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Biomedical subjects

K Koga

Publications and source records attributed to K Koga.

At least 91 records · Page 5Linked to original sources
PubMed2000

Histopathological study of venous aneurysms in patients with dural arteriovenous fistulas.

OBJECT: Of all intracranial dural arteriovenous fistulas (DAVFs), those with cortical venous drainage associated with cortical venous ectasia or varices are predisposed to an aggressive course and produce progressive neurological symptoms or hemorrhages. The authors undertook a histological examination of venous aneurysms and arterialized veins in the proximity of these aneurysms that had been surgically removed in patients with DAVFs. METHODS: Surgical specimens were obtained in eight patients. The excised venous aneurysms and the arterialized veins in their proximity were stained using hematoxylin and eosin, van Gieson's elastic, and Masson's trichrome stain. Immunostaining was also performed for alpha smooth-muscle actin, desmin, and factor VIII antigen. Five of the patients had presented with venous hypertension, and three had intracranial hemorrhages. The arterialized vein obtained in the proximity of the venous aneurysm exhibited local irregular intimal thickening; the internal elastic lamina (IEL) was grossly preserved. All venous aneurysms in patients with venous hypertension manifested medial thickening and local intimal thickening with loss of IEL; the thickness of the wall was relatively uniform. In contrast, the wall thickness of venous aneurysms in patients with hemorrhage was extremely irregular and there was no clear delineation between the media and the intima. In media with complete disappearance of IEL, there was scant muscle tissue. CONCLUSIONS: Degenerative changes in venous aneurysms in patients with hemorrhage were much greater than in patients with venous hypertension, possibly because hemorrhages result from a more complicated interplay of anatomical, hemodynamic, and degenerative factors.

Aged↗
PubMed2000

[The relationships of mononuclear leukocyte beta-adrenergic receptors to aerobic capacity and exercise-induced asthma in asthmatic children].

beta-adrenaline receptors exist on peripheral mononuclear leukocytes as well as in lung tissue. We assessed the relationships of plasma catecholamine release by exercise to aerobic capacity and to exercise-induced asthma (EIA) in asthmatic children (Study 1). We then measured mononuclear leukocyte beta-adrenergic receptor densities at rest and assessed the relationships of the number of receptors to aerobic capacity, EIA, and bronchial responsiveness to acetylcholine (Study 2). Study 1: Eleven children (9 males, 2 females; 11-16 years old) with bronchial asthma participated in this study. The subjects underwent an incremental aerobic exercise test on a cycle ergometer to determine their aerobic capacity at the lactic threshold (LT) and VO2max. Each subject underwent an EIA test of which the intensity was 175% of LT, and plasma catecholamine concentrations were measured before and after exercise. A significant negative relationship was found between the degree of EIA and % change of plasma adrenaline concentrations to rest level (p < 0.05), and a significant positive relationship was found between VO2 max/wt and % change of plasma adrenaline concentrations (p < 0.05). Study 2: Twelve asthmatic children (10 males, 2 females; 11-16 years old) participated in this study. Aerobic capacity, and degree of EIA were also measured in each subject by the same method as that used in Study. 1. The number of mononuclear leukocyte beta-adrenergic receptors at rest was determined by (-) [125I]-iodocyanopindolol binding in each subject. A significant negative relationship was found between the number of adrenergic receptors and Max. % fall in FEV1.0 (p < 0.01), and a significant positive relationship was found between the number of adrenergic receptors and VO2max/kg (p < 0.001). These results suggested that a reduced adrenaline production and a reduced number of beta-receptors contributed to the pathogenesis of EIA.

Adolescent↗
PubMed2000

Clinical characteristics of patients in their 40s with HCV antibody-positive hepatocellular carcinoma.

