principle experiments using a mobile, newly introduced picosecond infrared laser system, and indicate that wavelengths in the mid-infrared range centered at 3 μm are efficient for obtaining applanation-free deep cuts on porcine corneas.     

Regulation of human T lymphocyte surface antigen mobility by purinergic receptors

The present study was undertaken to establish whether the capping mechanism of normal human T lymphocytes is regulated by a purinergic receptor. Interaction of T lymphocytes with adenosine significantly increased the mobility of the T3, T4, and T8 surface antigens. This enhanced rate of capping was reflected by a significant decrement in the time intervals to achieve half-maximal capping. T lymphocytes preincubated with theophylline or isobutylmethylxanthine did not exhibit accelerated capping or a decrease in the time required for half-maximal capping in response to adenosine, suggesting that these agents inhibited the binding of adenosine to its receptor. A role for a cAMP-dependent pathway in capping was suggested by the observation that the phosphodiesterase inhibitor RO-201724 caused a decrease in the concentration of adenosine required to accelerate the capping process. Moreover, exposure of T lymphocytes to the cyclic nucleotide derivatives 8-N3-cAMP and 8-Br-cAMP mimicked the effect of adenosine, significantly reducing the time to half-maximal capping. Photoaffinity labeling of intracellular cAMP receptors with 32P-8-N3-cAMP indicated that adenosine caused occupancy of the receptors. This effect of adenosine was inhibited by theophylline, a known purinergic receptor blocker. The data support the concept that the T cell capping mechanism is mediated by an adenylate cyclase-coupled purinergic receptor that activates a cAMP-dependent pathway, and that this pathway is functional in the T3+, T4+, (inducer) and T3+, T8+ (suppressor) subsets.     

The origin of the nitrogen atom in the thiazole ring of thiamine in Escherichia coli

Methods are described for the isolation and gas chromatographic-mass spectrometric analysis of the 4-methyl-5-β-hydroxyethyl thiazole moiety of thiamine in microbial cells. Using these methods, it was determined that in Escherichia coli the nitrogen atom in the thiazole ring of thiamine is derived solely from l-tyrosine.     

Chemische Untersuchung der Nostochaceen

Ohne Zusammenfassung     

Inhibition of dehydration-induced fusion between liposomal membranes by carbohydrates as measured by fluorescence energy transfer

The relative abilities of a number of naturally occurring carbohydrates to inhibit dehydration-induced fusion between palmitoyloleoylphosphatidylcholine:phosphatidylserine (85:15) large unilamellar vesicles have been studied. Fusion events were quantified using a fluorescence resonance energy transfer technique. Trehalose was most effective at inhibiting fusion (0.4 g/trehalose/g lipid showed 30% probe intermixing), followed by maltose (60% intermixing), fructose (60%), sucrose (70%), glucose (80%), cellobiose, glycerol, raffinose, and myo-inositol (90%). The relative abilities of these carbohydrates to inhibit fusion correlate directly with their abilities to interact with phospholipids, maintain bilayer fluidity, and preserve biological membranes. The results are discussed in relation to the crystalline structure of the carbohydrates and their possible influence on level of interaction with phosphate head groups.     

The agonistic adrenal: melatonin elicits female aggression via regulation of adrenal androgens

Classic findings have demonstrated an important role for sex steroids as regulators of aggression, but this relationship is lacking within some environmental contexts. In mammals and birds, the adrenal androgen dehydroepiandrosterone (DHEA), a non-gonadal precursor of biologically active steroids, has been linked to aggression. Although females, like males, use aggression when competing for limited resources, the mechanisms underlying female aggression remain understudied. Here, we propose a previously undescribed endocrine mechanism regulating female aggression via direct action of the pineal hormone melatonin on adrenal androgens. We examined this in a solitary hamster species, Phodopus sungorus, in which both sexes are highly territorial across the seasons, and display increased aggression concomitant with decreased serum levels of sex steroids in short ‘winter-like'' days. Short- but not long-day females had increased adrenal DHEA responsiveness co-occurring with morphological changes in the adrenal gland. Further, serum DHEA and total adrenal DHEA content were elevated in short days. Lastly, melatonin increased DHEA and aggression and stimulated DHEA release from cultured adrenals. Collectively, these findings demonstrate that DHEA is a key peripheral regulator of aggression and that melatonin coordinates a ‘seasonal switch’ from gonadal to adrenal regulation of aggression by direct action on the adrenal glands.     

Influence of Nutrient Concentrations on MPN Quantification and Enrichment of Nitrate-Reducing Fe(II)-Oxidizing and Fe(III)-Reducing Bacteria from Littoral Freshwater Lake Sediments

The application of culture-dependent studies to quantify Fe-metabolizing microorganisms from the environment is a necessity, as there are so far no universal functional marker genes for application in culture-independent studies. Media composition can vary between studies, therefore, we determined the effects of three different growth media on the quantification (MPNs) and identity (via cloning and sequencing of dominant DGGE bands) of nitrate-reducing Fe(II)-oxidizers and lactate- or acetate-oxidizing Fe(III)-reducers from a lacustrine sediment: low sulphate freshwater medium (FWM), sterile filtered bicarbonate-buffered lake water (BLW) and a mixture of both (MIX). We consistently found fewer cells in the BLW than in the FWM and the MIX. The DGGE banding patterns of the microbial communities enriched in different media types clustered together according to the e^? donor and acceptor couples and not according to the medium used. Thus, although the medium composition significantly influenced the quantification and thereby conclusions on the abundance and potential significance of the targeted group within the ecosystem, biodiversity assessments through enrichment cultures were less influenced by the medium, but instead were affected by the type and concentration of the e^? donor/acceptor.     

Pronounced differences in the frequency of TaqI βA-inhibin alleles between sheep breeds with different reproductive performance

A total of 419 individuals of four breeds with differing fecundity (Rhoenschaf, Merinolandschaf, East Friesian Milksheep, Romanov) and several wild sheep of the Ovis musimon, O. orientalis, O. vignei and O. ammon groups were screened for genetic variation at the βA-inhibin (INHBA) locus with up to 11 enzymes. The four breeds differed significantly (P< 0.001) in TaqI allele frequencies. The frequency of the TaqI A allele coincided with the average litter size in each breed.     

Chemotaxis and phototaxis require a CheA histidine kinase in the archaeon Halobacterium salinarium.

Histidine kinases are part of the two-component signal transduction system responsible for eubacterial responses to diverse environmental signals. They have recently been detected in eukaryotes but their existence in the kingdom Archaea remains uncertain. Here we report the sequence and function of a histidine kinase (CheAH.s.) from Halobacterium salinarium, the first such transmitter in Archaea. The protein CheAH.s. (668 residues) has significant sequence identity with the CheA proteins known from eubacterial signal transduction (e.g. 34% identity with CheA from Bacillus subtilis). Antibodies were raised against CheAH.s. as expressed in Escherichia coli and were used in Western blotting to demonstrate the expression of cheAH.s. in H. salinarium. As has been observed for other halophilic proteins, CheAH.s. has a deviant electrophoretic migration, with an apparent molecular weight of 103 kDa on SDS-PAGE compared with a calculated molecular weight of 72 kDa. Deletion of a part of the cheAH.s. gene leads to loss of both chemotactic and phototactic responses in H. salinarium as measured by swarm plate assays, motion analysis and tethering experiments. This indicates that CheAH.s. plays a crucial role in chemical and light signal integration, presumably interacting with at least two phototransducers and a number of chemoreceptors.