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Biomedical subjects

K Doi

Publications and source records attributed to K Doi.

At least 55 records · Page 3Linked to original sources
PubMed2001

In vivo studies of the gamma subunit of retinal cGMP-phophodiesterase with a substitution of tyrosine-84.

The inhibitory rod cGMP phosphodiesterase gamma subunit (PDEgamma) is a major component of the photoresponse and is required to support rod integrity. Pdeg(tm1)/Pdeg(tm1) mice (which lack PDEgamma owing to a targeted disruption of the Pdeg gene) suffer from a very rapid and severe photoreceptor degeneration. The Y84G (Tyr(84)-->Gly) allele of PDEgamma has previously been shown in experiments carried out in vitro to reduce the regulatory control of the PDE catalytic core (PDEalphabeta) exerted by the wild-type gamma subunit. To determine the effects of this mutation on in vivo function, the murine opsin promoter was used to direct expression to the photoreceptors of +/Pdeg(tm1) mice of a mutant Y84G and a wild-type PDEgamma control transgene. The transgenic mice were crossed with Pdeg(tm1)/Pdeg(tm1) mice to generate animals able to synthesize only the transgenic PDEgamma. Our results showed that wild-type PDEgamma and Y84G transgenes could complement the Pdeg(tm1)/Pdeg(tm1) mutant for photoreceptor survival. The mutation caused a significant biochemical defect in PDE activation by transducin. However, the Y84G mutation did not fully eliminate the control of PDEgamma on the PDE catalytic core in vivo; the expression of the mutant subunit was associated with only a 10-fold reduction in the amplitude of the a-wave and a 1.5-fold decrease in the b-wave of the corneal electroretinogram. Unexpectedly, the mutation caused a much 'milder' phenotype in vivo than was predicted from the biochemical assays in vitro.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2001

cGMP-dependent protein kinase phosphorylates and inactivates RhoA.

Small GTPase Rho and cGMP/cGMP-dependent protein kinase (cGK) pathways exert opposing effects in specific systems such as vascular contraction and growth. However, the direct interaction between these pathways has remained elusive. We demonstrate that cGK phosphorylates RhoA in vitro at Ser188, the same residue phosphorylated by cAMP-dependent protein kinase. In HeLa cells transfected with constitutively active cGK (C-cGK), stress fiber formation induced by lysophosphatidic acid or V14RhoA was blocked. By contrast, C-cGK failed to inhibit stress fiber formation in cells transfected with mutant RhoA with substitution of Ser188 to Ala. C-cGK did not affect actin reorganization induced by Rac1 or Rho-associated kinase, one of the effectors for RhoA. Furthermore, C-cGK expression inhibited the membrane translocation of RhoA. Collectively, our findings suggest that cGK phosphorylates RhoA at Ser188 and inactivates RhoA signaling. The physiological relevance of the direct interaction between RhoA and cGK awaits further investigation.

Actins↗
PubMed2001

Fractal analysis of senile plaque observed in various animal species.

In the present study, the fractal dimension (FD), a concept to determine morphological complexity, was applied to morphological estimation of animal and human senile plaque using a computer-aided method. The FDs of mature plaque in a 17-year-old dog were significantly higher than those of diffuse plaque in 11- to 16-year-old dogs. In both types of plaque, the FD tended to increase as the size expanded and there was a significant difference between the slope values of the approximate line for diffuse and mature plaque. In humans, there was also a significant difference in FD value between diffuse and mature plaque. No significant differences were observed between the two types of plaque in a bear or a cynomolgus monkey. The FD of feline diffuse plaque was significantly lower than that of a camel, bear and monkey. These results indicated that the diffuse and mature plaque of the dog might form in a different manner, and similar events may occur in human senile plaque formation. In addition, specific shapes and different FD values of the diffuse plaque among animals suggested that the original conditions for plaque formation would be different.

Aging↗
PubMed2001

Vascular complication in free tissue transfer to the leg.

The lower-extremity free flap has a high incidence of vascular complication. A retrospective study of 70 free flap transplants in 70 patients (1987-2000) was conducted to investigate factors leading to vascular complication and free flap failure. The overall success rate was 92% (64 of 70 flaps); the incidence of vascular complications was 22% (16 of 70 flaps). Among 16 complicated flaps, 7 were transferred in severely crushed legs, and 4 were in multioperated legs attributable to chronic osteomyelitis. Venous thrombosis occurred in 12 flaps (86%). The success rate of the patients operated on at Yamaguchi University Hospital was higher (96%) than at other hospitals tested. The key factors contributing to improved outcome in free tissue transplantation in the leg were careful preoperative planning for highly traumatized legs and proper selection of the recipient vein and of the hospital at which immediate reexploration can be performed for vascular complicated flaps.