BACKGROUND: We investigated the clinical characteristics of hepatitis C virus (HCV) antibody-positive hepatocellular carcinoma (HCC) patients who developed HCC at a relatively young age. METHODS: Clinical characteristics of patients in their 40s were investigated and were compared with those of patients 50 years and older. The subjects were 648 HCC patients, 469 men (72%) and 179 women (28%), who were treated at our hospital between 1991 and 1997. RESULTS: No patient was under 40 years of age. Eighteen patients (3%) were in their 40s, 137 patients (21%) were in their 50s, 338 patients (52%) were in their 60s, 143 patients (22%) were in their 70s, and 12 patients (2%) were in their 80s. Fifteen of the patients (83%) in their 40s were male. The proportion of men in their 40s was higher than that of all men. Eight of the 15 men in their 40s (53%) were heavy drinkers, and 2 (14%) were habitual drinkers. Three of the 15 men (20%) were HBV carriers, and these 3 HBV carriers were not drinkers. The proportion of heavy drinkers and HBV carriers was significantly higher among the patients in their 40s than in the 60 patients randomly sampled from the patients 50 years of age and older. The mean ages of male patients with HCC who were heavy drinkers, habitual drinkers, occasional drinkers, or nondrinkers were 52.3, 58.9, 62.0, and 61.7 years, respectively. HCC occurred significantly earlier in heavy drinkers than in the other 3 groups. We compared laboratory data of the patients in their 40s with data of all of the patients of 50 years and older. Serum total bilirubin, prothrombin time, and platelet counts were significantly worse in the patients in their 40s. CONCLUSIONS: Logistic regression analysis revealed that heavy drinking and presence of HBV infection were independently related to HCV antibody-positive HCC development at a younger age.

Adult↗
PubMed2000

Gravity cue has implicit effects on human behavior.

Gravity modifies us without our knowing it. Possible functional disabilities of eye, head and body movements were investigated under 1 G and microgravity environments to evaluate the gravity cue for human behavior. The system for visual stability might be explained from the viewpoint of ordination between eye and head under microgravity. It is important ascertain the significance of gravity in the maintenance of human visual stability. Coordination of eye position and head motion behavior by neck muscle discharge was examined in the mission SL-J, as well as a subjective evaluation of visual stability during spaceflight. The results shows that: 1) poor performance of eye movement can be observed; 2) unusual neck muscle activity can be observed; 3) there is decreased visual stability in microgravity; and 4) egocentric body axis is emphasized under microgravity conditions.

Eye Movements↗
PubMed2000

Rotation in clinostat results in apoptosis of osteoblastic ROS 17/2.8 cells.

Clinostat is an effective, ground-based tool which can be used to verify data from space flight, and to test hypotheses and experimental conditions for eventual space flights. Rotation in clinostat appears to mimic the microgravity environment by nulling the gravitational vector by continuous averaging. In the present study, we exposed osteoblast-like ROS 17/2.8 cells to a vector-averaged gravity environment in a clinostat and found that the cells undergo apoptotic death during the first 24 hr of clino-rotation. We suggest that apoptosis might be one of the mechanisms for reduced bone formation as observed in actual space flights.

Apoptosis↗
PubMed1999

Ovalbumin in developing chicken eggs migrates from egg white to embryonic organs while changing its conformation and thermal stability.

Ovalbumin was detected in developing chicken eggs. The large majority of these ovalbumin molecules was found to be in a heat-stable form reminiscent of S-ovalbumin. About 83 and 90% of the ovalbumin population was in a heat-stable form in day 14 or stage 40 amniotic fluid and day 18 or stage 44 egg yolk, respectively, whereas ovalbumin in newly deposited eggs was in the heat-unstable, native form. Purified preparations of stable ovalbumin from egg white and amniotic fluid showed a less ordered configuration than native ovalbumin, as analyzed by circular dichroism and differential scanning calorimetry. In addition, mass spectrometric analysis exhibited distinct size microheterogeneity between the stable and native forms of ovalbumin. Immunohisotochemical study revealed that ovalbumin was present in the central nervous system and other embryonic organs. These results indicated that egg white ovalbumin migrates into the developing embryo while changing its higher order structure.

Amino Acid Sequence↗
PubMed1999

Adenoma arising from the cystic duct and extending to the confluence of the extrahepatic biliary tract.

