Biomedical subjects

K Urabe

Publications and source records attributed to K Urabe.

At least 55 records · Page 3Linked to original sources

PubMed1998

Reliability of the anteroposterior axis and the posterior condylar axis for determining rotational alignment of the femoral component in total knee arthroplasty.

We examined the reliability of the anteroposterior and posterior condylar axes for determining rotational alignment of the femoral component in total knee arthroplasty (TKA). A computed tomography scan was taken at the level of the femoral epicondyle in 84 knees (27 varus knees with medial femorotibial arthritis (FT-OA) in 26 patients, 17 knees with patellofemoral arthritis in 14 patients, and 40 normal knees in 40 volunteers). On the image, an anteroposterior axis, a line perpendicular to the anteroposterior axis, an epicondylar axis and a posterior condylar axis were drawn, and the relationship between the three axes was assessed. The mean values for the 84 knees were evaluated, and the posterior condylar axis was 6.0 degrees +/- 2.4 degrees internally rotated relative to the epicondylar axis, while the line perpendicular to the anteroposterior axis was 1.4 degrees +/- 3.3 degrees internally rotated relative to the epicondylar axis. The internal rotation angle of the posterior condylar axis relative to the epicondylar axis was 6.2 degrees +/- 1.9 degrees in the knees with medial femorotibial arthritis, 6.4 degrees +/- 2.4 degrees in the knees with patellofemoral arthritis, and 5.8 degrees +/- 2.7 degrees in the normal knees, showing consistent values in normal and osteoarthritic knees. The internal rotation angle of the line perpendicular to the anteroposterior axis relative to the epicondylar axis was 0.1 degrees +/- 3.3 degrees, 1.3 degrees +/- 3. 3 degrees, and 2.3 degrees +/- 3.1 degrees in the three groups, respectively (i.e., there were significant differences between the medial FT-OA knees and the normal knees). The results demonstrated that the anteroposterior axis was rotated externally to a significant degree in medial FT-OA knees and was less reliable than the posterior condylar axis for use in alignment for TKA on medial FT-OA knees.

Aged↗

PubMed1998

Inappropriate microvascular constriction produced transient ST-segment elevation in patients with syndrome X.

OBJECTIVES: The aim of this project was to study the responsible site(s) and underlying cardiac disease(s) of patients with transient ST-segment elevation and normal coronary angiograms. BACKGROUND: Transient ST-segment elevation has been demonstrated in patients with variant angina or unstable angina. In those patients, epicardial coronary arteries, not microvessels, are always the responsible site for the transient ST-segment elevation. METHODS: This study consisted of three cases with a transient ST-segment elevation and normal coronary angiograms. Treadmill testings were performed before coronary angiography in all cases. Coronary angiography was undertaken during the control state and during ST-segment elevation and, when possible, a Doppler guide wire was positioned in the left anterior descending artery (LAD). Coronary responses to vasodilators were observed. Finally, cardiac biopsy was performed and pathologic observation was conducted. RESULTS: All three cases had significant ST-segment depression during treadmill testing in II, III, aVF and V4-6 leads; however, no angiographic coronary stenosis was demonstrated and vasospasm was not provoked. A transient ST-segment elevation associated with chest pain was observed in V1-5 leads, but normal coronary angiograms during ST-segment elevation were observed in every case. Coronary blood flow (CBF) velocity profile remained normal during ST-segment elevation. In one case, vasodilator responses to the LAD during ST-segment elevation were also measured. A 0.5 mg intracoronary injection of nitroglycerin increased CBF velocity (220%), but ST-segment elevation was not normalized and chest pain persisted. A 10 mg intracoronary injection of papaverine (PVN) further increased CBF velocity up to 340%, and this normalized ST-segment elevation and relieved chest pain quickly. Either endothelium-dependent coronary flow reserve (CFR) measured with a 100 microg intracoronary infusion of acetylcholine, or flow-dependent CFR by a 10 mg intracoronary injection of PVN was reduced in one of two cases measured. Pathologic findings supported syndrome X as the underlying cardiac disease in all cases. CONCLUSIONS: These findings suggested a new clinical implication involving transient ST-segment elevation mimicking variant angina and normal coronary angiograms in patients with syndrome X. The major responsible site for this phenomenon was suggested to be coronary arterioles of less than 200 microm in diameter.

