Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where Tatsuya Nagai is active.

Publication


Featured researches published by Tatsuya Nagai.


Urologia Internationalis | 1988

Increased mast cells in the limiting membrane of seminiferous tubules in testes of patients with idiopathic infertility.

Junichi Hashimoto; Tatsuya Nagai; Hidenori Takaba; Masanori Yamamoto; Koji Miyake

In the course of our histological studies on the testes of idiopathically infertile men, we found an increased number of mast cells in the limiting membrane of the seminiferous tubule. In 16 patients with idiopathic infertility, quantification of mast cells within the limiting membrane of the seminiferous tubule was performed. There apparently was a tendency to increased numbers of mast cells in the seminiferous tubule wall with decreased sperm count and an average Johnsen score for each tubule. These findings suggest that quantification of mast cells in the seminiferous tubule wall may be a useful marker in the histopathological evaluation of testis biopsies in patients with idiopathic infertility.


The Journal of Urology | 1997

Trigonal Splitting is a Major Complication of Endoscopic Trigonoplasty at 1-Year Followup

Kikuo Okamura; Norio Kato; Shinichi Takamura; Junji Tanaka; Tatsuya Nagai; Hiroyuki Watanabe; Yoshikazu Tsuji; Yoshinari Ono; Shinichi Ohshima

PURPOSE The long-term results of endoscopic trigonoplasty in patients with vesicoureteral reflux were investigated. MATERIALS AND METHODS We performed endoscopic trigonoplasty in 28 patients with vesicoureteral reflux, including 6 girls 6 to 8 years old. Reflux was grade I in 14 reno-ureteral units, grade II in 15, grade III in 8, grade IV in 1 and grade V in 1. Median followup was 23 months. RESULTS At a median of 3 months postoperatively vesicoureteral reflux was not apparent in 37 units (95%) and it was downgraded in 1 (3%). At a median of 12 months postoperatively 27 (79%) and 4 (12%) of the 34 ureters had cessation and downgrading, respectively. Of the 13 select patients who underwent cystoscopy 3 had retreating ureteral orifices and 5 had trigonal splitting 6 to 12 months postoperatively. Vesicoureteral reflux was demonstrated in 3 of the 5 patients (4 ureters) with trigonal splitting and in 1 (1 ureter) with retreating ureteral orifices. At a median of 24 months after surgery voiding cystography showed reflux in only 1 of 15 units. No postoperative upper urinary tract dilatation was noted at followup. CONCLUSIONS Cessation rates of vesicoureteral reflux 12 months after endoscopic trigonoplasty were low with a high incidence of trigonal splitting. These unsatisfactory results mandate technical refinements to avoid trigonal splitting.


Urology | 1990

Primary transitional cell carcinoma of prostate : case with lymph node metastasis eradicated by neoadjuvant methotrexate, vinblastine, doxorubicin, and cisplatin (M-VAC) therapy

Munehisa Takashi; Takao Sakata; Tatsuya Nagai; Takanori Kato; Masafumi Sahashi; Takashi Koshikawa; Koji Miyake

A case of transitional cell carcinoma of the periurethral prostatic ducts received neoadjuvant chemotherapy consisting of methotrexate, vinblastine, doxorubicin, and cisplatin (M-VAC), which eradicated pelvic lymph node metastasis, followed by cystoprostatectomy. M-VAC therapy may be indicated for metastatic transitional cell carcinoma of the periurethral prostatic ducts.


Urological Research | 1990

Enolase isozymes in seminoma.

Munehisa Takashi; H. Haimoto; Tatsuya Nagai; Takashi Koshikawa; K. Kato

SummaryWe determined concentrations of α and γ-enolases in normal testis and in seminoma tissues by enzyme immunoassay. Concentrations of α-enolase were 4,170±2,040 ng/mg protein in normal testis (n = 8) and 8,140±4,480 ng/mg protein in seminoma (n = 8). Concentrations of γ-enolase in seminoma (460±571 ng/mg protein) were significantly higher than those of normal testis (59±15 ng/mg protein). Immunohistochemistry showed positive tumor cells for γ-enolase in 6 of 8 seminoma cases (75%). Serum γ-enolase levels were elevated (> 6.0 ng/ml) in 9 of 12 patients (75%) with seminoma: 60% of stage I, and 100% of stages II and III. In 10 patients treated by surgical excision and chemotherapy, serum γ-enolase was significantly reduced after the treatment. These findings indicate that elevated serum γ-enolase is derived from enhanced γ-enolase in seminoma tissues, and that serum γ-enolase could be a useful biomarker for staging and monitoring clinical course in patients with seminoma.


