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Hajime Yamazaki

Publications and source records attributed to Hajime Yamazaki.

At least 19 recordsLinked to original sources
PubMed2026

Mendelian Randomization Using a Japanese GWAS Identifies an HLA-Linked Causal Effect of Chronic Hepatitis B on Cholangiocarcinoma Risk.

BACKGROUND: Cholangiocarcinoma (CCA) is a highly malignant cancer that develops in the bile ducts. Its incidence is particularly high in East Asian populations, but the underlying genetic factors remain unclear. To investigate potential risk factors for CCA, we conducted a Mendelian randomization study to infer causality. METHODS: Using large-scale genome-wide association study data from the BioBank Japan resource, we systematically investigated the causal effects of genetic predisposition to seven conditions, chronic hepatitis B (CHB), chronic hepatitis C, autoimmune hepatitis, type 1 diabetes, type 2 diabetes, chronic gastritis, and chronic pancreatitis, on CCA risk. RESULTS: Our analysis reveals a significant association between genetic susceptibility to CHB with a 24% higher likelihood of developing CCA than non-susceptible individuals (Inverse-Variance Weighted Odds Ratio = 1.24, 95% Confidence Interval: 1.08-1.42; p = 0.002). This genetic association is significantly driven by instrumental variables enriched in the immune-regulatory HLA class II region (6p21), suggesting a plausible biological mechanism. For the primary outcome (CCA), statistical significance was assessed across seven exposures at a Bonferroni-corrected threshold (two-sided p<0.0071). Notably, the CHB-CCA association remains significant after correction. This primary finding is strongly supported by comprehensive sensitivity analyses that showed no evidence of confounding by horizontal pleiotropy or heterogeneity. Conversely, no significant causal effects on CCA were identified for the other six conditions. CONCLUSIONS: Our MR analysis supports a causal role of HBV infection in CCA development, highlighting the importance of targeted HBV screening and surveillance.

Female↗
PubMed2006

Effect of fluoride on artificial caries lesion progression and repair in human enamel: regulation of mineral deposition and dissolution under in vivo-like conditions.

OBJECTIVE: This study was carried out to determine in vitro the effect of fluoride on (1) the demineralization of sound human enamel and (2) the progression of artificial caries-like lesions, under relevant oral conditions. METHODS: Thin sections of sound human enamel were exposed to solutions undersaturated with respect to tooth enamel to a degree similar to that found in dental plaque fluid following sucrose exposure in vivo, containing fluoride concentrations (0-0.38ppm) found in plaque fluid. Mineral changes were monitored for 98 days, using quantitative microradiography. The effect of fluoride (1.0-25.0ppm) on the progression of artificial caries-like lesions was similarly studied. RESULTS: Fluoride concentrations of 0.19ppm and greater were found to prevent the demineralization of sound enamel in vitro. However, significantly higher concentrations of fluoride (25.0ppm) were required to prevent further demineralization of artificial caries-like lesions. Demineralizing solutions with intermediate fluoride concentrations (2.1-10.1ppm) induced simultaneously remineralization in the outer portion of the lesion and demineralization in the inner portion. Simultaneous remineralization and demineralization were also observed in hydroxyapatite pellets. CONCLUSIONS: Our results show that the observed effect of fluoride on enamel demineralization is not solely a function of bulk solution properties, but also depends on the caries-status of the enamel surface. A mechanistic model presented indicates that, in comparison to sound enamel surfaces, higher concentrations of fluoride are required to prevent the progression of artificial caries-like lesions under in vivo-like conditions since the diffusion of mineral ions that promote remineralization is rate-limiting.

Analysis of Variance↗
PubMed2006

Lymphoplasmacytic infiltration of multiple organs with immunoreactivity for IgG4: IgG4-related systemic disease.

We report three elderly men with high serum IgG4 concentrations and multiple lymphoplasmacytic inflammation of the salivary glands, lymph nodes, pancreas, and renal interstitium. The infiltrating plasma cells had strong immunoreactivity for IgG4, even in patients without pancreatic lesions. These cases show that IgG4 is associated not only with autoimmune pancreatitis, but also with other systemic lymphoplasmacytic disease.

Autoimmune Diseases↗
PubMed2006

Nephrotic syndrome and IgA nephropathy in polycystic kidney disease.

