A Calorimetric Characterization of Cr(VI)-Reducing Arthrobacter oxydans

This is the first of a series of calorimetric studies designed to characterize and understand survival mechanisms of metal-reducing bacteria isolated from metal-polluted environments. In this paper we introduce a new concept of thermal spectrum of the endothermic melting of complex biological systems (e.g., proteins, nucleic acids, ribosomes, membrane structures) in intact cells. All thermal spectra measured are thermograms that describe the temperature dependence of heat capacity change of the complex systems of biologically active substances in bacterial cells. This new concept of thermal spectrum was applied to investigate spectral features from intact cells of Cr(VI)-reducer Arthrobacter oxydans at different points of their growth conditions and stages. Over the temperature range of 40–105°C, we observed that spectral changes are particularly significant in the 40–90°C interval. This may correspond to the orderly changes in subcellular structural elements: proteins, ribosomes and RNA, membranes, and various structural elements of the cell wall during different points of the growth cycle and growth conditions. Spectral changes in the 90–105°C region are less pronounced, implicating that the structural composition of DNA-Protein (DNP) complexes may change little

Selective presynaptic terminal remodeling induced by spatial, but not cued, learning: a quantitative confocal study

The hippocampal mossy fibers (MFs) are capable of behaviorally selective, use-dependent structural remodeling. Indeed, we previously observed a new layer of Timm's staining induced in the stratum oriens (SO) in CA3 after spatial but not cued water maze learning (Rekart et al., (2007) Learn Mem 14:416-421). This led to the prediction that there is a learning-specific induction of presynaptic terminal plasticity of MF axons. This study confirms this prediction demonstrating, at the confocal level of analysis, terminal-specific, and behavior-selective presynaptic structural plasticity linked to long-term memory. Male adult Wistar rats were trained for 5 days to locate a hidden or visible platform in a water maze and a retention test was performed 7 days later. MF terminal subtypes, specifically identified by an antibody to zinc transporter 3 (ZnT3), were counted from confocal z-stacks in the stratum lucidum (SL) and the SO. In hidden platform trained rats, there was a significant increase in the number of large MF terminals (LMTs, 2.5–10 μm diameter, >2 μm2 area) compared to controls both in the proximal SL (P < 0.05) and in the SO (P < 0.01). Surprisingly, there was no detectable increase in small MF terminals (SMTs, 0.5–2 μm diameter, <2 μm2 area) in either SL or SO as a consequence of training. This distinction of the two MF terminal types is functionally important as LMTs synapse on CA3 pyramidal neurons, while SMTs are known to target inhibitory interneurons. The present findings highlight the pivotal role in memory of presynaptic structural plasticity. Because the “sprouting” observed is specific to the LMT, with no detectable change in the number of the SMT, learning may enhance net excitatory input to CA3 pyramidal neurons. Given the sparse coding of the MF-CA3 connection, and the role that granule cells play in pattern separation, the remodeling observed here may be expected to have a major impact on the long-term integration of spatial context into memory

Preliminary phytochemical and biological evaluation of daphne glomerata extracts

The article reports on the phytochemical and biological potentials of leaves and stems of Daphne glomerata Lam. (Fam. Thymelaeaceae). Study indicated that crude extracts from the leaves and stems of the plant have high biological activity. Cytotoxicity was assessed using resazurin on an automated 96-well Fluoroskan Ascent F1_ plate reader (Labsystems) using excitation and emission wavelengths of 530 nm and 590 nm, respectively. High cytotoxic activity (<1,563 µg/ml) of both extracts toward lung carcinoma cell lines was elucidated. The specificity of extracts to WS-1 human fibroblast cell lines was observed. For the first time, the profiles of compounds with terpenic and phenolic nature were described in Daphne glomerata leaves and stems MeOH extracts by TLC and (HPLC-DAD-MS) techniques