Conditional expression of MCM7 increases tumor growth without altering DNA replication activity

The minichromosome maintenance (MCM) 2-7 complex is a putative DNA helicase complex that facilitates the initiation of DNA replication. Here, we generated a cell line MCM7(+/-)/MCM7-FLAG, in which one allele of MCM7 is mutated whereas a tetracycline-repressible promoter could manipulate the expression of exogenous MCM7 protein. Overexpressed MCM7 protein supports efficient DNA replication of Epstein-Barr virus oriP and rapid formation of tumors in nude mice without altering the activity of cellular DNA replication. This system provides a unique setting for studying the function of MCM7 and for screening for potential therapeutics for malignant tumors.     

Innovativeness, population size and cumulative cultural evolution

Henrich [Henrich, J., 2004. Demography and cultural evolution: how adaptive cultural processes can produce maladaptive losses—the Tasmanian case. Am. Antiquity 69, 197-214] proposed a model designed to show that larger population size facilitates cumulative cultural evolution toward higher skill levels. In this model, each newborn attempts to imitate the most highly skilled individual of the parental generation by directly-biased social learning, but the skill level he/she acquires deviates probabilistically from that of the exemplar (cultural parent). The probability that the skill level of the imitator exceeds that of the exemplar can be regarded as the innovation rate. After reformulating Henrich’s model rigorously, we introduce an overlapping-generations analog based on the Moran model and derive an approximate formula for the expected change per generation of the highest skill level in the population. For large population size, our overlapping-generations model predicts a much larger effect of population size than Henrich’s discrete-generations model. We then investigate by way of Monte Carlo simulations the case where each newborn chooses as his/her exemplar the most highly skilled individual from among a limited number of acquaintances. When the number of acquaintances is small relative to the population size, we find that a change in the innovation rate contributes more than a proportional change in population size to the cumulative cultural evolution of skill level.     

Comparison of the usability of an automatic sleep staging program via portable 1-channel electroencephalograph and manual sleep staging with traditional polysomnography

Sleep and Biological Rhythms - Automatic algorithms are a proposed alternative to manual assessment of polysomnography data for analyzing sleep structure; however, none are acceptably accurate for...     

Mesophyll conductance in leaves of Japanese white birch (Betula platyphylla var. japonica) seedlings grown under elevated CO2 concentration and low N availability

To test the hypothesis that mesophyll conductance (g_m) would be reduced by leaf starch accumulation in plants grown under elevated CO₂ concentration [CO₂], we investigated g_m in seedlings of Japanese white birch grown under ambient and elevated [CO₂] with an adequate and limited nitrogen supply using simultaneous gas exchange and chlorophyll fluorescence measurements. Both elevated [CO₂] and limited nitrogen supply decreased area‐based leaf N accompanied with a decrease in the maximum rate of Rubisco carboxylation (V_c,max) on a CO₂ concentration at chloroplast stroma (C_c) basis. Conversely, only seedlings grown at elevated [CO₂] under limited nitrogen supply had significantly higher leaf starch content with significantly lower g_m among the treatment combinations. Based on a leaf anatomical analysis using microscopic photographs, however, there were no significant difference in the area of chloroplast surfaces facing intercellular space per unit leaf area among treatment combinations. Thicker cell walls were suggested in plants grown under limited N by increases in leaf mass per area subtracting non‐structural carbohydrates. These results suggest that starch accumulation and/or thicker cell walls in the leaves grown at elevated [CO₂] under limited N supply might hinder CO₂ diffusion in chloroplasts and cell walls, which would be an additional cause of photosynthetic downregulation as well as a reduction in Rubisco activity related to the reduced leaf N under elevated [CO₂].     

Mutant firefly luciferase enzymes resistant to the inhibition by sodium chloride

Objectives

Firefly luciferase, one of the most extensively studied enzymes, has numerous applications. However, luciferase activity is inhibited by sodium chloride. This study was aimed at obtaining mutant luciferase enzymes resistant to the sodium chloride inhibition.

Results

We first obtained two mutant luciferase enzymes whose inhibition were alleviated and determined the mutations to be Val288Ile and Glu488Val. Under medical dialysis condition (140 mM sodium chloride), the wild type was inhibited to 44% of its original activity level. In contrast, the single mutants, Val288Ile and Glu488Val, retained 67% and 79% of their original activity, respectively. Next, we introduced Val288Ile and Glu488Val mutations into wild-type luciferase to create a double mutant using site-directed mutagenesis. Notably, the double mutant retained its activity more than 95% of that in the absence of sodium chloride.

Conclusions

The mutant luciferase, named luciferase CR, was found to retain its activity in various concentrations of sodium chloride. The luciferase CR may be extensively useful in any bioassay which includes firefly luciferase and is employed in the presence of sodium chloride.

