Seasonal variation of calcium,magnesium, potassium,and manganese contents in xylem sap of beech(Fagus sylvatica L.) in a 35-year-old limestone beech forest stand

Summary In a 35-year-old calcareous beech forest stand five beech trees (Fagus sylvatica L.) were felled every 2 weeks, and xylem sap was obtained by means of water displacement from the lowest trunk sections, each 100 cm in length. From mid-October 1988 to mid-October 1989 a total of 130 trees were investigated. The seasonal variations of the Ca, Mg, K and Mn contents, as well as those of pH, show four characteristic phases. Additionally, distribution of the mineral contents along the trunk was studied in four trees. The seasonal increase and decrease of xylem sap mineral contents along the trunk is shown for the characteristic phenophases. The Ca, Mg, K, and Mn contents of xylem saps were determined by means of atomicabsorptionspectrophotometry.     

Membrane Orientation and Lateral Diffusion of BODIPY-Cholesterol as a Function of Probe Structure

Cholesterol tagged with the BODIPY fluorophore via the central difluoroboron moiety of the dye (B-Chol) is a promising probe for studying intracellular cholesterol dynamics. We synthesized a new BODIPY-cholesterol probe (B-P-Chol) with the fluorophore attached via one of its pyrrole rings to carbon-24 of cholesterol (B-P-Chol). Using two-photon fluorescence polarimetry in giant unilamellar vesicles and in the plasma membrane (PM) of living intact and actin-disrupted cells, we show that the BODIPY-groups in B-Chol and B-P-Chol are oriented perpendicular and almost parallel to the bilayer normal, respectively. B-Chol is in all three membrane systems much stronger oriented than B-P-Chol. Interestingly, we found that the lateral diffusion in the PM was two times slower for B-Chol than for B-P-Chol, although we found no difference in lateral diffusion in model membranes. Stimulated emission depletion microscopy, performed for the first time, to our knowledge, with fluorescent sterols, revealed that the difference in lateral diffusion of the BODIPY-cholesterol probes was not caused by anomalous subdiffusion, because diffusion of both analogs in the PM was free but not hindered. Our combined measurements show that the position and orientation of the BODIPY moiety in cholesterol analogs have a severe influence on lateral diffusion specifically in the PM of living cells.     

Interaction of the Human Papillomavirus E6 Oncoprotein with Sorting Nexin 27 Modulates Endocytic Cargo Transport Pathways

A subset of high-risk Human Papillomaviruses (HPVs) are the causative agents of a large number of human cancers, of which cervical is the most common. Two viral oncoproteins, E6 and E7, contribute directly towards the development and maintenance of malignancy. A characteristic feature of the E6 oncoproteins from cancer-causing HPV types is the presence of a PDZ binding motif (PBM) at its C-terminus, which confers interaction with cellular proteins harbouring PDZ domains. Here we show that this motif allows E6 interaction with Sorting Nexin 27 (SNX27), an essential component of endosomal recycling pathways. This interaction is highly conserved across E6 proteins from multiple high-risk HPV types and is mediated by a classical PBM-PDZ interaction but unlike many E6 targets, SNX27 is not targeted for degradation by E6. Rather, in HPV-18 positive cell lines the association of SNX27 with components of the retromer complex and the endocytic transport machinery is altered in an E6 PBM-dependent manner. Analysis of a SNX27 cargo, the glucose transporter GLUT1, reveals an E6-dependent maintenance of GLUT1 expression and alteration in its association with components of the endocytic transport machinery. Furthermore, knockdown of E6 in HPV-18 positive cervical cancer cells phenocopies the loss of SNX27, both in terms of GLUT1 expression levels and its vesicular localization, with a concomitant marked reduction in glucose uptake, whilst loss of SNX27 results in slower cell proliferation in low nutrient conditions. These results demonstrate that E6 interaction with SNX27 can alter the recycling of cargo molecules, one consequence of which is modulation of nutrient availability in HPV transformed tumour cells.     

Gene-targeted mice lacking the Trex1 (DNase III) 3'-->5' DNA exonuclease develop inflammatory myocarditis

TREX1, originally designated DNase III, was isolated as a major nuclear DNA-specific 3'-->5' exonuclease that is widely distributed in both proliferating and nonproliferating mammalian tissues. The cognate cDNA shows homology to the editing subunit of the Escherichia coli replicative DNA polymerase III holoenzyme and encodes an exonuclease which was able to serve a DNA-editing function in vitro, promoting rejoining of a 3' mismatched residue in a reconstituted DNA base excision repair system. Here we report the generation of gene-targeted Trex1(-/-) mice. The null mice are viable and do not show the increase in spontaneous mutation frequency or cancer incidence that would be predicted if Trex1 served an obligatory role of editing mismatched 3' termini generated during DNA repair or DNA replication in vivo. Unexpectedly, Trex1(-/-) mice exhibit a dramatically reduced survival and develop inflammatory myocarditis leading to progressive, often dilated, cardiomyopathy and circulatory failure.     

