BACKGROUND: Many animals such as chinchilla, guinea pig, rat and rabbit have been used for study of the otitis media and their morphology of the eustachian tube are well known. However, it is not easy to use these animals in Korea. Therefore, active morphological study of the eustachian tube related to otitis media have not been performed. The Mongolian gerbil is an easily maintained rodent which has been useful for investigations of the ear canal cholesteatoma and inner ear. However, histologic study of the eustachian tube of Mongolian gerbil has not been established. OBJECTIVES: The purpose of this study was to describe the light microscopic morphology and the ultrastructure of the eustachian tube in Mongolian gerbil in order to prepare basic morphological data for the future animal study concerning pathogenesis of otitis media. MATERIALS & METHOD: Eight normal adult(90 to 120 days old) Mongolian gerbils(16 ears) were used for this study. Eustachian tube specimen was obtained after perfusion fixation and fixed. After 3 weeks of decalcification, paraffin block and EPON 812 block were made and sectioned. Those were observed under light microscope and transmission electron microscope. RESULTS: The cartilage and muscular structure(tensor veli palatini muscle, levator veli palatini muscle) of the eustachian tube of Mongolian gerbil were similar to those of other experimental animals. The total length of eustachian tube of Mongolian gerbil was relatively short and natural infection was rare.In the epithelium of the eustachian tube of Mongolian gerbil, four types of epithelial cells, ie ciliated, nonciliated, secretory cells and basal cells were identified like other experimental animals. On transmission electron microscopic findings, three types of secretory cells, ie, dark granulated, light granulated and mixed granulated cells were observed. The subepitheial glandular structure was observed along the whole length of eustachian tube. CONCLUSION: In this study, we found that the morphology of the eustachian tube of Mongolian gerbil was similar to those of other experimental animals such as chinchilla, guinea pig, rat and we recognized that Mongolian gerbil is possible to be used as a good experimental model of eustachian tube study for otitis media research.
Animals ; Cartilage ; Chinchilla ; Cholesteatoma ; Ear Canal ; Ear, Inner ; Epithelial Cells ; Epithelium ; Eustachian Tube* ; Gerbillinae* ; Guinea Pigs ; Korea ; Models, Theoretical ; Otitis Media ; Paraffin ; Perfusion ; Rats ; Rodentia

Chigger mites are parasites of rodents and other vertebrates, invertebrates, and other arthropods, and are the only vectors of scrub typhus, in addition to other zoonoses. Therefore, investigating their distribution, diversity, and seasonal abundance is important for public health. Rodent surveillance was conducted at 6 districts in Shandong Province, northern China (114–112°E, 34–38°N), from January to December 2011. Overall, 225/286 (78.7%) rodents captured were infested with chigger mites. A total of 451 chigger mites were identified as belonging to 5 most commonly collected species and 3 genera in 1 family. Leptotrombidium scutellare and Leptotrombidium intermedia were the most commonly collected chigger mites. L. scutellare (66.2%, 36.7%, and 49.0%) was the most frequently collected chigger mite from Apodemus agrarius, Rattus norvegicus, and Microtus fortis, respectively, whereas L. intermedia (61.5% and 63.2%) was the most frequently collected chigger mite from Cricetulus triton and Mus musculus, respectively. This study demonstrated a relatively high prevalence of chigger mites that varied seasonally in Shandong Province, China.
Animals ; Arthropods ; Arvicolinae ; China* ; Cricetinae ; Cricetulus ; Humans ; Invertebrates ; Mice ; Mites* ; Murinae ; Neptune ; Parasites ; Prevalence ; Public Health ; Rats ; Rodentia* ; Scrub Typhus ; Seasons ; Trombiculidae* ; Vertebrates ; Zoonoses

OBJECTIVETo investigate differences between hepatic and biliary lipid metabolism and secretion of genetically gallstone-susceptible (C57L) and resistant (AKR) mice and the mechanism of cholesterol gallstone formation.

METHODSThe inbred C57L and AKR mice were fed a lithogenic diet containing 15% fat, 1.25% cholesterol and 0.5% cholic acid for four weeks. Hepatic cholesterol content and secretion rates of biliary lipids, as well as phenotypes of the liver and gallbladder were determined and examined before and after the feeding of the lithogenic diet.

RESULTSBoth before and after ingestion of the lithogenic diet, hepatic secretion rates of all biliary lipids in C57L mice were markedly higher than that of AKR mice (P < 0.05, P < 0.01, respectively), whereas hepatic cholesterol contents of C57L mice were significantly lower than that of AKR mice (P < 0.05). Furthermore, after consumption of the lithogenic diet, the increase in hepatic secretion rate of biliary cholesterol in C57L mice was significantly higher than that in AKR mice (P < 0.01). Cholesterol gallstones formed in C57L mice and fatty livers developed in AKR mice.

CONCLUSIONSBiliary cholesterol hypersecretion is the key pathophysiological defect of gallstone formation, lith genes have effects on biliary cholesterol hypersecretion and susceptibility to cholesterol gallstone formation in C57L mice. Lithogenic bile is formed at the canalicular membrane and precedes the development of cholesterol gallstones. It is most likely that cholesterol and bile acid hyposecretion make the AKR strain susceptible to the development of fatty livers and resistant to gallstone formation.