A 70-year-old man with polycystic kidney disease developed nephrotic syndrome, deteriorating to renal insufficiency. Histological examination revealed IgA nephropathy. With treatment of prednisolone, an angiotensin-converting enzyme inhibitor, and an angiotensin II receptor-blocker, his proteinuria markedly decreased and renal function was stabilized. This case supports the idea that renal biopsy is needed in patients with polycystic kidney disease with nephrotic-range proteinuria, for appropriate treatment and prevention of renal failure.

Aged↗
PubMed2004

Renal function at the time of renal biopsy as a predictor of prognosis in patients with primary AL-type amyloidosis.

BACKGROUND: Amyloid light-chain (AL)-type amyloidosis is a plasma cell disorder with a poor prognosis for survival. Although prognostic factors, such as the number of organs involved and heart function or failure in respond to therapy have been clarified based on studies including a large series of patients, there are large interindividual differences in the prognosis of patients with primary AL-type renal amyloidosis. METHODS: To clarify the prognostic factors of AL-type renal amyloidosis, we retrospectively investigated the clinical manifestations, histopathological data, and prognosis of 21 patients with amyloidosis, who had been diagnosed by renal biopsy. RESULTS: Eleven patients died, at a mean observational time of 21.7 months after renal biopsy, whereas the mean observational time was 51.0 months for the 10 patients who survived. The creatinine clearance rate was significantly higher, and the serum creatinine concentration and the grade of interstitial damage were significantly lower in surviving patients (P < 0.05). The presence of amyloid fibrils in organs other than the kidney did not influence prognosis for survival. However, the intraventricular septum was thinner in surviving patients (P < 0.1). Thirteen patients had undergone melphalan-prednisolone therapy, but it did not affect prognosis for survival. Cox proportional hazard regression analysis revealed that the renal function at the time of diagnosis was a significant and independent prognostic factor for survival. CONCLUSIONS: Our study demonstrated that renal function at the time of biopsy and renal interstitial damage are the best predictors of survival in AL-type renal amyloidosis.

Amyloid↗
PubMed2004

Differentiation-induced cultured podocytes express endocytically active megalin, a heymann nephritis antigen.

BACKGROUND/AIMS: Megalin is a multiligand endocytic receptor expressed in a number of epithelia. In the Lewis rat kidney, podocytes, as well as proximal tubule cells, express megalin that acts as a pathogenic antigen for Heymann nephritis (HN), an experimental model of membranous nephropathy. To obtain a tool to investigate the molecular mechanisms of megalin-mediated endocytosis and the pathogenesis of HN, we examined whether a differentiation-inducible mouse podocyte cell line expressed endocytically active megalin. METHODS: Immunofluorescence and immunoprecipitation analyses with an anti-rat megalin antibody were carried out to investigate whether megalin was expressed in the differentiated and undifferentiated podocytes. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed to elucidate whether the cells synthesize megalin mRNA. 125I-labeled receptor-associated protein (RAP), an endocytic ligand for megalin, was used for cellular internalization and degradation assays. RESULTS: Immunofluorescence, immunoprecipitation and RT-PCR analyses revealed that megalin was synthesized in both differentiated and undifferentiated cells and localized to the cell surfaces. Effective endocytosis of RAP via megalin was shown under the differentiated condition. CONCLUSION: Endocytically active megalin is expressed in differentiation-induced cultured podocytes. This cell line could be a useful tool for studies on megalin-mediated endocytosis and the pathogenesis of HN.

Animals↗
PubMed2004

Syndrome of inappropriate secretion of antidiuretic hormone and thrombocytopenia caused by cytomegalovirus infection in a young immunocompetent woman.

We report the first case of the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) associated with cytomegalovirus (CMV) infection. A 32-year-old woman was admitted to our hospital because of pandysautonomic signs and symptoms. Thrombocytopenia and hyponatremia were present. Serum anti-CMV IgM and IgG antibodies were positive. Despite hyponatremia, urinary osmolality exceeded plasma osmolality and plasma vasopressin levels related to plasma osmolality were high. Restriction of water intake and administration of dimethylchlorotetracycline improved hyponatremia, suggesting this patient had SIADH. In this patient, SIADH may have been caused by acute pandysautonomia that developed following CMV infection.

Adult↗
PubMed2004

[Perioperative management of a patient with polycythemia who developed massive hemorrhage].