Acetylcholine↗

PubMed1997

Renal hemodynamic and excretory responses in anesthetized rats to FK409, a novel nitric oxide donor.

Renal hemodynamic and excretory responses to (+/-)-(E)-4-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexenamide (FK409), a novel nitric oxide (NO) donor, were examined using anesthetized rats. When FK409 was infused into the renal artery of normal rats at 10 micrograms/kg per min, a moderate renal vasodilating effect was observed with a decrease in mean arterial blood pressure. Urine flow, urinary excretion of sodium and fractional excretion of sodium significantly increased by about 85%, 110% and 75%, respectively, compared with each control value. Simultaneously, urinary excretion of NO metabolites (UNOxV) was markedly increased with the administration of FK409. In hypertensive rats treated with NG-nitro-L-arginine (NOARG), the NO synthase inhibitor, FK409 produced a potent renal vasodilation, although the hypotensive effect of the agent was comparable to that seen in normal rats. In addition, glomerular filtration rate was significantly elevated by the agent. There were marked increases in the excretory responses, i.e., levels of urine flow, urinary excretion of sodium and fractional excretion of sodium were increased to about 3-, 6- and 5-fold of each control value, respectively. The extent of increment of UNOxV was similar to that seen in normal rats. These results clearly indicate that FK409 causes renal vasodilation and diuresis, via NO formation. Renal hemodynamic and excretory responses to the agent are sensitive in NO-depleted conditions. FK409 and related compounds may be useful for the treatment of renal diseases, in cases where the basal NO formation is impaired.

Anesthesia↗

PubMed1997

Malposition of the tibial tubercle during flexion in knees with patellofemoral arthritis.

OBJECTIVE: To assess the mechanisms contributing to the induction of patellofemoral arthritis (PF-OA). DESIGN AND PATIENTS: A computed tomography scan was taken at three levels of the lower extremity in full extension and at 30 degrees of flexion. The cuts were superimposed and 12 parameters were compared in 17 PF-OA knees and 27 normal knees to assess the rotation angle of the tibial tubercle. RESULTS: Although the tibial tubercle was in almost the same position in full extension in the normal and PF-OA knees, it was positioned significantly laterally at 30 degrees of flexion in PF-OA knees. Also the articular surface of the lateral femoral condyle was significantly narrower or steeper in PF-OA knees. CONCLUSION: Anatomic variations and mechanical abnormalities were identified in the PF-OA knees.

Adult↗

PubMed1997

Dyschromatosis.

The dyschromatoses are a group of disorders characterized by the presence of both hyperpigmented and hypopigmented macules, many of which are small in size and irregular in shape. There are two major forms-dyschromatosis symmetrica hereditaria (DSH) and dyschromatosis universalis hereditaria (DUH), both of which are seen most commonly in Japan. DSH was first described by Toyama in 1929 and is characterized by a symmetrical distribution of hyperpigmented and hypopigmented macules on the extremities, especially over the dorsa of the hands and feet. In 1933, Ichikawa and Hiraga were the first to describe DUH as well-demarcated brown macules admixed with various-sized hypopigmented macules in a generalized as opposed to acral distribution. DUH was noted to appear within the first month of life. Some clinicians have suggested that DSH might be a subtype of DUH; however, we have to wait for the cloning of the causal genes of these diseases before coming to any definite conclusions. The differential diagnosis of dyschromatosis includes xeroderma pigmentosum, dyschromic amyloidosis, and exposure to chemicals such as diphenylcyclopropenone and monobenzyl ether of hydroquinone.

Age Factors↗

PubMed1997

[Is reduced left ventricular volume related to mechanisms of dynamic mid-ventricular obstruction provoked by dobutamine infusion?].

