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Biomedical subjects

Masahiro Shin

Publications and source records attributed to Masahiro Shin.

7 recordsLinked to original sources
PubMed2003

Expression of DDSG1, a novel gene encoding a putative DNA-binding protein in the embryonic chicken nervous system.

In an attempt to clone genes expressed in the gizzard of the chicken embryo by differential display, we obtained a cDNA of a gene encoding a protein with a putative nuclear localization signal and a DNA-binding motif and designated it DDSG1 (differential display-screened gene expressed in the gizzard-1). Besides its expression in the gizzard, the gene is expressed in central and peripheral nervous systems such as brain, spinal cord and dorsal root ganglia in specific patterns.

Amino Acid Sequence↗
PubMed2002

Malignant transformation of a vestibular schwannoma after gamma knife radiosurgery.

Stereotactic radiosurgery is used to treat benign tumours, but its long-term effects are not fully understood. Here we describe a vestibular schwannoma that underwent malignant transformation 6 years after gamma knife radiosurgery applied to the tumour remnant after a primary resection. Histological specimens of the original specimen did not show any atypical features. Genotyping showed a TP53 mutation in the recurrent tumour, which did not exist in the original tumour. Our results suggest that radiosurgery induced the malignant transformation, and we propose a cautious application of this treatment for benign tumours.

Adult↗
PubMed2002

Gamma knife radiosurgery for pituitary adenoma.

For the treatment of pituitary adenomas, transsphenoidal surgery is established as a first choice of treatment. However, pituitary adenomas are often not curable with surgery alone, and further treatment including radiation therapy is required to control the disease. In this report, we review the literature of gamma knife radiosurgery for pituitary adenomas and discuss the efficacy of this modern technology. Radiosurgery achieved 85-100% of growth control rates with only mild and transient neurological complications in most cases. Endocrinological normalization was obtained in more than 65% of GH producing tumors. These hormonal control rates seemed to be slightly better in GH producing tumors compared to ACTH producing tumors. To normalize the excessive GH or ACTH levels, radiosurgery for functioning adenomas requires a relatively higher dose, ideally more than 35 Gy at tumor margin. However, the adjacent optic apparatus is less tolerable for irradiation, and the tumors have to be sufficiently separated from it to prevent the radiation-induced visual deficits. Therefore, the role of surgery should not be underevaluated, and even if radiosurgery alone may be able to achieve an excellent outcome in some cases, surgical resection will remain the primary treatment for pituitary adenomas. For high-risk patients or patients with residual tumors after transsphenoidal surgery, gamma knife radiosurgery can be a first choice of treatment, achieving both growth control and hormonal remission with minimum neurological complications, which is equivalent to conventional radiation therapy but with much less risk of radiation injury to the surrounding structures.

Humans↗
PubMed2002

Retrospective analysis of a 10-year experience of stereotactic radio surgery for arteriovenous malformations in children and adolescents.

OBJECT: To obtain information essential to the decision to perform radiosurgery for arteriovenous malformations (AVMs) in children and adolescents, the authors retrospectively analyzed their experience with gamma knife surgery for AVMs in 100 patients ranging in age from 4 to 19 years. METHODS: Follow-up periods ranged from 6 to 124 months (median 71 months), and the actuarial obliteration rates demonstrated by angiography were 84.1, 89.4, and 94.7% at 3, 4, and 5 years, respectively. Factors associated with better obliteration rates in univariate analysis included the following: a patient age of 12 years or younger; a mean nidus diameter of 2 cm or less; a nidus volume of 3.8 cm3 or less; a maximum diameter of the nidus less than 3 cm; and a Spetzler-Martin grade of III or less. Radiation-induced neuropathy was seen in four patients, and the risk factors were considered to be a nidus in the brainstem and a maximum radiation dose greater than 40 Gy. Hemorrhage developed during the latency interval in four patients, and one patient with a cerebellar AVM died of the hemorrhage. The annual bleeding rate was 1.5%. Feeding arteries located in the posterior cranial fossa and an AVM nidus located in the cerebellum were significantly associated with the risk of hemorrhage. After angiographically verified obliteration of the nidus, 51 patients continued to be observed from 1 to 110 months (median 67 months); hemorrhage developed in one patient 38 months after nidus obliteration. CONCLUSIONS: Radiosurgery is an acceptable treatment for small AVMs in children and adolescents in whom a higher obliteration rate can be achieved with lower risks of interval hemorrhage compared with the reported results in the general population. Careful follow-up observation seems to be required, however, even after angiographically verified obliteration.

Adolescent↗
PubMed2002

Radiosurgery for residual or recurrent nonfunctioning pituitary adenoma.

OBJECT: Nonfunctioning pituitary adenomas comprise approximately 30% of all pituitary tumors. The purpose of this retrospective study is to evaluate the efficacy and role of gamma knife radiosurgery (GKS) in the management of residual or recurrent nonfunctioning pituitary adenomas. METHODS: A review was conducted of the data obtained in 42 patients who underwent adjuvant GKS at the University of Pittsburgh between 1987 and 2001. Prior treatments included transsphenoidal resection, craniotomy and resection, or conventional radiotherapy. Endocrinological, ophthalmological, and radiological responses were evaluated. The duration of follow-up review varied from 6 to 102 months (mean 31.2 months). Fifteen patients were observed for more than 40 months. The mean radiation dose to the tumor margin was 16 Gy. Conformal radiosurgery planning was used to restrict the dose to the optic nerve and chiasm. Tumor control after GKS was achieved in 100% of patients with microadenomas and 97% of patients with macroadenomas. Gamma knife radiosurgery was equally effective in controlling adenomas with cavernous sinus invasion and suprasellar extension. No patient developed a new endocrinological deficiency following GKS. One patient's tumor enlarged with an associated decline in visual function. Another patient experienced a deterioration of visual fields despite a decrease in tumor size. CONCLUSIONS: Gamma knife radiosurgery can achieve tumor control in virtually all residual or recurrent nonfunctioning pituitary adenomas. Dose sparing facilitates tumor management even when the adenoma is close to the optic apparatus or invades the cavernous sinus.

Adenoma↗
PubMedDate not supplied

Two-dimensional magnetic resonance digital subtraction angiography using array spatial sensitivity encoding techniques in the assessment of intracranial hemodynamics.

OBJECTIVE: Array spatial sensitivity encoding techniques (ASSET) were employed to improve the temporal resolution of two-dimensional (2D) thick-slice contrast-enhanced magnetic resonance digital subtraction angiography (MRDSA). METHODS: 2D MRDSA using ASSET was performed in 28 patients via fast spoiled gradient-echo sequence (TR/TE 5.4/1.5 ms; FA 60; FOV 24x24 cm; matrix size 256x256; slicethickness 50-70 mm), followed by a bolus injection of gadolinium chelate and subsequent saline flush, for 40 seconds on a sagittal plane. Images were evaluated for visualization of normal intracranial vessels and brain lesions utilizing a three-point scale; additionally, in 10 of the 28 patients, results were compared with those of conventional 2D MRDSA. RESULTS: 2D MRDSA using ASSET, which improved temporal resolution from 1.45 to 0.77 seconds, displayed image quality comparable to that of conventional 2D MRDSA. Moreover, this technique afforded superior detectability with respect to early venous filling in patients with arteriovenous malformations (AVMs). CONCLUSION: ASSET improves the temporal resolution of 2D MRDSA without compromising spatial resolution.

Brain Neoplasms↗