We describe a rare case of adenoma with a few foci of severe atypia arising from the cystic duct in a 68-year-old woman, initially diagnosed by the presence of intracholecystic tumefactive sludge on abdominal ultrasonography. Endoscopic retrograde cholangiography (ERC) disclosed a tuberous filling defect at the orifice of the cystic duct. Pathology examination of the biopsied specimen obtained from ERC disclosed not a cancerous but an adenomatous lesion. Macroscopically, the resected specimen showed a superficially spreading and shallowly elevated lesion extending from the cystic duct to the common bile duct. Although a few sporadic foci of severe atypia were observed, microscopy did not reveal any cancer findings, but confirmed the tumorous lesion as benign adenoma, showing mild-to-moderate atypia. Postoperative immunohistochemistry revealed no expression of p53 protein. We briefly refer to the rarity of adenoma in the biliary tract and discuss the difficulty of differential diagnosis of neoplastic lesions in the extrahepatic biliary tract.

Aged↗
PubMed1999

Polyarthritis nodosa with mesenteric aneurysms demonstrated by angiography: report of a case and successful treatment of the patient with prednisolone and cyclophosphamide.

Polyarteritis nodosa is a necrotizing angitis that predominantly affects small and medium-sized arteries. The prognosis of untreated polyarteritis nodosa is very poor. Since symptoms are diverse and no serologic test is specific for polyarteritis nodosa, the diagnosis is difficult and often delayed. We describe a patient with polyarteritis nodosa who had gastrointestinal involvement with multiple aneurysms of the inferior mesenteric artery; only abdominal angiography provided a conclusive diagnosis. Alleviation of symptoms and regression of aneurysms were observed after combination therapy of an immunosuppressive agent, cyclophosphamide, and prednisolone. We emphasize the importance of early diagnosis by angiography and aggressive therapy in patients in whom physical signs indicating definite polyarteritis nodosa are not present.

Aneurysm↗
PubMed1999

Effects of denervation on energy metabolism of rat hindlimb muscles: application of (31)P-MRS and (19)F-MRS.

We studied the effects of denervation on the energy metabolism and peripheral circulation dynamics of rat hindlimb muscles during and after exercise. The sciatic nerves of male Wistar rats were cut to produce denervation. Energy metabolism was assessed by phosphorus-31 magnetic resonance spectroscopy (MRS), and circulation by fluorine-19 MRS. Exercise of rat hindlimb muscles was induced by electrical stimulation at 40 Hz. The inorganic phosphate (Pi) / ¿Pi + phosphocreatine (PCr)¿ ratio, an indicator of the energy level, was 0.795 immediately after denervation. The ratios 4 and 8 weeks after denervation were 0.870 and 0.853, respectively. The intracellular pH during the 4 min after initiation of stimulation was significantly reduced 4 and 8 weeks after denervation compared with the value immediately after denervation. The signal strength of the research perfluoro-carbon (FC-43; perfluorotributylamine) a measure of circulation dynamics, increased to 167% in controls during exercise, but an increase of only 134% was seen in rats 8 weeks after denervation. These results showed that the energy supply and circulation dynamics in denervated atrophic muscles decreased during exercise compared with findings in control muscles.

Animals↗
PubMed1999

Effects of hepatic impairment on the metabolism of fructose and 5-fluorouracil, as studied in fatty liver models using in vivo 31P-MRS and 19F-MRS.

The purpose of this study was to observe the effects of hepatic impairment on the metabolism of fructose and 5-fluorouracil (5-FU) in fatty liver models using in vivo 31P-MRS and 19F-MRS and to compare the results. In addition, we compared the results to those of other conventional tests such as laboratory examinations, imaging and pathology. Male SIc:Wistar rats were examined on BEM170/200 (4.7 T, Otsuka Electronics, USA) with 17-mm diameter surface coil. Fatty liver was induced by a choline deficient diet (CD diet) for 2 weeks. 31P-MRS were obtained for 90 min after intravenous (i.v.) injection of 1 g/kg of fructose and 19F-MRS were measured for 100 min after i.v. injection of 100 mg/kg of 5-FU. 1H-MRS and 1H-MRI were also performed. On 31P-MRS, there was no statistical difference in the time course of phosphomonoester (PME), adenosine triphosphate (ATP), and inorganic phosphate (Pi) between CD diet group and control group. On 19F-MRS, we detected high peak of fluoronucleotide (Fnct) and suppressed peak of alpha-fluoro-beta-alanine (FBAL) in CD diet group. We showed the metabolism of fructose and 5-FU by 31P-MRS and 19F-MRS, respectively. There was no difference in fructose metabolism but we observed increased fluoronucleotide and decreased a-fluoro-b-alanine in 5-FU metabolism of fatty liver. We speculate that the effects of hepatic impairment in fatty liver may be more severe on 5-FU metabolism and the increased fluoronucleotide may reflect cell proliferation.

