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Biomedical subjects

G Kudo

Publications and source records attributed to G Kudo.

At least 19 recordsLinked to original sources
PubMed2006

Seasonal changes in pollinator activity influence pollen dispersal and seed production of the alpine shrub Rhododendron aureum (Ericaceae).

In alpine ecosystems, microscale variation in snowmelt timing often causes different flowering phenology of the same plant species and seasonal changes in pollinator activity. We compared the variations in insect visitation, pollen dispersal, mating patterns, and sexual reproduction of Rhododendron aureum early and late in the flowering season using five microsatellites. Insects visiting the flowers were rare early in the flowering season (mid-June), when major pollinators were bumblebee queens and flies. In contrast, frequent visitations by bumblebee workers were observed late in the season (late July). Two-generation analysis of pollen pool structure demonstrated that quality of pollen-mediated gene flow was more diverse late in the season in parallel with the high pollinator activity. The effective number of pollen donors per fruit (N(ep)) increased late in the season (N(ep) = 2.2-2.7 early, 3.4-4.4 late). However, both the outcrossing rate (t(m)) and seed-set ratio per fruit were smaller late in the season (t(m) = 0.89 and 0.71, seed-set ratio = 0.52 and 0.18, early and late in the season, respectively). In addition, biparental inbreeding occurred only late in the season. We conclude that R. aureum shows contrasting patterns of pollen movement and seed production between early and late season: in early season, seed production can be high but genetically less diverse and, during late season, be reduced, possibly due to higher inbreeding and inbreeding depression, but have greater genetic diversity. Thus, more pollinator activity does not always mean more pollen movement.

Animals↗
PubMed2004

Landscape genetics of alpine-snowbed plants: comparisons along geographic and snowmelt gradients.

The genetic structure of three snowbed-herb species (Peucedanum multivittatum, Veronica stelleri, and Gentiana nipponica) was analyzed using allozymes across nine populations arranged as a matrix of three snowmelt gradients x three geographic locations within 3 km in the Taisetsu Mountains, northern Japan. Phenologically asynchronous populations are packed within a local area in alpine snowbeds, because flowering season of alpine plants depends strongly on the timing of snowmelt. Moderate genetic differentiation was detected among local populations in every species (FST=0.03-0.07). There was a significant correlation between the geographic distance and genetic distance in the P. multivittatum populations, but not in the V. stelleri and G. nipponica populations. On the other hand, a significant correlation between the phenological distance caused by snowmelt timing and genetic distance was detected in the V. stelleri and G. nipponica populations, but not in the P. multivittatum populations. The snowmelt gradient or geographic separation influenced hierarchical genetic structure of these species moderately (FRT <0.04). Restriction of gene flow due to phenological separation and possible differential selection along the snowmelt gradient may produce genetic clines at microgeographic scale in these species.

Enzymes↗
PubMed2001

Simple and low-cost tele-nuclear medicine conference system with the e-mail protocol.

PURPOSE: Because of the recent innovative growth in computer technology, digital imaging, and the Internet, we can take advantage of these facilities for education and clinical work in nuclear medicine. We developed a tele-nuclear medicine conference system with electronic mail (e-mail) on the Internet. METHODS: Twenty-one physicians (20 radiologists, 1 neurologist), 6 technologists and 2 medical students in six university hospitals (Japan 5, Canada 1), 5 local hospitals in Japan participated in this project. We used digital still cameras (330 k pixels) equipped with a floppy disk drive and 10 x optical zoom to digitize images with JPEG compression (640 x 480 matrix). The images were attached to e-mail messages (containing a brief description of each case). The mail was sent simultaneously to all members on the mailing list. Scintigram and SPECT images as well as other radiological images were sent by e-mail. Reply mails about each case were sent to all members via the mailing list. RESULTS: During a period of 6 months, 18 cases (tumor/infection: 7, bone: 6, cardiovascular: 1, neurology; 3, endocrine: 1) with 144 e-mails (average 5.6/case) were submitted to the conference. The average period of discussion was 15.6 days. The number of attached images was 1 to 9 (average, 4.2/e-mails). JPEG compression rate was 1/10 to 1/20. The quality of the images was good enough for discussion. Some cases required additional images for further discussion. CONCLUSION: Our tele-nuclear medicine conference with an electronic mailing list and digital camera was simple and low-cost. The conference system was useful for education and clinical work.

