Mutual recognition between polymerized liposomes. IV. Polysaccharide-lectin system.

As a model of cell-cell recognition processes, the association processes of a polysaccharide (mannan)-carrying liposome with a lectin (Concanavalin A, Con A)-carrying polymerized liposome were followed by turbidimetry. The association process was strongly inhibited by the addition of a low molecular weight sugar, methyl-alpha-D-mannopyranoside, which shows that the association between the liposomes is due to the specific interaction between Con A and mannan. The association rate constant obtained was much smaller than the theoretical value for a diffusion-controlled binary association process. This implies that the association rate of liposomes is limited by the recognition between complementary ligands bound on the liposome surfaces. Another reason for the smaller association rate constant in the liposome-liposome system is the repulsive hydration effect. The effect of the surface density of the lectin immobilized on the liposome on the recognition was also examined.     

Apterichtus keramanus, a new snake-eel from Okinawa, southern Japan (Ophichthinae, Ophichthidae)

A new snake-eel,Apterichtus keramanus, is described on the basis of a single 276-mm TL specimen trawled from the coast of Kerama Islands, Okinawa Prefecture, Japan. The species is unique in the genus in having the posterior nostril opening entirely inside the mouth and a dark band running from the anteroventral margin of the eye to the upper lip.     

Plant-growth regulators from common starfish (<Emphasis Type="Italic">Asterias amurensis</Emphasis> Lütken) waste

Starfish waste has been shown to be an effective compost material not only in the promotion of plant growth but also in terms of having insecticidal activity. In the present study, plant growth regulation by chemicals from starfish was examined. The aqueous fraction from a hot water extract of the starfish Asterias amurensis Lütken showed plant-growth activity, while the aqueous fraction from a methanol extract inhibited growth of Brassica campestris. The lipophilic fraction from the methanol extract also exhibited a plant growth-promoting effect. The active components from each extract were identified. Asterubine from the hot water extract promoted plant growth. A ceramide from the lipophilic fraction showed root growth promoting effect, and three glucocerebrosides had promotive effects on the entire plant. Asterosaponins were identified as the main growth inhibitors in the aqueous fraction of the methanol extract. These active compounds from starfish waste could be analyzed as potential plant growth regulators in agricultural applications in the future.     

Mutagenicity of N4-aminocytidine and its derivatives in Chinese hamster lung V79 cells. Incorporation of N4-aminocytosine into cellular DNA

N4-Aminocytidine induced mutation to 6-thioguanine resistance in Chinese hamster lung V79 cells in culture. Previous studies with experimental systems of in vitro DNA synthesis and of phage and bacterial mutagenesis have shown that this nucleoside analog induces base-pair transitions through its incorporation into DNA, with its erroneous base-pairing property. Incorporation of exogenously added [5-3H]N4-aminocytidine into the DNA of V79 cells was in fact observed in the present study. N4-Aminodeoxycytidine was not mutagenic for the V79 cells. Several alkylated N4-aminocytidine derivatives were tested for their mutagenicity in this system. Those with an alkyl group on the N'-nitrogen of the hydrazino group at position 4 of N4-aminocytidine were mutagenic, but those having an alkyl on the N4-nitrogen were not. These results are consistent with those previously observed in the bacterial mutagenesis systems, and agree with a mechanism of mutation in which a tautomerization of N4-aminocytosine is the necessary step for causing the erroneous base pairing.     

Elongation and shortening of time required for entry into S phase after release from G 1 and G 0 arrests in temperature-sensitive mutants of rat 3Y1 Cells

Temperature-sensitive (ts) mutants of rat 3Y1 fibroblasts representing four separate complementation groups (3Y1tsD123, 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203) are arrested mainly in the G1 phase when cells of randomly proliferating population at 33.8 degrees C are shifted to 39.8 degrees C (temperature arrest). We examined the time lag of the cellular entry into the S phase after release at 33.8 degrees C, both from the temperature arrest and from the arrest at 33.8 degrees C at a confluent cell density (density arrest). In the temperature-arrested cells, as the duration of temperature arrest increased, the time lag of entry into S phase after shift down to 33.8 degrees C was prolonged, in all four mutants. These observations suggest that the four different functional lesions, each causing arrest in the G1 phase, are also responsible for prolongation of the time lag of entry into the S phase in cells arrested in the G1 phase. The prolongation of the time lag in the temperature-arrested cultures was accelerated at a higher cell density, in medium supplemented with a lower concentration of serum, and at a higher restrictive temperature. In the density-arrested cells, as the duration of pre-exposure to 39.8 degrees C was increased, the time lag of entry into S phase at 33.8 degrees C after release from the arrest was drastically prolonged, in all four mutants. In 3Y1tsF121, 3Y1tsG125, and 3Y1tsH203, when the density-arrested cells were prestimulated by serum at 39.8 degrees C for various periods of time, the time lag of entry into S phase after release from the density arrest at 33.8 degrees C was initially shortened, and then, prolonged progressively as the period of prestimulation increased. These findings, taken together with other data, show that all four ts defects affect cells in states ranging from the deeper resting to mid- or late-G1 phase. It is suggested that events represented by these four mutants are required for entry into the S phase and normally operate in parallel but not in sequence in cells in states ranging from the deeper resting to the mid- or late-G1 phases, though they may affect each other.     