A 34-year-old man, 170 cm in height and 70 kg in weight, was scheduled for emergency operation because of gastric perforation due to gastric cancer under general anesthesia. His preoperative blood analysis showed 5.2 x 10(3) mm(-3) of red blood cell, 18 g x dl(-1) of hemoglobin and 48% of hematocrit. Based on this and other data, he was diagnosed as having polycythemia caused by stress. Anesthesia was induced with thiopental and maintained with O2-N2O-sevoflurane. The intraoperative blood loss reached approximately 7,000 ml. Although we administered only 4 units of fresh-frozen plasma (FFP) and 9,150 ml of fluid with no red cell concentrated, his hemodynamic state was stable during surgery. After the surgery, we administered the minimum amount of FFP according to his blood analysis. Although red cell concentrated was not administered in the perioperative period, his general condition remained stable.

Adult↗
PubMed2004

Straight advancement of epidural catheter--comparative assessments by method and site of epidural needle puncture and angle of puncture.

The catheter straight advancement rate for introduction into the epidural space was investigated using a radiopaque catheter. One hundred patients were divided into two groups and underwent thoracic or lumbar epidural punctures, with one of two different puncture methods: the median approach or paramedian approach. Two different angles of epidural puncture needle insertion, 50-60 degrees and 90 degrees to skin surface plane, were used. A catheter was inserted into the epidural space about 5 cm cephalad and the course of the inserted catheter was ascertained by radiography. The results have shown that punctures performed at an insertion angle of 50-60 degrees yielded higher catheter straight advancement rates than those performed at an angle of 90 degrees in both thoracic and lumbar epidural punctures.

Anesthesia, Epidural↗
PubMed2003

Two cases of hypertrophic pachymeningitis associated with myeloperoxidase antineutrophil cytoplasmic autoantibody (MPO-ANCA)-positive pulmonary silicosis in tunnel workers.

Two cases of hypertrophic pachymeningitis (HP) associated with pulmonary silicosis in tunnel workers are described. In both cases the myeloperoxidase antineutrophil cytoplasmic autoantibody (MPO-ANCA) was positive. Two patients with pulmonary silicosis developed headache and neurological disturbance, and a diagnosis of HP was made. In both cases the serum CRP level and the MPO-ANCA titer were elevated. Corticosteroid therapy produced a rapid improvement in all the clinical and laboratory parameters. Although an association has been noted between exposure to silica dust and ANCA-associated vasculitis, particularly glomerulonephritis, central nervous system involvement is rare. However, there have been some recent reports of HP cases that were positive for ANCA, and the association between HP and vasculitis has been discussed in the medical literature. HP may be one feature of multiorgan involvement in ANCA-associated disease, and the association between silica dust exposure and HP should be considered, as with other forms of ANCA-associated vasculitis.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed2003

Unusual left ventricular dilatation without functional or biochemical impairment in normotensive extremely overweight Japanese professional sumo wrestlers.

To explore the physiologic limit of left ventricular (LV) enlargement, we performed echocardiography and air displacement plethysmography to respectively assess LV dimension and function and the body composition of Japanese professional sumo wrestlers. After excluding subjects with cardiovascular disease, hypertension, plasma brain natriuretic peptide (BNP) > or =17.9 pg/ml, diabetes mellitus, or asthma, 331 subjects (mean +/- SD age, 21.6 +/- 3.7 years; height 179.2 +/- 5.3 cm; weight 1,17.9 +/- 21.5 kg; percent fat, 29.6 +/- 6.6%) were analyzed. LV end-diastolic dimension averaged 58.4 +/- 3.7 mm and was within the generally regarded normal limit (< or =54 mm) in 14.5% of subjects, but was > or =60 mm in 41.1% of subjects. LV septal and posterior wall thicknesses were 10.3 +/- 0.9 and 10.2 +/- 0.9 mm, respectively. Peak E- and A-wave velocities, E/A ratio, LV fractional shortening, and BNP were 96 +/- 16 and 51 +/- 13 cm/s, 2.0 +/- 0.7, 33.5 +/- 4.5%, and 3.1 +/- 3.7 pg/ml, respectively. LV end-diastolic dimension was not correlated with these indexes of LV function or with plasma BNP levels, but was significantly correlated with height, weight, body surface area, fat-free mass, and fat mass. These results show that among very large, highly trained, professional athletes, LV end-diastolic dimension frequently exceeds the traditionally accepted upper limit of normal for the general population. This increase in LV end-diastolic dimension may thus represent an extreme example of the physiologic adaptation of the athlete's heart.

Adolescent↗
PubMed2003

Identification of an apical sorting determinant in the cytoplasmic tail of megalin.

