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Biomedical subjects

K Katahira

Publications and source records attributed to K Katahira.

At least 19 recordsLinked to original sources
PubMed2006

Lead isotope ratios in urban road runoff.

Lead isotopic analyses of road runoff and airborne particulate matter have been carried out to elucidate sources of lead pollution at urban and suburban sites. While lead is often observed in road runoff in suspended form, suspended particle size had no relation to the lead isotopic distribution, as a result of comparison between runoff samples with total suspended solids and those with minute particles passed through a 75 microm sieve. Lead isotope ratios in airborne particulate matter in urban areas fell within a wider range than those in road runoff. Since there was little difference of the ratios between a heavy traffic-flow site and residential sites, airborne lead derived from vehicle exhaust was found to make little contribution to the contamination of road runoff. On the other hand, the ratios in road runoff at a suburban site showed the same range as those at an urban site. Lead in road runoff was therefore suggested to be produced on site by traffic related substances, such as tire wear, other than vehicle exhaust.

Air Pollutants↗
PubMed2005

Effects of spaceflight on postnatal development of arterial baroreceptor reflex in rats.

AIM: It has been reported that spaceflight attenuates the arterial baroreceptor reflex. As this reflex function changes dramatically during postnatal development, we hypothesized that space flight depresses the developmental changes of the reflex system. To test this hypothesis, we evaluated the baroreceptor reflex function in rats, which were exposed to a microgravity environment on a space shuttle 9-25 days after birth. METHODS: Baroreceptor reflex sensitivity and the afferent sensitivity were evaluated by measuring heart rate (HR) and aortic nerve activity (ANA) changes in response to an increase in mean arterial pressure (MBP) derived by phenylephrine injection (20-50 microg kg(-1)) under urethane-anaesthesia. RESULTS: Baroreceptor reflex sensitivity (% change of HR/% change of MBP) was lower in the flight group (FLT: -0.19 +/- 0.04, n = 4) than either the asynchronous ground control group (AGC: -0.47 +/- 0.06, n = 6, P < 0.01) or the vivarium group (VIV: -0.41 +/- 0.07, n = 6, P < 0.05). This was similar to the differences of the afferent sensitivity (% change of ANA/% change of MBP) between FLT (2.07 +/- 0.30) and the control groups (AGC: 2.71 +/- 0.22, n.s.; VIV: 3.00 +/- 0.32, P < 0.05). At the end of 30 days of recovery under normal gravity conditions, however, there were no significant group differences in these parameters. conclusion: These results suggest that the space environment attenuates the postnatal development of the arterial baroreceptor reflex function in rats, which may be partially because of a depression of the postnatal development of the baroreceptor afferents. These functional alterations, however, recover to their normal level on re-exposure to the Earth's gravity.

Animals↗
PubMed2004

Spaceflight alters the fiber composition of the aortic nerve in the developing rat.

Hydrostatic pressure gradients due to the gravitational force in blood vessels disappear under conditions of microgravity during spaceflight, and the ability of the baroreceptor reflex to control arterial pressure and blood distribution may be altered. We hypothesized, on the basis of the results obtained in our previous experiments using the head-down tilt method in rats and rabbits, that the range of increase in arterial pressure caused by animal behavior narrows under conditions of microgravity, affecting the development of high-threshold unmyelinated fibers in the rat aortic nerve which sends signals from baroreceptors located in the aortic wall to the reflex center. We verified this hypothesis using 9-day-old rat neonates housed with their dams for 16 days on the space shuttle Columbia in outer space (STS-90, Neurolab Mission). Age-matched neonatal rats with the dams remained on the ground as controls. After breeding was carried out in the three experimental groups (FLT, spaceflight; AGC, asynchronous ground control; VIV, vivarium ground control), specimens of the 25-day-old rats were excised and five left aortic nerves in each group were examined by electron microscopy. The number of aortic unmyelinated fibers was significantly less in the FLT group than in each ground control (mean+/-S.D.; 139+/-37 in the FLT, 207+/-36 in the AGC, 283+/-121 in the VIV; P<0.05), which may be related to the weakness of the baroreceptor reflex under conditions of microgravity in space. This result may contribute to understanding of the several cardiovascular issues which occur under microgravity and after reexposure to gravity in human.

Analysis of Variance↗
PubMed2002

Interleukin-5 transgenic mice show augmented resistance to Angiostrongylus costaricensis infection.