Adolescent↗
PubMed2001

Different forms of dizziness occurring after cochlear implant.

Dizziness after cochlear implant (CI) was studied in a series of 94 consecutive adult patients receiving a cochlear implant, 46 (49.0%) of whom experienced dizziness post-operatively. In 29 patients, post-operative dizziness occurred soon after surgery and subsided within one month. Dizziness of the continuous type, lasting more than 6 months, was a complaint in only two patients. In addition to these already known forms of dizziness, spells of vertigo occurring later than one month after cochlear implant were experienced by 15 patients (delayed-V). The spells of delayed-V occurred suddenly and persisted for several hours. Moreover, 85.7% of delayed-V patients complained of hearing and tinnitus abnormalities during these spells. The clinical features of delayed-V were similar to those in patients with Meniere's disease. The preoperative bithermal caloric test showed a significantly higher response for the delayed-V group than the other groups (ANOVA: P < 0.05) in terms of slow phase eye velocity of caloric nystagmus. These findings suggest that inner ear lesions due to cochlear implant surgery develop gradually. Similarities in clinical features between delayed-V and Ménière's disease indicate the presence of labyrinthine hydrops.

Adolescent↗
PubMed2001

Three-dimensional structures of canine senile plaques.

In this study, the three-dimensional structures of two types of canine senile plaques (SP), diffuse plaques (DP) and mature plaques (MP), were compared using a confocal laser scanning microscope. The three-dimensional observation revealed that canine DP were uneven nebula-like assemblies of amyloid-beta (Abeta), while MP were comparatively uniform assemblies of membrane-like or fibrous Abeta materials with some differences among subtypes (primitive, classic and compact). We also noticed the presence of areas with low-density Abeta deposition inside DP and MP, indicating degradation of Abeta. Double staining for Abeta and other SP constituents was also conducted. Amyloid precursor protein (APP) was mainly deposited as rough granules around Abeta assemblies in DP and both inside and around Abeta assemblies in MP. The patten of ubiquitin deposition was quite similar to that of APP. Glial fibrillary acidic protein-positive astroglial projections were found around and inside Abeta assemblies in both types of SP, but were more prominent in MP than DP. DP were often invaded by neurofilament-positive neuronal processes (neurites), while no such neurites were observed inside MP. Dystrophic neurites were, however, frequently detected around MP. These results clearly showed that canine DP and MP have completely different three-dimensional structures, consistent with different processes of DP and MP formation.

Aging↗
PubMed2001

Thiazolidinediones, peroxisome proliferator-activated receptor gamma agonists, regulate endothelial cell growth and secretion of vasoactive peptides.

Insulin resistance has been highlighted as a common causal factor for glucose intolerance, hypertension and dyslipidemia, all of which are cardiovascular risk factors. A new class of antidiabetic agents, thiazolidinediones (TZDs), has been developed and demonstrated to improve insulin sensitivity. TZDs are high affinity ligands for peroxisome proliferator-activated receptor gamma (PPARgamma), the crucial transcription factor for adipocytes. Recent studies showed that PPARgamma is also expressed in monocytes/macrophages and is suggested to be involved in atherosclerosis. We could detect PPARgamma gene transcript in several cultured endothelial cells (human aortic endothelial cells (HAoECs), human coronary artery endothelial cells (HCAECs), human umbilical vein endothelial cells (HUVECs) and bovine carotid artery endothelial cells (BAECs)) as well as human coronary arteries we examined. Since endothelial dysfunction is critical for atherosclerosis, we investigated the effects of TZDs, troglitazone (TRO) and pioglitazone (PIO), on endothelial cell growth and secretion of C-type natriuretic peptide (CNP), which we demonstrated as a novel endothelium-derived relaxing peptide, and endothelin (ET), a potent vasoconstrictor, using HAoECs, HCAECs, HUVECs and BAECs. When all these cultured endothelial cells were daily treated with TRO and PIO for 5 days, both TRO and PIO (10(-8)M) significantly stimulated (3)H-thymidine incorporation of all these endothelial cells. In contrast, higher dose of TRO and PIO (10(-5)M) significantly suppressed DNA synthesis. TRO and PIO also exerted the compatible effect on the increase of cell numbers. TRO and PIO significantly enhanced CNP secretion from BAECs. In contrast, ET secretion from BAECs was suppressed by both TRO and PIO in a dose-dependent manner. The results of the present study suggest that TZDs modulate endothelial functions, including regulation of endothelial cell growth and secretion of endothelium-derived vasoactive substances, which affect vascular tone and remodeling in the process of atherosclerosis.