Megalin is the main endocytic receptor of the proximal tubule and is responsible for reabsorption of many filtered proteins. In contrast to other members of the low-density lipoprotein (LDL) receptor gene family, it is expressed on the apical plasma membrane (PM) of polarized epithelial cells. To identify megalin's apical sorting signal, we generated deletion mutants and chimeric minireceptors composed of complementary regions of megalin and LDL receptor-related protein (LRP) and assessed the distribution of the mutants in Madin-Darby canine kidney (MDCK) cells by immunofluorescence and cell surface biotinylation. Megalin and LRP minireceptors are correctly targeted to the apical and basolateral PM, respectively, of MDCK cells. We found that the information that directs apical sorting is present in the cytoplasmic tail (CT) of megalin, which contains three NPXY motifs, YXXØ, SH3, and dileucine motifs, and a PDZ-binding motif at its COOH terminus. Deletion analysis established that amino acids 107-136 of the megalin-CT containing the second NPXY-like motif are critical for apical sorting and targeting, whereas the regions containing the first and third NPXY motifs are required for efficient endocytosis. We conclude that the megalin-CT contains a novel apical sorting determinant and that cytoplasmic sorting machinery exists in MDCK cells for some apical transmembrane proteins.

Animals↗
PubMed2003

Correlation between serum resistin level and adiposity in obese individuals.

OBJECTIVE: Resistin is associated with insulin resistance in mice and may play a similar role in humans. The aim of our study was to examine the relationship of serum resistin level to body composition, insulin resistance, and related obesity phenotypes in humans. RESEARCH METHODS AND PROCEDURES: Sixty-four young (age 32 +/- 10 years), obese (BMI 32.9 +/- 5.6), nondiabetic subjects taking no medication, and 15 lean (BMI 21.1 +/- 1.3) volunteers were studied cross-sectionally. Thirty-five of the subjects were also reevaluated after 1.5 years on a weight reduction program entailing dieting and exercise; changes of serum resistin were compared with changes of BMI, body composition, fat distribution, and several indices of insulin sensitivity derived from plasma glucose and serum insulin levels measured during 75-g oral glucose tolerance test. RESULTS: In a cross-sectional analysis, serum resistin was significantly higher in obese subjects than in lean volunteers (24.58 +/- 12.93 ng/mL; n = 64 vs. 12.83 +/- 8.30 ng/mL; n = 15; p < 0.01), and there was a correlation between resistin level and BMI, when the two groups were combined (rho = 0.35, p < 0.01). Although cross-sectional analysis in obese subjects revealed no correlation between serum resistin and parameters related to adiposity or insulin resistance, longitudinal analysis revealed change in serum resistin to be positively correlated with changes in BMI, body fat, fat mass, visceral fat area, and mean glucose and insulin (rho = 0.39, 0.40, 0.44, 0.50, 0.40, and 0.50; p = 0.02, 0.03, 0.02, <0.01, 0.02, and <0.01, respectively). DISCUSSION: Resistin appears to be related to human adiposity and to be a possible candidate factor in human insulin resistance.

Adipose Tissue↗
PubMed2003

Neonatal clinical outcome after elective cesarean section before the onset of labor at the 37th and 38th week of gestation.

BACKGROUND: Although elective cesarean sections are often performed after the 37th week of gestation without any complicating factor that may influence the timing of delivery,there is a possibility that infants born in the 37th week of gestation,especially early in the 37th week of gestation, do not obtain a satisfactory clinical outcome due to premature birth. METHODS: The authors analyzed the clinical course during the neonatal period in 96 infants born in the 37th (n = 81)and 38th (n = 15) week of gestation by an elective cesarean section. Subjects were retrospectively divided into two groups: infants born in the first half of the 37th week of gestation (37+0-37+3)(n = 48), and infants born from the latter half of the 37th week of gestation (37+4-37+6)through the 38th week of gestation (n = 48). Twin pregnancies, pregnancy with placenta previa, and pregnancy of women who had a diversity of medical complications were excluded from the present study, because of the possibility that these conditions may have affected the infants' status. The incidence of infants who showed clinical symptoms during the neonatal period and who needed medical care was compared between the two groups. RESULTS: Of the 96 subjects, 25 infants(26.0%) had significant clinical symptoms. The incidence of breathing difficulty was significantly higher in the infant group born in the first half of the 37th week of gestation than in the latter group. CONCLUSIONS: An elective cesarean section before the onset of labor early in the 37th week of gestation should not be routinely undertaken.