Canada↗
PubMed2001

Hyalinosis and Ym1/Ym2 gene expression in the stomach and respiratory tract of 129S4/SvJae and wild-type and CYP1A2-null B6, 129 mice.

The C57BL/6, 129, and B6,129 mouse strains or stocks have been commonly used to generate targeted mutant mice. The pathology of these mice is not well characterized. In studies of these aging mice, we found high incidences of hyalinosis (eosinophilic cytoplasmic change) in the glandular stomach, respiratory tract, bile duct, and gall bladder of B6,129 CYP1A2-null and wild-type mice as well as in both sexes of the background 129S4/SvJae strain. The gastric lesions of the glandular stomach were found in 95.7% of female CYP1A2-null mice as well as in 45.7% of female 129S4/SvJae animals. The eosinophilic protein isolated from characteristic hyaline gastric lesions was identified as Ym2, a member of the chitinase family. Immunohistochemistry, using rabbit polyclonal antibodies to oligopeptides derived from the Ym1 sequence, detected focal to diffuse reactivity within both normal and abnormal nasal olfactory and respiratory epithelium, pulmonary alveolar macrophages, bone marrow myeloid cells, and the squamous epithelium of the forestomach and epithelium of the glandular stomach. Alveolar macrophages in acidophilic pneumonia, a major cause of death of aging 129 mice, and in mice with the me mutation also were highly immunoreactive. The possible cause of this protein excess in gastric and other lesions and its possible functions are discussed.

Animals↗
PubMed1999

Targeted disruption of the microsomal epoxide hydrolase gene. Microsomal epoxide hydrolase is required for the carcinogenic activity of 7,12-dimethylbenz[a]anthracene.

Microsomal epoxide hydrolase (mEH) is a conserved enzyme that is known to hydrolyze many drugs and carcinogens, and a few endogenous steroids and bile acids. mEH-null mice were produced and found to be fertile and have no phenotypic abnormalities thus indicating that mEH is not critical for reproduction and physiological homeostasis. mEH has also been implicated in participating in the metabolic activation of polycyclic aromatic hydrocarbon carcinogens. Embryonic fibroblast derived from the mEH-null mice were unable to produce the proximate carcinogenic metabolite of 7,12-dimethylbenz[a]anthracene (DMBA), a widely studied experimental prototype for the polycylic aromatic hydrocarbon class of chemical carcinogens. They were also resistant to DMBA-mediated toxicity. Using the two-stage initiation-promotion skin cancer bioassay, the mEH-null mice were found to be highly resistant to DMBA-induced carcinogenesis. In a complete carcinogenesis bioassay, the mEH mice were totally resistant to tumorigenesis. These data establish in an intact animal model that mEH is a key genetic determinant in DMBA carcinogenesis through its role in production of the ultimate carcinogenic metabolite of DMBA, the 3,4-diol-1,2-epoxide.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Potentiated decrease of plasma folate levels caused by the coadministration of folic acid in rats treated with methotrexate.

The decrease of plasma 5-methyltetrahydrofolic acid (5-MF) levels, postulated as an indicator of folate status, was studied following the administration of both methotrexate (MTX) alone and MTX with folic acid (FA) using rats as our experimental model. Blood and urine samples were serially collected over a 9 hr period after the administration of MTX, MTX with FA and from a control group to examine the plasma kinetics and the renal clearance of 5-MF. The pharmacokinetics of MTX and the plasma protein binding of 5-MF were also examined. The concentrations of these analytes were assayed using high performance liquid chromatography (HPLC). MTX administration produced decreased plasma 5-MF levels. This observed decrease was potentiated by oral FA administration, suggesting that the folate status was more severely altered by the coadministration of FA. The renal clearance of 5-MF also increased dose-dependently with FA (0.05-5 mg/kg) coadministration. The plasma protein binding of 5-MF was not affected by the FA administration, which indicates that the fraction of 5-MF that was filtered through the glomerular apparatus appeared to be unchanged. In addition, the pharmacokinetic profiles of MTX also appeared not to be affected by the addition of FA. We conclude that the inhibition of reabsorption of 5-MF in the renal tube by concurrent administration of MTX and FA must be one of the causal factors for the demonstrated decrease in the plasma 5-MF levels in rats.

