Untersuchungen über den Gehörsinn bei Characiniden und Gymnotiden und den Bau Ihres Labyrinthes

Ohne Zusammenfassung     

DnaB proteolysis in vivo regulates oligomerization and its localization at oriC in Bacillus subtilis

Initiation of bacterial DNA replication at oriC is mediated by primosomal proteins that act cooperatively to melt an AT-rich region where the replicative helicase is loaded prior to the assembly of the replication fork. In Bacillus subtilis, the dnaD, dnaB and dnaI genes are essential for initiation of DNA replication. We established that their mRNAs are maintained in fast growing asynchronous cultures. DnaB is truncated at its C-terminus in a growth phase-dependent manner. Proteolysis is confined to cytosolic, not to membrane-associated DnaB, and affects oligomerization. Truncated DnaB is depleted at the oriC relative to the native protein. We propose that DNA-induced oligomerization is essential for its action at oriC and proteolysis regulates its localization at oriC. We show that DnaB has two separate ssDNA-binding sites one located within residues 1–300 and another between residues 365–428, and a dsDNA-binding site within residues 365–428. Tetramerization of DnaB is mediated within residues 1–300, and DNA-dependent oligomerization within residues 365–428. Finally, we show that association of DnaB with the oriC is asymmetric and extensive. It encompasses an area from the middle of dnaA to the end of yaaA that includes the AT-rich region melted during the initiation stage of DNA replication.     

The Identification of Congeners and Aliens by Drosophila Larvae

We investigated the role of Drosophila larva olfactory system in identification of congeners and aliens. We discuss the importance of these activities in larva navigation across substrates, and the implications for allocation of space and food among species of similar ecologies. Wild type larvae of cosmopolitan D. melanogaster and endemic D. pavani, which cohabit the same breeding sites, used species-specific volatiles to identify conspecifics and aliens moving toward larvae of their species. D. gaucha larvae, a sibling species of D. pavani that is ecologically isolated from D. melanogaster, did not respond to melanogaster odor cues. Similar to D. pavani larvae, the navigation of pavani female x gaucha male hybrids was influenced by conspecific and alien odors, whereas gaucha female x pavani male hybrid larvae exhibited behavior similar to the D. gaucha parent. The two sibling species exhibited substantial evolutionary divergence in processing the odor inputs necessary to identify conspecifics. Orco (Or83b) mutant larvae of D. melanogaster, which exhibit a loss of sense of smell, did not distinguish conspecific from alien larvae, instead moving across the substrate. Syn ^97CS and rut larvae of D. melanogaster, which are unable to learn but can smell, moved across the substrate as well. The Orco (Or83b), Syn ^97CS and rut loci are necessary to orient navigation by D. melanogaster larvae. Individuals of the Trana strain of D. melanogaster did not respond to conspecific and alien larval volatiles and therefore navigated randomly across the substrate. By contrast, larvae of the Til-Til strain used larval volatiles to orient their movement. Natural populations of D. melanogaster may exhibit differences in identification of conspecific and alien larvae. Larval locomotion was not affected by the volatiles.     

Multifunctional liposomes for nasal delivery of the anti-Alzheimer drug tacrine hydrochloride

The purpose of this study was the development of multifunctional liposomes for nasal administration of tacrine hydrochloride. Liposomes were prepared using traditional excipients (cholesterol and phosphatidylcholine), partly enriched with α-tocopherol and/or Omega3 fatty acids. This approach was chosen in order to obtain at the same time two positive results: an enhanced drug permeation through nasal mucosa and a concomitant neuroprotective effect. Several liposome formulations were prepared using the Reverse Phase Evaporation technique followed by membrane filter extrusion. In particular, liposome capacity to enhance drug permeation was evaluated by means of membrane permeation and cellular uptake studies. Furthermore, liposome effect on neuronal viability and intracellular ROS production was evaluated as well as their cytoprotective effect against oxidative stress. All liposome formulations showed a mean diameter in the range of 175?nm to 219?nm with polydispersity index lower than 0.22, a lightly negative zeta potential and excellent encapsulation efficiency. Moreover, along with good mucoadhesive properties, multifunctional liposomes showed a markedly increase in tacrine permeability, which can be related to liposome fusion with cellular membrane, a hypothesis, which was also supported by cellular uptake studies. Finally, the addition of α-tocopherol without Omega3 fatty acids, was found to increase the neuroprotective activity and antioxidant properties of liposomes.     