Cesarean Section↗
PubMed2003

Bioengineered implantation of megalin-expressing cells: a potential intracorporeal therapeutic model for uremic toxin protein clearance in renal failure.

Patients who have renal failure and are on dialysis therapy experience serious complications caused by low-molecular-weight uremic toxin proteins normally filtered by glomeruli and metabolized by proximal tubule cells (PTC). Dialysis-related amyloidosis is one such complication induced by systemic deposition of amyloid proteins derived from 12-kD beta(2)-microglobulin (beta(2)-m). Despite the use of high-flux membrane hemodialysis devices and direct absorbent columns, the removal of beta(2)-m is suboptimal, because the effects are transient and insufficient. Megalin is expressed in the apical membranes of PTC and recognized as a multiligand endocytic receptor that binds numerous low-molecular-weight proteins, including beta(2)-m. This study tested the feasibility of an intracorporeal therapeutic model of continuous beta(2)-m removal using megalin-expressing cell implantation. By cell association and degradation assays, rat yolk sac-derived L2 cells were identified to internalize and degrade beta(2)-m via megalin. The cells were effectively implanted within the subcutaneous tissues of nude mice using a type I collagen scaffold and a method inducing local angiogenesis. After nephrectomy and intraperitoneal injection with (125)I-beta(2)-m, it was found that the implanted cells took up the labeled ligand, efficiently removing it from the blood. Bioengineered implantation of megalin-expressing cells may represent a new supportive therapy for dialysis patients to compensate for the loss of renal protein metabolism and remove uremic toxin proteins.

Animals↗
PubMed2003

Acanthosis nigricans is a reliable cutaneous marker of insulin resistance in obese Japanese children.

BACKGROUND: Acanthosis nigricans (AN) is a skin condition characterized by darkening and thickening of skin with formation of irregular folds, usually limited to a few specific areas of the body. Recently, AN has been reported to be linked to hyperinsulinemia and obesity. The aim of the present study was to determine whether or not the presence of AN in obese Japanese children is a reliable cutaneous marker. METHODS: The authors analyzed the clinical characteristics of 439 obese Japanese children (260 boys, 179 girls; mean age 10.1 years; mean percentage overweight 51.9%), who had visited Tsuruoka City Shonai Hospital in 1990-2000. Eighty-two of the 439 children were examined using an oral glucose tolerance test (OGTT). Of these children, the authors retrospectively studied 16 subjects: eight with AN and eight without AN (age range: 10.8-13.9 years; percentage overweight range: 54.3-97.0%). They were age and percentage obesity-matched males with normal glucose tolerance during OGTT. Females with normal glucose tolerance during OGTT were excluded from the 16 subjects because the number was too small and children with impaired glucose tolerance or type 2 diabetes during OGTT were also excluded because of glucose toxicity. Eighty-two children including the 16 subjects were analyzed at their first visit for the presence or absence of AN on the posterior of the neck, and for characteristics including age, birthweight, body height, bodyweight, percentage overweight, blood pressure, liver function markers serum lipid concentrations, fasting plasma glucose concentrations and insulin concentrations shown by the results of OGTT. RESULTS: (1) Children with AN showed significantly more glucose intolerance including impaired glucose tolerance and type 2 diabetes compared with those children without AN, and fasting plasma insulin concentrations were most significantly correlated with the presence of AN. (2) Insulin resistance based on fasting plasma insulin concentrations was seen in significantly more children with AN than in children without AN, even in age and percentage obesity-matched subjects with normal glucose tolerance during OGTT. CONCLUSIONS: Acanthosis nigricans could be a reliable cutaneous marker of insulin resistance in obese Japanese children.

Acanthosis Nigricans↗
PubMed2003

Four cases of pheochromocytoma in patients with end-stage renal disease.

Although pheochromocytoma in a patient with end-stage renal disease (ESRD) is considered extremely rare, we recently encountered 4 ESRD patients with pheochromocytoma. Three were symptomatic, and in the fourth patient the tumor was discovered as an adrenal incidentaloma. Plasma catecholamine levels were significantly increased in two patients. In each case, 131I-MIBG scintigraphy showed accumulation of the radionuclide in the adrenal tumor, which was identified by MRI or CT scanning, and adrenalectomy was conducted without serious complications. Although paroxysmal hypertension is a common symptom in patients with ESRD, pheochromocytoma must be eliminated by careful evaluation.

Adrenal Gland Neoplasms↗