Mutagenesis and deoxyribonucleotide pool imbalance

Numerous studies have demonstrated that DNA-precursor pool imbalances are mutagenic and can modulate the lethality and mutagenicity of DNA-damaging agents. In addition, physical and chemical mutagens can induce alterations in DNA-precursor levels. Such findings suggest that regulation of intracellular concentrations of DNA precursors may be an important factor in environmental mutagenesis. In this article, results linking mutation and disturbances in DNA-precursor pools are reviewed.     

An electron-microscopic study of the bone-remodeling sequence in the rat

Summary A detailed chronological electron-microscopic study of the bone remodeling sequence has been performed in the rat based on a previously described model (Tran Van et al. 1982) in which the remodeling activity is synchronized. This allowed the observation of the cellular and extracellular events during the bone remodeling process, including the activation of the sequential process and the reversal phase, intermediate between osteoclastic resorption and osteoblastic formation. Most important is the fact that throughout the whole process cells with the morphological characteristics of mononuclear phagocytes have been observed in proximity or in contact with the bone surface and/or the various bone cells. Coated pits (receptor-mediated endocytosis) are frequently observed in close apposition to bone spicules and gap junctions are frequent between the cells. These observations suggest that, besides being likely candidates as osteoclast precursors, mononuclear phagocytes may play an important role in bone remodeling.     

Effects of antimycotics on the biosynthesis of cellular macromolecules inAspergillus niger protoplasts

The effects of nine antimycotics on the biosynthesis of cellular macromolecules were analyzed using the regenerating system of protoplats ofAspergillus niger. The incorporation of several specific radioactive precursors into major cellular components were measured in the presence or in the absence of respective agents. Miconazole, ketoconazole, and tolnaftate inhibited the lipid synthesis. 5-Fluorocytosine strongly inhibited the DNA and protein syntheses. Griseofulvin, however, specifically inhibited the synthesis of cell wall polysaccharides, i.e. chitin and glucan. Other agents showed non-specific inhibition effects. The significance of morphological change of hypha as an indicator of antimycotic action and its feasibility as a screening tool for novel antimycotic compounds are discussed.Abbreviations GRP germination of regenerating protoplasts - TCA trichloroacetic acid     

DISP3 promotes proliferation and delays differentiation of neural progenitor cells

DISP3 (PTCHD2), a sterol-sensing domain-containing protein, is highly expressed in neural tissue but its role in neural differentiation is unknown. In the present study we used a multipotent cerebellar progenitor cell line, C17.2, to investigate the impact of DISP3 on the proliferation and differentiation of neural precursors. We found that ectopically expressed DISP3 promotes cell proliferation and alters expression of genes that are involved in tumorigenesis. Finally, the differentiation profile of DISP3-expressing cells was altered, as evidenced by delayed expression of neural specific markers and a reduced capacity to undergo neural differentiation.     

Berberine and S allyl cysteine mediated amelioration of DEN + CCl4 induced hepatocarcinoma

Background

Diethylnitrosamine (DEN) and carbon tetrachloride (CCl4) have been used as initiator and promoter respectively to establish an animal model for investigating molecular events appear to be involved in development of liver cancer. Use of herbal medicine in therapeutics to avoid the recurrence of hepatocarcinoma has already generated considerable interest among oncologists. In this context studies involving S-allyl-cysteine (SAC) and berberine have come up with promising results. Here we have determined the individual effect of SAC and berberine on the biomolecules associated with DEN + CCl4 induced hepatocarcinoma. Effective therapeutic value of combined treatment has also been estimated.

Methods

ROS accumulation was analyzed by FACS following DCFDA incubation. Bcl2-Bax and HDAC1‐pMdm2 interaction were demonstrated by co-immunoprecipitation. Immunosorbent assay was performed to analyze PP2A and caspase3 activities. MMP was determined cytofluorimetrically by investigating JC-1 fluorescence. AnnexinV binding was demonstrated by labeling the cells with AnV-FITC followed by flow cytometry.

Results

CytochromeP4502E1 mediated bioactivation of DEN + CCl4 induced Akt dependent pMdm2‐HDAC1 interaction that led to p53 deacetylation, probable cause of its degradation. In parallel, oxidative stress dependent Nrf2‐HO1 activation increased Bcl2 expression which in turn stimulated cell proliferation. SAC in combination with berberine inhibited Akt mediated cell proliferation. Activation of PP2A as well as inhibition of JNK resulted in induction of apoptosis after 30 days of treatment. Extension of combined treatment reverted tissue physiology towards control. Co-treated group displayed normal tissue structure.

Conclusion and general significance

SAC and berberine mediated HDAC1/Akt inhibition implicates the efficacy of combined treatment in the amelioration of DEN + CCl4 induced hepatocarcinoma.     

NDP52 associates with phosphorylated tau in brains of an Alzheimer disease mouse model

We previously showed that NDP52 (also known as calcoco2) plays a role as an autophagic receptor for phosphorylated tau facilitating its clearance via autophagy. Here, we examined the expression and association of NDP52 with autophagy-regulated gene (ATG) proteins including LC3, as well as phosphorylated tau and amyloid-beta (Aβ) in brains of an AD mouse model. NDP52 was expressed not only in neurons, but also in microglia and astrocytes. NDP52 co-localized with ATGs and phosphorylated tau as expected since it functions as an autophagy receptor for phosphorylated tau in brain. Compared to wild-type mice, the number of autophagic vesicles (AVs) containing NDP52 in both cortex and hippocampal regions was significantly greater in AD model mice. Moreover, the protein levels of NDP52 and phosphorylated tau together with LC3-II were also significantly increased in AD model mice, reflecting autophagy impairment in the AD mouse model. By contrast, a significant change in p62/SQSTM1 level was not observed in this AD mouse model. NDP52 was also associated with intracellular Aβ, but not with the extracellular Aβ of amyloid plaques. We conclude that NDP52 is a key autophagy receptor for phosphorylated tau in brain. Further our data provide clear evidence for autophagy impairment in brains of AD mouse model, and thus strategies that result in enhancement of autophagic flux in AD are likely to be beneficial.