Bromodeoxyuridine uptake by early liver metastases in rats: a comparison of the hepatic artery and portal vein infusion routes

Liver metastases generated by the intraportal inoculation of ascites hepatoma cells in Donryu rats were labeled with bromodeoxyuridine (BrdU) through the hepatic artery, or through the portal vein with or without ligation of the hepatic artery, 3, 6, or 9 days after tumor inoculation. The distribution of BrdU-labeled cells was evaluated in 174 metastases, 110-1640 microm in diameter, by immunohistochemical methods. When a dual blood supply from the portal vein and hepatic artery existed, the BrdU-labeled cells were diffusely found in the metastases regardless of their size and the route of BrdU infusion. When blood supply to metastases larger than 610 microm in diameter was from a single source, namely the portal vein, the BrdU-labeled cells were located within 90-290 microm from the margin of the metastases. These results indicate first, that drug uptake by the inner part of the early metastatic liver tumors is achieved through the hepatic artery, and second, that drug uptake by early liver metastases through the portal vein is limited to within the extent of portal diffusion regardless of the size of the metastases. Thus, we conclude that prophylactic treatment against liver metastases would be more effective when given via the hepatic artery route rather than via the portal vein route.     

The cell cycle, including the mitotic cycle and organelle division cycles, as revealed by cytological observations

It is generally believed that the cell cycle consists essentially of the mitotic cycle, which involves mitosis and cytokinesis. These processes are becoming increasingly well understood at the molecular level. However, successful cell reproduction requires duplication and segregation (inheritance) of all of the cellular contents, including not only the cell-nuclear genome but also intracellular organelles. Eukaryotic cells contain at least three types of double membrane-bounded organelles (cell nucleus, mitochondria and plastids), four types of single membrane-bounded organelles (endoplasmic reticulum, Golgi apparatus, lysosomes and microbodies) and the cytoskeleton, which comprises tubulin-based structures (including microtubules, centrosome and spindle) and actin microfilaments. These membrane-bounded organelles cannot be formed de novo and daughter organelles must be inherited from parent organelles during cell cycle. Regulation of organelle division and its coordination with the progression of the cell cycle involves a sequence of events that are subjected to precise spatio-temporal control. Considering that the cells of higher animals and plants contain many organelles which tend to behave somewhat randomly, there is little information concerning the division and inheritance of these double- and single-membrane-bounded organelles during the cell cycle. Here, we summarize the current cytological and morphological knowledge of the cell cycle, including the division cycles of seven membrane-bounded and some non-membrane-bounded organelles. The underlying mechanisms and the biological relevance of these processes are discussed, particularly with respect to cells of the primitive alga Cyanidioschyzon merolae that have a minimum of organelles. We discuss unsolved problems and future perspectives opened by recent studies.     

Ce³+-induced exopolysaccharide production by Bradyrhizobium sp. MAFF211645

Ce³⁺, a rare earth element (REE), has been widely used in high-technology industries. Despite the importance of Ce³⁺ in the fields of chemistry and physics, the role of Ce³⁺ in biology has been ignored. To investigate physiological effects of Ce³⁺ on microorganisms, we screened microorganisms that showed peculiar growth in the presence of Ce³⁺. We isolated a free-living soil bacterium that produced exopolysaccharide (EPS) around its colonies on 1/100 nutrient agar with 30 μM CeCl₃ or 1.0% d-mannitol. The bacterium was identified as Bradyrhizobium sp. by morphological, biochemical, and physiological tests as well as 16S rDNA sequence analysis. La³⁺, Pr³⁺, and Nd³⁺ also induced EPS production in large quantities, while Sm³⁺ did in small amounts. However, other heavier REEs from Eu³⁺ to Lu³⁺, and metals such as Na⁺, Al³⁺, K⁺, Ca²⁺, V³⁺, Cr³⁺, Co²⁺, Ni²⁺, Sr²⁺, Ba²⁺, and Pb²⁺ did not induce EPS production. The mean molecular weight of EPS was estimated to be approximately 1 × 10⁶ by Sepharose CL-4B column chromatography. TLC revealed that EPS was composed of l-rhamnose. Quantitative analysis of alditol acetate derivatives of acid hydrolyzate of EPS by GLC revealed that EPS was composed of more than 95% l-rhamnose, indicating that this EPS was a rhamnan. The spectrum of FT-IR of the rhamnan demonstrated that l-rhamnose residues in the rhamnan were α-linked. GC/MS analysis of methylated alditol acetate derivatives of the rhamnan demonstrated that it was composed of main chain α-(1→4)-linked l-rhamnopyranosyl residues. From spectral analyses of ¹H-NMR and FT-IR, EPS produced in the presence of 1.0% d-mannitol was found to be structurally similar to rhamnans.     

