NESTMATE RECOGNITION AND KIN RECOGNITION IN ANTS

Abstract  All ants (Hymenoptera, Formicidae) are highly eusocial insects that are characterized by reproductive division of labor with sterile castes (worker and soldier) helping fertile castes (queen and male) to reproduce.
Ant societies, like other complex animal societies, have developed a sophisticated communication system, in which recognition behaviors are frequently involved Recognition abilities allow individuals to orient and modulate their behaviors effectively and appropriately in response to the characteristics andlor signals expressed by other organisms. Among recognition behaviors, nestmate recognition and kin recognition mechanisms have attracted great attention of sociobiologists, ecologists, insect physiologists and biochemists since 1970's. This is parallel with the popularization of Hamilton's kin selection theory. The present paper aims at reviewing the current understanding on nestmate/kin recognition in ants. This review consists of three parts. The first part concerns the diversity of recognition behaviors and their ecological implications with emphasis on nestmatelkin recognition; in the second part, the current understandings on the mechanism of nestmatelkin recognition are outlined; and in the third part, we discuss the ontogenetic development of nestmate recognition behavior and naturally mixed colonies. The study of the integration mechanism of social parasite may provide heuristic clues to the understanding of kin/nestmate recognition system.     

Membrane-bound lipoxygenase of rat cerebral microvessels

The microvessels isolated from rat cerebral cortex has arachidonate lipoxygenase activity, which was not due to possible contamination of the platelets. The major product was identified to be 12-hydroxyeicosatetraenoic acid. After homogenization and sonication of the microvessel preparations, the lipoxygenase activity was recovered both in the membrane- and the cytosol-fractions, whereas that in the platelets was recovered in the cytosol fraction. Membrane-bound lipoxygenase of the microvessels has apparent Km value of 3.8 microM for arachidonic acid, which was corresponded to 1/5 of that in the platelet enzyme. Microvessel lipoxygenase was inhibited by nordihydroguaiaretic acid but not by indomethacin.     

New human colorectal carcinoma cell lines that secrete proteinase inhibitors in vitro

Two new human cell lines, RCM-1 and CoCM-1, have been established from primary colorectal adenocarcinomas. Both cell lines were unique in that the cultures secreted trypsin inhibitors in vitro. The activities of these inhibitors were accumulated in serum-free media of both cell lines over a period of several days. Two inhibitors (PI-1 and PI-2) were isolated from serum-free conditioned medium in which RCM-1 was grown by anion-exchange and gel filtration high-performance liquid chromatography. PI-1 inhibited trypsin and chymotrypsin strongly, and pancreatic elastase weakly. Its molecular weight was about 57 kilodaltons (Kd) as determined by gel filtration chromatography. It cross-reacted with the antiserum elicited against human α₁-antitrypsin in double immunodiffusion. PI-1 corresponding to α₁ - antitrypsin was also demonstrated immunohistochemically in both cell lines. PI-2 inhibited trypsin strongly, and chymotrypsin, kallikrein and plasmin weakly. It had higher molecular weight (200–300 Kd) than that of PI-1, and did not crossreact with antisera against human α₁-antitrypsin, α₂-macroglobulin, α₁-antichymotrypsin, α₂-plasmin inhibitor, inter-α-trypsin inhibitor and urinary trypsin inhibitor. RCM-1 and CoCM-1 are the first colorectal adenocarcinoma cell lines that secrete functionally active trypsin inhibitors, including α₁-antitrypsin in vitro, and are useful for the study of tumor-cell derived proteinase inhibitors.     

Suppressive effect of spinach extract on the formation of melanin in B16 mouse melanoma cells

A non-dialyzable extract of fresh spinach leaves exhibited a strong antioxidant activity towards oxidation of linoleic acid and suppressed the melanin formation of a mouse melanoma cell line, B16 melanoma 4A5, without any significant effect on the proliferation of cells.     

Morphology and molecular phylogeny of the marine diatom genus Nagumoea (Bacillariophyceae) from Japan

The canal-bearing diatom genus Nagumoea, described based on only morphological evidence, was tentatively assigned to the order Bacillariales, although its phylogenetic position remained unclear. Because three isolates of Nagumoea (SK002, SK024 and SK053) were successfully established from Japanese coasts, we performed their morphological observations and molecular phylogenetic analyses to discuss the phylogeny and taxonomic position of this genus. Strains SK002 and SK024 were identified as Nagumoea africana, whereas SK053 conformed with Nagumoea serrata. There was high interspecific divergence between N. africana and N. serrata in the rbcL sequences (8.03–8.17%), indicating their distinctness. Furthermore, intraspecific variations were detected within N. africana (2.35%) in the rbcL, implying its cryptic diversity. The maximum likelihood and Bayesian phylogenetic trees inferred from the plastid rbcL, psbC and nuclear 18S rDNA genes recovered Nagumoea as monophyletic with strong statistical support and embedded within an unresolved, poorly supported lineage containing Achnanthes, Craspedostauros, Staurotropis and Undatella in the canal-bearing order Bacillariales (= the family Bacillariaceae). Although the constrained tree based on the monophyly of Nagumoea and the other canal-bearing clade (Surirellales and Rhopalodiales) was statistically rejected by the topology tests, the phylogenetic position of Nagumoea with other Bacillarialean members remains equivocal. The possession of two plastids positioned fore and aft, observed in the present study, and lack of keel, typical of the Bacillariales, indicate the possibility of Nagumoea being part of the ingroup of the Bacillariales or its closely related outgroup.     

Expression of neural cell adhesion molecule (N-CAM) in perisinusoidal stellate cells of the human liver

Neural cell adhesion molecule (N-CAM) is distributed in most nerve cells and some non-neural tissues. The present immunohistochemical study has revealed, for the first time, the expression of N-CAM in perisinusoidal stellate cells of the human liver. Liver specimens were stained with monoclonal antibody against human Leu19 (N-CAM) by a streptoavidin-biotin-peroxidase-complex method. Light- and electron-microscopic analyses have shown that N-CAM-positive nerve fibers are distributed in the periportal and intermediate zones of the liver lobule. Perisinusoidal stellate cells in these zones are also positive for N-CAM. N-CAM is expressed on the surface of the cell, including cytoplasmic projections. Close contact of N-CAM-positive nerve endings with N-CAM-positive stellate cells has been observed. On the other hand, stellate cells in the centrilobular zone exhibit weak or no reaction for N-CAM. Perivascular smooth muscle cells and fibroblasts in the portal area and myofibroblasts around the central veins are negative for N-CAM. The present results indicate that the perisinusoidal stellate cells in the periportal and intermediate zones of the liver lobule characteristically express N-CAM, unlike other related mesenchymal cells, and suggest that the intralobular heterogeneity of N-CAM expression by stellate cells is related to the different maturational stages of these cells.