Forty-seven patients with unexplained chest pain and normal resting echocardiograms were examined to see whether dynamic mid-ventricular obstruction (MVO) is induced by dobutamine infusion. Dynamic MVO was provoked in 17 patients (MVO group), but not in the other 30 patients (Non-MVO group). Before dobutamine infusion, the blood pressure in the MVO group was higher than that in the Non-MVO group (p < 0.05), but end-diastolic volume index (p < 0.001), end-systolic volume index (p < 0.01), stroke volume index (p < 0.001), cardiac index (p < 0.001), end-diastolic volume (p < 0.01) and end-systolic volume (p < 0.05) of the apical territory of the left ventricle in the MVO group were significantly less than those in the Non-MVO group. The left atrial function, left ventricular ejection fraction and ejection fraction of the apical territory of the left ventricle did not differ between the groups. Seven patients in the MVO group were re-examined by dobutamine stress echocardiography after beta-blocker administration, showing that the dynamic MVO was completely suppressed. The end-diastolic volume tended to increase after beta-blocker administration, but no significant difference was found in any other variables except heart rate. The results suggest that a smaller left ventricle and higher blood pressure are important characteristics in patients with dobutamine-induced dynamic MVO, and additionally, the difference in local myocardial contractility may be an important cause of the induction of dynamic MVO.

Adrenergic beta-Agonists↗

PubMed1997

Is patellar height really lower after high tibial osteotomy?

It has been reported that patellar position becomes lower after the high tibial osteotomy. However, the most commonly used methods for determining patellar height, namely, the Insall-Salvati and Blackburne-Peel methods, use a reference point on the tibia. Therefore, when a surgery is performed on the proximal tibia, the point of reference itself shifts, which may generate spurious values indicating a change when nothing has occurred. We developed a new method for measuring the change in patellar height in relation to the femur under the condition that the patella articulates with the femur, and not with the tibia. Contrary to published reports, we found that the patella height is unchanged or moves slightly proximal in relation to the femur following high tibial osteotomy.

Humans↗

PubMed1996

Relation between dynamic midventricular obstruction and unexplained chest pain in patients with normal echocardiograms at rest.

The relation between dynamic mid-ventricular obstruction provoked by dobutamine infusion and chest pain was investigated in 16 patients with normal echocardiograms at rest who had histories of unexplained chest pain. Chest pain was induced in 63% of dynamic mid-ventricular obstruction and beta blockers suppressed either dynamic mid-ventricular obstruction or Chest pain.

Acebutolol↗

PubMed1996

Characteristics of current induced potential oscillations of a triolein impregnated membrane placed between identical salt solutions.

Periodic oscillations of electric potential were induced by DC electric current between identical salt solutions separated by a membrane filter impregnated with triolein. The oscillation period was controlled by the base electric potential, and temperature dependence of base conductance and conductance amplitude were both close to that of the electric conductivity of the aqueous salt solution. Effects of salt concentration on membrane conductance and on oscillation characteristics were experimentally investigated, and the lifetime of the membrane and of each oscillation were much improved by regulating the concentration of the salt solution. Moreover, characteristics of oscillation curves could be controlled. All the experimental results could be explained by a model where the oscillation was generated by a periodic change of the diameter of a hole through the membrane, which opened in one of the pores filled with triolein.

Electric Conductivity↗

PubMed1996

Prevalence of hepatitis C virus infection among female prostitutes in Fukuoka, Japan.

To assess the risk of sexual transmission of hepatitis C virus (HCV), we surveyed female prostitutes to determine the prevalence of antibody to HCV (anti-HCV) and HCV RNA. Anti-HCV was examined with a second generation anti-HCV test employing a passive hemagglutination assay. HCV RNA was detected by two-stage polymerase chain reaction with primers deduced from the 5'-noncoding region of the HCV genome. All studies were performed in Fukuoka, Japan, from 1989 through 1992 and all subjects were Japanese and had no history of intravenous drug abuse. The prevalence of anti-HCV was significantly higher in the prostitutes (10.1%; 61/604) than in the controls (female blood donors; 0.8%; 52/6632) (P < 0.001). HCV RNA was found in 73.2% of the anti-HCV-positive prostitutes. The prevalence of anti-HCV among prostitutes increased with the number of years spent in prostitution (P < 0.05). Prostitutes with a history of syphilis had a higher prevalence of anti-HCV than those with no history of syphilis, irrespective of the number of years in prostitution. In a longitudinal study of 244 prostitutes, 2 of the 218 initially seronegative subjects showed anti-HCV and HCV RNA over the study period of 3 years. These two persons had no history of percutaneous exposure. Sexual transmission of HCV presents a risk for female prostitutes.