Animals↗
PubMed2001

Disruption of the hup gene encoding a histone-like protein HS1 and detection of HS12 of Streptomyces lividans.

When the latter half of the hup gene encoding a histone-like protein HS1 of Streptomyces lividans TK24 was replaced by the kanamycin resistance gene, the hup mutant EY1 grew slowly in liquid medium and this delay was overcome by introduction of the complete hup. EY1 sporulated normally on solid medium, with no serious defects as observed in hupAB mutants of Escherichia coli. Therefore, HS1 probably has a role in growth in the presence of liquid medium and this organism may possess another histone-like protein with functions overlapping those of HS1. We cloned the hup2 gene encoding another histone-like protein HS12, which has two motifs of prokaryotic histone-like protein and eukaryotic histone H1. The amount of HS12 increased in EY1, determined by western blotting analysis using an anti-His-tagged HS12 polyclonal antibody. We are entertaining the notion that the increased amount of HS12 partially suppressed the defects caused by the hup mutation.

Amino Acid Sequence↗
PubMed2001

Apoptosis in mouse fetuses from dams exposed to T-2 toxin at different days of gestation.

T-2 toxin (2 mg/kg b.w.) was orally inoculated to pregnant mice at gestational day (GD) 8.5, 9.5, 10.5, 11.5, 12.5, 13.5, 14.5, 15.5 and GD 16.5, respectively, and the fetuses were examined 24 hours later. The number and region of pyknotic or karyorrhectic cells varied according to inoculation date. In the GD 13.5-subgroup, a moderate to high number of pyknotic or karyorrhectic neuronal cells were observed in the central nervous system, peri-ventricular zone to subventricular zone, and pyknosis or karyorrhexis were also observed in a small number of chondroblasts and chondrocytes. In the GD 16.5-subgroup, a moderate to high number of pyknotic or karyorrhectic cells were observed in the thymus and renal subcapsular parenchyma. The nuclei of these pyknotic or karyorrhectic cells were strongly stained by the terminal deoxy nucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end labeling method widely used for the in situ detection of apoptotic nuclei. In addition, a few fetuses from dams which were given T-2 toxin at GD 13.5 or GD 14.5 and killed at GD 17.5 showed skeletal abnormalities such as wavy ribs and short scapula. From the present findings and the well known fact that T-2 toxin readily crosses the rat placenta, it seems that T-2 toxin-induced apoptosis in the developing mouse fetuses might be a direct effect of T-2 toxin on fetuses.

Abnormalities, Drug-Induced↗
PubMed2001

Kinetics of apoptosis-related genes mRNA expression in the dorsal skin of hypotrichotic WBN/ILA-ht rats after topical application of T-2 toxin.

The expression of apoptosis-related genes mRNAs was examined in the dorsal skin of hypotrichotic WBN/ILA-Ht rats topically applied with T-2 toxin (10 microl of 0.5 microg/microl solution). The total mRNA was obtained from skin biopsy samples from each rat at 3, 6, 12 and 24 hours after T-2 toxin treatment (HAT), and RT-PCR was carried out with pairs of oligonucleotide primers corresponding to the cDNA sequences of rat p53, bcl-2, c-ki-ras, c-fos and c-jun oncogenes. The expression of c-fos mRNA markedly increased at 3 HAT, peaked at 6 HAT, and greatly decreased at 12 HAT. However it maintained a higher level, compared with the control level, even at 24 HAT. Although not prominent, the expression of c-jun mRNA also showed significant elevation from 3 to 12 HAT. On the other hand, there were no changes in the expression of p53, bcl-2 and c-ki-ras mRNAs throughout the observation period. Judging from the present results and our previous report that epidermal cells developed apoptosis at 12 HAT (Histol Histopathol 1999; 14: 337-342), the induction of c-fos and perhaps of c-jun mRNAs may be associated with T-2 toxin-induced epidermal cell apoptosis.

