Morphological studies on the bathyal ascidian,Megalodicopia hians Oka 1918 (Octacnemidae,Phlebobranchia), with remarks on feeding and tunic morphology

Megalodicopia hians Oka is a solitary ascidian belonging to the family Octacnemidae inhabiting the bathyal /abyssal zone as well as other octacnemid ascidians. The phylogenetic relationship of octacnemids is open to argument because of its extraordinary morphological features due to habitat adaptation, e.g., a pharynx lacking ciliated stigmata. Aggregations of M. hians were discovered by the manned submersible Shinkai 2000 in the bathyal seafloor of Toyama Bay, Japan Sea, in 2000; this was the first in situ observation of M. hians in the Japanese coastal waters. In 2001, a total of 36 M. hians specimens were collected from the bay (592 to approximately 978 m deep). In situ observation indicated that M. hians usually opens its large oral apertures to engulf the drifting food particles in the water current. Microscopical observation of the gut contents also showed that M. hians is a non selective macrophagous feeding on small crustaceans, diatoms, detritus, and so on. Along with the position of the intestinal loop and gonad, the morphological characteristics of the tunic (integument of ascidians) suggest that M. hians is closely related to Cionidae and/or Corellidae. Some symbiotic/parasitic organisms were occasionally found in the tunic, including rod-shaped bacteria, fungi-like multicellular structure, and spawns of unknown animals.     

Significance of venous anastomosis in fingertip replantation

Adequate venous outflow is the most important factor for successful fingertip replantation. The authors have attempted venous anastomosis in all cases of fingertip replantation to overcome postoperative congestion. In this article, the significance of venous repair for fingertip replantation is described from the authors' results of 64 complete fingertip amputations in 55 consecutive patients, which were replanted from January of 1996 to June of 2001. The overall survival rate was 86 percent. Of the 44 replantations in zone I, 37 survived, and the success rate was 84 percent. Of the 20 replantations in zone II, 18 survived, and the success rate was 90 percent. Venous anastomosis was attempted in all cases, but it was possible in 39 zone I and in all zone II replantations. For arterial repair, vein grafts were necessary in 17 of the 44 zone I and in one of the 20 zone II replantations; for venous repair, they were necessary in six zone I replantations and one zone II replantation. Postoperative vascular complications occurred in 15 replantations. There were five cases of arterial thrombosis and 10 cases of venous congestion. Venous congestion occurred in nine zone I and one zone II replantations. In five of these 10 replantations, venous anastomosis was not possible. In another five replantations, venous outflow was established at the time of surgery, but occlusion occurred subsequently. Except for the five failures resulting from arterial thrombosis, successful venous repair was possible in 49 of 59 replantations (83 percent). Despite the demand for skillful microsurgical technique and longer operation time, the authors' results using venous anastomosis in successful fingertip replantations are encouraging. By performing venous anastomosis, external bleeding can be avoided and a higher survival rate can be achieved. Venous anastomosis for fingertip replantation is a reliable and worthwhile procedure.     

Xenogeneic rejection among three botryllids (compound Ascidians)

Xenogeneic rejection was observed among colonies of three botryllids, Botryllus scalaris, Botryllus primigenus, and Botrylloides simodensis. Allogeneic recognition occurs in each of these species, but the manner of allogeneic rejection differs among them. We studied xenogeneic rejection reactions among these species under the following conditions: colony contact at natural growing edges, colony contact at artificially cut surfaces, and injection of xenogeneic blood plasma into a vascular vessel. In the first two cases, xenogeneic rejection occurred only in Botryllus primigenus and Botrylloides simodensis. The features of that xenogeneic rejection were similar to those of allogeneic rejection in each of these two botryllids. Injection of xenogeneic blood plasma induced responses similar to those of allogeneic rejection in all three botryllids. It is interesting to note that colonies of Botryllus scalaris never showed any response against injected blood plasma from allogeneic incompatible colonies, unlike the responses seen in colonies of the other two botryllids under the same conditions. On the basis of these results, the relationship between allogeneic and xenogeneic rejection in botryllids is discussed.     

Studies on Japanese Botryllid Ascidians. III. A new species of the genus Botryllus with a vivid colony color from the vicinity of Shimoda

The morphology and life history of a new species of the genus Botryllus belonging to the family Botryllidae are described in detail. This ascidian was collected from the stony shore in the cove near Shimoda Marine Research Center, University of Tsukuba (Shimoda, Shizuoka Prefecture, Japan). The ascidian colony was easily distinguished from colonies of other botryllids because it was very thin and bright pink in color. The arrangement of ovary and testis in this ascidian was the same as that in other species of the genus Botryllus. This ascidian was prolific, with 1-5 embryos on each side of a zooid, and the embryos of this ascidian developed in the peribranchial cavity without any brooding organs as in Botryllus scalaris. We observed the processes and features of the allorecognition reaction in colony specificity and found that allorejection occurred after fusion of the vascular system between two incompatible colonies. This manner of allorejection is also shown in B. scalaris and Botryllus delicatus; however, the reaction speed of allorejection is faster than that of B. delicatus and similar to that of B. scalaris. These results indicate that this ascidian might be closely related to B. scalaris.     

