Biomedical subjects

Takao Obara

Publications and source records attributed to Takao Obara.

7 recordsLinked to original sources

PubMed2003

Recent advances in minimally invasive pancreatic surgery.

For curative resection of pancreatic endocrine tumours, minimally invasive methods of pancreatic surgery, such as laparoscopy, should be indicated only for benign tumours. Among these uncommon tumours, pancreatic insulinomas are mostly benign and solitary. Successful management of patients with insulinomas relies on accurate localization of the tumour and the use of appropriate surgical techniques. Because of the small size of these tumours, conventional intraoperative ultrasonography combined with palpation has been widely regarded as the best localization procedure. Because contact ultrasonography, a new technique for localization of pancreatic lesions, can be used laparoscopically, several surgeons have used laparoscopy not only for localization, but also for resection of insulinomas. In the era of minimally invasive surgery for benign pancreatic lesions, we attempted laparoscopic-focused exploration of the pancreas for resecting insulinomas based on preoperative localization. We describe the use of this technique for the detection and resection of insulinomas and the results obtained, with a review of previous reports.

Endosonography↗

PubMed2003

Demonstration of human telomerase reverse transcriptase (hTERT) in human parathyroid tumours by in situ hybridization with a new oligonucleotide probe.

BACKGROUND AND OBJECTIVE: Telomerase activity is present in most malignant tumours and might provide a mechanism for unlimited replication of neoplastic cells. Expression of the gene encoding human telomerase reverse transcriptase (hTERT), the telomerase catalytic subunit gene, is associated with telomerase activity, and it is overexpressed in most parathyroid carcinomas. We have therefore studied hTERT expression in parathyroid tumours. METHODS: In the present study, we assayed telomerase activity by the telomeric repeat amplification protocol (TRAP) and used in situ hybridization (ISH) to study hTERT mRNA expression in four parathyroid metastatic cancers, six adenomas and two parathyroid hyperplasia tissue specimens. RESULTS: Telomerase activity was detected by the TRAP assay in all of the parathyroid cancers (100%) but in none of the eight parathyroid benign lesions. hTERT gene expression was detected in the nuclei of the parathyroid cancer cells in all of the lesions (100%) but in none of the eight parathyroid benign lesions. CONCLUSIONS: Our results demonstrate a correlation between telomerase activity and hTERT gene expression measured by ISH (P < 0.001) in parathyroid tumours. We succeeded in very clearly and sensitively demonstrating hTERT mRNA in parathyroid tissues by using a new probe.

Adenoma↗

PubMed2003

Genes regulated by thyrotropin and iodide in cultured human thyroid follicles: analysis by cDNA microarray.

Thyrotropin (TSH) regulates a number of genes in thyrocytes, leading to iodide uptake, de novo synthesis and release of thyroid hormones, and cell proliferation, accompanied by increased blood flow. At higher doses of iodide, however, the TSH-induced increases in thyroid hormone release and blood flow are downregulated, and high iodide intake occasionally worsens autoimmune thyroiditis. To elucidate the genes involved in such effects, we cultured human thyrocytes and examined genes modulated by TSH and iodide, using a cDNA microarray study, which can analyze 2400 genes in each run. When thyroid follicles were cultured with TSH for 2 days, more than 100 genes were upregulated. These genes included those for enzymes involved in carbohydrate and lipid metabolism, adenylate and guanylate cyclases, and enzyme involved in cell proliferation. When thyroid follicles were cultured with high iodide concentrations (10(-5) M) for 24 hours, more than 100 genes were upregulated. Interesting genes were interleukin-8, IFP53, 90-kd heat shock protein, osteopontin, and intercellular adhesion molecule-1. These results were confirmed by reverse transcription-polymerase chain reaction (RT-PCR) followed by Southern blot hybridization. In summary, TSH upregulated a number of genes regulating thyroid functions. It is intriguing that thyroid follicles cultured with a high iodide concentration (10(-5) M) increased the expression levels of genes capable of modulating lymphocyte functions, even though immunocompetent cells were extensively removed by the present experimental culture conditions. Although we have analyzed only approximately 6%-8% of all human genes, the cDNA microarray study is a powerful tool to elucidate the effects of TSH and iodide on thyroid function.

Blotting, Southern↗

PubMed2003

Cushing's syndrome due to bilateral adrenocortical adenomas with unique histological features.