Adolescent↗

PubMed1996

Ectopic expression of MITF, a gene for Waardenburg syndrome type 2, converts fibroblasts to cells with melanocyte characteristics.

MITF (microphthalmia-associated transcription factor) encodes a transcription factor with a basic-helix-loop-helix-zipper (bHLH-Zip) motif. MITF mutations occur in patients with Waardenburg syndrome type 2, a disorder associated with melanocyte abnormalities. Here we show that ectopic expression of MITF converts NIH/3T3 fibroblasts into cells with characteristics of melanocytes. MITF transfectants formed foci of morphologically altered cells, which resemble those induced by oncogenes, but did not exhibit malignant phenotypes. Instead, they contained dendritic cells that express melanogenic marker proteins such as tyrosinase and tyrosinase-related protein 1. Most cloned cells of MITF transfectants exhibited dendritic morphology and expressed melanogenic markers, but such properties were not observed in cells transfected with closely related TFE3 cDNA. Our findings indicate that MITF is critically involved in melanocyte differentiation.

3T3 Cells↗

PubMed1996

Role of endogenous angiotensin II in renal hemodynamic and excretory responses to L-arginine infusion.

The purpose of this study was to investigate whether endogenous angiotensin II has a functional role in renal hemodynamic and excretory changes induced by L-arginine, a substrate for nitric oxide (NO), in anesthetized rats. During the intravenous infusion of L-arginine (50, 100, 200 mumol/kg.min), there was no significant change in systemic or renal hemodynamics, but urine flow and urinary sodium excretion markedly increased in a dose-dependent manner. Simultaneously, L-arginine infusion produced an increase in urinary excretion of NO metabolites, NO2- and NO3-. Treatment with L-158809 ¿5,7-dimethyl-2-ethyl-3-[[2'-(1H-tetrazol-5-yl) [1,1']-biphenyl-4-yl]methyl]-3H-imidazo[4,5-b]pyridine¿ (0.3 mg/kg), a selective angiotensin II type I receptor antagonist, caused a reduction in mean arterial pressure, and a rise in renal blood flow and glomerular filtration rate, with no changes in excretory responses. In the presence of L-158809, L-arginine-induced diuretic and natriuretic actions were observed to the same extent as seen in the absence of L-158809. These data suggest that the infusion of L-arginine causes diuresis and natriuresis, possibly via the formation of nitric oxide in the kidney, and that endogenous angiotensin II is not involved in the L-arginine-induced renal actions.

Anesthesia↗

PubMed1995

Changes in expression of putative antigens encoded by pigment genes in mouse melanomas at different stages of malignant progression.

Cutaneous melanomas of Tyr-SV40E transgenic mice (mice whose transgene consists of the tyrosinase promoter fused to the coding regions of simian virus 40 early genes) strikingly resemble human melanomas in their development and progression. Unlike human melanomas, the mouse tumors all arise in genetically identical individuals, thereby better enabling expression of specific genes to be characterized in relation to advancing malignancy. The products of pigment genes are of particular interest because peptides derived from these proteins have been reported to function as autoantigens with immunotherapeutic potential in some melanoma patients. However, the diminished pigmentation characteristic of many advanced melanomas raises the possibility that some of the relevant products may no longer be expressed in the most malignant cells. We have therefore investigated the contributions of several pigment genes in melanotic vs. relatively amelanotic components of primary and metastatic mouse melanomas. The analyses reveal marked differences within and among tumors in levels of mRNAs and proteins encoded by the wild-type alleles at the albino, brown, slaty, and silver loci. Tyrosinase (the protein encoded by the albino locus) was most often either absent or undetectable as melanization declined. The protein encoded by the slaty locus (tyrosinase-related protein 2) was the only one of those tested that was clearly present in all the tumor samples. These results suggest that sole reliance on targeting tyrosinase-based antigens might selectively favor survival of more malignant cells, whereas targeting the ensemble of the antigens tested might contribute toward a more inclusive and effective antimelanoma strategy.

