Somatic mtDNA mutations cause progressive hearing loss in the mouse

Mitochondrial dysfunction has been implicated in the commonly occurring age-associated hearing loss (presbyacusis). We have previously generated mtDNA mutator mice with increased levels of somatic mtDNA point mutations causing phenotypes consistent with premature ageing. We have now utilized these mice to investigate whether elevated levels of somatic mtDNA mutations affect the auditory system. The mtDNA mutator mice develop a progressive impairment of hearing (ABR thresholds). Quantitative assessment of hair cell loss in the cochlea did not show any significant difference between the mutator and wild-type mice. The mtDNA mutator mice showed progressive apoptotic cell loss in the spiral ganglion and increased pathology with increasing age in the stria vascularis. The neurons in the cochlear nucleus showed an accelerated progressive degeneration with increasing age in the mutator mice compared to the wild-type mice. Both physiological and histological characterization thus reveals a striking resemblance between the auditory system pathology of mtDNA mutator mice and humans with presbyacusis. Somatic mtDNA mutations accumulate during normal ageing and further studies in humans are now warranted to investigate whether presbyacusis can be linked to mitochondrial dysfunction.     

Establishment of association of an Mg2+-dependent endonuclease with the rat liver nuclear matrix in cryonecrosis

Previously, we characterized the endonucleolytic activity of the nuclear matrix prepared from rat liver cryopreserved in liquid nitrogen. The enzymic activity was attributed to a 23 kDa, Mg(2+)-dependent and sequence non-specific endonuclease (p23) stably associated with the nuclear matrix. Here we show that p23 was absent from the nuclear matrix prepared from fresh liver. Instead, both ex vivo (cryopreservation), as well as in vivo-induced necrosis by repeated freezing/thawing of liver tissue in an anaesthetized rat, promoted the activation and translocation of p23 to the nuclear matrix. Considering that ex vivo and in vivo freezing/thawing of the liver were accompanied by morphological (nuclear compaction) and biochemical events (increased LDH activity, disorderly genomic DNA degradation, absence of lamin proteolysis, appearance of 62 and 50 kDa necrotic cleavage products of PARP-1) commonly observed during necrosis, and because the association of p23 with the nuclear matrix was saturable, reflecting the existence of a limited number of distinct high affinity sites on the nuclear matrix for p23, we concluded that the activation of the nuclear matrix-associated endonuclease p23 is a feature of liver cryonecrosis. Although cryonecrosis represents a typical example of acute cell damage, our results suggest that it is realized by ordered molecular events.     

Cdc42 and phosphoinositide 3-kinase drive Rac-mediated actin polymerization downstream of c-Met in distinct and common pathways

Activation of c-Met, the hepatocyte growth factor (HGF)/scatter factor receptor induces reorganization of the actin cytoskeleton, which drives epithelial cell scattering and motility and is exploited by pathogenic Listeria monocytogenes to invade nonepithelial cells. However, the precise contributions of distinct Rho-GTPases, the phosphatidylinositol 3-kinases, and actin assembly regulators to c-Met-mediated actin reorganization are still elusive. Here we report that HGF-induced membrane ruffling and Listeria invasion mediated by the bacterial c-Met ligand internalin B (InlB) were significantly impaired but not abrogated upon genetic removal of either Cdc42 or pharmacological inhibition of phosphoinositide 3-kinase (PI3-kinase). While loss of Cdc42 or PI3-kinase function correlated with reduced HGF- and InlB-triggered Rac activation, complete abolishment of actin reorganization and Rac activation required the simultaneous inactivation of both Cdc42 and PI3-kinase signaling. Moreover, Cdc42 activation was fully independent of PI3-kinase activity, whereas the latter partly depended on Cdc42. Finally, Cdc42 function did not require its interaction with the actin nucleation-promoting factor N-WASP. Instead, actin polymerization was driven by Arp2/3 complex activation through the WAVE complex downstream of Rac. Together, our data establish an intricate signaling network comprising as key molecules Cdc42 and PI3-kinase, which converge on Rac-mediated actin reorganization essential for Listeria invasion and membrane ruffling downstream of c-Met.     