To determine the possible role of eosinophils in Angiostrongylus costaricensis infection, both interleukin-5 (IL-5) transgenic (Tg) and non-transgenic (non-Tg) C3H/HeN mice were infected with A. costaricensis third-stage larvae. IL-5 Tg mice demonstrated greater resistance than non-Tg mice to A. costaricensis, as shown by lower adult worm recovery, smaller adults, fewer eggs in the intestinal wall and fewer larvae passed in the feces. Both mice showed similar antigen-specific IgA and IgGI antibody responses, although IgA was more prominent than IgG1. Egg deposition and inflammatory responses in the intestinal walls were milder in IL-5 Tg mice than in non-Tg mice. The eggs with developed larvae, deposited in the intestinal walls of IL-5 Tg mice, were surrounded by numerous degranulating eosinophils and sometimes with Splendore-Hoeppli deposits. The data suggest that eosinophils are involved in the resistance of the mouse during primary infection with A. costaricensis.

Angiostrongylus↗
PubMed2001

[Global harmonization in the care and use of laboratory animals for the space life science research].

Space researches are supported with the international space agencies, NASA and NASDA. Animal experiments on the space life science must conform to the NIH policies and the NASA guide for the care and use of laboratory animals. The goal of the NIH policies is to promote the humane care of animals used biomedical and behavioral research, teaching, and testing. In each institute, the Institutional Animal Care and Use Committee (IACUC) plays an important role in conformity with NIH policies. The IACUC is charged with developing, recommending and monitoring NIH/NASA (ARC and KSC) policies, guides and rules relating to animal acquisition, care and use. In ARC and KSC, investigators will be responsible only for activities directly related to the conduct of their animal experiments. Even if researchers have protocols of the space science in Japan, the animal experiment should be carried out under the global harmonized conditions in accordance with NIH policies and NASA guides.

Animal Welfare↗
PubMed2000

Improved tissue characterization of focal liver lesions with ferumoxide-enhanced T1 and T2-weighted MR imaging.

The purpose of our study was to evaluate the potential value of ferumoxide-enhanced T1-weighted magnetic resonance (MR) imaging for tissue characterization of focal liver lesions when combined with T2-weighted sequences. Images were acquired within 30 minutes after the end of ferumoxide administration, when ferrite particles were not totally cleared from the intravascular compartment. Thirty-eight patients with 47 focal liver lesions underwent T1-weighted gradient-echo (TR/TE 150/4.1 msec) and T2-weighted fast spin-echo (3180-8638/90 msec) MR imaging at 1.5 T before and after intravenous administration of ferumoxides (10 micromol/kg body weight). A qualitative and quantitative analysis was performed. During the early phase after infusion of ferumoxide, blood vessels showed hypersignal intensity on T1-weighted fast low-angle shot (FLASH) images, while liver signal decreased. Hemangiomas showed both homogeneous and inhomogeneous enhancement patterns, and liver metastasis most typically showed ring enhancement. Hypervascular tumors (hepatocellular carcinomas and focal nodular hyperplasias) showed a slight degree of homogeneous enhancement. Quantitatively, the degree of enhancement and lesion-to-liver contrast on ferumoxide-enhanced images were significantly different among these tumors. Our results demonstrate that distinct enhancement patterns obtained on ferumoxide-enhanced T1-weighted MR imaging improve tissue characterization of focal liver lesions when combined with T2-weighted images.

Adult↗
PubMed2000

Pancreaticobiliary ductal system: value of half-Fourier rapid acquisition with relaxation enhancement MR cholangiopancreatography for postoperative evaluation.

PURPOSE: To assess the usefulness of half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance cholangiopancreatography (MRCP) for evaluation of postoperative changes in the pancreaticobiliary ductal system. MATERIALS AND METHODS: The study included 34 patients (20 men, 14 women; mean age, 65.5 years) who underwent surgery of the pancreaticobiliary ductal system. Half-Fourier RARE MRCP images were obtained after surgery. Qualitative evaluation included ratings by two observers for depiction of postoperative anatomy and for artifacts, as well as analysis of postoperative complications. Direct cholangiographic, computed tomographic, and ultrasonographic findings and 6-month follow-up results were the reference standard. Sensitivity, specificity, and accuracy were calculated for the evaluation of postsurgical complications seen at half-Fourier RARE MRCP. RESULTS: The sensitivity, specificity, and accuracy of MRCP for the evaluation of postsurgical complications were each 100% for ductal dilatation; 100%, 87%, and 89%, respectively, for choledochoenteric anastomotic stricture; 100%, 86%, and 87%, respectively, for pancreaticoenteric anastomotic stricture; 100% each for intraductal stones and anastomotic leakage; and 80%, 100%, and 94%, respectively, for cholangitis. CONCLUSION: Half-Fourier RARE MRCP is a reliable imaging technique for the evaluation of anatomy and of complications associated with a surgically altered pancreaticobiliary ductal system.

Adult↗
PubMed2000

Time-dependent change in baroreflex control capacity of arterial pressure by pentobarbital anesthesia in rabbits.

