A CASE OF CONGENITAL ABSENCE OF THE LOWER SECOND PREMOLARS IN CATTLE AND A PHYLOGENETIC CONSIDERATION OF ITS ORIGIN

A 7 year-old cow whose lower second premolar was absent on both sides of the jaw was examined. In order to establish whether its absence was congenital or of some other cause, such as caries, examinations were carried out and discussions were held. It was established that this was a case of congenital absence. This is of interest in connexion with the orthogenetic reduction of the cheek teeth on the ruminantia

Possible conservation units of the sun bear (Helarctos malayanus) in Sarawak based on variation of mtDNA control region.

The mitochondrial DNA control region of the sun bear（Helarctos malayanus） was sequenced using ２１DNA samples collected from confiscated sun bears to identify conservation units, such as evolutionarily significant units and management units, in Sarawak, Borneo Island. A total of １０ haplotypes were observed, indicating the presence of at least two lineages in the sun bear population in Sarawak. Presumably, these two lineages could represent evolutionarily significant units. However, the geographical distributions of the two lineages remained unknown due to the lack of information regarding the exact capture locations of the confiscated sun bears. It is essential to elucidate the geographical distributions of these lineages in order to create a proper conservation plan for the sun bears in Sarawak. Therefore, further studies examining the haplotype distributions using DNA samples from known localities are essential

Mitochondrial DNA variation in the Japanese marten Martes melampus and Japanese sable, Martes zibellina

Genetic relationship among Japanese sables, Marte zibellina and the introduced Japanese martens, Martes melampus in northern Japan was revealed by analyzing a 521-524bp DNA sequence from the cytochrome b (112bp)/transfer RNA-threonine (67bp)/tRNA-proline (65bp) and control region (277-280bp) of the mitochondrial genome. Intraspecific differences in sequences of M. zibellina and M. melampus (3.8-15.0％ and 1.9-16.4％, respectively) were similar to interspecific diffrences between these two species (5.8-16.6％). Comparison of sequence data exhibited five haplotypes of M. melampus and four haplotypes of M. zibellina, which clustered into two groups (clusters-A and-B). Cluster-A included two haplotypes of M. melampus and two haplotypes of M. zibellina, whereas cluster-B included three haplotypes of M. melampus and two haplotypes of M. zibellina. Results of this study lead three possible explanations. Firstly, past hybridization between M. zibellina and M. melampus might have occurred. Secondary, these two species might have similar heteroplasmy of mt DNA. Thirdly, these haplotypes might have come from nuclear genome. Although further intensive studies are needed to make a conclusion, detection of hybridization with the Japanese marten are occurred or not is quite important to conserve the Japanese sable

NUCLEAR BODIES IN CELLS OF VARIOUS LYMPHATIC ORGANS

The sizes and frequency of the nuclear bodies were observed in cells of the thymic cortex, thymic medulla, lymph node, spleen and patch of Peyer of mice. The nuclear bodies are most often found in small lymphocytes (32.3 to 37.1%) of the lymph node, spleen and patch of Peyer, but very rarely in small lymphocytes of the cortex (4.4%) and medulla (14.5%) of the thymus. The bodies are also often found in mesenchymal and epithelial reticular cells, but are variable in occurrence. From the frequency and size of the nuclear body in cells of lymphocytic series, it is suggested that in thymic cortex, about a half of the small lymphocytes contain a small nuclear body, and in the medulla all small lymphocytes contain a small or a large body, and in the other lymphatic organs all of small lymphocytes include two or more large, grouped, nuclear bodies. The outer filamentous coat of the nuclear bodies is closely related with nucleolus. No nuclear bodies were found in the large lymphocytes and mitotic cells. Thus the relationship between morphological changes of the nuclear body and differentiation of lymphocytes has been discussed in this paper

STRUCTURAL AND CELLULAR CHANGES IN THE LYMPH NODES OF YOUNG MICE

In this study, the writers concentrated their attention upon histological changes of structures and cells of mouse lymph nodes. According to the difference in structural maturity, the nodes were classified as to embryonic, immature and mature types. The "light zone" was found in immature type lymph nodes. The structure suggests the possibility of independent primitive lymphoid tissue of the lymph node in contrast to the "thymus-dependent area". The appearance and regional differences of large pyroninophilic cells, plasma cells, mast cells and PAS positive cells were also studied : Large pyroninophilic cells and mast cells were found in the lymph nodes of the neonatal mice and increased in number with age. Plasma cells began to appear in lymph nodes at the end of the first week and increased in number rapidly after the end of the third week. Regional differences of these cells were clear : Large pyroninophilic cells were dominant in the mesenteric lymph nodes. Plasma cells and mast cells were predominantly found in the submandibular lymph nodes. PAS positive cells were very rare in lymph nodes of young mice

Are ancient dugong bones useful for analyses?

December 15-17, 2007, Royal Phuket City Hotel, Phuket, ThailandThe Ryukyu Archipelago of Japan is the northern limit of the distribution of the dugong (Dugong dugon), and populations in Japanese waters are small. Therefore, little biological information is available on local dugong, and new specimens or techniques are necessary to help shed light on the populations of this region. We assessed the suitability of using ancient dugong bones collected from ruins on Shimoji Island, in the Yaeyama Islands, for biological investigations. We collected more than 1, 000 fragments of animal bone at the site. From these, we were able to reconstruct 91 dugong skulls, from which we estimated body length (124.2–301.2 cm) and age group compositions (43% adults, 29% adolescents, and 16% juveniles). Our estimation revealed a wide range of age groups, from neonates to mature adults. These results suggest that the ancient dugong population bred and spent all life stages along the coasts of the Yaeyama Islands. Moreover, our study shows that these ancient bones can be used for meaningful biological investigations on dugong, and should help to elucidate their historical distribution and population structure in this area

PECULIAR NUCLEAR INCLUSION, NUCLEOLOID BODY, IN LYMPHOCYTES

Peculiar nuclear inclusions, "nucleoloid bodies", were found in nuclei of several types of cells in mouse lymph nodes and in sheep hemal nodes. The nucleoloid bodies were morphologically independent of the nucleolus and the chromatin. They were spherical in shape, ranging from 200 to 900mμ in size, with outer and inner layers that could be differentiated. The outer layer consisted of numerous filaments arranged concentrically or spirally which encircle completely the inner layer. The filaments were helical coils, measuring 70〜80 Å in width. The diameter of the fibril coiled into the helix was approximately 20〜30 Å. The same helical fibrils were also found in the chromatins of nucleoplasm around the nucleoloid bodies. The inner layer was composed of a homogeneous substance of lower electron density and of a variable number of dense granules which were similar to ribosomes in appearance. At high magnification, however, the granules seemed to be twisted threads in which thinner fibrils were coiled. The threads were 200〜250 Å in width and the helical fibrils measured about 50 Å in diameter. The nucleoloid bodies were separated into two types. The first type was small, about 200〜300 mμ in size, and had no or a few dense granular elements in the inner layer. The second type was larger, over 400 mμ in size, whose inner layer had numerous granular elements. The nucleoloid bodies were most often observed in small lymphocytes, in particular the large bodies (second type) were almost limited to the small lymphocytes, though rarely in plasma cells as well. Even if nucleoloid bodies were found in cells other than small lymphocytes, it was rare finding and usually involved the small bodies (first type) only. The nucleoloid bodies seemed to derive from the true nucleoli and were observed in the chromosomes throughout mitosis. From the ultrastructure of the nucleoloid bodies, it was suggested that the bodies consist of a specialized nuclear protein unlike the chromosomes