Animals↗
PubMed1995

Effects of folic acid and pyrimethamine, a dihydrofolate reductase inhibitor, on intestinal absorption of folates in rats.

Oral co-administration of folic acid (pteroylglutamic acid, PteGlu) potentiates the decrease of plasma 5-methyltetrahydrofolic acid (5-CH3-H4PteGlu) concentration induced by pyrimethamine (PYR) in rats. To clarify the mechanisms of this potentiated decrease, we examined the effects of PteGlu and PYR on intestinal absorption of folates in rat jejunum loops, because plasma 5-CH3-H4PteGlu concentration is maintained by enterohepatic circulation of folates. The intestinal absorption of 5-[14C]CH3-H4PteGlu was inhibited by PteGlu, but not by PYR. The absorption of [3H]PteGlu was inhibited by reduced folates that exist in bile. These findings indicate that PteGlu competes with the bile reduced folates for the intestinal transport system. The bile secretion of reduced folates was also examined to observe the conversion of absorbed PteGlu to reduced folates in the liver in the presence of PYR. The bile secretion of reduced folates increased drastically after the administration of PteGlu alone, but not after the administration of PteGlu with PYR. These facts suggest that the absorbed PteGlu was not converted to reduced folates in the liver due to PYR. In conclusion, the potentiated decrease of plasma 5-CH3-H4PteGlu concentration must have resulted from a combination of the following two factors: the inhibition of reabsorption of bile reduced folates by PteGlu and the inhibition of PteGlu conversion to reduced folates in the liver by PYR.

Animals↗
PubMed1992

Effect of the new quinolone antibacterial agent levofloxacin on multiple organ carcinogenesis initiated with wide-spectrum carcinogens in rats.

A multiple organ carcinogenesis model was used in male F344 rats to test the carcinogenic potential of (-)-(S)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo- 7H-pyrido[1,2,3-de][1,4] benzoxazine-6-carboxylic acid hemihydrate (levofloxacin, DR-3355, CAS 10086-85-4). After sequential treatment with diethylnitrosamine (DEN: carcinogen for the liver), N-methylnitrosourea (MNU: carcinogen for the esophagus, forestomach and thyroid) and dihydroxy-di-N-propylnitrosamine (DHPN: carcinogen for the lungs, kidney and urinary bladder), rats were treated with DR-3355, N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), catechol (CC) or phenobarbital (PB) to examine whether these compounds modified the carcinogenesis in multiple organs. As a result of histopathological examinations at study week 20, DR-3355 did not induce neoplastic lesions, nor did it enhance the occurrences of proliferative preneoplastic lesions. In contrast, BBN increased the incidences of hyperplasias and papillomas of the urinary bladder. CC enhanced the occurrences of hyperplasias and papillomas of the forestomach as well as submucosal glandular growth for the glandular stomach. PB increased the number of altered cell foci in the liver and the incidence of follicular cysts and hyperplasias of the thyroid. These results indicate that DR-3355 is not capable of promoting the development of tumors in rat multiple organs.

Animals↗
PubMed1980

Multiple aneurysms of the visceral arteries with migrating vascular bruit on postural change: a case report.

Multiple aneurysms of the gastroepiploic artery and the ileocecal branch of the superior mesenteric artery were found in a 68-year-old male patient by angiography. The patient presented with one-hour postprandial epigastric pain of 10 years duration. Abdominal bruit was auscultated at the two different sites, one of which shifted downwards upon upright position. From the freely movable nature of the great omentum, this bruit, migrating upon postural change, was most likely from the gastroepiploic artery aneurysms. The aneurysms were excised and the abdominal bruit disappeared. The etiology of the aneurysms was suggested to be arterial fibrodysplasia histologically. From this experience, it was stressed that postural change should be added to a routine physical examination to rule out an aneurysm from the freely movable great omentum.

Aged↗