Mitochondrial dysfunction leads to reduced chronological lifespan and increased apoptosis in yeast

We previously isolated a Saccharomyces cerevisiae mutant (HsTnII), which displays 40% reduced chronological lifespan as compared to the wild type (WT). In this study, we found HsTnII cultures to be characterized by fragmented and dysfunctional mitochondria, and by increased initiation of apoptosis during chronological aging as compared to WT. Expression of genes encoding subunits of mitochondrial electron transport chain and ATP synthase is significantly downregulated in HsTnII, and as a consequence, HsTnII is not able to respire ethanol. All these data confirm the importance of functional mitochondria and respiration in determining yeast chronological lifespan and apoptosis.     

Recent findings in pulsed light disinfection

Nonthermal disinfection technologies are gaining increasing interest in the field of minimally processed food in order to improve the microbial safety or to extend the shelf life. Especially fresh‐cut produce or meat and fish products are vulnerable to microbial spoilage, but, due to their sensitivity, they require gentle preservation measures. The application of intense light pulses of a broad spectral range comprising ultraviolet, visible and near infrared irradiation is currently investigated as a potentially suitable technology to reduce microbial loads on different food surfaces or in beverages. Considerable research has been performed within the last two decades, in which the impact of various process parameters or microbial responses as well as the suitability of pulsed light (PL) for food applications has been examined. This review summarizes the outcome of the latest studies dealing with the treatment of various foods including the impact of PL on food properties as well as recent findings about the microbicidal action and relevant process parameters.     

Decorin gene expression and its regulation in human keratinocytes

In various cell types, including cancer cells, decorin is involved in regulation of cell attachment, migration and proliferation. In skin, decorin is seen in dermis, but not in keratinocytes. We show that decorin gene (DCN) is expressed in the cultured keratinocytes, and the protein is found in the cytoplasm of differentiating keratinocytes and in suprabasal layers of human epidermis. RT-PCR experiments showed that DCN expression is regulated by pro-inflammatory and proliferative cytokines. Our data suggest that decorin should play a significant role in keratinocyte terminal differentiation, cutaneous homeostasis and dermatological diseases.     

A hot-deck multiple imputation procedure for gaps in longitudinal recurrent event histories

We propose a regression-based hot-deck multiple imputation method for gaps of missing data in longitudinal studies, where subjects experience a recurrent event process and a terminal event. Examples are repeated asthma episodes and death, or menstrual periods and menopause, as in our motivating application. Research interest concerns the onset time of a marker event, defined by the recurrent event process, or the duration from this marker event to the final event. Gaps in the recorded event history make it difficult to determine the onset time of the marker event, and hence, the duration from onset to the final event. Simple approaches such as jumping gap times or dropping cases with gaps have obvious limitations. We propose a procedure for imputing information in the gaps by substituting information in the gap from a matched individual with a completely recorded history in the corresponding interval. Predictive mean matching is used to incorporate information on longitudinal characteristics of the repeated process and the final event time. Multiple imputation is used to propagate imputation uncertainty. The procedure is applied to an important data set for assessing the timing and duration of the menopausal transition. The performance of the proposed method is assessed by a simulation study.     

α-Tocopherol impairs 7-ketocholesterol-induced caspase-3-dependent apoptosis involving GSK-3 activation and Mcl-1 degradation on 158N murine oligodendrocytes

In important and severe neurodegenerative pathologies, 7-ketocholesterol, mainly resulting from cholesterol autoxidation, may contribute to dys- or demyelination processes. On various cell types, 7-ketocholesterol has often been shown to induce a complex mode of cell death by apoptosis associated with phospholipidosis. On 158N murine oligodendrocytes treated with 7-ketocholesterol (20 μg/mL corresponding to 50 μM, 24–48 h), the induction of a mode of cell death by apoptosis characterised by the occurrence of cells with condensed and/or fragmented nuclei, caspase activation (including caspase-3) and internucleosomal DNA fragmentation was observed. It was associated with a loss of transmembrane mitochondrial potential (ΔΨm) measured with JC-1, with a dephosphorylation of Akt and GSK3 (especially GSK3β), and with degradation of Mcl-1. With α-tocopherol (400 μM), which was capable of counteracting 7-ketocholesterol-induced apoptosis, Akt and GSK3β dephosphorylation were inhibited as well as Mcl-1 degradation. These data underline that the potential protective effects of α-tocopherol against 7-ketocholesterol-induced apoptosis do not depend on the cell line considered, and that the cascade of events (Akt/GSK3β/Mcl-1) constitutes a link between 7-ketocholesterol-induced cytoplasmic membrane dysfunctions and mitochondrial depolarisation leading to apoptosis.     

Knockdown of cyclin-dependent kinase inhibitors induces cardiomyocyte re-entry in the cell cycle

Proliferation of mammalian cardiomyocytes stops rapidly after birth and injured hearts do not regenerate adequately. High cyclin-dependent kinase inhibitor (CKI) levels have been observed in cardiomyocytes, but their role in maintaining cardiomyocytes in a post-mitotic state is still unknown. In this report, it was investigated whether CKI knockdown by RNA interference induced cardiomyocyte proliferation. We found that triple transfection with p21(Waf1), p27(Kip1), and p57(Kip2) siRNAs induced both neonatal and adult cardiomyocyte to enter S phase and increased the nuclei/cardiomyocyte ratio; furthermore, a subpopulation of cardiomyocytes progressed beyond karyokynesis, as assessed by the detection of mid-body structures and by straight cardiomyocyte counting. Intriguingly, cardiomyocyte proliferation occurred in the absence of overt DNA damage and aberrant mitotic figures. Finally, CKI knockdown and DNA synthesis reactivation correlated with a dramatic change in adult cardiomyocyte morphology that may be a prerequisite for cell division. In conclusion, CKI expression plays an active role in maintaining cardiomyocyte withdrawal from the cell cycle.     

Chlorine dioxide inactivation of bacterial threat agents

Aims: To evaluate the efficacy of chlorine dioxide (ClO₂) against seven species of bacterial threat (BT) agents in water. Methods and Results: Two strains of Bacillus anthracis spores, Yersinia pestis, Francisella tularensis, Burkholderia pseudomallei, Burkholderia mallei and Brucella species were each inoculated into a ClO₂ solution with an initial concentration of 2·0 (spores only) and 0·25 mg l^?1 (all other bacteria) at pH 7 or 8, 5 or 25°C. At 0·25 mg l^?1 in potable water, six species were inactivated by at least three orders of magnitude within 10 min. Bacillus anthracis spores required up to 7 h at 5°C for the same inactivation with 2·0 mg l^?1 ClO₂. Conclusions: Typical ClO₂ doses used in water treatment facilities would be effective against all bacteria tested except B. anthracis spores that would require up to 7 h with the largest allowable dose of 2 mg l^?1 ClO₂. Other water treatment processes may be required in addition to ClO₂ disinfection for effective spore removal or inactivation. Significance and Impact of Study: The data obtained from this study provide valuable information for water treatment facilities and public health officials in the event that a potable water supply is contaminated with these BT agents.