Animals↗
PubMed1999

Confined water in hydrophobic nanopores: dynamics of freezing into bilayer ice.

Molecular dynamics simulations for a thin film of water confined to a slit nanopore are performed in order to investigate the dynamic process of crystallization of the system. The system upon freezing creates a bilayer ice crystal composed of two layers of hexagonal rings. We perform one simulation at T=257 K during which the system remains a supercooled liquid state, and another one at T=253 K during which the system freezes. Many patterns of molecular arrangement are found upon freezing, and an account is given of the origin of multiple peaks in the distributions of binding energy and pair interaction energy. A definition of the solid-like cluster is introduced in order to analyze the time evolution of the clusters' population and their shapes. A large variety of shapes including highly nonspherical ones can be detected during simulations. A steady population of clusters is found at T=257 K, whereas at T=253 K a post-critical nucleus of the solid phase emerges within a few nanoseconds and continues to grow until the system freezes completely.

Journal Article↗
PubMed1999

Geographic dimorphism of the wild silkworm, Bombyx mandarina, in the chromosome number and the occurrence of a retroposon-like insertion in the arylphorin gene.

Individuals of the wild silkworm, Bombyx mandarina, collected in South Korea (Taegu City) and Japan (Tsushima Islands and Fukuoka City) had the chromosome number of 2n = 54, while those collected in China (Hangzhou City) had the chromosome number of 2n = 56. Analysis by PCR (polymerase chain reaction) showed that the 66-bp-long retroposon-like insertion known in the arylphorin gene was present in the B. mandarina specimens with 2n = 54, but not in those with 2n = 56. Thus, dimorphism in the chromosome number coincided with the occurrence of the insertion. It is likely that the boundary dividing the two geographic B. mandarina populations lies somewhere in the northern part of the Korean Peninsula.

Animals↗
PubMed1999

Modification of ceftibuten transport by changes in lipid fluidity caused by fatty acid glycerol esters.

The effects of various fatty acid glycerol esters (FAGE) on the transport of ceftibuten in rat intestinal brush-border membrane vesicles (BBMV) were investigated. The HLB numbers of FAGE used were in the range of 6.5 to 15.7. The ceftibuten uptake by BBMV was examined by a rapid filtration method in the presence or absence of FAGE of a non-solubilizing concentration (0.03%, w/v). Tetraglycerol monostearate, hexaglycerol monostearate, hexaglycerol sesquistearate, hexaglycerol tristearate and decaglycerol tristearate were found significantly to enhance the ceftibuten uptake under an inward H+-gradient condition, while FAGE with oleate or laurate did not affect it. The extent of ceftibuten uptake with FAGE correlated with the HLB of the esters (r= -0.90, p<0.001). To elucidate the mechanism of its enhancing action, the effects of FAGE on the membrane lipid fluidity were examined using the fluorescence probes diphenylhexatriene (DPH) and trimethylammonium diphenylhexatriene (TMA-DPH) which distribute in the hydrophobic inner and outer regions of the lipid layer, respectively. The increase in ceftibuten uptake induced by FAGE proved to correlate with an increase in fluidity of the outer lipid layer (r= -0.83, p<0.003) but not the inner lipid layer of BBMV. Hence, the enhancing effect of FAGE with the lower HLB on the ceftibuten transport in the presence of the H+-gradient should, at least in part, be explained by the interaction with the outer lipid regions of BBMV.

Animals↗
PubMed1999

Effects of fatty acid glycerol esters on intestinal absorptive and secretory transport of ceftibuten.