Animals↗

PubMed1995

Mitogenic and melanogenic stimulation of normal human melanocytes by melanotropic peptides.

The significance of melanotropic hormones as physiologic regulators of cutaneous pigmentation in humans is still controversial. Until recently, no direct effect for melanotropins could be demonstrated on human melanocytes. Here we present conclusive evidence that alpha-melanotropin (alpha-melanocyte-stimulating hormone, alpha-MSH) and the related hormone corticotropin (adrenocorticotropic hormone, ACTH) stimulate the proliferation and melanogenesis of human melanocytes maintained in culture in a growth medium lacking any AMP inducer. The minimal effective dose of either hormone is 0.1 nM. In time-course experiments, the increase in cell number and tyrosinase activity became evident after one treatment of the melanocytes with 100 nM alpha-MSH for 48 hr. The mitogenic effect gradually increased to 50-270% above control, depending on the individual melanocyte strain, with continuous treatment with 100 nM alpha-MSH for 8 days, whereas the melanogenic effect became maximal (70-450% increase above control) after 4 days of treatment. Western blot analysis of tyrosinase and the tyrosinase-related proteins TRP-1 and TRP-2 revealed that alpha-MSH increased the expression of those three melanogenic proteins. This was not accompanied by any change in their mRNA levels after brief (1.5-24 hr) or prolonged (6 days) treatment with 100 nM alpha-MSH, suggesting that the increased expression of these melanogenic proteins was due to posttranscriptional events. These results demonstrate both mitogenic and melanogenic effects of alpha-MSH and ACTH on human melanocytes. That both hormones are effective at subnanomolar concentrations, combined with the presence of melanotropin receptors on human melanocytes, strongly suggests that these melanotropins play a physiologic role in regulating human cutaneous pigmentation.

Adrenocorticotropic Hormone↗

PubMed1995

Sexual transmission of human T-lymphotropic virus type I among female prostitutes and among patients with sexually transmitted diseases in Fukuoka, Kyushu, Japan.

The authors investigated the prevalence of antibody to human T-lymphotropic virus type I (anti-HTLV-I) in 409 female prostitutes, 446 patients with an episode of sexually transmitted diseases, and 17,345 control blood donors. All subjects were Japanese and all studies were done in Fukuoka, Kyushu, Japan, in 1989. The prevalence of anti-HTLV-I was significantly higher in the prostitutes (5.1%, p < 0.001), in the male patients (2.8%, p < 0.05), and in the female patients (5.7%, p < 0.05) than in the controls (males 1.4%, females 2.2%). Prevalence of anti-HTLV-I in the prostitutes increased with the number of years spent in prostitution, but the increase was not statistically significant. Among the subjects with sexually transmitted diseases, female prostitutes with syphilis, male patients with non-gonococcal urethritis, female patients with syphilis, and female patients with gonorrhea had a significantly higher prevalence of anti-HTLV-I than did the controls. A longitudinal study was done on the 168 prostitutes. Two (1.3%) of the 158 initially seronegative subjects seroconverted over the period of 2 years. These data suggest that the risk of male-to-female transmission of HTLV-I through sexual contact is high among high risk groups in Japan, and they support the possibility of female-to-male transmission of HTLV-I.

Adolescent↗

PubMed1995

Impairment of the melanogenic pathway in B16 melanoma cells transfected with class I H-2 genes.