Characterization of tumor-associated fucogangliosides from PC 12 pheochromocytoma cells

PC 12h pheochromocytoma cells were subcutaneously transplanted into rat. We found the transplanted tumors accumulated some fucogangliosides associated with PC 12 cells. These gangliosides were isolated and purified by DEAE-Sephadex A-25 and Iatrobeads column chromatographies. Their structures were determined by fast atom bombardment mass spectrometry, proton nuclear magnetic resonance spectrometry, permethylation study, and sequential degradation using various exoglycosidases and mild acid hydrolysis. Two tumor-associated fucogangliosides were found to possess the blood group B determinant as follows: G6: IV2Fuc alpha, IV3Gal alpha, II3NeuAc, GgOse4Cer; G11: IV2Fuc alpha, IV3Gal alpha, II3 (NeuAc)2, GgOse4Cer. A ganglioside with the similar structure as ganglioside G6 was isolated from rat hepatoma cells (Holmes, E.H., and Hakomori, S-I. (1982) J. Biol. Chem. 257, 7698-7703). However, ganglioside G11 has not previously been reported in the literature. These fucogangliosides reacted with the monoclonal antibody prepared by immunizing mice with PC 12h cells. Other fucogangliosides were also found to accumulate in the transplanted tumor tissues. They were identified as fucosyl-GM1 and fucosyl-GDlb. These fucogangliosides did not react with the monoclonal antibody against PC 12h cells.     

Activation of mouse peritoneal macrophages by synthetic glyceroglycolipid liposomes

Summary Liposomes composed of chemically synthesized glyceroglycolipids, such as 1,2-dipalmityl-[-cellobiosyl-(1 3)]-glycerol (Cel-DAG), 1,2-dipalmityl-[-lactosyl-(1 3)]-glycerol, or 1,2-dipalmityl-[-maltosyl-(1 3)]-glycerol, were found to enhance protective immunity against transplantable tumor cells (sarcoma 180) in ICR mice. Peritoneal exudate cells prepared from mice treated in vivo with Cel-DAG showed cytostatic activity in vitro against the mouse leukemia cell line, EL-4. Adherent cells separated from this preparation showed similar activity. Peritoneal cells from polypeptone-injected mice acquired appreciable cytostatic activity when incubated in vitro in the presence of glyceroglycolipid liposomes. The adherent cell fraction alone showed rather weak cytostatic activity when pretreated with the glyceroglycolipids, and full activity was restored by supplementing with the nonadherent cell fraction. The ability of glycolipids to induce tumoricidal effects was affected by cholesterol content: with increasing cholesterol content, the activities decreased. Cholesterol-free glycolipid liposomes were taken more efficiently by macrophages than cholesterol-containing liposomes. Cholersterol modifies the surface property of glyceroglycolipid liposomes. Activation of macrophages is responsible for enhancement of protective immunity against tumor cells by injection of these glycolipids in vivo.This work was supported in part by Grants-in-Aid (Nos. 58010010, and 59870076) for Scientific Research from the Ministry of Education, Science and Culture of Japan     

The complete sequence of the rice (Oryza sativa) chloroplast genome: intermolecular recombination between distinct tRNA genes accounts for a major plastid DNA inversion during the evolution of the cereals

Summary The entire chloroplast genome of the monocot rice (Oryza sativa) has been sequenced and comprises 134525 bp. Predicted genes have been identified along with open reading frames (ORFs) conserved between rice and the previously sequenced chloroplast genomes, a dicot, tobacco (Nicotiana tabacum), and a liverwort (Marchantia polymorpha). The same complement of 30 tRNA and 4 rRNA genes has been conserved between rice and tobacco. Most ORFs extensively conserved betweenN. tabacum andM. polymorpha are also conserved intact in rice. However, several such ORFs are entirely absent in rice, or present only in severely truncated form. Structural changes are also apparent in the genome relative to tobacco. The inverted repeats, characteristic of chloroplast genome structure, have expanded outward to include several genes present only once per genome in tobacco and liverwort and the large single copy region has undergone a series of inversions which predate the divergence of the cereals. A chimeric tRNA pseudogene overlaps an apparent endpoint of the largest inversion, and a model invoking illegitimate recombination between tRNA genes is proposed which accounts simultaneously for the origin of this pseudogene, the large inversion and the creation of repeated sequences near the inversion endpoints.     

Polymorphism of T-cell receptor genes among laboratory and wild mice: Diverse origins of laboratory mice

Southern blots of genomic DNA from 23 strains of laboratory mice and 19 individual wild mice were examined for restriction fragment length polymorphisms in their loci encoding the T-cell receptors (Tcr): the constant regions of the α, β, and γ chains (C _α,C _β, andC _γ) and a variable region family of the β chain (V _β8). Only a few polymorphisms were observed for each locus in the laboratory mice after using three restriction enzymes,Bam HI,Eco RI, andHind III. All the laboratory mice examined fall into one of two types for theC _α,C _β andV _β8 loci and one of three types for theC _γ. These types are found in some of the wild mice studied, indicating that they were already present in the founder mice of laboratory mouse strains. In contrast, theTcr genes are highly polymorphic among wild mice. Analysis of the polymorphisms in these loci suggests that laboratory mice have inherited their genes not only fromMus musculus domesticus, but also from other subspecies, and much more than previously believed from Asian subspecies.