Animals ; Bile ; metabolism ; Cholelithiasis ; genetics ; metabolism ; Cholesterol ; analysis ; metabolism ; Fatty Liver ; etiology ; Genetic Predisposition to Disease ; Lipid Metabolism ; Liver ; metabolism ; Male ; Mice ; Mice, Inbred AKR ; Mice, Inbred C57BL

The small intestines of 6 species of rodents and 1 species of insectivore were examined seasonally for Plagiorchis muris infection in 3 different localities in northern Gyeonggi-do (Province), near the demilitarized zone (DMZ). A total of 1,496 animals, including 1,366 Apodemus agrarius, 54 Crocidura lasiura (insectivore), 32 Mus musculus, 28 Micronytus fortis, 9 Eothenomys regulus, 6 Micronys minutus, and 3 Cricetulus triton, were live-trapped at Yeoncheon-gun (n = 351), Paju-shi (804) and Pocheon-gun (343) at 3-mo intervals from December 2004 to September 2005. A total of 1,647 P. muris were collected from 72 (5.3%) A. agrarius. The infection rate was the highest in Pocheon-gun (8.2%), followed by Yeoncheon-gun (5.0%) and Paju-shi (4.2%). A higher infection rate was observed in A. agrarius captured during September (19.4%) than those captured during December (3.0%), June (2.6%), or April (0%). However, the worm burden was the highest in June (av. 32.1/animal), followed by September (24.7), December (4.0), and April (0). None of the other animal species were found infected with P. muris. The results reveal that A. agrarius is a natural definitive host for P. muris, and infection rates and worm burdens vary seasonally and geographically.
Animals ; Arvicolinae/parasitology ; Cricetinae ; Cricetulus/parasitology ; Insectivora/parasitology ; Intestine, Small/parasitology ; Korea/epidemiology ; Mice/parasitology ; Murinae/*parasitology ; Prevalence ; Rodent Diseases/epidemiology/*parasitology ; Rodentia ; Seasons ; Trematoda/*isolation & purification ; Trematode Infections/epidemiology/parasitology/*veterinary

Otitis media (OM) is one of the most common inflammatory illnesses in the pediatric population. OM is a multifactorial disease that develops as a result of complex interactions between bacterial infection, environmental risk factors, and host genetic factors. The high prevalence and recurrence of OM, coupled with the risk of developing hearing loss have meant that research to understand the mechanisms of OM and identify new therapeutic measures is urgent. Various experimental animals such as chinchilla, guinea pig, gerbil, rat and mouse have been used to investigate the pathogenesis and treatment of OM. Also, a lot of methods have been introduced to induce OM in animals including obstruction of E tube and direct injection of otopathogens into the middle ear. Recently there has been an increase in the use of the mouse for OM research due to the ability to easily manipulate their genetic components. The use of animal models has enabled researchers to identify a number of molecular mechanisms involved in the development of OM. Despite the real progresses obtained from animal models of OM, however, there are still several limitations to using them for OM research. In this review article, various animal models that have been introduced to investigate the pathogenesis of OM will be discussed briefly.
Animals ; Bacterial Infections ; Chinchilla ; Ear, Middle ; Gerbillinae ; Guinea Pigs ; Hearing Loss ; Mice ; Models, Animal* ; Otitis Media* ; Prevalence ; Rats ; Recurrence ; Risk Factors

BACKGROUND AND OBJECTIVES: Mucosal surfaces in the middle ear and eustachian tube are protected by several complex defense mechanisms, namely mucociliary clearance, immunoglobulins, cellular components, and antibacterial secretory enzymes. The secretory enzymes such as lysozyme and lactoferrin are found in various mucosal tissues and most of body secretions which cover the human mucosal surfaces. Because of their bactericidal activity, it has been suggested that these enzymes contribute to the defense against local mucosal infections. It has been known that lysozyme- and lactoferrin-secreting cells in tubotympanum were various in species such as human, chinchilla, guinea pig and Mongolian gerbil. The purpose of this study is to identify and localize the lysozyme- and lactoferrin-secreting cells in the eustachian tube of normal mice using histochemical and immunohistochemical techniques. MATERIALS AND METHODS: Normal mice (BALB/c, 60-120 days old, 10 heads) were used for staining of tubotympanum with hematoxylin-eosin stain, Alcian blue-periodic acid-Schiff (AB-PAS) stain and immunohistochemical stain (antihuman lysozyme, and antihuman lactoferrin antibodies). RESULTS: 1) Secretory cells in the epithelium and subepithelial glands are observed more in the pharyngeal portion than in the tympanic portion of eustachian tube. Subepithelial glands are also noted more in lower part than in upper part of eustachian tube. 2) Lysozyme was observed in the secreting cells of mucosal epithelium and the serous cells of subepithelial glands. 3) Lactoferrin was observed in the serous cells of subepithelial glands, but not in the epithelium. CONCLUSION: In the eustachian tube of BALB/c mouse, lysozyme and lactoferrin were detected in the serous cells in subepithelial glands and only lysozyme is observed in the secretory cells in the eustachian tube epithelium.
Animals ; Chinchilla ; Defense Mechanisms ; Ear, Middle ; Epithelium ; Eustachian Tube* ; Gerbillinae ; Guinea Pigs ; Humans ; Immunoglobulins ; Lactoferrin ; Mice* ; Mucociliary Clearance ; Mucous Membrane ; Muramidase