Transfection of class I H-2Kb or H-2Kd into cells of a pigmented subclone of B16-F10 BL6 (termed BL6-8) results in the loss of melanin production. In contrast, transfected BL6-8 cells expressing H-2Dd, H-2Ld, class I H-21Ak and/or the neor genes maintained their pigmented phenotype. Melanogenesis was also inhibited in cells which expressed the endogenous H-2Kb, but not the endogenous H-2Db, gene. In order to identify the specific defects in the melanogenic pathway responsible for the absence of melanin production, factors known to be related to the regulation of pigment formation were evaluated in H-2K-expressing cells. These studies showed that: (1) transfection of BL6-8 cells with the H-2Kb or H-2Kd, but not with the H-2Dd, H-2Ld or H-21Ak, genes was associated with complete inhibition of tyrosinase activity; (2) alpha-melanocyte-stimulating hormone (MSH) and theophylline (an inhibitor of cAMP phosphodiesterase) failed to stimulate tyrosinase activity in H-2K-positive cells, whereas tyrosinase activities in untransfected, or H-2DdH-2Ld, neor or H-21Ak-transfected cells were dramatically increased by those agents; (3) treatment with MSH had no effect on cAMP levels in H-2K-positive cells but stimulated cAMP levels more than 100-fold in H-2K-negative cells; (4) in contrast to MSH, forskolin, a stimulator of adenylate cyclase, was able to stimulate cAMP levels in all cell lines tested, but in H-2Kb-positive cells the levels of forskolin-induced cAMP were significantly less than those elicited in H-2Kb-negative cells; (5) electron microscopy showed that H-2K-positive cells lacked mature melanosomes; (6) Northern blot analyses showed that H-2K-positive cells lacked mRNA for tyrosinase or for the MSH receptor. Taken together, expression of the endogenous or transfected H-2K gene in BL6 melanoma cells results in down-regulation of the entire melanogenic pathway, including the inhibition of tyrosinase and MSH receptor gene expression, cAMP responses and melanosomal biogenesis.

Animals↗

PubMed1995

Differential cell- and immuno-biological properties of murine B16-F1 and F10 melanomas: oncogene c-fos expression, sensitivity to LAK cells and/or IL-2, and components of gangliosides.

Differential cell- and immuno-biological properties of two murine melanoma B16 variants, B16-F1 and F10, were investigated. Studies focused on the expression of proto-oncogene c-fos, sensitivities to LAK cells and/or IL-2, and modulation of the expression of ganglioside components after treatment with IL-2. Proto-oncogene c-fos was found to be highly expressed in F10 lines by an in situ hybridization technique and also in F10 lung metastatic nests by immunofluorescent staining with anti-c-fos antibody. F1 melanomas were more sensitive to local injection of IL-2. F10 melanomas hardly responded to IL-2 treatment, but successive injections of a combination of LAK cells and IL-2 did cause prolongation of survival rates, even of F10 melanoma-burdened mice. A major component of gangliosides of both F1 and F10 melanomas was GM3. Production of GM3 in F10 melanomas treated with IL-2 for 4 days increased, and, if the treatment was continued for 7 days, minor components of gangliosides, such as GM2, GM1, and GD1a, appeared only in F1 melanomas, while the increase of production of GM3 disappeared in both melanomas. These experimental results may provide clues for additional mechanisms which allow these two murine melanoma variants to show different implantation and metastasis rates.

Animals↗

PubMed1994

Tyrosinase related protein 1 (TRP1) functions as a DHICA oxidase in melanin biosynthesis.

Several genes critical to the enzymatic regulation of melanin production in mammals have recently been cloned and mapped to the albino, brown and slaty loci in mice. All three genes encode proteins with similar structures and features, but with distinct catalytic capacities; the functions of two of those gene products have previously been identified. The albino locus encodes tyrosinase, an enzyme with three distinct melanogenic functions, while the slaty locus encodes tyrosinase-related protein 2 (TRP2), an enzyme with a single specific, but distinct, function as DOPAchrome tautomerase. Although the brown locus, encoding TRP1, was actually the first member of the tyrosinase gene family to be cloned, its catalytic function (which results in the production of black rather than brown melanin) has been in general dispute. In this study we have used two different techniques (expression of TRP1 in transfected fibroblasts and immunoaffinity purification of TRP1 from melanocytes) to examine the enzymatic function(s) of TRP1. The data demonstrate that the specific melanogenic function of TRP1 is the oxidation of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) to a carboxylated indole-quinone at a down-stream point in the melanin biosynthetic pathway. This enzyme activity appears to be essential to the further metabolism of DHICA to a high molecular weight pigmented biopolymer.

Animals↗