Myung-Hee Yoon

Unusual Mitochondrial DNA Polymorphism of the Blue Mussel (Mytilus edulis) Species Complex on the Southern Coast of Korea

Mitochondrial DNA (mtDNA) from 54 specimens of the blue mussel (Mytilus edulis) species complex sampled from the southern coast of Korea was assayed for polymorphism with a portion of the COIII gene (336 bp). Fifteen haplotypes were found. PAUP, one-step networks, and PHYLIP analyses revealed the presence of two clearly differentiated mitochondrial clades (termed clades B and E), separated by 3.6% of minimum sequence divergence. The distribution pattern of the species appears to be consistent with category II of the phylogeographic pattern sensu (Avise et al., 1987): the presence of two discontinuous and distinct mtDNA genotypes in the same geographic region. This unusual mitochondrial polymorphism was explained by the presence of the Mediterranean species, M. galloprovincialis, possessing mtDNA of both M. galloprovincialis and M. edulis.

Effects of 4-t-octylphenol and Nonylphenol on the Reproduction of the Striped Field Mouse

Abstract To investigate the effects of octylphenol and nonylphenol on the reproduction of the striped field mouse, the mice were subcutaneousely injected with 4-t-octylphenol 800 mg/kg (OP800), nonylphenol 900 mg/kg (NP900) or OP800 + NP900 (OPNP), respectively, in two times a week for 2 months. As the results, there were no differences between the control and the compound-treated groups in the body weight in both sexes, and the GSI (gonadosomatic index) and SVI (seminal vesicles index) in the adult males. But histological abnormalities of the reproductive organs in the mice seems to be related to the compound. This suggestion is supported by the facts that most mice treated with the compounds had only a small number of spermatozoa in the shrunken epididymal tubules. In addition, the shrunken reproductive organ in one mouse treated with the NP, suggests that the abnormalities in the wild striped field mice might be induced by the compound. Furthermore, it is indicated that the compounds must be toxicants to inhibit pregnancy, judging from the fact that all the mice treated with the compounds had failed to deliver.

Comparative Ultrastructure of Secretory Granules of the Submandibular Gland in the Korean Spider Shrew, Sorex caecutiens, the Lesser White-toothed Shrew, Crocidura suaveolens and the Big White-toothed Shrew, Crocidura lasiura

The ultrastructure of the secretory granules of the submandibular gland was examined in the Korean spider shrew, Sorex caecutiens, lesser white-toothed shrew, Crocidura suaveolens and big white-toothed shrew, C. lasiura. The mucous and serous acinar granules of S. caecutiens with a border of the lucid corona differed from those of C. suaveolens and C. lasiurar with a dense lateral border. The mucous acinar granules of C. lasiura with several bands producing a variety of patterns in the matrix were similar to those of C. suaveolens. The serous acinar granules of C. lasiura had a homogenous pale center surrounded by minute dense specks or had an unusual substructure showing a geometric pattern according to the inclusions in the pale matrix of the granules. This is the first report of an unusual substructure showing a geometric pattern of the serous acinar granules of C. lasiura. The myelin-like body was observed in the granular duct cell of the three species of shrew. The myelin-like body of S. caecutiens with layers of unit membranes was different from that of C. suaveolens and C. lasiura with paired membranes. Therefore, the layers composing of the paired membranes of the myelin-like body might be one of the characteristics of Crocidura.

Effects of Short-Term Exposure with Tri-n-Butyltin Chloride (TBTCl) and Bisphenol A on the Reproduction of the Striped Field Mouse

To investigate the effects of short-term treatment with tri-n-butyltin chloride (TBTCl) and bisphenol A (BPA) on the reproduction of striped field mice, the mice were intramuscularly injected with TBTCl or BPA immediately before the reproductive season and examined in the reproductive season after keeping them for 4 months. As a result, there were no differences between the control and the compound-treated groups regarding body weight in both sexes, the residual levels of the compounds in the adult males, and the gonadosomatic index (GSI) and the histological structures with LM and EM of the testes and epididymides in both the adult and young males. The infant mortality and abortion rate, however, were high in the TBTCl-treated groups and BPA-treated groups respectively, compared to the control group. Conclusively, it was suggested that short-term treatment with TBTCl or BPA in mice in the non-reproductive season might have inhibited the development of the uterine embryos or fetuses, although it did not induce accumulations of these compounds or affect the reproductive organs of adult and young (F1) males.

Effect of the Deep Sea Water on the Blood Glucose and the Langerhans` Islet in the STZ-induced type I Diabetic Mice

Effects of deep sea water on blood glucose and the Langerhans` islet in STZ-induced type I diabetic mice were investigated. Results showed that diabetic symptoms in STZ-induced diabetic mice improve with a supplement of deep sea water. That is, the level of blood glucose was lower, the area of the Langerhan` islet was wider, and the number of pancreatic -cells was larger in the diabetic mice supplied with deep sea water than in the diabetic mice supplied with tap water. Such effects might be related to the high level of Mg in the deep sea water.