Animals↗
PubMed2001

ROC analysis of detection of metastatic pulmonary nodules on digital chest radiographs with temporal subtraction.

RATIONALE AND OBJECTIVES: The authors' purpose was to evaluate the effect of temporal subtraction on digital chest radiographs in the detection of metastatic pulmonary nodules. MATERIALS AND METHODS: The study included 21 cases with metastatic pulmonary nodule and 21 cases without metastatic nodule. Eleven radiologists, including eight residents and three certified radiologists, provided their confidence levels for the presence or absence of pulmonary nodules without and with temporal subtraction. Their performances without and with temporal subtraction were evaluated by means of receiver operating characteristic analysis with both independent and sequential tests. RESULTS: For the independent test, the radiologists' Az (area under the receiver operating characteristic curve) values were 0.871 without and 0.954 with temporal subtraction, compared with 0.882 and 0.955, respectively, for the sequential test. Diagnosis accuracy was significantly improved with the use of temporal subtraction. There was no significant difference in Az values between the independent and sequential tests. CONCLUSION: Temporal subtraction is useful in the detection of metastatic pulmonary nodules, and this technique augments the value of digital chest radiography.

Adult↗
PubMed2001

Effect of diet on changes in small intestinal blood flow following intracolonic administration of indomethacin to rats.

Liquid diet (LD) is known to be protective against indomethacin-induced enteropathy, which is thought to be associated with ischemic change. We tested the hypothesis that the solid component of diet modulates small intestinal blood flow (SIBF) following indomethacin administration. In the first experiment, male Wistar rats were divided into 18-hr-fasted and normal diet groups. Indomethacin (20 mg/kg) or vehicle was administered intracolonically. SIBF was measured on both the mesenteric and antimesenteric sides of the intestine, using the hydrogen gas clearance method. In the second experiment, rats were given LD alone or LD with increasing concentration of soluble/insoluble fiber for seven days. The baseline SIBF was significantly higher in the groups with normal diet and LD with fiber than in the fasting and LD groups. Following indomethacin administration, SIBF gradually decreased in the groups with normal diet and LD with insoluble fiber, while neither liquid diet nor fasting reduced SIBF. There was no difference in SIBF between the mesenteric and antimesenteric sides of the intestine in any group. Our findings suggest that solid components of diet increase basal SIBF and decrease SIBF following indomethacin administration.

Animals↗
PubMed2001

Clinical application of intraoperative measurement of choline acetyltransferase activity during functioning free muscle transfer.

Intraoperative measurement of choline acetyltransferase (CAT) activity was used for evaluation of the functional status of donor nerves during functioning free muscle transfer (FFMT). Twelve patients underwent the procedure. Seven patients had a brachial plexus injury, 3 Volkmann's contracture, 1 chronic peroneal nerve injury, and 1 forearm extensor muscle loss after wide resection of soft tissue sarcoma. The purpose of reconstruction using FFMT was to achieve wrist extension in 4 patients, simultaneous elbow flexion and finger extension in 3, elbow flexion in 2, finger extension in 1, finger flexion in 1, and ankle extension in 1 patient. The gracilis muscle was transferred in all cases. The donor nerves for FFMT that were evaluated by CAT activity included 5 spinal accessory nerves, 4 posterior interosseous nerves, 2 anterior interosseous nerves, and 1 deep peroneal nerve. Fascicles with greater than 2,000 cpm CAT activity were considered to reliable and used as donor motor nerves. All muscles had reinnervation by 3.2 months (range, 2-5 months) and obtained useful recovery. Intraoperative measurement of CAT activity can provide direct and quantitative information about the functional status of donor nerves during FFMT.

Adolescent↗
PubMed2001

Effects of bezafibrate on insulin sensitivity and insulin secretion in non-obese Japanese type 2 diabetic patients.