Effects of zinc on the mineralization of bone nodules from human osteoblast-like cells

Zinc is an important mineral that is required for normal bone development. However, the direct effects of zinc on the mineralization of bone cells of human origin are not clear. The objective of this study was to determine the effects of zinc on the differentiation of SaOS-2 human osteoblast-like cells and the formation of mineralized bone nodules. Cells were cultured for 8 d and then transferred to zinc-free medium and treated with varying concentrations (0–50 μM) of zinc. Alkaline phosphatase (ALP) activity was used as a measure of osteoblast differentiation, and bone nodules were detected by von Kossa staining. After 4, 6, and 8 d of treatment, zinc increased ALP activity at 1 and 10 μM, but decreased activity at 50 μM. After 9 d of treatment, zinc increased both the number and area of mineralized bone nodules at low concentrations (1 and 10 μM), but decreased both at higher concentrations (25 and 50 μM). These findings demonstrate that zinc has biphasic effects on the differentiation and mineralization of human osteoblast-like cells.     

Causes of precocious puberty in children referred for evaluation in hospital conditions

INTRODUCTION: Symptoms of precocious puberty (PP) in children always arouse anxiety in their parents. Many children with PP are being hospitalized for the detailed diagnostic work-up. The aim of our study was to analyze the frequency of the variants of PP in children referred to our department. MATERIAL: Retrospective analysis of 119 children (103 girls and 16 boys) referred for hospitalization in the years 2003-2005 due to signs of precocious puberty was performed. RESULTS: Premature thelarche, benign variant of puberty, was diagnosed in 62 (53%) girls, in the mean age of 3.39 (+/- 2.33) years. Their mean height was within 0.7 +/- 1.1 SD. Premature pubarche was diagnosed 30 (25%) children--22 girls and 8 boys in the mean age was 7.24 (+/- 0.81) years. Their mean height was 1.3 +/- 1.0 SD and was significantly higher than normal (p < 0.0001). Premature menarche was diagnosed in 8 (7%) girls in the mean age 4.81 +/-2.26 years. Mean height in this group was normal for age (0.9+/-0.8 SD). PP was diagnosed in 19 (16%) children (11 girls and 8 boys) in the mean age 5.91 +/- 1.63 years. Mean height in this group was 1.6 +/- 0.7 SD, and was significantly higher than the mean for age (p<0.0005). GnRH-dependent type was present in 15 children, diagnosed as idiopathic in 9 girls and 1 boy. In 5 children (4 boys and 1 girl) pathology of central nervous system was found. In 4 children GnRH-independent precocious puberty was diagnosed--in 3 caused by congenital adrenal hyperplasia and in 1 boy by tumour of testis (leydigioma). CONCLUSIONS: Girls with precocious thelarche without growth acceleration present the benign variant of puberty and need clinical follow up only. Boys with clinical signs of precocious puberty should be carefully evaluated to rule out the organic cause.     

Enzyme-linked immunosorbent assay in the diagnosis of campylobacteriosis

Campylobacter jejuni and Campylobacter coli are the bacterial cause of human gastroenteritis commonly reported worldwide. The serodiagnosis of Campylobacter infections is not routinely done in Poland so the aim of this study was to evaluation of ELISA in the diagnosis ofcampylobacteriosis. Serum samples obtained from 145 patients with gastroenteritis were tested by ELISA with 7 different heat-stable antigens of C. jejuni and one of C. coli and by the commercial Virion/Serion ELISA with purified 45 kDa outer membrane protein of C. jejuni. Antibodies for heat-stable antigens of C. jejuni were detected statistically more often than antibodies for heat-stable antigens of C. coli and for purifled protein of C. jejuni. We found significant differences in the frequency of detection of antibodies to different heat-stable antigens, ranged from 18.6% to 68.9% of positive results, what indicate for serological heterogenicity of C. jejuni strains isolated in Poland. The results of our study showed usefulness of ELISA in serological diagnosis of campylobacteriosis. However it is necessary to serotype the C. jejuni strains isolated in Poland to find the appropriate C. jejuni serotype for using in ELISA.     

Interaction of organoruthenium(II)-polypyridyl complexes with DNA and BSA

BioMetals - The interaction of four arene ruthenium complexes [(η6-p-cymene)Ru(Me2dppz)Cl]PF6 (1) with Me2dppz?=?11,12-dimethyldipyrido[3,2-a:2′,3′-c]phenazine,...