The effects of fatty acid glycerol esters and Tweens on the intestinal transport of ceftibuten were studied using a diffusion chamber system. The apparent permeation coefficient (P(app)) was used as an index of the mucosal permeability to ceftibuten. The P(app) markedly increased by the addition of hexaglycerol monostearate (HGMS) or hexaglycerol sesquistearate (HGSS) under an H+-gradient condition, while hexaglycerol tristearate (HGTS) and Tweens showed no effect on the absorptive ceftibuten permeability. These results are in agreement with those obtained in the previous study in the brush-border membrane vesicles. On the other hand, in the absence of an H+-gradient, the S-to-M transport of ceftibuten was proven to be significantly higher than the M-to-S one. In addition, either ATP-depletion of the mucosa or the addition of probenecid proved to enhance significantly the permeability of ceftibuten. These findings suggest the existence of an active secretory transport system for ceftibuten in the jejunal mucosa. To estimate potential effects of glycerol esters on efflux pumps as well as peptide transporters, the mucosal-to-serosal (M-to-S) and serosal-to-mucosal (S-to-M) permeability in the presence of the esters was further examined. HGMS, HGSS and HGTS markedly enhanced the M-to-S but not the S-to-M transport in the ATP-depleted jejunum without an H+-gradient, in which conditions contributions of both peptide transporter and efflux pump should be substantially small. HGMS and HGSS significantly enhanced the M-to-S ceftibuten transport in the ATP-depleted jejunum with an H+-gradient (p<0.01 vs. M-to-S transport without surfactant under the same conditions). Whereas, these glycerol esters were found hardly to affect the P(app) of the S-to-M transport. These results indicate that the enhanced intestinal transport of ceftibuten due to the glycerol esters may be based on their effects on peptide transporters but neither on efflux pumps nor on the passive permeation routes.

Adenosine Triphosphate↗
PubMed1999

Shift in arm-pointing movements during gravity changes produced by aircraft parabolic flight.

It has been shown that target-pointing arm movements without visual feedback shift downward in space microgravity and upward in centrifuge hypergravity. Under gravity changes in aircraft parabolic flight, however, arm movements have been reported shifting upward in hypergravity as well, but a downward shift under microgravity is contradicted. In order to explain this discrepancy, we reexamined the pointing movements using an experimental design which was different from prior ones. Arm-pointing movements were measured by goniometry around the shoulder joint of subjects with and without eyes closed or with a weight in the hand, during hyper- and microgravity in parabolic flight. Subjects were fastened securely to the seat with the neck fixed and the elbow maintained in an extended position, and the eyes were kept closed for a period of time before each episode of parabolic flight. Under these new conditions, the arm consistently shifted downward during microgravity and mostly upward during hypergravity, as expected. We concluded that arm-pointing deviation induced by parabolic flight could be also be valid for studying the mechanism underlying disorientation under varying gravity conditions.

Adult↗
PubMed1999

[Cochlear implantation in children with inner ear malformation and postoperative performance].

Cochlear implantation in children with cochlear malformation is on the rise. However, only one case has been reported in Japan. The objective of this paper is to report the authors' experiences with cochlear implants in children with cochlear malformations and, to investigate the morphological classification of cochlear malformation, surgical procedure, complications, and speech perceptions after implantation. Five children (6 ears, including 1 Usher's syndrome and 1 CHARGE association) with congenital inner ear malformations were implanted with multichannel cochlear implants (Nucleus Mini 22 device) between 1994 and 1998. Malformations included common cavity deformity 2, and incomplete partition 4. On the other hand, 4 cases with incomplete partition deformity underwent cochlear implantation by the transmastoid facial recess approach, 2 patients with common cavity deformity received implantation by the transmastoid labyrinthotomy approach. Complications such as facial twitching, cerebrospinal fluid (CSF) gusger, and flap-related problems were encountered. Facial twitching occurred in 1 of 2 patients with common cavity where the electrode array extended into the internal auditory canal. CSF gusher was encountered in 1 of 4 patients with incomplete partition, and revision surgery was performed one week later. One patient had delayed cochlear implant infection and a split pericranial flap was used to cover the defect in the skin flap. Within 6 months, however, the revised pedestal site broke down because of recurrent flap infection. Finally, the cochlear implant was explanted, and the patient underwent a new cochlear implantation in the contralateral ear. All the patients had satisfactory speech reception and word acquisition, but still poor phonetic expression.

Cerebrospinal Fluid Otorrhea↗