Altered Intracellular Localization of SOD1 in Leukocytes from Patients with Sporadic Amyotrophic Lateral Sclerosis

Several lines of evidence support the hypothesis of a toxic role played by wild type SOD1 (WT-SOD1) in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). In this study we investigated both distribution and expression profile of WT-SOD1 in leukocytes from 19 SALS patients and 17 healthy individuals. Immunofluorescence experiments by confocal microscopy showed that SOD1 accumulates in the nuclear compartment in a group of SALS subjects. These results were also confirmed by western blot carried out on soluble nuclear and cytoplasmic fractions, with increased nuclear SOD1 level (p<0.05). In addition, we observed the presence of cytoplasmic SOD1 aggregates in agreement with an increased amount of the protein recovered by the insoluble fraction. A further confirmation of the overall increased level of SOD1 has been obtained from single cells analysis using flow cytometry as cells from SALS patients showed an higher SOD1 protein content (p<0.05). These findings add further evidence to the hypothesis of an altered WT-SOD1 expression profile in peripheral blood mononuclear cells (PBMCs) from patients with ALS suggesting that WT-SOD1 species with different degrees of solubility could be involved in the pathogenesis of the disease.     

TBCD Links Centriologenesis,Spindle Microtubule Dynamics,and Midbody Abscission in Human Cells

Microtubule-organizing centers recruit α- and β-tubulin polypeptides for microtubule nucleation. Tubulin synthesis is complex, requiring five specific cofactors, designated tubulin cofactors (TBCs) A–E, which contribute to various aspects of microtubule dynamics in vivo. Here, we show that tubulin cofactor D (TBCD) is concentrated at the centrosome and midbody, where it participates in centriologenesis, spindle organization, and cell abscission. TBCD exhibits a cell-cycle-specific pattern, localizing on the daughter centriole at G1 and on procentrioles by S, and disappearing from older centrioles at telophase as the protein is recruited to the midbody. Our data show that TBCD overexpression results in microtubule release from the centrosome and G1 arrest, whereas its depletion produces mitotic aberrations and incomplete microtubule retraction at the midbody during cytokinesis. TBCD is recruited to the centriole replication site at the onset of the centrosome duplication cycle. A role in centriologenesis is further supported in differentiating ciliated cells, where TBCD is organized into “centriolar rosettes”. These data suggest that TBCD participates in both canonical and de novo centriolar assembly pathways.     

LIFE HISTORY AND GROWTH OF LAURENCIA BRACHYCLADOS (RHODOPHYTA,CERAMIALES)1

Laurencia brachyclados Pilger from Hawai'i completed a “Polysiphonia-type” tri-phasic life history in 21 weeks in laboratory culture. Tetraspores developed into gametophytes in a nearly 1:1:1 ratio of females: males: non-reproductive. Carpospores were released as early as 21 days after mixing virgin female and male gametophytes. Cultured thalli showed a “guerilla type” growth form. Other Hawaiian Laurencia species in culture had longer maturation times or remained non-reproductive. Variation in life history schedules may influence Laurencia species coexistence and algal community structure.     

Effect of transforming growth factor beta (TGF-β) on ATP citrate lyase in isolated hepatocytes

Summary Transforming growth factor beta (TGF-) activates ATP citrate lyase in freshly isolated rat liver hepatocytes in a time dependent manner. Maximal stimulation of the enzyme occurred with less than thirty minutes of incubation of the cells with TGF-. The half maximal effect on the enzyme determined in hepatocytes incubated with TGF- for 10 min at 37°C was elicited by TGF- concentrations in the 10^–11 – 10^–12 M range. The potential role of TGF- stimulation of ATP citrate lyase activity in new membrane synthesis is discussed.