Studies on Japanese botryllid ascidians. IV. A new species of the genus Botryllus with a unique colony shape, from the vicinity of Shimoda

The morphology and life history of a strange and unidentified botryllid ascidian were investigated. This ascidian was first collected from the stony shore of Ebisu Island in Shimoda, a city on Izu peninsula in central Japan. Unlike other botryllid ascidians, whose colonies are flat and smooth, this ascidian's colonies are rugged. In each colony, zooids are arranged into several oval systems, each of which has a thick part containing zooids and very thin parts that do not. The arrangement of ovary and testis in this species is the same as in other species of the genus Botryllus; the ovary is situated anterior to the testis. The embryo of this ascidian develops in the peribranchial cavity of its mother zooid without any brooding organs, as is the case with Botryllus scalaris and Botryllus puniceus. Meanwhile, the results of cut colony assay experiments did not show the existence of colony specificity in this ascidian. Even when two syngeneic colonies were brought into contact at their growing edges, none fused together. On the other hand, when two colonies were brought into contact with each other at their cut surfaces, they always fused into a single colony, regardless of their origin. Therefore, this species may be the only species that lacks colony specificity among the botryllids studied so far.     

A genomewide survey of developmentally relevant genes in Ciona intestinalis. X. Genes for cell junctions and extracellular matrix

Cell junctions and the extracellular matrix (ECM) are crucial components in intercellular communication. These systems are thought to have become highly diversified during the course of vertebrate evolution. In the present study, we have examined whether the ancestral chordate already had such vertebrate systems for intercellular communication, for which we have searched the genome of the ascidian Ciona intestinalis. From this molecular perspective, the Ciona genome contains genes that encode protein components of tight junctions, hemidesmosomes and connexin-based gap junctions, as well as of adherens junctions and focal adhesions, but it does not have those for desmosomes. The latter omission is curious, and the ascidian type-I cadherins may represent an ancestral form of the vertebrate type-I cadherins and desmosomal cadherins, while Ci-Plakin may represent an ancestral protein of the vertebrate desmoplakins and plectins. If this is the case, then ascidians may have retained ancestral desmosome-like structures, as suggested by previous electron-microscopic observations. In addition, ECM genes that have been regarded as vertebrate-specific were also found in the Ciona genome. These results suggest that the last common ancestor shared by ascidians and vertebrates, the ancestor of the entire chordate clade, had essentially the same systems of cell junctions as those in extant vertebrates. However, the number of such genes for each family in the Ciona genome is far smaller than that in vertebrate genomes. In vertebrates these ancestral cell junctions appear to have evolved into more diverse, and possibly more complex, forms, compared with those in their urochordate siblings.     

MAPKKK-Related protein kinase NPK1: Regulation of the M phase of plant cell cycle

The tobaccoNPK1 gene encodes a homolog of mitogenactivated protein kinase kinase kinases. We have recently identified tobacco kinesin-like proteins (NACK1/2) as activators for NPK1. Immunochemical analyses of NPK1 and NACK1 proteins suggest that NPK1 is involved in the regulation of some process in the M phase of the plant cell cycle. The extended abstract of a paper presented at the 13th International Symposium in Conjugation with Award of the International Prize for Biology “Frontier of Plant Biology”     

Micropropagation of Cypripedium macranthos var. rebunense through Protocorm-like Bodies Derived from Mature Seeds

Cypripedium macranthos var. rebunense is the most famous terrestrial orchid in Japan, since the variety has large beautiful yellowish-white flowers and is threatened with extinction. Establishment of an efficient method for micropropagation is urgently needed. When imbibed mature seeds of the orchid, that had been pre-chilled at 4°C for 3 months, were sown onto Hyponex-peptone medium that contained both α-naphthaleneacetic acid (NAA) and cytokinin, protocorm-like bodies (PLBs) were formed from germinated seeds. Although the growth of PLBs was very slow, plantlets were easily regenerated from the PLBs on hormone-free medium. The PLBs were subcultured eight times along 2 years without loss of ability to regenerate plantlets, and one aggregate of PLBs (ca. 5 mm in diameter) produced ca. 10 plants within a year. A reduction of commercial value through a large-scale micropropagation by this method will be able to prevent illegal collection from the wild populations.