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Biomedical subjects

F Tsai

Publications and source records attributed to F Tsai.

14 recordsLinked to original sources
PubMed2001

Endovascular repair of radiation-induced bilateral common carotid artery stenosis and pseudoaneurysms: a case report.

BACKGROUND: Radiation-induced damage to small and medium-sized vessels has been observed in both animals and humans. Changes may appear in the immediate postradiation period or many years later. In this case, we report an unusual presentation of bilateral radiation-induced carotid artery stenoses associated with pseudoaneurysms, and a previously unreported application of a recently established treatment. CASE DESCRIPTION: A 72-year-old African-American male presented with recurrent right hemispheric transient ischemic attacks (TIA) and neck pain. Thirteen years previously, the patient had received radiation therapy for laryngeal carcinoma. Diagnostic carotid angiography demonstrated moderate radiation-induced bilateral carotid artery stenosis and associated common carotid pseudoaneurysms. The patient was treated with bilateral endovascular stents and electrolytically detachable coils in staged procedures. At his most recent follow-up, there is no evidence of re-stenosis and the patient remains asymptomatic. CONCLUSIONS: This case illustrates a novel and successful treatment for the endovascular repair of post-radiation bilateral carotid artery stenosis and pseudoaneurysms. In our practice, we have seen three such cases of radiation-induced vasculopathy. Therefore, patients with a previous history of radiation therapy for head and neck neoplasms merit cautious monitoring and judicious use of stents and secondary coils, when necessary.

Aged↗
PubMed1999

Hyperacute cerebral enhancement: the earliest predictor of hemorrhage by MR imaging?

A test to detect very early hemorrhage in acute cerebral infarct could offer a substantial increase in the safety and success of advanced stroke therapies, particularly when the use of thrombolytic therapies is contemplated. Currently, computed tomography is the standard test for the detection of cerebral hemorrhage but is not a valid predictor of potential areas of hemorrhagic transformation. A technique to evaluate the risk of hemorrhagic transformation in infarcted cerebral tissue has been conducted with contrast-enhanced magnetic resonance imaging in various animal stroke models. Knight demonstrated Gadolinium-DTPA enhancement in the territory of occluded vessels immediately in rats after reperfusion. Gadolinium enhancement was thought to predict areas of hemorrhagic transformation. Yenari and associates demonstrated in rabbit models that contrast-enhanced T1-weighted scans can reveal regions of blood-brain barrier disruption, characterized as hemorrhagic transformation in ischemic tissue. The authors report a clinical example in which hyperacute contrast-enhanced magnetic resonance imaging was the first indication of hemorrhagic transformation within 24 hours of onset of an acute cerebral infarct.

Acute Disease↗
PubMed1998

tRNA(2Gln) mutants that translate the CGA arginine codon as glutamine in Escherichia coli.

We present a novel missense suppression system for the selection of tRNA(2GIn) mutants that can efficiently translate the CGA (arginine) codon as glutamine. tRNA(2Gln) mutants were cloned from a partially randomized synthetic gene pool using a plasmid vector that simultaneously expresses the tRNA gene and, to ensure efficient aminoacylation, the glutamine aminoacyl-tRNA synthetase gene (glnS). tRNA mutants that insert glutamine at CGA were selected as missense suppressors of a lacZ mutant (lacZ625(CGA)) that contains CGA substituted for an essential glutamine codon. Preliminary characterizations of four suppressors is presented. All of them contain two anticodon mutations: C-->U at position 34 and U-->C at position 35, which allow for cognate translation of CGA. U35 was previously shown to be an important determinant for glutaminylation of tRNA(2Gln) in vitro; suppression in vivo requires overexpression of the glutaminyl-tRNA synthetase gene (glnS). One tRNA variant contains no further mutations and has the highest missense suppression activity (8%). Three other isolates each contain an additional point mutation that alters suppression efficiency. This system will be useful for further studies of tRNA structure and function. In addition, because relatively efficient translation of the rare CGA codon as glutamine is not toxic for Escherichia coli, it may be possible to translate this sense codon with other alternate meanings, a property which could greatly facilitate protein engineering.

Alleles↗
PubMed1994

Localized cystic subdural hygroma: case report.

We report a new variant of subdural hygroma previously undocumented in the literature. A 29-year-old man had a skull mass and a progressive headache of 6 to 7 years duration. He was involved in a car crash 8 years earlier and had an unrecognized skull fracture. During surgery the lesion was found to be a localized, cystic subdural hygroma communicating with the subarachnoid space through a narrow opening. This lesion is unique because: (1) the subdural hygroma was limited by an adhesion between the dura and the arachnoid; (2) the actual communication between the subdural hygroma and the subarachnoid space was clearly identified; and (3) localized bulging of the skull is exceptional for a subdural hygroma. Differentiation from more common cystic lesions such as congenital arachnoid cysts, traumatic arachnoid cysts, intradiploic arachnoid cysts, and chronic subdural hematomas is discussed.

Adult↗
PubMed1994

Venous sinus occlusive disease: MR findings.

PURPOSE: To study MR patterns of venous sinus occlusive disease and to relate them to the underlying pathophysiology by comparing the appearance and pathophysiologic features of venous sinus occlusive disease with those of arterial ischemic disease. METHODS: The clinical data and MR examinations of 26 patients with venous sinus occlusive disease were retrospectively reviewed with special attention to mass effect, hemorrhage, and T2-weighted image abnormalities as well as to abnormal parenchymal, venous, or arterial enhancement after intravenous gadopentetate dimeglumine administration. Follow-up studies when available were evaluated for atrophy, infarction, chronic mass effect, and hemorrhage. RESULTS: Mass effect was present in 25 of 26 patients. Eleven of the 26 had mass effect without abnormal signal on T2-weighted images. Fifteen patients had abnormal signal on T2-weighted images, but this was much less extensive than the degree of brain swelling in all cases. No patient showed abnormal parenchymal or arterial enhancement. Abnormal venous enhancement was seen in 10 of 13 patients who had contrast-enhanced studies. Intraparenchymal hemorrhage was seen in nine patients with high signal on T2-weighted images predominantly peripheral to the hematoma in eight. Three overall MR patterns were observed in acute sinus thrombosis: 1) mass effect without associated abnormal signal on T2-weighted images, 2) mass effect with associated abnormal signal on T2-weighted images and/or ventricular dilatation that may be reversible, and 3) intraparenchymal hematoma with surrounding edema. CONCLUSION: MR findings of venous sinus occlusive disease are different from those of arterial ischemia and may reflect different underlying pathophysiology. In venous sinus occlusive disease, the breakdown of the blood-brain barrier (vasogenic edema and abnormal parenchymal enhancement) does not always occur, and brain swelling can persist up to 2 years with or without abnormal signal on T2-weighted images. Abnormal signal on T2-weighted images may be reversible and does not always indicate infarction.

Adolescent↗
PubMed1981

Therapeutic renal artery occlusion with a detachable balloon.

The use of a new detachable balloon for renal artery occlusion is described. Successful treatment of renal lesions in 5 patients, including 2 tumors, 2 arteriovenous fistulas and 1 case of malignant hypertension with renal failure, is reported.

Adult↗
PubMed1980

Preoperative embolization of meningiomas.

Embolization of very vascular meningiomas prior to operation will reduce the loss of blood during operation. The technique of preoperative embolization is discussed, and 11 cases are presented.

Adult↗