Adaptation for horizontal transfer in a homing endonuclease

Selfish genes of no function other than self-propagation are susceptible to degeneration if they become fixed in a population, and regular transfer to new species may be the only means for their long-term persistence. To test this idea we surveyed 24 species of yeast for VDE, a nuclear, intein-associated homing endonuclease gene (HEG) originally discovered in Saccharomyces cerevisiae. Phylogenetic analyses show that horizontal transmission has been a regular occurrence in its evolutionary history. Moreover, VDE appears to be specifically adapted for horizontal transmission. Its 31-bp recognition sequence is an unusually well-conserved region in an unusually well-conserved gene. In addition, the nine nucleotide sites most critical for homing are also unusually well conserved. Such adaptation for horizontal transmission presumably arose as a consequence of selection, both among HEGs at different locations in the genome and among variants at the same location. The frequency of horizontal transmission must therefore be a key feature constraining the distribution and abundance of these genes.     

CD28 costimulation mediates down-regulation of p27kip1 and cell cycle progression by activation of the PI3K/PKB signaling pathway in primary human T cells

CD28 provides a costimulatory signal that cooperates with the TCR/CD3 complex to induce T cell activation, cytokine production, and clonal expansion. We have recently shown that CD28 directly regulates progression of T lymphocytes through the cell cycle. Although a number of signaling pathways have been linked to the TCR/CD3 and to CD28, it is not known how these two receptors cooperate to induce cell cycle progression. Here, using cell-permeable pharmacologic inhibitors of phosphatidylinositol 3-hydroxykinase (PI3K) and mitogen-activated protein kinase kinase (MEK1/2), we show that cell cycle progression of primary T lymphocytes requires simultaneous activation of PI3K- and MEK1/2-dependent pathways. Decreased abundance of cyclin-dependent kinase inhibitor p27(kip1), which requires simultaneous TCR/CD3 and CD28 ligation, was dependent upon both MEK and PI3K activity. Ligation of TCR/CD3, but not CD28 alone, resulted in activation of MEK targets extracellular signal-related kinase 1/2, whereas ligation of CD28 alone was sufficient for activation of PI3K target protein kinase B (PKB; c-Akt). CD28 ligation alone was also sufficient to mediate inactivating phosphorylation of PKB target glycogen synthase kinase-3 (GSK-3). Moreover, direct inactivation of GSK-3 by LiCl in the presence of anti-CD3, but not in the presence of anti-CD28, resulted in down-regulation of p27(kip1), hyperphosphorylation of retinoblastoma tumor suppressor gene product, and cellular proliferation. Thus, inactivation of the PI3K-PKB target GSK-3 could substitute for CD28 but not for CD3 signals. These results show that the PI3K-PKB pathway links CD28 to cell cycle progression and suggest that p27(kip1) integrates mitogenic MEK- and PI3K-dependent signals from TCR and CD28 in primary T lymphocytes.     

The role of ascorbic acid role in the differentiation of sclerotia in Sclerotinia minor

Sclerotinia minor in culture produces ascorbic acid in levels dependent on oxidative growth conditions and stage of development. During differentiation reduced/oxidized ascorbate ratio decreased by 12 and 6 fold at high and low oxidative stress, respectively. Exogenous ascorbate caused a concentration-dependent decrease of oxidative stress (lipid peroxidation), inhibition of sclerotial differentiation (up to 100%) and delay of differentiatlon (up to 10 days). Ascorbic acid may be produced to help the fungus reduce oxidative stress during growth. The data of this study support our theory proposing that oxidative stress is the inducing factor of sclerotial differentiation in fungi.This revised version was published online in October 2005 with corrections to the Cover Date.     

Lipofuscins and sclerotial differentiation in phytopathogenic fungi

Lipofuscins of lipidic and proteinaceous origin were identified by their excitation and emission spectra in phytopathogenic fungal representatives of different sclerotial differentiation types. Lipofuscin pigments in Sclerotium rolfsii, Rhizoctonia solani, Sclerotinia minor and Sclerotinia sclerotiorum showed similar excitation and emission maxima (ex-em 330–450, 330–450, 330–470 and 3307–470 nm, respectively). Sclerotial differentiation of these fungi was proceeded by a 4.2, 2.5, 2.7, 2.5 and 6, 2.9, 3.8, 3.1 fold increase of lipofuscin accumulation (per lipid and protein content), per respective fungus, as compared to their undifferentiated stage. Lipofuscin levels were higher in older than in younger mycelia and this phenomenon was more profound in S. rolfsii. Since lipofuscins are considered as indicators of oxidative stress, these data are in accordance with the hypothesis that suggests oxidative stress to be a common underlying factor in sclerotial differentiation of sclerotia-forming filamentous phytopathogenic fungi. This revised version was published online in June 2006 with corrections to the Cover Date.     