Measurement of mandibular movements in patients with temporomandibular disorders and in asymptomatic subjects

The aim of the study was to investigate the range of mandibular movements and to analyze the difference in range of mouth opening, right and left lateral movements, and protrusive movement between patients with clinical diagnoses of temporomandibular disorders and asymptomatic subjects (control group) in a young male population. A total of 240 subjects, aged 19-28, were included in the study. The TMD sample comprised 180 patients (60 patients with muscle disorders; 60 patients with disc displacement with reduction; and 60 patients with muscle disorders and disc displacement with reduction) and was compared with 60 healthy control subjects. All participants were evaluated by the attending dentists at baseline by means of a physical examination of the masticatory system and a history questionnaire which included the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I measures. Analysis of variance (ANOVA) with the post hoc Bonferroni criteria showed significant difference in ranges of mandibular movements between and within the groups of asymptomatic subjects and TMD patients for active mouth opening (p = 0.001), right lateral movement (p = 0.002), left lateral movement (p = 0.006), and protrusive movement (p = 0.05). It has been found that there are statistically significant differences in the range of mandibular movements that separate asymptomatic subjects and patients with muscle disorders and disc displacements with reduction in this young male population. However, we cannot conclude that measurements of active mandibular movements can discriminate one group (TMD patients) from the other (asymptomatic subjects), because the mean ranges of these active movements between the groups were measured in clinically "normal" values.     

Partitioning of tRNA-dependent Editing between Pre- and Post-transfer Pathways in Class I Aminoacyl-tRNA Synthetases

Hydrolytic editing activities are present in aminoacyl-tRNA synthetases possessing reduced amino acid discrimination in the synthetic reactions. Post-transfer hydrolysis of misacylated tRNA in class I editing enzymes occurs in a spatially separate domain inserted into the catalytic Rossmann fold, but the location and mechanisms of pre-transfer hydrolysis of misactivated amino acids have been uncertain. Here, we use novel kinetic approaches to distinguish among three models for pre-transfer editing by Escherichia coli isoleucyl-tRNA synthetase (IleRS). We demonstrate that tRNA-dependent hydrolysis of noncognate valyl-adenylate by IleRS is largely insensitive to mutations in the editing domain of the enzyme and that noncatalytic hydrolysis after release is too slow to account for the observed rate of clearing. Measurements of the microscopic rate constants for amino acid transfer to tRNA in IleRS and the related valyl-tRNA synthetase (ValRS) further suggest that pre-transfer editing in IleRS is an enzyme-catalyzed activity residing in the synthetic active site. In this model, the balance between pre-transfer and post-transfer editing pathways is controlled by kinetic partitioning of the noncognate aminoacyl-adenylate. Rate constants for hydrolysis and transfer of a noncognate intermediate are roughly equal in IleRS, whereas in ValRS transfer to tRNA is 200-fold faster than hydrolysis. In consequence, editing by ValRS occurs nearly exclusively by post-transfer hydrolysis in the editing domain, whereas in IleRS both pre- and post-transfer editing are important. In both enzymes, the rates of amino acid transfer to tRNA are similar for cognate and noncognate aminoacyl-adenylates, providing a significant contrast with editing DNA polymerases.     

Cellular senescence and the myth of Janus

Cellular senescence is, essentially, a permanent proliferation arrest induced by various cellular stresses or inappropriate stimuli. This arrest, which is associated with dramatic changes in cell morphology, metabolism and gene expression, involves a complex signalling network aiming at stable inactivation of CDKs, major cell cycle regulators. Notably, several tumour suppressors, such as p53, pRb or p16(Ink4a), play key roles both in the initiation of the senescence program and in its maintenance, which often involves epigenetic changes. While having widely recognized roles in tumour suppression and wound healing, senescence, like the roman god Janus, recently revealed another darker face. Mostly due to altered secretion phenotype favouring inflammation, senescent cells strongly influence surrounding tissue contributing to the development of age-related pathologies, including cancer.     

Quantitative analysis of troponin I serum values in patients with acute cholecystitis

The diagnosis and staging of acute cholecystitis, upon a lot of diagnostic methods and some scoring systems, is still a great clinical problem. The aim of the study was to investigate if serum Troponin I is elevated in patients with acute cholecystitis. Following informed consent, 65 patients with clinical and laboratory signs of acute cholecystitis were enrolled. All patients had measured serum Troponin I level and an abdominal ultrasound was done before definitive treatment was performed. Increased serum Troponin I level was found in most patients with severe form of acute cholecystitis (p < 0.00001). It reached sensitivity of 94.5% and specificity of 57.1% of this test. In multiple regression analysis Troponin I significantly correlated (p < 0.05) with the serum aspartate aminotransferase (r = 0.27), gamma-glutamyl transferase (r = 0.25) and gallbladder wall (> 6 mm) thickness (r = 0.58). Our study confirms that in most patients with severe and acute cholecystitis, serum Troponin I is increased. Troponin I level is in a lower range than it would be in patients with cardiac muscle damage or necrosis. Measuring serum Troponin I is a fast, reliable and widely performed test that could, with other routinely measured parameters, help in early diagnosis of the severe form of acute cholecystitis.