     

Constant ratio of Cc to Ci under various CO2 concentrations and light intensities,and during progressive drought,in seedlings of Japanese white birch

Photosynthesis Research - Constant mesophyll conductance (gm), and two-resistance gm model (involved in resistances of cell wall and chloroplast), where gm reaches maximum under higher CO2...     

Bortezomib Reduces the Tumorigenicity of Multiple Myeloma via Downregulation of Upregulated Targets in Clonogenic Side Population Cells

Side population (SP) cells in cancers, including multiple myeloma, exhibit tumor-initiating characteristics. In the present study, we isolated SP cells from human myeloma cell lines and primary tumors to detect potential therapeutic targets specifically expressed in SP cells. We found that SP cells from myeloma cell lines (RPMI 8226, AMO1, KMS-12-BM, KMS-11) express CD138 and that non-SP cells include a CD138-negative population. Serial transplantation of SP and non-SP cells into NOD/Shi-scid IL-2γnul mice revealed that clonogenic myeloma SP cells are highly tumorigenic and possess a capacity for self-renewal. Gene expression analysis showed that SP cells from five MM cell lines (RPMI 8226, AMO1, KMS-12-BM, KMS-11, JJN3) express genes involved in the cell cycle and mitosis (e.g., CCNB1, CDC25C, CDC2, BIRC5, CENPE, SKA1, AURKB, KIFs, TOP2A, ASPM), polycomb (e.g., EZH2, EPC1) and ubiquitin-proteasome (e.g., UBE2D3, UBE3C, PSMA5) more strongly than do non-SP cells. Moreover, CCNB1, AURKB, EZH2 and PSMA5 were also upregulated in the SPs from eight primary myeloma samples. On that basis, we used an aurora kinase inhibitor (VX-680) and a proteasome inhibitor (bortezomib) with RPMI 8226 and AMO1 cells to determine whether these agents could be used to selectively target the myeloma SP. We found that both these drugs reduced the SP fraction, though bortezomib did so more effectively than VX-680 due to its ability to reduce levels of both phospho-histone H3 (p-hist. H3) and EZH2; VX-680 reduced only p-hist. H3. This is the first report to show that certain oncogenes are specifically expressed in the myeloma SP, and that bortezomib effectively downregulates expression of their products. Our approach may be useful for screening new agents with which to target a cell population possessing strong tumor initiating potential in multiple myeloma.     

Inhibition of Acidic Sphingomyelinase by Xanthone Compounds Isolated from Garcinia Speciosa

Sphingomyelinase is considered to be involved in the regulation of apoptosis and cell growth. In the course of our screening for acidic sphingomyelinase inhibitors we isolated three xanthone compounds, α-mangostin, cowanin, and cowanol, from the bark of Garcinia speciosa. These compounds competitively inhibited bovine brain-derived acidic sphingomyelinase with IC₅₀ values of 14.1, 19.2, and 10.9 μM, respectively and inhibited the acidic sphingomyelinase more effectively than the neutral sphingomyelinase of bovine brain. α-Mangostin inhibited the acidic sphingomyelinase in the most selective manner. α-Mangostin was chemically modified and its structure-activity relationships are discussed.     

Chemical Synthesis of Oligonucleotides Containing The (6-4) Photoproduct at the Thymine-Cytosine Site and Its Repair By (6-4) Photolyase

Abstract

A phosphoramidite building block of the T(6-4)C photoproduct was synthesized. One of the differences from T(6-4)T was formation of cytosine hydrates by UV irradiation, and the other was acylation of the amino function with the capping reagent. The capping step was omitted to improve the yield of the desired oligonucleotides. Characterization of the (6-4) photolyase using one of the oligonucleotides revealed that this enzyme restores the pyrimidines in T(6-4)C to their original structures.     

Expression of arginine vasotocin receptors in the developing zebrafish CNS

Vasotocin/vasopressin is a neuropeptide that regulates social and reproductive behaviors in a variety of animals including fish. Arginine vasotocin (AVT) is expressed by cells in the ventral hypothalamic and preoptic areas in the diencephalon during embryogenesis in zebrafish suggesting that vasotocin might mediate other functions within the CNS prior to the development of social and reproductive behaviors. In order to examine potential early roles for vasotocin we cloned two zebrafish vasotocin receptors homologous to AVPR_1a. The receptors are expressed primarily in the CNS in similar but generally non-overlapping patterns. Both receptors are expressed in the forebrain, midbrain and hindbrain by larval stage. Of note, AVTR_1a-expressing neurons in the hindbrain appear to be contacted by the axons of preoptic neurons in the forebrain that include avt+ neurons and sensory axons in the lateral longitudinal fasciculus (LLF). Furthermore, AVTR_1a-expressing hindbrain neurons extend axons into the medial longitudinal fasciculus (MLF) that contains axons of many neurons thought to be involved in locomotor responses to sensory stimulation. One hypothesis consistent with this anatomy is that AVT signaling mediates or gates sensory input to motor circuits in the hindbrain and spinal cord.