The aim of the present study was to investigate the effect of bezafibrate on insulin sensitivity and insulin secretion in 30 non-obese Japanese type 2 diabetic patients with hypertriglyceridemia (serum triglycerides > 150 mg/dL). Insulin sensitivity was measured with homeostasis model assessment insulin resistance (HOMA-IR) proposed by Matthews et al. HOMA-B-cell function, proposed by Matthews et al validated against minimal model-derived insulin secretion, was used to assess pancreatic insulin function. Twenty-two patients were treated with glibenclimide and the rest were treated with diet alone. All patients were treated with bezafibrate (400 mg/d) for 3 months. There were no changes in diet and the dose of any medications used throughout the study. Fasting glucose, insulin, triglycerides, HDL cholesterol, and total cholesterol levels were measured before and after treatment of bezafibrate. After treatment of bezafibrate for 3 months, serum triglyceride levels significantly decreased from 277 +/- 30 to 139 +/- 9 mg/dL (P <.001) and serum HDL cholesterol levels increased significantly from 45 +/- 2 to 52 +/- 2 mg/dL (P =.003). Serum cholesterol level was unchanged during the study (198 +/- 7 v 201 +/- 7 mg/dL, P =.383). Fasting glucose (163 +/- 8 v 139 +/- 6 mg/dL, P =.006) significantly decreased after the treatment with bezafibrate. HbA1c levels decreased, although not statistically significant (7.50 +/- 0.25 v 7.17% +/- 0.19%, P =.147). On the other hand, fasting insulin (9.3 +/- 0.7 v 7.3 +/- 0.5 microU/mL, P =.010) and HOMA-IR (3.61 +/- 0.24 to 2.53 +/- 0.20, P <.001) levels decreased significantly after the treatment with bezafibrate. In contrast, HOMA-B-cell function did not change during the study (41.4 +/- 5.5 v 41.8 +/- 4.7, P =.478). There was no significant difference in body mass index (BMI) levels before and after the therapy (23.0 +/- 0.4 v 23.1 +/- 0.4 kg/m(2), P =.483). From these results, it can be concluded that bezafibrate reduces serum triglycerides, insulin resistance, and fasting blood glucose levels in non-obese Japanese type 2 diabetic patients.

Adult↗
PubMed2001

Acute dorsal skin responses to UVB-irradiation in Wistar-derived hypotrichotic WBN/ILA-Ht rats.

Acute responses of the dorsal skin to UVB-irradiation (10 kJ/m2) were compared between Wistar-derived hypotrichotic WBN/ILA-Ht rats and Wistar rats. In the epidermis of WBN/ILA-Ht rats, intracellular edema of keratinocytes with or without nuclear shrinkage developed at 3 hours after irradiation mainly in the spinous layer. At 12 hours after irradiation, many sunburn cells characterized by eosinophilic cytoplasm and pyknotic nuclei were observed chiefly in the basal layer. Sunburn cells were mainly observed in the spinous and granular layers at 24 hours after irradiation, and they almost disappeared at 48 hours after irradiation when epidermal hyperplasia was detected. The nuclei of sunburn cells were strongly stained with TUNEL method, and they showed ultrastructural features characteristic for apoptotic nuclei. Moreover, the change in the percentage of TUNEL-positive keratinocytes corresponded well with that in the number of sunburn cells. In the dermis, inflammatory cell infiltration and edema with vascular dilatation were observed at 12 and 24 hours after irradiation. On the other hand, except for intracellular edema of keratinocytes mainly in the spinous layer, the intensity of skin lesions was greatly milder in Wistar rats. Especially, typical sunburn cells were only slightly observed in the basal layer at 24 hours after irradiation. Thus WBN/ILA-Ht rats were more sensitive to UVB-irradiation than Wistar rats, and WBN/ILA-Ht rats was considered to be a useful experimental animal in the field of photodermatology.

Acute Disease↗
PubMed2001

Carbon tetrachloride-induced acute liver injury in Mini and Wistar rats.

Acute liver injury induced by CCl4 injection (0.5 ml/kg b.w.) was compared between Mini and Wistar rats. Mini rats (Jcl:Wistar-TgN (ARGHGEN)1Nts strain) are Wistar-derived transgenic animals in which the expression of growth hormone (GH) gene is suppressed by the presence of an antisense transgene. The hepatic lesion appeared earlier and its recovery was delayed in Mini rats compared to in Wistar rats. The degree of the liver injury was more severe in Mini rats than in Wistar rats, and this corresponded well with the changes in serum AST level. Moreover, in accordance with the localization of CYP2E1-positive hepatocytes in the early stage after CCl4 treatment, the initial lesion characterized by ballooning of hepatocytes developed in the centrilobular zone in Wistar rats while it appeared in the middle zone in Mini rats. The changes in the percentage of PCNA-positive cells and the levels of HGF and TGF-beta1 mRNAs were clearly different between the two strains. These results indicate that the response of the liver to CCl4 is different between GH-suppressed Mini rats and Wistar rats.

Alkaline Phosphatase↗