The present study is designed to investigate the time-dependent effect of pentobarbital anesthesia on the baroreflex arterial pressure (AP) control system in rabbits. The overall AP control capacity of the baroreflex system was assessed with mean arterial pressure (MAP) responses to the rapid mild hemorrhage (2 ml/kg body weight) and an overall open-loop gain (G) of the system. The G value was determined by means of the following formula: G = delta API/delta APS-1, where delta APl is an immediate MAP fall and delta APS a steady-state fall after the rapid hemorrhage. Prior to the experiment, two catheters for AP measurement and hemorrhage were chronically in-dwelt in the aortic arch via the left subclavian and left common carotid arteries, respectively. Control mean arterial pressure averaged for 30 sec before the rapid hemorrhage (CMAP), delta API and delta APS significantly increased and reached the maximal value at 14 min (CAMP: p < 0.01) and 28 min (delta API: p < 0.01 and delta APS: p < 0.01) after the intravenous injection of sodium pentobarbital in a 25.0 mg/kg dose, respectively. These values gradually decreased in the course of time and tended to recover to near the preanesthetic level at 77-98 min after the anesthesia. The G value significantly decreased from 7.3 in the conscious state to 1.5 at 28 min after the anesthesia (p < 0.001), gradually increased with lapse of time and recovered to near the preanesthetic level at 77-98 min after the anesthesia. No significant difference in G was observed between in the conscious and anesthetized states beyond 70 min after the anesthesia (p > 0.05). These findings suggest that pentobarbital sodium exerts a time-dependent inhibitory effect on the baroreflex system but does not significantly affect the overall AP control capacity of the baroreflex system itself at least 70 min after the intravenous administration at a dose of 25.0 mg/kg.

Adaptation, Physiological↗
PubMed2000

Recording of blood pressure, heart rate and aortic nerve activity during parabolic flight in the rat via radio-telemetry.

Exposure to microgravity induces cardiovascular deconditioning characterized by orthostatic hypotension when astronauts return to the earth. In order to understand the mechanism of cardiovascular deconditioning, it is necessary to clarify the changes in hemodynamics and the cardiovascular regulation system over the period of space flight. The telemetry system applied to freely moving animals will be a useful and appropriate technique for this kind of long term study of the cardiovascular system in the conscious animal during space flight. The purpose of the present study is twofold: firstly, to observe the detailed changes of arterial pressure and heart rate (HR) during microgravity elicited by the parabolic flight in order to study the acute effect of microgravity exposure on the cardiovascular system; and secondly, to test the feasibility of the telemetry system for recording blood pressure, HR and autonomic nervous activities continuously during space flight.

Animals↗
PubMed2000

Mechanical tensile properties of the aortic wall in the premature rat exposed to the microgravity environment during space flight for 16 days.

Under microgravity environment, blood shifts headward and thereafter decrease in volume to adapt to the environment, which could affect cardiovascular hemodynamics and their regulatory mechanisms. Baroreceptor sensitivity is known to be reduced in newborn animals and to gradually increase with development. The baroreceptor is a stretch receptor; therefore its function is closely related to the rheological properties and fine structure of the aortic wall in which the baroreceptor lies. The mechanical and histological properties could be altered under microgravity conditions in the process of development with change in circulatory function. In the present study, we investigated the mechanical tensile characteristics and histological structure of the aortic wall in the proximal thoracic aorta of premature rats bred in the microgravity environment of the space shuttle for 16 days.

Animals↗
PubMed1999

Detection of hepatocellular carcinoma arising in cirrhotic livers: comparison of gadolinium- and ferumoxides-enhanced MR imaging.