Animals ; Cholelithiasis ; genetics ; Cholesterol ; metabolism ; Cholesterol 7-alpha-Hydroxylase ; genetics ; Genetic Predisposition to Disease ; Hydroxymethylglutaryl CoA Reductases ; genetics ; Liver ; enzymology ; Male ; Mice ; Mice, Inbred AKR ; Mice, Inbred C57BL ; Receptors, LDL ; genetics ; Sterol O-Acyltransferase ; genetics

OBJECTIVE: Recording the nystagmus of small experimental rodents is an integral technique in vestibular research. Theoretically, the size and the shape of markers strongly affect the analysis of 3 dimensional nystagmus. METHODS: The nystagmus of 6 healthy ICR mice were recorded and their gain values were compared using 200 µm, 300 µm, 400 µm, and 600 µm isosceles triangle markers at the peak velocity of 60°/sec and 100°/sec with the rotational stimulations of 0.1 Hz, 0.2 Hz, and 0.5 Hz. RESULTS: The gain values of 3 different sizes of the markers showed no significant differences in horizontal- vertical-torsional component. However, it was unable to record the nystagmus with 200 µm markers since the markers were too small to be placed and stayed on the center of the pupils. CONCLUSION: Technicians can decide the size of the markers from 200 to 600 µm to record the nystagmus of mice, depending on the technicians' skills.
Animals ; Mice ; Mice, Inbred ICR ; Pupil ; Reflex, Vestibulo-Ocular ; Rodentia

This study was carried out to determine the seropositivity for Orientia tsutsugamushi infection among wild rodents captured in farms and mountains of Korea. A total 965 wild rodents of 7 species and 48 Crocidura laciura were captured in farms and mountains of 6 province during 1997~2000 in Korea. Serological evidence for O. tsutsugamushi infection was obtained using O. tsutsugamushi antigens by indirect immunofluorescent antibody technique (IFA). Four hundred eighty four Apodemus agrariusus, 246 Apodemus peninsulae, 179 Eothenomys regulus, 44 Microtus fortis, 6 Micromys minutus, 5 Mus musculus, and 1 Cricetula triton were captured in Gyeonggi, Gangwon, Chungnam, Gyeongbuk, Gyeongnam, and Jeonbuk province. Among them, 59 (12.2%) A. agrariusus, 22 (8.9%) A. peninsulae, 12 (6.7%) E. regulus, 5 (11.4%) M. fortis and 1 (16.7%) M. minutus were IF antibody positive against O. tsutsugamushi Gilliam or Karp strain.
Animals ; Arvicolinae ; Chungcheongnam-do ; Gangwon-do ; Gyeonggi-do ; Gyeongsangbuk-do ; Jeollabuk-do ; Korea* ; Mice ; Murinae ; Neptune ; Orientia tsutsugamushi* ; Rodentia*

We previously determined that AKR/J mice housed in a low-dose-rate (LDR) (137Cs, 0.7 mGy/h, 2.1 Gy) gamma-irradiation facility developed less spontaneous thymic lymphoma and survived longer than those receiving sham or high-dose-rate (HDR) (137Cs, 0.8 Gy/min, 4.5 Gy) radiation. Interestingly, histopathological analysis showed a mild lymphomagenesis in the thymus of LDR-irradiated mice. Therefore, in this study, we investigated whether LDR irradiation could trigger the expression of thymic genes involved in the DNA repair process of AKR/J mice. The enrichment analysis of Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways showed immune response, nucleosome organization, and the peroxisome proliferator-activated receptors signaling pathway in LDR-irradiated mice. Our microarray analysis and quantitative polymerase chain reaction data demonstrated that mRNA levels of Lig4 and RRM2 were specifically elevated in AKR/J mice at 130 days after the start of LDR irradiation. Furthermore, transcriptional levels of H2AX and ATM, proteins known to recruit DNA repair factors, were also shown to be upregulated. These data suggest that LDR irradiation could trigger specific induction of DNA repair-associated genes in an attempt to repair damaged DNA during tumor progression, which in turn contributed to the decreased incidence of lymphoma and increased survival. Overall, we identified specific DNA repair genes in LDR-irradiated AKR/J mice.
Animals ; DNA Repair/*radiation effects ; Dose-Response Relationship, Radiation ; Female ; Gene Expression Regulation/*radiation effects ; Gene Regulatory Networks/radiation effects ; Lymphoma/etiology/*genetics ; Mice ; Mice, Inbred AKR ; Oligonucleotide Array Sequence Analysis ; *Radiation, Ionizing ; Reverse Transcriptase Polymerase Chain Reaction ; Thymus Gland/*radiation effects ; Thymus Neoplasms/etiology/*genetics