Urological Research | 1989

In-vitro contractility of human seminiferous tubules in response to testosterone, dihydrotestosterone and estradiol

Masanori Yamamoto; Tatsuya Nagai; Hidenori Takaba; Junichi Hashimoto; Koji Miyake

SummaryThe effects of steroids (testosterone, dihydrotestosterone and estradiol) on human seminiferous tubules in vitro were ascertained by recording the intratubular pressure with a servonull micropressure measuring device. We describe here the first response of the human seminiferous tubule to steroids. Testosterone and dihydrotestosterone had a biphasic effect on tubular contractility. Higher doses of both testosterone and dihydrotestosterone induced contractions of the seminiferous tubules whereas lower doses of these compounds induced relaxation. Estradiol (10-9 M to 10-6 M) induced relaxation of the seminiferous tubules in a dose-dependent manner. The results from these experiments suggested that steroids may be involved in the control of contraction of the human seminiferous tubule and may regulate the movement of spermatozoa from the tests.


Urologia Internationalis | 1989

Multivariate Evaluation of Determinants Affecting Regional Lymph Node Metastasis and Survival in Bladder Cancer Patients Who Underwent Radical Cystectomy

Munehisa Takashi; Tatsuya Nagai; Tatsuro Murase; K. Miyake; Nobuyuki Hamajima; S. Mizuno

To elucidate the relative importance of clinicopathologic factors affecting regional lymph node metastasis and survival in bladder cancer patients, multivariate analyses by the logistic regression model and proportional hazards model were performed for 86 patients who underwent radical cystectomy between 1978 and 1988. Clinicopathologic factors included in the analysis were sex, age, prior tumor history, time from onset of symptoms to cystectomy, and tumor characteristics (size, number, growth pattern, grade, stage, infiltration pattern, lymphatic invasion, lymphocytic infiltration around tumors, and lymph node metastasis). Nineteen of eighty-six patients (22%) had regional lymph node metastasis. Univariate analysis showed that lymph node metastasis was related to stage (p = 0.0006), lymphatic invasion (p = 0.006) and infiltration pattern (p = 0.02). Multivariate analysis revealed that stage is the only determinant of statistical significance for lymph node metastasis. High-stage tumors (pT3a-pT4) had 15 times higher risk for lymph node metastasis than low-stage tumors (pTis-pT2). The 5-year survival rates were 25 and 75% for patients with and without lymph node metastasis, respectively. Proportional hazards model revealed that stage is the most significant determinant (p = 0.0001) for survival, followed by lymph node metastasis with borderline significance (0.005 less than p less than 0.1). A two-factor model consisting of stage and lymph node metastasis yielded corrected hazard ratios of 14.7 for stage and 2.3 for lymph node metastasis. The present study quantitatively confirms previous univariate analyses of factors affecting lymph node metastasis and survival in patients undergoing radical cystectomy.


The Journal of Urology | 1993

Urodynamic Evaluation of Results of Endopyelotomy for Ureteropelvic Junction Obstruction

Momokazu Gotoh; Yoko Yoshikawa; Tatsuya Nagai; Toshihumi Sakakibara; Atsuo Kondo; Koji Miyake