Effects of Additives on the Ignition of AP-Based Propellants at subatmospheric pressures

The ammonium perchlorate (AP)-oxidized composite propellants, each of which contains separately copper chromite (CC) as a burning rate adjuster and carbon black (CB) as an opacifier, have been ignited at subatmospheric pressures of argon gas by means of a carbon dioxide laser, and the effects of the additives on the ignition behavior have been studied. It has been found that copper chromite shortens the ignition time especially below 100 torr and that at the same time it enhances the ignitability, i.e., self-sustaining ignition. Carbon black, being an opacifier decreasing reflectivity and increasing radiative absorption at propellant surface, can not be recognized to be an active catalyst in ignition at subatmospheric pressures. The data of differential thermal analysis (DTA) for above specimens have indicated that the maximum exothermic peak temperature is shifted toward a lower one with the increase in CC concentration, the exothermic peak structure becoming sharper. However, CB addition to the basic propellant makes exothermic peaks less distinct. The results of DTA support those obtained from the ignition experiments above.     

Max-Stretch Reduction for Tree Spanners

A tree t-spanner T of a graph G is a spanning tree of G whose max-stretch is t, i.e., the distance between any two vertices in T is at most t times their distance in G. If G has a tree t-spanner but not a tree (t−1)-spanner, then G is said to have max-stretch of t. In this paper, we study the Max-Stretch Reduction Problem: for an unweighted graph G=(V,E), find a set of edges not in E originally whose insertion into G can decrease the max-stretch of G. Our results are as follows: (i) For a ring graph, we give a linear-time algorithm which inserts k edges improving the max-stretch optimally. (ii) For a grid graph, we give a nearly optimal max-stretch reduction algorithm which preserves the structure of the grid. (iii) In the general case, we show that it is -hard to decide, for a given graph G and its spanning tree of max-stretch t, whether or not one-edge insertion can decrease the max-stretch to t−1. (iv) Finally, we show that the max-stretch of an arbitrary graph on n vertices can be reduced to s′≥2 by inserting O(n/s′) edges, which can be determined in linear time, and observe that this number of edges is optimal up to a constant.     

寻找无向图中回路的并行算法

对无向简单图Ｇ＝（Ｖ,Ｅ）,｜Ｖ｜＝ｎ,｜Ｅ｜＝ｍ,给出对下述问题的ＮＣ算法：（１）寻找Ｇ中最短回路;（２）寻找Ｇ中最短偶（奇）长度回路;（３）求解Ｃ_ｋ,ｋ＝３,４,这里Ｃ_ｋ表示Ｇ中长度为ｋ的回路．     

Negative air ions created by water shearing improve erythrocyte deformability and aerobic metabolism

To elucidate a potential mechanism by which negative air ions improve aerobic metabolism, changes in venous blood lactate levels, pH, erythrocyte deformability, and plasma superoxide dismutase activity and ceruloplasmin levels were examined during a 1-h exposure to negative air ions created by water shearing or corona discharge in nine adult healthy volunteers. The blood lactate level decreased from 1.3 +/- 0.3 to 1.0 +/- 0.2 mmol/l, pH increased from 7.388 +/- 0.025 to 7.417 +/- 0.036, and erythrocyte deformability improved from 37.0 +/- 2.2 to 35.1 +/- 3.0 s, expressed as the mean +/- s.d., when exposed to negative air ions created by water shearing, but did not change when exposed to negative air ions created by corona discharge. Other variables did not change in either exposure. The results obtained suggest that negative air ions created by water shearing improve aerobic metabolism by improving erythrocyte deformability. PRACTICAL IMPLICATIONS: The paper shows that negative air ions created by water shearing method improve aerobic metabolism only during a 1-h exposure, which may be caused by improvement of erythrocyte deformability, but negative air ions created by corona discharge have no effects. A potential mechanism is that negative air ions enter the circulating blood via the lungs and electrons of these ions are delivered to the plasma protein. Why negative air ions created by corona discharge have no effects is considered that water binding does not exist so that the lifetime of these ions is markedly short, by which the ions cannot reach the alveoli of the lungs sufficiently.     

The complexity of the Hajós calculus for planar graphs

The planar Hajós calculus is the Hajós calculus with the restriction that all the graphs that appear in the construction (including a final graph) must be planar. We prove that the planar Hajós calculus is polynomially bounded iff the Hajós calculus is polynomially bounded.