OBJECTIVE: We prospectively compared the detectability of hepatocellular carcinoma (HCC) arising in cirrhotic livers using dynamic gadolinium-enhanced fast low-angle shot (FLASH), ferumoxides-enhanced T2-weighted turbo spin-echo, and ferumoxides-enhanced T2*-weighted FLASH MR imaging. SUBJECTS AND METHODS: Fifty-three patients with HCC (32 men and 21 women) who were 33-86 years old (mean, 63 years old) were enrolled in a prospective MR study to assess hepatic lesions using both gadopentetate dimeglumine and ferumoxides. Dynamic gadolinium-enhanced imaging was obtained before and 30, 60, and 180 sec after rapid bolus injection of gadopentetate dimeglumine (0.1 mmol/kg). Ferumoxides-enhanced T2-weighted turbo spin-echo imaging and ferumoxides-enhanced T2*-weighted FLASH imaging were performed between 30 min and 2 hr after i.v. infusion of ferumoxides (10 micromol/kg). Images were analyzed qualitatively and quantitatively. A receiver operating characteristic curve study was performed to compare the diagnostic value of gadolinium-enhanced imaging with that of ferumoxides-enhanced imaging for the detection of HCC. RESULTS: Quantitative analysis revealed a significantly higher percentage of signal-intensity loss and higher liver-lesion contrast-to-noise ratio on ferumoxides-enhanced T2*-weighted FLASH imaging than on ferumoxides-enhanced T2-weighted turbo spin-echo imaging. The percentage of signal-intensity loss and liver-lesion contrast-to-noise ratio on ferumoxides-enhanced images was significantly higher in patients with mild liver cirrhosis (Child's class A) than in patients with severe liver cirrhosis (Child's class C). Qualitative analysis showed that dynamic gadolinium-enhanced images revealed significantly higher lesion conspicuity than did ferumoxides-enhanced T2-weighted turbo spin-echo images. According to receiver operating characteristic analysis, dynamic gadolinium-enhanced FLASH imaging achieved the highest sensitivity, and ferumoxides-enhanced T2*-weighted FLASH imaging was the second most sensitive. We found that ferumoxides-enhanced turbo spin-echo imaging was the least valuable technique for revealing HCC lesions. Gadolinium-enhanced imaging revealed more HCC lesions than did ferumoxides-enhanced imaging, particularly for lesions smaller than 2 cm in diameter. CONCLUSION: Ferumoxides-enhanced imaging revealed fewer findings, such as lesion conspicuity of HCCs arising in cirrhotic livers, than did gadolinium-enhanced FLASH imaging.

Adult↗
PubMed1999

Frequency distribution of axon diameters in the left aortic nerve of the rat raised in space--Neurolab Program.

INTRODUCTION: To study development of the aortic baroreflex mechanisms under conditions of microgravity, we carried out the various experiments in the neonate rats aged 25 days raised in microgravity for 16 days (flight: FLT group) in Neurolab program (STS-90, space shuttle Columbia, launch date: Apr 17, '98. Some results of the experiments were already reported. The results of histological examination of the aortic nerve which is the afferent of the aortic baroreflex showed that the number of unmyelinated fibers in FLT was significantly less in than those in two control groups and there was no difference between FLT and each control group in the analysis of myelin. In the present paper, the frequency distribution of axon diameters of the left aortic nerves in FLT was compared to that in two ground control groups to examine the growth of the aortic nerve fibers in space. METHODS: After breeding Sprague-Dawley rats for 16 days in the shuttle in space and in the animal center in the Kennedy space center, a total of 43 deeply anesthetized rats were perfused with 1% parahormaldehyde and 1% glutaraldehyde or 4% parahormaldehyde solution buffered at pH7.4 with 0.12 M phosphate solution. Concerning the control groups, one group was the asynchronous ground control (AGC) group in which the rats were housed in the same cages as those on the shuttle, and the other was the vivarium ground control (VIV) group in which the rats were housed in commercial cages. The cervical region of the left aortic nerve which is a branch of the vagus was cut off and stored in the same fixative as that used for perfusion, and postfixed in the solution of 1% OsO4, for 2 hours within 24 hours after the perfusion. The fixed specimens were embedded in epoxy resin blocks by the usual method for electron microscopy following dehydration. Electron microscopic montages of transverse sections of these nerve trunks were made from the five left aortic nerves in each group. The magnification of the montages was approximately 13400 times. The long and short axes (a and b) of the nerve fibers and the myelin thickness (T) were measured with a caliper and the axon diameters (R were calculated by following formula: R2=[(a-2T)2+(b-2T)2]/2.

Animals↗
PubMed1998

Histological analysis of the aortic nerve in the rat raised in space (Rapid communication on Neurolab Project).

To study development of the aortic nerve baroreflex under conditions of microgravity, we examined the cross section of the left aortic nerve (LAN), which is the afferent of the baroreflex, in the neonate rats aged 25 days raised in microgravity on the space shuttle Columbia (flight:FLT group) for 16 days. In this paper, we report a part of the result obtained from the data of the myelinated fibers of LAN analyzed with an electron microscope. Two kind of ground control groups were compared to the FLT group; one was asynchronous ground control (AGC) group where the rats were housed in the same cage as that on the shuttle, and the other was vivarium(VIV) group where the rats were housed in a commercial cage. The LANs in each group were extirpated the from rats perfused with a fixative and embedded for histological analysis. We observed the transverse sections of LAN and took pictures of several areas (magnified to x 2K to x 200K). No irregular myelination was found in all fibers of FLT group when they were compared with two control groups. The thickness of myelin of the maximally myelinated fibers were 0.55 +/- 0.17 micrometer in FLT(n=5), 0.45 +/- 0.10 micrometer in AGC(n=5), and O.47 +/- 0.06 micrometer meter in VIV(n=5). There was no significant difference among three groups (unpared t-test). The results suggest that there is no effect of space environment on the myelin formation of each nerve fiber in the aortic nerve.

Animals↗