Cushing's syndrome due to bilateral cortisol-secreting adenomas rarely occurs. We present a case of Cushing's syndrome due to bilateral adenomas. Both adenomas had distinct cell compositions, and were compared with emphasis on immunohistochemical and enzyme histochemical analysis for cytochrome P450(11beta) and 3beta-hydroxysteroid dehydrogenase (3betaHSD). A 37 year-old female was diagnosed with ACTH-independent Cushing's syndrome based on physical findings and hormonal evaluation. High-resolution CT scan showed bilateral adrenocortical adenomas and atrophied glands. 131I-methylnorcholesterol incorporation into both glands suggested both adenomas were functional. Clinical diagnosis prior to surgery was ACTH-independent Cushing's syndrome due to functioning bilateral adenomas. The left adrenal gland was totally resected, while the right one was partially resected by laparoscopic approach. Both adenomas were black on cut sections, and were comparatively evaluated by immunohistochemical and enzyme histochemical analysis for P450(11beta) and 3betaSD. The left adenoma was 1.6 cm in diameter and had a complex cellular composition and enzyme expression similar to that of primary pigmented nodular adrenocortical disease (PPNAD), while the right adenoma was 1.8 cm in diameter with compact cells typical of a solitary cortisol-producing adenoma. Adjacent bilateral adrenal cortex showed marked atrophy, but contained several micronodules. Serum cortisol levels, both at basal and after a low dodexamethasone, normalized thirteen months after surgery. In conclusion, the present case of Cushing's syndrome with bilateral adrenal adenomas demonstrated for the first time the simultaneous occurrence of two distinct adenomas, an ordinary cortisol-producing adenoma and a PPNAD-like adenoma. Further case reports of multiple adrenal adenomas should be well-analyzed to clarify whether the results from this case represent a new subgroup of ACTH-independent Cushing's syndrome.

Adrenal Cortex Diseases↗

PubMed2002

Consistent decrease in telomere length in parathyroid tumors but alteration in telomerase activity limited to malignancies: preliminary report.

Telomerase is known to be activated and telomere length altered in various types of malignant and benign tumors, but whether this is also the case for parathyroid lesions has hitherto been unclear. We therefore investigated telomerase activity and telomere length in 3 parathyroid metastatic cancers, 6 adenomas, 2 cases of parathyroid hyperplasia, and 16 samples of normal parathyroid tissue. Telomerase activity, assayed by the telomeric repeat amplification protocol, was detected in all of the parathyroid cancers (100%), in none of the 8 parathyroid benign lesions, and in only 1 of the 16 normal parathyroid samples (8.3%). Telomere length, determined by the terminal restriction fragment assay, was reduced in the tumor tissues with a mean telomere length of 8.23 +/- 0.86 kbp compared with the 12.61 +/- 0.81 kbp for the 16 age-matched subjects (p = 0.002). The results indicate that telomerase activity and telomere length may reflect the biologic behavior of individual parathyroid lesions.

Adenoma↗

PubMed2002

Outcome study of psychological distress and nonspecific symptoms in patients with mild primary hyperparathyroidism.

BACKGROUND: Primary hyperparathyroidism is a common endocrinopathy. The appropriate management of its mild form, however, remains controversial. HYPOTHESIS: Mild primary hyperparathyroidism is associated with psychological distress and other nonspecific symptoms that improve following parathyroidectomy. DESIGN: Two-year prospective before-after study. SETTING: University hospital. PATIENTS: Twenty-six consecutive patients with mild hypercalcemia (<12 mg/dL [<3 mmol/L]) due to primary hyperparathyroidism, without osteitis fibrosa cystica or urolithiasis were enrolled from January 11, 1997, through April 21, 1998. INTERVENTION: Parathyroidectomy. MAIN OUTCOME MEASURES: Primary outcome was psychological distress as measured by the 28-item version of the General Health Questionnaire. Secondary outcomes included body weight, joint pain, and occurrences of bowel movements and urination. RESULTS: Before surgery, 15 patients (58%; 95% confidence interval, 37%-77%) showed psychological distress (case group) while 11 patients did not (noncase group). A clinically and statistically significant reduction in the General Health Questionnaire score was detected at 3 months in the case group (-6.1; 95% confidence interval, -11.0 to -1.2), but the reduction was smaller (-1.9; 95% confidence interval, -6.9 to 3.0) at 24 months after surgery. No significant change in the General Health Questionnaire score was observed in the noncase group during the follow-up. No significant change was noted in any of the secondary outcomes. CONCLUSIONS: Psychological distress was associated with mild primary hyperparathyroidism and was ameliorated after surgery. The improvement, however, was limited in extent and duration.

Aged↗

PubMed2002

Minimally invasive endocrine surgery: laparoscopic resection of insulinomas.

Pancreatic insulinomas are mostly benign and solitary tumors. Successful management of patients with insulinoma relies on accurate localization of the tumors and the use of appropriate surgical techniques. However, preoperative radiological imaging studies often fail to localize the insulinomas because of the small tumor sizes. Conventional intraoperative ultrasonography combined with palpation has been widely used as the best localization tool. Since contact ultrasonography, a new technique for localizing pancreatic lesions, became available as a laparoscopic study, several surgeons have utilized laparoscopy for not only localization but also resection of insulinomas. Previous reports of laparoscopic ultrasonography for intraoperative identification of insulinomas showed a 100% success rate in cases with insulinoma localized by preoperative imaging studies, but a less satisfactory rate in cases with occult insulinoma. Laparoscopic resection of insulinomas located in the head of the pancreas is often difficult because of its anatomical relationship with important adjacent structures such as pancreatic duct and mesenteric vessels. In contrast, insulinomas located in the body or tail of the pancreas are laparoscopically resectable even when they are in close proximity to the major pancreatic duct. Laparoscopic procedure is a feasible technique with low morbidity for surgical management of insulinomas. Accurate preoperative localization is essential for safe performance of this minimally invasive procedure.

Endocrine Surgical Procedures↗