Clinical psychoacoustics in Alzheimer's disease central auditory processing disorders and speech deterioration

BACKGROUND: Difficulty in speech understanding in the presence of background noise or competing auditory signals is typically present in central auditory processing disorders. These disorders may be diagnosed in Alzheimer's disease as a result of degeneration in the central auditory system. In addition perception and processing of speech may be affected. MATERIAL AND METHODS: A MEDLINE research was conducted in order to answer the question whether there is a central auditory processing disorder involved in Alzheimer's disease. A second question to be investigated was what, if any is the connection, between central auditory processing disorders and speech deterioration?Articles were retrieved from the Medline to find relevance of Alzheimer's dis ease with central auditory processing disorders, they summed up to 34. Twelve papers were studied that contained testing for CAPD through psychoacoustic investigation. An additional search using the keywords 'speech production' and 'AD' produced a result of 33 articles, of them 14 are thoroughly discussed in this review as they have references concerning CAPD. The rest do not contain any relavent information on the central auditory system. RESULTS: Psychoacoustic tests reveal significantly lower scores in patients with Alzheimer's disease compared with normal subjects. Tests concerning sound localization and perception of tones as well as phoneme discrimination and tonal memory reveal deficits in Alzheimer's disease. Central auditory processing disorders may exist several years before the onset of clinical diagnosis of Alzheimer's disease. Segmental characteristics of speech are normal. Deficits exist concerning the supra-segmental components of speech. CONCLUSIONS: Central auditory processing disorders have been found in many cases when patients with Alzheimer's disease are tested. They may present as an early manifestation of Alzheimer's disease, preceding the disease by a minimum of 5 and a maximum of 10 years. During these years changes in the central auditory system, starting in the temporal lobe, may produce deficits in speech processing and production as hearing and speech are highly connected human functions. Another theory may be that spread of degeneration of the central nervous system has as a consequence, speech deterioration. Further research and central auditory processing disorders testing in the elderly population are needed to validate one theory over the other.     

Cationic double-hydrophilic model networks: synthesis,characterization, modeling and protein adsorption studies

Group transfer polymerization (GTP) was used for the preparation of eight networks based on two hydrophilic monomers, 2-(dimethylamino)ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methacrylate (PEGMA). Ethylene glycol dimethacrylate (EGDMA) served as the cross-linker, whereas 1,4-bis(methoxytrimethylsiloxymethylene)cyclohexane (MTSMC) was used as a bifunctional initiator. Seven of the networks had linear segments of accurate molecular weight between the cross-links, i.e., they were model networks, whereas the eighth was an equimolar randomly cross-linked network. Five of the seven model networks were based on ABA triblock copolymers with PEGMA midblocks and DMAEMA endblocks, in which the DMAEMA/PEGMA ratio was varied. The remaining two model networks were equimolar isomers, the one based on BAB triblocks (with a DMAEMA midblock) and the other based on the statistical copolymer. The degrees of swelling of all of the networks were measured as a function of pH and were found to increase below pH 7. The degrees of swelling at low pH values increased with the percentage of the DMAEMA monomer, which is ionized under these conditions. These swelling results were confirmed qualitatively by theoretical calculations. Finally, the pH-dependence of the adsorption of the proteins pepsin, bovine serum albumin, and lysozyme onto one of the model networks was studied.     

Disruption of the endocytic protein HIP1 results in neurological deficits and decreased AMPA receptor trafficking

Huntingtin interacting protein 1 (HIP1) is a recently identified component of clathrin-coated vesicles that plays a role in clathrin-mediated endocytosis. To explore the normal function of HIP1 in vivo, we created mice with targeted mutation in the HIP1 gene (HIP1(-/-)). HIP1(-/-) mice develop a neurological phenotype by 3 months of age manifest with a failure to thrive, tremor and a gait ataxia secondary to a rigid thoracolumbar kyphosis accompanied by decreased assembly of endocytic protein complexes on liposomal membranes. In primary hippocampal neurons, HIP1 colocalizes with GluR1-containing AMPA receptors and becomes concentrated in cell bodies following AMPA stimulation. Moreover, a profound dose-dependent defect in clathrin-mediated internalization of GluR1-containing AMPA receptors was observed in neurons from HIP1(-/-) mice. Together, these data provide strong evidence that HIP1 regulates AMPA receptor trafficking in the central nervous system through its function in clathrin-mediated endocytosis.     

Thyroid hormone and cardioprotection: Study of p38 MAPK and JNKs during ischaemia and at reperfusion in isolated rat heart

It has been recently shown that long-term thyroxine administration increases the tolerance of the heart to ischaemia. The present study investigated whether thyroxine induced cardioprotection involves alterations in the pattern of p38 mitogen activated protein kinase (p38MAPK) and c-Jun NH₂-terminal kinases (JNKs) activation during ischaemia-reperfusion. L-thyroxine (T4) was administered in Wistar rats (25 g/100 g/day, subcutaneously) for 2 weeks (THYR), while normal animals served as controls (NORM). NORM and THYR isolated rat hearts were perfused in Langendorff mode and subjected to 10 or 20 min of zero-flow global ischaemia only and also to 20 min of ischaemia followed by 10, 20 or 45 min of reperfusion. Postischaemic recovery of left ventricular developed pressure at 45 min of reperfusion was expressed as % of the initial value. Activation of p38 MAPK and JNKs was assessed at the different times of the experimental setting by standard Western blotting techniques using a dual phospho p38MAPK and phospho JNKs (p46/p54) antibodies. Activation of p38 MAPK was significantly attenuated during ischaemia and reperfusion in thyroxine treated hearts compared to normal hearts. JNKs were found to be activated only during the reperfusion period. The levels of phospho JNKs were found to be lower in thyroxine treated hearts as compared to untreated hearts, though not at a statistically significant level. Postischaemic functional recovery was higher in THYR as compared to NORM, p < 0.05. In summary, in hearts pretreated with thyroxine, p38 MAPK was attenuated during ischaemia and at reperfusion and this was associated with improved postischaemic recovery of function.