We treated 13 patients with unilateral ureteropelvic junction obstruction by percutaneous endopyelotomy, and they were urodynamically evaluated by the Whitaker test and diuresis renography, in addition to excretory urography (IVP). Surgery was uncomplicated in all patients except 1 who required repeat incision 4 weeks later. Obstruction was diagnosed preoperatively by the Whitaker test and diuresis renography in 10 cases, and by IVP in 13. Postoperatively, all 10 patients (100%) with a positive Whitaker test were free of obstruction with a significant reduction in the relative renal pelvic pressure from 35.0 to 8.1 cm. water (p < 0.01). Diuresis renography revealed no obstruction in 8 patients (80%) and persistent obstruction in 2. IVP demonstrated reduced hydronephrosis in 8 of 13 patients (62%) 12 weeks after surgery and in 11 of 13 patients (85%) 19 months later. However, a marked reduction in renal pelvic size was noted in only 3 patients (23%). Flank pain disappeared in 10 of 11 patients (91%) postoperatively. Overall, surgery was successful in 11 of the 13 patients (85%). Percutaneous endopyelotomy was effective in relieving obstruction at the ureteropelvic junction with minor morbidity. The Whitaker test was more sensitive for evaluating the results of surgery than diuresis renography and IVP, although diuresis renography appears to be useful in followup evaluation of hydronephrosis.


Nature Ecology and Evolution | 2017

Anatomical integration of the sacral–hindlimb unit coordinated by GDF11 underlies variation in hindlimb positioning in tetrapods

Yoshiyuki Matsubara; Tatsuya Hirasawa; Shiro Egawa; Ayumi Hattori; Takaya Suganuma; Yuhei Kohara; Tatsuya Nagai; Koji Tamura; Shigeru Kuratani; Atsushi Kuroiwa; Takayuki Suzuki

Elucidating how body parts from different primordia are integrated during development is essential for understanding the nature of morphological evolution. In tetrapod evolution, while the position of the hindlimb has diversified along with the vertebral formula, the mechanism responsible for this coordination has not been well understood. However, this synchronization suggests the presence of an evolutionarily conserved developmental mechanism that coordinates the positioning of the hindlimb skeleton derived from the lateral plate mesoderm with that of the sacral vertebrae derived from the somites. Here we show that GDF11 secreted from the posterior axial mesoderm is a key factor in the integration of sacral vertebrae and hindlimb positioning by inducing Hox gene expression in two different primordia. Manipulating the onset of GDF11 activity altered the position of the hindlimb in chicken embryos, indicating that the onset of Gdf11 expression is responsible for the coordinated positioning of the sacral vertebrae and hindlimbs. Through comparative analysis with other vertebrate embryos, we also show that each tetrapod species has a unique onset timing of Gdf11 expression, which is tightly correlated with the anteroposterior levels of the hindlimb bud. We conclude that the evolutionary diversity of hindlimb positioning resulted from heterochronic shifts in Gdf11 expression, which led to coordinated shifts in the sacral–hindlimb unit along the anteroposterior axis.The position of limbs varies across vertebrates. Here, the authors show that GDF11 is a key factor in the integration of sacral vertebrae and hindlimb positioning and underlies diversification of the hindlimb position in vertebrates.


Urologia Internationalis | 1991

Identification of collagens in the human testis.

Hidenori Takaba; Tatsuya Nagai; Junichi Hashimoto; Masanori Yamamoto; Koji Miyake

SDS-PAGE of pepsin-solubilized collagens obtained from testes of elderly men revealed types I, III, V, and VI but not type IV. The total collagen content was 21.3 +/- 1.96% (mean +/- SD) as determined by hydroxyproline assay. The ratio for the pepsin-soluble fraction was 7.98 +/- 3.27%, i.e. very low as compared with other tissues. Type I collagen was determined by SDS-PAGE of cyanogen bromide cleavage of the pepsin-insoluble residue.


International Journal of Urology | 1997

LONG-TERM EFFICACY OF A SELF-RETAINING INTRAURETHRAL CATHETER FOR THE TREATMENT OF PROSTATIC OBSTRUCTION

Tatsuya Nagai; Tetsushi Kondo; Toshifumi Sakakibara; Yoko Yoshikawa; Momokazu Gotoh; Takanori Katoh; Mineo Kobayashi

Background:

Collaboration


Dive into the Tatsuya Nagai's collaboration.

Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Top Co-Authors

Avatar
Researchain Logo
Decentralizing Knowledge